JPH05141420A - Bearing device - Google Patents

Abstract

PURPOSE:To provide a bearing device which is low in axial height, short in starting time, excellent in cost performance and mass-productivity, and suitable for an optical deflection device. CONSTITUTION:A sleeve 12 is rotatably fitted to a fixed shaft 12, while herringbone grooves 16 are formed on radial bearing surfaces 14, 15, and thereby a radial fluid bearing R is structured. A tip portion 18 formed by a magnetic body of the fixed shaft 12 is opposed to a cylindrical magnet 20 provided on the sleeve 13 in a non-contact condition, and thereby a thrust magnetic bearing S is structured. Rotor magnet members 61, 63 and a mirror 50 are provided on an outer peripheral surface 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. 2, for example. In this conventional example, a cylindrical hole 2 is formed at the center of a housing (sleeve) 1.
Is provided, and one cylindrical radial bearing surface 3 is provided on the inner peripheral surface of the cylindrical hole 2, and one thrust bearing surface 5 having a convex spherical projection 4 at the center is provided on the bottom surface. It is provided.

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,
The other radial bearing surface 7 facing the one radial bearing surface 3 is provided. Further, one end face of the shaft 6 is provided with the other planar thrust bearing surface 9 facing the one thrust bearing surface 5. The other radial bearing surface 7 of the shaft 6 is provided with a dynamic pressure generating groove 8 consisting of a spiral groove 8a acting as a thrust bearing and a herringbone groove 8b for radial bearings. A grooved fluid bearing (the fluid in this example is air) is configured.

When the shaft 6 is stationary, the other thrust bearing surface 9 at the lower end of the shaft 6 comes into contact with the raised portion 4 of one thrust bearing surface 5 of the housing and receives an axial load. But axis 6
At the time of rotation, the dynamic pressure generated by the spiral groove 8a provided on the radial bearing surface 7 due to the rotation is introduced between the thrust bearing surfaces 5 and 9, and the axial load is applied by the pressure. 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. The rotor magnet 61 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 that faces the rotor magnet 61 in the radial direction is attached to the housing 1. In the case of this conventional example, the mirror 50 and the rotor magnet case 63 are fitted to the outer diameter surface of the shaft 6 with a clearance fit, and the rotor magnet case 63 sandwiches the mirror 50 and the flange portion 6a of the shaft 6 is sandwiched. It is fixed with a screw 65. The rotor magnet 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 for supporting the axial load on the radial bearing surface.

On the other hand, from the viewpoint of operability, it is required that the starting time is short and the rising time until the rated speed is reached is short. That is, in the laser printer and the digital copying machine, it is preferable that the time from turning on the switch until it can be used is short, so that an optical deflecting device that requires as short a time as possible to reach the number of rotations used is required. However, in the conventional example, since the raised portion 4 of the thrust bearing surface 5 and the thrust bearing surface 9 are in contact with each other when stationary, the starting friction torque is large, and the inertia of the flange portion 6a of the shaft 6 is large. It was difficult to shorten it.

Further, as the recording density is improved and the printing speed is increased, there is an increasing demand for high speed rotation.
Moreover, in order to improve the print quality, it is necessary to suppress the vibration generated from the optical deflector during rotation as much as possible. As the number of revolutions increases, the centrifugal force due to the imbalance of the rotating parts increases in proportion to the square of the velocity, so it becomes more and more important to keep the imbalance small. However, when the number of rotations increases, the mirror 5
Since the heat generation due to the wind loss of 0 and the friction between the bearing surface and the air increases, no matter how precisely the imbalance correction (balance correction) is performed at room temperature, the linear expansion coefficient of each material will increase as the temperature rises. Due to the difference, the center of gravity of the mirror 50 and the rotor magnet 61 slightly moves with respect to the rotation center of the sleeve 1, and there is a problem that the vibration of the device increases with the passage of time.

Further, even if the imbalance is corrected beforehand in the high temperature state, the vibration in the initial stage of rotation at the normal temperature state becomes large, or the center of gravity moves irregularly due to the temperature rise, so that the vibration in the steady state is reduced. There was almost no effect. Such an irregular movement of the center of gravity during temperature change in the conventional example is caused by a slight gap in the fitting surface between the mirror 50 and the shaft 6 and between the rotor magnet case 63 and the shaft 6, and the rotor magnet 61. Case 6
It is considered that this is due to the phenomenon in which the members adjacent to the clearance and the adhesive layer slightly move due to thermal expansion in the clearance and the adhesive layer irregularly due to the fact that 3 and 3 are bonded by the adhesive.

With recent improvements in printing quality, it has become more and more demanded to reduce the vibration of the apparatus, which has not been a problem in the past, but the influence of vibration caused by imbalance caused by the heat generated by such high-speed rotation. Can no longer be ignored. In order to solve the various problems of the conventional bearing device as described above, the applicant of the present application previously proposed a bearing device in which an axial load is supported by a thrust magnetic bearing instead of a fluid bearing (Japanese Patent Application No. 3-234844). However, there is still room for improvement in terms of cost increase, assembling, balance of magnetic attraction force, etc. by using expensive and fragile permanent magnets in pairs.

Therefore, the present invention has a low axial height,
An object of the present invention is to provide a low-cost bearing device having a small orbital friction torque, a short rise time, easy assembly, and easy mass production.

[0012]

A bearing device according to the present invention for achieving the above object relates to a bearing device provided with a sleeve rotatably fitted and supported on a fixed shaft, the sleeve comprising:
A mirror and a rotor magnet member of a drive motor are fixed to the outer peripheral surface, and a herringbone-shaped groove for generating dynamic pressure is provided on at least one of the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve. The bearing is supported by a fluid bearing and a thrust magnetic bearing provided on the free end side of the fixed shaft, and the thrust magnetic bearing includes a tip end of the fixed shaft made of a magnetic material and an inner surface of a magnet fixed to the inner surface of the sleeve. Are supported by a suction force generated by facing each other with a gap.

[0013]

According to the present invention, since the magnetic bearing is used as the thrust bearing, the spiral groove which acts as the thrust bearing is not required on the radial bearing surface, and the axial height can be reduced and the thrust can be reduced. Since the bearing portion is in non-contact both when stationary and when rotating, the starting friction torque is small.

Further, since the fixed shaft is made of a magnetic material and the tip portion thereof is used as it is as one member of the thrust magnetic bearing, the permanent magnet can be omitted from the fixed shaft, and the assemblability can be improved and the cost can be reduced. Further, if the tip of the fixed shaft is integrated with the fixed shaft, it is easy to secure the coaxiality with the radial bearing surface, imbalance of the magnetic attraction force hardly occurs, and the number of parts is reduced.

[0015]

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 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 through a bearing clearance.

One radial bearing surface 14 is provided on the inner peripheral surface of the sleeve 13 and faces the other radial bearing surface 15 provided on the outer peripheral surface of the fixed shaft 12. At least one of the one radial bearing surface 14 and the other radial bearing surface 15 (one radial bearing surface 14 in this embodiment).
In addition, a herringbone-shaped groove 16 for generating a dynamic pressure is provided to form a radial fluid bearing R. On the other hand, a thrust magnetic bearing S is provided on the free end side of the fixed shaft 12. In the thrust magnetic bearing S, the sleeve 1 is attracted by the attraction force generated by the gap between the fixed shaft tip 18 made of a magnetic material and the inner surface of the cylindrical magnet 20 fixed to the inner surface of the sleeve 13 with a gap.
3 is supported by the fixed shaft 12 in a non-contact manner.

More specifically, the tip portion 18 of the fixed shaft 12 is made of, for example, stainless steel (SUS440C, SU).
S420J2 etc.), and may be separate or integral with the main body of the fixed shaft 12, but it is preferable to integrally form the fixed shaft 12 because the mounting accuracy is not affected and the number of parts is small. A peripheral groove 18a is provided near the tip portion 18 (between the fixed shaft body in the figure). Thus, the magnetic flux is concentrated on the outer diameter surface of the fixed shaft 12 on both sides of the circumferential groove 18a to determine the axial position of the sleeve 13 with respect to the fixed shaft 12, and without the circumferential groove 18a, the sleeve 1
The axial position of 3 becomes unstable. It is preferable that the main body of the fixed shaft 12 is made of rust-resistant stainless steel and has a hardened surface, but a non-magnetic hard aluminum alloy may be used as long as it is formed separately from the tip 18. In that case Can be integrated with the aluminum alloy housing 11.

The cylindrical magnet 20 is preferably a rare earth magnet having a strong attractive force, and a cylindrical step 19 is formed on the upper end of the sleeve 13.
And is attached by shrink fitting or press fitting so that the movement of the center of gravity of the magnet with respect to the center of rotation is small even if the temperature changes, thereby preventing the balance from deviating during rotation. However, the cylindrical magnet 20 may be fixed to the sleeve 13 by adhesion when the influence of temperature change due to heat generation due to high-speed rotation is small. The magnetization direction may be radial or axial. The sleeve 13 is preferably made of a non-magnetic material so as not to adversely affect the magnetic circuit of the thrust magnetic bearing S, and is an aluminum alloy of a non-magnetic material and a light material, especially a carbon fiber composite for improving wear resistance. Aluminum alloy is most suitable.

Fixed shaft tip 18 of thrust bearing S
The gap between the outer peripheral surface of and the inner peripheral surface of the cylindrical magnet 20 is larger than the radial bearing clearance of the radial fluid bearing R. This is because the thrust magnetic bearing S is brought into non-contact during stationary and rotation to reduce the starting friction torque of the rotation of the sleeve 13. When the thrust magnetic bearing S is used, since the rigidity in the axial direction is low, the rotating portion easily vibrates vertically due to external vibration. Therefore, in the present embodiment, the clearance between the lower outer peripheral surface of the sleeve 13 and the inner inner peripheral surface of the housing 11 is made small, and the air damper 22 is provided between the lower end portion of the sleeve 13 and the housing 11 to make the sleeve The movement of 13 in the axial direction is suppressed.

The sleeve 13 has a small flange 23 slightly protruding on the outer peripheral surface, and an aluminum alloy mirror 50 is provided on the outer peripheral surface of the sleeve 13 above the flange 23.
Are fitted tightly by shrink fitting or press fitting.
When the influence of temperature change due to heat generation due to high-speed rotation is small, the mirror 50 may be fitted to the outer peripheral surface of the sleeve 13 by a loose fit and fixed to the flange 23 with a screw. Further, a ferrous alloy case 63 to which a rotor magnet 61 of the drive motor 60 is attached is fitted to the outer peripheral surface of the sleeve 23 below the flange 23 without shrinkage by shrink fitting or press fitting. The rotor magnet 6
The rotor magnet member constituted by 1 and the case 63 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.

By eliminating the fitting clearance by shrinkage fitting or press fitting, the center of gravity of the case 63 constituting the mirror 50 and the rotor magnet member is the sleeve 13 due to the difference in linear expansion coefficient during heat generation due to high speed rotation and thermal deformation. This prevents the balance from being lost due to movement with respect to the center of rotation. By shrink-fitting or press-fitting between the rotor magnet 61 and its case 63, it is possible to further reduce the imbalance in balance due to the movement of the center of gravity of the rotor magnet members 61 and 63 at high temperatures.

Further, the case 63 of the rotor magnet 61
The outer peripheral surface 63a of the
It is arranged so as to face 1a. Even if the rotor magnet 61 is destroyed due to the high speed rotation, safety measures are taken so as to prevent the fragments from flying out due to centrifugal force. The stator coil 64, which faces the rotor magnet 61 in the radial direction, includes the housing 1
It is attached to the bottom of 1.

Further, an adhesive for correcting the balance can be attached to the boundary portion 13a between the upper surface of the cylindrical magnet 20 on the rotating side and the inner surface of the sleeve 13 and the circumferential groove 25 provided on the lower end surface of the sleeve 13. It has become. 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.

Next, the operation will be described. In the bearing device configured as described above, the sleeve 13 is axially supported by the fixed shaft 12 by the thrust magnetic bearing S. Therefore, it is not necessary to provide the radial fluid bearing R with a spiral groove that acts as a thrust bearing, and therefore the axial height of the device is low and the structure is simple.

Further, since the tip of the fixed shaft 12 is made of a magnetic material and used as it is as one member of the thrust magnetic bearing, it is not necessary to provide a permanent magnet which is easily broken at the tip of the fixed shaft 12. Is easy to assemble when it is assembled to the fixed shaft 12, and the assemblability is improved. further,
It suffices to provide expensive permanent magnets only on the sleeve 13 side,
Since it is not necessary to use it on the side of the fixed shaft 12 facing this,
Only one is enough and the cost is low.

Further, since the thrust magnetic bearing S is a magnetic bearing having a radial clearance larger than the radial bearing clearance of the radial fluid bearing R, the thrust bearing portion supporting the own weight of the rotating portion is not in contact either at rest or during rotation. , 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 motor 60, the pumping action of the herringbone-shaped groove 16 causes the radial direction between the radial bearing surface 14 of the radial fluid bearing R and the radial bearing surface 15 of the other radial direction. A dynamic pressure is generated in the bearing clearance of the sleeve 13, the sleeve 13 is supported in the radial direction in a completely non-contact manner, and high speed rotation can be reached in a short rising time.

The case 63 of the mirror 50 and the rotor magnet 61 and the sleeve 13 are fitted together by shrink fitting or press fitting, and since there is no clearance on the mating surfaces, the temperature is increased by heat generated during rotation. Even if it goes up, the center of gravity of the mirror 50 and the case 63 of the rotor magnet does not move with respect to the rotation center of the sleeve 13. Therefore, the balance is small, the balance of rotation is maintained, and the vibration of the device is small. It should be noted that the rotor magnet member may be composed of only the rotor magnet 61, and the rotor magnet 61 may be shrink-fitted onto the outer peripheral surface of the sleeve 13 and fixed by press-fitting or adhesion so that the rotor magnet 61 faces the stator 64. good.

[0028]

As described above, according to the present invention, since the axial magnetic load is supported by the thrust magnetic bearing provided at the tip of the fixed shaft, the spiral groove for acting the thrust bearing on the radial bearing surface is unnecessary. The effect that the height in the axial direction can be reduced is obtained. Further, since the thrust magnetic bearing is in non-contact both when stationary and when rotating, the starting friction torque can be reduced.

Further, since at least the tip of the fixed shaft is made of a magnetic material and the tip is used as it is as one member of the thrust magnetic bearing, the fragile and expensive permanent magnet can be omitted accordingly. Also, if the tip part is integrated with the fixed shaft, it is easy to secure the coaxiality with the radial bearing surface, so imbalance of magnetic attraction force does not easily occur, and the number of parts can be reduced, resulting in easy assembly and suitable for mass production. A bearing device having high rotation accuracy can be provided at low cost.

[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 showing an example of a conventional bearing device.

[Explanation of symbols]

 12 Fixed Axis 13 Sleeve 16 Herringbone-shaped (for Dynamic Pressure Generation) Groove 18 (Fixed Axis) Tip 18a Circumferential Groove 20 Cylindrical Magnet 50 Mirror 61 Rotor Magnet 63 Case R Radial Fluid Bearing S S Thrust Magnetic Bearing

Claims (1)

[Claims] 1. A bearing device including a sleeve rotatably fitted and supported on a fixed shaft, wherein the sleeve has a mirror and a rotor magnet member of a drive motor fixed to an outer peripheral surface of the sleeve. Supported by at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, a radial fluid bearing provided with a herringbone-shaped groove for generating dynamic pressure, and a thrust magnetic bearing provided on the free end side of the fixed shaft, The thrust magnetic bearing is a bearing device having a structure in which a tip end of a fixed shaft made of a magnetic material and an inner surface of a magnet fixed to an inner surface of a sleeve are supported by an attractive force generated by facing each other across a gap.