JPS586062B2 - Diesel engine fuel injection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a diesel engine,
More specifically, the present invention relates to a fuel injection device for a diesel engine that matches fuel injection pressure and engine rotation speed as much as possible.

A diesel engine is provided with a fuel injection nozzle for each combustion chamber, and the injection pressure, injection timing, and injection amount are simultaneously controlled by a plunger synchronized with the crankshaft.

On the other hand, in a diesel engine, in order to achieve good combustion, the air and fuel must be mixed well.

In order to improve the above-mentioned mixing state, a swirl is usually given to the intake air and the injection pressure is increased to make the spray finer.

However, conventional fuel injection devices have the following drawbacks.

The fuel injection pressure (that is, the degree of atomization of the fuel) and the swirl strength are proportional to the engine speed, and decrease as the engine speed decreases.

To explain this with reference to FIG. 1, the characteristic curve S indicating the swirl strength is weak in a low engine speed range, and becomes stronger as the engine speed moves to a high range.

Furthermore, the custom-made curve P indicating the injection pressure also increases as the engine speed increases.

It is obvious that when the engine is in the low rotational speed range, the intake air inflow speed is low, so the swirl is weak. Therefore, if we take only the custom injection pressure curve, it will increase as the rotational speed decreases. It is desirable to do so.

That is, when the swirl effect weakens, it is desirable to increase the injection pressure to prevent the mixture state of air and fuel from deteriorating.

However, since the known fuel injection device has the characteristics shown in Figure 1, the mixture state of fuel and intake air deteriorates in the low rotation range, the combustion state worsens, and fuel consumption increases.
Another object of the present invention, which causes deterioration of exhaust smoke, is to provide a fuel injection device for a diesel engine that improves the above-mentioned drawbacks and improves the mixing state of intake fuel, especially in a low rotation range.

This will be explained in detail below with reference to the drawings.

The fuel in the fuel tank 1 is pressurized by the fuel pump 2 and stored in the pressure accumulating chamber 3.

The fuel in the pressure accumulation chamber 3 is sent through the passage 4 to the fuel injection nozzle 5, and is sprayed into the combustion chamber 6 by the fuel injection nozzle 5.

A solenoid valve 7 is provided in a portion of the passage near the fuel injection nozzle 5, and controls the amount of fuel sprayed from the fuel injection nozzle 5, injection timing, etc.

The solenoid valve 7 is given an opening/closing signal by a controller 8.

The controller 8 calculates the factors detected by the various sensors 9, calculates the optimal injection timing, injection amount, etc., and sends an opening/closing signal to the solenoid valve 7.

Detection factors of the various sensors 9 include cooling water temperature, intake air temperature, load, etc.

In addition to the above, the controller 8 also includes a pressure accumulator 3 that determines the injection pressure.
A signal is also sent to a pressure control valve 10 that controls the pressure inside.

The pressure control valve 10 releases the fuel in the pressure accumulation chamber 3 to the fuel tank 1, and is provided in a passage connecting the fuel tank 1 and the upstream side of the fuel pump 2.

The operation of the present invention configured as described above is as follows.

Fuel in the fuel tank 1 is fed into the pressure accumulation chamber 3 by the fuel pump 2.

The rotational state of the engine is detected by a sensor 9, calculated by a controller 8, and sent an opening/closing signal to the solenoid valve 7 for each cylinder.

This opening/closing signal gives the timing and time when the solenoid valve 7 opens, and the amount of injection from the fuel injection nozzle 5 is determined by the opening time of the solenoid valve 7.

If the engine speed is now in a low rotation range, a signal is sent from the controller 8 to the pressure control valve 10 to increase the set pressure of the pressure control valve 10.

Then, the fuel pressure in the pressure accumulation chamber 3 increases, and the fuel sprayed from the fuel injection nozzle 5 is further atomized.

In this case, since the rotating iron of the engine is lowered, the swirl of the intake air in the combustion chamber 6 is weaker, but the injection pressure is higher, so the deterioration of the mixture state of the intake air and fuel is prevented. .

Subsequently, when the engine speed increases, a signal is sent from the controller 8 to the pressure control valve 10, and the set pressure of the pressure control valve 10 is set slightly lower.

Then, the pressure of the fuel sprayed from the fuel injection nozzle decreases, but in this case, the engine speed is high, so the intake swirl is strong, and deterioration of the mixture of intake air and fuel is relatively prevented. has been done.

This is shown in the characteristic curve of FIG. 1, where the injection pressure P1 decreases as the engine speed increases.

As explained above, according to the present invention, it is possible to prevent the deterioration of the mixing condition of intake air and fuel in the low engine speed range, reduce fuel consumption in the low engine speed range, and improve exhaust smoke. .

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the characteristics of injection pressure and swirl strength with respect to engine speed, and FIG. 2 is a schematic diagram showing an example of the present invention. 1... Fuel tank, 2... Fuel pump, 3... Pressure accumulator,
5... Fuel injection nozzle, 7... Solenoid valve, 8... Controller, 9... Sensor, 10... Pressure control valve.

Claims (1)

[Claims] 1. A fuel pump that boosts the pressure of fuel to injection pressure in a diesel engine that utilizes swirl; a pressure accumulator that stores the fuel pressurized by the fuel pump; a pressure control valve that controls the fuel pressure in the accumulator to a predetermined pressure; and the accumulator A fuel injection nozzle that communicates with the fuel injection nozzle to inject fuel into the combustion chamber, an electromagnetic valve that determines the injection timing and injection time of the fuel injected from the fuel injection nozzle, a controller that provides an opening/closing signal to the electromagnetic valve, and a controller that provides an opening/closing signal to the electromagnetic valve. 1. A fuel injection device for a diesel engine, comprising various input sensors, the pressure control valve being controlled by a controller to reduce the fuel injection pressure as the engine rotational speed increases.