JP4413303B2 - motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor that applies a magnetic biasing force in an axial direction to a rotor body by a magnetic action of a magnet.
[0002]
[Prior art]
A motor for rotationally driving a recording medium (for example, a CD-ROM) includes a stationary member and a rotor that is rotatably supported by the stationary member via bearing means, and a rotor magnet is attached to the rotor. A stator is mounted on the stationary member so as to face the rotor. A centering member is attached to the rotor so as to rotate integrally therewith, and the recording medium is centered by the centering member and attached to the rotor.
[0003]
In such a motor, an oil-impregnated sleeve bearing formed of a porous metal and retaining lubricating oil is generally used as a bearing means in order to reduce the cost. However, the oil-impregnated sleeve bearing is in contact with the rotor. Since the surface is used as a sliding surface, the rotor is axially supported without being fixed to the stationary member. For this reason, the rotor vibrates in the axial direction due to the action of levitation force or the like during rotation, but such vibration causes a read / write error to the recording medium. Therefore, the magnetic center of the rotor magnet and the magnetic center of the stator are slightly shifted in the axial direction, and the rotor is magnetically biased by the magnetic attractive force acting between the rotor magnet and the stator. This is used to suppress the vibration of the rotor and the recording medium.
[0004]
[Problems to be solved by the invention]
In recent years, with an increase in the rotational speed of a recording medium, the vibration in the axial direction of the rotor and the recording medium generated during the rotation has also increased. When the vibration becomes large in this way, it is necessary to increase the bias force for suppressing the vibration. As one of the means, a material having excellent magnetic characteristics, currently a rare earth magnet (for example, Nd-Fe-B magnet) Can be considered.
[0005]
However, when a rare earth magnet is used, the magnet material itself is expensive, so the price of the magnet is high, and the use of such a magnet leads to an increase in the cost of the motor, and sufficiently corresponds to the recent trend of lower prices. I can't. Such a problem also exists in motors for driving other recording media (CD, MO, DVD, etc.) other than the CD-ROM driving motor, and also in general DC motors. An object of the present invention is to provide a motor capable of imparting a desired magnetic biasing force in Russia over data. A further object of the present invention is to provide a motor that is inexpensive to manufacture.
[0006]
[Means for Solving the Problems]
The present invention relates to a stationary member, a rotor that is rotatable with respect to the stationary member, bearing means interposed between the stationary member and the rotor, a rotor magnet mounted on the rotor, and the rotor In the motor comprising a stator mounted on the stationary member so as to face the magnet, the rotor includes a cup-shaped rotor body made of a magnetic material having a peripheral side wall and an end wall provided at one end of the peripheral side wall. The rotor magnet is attached to the inner peripheral surface of the peripheral side wall of the rotor body in a ring shape, and the stationary member has a base housing and one end mounted on the base housing. A cylindrical support sleeve wall in which bearing means is disposed, and the rotor includes a rotating shaft attached to a substantially central portion of the end wall, and the rotating shaft is supported by the bearing hand. A magnetic biasing magnet that is rotatably supported by the support sleeve wall via the shaft and faces the end wall of the rotor body and magnetically biases the rotor in the axial direction is made of a magnetic material. The holder has a small-diameter mounting portion, a large-diameter portion, and a connection support portion for connecting them, and the small-diameter mounting portion is attached to the other end of the support sleeve wall. The magnetic biasing means is mounted.
[0007]
According to the present invention, the magnetic urging means includes a magnetic urging magnet fixed to an annular holder made of a magnetic material, and the holder attached to the other end of the support sleeve wall. Therefore, the magnet can be arranged close to the rotor body, and a large magnetic biasing force in the axial direction can be obtained even with a relatively small magnet or even if the magnetic characteristics are not very excellent.
In the present invention, the rotor magnet is formed of a ferrite sheet-like rubber magnet.
[0008]
According to the present invention, since the rotor magnet is formed of a ferrite-based magnet, the manufacturing cost can be further reduced while securing desired magnetic characteristics in relation to the magnet.
In the present invention, the magnetic urging means includes a ferrite sintered magnet. Therefore , the manufacturing cost can be reduced even in relation to the magnet that applies the magnetic biasing force. In addition, sintered magnets with high dimensional accuracy, especially surface accuracy, can be easily manufactured. By increasing the surface accuracy of the attraction surface of the ferrite-based sintered magnet facing the rotor body, magnetic energization can be achieved. Magnetic undulation occurs between the means and the rotor body, which can more effectively suppress the vibration of the rotor. Such a configuration can be applied to a drive motor such as a CD, CD-ROM, MO, and DVD, and a motor such as a general DC motor.
[0009]
Further, in the present invention, before Symbol rotor includes a rotary shaft which is mounted in a substantially central portion of said end wall, said rotary shaft is rotatably supported to the support sleeve wall via the bearing means Tei Rukoto It is characterized by.
[0010]
Further, in the present invention, the ferrite sintered magnet is characterized in that it is single-pole magnetized in the axial direction.
[0011]
According to the present invention, since the ferrite-based sintered magnet is unipolarly magnetized in the axial direction, the magnetic force in the circumferential direction of the sintered magnet is substantially uniform, and the magnetic biasing force in the circumferential direction is made constant. Can do. Further, since it is unipolar magnetization, no eddy current is generated at the time of rotation, so that iron loss is small and the driving current of the motor can be reduced.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a motor according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of a motor according to the present invention. In the following embodiments, a CD-ROM as a recording medium is applied to a motor for rotationally driving, but the present invention can also be applied to other various motors.
[0013]
Referring to FIG. 1, the illustrated motor includes a stationary member 2 and a rotor 4 that is rotatable relative to the stationary member 2, and bearing means 6 is disposed between the stationary member 2 and the rotor 4. Has been. The stationary member 2 includes a base housing 8 having a circular plate shape. A circular opening is formed in a substantially central portion of the base housing 8, and one end portion (base side end portion) of the support sleeve member 10 functioning as a support sleeve wall is fixed to the opening by means such as caulking, for example. The other end side of the support sleeve wall 10 extends substantially vertically upward from the base housing 8. The support sleeve member 10 can be formed integrally with the base housing 8.
[0014]
The rotor 4 includes a rotor body 14, and a rotating shaft 16 of the rotor body 14 is rotatably supported on the support sleeve wall 10 via a bearing means 6. In this embodiment, the bearing means 6 is composed of a combination of a radial sleeve bearing 18 and a thrust bearing piece 20. The radial sleeve bearing 18 is composed of an oil-impregnated sleeve bearing which is porous and contains lubricating oil inside. The radial sleeve bearing 18 is mounted on the inner peripheral surface of the support sleeve member 10 and supports the radial load acting on the rotary shaft 16 by contacting the outer peripheral surface of the rotary shaft 16. The thrust bearing piece 20 is composed of a synthetic resin (or ceramic) bearing piece that is highly wear resistant and slippery. A closing cap 22 is fixed to one end of the support sleeve member 10 by means such as caulking, and a thrust bearing piece 20 is mounted on the inner surface side of the closing cap 22. This thrust bearing piece 20 supports a load in the thrust direction that acts on the rotating shaft 16 by contacting one end surface of the rotating shaft 16 (a tip surface protruding in an arc shape). In this embodiment, a combination of a radial sleeve bearing 18 and a thrust bearing piece 20 is used as the bearing means 6, but instead of such a configuration, a radial fluid dynamic pressure bearing and a thrust that support the rotor in a non-contact manner are used. A combination with a fluid dynamic bearing can also be employed.
[0015]
The rotor body 14 is formed of a magnetic material such as iron, and has a cylindrical peripheral side wall 24 and an end wall 26 provided at one end (upper end in FIG. 1) of the peripheral side wall 24. It is a cup shape with the lower end surface in FIG. An inner annular protrusion 28 that protrudes inward in the axial direction (vertical direction in FIG. 1) is provided at the center of the end wall 26, and this inner annular protrusion 28 is the other end (the upper end in FIG. 1). The rotary shaft 16 is driven to rotate integrally with the rotor body 14 by means such as press fitting.
[0016]
An annular rotor magnet 30 is mounted on the inner peripheral surface of the peripheral side wall 24 of the rotor main body 14, and a stator 32 is disposed on the radially inner side so as to face the rotor magnet 30. The stator 32 includes a stator core 34 formed by stacking a plurality of core plates and a coil 36 wound around the stator core 34 as required. The stator core 34 is attached to the outer peripheral surface of the support sleeve member 10. Has been. The rotor magnet 30 and the configuration related thereto will be described in detail later.
[0017]
In this embodiment, as shown in FIG. 1, the rotor magnet 30 and the stator 32 are arranged in a lower space in the rotor body 14, and a balance means 37 and a magnetic biasing means 35 are arranged in the upper space in the rotor body 14. The magnetic biasing means 35 includes a ferrite sintered magnet 38. The balance means 37 includes a ring-shaped case main body 40 that is open at the bottom, and the case main body 40 is attached to the corners of the peripheral side wall 24 and the end wall 26 of the rotor main body 14, and Has been placed. A cover 42 is attached to the opening of the case body 40 so as to cover it, and a plurality of steel balls 44 as a balance body are movably disposed in an annular movement space defined by the case body 40 and the cover 42. It is installed. In such a balance means 37, when the rotor 4 rotates and exceeds the critical speed, that is, when the vibration generated by the rotational vibration of the balance body exceeds the predetermined speed at which the primary vibration frequency of the motor resonates, the balance body moves in the moving space. In this case, the weight unbalance during the high-speed rotation of the rotor 4 is eliminated.
[0018]
In relation to the balancing means 37, the lower surface of the cover 42 and the upper end surface of the rotor magnet 30 are in contact with each other. With this configuration, the axial positioning of the rotor magnet 30 with respect to the stator 32 can be accurately performed. In addition, the adhesive can be omitted when the case body 40 and the cover 42 are joined. Further, since the case main body 40 of the balancing means 37 and the cover 42 attached thereto define a substantially closed annular moving space, even if the lubricating oil or the like scatters from the radial sleeve bearing 18, the scattered lubricating oil or the like Can be prevented from flowing into the annular movement space, and the correction accuracy of the weight imbalance can be maintained with high accuracy.
[0019]
On the other hand, the ferrite-based sintered magnet 38 of the magnetism imparting means 35 is disposed on the inner peripheral portion of the upper space. In this embodiment, the magnetism imparting means 35 further includes an annular holder 46, and this holder 46 is attached to the other end portion (tip portion) of the support sleeve member 10. The holder 46 is made of a magnetic material such as iron, and has a small diameter mounting portion 48 provided on the lower end side, a large diameter portion 50 provided on the upper end side, and a connection for connecting the small diameter mounting portion 48 and the large diameter portion 50. The small-diameter mounting portion 48 is attached to the outer peripheral surface of the support sleeve member 10. In this embodiment, the sintered magnet 38 is formed of a ring-shaped magnet, and is formed on the upper surface of the connection support portion 52 inside the large diameter portion 50 (that is, on the surface facing the end wall 26 of the rotor body 14). It is attached. With this configuration, the sintered magnet 38 can be disposed close to the inside of the end wall 26 of the rotor body 14, and the magnet 38 can be attached with magnetism in the axial direction (vertical direction in FIG. 1). The power can be increased.
[0020]
By configuring the magnet of the magnetic biasing means 35 from the ferrite sintered magnet 38, the following effects can be obtained. Ferrite magnets are generally low in manufacturing cost. Therefore, by forming from such a material, the magnet of the magnetic biasing means 35 can be manufactured at low cost, and the manufacturing cost of the motor can be reduced. Can do. Moreover, a sintered magnet can generally be formed relatively easily with high accuracy, and high surface accuracy can be obtained. If the surface accuracy of the end face of the magnet of the magnetic biasing means 35 facing the end wall 26 of the rotor body 14 is poor, the distance between the end face 26 of the magnet and the end wall 26 becomes non-uniform, and magnetism occurs when the rotor 4 rotates. This causes a waviness and causes the rotor 4 to run out. On the other hand, when formed from the sintered magnet 38, the gap between the end face of the magnet 38 and the end wall 26 of the rotor body 14 is substantially uniform, thereby hardly causing the magnetic swell as described above. The rotor 4 can be rotated stably.
[0021]
It is desirable that the ferrite-based sintered magnet 38 is monopolarly magnetized in the axial direction (vertical direction in FIG. 1). That is, one end portion (upper end portion in FIG. 1) of the sintered magnet 38 is, for example, an N pole (or S pole), and the other end portion (lower end portion in FIG. 1) is an S pole (or N pole). It is desirable to magnetize. By magnetizing this good cormorants can circumferential direction of the magnetic force of the ferrite sintered magnet 38 becomes substantially uniform, to impart a uniform magnetic biasing force in the circumferential direction in the rotor body 14. Further, by unipolar magnetization, the rotor body 14 is driven to rotate in a predetermined direction so that no current is generated. Therefore, the iron loss is small and the motor drive current, that is, the current supplied to the coil 36 is small. However, a large driving torque can be obtained, thereby reducing the power consumption of the motor.
[0022]
In this embodiment, the ferrite-based sintered magnet 38 is formed from a single ring-shaped magnet. However, it is not always necessary to form the ferrite-based sintered magnet 38 in this manner. may also be a ring-shaped, also in this case, each segment of the ferrite sintered magnet is desirable to unipolar magnetized in the axial direction.
[0023]
The other end portion (upper end portion) of the rotating shaft 16 penetrates the end wall 26 of the rotor body 14 and protrudes outward, and a centering means 56 is attached to the protruding end portion. The centering means 56 includes a centering member 58 having a tip formed in a tapered shape. An annular recess is provided on the front end surface of the centering member 58, and a ring-shaped attracting magnet 60 is mounted in the annular recess. Further, an elastic holding portion 62 that extends toward the end wall 26 of the rotor body 14 is provided on the outer peripheral portion of the centering member 58. Further, a ring-shaped support member 64 made of, for example, elastic rubber is attached to the outer peripheral portion of the end wall 26 of the rotor body 14.
[0024]
Although not shown, a CD-ROM as a recording medium is detachably mounted on this motor. A circular opening is formed in the center of the CD-ROM, and the centering means 56 is positioned in the circular opening, whereby the CD-ROM to be mounted is centered. The centered CD-ROM is placed on a support member 64, the inner periphery thereof is elastically held by an elastic holding portion 62, and a clamp member (not shown) is magnetically attracted to the attracting magnet 60. As a result, the clamp member is clamped between the end wall 26 of the rotor body 14 and the rotor body 14 is driven to rotate integrally.
[0025]
In such a motor, when a drive current is supplied to the coil 36, the stator core 34 is magnetized, and the rotor 4 and a CD-ROM (not shown) attached to the rotor 4 are mounted by the mutual magnetic action between the stator core 34 and the rotor magnet 30. It is rotationally driven in a predetermined direction. At this time, since the ferrite-based sintered magnet 38 is positioned to face the end wall 26 of the rotor body 14, the sintered magnet 38 magnetically attracts the end wall 26, and this attracting force causes the rotor body 14 to attract to the rotor body 14. A magnetic urging force is applied downward in the axial direction, and the magnetic urging force suppresses the occurrence of vibration, chatter, and the like of the rotor 4 in the vertical direction.
[0026]
Next, the rotor magnet 30 and the related configuration will be described. It is important to form the rotor magnet 30 from a sheet-like rubber magnet. The sheet-like rubber magnet is generally low in manufacturing cost. Therefore, by forming from such a magnet, the rotor magnet 30 can be manufactured at low cost, and the manufacturing cost of the motor can be reduced. The rotor magnet 30 is preferably formed from a ferrite rubber magnet. By configuring in this way, the manufacturing cost can be further reduced, and the cost of the motor can be further reduced.
[0027]
Alternately sheet rubber magnet is mounted have use, for example, adhesive such that the ring on the inner peripheral surface of the peripheral side wall 24 of the rotor body 14, after attachment in this manner, the N and S poles circumferentially The rotor magnet 30 is formed in this way.
[0028]
In such a motor, since the sintered magnet 38 for applying a magnetic biasing force is provided, the magnetic center in the axial direction of the rotor magnet 30 and the magnetic center in the axial direction of the stator 32 are shifted in the axial direction. However, in order to obtain a larger magnetic urging force in the axial direction, the above-mentioned axial centers may be somewhat shifted from each other in the axial direction.
[0029]
Although one embodiment of the motor according to the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and corrections can be made without departing from the scope of the present invention.
[0030]
【The invention's effect】
According to the motor of the first aspect of the present invention, the magnetic urging means can be arranged close to the rotor body, and even if it is a relatively small magnet or a magnetic characteristic is not very excellent, a large magnetism can be obtained. A biasing force can be obtained.
[0031]
According to the motor of the second aspect of the present invention, it is possible to further reduce the manufacturing cost while ensuring desired magnetic characteristics in relation to the rotor magnet.
[0032]
Further, according to the motor of the third aspect of the present invention, the manufacturing cost can be reduced even in connection with the magnet of the magnetic biasing means. Furthermore, by forming the magnet of the magnetic biasing means from a sintered magnet, the surface accuracy can be increased and the vibration of the rotor can be suppressed more effectively.
[0033]
Furthermore, according to the motor of the fourth aspect of the present invention, the magnetic biasing force in the circumferential direction can be made substantially uniform, and the rotor can be driven to rotate stably. Further, no eddy current is generated during rotation, and the motor drive current can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a motor according to the present invention.
[Explanation of symbols]
2 Static member 4 Rotor 6 Bearing means 8 Base housing 10 Support sleeve member 14 Rotor body 16 Rotating shaft 24 Peripheral side wall 26 End wall 30 Rotor magnet 32 Stator 35 Magnetic biasing means 37 Balance means 38 Ferrite sintered magnet 46 Holder 56 Centering means

Claims (5)

A stationary member, a rotor rotatable with respect to the stationary member, bearing means interposed between the stationary member and the rotor, a rotor magnet mounted on the rotor, and the rotor magnet facing the rotor magnet. A motor having a stator attached to the stationary member.
The rotor includes a cup-shaped rotor body made of a magnetic material having a peripheral side wall and an end wall provided at one end of the peripheral side wall,
The rotor magnet is attached to the inner peripheral surface of the peripheral side wall of the rotor body in a ring shape,
The stationary member includes a base housing, and a cylindrical support sleeve wall having one end mounted on the base housing and bearing means disposed on the inner periphery.
The rotor includes a rotation shaft attached to a substantially central portion of the end wall, and the rotation shaft is rotatably supported by the support sleeve wall via the bearing means,
The rotor faces the end wall of the body, the magnetic biasing magnet for magnetically biasing the axial direction with respect to the rotor, is fixed to an annular holder made of a magnetic material, the holder is small mounting portion and the large A motor comprising a magnetic biasing means having a diameter part and a connection support part for connecting them, wherein the small diameter attachment part is attached to the other end of the support sleeve wall .   The motor according to claim 1, wherein the rotor magnet is formed of a ferrite-based sheet-like rubber magnet.   The motor according to claim 1, wherein the magnetic biasing magnet is formed of a ferrite-based sintered magnet.   2. The rotor according to claim 1, wherein the rotor includes a rotating shaft attached to a substantially central portion of the end wall, and the rotating shaft is rotatably supported by the support sleeve wall via the bearing means. The motor in any one of -3.   The motor according to claim 1, wherein the ferrite-based sintered magnet is single-pole magnetized in the axial direction.

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