JPH0422059Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a pressure booster plunger type fuel injection device.

[Prior art]

As a fuel injection device for an internal combustion engine, the pressure booster plunger is driven by a spool valve that is controlled by various signals depending on the operating status of the internal combustion engine, and the fuel sent from the fuel pump is sucked into the plunger pump. A pressure boosting plunger type fuel injection device is known which is configured to measure fuel in a metering section in parallel with this, and to supply the measured fuel to an injection nozzle and inject it into a fuel chamber.

This conventional device is configured to adjust the stroke of the pressure booster plunger and meter the amount of fuel delivered from the pressure booster plunger to the amount required for one injection and supply it to the nozzle. However, this device has the following drawbacks.

FIG. 1 is a diagram showing the relationship between the fuel injection amount from the pressure curve inside the pipe, with the vertical axis representing the pressure P in the pipe leading to the fuel injection nozzle and the horizontal axis representing the injection time T. When the fuel injection amount is small, that is, when operating under low load, the maximum pressure inside the pipe is Pa as shown by the dotted curve A, and the pressure inside the pipe does not become high.

However, when the fuel injection amount is large, that is, during high-load operation, the maximum pipe internal pressure is Pb, as shown by the solid line curve B, and the pressure inside the pipe is maintained high.

As a result, the maximum pressure inside the pipe changes depending on the load condition of the internal combustion engine. That is,
In conventional pressure booster plunger type fuel injection devices, the pressure fluctuation in the pipe that supplies fuel to the fuel injection nozzle is approximately 500 kg/cm ² at low load, and about 500 kg/cm 2 at high load, for example when the internal combustion engine is a diesel engine. The pressure will be about 700Kg/cm ² or more. As described above, the conventional pressure booster plunger type fuel injection device has the disadvantage that the pressure within the pipe communicating with the fuel injection nozzle fluctuates significantly in relation to the load of the internal combustion engine.

The above-mentioned fluctuation in the pressure of the fuel supplied to the injection nozzle means that when the internal combustion engine is under low load, low-pressure fuel is supplied to the fuel injection nozzle; In this case, high pressure fuel is supplied to the fuel injection nozzle. This causes variations in the spray state of the fuel injected from the same fuel injection nozzle, and in the low load range of the internal combustion engine, the fuel may not become sufficiently fine particles, resulting in poor mixing with air. This resulted in disadvantages such as the deterioration of the engine's performance, the generation of smoke, and a decrease in output.

Such a problem can be caused by a fuel injection system that lowers the opening pressure of the injection nozzle when the engine is under low load, as in the fuel injection devices described in Japanese Patent Application Laid-Open No. 54-113730 and Japanese Patent Application Laid-Open No. 57-73857. If you do so, there is a risk that it will grow even further.

In addition, in conventional devices, the pressure booster plunger always makes a full stroke, so it is necessary to measure the fuel supplied to the fuel chamber of the pressure booster plunger.This metering is controlled by the opening time of the solenoid valve, etc. There is also the problem that metering accuracy is not achieved due to valve operation delays, and the correct injection amount cannot be consistently obtained.

Furthermore, the fuel injection device described in Japanese Utility Model Application Publication No. 58-14456 is also equipped with a variable pressure regulator that pressurizes the piston provided at the back of the fuel injection nozzle when the engine load is low and releases the pressure when the engine load is high. Therefore, the problems mentioned above could not be solved.

[Purpose of invention]

The present invention was developed in order to eliminate the drawbacks of the conventional pressure booster plunger type fuel injection device, and is aimed at controlling the opening pressure of the fuel injection nozzle according to the load of the internal combustion engine to inject fuel. Adjust the injection amount,
An object of the present invention is to provide a pressure boosting plunger type fuel injection device that always uses the maximum pressure of a predetermined plunger pump to inject fuel at a high level and is configured to eliminate fuel metering errors.

The configuration of the present invention for achieving the above object is that a piston operated by fluid pressure is provided on the back side of a fuel injection nozzle operated by a pressure booster plunger, and a variable pressure regulator for increasing or decreasing the fluid pressure is provided. A fuel injection device for an internal combustion engine is provided with a control device that controls the variable pressure regulator so as to increase the fluid pressure when the load is low and to decrease the fluid pressure when the load is high.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 2 is a piping diagram of a pressure booster plunger type fuel injection system, showing a spool valve 1 driven by signals such as the rotational speed and load of the internal combustion engine, and an increaser controlled by this spool valve 1. pressure plunger 2;
A fuel injection nozzle 5 connected to the discharge port of the plunger 3 of the pressure booster plunger 2 by a pipe 4;
A variable pressure regulator 6 that controls the valve opening pressure of the fuel injection nozzle 5, a constant pressure fuel pump 7, an accumulator 8, and a control unit 9 that controls the spool valve 1 and the variable pressure regulator 6.
A regulator 10 for controlling the pressure in the discharge line of the constant pressure pump 7 is provided.

In the present invention, a piston 5b is provided on the valve body 5a of the fuel injection nozzle 5 in the device, and fuel regulated by the variable pressure regulator 6 is supplied to the piston 5b via the pipe 18. It is configured. Further, the flow rate of the fuel supplied to the variable pressure regulator 6 is adjusted by a throttle 19 or the like.

Further, the control unit 9 controls the variable pressure regulator 6 so as to increase the fuel pressure acting on the upper part of the piston 5b when the load is low, and to decrease the fluid pressure when the load is high.

[Inhalation stroke]

Now, during the fuel suction stroke, the device controls the spool valve 1 according to a signal from the control unit 9.
is operated to open the piston chamber 2b to the atmosphere. The fuel from the constant pressure pump 7 is supplied to the pipe 1
1 flows as shown by arrow A, presses the lower surface of piston 2a, and rises as shown by arrow B. At this time, fuel flows in the direction of arrow C via the pipe 12 and check valve 13 into the plunger chamber 3a. In this case, the fuel stored in the piston chamber 2b at the upper part of the piston 2a flows through the pipe 15 in the direction of arrow D via the spool valve 1 which is open to the atmosphere, and returns to the fuel tank 16. .

[Injection stroke]

Next, to explain the fuel injection stroke, when a "fuel injection" signal is issued from the control unit 9, the valve body 1b of the spool valve 1 moves to the right in the figure by the action of the solenoid coil 1a, and the constant pressure pump 7 The fuel flows through the pipe 17 in the direction of arrow E, fills the piston chamber 2b, and presses the piston 2a at high speed.

Since fuel is sucked into the plunger chamber 3a during the upward stroke (suction stroke) of the piston 2a,
As the plunger 3 directly connected to the piston 2a descends, the increased pressure of the fuel is supplied to the fuel injection nozzle 5 via the pipe 4 and injected into the combustion chamber of the internal combustion engine.

[Control of injection pressure]

In this invention, the fuel injection nozzle 5 is particularly adopted.
The piston 5b is connected to the upper part, and the valve body 5a is pressed in the closing direction by the spring 20, but the elastic force of the spring 20 is further affected by the pressure of the fluid applied to the back surface of the piston 5b. Yes.
The pressure on the back surface of the piston 5b is controlled by a variable pressure regulator 6, which is configured to be controlled by the value of the engine load EL supplied to the control unit 9. There is. ER is an engine rotational speed signal necessary for switching control of the spool valve 5.

Therefore, when the pressure on the back surface of the piston 5b is large, the closing pressure of the valve body 5a becomes large, so the valve closes at a high fuel pressure, and as a result, a small amount of fuel passes through the fuel injection nozzle 5. The fuel is then injected into the combustion chamber. When a small amount of fuel is injected in this way, the internal combustion engine is under low load.

Next, when the pressure on the back surface of the piston 5b is small, the valve body 5a starts to open earlier than in the above case and closes later, so that a large amount of fuel is injected. This state is a high load state.

FIG. 3 shows the operating state of the fuel injection device according to the present invention, and the vertical axis shows the pressure P inside the pipe 4.
The horizontal axis shows the fuel injection time T.

As the plunger 3 moves downward, the inside of the pipe 4 is pressurized and depressurized as shown by curve C.

When the internal combustion engine is under low load, the fuel injection nozzle 5
Since pressure is applied to the back surface of the piston 5b so that the valve opening pressure becomes Pc, the fuel injection nozzle 5 opens at point A and closes at point B. Therefore,
The area between the straight line Pc indicating this pressure value and the curve C indicates the amount of fuel injected at low load.

Next, when the load is high, pressure is applied to the back surface of the piston 5b so that the fuel injection nozzle 5 opens at point C and closes at point D. Therefore, the area surrounded by the upper part of the straight line Pd and the curve C indicates the amount of fuel injected into the fuel chamber under high load.

Therefore, in the device of the present invention, the pressure booster plunger does not make a full stroke, and the fuel injection amount is determined in 1:1 correspondence to the valve opening pressure of the fuel injection nozzle 5, so the valve opening pressure stored in the control unit 9 in advance If the valve opening pressure of the fuel injection nozzle 5 is controlled based on the pressure-fuel injection amount characteristic, there is no need to measure the amount of fuel supplied to the fuel chamber of the pressure booster plunger.

[About variable regulator]

In the device according to the present invention, it is necessary to control the pressure of the fuel that pressurizes the back surface of the piston 5b that presses the valve body 5a, depending on the load condition of the internal combustion engine. A variable pressure regulator 6 is used.

Various types of variable pressure regulators can be used as the variable pressure regulator 6, and for example, the devices shown in FIGS. 4 and 5 can be used.

This variable pressure regulator 6 houses a plunger 31 in a main body 30, a pinion 33 is engaged with a rack 32 provided on the plunger 31, and the pinion 33 is connected to a stepping motor 34, for example.
etc., so as to be configured to be driven in accordance with the load signal of the internal combustion engine.

The main body 30 has a fuel supply port a and a fuel delivery port b.
and a reflux port c are provided, and the fuel from the constant pressure pump 7 is supplied to the delivery port c via the passage 35 provided in the plunger 31 via the supply port a.
It is supplied into the piston chamber 5c above the piston 5b. The amount of fuel passing through the passage 35 is larger than the amount of fuel that drives the piston 5b, and is constantly being recirculated via the recirculation port b.

The reflux port b is connected to the slit groove 3 as shown in FIG.
6 is formed, and the amount of recirculated fuel is adjusted depending on the state in which the plunger 31 closes this slit groove 36.

The relationship between the slit groove 36 and the plunger 31 is a kind of on-off valve, and it is preferable that the movement of the plunger 31 and the amount of recirculation be linearly proportional.

[Effect of idea]

As described in detail above, the fuel injection device for an internal combustion engine according to the present invention is provided with a piston operated by fluid pressure on the back side of the fuel injection nozzle operated by the pressure booster plunger, and increases or decreases the fluid pressure. The present invention is characterized in that a variable pressure regulator is provided to control the variable pressure regulator, and a control device is provided to control the variable pressure regulator so as to increase the fluid pressure when the load is low and to reduce the fluid pressure when the load is high.

Therefore, the fuel injection device for an internal combustion engine of the present invention has the following features:
As shown in FIG. 3, fuel is injected by opening and closing the valve.

In the fuel injection state of the conventional device shown in FIG. 1, there was a drawback that the injection pressure inevitably decreased when the load of the internal combustion engine was low, but in the device according to the present invention, the fuel injection state shown in FIG. The fuel injection valve is configured to operate as follows, without being affected by the load on the internal combustion engine, by adjusting the valve opening pressure of the fuel injection nozzle to adjust the fuel injection amount, and to ensure that fuel is injected at the maximum pressure of the plunger pump.

Utilizing the maximum pressure in this way has an important meaning, as it can sufficiently atomize the fuel even at low speed rotation of the internal combustion engine, and improves the mixing of fuel and air to produce smoke. It is possible to prevent such things from occurring or reducing the output of the engine.

This atomization behavior of the fuel occurs from low to high loads, so the internal combustion engine is driven smoothly regardless of load fluctuations.

Note that the fuel injection device according to the present invention is particularly effective when used for a diesel engine.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the fuel injection pressure of a conventional internal combustion engine, Fig. 2 is a piping diagram showing an outline of the pressure booster plunger type fuel injection device according to the present invention, and Fig. 3 is a diagram showing the fuel injection in the device according to the present invention. A diagram showing pressure, FIG. 4 is a front sectional view showing an example of a variable pressure regulator,
FIG. 5 is a plan cross-sectional view of FIG. 4. 1... Spool valve, 2... Pressure booster plunger, 2
a... Piston, 2b... Piston chamber, 3... Plunger, 3a... Plunger chamber, 5... Fuel injection nozzle, 5a... Valve body, 5b... Piston, 6
...Variable regulator, 7...Constant pressure pump, 9...
...Control unit, 10...Regulator.

Claims (1)

[Scope of utility model registration request] A piston operated by fluid pressure is provided on the back side of the fuel injection nozzle operated by the pressure booster plunger, and a variable pressure regulator is provided to increase or decrease the fluid pressure. A fuel injection device for an internal combustion engine, comprising a control device that controls the variable pressure regulator to reduce the fluid pressure at certain times.