SAFETY DEVICE FOR LIMITING THE ROTATIONAL SPEED OF INTERNAL COMBUSTION ENGINES
United States Patent 3661130
An electronically controlled diesel engine wherein the high-pressure chamber of the fuel injection pump is connected with the low-pressure chamber by a passage controlled by an electromagnetic valve which opens or closes when the rotational speed of the engine reaches a maximum permissible value. The speed is detected by an electrical counter which effects opening of the valve if the latter is installed in a passage which conveys fuel from the high-pressure chamber, or closing of such valve if the latter is installed in a passage which supplies fuel to the high-pressure chamber, whenever the engine speed reaches the maximum permissible value. The electrical connection between the speed counter and the valve comprises an amplifier whose input circuit contains an inductance of the speed counter and a first safety fuse and whose output circuit contains a relay switch for the circuit of the winding in the valve and a second safety fuse. The circuit of the winding can be completed by an auxiliary switch in response to actuation of the starter for the engine.
US Patent References:
Spark ignition circuit
Jukes - December 1967 - 3356082
Engine speed governor
Kerr - July 1963 - 3099254
Speed responsive switching apparatus
Schneider et al. - May 1965 - 3182648
Magneto ignition system for internal combustion engines and the like
McMillen - June 1967 - 3326199
Spark ignition circuit
Jukes - December 1967 - 3356082
Engine speed governor
Kerr - July 1963 - 3099254
Speed responsive switching apparatus
Schneider et al. - May 1965 - 3182648
Magneto ignition system for internal combustion engines and the like
McMillen - June 1967 - 3326199
Application Number:
05/020276
Publication Date:
05/09/1972
Filing Date:
03/17/1970
View Patent Images:
Export Citation:
Assignee:
Robert Bosch GmbH (Stuttgart, DT)
Primary Class:
Other Classes:
123/357, 123/506, 123/358
International Classes:
F02M41/12; F02M63/02; F02B3/06; F02M41/08; F02M63/00; F02B3/00; F02D5/00
Field of Search:
123/139E,97,104,102,140,198DB
Primary Examiner:
Goodridge, Laurence M.
Claims:
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims
1. In an internal combustion engine, a combination comprising a fuel injection pump having a high-pressure fuel chamber, a low-pressure fuel chamber, and a passage connecting said chambers; a rotary member arranged to rotate at a variable speed which is proportional to the operating speed of the engine; electromagnet safety valve means including a valve member installed in said pump and movable between open and closed positions in which it respectively permits and prevents the flow of fuel through said passage, said valve member being arranged to assume one of said positions in response to energization and the other of said positions in response to deenergization of said valve means; electrical speed counter means comprising a serrated ferromagnetic element driven by said rotary member, a yoke having at least one serrated portion adjacent to said ferromagnetic element, a first and a second inductance on said yoke; a regulating circuit connecting said first inductance to said safety valve means to effect a change in the condition of energization of said safety valve means when the speed of said rotary member reaches a predetermined value; an electric control circuit connected to said second inductance; and means connected to said electronic control circuit for regulating supply of fuel by said injection pump to said engine in dependence on the speed of said rotary member.
2. A combination as defined in claim 1, wherein said passage is arranged to supply fuel from said low-pressure chamber to said high-pressure chamber and wherein said valve member is moved to closed position in response to said change in the condition of energization of said safety valve.
3. A combination as defined in claim 1, wherein said passage is arranged to convey fuel from said high-pressure chamber to said low-pressure chamber and wherein said valve member is moved to open position in response to said change in the condition of energization of said safety valve.
4. A combination as defined in claim 1, wherein said regulating circuit connecting said speed counter means with said valve comprises amplifier means having an input circuit including a portion of said speed counter means and an output circuit arranged to effect changes in energization of said safety valve means in dependency on the condition of said input circuit.
5. A combination as defined in claim 4, wherein said output circuit includes a relay having a switch in circuit with said safety valve means.
6. A combination as defined in claim 5, wherein at least one of said input and output circuits includes a safety fuse arranged to open the respective circuit when the speed of said rotary member reaches said predetermined valve.
7. A combination as defined in claim 6, wherein said fuse is an electronic fuse.
8. A combination as defined in claim 6, wherein each of said input and output circuits includes at least one fuse.
9. A combination as defined in claim 1, further comprising starter means actuatable to start the engine and means for effecting a change in the condition of energization of said valve means in response to actuation of said starter means.
1. In an internal combustion engine, a combination comprising a fuel injection pump having a high-pressure fuel chamber, a low-pressure fuel chamber, and a passage connecting said chambers; a rotary member arranged to rotate at a variable speed which is proportional to the operating speed of the engine; electromagnet safety valve means including a valve member installed in said pump and movable between open and closed positions in which it respectively permits and prevents the flow of fuel through said passage, said valve member being arranged to assume one of said positions in response to energization and the other of said positions in response to deenergization of said valve means; electrical speed counter means comprising a serrated ferromagnetic element driven by said rotary member, a yoke having at least one serrated portion adjacent to said ferromagnetic element, a first and a second inductance on said yoke; a regulating circuit connecting said first inductance to said safety valve means to effect a change in the condition of energization of said safety valve means when the speed of said rotary member reaches a predetermined value; an electric control circuit connected to said second inductance; and means connected to said electronic control circuit for regulating supply of fuel by said injection pump to said engine in dependence on the speed of said rotary member.
2. A combination as defined in claim 1, wherein said passage is arranged to supply fuel from said low-pressure chamber to said high-pressure chamber and wherein said valve member is moved to closed position in response to said change in the condition of energization of said safety valve.
3. A combination as defined in claim 1, wherein said passage is arranged to convey fuel from said high-pressure chamber to said low-pressure chamber and wherein said valve member is moved to open position in response to said change in the condition of energization of said safety valve.
4. A combination as defined in claim 1, wherein said regulating circuit connecting said speed counter means with said valve comprises amplifier means having an input circuit including a portion of said speed counter means and an output circuit arranged to effect changes in energization of said safety valve means in dependency on the condition of said input circuit.
5. A combination as defined in claim 4, wherein said output circuit includes a relay having a switch in circuit with said safety valve means.
6. A combination as defined in claim 5, wherein at least one of said input and output circuits includes a safety fuse arranged to open the respective circuit when the speed of said rotary member reaches said predetermined valve.
7. A combination as defined in claim 6, wherein said fuse is an electronic fuse.
8. A combination as defined in claim 6, wherein each of said input and output circuits includes at least one fuse.
9. A combination as defined in claim 1, further comprising starter means actuatable to start the engine and means for effecting a change in the condition of energization of said valve means in response to actuation of said starter means.
Description:
BACKGROUND OF THE INVENTION
The present invention relates to internal combustion engines in general, and more particularly to improvements in safety devices which limit the rotational speed of internal combustion engines, especially of electronically controlled diesel engines. Still more particularly, the invention relates to improvements in safety devices for internal combustion engines with fuel injection.
It is well known that a diesel engine cannot be operated at speeds which exceed a certain value. Such value is determined by the structural characteristics of a particular engine. If the engine operates at a maximum permissible speed and its cylinders continue to receive fuel, the speed can increase beyond the permissible value but with the attendant danger of substantial damage. The likelihood of overspeeding is less pronounced in gasoline driven engines where the speed is limited by flow resistance of fuel supplying passages.
At the present time, diesel engines are normally equipped with centrifugal governors which control the flow of fuel to the fuel injection pump. The rate of fuel flow is reduced whenever the centrifugal governor detects a certain operating speed which should not be exceeded. Such centrifugal governors are rather bulky and expensive. Also, they are not ideally suited for use in internal combustion engines, particularly diesel engines, whose operation is regulated by an electronic control circuit.
SUMMARY OF THE INVENTION
An object of the invention is to provide an internal combustion engine, particularly an electronically controlled diesel engine, with a novel and improved safety device which limits the speed of the engine and is just as reliable as but more compact than a conventional centrifugal governor.
A further object of the invention is to provide a versatile safety device which can be used in many types of internal combustion engines.
An additional object of the invention is to provide a safety device which is constructed and assembled in such a way that it can prevent overspeeding of the engine even if one or more of its components happen to be defective.
An ancillary object of the invention is to provide a safety device which can be combined with or incorporated into the fuel injection pump of a diesel engine.
The invention is embodied in an internal combustion engine, particularly in an electronically controlled diesel engine, which comprises a fuel injection pump having a high-pressure fuel chamber, a low-pressure fuel chamber and a passage connecting the two chambers, a rotary member arranged to rotate at a variable speed which is proportional to (and may be identical with) the operating speed of the engine, electromagnetic safety valve means including a valve member installed in the fuel injection pump and movable between open and closed positions in which it respectively permits and prevents the flow of fuel though the passage, the valve member assuming one of its positions in response to energization and the other position in response to deenergization of the valve means, and electrical speed counter means operatively associated with the rotary member and arranged to effect a change in the condition of energization of the valve means when the speed of the rotary member reaches a predetermined maximum value.
The valve member is moved to closed position in response to deenergization of the valve means if it is installed in a passage which supplies fuel from the low-pressure chamber, and such deenergization takes place in response to a signal furnished by the speed counter means when the speed of the rotary member reaches the predetermined value.
If the valve member is installed in a passage which conveys fuel from the high-pressure chamber to the low-pressure chamber, it is caused to open in response to deenergization of the valve means, and such deenergization again takes place when the speed counter means produces a signal which is indicative of the predetermined maximum permissible speed of the rotary member.
The operative connection between the speed counter means and the winding of the valve means preferably includes an electrical or electronic regulating circuit having an amplifier whose input circuit contains an inductance of the speed changer means and a first safety fuse and whose output circuit preferably contains a second safety fuse and a relay whose switch is in circuit with the winding of the valve means.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved safety device itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary partly diagrammatic and partly sectional view of a diesel engine which embodies one form of the improved safety device; and
FIG. 2 is a similar view of a diesel engine which embodies a modified safety device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a portion of a fuel injection pump which may be of the type disclosed in the copending application, Ser. No. 12,409 filed Feb. 18, 1970 by Eheim et al. and assigned to the same assignee. The pump includes a pump piston 13 which is reciprocable and rotatable in a pump housing 51 by the rotary output shaft 50 of a diesel engine and serves to supply measured quantities of fuel to several fuel lines 33 (only one shown). The fuel metering unit which determines the beginning and the end of the interval of fuel injection into each fuel line 33 comprises a collar 10 which is movable axially of the piston 13, a rotary electromagnet 11, and an electronic control circuit 12a which supplies to the electromagnet 11 signals by way of an electrical connection 12, such signals serving to determine the extent of energization of the electromagnet 11 and hence the axial position of the collar 10. The manner in which the pump piston 13 is rotated and moved axially in response to rotation of the rotary member 50 is fully disclosed in the aforementioned application of Eheim et al. The housing 51 of the fuel injection pump defines a high-pressure fuel chamber 14 which is connected with a low-pressure fuel chamber 114 by a fuel supplying passage 24 controlled by the pump piston 13 and by a novel electromagnetic safety valve 20. The shaft 50 carries a toothed gear-shaped element 34 of ferromagnetic material which cooperates with a yoke 15 having two serrated or toothed arms or extensions which are adjacent to the teeth of the element 34. The yoke 15 carries two inductance coils 16 and 17. The coil 16 serves to transmit to the control circuit 12a signals (by way of the connection 18) which are indicative of rotational speed of the shaft 50. Such signals influence the energization of the electromagnet 11. The coil 17 supplies similar signals to an electronic regulating circuit 19 which controls the safety valve 20. The parts 34, 15 and 17 constitute a speed counter which effects closing of the safety valve 20 when the rotational speed of the shaft 50 reaches a predetermined maximum permissible value.
The valve 20 comprises a ferromagnetic core 21 which is biased by a spring 22 and carries at one end a valve member 23. When the spring 22 is free to expand, the valve member 23 engages a seat 24a in the fuel-supplying passage 24 to prevent the flow of fuel from the lower pressure chamber 114 to the higher pressure chamber 14. The interior of the safety valve 20 is connected with the low-pressure chamber 114 by bores 25 which compensate for differences in pressure and insure that the core 21 can move axially in response to energization or deenergization of the winding 20a.
The regulating circuit 19 includes an electronic amplifier 26 whose input is connected with the inductance 17 on the yoke 15. A first safety fuse 27 is installed in the input circuit of the amplifier 26 and a second safety fuse 29 is installed in its output circuit which further includes a relay 28 having a relay switch 30 in the circuit of the winding 20a. The latter circuit further includes a separate energy source 31. The relay switch 30 is connected in parallel with a normally open auxiliary switch 32; the switch 32 closes for a short interval of time in response to actuation of the starter 52. Each fuel line 33 delivers pressurized fuel to a separate fuel injection nozzle (not shown).
The operation:
When the engine is idle, i.e., when the shaft 50 is at a standstill, the amplifier 26 does not receive signals from the inductance 17 and the relay 28 is deenergized. Thus, the relay switch 30 is open and the winding 20a of the safety valve 20 is deenergized so that the spring 22 maintains the valve member 23 in engagement with the seat 24a and prevents entry of fuel into the high-pressure chamber 14. If the driver wishes to start the engine, the starter 52 is actuated and closes the auxiliary switch 32 to complete the circuit of the winding 20a which moves the core 21 against the opposition of the spring 22 so that the chamber 14 communicates with the chamber 114 by way of the passage 24. The auxiliary switch 32 opens automatically when the starter 52 is inactive but the engine is on and its shaft 50 rotates the element 34 of the speed counter to induce in the inductance 17 a voltage which causes the amplifier 26 to energize the relay 28 and to thus close the switch 30. The circuit of the winding 20a is completed and the valve member 23 is held in open position even though the auxiliary switch 32 is open. The shaft 50 effects axial and angular movements of the pump piston 13 which delivers to fuel lines 33 metered quantities of fuel from the high-pressure chamber 14. The quantities of such fuel are determined by the collar 10 whose axial position is a function of rotational speed of the shaft 50 (see the inductance coil 16) and also a function of certain other factors which influence the output signal from the control circuit 12a to the electromagnet 11. Such additional factors include the position of the gas pedal, the atmospheric pressure, and/or others.
The amplifier 26 is designed in such a way that it offers an accurately determined constant input resistance which remains unchanged during prolonged operation of the diesel engine. The strength of the current flowing in the input circuit of the amplifier 26 is proportional to voltage in the inductance 17, i.e., to rotational speed of the shaft 50. When the speed of the shaft 50 exceeds a permissible maximum value, the safety fuse 27 responds and opens the input circuit to deenergize the relay 28 in the output circuit of the amplifier 26. The relay switch 30 opens and the winding 20a is deenergized to permit closing of the valve member 23 under the action of the spring 22 so that the flow of fuel from the chamber 114 to the chamber 14 is interrupted in response to an increase in rotational speed of the shaft 50 beyond the permissible value.
The second safety fuse 29 constitutes an optional feature of the regulating circuit 19. This fuse is provided to effect deenergization of the relay 28 and opening of the switch 30 in the event of failure of one or more electronic or other components of the amplifier 26. For example, if a transistor in the amplifier 26 is damaged or destroyed, the output circuit of this amplifier might continue to furnish a high voltage signal subsequent to opening of the input circuit by the safety fuse 27. The fuse 29 is designed to open the output circuit and to deenergize the relay 28 in response to the flow of a current which is indicative of the maximum permissible rotational speed of the shaft 50. Thus, the winding 20a can be deenergized by the fuse 27 or by the fuse 29.
It will be noted that the regulating circuit 19 serves the sole purpose of establishing an operative connection between the speed counter 15, 17, 34 and the safety valve 20. The inductance 17 constitutes a discrete galvanically separated output element of the speed counter; this insures that the functioning of the improved safety device is independent of adverse influences on the control circuit 12a or other parts of the engine.
FIG. 2 illustrates a portion of a second fuel injection pump wherein the safety valve 20' is installed in a fuel returning passage 42 which can deliver fuel from the high-pressure chamber 14 to the low-pressure chamber 114. The body 40 of the safety valve 20' is immediately adjacent to the chamber 14 and is provided with ducts 41 which can establish a connection for the flow of fuel from the chamber 14 to the passage 42 when the winding 20a' is deenergized in response to opening of the switch 30. The valve member 23' of the core 21' is of conical shape and its conical surface is biased away from a seat in the valve body 40 by the spring 22' as soon as the circuit of the winding 20a' opens, i.e., whenever the switch 30 is opened while the auxiliary switch 32 is open.
When the engine is idle, the switches 30, 32 are open, the winding 20a' is deenergized and the spring 22' maintains the valve member 23' in open position. Thus, the passage 42 between the chambers 114, 14 is open and fuel cannot be forced into the fuel lines 33. When the winding 20a' is energized in response to closing of the switch 30 or 32 in a manner as described in connection with FIG. 1, the core 21' is moved axially against the opposition of the spring 22' and the valve member 23' moves to closed or sealing position to prevent the flow of fuel from the chamber 14 to the chamber 114. Thus, the pressure in chamber 14 can be built up sufficiently to equal that pressure which is necessary to effect admission of fuel into the cylinders of the engine. The rising pressure in the chamber 14 acts on the valve member 23' and assists the winding 20a' in maintaining the safety valve 20' in sealing position.
When the circuit of the winding 20a' is opened on deenergization of the realy 28, the spring 22' is free to return the valve member 23' to open position so that the pressure in the chamber 14 drops below that which is necessary for admission of fuel into the cylinders. The valve member 23' can move to sealing position (under the action of spring 22') not later than in response to the first suction stroke of piston 13 following the opening of switch 30. During such suction stroke of the piston 13, the pressure in the chamber 14 drops sufficiently to permit opening of the valve member 23' under the bias of the spring 22'.
At least one of the safety fuses 27, 29 may be an electronic fuse which is responsive to a predetermined voltage or intensity of current and which opens when the current intensity or voltage in the corresponding (input or output) circuit of the amplifier 26 exceeds a predetermined value corresponding to the maximum permissible rotational speed of the shaft 50. Also, at least one of these fuses can be designed to complete the circuit as soon as the voltage or current strength drops below that which is indicative of excessive rotational speed of the shaft 50. In its simplest form, the fuse 27 and/or 29 may include a fusible conductor which melts when the strength of the current in the corresponding circuit rises beyond a permissible value.
It was found that the improved safety device (including the speed counter 15, 17, 34, the regulating circuit 19 and the safety valve 20 or 20') is at least as reliable as conventional centrifugal governors which are used in many presently known diesel engines. It was also found that the expenditures involved in the provision and mounting of such safety device in an engine whose operation is regulated by an electronic control circuit are warranted and reasonable, partly because the amplifier 26 can receive current from the source which supplies current to the control circuit 12a and also because at least some components (such as the inductance 17) can be mounted on parts (yoke 15) which are necessary for proper operation of the control circuit. The overall cost of the components of the safety device is considerably less than that of a conventional centrifugal governor. Furthermore, the improved safety device is so versatile that it can be used in nearly all types of electronically controlled diesel engines. The amplifier 26 and the fuses 27, 29 can be readily designed to respond to a predetermined maximum speed of the engine. Still another advantage of the improved safety device is that the fuel injection pump can deliver fuel to the fuel lines 33 only at a time when the energy source 31 is in circuit with the winding 20a or 20a' of the safety valve 20 or 20'. Thus, eventual damage to or malfunction of that part of the regulating circuit 19 which includes the amplifier 26 merely results in closing of the safety valve (FIG. 1) or opening of such valve (FIG. 2) to prevent delivery of fuel to the fuel lines 33.
Each circuit of the amplifier 26 can include two or more fuses.
A circuit, which works as a electronic fuse, is disclosed in the Publication from Siemens, Schaltungen mit Halbleiterbauelementen, Band 2, 1965, page 163. An amplifier, capable of being used in the circuit 19 FIG. 1 or FIG. 2 is disclosed in the same publication on page 117.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.
The present invention relates to internal combustion engines in general, and more particularly to improvements in safety devices which limit the rotational speed of internal combustion engines, especially of electronically controlled diesel engines. Still more particularly, the invention relates to improvements in safety devices for internal combustion engines with fuel injection.
It is well known that a diesel engine cannot be operated at speeds which exceed a certain value. Such value is determined by the structural characteristics of a particular engine. If the engine operates at a maximum permissible speed and its cylinders continue to receive fuel, the speed can increase beyond the permissible value but with the attendant danger of substantial damage. The likelihood of overspeeding is less pronounced in gasoline driven engines where the speed is limited by flow resistance of fuel supplying passages.
At the present time, diesel engines are normally equipped with centrifugal governors which control the flow of fuel to the fuel injection pump. The rate of fuel flow is reduced whenever the centrifugal governor detects a certain operating speed which should not be exceeded. Such centrifugal governors are rather bulky and expensive. Also, they are not ideally suited for use in internal combustion engines, particularly diesel engines, whose operation is regulated by an electronic control circuit.
SUMMARY OF THE INVENTION
An object of the invention is to provide an internal combustion engine, particularly an electronically controlled diesel engine, with a novel and improved safety device which limits the speed of the engine and is just as reliable as but more compact than a conventional centrifugal governor.
A further object of the invention is to provide a versatile safety device which can be used in many types of internal combustion engines.
An additional object of the invention is to provide a safety device which is constructed and assembled in such a way that it can prevent overspeeding of the engine even if one or more of its components happen to be defective.
An ancillary object of the invention is to provide a safety device which can be combined with or incorporated into the fuel injection pump of a diesel engine.
The invention is embodied in an internal combustion engine, particularly in an electronically controlled diesel engine, which comprises a fuel injection pump having a high-pressure fuel chamber, a low-pressure fuel chamber and a passage connecting the two chambers, a rotary member arranged to rotate at a variable speed which is proportional to (and may be identical with) the operating speed of the engine, electromagnetic safety valve means including a valve member installed in the fuel injection pump and movable between open and closed positions in which it respectively permits and prevents the flow of fuel though the passage, the valve member assuming one of its positions in response to energization and the other position in response to deenergization of the valve means, and electrical speed counter means operatively associated with the rotary member and arranged to effect a change in the condition of energization of the valve means when the speed of the rotary member reaches a predetermined maximum value.
The valve member is moved to closed position in response to deenergization of the valve means if it is installed in a passage which supplies fuel from the low-pressure chamber, and such deenergization takes place in response to a signal furnished by the speed counter means when the speed of the rotary member reaches the predetermined value.
If the valve member is installed in a passage which conveys fuel from the high-pressure chamber to the low-pressure chamber, it is caused to open in response to deenergization of the valve means, and such deenergization again takes place when the speed counter means produces a signal which is indicative of the predetermined maximum permissible speed of the rotary member.
The operative connection between the speed counter means and the winding of the valve means preferably includes an electrical or electronic regulating circuit having an amplifier whose input circuit contains an inductance of the speed changer means and a first safety fuse and whose output circuit preferably contains a second safety fuse and a relay whose switch is in circuit with the winding of the valve means.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved safety device itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary partly diagrammatic and partly sectional view of a diesel engine which embodies one form of the improved safety device; and
FIG. 2 is a similar view of a diesel engine which embodies a modified safety device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a portion of a fuel injection pump which may be of the type disclosed in the copending application, Ser. No. 12,409 filed Feb. 18, 1970 by Eheim et al. and assigned to the same assignee. The pump includes a pump piston 13 which is reciprocable and rotatable in a pump housing 51 by the rotary output shaft 50 of a diesel engine and serves to supply measured quantities of fuel to several fuel lines 33 (only one shown). The fuel metering unit which determines the beginning and the end of the interval of fuel injection into each fuel line 33 comprises a collar 10 which is movable axially of the piston 13, a rotary electromagnet 11, and an electronic control circuit 12a which supplies to the electromagnet 11 signals by way of an electrical connection 12, such signals serving to determine the extent of energization of the electromagnet 11 and hence the axial position of the collar 10. The manner in which the pump piston 13 is rotated and moved axially in response to rotation of the rotary member 50 is fully disclosed in the aforementioned application of Eheim et al. The housing 51 of the fuel injection pump defines a high-pressure fuel chamber 14 which is connected with a low-pressure fuel chamber 114 by a fuel supplying passage 24 controlled by the pump piston 13 and by a novel electromagnetic safety valve 20. The shaft 50 carries a toothed gear-shaped element 34 of ferromagnetic material which cooperates with a yoke 15 having two serrated or toothed arms or extensions which are adjacent to the teeth of the element 34. The yoke 15 carries two inductance coils 16 and 17. The coil 16 serves to transmit to the control circuit 12a signals (by way of the connection 18) which are indicative of rotational speed of the shaft 50. Such signals influence the energization of the electromagnet 11. The coil 17 supplies similar signals to an electronic regulating circuit 19 which controls the safety valve 20. The parts 34, 15 and 17 constitute a speed counter which effects closing of the safety valve 20 when the rotational speed of the shaft 50 reaches a predetermined maximum permissible value.
The valve 20 comprises a ferromagnetic core 21 which is biased by a spring 22 and carries at one end a valve member 23. When the spring 22 is free to expand, the valve member 23 engages a seat 24a in the fuel-supplying passage 24 to prevent the flow of fuel from the lower pressure chamber 114 to the higher pressure chamber 14. The interior of the safety valve 20 is connected with the low-pressure chamber 114 by bores 25 which compensate for differences in pressure and insure that the core 21 can move axially in response to energization or deenergization of the winding 20a.
The regulating circuit 19 includes an electronic amplifier 26 whose input is connected with the inductance 17 on the yoke 15. A first safety fuse 27 is installed in the input circuit of the amplifier 26 and a second safety fuse 29 is installed in its output circuit which further includes a relay 28 having a relay switch 30 in the circuit of the winding 20a. The latter circuit further includes a separate energy source 31. The relay switch 30 is connected in parallel with a normally open auxiliary switch 32; the switch 32 closes for a short interval of time in response to actuation of the starter 52. Each fuel line 33 delivers pressurized fuel to a separate fuel injection nozzle (not shown).
The operation:
When the engine is idle, i.e., when the shaft 50 is at a standstill, the amplifier 26 does not receive signals from the inductance 17 and the relay 28 is deenergized. Thus, the relay switch 30 is open and the winding 20a of the safety valve 20 is deenergized so that the spring 22 maintains the valve member 23 in engagement with the seat 24a and prevents entry of fuel into the high-pressure chamber 14. If the driver wishes to start the engine, the starter 52 is actuated and closes the auxiliary switch 32 to complete the circuit of the winding 20a which moves the core 21 against the opposition of the spring 22 so that the chamber 14 communicates with the chamber 114 by way of the passage 24. The auxiliary switch 32 opens automatically when the starter 52 is inactive but the engine is on and its shaft 50 rotates the element 34 of the speed counter to induce in the inductance 17 a voltage which causes the amplifier 26 to energize the relay 28 and to thus close the switch 30. The circuit of the winding 20a is completed and the valve member 23 is held in open position even though the auxiliary switch 32 is open. The shaft 50 effects axial and angular movements of the pump piston 13 which delivers to fuel lines 33 metered quantities of fuel from the high-pressure chamber 14. The quantities of such fuel are determined by the collar 10 whose axial position is a function of rotational speed of the shaft 50 (see the inductance coil 16) and also a function of certain other factors which influence the output signal from the control circuit 12a to the electromagnet 11. Such additional factors include the position of the gas pedal, the atmospheric pressure, and/or others.
The amplifier 26 is designed in such a way that it offers an accurately determined constant input resistance which remains unchanged during prolonged operation of the diesel engine. The strength of the current flowing in the input circuit of the amplifier 26 is proportional to voltage in the inductance 17, i.e., to rotational speed of the shaft 50. When the speed of the shaft 50 exceeds a permissible maximum value, the safety fuse 27 responds and opens the input circuit to deenergize the relay 28 in the output circuit of the amplifier 26. The relay switch 30 opens and the winding 20a is deenergized to permit closing of the valve member 23 under the action of the spring 22 so that the flow of fuel from the chamber 114 to the chamber 14 is interrupted in response to an increase in rotational speed of the shaft 50 beyond the permissible value.
The second safety fuse 29 constitutes an optional feature of the regulating circuit 19. This fuse is provided to effect deenergization of the relay 28 and opening of the switch 30 in the event of failure of one or more electronic or other components of the amplifier 26. For example, if a transistor in the amplifier 26 is damaged or destroyed, the output circuit of this amplifier might continue to furnish a high voltage signal subsequent to opening of the input circuit by the safety fuse 27. The fuse 29 is designed to open the output circuit and to deenergize the relay 28 in response to the flow of a current which is indicative of the maximum permissible rotational speed of the shaft 50. Thus, the winding 20a can be deenergized by the fuse 27 or by the fuse 29.
It will be noted that the regulating circuit 19 serves the sole purpose of establishing an operative connection between the speed counter 15, 17, 34 and the safety valve 20. The inductance 17 constitutes a discrete galvanically separated output element of the speed counter; this insures that the functioning of the improved safety device is independent of adverse influences on the control circuit 12a or other parts of the engine.
FIG. 2 illustrates a portion of a second fuel injection pump wherein the safety valve 20' is installed in a fuel returning passage 42 which can deliver fuel from the high-pressure chamber 14 to the low-pressure chamber 114. The body 40 of the safety valve 20' is immediately adjacent to the chamber 14 and is provided with ducts 41 which can establish a connection for the flow of fuel from the chamber 14 to the passage 42 when the winding 20a' is deenergized in response to opening of the switch 30. The valve member 23' of the core 21' is of conical shape and its conical surface is biased away from a seat in the valve body 40 by the spring 22' as soon as the circuit of the winding 20a' opens, i.e., whenever the switch 30 is opened while the auxiliary switch 32 is open.
When the engine is idle, the switches 30, 32 are open, the winding 20a' is deenergized and the spring 22' maintains the valve member 23' in open position. Thus, the passage 42 between the chambers 114, 14 is open and fuel cannot be forced into the fuel lines 33. When the winding 20a' is energized in response to closing of the switch 30 or 32 in a manner as described in connection with FIG. 1, the core 21' is moved axially against the opposition of the spring 22' and the valve member 23' moves to closed or sealing position to prevent the flow of fuel from the chamber 14 to the chamber 114. Thus, the pressure in chamber 14 can be built up sufficiently to equal that pressure which is necessary to effect admission of fuel into the cylinders of the engine. The rising pressure in the chamber 14 acts on the valve member 23' and assists the winding 20a' in maintaining the safety valve 20' in sealing position.
When the circuit of the winding 20a' is opened on deenergization of the realy 28, the spring 22' is free to return the valve member 23' to open position so that the pressure in the chamber 14 drops below that which is necessary for admission of fuel into the cylinders. The valve member 23' can move to sealing position (under the action of spring 22') not later than in response to the first suction stroke of piston 13 following the opening of switch 30. During such suction stroke of the piston 13, the pressure in the chamber 14 drops sufficiently to permit opening of the valve member 23' under the bias of the spring 22'.
At least one of the safety fuses 27, 29 may be an electronic fuse which is responsive to a predetermined voltage or intensity of current and which opens when the current intensity or voltage in the corresponding (input or output) circuit of the amplifier 26 exceeds a predetermined value corresponding to the maximum permissible rotational speed of the shaft 50. Also, at least one of these fuses can be designed to complete the circuit as soon as the voltage or current strength drops below that which is indicative of excessive rotational speed of the shaft 50. In its simplest form, the fuse 27 and/or 29 may include a fusible conductor which melts when the strength of the current in the corresponding circuit rises beyond a permissible value.
It was found that the improved safety device (including the speed counter 15, 17, 34, the regulating circuit 19 and the safety valve 20 or 20') is at least as reliable as conventional centrifugal governors which are used in many presently known diesel engines. It was also found that the expenditures involved in the provision and mounting of such safety device in an engine whose operation is regulated by an electronic control circuit are warranted and reasonable, partly because the amplifier 26 can receive current from the source which supplies current to the control circuit 12a and also because at least some components (such as the inductance 17) can be mounted on parts (yoke 15) which are necessary for proper operation of the control circuit. The overall cost of the components of the safety device is considerably less than that of a conventional centrifugal governor. Furthermore, the improved safety device is so versatile that it can be used in nearly all types of electronically controlled diesel engines. The amplifier 26 and the fuses 27, 29 can be readily designed to respond to a predetermined maximum speed of the engine. Still another advantage of the improved safety device is that the fuel injection pump can deliver fuel to the fuel lines 33 only at a time when the energy source 31 is in circuit with the winding 20a or 20a' of the safety valve 20 or 20'. Thus, eventual damage to or malfunction of that part of the regulating circuit 19 which includes the amplifier 26 merely results in closing of the safety valve (FIG. 1) or opening of such valve (FIG. 2) to prevent delivery of fuel to the fuel lines 33.
Each circuit of the amplifier 26 can include two or more fuses.
A circuit, which works as a electronic fuse, is disclosed in the Publication from Siemens, Schaltungen mit Halbleiterbauelementen, Band 2, 1965, page 163. An amplifier, capable of being used in the circuit 19 FIG. 1 or FIG. 2 is disclosed in the same publication on page 117.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.