JPS61269115A - Device for supporting rotary body - Google Patents

Abstract

PURPOSE:To obtain a highly reliable rotary body resisting high speed rotation by providing an inner ring of a thrust load supporting magnetic bearing to a fixed shaft and fixing an outer ring to the inside of a rotary assembly body so that a specific gap is formed between the inner ring and the end part of a supporting part of the fixed shaft. CONSTITUTION:A gap >=0.5mm is formed between the fixed side magnetic ring forming the thrust load supporting magnetic bearing and the supporting part 41 of the fixed shaft. Consequently, high thrust load resisting force is obtained. In addition, even if centrifugal force is applied to the rotation side magnetic ring 54 by the high speed rotation of the rotary assembly body, the centrifugal force is offset by the stress of the cylinder 51 because the ring 54 is fitted and fixed with/to the inside of the cylinder, so that the device is protected from damage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotating body support device suitable for supporting a rotating body that rotates at high speed, such as a rotating polyhedral optical deflector.

[Technical background of the invention and its problems] In recent years, the amount of information that needs to be transmitted and recorded has increased significantly in various industrial fields. Along with this, the speed of printers, which are a type of information recording equipment, has rapidly increased, and recently, laser printers capable of high-speed printing of 10,000 lines per minute or more have become popular.

As shown in FIG. 9, the laser printer emits laser light WA1.
And a rotating polyhedral mirror device that deflects the laser beam 2 emitted from this laser light source! 3, an imaging lens unit (f-theta lens) 4 that forms an image of a deflected laser beam, and a photoreceptor 5 that is scanned by the laser beam that has passed through this lens unit. An electrostatic latent image is formed on the photoreceptor 5 by scanning the charged photoreceptor 5 with a laser beam 2 deflected by a rotating polyhedron [3 that rotates at high speed.

FIG. 10 shows a specific example of the configuration of the rotating polygon mirror device 23 described above. In the same figure, the lower end mounting portion 10a and the upper end mounting portion 10b of the fixed shaft 10 are fitted into mounting holes 13a and 13b transparently provided in the motor casing 11 and the cover 12 that opens the upper end, respectively, and are fitted with fixing screws. It is fixed by 14.

Slightly inside the lower and upper ends of the fixed shaft 10, support parts 16a and 16b are formed with herringbone grooves 15 carved in the upper and lower ends. The herringbone grooves 15 are carved in pairs so that their arrow-shaped tips face the rotational direction of the rotating assembly, which will be described later, to form a hydrodynamic air journal bearing.

The fixed ring 10 has a diameter of 3 μm with respect to the supporting parts 16a and 16b.
A hollow cylindrical cylinder 17 constituting a journal bearing portion is loosely fitted with a clearance of about −7 μm. A motor magnet rotor 18 is fixed to this cylinder, and a polyhedral casing 19 and an inner magnetic ring 20a of a thrust load supporting magnetic bearing 20 are fitted and bonded. Further, inside the motor casing 11, an outer magnetic ring 20 is disposed opposite to the inner magnetic ring 20a.
b is installed.

Drive coils 21 are arranged outside the motor magnet rotor 18 at appropriate intervals. Electric power is input to this drive coil through a motor drive circuit board 23 suspended by a fixing screw 22 inside the cover 2, and the motor magnet rotor 18 and the polyhedral body 19 connected thereto via a cylinder 17 are driven at high speed. Rotate.

A window 11a is formed in the motor casing 11 at a position outside the polyhedron 19 to allow the laser beam to pass therethrough.

Further, 24 indicates a fixing screw for transportation. Normally, this fixing screw is loosened as shown in Fig. 10, and an appropriate distance is maintained between its tip and the ring-shaped groove 17a of the cylinder 17. However, when transporting the rotating body support device, The tip is screwed in to the position where it comes into pressure contact with the ring-shaped groove 17a, thereby locking the rotating assembly 25 consisting of the cylinder 17, motor magnet rotor 18, polyhedral body al119, and inner magnetic ring 20a, and blocking movement in the thrust direction.

In the rotating body support device configured as described above, when power is supplied to the drive coil 21 through the motor drive circuit board 23, a rotational force is generated in the motor magnet rotor 18, and the rotation assembly 25 rotates.

As mentioned above, the rotating assembly 25 is supported by a herringbone groove type hydrodynamic air journal bearing with a minute gap of about 3 μm to 7 μm, so that when the rotating assembly 25 starts rotating, the air flows through the herringbone groove 15. The air flow sucked into the minute gap increases the pressure at the center of the bearing, and this pressure distribution causes a radial force to act on the inner surface of the cylinder 17.

On the other hand, the rotating assembly 25 is maintained in a state balanced with the thrust load by the attraction force between the magnetic ring 20a fixed to its lower end and the outer magnetic ring 20b fixed to the motor casing 11 side. When the solid body 25 begins to rotate and the pressure of the hydrodynamic air journal bearing increases, the cylinder 17 comes into a completely non-contact state with respect to the support parts 16a, 16b of the fixed shaft 10, and shifts to high speed rotation.

However, in the conventional rotating body support device configured as described above, high accuracy is required for the dimensional accuracy of the inner and outer diameters of the journal bearing, cylindricity, coaxiality, etc., so if the bearing is long, machining It takes a long time, reduces mass productivity, and increases the size and weight of the structure. In addition, since the thrust magnetic bearing 20 is installed separately on the motor casing 11 side and the rotating assembly 25 side, it may not rotate unless the fixed shaft 10 stands vertically. is externally fitted on the cylinder 17, so if the fixed shaft is tilted, the coaxiality will shift and it will become impossible to rotate.Therefore, it is necessary to increase the rigidity of the casing and improve the assembly accuracy.Moreover, when the cylinder rotates at high speed, However, there was a drawback that a large centrifugal force acts on the inner ring 20a of the magnetic ring, causing it to break.

[Object of the Invention] The present invention has been made in order to eliminate the above-mentioned drawbacks in the background art, and it is an object of the present invention to provide a highly reliable rotating body support device that is small in size, has excellent mass productivity, and can sufficiently withstand high-speed rotation. The purpose is to

[W4 essential point of the invention] In order to achieve the above-mentioned object, the rotating body support device of the present invention includes a fixed shaft made of a magnetic material, a fixed shaft that is externally fitted on the fixed shaft via a journal bearing part, and a rotating body supporting device that is mounted on the fixed shaft with the center of the fixed shaft. In a rotating body support device comprising a rotating assembly including a motor rotor that rotates as It is characterized in that opposing outer rings are fixed to the inside of the rotating assembly, and a gap of 0.5 mm or more is formed between the inner ring and the end of the support part of the fixed shaft.

[Embodiment 1 of the Invention] Hereinafter, the present invention will be described in detail with reference to FIGS. 1 to 8.

FIG. 1 shows a rotating polyhedral optical deflection device to which the present invention is applied.

This optical deflector includes a casing 30 consisting of an upper casing 31 and a lower casing 32 that closes the lower end of the casing 30. The casing 30 is installed in the center of the casing, and the lower and upper ends are fixed to the casing 30 by fixing screws 33. The rotating assembly 50 is composed of a fixed shaft 40 fixed to the fixed shaft 40, a rotating assembly 50 loosely fitted to the fixed shaft via a journal bearing, and a drive mechanism 60 for rotating the rotating assembly. 70 indicates a buffer member.

The fixed shaft 40 is made of a very hard magnetic material that has been surface-hardened with cemented carbide or silicon nitride, and has a single support portion 41 formed slightly above the center in the axial direction, as shown in FIG. There is. A herringbone groove 42 inclined in the rotational direction of the rotary assembly 50 is cut from the upper and lower ends of the supporting portion toward the vicinity of the central portion to a depth of several μm. Also,
A fixed magnetic ring 43 of a magnetic bearing for supporting a thrust load is fitted onto a small diameter portion formed on the lower side of the support portion 41 and fixed thereto by adhesive or the like. Here, a gap a is formed between the lower end of the support part 41 and the fixed side magnetic ring 43, as shown in FIG.

The rotating assembly 50 includes a cylinder portion 51 as shown in FIG.
a journal bearing part 53 that is fitted and adhered to the upper inside of the polyhedral part 52; a rotating side magnetic ring 54 of a thrust load supporting magnetic bearing that is fitted and fixed to the inside of the lower end of the cylinder part 51; It consists of a motor magnet rotor 55 that is fitted and fixed to the outside of the cylinder part 51.

The journal bearing portion 53 is made of a very hard material like the fixed shaft 40 described above, and its inner diameter is such that a minute gap of about 3 μm to 7 μm is formed with respect to the outer diameter of the support portion 41 of the fixed shaft 40. has been done. Furthermore, the inner diameter of the rotating side magnetic ring (outer ring) 54 is dimensioned to form an appropriate minute gap between it and the stationary side magnetic ring (inner ring) 43.
These magnetic rings are arranged facing each other as shown in FIG. 1 to form a thrust load supporting magnetic bearing.

The drive mechanism 8560 includes magnetic poles 61 installed at predetermined intervals in the circumferential direction so as to surround the motor magnet rotor 55, and a drive coil 62 attached to these magnetic poles.
It consists of a motor drive circuit board 63 that controls the timing of the current supplied to these drive coils, and is fixed on the lower casing 32 with a twisting fix.

Note that the upper casing 31 of the optical deflector includes a light entrance section 80 equipped with a laser emitting unit 81, as shown in FIG.
Light emitting unit 9 equipped with a lens unit (f-θ lens) 91
0 are airtightly fixed, and clean air is sealed inside the casing.

As described above, in the rotating body support device of the present invention, a hydrodynamic air type journal bearing is formed between the support part 41 of the fixed shaft 40 and the bearing part 53 of the rotating assembly 50, and Fixed side magnetic ring 43 and rotating assembly 50 fitted together
A rotating side magnetic ring 54 fixed inside the cylinder 51 of
A thrust load supporting magnetic bearing is formed by the above, so when a rotating magnetic field is generated in the drive mechanism section 60 through the motor drive circuit board 63, the motor magnet rotor 55 is attracted to this and rotates, and the polyhedral technique 52 It also rotates. Therefore, the laser beam incident from the laser emitting unit 81 is reflected by the polyhedron 152 rotating at high speed, and the lens unit (f-theta lens) 91
Light is emitted through the photoreceptor and scanned over the photoreceptor. As shown in FIG. 5, when the upper end of the thrust load supporting magnetic ring 43 is brought into contact with the lower end of the support of the fixed shaft 40, many lines of magnetic force are generated between the magnetic ring 43 and the fixed shaft 4o. Although the thrust load supporting force decreases, in the present invention, as explained with reference to FIG.
Since a gap is formed between the magnetic ring 1 and the fixed II (inner) magnetic ring 43, fewer lines of magnetic force escape from the magnetic ring 43 to the fixed shaft 40, as shown in FIG. .54111 magnetic field lines increase.Therefore, the thrust bearing force increases.In other words, the 7th
When the thrust load capacity W is measured while changing the gap between the fixed shaft 40 and the magnetic ring 43 as shown in the figure, the results shown in Figure 8 are obtained (in the case of a surface magnetic velocity density of 600 Gauss).
. As is clear from this figure, the slope of W is J-0.5mm
The gap increases rapidly in the vicinity, so if a gap of around 1-0,5 mm is adopted, the thrust load capacity can be efficiently increased.

As mentioned above, in the rotating body support device of the present invention, the fixed shaft is shortened, and the supporting portion of the hydrodynamic air journal bearing is made short.
Since only one piece is formed, the time required for machining the bearing portion is shortened and mass productivity is improved. Further, the axial length of the rotating assembly is shortened and the center of gravity can be placed near the center of the bearing portion 53, so that a small and well-balanced rotating assembly can be constructed.

In addition, there is a distance Q of 5 mm between the fixed side magnetic ring 43 forming the thrust load supporting magnetic bearing and the fixed shaft support part 41.
Since the above-mentioned gap is formed, an excellent thrust load capacity can be obtained, and since the rotating side magnetic ring 54 is fitted and fixed inside the cylinder 51, the rotating side magnetic ring 54 can be rotated at high speed by the rotating assembly. Even if centrifugal force acts on the cylinder 51, the stress from the cylinder 51 reduces the centrifugal force and protects it from destruction.

Note that the rotating body support device of the present invention is not limited to the above-mentioned laser printer, but can be widely applied to supporting various high-speed rotating bodies.

[Effects of the Invention] As described above, according to the present invention, it is possible to configure a rotating assembly that is small and well-balanced and is excellent in mass production, and has improved thrust load capacity. Since it is protected, it can be prevented from being destroyed by centrifugal force during high-speed rotation, and the reliability of the rotating body support device can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, and FIG.
3 is a perspective view showing the rotating assembly in FIG. 1; FIG. 4 is a cross-sectional view illustrating the rotating body support V4M of the present invention incorporated into a rotating polygon mirror device. , FIG. 5 is an explanatory diagram showing the magnetic flux distribution in the rotating body support device not according to the present invention, FIG. 6 is an explanatory diagram showing the magnetic flux distribution in the device of the present invention, and FIG. 7 is an explanatory diagram showing the magnetic flux distribution in the rotary body supporting device according to the present invention. FIG. 8 is a graph showing the measurement results; FIG. 9 is a perspective view illustrating a laser printer to which the rotating body support device of the present invention is applied; FIG. 10 FIG. 2 is a vertical cross-sectional view illustrating a conventional rotating body support device. 1...Laser light source 2...Laser beam 3...Rotating polygon mirror device 4...Lens unit 5...Photoreceptor 10.40...Fixed shaft 11.30 Motor casing 15.42.・・Herringbone groove 16a, 16b 141・”Support part 17.51・Cylinder 18.55・Motor magnet rotor 19.52
...Polyhedral mirror 20...Magnetic bearings 20a, 54 for supporting thrust load
...Rotating side magnetic ring 20b, 43...Fixed side magnetic ring 21.62...Drive coil 23.63...Motor drive circuit board 24...Fixing screw for transportation 25.50...Rotation Assembly 53...bearing part 60...drive mechanism part 61...magnetic pole 70...11 member 80...light entrance part 81...laser emitting unit 90...light emitting part 91...lens Unit (f-theta lens) applicant
Toshiba Corporation Patent Attorney Satoshi Suyama - Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure L Figure 8

Claims (2)

[Claims] (1) A rotating assembly that includes a fixed shaft made of a magnetic material, a motor rotor that is fitted onto the fixed shaft via a journal bearing and rotates around the fixed shaft, and a drive that rotates the rotating assembly. In the rotating body support device comprising a mechanism section, the thrust load supporting magnetic bearing has an inner ring provided on the fixed shaft, an outer ring opposite to the inner ring fixed to the inside of the rotating assembly, and the inner ring and the fixed shaft A rotating body support device characterized in that a gap of 0.5 mm or more is formed between the ends of the support parts. (2) The lower end of the fixed shaft is the free end, and this fixed ring has
Claim 1 or 2, characterized in that a single hydrodynamic air journal bearing with a pair of herringbone grooves, a thrust load supporting magnetic bearing inner ring, and a drive mechanism are fixed. The rotating body support device described in .