JPS6039487Y2 - Pressure boosting unit injector - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pressure boosting unit injector for use in a diesel engine.

The pressure boosting unit injector A is shown in FIG. 1, and its servo piston chamber 1 is connected to the supply port 3 of the rotary valve 2.
The pressure booster piston 4 in the servo piston chamber 1 is pushed against the return spring 5 by the high-pressure fuel supplied from is injected from the nozzle 8.

When the rotary valve 2 is switched and the pressure in the servo piston chamber 1 becomes low, the pressure increasing piston 4 and the plunger 6 are returned by the return spring 5, and the urging force of the return spring 5 and the servo piston chamber 1 are
It is returned to a position where it balances the internal pressure.

Then, an amount of fuel corresponding to the return amount of the plunger 6 at this time flows from the servo piston chamber 1 into the pressure boosting chamber 7 from the metering circuit 10 in which the check valve 9 is interposed, and is metered. There is.

Reference numeral 11 designates a suction valve from which fuel in the pressure increase chamber 7 leaks through a leak hole 12 provided in the plunger 6 at the end of the injection stroke.

Such a pressure boosting unit injector A has a metering circuit 1 that communicates the servo piston chamber 1 and the pressure boosting chamber 7.
0 was equipped with one normally closed check valve 9 that only allowed flow in the direction of the pressure booster chamber, so fluctuations in the pressure inside the servo piston chamber 1, overshoot of the return spring 5, etc. 4, if the metering movement exceeds the desired metering height, the metering amount, which is the next injection amount that flows into the pressure boosting chamber 7 through the check valve 9, will be lower than the desired injection amount. It ends up being too many.

This phenomenon occurs because the metered amount once flowing through the check valve 9 does not flow back.

For this reason, in the above-mentioned pressure boosting unit injector using one normally closed check valve 9, the injection amount tends to vary, and since the injection amount can only be reduced after one cycle, the deceleration of the engine decreases. There was a problem with that.

The present invention was developed in consideration of the above-mentioned issues, and by making it possible to connect the metering circuit with the pressure booster piston in its returned state, that is, in the metering state, the pressure increase system during metering is improved. The piston can be stopped at a predetermined position only by the balance between the pressure inside the servo piston and the biasing force of the return spring, making it possible to always obtain the desired metering amount stably without variation, and also improve engine deceleration. The present invention aims to provide a pressure-increasing unit injector that can improve the performance.

The configuration will be explained below based on the embodiment shown in FIG.

Note that in this embodiment, the same
Constituent members are indicated by the same reference numerals and explanations are omitted.

A metering circuit 13 is installed at the servo piston chamber 1 side end of the metering circuit 13 that communicates the servo piston chamber 1 and the pressure increase chamber 7, and is normally open and only when the piston operating pressure is reached in the servo piston chamber 1. A first check valve 14 is interposed so as to close against splashing.

In addition, the end of the metering circuit 13 on the pressure intensifying chamber 7 side is normally open.
In addition, a second check valve 15 is interposed which closes against a spring only when the pressure in the pressure increase chamber 7 reaches the pressure for fuel injection.

In the above configuration, during fuel injection when high-pressure fuel acts in the servo piston chamber 1 and the pressure booster piston 4 is pushed against the return spring 5, the first check valve 1
4 is closed by the operating pressure in the servo piston chamber 1,
Further, the second check valve 15 is closed by the pressure in the pressure increase chamber 7 during injection, and the fuel in the pressure increase chamber 7 is injected from the nozzle 8.

At the end of the injection stroke, the leak hole 12 provided in the plunger 6
communicates with the suction return hole, and the pressure inside the pressure intensifying chamber 7 becomes low.

At this time, the second check valve 15 is opened, but the pressure inside the servo piston chamber 1 is still at the operating pressure, and the first check valve 15 is opened.
Since the second check valve 15 is open, the fuel in the servo piston chamber 1 will not leak from the leak hole 12.

Next, the rotary valve 2 switches and the servo piston chamber 1
When the pressure becomes low, the pressure increasing piston 4 is returned by the return spring 5, and the plunger 6 is returned together with it.

At this time, the pressure in the servo piston chamber 1 and the pressure increase chamber 7 becomes low, so that the first. The second check valves 14 and 15 are opened, and as the plunger 6 returns, the fuel in the servo piston chamber 1 flows into the pressure increase chamber 7 through the metering circuit 13 and is metered.

The open state of both check valves 14 and 15 is maintained until the end of metering and the start of the injection stroke, during which time the pressures in the servo piston chamber 1 and the pressure increase chamber 7 are approximately the same.

Therefore, even if the pressure booster piston 4 moves beyond the desired metering height due to pressure fluctuations in the servo piston chamber 1, overshoot of the return spring 5, etc. during the metering, the pressure booster piston 4 It can return without being disturbed by the fuel in the servo piston chamber 1, and is stopped at a position balanced by the pressure inside the servo piston chamber 1 and the return spring 5, that is, at the desired metering height.

The present invention is as described above, and the servo piston chamber 1 is connected to the supply port of the rotary valve 2. The pressure booster piston 4 is operated by the pressure booster piston 4 and is connected to the servo piston chamber 1 via the metering circuit 13, and the metering circuit 13 is connected to the servo piston chamber 1 during the metering operation of the pressure booster piston 4. The pressure boosting unit injector is composed of a pressure boosting chamber 7 into which fuel flows and is metered, and the fuel in the pressure boosting chamber 7 is injected from a nozzle 8 by the operation of the pressure boosting piston 4. At the servo piston chamber 1 side end of the metering circuit 13 that communicates the piston chamber 1 and the pressure boosting chamber 7, there is a normally open circuit that closes only when the pressure in the servo piston chamber 1 reaches the piston operating pressure. A normally open second check valve that closes only when the pressure in the pressure intensification chamber 7 reaches the fuel injection pressure is provided at the end of the metering circuit 13 on the pressure intensification chamber 7 side. The metering circuit 1 communicates the servo piston chamber 1 and the pressure increase chamber 7 because the pressure increase type unit injector is constructed by interposing the servo piston chamber 1 and the pressure increase chamber 7.
3 can be kept in an open state during metering, whereby the pressure booster piston 4 can be stopped at a predetermined position only by the balance between the internal pressure of the servo piston chamber 1 and the biasing force of the return spring 5 during metering. is possible,
The desired metering amount can always be obtained stably without variation.

Further, since the injection amount can be set by a predetermined amount for each cycle, the injection amount can be decreased for each cycle, and the deceleration performance of the engine can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional example, and FIG. 2 is a sectional view showing an embodiment of the present invention. 1 is a servo piston chamber, 2 is a low pressure valve, 4 is a pressure increase piston, 5 is a return spring, 7 is a pressure increase chamber, 8 is a nozzle, 1
3 is the metering circuit, 14.15 is the check valve.

Claims (1)

[Scope of utility model registration request] It is operated by the pressing force of the servo piston chamber 1 connected to the supply port of the rotary valve 2 and the high pressure fuel fitted into the servo piston chamber 1 and supplied into the servo piston chamber 1. The pressure booster piston 4 that operates as a ring communicates with the servo piston chamber 1 via a metering circuit 13, and when the pressure booster piston 4 is metering, fuel flows through this metering circuit 13 and the fuel is metered. In a pressure boosting unit injector, the servo piston chamber 1 and the pressure boosting chamber 7 are connected to each other in a pressure boosting unit injector, which consists of a pressure chamber 7, and fuel in the pressure boosting chamber 7 is injected from a nozzle 8 by the operation of the pressure boosting piston 4. At the servo piston chamber 1 side end of the metering circuit 13,
A normally open first check valve 14 that closes only when the pressure in the servo piston chamber 1 reaches the piston operating pressure is installed at the end of the metering circuit 13 on the pressure increasing chamber 7 side. The normally open second valve closes only when the internal pressure reaches the fuel injection pressure.
A pressure boosting unit injector characterized in that a check valve 15 is interposed in each of the injectors.