JPH0521725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of forming a bottomed cylindrical piston with one end closed.

(Prior Art) For example, as a cylinder device for a control valve that operates the clutch of a torque converter with a lock-up mechanism, there is a structure shown in FIG. 5.

That is, a stepped bottomed cylindrical cylinder 2 whose left part is connected to a large diameter chamber 2a, whose right part is connected to a small diameter chamber 2b, and whose right end is closed is fixed to the control body 1. A piston 3 of the shape is slidably fitted.

The piston 3 connects the right part of the body part 3a whose right end part is closed by the bottom wall 3b to the small diameter chamber of the cylinder 2.
b, the left part of the body part 3a is exposed to the large-diameter chamber 2a side of the cylinder 2, and a large-diameter flange 3c is formed at the left end. Divided into.

Then, the piston 3 is moved by the coil spring 4.
There is a structure in which the cylinder chamber 2 is pressed against the right side of the cylinder chamber 2.

By the way, as a method for molding the piston 3, there have conventionally been methods shown in FIGS. 6 to 8.

In FIG. 6, 5 is a molding device, which is constructed as follows.

That is, a bottomed cylindrical outer periphery mold 7 is fitted onto the outer periphery of a columnar inner periphery mold 6 to form a bottomed cylindrical cavity 10 therebetween.

A cylindrical protrusion pin 6 for extruding a molded product is slidably fitted into the inner peripheral mold 6 at its axial center.

Further, the outer peripheral mold 7 surrounds the circumferential surface of the inner peripheral mold 6 with upper and lower molds 8, 8 divided into upper and lower parts, and surrounds the right end surface, that is, the bottom surface of the inner peripheral mold 6 with a cylindrical horizontal mold 9. A bush 17 is removably fitted into the axial center of the horizontal mold 9.

A cylindrical sprue 11 is formed at the axial center of the bush 17 and widens at a small angle toward the right, and the left end of the sprue 11 is communicated with the bottom 10a of the cavity 10.

Then, as shown in FIG. 7, molten plastic material is injected into the cavity 10 from the sprue 11, and is hardened to form the piston molded body 12.
form.

Next, the piston molded body 12 is removed from the mold device 5, and as shown in FIG. 8, the cylindrical sprue solidified material 12c is broken off and removed from its base to obtain the piston 12a.

(Problems to be Solved by the Invention) The above conventional method has a columnar sprue solidified material 12c.
was directly fixed to the axial center of the bottom wall 12b of the piston 12a, so when the sprue condensate 12c was bent and removed from the bottom wall 12b, a recess was formed in the axial center of the bottom wall 12b, as shown in FIG. 12d was generated, resulting in a disadvantage that the strength of the bottom portion 12b was reduced.

An object of the present invention is to obtain a novel piston molding method that eliminates the above-mentioned drawbacks.

(Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows.

That is, a cylindrical outer periphery mold with a bottom is fitted onto the outer periphery of a columnar inner periphery mold to form a bottomed cylindrical cavity between the two, and an outer cylindrical cavity is formed between the outer periphery and the bottom axis of the outer periphery mold. A constriction part is formed that tapers toward the end, a sprue is connected to the constriction part, and the molten material is injected into the cavity from the sprue.

(Function) Since the present invention has the above-mentioned configuration, the molded body formed by the inner peripheral mold and the outer peripheral mold has a bottom wall of the piston in the shape of a cylinder with a bottom formed by the cavity part, and a sprue part. A constriction formed by the constriction part will be generated between the sprue and the sprue solidified material formed by the sprue.

Then, when the sprue solidified material is bent, the constricted portion where the bending rigidity is reduced will break.

(Example) Embodiments of the present invention will be described below based on the drawings.

In the drawings, FIG. 1 is a cross-sectional view of a mold device showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing its molding state, FIG. FIG. 4 is an enlarged sectional view of main parts showing another embodiment.

In FIGS. 1 to 4, parts having the same structure as those in FIGS. 6 to 8 are given the same reference numerals as those in FIGS. 6 to 8, and explained. omitted.

A bushing 17 is removably inserted and fixed into the axial center of the horizontal mold 9 that surrounds the right end surface of the inner peripheral mold 6, and a bushing 17 is inserted into the axial center of the bushing 17 and is compressed at an angle of about 45 degrees toward the right. A tapered constricted part 13 and a tapered sprue 14 that widens at an angle of about 1 degree toward the right from the right end small diameter part 13a of this constricted part 13 are continuously formed.

Then, as shown in FIG. 2, molten plastic material is injected into the cavity 10 from the sprue 14, and is hardened to form the piston molded body 15.
form.

Next, the piston molded body 15 is separated from the mold device 5, and as shown in FIG. shaped piston 1
Get 5a.

In this case, when the sprue coagulated material 15c is bent, a high stress concentration will occur in the constricted portion 15d formed by the constricted portion 13, and the sprue coagulated material 15c will break from this portion.

As shown in FIG. 4, a tapered widening section 15c-1 that widens at an angle of about 30 degrees toward the right from the constriction section 15d is provided at the left end, that is, at the base of the sprue solidified material 15c. You may form it.

In this way, when the sprue solidified material 15c is bent, it will break more effectively at the constricted portion 15d.

(Effects of the Invention) As is clear from the above description, the present invention has a constriction formed between the bottom wall of the piston and the sprue solidified material fixed to the bottom wall, so that the bottom of the piston The sprue coagulum can be broken off and removed without reducing the wall thickness, and a bottomed cylindrical piston with high strength can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a mold device showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing its molding state, Fig. 3 is a cross-sectional view showing a molded article molded by the mold device, and Fig. 4 is an enlarged sectional view of main parts showing another embodiment,
Fig. 5 is a sectional view showing how the bottomed cylindrical piston is used, Fig. 6 is a sectional view of a mold device showing a conventional example, and Fig. 7 is a sectional view showing how the bottomed cylindrical piston is used.
The figure is a cross-sectional view showing the molding state, and FIG. 8 is a cross-sectional view showing the molded body molded by the mold device. 6: Inner periphery mold, 7: Outer periphery mold, 8, 8: Upper and lower molds, 9: Horizontal mold, 10: Cavity, 13: Squeezed part, 14: Sprue, 15: Piston molded body, 15
a: piston, 15b: bottom wall, 15c: sprue solidified material, 15d: constriction, 16: ejector pin, 17:
Butsuyuu.

Claims (1)

[Claims] 1. A bottomed cylindrical outer mold is fitted onto the outer periphery of a columnar inner mold to form a bottomed cylindrical cavity between the two. 1. A method for forming a bottomed cylindrical piston, characterized in that a constricted part is formed in a tapered shape toward the opposite end, a sprue is connected to the constricted part, and a molten material is injected into the cavity from the sprue.