JP4342380B2 - Flat motor - Google Patents

Description

  The present invention relates to a flat motor, and more particularly, to a so-called axial gap type flat motor in which a driving magnet and a driving coil are arranged to face each other on a plane orthogonal to a rotation axis.

  As a spindle motor for a flexible disk drive (FDD), a so-called axial gap type flat motor that is thinned by arranging a driving magnet and a driving coil so as to face each other on a plane substantially orthogonal to the rotation axis is suitable. Can be used. A conventional example of this flat motor is shown in FIG.

In FIG. 8, a bearing 106 that rotatably supports a shaft 105 is fixed on a back yoke 101, and a plurality of coils 102 are concentrically arranged around the rotation axis.
A rotor yoke 104 is fixed to the shaft 105, and a magnet 103 is fixed to the inner surface of the rotor yoke 104 so as to face the coil 102 with a gap G therebetween.
In this configuration, when the coil 102 is energized, the rotor including the shaft 105, the rotor yoke 104 and the magnet 103 rotates with respect to the back yoke 101.

As other examples of the conventional flat motor, there are those described in Patent Document 1 and Patent Document 2 filed by the present applicant.
Japanese Utility Model Publication No. 6-11163 Japanese Patent Laid-Open No. 2004-40840

By the way, in recent years, the demand for downsizing of information equipment from the market has become stronger, and the demand has also reached the motor mounted on the FDD. In particular, the reduction in thickness is remarkable.
As one of the methods for making the above flat motor thinner, it has been pursued to make the gap G between the coil and the magnet as small as possible.

In order to increase the operation efficiency while reducing the thickness of the motor, a rare earth magnet such as an Nd—Fe—B (neodymium-iron-boron) system that exhibits a strong magnetic force is used as a magnet material.
Therefore, as shown in FIG. 9, the back yoke 101 is attracted by the magnet 103 and deformed toward the magnet 103 side.
Accordingly, the gap G between the coil 102 and the magnet 103 is narrowed on the outer peripheral side of the back yoke 101, and in some cases, the gap disappears and the two contact each other as shown in FIG.

In order to solve this, the applicant of the present application proposes a flat motor in which the back yoke is deformed in a bowl shape so as to be separated from the magnet as it moves away from the rotation center in Patent Document 1 described above. A flat motor has been proposed in which a bent portion is provided at the boundary between the bearing mounting portion of the back yoke and the coil mounting portion on the outer peripheral side, and the coil mounting portion is inclined in a direction away from the magnet.
According to these flat motors, the gap can be further reduced, and the motor can be effectively reduced in thickness.

  However, there are cases where electronic parts for driving the motor are soldered to the back yoke, or a copper foil pattern must be formed by printing for electrical connection of these electronic parts. In this case, it is extremely difficult to solder an electronic component or print a copper foil pattern on a non-planar back yoke deformed in advance, and there is a limit to improvement in productivity.

  In addition, if an electronic component is soldered on a flat back yoke or a copper foil pattern is printed and then deformed, the force applied by the deformation damages the electronic component or the copper foil pattern, resulting in high reliability. There was a possibility that it could not be obtained.

  Therefore, the problem to be solved by the present invention is to provide a flat motor capable of improving productivity, obtaining high reliability, and capable of further thinning.

In order to solve the above problems, the present invention has the following configuration as means.
That is, the invention according to claim 1 is a stator (51) having a stator yoke (1) in which a plurality of drive coils (2) are arranged on a plane, and an annular magnet so as to face the drive coil (2). A rotor yoke (4, 4B, 4D) in which (3, 3A to 3D) is disposed, and a rotor (52) that rotates relative to the stator (51), and the magnet (3, 3A to 3D) A flat surface characterized in that gap expansion portions (3Aa2, 3Ca2) that move away from the drive coil (2) as they move away from the center of rotation are provided on the surfaces (3a, 3Aa-3Da) facing the drive coil (2). It is a motor (55).

  According to the present invention, the productivity is excellent, the reliability is high, and the thickness can be reduced.

The preferred embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing an embodiment of the flat motor of the present invention,
FIG. 2 is a sectional view for explaining an embodiment of the flat motor of the present invention.
FIG. 3 is a cross-sectional view of a main part for explaining a first modification of the flat motor of the present invention.
FIG. 4 is a cross-sectional view of a main part for explaining a second modification of the flat motor of the present invention.
FIG. 5 is a cross-sectional view of an essential part for explaining a third modification of the flat motor of the present invention.
FIG. 6 is a cross-sectional view of a main part for explaining a fourth modification of the flat motor of the present invention.
FIG. 7 is a perspective view showing the appearance of an embodiment of the flat motor of the present invention.

The external appearance of the flat motor 55 of an Example is shown in FIG. 7, and the detail is demonstrated below using FIG. 1, FIG.
The flat motor 55 includes a stator 51 having a back yoke 1 serving as a stator yoke, a bearing 6 and a coil 2 fixed thereto, a shaft 5, a rotor yoke 4 fixed thereto, and a magnet fixed to the rotor yoke 4. And a rotor 52 having three.

The back yoke 1 has a flat plate shape and is made of a soft magnetic material such as a silicon steel plate.
A bearing 6 that supports the shaft 5 is fixed at substantially the center thereof.
A copper foil circuit pattern 1a is formed on one surface of the back yoke 1, and the surface of the circuit pattern 1a is insulated.
On the circuit pattern 1a, a plurality of coils 2 are arranged concentrically around the axis of the bearing 6.

A substantially disc-shaped rotor yoke 4 is fixed to the shaft 5 that is pivotally supported by the bearing 6. The rotor yoke 4 is formed by press forming a galvanized steel plate.
A flat annular magnet 3 is fixed to the inner surface of the rotor yoke 4 so as to face the coil 2 with a predetermined gap G (G1 to G2). Details of the gap G will be described later. The magnet 3 is formed of an Nd—Fe—B (neodymium-iron-boron) rare earth hard magnetic material.
With this configuration, the rotor 52 rotates with respect to the stator 51 when a current is applied to the coil 2 by a predetermined method.

Next, the gap G (G1 to G2) between the magnet 3 and the coil 2 will be described in detail.
The magnet 3 in the embodiment has a trapezoidal cross section as shown in FIG.
Specifically, in the axial thickness, the outer peripheral thickness is thinner than the inner peripheral thickness, and the opposing surface 3a facing the coil 2 is inclined in a direction away from the coil 2 toward the outer peripheral side. It has a trapezoidal cross section. The gap G with the coil 2 on the inner peripheral side and outer peripheral side of the magnet 3 is G1 and G2.
And the difference (henceforth thickness difference) of the thickness of the outer peripheral side of this magnet 3 and the thickness of an inner peripheral side is shown as (DELTA) g in FIG.

  Therefore, in the assembled state of the motor, as shown in FIG. 2, the rotor yoke 4 and the back yoke 1 are deformed in a direction approaching each other due to the strong attractive force of the magnet 3, but the facing surface 3a of the magnet 3 is inclined. The thickness difference Δg (see FIG. 1) causes the magnet 3 (or the rotor yoke 4) and the coil 2 to come into contact with each other leaving a slight gap g1 even on the outer peripheral side where the amount of deformation is the largest. There is no.

  This thickness difference Δg can be set so as to be optimal for each motor specification, such as the magnet's magnetic force and the size of each part. However, as an example, the thickness difference Δg generally corresponds to the outer diameter φ39.5 mm of the magnet 3. It is about 0.1 mm to 0.2 mm.

In the present invention, it is only necessary to provide a gap expanding portion on the surface of the magnet that faces the coil in a state where there is no magnetic attraction of the magnet so that the gap between the magnet and the coil becomes wider toward the outer periphery. The gap enlarging portion may be an inclined surface, the inclined surface may be stepped, and the surface facing in parallel with the coil is stepped to expand the gap. Also good. Further, it may be an inclined surface with a portion facing in parallel with the coil. The inclined surface may be a flat surface or a curved surface.
Hereinafter, some of the modifications will be described. However, the present invention is not limited to the above-described embodiments and the following modifications, and various modifications can be made without departing from the scope of the invention.

A first modification is shown in FIG.
In this example, the opposing surface 3Aa of the magnet 3A has an inner peripheral portion 3Aa1 having a certain gap from the coil and an inclined portion 3Aa2 inclined in a direction away from the coil 2 when there is no magnetic attraction. is there.

Therefore, if the opposing surface 2a facing the magnet 3A of the coil 2 is formed as a surface orthogonal to the axis CL, the inner peripheral portion 3Aa1 is a surface parallel to the surface.
When the magnet 3A having this shape is stored as a single magnet, the magnet 3A is stably stacked, and the boundary line 3Ac between the inner peripheral portion 3Aa1 and the inclined portion 3Aa2 is clearly formed, so that the front and back can be easily distinguished. Is.

By forming the inner peripheral portion 3Aa1, the gap must be made wider than when the magnet 3 without the inner peripheral portion is used, and the torque constant is slightly reduced, but the torque contributes to the inner peripheral side of the magnet. Since it is on the outer peripheral side, the torque is not significantly reduced.
Practically, it is desirable that the torque performance equivalent to that of the magnet 3 is exhibited if it is set within the range of the following (formula 1).
That is, the radius r2 of the boundary line 3Ac is smaller than the inner diameter r1 and the outer diameter r3 of the magnet 3A.
r2 ≦ r1 + 0.7 × (r3−r1) (Formula 1)
It is desirable to set the range.

A second modification is shown in FIG.
In this example, the opposing surface 3Ba of the magnet 3B and the opposite surface 3Bb are inclined surfaces.
Therefore, the rotor yoke 4B is also formed in a shape that the outer peripheral side approaches the coil 2 side in accordance with the surface 3Bb, which is suitable when it is desired to reduce the thickness of the entire motor at the outer peripheral portion.
When the inclination amount Δg1 (see FIG. 4) of the opposing surface 3Ba and the opposite surface 3Bb is the same, the magnet 3B having this shape does not need to be discriminated in the direction of the front and back in the mounting, and the operation becomes extremely easy.

A third modification is shown in FIG.
In this example, the magnet 3C is made up of the inner peripheral portion 3Ca1 and the inclined portion 3Ca2 as opposed to the opposing surface 3Ca and the opposite surface 3Cb as in the first modified example with respect to the magnet 3B of the second modified example. This is an example in which both are provided with magnets.
In this modified example, as in the second modified example, the rotor yoke 4C is also formed in a shape that brings the outer peripheral side closer to the coil 2 side in accordance with the inclined portion 3Cb2, so that the thickness of the entire motor on the outer peripheral side is reduced. It is suitable when you want to.

A fourth modification is shown in FIG.
In this example, the thickness of the magnet 3D is made constant, and the rotor yoke 4D is deformed by Δg2 in a direction away from the coil 2 so that the gap with the coil 2 is widened by Δg2 on the outer peripheral side, and the magnet 3D is formed in a shape along the deformation. It is a thing. Therefore, the surface shape of the magnet 3D becomes a part of the conical surface.
This modification is suitable when it is desired to reduce the thickness of the motor near the rotation center.
If the magnet 3D is formed of a flexible material (for example, a rubber magnet), it is preferable because it can be deformed and fixed along the rotor yoke 4D.

  In the above-described embodiments and modifications, a so-called shaft rotation type flat motor in which the shaft rotates has been described. However, the shaft is fixed to the back yoke side and the shaft is inserted through the rotor yoke side. Needless to say, it may be a so-called shaft-fixed flat motor in which the rotor rotates.

It is sectional drawing which shows the Example of the flat motor of this invention. It is sectional drawing explaining the Example of the flat motor of this invention. It is principal part sectional drawing explaining the 1st modification of the flat motor of this invention. It is principal part sectional drawing explaining the 2nd modification of the flat motor of this invention. It is principal part sectional drawing explaining the 3rd modification of the flat motor of this invention. It is principal part sectional drawing explaining the 4th modification of the flat motor of this invention. It is a perspective view which shows the external appearance in the Example of the flat motor of this invention. It is a figure explaining the conventional motor. It is another figure explaining the conventional motor.

Explanation of symbols

1 Back yoke (stator yoke)
DESCRIPTION OF SYMBOLS 1a Circuit pattern 2 Coil 2a Opposite surface 3, 3A-3D Magnet 3a (3Aa-3Da) Opposite surface 3Aa1, 3Ca1 Inner peripheral part 3Aa2, 3Ca2 Inclined part (gap expansion part)
3Ac Boundary lines 3Bb, 3Cb (opposite side) surfaces (3A-3D) Magnets 4, 4B, 4D Rotor yoke 5 Shaft 6 Bearing 51 Stator 52 Rotor 55 Flat motor G, G1, G2, g1 Gap Δg Thickness difference Δg1, Δg2 Inclination amount

Claims (5)

A stator having a stator yoke in which a plurality of drive coils are arranged on a plane;
A rotor yoke having an annular magnet disposed so as to face the drive coil, and a rotor that rotates relative to the stator;
A copper foil circuit pattern is formed on the plane of the stator yoke,
A flat motor having a gap expanding portion that is separated from the coil as the distance from the rotation center increases on a surface of the magnet facing the drive coil. An electronic component for driving the flat motor is soldered to the plane of the stator yoke,
The flat motor according to claim 1, wherein the circuit pattern of the copper foil is formed so as to electrically connect the electronic components. The flat motor according to claim 1, wherein the magnet is made of an Nd—Fe—B (neodymium-iron-boron) rare earth hard magnetic material. A stator having a stator yoke in which a plurality of drive coils are arranged on a plane;
A rotor yoke having an annular magnet disposed so as to face the drive coil, and a rotor that rotates relative to the stator;
On the surface of the magnet that faces the drive coil, an inner circumferential portion that faces the drive coil in parallel, and a gap that moves away from the rotation center as the distance from the rotation center is greater than the inner circumference as viewed from the rotation center. A flat motor comprising an enlarged portion. When writing the radius of the boundary line between the inner peripheral portion and the gap enlarged portion as r2, the inner diameter of the magnet as r1, and the outer diameter of the magnet as r3,
The flat motor according to claim 4, wherein a radius of the boundary line is set in a range of the following formula 1.
r2 ≦ r1 + 0.7 × (r3−r1) (Formula 1)

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