JPH09230269A - Bearing structure for polygon mirror and polygon scanner driving device having the bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a deflective rotation due to a half whirl at the time of a high speed rotation. SOLUTION: This bearing structure is provided with a sliding bearing 9 axially supporting in a radial direction, a fixed shaft 1 supported freely rotatably to the sliding bearing 9, a mean relatively rotating the sliding bearing 9 and the fixed shaft 1 and a polygon mirror 13 fixed to one side among the fixed shaft 1 and the sliding bearing 9. In this case, a magnetized part MM and a magnetic material are made so as to attract each other by constituting one side of a ring-shaped magnet M enclosing the outer circumference of the sliding bearing and the fixed shaft with magnetic material and by constituting a magnetic circuit Z in-between a magnetized part MM and the magnetic material while forming the magnetized part MM in one part of the radial direction of the other side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a polygon mirror used for scanning laser light in laser beam printers, digital copying machines and the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a polygon scanner driving device in which a polygon mirror 23 is attached to a rotary member such as a flange member 22 is used for scanning laser light in a laser printer or the like.

This polygon scanner driving device is provided with a face-to-face brushless DC motor having a stator portion and a rotor portion, and a flange member 22 of the rotor portion axially supported by a fixed shaft 1 of the stator portion through a slide bearing 9. Are configured to be rotationally driven together with the polygon mirror 23.

The stator portion has a fixed shaft 1 having a spherically shaped tip, a collar 2 into which the fixed shaft 1 is press-fitted, and a base member 3 for fixing the collar 2 so that the shaft center is vertical. A substrate 4 to which a screw (not shown) is fixed on the base member 3, a winding coil 5 which is bonded and fixed to a predetermined position of the substrate 4, and a substrate 4 at a predetermined position in the winding coil 5.
And a Hall element 6 for detecting the magnetic pole of the rotor magnet 15, a control circuit 7 fixed on the substrate 4 for switching the excitation, and a connector 8.

The rotor portion includes a thrust cover 11 to which a thrust plate 10 axially supporting the radial direction is fixed, and a flange member 22 to which the thrust cover 11 is adhesively fixed.
A female screw portion 22b provided near the outer periphery of the flange member 22, a polygon mirror 23 inserted into and attached to the cylindrical protrusion 22c of the flange member 22, and a rotor yoke 14 attached to the lower surface of the flange member 22.
And a rotor magnet 15 bonded to the rotor yoke 14.

In this conventional polygon scanner driving device, as shown in FIG. 4, the rotor yoke 14 is fixed to the lower surface of the flange member 22 to which the polygon mirror 23 is attached, and the rotor magnet 15 is fixed to the lower surface of the rotor yoke 14. Further, the fixed shaft 1 is mounted in the through hole 22a at the center of the flange member 22 via the slide bearing 9, the thrust plate 10, and the thrust cover 11, and the lower end portion of the fixed shaft 1 is connected via the collar 2. The base member 3 and the substrate 4 are fixed. On the substrate 4, a winding coil 5 facing the rotor magnet 15 via a predetermined gap, a Hall element 6 in the winding coil 5, a control circuit 7 for switching excitation, and a connector 8 are provided.

The polygon mirror 23 of such a polygon scanner driving device has six reflecting surfaces 2 on the outer peripheral surface (side surface).
It is a regular hexagonal columnar body having 3r. Further, a mounting hole 23a having a circular cross section is formed in the polygon mirror 23 so as to be coaxial therewith, and penetrates from the top surface to the bottom surface.
Around the periphery of 3a, an axial through hole 23b into which the tightening screw 16 is fitted is formed. Further, the flange member 22 to which the polygon mirror 23 is attached has a female screw portion 22b into which the tightening screw 16 is screwed.
Is formed corresponding to the through hole 23b.

As shown in FIG. 4, in order to attach such a polygon mirror 23 to the flange member 22, first,
A mounting hole 23 a of a regular hexagonal columnar body forming the polygon mirror 23 is fitted to the flange member 22. Next, the tightening screw 16 is inserted into the through hole 23b, and the tightening screw 16 is screwed into the female screw portion 22b of the flange member 22 and tightened to attach the polygon mirror 23. The polygon mirror 23 mounted in this way scans the light beam on the side reflection surface 23r while rotating about the axis of the regular hexagonal prism.

In the polygon scanner driving device as described above, there has recently been a demand for higher speed and smaller size as the laser beam printer becomes faster.

[0010]

However, since the conventional slide bearing structure described above is a true circular dynamic pressure bearing in the radial direction, the radial gap between the fixed shaft and the slide bearing causes a 1/2 whirl. There is a problem that whirling occurs due to the whirling and swirling phenomenon of a 1/2 rotation component of the rotation frequency. Therefore, the laser beam printer using the conventional polygon scanner driving device having the bearing structure of the polygon mirror may deteriorate the print quality when the speed is increased.

Therefore, it is an object of the present invention to provide a polygon mirror bearing structure in which whirling due to 1/2 whirl during high speed rotation is reduced, and a polygon scanner driving device having this bearing structure.

[0012]

In order to achieve the above object, in a bearing structure for a polygon mirror according to the present invention, a slide bearing axially supporting the radial direction, and a shaft rotatably supported by the slide bearing are provided. In a bearing structure of a polygon mirror, comprising: a means for relatively rotating the slide bearing and a shaft; and a polygon mirror fixed to one side of the shaft and the slide bearing, a ring surrounding the outer periphery of the slide bearing and the shaft. One of them is composed of a magnetic material, and a magnetized portion is formed in a part of the other in the radial direction, and a magnetic circuit is formed between the magnetized portion and the magnetic material so as to attract each other. It has a feature.

According to another aspect of the present invention, there is provided a bearing structure for a polygon mirror, a slide bearing axially supporting the radial direction, a shaft rotatably supported by the slide bearing, and the slide bearing and the shaft relatively rotating. In the bearing structure of the polygon mirror, the shaft is made of a magnetic material and a ring-shaped magnet is arranged on the outer circumference of the slide bearing. In the radial direction of the ring-shaped magnet, a magnetized portion and a non-magnetized portion are formed, and a magnetic circuit is formed between the magnetized portion and the shaft of the ring-shaped magnet so as to attract each other. It has a feature.

According to the polygon mirror bearing structure of claim 3, in the polygon mirror bearing structure of claim 1 or 2, the central angle θ of the magnetized portion is 0 ° <θ <18.
It is characterized by satisfying 0 °.

Further, a polygon scanner drive device according to a fourth aspect is characterized by having the bearing structure of the polygon mirror according to any one of the first to third aspects.

Further, in the polygon scanner driving device of the fifth aspect, a fixed shaft fixed to the base via a collar,
A substrate attached to the base, a coil attached to the substrate, a flange member in which a rotor magnet facing the coil is bonded via a rotor yoke, a polygon mirror fixed to the flange, and a radial direction of the fixed shaft. In a polygon scanner driving device including a slide bearing that axially supports and a thrust plate that axially supports the thrust direction of the fixed shaft, the fixed shaft is made of a magnetic material, and a ring-shaped magnet is arranged on the outer circumference of the slide bearing. Then, the radial direction of the ring-shaped magnet is composed of a magnetized portion and a non-magnetized portion, and a magnetic circuit is formed between the magnetized portion of the ring-shaped magnet and the fixed shaft to attract each other. It is characterized by that.

In the bearing structure of the polygon mirror of the present invention,
One of the shafts supported by the surrounding ring and the slide bearing on the outer circumference of the slide bearing is made of a magnetic material, and a magnetized portion is formed in a part of the other radial direction. Since the magnetic circuit is configured in the above, a magnetic attraction force is generated between the magnetized portion and the magnetic body. Therefore, the polygon mirror rotates in a state where it is attracted by the bearing clearance in the radial direction with respect to the shaft, so that whirling due to 1/2 whirl does not occur and the polygon mirror can rotate more uniformly. In addition, the ring surrounding the outer circumference of the slide bearing is a rotating body centered on the axis of rotational symmetry, so that the weight is balanced with respect to the shaft center. Therefore, the weight balance does not deteriorate when the ring is added, and the uniformity of rotation is not adversely affected.

Further, in the bearing structure of the polygon mirror of the present invention, the shaft is made of a magnetic material, and a ring-shaped magnet is arranged on the outer periphery of the slide bearing, and the ring-shaped magnet is composed of a magnetized portion and a non-magnetized portion. Since the magnetic circuit is configured between the magnetized portion of the ring-shaped magnet and the fixed shaft, a magnetic circuit is configured between the magnetized portion of the ring-shaped magnet and the magnetized portion of the ring-shaped magnet. The force acts between the ring-shaped magnet of the magnetized portion and the fixed shaft. Therefore, the polygonal mirror, which is a rotating body, rotates while being attracted to the fixed shaft by the radial bearing clearance (clearance), so that whirling due to 1/2 whirl does not occur and more uniform rotation is possible. Become. Also, since the ring-shaped magnets arranged on the outer circumference of the slide bearing are rotating bodies centered on the axis of rotational symmetry,
The weight is balanced with respect to the shaft center. Therefore, the weight balance does not deteriorate when the ring-shaped magnet is added, and the uniformity of rotation is not adversely affected.

Further, since the polygon scanner driving device of the present invention is provided with a polygon mirror bearing structure which prevents whirling due to 1/2 whirl, the polygon mirror which greatly improves the uniformity of the rotation makes it possible to generate a laser beam. It is possible to perform scanning, and it is possible to prevent a laser beam scanning deviation.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional side view showing an embodiment of a polygon scanner driving device according to the present invention, and is a view showing an embodiment to which the present invention is applied to a polygon scanner driving device used in a laser beam printer. In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

This polygon scanner driving device is provided with a face-to-face brushless motor having a stator portion and a rotor portion, like the conventional polygon scanner driving device.

In this embodiment, a strain absorbing groove 13b is formed outside the mounting hole 13a of the polygon mirror 13, that is, at a position closer to the outer periphery by a predetermined length from the mounting hole 13a. Here, the predetermined length means a length sufficient to absorb strain. Further, the strain absorbing groove 13b is formed to a depth of 0.5 mm in the present embodiment.

Further, the cylindrical projection 12 of the flange member 12
On the upper surface of a, a ring-shaped protruding portion 12c formed on the outermost periphery and a ring-shaped groove portion 12b adjacent to the inner side of the protruding portion 12c for facilitating plastic deformation of the protruding portion 12c are formed.

To attach the polygon mirror 13 to the flange member 12 of the rotor portion, first, the flange member 1 is attached.
The mounting hole 1 for the polygon mirror 13 is attached to the cylindrical protrusion 12a of 2
3a is fitted. Next, the attachment surface 13c of the polygon mirror 13 is brought into close contact with the highly accurate positioning surface 12d of the flange member 12. Then, the flange member 12
The polygonal mirror 13 is fixed to the flange member 12 by plastically deforming the protruding portion 12c of the cylindrical protruding portion 12a by an outer caulking joint using a caulking type, for example. At this time,
Positioning surface 12 of flange member 12 formed with high precision
Since the mounting surface 13c of the polygon mirror 13 is pressed against d, the reflecting surface 13r on the side surface of the polygon mirror 13 is positioned with high accuracy.

Further, similarly to the conventional case, the rotor magnet 15 adhered to the rotor yoke 14 is attached via the rotor yoke 14 so as to maintain a predetermined axial gap with the winding coil 5 adhered and fixed on the substrate 4. Has been.

As described above, the rotor magnet 15 integrally attached to the flange member 12 faces the winding coil 5 attached on the substrate 4 with a predetermined axial gap therebetween. The winding coil 5 and the winding coil 5 form a motor. Winding coil 5 of this motor
By applying a predetermined current to the rotor magnet 15
A rotational force is generated in the center hole 12e of the flange member 12
The rotating body pivotally supported by the slide bearing 9 and the thrust plate 10 fitted in the shaft rotates. In this way, when the polygon mirror 13 integrally attached to the flange member 12 rotates, the laser light reflected by the polygon mirror 13 is emitted to the outside.

To fix the polygon mirror 13 to the flange member 12, the protrusion 12c is plastically deformed outward by, for example, a caulking type, and the positioning surface of the flange member 12 is plastically deformed by the caulking part K. The polygon mirror 13 is pressed onto 12d. At this time, since the protruding portion 12c of the flange member 12 is plastically deformed, it is possible to join at a portion closer to the center (that is, farther from the reflection surface) than in the case of conventional screw tightening, and the inner peripheral portion of the polygon mirror 13 is slightly deformed. Even if it does, it is difficult for the deformation to reach the reflecting surface 13r.

Further, even if the inner peripheral portion of the mounting hole 13 of the polygon mirror 13 is deformed a little more, the strain absorbing groove 1
Since the deformation is absorbed by 3b, the strain absorbing groove 13
It is possible to prevent the outside of b from being deformed, and thus prevent the distortion of the reflecting surface.

The caulking position for fixing the polygon mirror 13 is a straight line extending from the axis of the polygon mirror 13 to each connecting point (corner apex) of the adjacent reflecting surfaces 13r and the cylindrical projection 12a of the flange member 12. It is at the intersection with the ring-shaped protrusion 12c provided on the. That is, the crimped portion K is provided at a portion where the line connecting the rotation center of the polygon mirror 13 in plan view and the corner vertex is intersected with the annular fitting portion. Therefore, since they are equidistant from the axis O, that is, on the circumference centered on the axis O, the caulking portions K can have equal intervals in the circumferential direction.

2A and 2B are views showing a ring-shaped magnet provided in the bearing structure of the polygon scanner driving device according to the present invention, FIG. 2A being a plan view and FIG. 2B being a sectional view taken along line AA. As shown in FIG. 2A, the ring-shaped magnet M has a magnetized portion MM in the range of the center O of the axis O and a central angle θ, and the other portions are non-magnetized portions NM. Since the ring-shaped magnet M is a rotating body in structure, the weight in the circumferential direction is balanced. Further, as shown in FIG. 2B, the magnetized portion MM is magnetized in the axial direction by NS with one magnetic pole pair.

FIG. 3 is an enlarged vertical sectional view showing a magnetic circuit of the bearing structure of the polygon scanner driving device according to the present invention. As shown in FIG. 3, the slide bearing 9 is made of a hollow cylindrical lubricating resin, for example, Vespel material (trade name of DuPont). A ring-shaped magnet M is attached to the outer circumference of the slide bearing 9, and a magnetic circuit Z is formed between the ring-shaped magnet M and the fixed shaft 1. The ring-shaped magnet M is fixed coaxially with the slide bearing 9 along the outer circumference of the slide bearing, that is, surrounding the outer circumference.

The rotating body such as the polygon mirror 13 and the like with respect to the fixed shaft 1 of the polygon scanner driving device has its thrust direction brought into contact with the spherical portion at the tip of the fixed shaft 1 by means of a slide bearing 9. It is pivotally supported by 10. Further, a ring-shaped magnet M having a magnetized portion MM and a non-magnetized portion NM is provided on the outer periphery of the slide bearing 9 and below the flange member 12. A magnetic circuit Z is formed between the fixed shaft 1 made of a magnetic material and the magnetized portion MM of the ring-shaped magnet M. With this structure, a magnetic attraction force in the radial direction is generated between the magnetized portion MM of the ring-shaped magnet M and the fixed shaft 1 made of a magnetic material such as iron.

Therefore, when the polygon scanner driving device is rotated, the clearance between the inner diameter of the slide bearing 9 and the outer diameter of the fixed shaft 1 rotates while being always kept in contact by the magnetic attraction force. It is possible to prevent the whirling phenomenon due to the 1/2 whirl that is generated by the radial gap between the fixed shaft 1 and the slide bearing 9. The central angle θ, which is the magnetization angle of the ring-shaped magnet M in the above embodiment, is preferably set in the range of 0 ° <θ <180 °.

In the above embodiment, the shaft serving as the center of rotation of the polygon mirror 13 is the fixed shaft 1 fixed to the stator side. However, the slide bearing 9 is provided on the stator side and the fixed shaft 1 is fixed to the rotor side. You may.

In the above embodiment, the case where the ring-shaped magnet M is attached to the outer circumference of the slide bearing 9 has been described.
On the contrary, even when a magnetized portion MM and a non-magnetized portion NM are provided on the fixed shaft 1 side and a ring made of a magnetic material is fitted on the outer circumference of the slide bearing 9 at a position facing the magnetized portion MM, The same action and effect as when mounted on the outer periphery of the slide bearing 9 can be obtained.

In the above embodiment, the ring-shaped magnet M is used.
The upper and lower magnetic poles are arranged so that the upper pole is the N pole, but the lower pole is the N pole.
It may be a pole.

[0037]

As is apparent from the above description, according to the present invention, it is possible to eliminate the whirling phenomenon due to 1/2 whirl that occurs when the polygon mirror is rotated at a high speed. By applying the present invention to the scanner driving device, it is possible to improve the printing quality.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a polygon scanner driving device according to the present invention.

2A and 2B are diagrams showing a ring-shaped magnet provided in a bearing structure of a polygon scanner driving device according to the present invention, FIG. 2A being a plan view and FIG. 2B being a sectional view taken along line AA.

FIG. 3 is an enlarged vertical sectional view showing a magnetic circuit of a bearing structure of the polygon scanner driving device according to the present invention.

FIG. 4 is a vertical sectional view of a conventional polygon scanner driving device.

[Explanation of symbols]

 1 Fixed shaft 4 Substrate 5 Winding coil 9 Sliding bearing 12 Flange member 13 Polygon mirror 14 Rotor yoke 15 Rotor magnet M Ring magnet MM Magnetized part NM Non-magnetized part Z Magnetic circuit θ Central angle

Claims (5)

[Claims] 1. A slide bearing that axially supports in a radial direction,
A bearing of a polygon mirror including a shaft rotatably supported by the slide bearing, means for relatively rotating the slide bearing and the shaft, and a polygon mirror fixed to one side of the shaft and the slide bearing. In the structure, one of the ring surrounding the slide bearing outer circumference and the shaft is made of a magnetic material, and a magnetized portion is formed in a part of the other radial direction, and between the magnetized portion and the magnetic material. A bearing structure for a polygon mirror, characterized in that a magnetic circuit is configured to attract each other. 2. A slide bearing which axially supports in a radial direction,
A bearing of a polygon mirror including a shaft rotatably supported by the slide bearing, means for relatively rotating the slide bearing and the shaft, and a polygon mirror fixed to one side of the shaft and the slide bearing. In the structure, the shaft is composed of a magnetic material, and a ring-shaped magnet is arranged on the outer circumference of the slide bearing, and the ring-shaped magnet is composed of a magnetized portion and a non-magnetized portion in the radial direction. A bearing structure for a polygon mirror, characterized in that a magnetic circuit is formed between the magnetized portion and the shaft so as to attract each other. 3. The central angle θ of the magnetized portion is 0 ° <θ <18
The bearing structure for a polygon mirror according to claim 1, wherein the bearing structure satisfies 0 °. 4. A polygon scanner driving device comprising the bearing structure for a polygon mirror according to claim 1. Description: 5. A flange member in which a fixed shaft fixed to a base via a collar, a substrate attached to the base, a coil attached to the substrate, and a rotor magnet facing the coil are adhered via a rotor yoke. And a polygon mirror fixed to the flange, a slide bearing that axially supports the fixed shaft in the radial direction, and a thrust plate that axially supports the thrust direction of the fixed shaft. And a ring-shaped magnet is arranged on the outer circumference of the slide bearing, the radial direction of the ring-shaped magnet is composed of a magnetized portion and a non-magnetized portion, and the magnetized portion of the ring-shaped magnet is A polygon scanner drive device characterized in that a magnetic circuit is formed between the fixed shaft and the fixed shaft so as to attract each other.