JPH05332218A - Fuel injector of diesel engine - Google Patents

Abstract

PURPOSE:To provide an ideal injection property by depressing a trigger valve in an instant with high pressure fuel to inject fuel when an accumulator chamber is formed in an injection nozzle to supply the high pressure fuel and the trigger valve is moved downward by low pressure fuel supplied through a solenoid valve. CONSTITUTION:While fuel is supplied to a fuel chamber 3e of an injection nozzle 3 provided in a cylinder head 2 by a feed pump 11, high pressure fuel P1 boosted by a fuel pump 15 driven by a cam 16 is supplied to an accumulator chamber 3b so that the high pressure fuel P1 acts on the peripheral surface of a trigger valve 5. When a solenoid valve 7 is electrified by a computer 10 to open the valve element 7a in the start of fuel injection, low pressure is adapted to flow into a recess 5a on the trigger valve 5 from the feed pump 11 to depress the trigger valve 5. The trigger valve 5 is depressed in an instant by high pressure fuel, and fuel in the fuel chamber 3e is pressurized by a needle valve 4 to be injected into a cylinder 1b from a nozzle 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine improved to obtain an ideal injection characteristic.

[0002]

2. Description of the Related Art The following conditions are required for a fuel injection device used in a conventional diesel engine. (1) Fuel injection timing can be controlled according to engine rotation and load, (2) High-pressure injection of 1500 kg / cm ² or more is possible, (3) Relatively low injection during initial injection, and late injection Is capable of injecting with a high injection pressure, (4) the high pressure state is sharply cut when the valve is closed, and is not gradually closed, and (5) a high injection pressure is obtained even in a low speed range, (6) Various improvements have been made in the past in order to control the injection pressure and to satisfy the above conditions. A conventional fuel injection system is shown in FIGS.

[0003]

However, in the conventional fuel injection system described above, an ideal fuel injection system that satisfies all of the above conditions (1) to (6) is realized. It has not been. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection device for a diesel engine that can satisfy all of the above conditions.

[0004]

In order to achieve the above object, the present invention forms a pressure accumulating chamber in an injection nozzle provided in a cylinder head of an engine body, and provides a trigger valve in the accumulating chamber, and Above this trigger valve,
An electromagnetic valve that lowers the trigger valve by using the low pressure from the feed pump is provided, and a high pressure is supplied from the fuel pump into the pressure accumulating chamber, and the trigger valve is instantaneously driven by this high pressure as the trigger valve moves downward. The needle valve is connected to the trigger valve, and the needle valve pressurizes the fuel in the fuel chamber to inject the fuel at a high pressure from the injection hole at the tip of the injection nozzle. is there.

[0005]

With the above structure, it is possible to provide a fuel injection device having ideal injection conditions.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail with reference to the drawings shown in FIGS. FIG. 2 shows a main body 1 of a diesel engine, in which a cylinder head 2 provided at an upper portion is provided with a fuel injection nozzle 3 for each cylinder 1a. As shown in FIG. 3, the fuel injection nozzle 3 has a needle valve 4 that opens and closes an injection hole 3a opened at the tip of the nozzle 3, and the upper end of the needle valve 4 is inside a pressure accumulating chamber 3b. It is connected to the provided trigger valve 5. The trigger valve 5 is biased upward (in the opening direction of the needle valve 4) by the compression spring 6 housed in the spring chamber 3c, and the peripheral edge 5b of the recess 5a formed on the upper surface of the trigger valve 5 is It is pressed against the upper surface of the pressure accumulating chamber 3b.

An electromagnetic valve 7 whose valve opening timing is controlled by a computer 10 is provided above the injection nozzle 3 to shut off the low pressure flowing from the feed pump 11 into the recess 5a of the trigger valve 5. The open valve body 7a is opened and closed. The feed pump 11 discharges a low pressure of, for example, 20 kg / cm ² , the discharge pressure is supplied from the fuel supply passage 3d of the injection nozzle 3 to the fuel chamber 3e at the tip of the nozzle 3, and the surplus fuel is supplied from the return passage 3f. It is adapted to be returned to the tank 13 via the passage 12.

On the other hand, reference numeral 15 in the figure is a pressurizing device installed on the side of the engine body 1 as shown in FIG. 3, and has a plunger 15a driven by a cam 16 and, for example, 100 kg / high-pressure cm ² P1
Is to occur. This high pressure is supplied to the pressure accumulating chamber 3b of the injection nozzle 3 through a pipe line 17, and the pressure accumulating chamber 3b is connected to the tank 13 by a pipe line 19 provided with a pressure regulating valve 18 whose opening is controlled by the computer 10.
It is connected to the. The pressure in the pressure accumulating chamber 3b is detected by the internal pressure detector 20 and input to the computer 10.

The operation will now be described. A constant amount of fuel is supplied to the fuel chamber 3e of the injection nozzle 3 by the feed pump 11, and the pressure chamber 3b is driven by the fuel pump 15 driven by the cam 16. High pressure P1 is supplied,
The pressure in the pressure accumulating chamber 3b gradually rises as shown in FIG. Even if the pressure in the pressure accumulating chamber 3b rises to, for example, 100 kg / cm ² , this high pressure P1 only acts on the peripheral surface of the trigger valve 5, and the trigger valve 5 does not start operating.
At the injection start timing thereafter, a signal from the computer 10 first energizes the solenoid valve 7 to open the valve body 7a, whereby the low pressure from the feed pump 11 flows into the recess 5a of the trigger valve 5 and the trigger valve Since 5 is pressed downward, the high pressure P1, which has been acting on the peripheral surface of the trigger valve 5 until now, also acts on the upper surface of the trigger valve 5, and presses the trigger valve 5 with a force of 314 kg, for example.

If the spring force of the compression spring 6 is 20 kg, for example, the needle valve is pushed downward with a pressing force of 314-20 = 294 kg. As a result, π × 0.52 × P2 / 4 = 29
4, the needle valve 4 pressurizes the fuel in the fuel chamber 3e, and the fuel is injected from the injection hole 3a into the cylinder 1b at a high pressure of P2 = 1500 kg / cm ² . Thereafter, as the discharge pressure of the fuel pump decreases, the pressure in the pressure accumulating chamber 3b also decreases as shown in FIG. 4, and the trigger valve 5 is raised by the compression spring 6 and returns to its original position. The valve body 7a of the solenoid valve 7 is closed at the same time when the trigger valve 5 starts to descend, so that the high pressure P1 in the pressure accumulating chamber 3b does not escape.

The above is the first embodiment in which the fuel pump 15 driven by the cam 16 is used. As in the second embodiment shown in FIGS. 5 to 7, a high pressure is applied to the fuel pump 15. The resulting gear pump may be used.
In this case, the high pressure P1 always acts in the pressure accumulating chamber 3b and the trigger valve 5 does not rise even after the fuel injection. Is provided, and by repeatedly opening and closing the distribution valve 22, pressurization and depressurization are repeated, so that a pressure pattern as shown in FIG. 7 is obtained in the pressure accumulating chamber 3b.

Further, the trigger valve 5 is provided so that a low injection pressure is obtained in the initial stage of fuel injection and a high injection pressure is obtained in the latter stage.
A notch 5c or 5d is formed in the peripheral edge portion 5b as shown in (a) or (b) of FIG. As a result, the accumulator 3
Even if the pressure P1 in b is constant, a low injection pressure is obtained in the initial stage and a high injection pressure is obtained in the latter period.

[0013]

As described above in detail, according to the present invention, the injection timing can be freely controlled by controlling the opening / closing timing of the solenoid valve, and the fuel can be injected at a high pressure of 1500 kg / cm ² or more. Further, fuel can be injected at a low pressure in the initial stage of injection and at a high pressure in the latter period, and the needle valve is seated in a state where high pressure is applied after the injection, so that a sharp cut at the time of valve closing becomes possible. Further, by increasing the discharge pressure of the fuel pump, a high injection pressure can be obtained from a low speed range, and by controlling the pressure regulating valve, the injection pressure can be freely controlled, and various conditions (1) to (6) are satisfied. An ideal fuel injection device that satisfies all of the requirements can be obtained.

[Brief description of drawings]

1A to 1C are configuration diagrams showing a conventional fuel injection system.

FIG. 2 is a perspective view of a diesel engine including a fuel injection device according to an embodiment of the present invention.

FIG. 3 is a sectional view of a fuel injection device according to a first embodiment of the present invention.

FIG. 4 is a diagram showing a pressure change in a pressure accumulating chamber of the fuel injection device according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a fuel injection device according to a second embodiment of the present invention.

6 (a) and 6 (b) are explanatory views showing the shape of a trigger valve devised so as to have an injection characteristic that the pressure is low in the initial stage of injection and becomes high in the latter stage.

FIG. 7 is a diagram showing a pressure change in a pressure accumulating chamber of the fuel injection device according to the second embodiment of the present invention.

[Explanation of symbols]

 1 Engine Main Body 2 Cylinder Head 3 Injection Nozzle 3a Injection Hole 3b Accumulation Chamber 3e Fuel Chamber 4 Needle Valve 5 Trigger Valve 7 Electromagnetic Valve 11 Feed Pump 15 Pressurizer

Claims (2)

[Claims] 1. A pressure accumulating chamber 3b is formed in an injection nozzle 3 provided in a cylinder head 2 of an engine body 1, and a trigger valve 5 is provided in the pressure accumulating chamber 3b. Above the trigger valve 5, An electromagnetic valve 7 for lowering the trigger valve 5 using the low pressure from the feed pump 11 is provided, and a high pressure is supplied from the fuel pump 15 into the pressure accumulating chamber 3b so that the trigger valve 5 moves downward. The high pressure causes the trigger valve 5 to be pushed down instantly, and the needle valve 4 is connected to the trigger valve 5 to pressurize the fuel in the fuel chamber 3e by the needle valve 4 to inject the injection at the tip of the injection nozzle. A fuel injection device for a diesel engine, which is configured to inject fuel at a high pressure through a hole 3a. 2. The high pressure supplied to the pressure accumulating chamber 3b is regulated by the pressure regulating valve 1.
The fuel injection device according to claim 1, wherein the injection pressure can be controlled by controlling the fuel injection pressure by the control unit 8.