JPH0729729Y2 - motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a motor.

[Problems to be solved by conventional techniques and devices]

Generally, a motor has a shaft and a cylindrical portion rotatably supported by the shaft via a bearing. For example, as shown in FIG. 4, a motor for a laser beam printer has a shaft c pivotally supported by a cylindrical portion b of a bracket a.
A stator d fitted on the cylindrical portion b and a shaft c
A rotor holder e fixed to one end of the rotor holder, a rotary polygon mirror g attached to the rotor holder e with a bolt m via a mounting board f, and a rotor magnet h attached to the rotor holder e. i is the rotor yoke, j
Is a bearing, k is a control board, and n is a Hall element.

Therefore, the rotor holder e, the polygonal mirror body g, and the like are supported by the shaft c in a cantilevered manner, so that the shaft c must be made rigid. That is, the shaft c needs to be a metal shaft. However, the use of a metal shaft has a drawback that the transmission rate of vibration, noise, etc. during rotation becomes high. In addition, in order to suppress vibration and noise,
If a plastic shaft is used, there is a drawback that its diameter becomes large.

Further, the axial dimension of the rotating portion such as the polygonal mirror body g occupies a large proportion of the entire motor, which makes it difficult to make it compact.

Therefore, an object of the present invention is to provide a motor for a laser beam printer which can reduce vibration and noise and can be made compact.

[Means for Solving the Problems]

In order to achieve the above object, one end of a shaft is fixed to a bracket to which a circuit board is attached so as to stand upright, and a rotary polygon mirror for a laser beam printer is attached to the shaft through a pair of bearings. A rotary rotatably supported motor, wherein the rotary polygon mirror body is formed by extending a flat plate portion from a central portion in an axial direction of a cylindrical portion forming a rotation center portion to an outer peripheral direction. Both ends of the shaft are pivotally supported by the pair of bearings on both ends of the shaft, and the shaft has an outer peripheral surface of a metal main body forming a shaft center, and a coating layer of an elastic body relatively less rigid than the main body. Further, a concave circumferential groove is provided on the inner end surface of the flat plate portion, and an annular flat plate-shaped rotor magnet is provided in the concave circumferential groove, and a flat coil is provided on the circuit board or the bracket. A small gap with the rotor magnet It has been provided on a surface opposite shape.

[Action]

A coating layer is interposed between the metal main body and the bearing fitted in the cylindrical portion, and during rotation, when the shaft is fixed, the vibration of the cylindrical portion is caused by the vibration-proof material. The vibration is transmitted to the metal main body through the layer, and the vibration is hardly transmitted to the fixed side holding the metal main body. Therefore, it is possible to prevent vibration and noise due to resonance with a part of the fixed side. Further, the rotary polygonal mirror body is formed by extending a flat plate portion from an axial center portion of a cylindrical portion forming a rotation center portion to an outer peripheral direction, and both ends of the cylindrical portion are pivotally supported by a pair of bearings on both ends of the shaft. As a result, the center of gravity of the rotating part such as the rotating polygon mirror approaches the root side of the shaft, and the rotational balance becomes good. In addition, a concave circumferential groove is provided on the inner end surface of the flat plate portion of the rotary polygon mirror, and an annular flat plate-shaped rotor magnet is provided in the concave circumferential groove, and a flat coil is attached to the circuit board or the bracket. Since the rotor magnets are provided in a face-to-face relationship with a small gap therebetween, the overall height of the motor can be made smaller than in the past, and the size can be reduced.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

As shown in FIG. 1, FIG. 2 and FIG. 3, according to the present invention, one end of a shaft 4 is fixed to a bracket 20 to which a circuit board 12 is attached so as to stand upright. A motor that rotatably supports a rotary polygonal mirror body 3 for a laser beam printer via bearings 8, 8.
The rotary polygon mirror body 3 is formed by extending a flat plate portion 2 from an axial center portion of a cylindrical portion 1 serving as a rotation center portion to an outer peripheral direction, and both ends of the cylindrical portion 1 are provided at both ends of the shaft 4 as a pair. Above bearing
While the shaft 4 is pivotally supported by 8, 8, the shaft 4 covers the outer peripheral surface 15 of the metal main body 14 that forms the center of the shaft with an elastic coating layer 16 that is relatively less rigid than the main body 14. Further, a concave circumferential groove 9 is provided on the inner end surface 5 of the flat plate portion 2, the annular flat plate-shaped rotor magnet 6 is housed in the concave circumferential groove 9, and the circuit board 12 to the bracket 20 are provided. The planar coil 7 is provided so as to face the rotor magnet 6 with a minute gap.

Specifically, as shown in FIG. 2, in the rotary polygon mirror 3, the flat plate portion 2 has a hexagonal shape (in the present embodiment) in plan view, and the outer peripheral surface thereof is the mirror surface 13, and the cylindrical portion. Bearings 8 and 8 are provided at both ends of the shaft 1. The cylindrical portion 1 is pivotally supported by a shaft 4 through the bearings 8 and 8. A rotor yoke 10 is provided in the flat plate portion 2. The rotor yoke 10 is a flat plate-shaped ring body, and an outer peripheral edge portion thereof is formed.
11 is bent so that the outer peripheral surface of the rotor magnet 6 is surrounded. The planar coil 7 is arranged on the control board 12. A concave circumferential groove 9 is provided on the interior surface 5 of the flat plate portion 2, and the rotor magnet 6 is fitted in the concave circumferential groove 9.

As shown in FIG. 1, the shaft 4 has a metallic main body 14 and a coating layer 16 for coating the outer peripheral surface 15 of the main body 14.
Consists of. The main body 14 is made of metal such as steel,
An outer collar 17 is formed at one end of the outer collar 17 and a concave circumferential groove 18 is formed therein.
Further, the coating layer 16 is formed of a material having rigidity (hardness) smaller than that of the main body 14 such as plastic or rubber, acts as a vibration isolator, and its thickness dimension is t, in the case of injection molding. , T ≧ 1 (mm), preferably t ≧ 2 (mm)
It is said that In addition to the injection molding, the coating layer 16 can be formed by pressing molding or the like, and in these cases, the thickness dimension of the coating layer 16 can be set to 1 mm or less. In short, the coating layer 16 is made of a material having a relatively small elastic modulus (Young's modulus) such as plastic or rubber and has a low hardness.

The substrate 12 is attached to the bracket 20 via the back yoke 19, and the shaft 4 is fixed to the back yoke 19 and the bracket 20. That is, the back yoke 19 has a through hole.
21 is provided, and the peripheral portion of the through hole 21 is a concave circumferential groove of the shaft 4.
Since it is fitted to 18, the main body 14 is fixed to the fixed side. Reference numeral 22 is a cap that covers the opening of the cylindrical portion 1 on the side opposite to the flange.

Therefore, the vibration due to the rotation of the rotary polygon mirror 3 is caused by the coating layer 16
Since it is not directly transmitted to the main body portion 14 and the main body portion 14 hardly vibrates, no vibration is transmitted to the bracket 20 to which the main body portion 14 is attached, no vibration is transmitted to the chassis side, and resonance occurs. There is no noise.

Thus, in the motor of the embodiment, the flat plate portion 2 of the rotary polygonal mirror body 3 is arranged substantially at the center of the shaft 4 in the axial direction, and the bearings 8, 8 are arranged at both ends of the cylindrical portion 1. Therefore, it is possible to reliably prevent mutual inclination between the axis of the rotating polygon mirror 3 and the axis of the shaft 4. Further, the dimension between the substrate 12 and the inner surface 5 of the mirror body 3 can be made extremely small.
The size between 12 and the outer surface 22 of the mirror body 3 can be made small, and the overall size is made compact.

Therefore, in this motor, the mass of the rotating portion is remarkably smaller than that of the conventional motor, the moment of inertia during rotation is reduced, and the cylindrical portion 1 is pivotally supported at both ends of the shaft 4, and the flat plate portion 2 is Since it is extended substantially in the central portion in the axial direction of 1, even if the rigidity of the shaft 4 is made smaller than before,
This motor can perform precise rotation. That is,
Since the required rigidity of the shaft 4 can be reduced,
Even if the metal main body 14 is coated with the coating layer 16 like the shaft according to the present invention, it can be sufficiently used.

[Effect of device]

The present invention has the above-mentioned configuration and has the following remarkable effects.

(6 to 18) × 10 ³ rpm Since high speed rotation is required, the coating layer 16 acts as a vibration-proof material even if the rotary polygonal mirror body 3 for a laser beam printer is apt to cause high vibration and noise. Thus, the vibration of the rotary polygon mirror 3 is hardly transmitted to the fixed side of the metal main body portion 14 and the bracket 20 and the like, so that the generation of vibration and noise due to resonance with a part of the fixed side can be prevented.

Compared with a conventional cantilever-supported motor, the center of gravity of the rotating portion such as the rotating polygon mirror body 3 approaches the root side of the shaft 4, resulting in good rotational balance, and the rotating polygon mirror at both ends of the shaft 4. Since the body 3 is pivotally supported, the metal body 14
The rigidity required for anti-vibration is less than before,
Even if the main body portion 14 is covered with the coating layer 16, it is not necessary to make the outer diameter dimension of the shaft 4 larger than before, and when the shaft 4 has the same rigidity as the conventional one, the deflection of the shaft 4 is reduced. The rotation accuracy of the rotary polygon mirror 3 is improved.

Using the thickness of the flat plate portion 2 which must be made thick to form the mirror surface 13, the rotor magnet 6
In addition, since the internal coil is used and the planar coil 7 is used, the overall height of the motor can be made smaller than in the conventional case, and the size can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing a shaft used in an embodiment of the present invention, FIG. 2 is a sectional view of a motor, and FIG. 3 is a plan view of the motor. FIG. 4 is a sectional view of a motor using a conventional shaft. DESCRIPTION OF SYMBOLS 1 ... Cylindrical part, 4 ... Shaft, 14 ... Metal main body part, 15 ... Outer peripheral surface, 16 ... Coating layer.

Claims (1)

[Scope of utility model registration request] 1. A bracket 20 having a circuit board 12 attached thereto.
A shaft 4 is fixed to one end of the shaft 4 so as to stand upright, and a rotary polygon mirror body 3 for a laser beam printer is rotatably supported on the shaft 4 via a pair of bearings 8, 8. The rotary polygon mirror body 3 is formed by extending a flat plate portion 2 from an axial center portion of a cylindrical portion 1 forming a rotation center portion to an outer peripheral direction, and both ends of the cylindrical portion 1 are both ends of the shaft 4. While the shaft 4 is pivotally supported by a pair of the bearings 8 and 8, the shaft 4 has an outer peripheral surface 15 of a metal main body 14 that is covered with an elastic body having a relatively smaller rigidity than the main body 14. The inner peripheral surface 5 of the flat plate portion 2 is covered with a layer 16, and a concave circumferential groove 9 is provided in the concave circumferential groove 9 to house an annular flat plate-shaped rotor magnet 6 and the circuit board. 12 to the bracket 20, the plane coil 7 is face-to-face with the rotor magnet 6 with a minute gap. Motor, characterized in that digit.