JPS6013972A - Fuel injection device for direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To restrict the deterioration of fuel consumption rate and smoke through diffusion combustion after ignition and reduce NOx in exhaust gas by a method wherein a fuel reservoir is provided in the path of injecting fuel through a branch path provided with an opening and closing valve, opened and closed in accordance with the pressure of the injecting fuel. CONSTITUTION:The fuel reservoir 14 is provided in the path 12 of injecting fuel through the branch path 13 provided with the opening and closing valve 15, opened and closed in accordance with the pressure of the injecting fuel. Injection is stopped temporarily after the beginning of the fuel injection and, thereafter, the injection is reopened when the pressure of the fuel has arrived at the intital stage valve opening pressure of a fuel injection nozzle 4. The internal pressure of a fuel injection pipe 6 is increased successively, however, the fuel reservoir 14 is filled with the fuel this time and the fuel pressure in the reservoir is high while the fuel pressure is being applied on the valve body 17 of the opening and closing valve 15, therefore, the valve 15 will never be opened. Accordingly, the internal pressure of the fuel injection pipe 6 is increased so as to exceed the second stage valve opening pressure of the fuel injection nozzle 4 and thereby bringing a needle valve 26 into fully opened condition.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fuel injection device for a direct injection diesel engine.

<Prior Art> As shown in FIG. 1, a conventional fuel injection device for a direct-injection diesel engine includes, for example,
A fuel injection nozzle 4 is attached facing the combustion chamber 3 formed between the fuel injection pump 2 and the piston 2, and a fuel injection pipe 6 from a fuel injection pump 5 is connected to the fuel injection nozzle 4. In this way, the fuel pressurized by the fuel injection pump 5 is supplied to the fuel injection nozzle 4 through the fuel injection pipe 6, and the needle valve is lifted by the increase in fuel pressure in the fuel injection nozzle 4, and the fuel is injected into the combustion chamber 3. Inject. At this time, combustion chamber 3
Inside, the intake air is compressed by the rise of the piston 2, so fuel is injected into this compressed air, leading to ignition and combustion. (Refer to "Diesel Engine", Vol. 5 of Automotive Engineering Complete Book, published by Sankaido, March 1983) However, in the fuel injection device of such a conventional direct injection diesel engine, for example, a hole is used as the fuel injection nozzle. The shape of the nozzle tip of this hole-type fuel injection nozzle is as shown in Figure 2, and the fuel injection rate rapidly increases immediately after the valve is opened, as shown in Figure 3. Because of the rising shape, most of the fuel is injected into the combustion chamber during the ignition delay period from the start of fuel injection to ignition. Therefore, combustion after ignition is dominated by premixed combustion, which causes problems such as rapid combustion, worsening fuel consumption and smoke, and increasing NOx concentration in the exhaust. there were.

<Object of the Invention> In view of these conventional problems, the present invention improves the fuel consumption rate and smoke by appropriately controlling the fuel injection rate and making the combustion after ignition diffuse combustion. The purpose is to reduce NOx in exhaust gas.

<Structure of the Invention> For this reason, the present invention provides a fuel reservoir that communicates with the injected fuel passage via a branch passage, and also provides an on-off valve in the branch passage that opens and closes depending on the pressure of the injected fuel. During the fuel injection during one cycle, the amount of fuel that can be ignited is injected in advance (pilot injection), and the main injection (main injection) is performed after a time delay corresponding to the ignition delay period. be.

<Example> The present invention will be explained in detail below.

FIG. 4 shows a first embodiment.

To explain the structure, a pressure regulating device 10 is provided in the middle of a fuel injection pipe 6 from a fuel injection pump 5.

A fuel passage 12 connected to the fuel injection pipe 6 is formed in the housing 11 of the pressure regulator 10, and a branch passage 13 from this fuel passage 12 is also formed. The branch passage 13 is a fuel reservoir 1 formed in the housing 11.
It communicates with 4. An on-off valve 15 is provided at the entrance of the branch passage 13. The on-off valve 15 includes a valve body 17 facing a seat surface 16 formed at the entrance of the branch passage 13, and a valve body 17 housed in a chamber 18 behind the valve body 17 to act on the valve body 17 in the valve closing direction. It is composed of a spring 19. Here, the chamber 18 communicates with the fuel reservoir 14, and the pressure of the fuel in the fuel reservoir 14 is applied to the valve body 17 in the valve closing direction. Further, the fuel reservoir 14 communicates with a fuel return passage 21 to a fuel tank (not shown) via a normally closed solenoid valve 20, and the solenoid valve 20 is controlled by a signal from a controller 22. It has become.

Further, in this embodiment, the fuel injection nozzle 4 is constructed as shown in FIG.

A nozzle seat portion 24 and a nozzle hole 25 are formed in the nozzle body 23. A needle valve 26 is slidably housed in the nozzle body 23, and the needle valve 26 is formed with a needle face portion 27 and a pressure stage 28. The pressure stage 28 has a nozzle body 2.
The pressure in the valve chamber 29 between the needle valve 26 and the needle valve 26 acts.

The nozzle body 23 is joined to the tip of the nozzle holder 30 via a distance piece 31, and the nozzle nut 32
The maximum lift of the needle valve 26 (
L) is regulated by a distance piece 31. Nozzle holder 30. distance piece 3
A fuel passage 33 is formed in series between the fuel injection pipe 1 and the nozzle body 23 to guide fuel from the fuel injection pipe 6 to the valve chamber 29.

A spring retainer 34 is fixed to the back of the needle valve 26, and a spring 36 is installed between the end surface of the sleeve 35 inside the nozzle holder 30 and the spring retainer 34.
is interposed.

A bushing rod 37 is slidably inserted into a sleeve 35 inside the nozzle holder 30.
A spring 39 is applied to the spring retainer 38 attached to the proximal end of the sleeve 35 to urge the bushing rod 37 downward as shown in the figure.
It is placed in contact with the end face of the In this state, a predetermined distance L+ (<L) is formed between the tip of the bushing rod 37 and the spring retainer 34.

Therefore, this fuel injection nozzle 4 can be operated by the gap L1 when the internal pressure of the fuel injection pipe 6 (pressure in the valve chamber 29) is equal to or higher than the relatively low valve opening pressure (initial valve opening pressure) corresponding to the elastic force of the spring 36. and two more springs 36.3
The maximum lift L is greater than the gap L1 at a valve opening pressure (second stage valve opening pressure) higher than the first stage valve opening pressure corresponding to the total elastic force of 9.
It is supposed to lift up to.

Further, the opening pressure of the on-off valve 15 is higher than the first stage valve opening pressure and lower than the second stage valve opening pressure.

Next, the effect will be explained.

When the fuel is pressurized and discharged by the fuel injection pump 5, it is sent to the fuel injection nozzle 4 through the fuel injection pipe 6, and when the internal pressure of the fuel injection pipe 6 exceeds the first stage valve opening pressure of the fuel injection nozzle 4, In the fuel injection nozzle 4, the needle valve 2
6 is lifted by the gap LI against the spring 36, and injection is performed.

Even after the injection starts, the oil delivery rate of the fuel injection pump 5 exceeds the injection rate of the fuel injection nozzle 4, so the pressure inside the fuel injection pipe 6 continues to rise.

When the internal pressure of the fuel injection pipe 6 exceeds the opening pressure of the on-off valve 15 of the pressure regulating device 10 provided in the middle of the fuel injection pipe 6, the valve body 17 moves to the right in the figure and opens the valve. , fuel temporarily flows out from the fuel passage 12 to the fuel reservoir 14 via the branch passage 13. Then, the pressure inside the fuel injection pipe 6 temporarily drops, and the on-off valve I5 of the pressure regulator 10 closes, and the needle valve 2G of the fuel injection nozzle 4 closes. - Therefore, injection is temporarily stopped.

After that, since the fuel injection pump 5 continues to feed oil, the pressure inside the fuel injection pipe 6 starts to rise again.

When the first-stage valve opening pressure of the fuel injection nozzle 4 is reached again, the needle valve 26 of the fuel injection nozzle 4 is shifted by the gap L1 and injection is restarted. The internal pressure of the fuel injection pipe 6 continues to rise, but this time the fuel reservoir 14 is filled with fuel and the internal fuel pressure is high, and this fuel pressure is applied to the valve body 17 of the on-off valve 15. Therefore, on-off valve 15
will never open. Therefore, the pressure inside the fuel injection pipe 6 rises to exceed the second stage valve opening pressure of the fuel injection nozzle 4, and as a result, the needle valve 26 lifts while pushing up the bushing rod 37 against the two springs 36 and 39. , it becomes fully open.

That is, fuel injection is performed twice during one cycle, and the first fuel injection is performed by the needle valve 26 of the fuel injection nozzle 4.
The second fuel injection is performed by maximizing the lift of the needle valve 26 of the fuel injection nozzle 4 to perform main fuel injection. Here, the interval between these two fuel injections can be set based on the volume of the fuel reservoir 14 and the oil feed rate of the fuel injection pump 5.

Therefore, the amount of fuel that can be ignited (pilot injection) can be performed in advance of the main fuel injection (main injection) by the ignition delay period, and the fuel injected into the combustion chamber 3 by the pilot injection is Ignition combustion occurs after the ignition delay period has elapsed.

Main injection starts immediately after this, but since the air in the combustion chamber 3 is at a high temperature due to the heat generated by the fuel injected by the pilot injection, the fuel injected by the main injection reaches evaporative combustion immediately after injection. It becomes possible to Therefore, the fuel injected by the main injection does not undergo premix combustion but diffuse combustion. Therefore, it is possible to suppress rapid combustion due to premix combustion, suppress deterioration of fuel consumption rate and smoke, and reduce the concentration of NOx. In addition, the fuel injected by the main injection evaporates instantly,
Since ignition combustion occurs, fuel does not adhere to the wall surface, and HC in the exhaust gas can also be reduced.

After the fuel injection ends, the solenoid valve 20 is opened at an appropriate time, for example at the top dead center of the exhaust stroke, by a signal from the controller 22. This is to reduce the fuel pressure in the fuel reservoir 14 by letting the fuel remaining in the fuel reservoir 14 escape through the fuel return passage 21.

FIG. 6 shows a second embodiment.

This embodiment is applied to a unit injector driven by a camshaft directly attached to a cylinder head.

The pump part includes a barrel 41 attached to the upper end of the holder 40.
The plunger 42 is inserted into the
By reciprocating the fuel by the camshaft 43, the fuel in the pressure chamber 44 is compressed and delivered.

45 is a spring rite, 46 is a spring, '47
is a pin to prevent it from coming out.

The nozzle part accommodates a needle valve 51 in a nozzle body 48, and connects this nozzle body 48 to the lower end of the boulder 4o via a distance piece 55, and attaches the nozzle nut 56.
It is fixed by A nozzle seat 49 and a nozzle hole 5o are formed in the nozzle body 48, and a needle valve 5
1 includes a needle face portion 52 and a pre-social stage 5.
3 is formed. The pressure in the valve chamber 54 between the nozzle body 48 and the needle valve 51 acts on the pressure stage 53.

57 is a spring retainer, and 5th is a spring.

The pressure chamber 44 of the pump section and the valve chamber 54 of the nozzle section communicate with each other through a fuel passage 59. 77 and 78 are fuel return passages for returning spilled fuel to the fuel tank.

A branch passage 60 is provided in the middle of the fuel passage 59, and this branch passage 60 returns fuel to the fuel tank via a normally open solenoid valve 61. & (not shown), and by controlling this electromagnetic valve 61, the injection timing and injection amount are controlled.

Further, another branch passage 62 is provided in the middle of the fuel passage 59, and this branch passage 62 communicates with a fuel reservoir 63.

Further, an on-off valve 64 is provided in the middle of the branch passage 62. The on-off valve 64 includes a valve body 66 facing a seat surface 65 formed in the middle of the branch passage 62, and is housed in a chamber 67 behind the valve body 66 and acts on the valve body 66 in the valve closing direction. It is composed of a spring 68.

69 is a support body for the spring 68, which also serves as a stopper for the valve body 66.

One side of the fuel reservoir 63 is partitioned by a slidable piston 70, which is connected to a chamber 7 behind the piston 70.
1 is biased in a direction to reduce the volume of the fuel reservoir 63. 73 is a support body for the spring 72, and 74 is a stopper for the piston 70, which is fixed to the support body 73 so that its position can be adjusted.

Numerals 75 and 76 are fuel return passages from the chambers 67 and 71.

Next, the effect will be explained.

While the plunger 42 is moved downward by the camshaft 43, an applied voltage having the characteristics as shown in FIG. The injection timing and injection amount are controlled by the valve start timing and period.

When the solenoid valve 61 closes, the downward movement of the plunger 42 causes the fuel pressure in the pressure chamber 44 to quickly rise, causing the fuel to flow out.

Fuel is guided from passage 59 to valve chamber 54 . Then, when the fuel pressure exceeds the opening pressure of the needle valve 51 (FIG. 7, C+), the needle valve 51 lifts (FIG. 7, F1), and fuel is injected from the injection hole 50.

After the injection starts or after a predetermined desired time has elapsed, the valve body 66 of the on-off valve 64 is opened by the fuel pressure (D1 in FIG. 7), and the fuel from the pressure chamber 44 flows out from the branch passage 62 to the fuel reservoir 63. . When the pressure in the fuel reservoir 63 reaches a predetermined pressure, the piston 70 is moved by the force (FIG. 7 F1), and the movement of the piston 70 performs a suction action.

Due to this suction action, the fuel pressure decreases, the needle valve 51 closes, and the pyro injection (F2) in FIG. 7 is stopped.

Thereafter, when the fuel pressure increases again and reaches the opening pressure of the needle valve 51 (FIG. 7, 03), the needle valve 51 opens again (FIG. 7, F3), and main injection is performed.

Then, the main injection ends when the solenoid valve 61 opens.

<Effects of the Invention> As explained above, according to the present invention, a fuel reservoir portion communicating with the injected fuel passage via a branch passage is provided, and
By providing an on-off valve that opens and closes in accordance with the pressure of the injected fuel in the branch passage, the main fuel injection is performed during the fuel injection during the first cycle when the piston is approximately at compression top dead center, Furthermore, fuel can be injected in an amount sufficient to ignite prior to the main fuel injection for a time corresponding to the ignition delay period. Therefore, the fuel injected during the main fuel injection period undergoes evaporative combustion instantly after injection. For this reason, the fuel injected during the main fuel injection period does not undergo premix combustion but undergoes diffusion combustion, so that deterioration of fuel consumption rate and smoke can be suppressed and NOx can be reduced.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing a conventional example of a fuel injection device for a direct injection type diesel engine, Figure 2 is a sectional view showing the shape of the tip of a hole-type fuel injection nozzle, and Figure 3 shows the conventional injection rate characteristics. 4 is a configuration diagram of a fuel injection device showing a first embodiment of the present invention, FIG. 5 is a sectional view of a fuel injection nozzle in the first embodiment, and FIG. FIG. 7 is a cross-sectional view of a unit injector showing an embodiment, and is a diagram showing operating characteristics of the second embodiment. 4...Fuel injection pump 6...Fuel injection pipe IO...
・Pressure adjustment device 12...Fuel passage 13...Branch passage 14...Fuel reservoir 15...Opening/closing valve 20
... Solenoid valve 26 ... Needle valve 36 ... Spring 37 ... Bush rod 39 ... Spring 42 ... Plunger 43 ... Camshaft 44.
...Pressure chamber 51...Needle valve 58...Spring 59...Fuel passage 61...Solenoid valve 62...
- Branch passage 63...Fuel reservoir 64...Opening/closing valve 70...Piston 72...Spring Patent applicant Nissan Motor Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 1 Figure 2 Figure 3 Kufun Yuuma

Claims (1)

[Claims] In a fuel injection device for a direct injection diesel engine, a fuel reservoir is provided in the injected fuel passage and communicated with through a branch passage, and the branch passage is provided with an on-off valve that opens and closes depending on the pressure of the injected fuel. A fuel injection device for a direct injection diesel engine featuring: