JP2000347123A - Light deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb variance of precision of parts and precision of assembling and moreover to hold an optimal magnetic gap even in the direction of various kinds of attaching. SOLUTION: This light deflector 1 is provided with a polygonal rotary polygon mirror 2 in the peripheral surfaces of which plural reflecting surfaces are formed, a motor 3 which rotates the rotary polygon mirror 2 at a constant high speed and is composed of a magnet 7 and driving coil 10 which are disposed facing each other, and a back yoke 15 which is fixed to a housing 114 facing the driving coil 10. In this case, a position adjusting means 120 which adjusts the position of the back yoke 15 in the axial direction of the light deflector is provided, the back yoke 15 is disposed and is movable in the axial direction of the light deflector, and a fixing means 115 which fixes the yoke holder the position of which in the axial direction is adjusted by the position adjusting means 120 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to an optical deflector used in an image forming apparatus such as a digital copying machine.

[0002]

FIG. 8 is a conceptual sectional view showing a conventional optical deflector 1. As shown in FIG.

The light deflector 1 comprises a polygonal rotary polygonal mirror 2 having a plurality of reflection surfaces 2a formed on a peripheral surface thereof, and a motor 3 for rotating the polygonal mirror 2 at a constant speed.

The motor 3 is a motor having a dynamic pressure spindle bearing which will be described later. The rotating shaft 4 of the motor 3 has a hollow cylindrical shape made of metal or ceramic, and its inner peripheral surface 4a has a substantially mirror surface. It has been processed.

A flange 5 is fixed to the rotary shaft 4 with an adhesive or the like. The rotary polygon mirror 2 is mounted on the flange 5 and is urged by an elastic member 6.

A rotor magnet 7 which acts on a drive coil 10 mounted on a substrate 11 to obtain a rotational force and a FG pattern (not shown) mounted on the substrate 11 act on a lower portion of the flange 5. The FG magnet 8 that performs speed detection is fixed by an adhesive or the like.

A thrust magnet 9 for supporting the rotating shaft 4 in the thrust direction by magnetic attraction with the second thrust magnet 12 is fixed to a side surface of the flange 5 by an adhesive or the like.

A groove 5a is formed in the upper part of the flange 5 along the circumferential direction. In the groove 5a, an appropriate amount of a balance weight 17 for adjusting the dynamic balance of the rotating shaft 4 is applied to an appropriate position. ing.

On the other hand, a metal or ceramic fixed shaft 16 of the motor 3 having a dynamic pressure spindle bearing is fixed to a housing 14, and the outer peripheral surface of the fixed shaft 16 is used for generating dynamic pressure by etching or the like. Spiral groove 16
a is formed.

The dynamic pressure spindle bearing comprises the thrust magnet 9 in which the rotating shaft 4 is fitted to the fixed shaft 16 and is fixed to the rotating shaft, and the second thrust magnet 12 fixed to the housing 14. And is supported in the thrust direction.

When power is applied and the rotating shaft 4 rotates, the spiral groove 16a formed in the fixed shaft 16 is formed.
A dynamic pressure of air is generated between the rotating shaft 4 and the inner peripheral surface 4a of the rotating shaft 4, and the radial direction of the rotating shaft 4 is supported by the fixed shaft 16 in a non-contact manner by the dynamic pressure.

The magnetic field generated by the rotor magnet 7 is turned upward by the back yoke 15 to form a magnetic circuit between the rotor magnet 7 and the back yoke 15.

When a control current flows from a control circuit (not shown) to the drive coil 10 disposed between the rotor magnet 7 and the back yoke 15, the drive coil 10 acts on the magnetic circuit to rotate the rotary shaft 4. Power is gained.

Here, the positional relationship between the rotor magnet 7 and the back yoke 15 is set to an optimum distance for reducing motor loss, improving magnetic efficiency, and the like.

However, when the size of the rotary polygon mirror 2 changes, the position of the rotor magnet 7 changes in the vertical direction due to the change in the weight of the rotary polygon mirror 2, so that the rotor magnet 7 and the back yoke 15 The problem arises that the optimal positional relationship between the two is lost.

As for such a problem, an optical deflector for adjusting the height of the rotary polygon mirror M with a thrust magnet FM and a second thrust magnet SM as shown in FIG. .

[0017]

However, Japanese Unexamined Patent Publication No.
The technique disclosed in Japanese Patent No. 289813 does not take into account the variation in component accuracy or the variation in assembly accuracy, and easily determines the optimal positional relationship between the rotor magnet RM and the back yoke Y after assembly. It cannot be adjusted.

In recent years, optical deflectors are required to have high speed and high reliability. Therefore, the above-mentioned problem becomes more remarkable when the polygon mirror is rotated at high speed to increase the recording density.

Further, the conventional optical deflector is disclosed in
Although the bearing is used in a vertical state as disclosed in Japanese Patent No. 289813, the bearing may be used in reverse or sideways due to recent diversification of mounting directions.

The diversification of the mounting direction is such that when the bearing rigidity of the thrust magnetic bearing for supporting the rotating shaft in the thrust direction is low, the floating position of the rotating shaft changes due to a change in the direction of gravity of the rotating shaft. As a result, the positional relationship between the rotor magnet RM and the back yoke Y fluctuates, and the above-described problem occurs.

Therefore, the present inventor has proposed a polygonal rotary polygonal mirror having a plurality of reflective surfaces formed on a peripheral surface thereof, and magnets disposed opposite to each other for rotating the rotary polygonal mirror at a high speed at a constant speed. In an optical deflector provided with a motor composed of a drive coil and a back yoke fixed to a housing facing the drive coil, the present invention adjusts the position of the back yoke in the axial direction of the optical deflector. Focusing on the technical concept of, and as a result of further research and development, we have provided an optical deflector that can absorb variations in component accuracy and assembly accuracy and maintain an optimal magnetic gap even in various mounting directions The present invention has been achieved which achieves the object of doing so.

[0022]

According to a first aspect of the present invention, there is provided an optical deflector comprising: a polygonal rotary polygon mirror having a plurality of reflection surfaces formed on a peripheral surface; A motor comprising a magnet and a drive coil disposed opposite to each other for rotating the mirror at a high speed at a constant speed, and an optical deflector comprising a back yoke fixed to a housing opposite to the drive coil, Position adjusting means for adjusting the position of the back yoke in the axial direction of the optical deflector is provided.

According to a second aspect of the present invention, in the optical deflector according to the first aspect, the back yoke is provided and is movable in an axial direction of the optical deflector. A fixing means is provided for fixing the yoke holder whose position in the axial direction has been adjusted by the position adjusting means.

[0024]

In the optical deflector of the first invention having the above-described structure, the position of the back yoke in the axial direction of the optical deflector is adjusted by the position adjusting means in accordance with variations in component accuracy and assembly accuracy. Since the adjustment is performed, it is possible to absorb variations in component accuracy and assembly accuracy, and to maintain an optimum magnetic gap in various mounting directions.

The optical deflector of the second invention having the above configuration is
In the first invention, the back yoke is provided, and the yoke holder movable in the axial direction of the optical deflector is fixed to the position in the axial direction adjusted by the position adjusting means by the fixing means. So
There is an effect that an optimum magnetic gap can be reliably maintained in various mounting directions.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are described below.
This will be described with reference to the drawings. The same parts as those in the conventional example described with reference to FIG. 8 are denoted by the same reference numerals, and detailed description is omitted.

(First Embodiment) An optical deflector according to the first embodiment comprises a polygonal rotary polygon mirror 2 having a plurality of reflecting surfaces formed on a peripheral surface as shown in FIGS. A motor 3 comprising a magnet 7 and a drive coil 10 which are arranged opposite to each other for rotating the rotary polygon mirror 2 at a high speed at a constant speed; and a housing 114 which faces the drive coil 10
And a back yoke 15 fixed to the optical deflector 1, a position adjusting means 120 for adjusting the position of the back yoke 15 in the axial direction of the optical deflector is provided, and the back yoke 15 is provided. The optical deflector comprises a fixing means 115 which is movable in the axial direction and fixes the yoke holder whose position in the axial direction has been adjusted by the position adjusting means 120.

FIGS. 1 and 2 are cross-sectional views schematically showing an optical deflector according to the first embodiment. Hereinafter, details of the optical deflector according to the first embodiment will be described.

The back yoke 15 is fixed to a yoke holder 118 with an adhesive or the like, and a male screw 118a constituting the position adjusting means 120 is formed all around the outer periphery of the yoke holder 118. I have.

On the other hand, on the inner periphery of the joint of the housing 114 and the yoke holder 118, a female screw 114a constituting the position adjusting means 120 screwed to the male screw 118a is formed over the entire circumference. .

The attachment of the back yoke 15 to the rotor magnet 7 is performed by screwing the female screw 114a and the male screw 118a. By changing the amount of screwing, the rotor yoke 15 and the back yoke 15 are attached. 1
The position of the optical deflector 5 in the axial direction can be adjusted to an optimal position.

The position of the back yoke 15 can be adjusted in a state where the optical deflector is assembled, and as shown in Table 1 and FIG. The optimum position is determined by changing the screwing amount.

[Table 1]

After the position of the back yoke 15 is adjusted, the back yoke 15 is fixed to the housing 114 by tightening a fixing screw 115 as fixing means inserted radially inward from the outer peripheral wall of the housing 114. Is done.

If the position adjustment of the back yoke 15 is not performed repeatedly, after the position adjustment of the back yoke 15, the screw portion may be fixed from the outside with an adhesive or the like.

In the optical deflector according to the first embodiment, the rotor magnet 7 and the back yoke are controlled by the position adjusting means 120 in order to prevent variations in component precision and assembly precision and diversification of mounting directions of the optical deflector. The 15 positional relations (magnetic gaps) are always adjusted to the optimal set values.

The back yoke 15 and the yoke holder 118, whose positional relationship (magnetic gap) between the rotor magnet 7 and the back yoke 15 is always adjusted to an optimum set value, tighten the fixing screws 115 as fixing means. Thereby, it is fixed and held by the housing 114.

The optical deflector according to the first embodiment having the above-described operation is provided by the back yoke 15 and the yoke holder 11.
8 is fixedly held at a position where the magnetic gap of the housing 114 is optimized by the fixing screw 115 as fixing means, so that iron loss, current value, and calorific value can be reduced, and reliability can be improved. This provides an effect that it is possible to provide an optical deflector with high performance.

That is, in the optical deflector according to the first embodiment, as described above, the position of the back yoke 15 disposed in the motor housing 114 can be varied in the thrust direction by providing the position adjusting means 120. The positional relationship (magnetic gap) between the back yoke 7 and the back yoke 15 can be set to an optimum value, and the following effects can be obtained.

First, since the iron loss, the current value, and the heat value can be reduced, the reliability of the optical deflector can be improved and the life can be extended. Second, since the variation in component accuracy and the variation in assembly accuracy can be absorbed, the performance of the optical deflector can be improved without changing the specifications of component accuracy and assembly accuracy. Third, it is possible to cope with diversification of mounting directions of the optical deflector such as a reverse direction and a horizontal direction.

(Second Embodiment) FIGS. 4 to 6 are sectional views schematically showing an optical deflector according to the second embodiment. Hereinafter, the optical deflector according to the second embodiment will be described focusing on differences from the first embodiment and the conventional example.

At least three female screws 118 b as position adjusting means 120 are provided on the outer peripheral surface of the yoke holder 118.
An adjusting groove 114b is formed in the housing 114 at a position corresponding to the female screw 118b, and the female screw 118b is inserted into the female screw 118b through the adjusting groove 114b.
5 are attached.

The position of the back yoke 15 can be adjusted with the optical deflector assembled.
While measuring the current value after rotation, the position adjusting means 12
This is performed by changing the screw position within the range of the groove length of the adjustment groove 114b as 0.

(Third Embodiment) FIG. 7 is a sectional view schematically showing an optical deflector according to the third embodiment. Hereinafter, the optical deflector according to the third embodiment will be described focusing on differences from the first embodiment and the conventional example.

As shown in FIG. 7, an elastic member 117, a back yoke 15, and a yoke holder 118 are placed below the substrate 11 fixed to the housing 114 in this order.

At the bottom of the housing 114, at least three screw holes 119 as position adjusting means 120 are provided.
The yoke holder 118 is configured to be vertically movable by the screw holes 119 and the screws 116.

Accordingly, since the back yoke 15 and the yoke holder 118 are constantly urged downward by the elastic member 117, the back yoke 15 can be adjusted to any position by the screw 116.

The elastic member 117 is not limited as long as it has a size capable of constantly biasing the back yoke 15 and is an elastic body of a magnetic body such as a rubber plate.

The position of the back yoke 15 can be adjusted with the optical deflector assembled.
The measurement is performed by rotating the screw within the range of the length of the screw 116 while measuring the current value or the like after the rotation.

After the position of the back yoke 15 is adjusted, the screws 116 are fixed with an adhesive or the like, so that the back yoke 15 is fixed.

Each of the above embodiments has been described by way of example only, and the present invention is not limited to those embodiments. A person skilled in the art will understand from the claims, the detailed description of the invention, and the drawings. Modifications and additions are possible without departing from the technical idea of the present invention that can be recognized.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an optical deflector according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a back yoke and a yoke holder according to the first embodiment.

FIG. 3 is a diagram showing a relationship between a position of a back yoke and a current value in the first embodiment.

FIG. 4 is a sectional view schematically showing an optical deflector according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating an adjustment groove according to the second embodiment.

FIG. 6 is a sectional view showing a back yoke and a yoke holder according to the second embodiment.

FIG. 7 is a sectional view schematically showing an optical deflector according to a third embodiment of the present invention.

FIG. 8 is a sectional view schematically showing a conventional optical deflector.

FIG. 9 is a sectional view showing an optical deflector for adjusting the height of a rotary polygon mirror M by a conventional magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical deflector 2 Rotating polygon mirror 3 Motor 7 Magnet 10 Drive coil 15 Back yoke 114 Housing 115 Fixing means 120 Position adjusting means

Claims (2)

[Claims] 1. A polygonal rotating polygonal mirror having a plurality of reflecting surfaces formed on a peripheral surface thereof, and a magnet and a driving coil disposed opposite to each other for rotating the rotating polygonal mirror at a high speed at a constant speed. And a back yoke fixed to a housing in opposition to the drive coil, wherein a position adjusting means for adjusting the position of the back yoke in the axial direction of the optical deflector is provided. A light deflector. 2. The yoke holder according to claim 1, wherein the back yoke is provided and is movable in the axial direction of the optical deflector, and the position of the yoke holder is adjusted in the axial direction by the position adjusting means. An optical deflector comprising fixing means.