JPH10309641A - Method to improve fatigue strength by repeated pressure at branch hole part on member for high pressure fluid and branch hole part of member for high pressure fluid provided by this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain generation of tensile stress on an inner peripheral edge on a lower end of a branch hole by offsetting it by compression residual stress by drilling the branch hole to open to a hollow part on a deformed part and making the compression residual stress exist at least on a peripheral edge of the branch hole. SOLUTION: A hollow part 1-1 is formed in the inside of a member 1 for high pressure fluid by mechanical work of boring, etc., and this member 1 for high pressure fluid has a comparatively thick part. A branch hole part 2 where compression residual stress is generated is formed by projecting the side of the hollow part 1-1 so as to be roughly circular and at least roughly flat by pressing the thick part under a pressing method by using a punch or a rod inward in the diametrical direction from outside. Thereafter, a branch hole 1-2 is drilled by cutting it, for example, with a drill, etc., so as to have an outlet roughly on a central part of the branch hole part 2 formed as above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection system component constituting a fuel injection system for a diesel engine, such as a fuel injection pump, a fuel injection nozzle, a fuel injection pipe, and a common rail, an injection pump, and an injection for a fuel pressure accumulating system. The present invention relates to a method for improving the fatigue strength of a high pressure fluid member such as a nozzle, an injection pipe, a feedback pipe, a pressure pipe or the like for a high pressure fluid member due to repetitive pressure at a branch hole portion, and a branch hole portion of a high pressure fluid member obtained by the method. is there.

[0002]

2. Description of the Related Art Conventionally, a branch formed by a branch hole formed in a thick portion of a high-pressure fluid member in order to communicate a hollow portion of such a high-pressure fluid member with a flow path of a branch hole member. In the hole, a branch hole was formed in a hollow portion having an inner peripheral surface having a circular cross section to allow communication with the flow path of the branch hole member.

[0003]

However, in a structure in which a branch hole is simply formed in a hollow part having a perfect circular cross section of a member for high pressure fluid having a perfect circular cross section to communicate with a flow path of the branch hole member, a high pressure fluid is required. When a high internal pressure acts on the hollow portion of the high-pressure fluid member, the largest tensile stress is generated at the open end of the outlet of the branch hole in the hollow portion of the high-pressure fluid member. Cracks are likely to occur due to metal fatigue, which may lead to fluid leakage.

[0004] As a method of improving the fatigue strength due to such repetitive pressure, an annular groove is formed on the inner peripheral surface of the hollow portion including the exit position of the branch hole, or a pocket is formed at the exit of the branch hole. However, in the former case, it is necessary to employ mechanical processing to accurately form the annular groove including the outlet of the branch hole, and the work is extremely troublesome, It is completely unsuitable for recent mass production systems, and may cause scratches or damages not only on parts requiring machining but also on other inner peripheral surfaces. Although it conforms to the above-mentioned mass production method because it is performed chemically,
Actually, since the tensile stress concentrates on the opening end of the outlet of the branch hole in the hollow portion of the high-pressure fluid member, even if such a process is performed, the effect of improving the fatigue strength is not so significant.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem of the branch hole of the conventional high-pressure fluid member. A method for improving fatigue strength due to repetitive pressure at a branch hole in a member for high-pressure fluid, which is capable of further improving internal pressure fatigue strength by lowering the maximum tensile stress value to be generated, and for high-pressure fluid obtained by the method. It is an object to provide a branch hole of a member.

[0006]

According to a first aspect of the present invention, there is provided a high-pressure fluid member having a hollow portion, wherein a branch hole communicating with the hollow portion is formed.
The high-pressure fluid member is pressed inward from the outside to deform the inner peripheral surface of the hollow portion side to form a deformed portion in which a compressive stress remains, and then the deformed portion has a branch hole opened to the hollow portion. It is characterized in that the compression residual stress is formed at least in the periphery of the branch hole by drilling.

According to a second embodiment of the present invention, when a branch hole communicating with the hollow portion is formed in a member for high pressure fluid having a hollow portion, a branch opening on the inner peripheral surface of the member for high pressure fluid is provided. A hole is formed, and then the branch hole of the high-pressure fluid member is pressed inward from the outside to deform the hollow-portion-side inner peripheral surface so that a compressive stress remains at least at a part of the peripheral edge of the branch hole. It is characterized by becoming.

According to a third embodiment of the present invention, when a branch hole communicating with the hollow portion is formed in the high-pressure fluid member having a hollow portion, the high-pressure fluid member is pressed inward from the outside. The inner peripheral surface of the hollow portion side is deformed to form a deformed portion in which the compressive stress remains, and at the same time, a branch hole opened in the hollow portion is punched in the deformed portion, and the compressive residual stress is present at the peripheral edge of the branch hole. It is characterized by becoming.

According to a fourth embodiment of the present invention, when a branch hole communicating with the hollow portion is formed in a member for high pressure fluid having a hollow portion, the member is slightly eccentric from a position where the branch hole is provided. It is characterized in that the member is pressed inward from the outside so that residual compressive stress is present at the periphery of the branch hole.

According to a fifth embodiment of the present invention, when a branch hole communicating with the hollow portion is formed in the high-pressure fluid member having the hollow portion, the branch member is slightly eccentric from the position where the branch hole is provided. The structure is characterized in that the member is pressed inward from the outside at least at two places in the diametrical direction, and compressive residual stress is present at least at two places in the diametrical direction on the peripheral edge of the branch hole.

In a sixth embodiment of the present invention, when a branch hole communicating with the hollow portion is formed in a high-pressure fluid member having a hollow portion, the high-pressure fluid member is pressed inward from the outside. The hollow part side inner peripheral surface is deformed to form a deformed part in which compressive stress remains in a wider area than the area where the branch hole is provided, and a branch hole is formed in the center of the deformed part. Is what you do.

A seventh embodiment of the present invention is directed to a high-pressure fluid member having a hollow portion, wherein a branch hole communicating with the hollow portion is formed in the high-pressure fluid member. It is characterized by having residual stress.

That is, according to the present invention, by providing a compressive residual stress around the opening end of the outlet of the branch hole communicating with the flow path of the branch hole member in the hollow portion of the high-pressure fluid member,
A high internal pressure in the hollow portion of the high-pressure fluid member, and in some cases, a tensile stress generated at the lower peripheral edge of the lower end of the branch hole due to a radial force applied to the thick portion of the high-pressure fluid member when connecting the branch hole member. Is also offset by the compressive residual stress, thereby lowering the maximum tensile stress value generated at the inner peripheral edge of the lower end of the branch hole. The residual compressive residual around the opening end of the outlet of the branch hole in the hollow portion of the high-pressure fluid member. As a method of generating stress,
This is a method using the method described in the first to seventh embodiments.

Here, as a method of applying a pressing force to the high-pressure fluid member from the outside, for example, with the high-pressure fluid member fixed to the lower mold, a radially inward direction from the outside of the high-pressure fluid member is provided. And pressurizing using a punch or a rod.

As described above, in the present invention, the compressive residual stress exists around the opening end of the branch hole in the branch hole on the hollow side of the high-pressure fluid member, so that the tensile stress at the lower end inner peripheral edge of the branch hole is formed. Can be effectively suppressed by being offset by the compressive residual stress, and the internal pressure fatigue strength at the branch hole of the high-pressure fluid member can be improved.

[0016]

1 is a partially enlarged cross-sectional view of an embodiment of a high-pressure fluid member having a branch hole according to the present invention.
FIGS. 1A and 1B are cross-sectional views illustrating an embodiment of a method for improving fatigue strength according to the present invention, in which FIG. 1A is a view before a branch hole is formed after a pressing force is applied, and FIG. FIG. 3 is a cross-sectional view illustrating another embodiment of the method for improving fatigue strength according to the present invention, in which FIG. 3A is a view after a branch hole is drilled, and FIG. FIG. 4 is a longitudinal sectional view of FIG. 1, and FIG. 5 to FIG. 8 illustrate another embodiment of a method for improving fatigue strength according to the present invention. FIG. 5 is a schematic plan view showing a method of applying a pressing force with a slight eccentricity from a location where a branch hole is provided, and FIG. 6 is a diagram illustrating a method of applying a pressing force to two diametrical locations with a slight eccentricity from a location where a branch hole is provided. FIG. 7 is a schematic plan view showing a method, and FIG. 7 shows a method of applying a pressing force such that a compressive stress is generated in a wider area than a region where a branch hole is provided. FIG. 8 is a schematic plan view showing another embodiment of a method for applying a pressing force such that a compressive stress is generated in a wider area than a region where a branch hole is provided, and FIG. 9 is a view showing a member for high-pressure fluid according to the present invention. FIG. 4 is a longitudinal sectional view showing another embodiment, wherein 1 is a high-pressure fluid member, and a fuel injection system component constituting a fuel injection system for a diesel engine, for example, a fuel injection pump, a fuel injection nozzle, a fuel injection pipe, And a common rail for a fuel pressure accumulator system, an injection pump, an injection nozzle, an injection pipe, a feedback pipe, a pressure vessel, and the like.

The high-pressure fluid member 1 has a hollow part 1-1 having a substantially circular inner peripheral surface inside the high-pressure fluid member 1, and communicates a flow path of a branch hole member (not shown) with the hollow part 1-1. Hole 1-2 is formed through the thick portion of the high-pressure fluid member, and the hollow portion 1-1 is formed around the opening end of the branch hole 1-2 substantially at the center. Are projected so as to be substantially circular and at least substantially flat, thereby forming a branch hole 2 in which compressive residual stress is generated.

Next, a method for improving the fatigue strength of the high-pressure fluid member 1 according to the present invention due to the repeated pressure in the branch hole 2 will be described with reference to FIG.

According to the process shown in FIG. 2, the high-pressure fluid member 1 according to the present invention has a hollow portion 1-1 formed therein by machining such as boring and has a relatively thick wall portion. It is. Then, the thick portion is pressed radially inward from the outside by a press method using a punch or a rod, and the hollow portion 1-1 is projected so as to be substantially circular and at least substantially flat. As a result, the branch hole portion 2 in which the compressive residual stress is generated is formed (see FIG. 2A).

Although the pressing force at this time is not particularly limited, at least the hollow portion 1 of the high-pressure fluid member 1 is used.
It is necessary that the inner peripheral surface of -1 be slightly flattened. The pressing force of the pressing method such as a punch causes the hollow portion 1
The inner peripheral surface of -1 is slightly flattened, and when the pressing force is applied, a plastically deformed portion and an elastically deformed portion are generated. When the pressing force is removed, a branch is generated due to a difference in return amount. A compressive residual stress is generated around the hole 2.

Next, the branch hole 1-2 is cut and drilled by, for example, a drill or the like so as to have an outlet at a substantially central portion of the formed branch hole portion 2 (see FIG. 2B).

In the above embodiment, first, the thick portion of the high-pressure fluid member is pressed radially inward from the outside by a pressing method using a punch or the like, so that a branch hole 1-to be formed later is formed. The hollow portion 1-1 of the high-pressure fluid member 1 corresponding to the two portions is made to protrude so as to be substantially circular and at least substantially flat, thereby forming a branch hole portion 2 to generate compressive residual stress. Next, since the branch hole 1-2 is formed so as to penetrate through the thick portion of the high-pressure fluid member 1 so as to have an outlet at a substantially central portion of the branch hole portion 2, the hollow portion 1- of the high-pressure fluid member is formed. In some cases, the tensile stress generated at the inner peripheral edge of the lower end of the branch hole 1-2 by the radial force applied to the thick portion of the high-pressure fluid member 1 when the branch hole member is connected is also increased. The maximum tensile stress value generated at the inner peripheral edge of the lower end of the branch hole 1-2 is largely reduced by being offset by the compressive residual stress.

The method for improving the fatigue strength by the repetitive pressure in the present invention is not limited to the step shown in FIG.
It can also be carried out by the step. According to FIG. 3, a branch hole 1-2 is first drilled by, for example, a drill or the like so as to penetrate the thick portion of the high-pressure fluid member 1 having the hollow portion 1-1 as described above (see FIG. )reference).

Next, the thick portion is pressed radially inward from the outside by a press method in the same manner as described above, so that the outlet of the branch hole 1-2 is substantially at the center. −
One side is made to protrude so as to be substantially circular and at least substantially flat, thereby forming a branch hole portion 2 in which compressive residual stress has been generated (see FIGS. 3B and 4).

Also in the method shown in FIG. 3, the high internal pressure of the hollow portion 1-1 of the high-pressure fluid member may be increased in the same manner as described above. The tensile stress generated at the lower end inner peripheral edge of the branch hole 1-2 due to the radial force applied is also offset by the compressive residual stress, and the maximum tensile force generated at the lower end inner peripheral edge of the branch hole 1-2 is reduced. The stress value can be greatly reduced.

In the embodiment shown in FIG. 2, the branch hole portion 2 is formed by first pressing the thick portion of the high-pressure fluid member radially inward from the outside by a pressing method using a punch or the like. Then, a method of drilling the branch hole 1-2 is adopted. In the embodiment shown in FIG. 3, a method of first drilling the branch hole 1-2 with a drill or the like, and then pressing the portion by a press method is used. However, the branch hole 1-2 can be punched out simultaneously with pressing by a punch or the like. in this case,
It can be implemented by using a punch or rod having a punch or rod having substantially the same diameter as the branch hole 1-2 and a large-diameter punch or rod for forming a deformed portion for generating compressive residual stress. .

Means for forming a branch hole 2 in which a compressive residual stress is generated by pressing a thick portion of the high-pressure fluid member radially inward from the outside by a pressing method using a punch or the like. Alternatively, the method shown in FIGS. 5 to 8 can be used in addition to the above embodiment.

That is, FIG. 5 shows that when the branch hole 1-2 communicating with the hollow portion is formed in the high-pressure fluid member 1 having the hollow portion 1-1, the branch hole 1-2 is slightly deviated from the place where the branch hole 1-2 is provided. The pressurized high-pressure fluid member 1 is pressed using a punch or a rod or the like to generate a compressive residual stress in a part of the peripheral portion of the branch hole 1-2 (particularly, a portion that easily becomes a starting point of crack generation). 1-3 indicates a pressing range by a punch or a rod or the like, and 1-4 indicates a range in which compressive residual stress is generated.

FIG. 6 is a view showing a state in which a branch hole communicating with the hollow portion is formed in the high pressure fluid member 1 having a hollow portion by a press method using a punch or a rod. The high-pressure fluid member 1 is pressed eccentrically at least two places in the diametric direction from the outside with a slight eccentricity from the place where the hole 1-2 is provided, and compressive residual stress is generated at least at two places in the diametric direction of the peripheral edge of the branch hole. FIG. Here, the two locations in the diameter direction refer to a portion that is likely to be a starting point of crack generation as described above.

FIG. 7 shows a high pressure fluid member 1 having a hollow portion 1-1 formed by pressing a high pressure fluid member 1 from the outside using a punch or a rod or the like, and a branch hole 1 communicating with the hollow portion.
When forming -2, using a punch or rod or the like having a smaller diameter than the branch hole 1-2, a deformed portion in which compressive stress remains in a wider area than the region where the branch hole is formed is formed, and a branch is formed at the center of the deformed portion. 4 illustrates a method of forming a hole.

FIG. 8 shows a high pressure fluid member 1 having a hollow portion 1-1 formed by pressing the high pressure fluid member 1 from the outside using a punch or a rod or the like, and a branch hole 1 communicating with the hollow portion.
In forming -2, using a punch or rod or the like having a larger diameter than the branch hole 1-2, a deformed portion in which compressive stress remains in a wider area than the region where the branch hole is provided is formed, and a central portion of the deformed portion is formed. It shows a method of drilling a branch hole 1-2.

In the embodiment described above, an example is described in which the branch hole 1-2 is formed in a direction substantially perpendicular to the central axis of the hollow portion 1-1. However, the present invention is not limited to this, and FIG. As shown, the branch hole 1-2 can be provided at an angle with respect to the center axis of the hollow portion 1-1. In this case, the thick portion of the high-pressure fluid member 1 may be pressed at a desired angle by a punch or the like, and the surface of the branch hole 2 also has an angle with respect to the central axis.

[0033]

As described above, according to the present invention, the generation of tensile stress at the inner peripheral edge at the lower end of the branch hole can be effectively suppressed by canceling out the residual stress by the compressive residual stress. Since the strength can be improved, the durability is excellent, and there is an excellent effect that a fluid leak due to the generation of cracks can be eliminated and a stable function can be surely exhibited. In addition, since it is only necessary to add a pressing force applying step to the normal manufacturing process, and there is no need for complicated equipment, there is almost no problem such as an increase in equipment cost and a decrease in productivity due to an increase in the number of steps. There is a great effect that a high-pressure fluid member of high quality can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of one embodiment of a high-pressure fluid member having a branch hole according to the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating an embodiment of a method for improving fatigue strength according to the present invention, wherein FIG. 2A is a diagram before a branch hole is formed after a pressing force is applied, and FIG. It is a figure after drilling a hole.

3A and 3B are cross-sectional views illustrating another embodiment of the method for improving fatigue strength according to the present invention, in which FIG. 3A is a diagram after a branch hole is formed, and FIG. FIG. 4 is a view showing a state in which a pressing force is applied after the pressing.

FIG. 4 is a longitudinal sectional view of FIG.

FIG. 5 is a view for explaining another embodiment of the method for improving the fatigue strength according to the present invention, and is a schematic plan view showing a method for applying a pressing force with a slight eccentricity from a location where a branch hole is provided.

FIG. 6 is a view for explaining another embodiment of the method for improving the fatigue strength according to the present invention, and is a schematic plan view showing a method of applying a pressing force to two diametrical locations with a slight eccentricity from a location where a branch hole is provided. FIG.

FIG. 7 is a view for explaining another embodiment of the method for improving fatigue strength according to the present invention, and is a schematic plan view showing a method for applying a pressing force so that a compressive stress is generated in a wider area than a region where a branch hole is provided. It is.

FIG. 8 is a view for explaining another embodiment of the method for improving fatigue strength according to the present invention, and is another embodiment of a method for applying a pressing force so that a compressive stress is generated in a wider area than a region where a branch hole is provided. FIG.

FIG. 9 is a longitudinal sectional view of another embodiment of the high-pressure fluid member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure fluid member 1-1 Hollow part 1-2 Branch hole 1-3 Pressing range 1-4 Range where compressive residual stress occurred 2 Branch hole

Claims (7)

[Claims] When forming a branch hole communicating with the hollow portion in a member for high-pressure fluid having a hollow portion, the member for high-pressure fluid is pressed inward from the outside so that the inner peripheral surface on the hollow portion side is formed. Forming a deformed portion in which compressive stress remains by deforming, and then forming a branch hole opening in the hollow portion in the deformed portion so that the compressive residual stress is present at least on the periphery of the branch hole. A method for improving fatigue strength due to repetitive pressure at a branch hole in a high-pressure fluid member. 2. When forming a branch hole communicating with the hollow portion in a member for high pressure fluid having a hollow portion, a branch hole opening on an inner peripheral surface of the member for high pressure fluid is formed in the member for high pressure fluid. The high pressure fluid is characterized in that the branch hole of the high pressure fluid member is pressed inward from the outside to deform the inner peripheral surface of the hollow portion side so that a compressive stress remains on at least a part of the periphery of the branch hole. A method for improving fatigue strength due to repeated pressure at a branch hole in a fluid member. 3. When forming a branch hole communicating with the hollow portion in the high-pressure fluid member having a hollow portion, the high-pressure fluid member is pressed inward from the outside to remove the hollow portion side inner peripheral surface. Forming a deformed portion in which the compressive stress remains by deforming, and punching a branch hole opened in the hollow portion in the deformed portion, so that the compressive residual stress is present around the branch hole. A method for improving fatigue strength due to repeated pressure at a branch hole in a fluid member. 4. When forming a branch hole communicating with the hollow portion in the high-pressure fluid member having a hollow portion, the member for a high pressure fluid is slightly eccentrically pressed from a location where the branch hole is provided to press the high-pressure fluid member inward from the outside. A method for improving the fatigue strength of a member for high-pressure fluid due to repetitive pressure at a branch hole portion, wherein compressive residual stress is present at the periphery of the branch hole. 5. When forming a branch hole communicating with the hollow portion in the member for high pressure fluid having a hollow portion, the member for high pressure fluid is at least slightly eccentric from a position where the branch hole is provided to inward from the outside. The fatigue strength due to the repetitive pressure at the branch hole in the high-pressure fluid member is characterized in that the member is pressed at two points in the diameter direction and compressive residual stress is present at least at two points in the diameter direction of the periphery of the branch hole. How to improve. 6. When forming a branch hole communicating with the hollow portion in the high-pressure fluid member having a hollow portion, the high-pressure fluid member is pressed inward from the outside to remove the hollow portion side inner peripheral surface. Forming a deformed portion in which compressive stress remains in a wider area than a region where the branch hole is formed by deforming, and forming a branch hole in a central portion of the deformed portion; Method to improve fatigue strength by repeated pressure in the part. 7. A branch hole portion in which a branch hole communicating with the hollow portion is formed in a high-pressure fluid member having a hollow portion,
A branch hole for a high-pressure fluid member, wherein the branch hole has a compressive residual stress at an inner peripheral edge thereof.