JPS6339792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge valve for a fuel injection pump of an internal combustion engine, and more specifically, a so-called discharge valve having a first valve body that opens when fuel is pumped and a second valve body that opens in the opposite direction. Regarding a constant residual pressure discharge valve.

In order to prevent secondary injection and irregular injection in fuel-injected internal combustion engines, a first valve element (delivery valve) that opens when fuel is pumped is provided on the plunger discharge side of a fuel injection pump, and what it is. Some valves are combined with a second valve body that opens in the opposite direction. Immediately after the fuel injection operation when the first valve body closes, the pressure in the fuel pipe leading to the fuel injection nozzle (so-called residual pressure)
As is well known, when the pressure is high, the second valve element opens, and as a result, the high pressure there is eliminated, maintained at a predetermined value, and irregular injection is prevented.

As a conventional structure of such a constant residual pressure discharge valve, the first
There are valve bodies in which a second valve body and a second valve body are arranged in parallel or in series with an interval between them. However, the external size of this structure is too large, and it is impossible to replace it with the discharge valve of a commercially available small fuel injection pump and use it as is, and it is necessary to change the dimensions of the pump body, the dimensions for mounting it on the engine, etc. be.

Another constant residual pressure discharge valve is known in which a second valve body is housed within a first valve body (U.S. Pat.
No. 3364863). According to this structure, it is possible to reduce the external dimensions of the discharge valve, so that the above-mentioned drawbacks are solved. However, in this discharge valve, the second
The disadvantage is that it has a complicated structure in which the spring that biases the first valve body in the valve-closing direction is supported by a disk that is secured to a pin that is press-fitted into the first valve body. The number of points increases, and the production cost increases. In addition, because the disk, which serves as the spring seat, is fixed by press-fitting a pin, it is impossible to adjust the spring load with shims, etc., and as a result, the second valve body is Fluctuations in valve opening pressure are particularly likely to occur when the discharge valve is small. Further, since the pin is subjected to impact when the valve body is seated, there is a risk that the pin may fall off due to long-term use.

Therefore, in view of the drawbacks of the conventional constant residual pressure discharge valve, the object of the present invention is to provide a valve that is small in size and can be used as is in a conventional pump, yet has a simple structure and is advantageous in terms of cost. It is an object of the present invention to provide an improved discharge valve that allows easy adjustment of valve opening pressure and has sufficient strength.

The present invention will be explained below with reference to the accompanying drawings.
In FIG. 1, a plunger 10 is slidably provided within a cylinder 12 and is driven up and down by a cam (not shown). An oil supply/drainage hole 16 is bored in the cylinder 12 . A plunger chamber 18 is formed on the upper side of the plunger 10, which communicates with an inclined notch 20 formed in the surface of the plunger 10, which notch 20 is formed on the upper side of the plunger 10.
plunger chamber 1 until electrical conduction occurs between the
It is well known that the compressing action of the fuel in the fuel cell 8 is performed.

The discharge valve is a first valve body 2 that is used for pumping fuel.
2, and a second valve body 23 that opens in the opposite direction. As shown in an enlarged view in FIG.
The first spring 26 is slidably provided on a substantially cylindrical valve seat member 24 fixed to the upper end of the first valve body 22 , and the first spring 26 connects the tapered portion 22 a of the first valve body 22 to the valve seat member 2 .
4, a biasing force is generated to force it to sit. 1st
As shown in FIG. 3, the lower part of the first valve body 22 has a plurality of longitudinal notches at the sliding part with the valve seat member 24 to form an oil supply groove 27. This allows fuel to pass through when the valve is open.

The second valve body 23 as a whole has a valve seat member 24
The upper end guide pin portion 23a
is fitted into the center hole 27 of the first valve body 22. As shown in FIG. 3, the guide pin portion 23a has a plurality of longitudinal notches to form a relief groove 28, which allows fuel to return when the second valve body 23 is opened. The diameter of the middle portion of the second valve body 23 is enlarged to form a valve portion 23b. This valve part 2
3b is the plunger side end surface 22c of the first valve body 22
so that this end surface 22
c constitutes the valve seat surface of the second valve body 23. The second spring 30 urges the valve body 23 to sit on the valve seat surface 22c, in other words to close the valve, and its upper end abuts against the valve portion 23b of the second valve body 23. On the other hand, the lower end is received on an annular shelf 24a formed at the lower end of the valve seat member 24 via a shim 32.

As shown in FIG. 2, a throttle 34 is formed in the center hole of the first valve body 22, and an expansion chamber 36 is formed on the plunger side. On the other hand, the side opposite to the plunger forms a discharge valve chamber 38, which leads to a fuel injection nozzle of each combustion chamber (not shown).

To explain the operation of the fuel injection pump equipped with the discharge valve according to the present invention as described above, in FIG. It is compressed by the rise of the driven plunger 10, passes through the lower inflow hole 40, pushes up the first valve body 22 against the spring 26 to open it, and flows through the oil supply groove 27 into the discharge valve chamber. 38 and reaches the corresponding fuel injection valve via a pipe (not shown). Here, plunger 1
During the 0 compression stroke, the second valve body 23
Since the opening of the center hole 27 on the plunger chamber 18 side is closed, the fuel pressure inside the plunger chamber 18 does not leak and the plunger chamber 18
The airtightness inside is maintained. When the plunger 10 rises until its notch 20 communicates with the oil supply/drainage hole 16, oil escapes from here due to the force of the spring 26 and the first
As a result of the valve body 22 closing, the discharge action ends.

Immediately after this ends, if the residual pressure in the fuel piping system from the discharge valve chamber 38 to the fuel injection nozzle (not shown) differs from the pressure in the plunger chamber 18 by a predetermined value or more, the second valve body 23 resists the spring 30. The valve opens in the opposite direction to the first valve body 22 as shown in FIG. 4, and returns from the discharge valve chamber 38 to the plunger chamber 18 via the relief groove 28 occurs as shown by the arrow, reducing the residual pressure to below the set value. Return to During this return, pressure vibrations in the discharge valve chamber 38 are absorbed by the action of the throttle 34 and the expansion chamber 36.
So-called cavitation erosion and secondary injection are prevented.

In the present invention, the lower end of the spring 30 that opens and closes the second valve body 23 is connected to the shelf part 24 that is integrated with the valve seat member 24.
Since it is designed to be exposed at point a, it is improved in strength compared to conventional products, does not cause damage even after long-term use, and has fewer parts, which is advantageous in terms of cost. Since the structure is simple, it is also advantageous in manufacturing. In addition, by replacing the shim 32 shown in FIG.
It is possible to change and adjust the load.

In addition, in FIG. 2, the guide pin portion 23a of the second valve body 23 that is fitted into the first valve body 22 is not an essential structure, and may be omitted.

In the second embodiment of the present invention shown in FIG.
24 so as to fit tightly. This valve portion 123b has a notch 1 that serves as an oil passage as shown in FIG.
23c. Note that a suction collar 122d having an appropriate suction amount (maximum load 0.5 to 20%) is formed on the first valve body 122. Also, spring 13
0 is an annular plate 12 separate from the valve seat member 124
4a.

In the modification shown in FIG. 7, the second valve body is a ball-shaped valve body 223 having a diameter larger than that of the center hole, and this second valve body 223 is located at the plunger chamber 18 side opening of the center hole. It is designed to be seated on a seat portion formed in the.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fuel injection pump having a constant residual pressure discharge valve according to the present invention, FIG. 2 is an enlarged view of this constant residual pressure discharge valve, and FIG. 3 is a line taken along the line - - in FIG. FIG. 4 is the same as FIG. 2 but shows when the second valve body is open, FIG. 5 is a view showing another embodiment, and FIG. 6 is the same as FIG. 5. FIG. 7 is a cross-sectional view taken along line - 7, and is a diagram showing still another embodiment using a ball-shaped second valve body. 10... Plunger, 22... First valve body, 2
2c... Valve seat surface, 23... Second valve body, 24...
Valve seat member, 26...first spring, 30...second spring.

Claims (1)

[Scope of Claims] 1. A fuel injection pump for an internal combustion engine that pressurizes fuel in a plunger chamber to high pressure by the compression movement of a plunger and injects it from an injection nozzle, provided between the plunger chamber and the injection nozzle. The discharge valve includes a substantially cylindrical valve seat member, a first valve body that is detachably provided to the valve seat member and opens in response to fuel pressure on the plunger chamber side, and the first valve body. a first spring that always biases the first valve body in the valve-closing direction; and a first spring configured to close the plunger chamber side opening of a center hole formed in the valve seat member and penetrating the first valve body. a second valve element that opens in response to fuel pressure on the injection nozzle side; and a second valve element that is provided within the valve seat member, with one end acting on the second valve element and the other end acting on the second valve element. a second spring that normally biases the second valve element in the closing direction by acting on the valve seat member, and the second valve element is positioned at the other end of the center hole during the compression stroke of the plunger. A discharge valve for a fuel injection pump, characterized in that a side opening is closed to maintain fuel pressure in the plunger chamber airtight. 2. The second valve element is a bead-shaped valve element having a diameter larger than the center hole, and the bead-shaped valve element is biased in the valve-closing direction by the second spring. The fuel for an internal combustion engine according to claim 1, wherein the fuel for an internal combustion engine according to claim 1 is configured to close an opening of the center hole on the plunger chamber side by sitting on a seat formed in the opening of the center hole on the plunger chamber side. Discharge valve for injection pump.