JPH01237354A - Delivery valve of fuel injector - Google Patents

Abstract

PURPOSE:To enable a high precision machining work by arranging the check valve seat of an isobaric valve installed inside a delivery valve with its seat surface positioned inside and forcibly fitting and fixing it into a cylindrical part formed in the delivery valve. CONSTITUTION:A delivery valve 4 is housed in a delivery valve chamber 3 formed in a valve holder 1, and said valve 4 is pressed on a valve seat 2 by means of energizing power of a valve spring 5 so that a fuel lead-in passage 6 may be closed. Then, an isobaric valve 10 consisting of a check valve 17 and a valve spring 18 is housed in the delivery valve 4. In this case, a cylindrical part 30 laid along the axial direction is formed in one body with the delivery valve 4 and a valve seat 31 which is a member separated from the delivery valve 4 is forcibly fitted and fixed in said cylindrical part 30. Then, a passage 15, a seat surface 19 and a release part 32 of a small diameter are formed on the valve seat 31 before it is forcibly fitted in the delivery valve 4 so that machining work therefor may be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a delivery valve provided in a fuel passage for passing fuel from a fuel injection pump toward a fuel injection nozzle in a fuel injection device such as a diesel engine.

[Conventional technology]

In a fuel injection device such as a diesel engine, a delivery valve is provided in a fuel passage through which fuel flows from a fuel injection pump to a fuel injection nozzle, and this delivery valve prevents backflow of fuel.

By the way, some of the above delivery valves are provided with an equal pressure valve (constant residual pressure valve) that keeps the residual pressure on the injection nozzle constant in order to improve the injection quantity characteristics and prevent secondary injection.

The structure of a conventional delivery valve with an equal pressure valve will be explained in detail with reference to FIG.

In the figure, 1 is a valve holder, and a delivery valve seat 2 is provided at one end, and a delivery valve chamber 3 is formed inside. A delivery valve 4 and a delivery valve spring 5 are housed in the delivery valve chamber 3, and the delivery valve 4 is pressed against the delivery valve seat 2 by the delivery valve spring 5. Passage 6 is closed. Note that this fuel introduction passage 6
is connected to a fuel injection pump (not shown).

A fuel delivery passage 7 communicating with the delivery valve chamber 3 is formed at the other end of the valve holder 1, and this fuel delivery passage 7 is connected to a fuel injection nozzle (not shown) via a fuel injection pipe 8. .

An equal pressure valve (constant residual pressure valve) 10 is accommodated within the delivery valve 4 .

That is, the end of the check valve seat 11 is joined to the delivery valve 4 by welding 12, and the delivery valve 4 and check valve seat 11 are
A communication path 13 connecting the upstream and downstream directions is formed. This communication passage 13 includes a passage 14 formed in the delivery valve 4 and opened to the fuel introduction passage 6, and a check valve seat 1.
1 and connected to the delivery valve chamber 3;
, and a check valve chamber 16 formed between these passages 14 and 15. The check valve chamber 16 accommodates a check valve 17 and a check valve spring 18 that presses the check valve 17 against the check valve seat 11.

The check valve 17 has a spherical shape made of bearing steel, for example, and has a seat surface 1 formed on the check valve seat 11.
9 and closes a passage 15 connected to the delivery valve chamber 3. When the fuel pressure on the fuel injection nozzle side, that is, in the delivery valve chamber 3, exceeds a predetermined pressure, this check valve 17 is pushed by this fuel pressure and seats against the pressing force of the check valve spring 18. Stroke away from surface 19.

Note that 20 is a spring seat.

Moreover, the passage 14 formed in the delivery valve 4 is
It is formed halfway inside the delivery valve 4 , and is formed outside the delivery valve 4 from the middle and communicates with the fuel introduction passage 6 .

The delivery valve having such a configuration has the following effects.

When the fuel is pumped by the fuel injection pump, if this fuel pressure exceeds the set load of the delivery valve 4 by the delivery valve spring 5, the delivery valve 4
is separated from the delivery valve seat 2, so that the fuel introduction passage 6 is communicated with the delivery valve chamber 3. Therefore, the fuel pressure-fed from the fuel injection pump is supplied from the fuel introduction passage 6 to a fuel injection nozzle (not shown) via the delivery valve v3, the fuel delivery passage 7, and the fuel injection pipe 8. Note that in this case, the check valve 17 remains pressed against the seat surface 19 and closes the passage 15.

The fuel supplied to the fuel injection nozzle injects the fuel into the engine when the pressure of the fuel injection nozzle becomes equal to or higher than the valve opening pressure. Then, when the fuel pressure in the fuel injection nozzle becomes equal to or lower than the valve opening pressure due to this injection, the injection is terminated.

In this state, residual pressure exists within the fuel injection pipe 8. There are concerns that such residual pressure may worsen the fuel cut-off of the fuel injection nozzle, cause undesired secondary injection, or cause fluctuations in the optimum injection characteristics.

On the other hand, the delivery valve shown in FIG.
Since this is provided, the above-mentioned problems can be solved.

In other words, after the fuel injection pump has finished pressurizing the fuel,
After the delivery valve 4 is pushed by the delivery valve spring 5 to close the delivery valve seat 2, if the residual pressure in the fuel injection pipe 8 is higher than the set valve opening pressure of the check valve 17, this residual pressure is transferred to the delivery valve chamber 3. The passage 15 acts on the check valve 17 through the passage 15, and the check valve 17 moves away from the seat surface 19 against the pressing force of the check valve spring 18.

Therefore, the fuel in the fuel injection pipe 8 is returned from the passage 15 through the recovery valve chamber 3 to the fuel injection pump side via the check valve chamber 16 and the passage 14, and the residual pressure in the fuel injection pipe 8 is released. .

In this way, when the residual pressure in the fuel injection pipe 8 becomes lower than the set valve opening pressure of the check valve 17, the check valve 17 is pushed by the check valve spring 18 and seats on the seat surface 19, closing the passage 15.

As a result, the residual pressure in the fuel injection pipe 8 is maintained at the same pressure as the set valve opening pressure of the equal stop valve 10, improving the fuel cutting of the fuel injection nozzle and preventing undesired secondary injection.
Fluctuations in injection amount characteristics can be eliminated.

[Problem to be solved by the invention]

According to the above conventional structure, the check valve seat 11 of the equal stop valve 10 has a substantially bottomed cylindrical shape, the open end thereof is welded 12 to the delivery valve 4, and the seat surface 19 is the check valve seat. It is formed on the back surface of hole No. 11.

In such a structure, the seat surface 19 is located deep inside the hole in the check valve seat 11, so
It is difficult to process and has the disadvantage of not being able to process with high precision. For this reason, when the check valve 17 is seated, it may not be possible to maintain close contact with high accuracy.

Furthermore, since the check valve seat 11 is welded 12 to the delivery valve 4, the check valve seat 11 may fluctuate due to welding even if the opening pressure of the check valve 17 is adjusted with high precision in advance before welding. In such a case, the valve opening pressure will change.

The present invention aims to provide a delivery valve for a fuel injection device that is easy to process, maintains the closeness of the check valve with high precision, and allows the opening pressure of the check valve to be set with high precision. It is.

[Means to solve the problem]

In order to achieve the above object, the present invention makes the delivery valve and the check valve seat separate members, forms a cylindrical part extending in the axial direction in the delivery valve, and has a seat on the end surface of the check valve seat on which the check valve approaches and separates. The check valve seat is press-fitted into the end of the cylindrical portion with the seat surface positioned inside.

[Effect]

According to the present invention, since the check valve seat is press-fitted into the cylindrical portion of the delivery valve with its seat surface facing the inner end, the end of the check valve seat is machined with a seat surface before being press-fitted into the delivery valve. can,
Since this surface becomes a protruding surface, it is easy to process and can be processed with high precision. Furthermore, since the check valve seat is fixed to the delivery valve by press fitting, it is easy to position the check valve seat with respect to the delivery valve with high precision, and the opening pressure of the check valve can be set with high precision.

〔Example〕

The present invention will be explained below based on an embodiment shown in FIG.

In this embodiment, parts that may be the same as those in the conventional system shown in FIG. 3 are given the same numbers and their explanations will be omitted.

The delivery valve 4 housed in the delivery valve chamber 3 is integrally formed with a cylindrical portion 30 extending in the axial direction, that is, toward the fuel delivery passage 7 side, and a check valve seat 31 is press-fitted into the cylindrical portion 30. Fixed by

The check valve seat 31 is a separate member from the delivery valve 4, and has a passage 15 formed in its center and a seat surface 19 formed on its inner end surface.

Further, this check valve seat 31 has a small diameter relief portion 32 formed on the outer circumferential surface of its insertion side end portion, which serves as a guide surface for insertion.

The check valve seat 31 has a passage 15, a seat surface 19, and a small diameter relief part 32 formed in advance before being press-fitted into the delivery valve 4, and is fixed by being press-fitted into the cylindrical part 30 of the delivery valve 4. In this case, a check valve chamber 16 is formed inside the delivery valve 4. The check valve chamber 16 accommodates a check valve 17 and a check valve spring 18, as in the case shown in FIG.

In an embodiment with such a configuration, the operation is similar to that in the case of FIG. 3 above.

In the case of the configuration of the above embodiment, since the check valve seat 31 is press-fitted into the cylindrical portion 30 of the delivery valve 4 and fixed, the end portion of the check valve seat 31 is pre-fitted before being press-fitted into the delivery valve 4. Seat surface 19
can be processed. Since this seat surface 19 is located at the protruding end surface of the substantially cylindrical check valve seat 31, it is much easier to process the seat surface 19 than at a recessed position in the past. It can be processed into Therefore, the adhesion with the check valve 17 is improved, and the sealing performance when the valve is closed is improved.

Further, since the check valve seat 31 is fixed to the delivery valve 4 by press fitting, the check valve seat 31 can be positioned with respect to the delivery valve 4 with high precision. Therefore, the opening pressure of the check valve 17 can be set with high precision.

During such press-fitting, the small-diameter relief part 32 formed in the check valve seat 31 guides the press-fitting, resulting in good workability, and this small-diameter relief part 32 prevents distortion that would occur in the check valve seat 31 due to press-fitting. , maintains even better adhesion with the check valve 17.

In the case of the embodiment shown in FIG. 1, the passage 14 formed in the delivery valve 4 is partially
It is formed inside the delivery valve 4 and connected to the fuel introduction passage 6 from the middle of the delivery valve 4. However, as shown in FIG. 2 as another embodiment, the passage 1
4 may be entirely formed inside the delivery valve 4.

〔Effect of the invention〕

As explained above, according to the present invention, the check valve seat is press-fitted into the cylindrical portion of the delivery valve with its seat surface facing the inner end. The sheet surface can be processed, and since this surface becomes a protruding surface, it is easy to process and can be processed with high precision. Therefore, the tightness of the check valve becomes highly accurate. Further, since the check valve seat is fixed to the delivery valve by press fitting, it is easy to position the check valve seat with respect to the delivery valve with high precision, and the opening pressure of the check valve can be set with high precision.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of main parts showing another embodiment of the present invention, and FIG. 3 is a cross-sectional view showing a conventional structure. DESCRIPTION OF SYMBOLS 1... Valve holder, 2... Delivery valve seat, 3... Delivery valve chamber, 4... Delivery valve, 5... Delivery valve spring, 6... Fuel introduction passage, 7... Fuel delivery passage, 8... Fuel injection pipe, 10... Equal stop valve (constant residual pressure valve), 13... Communication passage, 16... Check valve chamber, 17... Check valve, 18...・Check valve spring, 19
... Seat surface, 30... Cylindrical part, 31... Check valve seat, 32... Relief part.

Claims (1)

[Claims] A delivery valve that prevents backflow from the fuel injection nozzle side is provided in the passage that sends fuel from the fuel injection pump toward the fuel injection nozzle, and a communication passage that communicates between upstream and downstream is formed within this delivery valve. An equal pressure valve is provided in the passage that opens when the fuel pressure is higher than a predetermined pressure from the injection nozzle side, and this equal pressure valve closes when the check valve, which is biased by the check valve spring, is pressed against the check valve seat. In a delivery valve for a fuel injection device that has a structure that maintains a valve state, the delivery valve and check valve seat are separate members, a cylindrical portion extending in the axial direction is formed in the delivery valve, and a check valve is provided on the end face of the check valve seat. A delivery valve for a fuel injection device, characterized in that the check valve seat is fixed to an end of the cylindrical portion by press fitting, with the check valve seat forming a seat surface that approaches and separates, and with the seat surface located inside.