JPH05215136A - Radial bearing - Google Patents

Abstract

PURPOSE:To prevent generation of peeling or cracks in a track surface by forming a recessed surface to prevent an excessive stress applied to the track surface by thermal expansion in a shaft diameter direction in an inner circumference of an inner ring. CONSTITUTION:A recessed surface 20 facing in a diameter direction to a track surface 11a is formed along the whole circumference almost at a center part of an inner circumferential surface of an inner ring 11. Even when a shaft 1 is thermally expanded by a temperature rise by the recessed surface 20, an outer circumference of the shaft 1 becomes hard to contact with the track surface 11a under it, so generation of a large circumferential stress at the track surface 11a can be prevented. If a load from a ball 13 is applied on the track surface 11a, generation of peeling or cracks can be prevented. The circumferential stress is generated on both sides of the recessed surface 20 to a certain degree, but because there is no direct application of a load by roll of the ball 13 here, bad effects are not given to the track surface 11a. By providing a large interference at the parts, therefore, desired engagement can be secured even under a low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial bearing, and more particularly to a radial bearing in which the inner circumference of the inner ring is press-fitted and fixed to a shaft having a large volume expansion coefficient.

[0002]

2. Description of the Related Art Generally, this type of radial bearing is
An inner ring fixed by being press-fitted to the shaft and an outer ring arranged on the outer periphery of the inner ring are provided. Raceways are formed on the outer circumference of the inner ring and the inner circumference of the outer ring, respectively, and a large number of rolling elements rollingly contacting the raceways are provided between the outer ring and the inner ring. In the above conventional structure, the inner circumference of the inner ring is pressed against the shaft almost entirely.

[0003]

If the shaft to which the inner ring is fixed is made of a material having a large volume expansion coefficient such as aluminum, when the temperature rises during use and the shaft expands in the radial direction. However, the fitting force between the shaft and the inner ring becomes too large, which may cause a large tensile stress in the circumferential direction of the inner ring. However, in the above-mentioned conventional configuration, since the inner peripheral surface of the inner ring is pressed against the shaft over almost the entire surface, when a load is applied from the rolling element to the raceway surface while a large tensile stress is generated on the raceway surface of the inner ring, There is a risk that peeling or cracking may occur on the raceway surface early and the life of the bearing may be shortened. Therefore, it is possible to set the interference to be small and set the fit loosely, but in that case, if the bearing is used in a situation where the temperature during use is low, the interference of the inner ring with respect to the shaft will be insufficient, The problem that loosening occurs occurs.

The present invention has been made in view of the above problems, and even when the inner ring is press-fitted to the shaft having a large volume expansion coefficient, it is possible to prevent the life reduction due to the thermal expansion and the thermal contraction. Is intended to provide.

[0005]

In order to solve the above-mentioned problems, a radial bearing of the present invention has a raceway surface on which rolling elements make rolling contact, and an inner ring whose inner circumference is press-fitted into a shaft. In the bearing, a concave surface for preventing excessive stress from acting on the raceway surface due to the radial thermal expansion of the shaft is formed on the inner circumference of the inner ring.

[0006]

According to the radial bearing having the above structure, since the concave surface is formed on the inner circumference of the inner ring, even if the shaft is thermally expanded due to the temperature rise, a large circumferential stress is generated. Can be prevented from occurring on the raceway surface.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of a radial bearing 10 according to an embodiment of the present invention. Referring to the figure, the radial bearing 10 includes an inner ring 11 fixed by being press-fitted onto the shaft 1. The shaft 1 is made of a material having a relatively high volume expansion coefficient such as aluminum or aluminum alloy. An outer ring 12 is arranged on the outer periphery of the inner ring 11. Raceway surfaces 11a and 12a are formed on the outer circumference of the inner ring 11 and the inner circumference of the outer ring 12, respectively.
Further, a large number of balls 13 as rolling elements are interposed between the outer ring 12 and the inner ring 11, and each raceway surface 1
It is in rolling contact with 1a and 12a. Each ball 1
3 is held by a holder 14. The ball 1
Annular seals 15 and 16 are arranged on both sides of 3, and the inner and outer peripheries are fitted into fitting grooves 11b and 12b formed in the outer circumference of the inner ring 11 and the inner circumference of the outer ring 12, respectively.

With the above-mentioned structure, in this embodiment, the shaft 1 is moved to the raceway surface 11a by the thermal expansion in the radial direction.
In order to prevent excessive stress from acting on the inner ring 11,
A concave surface 20 that faces the raceway surface 11a in the radial direction is formed over the entire circumference in a substantially intermediate portion of the inner peripheral surface of the. Figure 2
FIG. 4 is a schematic cross-sectional view showing a manufacturing process of the inner race 11 having the concave surface 20. Referring to FIG. 1A, in order to form this concave surface 20, first, when forming the inner ring 11, two grooves 21 and 22 are formed on the inner peripheral surface. These grooves 21, 22
Are formed so as to substantially oppose each other at both widthwise ends of the raceway surface 11a of the inner ring 11. Next, as shown in FIG. 2B, when the raceway surface 11a of the inner ring 11 is tightened by the annular clamp 2, the inner peripheral surface of the inner ring 11 projects radially inward between the grooves 21 and 22. Then, in this state, FIG.
By polishing between the grooves 21 and 22 as indicated by the chain double-dashed line X in (C), a concave surface 20 having a predetermined dimensional tolerance is formed over the entire circumference as shown in FIG. 2 (D). You can

The dimensional tolerance of polishing of the concave surface 20 with respect to the shaft 1 is the most preferable size according to various conditions such as the volume expansion coefficient of the shaft 1, the radial thickness of the inner ring, and the temperature range that changes during use. Is set to. For example, in the case of this embodiment, the diameter of the shaft 1 is set to 20 mm at room temperature, and the dimensional tolerance of polishing the concave surface 20 in that case is set to about +0 to +20 microns. In addition, the concave surface 20 of the inner circumference of the inner ring 11
In view of the fact that the concave surface 20 is formed, it is preferable that the interference tolerances other than those are set to be slightly larger, and the dimensional tolerance of the inner periphery of the conventional product is 0 to -8 microns. On the other hand, in the case of this embodiment, it is -5 to -15 microns.

According to the above construction, by forming the concave surface 20, the outer periphery of the shaft 1 is pressed directly below the raceway surface 11a even when the shaft 1 is thermally expanded due to temperature rise. Since it becomes difficult, it is possible to prevent a large circumferential stress from occurring on the raceway surface 11a. Therefore, according to the present embodiment, even if the load from the ball 13 is applied to the raceway surface 11a of the inner ring 11 while the shaft 1 is thermally expanded, it is possible to prevent peeling or cracking from occurring on the raceway surface 11a. There is a remarkable effect that can be. A large amount of circumferential stress is generated on both sides of the concave surface 20 on the inner circumference of the inner ring.
Since the load caused by rolling of the ball 13 is not directly applied, it does not have a great adverse effect on the raceway surface 11a. Therefore, by providing a large amount of interference in this portion, a desired fit can be secured even at a low temperature.

Moreover, in this embodiment, since the two grooves 21 and 22 are formed on the inner circumference of the inner ring 11, the inner ring 11 is ground when it is tightened by the annular clamp 2 on the raceway surface 11a of the inner ring 11. It is possible to accurately determine the width dimension of the part to be used. Therefore, there is an advantage that it becomes easy to accurately set the width of the concave surface 20 according to the width of the raceway surface 11a.

As shown in FIG. 3, the concave surface 20 is formed by crowning the inner circumference of the inner ring 11, for example.
It goes without saying that various design changes can be made without departing from the spirit of the present invention.

[0013]

As described above, according to the radial bearing of the present invention, it is possible to prevent a large circumferential stress from being generated on the raceway surface even when the shaft is thermally expanded due to the temperature rise. Therefore, even if a load is applied from the rolling element to the raceway surface while the shaft is thermally expanding, it is possible to prevent peeling and cracking from occurring on the raceway surface at an early stage, reducing the life of the product. The remarkable effect that it can be prevented is exhibited. Also, since it is possible to set a large interference on both sides of the concave surface of the inner ring, it is possible to set a sufficient interference even if the temperature during use is low. However, there is an advantage that loosening can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a radial bearing according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the inner ring in the embodiment of FIG. 1, and FIG. 2 (A) is a sectional view in one manufacturing process of the inner ring;
(B) is a cross-sectional view showing the next manufacturing process, (C) is a cross-sectional view showing the next manufacturing process, and (D) is the above (A)-
It is sectional drawing of the inner ring formed by the process of (C).

FIG. 3 is a schematic sectional view of a radial bearing according to another embodiment of the present invention.

[Explanation of symbols]

 10 Radial bearing 11 Inner ring 11a Raceway surface 12 Outer ring 13 Ball (rolling element) 20 Concave surface

Claims (1)

[Claims] 1. A radial bearing having a raceway surface with which rolling elements make rolling contact in the outer circumference and having an inner race in which the inner circumference is press-fitted into the shaft, wherein the raceway surface has an excessively large amount due to thermal expansion in the radial direction of the shaft. A radial bearing characterized in that a concave surface for preventing stress is formed on the inner circumference of the inner ring.