JPH0144407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a bottomed cylindrical piston used in a hydraulic cylinder or the like.

[Prior Art] A bottomed cylindrical piston is generally manufactured by casting or by cold forging from a cylindrical material. However, casting is expensive, and when cold forging from a cylindrical material, the degree of plastic deformation is large, so not only does the die wear out rapidly, but an annealing process is required midway, and the material is not lubricated. Bonde treatment (zinc plating)
This also has the disadvantage of high cost since it requires many processing steps such as .

On the other hand, many attempts have been made to manufacture pistons by using plate material of an appropriate thickness and deep drawing it into a cylindrical shape with a bottom. There are three points. That is,
First, in normal deep drawing, the radius of curvature of the corner where the outer circumferential surface and the lower surface of the product join is large and, in short, it cannot be formed into a square shape, so the effective length of the piston is shortened. Second, due to the process of sequentially deep-drawing a flat plate, a portion of the peripheral wall of the product with extreme thickness changes called a shock line occurs. Thirdly, if the product is left deep drawn, the outer periphery of the product will be tapered, so it will have to be cut straight, and if this is done, the product will become thinner towards the opening side, causing strength problems. .

[Object of the Invention] The present invention aims to solve the above-mentioned problems and provide a method of manufacturing a piston from a metal plate material at low cost.

[Means for Achieving the Object] In order to achieve the object, the piston manufacturing method according to the present invention includes a deep drawing process in which a metal plate material is subjected to drawing several times using a drawing die to form a bottomed cylinder. After raising the bottom wall of the bottomed cylindrical body and bulging it into a bottom shape, the bottomed cylindrical body is placed in a female mold with an angular bottom periphery and an inner peripheral surface facing the opening and expanding into a tapered shape. an edge forming step in which a male mold is simultaneously pressed against the opening edge of the bottomed cylindrical body and the raised bottom-like bulge portion to compress the bottomed cylindrical body; and after the edge forming process, the bottomed cylindrical body is molded into a die This method is characterized by an outer periphery processing step in which the outer periphery is formed into a straight shape.

[Function] By simultaneously compressing the opening edge and the raised bottom-like bulge of the bottomed cylindrical body with a male mold in a female mold, an angular edge part is formed on the bottomed cylindrical body, and a (thickness variation) can be eliminated at the same time. In addition, by pressing the die and forming the outer periphery straight, the wall thickness is prevented from becoming thinner toward the opening edge, which occurs during cutting.

[Example] An example of a piston of a hydraulic cylinder for a disc brake will be described below.

First, the deep drawing process will be explained with reference to FIG.
First, a metal plate 1 shown in FIG. 1A is formed by punching a 3-10 mm thick steel plate into a disk shape using a transfer press or the like. This metal plate material 1 is pressed in order using a drawing die with progressively deeper holes, and is gradually deep drawn at a drawing ratio of 60% to 85% as shown in Fig. 1 B, C, and D to form a cylinder with a bottom. Mold 2. Next, the edge forming process will be explained with reference to FIG.
The bottom wall of this bottomed cylindrical body 2 is bulged inward in a raised bottom shape to form a raised bottom shaped bulged portion 3 as shown in FIG. 2A. Next, as shown in FIG. 2B, this bottomed cylindrical body 2 is placed in a female mold 7 whose bottom peripheral edge 4 is square and whose inner circumferential surface 5 is tapered toward the opening 6.
The peripheral step part 10 of the male mold 9 and the punch 1 are loaded onto the opening edge 8 of the bottomed cylindrical body 2 and the raised bottom-like bulge part 3.
The tip surfaces 12 of 1 are pressed against each other and compressed. By this compression, the corner portion where the outer circumferential surface and the lower surface of the bottomed cylindrical body 2 are joined is squared to a radius of curvature of about 2 mm to form an edge portion 13. The outer circumferential surface of the punch 11 is formed to have a draft angle that is gentler than the taper of the inner circumferential surface 5 of the female die 7 and is almost straight. Therefore, the circumferential wall 14 of the bottomed cylindrical body 2 is compressed by the inner circumferential surface 5 of the female mold 7 and the outer circumferential surface of the punch 11, and local variations in the wall thickness of the circumferential wall 14 are corrected, resulting in a so-called shock. As soon as the line is resolved,
The thickness of the peripheral wall 14 tapers toward the opening edge 8. Next, the process of machining the outer periphery of the bottomed cylindrical body 2 shown in FIG. 2C will be explained with reference to FIG. 3.
In this step, the bottomed cylindrical body 2 is pushed into the die mold 15 from the opening edge 8 side thereof, and 16 indicates a pressing member for pushing the body. Through this processing step, the outer circumferential surface of the bottomed cylindrical body is squeezed and deformed so that the inner diameter of the opening edge 8 is narrowed, and at the same time, the outer circumferential surface of the peripheral wall 14 is formed into a straight shape. If necessary, the outer circumferential surface of the bottomed cylindrical body 2 can be mirror-finished with high precision by performing this outer circumferential processing step in two or more steps and sequentially pushing the outer circumference into a die mold having a slightly smaller inner diameter.

As shown in FIG. 4, the piston manufactured in this manner has a straight outer circumferential surface and a tapered inner diameter facing the opening edge 8, and the thickness of the peripheral wall 14 may be slightly thicker toward the opening edge 8. It becomes almost uniform. Furthermore, since the edge portion 13 is angular, the ratio of the effective length L to the total length is high.

[Effects of the invention] (1) Molded from a metal plate material and has a relatively low degree of plastic deformation. Therefore, there is no need for annealing, bonding, etc., which are necessary when the degree of plastic deformation is large, and there is little wear on the mold.

(2) The effective length of the piston is long because the corners of the outer circumferential surface and the lower surface can be formed into angular shapes.

(3) The outer peripheral surface can be finished with high precision.

(4) Since the opening edge can be sufficiently thick, there will be no lack of strength even if the opening edge is machined.

(5) Since it can be manufactured with fewer processing steps, it is suitable for mass production with low manufacturing costs.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
Figures A, B, C, and D are longitudinal cross-sectional views showing the deformation of the material in the deep drawing process in order; Figure 2 A, B, and C are longitudinal cross-sectional views showing the deformation of the material in the edge forming process; and Figure 3. is a longitudinal sectional view of the outer periphery processing step, and FIG. 4 is a longitudinal sectional view of the product. DESCRIPTION OF SYMBOLS 1... Metal plate material, 2... Bottomed cylindrical body, 3... Raised bottom bulge, 4... Bottom periphery, 5... Inner peripheral surface, 6... Opening, 7... Female mold, 8 ...opening edge,
9...Male mold, 10...Peripheral step, 11...Punch, 12...Tip surface, 13...Edge part, 14...
... Peripheral wall, 15 ... Dice type, 16 ... Pressing member.

Claims (1)

[Claims] 1. A deep drawing process in which a metal plate material is drawn several times with a drawing die to form a bottomed cylinder, and the bottom wall of the bottomed cylinder is raised to bulge out into a bottom shape, and then the bottomed cylinder is is loaded into a female mold whose bottom peripheral edge is angular and whose inner peripheral surface faces the opening and expands into a tapered shape, and the male mold is simultaneously applied to the opening edge of the bottomed cylinder and the raised bottom-like bulge. An edge forming process that presses and compresses the
A method for manufacturing a piston, which comprises a peripheral processing step of pressing the bottomed cylindrical body into a die mold to form a straight outer peripheral surface after the edge forming step.