JP2955339B2 - Diesel engine fuel injection system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine, and more particularly, to a structure for changing a fuel discharge amount.

[Prior Art] A fuel injection device used for a diesel engine includes a plunger type fuel injection pump for pressurizing an appropriate amount of fuel,
A fuel injection valve for injecting the pressurized fuel into the combustion chamber of the engine is provided.

In the fuel injection pump, a plunger driven by power transmission from an engine is slidably accommodated in a cylinder of a pump housing in an axial direction, and a fuel is provided between a tip of the plunger and a terminal of the cylinder. A pump chamber for sucking and compressing is formed. A fuel injection passage for guiding pressurized fuel to the fuel injection valve is connected to a discharge port of the pump chamber.

By the way, in this type of fuel injection device, conventionally, for the purpose of equalizing the fuel pressure supplied to the fuel injection valve or performing the fuel injection even when the fuel injection pump is in the suction stroke, the fuel injection passage is There is known a device provided with a large-capacity pressure storage chamber for storing pressurized fuel on the way.

In addition, a mechanism for controlling the fuel injection amount in accordance with the operating condition of the engine is added to this accumulator type fuel injection device. This conventional control mechanism includes a fuel release passage connected to the fuel injection passage or the accumulator, and a fuel release valve provided in the fuel release passage. By opening and closing the fuel release valve, a pump is provided. A system is used in which a part of the fuel pressurized in the chamber is released.

[Problems to be Solved by the Invention] However, according to this conventional configuration, the plunger of the fuel injection pump compresses all of the fuel sucked into the pump chamber even in an operation region where the required fuel injection amount is small. Therefore, when the plunger reaches the compression stroke, the resistance to push back the plunger increases.

For this reason, there is a problem that the torque required for driving the plunger increases, and the loss horsepower of the engine increases.

The present invention has been made in view of such circumstances, and in the region where the required injection amount is small, the driving torque of the plunger can be reduced by directly escaping the fuel in the pump chamber, and the loss of the driving force of the engine can be reduced. Can be reduced,
It is an object of the present invention to provide a fuel injection device for a diesel engine that can supply a necessary amount of fuel to continue operating the fuel injection valve even if the fuel release passage is kept open due to a failure of the fuel release valve. .

[Means for Solving the Problems] In order to achieve the above object, a fuel injection device for a diesel engine according to the present invention according to claim 1 includes a plunger driven by power transmission from an engine in a pump housing in an axial direction. A fuel injection pump accommodating slidably and having a pump chamber formed between the tip of the plunger and the pump housing; an intake passage for guiding fuel to the pump chamber of the fuel injection pump; A fuel passage connected to the pump chamber of the injection pump and guiding the fuel pressurized by the plunger to the fuel injection valve; controlling the pressure of the fuel supplied to the fuel injection valve to an optimum value according to the engine operating condition Control means for performing the operation.

A fuel release passage is connected to the pump chamber and located within a stroke range of the plunger. The fuel release passage has a release opening that is opened and closed by the plunger, and the release opening is compressed by the plunger. At a position deviated from the maximum stroke position in the direction of the plunger in the suction direction, and a fuel release valve that is closed at least when the engine is started is provided in the fuel release passage, and the fuel release valve moves in the compression direction of the plunger. The stroke is controlled so that the plunger starts to be opened before closing the escape port, and the opening timing is delayed as the required fuel injection amount increases.

In order to achieve the above object, a fuel injection device for a diesel engine according to the present invention according to claim 2 includes a pump housing in which a plunger driven by power transmission from the engine is slidably accommodated in an axial direction. A fuel injection pump having a pump chamber formed between the tip of the plunger and the pump housing; a suction passage for leading fuel to the pump chamber of the fuel injection pump; A fuel passage for guiding the fuel pressurized by the plunger to a fuel injection valve; control means for controlling the pressure of the fuel supplied to the fuel injection valve to an optimum value according to an engine operating condition; Is provided.

A fuel release passage is connected to the pump chamber and located within a stroke range of the plunger. The fuel release passage has a release opening that is opened and closed by the plunger, and the release opening is compressed by the plunger. At a position deviated from the maximum stroke position in the direction of the plunger in the suction direction, and a fuel release valve for opening and closing the fuel release passage is provided in the fuel release passage. The fuel release valve has a required fuel injection amount. Is fully opened in an operation range where the fuel injection amount is small, and is controlled so as to reduce the fully closed or open degree in an operation range where the required fuel injection amount is large.

[Operation] According to the configuration of claim 1, a part of the fuel sucked into the pump chamber is at least part of the fuel sucked into the pump chamber until the plunger shifted to the compression stroke closes the relief opening of the fuel release passage except at the time of starting the engine. Inside, it flows out of the pump chamber through the fuel release passage from the release port. Therefore, the fuel sucked into the pump chamber is released from the pump chamber at a low pressure before being compressed by the plunger.

Therefore, in the operation region where the required fuel injection amount is small, the amount of fuel compressed by the plunger is substantially reduced, and the driving torque of the plunger can be reduced accordingly.

In addition, even if the fuel release valve fails and the fuel release passage is left open, the opening position of the release port with respect to the pump chamber is larger than the maximum compression position of the plunger in the suction direction of the plunger. , The plunger can pressurize the fuel in the pump chamber by a stroke corresponding to the displacement. Therefore, the fuel can be continuously supplied to the fuel injection valve, and the operation of the engine can be continued.

According to the configuration of the second aspect, the escape port is open during the period until the plunger that has shifted to the compression stroke reaches the relief port of the fuel release path, so that the pump chamber and the fuel release path communicate with each other. It is kept in. At this time, in an operation region where the required injection amount is large, such as when the engine is started or during a high-load / high-speed operation, the fuel relief valve is controlled in a direction to fully close or reduce the opening degree. During the period up to the outlet, even if the outlet is opened, the outflow of fuel from the pump chamber is stopped or restricted. Therefore, the amount of fuel actually pressurized in the pump chamber increases, and the amount of fuel discharged from the pump chamber increases.

On the other hand, in an operation region where the required injection amount is small, such as during low-load / low-speed operation, the fuel relief valve is fully opened. It flows out of the pump chamber through the fuel outlet passage from the outlet. Therefore, the fuel sucked into the pump chamber is released from the pump chamber at a low pressure before being compressed by the plunger.

Therefore, in the operation region where the required fuel injection amount is small, the amount of fuel compressed by the plunger is substantially reduced, and the driving torque of the plunger can be reduced accordingly.

Further, even if the fuel release valve fails and the fuel release passage remains open, the opening position of the release port with respect to the pump chamber is shifted in the suction direction of the plunger from the maximum compression position of the plunger. Therefore, the plunger can pressurize the fuel in the pump chamber by a stroke corresponding to the displacement. Therefore, the fuel can be continuously supplied to the fuel injection valve, and the operation of the engine can be continued.

[Embodiment] A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 and FIG. 6 show a fuel injection device 1, which has a casing 2. A drive shaft 3 is supported in the casing 2,
The drive shaft 3 is a crankshaft 5 of a diesel engine 4.
Is driven to rotate. The drive shaft 3 drives the rotary feed pump 6 in the casing 2 to rotate.
The feed pump 6 sucks the fuel in the fuel tank 7 and then supplies the fuel to the low-pressure fuel chamber 8 in the casing 2.

A cam plate 10 is connected to one end of the drive shaft 3 via a coupling 9. On one end surface of the cam plate 10, a plurality of face cams corresponding to the number of cylinders of the engine 4 are provided.
The face cam 11 has a plurality of rollers.
It touches 12. The roller 12 is a ring-shaped roller holder
It is supported by the casing 2 via 13.

Therefore, when the drive shaft 3 rotates, the cam plate 10
Face cam 11 comes in contact with the roller 12 sequentially,
The cam plate 10 is reciprocated in the axial direction of the drive shaft 3 by a number corresponding to the number of cylinders of the engine 4 during one rotation.

A pump housing 14 is connected to the casing 2. The pump housing 14 faces the cam plate 10, and a plunger-type fuel injection pump 15 is provided in the pump housing 14.

The fuel injection pump 15 includes a cylinder 16 that opens into the low-pressure fuel chamber 8. A plunger 17 is slidably mounted in the cylinder 16 in the axial direction. One end of the plunger 17 is coaxially connected to the cam plate 10, and the plunger 17 reciprocates in the axial direction while rotating integrally with the cam plate 10.

A pump chamber 18 is formed between the plunger 17 and the end of the cylinder 16. A suction passage 19 connected to the low-pressure fuel chamber 8 is opened on the peripheral surface of the pump chamber 18. Inhalation passage
The opening end of the pump chamber 18 into the pump chamber 18 is
When the fuel is extracted from the pump 16, it communicates with the pump chamber 18, and the fuel in the low-pressure fuel chamber 8 is removed by this communication.
It is sucked into the pump chamber 18 via the check valve 19a.

A recess 20 is formed on a side surface of the pump housing 14. The recess 20 is covered by a chamber case 21 bolted to the pump housing 14, and a large-capacity pressure accumulating chamber 22 is formed between the chamber case 21 and the recess 20. The pressure accumulating chamber 22 is provided integrally with the pump housing 14 in a state adjacent to the pump chamber 18. At the end of the pump chamber 18, a discharge port 23 for pressurized fuel is provided.
Are formed. This discharge port 23 is
An opening is formed in the pressure accumulating chamber 22 in the interior.

Therefore, when the plunger 17 is pushed into the cylinder 16, the fuel sucked into the pump chamber 18 is pressurized, discharged from the discharge port 23 to the pressure accumulating chamber 22, and stored in the pressure accumulating chamber 22. I have.

A discharge valve that allows only the flow of fuel from the pump chamber 18 to the pressure accumulating chamber 22 is provided at a communication portion between the discharge port 23 and the pressure accumulating chamber 22.
24 are provided. The delivery valve 24 includes a cylindrical valve body 26 that holds a valve body 25. Valve body 26
Protrudes into the accumulator chamber 22, and this valve body 26
An opening 27 that guides the pressurized fuel to the pressure accumulating chamber 22 is formed at the protruding tip end.

Between the pump housing 14 and the chamber case 21,
The fuel filter 30 is sandwiched. Fuel filter 30
Is the upstream chamber into which fuel from the pump chamber 18 flows
22a and a downstream chamber 22b on the chamber case 21 side. Further, a fuel distribution pipe 31 that supplies the fuel in the downstream chamber 22b to the fuel injection valve 32 is connected to the chamber case 21.

Therefore, in the case of the present embodiment, a fuel passage 33 that guides the pressurized fuel to the fuel injection valve 32 is formed by a system path from the pump chamber 18 to the fuel distribution pipe 31, and is formed in the middle of the fuel passage 33. The pressure accumulating chamber 22 is located at the center.

The fuel injection valve 32 is described in, for example,
No. 48, the valve body
This is an accumulator type having a fuel accumulator chamber opened and closed by an electromagnetic valve in 32a. The fuel injection valve 32 is controlled by a computer at a predetermined timing with a solenoid valve.
The fuel is injected, and the fuel injection period is defined within a substantially constant crank angle range over the entire rotation range including idling.

On the other hand, a concave portion 35 is formed on the upper surface of the pump housing 14. A variable pressure device 36 is attached to the recess 35. The pressure varying device 36 has a housing 37 fitted into the recess 35. A first cylinder 38 is formed at the center of the housing 37,
38 is opened in the upper surface of the housing 37. And
The housing 37 is a cylindrical nut screwed into the recess 35
39 prevents the pump housing 14 from falling off. The first cylinder 38 is connected to a pressure accumulating chamber via a bottom surface of the housing 37 and an introduction passage 40 formed in the pump housing 14.
The first cylinder 38 is connected to the upstream chamber 22a of the first cylinder 38.
Inside, a part of the fuel pressurized by the plunger 17 is introduced.

On the upper surface of the pump housing 14, a piston case 42 is attached. In the piston case 42, the housing 37 covers and hides the nut 39. Inside the piston case 42, a second cylinder 43 that opens to the lower surface of the piston case 42 is formed. Second cylinder 43
Are arranged coaxially with the first cylinder 38, and are formed to be much larger in diameter than the first cylinder 38. A piston 44 is fitted in the second cylinder 38 so as to be slidable in the axial direction. A small-diameter portion 45 is provided coaxially at the center of the lower surface of the piston 44. Small diameter part
45 is fitted in the first cylinder 38 so as to be slidable in the axial direction, and between the tip of the small diameter portion 45 and the bottom surface of the first cylinder 38, a lower portion where the introduction passage 40 is opened. A pressure chamber 46 is formed.

On the upper surface of the piston 44, a concave portion 47 having a size substantially over the entire surface is provided.
Are formed. An upper pressurizing chamber 48 having a larger capacity than the lower pressurizing chamber 46 is formed between the concave portion 47 and the upper end surface of the second cylinder 43. On the bottom of the recess 47, a small diameter part
A vertical passage 49 extending into 45 is formed. This vertical passage 49
Communicates with a communication port 50 opened at the end face of the small-diameter portion 45. The lower pressurizing chamber 46 and the upper pressurizing chamber 48 communicate with each other through the vertical passage 49 and the communication port 50. The lower pressurizing chamber 46 is provided with a ball valve 51 that allows only the flow of fuel from the accumulator 22 to the upper pressurizing chamber 48.

Therefore, part of the fuel in the accumulator 22 is
The piston 44 facing the upper pressurizing chamber 48 has a larger diameter than the small diameter portion 45 facing the lower pressurizing chamber 46, and the fuel receiving pressure area is increased. Since the force is large, the force pressing the piston 44 downward is larger than the force pressing the piston 44 upward. For this reason, the piston 44 presses the ball valve 51 through the small-diameter portion 45 against the opening of the introduction path 40, and interrupts the communication between the pressure accumulating chamber 22 and the lower pressurizing chamber 46.

As shown in FIG. 5, on the side of the piston case 42,
A pressure sensor 55 is attached. The pressure sensor 55 is
The upper pressurizing chamber 48 through the pressure introducing passage 56 of the piston case 42
The fuel pressure in the upper pressurizing chamber 48 is detected.

A mounting recess 57 is formed on the upper surface of the piston case 42. On the bottom surface of the mounting recess 57, a fuel escape hole 58 connected to the upper pressurizing chamber 48 is formed. A holder 59 is fitted into the mounting recess 57 and is fixed by a nut 60 to prevent the holder 59 from coming off. The holder 59 has a cylindrical shape whose upper surface is closed. As shown in FIG. 7, the holder 59 accommodates an electromagnetic on-off valve 61 as control means.

The on-off valve 61 opens and closes the fuel escape hole 58,
This is for changing the pressure of the fuel supplied to the fuel injection valve 32 according to the engine operating condition.
A base 62 is located within 57. On the base 62,
A valve hole 63 connected to the fuel escape hole 58 is formed. A ball-shaped valve body 64 that opens and closes the valve hole 63 is provided at an open end of the valve hole 63 into the holder 59.

An electromagnet 65 serving as a drive unit of the on-off valve 61 is accommodated in the holder 59. The electromagnet 65 is composed of a core 66, a coil 67 wound around the outer periphery of the core 66, and a yoke 68 covering the periphery of the coil 67 and the core 66.
It is located above 62. The lower end of the yoke 68 is screwed into the outer periphery of the base 62, and the yoke 68 and the holder
A gap 69 for fuel distribution is formed between the gap 59 and the gap 59.

In a space 70 between the core 66 and the base 62, an armature 71 for opening and closing the valve body 64 is arranged. The armature 71 includes a guide shaft 72 that penetrates the center of the core 66, and the distal end of the guide shaft 72 is pressed downward by a linear spring member 73. By this pressing, the armature 71 presses the valve body 64 against the opening edge of the valve hole 63, and the valve hole 63 is closed.

Further, the yoke 68 has a communication port 74 for communicating the space 70 with the gap 69. The communication port 74 is connected to the fuel return port 75 at the upper part of the holder 59 via the gap 69. The fuel return port 75 is connected to the fuel tank 7 via a fuel return pipe 76.

Therefore, in the case of the present embodiment, a part of the fuel pressurized by the plunger 17 is reduced by various holes, passages, gaps, and the like from the introduction path 40 connected to the pressure accumulation chamber 22 to the fuel return port 75 of the holder 59. A fuel return passage 77 for returning to the fuel tank 7 is formed.

By the way, the fuel injection device 1 having such a configuration changes the fuel pressure supplied to the fuel injection valve 32 by exciting the electromagnet 65 of the on-off valve 61, and changes the actual fuel injection amount to the engine operating condition. It is controlled according to.

That is, when the electromagnet 65 is excited, the armature 71
Is pressed, the pressing of the valve body 64 is released, and this valve body 64 is released.
64 is separated from the valve hole 63 by receiving the pressure of the fuel in the valve hole 63. Then, the valve hole 63 is opened, and the fuel in the upper pressurizing chamber 48 flows out to the fuel return pipe 76.

For this reason, the force pressing the piston 44 downward disappears, and the piston 44 rises by receiving the fuel pressure applied to the small diameter portion 45. Due to the rise of the piston 44, the ball valve 51 also receives the fuel pressure in the introduction path 40 and separates from the open end of the introduction path 40. After that, it flows out to the upper pressurizing chamber 48.

Therefore, the fuel pressure in the pressure accumulating chamber 22 is reduced by the amount of the fuel flowing out, so that the fuel pressure supplied to the fuel injection valve 32 is also reduced. In this case, the force for attracting the armature 71 changes depending on the magnitude of the voltage applied to the electromagnet 65.
The force for sucking 71 is increased, and the valve body 64 is largely separated from the valve hole 63, so that the amount of fuel flowing out increases. On the other hand, when the voltage applied to the electromagnet 65 is low, the force for attracting the armature 71 becomes weak, and conversely, the opening degree of the valve hole 63 becomes small, and the amount of fuel flowing out decreases. From this, the electromagnet 65
Depends on the magnitude of the voltage applied to the fuel cell, the amount of fuel flowing out and, consequently, the fuel pressure supplied to the fuel injection valve 32 change.

On the other hand, when the excitation of the electromagnet 65 is released, the armature 71
Is pressed downward by the spring member 73, and the valve body 64 is
So that the pressure in the upper pressurizing chamber 48 rises and the piston
44 is pressed downward again. Due to this pressing, the communication between the lower pressurizing chamber 46 and the pressure accumulating chamber 22 is interrupted, the outflow of fuel from the pressure accumulating chamber 22 is stopped, and the fuel pressure supplied to the fuel injection valve 32 increases.

The voltage applied to the electromagnet 65 is controlled by a signal output from the microcomputer 80 during the operation of the engine.

That is, during the operation of the engine, as the data indicating the operation state of the engine, an engine load corresponding to the engine speed and the accelerator opening and a signal indicating the fuel pressure from the pressure sensor 55 are input to the microcomputer 80. . Then, the microcomputer 80 determines an engine operating condition based on these signals, and determines a voltage to be applied to the electromagnet 65.

When determining this voltage, the microcomputer
Reference numeral 80 designates an electromagnet 65 that is optimal for the engine operating condition at that time based on the engine speed and the engine load.
A map for deriving the applied voltage is stored in advance.

FIG. 8 shows an example of a map for deriving the voltage applied to the electromagnet 65, and FIG. 9 shows a map for deriving an optimum fuel pressure for the engine operating condition at that time based on the engine speed and the engine load. An example is shown.

As can be seen from the map, the reference voltage V ₂ is 0.47
(V) varies within the range of to 4.8 (V), the reference voltage V ₂
The fuel pressure supplied to the fuel injection valve 32 is defined to change within the range of 83.5 (kg / cm ² ) to 300 (kg / cm ² ) in accordance with the change in the pressure.

Here, the processing contents performed by the microcomputer 80 will be described with reference to FIG.

First, to convert the fuel pressure fed from the microcomputer 80, the pressure sensor 55 into a voltage V _1. At the same time, the microcomputer 80, based on the actual engine speed and the engine load detected, the voltage to be applied to the electromagnet 65 from the above map, that is, searches the reference voltage V _2, the reference voltage V comparing the voltages V ₁ showing the ₂ and the actual fuel pressure.

This comparison, actual detection voltages V ₁ is determined to exceeds the reference voltage V _2, the microcomputer 80,
A drive pulse for exciting this is sent to the electromagnet 65.

That is, FIG. 11 shows a relation between the fuel pressure in the movement and the upper pressure chamber 48 of the plunger 17 (accumulator 22), a pressure signal sent from the pressure sensor 55, proportional to the voltages V ₁ In a relationship. Here, in FIG. 11 (a) shows the relationship between the motion and the voltage V ₁ of the plunger 17 when not controlling the fuel pressure in Fig. 11 (b), the plunger in the case of controlling the fuel pressure 17 shows the relationship between the movement of _No. 17 and the voltage V1.

As shown in this FIG. 11 (b), voltages V ₁ showing a fuel pressure in the upper pressurizing chamber 48 is above the optimal reference voltage V ₂ to the driving conditions at that time, the drive pulses from the microcomputer 80 Then, the electromagnet 65 is excited. This electromagnet 65
As a result, the open / close valve 61 is opened, the fuel in the pressure accumulating chamber 22 and the upper pressurizing chamber 48 is released to the fuel return pipe 76, and the fuel pressure in the pressure accumulating chamber 22 and the upper pressurizing chamber 48 decreases. Therefore, the voltage V ₁
And the fuel pressure supplied to the fuel injection valve 32 also decreases.

The outflow of the fuel, the voltages V ₁ falls below the reference voltage V _2, the energization of the electromagnet 65 is stopped, the excitation of the electromagnet 65 is canceled. Then, the on-off valve 61 is closed, and the outflow of fuel from the pressure accumulating chamber 22 and the upper pressurizing chamber 48 is stopped, so that the fuel pressure in the pressure accumulating chamber 22 and the upper pressurizing chamber 48 increases again.
Therefore, the the voltages V ₁ rises, the fuel pressure supplied to the fuel injection valve 32 is increased.

By increasing the voltages V _1, when the voltage V ₁ is higher than the reference voltage V _2, the output drive pulse to the electromagnet 65 again, since on-off valve 65, so that the voltages V ₁ matches the reference voltage V ₂ The opening and closing operations are repeated.

Therefore, the fuel pressure actually supplied to the fuel injection valve 32 is controlled so as to match a fuel pressure optimal for a predetermined engine operating condition.

On the other hand, the pump housing 14 is formed with a fuel release passage 85 that opens on the peripheral surface of the pump chamber 18. The opening of the fuel release passage 85 to the pump chamber 18, that is, the release port 86, is located within the stroke range S of the plunger 17, as shown in FIG. Moreover, this escape port 86 is
On the other hand, a position shifted in the suction direction of the plunger 17 from the maximum stroke position of the plunger 17 in the compression direction of the plunger 17, in the case of the present embodiment, only half the stroke amount S / 2 of the plunger 17 in the suction direction of the plunger 17 It is opened at the position shifted to.

The fuel release passage 85 is connected to the fuel return pipe 76. An electromagnetic fuel release valve 87 that opens and closes the fuel release passage 85 is provided in the fuel release passage 85. The fuel relief valve 87 is configured to be closed when the diesel engine 4 is started and when the engine 4 reaches a rotational speed at which the maximum torque is generated. The fuel relief valve 87 opens and closes the fuel release passage 85. The timing of the operation is controlled by the microcomputer 80.

That is, for example, in an operating condition in which the engine 4 is in a low load / low speed range including idling, the fuel pressure supplied to the fuel injection valve 32 is low, as is apparent from FIG. The number of times the opening / closing valve 61 of the variable device 36 operates per unit time increases. Therefore, the third
As shown in the figure, the microcomputer 80 detects the number of times of operation of the on-off valve 61 and, based on the number of times of operation,
Is in an operating range in which the fuel relief valve 87 is opened.

Here, the microcomputer 80 stores in advance a map for determining whether or not the engine 4 is in an operation region in which the fuel release valve 87 is opened based on the number of times of operation of the on-off valve 61. When the microcomputer 80 determines that the engine 4 is in the operating range in which the fuel release valve 87 is opened,
The opening timing of the fuel relief valve 87 corresponding to the operating condition of the engine 4 at that time is read from the built-in operation frequency-opening timing map, and a signal for realizing this is sent to the driving unit of the fuel relief valve 87.

Therefore, as shown in FIG. 4, in the region where the fuel pressure supplied to the fuel injection valve 32 is low, the timing A at which the fuel release valve 87 starts to open with respect to the stroke of the plunger 17 in the compression direction is earlier. . Then, even while the plunger 17 is stroked in the compression direction, this plunger
During the period t until the 17 closes the release port 86, the fuel sucked into the pump chamber 18 flows out of the release port 86 through the fuel release passage 85, so that the discharge amount of the fuel does not change, and the plunger 17 does not change.
The actual amount of fuel discharged per stroke is reduced.

Similarly, in a region where the fuel pressure supplied to the fuel injection valve 32 is high, such as a high load / high rotation region, the timing A at which the fuel relief valve 87 starts to open is delayed, so that the period t during which the fuel discharge amount does not change And the actual fuel discharge amount per stroke of the plunger 17 increases.

In a region where the required fuel injection amount is large, such as when the diesel engine 4 is started or when the engine 4 is operating at a rotation speed at which the engine 4 generates the maximum torque, the fuel relief valve 87 is fully closed. Therefore, as shown by B in FIG. 4, all of the fuel sucked into the pump chamber 18 is compressed, and the amount of discharged fuel is maximized.

According to such a first embodiment of the present invention, the fuel injection valve
In the operating region where the fuel pressure supplied to the fuel chamber 32 is low and the required fuel injection amount is small, a part of the fuel sucked into the pump chamber 18 flows out to the fuel tank 7 through the fuel release passage 85. The fuel in the chamber 18 is released from the pump chamber 18 at a low pressure before being compressed.

Then, since the substantial amount of fuel compressed by the plunger 17 decreases, the force for pushing back the plunger 17 decreases accordingly. Therefore, the driving torque of the plunger 17 can be reduced, and the loss of the driving force (loss horsepower) of the diesel engine 4 can be reduced.

In addition, the release port 86 of the fuel release passage 85 is displaced in the pump chamber 18 in the suction direction of the plunger 17 by a half S / 2 of the stroke amount of the plunger 17 from the maximum stroke position in the compression direction of the plunger 17. 4, the fuel release valve 87 fails and the fuel release passage 85 remains open, but as shown in FIG. The fuel can be compressed in the stroke.

Therefore, even if the fuel relief valve 87 fails, the fuel injection pump 15 can supply the fuel with a discharge amount Q that is half the maximum discharge amount to the fuel injection valve 32, and the diesel engine 4
Can be maintained.

The present invention is not limited to the first embodiment, and FIGS. 12 and 13 show a second embodiment of the present invention.

The second embodiment differs from the second embodiment in that the opening and closing timing of the fuel relief valve 87 is controlled based on the engine speed and the engine load.

That is, the microcomputer 4 includes the engine 4
As the data indicating the operation status of the vehicle, a signal indicating the engine load corresponding to the engine speed and the accelerator opening is input. At this time, the microcomputer 80 stores in advance a map for guiding the opening timing of the fuel relief valve 87 corresponding to the operating condition at that time based on the engine speed and the engine load.

FIG. 13 shows an example of a map for deriving the opening timing of the fuel relief valve 87 from the engine speed and the engine load. As can be seen from this map, during low-load and low-speed operation including idling, the microcomputer
80 sends a signal to fully open the fuel relief valve 87 to the drive unit of the fuel relief valve 87, and changes the opening degree of the fuel relief valve 87 according to the engine speed or the like during medium load / medium rotation operation. Send a signal.

Further, at the time of starting the diesel engine 4 in which the required injection amount is large, and at the time of high load / high rotation operation including the operation at the rotation speed at which the engine 4 generates the maximum torque, the signal to close the fuel relief valve 87 fully. Is sent to the drive unit of the fuel relief valve 87.

Therefore, when the data indicating the engine speed or the like is input, the microcomputer 80 reads the opening timing of the fuel relief valve 87 from the map, and outputs a signal for realizing the timing to drive the fuel relief valve 87. To the department.

According to the second embodiment, until the plunger 17 that has shifted to the compression stroke reaches the relief port 86, the relief port 86
Is open, the pump chamber 18 and the fuel release passage 85 are kept in communication with each other.

At this time, in an operation region where the required injection amount is large, such as at the time of engine start or high load / high rotation operation, the fuel relief valve 87 is controlled to be fully closed, and at the time of medium load / medium rotation operation. In the transition region, the fuel relief valve 87 is controlled in a direction to reduce the opening degree from the time of full opening, so even if the relief port 86 is opened as described above, the outflow of fuel from the pump chamber 18 is stopped or Limited.

Therefore, the amount of fuel actually pressurized in the pump chamber 18 increases, and the amount of fuel discharged from the pump chamber 18 increases.

On the other hand, in an operation region where the required injection amount is small, such as during low-load / low-speed operation, the fuel relief valve 87 is fully opened, so that the plunger 17 closes the relief port 86 of the fuel relief passage 85 during the period. Then, the fuel flows out of the pump chamber 18 from the release port 86 through the fuel release passage 85.

Therefore, part of the fuel sucked into the pump chamber 18 is
Pump chamber during low pressure before being compressed by plunger 17
As a result, the same effect as in the first embodiment can be obtained.

In the second embodiment, the fuel relief valve 87 is fully closed during a high-load / high-speed operation including an operation at a speed at which the engine 4 generates the maximum torque. However, the present invention is not limited to this, and the opening degree of the fuel release valve 87 may be reduced so that the fuel in the pump chamber 18 flows out slightly.

Further, in the above embodiment, the on-off valve, the variable pressure device operated by the on-off valve, and the fuel relief valve are integrated into the pump housing of the fuel injection device.
The present invention is not limited to this, and the on-off valve, the variable pressure device and the fuel relief valve may be provided separately from the pump housing.

[Effects of the Invention] According to the present invention described in detail above, in the operation region where the required fuel injection amount is small, the fuel in the pump chamber is directly discharged from the pump chamber during the low pressure before the plunger reaches the end of the compression stroke. Because of the escape, a substantial amount of fuel is compressed by the plunger. Therefore, the driving torque of the plunger can be reduced, and the loss of the driving force of the engine can be reduced.

At the same time, even if the fuel relief valve fails and the fuel relief passage remains open, the plunger can pressurize the fuel at the end of its compression stroke. Therefore, fuel can be continuously supplied to the fuel injection valve,
There is an advantage that the operation of the diesel engine can be continued.

[Brief description of the drawings]

1 to 11 show a first embodiment of the present invention. FIG. 1 is a sectional view of the entire fuel injection device, and FIG. 2 shows a positional relationship between a plunger of a fuel injection pump and a fuel escape passage. FIG. 3 is a flowchart showing the processing contents of the microcomputer when driving the fuel relief valve. FIG. 4 is a characteristic diagram showing the relationship between the stroke amount of the plunger and the fuel discharge amount. FIG. 1 is a cross-sectional view taken along the line VV in FIG. 1, FIG. 6 is a configuration diagram schematically showing a fuel injection device, FIG. FIG. 9 is a diagram for explaining an applied voltage of an electromagnet that is optimal for an engine operating condition at that time on the basis of the engine speed and the engine load. FIG. Optimal fuel pressure FIG. 10 is a flow chart showing the processing contents of the microcomputer when driving the on-off valve. FIG. 11 is a diagram showing the relationship between the reference voltage and the detection voltage, and the driving pulse output from the microcomputer. FIGS. 12 and 13 show a second embodiment of the present invention. FIG. 12 is a flowchart showing the processing contents of a microcomputer when driving a fuel relief valve. The figure is a diagram for explaining the opening timing of the fuel relief valve corresponding to the operating condition at that time based on the engine load and the engine speed. 4 ... Diesel engine, 14 ... Pump housing,
15 ... fuel injection pump, 17 ... plunger, 18 ... pump chamber, 19 ... suction passage, 32 ... fuel injection valve, 33 ... fuel passage, 61 ... control means (open / close valve), 85 ... Fuel spill passage, 86… Escape port, 87… Fuel spill valve.

Continuation of the front page (56) References JP-A-50-127016 (JP, A) JP-A-3-23361 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 59 / 20 F02M 59/34 F02M 59/36 F02M 59/04 F02M 57/02 310 F02M 57/02 320

Claims (2)

(57) [Claims] 1. A fuel comprising a plunger driven by power transmission from an engine in a pump housing slidably in an axial direction, and a pump chamber formed between the tip of the plunger and the pump housing. An injection pump; a suction passage for guiding fuel to a pump chamber of the fuel injection pump; and a fuel passage connected to the pump chamber of the fuel injection pump and guiding fuel pressurized by the plunger to a fuel injection valve; Control means for controlling the pressure of the fuel supplied to the fuel injection valve to an optimum value according to the engine operating condition;
A fuel release passage connected to the pump chamber within a stroke range of the plunger, the fuel release passage having a relief opening and closing by the plunger, and connecting the relief opening to the plunger. At a position shifted in the direction of suction of the plunger from the maximum stroke position in the compression direction of the plunger, and a fuel release valve which is closed at least when the engine is started is provided in the fuel release passage. The fuel for a diesel engine is controlled such that, with respect to the stroke in the direction, the plunger starts opening before closing the release port, and the opening start timing is delayed as the required fuel injection amount increases. Injection device. 2. A fuel comprising a plunger driven by power transmission from an engine in a pump housing slidably in an axial direction, and a pump chamber formed between the tip of the plunger and the pump housing. An injection pump; a suction passage for guiding fuel to a pump chamber of the fuel injection pump; and a fuel passage connected to the pump chamber of the fuel injection pump and guiding fuel pressurized by the plunger to a fuel injection valve; Control means for controlling the pressure of the fuel supplied to the fuel injection valve to an optimum value according to the engine operating condition;
A fuel release passage connected to the pump chamber within a stroke range of the plunger, the fuel release passage having a relief opening and closing by the plunger, and connecting the relief opening to the plunger. And a fuel release valve for opening and closing the fuel release passage is provided in the fuel release passage, and the fuel release valve is provided with a fuel demand valve. A fuel injection device for a diesel engine, wherein the fuel injection device is fully opened in an operation region where the injection amount is small and is controlled to be fully closed or the opening degree is reduced in an operation region where the required fuel injection amount is large.