JPH0595656A - Spindle motor - Google Patents

Abstract

PURPOSE:To maintain good accuracy of rotation attained by preventing stress from concentrating on a pre-load directional line in a part where inner/outer rings of a ball bearing are secured, and to prevent resonance by changing the natural frequency in accordance with a utilized device without changing the external shape. CONSTITUTION:Adhesive agent accumulating grooves 48, 50, 52 in which an adhesive agent is received or a chamfered part 56 is provided on a pre-load directional line of each ball bearing 26, 28. Stress generated in a bearing holding part 12 and a rotary shaft 24 by a pre-load and an external force is not concentrated in a part on a pre-load directional line on outer ring fixing surfaces 40, 42 and inner ring fixing surfaces 44, 46 but dispersed. A sleeve member 58 is externally fitted and fixed to a part of the rotary shaft 24 between both the ball bearings 26, 28. When the mass, shape, etc., of the sleeve member 58 are selected, the natural frequency of a rotary part can be changed. Also rigidity of the rotary shaft 24 is increased. Change of the external shape of a spindle motor is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor in which a rotating portion is rotatably supported by a fixed portion via a ball bearing.

[0002]

2. Description of the Related Art In a spindle motor used for driving a hard disk or the like, the inner ring and the outer ring of a ball bearing are fixed in a fixed position on the inner ring fixing surface or the outer ring fixing surface of a fixed portion or a rotating portion, respectively. , The stress generated in the fixed part and rotating part due to preload is concentrated on the preload direction line in the inner ring fixing surface or outer ring fixing surface, so the preload direction in the inner ring fixing surface or outer ring fixing surface The rotation accuracy was sometimes impaired due to the deformation caused by the concentration of strain near the line.
Further, even when an external force is applied, the stress due to it is concentrated on the preload direction line in the inner ring fixing surface or the outer ring fixing surface, so the preload state of the ball bearing changes due to the reaction force,
The rotation accuracy was sometimes impaired.

On the other hand, due to the relationship with the natural frequency of a device that uses a spindle motor, the rotational accuracy of the device may be impaired because the rotating portion of the spindle motor resonates with the device. To avoid this, the natural frequency of the rotating part should be changed according to the natural frequency of the target device.
There is a problem in practicality unless such a change in natural frequency is accompanied by enlargement or deformation of the outer shape and cannot be performed to some extent.

The present invention has been made in view of the above problems existing in the prior art, and an object of the present invention is to fix a portion for fixing an inner ring of a preloaded ball bearing and an outer ring. It is possible to prevent stress from concentrating on the preload direction line at the part that secures the spindle, and to maintain and maintain good rotation accuracy. It is an object of the present invention to provide a spindle motor that can change the frequency and prevent resonance to achieve good rotation accuracy.

[0005]

In order to achieve the above object, in a spindle motor of the present invention, an inner ring and an outer ring of a ball bearing are adhesively bonded to an inner ring fixing surface or an outer ring fixing surface of a fixing portion or a rotating portion, respectively. Is a spindle motor that is fixed in a fixed position preload state by using a ball bearing, and the rotating portion is rotatably supported by the fixing portion via its ball bearing. On the surface, on the preload direction line of the ball bearing, there is provided an adhesive accumulating groove or a notch in which the adhesive is accommodated.

The spindle motor of the present invention is a spindle motor in which a rotary shaft protruding from the center of a rotor is rotatably supported by a ball bearing, and an axial distance is provided on the outer peripheral portion of the rotary shaft. It is assumed that the sleeve member is externally fitted and fixed to a portion of the rotating shaft between the two ball bearings arranged apart from each other.

[0007]

According to the first aspect of the present invention, an adhesive agent accommodating groove containing an adhesive agent is provided on the inner ring fixing surface or the outer ring fixing surface of the fixing portion of the spindle motor and the rotating portion of the spindle motor, on the preload direction line of the ball bearing. Since it has a notch,
The stress generated in the fixed portion and the rotating portion by the preload and the stress caused by the external force applied are dispersed without being concentrated on the preload direction line in the inner ring fixing surface or the outer ring fixing surface.

In the invention of claim 2, the sleeve member is externally fitted and fixed to the part of the rotary shaft between the two ball bearings which are arranged on the outer peripheral part of the rotary shaft at a distance in the axial direction. , The natural frequency of the rotating part of the spindle motor can be determined by selecting the mass and shape of the sleeve member while avoiding the expansion of the diameter of the ball bearing due to the expansion of the diameter of the rotating shaft and the change of the outer shape of the spindle motor. Can be changed. The sleeve member also increases the rigidity of the rotating shaft.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a spindle motor for driving a hard disk as one embodiment of the present invention.

Reference numeral 10 is a stainless steel stator frame. In the central portion of the stator frame 10, a cylindrical bearing holding portion 12 is integrally provided so as to project upward in FIG. An outer peripheral portion of the base of the bearing holder 12 in the stator frame is formed in the annular recess 14. The stator core 1 is provided on the outer peripheral portion of the bearing holding portion 12 at an intermediate position.
6 is externally fitted and fixed, and a stator coil 18 is wound around the stator core 16. The lower end opening of the bearing holder 12 is sealed by a seal member 19.

Reference numeral 20 is a cup-shaped rotor hub made of aluminum. At the center of the base portion 22 of the rotor hub 20, a rotating shaft 24 is vertically provided inward. The rotating shaft 24 is rotatably supported via a first ball bearing 26 and a second ball bearing 28 arranged vertically inside the bearing holder 12. Outer peripheral wall 30 of rotor hub 20
A cylindrical rotor yoke 32 is fixed to the inner peripheral surface of
A cylindrical rotor magnet 34 is fixed to the inner peripheral surface of the rotor yoke 32. The opening of the outer peripheral wall 30, that is, the lower end is inserted into the annular recess 14 with a slight gap. Further, on the outer peripheral portion of the lower end portion of the outer peripheral wall 30, there is provided an overhanging portion 36 for supporting the lower surface of the inner peripheral portion of a hard disk (not shown) fitted on the outer peripheral portion 30. A screw hole 37 provided at the base is for screwing a clamp member (not shown) for fixing a hard disk.

An inwardly extending portion 38 is formed on the entire inner circumference of the bearing holder 12 on the inner circumference side. The upper part and the lower part of the inward projecting part 38 on the inner peripheral surface of the bearing holding part 12 are outer ring fixing surfaces 40 and 42, respectively, and the upper end part and the lower end part on the outer peripheral surface of the rotating shaft 24 are respectively the inner ring fixing surface 44. And 46.

The outer ring 26a of the first ball bearing 26 is fixed to the outer ring fixing surface 40 while the lower end surface of the outer ring 26a is in contact with the upper surface of the inward projection 38, and the upper end surface of the inner ring 26b is the base portion 22 of the rotor hub 20. The inner ring fixing surface 44 in contact with the lower surface of the
Are fixed using an adhesive. The second
The outer ring 28a of the ball bearing 28 is fixed to the outer ring fixing surface 42 while the upper end surface thereof is in contact with the lower surface of the inward projecting portion 38, and the inner ring 28b is fixed to the inner ring fixing surface 46 with an adhesive, respectively. There is.

At the time of adhesive fixing, until the adhesive is hardened,
The clamping force corresponding to the required preload is applied and maintained between the upper surface of the base portion 22 of the rotor hub 20 and the lower end surface of the inner ring 28b of the second ball bearing 28. Then, the preload along the preload direction lines shown by the one-dot chain line in FIG.
The outer rings 26a and 28a and the inner rings 26b and 28b of the ball bearings 26 and 28 are fixed in a fixed position preload state acting on the ball bearings 26 and the second ball bearings 28.

The reference numerals 48, 50, 52 and 54 are provided one by one over the entire circumference of the upper and lower outer ring fixing surfaces 40 and 42 and the upper and lower inner ring fixing surfaces 44 and 46 on the inner peripheral surface of the bearing holder 12. The adhesive collecting groove, 56 is the rotary shaft 24.
Is a chamfered portion (an example of a cutout portion) provided on the outer peripheral portion of the lower end of the. These adhesive reservoir grooves 48, 5 are used for adhesive fixing.
Adhesives accumulating at 0, 52, and 54 ensure the reliability of the adhesion. The adhesive reservoir groove and the cutout portion are preferably continuous in the circumferential direction.

Further, on the preload direction lines of the ball bearings 26 and 28, the adhesive accumulating grooves 48, 50 and 5 in which the adhesive is contained are provided.
2 or the chamfered portion 56, the bearing holding portion 12 and the rotary shaft 2 due to the preload or the application of an external force.
The stress generated in No. 4 is dispersed without being concentrated on the preload direction line in the outer ring fixing surfaces 40 and 42 and the inner ring fixing surfaces 44 and 46.

When the adhesive is not accommodated in the adhesive reservoir groove, it is recognized as one of the cutouts.

Reference numeral 58 designates the first ball bearing 26 and the second ball bearing 2.
8 is a sleeve member which is externally fitted and fixed to the portion of the rotary shaft 24. FIG. 2 is a fragmentary sectional view of the sleeve member 58. The sleeve member 58 has a cylindrical shape, and the upper and lower outer peripheral ends thereof are chamfered. The mass distribution and shape of the sleeve member 58 are preferably rotationally symmetrical in order to prevent vibration and uneven rotation. The rotating part of the spindle motor includes a rotor hub 20 and a rotating shaft 2.
4, the rotor yoke 32, the rotor magnet 34, the sleeve member 58, and the like. The fixed portion is composed of the stator frame 10, its bearing holding portion 12, the stator core 16, the stator coil 18, and the like.

By selecting the mass and shape of the sleeve member 58, the natural frequency of the rotating portion of the spindle motor can be changed. Further, the sleeve member 58 also increases the rigidity of the rotary shaft that connects the sleeve member 58 and the rotary shaft 24. Then, the sleeve member 58 is provided between the first ball bearing 26 and the second ball bearing 28 so that the rotary shaft 2
4 is externally fitted and fixed to the rotary shaft 24.
The diameter expansion of the ball bearing due to the diameter expansion of, and the change of the outer shape of the spindle motor are avoided.

3 and 4 are fragmentary sectional views showing another embodiment of the sleeve member. In the sleeve member 60 shown in FIG. 3, the mass is reduced by providing the annular groove portion 62 on the outer peripheral portion of the sleeve member 58 of FIG. Further, in the sleeve member 64 shown in FIG. 4, the mass is slightly reduced by providing a hemispherical small recess 66 in the outer peripheral portion of the sleeve member 58 of FIG. Thus, the natural frequency of the rotating part of the spindle motor can be freely changed by providing a groove or a recess in the same sleeve member and changing the number, width, depth, etc. it can.

[0021]

In the spindle motor according to the first aspect of the present invention, the notch or the adhesive accumulating groove in which the adhesive is accommodated is provided on the inner ring fixing surface or the outer ring fixing surface for adhering the ball bearing. By this, the stress generated in the fixed part and the rotating part by the preload can be dispersed without being concentrated on the preload direction line in the part of the inner ring fixed surface or the outer ring fixed surface, so that the preload in the part of the inner ring fixed surface or the outer ring fixed surface Rotation accuracy is prevented from being impaired by deformation due to strain concentration on the direction line part, and even when external force is applied, the stress caused by it is on the preload direction line on the inner ring fixing surface or outer ring fixing surface. Since the particles are dispersed without being concentrated, it is possible to prevent the preload state of the ball bearing from changing due to the reaction force, and it is possible to maintain the rotation accuracy.

According to another aspect of the spindle motor of the present invention, the natural frequency of the rotating portion of the spindle motor is selected by selecting the sleeve member according to the device using the spindle motor while avoiding the change of the outer shape of the entire spindle motor. It can be easily changed, whereby resonance with the device can be prevented and good rotational accuracy can be realized. Moreover, since the rigidity of the rotating shaft is increased, it is suitable for improving the rotation accuracy.

[Brief description of drawings]

FIG. 1 is a half sectional view of a spindle motor.

FIG. 2 is a fragmentary sectional view of a sleeve member.

FIG. 3 is a fragmentary sectional view of another sleeve member.

FIG. 4 is a fragmentary sectional view of yet another sleeve member.

[Explanation of sign]

 20 rotor hub 24 rotating shaft 26 first ball bearing 26a outer ring 26b inner ring 28 second ball bearing 28a outer ring 28b inner ring 40 outer ring fixing surface 42 outer ring fixing surface 44 inner ring fixing surface 46 inner ring fixing surface 48 adhesive pool groove 50 adhesive pool groove 52 Adhesive collecting groove 56 Chamfer 58 Sleeve member

Claims (2)

[Claims] 1. An inner ring and an outer ring of a ball bearing are fixed to an inner ring fixing surface or an outer ring fixing surface of a fixed portion or a rotating portion, respectively, with an adhesive agent in a fixed position preload state, and are rotated through the ball bearing. A spindle motor in which a portion is rotatably supported with respect to a fixed portion, and an adhesive containing an adhesive on a preload direction line of a ball bearing on an inner ring fixing surface or an outer ring fixing surface of the fixing portion and the rotating portion. A spindle motor having a ditch or notch. 2. A spindle motor in which a rotating shaft projectingly provided in a central portion of a rotor is rotatably supported by a ball bearing, and is arranged on an outer peripheral portion of the rotating shaft at an axial distance. In the part of the rotating shaft between the two ball bearings,
A spindle motor in which a sleeve member is fitted and fixed.