JPS59703B2 - internal combustion engine fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection pump for an internal combustion engine.

A typical fuel injection pump has a structure shown in FIG.

This pump has a plunger 2 having an inclined notch 1 on its outer periphery, and a delivery valve 4 which is pressed against a valve 7 by a spring 3.

The plunger 2 is pushed downward by a spring 7, and a roller 8 at the lower end is in pressure contact with a cam 9.

When the cam 9 rotates counterclockwise from the state shown in FIG. The delivery valve 4 moves up and delivers fuel oil as shown.

Next, as shown in C, when the notch 1 of the plunger faces the suction/discharge hole 5 of the plunger barrel, the pressure inside the plunger chamber 6 drops rapidly, the delivery of fuel oil stops, the delivery valve moves down, and at that time the piston The lowering of the portion 7 causes the fuel to be sucked back.

Thereafter, the plunger further rises to reach state d, and then descends to return to state a.

Such a fuel injection pump has a drawback in that when the delivery valve descends, the delivery valve collides with the valve seat due to the elasticity of the spring 3 and the reduced pressure in the plunger chamber 6, resulting in loud noise.

The present invention aims to provide a fuel injection pump that eliminates such drawbacks, and has a structure in which the fuel oil pressure in the plunger chamber can be adjusted, and by slowing down the descending speed of the delivery valve, noise can be reduced. It is characterized by being able to reduce the amount of fuel and maintain the fuel sucking back effect.

In addition, in the fuel injection pump of an internal combustion engine, the pump driving cam is of an asymmetrical type with a descending surface cut from the lift surface, so that when the engine rotates in reverse, the injection timing is delayed to prevent combustion and thus reverse drive. The prior art is disclosed in Utility Application No. 50-12944 (Utility Patent Application No. 51-9612).
With the microfilm photographing the contents of the specification and drawings attached to the request No. 3), and with respect to the same pump,
The prior art, which automatically switches cams with different profiles at startup and during high-speed operation to control fuel injection timing, injection period, fuel injection amount, etc.
No. 7-12669 (Utility Model Application No. 48-87414) is known from the microfilm photographing the contents of the specification and drawings attached to the application.

This will be explained below with reference to the drawings.

As shown in FIG. 2, in the present invention, plunger 2
The notch 1a is provided in an open manner above the plunger.

In the pump shown in FIG. 1, the notch 1 is provided at a position spaced downward from the top surface of the plunger, and the length from the top surface of the plunger to the notch 11 is the effective stroke of the fuel discharge reservoir. In the plunger, fuel discharge begins after the notch 1a passes through the intake/discharge hole 5, enters the effective stroke, and ends at the end of the upward stroke of the plunger, as will be described in detail later.

Furthermore, during the downward stroke of the plunger, the plunger chamber 6 remains at a high pressure, so that the delivery valve descends as the plunger descends.

Therefore, in the present invention, by selecting the shape of the cam,
At the beginning of the descent, the plunger rapidly descends to perform a suction-back action, and thereafter the plunger gradually descends and hits the valve seat at a low speed.

Figure 3 shows the shape of the cam 10, where point a is the maximum lift and the end of the upward stroke of the plunger, followed by a steep slope that rapidly descends from that point, followed by a gentle slope C. After that, the lowest point d is reached.

Next, to explain the operation of the present invention, FIG. 2a shows the descending end of the plunger 2. From this position, the cam 10 rotates counterclockwise, the plunger rises, and the notch 1a passes through the suction and exhaust hole 5. However, when the pressure within the plunger chamber 6 becomes greater than the force of the spring 3, the delivery valve 4 rises as shown in Figure C, and fuel begins to be discharged.

FIG. 2d shows the end of the plunger's upward stroke and then begins its downward movement.

At this time, the pressure inside the plunger chamber 6 remains high! ! that's why,
The delivery valve 4 does not suddenly descend as in the example shown in FIG. 1, but begins to descend following the descent of the plunger, that is, according to the shape of the cam 10.

At the beginning of the downward stroke, the cam is provided with a steep slope so that the plunger descends rapidly and the delivery valve accordingly descends rapidly.

This rapid descent allows a reliable suction-back effect to be obtained.

Subsequently, the downward speed of the plunger decreases due to the gentle slope C of the cam, and the delivery valve contacts the valve seat at a low speed in Figure f.

As the notch 1a further descends from the intake/discharge hole 5, fuel is sucked into the plunger chamber 6 and reaches the descending end a.

Thereafter, the same operation as above is repeated to deliver fuel.

As is clear from the above, according to the present invention, the descending speed of the delivery valve is determined according to the descending speed of the plunger, so by selecting the shape of the cam, the speed at the end of the descent of the side delivery valve is reduced, and the valve seat is It is possible to prevent noise by avoiding collision with the vehicle.

Furthermore, the initial downward speed of the delivery valve can be increased to ensure a suction-back effect.

[Brief explanation of drawings]

Figure 1 a% d is a sectional view showing a conventional fuel injection pump, Figure 2 a=f is a sectional view showing a fuel injection pump according to the present invention, and Figure 3 is a view showing a cam. ...
Notch, 2...Plunger, 5...Suction/exhaust hole 6...Plunger chamber, 7...Spring, 8...Roller, 9
．． 10...cam.

Claims (1)

[Claims] 1. A plunger that moves up and down in the plunger barrel by a cam, a plunger chamber at the top of the plunger, a delivery valve that is pressed against a valve seat by a spring and rises due to the pressure in the plunger chamber, and a delivery valve that is provided in the plunger barrel and inside the plunger chamber. A notch is provided on the side surface of the plunger to open the plunger chamber above the plunger, and the plunger chamber is compressed as the notch passes through the suction and exhaust hole during the upward stroke of the plunger. A fuel injection pump for an internal combustion engine, characterized in that a cam is configured such that the cam descends rapidly at the beginning of a descending stroke and then reduces the descending speed.