JP2001200835A - Pivot bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pivot bearing structure capable of high precision positioning in the axial direction. SOLUTION: The pivot bearing structure is provided with adjusting shafts 5, 5 capable of adjusting advance and retract of stator frame 4, 4a in the axial direction to be structured to support axial force of a rotor 1a at one point between the adjusting shafts 5, 5 and the rotor 1a. The adjusting shafts 5, 5 are inserted through sleeve-like rings 6, 6 which are very closely fitted in the stator frames 4, 4a to retain their outer peripheral surfaces to the stator frames 4, 4a. The rings 6, 6 are provided with pressing members 7, 7 for pressing their outer peripheral surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pivot bearing structure for receiving an axial force at one point, and more particularly to a pivot bearing structure capable of highly accurate axial positioning.

[0002]

2. Description of the Related Art FIG. 4 is a conceptual view showing a structure for supporting a rotating shaft by two pivot bearings. The rotating shaft 101 is supported in both axial directions by magnetic radial bearings 102 and 102 and is supported in the axial direction by two pivot members 103 and 103 such as hard spheres. This pivot member 103,
Reference numeral 103 denotes a rotor disposed at a predetermined limited position in order to hold the rotor at a position immediately near a neutral point where the total weight of the rotor acting on the rotating shaft 101 and the axial force by the magnetic radial bearings 102 and 102 becomes zero. By doing so, the quasi-non-contact support is made possible by keeping the axial force small. In detail, the adjusting shafts 105, 10 having receiving plates 103a, 103a for receiving the pivot members 103, 103, respectively.
5 is provided so as to be able to advance and retreat with respect to the stator frame 104, and a fixing means is provided. After adjusting each of the adjustment shafts 105, 105 at a position separated by a predetermined small gap from the neutral point, the fixing means is tightened by the fixing means. The adjustment shafts 105, 105 are fixed at that position.

[0003]

However, despite the fact that the adjusting shafts 105 and 105 are aligned with high accuracy, it has become apparent that a predetermined positional accuracy cannot be finally secured. The positioning accuracy of the adjusting shafts 105, 105 is required to be within a predetermined allowable dimensional range on the order of μm. In order to satisfy this condition, it is necessary to secure not only the positioning accuracy of the adjustment shafts 105 and 105 but also the accuracy at the time of fastening and fixing. However, as described below, it has been found that the required fixing accuracy cannot be obtained by the tightening and fixing with the general fixing structure.

FIG. 5 is a conceptual diagram showing a general structure for fixing an adjusting shaft of a pivot bearing. FIG. 7A shows an adjustment shaft 105 with a set screw 112 via a pressing sphere 111.
Is an example of pressing and fixing from the side. FIG. 2B shows an example of split fastening in which fastening pieces 114 and 114 are formed by slits 113 reaching holes through which the adjustment shaft 105 is inserted, and the adjustment shaft 105 is fastened and fixed via screws 115. It has been found that any of these general fixing structures causes the adjusting shaft 105 to be deformed in the axial direction upon tightening, and the required fixing accuracy cannot be satisfied. Since the pressing sphere 111 contacts the side surface of the adjusting shaft 105 in FIG. (A), the adjusting shaft 105 is affected by the rotation of the pressing sphere 111 due to the rotation of the set screw 112, and the adjusting shaft 105 in FIG. The cause is considered to be the influence of the circumferential movement of the tightening pieces 114, 114 for tightening the outer peripheral surface. An object of the present invention is to provide a pivot bearing structure capable of performing high-precision positioning in the axial direction.

[0005]

In order to solve the above-mentioned problems, an adjusting shaft is provided which is adjustable in the axial direction with respect to the stator frame, and the axial force of the rotor is adjusted between the adjusting shaft and the rotor. In the pivot bearing structure supporting at one point, the adjusting shaft is closely fitted to the stator frame without any gap, and is inserted through a sleeve-like ring whose outer peripheral surface is restrained by the stator frame, and this ring presses the outer peripheral surface. A pressing member is provided.

In the above-structured pivot bearing structure, since the outer peripheral surface of the ring is restrained by the stator frame, when the outer peripheral surface of the ring is pressed by the pressing member,
The ring remains fixed relative to the stator frame,
Strain deformation in the radial direction causes the inner peripheral surface to be reduced in diameter. Therefore, the adjusting shaft having an outer diameter dimension within the range of the strain deformation is pressed and fixed by the inner circumferential surface of the ring without its outer circumferential surface being subjected to axial deformation.

[0007] The pressing member is formed by a set screw which is screwed to the stator frame at right angles to the axial direction, so that the fixing accuracy can be easily secured.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a rotary mirror device to which the pivot bearing structure of the present invention is applied, partially cut away, FIG. 2 is an enlarged view of the pivot portion of FIG. 1, and FIG.
FIG. The sleeve body 1 holding the rotor 1a of the rotary mirror device is supported by radial magnetic bearings 2 and 2 provided at both ends thereof in a radial direction, and is supported by a pivot member 3 such as a sphere fixed to a hollow portion of the sleeve body 1. Boards 3a, 3
a) in the axial direction by two pivot bearings.

The radial magnetic bearings 2, 2 oppose magnetic poles in the axial direction so as to attract two ring-shaped magnets magnetized in the direction of the rotation axis L to each other, and form a sleeve body 1 and a temperature compensating member in the axial direction. The rotor frame 4b is provided concentrically with the rotation axis L on the stator frames 4 and 4a.

Receiving plates 3a, 3a constituting a pivot bearing
Are provided at respective ends of the adjustment shafts 5 provided on the stator frame 4 along the rotation axis L, and receive axial force of the pivot member.

The adjusting shafts 5, 5 are slidably inserted into sleeve-shaped rings 6, 6 whose outer peripheral surfaces are restrained and fitted to the stator frame 4 without any gap by press fitting or the like. This ring 6,
6 is provided with a set screw 7 of FIG. The push screw 7 is engaged with the stator frame 4 so as to be able to advance and retreat at right angles to the adjustment shaft 5. These rings 6, 6 and their set screws 7, 7
It constitutes means for fixing the adjustment shafts 5,5.

In the pivot bearing provided with the fixing means, when the push screw 7 is screwed into the ring 6 to press the ring 6, the outer peripheral surface of the ring 6 is in close contact with the stator frame 4. Deformation is regulated. Therefore, if there is another free space, a strain deformation occurs toward this free space. That is, if there is a gap between the ring 6 and the adjustment shaft 5 on the inner peripheral surface thereof,
Reduce the diameter to fill the free space.

The diameter reduction of the ring 6 due to strain deformation is as follows.
Since the ring 6 is fixed to the stator frame 4, the adjusting shaft 5 can be tightened and fixed at that position without causing relative movement with respect to the stator frame 4.

In addition, a polygon mirror 12 is mounted on the sleeve body 1 via a holder 11, and further a magnet 1
3 and yoke 14 are attached to the sleeve body 1 and a coil 15 for generating a rotating magnetic field is attached to the stator frame 4 to constitute a rotating mirror device.

The assembly adjustment of the rotary mirror device using the pivot bearing having the above configuration will be described. When the position of the rotor 1a is set at a neutral point where the sum of the attraction force by the radial magnetic bearings 2, 2 and its own weight and the axial force acting on the rotor 1a becomes zero, the pivot member 3 and the receiving plate 3a,
In order to secure a predetermined optimum pivot gap G between the adjusting shafts 5 and 3a, the adjusting shafts 5 and 5 are respectively aligned with required accuracy. In this state, push the screw 7 into the ring 6,
By pressing 6, the adjusting shafts 5, 5 can be fixed without impairing the positioning accuracy.

The dimension setting of the pivot gap needs to be as small as possible in order to reduce the axial force due to the deviation from the neutral point of the rotor. On the other hand, the pivot gap G fluctuates with a change in environmental temperature due to a difference in temperature coefficient of each member, and also fluctuates with a change in driving conditions that causes a temperature difference in the apparatus due to heat generation of the coil. A dimension that satisfies the fluctuation factors is required. Therefore, in order to realize the quasi-non-contact support while suppressing the axial force while satisfying the above-mentioned fluctuation factors, the pivot gap G is required to have high-precision dimensional control.

Under such severe conditions, the pivot bearing structure can fix the adjusting shafts 5 and 5 with high precision, so that a pivot gap G having an optimum size that satisfies the above-mentioned fluctuation factors can be realized.

In addition, the pivot member 3 and the temperature compensating member 4b are configured to suppress the fluctuation of the pivot gap G and to improve the rotation characteristics.
The following is a supplement to its contents.

The pivot member 3 can be configured to have a small axial length between the two holding shafts 5, 5 even when the sleeve body 1 is long in the axial direction.
The amount of change in thermal expansion of the pivot member 3 is suppressed to a small value.

Therefore, even if a temperature difference occurs between the stator frames 4, 4a and the rotor 1a, the pivot member 3
Since the positions of the two fulcrums do not greatly change, an excessive change in the pivot pressure can be avoided by keeping the pivot gap G substantially constant.

The pivot members 5 are disposed at equal distances from the radial magnetic bearings 4 at both ends of the sleeve body 3 so that the stator frames 4 and 4a and the rotor 1a
Even if a temperature difference occurs between the two, the balance between the two magnetic gaps C1 and C2 is maintained, so that the fluctuation of the neutral point of the rotor 1a is suppressed. Further, by disposing the center of gravity of the rotor 1a at the center of the pivot member 3, the resonance mode defining the dynamic behavior of the rotor 1a is limited to a specific vibration pattern having the center of gravity as a fixed node. The rotation of the rotor 1a can be easily stabilized. In addition, even when the rotation axis L is inclined by the moment applied to the rotor 1a, the eccentricity of the pivot member is small, so that the sliding wear can be reduced.

The temperature compensating member 4b has a size and a temperature coefficient for suppressing a dimensional change of the pivot gap G due to a difference in the amount of thermal expansion of the member.
Since the pivot member 3 is provided with a degree of freedom without being restricted by a material and a shape dimension, the pivot member 3 can be formed of an optimum material in terms of workability, wear resistance, and the like. .

The applicable range of the pivot bearing structure of the present invention is as follows.
The present invention is not limited to the rotary mirror device described above, but is widely applicable to general pivot bearings including the general rotary shaft support structure shown in FIG. Therefore, the description is omitted.

[0024]

The pivot bearing structure of the present invention has the following effects. In the pivot bearing structure having the above configuration, since the outer peripheral surface of the ring is constrained by the stator frame, when the outer peripheral surface of the ring is pressed by the pressing member, the ring is fixed to the stator frame in the radial direction. The diameter of the inner peripheral surface is reduced by the strain deformation. Therefore, the adjusting shaft having an outer diameter dimension within the range of the strain deformation is pressed and fixed by the inner circumferential surface of the ring without its outer circumferential surface being subjected to axial deformation.

Therefore, the pivot bearing structure of the present invention does not undergo displacement in the axial direction when the adjusting shaft is fixed.
It is possible to accurately fix and fix the adjustment shaft at that position without impairing the positioning accuracy of the adjustment shaft with respect to the stator frame.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a rotary mirror device to which a pivot bearing structure according to the present invention is applied, which is partially cut away.

FIG. 2 is an enlarged view of a pivot portion of FIG.

FIG. 3 is a view taken in the direction of arrow A in FIG. 1;

FIG. 4 is a conceptual diagram showing a support structure of a rotating shaft by two pivot bearings.

FIG. 5 is a conceptual diagram showing a general fixing structure of an adjusting shaft of a pivot bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sleeve body 1a Rotor 2 Radial magnetic bearing 3 Pivot member 3a Receiving plate 4 Stator frame 4a Stator frame 4b Temperature compensation member 5 Adjusting shaft 6 Ring 7 Push screw (pressing means) C1, C2 Magnetic gap G Pivot gap L Rotation axis

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazushi Hayashi 110-1 Shinkushita-Nita, Iruma-shi, Saitama F-term (reference) at Nidec Copal Electronics Corporation Iruma Office 3J011 AA02 BA10 KA03 MA12 3J102 AA01 BA03 BA17 CA11 DA03

Claims (2)

[Claims] 1. A pivot bearing structure comprising an adjusting shaft capable of adjusting the axial movement of a stator frame in an axial direction, and supporting a single axial force of the rotor between the adjusting shaft and the rotor. A pivot, which is fitted closely to the stator frame without any gap, and is inserted into a sleeve-like ring whose outer peripheral surface is restrained by the stator frame, and the ring is provided with a pressing member for pressing the outer peripheral surface thereof. Bearing structure. 2. The pivot bearing structure according to claim 1, wherein said pressing member is constituted by a set screw which is screwed to a stator frame at right angles to an axial direction.