JPH08114229A - Bearing device - Google Patents

Abstract

PURPOSE: To provide a bearing device with small rotation resistance and without a shaft being caught in a bearing, which can reduce the requirment of magnetic lubricating fluid at the assembly time of a bearing device. CONSTITUTION: A bearing device is provided with a shaft 2 on which a pair of large diameter shaft parts 2a, 2a are formed and a pair of bearings 10, 10 on which a pair of large diameter shaft parts 2a, 2a are supported respectively. The shaft 2 and a pair of bearings 10, 10 are formed together by a magnetic substance. A magnet 13 for a magnetic bearing magnetized in an axial direction is arranged between a pair of bearings 10, 10 and a magnetic circuit is formed between the shaft 2 and the magnet. An non-magnetic member 14 having an outer diameter nearly equal to the outer diameters of the large diameter shaft parts 2a, 2a across a pair of large diameter shaft parts 2a, 2a is installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device, and in particular,
The present invention relates to a bearing device that has the functions of a dynamic pressure bearing that supports a radial load and a magnetic bearing that supports a thrust load.

[0002]

2. Description of the Related Art Some conventional bearing devices support a thrust load acting on a shaft by a magnetic attraction force of a magnet for a magnetic bearing. FIG. 4 shows a polygon mirror motor as an example of using the bearing device. The polygon mirror motor is used for rotationally driving a polygon mirror used in a laser printer or the like. The polygon mirror reflects a light beam, such as a laser beam, which transmits image information emitted from a light source, on a large number of reflecting mirror surfaces in the shape of a polygonal column, and scans the surface of a photosensitive drum or the like with the rotation of the reflecting mirror surface. It is used to form a latent image.

In FIG. 4, a polygon mirror (not shown) is attached to the upper end of the shaft 2 so as to rotate together with the shaft 2 which is rotatably supported by upper and lower bearings 10 and 10. Further, a flange 16 is fixed to the shaft 2, a motor driving magnet 3 is fixed to the flange 16, and a plurality of magnetized portions (not shown) are formed on the peripheral portion of the motor driving magnet. Has been done.

The housing 1 is provided with a laminated core 4 formed of laminated iron plates or the like. The laminated core 4
Has a general tooth structure, and a plurality of driving coils 5 are wound around the tooth portion. Laminated core 4
Is arranged such that its peripheral portion faces the magnetized portion of the motor driving magnet 3. A circuit board 6 on which a drive control circuit (not shown) is mounted for rotatively driving the polygon mirror motor is arranged on the housing 1.
Further, on the circuit board 6, in order to detect the rotational position of the motor driving magnet 3, a position detecting element 7 formed of a Hall element or the like is provided.

On the other hand, the bearing 10 is formed of a magnetic material in an annular shape, and is fixed inside the collar 12 mounted in the bearing hole 1a of the housing 1 by means such as adhesion or press-fitting, and is vertically moved. Two are provided at intervals. A magnet 13 for a magnetic bearing is arranged between the upper and lower bearings 10, 10. The magnetic bearing magnet 13 is, for example, formed in a hollow cylindrical shape that concentrically surrounds the shaft 2, is magnetized in the axial direction, and has magnetic poles on both end surfaces. The shaft 2 supported by the upper and lower bearings 10 and 10 is made of a magnetic material similarly to the bearing 10, and has large-diameter shaft portions 2a at two upper and lower positions corresponding to the respective bearings 10.

Further, the large-diameter shaft portions 2a, 2 above and below the shaft 2 are provided.
Between a, a reduced diameter portion 2 having a diameter smaller than that of the large diameter shaft portion 2a.
b is formed. A magnetic lubricating fluid 9 is sealed in a gap between the large diameter shaft portion 2a and the bearing 10 to maintain a lubricated state. The magnetic lubricating fluid 9 is also used for the magnetic bearing magnet 1
3 is also filled in the gap between the reduced diameter portion 2b.
A magnetic circuit is formed between the magnet 13 for the magnetic bearing, the upper and lower bearings 10, and the large-diameter shaft portion 2a facing each of these bearings, and between the large-diameter shaft portion 2a and the bearing 10. The magnetic attraction is working. The magnetic attraction force also holds the magnetic lubricating fluid 9 between the bearing 10 and the large-diameter shaft portion 2a so as not to flow out.

An airflow separator 11 is attached to the upper end of the collar 12 so as to face the lower surface of the flange 16. The air flow separator 11 is an air flow generated on the lower surface of the flange 16 by the rotation of the flange 16, so that the magnetic lubricating fluid 9 between the upper bearing 10 and the large diameter shaft portion 2a is not scattered to the outside. It is provided to shut off the bearing 10 side from. The lower end of the bearing hole 1a of the housing 1 is closed by the bottom plate 8, and the lower end of the shaft 10 is the bottom plate 8.
The upper and lower bearings 10, 1 with a gap between
It is levitated and supported by the magnetic attraction force from 0.

In the polygon mirror motor configured as described above, when a plurality of coils 5 are energized through the drive control circuit formed on the circuit board 6, a drive torque is generated in the motor drive magnet 3 to cause the shaft 2 to move. Is rotated with. When the position detection element 7 detects the rotational position of the magnetic pole of the motor driving magnet 3, the position detection element 7 generates a rotational position detection signal, and the rotational position detection signal is provided on the circuit board 6. It is input to an element of a drive control circuit that does not exist, and current is supplied only to the coil necessary for rotational driving among the plurality of coils 5, so that the motor driving magnet 3 continues to rotate.

The shaft 2 has a large-diameter shaft portion 2a at the start of rotation.
Are supported in fluid contact with the bearing 10 through the magnetic lubricating fluid 9, and are filled between the bearing 10 and the large diameter shaft portion 2a as the rotation speed of the shaft 2 increases. A dynamic pressure action occurs in the magnetic lubricating fluid 9. Magnetic lubricating fluid 9
Due to the dynamic pressure generated in the bearing 10, the radial load of the shaft 2 is supported by the bearing 10 in a non-contact state. Further, the thrust load applied to the shaft 2 due to the weight of the motor driving magnet 3 is supported by the magnetic attraction force acting between the upper and lower bearings 10 and 10 and the large diameter shaft portions 2a, 2a. Further, since the magnetic lubricating fluid 9 as the lubricant is attracted by the magnetic attraction force acting between the large-diameter shaft portion 2a and the bearing 10, even if the centrifugal force acts due to the rotation of the shaft 2, it is exposed to the outside. Less scattered.

[0010]

In the bearing device having the above-described structure, as shown in FIG. 5, in order to support the thrust load acting on the shaft 2 by the magnetic attraction force of the bearing 10, the shaft 2 has a large diameter shaft. The part 2a is provided. That is, the large-diameter shaft portion 2 having a small magnetic resistance is used to prevent the magnetic flux entering the shaft 2 from the bearing 10.
A restoring force for returning the large-diameter shaft portion 2a to the bearing 10 side is obtained with respect to axial displacement of the large-diameter shaft portion 2a with respect to the bearing 10

For the above reasons, the large diameter shaft portion 2 is attached to the shaft 2.
There is a step between a and the reduced diameter portion 2b, and the magnetic bearing magnet 1 is larger than the inner diameter between the upper and lower bearings 10 and 10.
Since 3 is arranged on the outer side in the radial direction, the stepped portion of the shaft 2 is located at the step portion of the shaft 2 when the bearing device is assembled.
The assembly work was extremely difficult because the end of the shaft 2 and the end faces of the pair of bearings 10, 10 facing each other were attracted by the magnetic attraction force of No. 3 and caught by the bearing 10. Further, since the gap A between the reduced diameter portion 2b of the shaft 2 and the magnetic bearing magnet 13 is wide and the gap A is filled with the magnetic lubricating fluid 9, a large amount of the magnetic lubricating fluid 9 is formed.
Was needed. Further, the rotation of the shaft 2 increases due to the flow of the magnetic lubricating fluid 9 between the reduced diameter portion 2b and the magnetic bearing magnet 13 as the shaft 2 rotates. When used as a device,
There was a drawback that the power consumption increased.

[0012]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above problems, prevents the shaft from being caught by the bearing during the assembly of the bearing device, reduces the required amount of the magnetic lubricating fluid, and has a small rotational resistance. An object is to provide a bearing device.

[0013]

In order to achieve the above object, a bearing device of the present invention comprises a shaft having a pair of large diameter shaft portions and a pair of bearings respectively supporting the pair of large diameter shaft portions. The shaft and the pair of bearings are both made of a magnetic material, and a magnetic bearing magnet magnetized in the axial direction is disposed between the pair of bearings, and In a bearing device having a magnetic circuit formed therein, a non-magnetic member having an outer diameter substantially equal to the outer diameter of the large diameter shaft portion is mounted between the pair of large diameter shaft portions. It is preferable that a non-magnetic member having an inner diameter substantially equal to the inner diameter of the bearing is mounted inside the magnetic bearing magnet across the pair of bearings.

[0014]

In the bearing device of the present invention, when the shaft is inserted into the pair of bearings and assembled, a magnetic attraction force acts between the pair of bearings magnetized by the bearing magnet and the shaft, and the two attract each other. To be However, since the non-magnetic member mounted between the pair of large-diameter shaft portions formed on the shaft is formed to have substantially the same diameter as the outer diameter of the large-diameter shaft portions, The step is eliminated, and it is prevented from being caught during insertion into the bearing. Further, since the gap between the magnetic bearing magnet disposed between the pair of bearings and the shaft is narrowed by the non-magnetic member mounted on the shaft, the amount of magnetic lubricating fluid stored in the gap is reduced. The rotation resistance of the shaft due to the flow of the magnetic lubricating fluid is reduced.

Further, when a non-magnetic member having an inner diameter substantially equal to the inner diameter of the bearing is mounted inside the bearing magnet across the pair of bearings, the end surfaces of the pair of bearings on the opposite surface side. It is also possible to prevent the end face of the shaft from being caught. Moreover, by mounting the non-magnetic member having an inner diameter substantially equal to that of the bearing, the gap for storing the magnetic lubricating fluid becomes smaller, and as a result, the amount of the magnetic lubricating fluid stored in the bearing device becomes smaller. The rotation resistance of the shaft due to the flow of the magnetic lubricating fluid is further reduced. In addition, the magnetic lubricating fluid trapped in the small gap between the non-magnetic member mounted on the shaft side and the non-magnetic member mounted inside the magnet for the magnetic bearing generates dynamic pressure due to the rotation of the shaft. The vibration of the shaft during high speed rotation is suppressed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows one embodiment of the bearing device of the present invention, and shows an example of use as a bearing device for a polygon mirror motor, as in FIG. 4 described above. In the figure, a pair of bearings 10 are vertically fixed in a collar 12 mounted in a bearing hole 1 a of a housing 1, and a magnetic bearing magnet 13 is arranged between the two bearings 10.
A lower end of the bearing hole 1a of the housing 1 is closed by a bottom plate 8, and an upper portion of the collar 12 projects from the bearing hole 1a and an airflow separating plate 11 is provided at an upper end thereof. Further, a laminated core 4 around which a large number of coils 5 are wound is attached to the housing 1.

A flange 16 is fixed to the upper portion of the shaft 2, and a motor driving magnet 3 is fixed to the flange 16 so as to rotate integrally therewith. The motor driving magnet 3 has a plurality of magnetized portions formed on the opposing surfaces of the peripheral edge of the laminated core 4. The motor drive magnet 3 is rotationally driven by controlling the energization of the plurality of coils 5 by a drive control circuit (not shown) on the circuit board 6 provided on the upper surface of the housing 1.
The rotational position of the motor driving magnet 3 is detected by the position detecting element 7 including a Hall element or the like. The rotational position detection signal generated by the position detection element 7 is input to the drive control circuit, and by energizing a necessary coil among the plurality of coils 5, a torque from the coil 5 is applied to the motor drive 3. Given, the rotation of shaft 2 is continued.

Next, the structure of the bearing device used in the polygon mirror motor having the structure shown in FIG. 1 will be described in detail. The shaft 2 to which the flange 16 is attached is
It is made of a magnetic material such as iron and has a pair of large-diameter shaft portions 2a at two axial positions, that is, at the upper and lower positions in FIG. The shaft 2 is rotatably supported by a pair of upper and lower bearings 10 and 10 arranged corresponding to the respective positions of the upper and lower large-diameter shaft portions 2a and 2a. The gap between the large-diameter shaft portion 2a and the bearing 10 is filled with the magnetic lubricating fluid 9, and the shaft 2 has a large-diameter shaft portion 2a.
In the portion, the bearing 10 is indirectly supported by the bearing 10 via the magnetic lubricating fluid 9. The bearing 10 can be formed of a magnetic material such as an iron-based material like the shaft 2, but can be formed of a sintered material of a magnetic material such as an iron-based material for ease of manufacturing.

The above-mentioned magnetic bearing magnet 13 is
It is formed into a hollow cylinder and is magnetized in the axial direction. The upper and lower end surfaces that are both magnetic poles of the magnetic bearing magnet 13 are in contact with the lower end surface of the upper bearing 10 and the upper end surface of the lower bearing 10, respectively, and inside the collar 12 together with the upper and lower bearings 10. It is fixed by means such as adhesion or press fitting. FIG. 2 is an enlarged partial cross-sectional view showing a state where the large-diameter shaft portion 2a of the shaft 2 is supported by the bearing 10. The large-diameter shaft portion 2a has a slight gap S with the bearing 10. Are facing through. On the other hand, a reduced diameter portion 2b is formed between the upper and lower large diameter shaft portions 2a.
A non-magnetic member 14 having an outer diameter substantially equal to that of the large-diameter shaft portion 2a is mounted around b. The non-magnetic member 14 can be formed around the reduced diameter portion 2b of the shaft 2 using a plastic material such as nylon by injection molding or the like. By the magnetic bearing magnet 13 sandwiched between the pair of upper and lower bearings 10, 10, the upper and lower bearings 1
0 and 10 are magnetized, and a closed magnetic circuit is formed between the upper and lower large-diameter shaft portions 2a facing each other.

The magnetic flux entering the shaft 2 from the bearing 10 concentrates on the large-diameter shaft portion 2a having a small magnetic resistance, so that the large-diameter shaft portion 2a is displaced with respect to the axial displacement of the large-diameter shaft portion 2a with respect to the bearing 10. A magnetic restoring force that returns the bearing 10 is generated, and the restoring force supports the thrust load. Further, the magnetic flux passing through the gap between the bearing 10 of the magnetic circuit and the large-diameter shaft portion 2a is
The magnetic lubricating fluid 9 is suction-held in the gap portion, and the magnetic lubricating fluid 9 is prevented from being scattered to the outside of the bearing device by the centrifugal force generated by the rotation of the shaft 2. Further, since the gap between the inner surface of the magnetic bearing magnet 13 and the reduced diameter portion 2b of the shaft 2 is narrowed by the provision of the non-magnetic member 14, the magnetic lubricating fluid 9 filled in the gap. Is smaller than that of the conventional bearing device shown in FIGS. 4 and 5.

In the structure shown in FIGS. 1 and 2, when the shaft 2 is stopped or at the beginning of rotation, the large-diameter shaft portion 2a has the bearing 1
0 is supported by being in fluid contact with the magnetic bearing 9 through the magnetic lubricating fluid 9, but as the rotation of the shaft 2 increases, the bearing 1
A dynamic pressure action is generated in the magnetic lubricating fluid 9 filled between 0 and the large diameter shaft portion 2a. Due to the dynamic pressure generated in the magnetic lubricating fluid 9, the radial load of the shaft 2 does not come into contact with the bearing 10.
Supported by. During the rotation of the shaft 2, the gap between the inside of the magnetic bearing magnet 13 and the outer peripheral surface of the non-magnetic member 14 is narrow, so that the rotational resistance due to the disturbance of the flow state of the magnetic lubricating fluid 9 as the rotation speed increases Increase is small.

In the above embodiment, the magnetic bearing magnet 13 has substantially the same inner diameter as the upper and lower bearings 10 and 10, and the gap can be brought close to the gap S between the large diameter shaft portion 2a and the bearing 10. . By setting the magnetic bearing magnet 13 to have an inner diameter that is substantially the same as the inner diameter of the bearing 10, it is possible to suppress disturbance of the flow state of the magnetic lubricating fluid 9 and extremely reduce the rotational resistance. In addition, the gap between the magnetic bearing magnet 13 and the non-magnetic member 14 is provided in the bearing 1
Since the gap S between 0 and the large-diameter shaft portion 2a can be made substantially equal, the magnetic lubricating fluid 9 between the magnetic bearing magnet 13 and
In addition, a dynamic pressure is generated when the shaft 2 rotates, and vibration generated during the rotation of the shaft 2 can be suppressed. In this case, if the magnetic bearing magnet 13 is a plastic magnet formed by mixing magnetic powder into a synthetic resin material, an inner diameter suitable for the inner diameter of the bearing 10 can be easily obtained.

[0023]

[Embodiment 2] FIG. 3 is a partial cross-sectional view showing a second embodiment of the bearing device of the present invention, in which portions having the same structures as those of the above-mentioned embodiment shown in FIGS. The same reference numerals are given and the description thereof is omitted. In this embodiment, the non-magnetic member 15 is disposed inside the magnetic bearing magnet 13 disposed between the upper and lower bearings 10 and 10 so as to face the non-magnetic member 14 disposed between the large-diameter shaft portions 2a. is there. The inner surface of the non-magnetic member 15 is finished to be a cylindrical surface surrounding the shaft 2, and is formed to have an inner diameter substantially equal to the inner diameters of the upper and lower bearings 10, 10. The non-magnetic member 15 can be formed by a means such as injection molding using a plastic member such as nylon in the same manner as the non-magnetic member 14 attached to the reduced diameter portion 2b of the shaft 2.

According to this embodiment, the gap T between the non-magnetic member 14 and the non-magnetic member 15 is narrowed to almost the same extent as the gap S between the bearing 10 and the large diameter shaft portion 2a of the shaft 2. Has been. The magnetic lubricating fluid 9 is filled in a small space between the gap T and the gap S, and between the upper and lower bearings 10 and 10 and the large-diameter shaft portions 2a and 2a facing the bearings 10 and 10, respectively. The magnetic flux from the magnetic bearing magnet 13 that passes through is blocked from flowing out.

In the configuration of the bearing device shown in FIG. 3, the shaft 2
The radial load and thrust load applied to the pair of upper and lower bearings 1 are the same as those in the embodiment of FIGS. 1 and 2 described above.
Held by 0, 10. On the other hand, in the present embodiment, the magnetic lubricating fluid 9 filled in the gap T between the non-magnetic member 14 mounted on the shaft 2 side and the non-magnetic member 15 mounted on the magnetic bearing magnet 13 side is Since the gap T is narrow, the increase in rotational resistance due to the disturbance of the flow state is extremely small. Further, during rotation, dynamic pressure is also generated in the magnetic lubricating fluid 9 filling the gap T, and this dynamic pressure causes
Vibrations that accompany the rotation of the shaft 2 are suppressed. Although the shaft 2 side is rotated in each of the embodiments described above, the shaft 2 may be fixed to the housing 1 side and the bearing 10 side may be rotated together with the collar 12 and the magnetic bearing amount magnet 13. .

[0026]

As described above, according to the bearing device of the present invention, a bearing having a large diameter is formed between a pair of large-diameter shaft portions formed on the shaft.
Since a non-magnetic member having an outer diameter substantially equal to the outer diameter of the large diameter shaft portion is mounted, it is possible to prevent the large diameter shaft portion from being attracted and caught by the bearing magnetized by the magnetic bearing magnet when the bearing device is assembled. . As a result, the assembly work becomes easy. Further, since the gap between the magnetic bearing magnet that surrounds the shaft and the shaft is reduced by the non-magnetic member, the amount of the magnetic lubricating fluid filled in the bearing device can be reduced. Further, since the gap is reduced, the flow of the magnetic lubricating fluid in the bearing device due to the rotation of the shaft is suppressed,
Rotational resistance is reduced. As a result, power consumption can be reduced particularly when used as a bearing device for a motor.

In the present invention, when a non-magnetic member having an inner diameter substantially equal to the inner diameter of the bearing is mounted inside the magnet for magnetic bearing between the pair of bearings, the end portion of the shaft is assembled at the time of assembling the bearing device. It is also possible to avoid catching between the pair of bearings and the end faces on the opposite face side, and the assembly work can be performed more easily. Also, the gap between the non-magnetic member mounted on the shaft side and the non-magnetic member mounted inside the magnet for the magnetic bearing can be narrowed to about the same as the gap between the bearing and the large diameter shaft portion. The amount of magnetic lubricating fluid filled in the device can be extremely reduced. Therefore, the increase in rotation resistance due to the flow of the magnetic lubricating fluid can be further reduced. Further, the dynamic pressure of the magnetic lubricating fluid generated by the narrowing of the gap can suppress the vibration of the shaft during high speed rotation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a bearing device of the present invention.

FIG. 2 is an enlarged partial sectional view of a main part of FIG.

FIG. 3 is an enlarged partial sectional view of a main part of a second embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a conventional bearing device.

FIG. 5 is an enlarged partial sectional view of a main part of a conventional bearing device.

[Explanation of symbols]

1 housing, 1a bearing hole, 2 shafts,
2a large diameter shaft portion, 2b reduced diameter portion, 9 magnetic lubricating fluid, 10 bearing, 12 collar, 13 magnetic bearing magnet, 14 · 15 non-magnetic member.

Claims (2)

[Claims] 1. A shaft provided with a pair of large-diameter shaft portions, and a pair of bearings respectively supporting the pair of large-diameter shaft portions, wherein both the shaft and the pair of bearings are made of a magnetic material. A magnetic bearing magnet magnetized in the axial direction is disposed between the pair of bearings, and a magnetic circuit is formed between the pair of bearings, and the pair of large-diameter shaft portions. A bearing device, wherein a non-magnetic member having an outer diameter substantially equal to the outer diameter of the large-diameter shaft portion is mounted over the space. 2. A non-magnetic member having an inner diameter substantially equal to the inner diameter of the bearing is mounted inside the magnetic bearing magnet across the pair of bearings.
Bearing device.