JP2003315720A - Optical beam scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical beam scanner constituted so that several rotary polygon mirrors can be layered in the thickness direction without increasing a noise. <P>SOLUTION: As for the optical beam scanner 10 provided with light beams from semiconductor laser units 5B and 5R, the rotary polygon mirror 1 for separately reflecting the light beams and scanning with the beams through the 1st and 2nd polygon mirrors 1B and 1R layered in the thickness direction, and several scanning optical systems arranged corresponding to respective light beams so as to image-form the light beams, the 1st polygon mirror 1B is arranged so that the reflection surface of the 1st polygon mirror 1B is shifted from the reflection surface of the 2nd polygon mirror in the rotating direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device using a rotary polygon mirror and an image forming apparatus for performing optical writing by the light beam scanning device.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, a light beam scanning device performs optical writing on a photosensitive member and develops a latent image formed by the optical writing. An image is being formed. The light beam scanning device is equipped with an optical system including a laser light source, a rotating polygon mirror, an imaging lens, a cylindrical lens, and a mirror, and the rotating polygon mirror scans the laser beam from the light source to electrostatic latent image on the photoconductor. It is designed to form an image. In such an image forming apparatus, in recent years, high speed and high density are required, and with this trend, the number of rotations of the rotary polygon mirror of the light beam scanning device tends to increase. When the rotation of the rotary polygon mirror increases, the windage loss increases with this increase. The increase in wind loss results in an increase in noise due to wind noise, in addition to an increase in internal atmospheric temperature.

Among the image forming apparatuses, since a light beam for each color is mounted in a two-color machine or a full-color machine, the rotary polygon mirror correspondingly changes the respective light beams in the thickness direction of the rotary polygon mirror. It is configured to reflect and scan at different positions. In the case of such a configuration, in order to cope with not only high speed but also high density, the rotation speed of the rotary polygon mirror is naturally increased, and the dimension in the thickness direction and the surface area of the rotary polygon mirror are further increased. The increase in size, the increase in surface area, and the increase in the number of rotations further increase the wind loss as compared with the conventional light beam scanning device, which increases the internal atmosphere temperature and the noise due to the wind noise. There is a hand.

Therefore, the applicant of the present invention has filed Japanese Patent Application Laid-Open No. 8-14633.
In Japanese Patent No. 0, the circumference of the rotary polygon mirror is covered with a cover,
A transparent member is arranged in the cover portion through which the light beam passes, and the end of the transparent member is positioned on the inner wall surface near the opening edge on the downstream side in the rotation direction of the rotating polygon mirror, whereby the rotating polygon mirror rotates. We proposed to prevent the occurrence of turbulent flow due to the collision of the air flow generated on the inner wall surface near the opening edge on the downstream side in the rotational direction, and to maintain the laminar flow state to suppress the generation of noise.

[0005]

According to this conventional technique, the laminar flow state of the air flow generated when the rotary polygon mirror is rotated is maintained to suppress the generation of noise, so that the laminar flow state is maintained. As much as possible, it is possible to suppress the generation of noise after transition to a turbulent state, but avoid increasing noise and heat generation due to the increase in the dimension of the rotating polygon mirror in the thickness direction and the increase in surface area. I can't. Such noise is caused by a relatively high pressure on the reflecting surface on the downstream side in the rotation direction and a relatively low pressure on the reflecting surface on the downstream side with respect to the corner where the two adjacent reflecting surfaces of the rotary polygon mirror contact. It is considered that the cause is the occurrence of non-uniform fluid flow due to the above. This will be specifically described with reference to FIG. FIG. 7 is a plan view schematically showing generation states of a high voltage portion and a low voltage portion of a rotary polygon mirror in a conventional light beam scanning device. In FIG. 7, assuming that the rotary polygon mirror 100 rotates counterclockwise as indicated by an arrow, the corner portion 100 where two adjacent reflecting surfaces 100b and 100c of the rotary polygon mirror 100 are in contact with each other.
A high voltage portion A as indicated by hatching is generated on the reflecting surface 100b on the downstream side in the rotation direction at a, and a low voltage portion B is already generated on the reflecting surface 100c on the upstream side in the rotation direction. The high pressure portion A and the low pressure portion B are relative to each other, but due to the pressure difference generated between them, an uneven fluid flow is formed in the low pressure portion B in order to make the pressure difference uniform. Due to this nonuniform fluid flow formation, wind loss increases, internal atmospheric temperature rises, and noise due to wind noise is generated.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and the first object thereof is a light beam in which a plurality of rotary polygon mirrors can be stacked in the thickness direction without increasing noise. It is to provide a scanning device.

A second object of the present invention is to provide an image forming apparatus equipped with a light beam scanning device capable of stacking a plurality of rotary polygon mirrors in the thickness direction without increasing noise.

[0008]

In order to achieve the first object, the first means is a light reflection having a plurality of light beam emitting means and a plurality of rotating polygon mirrors laminated in the axial direction of the rotation axis. Means and a plurality of scanning optical systems for causing the light beams emitted from the light beam emitting means to be incident on the different rotating polygon mirrors for reflection scanning and for forming an image of each light beam on the photoconductor. In the light beam scanning device, the plurality of laminated rotary polygon mirrors are arranged such that a reflection surface for reflecting and scanning the light beam is displaced from a reflection surface of another rotary polygon mirror in the rotation direction. Is characterized by.

A second means is characterized in that, in the first means, the plurality of rotary polygon mirrors are laminated in a state in which axial end faces thereof are in close contact with each other.

A third means is characterized in that, in the first means, the plurality of rotary polygon mirrors are laminated with their axial end faces having a preset interval.

A fourth means is characterized in that, in the first to third means, the plurality of rotary polygon mirrors have the same size and shape.

According to a fifth means, in the first to fourth means, the rotary polygon mirror and the driving means for driving the rotary polygon mirror are housed in a sealed container, and at least enter the rotary polygon mirror and are reflected. A light beam passing portion of the hermetically sealed container is formed of a light transmissive material.

A sixth means is a light beam scanning device according to any one of the first to fifth means, and an image forming means for forming an image written by the light beam scanning device on a recording medium as a visible image. The image forming apparatus is configured to include and.

According to the first means, since the reflecting surfaces of a plurality of laminated rotary polygon mirrors are displaced in the rotational direction, the pressure fluctuations due to the high speed rotation of the rotary polygon mirrors are averaged and the generation of noise is suppressed. To be done.

According to the second means, since the plurality of rotary polygon mirrors are laminated with their axial end faces in close contact with each other, the dimension in the thickness direction can be reduced.

According to the third means, since the plurality of rotary polygon mirrors are laminated with the end faces in the axial direction having a preset interval, the intervals of the light beams to be incident on the respective rotary polygon mirrors. Even when it is wide, it is possible to minimize the thickness of the rotary polygon mirror.

According to the fourth means, by making the sizes and shapes of the rotary polygon mirrors the same, it is possible to superimpose a large number of rotary polygon mirrors and then collectively perform the processing of the reflecting surface. Therefore, the processing of the rotary polygon mirror can be efficiently performed.

According to the fifth means, since the rotary polygon mirror is housed in the hermetically sealed container together with the driving means, noise generated in the hermetically sealed container is unlikely to leak to the outside.

According to the sixth means, it is possible to provide an image forming apparatus capable of suppressing the generation of noise due to windage loss as much as possible.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following respective embodiments, the same reference numerals are given to the respective parts that can be regarded as equivalent,
Overlapping description will be omitted as appropriate.

<First Embodiment> FIG. 1 is a perspective view schematically showing a schematic configuration of a light beam scanning device according to a first embodiment. 2A and 2B are diagrams schematically showing the configuration of the rotary polygon mirror unit in FIG. 1, where FIG. 2A is a plan view and FIG. 2B is a side view. However, in FIG. 1, the rotating polygon mirror has five faces, and in FIG. 2, it has six faces.

The light beam scanning device according to the first embodiment of FIG. 1 is one of two full-color tandem image forming devices.
The configuration of the color writing unit is shown, and the latter two colors are omitted. In FIG. 1, a light beam scanning device 10 forms a spot-shaped image on a photoconductor drum (not shown) in each direction with the photoconductor drum axial direction as the main scanning direction and the photoconductor drum rotation direction as the sub-scanning direction. It has a configuration to do. The light beam scanning device 10 includes a semiconductor laser unit 5
Each of the outgoing beams modulated by the image signals from R and 5B strikes different positions in the thickness direction of the rotary polygon mirror 1 and is reflected and scanned to form the imaging lenses 2B and 2B, respectively.
Through the R, the mirrors 3B1, 3B2, 3Rl, 3R2, the cylindrical lenses 4B, 4R, and the mirrors 3B3, 3R3, an image is formed in a spot shape on a photosensitive drum (not shown) and scanning is performed in the main scanning direction. The scanning position in the sub-scanning direction is determined by the rotation of a photosensitive drum (not shown), and the scanning in the main scanning direction is performed again at that position. As a result, an image is formed in each scanning direction, and an electrostatic latent image is formed by scanning.

As shown in FIG. 2, the rotary polygon mirror 1 has a rotary reflecting surface formed in two steps in the axial direction of the rotary shaft. That is, the first polygon mirror 1B and the second polygon mirror 1R are laminated, and the positional relationship between them is shifted by 360 ° / the number of reflecting surfaces / 2. Therefore, the number of apparent reflective surfaces is twice the actual number of reflective surfaces,
In terms of shape, the number of corners is doubled. In the case of FIG. 2, each of the first polygon mirror 1B and the second polygon mirror 1R has six reflecting surfaces, so the number of apparent reflecting surfaces is 12, and the number of corners is 12 in terms of shape. Become. In this way, since the rotary polygon mirror 1 has an apparent number of angles of 12 and becomes closer to a circle, the boundary (edge) where two adjacent reflecting surfaces of the rotary polygon mirror 1 are in contact with each other. It is possible to reduce the pressure difference between the high pressure region and the low pressure region which is generated by the above. Therefore, it is possible to suppress the formation of the vortex flow, increase the wind loss due to the formation of the vortex flow, raise the temperature of the internal atmosphere, and suppress the noise due to the wind noise.

In the first embodiment, the reflecting surfaces are provided in two stages of six surfaces, but in the other cases, the positional relationship of the polygon mirror is 360 ° / the number of reflecting surfaces / the number of polygon mirrors. It is sufficient to shift the number of steps (the number of light beams). The apparent number of reflecting surfaces and the number of geometrical corners are the number of reflecting surfaces x the number of polygon mirror steps (the number of light beams).

<Second Embodiment> FIG. 3 is a view schematically showing the structure of a rotary polygon mirror section in the second embodiment (a).
Is a plan view, (b) is a side view, and FIG. 4 is a light beam scanning device 1
It is a figure which shows schematic structure of 0. Note that this embodiment is
In the example in which a plurality of (two-color) images are written on one photoconductor, each part not particularly described is configured in the same manner as in the first embodiment.

Also in the second embodiment, the rotary reflecting surface has two stages as in the first embodiment, and the rotary polygon mirror 20 includes a first polygon mirror 1B and a second polygon mirror 1R. The spacer 1S is incorporated between them. The first polygon mirror 1B, the second polygon mirror 1R, and the spacer 1S are separate bodies,
One rotary polygon mirror 20 is configured by combining them. Since the first polygon mirror 1B and the second polygon mirror 1R overlap with each other with the clearance of the spacer 1S in this way, even when the distance between the light beams to be incident on the respective polygon mirrors is wide, The thickness dimension of the mirror can be minimized. This makes it possible to prevent an increase in the area of the polygon mirror and reduce the length of the ridge that causes a pressure change. Therefore, even when the distance between the light beams is wide as described above, it is possible to suppress an increase in wind loss, an increase in internal atmosphere temperature, a noise due to wind noise, and the like.

FIG. 4 shows an example of the light beam scanning device 10 using the rotating polygon mirror 20. FIG. 4 is a diagram showing a schematic configuration of the light beam scanning device 10 in this embodiment.
As can be seen from FIG. 4, the first polygon mirror 1B
The light beam reflected by 2 passes through the two imaging lenses 2B and 2B, is reflected by the mirrors 3B1 and 3B2, and then passes through the other imaging lens 2B, and then from the third mirror 3B3 onto the photosensitive drum 9B. A spot-like image is formed on the. on the other hand,
The light beam reflected by the second polygon mirror 1R passes through the two imaging lenses 2R, 2R, is reflected by the mirror 3R1, and then passes through the other imaging lens 2R, and then by the second mirror 3R2. The spot-shaped image is formed on the portion of the photosensitive drum 9 upstream of the image forming position by the light beam reflected by the polygon mirror 1B. Reference numeral 6 is a motor for driving the rotary polygon mirror 20 to rotate.

<Third Embodiment> FIG. 5 is a side view schematically showing the structure of a rotary polygon mirror section in the third embodiment. In this third embodiment, the structure of the rotary polygon mirror 20 is the same as that of FIG. 3, but the rotary polygon mirror 20 and the motor 6 are sealed in a hermetic container 7. A passage portion 8 made of a light-transmissive material is attached to a part of the hermetic container 7 so that a light beam can be incident on and reflected by the rotary polygon mirror 20. As described above, by housing the rotary polygon mirror 20 and the motor 6 in the sealed container 7, it is possible to further enhance the effects of increasing windage loss, increasing internal ambient temperature, and suppressing noise due to wind noise. .

The first and second polygon mirrors 1B and 1R in each of these embodiments are configured to have the same size and the same shape. As a result, the number of reflection surface processing steps for these polygon mirrors 1B and 1R can be reduced. That is, the polygon mirror has a plurality of plate-shaped members superposed on each other. However, when a reflecting surface is formed on the side surface of the plate-shaped members, the plurality of plate-shaped members are superposed on each other and then the reflection surface is formed. Can be done at the same time.
On the other hand, when processing each plate member one by one,
It is necessary to process as many reflective surfaces as the number of reflective surfaces x the number of layers.
Therefore, for example, when the rotating polygon mirror is configured by stacking two reflecting surfaces with six surfaces, the number of times the reflecting surface is processed is twelve. When this is processed by superposition as in the present invention, a plurality of polygon mirrors are superposed so that their reflecting surfaces coincide with each other, and are processed at one time, and then they are assembled in a state in which they are shifted by a required angle in the rotational direction. do it. That is, in the same manner as described above, when the rotary polygonal mirror is constructed by stacking two sheets with six reflecting surfaces, the number of processing of the reflecting surface can be increased by stacking ten plate-like members when processing the reflecting surface. Five sets of rotary polygon mirrors can be processed by six times, and a large number of rotary polygon mirrors can be provided with a small number of reflective surface processes.

<Fourth Embodiment> In the first embodiment,
Although the writing system for two colors out of four colors is illustrated and described, it can be applied to a writing system for a full-color so-called tandem type image forming apparatus. A tandem type image forming apparatus forms a single color toner image on each of a plurality of photoconductor drums arranged in parallel, and transfers the single color toner image to an intermediate transfer body or direct transfer paper to record a composite color image. The image forming method is to perform. Less than,
An example of a tandem type image forming apparatus will be described with reference to FIG. FIG. 6 is a schematic configuration diagram for explaining the path of a light beam when the rotary polygon mirror unit of FIG. 3 is applied to a tandem type image forming apparatus. The image forming lens and the semiconductor laser units of respective colors are not shown. Further, since developing means for visualizing the image on the photosensitive drum and fixing means for fixing the image transferred on the transfer paper are well known, illustration and description thereof will be omitted.

The tandem type image forming apparatus shown in FIG. 6 is a direct transfer system for transferring a monochromatic image formed on each photoconductor drum onto a transfer paper, and forms a toner image of each color of cyan, magenta, black and yellow. The photoconductor drums 9C, 9M, 9B, 9Y to be formed are arranged in parallel on the conveyor belt 31 which conveys the transfer paper P. Rotating polygon mirror means 20
The first polygon mirror 1B is arranged to reflect the magenta and black light beams, and the second polygon mirror 1R is arranged to reflect the cyan and yellow light beams. Then, the cyan light beam is reflected by the second polygon mirror 1R, and the mirrors 3C1, 3C2 and 3C
An image is formed on the photosensitive drum 9C via C3, and the magenta light beam is reflected by the first polygon mirror 1B,
An image is formed on the photosensitive drum 9M via the mirrors 3M1, 3M2 and 3M3. Similarly, the black light beam is reflected by the first polygon mirror 1B, and the mirror 3B
1, 3B2 and 3B3, and the yellow light beam is reflected by the lower rotary polygon mirror 1R, and passes through the mirrors 3Y1, 3Y2 and 3Y3 and the photosensitive drum 9C.
Are imaged respectively.

Although not shown, a tandem image of an indirect transfer system in which the image of the photosensitive drum of each color is transferred to an intermediate transfer member such as an intermediate transfer belt, and the image of the intermediate transfer member is transferred to a transfer paper. Of course, it can be applied to the light beam scanning device of the forming apparatus.

[0033]

As described above, according to the present invention, a plurality of rotary polygon mirror bodies are arranged in a state in which a reflecting surface for reflecting and scanning a light beam is deviated from a reflecting surface of another rotary polygon mirror in the rotational direction. Therefore, it is possible to reduce the pressure difference between the high pressure region and the low pressure region caused by the ridge between the two adjacent reflecting surfaces in the rotating polygon mirror, and as a result, increase the noise. It is possible to provide a light beam scanning device and an image forming device in which a plurality of rotary polygon mirrors are stacked in the thickness direction that does not exist.

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts schematically showing a schematic configuration of a light beam scanning device according to a first embodiment of the present invention.

2A and 2B are diagrams schematically showing a configuration of a polygon mirror according to the first embodiment, in which FIG. 2A is a plan view and FIG. 2B is a side view.

3A and 3B are diagrams schematically showing a configuration of a polygon mirror according to a second embodiment, FIG. 3A is a plan view and FIG. 3B is a side view.

FIG. 4 is a diagram showing a schematic configuration of a main part of a light beam scanning device according to a second embodiment.

FIG. 5 is a side view schematically showing a configuration of a rotary polygon mirror in a third embodiment.

FIG. 6 is a diagram showing a main part of an image forming apparatus in which a rotary polygon mirror according to a second embodiment is applied to a tandem type image forming apparatus.

FIG. 7 is a plan view schematically showing generation states of a high voltage portion and a low voltage portion of a rotary polygon mirror in a conventional light beam scanning device.

[Explanation of symbols]

1, 20 Rotating polygonal mirror 1B First polygon mirror 1R Second polygon mirror 1S Spacers 2B, 2R Imaging lenses 3B1, 3B2, 3B3, 3Rl, 3R2, 3R3 Mirrors 4B, 4R Cylindrical lenses 5B, 5R Semiconductor laser unit 6 Motor 7 Sealed container 8 Passing part 10 Light beam scanning device

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 BA05 DA23                 2H045 AA07 AA46 BA22 BA34 DA02                       DA41                 5C051 AA02 CA07 DB24 DC07 EA01                 5C072 AA03 DA02 DA04 DA21 HA02                       HA06 HA09 HA13 QA14 XA05

Claims (6)

[Claims] 1. A plurality of light beam emitting means, a light reflecting means having a plurality of rotating polygonal mirrors stacked in the axial direction of the rotation axis, and a rotating polygonal surface in which the light beams emitted from the light beam emitting means are different from each other. It is incident on a mirror and reflected and scanned,
In a light beam scanning device including a plurality of scanning optical systems for forming an image of each light beam on a photoconductor, the plurality of laminated rotary polygon mirrors have a reflecting surface for reflecting and scanning the light beam from another. A light beam scanning device, wherein the light beam scanning device is arranged in a state of being displaced from a reflecting surface of a rotary polygon mirror with respect to a rotation direction. 2. The light beam scanning device according to claim 1, wherein the plurality of rotary polygon mirrors are stacked with their axial end faces in close contact with each other. 3. The light beam scanning device according to claim 1, wherein the plurality of rotary polygon mirrors are laminated with axial end faces having a preset interval. 4. The light beam scanning device according to claim 1, wherein the plurality of rotary polygon mirrors have the same size and shape. 5. The rotary polygonal mirror and driving means for rotating the rotary polygonal mirror are housed in a hermetically sealed container, and at least a light beam passing portion of the hermetically sealed container that is incident on and reflected by the rotary polygonal mirror is a light transmissive material. 5. The light beam scanning device according to claim 1, wherein the light beam scanning device is formed of: 6. A light beam scanning device according to claim 1, and an image forming means for forming an image written by the light beam scanning device on a recording medium as a visible image. Image forming apparatus equipped.