JPH0735758B2 - Accumulation type fuel injector for diesel engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation fuel injection device for a diesel engine, and more particularly, to an injection timing that can be easily and accurately determined, and the structure can be simplified. The present invention relates to a pressure accumulation type fuel injection device for a diesel engine.

<Premise Structure> The present invention is intended for those having the following premise structure as shown in, for example, FIG. 1 (present invention) or FIG. 15 (prior art).

That is, the fuel tank 1 is communicatively connected to the pressure accumulating fuel injector 29 via the fuel metering supply device 2, the pressure feeding passage 17, the supply timing determining valve 18, the outlet passage 24, and the fuel injection pump 26 to determine the supply timing. The valve 18 is configured such that the pressure feed passage 17 is intermittently communicated with the outlet passage 24 by the valve opening / closing operation of the supply timing determining valve body passage 58, and when the valve is opened, the fuel amount adjusting device 2
The fuel metered by the fuel injection pump 26 is allowed to be supplied to the fuel injection pump 26, while the fuel discharged from the fuel injection pump 26 is prevented from flowing back to the fuel metering supply device 2 when the valve is closed. The valve box 56 of the supply timing determination valve 18 is provided with the above-mentioned pressure passage 17 and outlet passage 24.
And the valve body 57 of the supply timing determination valve 18 is provided with the valve body passage 58 for supply timing determination, which is a pressure accumulation type fuel injection device for a diesel engine.

Here, the pressure accumulating fuel injector 29 is, as illustrated in FIG. 11, closed after the fuel is injected into the injected fuel pressure accumulating chamber 86 through the valve closing pressurizing fuel chamber 85 and the check valve 95. Fuel chamber for valve pressurization 85
When the internal pressure of the valve closing pressurizing fuel chamber 85 falls below a predetermined value, the internal pressure of the injected fuel pressure accumulating chamber 86 overcomes the valve closing biasing force of the valve closing spring 91 and the internal pressure of the valve closing pressurizing fuel chamber 85. Injection valve
It is an injector 29 in which the valve 88 is opened and the fuel in the injected fuel pressure accumulating chamber 86 is injected from the injection hole 87. The valve closing pressurizing fuel chamber 85 is normally communicated with the pump chamber 82 of the fuel injection pump 26.

<Prior Art> Conventionally, the internal pressure of the valve closing pressurizing fuel chamber 85 is reduced by opening the check valve 85 from the pump chamber 82 to press the fuel into the injected fuel pressure accumulating chamber 86 and then raising the plunger 81. To be done.
Then, the plunger 81 is raised as shown in FIG.
It is limited directly by the fuel injection cam 30 of the drive device 5 that interlocks with the crankshaft, or via the cam follower 31, the push rod 32, the rocker arm 33, and the like.

<Problems to be Solved by the Invention> By the way, in the conventional pressure-accumulation fuel injection device for a diesel engine, the ascending stroke of the plunger 81 differs depending on the amount of fuel supplied by the fuel metering supply device 2, and the driving device 5 There is a problem in that a gap is created between each component or between the drive device and the plunger 81, and they strike each other to generate operating noise. Further, when such a gap is generated, there is a problem that the cam follower 31, the push rod 32 or the rocker am 33 of the drive device 5 freely vibrates and the timing such as the injection timing is deviated.

In order to prevent such driving noise and timing control error from occurring, a technique is known in which a spring is interposed between parts of the drive device 5 or between the drive device 5 and the plunger 81. However, with this technique, it is possible to prevent operating noise, but there is great dissatisfaction with respect to preventing vibration of components of the driving device 5 and eliminating an error in timing control.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a pressure-accumulation fuel injection device for a diesel engine, which can determine the injection timing with high accuracy by a simple principle and has a simple structure.

<Means for Solving Problems> In the pressure-accumulation fuel injection device for a diesel engine according to the present invention, in the pressure-accumulation fuel device for a diesel engine having the above-described prerequisite structure, in order to achieve the above object,
For example, as shown in FIGS. 1 to 11, the following technical measures are taken.

That is, the valve body 57 of the supply timing determining valve 18 is time-interlocked with the crankshaft of the engine, and the fuel injection pump 26 and the supply timing determining valve 18 are connected to the fuel closing valve fuel chamber 85 of the fuel injector 29. Via exit way 24,
The injection timing determination pressure release valve 19 is communicated with the pressure release valve 19 by providing the valve body 57 of the supply timing determination valve 18 with the pressure release valve body passage 59 independent of the supply timing determination valve body passage 58. The pressure relief valve body passage 59 is formed by the outlet passage 24 of the supply timing determination valve 18.
On the other hand, it is configured to open intermittently at a time different from the supply timing determining valve body passage 58, and the fuel injection is performed from the timing when the supply timing determining valve body passage 58 is closed to the outlet passage 24. After the period in which the plunger 81 of the pump 26 discharges, and during the period in which the pump chamber 82 of the fuel injection pump 26 is maintained at a high pressure by this discharge operation, the depressurization valve body passage 59 to the outlet passage 24. Is configured to be opened.

<Operation of the Invention> According to the present invention thus configured, when the outlet passage 24 of the valve box 56 connected to the fuel injector 29 and the depressurizing valve body passage 59 communicate with each other, the valve closing operation is performed. The fuel in the pressure fuel chamber 85 is released to the outside of the valve closing pressurization fuel chamber 85 via the pressure release valve 19, the pressure in the valve closing pressurization fuel chamber 85 is reduced, and the injection valve 88 is opened. The fuel injection timing to the injector 29 depends on the timing at which the outlet passage 24 and the pressure relief valve body passage 59 communicate with each other. The timing at which the outlet passage 24 and the pressure relief valve body passage 59 communicate with each other is determined by the supply timing determination valve that is timed in conjunction with the crankshaft.
Since it is determined by the operation of the valve element 57 that is common to 18, the injection timing is determined with high precision in synchronization with the crankshaft by a simple principle.

Further, the valve box 56 and the valve body of the pressure relief valve 19 and the supply timing determination valve 18
Since 57 is also used, the structure of the valve and the fuel passage is simplified, and the drive mechanism thereof is also simplified.

<Examples> Examples of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the fuel system of this diesel engine measures the fuel in the fuel tank 1 by the metering and supplying device 2 in accordance with the load condition of the engine, and supplies the timing control composite valve device 3 with the timing. The fuel is supplied to the unit injector 4 at a predetermined timing via the decision valve 18, and the fuel injection pump
26 is driven by the drive unit 5 to accumulate pressure
After press-fitting into 29, the injection timing setting pressure plate valve 19 and the injection timing adjusting advance valve 20 of the timing control combined device 3 depressurize the fuel in the valve closing pressurization fuel chamber 85 of the accumulator fuel injector 29. The fuel is released to the chamber 21 to reduce the internal pressure of the valve closing pressurizing fuel chamber 85, thereby opening the injection valve 88 and injecting the fuel accumulation chamber 86.
Fuel is injected from the injection hole 87 through the injection hole 87, and the fuel in the depressurized fuel breathing chamber 21 is discharged back to the unit injector 4 through the depressurized fuel return passage 22 at a predetermined timing after the end of the injection to be depressurized. The reduced fuel is returned to the unit injector 4, and thereafter, the initial pressure supply passage 23 of the timing control combined valve device 3 is communicated with the unit injector 4 to return the unit injector 4 to the initial state.

As shown in FIG. 2, the metering and feeding device 2 is a transfer pump incorporated in a thick-walled cylindrical casing 6.
10, pressure regulator 12 (Fig. 4), metering device 14 and pressure pump
16, the fuel pump 1 pumps fuel from the fuel tank 1 through the fuel pipe inlet joint 8 (FIG. 4) and the inlet passage 9 (FIG. 4) (not shown), and the pressure of the fuel discharged from the transfer pump 10. Is adjusted by the pressure adjusting device 12 according to the engine speed (for example, in direct proportion), and the pressure-adjusted fuel is adjusted by the amount adjusting device 14 according to the load condition of the engine. The metered fuel is pumped to the timing control combined valve device 3 by the pressure pump 16.

The transfer pump 10 has a pump chamber 34 formed at the front end portion of the casing 6, and in the pump chamber 34, as shown in FIG. 3, an inner rotor 35 fixed to the main shaft 7 penetrating the casing 6 and The eccentrically meshed outer rotor 36 is inserted into this, and the fuel is sucked from the inlet passage 9 through the suction port 37 into the space between the rotors 35 and 36, and then discharged from the discharge port 38 to the discharge passage 11 (Fig. 4). It is designed to discharge.

As shown in FIG. 4, the pressure adjusting device 12 is connected to the discharge passage 11 in a branched manner, and has a pressure adjusting plug 39 screwed to the casing 6,
A pressure regulating valve body 40 slidably fitted therein is provided, and a valve closing spring 41 for urging the pressure regulating valve body 40 to a valve closing position. A pressure regulating valve hole 42 is opened in the peripheral wall of the pressure regulating plug 39, and the pressure regulating valve hole 42 is communicated with the inlet passage 9. The discharge pressure of the transfer pump 10 corresponds to the engine speed 2
It changes in a quadratic function, and in response to this discharge pressure, the pressure regulating valve body 40 is urged against the valve closing spring 41 in the valve opening direction. This pressure regulator
In 12, by appropriately setting the opening area of the pressure regulating valve hole 42 with respect to the displacement amount of the pressure regulating valve body 40 from the closed position, the fuel escaped from the pressure regulating device 12 to the inlet passage 9 in correspondence with the rotation speed of the engine. By adjusting the amount, the internal pressure of the discharge passage 11 is accurately increased or decreased in direct proportion to the rotation speed of the engine. However, the correspondence relationship between the internal pressure of the discharge passage 11 controlled by the pressure regulator 12 and the rotation speed of the engine is not limited to the direct proportion, and for example, the increase rate of the internal pressure of the discharge passage 11 decreases as the speed increases. Alternatively, the increasing rate of the internal pressure of the discharge passage 11 may increase as the speed increases. A drain pipe joint 43 for connecting a drain pipe (not shown) for discharging fuel leaked from between the pressure regulating plug 39 and the pressure regulating valve body 40 is connected to the pressure regulating plug 39.

As shown in FIG. 2, the metering device 14 includes a metering piston 44 which is fitted in the front half of the main shaft 7 so as to be able to move forward and backward. The metering piston 44 is driven in the fuel reducing direction (here, forward) against the pressure of the governor spring 46 by the thrust of the flyweight 45 corresponding to the rotation speed of the engine. A metering valve hole 47 communicating with the discharge passage 11 is opened in the inner peripheral surface of the main shaft 7, and the metering piston hole 47 is opposed to the metering valve hole 47.
A metering valve body passage 48 is provided on the peripheral surface of the groove 44 along the entire circumference thereof. Then, as the metering piston 44 moves back and forth according to the engine speed, the connection area between the metering valve hole 47 and the metering valve body passage 48 is changed so as to correspond to the engine speed. The flow rate is adjusted and the spindle 7
Further, the fuel is guided to the pressure feed pump 16 through the outlet passage 49 formed in the casing 6. The pressure of the governor spring 46 can be changed and set by swinging the speed setting lever 50.

As shown in FIGS. 2 and 5, the pressure pump 16 has a swing arm formed by a drive cam 51 formed on the peripheral surface of the main shaft 7.
A plunger 53 driven via 52 and a pump chamber 54 whose volume changes as the plunger 53 moves forward and backward are provided. Further, the pressure pump 16 is configured to obtain pump characteristics corresponding to various torque characteristics suitable for engine applications by changing and setting the stroke of the plunger 53 by the torque characteristic setting device 55.

The timing control combined valve device 3 is incorporated in the casing 6 of the metering and feeding device 2 as shown in FIGS. 2 and 6 to 8 in order to achieve downsizing and compactness. The timing control combined valve device 3 essentially comprises a supply timing determination valve 18, an injection timing setting pressure relief valve 19, and an injection timing adjustment valve that can be provided independently as shown in FIG. The square valve 20 and the depressurized fuel breathing chamber 21 are integrally combined for downsizing and size reduction.

That is, as shown in FIG. 2 and FIGS. 6 to 8, the supply timing determination valve 18 that determines the timing at which the fuel is pressure-fed to each unit injector 4 and the injection timing setting depressurization valve 19 are the latter half of the casing 6. A common valve box 56 made up of parts and a common valve body 57 made up of the latter half of the main shaft 7 are provided. At the rear end of the inner peripheral surface of the casing 6, there is opened a pressure feeding passage 17 that is led out from the pressure feeding pump 16 of the metering and feeding device 2, and a little ahead of it, an outlet passage (distribution passage, hereinafter referred to as an inlet / outlet passage) to each unit injector 4. Called passages) 24 are opened at equal intervals in the circumferential direction. A communication groove portion 58a of the supply timing determining valve body passage 58 is recessed over the entire circumference in the portion of the main shaft 7 facing the pressure feeding passage 17, and the passage locus of the inlet / outlet passage 24 from one position in the circumferential direction of the communication groove portion 58a. The supply timing determining groove portion 58b is continuously extended in the axial direction along the peripheral surface up to the outer peripheral surface portion of the main shaft 7 opposed to l. Then, the main shaft 7 rotates in conjunction with a crank shaft (not shown), and the supply timing determining groove portion 58b and the inlet / outlet passage 24 overlap with each other to communicate with each other, so that the supply timing determining groove portion 58b and the inlet / outlet passage 24 communicate with each other through the supply timing determining valve body passage 58. The pressure-controlled / metered fuel is press-fitted into the inlet / outlet passage 24. In addition, in the portion of the outer peripheral surface of the main shaft 7 facing the passage locus 1 of the passage 24,
The pressure release valve body passage 59 of the injection timing setting pressure release valve 19 which is communicated with the inlet / outlet passage 24 is opened at a predetermined timing after the supply timing determination groove 58b.

The latter half of the main shaft 7, which is the common valve body 57 of the supply timing determination valve 18 and the injection timing setting pressure relief valve 19, further serves as a valve box of the injection timing adjusting advance valve 20. That is, a cylindrical advancing valve chamber 60 is formed concentrically in the latter half of the main shaft 7, and an advancing valve body 61 advances and retreats in the axial direction of the main shaft 7 in the advancing valve chamber 60. It is stored as much as possible. In the valve body 57, three pressure relief valve body passages 59 whose opening positions on the inner peripheral surface are different from each other in the rotation direction and the axial direction of the main shaft 7 are formed so as to penetrate the peripheral wall thereof, and are used for advancing. An advancing valve body passage 62 is formed on the circumferential surface of the valve body 61 so as to communicate with one of the three depressurizing valve body passages 59 or two adjacent ones. The advance valve body passage 62 is formed of a circumferential groove that is recessed over the entire circumference of the advance valve body 61. The advance valve chamber 60 has the advance valve body 61.
It is divided into an advance angle pressure receiving chamber 63 and a retard angle biasing chamber 64. Then, the advancing pressure receiving chamber 63 is communicated with the discharge passage 11 whose pressure is regulated by the pressure regulating device 12, the retard urging chamber 64 is communicated with the inlet passage 9 which is kept at a substantially constant pressure, and Chamber 64
A retard urging means 65 for urging the advance valve body 61 in the retard direction is housed inside, and the position of the advance valve body 61 is set to the engine rotation speed of the pressure adjusting device 12 as described later. It is configured so that it can be easily controlled with high precision depending on the pressure regulating characteristics for the advance angle valve element 61 is moved in the axial direction to selectively move to the pressure relief valve element passage 59. The valve body 61 for advancing is rotated around the axis according to the rotation speed of the engine and selectively communicated with the valve body passage 59 for pressure release. It is also possible.

The depressurized fuel breathing chamber 21 is formed inside the advance valve body 61 for downsizing and compactification. That is, a stepped cylindrical cavity 66 is formed inside the advance valve body 61.
66 is divided into a pressure-release fuel breathing chamber 21 and a discharge return urging chamber 68 by a piston 67 slidably fitted inside thereof. The discharge return urging chamber 68 communicates with the inlet passage 9 via the retard angle urging chamber 64, and stores the discharge return urging means 69 therein. The depressurized fuel breathing chamber 21 is connected to the advance valve body passage 62 by the breathing passage 70.

First, when the plunger 81 of the fuel injection pump 26 is driven to discharge by the fuel injection cam of the drive device 5, the fuel in the pump chamber 82 is pressurized and passes through the valve closing pressurizing fuel chamber 85 and the check valve 95. ,
It is pressed into the injected fuel pressure accumulating chamber 86.

Then, the plunger 81 is held at the discharge end position by the fuel injection cam for a certain period of time (between time points fm in FIG. 13). In this state, the check valve 95 is closed, but the valve closing pressurizing fuel chamber 85 / pump is closed. The chamber 82 and the passage 24 are maintained at a high pressure.

In this high pressure holding state, when the inlet / outlet passage 24 communicates with the depressurized fuel breathing chamber 21 through the pressure relief valve body passage 59, the advance valve body passage 62 and the breathing passage 70, the high pressure fuel on the inlet / outlet passage 24 side is communicated. The pressure causes the piston 67 to be pushed into the discharge return urging chamber 68 side, and the fuel is pressed into the depressurized fuel breathing chamber 21. As a result, the internal pressure of the valve closing pressurizing fuel chamber 85 of the pressure accumulating fuel injector 29 communicating with the inlet / outlet passage 24 is reduced, and the injection valve 88 is opened to inject fuel. At this time, the pressure in the depressurized fuel breathing chamber 21 rises by the amount of the injected fuel.

A pressure release fuel return passage 22 communicating with the inlet / outlet passage 24 is formed at a predetermined timing after the pressure release valve body passage 59 at a portion of the peripheral wall of the main shaft 7 facing the passage locus 1 of the inlet / outlet passage 24. There is.

First, after the fuel injection is completed, when the plunger 81 of the fuel injection pump 26 is actuated to the suction side, the internal pressure of the pump chamber 82 is reduced and the inlet / outlet passage 24 is also reduced in pressure.

Next, in the low pressure state of the pump chamber 82 and the inlet / outlet passage 24, the pressure-removed fuel breathing chamber 21 whose pressure has been increased is passed through the breathing passage 70, the advance valve body passage 62, and the pressure-release fuel return passage 22. By being communicated with the inlet / outlet passage 24, the discharge return urging means 69 pushes the piston 67 back to the pressure-release fuel breathing chamber 21 side, and the fuel press-fitted into the pressure-release fuel breathing chamber 21 flows through the inlet / outlet passage 24 in the low pressure state. After that, it is discharged back to the unit injector 4.

Further, an initial pressure supply passage 23, which communicates with the inlet / outlet passage 24 at a predetermined timing after the depressurized fuel return passage 22, is provided in the peripheral wall portion of the main shaft 7 facing the passage locus 1 of the inlet / outlet passage 24. There is. The initial pressure supply passage 23 communicates with the discharge passage 11 whose pressure is regulated by the pressure regulating device 12.

As shown in FIGS. 1 and 11, the unit injector 4 includes a compound shutoff valve 25 connected to the inlet / outlet passage 24, a fuel injection pump 26, a pump return pressure accumulator chamber 27, and a shutoff valve return accumulator chamber 28. And a pressure-accumulation type fuel injector 29, the fuel injection pump 26 is built in the body 83 of the injector 29, and the composite cutoff valve 25
Is further built into the plunger 81 of the fuel injection pump 26.

That is, the fuel injection pump 26 has the injection pipe 84 on one side of the body 83.
Plunger 81 fitted in parallel to and vertically movable
And a pump chamber 82 partitioned by a body 83 and a plunger 81. The plunger 81 is formed in the shape of a hollow cylinder whose both ends are closed, and the internal space thereof is the valve chamber 71 of the composite shutoff valve 25.
Are configured. A spool 72 is slidably inserted in the valve chamber 71, and the spool 72 causes the valve chamber 71 to
Accumulation chamber for pump return 27 on the bottom dead center side of the moving stroke of 72
And the shut-off valve return biasing chamber 73 on the top dead center side. The shut-off valve return bias chamber 73 is a shut-off valve return accumulator chamber 28.
Is in communication with. An inner entrance / exit passage 74 communicating with the entrance / exit passage 24 is opened at an intermediate height portion of the peripheral wall of the plunger 81, a pump communicating passage 75 communicating with the pump chamber 82 is opened at a lower portion thereof, and a shutoff valve recovery passage is provided at an upper portion thereof. A pressure accumulation communication passage 76 communicating with the dynamic pressure accumulation chamber 28 and the shutoff valve return urging chamber 73 is opened. The spool 72 is formed with a hollow hole 77 extending upward from the lower end surface thereof, and the peripheral wall of the spool 72 is a communication hole extending from the intermediate height thereof to the peripheral surface and constantly communicating with the internal inlet / outlet passage 74.
78, a pump valve hole 79 extending from its lower portion to the peripheral surface and communicating with the pump communication passage 75 when the spool 72 is located below the top dead center, and extending from the upper end portion to the peripheral surface, Accumulation passage when spool 72 is located at top dead center and bottom dead center
An accumulator valve hole 80 communicating with 76 is formed.

The pressure-accumulation fuel injector 29 includes an injection pipe 84 fitted inside the other side of the body 83, and a valve closing pressurizing fuel chamber 85 and a first pressure accumulation chamber 96 are vertically arranged in a lower half portion of the injection pipe 84. Injection pipe formed in series
One or more (two in this case) injection holes 87 are formed at the lower end of 84. The injection valve 88 that closes the connection between the first pressure accumulating chamber 96 and the injection hole 87 in the vicinity of the injection hole 87 is a needle valve, and the upper end of the valve shaft 89 is formed in the upper half of the injection pipe 84. The valve closing spring chamber 90 is made to plunge. Valve closing spring chamber 90
A valve-closing spring 91 for urging the injection valve 88 to be closed is housed in the valve. An adjusting nut 92 for adjusting the urging force of the valve-closing spring 91 is screwed to the upper end of the injection pipe 84 in an oil-tight manner. Covered by cover nut 93. The inner space 94 of the cover nut 93 is a valve closing spring chamber.
It communicates with 90, and together with this, constitutes a pressure accumulation chamber 28 for shut-off valve return. The valve closing pressurization fuel chamber 85 and the first pressure accumulation chamber 96 are partitioned by a check valve 95. The check valve 95 includes a valve seat 100 formed by enlarging a part of a valve shaft 89, an annular valve body 101 that contacts and separates from a lower surface of the valve seat 100, and a valve closing spring 102 that urges the valve to close.
Consists of. Around the middle height of the injection pipe 84, an annular second pressure accumulation chamber 97 partitioned by this and the body 83 is provided. This second pressure accumulation chamber 97 is located on the opposite side of the fuel injection pump 26. The second pressure accumulation chamber check valve 98 and the second pressure accumulation chamber pressure accumulation setting valve 99 arranged inside the body 83 are connected to the first pressure accumulation chamber 96, and together with the first pressure accumulation chamber 96 form the injected fuel pressure accumulation chamber 86. ing. The first pressure accumulating chamber 96 has a relatively small volume,
The second pressure accumulation chamber 97 has a relatively large volume.

The discharge passage 11 can be shut off by a solenoid valve 13 for emergency stop immediately before the metering device 14, and the outlet passage 49 can be shut off by a manual stop valve 15.

Next, the operation of this fuel system will be described.

As shown in Fig. 12 (1), in the initial state, the plunger
81 is located at the top dead center, and the spool 72 is located at the bottom dead center. Further, the internal pressures of the shutoff valve return pressure accumulation chamber 28, the pump return pressure accumulation chamber 27, the shutoff valve return biasing chamber 73, and the pump chamber 82 are reference pressures adjusted by the pressure adjusting device 12. Here, time point a in FIGS. 13 (1) to 13 (6) [hereinafter, simply referred to as time point a]. 13 (1) to 13 (6) is the same as the above), the supply timing determining groove portion 58b of the supply timing determining valve 18 and the inlet / outlet passage 24 are communicated with each other from time b to time b. The pressurized fuel Vin is press-fitted into the unit injector 4. First, this fuel Vin is shown in Fig. 12 (2).
As shown in FIG. 7, the spool 72 is pressed into the pump return pressure accumulating chamber 27, and the spool 72 is pushed up from the bottom dead center to the intermediate height. When the plunger 81 is lowered by the drive device 5 from the time point c after this, the internal pressures of the pump chamber 82, the pump return pressure accumulation chamber 27, the shutoff valve return biasing chamber 73, and the shutoff valve return pressure accumulation chamber 28 gradually increase. Ascend, and as shown in FIG. 12 (3), the pump chamber 82
When the amount of fuel equal to the maximum injection amount Vmax is injected into the pump return pressure accumulating chamber 27 from, that is, the amount of fuel pushed out from the pump chamber 82 in the remaining stroke of the plunger 81 becomes equal to the injected fuel Vin. When spool 72
Is raised to top dead center. Since the check valve 95 of the fuel injector 29 is closed during the downward stroke of the plunger 81 from the time point c to the time point d when the spool 72 reaches the top dead center, the fuel is not injected into the fuel injector 29. Called invalid stroke. When the spool 72 reaches the top dead center, the internal pressure of the pump chamber 82 reaches the valve opening pressure of the check valve 95 and the pump communication passage
75 and the pump valve hole 79 are shut off. Further, the pressure accumulation valve hole 80 is communicated with the pressure accumulation communication passage 76, and the internal pressure of the pump return pressure accumulation chamber 27 is corrected so as to match the internal pressures of the shutoff valve return accumulation chamber 28 and the shutoff valve return biasing chamber 73. . After this time point d, the fuel Vin is injected into the injected fuel pressure accumulating chamber 86 as the plunger 81 descends and the internal pressure of the pump chamber 82 further increases. The fuel injected into the injected fuel pressure accumulating chamber 86 is exclusively pressed into the first pressure accumulating chamber 96 until the pressure e reaches the internal pressure of the second pressure accumulating chamber 97, and the pressure exceeds the internal pressure of the second pressure accumulating chamber 97. Then, the check valve 98 for the second pressure accumulating chamber is opened and pressed into the second pressure accumulating chamber 97. Plunger 81 as shown in Fig. 12 (4)
At time f when the bottom dead center is reached, the fuel pressure stops increasing, the check valve 95 is closed, and the fuel Vin is injected into the injected fuel pressure accumulating chamber 86.
Is stored at high pressure. Then, at a predetermined time point g thereafter, the entrance / exit passage 24 is communicated with the depressurized fuel breathing chamber 21 through the pressure-release valve body 59, the advance valve body passage 62 and the breathing passage 70, and the entrance / exit passage 24 The internal pressure begins to decrease. The timing for starting the pressure reduction is set by the pressure relief valve body passage 59 communicating with the advance valve body passage 62 communicating with the inlet / outlet passage 24, and therefore is standard when the engine speed is high. It becomes faster than the normal timing, and becomes slower than the standard timing when the engine speed is slow.

Here, as the engine speed increases, the internal pressure of the advance pressure receiving chamber 63 increases in direct proportion to the engine speed, the advance valve body 61 moves in the advance direction, and the main shaft 7 rotates on the best hand side. The pressure relief valve body passage 59 and the advance valve body passage 62 communicate with each other, so that the central pressure relief valve body passage 59 and the advance valve body passage
The entrance / exit passage 24 is communicated with the advance valve body passage 62 through the pressure-release valve body passage 59 earlier than the case where 62 is communicated, so that the injection timing is advanced. Further, when the engine speed decreases, the pressure relief valve body passage 59 on the rotation lower side of the main shaft 7 and the advance valve body passage 62 communicate with each other, thereby advancing to the center pressure relief valve body passage 59. The inlet / outlet passage 24 is communicated with the advance valve body passage 62 via the pressure release valve body passage 59 later than the case where the angle valve passage 62 is communicated, and the injection timing is delayed. At an intermediate speed, the central pressure relief valve body passage 59 and the advance valve body passage 62 communicate with each other, and the passageway enters and leaves at standard timing.
24 is connected to the advance valve body passage 62 through the pressure relief valve body passage 59, and the pressure relief for injection is performed at standard timing. The advance valve body passage 62 not only selectively communicates with the respective pressure relief valve body passages 59, but also in the transitional region corresponding to the pressure relief valve body passages 59, the center and the uppermost pressure relief valve body passages. 59 or two pressure release valve body passages 59 in the center and the lowermost pressure release valve body passage 59 can be communicated at the same time. Depending on the ratio of the connection area with both pressure release valve body passages 59, the rise characteristics of the pressure release Is changing. In this manner, the position of the advance valve body 61 can be easily and highly accurately controlled depending on the pressure adjusting characteristic of the pressure adjusting device 12 with respect to the engine rotation speed, so that the advance angle can be easily and accurately controlled. become.

When the pressure release starts, the spool 72 descends from the top dead center,
From the time h when the communication between the pump valve hole 79 and the pump communication passage 75 is restored, the internal pressure of the valve closing pressurizing fuel chamber 85 suddenly decreases, and the internal pressure of the valve closing pressurizing fuel chamber 85 drops to a predetermined valve opening pressure. From the time i, the differential pressure acting on the check valve 95 overcomes the biasing force of the valve closing spring 91 and the injection valve 88 is opened.

As described above, when the spool 72 reaches the top dead center, the pressure accumulation valve hole 80 and the pressure accumulation communication passage 76 communicate with each other, so that the injector 29
When the fuel is injected into the
The rise in the internal pressure of the pump return pressure accumulator chamber 27 caused by the leak fuel to the pump is corrected, and the timing at which the pump communication passage 75 and the pump valve hole 79 communicate with each other at the time of depressurization is prevented from being delayed. Then, the occurrence of an injection timing error (delay) due to this communication delay is prevented.

Here, the pump communication passage 75 is composed of a small-diameter pump communication passage 75a and a large-diameter pump communication passage 75b which are vertically arranged, and the spool 72
Starts to descend from the top dead center and the small-diameter pump communication passage 75a communicates with the pump valve hole 79 first, so that the decrease in the internal pressure of the valve closing pressurization fuel chamber 85 is suppressed relatively slowly, and the valve opening amount of the injection valve 88 is reduced. Is suppressed to a small amount and the amount of fuel injection is suppressed to a small amount, and the reduction of the internal pressure of the injected fuel pressure accumulating chamber 86 due to the fuel injection is suppressed to be small. Then, when the spool 72 further descends and reaches, for example, a time point j corresponding to the ignition time point at the rated rotation speed, the large diameter pump communication passage 75b communicates with the pump valve hole 79, and the valve closing pressurization fuel chamber is suddenly opened. The internal pressure of 85 is reduced, the injection valve 88 is suddenly and largely opened, and a large amount of fuel is vigorously injected at high pressure. In this way, by suppressing the fuel injection amount before ignition to a small amount, it is possible to reduce the explosion sound at the time of ignition and prevent operating noise. Further, by injecting a large amount of fuel at a high pressure after ignition, it is possible to obtain the maximum thermal efficiency as long as it is allowed to reduce the operating noise. Further, since the injection pressure is a high pressure inside the injected fuel pressure accumulating chamber 86, it is possible to inject a predetermined amount of fuel amount Vin in a short time. Then, after the time point k when the internal pressure of the injected fuel pressure accumulating chamber 86 becomes equal to or lower than the setting pressure of the pressure accumulating setting valve 99 for the second pressure accumulating chamber, the pressure accumulating setting valve 99 is closed and the internal pressure of the second pressure accumulating chamber 97 is set to that value. Hold on to pressure. On the other hand, the volume of the injected fuel pressure accumulating chamber 86 communicating with the injection hole 87 is substantially reduced to that of the first pressure accumulating chamber 96, and even if a small amount of fuel is injected, the internal pressure of the first pressure accumulating chamber 96 is reduced. Then, the internal pressure is reduced to a predetermined valve closing pressure in a short time, and the injection valve 88 is closed (at a time point 1). Therefore, the injection time can be greatly shortened, which is advantageous in increasing the engine speed. At a predetermined time point m after the fuel injection ends, the fuel injection cam of the drive device 5
The cam lift of 30 starts to decrease, and the plunger 81 rises while being pressed against the rocker arm 33 of the drive device 5 by the internal pressure of the pump chamber 82. As the plunger 81 rises, the volume of the pump chamber 82 increases and the internal pressures of the pump chamber 82 and the pump return pressure accumulator chamber 27 are reduced.
The spool 72 is lowered by the pressure of 73 and the fuel is pushed from the pump return pressure accumulation chamber 27 into the pump chamber 82 until the amount of fuel equal to the maximum injection amount Vmax is injected from the pump return pressure accumulation chamber 27 into the pump chamber 82. To be

By the way, during the depressurization period after the time point g, fuel escapes from the pump return pressure accumulating chamber 27 to the depressurized fuel breathing chamber 21 side. Therefore, if the spool 72 is lowered to the bottom dead center as it is, the timing control composite is performed. The amount of fuel filled from the valve device 3 to the unit injector 4 side becomes smaller than in the initial state, and when the pressure-adjusted / metered fuel is next pressed into the unit injector 4, the spool 72 corresponds to the press-fitted amount. As a result, only a position lower than the height to be raised rises, which causes a problem that the fuel injection amount becomes insufficient.

Therefore, at time n when the spool 72 descends to the vicinity of the bottom dead center, the pressure-release fuel breathing chamber 21 has the breathing passage 70 and the pressure-release fuel returning passage.
The fuel that has been communicated with the inlet / outlet passageway 24 via 22 and has been pushed into the depressurized fuel breathing chamber 21 for depressurization is discharged back into the inlet / outlet passage 24 by the discharge return urging means 69, and further the pump return pressure accumulation pressure It is discharged back into the chamber 27 and the pump chamber 82. By discharging the fuel thus sucked back to the unit injector 4, a fuel shortage at the next injection is prevented. However, since the fuel contained in the depressurized fuel breathing chamber 21 is higher than the initial pressure, the internal pressure of the pump return pressure accumulating chamber 27 and the pump chamber 82 becomes higher than the initial state, and the spool 72 is lowered. It is moved to the top dead center side from the vicinity of the dead center. Therefore, in order to return from this state to the initial state, the initial pressure supply passage 23 is finally communicated with the inlet / outlet passage 24 at the predetermined time point o, and the shut-off valve return pressure accumulation chamber 28,
The internal pressures of the pump return pressure accumulation chamber 27, the shutoff valve return biasing chamber 73, and the pump chamber 82 are returned to the reference pressure adjusted by the pressure adjusting device 12, and the spool 72 is returned to the bottom dead center.

By the way, the internal pressures of the shut-off valve return accumulator chamber 28 and the shut-off valve return energizing chamber 73 are increased due to fuel leakage from the second accumulator chamber 97, or due to leaks to the pump return accumulator chamber 27 during depressurization. It may be decompressed. If the internal pressures of the shutoff valve return pressure accumulating chamber 28 and the shutoff valve return biasing chamber 73 increase, the spool is driven by the internal pressure of the shutoff valve returning pressure accumulating chamber 28 when fuel is injected from the metering supply device 2 next time. The rise of 72 is hindered, and the pressure accumulation volume of the pump return pressure accumulation chamber 27 is narrowed. As a result, after the fuel is press-fitted into the injector 29, when the plunger 81 rises, the pump return pressure accumulating chamber 27 to the pump chamber 82
Since the amount of fuel injected into the cylinder is insufficient, the plunger 81 cannot rise to the top dead center, resulting in operating noise. Further, if the internal pressures of the shutoff valve return accumulator chamber 28 and the shutoff valve return biasing chamber 73 are reduced, fuel is injected from the metering supply device 2 next time, and when the plunger 81 is lowered, the pump communication passage 75 and The timing at which the pump valve hole 79 is shut off is delayed, and the fuel injection amount is reduced.

Here, when the spool 72 is returned to the bottom dead center,
80 again communicates with the pressure accumulation communication passage 76, and the pressure accumulation chamber 28 for shut-off valve return movement
Since the internal pressure of the shut-off valve return urging chamber 73 is corrected to the reference pressure (initial pressure), the generation of operating noise due to the increase of these internal pressures and the occurrence of the injection amount error (decrease) due to the pressure reduction are prevented. It will be done.

<Effects of the Invention> As described above, according to the present invention, the timing at which the fuel injection operation is started is the timing at which the outlet passage of the valve box connected to the fuel injector communicates with the pressure relief valve body passage. Will depend on. Since the timing at which the outlet passage communicates with the pressure relief valve body passage is determined by the operation of the valve body that is common with the supply timing determination valve that is timed in conjunction with the crankshaft, the injection timing is high by a simple principle. Accurately determined with the crankshaft.

Further, since the valve box and the valve body of the pressure release valve and the supply timing determining valve are used in common, the structure of the valve and the fuel passage is simplified, and the drive mechanism thereof is also simplified.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram showing an overall configuration of a pressure-accumulation fuel injection device for a diesel engine according to an embodiment of the present invention.
FIG. 4 is a vertical sectional side view of the fuel metering supply device, FIG. 3 is a vertical sectional front view of the transfer pump, FIG. 4 is a vertical sectional front view of the pressure regulating device, and FIG. 5 is a vertical sectional front view of the pressure pump. 6 is a vertical sectional side view of the timing control combined valve device, FIG. 7 is a vertical front view of the timing control combined valve device, FIG. 8 is a perspective view of the common valve body, and FIG. 10 is the common valve body. FIG. 9 is a development view showing the arrangement of valve body passages, pressure release fuel return passages, and initial pressure supply passages formed on the peripheral surface of FIG. The figure is a vertical sectional view of the unit injector, and Fig. 12 (1) to 12
Fig. (4) is a schematic diagram showing the operation of the pump return pressure accumulating chamber in order, and Figs. 13 (1) to 13 (6) are operation timings, pressure changes and timings of the respective parts of the unit injector. Each timing diagram showing the relationship of the operation timing of the control combined valve device, FIG. 14 is a configuration diagram of a conventional fuel injection pump drive device and advance angle device, FIG. 15 is a conventional diesel engine pressure accumulation type fuel injection device It is an equivalent circuit diagram which shows the whole structure. 1 ... Fuel tank, 2 ... Fuel metering supply device, 17 ... Pumping passage, 18 ... Supply timing determination valve, 19 ... Injection timing setting pressure relief valve, 24 ... Exit passage, 26 ... Fuel injection Pump, 29 ……
Accumulation type fuel injector, 56 …… Valve box, 57 …… Valve disc, 58 …… Valve passage for determining supply timing, 59 …… Valve passage for pressure release, 81 ……
Plunger, 82 ... Pump chamber, 85 ... Fuel chamber for valve closing pressurization.

Claims (1)

[Claims] 1. A fuel tank (1) is provided with a fuel metering supply device (2), a pressure feeding passage (17), a supply timing determining valve (18), an outlet passage (24), and a fuel injection pump (26). Connected to the pressure accumulation type fuel injector (29), the supply timing determination valve (18) is connected to the supply timing determination valve body passage (5
By the valve opening / closing operation of 8), the pressure feeding circuit (17) is connected to the outlet passage (2
4) is intermittently connected to allow the fuel metered by the fuel quantity metering device (2) to be supplied to the fuel injection pump (26) when the valve is opened. On the other hand, when the valve is closed, the fuel discharged from the fuel injection pump (26) is configured so as to be prevented from flowing backward to the fuel metering supply device (2), and the valve box (56) of the supply timing determination valve (18) is provided. ) To the pressure passage (1
7) and the outlet passage (24) are formed, and the supply timing determination valve (18)
In a pressure-accumulation type fuel injection device for a diesel engine, the valve body (57) of which is provided with the valve body passage (58) for determining the supply timing, the valve body (57) of the supply timing determining valve (18) Of the fuel injection pump (26) and the outlet passage (24) of the supply timing determination valve (18) in the valve closing pressurization fuel chamber (85) of the fuel injector (29). Through the injection timing determining pressure relief valve (19), and the pressure relief valve (19) has the pressure relief valve body passageway (59) in the valve body (57) of the supply timing determination valve (18). The pressure release valve body passage (59) is formed independently of the supply timing determination valve body passageway (58), and the pressure release valve body passageway (59) is provided with respect to the outlet passageway (24) of the supply timing determination valve (18). Valve passage for determining the supply timing (58)
And the plunger (81) of the fuel injection pump (26) from the time when the supply timing determining valve body passage (58) is closed to the outlet passage (24). ) Is discharged to the outlet passage (24) within a period in which the pump chamber (82) of the fuel injection pump (26) is maintained at a high pressure by the discharge operation. A pressure-accumulation fuel injection device for a diesel engine, which is configured so that the passage (59) is opened.