JP2000292733A - Deflecting scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the startup time of a device by reducing the inertia of a rotary polygon mirror. SOLUTION: The rotary polygon mirror E1 has a prismatic main body 10 and is provided with reflecting surfaces 11 as its outer peripheral surface. Annular grooves 13 and 14 which are vertically symmetrical are cut in both the end surfaces of the main body 10 to reduce the inertia of the rotary polygon mirror E1. The inertia is effectively reduced without making the mechanical strength uneven vertically and circumferentially and the annular grooves 13 and 14 are usable as balance correcting grooves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device used for an image forming apparatus such as a laser beam printer and a digital copying machine.

[0002]

2. Description of the Related Art A deflection scanning device used in an image forming apparatus such as a laser beam printer or a digital copying machine reflects a light beam such as a laser beam by a rotary polygon mirror and performs deflection scanning by high-speed rotation of the rotary polygon mirror. The scanning light obtained in this way is formed on a photoreceptor on a rotating drum to form an electrostatic latent image. Next, the electrostatic latent image on the photoreceptor is visualized into a toner image by a developing device, transferred to a recording medium such as recording paper, sent to a fixing device, and printed by heating and fixing the toner on the recording medium ( Print) is performed.

In recent years, the speed of the deflection scanning device has been increased, and a rotating polygon mirror having a rotation speed exceeding 10,000 rpm has been developed.

FIG. 5 shows a rotary polygon mirror E _{0 according} to a conventional example, which has a polygonal column-shaped main body 110 having a plurality of reflection surfaces 111 as side surfaces, and a central hole 112 of the main body 110.
Fitted to a motor rotation shaft (not shown) or the like, is integrally coupled to the rotary polygon mirror E ₀ and the motor rotor by the pressing spring. By supplying a drive current to a stator disposed opposite to the rotor to excite it, the rotor and the rotating polygon mirror E ₀ are supplied.
Are rotated integrally.

[0005] The reflection surface of such a rotary polygon mirror is required to have high flatness and dimensional accuracy. In addition, in order to shorten the rise time at the time of starting the apparatus, it is preferable that the inertia of the rotary polygon mirror is small. However, if lightening is performed on one surface such as the upper surface of the rotary polygon mirror, mechanical rotation is performed above and below the rotary polygon mirror. The intensity becomes non-uniform, and the centrifugal force during rotation of the rotary polygon mirror may cause image deterioration due to deformation or fall of the reflection surface.
Therefore, generally, no lightening is performed.

[0006]

However, according to the above-mentioned prior art, the main body of the rotary polygon mirror is a solid member having a polygonal columnar outer shape, and has a predetermined thickness in order to secure necessary mechanical strength. There is an unsolved problem that the thickness cannot be reduced to less than the thickness, and therefore the inertia is large and the rise time of the device cannot be sufficiently reduced.

If the upper surface of the rotary polygon mirror is cut to reduce the inertia of the rotary polygon mirror, for example, as described above, the mechanical strength and the like above and below the rotary polygon mirror become non-uniform and the reflection occurs. There is a possibility that the surface may be tilted or chatter vibration may occur in the vertical direction of the rotary polygon mirror.

A groove for so-called balance correction for reducing dynamic imbalance during rotation of the rotary polygon mirror may be provided on the upper surface of the rotary polygon mirror or the like. It is of little help in reducing inertia.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and provides a deflection scanning device capable of effectively reducing the inertia of a rotary polygon mirror and greatly shortening the rise time of the device. It is intended to provide.

[0010]

In order to achieve the above object, a deflection scanning apparatus according to the present invention comprises a rotating polygon mirror having a plurality of reflecting surfaces for reflecting a light beam, and a rotating polygon mirror having a central axis. Driving means for rotating around, and an image forming optical system for forming an image of the light beam on an image forming surface through the rotating polygon mirror, wherein the rotating polygon mirror has a polygon with the plurality of reflection surfaces as side surfaces. It has a pillar-shaped main body, and is characterized in that an annular lightened portion formed coaxially with the central axis is provided on each of both end faces of the main body.

It is preferable that the both ends of the body of the rotary polygon mirror are provided with lightening portions which are vertically symmetrical.

The rotating polygon mirror may be provided with lightening portions of the inverted shape on both end surfaces of the main body.

It is preferable that the lightening portions on both end surfaces of the main body of the rotary polygon mirror have a plurality of annular grooves each having a vertically symmetric shape.

The lightening portions at both end faces of the main body of the rotary polygon mirror may have a plurality of annular grooves each having an upside-down shape.

The lightening portions at both end faces of the main body of the rotary polygon mirror may have radial rib-shaped portions.

A weight for correcting the balance may be attached to the lightening portion.

[0017]

[Function] The inertia of the rotating polygon mirror is reduced by providing a vertically symmetrical or inverted upside-down annular hollow portion formed coaxially with the center axis of the rotating polygon mirror on both upper and lower end faces of the rotating polygon mirror. In addition, the start-up time of the motor for rotating the rotating polygon mirror, that is, the rise time of the apparatus is greatly reduced.

By forming annular hollow portions on both the upper surface and the lower surface coaxially with the center axis which is the center of rotation of the rotary polygon mirror, the mechanical strength is non-uniform in the circumferential and vertical directions of the rotary polygon mirror. And it is possible to avoid troubles such as deformation or tilting of the reflecting surface due to centrifugal force during rotation of the rotary polygon mirror, or occurrence of chatter vibration.

If the rotating polygon mirror is provided with a vertically symmetrical lightening portion on both end faces of the main body of the rotating polygon mirror, the mechanical strength becomes extremely uniform above and below the rotating polygon mirror. Has a greater effect in preventing

If the body of the rotary polygonal mirror is provided with hollow portions of upside down shapes on both end surfaces, it is possible to avoid the thickness of the rotary polygonal mirror from being locally reduced. Therefore, it is possible to further reduce the inertia by increasing the entire lightening amount.

If the hollow portions at both end surfaces of the body of the rotary polygon mirror have a plurality of vertically symmetrical annular grooves, the ribs between the annular grooves locally increase the thickness, and Since the mechanical strength of the mirror increases, there is a great effect in preventing chattering vibration of the rotating polygon mirror.

If the lightening portions at both end surfaces of the main body of the rotary polygon mirror have radial rib-shaped portions, it is easy to lighten a large area by pressing.
Further, there is an advantage that the composition of the material can be improved by work hardening by press working.

Further, since the lightening portion can be widely used as a balance correcting groove for attaching a balance correcting weight, the dynamic imbalance of the rotary polygon mirror can be reduced very effectively. That is, the accuracy of the balance correction and the working efficiency can be greatly improved.

[0024]

Embodiments of the present invention will be described with reference to the drawings.

[0025] Figure 1 shows a rotary polygon mirror E ₁ of the deflector of the first embodiment, which has a polygonal shaped body 10 to a plurality of reflecting surfaces 11 and the side surface, the main body 1
0 center hole 12 fitted to the rotation shaft of the motor (not shown) of, is integrally coupled to the rotary polygon mirror E ₁ and the motor rotor by the pressing spring. By energizing supplies a drive current opposite to the rotor disposed stator, the rotor and the rotary polygon mirror E ₁ is rotated integrally.

In order to reduce the inertia of the rotary polygon mirror E ₁ , a plurality of annular grooves 13, which are annular hollow portions formed coaxially with a center hole 12 which is the center of rotation, are formed on both end surfaces of the main body 10. , 14 are provided. As shown in FIG. 1B, the annular groove 13 on the upper surface and the annular groove 14 on the lower surface of the main body 10 have the same shape, that is, a vertically symmetric shape, facing up and down.

Since the lightening portions for reducing the inertia are the vertically symmetrical annular grooves 13 and 14, the body 10
Can be prevented from becoming uneven in the circumferential direction or the vertical direction. Therefore, when the rotary polygon mirror E ₁ is applied centrifugal force by high-speed rotation, without such inclination inclination that is, the surface of the reflection surface 11 in the direction is generated as indicated by the arrow A, also the deformation of the reflecting surface 11 by centrifugal force Few.

In addition, annular rib-shaped portions 15 and 16 are formed between the annular grooves 13 and 14, and the original thickness of the main body 10 is left. Chatter vibration in the direction of arrow B due to the middle centrifugal force can be significantly reduced.

When the rotary polygon mirror is operated at a relatively low speed, the centrifugal force is small and there is no possibility that the chattering vibration is generated. Therefore, in such a model, both end surfaces of the main body of the rotary polygon mirror may be largely thinned by wide annular grooves without leaving the rib-shaped portions.

Further, each of the annular grooves 13 and 14, can be utilized as a so-called balance correction groove for reducing the dynamic imbalance during rotation of the rotary polygon mirror E _1.

[0031] Since a plurality of weights for balance correction to a wide range of body 10 of the rotary polygon mirror E ₁ all the balance correction groove of the annular groove 13, 14 can be mounted arbitrarily, greatly the work efficiency of the balance correction , And
There is an advantage that extremely accurate balance correction can be performed.

According to the present embodiment, the reflecting surface is deformed by centrifugal force by uniformly removing the both end surfaces of the main body of the rotary polygon mirror in the circumferential direction and the axial direction (vertical direction) by the plurality of annular grooves. The inertia of the rotary polygon mirror is greatly reduced without causing troubles such as tilting, tilting and chattering vibration, and the rise time of the deflection scanning device can be shortened. As a result, it is possible to realize a high-quality deflection scanning device that has high image quality, is suitable for high-speed operation, and has extremely fast first printing.

FIG. 2 shows a rotary polygon mirror E _{2 according} to a _second embodiment. This has a plurality of annular grooves 23 and 24 coaxial with the center hole 22 at both end surfaces of the main body 20 having the reflecting surface 21, and the annular groove 23 on the upper surface and the annular groove 24 on the lower surface are upside down. It is formed in. That is, the annular groove 23 on the upper surface is formed behind the rib-shaped portion 26 on the lower surface, and the rib-shaped portion 25 between the annular grooves 23 on the upper surface is formed on the back side of the annular groove 24 on the lower surface.

By arranging the upper and lower annular grooves alternately in this manner, it is possible to prevent the thickness of the main body of the rotary polygon mirror from becoming extremely thin due to lightening.

As compared with the case where an annular groove having a vertically symmetrical shape is provided, an advantage that the thickness can be greatly reduced while maintaining the mechanical strength is added.

The other points are the same as in the first embodiment.

FIG. 3 shows a rotary polygon mirror E _{3 according} to the _third embodiment. This is provided with wide annular concave portions 33 and 34 which are annular hollow portions coaxial with the center hole 32 on both end surfaces of the main body 30 having the reflecting surface 31. The annular recess 33 on the upper surface and the annular recess 34 on the lower surface have a vertically symmetrical shape, and are provided with radial rib-shaped portions 35 and 36, respectively, which extend perpendicularly to the reflecting surface 31, that is, at an angle of 90 ° in the radial direction. ing.

Since the upper and lower annular recesses 33 and 34 can be processed by press (forging) processing, the composition of the material can be improved by work hardening of the lightened portion, and the mechanical strength can be greatly improved. Is added.

Instead of arranging the ribs perpendicular to the reflecting surfaces, radial ribs extending radially toward the corners between the reflecting surfaces may be provided.

The other points are the same as in the first embodiment.

FIG. 4 shows the entire deflection scanning device.
It has a light source 51 for generating a light beam such as a laser beam (light flux), and a cylindrical lens 51a for condensing the light beam into a linear shape on the reflective surface 11 of the rotating polygon mirror E _1, the light beam Is deflected and scanned by the rotation of the rotary polygon mirror E ₁ , and forms an image on a photosensitive member 53 on a rotating drum via an imaging lens system 52. The imaging lens system 52 is a spherical lens 52
a, a toric lens 52b, etc., and has a so-called fθ function of correcting the scanning speed of a point image formed on the photoconductor 53.

The rotating polygon mirror E is driven by the motor.₁ Turns
Then, the reflecting surface 11 becomes a rotating polygon mirror E.₁ The axis of the turn
It rotates at a constant speed. As described above, the light source 51
And the light collected by the cylindrical lens 51a.
Beam path and rotating polygon mirror E ₁ Is normal to the reflection surface 11
Angle, that is, incidence of a light beam on the reflecting surface 11
The corner is a rotating polygon mirror E₁ Changes over time with the rotation of
Similarly, since the reflection angle also changes, the light beam
The point image formed by the light is focused in the axial direction of the rotating drum (main scanning
Direction).

The imaging lens system 52 focuses the light beam reflected by the rotary polygon mirror E ₁ on the photosensitive member 53 into a point image having a predetermined spot shape, and scans the point image in the main scanning direction. It is designed to keep the speed constant.

[0044] The point image formed on the photosensitive member 53, a main scanning by rotation of the rotary polygon mirror E _1, the photosensitive member 53 becomes accompanied in the sub-scanning by rotating around the axis of the rotary drum, an electrostatic latent Form an image.

Around the photosensitive member 53, a charging device for uniformly charging the surface of the photosensitive member 53, and a charging device for visualizing an electrostatic latent image formed on the surface of the photosensitive member 53 into a toner image. A developing device, a transfer device (not shown) for transferring the toner image to recording paper, and the like are arranged, and recording information by a light beam generated from the light source 51 is printed on recording paper or the like.

The detection mirror 54 reflects the light beam on the upstream side in the main scanning direction from the optical path of the light beam incident on the recording information writing start position on the surface of the photosensitive member 53, and receives a light receiving element 55 having a photodiode or the like. To the light receiving surface of The light receiving element 55 outputs a scanning start signal for detecting a scanning start position (write start position) when the light receiving surface is irradiated with the light beam.

The light source 51 generates a light beam corresponding to a signal given from a processing circuit for processing information from the host computer. The signal given to the light source 51 corresponds to information to be written on the photoconductor 53, and the processing circuit represents information corresponding to one scanning line which is a locus formed by a point image formed on the surface of the photoconductor 53. The signal is given to the light source 51 as one unit. This information signal is transmitted in synchronization with a scanning start signal given from the light receiving element 55.

The rotating polygon mirror E ₁ and the imaging lens system 52
Are housed in the optical box 50, and the light source 51 and the like are attached to the side wall of the optical box 50. In the optical box 50, a rotating polygon mirror E ₁ ,
After the imaging lens system 52 and the like are assembled, a lid (not shown) is attached to the upper opening of the optical box 50.

[0049]

Since the present invention is configured as described above, the following effects can be obtained.

By performing uniform lightening in the vertical and circumferential directions of the rotary polygon mirror, inertia of the rotary polygon mirror can be effectively reduced without causing unevenness in mechanical strength and the like, and the rise time of the apparatus can be reduced. Can be greatly reduced. In addition, by using the lightened portion as the balance correction groove, the accuracy of balance correction and work efficiency can be greatly improved.

As a result, it is possible to contribute to an increase in speed and performance of the deflection scanning device.

[Brief description of the drawings]

1A and 1B show a rotary polygon mirror according to a first embodiment, wherein FIG. 1A is a plan view and FIG. 1B is a cross-sectional view.

FIGS. 2A and 2B show a rotary polygon mirror according to a second embodiment, in which FIG. 2A is a plan view and FIG.

3A and 3B show a rotary polygon mirror according to a third embodiment, wherein FIG. 3A is a plan view and FIG. 3B is a cross-sectional view.

FIG. 4 is a diagram showing the entire deflection scanning device.

FIG. 5 shows a rotary polygon mirror according to a conventional example.
(A) is a plan view and (b) is a sectional view.

[Description of Signs] E ₁ , E ₂ , E ₃ rotating polygon mirror 10, 20, 30 Main body 11, 21, 31 Reflecting surface 12, 22, 32 Center hole 13, 14, 23, 24 Annular groove 15, 16, 25 , 26, 35, 36 Rib-shaped part 33, 34 Annular concave part

Claims (7)

[Claims] A rotating polygon mirror having a plurality of reflecting surfaces for reflecting the light beam; a driving means for rotating the rotating polygon mirror about its central axis; and forming an image of the light beam via the rotating polygon mirror. An imaging optical system for forming an image on a surface is provided, and the rotating polygon mirror has a polygonal prism-shaped main body having the plurality of reflection surfaces as side surfaces, and the center axis and the center axis are respectively provided on both end surfaces of the main body. A deflection scanning device comprising an annular lightened portion formed coaxially. 2. The deflection scanning device according to claim 1, wherein a vertically symmetrical hollow portion is provided on both end surfaces of the main body of the rotary polygon mirror. 3. The deflection scanning device according to claim 1, wherein the rotating polygon mirror is provided with hollow portions of upside down shapes on both end surfaces of a main body of the rotating polygon mirror. 4. The deflection scanning apparatus according to claim 1, wherein the hollow portions on both end surfaces of the main body of the rotary polygon mirror have a plurality of vertically symmetric annular grooves. 5. The deflection scanning device according to claim 1, wherein the lightening portions on both end surfaces of the main body of the rotary polygon mirror have a plurality of annular grooves each having an upside down shape. 6. The deflection scanning device according to claim 1, wherein the lightening portions at both end surfaces of the main body of the rotary polygon mirror each have a radial rib-shaped portion. 7. A weight for correcting balance is attached to a lightening portion.
The deflection scanning device according to claim 1.