JPH0690365B2 - motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor, and more particularly to a motor using a fluid bearing or a sliding bearing as a radial bearing of a rotor (rotor).

(Prior Art) A motor requires a bearing that supports the radial direction of the rotor (hereinafter referred to as a radial bearing) and a bearing that supports the thrust direction (hereinafter referred to as a thrust bearing). For example, as a radial bearing, When a rolling bearing having balls or rollers is used, the rolling bearing may also have the function of a thrust bearing depending on the rotational speed and load of the motor.

On the other hand, when a hydrodynamic bearing or a hydrostatic fluid bearing is used as the radial bearing, a thrust bearing using a fluid bearing or a magnetic bearing is indispensable.

A conventional motor to which a fluid bearing is applied as the radial bearing will be briefly described below.

FIG. 3 is a schematic vertical sectional view of an example of an optical deflector used in a laser beam printer. This optical deflector is configured by attaching a polygon mirror 4 to the rotor of a toroidal motor (DC brushless motor).

In FIG. 3, the main shaft 1 is disposed in the housings 6A and 6B that form the housing of the optical deflector and is supported horizontally.

A rotary sleeve 2 (rotor) having a polygon mirror 4 fixed to the outer periphery thereof is rotatably mounted on the main shaft 1. Grooves (not shown) are formed in the inner peripheral surface of the rotary sleeve 2 and / or the outer peripheral surface of the main shaft 1, respectively, and these grooves form a radial fluid bearing of the rotary sleeve 2.

A thrust bearing member 14 is arranged at the end of the main shaft 1. The thrust bearing member 14 and / or the rotary sleeve 2 are provided with grooves (not shown) on their opposing surfaces, and these grooves form thrust fluid bearings of the rotary sleeve 2.

A cylindrical magnet 3 is fixed to the outer peripheral portion of the rotary sleeve 2 via a magnet yoke 11. The magnet yoke 11 forms a magnetic path of magnetic lines of force generated from the inner surface of the magnet 3,
It is arranged in order to increase the magnetic flux density of the lines of magnetic force generated from the outer surface, but it may not be particularly provided. The magnet 3 is evenly divided about the central axis of the main shaft 1 so as to have a plurality of magnetic poles.

An annular stator core 5 is fixed to the inner wall of the housing 6B so as to face the magnet 3.
A plurality of coils (not shown) are wound around the stator core 5.

Reference numeral 13 is a substrate for mounting the Hall IC 12. hole
The IC 12 is provided to detect the change in the magnetic field of the magnet 3, that is, the rotation angle of the magnet 3.

A window 15 is formed in the housing 6B for allowing light to enter the polygon mirror 4 and directing the light reflected by the polygon mirror 4 to a photoconductor (not shown) or the like. The cover glass 8 closes the window 15.

Reference numeral 9 is a balance correction member for the polygon mirror 4.

Reference numeral 7 is a plate for fixing the optical deflector for horizontally disposing the main shaft 1.

In the toroidal motor having the above configuration, when the plurality of coils wound around the stator core 5 are urged by the drive means (not shown), the rotary sleeve 2 rotates in a predetermined direction.

(Problems to be Solved by the Invention) The above-described conventional technique has the following problems.

(1) As is well known, in a dynamic pressure type or static pressure type fluid bearing, it is necessary to form a groove for pressure generation in at least one of the rotor and the support of the rotor for both the radial bearing and the thrust bearing. is there. Therefore, in general, hydrodynamic bearings and hydrostatic bearings are more complicated to manufacture and expensive than other types of bearings.

In particular, when the fluid bearing is applied to the thrust bearing, the squareness of the end face and the side face of the rotor must be set extremely strictly, and when the rotor end face is molded into a spherical surface and supported, the spherical surface of the spherical surface is used. Since the degree of precision and the degree of sphericity of the support surface that supports the spherical surface require high precision, their fabrication is extremely troublesome.

(2) A rotary sleeve rotates around a main shaft that is vertically fixed to a housing, and compressed air generated by a radial fluid bearing of the rotary sleeve is introduced into the lower surface of the rotary sleeve to thrust the rotary sleeve. In a motor configured to perform directional support, a predetermined gap is formed between the upper end of the main shaft and the housing in order to keep the pressure inside the housing constant. Since the main shaft is supported only at its lower end, the rigidity of the main shaft cannot be increased so much.

As a result, the rotation of the rotary sleeve may increase the vibration of the motor.

The present invention has been made to solve the above problems.

(Means and Actions for Solving Problems) In order to solve the above problems, the present invention provides a motor in which an external force is not applied in the thrust direction of the rotor.
It is attached to a rotating sleeve made of a magnetic material and is fixed to an annular core around which multiple coils are wound at equal intervals in the vicinity of the outer circumference of a cylindrical magnet that has multiple magnetic poles divided in the circumferential direction. Provided in the thrust core, the cylindrical magnet strengthens the magnetic attraction exerted on the annular core, thereby supporting the rotor in the thrust direction in which the radial direction is supported by a fluid bearing or a sliding bearing.
The thrust bearing is not used, and only the magnetic attraction force generated between the stator (stator) and the rotor is used, which simplifies the structure of the motor and significantly reduces its manufacturing cost. The point is characteristic.

(Example) Hereinafter, the present invention will be described in detail with reference to an example in which it is applied to an optical deflector used in a laser beam printer.

FIG. 1 is a schematic vertical sectional view of an optical deflector to which the first embodiment of the present invention is applied. In the figure, the same reference numerals as those in FIG. 3 represent the same or equivalent portions, and thus the description thereof will be omitted.

The optical deflector shown in FIG. 1 is configured by attaching a polygon mirror 4 to a rotor (rotating sleeve 2) of a toroidal motor. Further, grooves (not shown) are formed in the inner peripheral surface of the rotary sleeve 2 and / or the outer peripheral surface of the main shaft 1, and these grooves form a radial fluid bearing.

Both ends of the main shaft 1 are fixed to the housings 6A and 6B.

Reference numeral 10 is a mirror pressing member of the polygon mirror 4.

In the first embodiment of the present invention, as described above, the radial fluid bearing is formed between the inner peripheral surface of the rotary sleeve 2 and the outer peripheral surface of the main shaft 1. No thrust bearing is installed.

However, since the stator core 5 is arranged close to the periphery of the magnet 3 fixed to the rotating sleeve 2, a strong magnetic attraction force is generated between the stator core 5 and the magnet 3. Due to this magnetic attraction, the magnet 3
Tries to stay in the center of the stator core 5. Therefore, unless a large external force is applied to the rotary sleeve 2, the rotary sleeve 2 can be supported in the thrust direction by the magnetic attraction force.

FIG. 2 is a schematic vertical sectional view of an optical deflector to which the second embodiment of the present invention is applied. In FIG. 2, the same reference numerals as those in FIGS. 1 and 3 represent the same or equivalent portions,
The description is omitted.

6 is a housing of the motor.

Also in this example, radial fluid bearings are formed on the inner peripheral surface of the rotary sleeve 2 and the outer peripheral surface of the main shaft 1.

In the first embodiment, the rotary sleeve 2 is supported horizontally, whereas in this embodiment the rotary sleeve 2 is supported vertically. When the rotor is supported vertically as described above, the weight of the rotor is relatively small, the magnetic attraction between the magnet 3 and the stator core 5 is strong, and the rotor is like the optical deflector. It is possible to support the rotor in the thrust direction by the magnetic attraction force only for a device to which an external force is not applied.

In this embodiment, the rotary sleeve 2 is made of a magnetic material and also serves as a magnet yoke.

Although the present invention is applied to the toroidal motor used in the optical deflector in each of the above-described embodiments, the present invention is not particularly limited to this. As a matter of course, it may be applied to any type of motor as long as it has a magnetic attraction force.

Further, in each of the above-described embodiments, the present invention is described as being applied to a motor of the type in which the rotary sleeve 2 rotates around the main shaft 1, but the present invention is not particularly limited to this. Instead, it may be applied to a shaft rotation type motor in which a main shaft rotates.

Furthermore, in each of the above-described embodiments, the present invention is described as being applied to a motor that uses a fluid bearing as a radial bearing, but the present invention is not particularly limited to this, and a sliding bearing can be used. Of course, it may be applied to the used motor.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) In a motor provided with a radial fluid bearing or a radial slide bearing, in which an external force is not so much applied in the thrust direction, the thrust direction of the rotor is supported by magnetic attraction between the rotor and a stator arranged in the vicinity of the rotor. Since only the force is used, the thrust bearing is unnecessary and the length of the motor in the main shaft direction can be shortened. Therefore, the configuration of the motor is simplified and miniaturized,
The production cost is reduced.

(2) Since a pressure generating surface for applying a force in the thrust direction is not required, in the rotor of the sleeve rotation type, the wall thickness at both ends of the rotor can be reduced, and in the rotor of the axial rotation type. Can shorten the rotor. As a result, the weight and moment of inertia of the rotor can be significantly reduced, and the motor is lightened. Further, since the load applied to the radial bearing is reduced, the life of the motor is extended and its responsiveness is improved.

(3) As the magnet on the rotor side, a cylindrical magnet having a plurality of magnetic poles divided in the circumferential direction is used, and the magnet is mounted on the rotary sleeve made of a magnetic material. The magnetic attraction exerted on the annular core of the can be enhanced.

(4) Even when the present invention is applied to a motor in which the main shaft is arranged vertically and the rotor rotates around the main shaft, both ends of the main shaft can be fixed, so that the rigidity of the main shaft is improved. Therefore, the vibration of the motor is extremely reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an optical deflector to which the first embodiment of the present invention is applied, and FIG. 2 is a schematic vertical sectional view of an optical deflector to which the second embodiment of the present invention is applied. FIG. 3 is a schematic vertical sectional view of an example of a conventional optical deflector. 1 ... Spindle, 2 ... Rotating sleeve, 3 ... Magnet, 4 ... Polygon mirror, 5 ... Stator core, 6,6A, 6B ... Housing, 7 ... Fixing plate, 8 ... Cover glass, 11 ... Magnet yoke, 12 ... Hall IC , 15 ...
window

Claims (1)

[Claims] 1. A motor using a fluid bearing or a sliding bearing as a radial bearing, which is mounted on a rotary sleeve made of a magnetic material and has a cylindrical magnet having a plurality of magnetic poles divided in a circumferential direction. A ring-shaped core, in which a plurality of coils are wound at equal intervals, is fixedly provided in the vicinity of the outer periphery, and the thrust direction of the rotor of the motor is supported only by magnetic attraction without providing a thrust bearing, A motor characterized in that the rotor is driven by energizing the coil.