JP3191585B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device that irradiates light to a side surface of a rotating polygon mirror and performs scanning by reflected light.

[0002]

2. Description of the Related Art This type of apparatus is used for various image forming apparatuses, and the following improvements have been made conventionally. For example, it is generally known that, in a printer, a facsimile machine, and the like, it is easier to perform a process such as a paper jam when a recording paper conveyance path is disposed above the optical scanning device. Therefore, it has been considered to dispose the optical scanning device below the photosensitive drum. When the optical scanning device is provided below the photosensitive drum, it is necessary to prevent toner and the like from entering the optical system of the optical scanning device. For this reason, it has been considered to cover the optical scanning device with the housing from above. In this case, it is desirable to provide the rotary polygon mirror on the lower surface of the housing via the shaft member in order to improve the positioning accuracy and facilitate the adjustment of the optical system.

On the other hand, various bearing mechanisms between a housing or a rotary polygon mirror and a shaft member have been studied. For example, as described in Japanese Patent Publication No. 6-81963, it has been considered to provide a so-called fluid bearing utilizing fluid pressure such as air dynamic pressure between a housing and a shaft member. When this fluid bearing is used, the frictional resistance against rotation of the rotary polygonal mirror becomes extremely small, and the rotary polygonal mirror can be rotated at high speed and stably. Then, when such an optical scanning device is applied to an image forming apparatus such as a printer or a facsimile machine, the time required for image formation can be reduced and the image can be sharpened.

[0004]

However, if the fluid bearing is applied as it is to an optical scanning device having a rotating polygon mirror provided on the lower surface of the housing, the rotating polygon mirror will fall.
For this reason, in this type of optical scanning device, a bearing mechanism, such as a ball bearing, that can prevent the rotating shaft from coming off is employed. Therefore, in this type of optical scanning device, the rotary polygon mirror cannot be rotated at a sufficiently high speed.

When the rotating polygon mirror is driven by a motor fixed to the rotating polygon mirror and the stator to the housing, an electromagnetic attraction force acts between the rotating polygon mirror and the housing. Therefore, it is conceivable to use a fluid bearing as the bearing mechanism and prevent the rotating polygon mirror from falling by this electromagnetic attractive force, but it is difficult to sufficiently increase the electromagnetic attractive force. Therefore, when such an optical scanning device is applied to an image forming apparatus, the image may be distorted by the rotary polygon mirror easily swinging up and down due to external vibration.

Accordingly, an object of the present invention is to rotate a rotating polygon mirror at high speed and stably in an optical scanning device provided with a rotating polygon mirror on a lower surface of a housing.

[0007]

According to the first aspect of the present invention, there is provided a rotary polygon mirror provided rotatably on a lower surface of a housing via a shaft member, and a rotary polygon mirror for rotating the rotary polygon mirror. A fluid bearing provided between the housing or the rotating polygon mirror and the shaft member, in an optical scanning device including a driving means for driving and an irradiation means for irradiating light to a reflection surface of the rotating polygon mirror; And an elastic member that abuts the shaft member or the rotating polygon mirror from below the center of rotation with a predetermined elastic force to prevent the rotating polygon mirror from moving downward.

According to a second aspect of the present invention, the housing or the rotary polygon mirror provided with the fluid bearing surrounds an end of the shaft member in a sealed manner. The gist is a scanning device. The invention according to claim 3 further comprises a blocking member disposed below the elastic member and configured to prevent downward displacement of the elastic member by a predetermined amount or more. The gist is the optical scanning device described.

[0009]

According to the first aspect of the present invention, the rotary polygon mirror provided on the lower surface of the housing via the shaft member is driven to rotate by the driving means. When the irradiating means irradiates the reflecting surface of the rotary polygon mirror with light, the reflected light can scan in the rotation direction of the rotary polygon mirror.

A fluid bearing is provided between the housing or the rotary polygon mirror and the shaft member, and a frictional resistance acting between the housing or the rotary polygon mirror and the shaft member abuts at the shaft end. Since it occurs only at the center of rotation, its frictional resistance is extremely small. Further, an elastic member is in contact with the shaft member or the rotary polygon mirror from below the center of rotation with a predetermined elastic force. For this reason, the downward movement of the rotary polygon mirror due to extraneous vibration or the like is prevented, the rotary polygon mirror does not swing up and down, and further, uneven rotation caused by a sudden change in frictional force due to separation of the contact portion is eliminated. Does not occur. When the elastic member comes into contact with the shaft member or the rotary polygon mirror, frictional resistance against the rotation of the rotary polygonal mirror acts between the two members. Has almost no effect on the rotation of.

Therefore, according to the present invention, the frictional resistance against rotation of the rotary polygonal mirror can be extremely reduced, and the rotary polygonal mirror can be prevented from swinging up and down. Therefore, the rotating polygon mirror can be rotated at a high speed and stably, and the time required for image formation in the image forming apparatus to which the present invention is applied can be shortened, and the image can be sharpened. .

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the end of the shaft member is hermetically surrounded by a housing or a rotary polygon mirror provided with a fluid bearing. For this reason, when the shaft member comes out of the housing or the rotary polygon mirror, it acts in a direction to prevent the atmospheric pressure from being released. Accordingly, the downward movement of the rotary polygon mirror can be more favorably prevented. That is, according to the present invention, in addition to the effect of the first aspect, the rotating polygon mirror can be rotated more stably, and furthermore, the image in the image forming apparatus to which the present invention is applied can be sharpened. The effect that it can be done.

[0013] The invention according to claim 3 is the invention according to claim 1 or 2.
In addition to the configuration of the invention described above, the vehicle further includes a blocking member disposed below the elastic member and configured to prevent a downward displacement of the elastic member by a predetermined amount or more. When the rotary polygon mirror moves downward, the elastic member also displaces downward, but this displacement is suppressed to less than the predetermined amount by the blocking member. For this reason, in the present invention, it is possible to reliably prevent the rotating polygonal mirror from excessively moving downward, and there is no excessive increase in the frictional force even at the time of the maximum movement. Can be minimized. Therefore, in the present invention, in addition to the effects of the invention described in claim 1 or 2,
In the image forming apparatus to which the present invention is applied, it is possible to reliably prevent an image from being excessively unclear.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view illustrating a configuration of a printer 1 as an image forming apparatus to which the present invention has been applied. Printer 1
A paper feed roller 3 that has a paper feed tray 3 at an upper portion thereof and takes out recording paper 5 one by one from the paper feed tray 3, an image forming unit 9 that forms an image on the surface of the recording paper 5 with toner, A fixing roller 11 for fixing the image formed on the surface of the recording paper 5 by pressurization and heating at 9 and a discharge roller 15 for discharging the recording paper 5 discharged from the fixing roller 11 onto a discharge tray 13 are built in. are doing.

A scanner unit 21 as an optical scanning device for irradiating the photosensitive drum 19 of the image forming unit 9 with light based on the received image data is provided below the image forming unit 9. An electrostatic latent image corresponding to the image data is formed on the photosensitive drum 19 irradiated with light by the scanner unit 21, and toner adheres to the electrostatic latent image to form a recording paper 5.
The image is formed on the recording paper 5 by being transferred to the recording paper 5.

The scanner unit 21 has a housing 23 having an open lower end surface. A laser diode 27 as an irradiation means for generating a laser beam 25 and a polygon mirror as a rotating polygon mirror are provided on the lower surface of the housing 23. 31, an Fθ lens 33 and a cylinder lens 35 for condensing the laser beam 25 reflected by the polygon mirror 31, and a folding mirror 37 for reflecting the laser beam 25 passing through the lenses 33 and 35 toward the photosensitive drum 19. Is attached.

The polygon mirror 31 is formed in a regular hexagonal flat plate shape (see FIG. 4), and is rotatably fixed to the lower surface of the housing 23 via a scanner motor 41 as a driving means and a bracket 43 as shown in FIG. ing. The laser diode 27 irradiates the polygon mirror 31 with the laser beam 25 from a direction substantially orthogonal to the direction in which the Fθ lens 33 is provided. For this reason, the laser beam 25
Six times per rotation of the polygon mirror 31, the photosensitive drum 1
9 is scanned in the length direction. Further, the scanner unit 21
A projection 47 as a blocking member protruding toward the center of the polygon mirror 31 is formed on a base portion 45 of the printer 1 disposed below.

Next, the configuration of the polygon mirror 31 will be described in detail with reference to FIGS. FIG. 1 is a sectional view showing the configuration around the polygon mirror 31, and FIG. 4 is a bottom view thereof. As shown in FIG. 1, the polygon mirror 31 is fixed to one end of a rotating shaft 53 as a shaft member via a rotor boss 51. The rotation shaft 53 has a so-called pivot shape in which both ends are formed in a spherical shape.
Is rotatably supported by the bracket 43 via a bearing 55. A radial bearing surface 57 is formed on the inner surface of the bearing portion 55 facing the rotating shaft 53, and a dynamic pressure group (not shown) is also formed on the outer periphery of the rotating shaft 53. Therefore, the rotation of the rotating shaft 53 generates an air dynamic pressure between the outer periphery of the rotating shaft 53 and the radial bearing surface 57, and
A so-called hydrodynamic bearing for fixing the center of rotation is formed.
The configuration and operation of this type of fluid bearing are described in the magazine "N.
national Technical Report
Vol. 40 Oct. 1994 "pp. 567-57
3 and will not be described in detail here. Also, the bearing 5
5 is sealed by a sealing member 59. Therefore, the other end of the rotating shaft 53 is hermetically surrounded by the bearing portion 55 and the sealing member 59.

Next, the rotor yoke 6 is attached to the rotor boss 51.
1, a rotor magnet 63 is fixed to the bracket 43, and a stator coil 65 is fixed to the bracket 43. Therefore, when power is supplied to the stator coil 65, the polygon mirror 31 rotates. A leaf spring 71 as an elastic member is fixed to one end of the bracket 43 via a fixture 67. The leaf spring 71 has a substantially L-shape in which one end 71a extends in the vertical direction and is fixed to the fixture 67, and the other end 71b extends in a substantially horizontal direction. The other end 7
1b is in contact with the rotating shaft 53 from below the center of rotation of the rotating shaft 53 with an urging force having the following magnitude. In addition,
Instead of providing the fixture 67, one end 71a of the leaf spring 71
Is extended and fixed to one end of the bracket 43 in the same manner as the fixing tool 67, the number of parts can be reduced.

The total weight of the polygon mirror 31, the rotor boss 51, the rotating shaft 53, the rotor yoke 61, and the rotor magnet 63 of this embodiment is about 26 g. In addition, when the stator coil 65 is energized, a force for lifting the rotor magnet 63 upward by about 33 gf acts. Therefore, by energizing the stator coil 65, it is possible to temporarily prevent the polygon mirror 31 from falling. However, in this case, since the fall of the polygon mirror 31 is prevented by the force of 7 gf, when an external vibration or the like generated by a person walking near the printer 1 is applied, the rotating shaft 53 is moved to the sealing member 59. Contact with and away from. In this case, the frictional resistance against the rotation of the polygon mirror 31 fluctuates rapidly, and the rotation speed of the polygon mirror 31 also fluctuates. Then, an accurate electrostatic latent image cannot be formed on the photosensitive drum 19, and the image formed on the recording paper 5 may be distorted. Therefore, the leaf spring 71 is
Is brought into contact with the rotating shaft 53 with an urging force having a magnitude capable of constantly and stably coming into contact with the sealing member 59.

As shown in FIG. 4, a projecting piece 71c is formed at the other end 71b of the leaf spring 71 so as to protrude in three directions around the rotating shaft 53 and bend downward. The projecting piece 71c facilitates insertion of the polygon mirror 31 and the rotating shaft 53 when the polygon mirror 31 is mounted after the leaf spring 71 is fixed.

The scanner unit 2 configured as described above
In 1, a fluid bearing constituted by a radial bearing surface 57 and the like is provided between the rotating shaft 53 and the bearing portion 55.
Therefore, the frictional resistance acting between the bearing 55 and the rotating shaft 53 is extremely small. Further, a leaf spring 71 is in contact with the rotating shaft 53 from below the center of rotation by the elastic force. Therefore, the downward movement of the polygon mirror 31 is prevented, and the polygon mirror 31 does not swing up and down. Moreover, the rotating shaft 53 is always stably abutted against the sealing member 59. When the leaf spring 71 comes into contact with the rotating shaft 53, frictional resistance against rotation of the polygon mirror 31 acts between the two. However, since this frictional resistance acts near the center of the rotating shaft 53, the polygon mirror 31 The effect on the rotation of is very small. In particular, since the lower end of the rotating shaft 53 has a pivot shape, this frictional resistance is extremely small.

For this reason, in this embodiment, the frictional resistance against the rotation of the polygon mirror 31 can be extremely reduced, and the polygon mirror 31 can be prevented from swinging up and down. Therefore, the rotation shaft 53 is always stably brought into contact with the sealing member 59 to prevent the frictional resistance from fluctuating. Therefore, the polygon mirror 31 can be rotated stably at high speed, and the time required for forming an electrostatic latent image on the photosensitive drum 19 is shortened, and the time required for image formation by the printer 1 is shortened. At the same time, the image can be sharpened.

In this embodiment, the rotating shaft 53 is hermetically surrounded by the bearing 55 and the sealing member 59. For this reason, when the polygon mirror 31 moves even slightly downward and the rotating shaft 53 comes off from the bearing 55, it acts in a direction to prevent the atmospheric pressure from being released. Accordingly, the downward movement of the polygon mirror 31 can be further effectively prevented. That is, the polygon mirror 31 can be rotated more stably, and the image of the printer 1 can be further sharpened.

Further, in this embodiment, a projection 47 is formed below the rotating shaft 53. Therefore, even if the polygon mirror 31 moves downward, the rotating shaft 53 is
Abuts on the projection 47 via Then, the downward movement of the polygon mirror 31 is reliably prevented. Therefore,
In the present embodiment, it is possible to reliably prevent the polygon mirror 31 from moving excessively downward, and at the time of this maximum movement, the frictional force only acts on the center of the rotating shaft 53. Since the frictional force does not increase excessively, the rotation unevenness of the polygon mirror 31 can be minimized. For this reason, it is possible to reliably prevent the image formed by the printer 1 from being excessively unclear (for example, to the extent that printed characters cannot be read).

It should be noted that the present invention is not limited to the above-described embodiment at all, and can be implemented in various modes without departing from the gist of the present invention. For example, as in a second embodiment illustrated in the cross-sectional view of FIG.
3, the polygon mirror 31 may be rotatably provided on the rotating shaft 81 via the rotor boss 85. In this case, the rotor boss 85 is formed in a pivot shape, and a radial bearing surface 87 is provided on the inner surface of the rotor boss 85 to form a fluid bearing. In this case, substantially the same operation and effect as in the first embodiment can be obtained.

Further, as in a third embodiment whose side view and bottom view are illustrated in FIGS. 6A and 6B, a blocking member 91 for preventing the polygon mirror 31 and the leaf spring 71 from excessively moving is provided. It may be fixed to the bracket 43. The blocking member 91 of this embodiment includes a vertical portion 91a fixed to the edge of the bracket 43 and extending vertically, and a horizontal portion 91b extending horizontally from the lower end of the vertical portion 91a to the lower portion of the rotation center of the polygon mirror 31. , And a protruding portion 91c protruding from the tip of the horizontal portion 91b toward the rotation axis of the polygon mirror 31 is integrally formed of resin.

When such a blocking member 91 is used,
The following functions and effects are obtained in addition to the functions and effects similar to those of the above embodiments. That is, since the blocking member 91 is fixed to the bracket 43, the distance between the protruding portion 91c and the rotation axis of the polygon mirror 31 can be set accurately.

In FIGS. 5 and 6A and 6B, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment. Detailed description is omitted. Further, in each of the above embodiments, the leaf spring 71 is brought into contact with the rotation shaft 53 of the polygon mirror 31 or the rotation center of the rotor boss 85 below, but various other configurations may be applied as the elastic member. it can. That is, it can be constituted by a spring member other than a leaf spring, rubber, synthetic resin, or the like. For example, the protrusion 47 in FIG. 3 may be made of a synthetic resin having a predetermined elasticity, and may be designed to have a slightly higher height so as to be brought into contact with the rotating shaft 53.
In this case, the cost can be reduced by omitting the number of parts constituting the scanner unit 21.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration around a polygon mirror according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating a configuration of the printer according to the first embodiment.

FIG. 3 is an enlarged sectional view illustrating a configuration around a polygon mirror of the printer.

FIG. 4 is a bottom view illustrating a configuration around the polygon mirror according to the first embodiment.

FIG. 5 is a sectional view illustrating a configuration around a polygon mirror according to a second embodiment.

FIG. 6 is a side view and a bottom view showing a configuration around a polygon mirror according to a third embodiment.

[Explanation of symbols]

1. Printer 19 Photosensitive Drum 21
… Scanner unit 23… Housing 25… Laser beam 27
... Laser diode 31 ... Polygon mirror 41 ... Scanner motor 47
... Projections 53, 81 ... Rotating shaft 55 ... Bearing 5
7, 87 radial bearing surface 59 sealing member 71 leaf spring 91
... Blocking member

Claims (3)

(57) [Claims] 1. A rotating polygon mirror rotatably provided on a lower surface of a housing via a shaft member, a driving means for rotating and driving the rotating polygon mirror, and an irradiating means for irradiating light to a reflection surface of the rotating polygon mirror. And a fluid bearing provided between the housing or the rotating polygon mirror and the shaft member; and a predetermined elastic force applied to the shaft member or the rotating polygon mirror from below a center of rotation. And an elastic member that abuts at and stops the downward movement of the rotary polygon mirror. 2. The optical scanning device according to claim 1, wherein the housing provided with the fluid bearing or the rotary polygon mirror hermetically surrounds an end of the shaft member. 3. The semiconductor device according to claim 1, further comprising:
The optical scanning device according to claim 1, further comprising a blocking member configured to block downward displacement of the elastic member by a predetermined amount or more.