JP3254732B2 - Metal bearing motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal bearing type motor most suitable for application to a spindle motor of a floppy disk, for example.

[0002]

2. Description of the Related Art First, referring to FIGS. 4 and 5, a metal bearing type motor conventionally used as a spindle motor of a floppy disk of a video still image camera conventionally called a Mbica camera (trade name of Sony Corporation) is shown. explain.

This metal bearing type motor comprises a plurality of printed coils 2 which are printed on the upper surface of a printed circuit board 1.
And a stator yoke 3 made of a permalloy plate or the like fixed to the lower surface of the printed board 1 by bonding or the like. The rotor is constituted by a circular rotor yoke 4 pressed by a permalloy plate or the like, and an annular rotor magnet 5 fixed to the lower surface thereof by bonding or the like. Then, the cylindrical metal bearing 6 whose lower end is closed is swaged integrally with the stator yoke 3, and the rotor shaft 7 is inserted into the metal bearing 6 to be rotatably supported on the ball 8, so that the rotor magnet 5 is moved. It is close to a plurality of printed coils 2.

A circular disk table 9 formed by pressing a permalloy plate or the like is fixed to the center of the rotor yoke 4 by press fitting or the like, and the center of a center hub 10 formed in the center of the disk table 9 is fixed to the upper end of the rotor shaft 7. And an annular chucking magnet 11 is fixed to the outer periphery of the upper surface of the disk table 9 by bonding or the like. The center core (not shown) of the floppy disk is fitted on the outer periphery of the center hub 10 and the disk table 9 is magnetically chucked by the chucking magnet 11.

The print coil 2 has six poles and the rotor magnet 5 has eight poles, and the rotor is rotated by a main magnetic path M ₁ formed between the print coil 2 and the rotor magnet 5 when the print coil 2 is energized. The floppy disk is driven to rotate integrally with the rotor.

In this main metal bearing type motor,
By pressing a step between the proximity piece 3a and the separation piece 3b with respect to the rotor magnet 5 on both sides of the metal bearing 6 of the stator yoke 3 so as to press the rotor shaft 7 with respect to the metal bearing 6, the arrow on the proximity piece 3a side. The configuration is such that the rotor is stabilized in the state of being inclined in the direction a to prevent rattling, surface runout and the like of the rotor.

[0007]

However, in the conventional metal bearing type motor, the distance between the stator yoke 3 and the rotor magnet 5 is at a stable point (0 °) at the center of the adjacent piece 3a due to the inclination of the rotor shaft 7. minimum S ₁ becomes in position), in order to a maximum S ₂ at the center and is unstable point spaced strips 3b (180 ° position), the axial direction of the rotor shaft 7 acting between the stator yoke 3 and the rotor magnet 5 The magnetic attractive force in the vertical direction parallel to the above becomes maximum at the stable point and minimum at the unstable point.

Therefore, as shown in FIG. 6A, when each magnetic pole sequentially passes through the stable point in the direction of arrow b during one rotation of the rotor magnet 5, as shown by a solid line in FIG. In addition, as the magnetic pole approaches the stable point, the rotational speed of the rotor magnet 5 is increased by the magnetic attractive force, and the rotational speed of the rotor magnet 5 is reduced after passing through the stable point. Periodic rotation unevenness (torque ripple) always occurs. In addition,
This rotation unevenness has high reproducibility and is stable.

[0009] When such a periodic rotation unevenness occurs, when a video signal is recorded and reproduced on a floppy disk, a fixed pattern jitter that does not fluctuate with time is generated. In particular, in a still image, the influence of the jitter is large, and there is an adverse effect such that a vertical line image looks curved.

[0010] Conventionally, attempts have been made to correct rotation unevenness by software servo. However, the value is large compared to other general rotation unevenness components, and it is difficult to control only by servo. There was a problem to say.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to reduce periodic rotation unevenness of a metal bearing type motor with a simple structure.

[0012]

According to the present invention, there is provided a metal bearing type motor for stabilizing a rotor shaft in a state of being inclined in one direction with respect to a metal bearing by a shape of a stator yoke. In the metal bearing type motor configured as described above, an auxiliary magnetic path having a magnetic pole pitch of about an integral multiple of the magnetic pole pitch of the rotor magnet is provided near the rotor magnet. In this case, it is preferable that the auxiliary magnetic path is disposed in a leakage magnetic flux region on the outer periphery of the rotor magnet.

[0013] The metal bearing type motor of the present invention configured as described above controls the periodic rotation fluctuation of the rotor magnet caused by the inclination of the rotor shaft by controlling the periodic rotation speed of the rotor magnet by the auxiliary magnetic path. Can be controlled to cancel.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a metal bearing type motor to which the present invention is applied will be described below with reference to FIGS. FIG.
6 are denoted by the same reference numerals, and the description thereof will not be repeated.

First, as shown in FIGS. 1 and 2, the outer peripheral lower end 5a of the rotor magnet 5 projects several millimeters below the outer peripheral lower end 4a of the rotor yoke 4, and the outer peripheral lower end 5a has an outer periphery. A leakage magnetic flux region 12 is formed.

A substantially arc-shaped auxiliary yoke 13 made of a permalloy plate or the like is formed in the leakage magnetic flux region 12.
Are arranged horizontally along the outer periphery of the rotor magnet 5,
Magnetic poles (N and S poles) 13a at both ends of the auxiliary yoke 13,
13b is attached to the lower end 5a of the outer periphery of the rotor magnet 5 by about 0.1 mm.
The lower end 5a of the outer peripheral portion and the auxiliary yoke 1
Between the 3, the horizontal auxiliary magnetic path M ₂ which leakage flux from the peripheral portion the lower end 5a of the rotor magnet 5 can pass is formed.

The auxiliary yoke 13 has a thickness of about 0.1 m.
It is fixed on the upper surface of the printed circuit board 1 with an adhesive or the like via an insulating spacer 14 of about m.

While the magnetic pole pitch P _{1 of} the eight magnetic poles (N and S poles) magnetized on the rotor magnet 5 is formed at 45 °, the auxiliary yoke 1 of the auxiliary magnetic path M ₂ is formed.
3 of magnetic poles 13a, pole pitch P ₂ between 13b are formed at 90 ° which is an even multiple (2 times). Then, a reference line P connecting the magnetic field center P ₃ of the auxiliary magnetic path M _{2 to} the stable point (0 ° position) and the unstable point (180 ° position).
₄ at a predetermined angle θ of 45 ° or less (for example, about 25
°).

According to the metal bearing type motor configured as described above, the lower end 5a of the outer peripheral portion of the rotor magnet 5 is formed.
And between the auxiliary yoke 13, it is always formed an auxiliary magnetic path M ₂ due to the leakage magnetic flux from the outer peripheral portion lower end 5a of the rotor magnet 5, during one rotation of the rotor magnet 5, N of the rotor magnet 5, the same S-pole An unstable operation in which the magnetic poles simultaneously approach the magnetic poles 13a and 13b of the auxiliary yoke 13 occurs repeatedly.

At this time, for example, when a pair of N poles of the rotor magnet 5 pass through the magnetic poles 13a and 13b of the auxiliary yoke 13 in the direction of arrow b, as shown by a dotted line in FIG. As the poles approach the magnetic poles 13a, 13b in the direction of arrow a, the rotational speed of the rotor magnet 5 is reduced by the magnetic repulsion between them, and after a pair of N poles pass through the magnetic poles 13a, 13b in the direction of arrow b. The control operation in which the rotational speed of the rotor magnet 5 is increased by the magnetic repulsive force between them periodically and stably occurs.

The periodic rotation speed control operation of the rotor magnet 5 shown by the dotted line in FIG. 6B is performed by the above-described inclination of the rotor shaft 7 shown by the solid line in FIG. It functions to cancel out periodic rotation fluctuations (rotation unevenness).

As a result, periodic uneven rotation of the rotor can be reduced, so that stable rotation of the rotor can be realized.

FIG. 3 shows a modification of the auxiliary magnetic path M ₂ , wherein the magnetic field pitch P ₂ of the auxiliary yoke 13 is an odd multiple (one time) of the magnetic pole pitch P ₁ of the rotor magnet 5. It was formed at 45 °.

In this case, during one rotation of the rotor magnet 5, the adjacent N pole of the rotor magnet 5 and S
The magnetic poles 13a and 13 of the auxiliary yoke 13 are different from each other.
b, a repetitive stabilizing operation occurs, and when the N and S poles approach both magnetic poles 13a and 13b from the direction of arrow a, the rotational speed of the rotor magnet 5 is reduced by the magnetic attraction between them. After the N-pole and the S-pole have passed through the magnetic poles 13a and 13b in the direction of the arrow b, the control operation of reducing the rotation speed of the rotor magnet 5 by the magnetic attraction force therebetween is periodically stabilized. And occur.

Since the periodic rotation speed of the rotor magnet 5 can be controlled, the above-described periodic rotation unevenness caused by the inclination of the rotor shaft 7 can be canceled.
Periodic rotation unevenness of the rotor can be reduced.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of the present invention. Further, the present invention is not limited to the spindle motor of the floppy disk shown in the above embodiment, but can be applied to various metal bearing type motors.

[0027]

The metal bearing type motor of the present invention having the above-described structure has the following effects.

The periodic rotation fluctuation of the rotor magnet caused by the inclination of the rotor shaft of the metal bearing type motor can be controlled so as to be canceled by controlling the periodic rotation speed of the rotor magnet by the auxiliary magnetic path. Rotation unevenness of the rotor can be reduced, and the rotor can be rotated stably.

The control load for correcting the unevenness of the rotation of the rotor by the software servo can be reduced, and the servo design is easy.

Since the auxiliary magnetic path can be formed by utilizing the leakage magnetic flux on the outer periphery of the rotor magnet, the structure is simple and inexpensive.

[Brief description of the drawings]

FIG. 1 is a plan view of a metal bearing type motor according to an embodiment of the present invention, taken along line AA of FIG. 2;

FIG. 2 is a cross-sectional side view taken along line BB of FIG.

FIG. 3 is a plan view similar to FIG. 1, showing a modification of the auxiliary yoke of the metal bearing type motor of the present invention.

FIG. 4 shows a conventional metal bearing type motor of FIG.
FIG.

FIG. 5 is a cross-sectional side view taken along the line DD of FIG. 4;

FIG. 6A is a diagram illustrating a rotation period of a magnetic pole of a rotor magnet, and FIG. 6B is a diagram illustrating a rotation variation of a rotor magnet and a control operation thereof.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 printed board 2 print coil 3 stator yoke 4 rotor yoke 5 rotor magnet 6 metal bearing 7 rotor shaft 12 leakage magnetic flux area 13 auxiliary yoke M ₁ main magnetic path M ₂ auxiliary magnetic path P ₁ magnetic pole pitch of rotor magnet P _{2 of} auxiliary magnetic path Magnetic pole pitch

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Higuchi 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-U 4-58065 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 21 / 00,29 / 00,5 / 24 H02P 7/10

Claims (4)

(57) [Claims] 1. A metal bearing type motor in which a rotor shaft is configured to be stabilized in a state of being inclined in one direction with respect to a metal bearing by a shape of a stator yoke. A metal bearing type motor wherein an auxiliary magnetic path having a pitch is provided near the rotor magnet. 2. The metal bearing type motor according to claim 1, wherein said auxiliary magnetic path is arranged in a leakage magnetic flux area on an outer periphery of said rotor magnet. 3. The metal bearing motor according to claim 1, wherein the magnetic pole pitch of the auxiliary magnetic path is set to an even multiple of the magnetic pole pitch of the rotor magnet. 4. The metal bearing type motor according to claim 1, wherein a magnetic pole pitch of said auxiliary magnetic path is set to an odd multiple of a magnetic pole pitch of said rotor magnet.