JPH0614512A - Motor - Google Patents

Abstract

PURPOSE:To reduce deterioration of shaft resonance characteristics effectively when a soft base is used as a fixing shaft and at the same time prevent pre-load relief of a bearing or distortion of the fixing shaft due to temperature change in a motor for retaining the rotor part at the fixing shaft which is formed at the center of a flange so that it can be rotated freely via the bearing. CONSTITUTION:By inserting a sleeve 22 with almost the same thermal coefficient of expansion as that of a housing 23 of a rotor part 24 between a fixing shaft 21A and a bearing 4A, the sleeve 22 can be expanded or contracted in almost the same ratio as that of the housing 23 for temperature change, effectively preventing pre-load relief or distortion of the bearings 4A and 4B due to temperature change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor, and is preferably applied to a flat type DC brushless motor used when rotating a hard disk such as a computer.

[0002]

2. Description of the Related Art Conventionally, flat type brushless motors have been
There is a so-called magnet rotation type in which a yoke forming a magnetic path is driven to rotate together with a rotor magnet. That is, as shown in FIG. 3, in the motor 1 of this type, a fixed shaft 3 is erected at the center of a dish-shaped flange 2, and the fixed shaft 3 is magnetized via ball bearings 4A and 4B. A dish-shaped hub 5 made of a material is rotatably engaged with a cylindrical bearing hole 5A formed at the center.

A rotor magnet 6 is attached to the lower surface of the hub 5 so as to face the coil 8 of the printed coil portion 7 fixed to the stepped portion 2A of the flange 2 via a slight air gear. The hub 5 has a bearing hole 5A.
The inner peripheral portion of the disk-shaped yoke 9 having a through hole at the center thereof is fixed to the front end surface of the disk using a method such as welding or caulking, whereby the yoke 9 and the surface of the print coil 6 on the flange side are slightly separated. It is arranged to face each other via an air gear cup.

Thus, in the motor 1, a magnetic circuit of the rotor magnet 6, the coil 8, the yoke 9 and the hub 5 is constructed, and thus when the drive current is conducted to the coil 8, the hub 5, the rotor magnet 6 and the yoke 9 are formed. The rotor unit 10 is composed of a rotor 10 and is rotatably driven about the fixed shaft 3. At this time, in the motor 1, the screw 11
The disk 13 can be sandwiched between the hub 5 and the disk fixing plate 12 by being screwed into the screw hole 5B through the disk-shaped disk fixing plate 12, and thus the hard disk 13 is rotationally driven together with the rotor portion 10. It is designed to do.

[0005]

In the flat brushless motor, it has been proposed to integrally form the fixed shaft 3 at the center of the flange 2 by forging or casting. However, when the flange 2 is formed by forging, for example, a soft base material such as aluminum is used as the base material, so that the strength of the fixed shaft 3 is low, and thus the problem of axial resonance characteristics deteriorates. It was Further, in this case, it is difficult to obtain the processing accuracy in forging, and for example, the convex portion of the fixed shaft 3 or the like needs to be finished, so that there is a problem that the working process becomes complicated as compared with the case where the fixed shaft 3 is planted. .

Further, in the motor 1 of this type, normally, the disc spring 1 is provided on the inner peripheral side between the ball bearings 4A and 4B.
4 and a ring 15 is provided on the outer peripheral side of the ball bearings 4A and 4B to apply a pressure in the direction of the fixed shaft 3 to the outer ring or the inner ring of the ball bearings 4A and 4B. It is designed to give. However, when the base materials of the fixed shaft 3 contacting the inner rings of the ball bearings 4A and 4B and the hub 5 contacting the outer ring are different, the ball bearings 4A are affected by the temperature change.
If the preload of 4 and 4B is released (preload release), or the ball bearings 4A and 4B are stressed, noise may occur or the fixed shaft 3 may be distorted, which may cause a problem.

The present invention has been made in consideration of the above points, and it is possible to effectively reduce the deterioration of the shaft resonance characteristics when a soft base material is used as the fixed shaft, and to preload the bearing due to temperature change. The present invention is intended to propose a motor capable of practically sufficiently preventing the omission or the distortion of the fixed shaft.

[0008]

In order to solve such a problem, according to the present invention, a rotor shaft 24 is rotatably mounted on a fixed shaft 21A which is vertically formed at the center of a flange 21 via bearings 4A and 4B. In the holding motor 20,
A sleeve 2 inserted between the fixed shaft 21A and the bearings 4A and 4B and having a thermal expansion coefficient substantially the same as that of the housing 23.
2 was provided.

Further, in the present invention, the rotor portion 24 is fitted with the outer peripheral portions of the bearings 4A and 4B, and the flange 21
The rotor magnet 6 facing the coil 8 arranged above
It has a housing 23 for holding.

Further, in the present invention, the housing 23
Is a back yoke portion 2 facing the one side of the coil 8 at the peripheral end portion.
3A, the rotor magnet 6 is fixedly held so as to face the back yoke portion 23B with the coil 8 interposed therebetween.

[0011]

The sleeve 22 having a thermal expansion coefficient substantially the same as that of the housing 23A of the rotor portion 24 fitted between the fixed shaft 21A and the bearings 4A and 4B and the outer peripheral portions of the bearings 4A and 4B.
Since the rigidity of the shaft portion is increased and the deterioration of the shaft resonance can be reduced, the sleeve 22 expands or contracts at substantially the same rate as the housing 23A with respect to the temperature change, and thus, due to the temperature change. Bearings 4A and 4B
It is possible to effectively prevent the preload loss, strain, and the like.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 3 are designated by the same reference numerals, in a flat magnet type DC brushless motor 20 of rotary magnet type, a cylinder is formed at the center of a plate-shaped flange 21 formed by forging. A fixed shaft 21A having a shape is projected. A cylindrical sleeve 22 is fitted and fixed to the outer peripheral surface of the fixed shaft 21A, and a rotor portion 24 including a yoke 23 formed in a hat shape via two corrugated cardboard bearings 4A and 4B is rotatably attached to the sleeve 22. Engaged.

The yoke 23 is made of a ferromagnetic material and fits with the outer rings of the ball bearings 4A and 4B on the inner wall of the cap-shaped housing portion 23A formed in the center portion, and is in the form of a flange which is circumferentially contacted with the lower end of the housing portion 23A. The height of the housing portion 23A is selected and formed such that the back yoke portion 23B of the housing 23A faces the surface of the print coil portion 7 on the side of the flange 21 via a slight air gear gap. At this time, the sleeve 22 is formed by using the same base material as that of the yoke 23, so that the preload loss or distortion of the ball bearings 4A and 4B due to temperature change is prevented.

Further, a dish-shaped hub 25 made of a magnetic material is fixed to the outer peripheral surface of the housing portion 23A of the iron core yoke member 23, and the lower surface of the hub 25 is opposed to the coil 8 with a slight air gear gap. The rotor magnet 6 is attached in such a manner that the magnetic circuit of the rotor magnet 6, the yoke 23, and the hub 25 is configured. Further, as shown in FIG. 2, the coil 8 is formed into a fan shape that expands in the radial direction, and nine coils are arranged at intervals of 40 degrees. Thus, by supplying a driving current to the coil 8, the yoke 23 and The rotor portion 24 is rotatably driven about the fixed shaft 21A and the sleeve 22.

The hub 25 has a screw hole 2 on the upper surface.
5A is bored, and a stepped ring 26 is attached to the outer peripheral surface so that the hard disk can be held together with the disk fixing plate (not shown).
In the above configuration, the sleeve 22 expands or contracts at the same rate as the yoke 23 with respect to the temperature change of the motor 20,
Thus, at this time, the outer ring side and the inner ring side of the ball bearings 4A and 4B move in the radial direction of the fixed shaft 21A to the same extent, so that the preload loss of the ball bearings 4A and 4B or the distortion of the fixed shaft 21A can be effectively prevented.

In the above structure, the rotor portion 24 is rotationally driven about the fixed shaft 21A and the sleeve 22 (hereinafter referred to as the shaft portion), and the rigidity of the shaft portion is increased in this way, so that the shaft resonance characteristic is improved. Deterioration can be reduced. According to the above configuration, the sleeve 22 made of the same material as that of the yoke 23 capped on the fixed shaft 21A via the ball bearings 4A and 4B is fitted and fixed to the outer peripheral surface of the fixed shaft 21A, so that the temperature Preload release of ball bearings 4A and 4B due to changes or ball bearing 4A
And the noise generated by the stress on 4B or the fixed shaft 21
It is possible to sufficiently prevent the distortion of A in practical use, and thus it is possible to maintain the original life of the ball bearings 4A and 4B.

Further, according to the above construction, the deterioration of the shaft resonance characteristic can be reduced because the rigidity of the shaft portion is increased. Further, according to the above configuration, since the yoke 23 is formed in a hat shape, the number of parts can be reduced and thus the manufacturing process of the motor 20 can be simplified.

In the embodiment described above, the sleeve 2
The case where 2 is formed from the base material of the same material as the iron core yoke member 23 has been described, but the present invention is not limited to this, and the base material of the sleeve has a thermal expansion coefficient equal to or close to that of the iron core yoke member 23. If so, various base materials can be applied. Further, in the above-described embodiment, the case where the present invention is applied to the motor 20 in which the fixed shaft 21A is integrally formed in the central portion of the flange 21 by forging has been described, but the present invention is not limited to this, and the fixed shaft is not limited thereto. The same effect can be obtained even if the motor 21A is integrally formed by casting at the center of the flange 21 or the motor 21A is fixedly formed at the center of the flange 21.

Further, in the above embodiment, the fixed shaft 2
Although the case where 1A is hollow has been described, the present invention is not limited to this, and can be applied to the case where the fixed shaft 21A is cylindrical. Further, in the above-described embodiment, the case where the present invention is applied to the motor 20 in which the yoke 23 is formed in a hat shape has been described, but the present invention is not limited to this, and the hub 5 as shown in FIG. It can also be applied to the motor 1 that engages with the fixed shaft 3 via the ball bearings 4A and 4B.

[0021]

As described above, according to the present invention, in the motor in which the rotor portion is rotatably engaged with the fixed shaft which is formed in the central portion of the flange through the bearing, between the fixed shaft and the bearing. By inserting the sleeve having a thermal expansion coefficient substantially similar to that of the housing of the rotor part, the sleeve can be expanded or contracted at substantially the same rate as the housing with respect to temperature change, and thus the bearing due to temperature change It is possible to effectively prevent the preload loss, strain, and the like.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a motor according to the present invention.

FIG. 2 is a partial cross-sectional view showing the internal configuration of the motor shown in FIG.

FIG. 3 is a cross-sectional view showing a conventional example.

[Explanation of Codes] 1, 20 ... Motor, 2, 21 ... Flange, 3, 21
A: Fixed axis, 4A, 4B: Ball bearing, 5,
25 ... Hub, 6 ... Rotor magnet, 8 ... Coil, 9, 23 ... Yoke, 10, 24 ... Rotor part, 1
4 ... Disc spring, 15 ... Ring, 22 ... Sleeve, 2
3A: housing part, 23B: back yoke part.

Claims (3)

[Claims] 1. A motor for rotatably holding a rotor portion through a bearing on a fixed shaft that is formed upright in the center of a flange, and is inserted between the fixed shaft and the bearing and is substantially the same as the housing. A motor comprising a sleeve having a coefficient of thermal expansion of. 2. The rotor portion has a housing which fits with an outer peripheral portion of the bearing and holds a rotor magnet which faces a coil disposed on the flange. Motor described. 3. The housing has a back yoke portion facing one side of the coil at a peripheral end portion thereof, and the rotor magnet is fixedly held so as to face the back yoke portion with the coil sandwiched therebetween. The motor according to claim 2.