JPH06105520A - Spindle motor - Google Patents

Abstract

PURPOSE:To bring a main magnet and a magnetism detecting element close to each other and to stabilize the detected output by processing a back yoke in one body by press working and is press-fitted into a shaft and by fixing an FG magnet on the main magnet. CONSTITUTION:A back yoke 4 has a press-worked long press-fitting section 4a which is to be inserted into a shaft 1 and is so located that it may form a magnetic circuit of a chucking magnet 5 which generates a disc attracting force. The back yoke 4 is also provided with a step 4b on which a spindle 2 which axially supports the disc is fixed by press-fitting or adhesion. A main magnet 6 is fixed inside of the back yoke 4. The main magnet 6 and a core 12 around which a winding 13 is wound constitute a magnetic circuit. An FG magnet 8 is fixed on an external lower part 6a of the main magnet 6 and a magnetism detecting element 10 is located on a circuit board 9. The circuit board 9 and the core 12 are fixed in a housing 11 in one body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for rotating a recording medium such as a magneto-optical disk.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional spindle motor. In FIG. 3, a spindle 2 for axially supporting the disc is press-fitted onto a shaft 1 for radially supporting the disc, and is rotatably supported by a bearing 3 together with the spindle 2. Further, a chucking magnet 5 for generating a chucking force with a disk is integrally fixed to the spindle 2 together with a back yoke 4 arranged so as to form a magnetic circuit with the chucking magnet 5 by adhesion or the like. Has been done. In addition, the main magnet 6 that generates a torque for rotating the motor
Are integrally arranged on the inner peripheral side of the back yoke 7 arranged so as to form a magnetic path. This back yoke 7
Is integrally fixed to the spindle 2 together with the chucking magnet 5 and the like.

Further, an FG magnet 8 is arranged together with a back yoke 7 at a position facing a circuit board 9 in which a pattern is radially formed so as to obtain a rotation speed signal. On the other hand, a core 12 around which a winding 13 is wound is arranged at a position facing the inside of the main magnet 6, and is integrally fixed to a housing 11 supporting the motor itself together with the circuit board 9. The spindle 2, the back yoke 7, the main magnet 6 and the like constitute a rotor. With the rotation of the rotor, the leakage magnetic flux of the main magnet 6 is detected, and the timing for energizing the winding 13 is smoothly switched. The magnetic detection element 10 is arranged on the circuit board 9.

Here, when the magnetic flux leaking from the main magnet is detected by the magnetic detecting element 10 and the corresponding current is applied to the winding 13, the rotor rotates and the disk supported on the spindle 2 of the rotor moves. Driven.

[0005]

However, the above-mentioned conventional example has the following drawbacks. (1) Since the spindle 2 is usually made of aluminum, the back yoke 4 which is a separate member is required to form the magnetic circuit of the chucking magnet 5.
There is a drawback that the number of parts increases and the yoke becomes thick. (2) Since the spindle is required to have a considerable rigidity in the use of the motor, the press-fitting portion 2a is cut to secure the rigidity, and there is a drawback that the cost is high. (3) Since it is difficult to make the FG magnet very thin due to its nature, the FG magnet had to be supported radially inside the end 7a of the back yoke 7. As a result, since the main magnet 6 cannot be arranged below this, the distance between the magnetic detection element 10 and the main magnet 6 becomes large, and the output of the magnetic detection element cannot be large.

Therefore, it is an object of the present invention to provide a spindle motor having a novel structure that solves the above-mentioned drawbacks.

[0007]

In order to achieve the above object, the present invention provides a chucking member for axially supporting a disk, a chucking magnet for generating an attractive force to the disk, and A first back yoke arranged so as to form a magnetic path of a chucking magnet, a shaft fixed to the first back yoke, and arranged so as to form a magnetic path of a main magnet for generating a rotational force of a motor. The spindle motor is characterized in that it has a second back yoke and a FG magnet arranged so as to obtain a velocity signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the present invention. The shaft 1 is rotatably supported by a bearing 3 and also supports a disk (not shown).
The back yoke 4 has a long press-fitting portion 4a formed by press working so as to secure high rigidity with respect to the shaft 1, and is arranged so as to form a magnetic circuit of a chucking magnet that generates an attractive force with a disk. Has been done. Further, the back yoke 4 is a step portion 4 formed so as to fix the spindle 2 for axially supporting the disk by press fitting or bonding.
b. A main magnet 6 that generates a rotating torque of the motor is fixed inside the back yoke 4, and constitutes a magnetic circuit together with a core 12 around which a winding 13 is wound. As is apparent from FIG. 1, the back yoke 4 is a dish-shaped member having an inverted L-shaped cross section.

The FG magnet 8 is supported and fixed to the lower outer peripheral portion 6a of the main magnet 6 in both radial and axial directions. On the other hand, a magnetic detection element 10 for detecting the leakage magnetic flux of the main magnet is arranged on the circuit board 9 which faces the FG magnet 8 in the axial direction. There is.

Since the back yoke 4 is a direct back yoke of the chucking 5, it is effective for thinning the motor, and the press-fitting portion 4a which is convex in the vertical direction is formed by press working. , High rigidity is secured for the shaft 1. Moreover, since the back yoke of the main magnet 6 is formed integrally with the above-mentioned back yoke 4, the number of parts is reduced. Further, the positioning of the FG magnet 8 is performed by positioning the lower peripheral portion 6a of the main magnet 6
By doing so, the distance between the main magnet 6 and the magnetic detection element 10 can be reduced without impairing the thickness of the FG magnet 8, and a large output can be obtained.

(Other Embodiments) FIG. 2 is a sectional view showing another embodiment of the present invention. In the figure, reference numeral 1 indicates an axis, and reference numeral 4 indicates a back yoke forming a magnetic path of a chucking magnet, which is fixed to a spindle 2. Reference numeral 14
Indicates a back yoke dedicated to the main magnet, which is similarly fixed to the spindle 2.

In this embodiment, the back yoke is 4, 14
Although it is composed of two parts shown by, the press-fitted portion 4a of the shaft by press working has high rigidity and can be made thin. Similarly, the distance between the magnetic detection element 10 and the FG magnet 8 is reduced.

As described above, by integrally processing the back yoke by press working, the back yoke can be connected to the shaft, and both high rigidity and thinness are achieved. In addition, the number of parts can be reduced.

Further, by positioning the FG magnet by the main magnet, the position of the main magnet can be brought close to the magnetic detection element, which enables stable motor driving.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a spindle motor of the present invention.

FIG. 2 is a sectional view of another embodiment of the spindle motor of the present invention.

FIG. 3 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 1 axis 2 spindle 4 back yoke 5 chucking magnet 6 main magnet 8 FG magnet 9 circuit board 10 magnetic detection element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Fukushima 2-4-19 Nakane, Meguro-ku, Tokyo Canon Seiki Co., Ltd.

Claims (6)

[Claims] 1. A chucking member for axially supporting a disk, a chucking magnet for generating an attractive force to the disk, and a first back arranged so as to form a magnetic path of the chucking magnet. A yoke, a shaft fixed to the first back yoke, a second back yoke arranged so as to form a magnetic path of a main magnet for generating a rotational force of a motor, and arranged so as to obtain a speed signal. A spindle motor having an FG magnet. 2. The spindle motor according to claim 1, wherein the first back yoke fixed to the shaft has a vertical protrusion formed by processing a press-fitted portion of the first back yoke. 3. The spindle motor according to claim 1, wherein the first back yoke and the second back yoke are integrally formed. 4. The spindle motor according to claim 3, wherein the back yoke formed integrally has a step portion for fixing the spindle. 5. The spindle motor according to claim 1, wherein the first back yoke and the second back yoke are fixed to each other via a spindle. 6. The spindle motor according to claim 1, wherein the FG magnet is fixed to an outer peripheral portion of the main magnet.