JPH06101596A - Discharge device of fuel injection pump - Google Patents

Abstract

(57) [Summary] [Purpose] To avoid the overshoot phenomenon of the valve disc. [Structure] A cylindrical extension 13 is provided on an upper portion of the valve body 3, and a notch groove 14 formed in the cylindrical extension 13 and extending in a horizontal direction.
Is provided with a stopper 12. Further, the valve housing 1 is provided with a stopper receiver 15 for receiving the stopper 12. Then, the stopper 12 receives the stopper receiver 15
The maximum head position where the fuel oil collides with is the position where the flow passage area of the fuel oil is maximum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge valve device for a fuel injection pump, and more particularly to a discharge device for a fuel injection pump in which residual pressure in a fuel injection system is stabilized.

[0002]

2. Description of the Related Art As a conventional discharge valve device for a fuel injection pump, there is, for example, one shown in FIG. 3 (see, for example, Japanese Utility Model Laid-Open No. 51-141723).

That is, a valve body 3 consisting of a seat portion 4 in contact with a seating surface 2 of a valve housing 1, a piston portion 5 and a guide portion 6 below the seat portion 4, and an inlet portion of a hole 7 of a valve housing 1 into which the seating surface 2 is seated. A taper portion 9 is provided between the straight portion 8 and the straight portion 8.

When oil is not being pumped from an injection pump (not shown), the seat portion 4 of the valve body 3 is in pressure contact with the seating surface 2 of the valve housing 1. When the pumping of oil is started from the injection pump, the valve body 3 overcomes the biasing force of the valve spring 10 and starts sliding upward in the drawing. Since the straight portion 8 of the valve housing 1 slides on the piston portion 5 at the beginning, the flow passage 11 of the valve portion is blocked. When the valve body 3 is further lifted,
Eventually, the lower end 5a of the piston portion 5 reaches the taper portion 9 to open the flow passage 11, and the fuel oil is sent to the injection valve via the injection pipe (not shown). When the oil supply is stopped, the valve body 3
Is returned by the force of the valve spring 10. When the piston valve 5 descends after reaching the taper portion 9, the fuel oil above the valve body 3 is forcibly sucked back partially. further,
When the valve body 3 descends, the seat portion 4 comes into close contact with the seating surface 2 and the upper and lower flow paths of the valve body 3 are completely cut off. The suck-back action has the effect of improving the fuel shortage at the end of injection and preventing the residual pressure in the injection pipe and the like from rising abnormally. Further, the non-return action after the valve body 3 is seated on the seating surface 2 maintains the residual pressure at a predetermined pressure and secures the next stable injection.

The taper portion 9 is provided to suppress a change in residual pressure with respect to operating conditions. The flow passage area 11 starts to increase due to the increase in the sliding amount of the valve body 3 after the piston portion 5 moves up and moves to the taper portion 9, but since the taper portion 9 is provided, the flow passage area is increased. The maximum value of 11 can be set large. Therefore, since a sufficiently large flow passage area can be secured even in the high speed region, the overshoot phenomenon in the high speed region of the valve body 3 is less likely to occur than in the case where the tapered portion 9 is not provided.

[0006]

However, in such a conventional fuel injection pump discharge device, since the flow passage area 11 is enlarged by the taper portion 9, a sufficiently large flow passage area is provided. In order to obtain it, a large lift of the valve body 3 is required. Therefore, the sliding amount of the valve body 3 inevitably increases in the high speed range, and it is difficult to avoid a time delay until the piston portion 5 reaches the lower end of the taper portion 9 when the valve body 3 descends.

For this reason, the occurrence of the suction-back action in the high speed region is delayed, and the suction pressure is further released after the hydraulic pressure has escaped to some extent, so that there is a problem that the residual pressure is too low and cavitation is likely to occur.

The present invention has been made by paying attention to such a conventional problem, and an object thereof is to avoid the overshoot phenomenon of the valve element, to stabilize the fuel injection and to suppress the occurrence of cavitation. .

[0009]

Therefore, the present invention is directed to a fuel injection pump for a diesel engine, which is provided in a fuel injection pump for a diesel engine and has a check valve action and a suction return action. A mechanism was provided to forcibly suppress the lift expansion beyond the valve lift where the flow passage area reached the maximum value.

[0010]

[Function] Since the valve lift is limited, the valve body does not overshoot. Further, since the maximum lift position is suppressed at the position where the flow area of the fuel oil has the maximum value, the fuel amount can be secured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of the present invention.

First, the structure will be described with reference to FIG. The same components as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

A valve housing 1 having a seating surface 2 at its upper end.
A valve housing 3 having a seat portion 4, a piston portion 5 and a guide portion, a valve spring 10 for pressing the valve body 3 against the seating surface 2, and a valve body 3 having a straight portion 8
In the discharge valve device of the fuel injection pump having the hole 7 of
A cylindrical extension 13 and a cylindrical extension 1 are provided on the valve body 3.
3 is provided with a stopper 12 having a notch groove 14 extending in the horizontal direction. Further, the valve housing 1 is provided with a stopper receiver 15 for receiving the stopper 12.

Then, as shown in FIG. 2, the maximum lift Lmax at which the stopper 12 of the valve body 3 collides with the stopper receiver 15
The position is a position where the flow path area 11 has a substantially maximum value.

Next, the operation will be described. When the fuel injection pump (not shown) starts to pump the fuel oil, the valve body 10 is urged by the valve spring 10 and presses the seat portion 4 against the seating surface 2.
Start sliding upward in the figure.

At first, since the piston portion 5 slides in the straight portion 8 of the valve housing 1, even if the seating surface 2 and the seat portion 4 are separated from each other, no flow passage is formed in the front and rear of the valve body 3.

Further, when the valve body 3 slides upward and the lower end 5a of the piston portion 5 exceeds the corner portion 8a of the straight portion 8, a flow passage 11 is formed in the front and rear of the valve body 3 and thereafter. Disc 3
The flow path area 11 gradually increases in accordance with the lifting height of.

Then, as shown in FIG. 2, the stopper 12 is at the lift Lmax position where the expansion of the flow passage area with respect to the increase of the lift of the valve body 3 is almost saturated and the flow passage area has a substantially maximum value.
Collides with the stopper receiver 15, and further sliding of the valve body 3 is forcibly suppressed. Even in this state, the stopper 1
The fuel oil continues to flow out through the groove 14 bored in 2.

When the oil supply from the injection pump is stopped, the valve element 3 is pushed back by the force of the valve spring 10. In the downward movement after the lower end 5a of the piston portion 5 reaches the corner portion 8a of the straight portion 8, a sucking back action acts on the volume of the upper portion of the valve body 3.

When the valve body 3 further descends and the seat portion 4 is pressed against the seating surface 2, the check function of the valve body 3 is exerted thereafter.

As described above, the maximum lift L of the valve body 3
Since max is defined by the initial gap between the stopper 12 and the stopper receiver 15, the overshoot phenomenon of the valve body 3 does not occur under any operating condition. Therefore, the predetermined suction-back amount is surely sucked back after being lowered by the specified amount. Therefore, under any condition, the predetermined residual pressure is stably secured, the injection is stable, and the abnormal decrease in residual pressure is prevented, so that the occurrence of cavitation is prevented.

Further, in this embodiment, since the stopper 12 is provided on the valve body 3, the maximum lift Lmax can be adjusted easily and accurately by machining the end face of the stopper 12.

[0023]

As described above, according to the present invention, the overshoot phenomenon of the valve element can be avoided under any operating condition, and the abnormal reduction phenomenon of the residual pressure in the high speed operation range can be prevented. Therefore, stable fuel injection can be performed, and the occurrence of cavitation can be suppressed.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a side sectional view similarly illustrating the operation of the embodiment.

FIG. 3 is a side sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Valve housing 2 ... Seating surface 3 ... Valve body 4 ... Seat part 5 ... Piston part 8 ... Straight part 10 ... Valve spring 11 ... Flow path 12 ... Stopper 13 ... Cylindrical extension 14 ... Groove 15 ... Stopper receiving

Claims (1)

[Claims] 1. A discharge device for a fuel injection pump, which is provided in a fuel injection pump for a diesel engine and has a check valve action and a suction return action, in which a flow passage area of fuel oil in a valve portion has a substantially maximum value. A discharge device for a fuel injection pump, which is provided with a mechanism for forcibly suppressing an increase in lift more than a lift.