JPS622295Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fuel injection device for an internal combustion engine.

Conventional fuel injection devices for internal combustion engines, such as bottle-type fuel injection devices, have a fuel injection valve attached to each cylinder of the engine, and a high-pressure fuel injection valve that increases the pressure of low-pressure fuel sent from a fuel tank and sends it to the fuel injection valve. The fuel pump has a number of plunger pumps corresponding to each cylinder,
The plunger pump and the fuel injection valve are connected by high-pressure pipes whose number is equal to the number of cylinders. On the other hand, the amount of fuel injection is adjusted by connecting sleeves that adjust the escape amount of each plunger pump with a rack and pinion, and adjusting the amount of movement of this rack. The fuel injection amount characteristics at this time vary depending on the engine speed.

However, the fact that the fuel injection amount characteristics change depending on the engine speed when the torque is constant is disadvantageous as it may cause engine hunting, especially in areas where the fuel injection amount changes significantly in response to changes in the engine speed. be. In other words, the pressure vibrations, pressure waves, and pressure loss of the pressure fluid that occur in the high-pressure pipes that send high-pressure fuel from each plunger pump of the fuel pump to the fuel injection valves directly affect the opening and closing of the fuel injection valves, and this affects the engine. This is because it changes depending on the rotation speed. This actually becomes an element of instability and requires a complicated governor mechanism.

The present invention was developed in consideration of the above-mentioned issues, and it is possible to create a space in the metering chamber that changes in proportion to the predetermined amount of fuel flowing in from the fuel pump without changing the injection amount. It is an object of the present invention to provide a fuel injection device for an internal combustion engine in which the injection characteristics are not limited to the rotational speed by determining the injection characteristics based on this space.

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

In the figure, 1 is a unit injector, 2 is its nozzle, 3 is a needle that faces this nozzle 2 and is biased in the closing direction by a spring 3a, and 4 is a unit injector whose pressure-receiving surface is opposite to the needle 3. This is a high pressure chamber that communicates with the nozzle 2 via. Reference numeral 5 denotes a metering chamber, and the bottom of the pressure regulating chamber 5 communicates with the high pressure chamber 4 and the fuel inlet 6. A check valve 7 is interposed in a passage connecting the metering chamber 5 and the fuel inlet 6 to allow flow in the direction of the metering chamber 5. A metering piston 8 having one end facing the metering chamber 5 is fitted in the metering chamber 5 in a slidable and fluid-tight manner. 9 is a push rod whose tip is slidably provided opposite the other end of the metering piston 8; 10 is this push rod 9;
This is a return spring that urges the metering piston 8 away from the metering piston 8. And 11 is pushy rod 9
This is a cam that comes into contact with the end face of the The relationship between the length of the push rod 9 and the size of the cam 11 is as follows:
1, when the push rod 9 is pushed in the most, the metering piston 8 is moved by the push rod 9 over a predetermined distance in a direction to reduce the volume inside the metering chamber 5, and the push rod 9 is returned by the return spring 10. In this state, there is a gap between the metering piston 9 and the other end. The chamber between the metering piston 8 and the push rod 9 and the spring chamber of the needle 3 are connected to the drain circuit 1.
It is connected to 2.

The fuel inlet 6 of the unit injector 1 having the above structure is connected to a fuel pump 13, for example, a variable fuel discharge pump. The variable fuel flow rate discharge pump 13 is configured to intermittently feed a determined injection amount into the unit injector 1 in synchronization with the rotation of the engine before the injection timing of the unit injector 1. The discharge pressure only needs to be enough to push up the metering piston 8 of the unit injector 1.

The operation of the above embodiment will be explained below.

Unit injector 1 in the state shown in the drawing
is the state before the start of fuel injection, but when fuel is intermittently fed from the fuel pump 13 at this time, the fuel pushes open the check valve 7, enters the metering chamber 5, and pushes the metering piston 8. Push up. At this time, since there is a space above the metering piston 8 that communicates with the drain passage 12, the metering piston 8 is connected to the fuel pump 1.
The injection amount increases by the amount determined in step 3.

Then the cam 11 rotates and the push rod 9 begins to be pushed down. Note that at this time, oil supply from the variable fuel flow rate discharge pump 13 has ended. When the tip of the downwardly moving push rod 9 comes into contact with the metering piston 8 and begins to push it down, the fuel in the metering chamber 5 begins to be compressed and pressure is generated. At the same time, the check valve 7 is closed, and pressure is also generated in the high pressure chamber 4 communicating with the nozzle 2. Further, when the metering piston 8 is lowered together with the push rod 9, the pressure in the high pressure chamber 4 increases, and the needle 3 is moved by the spring 3.
The nozzle 2 is moved upward against the pressure a, and fuel is injected from the nozzle 2.

Next, when the push rod 9 passes the stroke end, compression ends and the pressure in the metering chamber 5 begins to drop. When this drops to a certain extent, the needle 3 is moved downward by the spring 3a, the nozzle 2 is closed, and the secondary injection is started. Being held down.

When the cam 11 further rotates, the push rod 9 begins to be pushed up by the return spring 10, but the upper side of the metering piston 8 is connected to the drain circuit 12.
Since the lower metering chamber 5 is filled with fuel and sealed by the check valve 7 and needle 3, the metering piston 8 does not rise.

The above action is repeated in synchronization with engine rotation.

The present invention is as described above, and by applying high pressure fuel to the opening pressure surface of the nozzle 2, the needle 3 is opened against the spring 4a, and the high pressure fuel is supplied from the nozzle 2. In the unit injector 1 configured to inject, a metering piston 8 is slidably connected to a metering chamber 5 communicating with a high pressure chamber 4 facing the pressure receiving surface of the needle 3, and one end surface is connected to the metering chamber 5. The other end of the metering piston 8 is fitted with the other end facing the drain circuit, and the other end of the metering piston 8 is
A push rod 9 that pushes the metering piston 8 by moving with a cam 11 that rotates in synchronization with the rotation of the engine is placed in opposition, and a fuel pump 13 is connected to the metering chamber 5 via a check valve 7. The parts where high pressure is generated are the metering chamber 5 and the needle 3.
The pressure-receiving surface of the high-pressure chamber 4 faces the high-pressure chamber 4, and there is only a passage communicating between the two, pressure vibrations, pressure waves, and pressure loss of the fuel oil are almost unaffected, and all the fuel that enters from the fuel pump 13 is injected. Even if the engine speed changes, the fuel injection amount does not change. In addition, since the fuel pump 13 only needs to intermittently supply fuel into the metering chamber 5, low pressure can be achieved and costs can be reduced.

[Brief explanation of the drawing]

The drawing is a configuration explanatory diagram showing a main part of an embodiment of the present invention in cross section. 1 is a unit injector, 2 is a nozzle, 3 is a needle, 3a is a spring, 4 is a high pressure chamber, 5 is a metering chamber, 7 is a check valve, 8 is a metering piston, and 13 is a fuel pump.

Claims (1)

[Scope of utility model registration request] A needle 3 having a pressure-receiving surface for opening is provided at the opening of the nozzle 2, and by applying high-pressure fuel to the pressure-receiving surface, the needle 3 is opened against the spring 3a, and the high-pressure fuel is transferred to the nozzle 2. In the unit injector 1 configured to inject air from above, a metering piston 8 is slidably inserted into a metering chamber 5 communicating with a high pressure chamber 4 facing the pressure receiving surface of the needle 3.
The metering piston 8 is fitted with one end facing the metering chamber 5 and the other end facing the drain circuit.
A push rod 9 that pushes the metering piston 8 by moving with a cam 11 that rotates in synchronization with the engine rotation is opposed to the other end, and fuel is further supplied to the metering chamber 5 via a check valve 7. A fuel injection device for an internal combustion engine, characterized in that a pump 13 is connected.