JP2000321521A - Polygon mirror scanner motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the motor whose bearing part can be prolonged in life by suppressing a decrease in the amount of a lubricant between a rotary shaft and a bearing as a polygon mirror scanner motor used for the deflection scan of a laser in a laser beam printer, a laser copying machine, etc. SOLUTION: When a flow J1 of air is generated from the gap between a rotor frame 7 and a substrate 9 to outside the motor, a flow J2 of air is generated from below the substrate 9 which is free from the effect of an atmospheric pressure difference due to the rotation of a polygon mirror to inside the motor by forming a through hole 11 in the bearing on the opposite side from the rotor, so the atmospheric pressure between the rotor frame 7 and stator coil 10 does not drop to prevent the lubricant between the rotary shaft 1 and bearing 2 from being sucked up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon mirror scanner motor mainly used for laser deflection scanning in a laser beam printer, a laser copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, a polygon mirror scanner motor (hereinafter simply referred to as a motor) for rotating a polygon mirror in a laser beam printer or the like has been required to rotate at a high speed in terms of high printing speed and high precision printing. Highly required.

In FIG. 2, a rotating shaft 1 is rotatably supported via a lubricating oil in an inner diameter hole of a bearing 12 fixed to a substrate 9, and a rotor boss 3 is fixed. A polygon mirror 4 and a mirror holding plate 5 are fixed to the upper part of the rotor boss 3 by a grip ring 6. A cup-shaped rotor frame 7 drawn by a die is fixed to a lower portion of the rotor boss 3, and a rotor magnet 8 is fixed to an inner periphery of the rotor frame 7. The rotor frame 7 is made of a thin iron plate capable of high-precision drawing, and the rotor magnet 8 is made of a rubber magnet. A stator coil 10 is arranged on the substrate 9 at a position facing the rotor magnet 8.

In the motor configured as described above, a current flows through the stator coil 10 to generate a driving force between the stator coil 10 and the rotor magnet 8, and the polygon mirror 4 and the rotating shaft 1 rotatably supported by the bearing 12. Starts rotating and performs deflection scanning.

[0005]

However, in the conventional structure, when the polygon mirror 4 rotates at a high speed, a pressure difference occurs between the inside and outside of the motor. An air flow occurs, and the air pressure between the rotor frame 7 and the stator coil 10 decreases. As a result, the lubricating oil between the rotating shaft 1 and the bearing 12 is sucked up in the direction of the rotor boss 3, causing metal contact between the rotating shaft 1 and the bearing 12, which has a problem that the life of the bearing portion is significantly reduced.

Further, there is a problem that the lubricating oil sucked up and leaked to the outside adheres to a mirror portion of the motor and an optical unit portion outside the motor, which hinders deflection scanning.

One method of preventing running out of lubricating oil due to a change in atmospheric pressure is disclosed in Japanese Patent Application Laid-Open No. 7-46787.
The embodiment is cited in FIG.

In this method, a small hole 110c is provided between two grooves of the bearing 110, and the small hole 110c of the bearing is provided on the side opposite to the rotor.
And a notch 116a of the thrust plate 116 and a notch 117a of the bottom plate 117 are provided. As a result, a ventilation path is formed, and a motor capable of preventing the leakage of lubricating oil due to a change in air pressure and extending the life of the bearing is obtained.

However, this configuration is an effective technique for lubricating oil leakage due to pressure change on the side opposite to the rotor, and it is difficult to prevent lubricating oil leakage due to pressure change on the rotor side. In addition, it is necessary to add a small hole to the bearing, add a gap, add a notch to the thrust plate and the bottom plate, and so on, so that the cost of parts increases and it is sometimes difficult to reduce the cost.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and reduces a pressure difference between the inside and outside of a motor due to a high-speed rotation of a polygon mirror, and reduces a lubricating oil between a rotating shaft and a bearing. It is an object of the present invention to realize a motor that can suppress the lubrication oil, extend the life of the bearing portion, and prevent leakage of lubricating oil to the outside of the motor.

[0011]

According to the present invention, there is provided a motor in which a bearing is provided with a through hole from the rotor side and from the rotor side.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a motor according to the present invention. In FIG. 1, a rotating shaft 1 has a through hole 11 fixed to a substrate 9 and has a herringbone groove formed in the inner diameter. The rotor boss 3 is fixed while being rotatably supported. A polygon mirror 4 and a mirror holding plate 5 are fixed to the upper part of the rotor boss 3 by a grip ring 6.
A cup-shaped rotor frame 7 drawn by a die is fixed to a lower portion of the rotor boss 3, and a rotor magnet 8 is fixed to an inner periphery of the rotor frame 7. The rotor frame 7 is made of a thin iron plate capable of high-precision drawing, and the rotor magnet 8 is made of a rubber magnet. A stator coil 10 is arranged on the substrate 9 at a position facing the rotor magnet 8.

In the motor configured as described above, a current flows through the stator coil 10 to generate a driving force between the stator coil 10 and the rotor magnet 8, and the polygon mirror 4 together with the rotating shaft 1 rotatably supported by the bearing 2. Starts rotating and performs deflection scanning.

As described above, when the polygon mirror 4 rotates at a high speed, a pressure difference occurs between the inside and outside of the motor, and the air flow J1 from the gap between the rotor frame 7 and the substrate 9 to the outside of the motor occurs. By providing the through hole 11 in the bearing 2 on the side opposite to the rotor side from the rotor side, an air flow J2 from the lower side of the substrate 9 to the inside of the motor which is not affected by the pressure difference due to the rotation of the polygon mirror 4 is generated. The pressure between the frame 7 and the stator coil 10 does not decrease, preventing the lubricating oil from being sucked up between the rotating shaft 1 and the bearing 2, and significantly reducing the life of the bearing due to metal contact between the rotating shaft 1 and the bearing 2. In addition, it is possible to prevent the lubricating oil from leaking out of the motor.

Although FIG. 1 shows a configuration in which a hydrodynamic bearing is used for the bearing 2, the same applies when an oil-impregnated metal is used for the bearing 2.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various applications and developments are possible within the scope of the present invention.

[0018]

As described above, in the motor according to the present invention, even if a pressure difference occurs between the inside and outside of the motor due to the high speed rotation of the polygon mirror, the bearing has a through hole from the rotor side to the counter rotor side. Since the air flow from the lower side of the substrate to the rotor side is not affected by the rotation of the polygon mirror due to the rotation of the polygon mirror, the pressure drop between the rotor frame and the stator coil does not occur. Lubrication oil can be prevented from being sucked up, and the life of the bearing part can be prevented from significantly shortening due to metal contact between the rotating shaft and the bearing. Can be prevented.

Further, since the pressure difference between the inside and outside of the motor increases as the rotation speed of the motor increases, it is possible to realize a motor capable of increasing the rotation speed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a motor according to the present invention.

FIG. 2 is a sectional view of a conventional motor.

FIG. 3 is a cross-sectional view of another conventional motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation shaft 2, 12, 110 Bearing 3 Rotor boss 4 Polygon mirror 5 Mirror holding plate 6 Grip ring 7 Rotor frame 8 Rotor magnet 9 Substrate 10 Stator coil 11 Bearing through-hole J1 Flow of air outside motor J2 Inside of motor Air flow 110c Bearing hole 116 Thrust plate 116a Thrust plate cutout 117 Bottom plate 117a Bottom plate cutout 121 Bearing gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichiro Ohata 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference)

Claims (3)

[Claims] 1. A rotating shaft, a rotor boss fixed to an outer periphery of the rotating shaft, a polygon mirror fixed to the rotor boss, a rotor magnet forming a magnetic circuit, and a rotor magnet held by the rotor boss. A rotor portion having a fixed cup-shaped rotor frame, a stator portion having a stator coil opposed to the rotor magnet, and a metal base printed circuit board to which a bearing rotatably supporting a rotating shaft is fixed. A polygon mirror scanner motor, wherein a through hole is provided in the bearing from the rotor side to the anti-rotor side. 2. The polygon mirror scanner motor according to claim 1, wherein the polygon mirror scanner motor is a moving body fluid bearing having a herringbone groove for generating a dynamic pressure on one of a rotating shaft and a bearing. 3. The polygon mirror scanner motor according to claim 1, wherein the bearing is an oil-impregnated metal.