JPH09250543A - Bearing device, motor and scanner motor for driving polygon mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the bearing device which can be favorably used in a wide range from the low speed up to the high speed, and does not require any control for floating. SOLUTION: A cylindrical outer magnet 27 is provided for a housing 21 at the stationary side via a cylindrical yoke 26, a cylindrical inner magnet 36 is provided for a shaft. 34 at the rotating side, and the inner magnet 36 is so disposed as to be inserted into the inside of the outer side magnet 27. A bearing gap 37 is formed in the radial direction between the outer side magnet 27 and the inner side magnet 36. The flux of the outer side magnet 27 and the flux of the inner side magnet 36 pass through the bearing gap 37 in the idential direction, its flux density is thereby increased within the bearing gap 37, concurrently both the magnets repulse each other, and a magnetic action thereby causes the uniform bearing gap 37 to be formed along the entire circumference of a space between the outer side magnet 27 and the inner side magnet 36. As a result, the shaft 34 can be floated in the radial direction regardless of times when the shaft 34 is in operation and out of operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device having improved bearing means in the radial direction, a motor provided with the bearing device, and a scanner motor for driving a polygon mirror.

[0002]

FIG. 10 shows a conventional structure in which a motor having a dynamic pressure air bearing as a radial direction bearing means is applied to a polygon mirror driving scanner motor used for laser scanning of a laser beam printer. Will be described with reference to.

The fixed-side housing 1 has a plurality of recessed portions on the upper surface side and a cylindrical portion 2 at the bottom of the central portion, and the cylindrical portion 2 has a cylindrical bearing cylinder 3 made of ceramic. Is inserted and fixed by adhesion, and the bottom cover 4 is screwed to the bottom of the tubular portion 2. A cover 5 is screwed onto the upper surface of the housing 1 so as to cover the bearing cylinder 3, and the housing 1 and the cover 5 form a hermetically sealed motor case 6. This motor case 6
Inside, a wiring board 7 is screwed to the upper part of the housing 1, and a plurality of stator coils 8 are adhesively fixed to the upper surface of the wiring board 7.

Inside the motor case 6, a rotor 10 having a rotating shaft 9 made of stainless steel is arranged. The rotating shaft 9 has two sets of upper and lower herringbone-shaped grooves 11a forming a part of the dynamic pressure air bearing 11 formed on the outer peripheral surface thereof, and is rotatably inserted and supported in the bearing cylinder 3. The rotary shaft 9 and the bearing sleeve 3 form a dynamic pressure air bearing 11 using air as gas.

A mirror mounting member 12 is mounted and fixed on the upper portion of the rotary shaft 9, and a rotor yoke 13 is bonded and fixed to the lower surface of the mirror mounting member 12. An annular rotor magnet 14 is adhered and fixed to the lower surface of the rotor yoke 13, and the rotor magnet 14 is arranged so as to face the stator coil 8 from above with a predetermined gap in the axial direction. A polygon mirror 15 is attached to the outer peripheral portion of the mirror attachment member 12 via a mirror retainer 16. In the cover 5, an opening 5a through which laser light enters and exits is formed at one location corresponding to the outer peripheral portion of the polygon mirror 15,
A translucent member 5b made of glass capable of entering and exiting laser light is attached to the opening 5a.

An attachment member 17 is attached and fixed to the lower portion of the mirror attachment member 12 so as to rotate integrally with the rotary shaft 9. The mounting member 17 penetrates through the wiring board 7 so as to surround the bearing cylinder 3 from above, and the rotating yoke 17
a is mounted below the wiring board 7 and has an annular rotor-side magnetic levitation magnet 18a.
Is attached. Further, on the housing 1 side, so as to surround the rotor-side magnetic levitation magnet 18a,
The annular stator-side magnetic levitation magnet 18b is fixed, and the thrust load of the rotor 10 is received by using the magnetic repulsive force of the rotor-side magnetic levitation magnet 18a and the stator-side magnetic levitation magnet 18b. ing.

In the above structure, however, the rotor 10
When is driven to rotate, due to the action of the herringbone-shaped groove portion 11a, air is drawn into the bearing gap 19 of several μm between the inner peripheral surface of the bearing tube 3 and the outer peripheral surface of the rotating shaft 9 to move the high pressure fluid. Pressure is generated, and by the action of the dynamic pressure air bearing 11, the rotating shaft 9 is rotated in a non-contact state with respect to the bearing sleeve 3, and the rotating shaft 9
The polygon mirror 15 is also rotated integrally with this. A motor using such a dynamic pressure air bearing 11 is suitable for high speed rotation.

By the way, the dynamic pressure air bearing 11 having the above-mentioned structure and the conventional general ball bearings have the following problems. With a bearing that uses a ball bearing, the maximum speed that can be obtained is 2
It is up to 5000 rpm, and no higher speed rotation can be obtained. In addition, higher speed rotation (30000)
In the motor using the dynamic pressure air bearing 11 as described above, which has been developed for obtaining a bearing gap 19 and a herringbone-shaped groove portion 11a,
The design is made according to the number of revolutions used, and at a number of revolutions lower than the set proper number of revolutions, the rotary shaft 19 does not completely float (in the radial direction) and becomes a plain bearing state. On the contrary, at a rotational speed higher than the appropriate rotational speed, an excessive load capacity is generated and increases, resulting in an increase in power consumption of the motor, a rise in motor temperature, vibration, noise, etc. This will deteriorate the characteristics of the motor. Furthermore, the dynamic pressure air bearing 11 requires high-precision machining, which increases the cost.

On the other hand, a magnetic bearing using an electromagnet is known as a bearing for supporting the rotating shaft in a non-contact state. This magnetic bearing has a plurality of electromagnets arranged around the rotating shaft,
The rotating shaft is supported (flying) in the radial direction in a non-contact state by the magnetic attraction force of these electromagnets. However, in a magnetic bearing using such an electromagnet, it is necessary to detect the eccentricity of the rotating shaft and control the attraction force of each electromagnet based on this.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is that it can be satisfactorily used in a wide rotation range from low speed to high speed, and machining with such high accuracy is possible. (EN) It is possible to provide a bearing device that does not require any control for levitation and a motor including the bearing device and a scanner motor for driving a polygon mirror.

[0011]

In order to achieve the above object, the invention of claim 1 is provided with a shaft-shaped member, a peripheral member arranged around the shaft-shaped member, and the peripheral member. , A cylindrical outer magnet for a bearing magnetized so as to have different magnetic poles at both ends in the axial direction, and the axial magnet provided on the shaft-shaped member and having a length substantially equal to the axial length of the outer magnet. In addition, it is magnetized to have different magnetic poles at both ends in the axial direction, the outer peripheral surface forms a bearing gap in the radial direction with the inner peripheral surface of the outer magnet, and the direction of the magnetic pole is the same as that of the outer magnet. And an inner magnet for a bearing arranged such that the positions of both ends in the axial direction are substantially the same as the outer magnet, and one of the peripheral member and the shaft-shaped member is fixed to the other, Is set to the rotation side.

According to this structure, the magnetic flux of the outer magnet provided on the peripheral member and the magnetic flux of the inner magnet provided on the shaft-shaped member pass through the bearing gap between them in the same direction, and the bearing gap is generated. The magnetic flux density in the inside is increased and both magnets repel each other, and this magnetic action forms a uniform bearing gap between the outer magnet and the inner magnet over the entire circumference. As a result, the member on the rotation side can be supported (floated) in the non-contact state in the radial direction. Therefore, regardless of whether the member on the rotation side is rotated or stopped, the member can be levitated in a non-contact state at all times, and highly precise machining is not required. Further, both the outer magnet and the inner magnet are permanent magnets and do not require control for levitation.

In order to achieve the same object, a second aspect of the invention is characterized in that a plurality of outer magnets and a plurality of inner magnets are arranged in the axial direction.

According to a third aspect of the present invention, two outer magnets and two inner magnets are arranged in the axial direction, respectively. In this case, the axial positions of the corresponding outer magnets and the inner magnets are relatively displaced, or the relative positions of the outer magnets and the inner magnets are relatively shifted. The feature is that the corresponding outer magnets and inner magnets have different axial lengths.

According to the invention of claim 3, like the invention of claim 1, by the magnetic action of the outer magnet and the inner magnet,
In addition to being able to support (float) the rotating member in a non-contact state in the radial direction, the following action is also obtained. That is, when the member on the rotation side is displaced in the axial direction (thrust direction), a force in a direction to return the member on the rotation side acts due to the magnetic action of the outer magnet and the inner magnet. It is possible to magnetically levitate.

According to a fourth aspect of the present invention, in the third aspect of the present invention, an inner magnet is further provided between the two inner magnets of the shaft-shaped member so that the magnetic poles of the inner magnet and the magnetic poles have the same direction. Alternatively, an outer magnet is further provided between the two outer magnets in the surrounding member so that the outer magnet has the same magnetic pole direction.

According to a fifth aspect of the invention, in order to achieve the same object as the third and fourth aspects, one of the outer magnet and the inner magnet is axially separated from each other, and two of them are arranged, while the other is disposed. It is characterized in that it is located at a position corresponding to the space between the two, and that both ends in the axial direction are located in the vicinity thereof.

The invention of claim 11 is characterized in that, in addition to the magnetic bearing means by a permanent magnet, a dynamic pressure fluid bearing means is provided between the peripheral member and the shaft-like member.

According to a twelfth aspect of the present invention, a bearing device provided with the above-mentioned magnetic bearing means using a permanent magnet is applied to a motor, and the thirteenth aspect of the present invention provides the bearing device. It is characterized by being applied to a scanner motor for driving a polygon mirror.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a scanner motor for driving a polygon mirror used for laser scanning of a laser beam printer will be described below with reference to FIGS. 1 and 2.

First, in FIG. 1 showing the overall structure, a fixed-side housing 21 constitutes a peripheral member of the present invention, and is made of, for example, aluminum, and has three recesses 22a to 22c on the upper surface side. In addition to that, it has a tubular portion 23 at the bottom of the central portion. A bottom lid 24 is attached to the bottom of the tubular portion 23 with screws 25. Tube 2
As shown in FIG. 2, an outer magnet 27 for a bearing, which is a cylindrical permanent magnet, is fixedly provided on the inner side of the magnet 3 through a cylindrical yoke 26 made of a magnetic material. The outer magnet 27 is magnetized so that one end in the axial direction, which is the upper end in the figure, is the N pole, and the other end, the lower end, is the S pole. The cylindrical yoke 26 constitutes a part of a peripheral member together with the housing 21.

A wiring board 28 is attached and fixed to the upper concave portion 22a of the housing 21 with screws 29, and a plurality of stator coils 30 are adhesively fixed to the upper surface of the wiring board 28. An annular stator-side magnetic levitation magnet 31 is fixed to the lower recess 22c of the housing 21, and an annular yoke 32 is fixed to the upper surface of the magnet.

The rotor 33 on the rotating side is provided with a shaft 34 which constitutes a shaft-shaped member. The shaft 34 is made of a magnetic material, for example, stainless steel, and a shaft portion 35, which is thinner than the other portions, is integrally provided in the lower portion. A bearing inner magnet 36 made of a cylindrical permanent magnet is attached to the outer peripheral portion of the shaft portion 35. The outer peripheral surface of the inner magnet 36 and the outer peripheral surface of the shaft 34 are set to be substantially flush with each other. Further, the inner magnet 36 is set to have a length substantially equal to the axial length of the outer magnet 27, and like the outer magnet 27, the upper end portion in the drawing which is one end portion in the axial direction is N.
The lower end in the figure which is the pole and the other end is magnetized to the S pole,
It is rotatably inserted inside the outer magnet 27. In the inserted state, a predetermined bearing gap 37 is formed in the radial direction between the inner peripheral surface of the outer magnet 27 and the outer peripheral surface of the inner magnet 36, and the outer magnet 27 and the inner magnet 36 are The positions of both ends in the axial direction are arranged to be substantially the same.

A mirror mounting member 38 is mounted on the upper portion of the shaft 34, and a rotor yoke 39 is bonded and fixed to the lower surface of the mirror mounting member 38. Rotor yoke 3
An annular rotor magnet 40 is adhered and fixed to the lower surface of the rotor 9, and the rotor magnet 40 is opposed to the stator coil 30 from above with a predetermined gap in the axial direction. A polygon mirror 41 is attached to the outer peripheral portion of the mirror attachment member 38 via a mirror retainer 42.

An attachment member 43 is attached and fixed to the lower portion of the mirror attachment member 38 so as to rotate integrally with the shaft 34. The mounting member 43 penetrates the wiring board 28 so as to surround the cylindrical yoke 26 from above, and the rotary yoke 44 is mounted below the wiring board 28 and is attached to the lower portion of the mounting board 43. A rotor side magnetic levitation magnet 45 is attached. The rotary yoke 44 is a yoke for concentrating the magnetic field, and the magnetic attraction force of the rotor magnet 40 always acts on the rotary yoke 44 to try to attract it.
Since 4 is fixed to the shaft 34 via the mirror mounting member 38 or the mounting member 43, these distances are always maintained constant without change. Therefore, the magnetic attraction force of the rotor magnet 40 can be canceled in the rotor 33, and as a result, the thrust load can be reduced to only the own weight of the rotor 33.

A predetermined gap is formed between the inner peripheral surface of the mounting member 43 and the outer peripheral surface of the cylindrical yoke 26. Also,
The rotor-side magnetic levitation magnet 45 is inserted into the stator-side magnetic levitation magnet 31, and the outer peripheral surface of the rotor-side magnetic levitation magnet 45 and the inner circumference of the stator-side magnetic levitation magnet 31. A predetermined gap is also formed between the surfaces. Rotor side magnetic levitation magnet 45 and stator side magnetic levitation magnet 3
No. 1 is magnetized so that the upper part has an N pole and the lower part has an S pole. The thrust load of the rotor 33 is magnetically repelled by the rotor-side magnetic levitation magnet 45 and the stator-side magnetic levitation magnet 31. It is configured to receive it by using power.

A rotor 33 is provided on the upper surface side of the housing 21.
A cover 46 is attached by screws 47 so as to cover the polygon mirror 41 and the like from above, and the housing 21 and the cover 46 form a hermetically sealed motor case 48. In the cover 46, an opening 49 through which laser light enters and exits is formed at one location corresponding to the outer periphery of the polygon mirror 41, and this opening 49 is made of a glass transparent material through which laser light can enter and exit. The optical member 50 is attached. A substrate 51 having a drive circuit (not shown) is arranged below the housing 21. The substrate 51 is attached and fixed to the housing 21 via a spacer 52 with screws 53. The circuit of the board 51 and the circuit of the wiring board 28 are connected by a connector 54.
Are electrically connected via

Thus, in the above structure, the rotor 33
Is driven to rotate, the polygon mirror 4 is integrated with the shaft 34.
1 is also rotated. At this time, the magnetic flux of the outer magnet 27 on the bearing side passes from the N pole to the S pole through the cylindrical yoke 26 existing on the outer peripheral portion of the outer magnet 27 and the magnetic flux passing through the bearing gap 37 on the inner peripheral side of the outer magnet 27. There are things that can be understood. Further, the magnetic flux of the inner magnet 36 on the shaft 34 side changes from the N pole to the S pole,
Some of them communicate with each other through the shaft portion 35 existing in the inner peripheral portion of the inner magnet 36, and some of them communicate with each other through the bearing gap 37 on the outer peripheral side of the inner magnet 36.

Thus, the outer magnet 27 and the inner magnet 36 are
In the bearing gap 37 between the outer magnet 27 and the inner magnet 37
Both magnetic fluxes pass in the same direction, the magnetic flux density in the bearing gap 37 is increased, and both magnets repel each other. Due to this magnetic action, the outer magnet 27 and the inner magnet 3
A uniform bearing gap 37 is formed between the bearing 6 and the bearing 6. As a result, the shaft 34, which is a member on the rotation side,
Can be supported (float) in a non-contact state in the radial direction. The cylindrical yoke 26 has an outer magnet 27.
Has the effect of preventing the magnetic leakage to other parts, and the effect of preventing the generation of eddy current due to the leakage magnetic flux in the other parts (the parts other than the cylindrical yoke 26).

In this case, the load applied to the rotor 33 in the thrust direction is such that the stator side magnetic levitation magnet 3
1 and the magnetic repulsion force of the magnetic levitation magnet 45 on the rotor side.
Is also flying upward in the axial direction. Therefore, in this embodiment, the shaft 34 of the rotor 33 can be supported without contact in both the radial direction and the thrust direction. In order to regulate the position of the rotor 33 in the thrust direction, a thrust receiver that receives the lower end of the shaft 34 (shaft portion 35) may be provided inside the bottom lid 24.

According to such a first embodiment, the following effects can be obtained. That is, since the bearing means in the radial direction is composed of the fixed outer magnet 27 and the rotating inner magnet 36, there is no loss due to rolling friction in the ball bearing or loss due to viscous resistance of air in the dynamic pressure air bearing. In comparison, the loss that occurs is extremely small, and therefore ultra-high speed rotation can be realized with low power consumption. In addition, the shaft 34 of the rotor 33 is in a state of being levitated in the radial direction regardless of whether it is rotating or stopped, and therefore can be favorably used in a wide rotation range from low speed to high speed.

Further, the outer magnet 27 and the inner magnet 36 do not require high precision machining as in the case of the dynamic pressure air bearing. Moreover, since the outer magnet 27 and the inner magnet 36 are both permanent magnets, unlike the case of a magnetic bearing using an electromagnet, control for levitation is not required, which is inexpensive and can be downsized. In addition, it can be used in a vacuum environment and can be applied to applications other than a scanner motor for driving a polygon mirror.

In the above embodiment, the shaft 34 of the rotor 33 is also levitated in the axial direction by the magnet 31 for magnetic levitation on the stator side and the magnet 45 for magnetic levitation on the rotor side. Can be magnetically levitated in both the radial direction and the thrust direction, and the loss generated in the bearing portion can be made extremely small.

FIG. 3 shows a second embodiment of the present invention. This second embodiment differs from the above-mentioned first embodiment in the following points. That is, two outer magnets 61, 61 each having a cylindrical shape are axially separated from each other on the inner peripheral portion of the cylindrical yoke 26 on the fixed side and are arranged vertically, and between the two outer magnets 61, 61. A cylindrical spacer 62 made of a non-magnetic material is arranged in the. Further, two inner magnets 63, 63 having a cylindrical shape are axially separated from each other on the outer peripheral portion of the shaft portion 35 of the rotation-side shaft 34 in the axial direction, and these two inner magnets 63, 63 are arranged. A non-magnetic cylindrical spacer 64 is disposed between the two. here,
The spacer 62 on the fixed side constitutes a peripheral member together with the housing 21, and the spacer 64 on the shaft 34 side includes the shaft 34.
Together with this, it constitutes a shaft-shaped member.

Each outer magnet 61 is magnetized so that the upper end side which is one end in the axial direction is an N pole and the lower end side which is the other end is an S pole. Each inner magnet 63 has a corresponding outer magnet 61.
Has a length substantially the same as the axial length of the above, and is magnetized to the N pole on the upper end side and the S pole on the lower end side, like the corresponding outer magnets 61, and is rotatable inside each outer magnet 61. Has been inserted into. In the inserted state, a predetermined radial distance is provided between the inner peripheral surface of the outer magnet 61 and the outer peripheral surface of the inner magnet 63, and between the inner peripheral surface of the outer spacer 62 and the outer peripheral surface of the inner spacer 64. The bearing gap 37 is formed, and the corresponding outer magnet 61 and inner magnet 63 are arranged such that the positions of both ends in the axial direction are substantially the same.

In the second embodiment as described above, the radial bearing means is provided at two upper and lower positions in the axial direction. In this case, paying attention to the fact that the magnetic repulsive force in the radial direction by the outer magnet 61 and the inner magnet 63 becomes maximum at the end face of each magnet, and in this second embodiment,
Since the number of end faces in the vertical direction of the outer magnet and the inner magnet is twice that in the first embodiment, there is an advantage that the load capacity in the radial direction can be further increased by that much.

In the second embodiment, the outer magnet and the inner magnet having the same structure as those between the upper and lower outer magnets 61 and 61 and between the upper and lower inner magnets 63 and 63 are used. It is also possible to provide one magnet or a plurality of magnets.

FIG. 4 shows a third embodiment of the present invention. This third embodiment differs from the above-mentioned first and second embodiments in the following points. That is, in the same manner as in the second embodiment, the two outer magnets 61, 61 are axially separated from each other on the inner peripheral portion of the cylindrical yoke 26 on the fixed side, and are vertically arranged. , 61 is provided with a spacer 62 forming a part of the surrounding member. Further, on the outer peripheral portion of the shaft portion 35 of the rotation-side shaft 34, two cylindrical inner magnets 65, 65 are axially spaced apart from each other and arranged vertically, and the two inner magnets 65, 65
Between the two, one cylindrical inner magnet 67 is arranged via a spacer 66 made of a non-magnetic material that constitutes a part of the shaft-shaped member.

In this case, the two inner magnets 65 located above and below are 1 / th of the axial length of the corresponding outer magnets 61.
The length is set to be about 4 short and is rotatably inserted inside each outer magnet 61. The inner magnet 67 located in the middle is set to have a length corresponding to the distance between the two outer magnets 61, 61, and the upper end side which is one end portion in the axial direction is the N pole and the lower end portion which is the other end portion. Side is magnetized to S pole,
It is rotatably inserted inside the spacer 62.

In the inserted state, the inner magnet 65 located on the upper side
Is set such that the upper end of the inner magnet 65 is located at substantially the same height as the upper end of the outer magnet 61 located at the upper part, and the lower end of the inner magnet 65 located at the lower part of the outer magnet 61 located at the lower part. The height is set to be substantially the same as the lower end. In addition, the inner magnet 67 located in the middle
Is set such that the upper end is at substantially the same height as the lower end of the upper outer magnet 61, and the lower end is at substantially the same height as the upper end of the lower outer magnet 61. Is set.

In the first and second embodiments, the stator side magnetic levitation magnet 31 is provided on the stator side and the rotor side magnetic levitation magnet 45 is provided on the rotor side. In the three examples, they are not provided.

In the third embodiment, the shaft 34 is moved by the magnetic action of the two outer magnets 61, 61 and the three inner magnets 65, 65, 67 as in the first and second embodiments. Can be levitated in the radial direction. At the same time, especially in this case, when the shaft 34 moves in the axial direction (up and down direction), the shaft 34 is returned between the outer magnets 61, 61 and the inner magnets 65, 65, 67 in a direction of returning to the original position. Power comes to work. Therefore, in the third embodiment, by these outer magnets 61, 61 and inner magnets 65, 65, 67,
Complete magnetic levitation is possible in both the radial and thrust directions of the shaft 34. As a result, it becomes possible to eliminate the need to separately provide the dedicated stator-side magnetic levitation magnet 31 and rotor-side magnetic levitation magnet 45.

The outer magnet 61 on the side of the cylindrical yoke 26,
61 and spacer 62, and inner magnets 65, 6 on the shaft 34 side
The arrangement configuration of 5, 67 and the spacer 66 may be reversed from that of the third embodiment.

FIG. 5 shows a fourth embodiment of the present invention. This fourth embodiment differs from the above-mentioned third embodiment in the following points. That is, the two cylindrical outer magnets 68 provided on the inner peripheral portion of the stationary-side cylindrical yoke 26,
68 is set such that its axial length is substantially the same as the axial length of the corresponding upper and lower inner magnets 65, 65. Also, these two outer magnets 68, 68
Shifts the axial position with respect to the corresponding upper and lower inner magnets 65, 65 by about ¼ of the axial length.

Specifically, the upper outer magnet 68 has an upper end located below the upper end of the upper inner magnet 65, and a lower end located below and lower than the lower end of the upper inner magnet 65. It is located at substantially the same position as the upper end of the inner magnet 67. The lower outer magnet 68 has a lower end located above the lower end of the lower inner magnet 65, and an upper end located above and above the upper end of the lower inner magnet 65. It is located at substantially the same position as the lower end of 67. Above the upper outer magnet 68 and below the lower outer magnet 68, spacers 69 made of a non-magnetic material are arranged, each of which constitutes a part of the surrounding member. Also in such a fourth embodiment, it is possible to obtain the same effects as those of the third embodiment.

FIG. 6 shows a fifth embodiment of the present invention. This fifth embodiment differs from the third embodiment (see FIG. 4) in the following points. That is, the shaft 34 has two upper and lower
There is no one inner magnet, and one cylindrical inner magnet 70 is arranged at a portion corresponding to between the two outer magnets 61, 61. The inner magnet 70 has a length such that both upper and lower ends thereof partially overlap the upper and lower outer magnets 61, 61. On the upper and lower sides of the inner magnet 70, spacers 71 made of a non-magnetic material and respectively constituting a part of the shaft-shaped member are arranged. In the fifth embodiment, although the load capacity is smaller than that in the third and fourth embodiments, magnetic levitation is possible in both the radial direction and the thrust direction.

FIG. 7 shows a sixth embodiment of the present invention. This sixth embodiment differs from the second embodiment (see FIG. 3) in the following points. That is, the positions of the two outer magnets 61 in the axial direction are displaced with respect to the two inner magnets 63. Specifically, the upper outer magnet 61 is shifted downward with respect to the upper inner magnet 63 so as to partially overlap with the upper inner magnet 63, and the lower outer magnet 61 is moved downward.
It is shifted upward with respect to No. 3 so as to partially overlap it. Along with this, spacers 72, 73 made of a non-magnetic material are arranged between the two outer magnets 61, 61 and on the upper and lower sides, respectively, which form a part of the peripheral member. In the sixth embodiment as well, although the load capacity is smaller than that in the third and fourth embodiments, magnetic levitation is possible in both the radial direction and the thrust direction.

FIG. 8 shows a seventh embodiment of the present invention. This seventh embodiment differs from the third embodiment (see FIG. 4) in the following points. That is, the two outer magnets 61,
61 and a plate member 74 made of a magnetic material are provided at both axial ends of each of the three inner magnets 65, 65, 67. Each of these plate members 74 has a function of converging the magnetic flux of the magnet to this portion, and it becomes possible to obtain a larger load capacity. Further, each plate member 74 has an effect of simultaneously preventing magnetic leakage to other portions and preventing generation of eddy current due to leakage magnetic flux.

Further, in this embodiment, the inner peripheral surfaces of the outer magnets 61 and the spacers 62 on the bearing side, and the inner magnets 65 and 67 and the spacers 6 on the side of the shaft 34 facing the inner peripheral surfaces of the outer magnets 61 and the spacers 6 are opposed.
The outer peripheral surface of 6 is coated with a non-magnetic material having high wear resistance, such as ceramics.

By the way, in this type of bearing device, the rotating shaft 34 is in a non-contact floating state with respect to the outer magnet 61 and the spacer 62 on the bearing side even in the stopped state. , Due to the unstable behavior of the shaft 34,
The inner magnets 65, 67 on the shaft 34 side and the spacer 67 may come into contact with the outer magnet 61 on the bearing side and the spacer 62 to cause a sliding bearing state. When such a state occurs, each member is easily worn. In this respect, the wear of the respective members can be prevented as much as possible by applying a ceramic coating to the surface of each member as in the present embodiment.

Further, instead of the above ceramic coating, solid lubrication such as molybdenum disulfide which is excellent in lubrication antifriction, load resistance, heat resistance, cold resistance, scientific stability, corrosion resistance, non-adhesiveness, etc. The agent may be coated. In this case, the unstable behavior of the shaft 34 at the time of starting the motor can be smoothly stabilized in a short time, and the sliding bearing state can be prevented as much as possible.

FIG. 9 shows an eighth embodiment of the present invention. This eighth embodiment differs from the second embodiment (see FIG. 3) in the following points. That is, on the shaft 34 side, a herringbone-shaped groove portion 75 is formed on the outer peripheral surface of the spacer 64 forming a part of the shaft-shaped member.
And the spacer 62 forming a part of the surrounding member,
The hydrodynamic bearing 76 is configured.

In the case of such an embodiment, in the low speed rotation region from the stopped state, the shaft 34 is levitated in the radial direction by the magnetic bearing by the outer magnet 61 and the inner magnet 63.
In the rated high-speed rotation range, it can be used to levitate by the action of the above-mentioned hydrodynamic bearing 76. Therefore, it becomes possible to rotate more favorably from low speed to high speed.

The present invention is not limited to the above embodiments, but can be modified or expanded as follows. For example, it is possible to adopt a configuration in which the side of the shaft-shaped member to which the inner magnet is attached is the fixed side and the side of the peripheral member to which the outer magnet is attached is the rotating side. Further, the outer magnets and the inner magnets are not limited to a cylindrical one-piece member, and a plurality of magnets divided in the circumferential direction may be arranged in a cylindrical shape. Furthermore, the inner magnet may have a cylindrical shape instead of a cylindrical shape.

Further, the bearing device of the present invention is not limited to the scanner motor for driving the polygon mirror described above, but may be used for a general motor, a generator, a flyhole, or the like.

[0056]

According to the bearing device of the first and second aspects of the present invention, since the radial direction magnetic bearing is constituted by the outer magnet and the inner magnet, each of which is a permanent magnet, a wide rotation range is obtained from low speed to high speed. It has excellent effects that it can be used satisfactorily, and that it does not require highly precise processing and that it does not require control for levitation.

According to the bearing device of the third, fourth, and fifth aspects, magnetic levitation is possible in both the radial direction and the thrust direction. Therefore, in addition to the effects described above, the loss generated in the bearing portion can be further reduced. There are advantages.

According to the bearing device of the sixth aspect, since the cylindrical yoke forms the magnetic path of the outer magnet and at the same time prevents magnetic leakage to other portions, it is possible to prevent generation of eddy current due to leakage magnetic flux. According to the bearing device of the eighth aspect, since the plate member has an action of converging the magnetic flux of the magnet to this portion, it is possible to obtain a larger load capacity. Further, since the plate member prevents magnetic leakage to other portions, it also has an effect of preventing generation of eddy current due to leakage magnetic flux.

According to the bearing device of the ninth aspect, by coating a non-magnetic material having high wear resistance, wear of the coated member can be prevented as much as possible. Further, according to the bearing device of the tenth aspect, by coating with a solid lubricant such as molybdenum disulfide, it is possible to prevent the sliding bearing state as much as possible. According to the bearing device of the eleventh aspect, by providing the dynamic pressure fluid bearing means, it becomes possible to rotate the member on the rotating side from low speed to high speed more favorably.

According to the motor of claim 12, by using the bearing device as described above, from low speed to high speed,
It can be used well in a wide rotation range. Claim 1
According to the polygon mirror driving scanner motor of No. 3, it is possible to perform high-precision and high-performance scanning for a long period of time by using the bearing device as described above.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 5 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1 showing a fifth embodiment of the present invention.

FIG. 7 is a diagram corresponding to FIG. 1 showing a sixth embodiment of the present invention.

FIG. 8 is a view corresponding to FIG. 1 showing a seventh embodiment of the present invention.

FIG. 9 is a view corresponding to FIG. 1 showing an eighth embodiment of the present invention.

FIG. 10 is a diagram corresponding to FIG. 1 showing a conventional configuration.

[Explanation of symbols]

Reference numeral 21 is a housing (surrounding member), 26 is a cylindrical yoke (surrounding member), 27 is an outer magnet, 33 is a rotor, 34 is a shaft (axial member), 35 is a shaft portion, 36 is an inner magnet, 37 is a bearing gap, 41 is a polygon mirror, 61 is an outer magnet, 62
Is a spacer (surrounding member), 63 is an inner magnet, 64 is a spacer (axial member), 65 and 67 are inner magnets, 66 is a spacer (axial member), 68 is an outer magnet, 69 is a spacer (surrounding member), 70 is an inner magnet, 71 is a spacer (axial member), 72 and 73 are spacers (surrounding members), 74 is a plate member, 75 is a groove, and 76 is a hydrodynamic bearing.

Claims (13)

[Claims] 1. A shaft-shaped member, a peripheral member arranged around the shaft-shaped member, and a cylindrical member provided on the peripheral member and magnetized to have different magnetic poles at both ends in the axial direction. And an outer magnet for a bearing, which is provided on the shaft-shaped member, has a length substantially the same as the axial length of the outer magnet, and is magnetized to have different magnetic poles at both ends in the axial direction. The surface forms a bearing gap with the inner peripheral surface of the outer magnet in the radial direction, the direction of the magnetic pole is the same as that of the outer magnet, and the positions of both axial ends are almost the same as the outer magnet. And a bearing inner magnet disposed on the other side, wherein one of the peripheral member and the shaft-shaped member is set on a fixed side and the other is set on a rotating side. 2. A shaft-shaped member, a peripheral member disposed around the shaft-shaped member, and a peripheral member provided in the peripheral member so as to be separated from each other in the axial direction. And a plurality of cylindrical outer magnets for bearings that are magnetized as described above, and are provided in the axial member in a state of being separated from each other in the axial direction, and have substantially the same axial length as the corresponding outer magnets. The length of the magnetic pole is magnetized so that the magnetic poles have different lengths at both ends in the axial direction, and the outer peripheral surface forms a bearing gap in the radial direction between the outer peripheral surface and the inner peripheral surface of the corresponding outer magnet. A plurality of bearing inner magnets that are arranged such that the directions of the two are the same as the corresponding outer magnets, and the positions of both ends in the axial direction are substantially the same as the corresponding outer magnets. One of the peripheral member and the shaft-shaped member is fixed, the other is Bearing device is characterized in that setting the rotation side. 3. A shaft-shaped member, a peripheral member arranged around the shaft-shaped member, and a peripheral member provided in the peripheral member so as to be separated from each other in the axial direction. And two outer magnets for a cylindrical bearing that are magnetized as described above, and the shaft-shaped member are provided in a state of being separated from each other in the axial direction, and are magnetized to have different magnetic poles at both ends in the axial direction. Two magnets that are magnetized to form a bearing gap in the radial direction between the outer peripheral surface and the inner peripheral surface of the corresponding outer magnet, and that the orientation of the magnetic poles is the same as that of the corresponding outer magnet. The inner magnet for the bearing of, the axial position of the corresponding outer magnet and the inner magnet is relatively displaced, or the axial length of the corresponding outer magnet and the inner magnet are different, One of the peripheral member and the shaft-like member is fixed, the other is Bearing device is characterized in that set in rotation side. 4. An inner magnet is further provided between two inner magnets of the shaft-shaped member so that the magnetic poles of the inner magnet and the inner magnet have the same orientation, or two of the inner magnets of the surrounding member.
4. The bearing device according to claim 3, wherein an outer magnet is further provided between the outer magnets so that the magnetic poles of the outer magnet have the same direction. 5. A shaft-shaped member, a peripheral member arranged around the shaft-shaped member, and a cylindrical member provided on the peripheral member and magnetized to have different magnetic poles at both ends in the axial direction. The outer magnet for the bearing is formed on the shaft-shaped member, and is magnetized to have different magnetic poles at both ends in the axial direction, and the outer peripheral surface is radially supported between the outer peripheral surface and the inner peripheral surface of the outer magnet. An inner magnet for a bearing which is arranged such that a gap is formed and the direction of the magnetic pole is the same as that of the outer magnet, and one of the outer magnet and the inner magnet is axially separated from each other to form two magnets. While arranging, the other is positioned at a corresponding portion between them, and arranged so that both axial end portions are positioned in the vicinity thereof, and one of the peripheral member and the shaft-shaped member is fixed side, A bearing device characterized in that the other side is set on the rotation side. 6. The bearing device according to claim 1, wherein the peripheral member includes a cylindrical yoke made of a magnetic material on an outer peripheral portion of the outer magnet. 7. The shaft-shaped member is provided with a shaft portion made of a magnetic material and extending in the axial direction at the center of the inner magnet. Bearing device. 8. The bearing device according to claim 1, wherein a plate member made of a magnetic material is provided at axial ends of the outer magnet and the inner magnet. 9. The non-magnetic material having high wear resistance is coated on one or both of the inner peripheral surface of the outer magnet and the outer peripheral surface of the inner magnet.
The bearing device according to any one of 3 and 5. 10. A solid lubricant such as molybdenum disulfide is coated on one or both of the inner peripheral surface of the outer magnet and the outer peripheral surface of the inner magnet. The bearing device according to any one of 1. 11. A hydrodynamic bearing means is provided between the peripheral member and the shaft-shaped member.
The bearing device according to any one of 3 and 5. 12. A motor comprising the bearing device according to any one of claims 1 to 11. 13. A scanner motor for driving a polygon mirror, comprising the bearing device according to any one of claims 1 to 11, and a polygon mirror provided on a rotating member.