JPH0610546Y2 - Spindle motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a spindle motor.

[Conventional technology and its problems]

In conventional spindle motors, multiple ball bearings were used for pivotal support.However, if the ball bearings on the magnetic disk mounting side have radial rattling due to variations in ball diameter, etc. There was a radial deflection of the sex. Therefore, especially as a disk motor, a magnetic head writes information to tracks on a magnetic disk.
There has been a problem that a malfunction (such as off-track) occurs in reading.

An object of the present invention is to provide a spindle motor that solves the above problems.

[Means for Solving the Problems] According to the present invention, a pair of ball bearings for externally fitting a radial load and a minute thrust load on the one end side of a rotary shaft to restrict movement of the rotary shaft in the thrust direction are externally fitted. At the same time, a fluid dynamic pressure bearing for receiving a radial load, which is provided with a groove for fluid retention over the entire circumference in the circumferential direction, is formed on the middle or other end side of the rotary shaft, and the fluid dynamic pressure bearing and the pair of balls are formed. The rotating shaft is rotatably supported by a bearing, and the center of load of the fluid dynamic pressure bearing is made to correspond to the center of load of the fluid dynamic pressure bearing. When the center distance between the ball bearing on the bearing side and the fluid dynamic bearing is a and the center distance between the pair of ball bearings is b, a> b is set.

[Action]

Since the center of load of the fluid dynamic pressure bearing, which maximizes the fluid pressure of the fluid dynamic pressure bearing, corresponds to the center of load of the load such as the hub, the runout in the radical direction does not occur during rotation.

Further, this fluid dynamic pressure bearing cannot receive the thrust load, but the pair of ball bearings can reliably receive the thrust load.

Moreover, since the center distance between the fluid dynamic pressure bearing side ball bearing and the fluid dynamic pressure bearing is larger than the center distance between the pair of ball bearings, it is possible to effectively prevent thrust play and radial play.

〔Example〕

 An embodiment of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 denotes a spindle motor according to the present invention, which is a motor bracket 3 having a cylindrical portion 2.
A rotary shaft 5 rotatably supported by the cylindrical portion 2 of the motor bracket 3 via two ball bearings 4 and 4, a rotor 7 fixed to one end 6 of the rotary shaft 5, and a motor. And a stator 9 which is externally fitted to the cylindrical portion 2 of the bracket 3 and has coils 8 ...
A hub 12 attached to the rotary shaft 5 is fixed to the other end 13 of the rotary shaft 5. Reference numeral 14 denotes a rotor magnet that closely faces the stator 9, and is an outer peripheral wall of a rotor holder 15 formed in a shallow dish shape.
It is attached to 16. The ball bearings 4 and 4 are fitted onto the rotary shaft 5 and are held by the cylindrical portion 2. Reference numeral 17 denotes a flange portion of the motor bracket 3, which is protruded from the outer peripheral surface of the cylindrical portion 2 in an outer flange shape, and the flange portion 17 is attached to another member 18 shown by an imaginary line by a screw or the like not shown.
Reference numeral 19 denotes a disk spacer interposed between the magnetic disks 10 and 20 denotes a disk clamp for clamping and holding the magnetic disks 10.

Thus, the rotary shaft 5 is pivotally supported by the fluid dynamic bearing 21 that receives only the radial load and the two ball bearings 4 and 4 that receive the radial load and the minute thrust load. The two ball bearings 4 and 4 are fitted in the shaft center hole 24 of the cylindrical portion 2 and are arranged at positions closer to the rotor 7 side. Between both ball bearings 4 and 4, a circular protrusion 22 protruding in the inner diameter direction is provided.
And a preload spring 23 that elastically presses the outer ring of the ball bearing 4 on the rotor 7 side in the axial direction. The fluid dynamic pressure bearing 21 is formed of an annular pressure receiving member 25 fixed to the inner peripheral surface of the shaft hole 24, and a groove forming portion 26 provided on the outer peripheral surface of the rotary shaft 5. The groove forming portion 26 is located at the same position as the pressure receiving member 25 in the axial direction, and is provided to face the circumferential pressure receiving surface 27 of the pressure receiving member 25 with a minute gap. The groove forming portion 26 is provided with a large number of parallel inclined grooves along the outer peripheral surface of the rotating shaft 5 so as to be symmetrical with respect to the center C of the width H in the axial direction. By rotating the rotary shaft 5 in the direction of arrow A at a predetermined number of rotations, the dynamic pressure of the air near the center of the dynamic pressure bearing 21 is increased, and the pressure applied between the pressure receiving member 25 and the groove forming portion 26 is increased. The pressure of the generated fluid has a pressure distribution as shown in FIG. Although the case where the fluid is air is shown, other fluids may be used. Therefore, the pair of ball bearings 4 and 4 are externally fitted to the one end 6 side of the rotary shaft 5, and the axial center direction (thrust direction) of the rotary shaft 5 is fitted.
Regulate the movement of.

Further, the fluid dynamic pressure bearing 21 is provided with a groove for fluid retention over the entire circumference in the circumferential direction on the side from the middle to the other end 13 of the rotary shaft 5.

That is, the fluid dynamic pressure bearing 21 and the pair of ball bearings 4 and 4 cooperate to pivotally support the rotary shaft 5.

In this case, the hub 12, the disk spacers 19 and the disk clamp 20 are arranged so that the load center of gravity in the state shown in FIG. To do. Furthermore, ball bearings 4,
4 is arranged so as to be outside the region where the pressure in the pressure distribution curve of FIG. 3 is positive. That is, fluid dynamic bearing
When the center distance between the ball bearing 4 and the fluid dynamic pressure bearing 21 on the 21 side is a and the center distance between the ball bearings 4 and 4 is b, a> b as shown in FIG.

A load F in the radial direction acts on the magnetic disks 10 and the hub 12 and the like, and the load F is supported via an air layer between the groove forming portion 26 and the pressure receiving member 25 whose pressure is increased, Radial runout is prevented. Further, in this case, a minute thrust load acts on the rotary shaft 5,
It is supported by the ball bearing 4 on the left side of the figure. That is, the inner ring of the ball bearing 4 on the left side of the figure and the rotary shaft 5 are fixed by a C-shaped stop ring 31 or the like or fixed by an adhesive so as not to move in the axial direction. Moreover, the preload spring 23 constantly elastically presses the rotor side (right side in the drawing) bearing 4, so that rattling in the axial direction does not occur. That is, in the ball bearing 4 on the right side of the drawing, the outer ring is loosely fitted in the hole 24 and is movable in the axial direction, and the preload spring 23 presses the outer ring.

Unlike the case of the above embodiment, as shown in FIG. 4, the rotary shaft 5 may be a vertical type, and the hub 12 may also be a motor having a structure that also serves as the rotor holder 15. The radial load F in this case is compared with the case of the embodiment of FIG.
The proportion of static load becomes smaller.

The pressure receiving member 25 of the dynamic pressure bearing 21 may be formed integrally with the cylindrical portion 2.

[Effect of device]

The present invention has the following remarkable practical effects due to the above configuration.

The rotating shaft 5 supported by the fluid dynamic pressure bearing 21 in a non-contact manner does not cause non-periodic radial runout. Especially, the center of the fluid dynamic pressure bearing is made to correspond to the load center of gravity by the hub 12 or the like. Therefore, even when the hub 12 of the spindle motor is rotated, radial runout does not occur, and when the magnetic disks 10 are attached and used, malfunction such as off-track does not occur.

Although the thrust load is very small, this thrust load is
The rotary shaft 5 is effectively received by the pair of ball bearings 4, 4.
It is positionally controlled in the thrust direction and is rotatably supported. In particular, since the center distance between the ball bearing 4 on the fluid dynamic pressure bearing 21 side and the fluid dynamic pressure bearing 22 is larger than the center distance between the pair of ball bearings 4 and 4, thrust play and radial play can be effectively prevented.

The use of the fluid dynamic bearing 21 also has the advantage of reducing mechanical loss.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged main portion sectional view, FIG. 3 is a pressure distribution curve diagram of a fluid layer, and FIG. 4 is a sectional view showing another embodiment. is there. 4 ... Ball bearing, 5 ... Rotating shaft, 21 ... Fluid dynamic bearing.

Claims (1)

[Scope of utility model registration request] 1. A pair of ball bearings 4, 4 for externally fitting a radial load and a minute thrust load on the one end 6 side of a rotary shaft 5 to restrict movement of the rotary shaft 5 in the thrust direction.
A fluid dynamic pressure bearing 21 for receiving a radial load, which is provided with a groove for fluid retention over the entire circumference in the circumferential direction, is formed on the side from the middle to the other end 13 of the rotary shaft 5, and the fluid dynamic pressure bearing 21 and a pair of The ball bearings 4 and 4 rotatably support the rotary shaft 5 and the load center of gravity of the hub 12 is placed at the fluid dynamic bearing center position where the fluid pressure of the fluid dynamic bearing 21 is maximized. When the center distance between the ball bearing 4 on the fluid dynamic pressure bearing 21 side and the fluid dynamic pressure bearing 21 is a and the center distance between the pair of ball bearings 4 and 4 is b, a> b A spindle motor characterized by being set so that