JP2002335658A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor which reduces cogging torque caused by the magnetic force of a permanent magnet. SOLUTION: This motor has a rotor (20) including a magnetic body (22) in which positive and negative poles are alternately formed around a rotating shaft, a stator including a plurality of stator cores (12a, 12b) arranged so as to face the poles of the magnetic body, and in which windings (13a, 13b) for forming rotating fields are wound, and a bearing (15) for rotatably retaining the rotor (20) at the stator. The magnetic body (22) is disc-shaped or annular- shaped (or cylindrical), and generates a magnaflux from the respective poles formed at the front surface and the back surface. The stator cores (12a, 12b) include a first stator core layout (12a) facing the respective poles on the surface of the magnetic body (22) and arranged in an annular-shape with the rotating shaft centered, and a second stator core layout (12b) facing the respective poles on the back surface of the magnetic body and arranged in an annular-shape with the rotating shaft centered. The cogging torque can thus be offset, by using the magnetic force of the poles on both surfaces of the disc-shaped or annular-shaped magnetic body for the generation of torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a motor using a permanent magnet.

[0002]

2. Description of the Related Art FIG. 11 is a partial sectional view illustrating a conventional example of a brushless motor using a cylindrical magnet as a rotor magnet. As shown in FIG.
A stator core 12 formed in an annular shape is attached to an inner periphery of the stator core 1. The stator core 12 includes a plurality of radially inwardly projecting pole pieces 121, each of which has a pole piece 12.
1, a winding 13 for generating a magnetic flux is wound. A rotating magnetic field can be generated by sequentially exciting the plurality of windings 13. A fixed shaft 14 is arranged at the axis of the cylinder of the base 11. A rotor 20 having the axis of the fixed shaft 15 as the center axis of rotation is rotatably mounted on the fixed shaft 14 via a bearing 15. Rotor 20
Is composed of a cylindrical base 21 in which the bearing 15 is fitted, and a cylindrical (or annular) permanent magnet 22 attached to the base 21. An N pole and an S pole are alternately formed in the rotation direction on the outer periphery of the cylindrical permanent magnet portion 22 by magnetization in the radial direction. Each magnetic pole faces the magnetic pole piece 121 of the stator core 12 at a fixed interval.
The rotation angle of the rotor 20 is detected by a rotation detector 30 and supplied to a motor control device (not shown). The rotation detector 30 includes, for example, a rotation plate 31 provided on the outer periphery of the rotor base 21 and having a marker such as a transmission hole formed thereon,
It is composed of a sensor 32 composed of a light-emitting device and a light-receiving device provided on the base 11 with the rotating plate 31 interposed therebetween. The motor control device monitors the output of the rotation detector 30 and rotates the magnetic field by sequentially switching the excitation of the field winding 13 according to the rotation position of the magnetic pole 221 of the magnet unit 22 of the rotor 20 to rotate the magnetic field. The child 20 is rotated.

[0003]

However, since a permanent magnet 22 is used for the rotor 20 and a silicon steel plate is generally used for the stator core 12, magnetic attraction acts between the two. Further, variations may occur in the assembled shapes of the rotor 20 and the stator core 12. As a result, when the rotor is rotated, fluctuations in torque due to magnetic attraction, so-called cogging, occur. When the cogging torque is large, it causes vibration and noise of the motor.

[0004] The cylindrical magnet portion 22 of the rotor 20 is
The magnetic poles of the N and S poles (positive and negative poles) are formed not only on the outer periphery but also on the inner periphery.
Only the magnetic force of 21 can be used to generate the torque of the rotor 20.

Therefore, an object of the present invention is to provide a motor in which cogging torque due to the magnetic force of a permanent magnet is reduced.

Another object of the present invention is to provide a motor that effectively uses the magnetic forces of the positive and negative magnetic poles of a permanent magnet.

[0007]

In order to achieve the above object, a motor according to the present invention comprises a rotor including a magnet body having positive and negative magnetic poles alternately formed around a rotation axis, and a rotor facing the magnetic pole of the magnet body. And a bearing that rotatably holds the rotor to the stator, the stator including a plurality of stator cores provided with windings forming a rotating magnetic field, and the magnet body is A magnetic flux is generated from each of the magnetic poles formed in a disk shape or an annular shape (or a cylindrical shape) on the front and back surfaces. A first stator core array arranged annularly as a second stator core array opposed to each magnetic pole on the back side of the magnet body and annularly arranged around the rotation axis;
including.

With this configuration, it is possible to use the magnetic force of the magnetic poles on both surfaces of the disk-shaped or annular magnet body for generating torque.

Preferably, in the disk-shaped magnet body, each magnetic pole extends in a radial direction, and positive and negative magnetic poles are alternately arranged in a circumferential direction. In the annular magnet body, each magnetic pole extends in the rotation axis direction, and positive and negative magnetic poles are alternately arranged in the circumferential direction.

[0010] Preferably, the first and second stator core arrangements sandwich the magnet body. Thereby, the magnet body can be driven to rotate from both sides.

Preferably, the rotor and the stator are formed in a cylindrical shape. Thereby, the rotor and the stator formed in an annular or cylindrical shape can be assembled in a concentric arrangement.

Preferably, the first and second stator core arrangements arranged concentrically comprise the same number of stator cores, and the angular position of each stator core of the first stator core arrangement And the angular position of each stator core of the second stator core arrangement corresponding thereto is shifted to reduce the cogging torque.

With this configuration, a phase difference occurs between the cogging torque generated by the first stator core arrangement and the cogging torque generated by the second stator core arrangement, and their combined value becomes a single stator. The cogging torque is lower than that of the core arrangement.

Preferably, each of the windings of the first stator core arrangement and each of the windings of the second stator core arrangement can be switched between series connection or parallel connection. Thereby,
It is possible to change the torque generation characteristics of the motor.

Preferably, the end of the winding of each stator core can be taken out to the outside. This makes it possible to perform torque control and the like by changing the connection mode of the windings.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which parts corresponding to those in FIG. 11 are denoted by the same reference numerals.

As shown in FIG. 1, an annular first stator core 12a is arranged and mounted on the inner periphery of a cylindrical base 11 of the motor 1. Stator core 1
2a is made of, for example, a silicon steel plate. The stator core 12a includes a plurality of radially inwardly projecting pole pieces 1.
21a, and a winding 13a for generating a magnetic flux is wound around each magnetic pole piece 121a. A rotating magnetic field can be generated by sequentially exciting the plurality of windings 13a. A fixed shaft 14 is formed at the axis of the cylinder of the base 11. The fixed shaft 14 is a central axis of rotation of the motor 1. A second stator core 12b is annularly arranged and attached to the outer periphery of the fixed shaft 14. A rotating magnetic field can be generated by sequentially exciting the plurality of windings 13a.

The rotor 20 is mounted on the fixed shaft 14 via the bearing 15.
Is attached. In this embodiment, as the bearing 15, a combination of two angular ball bearings is used. However, the present invention is not limited to this. For example, a combination of two conical roller bearings, a cross roller bearing, or the like is used. Various bearings (including those other than the rolling shaft) may be used according to the requirements. The rotor 20 includes a cylindrical base 21 in which the bearing 15 is fitted, and an annular or cylindrical permanent magnet 22 attached to the base 21. Here, an annular shape or a cylindrical shape means the same kind of shape. In addition, as described later, the permanent magnet portion 22 may be formed in a disk shape. Various types of permanent magnets can be used, and in particular, a high magnetic flux density can be obtained. For example, a samarium-cobalt magnet, neodymium-
Rare earth magnets, such as iron-boron magnets, are preferred. The permanent magnet is fixed by an appropriate means such as bonding or fixing the permanent magnet with a bolt by penetrating the permanent magnet in the axial direction.

N-poles and S-poles are alternately formed in the rotation direction on the outer periphery of the permanent magnet portion 22 by radial magnetization. Correspondingly, S-poles and N-poles having the opposite polarity to the outer circumference are formed alternately in the rotation direction on the inner circumference of the permanent magnet portion 22.

Each magnetic pole on the outer periphery of the permanent magnet portion 22 faces the magnetic pole piece 121a in the row of the first stator core 12a at a constant interval. Further, each magnetic pole on the inner periphery of the permanent magnet portion 22 faces the magnetic pole piece 121b in the row of the second stator core 12b at a constant interval. As described above, by sandwiching the rotating magnet portion 22 from both sides between the stator cores 12a and 12b, the magnetic flux of the magnet portion 22 can be effectively used.

Therefore, the permanent magnet section 22 is composed of the first and second magnets.
A rotating force is generated by a magnetic force approximately doubled by the stator cores 12a and 12b. This makes it possible to relatively reduce the thickness (radial width) of the motor when obtaining the same torque. Further, by disposing the magnetic pole pieces (silicon steel plates) on both sides of the permanent magnet, the magnetic attraction force is canceled out, and the magnetic attraction force is balanced to reduce variation.

Here, the first and second stator cores 12a
And 12b will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 and FIG. 3 are cross-sectional views showing a plane perpendicular to the rotation axis of the motor in the AA ′ part of FIG. 1. In both figures, parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

In the example shown in FIG. 2, the center position of the stator core 12a in the unit of the first core row and the center position of the stator core 12b in the unit of the second core row are shifted by θ. I have. Further, in the example shown in FIG. 3, the width of the pole piece of the stator core 12a in the unit of the first core row and the width of the stator core 12b in the unit of the second core row are shifted by gamma. I have. Thereby, the magnet part 22 and the stator core 1
2 to reduce the cogging torque due to the repulsion / suction force.

FIGS. 4 and 5 are explanatory diagrams for explaining a reduction in cogging torque due to a configuration in which the positions of the first and second core rows are shifted from each other. FIG. 4 shows an example of cogging torque according to a conventional configuration. The change in the cogging torque f with respect to the rotation angle of the motor is represented by f = Asinωt, and is determined by the positional relationship between the rotor 20 and the stator 11.

On the other hand, in the configuration of the embodiment, since the motor generates about twice the torque, the magnetic force of the permanent magnet can be reduced to half if it is assumed that the same torque as in the conventional configuration is obtained. Accordingly, as shown in FIGS. 5A and 5B, the first cogging torque f1 due to the arrangement of the permanent magnets 22 and the first stator cores 12a, the permanent magnet 22 and the second stator cores 12b and the second cogging torque f2
And synthesis. The first cogging torque f1 is calculated as f1 =
(1/2) Asinωt, second cogging torque f2
Is expressed as f2 = (1/2) Asin (ωt−θ).
As shown in FIG. 5C, the combined cogging torque ft is ft = Asin (ωt− (１ ／) θ) cos (1)
/ 2) θ. Here, θ is a phase difference due to a shift between the arrangement of the first stator cores 12a and the arrangement of the second stator cores 12b. Since | f | = A and | ft | <A, | ft | <| f |, which indicates that the cogging torque can be reduced by shifting the arrangement of the two rows of stator cores. A similar tendency occurs when the phase difference is γ shown in FIG.

The rotation angle of the rotor 20 is determined by the rotation detector 30.
And supplied to a motor control device (not shown). The rotation detector 30 includes, for example, a rotating plate 31 provided on the outer periphery of the rotor base 21 and having a marker such as a transmission hole formed thereon, and the base 1 sandwiching the rotating plate 31 therebetween.
1 and a sensor 32 composed of a light emitting device and a light receiving device. The motor control device monitors the output of the rotation detector 30 and rotates the magnetic field by sequentially switching the excitation of the field windings 13a and 13b according to the rotation position of the magnetic pole of the magnet unit 22 of the rotor 20, Rotor 20
Is rotated to perform speed control. As the speed control, a known speed control used for a non-commutator motor can be applied.

The motor control device can change the speed-torque characteristic of the motor by switching the connection between the stator windings formed twice.

FIG. 6 shows an example in which the winding of each stator is constituted by a three-phase winding. Of course, it is not limited to the three-phase winding. In this example, the first stator core 12 is connected to a terminal of a three-phase power supply supplied from the control device.
a, V-shaped stator windings U1, V1
And W1, and the Y-connected stator windings U2, V2 and W2 formed in the row of the second stator cores 12b are connected in parallel.

In the example of FIG. 7, the terminals of the three-phase power supply supplied from the control device are connected to the first stator core 12a.
And the Y-connected stator windings U1, V1, and W1 formed in the row of the second stator core 12b.
The connected stator windings U2, V2 and W2 are connected in series.

The switching between the parallel connection and the series connection is performed by switching a relay switch mechanism (not shown) by the motor control device. Alternatively, the terminals of each winding may be drawn out of the motor, and these may be appropriately connected and used. In any case, as described above, the coils can be easily switched between series and parallel because the respective coils need only be appropriately connected to the ends of the respective windings drawn out without being separated.

FIG. 8 is a graph showing torque characteristics when two stator windings are connected in parallel and when two stator windings are connected in series. As shown in the figure, it is easier to obtain a higher rotation speed by connecting in parallel. Further, by connecting in series, it becomes easy to obtain a high torque at a lower rotation speed.

FIG. 9 shows a second embodiment of the present invention. In the figure, parts corresponding to those in FIG.

In this example, the rotor 20 is rotatably held by using two bearings 15 and 15. Rotor 20
Is held by two bearings spaced apart in the direction of the rotation axis, thereby withstanding a larger thrust load and less deviation of the shaft center. As the bearing 15, various bearings (including those other than rolling bearings) can be used in consideration of applications, such as various ball bearings, cylindrical roller bearings, and conical roller bearings.

FIG. 10 shows a third embodiment of the present invention. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description of such parts is omitted.

In this example, the magnet part 22 of the rotor 20 is formed in a disk shape. A plurality of magnetic poles extending in the radial direction and arranged in the circumferential direction are formed in the disk-shaped magnet portion 22. The stator cores 12a and 12b are arranged in two rows on both sides of the disk so as to face the magnetic poles. Therefore, the same effect as that of the configuration shown in FIG. 1 can be obtained. With such a configuration, a motor having a short dimension in the rotation axis direction can be obtained. Further, the rotor 20 is rotatably held by using two bearings 15 and 15. Rotor 20
Is held by two bearings spaced apart in the direction of the rotation axis, the deviation of the shaft center is reduced.

As described above, according to the embodiment of the present invention, the field winding is provided on the inner and outer peripheral sides of the cylindrical (or annular) magnet or on both sides of the disc-shaped magnet so as to face the magnetic poles. Since the line arrays are arranged and the field winding arrays are formed in a double structure, the magnetic attraction of the permanent magnets is generated radially outward and inward, and the magnetic attraction is canceled out with each other, and the magnetic attraction is canceled. The suction power decreases. This reduces shaft deflection due to forces acting on the rotor shaft. Cogging torque also decreases. Further, the cogging torque can be further reduced by shifting the center position of the inner and outer stator cores or the width of the pole pieces.

Further, since the magnetic force on both sides of the cylindrical magnet and the disk magnet of the rotor is effectively used and the torque increases, the required torque is secured even if the axial length of the motor is relatively shortened. This makes it possible to form a flat motor.

Further, since the double field winding is provided, it is possible to operate the motor with different characteristics by changing these connection modes.

[0040]

As described above, according to the motor of the present invention, since the cogging generated in the permanent magnet motor is small, it is possible to obtain a motor having a small torque and a large torque.

[Brief description of the drawings]

FIG. 1 is a partial sectional view illustrating a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a cross section taken along the line AA ′ of the first embodiment.

FIG. 3 is a cross-sectional view showing a cross section taken along line AA ′ (another configuration example) of the first embodiment.

FIG. 4 is a graph illustrating an example of a cogging torque of a motor having a conventional configuration.

FIGS. 5A to 5C are graphs illustrating the improvement of the cogging torque according to the present embodiment.

FIG. 6 is a circuit diagram illustrating an example in which the double stator windings of the embodiment are connected in parallel.

FIG. 7 is a circuit diagram illustrating an example in which the double stator windings of the embodiment are connected in series.

FIG. 8 is a graph illustrating torque characteristics of a motor when a double stator winding is connected in parallel and when a double stator winding is connected in series.

FIG. 9 is an explanatory diagram illustrating a second embodiment of the present invention.

FIG. 10 is an explanatory diagram illustrating a third embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating an example of a conventional motor.

[Explanation of symbols]

 Reference Signs List 1 motor 11 base 15 bearing 12, 12a, 12b stator core 13, 13a, 13b winding 20 rotor 21 rotor base 22 magnet unit 30 rotation detector

Claims (8)

[Claims] 1. A rotor including a magnet body having positive and negative magnetic poles alternately formed around a rotation axis, and a winding arranged to face the magnetic poles of the magnet body and forming a rotating magnetic field. A stator including a plurality of stator cores; a bearing rotatably holding the rotor on the stator;
The magnet body is disk-shaped or annular and generates magnetic flux from each magnetic pole formed on the front and back thereof, and the stator core faces each magnetic pole on the front side of the magnet body, and the rotating shaft A first stator core array arranged in a ring around the center, and opposed to each magnetic pole on the back side of the magnet body;
A second stator core array arranged annularly about the rotation axis. 2. The motor according to claim 1, wherein each magnetic pole of the disk-shaped magnet body extends in a radial direction, and positive and negative magnetic poles are alternately arranged in a circumferential direction. 3. The motor according to claim 1, wherein each magnetic pole of the annular magnet body extends in a rotation axis direction, and positive and negative magnetic poles are alternately arranged in a circumferential direction. 4. The motor according to claim 1, wherein said first and second stator core arrangements have a structure sandwiching said magnet body. 5. The motor according to claim 1, wherein said rotor and said stator are formed in a cylindrical shape. 6. The first and second stator core arrangements which are arranged concentrically comprise the same number of stator cores, and each of the stator cores of the first stator core arrangement has an angular position and The motor according to any one of claims 1 to 5, wherein a cogging torque is reduced by shifting a corresponding angular position of each stator core of the second stator core arrangement. 7. The mechanism according to claim 1, wherein each of the windings of the first stator core arrangement and each of the windings of the second stator core arrangement can be connected to each other in series or in parallel. A motor according to claim 1. 8. The motor according to claim 7, wherein the ends of the windings of each stator core can be taken out to the outside.