Title:
Wheel Loader
Kind Code:
A1


Abstract:
A wheel loader includes: an operating state detecting unit detecting an operating state; a target setting unit setting a relationship between a target position of a working equipment and a travel distance of the wheel loader for the operating state detected by the operating state detecting unit; a travel distance detecting unit detecting the travel distance of the wheel loader; and a working equipment controlling unit moving a boom and a bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit.



Inventors:
Imaizumi, Masaaki (Mooka-shi, Tochigi, JP)
Application Number:
14/767475
Publication Date:
09/29/2016
Filing Date:
03/25/2015
Assignee:
KOMATSU LTD. (Minato-ku, Tokyo, JP)
Primary Class:
International Classes:
E02F3/43; E02F3/28; E02F9/20
View Patent Images:



Primary Examiner:
RINK, RYAN J
Attorney, Agent or Firm:
FISH & RICHARDSON P.C. (DC) (MINNEAPOLIS, MN, US)
Claims:
1. A wheel loader comprising: working equipment comprising a boom and a bucket attached to the boom; an operating state detecting unit configured to detect an operating state of the wheel loader; a target setting unit configured to set a relationship between a target position of the working equipment and a travel distance of the wheel loader for the operating state detected by the operating state detecting unit; a travel distance detecting unit configured to detect the travel distance of the wheel loader; and a working equipment controlling unit configured to move the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit.

2. The wheel loader according to claim 1, wherein the operating state detecting unit comprises: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is loaded and the forward/reverse travel determining unit determines that the wheel loader reverses, the operating state is detected to be a loaded reverse traveling state, the target setting unit sets the relationship between the target position of the working equipment and the travel distance of the wheel loader for the loaded reverse traveling state, and the working equipment controlling unit moves the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the loaded reverse traveling state.

3. The wheel loader according to claim 1, wherein the operating state detecting unit comprises: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is loaded and the forward/reverse travel determining unit determines that the wheel loader travels forward, the operating state is detected to be a loaded forward traveling state, the target setting unit sets the relationship between the target position of the working equipment and the travel distance of the wheel loader for the loaded forward traveling state, and the working equipment controlling unit moves the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the loaded forward traveling state.

4. The wheel loader according to claim 1, wherein the operating state detecting unit comprises: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is unloaded and the forward/reverse travel determining unit determines that the wheel loader reverses, the operating state is detected to be an unloaded reverse traveling state, the target setting unit sets the relationship between the target position of the working equipment and the travel distance of the wheel loader for the unloaded reverse traveling state, and the working equipment controlling unit moves the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the unloaded reverse traveling state.

5. The wheel loader according to claim 2, wherein the target setting unit: sets a boom angle in proportion to the travel distance to define a target position of the boom for the loaded reverse traveling state, the boom angle varying from a value at a start of a movement of the boom in the loaded reverse traveling state to a value at which the boom is to get horizontal when the travel distance of the wheel loader reaches a distance L1; and sets a bucket cylinder length where the bucket is maintained at a tilting position in accordance with the boom angle to define a target portion of the bucket for the loaded reverse traveling state.

6. The wheel loader according to claim 3, wherein the target setting unit sets a distance L2 as a target travel distance for the loaded forward traveling state, a first interim distance less than the distance L2, and a second interim distance equal to or more than the first interim distance but less than the distance L2, when the travel distance is less than the first interim distance, the target setting unit: sets a first boom angle at which the boom is to get horizontal to define a target position of the boom for the loaded forward traveling state; and sets a first bucket cylinder length where the bucket is maintained at a tilting position to define a target position of the bucket for the loaded forward traveling state, when the travel distance is equal to or more than the first interim distance but less than the second interim distance, the target setting unit: sets a second boom angle in proportion to the travel distance to define the target position of the boom for the loaded forward traveling state, the second boom angle varying from a value at a time when the travel distance reaches the first interim distance to a value at which the boom is to reach a preset lifted positioner position when the travel distance reaches the second interim distance; and sets a second bucket cylinder length where the bucket is maintained at the tilting position in accordance with the second boom angle to define a target portion of the bucket for the loaded forward traveling state, and when the travel distance is in a range from the second interim distance to the distance L2, the target setting unit: sets a third boom angle at which the boom is to reach the lifted positioner position to define the target position of the boom for the loaded forward traveling state; and sets a third bucket cylinder length where the bucket is maintained at the tilting position to define the target position of the bucket for the loaded forward traveling state.

7. The wheel loader according to claim 4, wherein the target setting unit sets a distance L2 as a target travel distance for the unloaded reverse traveling state, a third interim distance less than the distance L2, and a fourth interim distance equal to or more than the third interim distance but less than the distance L2, when the travel distance is less than the third interim distance, the target setting unit: sets a first boom angle at which the boom is to reach a preset lifted positioner position to define a target position of the boom for the unloaded reverse traveling state; and sets a first bucket cylinder length in proportion to the travel distance to define a target position of the bucket for the unloaded reverse traveling state, the first bucket cylinder length varying from a value at a start of a movement of the bucket in the unloaded reverse traveling state to a value where the bucket is to reach a preset initial position when the travel distance of the wheel loader reaches the third interim distance, when the travel distance is equal to or more than the third interim distance but less than the fourth interim distance, the target setting unit: sets a second boom angel in proportion to the travel distance to define the target position of the boom for the unloaded reverse traveling state, the second boom angle varying from a value at a time when the travel distance reaches the third interim distance to a value at which the boom is to get horizontal when the travel distance reaches the fourth interim distance; and sets a second bucket cylinder length where the bucket is maintained at the preset initial position to define the target position of the bucket for the unloaded reverse traveling state, and when the travel distance is in a range from the fourth interim distance to the distance L2, the target setting unit: sets a third boom angle in proportion to the travel distance to define the target position of the boom for the unloaded reverse traveling state, the third boom angle varying from a value at a time when the travel distance reaches the fourth interim distance to a value at which the boom is to reach a preset lowered positioner position when the travel distance reaches the distance L2; and sets a third bucket cylinder length where the bucket is maintained at the preset initial position to define the target position of the bucket for the unloaded reverse traveling state.

8. The wheel loader according to claim 1, further comprising: a boom position detecting unit configured to detect a current position of the boom; and a bucket position detecting unit configured to detect a current position of the bucket, wherein the target setting unit calculates a current target position of each of the boom and the bucket from the current travel distance detected by the travel distance detecting unit, the working equipment controlling unit calculates a deviation between the current target position of the boom and the current position of the boom detected by the boom position detecting unit and a deviation between the current target position of the bucket and the current position of the bucket detected by the bucket position detecting unit, and each of the boom and the bucket is moved based on the deviations.

9. The wheel loader according to claim 1, further comprising: a boom lever for operating the boom; and a bucket lever for operating the bucket, wherein the working equipment controlling unit adds displacement of the boom lever and the bucket lever by a manual operation to move the working equipment.

10. The wheel loader according to claim 1, further comprising: a boom lever for operating the boom; and a bucket lever for operating the bucket, wherein the working equipment controlling unit stores a travel distance at a time when the working equipment reaches the target position when displacement of the boom lever and the bucket lever by a manual operation is added, and the target setting unit corrects the travel distance of the wheel loader defined by the relationship between the position of the working equipment and the travel distance of the wheel loader with the travel distance stored when the working equipment reaches the target position.

Description:

TECHNICAL FIELD

The present invention relates to a wheel loader.

BACKGROUND ART

A wheel loader often repeats excavation and loading for the excavated substance on, for instance, the vessel of a dump truck. In particular, a large-sized wheel loader often repeats a so-called V-shape operation for a long time, which results in an increased workload on an operator. Accordingly, in order to reduce the workload on the operator, a mode for assisting loading on a vessel or the like may be installed in a wheel loader provided with semi-automatic boom and bucket (see, for instance, Patent Literature 1).

In the wheel loader of Patent Literature 1, loading from the bucket is automatically started when a predetermined operation is performed on a boom operation lever. The operator can thus only have to operate the boom lever to perform loading from the bucket.

CITATION LIST

Patent Literature(s)

  • Patent Literature 1: JP-A-2009-197425

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

When a wheel loader is used for excavation, a distal end of the boom is lowered to be positioned near the ground. In contrast, when a wheel loader is used for loading, the distal end of the boom is lifted to be positioned above the vessel of a haulage vehicle or a dump truck. Accordingly, in order to efficiently repeat excavation and loading, the wheel loader needs to travel with working equipment being moved.

The operator thus needs to operate the working equipment with his/her right hand while operating the wheel loader by, for instance, a combination of an accelerator operation (right foot), a brake operation (left foot) and a steering operation (left hand). Such a complicated operation entails an increased workload, so that an efficient operation is difficult for, especially, an inexperienced operator.

An object of the invention is to provide a wheel loader capable of easily transporting and loading, for instance, excavated soil and sand.

Means for Solving the Problem(s)

According to an aspect of the invention, a wheel loader includes: working equipment including a boom and a bucket attached to the boom; an operating state detecting unit configured to detect an operating state of the wheel loader; a target setting unit configured to set a relationship between a target position of the working equipment and a travel distance of the wheel loader for the operating state detected by the operating state detecting unit; a travel distance detecting unit configured to detect the travel distance of the wheel loader; and a working equipment controlling unit configured to move the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit.

In the aspect, when the wheel loader is in any one of predetermined operating states, including a loaded reverse traveling state, a loaded forward traveling state and an unloaded reverse traveling state, and travels, the target setting unit sets a target position of the working equipment in accordance with the operating state and the travel distance of the wheel loader, and the working equipment controlling unit moves the boom and the bucket to the target position. The exemplary embodiment thus eliminates a necessity for an operator to operate the boom lever and/or the bucket lever to move the working equipment simultaneously when operating a steering and/or an accelerator. The operator is merely required to mainly operate the steering, accelerator and brake. Consequently, even an inexperienced operator can easily operate the wheel loader.

Further, the working equipment is automatically moved to an appropriate position during the travel of the wheel loader, which results in an improved operating efficiency and a fuel-saving driving as compared with an instance where the working equipment is moved after the travel of the wheel loader.

In the wheel loader of the above aspect, it is preferable that the operating state detecting unit include: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is loaded and the forward/reverse travel determining unit determines that the wheel loader reverses, the operating state be detected to be a loaded reverse traveling state, the target setting unit set the relationship between the target position of the working equipment and the travel distance of the wheel loader for the loaded reverse traveling state, and the working equipment controlling unit move the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the loaded reverse traveling state.

In the wheel loader of the above aspect, it is preferable that the operating state detecting unit include: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is loaded and the forward/reverse travel determining unit determines that the wheel loader travels forward, the operating state be detected to be a loaded forward traveling state, the target setting unit set the relationship between the target position of the working equipment and the travel distance of the wheel loader for the loaded forward traveling state, and the working equipment controlling unit move the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the loaded forward traveling state.

In the wheel loader of the above aspect, it is preferable that the operating state detecting unit include: a load determining unit configured to determine whether or not the bucket is loaded; and a forward/reverse travel determining unit configured to determine whether the wheel loader travels forward or reverses, when the load determining unit determines that the bucket is unloaded and the forward/reverse travel determining unit determines that the wheel loader reverses, the operating state be detected to be an unloaded reverse traveling state, the target setting unit set the relationship between the target position of the working equipment and the travel distance of the wheel loader for the unloaded reverse traveling state, and the working equipment controlling unit move the boom and the bucket to the target position of the working equipment determined depending on the travel distance detected by the travel distance detecting unit when the operating state is the unloaded reverse traveling state.

In the wheel loader of the above aspect, it is preferable that the target setting unit: set a boom angle in proportion to the travel distance to define a target position of the boom for the loaded reverse traveling state, the boom angle varying from a value at a start of a movement of the boom in the loaded reverse traveling state to a value at which the boom is to get horizontal when the travel distance of the wheel loader reaches a distance L1; and set a bucket cylinder length where the bucket is maintained at a tilting position in accordance with the boom angle to define a target portion of the bucket for the loaded reverse traveling state.

In the wheel loader of the above aspect, it is preferable that the target setting unit set a distance L2 as a target travel distance for the loaded forward traveling state, a first interim distance less than the distance L2, and a second interim distance equal to or more than the first interim distance but less than the distance L2, when the travel distance is less than the first interim distance, the target setting unit: set a first boom angle at which the boom is to get horizontal to define a target position of the boom for the loaded forward traveling state; and set a first bucket cylinder length where the bucket is maintained at a tilting position to define a target position of the bucket for the loaded forward traveling state, when the travel distance is equal to or more than the first interim distance but less than the second interim distance, the target setting unit: set a second boom angle in proportion to the travel distance to define the target position of the boom for the loaded forward traveling state, the second boom angle varying from a value at a time when the travel distance reaches the first interim distance to a value at which the boom is to reach a preset lifted positioner position when the travel distance reaches the second interim distance; and set a second bucket cylinder length where the bucket is maintained at the tilting position in accordance with the second boom angle to define a target portion of the bucket for the loaded forward traveling state, and when the travel distance is in a range from the second interim distance to the distance L2, the target setting unit: set a third boom angle at which the boom is to reach the lifted positioner position to define the target position of the boom for the loaded forward traveling state; and set a third bucket cylinder length where the bucket is maintained at the tilting position to define the target position of the bucket for the loaded forward traveling state.

In the wheel loader of the above aspect, it is preferable that the target setting unit set a distance L2 as a target travel distance for the unloaded reverse traveling state, a third interim distance less than the distance L2, and a fourth interim distance equal to or more than the third interim distance but less than the distance L2, when the travel distance is less than the third interim distance, the target setting unit: set a first boom angle at which the boom is to reach a preset lifted positioner position to define a target position of the boom for the unloaded reverse traveling state; and set a first bucket cylinder length in proportion to the travel distance to define a target position of the bucket for the unloaded reverse traveling state, the first bucket cylinder length varying from a value at a start of a movement of the bucket in the unloaded reverse traveling state to a value where the bucket is to reach a preset initial position when the travel distance of the wheel loader reaches the third interim distance, when the travel distance is equal to or more than the third interim distance but less than the fourth interim distance, the target setting unit: set a second boom angel in proportion to the travel distance to define the target position of the boom for the unloaded reverse traveling state, the second boom angle varying from a value at a time when the travel distance reaches the third interim distance to a value at which the boom is to get horizontal when the travel distance reaches the fourth interim distance; and set a second bucket cylinder length where the bucket is maintained at the preset initial position to define the target position of the bucket for the unloaded reverse traveling state, and when the travel distance is in a range from the fourth interim distance to the distance L2, the target setting unit: set a third boom angle in proportion to the travel distance to define the target position of the boom for the unloaded reverse traveling state, the third boom angle varying from a value at a time when the travel distance reaches the fourth interim distance to a value at which the boom is to reach a preset lowered positioner position when the travel distance reaches the distance L2; and set a third bucket cylinder length where the bucket is maintained at the preset initial position to define the target position of the bucket for the unloaded reverse traveling state.

It is preferable that the wheel loader of the above aspect further include a boom position detecting unit configured to detect a current position of the boom; and a bucket position detecting unit configured to detect a current position of the bucket, in which the target setting unit calculates a current target position of each of the boom and the bucket from the current travel distance detected by the travel distance detecting unit, the working equipment controlling unit calculates a deviation between the current target position of the boom and the current position of the boom detected by the boom position detecting unit and a deviation between the current target position of the bucket and the current position of the bucket detected by the bucket position detecting unit, and each of the boom and the bucket is moved based on the deviations.

It is preferable that the wheel loader of the above aspect further include a boom lever for operating the boom; and a bucket lever for operating the bucket, in which the working equipment controlling unit adds displacement of the boom lever and the bucket lever by a manual operation to move the working equipment.

It is preferable that the wheel loader of the above aspect further include a boom lever for operating the boom; and a bucket lever for operating the bucket, in which the working equipment controlling unit stores a travel distance at a time when the working equipment reaches the target position when displacement of the boom lever and the bucket lever by a manual operation is added, and the target setting unit corrects the travel distance of the wheel loader defined by the relationship between the position of the working equipment and the travel distance of the wheel loader with the travel distance stored when the working equipment reaches the target position.

BRIEF DESCRIPTION OF DRAWING(S)

FIG. 1 is a side view of a wheel loader according to an exemplary embodiment of the invention.

FIG. 2 schematically illustrates a drive mechanism for working equipment.

FIG. 3 is a block diagram showing an arrangement of a working equipment controller.

FIG. 4 schematically illustrates a V-shape operation of the wheel loader.

FIG. 5 schematically illustrates a process of the V-shape operation.

FIG. 6 is a flow chart showing a working equipment controlling process for the V-shape operation.

FIG. 7 is a graph showing a relationship between a travel distance and a target position of the working equipment in a loaded reverse traveling state.

FIG. 8 is a graph showing a relationship between the travel distance and the target position of the working equipment in a loaded forward traveling state.

FIG. 9 is a graph showing a relationship between the travel distance and the target position of the working equipment in an unloaded reverse traveling state.

FIG. 10 is a flow chart showing a working equipment controlling process in the loaded reverse traveling state.

FIG. 11 is a flow chart showing a working equipment controlling process in the loaded forward traveling state.

FIG. 12 is a flow chart showing a working equipment controlling process in the unloaded reverse traveling state.

FIG. 13 is a flow chart showing the working equipment controlling process in the unloaded reverse traveling state.

FIG. 14 is a graph showing a relationship between a boom deviation angle and a target flow rate.

FIG. 15 is a graph showing a relationship between a bucket deviation length and the target flow rate.

DESCRIPTION OF EMBODIMENT(S)

Overall Arrangement of Wheel Loader

FIG. 1 is a side view of a wheel loader 1 according to an exemplary embodiment of the invention. The wheel loader 1 is a large-sized wheel loader 1 intended to be used in mines and the like.

The wheel loader 1 includes a vehicle body 2 including a front vehicle body 2A and a rear vehicle body 2B. The front vehicle body 2A has a front side (the left side in FIG. 1) provided with hydraulic working equipment 3 including an excavating/loading bucket 31, a boom 32, a bell crank 33, a connecting link 34, a bucket cylinder 35 and a boom cylinder 36.

The rear vehicle body 2B includes a rear vehicle body frame 5 formed from a thick metal plate or the like. The rear vehicle body frame 5 has a front side provided with a box-shaped cab 6 in which an operator is to be seated and a rear side where, for instance, an engine (not shown) and a hydraulic pump configured to be driven by the engine are mounted.

Drive Mechanism for Working Equipment

FIG. 2 schematically illustrates a drive mechanism for the working equipment 3. The wheel loader 1 includes a working equipment controller 10, an engine 11 and a power take-off (PTO) 12. The PTO 12 distributes an output from the engine 11 to a travel system for driving wheels (tires) 7 and a hydraulic system for driving the working equipment 3.

Arrangement of Travel System

The travel system, which is a mechanism (traveling unit) allowing the wheel loader 1 to travel, includes not only a transmission and an axle (both not shown) but also a torque converter (T/C) 15. A power outputted from the engine 11 is transmitted to the wheels 7 through the PTO 12, the torque converter 15, the transmission and the axle.

Arrangement of Hydraulic System

The hydraulic system 30 is a mechanism for driving mainly the working equipment 3 (e.g., the boom 32 and the bucket 31). The hydraulic system includes: a hydraulic pump 21 for the working equipment driven by the PTO 12; hydraulic pilot valves including a bucket operation valve 22 and a boom operation valve 23 provided in a discharge circuit of the hydraulic pump 21; solenoid proportional pressure control valves 24, 25 for the bucket independently connected to pilot-pressure receiving portions of the bucket operation valve 22; and solenoid proportional pressure control valves 26, 27 for the boom independently connected to pilot-pressure receiving portions of the boom operation valve 23.

The solenoid proportional pressure control valves 24 to 27 are connected to a pilot pump (not shown) to independently control the supply of a hydraulic oil to the pilot-pressure receiving portions in accordance with a control signal from the working equipment controller 10.

Specifically, the solenoid proportional pressure control valve 24 switches the bucket operation valve 22 so that the bucket cylinder 35 is retracted to move the bucket 31 to a loading position. Similarly, the solenoid proportional pressure control valve 25 switches the bucket operation valve 22 so that the bucket cylinder 35 is extended to move the bucket 31 to a tilting position.

The solenoid proportional pressure control valve 26 switches the boom operation valve 23 so that the boom cylinder 36 is retracted to lower the boom 32. Similarly, the solenoid proportional pressure control valve 27 switches the boom operation valve 23 so that the boom cylinder 36 is extended to raise the boom 32.

Devices Connected to Working Equipment Controller

As shown in FIG. 3, the working equipment controller 10 is connected to: a boom lever 41 and a bucket lever 42 both disposed in the cab 6; a semi-auto mode selecting unit 431 and an approach length setting unit 432 both provided to a monitor 43 disposed in the cab 6; a boom angle sensor 44; a bucket angle sensor 45; a boom-bottom pressure sensor 46; an engine controller 47; and a transmission controller 48.

The boom lever 41 includes a lever angle sensor for detecting a lever angle. When an operator operates the boom lever 41, the lever angle sensor detects a lever angle corresponding to displacement of the boom lever 41, and outputs the lever angle in the form of a boom lever signal to the working equipment controller 10.

The bucket lever 42 includes a lever angle sensor for detecting a lever angle. When an operator operates the bucket lever 42, the lever angle sensor detects a lever angle corresponding to displacement of the bucket lever 42, and outputs the lever angle in the form of a bucket lever signal to the working equipment controller 10.

The semi-auto mode selecting unit 431 displays a mode selection button on the monitor 43. When an operator operates the mode selection button to select a semi-auto loading mode, the semi-auto mode selecting unit 431 outputs an ON signal as a semi-auto mode selection signal and, otherwise, outputs an OFF signal as the semi-auto mode selection signal.

As shown in FIG. 4, the approach length setting unit 432 sets travel distances for a V-shape operation, including: a travel distance L1 for the wheel loader 1 to be reversed with, for instance, soil and sand being loaded in the bucket 31 after excavation of the soil and sand is completed; and a travel distance L2 for the wheel loader 1 to be moved toward a dump truck 60 after being reversed for the travel distance L1 and stopped. In FIG. 4, L represents the entire length of the wheel loader 1. L1 and L2 are each provided in the form of a ratio to the entire vehicle length L of the wheel loader 1, and respective default values thereof are: L1=1 (equal to the entire vehicle length) and L2=0.8 (equal to 80% of the entire vehicle length). The approach length setting unit 432 displays the respective default values “1” and “0.8” of the approach lengths L1, L2 on the monitor 43. When an operator changes these numerical values, the approach length setting unit 432 stores the inputted values as preset values and outputs the inputted values to the working equipment controller 10.

The boom angle sensor 44, which may include a rotary encoder provided to an attached portion (a support shaft) of the boom 32 relative to the vehicle body 2 as shown in FIG. 2, detects a boom angle between the center axis of the boom 32 and a horizontal axis and outputs the detection signal. The boom angle sensor 44 thus serves as a boom position detecting unit. The center axis of the boom 32, which is represented by a line Y-Y in FIG. 2, connects the attached portion of the boom 32 (i.e., the center of the support shaft) relative to the vehicle body 2 and an attached portion of the bucket 31 (the center of a bucket support shaft). Specifically, when the line Y-Y in FIG. 2 is set along the horizontal axis, the boom angle sensor 44 outputs a boom angle of zero degree. Further, the boom angle sensor 44 outputs a positive value when a distal end of the boom 32 is lifted from a position of the zero-degree boom angle, and outputs a negative value when the distal end of the boom 32 is lowered.

The bucket angle sensor 45, which may include a rotary encoder provided to a rotation shaft of the bell crank 33, outputs zero degree when the bucket 31 is in contact with the ground with a blade edge of the bucket 31 being horizontal on the ground. Further, the bucket angle sensor 45 outputs a positive value when the bucket 31 is moved toward the tilting position (upward), and outputs a negative value when the bucket 31 is moved toward the loading position (downward). The bucket angle sensor 45 thus serves as a bucket position detecting unit.

The boom-bottom pressure sensor 46 detects a boom-bottom pressure of the boom cylinder 36. The boom-bottom pressure is increased when the bucket 31 is loaded, and decreased when the bucket 31 is unloaded.

The engine controller 47 communicates with the working equipment controller 10 through a controller area network (CAN), and outputs engine operation information including the speed of the engine 11 to the working equipment controller 10.

The transmission controller 48 communicates with the working equipment controller 10 through the CAN, and outputs FR information and vehicle speed information to the working equipment controller 10, the FR information indicating a travel direction of the wheel loader 1 (i.e., forward or reverse) selected using an FR lever 49, the vehicle speed information being received from a vehicle speed sensor 50. It should be noted that the vehicle speed sensor 50 is configured to detect the vehicle speed based on, for instance, the rotation of drive shaft(s) of the tire(s) 7, and the vehicle speed information detected by the vehicle speed sensor 50 is outputted to the working equipment controller 10 via the transmission controller 48.

Arrangement of Working Equipment Controller

The working equipment controller 10 includes an operating state detecting unit 110, a target setting unit 120, a travel distance detecting unit 130, a working equipment controlling unit 140, and a storage 150.

The operating state detecting unit 110 includes a load determining unit 111 and a forward/reverse travel determining unit 112. The load determining unit 111 determines whether or not the bucket 31 is loaded based on an output value from the boom-bottom pressure sensor 46.

The forward/reverse travel determining unit 112 determines whether the wheel loader 1 is in a forward traveling state or a reverse traveling state based on the FR information outputted from the transmission controller 48 in accordance with an operation on the FR lever 49.

Operating State Detecting Unit

The operating state detecting unit 110 detects an operating state based on the determination result of the load determining unit 111 and the determination result of the forward/reverse travel determining unit 112. In the exemplary embodiment, the operating state detecting unit 110 is configured to at least detect: a loaded reverse traveling state where the wheel loader 1 is reversed after excavation is completed; a loaded forward traveling state where the wheel loader 1 in a loaded state is moved forward to transport the load to the dump truck 60 or the like; and an unloaded reverse traveling state where the wheel loader 1 is reversed after discharging the load onto the dump truck 60 or the like.

Target Setting Unit

Based on the operating state detected by the operating state detecting unit 110, the target setting unit 120 determines a relationship between a travel distance of the wheel loader 1 and a target position of the working equipment 3. In the exemplary embodiment, the relationship is determined by assigning a current travel distance to a numerical expression for calculating the target position of the working equipment 3 (i.e., the boom angle of the boom 32 and the bucket cylinder length of the bucket 31) as described later. Alternatively, the relationship between the travel distance and the target position may be stored in the form of a table.

Travel Distance Detecting Unit

The travel distance detecting unit 130 receives the vehicle speed information detected by the vehicle speed sensor 50 from the transmission controller 48, and calculates the current travel distance of the wheel loader 1.

Working Equipment Controlling Unit

Based on the various pieces of inputted information, the working equipment controlling unit 140 outputs control signal(s) to the solenoid proportional pressure control valves 24 to 27 to actuate the bucket 31 and/or the boom 32.

Further, the working equipment controller 10 outputs an indicator command and/or a buzzer command to the monitor 43. Upon reception of the indicator command, the monitor 43 controls the display of an indicator 435 provided to the monitor 43 to present information to an operator.

Upon reception of the buzzer command, the monitor 43, which is provided with a buzzer 436 capable of beeping, activates the buzzer 436 to beep to warn an operator. The storage 150 stores not only various pieces of data inputted to the working equipment controller 10 but also various parameters required for controlling the working equipment 3.

V-shape Operation Processes

Next, the V-shape operation by the wheel loader 1 will be described with reference to FIGS. 4 and 5. The V-shape operation includes the following plurality of operation processes.

1. Unloaded Stop to Excavation

A state where front ends of front ones of the tires 7 of the wheel loader 1 in an unloaded state (i.e., the bucket 31 is unloaded with a load such as soil and sand) are positioned on a spot A as shown in FIG. 4 is referred to as an unloaded stopped state (a start position).

Subsequently, an operator drives the wheel loader 1 in the unloaded state forward to a bank or the like as shown in FIG. 5(A). Specifically, the operator should preferably drive the wheel loader 1 forward for a distance L1 until the front ends of the tires 7 reach a spot B, as shown in FIG. 4.

The bucket 31 then performs excavation of the bank, and soil and sand is loaded in the bucket 31 as shown in FIG. 5(B).

2. Completion of Excavation to Loaded Reverse Travel

As shown in FIG. 5(C), after the completion of the excavation, the operator reverses the wheel loader 1 in the loaded state with the bucket 31 being loaded with, for instance, soil and sand to an unloaded stop position (the position of the spot A in FIG. 4). In other words, the wheel loader 1 is reversed for the distance L1.

3. Loaded Reverse Travel to Loaded Forward Travel

After stopping the wheel loader 1 at the unloaded stop position, the operator drives the wheel loader 1 in the loaded state forward to the dump truck 60 as shown in FIG. 5(D). As shown in FIG. 4, an angle difference θ between a direction for the wheel loader 1 to face the bank and a direction for the wheel loader 1 to face the dump truck 60 usually falls approximately within a range from 45 to 60 degrees. A travel distance to the dump truck 60 is set at the above distance L2. The operator operates the steering to turn and move the wheel loader 1 for the travel distance L2. When the wheel loader 1 reaches a side of the dump truck 60, the operator stops the wheel loader 1 by a brake operation.

4. End of Loaded State to Loading

As shown in FIG. 5(E), the operator moves the bucket 31 to the loading position to load the sand and soil from the bucket 31 onto the vessel 61.

5. Unloaded Reverse Travel to Unloaded Stop

After the completion of the loading, the operator reverses the wheel loader 1 in the unloaded state as shown in FIG. 5(F). The operator operates the steering while reversing the wheel loader 1 so that the wheel loader 1 in the unloaded state is reversed for the distance L2 and stopped. A position where the wheel loader 1 in the unloaded state is stopped is the same as the start position (the unloaded stop position) as shown in FIG. 5(G).

The operator repeats the above processes to move the wheel loader 1 along a substantially V-shaped locus (V-shape operation).

Semi-Automatic Control

For excavation as shown in FIG. 5(B) in the V-shape operation, a control allowing the bucket 31 to move in conjunction with the movement of boom 32 has been employed. Therefore, it is not necessary for the operator to operate the boom lever 41 and the bucket lever 42 to move the bucket 31 and the boom 32 during excavation.

Typically, the processes other than excavation have required a manual operation by the operator. In contrast, in the exemplary embodiment, when the semi-auto mode selection signal set by the semi-auto mode selecting unit 431 is ON, the working equipment controller 10 enables an automatic control of the working equipment 3 in the processes other than excavation (e.g., a process where the wheel loader 1 is to be driven). In the exemplary embodiment, when the automatic control of the working equipment 3 is enabled, a semi-automatic control accepting a manual operation of the boom lever 41 and the bucket lever 42 by the operator is also enabled.

Specifically, the semi-automatic control is performed during the loaded reverse travel of FIG. 5(C), the loaded forward travel of FIG. 5(D) and the unloaded reverse travel of FIG. 5(F).

Description will be made on a process of the semi-automatic control performed by the working equipment controller 10.

When the process is started in response to an ON-operation by an engine key, the working equipment controller 10 first initializes lever operation commands (i.e., a boom lever operation command: cmd_bm and a bucket lever operation command: cmd_bk) to “0”, and initializes a variable sL representing a start-time distance for a loaded forward travel control and an unloaded reverse travel control to “0”, as shown in FIG. 6 (Step S1).

Next, the working equipment controller 10 determines whether or not the semi-auto mode selection signal outputted from the semi-auto mode selecting unit 431 indicates that the semi-auto loading mode is “ON” (Step S2). When the semi-auto loading mode is “OFF”, the determination result by the working equipment controller 10 is “NO” in Step S2. The working equipment controller 10 then outputs the indicator command to the monitor 43 so that an indicator indicating that the semi-auto loading mode is on (if any) disappears from the monitor 43 (Step S3). The working equipment controller 10 repeats Steps S1 to S3 until the semi-auto loading mode is turned “ON”.

When the semi-auto loading mode is “ON”, the determination result by the working equipment controller 10 is YES in Step S2. The working equipment controller 10 then outputs the indicator command to the monitor 43 so that the monitor 43 displays the indicator indicating that the semi-auto loading mode is on (Step S4).

Operating State Detecting Process

The load determining unit 111 determines whether the wheel loader 1 is in the loaded state or the unloaded state based on a boom-bottom pressure sensor signal outputted from the boom-bottom pressure sensor 46. The forward/reverse travel determining unit 112 determines whether the wheel loader 1 is in the forward traveling state or the reverse traveling state based on the FR information outputted from the transmission controller 48. Based on the above pieces of information, the operating state detecting unit 110 can detect that the wheel loader 1 is in the loaded reverse traveling state, the loaded forward traveling state or the unloaded reverse traveling state.

Loaded Reverse Travel Detection

The operating state detecting unit 110 of the working equipment controller 10 determines whether or not a loaded reverse travel detection is turned ON from OFF (Step S5). When it is detected that the loaded reverse travel detection is turned ON from OFF, the determination result by the working equipment controller 10 is “YES” in Step S5. In this case, a variable STAGE representing an operation stage is set at “2”, a variable L representing a travel distance is set at a default value “0”, and a variable sp_bm (a boom angle) and a variable sp_bk (a bucket cylinder length) representing the start position of the working equipment are each set at a value corresponding to the current position (Step S6). In Step S6, the working equipment controller 10 sets sp_bm at the current boom angle based on a detection value of the boom angle sensor 44 and sp_bk at the current bucket cylinder length based on a detection value of the bucket angle sensor 45.

Loaded Forward Travel Detection

When the determination result is “NO” in Step S5, the operating state detecting unit 110 of the working equipment controller 10 determines whether or not a loaded forward travel detection is turned ON from OFF (Step S7). When the determination result is “YES” in Step S7 (it is detected that the loaded forward travel detection is turned ON), the working equipment controller 10 sets the variable STAGE representing the operation stage at “3”, the variable L representing the travel distance at the default value “0”, sp_bm at the current boom angle, and sp_bk at the current bucket cylinder length (Step S8).

Unloaded Reverse Travel Detection

When the determination result is “NO” in Step S7, the operating state detecting unit 110 of the working equipment controller 10 determines whether or not an unloaded reverse travel detection is turned ON from OFF (Step S9). When the determination result is “YES” in Step S9 (it is detected that the unloaded reverse travel detection is turned ON), the working equipment controller 10 sets the variable STAGE representing the operation stage at “4”, the variable L representing the travel distance at the default value “0”, sp_bm at the current boom angle, and sp_bk at the current bucket cylinder length (Step S10).

Termination Condition Determination

After the variables are initialized in Steps S6, S8, S10 or when the determination result is NO in Step S9, the working equipment controller 10 determines whether or not termination conditions are satisfied (Step S11).

Specifically, the termination conditions to be satisfied include the following six conditions 1 to 6.

A termination condition 1 is satisfied when a semi-auto mode is disabled in accordance with the output from the semi-auto mode selecting unit 431 of the monitor 43.

A termination condition 2 is satisfied when the operating state detecting unit 110 detects either an unloaded forward travel state or an excavation state. The unloaded forward traveling state may be determined based on the signal from the boom-bottom pressure sensor and the FR information, and the excavation state may be determined based on the signal from, for instance, boom-bottom pressure sensor, the boom angle and the bucket cylinder length.

A termination condition 3 is satisfied when a lever gear position is F3 (third forward speed) or greater. The lever gear position to be selected is F2 or less when the wheel loader 1 is in the V-shape operation. Therefore, in the case where the lever gear position is F3, the wheel loader 1 is supposed not to work but travel.

A termination condition 4 is satisfied when the working equipment 3 is locked. The wheel loader 1 is provided with a lock button to prevent the working equipment 3 from moving during travel. Therefore, in the case where the operator operates the lock button, the wheel loader 1 is determined not to work but to travel.

A termination condition 5 is satisfied when a failure mode effect analysis (FMEA) indicates that the sensor(s) and/or the solenoid proportional pressure control valve(s) (EPC valves) 24 to 27 should have a malfunction requiring termination of the semi-auto mode.

A termination condition 6 is satisfied when the engine operating state inputted from the engine controller 47 indicates that the engine is stopped.

When any one of the termination conditions 1 to 6 is satisfied, the determination result by the working equipment controller 10 is YES in Step S11. In this case, the working equipment controller 10 sets the variable STAGE at “1” meaning a stand-by state. Further, when any one of the conditions other than the termination condition 2 is satisfied, the working equipment controller 10 outputs the buzzer command to the monitor 43 to emit an abnormal termination beep (Step S13). The working equipment controller 10 then continues the process from Step S1.

Setting Information for Semi-automatic Control

When the determination result is “NO” (none of the termination conditions is satisfied) in Step S11, the working equipment controller 10 checks the value of the variable STAGE representing the operation stage. The working equipment controller 10 performs: a loaded reverse travel control when STAGE=2; a loaded forward travel control when STAGE=3; and an unloaded reverse travel control when STAGE=4, as described later (Step S12).

It should be noted that these controls are each independently based on a relationship between the travel distance of the wheel loader 1 and the target position of the working equipment 3, which depends on the operating state related to each of the controls. Specifically, the target position of the working equipment 3 is a position where the working equipment 3 is to reach when the wheel loader 1 travels a predetermined distance. Tables 1 and 2 show examples of the target position of the working equipment 3, and FIGS. 7 to 9 show relationships between the travel distance and the target position determined based on Tables 1 and 2. It should be noted that parameters defined in Tables 1 and 2 are stored in the storage 150 of the working equipment controller 10.

In Table 1, “lifted positioner position” and “lowered positioner position” in a column of boom angle mean boom angles preset by the operator. “Positioner position” in a column of bucket cylinder length is set at a position where the bucket angle becomes zero degrees when the boom 32 is lowered to bring the bucket 31 into contact with the ground.

TABLE 1
Working EquipmentBucket Cylinder
TargetBoom AngleLength
Loaded Reverse (TP1)Horizontal (0 deg)See Table 2
Loaded Forward (TP2)Lifted Positioner PositionSee Table 2
Unloaded Reverse (TP3)(Not Operated)Positioner Position
Unloaded Reverse (TP4)Horizontal (0 deg)Positioner Position
Unloaded Reverse (TP5)Lowered PositionerPositioner Position
Position

TABLE 2
Bucket Cylinder
Length
Boom AngleBucket AngleHigh LiftSTD
−α1β1A1B1
0β2A2B2
  α2β3A3B3

Relationship Between Travel Distance and Target Position of Working Equipment in Loaded Reverse Traveling State

In the loaded reverse travel control, while the wheel loader 1 is reversed for the predetermined distance L1 from a position at the time of the completion of excavation, the working equipment 3 is moved to a target position TP1 from the current position thereof at the time of the completion of excavation, as shown in FIG. 7. In other words, the boom angle, which changes in proportion to the travel distance, reaches zero degrees (TP1) when the travel distance reaches L1 as shown in Table 1. The bucket cylinder length is set to allow the bucket 31 to be maintained at a lifted position to prevent the load in the bucket 31 from falling out irrespective of a change in the boom angle.

For instance, according to the example of Table 2, the bucket cylinder length is set to allow the bucket angle to become β2 when the boom angle reaches zero degrees. According to the example of Table 2, the bucket cylinder length is set at A2 when the boom 32 attached to the wheel loader 1 is a high-lift boom, and is set at B2 when the boom 32 attached to the wheel loader 1 is a standard boom.

In the loaded reverse travel control, the operator is supposed to linearly reverse the wheel loader 1 without turning the steering, so that the working equipment 3 may be set to continuously move in proportion to the travel distance.

Relationship between Travel Distance and Target Position of Working Equipment in Loaded Forward Traveling State

In the loaded forward travel control, as shown in FIG. 8, the working equipment 3 is maintained at the position TP1 until the travel distance of the wheel loader 1 reaches a distance K1×L2 (a first interim distance), and is moved from the position TP1 to a position TP2 in proportion to the travel distance while the travel distance is increased from the distance K1×L2 to a distance K2×L2 (a second interim distance).

The working equipment 3 is maintained at the position TP2 while the travel distance of the wheel loader 1 is increased from the distance K2×L2 to the distance L2. A default value of K1 and a default value of K2 are respectively, for instance, 0.5 and 0.8. However, these distance coefficients may be changed by the operator or the like.

TP2 is set so that the boom angle corresponds to the raised positioner position as shown in Tables 1 and 2. The raised positioner position is determined by the operator in accordance with the level of the vessel 61 of the dump truck 6 where a load such as soil and sand is to be loaded from the wheel loader 1. The bucket cylinder length is appropriately set so that the bucket 31 is kept at the lifted position to prevent the load in the bucket 31 from falling out irrespective of a change in the boom angle.

In the loaded forward travel control, the operator is supposed to turn the steering to direct the wheel loader 1 toward the dump truck 60 until the travel distance reaches K1×L2, so that the position of the working equipment 3 should preferably be maintained. In contrast, the working equipment 3 is moved to the lifted positioner position while the travel distance is increased from K1×L2 to K2×L2, and is maintained at the lifted positioner position while the travel distance is increased from K2×L2 to L2, thereby preventing interference between the bucket 31 and the vessel 61.

Relationship between Travel Distance and Target Position of Working Equipment in Unloaded Reverse Traveling State

In the unloaded reverse travel control, as shown in FIG. 9, the working equipment 3 is maintained at a position TP3 until the travel distance of the wheel loader 1 reaches a distance K3×L2 (a third interim distance), and is moved from the position TP3 to a position TP4 in proportion to the travel distance while the travel distance is increased from the distance K3×L2 to a distance K4×L2 (a fourth interim distance).

Further, the working equipment 3 is moved from the position TP4 to a position TP5 in proportion to the travel distance while the travel distance of the wheel loader 1 is increased from the distance K4×L2 to the distance L2. A default value of K3 and a default value of K4 are respectively, for instance, 0.2 and 0.5. However, these distance coefficients may be changed by the operator or the like.

As shown in Table 1, the boom angle is “Not Operated” at TP3. The boom angle is maintained at the lifted positioner position until the completion of the loading from the completion of the loaded forward travel, so that the boom angle is still the lifted positioner position at TP3 for the unloaded reverse travel control. The bucket cylinder length is set to allow the bucket angle to become zero degrees when the bucket 31 is brought into contact with the ground by lowering the boom 32 (i.e., the positioner position).

As shown in Table 1, the boom angle is zero degrees and the bucket cylinder length is the positioner position at TP4. The boom angle is the lowered positioner position and the bucket cylinder length is the positioner position at TP5.

In the unloaded reverse travel control after loading, the working equipment 3 is maintained at the lifted positioner position with the bucket 31 being at the positioner position until the travel distance of the wheel loader 1 reaches the distance K3×L2, thereby preventing interference between the bucket 31 and the vessel 61. The boom 32 is then moved to a horizontal position while the travel distance of the wheel loader 1 is increased from the distance K3×L2 to the distance K4×L2. Further, the boom 32 is gradually moved to the lowered positioner position while the travel distance of the wheel loader 1 is increased from the distance K4×L2 to the distance L2 and, simultaneously, the operator operates the steering to move the wheel loader 1 to the unloaded stop position (i.e., the original position).

Next, the controls to be selected in S12 in FIG. 6 will be described also with reference to FIGS. 10 to 12.

STAGE=2: Loaded Reverse Travel Control

In the loaded reverse travel control, as shown in FIG. 10, the working equipment controller 10 determines whether or not a travel distance L obtained by the travel distance detecting unit 130 is less than the preset value L1 (Step S21).

Calculation of Current Travel Distance

When the determination result by the working equipment controller 10 is “YES” in Step S21, the travel distance detecting unit 130 calculates the current travel distance L (Step S22). The current travel distance L is calculated by ∫(abs(V)*1000/3600*Δt). V, which represents a vehicle speed (km/h), is multiplied by 1000/3600 to be converted to meters per second (m/s). Δt represents a program-execution cycle (sec) for the working equipment controller 10, and may be 0.01 sec.

When the determination result is “NO” in Step S21 (i.e., the travel distance has already reached the distance L1), the working equipment controller 10 skips the calculation of the current travel distance L in Step S22.

Calculation of Boom Target Position

After Step S22 or when the determination result is “NO” in Step S21, the target setting unit 120 of the working equipment controller 10 calculates a boom target position (Step S23). For the loaded reverse travel, the angle of the boom 32 is controlled in proportion to the travel distance as shown in FIG. 7. A boom target position tp_bm(t) at the travel distance L can thus be calculated by L/L1*(TP1_bm−sp_bm)+sp_bm. TP1_bm represents a boom angle at the target position TP1, and sp_bm represents the start position of the boom 32 set in Step S6. In other words, the boom target position tp_bm(t) can be obtained by multiplying a ratio of the travel distance L to the preset distance L1 and a difference between the target position and start position of the boom 32, and adding the start position (the default value).

Calculation of Bucket Target Position

After Step. S23, the target setting unit 120 of the working equipment controller 10 calculates a bucket target position (Step S24). The bucket target position can be calculated in the same manner as the boom target position. In other words, for the loaded reverse travel, the angle of the boom 32 is controlled in proportion to the travel distance as described above. Specifically, as shown in Table 2, the bucket angle is set in accordance with the boom angle, and the bucket cylinder length is set in accordance with the bucket angle. The cylinder length of the bucket cylinder 35, which actuates the bucket 31, is thus controlled in accordance with the angle of the boom 32.

A bucket target position p_bk(t) at the travel distance L can thus be calculated by L/L1*(TP1_bk−sp_bk)+sp_bk. TP1_bk represents a bucket cylinder length at the target position TP1, and sp_bk represents the start position of the bucket 31 set in Step S6. In other words, the bucket target position tp_bk(t) can be obtained by multiplying a ratio of the travel distance L to the preset distance L1 and a difference between the target position and start position of the bucket 31, and adding the start position (the default value). The target setting unit 120 thus sets the bucket cylinder length (i.e., the bucket target position tp_bk(t) at the travel distance L) in proportion to the travel distance, the bucket cylinder length varying from a bucket cylinder length at the start of the movement in the loaded reverse traveling state to a bucket cylinder length where the bucket is to reach the tilting position when the travel distance of the wheel loader reaches the distance L1. In other words, the target setting unit 120 sets the bucket cylinder length in accordance with the boom angle to maintain the bucket 31 at the tilting position.

Calculation of Deviation

Next, the working equipment controlling unit 140 of the working equipment controller 10 calculates a deviation between an actual boom angle detected by the boom angle sensor 44 and the target position and a deviation between an actual bucket cylinder length detected based on the detection value of the bucket angle sensor 45 and the target position (Step S25). Specifically, a boom target deviation angle Δbm is calculated by boom target position tp_bm(t)−actual boom angle BmAngle, and a bucket target deviation length Δbk is calculated by bucket target position tp_bk(t)−actual bucket cylinder length BkLength.

Calculation of Boom Lever Operation Command

After Step S25, the working equipment controlling unit 140 of the working equipment controller 10 calculates a boom lever operation command cmd_bm (Step S26). The boom lever operation command cmd_bm, which specifies the flow rate of the hydraulic oil in each of the solenoid proportional pressure control valves 26, 27 in a range from −100% to +100%, is calculated by adding an auto-boom command based on the boom target deviation angle Δbm calculated in Step S25 and a boom lever command BmLever inputted when the operator operates the boom lever 41.

The auto-boom command is calculated by a function interp (Δbm, BmCmdFlow, DeltaBmAngle) for obtaining a target flow rate corresponding to the boom target deviation angle Δbm with reference to a boom flow rate table BmCmdFlow defining a relationship between the boom deviation angle and the target flow rate shown in FIG. 14. When the boom lever 41 is manually operated, the auto-boom command (%) is added with the boom lever command.

As shown in FIG. 14, when the boom deviation angle is small (e.g., −2 to 2 degrees), the auto-boom command specifies a small target flow rate such as approximately −20 to +20%, and thus the movement speed of the boom 32 becomes slow. In this case, the operator may operate the boom lever 41 to increase the value of the target flow rate and, consequently, to increase the movement speed of the boom 32.

Calculation of Bucket Lever Operation Command

After Step S26, the working equipment controlling unit 140 of the working equipment controller 10 calculates a bucket lever operation command cmd_bk (Step S27). The bucket lever operation command cmd_bk, which specifies the flow rate of the hydraulic oil in each of the solenoid proportional pressure control valves 24, 25 in a range from −100% to +100%, is calculated by adding an auto-bucket command based on the bucket target deviation length Δbk calculated in Step S25 and a bucket lever command BkLever inputted when the operator operates the bucket lever 42.

The auto-bucket command is calculated by a function interp (Δbk, BkCmdFlow, DeltaBmLength) for obtaining a target flow rate corresponding to the bucket target deviation length Δbk with reference to a bucket flow rate table BkCmdFlow defining a relationship between the bucket deviation length and the target flow rate shown in FIG. 15. When the bucket lever 42 is manually operated, the auto-bucket command (%) is added with the bucket lever command. As shown in FIG. 15, when the bucket deviation length is small (e.g., −20 to 20 mm), the auto-bucket command also specifies a small target flow rate such as approximately −20 to +20%, and thus the movement speed of the bucket 31 becomes slow. In this case, the operator may operate the bucket lever 42 to increase the value of the target flow rate and, consequently, to increase the movement speed of the bucket 31.

The boom lever operation command cmd_bm and the bucket lever operation command cmd_bk calculated in Steps S26, S27 are inputted from the working equipment controlling unit 140 to the solenoid proportional pressure control valves 24 to 26 to control the action of each of the bucket operation valve 22 and the boom operation valve 23 so that the bucket cylinder 35 and the boom cylinder 36 actuate the working equipment 3.

Referring back to FIG. 6, the working equipment controller 10 again performs the process from Step S5 after Step S27. When the loaded reverse travel still continues, the determination results are NO (i.e., the loaded reverse travel detection is already ON) in Step S5, NO in each of Steps S7, S9, NO in Step S11, and “2” in Step S12. Consequently, the loaded reverse travel control shown in FIG. 10 is repeated.

It should be noted that the working equipment 3 is to be moved to the target position TP1 when the travel distance reaches L1 as shown in FIG. 7 during the loaded reverse travel, but the working equipment 3 may reach the target position TP1 before the travel distance reaches L1 when a value corresponding to the lever operation by the operator is added. When the working equipment 3 reaches the target position TP1, the deviation calculated in Step S25 becomes zero, and the working equipment 3 is maintained at the target position TP1.

However, when the travel speed is increased much more than usual by the accelerator operation, which is performed by the operator as well as the steering operation, a supply flow rate of the hydraulic oil to the working equipment may fail to meet the increase in the travel speed and, consequently, the travel distance may reach the distance L1 before the completion of the movement of the working equipment 3. In this case, only the working equipment 3 is to be moved after the completion of the travel of the wheel loader 1.

STAGE=3: Loaded Forward Travel Control

FIG. 11 is a process flow of the loaded forward travel control. A part of the process shown in FIG. 11 is identical to that of the process of the loaded reverse travel control shown in FIG. 10, and thus description thereof is simplified.

The working equipment controller 10 determines whether or not the travel distance L obtained by the travel distance detecting unit 130 is less than the preset value L2 (Step S31).

When the determination result by the working equipment controller 10 is “YES” in Step S31, the travel distance detecting unit 130 calculates the current travel distance in the same manner as in Step S22 (Step S32).

When the determination result is “NO” in Step S31 (i.e., the travel distance has already reached the distance L2), the working equipment controller 10 skips the calculation of the current travel distance L in Step S32.

After Step S32 or when the determination result is “NO” in Step S31, the working equipment controller 10 determines whether or not the travel distance L is equal to or more than K1×L2 but less than K2×L2 (Step S33). When the travel distance L is less than K1×L2, the determination result by the working equipment controller 10 is NO in Step S33. For instance, when a distance coefficient K1 is 0.5 and the travel distance L1 does not reach a half of the preset distance L2, the determination result by the working equipment controller 10 is NO in Step S33.

When the determination result is NO in Step S33, the target setting unit 120 of the working equipment controller 10 assigns the actual boom angle BmAngle to the boom target position tp_bm(t) (Step S34), and assigns the actual bucket cylinder length BkLength to the bucket target position tp_bk(t) (Step S35). In other words, the target setting unit 120 sets each of the boom target position and the bucket target position at the current position.

Therefore, in a deviation calculating process (Step S39), which is identical to the process of Step S25, the boom target deviation angle Δbm calculated by boom target position tp_bm(t)−actual boom angle BmAngle and the bucket target deviation length Δbk calculated by bucket target position tp_bk(t)−actual bucket cylinder length BkLength b each become zero.

As a result, in a boom lever operation command calculating process (Step S40) and a bucket lever operation command calculating process (Step S41), which are respectively identical to the processes of Steps S26, S27, the auto-boom command and the auto-bucket command each specify a flow rate of 0% in accordance with the deviation of zero. A flow rate corresponding to the boom lever command or the bucket lever command is thus calculated as the operation command only when the boom lever 41 or bucket lever 42 is manually operated.

Consequently, when the travel distance L of the wheel loader 1 is less than K1×L2, the working equipment 3 is maintained at TP1 according to the automatic control by the working equipment controller 10, but may be moved in accordance with a manual operation by the operator.

When the determination result is “YES” in Step S33 (i.e., the travel distance L is K1×L2 or more but less than K2×L2), the working equipment controller 10 determines whether or not the start-time distance sL is set at K1×L2 (Step S36). When the determination result is “NO” in Step S36, the working equipment controller 10 sets: the start-time distance sL at K1×L2 (i.e., the first interim distance); sp_bm at the current boom angle (i.e., a boom angle at the time when the first interim distance is reached); and sp_bk at the current bucket cylinder length (i.e., a bucket cylinder length when the first interim distance is reached) (Step S36A). In other words, when performing the determining process of Step S36 for the first time in the process flow of the loaded forward travel control shown in FIG. 11, the working equipment controller 10 sets the start-time distance sL at K1×L2 in Step S36A. Otherwise, since sL has already been set at K1×L2, the determination result is “NO” in Step S36, and the flow proceeds to Step S37. The working equipment controller 10 thus performs the process of Step S36A only once. As shown in FIG. 8, when the travel distance L is =K1×L2, the working equipment 3 is normally maintained at the target position TP1, but may not be positioned at TP1 in the case where the operator manually operates the working equipment 3. Accordingly, in Step S36A, sp_bm and sp_bk are respectively set at the boom angle and the bucket cylinder length at the time when the travel distance L reaches the first interim distance (K1×L2).

Subsequently, the target setting unit 120 of the working equipment controller 10 calculates the boom target position as in Step S23 (Step S37). During the loaded forward travel from a spot of K1×L2 to a spot of K2×L2, the angle of the boom 32 is controlled in proportion to the travel distance as shown in FIG. 8. The boom target position tp_bm(t) at the travel distance L can thus be calculated by (L−sL)/(L2*(K2−K1))*(TP2_bm−sp_bm)+sp_bm. TP2_bm represents the boom angle at the target position TP2, and sp_bm represents the start position for a lifting control of the boom 32 determined in Step S36A. L−sL represents a travel distance from the spot of K1×L2 (the first interim distance), and (L2*(K2−K1)) represents a distance from the spot of K1×L2 to the spot of K2×L2 (the second interim distance). In other words, the boom target position tp_bm(t) can be obtained by multiplying a ratio (L−sL) of the travel distance from the spot of K1×L2 relative to the distance (L2*(K2−K1)) defined from the spot of K1×L2 to the spot of K2×L2 and a difference (TP2_bm−sp_bm) between the target position and start position of the boom 32, and adding the start position (sp_bm) (the default value). Consequently, in the case where the boom angle sp_bm at the time when the travel distance L is =K1×L2 is smaller than the target speed TP1, a variation of the boom angle relative to the travel distance becomes large as compared with the variation shown by the graph of FIG. 8. In contrast, in the case where the boom angle sp_bm at the time when the travel distance L is =K1×L2 is larger than the target speed TP1, a variation of the boom angle relative to the travel distance becomes small as compared with the variation shown by the graph of FIG. 8.

Subsequently, the target setting unit 120 of the working equipment controller 10 calculates the bucket target position as in Step S24 (Step S38). Specifically, the bucket target position tp_bk(t) at the travel distance L can be calculated by (L−sL)/(L2*(K2−K1))*(TP2_bk−sp_bk)+sp_bk.

In other words, when the travel distance is the first interim distance or more but less than the second interim distance, the target setting unit 120 sets the boom angle (i.e., a boom target position for the loaded forward traveling state) in proportion to the travel distance, the boom angle varying from a boom angle at the time when the travel distance reaches the first interim distance to a boom angle where the boom 32 is to reach the preset lifted positioner position when the travel distance reaches the second interim distance. Similarly, the target setting unit 120 sets the bucket cylinder length (i.e., a bucket target position for the loaded forward traveling state) in proportion to the travel distance, the bucket cylinder length varying from a bucket cylinder length at the time when the travel distance reaches the first interim distance to a bucket cylinder length where the bucket 31 is to reach the tilting position when the travel distance reaches the second interim distance. In other words, the target setting unit 120 sets the bucket cylinder length in accordance with the boom angle to maintain the bucket 31 at the tilting position.

After Step S35 or Step S38, the working equipment controlling unit 140 of the working equipment controller 10 calculates a deviation between each of the actual boom angle and bucket cylinder length and the target position as in Step S25 (Step S39).

Subsequently, after Step S39, the working equipment controlling unit 140 of the working equipment controller 10 calculates the boom lever operation command cmd_bm (Step S40) and the bucket lever operation command cmd_bk (Step S41). The process of Step S40 and the process of Step S41 are respectively identical to those of Step S26, Step S27, and thus description thereof is omitted.

The boom lever operation command cmd_bm and the bucket lever operation command cmd_bk calculated in Steps S40, S41 are inputted from the working equipment controlling unit 140 to the solenoid proportional pressure control valves 24 to 26 to control the action of each of the bucket operation valve 22 and the boom operation valve 23 so that the bucket cylinder 35 and the boom cylinder 36 actuate the working equipment 3.

Referring back to FIG. 6, the working equipment controller 10 again performs the process from Step S5 after Step S41. When the loaded reverse travel still continues, the determination results are NO (i.e., the loaded reverse travel detection is already ON) in Step S7, NO in each of Steps S5, S9, NO in Step S11, and “3” in Step S12. Consequently, the loaded reverse travel control shown in FIG. 11 is repeated.

It should be noted that, in the loaded forward travel control, the working equipment 3 is controlled to reach the target position TP2 when the travel distance of the wheel loader 1 reaches K2×L2 as shown in FIG. 8. After the working equipment 3 reaches the target position TP2, L is determined to be K2×L2 or more in Step S33 (the determination result is “NO”), so that the processes of Steps S34, S35 are performed and the deviation is determined to be “0” in Step S39 as described above. The working equipment 3 is thus maintained at the target position TP2. When the operator manually operates the working equipment 3, the working equipment 3 may be moved to and maintained at any position in accordance with the manual operation.

STAGE=4: Unloaded Reverse Travel Control

FIGS. 12 and 13 show a process flow of the unloaded reverse travel control. A part of the process shown in FIGS. 12 and 13 is identical to that of the process shown in FIGS. 10 and 11, and thus description thereof is simplified.

The working equipment controller 10 checks whether or not the wheel loader 1 is “Unloaded” by comparison between the boom-bottom pressure and a preset value A(kg) (Step S51). When the boom-bottom pressure is less than the preset value A and, consequently, the determination result is NO (the loaded state) in Step S51, the working equipment controller 10 completes the unloaded reverse travel control and the flow returns to the process shown in FIG. 6. This results in preventing the boom 32 from being controlled to be lowered in the loaded state.

When the determination result is YES in Step S51, the working equipment controller 10 determines whether or not the travel distance L obtained by the travel distance detecting unit 130 is less than the preset value L2 (Step S52).

When the determination result by the working equipment controller 10 is “YES” in Step S52, the travel distance detecting unit 130 calculates the current travel distance L in the same manner as in Steps S22, S32 (Step S53).

When the determination result is “NO” in Step S52 (i.e., the travel distance has already reached the distance L2), the working equipment controller 10 skips the calculation of the current travel distance L in Step S53.

After Step S52 or when the determination result is “NO” in Step S52, the working equipment controller 10 determines whether or not the travel distance L is less than K3×L2 (the third interim position) (Step S54).

For instance, when K3 is 0.2 and the travel distance L does not reach 20% of the preset distance L2, the determination result by the working equipment controller 10 is YES in Step S54.

When the determination result is YES in Step S54, the target setting unit 120 of the working equipment controller 10 determines whether or not a deviation length between an absolute value of the actual bucket cylinder length BkLength and a bucket target position TP3_bk exceeds a preset value (e.g., 10 mm) (Step S55). As shown in Table 1, at the working equipment target TP3 for the unloaded reverse travel control, the boom 32 is not operated and only the bucket 31 is moved to the positioner position. The bucket 31 is positioned not at the positioner position but at the loading position immediately after the completion of loading, the determination result by the working equipment controller 10 is YES in Step S55.

When the determination result is YES in Step S55, the target setting unit 120 of the working equipment controller 10 calculates the boom target position (Step S56) and calculates the bucket target position (Step S57).

Since the boom 32 is not operated, the target setting unit 120 assigns the actual boom angle BmAngle to the boom target position tp_bm(t) in Step S56 (Step S56).

Further, the bucket target position is calculated by tp_bk(t)=L/(K3*L2)*(TP3 bk−sp_bk)+sp_bk as in Step S24 to move the bucket 31 from the loading position to the positioner position while the wheel loader 1 is moved to a spot of K3×L2 (Step S57). In other words, the target setting unit 120 sets the bucket cylinder length in proportion to the travel distance, the bucket cylinder length varying from a bucket cylinder length at the start of the movement in the unloaded reverse traveling state to a bucket cylinder length where the bucket 31 is to reach a preset initial position (the positioner position in the exemplary embodiment) when the travel distance of the wheel loader 1 reaches the third interim distance.

When the target setting unit 120 of the working equipment controller 10 determines that the deviation length between the absolute value of the actual bucket cylinder length BkLength and the bucket target position TP3 bk falls below 10 mm, the determination result is NO in Step S55. In this case, the bucket 31 is supposed to almost reach the positioner position, so that it is not necessary for the working equipment controller 10 to further move the bucket 31. Therefore, the target setting unit 120 assigns the actual boom angle BmAngle to the boomtarget position tp_bm(t) (Step S58) and assigns the actual bucket cylinder length BkLength to the bucket target position tp_bk(t) (Step S59) as in Steps S34, S35.

When the travel distance L does not reach K3×L2, the determination result by the working equipment controller 10 is NO in each of Steps S60, S64 as described later. The working equipment controller 10 thus performs the deviation calculating process (Step S68), the boom lever operation command calculating process (Step S69) and the bucket lever operation command calculating process (Step S70) as in Steps S25 to S27 and Steps S39 to S41.

Consequently, until the travel distance L reaches K3×L2, the boom 32 is maintained at the lifted positioner position, and the bucket 31 is moved to and maintained at the positioner position.

When the travel distance L of the wheel loader 1 reaches K3×L2 (the third interim distance) or more but less than K4×L2 (the fourth interim position), the determination result by the working equipment controller 10 turns NO in each of Steps S54, S64 and YES in Step S60.

When the determination result is “YES” in Step S60, the working equipment controller 10 determines whether or not the start-time distance sL is set at K3×L2 (Step S61). When the determination result is “NO” in Step S61, the working equipment controller 10 sets the start-time distance sL at K3×L2, sp_bm at the current boom angle, and sp_bk at the current bucket cylinder length (Step S61A). The working equipment controller 10 thus performs the process of Step S61A only once in the same manner as Step S36A.

Subsequently, the working equipment controller 10 calculates the boom target position as in Step S37 (Step S62). During the unloaded reverse travel from the spot of K3×L2 to a spot of K4×L2, the angle of the boom 32 is controlled to be reduced in proportion to the travel distance as shown in FIG. 9. The boom target position tp_bm(t) at the travel distance L can thus be calculated by (L−sL)/(L2*(K4−K3))*(TP4_bm−sp_bm)+sp_bm. TP4 bm represents a boom angle at the target position TP4, which is set at zero degrees (horizontal). sp_bm represents a start position for the control of reducing the angle of the boom 32 set in Step S61A. The boom angle is maintained at the lifted positioner position until L reaches K3×L2 unless the operator manually operates the boom 32, so that sp_bm is set at the lifted positioner position. L−sL represents a travel distance from the spot of K3×L2, and (L2*(K4−K3)) represents a distance from the spot of K3×L2 to the spot of K4×L2. In other words, the boom target position tp_bm(t) can be obtained by multiplying a ratio of the travel distance from the spot of K3×L2 relative to a distance from the spot of K3×L2 to the spot of K4×L2 and a difference between the target position and control start position of the boom 32, and adding the start position (the default value). The target setting unit 120 thus sets the boom angle (i.e., a target position of the boom 32 for the unloaded reverse traveling state) in proportion to the travel distance, the boom angle varying from a boom angle at the time when the travel distance reaches the third interim distance to a boom angle at which the boom 32 is to get horizontal when the travel distance reaches the fourth interim distance.

Subsequently, the working equipment controller 10 calculates the bucket target position as in Step S38 (Step S63). Specifically, the bucket target position tp bk(t) at the travel distance L can be calculated by (L−sL)/(L2*(K4−K3))*(TP4 bk−sp_bk)+sp_bk. The target setting unit 120 thus sets a bucket cylinder length where the bucket 31 is maintained at the preset initial position (the positioner position in the exemplary embodiment), the bucket cylinder length defining the target position of the bucket 31 for the unloaded reverse traveling state.

After Step S63, the working equipment controller 10 performs the above processes of Steps S68 to S70.

When the travel distance L of the wheel loader 1 reaches K4×L2 (the fourth interim distance) or more, the determination result by the working equipment controller 10 turns NO in each of Steps S54, S60 and YES in Step S64.

When the determination result is “YES” in Step S64, the working equipment controller 10 determines whether or not the start-time distance sL is set at K4×L2 as in Step S61 (Step S65). When the determination result is “NO” in Step S65, the working equipment controller 10 sets the start-time distance sL at K4×L2, sp_bm at the current boom angle, and sp_bk at the current bucket cylinder length (Step S65A). The working equipment controller 10 thus performs the process of Step S65A only once in the same manner as Steps S36A, S61A.

Subsequently, the working equipment controller 10 calculates the boom target position as in Step S62 (Step S66). During the unloaded reverse travel from the spot of K4×L2 to a spot of L2, the angle of the boom 32 is controlled to be moderately reduced in proportion to the travel distance as shown in FIG. 9. The boom target position tp_bm(t) at the travel distance L can thus be calculated by (L−sL)/(L2*(1−K4))*(TP5_bm−sp_bm)+sp_bm. TP5 bm represents a boom angle at the target position TP5, which is set at a lowered positioner position settable by the operator. sp_bm represents the control start position of the boom 32 set in Step S65A, and is the target value TP4 as long as the automatic control is enabled. L−sL represents a travel distance from the spot of K4×L2, and (L2*(1−K4)) represents a distance from the spot of K4×L2 to the spot of L2. In other words, the boom target position tp_bm(t) can be obtained by multiplying a ratio of the travel distance from the spot of K4×L2 relative to a distance from the spot of K4×L2 to the spot of L2 and a difference between the target position and control start position of the boom 32, and adding the start position (the default value). The target setting unit 120 thus sets the boom angle (i.e., a target position of the boom 32 for the unloaded reverse traveling state) in proportion to the travel distance, the boom angle varying from a boom angle at the time when the travel distance reaches the fourth interim distance to a boom angle at which the boom 32 is to get horizontal when the travel distance reaches the distance L2.

Subsequently, the working equipment controller 10 calculates the bucket target position as in Step S63 (Step S67). Specifically, the bucket target position tp_bm(t) at the travel distance L can be calculated by (L−sL)/(L2*(1−K4))*(TP5_bk−sp_bk)+sp_bk. The target setting unit 120 thus sets a bucket cylinder length where the bucket 31 is maintained at the preset initial position (the positioner position in the exemplary embodiment), the bucket cylinder length defining the target position of the bucket 31 for the unloaded reverse traveling state.

After Step S67, the working equipment controller 10 performs the above processes of Steps S68 to S70.

The V-shape operation can be repeated by repeating the above control process.

Advantage(s) of Exemplary Embodiment(s)

In the above exemplary embodiment, the bucket 31 and the boom 32 of the working equipment 3 are automatically moved to the respective target positions in accordance with the travel distance of the wheel loader 1 under the control by the working equipment controller 10 during the loaded reverse travel, the loaded forward travel and the unloaded reverse travel. The exemplary embodiment thus eliminates a necessity for an operator to simultaneously operate the boom lever 41 and the bucket lever 42 along with the steering and/or the accelerator. The operator is thus merely required to mainly operate the steering, accelerator and brake. Consequently, even an inexperienced operator can easily operate the wheel loader 1.

Further, the working equipment 3 is automatically moved to an appropriate position during the travel of the wheel loader 1, which results in an improved operating efficiency and a fuel-saving driving as compared with an instance where the working equipment 3 is moved after the travel of the wheel loader 1.

In the loaded reverse travel, the loaded forward travel and the unloaded reverse travel, the working equipment controller 10 performs the semi-automatic control, so that an operator can manually operate the boom lever 41 and the bucket lever 42 to interrupt the automatic control of the working equipment 3. The intention of the operator can be reflected in the movement of the working equipment 3. For instance, the working equipment 3 may be moved at a high speed to improve the operability.

Incidentally, it should be understood that the scope of the invention is not limited to the above-described exemplary embodiment(s), but includes modifications and improvements compatible with the invention.

In the exemplary embodiment, the semi-automatic control according to the invention is performed during operations including the loaded reverse travel, the loaded forward travel and the unloaded reverse travel, but may be performed only during one or two of these operations.

The relationship between the travel distance of the wheel loader 1 and the target position of the working equipment 3 for each of the operations may be different from those of FIGS. 7 to 9. For instance, in the loaded reverse travel control, the working equipment 3 may be moved to the target position TP1 when the wheel loader 1 reaches not the travel distance L1 but an interim spot therebefore. In the loaded forward travel control, the boom 32 may be moderately lifted to a new target position defined between the target positions TP1 and TP2 without being maintained until the travel distance reaches the first interim distance (K1×L2). Further, in the unloaded reverse travel control, the working equipment 3 may be moved to the lowered positioner position when the travel distance reaches the fourth interim distance (K4×L2) and then be maintained at the position TP5.

Further, an operator may set the relationship between the travel distance of the wheel loader 1 and the target position of the working equipment 3 for each of the operations. For instance, an operator may change the relationship between the travel distance of the wheel loader 1 and the target position of the working equipment 3 for each of the operations by changing the values of the distance coefficients K1 to K4 displayed on the monitor 43 and storing the changed values in the storage 150.

Further, since the semi-automatic control according to the invention accepts a manual operation of the boom lever 41 and the bucket lever 42, an operator may change the relationship between the travel distance of the wheel loader 1 and the target position of the working equipment 3 for each of the operations by storing a distance where the working equipment 3 is moved to the target position by the manual operation in the storage 150 and changing, for instance, the values of the distance coefficients K1 to K4 in accordance with the distance stored in the storage 150. For instance, in the loaded forward travel control, K1 is 0.5 and thus the working equipment 3 is maintained at the target position TP1 until the wheel loader 1 reaches not L2 but an interim spot therebefore. However, in the case where an operator operates the boom lever 41 to move the working equipment 3 toward the target position TP2 before the wheel loader 1 reaches the interim spot (e.g., at a spot of 0.4×L2), the distance coefficient K1 may be changed to 0.4. In this manner, the preference of operation of each operator can be reflected in the semi-automatic control of the working equipment 3.

It should be noted that the exemplary embodiment employs the semi-automatic control accepting interruption of a manual operation of the boom lever 41 and/or the bucket lever 42 in the control of the working equipment 3, but the control of the working equipment 3 may be a fully automatic control inhibiting interruption of a manual operation in the control of the working equipment 3. Further, the semi-automatic control and the automatic control may be selectable. Especially, in the case where an inexperienced operator operates, interruption of the manual operation may lead to a reduction in operating efficiency. In such a case, a mode inhibiting interruption of the manual operation may be selected.

Further, the target travel distance and actual travel distance of the wheel loader 1 and the target position and actual position of the working equipment 3 may be displayed on the monitor 43 during the semi-automatic control to assist an operator.

EXPLANATION OF CODE(S)

1 . . . wheel loader, 3 . . . working equipment, 10 . . . working equipment controller, 21 . . . hydraulic pump, 22 . . . bucket operation valve, 23 . . . boom operation valve, 24 to 27 . . . solenoid proportional pressure control valve, 31 . . . bucket, 32 . . . boom, 35 . . . bucket cylinder, 36 . . . boom cylinder, 41 . . . boom lever, 42 . . . bucket lever, 43 . . . monitor, 44 . . . boom angle sensor, 45 . . . bucket angle sensor, 46 . . . boom-bottom pressure sensor, 47 . . . engine controller, 48 . . . transmission controller, 49 . . . FR lever, 50 . . . vehicle speed sensor, 60 . . . dump truck, 61 . . . vessel, 110 . . . operating state detecting unit, 111 . . . load determining unit, 112 . . . forward/reverse travel determining unit, 120 . . . target setting unit, 130 . . . travel distance detecting unit, 140 . . . working equipment controlling unit, 150 . . . storage, 431 . . . semi-auto mode selecting unit, 432 . . . approach length setting unit, 435 . . . indicator, 436 . . . buzzer