JPS588929B2 - Manufacturing method of bottom valve seat for shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shock absorber, and more particularly to a method for manufacturing a bottom valve seat of a shock absorber having a fluid passage defining protrusion on the lower cover, the invention comprising: a steel plate having a predetermined thickness; punching out a circular blank having predetermined dimensions from the blank; bending the blank into a flanged cup shape; pressing the bottom of the cup shape inward to form a tapered valve seat surface at the bottom; This invention relates to a method for manufacturing a bottom valve seat in which a valve seat having a valve seat surface and a through hole in a cup-shaped bottom is manufactured by press molding from a metal plate, which comprises the steps of punching out the center area and forming a through hole. .

As will be understood by those skilled in the art, in the hydraulic shock absorber shown in FIG. The surrounding outer cylinder, 6 and 7 are upper and lower lids fixed to the outer cylinder, 8 is a Ron guide that guides the sliding movement of the piston rod 3, and 9 is a seal packing that seals the through hole of the upper lid 60.

When the piston 2 slides downward within the cylinder 1 and compresses the hydraulic shock absorber, the oil in the lower chamber A of the piston 2 flows into the outer peripheral portion of the valve retainer 10 and the annular portion, as shown in detail in FIG. While pressing the outer peripheral portion of the biplane valve 11 against the valve seat surface 4a of the bottom valve seat 4, press the valve retainer 100.
It passes through the through hole 10a, then bends the inner peripheral portion of the valve 11 downward, and flows into the central opening 4b of the bottom valve seat 4 as shown by the arrow 20.

It then passes through an oil passage 7a formed between several protrusions on the upper surface of the lower lid 7, and enters the reservoir chamber C as shown by an arrow 21.
flows into.

Incidentally, when the piston 2 moves downward, the annular biplane valve 24 provided on the piston 2 closes the through hole 25a of the valve retainer 250 and slides upward against the spring force integrally with the valve retainer 250 through hole 25a. Oil from A flows directly into chamber B without resistance.

Next, when the piston 2 slides upward in the cylinder 1 to extend the shock absorber, the oil in the upper chamber B of the piston 2 flows into the chamber A through the valve 24 provided in the piston 2.
At this time, a hydraulic resistance force is generated and the oil in the reservoir chamber C is moved as shown by the arrow 26 in FIG. As clearly shown at 28, the oil first passes through the oil passage 7a of the lower cover 7, then passes through the hole 4b of the valve seat 4, and pushes up the valve 11 and the valve retainer 10 against the force of the spring 27.

In this way, the oil is further transferred to the valve seat surface 4 of the bottom valve seat 4.
a and the valve 11, and reaches the chamber A through the gap between the valve 11, the valve retainer 10, and the valve guide 12.

In this way, by providing a time difference in the flow of oil in response to the reciprocating motion of the piston 2, a buffering effect is obtained.

However, in this type of hydraulic shock absorber, the valve seat 4 is in charge of an extremely important function, and damage to a portion of the valve seat 4 may be fatal to the shock absorber as a whole.

Furthermore, the valve seat 4 has a very complex shape.

Therefore, various methods have been developed to mass-produce valve seats that are as strong as possible, prevent damage, and can be adapted to any complex shape under precise dimensional control. Production methods were tried.

As a result, it has become common knowledge that the sintering method is the best method for manufacturing valve seats.

The one shown in FIG. 4 is a normal sintered valve seat.

Nowadays, most of the bottom valve seats are made of iron-based sintered products made by pressing and sintering iron powder.

As mentioned above, this is due to limitations in strength or materials and problems in processing.

However, manufacturing such products using the sintering method is not without problems.

For example, when manufacturing using the sintering method, there is a powder compaction process in which several molds are first assembled, iron powder is poured into the spaces between the molds, and then the iron powder is compressed and solidified to a specified density. After that, the compressed and hardened iron powder material is taken out of the mold and put into a furnace.
After going through a sintering process in which the product is baked and hardened at a temperature of 100 to 1200°C for about 2 to 3 hours, the product is finally removed from the furnace and then undergoes a dimensional correction process in which the dimensions are corrected using a straightening mold to obtain the specified dimensional accuracy. This requires complicated work processes such as hanging.

Furthermore, iron-based sintered products are more susceptible to impact and brittle than steel products, so they must be handled with great care during manufacturing and transportation. It also has the disadvantage of having large tolerances in longitudinal dimensions.

Moreover, in addition to the complicated work steps mentioned above, the iron powder as a raw material and the overhead costs associated with this work are quite high, resulting in a disadvantage that the product cost is high.

In order to eliminate the various drawbacks of such conventional products, the present invention has the following features:
The bottom valve seat is manufactured by a press molding method that is known per se.

FIG. 5 shows an embodiment of the present invention.

Step 1 is a step of punching out a circular blank having a predetermined size from a steel plate having a predetermined thickness using a known device.

The blank is then preformed into a ridge (or trough) shape while its outer periphery is clamped in a known manner (
In the following explanation, it is assumed that the preform is shaped like a mountain according to the figure).

The part is then final formed into a seven-lunged comp shape (FIG. 5, 11).

At step 110, the outer diameter d1 of the cup-shaped part is larger than the outer diameter d, D, of the finished product 4, and its height l
1 is also larger than the height l of the finished product 4.

Next, pressure is applied to the member from above and below.

The purpose of this operation is to provide the side wall sections with the required deflection characteristics for subsequent processing.

In other words, as is clear from 111, the side wall portion goes from a generally straight state at 11 to approximately the center of the height I, and draws a transition curve from the upper part to the cup-shaped bottom and the lower part to the flange part. .

At this time, the outer diameter d2 of the piece has the relationship d1>d2>d, and the height l2 has the relationship 1>12>1.

In a fourth step, the piece is subjected to preforming for dimensioning in its spiral section.

That is, the side wall portions are vertically raised on the upper and lower sides of the boundary portion based on the design dimensions in order to define the outer diameter, respectively, prior to the next step.

In the fifth step, the piece is further pressurized from above and below.

At this time, the outer diameter of the piece is defined by a stepped outer diameter finishing die following the fourth step, and diameters d and D1 are defined at the upper and lower portions of the side walls, respectively.

In a fifth step, a substantially right angle is formed in the continuation area of the flange portion and the large diameter portion, while forming a side wall having an outer surface perpendicular to the dog diameter portion.

Therefore, when the valve guide 12 is fitted to the valve seat 4,
The bottom surface of the valve guide 12 and its lower inner wall are connected to the valve seat 4.
The flange surface and the outer surface of the large diameter portion can be tightly fitted to provide a satisfactory seal between the valve seat 4 and the vanoleve guide 12.

Further, in this fifth step, the upper surface of the valve seat is also molded simultaneously with the side wall molding.

That is, the upper die forms a concave dish shape on the upper surface of the piece.

This work has deep interaction with the work described below.

The upper outer peripheral edge of the valve seat 4 according to the present invention has a valve seat surface 4.
A is provided in the same manner as a known valve seat, but in particular in the case of the present invention has a substantially flat biplane valve support surface at the upper edge of the surface 4a.

This support surface, by providing a predetermined radius on its inner edge, provides a significant effect in extending the life of the biplane valve.

This is because the biplane valve is satisfactorily supported during operation.

However, in the fifth step, the upper die is provided with an annular recessed cavity having a predetermined depth.

In this cavity, due to the pressing force applied to the material when the medium recess is formed, the material escapes from the outer circumference of the medium recess, and as a result, the surrounding material on the upper surface of the material flows into this cavity, forming the desired flat shape. is formed.

This flat section is substantially perpendicular to the small diameter section of the side outer wall.

In this manner, in the fifth step, the side wall of the valve seat 4 having the large diameter portion and the small diameter portion, the flat biplane valve support surface, and the upper surface having the central concave portion are formed.

The sixth step is a step of punching out the flange portion.

In this step, the flange portion is punched out to a predetermined length.

In the seventh step, a predetermined opening 4b is formed in the upper surface of the valve seat 4 and in the concave portion thereof.

This opening can be easily formed using a known device, and the opening provides a passage for oil to pass through the valve seat 4.

Note that this valve seat forming process is merely an example and does not limit the present invention in any way.

For example, although the step of forming the opening 4b is performed in the final step, it is of course possible to perform this step simultaneously with the blank punching operation of the first step.

It would also be possible to carry out the cutting step (sixth step) shown in FIG. 5 in an appropriate prior step.

Using this method, valve seats can be manufactured extremely easily, the manufacturing equipment requires only a normal press machine, mass production is possible, and the raw material and manufacturing costs are extremely low. It has significant advantages such as providing strength, dimensional accuracy, and performance superior to sintered products, and being much lighter in weight than conventional products.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a shock absorber equipped with a valve seat manufactured by the method of the present invention, FIGS. 2 and 3 are diagrams illustrating fluid flow at the bottom of FIG. 1, and FIG. 4 is a view of a known valve seat. Cross section, 5th
The figure is a diagram showing a method for manufacturing a valve seat according to the present invention. Explanation of symbols: 4...Valve seat, 4a...Valve seat surface, 4b...Through hole.

Claims (1)

[Claims] 1. A method for manufacturing a bottom valve seat of a shock absorber having a projection for defining a fluid passage on a lower cover, the method comprising punching a circular blank having a predetermined dimension from a flat plate having a predetermined thickness, and forming the blank with a flange. bending it into a cup shape, forming a cylindrical wall part of a predetermined length on the outer surface of the side wall of the cup shape, forming an annular flat part around the outside of the bottom part while pushing the bottom part of the cup shape inward, and flange part. A valve having an annular flat part and a through hole at the bottom, and a flange part forming the same plane on the opposite side of the bottom. A valve seat manufacturing method in which the seat is manufactured from a flat plate by press molding.