JPH0633935A - Molded bearing - Google Patents

Abstract

PURPOSE:To reduce the sliding resistance of a molded bearing as to the axial movement and rotary movement of a shaft by providing at the inner peripheral face of the bearing a top portion which extends circumferentially and projects inward to make linear contact with the shaft. CONSTITUTION:A bearing 1 is molded from resin such as a polyolefine and nylon and has a circumferentially-extending, inwardly-projecting top portion 2 on its inner peripheral face, the top portion 2 having a triangular or circular cross section. The shaft is made greater in exit bore 5 than in entrance bore 3 in consideration for a clearance so as to form a grease reservoir 6 at the exit. Because of the top portion 2 making linear contact with the shaft, the bearing 1 is reduced in sliding resistance as to the axial movement and rotary movement of the shaft, and the presence of the grease reservoir 6 assists lubrication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molded bearings, and more particularly to molded bearings for supporting shafts that undergo rotational and axial movements.

[0002]

2. Description of the Related Art As shown in FIG. 8, two types of bearings, a rolling bearing and a molded bearing, which is a sliding bearing, are used as a bearing 1 for supporting a shaft 4 which performs a rotary motion and an axial motion. The former has a characteristic that the coefficient of dynamic friction is small, but when the shaft 4 is used for a drive shaft of an electric toothbrush that is subjected to an unbalanced load due to a one-way load, the shaft surface is likely to be damaged, resulting in It often increases and causes image sticking. Therefore, as the bearing 1 for the drive shaft of the electric toothbrush, a molded bearing is more frequently used than a rolling bearing.

[0003]

However, in the molded bearing, since the contact with the shaft is not the point contact of the rolling bearing but the contact of the cylindrical surface, the sliding resistance is large.
It has the drawback of poor initial properties. The present invention has been made in view of the above points, and an object thereof is to provide a molded bearing having low sliding resistance.

[0004]

SUMMARY OF THE INVENTION The present invention, however, is characterized in that the inner peripheral surface is provided with a top portion that extends in the circumferential direction and projects inward so as to make line contact with the shaft.

[0005]

According to the present invention, since the inner peripheral surface is provided with the top portion that makes linear contact with the shaft, the sliding resistance is reduced as compared with the conventional one in which the entire inner peripheral surface contacts the shaft. You can

[0006]

EXAMPLES The present invention will be described in detail below with reference to the illustrated examples. The illustrated bearing 1 is a molded bearing made of a resin such as polyolefin, polyacetal, nylon, fluorine, Teflon, etc. The inner peripheral surface is provided with a top portion 2 projecting toward one side. In the embodiment shown in FIG. 1, the apex 2 has a triangular cross section, but as shown in FIG. 2, it may have an arcuate cross section. In this case, the grease reservoir 6 is formed on the outlet side by making the outlet inner diameter 5 larger than the inlet inner diameter 3 designed in consideration of the clearance amount in the diameter of the shaft 4.

In the embodiment shown in FIG. 3, the grease reservoir 6 is formed between the tops 2 and 2 so that the tops 2 are not continuous in the circumferential direction but project inward at intervals in the circumferential direction. Showing things. As shown in FIG. 4, the grease reservoir 6 may be formed by notching the top portion 2 formed to be continuous in the circumferential direction at appropriate intervals in the circumferential direction.

FIG. 7 shows an example in which the bearing 1 having the top portion 2 formed in this manner is incorporated for supporting the drive shaft 4 of the electric tooth flapping. In the figure, 40 is a motor, 41 is a motor 40.
Is a cam portion for selectively converting the rotation of the drive shaft into the axial reciprocating motion of the drive shaft 4 and the reciprocating rotary motion of the drive shaft 4 about its axis.
Since the molded bearing 1 has the top portion 2 that makes a line contact with the shaft 4, the sliding resistance against the axial motion and the rotational motion of the shaft 4 is low, and the grease reservoir 6 Presence is to aid lubrication.

Further, like the drive shaft 4 of the electric toothbrush,
In the case of receiving an unbalanced load, as shown in FIG. 5, a cylindrical buffer body 8 made of an elastic body such as rubber or urethane resin is arranged on the outer peripheral surface, or as shown in FIG. When the buffer body 8 composed of a plurality of spring pieces is formed on the outer peripheral side,
The self-centering structure is provided, and the increase in sliding resistance due to extreme pressure can be alleviated.

[0010]

As described above, according to the present invention, since the inner peripheral surface is provided with the apex which is in line contact with the shaft, the shaft of the shaft can be compared with the conventional one in which the entire inner peripheral surface is in contact with the shaft. It is possible to reduce the sliding resistance with respect to the axial movement and the rotational movement, and it is possible to eliminate the problem that the molded bearing has poor initial characteristics.

[Brief description of drawings]

1A is a plan view of an embodiment, and FIG. 1B is a sectional view of the same.

FIG. 2 is a cross-sectional view of another embodiment.

3A is a plan view of another embodiment, and FIG. 3B is a sectional view of the same.

4A is a plan view of another embodiment, and FIG. 4B is a sectional view of the same.

5A is a sectional view of another embodiment, and FIG. 5B is a perspective view of the same.

FIG. 6A is a sectional view of still another embodiment, and FIG. 6B is a perspective view of the same.

FIG. 7 is a cross-sectional view of a state where the electric toothpaste is incorporated.

FIG. 8 is a perspective view of a shaft and a bearing.

[Explanation of symbols]

 1 bearing 2 top

Claims (4)

[Claims] 1. A molded bearing characterized in that the inner peripheral surface is provided with a top portion that extends in the circumferential direction and projects inward so as to make line contact with the shaft. 2. The molded bearing according to claim 1, wherein the top portions are formed at intervals in the circumferential direction. 3. The molded bearing according to claim 2, wherein grease is accumulated between the tops. 4. The molded bearing according to claim 1, wherein an elastic cushioning body is provided on the outer peripheral surface.