JP3240637B2 - Bearing device - Google Patents

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 deflecting device used for information equipment and video equipment.

[0002]

2. Description of the Related Art As a conventional bearing device for this type of light deflecting device, for example, there is one shown in FIG. In this conventional example, a cylindrical hole 2 is formed at the center of a housing (sleeve) 1.
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. Is provided.

A shaft 6 as a rotating member is provided 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 one radial bearing surface 3 is provided. Also, on one end face of the shaft 6,
The other thrust bearing surface 9 is provided in a planar shape and faces the one thrust bearing surface 5. On the other radial bearing surface 7 of the shaft 6, a spiral groove 8 for a thrust bearing is provided.
a and a dynamic pressure generating groove 8 composed of a herringbone-shaped groove 8b for a radial bearing are provided to form a radial dynamic pressure groove bearing and a thrust dynamic pressure groove bearing.

A mirror 50 is mounted on the upper part of the shaft 6. The mirror 50 is rotationally driven by a drive motor 60 together with the shaft 6. The rotor magnet 61 of the drive motor 60 is attached to the shaft 6 via a case 63 made of an iron alloy. On the other hand, a stator coil 64 radially facing the rotor magnet 61 is attached to the housing 1. In this case, the mirror 50 and the rotor magnet case 63 are loosely fitted to the outer diameter surface of the shaft 6, and the rotor magnet case 63 is screwed to the flange 6 a of the shaft 6 with the mirror 50 interposed therebetween. It is fixed at. The rotor magnet 61 is provided in the case 6
3 is fixed by an adhesive.

When the shaft 6 is stationary, the other thrust bearing surface 9 at the lower end of the shaft is in contact with the raised portion 4 of the one thrust bearing surface 5 of the housing. When the shaft 6 rotates, a dynamic pressure is generated by the pumping action of the spiral groove 8a and the herringbone groove 8b provided on the radial bearing surface 7 of the shaft along with the rotation of the shaft. Supported in a non-contact direction.

[0006]

The light deflecting device is used for a laser printer or a digital copying machine, but in order to reduce the size of the entire device, a device having a low axial height is required. However, conventionally, at least one of the radial bearing surfaces 3 and 7 of the bearing device is provided with a spiral groove 8a which is long in the axial direction to support an axial load, so that the height in the axial direction cannot be reduced. There was a problem.

[0007] From the viewpoint of operability, there is a demand for a device having a short start-up time and a short start-up time until reaching a rated rotation speed. That is, in a laser printer and a digital copying machine, it is preferable that the time from when the switch is turned on to when it can be used is short. However, in the conventional example, since the thrust bearing surfaces 5 and 9 are in contact at rest, the friction torque at the time of startup is large, and the inertia of the flange portion 6a of the shaft 6 is large, so that it is difficult to shorten the rising time. There was a problem.

Further, with the improvement in recording density and the increase in printing speed, there is an increasing demand for higher speed rotation.
Moreover, in order to improve the printing quality, it is necessary to minimize the vibration generated from the light deflecting device during rotation. As the rotational speed increases, the centrifugal force due to the unbalance of the rotating portion increases in proportion to the square of the speed, and it is increasingly important to reduce the unbalance. However, as the rotation speed increases, the mirror 50
Since the heat loss due to windage loss and friction between the bearing surface and air increases, the linear expansion coefficient of the component material of the rotating member can be adjusted no matter how precisely the center of gravity of the rotating member matches the center of rotation at room temperature. Of the mirror 5
0 and the center of gravity of the rotor magnet 61 slightly move with respect to the rotation center of the shaft 6. Then, as time passes, the vibration of the device increases. Conversely, even if the imbalance is corrected in advance at a high temperature, the vibration at the initial stage of rotation at a normal temperature will increase, or the center of gravity will move irregularly due to a rise in temperature. There was a problem that there was almost no effect.

The irregular movement of the center of gravity at the time of temperature fluctuation is considered to be caused by the following phenomenon. The mirror 50 and the case 63 of the rotor magnet expand and contract around one of the three screwing locations in the circumferential direction due to the vertical movement of the temperature. Each time the temperature changes, the screw point, which is the center of expansion and contraction, changes from one screw point to another screw point. In this way, the center of gravity moves irregularly due to the temperature change. Therefore, even if the balance is corrected in advance, there is almost no effect of reducing the steady-state vibration. Incidentally, this phenomenon is caused by a phenomenon that the mirror 50 and the rotor magnet 63 move irregularly due to thermal expansion because there is a slight clearance between the fitting surface of the shaft 6 and the mirror 50. The rotor magnet 61 and the case 63 are bonded with an adhesive, but the adhesive is deformed by heat, so that the center of gravity of the rotating member moves irregularly.

[0010] With the recent improvement in printing quality, lowering of the vibration of the apparatus is increasingly required, and the influence of the vibration caused by the imbalance caused by the heat generated by such high-speed rotation, which has not been considered so far, has been greatly reduced. It can no longer be ignored. The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a bearing device having a low axial height, a short rise time, and a small vibration due to a temperature change. .

[0011]

To achieve the above object, the invention of a bearing device according to the first aspect of the present invention is directed to a rotating device having a fixed shaft.
Radial sleeve on the inner peripheral surface of the sleeve
Fixed shaft outer surface facing the receiving surface via radial bearing clearance
At least one of the radial bearing surfaces
A groove for generating dynamic pressure is provided to support radial loads.
A magnet member or a magnetic member attached to the sleeve
And a fixed shaft facing this with a radial gap
Thrust bearing of suction type between attached magnet member
And the axial load is
Supported.

[0012] The invention according to claim 2 is the invention according to claim 1.
The radial gap of the thrust bearing
It was larger than the clearance. The invention according to claim 3 is a contract
2. The housing of claim 1, wherein said housing supports said fixed shaft.
Inner peripheral surface facing the outer peripheral surface of the sleeve, and outer peripheral surface of the sleeve.
The clearance between the lower end of the sleeve and the
An air damper was provided between the housing and the housing. Claim 4
In the first aspect, the sleeve is made of a non-magnetic material.
Configured.

[0013]

According to the present invention, since a magnetic bearing is used for the thrust bearing, no spiral groove for the thrust bearing is required on the radial bearing surface, and the height in the axial direction can be reduced. Further, since the thrust bearing portion is not in contact with both at rest and during rotation, the starting friction torque is small. In particular,
Suction-type that acts radially between the fixed shaft and the sleeve
By using thrust bearings, the height in the axial direction is
Can be further reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, the same or corresponding portions are denoted by the same reference characters, and redundant description will be omitted. FIG. 1 is a longitudinal sectional view of the first embodiment. The housing 11 has a structure in which a gas such as air can be sealed by attaching an upper member (not shown).
2 are erected. A sleeve 13 is rotatably fitted to the fixed shaft 12 via 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 (in this embodiment, one radial bearing surface 14) is a groove for generating a dynamic pressure for supporting a radial load. A herringbone-shaped groove 16 is provided to constitute a radial fluid bearing R.

A magnet member 18 made of a permanent magnet is attached to the free end of the fixed shaft 12, while a step 19 formed at the upper end of the sleeve 13 and a large-diameter surface 13a of the sleeve 13 adjacent to the step 19 are provided. Attach another magnet member (or a magnetic material member) 20, and attach both magnet members 18, 2.
0 constitutes a thrust magnetic bearing S by sucking in a non-contact manner. The magnetization directions of the magnet members 18 and 20 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. Sleeve 13
The material is preferably a non-magnetic and light-weight aluminum alloy, and a carbon fiber composite aluminum alloy is optimal for improving abrasion resistance.

On the other hand, it is preferable that the fixed shaft 12 is made of stainless steel which does not easily rust and whose surface is hardened. If the fixed shaft 12 is made of a hard aluminum alloy, the difference in the coefficient of thermal expansion between the shaft and the sleeve when using a sleeve made of an aluminum alloy can be reduced, so that the change in the bearing clearance at the time of temperature change is reduced to almost zero. Is preferred. When the shaft is made of an aluminum alloy, the shaft may be integrated with the aluminum alloy housing 11.

The thrust magnetic bearing S will be described in more detail. Magnet member 18 fixed to the tip of fixed shaft 12
The magnet member 20 fixed to the inner peripheral portion of the sleeve 13 is cylindrical, and the outer peripheral surface of the magnet member 18 and the magnet member 2 are fixed.
0 is opposed to the inner peripheral surface of the radial fluid bearing R with a gap larger than the radial bearing clearance. This is because the thrust magnetic bearing S is kept out of contact with both stationary and rotating to reduce the starting friction torque of the rotation of the sleeve 13. When the magnet member 20 on the rotating side is attached to the sleeve 13 by shrink fitting or press fitting, the center of gravity of the magnet member 20 moves little with respect to the rotation center even when the temperature changes.

The sleeve 13 is axially supported by the magnetic attraction of the thrust magnetic bearing S. The outer peripheral surface of the magnet member 18 fixed to the distal end portion of the fixed shaft 12 has a diameter substantially the same as or slightly smaller than the other radial bearing surface 15 of the fixed shaft 12 and is provided close to the radial fluid bearing R. I have. This is for the purpose of facilitating assembly and reducing the height in the axial direction. Further, the magnet member 20 fixed to the sleeve 13
Inner peripheral surface of one of the radial bearing surfaces 14 of the sleeve 13
The diameter is almost the same as or slightly larger than. Small-diameter surface 1 of fixed shaft for mounting magnet members 18 and 20 of thrust magnetic bearing S
2a and the large-diameter surface 13a of the sleeve are connected to the radial fluid bearing R
Can be processed simultaneously with the bearing surfaces 14 and 15, respectively, so that the coaxiality is improved and the processing is extremely easy. When the thrust magnetic bearing S is used, since the rigidity in the axial direction is low, the rotating portion is easily vibrated up and down by external vibration. Therefore , in the present embodiment, the clearance between the lower outer peripheral surface 13c of the sleeve 13, which is a rotating body, and the inner inner peripheral surface 11b of the housing 11 is reduced to 150 μm or less.
By providing the air damper 22 between the lower end of the housing 11 and the housing 11, the inflow and outflow of air is suppressed, and the axial movement is suppressed.

The sleeve 13 has a small flange 23 slightly protruding from the outer peripheral surface thereof, and a mirror 50 made of an aluminum alloy is fitted to the outer peripheral surface above the flange 23 without any clearance by shrink fitting or press fitting. ing. Also flange 2
An iron alloy case 63 to which a rotor magnet 61 of a drive motor 60 is attached is fitted to the lower outer peripheral surface of the lower part 3 by shrink fitting or press fitting without any gap. The rotor magnet 61 and the case 63 constitute a rotor magnet member. By eliminating the fitting gap by shrink fitting or press fitting, the center of gravity of the case 63 constituting the mirror 50 and the rotor magnet member is brought to the center of rotation of the sleeve 13 due to the difference in linear expansion coefficient and thermal deformation during heat generation due to high speed rotation. This prevents the balance from being lost due to movement. If shrink-fitting or press-fitting is also applied between the rotor magnet 61 and its case 63, the loss of balance due to the movement of the center of gravity at a high temperature can be further reduced. Flange 2 of sleeve 13 of this embodiment
The difference between the outer diameter of No. 3 and the inner diameter of the mirror 50 is 8 mm or less, so that the material cost and the processing cost of the sleeve 13 are reduced, and the windage loss and the inertia are reduced.

The case 63 of the rotor magnet 61
The outer peripheral surface 63 a of the inner peripheral surface 1
It is arranged so as to face 1a. In this case, even if the rotor magnet 61 is broken due to high-speed rotation, safety measures are taken so as to prevent fragments from jumping out due to centrifugal force. The stator coil 64 radially opposed to the rotor magnet 61 is
1 is attached to the lower part.

An adhesive for correcting the balance is applied to the large-diameter surface 13a at the upper end of the sleeve 13 adjacent to the step 19 for attaching the magnet member 20 and the circumferential groove 25 provided at the lower end of the sleeve 13. It can be attached. This
Both end portions of the center of gravity of the unbalance correction of Rikai rolling member becomes possible, thereby improving the accuracy of the unbalance modifications to the moment, it is to prevent the scattering of the adhesive by the centrifugal force during rotation.

Next, the operation will be described. In the bearing device having the above configuration, the sleeve 13 is axially supported on the fixed shaft 12 by the thrust magnetic bearing S. Therefore, it is not necessary to provide a spiral groove for the thrust bearing in the radial fluid bearing R, so that the height of the device in the axial direction is low and the structure is simple. Also, 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, so that there is no contact both at rest and during rotation. Both the small-diameter surface 112a of the fixed shaft and the large-diameter surface 13a of the sleeve can be processed simultaneously with the bearing surface of the radial fluid bearing R, so that good coaxiality is obtained and magnetic unbalance in the radial direction is small. Therefore, the contact between the radial bearing surfaces 14 and 15 at the time of starting is small, the starting friction torque of the radial fluid bearing R is small, and the damage at the time of starting and stopping is small.

Further, since the sleeve 13 has no large flange but only the slightly protruded flange 23, 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 the radial fluid bearing R to move radially between the one radial bearing surface 14 and the other radial bearing surface 15. Dynamic pressure is generated in the bearing clearance of the sleeve 13
Is completely non-contactingly supported in the radial direction, and can reach high-speed rotation with a short rise time.

The fitting between the mirror 50 and the case 63 of the rotor magnet 61 and the sleeve 13 is performed by shrink fitting or press fitting, and there is no clearance in the fitting surface. Even if it rises, the center of gravity of the mirror 50 and the case 63 of the rotor magnet rarely moves with respect to the rotation center of the sleeve 13. Therefore, there is little loss of balance and the balance of rotation is maintained.

FIG. 2 shows a second embodiment. In the thrust magnetic bearing S of this embodiment, the magnet member 18 fixed to the free end of the fixed shaft 12 made of a nonmagnetic material is magnetized in the axial direction by two disk-shaped magnetic yokes 30a. The upper and lower surfaces of the formed cylindrical permanent magnet 30b are sandwiched. On the other hand, a magnetic member 20 made of a magnetic material having a U-shaped cross section
The yoke 30 of the magnet member 18 is
It is attached to the inner peripheral surface of a sleeve 13 made of a non-magnetic material so as to face a.

In this thrust magnetic bearing S, since a permanent magnet having a weak strength is not attached to the sleeve 13, it can withstand a large centrifugal force, and can operate at a higher speed than those of the first and second embodiments. Suitable for rotation. FIG. 3 shows a third embodiment. In this embodiment, the case 63 of the rotor magnet is fixed to the sleeve 13 by caulking, and the case 63 and the sleeve 13 are integrated by plastic deformation. Therefore, the center of gravity of the case 63 is changed by the difference in the linear expansion coefficient during heat generation due to high-speed rotation.
To the center of rotation. The mirror 50 is screwed to the flange 23 with a screw 70. The difference between the outer diameter of the flange 23 and the inner diameter of the mirror 50 is set to 8 mm or less. When the outer diameter of the mirror 50 is smaller than the outer diameters of the rotor magnet members 61 and 63, the rotor magnet members 61 and 63 are shrink-fitted, attached to the sleeve 13 by press-fitting or crimping.
May be loosely fitted into the sleeve 13 and screwed to the flange 25. That is, if one of the mirror 50 and the rotor magnet members 61 and 63 that is dominant in the movement of the center of gravity of the rotating member is shrink-fitted to the sleeve 13 and attached by press-fitting or crimping, the other is fitted to the sleeve 13 by a loose fit. In addition, even if the screw is screwed to the flange 23, vibration caused by imbalance caused by heat generated by high-speed rotation can be reduced.

An annular non-magnetic spacer 71 is provided between the yoke 30a and the step surface of the fixed shaft 12. In this way, even when the fixed shaft 12 is made of a magnetic material, the magnetic flux concentrates between the magnetic member 20 and the yoke 30a. The magnet member 18 may be attached to the fixed shaft 12 with an adhesive, and an axial clearance may be provided between the magnet member 18 and the step surface of the fixed shaft 12 except for the spacer 71.

The fixed shaft 12, the spacer 71, and the magnet member 1
8 is fixed with an adhesive, and a radial clearance is provided between the inner diameter surface of the magnet member 18 and the fixed shaft 12. Even if the fixed shaft 12 is made of a magnetic material, the gap between the magnetic member 20 and the yoke 30 a is increased. The magnetic flux is further concentrated. In addition, a cylindrical spacer may be provided in a radial gap between the inner diameter surface of the magnet member 18 and the fixed shaft 12.

FIG. 4 shows a fourth embodiment. In this embodiment, a rotor magnet 61 as a rotor magnet member of the drive motor 60 is directly fixed to the outer peripheral surface of the sleeve 13 to constitute an inner rotor type drive motor. The stator 64 that is circumferentially opposed to the rotor magnet 61 is attached to the inner circumferential surface of the housing 11. The rotor magnet 61 may be fixed to the outer peripheral surface of the sleeve 13 by adhesion. However, it is preferable that the rotor magnet 61 is attached by shrink fitting or press fitting for high-speed rotation to eliminate the clearance.

In the thrust magnetic bearing S of this embodiment, the fixed-side magnet member 18 is the same as that of the third embodiment. On the other hand, the rotating magnet member 20 is
Similarly, the upper and lower surfaces of the cylindrical permanent magnet 30b are sandwiched by two disk-shaped magnetic yokes 30a, and the inner peripheral surface of the yoke 30a of the magnet member 20 is The magnet member 20 is fixed to the inner peripheral surface of the sleeve 13 so as to face the outer peripheral surface. The permanent magnet 30b fixed to the fixed shaft 12 and the permanent magnet 30b fixed to the sleeve 13 are both magnetized in the axial direction.
The directions of magnetization are opposite.

The magnet members 18 and 20 of the thrust magnetic bearing S shown in FIG. 1 are magnetized in the radial direction or the axial direction. On the other hand, the magnet members 18, 20 of the thrust magnetic bearing S shown in FIGS.
Are magnetized in the axial direction. Note that the magnetization in the axial direction has an advantage that the manufacture of the magnet is easier than the magnetization in the radial direction.

[0032]

As described above, according to the present invention,
Since the axial load is supported by the thrust magnetic bearing, there is no need for a spiral groove for the thrust bearing on the radial bearing surface, and the effect of reducing the axial height can be obtained. In particular, the radius between the fixed shaft and the sleeve
By using a suction type thrust bearing that acts in the direction,
Also in this regard, the axial height can be further reduced
You. In addition, since the thrust magnetic bearing is not in contact at the time of standstill or at the time of rotation, the effect that the starting friction torque can be reduced can be obtained.

According to the second aspect of the present invention, both when stationary and when rotating
Are also non-contact in the thrust magnetic bearing,
There is an effect that the friction torque can be more reliably reduced.
According to the third aspect of the present invention, the air enters and exits by the air damper.
The sleeve movement in the axial direction
Axial rigidity of a bearing device using a thrust magnetic bearing
Can be increased.

According to the fourth aspect of the present invention, the sleeve is
Must not adversely affect the magnetic circuit of the strike magnetic bearing
This has the effect.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a third embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a fourth embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing an example of a conventional bearing device.

[Explanation of symbols]

 12 Fixed shaft 13 Sleeve 14 One radial bearing surface 15 The other radial bearing surface 16 Herringbone-shaped groove 18 Magnet member (fixed side) 20 Magnet member or magnetic member 50 Mirror 61 Rotor magnet (rotor magnet member) 63 Case ( Rotor magnet member)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F16C 32/00-32/06 F16C 17/02 G02B 26/10

Claims (4)

(57) [Claims] A fixed shaft provided with a rotatable sleeve;
Radial bearing surface on inner peripheral surface of sleeve and radial bearing clearance
Radial bearing surfaces on the outer peripheral surface of the fixed shaft
In addition, a groove for generating dynamic pressure is provided on at least one of the bearing surfaces.
While supporting the radial load,
Magnet member or magnetic member attached to the
Magnet member attached to the fixed shaft opposite to each other with a gap
Constitutes a suction type thrust bearing between
A bearing device wherein an axial load is supported by a bearing. 2. The radial gap of a thrust bearing is
The bearing device according to claim 1, wherein the clearance is larger than the radial bearing clearance . 3. A three-part housing for supporting a fixed shaft.
Between the inner inner peripheral surface facing the outer peripheral surface of the sleeve and the outer peripheral surface of the sleeve.
Reduce the clearance to 150mμ or less, and
The bearing device according to claim 1, wherein an air damper is provided between the housing and the housing . 4. The bearing device according to claim 1, wherein the sleeve is made of a non-magnetic material .