JP2006301673A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep a transfer section stably in contact with a photoreceptor drum with simple configuration. <P>SOLUTION: An image forming apparatus is equipped with a plurality of photoreceptor drums and a plurality of transfer units provided opposite to the photoreceptor drums, and the array direction of a plurality of image carriers is slanted to the perpendicular direction so that an upper photoreceptor drum is more apart from the transfer unit side than a lower photoreceptor drum. The transfer units are enabled to rotate around fulcra provided below to thereby contact and leave the plurality of photoreceptor drums, and the transfer units are energized toward the plurality of photoreceptor drums by the gravity when contacting the plurality of photoreceptor drums. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and is particularly suitable for application to a color image forming apparatus using an electrophotographic system.

  In recent years, with the widespread use of electrophotographic color image forming apparatuses, there has been an increasing demand for speeding up color output in addition to demand for color image printing quality.

  In order to meet this demand, several proposals have been made for image forming methods. Among these proposals, there is a color image forming method called a tandem type.

  In this tandem color image forming system, first, images of Bk (black) toner, C (cyan) toner, M (magenta) toner, and Y (yellow) toner are respectively formed on a drum-shaped image carrier. The respective colors are sequentially transferred by the transfer means to the transfer material conveyed by the transfer conveyance belt, and finally the fixing is performed.

  Above the optical path of the exposure means for exposing such a drum-shaped image carrier, a charging means for charging the individual drum-shaped image carrier, and a cleaning means for cleaning the individual drum-shaped image carrier, An example of an image forming apparatus having a developing unit for visualizing each electrostatic latent image below the optical path of the exposure unit is disclosed in, for example, Patent Document 1.

  FIG. 6 shows the above-described tandem type color image forming apparatus. In this color image forming apparatus, the transfer material S is fed one by one by a paper feed roller 18 provided at the lower part of the main body apparatus, and fed to the image forming unit by a roller pair 19.

  In the image forming unit, a transfer conveyance belt 11 that conveys the transfer material S is stretched in the paper conveyance direction (from bottom to top in FIG. 6) by a plurality of rotating rollers. Further, at the most upstream portion of the transfer / conveyance belt 11, the transfer material S is electrostatically adsorbed to the transfer / conveyance belt 11 by the suction roller 22 to which a bias is applied.

  Further, four drum-shaped image carriers (hereinafter referred to as “photosensitive drums”) 1a, 1b, 1c, and 1d are arranged in a straight line so as to face the belt conveyance surface to constitute an image forming unit. .

  Also, in the vicinity of the peripheral surface of the photosensitive drum 1, image carriers 7a, 7b, 7c, 7d holding cleaners 6a, 6b, 6c, 6d and chargers 2a, 2b, 2c, 2d, and Developing units 4a, 4b, 4c and 4d are provided.

  Further, transfer members 12 a, 12 b, 12 c, and 12 d are arranged in the vicinity of the peripheral surface of the photosensitive drum 1 so as to sandwich the conveyance surface of the transfer conveyance belt 11. The image carrier units 7a, 7b, 7c, and 7d and the developing units 4a, 4b, 4c, and 4d are separated by a predetermined gap, and the exposure units 3a and 3b are separated through the gap. , 3c, 3d, exposure exposure is performed on the peripheral surfaces of the photosensitive drums 1a, 1b, 1c, 1d.

  In this color image forming apparatus, the transfer material belt 11 is circulated and moved in the clockwise direction in FIG. 6 so that the transfer material S is conveyed, and the chargers 2a, 2b, 2c, and 2d respectively. The peripheral surfaces of the photosensitive drums 1a, 1b, 1c, and 1d are configured to be able to be charged uniformly with a predetermined charge.

  In addition, the exposure units 3a, 3b, 3c, and 3d expose the peripheral surfaces of the charged photosensitive drums 1a, 1b, 1c, and 1d according to image information, thereby forming an electrostatic latent image. Then, the developing devices 4a, 4b, 4c, and 4d transfer the toner to the low potential portions of these electrostatic latent images to form a toner image (development).

  The toner images formed (developed) on the peripheral surfaces of the photosensitive drums 1a, 1b, 1c, and 1d as the respective drum-shaped image carriers are formed by the transfer members 12a, 12b, 12c, and 12d corresponding thereto. The image is transferred onto the transfer material S surface by a transfer electric field.

  On the transfer material S onto which the toner image is transferred in this way, the toner image is heat-fixed on the paper surface by the fixing unit 20 composed of the pressure roller 21b and the heat generating roller 21a, and the discharge roller pair 23 fixes the toner image on the discharge tray 24. To be discharged.

As described above, the configuration of Patent Document 1 is such that the respective image carrier units 7a, 7b, 7c, and 7d having the respective photosensitive drums 1a, 1b, 1c, and 1d are arranged vertically stacked. The color image forming apparatus described in Patent Document 1 has the advantage that the installation area of the apparatus can be made smaller than the type in which the two are arranged side by side. Can be easily detached from the right side, respectively, and the exchangeability can be improved.
Japanese Patent Laid-Open No. 2002-062707 JP 2002-214868 A JP 2002-144633 A

  In this type of apparatus, in order to attach and detach the image carrier unit, it is possible to open and close the transfer conveyance belt. Depending on how the transfer conveyance belt is supported, for example, when the maintenance inside the apparatus is being performed In some cases, the transfer / conveying belt may inadvertently fall to the open side, and further improvement in the method of supporting the transfer / conveying belt has been desired.

  Therefore, the object of the present invention is that the weight of the transfer unit can contribute to the contact between the transfer unit and the image carrier, and the stable position can be obtained with a simple configuration by selecting the position of the rotation fulcrum of the transfer unit. Accordingly, an object of the present invention is to provide an image forming apparatus capable of ensuring the contact state of the transfer unit to the image carrier.

In order to achieve the above object, the first invention of the present invention provides:
A plurality of image carriers that carry toner images;
A transfer unit provided facing the plurality of image carriers, and transferring a toner image on the plurality of image carriers onto a transfer material,
The plurality of image carriers have an image formation in which the arrangement direction of the plurality of image carriers is inclined with respect to the vertical direction so that the upper image carrier is separated from the transfer unit side from the lower image carrier. In the device
The transfer unit is pivotable about a fulcrum provided below the transfer unit, and can take a state in contact with the plurality of image carriers and a state apart from the plurality of image carriers.
The transfer unit is biased toward the plurality of image carriers by its own weight when in contact with the plurality of image carriers.

The second invention of the present invention is:
A plurality of image carriers that carry toner images;
A transfer unit provided facing the plurality of image carriers, and transferring a toner image on the plurality of image carriers onto a transfer material,
The plurality of image carriers have an image formation in which the arrangement direction of the plurality of image carriers is inclined with respect to the vertical direction so that the upper image carrier is separated from the transfer unit side from the lower image carrier. In the device
The transfer unit is pivotable about a fulcrum provided below the transfer unit, and can take a state in contact with the plurality of image carriers and a state apart from the plurality of image carriers.
The transfer unit is inclined in the arrangement direction of the plurality of image carriers when in contact with the plurality of image carriers.

  In the present invention, typically, the plurality of drum-shaped image carriers include an axial center of the most upstream drum-shaped image carrier and a shaft of the most downstream drum-shaped image carrier. The straight line connecting the center is arranged so as to incline to the exposure means side with respect to the vertical direction.

  In the present invention, it preferably has a transfer unit including a belt-shaped transfer member and a plurality of transfer means disposed on the back surface of the belt-shaped transfer member, and the transfer unit can be separated from the drum-shaped image carrier. In addition, the transfer unit is configured to be able to bias the contact with the drum-shaped image carrier due to the weight of the transfer unit when contacting the drum-shaped image carrier.

  As described above, according to the present invention, it is possible to secure a stable contact state of the transfer unit to the image carrier with a simple configuration, and to prevent the transfer unit from inadvertently falling to the open side. Is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals. The vertical direction and the horizontal direction are a parallel direction and a vertical direction with respect to the direction of gravity, respectively.

[First Embodiment]
First, a color image forming apparatus as an image forming apparatus according to a first embodiment of the present invention will be described. FIG. 1 shows a color image forming apparatus according to the first embodiment.

  As shown in FIG. 1, in the color image forming apparatus according to the first embodiment, yellow (Y), magenta as an electrophotographic drum-shaped image carrier inclined in the vertical direction (gravity direction). Four photosensitive drums 31y, 31m, 31c, and 31k (hereinafter referred to as photosensitive drum 31) of (M), cyan (C), and black (Bk) are arranged in parallel.

  Further, in this color image forming apparatus, a transfer material transport belt is disposed facing each photoconductor drum 31 as a belt-shaped transfer member that attracts and carries the transfer material S by electrostatic adsorption. .

  Each of these photosensitive drums 31 is configured by applying an organic photoconductor layer (OPC) to the outer peripheral surface of a cylinder made of, for example, aluminum (Al) having a diameter of, for example, 30 mm.

Further, both end portions of these photosensitive drums 31 are rotatably supported by flanges (not shown). A driving force from a driving motor (not shown) is transmitted to one end of the both ends, so that it is rotated counterclockwise in FIG.

  Around each photosensitive drum 31, chargers 33y, 33m, 33c, and 33k (charging means for uniformly charging the surface of the photosensitive drum 31 in order from the upstream side in the rotation direction of the photosensitive drum 31). Hereinafter, a charger 33) is arranged.

  The charger 33 is composed of a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 31, and a charging bias voltage is applied by a bias power source (not shown). The surface of the photosensitive drum 31 is uniformly charged.

  Further, exposure units 34y, 34m, 34c, and 34k (hereinafter, exposure unit 34) are arranged on the downstream side of the charger 33 in the rotation direction of the photosensitive drum 31. These exposure units 34 form an electrostatic latent image on the surface of the photosensitive drum 31 by irradiating the surface of the photosensitive drum 31 uniformly charged by the charger 33 with a laser beam based on image information. It is configured to be possible.

  Each of these exposure units 34 is provided with a polygon mirror. Then, image light corresponding to the image signal is emitted from a laser diode (not shown), and through these polygon mirrors, four process cartridges 37y, 37m, 37c, 37k (hereinafter referred to as cartridges) are integrally formed. The photosensitive drum 31 is irradiated through the inside of the process cartridge 37). By this exposure, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

  Further, developing devices 35y, 35m, and 35c that visualize the toners of the respective colors attached to the surface of the photosensitive drum 31 on which the electrostatic latent image is formed as a toner image around the photosensitive drum 31. , 35k (hereinafter, referred to as developing unit 35).

  Each developing device 35 is provided with toner storage portions 39y, 39m, 39c, and 39k (hereinafter, toner storage portions 39) that store toners of yellow, magenta, cyan, and black, respectively.

  Then, it is adjacent to the surface of the photosensitive drum 31 and is driven to rotate by a driving unit (not shown), and development is performed by applying a developing bias voltage from a developing bias power source (not shown).

  Subsequently, the image on the photosensitive drum visualized as a toner image by the developing unit 35 is transferred to the transfer material S in the transfer unit.

  Transfer rollers 38y, 38m, 38c, and 38k (hereinafter referred to as transfer rollers 38) disposed inside the transfer material conveyance belt 32 face the four photosensitive drums 31 so as to contact the transfer material conveyance belt 32. It is configured.

  These transfer rollers 38 are connected to a transfer bias power source (not shown). Then, a positive charge is applied to the transfer material S from the transfer roller 38 via the transfer material conveyance belt 32. Then, due to this electric charge, the negative color toner images on the surface of the photosensitive drum 31 are sequentially transferred to the transfer material S in contact with the photosensitive drum 31 to form a color image.

  In addition, cleaning units 36y, 36m, 36c, and 36k (hereinafter, cleaning unit 36) for removing toner remaining on the surface of the photosensitive drum 31 after the transfer are disposed.

  Further, toner containers 51y, 51m, 51c, and 51k (hereinafter, toner container 51) are provided so as to be adjacent to the cleaning unit 36. These toner containers 51 are containers for collecting the toner removed from the surface of the corresponding photosensitive drum 31.

  In the process cartridge 37, the photosensitive drum 31, the charger 33, the developing unit 35, and the cleaning unit 36 are integrally formed into a cartridge and configured to be detachable from the image forming apparatus main body.

  Here, in the first embodiment, the straight lines passing through the centers of the respective photosensitive drums 31 are disposed so as to be inclined toward the exposure unit 34 with respect to the vertical direction. That is, as is apparent from FIG. 1, the plurality of photosensitive drums 31 include the upper photosensitive drum (for example, 31k) and the lower photosensitive drum (for example, 31c) than the transfer material conveyance belt 32 (to be described later in a transfer unit 54). The arrangement direction of the plurality of photoconductive drums 31 is inclined with respect to the vertical direction so as to be separated from the side. As a result, the attaching / detaching direction of the process cartridge 37 can be similarly inclined. Therefore, when the user attaches / detaches the process cartridge 37, operability can be improved.

  Next, the transfer operation of the transfer material S in the color image forming apparatus configured as described above will be described.

  The transfer material S accommodated in a feeding cassette 41 provided at the lower part of the color image forming apparatus is separated and fed by a pickup roller 42 and a separation roller 43 provided on the downstream side of the pickup roller 42. The registration roller pair 44 is reached.

  Then, the timing between the image and the transfer material S is determined and fed from the registration roller pair 44. The transfer material S is electrostatically adsorbed by the transfer material conveying belt 32 and is held in the image forming means. To the transfer position between the photosensitive drum 31 and the transfer roller 38.

  Subsequently, the toner images formed on the surfaces of the respective photosensitive drums 31 are sequentially transferred onto the transfer material S to record color images. Thereafter, when the transfer material S passes through the fixing unit 45 having the heating roller 45a that rotates and the pressure roller 45b that is driven to rotate while being in pressure contact with the heating roller 45a, the heating process and the pressure process are executed. As a result, the toner image is fixed. The transfer material S on which the toner image is fixed is discharged by a discharge roller pair 46 onto a discharge tray 47 provided on the upper part of the image forming apparatus.

  Here, the cleaning unit 36 used in the color image forming apparatus according to the first embodiment will be described.

  Generally, the cleaning unit 36 cleans the surface of the photosensitive drum 31 by scraping off the toner adhering to the surface of the photosensitive drum 31 with an edge of a rubber plate called a blade. The cleaning performance is affected by the installation angle of the cleaning unit 36.

  Specifically, as the installation angle of the cleaning unit 36 increases in the counterclockwise direction in FIG. 1, that is, as the cleaning unit 36 is inclined counterclockwise, the toner accumulated in the cleaning unit 36 moves to the toner container 51. It becomes easy. This facilitates the movement of the toner at the blade edge portion, thereby improving the cleaning performance.

On the other hand, as the installation angle of the cleaning unit 36 increases in the clockwise direction in FIG. . As a result, the toner at the blade edge portion is also difficult to move, and the cleaning performance is degraded.

  Therefore, in order to improve the cleaning performance, it is effective to install the cleaning unit 36 in a state rotated counterclockwise by an angle θ, for example, θ = 10 °. As shown in FIG. 9, the installation state of the cleaning unit according to the prior art is inclined at θ = about 13 ° with respect to the horizontal direction (direction perpendicular to the direction of gravity).

  Further, as shown in FIG. 2, a method of reducing the charger 33 serving as charging means for uniformly charging the surface of the photosensitive drum 31 is conceivable.

  However, the charger 33 is configured to urge the photosensitive drum 31 with a predetermined pressure. For this reason, if the diameter of the charger 33 is made too small, the charger 33 itself bends and uniform contact is difficult over the longitudinal direction of the photosensitive drum 31, so that uniform charging cannot be performed.

  Therefore, the pressure for urging the charger 33 to the photosensitive drum 31 is usually about 1.47 N (150 gf) per side. Therefore, in order to prevent the charger 33 from being bent at this pressure, The diameter of the vessel 33 must be at least 8 mm.

  Further, if the diameter of the charger 33 is reduced, the number of rotations is increased accordingly, and the deterioration of the charger 33 is promoted. Also from this viewpoint, the diameter of the charger 33 is required to be 8 mm or more.

  Thus, there is a limit in making the charger 33 small. Therefore, in the first embodiment, as shown in FIG. 1, the straight lines passing through the centers of the respective photosensitive drums 31 are arranged so as to be inclined toward the exposure unit 34 with respect to the vertical direction. The light path of the exposure unit 34 is disposed so as to be inclined with respect to the horizontal direction so that the irradiation position on the photosensitive drum 31 is higher than the emission position of the exposure unit 34. As a result, as shown in FIG. 3, the charger 33 can be rotated and arranged counterclockwise in FIG.

  In the first embodiment, the optical path of the exposure unit 34 is arranged so as to be inclined by an angle α, for example, α = 10 ° with respect to the horizontal direction. Further, the angle α for inclining the optical path from the exposure unit 34 is allowed up to 25 ° in order to appropriately supply the toner in the toner storage portion 39y to the developing device 35.

  As shown in FIG. 4, in the first embodiment, a transfer unit 54 having a transfer material conveyance belt 32 and a transfer roller 38 disposed inside is provided as a fulcrum provided below the transfer unit 54. 55 is supported so as to be rotatable around 55.

  The position of the fulcrum 55 is arranged so that the weight F of the transfer unit 54 urges the contact of the transfer unit 54 to the photosensitive drum 31 in a state where the transfer unit 54 is in contact with the photosensitive drum 31. ing. That is, as apparent from FIG. 4, the transfer unit 54 is inclined in the arrangement direction of the plurality of photosensitive drums 31 when in contact with the plurality of photosensitive drums 31. It is urged to the photosensitive drum 31 side.

  By adopting such a configuration, it is not necessary to use a spring or the like in order to urge the transfer unit 54 to the photosensitive drum 31, so that the image forming apparatus can be simplified and a stable contact state can be achieved. It can be secured.

[Second Embodiment]
Next explained is a color image forming apparatus according to the second embodiment of the invention. FIG. 5 shows an image forming apparatus using the intermediate transfer belt 63 according to the second embodiment.

  As shown in FIG. 5, in the second embodiment, the toner image formed on the photosensitive drum 31 is not directly transferred to the transfer material S but is transferred via transfer to the intermediate transfer belt 63. It has been adopted.

Inside the intermediate transfer belt 63, transfer rollers 38y, 38m, 38c, and 38k (hereinafter, transfer roller 38) are arranged. Each transfer roller 38 is in contact with the intermediate transfer belt 63 so as to face each of the four photosensitive drums 31.

  These transfer rollers 38 are connected to a transfer bias power source (not shown). A positive charge is applied from the transfer roller 38 to the intermediate transfer belt 63. Due to the electric field generated by this electric charge, each negative color toner image on the surface of the photosensitive drum 31 is sequentially transferred to the intermediate transfer belt 63 in contact with the photosensitive drum 31, and a color image is formed on the intermediate transfer belt 63. Is done.

  In this manner, the color image formed on the intermediate transfer belt 63 reaches the secondary transfer portion having the secondary transfer roller 64 as the intermediate transfer belt 63 rotates clockwise in FIG.

  These secondary transfer rollers 64 are connected to a transfer bias power source (not shown), and each color toner image is transferred from the intermediate transfer belt 63 at a time by an electric field to form a color image on the transfer material S. Is done.

  Further, in the transfer material S after the color image is transferred, flappers 49 and 50 are provided on the downstream side where the fixing is performed, and the path of the transfer material S can be changed to three states. Since this configuration is the same as that of the first embodiment except that this configuration is adopted, the description thereof is omitted.

  First, when the flapper 49 is at the position of the solid line in FIG. 5, the transfer material S follows the normal discharge path and is discharged onto a discharge tray 47 provided on the upper portion of the image forming apparatus by the discharge roller pair 46. .

  Next, when the flapper 49 is in the position of the two-dot chain line in FIG. 5 and the flapper 50 is in the position of the two-dot chain line in FIG. 5, the transfer material S is discharged by the paper discharge driving roller 48a and the driven roller 48c. It is discharged to the paper tray 61. In the case of this path, since the path of the transfer material S after fixing can be configured linearly, it is possible to obtain an optimal situation for discharging stiff paper such as thick paper.

  Next, when the flapper 49 is at the position of the two-dot chain line in FIG. 5 and the flapper 50 is at the position of the solid line in FIG. At this time, the transfer material S is conveyed to the transfer material reversing unit 53 by the paper discharge driving roller 48a and the driven roller 48b.

  The transfer material S conveyed to the transfer material reversing unit 53 is reversed by the reversing operation of the paper discharge driving roller 48 a and reaches the secondary transfer unit again via the reversing conveyance path 52. As a result, the image is transferred to the back surface. The path after the transfer is the same as when the flapper 49 is at the position of the solid line in FIG.

  As a comparative example of a conventional tandem-type color image forming apparatus in which four photosensitive drums according to the prior art are inclined with respect to the image forming apparatuses according to the first and second embodiments configured as described above. There is an image forming apparatus described in Patent Document 2. This tandem type color image forming apparatus is shown in FIG.

  As shown in FIG. 7, in this tandem color image forming apparatus, the transfer material P stored in the lower part of the main body apparatus is conveyed to the image forming unit by the conveying means 115. In the image forming unit, four photosensitive drums 121, 131, 141, 151 are arranged in an inclined state.

  Further, an intermediate transfer belt 113 is disposed so as to face the photosensitive drums 121, 131, 141, and 151. The intermediate transfer belt 113 is stretched around a driving roller 111 and a tension roller 112.

  However, in the color image forming apparatus described in Patent Document 2, a charging unit for charging each photosensitive drum and a respective drum-shaped image carrier are disposed above the optical path of the exposure unit for exposing the photosensitive drum. The image forming apparatus has a cleaning means for cleaning, and is provided with a developing means for visualizing the electrostatic latent images individually below the optical path of the exposure means. Different.

  As another comparative example of a conventional tandem type color image forming apparatus in which four drum-shaped image carriers are arranged at an angle, there is a color image forming apparatus described in Patent Document 3. This color image forming apparatus is shown in FIG.

  As shown in FIG. 8, in the image forming apparatus described in Patent Document 3, an intermediate belt 204 composed of an endless belt having both ends stretched by rollers 203a and 203b is provided so as to be inclined by 45 ° from a horizontal plane. In addition, four photosensitive drums 205 are provided so as to be in rolling contact with the upper surface of the intermediate belt 204.

  One folding mirror 210 is provided on each photosensitive drum 205, and a polygon mirror 208 is provided on the same horizontal plane as the folding mirror 210. The polygon mirror 208 is provided on the side of the folding mirror 210 having the longest optical path length between the folding mirror 210 and the corresponding photosensitive drum 205, and the optical path length from the polygon mirror 208 to the photosensitive drum 205. However, the photosensitive drums 205 are configured to be equal to each other.

  However, the color image forming apparatus described in Patent Document 3 includes a charging unit that charges each drum-shaped image carrier above the optical path of an exposure unit that performs exposure on the drum-shaped image carrier, Cleaning means for cleaning the drum-shaped image carrier, and a developing means for visualizing the electrostatic latent image of each drum-shaped image carrier is not provided below the optical path of the exposure means. It does not correspond to the image forming apparatus according to the present invention, and its technical idea is greatly different.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible.

  For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

Further, for example, in the above-described embodiment, a color image forming apparatus is cited as a configuration example of the image forming apparatus. However, the present invention is not limited to this, and any image forming apparatus having a plurality of drum-shaped image carriers. It is possible to apply to.

  Further, for example, in the first and second embodiments described above, the photosensitive drum 31 is arranged such that a straight line passing through these centers is inclined toward the exposure unit 34 with respect to the vertical direction. By reducing the size of the means, the straight line passing through the center of the photosensitive drum 31 is configured to be parallel to the vertical direction, and the irradiation position on the photosensitive drum 31 is higher than the emission position of the exposure unit 34. The optical path of the exposure unit 34 can be arranged to be inclined with respect to the horizontal direction.

  Moreover, this invention is not limited to the above-mentioned embodiment, The following technical thought is included and all the combinations of these technical thought are included.

1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment of the present invention. It is a basic diagram which shows the outline of the process cartridge by 1st Embodiment of this invention. It is a basic diagram which shows the outline of the process cartridge by 1st Embodiment of this invention. It is sectional drawing which shows the transfer unit part by 1st Embodiment of this invention. It is the schematic which shows the image forming apparatus by 2nd Embodiment of this invention. It is the schematic which shows the color image forming apparatus by a prior art. It is the schematic which shows the color image forming apparatus by a prior art. It is sectional drawing which shows the color image forming apparatus by a prior art. It is a basic diagram which shows the process cartridge by a prior art.

Explanation of symbols

1, 1a-1d, 31, 31y-31k, 121, 131, 141, 151,
205 Photosensitive drums 2a-2d, 33, 33y-33k Chargers 3a-3d, 34, 34y-34k Exposure units 4a-4d, 35, 35y-35k Developers 6a, 6b, 6c, 6d Cleaners 7a, 7b, 7c , 7d Image carrier unit 11 Transfer conveyor belt 12a, 12b, 12c, 12d Transfer member 18 Paper feed roller 19 Roller pair 20 Fixing portion 21a Heat generating roller 21b Pressure roller 22 Adsorption roller 23 Paper discharge roller pair 24 Paper discharge tray 32 Transfer material Conveying belt 36, 36y, 36m, 36c, 36k Cleaning unit 37, 37y, 37m, 37c, 37k Process cartridge 38, 38y, 38m, 38c, 38k Transfer roller 39, 39y, 39m, 39c, 39k Toner storage unit 41 Feeding Cassette 42 Pickup roller 4 3 Separation roller 44 Registration roller pair 45 Fixing portion 45a Heating roller 45b Pressure roller 46 Discharge roller pair 47 Discharge tray 48a Discharge drive roller 48b, 48c Driven roller 49, 50 Flapper 51, 51y, 51m, 51c, 51k Toner container 52 Reverse transfer path 53 Transfer material reversing part 54 Transfer unit 55 Support point 61 Paper discharge tray 63,113 Intermediate transfer belt 64 Secondary transfer roller 111 Driving roller 112 Tension roller 115 Conveying means 203a, 203b Roller 204 Intermediate belt 208 Polygon mirror 210 Folding mirror P, S transfer material

Claims (4)

A plurality of image carriers that carry toner images;
A transfer unit provided facing the plurality of image carriers, and transferring a toner image on the plurality of image carriers onto a transfer material,
The plurality of image carriers have an image formation in which the arrangement direction of the plurality of image carriers is inclined with respect to the vertical direction so that the upper image carrier is separated from the transfer unit side from the lower image carrier. In the device
The transfer unit is pivotable about a fulcrum provided below the transfer unit, and can take a state in contact with the plurality of image carriers and a state apart from the plurality of image carriers.
The image forming apparatus, wherein the transfer unit is biased toward the plurality of image carriers by its own weight when in contact with the plurality of image carriers.   The image forming apparatus according to claim 1, wherein the transfer unit includes a belt-shaped transfer member. A plurality of image carriers that carry toner images;
A transfer unit provided facing the plurality of image carriers, and transferring a toner image on the plurality of image carriers onto a transfer material,
The plurality of image carriers have an image formation in which the arrangement direction of the plurality of image carriers is inclined with respect to the vertical direction so that the upper image carrier is separated from the transfer unit side from the lower image carrier. In the device
The transfer unit is pivotable about a fulcrum provided below the transfer unit, and can take a state in contact with the plurality of image carriers and a state apart from the plurality of image carriers.
The image forming apparatus, wherein the transfer unit is inclined in an arrangement direction of the plurality of image carriers when in contact with the plurality of image carriers.   The image forming apparatus according to claim 3, wherein the transfer unit includes a belt-shaped transfer member.

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