JPH051608A - Fuel injection device of diesel engine - Google Patents

Abstract

(57) [Abstract] [Object] The present invention provides a method for accurately adjusting the fuel pressure supplied to a fuel injection valve in accordance with the operating condition of an engine when keeping a fuel injection period within a constant crank angle range. It is also an object of the present invention to provide a diesel engine fuel injection device that can be reliably controlled. A fuel return passage is connected to a fuel passage connecting a fuel injection pump and a fuel injection valve, and the fuel return passage is connected to the fuel return passage.
There is provided an opening / closing valve that opens / closes the portion of the fuel to change the pressure of the fuel supplied to the fuel injection valve. The arithmetic processing unit that controls the drive unit of this on-off valve stores the fuel pressure that is optimum for the operating condition at that time as a reference value based on the data that indicates the operating condition of the engine. It is characterized in that the fuel pressure introduced is detected and the on-off valve is opened / closed so that the detected value approaches the reference value.

Description

Detailed Description of the Invention

[0001]

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 the fuel pressure supplied to the fuel injection valve according to the operating condition of the engine.

[0002]

2. Description of the Related Art A fuel injection device used in a diesel engine includes a fuel injection pump for pressurizing an appropriate amount of fuel and a fuel injection valve for injecting the pressurized fuel into a combustion chamber of the engine.

In the diesel engine, the output is controlled by adjusting the amount of fuel injected into the combustion chamber.
The required injection amount of fuel is set to increase as the engine load and engine speed increase. In this case, if the fuel injection amount is adjusted by changing the fuel injection period (crank angle), the concentration of harmful components in the exhaust gas, especially nitrogen oxides (NO _x ), tends to increase, which is disadvantageous in terms of exhaust gas countermeasures. The problem arises that

For this reason, a diesel engine having a wide range of normal rotation speed, such as a diesel engine for a vehicle, is used.
In a Zel engine, it is desirable to change the fuel injection amount without changing the fuel injection period (crank angle) even if the engine speed changes.

Therefore, in order to meet this demand, the present applicant changes the fuel pressure supplied to the fuel injection valve by releasing a part of the fuel pressurized by the fuel injection pump to change the fuel pressure. Attempts are being made to control the actual injection amount according to the operating conditions of the engine.

[0006]

However, since the engine speed fluctuates momentarily during engine operation, it is necessary to accurately control the fuel pressure supplied to the fuel injection valve in accordance with the engine speed. A new device was needed separately, and there was still room for improvement in this respect.

The present invention has been made under such circumstances, and in keeping the fuel injection period within the range of a constant crank angle, the fuel pressure supplied to the fuel injection valve is controlled by the operating condition of the engine. It is an object of the present invention to provide a fuel injection device for a diesel engine that can be accurately and reliably controlled according to the above.

[0008]

Therefore, in the present invention, a fuel passage connecting the fuel injection pump and the fuel injection valve, and a fuel return passage connected in the middle of the fuel passage,
An on-off valve provided in the fuel return passage for opening and closing the fuel return passage to escape a part of the fuel in the fuel passage to change the fuel pressure supplied to the fuel injection valve; A control means for controlling the drive part of the on-off valve, the control means preliminarily sets a fuel pressure optimum for the operating condition at that time as reference data based on data indicating the operating condition of the engine. It is memorized, during operation of the engine, the fuel pressure introduced to the fuel injection valve is detected,
The on-off valve is opened / closed so that the detected data approaches the reference data.

[0009]

According to this structure, when the actual fuel pressure supplied to the fuel injection valve deviates from the reference data during engine operation, the on-off valve causes the fuel pressure in the fuel passage to approach the reference data. Repeat the opening and closing operations. Therefore, as a measure for exhaust gas, even when the fuel injection period is kept within a certain crank angle range, the fuel pressure supplied to the fuel injection valve is
It is possible to accurately and surely control the reference data as a target.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
It will be explained based on 5.

1 to 3 show a fuel injection device 1, which is equipped with a casing 2. A drive shaft 3 is supported in the casing 2, and the drive shaft 3 is rotationally driven by a crank shaft 5 of a diesel engine 4. The drive shaft 3 rotationally drives a rotary feed pump 6 in the casing 2. The feed pump 6 sucks up 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. A plurality of face cams 11 corresponding to the number of cylinders of the engine 4 are formed on one end surface of the cam plate 10.
1 is in contact with a plurality of rollers 12. Roller 12 is
It is supported by the casing 2 via a ring-shaped roller holder 13. Therefore, when the drive shaft 3 rotates, the face cam 11 of the cam plate 10 sequentially contacts the roller 12, so that the cam plate 10 corresponds to the number of cylinders of the engine 4 during one rotation. It is reciprocated in the axial direction of the drive shaft 3 by a number.

A plunger housing 14 is connected to the casing 2. The plunger housing 14 is
A plunger type fuel injection pump 15 is provided in the plunger housing 14 so as to face the cam plate 10.
Is built in. The fuel injection pump 15 includes a cylinder 16 that opens into the low pressure fuel chamber 8. Cylinder 1
A plunger 17 is mounted in the shaft 6 so as to be slidable in the axial direction. One end of the plunger 17 has a cam plate 10
The plunger 17 is reciprocally moved 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. Pump room 18
A suction passage 19 communicating with the low-pressure fuel chamber 8 is opened on the peripheral surface of the. The opening end of the suction passage 19 to the pump chamber 18 is configured to communicate with the pump chamber 18 when the plunger 17 is pulled out from the cylinder 16, and this communication allows the fuel in the low-pressure fuel chamber 8 to flow. Inhaled to 18.

A concave portion 20 is formed on the side surface of the plunger housing 14. The recess 20 is covered with a chamber case 21 that is bolted to the plunger housing 14, and the chamber case 21 is covered with the recess 20.
A large-capacity pressure accumulating chamber 22 is formed between and. Accumulation chamber 2
2 is connected to the discharge port 23 at the end of the pump chamber 18. Therefore, when the plunger 17 is pushed into the cylinder 16, the fuel sucked into the pump chamber 18 is pressurized and discharged from the discharge port 23 to the pressure accumulating chamber 22.

A delivery valve 24 is provided in the communicating portion between the discharge port 23 and the pressure accumulating chamber 22 to allow only the flow of fuel from the pump chamber 18 toward the pressure accumulating chamber 22. Delivery valve 24
Includes a tubular valve body 26 that holds the valve body 25. The valve body 26 projects into the recess 20. An opening 27 is formed at the protruding tip of the valve body 26 to guide the pressurized fuel to the pressure accumulating chamber 22.

Plunger housing 14 and chamber case
The fuel filter 30 is sandwiched between the space 21 and the space 21. The fuel filter 30 includes an upstream chamber 22 a into which fuel from the pump chamber 18 flows in the pressure accumulating chamber 22, and a chamber case 2.
It is partitioned into the downstream chamber 22b on the first side. A fuel injection valve 32 is connected to the chamber case 21 via a fuel distribution pipe 31. Therefore, in the case of the present embodiment, the fuel passage 29 for guiding the pressurized fuel to the fuel injection valve 32 is constituted by the system passage from the pump chamber 18 to the fuel distribution pipe 31. Next, this fuel injection valve 32
Will be described in detail with reference to FIGS. 9 and 10.

The fuel injection valve 32 has a cylindrical valve body 33 which is screwed into the cylinder head of the engine 4. At the tip of the valve body 33, the nozzle body 34
Is screwed in, and a nozzle port 35 for injecting fuel is opened in the nozzle body 34. An electromagnetic valve housing box 36 is fitted into the base end opening of the valve body 33, and is fixed by a cap 37 so as not to come off. A disc-shaped partition member 38 that vertically partitions the interior of the valve body 33 is sandwiched between the tip of the electromagnetic valve housing box 36 and the inner surface of the valve body 33. A cylinder portion 39 that opens toward the nozzle body 34 is formed in the center of the partition member 38. A needle 40 that opens and closes the nozzle port 35 is supported between the cylinder portion 39 and the nozzle body 34.

The needle 40 has a pair of guide portions 42a and 42b slidably fitted and held by the cylinder portion 39 and the nozzle body 34. These guide portions 42 are provided.
A flange-shaped locking portion 43 is formed between a and 42b.

As shown in FIG. 11A, the needle 4
The tip portion of 0 forms a seal portion 44 which is inclined in a tapered shape. A nozzle port 35 is provided at the tip of the seal portion 44.
A convex portion 45 that enters the inside is formed. The outer diameter R ₁ of the convex portion 45 is set to be slightly smaller than the inner diameter R _{2 of the} nozzle opening 35, and a gap S _{1 of} several μ is formed between the convex portion 45 and the nozzle opening 35. It has become so.
A small diameter portion 46 for guiding the fuel injection direction is coaxially provided at the tip of the convex portion 45.

A taper-shaped valve seat surface 47 is formed at the opening of the nozzle port 35 to the nozzle body 34 so that the seal portion 44 can removably contact it. This valve seat surface 4
When the seal portion 44 of the needle 40 comes into contact with 7, the nozzle port 35 is closed.

A large-capacity fuel pressure accumulating chamber 50 is formed inside the valve body 33. Fuel storage chamber 50
Is located between the nozzle body 34 and the partition member 38,
The needle 40 penetrates the inside of the fuel pressure accumulating chamber 50.
The fuel pressure accumulating chamber 50 includes a nozzle body 34 and a needle 40.
It is connected to the nozzle port 35 through a gap between and.

Inside the valve body 33, a first electromagnet 51 is arranged between the partition member 38 and the fuel pressure accumulating chamber 50. The first electromagnet 51 includes a cylindrical core 52, a coil 53 wound around the outer periphery of the core 52, the coil 53, and the core 5
2 and a yoke 54 screwed onto the outer periphery of the same. The yoke 54 is provided with a flange portion 55 at one end, and the first electromagnet 51 is positioned by sandwiching the flange portion 55 between the partition member 38 and the inner surface of the valve body 33. .. A through hole 56 through which the needle 40 penetrates is formed in the core 52, and the locking portion 43 of the needle 40 is located inside the through hole 56. On the inner surface of the through hole 56 and the outer periphery of the needle 40 protruding from the through hole 56, spring supports 57a,
57b is attached. These spring supports 57a,
A compression coil spring 58 is interposed between 57b in a compressed state, and the compression coil spring 58 constantly presses the needle 40 in a direction of closing the nozzle port 35.

A ring-shaped armature 60 is arranged between the core 52 of the first electromagnet 51 and the partition member 38. At the center of the armature 60, a cylindrical stopper 61 through which the needle 40 passes is attached. The stopper 61 is fitted and held in the through hole 56 of the core 52 so as to be slidable in the axial direction, and the tip thereof is a knee.
It is close to the locking portion 43 of the dollar 40.

A fuel supply passage 65 is formed in the electromagnetic valve housing box 36 and the partition member 38. The upstream end of the fuel supply passage 65 is connected to the fuel distribution pipe 31, and the downstream end thereof includes the partition member 38 and the first electromagnet 5.
It is connected to the space 66 between 1 and 1. This space 66 is
The gap between the stopper 61 and the needle 40 and the core 5
It is connected to the fuel pressure accumulating chamber 50 through the second through hole 56.

As shown enlarged in FIG. 10, the needle 4
A small-capacity pressure chamber 68 is formed between the upper guide portion 42a of 0 and the end of the cylinder portion 39. The cross-sectional area of the pressure chamber 68 along the radial direction of the needle 40 is equal to the pressure accumulation chamber 5
It is formed much smaller than the cross-sectional area of 0. A fuel introduction path 69 opening to the space 66 is formed inside the guide portion 42a. The fuel introduction path 69 is connected to the pressure chamber 68 via an orifice hole 70 that opens at the tip surface of the guide portion 42a.

Therefore, the fuel pressurized by the fuel injection device 1 is supplied not only to the fuel pressure accumulating chamber 50 but also to the pressure chamber 68. At this time, since the guide portion 42a of the needle 40 facing the pressure chamber 68 has a larger diameter than the portion of the needle 40 penetrating the fuel pressure accumulating chamber 50, the needle 40 has a large diameter.
, A force is applied to press this toward the nozzle port 35 side. As a result, the needle 40 is compressed by the compression coil spring 58.
The seal portion 44 is constantly pressed against the valve seat surface 47 by being pressed in the direction of closing the nozzle port 35 together with the urging force of the valve.

The central portion of the partition member 38 is inserted into the electromagnetic valve housing box 36. As shown in FIG. 10, on the upper surface of the central portion of the partition member 38, a pressure release hole 72 for communicating the pressure chamber 68 with the space 71 inside the electromagnetic valve housing box 36.
Are formed. A second electromagnet 75 for opening and closing the pressure relief hole 72 is housed in the space 71. The second electromagnet 75 is composed of a core 76, a coil 77 and a yoke 78, like the first electromagnet 51, and the lower end of the yoke 78 is screwed into the partition member 38. The yoke 78 has a support wall 79 interposed between the partition member 38 and the core 76. A guide hole 80 that is coaxial with the cylinder portion 39 is formed in the support wall 79, and a plunger-shaped armature 81 is fitted in the guide hole 80 so as to be slidable in the axial direction. A
The upper surface of the armature 81 is close to the lower surface of the core 76, and the cross-sectional area along the radial direction of the armature 81 has a flat plate-shaped armature 60 operated by the first electromagnet 51.
Is formed smaller than the cross-sectional area of. Then, the lower surface of the armature 81 is in contact with the upper surface of the partition member 38 so that the armature 81 can come into contact with and separate from the upper surface of the partition member 38 to open and close the pressure relief hole 72.
Is provided.

The armature 81 is provided at the center of the core 76.
Is formed in the upper surface of the armature 81 and the spring receiver 84 provided at the upper end of the through hole 83 and the upper surface of the armature 81 in the direction in which the pressure relief hole 72 is always closed. A compression coil spring 85 for urging is interposed. The pressure relief hole 72 is communicated with the upper portion of the space 71 via a communication hole 86 provided in the armature 81 and the support wall 79 and a discharge hole 87 provided in the spring receiver 84.
The upper portion of this space 71 is connected to a fuel return port 88 on the upper surface of the solenoid valve housing box 36, and this fuel return port 88 is connected to the fuel tank 7 via a fuel return pipe 89.
By the way, in the fuel injection valve 32, the opening / closing control of the nozzle port 35 is performed by exciting the two electromagnets 51 and 75 incorporated in the valve body 33.

That is, when the first electromagnet 51 is excited, the armature 60 is attracted to the core 52, so that the stopper 61 moves toward the nozzle port 35, and the tip of the stopper 61 is a needle. It approaches the locking portion 43 of 40. When the second electromagnet 75 is excited in this state, the armature 81 is attracted to the core 76, the protrusion 82 thereof is separated from the upper surface of the partition member 38, and the pressure relief hole 72 is opened.
Then, the high-pressure fuel in the pressure chamber 68 is discharged to the space 71 in the electromagnetic valve housing box 36, so that part of the force pressing the needle 40 in the closing direction is lost. Therefore, the needle 4
0 lifts in the direction in which the seal portion 44 is separated from the valve seat surface 47 of the nozzle port 35.

At this time, since the stopper 61 of the armature 60 is approaching the locking portion 43 of the needle 40 by the excitation of the first electromagnet 51, the lift of the needle 40 is locked by the locking portion 43. Is abutted against the stopper 61, and the lift amount LH of the needle 40 is reduced as shown in FIG. As a result, the gap S ₁ between the valve seat surface 47 of the nozzle opening 35 and the small diameter portion 46 of the needle 40 is kept narrow, and the fuel injected from this nozzle opening 35 is throttled.

On the other hand, when the excitation of the first electromagnet 51 is released, the stopper 61 becomes free to move, and the lift restriction of the needle 40 by the stopper 61 is released. When the second electromagnet 75 is excited in this state, the seal portion 44 of the needle 40 largely separates from the valve seat surface 47, and the lift amount of the needle 40 as shown in FIG. 11 (c). LH becomes large. Therefore, the gap S ₁ between the valve seat surface 47 of the nozzle opening 35 and the small diameter portion 46 of the needle 40 is expanded to several tens of μ, and the fuel injection amount from the nozzle opening 35 is increased. Such control of the fuel injection amount is performed by the first electromagnet 5
This is performed by changing the energization time of 1 in the fuel injection period.

12A to 12C show the relationship between the drive pulse A for the first electromagnet 51 and the drive pulse B for the second electromagnet 75, where T is the fuel injection. The period is shown. The fuel injection period T is set in the range of 20 ° to 24 ° in crank angle, but may be set in the range of 15 ° to 30 °, for example.

FIG. 12A shows driving pulses for the electromagnets 51 and 75 during low load / low rotation operation. During low load / low rotation operation, the fuel injection period T is fixed at 20 °, and both electromagnets 51 and 75 are excited during this fuel injection period. Therefore, as shown in FIG.
The lift amount LH of the needle 40 during the fuel injection period becomes small.

FIG. 12B shows driving pulses for the electromagnets 51 and 75 during high load / high rotation operation. During high load / high speed operation, the fuel injection period T is 20 ° to 24
Within the range of .degree. And only the second electromagnet 75 is excited during this fuel injection period. Therefore, as shown in (b) of FIG. 13, the lift amount LH of the needle 40 during the fuel injection period becomes large on the contrary.

Further, FIG. 12C shows driving pulses for the electromagnets 51 and 75 during the medium load / medium rotation operation. During medium load / medium rotation operation, the fuel injection period T is 20
Is fixed at .degree., And during this fuel injection period, the excitation period of the first electromagnet 51 is controlled according to the engine operating condition. Therefore, as shown in (c) of FIG. 13, the lift amount LH of the needle 40 becomes long during the period E in which the first electromagnet 51 is de-excited, and during the fuel injection period, the nozzle opening 35. The opening area of changes.

Then, such two electromagnets 51, 7
In No. 5, during the engine operation, the excitation period is controlled by a signal output from the central processing unit 90 as a control unit.

That is, the engine load corresponding to the engine speed and the accelerator opening is input to the central processing unit 90 as data indicating the operating condition of the engine 4, and the central processing unit 90 receives these data. The lift amount LH of the needle 40 based on the
Determine the opening area of.

In determining the lift amount LH, the central processing unit 90 uses the engine speed and the engine load as a reference to determine the optimum needle 4 for the operating condition at that time.
A lift amount LH of 0, that is, a map for guiding the excitation period (crank angle) of the first electromagnet 51 is stored in advance. FIG. 14 shows an example of a map for guiding the excitation period (crank angle) of the first electromagnet 51, and the central processing unit 90 is based on the actual data detected from this map. Then, the excitation period of the first electromagnet 51 is searched.

For example, the engine speed is 3000 rpm
So, in an operating situation where the engine load is full load,
The central processing unit 90 determines that the excitation period of the first electromagnet 51 is 0 ° (crank angle) based on the map search, and outputs a control signal indicating the excitation period to the first electromagnet 51. .. Similarly, the engine speed is 1500
In an operating condition where the engine load is medium load at rpm, the central processing unit 90 enters the transient region where the excitation period of the first electromagnet 51 is changed from 8 ° to 11 ° based on the map search. It is determined that there is, and a control signal indicating this excitation period is output to the first electromagnet 55.

From the above, in the operating condition in which the engine speed is in the full speed range from idling to 5000 rpm and the engine load is low including idling, as shown in FIG. The exciting period of the electromagnet 51 is determined to be 22 ° over the entire fuel injection period T, and the gap S ₁ between the valve seat surface 47 of the nozzle port 35 and the small diameter portion 46 of the needle 40 is kept narrow, so that the nozzle The fuel passing through the mouth 35 is squeezed. Due to this restriction, in the low load / low rotation operation region where the fuel injection amount is small, the flow of the fuel ejected from the nozzle port 35 becomes a laminar flow with less disturbance, and the variation in the flow rate is reduced.

Therefore, for example, the viscosity of the fuel changes due to the influence of the outside air temperature, and the fuel injection device 1 to the fuel injection valve 32 changes.
Even if the fuel pressure supplied to the
_As shown in ₁ , the fluctuation ratio of the fuel injection amount with respect to the fuel pressure is suppressed to a low level, and the engine rotation becomes stable in a low rotation operation range including idling.

On the other hand, the first electromagnet 51 is moved toward the high load / high rotation operating range where the required fuel injection amount increases.
Since the excitation period of 0 becomes 0 °, the valve seat surface 4 of the nozzle port 35
7, the gap S ₁ between the small diameter portion 46 of the needle 40 widens,
More fuel is ejected from the nozzle port 35.
As a result, the flow of fuel ejected from the nozzle port 35 becomes turbulent, but as shown by X ₂ in FIG.
It is possible to secure an injection amount that can satisfy the required injection amount in the high speed operation range.

Further, the maximum permissible rotation speed of the engine 4 of the present embodiment is regulated to 5000 rpm, and the central processing unit 90 causes the electromagnet 51 of the fuel injection valve 32 at the time when the engine rotation speed exceeds 5000 rpm. , 75 is stopped. Then, since the protrusion 82 of the armature 81 closes the pressure relief hole 72, the pressure in the pressure chamber 68 increases and the needle 40 is pressed toward the nozzle port 35. As a result, the seal portion 44 of the needle 40 is pressed against the valve seat surface 47 of the nozzle port 35 and the nozzle port 35 is closed, so that fuel injection is stopped.

In addition, in the case of the fuel injection valve 32 having the above construction, the pressure relief hole 7 having a small diameter is excited by the excitation of the second electromagnet 75.
2 is opened, the high-pressure fuel in the pressure chamber 68 releases the high pressure fuel 7
Since it is jetted into the space 71 through 2, the bubbles may be generated in the jetted fuel. If the air bubbles enter between the armature 81 and the core 76 through the communication hole 86 together with the fuel, an air layer is formed between the armature 81 and the core 76, and the armature 81 smoothly moves. There is a possibility that the operation may be hindered or the responsiveness may deteriorate.

However, in this embodiment, the armature 8 is used.
Since 1 is a plunger-shaped small-diameter and has a substantially opposed area with the core 76, the probability that air bubbles enter between the core 76 and the armature 81 is small, and even if the air bubbles have entered. Even so, the air layer formed here is extremely small. For this reason, the operation of the armature 81 is less likely to be affected by bubbles, and the operation is more stable than when the armature 81 is flat.

On the other hand, as shown in FIGS. 2 and 4, a concave portion 93 is formed on the upper surface of the plunger housing 14 of the fuel injection device 1. A pressure varying device 94 for adjusting the fuel pressure in the pressure accumulating chamber 22 is attached to the concave portion 93. The pressure varying device 94 has a housing 94 a fitted in the recess 93. Housing 94
A first cylinder 95 is formed in the center of a, and the cylinder 95 is opened in the upper surface of the housing 94a. Then, the housing 94a has the concave portion 9
It is fixed to the plunger housing 14 by a cylindrical nut 96 screwed into the stopper 3.

The first cylinder 95 has a housing 94a.
Is connected to the upstream chamber 22a of the pressure accumulating chamber 22 through a bottom surface of the pressure chamber 22 and the introduction passage 97 formed in the plunger housing 14, and a part of the fuel pressurized by the plunger 17 is introduced into the first cylinder 95. To be done.

A piston case 98 is attached to the upper surface of the plunger housing 15. Piston case
The housing 98 covers and hides the housing 94a and the nut 96. Inside the piston case 98, a second cylinder 99 that opens to the lower surface of the piston case 98 is formed. The second cylinder 99 is the first cylinder 95.
Is arranged coaxially with the first cylinder 95 and has a diameter significantly larger than that of the first cylinder 95. A piston 100 is fitted in the second cylinder 99 so as to be slidable in the axial direction, and an O-ring 100 a that is in sliding contact with the inner surface of the second cylinder 99 is provided on the outer peripheral surface of the piston 100. ing. At the center of the lower surface of the piston 100, the small diameter portion 1
01 is coaxially projected. This small diameter portion 101 is
It is fitted in the first cylinder 95 so as to be slidable in the axial direction, and the first cylinder 9 is attached to the outer peripheral surface of the small diameter portion 101.
An O-ring 101a is provided which is in sliding contact with the inner surface of No. 5.

On the upper surface of the piston 100, a recess 102 having a size substantially covering the entire surface is formed. This recess 102
An upper pressurizing chamber 103 having a large capacity is formed between and the upper end surface of the second cylinder 99. A vertical passage 104 that extends into the small diameter portion 101 is opened at the bottom surface of the recess 102. The vertical passage 104 communicates with the first cylinder 95 via a communication port 105 that opens at the tip surface of the small diameter portion 101. A lower pressurizing chamber 106 is formed between the bottom surface of the first cylinder 95 and the tip of the small diameter portion 101, and only the flow of fuel from the pressure accumulating chamber 22 is allowed in the lower pressurizing chamber 106. A ball valve 107 is provided.

Therefore, a part of the fuel in the pressure accumulating chamber 22 is introduced into both the lower pressurizing chamber 106 and the upper pressurizing chamber 103. At this time, the piston 1 facing the upper pressurizing chamber 103.
00 is larger in diameter than the small diameter portion 101 facing the lower pressurizing chamber 106 and has a large fuel pressure receiving area, so that the force pressing the piston 100 downward is larger. From this,
The piston 100 has a ball valve 10 through a small diameter portion 101.
7 is pressed against the opening of the introduction path 97, and
The communication between the lower pressurizing chamber 106 and the lower pressurizing chamber 106 is blocked.

As shown in FIG. 3, a pressure sensor 110 is attached to the side surface of the piston case 98. The pressure sensor 110 faces the upper pressurizing chamber 103 via a pressure introducing passage 111 provided in the piston case 98, and detects the fuel pressure in the upper pressurizing chamber 103.

In this case, as described above, the upper pressure chamber 103
The diameter of the piston 100 forming the lower pressurizing chamber 106 is larger than that of the small diameter part 101 forming the lower pressurizing chamber 106. Therefore, the upper pressurizing chamber 10 is divided by the area ratio of the piston 100 and the small diameter part 101.
The fuel pressure acting on 3 is reduced. Therefore, it is not necessary to directly apply a high pressure fuel pressure to the pressure sensor 110, and an expensive high pressure resistant pressure sensor becomes unnecessary.

A mounting recess 112 is formed on the upper surface of the piston case 98. A fuel escape hole 113 that communicates with the upper pressurizing chamber 103 is formed on the bottom surface of the mounting recess 112. A holder 114 is fitted in the mounting recess 112, and is fixed by a nut 115 so as not to come off. The holder 114 has a cylindrical shape with an upper surface closed, and as shown in FIG. 4, an electromagnetic on-off valve 120 for opening and closing the fuel escape hole 113 is accommodated in the holder 114. The on-off valve 120 is for changing the fuel pressure supplied to the fuel injection valve 32 according to the engine operating condition, and is located in the mounting recess 112.
Is equipped with. A valve hole 122 is formed in the base 121 so as to be continuous with the fuel escape hole 113. At the opening end of the valve hole 122 into the holder 114, a ball-shaped valve body for opening and closing the valve hole 122 is formed. 123 is provided.

In the holder 114, an electromagnet 124 which serves as a drive unit for the on-off valve 120 is housed. Electromagnet 124
Is composed of a core 125, a coil 126 wound around the outer periphery of the core 125, and a yoke 127 covering the periphery of the coil 126 and the core 125. The core 125 is located above the base 121. It is located. The lower end of the yoke 127 is screwed into the outer periphery of the base 121, and a gap 128 for fuel flow is provided between the yoke 127 and the holder 114.

Space 1 between core 125 and base 121
An armature 1 for opening and closing the valve body 123 is shown at 29.
30 are arranged. Armature 130 is core 1
25 is provided with a guide shaft 131 penetrating the central portion,
The tip of the guide shaft 131 is pressed downward by the linear spring member 132. By this pressing,
The mature body 130 presses the valve body 123 against the opening edge of the valve hole 122, and the valve hole 122 is closed.

Further, the yoke 127 is formed with a communication port 133 for communicating the space 129 with the gap 128. This communication port 133 is inserted into the holder 1 through the gap 128.
It is connected to the fuel return port 134 at the upper part of 14. The fuel return port 134 is connected to the fuel tank 7 via a fuel return pipe 89. Therefore, in the case of this embodiment,
A fuel return passage 135 for returning a part of the fuel pressurized by the plunger 17 to the fuel tank 7 is formed by various holes, passages and gaps from the introduction passage 97 connected to the pressure accumulating chamber 22 to the fuel return port 134 of the holder 114. It is configured.

Further, the plunger housing 14 is formed with a fuel escape passage 140 opening to the peripheral surface of the pump chamber 18. The fuel escape passage 140 is connected to the fuel return pipe 89. An electromagnetic valve 141 that opens and closes the fuel escape passage 140 is provided in the middle of the fuel escape passage 140. Solenoid valve 14
1 is adapted to be closed when the engine 4 is started and when the engine 4 reaches the number of revolutions at which maximum torque is generated. 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 124 of the on-off valve 120.

That is, when the electromagnet 124 is excited,
Since the armature 130 is sucked by the core 125, the pressing force of the valve body 123 is released, and the valve body 123 is closed by the valve hole 1
It receives the pressure of the fuel in 22 and separates from the valve hole 122.
Then, the valve hole 122 is opened and the fuel in the upper pressurizing chamber 103 flows out to the fuel return pipe 89. Therefore, the force pressing the piston 100 downward is reduced, and the ball valve 107
Is pushed up by the fuel pressure applied through the introduction path 97. Due to the rise of the ball valve 107, the small diameter portion 10
While the piston 100 is pushed up via 1,
The introduction passage 97 and the lower pressurizing chamber 106 are communicated with each other, and the pressure accumulating chamber 2
A part of the fuel in 2 flows from the lower pressurizing chamber 106 to the vertical passage 104.
And flows out to the upper pressurizing chamber 103.

Therefore, as much as this fuel flows out,
Since the fuel pressure in the pressure accumulating chamber 22 becomes low, the fuel injection valve 3
The fuel pressure supplied to 2 is also low. Then, in this case, depending on the magnitude of the voltage applied to the electromagnet 124,
Since the force for sucking the armature 130 changes, if this voltage is high, the force for sucking the armature 130 becomes large, the valve body 123 is largely separated from the valve hole 122, and a large amount of fuel flows out. Become. On the other hand, the electromagnet 12
When the voltage applied to No. 4 is low, the force for attracting the armature 130 is weakened, so that the opening of the valve hole 122 is decreased and the amount of fuel outflow is decreased. From this, the amount of outflow of fuel and eventually the fuel pressure supplied to the fuel injection valve 32 changes depending on the magnitude of the voltage applied to the electromagnet 124.

On the other hand, when the excitation of the electromagnet 124 is released,
Since the armature 130 is pressed downward by the spring member 132 and the valve body 123 closes the valve hole 122, the pressure in the upper pressurizing chamber 103 rises and the piston 100 is pressed downward again. By this pressing, the communication between the lower pressurizing chamber 106 and the pressure accumulating chamber 22 is cut off, so that the outflow of fuel from the pressure accumulating chamber 22 is stopped and the fuel pressure supplied to the fuel injection valve 32 becomes high. The voltage thus applied to the electromagnet 124 is controlled by the signal output from the central processing unit 90.

That is, a signal indicating the fuel pressure in the upper pressurizing chamber 103 is input to the central processing unit 90 via the pressure sensor 110, in addition to the signals indicating the engine speed and the engine load. And the central processing unit 9
0 determines the voltage to be applied to the electromagnet 124 based on these signals.

When determining this voltage, the central processing unit 90 stores in advance a map for deriving the voltage applied to the electromagnet 124 that is most suitable for the engine operating condition at that time, based on the engine speed and the engine load. ing.

FIG. 5 shows how to apply the voltage applied to the electromagnet 124.
Fig. 6 shows an example of a map for
Engine at that time, based on number and engine load
Show an example of a map that guides the optimum fuel pressure to the driving situation
There is. As you can see from these maps, to the electromagnet 124
Applied voltage is within the range of 0.47 (V) to 4.8 (V)
The fuel injection valve 32 changes in accordance with the change in the applied voltage.
The fuel pressure supplied to is 83.5 (kg / cm² ) ~
300 (kg / cm² ) Specified to change within the range
Has been done. Here, the processing performed by the central processing unit 90
The contents will be described with reference to FIG. 7.

First, the central processing unit 90 converts the fuel pressure signal sent from the pressure sensor 110 into the voltage V ₁ . At the same time, this central processing unit 90
Is a voltage to be applied to the electromagnet 124, that is, the reference voltage V ₂ is searched from the map shown in FIG. 5 based on the detected actual engine speed and engine load, and the reference voltage V ₂ Voltage V ₁ indicating the actual fuel pressure
Compare with.

By this comparison, the voltage V ₁ is the reference voltage V ₂
If it is above, the central processing unit 90 sends a drive pulse to the electromagnet 124 to excite it.
That is, FIG. 8 shows the relationship between the movement of the plunger 17 and the fuel pressure in the upper pressurizing chamber 103 (accumulation chamber 22). The pressure signal sent from the pressure sensor 110 is proportional to the voltage V _1. It is in. Here, (a) of FIG. 8 shows the relationship between the movement of the plunger 17 and the voltage V ₁ when the fuel pressure is not controlled, and (b) of FIG. 8 shows the plunger 17 when the fuel pressure is controlled. The relationship between movement and voltage V ₁ is shown.

As shown in FIG. 8B, when the voltage V ₁ indicating the fuel pressure in the upper pressurizing chamber 103 exceeds the reference voltage V ₂ optimum for the operating condition at that time, the central processing unit 90 Drive pulse is emitted from the electromagnet 124 to excite the electromagnet 124. The opening / closing valve 120 is opened by the excitation of the electromagnet 124, and the fuel in the pressure accumulating chamber 22 or the upper pressurizing chamber 103 is released to the fuel return pipe 89. From this, the fuel pressure in the pressure accumulating chamber 22 and the upper pressurizing chamber 103 is suppressed from increasing, and the fuel pressure starts to decrease with the passage of time. As a result, the voltage V ₁ drops and the fuel pressure supplied to the fuel injection valve 32 also drops.

When the voltage V ₁ falls below the reference voltage V ₂ due to this fuel outflow, the energization of the electromagnet 124 is stopped,
The excitation of the electromagnet 124 is released. Then, the on-off valve 12
Since 0 is closed and the outflow of fuel from the pressure accumulating chamber 22 and the upper pressurizing chamber 103 is stopped, the fuel pressure in the pressure accumulating chamber 22 and the upper pressurizing chamber 103 rises again. Therefore, the voltage V ₁ rises and the fuel pressure supplied to the fuel injection valve 32 rises. When the voltage V ₁ exceeds the reference voltage V ₂ due to the rise of the voltage V ₁ , a drive pulse is output to the electromagnet 124 again, and thereafter, the on-off valve 120 is set to the voltage V 1.
_The opening / closing operation is repeated so that 1 becomes equal to the reference voltage V ₂ .

Further, in the case of the present embodiment, the fuel injection valve 32 stops the fuel injection at the time when the engine speed exceeds 5000 rpm as described above. The voltage V ₂ is drastically reduced, and the fuel pressure supplied to the fuel injection valve 32 is further lowered than in the low load / low rotation range including idling.

Explaining the reason for this, the fuel injection is stopped by the two electromagnets 5 of the fuel injection valve 32 as described above.
Since it is performed by stopping the energization to 1, 75, the fuel pressure introduced to the fuel injection valve 32 may be high or low from the viewpoint of injection stop. However, if the fuel pressure remains high, the loss horsepower of the plunger 17 increases, and conversely, if the fuel pressure is too low, bubbles easily occur in the fuel. Therefore, in the present embodiment, the fuel introduced to the fuel injection valve 32 is added to a value lower than the low load / low speed range even during the period when the fuel injection valve 32 stops the fuel injection. The generation of bubbles is prevented without pressing and increasing the loss horsepower of the plunger 17.

According to such an embodiment of the present invention, the on-off valve 120 of the fuel return passage 135 causes the fuel pressure in the pressure accumulating chamber 22 to approach the optimum fuel pressure according to the engine operating condition at that time. Since the opening / closing operation is repeated, the fuel pressure supplied to the fuel injection valve 32 is accurately and reliably controlled as desired even when the fuel injection period is kept within a certain crank angle range as a measure for exhaust gas. be able to.

In the first embodiment, the on-off valve 120
The optimum reference voltage V ₂ to be applied to the electromagnet 124 of _{No. 1} is compared with the voltage V ₁ indicating the fuel pressure sent to the fuel injection valve 32, and the opening / closing valve 120 is opened / closed according to the comparison result. However, the present invention is not limited to this, and FIG. 16 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment mainly in the means for determining the opening / closing timing of the on-off valve 120.

As shown in FIG. 16, the central processing unit 9
0 is the open operation voltage V _{3 which} is a reference when the open / close valve 120 is opened based on the reference voltage V ₂ , and the open / close valve 1
The closing operation voltage V _{4 which is a} criterion for closing 20
Are stored individually. The open operating voltage V ₃ is set higher than the reference voltage V ₂ , and the close operating voltage V ₄ is set lower than the reference voltage V ₂ .

Then, the central processing unit 90 compares the voltage V ₁ indicating the fuel pressure sent to the fuel injection valve 32 with the open operation signal V ₃ and the close operation signal V ₄ during engine operation. According to this comparison, the voltage V ₁ is the open operation voltage V ₃
If it exceeds the value, the central processing unit 90 sends a drive pulse for exciting it to the electromagnet 124. When the opening / closing valve 120 is opened by the excitation of the electromagnet 124, the fuel in the pressure accumulating chamber 22 and the upper pressurizing chamber 103 is released to the fuel return pipe 89, and the increase in the fuel pressure in these chambers 22 and 103 is suppressed. At the same time, the fuel pressure begins to gradually decrease over time.

[0075] This reduction in fuel pressure, it means a reduction in the voltages V _1, the voltages V ₁ by the outflow of the fuel is below the closing operation voltage V _4, the central processing unit 90, the drive to the electromagnet 124 Stop sending pulses. Therefore, the excitation of the electromagnet 124 is released, and the on-off valve 120 is closed. By this closing operation, the pressure accumulating chamber 22 and the upper pressurizing chamber 10
Since the outflow of fuel from 3 is stopped, these two chambers 2
The fuel pressure of 2,103 rises again and the voltage V ₁ rises. Therefore, the central processing unit 90 sends a drive pulse to the on-off valve 120 so that the voltage V ₁ converges between the open operating voltage V ₃ and the close operating voltage V ₄ .

According to such a second embodiment, the voltage V ₁
Is controlled so as to converge between the open operating voltage V ₃ and the close operating voltage V _4, which are set to have a width above and below the reference voltage V _2, so that the voltage V ₁ is the reference voltage V ₂ The value of this voltage V ₁ remains open operating voltage V ₃
And the closing operation voltage V ₄ are satisfied, the central processing unit 90 does not send a drive pulse to the solenoid valve 124, and the on-off valve 120 is kept closed.

Therefore, apparently, the value of the reference voltage V ₂ is the same as having the upper and lower widths, and the opening / closing frequency of the opening / closing valve 120 is reduced as compared with the first embodiment. From this, it is possible to suppress wear of the valve body 123 and the valve hole 122, which are actually operating parts of the on-off valve 120, to be small, and there is an advantage that maintenance management becomes easy.

Further, FIG. 17 shows a third embodiment of the present invention. Also in this third embodiment, the on-off valve 120 is mainly used.
The means for determining the opening / closing timing of is different from that of the first embodiment.

That is, in the first embodiment, the voltage V ₁
When the voltage exceeds the reference voltage V ₂ , a drive pulse is sent to the electromagnet 124, and when the voltage V ₁ is below the reference voltage V ₂ , the drive pulse is stopped to be sent to the electromagnet 124. On the other hand, in the third embodiment, when the voltage V ₁ exceeds the reference voltage V ₂ , the voltage V ₁ and the reference voltage V 2
The ON period t of the drive pulse is determined according to the magnitude of the difference D from ₂ and the voltage V ₁ is controlled so as to converge to the reference voltage V ₂ .

Specifically, the central processing unit 90 has a constant cycle C synchronized with the rotation of the drive shaft 3 of the fuel injection device 1, that is, every time the drive shaft 3 makes one rotation or at a constant rotation angle. The value of the voltage V ₁ is read. Then, in the central processing unit 90, read only when the value of the voltages V ₁ is higher than the reference voltage V _2, the process for calculating the difference D between the values of the value and the reference voltage V ₂ voltages V ₁ row Be seen. In the case of this embodiment, the central processing unit 9
In 0, a map is stored in advance in order to derive the excitation period of the electromagnet 124, that is, the ON period t of the drive pulse, which is optimum for the operating condition at that time, based on the voltage value difference D and the engine speed.

Therefore, the central processing unit 90 determines the ON period t of the drive pulse from the map based on the calculation result of the voltage value, and sends this drive pulse to the electromagnet 124. The ON period t of the drive pulse is set longer as the difference between the voltage V ₁ and the reference voltage V ₂ is larger.

In the third embodiment as described above, the on-off valve 120
The period during which the open operation is performed is appropriately determined to be an optimum value according to the magnitude of the difference D between the voltage V ₁ and the reference voltage V ₂ , and
The drive pulse for opening the on-off valve 120 is
Since the output is performed at a constant cycle C synchronized with the rotation of the drive shaft 3, the value of the voltage V ₁ can be brought close to the reference voltage V ₂ with high accuracy in a short period of time. Therefore, the fuel injection valve 32
It is possible to control the fuel pressure supplied to the fuel cell as desired and reduce the deviation from the target value.

The cycle C for reading the voltage V ₁ is not limited to that in which the drive shaft 3 of the fuel injection device 1 is synchronized. For example, the central processing unit 90 is provided with a constant frequency oscillating means.
The constant frequency oscillating means may set the cycle C irrespective of the rotation of the drive shaft 3. In this case, when the cycle C is synchronized with the drive shaft 3, the cycle C is affected by the rotation fluctuation of the engine, whereas when the cycle C is set by the constant frequency oscillating means, the setting of the transmitting means is not changed. As long as the period C is kept constant at all times.

Further, the ON period t of the drive pulse is not limited to the search from the map, and for example, the central processing unit 9
When calculating the difference D between the values of the voltage V ₁ and the reference voltage V ₂ at 0, the ON period t of the drive pulse may be calculated based on the difference D and the engine speed.

Further, FIG. 18 discloses a fourth embodiment of the present invention. This fourth embodiment also mainly uses the on-off valve 12
The means for determining the opening / closing timing of 0 is different from that of the first embodiment.

[0086] In the fourth embodiment, Du driving pulse is ON - the tee t, and steplessly determined by the value of the voltages V _1, is controlled so that the voltages V ₁ converges to the reference voltage V ₂ There is.

That is, the central processing unit 90, as in the case of the third embodiment, has a voltage V at a constant cycle C synchronized with the rotation of the drive shaft 3 or at a cycle C set by the constant frequency oscillating means. ₁ is read, and the duty with which the drive pulse is turned on is determined according to the value of this voltage V ₁ . The method for determining the duty will be specifically described. Now, an arbitrary voltage value A smaller than the reference voltage V ₂
Assuming that the duty at 0 is set to 0% and the duty at an arbitrary voltage value B greater than the reference voltage V ₂ is set to 100%, the central processing unit 90 determines that the read value of the voltage V ₁ and the voltage values A and B are equal to each other. To compare. When the relationship of voltage V ₁ <voltage value A is established, the duty is 0
%, And when the relationship of voltage V ₁ > voltage value B is established, it is determined that the duty is 100%. When the relationship of voltage value A ≤ voltage V ₁ ≤ voltage value B is established, calculation is performed based on the formula (voltage value V ₁ -voltage value A) / (voltage value B-voltage value A) x 100. The duty is determined steplessly.

In the fourth embodiment, the duty with which the drive pulse is turned on is set steplessly at every predetermined cycle C, so that the voltage V ₁ becomes the reference voltage V ₂ as shown in FIG. Even at a stage where it does not reach, a drive pulse is sent to the solenoid valve 124, and the opening / closing valve 120 is opened. Therefore, since the rise of the fuel pressure supplied to the voltages V ₁ and thus the fuel injection valve 32 is suppressed, can control the voltages V ₁ by the prediction previously the voltages V ₁ exceeds the reference voltage V _2, the voltages V ₁ It becomes easy to converge to the reference voltage V ₂ . Therefore, the fuel pressure supplied to the fuel injection valve 32 can be controlled to approach the target value within a short time.

In the fourth embodiment, the duty for turning on the drive pulse is set steplessly. However, for example, this duty is set stepwise in advance from 0% to 100%, and the voltage V The difference between the value of _{1 and} the value of the reference voltage V ₂ may be compared with the duty, and the drive pulse may be turned on at the duty with which the difference is the same or closest.

The open / close valve 120 of the first embodiment is
A ball-shaped valve element 123 is used to open and close the valve hole 122. However, the configuration of the on-off valve 120 is not limited to this, and for example, a needle valve is used as the valve element, the needle valve is inserted into the valve hole, and the insertion amount of the needle valve is set to the electromagnetic valve 124. It may be adjusted with.

According to this structure, the opening area of the valve hole can be changed steplessly by adjusting the insertion amount of the needle valve. Therefore, for example, the value of the voltage V ₁ and the reference voltage V
_When the escape amount of the fuel in the upper pressurizing chamber 103 is changed according to the difference between the _two values, the escape amount of the fuel can be changed steplessly.

On the other hand, FIG. 19 discloses a fifth embodiment of the present invention. In the fifth embodiment, the mounting position of the pressure sensor 110 for detecting the fuel pressure is mainly different from that of the first embodiment. In the fifth embodiment, the same components as those of the first embodiment are provided. Are assigned the same reference numerals and explanations thereof are omitted.

As shown in FIG. 19, a sensor mounting portion 200 is provided on the side surface of the plunger housing 14. The sensor mounting portion 200 has a pressure introducing path 201.
Is connected to the recess 20 (the upstream chamber 22a of the pressure accumulating chamber 22) via the pressure sensor 1 and the pressure sensor 1
10 is attached.

Therefore, the fuel in the pressure accumulating chamber 22 is introduced into the sensor mounting portion 200 through the pressure introducing path 201, and the pressure sensor 110 directly detects the fuel pressure in the pressure accumulating chamber 22 connected to the fuel injection valve 32. Is becoming

According to the fifth embodiment having such a structure, the fuel pressure in the pressure accumulation chamber 22 to be controlled can be directly detected, and the fuel pressure detection accuracy can be further improved.

Further, FIG. 20 discloses a sixth embodiment of the present invention. In the sixth embodiment, the mounting position of the pressure sensor 110 for detecting the fuel pressure and the opening / closing valve 1 are mainly used.
The mounting position of 20 is different from that of the first embodiment,
In the sixth embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 20, the piston case 98
A sensor mounting portion 300 is provided on the upper surface of the. The sensor mounting portion 300 is connected to the upper pressurizing chamber 103 on the low pressure side via the pressure introducing passage 301, and the pressure sensor 110 is mounted on the sensor mounting portion 300. Then, the upper pressurizing chamber 103 is connected to the fuel return pipe 89 via an escape passage having a pressure reducing means such as an orifice and a valve (not shown).

A mounting recess 302 is provided on the side surface of the plunger housing 14. Mounting recess 302
Is connected to the recess 20 (the upstream chamber 22a of the pressure accumulating chamber 22) via the pressure introducing passage 303, and the mounting recess 302 is provided with the opening / closing valve 120 having the same configuration as that of the first embodiment. Therefore, the valve hole 122 of the on-off valve 120
Is connected to the pressure accumulating chamber 22 via a pressure introducing passage 303, and the fuel pressure of the pressure accumulating chamber 22 connected to the fuel injection valve 32 directly acts on the valve element 123 of the on-off valve 120.

According to the sixth embodiment having such a configuration, the passage length from the pressure-accumulation chamber 22 to be controlled to the fuel return pipe 89 is remarkably shortened, so that the fuel in the pressure-accumulation chamber 22 can be released accurately. The fuel pressure supplied to the fuel injection valve 32 can be controlled more accurately.

When a pressure reducing means is provided in the passage for returning the fuel in the upper pressurizing chamber 103 to the fuel return pipe 89, if an orifice is used as the pressure reducing means, the upper pressurizing chamber 103 can be used.
The fuel inside will be throttled by the orifice and gradually escape. Therefore, unlike the case where the valve is used, there is an advantage that fuel pulsation does not occur in the upper pressurizing chamber 103 due to opening and closing of the valve, and the detection accuracy of the fuel pressure by the pressure sensor 110 is stable.

Furthermore, in the first embodiment, the piston 100 constituting the pressure varying device 94 is the second cylinder 9
An O-ring 100a is fitted on the outer peripheral surface of the piston 100 and is in sliding contact with the inner surface of the second cylinder 99.

According to this structure, sliding resistance is generated between the cylinder 99 and the piston 100 and the O-ring 100a.
8 may be attached in a floating state via a diaphragm so as to eliminate sliding resistance generated between the piston 8 and the second cylinder 99 when the piston 100 operates.

In addition, in the above embodiment, the on-off valve and the pressure varying device operated by this on-off valve are integrally incorporated in the plunger housing of the fuel injection device, but the present invention is not limited to this, and the on-off valve and The pressure varying device may be separated from the plunger housing.

[0104]

According to the present invention described in detail above, the opening / closing valve of the fuel return passage repeats the opening / closing operation so that the fuel pressure in the fuel passage approaches the optimum fuel pressure according to the engine operating condition at that time. Therefore, as a measure for exhaust gas, even when the fuel injection period is kept within a certain crank angle range, the fuel pressure supplied to the fuel injection valve can be accurately and reliably targeted by the predetermined reference data. Can be controlled.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a fuel injection device in a first embodiment of the present invention.

FIG. 2 is a sectional view of the entire fuel injection device.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is an enlarged cross-sectional view showing the periphery of the pressure varying device.

FIG. 5 is a diagram for explaining an applied voltage of an electromagnet most suitable for an engine operating condition at that time with reference to an engine speed and an engine load.

FIG. 6 is a diagram for explaining an optimum fuel pressure for an engine operating condition at that time with reference to an engine speed and an engine load.

FIG. 7 is a flowchart showing the processing contents of the central processing unit.

FIG. 8 is a diagram showing a relationship between a reference voltage applied to an electromagnet, a voltage indicating fuel pressure, and a drive pulse output from a central processing unit.

FIG. 9 is a sectional view of a fuel injection valve.

FIG. 10 is a sectional view showing a positional relationship between a plunger driven by a second electromagnet of the fuel injection valve and a pressure relief hole.

FIG. 11A is a cross-sectional view showing a state in which a nozzle port of a fuel injection valve is closed. (B) is sectional drawing of a nozzle opening at the time of low load and low rotation operation. (C) is a cross-sectional view of the nozzle port during high load / high rotation operation.

FIG. 12A is a diagram showing drive pulses output from the central processing unit during low load / low rotation operation. (B) is a figure which shows the drive pulse output from a central processing unit at the time of high load and high rotation driving. (C) is a figure which shows the drive pulse output from a central processing unit at the time of middle load / middle rotation driving.

FIG. 13A is a diagram showing a lift amount of a needle of a fuel injection valve during low load / low rotation operation. FIG. 6B is a diagram showing the lift amount of the needle of the fuel injection valve during high load / high rotation operation. FIG. 6C is a diagram showing the lift amount of the middle of the fuel injection valve during medium load / medium rotation operation.

FIG. 14 is a diagram for explaining an energization period to an electromagnet, which is optimum for an engine operating condition at that time, based on an engine speed and an engine load.

FIG. 15 is a characteristic diagram showing the relationship between fuel pressure and fuel injection amount.

FIG. 16 is a diagram showing the relationship between drive pulses and voltages in the second embodiment of the present invention.

FIG. 17 is a diagram showing the relationship between drive pulses and voltages in the third embodiment of the present invention.

FIG. 18 is a diagram showing the relationship between drive pulses and voltages in the fourth embodiment of the present invention.

FIG. 19 is a sectional view showing a pressure varying device according to a fifth embodiment of the present invention.

FIG. 20 is a sectional view showing a pressure varying device according to a sixth embodiment of the present invention.

[Explanation of symbols]

15 ... Fuel injection pump, 29 ... Fuel passage, 32 ... Fuel injection valve, 90 ... Control means (central processing unit), 120 ...
On-off valve, 124 ... Drive unit (electromagnet), 135 ... Fuel return passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidetaka Suhara Hidetaka Suhara 2500 Shinkai, Iwata, Shizuoka Prefecture Yamaha Motor Co., Ltd. (72) Yoshikazu Nakamura 2500, Shinkai, Iwata, Shizuoka Yamaha Motor Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A fuel passage connecting a fuel injection pump and a fuel injection valve, a fuel return passage connected in the middle of the fuel passage, and a fuel return passage provided in the fuel return passage. An opening / closing valve for changing the pressure of the fuel supplied to the fuel injection valve by opening / closing the valve, and a control means for controlling the drive part of the opening / closing valve. The control means prestores the optimum fuel pressure for the operating condition at that time as the reference data based on the data indicating the operating condition of the engine. The fuel pressure introduced to the valve is detected so that the detected data approaches the reference data.
A fuel injection device for a diesel engine, which opens and closes the on-off valve.