JP7034652B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus using electrophotographic technology.

As an example of a color image forming apparatus using electrophotographic technology, the configuration shown in FIG. 5 has been used (Patent Document 1). Patent Document 1 discloses a configuration in which four sets of a photoconductor and a developer are arranged horizontally so as to correspond to four colors of yellow, magenta, cyan, and black. Further, as a scanning optical device corresponding to these four colors, two scanning optical devices corresponding to two colors are mounted.

On the other hand, as another configuration, a color image forming apparatus as in Patent Document 2 has also been proposed (FIG. 6). Patent Document 2 discloses an image forming apparatus using a scanning optical apparatus corresponding to four colors in one. Further, in order to narrow the width of the color image forming apparatus, a plurality of photoconductors are arranged so as to be inclined with respect to a horizontal plane.

Japanese Patent Application Laid-Open No. 2003-131158 Japanese Unexamined Patent Publication No. 2012-27335

The color image forming apparatus of Patent Document 1 has a problem that the main body of the image forming apparatus becomes expensive due to the convenience of the scanning optical apparatus. In the scanning optical device used in the image forming apparatus of Patent Document 1, it is necessary to arrange the scanning lens even after the folded mirror. If the scanning lens is placed only in front of the folded mirror, the sub-scanning magnification ((i) the ratio between the distance between the polygon mirror and the scanning lens and (ii) the distance between the scanning lens and the photoconductor). Will be higher. In that case, the position of the laser beam, which is the scanning line on the photoconductor, which is the image carrier, may shift due to thermal deformation or vibration.

On the other hand, in the image forming apparatus of Patent Document 2, it is possible to reduce the sub-scanning magnification. In addition, we have succeeded in downsizing the device by effectively using the space created by arranging a plurality of photoconductors in an inclined manner. However, since the long optical path is folded many times by a plurality of folded mirrors, the tilt errors of the folded mirrors are accumulated, and there is a possibility that the position of the laser beam, which is the scanning line on the photoconductor, which is the image carrier, may be scattered. ..

Therefore, in the present invention , the first image carrier and the second image carrier arranged in an inclined direction with respect to the horizontal plane, and the first image carrier and the second image carrier are combined with the first laser light and the second laser. An image forming device having a scanning optical device that scans with light and is arranged below the first and second image carriers in the vertical direction to form a toner image on a recording material. In the device, the second image carrier is arranged at a position lower than the first image carrier in the vertical direction, and the scanning optical device includes a first light source, a second light source, and the first light source . The first image carrier is scanned by the deflector that deflects the first laser beam emitted from the first laser beam and the second laser beam emitted from the second light source, and the first laser beam deflected by the deflector. A first optical system for scanning the second image carrier with the second laser beam deflected by the deflector, and a second optical system for scanning the first image carrier in the rotation axis direction of the first image carrier. The second optical system is arranged in the opposite direction with respect to the deflector when viewed in the above, and the number of lenses and mirrors of the first optical system and the lens of the second optical system. The number of mirrors is two lenses and one mirror, and the mirror of the first optical system is arranged between the two lenses in the optical path of the first laser beam, and the two mirrors are arranged. The lens, which is one of the two lenses and through which the first laser beam reflected by the mirror passes, is arranged at a position closer to the first image carrier than the mirror, and is the second optical system. The mirror is arranged at a position after the second laser beam has passed through the two lenses, and the optical path length of the first laser beam from the deflector to the mirror of the first optical system is the deflection. It is characterized in that it is shorter than the optical path length of the second laser beam from the device to the mirror of the second optical system .

In addition, the present invention
An image forming apparatus having at least two first and second image carriers arranged in an inclined direction with respect to a horizontal plane, and having a scanning optical device for scanning the first and second image carriers with a laser beam. And
The second image carrier is arranged at a position lower than that of the first image carrier.
The scanning optical device includes a first light source, a second light source, a deflector that deflects laser light emitted from the first and second light sources, and the first of the laser beams deflected by the deflector. The first optical system for scanning the first image carrier with the first laser beam emitted from the light source, and the second laser beam emitted from the second light source among the laser beams deflected by the deflector. It has a second optical system for scanning the second image carrier, and a cover member through which the first laser beam and the second laser beam pass.
The first optical system includes eleventh and twelfth lenses and a first mirror.
The first mirror is arranged between the eleventh and the twelfth lenses in the optical path of the first laser beam.
The second optical system includes a second lens and a second mirror.
The second mirror is arranged between the second image carrier and the second lens in the optical path of the second laser beam.
The first portion of the cover member through which the first laser beam passes through the cover member is an image forming apparatus arranged at a position higher than the second portion of the cover member through which the second laser beam passes through the cover member. Is to provide.

INDUSTRIAL APPLICABILITY According to the present invention, it becomes possible to provide an image forming apparatus that reduces the displacement and variation of the position of the laser beam that scans the image carrier.

It is sectional drawing explaining the image forming apparatus which concerns on Example. It is a perspective view explaining the scanning optical apparatus which concerns on embodiment. It is sectional drawing explaining the scanning optical apparatus which concerns on Example. It is a developed view explaining the optical system of the scanning optical apparatus which concerns on Example. It is sectional drawing explaining the conventional image forming apparatus. It is sectional drawing explaining the conventional image forming apparatus.

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplary with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

FIG. 1 is a diagram showing an outline of an image forming apparatus, and as an example, shows a color laser printer that records an image on a recording material by an electrophotographic method. The image forming apparatus of this embodiment is a color image forming apparatus that forms a full-color image by superimposing four color toners of yellow, magenta, cyan, and black.

In FIG. 1, reference numerals 1a and 1b are scanning optical devices such as a first scanning optical device and a second scanning optical device, and reference numerals 2Y, 2M, 2C, and 2K are process cartridges, which are yellow Y, magenta M, and cyan C. It contains toner, which is a developer of black K. The process cartridge has a photosensitive drum (3Y, 3M, 3C, 3K) and a charging roller (4Y, 4M, 4C, 4K), each of which is an image carrier. Further, the process cartridge of this embodiment includes a developing roller (5Y1, 5M1, 5C1, 5K1) which is a developer carrier, a developer (5Y, 5M, 5C, 5K) having a toner which is a developer, and the like. ing. In this embodiment, the number of cartridges is 4, but the number of cartridges is not limited to this. For example, a drum cartridge having a photosensitive drum and a charging roller as an image carrier, and a developing cartridge having a developing roller and toner may be independently attached to and detached from the image forming apparatus. Considering the image forming apparatus of FIG. 1, there are eight cartridges.

Further, in FIG. 1, reference numerals 6Y, 6M, 6C, and 6K are primary transfer rollers, reference numeral 7 is an intermediate transfer belt, reference numeral 8 is a secondary transfer roller, reference numeral 9 is a fuser, reference numeral 10 is a paper cassette, and reference numeral 11. Is a recording paper which is a recording material placed on the paper feed cassette 10. Further, reference numeral 12 is a pickup roller, and reference numeral 13 is a paper discharge loading unit.

Further, in the image forming apparatus of this embodiment, the paper feed cassette 10, the scanning optical devices 1a and 1b, the process cartridges 2Y, 2M, 2C, 2K, the intermediate transfer belt 7, and the paper ejection loading portion 13 are arranged vertically. There is. The image forming apparatus of this embodiment has a configuration in which the paper path 14 from the paper feed cassette 10 to the paper discharge loading unit 13 is C-shaped.

Next, the operation of the image forming apparatus will be described.

The scanning optical devices 1a and 1b irradiate a scanning line composed of laser light, each of which blinks with image information of two colors, and are uniformly charged by charging rollers 4Y, 4M, 4C, and 4K. An electrostatic latent image is formed on 3C and 3K. This electrostatic latent image is developed into a toner image by toner stored in the developing devices 5Y, 5M, 5C, and 5K, and is transferred onto the intermediate transfer belt 7 by the primary transfer rollers 6Y, 6M, 6C, and 6K.

On the other hand, the recording paper 11 which is a recording material placed on the paper cassette 10 is fed by the pickup roller 12 at the same timing as the above process, and follows the paper path 14 to reach the secondary transfer roller 8. , The toner image on the intermediate transfer belt 7 is transferred onto the recording paper 11. After that, the recording paper 11 on which the toner image is transferred is heated and compressed by passing through the fixing device, and the toner image is fixed. Finally, the recording paper 11 is discharged to the paper discharge loading unit 13 and loaded.

Here, in the image forming apparatus of this embodiment, the first to fourth photosensitive drums (3Y, 3M, 3C, 3K) which are the first to fourth image carriers are installed in the state where the image forming apparatus is installed. They are arranged in a row in the direction of inclination with respect to the horizontal plane. The arrangement direction of the four photosensitive drums (3Y, 3M, 3C, 3K) that are the image carriers is a direction that is inclined with respect to the horizontal plane so that the secondary transfer roller 8 side is lowered. In this embodiment, the fourth photosensitive drum 3K, which is the fourth image carrier arranged on the 8th side of the secondary transfer roller, is arranged at the lowest position, and then on the 8th side of the secondary transfer roller. The third photosensitive drum 3C, which is the arranged third image carrier, is arranged at the second lowest position. Further, when the axes of the four photosensitive drums are arranged on one straight line, it is preferable that the straight lines are arranged so as to be inclined when comparing the straight lines with the horizontal lines. However, the present invention is not limited to the device in which the axes of the four photosensitive drums are arranged on one straight line, and the arrangement of the photosensitive drums may be relatively inclined with respect to the horizontal plane. As a result, the width of the main body of the image forming apparatus is narrowed and the ground contact area is reduced while maintaining the distance between the process cartridges (2Y, 2M, 2C, 2K) having the photosensitive drum. Furthermore, it is possible to mount a large-capacity process cartridge in spite of its small size.

Further, the paper ejection loading unit 13 is inclined in a direction in which the paper ejection port 13a side is lowered with respect to the horizontal plane in order to improve the alignment of the ejected recording paper. The intermediate transfer belt 7 is arranged at an angle along the inclination of the paper ejection loading portion 13. Further, the first image carrier to the fourth image carrier, the first photosensitive drum to the fourth photosensitive drum 3Y, 3M, 3C, and 3K are also arranged so as to be inclined in the same direction. Further, each photosensitive drum is arranged at a position lower than the intermediate transfer belt 7 on a straight line in the direction of gravity passing through the axis of each photosensitive drum. In this embodiment, the first developer that develops the latent image on the first image carrier with the developer is arranged between the intermediate transfer belt and the scanning optical device in the direction of gravity. Similarly, a second developer that develops a latent image on the second image carrier with a developer is arranged between the intermediate transfer belt and the scanning optics in the direction of gravity. By arranging in this way, the internal space can be effectively utilized, the width of the apparatus main body of the above-mentioned image forming apparatus can be reduced, and the height of the apparatus can be lowered.

Next, the first scanning optical device 1a and the second scanning optical device 1b, which are scanning optical devices, will be described with reference to FIGS. 2 and 3. The image forming apparatus of this embodiment is equipped with the same first scanning optical device 1a and second scanning optical device 1b.

In FIG. 2, reference numerals 21a and 21b are laser light sources, reference numeral 22 is a cylindrical lens, reference numeral 23 is a polygon mirror which is a part of a deflector, and reference numeral 24 is a scanner motor which is a part of a deflector. Reference numerals 25a and 25b are the 11th lens 25a and the 21st lens 25b, which are the first scanning lenses. Reference numerals 26a and 26b are the 12th lens 26a and the 22nd lens 26b, which are the second scanning lenses. Reference numerals 27a and 27b are first mirrors 27a and second mirrors 27b, which are folded mirrors, reference numeral 28 is a laser drive substrate, reference numeral 29 is a housing member on which the above components are mounted, and reference numeral 30 is a cover member. Further, reference numerals 31a and 31b are cover glasses that are a part of the cover member, and reference numerals 32a and 32b are scanning lines that are laser beams that scan on the photosensitive drums 3Y, 3M, 3C, and 3K to form an electrostatic latent image. be. In FIG. 2, the cover member 30, the cover glasses 31a, and 31b are not shown for the sake of explanation.

Here, as shown in FIG. 1, the first and second scanning optical devices 1a and 1b of the present embodiment are photosensitive drums with scanning lines 32a and 32b, which are laser beams corresponding to image data for two colors, respectively, as shown in FIG. It is configured to scan above. Further, the second scanning optical device is arranged at a position lower than that of the first scanning optical device in the image forming apparatus.

That is, the scanning line 32a, which is the first laser beam, is the first composed of a laser first light source 21a, a first scanning lens, an eleventh lens 25a, a second scanning lens, a twelfth lens 26a, and a folded mirror 27a. It is formed by the optical system 41a. Further, the scanning line 32b, which is the second laser beam, is composed of a second laser light source 1b, a first scanning lens, a 21st lens 25b, a second scanning lens, a 22nd lens 26b, and a folded mirror 27b. It is formed by the optical system 41b.

Then, the scanning lines 32a and 32b, which are laser beams emitted from the first scanning optical device 1a, scan on the first photosensitive drum 3Y which is the first image carrier and the second photosensitive drum 3M which is the second image carrier, respectively. do. Similarly, the scanning lines 32a and 32b, which are laser beams emitted from the second scanning optical device 1b, are placed on the third photosensitive drum 3C which is the third image carrier and the fourth photosensitive drum 3K which is the fourth image carrier, respectively. Scan.

FIG. 4 is a developed view of the optical system of the first and second scanning optical devices 1a and 1b. The operation of the scanning optical device will be described with reference to FIG.

First, the first and second laser beams 42a and 42b emitted from the laser first and second light sources 21a and 21b, respectively, are incident on the opposing reflecting surfaces 43a and 43b of the polygon mirror 23 which is a part of the deflector. The polygon mirror 23, which is a part of the deflector, is rotationally driven in the direction of arrow A by the scanner motor 24, which is a part of the deflector, and deflects the first and second laser beams 42a and 42b in opposite directions. .. After that, the first laser beam 42a is imaged by the first scanning lens 25a and the second scanning lens 26a of the first optical system 41a, and is reflected by the folded mirror 27a to change the direction. Then, the first laser beam of the first scanning optical device forms a scanning line 32a which is a laser beam that scans the surface of the first photosensitive drum 3Y at a constant velocity in the direction of the arrow B. Further, the first laser beam of the second scanning optical device forms a scanning line 32a which is a laser beam that scans the surface of the third photosensitive drum 3C at a constant velocity in the direction of the arrow B.

Similarly, the second laser beam 42b is changed in direction while being imaged by the second optical system 41b, and is indicated by an arrow on the surface of the photosensitive drum 3M in the first scanning optical device and the photosensitive drum 3K in the second scanning optical device. The scanning line 32b is formed by a laser beam that scans in the direction of C at a constant velocity.

Here, in the scanning optical device mounted on the image forming apparatus of the present embodiment, in the first optical system 41a, the folded mirror 27a is arranged between the first scanning lens 25a and the second scanning lens 26a. Further, in the scanning optical device mounted on the image forming apparatus of this embodiment, the folded mirror 27b is arranged after the second scanning lens 26b in the second optical system 41b.

As a result, in the second optical system 41b in which the folded mirror is arranged after the second scanning lens, the second laser beam is deflected by the folded mirror 27b and then reaches the photosensitive drum directly without passing through the lens. Further, the second laser beam does not pass through the lens after being reflected by the folded mirror 27b, reaches the cover glass which is a part of the cover member, passes through and passes through the cover glass, and passes through another lens. Scan the photosensitive drum without any. Depending on the configuration of the device, the cover member may have an opening instead of the cover glass which is a part of the cover member. In this case, the second laser beam passes through the opening of the cover member. As described above, since the lens is not arranged between the folded mirror 27b and the photosensitive drum, the height of the image forming apparatus can be lowered. Further, in this embodiment, the polygon mirror 23, which is a part of the deflector, is arranged closer to the left side in the scanning optical device as shown in FIG. As a result, the distance from the polygon mirror 23 to the second scanning lens 26b can be sufficiently increased, and an optical system with a low magnification can be realized. Further, the fact that the polygon mirror 23, which is a part of the deflector, is arranged closer to the left side means that the cover glass through which the first laser beam passes is more than the cover glass 31b through which the second laser beam passes in the horizontal direction. It also means that it is arranged on the side closer to 31a.

On the other hand, on the opposite side of the first optical system 41a, the folded mirror 27a is arranged between the first scanning lens 25a and the second scanning lens 26a. That is, the first laser beam passes through and passes through the lens after being reflected by the folded mirror 27a, and then reaches the photosensitive drum. Further, the first laser beam reaches the cover glass of the cover member via the lens after being reflected by the folded mirror 27a, passes through the cover glass, and is exposed without passing through or passing through another lens. Scan the drum. Due to such a configuration, the width of the first optical system 41a side can be kept narrow.

As a result, the distance between the first and second scanning optical devices 1a and 1b can be narrowed, and the distance between the process cartridges 2Y, 2M, 2C, and 2K can also be kept narrow. Further, by arranging in this way, the optical path length La1 of the first laser beam from the reflecting surface of the polygon which is a part of the deflector to the first mirror 27a is from the reflecting surface of the polygon which is a part of the deflector. It can be shorter than the optical path length La2 of the second laser beam up to the second mirror 27b.

Further, when the scanning optical devices 1a and 1b are arranged inside the image forming apparatus, the photosensitive drums 3M arranged at the lower position among the plurality of photosensitive drums 3Y, 3M, 3C, and 3K arranged in an inclined manner. It is installed so that the second optical system 41b side comes to the side corresponding to 3K. (See Fig. 1)
Thereby, the first and second scanning optical devices 1a and 1b can be arranged so as to fit in the triangular space formed between the process cartridges 2a, 2b, 2c and 2d and the paper feed cassette 10. Therefore, the folded mirror 27a is arranged between the first scanning lens 25a and the second scanning lens 26b, and the height of the scanning optical devices 1a and 1b is the image forming device even on the high first optical system 41a side. There is no restriction on the height of the main body of the device.

In this embodiment, the optical path length Lb of the second optical system 41b is set shorter than the optical path length La of the first optical system 41a to further enhance the above effect. However, in this case, since the scanning speeds for scanning on the photosensitive drums 2Y, 2M, 2C, and 2K differ between the first optical system 41a and the second optical system 41b, the laser first and second light sources 21a and 21b have different scanning speeds. This can be handled by changing the writing frequency of the image.

Further, in this embodiment, the first optical system 41a and the second optical system 41b each have two scanning lenses, but the number of scanning lenses may be larger than that. It is preferable that the first optical system 41a arranges the folding mirror between the scanning lenses, and the second optical system 41b arranges the folding mirror after all the scanning lenses.

1a, 1b Scanning optics 3Y, 3M, 3C, 3K Photosensitive drum 21a, 21b Light source 23 Polygon mirror (deflector)
24 Scanner motor (deflector)
25a, 25b 1st scanning lens 26a, 26b 2nd scanning lens 27a, 27b Folded mirror 32a, 32b Laser beam 41a 1st optical system 41b 2nd optical system

Claims (3)

The first image carrier and the second image carrier arranged in an inclined direction with respect to the horizontal plane, and the first image carrier and the second image carrier are scanned by the first laser beam and the second laser beam , respectively . An image forming apparatus having a scanning optical apparatus which is arranged below the first and second image carriers in the vertical direction, and which forms a toner image on a recording material .
The second image carrier is arranged at a position lower than the first image carrier in the vertical direction .
The scanning optical device includes a first light source, a second light source, a deflector that deflects the first laser beam emitted from the first light source , and the second laser beam emitted from the second light source, and the above-mentioned deflector. The first optical system for scanning the first image carrier with the first laser beam deflected by the deflector and the second image carrier scanned with the second laser beam deflected by the deflector. The second optical system for this purpose is provided with a second optical system arranged in the opposite direction with respect to the deflector when viewed in the rotation axis direction of the first image carrier .
The number of lenses and mirrors of the first optical system and the number of lenses and mirrors of the second optical system are both two lenses and one mirror .
The mirror of the first optical system is arranged between the two lenses in the optical path of the first laser beam, and is one of the two lenses and is reflected by the mirror. The lens through which the laser beam passes is arranged at a position closer to the first image carrier than the mirror.
The mirror of the second optical system is arranged at a position after the second laser beam has passed through the two lenses .
The optical path length of the first laser beam from the deflector to the mirror of the first optical system is shorter than the optical path length of the second laser beam from the deflector to the mirror of the second optical system. Image forming apparatus. The scanning optical device includes an optical box accommodating the first optical system and the second optical system, a first portion of a cover member covering the opening of the optical box through which the first laser beam passes, and the first portion. 2 With a cover member having a second portion through which the laser light passes,
The image forming apparatus according to claim 1, wherein the first portion is arranged at a higher position in the vertical direction than the second portion . The optical path length of the second laser beam from the second light source to the second image carrier is shorter than the optical path length of the first laser beam from the first light source to the first image carrier. The image forming apparatus according to claim 1 or 2 .

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