JP2002168243A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing device capable of obtaining a stabilized pressurization without an influence of the change in temperature by approximating coefficients of linear expansion of a bearing raceway wheel, a rolling body and a shaft each other in a bearing pressurized in place, and capable of solving the problem of motor stiffness and the variation of resonance frequency. SOLUTION: In the bearing device pressurized in place, the coefficients of linear expansion of the shaft, the bearing and the rolling body are approximated to each other for the purpose of the improvement of high-speed resistance and the life of fretting caused by an oscillation motion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device used for a bearing unit of, for example, OA information equipment and AV equipment.

[0002]

2. Description of the Related Art Motor bearings for OA information equipment and AV equipment are usually used at a fixed position preload, and the bearing is bonded to a shaft or a housing or lightly press-fitted and preloaded with a dead weight. HDD (HDD: Hard Disk Drive)
In the case of a motor, the shaft is made of austenitic or martensitic stainless steel, and the housing (hub) is made of aluminum or austenitic stainless steel. Further, since the recent fretting durability by high durability and oscillating motion, while others use a ceramic rolling elements of the bearing,
This ceramic is usually silicon nitride.

Meanwhile, the bearing ring normal bearing steel is used, the coefficient of linear expansion is 12.6 × ^{10 -6} / ℃. On the other hand, the silicon nitride of the rolling elements is 3 × 10 ⁻⁶ / ° C. Furthermore, the shaft stainless steel is 16
× 10 ⁻⁶ / ° C., 10 × 10 ^{−6 for} martensite
/ ° C. 16 × 10 ⁻⁶ / ° C for austenitic stainless steel housing, 24 × 10 ^{−6 for} aluminum
/ ° C.

[0004]

However, in the case of the fixed-position preload, the preload sometimes changes with the temperature change due to the difference in the dimensional change of each part with respect to the temperature change of the motor during rotation. For this reason, zirconia or the like has been used in order to give a linear expansion coefficient close to that of the bearing ring only to the ceramic ball in the bearing.

However, since the material of the shaft and the housing is different from that of the bearing ring, a change in the preload due to the difference in linear expansion coefficient occurs due to a temperature change. This change is mitigated when zirconia than the case of silicon nitride, in which low vibration due to the accuracy of a motor for an HDD becomes increasingly necessary, the axial dimension as well as radial Since a slight change in the preload due to the difference appears as a change in the motor stiffness and the resonance frequency, it is no longer sufficient to make the linear expansion coefficient of this ceramic ball close to the linear expansion coefficient of the bearing ring.

[0006] The present invention has been made in view of the above-mentioned problems of the prior art.
By bringing the linear expansion coefficients of the bearing raceway, rolling element and shaft close to each other in fixed-position preloaded bearings, a stable preload is obtained without being affected by temperature changes, solving the problems of motor rigidity and resonance frequency changes. The purpose of the present invention is to provide a bearing device.

[0007]

In order to achieve the above object, the present invention provides a bearing device which is pre-loaded in a fixed position and has a coefficient of linear expansion of a ball of ⁶ to 13 × 10 ^-6 / ° C. And the linear expansion coefficient of the shaft was set to 11 to 13.5 × 10 ⁻⁶ / ° C.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a rolling bearing according to an embodiment of the present invention. Note that this embodiment is merely an embodiment of the present invention, and is not to be construed as being limited to this embodiment.

FIG. 1 is a schematic sectional view of a spindle motor for driving an information recording disk such as an HDD including a bearing device according to an embodiment of the present invention. 1 to 4 show the first to fourth embodiments of the outer ring rotation type, and FIGS. 5 to 8 show the fifth to sixth embodiments of the inner ring rotation type. Needless to say, the bearing device of the present invention can be used in a spindle motor for driving a polygon mirror.

[First Embodiment] In a first embodiment shown in FIG. 1, a stator 3 is fitted to a motor base 2 mounted on a fixed shaft 1, and the fixed shaft 1 is vertically rolled with ball bearings. (Lower bearing 10, upper bearing 15) are provided,
These bearings rotatably support a hub 4 for holding an information recording disk such as a hard disk, and a rotor 7 is fixed to the inner peripheral surface of the hub 4. In the figure, reference numeral 6 denotes a cover plate fixed to the inner periphery of the hub 4. An information recording disk (not shown) is fixed to a disk mounting surface 5 provided on the outer periphery of the hub 4.

The lower bearing 10 incorporates a plurality of rolling elements (balls) 14 between a groove 1 a provided on the outer periphery of the shaft 1 and an inner peripheral groove 12 of the outer ring 11. A plurality of rolling elements (balls) 14 are incorporated between the outer peripheral groove 17 of the inner ring 16 fixed to the inner ring 16 and the inner peripheral groove 12 of the outer ring 11.

In this embodiment, the shaft 1 is made of bearing steel (linear expansion coefficient: 12.6 × 10 ⁻⁶ / ° C.), and the bearing outer ring 11.
The inner ring 16 has a bearing steel or a linear expansion coefficient of 11 to 13.5.
× using 10 -6 ^/ ° C. stainless steel, balls as the rolling elements 14, a ceramic material linear expansion coefficient of 6 to 13 × 10 -6 ^/ ° C., for example zirconia avenues are used as an example. This embodiment is not to be construed as being limited, and can be changed within the scope of the present invention as long as the linear expansion coefficients of the shaft, the bearing, and the rolling element are close to each other.

In the present embodiment, the outer ring 11 of the upper bearing 15 and the lower bearing 10 is made common, and a narrow ridge 4a is further provided on the inner periphery of the hub 4 to form the two grooves 12, 12.
The hub 4 and the outer ring outer diameter surface 13 are bonded to each other with a narrow width therebetween, and the outer diameter surface 13 immediately adjacent to the groove 1a is not bonded. In the drawing, reference numeral 9 denotes a bonding portion. The reason for limiting the adhesion between the hub 4 and the outer ring outer diameter surface 13 is that the hub 4 is usually made of aluminum having a coefficient of linear expansion of 24 × 10 ⁻⁶ / ° C.
Since austenitic stainless steel of × 10 ⁻⁶ / ° C. is used and there is a difference in linear expansion coefficient from the outer race 11, the dimensional change of the outer raceway diameter due to the temperature and the axial dimensional change between both grooves 1a, 1a due to this. This is to prevent a change in pitch.

The inner ring 16 may be press-fitted or bonded to the outer periphery of the shaft 1. When press-fitting the inner ring 16,
Stiffness is controlled at the resonance frequency. In the case of adhesive fixing, a preload is applied with a dead weight (see FIG. 9).

As a result, the change in rigidity is suppressed, so that the environmental temperature for measuring the axial resonance frequency may be measured at room temperature ± 10 ° C. as a guarantee for shipment, and it is no longer necessary to perform measurement in a conventional constant temperature room.

[Second Embodiment] A second embodiment shown in FIG. 2 shows an outer race 11 divided into two parts in the axial direction. Other configurations and operations are the same as those of the first embodiment, and thus the same portions are denoted by the same reference numerals and description thereof will be omitted.

"Third Embodiment" In the third embodiment shown in FIG. 3, the outer ring 11 is common, the inner ring 16 is
Shows what is fixed to. Other configurations and operations are the same as those of the first embodiment, and thus the same portions are denoted by the same reference numerals and description thereof will be omitted.

Fourth Embodiment FIG. 4 shows a fourth embodiment in which the outer race 11 is divided into two parts in the axial direction, and the inner race 16 is fixed to the fixed shaft 1 at each of the upper and lower sides. Other configurations and operations are the same as those of the first embodiment, and thus the same portions are denoted by the same reference numerals and description thereof will be omitted.

Fifth Embodiment A fifth embodiment shown in FIG. 5 is an inner ring rotating type, in which rolling ball bearings (lower bearing 10 and upper bearing 15) are arranged above and below a rotating shaft 1 ', respectively.
Housing 8 is fixed to the outer ring 11 the outer periphery thereof bearing,
The hub 4 is rotatably supported on the outer periphery of the rotating shaft 1 ′ above the upper bearing 15, and the rotor 7 is fixed to the inner peripheral surface of the hub 4. In the drawing, 3 is a stator fixed to the housing, 18 is the inner peripheral surface of the hub 4 and the outer diameter surface 13 of the outer ring 11.
And a long labyrinth seal formed between them.

In this embodiment, the upper bearing 15 incorporates a plurality of rolling elements (balls) 14 between the groove 1 a provided on the outer periphery of the rotating shaft 1 ′ and the inner peripheral groove 12 of the outer ring 11. The side bearing 10 has an outer peripheral groove 1 of an inner ring 16 fixed to the rotating shaft 1 ′.
Plural rolling elements (balls) between the inner ring 7 and the inner peripheral groove 12 of the outer ring 11
14 is incorporated. Note that, also in the present embodiment, the outer ring 11 of the upper bearing 15 and the lower bearing 10 is shared.

The bearing outer ring 11, the inner ring 16, and the rolling element 1
Reference numeral 4 denotes a material having the same linear expansion coefficient as that of the first embodiment, and rotation shaft 1 'is a material having the same linear expansion coefficient as fixed shaft 1 of the first embodiment.

Further, in this embodiment, both grooves 12, 12
A narrow width between the end face 8a of the housing 8 and the outer ring outer diameter surface 13
Are bonded, and the outer diameter surface 13 immediately adjacent to the groove 12 is not bonded. In the drawing, reference numeral 9 denotes an adhesive portion, and 8b denotes an adhesive groove in which the adhesive is stored. The reason why the bonding between the end face 8a of the housing 8 and the outer ring outer diameter surface 13 is limited is that the housing 8 is usually made of aluminum having a coefficient of linear expansion of 24 × 10 ⁻⁶ / ° C. or of 16 × 10 ⁻⁶ / ° C. Austenitic stainless steel is used, and there is a difference in the coefficient of linear expansion from the outer ring 11, so that the change in the outer ring raceway diameter due to temperature and the change in the pitch between the two grooves 12, 12 due to the dimensional change in the axial direction are prevented. is there.

The inner ring 16 may be press-fitted or bonded to the outer circumference of the rotating shaft 1 '. When the inner ring 16 is press-fitted, the rigidity is controlled at the resonance frequency. In the case of adhesive fixing, a preload is applied with a dead weight (FIG. 9).

As a result, the change in rigidity can be suppressed, so that the environmental temperature for measuring the resonance frequency can be measured at room temperature ± 10 ° C. as a guarantee for shipment, eliminating the need to perform measurement in a conventional constant temperature room.

Sixth Embodiment A sixth embodiment shown in FIG. 6 shows an outer ring 11 divided into two parts in the axial direction. As described other structure and operation are denoted by the same reference numerals to the same place because it is the same as the fifth embodiment is omitted.

[Seventh Embodiment] A seventh embodiment shown in FIG. 7 shows an embodiment in which the outer ring 11 is common and the inner ring 16 is fixed to the rotating shaft 1 'at each of the upper and lower sides. Other configurations and operations are the same as those of the fifth embodiment, and thus the same portions are denoted by the same reference numerals and description thereof will be omitted.

Eighth Embodiment An eighth embodiment shown in FIG. 8 shows an outer ring 11 divided into two parts in the axial direction, and an inner ring 16 fixed to the rotating shaft 1 'at each of the upper and lower sides. Other configurations and operations are the same as those of the fifth embodiment, and thus the same portions are denoted by the same reference numerals and description thereof will be omitted.

[0028]

According to the present invention, a linear expansion of a shaft, a race and a rolling element in a fixed-position preload bearing device is provided to improve the high-speed durability and the fretting life by oscillating motion. By bringing the coefficients closer to each other, a stable preload can be obtained without being affected by a temperature change, and a bearing device that solves the problems of motor rigidity and resonance frequency change can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a part of a first embodiment incorporating a bearing device of the present invention.

FIG. 2 is a longitudinal sectional view showing a part of the second embodiment.

FIG. 3 is a longitudinal sectional view showing a part of a third embodiment.

FIG. 4 is a longitudinal sectional view showing a part of a fourth embodiment.

FIG. 5 is a longitudinal sectional view showing a part of a fifth embodiment.

FIG. 6 is a longitudinal sectional view showing a part of a sixth embodiment.

FIG. 7 is a longitudinal sectional view showing a part of a seventh embodiment.

FIG. 8 is a longitudinal sectional view showing a part of the eighth embodiment.

FIG. 9 is a diagram showing a state in which a preload is applied by a dead weight.

[Explanation of symbols]

 1: Fixed shaft 1 ': Rotating shaft 2: Motor base 3: Stator 4: Hub 5: Disk mounting surface 6: Cover plate 7: Rotor 8: Housing 9: Adhesive part 10: Lower bearing 11: Outer ring 14: Rolling element 15: Upper bearing 16: Inner ring

Claims (1)

[Claims] 1. A fixed-position preloaded bearing device, wherein the ball has a linear expansion coefficient of ⁶ to 13 × 10 ⁻⁶ / ° C. and a shaft has a linear expansion coefficient of 11
-13.5 × 10 ⁻⁶ / ° C.