JP2569244Y2 - Polygon mirror rotation drive - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon mirror rotation driving device used as an optical scanning device such as a laser beam printer and a facsimile. More specifically, the present invention relates to a polygon mirror rotation driving device in which a polygon mirror is covered with a cover member.

[0002]

2. Description of the Related Art A conventional polygon mirror rotation driving device used as an optical scanning device such as a laser beam printer is, for example, as shown in FIG. 3, a polygon mirror which is directly fixed to a rotation driving source such as a motor and rotates. 101 is provided to cover the mirror surface with a cover member 106 to protect the mirror surface from dust and the like.

[0003] A motor 103 as a rotary drive source includes a rotor 102 mounted with a polygon mirror 101 and rotated,
A substantially cylindrical bearing member 105 rotatably supported by forming a dynamic pressure bearing 104 with the rotor 102, a stator coil 109 fixed to a center pole 108 inside the rotor 102, and an inner periphery of the rotor 102. And a rotor magnet 110 fixed to the surface. The rotor 102 is floated in the thrust direction by using the attraction force of the magnets 111 and 112 of the magnetic thrust bearing disposed between the center pole 108 and the rotor 102, and is generated in the dynamic pressure bearing during rotation. It is supported in the radial direction by dynamic pressure.

[0004] The cover member 106 has, for example, a main body 106a fixed or integrally formed on the bearing member 105 in advance, and a lid 106b having a light-transmitting window to be covered after the polygon mirror 101 is mounted on the rotor 102.
It is composed of The internal space 107 partitioned by the cover member 106 has a different internal structure between the upper side and the lower side of the polygon mirror 101 due to the balance plate 113 projecting above the polygon mirror 101.

[0005]

However, in the conventional polygon mirror rotation driving device shown in FIG. 3, as the diameter of the polygon mirror 101 increases and the speed of the polygon mirror 101 increases, the peripheral polygon mirror 101 which rotates with the polygon mirror 101 is increased. The flow velocity of the air rises, and a negative pressure is generated above and below the polygon mirror 101. In addition, the negative pressure is not the same because the internal structure sealed by the cover member 106 is different between the upper and lower portions of the polygon mirror 101. Therefore, when the rotor 102 is levitated using a magnetic thrust bearing composed of a pair of magnets 111 and 112, there is a problem that the polygon mirror 101 moves easily.

An object of the present invention is to provide a polygon mirror rotation driving device for stabilizing the rotation position of a polygon mirror.

[0007]

Means for Solving the Problems] To achieve the above object, the present invention includes a polygon mirror, a rotor for supporting the polygon mirror, a rotation drive source for rotating the rotor, a cover member for covering the port Rigonmira in the polygon mirror rotary drive comprising a thrust direction of the rotor
In addition to having a magnetic thrust bearing that floats on the inner surface of the cover member, the upper and lower sides in the axial direction of the polygon mirror are
Air flow suppression means to balance the negative pressure
I am trying to.

[0008]

Therefore, the air around the polygon mirror tends to rotate together with the polygon mirror due to the viscosity due to the rotation of the polygon mirror. However, the flow of the air is hindered by the air flow suppressing means and the generation of the negative pressure is suppressed. For this reason, the pressures above and below the polygon mirror in the axial direction are balanced, and the negative pressure is balanced , and the magnetic thrust is reduced.
Rotor supported by the bearing and supported by this rotor
It is to prevent movement in the axial direction of the polygon mirror is.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the embodiment shown in FIG.

FIG. 1 shows an embodiment of a polygon mirror rotation driving device to which the present invention is applied. This polygon mirror rotation
The driving device includes a polygon mirror 1, a rotation drive source 3 that supports and rotates the polygon mirror 1, and a cover member 6 that covers the polygon mirror 1.

As the rotary drive source 3, for example, in the case of this embodiment, a motor is used. The motor 3 includes a rotor 2 on which a polygon mirror 1 is mounted and which rotates, a substantially cylindrical bearing member 5 which forms a dynamic pressure bearing 4 between the rotor 2 and rotatably supports the rotor 2, It comprises a stator coil 9 fixed to the inner center pole 8 and a rotor magnet 10 fixed to the inner peripheral surface of the rotor 2. The rotation of the motor 3 is obtained by controlling the exciting current by, for example, a brushless control method. Further, the rotor 2 is floated in the thrust direction by utilizing the attraction force of the pair of magnets 11 and 12 of the magnetic thrust bearing disposed between the center pole 8 and the rotor 2, while the rotor 2 is rotated by the dynamic pressure bearing 4 during rotation. It is supported in the radial direction by the generated dynamic pressure.

As the bearing member 5, it is preferable to use, for example, aluminum or an aluminum alloy which is easy to carry out precision processing, and a surface treatment for improving its abrasion resistance and the like,
For example, a surface treatment disclosed in JP-A-63-235719 is applied. Similarly, on the rotor 2 side, aluminum or aluminum alloy is adopted, and the surface thereof is appropriately subjected to surface treatment. Rotor 2
As shown in the figure, a small-diameter portion penetrating the polygon mirror 1 is provided at one axial end to form a bottomed cylindrical shape in which the polygon mirror 1 can be mounted, and the polygon mirror 1 is connected to the bottom portion via a spring washer 14 or the like. To prevent distortion.
Grooves 15 for generating dynamic pressure are formed on the outer peripheral surface 2 a of the rotor 2 (or the inner peripheral surface of the bearing member 5), and the dynamic pressure bearing 4 is formed between the rotor 2 and the bearing member 5. The dynamic pressure bearing 4 is configured such that a gap of several microns to several tens of microns is formed between the outer peripheral surface of the rotor 2 and the inner peripheral surface of the bearing member 5, and is formed by the dynamic pressure of the fluid generated in the groove 12 during rotation. The rotor 2 is supported in the radial direction. In addition, as the dynamic pressure fluid, a liquid or other appropriate fluid can be used in addition to the air of the present embodiment.

[0013] The cover member 6 protects it covers the polygon mirror 1, such as from dust, and also because it is used for installing other devices member (not shown) the entire polygon mirror rotary drive if necessary is there. In the case of this embodiment, the cover member 6 is composed of a main body 6a integrally formed with the bearing member 5, and a lid 6b having a light-transmitting window that is covered after the polygon mirror 1 is mounted on the rotor 2. I have. Of course, the main body 6a of the cover member 6 and the bearing member 5 may be formed separately, and fixed using screws or the like. Note that reference numeral 13 in the figure is a balance plate.

On the inner surface of the cover member 6, a polygon mirror
An airflow suppressing means 7 is provided to balance the negative pressure generated on the upper side and the lower side in the axial direction . This air flow suppressing means 7
Is for obstructing the flow of air around the polygon mirror 1 caused by the rotation of the polygon mirror 1, and is constituted by grooves or projections. The arrangement position, the number, the arrangement direction, and the like of the airflow suppressing means 7 are not particularly limited to those shown in the drawings, and it is preferable to select a shape, the number, and the arrangement direction suitable for obstructing the flow. . For example, in the present embodiment, the projections are arranged at 90 ° intervals in the radial direction on the main body 6a at a position facing the lower surface of the polygon mirror 1, while the projections are also radially formed on the lid 6b at a position facing the upper surface of the polygon mirror 1. Are arranged at 90 ° intervals. In the case of this embodiment, these projections
The positions of the upper and lower projections are shifted and changed in shape, but the present invention is not particularly limited to this, and airflow suppression means having a completely symmetrical shape and arrangement may be provided. Then, airflow suppression means having completely different shapes may be adopted, or they may be arranged at different positions, for example, at different positions in the radial or circumferential direction. Further, only one of the upper and lower sides of the polygon mirror 1 may be used. It may be provided. The point is that a shape or an arrangement that balances the negative pressure generated above and below the axial direction of the polygon mirror 1 when the polygon mirror 1 rotates may be adopted.

The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the case of the present embodiment, the projections serving as the airflow suppressing means 7 are arranged in a radial direction orthogonal to the rotation direction of the polygon mirror 1, but are not particularly limited to this, and are arranged in the circumferential direction. A similar effect was observed. This is presumably because it is effective to prevent the flow in the centrifugal direction due to the rotation of the polygon mirror 1.

[0016]

[Effects of the Invention] As is clear from the above description, the polygon mirror rotation driving device of the present invention comprises a polygon mirror,
A rotor supporting the polygon mirror, and rotating the rotor
Rotating drive source and a cover member to cover the polygon mirror
In the polygon mirror rotation driving device consisting of
With a magnetic thrust bearing that lifts the rotor in the thrust direction
And the inner surface of the cover member has a polygon mirror axis
Airflow suppression that balances the negative pressure generated in the upper and lower directions
Since the control means is provided, even if the structure inside the cover member is different between the upper and lower sides of the polygon mirror, the flow of the surrounding air generated by the rotation of the polygon mirror is obstructed by the air flow suppressing means, and To suppress the generation of pressure, the pressures above and below the polygon mirror in the axial direction are balanced to balance the negative pressure, and the magnetic thrust bearing
An axial movement of the supported rotor and the polygon mirror supported by the rotor is prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a polygon mirror rotation driving device according to the present invention, in which a bearing member, a cover member, and a part of a rotor are cross-sectioned;

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a partial longitudinal sectional view of a conventional polygon mirror rotation driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon mirror 2 Rotor 3 Rotation drive source 4 Dynamic pressure bearing 5 Bearing member 6 Cover member 7 Air flow suppression means

Claims (1)

(57) [Scope of request for utility model registration] And 1. A polygon mirror, a rotor for supporting the polygon mirror, a rotation drive source for rotating the rotor, the polygon mirror rotary drive comprising a cover member for covering the polygon mirror, slide the rotor
With a magnetic thrust bearing that floats in the strike direction
On the inner surface of the cover member, the polygon mirror
A polygon mirror rotation drive device, further comprising: an airflow suppression unit that balances a negative pressure generated on an upper side and a lower side in an axial direction .