JPS63134853A - Accumulator fuel injection device for diesel engine - Google Patents

Abstract

PURPOSE:To make the precise determination of injection time possible by the simple composition of a fuel injection device by communicating a pressure relief fuel breathing chamber with the valve closing pressure fuel chamber of a fuel injector individually through the pressure relief passage of a pressure relief valve for determining injection time and a fuel return passage. CONSTITUTION:A pressure relief fuel breathing chamber 21 communicates with the valve closing pressure fuel chamber 85 of a fuel injector 29 individually through the pressure relief passages 59 for pressure relief valve 19 for determining injection time and a fuel return passage 22 to timingly interlock the pressure relief valve 19 with a crankshaft. The passages 59 causes the fuel chamber 85 to communicate with the fuel breathing chamber 21 during fuel injection, and the fuel in the fuel chamber 85 is therefore set free into the fuel breathing chamber 21 to reduce internal pressure in the fuel chamber 85. Thus since the injection time is determined in dependence of the valve opening time of the pressure relief valve 19 opened and closed with timing control made on the crankshaft, the injection time can be simply and precisely determined. In addition to that, the fuel return passage 22 causes the fuel breathing chamber 21 to communicate with the fuel chamber 85 after the fuel injection to discharge back the fuel in the fuel breathing chamber 21 into the fuel chamber 85.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a pressure accumulation type fuel injection device for a diesel engine, and in particular, it is capable of determining injection timing with high precision without causing errors in injection amount control, and furthermore, This invention relates to a pressure accumulation type fuel injection device for a diesel engine, which has a simple structure as a whole.

As shown in FIG. It was invented as a premise. Here, the pressure accumulator fuel injector 29 is, as illustrated in FIG. 11,
After the fuel is pressurized into the injection fuel accumulating chamber 86 through the fuel chamber 85 for valve closing pressurization and the check valve 95, the fuel chamber 85 for pressurizing valve closing
When the internal pressure of the valve closing pressurizing fuel chamber 85 falls below a predetermined value, the internal pressure of the injected fuel 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. The injector 2 is configured to open the injection valve 88 and inject the fuel in the injection fuel pressure accumulation chamber 86 from the injection hole 87.
Say 9. This valve closing pressurizing fuel chamber 85 communicates with a pump chamber 82 of the fuel injection pump 26 .

<Prior Art> Conventionally, this valve-closing pressurization fuel chamber 85 opens the check valve 95 from the pump chamber 81 to pressurize fuel into the injection fuel pressure accumulation chamber 86, and then raises the plunger 81 of the fuel injection pump 26. Therefore, the pressure is reduced.

As shown in FIG. 14, the plunger 81 is raised by the cam follower 31 and the bushing rod 32 by the fuel injection cam 30 which is linked to the crankshaft C (shown in FIG. 2).
, and restricted via the rocker arm 33.

In such a conventional pressure accumulation type fuel injection device for a diesel engine, the amount of rise of the plunger 81 from the bottom dead center varies depending on the amount of fuel injected into the pump chamber 82 of the fuel injection pump 26. pump 26
A gap will be created between the parts of the drive device 5 that drives the drive device 5 or between the drive device 5 and the plunger 81. As a result, the parts of the drive device 5 or the drive device 5 and the plunger 81 hit each other, causing operational noise. Further, due to the occurrence of such a gap, the cam follower 31, bushing rod 32, rocker arm 33, etc. of the drive device 5 vibrate, causing errors in injection timing, etc., and there is a drawback that the injection timing cannot be determined with high precision.

In order to solve this problem, a technique is known in which a spring is interposed between the parts of the drive device 5 or between the drive device 5 and the plunger 81.

In this case, the occurrence of the gap as described above is eliminated by the expansion and contraction of the spring, and the occurrence of impact noise can be sufficiently prevented, but since the spring is elastically deformed, the cam follower 31 of the drive device 5,
It is not possible to sufficiently prevent vibrations of the bushing rod 32, rocker arm 33, etc., and there remains a huge dissatisfaction in terms of preventing errors in injection timing, etc., and also in the accuracy of determining the injection timing.

Prior invention> Prior to the present invention, as shown in FIG.
The fuel chamber 85 for pressurizing valve closing of the pressure accumulation type fuel injector 29 is connected to the pressure relief valve 19 for determining injection timing, and the pressure relief valve 19 is opened in synchronization with the crankshaft C to close the fuel chamber 85 for pressurizing the valve. We have invented a pressure accumulation type fuel injection device for a diesel engine that reduces the internal pressure of the valve closing pressurizing fuel chamber 85 by releasing fuel from the valve closing pressurizing fuel chamber 85. In this case, the fuel injection cam 30 is given a cam profile that continuously maximizes the cam lift amount after the injection of fuel into the fuel injector 29 ends until the fuel injection ends.

In this case, the pressure reduction timing of the valve closing pressurizing chamber 85 is as follows.
Since it is determined depending on the opening of the pressure relief valve 19, the injection timing can be accurately timed with the rotation of the crankshaft C, and the injection timing can be determined with high precision.

<Problems to be Solved by the Invention> However, in this case, when releasing fuel from the valve-closing pressurizing fuel chamber 85 for fuel injection, the pump chamber 82 communicating with the valve-closing pressurizing fuel chamber 85 Fuel also escapes from the pump, and when the plunger 81 is raised, there is insufficient fuel flowing into the pump chamber 82, making it impossible for the plunger 81 to return to top dead center, causing operational noise and errors in injection timing. It has been found that the next time fuel is supplied from the tA amount supply device 2 and press-fitted into the injector 29, the amount of fuel press-fitted into the fuel injector 29 is insufficient, resulting in a problem that the injection quantity is insufficient. Also, in order to solve such problems,
After completion of fuel injection, it is necessary to add a mechanism for replenishing the valve closing pressurizing fuel chamber 85 from a pressure regulator, for example, with an amount of fuel corresponding to the fuel that escaped during injection, which may cause the problem of a complicated configuration. Understood.

The present invention has been made in consideration of the above circumstances, and allows the injection timing to be determined easily and with high precision. To provide a pressure accumulation type fuel injection device for a diesel engine which can prevent the occurrence of operational noise, error in injection timing, and shortage of next injection amount, and has a simple configuration.

<Means for Solving the Problems> In the pressure accumulation type fuel injection device for a diesel engine according to the present invention, in order to achieve the above object, in the pressure accumulation type fuel injection device for a diesel engine having the above-mentioned prerequisite configuration, Technical measures such as:

That is, the pressure relief passage 59 of the injection timing determination pressure relief valve 19 and the fuel return passage 22 are connected to the fuel chamber 85 for closing and pressurizing the fuel injector 29 .
The depressurizing fuel breathing chamber 21 is connected to the depressurizing fuel breathing chamber 21 through the depressurizing fuel chamber 21 and the depressurizing fuel breathing chamber 21 is connected to the depressurizing fuel chamber 21 through the depressurizing fuel chamber 21 and the depressurizing fuel chamber 21 is connected to the depressurizing fuel chamber 21 through the depressurizing fuel chamber 21. The fuel chamber 85 for valve opening pressurization is communicated with the breathing chamber 21, and the fuel in the fuel chamber 85 for valve opening pressurization is released into the depressurizing fuel breathing chamber 21 to lower the internal pressure of the fuel chamber 85 for valve opening pressurization, and after the fuel injection is completed, the fuel return passage 22 is The depressurized fuel breathing chamber 21 is configured to communicate with the valve-closing pressurizing fuel chamber 85, and the fuel in the depressurizing fuel breathing chamber 21 is discharged back to the valve-closing pressurizing pressure accumulating chamber 85.

<Operation of the invention> In the above configuration, when the pressure relief valve 19 is opened in synchronization with the crankshaft C, the high pressure fuel in the valve closing pressurization fuel chamber 85 is depressurized via the pressure relief valve 19. The fuel is released into the breathing chamber 21, the internal pressure of the valve closing pressurizing fuel chamber 85 is reduced, and the injection valve 88 is opened.

Therefore, the injection timing can be determined with high accuracy based on the crankshaft. Further, after the end of fuel injection, the injected fuel breathing chamber 21 is communicated with the valve closing pressurization fuel chamber 85 via the fuel return passage 22. Fuel breathing chamber 21 during fuel injection
The pressure of the released fuel is almost the same as the internal pressure of the injection fuel accumulation chamber 86 of the injector 29, and the pressure of the fuel is high.
Although the density of the fuel injected into 1 is high, the injected fuel breathing chamber 2
1 is communicated with the valve-closing pressurizing fuel chamber 85 via the fuel return passage 22, and as the plunger 81 rises, the internal pressure of the valve-closing pressurizing fuel chamber 85 is reduced to a pressure lower than the reference pressure. Therefore, simply by connecting the injected fuel breathing chamber 21 to the valve-closing pressurizing fuel chamber 85 via the fuel return passage 22, the fuel in the depressurized fuel injection chamber 21 expands and is discharged into the valve-closing pressurizing fuel chamber 85. be returned. And with this regurgitation,
A fuel chamber 85 for pressurizing valve closing and a pump chamber 81 communicating therewith.
The amount of fuel within is fully recovered, the plunger 81 is returned to the top dead center, and insufficient injection amount during fuel injection is prevented.

<Example> Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, this diesel engine fuel system uses a metering supply device 2 to supply 5 JtJffl of fuel in a fuel tank 1 according to the engine load conditions, and uses a timing control system. 11 Supply to the unit injector 4 at a predetermined timing via the supply timing determining valve 18 of the compound valve device 3, pressurize the fuel injection pump 26 with the drive device 5 to pressurize it into the accumulator fuel injector 29, and then set the timing. The pressure relief valve 19 for injection timing setting and the advance valve 20 for injection timing adjustment of the control complex valve device 3 release the fuel in the pressurizing fuel chamber 85 of the pressure accumulation type fuel injector 29 to the pressure relief fuel breathing chamber 21 and open it. The internal pressure of the valve pressurizing fuel chamber 85 is reduced, thereby opening the injection valve 88 and injecting fuel from the injection fuel accumulation chamber 86 to the injection hole 87.
At a predetermined timing after the end of injection, the fuel in the depressurized fuel breathing chamber 21 is discharged back to the unit injector 4 through the depressurized fuel return passage 22 to recover the fuel that has been reduced in volume due to depressurization. is returned to the unit injector 4, and thereafter, the initial pressure supply path 23 of the timing control compound valve device 3 is communicated with the unit injector 4 to return the unit injector 4 to its initial state.

As shown in FIG. 2, the metering supply device 2 includes a transfump pump IO1 pressure regulating device 12 (FIG. 4), a metering device 14, and a pressure pump 16 built into a thick-walled cylindrical casing 6. The transfer pump 10 pumps fuel from the fuel tank 1 through a fuel pipe (not shown), an inlet joint 8 (FIG. 4), and an inlet passage 9 (FIG. 4), and the pressure of the fuel discharged from the transfer bomb 10 is maintained. The pressure regulating device 12 increases or decreases the fuel in accordance with the rotational speed of the engine (for example, in direct proportion), and the regulated fuel is metered in the metering device 14 in accordance with the engine load condition, and the pressure is regulated. U
Is the timing system for @I fuel using pressure pump 16? 11
1? J! It is configured to be fed under pressure to the joint venture device 3.

The transfer pump 10 has a pump chamber 34 formed at the front end of the casing 6, and inside this pump chamber 34,
As shown in FIG. 3, an inner rotor 35 fixed to the main shaft 7 passing through the casing 6 and an outer rotor 36 eccentrically meshed with the inner rotor 35 are inserted, and fuel is supplied to both rotors from the inlet passage 9 through the suction port 37. 35 and 36, and is discharged from the discharge port 38 into the discharge passage 11.

As shown in FIG. 4, the pressure regulating device 12 includes a pressure regulating plug 3 that is branch-connected to the discharge passage 11 and screwed onto the casing 6.
9, a pressure regulating valve body 40 slidably fitted therein, and a valve closing spring 41 biasing the pressure regulating valve body 40 to the valve closing position. A pressure regulating valve hole 42 is opened in the peripheral wall of the pressure regulating plug 39, and this pressure regulating valve hole 42 communicates with the inlet passage 9. The discharge pressure of the transfer pump 1o changes quadratically in response to the rotational speed of the engine, and in response to this discharge pressure, the pressure regulating valve body 40 is urged in the valve opening direction against the valve closing spring 41. Ru. In this pressure regulating device 12, by appropriately setting the opening area of the pressure regulating valve hole 42 with respect to the amount of displacement of the pressure regulating valve body 40 from the closed position, the pressure regulating device 12 can be connected to the inlet passage 9 in response to the rotational speed of the engine. The internal pressure of the discharge passage 11 is increased or decreased in exact proportion to the rotational 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 engine rotational speed is not limited to being directly proportional; for example, the rate of increase in the internal pressure of the discharge passage 11 decreases as the speed increases. Alternatively, the rate of increase in the internal pressure of the discharge passage 11 may be increased as the speed increases. A drain vibe joint 43 is connected to the pressure regulating plug 39 to connect a drain pipe (not shown) for discharging leaked fuel from between the pressure regulating plug 39 and the pressure regulating valve body 42.

As shown in FIG. 2, the metering device 14 includes a metering piston 44 fitted into the front half of the main shaft 7 so as to be movable forward and backward. This iIi1m piston 44 is moved in the direction of fuel reduction (in this case, forward) by the thrust of the flyweight 45 against the pressure of the governor spring 46 in accordance with the rotational speed of the engine.
It is designed to be driven by A metering valve hole 47 that communicates with the discharge passage 11 is opened in the inner peripheral surface of the main shaft 7, and a metering valve body passage 48 is recessed in the circumferential surface of the metering piston 44 over its entire circumference. has been done. By moving the metering piston 44 forward and backward in response to the rotational speed of the engine, the connecting area between the metering valve hole 47 and the metering valve body passage 48 is changed to correspond to the rotational speed of the engine. The flow rate is regulated and the fuel is led to the pressure pump 16 via the main shaft 7 and the outlet passage 49 formed in the casing 6.

The pressure of the governor spring 46 is controlled by the speed setting lever 50.
The settings can be changed by rotating the .

As shown in FIGS. 2 and 5, the pressure pump 16 includes a plunger 53 that is driven via a swing arm 52 by a drive cam 51 formed on the circumferential surface of the main shaft 7, and a plunger 53 that moves forward and backward as the plunger 53 moves back and forth. A pump chamber 54 whose volume changes. Further, the pressure pump 16 is configured so that the stroke of the plunger 53 can be changed and set by a torque characteristic setting device 55 to obtain pump characteristics corresponding to various torque characteristics suitable for the application of the engine.

In order to achieve miniaturization and compactness, the timing control compound valve device 3 is incorporated into the metering supply device 2 as shown in FIG. 2 and FIGS. 6 to 8. This timing control composite valve device 3 essentially consists of supply timing determining valves 1 that can be provided independently, as shown in FIG.
8, a pressure relief valve 19 for setting injection timing, an advance valve 20 for adjusting injection timing, and a pressure relief fuel breathing chamber 21 are integrally combined in order to achieve downsizing and compactness.

That is, as shown in FIGS. 2 and 6 to 8, the supply timing determining valve 18 that determines the timing of pumping fuel to each unit injector 4 and the pressure relief valve 19 for setting the injection timing are located in the rear half of the casing 6. A common valve body 56 consisting of the main shaft 7 and a common valve body 57 consisting of the rear half of the main shaft 7 are provided. A pressure feeding passage 17 led out from the pressure pump 16 of the metering supply device 2 is opened at the rear end of the inner peripheral surface of the casing 6, and an inlet/outlet passage to each unit injector 4 (
Distribution passages 24 are opened at equal intervals in the circumferential direction. A communication groove 58a of a valve body passage 58 for supply timing determination is recessed over the entire circumference in the part of the main shaft 7 facing the pressure feeding passage 17, and the passage path of the inlet/outlet passage 24 starts from one point in the circumferential direction of the communication groove 58a. A supply timing determining groove portion 58 extends in the axial direction along the circumferential surface up to the portion of the outer circumferential surface of the main shaft 7 opposite to l.
b is taken out consecutively. Then, the main shaft 7 rotates in conjunction with a crankshaft (not shown), and the supply timing determining groove portion 58b communicates with the inlet/outlet passage 24 by overlapping inside and outside, so that the supply timing determining groove portion 58b communicates with the inlet/outlet passage 24 from the pressure feeding passage 17 via the valve body passage 58 for determining the supply timing. Pressure-regulated and metered fuel is forced into the inlet/outlet passage 24. In addition, a pressure relief valve element of a pressure relief valve 19 that communicates with the entrance and exit passage 24 at a predetermined timing after the supply timing determining groove 58a is provided on the outer circumferential surface of the main shaft 7 facing the passage path i of the entrance and exit passage 24. Passage 59 is opened.

The rear half of the main shaft 7, which is the common valve body 57 of the supply timing determining valve 18 and the pressure relief valve 19 for setting the injection timing, also serves as a valve box for the advance valve 20 for adjusting the injection timing. That is,
A cylindrical advance valve chamber 60 is formed concentrically within the rear half of the main shaft 7, and an advance valve body 6 is formed in this advance valve chamber 60.
1 is housed so that it can move forward and backward in the axial direction of the main shaft 7. The valve body 57 has three pressure relief valve body passages 59 whose opening positions on the inner circumferential surface are different in the rotational direction and the axial direction of the main shaft 7.
is formed so as to pass through its peripheral wall, and the advancing valve body 61
One of the three pressure relief valve body passages 59 is provided on the circumferential surface of the
An advance valve body passage 62 is formed that communicates with one or two adjacent valves. The advance valve body passage 62 is constituted by a circumferential groove recessed over the entire circumference of the advance valve body 61 .

The advance valve chamber 60 is divided into an advance pressure receiving chamber 63 and a retard biasing chamber 64 by an advance valve body 61 . Then, the pressure in the advance pressure receiving chamber 63 is adjusted by the pressure regulating device 12 in the discharge passage 1.
1, and the retard angle biasing chamber 64 is communicated with the inlet passage 9 which is maintained at a substantially constant pressure.Inside the retard angle biasing chamber 64, an advance angle valve body 61 is arranged in the retard direction. A retard energizer stage 65 for energizing is housed, and an advance valve body 61 is installed as described later.
The position of the engine is configured to be able to be controlled with high precision depending on the pressure regulation characteristics with respect to the rotational speed of the engine.

Here, the advance valve body 61 is moved in the axial direction to selectively communicate with the pressure relief valve body passage 59, but the advance angle valve body 61 is moved in the axial direction to selectively communicate with the pressure relief valve body passage 59. It is also possible to configure the valve body 61 to rotate around the axis and selectively communicate with the pressure relief valve body passage 59.

The depressurizing fuel breathing chamber 21 is formed inside the advance valve body 61 in order to achieve miniaturization and compactness. That is, a stepped cylindrical cavity 66 is formed inside the advance valve body 61.
This cavity 66 is formed into a depressurizing fuel breathing chamber 21 and a discharge biasing chamber 6 by a piston 67 slidably fitted inside the cavity 66.
It is divided into 8. The retardation biasing chamber 68 communicates with the inlet passage 9 via the retardation biasing chamber 64, and accommodates a retrieval biasing means 69 therein. The pressure relief fuel breathing chamber 21 is communicated with the advance valve body passage 62 through a breathing passage 70 . When the inlet/outlet passage 24 communicates with the depressurizing fuel breathing chamber 21 via the pressure relief valve body passage 59, the advance valve body passage 62, and the breathing passage 70, the piston 67 is moved by the fuel pressure in the inlet/outlet passages 24. The fuel is pushed into the discharge biasing chamber 68 side, and the fuel is pressurized into the depressurized fuel breathing chamber 21. As a result, the internal pressure of the valve-closing pressurizing fuel chamber 85 of the pressure accumulation type fuel injector 29 communicating with the inlet/outlet passage 24 is reduced, and the injection valve 87 is opened to inject fuel.

A depressurizing fuel return passage 22 is formed in a portion of the peripheral wall of the main shaft 7 facing the passage path l of the inlet/outlet passage 24, and communicates with the inlet/outlet passage 24 at a predetermined timing after the pressure relief valve body passage 59. There is. Then, the depressurized fuel breathing chamber 21 is communicated with the inlet/outlet passage 24 via the breathing passage 70 , the advance valve body passage 62 , and the depressurized fuel return passage 22 , so that the discharge biasing means 69 pushes the piston 67 . The fuel that is pushed back toward the depressurized fuel breathing chamber 21 and pressurized into the depressurized fuel breathing chamber 21 is discharged back to the unit injector 4 through the inlet/outlet passage 24.

Further, an initial pressure supply passage 23 is recessed in a portion of the peripheral wall of the main shaft 7 facing the passage locus l of the inlet/outlet passage 24, and communicates with the inlet/outlet passage 24 at a predetermined timing after the depressurization fuel return passage 22. There is. This initial pressure supply path 23 is connected to the pressure regulating device 1
It communicates with a discharge passage 11 whose pressure is regulated by 2.

As shown in FIGS. 1 and 11, the unit injector 4 includes a compound cutoff valve 25 connected to the inlet/outlet passage 3, a fuel injection pump 26, a pressure accumulation chamber 27 for double-action pump operation, and a pressure accumulation chamber 28 for double-operation cutoff valve. and a pressure accumulator fuel injector 29, the fuel injection pump 26 is built into the body 83 of the injector 29, and the compound cutoff valve 25 is further built into the plunger 81 of the fuel injection pump 26.

That is, the fuel injection pump 26 has a plunger 81 fitted on one side of the body 83 in parallel with the injection pipe 84 and movable up and down, and a pump chamber 82 partitioned by the body 84 and the plunger 81. The plunger 81 is formed into a hollow cylindrical shape with both ends closed, and its internal space constitutes the valve chamber 71 of the composite shutoff valve 25. A spool 72 is slidably inserted into this valve chamber 71.
As a result, the valve chamber 71 is divided into a pressure accumulation chamber 27 for pump return movement on the bottom dead center side of the movement stroke of the spool 72, and a biasing chamber 73 for shutoff valve return movement on the top dead center side.

This biasing chamber 73 for shutoff valve double operation is the pressure accumulator chamber 28 for double operation of the shutoff valve.
, is communicated with. An internal inlet/outlet passage 74 communicating with the inlet/outlet passage 24 is opened at the intermediate height of the peripheral wall of the plunger 81, a pump communication passage 75 communicating with the pump chamber 82 is opened at the lower part thereof, and a shutoff valve is connected at the upper part thereof. Dynamic pressure storage chamber 2
8 and the pressure accumulation communication passage 7 that communicates with the biasing chamber 73 for double operation of the shutoff valve.
6 is open. The spool 72 is formed with a hollow hole 77 extending upward from its lower end surface, and the peripheral wall of the spool 72 is provided with a communication hole 78 extending from an intermediate height to the peripheral surface and always communicating with the internal entrance/exit passage 74. A pump valve hole 79 extends from the lower part to the circumferential surface and communicates with the pump communication path 75 when the spool 72 is located below the top dead center; A pressure accumulation valve hole 80 is formed which communicates with the pressure accumulation communication passage 76 when the vehicle is located at the top dead center and the bottom dead center.

The pressure accumulation type fuel injector 29 includes an injection pipe 84 fitted inside the other side of the body 83, and a fuel chamber 85 for valve closing pressurization and a first pressure accumulation chamber 96 are arranged in the lower half of the injection pipe 84, which are arranged vertically. One or more (here, two) injection holes 87 are formed in a series at the lower end of the injection pipe 84 . The injection valve 88 that cuts off the connection between the first pressure accumulation chamber 96 and the injection hole 87 near the injection hole 87 is composed of a needle valve, and the upper end of the valve shaft 89 is formed in the upper half of the injection pipe 84. Valve closing spring chamber 90
Let's rush into it. A valve-closing spring 91 that biases the injection valve 88 to close is housed in the valve-closing spring chamber 90 .
An adjustment nut 92 that adjusts the biasing force is covered by a cover nut 93 that is screwed onto the upper end of the injection pipe 84 in an oil-tight manner. The internal space 94 of the cover nut 93 is the valve closing spring chamber 9
1, and together with this, constitutes a pressure accumulation chamber 28 for double operation of the shutoff valve. Valve closing pressurization fuel chamber 85 and first pressure accumulation chamber 96
and are separated by a check valve 95. This check valve 95 includes a valve seat 100 formed by enlarging the diameter of a portion of the valve shaft 89, an annular valve body 101 that approaches and separates from the plate surface of the valve seat 100, and a valve closing spring 102 that urges the valve to close. Consisting of Further, a second pressure accumulation chamber 97 in an annular shape is provided around the middle height portion of the injection pipe 84 and the body 83, and this second pressure accumulation chamber 97 is located on the opposite side from the fuel injection pump 26. It is connected to the 1I royal house 96 by a second pressure accumulation chamber check valve 98 and a second N pressure chamber pressure accumulation setting valve 99 arranged inside the body 83, and forms the injection fuel pressure accumulation chamber 86 together with the first pressure accumulation chamber. . still,
The first pressure accumulation chamber 96 is formed to have a relatively small volume, and the second pressure accumulation chamber 97 is formed to have a relatively large volume.

The discharge passage 11 can be shut off by an emergency stop solenoid valve 13 immediately before the metering device 12.
Further, the outlet passage 49 can be shut off by a manual stop valve 15.

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

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 double-acting pressure storage chamber 28, the pump double-acting pressure storage chamber 27, the shutoff valve double-acting biasing chamber 73, and the pump chamber 82 are at the reference pressure regulated by the pressure regulating device 12. Here, time a in FIGS. 13(1) to 13(6) [hereinafter simply referred to as time a]. The same applies to the other points in FIG. 13(1) to FIG. 13(6)] to point b, the supply timing determining groove 58a of the supply timing determining valve 18 and the inlet/outlet passage 24 are communicated, and metering/adjustment is performed. The pressurized fuel Vin is press-fitted into the unit injector 4. This fuel Vin is first pressurized into the pump double-acting pressure storage chamber 27 as shown in FIG. 12(2), and the spool 72 is pushed up from the bottom dead center to an intermediate height. When the plunger 81 is lowered by the drive device 5 from the subsequent time point C,
The internal pressures of the pump chamber 82, the pressure accumulation chamber 27 for double action of the pump, the biasing chamber 73 for double action of the cutoff valve, and the pressure storage chamber 28 for double action of the cutoff valve gradually rise, and as shown in FIG. 12(3), the pressure in the pump chamber 82
When a level of fuel equal to the maximum injection 11V δX is injected into the pump reciprocating pressure accumulator 27 from When they are equal, the spool 72 is raised to top dead center. During the downward stroke of the plunger 81 from time C to time d when the spool 72 reaches the top dead center, the check valve 95 of the fuel injector 29 is closed and no fuel is pressurized into the fuel injector 29. This is called an invalid stroke. Spool 72
When the pump reaches the top dead center, the internal pressure of the pump chamber 82 reaches the opening pressure of the check valve 95, and the pump communication passage 75 and the pump valve hole 79 are cut off. Further, the pressure accumulation valve hole 80 is communicated with the pressure accumulation communication passage 76, and the internal pressure of the pump double-action pressure accumulation chamber 27 is corrected to match the internal pressure of the shutoff valve double-stroke pressure storage chamber 28 and the shutoff valve double-stroke biasing chamber 73. . After time d, as the plunger 81 descends and the internal pressure of the pump chamber 82 further increases, the fuel Vin is pressurized into the injected fuel pressure accumulation chamber 86. The fuel pressurized into the injected fuel accumulator 86 is exclusively pressurized into the first pressure accumulator 98 until the time e when its pressure reaches the internal pressure of the second pressure accumulator 97, and the fuel is pressurized into the second pressure accumulator 98.
When the internal pressure exceeds 7, the second pressure accumulation chamber check valve 98 is opened and the second pressure accumulation chamber 97 is also pressurized. When the internal pressure of the second pressure accumulation chamber 97 exceeds the set pressure of the pressure accumulation setting valve 99, the pressure accumulation setting valve 9
9 is opened, and check valve 98 is closed. Figure 12 (4
), at time point f when the plunger 81 reaches the bottom dead center, the fuel pressure stops rising, the check valve 95 is closed, and the fuel Vin is accumulated at high pressure in the injected fuel pressure accumulation chamber 86. Then, at a predetermined time g thereafter, the inlet/outlet passage 24 is communicated with the pressure relief fuel breathing chamber 21 via the pressure relief valve body passage 59, the advance valve body passage 62, and the breathing passage 70, and the inlet/outlet passage 24 The internal pressure begins to decrease. The timing for starting this pressure reduction is set by communicating the pressure relief valve body passage 59, which communicates with the advance valve body passage 62, with the inlet/outlet passage 24, so it is standard when the engine rotation speed is high. The timing will be faster than the standard timing, and if the engine speed is slow, it will be slower than the standard timing.

That is, when the engine rotational speed increases, the internal pressure of the advance pressure receiving chamber 63 increases in direct proportion to the engine rotational speed, and the advance valve body 61 is moved in the advance direction, causing By communicating the pressure relief valve body passage 59 and the advance valve body passage 62, the pressure in the inlet/outlet passage 24 is reduced earlier than when the central pressure relief valve body passage 59 and the advance valve body passage 62 communicate with each other. It communicates with the advance valve body passage 62 via the extraction valve body passage 59, so that the injection timing can be advanced.

Furthermore, when the engine speed becomes low, the pressure relief valve passage 59 and the advance angle valve passage 62 on the rotationally downstream side of the main shaft 7 are
By communicating with each other, the entrance/exit passage 2 is opened later than when the center pressure relief valve body passage 59 and the advance valve body passage 62 communicate with each other.
4 is communicated with the advance valve body passage 62 via the pressure relief valve body passage 59, so that the injection time is delayed. At intermediate speeds, the central pressure relief valve passage 59 and the advance angle valve passage 6
2 are in communication, the inlet/outlet passage 24 is communicated with the advance valve element passage 62 via the pressure relief valve element passage 59 at standard timing, and pressure relief for injection is performed at standard timing. The advance valve body passage 62 not only selectively communicates with each pressure relief valve body passage 59, but also communicates with the central and most advanced pressure relief valve body passages in the transient region of the corresponding rotational speed region. 59 or the two pressure relief valve body passages 59, the center and the lowest pressure relief valve body passages 59, can be communicated simultaneously, and both the positive pressure relief valve body passages 59
The rise characteristics of pressure relief change depending on the ratio of the connection area with the In this way, the position of the advance valve body 61 can be easily and highly accurately controlled depending on the pressure regulation characteristics of the pressure regulator 12 with respect to the engine rotational speed, so the advance timing can be easily and highly accurately controlled. become.

From the time h when the spool 72 gradually descends from the top dead center and the communication between the pump valve hole 79 and the pump communication passage 75 is restored, the internal pressure of the fuel chamber 85 for valve closing pressurization decreases rapidly, and the predetermined valve opening pressure is reached. From time point i, when the internal pressure of the fuel chamber 85 for valve closing pressurization has dropped to the point 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 mentioned above, when the spool 72 reaches the top dead center,
Since the pressure accumulation valve hole 80 and the pressure accumulation communication passage 76 are communicated with each other, the internal pressure of the pump double-action pressure storage chamber 27 is increased due to leakage of fuel from the pump chamber 82 to the pump double-stroke pressure storage chamber 27 when fuel is pressurized into the injector 29. is corrected, and the timing at which the pump communication passage 75 and the pump valve hole 79 communicate with each other during pressure relief is prevented from being delayed. This prevents an error (delay) in injection timing from occurring due to this communication delay.

Here, the pump communication passage 75 is composed of a small diameter pump communication passage 75B and a large diameter pump communication passage 75b arranged vertically, and when the spool 72 starts to descend from the bottom dead center, the small diameter pump communication passage 75a first connects to the pump valve hole 79. The injection valve 88 is connected to
The valve opening amount is limited to a small value, the fuel injection amount is suppressed to a small amount, and the decrease in the internal pressure of the injected fuel pressure accumulation chamber 86 due to fuel injection is suppressed to a small value. Then, when the spool 72 further descends and reaches, for example, time j corresponding to the ignition time at the rated rotational speed, the large diameter pump communication passage 75b communicates with the pump valve hole 79, and the valve suddenly closes and the pressurizing fuel chamber is closed. The internal pressure of 85 is reduced, and the injection valve 88 is suddenly opened widely.
A large amount of fuel is injected with high pressure and force. In this way, by suppressing the amount of fuel injected before ignition to a small amount, it is possible to reduce the explosion noise at the time of ignition and prevent operational noise. In addition, by injecting a large amount of fuel at high pressure after ignition, it is possible to obtain the maximum thermal efficiency allowed while reducing operating noise. Furthermore, since the internal pressure of the injection fuel accumulating chamber 86 is high, a predetermined amount of the fuel Vin can be completely injected in a short time. and,
The internal pressure of the injected fuel pressure accumulation chamber 86 is set to the second pressure accumulation chamber pressure accumulation setting valve 9.
After the point in time when the pressure falls below the set pressure of 9, this pressure accumulation setting valve 9
9 is closed, and the internal pressure of the second pressure accumulating chamber 97 is maintained above its set pressure. On the other hand, the volume of the injected fuel pressure accumulation chamber 86 communicating with the injection hole 87 is substantially reduced to that of the first pressure accumulation chamber 96, and even if a small amount of fuel is injected, the internal pressure of the first pressure accumulation chamber 96 is greatly reduced. This internal pressure is reduced to a predetermined valve closing pressure in a short period of time, and the injection valve 88 is closed (time 1).
Therefore, the injection time can be significantly shortened, which is advantageous in increasing the speed of the engine. At a predetermined time point m after the fuel injection ends, the cam lift of the fuel injection cam 30 with a drive value of 25 begins to decrease, and the internal pressure of the pump chamber 82 causes the plunger 81 to move toward the rocker arm 33 of the drive device 5.
It rises while being pressed against.

As the plunger 81 rises, the volume of the pump chamber 82 is expanded, and the internal pressure of the pump chamber 82 and the pressure accumulation chamber 27 for double action of the pump is reduced, so that the spool 72 is The pump is lowered, and fuel is forced into the pump chamber 82 from the pump reciprocating pressure accumulator 27 until an amount of fuel equal to the maximum injection amount Vmax is pressurized from the pump reciprocating pressure accumulator 27 into the pump chamber 82 .

By the way, during the pressure relief period after time g, fuel is released from the pump double-acting pressure accumulation chamber 27 to the pressure relief fuel breathing chamber 21 side, so if the spool 72 is lowered to the bottom dead center, the timing control complex The amount of fuel injected from the valve device 3 into the unit injector 4 side becomes smaller than the initial state, and then the pressure is regulated and IN! When the spool 72 is pressurized into the unit injector 4, the spool 72 rises only to a lower position than it should rise in response to the amount of fuel injected, which causes operational noise and errors in injection timing control, and also causes problems during the next fuel injection. Inconveniences such as insufficient quantity will occur.

Therefore, at time point n when the spool 72 descends to the vicinity of the bottom dead center, the depressurized fuel breathing chamber 21 is communicated with the inlet/outlet passage 24 via the breathing passage 70 and the depressurized fuel return passage 22, and the discharge urging means 69 As a result, the fuel that had been forced into the depressurizing fuel breathing chamber 21 for depressurization is discharged back into the inlet/outlet passage 24, and is further discharged into the pump reciprocating pressure accumulating chamber 27 and the pump chamber 82. By spitting out the fuel sucked out in this way back to the unit injector 4, occurrence of fuel shortage during the next injection is prevented. However, since the pressure of the fuel contained in the depressurized fuel breathing chamber 21 is higher than the initial pressure,
The internal pressure becomes higher than the initial state, and the spool 72 is moved slightly from the vicinity of the bottom dead center toward the top dead center. Therefore, in order to return from this state to the initial state, finally at a predetermined time point 0, the initial pressure supply path 23 is communicated with the inlet/outlet passage 24, and the shutoff valve double-acting pressure accumulator 28, the pump double-acting pressure accumulator 27, and the shutoff valve The internal pressures of the double-acting biasing chamber 73 and the pump chamber 82 are returned to the reference pressure regulated by the pressure regulating device 12, and the spool 72 is returned to the bottom dead center.

By the way, the internal pressures of the shutoff valve double-acting pressure accumulator 28 and the shutoff valve double-actuate biasing chamber 73 are increased due to fuel leak from the second pressure accumulator 97, or due to leakage to the pump double-acting pressure accumulator 27 when the pressure is released. It is possible that the pressure is reduced. If the internal pressures in the pressure accumulation chamber 28 for shutoff valve return operation and the biasing chamber 73 for return operation of the cutoff valve increase, the spool 72 will be increased by the internal pressure of the pressure accumulation chamber 28 for return operation of the cutoff valve when fuel is pressurized from the iPI quantity supply device 2 next time. , and the pressure accumulation volume of the pressure accumulation chamber 27 for pump double action is narrowed. As a result, after fuel is pressurized into the injector 29, when the plunger 81 rises, the amount of fuel pressurized from the pump reciprocating pressure accumulation chamber 27 into the pump chamber 82 is insufficient, and the plunger 81 cannot rise to the top dead center. Operation noise will be generated. Furthermore, if the internal pressures of the shutoff valve double-acting pressure accumulation chamber 28 and the shutoff valve double-acting energizing chamber 73 decrease, fuel will be pressurized from the metering supply device 2 next time, and when the plunger 81 is lowered, the pump communication passage 75 will be The timing at which the pump valve hole 79 is shut off is delayed, and the amount of fuel injection is reduced.

Here, when the spool 72 is returned to the bottom dead center, the pressure accumulation valve hole 80 communicates with the pressure accumulation communication passage 76 again, and the internal pressures of the pressure accumulation chamber 28 for shutoff valve return operation and the biasing chamber 73 for cutoff valve return operation are set to the reference pressure (
Since the internal pressure is corrected to the initial pressure, it is possible to prevent the occurrence of operational noise due to an increase in these internal pressures and the occurrence of an error (reduction) in the injection amount due to a decrease in pressure.

<Effects of the Invention> As described above, according to the pressure accumulation type fuel injection device for a diesel engine according to the present invention, the injection timing is adjusted to the opening timing of the pressure relief valve for determining the injection timing, which opens and closes in time with the crankshaft. Since the injection timing is determined depending on the injection timing, the injection timing can be easily determined with high precision. In addition, in order to reduce the internal pressure of the valve-closing pressurizing pressure accumulator, the fuel released from the valve-closing pressurizing pressure accumulating chamber, the fuel injection pump, and the pump reciprocating pressure accumulating chamber is released from the depressurizing fuel breathing chamber after the valve-closing pressurization is applied. Since it is discharged back to the pressure accumulator, the fuel injection pump, and the pump reciprocating pressure accumulator, it is possible to prevent insufficient rise of the plunger and the occurrence of operating noise and errors in injection timing due to this, and it is also possible to prevent the next injection fuel shortage from occurring. . Moreover, the configuration is simple, and the operation of the depressurizing fuel breathing chamber is performed using the difference in fuel pressure between the pressure accumulating chamber for closing the valve and the depressurizing fuel breathing chamber. Another advantage is that no energy source is required.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram showing the overall configuration of a pressure accumulation type fuel injection device for a diesel engine according to an embodiment of the present invention, and FIG.
FIG. 3 is a longitudinal sectional view of the fuel metering supply device, FIG. 3 is a longitudinal sectional front view of the transfer pump, FIG. 4 is a longitudinal sectional front view of the pressure regulating device, and FIG. 5 is a longitudinal sectional front view of the pressure pump.
Fig. 6 is a longitudinal sectional side view of the timing control fi compound valve device, Fig. 7 is a longitudinal sectional front view of the timing control compound valve device, /θ Fig. 8 is a perspective view of the common valve body, and Fig. 1 is its A developed view showing the arrangement of each valve body passage, depressurizing fuel return passage, and initial pressure supply passage formed on the circumferential surface of the common valve body. Figure 1 shows a portion of the advance angle adjustment valve body removed. FIG. 11 is a vertical sectional view of the unit injector, FIGS. 12 (1) to 12 (4) are schematic diagrams showing the operation of the pump reciprocating pressure accumulator chamber, and FIG. 13 is a perspective view. Figure (1)
~Figure 13 (6) is a timing diagram showing the relationship between the operation timing of each part of the unit injector, pressure change, and operation timing of the timing control compound valve device, Fig. 14
The figure is a configuration diagram of a conventional fuel injection pump drive device and advance device. l...Fuel tank, 2...Fuel quantity supply device, 1
9...Pressure relief valve for determining injection timing, 20...Advance valve for adjusting injection timing, 21...Pressure relief fuel breathing chamber, 26...Fuel injection pump, 29...Pressure accumulation type fuel injector , 85...
・Pressure accumulation chamber for pressurizing valve closing, C...Crankshaft. Patent applicant: Kubota Iron Works Co., Ltd.
Professor Hisashi Kitatani: ,'j
: ” 1.), Figure 3, Figure 4, Figure 5, Figure 6, Figure 10, Figure 12 (1) Figure 12 (2) B\n0 Figure 14

Claims (1)

[Claims] 1. A pressure accumulation type diesel engine in which a fuel tank 1 is connected in communication with a pressure accumulation type fuel injector 29 via a fuel metering supply device 2, a supply timing determining valve 18, and a fuel injection pump 26. In the fuel injection device, the depressurized fuel breathing chamber 21 is communicated with the valve closing pressurizing fuel chamber 85 of the fuel injector 29 via the depressurizing passage 59 of the injection timing determining depressurizing valve 19 and the fuel return passage 22, respectively. The pressure relief valve 19 is timed and linked to the crankshaft C, and at the time of fuel injection, the pressure relief passage 59 communicates the fuel chamber 85 for valve closing pressurization with the pressure relief fuel breathing chamber 21, so that the pressure relief valve 19 communicates with the pressure relief fuel chamber 85 for valve opening pressurization. The fuel is released to the depressurized fuel breathing chamber 21 to lower the internal pressure of the valve-open pressurizing fuel chamber 85, and after fuel injection is completed, the fuel return passage 22 releases the depressurized fuel breathing chamber 21 to the valve-closing pressurizing fuel chamber 85. A pressure accumulation type fuel injection device for a diesel engine, characterized in that the fuel in the pressure relief fuel breathing chamber 21 is discharged back to the valve closing pressurization pressure accumulation chamber 85 through communication.