JPH0735762B2 - Accumulation type two-stage injection type fuel injection device for diesel engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation two-stage injection fuel injection device for a diesel engine, and more particularly, to improve the accuracy of fuel injection amount and injection timing control and to reduce the size thereof. The present invention relates to a pressure-accumulation two-stage injection fuel injection device for a diesel engine, which can be realized.

<Prior Art> A conventional pressure-accumulation two-stage injection type fuel injection device for a diesel engine is, for example, as shown in FIGS. 8 and 9, a pressure-accumulation fuel injector 7 and a fuel for supplying the fuel to the pressure-accumulation fuel injector 7. A pressure adjustment amount supply device 1, an injection pump 6 that pressurizes the supplied fuel and press-fits it into a pressure accumulation type fuel injector 7, and an injection start command device 2 that commands the start of injection of the pressure accumulation type fuel injector 7. I have it.

The accumulator fuel injector 7 is a fuel injector that injects fuel that has been accumulated and stored at a high pressure such as 700 to 1200 atm.
Fuel is accumulated in the fuel pressure accumulation chamber 73 via the 716 and the check valve 63, and when the injection valve 72 is opened, fuel is injected from the fuel pressure accumulation chamber 73 through the injection valve 72 and the injection port 74 into the combustion chamber. It is supposed to do.

The fuel pressure accumulating storage chamber 73 includes a main pressure accumulating chamber 731 and a sub pressure accumulating chamber 732, and a non-return outward path 733 and a throttle return path 735 that connect the two, and the non-return outward path 733 connects the sub accumulator chamber 732 to the main accumulator chamber 731. A check valve 734 for preventing backflow is provided, and a pressure setting valve 736 for keeping the internal pressure of the auxiliary pressure accumulating chamber 732 at a certain level or more is interposed in the throttle return path 735. The injection valve 72 is urged to open by the internal pressure of the main pressure accumulating chamber 731, and is urged by the internal pressure of the valve closing pressurizing chamber 716 and the elastic force of the valve closing spring 717. .

The injection pump 6 exerts a pump function when the fuel is injected into the pressure-accumulation fuel injector 7, and therefore has a function as an inlet check valve for preventing backflow to the upstream side, the shuttle valve 5, the plunger chamber 61, The plunger 62 and the check valve 63 for preventing backflow from the downstream side are provided.

In this shuttle valve 5, after the fuel is injected into the pressure-accumulation fuel injector 7, the valve closing pressurizing chamber 716 is moved to the pre-injection depressurizing chamber 9.
Is formed integrally with the pre-injection control valve 8 which is communicated with the injection pump 6, and also has a function of an inlet check valve of the injection pump 6 and a pressurizing chamber for closing the valve.
It also has the function of a main injection control valve that connects the 716 to the injection command decompression chamber 23 via the injection command valve 21 and the advance control valve 22 of the injection start command device 2. That is, as shown in FIG. 4, the shuttle valve 5 includes a plunger 62 and a valve case.
51 (hereinafter, referred to as a plunger 62 when describing the function of the injection pump 6, and referred to as a valve case 51 when describing the function of the shuttle valve 5), a shuttle valve body 52, and FIGS. The valve-accumulation chamber 53 shown in FIG. 9 is provided.

As shown in FIG. 4, the valve case 51 is formed into a hollow cylindrical shape whose both ends are closed, and the hollow portion inside thereof forms a shuttle valve chamber 511. The shuttle valve body 52 is slidably inserted into the shuttle valve chamber 511. The shuttle valve body 52 is formed in a cylindrical shape with one end (upper end) closed, and the shuttle valve chamber 511 is a primary side that penetrates the hollow portion 521 of the shuttle valve body 52 and the intermediate portion of the valve case 51 and the shuttle valve body 52. Upstream fuel pressure adjustment amount supply device 1 via inlets and outlets 512 and 522
And the injection start command device 2 are connected in parallel. Further, the shuttle valve chamber 511 is connected to the plunger chamber 61 via a shuttle valve opening 523 formed in the lower portion of the shuttle valve body 52 and a secondary side inlet / outlet 513 formed in the lower portion of the valve case 51. . The shuttle valve body pressurizing chamber 514 partitioned from the shuttle valve chamber 511 by the shuttle valve body 52 and the shuttle valve body 52 in the valve case 51 has a shuttle valve body when the shuttle valve body 52 is located at the top dead center and its vicinity. Communication valve hole formed on the upper part of 52
524 or through the primary inlet / outlet 522 and the communication passage 515 formed in the valve case 51, it is communicated with the hollow portion 521 of the shuttle valve body 52, while it is always communicated with the valve opening accumulator chamber 53.

As shown in FIGS. 8 and 9, the valve opening pressure accumulating chamber 53 is divided into a first pressure accumulating chamber 531 and a second pressure accumulating chamber 533 which are directly connected to the shuttle valve opening pressurizing chamber 514. First and second accumulators 5
31 and 533 are freely communicated with each other through a communication passage 534.

As shown in FIG. 4, the pre-injection control valve 8 is provided with pre-injection depressurizing passages 81 and 83 which penetrate the peripheral wall of the valve case 51 below the secondary inlet / outlet 513 and the shuttle valve port 523. The pre-injection decompression chamber 9 is composed of the pre-injection valve opening 82 formed in the lower surface of the shuttle valve body 52 at the lower side thereof.
It is molded between the Ben case 51 and the shuttle valve body 52 by partially recessing the peripheral surface of the. The pre-injection decompression chamber 9 is further communicated with the shuttle valve chamber 511 via a pressure relief throttle passage 10 '.

In this conventional example, in the initial state, the plunger 62 is located at the top dead center, the shuttle valve body 52 is located at the bottom dead center, and the shuttle valve port 523 is communicated with the plunger chamber 61. Then, when the fuel supply from the fuel pressure adjusting device 1 is started, the internal pressure of the shuttle valve chamber 511 rises, and the spool valve body 52
Starts to rise, and when the metered fuel is injected, the shuttle valve element 52 temporarily stops at a height between bottom dead center and top dead center.
After that, the plunger 62 is pushed down and the shuttle valve chamber 51
1 and the internal pressure of the plunger chamber 61 increases, the shuttle valve body 5
22 further rises, the shuttle valve port 523 is blocked from the plunger chamber 61 and the secondary side inlet / outlet port 513, and the shuttle valve 5 is opened. After the shuttle valve 5 is closed, the shuttle valve element 52 is pre-injected by the pre-injection valve port 82 of the pre-injection control valve 8 due to the difference between the internal pressures of the shuttle valve opening pressurizing chamber 514 and the shuttle valve chamber 511. The pressure reducing passages 81 and 83 are raised until they are located on the valve closing side, that is, on the upper side. Further, after the shuttle valve 5 is closed, the plunger 62 is further pushed down,
The internal pressure of the plunger chamber 61 is increased to open the check valve 63, and the fuel is pressed into the injection pressure accumulating chamber 73. Then, when the internal pressure of the valve closing pressurizing chamber 716 and the internal pressure of the injection pressure accumulating chamber 73 become substantially the same, the check valve 63 is closed and preparation for fuel injection is completed.

After that, the injection command valve 21 of the injection start command device 2 is opened to set the shuttle valve chamber 511 of the shuttle valve 5 to the injection command decompression chamber 2
3, the internal pressure of the shuttle valve chamber 511 is reduced by the internal pressure of the shuttle valve pressurizing chamber 514, and the shuttle valve body 52
Moves to the valve opening side, that is, to the lower side. By this movement, first, the pre-injection control valve 8 is opened to close the pressurizing chamber for valve closing.
The internal pressure of 716 is slightly released to the pre-injection decompression chamber 9, the injection valve 72 is slightly pushed open by the valve opening force of the pressure of the main pressure accumulating chamber 731, and the fuel in the main pressure accumulating chamber 731 is pre-injected from the injection port 74. First, next, as the pre-injection proceeds, the valve opening force decreases, the injection valve 72 is closed with the valve closing force, and the pre-injection ends. Then, the fuel in the auxiliary pressure accumulating chamber 732 is pressed into the main pressure accumulating chamber 731 from the throttle return path 735 to increase the valve opening force, while the shuttle valve 5 is opened and the internal pressure of the valve closing pressurizing chamber 716 is changed to the shuttle valve. 5 is largely released to the injection command decompression chamber 23 via the injection command valve 21, and the injection valve 72 is largely pushed open by the valve opening force formed by the pressure of the main pressure accumulation chamber 731, so that the sub pressure accumulation chamber 732 and the main pressure accumulation chamber 732 are opened. 7
The fuel in 31 starts main injection from the injection port 74, and thereafter, as the main injection proceeds, the valve opening force decreases and the injection valve 72 is closed by the valve closing force, so that the main injection ends. It The pressure released to the pre-injection decompression chamber 9 is the pressure in the throttle passage.
It is gradually discharged to the shuttle valve chamber 511 via 10 '.

<Problems to be Solved by the Invention> In this conventional example, since the shuttle valve opening pressurizing chamber 514 is communicated with the valve opening pressure accumulating chamber 53, the valve opening pressurizing with respect to the movement amount of the shuttle valve body 52 is performed. Pressure fluctuations in chamber 514 are less sensitive than pressure fluctuations in shuttle valve chamber 511. And the following problems are derived from this.

(A) First, there is a disadvantage in improving the control accuracy of the fuel injection amount.

That is, the fuel supply from the fuel pressure adjustment amount supply device 1 is completed, the plunger 62 is pushed down, and the shuttle valve chamber 511.
When the internal pressure of the shuttle valve body 52 increases, the moving speed of the shuttle valve element 52 in the upward direction, that is, the moving speed toward the valve closing side becomes faster, and an error in the fuel supply amount caused by a slight timing error (the shuttle valve chamber 511 when the plunger 62 descends). The error in the amount of fuel returned to the side and the error in the amount of fuel trapped in the plunger chamber 61 and the valve closing pressurization chamber 716 become relatively large.
Therefore, it is disadvantageous in improving the control accuracy of the fuel injection amount.

(B) Two-stage injection may not be possible.

That is, after the shuttle valve 5 is closed, the movement amount by which the shuttle valve body 52 is further moved to the valve closing side until the internal pressure of the shuttle valve pressurizing chamber 514 and the internal pressure of the shuttle valve chamber 511 are balanced, that is, However, the additional lift amount becomes relatively small, and in an extreme case, the pre-injection control valve 8 may remain open, and the two-stage injection may not be possible.

(C) Furthermore, if it is attempted to reliably realize the two-stage injection, the size becomes large.

That is, in order to additionally lift the valve valve body 5 until the pre-injection control valve 8 is closed, it is necessary to increase the total volume of the shuttle valve opening pressurizing chamber 514 and the valve closing accumulating chamber 53. However, the problem of large size occurs.

(D) In addition, it is disadvantageous in improving the control accuracy of the injection start timing.

That is, after the shuttle valve opening 523 is closed, the shuttle valve opening pressurizing chamber 514 that balances the internal pressure of the shuttle valve chamber 511.
Since the internal pressure of is also relatively low, the pressure reduction rate of the internal pressure of the shuttle valve chamber 511 becomes relatively slow after the injection command valve 21 is opened after the injection of fuel into the pressure-accumulation fuel injector 7 is completed. Since the movement speed of the shuttle valve body 52 becomes slow, the timing error of opening the pre-injection valve port 82 and the shuttle valve port 523 becomes relatively large with respect to a slight pressure error, and the opening of the pre-injection control valve 8 is started. The timing and the opening timing of the shuttle valve 5 vary greatly, which is disadvantageous in improving the control accuracy of the start timing of the pre-injection and the main injection.

Therefore, the shuttle valve-opening pressurizing chamber 514 and the valve-opening accumulating chamber 53 are communicated with each other via a throttle passage to make the pressure fluctuation of the valve-opening pressurizing chamber 514 sensitive to the movement amount of the shuttle valve body 52. Tried to do. However, in this case, it has been found that the following problems occur.

(E) The output may be reduced.

That is, when the pressure fluctuation of the valve opening pressurizing chamber 514 becomes sensitive to the movement amount of the shuttle valve body 52 and the plunger 62 is pushed down to increase the internal pressure of the shuttle valve body 511, the shuttle valve body 52 rises. Direction, that is, the moving speed toward the valve closing side becomes too slow and the amount of fuel returned to the shuttle valve chamber 511 increases, and the fuel from the plunger chamber 61 and the valve closing pressurizing chamber 716 to the pressure accumulating fuel injector 7 flows. There is a risk that the press-fitting amount will decrease and output will decrease.

(F) Further, the effect of the two-stage injection may not be produced.

That is, after the shuttle valve port 523 is closed, the pressure in the shuttle valve opening pressurizing chamber 514 is gradually released from the throttle passage to the valve opening pressure accumulating chamber 53, and the shuttle valve body 52 is additionally lifted to the valve closing end position. You can, but after this, the plunger
When the internal pressure of the shuttle valve chamber 511 starts to decrease by opening the injection command valve 21 while 62 is held at the bottom dead center, the pressure in the shuttle valve opening pressurizing chamber 514 becomes relatively high. Therefore, the shuttle valve body 52 descends too fast, and the interval between the pre-injection and the main injection becomes narrower. In particular, the main injection is started before the ignition of the pre-injected fuel, and the fuel due to the two-stage injection is injected. The improvement effect will not occur.

The present invention has been made in consideration of the above circumstances,
An object of the present invention is to provide a pressure-accumulation two-stage injection type fuel injection device for a diesel engine, which is capable of preventing output reduction, improving accuracy of injection timing control and injection amount control, and downsizing the device. .

<Means for Solving the Problems> The pressure-accumulation two-stage injection fuel supply device for a diesel engine according to the present invention is premised on the following configuration shown in FIG. 1, for example.

That is, the fuel pressure adjusting amount supply device 1 is arranged in the shuttle valve chamber 51 of the push-back shuttle valve 5 of the plunger chamber 62 of the injection pump 6.
1, shuttle valve port 523, plunger chamber 61 of injection pump 6,
The pressurizing chamber 716 for closing the injection valve 72 of the pressure accumulating fuel injector 7, the check valve 63, the main pressure accumulating chamber 731, and the injection valve seat 723 are sequentially connected to the injection port 74, and the shuttle for pushing back the plunger. The valve 5 pressurizes the shuttle valve body 52 to the valve opening side by the stored pressure of the opening / closing pressure accumulating chamber 53 via the shuttle valve pressurizing chamber 514, whereas it presses the shuttle valve body 52 to the valve closing side by the fuel pressure of the shuttle valve chamber 511. The injection valve 72 is configured to pressurize, and the injection valve 72 is pressed toward the valve closing side by the valve closing force that is the combined force of the spring force of the valve closing spring 717 and the pressure of the valve closing pressurizing chamber 716, and the main pressure accumulating chamber 731. It is configured to press the valve to the valve-opening side by the valve-opening force consisting of the pressure of the above, and the main pressure-accumulating chamber 731 is made to communicate with the auxiliary pressure-accumulating chamber 732 at least through the throttle return path 735, and the valve closing pressurizing chamber 716 is pre-injected. The pre-injection decompression chamber 9 is communicated via the valve 8, and the pre-injection valve port 82 of the pre-injection control valve 8 is provided so as to be movable together with the shuttle valve body 52. At the end of the operation of the valve body 52 toward the valve closing side, the pre-injection valve port 82 is configured to be closed after the shuttle valve port 7 is closed, and the pre-injection valve port 511 is arranged in the shuttle valve chamber 511 via the injection command valve 21 for injection command decompression. Based on the fact that the chamber 23 is in communication and the injection command valve 21 opens, the shuttle valve chamber 51
The pressure in 1 is released to the injection command decompression chamber 23. First, the pre-injection valve port 82 is opened and the pressure in the valve closing pressurization chamber 716 is released to the pre-injection decompression chamber 9 and closed. The valve force is reduced, the injection valve 72 is pushed open by the valve opening force formed by the pressure of the main pressure accumulating chamber 731, the fuel in the main pressure accumulating chamber 731 starts to be pre-injected from the injection port 74, and then the pre-injection proceeds. The valve opening force decreases and the injection valve
72 is closed by the valve closing force and pre-injection is completed, and the fuel in the auxiliary pressure accumulating chamber 732 is pressed into the main pressure accumulating chamber 731 from the throttle return path 735 to increase the valve opening force. 523 is opened, the internal pressure of the valve closing pressurizing chamber 716 is rapidly released from the shuttle valve chamber 511 to the injection command depressurizing chamber 23, the valve closing force is rapidly reduced, and the injection valve 72 is opened by the valve opening force. The fuel in the sub pressure accumulation chamber 732 and the main pressure accumulation chamber 731 is pushed again to start main injection from the injection port 74, and thereafter, as the main injection proceeds, the valve opening force decreases and the injection valve 92 closes with the valve closing force. The present invention is premised on a pressure-accumulation two-stage injection type fuel injection device for a diesel engine which is configured to be valved to terminate main injection, and in order to achieve the above object, the following means are taken. There is.

That is, the valve-opening pressure accumulation chamber 53 of the shuttle valve 5 is formed by communicating the first pressure-accumulation chamber 531 with the second pressure-accumulation chamber 532 through the throttle passage 532, and the first pressure-accumulation chamber 531 is connected to the shuttle-valve pressurization chamber. 514 connected to the throttle valve passage 52 when the shuttle valve element 52 is operated toward the valve closing side.
The throttling action reduces the pressure rising speed of the second pressure accumulating chamber 532 to be lower than the pressure rising speed of the first accumulating chamber 531. Even after the shuttle valve port 523 is closed, the pressure of the first pressure accumulating chamber 531 is reduced.
As the pressure gradually decreases from 532 to the second pressure accumulating chamber 532, the shuttle valve body 52 moves from the closed position of the shuttle valve port 523 to the closed position of the pre-injection port 82 to the valve closing end position. In the additional lift stroke, the pressure in the shuttle valve chamber 511 is closed and the valve is additionally moved.

<Operation> According to the present invention, the valve-opening pressure-accumulating chamber 53 of the shuttle valve 5 includes the first pressure-accumulating chamber 531 and the second pressure-accumulating chamber 533 that communicates with the first pressure-accumulating chamber 531 via the throttle passage 532. Since the chamber 531 is communicated with the shuttle valve opening pressurizing chamber 514, the fuel supply from the fuel pressure adjusting amount supply device 1 to the injection pump 6 is completed, and the plunger 5
62 is pushed down and the internal pressure of the shuttle valve chamber 511 rises,
When the shuttle valve body 52 is moved in the valve closing direction, the throttle passage
By the throttling action of 532, the pressure increase rate of the second pressure accumulation chamber 533 is made lower than the pressure increase rate of the first pressure accumulation chamber 531.
Pressurization chamber 51 for opening the shuttle valve for movement of the shuttle valve body 52
Internal pressure rise of 4 is due to shuttle opening valve pressurizing chamber 514 and valve opening accumulating chamber
It becomes less sensitive than the case where a throttle passage is interposed between the first pressure accumulating chamber 531 and the second pressure accumulating chamber 531 and the pressure increasing speed of the first pressure accumulating chamber 531 and the second pressure accumulating chamber It becomes more sensitive than the conventional example in which the pressure rise rate of 533 is the same.

Therefore, the pressurizing chamber 514 for opening the shuttle valve and the first accumulating chamber 531
Shuttle valve disc 52
When the shuttle valve chamber 511 pressure is optimized, that is, when the maximum injection amount is taken as an example, the shuttle valve port 523 closes when the check valve 63 opening pressure becomes the same. Can be done. As a result, on the other hand, the shuttle valve chamber 511 is closed while the internal pressure is lower than the opening pressure of the check valve 63, so that the ineffective stroke of the plunger 62 is increased and the fuel injected into the pressure accumulating fuel injector 7 is injected. It is possible to prevent the amount of fuel from decreasing, and on the other hand, delaying the closing of the shuttle valve 5 causes the fuel to flow backward to the upstream side of the shuttle valve 5 and the amount of fuel to be injected into the pressure accumulating fuel injector 7 becomes insufficient. Can be prevented.

Further, after the shuttle valve port 523 is closed, the first pressure accumulating chamber 531
As the pressure in the shuttle valve chamber 511 gradually decreases from the throttle passage 532 to the second pressure accumulation chamber 533, the pressure in the shuttle valve chamber 511 causes the shuttle valve element 52 to move from the closed position of the shuttle valve port 523 to the pre-injection valve. Although it is possible to additionally move through the closing position of the mouth 82 to the valve closing end position, since the internal pressure of the second pressure accumulating chamber 533 becomes smaller than the internal pressure of the first pressure accumulating chamber 531 at the start of the additional movement, First accumulator 531 at the start of additional movement
The total volume of the first pressure accumulation chamber 531 and the second pressure accumulation chamber 533 required to obtain the same additional lift amount can be reduced as compared with the conventional example in which the internal pressure of the second pressure accumulation chamber and the internal pressure of the second pressure accumulation chamber 533 are equal. .

Then, after this, when the injection command valve 21 is further opened, the internal pressure of the shuttle valve pressurizing chamber 514 is higher than the conventional pressure, so that the depressurizing speed of the shuttle valve chamber 511 is higher than that of the conventional example. Further, the movement speed of the shuttle valve body 52 to the valve opening side is increased, and the variation in the pre-injection start timing and the main injection start timing can be reduced.

In the present invention, the method for forming the throttle passage 532 that connects the first pressure accumulation chamber 531 and the second pressure accumulation chamber 533 is not particularly limited,
For example, the throttle passage 532 can be configured by a screw fitting gap, the throttle passage 532 can be configured by a machined hole, and the throttle passage 532 can be configured by a precision machined hole such as a laser machined hole. Among these, it is recommended to construct the throttle passage 532 with a machined hole that is economically inexpensive and can be formed relatively accurately.

<Effects of the Invention> The present invention is configured and operates as described above, so that the following effects can be obtained.

(A) The control accuracy of the fuel injection amount can be improved.

That is, the valve-opening pressure accumulating chamber is composed of the first pressure accumulating chamber and the second pressure accumulating chamber communicating with the first pressure accumulating chamber via the throttle passage, and the first pressure accumulating chamber is communicated with the shuttle valve-opening pressurizing chamber. Of the volume of the valve opening pressure accumulating chamber, the volume that directly affects the pressure change rate of the shuttle valve opening pressurizing chamber with respect to the movement of the shuttle valve body is limited to a small volume excluding the second pressure accumulating chamber. As a result, the pressure change rate of the shuttle valve pressurizing chamber with respect to the movement of the shuttle valve body is made larger than before, the moving speed of the shuttle valve body is reduced, and the shuttle valve chamber is closed before the shuttle valve opening is closed. It is possible to reduce the control error of the amount of fuel returned and the amount of fuel sealed in the plunger chamber and the valve closing pressure chamber.
Therefore, the control error of the amount of fuel press-fitted into the pressure accumulation type fuel injector becomes small, and the control accuracy of the fuel injection amount can be improved.

(B) Secure the additional lift of the shuttle valve body to ensure 2
Stage injection can be performed.

That is, since the pressure of the first pressure accumulating chamber is gradually released from the throttle passage to the second pressure accumulating chamber after closing the shuttle valve port, the shuttle valve opening pressurizing chamber is gradually depressurized and the shuttle valve chamber pressure is applied to the shuttle valve opening pressure chamber. The valve can be reliably additionally moved from the closed position of the shuttle valve opening to the closing end position of the pre-injection valve opening. Therefore, it is possible to surely prevent the pre-injection valve opening from being left open so that the two-stage injection cannot be performed.

(C) The size can be reduced.

That is, since the pressure of the second pressure accumulating chamber is lower than the pressure of the first pressure accumulating chamber when the shuttle valve port is closed,
When the shuttle valve opening is closed, the pressure in the first accumulator and the second
As compared with the conventional example in which the pressure in the pressure accumulating chamber is the same, the volume of the second pressure accumulating chamber required to obtain the same additional lift amount can be reduced, and the overall size of the device can be reduced.

(D) Furthermore, the accuracy of controlling the injection start timing can be improved.

That is, since the pressure in the shuttle valve chamber when the shuttle valve port is closed is higher than before, the pressure in the valve-opening pressurizing chamber that balances this pressure becomes higher, and the injection command valve is opened to open the shuttle valve chamber. The pressure reduction speed of the shuttle valve chamber when releasing the pressure to the injection command decompression chamber becomes larger than that of the conventional example, the error range of the start timing of the pre-injection and the main injection can be reduced, and the pre-injection start timing and the main injection start timing The control accuracy can be improved.

Further, the following effects can be obtained as compared with the case where the throttle passage is provided between the shuttle valve opening pressure chamber and the valve opening pressure accumulation chamber.

(E) Output reduction can be prevented.

That is, compared with the case where a throttle passage is provided between the shuttle valve opening pressurizing chamber and the valve opening pressure accumulating chamber, the pressure change rate of the valve opening pressurizing chamber becomes smaller with respect to the movement amount of the shuttle valve body. ,
The movement speed of the shuttle valve body toward the valve closing side becomes faster, and the amount of fuel returned to the shuttle valve chamber before the shuttle valve opening is closed can be suppressed to an appropriate amount. It is possible to prevent the fuel injection amount from the pressure chamber into the pressure accumulating fuel injector to decrease, and to prevent the output from decreasing due to the insufficient fuel injection amount.

(F) The effect of the two-stage injection is not impaired.

That is, the pressure in the shuttle valve chamber when the shuttle valve port is closed is lower than that in the case where the throttle passage is provided between the shuttle valve opening pressure chamber and the valve opening pressure accumulation chamber, and therefore, the pressure is balanced with this pressure. Since the pressure in the valve opening pressurization chamber is low, the pressure reduction speed in the shuttle valve chamber can be reduced when the injection command valve is opened to release the pressure in the shuttle valve chamber to the injection command pressure reduction chamber.
The time interval between the start timing of the pre-injection and the start timing of the main injection can be made sufficiently long, and the main injection can be started after the fuel that has been pre-injected is reliably ignited. It is possible to eliminate the possibility of impairing efficiency improvement.

(E) Furthermore, the following effects can be obtained by forming the throttle passage with a machined hole.

The throttle passage can be formed at a significantly lower cost than the case where the throttle passage is formed by precision processing such as laser processing or plasma processing.

Further, as compared with the case where the throttle passage is formed by the screw fitting gap, the processing error range can be reduced and the control accuracy of the fuel injection amount can be further improved.

Further, the processing error range can be made smaller than the case where the throttle passage is formed by the screw fitting gap, the additional lift amount can be made small, and the shuttle valve can be made compact.

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

FIG. 1 is an equivalent circuit diagram of a pressure-accumulation type two-stage injection type fuel injection device for a diesel engine according to an embodiment of the present invention.

As shown in this figure, this device comprises a fuel tank T, a metering unit M, and a unit injector U. The metering unit M includes a fuel pressure adjustment amount supply device 1 and an injection start command device 2. It has been incorporated.

On the other hand, the fuel pressure adjusting / quantity supplying device 1 supplies the fuel whose pressure is adjusted to the injection pump 6 at a predetermined timing, so that the fuel pump 11 pumps out the fuel from the fuel tank T.
The pressure of the fuel discharged from the fuel pump 11 is adjusted by the pressure adjusting device 12 in accordance with, for example, the engine speed, and further adjusted by the pressure adjusting device 13 in accordance with the load state of the engine, and then the pressure pump 14 The fuel supplied from the pressure pump 14 is pressurized by the fuel supply valve 15 and is timing-controlled by the fuel supply valve 15 to be supplied to the injection pump 6. On the other hand, the fuel pressure adjustment amount supply device 1 returns the internal pressure of each part of the injection pump 6 to the initial state before the fuel injection is finished and the fuel supply to the next injection pump 6 is started. In order to do so, a pressure transmission path 16 for initial pressure adjustment that bypasses the metering device 13, the pressure feed pump 14, and the fuel supply valve 15 and connects the injection pump 6 to the pressure regulator 12.
An initial pressure adjusting opening / closing valve 17 for opening / closing the initial pressure adjusting pressure transmission path 16 at a predetermined timing is provided.

Further, the injection start command device 2 includes an injection command valve 21, an advance control valve 22 and an injection command decompression chamber 23 which are sequentially connected to the unit injector U, and an injection command decompression chamber 23 which advances the control valve 22 and an injection command. The discharge pressure reducing chamber 23 is bypassed and connected to the unit injector U, and a discharge return passage 24 and a discharge return valve 25 that opens and closes the discharge return passage 24 at a predetermined timing are provided.

FIG. 2 is a vertical sectional view of the unit injector U. As shown in the figure, the body 3 of the unit injector U has an edge filter 4 for filtering fuel and an injection pump 6
And the pressure-accumulation fuel injector 7 are assembled, and the edge filter 4 is inserted into a circular hole-shaped filter chamber 31 opened to the lower surface on one side of the body 3.

The injection pump 6 has a circular hole-shaped plunger chamber 61 that is open to the upper surface at the center of the body 3, a plunger 62 that is fitted in the plunger chamber 61 so that it can move forward and backward, and a shuttle valve 5 that opens and closes the upstream side of the plunger chamber 61. , The pressure accumulating fuel injector 7 is incorporated into the accumulating fuel injector 7 from the injection accumulating chamber 73 to the plunger chamber 61.
And a check valve 63 for preventing backflow to the.

FIG. 3 is an enlarged vertical sectional view of the shuttle valve 5. As shown in the figure, the shuttle valve 5 is integrally provided with a pre-injection control valve 8 for controlling pre-injection, a pre-injection decompression chamber 9, and a pressure relief valve 10 of the pre-injection decompression chamber 9. That is, the valve case 51 is composed of a cylindrical plunger 62 whose upper and lower ends are closed, and a shuttle valve body 52 that is inserted into the valve case 51 so as to be able to move forward and backward.
The space within 51 is partitioned by the shuttle valve body 52 into a shuttle valve chamber 511 below the shuttle valve body 52 and a shuttle valve pressurizing chamber 514 above the shuttle valve body 52. Shuttle valve body 5
2 is formed in a cylindrical shape with the upper end closed, and its hollow portion 521
Is always connected to the shuttle valve chamber 511. Further, at the intermediate height between the valve case 51 and the shuttle valve body 52, the hollow portion 521 of the shuttle valve body 52 is always provided with a filter chamber (reference numeral 31 in FIG. 2).
Primary inlet / outlet 512/522 is formed to communicate with (shown by). A shuttle valve port 523, which is essential for the shuttle valve 5, is formed in the lower part of the shuttle valve body 52, and the valve case 5 is correspondingly formed.
A shuttle valve chamber 511 is provided on one side of the lower part of 1 with a shuttle valve opening.
Secondary side entrance / exit 5 communicating with the plunger chamber 61 via 523
13 are formed.

The outer peripheral surface of the valve case 51 is recessed between the outer peripheral surface of the valve case 51 opposite to the secondary inlet / outlet 513 and the inner peripheral surface of the plunger chamber 61. A decompression chamber 9 for pre-injection extending to and is formed. The pre-injection decompression chamber 9 is connected to the plunger chamber 61 via the pre-injection control valve 8 on the one hand, and is connected to the hollow portion 521 of the shuttle valve body 52 via the pressure relief valve 10 on the other hand. The pre-injection control valve 8 includes a pair of pre-injection depressurizing passages 81 and 83 provided below the secondary inlet / outlet 513 of the valve case 51 so as to face each other with the shuttle valve body 52 interposed therebetween, and the shuttle valve port 523. And a pre-injection valve port 82 formed of a circumferential groove formed on the outer peripheral surface of the shuttle valve body 5 below, and the pressure relief valve 10 is hollow through the primary side inlet / outlet 522 when the shuttle valve body 52 is located at the bottom dead center. The pressure relief valve opening which is communicated with the hollow portion 521 through the shuttle valve opening 523 when the shuttle valve body 52 is located at the top dead center.
Equipped with 101.

Instead of the pressure relief valve 10, for example, a pressure relief throttle passage 10 'is formed in the valve case 51 as shown in FIG. 4, so that the pre-injection decompression chamber 9 is constantly released. It may be configured to communicate with the hollow portion 521 via the shuttle valve port 523.

The shuttle valve body 52 is biased to the valve closing side by the internal pressure of the shuttle valve chamber 511, and is biased to the valve opening side by the internal pressure of the shuttle valve opening pressurizing chamber 514. Pressurization chamber for shuttle valve opening 514
Is communicated with the hollow portion 521 of the shuttle valve body 52 through the communication valve port 524 formed in the upper part of the shuttle valve body 52 when the shuttle valve body 52 moves to the top dead center, and the shuttle valve body 52 is at the bottom dead center. When one side of the outer peripheral surface of the valve case 51 is recessed when it is moved to, the communication passage 515 formed between the valve case 51 and the peripheral surface of the plunger chamber 61 and the communication valve opening 524 are connected. Hollow part
It is designed to communicate with the 521. The shuttle valve opening pressurizing chamber 514 communicates with a valve opening pressure accumulating chamber (indicated by reference numeral 53 in FIGS. 1 and 2) via a communication passage 515 and a communication passage 32 formed in the body 3. Has been done.

As shown in FIG. 1 and FIG. 2, the valve-opening pressure accumulating chamber 53 includes a first pressure accumulating chamber 531, a second pressure accumulating chamber 533, and a throttle passage 532 that connects these to each other. 531 is a passage
The shuttle valve opening pressurizing chamber 514 is communicated via 515 and 32.

As shown in FIG. 2, the first pressure accumulating chamber 531 is also used as a valve closing spring chamber formed in the injection valve driving portion 71 of the pressure accumulating fuel injector 7 described later, and the second pressure accumulating chamber 533 is An adjusting plug 718 for adjusting the spring force of a valve closing spring 717 arranged in the valve closing spring chamber and a stopper bolt 719 screwed into the adjusting plug 718.
And a cap 713 screwed onto the upper end of the body 711 of the injection valve drive unit 71 so as to cover them. Then, the throttle passage 532
Is formed in the upper portion of the stopper bolt 719 by cutting.

As shown in FIGS. 1 and 2, the pressure accumulation type fuel injector 7
Is an injection valve drive unit 71, an injection valve 72, and an injection pressure accumulating chamber 73.
And an injection port 74 formed at the tip of the injection pipe 721 of the injection valve 72.
It has and.

As shown in FIG. 2, the injection valve drive unit 71 has a body 711 fitted in the body 3 of the unit injector U,
A spindle 712 is inserted in the center of the body 711 so as to be able to move back and forth in the axial direction. A valve closing spring chamber that also serves as the first pressure accumulating chamber 531 is formed in the upper half portion of the body 711, and a valve closing pressurizing chamber 716 and the valve chamber 7 of the check valve 63 are formed in the lower portion.
14 and a part of the main pressure accumulation chamber 731 of the injection pressure accumulation chamber 73 are sequentially formed.

The spindle 712 includes the first pressure accumulating chamber 531 to the valve closing pressurizing chamber.
716 Body 711 penetrates, and further, valve chamber 714 and main accumulator chamber 731
Is extended through the inside of the injection pipe 721 of the injection valve 72,
A piston 715 is provided which is enlarged in the outer diameter direction in the valve closing pressurizing chamber 716 or the valve chamber 714. Check valve 63 is this piston 7
It is provided with a cylindrical check valve body 631 that is received on the lower surface of 15 and a valve closing spring 632 that biases this upward, and by closing the valve from the valve closing pressurizing chamber 716 on the upstream side thereof. It is configured to shut off the main accumulator 731. The spindle 712 is a valve closing pressurizing chamber received on the upper surface of the piston 715.
Closing spring that receives pressure of 716 and upper end of spindle 712
The valve closing force of the spring force of 717 urges the valve in the valve closing direction, and the pressure of the main accumulator 731 received on the lower surface of the piston 715 urges the valve in the valve closing direction.

The injection valve 72 includes an injection pipe 721, an injection valve body 722 connected to a lower end portion of a spindle 712 extending therein, and an injection pipe 72.
An injection valve seat 723 formed to face the injection valve body 722 is provided on the inner surface of the tip portion of 1.

Further, the injection pressure accumulating chamber 73 is a small-capacity main pressure accumulating chamber 731 formed around the spindle 712 from the check valve 63 of the body 711 to the injection valve seat 723 of the injection pipe 721 of the injection valve 72.
And the body 3 of the unit injector U and the injection valve drive section
A large-volume sub-accumulation chamber 732 formed in an annular shape is provided between the body 711 and the body 711, and the main pressure-accumulation chamber 731 and the sub-accumulation chamber 732 form a non-return outward path 733 formed in the body 3. Return trip
Communicated by 735. A secondary pressure accumulator 73 is provided in the check outward path 733.
A check valve 734 for preventing backflow from 2 to the main accumulator 731 is interposed, and a pressure setting valve 736 for maintaining the internal pressure of the auxiliary accumulator 732 at a certain level or more is interposed in the throttle return path 735.

FIG. 5 is a timing chart for one entire cycle of the operation of this device, and FIG. 6 is a timing chart showing the pressure change of each part of the shuttle valve 5 particularly at the fuel injection stage.

Next, the operation of this device will be described with reference to FIGS. 5 and 6.

In this device, the operations of fuel supply, fuel injection, pre-injection, main injection, and return to the initial state are periodically repeated from the initial state.

That is, as shown in FIG. 5, in the initial state, in the initial state, the fuel supply valve 15 and the initial pressure setting opening / closing valve 17 of the fuel pressure adjusting / supplying device 1, the injection command valve 21 and the discharge return valve of the injection start commanding device 2 are shown.
25 is closed, the plunger 62 is located at the top dead center, the shuttle valve body 52 is located at the bottom dead center, the shuttle valve opening 52, the pressure relief valve opening 101 and the communication valve opening 524 are opened, and the pre-injection valve The port 82 is closed, and the check valve 63, the injection valve 72, and the check valve 73 of the injection pressure accumulating chamber 73 are closed.
4 and the pressure setting valve 736 are closed. Then, the pressure P ₀ of the shuttle valve chamber 511 and the pressure chamber 5 for opening the shuttle valve 5
14 and pressure P ₀₁ of the first pressure accumulating chamber 531, pressure P ₀₁ of the second pressure accumulating chamber 533
_02, the internal pressure P ₁ of the plunger chamber 61 and the valve-closing pressure chamber 716, the pressure P ₄ for pre-injection vacuum chamber 9 is equal to a predetermined minimum pressure, the pressure in the main accumulator 731 for injection than this The pressure becomes a predetermined high pressure, and the pressure in the sub-accumulation chamber 732 is a higher pressure set by the pressure setting valve 736, for example, 700 to 1200 atm.

At the fuel supply stage, only the fuel supply valve 15 of the fuel pressure adjustment control supply device 1 is opened, and the other initial pressure setting opening / closing valve 17, the injection command valve 21 and the discharge return valve 25 of the injection start command device 2 are opened. Is closed. Then, the pressure-adjusted fuel is pressed into the hollow portion 521 of the shuttle valve body 52, the shuttle valve chamber 511, the plunger chamber 61, and the valve closing pressure chamber 716 by the pressure pump 14. Since the pressure P ₀ of the shuttle valve chamber 511 rises after the point a at which the press-fitting starts, the shuttle valve body is adjusted so that the pressure P ₀ of the shuttle valve chamber 511 and the pressure P _{01 of the} shuttle valve pressurizing chamber 514 are balanced.
52 starts moving to the valve closing side, communication valve port 524, pressure relief valve port 1
After 01 is closed, the fuel supply valve 15 is closed at a predetermined timing to end the fuel supply (time b). Since the pressure P ₀ of the shuttle valve chamber 511 and the pressure P ₀₁ of the shuttle valve pressurizing chamber 514 during this period are relatively slow to increase, the first pressure accumulating chamber 531 and the second pressure accumulating chamber 533 are connected. The throttling effect of the throttling passage 532 is hardly exhibited, and the second accumulator 5
The pressure P ₀₂ of 33 is the first accumulator 531 and the pressurizing chamber for opening the shuttle valve.
Pressure rises at the same rate as pressure P _{01 at} 514. Further, the pressure P ₄ in the pre-injection decompression chamber 9 becomes constant after the pressure relief valve port 101 is closed.

Thereafter, the fuel injection stage is started from the time point c when the depression of the plunger 62 toward the bottom dead center is started. As shown in FIGS. 5 and 6, when the pushing down of the plunger 62 is started, the internal pressures of the shuttle valve chamber 511, the plunger chamber 61, and the valve closing pressurizing chamber 716 are rapidly increased, and the shuttle valve body 5
2 further rises, the pre-injection valve port 82 is opened at the time point c ′,
At the time point d, the shuttle valve port 523 is closed. During this time, the pressure P _{0 in} the shuttle valve chamber 511 and the pressure in the pressurizing chamber 514 for opening the shuttle valve
The pressure rising speed of P ₀₁ is rapid, and the throttling effect of the throttling passage 532 is exerted, so that the pressure of the first pressure accumulating chamber 531 and the shuttle opening pressurizing chamber 514 is higher than the pressure P ₀₁ of the second accumulating chamber. Chamber 533
Pressure P ₀₂ The pressure rise is delayed. Therefore, at the time d when the shuttle valve port 523 is closed, the pressure P _{02 in} the second pressure accumulating chamber is increased.
Is the pressure P of the first accumulator 531 and the shuttle valve pressurizing chamber 514.
_It is lower than ₀₁ . Shuttle valve chamber 51 after time d
The pressure P ₀ of 1 does not increase, and the pressure P _{01 of} the first pressure accumulating chamber 531 and the shuttle valve opening pressurizing chamber 514 is released from the throttle passage 532 to the second pressure accumulating chamber 533. 511
At the pressure of P ₀ , the shuttle valve body 52 further closes the pre-injection valve port 82 in the valve closing direction from the position where the shuttle valve port 523 is closed, the pressure relief valve port 101 is opened, and the valve closing end position, that is, , Is additionally moved to a predetermined top dead center. When the shuttle valve body 52 rises to the top dead center, the communication valve opening 52
4 is communicated with the communication passage 515, the pressure P ₀ of the shuttle valve chamber 511,
Pressure P _{01 in} the first pressure accumulating chamber 531 and the shuttle valve pressurizing chamber 514
Becomes almost the same, and at the same time as this, the pressure P _{02 in} the second accumulator
Will be the same.

The shuttle valve chamber 5 when the shuttle valve opening 532 is closed
The pressure P _{0 of} 11 and the internal pressure P ₁ of the plunger chamber 61 and the valve closing pressurizing chamber 716 differ depending on the amount of fuel supplied to the injection pump 6 at the fuel supply stage, and the supplied fuel is the maximum injection amount. Is set to a predetermined shuttle valve port closing maximum pressure lower than the valve opening pressure of the check valve 63, and becomes lower as the amount of supplied fuel decreases.

In the fuel injection stage, after the shuttle valve port 523 is closed, the internal pressure P ₁ of the plunger chamber 61 and the valve closing pressurization chamber 716 rises more rapidly, and reverses at time e, which exceeds the pressure of the main accumulator chamber 731. The stop valve 63 is opened, and the injection of fuel into the main accumulator 731 begins. Then, the plunger chamber 61 and the valve closing pressurizing chamber 716.
After the time point g at which the pressure P _{1 of} the main accumulator chamber 731 and the pressure P ₂ of the main accumulator chamber 731 exceed the pressure P ₃ of the sub accumulator chamber 732, the check valve 734 is opened and fuel is also injected into the sub accumulator chamber 732. The injection of fuel is completed at time h when the plunger 62 reaches the bottom dead center, and the check valves 63 and 734 are closed at this time h. The internal pressure of the pre-injection decompression chamber 9 rises in the same manner as the pressure P _{1 of the} plunger chamber 61 and the valve closing pressurization chamber 716 while the pre-injection control valve port 82 is opened, but the pre-injection is performed at the time point f. After the control valve port 82 is closed, the pressure relief valve port 101 is opened at the time point f ', so that the shuttle valve chamber 511 is reached when the shuttle valve body 52 reaches the top dead center.
Pressure P ₀ , the first pressure accumulating chamber 531 and the shuttle valve opening pressurizing chamber 514
The pressure becomes the same as the pressure P _{01 in} the second accumulator chamber and becomes almost the same as the pressure P _{02 in} the second accumulator.

The injection command valve 21 is opened at time i after the injection of fuel into the pressure accumulating fuel injector 7 is completed, and the pressure P in the shuttle valve chamber 511 is increased.
_{When 0} starts to escape to the injection command decompression chamber 23, the shuttle valve body 52 starts to move in the valve opening direction due to the pressure P ₀₁ of the shuttle valve opening pressure chamber 514. And first, the pressure relief valve opening 10
When 1 is closed at time j and the pre-injection valve port 82 is opened at time k, the pressure P in the plunger chamber 61 and the valve closing pressurizing chamber 716 is increased.
₁ is released from the pressure relief valve 8 to the pre-injection vacuum chamber 9, l when the pressure difference between the pressure P ₂ of the pressure P ₁ and the main accumulation chamber 731 of the valve-closing pressure chamber 716 becomes equal to or larger than a predetermined value Then, the injection valve 72 is opened and pre-injection is started.

In the pre-injection, since the pre-injection decompression chamber 9 has a small volume, the pressure P _{1 in the} valve closing pressurization chamber 716 and the pressure in the main pressure accumulation chamber 731.
The pressure difference from P ₂ is not so large, and the valve opening amount of the injection valve 72 is suppressed to a small value. Then, the pressure P _{2 in the} main pressure accumulating chamber 731 decreases after the time point m when the pre-injection starts by opening the injection valve 72, and the pressure P ₁ in the valve closing pressurizing chamber 716 and the main pressure accumulating chamber 716 within a short time. The pressure difference from the pressure P _{2 of} 731 falls below a predetermined value, and at time n, the valve is closed by the valve closing force composed of the pressure P ₁ of the valve closing pressurizing chamber 716 and the spring force of the valve closing spring 717. . Therefore, in the pre-injection, a small amount of fuel accumulated in the main accumulator 731 is injected exclusively.

When a small amount of fuel accumulated in the main pressure accumulation chamber 731 is injected in the pre-injection, the pressure P _{3 in the} sub pressure accumulation chamber 732 is released from the throttle passage 735 to the main pressure accumulation chamber 731, which causes the pressure in the main pressure accumulation chamber 731. While P ₂ rises, the shuttle valve body 52 is further lowered,
Plunger chamber 6 after the point o when the shuttle valve opening 523 is opened
1 and the pressure P ₁ of the pressurizing chamber 716 for closing the valve are changed from the shuttle valve port 523 to the hollow portion 521, the filter chamber 31, the injection command valve 21, and the advance control valve 2.
After passing through 2, it is largely released to the injection command decompression chamber 23. As a result, the pressure P _{1 in} the plunger chamber 61 and the valve closing pressure chamber 716 is
Is rapidly reduced pressure, the pressure differential injection valve 92 greatly exceeds the predetermined value is larger opening the main injection and the pressure P ₂ of the pressure P ₁ and the main accumulation chamber 731 of the valve-closing pressure chamber 716 is started It

When the main injection is started, the pressure in the main pressure accumulating chamber 731 is reduced more than the pressure released from the sub pressure accumulating chamber 732.
The fuel in the sub pressure accumulating chamber 732 flows into the main pressure accumulating chamber 731 until the pressure of 32 drops to a predetermined set pressure. Therefore, the sub-accumulation chamber 7
By the time q when 32 fuels flow into the main accumulator 731
2 reaches the maximum opening, and the fuel injection rate increases. At time point q, the pressure setting valve 736 closes and the replenishment of fuel from the sub-accumulation chamber 732 to the sub-accumulation chamber 731 is stopped. Therefore, the fuel injection rate decreases at a constant rate, and the valve is closed. in response to a decrease in the opening degree of r when the opening degree of the injection valve 92 a pressure differential starts to decrease starts to decrease the pressure P ₂ of the pressure P ₁ and the main accumulation chamber 731 of the use pressurizing chamber 716 reduced, the main injection pressure difference is closed the injection valve 72 by the valve closing force by s time below a predetermined value of the pressure P ₂ of the pressure P ₁ and the main accumulation chamber 731 of the valve-closing pressure chamber 716 finish.

The injection command valve 21 is closed between the time points q and r.

At the stage of returning to the initial release state, the force to hold down the plunger 62 is released from an appropriate time t after the end of the main injection, and the shuttle valve body 52 reaches the bottom dead center by the pressure P ₀₁ of the shuttle valve opening pressurizing chamber 514. While being moved, the pressure P ₁ of the plunger chamber 61 is increased by the fuel pushed out from the shuttle valve chamber 511 into the plunger chamber 61, and the plunger 62 is returned to the top dead center. Then, the discharge valve 25 is opened between the final time u when the plunger 62 returns to the top dead center and the time v when the plunger 62 reaches the top dead center, so that the fuel contained in the injection command decompression chamber 23 is removed. Return to the shuttle valve chamber 511 and inject pump 6
By recovering the amount of fuel stored in the plunger 62 to surely raise the plunger 62 to the top dead center, and then opening the initial pressure adjusting on-off valve 17 from the time point w to the time point x,
The internal pressure of each part in the injection pump 6 is returned to each initial pressure.

According to this pressure-accumulation two-stage injection fuel supply device for a diesel engine, the valve-accumulation chamber 53 of the shuttle valve 5 is communicated with the first pressure-accumulation chamber 531 through the throttle passage 532. And the first pressure accumulation chamber 531 is connected to the shuttle valve opening pressurizing chamber 514, the shuttle valve opening pressurizing chamber 514
If the change in the pressure P _{01 in} the first pressure accumulating chamber 531 is rapid, due to the throttling action of the throttle passage 532, the change is faster than the changing speed of the pressure P _{01 in} the shuttle valve opening pressurizing chamber 514 and the first accumulating chamber 531. 2 pressure chamber
The rate of change of pressure P ₀₂ of 533 is delayed. Therefore, at the time of fuel supply in which the pressure in the shuttle valve chamber 511 is relatively slow,
Pressure P _{01 in} shuttle pressurizing chamber 514 and first pressure accumulating chamber 531
And the pressure P ₀₂ of the second accumulator 533 increase in the same manner as the pressure increase of the shuttle valve chamber 511, but at the time of fuel injection where the pressure increase of the shuttle valve chamber 511 becomes sharp, the shuttle valve is caused by the throttle action of the throttle passage 532. The pressure P ₀₁ in the shuttle valve opening pressurizing chamber 514 and the first pressure accumulating chamber 531 is sensitively increased in response to the increase in the pressure in the chamber 511, and the movement speed of the shuttle valve body 52 is prevented from becoming excessive. As a result, the pressure P ₀ of the shuttle valve chamber 511 by the time the shuttle valve port 523 is closed and the pressure P _{01 of} the shuttle valve opening pressurizing chamber 514 and the first pressure accumulating chamber 531 that change so as to balance with the pressure P _0. Can be increased to an optimum pressure, for example, to a pressure almost equal to the valve opening pressure of the check valve 63 in the case of the maximum injection amount.

Here, the pressure P ₀ of the shuttle valve chamber 511 and the plunger chamber 61
When the shuttle valve port 523 is closed in a low state pressure P ₁ of the following, the valve opening pressure of the pressure P ₁ of the plunger chamber 61 a check valve 63, i.e., the pressure P ₂ or more main accumulation chamber 731 The descending stroke of the plunger 62 until the pressure is increased to, that is, the ineffective stroke in which the fuel is not injected into the pressure-accumulation injector 7 becomes large, and the fuel injected into the pressure-accumulation injector 7, that is, the fuel injection amount is It may decrease and output may decrease. In contrast, according to this embodiment, it pressure P ₀ of the plunger chamber 511 when the shuttle valve port 523 is closed, the pressure P ₁ of the valve-closing pressure chamber 716 and the plunger chamber 61 to an optimum pressure Therefore, the ineffective stroke can be shortened to the necessary minimum, the reduction of the fuel injection amount and the output reduction due to this can be prevented, and the stroke of the plunger 61 can be shortened and downsized.

Further, when the pressure P ₁ of the pressure P ₀ and the plunger chamber 61 of the shuttle valve chamber 511 is a shuttle valve port 523 is closed at a high state, the plunger chamber before the shuttle valve port 511 is closed 6
There is a risk that the fuel will flow backward from 1 to the upstream side and will be injected into the pressure-accumulation injector 7, that is, the fuel injection amount will decrease and the output will decrease. On the other hand, in this embodiment, the pressure in the plunger chamber 511 when the shuttle valve port 523 is closed.
Since P ₀ , the pressure P ₁ in the valve closing pressurizing chamber 716 and the plunger chamber 61 can be set to the optimum pressures, a decrease in the fuel injection amount due to the reverse flow before the closing of the shuttle valve 5 and an output decrease due to this can be prevented. can do.

Further, in this embodiment, after the shuttle valve port 523 is closed, the pressure P ₀₁ of the shuttle valve opening pressurizing chamber 514 and the first pressure accumulating chamber 531 is released from the throttle passage 532 to the second pressure accumulating chamber 533. Therefore, the shuttle valve body 52 can be reliably moved in the valve closing direction by the pressure P ₀ of the shuttle valve chamber 511 until the pre-injection valve port 82 is closed and the top dead center is reached. Therefore, the rise of the shuttle valve body 52 is caused by the pre-injection valve opening.
It is possible to reliably prevent that 82 is stopped in the open state, and thereby, it is possible to prevent the two-stage injection from becoming impossible at the time of fuel injection and the combustion efficiency is reduced, and the output reduction due to the reduction of the combustion efficiency is prevented.

When the plunger 62 begins to descend and the pressure in the shuttle valve chamber 511 rapidly increases, the pressure increasing rate of the second pressure accumulating chamber 533 is reduced by the throttling action of the throttling passage 532 so that the first pressure accumulating chamber 531 and the shuttle valve pressurizing chamber 531 are opened. When the shuttle valve opening 523 is closed because the pressure rise speed of 514 becomes slower, the second pressure accumulation chamber 5
The pressure P _{02 of} 33 is the first pressure accumulating chamber 531 and the pressurizing chamber for opening the shuttle valve.
Since the pressure is lower than the pressure P _{01 of} 514, the total volume of the first pressure accumulating chamber 531 and the second pressure accumulating chamber 533 required for additional lift of the shuttle valve body 52 can be made smaller than the conventional example, and the size can be reduced. it can.

Further, since the pressure P ₀₁ of the shuttle valve opening pressurizing chamber 514 when the injection command valve 21 is opened is higher than the conventional pressure, the shuttle valve chamber 511 of the shuttle valve chamber 511 after the injection command valve 21 is opened. The decompression speed becomes faster and the shuttle valve body 52 moves faster.
As a result, it is possible to reduce variations in the pre-injection start timing and the main injection start timing, and improve the control accuracy of the injection start timing.

Further, in this embodiment, as shown in FIG. 3, the pre-injection decompression chamber 9 is operated by the pressure relief valve 10 at least from the start of pre-injection to the start of main injection in the shuttle valve chamber 511.
Since it is shut off from the
6 and the pressure P ₁ of the plunger chamber 61 and the pressure P ₄ of the pre-injection decompression chamber 9 can be kept constant, and there is no variable factor for the control of the start timing of the main injection, so that the control of the main injection is simplified. The control accuracy can be further enhanced.

In addition, the throttle passage 532 of the valve-opening pressure accumulating chamber 53 can be configured by, for example, a screw fitting gap between the adjusting plug 718 and the stopper bolt 719. In this case, for example, the seventh
As shown in the figure, the dimensional variation of the screw fitting gap is relatively large. Therefore, as shown by the thin line a in FIG. 7, on the other hand, the surplus lift amount from the allowable minimum amount Min. Of the additional lift amount is large. On the other hand, on the other hand, as indicated by the axis line b in the figure, the lift time for obtaining stable injection becomes too long, and the pressure P _{4 in} the pre-injection decompression chamber 9 becomes too large, and pre-injection tends to be disabled.

On the other hand, when the throttle passage 532 is formed by a machined hole, the dimensional variation of the throttle passage 532 is relatively small. Therefore, on the other hand, as shown by the thick line c in FIG. The surplus lift amount from the allowable minimum amount Min. Can be reduced, and on the other hand, as shown by the thick line d in the figure,
It is possible to shorten the lift time for obtaining stable injection, prevent the pressure P _{4 of} the pre-injection decompression chamber 9 from becoming excessive, and reliably perform pre-injection.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a pressure-accumulation type two-stage injection fuel supply device for a diesel engine according to an embodiment of the present invention, FIG. 2 is a vertical sectional view of a unit injector U thereof, and FIG. 3 is a shuttle valve 5 thereof. FIG. 4 is an enlarged vertical sectional view of a modification of the shuttle valve 5, FIG. 5 is a timing chart for one entire cycle of the operation of the apparatus, and FIG. 6 is particularly in the stage of fuel injection. FIG. 7 is a timing diagram showing the pressure change of each part of the shuttle valve 5, FIG. 7 is a characteristic diagram of the shuttle valve 5, FIG. 8 is an equivalent circuit diagram of a conventional example, and FIG. 9 is a vertical sectional view of a conventional unit injector. . DESCRIPTION OF SYMBOLS 1 ... Fuel pressure regulation amount supply device, 5 ... Shuttle valve, 6 ... Injection pump, 7 ... Accumulation type fuel injector, 8 ... Pre-injection control valve,
9 ... Pre-injection decompression chamber, 21 ... Injection command valve, 23 ... Injection command decompression chamber, 52 ... Shuttle valve body, 53 ... Valve opening accumulation chamber, 61 ...
Plunger chamber, 62 ... Plunger, 63 ... Check valve, 72 ... Injection valve, 74 ... Injection port, 82 ... Pre-injection valve port, 511 ... Shuttle valve chamber, 514 ... Shuttle valve opening pressurizing chamber, 523 ... Shuttle valve port ,
531 ... 1st accumulator, 532 ... throttle passage, 533 ... 2nd accumulator, 7
16 ... Valve closing pressurizing chamber, 717 ... Valve closing spring, 723 ... Injection valve seat, 73
1 ... Main accumulator, 732 ... Sub accumulator, 735 ... Throttle return path.

Claims (3)

[Claims] 1. A shuttle valve (5) for pushing back a plunger (62) of an injection pump (6) of a fuel pressure regulating / quantity supply device (1) of a pressure-accumulation type two-stage injection type fuel injection device for a diesel engine.
Shuttle valve chamber (511), shuttle valve port (523), plunger chamber (61) of the injection pump (6), and pressurizing chamber (716) for closing the injection valve (72) of the pressure accumulating fuel injector (7). ), The check valve (63), the main accumulator (731), and the injection valve seat (723) in order to communicate with the injection port (74), and the shuttle valve (5) for pushing back the plunger is a shuttle valve body. (52) is pressurized to the valve opening side by the accumulated pressure in the valve opening pressure accumulating chamber (53) via the shuttle valve opening pressurizing chamber (514), while closed by the fuel pressure in the shuttle valve chamber (511). The injection valve (72) is pressed toward the valve closing side by the valve closing force composed of the spring force of the valve closing spring (717) and the pressure of the valve closing pressurizing chamber (716). In addition, the main accumulator (731) is configured to be pressed toward the valve opening side by the valve opening force formed by the pressure, and the sub accumulator (732) is connected to the main accumulator (731) through at least the throttle return path (735). Continuous Then, the pre-injection decompression chamber (9) is communicated with the closing valve pressurizing chamber (716) through the pre-injection control valve (8), and the pre-injection valve port (82) of the pre-injection control valve (8) is opened. The shuttle valve body (52) is provided so as to be movable together, and at the end of the operation of the shuttle valve body (52) toward the valve closing side, the pre-injection valve port (82) is closed after the shuttle valve port (523) is closed. The shuttle valve chamber (511) is connected to the injection command decompression chamber (23) via the injection command valve (21), and the shuttle valve chamber (23) is opened. The pressure in 511) is released to the injection command decompression chamber (23). First, the pre-injection valve port (82) is opened and the valve closing pressure chamber (71) is opened.
The pressure of 6) is released to the pre-injection decompression chamber (9) to reduce the valve closing force, and the injection valve (72) is pushed open by the valve opening force of the pressure of the main pressure accumulating chamber (731). The fuel in the main accumulator (731) begins to be pre-injected from the injection port (74), and then the valve opening force decreases as the pre-injection proceeds, and the injection valve (72) is closed by the valve opening force. The pre-injection is completed, and the fuel in the sub pressure accumulator (732) is pressed into the main accumulator (731) from the throttle return path (735) to increase the valve opening force and the injection valve (72) opening force. It is pushed open again in the sub accumulator (73
2) and the fuel in the main accumulator (731) begins to be injected from the injection port (74), and as the main injection proceeds thereafter, the valve opening force decreases and the injection valve (72) closes with the valve closing force. In the pressure-accumulation two-stage injection fuel injection device for a diesel engine configured to terminate the main injection, the valve-accumulation chamber (53) of the shuttle valve (51) is the first pressure-accumulation chamber (531). The second pressure accumulating chamber (533) through the throttle passage (532)
The first accumulator chamber (531) communicates with the shuttle valve pressurizing chamber (514), and when the shuttle valve body (52) is operated toward the valve closing side, the throttle passage (532) is throttled. Due to the action, the pressure increase rate of the second pressure accumulation chamber (533) is made lower than the pressure increase rate of the first pressure accumulation chamber (531), and the first pressure accumulation chamber (5) remains even after the shuttle valve port (523) is closed.
As the pressure of 31) gradually escapes from the throttle passageway (532) to the second pressure accumulating chamber (533) and decreases, the shuttle valve body (52) moves from the closed position of the shuttle valve opening (523) to the pre-position. Diesel characterized by being configured to be additionally moved after the valve is closed by the pressure in the shuttle valve chamber (511) in the additional lift stroke from the closing position of the injection valve port (82) to the closing end position. Accumulation type two-stage injection type fuel injection device for engine 2. A pressure accumulating chamber (5) for opening the shuttle valve (5).
The pressure-accumulation type two-stage injection fuel injection device for a diesel engine according to claim 1, wherein the throttle passage (532) of 3) is formed by a screw fitting gap. 3. A pressure accumulation chamber (5) for opening the shuttle valve (5).
The pressure-accumulation two-stage injection fuel injection device for a diesel engine according to claim 1, wherein the throttle passage (532) of 3) is formed by a machined hole.