JPH0286958A - Two-way delivery valve gear for fuel injection pump - Google Patents

Abstract

PURPOSE:To uniformize residual pressure in an injection pipe as well as to make stable performance fully demonstrable over the whole driving range by installing a residual pressure compensating piston in an interval between a delivery valve holder and a delivery valve seat. CONSTITUTION:A fuel injection pump 1 attaches a delivery valve holder 4 to a part of the distributing head 2 by means of screwing, while a delivery valve seat 8 is fixed to the lower part, and a delivery valve 9 is made contact or separate to or from this seat 8. In this case, a cylindrical residual pressure compensating piston 22 is installed slidably for reciprocation between a step part 20 of the delivery valve holder 4 and another step 21 of the delivery valve seat 8, and this piston is always energized upward by a spring 23. Then, the inside of an injection pipe 6 and a return passage 29 are interconnected to each other by a down of the residual pressure compensating piston 23 by reflected pressure in this injection pipe 6 at time of high speed driving other that at time of low speed driving as as idling range or the like, whereby fuel conformed to energizing force of the spring 23 is made returnable by suction, thus residual pressure in the injection pipe 6 is kept constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an equal pressure valve device for a fuel injection pump.
In particular, the present invention relates to an equal pressure valve device for a fuel injection pump that improves the accuracy of residual pressure correction in an injection pipe during low-speed operation of a diesel engine.

[Prior Art] Conventionally, a delivery valve is provided between a fuel injection pump and an injection pipe that connects the fuel injection pump to an injection nozzle, so that the fuel injection pump and the injection pipe communicate with each other during pressure feeding of fuel. After the completion of fuel pumping, the communication between the fuel injection pump and the injection pipe is cut off to maintain a predetermined residual pressure, and the timing between the start of pumping of the fuel injection pump and the start of injection from the injection nozzle at the time of the next pumping of fuel is cut off. I'm trying to minimize the time lag. In addition, by controlling the residual pressure after the end of fuel injection in the injection pipe, the fuel injection into the delivery valve is improved to improve fuel injection cut-off and to prevent abnormal injections such as leakage and secondary injection. In order to provide a return function and further enhance this function, the fuel injection pump incorporates a fuel pressure control device called an equal pressure valve.

For example, there is Japanese Patent Application Laid-Open No. 58-859Eie.

At t7, in the current injection system including the fuel injection pump, injection pipe, and injection nozzle, the pressure spring in the injection nozzle wears out over time, and the valve opening pressure decreases over time, causing the pressure of the fuel injection pump to decrease over time. If the effective stroke of the plunger, that is, the amount of fuel pumped or the pumping pressure, does not change, the needle valve of the injection nozzle will open before it reaches the pressure at which it should normally open, and the valve closing timing will also be delayed. There is a problem that the amount increases from the initial setting value. Furthermore, since the pressure spring's fatigue over time is not uniform among the cylinders, the rate of increase also differs among the cylinders, and variations throughout the diesel engine also pose a problem.

This problem of increased fuel injection amount is noticeable in fuel injection pumps equipped with the above-mentioned equal pressure valve device, and although it is not a major problem when the diesel engine is operating at high speeds, it may cause combustion noise when operating at low speeds such as idling. Problems include an increase in the amount of CO1 hydrocarbons and smoke in the exhaust gas, and furthermore, it causes unstable operation such as diesel knock, making it impossible to exhibit stable and smooth operating performance.

These circumstances will be explained based on FIGS. 9 and 10.

That is, FIG. 9 is a graph showing the relationship between the cam rotation angle of the injection pump, the pressure in the injection pipe, and the injection rate during high-speed operation with a large amount of fuel pumped, and the pressure in the injection pipe originally exceeds the nozzle opening pressure. Since the injection amount has increased significantly, the nozzle opening pressure has reached its initial setting pressure value PO1.
Even if PO2 decreases from PO2 to a certain value, the proportion of increase in the injection amount and injection rate due to this decrease is small, so it does not have a large effect on changes in the overall injection amount and injection rate.

On the other hand, FIG. 10 is a graph showing the relationship between the cam rotation angle, the pressure in the injection pipe, and the injection rate during low-speed operation such as idling when the amount of fuel pumped is small, and in this case, the pressure in the injection pipe is set at the initial setting. Since it only slightly exceeds the pressure value Pot, the injection amount is originally small, and when the nozzle opening pressure decreases from its initial setting pressure value Pot to a certain value PO2, the injection amount and injection rate will change to the shaded area in the diagram. The fuel injection rate increases by the amount shown, and this increase is a non-negligible amount for changes in the overall injection amount and injection rate.

Furthermore, there is a difference between the conventional delivery valve described above and the equal pressure valve device in the situation in which the fuel injection amount changes as the nozzle opening pressure decreases as described above.

In other words, in a conventional fuel injection pump equipped with a standard delivery valve, the fuel pumped by the reciprocation of the plunger lifts the delivery valve and discharges the fuel from the fuel outlet through the injection pipe to the injection nozzle. After completion, a predetermined amount of fuel is sucked back by lowering the relief valve part that formed the Angleich cut.

However, when a diesel engine is operating at low speeds, such as when idling, the relief valve part of the delivery valve is not in a complete lift state, and the orifice of the Angleich cut reduces the wave area in this part while pumping the fuel, power, and offloading. As a result, the residual pressure in the injection pipe also decreases as the nozzle opening pressure decreases, as shown by the broken line in FIG. Therefore, as shown by the broken line in Fig. 12, even if the nozzle opening pressure decreases, the fuel injection amount also decreases in accordance with the decrease, and the increase in the fuel injection amount especially during low speed operation is caused by the decrease in the nozzle opening pressure. The percentage is small.

Next, in a fuel injection pump equipped with a conventional standard equal pressure valve device, the equal pressure valve set spring biases the valve in the valve closing direction so that it is opened by the reflected pressure of the fuel from the injection pipe. By providing an equal pressure valve below the delivery valve, the residual pressure in the injection pipe can be controlled.

However, - the above-mentioned equal pressure valve was originally provided to vary the amount of fuel sucked back according to the reflected pressure of the fuel and to maintain the residual pressure constant; Although it has advantages such as increasing the pressure of fuel injection, preventing abnormal injection such as secondary injection, preventing cavitation erosion, and preventing backflow of fuel gas from the combustion chamber,
In particular, disadvantages such as instability in the fuel injection amount when starting a diesel engine and low-speed operation, and large fluctuations in cycle repeatability during low-speed operation cannot be denied, and most of these disadvantages occur during low-speed operation such as idling. This is due to the lack of a residual pressure correction function during operation.

In other words, as shown by the solid line in Fig. 11, in the case of a fuel injection pump equipped with an equal pressure valve, even when the nozzle opening pressure decreases, the residual pressure is reduced by the biasing force set by the equal pressure valve set spring. remains almost constant.

In reality, when the nozzle opening pressure is high, the residual pressure will decrease somewhat due to overshoot of the valve element of the equal pressure valve.In other words, when the nozzle opening pressure decreases, the residual pressure will remain almost constant but increase slightly. do. Therefore, as shown by the solid line in Figure 12, when the nozzle opening pressure decreases, the fuel injection amount increases more than in a fuel injection pump equipped with a standard delivery valve. .

As mentioned above, although fuel injection pumps equipped with equal pressure valves have many advantages, they only have a single orifice and equal pressure valve spring set pressure on the fuel suction and return side, so the nozzle opening pressure is As a result, when the fuel injection amount decreases, the fuel injection amount increases, which has a problem of adversely affecting the performance of the diesel engine, especially during low-speed operation such as idling.

Although it is possible to solve this problem by controlling the fuel injection amount according to the operating state using an electronic control means, there is another problem of high cost.

[Problems to be Solved by the Invention] The present invention was conceived in view of the above-mentioned problems.In a fuel injection pump equipped with a delivery valve, during steady operation such as high-speed operation, the conventional equal pressure valve is not used. In addition to providing this function to enable the pump to take advantage of the advantages of the fuel injection pump, it also functions as a fuel injection pump equipped with a conventional standard delivery valve during low-speed operation such as idling. This is a fuel injection pump that corrects the residual pressure to decrease by the same amount as the nozzle opening pressure decreases, and improves its performance by preventing the amount of fuel injected from increasing even during low-speed operation. The present invention attempts to provide an equal pressure valve device.

[Means for Solving the Problems] That is, the present invention is an equal pressure valve device provided in a delivery valve that opens and closes a fuel outlet from a fuel injection pump to an injection pipe in a diesel engine, which comprises a delivery valve holder of the delivery valve and a delivery valve device. A residual pressure compensating piston provided to be able to reciprocate and slide between the valve seat and at least one of the residual pressure compensating piston and the above-mentioned delivery valve holder; By providing a communication hole that can be opened and closed by reciprocating sliding and communicates with a low pressure side such as a pump chamber of a fuel injection pump or a fuel tank, and a piston spring that biases the residual pressure correction piston in the direction of closing the communication hole. This is an equal pressure valve device for a fuel injection pump, characterized in that it has a residual pressure correction function during low speed operation such as idling.

[Function] In the equal pressure valve device according to the present invention, when the diesel engine is operating at low speed such as idling, the residual pressure correction piston does not open the communication hole due to the biasing force of the piston spring, which is similar to the conventional delivery valve. Fuel is discharged and sucked back only by the throttling effect at the cut portion. Furthermore, during high-speed operation of the diesel engine, the residual pressure correction piston slides in the direction of sucking back the fuel due to the high reflected pressure of the fuel in the injection pipe against the biasing force of the piston spring, causing the above-mentioned communication. By communicating with the hole, the fuel is delivered from the discharge boat side of the delivery valve, that is, the downstream side, to the fuel pump chamber, fuel tank, etc. so that the residual pressure in the injection pipe is kept almost constant, without going through the delivery valve as in the past. It is designed to return directly to the low pressure side, that is, to the upstream side.

Therefore, during low-speed operation, it is possible to change the residual pressure in the injection pipe according to changes in the nozzle opening pressure, and furthermore, during high-speed operation other than low-speed operation, the residual pressure in the injection pipe is kept constant. Since the function of the equal pressure valve from
Even if the nozzle opening pressure decreases, stable operation of the diesel engine can be guaranteed without increasing the fuel injection amount especially during low speed operation.

[Embodiment] Next, an example in which an embodiment of the present invention is applied to a distribution type fuel injection pump will be described based on FIGS. 1 to 3.

FIG. 1 is a longitudinal cross-sectional view of a fuel injection pump 1 according to the above-mentioned embodiment, in which a delivery valve holder 4 is screwed into the distribution head 2 portion of the pump 1 through an O-ring 3 to be fixed thereto. The delivery valve holder 4 has a fuel outlet 5 at its upper end and is connected to a fuel injection nozzle 7 via an injection pipe 6.

A delivery valve seat 8 is fixed to the lower part of the delivery valve holder 4, and a delivery valve 9 is housed within the delivery valve seat 8 so as to be able to slide back and forth. This delivery valve 9 has a rod part lO and a seat part 1.
1 and a relief valve part 12. A fuel discharge passage 14 is formed between the rod portion 10 and the delivery valve seat 8 by providing a plurality of blade portions 13 radially protruding from the rod portion 10 . This fuel discharge passage 14 communicates with a distribution passage 15 for distributing high-pressure fuel from a pump chamber (path shown) via a high pressure chamber (path shown).

By providing a delivery valve set spring 17 between the delivery valve 9 and the spring seat 16, the seat portion 11 of the delivery valve 9 is constantly pressed against the seat surface 18 of the delivery valve seat 8.

In addition, the relief valve portion 12 of the delivery valve 9 includes:
An Angleich cut 19 is formed, and an orifice formed between this Angleich cut 19 and the inner wall of the delivery valve seat 8 makes it possible to narrow down the flow path area.

A cylindrical residual pressure correction piston 22 is provided between the stepped portion 20 of the delivery valve holder 4 and the stepped portion 21 of the delivery valve seat 8 so as to be able to slide vertically and reciprocally, and a piston spring 23 is used to constantly push the piston upward in the figure. It is strongly encouraged. Furthermore, there are adjustment shims 24 above and below the piston spring 23.
．． Place 25.

An inner annular groove 26 is formed on the inner wall surface of the delivery valve holder 4 within the range in which the residual pressure correction piston 22 slides up and down.
Return communication holes 27 are formed at a plurality of predetermined locations in the inner annular groove 26, and an outer annular groove 28 is formed in the outer wall surface of the delivery valve holder 4. Return passages 29 communicating with the pump chamber (the illustrated passage) of the fuel injection pump 1 are formed at a plurality of predetermined locations in the outer annular groove 28 .

The operation of the fuel injection pump l having such a configuration will be explained below.

The fuel pumped from the distribution passage 15 by the reciprocation of the plunger (the illustrated path) of the fuel injection pump 1 is pushed against the biasing force of the delivery valve set spring 17 to the delivery valve 9.
is lifted from the seat surface 18 and is discharged from the fuel outlet 5 through the injection pipe 6 to the injection nozzle 7. After the fuel has been discharged, the relief valve part 12 forming the angle 19 is lowered to suck the fuel back and perform the same function as the normal delivery valve 9, but at this time, if the engine speed range is the idling range or Depending on the high speed rotation range, the relief valve section 12 may be lowered or the residual pressure correction piston 2 may be lowered.
2, different amounts of fuel will be sucked back.

That is, in the above idling range, even if the residual pressure correction piston 22 moves down a little due to the reflected pressure of the fuel in the injection pipe 6, the upper end of the residual pressure correction piston 22 and the upper edge of the inner annular groove 26 When moving up and down within the first stroke Sl between
7 is not opened, the injection pipe 6 and the return passage 29
Furthermore, there is no communication with the pump chamber, and the fuel is sucked and returned only through the Angleich cart 19, and the residual pressure can be varied using the conventional delivery valve 9 (see Fig. 2 and (See Figure 3).

Next, when the engine is in other rotational ranges such as a high-speed rotational range, the reflected pressure of the fuel in the injection pipe 6 becomes high, so the residual pressure correction piston 22 is connected to its lower end and the delivery valve seat 8.
Since the fuel outlet 5 side and the return passage 29 side communicate with each other via the return communication hole 27, most of the fuel sucked back is The liquid is directly spilled into the pump chamber without passing through the delivery valve 9 section.

Therefore, in the fuel injection pump 1 according to this embodiment, even if the nozzle opening pressure decreases, the residual pressure can be reduced as in the conventional fuel injection pump, as shown by the broken line in FIG. As shown by the broken line in FIG. 12, like the conventional fuel injection pump, even if the nozzle opening pressure decreases, the fuel injection amount can be decreased in accordance with the decrease.

It should be noted that, other than during low-speed operation such as in the idling range, for example during high-speed operation, the lowering of the residual pressure correction piston 22 brings the inside of the injection pipe 6 into communication with the return passage 29, and fuel is supplied according to the biasing force of the piston spring 23. Since the fuel is sucked back, it can perform the same function as a conventional equal pressure valve, that is, the function of making the residual pressure in the injection pipe 6 constant by varying the amount of fuel sucked back.

Next, FIG. 4 is a sectional view of a main part showing a distribution type fuel injection pump 30 according to another embodiment of the present invention, and the same parts as those of the fuel injection pump l according to the above-mentioned embodiment are denoted by the same reference numerals. , and the detailed description thereof will be omitted and will be explained below.

In this fuel injection pump 30, the inner annular groove 26, the return communication hole 27, and the outer annular groove 28 are formed in the delivery valve holder 4, and the residual pressure correction piston is located slightly above these. 31, an inner annular groove 32, a return communication hole 33, and an outer annular groove 34 are formed. Note that an inner flange portion 35 is formed on the inner wall surface of the residual pressure correction piston 31, and a clearance 36 is provided between the piston 31 and the delivery valve 9 to the extent that a throttling effect is produced.

Also in the fuel injection pump 30 having such a configuration,
Similar to the fuel injection pump 1 described above, when sucking back fuel during idling, the reflected pressure from the injection pipe 6 is low and the pressure transmission speed is slow, so the residual pressure correction piston 31
does not fall (see Figures 5 and 6).

However, as the rotational speed increases, the residual pressure correction piston 31 begins to descend, and the return communication hole 33 and the return communication hole 27 communicate with each other, so that the inside of the injection pipe 6 and the return passage 29 are connected to each other. It connects and begins sucking fuel directly back into the pump chamber.

If the rotation speed further increases, the residual pressure correction piston 31 will come into close contact with the lower part, and the residual pressure correction piston 31 will come into close contact with the lower part.
To reliably maintain residual pressure due to the difference in pressure receiving area between the first side and the bottom side.

In addition, due to the clearance 36 between the delivery valve 9 and the inner flange portion 35 of the residual pressure correction piston 31,
The reliability of the delivery valve 9 can be improved by controlling the initial injection rate, improving combustion in the low speed rotation range, damping effect, etc.

In addition, in any embodiment, the clearance 36 between the delivery valve 9 and the residual pressure correction piston 31, the strokes S1 and S2, and the piston spring 23
The settings of the spring coefficient, etc. shall be selected so that the above functions can be obtained.

In addition, in the present invention, the shape of the residual pressure correction piston 22.31 is arbitrary in any of the embodiments. In addition, if too much fuel is sucked back, an Angleich cut 40 (see Fig. 7) similar to the Angleich cut 19 may be formed on the residual pressure correction piston 31 (or in other words, the residual pressure correction piston 22). You can also do it. The throttling effect of this Angleich cut 40 makes it possible to prevent the above-mentioned excessive suction back.

Furthermore, as shown in FIG. 8, if residual pressure correction in the idling range is not considered, the delivery valve seat and the residual pressure correction piston may be integrally formed as a delivery valve seat 50. That is, the delivery valve seat 50, which can seat the check pole 51 and can reciprocate within the delivery valve holder 4, is urged upward by the piston spring 23. Further, a communication hole 33 is formed in the side wall of the delivery valve seat 50, so that the communication hole 27 formed in the delivery valve holder 4 can communicate with the communication hole 33.

With this configuration, when discharging fuel, the check pole 51 lifts against the biasing force of the delivery valve spring 17, and when sucking back fuel, the delivery valve seat 50 lifts against the biasing force of the piston spring 23. The communication hole 33 and the communication hole 27 are connected to each other by descending, and the fuel can be directly returned to the pump chamber via the return passage 29.

In addition, in each of the above-mentioned embodiments, the return communication hole 27.3
3, the fuel is returned to the pump chamber through the pump chamber, but the fuel may be returned not only to the pump chamber but also to a fuel tank or the like, at least on the lower pressure side or upstream side of the fuel pressure chamber such as the distribution passage 15 or the plunger pressure chamber. It is sufficient to do so.

[Effect of the invention 1] As explained above, according to the present invention, by providing the residual pressure correction piston between the delivery valve holder and the delivery valve seat, only the residual pressure correction function of the conventional delivery valve can be used in the idling rotation range. It is possible to maintain the residual pressure constant in the same way as a conventional equal pressure valve so that the function of the equal pressure valve is exerted from above a specified rotation range, so it takes advantage of the advantages of the equal pressure valve and compensates for its shortcomings. The fuel injection pump can exhibit stable performance over the entire operating range.

Figure 9 is a graph of the pressure inside the injection pipe 6 and injection rate versus cam rotation angle during high-speed operation of a general fuel injection pump, Figure 10 is a graph of the same during low-speed operation, and Figure 11 is a graph versus nozzle opening pressure. The graph of residual pressure, FIG. 12, is a graph of injection amount versus nozzle opening pressure.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a main part of a residual pressure correction piston 22 portion of a fuel injection pump 1 according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between residual pressure and pump rotation speed, and FIG.
The same figure shows a graph showing the relationship between the piston stroke and the pump rotation speed, FIG. 4 is a longitudinal cross-sectional view of a main part of the residual pressure correction piston 31 portion of a fuel injection pump 30 according to another embodiment of the present invention, and FIG. 5 is a graph showing the relationship between the residual pressure and the pump rotation speed, FIG. 6 is a graph showing the relationship between the piston stroke and the pump rotation speed, and FIG. FIG. 8 is a first sectional view showing still another modification of the present invention. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12゜13゜90 distribution type fuel injection pump 60 distribution head 6.0 ring 6. Delivery valve holder 0. Fuel outlet 0. Injection pipe, 6 fuel injection nozzles 0. Delivery valve seat 0. Delivery valve 0. Rod portion 6 of delivery valve 9. Seat portion of delivery valve 9 Relief valve portion of delivery valve 96. Vane portion 14°15 of delivery valve 9. 16. 17. 18. 19. 20. 21°22. 23. 24. 26. 27. 28. 29. 30. 31. 32. 33. 34. 16. Fuel discharge passage 100 distribution passage 00. Spring seat 09. Delivery valve set spring 8. Seat surface 11 of delivery valve seat 8. Angleich cut 90. Step portion 80 of delivery valve holder 4. Step portion 09 of delivery valve seat 8. Residual pressure correction piston 10. Piston spring 25, adjustment shim 60. Inner annular groove 00. Return communication hole 00. Outer annular groove 99. Return passage 090 distribution type fuel injection pump 19. Residual pressure correction piston 69. Inner annular groove 11. Return communication hole 90. Outer annular groove 35. 36. 40. 50. 51. OI O2, inner flange, clearance, Angleich cut, delivery valve seat, check pole, initial setting value of nozzle opening pressure, reduced value of nozzle opening pressure Patent applicant: Diesel Equipment Co., Ltd.

Claims (1)

[Scope of Claims] An equal pressure valve device provided in a delivery valve that opens and closes a fuel outlet from a fuel injection pump to an injection pipe in a diesel engine, comprising a reciprocating sliding mechanism between a delivery valve holder and a delivery valve seat of the delivery valve. a piston for correcting residual pressure movably provided; the piston for correcting residual pressure or the delivery valve holder; An equal pressure valve device for a fuel injection pump, comprising: a communication hole that communicates with a low pressure side; and a piston spring that biases the residual pressure correction piston in a direction in which the communication hole is closed.