JPH05172141A - Bearing device - Google Patents

Abstract

PURPOSE:To reduce the bearing height of a bearing device incorporating a sleeve adapted to be fitted on a stationary shaft, by supporting the sleeve at its inner peripheral side with a radial fluid bearing formed with a herringbone- like dynamic pressure generating grooves, and at its outer peripheral side with a magnetically attractive type thrust bearing. CONSTITUTION:In a baring device for a light deflecting device or the like adapted to be used for a data processing apparatus, a stationary shaft is planted upright in the center part of a housing 11 having such a structure that gas such as air is sealingly enclosed therein as necessary, and a sleeve 13 attached thereto with a mirror 50 is fitted on the shaft 11 with a radial bearing gap C therebetween so that the sleeve 13 is rotated by a motor 60. Either the inner surface of the sleeve 13 serves as a cylindrical bearing surface 14 or the outer peripheral surface of the stationary shaft as a radial receiving surface 15 is formed thereon with herringbone-like dynamic pressure generating grooves 16 so as to constitute a radial bearing R. Further, a magnetically attractive type thrust bearing S composed of permanent magnets 18, 19 which are attractive one another is arranged outside of the sleeve 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a bearing device such as an optical deflector used in information equipment, video equipment and the like.

[0002]

2. Description of the Related Art As a conventional bearing device for an optical deflecting device of this type, there is one shown in FIG. In this conventional example, a cylindrical hole 2 is formed at the center of a housing (sleeve) 1.
Is provided, and a cylindrical radial bearing surface 3 is provided on the inner peripheral surface of the cylindrical hole 2, and a thrust bearing surface 5 having a convex spherical protrusion 4 at the center is provided on the bottom surface. ..

A shaft 6 which is a rotating member is fitted in the cylindrical hole 2 of the housing 1. On the outer peripheral surface of this shaft 6,
A radial receiving surface 7 that faces the radial bearing surface 3 is provided. In addition, one end surface of the shaft 6 is provided with the other flat thrust bearing surface 9 facing the thrust bearing surface 5.
Is provided. The radial receiving surface 7 of the shaft 6 is provided with a dynamic pressure generating groove 8 including a spiral groove 8a acting as a thrust bearing and a herringbone groove 8b for the radial bearing, which is provided with a dynamic pressure groove. A fluid bearing (the fluid in this example is air) is configured.

When the shaft 6 is stationary, the thrust receiving surface 9 at the lower end of the shaft 6
Contacts the raised portion 4 of the thrust bearing surface 5 of the housing and receives an axial load. However, when the shaft 6 rotates, the dynamic pressure generated by the spiral groove 8a provided on the radial receiving surface 7 due to the rotation is introduced between the thrust bearing surface 5 and the thrust receiving surface 9, and the resulting pressure is used. It receives an axial load. Therefore, during the rated operation of the bearing device, the shaft 6 rotates without contacting the housing (sleeve) 1.

A mirror 50 is attached to the upper portion of the shaft 6. The mirror 50 has a drive motor 6 together with the shaft 6.
It is driven to rotate at 0. A rotor 61, which is a permanent magnet of the drive motor 60, is attached to the shaft 6 via a case 63 made of iron alloy. On the other hand, a stator coil 64, which faces the rotor 61 in the radial direction, is attached to the housing 1. In the case of this conventional example, the mirror 50 and the rotor case 63 are fitted to the outer diameter surface of the shaft 6 with a clearance fit, and the rotor case 63 sandwiches the mirror 50 and is screwed to the flange portion of the shaft 6 with a screw 65. It is fixed at. Also,
The rotor 61 is fixed to the case 63 with an adhesive.

[0006]

Such an optical deflecting device is used in a laser printer or a digital copying machine, but it is required to have a low axial height in order to downsize the entire device. However, in the conventional example, there is a problem that the axial height cannot be reduced because the spiral groove 8a having a long axial length is required to support the axial load on the radial receiving surface.

Therefore, an object of the present invention is to provide a bearing device having a low axial height.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention relates to a bearing device having a sleeve rotatably fitted and supported on a fixed shaft, the sleeve being fixed to an inner peripheral surface of the sleeve. It is supported by a radial fluid bearing having a herringbone-shaped groove for generating a dynamic pressure on at least one of the outer peripheral surface of the shaft and a magnetic attraction type thrust bearing arranged outside the sleeve. ..

[0009]

According to the present invention, since the magnetic attraction type thrust bearing is provided on the outer side of the sleeve, the spiral groove acting as the thrust bearing is not required on at least one of the radial bearing surface and the Asian bearing surface, and the axial direction is eliminated. The height of can be lowered.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The same or corresponding parts as those of the conventional example are designated by the same reference numerals. FIG. 1 is a vertical sectional view of one embodiment. The housing 11 has a structure in which a gas such as air can be sealed as needed by attaching an upper member (not shown), and a fixed shaft 12 is provided upright in the center thereof. A sleeve 13 is rotatably fitted to the fixed shaft 12 via a radial bearing clearance C1.

Inside the sleeve 13, that is, the sleeve 13
A cylindrical radial bearing surface 14 is provided on the inner peripheral surface of
It faces a radial receiving surface 15 provided on the outer peripheral surface of the fixed shaft 12. Then, the radial bearing surface 14 and the radial receiving surface 1
5 and at least one of them (on the radial bearing surface 14 in this embodiment), a herringbone-shaped groove 16 for generating a dynamic pressure.
Are provided to constitute the radial fluid bearing R.

On the other hand, the thrust bearing S is a suction type magnetic bearing and is provided outside the sleeve 13. That is, the ring-shaped permanent magnet 18 is fixed to the step portion formed at the lower end of the outer peripheral surface of the sleeve 13 with a small diameter, and the stepped portion at the position on the inner peripheral surface of the housing 11 facing the permanent magnet 18. Another ring-shaped permanent magnet 19 is fixed to the portion formed on the outer peripheral surface of the permanent magnet 18 and the inner peripheral surface of the permanent magnet 19 in the thrust bearing clearance C.
The two are opposed to each other via 2. The permanent magnets 18, 19 may be magnetized in the radial direction or the axial direction.

In order to prevent the magnetic circuit of the thrust bearing S from being adversely affected, the materials of the sleeve 13 and the housing 11 of this embodiment are preferably non-magnetic materials. Moreover, the sleeve 13 is preferably made of a light material, that is, an aluminum alloy, and from the viewpoint of wear resistance, a carbon fiber or silicon carbide composite aluminum alloy is most suitable. Further, as the permanent magnets 18 and 19, rare earth magnets having a strong attractive force are optimal. The fixed shaft 12 is preferably made of rust-resistant stainless steel and has a hardened surface, but a non-magnetic hard aluminum alloy may be used, in which case the aluminum alloy housing 1
It can also be integrated with 1.

When the magnetic bearing is used as the thrust bearing S as described above, since the axial rigidity is low, the sleeve 13, which is the rotating portion, easily vibrates vertically due to external vibration. Therefore, the clearance C2 between the lower outer peripheral surface of the sleeve 13 and the inner peripheral surface of the housing 11 is made small, and the air damper in the space between the lower surface of the sleeve 13 and the housing 11 due to resistance at the time of inflow and outflow from the clearance C2. By providing 20, the movement of the sleeve 13 in the axial direction is suppressed.

The size of the gap of the thrust bearing clearance C2 is larger than the radial bearing clearance C1 of the radial fluid bearing R. This is to make the thrust bearing S non-contact both when stationary and rotating to reduce the starting friction torque of the rotation of the sleeve 13. The sleeve 13
Has a small flange 23 slightly protruding on the outer peripheral surface, and an aluminum alloy mirror 50 is fitted tightly on the outer peripheral surface of the sleeve 13 on the flange 23 by shrink fitting or press fitting. When the influence of the temperature change due to the heat generation due to the high speed rotation is small, the mirror 50 is fitted to the outer peripheral surface of the sleeve 13 with a clearance fit and the flange 23 is fitted.
It may be fixed with a screw. Further, on the outer peripheral surface of the sleeve 13 below the flange 23, the rotor 61 of the drive motor 60 is
A case 63 made of an iron alloy to which is attached is fitted with no clearance by shrink fitting, crimping or press fitting. A rotor member 65 including the rotor 61 and the case 63 is provided.
May be fixed to the outer peripheral surface of the sleeve 13 by adhesion, but for high speed rotation, it is preferable to reduce the clearance by shrink fitting or press fitting.

Further, the outer peripheral surface 63a of the rotor case 63 is
Are arranged so as to face the inner peripheral surface 11a of the outer portion of the housing 11. This is because safety measures have been taken to prevent the fragments from flying out by centrifugal force even if the rotor 61 should break due to high speed rotation. Stator coil 6 that faces rotor 61 in the radial direction
4 is attached to the housing 11.

Further, an adhesive for correcting the balance can be attached to the circumferential groove-shaped step 24 on the inner peripheral surface of the upper end portion of the sleeve 13 and the circumferential groove-shaped step 25 of the case 63 of the rotor. .. This makes it possible to correct the unbalance of the centers of gravity of the both ends of the rotating member, improve the accuracy of the unbalance correction with respect to the moment, and prevent the adhesive from scattering due to the centrifugal force during rotation.

Reference numeral 26 is a motor substrate. Next, the operation will be described. In the bearing device configured as described above, the sleeve 13 is supported in the axial direction with respect to the fixed shaft 12 by the magnetic attraction type thrust bearing S. Therefore, the radial fluid bearing R
Since it is not necessary to provide a spiral groove for acting as a thrust bearing, the axial height of the device can be reduced and the structure can be simplified because the thrust bearing S is provided outside the sleeve 13.

Further, since the sleeve 13 is always attracted to the housing 11 by the magnetic attraction force, it is not necessary to provide any means for preventing the sleeve 13 from coming off during transportation. Further, since the thrust magnetic bearing S is a magnetic bearing having a radial clearance C2 larger than the radial bearing clearance C1 of the radial bearing R,
Rotating sleeve 13, mirror 50, rotor member 6
The thrust bearing portion supporting the own weight of No. 5 is in non-contact both at rest and during rotation, and the starting friction torque is small.

Further, since the sleeve 13 has no large flange, the inertia is small. Therefore, when the sleeve 13 is rotated by the drive of the drive motor 60, the pumping action of the herringbone-shaped groove 16 causes a radial bearing clearance C1 between the radial bearing surface 14 and the radial receiving surface 15 of the radial fluid bearing R. Since a dynamic pressure is generated in the sleeve 13, the sleeve 13 is supported in the radial direction in a completely non-contact manner, and can reach high speed rotation in a short rising time.
Alternatively, a magnetic ring may be fixed to the sleeve 13 without fixing the permanent magnet 18, and the magnetic attraction ring and the permanent magnet 19 of the housing may constitute a magnetic attraction type thrust bearing.

FIG. 2 shows a second embodiment of the present invention. In the bearing device of this embodiment, the material of the sleeve 13 is a magnetic material such as martensitic stainless steel. The thrust bearing S is a magnetic thrust bearing of the suction type as in the first embodiment, but the permanent magnet is not fixed to the sleeve 13 that is the rotating member. That is, the sleeve 1
An outer peripheral groove 30 is formed in the vicinity of the lower end of the outer peripheral surface of No. 3, and the outer peripheral surface of the portion 31 below the outer peripheral groove 30 is the housing 11
The inner circumferential surface of the permanent magnet 19 on the inner circumferential surface of the above is radially opposed via the thrust bearing clearance C2.

Since the magnetic flux of the permanent magnet 19 concentrates on the portion below the side surface of the outer peripheral groove 30, the sleeve 13 is axially supported by the permanent magnet 19. According to the second embodiment, it is sufficient to provide the expensive permanent magnet only on the housing 11 side, and it is not necessary to use it on the sleeve 13 side facing the housing 11, so that the cost is low. Moreover, since the rotating sleeve 13 is made of a magnetic material having a strong resistance to centrifugal damage, it has an advantage of being suitable for high speed rotation.

Other functions and effects are similar to those of the first embodiment.

[0024]

As described above, in the bearing device of the present invention, the axial load is supported by the magnetic attraction type thrust bearing disposed on the outer side of the sleeve. The effect is that the spiral groove that operates is not necessary, and as a result, the height in the axial direction can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a vertical sectional view of another embodiment of the present invention.

FIG. 3 is a vertical sectional view showing an example of a conventional bearing device.

[Explanation of symbols]

 11 Housing 12 Fixed Shaft 13 Sleeve 16 Groove for Dynamic Pressure Generation 18 Permanent Magnet 19 Permanent Magnet 50 Mirror 61 Rotor Magnet 63 Case R Radial Fluid Bearing S S Thrust Bearing

Claims (1)

[Claims] 1. A bearing device comprising a sleeve rotatably fitted and supported on a fixed shaft, wherein the sleeve has a herringbone shape on at least one of an inner peripheral surface of the sleeve and an outer peripheral surface of the fixed shaft. A bearing device characterized by being supported by a radial fluid bearing provided with a groove for generating dynamic pressure and a magnetic attraction type thrust bearing arranged outside the sleeve.