JP2990304B2 - Rotating machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a motor made of two materials having different expansion coefficients, such as a motor in which an iron cylindrical rotor yoke is fixed to the inside of a peripheral wall of an aluminum cup-shaped rotor hub by fitting pressure. The present invention relates to a rotating machine having a peripheral wall fixed by a fitting pressure.

[0002]

2. Description of the Related Art As in a case where an iron cylindrical rotor yoke is fitted to the inside of a peripheral wall of an aluminum cup-shaped rotor hub and fixed by pressure,
When two peripheral walls made of materials having different coefficients of expansion are fixed by a fitting pressure, the peripheral walls are fixed to each other by applying a fitting pressure over the entire surface by shrink fitting or the like. As a result, both peripheral wall portions are curved. Conventionally, as a technique for preventing this, a technique of shrink-fitting only one end in the axial direction of both peripheral walls and a technique of shrink-fixing only the central portion in the axial direction of both peripheral walls are known.

However, according to such a known technique, although the curving of both the peripheral walls is substantially prevented, since both of them are shrink-fitted only in one annular portion, the axes of the both peripheral walls are displaced. In the state, fitting is easily performed, and there is a problem in accuracy. The present invention has been made in view of the above-described problems in the prior art, and the object thereof is to be able to accurately fit the peripheral wall portions together, and after the fitting. It is an object of the present invention to provide a rotating machine in which both peripheral wall portions are prevented from bending due to a temperature change.

[0004]

In order to achieve the above-mentioned object, a rotating machine according to the present invention has two peripheral wall portions, both peripheral portions of which are provided.
The walls are made of materials having different coefficients of expansion, and the outer peripheral surface of one of the peripheral walls and the inner peripheral surface of the other peripheral wall are press-fitted and fixed by fitting pressure in two or more annular portions separated from each other in the axial direction. Rotating machine, wherein the fitting pressure in one of the annular portions is
Due to a temperature change that is stronger than the fitting pressure and exceeds a certain limit, both peripheral walls maintain a fixed state in the annular part where the fitting pressure is relatively strong, and both peripheral walls in the annular part where the fitting pressure is relatively weak. It is assumed that they are shifted from each other.

[0005]

The outer peripheral surface of one peripheral wall portion and the inner peripheral surface of the other peripheral wall portion are press-fitted and fixed by fitting pressure in two or more annular portions, and these annular portions are separated from each other in the axial direction. As a result, the fitting in the state where the axes of both the peripheral walls are displaced is prevented, and the deformation due to the bending of the both peripheral walls is less likely to occur even after the fitting. When the temperature change does not exceed a certain limit, both peripheral wall portions keep a fixed state in any of the annular portions, but the bending stress due to the difference in expansion coefficient between the two is sufficiently small, and almost no bending occurs.
When the temperature change exceeds a certain limit, both peripheral wall portions keep a fixed state in the annular portion where the fitting pressure is relatively strong, but both peripheral wall portions are displaced in the annular portion where the fitting pressure is relatively weak. The generation of stress is substantially avoided and bending is prevented.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic half sectional view of a brushless motor for driving a hard disk as one embodiment of the present invention. 10
Denotes a fixed shaft, 12 denotes a stator core made of a silicon steel plate fitted and fixed to the fixed shaft 10, and 14 denotes a stator coil wound around the stator core 12.

Reference numeral 16 denotes a substantially cylindrical rotor hub (peripheral wall) made of aluminum. The rotor hub 16 includes a large outer diameter portion 16a to which a hard disk is fixed on an outer peripheral portion, and a shoulder portion 16 forming an upper end of the large outer diameter portion 16a in FIG.
b and a small outer diameter portion 16 located above the shoulder 16b.
c and an outwardly projecting portion 16d that projects outward at the lower end of the large outer diameter portion 16a. The inner diameter of the large outer diameter portion 16a is reduced at the shoulder 16b to an intermediate diameter with the inner diameter of the small outer diameter portion 16c. The large outer diameter portion 16a has a lower annular protrusion 18 and an upper annular protrusion 20 slightly below the lower end and upper end of the large diameter inner peripheral surface, respectively. A substantially cylindrical rotor yoke 22 (peripheral wall) made of an iron-based material is fixed to the inside of the large outer diameter portion 16a by shrink-fitting between the lower annular protrusion 18 and the upper annular protrusion 20. I have. Except for the lower annular protrusion 18 and the upper annular protrusion 20, a gap is provided between the rotor yoke 22 and the rotor hub 16.

The rotor yoke 2 at the lower annular projection 18
2 and the inner peripheral surface of the rotor hub 16 have a relatively high fitting pressure, and the fitting pressure at the upper annular projection 20 is relatively weak. Although the expansion coefficients of the rotor hub 16 and the rotor yoke 22 are largely different from each other due to their materials, when the temperature change does not exceed a certain limit, the rotor hub 16 and the rotor yoke 22 maintain a fixed state at any of the annular protrusions. But,
The bending stress due to the difference between the two expansion coefficients is sufficiently small, and almost no bending occurs. If the temperature change exceeds a certain limit, the rotor hub 16 and the rotor yoke 22 are kept fixed at the lower annular projection 18 where the fitting pressure is relatively strong, but the upper annular projection 2 where the fitting pressure is relatively weak.
At 0, the two are shifted, so that the generation of bending stress is substantially avoided, and the bending is prevented.

Further, the outer peripheral surface of the rotor yoke 22 and the inner peripheral surface of the rotor hub 16 are crimped over the entire circumference at the upper annular projection 20 and the lower annular projection 18 by the fitting pressure of shrink fitting. Since the annular projections are separated from each other in the axial direction, the fitting of the rotor yoke 22 and the rotor hub 16 in a state where the axes thereof are displaced is prevented, and the deformation due to the bending of the two is less likely to occur even after the fitting. Become. In any of the annular portions, the magnitude of the fitting pressure per unit area is almost the same, but since the axial length of the lower annular projection 18 is about twice that of the upper annular projection 20, the fitting pressure is small. Is also about double.

It is to be noted that the fitting pressure is not provided depending on the fitting area as in this embodiment, but the fitting pressure is provided depending on the strength of the fitting pressure per unit area or in combination with the fitting area. Of course, it does not matter. Further, the fitting pressure does not necessarily have to act on the entire circumference of each annular projection. Furthermore, the annular protrusion is connected to the rotor yoke 22
Can also be provided. Further, the annular portion on which the relatively weak fitting pressure acts may be provided at a plurality of locations. Furthermore, it is desirable that the annular portions on which the fitting pressure acts are separated as much as possible in the axial direction. This is to make it more effective to prevent the fitting in the state where the axes of both the peripheral walls are displaced and to prevent the deformation due to the bending of the both peripheral walls after the fitting.

A magnet 24 for a frequency generator is fixed via a yoke 26 below the outwardly extending portion 16 d of the rotor hub 16. Also, the shoulder 16 of the rotor hub 16
A screw hole 28 for fixing a hard disk fixing clamp is provided in b. A cylindrical rotor magnet 29 is adhesively fixed inside the large diameter portion 22a of the rotor yoke 22. The rotor mainly composed of the rotor hub 16 and the rotor yoke 22 is rotatably supported on the fixed shaft 10 via ball bearings 32 and 34 at the annular bush 30 and the upper reduced diameter portion 22b fixed to the inner peripheral side at the lower end of the rotor yoke 22. Have been. As a result, the rotor magnet 29 and the stator core 12 face each other in the radial direction.

Reference numerals 36 and 38 denote magnetic fluid seals,
Each is fixed inside the small outer diameter portion 16 c of the rotor hub 16 and inside the holder 40 attached to the annular bush 30, and seals between the fixed shaft 10. 42 is a protective cap. Since the fixed shaft 10, the ball bearings 32 and 34, the bush 30, and the rotor yoke 22 are all made of an iron-based material, there is not much difference in the coefficient of expansion. Therefore, no deformation is caused between them by a temperature change.

[0013]

According to the rotating machine of the present invention, compared with the case where the shrink fitting is performed in one annular portion as in the conventional motor,
It is possible to fit the peripheral wall portions with high accuracy, and after the fitting, unlike the case where the peripheral wall portions are fitted over the entire surface, the curvature of both the peripheral wall portions due to a temperature change is prevented, and the required shape is formed. Well maintained.

[Brief description of the drawings]

FIG. 1 is a schematic half sectional view of a brushless motor for driving a hard disk as one embodiment of the present invention.

[Description of sign]

 16 rotor hub 18 lower annular projection 20 upper annular projection 22 rotor yoke

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02K 1/27 502 H02K 1/28 H02K 21/22 H02K 29/00-29/14 G11B 19/20

Claims (1)

(57) [Claims] (1)It has two peripheral walls, and both peripheral walls are mutually
Made of materials with different expansion ratesOne of the surrounding walls
Outer peripheral surface and the inner peripheral surface of the other peripheral wall portion
At two or more annular parts separated by
A rotary machine fixed by crimping, wherein a fitting pressure in one of the annular portions is, Other rings
Stronger than the fitting pressure in the  Fit pressure is compared by temperature change exceeding a certain limit
In the strong annular part, both peripheral wall parts keep the fixed state.
In the annular part where the fitting pressure is relatively weak, both peripheral walls
A rotating machine characterized in that parts are displaced from each other.