JPS6111502Y2 - - Google Patents

Description

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

This type of pressure boosting unit injector A is the first
As shown in the figure, the head of the servo piston chamber 1 is connected to the supply port 3 of the rotary valve 2.
The pressure increasing piston 4 in the servo piston chamber 1 is pushed against the return spring 5 by the high-pressure fuel supplied from this supply port 3, and the plunger 6 that operates together with the pressure increasing piston 4 is pressed against the return spring 5. Fuel metered into the pressure chamber 7 is injected from the nozzle 8. 9 is a drain passage opened at the bottom of the servo piston chamber 1;
During operation, fuel on the bottom side of the servo piston chamber 1 is drained from this drain passage 9.

By the way, the conventional pressure booster unit injector A
In this case, the drain passage 9 was opened on the side surface of the bottom of the servo piston chamber 1, and the lower end surface of the pressure booster piston 4 was flat, so that the pressure booster piston 4 did not approach the bottom. Then, when the stroke end state is reached, the fuel on the bottom side of the servo piston chamber 1 is trapped in this chamber and its pressure is increased, which causes the pressure increase piston 4 to operate near the stroke end in the pressure increase operation direction. A problem arises in that the speed decreases and the desired injection pressure cannot be obtained.

On the other hand, in order to solve this problem, the drain passage 9
By providing it on the bottom of the servo piston chamber 1, etc.
If the opening area of the drain passage 9 is not changed by the operation of the pressure booster piston 4, the operating speed of the pressure booster piston 4 will not decrease and the injection pressure will increase. It violently collides with the bottom of the piston chamber 1, generating impact noise and shock waves.

The above-mentioned impact sound causes noise, and there is a problem that the impact force reduces the durability of the injector.The impact wave also advances to the rotary valve 2, where it reverses and returns to the injector side as a negative pressure wave. There is a risk that the pressure boosting piston 4 will operate due to this negative pressure.

The present invention was developed in view of the above, and includes a throttle opening at the end of the pressure increasing piston that communicates with a drain passage provided in the servo piston chamber at the end of the stroke of the pressure increasing piston in the pressure increasing operation direction. By providing this, when the pressure increasing piston operates to increase the pressure, it is possible to prevent the end face of the pressure increasing piston from shockingly colliding with the bottom surface of the servo piston chamber at the end of the stroke, and also prevent the end face of the pressure increasing piston from impacting the bottom surface of the servo piston chamber at the end of the stroke. An object of the present invention is to provide a pressure-increasing unit injector that can suppress a decrease in the operating speed of the pump.

The configuration will be explained below based on the embodiment shown in FIG. Note that the parts not shown in this figure are
It has the same configuration as the conventional example shown in the figure.

In the figure, reference numeral 10 denotes a pressure boosting piston fitted into the servo piston chamber 1. A slit 11 is provided in the lower end surface of the pressure boosting piston 10 in the radial direction, and this slit 11 corresponds to the drain passage 9. The drain passage 9 is connected to the pressure increasing piston 10 from near the stroke end to the stroke end in the pressure increasing operation direction of the pressure increasing piston 10 .

By supplying high-pressure fuel from the rotary valve 2 into the servo piston chamber 1, the pressure increasing piston 10 moves in the pressure increasing operation direction. When this approaches the stroke end position, the drain passage 9 is constricted by the lower end of the pressure booster piston 10, and reaches the stroke end while receiving a buffering effect from this constriction. On the other hand, at the end of this stroke, the inside of the pressure boosting piston 10 is slit 1.
1, the pressure increasing piston 10 is connected to the drain passage 9 at the end of the stroke.
Fuel is no longer trapped within the stroke end, and the speed reduction of the pressure booster piston 10 near the stroke end is suppressed to the speed reduction range due to the above-mentioned buffering effect, and the speed of the pressure booster piston 10 does not drop more than necessary. .

In the above embodiment, the pressure boosting piston 10 is provided with the slit 11, but the slit 11 is not limited to the slit, and may be a fine hole.

The present invention is as described above, and high pressure fuel is supplied from the rotary valve 2 to the head of the servo piston chamber 1 partitioned by the pressure booster piston 10, and the pressure booster piston 10 is actuated by the pressing force at this time. By doing so, metered fuel is injected into the pressure boosting chamber 7, and on the bottom side of the servo piston chamber 1 partitioned by the pressure boosting piston 10,
In a pressure boosting unit injector having a drain passage 9 for draining fuel from the bottom side of the servo piston chamber 1 when the pressure boosting piston 10 is activated, one end of the pressure boosting piston 10 and the end on the bottom side of the servo piston chamber 1 In addition, when the pressure increase piston 10 moves to the vicinity of the stroke end in the pressure increase operation direction, a throttle opening such as a slit 11 is provided in the radial direction, which communicates the drain passage 9 with the inside of the pressure increase piston 10. Therefore, in the pressure increasing operation of the pressure increasing piston 10, the end surface of the pressure increasing piston 10 is
This prevents the piston from impacting the bottom surface of the servo piston chamber 1 at the end of its stroke, and also suppresses a decrease in the operating speed of the pressure booster piston 10 at the end of its stroke, thereby reducing noise and shock waves. can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a pressure boosting unit injector to which the present invention is applied, and FIG. 2 is a cross-sectional view showing the main parts of the present invention. 1 is the servo piston chamber, 2 is the rotary valve,
7 is a pressure boosting chamber, 9 is a drain passage, and 10 is a pressure boosting piston.

Claims (1)

[Scope of utility model registration request] High pressure fuel is supplied from the rotary valve 2 to the head of the servo piston chamber 1 partitioned by the pressure booster piston 10, and the pressure booster piston 10 is actuated by the pressing force at this time, thereby increasing the pressure in the pressure booster chamber 7. The metered fuel is injected into the bottom side of the servo piston chamber 1 partitioned by the pressure boosting piston 10, and when the pressure boosting piston 10 is activated, the fuel on the bottom side of the servo piston chamber 1 is injected. In a pressure boosting unit injector having a drain passage 9 for draining water, the pressure boosting piston 10 is placed at one end of the pressure boosting piston 10 and at the end on the bottom side of the servo piston chamber 1 until the pressure boosting piston 10 reaches the vicinity of the stroke end in the pressure boosting operation direction. A pressure boosting unit injector characterized in that a throttle opening such as a slit 11 is provided in the radial direction to communicate the drain passage 9 with the inside of the pressure boosting piston 10 when the unit moves.