JPH04172956A - Motor - Google Patents

Abstract

PURPOSE:To realize accurate detection of rotational speed and position and to make thin a motor by forming a rotational speed detecting face on a rotor oppositely to a frame while furthermore forming an index detecting face on the rotor oppositely to the frame while separating farther than the distance between the rotational speed detecting face and the frame from the frame. CONSTITUTION:A ferromagnetic rotor yoke 24 is mounted on the inner peripheral face of a rotor driving magnet 25 and a multipolar rotational speed detecting face 27 is provided in the axial direction of the rotor yoke 24 while furthermore an index detecting face 28 is provided on the inside thereof. The rotational speed detecting face 27, the index detecting face 28, a rotary body 22, the rotor yoke 2 and a rotary shaft 21 are molded integrally and a predetermined step is provided between the rotational speed detecting face 27 and the index detecting face 28 on the rotor. Furthermore, a rotation detecting pattern is printed on the surface of a frame 40 spaced through a slight gap from the rotational speed detecting face 27, and an index detecting element 47 is mounted on the surface of the frame 40.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electric motor, and in particular to a recording device used in a device having a magnetic head for reading and writing magnetic recording signals on a magnetic disk, which is a disc-shaped recording medium. The present invention relates to an electric motor for driving rotation of a medium.

[Prior art] As a conventional electric motor of this type, Utility Model Application No. 60-13586
The technology published in Publication No. 3 can be mentioned.

FIG. 2 is a sectional view showing a conventional electric motor.

In the figure, (1) is the rotating shaft of the electric motor, (2) is a rotating body that has a magnetic disk holding function;
) rotates integrally with the rotating shaft (1). (3) is the rotor of the electric motor, (4) is the yoke of the rotor (3), (
5) is a permanent magnet arranged on the outer periphery of the yoke (4), (
6) is the screw fixing the rotor (3) and the rotating shaft (1), (7) is the stator of the motor, and (8) is the stator (
7) is the iron core, (9) is the coil wound around the iron core (8),
(10) is a bearing mounting member, and (11) and (12) are bearings that are mounted on the bearing mounting member (11) and rotatably support the rotating shaft (1). (13) is the frame of the electric motor, (
14) is a screw fixing the stator (7) and the bearing mounting member (10), and (15) is a drive pin attached to the rotating body (2), and this drive pin (15) is a screw that fixes the stator (7) and the bearing mounting member (10). It engages with a window hole (not shown) in a rotary plate fixed to the rotary plate.

(16) is an index detection element disposed on the frame (13), (17) is an index detection magnet disposed on the rotor (3), and this index detection element (
16) and the index detection magnet (17) generate one pulse per rotation.

The electric motor with the above configuration has a rotor (3) on the outside of the stator (7).
The permanent magnet (5) of the rotor (3) generates a magnetic field in the radial direction of rotation.

[Problems to be Solved by the Invention] The conventional outer rotor type electric motor as described above requires a certain amount of space between the rotor (3) and the stator (7). In addition, the frame (13) or the bearing mounting member (10) connects the stator (7) and rotor (3) to the magnetic disk and magnetism. It was interposed between the Therefore, there is a limit to how thin the electric motor can be made. For this reason, it has been considered to create a thin inner rotor type electric motor in which the stator (7) is located outside the rotor (3).

However, in order to use this type of electric motor in a disk device, the rotor must have a disk mounting function.
It was also necessary to detect the rotational speed and rotational position of the rotor. For this reason, a disk mounting function has been added to the rotor, and magnets for detecting the rotational speed and rotational position of the rotor have been attached. However, these magnets
The other detection parts on the frame side facing the component have different protrusion amounts, and it cannot be solved by simply attaching magnets to the rotor to detect the rotation speed and rotation position. Accurate detection could not be achieved if the positional relationship between the two was inappropriate.

Therefore, it is an object of the present invention to provide a thin electric motor that can accurately detect the rotational speed and rotational position of a rotor and that is thin.

[Means for Solving the Problems] The electric motor according to the present invention has a rotatably supported rotary shaft (21), rotates integrally with the rotary shaft (21), and applies a magnetic field to the outer circumference in the direction of the rotation radius. A rotor is provided with a ring-shaped driving magnet (25) and a plurality of coils (3
2), a rotation speed detection surface (27) located on the frame-opposed surface of the rotor and generating a magnetic field for rotation speed detection, and a rotation speed detection surface (27) that generates a magnetic field for rotation speed detection, and The index detection surface (28) is located further away from the frame (40) than the distance between the number detection surface (27) and the frame (40), and generates a magnetic field for index detection.

[Function] In the electric motor of the present invention, the rotation speed detection surface (27) that generates a magnetic field for rotation speed detection is located on the frame-facing surface of the rotor, and the index detection surface (28) that generates a magnetic field for index detection is located on the rotor frame-facing surface. ) is located on the frame-opposed surface of the rotor further away from the frame (40) than the distance between the rotation speed detection surface (27) and the frame (40), so the rotation speed detection surface (27) and Index detection surface (
28) can correspond to the amount of protrusion from the surface of the frame (40), the distance between the rotation speed detection surface (27) and the rotation detection pattern, and the distance between the index detection surface (28) and the index detection element (47). is maintained properly, and each detection section has an appropriate positional relationship. - [Examples] Examples of the present invention will be described below.

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

In the figure, (21) is a rotating shaft of an electric motor, and (22) is a rotating body made of a plastic magnet having a magnetic disk holding function, and this rotating body (22) rotates integrally with the rotating shaft (21).

(23) is a disk mounting surface formed on the rotating body (22), (24) is a rotor yoke embedded in the rotating body (22), and (25) is a permanent magnet arranged on the outer periphery of the rotor yoke (24). A driving magnet (26) is a driving pin attached to a rotating body (22), and this driving pin (26) engages with a window hole (not shown) in a rotating plate fixed to a magnetic disk. do. (27) is a rotation speed detection surface that generates a magnetic field for rotation speed detection, and (28) is an index detection surface that generates a magnetic field for index detection.

In addition, the above-mentioned disk mounting surface (23) and rotation speed detection surface (
27) and the index detection surface (28) are the rotating body (22).
) is integrally molded. (29) is the drive pin (26)
An arm plate made of a rigid body that supports, (31) is a stator core,
(32) is a coil wound around the stator core (31). This stator core (31) and coil (32) constitute a stator of the electric motor. (40) is a frame that also serves as a circuit board, (41) is a bearing mounting member attached to the frame (40), (42) is a sintered oil-impregnated bearing that rotatably supports the rotating shaft (21), (43) ) is a sliding member with a low coefficient of friction that is interposed between the rotating body (22) and the sintered oil-impregnated bearing (42). (47) is an index detection element arranged on the frame (40), and the index detection surface (
28) to output a signal for index detection. (50) is a magnetic shielding plate made of a ferromagnetic electromagnetic shielding material such as an iron plate, which covers the exposed part of the coil (32) wound around the stator core (31), and also serves as a magnet for driving the rotor. (25) disk mounting surface (2
3) Covers the exposed parts on the sides.

The electric motor of this embodiment is constructed as described above, and the stator core (31) is capable of passing magnetic flux in the direction of the rotation radius of the electric motor. Iron core teeth are formed at 15 angles, and 15 coils (32) are wound around the iron core teeth. The outer circumferential surface of the core at locations corresponding to the three core teeth is concave toward the inner circumferential surface, and the inner circumferential surface is connected by the core. This concave portion allows the magnetic head to move without interfering with the stator. Further, the rotor driving magnet (25) located on the inner circumferential side of the stator is divided into 24 equal parts around the entire circumference, for example, N and S.
The poles are magnetized in the direction of the rotation radius of the rotor. The 15 coils (32) of the stator are wound every second in three phases, and are energized 120 degrees in accordance with the rotation angle of the rotor to generate rotational torque in a fixed direction.

As described above, the electric motor of this embodiment is an inner rotor type in which the stator is located outside the rotor, and the stator is formed with a concave portion for moving the magnetic head, unlike the conventional outer rotor type. Since the gap for avoiding interference between the stator and rotor and the magnetic disk and magnetic head can be omitted, as in the case of the electric motor, the thickness of the entire electric motor can be reduced.

Moreover, in this embodiment, a rotor yoke (24) made of ferromagnetic material is provided on the inner peripheral surface of the rotor driving magnet (25) of the rotor, and the rotor yoke (24) is provided with a multi-pole magnetization in the axial direction. It has a rotation speed detection surface (27), and further includes:
It has an index detection surface (28) inside. The rotation speed detection surface (27) and index detection surface (28) of this rotor are both made of the same material, plastic magnets, and similarly, the rotating body (22) is also made of plastic magnets, and these are connected to the rotor yoke (24).
) and the rotating shaft (21).

When an electric motor having a rotor with this configuration is used in a multi-disk device, the magnetic disk mounting surface (
23) attracts a metallic rotating plate (not shown) fixed to the center of the magnetic disk, and rotates together with the rotor. In addition, the rotation speed detection surface (27) by multi-pole magnetization is equipped with a magnetization pattern for a rotation signal for detecting the rotation speed and rotation angle of the rotor, and is slightly different from this rotation speed detection surface (27). A rotation detection pattern (not shown) is formed by printed wiring on the surface of the frame (40) with a gap between the two. A rotation signal (FG output signal) proportional to the rotation speed is output by a rotation detection pattern (not shown) facing the rotation speed detection surface (27). Furthermore, the index detection surface (28) has an index detection element (47).
outputs an index detection signal for detecting the magnetic pole position of the rotor. Note that known techniques have already been adopted for detecting the number of rotations and detecting the index.

Further, both the index detection element (47) and the rotation detection pattern (not shown) are arranged on the rotor side surface of the frame (40), but the index detection element (47) is formed by printed wiring. The element itself is thicker than the conventional rotation detection pattern (not shown). Therefore, the index detection element (47) protrudes more from the surface of the frame (40) than the rotation detection pattern. However, in this embodiment, the rotation speed detection surface (27) and the inner and outer detection surfaces (28) are formed on the rotor with a predetermined step according to the amount of protrusion. 27) and the rotation detection pattern, and the distance between the index detection surface (28) and the index detection element (47) are maintained appropriately.

In addition, in this example, the rotation speed detection surface (27
) is located on the outside of the rotor in the direction of the rotation radius, and the index detection surface (28) is located on the inside thereof. In this way, by arranging the rotation speed detection surface (27) as close to the outside of the rotor as possible, multi-pole magnetization can be easily achieved, and a small detection error can be prevented from causing a large error displacement. Accurate detection becomes possible.

As mentioned above, the electric motor of this example has a sintered oil-impregnated bearing (
a rotating shaft (21) rotatably supported by 42);
a ring-shaped driving magnet (2) that rotates integrally with the rotating shaft (21) and generates a magnetic field in the rotational radial direction on its outer circumference;
5), a stator located outside the rotor and having a plurality of coils (32) wound around a stator core (31), and a rotor on the frame-opposed surface of the rotor. Position to,
A rotation speed detection surface (27) that generates a magnetic field for rotation speed detection, and a rotation speed detection surface (27) on the frame-opposing surface of the rotor.
frame (40) than the distance between frame (7) and frame (40).
) and an index detection surface (28) that generates a magnetic field for index detection.

That is, in the electric motor of this embodiment, the rotation speed detection surface (27) that generates a magnetic field for rotation speed detection is located on the surface facing the frame of the rotor, and the index detection surface (28) that generates a magnetic field for index detection is located on the rotor frame-facing surface. is located on the frame-opposed surface of the rotor at a distance from the frame (40) that is greater than the distance between the rotation speed detection surface (27) and the frame (40).

Therefore, the rotation speed detection surface (27) and the index detection surface (28) can correspond to the amount of protrusion from the surface of the frame (40), and the distance between the rotation speed detection surface (27) and the rotation detection pattern and the index detection surface can be adjusted. Since the distance between the surface (28) and the index detection element (47) is maintained appropriately, and each detection part has an appropriate positional relationship, each detection becomes accurate.

As a result, a highly reliable and thin electric motor is obtained.

[Effects of the Invention] As described above, the electric motor of the present invention includes a rotatably supported rotating shaft, a rotor that rotates integrally with the rotating shaft, and a stator located outside the rotor. It has a rotation speed detection surface that generates a magnetic field for rotation speed detection, and an index detection surface that generates a magnetic field for index detection. With a simple configuration in which the rotor's frame facing surface is located further away from the frame than the distance between the rotation speed detection surface and the frame, the rotation speed detection surface and the index detection surface can correspond to the amount of protrusion from the frame surface. , since the distance between the rotation speed detection surface and the rotation detection pattern and the distance between the index detection surface and the index detection element are maintained appropriately, and each detection part has an appropriate positional relationship, each detection can be performed accurately. Improved reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electric motor according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional electric motor. In the figure, 21: Rotating shaft 22: Rotating body 23: Disk mounting surface 24: Rotor yoke 25: Driving magnet 27: Rotation speed detection surface 28: Index detection surface 31: Stator core 32: Coil 40: Frame 47 [Index detection It is element. In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts. Agent: Patent attorney Masuo Oono and 2 others

Claims (1)

[Scope of Claims] A rotating shaft rotatably supported; a rotor that rotates integrally with the rotating shaft and is provided with a ring-shaped driving magnet that generates a magnetic field on its outer periphery; and the rotor. a stator located on the outside of the rotor and having a plurality of coils wound around the stator core; a rotation speed detection surface located on a surface of the rotor facing the frame and generating a magnetic field for detecting the rotation speed; An electric motor comprising an index detection surface located further away from the frame than the distance between the rotation speed detection surface and the frame on a frame-opposed surface of the child and which generates a magnetic field for index detection.