JPH02304514A - Rotary body supporting device - Google Patents

Abstract

PURPOSE:To surely prevent the trouble that a rotary sleeve rubs against a fixed shaft, to increase the rotary load or damage the fixed shaft at the time of starting by providing a magnetic thrust bearing to prevent the force in the radial direction from acting on the rotary sleeve. CONSTITUTION:A first annular yoke member 31 fixed to a rotary sleeve 24, a first annular permanent magnet 32 fitted and fixed to an annular groove on the lower face of the member 31, a second yoke member 33 which faces the lower side of the first yoke member 31 and is fixed to a casing 22, and a second annular permanent magnet 34 fitted and fixed to an annular groove on the upper face of the member 33 are provided. The magnetic thrust bearing is provided which has such constitution that equal polarities of first and second annular permanent magnets 32 and 34 vertically face each other. In such a case, first and second yoke members 31 and 33 limit the spread of the luminous flux from first and second permanent magnets 32 and 34, and the displacing force in the radial direction does not act on the rotary sleeve 24. Thus, the rotary sleeve 24 is not deflected in the radial direction, and is not brought into contact with a fixed shaft 23 at the time of starting, and a dynamic pressure pneumatic journal bearing 25 is prevented from being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Summary) Regarding an outer rotor type rotating body support device that supports a rotating polygon mirror for scanning a laser beam in a laser printer, for example, it is possible to thrust the rotating sleeve without causing any force in the radial direction. A rotating sleeve is fitted onto the fixed shaft via a hydrodynamic air journal bearing and has a polygon mirror fixed thereto, and a casing accommodates the rotating sleeve and the polygon mirror inside. A rotating body support device comprising: a first circular ring member fixed to the rotary sleeve; A first annular permanent magnet fitted and fixed thereto, and a second yoke member fixed to the casing opposite to the lower side of the first yoke member are magnetized in the axial direction. A second annular permanent magnet is fitted and fixed in an annular groove on the upper surface of the second yoke member, and the first and second annular permanent magnets have the same polarity facing each other vertically. It is configured with a magnetic thrust bearing.

[Industrial application field]

The present invention relates to a seven rotor-type rotating body support device that supports a rotating polygon mirror for scanning a laser beam in a laser printer, for example. , high reliability is required for the thrust bearing.

A magnetic thrust bearing is used as the thrust bearing.

(Prior art) Fig. 6 shows a rotating body support device (rotating multi-faceted V1 mounting) 1 for an outer rotor shown in Japanese Patent Application Laid-Open No. 61-269115.
In the 1° diagram showing the
is the magnet rotor, and 6 is the drive! l] Coil, 7 is a casing.

The rotating sleeve 3 is supported in the radial direction by a hydrodynamic air journal bearing 8 and in the thrust direction by a magnetic thrust bearing 9.

As shown in an enlarged view in FIG. 7, this magnetic thrust bearing 9 includes a pair of annular permanent magnets 10 that are both magnetized in the axial direction.
．． Of the 11 parts, - is fixed to the rotating sleeve 3, and the other parts are fixed to the casing 7, and the circumferential sides thereof are arranged facing each other.

A magnetic flux flows as shown at 12, and the magnets 10 and 11 are magnetically coupled and support the rotating sleeve 3 in the thrust direction.

[Problem to be solved by the invention]

A loop of the magnetic flux 12 is formed by the magnet 11 on the fixed side and the magnet 10 on the rotating side.

Therefore, the magnetic thrust bearing 9 generates not only a force in the thrust direction but also a force in the radial direction, albeit to a small extent.

Therefore, when the hydrodynamic air journal bearing 8 is not sufficiently dynamic and the rotary sleeve 3 is started, the rotary sleeve 3 is pushed in the radial direction and comes into contact with the fixed shaft 2, causing friction and causing the starting torque to be turn into.

Moreover, when starting and stopping, the rotating sleeve 3 rubs against the fixed shaft 2, causing scratches, which impairs the reliability of the hydrodynamic air japle bearing 8.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotating body support device that can support a rotating sleeve in the thrust direction without causing any force in the radial direction.

(Means for Solving the Problems) The present invention provides a rotating body support device comprising a rotating sleeve externally fitted onto a fixed shaft via a hydrodynamic air journal bearing, and a casing that accommodates the rotating sleeve inside. , a first annular yoke member fixed to the rotating sleeve, and a first yoke member magnetized in the @h direction and fitted and fixed in an annular groove on the lower surface of the first yoke member. An annular permanent magnet, a second yoke member fixed to the casing opposite to the lower side of the first yoke member, magnetized in the axial direction, and an upper surface of the second yoke member a second annular permanent magnet fitted and fixed in the annular groove;
゜The magnetic thrust bearing is configured such that the same poles of the second annular permanent magnets are vertically opposed to each other.

Further, the present invention includes a space that acts as a fluid capacity between the first yoke member and the second yoke member, and a gap that acts as a fluid resistance on the inner and outer peripheral sides of the first yoke member. 3゜[Credit] 1st, which has a configuration further including an air damper. The second yoke member includes the first yoke member. Limiting the spread of magnetic flux from the second permanent magnet. As a result, firstly, the magnetic flux does not interlink with the fixed shaft, and unnecessary displacement force in the radial direction does not act on the rotating sleeve.

Secondly, the magnetic flux density between the 1111 stones facing each other increases, and the rigidity of the bearing increases.

The air damper suppresses vibrations in the axial direction of the rotating sleeve.

〔Example〕

FIG. 1 shows a rotating body support device (rotating polygon mirror device) 20 according to an embodiment of the present invention.

21 is a polygon mirror, and 22 is a casing.

A fixed shaft 23 is vertically fixed to the casing 22, and a rotating sleeve 24 is externally fitted onto the shaft 23. The rotating system consists of the outer rotor type shaft 23 and the sleeve 2.
4 constitutes a hydrodynamic air journal bearing 25. This bearing 25 is provided at the upper side of the shaft 23 and at the lower side.

The multifaceted tA21 is fixed to the upper part of the sleeve 24.

A rotor 26 is fixed to the center of the sleeve 24.

27 is a stator, which is fixed to the casing 22.

A magnetic thrust bearing 30 is a main part of the present invention, and is provided on the lower end side of the sleeve 24.

As shown in FIG. 2, this magnetic thrust bearing 30 includes a first annular yoke member 31, a first annular permanent magnet 32, a second annular yoke member 33, and a second annular yoke member 31. It is composed of an annular permanent magnet 34. 1st. The second permanent magnets 32, 34 are of the same size.

The first yoke member 31 is fixed to the lower end of the rotating sleeve 24 and rotates integrally with the rotating sleeve 24.

An annular ring 31b having a size corresponding to the first permanent magnet 32 is formed on the lower surface 31a of the first yoke member 31.

The first permanent magnet 32 is magnetized in the axial direction.
3Ib and is fixed.

The second yoke member 33 is fixed to the casing 22. An annular 1I 33b having a size corresponding to the second permanent magnet 33 is formed on the upper surface 33a.

The second permanent magnet 34 is magnetized in the axial direction, and the groove 3
3b and is fixed.

1st. The second permanent magnets 32, 34 are exactly opposite each other, with the same magnetic poles, for example north poles, facing each other.

Therefore, the magnetic flux of the first permanent magnet 32 flows around the permanent magnet 32 itself, as shown by the symbol 35, and the magnetic flux of the second permanent magnet 34 flows around the permanent magnet 34 itself, as shown by the symbol 36. flows to

Due to the magnetic repulsion force F between the magnetic fluxes 35 and 36 (between magnetic poles N), the rotating sleeve 24 is supported in a floating state by a dimension Q relative to the second yoke member 33.

The magnetic flux 35 flows only around the permanent magnet 32 on the rotating side, the magnetic flux 36 flows only around the permanent magnet 34 on the stationary side, and there is no magnetic flux between the permanent magnet 34 on the stationary side and the permanent magnet 32 on the rotating side. There is no flow.

Therefore, the magnetic thrust bearing 30
Only the axial force F is applied to the rotating sleeve 24, and no radial force is applied to the rotating sleeve 24.

Therefore, the rotating sleeve 24 is not brought into contact with the fixed shaft 23 in the radial direction, and the dynamic pressure air journal bearing 25 is prevented from being faked. In addition, the load at startup does not increase, and startup is smooth.

In addition, as shown in FIG. 3, simply annular permanent magnet 40.4
1 are placed opposite each other with the same poles facing each other, the magnetic flux widely spreads around each permanent magnet 40, 41 as shown by reference numerals 842, 43, resulting in the following inconvenience.

- The magnetic flux 42 interlinks with the fixed shaft 44, and a radial force acts on the rotating sleeve 45, causing the rotating sleeve 45 to rub against the fixed shaft 44.

■ Since the spread of magnetic flux 42, 43 is large, the magnetic flux density is small, and the repulsive force F is weaker than that of the present invention by the number 46, as shown by line ■ in Figure 4, and the rigidity as a magnetic bearing is low. , weak against impact.

On the other hand, in the magnetic thrust bearing 30 described above,
1st. The second permanent magnets 32, 34 are entirely surrounded by a yoke member outside the opposing positions. That is, the inner peripheral side of the first permanent magnet 32 is occupied by a yoke part 31C9, the outer peripheral side is occupied by a yoke part 31d, and the opposite side to the surface facing the second permanent magnet 34 is occupied by a yoke part 31e. Similarly, the inner circumferential side of the second permanent magnet 34 is occupied by a yoke portion 33c, the outer circumferential side is occupied by a yoke portion 33d, and the side opposite to the surface facing the first permanent magnet 32 is occupied by a three-way portion 33e.

Therefore, the magnetic flux 35 emitted from the N pole of the first permanent magnet 32
without expanding, it immediately enters the inner and outer yoke parts 33c and 33d, and the yoke parts 33c and 33d
The liquid flows inside the yoke portion 33e, and further flows through the inside of the yoke portion 33e to reach the S pole.

Similarly, the magnetic flux 36 emitted from the Ni of the second permanent magnet 34 does not spread and immediately reaches the yoke portions 3 on the inner and outer circumferential sides.
3C and 33d, flows through yoke portions 33c and 33d, and further flows through yoke portion 33e to reach s#fA.

Here, the function of each yoke portion will be explained.1゜■ Function of the inner peripheral side yoke portions 31c and 33c.

The magnetic flux 35.36 coming out from the N pole immediately reaches the inner yoke part 3.
1C, 33c, magnetic flux 35°36 is fixed axis 2
It does not interlink with 3.

That is, generation of a radial displacement force on the rotating sleeve 24 is prevented.

(2) Actions of the inner yoke portions 31c, 33c and the outer yoke portions 31d, 33d.

Preventing the magnetic flux 35.36 from spreading, the magnet 32.34
The magnetic flux density of the surface portions of the opposing 'IIa poles is improved.

■ Function of the yoke parts 31e and 33e on the back side.

Reduce magnetic resistance. As a result, the strength of the magnetic field at the portion where the magnets 32 and 34 face each other becomes human.

The inner yoke portions 31c, 33c and the outer yoke portions 31d, 33d also have the effect of reducing magnetic resistance.

Due to the action of ■■ above, as shown by the middle line ■ in Figure 4,
The repulsive force F acting on the rotating sleeve 24 becomes large, and the magnetic thrust bearing 3o has high rigidity as a bearing.

Furthermore, the relationship between the distance Q between the magnets 32 and 34 of the magnetic thrust bearing 3o and the repulsive force F is as shown by the middle line ■ in Fig. 4. As the distance q becomes narrower, the repulsive force F increases non-linearly. There is a relationship where .

Therefore, even if a vM shock is applied to the device 20, the permanent magnet 3.
2 collides with the permanent magnet 34, and the magnetic thrust bearing 30 has good impact resistance.

■Each yoke portion 31c of the rotating yoke member 31.

31d, 31e (7) for fl.

The mechanical strength of the annular permanent magnet 32 rotating at high speed is reinforced.

Although a large centrifugal force acts on the permanent magnet 32, an accident in which the permanent magnet 32 is damaged is reliably prevented.

Next, the configuration of the air damper 50 provided at the magnetic thrust bearing 3o will be described.

Between the lower surface 31a of the annular yoke member 31 and the upper surface 31a of the annular yoke member 33, a non-magnetic cylindrical portion 22a, which is a part of the casing 22, is provided with a height of the floating gap Q and an inner diameter of the fixed shaft 23. A space vg having an outer diameter is formed.

The outer peripheral surface 3N of the annular yoke member 31 and the above-mentioned cylindrical portion 22
A first gap c1 is formed between the first gap c1 and the first gap c1.

A rotary sleeve 24 is also provided on the inner peripheral side of the annular yoke member 31.
A second gap C2 is formed between the fixed shaft 23 and the fixed shaft 23.

The second gap C2 is a hole 23a in the radial direction of the fixed shaft 23, @
It communicates with the atmosphere through the directional hole 23b.

The above space ■9 becomes the fluid capacity, and the first. second void C
+ and C2 both serve as fluid resistance, and constitute the air damper 50. .

As a result, the vibration of the rotating sleeve 24 in the thrust direction is increased by I+1 as shown by the line ■ in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, since the rotating sleeve does not rely on radial force, the rotating sleeve rubs against the fixed shaft, which increases the rotational load at startup and prevents damage. This can be prevented and reliability can be improved.

Furthermore, by providing an air damper, the floating of the rotating sleeve can be maintained stably. 1

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a rotating body support device according to an embodiment of the present invention, Fig. 2 is an enlarged view of the magnetic thrust bearing part in Fig. 1, and Fig. 3 is a diagram showing a magnetic thrust bearing 1 without a yoke. - Diagram showing the bearing, Figure 4 is a diagram showing the relationship between the gap size and repulsive force of a magnetic thrust bearing, Figure 5 is a diagram showing the characteristics of an air damper, and Figure 6 is a diagram showing a conventional rotating body support device. , FIG. 7 is a diagram showing the magnetic thrust bearing in FIG. 6. In the figure, 20 is a rotating body support device, 21 is a polygon mirror, 22 is a casing, 23 is a fixed shaft, 24 is a rotating sleeve, 25 is a hydrodynamic air journal bearing, 30 is a magnetic thrust bearing, and 31 is a first annular ring. Yoke member, 31b, 32b are grooves, 31c to 31e, 32c to 32e are yoke parts, 3
2 is the first annular permanent magnet, 33 is the second annular yoke member, 34 is the second annular permanent magnet, 35.36 is the magnetic flux, 50 is the air damper, V (+ is the air gap, C+, 02 is Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) Dynamic pressure air journal bearing (25
), and a casing (22) that accommodates the rotary sleeve therein, the rotating body support device includes a rotary sleeve (24) that is fitted onto the outside through a rotary sleeve (24), and a casing (22) that accommodates the rotary sleeve inside. The first yoke member (31) is magnetized in the axial direction, and the first yoke member (31) is magnetized in the axial direction.
The annular groove (3) on the lower surface (31a) of the yoke member (31)
1b), the first annular permanent magnet (32
), and a second yoke member (33) fixed to the casing (22) opposite to the lower side of the first yoke member.
The second yoke member (33
), and the second annular permanent magnet (34) is fitted and fixed in the annular groove (33b) of the upper surface (33a), and the same polarity (N A rotating body support device comprising a magnetic thrust bearing in which the poles (poles) are vertically opposed to each other. (2) A space (Vg) formed between the first yoke member (31) and the second yoke member (33) and acting as a fluid capacity, and a space (Vg) formed on the inner and outer peripheral sides of the first yoke member. 2. The rotating body support device according to claim 1, further comprising an air damper (50) comprising gaps (C_1, C_2) acting as fluid resistance.