JP5090429B2 - Color image forming apparatus - Google Patents

Description

The present invention relates to a color image forming apparatus such as a color copying machine or a color printer including an optical scanning equipment for optically scanning the photosensitive member.

  In an image forming apparatus such as a copying machine or a printer, a photoconductor whose surface is uniformly charged by a charger is optically scanned by an optical scanning device, and an electrostatic latent image corresponding to image information is formed on the surface. . The electrostatic latent image is developed by a developing device using toner as a developer to be visualized as a toner image. The toner image is transferred onto a sheet by a transfer device and then heated and heated by a fixing device. A series of image forming operations is completed by discharging the sheet having the toner image fixed thereon by being pressed and fixed on the sheet.

  By the way, an optical scanning device that optically scans a photoconductor to form an electrostatic latent image on the surface thereof includes a deflector such as a polygon mirror that deflects a light beam emitted from a light source, and light deflected by the deflector. A scanning optical system including an imaging lens that converts a beam into constant speed scanning light and a plurality of reflecting mirrors that fold back the constant speed scanning light and guide it to the photosensitive member is housed in a housing.

  With regard to such an optical scanning device, for example, Patent Document 1 proposes a configuration in which a single deflector is arranged in the center of the housing and the light beam is distributed and deflected in two symmetrical directions by the deflector. .

  Patent Document 2 proposes an optical scanning device in which two housings (optical boxes) for scanning one light beam in two symmetrical directions around a deflector are arranged side by side. According to this optical scanning device, since one housing is small, the positional deviation of the scanning line is suppressed to be small, and the problem of color deviation is less likely to occur. Further, by setting the number of folding mirrors to one, it is possible to reduce the influence of the folding mirrors on color misregistration.

JP 2002-148542 A JP 2002-031772 A

  However, in the configuration proposed in Patent Document 1, two light beams are scanned in one direction, and it is necessary to separate the two light beams and guide them to the photosensitive member. There is a problem that the housing needs to be secured and the housing becomes large. or. It is necessary to increase the width in the height direction of the imaging lens provided to scan the two light beams at a constant speed, and an increase in cost cannot be avoided. Furthermore, since all four optical systems for scanning four light beams are accommodated in one housing, the housing becomes large. For this reason, the amount of thermal deformation of the housing due to a temperature change increases, and the scanning position of the light beam shifts and a problem of color misregistration tends to occur.

  In addition, the optical scanning device proposed in Patent Document 2 has a problem that the width in the height direction of the housing increases because the optical path from the deflector to the photosensitive member is folded once. In particular, when an imaging lens having a long focal length is used, the height of the housing increases in proportion to the focal length, which increases the size of the housing.

The present invention has been made in view of the above problems, processing and its object is to provide a color image forming apparatus capable of substantially equalizing the pitch between the sensitive light body.

In order to achieve the above object, the present invention provides a deflector that deflects a light beam emitted from a light source, an imaging lens that converts the light beam deflected by the deflector into constant-speed scanning light, and constant-speed scanning light. In a color image forming apparatus including an optical scanning device in which a scanning optical system including first, second, and third reflecting mirrors that are folded and guided to a photosensitive member is housed in a housing ,
The two scanning optical systems are symmetrically arranged with the deflector as a center, a substrate that divides the housing vertically is formed in the housing, and the deflector and the scanning optical system are formed on one surface of the substrate. The imaging lens and the first reflecting mirror are disposed along the traveling direction of the light beam, and the second and third reflecting mirrors of the scanning optical system are disposed along the traveling direction of the light beam on the other surface of the substrate. And a first opening is formed on the optical path connecting the third reflection mirror of the substrate and the photoconductor and between the imaging lens and the first reflection mirror, and the first of the substrate is formed. An optical scanning device in which a second opening is formed on an optical path connecting the reflecting mirror and the second reflecting mirror ,
Two units are arranged in parallel in the paper conveyance direction .

According to the present invention, since the two optical scanning devices capable of optically scanning the two photosensitive members simultaneously are arranged in the color image forming apparatus, the image information of four colors (magenta, cyan, yellow, and black) can be used. A total of four photoconductors are optically scanned by the light beam, but on the optical path connecting the third reflection mirror of the substrate formed on the housing of each optical scanning device and the photoconductor, and the imaging lens and the first reflection. Since the first opening is formed between the mirrors, the pitch between the four photoconductors can be substantially equalized.

1 is a side sectional view of an image forming apparatus (color laser printer) according to the present invention. FIG. 3 is a main scanning sectional view of one optical scanning device provided in the image forming apparatus according to the present invention. FIG. 2 is a main scanning sectional view of two optical scanning devices provided in the image forming apparatus according to the present invention. FIG. 6 is a cross-sectional view in the main scanning direction of two optical scanning devices according to a reference example. FIG. 6 is a cross-sectional view in the main scanning direction of two optical scanning devices according to a reference example.

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

[Image forming apparatus]
FIG. 1 is a cross-sectional view of a color laser printer as an embodiment of an image forming apparatus according to the present invention. The illustrated color laser printer is a tandem type, and a magenta image forming unit is provided at the center of the main body 100. 1M, a cyan image forming unit 1C, a yellow image forming unit 1Y, and a black image forming unit 1K are arranged in tandem at regular intervals.

  In each of the image forming units 1M, 1C, 1Y, and 1K, photosensitive drums 2a, 2b, 2c, and 2d, which are photosensitive members, are arranged, respectively, and around each of the photosensitive drums 2a to 2d, a charger 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Here, the photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving motor (not shown). The chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image to visualize each electrostatic latent image as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the driving roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The driving roller 8 is a secondary roller. The transfer unit is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the printer main body 100. It is installed.

  Further, below the image forming units 1M, 1C, 1Y, and 1K in the printer main body 100, two optical scanning devices 13 are arranged in parallel in the paper transport direction, and the printer main body below these optical scanning devices 13 is provided. A paper feed cassette 14 is detachably installed at the bottom of 100. A plurality of sheets of paper (not shown) are stacked and stored in the paper feed cassette 14. A pickup roller 15 for picking up paper from the paper feed cassette 14 and a picked up paper are located near the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for separating the toner and feeding them one by one to the transport path S.

  Further, the conveyance path S extending in the vertical direction on the side of the printer main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to a secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the transport path S, another transport path S ′ that is used when images are formed on both sides of the paper is formed. A plurality of reversing roller pairs 20 are appropriately used for the transport path S ′. Are provided at regular intervals.

  By the way, the conveyance path S arranged in the vertical direction on one side of the printer main body 100 extends to the paper discharge tray 21 provided on the upper surface of the printer main body 100, and the fixing device 22 and the discharge path are disposed in the middle. Paper roller pairs 23 and 24 are provided.

  Next, an image forming operation by the color laser printer having the above configuration will be described.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow (clockwise) in the image forming units 1M, 1C, 1Y, and 1K, and these photosensitive drums 2a. ˜2d are uniformly charged by the chargers 3a to 3d. Each optical scanning device 13 emits a light beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with each light beam, and each color on each photosensitive drum 2a to 2d. The electrostatic latent images corresponding to the color image signals are respectively formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is moved in the direction of the arrow in the figure by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied in the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 that is rotationally driven.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, in accordance with the timing at which the front end of the full-color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the drive roller 8 and the secondary transfer roller 10, The sheet fed to the transport path S by the feed roller 16 and the retard roller 17 is transported to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 and 24, and a series of image forming operations is completed. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

[Optical scanning device]
Next, a description will be given of a prior SL optical scanning device 13 in FIGS. 2 is a main scanning sectional view of one optical scanning device, and FIG. 3 is a sub-scanning sectional view of two optical scanning devices.

  Since the basic configuration of the two optical scanning devices 13 shown in FIG. 3 is the same, the configuration of one optical scanning device 13 will be described with reference to FIG. 2. The optical scanning device 13 is integrally formed of resin. The housing 25 is integrally formed with a horizontal substrate 25A that divides the interior of the housing 25 in the vertical direction. A polygon mirror 26, which is a deflector, is disposed at the center of the upper surface of the substrate 25A of the housing 25. The upper and lower surfaces of the substrate 25A in the housing 25 are on both sides of the polygon mirror 26 as a center. Two scanning optical systems 30 and 40 are arranged symmetrically.

  The scanning optical systems 30 and 40 include the first imaging lenses 31 and 41 and the first reflection mirrors 32 and 42 disposed along the traveling direction of the light beam on the upper surface of the substrate 25A in the housing 25, and the substrate 25A. The second reflection mirrors 33 and 43, the second imaging lenses 34 and 44, and the third reflection mirrors 34 and 45 are provided on the lower surface along the traveling direction of the light beam. Although not shown, each of the scanning optical systems 30 and 40 also includes a laser diode, a collimator lens, and a cylindrical lens as light sources accommodated in the housing 25.

  Incidentally, one optical scanning device 13 shown in FIG. 2 performs exposure scanning on the photosensitive drum 2a of the magenta image forming unit 1M and the photosensitive drum 2b of the cyan image forming unit 1C shown in FIG. On the optical path connecting the third reflecting mirrors 35 and 45 constituting the systems 30 and 40 and the photosensitive drums 2a and 2b, and between the first imaging lenses 31 and 41 and the first reflecting mirrors 32 and 42, Are formed, and second openings 37 and 47 are formed on the optical path connecting the first reflecting mirrors 32 and 42 and the second reflecting mirrors 33 and 43 of the substrate 25A, respectively.

  Thus, a light beam emitted from a laser diode (not shown) provided in each of the scanning optical systems 30 and 40 in one optical scanning device 13 is collected into a linear light beam by a collimator lens and a cylindrical lens (not shown). After being illuminated, the light enters the polygon mirror 26 that is rotationally driven from two symmetrical directions.

  As described above, each light beam incident on the polygon mirror 26 is deflected by the polygon mirror 26 and then converted into constant speed scanning light by passing through the first imaging lenses 31 and 41. The constant-speed scanning light is folded downward at a right angle by the first reflection mirrors 32 and 42, passes through the second openings 37 and 47 formed in the substrate 25A, and passes through the second reflection mirrors 33 and 47. 43, the second reflecting mirrors 33 and 43 are folded at a right angle and proceed horizontally along the lower surface of the substrate 25A. Thereafter, the light beam passes through the second imaging lenses 34 and 44 to reach the third reflecting mirrors 35 and 45, and is folded upward at a right angle by the third reflecting mirrors 35 and 45, and is formed on the substrate 25A. The photosensitive drums 2a and 2b are passed through the openings 36 and 46, and are exposed and scanned.

  The one optical scanning device 13 shown in FIG. 2 scans the photosensitive drum 2a of the magenta image forming unit 1M and the photosensitive drum 2b of the cyan image forming unit 1C shown in FIG. As shown in FIG. 3, two similar optical scanning devices 13 are arranged side by side in the laser printer. The two optical scanning devices 13 allow the respective yellow image forming units 1Y and Bralac image forming units 1K to be exposed to light. All of the four photosensitive drums 2a to 2d including the drums 2c and 2d are exposed and scanned by the light beam. In FIG. 3, the same elements constituting the two optical scanning devices 13 are denoted by the same reference numerals.

As described above, in the optical scanning device 13 according to the present embodiment, the light beam deflected by the polygon mirror 26 is folded back by the first reflecting mirrors 32 and 42 and the second reflecting mirrors 33 and 43 to be the substrate 25A of the housing 25. Therefore, the width of the housing 25 in the height direction is suppressed to be small, so that the housing 25 can be reduced in size, and the optical scanning device 13 as a whole can be reduced in size.

  In the present embodiment, since the two scanning optical systems 30 and 40 are symmetrically arranged on both sides of the polygon mirror 26 arranged at the center in the housing 25, the optical scanning device 13 can Two photosensitive drums 2a, 2b or 2c, 2d can be optically scanned simultaneously.

Since the two optical scanning devices 13 capable of simultaneously scanning the four photosensitive drums 2a to 2d as described above are arranged in parallel with the color laser printer shown in FIG. 1, four colors (magenta, cyan, yellow, and yellow) are arranged. A total of four photosensitive drums 2a to 2d are optically scanned by a light beam corresponding to the image information of black), and the third reflecting mirrors 35 and 45 of the substrate 25A formed on the housing 25 of each optical scanning device 13 are photosensitive. Since the first openings 36 and 46 are formed on the optical path connecting the drums 2a to 2d and between the first imaging lenses 31 and 41 and the first reflection mirrors 32 and 42, the four photosensitive drums 2a to 2d are formed. The pitches L and L ′ can be substantially equalized, and the light guide distance of the folded optical path on the lower surface side of the substrate 25A can be utilized to the maximum.

  Incidentally, as shown in FIG. 4, when the first openings 36 and 46 are formed between the polygon mirror 26 and the first imaging lenses 31 and 41, the second reflection mirrors 33 and 43 and the third Although the return optical path of the reflection mirrors 35 and 45 can be made long, generally, the first imaging lenses 31 and 41 are often arranged in the vicinity of the polygon mirror 26. When such a configuration is adopted, The pitch L between the photosensitive drums 2a and 2b and between 2c and 2d in each optical scanning device 13 ′ is shortened. For this reason, when the two optical scanning devices 13 'are arranged in the paper conveyance direction as shown in the drawing, the pitch L' between the photosensitive drums 2b and 2c becomes larger than the pitch L, and the four-color photosensitive drums 2a to 2d. It becomes difficult to equalize the pitches L and L ′.

In order to equalize the pitches L and L ′ between the four color photosensitive drums 2a to 2d, the pitch L ′ between the photosensitive drums 2b and 2c may be reduced. However, the pitch L ′ between the photosensitive drums 2b and 2c is reduced. In order to reduce the size, it is necessary to adopt the configuration shown in FIG. 5. In such a configuration, the width D ′ in the height direction of the housing 25 of each optical scanning device 13 ″ is the optical scanning device 13 shown in FIGS. 3 and 4. , 13 'becomes larger than the width B ( D '>> D ), and the housing 25 is enlarged.

The above has been described embodiments of applying for the present invention to a color laser printer, the present invention is, similarly for the any other color image forming equipment of the color copying machine or the like other than color printer Of course, it is applicable.

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum (photoconductor)
3a to 3d charger 4a to 4d developing device 5a to 5d transfer roller 6a to 6d drum cleaning device 7 intermediate transfer belt 8 drive roller 9 tension roller 10 secondary transfer roller 11 belt cleaning device 12a to 12d toner container 13 optical scanning device 14 Paper cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Transport roller pair 19 Registration roller pair 20 Transport roller pair 21 Paper discharge tray 22 Fixing device 23, 24 Paper discharge roller pair 25 Housing 25A Housing substrate 26 Polygon mirror (deflector) )
30, 40 Scanning optical system 31, 41 First imaging lens 32, 42 First reflecting mirror 33, 43 Second reflecting mirror 34, 44 Second imaging lens 35, 45 Third reflecting mirror 36, 46 First aperture Portions 37, 47 Second opening D Width in housing height direction L, L 'Pitch between photosensitive drums S, S' Transport path

Claims (1)

A deflector that deflects the light beam emitted from the light source, an imaging lens that converts the light beam deflected by the deflector into constant-speed scanning light, and first and second guides that repeat the constant-speed scanning light to the photoreceptor. In a color image forming apparatus including an optical scanning device in which a scanning optical system including the second and third reflecting mirrors is accommodated in a housing,
The two scanning optical systems are symmetrically arranged with the deflector as a center, a substrate that divides the housing vertically is formed in the housing, and the deflector and the scanning optical system are formed on one surface of the substrate. The imaging lens and the first reflecting mirror are disposed along the traveling direction of the light beam, and the second and third reflecting mirrors of the scanning optical system are disposed along the traveling direction of the light beam on the other surface of the substrate. And a first opening is formed on the optical path connecting the third reflection mirror of the substrate and the photoconductor and between the imaging lens and the first reflection mirror, and the first of the substrate is formed. An optical scanning device in which a second opening is formed on an optical path connecting the reflecting mirror and the second reflecting mirror,
2. A color image forming apparatus comprising two units arranged in parallel in a sheet conveying direction.

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