JPH09177847A - Resin-made disk brake piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable manufacturing a resin-made disk brake piston inexpensively while satisfying the performance to be required for the disk brake piston by hemispherically shaping a recess part tip end shape of the resin-made disk brake piston. SOLUTION: In a resin-made disk brake piston, when the outer diameter of a piston, for example, is ϕ30mm and the inner diameter thereof is ϕ20mm, a tip end part 3 of a recess part 1 on the inner diameter side is formed into the hemispherical shape of a 10mm radius, and the minimum thickness of the ceiling side is 5mm. Preferably, a ratio of the thickness of the piston to the outer diameter is set in the range of 1/5 to 1/7 in a balance between levels of a low cost and required withstand pressure strength. Thus, an inexpensive resin-made disk brake piston can be provided in comparison with the metallic piston, which could not be achieved in the conventional shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight, low-cost resin disc brake piston having a specific shape.

[0002]

2. Description of the Related Art Resin disc brake pistons are generally made of a molding material in which a reinforcing material such as glass fiber is added to phenol resin. Only the degree of increasing the thickness has been examined, and the shape is not necessarily optimal from the economical point of view. From this point, in spite of the great merit of weight reduction, the economical merit has not fully appeared in comparison with the metal piston, and the resin piston has not been widely used at present. Is.

[0003]

As described above, the resin disc brake piston having the conventional shape has a relatively high cost, and therefore the change from the metal piston has been delayed. The present invention has been completed as a result of various studies in order to solve the above-mentioned problems, and while satisfying the performance required for a disc brake piston, it is a resin disc that is cheaper than a metal piston. The purpose is to provide a brake piston.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a resin disc brake piston, characterized in that the shape of the tip of the concave portion on the inner diameter side is hemispherical, and preferably the piston has a wall thickness of the piston. 1/5 to 1 / outer diameter
The present invention relates to a resin disc brake piston having a range of 7.

The shape of the resin disc brake piston according to the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the shape of a resin disc brake piston according to the present invention. The outer diameter of the piston is φ30
mm, and the inner diameter is φ20 mm. The tip 3 of the recess 1 on the inner diameter side is hemispherical with a radius of 10 mm, and the minimum wall thickness on the ceiling side is 5 mm. The thickness of the side wall is also 5 mm. In this case, the ratio of the thickness of the piston to the outer diameter is 5/30 = 1/6.

In the conventional resin disc brake piston shown in FIG. 2, the tip shape 4 of the recess 2 on the inner diameter side is not hemispherical, but only the corner 5 is curved. In this case, when the brake fluid pressure is not applied, stress concentrates on the corners, and the pressure resistance decreases. for that reason,
In order to impart strength equivalent to that when the tip shape of the recess on the inner diameter side is made hemispherical, it is necessary to make the wall thickness thicker. As a result, the weight of the molded product increases, resulting in higher cost.

Further, in the present invention, the ratio of the wall thickness of the piston to the outer diameter is 1/5 to 1 in view of the balance between the required level of pressure resistance and cost reduction.
/ 7 is desirable. Of course, in order to satisfy the pressure resistance strength level required by this ratio, it is needless to say that the shape of the tip of the concave portion on the inner diameter side is hemispherical. If this ratio exceeds 1/5, the weight of the molded product increases, resulting in higher cost. Also 1 /
If it is less than 7, it becomes difficult to satisfy the required pressure resistance strength level.

[0008]

EXAMPLES Examples according to the present invention are shown in Table 1 together with comparative examples. In each of the examples, the shape of the tip of the concave portion on the inner diameter side is a hemispherical shape, and the ratio of the wall thickness of the piston to the outer diameter is 1/5 in the first embodiment and 1 / th in the second embodiment, respectively.
It is set to 6. In each of the comparative examples, the shape of the tip of the concave portion on the inner diameter side is not a hemispherical shape, but only the corner portion has a curved surface shape (radius 5 mm). In Comparative Example 1, the ratio of the thickness of the piston to the outer diameter is set to 1/5, which is the same as in Example 1. Further, in Comparative Example 2, in order to make the strength equivalent to that of Example 2, the wall thickness was increased until the ratio became 1 / 1.3. From the comparison between Example 1 and Comparative Example 1, the effect of making the shape of the tip of the recess a hemisphere is clear. Further, in comparison between Example 2 and Comparative Example 2, it is found that the capacity (weight) needs to be increased by 24% in order to obtain the same strength.

[0009]

[Table 1]

[0010]

As is clear from the above results, the shape of the resin-made disc brake piston of the present invention satisfies the performance required for the disc brake piston,
It is possible to provide a resin disc brake piston that is inexpensive even in comparison with a metal piston, which cannot be achieved by the conventional shape. Further, since the weight can be further reduced, it also has an effect of improving fuel efficiency when mounted on an automobile or a two-wheeled vehicle, which is industrially useful.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a resin disc brake piston shape (one example) according to the present invention.

FIG. 2 is a vertical cross-sectional view of a conventional resin-made disc brake piston shape (one example).

[Explanation of symbols]

 1 recessed part 2 recessed part 3 recessed part tip part 4 recessed part tip part 5 corner

Claims (2)

[Claims] 1. A resin-made disc brake piston, wherein the shape of the tip of the recess on the inner diameter side is hemispherical. 2. The thickness of the piston is 1/5 of the piston outer diameter.
The resin disc brake piston according to claim 1, which is in a range of 1/7.