Title:
Eccentric Radial Piston Pump and Eccentric Radial Piston Motor
Kind Code:
A1


Abstract:
In an eccentric radial piston pump, a rib 12 protruded in a radial direction is formed on an inner peripheral surface of an end portion on a discharge side of an eccentric cam ring 3 over a prescribed range. In an eccentric radial piston motor, a rib 12 protruded in a radial direction is formed on an inner peripheral surface of an end portion on a high pressure side of an eccentric cam ring 3 over a prescribed range. By the rib 12 formed in the radial direction, a rigidity of the eccentric cam ring 3 can be improved, and the eccentric cam ring can be prevented from being deformed by a thrust from the piston. Thus, the rigidity of the eccentric cam ring can be increased without increasing the thickness of the eccentric cam ring, and further the eccentric radial piston pump and the eccentric radial piston motor in which outside dimensions in the radial direction are reduced can be provided.



Inventors:
Morino, Kenji (Tochigi, JP)
Nakagawa, Tadashi (Tochigi, JP)
Iitani, Hideshi (Fukushima, JP)
Application Number:
11/887796
Publication Date:
02/19/2009
Filing Date:
03/24/2006
Assignee:
Komatsu Ltd. (Tokyo, JP)
Primary Class:
International Classes:
F04B1/04
View Patent Images:
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Primary Examiner:
STIMPERT, PHILIP EARL
Attorney, Agent or Firm:
FISH & RICHARDSON P.C. (DC) (MINNEAPOLIS, MN, US)
Claims:
1. An eccentric radial piston pump in which a displacement volume of pressure oil is changed in accordance with an eccentric amount of an eccentric cam ring, wherein the eccentric cam ring is slidably disposed between a pair of guiding surfaces which are opposingly disposed inside a casing of the eccentric radial piston pump, and a rib protruded in a radial direction is disposed on an inner peripheral surface of an end portion on a discharge side of the eccentric cam ring over a prescribed range.

2. The eccentric radial piston pump according to claim 1, wherein the rib is disposed covering an entire inner periphery of the inner peripheral surface of the end portion.

3. The eccentric radial piston pump according to claim 1 or 2, wherein a thickness of the eccentric cam ring is approximately equal to that of the rib.

4. The eccentric radial piston pump according to claim 1 or 2, wherein a rotation stop engaging member being used when the eccentric cam ring is made eccentric and/or an engaging member engaging an operative mechanism which imparts the eccentric amount to the eccentric cam ring is/are provided on an outer side surface of the rib which is parallel to an eccentric direction of the eccentric cam ring.

5. The eccentric radial piston pump according to claim 3, wherein a rotation stop engaging member being used when the eccentric cam ring is made eccentric and/or an engaging member engaging an operative mechanism which imparts the eccentric amount to the eccentric cam ring is/are provided on an outer side surface of the rib which is parallel to an eccentric direction of the eccentric cam ring.

6. An eccentric radial piston motor in which a displacement volume of pressure oil is changed in accordance with an eccentric amount of an eccentric cam ring, wherein the eccentric cam ring is slidably disposed between a pair of guiding surfaces which are opposingly disposed inside a casing of the eccentric radial piston motor, and a rib protruded in a radial direction is provided on an inner peripheral surface of an end portion on a high-pressure side of the eccentric cam ring over a prescribed range.

7. The eccentric radial piston motor according to claim 6, wherein the rib is disposed covering an entire inner periphery of the inner peripheral surface of the end portion.

8. The eccentric radial piston motor according to claim 6 or 7, wherein a thickness of the eccentric cam ring is approximately equal to that of the rib.

9. The eccentric radial piston motor according to claim 6 or 7, wherein a rotation stop engaging member being used when the eccentric cam ring is made eccentric and/or an engaging member engaging an operative mechanism which imparts the eccentric amount to the eccentric cam ring is/are provided on an outer side surface of the rib which is parallel to an eccentric direction of the eccentric cam ring.

10. The eccentric radial piston motor according to claim 8, wherein a rotation stop engaging member being used when the eccentric cam ring is made eccentric and/or an engaging member engaging an operative mechanism which imparts the eccentric amount to the eccentric cam ring is/are provided on an outer side surface of the rib which is parallel to an eccentric direction of the eccentric cam ring.

Description:

TECHNICAL FIELD

The present invention relates to an eccentric radial piston pump and an eccentric radial piston motor.

BACKGROUND ART

In an eccentric radial piston pump or an eccentric radial piston motor, the center of an eccentric cam ring and the rotation center of the casing in a radial piston pump or an eccentric radial piston motor are made eccentric, and by changing this eccentric amount, the stroke amount of the piston in a cylinder block is changed. By changing the stroke amount of the piston, displacement volume of pressure oil by the piston is changed so that the volume of the eccentric radial piston pump or the eccentric radial piston motor can be variably controlled.

An eccentric radial piston pump having a structure as disclosed in Patent Document 1 has been employed conventionally. In the eccentric radial piston pump disclosed in Patent Document 1, the arrangement relationship of a control piston for driving an eccentric cam ring and a servo control valve is specified, so that the occupancy space in the radial direction is attempted to be reduced.

A cross-sectional shape of the eccentric radial piston pump described in Patent Document 1 is shown in FIG. 13 as a prior art example in the present invention. Respective pistons 41 are disposed in respective cylinder bores of a cylinder block 40. Respective connecting rods 42 having respective piston shoes 42a are rotatably coupled with the respective pistons 41. The piston shoe 42a slides along the inner peripheral surface of an eccentric cam ring 43 disposed in the outer periphery side of the cylinder block 40.

A pintle 44 having an intake port and a discharge port is disposed at the center of the cylinder block 40, and the center of the pintle 44 and the center of the eccentric cam ring 43 can be disposed such that they are eccentric. The eccentric cam ring 43 can eccentrically move while maintaining a parallel condition with respect to the center axis line of the cylinder block 40.

The eccentric amount of the eccentric cam ring 43 is controlled by control pistons 46, 47. The respective ends of the control pistons 46, 47 make contact with the eccentric cam ring 43 and press the eccentric cam ring 43 from the both sides by the urging force of springs 48, 49. The eccentric cam ring 43 can be eccentric with respect to the center axis of the pintle 44 by pressure oil that acts on the control piston 46.

Pressure oil supplied to the control piston 46 is controlled by a servo control valve 50 disposed to be tilted in a circumferential direction of a casing 45.

Patent Document 1: Japanese Patent Laid-open Publication No. 2004-68796

DISCLOSURE OF THE INVENTION

Problem to Be Solved by the Invention

In the eccentric radial piston pump or the eccentric radial piston motor, the eccentric amount of the center of the eccentric cam ring and the rotation center of the casing in the radial piston pump or the eccentric radial piston motor is controlled by the movement amount of the eccentric cam ring. Thrust force generated by the piston is supported by the inner peripheral surface of the eccentric cam ring. Thus, the entire thrust force from the piston is supported in such a way that a concentrated load is supported on the lower surface of the eccentric cam ring.

Accordingly, when rigidity of the eccentric cam ring is small, and for example, when the thickness of the eccentric cam ring is thin, the eccentric cam ring is deformed to be a triangular shape by a thrust force from the piston. That is, as shown in FIG. 14, the eccentric cam ring which is circular in an unloaded condition receives a thrust force (indicated by arrows in FIG. 15) from the pistons whose cylinder bores' insides are at high pressure, so that the eccentric cam ring receives a deformation stress from the inside thereof to be deformed. Thus, the eccentric cam ring, while being circular in an unloaded condition as shown in FIG. 14, is deformed to be a triangular shape by receiving the deforming stress as shown in FIG. 15.

In the case where deformation occurs in the eccentric cam ring, the cylindrical surface of the piston shoe sliding along the inner peripheral surface of the eccentric cam ring is not in complete contact with the inner peripheral surface of the deformed eccentric cam ring along their whole surfaces, so that a gap is generated. Due to this gap, the contact of the piston shoe against the inner peripheral surface of the eccentric cam ring becomes nonuniform.

For example, while the piston shoe is sliding along the inner peripheral surface of the eccentric cam ring, when it reaches a place where the outer diameter on the cylindrical surface of the piston shoe is larger than the inner diameter of the eccentric cam ring, only both end edge sides in the circumferential direction of the piston shoe slide on the inner diameter of the eccentric cam ring, so that a large surface pressure is applied to the both end edge sides. By the large surface pressure applied to the both end edge sides in the circumferential direction of the piston shoe, bending stress is generated in the piston shoe. Further, when it reaches a place where the outer diameter on the cylindrical surface of the piston shoe is smaller than the inner diameter of the eccentric cam ring, the contact of the piston shoe becomes less, so that it is likely to float.

With respect to Patent Document 1, as shown in FIG. 13, in the conventional eccentric radial piston pump or the eccentric radial piston motor, the thickness of the eccentric cam ring is configured to be thick in order to prevent the eccentric cam ring from being deformed.

However, in the case where the thickness of the eccentric cam ring is configured to be thick, a problem arises in that the outside dimension in the radial direction in the eccentric radial piston pump or the eccentric radial piston motor becomes large. Specifically, in the eccentric radial piston pump or the eccentric radial piston motor, while the outside dimension in the radial direction is required to be constructed as small as possible, making the outside dimension in the radial direction large runs counter to the requirement.

An object of the present invention is to solve the problems in the prior art and to provide an eccentric radial piston pump and an eccentric radial piston motor by which the rigidity of an eccentric cam ring can be increased even when the thickness of the eccentric cam ring is not configured to be thick, and the outside dimension in the radial direction can be configured to be small.

Means to Solve the Problems

Objects of the present invention can be achieved by respective inventions described in claims 1 to 10.

That is, in the first present invention, an eccentric radial piston pump in which a displacement volume of pressure oil is changed in accordance with an eccentric amount of an eccentric cam ring is most mainly characterized in that a rib protruded in a radial direction is provided on an inner peripheral surface of an end portion on a discharge side of the eccentric cam ring over a prescribed range.

In the second present invention, the shape of the rib is defined, and that is the main characteristic.

Further, in the third present invention, the relationship of the thickness of the eccentric cam ring and that of the rib is defined, and that is the main characteristic.

Moreover, in the fourth and fifth present inventions, the structure in a side end surface of the rib is defined, and that is the main characteristic.

In the sixth present invention, an eccentric radial piston motor in which a displacement volume of pressure oil is changed in accordance with an eccentric amount of an eccentric cam ring is most mainly characterized in that a rib protruded in a radial direction is provided on an inner peripheral surface of an end portion on a high-pressure side of the eccentric cam ring over a prescribed range.

In the seventh present invention, the shape of the rib is defined, and that is the main characteristic.

Further, in the eighth present invention, the relationship of the thickness of the eccentric cam ring and that of the rib is defined, and that is the main characteristic.

Moreover, in the ninth and tenth present inventions, the structure in a side end surface of the rib is defined, and that is the main characteristic.

EFFECT OF THE INVENTION

In the present invention, in an eccentric radial piston pump and an eccentric radial piston motor, by forming a rib in the radial direction on the inner peripheral surface of the eccentric cam ring without increasing the thickness of the eccentric cam ring, the rigidity of the eccentric cam ring can be increased.

Furthermore, by forming the rib on the inner peripheral surface of the end portion on the discharge side of the eccentric cam ring in the eccentric radial piston pump, and by forming the rib on the inner peripheral surface of the end portion on the high pressure side of the eccentric cam ring in the eccentric radial piston motor, the eccentric cam ring can be prevented from being deformed by a thrust from the piston.

In the present invention, the rib can also be disposed covering the entire inner periphery of an inner peripheral surface of the end portion of the eccentric cam ring. By disposing the rib covering the entire inner periphery of the inner peripheral surface of the end portion, deformation prevention of the eccentric cam ring can be further rigidly achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic vertical cross-sectional view of an eccentric radial piston pump (First Embodiment).

FIG. 2 is a vertical cross-sectional view of an eccentric cam ring (First Embodiment).

FIG. 3 is a vertical cross-sectional view of another eccentric cam ring (First Embodiment).

FIG. 4 is a vertical cross-sectional view of yet another eccentric cam ring (First Embodiment).

FIG. 5 is a perspective view of an eccentric cam ring (First Embodiment).

FIG. 6 is another perspective view of an eccentric cam ring (First Embodiment).

FIG. 7 is yet another perspective view of an eccentric cam ring (First Embodiment).

FIG. 8 is a model view for analyzing the rigidity of an eccentric cam ring (First Embodiment).

FIG. 9 is a view showing stress distribution of the analytical model (First Embodiment).

FIG. 10 is a table showing analysis results (First Embodiment).

FIG. 11 is a schematic vertical cross-sectional view of an eccentric radial piston pump (Second Embodiment).

FIG. 12 is a schematic vertical cross-sectional view of an eccentric radial piston motor (Third Embodiment).

FIG. 13 is a schematic vertical cross-sectional view of an eccentric radial piston pump (Conventional example).

FIG. 14 is a configuration view of an eccentric cam ring in an unloaded condition (Explanatory example).

FIG. 15 is a deformed view of the eccentric cam ring when a load is applied (Explanatory example).

EXPLANATION OF REFERENCE NUMERALS

  • 1 eccentric radial piston pump
  • 3 eccentric cam ring
  • 4 cylinder block
  • 5 piston
  • 8 pintle
  • 10 intake port
  • 11 discharge port
  • 12 rib
  • 15a, 15b piston
  • 22, 23 operative mechanism
  • 25a, 25b piston
  • 28a, 28b pressing member
  • 30, 31 engaging member
  • 32 eccentric radial piston motor
  • 33 pintle
  • 34, 35 port
  • 40 cylinder block
  • 41 piston
  • 43 eccentric cam ring
  • 44 pintle
  • 46, 47 control piston
  • 50 servo control valve

BEST MODE FOR CARRYING OUT THE INVENTION

A suitable embodiment of the present invention will be described specifically below with reference to the accompanying drawings. As the structures of an eccentric radial piston pump and an eccentric radial piston motor of the present invention, configurations and arrangement structures through which the problems of the present invention can be solved can also be adopted, other than configurations and arrangement structures described below. Thus, the present invention is not limited to embodiments described below, and various modifications are possible.

An eccentric radial piston pump or an eccentric radial piston motor according to the present invention also includes an eccentric radial piston pump/motor which can employ both pump operation and motor operation.

FIRST EMBODIMENT

FIG. 1 illustrates a schematic vertical cross-sectional view of an eccentric radial piston pump 1 according to an embodiment of the present invention. FIG. 2 illustrates a vertical cross-sectional view of an eccentric cam ring 3. As shown in FIG. 1, the eccentric cam ring 3 is disposed in a casing 2, and a cylinder block 4 is rotatably disposed inside the eccentric cam ring 3. In the cylinder block 4, a plurality of cylinder bores 7 are formed in the radial direction thereof, and respective pistons 5 are slidably disposed in the respective cylinder bores 7.

A piston shoe 6 is swingably supported in the piston 5. The piston shoe 6 slides on a cam surface 3A of the eccentric cam ring 3 and slides on the cam surface 3A in accordance with the rotation of the cylinder block 4. Sliding of the piston shoe 6 on the cam surface 3A can impart reciprocating motion to the piston 5.

A pintle 8 disposed in the casing 2 is fitted into a pintle inserting portion 9 of the cylinder block 4 to rotatably support the cylinder block 4. In the pintle 8, an intake port 10 and a discharge port 11 are formed. By the rotation of the cylinder block 4, the piston 5 repeats an intake process and a discharge process.

In the intake process, the piston 5 slides in a direction in which the piston 5 protrudes from the cylinder bore 7 from the top dead center to the bottom dead center to suck pressure oil from the intake port 10 to the inside of the cylinder bore 7. In the discharge process, the piston 5 slides from the bottom dead center to the top dead center to compress the pressure oil in the cylinder bore 7. The pressure oil which became high pressure by the compression is discharged from the discharge port 11.

As shown in FIG. 2, a ring-shaped rib 12 is formed along the inner peripheral surface of the eccentric cam ring 3. In FIG. 1, the ring-shaped rib 12 formed along the inner peripheral surface of the eccentric cam ring 3 is illustrated as a shape in which it extends from the cam surface 3A to the center side of the eccentric cam ring 3.

In the left and right sides of the casing 2, cylinder chambers 14a, 14b are formed, and in the respective cylinder chambers 14a, 14b, pistons 15a, 15b making contact with the outer peripheral surface of the eccentric cam ring 3 are slidably disposed respectively. The respective pistons 15a, 15b are urged by springs 16a, 16b, respectively, and top end portions of the respective pistons 15a, 15b make contact with the outer peripheral surface of the eccentric cam ring 3, while pressing it constantly.

By a switching operation of a switching valve 18, pressure oil from a hydraulic pump 19 is supplied to one side cylinder chamber 14a or the cylinder chamber 14b, and pressure oil in the other side cylinder chamber 14b or the cylinder chamber 14a can be discharged to a tank 20.

The outer peripheral surface of the eccentric cam ring 3 slides on guiding surfaces 13 formed on upper and bottom portions of the casing 2. By activating the pistons 15a, 15b in accordance with the switching operation of the switching valve 18, the eccentric cam ring 3 can be moved along the guiding surfaces 13, and the eccentric amount with respect to the rotational center of the cylinder block 4 can be adjusted.

As shown in FIG. 2, the rib 12 is formed on the inner peripheral surface of the end portion of the eccentric cam ring 3, circularly toward the inside in the radial direction, so that the rigidity of the eccentric cam ring 3 is increased by the rib 12.

Since the rigidity of the eccentric cam ring 3 is increased by forming the rib 12 so that its deformation can be prevented, the cam surface 3A of the eccentric cam ring 3 can constantly maintain a certain shape. Thus, a sliding condition of the piston shoe 6 and the cam surface 3A can be maintained in an excellent condition constantly, and the piston shoe 6 can be prevented from floating from the cam surface 3A.

The rib 12 may be constructed integrally with the eccentric cam ring 3 or may be constructed as a distinct body form the eccentric cam ring 3. In the case where the rib 12 is constructed as a distinct body, the rib 12 may be fixedly fitted into the inner peripheral surface of the eccentric cam ring 3 by using pressure or the like, or may be fixedly secured to the eccentric cam ring 3 by employing a fixing means such as welding or the like.

The rib 12 needs to be constructed in such a way that the protrusion amount of the rib 12 in the radial direction is set to an amount by which the rib 12 can have an enough rigidity to prevent the eccentric cam ring from being deformed by a thrust from the piston 5. Further, in the relationship between the material and thickness of the rib 12, the protrusion amount in the radial direction can be adjusted.

As shown in FIG. 3, as the ribs 12 respectively disposed on both end portions of the eccentric cam ring 3, one rib may be constructed integrally with the eccentric cam ring 3, and the other rib 12 may be constructed as a distinct body from the eccentric cam ring 3. The rib 12 constructed as the distinct body may be structured in such a way that it has a flange portion projecting toward the inner peripheral surface side of the eccentric cam ring 3 as shown in FIG. 3, or the rib 12 may be constructed in such a way that it has flange portions projecting toward the inner peripheral surface side and the outer circumferential surface side of the eccentric cam ring 3, respectively, as shown in FIG. 4. The rib 12 constructed as the distinct body can be fixed to the eccentric cam ring 3, by employing a fitting fixing method by using pressure or the like, or a fixing method such as welding or the like.

The structure of the rib 12 may have shapes shown by perspective views of the eccentric cam ring 3 illustrated in respective FIGS. 5 to 7 other than the circular rib shape. The shapes of the rib 12 shown in FIGS. 5 to 7 are examples, and the present invention is not limited to those shapes. These shapes can be employed as the rib of the present invention as far as it is a rib shape by which rigidity of the eccentric cam ring 3 can be increased, and the rib shape at that time is included in the present invention.

As shown in FIG. 5, the rib 12 can be disposed on a portion of the inner peripheral surface of one end portion of the eccentric cam ring 3. In this case, the same rib 12 can be disposed on a portion to which a thrust from the piston 5 disposed on the cylinder block 4 is largely applied. That is, the rib 12 can be disposed on the inner peripheral surface of the end portion on a discharge side of the eccentric cam ring 3.

The structure in which the rib 12 is disposed on the inner peripheral surface of the end portion may include both structures in which the rib 12 is disposed inside the inner peripheral surface of the eccentric cam ring 3 and in which a side surface of the rib 12 and an end portion surface of the eccentric cam ring 3 are in firmly contact with each other.

As shown in FIG. 6, the ribs 12 may also be disposed on both end portions of the eccentric cam ring 3 to which a thrust from the piston 5 is largely applied respectively. Further, as shown in FIG. 7, the ribs 12 may be disposed on the inner peripheral surface of the end portion on both port sides of the eccentric cam ring respectively.

Thus, the rib 12 can be formed in an area of the inner peripheral surface of the end portion of the eccentric cam ring 3 which receives a large deformation load. By constructing it in this way, the eccentric cam ring can be efficiently prevented from being deformed by the rib 12 which is disposed over a required minimum range.

As is apparent from the foregoing, the rib 12 disposed on the inner peripheral surface of the end portion of the eccentric cam ring 3 may be formed covering the entire circle of the inner peripheral surface of the end portion of the eccentric cam ring 3, or may also be formed in an area of the inner peripheral surface of the end portion of the eccentric cam ring 3 which receives a large deformation load as a thrust from the piston 5 since pressure oil inside the cylinder bore 7 is at a high pressure.

In the case where the rib 12 is disposed on a part of the inner peripheral surface of the end portion of the eccentric cam ring 3, it is necessary that the rib 12 is constructed in such a way that concentrated load is not applied to the boundary between the portion where the rib 12 is disposed and the portion where it is not disposed, that is, the boundary between the rib 12 and one end portion surface of the eccentric cam ring 3.

In the case where the ribs 12 is disposed on inner peripheral surfaces of both end portions the eccentric cam ring 3 respectively, the rib 12 disposed at least one end side may have a divided shape and may be constructed as a distinct body from the eccentric cam ring 3. Or, as shown in FIG. 6, the rib 12 may be constructed in such a way that the protrusion amount in the radial direction of the rib 12 disposed on one end side is smaller than that in the radial direction of the rib 12 disposed on the other end portion side.

By constructing in such a way, at the time of assembling the eccentric radial piston pump 1, rib pieces formed as distinct bodies by dividing the rib 12 into several pieces may be assembled sequentially in accordance with insertion and assembly of the piston into the cylinder block.

Alternatively, the outer circumferential diameter including the piston shoes 6 of when the respective pistons 5 are inserted into the respective cylinder bores 7 of the cylinder block 4 until the top dead center may be set to be an outer circumferential diameter which enables to be inserted through the opening, which is formed by the upper end of the rib 12 on the side where the protrusion amount in the radial direction of the rib 12 is lowered and by the inner peripheral surface of the eccentric cam ring 3.

Thus, the ribs can be disposed on both ends of the eccentric cam ring, and assembly work in which the pistons 5 are attached to the cylinder block 4 disposed inside the eccentric cam ring 3 can be done easily.

The thickness of the rib 12 is desired to be approximately equal to the thickness of the eccentric cam ring 3. FIG. 8 shows an analyzing model view showing the relationship between the thickness t1 of the eccentric cam ring 3 and the thickness t2 of the rib 12, and shows the cross-sectional shape of an adjacent region of the eccentric cam ring 3.

Respective models of the eccentric cam ring 3 in which the ratio of the thickness t1 of the eccentric cam ring 3 and the thickness t2 of the rib 12 is changed were made under conditions in which the inner diameter, flange inner diameter, and cam width of the eccentric cam ring 3 are fixed sizes, employing the eccentric cam ring 3 shown in FIG. 8, and analysis by finite element method was done with respect to cam stresses in the respective models. While the analysis by the finite element method was done, the ratio of the thickness t1 and the thickness t2 was changed under the condition in which the mass of the eccentric cam ring 3 is approximately constant.

Stress distribution of the cam stress calculated by employing the finite element method became the stress distribution as shown in FIG. 9. FIG. 9 is a principal part perspective view in which a portion where the eccentric cam ring 3 makes contact with the guiding surface 13 of the casing 2 is the center thereof. As is apparent from FIG. 9, maximum stress σ1 is generated at a portion where the eccentric cam ring 3 on the discharge side makes contact with the guiding surface 13 of the casing 2. Further, it is apparent that the stress becomes smaller from σ2 to σ3, and σ4 in accordance with the distance from the portion where it makes contact with the guiding surface 13 becoming larger.

Further, as is apparent from FIG. 9, in the portion where at least maximum stress σ1 is generated, or in a portion where stress which is larger than a desired stress (for example, stress larger than σ3) is generated, by forming another rib on one end portion of the eccentric cam ring 3, stress generated can be suppressed small. That is, in FIG. 9, although an example in which the rib 12 is formed on one side of the eccentric cam ring 3 is shown, for example, the rib 12 may be formed on both end sides of the eccentric cam ring 3 as shown in FIG. 6, so that the eccentric cam ring 3 can have a structure which is further hard to be deformed.

FIG. 9 is a table showing analysis results of the cam stress calculated through the finite element method under the above-mentioned conditions in the above-mentioned respective models. As is apparent from FIG. 9, when the ratio of the thickness t1 of the eccentric cam ring 3 and the thickness t2 of the rib 12 is 1:1, the cam stress is minimum. Moreover, maximum cam stress generated at that time can be in an allowable range. Further, when the ratio of the thickness t1 and the thickness t2 is 1:1, the outside dimension of the eccentric cam ring 3 can be minimum.

Thus, when the ratio of the thickness t1 and the thickness t2 is 1:1, the dimension of the eccentric radial piston pump 1 in the radial direction can be configured to be small. Further, the rigidity of the eccentric cam ring 3 can be strong enough to prevent the eccentric cam ring 3 from being deformed.

In this way, by the structure in which the thickness t1 of the eccentric cam ring 3 is approximately equal to the thickness t2 of the rib 12, the eccentric cam ring 3 can be provided with a rigidity by which deformation due to a thrust from the piston can be prevented, and further the dimension of the eccentric cam ring 3 can be minimum.

Moreover, sliding stability of the piston shoe 6 can be obtained, and the eccentric radial piston pump 1 can be stably driven. Furthermore, the rigidity of the eccentric cam ring 3 can be increased without increasing the thickness t1 of the eccentric cam ring 3. Thus, the outside dimension of the eccentric radial piston pump 1 in the radial direction thereof can be configured to be small, and further, volume efficiency can be improved.

Even when an operative mechanism or the like of the eccentric cam ring 3 is disposed inside the eccentric radial piston pump 1, the outside dimension of the eccentric radial piston pump 1 in the radial direction thereof can be reduced.

When the operative mechanism or the like which imparts the eccentric amount to the eccentric cam ring 3 is disposed outside the eccentric cam ring 3 in the axial direction thereof, the length of the eccentric radial piston pump 1 in the axial direction thereof is long. However, since the outside dimension of eccentric radial piston pump 1 in the radial direction thereof can be reduced, as a result, the maximum dimension including the vertical and horizontal lengths and the height of the eccentric radial piston pump 1 can be configured to be small.

Further, since the outside dimension of the eccentric radial piston pump 1 in the radial direction thereof is reduced, the area on which the eccentric radial piston pump 1 is disposed can be reduced, so that it can be disposed effectively even on a compact hydraulic machine or the like.

SECOND EMBODIMENT

FIG. 11 shows a schematic vertical cross-sectional view of another eccentric radial piston pump 1 according to an embodiment of the present invention. In the first embodiment, as a structure for making the eccentric cam ring 3 eccentric, by operation of pistons 15a, 15b provided on left and right sides of the casing 2, the eccentric cam ring 3 can be eccentric.

On the other hand, in the second embodiment, engaging members 30, 31 are formed on a side surface of the rib 12 disposed on the eccentric cam ring 3, and operative mechanisms 22, 23 imparting an eccentric amount is allowed to affect the engaging members 30, 31, so that the eccentric cam ring 3 is allowed to be eccentric.

The second embodiment has this structure which is different from the structure of the first embodiment. Other structures are similar to those of the first embodiment. Thus, like reference numerals designating corresponding structures in the second embodiment, and explanation thereof will be omitted.

The engaging members 30, 31 formed on a side surface of the rib 12 may be disposed on it as members which are fitted into a hole 12a shown in FIG. 2, or they may be formed integrally with the rib 12. The operative mechanism 22 is provided with a pair of pistons 25a, 25b which receive pressure oil from the hydraulic pump 19 to press the engaging member 30 and springs 26a, 26b pressing the pair of pistons 25a, 25b toward the engaging member 30 side respectively. The operative mechanism 23 is provided with a pair of pressing members 28a, 28b pressing from both ends of the engaging member 31 and springs 29a, 29b urging pressing force to the pair of pressing members 28a, 28b.

The pair of pistons 25a, 25b and the springs 26a, 26b in the operative mechanism 22 are disposed inside cylinder chambers 24a, 24b, respectively. By switching of the switching valve 18, pressure oil from the hydraulic pump 19 is supplied to the cylinder chamber 24b, and when pressure oil inside the cylinder chamber 24a is discharged to the tank 20, the piston 25b slides toward the left direction in FIG. 11, and the eccentric cam ring 3 also moves toward the left direction in FIG. 11. When this switching valve 18 is switched from the switching position thereof to the opposite switching position, the eccentric cam ring 3 can be moved toward the right direction in FIG. 11.

The pair of pressing members 28a, 28b in the operative mechanism 23 are urged toward a direction in which they come close to each other by the urging force of the springs 29a, 29b disposed inside spring chambers 27a, 27b, respectively. A rotation stop mechanism of the eccentric cam ring 3 is formed by the pair of pressing members 28a, 28b.

When the eccentric cam ring 3 moves by the operation of the pair of pistons 25a, 25b in the operative mechanism 22, the springs 29a, 29b are deformed, respectively, and the eccentric cam ring 3 can be moved in parallel.

The disposed position of the cylinder chamber 24b and the disposed position of the spring chamber 27a provided with the pressing member 28a may be reversed to construct the operative mechanism 22 and the operative mechanism 23. At this time, the operative mechanism 22 is composed of the cylinder chamber 24a provided with the piston 25a and the spring chamber 27a provided with the pressing member 28a disposed in place of the cylinder chamber 24b, and the operative mechanism 23 is composed of the cylinder chamber 24b provided with the piston 25b disposed in place of the spring chamber 27a and the spring chamber 27b provided with the pressing member 28b.

Further, similarly, the disposed position of the cylinder chamber 24b and the disposed position of the spring chamber 27b provided with the pressing member 28b may be reversed to construct the operative mechanism 22 and the operative mechanism 23.

Even when such a structure is made, pressure oil discharged from the switching valve 18 is selectively supplied to the cylinder chamber 24a and the cylinder chamber 24b, so that movement of the eccentric cam ring 3 can be controlled.

In the structure of the second embodiment, pairs of pistons making contact with both sides of the engaging members 30, 31 shown in FIG. 11, respectively, may be disposed at both sides of the engaging members 30, 31, respectively.

As shown in FIG. 11, since the operative mechanisms 22, 23 can be disposed on the outside of the eccentric cam ring 3 in the axial direction thereof and even on the inner diameter side of the eccentric cam ring 3, the outer shape of the eccentric radial piston pump 1 in the radial direction thereof can be configured to be small.

In this case, since the operative mechanisms 22, 23 imparting the eccentric amount to the eccentric cam ring 3 are disposed on the outside of the eccentric cam ring 3 in the axial direction thereof, the length of the eccentric radial piston pump 1 in the axial direction thereof becomes longer.

However, since the outside dimension of the eccentric radial piston pump 1 in the radial direction thereof can be made small, as a result, the maximum dimension including the vertical and horizontal lengths and the height of the eccentric radial piston pump 1 can be configured to be small.

Instead of the structure in which the hole 12a shown in FIG. 2 is employed as a hole for attaching the engaging members 30, 31 engaging the operative mechanisms 22, 23, the hole 12a may be employed as a rotation stop member for stopping the rotation of the eccentric cam ring 3. Further, instead of the structure in which the hole 12a is formed on a side surface of the rib 12, a rotation stop member may be constructed integrally with the eccentric cam ring.

THIRD EMBODIMENT

FIG. 12 shows a schematic vertical cross-sectional view of an eccentric radial piston motor 32 according to an embodiment of the present invention. The third embodiment has a structure similar to that of the eccentric radial piston pump 1 in the first embodiment except that it shows the structure of the eccentric radial piston motor 32. Thus, as to the similar structures to the eccentric radial piston pump 1, the explanation of the reference numerals will be omitted below by employing the reference numerals used in FIG. 1.

The eccentric radial piston motor 32 has a structure in which the cylinder block 4 and a pintle 33 rotate integrally. Thus, passages of pressure oil formed in the pintle 33, which are communicated with ports 34, 35, respectively, are formed to have the same diameter.

In this connection, the eccentric radial piston pump 1 is constructed in such a way that the pintle 8 does not rotate while the cylinder block 4 rotates. Thus, with respect to the passages of pressure oil formed in the pintle 33, the diameter of the passage communicated with the intake port 10 is larger than that of the passage communicated with the discharge port 11.

The eccentric radial piston pump 1 may be constructed in such a way that the diameter of the passage communicated with the intake port 10 is the same as that of the passage communicated with the discharge port 11. Specifically, in the eccentric radial piston pump/motor, it is necessary that the diameter of the passage communicated with the intake port 10 is the same as that of the passage communicated with the discharge port 11.

Although FIG. 1 shows a structural example in which the intake port 10 is arranged in a lower side in the drawing and in which the discharge port 11 is arranged in an upper side in the drawing, arrangement positions of the intake port 10 and the discharge port 11 may be reversed with respect to the arrangement positions of FIG. 1.

In the eccentric radial piston motor 32 shown in FIG. 12, for example, the port 34 located in a lower side in FIG. 12 is communicated with pressure oil of a high pressure side, and the port 35 located in an upper side is communicated with pressure oil of a low pressure side. When the port 35 communicated with the low pressure side in the upper side goes in a lower side by the rotation of the cylinder block 4 and the pintle 33, it is communicated with pressure oil of the high pressure side this time.

At the same time, the port 34 communicated with the high pressure side in the lower side is communicated with pressure oil of the low pressure side. That is, the ports 34, 35 are communicated with pressure oil of the high pressure side and pressure oil of the low pressure side, alternately, respectively, in accordance with the rotation of the cylinder block 4 and the pintle 33.

High pressure oil is supplied from the port 34 or the port 35 which is communicated with pressure oil of the high pressure side into the cylinder bore 7. By High pressure oil supplied into the cylinder bore 7, the piston 5 inside the cylinder bore 7 is pressed to rotate the cylinder block 4.

Similarly to the description of the case of the eccentric radial piston pump 1 in the first embodiment, the rib 12 may be constructed in such a way that it protrudes in the radial direction over a predetermined area of the inner peripheral surface of the end portion on at least the high pressure side of the eccentric cam ring 3. By constructing the rib 12, the rigidity of the eccentric cam ring 3 can be increased so that the eccentric cam ring 3 is not deformed.

The rib 12 may be constructed similarly to those shown in FIGS. 2 to 7. As described in the description of the first embodiment, as far as the rib shape can increase the rigidity of the eccentric cam ring 3, those shapes can be employed as a rib of the present invention.

By providing the rib 12 on the eccentric cam ring 3, working effects similar to those of the case of the first embodiment in which the eccentric cam ring 3 having the rib 12 is employed in the eccentric radial piston pump 1 can be produced. The results of the analysis models described employing FIGS. 8 to 10 can be applied to the case of the eccentric radial piston motor 32 without any changes.

The structure of the eccentric radial piston motor 32 may be similar to the eccentric radial piston pump 1 shown in FIG. 11 other than the structure shown in FIG. 12. At this time, it is desired that the diameters of the passages formed on the pintle communicated with the intake port 10 and the discharge port 11, respectively, have the same diameters.

Similarly to the description in the second embodiment, a rotation stop engaging member being used when the eccentric cam ring is made eccentric or an engaging member with respect to an operative mechanism imparting an eccentric amount to the eccentric cam ring can be provided on a side surface of the rib 12 disposed on the eccentric cam ring 3.

Although the structure of the eccentric radial piston pump 1 and the structure of the eccentric radial piston motor 32 are described in the embodiments described above, the structure of the eccentric radial piston pump or the eccentric radial piston motor described in the embodiments includes the structure of an eccentric radial piston pump/motor.

INDUSTRIAL USABILITY

In the present invention, technical idea of the present invention can be applied to a device or the like to which the technical idea of the present invention can be applied.