JPH03199664A - Fuel injection valve of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve combustion characteristics of an internal combustion engine by suppressing pressure attenuation of a needle back pressure chamber after fuel injection in comparison with attenuation of fuel pressure from a fuel injection pump. CONSTITUTION:When closed, a needle valve 26 is closed by the pressure of a spring 46 and a spring chamber 42 serving as a back pressure chamber. A reducing valve 50 as pressure control means of the back pressure chamber changes fuel injection pressure applied to the spring chamber 42 by a fuel injection pump 10 from fuel injection pressure applied to the needle valve 26 to open the needle valve 26 by fuel injection pressure. When a valve opening force by injection pressure applied to the needle 26 exceeds a valve closing force by pressure of the spring 46 and the spring chamber 42, the needle valve 26 is opened and fuel injection is made. After the completion of fuel injection, orifices 54 and 56 serving as a throttling means maintain the pressure of the spring chamber 42 for a while, so that the needle valve 26 is closed promptly by the closing force of the above pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection valve for an internal combustion engine in which a back pressure chamber is formed on the side of the needle opposite to the valve seat.

[Conventional technology]

BACKGROUND ART A fuel injection valve for an internal combustion engine is configured to apply pressure from a fuel injection pump to a needle to open the needle against a spring, thereby injecting fuel. The spring chamber formed at the end of the needle opposite the valve seat where the spring is located is usually connected to the low pressure side of the fuel system, and is used when the fuel pressure applied to the needle exceeds the closing force of the spring. The needle opens the valve.

On the other hand, in order to improve combustion performance in diesel engines and the like, it is preferable that the fuel injection pressure be high.

For this purpose, the spring must be made strong, and the closing pressure when the needle is seated on the valve seat is large, which is unfavorable in terms of durability.

Therefore, in Utility Model Application Publication No. 55-9854, a system was proposed in which the pressure from the fuel supply pump is introduced into the spring chamber (back pressure chamber), and a closing force is applied to the needle by the fuel supply pump pressure in addition to the closing force caused by the spring. are doing. A conventional fuel injection pump is arranged between the fuel supply pump and the needle of the fuel injection valve. When the fuel injection valve is not in operation, the pressure in the back pressure chamber and the needle are equal, and the valve is closed by a spring. During fuel injection, the valve-opening pressure applied to the needle by the pressure from the fuel injection pump becomes higher than the valve-closing pressure applied from the back pressure chamber, so that the needle remains open and fuel injection is performed. In this prior art, since the spring only needs to overcome the longitudinal pressure of the fuel injection pump, the aim is to increase the fuel injection pressure from the fuel injection valve without increasing the strength of the spring.

[Problem to be solved by the invention]

In the prior art, pressure from a fuel supply pump is applied to the back pressure chamber, and pressure from a fuel injection pump is applied to the needle. In order to increase the fuel injection pressure and make it possible to use a weak spring, the pressure from the fuel supply pump is applied to the back pressure chamber, and the needle pressure is reduced by the front and back pressure of the fuel injection pump. This is to enable the valve to open when it rises. In this case, the operation of the fuel injection valve is controlled according to the attenuation characteristic of the discharge pressure from the fuel injection pump, and the fuel injection pressure from the fuel injection pump rapidly attenuates with the end of fuel injection. This is because the end of fuel injection is required to be sharp in order to improve combustibility. However, in the conventional technology, the behavior at the time of closing is controlled by the pressure from the fuel injection pump itself, so if a characteristic that speeds up the pressure decay after fuel injection is selected, the pressure (residual pressure) in the nozzle chamber when the needle closes This may cause a backflow of combustion gas from the cylinder pressure to the nozzle chamber, which may be unfavorable in terms of the durability of the nozzle needle seat.

The present invention aims to solve the above problem by suppressing the attenuation of the pressure in the needle back pressure chamber after the end of fuel injection compared to the attenuation of the fuel pressure from the fuel injection pump.

[Means to solve the problem]

According to this invention, in a fuel injection valve for an internal combustion engine that applies a force in a closing direction to a needle by a spring and applies fuel pressure to a back pressure chamber formed on the opposite side of the valve seat with respect to the needle, The discharge pressure from the fuel injection pump is introduced into the pressure chamber, and the pressure characteristics of the needle in the valve closing direction due to the discharge pressure applied to the back pressure chamber are changed from the pressure characteristics of the needle in the valve opening direction. A back pressure chamber pressure control means for opening the needle, and a throttling means provided in the piping system from the fuel injection pump to the back pressure chamber to maintain the pressure in the back pressure chamber immediately after the needle valve is closed. A fuel injection valve for an internal combustion engine is provided.

[Effect]

When the valve is closed, the needle is closed by the valve closing force determined by the spring and the pressure in the back pressure chamber.

The back pressure chamber pressure control means changes the fuel injection pressure applied to the back pressure chamber from the fuel injection pump from the fuel injection pressure applied to the needle, so that the needle is opened by the fuel injection pressure. That is, when the valve opening force due to the injection pressure applied to the needle exceeds the valve closing force due to the spring plus the pressure in the back pressure chamber, the needle opens and fuel injection is performed.

At the end of fuel injection, the throttle means maintains the pressure in the back pressure chamber for a while, and the closing force caused by this pressure quickly causes the needle to close.

〔Example〕

In FIG. 1, the diesel engine has a size-type fuel injection pump 1O, and the size-type fuel injection pump 1O has a fuel discharge part 12 connected to the fuel injection valve 11 of each cylinder, and is connected to a fuel tank 14. be done.

The fuel injection pump IO is not limited to the size type, and may be of the distribution type.

Fuel injection valve 1 provided in cylinder head 16 of each cylinder
1 has a nozzle body 18, a spacer 20, and a spring chamber body 22 arranged in series, which are interconnected by a holder sleeve 24 and a nut member 25. A needle 26 is fitted into the nozzle body I8 so as to be slidable up and down, and the needle 26 opens and closes a valve seat 28 formed at the lower end of the nozzle body 18 to control fuel injection from the nozzle 30. The upper end 26-1 of the needle 26 forms a portion with a somewhat larger diameter, and a pressure receiving surface 26-1 is formed at the connection point with the lower end.
2 is formed, and a fuel reservoir 32 is formed within the nozzle body around the pressure receiving surface 26-2, and the valve opening of the needle 26 is controlled by the fuel pressure applied to this fuel reservoir 32. That is, the fuel reservoir chamber 32 communicates with the fuel receiver at the upper end of the fuel injection valve via the main fuel passage 34, and the needle 3
0 and the nozzle body 18 via the passage 40 between the valve seat 28 and the nozzle body 18.
It extends to

A spring chamber 42 serving as a back pressure chamber in this embodiment is formed inside the spring chamber main body 22, and a busher 44 is connected to the upper end of the needle 26 within the spring chamber 42. The lower end of the spring 46 contacts this bushing 44,
The upper end of the spring 46 is connected to a pressure reducing valve 50 via a shim 48.

The pressure reducing valve 50 is formed into a rod shape with a flange 50 - 1 formed at the upper end, and the flange portion 50 - 1 is urged toward the lower surface of the nut member 25 by the spring 44 . The pressure reducing valve 50 has an orifice 54 passing through it in the direction of its central axis, one end of the orifice 54 opening into the spring chamber 42, and the other end opening into the recess 2 formed by the nut member 25.
It opens at 5a. On the other hand, the nut member 25 has an orifice 56 formed in the direction of its central axis, one end of which opens into the recess 25a, and the other end of which opens into the chamber 38 for receiving fuel from the discharge portion 12 of the fuel injection pump 10.

To explain the operation of this embodiment, the pressure from the fuel injection pump IO starts to rise when the fuel injection timing for that cylinder comes (FIG. 2 (0) f). This pressure is introduced into the fuel reservoir 32 via the passage 34 and causes the needle 26 to move against the spring 4.
6 and urge it upward. On the other hand, the fuel injection pump 10
Pressure from is introduced into the spring chamber 42 through the orifice 56,54 to bias the needle 26 in the closing direction. Spring chamber 4 due to the presence of orifice 56.54
The pressure increase of 2 has a characteristic of m which is slower than the pressure increase characteristic of the fuel reservoir chamber 32 (FIG. 2(b)). When the upward force due to the fuel pressure applied to the second needle 26 exceeds the downward force due to the fuel pressure in the spring chamber 42, the needle lifts and fuel injection begins via the passage 40 and the valve seat 28 ( (A) Line X).

In the process of increasing the fuel pressure from the fuel injection pump 10, when the differential pressure across the pressure reducing valve 50 overcomes the spring 46, the pressure reducing valve 50 moves downward (a in FIG. 2(c)), and the nut member 25 The pressure in the spring chamber 42 increases more rapidly than before due to the distance from the lower surface (m'
). When the pressure difference before and after the pressure reducing valve is eliminated, the pressure reducing valve 50
sits down on Natsuto's face again.

The injection pressure from the fuel injection pump 10 reaches its peak and then starts to drop (line n), and the pressure in the fuel reservoir 32 drops along this line n. On the other hand, the pressure reducing valve 50 is seated in the spring chamber 42, and pressure is released through the orifices 54 and 56. Therefore, the pressure drop characteristic becomes slow as shown in p, and the spring chamber 42 remains at high pressure for a while. maintained. As a result, a large force in the valve closing direction is still applied to the needle 26, and the needle 26 is rapidly closed (y in Fig. 2 (a)), achieving both early injection termination and high valve closing pressure. can be done.

In this embodiment, the pressure reducing valve 50 can be omitted. In this case, the pressure change in the spring chamber 42 is
It becomes like q in figure (0). Even in this case, there is an effect that the pressure in the spring chamber 42 when the valve is closed is higher than in the normal case.

The second embodiment shown in FIG. 3 is characterized in that a check valve 60 is provided. A fuel receiver of the check valve 60 is provided between the chamber 38 and the pressure reducing valve 50, and a spring 62 urges the check valve 60 to contact the upper surface of the flange portion 50-l of the pressure reducing valve 50. The check valve 60 and the pressure reducing valve 50 have an appropriate rear lance or groove between them and the inner periphery of the main body 20, through which fuel can pass (see FIGS. 4 and 5).

To explain the operation of this second embodiment, when the pressure from the fuel injection pump increases (FIG. 6(o) 1-1), the pressure reducing valve 50 initially maintains a seated state on the nut member 25, Since the orifice 54 is closed by the check valve 60, the spring chamber 42 maintains the initial pressure k.

When the pressure difference across the pressure reducing valve 50 overcomes the spring 46, the pressure reducing valve 50 moves downward together with the check valve 60 (a-1 in FIG. 6(c)). Therefore, the fuel injection pressure is applied to the spring chamber through the orifice formed by the gap between the check valve 6o and the main body 22 (Fig. 4) and the gap between the pressure reducing valve 5o and the main body 22 (Fig. 5). 42 was introduced. That is, the pressure in the spring chamber increases (m- in Fig. 6).
1) is performed with a predetermined time delay from the increase in fuel injection pressure.

Further, since the clearance of the check valve 60 is extremely small, the pressure rise in the back pressure chamber at the initial stage of injection can be reduced, and there is an advantage that the change in the valve opening pressure of the needle is small.

When the pressure difference applied to the needle 26 overcomes the spring 46, the needle 26 begins to lift (Fig. 6(a)).
X). When the needle starts moving, the volume of the spring chamber 42 decreases, the pressure of the spring chamber 42 increases, and the downward force increases, so the initial needle lift amount can be suppressed, and the initial injection rate can be reduced. .

After the fuel injection pressure reaches the maximum, when the pressure difference between the front and rear of the pressure reducing valve 50 becomes smaller than the set pressure of the spring 46, the pressure reducing valve 50 seats on the lower surface of the nut 25, and when the fuel injection pressure decreases, the pressure in the spring chamber 42 decreases. acts on the lower surface of the check valve 6° through the orifice 54, and
is separated from the pressure reducing valve 50 against the spring 62, and the fuel in the spring chamber 42 is gradually released. Therefore,
The pressure in the spring chamber near the fuel injection path can be maintained high (FIG. 6(0) p-1). When the pressure release from the spring chamber 42 progresses to a certain extent, the check valve 6o comes into contact with the pressure reducing valve 50 again by the spring 62, and the pressure in the spring chamber is maintained at an appropriate value in order to close the orifice 54. Figure (b) k). That is, the pressure receiving surface of the check valve on the pressure reducing valve side and the spring 62
It becomes possible to appropriately adjust the valve opening pressure of the needle 26 by setting the force of .

FIG. 7 shows a third embodiment, which is a modification of the first embodiment and differs in the following points. That is, a pressure chamber 70 as a back pressure chamber is formed on the lower surface of the pressure reducing valve 50, and the pressure in the pressure chamber 70 is transmitted to the needle 26 via a command piston 72. A shim 73 adjusts the closing force of the needle 26 by the spring 46. Fuel pressure is introduced into the pressure chamber 70 through the orifice 56 and the command piston 7
A force in the closing direction is applied to the needle 26 via the needle 26. The operation of the pressure reducing valve 50 during the process of increasing the fuel injection pressure is the same as in the first embodiment. In the process of increasing the fuel injection pressure, the pressure reducing valve 50 suppresses the pressure increase in the pressure chamber 70 as a back pressure chamber more than the increase in the fuel injection pressure, increases the pressure before and after the needle, and causes the needle to open. When the fuel injection pressure to end fuel injection decreases, the pressure reducing valve 50 is seated;
To gradually release pressure from the pressure chamber 70 through the orifice 56, to make the rate of pressure drop in the pressure chamber 70 considerably slower than the rate of drop in fuel injection pressure, and to increase the force in the needle closing direction to rapidly stop the injection. I can do it.

In the fourth embodiment shown in FIG. 8, the command piston is connected to the pressure chamber 70.
It is constituted by a two-stage piston in series, a first piston 90 on the side of the needle 26, and a second piston 92 on the side of the needle 26. The upper end of the spring 46 is engaged with the flange portion 92 - 1 at the upper end of the second piston 92 , and the first piston 90 is urged upward by the spring 46 via the second piston 92 .

The operation of the pressure reducing valve 50 is the same as in the first and third embodiments. That is, in the process of increasing the fuel injection pressure, the pressure reducing valve 50 controls the pressure increasing characteristic of the pressure chamber 70 and controls the fluid pressure applied to the needle 26 in the closing direction. The force applied to the needle can also be adjusted by the area of the flange portion 92-1. In the process of ending fuel injection, the pressure reducing valve 50 is seated and the pressure in the pressurizing chamber 70 is gradually released through the orifice 56, thereby maintaining a large closing force on the needle and quickly ending the injection.

Furthermore, in the fourth embodiment shown in FIG. 8, a two-stage valve opening characteristic can be obtained by providing some clearance between the bushing 44 and the second piston 92.

The third and fourth embodiments have the advantage that the downward force can be adjusted by changing the diameter of the command piston.

[Effect] According to this invention, the pressure from the fuel injection pump is guided not only to the needle but also to the back pressure chamber, and the pressure in the back pressure chamber is adjusted to the needle pressure by the throttle 54, 56, pressure reducing valve 50 or check valve 60. By controlling the pressure to change and opening the needle, while temporarily maintaining the pressure in the back pressure chamber at the end of injection using the throttle means, it is possible to achieve rapid injection path deflection characteristics, which improves the internal combustion engine. It is possible to improve the combustion characteristics of

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main structure of a fuel injection valve according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating the operation of the embodiment shown in FIG. 1 during fuel injection. FIG. 3 is a cross-sectional view showing the main structure of a fuel injection valve according to a second embodiment of the present invention. 4 and 5 are cross-sectional views of the check valve and pressure reducing valve in FIG. 3 (the clearance state is exaggerated). FIG. 6 is a diagram illustrating the operation of the second embodiment of FIG. 3 during fuel injection. FIG. 7 and FIG. 8 are sectional views showing the configuration of main parts of fuel injection valves of a third embodiment and a fourth embodiment, respectively. 10...Fuel injection pump, 11...Fuel injection valve, 1
2...Fuel discharge part, 14...Fuel tank, 16...
・Cylinder head, 18... Nozzle body, 20...
Spacer, 24... holder, 25... nut member,
26... Needle, 28... Valve seat, 30.
...Nozzle, 32...Fuel reservoir chamber, 38...Fuel receiver chamber, 42...Spring chamber, 44...Button, 4
6... Spring, 50... Pressure reducing valve, 54.56.
... Orifice, 60 ... Check valve, 70 ... Pressure chamber, 72 ... Command piston, 90 ... First piston, 92 ... Second piston. To other cylinder injection valves 〆-ノ(-) 14... Fuel tank 18... Nozzle body 26... Needle 28... Valve seat 30... Nozzle 50... Pressure valve 54.56... - Orifice Fig. 2 Fig. 3 Fig. 6 o... Check valve No. 7 Fig. 26-N Needle 50... Pressure reducing valve 70... Pressure chamber 72... Command piston Fig. 6 Check valve displacement 100 yen Fig. 50 ...Reducing valve 60...Check valve 26...Needle 92...Second piston

Claims (1)

[Claims] In a fuel injection valve for an internal combustion engine that applies a force in the closing direction by a spring to the needle and also applies fuel pressure to a back pressure chamber formed on the opposite side of the valve seat with respect to the needle, a fuel injection pump is installed in the back pressure chamber. A passageway is provided in the passageway to guide the discharge pressure from the back pressure chamber, and the pressure characteristic in the valve closing direction of the needle due to the pressure applied to the back pressure chamber is changed from the pressure characteristic in the valve opening direction applied to the needle to respond to the discharge pressure. 1. A fuel injection valve for an internal combustion engine, comprising a throttle means for opening a needle and maintaining pressure in a back pressure chamber immediately after the needle is closed.