JP2001204155A - Magnetic support structure of rotary unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic support structure of a rotary unit which can suppress an axial force and secure durability regardless of driving conditions such as evolution, etc. SOLUTION: This magnetic support structure 1 of a rotary unit comprises two radial magnetic beraings 4 and 4 which are provided between a stator frame 2 and a rotor 3a of a rotation apparatus, and two pivot bearing which receive an axial force applied to the rotor 3a. The rotor 3a is supported rotatably in a quasi-noncontact state by the pivot bearings in the neighborhood of a neutral point of the balance in an axial direction. The rotor 3a has a sleeve 3 concentric, with its rotation axis L. The radial magnetic bearings 4 and 4 are provided on both the ends of the sleeve 3. The pivot bearings comprise a pivot element 5 provided in the hollow part of the sleeve 3, and two holding shafts 6 and 6 provided on the stator frame 2 so as to hold the pivot element 5 between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic support structure for a rotating body that supports a high-speed rotating body, and more particularly to a rotating structure capable of suppressing a pivot pressure and ensuring durability without depending on driving conditions such as a rotating speed. It relates to the magnetic support structure of the body.

[0002]

2. Description of the Related Art FIG. 5 is a conceptual view showing the structure of a general magnetic support structure for a rotating body. A general rotating body support structure 101 using a radial magnetic bearing is configured to rotatably support a rotor on a stator frame 102. The rotor is
A rotating shaft 10 supporting a load (not shown) about a rotating axis L
Axial radial magnetic bearings 10 at both ends
4, 104, and a pivot bearing that receives an axial force at one point. This pivot bearing is composed of hard balls 105, 1
05 and a receiving plate 105 provided on the stator frame 102.
a and 105a. In addition to the temperature compensation member 106 provided on the stator frame 102, a drive system including a drive coil 107 and a magnet 108 opposed thereto is provided. The two pivot bearings composed of the hard spheres 105, 105 and their receiving plates 105a, 105a rotate by holding the rotating shaft 103 at a position near a neutral point where the total axial force received by the rotor becomes zero. The shaft 103 can be supported in a quasi-non-contact state. When the coefficients of thermal expansion of the members are different from each other, by selecting the size and material of the temperature compensating member 106, the mutual change of the member dimensions due to the environmental temperature change can be canceled and the fluctuation of the pivot gap can be suppressed. Drive coil 1
In the case where heat is generated inside the device due to the excitation of 07 or the like, since the heat transfer is hindered by the pivot gap of the pivot bearing and the fulcrum of the point contact, a temperature difference is generated between the stator frame and the rotor. By providing a temperature compensating member that suppresses this temperature difference and a corresponding dimensional change between the two, it is possible to suppress a dimensional change in the pivot gap.

[0003]

However, the amount of heat generated due to the excitation of the drive coil 107 changes according to the driving conditions such as the rotational speed. Therefore, depending on the temperature compensating member having a predetermined compensation accuracy at the predetermined temperature, There is a problem that compensation accuracy over the entire range of various driving conditions cannot be ensured. In particular, in the case where the inside of the device is exhausted and depressurized in order to suppress the rotational resistance of the rotor, heat transfer due to convection is reduced, so that the temperature difference between the stator frame and the rotor is further increased. As a result, when the gap is eliminated, the pivot bearing generates an excessive contact pressure, and when the gap dimension is too large, the rotating shaft 103 deviates from the neutral position to generate a large pivot pressure, thereby lowering the durability. Invite. In addition, since the rotor is levitated and supported by two radial magnetic bearings, an unstable combination of vibration modes may cause unstable rotational vibration. Further, a moment that tilts the rotational axis L may be generated. It also has a problem that when it is received, wear due to eccentricity of the pivot fulcrum cannot be avoided.

[0004] It is an object of the present invention to provide a magnetic support structure for a rotating body capable of suppressing the pivot pressure and ensuring durability without depending on driving conditions.

[0005]

In order to solve the above-mentioned problems, two radial magnetic bearings interposed between a stator frame of a rotating device and a rotor, and two pivots receiving axial force acting on the rotor. Consisting of bearings
In a magnetic support structure of a rotating body that rotatably supports a rotor near a neutral point balanced in the axial direction by the pivot bearing in a quasi-non-contact state, the rotor includes a sleeve body concentric with its rotation axis. The radial magnetic bearings are arranged at both ends of the sleeve body, a pivot member is provided in a hollow portion of the sleeve body, and the stator frame is provided with two holding shafts supporting the pivot member so as to sandwich the pivot member from both sides in the axial direction. Make up the bearing.

With the above structure, only the pivot member affects the pivot gap, and the axial length of the pivot member is reduced between the two holding shafts even when the sleeve is long in the axial direction. can do. Therefore, even if a temperature difference occurs between the stator frame and the rotor, the pivot gap does not greatly change, so that the pivot gap is kept substantially constant even by a change in the amount of heat generated in the device according to the driving conditions. Fluctuation of the pivot pressure can be avoided.

[0007] By disposing the pivot member at an equal distance from the radial magnetic bearings at both ends of the sleeve body, even if a temperature difference occurs between the stator frame and the rotor, the balance between the two magnetic gaps is maintained. Fluctuation of the neutral point of the rotor is suppressed. By forming the pivot member from a single sphere having a constant radius, a high-precision pivot bearing can be easily configured. By arranging the center of gravity of the rotor at the center of the pivot member, the resonance mode that defines the dynamic behavior of the rotor is limited to a specific vibration pattern having the center of gravity as a fixed node,
Stabilization of the rotor rotation is facilitated. Further, even when the rotor receives a moment that tilts the rotation axis, the pivot fulcrum is located near the pivot member and its eccentric amount is small, so that sliding wear can be suppressed to a small value.
Since the stator frame includes a temperature compensating member that suppresses a dimensional change of a pivot gap due to a difference in thermal expansion between members, a degree of freedom in selecting a member is secured, so that a pivot bearing can be configured using an optimal material. it can. Since the holding shaft is provided with a collar-shaped ring whose outer peripheral surface is constrained to the stator frame and a pressing member that presses the outer peripheral surface of the ring, the holding shaft can be fixed without moving in the axial direction. The pivot bearing enables highly accurate positioning in the axial direction.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing the basic configuration of the present invention, and FIG. 2 is an enlarged view of a main part of FIG. The magnetic support structure 1 includes a stator frame 2 and a rotor 3
It is configured to rotatably support a. This rotor 3a
The axially arranged radial magnetic bearings 4 and 4 are provided at both ends of a sleeve 3 that supports a load (not shown), and a pivot member 5 such as a sphere is fixed to the center of the sleeve 3. In order to support the pivot member 5 in the axial direction, holding shafts 6, 6 which respectively enter into the hollow portion of the sleeve body 3 from both ends thereof, protrude from the stator frame 2.

A pivot bearing is formed by providing receiving plates 5a, 5a for receiving the pivot member 5 at the ends of the holding shafts 6, 6. The pivot member 5 serves as a pivot fulcrum and supports the rotor 3a in the axial direction. Further, a temperature compensating member 7 acting in the axial direction is provided on the stator frame 2, and a drive system including a drive coil 8 and a magnet 9 opposed thereto is provided.

The radial magnetic bearings 4, 4 are arranged concentrically with the rotation axis L with their magnetic poles facing each other in the axial direction so as to attract two ring-shaped magnets magnetized in the direction of the rotation axis L. The rotor 3a is positioned at a neutral point where the sum of the attraction force of the radial magnetic bearings 4, 4 and its own weight and other acting forces of the rotor 3a in the axial direction become zero, and the pivot member 5 and the receiving plates 5a, 5a And two pivot bearings are arranged with an optimum pivot gap G therebetween.

In the magnetic support structure having the above structure, the pivot member 5 supports the rotor 3a in the axial direction. Even when the sleeve body 3 is long in the axial direction, the pivot member 5 can be configured to have a small axial length between the two holding shafts 6.

Therefore, even if a temperature difference is generated between the rotor 3a and the stator frame 2 due to heat generation of the drive coil 8 or the like, an excessively large pivot pressure is avoided by keeping the dimension of the pivot gap G substantially constant. be able to.
Regarding the configuration of the pivot bearing, a similar operation and effect can be obtained by configuring a known pivot bearing regardless of the shape of the pivot fulcrum such as a sphere or a cone.

The position of the pivot member 5 is set at the same distance from the radial magnetic bearings 4, 4 at both ends of the sleeve body 3, so that even if a temperature difference occurs between the stator frame 2 and the rotor 3a, Since the balance between the two magnetic gaps C1 and C2 is maintained, the fluctuation of the neutral point of the rotor 3a is suppressed. Further, since the stator frame 2 is provided with a temperature compensating member having a dimension and a temperature coefficient for suppressing a dimensional variation of the pivot gap G due to a difference in thermal expansion between the members, the pivot member is restricted by a material and a shape dimension. Therefore, the pivot bearing can be made of an optimum material in terms of workability, wear resistance and the like.

FIG. 3 is a cross-sectional view of the rotary mirror device to which the magnetic support structure of the present invention is applied, which is partially cut away, and FIG. 4 is a view taken in the direction of arrow A in FIG. The rotating mirror device 11 is configured by rotatably supporting a rotor 10 as a rotating body on a substantially rectangular stator frame 12. The rotor 10 has a polygon mirror 13
a, a sleeve body 13 for supporting the polygon mirror 13a on the rotation axis L, and the like. Axial radial magnetic bearings 14, 14 are formed at both ends of the sleeve body 13, and the center of the sleeve body 13 equidistant from the radial magnetic bearings 14, 14 is aligned with the center of gravity of the rotor 10, and is fixed. The pivot member 15 made of a single sphere having a radius is fixed by press-fitting or the like. In order to receive the pivot member 15 in the axial direction, holding shafts 16, 16 which respectively enter the hollow portion of the sleeve body 13 from both ends thereof are protruded from the stator frame 12.

A temperature compensating member 17 acting in the axial direction is interposed on the stator frame 12, and is attached to a driving coil 18, a magnet 19 opposed thereto and holding members 13b and 13c for fixing the polygon mirror 13a. A drive system including a yoke 19a is provided.

At the ends of the holding shafts 16, 16, receiving plates 15a, 15a made of wear-resistant ceramic or the like for receiving the pivot member 15 in the axial direction are provided. Rings 20 and 20 having a collar shape for fixing the holding shafts 16 and 16 at predetermined positions and a set screw 21 shown in FIG. 4 serving as a pressing member for pressing the outer peripheral surfaces of the collars are provided. Ring 20, 2
0 is tightly constrained by the stator frame 12 by press fitting or the like, and each set screw 21 is screwed to the stator frame 12 at right angles to the rotation axis L so as to press each side surface of the rings 20, 20. Combine.

The operation and effect of the magnetic support structure having the above configuration will be described below. The axial length of the pivot member 15 is reduced by the spherical body, and a high-precision pivot bearing can be easily formed. Therefore,
Even when a temperature difference occurs between the rotor 10 and the stator frame 12 due to heat generated inside the device, the fluctuation of the pivot gap G can be suppressed to a small amount because the amount of thermal expansion in the axial direction is small.

Specifically, the dimensional change in the axial direction of a sphere having a diameter of 2 mm due to the bearing steel is 0.1 mm at a temperature difference of 5 ° C.
It can be suppressed to 13 μm. This dimensional change has a length of 20m
m is about 1/20 due to the size effect and the temperature coefficient effect in comparison with the thermal expansion change of the aluminum shaft of 2.4 μm.
Thus, a predetermined pivot gap can be substantially maintained.

The resonance mode that defines the dynamic behavior of the rotor 10 is such that the rotor 10 is positioned at the center of a sphere 15 that is a pivot member.
By adjusting the position of the center of gravity, the vibration is limited to a specific vibration pattern having the center of gravity as a fixed node, so that the rotation of the rotor can be easily stabilized. Further, even when the rotation axis L of the rotor 10 is tilted due to the moment applied to the rotor 10, the amount of eccentricity of the pivot fulcrum is small, so that the eccentric load and sliding wear can be reduced.

The pivot member 15 and the two holding shafts 1
By forming the pivot bearing with the receiving plates 15a, 15a provided at the ends of the 6, 6 end, a high-precision pivot bearing can be easily configured.

Since the outer surfaces of the rings 20, 20 are restrained by the stator frame 12, after the holding shafts 16, 16 are set at predetermined positions, the setscrews 21, 2 are set.
By pressing the outer peripheral surface with 1, the rings 20, 20 receive strain in the inner circumferential direction, and the strain does not cause the holding shafts 16, 16 to move in the axial direction.
The holding shafts 16 can be fixed. Therefore, an optimal gap can be secured with high accuracy in order to hold the rotor 10 near its neutral point.

As described above, the above-described rotating mirror device can secure stable high-speed rotation and durability in a quasi-non-contact state without depending on a change in driving conditions such as a rotating speed, by the magnetic support structure. it can.

[0023]

The magnetic support structure for a rotating body according to the present invention has the following effects. Due to the magnetic support structure of the rotating body having the above structure, only the pivot member affects the pivot gap, and even if the sleeve body is long in the axial direction, the axial length of the pivot member between the two holding shafts is reduced. It can be configured to be small.

Therefore, even if a temperature difference occurs between the stator frame and the rotor, the pivot gap is not greatly changed, so that the pivot gap can be substantially changed by a change in the amount of heat generated in the device according to the driving conditions. It can be kept constant to avoid fluctuations in the pivot pressure.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the basic configuration of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1;

FIG. 3 is a cross-sectional view of a rotating mirror device to which the magnetic support structure of the present invention is applied, which is partially cut away.

FIG. 4 is a view taken in the direction of arrow A in FIG. 3;

FIG. 5 is a conceptual diagram of a configuration of a general magnetic support structure of a rotating body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic support structure 2 Stator frame 3 Sleeve body 3a Rotor 4 Radial magnetic bearing 5 Pivot member 5a Receiving plate 6 Holding shaft 7 Temperature compensating member 8 Drive coil 10 Rotor 11 Rotating mirror device 12 Stator frame 13 Sleeve body 14 Magnetic bearing 15 Pivot member 16 Holding shaft 17 Temperature compensation member 20 Ring 21 Set screw (pressing member) 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 Nidec Copal Electronics Co., Ltd. Iruma F-term (reference) 3J011 AA20 BA08 DA01 3J102 AA01 AA07 BA04 BA17 BA18 CA04 DA02 DA06 DA12 GA01 5H605 AA04 CC01 CC03 CC04 EA02 EB04 EB16 FF10 5H607 AA03 AA04 BB14 DD01 DD02 DD05 DD09 DD16 GG01 GG04 GG17

Claims (6)

[Claims] The present invention comprises two radial magnetic bearings interposed between a stator frame of a rotating device and a rotor, and two pivot bearings for receiving an axial force acting on the rotor. In a magnetic support structure of a rotating body that rotatably supports a rotor in a quasi-non-contact state near a neutral point to be balanced, the rotor includes a sleeve body concentric with its rotation axis,
The radial magnetic bearings are arranged at both ends of the sleeve body, a pivot member is provided in a hollow portion of the sleeve body, and two holding shafts that support the pivot member so as to sandwich the pivot member from both sides in the axial direction are provided on the stator frame. A magnetic support structure for a rotating body, characterized by comprising the above-mentioned pivot bearing. 2. The magnetic support structure for a rotating body according to claim 1, wherein the pivot members are arranged at equal distances from radial magnetic bearings at both ends of the sleeve body. 3. The magnetic support structure for a rotating body according to claim 1, wherein the pivot member is formed of a single sphere having a constant radius. 4. The magnetic support structure for a rotating body according to claim 1, wherein the center of gravity of the rotor is arranged at the center of a pivot member. 5. The magnetic support structure for a rotating body according to claim 1, wherein the stator frame includes a temperature compensating member for suppressing a change in a pivot gap dimension of the pivot bearing due to a difference in thermal expansion between the members. 6. The rotating body according to claim 1, wherein the holding shaft includes a collar-shaped ring whose outer peripheral surface is restrained by a stator frame, and a pressing member that presses the outer peripheral surface of the ring. Magnetic support structure.