JP2011148158A - Piston - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a piston having excellent mold releasability from a molding mold, and wherein a cap is prevented from floating or running off from a piston body, when removing the mold from the molding mold. <P>SOLUTION: In the piston 21, the metal cap 31 covering an outer peripheral surface, an inner peripheral surface and an opening end surface is integrally joined to the opening end 24 of the cup-shaped synthetic resin-made piston body 23. In the cap 31, a projection part 36 or a recessed part is continuously formed on the whole circumference of a cap side surface 32a corresponding to the outer peripheral surface or the inner peripheral surface of at least the opening end 24, and linearly contacted with the inner wall surface of the molding mold for resin-molding the piston body 23. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a piston in which a metal cap that covers an outer peripheral surface, an inner peripheral surface, and an open end surface of an open end is integrally coupled to an open end of a cup-shaped synthetic resin piston main body.

  6 to 8 show a disc brake piston disclosed in Patent Document 1 below and a metal cap that is integrally mounted on the piston.

  A disc brake device 1 shown in FIG. 6 includes a disc rotor 2, a friction pad 3 pressed against the disc rotor 2, a piston 5 for pressing the friction pad 3 against the disc rotor 2, and the piston 5 And a caliper 6 having a cylinder portion 6a that can be moved forward and backward toward the disk rotor 2.

  The piston 5 has a configuration in which a metal cap 9 that covers the outer peripheral surface, inner peripheral surface, and open end surface of the open end 7a is integrally coupled to the open end 7a of the cup-shaped synthetic resin piston main body 7. ing.

  As shown in FIGS. 7 and 8, the cap 9 includes an outer cylindrical wall 9a that covers the outer peripheral surface of the opening end 7a, an inner cylindrical wall 9b that covers the inner peripheral surface of the opening end 7a, and an opening end 7a. When the piston body 7 is molded, it is integrated with the piston body 7 by insert molding (molding) when the piston body 7 is molded with a configuration including an end surface wall 9c that covers the opening end surface and connects the outer cylinder wall 9a and the inner cylinder wall 9b. Combined.

  In order to increase the coupling strength between the cap 9 and the piston body 7, the inner cylinder wall 9b of the cap 9 is formed with protrusions 9d that protrude into the opening end 7a at a plurality of locations in the circumferential direction by cutting and raising. ing.

US Pat. No. 5,713,435

By the way, when the cap 9 is insert-molded, as shown in FIG. Thirteen fillings are performed. If the resin 13 filled inside the cap 9 flows out between the inner peripheral surface 12a of the upper mold 11 surrounding the outer periphery of the outer cylindrical wall 9a and the outer cylindrical wall 9a, a burr is formed.
Therefore, normally, in order to suppress the outflow of resin serving as a burr, the inner diameter of the inner peripheral surface 12a is set so that the clearance with the outer cylinder wall 9a is as small as possible.

However, in the cap 9 described in Patent Document 1, the outer cylindrical wall 9a is a simple cylindrical shape, and the contact with the inner peripheral surface 12a is a surface contact. Therefore, between the inner peripheral surface 12a and the outer cylindrical wall 9a. Since the clearance is set small, the contact friction between the inner peripheral surface 12a and the outer cylinder wall 9a becomes very large, and the releasability from the mold becomes worse.
As a result, when the mold is removed from the mold, an unreasonable load is applied to the cap 9, and there arises a problem that the cap 9 is lifted or removed from the piston body 7, resulting in a decrease in yield.

  On the other hand, if the clearance between the inner peripheral surface 12a and the outer cylindrical wall 9a is set large in order to improve releasability, the resin between the inner peripheral surface 12a of the upper mold 11 and the outer cylindrical wall 9a The outflow increases and the molded product has a large amount of burrs on the outer periphery of the end wall 9c, which takes time for deburring after the molding, resulting in a problem of reduced productivity.

  The present invention relates to solving the above-described problems, and provides a piston that is excellent in releasability from a mold and that does not cause the cap to float or come off from the piston body when the mold is removed from the mold. Objective. Furthermore, it aims at providing the piston which can abolish or reduce the deburring operation | work after shaping | molding of a piston main body, and can improve productivity.

The above-described object of the present invention is achieved by the following configuration.
(1) A piston in which a metal cap that covers an outer peripheral surface, an inner peripheral surface, and an open end surface of the open end is integrally coupled to an open end of a cup-shaped synthetic resin piston body,
The cap has at least a convex portion or a concave portion formed continuously on the entire circumference of the side surface of the cap corresponding to the outer peripheral surface or inner peripheral surface of the opening end portion, and is in line contact with the inner wall surface of the molding die for resin molding the piston body. Piston characterized by being made.

  (2) The above-mentioned (1), wherein the convex portion formed on the side surface of the cap corresponding to the outer peripheral surface of the opening end portion also serves as a barrier for suppressing outflow of the resin filled in the mold. The piston described in 1.

  In the piston according to the above (1), when the piston main body and the metal cap are integrally formed by insert molding, the contact between the molding die covering the cap and the cap becomes a line contact by the convex portion of the cap side surface. Compared with the case of the conventional piston in which the surface contact is made, the contact friction between the side surface of the cap and the mold is reduced, and the mold release property from the mold is excellent. In addition, the resin filled inside the cap enters the inside of the convex part, and the cap and the opening end are in an uneven fitting state over the entire circumference, so the coupling force between the cap and the opening end is also improved. Can be made.

  In the piston described in (2) above, when the piston main body is molded, the protrusion provided on the side surface of the cap serves as a barrier that prevents the resin from flowing out between the mold and the cap, The outflow of resin is suppressed. Therefore, it is difficult to form burrs around the cap on the molded piston, and productivity can be improved by eliminating or reducing the deburring operation after molding.

It is the side view which carried out the partial cross section of 1st Embodiment of the piston which concerns on this invention. It is sectional drawing of the principal part of the metal cap shown in FIG. It is operation | movement explanatory drawing at the time of integrally molding the piston main body shown in FIG. It is sectional drawing of the principal part of 2nd Embodiment of the metal cap used for the piston which concerns on this invention. It is sectional drawing of the principal part of 3rd Embodiment of the metal cap used for the piston which concerns on this invention. It is a longitudinal cross-sectional view which shows schematic structure of the conventional disc brake apparatus. It is a top view of the metal cap used for the piston shown in FIG. It is AA sectional drawing of FIG. It is explanatory drawing at the time of integrally molding the piston main body shown in FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a piston according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional side view of a first embodiment of a piston according to the present invention.

  The piston according to the first embodiment is attached to the cylinder portion of the caliper of the disc brake device in order to press the friction pad against the disc rotor of the disc brake device.

  The piston 21 of the first embodiment is a metal that covers the outer peripheral surface, inner peripheral surface, and open end surface of the open end 24 on the open end 24 of a synthetic resin-made piston main body 23 formed in a cup shape. The cap 31 is joined together.

  In the case of the present embodiment, the cap 31 is a press-formed product of a metal plate, and as shown in FIG. 2, an outer cylindrical wall 32 that covers the outer peripheral surface of the opening end 24 and an inner peripheral surface of the opening end 24. An inner cylinder wall 33 to be covered and an end face wall 34 that covers the opening end face of the opening end 24 and connects the outer cylinder wall 32 and the inner cylinder wall 33 are provided.

In the case of the present embodiment, a convex portion 36 is formed on the cap side surface 32 a that is the outer peripheral surface of the outer cylindrical wall 32 corresponding to the outer peripheral surface of the opening end 24.
This convex part 36 is what is called a convex strip formed continuously over the perimeter of the cap side surface 32a which is a cylindrical surface.

The metal cap 31 is integrally coupled to the piston body 23 by insert molding (molding) when the piston body 23 is molded.
Specifically, when the cap 31 is insert-molded, as shown in FIG. 3, the cap 31 is attached to the cavity 42 of the upper mold (molding die) 41 for insert molding and is not abutted against the upper die 41. The resin 51 is filled from the lower mold side shown in the figure.
As shown in FIG. 3, the cap 31 attached to the upper mold 41 is in line contact with the inner wall surface 43 of the upper mold 41 whose resin 36 is formed on the piston body 23 of the convex portion 36.

Furthermore, in the case of the present embodiment, the convex portion 36 of the cap side surface 32 a corresponding to the outer peripheral surface of the opening end 24 is a gap between the cap side surface 32 a and the inner wall surface 43 where the resin 51 filled in the mold 41 is formed. It also serves as a barrier that suppresses outflow to S.
That is, the convex portion 36 prevents the resin 51 from flowing out into the gap S between the cap side surface 32 a and the inner wall surface 43 beyond the convex portion 36.

In the piston 21 of the first embodiment described above, when the piston main body 23 and the metal cap 31 are integrally formed by insert molding, the contact between the upper mold 41 and the cap 31 covering the cap 31 is caused by the cap side surface 32a. Compared with the case of the conventional piston (see FIG. 9) in which the cap side surface is in surface contact, the contact friction between the cap side surface 32a and the upper mold 41 is reduced because of the line contact by the convex portion 36. Excellent releasability from the mold 41. In addition, since the resin 51 filled inside the cap 31 enters the inside of the convex portion 36 and the cap 31 and the opening end 24 are in a concavo-convex fitting state over the entire circumference, the cap 31 and the opening end The coupling force with the part 24 can also be improved.
Therefore, when the die is removed from the upper die 41, the cap 31 is not lifted or detached from the piston main body 23, and the yield can be improved.

  In the piston 21 of the first embodiment described above, when the piston main body 23 and the metal cap 31 are integrally formed, the contact between the upper mold 41 and the cap 31 is a line contact as described above. Thus, even if the clearance between the inner wall surface 43 of the upper mold 41 and the cap side surface 32a is reduced, good releasability can be ensured. Therefore, by setting the clearance smaller, the inner wall surface 43 of the upper mold 41 It is also possible to reduce the burr generated around the cap 31 by reducing the outflow of the resin 51 into the gap S between the cap side surface 32a.

  Furthermore, in the piston 21 of the first embodiment, the convex portion 36 formed on the cap side surface 32 a corresponding to the outer peripheral surface of the opening end portion 24 is a barrier that suppresses the outflow of the resin 51 filled in the upper mold 41. For this reason, the molded piston 21 is less likely to form burrs around the cap 31, so that the deburring work after molding can be eliminated or reduced to improve productivity.

From the viewpoint of improving the coupling force between the cap 31 and the piston main body 23, as shown in FIG. 4, a convex portion protruding toward the center of the opening end 24 on the inner cylindrical wall 33 of the cap 31. It is also effective to equip 37 as a ridge which continues over the entire circumference. Further, as shown in FIG. 5, even if the inner cylinder wall 33 of the cap 31 is provided with a recess 38 that is recessed toward the center of the open end 24 as a continuous groove over the entire circumference, The coupling force with the piston body 23 can be improved.
Therefore, the metal cap used for the piston according to the present invention has at least a convex portion or a concave portion continuously formed on the entire circumference of the side surface of the cap corresponding to the outer peripheral surface or the inner peripheral surface of the opening end 24, and the piston main body 23 is made of resin. What is necessary is just to set it as the structure which carries out line contact with the inner wall face of the shaping | molding die to shape | mold.

  The piston of the present invention is not limited to the above-described embodiment, and can be appropriately modified and improved. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

21 Piston 23 Piston body 24 Open end 31 Cap 32 Outer cylinder wall 32a Cap side surface (outer peripheral surface)
33 Inner cylinder wall 34 End face wall 36 Convex part 37 Convex part 38 Concave part

Claims (2)

A piston in which a metal cap that covers an outer peripheral surface, an inner peripheral surface, and an open end surface of the open end is integrally coupled to an open end of the cup-shaped synthetic resin piston body,
The cap has at least a convex portion or a concave portion formed continuously on the entire circumference of the side surface of the cap corresponding to the outer peripheral surface or inner peripheral surface of the opening end portion, and is in line contact with the inner wall surface of the molding die for resin molding the piston body. Piston characterized by being made.   2. The piston according to claim 1, wherein the convex portion formed on the side surface of the cap corresponding to the outer peripheral surface of the opening end portion also serves as a barrier that suppresses the outflow of the resin filled in the mold. .

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