JP2000069711A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor which can retain a rotor structure surely in the specified position in axial direction without applying excessive axial force (thrust force) to a thrust bearing. SOLUTION: For a motor, the rotor body 5 of a rotor structure 7 integrated with a motor shaft 8 is confronted in axial direction with a stator 4, and the motor is equipped with an axial force applying means (a permanent magnet 23 and a peripheral wall 18 made of soft magnetic material) which exerts such axial force F as to about the end 8a on bearing side of the motor shaft 8 against the thrust bearing 12 within the bearing housing 10 of a chassis structure 2 upon the rotor structure 7, between the rotor structure 7 and the chassis structure 2. For the axial force applying means (a permanent magnet 23 and a peripheral wall 18 made of soft magnetic material), the upper section 27 than the section A of the permanent magnet 28 confronts in diametrical direction the peripheral wall 18 made of soft magnetic material, so that the axial force F may be smaller as the end 8a on bearing side comes closer to the thrust bearing 12 when the end 8a on bearing side of the motor shaft 8 is near the thrust bearing 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor, and more particularly, to a thrust bearing in a bearing housing portion of a chassis structure in which a rotor body of a rotor structure integral with a motor shaft is axially opposed to a stator. The present invention relates to a motor provided with an axial force applying means for applying an axial force to a rotor structure so as to bring a bearing end of a motor shaft into contact with the rotor structure between the rotor structure and the chassis structure. This type of motor can be flattened and is used, for example, for rotating a portable tape recorder or a CD-ROM drive.

[0002]

2. Description of the Related Art As a conventional motor of this type, for example, a motor 100 as shown in FIG. In this motor 100, a motor shaft 101
Rotor body 103, 1 of rotor structure 102 integrated with
03 faces the stator 104 in the axial direction. Also, in this motor 100, the chassis structure 10
Thrust bearing 1 supported by the bearing housing part 106 of No. 5
07 with respect to the bearing end 101 of the motor shaft 101
a is applied to the rotor structure 102
On the body (chassis body or bottom wall) 112 of the chassis structure 105 so as to face the bottom surface (bottom wall) 110 of the soft magnetic material yoke 109 of the rotor body 103 of the rotor structure 102 in the axial direction. Annular permanent magnet 11
1 is attached.

In this motor 100, the end 108 of the motor shaft 101 is brought into contact with the thrust bearing 107 by pulling the yoke 109 in the V direction along the axial direction by the permanent magnet 111, so that the rotor The motor 100 is operated in a state where the relative positions of the main bodies 103 and 103 with respect to the stator 104 in the axial direction are stabilized.

[0004]

However, in this motor 100, as the rotor structure 102 is moved in the V direction, the bottom wall 110 of the yoke 109 becomes closer to the permanent magnet 111 in the V direction with respect to the rotor structure 102. Strengthens. That is, the lower end 101a of the motor shaft 101
V is the axial distance between the thrust bearing 107 and Y
Assuming that the axial force acting in the direction is F, the force F monotonically decreases as the distance Y increases (as shown by the broken line PA in FIG. 4) (monotonically increases as the distance Y decreases). Depends on the distance Y. As a result, the motor shaft 101 may be excessively strongly pressed against the thrust bearing 107, and the abrasion and deterioration of the thrust bearing 107 may be accelerated or the rotation may be inappropriately supported. In this case,
When viewed in the axial direction, the rotor structure 102 is
As the distance from the motor shaft 101 increases, the attraction force in the V direction toward the rotor structure 102 decreases.
If the axial load applied to the thrust bearing 107 is reduced when 01a is in contact with the thrust bearing 107, it is difficult to return the motor shaft 101 to the original contact position once the motor shaft 101 separates from the thrust bearing 107. There is a fear.

Further, as shown in FIG. 8B, an annular permanent magnet 121 magnetized in the axial direction is attached to the lower end of the boss 122 of the rotor structure 102 to form a chassis structure 105.
Although a motor 130 is known which faces the chassis body (bottom wall) 112 made of a soft magnetic material in the axial direction, this motor 130 has the same disadvantages as the motor 100.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a rotor structure in an axial direction without exerting an excessive axial force (thrust force) on a thrust bearing. To provide a motor that can be reliably held at a predetermined position.

[0007]

According to the motor of the present invention, in order to achieve the above-mentioned object, a rotor body of a rotor structure integral with a motor shaft is axially opposed to a stator to form a chassis structure. A motor provided with an axial force applying means for applying an axial force to the rotor structure such that the bearing side end of the motor shaft comes into contact with the thrust bearing in the bearing housing portion between the rotor structure and the chassis structure. The axial force applying means is configured such that, when the bearing-side end of the motor shaft is near the thrust bearing, the axial force becomes smaller as the bearing-side end approaches the thrust bearing. .

In the motor according to the present invention, the axial force applying means for applying an axial force to the rotor structure such that the bearing end of the motor shaft comes into contact with the thrust bearing in the bearing housing portion of the chassis structure is provided by the rotor. It is provided between the structure and the chassis structure '', so that the motor can be operated by stabilizing the axial relative position of the rotor to the stator by contacting the bearing end of the motor shaft with the thrust bearing. In particular, the axial force applying means is configured such that, when the bearing end of the motor shaft is in the vicinity of the thrust bearing, the closer the bearing end is to the thrust bearing, the smaller the axial force becomes. The rotor structure can be securely held at a predetermined position in the axial direction without applying excessive axial force to the thrust bearing, and efficient rotation of the rotor can be performed stably. It may have.

In this specification, unless otherwise specified, the term "axial direction" refers to the direction in which the rotation axis of the motor shaft or the motor extends, and the term "radial direction" refers to the center of the rotation axis of the motor shaft. Refers to the radial direction. The term "facing in the radial direction" refers to facing in the radial direction at substantially the same position (level) as viewed in the axial direction. In this specification, “upper” refers to a side where the bearing housing is located with respect to the extending surface of the chassis main body (chassis bottom wall), and unless otherwise specified, the bearing housing is perpendicular to the chassis main body. The present invention is not limited to the case where the chassis structure is disposed so as to be located in the upper direction (above the ground). In addition,
The terms “bottom” and “bottom” are used in a similar manner.

The axial force applying means typically comprises a magnetostatic interaction applying means including a permanent magnet. However, as long as the axial force having the above characteristics can be applied, the electromagnetic interaction applying means may also be used. Alternatively, it may be a means for giving an electrostatic interaction or a means for giving another kind of interaction. Regarding the axial force applying means, "having (provided) between the rotor structure and the chassis structure" means that the rotor structure and the chassis structure themselves partially or wholly constitute the axial direction applying means. This also includes a case where the axial force applying means is formed by another member other than the rotor structure and the chassis structure.

When the axial force applying means comprises a magnetostatic means, the axial force applying means preferably comprises a peripheral wall of the rotor structure and a portion of the chassis structure radially facing the peripheral wall. One of the permanent magnets and the other, a ferromagnetic material provided at a position radially facing a part of the permanent magnet in the axial direction when the bearing end of the motor shaft comes into contact with the thrust bearing. Consisting of parts.

Here, the "peripheral wall" of the rotor structure is preferably an inner peripheral wall (inner peripheral wall) of the rotor structure in order to minimize the radial size of the motor. May be its outer peripheral wall. Regarding the mounting position of the permanent magnet, one of “the peripheral wall of the rotor structure and a portion of the chassis structure radially facing the peripheral wall (hereinafter, also referred to as a“ radially facing portion of the chassis structure ”). "" Means "the circumferential wall of the rotor structure or the radially facing portion of the chassis structure" itself, but instead, is adjacent to the circumferential wall or the radially facing portion and the circumferential wall or the radially facing portion. May be an integral part.
"Integrally" means that the motor does not move relative to each other when the motor operates, and is not limited to being integrally formed. A “ferromagnetic material” is typically a material that is magnetically soft and has high permeability (herein,
However, in some cases, it may be a hard magnetic material such as a permanent magnet.
In this specification, “ferromagnetic” is used in a broad sense including ferrimagnetism and the like, and a ferromagnetic material is synonymous with a so-called “magnetic material” in a narrow sense.

In the case where the soft magnetic material portion is configured to face a portion of the permanent magnet in the axial direction when the bearing end of the motor shaft comes into contact with the thrust bearing, the soft magnetic material may be used. Since the portion receives an axial force such that it is directed to a position facing the radial direction with respect to the entire axial direction of the permanent magnet, the bearing-side end of the motor shaft is pressed against the thrust bearing. On the other hand, the lower the proportion of the portion of the permanent magnet in the axial direction that faces the soft magnetic material in the radial direction, the lower the ratio of the magnetic flux of the permanent magnet to the soft magnetic material in the axial direction. The axial force on the soft magnetic material increases because the proportion of the magnetic flux extending in the pulling direction increases. In other words, the closer the bearing end of the motor shaft is to the thrust bearing, and the higher the proportion of the axially facing portion of the permanent magnet facing the soft magnetic material in the radial direction, the higher the ratio of the permanent magnet to the thrust bearing. On the other hand, the magnitude of the axial force acting between the soft magnetic material portions facing in the radial direction becomes smaller.

Even if the permanent magnet is symmetrically magnetized with respect to a plane passing through the midpoint in the axial direction and perpendicular to the axis, the soft magnet on both sides of the permanent magnet when viewed in the axial direction. As long as the distribution of the magnetic material is not symmetric about the plane,
Even if the entire peripheral wall of the permanent magnet faces the soft magnetic material portion in the radial direction, the axial force remains, and in some cases, in a state where the end of the motor shaft is in contact with the thrust bearing, Not only a part of the peripheral wall of the permanent magnet but also the whole may face the soft magnetic material part in the radial direction.

[0015] In the case where the inner peripheral area of the rotor structure is used, the permanent magnet may be mounted on the outer periphery of the bearing housing.
It may be attached to the inner peripheral wall of the rotor structure. In the former case,
An annular permanent magnet is attached around the bearing housing portion of the chassis structure, and the inner peripheral wall of the rotor structure facing the bearing housing portion is formed of a soft magnetic material. In the latter case, the bearing housing portion of the chassis structure An annular permanent magnet structure is attached to the inner peripheral wall of the rotor structure facing the inner peripheral wall, and the bearing housing portion facing the inner peripheral wall is formed of a soft magnetic material.

For example, when an annular permanent magnet is mounted around the bearing housing portion of the chassis structure, instead of directly mounting the annular permanent magnet on the outer peripheral surface of the bearing housing portion, the chassis body is integrated with the bearing housing portion. An annular permanent magnet may be attached to a portion near the bearing housing. The same applies to the case where an annular permanent magnet structure is attached to the inner peripheral wall of the rotor structure.

In this specification, the term "annular" includes those having a larger or smaller radial length (thickness) than the length in the axial direction. Is larger than the radial length. The cross-sectional shape of each of the outer peripheral surface and the inner peripheral surface may be circular or other than circular.

Incidentally, the permanent magnet may be formed in an annular shape concentric with the rotation axis of the motor, or may be eccentric with respect to the rotation axis of the motor. The term "annular" means that both the outer periphery and the inner periphery are circular in cross section. In the latter case,
The annular permanent magnet may be mounted at a position eccentric with respect to the rotation axis of the motor, or may be an eccentric body having an outer peripheral surface eccentric with respect to the inner peripheral surface.

When the permanent magnet is eccentric with respect to the axis of rotation of the motor, the radial gap between the permanent magnet and the peripheral wall of the magnetic material facing the permanent magnet is smaller on the side where the gap is larger than on the side where the eccentricity is larger. Since the magnetostatic attraction between the permanent magnet and the peripheral wall of the magnetic material is increased, the motor shaft integral with the rotor structure is slightly inclined toward the side with the larger magnetostatic attraction, and is inserted into the bearing housing. The journal bearing is rotated in a state of contact with the journal bearing, and the journal bearing can be stably supported in the same manner as in JP-A-6-153452.

The permanent magnet may be magnetized in the axial direction, may be magnetized in a plane perpendicular to the axial direction, or may be magnetized in another state. From the viewpoint of maintaining, it is preferable that the magnet is magnetized in the axial direction.

In this motor, the "rotor structure"
The rotor body facing the stator in the axial direction,
Preferably, it is provided on both sides in the axial direction of the stator. Each rotor body is typically made of a permanent magnet structure in which the direction of magnetization of a fan-shaped portion magnetized in the axial direction alternately changes in the circumferential direction and a soft magnetic material supporting the permanent magnet structure. It consists of a yoke. Note that one of the rotor bodies may be composed of only the yoke. The “stator” typically includes a plurality of fan-shaped or trapezoidal air-core coils arranged in a circumferential direction on a stator substrate fixed and supported by a chassis structure. Even though the stator substrate is configured to support the entire coil, it is configured to support a part of the coil in the radial direction as disclosed in JP-A-10-174399 and JP-A-10-174400. You may.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to some embodiments shown in the accompanying drawings.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Preferred Embodiment Motor 1 according to the present invention
Will be described with reference to FIGS.

The motor 1 has a stator 4 fixed to a side wall (peripheral wall) 3 of a chassis structure 2 forming a motor housing, a pair of rotor bodies 5, 5A facing the stator 4 in the axial direction, and It has a rotor structure 7 having wheels or bosses 6 integral with the rotor bodies 5 and 5A, and a motor shaft 8 fixed to the boss 6 of the rotor structure 7. Chassis body (bottom wall) 9 of chassis structure 2
Journal housing 11 such as an oil-impregnated bearing made of a sintered body impregnated with lubricating oil
And a thrust bearing 12 made of a wear-resistant material such as nylon. Thrust bearing 1
The upper surface of 2 is located on substantially the same plane as the upper surface of chassis body 9.

The rotor bodies 5, 5A of the rotor structure 7 are
Each of the substantially annular permanent magnet structures 13 and 14 (FIG. 5 (b)) provided with an even number of substantially fan-shaped portions that are magnetized in the axial direction so as to give an alternating axial magnetic field when viewed in the circumferential direction. )) And soft magnetic material yokes 15 and 16 fixed to the permanent magnet structures 13 and 14. The lower yoke 15 has an annular radially extending portion (bottom wall) 17 to which the permanent magnet structure 13 is fixed, and a cylindrical shape extending axially upward from a radially inner peripheral edge of the radially extending portion 17. It has an axially extending portion (inner peripheral wall) 18 and an engaging / fixing portion 19 extending radially inward at the upper end of the axially extending portion 18. When the lower end of the motor shaft 8, that is, the bearing end 8 a is in contact with the thrust bearing 12, the bottom wall 1 of the yoke 15
7 is located above the thrust bearing 12.

The stator 4 includes a stator substrate 20 and a plurality of substantially fan-shaped or substantially trapezoidal air-core stator coils 21 arranged in the circumferential direction on the stator substrate 20. Coil 21
And a wiring pattern 20a are formed (FIG. 5A).

When the stator coil 21 is sequentially energized in a desired energization pattern (sequence) via the energization terminals and the wiring pattern 20a, the stator coil 21 is formed by the pair of rotor bodies 5, 5A of the permanent magnet structures 13, 14 of the rotor structure 7. Coil 2 due to the alternating axial magnetic field seen in the circumferential direction
1 (more specifically, the coil pairs 21 and
As a reaction of the torque applied to 1), the rotor structure 7
Are rotated in a desired pattern (mode).

The sleeve or cylindrical peripheral wall portion 22 of the bearing housing portion 10 integrally formed with the chassis main body 9 by deep drawing, reverse drawing or the like is substantially mounted and fixed on the chassis main body 9. An annular or cylindrical permanent magnet 23 is fitted and fixed. In addition, even if the permanent magnet 23 is loosely fitted to the bearing housing 10 and fixed to the upper surface of the chassis main body 9, the permanent magnet 23 is spaced from the upper surface of the chassis main body 9 and is spaced from the peripheral wall 22 of the bearing housing 10.
It may be fitted to.

When the lower end 8a of the motor shaft 8 is in contact with the thrust bearing 12, the bottom wall 17 of the yoke 15
Is located above the lower end 24 of the permanent magnet 23, and the upper end 25 of the permanent magnet 23 faces the portion E of the inner peripheral wall 18 of the yoke 15 in the radial direction. Therefore, the permanent magnet 23
Is radially opposed to the inner peripheral wall 18 of the yoke 15 at a portion 26 between a portion A facing the lower end of the bottom wall 17 of the yoke 15 and an upper end 25 thereof. The portion below the portion A of the permanent magnet 23 does not face the inner peripheral wall 18 of the yoke 15 in the radial direction.

Although the permanent magnet 23 is uniformly magnetized in the axial direction as shown in FIG. 3A, the permanent magnet 23 may be unidirectionally magnetized in a plane perpendicular to the axial direction as shown in FIG. It may be magnetized, may be magnetized in a plurality of directions such as the radial direction, may be magnetized obliquely to the axial direction, or may not have a uniform magnetization magnitude. For example, from the viewpoint of rotational symmetry,
It is preferable that the magnet is magnetized in the axial direction as shown in FIG.

In this case, even when the bearing-side end 8a of the motor shaft 8 comes into contact with the thrust bearing 12, the soft magnetic material portion (peripheral wall of the yoke 15) 18 is radially aligned with the axial portion 26 of the permanent magnet 23. Therefore, the peripheral wall 18 of the yoke 15 receives an axial force F directed to a lower position in the V direction so as to face the entire permanent magnet 23 in the radial direction, The bearing-side end 8a of the motor shaft 8 is pressed against the thrust bearing 12 in the V direction. In this state, a part of the magnetic flux of the permanent magnet 23 extends substantially radially to the yoke peripheral wall portion located below the portion E of the peripheral wall 18 of the yoke 15 and facing the permanent magnet 23 in the radial direction. The remaining magnetic flux extends obliquely upward with respect to the yoke peripheral wall portion above the portion E. Roughly speaking, a force in the V direction acts on the upper yoke peripheral wall portion due to the magnetic flux portion extending obliquely upward.

On the other hand, if it is assumed that the motor shaft 8 is located slightly above the contact position in FIG. 1, a portion of the axial portion of the permanent magnet 23 that faces the peripheral wall 18 of the yoke 15 in the radial direction. And the ratio of the magnetic flux of the permanent magnet 23 that extends substantially in the radial direction to the radially facing portion of the peripheral wall 18 of the yoke 15 decreases, and the yoke peripheral wall portion above the upper end 25 of the permanent magnet 23 , The proportion of the magnetic flux extending obliquely upward increases. Therefore, roughly speaking, the force F in the V direction acting on the upper yoke peripheral wall portion
Becomes larger. Therefore, in this case, qualitatively, an axial force F as shown by a solid line G in FIG. 4 acts on the rotor structure 7 and the motor shaft 8. In FIG. 4, the solid line G is shown linearly in the region G1 where Y is small, but as long as it monotonically increases with the increase in Y, instead of a straight line, it may be a curved line convex upward or downward. Shape (characteristics). In any case, the bearing-side end 8a of the motor shaft 8 approaches the thrust bearing 12,
As the ratio of the peripheral wall portion of the peripheral wall of the permanent magnet 23 radially facing the peripheral wall 18 of the yoke 15 increases, the magnitude of the axial force F acting between the permanent magnet 23 and the yoke peripheral wall 18 increases. Become smaller. Therefore, the motor shaft 8
Is pressed against the thrust bearing 12 in the V direction, but the pressing force F can be prevented from excessively increasing. As a result, during the rotation operation of the motor 1, the rotor structure 7 can be securely held at a predetermined position in the axial direction without exerting an excessive thrust force on the thrust bearing 12, and the motor 1 can be efficiently rotated. Can be performed.

Strictly speaking, when the direction of magnetization and the distribution of the magnitude of the magnetization of the permanent magnet 23 change, the permanent magnet 23 and the soft magnetic yoke peripheral wall 18 around the magnet 23 are three-dimensionally viewed. , The distribution of the magnetic field or magnetic flux density also differs, and the characteristic G of the axial force F also changes.

As can be seen from FIG. 4, in this example, the force F rapidly decreases in the region G2 where Y is large. This is because when the permanent magnet 23 and the peripheral wall 18 no longer face each other in the radial direction, the magnetostatic force decreases depending on the power of the reciprocal of the distance Y. However, characteristics such as the region G2 may not be required.

In the case where the inner peripheral area of the rotor structure is used, as shown in FIG.
Instead of being provided on the outer periphery of the rotor 2, it may be provided on the side of the rotor structure as shown in FIG. In the motor 31 of FIG. 2, the same or similar members, elements, or portions as those of the motor 1 of FIG. 1 are denoted by the same reference numerals. In addition, in the motor 1 shown in FIG.
The code a is added after the same code.

In the motor 31, a boss 6a made of a so-called non-magnetic material such as brass is mounted on a wheel-shaped boss body 32.
And a cylindrical portion 33 extending in the axial direction from the main body portion 32. The yoke 15a of the rotor main body 5a is fixed to the lower end of the cylindrical portion 33. In the motor 31, an annular permanent magnet 23 a is fixed to the upper end of the inner peripheral surface of the cylindrical portion 33 of the boss 6 a and to the lower surface of the boss main body 32.

In the case of this motor 31, the motor shaft 8
The lower end 24a of the permanent magnet 23a is located lower than the upper end 34 of the peripheral wall 22 of the bearing housing portion 10 made of a soft magnetic material, and the lower end 8a of the permanent magnet 23a is in contact with the thrust bearing 12. The upper end 34 of the peripheral wall 22 is opposite to the upper end 25a of the permanent magnet 23a.
Portion Aa of the inner peripheral surface of the permanent magnet 23a positioned below
Face in the radial direction. Therefore, the permanent magnet 23a
Faces the peripheral wall 22 in the radial direction at a portion 26a between a portion Aa facing the upper end 34 of the peripheral wall 22 and the lower end 24a. The portion of the permanent magnet 23a above the portion Aa does not face the peripheral wall 22 in the radial direction.

In the case of this motor 31, qualitatively,
It will be clear that an axial force F having the characteristic indicated by reference symbol G in FIG. 4 is obtained.

The permanent magnets may be eccentric instead of being formed and arranged rotationally symmetrically around the axis of rotation of the motor as shown in FIG. Two examples are shown in FIGS.
6 and 7, the same or similar members, elements, or portions as those of the motor 1 of FIG. 1 are denoted by the same reference numerals. Further, parts or elements of the motor 1 shown in FIG. 1 which are partially changed are further denoted by the same reference numerals b or c after the same reference numerals, respectively.

In the motor 41 shown in FIG. 6, (a) and (b)
As shown in FIG.
An annular permanent magnet 23b having an inner diameter larger than the outer diameter of the peripheral wall 22 is surrounded by the chassis so as to surround the peripheral wall 22 of the bearing housing portion 10 with its center axis C1 shifted with respect to the rotation axis C of the motor 41. It is arranged on the main body 9. In this example, although the inner peripheral surface of the permanent magnet 23b is in contact with the outer peripheral surface of the peripheral wall 22 on the left side in FIG. 6, the two surfaces may not be in contact at all.

It will also be apparent that this motor 41 can function similarly to motor 1. In the motor 41, the peripheral wall portion 4 on the right side of the permanent magnet 23b in FIG.
2 is located closer to the peripheral wall 18 of the yoke 15 of the rotor structure 7 than the left peripheral wall portion 43, so that the rotation axis of the motor shaft 8 is exaggerated in FIG. Is always applied to the rotor structure 7 so as to make the state Ct inclined in the J direction with respect to the center axis C of the motor 41. As a result, as in the case of JP-A-6-153452, the motor shaft 8 is rotated in a state of being supported against the upper right shoulder 44 of the journal bearing 11 as seen in FIG. Therefore, the motor shaft 8 is always fixed to the journal bearing 11 irrespective of the size and shape of the minute gap unavoidable to allow the rotation of the motor shaft 8 between the motor shaft 8 and the journal bearing 11. Can be rotated in contact,
There is little possibility that the rotation axis Ct of the motor shaft 8 is blurred,
For example, the access condition of the head to the surface of a disc-shaped information recording medium such as a CD-ROM which may vary depending on the direction of the motor shaft 8 is less likely to vary.

In order to make the permanent magnet eccentric, the permanent magnet itself may be formed by an eccentric body instead of disposing the annular permanent magnet at the eccentric position. In the motor 51 shown in FIG. 7A, the permanent magnet 23c is formed of an eccentric body in which the outer peripheral surface 53 (center C1) is eccentric with respect to the inner peripheral surface 52 (center C). The permanent magnet 2 is fitted and fitted on the outer periphery of the peripheral wall 22.
7 (a) and 7 (b), the outer peripheral surface of the yoke 15 is larger in the right side portion 54 than in the left side portion 55 in FIGS.
, And operates similarly to the motor 41 of FIG.

[Brief description of the drawings]

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

FIG. 2 is an explanatory sectional view of a motor according to another preferred embodiment of the present invention.

FIG. 3 is an explanatory view of a preferred example of a permanent magnet used in the motor of FIG. 1;

FIG. 4 is a graph qualitatively showing an axial force acting on a rotor structure or a motor shaft in the motor of FIG.

FIG. 5 is an explanatory view of parts used in the motor of FIG. 1,
(A) is a plane explanatory view of a stator, (b) is a plane explanatory view of a permanent magnet structure of a rotor main body.

FIGS. 6A and 6B are explanatory views of a motor according to still another preferred embodiment of the present invention, in which FIG. 6A is a cross-sectional explanatory view, and FIG. 6B is a plan view showing an arrangement of permanent magnets used in the motor of FIG. FIG.

FIGS. 7A and 7B are explanatory views of a motor according to still another preferred embodiment of the present invention, in which FIG. 7A is a cross-sectional explanatory view, and FIG. 7B is a plan view showing an arrangement of permanent magnets used in the motor of FIG. FIG.

FIG. 8 is an explanatory sectional view of a conventional motor.

[Explanation of symbols]

1, 31, 41, 51 Motor 2 Chassis structure 3 Side wall (outer peripheral wall) 4 Stator 5, 5A, 5a Rotor body 6, 6a Boss 7, 7a Rotor structure 8 Motor shaft 8a Bearing end of motor shaft (lower end) 9) Chassis body 10 Bearing housing part 11 Journal bearing 12 Thrust bearing 13, 14 Permanent magnet structure 15, 15a, 16 Yoke 17 Cylindrical bottom wall 18 Cylindrical peripheral wall 19 Fixing / engaging part 20 Stator substrate 21 Stator coil 22 Bearing housing Peripheral wall (sleeve) 23, 23a, 23b, 23c Permanent magnet 24, 24a Lower end of permanent magnet 25, 25a Upper end of permanent magnet 26, 26a Part (region) radially facing permanent magnet 32 Boss body (wheel) 33 Cylindrical part 34 Upper end of peripheral wall of bearing housing 42, 54 Right part 43, 55 Left part 44 Shoulder 52 Inner peripheral surface 53 Outer peripheral surface A, Aa Permanent magnet portion facing end of peripheral wall C Center axis of motor C1 Center position eccentric Ct Rotation axis when motor shaft is tilted E , Ea A portion of the peripheral wall facing the end of the permanent magnet F Axial force G, G1, G2 A line indicating the dependence of the axial force on the distance J Inclination direction V A direction in which the axial force acts Y A bearing end of the motor shaft And the distance between the thrust bearing

Claims (9)

[Claims] 1. A rotor body of a rotor structure integral with a motor shaft is axially opposed to a stator, and a bearing end of the motor shaft is brought into contact with a thrust bearing in a bearing housing of the chassis structure. A motor provided with an axial force applying means for applying such an axial force to the rotor structure between the rotor structure and the chassis structure, wherein the axial force applying means is a bearing-side end of the motor shaft. A motor in which the axial force decreases as the end on the bearing side approaches the thrust bearing when is near the thrust bearing. 2. A permanent magnet provided on one of a peripheral wall of a rotor structure and a portion of a chassis structure radially facing the peripheral wall, and a motor provided on the other side. 2. The motor according to claim 1, wherein when the bearing-side end of the shaft abuts on the thrust bearing, the permanent magnet includes a part in the axial direction and a ferromagnetic material part provided at a position facing the radial direction. 3. The rotor structure according to claim 2, wherein the permanent magnet comprises an annular permanent magnet mounted around a bearing housing of the chassis structure, and the ferromagnetic material portion comprises an inner peripheral wall made of a soft magnetic material of the rotor structure. A motor according to claim 1. 4. A permanent magnet comprising an annular permanent magnet mounted on an inner peripheral wall of a rotor structure facing a bearing housing portion of a chassis structure, wherein said ferromagnetic material portion is soft magnetic facing said inner peripheral wall. 3. The motor according to claim 2, comprising a bearing housing portion made of a material. 5. The motor according to claim 3, wherein the permanent magnet is eccentric with respect to the rotation axis of the motor, and the bearing housing supports a journal bearing. 6. A motor according to claim 5, wherein said permanent magnet comprises an annular permanent magnet mounted at a position eccentric with respect to the rotation axis of the motor. 7. The motor according to claim 5, wherein said permanent magnet comprises an eccentric body having an outer peripheral surface eccentric with respect to an inner peripheral surface. 8. The motor according to claim 3, wherein the permanent magnet is magnetized in an axial direction. 9. The motor according to claim 3, wherein the permanent magnet is magnetized in a plane perpendicular to the axial direction.