JPH05289012A - Rotary polygonal mirror - Google Patents

Abstract

PURPOSE:To reduce a breezing tone during rotation and the current value of a driving motor and to keep a low noise and a long service life by forming conical tapered places at the upper and lower edge parts of the mirror surface part of a rotary polygonal mirror, and setting a conical tapered angle within a prescribed range. CONSTITUTION:The conical tapered planes are formed at the upper and lower edge parts of the mirror surface part in the rotary polygon mirror 5 mounted on a rotary shaft rotating with the rotary shaft and provided with plural mirror surface parts to deflect a light beam on an outer periphery, and the conical tapered angle is set at a value between 10-20 deg.C. Also, the corner part of the rotary polygon mirror 5 formed by the ridge parts of adjacent mirror surface parts is roundly chamfered, and a certain angle is provided on a roundly chamfered part to a mirror reflection part so as not to project the reflecting light of the roundly chamfered part on a photosensitive drum that is a medium to be scanned. The height of the conical tapered plane is set at 40-60% of that of the mirror surface part, thereby, the breezing tone can be reduced, and blur on the mirror surface part can be reduced, and the current value of the driving motor of the rotary ploygon mirror can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary polygon mirror used in a scanning optical device used in laser beam printers, laser facsimiles and the like.

[0002]

2. Description of the Related Art FIG. 15 shows a conventional optical deflection scanning device for a laser beam printer, in which a rotary shaft 1 is rotatably fixed to a housing 3 via a ball bearing 2.
The flange 4 is fixed to the upper part of the rotary shaft, and the flange 4
A rotary polygon mirror 5 which is a deflector is pre-loaded by a spring 6 and fixed by a stopper plate 7 on the upper part of the yoke, and a yoke in which a drive magnet 8 is fixed on the inner peripheral surface side of the lower part of the flange 4. 9 is fixed, and an FC for rotation control is provided on the outer edge of the yoke.
The magnet 10 is fixed. Further, a coil 12 fixed on the driving motor substrate 11 is provided at a position facing the driving magnet 8, and an FG pattern is provided on the motor substrate 11 at a position facing the FG magnet 10. Here, after the laser light emitted from the semiconductor laser (not shown) is deflected and scanned by the rotating rotary polygon mirror 5, an image is formed on the surface of the photosensitive drum 14 by the imaging lens 13.

In a scanning optical device used in a laser beam printer, a laser facsimile, etc., a photosensitive member is scanned with a light beam deflected and scanned by a deflector to form an electrostatic latent image. This electrostatic latent image is visualized as a toner image by a developing device, this toner image is transferred to a recording paper, and then the toner is heated and fixed on the recording paper after the transfer of the toner image by a fixing device. Printing is done.

FIG. 16 is a plan view for explaining the structure of a conventional scanning optical device used in a laser beam printer to scan a photosensitive member with a light beam. Figure 4
FIG. 6 is a diagram for explaining a function in a cross section parallel to a deflecting surface (a ray bundle surface formed by a light beam deflected by a deflecting / reflecting surface of a deflector over time).

The scanning optical device is a scanner body (optical box) 1
FIG. 16 shows a plan view in which the lid body is removed, and the plan view is shown in FIG. The scanning optical device includes a semiconductor laser device 101, a collimator lens 102 that collimates the light flux generated from the semiconductor laser device 101, a cylindrical lens 103 that linearly condenses the parallel light flux from the collimator lens 102, and the cylindrical lens. The rotating polygonal mirror 5 having a deflecting / reflecting surface 5a in the vicinity of the line image of the light flux formed by 103 and the fθ lens 150
And so on. The light flux deflected and reflected by the deflective reflection surface 5 a enters the reflecting mirror 107 through the fθ lens 150, is reflected by the reflecting mirror 107, and
Irradiate the photoconductor.

The fθ lens 150 is designed so that the light beam reflected by the deflecting / reflecting surface 5a is condensed so as to form a spot on the photosensitive member, and the scanning speed of the spot is kept constant. There is. In order to obtain such characteristics of the fθ lens 150, the fθ lens 150 is composed of two lenses, a spherical lens 105 and a toric lens 106.

The rotation of the rotary polygon mirror 5 causes main scanning by the light beam on the photosensitive member, and sub-scanning by rotationally driving the photosensitive member around the axis of the cylinder. In this way, an electrostatic latent image is formed on the surface of the photoconductor.

[0008]

Particularly in recent years, the rotary polygon mirror 5 is often rotated at high speed because of its high speed and high definition. However, if the rotary polygon mirror of the conventional example is used as it is, when it is rotated at a high speed, a large current flows in the drive motor of the rotary polygon mirror, so that the temperature is raised and the life of the motor is shortened. Further, there are problems that the rotary polygon mirror is dirty and that the wind noise is loud.

[0009]

According to the present invention, conical taper surfaces are formed on the upper and lower peripheral edges of the mirror surface portion of a rotary polygon mirror,
Since the height of the conical taper surface is 40 to 60% of the height of the mirror surface portion, wind noise is reduced, fogging of the mirror surface portion is reduced, and the current value of the drive motor of the rotary polygon mirror can be reduced. A highly reliable scanning optical device can be provided.

According to the present invention, the corners which are the ridges of the adjacent mirror surface portions of the rotary polygonal mirror are chamfered so that the light reflected by the chamfered portion is not exposed onto the photosensitive drum which is the medium to be scanned. In addition, since the R chamfered portion has an angle with respect to the specular reflection portion, wind noise is reduced, and fogging of the reflection surface is prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The shape of a rotary polygon mirror 5 of the present invention is shown in FIG.
FIG. 2 shows the shape of a general rotary polygon mirror 5 that is usually used for comparison. Here, in the place where the reflecting surface 40 of the rotary polygon mirror 5 of FIG. 2 is soiled, when the rotary polygon mirror 5 rotates in the direction of the arrow in FIG. Due to the occurrence of this stain, the reflectance of the reflecting mirror surface is reduced, and the amount of light to the photosensitive drum 14 in FIG. 15 is reduced, resulting in image unevenness.

FIG. 1 shows a rotary polygon mirror 5 which is an embodiment of the present invention. Here, the rotating polygon mirror 5 having a hexahedron will be described. When the normal rotary polygon mirror 5 is rotated at a high speed, the rigidity of the reflecting surface 40 is insufficient due to the centrifugal force, and thus the accuracy of the reflecting surface 40 becomes poor. Therefore, at about 20,000 rpm, one of the circumscribed circles of the rotary polygon mirror 5
Although a thickness of about / 10 is required, in order to reduce the inertia of the rotary polygon mirror 5, the mounting reference plane 42 of the rotary polygon mirror 42 is used.
In order to obtain as large as possible, only the height of the reflecting surface 40 is made slightly smaller than the thickness of the rotary polygon mirror 5.

Here, the conical taper angle C is determined by the height a of the reflecting surface and the remaining portion b scraped off by the conical taper.
For example, if b is reduced as shown in FIG. 3, the conical taper angle C
However, the stain area 41 on the reflecting surface 40 is denser than the stain area 41 on the reflecting surface 40 of the ordinary rotary polygon mirror 5 shown in FIG.

Further, as shown in FIG. 4, when b is increased, the conical taper angle C is decreased. However, this not only cannot reduce the current value of the drive motor of the rotary polygon mirror, but also the rotary polygon mirror 5 The noise level increases due to the wind noise.

That is, as shown in FIGS. 5 to 7, when the conical taper angle C is 10 ° or less, the current value and noise of the drive motor are not significantly reduced. However, if the conical taper angle C is set to 20 ° or more, dust, dust, and the like tend to adhere to the reflecting surface 40 of the rotary polygon mirror 5 during rotation, the reflectance of the reflecting surface 40 decreases, and density unevenness occurs in the image. Resulting in.

FIG. 8 shows the noise and the current value of the motor when a hexahedral rotating mirror having a circumscribed circle of about φ40, which is an embodiment of the present invention, is rotated at about 20,000 rpm. Both the noise and the current value are about 10%, which is lower in the rotary mirror of the present invention than in the general rotary mirror. Further, the decrease in the reflectance of the reflecting surface 40 was almost the same as that of a general rotating mirror even after the rotation durability.

As described above, in the rotary polygon mirror of the present invention, conical taper surfaces are formed on the upper and lower peripheral edges of the mirror surface portion, and the conical taper angle is C,

[0018]

[Outside 3] In this case, 10 ° <C <20 °.

Here, in FIG. 1, the mirror surface height is a,
The height of the remaining mirror surface part left uncut by the conical taper surface is b
(The height of the smallest mirror surface). Further, (radius of circumscribed circle of rotary polygon mirror-radius of inscribed circle of rotary polygon mirror) is D.

Although one embodiment of the present invention has been described with reference to the hexahedral rotary polygon mirror, the conical taper angle C of the rotary polygon mirror 31 of the octahedron as shown in FIG. 9 is 10 ° to 20 °.
By setting to, an effect similar to that of a hexahedral rotating polygon mirror can be obtained.

Further, also in the tetrahedral rotating polygon mirror 32 as shown in FIG. 10, the conical taper angle C is 10 ° to 2 °.
By setting the angle to 0 °, the same effect as that of the hexahedral rotating polygon mirror can be obtained.

A further embodiment of the present invention will be described below. For example, by providing the R chamfered portion 200 on the ridges of the adjacent reflecting surfaces 40 of the rotary polygon mirror 5 as shown in FIG. 11, it is possible to reduce the current value of the drive motor of the rotary polygon mirror. It is possible to extend the life and reduce the dirty area 41 as shown in the reflecting surface 40 of FIG. The rotating polygon mirror shown in FIG.
As shown in FIG. 12, if the rotation speed is about 20,000 rpm, 1
The current can be reduced by about 5 to 20%. Also, the noise level is about 5
Noise can be reduced by about db.

However, the R chamfered portion 200 of the rotary polygon mirror shown in FIG. 11 has a reflecting surface 40 for the incident light beam.
Because of the same angle as above, when the light beam hits the R chamfered portion 200, the light beam was exposed to the photoconductor drum 14 and appeared in the image as a so-called ghost.

Therefore, as shown in FIG. 13, the R chamfered portion is formed into a taper R chamfered portion 201 so that the R chamfered portion has an angle inclined with respect to the reflection surface 40, and the photosensitive drum 14 is provided with the R chamfered portion. The reflected beam of does not reach.

Specifically, as shown in FIG. 14, the distance from the taper R chamfered portion 201 of the polygon (rotating polygonal mirror) 5 to the center of the photosensitive drum 14 is S, and the radius of the photosensitive drum is T, When the angle formed by the regular reflection surface 40 which is a mirror surface and the taper R chamfered portion 201 is θ, the incident beam 50
On the other hand, the taper R chamfered reflected light 52 is 2 in the vertical direction in the figure.
θ swings.

[0026]

[Outside 4] Since the reflected light 52 of the tapered R chamfered portion is not exposed to the photosensitive drum 14, it does not appear in the image as a so-called ghost, so that a highly reliable and long-life scanning optical device can be provided.

In this embodiment, the taper R chamfer reflection light 52 is reflected downward, but the same effect can be obtained by conversely reflecting the taper R chamfer reflection light 52 upward. Further, in FIG. 14, members having the same function as the members described with reference to FIG. 15 are designated by the same reference numerals and the description thereof is omitted.

[0028]

As described above, in the rotary polygon mirror of the present invention, conical taper surfaces are formed on the upper and lower peripheral edges of the mirror surface portion of the rotary polygon mirror, and the conical taper angle is set to 10 ° to 20 °. Since the wind noise during rotation is reduced and the current value of the drive motor is reduced, it is possible to provide a scanning optical device using a rotating polygon mirror with low noise and long life.

Further, in the rotary polygon mirror of the present invention, the chamfering of the corners of the rotary polygon mirror is performed by tapering, so that the current of the drive motor can be reduced, the noise can be reduced, the reflection surface can be prevented from being dirty, and the life can be prolonged. Planned.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of an embodiment of a rotary polygon mirror of the present invention.

FIG. 2 is a diagram illustrating a configuration of a general rotary polygon mirror.

FIG. 3 is a diagram illustrating a configuration of a rotary polygon mirror when a cone taper angle is increased.

FIG. 4 is a diagram illustrating a configuration of a rotary polygon mirror when a conical taper angle is reduced.

FIG. 5 is a diagram illustrating a relationship between a conical taper angle and a motor current value.

FIG. 6 is a diagram illustrating a relationship between a conical taper angle and a reflectance of a reflecting surface.

FIG. 7 is a diagram illustrating a relationship between a conical taper angle and motor noise.

FIG. 8 is a diagram comparing a general rotary polygon mirror with a rotary polygon mirror of the present invention.

FIG. 9 is a diagram illustrating a configuration of another embodiment of the rotary polygon mirror of the present invention.

FIG. 10 is a diagram illustrating a configuration of another embodiment of the rotary polygon mirror of the present invention.

FIG. 11 is a diagram illustrating a configuration of an R-chamfered rotary polygon mirror.

FIG. 12 is a diagram comparing a general rotary polygon mirror with a R-chamfered rotary polygon mirror.

FIG. 13 is a diagram illustrating a configuration of another embodiment of the rotary polygon mirror of the present invention.

FIG. 14 is a diagram illustrating a configuration of a scanning optical device using the rotating polygon mirror of the present invention.

FIG. 15 is a diagram illustrating a configuration of a scanning optical device using a conventional rotary polygon mirror.

FIG. 16 is a diagram illustrating a configuration of a scanning optical device using a conventional rotary polygon mirror.

[Explanation of symbols]

 5 Rotating polygonal mirror 14 Photosensitive drum 40 Reflecting surface 42 Reference surface

Claims (3)

[Claims] 1. A rotary polygon mirror having a plurality of mirror surface portions mounted on a rotation shaft and rotating together with the rotation shaft for deflecting a light beam on an outer periphery, wherein conical taper surfaces are formed at upper and lower peripheral edge portions of the mirror surface portion. The conical taper angle is C [External 1] When it is set, it is 10 degrees <C <20 degrees, The rotating polygonal mirror characterized by the above-mentioned. 2. A rotary polygonal mirror having a plurality of mirror surface portions mounted on a rotary shaft and rotating together with the rotary shaft for deflecting a light beam on an outer periphery, wherein ridges of adjacent mirror surface portions of the rotary polygonal mirror are rotated. R chamfering is applied to the center of the polygon mirror, and the R
A rotary polygon mirror, wherein the chamfer has a taper with respect to the mirror surface. 3. The angle formed by the mirror surface portion and the R chamfered portion is θ
And the distance from the mirror surface portion to the center of the photoconductor drum irradiated with the light beam deflected and reflected by the mirror surface portion is S
If the radius of the photosensitive drum is T, then The rotary polygonal mirror according to claim 2, wherein the following relation holds.