JPH0355807Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel feed pressure control valve for adjusting the fuel pressure in a fuel chamber provided in a pump housing in a distribution type fuel injection pump.

[Conventional technology]

It is known that a distribution type fuel injection pump has a structure shown in FIG. That is, the seventh
In the figure, reference numeral 1 denotes a drive shaft driven by a diesel engine, and this drive shaft 1 drives a rotary feed pump 3 in a pump housing 2 and also rotates a plunger 4.

The feed pump 3 introduces fuel from the fuel tank 5 and supplies it to a fuel chamber 6 within the pump housing 2. The fuel pressure in this fuel chamber 6 increases according to the rotational speed of the engine, that is, the rotational speed of the feed pump 3, but this fuel chamber 6 is connected to a timer 7, and the pressure is the same as the fuel pressure in the fuel chamber 6. is applied to the timer piston 8 to control the fuel injection timing.

Therefore, the fuel pressure within the fuel chamber 6 affects the fuel injection timing, and thus influences engine performance and exhaust gas characteristics, and must be managed with high precision.

For this reason, conventionally, the discharge side passage 9 of the feed pump 3 is connected to the suction side passage 11 of the feed pump 3 via a bypass passage 10, and a fuel supply pressure control valve 12 is provided in the bypass passage 10.

The fuel oil supply pressure control valve 12 supplies the fuel on the discharge side to the bypass passage 10 when the discharge pressure of the feed pump 3 is higher than a predetermined pressure in relation to the rotation speed.
The fuel is returned to the suction side passage 11 via the fuel chamber 6, thereby maintaining the fuel pressure in the fuel chamber 6 at a predetermined pressure in relation to the rotational speed.

The conventional fuel oil supply pressure control valve was developed in 1982.
As disclosed in No. 184230, the piston is configured to be biased by a spring, the piston is actuated by the pressure of the fuel supplied from the feed pump, and the actuation of the piston causes the piston to be formed on the side wall of the valve casing. By controlling the opening amount of the relief hole, a portion of the fuel supplied from the feed pump is returned to the bypass passage side.

[Problem that the invention attempts to solve]

The conventional fuel oil supply pressure control valve described above controls the opening amount of the relief hole against the biasing force of the spring, that is, controls the amount of relief, so the fuel pressure in the fuel chamber 6, that is, the internal pressure. The relationship between rotation speed is
As shown by the characteristics in FIG. 8, it was determined uniquely.

However, in this type of distribution fuel injection pump, variations in the internal pressure due to variations in the spring characteristics of the springs, or variations in the processing and assembly of each part of the timer 7, cause variations in fuel injection timing. In order to correct such characteristics, it is often necessary to modify the relationship between internal pressure and rotational speed from characteristic A shown in FIG. 9 to characteristic B. The characteristic B shown in FIG. 9 has a slope different from that of the characteristic A, and it is not easy to adjust such a characteristic.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fuel supply pressure control valve for a distribution type fuel injection pump that allows for easy adjustment of internal pressure characteristics from the outside and has a simple structure.

[Means for solving problems]

In this invention, the valve casing of the fuel oil supply pressure control valve is rotatably attached to the pump housing,
This rotation adjusts the length of the communication path connecting the relief hole formed in the side wall of the valve casing and the bypass path formed in the pump housing.

[Effect]

By rotating the valve casing, the length of the communication path between the relief hole opened in the side wall of the valve casing and the bypass passage formed in the pump housing can be changed.
Even if the opening amount of the relief hole by the piston is the same, the flow path resistance changes depending on the length of the communication path, so the amount of fuel released to the bypass path changes,
Therefore, even if the rotation speed is the same, the internal pressure can be adjusted depending on the length of the communication path.

[Example of idea]

The present invention will be explained below based on an embodiment shown in FIGS. 1 to 4.

In this embodiment, the overall structure of the fuel injection pump may be the same as the conventional one shown in FIG. 7, so its explanation will be omitted.

In FIG. 1, a bore 20 is formed in the pump housing 2, and the bore 20 communicates with the discharge side passage 9 of the feed pump 3 at its lower end, and has a bypass passage 10 opened on its side. Note that a constricted portion 21 is formed in the bypass passage 10.

A fuel oil supply pressure control valve 22 is inserted into the bore 20 .

The fuel oil supply pressure control valve 22 has a piston 24 slidably housed in a substantially cylindrical valve casing 23, and the piston 24 is urged downward in the drawing by a spring 25.

The downward stroke of the piston 24 is regulated by a bushing 26 press-fitted into the lower end of the valve casing 23. The upper end of the spring 25 is connected to a plug 27 that is press-fitted into the upper part of the valve casing 23.
Supported by

For example, two relief holes 28, 28 spaced apart in the circumferential direction are opened in the side wall of the valve casing 23. These relief holes 28, 28 are located in the valve casing 23, as shown in FIGS. 3 and 4.
It is communicated with the bypass passage 10 (throttled portion 21) through a gap formed between the outer peripheral surface of the pump housing 2 and the inner surface of the bore 20 of the pump housing 2, that is, a communication passage 29 that is continuous in the circumferential direction.

Since the lower end opening of the valve casing 23 communicates with the discharge side passage 9, this discharge side passage 9
It is connected to the bypass passage 10 through the inside of the valve casing 23, relief holes 28, 28, and communication 29.

When the piston 24 operates, the lower end surface of the piston 24 opens and closes the relief holes 28, 28, and fuel is released from the discharge side passage 9 to the bypass passage 10 side according to the opening amount of the relief holes 28, 28. The amount is adjusted.

Thus, the valve casing 23 is inserted into the bore 20 of the pump housing 2 so as to be rotatable about the central axis.

When the valve casing 23 is rotated, the relief holes 28, 28 are displaced in the circumferential direction, as shown in FIGS. 3 and 4.

Note that 30 and 30 are O-rings that maintain liquid tightness.

The upper end of the valve casing 23 is connected to the pump housing 2
As shown in FIG. 2, a plurality of locking projections 31 are formed at equal intervals in the circumferential direction around this projection. The locking protrusions 31 are engaged with locking holes 33 provided in the stopper plate 32. The locking projections 31 of this embodiment are formed in a star shape, and the locking holes 33 of the stopper plate 32 are also formed in a star shape. Therefore, by inserting the locking protrusions 31 into the locking holes 33, the valve casing 23 is unrotatably engaged with the stopper plate 32.

The stopper plate 32 has an arc-shaped mounting hole 34.
, insert a screw 35 into this mounting hole 34,
By screwing this screw 35 into the pump housing 2, the stopper plate 32 is fixed to the pump housing 2.

Therefore, the valve casing 23 is unrotatably fixed to the pump housing 2 via the stopper plate 32 after the adjustment described below is completed.

Fuel feed pressure control valve 22 with such a configuration
Explain the effect of

When fuel is supplied to the discharge side passage 9 by the rotation of the feed pump 3 shown in FIG. 7, the piston 24 is pushed up against the spring 25 by the pressure of the fuel sent through the discharge side passage 9. 24 has relief holes 28, 28
Since it is opened, the discharged fuel sent through the discharge side passage 9 is returned to the suction side passage 11 via the bypass passage 10.

As a result, the fuel pressure in the fuel chamber 6 is maintained at a predetermined pressure in relation to the rotational speed of the feed pump 3, as shown in FIG.

By the way, when the position of the valve casing 23 is set such that the relief hole 28 is directly facing the bypass passage 10 toward the open end, as shown in FIG. The fuel immediately flows into the bypass passage 10, and the distance to pass through the communication passage 29 is short. Therefore, in this case, the flow resistance due to the communication passage 29 is small, and the fuel pressure in the fuel chamber 6 is controlled in relation to the rotational speed as shown in characteristic A in FIG. 9.

If it is desired to change the characteristic A shown in FIG. 9 to, for example, characteristic B, the stopper plate 32 is opened by removing the screw 35, so that the valve casing 23 can be rotated.

If the position of the valve casing 23 is changed, for example, in a direction such that the relief hole 28 is perpendicular to the opening end of the bypass passage 10, as shown in FIG. is communication path 2
9 and flows into the bypass passage 10. In this case, the distance through the communication passage 29 is longer than in the case of FIG. Control is performed as shown in characteristic B in FIG.

The flow resistance of the communication passage 29 becomes more effective as the flow rate increases, so in the region where the rotational speed is high, characteristic B is different from characteristic A.
makes a bigger difference.

Once this adjustment is completed, the valve casing 2
While holding 3 in the relevant position, press the stopper plate 3.
2 and fix it with the screw 35.

In this case, since the locking protrusions 31 are formed at intervals in the circumferential direction, the rotation angle of the valve casing 23 is limited by the pitch interval in the circumferential direction of the locking protrusions 31 and becomes stepwise. , stopper plate 32
Since the mounting hole 34 through which the screw 35 is inserted is formed in an arc shape, the circumferential pitch between the locking protrusions 31 is absorbed at the position of the mounting hole 34, and the rotation angle of the valve casing 23 can be adjusted steplessly. can be adjusted to enable highly accurate control.

In the above embodiment, the valve casing 23 is rotatably inserted into the bore 20 and held by the stopper plate 32, but the present invention has a structure as shown in FIGS. 5 and 6. It can also be implemented.

That is, in the embodiment shown in FIGS. 5 and 6, the valve casing 23 is inserted into the bore 20 and the threaded portion 4
0, and the characteristics are changed by rotation by advancing and retracting the screw.

After the adjustment, one side 42 of the stopper plate 41 is deformed in an upright manner to be locked to the hexagonal head at the upper end of the valve casing 23, and the other side 42 of the stopper plate 41 is
The valve casing 23 is prevented from rotating by deforming the valve 3 downward and engaging the side surface of the pump housing 2.

Note that 44 is a spring washer.

Even with such a configuration, the
It has the same effect as the embodiment shown in the figure.

[Effect of idea]

As explained above, according to the present invention, as the valve casing rotates, the length of the communication path connecting the relief hole formed in the side wall of the valve casing and the bypass passage formed in the pump housing changes, so that the relief hole formed by the piston changes. Even if the opening amount of the bypass passage is the same, the amount of fuel that escapes to the bypass passage changes due to the change in flow resistance depending on the length of the communication passage. The internal pressure can be adjusted depending on the length.

Therefore, this device is easy to operate because it can be adjusted simply by rotating the valve casing, and the structure is simple because the valve casing can be rotated and attached to the pump housing. .

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a cross-sectional view of the installation part of the fuel oil supply pressure control valve, FIG. 3 and 4 are sectional views taken along the line - in FIG. 1 in different operating states; FIGS. 5 and 6 show other embodiments of the present invention; FIG. A cross-sectional view of the valve installation part, Figure 6 is
FIG. 7 is a sectional view showing the entire distribution type fuel injection pump for explaining the conventional technology, and FIGS. 8 and 9 are characteristic diagrams, respectively. 1... Drive shaft, 2... Pump housing, 3...
...Feed pump, 5...Fuel tank, 9...Fuel discharge passage, 10...Bypass passage, 11...Fuel suction passage, 22...Fuel feed pressure control valve, 23
... Valve casing, 24 ... Piston, 25 ...
Spring, 28... Relief hole, 29... Communication path,
32, 41...Stotsupa plate.

Claims (1)

[Scope of utility model registration request] A distribution type fuel injection pump that supplies fuel from a fuel tank to a fuel chamber in a pump housing by a feed pump, and adjusts the pressure of the supplied fuel with a fuel feed pressure control valve, the fuel feed pressure control valve as described above. A piston pressed by a spring is provided in the valve casing fitted into the pump housing, and the piston is actuated by the pressure of the fuel supplied from the feed pump. In the fuel feed pressure control valve, the opening amount of the relief hole is controlled and the fuel supplied from the feed pump is returned from the relief hole to the fuel suction passage of the feed pump via the bypass passage. A fuel feed pressure control valve for a distribution type fuel injection pump, characterized in that it is rotatably attached to a housing, and the length of a communication path connecting the relief hole and the bypass passage is changed by the rotation.