JP3196306B2 - Pipe end closure molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pipe end block used for forming a bottom portion of an outer cylinder (reservoir tube) in a hydraulic shock absorber for an automobile, for example.

[0002]

2. Description of the Related Art Conventionally, a pipe end block forming method for forming a block surface at the bottom of an outer cylinder in a hydraulic shock absorber for an automobile has been disclosed in, for example, JP-A-59-125221. In this pipe end closing molding method, after forming an annular step portion by pressing while leaving an amount of closing molding at the end of the tube body, a closing surface portion is formed by spinning at the step portion, thereby forming the closing surface portion. Is provided with a step. A bottom body attached to the lower end of the inner cylinder is seated on this step, and the lower ends of the outer cylinder and the inner cylinder are held concentrically via the bottom body, and a reservoir chamber is provided between the two cylinders. Is formed.

[0003]

However, in the conventional pipe end block forming method, since the step on which the bottom body is seated is formed in an annular shape, the reservoir is located between the bottom body and the lower end of the outer cylinder. A passage for communicating the chamber with the inner cylinder is not formed. For this reason, it is necessary to provide not only the bottom valve but also the passage leading to the bottom valve in the bottom body, and the bottom body has a complicated and bulky configuration.

Therefore, after forming the end of the outer cylinder into a hemispherical closed surface by spinning, a projection is formed on the inner surface of the closed surface, and the outer cylinder is inserted through a bottom body seated on the projection. It would be very convenient if a passage could be formed between the bottom body and the lower end of the outer cylinder, between the bottom body and the lower end of the outer cylinder, while maintaining the lower end of the inner cylinder and the lower end of the inner cylinder concentrically. good.

[0005] As a method of forming such a tube end blockage, a method which has been already filed by the present applicant will be described with reference to FIGS. 4 to 6.

[0006] First, as shown in FIG.
a, the forced drive roller 5 is pressed at right angles to the axis thereof, and the rotation of the forced drive roller 5 causes the end 1a of the tubular body 1 to rotate at high speed about the axis while the friction roller 6 is rotated.
Is pressed against the end 1a of the tubular body 1 at right angles to the axis thereof, and the end 1a is moved along the arc-shaped guide rail 7.
Move gradually toward the tip of. By this spinning, the end 1a of the tube 1 is deformed, and at the same time, heat is generated by friction between the end 1a of the tube 1 rotating at a high speed and the friction roller 6. Then, as the friction roller 6 moves toward the tip of the end 1a along the arc-shaped guide rail 7, the thickness of the end 1a gradually increases from the tube body side to the tip side, and the pipe is formed at the tip contact portion 2a. The body 1 is crimped to a thickness approximately three times that of the body 1, and the hemispherical closed surface 2 is formed.

Next, as shown in FIG. 5, after the closing surface 2 of the tube 1 is set on the projection forming die 9, as shown in FIG. 2
a in the axial direction of the tube 1, and in this state, the forming punch 10
Is lowered to form the protrusion 11 on the inner surface of the closed surface portion 2, and after the forming, the forming punch 10 and the pressing punch 8A are sequentially removed. Unless the tip contact portion 2a of the closing surface portion 2 is pressed down in the axial direction of the tube 1, the plate thickness of the tube 1 (outer cylinder) is increased in strength, and the plate thickness of the closing surface portion 2a is made by spinning. This is because the thickness of the pipe 1 becomes approximately three times as large as the normal thickness, and there is a great possibility that a minute gap will be formed at the tip contact portion of the closed surface portion 13a when the projection 11 is formed.

However, in the forming method according to the above-mentioned application, since the pressing surface of the pressing punch 8A is a flat surface, in order to maintain the closed end at the time of forming, the pressing load of the pressing punch 8A is required. Must be sufficiently larger than the pressing load of the projection forming die 9 for forming the projections 11, and there is an inconvenience that a large-capacity equipment is required because a pressing device having high capability and rigidity is required.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a disadvantage, and it is an object of the present invention to provide a pipe end block forming method capable of greatly reducing a pressing load of a pressing punch.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method of forming a closed surface portion by spinning an end of a tubular body, and thereafter, pressing a closed end portion of the closed surface portion with a pressure punch. A projection is pressed and formed on the inner surface of the closed surface portion by a forming punch while being surrounded by a ring-shaped claw protruding from the distal end and being pressed in the axial direction of the tubular body.

[0011]

According to the above configuration, the tip contact portion can be reliably restrained so that a small gap is not generated while reducing the load of the pressure punch.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 and FIG. 2 are explanatory views showing a step of forming a projection.

First, after the closing surface 2 is formed on the end 1a of the tube 1 by the same spinning process as shown in FIG. 4, the closing surface 2 is set on the projection forming die 9.

Next, the pressure-contact punch 8 presses the tip contact portion 2a of the closing surface portion 2 in the axial direction of the tubular body 1.

At the tip of the pressure punch 8, FIG.
As shown in (b), when the closed surface 2 of the tubular body 1 is pressurized, a ring-shaped claw 8a having a diameter smaller than the outer diameter of the punch surrounding the tip contact portion 2a is formed in line contact with the closed surface 2. .

Pressing is performed by the pressing punch 8, and the pressing punch 8A is pressed against the protrusion forming die 9 with a smaller pressing force than the pressing punch 8A of the prior application, surrounding the tip contact portion 2a of the closing surface portion 2.

Next, the forming punch 10 is held in the holding state.
Is lowered, and the projection 11 is pressed and formed on the inner surface of the closed surface portion 2.

Thereafter, the pressing force of the forming punch 10 is removed while the pressing punch 8 is kept in a pressed state, and the pressing force of the pressing punch 8 is removed slightly later.

When the projection 11 is formed on the inner surface of the closed surface portion 2, the tip contact portion 2 a of the closed surface portion 2 is formed in a ring shape protruding from the distal end of the pressure punch 8. Since it is surrounded by the claws 8a and pressed in the axial direction of the tube 1,
There is no generation of a minute gap due to molding in the tip contact portion 2a of the closing surface portion 2.

[0021]

As described above, according to the present invention, after forming a closed surface portion by spinning at the end of the tube, the contact portion at the front end of the closed surface portion is formed into a ring shape projecting from the front end of the pressure punch. While surrounding with claws, and pressing in the axial direction of the tube,
Since the projections are formed by pressing the projections on the inner surface of the closed surface with the forming punch, deformation during the formation of the projections by the forming punch is suppressed by the pressure punch. No gaps are created. Therefore, complete airtightness of the closed surface can be ensured, and repair by welding or the like becomes unnecessary.

Further, since the contact portion at the end of the closed surface is pressed by a ring-shaped claw protruding from the end of the pressing punch,
It is possible to press and hold the tip contact portion with a smaller load than that of pressing with a flat surface at the tip of the pressure punch, thereby enabling molding with a pressure device having small capacity and rigidity. Therefore, the size of the equipment can be reduced and the equipment cost can be reduced, and the pressure punch does not need to have high rigidity to withstand a high load.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state before a step of forming a projection of a closed surface portion according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a state during a step of forming a projection of a closed surface according to an embodiment of the present invention.

FIG. 3A is a cross-sectional view showing the shape of the tip of a pressure punch used for holding a closed surface portion according to an embodiment of the present invention. (B) It is a plan view of the tip end surface.

FIG. 4 is an explanatory view showing a spinning forming step of a closed surface portion in a method according to the present applicant's application.

FIG. 5 is an explanatory view showing a projection forming step in the method shown in FIG. 4;

FIG. 6 is an explanatory view showing a state in which a tip contact portion of a closed surface portion is pressed in the projection forming step of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube 1a End part 2 Closed surface part 2a Tip contact part 5 Forced drive roller 6 Friction roller 8 Pressing punch 8a Ring-shaped claw 9 Die for protrusion forming 10 Forming punch 11 Protrusion

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21D 41/04 B21D 22/02 B21D 53/86-53/88 B60G 13/08 F16F 9/32

Claims (1)

(57) [Claims] After forming a closed surface portion by spinning at an end portion of a tube, a tip contact portion of the closed surface portion is surrounded by a ring-shaped claw protruding from a tip of a pressure punch, and the end of the tube is closed. A method for forming a tube end blockage, wherein a protrusion is pressed and formed on an inner surface of the closed surface portion by a forming punch while being pressed in an axial direction.