JPH08280153A - Polygon mirror scanner motor - Google Patents

Abstract

PURPOSE: To provide a highly reliable polygon mirror scanner motor for an LBP which has high printing accuracy and does not produce much noise by suppressing the out-stepping of a polygon mirror when the mirror is rotated at a high speed. CONSTITUTION: Of the two ball bearings 2 and 3 rotatably supported a shaft 1, the outer ring of the bearing 2 on a polygon mirror side is directly fixed to a bracket 14 and the outer ring of the other bearing 3 is held by the bracket 14 through a ring-like elastic body 13. In addition, a projecting section 13a is provided on the outer periphery of the elastic body 13. Therefore, the out-stepping of a polygon mirror can be suppressed by utilizing the side pressure of the elastic body 13 even when the polygon mirror is unbalanced. Moreover, a highly reliable low-noise polygon mirror scanner motor can be obtained, because the elastic body 13 acts as a cushioning material between the bearing 3 and bracket 14 and absorbs the vibration of the shaft 1 when the shaft 1 is rotated at a high speed.

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 used in the field of office automation.

[0002]

2. Description of the Related Art In recent years, a polarization scanning motor for rotating and driving a polygon mirror in a laser beam printer or the like is rotating at a high speed, and shaft runout and rotation accuracy affect the position accuracy of the polygon mirror, which affects the printing accuracy of the laser beam printer. A bearing mechanism that suppresses the runout and tilt of the shaft and has high reliability is directly important because it directly influences.

A conventional polygon mirror scanner motor will be described below. FIG. 2 is a sectional view of a conventional polygon mirror scanner motor. In FIG.
The shaft 1 is rotatably fitted in the inner diameter holes of the two ball bearings 2 and 3, and the rotor boss 4 is fixed. A polygon mirror 5 is fixed to the upper part of the rotor boss 4 with screws and the like using a pressing plate 6, and a rotor yoke 7 and a magnet 8 are fixed to the lower part.

The outer rings of the two ball bearings 2 and 3 are fitted to the bracket 9 by a clearance fit or are fixed by adhesion, and a stator coil 10 facing the magnet 8 is arranged. Furthermore, a Hall element for detecting the position during rotation is installed. Furthermore, ball bearing 2
Nos. 3 and 3 have a bearing structure in which the compression amount of the spring 12 is determined and fixed by the C-shaped snap ring 11 so that the preload becomes a constant value.

The operation of the polygon mirror scanner motor configured as described above will be described below. First, a current flows through the stator coil 10, a driving force is generated between the stator coil 10 and the magnet 8, the current is switched by the Hall element, and the polygon mirror 5 starts rotating to perform polarization scanning.

[0006]

However, in the above-mentioned conventional structure, when the outer ring of the two ball bearings 2 and 3 and the bracket 9 are fitted with a gap, when the motor rotates at a high speed, the imbalance of the polygon mirror 5 and the external force. There is a problem that vibration is applied to the ball bearing, and the ball bearing shakes by the gap between the outer ring of the ball bearing and the bracket, which causes whirling of the polygon mirror 5 and reduces the printing accuracy.

Further, in order to solve the above problems, there is a means of fixing the outer rings of the two ball bearings 2 and 3 and the bracket 9 by adhesive bonding, but in this case, resonance due to rotational vibration of the rotor and stator coil. There is a problem that resonance occurs due to the switching vibration of No. 10 and abnormal noise of high frequency is generated. Further, the bracket 9 and the shaft 1 generally have a large difference in coefficient of thermal expansion, and excessive stress in the thrust direction is applied to the ball bearing due to thermal expansion at a high temperature, which shortens the life of the ball bearing. I had a problem.

The present invention solves the above-mentioned problems of the prior art, and can prevent abnormal noise due to whirling and resonance of the polygon mirror that occur during high-speed rotation, and further extend bearing life with high printing accuracy and low noise. , And to provide a highly reliable polygon mirror scanner motor.

[0009]

In order to achieve this object, a polygon mirror scanner motor of the present invention has an outer ring of a ball bearing on the polygon mirror side of two ball bearings that rotatably support a shaft. The outer ring of the other ball bearing is directly fixed to the bracket, and the outer ring of the other ball bearing is held by the bracket via a ring-shaped elastic body, and a convex portion is provided on the outer circumference of the ring-shaped elastic body.

[0010]

With this configuration, even if the polygon mirror is unbalanced, the outer ring of the ball bearing on the polygon mirror side is bonded and fixed to the bracket, and the outer ring of the ball bearing on the opposite side is subjected to lateral pressure by the convex portion on the outer periphery of the ring-shaped elastic body. The whirling of the polygon mirror during high speed rotation can be suppressed, and high printing accuracy can be secured.

Further, since the ring-shaped elastic body located between the outer ring of the ball bearing on the side opposite to the polygon mirror and the bracket acts as a cushioning material, it is possible to absorb vibration during high-speed rotation and suppress resonance noise.

Further, when the bracket thermally expands at a high temperature, the outer ring of the ball bearing on the side opposite to the polygon mirror moves in the thrust direction, so that the ball bearing is not subjected to excessive stress and reliability can be improved.

[0013]

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

FIG. 1 (a) is a sectional view of a polygon mirror scanner motor according to an embodiment of the present invention, FIG. 1 (b) is a sectional view of an anti-polygon mirror side ball bearing portion, and FIG. 1 (c) is a ring-shaped elastic member. It is sectional drawing of a body. In FIG. 1, the shaft 1
Is rotatably fitted in the inner diameter holes of the two ball bearings 2 and 3, and the rotor boss 4 is fixed. A polygon mirror 5 is fixed to the upper part of the rotor boss 4 with screws and the like using a pressing plate 6, and a rotor yoke 7 and a magnet 8 are fixed to the lower part.

The outer ring of the ball bearing 2 on the polygon mirror side is directly fixed to the inner peripheral surface of the bracket with an adhesive or the like, while the outer ring of the ball bearing 3 on the opposite side is fitted in a peripheral groove 14a provided on the inner peripheral surface of the bracket. Ring-shaped elastic body 1 such as rubber attached
It is held by the bracket 14 via 3. At this time,
The C-shaped retaining ring 11 has a bearing structure in which the compression amount of the spring 12 is determined so that the preload becomes a constant value.

Further, the ring-shaped elastic body 13 has a convex portion 13a formed on the outer periphery thereof, and the compression rate of the convex portion 13b is larger than that of the non-convex portion 13c. Lateral pressure is applied to the.

Generally, in the polygon mirror scanner motor, since the polygon mirror 5 occupying most of the rotor inertia is arranged above the two ball bearings, the unbalanced force by the polygon mirror 5 is the ball bearing 2 on the polygon mirror side.
Great power is added to. Therefore, the outer ring of the polygon mirror side ball bearing 2 to which this large force is applied is directly adhered to the bracket 14, and the ball bearing 3 on the opposite side to which a relatively small force is applied.
The outer ring of the ring-shaped elastic body 1 is provided with a convex portion 13a on the outer circumference.
By holding the bracket 14 through 3 to apply lateral pressure, whirling at high speed rotation can be suppressed and high printing accuracy can be secured.

Further, since the ring-shaped elastic body 13 between the outer ring of the ball bearing 3 on the side opposite to the polygon mirror and the bracket 14 acts as a cushioning material, it absorbs vibrations during high-speed rotation to suppress resonance noise and reduce noise. Can be achieved.

Further, since the outer ring of the ball bearing 3 on the side opposite to the polygon mirror moves in the thrust direction, stress due to the difference in thermal expansion between the bracket 14 and the shaft 1 is not applied to the ball bearing, and high reliability can be maintained.

The depth of the peripheral groove 14a provided on the inner peripheral surface of the bracket and the size of the ring-shaped elastic body 13 are as follows.
The ring-shaped elastic body 13 is used because of the relationship between the ease of insertion and the compressive force.
It is desirable that the compression rate of the portion 13b having the convex portion on the outer periphery of the is less than or equal to twice the compression rate of the portion 13c having no convex portion.

In this embodiment, the outer ring of the polygon mirror side ball bearing 2 and the bracket 14 are bonded and fixed, but they may be press-fitted or heat-fitted and fixed.

[0022]

As described above, according to the present invention, of the two ball bearings that rotatably support the shaft, the outer ring of the ball bearing on the polygon mirror side is directly fixed to the bracket, and the outer ring of the other ball bearing. Is held on the bracket via a ring-shaped elastic body, and by providing a convex portion on the outer circumference of this ring-shaped elastic body, abnormal noise due to whirling and resonance of the polygon mirror that occurs during high-speed rotation can be prevented, and the bearing life is long. It is possible to realize an excellent polygon mirror scanner motor with high printing accuracy, low noise, and high reliability that can be extended.

[Brief description of drawings]

FIG. 1A is a sectional view of a polygon mirror scanner motor according to an embodiment of the present invention. FIG. 1B is a sectional view of an anti-polygon mirror side ball bearing portion of the embodiment. Cross section

FIG. 2 is a sectional view of a conventional polygon mirror scanner motor.

[Explanation of symbols]

 1 Shaft 2, 3 Ball Bearing 4 Rotor Boss 5 Polygon Mirror 6 Holding Plate 7 Rotor Yoke 8 Magnet 9, 14 Bracket 10 Stator Coil 11 C-Type Retaining Ring 12 Spring 13 Ring-like Elastic Body 13a Convex 13b Convex 13c Convex No groove 14a Circumferential groove

Claims (2)

[Claims] 1. A polygon mirror comprising a shaft, a rotor boss fixed to the outer periphery of the shaft, a polygon mirror fixed to the rotor boss, two ball bearings and a bracket for rotatably supporting the shaft. The outer ring of the ball bearing on one side is directly fixed to the bracket, and the outer ring of the other ball bearing is held on the bracket via a ring-shaped elastic body, and a convex portion is provided on the outer periphery of this ring-shaped elastic body. Scanner motor. 2. The polygon mirror scanner motor according to claim 1, wherein the ring-shaped elastic body has a compression rate of a portion provided with a convex portion on the outer periphery thereof is not more than twice the compression rate of a portion having no convex portion on the opposite side.