JPH0257323B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a floppy magnetic disk device (FDD).
The present invention relates to permanent magnets for spindle motors (brushless motors) used in other applications.

(Prior Art) Brushless motors conventionally used in magnetic disk devices and the like generally have a configuration as shown in FIG. Referring to FIG. 3, rotor assembly 1
are the rotating shaft 2, the turntable 3 fixed to the rotating shaft 2, the rotor yoke mounting boss 4 fixed to the rotating shaft 2, the rotor yoke 5 fixed to the rotor yoke mounting boss 4, and the inner peripheral surface of the rotor yoke 5. The magnet 6 is fixed to the magnet 6. Further, the stator assembly 7 is composed of a stator yoke 8 and a stator winding 9, which are arranged opposite to the magnet 6 with a predetermined gap in the radial direction, and is fixed to the housing assembly 10. The housing assembly 10 includes bearings 11 and 12 that rotatably support the rotating shaft 2, and a housing 13 in which the bearings 11 and 12 are incorporated. On the other hand, a printed circuit board 14 is fixed to the housing assembly 10, and the printed circuit board 14 performs rotation speed detection, mounting of a position detection element, and connection of stator windings. A rotation speed detection coil (frequency generator coil) 14a is mounted on the printed circuit board 14 facing the magnet 6. Generally, this rotation speed detection coil 14a is mounted on the printed circuit board 14 as shown in FIG. It is formed in a zigzag coil shape on the top.

FIG. 4 shows a conventional frequency generator section, in which the inner circumferential surface 6a of the magnet 6 is magnetized in a direction perpendicular to the rotating shaft 2 (radial direction) for driving and position detection. End face 6b of magnet 6
is magnetized parallel to the rotating shaft 2 (in the axial direction) for use as a frequency generator.

When the rotor assembly 1 rotates (that is, the brushless motor rotates), the magnetic flux emitted from the magnet end face 6b cuts the frequency generator coil 14a, so that the rotational speed of the brushless motor is transmitted to the terminals A and B of the frequency generator coil 14a. An alternating current voltage with a frequency proportional to is generated, and the frequency of the alternating voltage is used to detect the rotational speed of the brushless motor.

The magnet used in the brushless motor mentioned above is a resin magnet from the viewpoint of weight reduction, and this resin magnet is described in, for example, Japanese Patent Application No. 34460/1983. Also,
A method for manufacturing such a resin magnet is described, for example, in Japanese Patent Application No. 34461/1983.

(Problems to be Solved by the Invention) Generally, the inner peripheral surface 6a of the magnet is magnetized to a point very close to the end surface 6b of the magnet. Therefore, since the distance from the magnet end face 6b to the frequency generator coil 14a and the shortest distance between the magnet inner circumferential surface 6a and the frequency generator coil 14a are approximately equal, the distance of the magnet inner circumferential surface 6a toward the printed circuit board 14 is approximately the same. The magnetic flux acts on the frequency generator coil 14a, causing the frequency generator coil 14 to
An alternating current voltage is generated between terminals A and B of a. Generally, the frequency of the AC voltage generated between terminals A and B of the frequency generator coil 14a due to the magnetic flux of the magnet end face 6b and the AC voltage generated by the magnetic flux of the magnet inner peripheral surface 6a are different in frequency. The AC voltage between terminals A and B of the machine coil 14a is a mixture of two types of frequencies, and there is a problem in that accurate rotation speed detection cannot be performed.

On the other hand, if the magnet end face 6b has the same magnetic pole distribution as the magnet inner circumferential face 6a, the alternating current voltage between the terminals A and B of the frequency generator coil 14a due to the magnetic flux of the magnet end face 5b and the magnet inner circumferential face 6
The frequency of the alternating current voltage between terminals A and B of the frequency generator coil 14a due to the magnetic flux of a is exactly the same and accurate rotation speed detection is possible.
The number of magnetic poles of a is generally as small as 24 poles, even if it is large.
When the magnet end face 6b has the same number of magnetic poles as the magnet inner circumferential face 6a, when the rotation speed is controlled, sufficient gain cannot be obtained in the control system.
This results in unstable rotation speed control. Therefore, 60 to 150 magnetic poles are provided on the magnet end face 6b.
The frequency of the AC signal output from the frequency generator section is increased to sufficiently increase the gain of the control system to perform stable rotation speed control. Therefore, the magnetic pole distributions of the magnet end face 6b and the magnet inner circumferential face 6a cannot be made the same.

In addition, in a brushless motor, position detection is generally performed using leakage magnetic flux of the magnetic flux for driving the brushless motor, but in the case of the conventional configuration, the magnet end face 6b is magnetized for use as a frequency generator. The position detecting element 15 must be arranged so as to receive the driving magnetic flux of the inner circumferential surface 6a of the magnet as shown in FIG. Therefore, the magnet 6 becomes longer by the length required for position detection. However, since the position detecting section of the magnet 6 cannot be shortened unless the position detecting element 15 is made smaller, there is a problem in that it is difficult to make the brushless motor thinner.

By the way, as mentioned above, the structure of the resin magnet is described in Japanese Patent Application No. 60-34461, and in this resin magnet, the magnetic field orientation in the radial direction and the magnetic field orientation in the axial direction are extremely close to each other. Therefore, there is a large variation in the thickness of the region where the magnetic field orientations are separated, that is, where the radial and axial magnetic orientations are mixed, and when this resin magnet is used, it is difficult to use it as a motor in the mass production process. There are problems in terms of gain quality control, and there are also problems in motor productivity.

An object of the present invention is to solve the above-mentioned problems, and to provide a resin magnet that is equipped with a frequency generator section that can accurately detect the number of rotations, and that can realize a brushless motor that can be made thinner. .

(Means for Solving the Problems) The present invention is characterized in that a first magnet portion that is magnetically oriented in the radial direction and a second magnet portion that is magnetically oriented in the axial direction are integrated. a molded annular resin magnet, the second
The magnet portion protrudes in the radial direction from the outer peripheral surface of the first magnet portion, and
The annular resin magnet is characterized in that the magnet part is substantially separated from the first magnet part and is located at one end of the first magnet part.

(Example) The present invention will be explained below with reference to Examples.

FIGS. 1a and 1b are a plan view and a sectional view, respectively, showing an embodiment of the annular resin magnet according to the present invention, and FIG. 1c is an enlarged view of a part of FIG. 1b.

Referring to FIGS. 1a, b, and c, the annular resin magnet 6 includes a first magnet portion 61 that is magnetically oriented and magnetized in the radial direction, and a first magnet portion 61 that is magnetically oriented and magnetized in the axial direction. The first and second magnet parts 61 and 62 are integrally molded. The second magnet part 62 is a joint part (boundary part)
The second magnet part 62 is disposed at the upper end of the first magnet part 61 via a magnet part 63, and as shown in the figure, the second magnet part 62 projects from the outer peripheral surface of the first magnet part 61 in the radial direction.

As shown in the figure, the upper end surface 61a of the first magnet section 61 and the upper end surface 62a of the second magnet section 62
are not on the same plane, that is, do not coincide with each other, and the upper end surface 61a is located below the upper end surface 62a. On the other hand, the upper end surface 61 of the first magnet section 61
a and the lower end surface 62b of the second magnet portion 62 are molded so that they are substantially on the same plane.

In this way, the first magnet part 61 and the second magnet part 62 are connected via the joint part 63,
As shown, since the second magnet section 62 is substantially separated from the first magnet section 61, problems caused by magnetic leakage from the first and second magnet sections 61 and 62 can be eliminated. The joint (boundary) 63 is a part that does not participate magnetically, but in the integral molding of the annular resin magnet, it is used to prevent magnetic interference between the first magnet part 61 and the second magnet part 62. This is an absolutely necessary part, and this joint (boundary part)
63 makes it possible to extremely minimize variations in the magnetic properties of the first magnet section 61 and the second magnet section 62.

FIG. 2 shows an enlarged view of the main part of the frequency generator section of a brushless motor in which the above-mentioned annular resin magnet 6 is incorporated. Referring to FIG. 2, the annular resin magnet 6 has the outer peripheral surface and lower end surface of the first magnet section 61 fixed to the inner wall surface and bottom surface of the rotor yoke 5, respectively, with adhesive, while the lower end surface of the second magnet section 62 is fixed with adhesive. The end face is fixed to the upper end face of the rotor yoke 5 with an adhesive, and the rotor yoke 5 is disposed thereon. A frequency generating coil 14a is disposed on the printed circuit board 14 facing the second magnet section 62, and the upper end surface 61 of the first magnet section 61
A position detection element 15 is arranged opposite to a.

When the annular resin magnet according to the present invention is used in a brushless motor, the position detecting element 15 can be placed on the printed circuit board, and the position detecting element 15 can be placed on the printed circuit board 14 at the portion facing the upper end surface of the first magnet part 61. 15, the distance between the printed circuit board 14 and the resin magnet can be reduced, so that the brushless motor can be made thinner.

Furthermore, as shown in FIG. 2, when the annular resin magnet according to the present invention is used in a brushless motor, it is possible to arrange the second magnet part 62 so that it is located on the upper end surface of the rotor yoke 5. Since the rotor yoke 5 effectively contributes to the second magnet part 62 in terms of the magnetic circuit, the magnetic characteristics of the second magnet part 62 can be substantially improved, and the thickness of the second magnet part 62 can be made thinner. becomes possible. As a result, the brushless motor itself can be made thinner.

(Effects of the Invention) As explained above, according to the annular resin magnet of the present invention, the first magnet part magnetically oriented in the radial direction and the second magnet part magnetically oriented in the axial direction are substantially Since they are separated, there is very little magnetic interference between the first and second magnet parts, and variations in the magnetic properties of the first and second magnet parts can be made very small.

Further, when the annular resin magnet according to the present invention is used in a brushless motor, the leakage magnetic flux of the first magnet part does not act on the frequency generator coil, so that accurate rotation speed detection is possible. Furthermore, if the annular resin magnet according to the present invention is used, the position detection element can be disposed on the printed circuit board.
It becomes possible to make the brushless motor thinner.

[Brief explanation of drawings]

FIGS. 1a and 1b are a plan view and a sectional view showing an embodiment of the annular resin magnet according to the present invention, respectively, and FIG.
Figure c is an enlarged view of a part of Figure 1 b;
The figure is an enlarged view of the main part of the frequency generator section of the brushless motor incorporating the annular resin magnet according to the present invention, Figure 3 is a diagram showing the configuration of the brushless motor, and Figure 4 is shown in Figure 3. FIG. 5 is an enlarged view of the frequency generator section of the brushless motor, and FIG. 5 is a diagram showing the rotation speed detection coil (frequency generator coil). 1... Rotor assembly, 2... Rotating shaft, 3... Turntable, 4... Rotor yoke mounting boss, 5
...Rotor yoke, 6...Resin magnet, 7...
...Stator assembly, 8...Stator yoke, 9...
... Stator winding, 10 ... Housing assembly, 1
1, 12...Bearing, 13...Housing,
14... Printed circuit board, 15... Position detection element.

Claims (1)

[Claims] 1. An annular resin magnet in which a first magnet portion magnetically oriented in the radial direction and a second magnet portion magnetically oriented in the axial direction are integrally molded, the second magnet portion being the same as the first magnet portion. The second magnet part protrudes in the radial direction from the outer circumferential surface of the first magnet part, and the second magnet part is substantially separated from the first magnet part and is located at one end of the first magnet part. An annular resin magnet characterized by comprising: