JP4296506B2 - Image forming apparatus and belt unit - Google Patents

Description

  The present invention relates to an image forming apparatus such as a laser printer, and a belt unit attached to the image forming apparatus.

Conventionally, so-called tandem color laser printers are known in which process cartridges corresponding to yellow, magenta, cyan, and black are arranged in parallel in the horizontal direction.
In such a tandem type color laser printer, for example, a belt supported by a plurality of rollers so as to be able to move around is arranged so as to come into contact with a photosensitive member included in a process cartridge of each color from below. Thus, the paper is conveyed so as to pass between the belt and each photoconductor in sequence, and during the conveyance, the toner image carried on each photoconductor is transferred onto the paper in a color superimposed manner. As a result, a color image is formed on the paper at approximately the same speed as that for forming a monochrome image.

In order to enable belt replacement and maintenance, it is necessary to remove the belt from the apparatus main body. Therefore, the transfer belt that contacts the photosensitive drums of the respective colors from below is moved downward, and after the transfer belt is separated from the photosensitive drum, the transfer belt is moved in a direction parallel to the paper conveyance direction by the transfer belt ( There has been proposed a configuration in which it is pulled out in the direction along the surface of the transfer belt and detached from the main body housing (see, for example, Patent Document 1).
Japanese Patent No. 3323732

  However, in the configuration described in Patent Document 1, an operation of lowering the transfer belt and an operation of pulling out the transfer belt are required, and it cannot be said that the detachability of the transfer belt is good. In addition, the configuration for guiding the movement of the transfer belt becomes complicated, and there is a problem that the cost increases. Furthermore, since it is necessary to secure a space for moving the transfer belt downward, there is a problem that the size of the image forming apparatus increases.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing the cost and reducing the size while improving the detachability of the belt unit, and the detachability of the image forming apparatus. An object of the present invention is to provide a belt unit that can reduce the cost and size of an image forming apparatus while being able to improve.

In order to achieve the above object, the invention according to claim 1 is directed to a belt unit including a plurality of rollers, a belt supported by the plurality of rollers so as to be capable of circular movement, and a circumferential movement direction of the belt. disposed Te, an image forming apparatus including a plurality of photoreceptors in contact with the surface of the belt, the belt unit, to the image forming apparatus detachably mounted along a straight detachable path, wherein The belt has a contact position with each photoconductor in a state in which the belt unit is detached from the image forming apparatus due to the elastic force of the compression spring and in a state in which the belt unit is attached to the image forming apparatus. The belt unit is configured to float in a direction perpendicular to a direction in which the belt unit is detached and a rotation axis direction of the roller, and the plurality of photosensitive members are separated from the belt unit. The position in the direction perpendicular to the direction of the rotation axis of the roller and the roller unit is shifted from the upstream side of the belt unit in the separation direction so as to be increased by a predetermined amount. It is characterized in that it is set to be more than the lifting amount of the belt when it is detached from the apparatus .

According to such a configuration, the angle formed by the moving direction of the belt at the contact position with the photosensitive member and the detaching direction of the belt unit releases the contact between the surface of the belt and the photosensitive member by the detachment of the belt unit. predetermined angle and a Runode, when the belt unit is detached along a straight detachable path, along with the withdrawal, the contact between the surface of the belt and the photosensitive member is released. Therefore, the operation of moving the belt unit in a direction crossing the direction of detachment of the belt unit in order to separate the belt from the photosensitive member can be eliminated, and the operability when the belt unit is detached from the image forming apparatus is improved. Can be achieved.
Further, the positions of the photoconductors adjacent to each other in the belt unit detaching direction are deviated by a belt lifting amount or more in the direction orthogonal to the detaching direction and the rotation axis direction of the roller. For this reason, when the belt unit is detached from the image forming apparatus, even if the contact portion of the belt with the photosensitive member is lifted, the photosensitive member is opposed to the photosensitive member adjacent to the downstream side in the separation direction with respect to the photosensitive member. A space can be secured between the belt and the belt. Therefore, when the belt unit is detached from the image forming apparatus, it is possible to prevent the belt and the photoconductor from rubbing. As a result, it is possible to prevent the photoreceptor or the belt from being damaged due to the friction between the belt and the photoreceptor.

  On the other hand, when the belt unit is attached to the image forming apparatus, if the belt unit is attached along the linear attachment / detachment path, the surface of the belt comes into contact with the photoreceptor along with the attachment. Therefore, after moving the belt unit in the direction along the attachment / detachment path, it is possible to eliminate the operation of moving the belt unit in a direction crossing that direction in order to bring the belt into contact with the photosensitive member. The operability when mounting on the forming apparatus can be improved.

  Further, when the belt unit is attached to or detached from the image forming apparatus, it is not necessary to move the belt unit in a direction crossing the direction along the attachment / detachment path, so that the configuration for guiding the movement of the belt unit can be simplified. Cost can be reduced. In addition, since a space for moving the belt unit in a direction intersecting the direction along the attachment / detachment path is not required, the image forming apparatus can be reduced in size.

As a result, it is possible to reduce the cost and size while improving the detachability operability of the belt unit.
The angle formed by the direction immediately after the start of detachment of the belt separated along the attachment / detachment path and the movement direction of the belt at the contact position with the photoconductor is the predetermined angle, and the attachment / detachment path is A path may be used in which the belt is moved in a straight line from the start of belt detachment to the completion of detachment without being bent halfway.

The invention described in claim 2 is characterized in that, in the invention described in claim 1, the detachment direction of the belt unit is a substantially horizontal direction.
According to such a configuration, the belt unit can be easily detached from the image forming apparatus because the belt unit is detached in a substantially horizontal direction. Therefore, further improvement in the detachability operability of the belt unit can be achieved.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the photosensitive member is rotatable about an axis extending in a rotation axis direction of the roller, and the belt unit is detached. Is a direction perpendicular to the axis of the photoconductor.
According to such a configuration, the belt unit is detached in the direction orthogonal to the axis of the photosensitive member, so that the contact between the surface of the belt and the photosensitive member can be released immediately after the belt unit moves in the removing direction. . Therefore, sliding between the belt and the photosensitive member can be prevented. Therefore, it is possible to prevent damage to the photoconductor or the belt due to the friction between the belt and the photoconductor.

According to a fourth aspect of the invention, there is provided a guide member for guiding movement of the belt unit when the belt unit is detached from the image forming apparatus according to the first aspect of the invention. It is characterized by having.
According to such a configuration, since the movement of the belt unit is guided by the guide member, the belt unit can be easily detached from the image forming apparatus. Therefore, further improvement in the detachability operability of the belt unit can be achieved.

According to a fifth aspect of the present invention, there is provided the recording medium accommodating unit according to any one of the first to fourth aspects, wherein the recording medium is accommodated and detachably attached to the image forming apparatus. The detaching direction of the recording medium accommodation unit and the detaching direction of the belt unit are the same direction.
According to such a configuration, the belt unit and the recording medium accommodation unit can be detached in the same direction, so that the maintenance work by the user can be facilitated.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the belt unit and the recording medium accommodation unit are detachably attached to the image forming apparatus. It is said.
According to such a configuration, the belt unit and the recording medium housing unit can be integrally detached from the image forming apparatus. Therefore, the belt unit and the recording medium accommodation unit can be detached with a single operation. As a result, it is possible to improve operability when the belt unit and the recording medium housing unit are detached.

According to a seventh aspect of the present invention, in the invention of the fifth or sixth aspect, the belt unit is arranged so that a part of the belt unit overlaps the recording medium accommodation unit in a direction in which the belt unit is detached. It is characterized by having.
According to such a configuration, the belt unit and the recording medium housing unit are arranged so as to overlap in the direction in which the belt unit is detached, so that the size in the direction perpendicular to the direction in which the belt unit is removed in the image forming apparatus can be reduced. Can do.

The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the belt unit is provided at an end of the belt unit on the downstream side in the mounting direction with respect to the image forming apparatus. A power supply terminal for supplying power to the belt unit is provided.
According to such a configuration, since the power supply terminal is provided at the end on the downstream side in the mounting direction of the belt unit, the power supply terminal is not exposed until the belt unit is completely detached from the image forming apparatus. Therefore, it is possible to prevent the user from touching the power supply terminal. Further, when the belt unit is mounted on the image forming apparatus, the electrode connected to the power supply terminal is disposed on the downstream side (back side) in the mounting direction with respect to the belt unit, so that the user may touch the electrode. Can be prevented. As a result, contamination of the power supply terminal and the electrodes connected to the power supply terminal can be prevented.

The invention according to claim 9 is the invention according to claim 8, wherein a plurality of the power supply terminals are provided along the rotation axis direction of the roller.
According to such a configuration, the connection between the plurality of power supply terminals and the electrodes can be achieved simultaneously.
According to a tenth aspect of the present invention, in the ninth aspect of the invention, the belt unit is provided with an electrode connected to each of the power supply terminals in a state where the belt unit is mounted on the image forming apparatus. At the time of mounting on the image forming apparatus, the contact of the belt with the photosensitive member is achieved after the connection between the power supply terminals and the electrodes.

  According to such a configuration, when the belt unit is attached to the image forming apparatus, the belt contacts the photoconductor at the same time or after the power supply terminal and the electrode are connected. After that, it is not necessary to further slide the belt unit for connection between the power supply terminal and the electrode, and the friction between the belt and the photosensitive member can be prevented. Therefore, it is possible to prevent damage to the photoconductor or the belt due to the friction between the belt and the photoconductor.

According to an eleventh aspect of the present invention, in the invention according to the tenth aspect, the power supply terminal faces the downstream side in the mounting direction of the belt unit with respect to the image forming apparatus along the bottom surface of the belt unit. The electrode extends to the upstream side in the mounting direction of the belt unit with respect to the image forming apparatus.
According to a twelfth aspect of the present invention, in the invention according to any one of the eighth to eleventh aspects, the power supply terminal is a transfer bias for transferring a developer image carried on the photosensitive member to a recording medium. It is characterized by including a terminal for supplying.
According to such a configuration, contamination of the terminal for supplying the transfer bias and the electrode connected to the terminal can be prevented.

According to a thirteenth aspect of the present invention, in the invention of the twelfth aspect , the power supply terminal includes a terminal for supplying a cleaning bias for cleaning the belt and a bias for discharging the belt. It includes at least one of a terminal for supplying and a terminal for ground connection of the belt unit.
According to such a configuration, the terminal for supplying the cleaning bias, the terminal for supplying the bias for neutralizing the belt, and / or the terminal for grounding the belt unit and the contamination of the electrode connected thereto Can be prevented.

The invention according to claim 14 is the invention according to any one of claims 1 to 13 , wherein a plurality of the photoreceptors are provided along a moving direction of the belt, and the belt unit is arranged in the separating direction. The contact with a plurality of the photoconductors is simultaneously released by the movement to the position.
According to such a configuration, even in a configuration including a plurality of photoconductors, when the belt unit is detached, an operation of moving the belt unit in a direction crossing the separation direction can be eliminated. Therefore, it is possible to improve operability when the belt unit is detached from the image forming apparatus.

According to a fifteenth aspect of the invention, in the invention according to any one of the first to fourteenth aspects, the belt is a conveyance belt for conveying a recording medium.
According to such a configuration, it is possible to improve the detachability operability of the belt unit including the conveyor belt.
According to a sixteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the recording medium is picked up in an image forming apparatus provided with the process cartridge provided with the photoconductor for each color. A supply means for supplying the recording medium and a discharge means for discharging the recording medium, and the process cartridges of the respective colors are arranged between the supply means and the discharging means in a conveyance path of the recording medium, The pickup direction of the recording medium picked up by the supply means and the conveyance direction of the recording medium at the image forming position where the images are sequentially formed by the process cartridges of the respective colors are opposite directions, and at the image forming position. Arrange so that the conveyance direction of the recording medium is opposite to the ejection direction of the recording medium ejected by the ejection means. It is characterized in that it is.

According to such a configuration, the recording medium pickup direction and the recording medium conveyance direction at the image forming position are opposite directions, and the recording medium conveyance direction and the recording medium ejection direction at the image formation positions are opposite directions. Therefore, the apparatus can be miniaturized while securing a conveyance path for the recording medium.
According to a seventeenth aspect of the present invention, in the invention according to the sixteenth aspect, the process cartridge has a recording medium transport direction at the image forming position and a thickness direction of the recording medium perpendicular thereto. It is characterized by being attached and detached along the direction of inclination.

According to such a configuration, the process cartridge is attached and detached along the direction inclined with respect to the recording medium conveyance direction at the image forming position and the thickness direction of the recording medium orthogonal to the recording medium conveyance direction. The detachability operability can be improved.
According to an eighteenth aspect of the present invention, in the invention of the sixteenth or seventeenth aspect, a plurality of exposure devices are provided corresponding to the process cartridges of the respective colors, and the recording medium at the image forming position is provided. In the transport direction, the process cartridges of the respective colors and a plurality of exposure apparatuses corresponding to the process cartridges are alternately arranged.

According to such a configuration, a plurality of process cartridges and a plurality of exposure apparatuses corresponding to the process cartridges are alternately arranged. Therefore, these efficient arrangement, Ru can be miniaturized.

According to the first aspect of the present invention, it is possible to reduce the cost and the size while improving the detachability operability of the belt unit.
According to invention of Claim 2, the further improvement of the attachment or detachment operativity of a belt unit can be aimed at.
According to the third aspect of the present invention, it is possible to prevent the photoreceptor or the belt from being damaged by the friction between the belt and the photoreceptor.

According to the fourth aspect of the present invention, it is possible to further improve the detachability operability of the belt unit.
According to the fifth aspect of the present invention, since the belt unit and the recording medium accommodation unit can be separated in the same direction, the maintenance work by the user can be facilitated.
The invention described in claim 6 can improve the operability when the belt unit and the recording medium housing unit are detached.

According to the seventh aspect of the present invention, the size of the image forming apparatus in the direction orthogonal to the belt unit separating direction can be reduced.
According to the eighth aspect of the present invention, contamination of the power supply terminal and the electrode connected thereto can be prevented.
According to the ninth aspect of the present invention, the connection between the plurality of power supply terminals and the electrodes can be achieved simultaneously.

According to the tenth aspect of the present invention, it is possible to prevent the photosensitive member or the belt from being damaged by the friction between the belt and the photosensitive member.
According to the twelfth aspect of the present invention, contamination of the terminal for supplying the transfer bias and the electrode connected thereto can be prevented.
According to the thirteenth aspect of the present invention, a terminal for supplying a cleaning bias, a terminal for supplying a bias for neutralizing the belt, and / or a terminal for ground connection of the belt unit and the terminal are connected thereto. Contamination of the electrodes can be prevented.

According to the fourteenth aspect of the present invention, it is possible to improve the operability when the belt unit is detached from the image forming apparatus even in the configuration including a plurality of photoconductors.
According to the fifteenth aspect of the invention, it is possible to improve the detachability operability of the belt unit including the conveyor belt.

According to the sixteenth aspect of the present invention, it is possible to reduce the size of the apparatus while securing a conveyance path for the recording medium.
According to the seventeenth aspect of the present invention, the operability of attaching and detaching the process cartridge can be improved.
According to the eighteenth aspect of the present invention, the apparatus can be reduced in size by an efficient arrangement of a plurality of process cartridges and a plurality of exposure apparatuses corresponding thereto.

FIG. 1 is a side sectional view showing an embodiment of a color laser printer as an image forming apparatus of the present invention.
The color laser printer 1 is a horizontal tandem type color laser printer in which a plurality of process units 17 are arranged in parallel in the horizontal direction, and a sheet 3 as a recording medium is placed in a main body casing 2. A paper feed unit 4 for feeding paper, an image forming unit 5 for forming an image on the fed paper 3, and a paper discharge unit 6 for discharging the paper 3 on which the image is formed are provided.

  The main casing 2 has a box-like shape that is substantially rectangular in a side view with the upper side opened, and a top cover 7 is provided on the upper side. The top cover 7 is rotatably supported via a cover shaft 8 provided on the rear side of the main casing 2 (in the following description, the left side in FIG. 1 is the rear side and the right side is the front side). The main casing 2 can be opened and closed.

  The paper feed unit 4 includes a paper tray 9 provided at the bottom of the main body casing 2, a pickup roller 10 and a paper feed roller 11 as supply means provided above the front side of the paper tray 9, and a front side of the paper feed roller 11. A sheet feeding side U-shaped path 12 provided above, a pair of conveying rollers 13 and a pair of registration rollers 14 provided in the middle of the sheet feeding side U-shaped path 12 are provided.

In the paper tray 9, the paper 3 is stacked, and the topmost paper 3 is first picked up by the pickup roller 10 and conveyed forward, and then fed by the paper feed roller 11 to the paper feed side U. The paper is fed to the character path 12.
The feed-side U-shaped path 12 has an upstream end adjacent to the feed roller 11 at the lower side so that the paper 3 is fed forward, and a downstream end at the upper side, which will be described later. It is formed as a substantially U-shaped sheet 3 conveying path that is adjacent to the conveying belt 38 so that the sheet 3 is discharged rearward.

Then, the sheet 3 fed forward to the upstream end of the sheet feeding side U-shaped path 12 is conveyed by the conveying roller 13 in the sheet feeding side U-shaped path 12 and the conveying direction is reversed. After registration by the registration roller 14, the paper is discharged backward by the registration roller 14.
The image forming unit 5 includes a process unit 17, a transfer unit 18, and a fixing unit 19.

  The process unit 17 is provided for each color of a plurality of colors of toner. That is, the process unit 17 includes four units, that is, a yellow process unit 17Y, a magenta process unit 17M, a cyan process unit 17C, and a black process unit 17K. The process units 17 are sequentially arranged in parallel so as to be overlapped in the horizontal direction at intervals from the front to the rear.

Each process unit 17 includes a scanner unit 20 as an exposure apparatus fixedly disposed in each process unit 17, and a process cartridge 21 that is detachably attached to each process unit 17.
The scanner unit 20 includes a laser light emitting unit (not shown), a polygon mirror 22, a lens 23, and a reflecting mirror 24. In the scanner unit 20, the laser light based on the image data emitted from the laser light emitting unit is reflected by the polygon mirror 22, passes through the lens 23, is reflected by the reflecting mirror 24, and is directed to the photosensitive drum 25 described later. Are emitted.

Each process cartridge 21 is inclined in the front-rear direction and the vertical direction (the thickness direction of the paper 3), that is, in the direction inclined from the upper side to the lower side toward the rear side (the direction in which the upper side is inclined toward the front side). A photosensitive drum 25 as a photosensitive member, a scorotron charger 26, a developing roller 27, and a supply roller 28 are provided.
The photosensitive drum 25 has a cylindrical shape, and a drum main body 29 formed by a positively chargeable photosensitive layer whose outermost layer is made of polycarbonate or the like, and an axial center of the drum main body 29 along the axial direction of the drum main body 29. The drum shaft 30 extends. The drum body 29 is provided so as to be rotatable with respect to the drum shaft 30, and the drum shaft 30 rotates on both side walls in the width direction of the casing of the process cartridge 21 (the direction orthogonal to the front-rear direction and the vertical direction, the same applies hereinafter). It is supported impossible. The photosensitive drum 25 is rotationally driven in the same direction (clockwise in the drawing) as the movement direction of the conveyance belt 38 at a contact position (image formation position) with the conveyance belt 38 described later during image formation.

The scorotron charger 26 is a positively charged scorotron charger that includes a wire and a grid, and generates corona discharge. The scorotron charger 26 is disposed behind the photosensitive drum 25 so as not to come into contact with the photosensitive drum 25 with an interval therebetween. Has been.
The developing roller 27 is disposed above the photosensitive drum 25 so as to face the photosensitive drum 25 and is in pressure contact with the photosensitive drum 25. In the developing roller 27, a metal roller shaft 31 is covered with a roller portion 32 made of an elastic member such as a conductive rubber material. More specifically, the roller portion 32 is covered with an elastic roller portion made of conductive urethane rubber, silicone rubber, EPDM rubber, or the like containing carbon fine particles, and the surface of the roller portion. It is formed of a two-layer structure with a coat layer mainly composed of resin, polyimide resin or the like. The roller shaft 31 is rotatably supported on both side walls in the width direction of the process cartridge 21.

The supply roller 28 is disposed above the developing roller 27 so as to face the developing roller 27 and is in pressure contact with the developing roller 27. In the supply roller 28, a metal roller shaft 33 is covered with a roller portion 34 made of a conductive sponge member. The roller shaft 33 is rotatably supported on both side walls in the width direction of the process cartridge 21.
The upper part of the process cartridge 21 is formed as a toner storage chamber 35 for storing toner, and stores toner for each color. That is, in the toner storage chamber 35, for each process unit 17, yellow for the yellow process unit 17Y, magenta for the magenta process unit 17M, cyan for the cyan process unit 17C, and black for the black process unit 17K. A positively chargeable non-magnetic one-component polymerized toner having the following characteristics is accommodated.

  More specifically, as the toner for each color, a substantially spherical polymerized toner obtained by a polymerization method is used. The polymerization toner is a known polymerization such as a suspension polymerization of a styrene monomer such as styrene or an acrylic monomer such as acrylic acid, alkyl (C1 to C4) acrylate, or alkyl (C1 to C4) methacrylate. The main component is a binder resin obtained by copolymerization according to the method, and a toner base particle is formed by adding a colorant, a charge control agent, a wax, etc. to this, and further improves the fluidity. In order to achieve this, an external additive is added.

  As the colorant, the above-mentioned yellow, magenta, cyan and black colorants are blended. Moreover, as a charge control agent, for example, an ionic monomer having an ionic functional group such as an ammonium salt and an ionic monomer such as a styrene monomer or an acrylic monomer can be copolymerized. A charge control resin obtained by copolymerization with a monomer is blended. As external additives, for example, powders of metal oxides such as silica, aluminum oxide, titanium oxide, strontium titanate, cerium oxide and magnesium oxide, inorganic powders such as carbide powders and metal salt powders are blended. Has been.

In each process unit 17, during the image forming operation, the toner for each color stored in each toner storage chamber 35 is supplied to the supply roller 28, and is supplied to the developing roller 27 by the rotation of the supply roller 28. . At this time, the toner is positively frictionally charged between the supply roller 28 and the developing roller 27 to which a developing bias is applied.
On the other hand, the scorotron charger 26 generates a corona discharge by applying a charging bias to uniformly positively charge the surface of the photosensitive drum 25. The surface of the photosensitive drum 25 is uniformly positively charged by the scorotron charger 26 as the photosensitive drum 25 rotates, and then exposed by high-speed scanning of laser light from the scanner unit 20 to form on the paper 3. An electrostatic latent image corresponding to the image to be formed is formed.

  When the photosensitive drum 25 is further rotated, the toner held on the surface of the developing roller 27 and positively charged toner comes into contact with the photosensitive drum 25 by the rotation of the developing roller 27 so as to face the photosensitive drum 25. The electrostatic latent image formed on the surface, that is, the surface of the photosensitive drum 25 that is uniformly positively charged, is supplied to an exposed portion that is exposed to laser light and has a lowered potential. As a result, the electrostatic latent image on the photosensitive drum 25 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 25 for each color.

  Further, the process cartridges 21 of the respective colors are mounted at a higher position as the front process unit 17. Specifically, the mounting position of the process cartridge 21 is increased by a predetermined amount between the adjacent process units 17 in the order of the black process unit 17K, the cyan process unit 17C, the magenta process unit 17M, and the yellow process unit 17Y. Is set.

  As a result, in a state where the process cartridges 25 for each color are mounted on the process unit 17, the photosensitive drum 25 of the process cartridge 21 for each color has a straight line connecting the lower ends of the respective photosensitive drums 25 with respect to the horizontal direction. The unit 60 is disposed so that the upstream side (front side) in the mounting direction extends upward (inclination direction in which the downstream side in the mounting direction of the belt unit 60 is downward).

  In addition, by arranging the photosensitive drum 25 (process cartridge 21) in this way, below the image forming unit 5 where the process unit 17 is arranged side by side and above the paper tray 9 (a paper feeding unit 70 described later). This space has a tapered shape in which the width in the vertical direction becomes narrower toward the rear side (the back side of the main body casing 2) in side view. This tapered space is a mounting space in which a belt unit 60 to be described later is mounted. Corresponding to the tapered shape of the mounting space, the overall shape of the belt unit 60 in the side view is higher and lower on the downstream side in the mounting direction. It is formed in a tapered shape with a narrower width in the direction.

The transfer unit 18 is disposed in the main casing 2 above the sheet feeding unit 4 and below the process unit 17 along the front-rear direction. The transfer unit 18 is a driving roller 36 as a roller, a driven roller 37 as a roller, and a belt. A transfer belt 38, a transfer roller 39, and a belt cleaning device 40.
The drive roller 36 is disposed at a position behind the photosensitive drum 25 of the process cartridge 21 mounted in the black process unit 17K so as not to overlap the photosensitive drum 25 in the horizontal direction. The drive roller 36 is driven to rotate in the direction opposite to the rotation direction of the photosensitive drum 25 (counterclockwise in the figure) during image formation.

The driven roller 37 is disposed in front of the photosensitive drum 25 of the process cartridge 21 mounted on the yellow process portion 17Y and above the driving roller 36. When the drive roller 36 is driven to rotate, the driven roller 37 is driven to rotate in the same direction (counterclockwise in the figure) as the moving direction of the conveying belt 38 at the contact portion with the conveying belt 38 described below.
The conveyor belt 38 is made of an endless belt, and is formed of a resin such as conductive polycarbonate or polyimide in which conductive particles such as carbon are dispersed. The conveying belt 38 is wound between a driving roller 36 and a driven roller 37, and an upper portion thereof (the driven roller 37 on the upstream side in the moving direction of the conveying belt 38 is disposed, and the driving roller 36 is disposed on the downstream side. Are extended in an inclined plane shape that becomes higher toward the front side, and are provided so as to face and contact the photosensitive drum 25 of the process cartridge 21 mounted on each process unit 17 from below. More specifically, the upper portion of the conveyor belt 38 has an angle formed by the movement direction of the upper portion of the driving roller 36 and a horizontal direction, which is a detachment direction of the belt unit 60 described later, due to the detachment of the belt unit 60. It is inclined so as to have an angle at which the contact between the surface of the conveyor belt 38 and each photosensitive drum 25 is released.

  Then, the driven roller 37 is driven by the driving roller 36, and the image forming position where the conveying belt 38 contacts the photosensitive drum 25 of each process unit 17 between the driving roller 36 and the driven roller 37. In FIG. 2, it is moved so as to rotate in the same direction as the photosensitive drum 25. At this time, the drive roller 36 is disposed on the downstream side and the driven roller 37 is disposed on the upstream side in the moving direction of the conveyance belt 38 at the contact position with the photosensitive drum 25, whereby the conveyance belt 38 and the photosensitive drum 25. It is possible to prevent the slack from occurring in the upper portions facing each other. Therefore, the paper 3 can be accurately conveyed by the conveyance belt 38.

  In addition, the transfer roller 39 is disposed so as to face the photosensitive drum 25 of each process unit 17 and the conveyor belt 38 in the conveyor belt 38 wound between the driving roller 36 and the driven roller 37. In the transfer roller 39, a metal roller shaft 41 is covered with a roller portion 42 made of an elastic member such as a conductive rubber material. Further, as shown in FIG. 7, the transfer roller 39 is rotatably supported at both shaft end portions of a roller shaft 41 by a bearing 43 having conductivity.

  Each bearing 43 is elastically supported by a belt unit frame 61 described later via a compression spring 44, and the transfer roller 39 is always pressed against the photosensitive drum 25 by the elastic force of the compression spring 44. Is being energized. Accordingly, the conveyance belt 38 is pressed against the photosensitive drum 25 at an image forming position where the transfer roller 39 and the conveyance belt 38 face each other, and a nip is formed between the photosensitive drum 25 and the conveyance belt 38. As will be described later, when the belt unit 60 is detached from the main casing 2 and the nip between the photosensitive drum 25 and the conveying belt 38 is released, the transfer roller 39 moves upward by the elastic force of the compression spring 44. Then, the upper part of the conveyor belt 38 is lifted upward.

  A transfer bias line 93, which will be described later, is connected to the compression spring 44 coupled to at least one of the bearings 43. At the time of transfer, the transfer roller is transferred from the transfer bias line 93 via the compression spring 44 and the bearing 43. A transfer bias is applied to 39. Further, the transfer roller 39 rotates in the same direction (counterclockwise in the figure) as the circumferential movement direction of the conveyance belt 38 at an image forming position where the transfer roller 39 faces and contacts the conveyance belt 38.

  With reference to FIG. 1, the sheet 3 fed from the sheet feeding unit 4 is moved from the front to the rear by a conveyor belt 38 that is circulated by driving of the driving roller 36 and driven of the driven roller 37. The image forming position between the conveying belt 38 and the photosensitive drum 25 of each process unit 17 is conveyed so as to sequentially pass, and during the conveyance, for each color carried on the photosensitive drum 25 of each process unit 17. The toner images are sequentially transferred, whereby a color image is formed on the paper 3.

  That is, for example, when the yellow toner image carried on the surface of the photosensitive drum 25 of the yellow process unit 17Y is transferred to the paper 3, the magenta toner carried on the surface of the photosensitive drum 25 of the magenta process unit 17M is then transferred. The toner image is transferred onto the sheet 3 on which the yellow toner image has already been transferred, and the cyan toner image carried on the surface of the photosensitive drum 25 of the cyan process unit 17C and the black process unit 17K are operated in the same manner. The black toner image carried on the surface of the photosensitive drum 25 is transferred in a superimposed manner, whereby a color image is formed on the paper 3.

  In the formation of such a color image, the color laser printer 1 has a tandem apparatus configuration in which a plurality of process cartridges 21 are provided for each color in each process unit 17, so that the speed for forming a monochrome image is increased. A toner image for each color can be formed at approximately the same speed to achieve rapid color image formation. Therefore, it is possible to form a color image while reducing the size.

The belt cleaning device 40 is disposed below the transport belt 38 and in a relatively large space formed near the driven roller 37 (a space larger than a space formed near the driving roller 36). The belt cleaning device 40 includes a cleaning box 46 and a cleaning roller 47.
The cleaning box 46 has a box shape and opposes the lower portion of the conveyance belt 38 (the portion where the driving roller 36 is disposed upstream and the downstream driven roller 37 is disposed in the moving direction of the conveyance belt 38). An opening is formed in a part of the side, and the internal space is formed as a removed matter storage part that stores the deposits removed from the conveyor belt 38.

  The cleaning roller 47 is made of a metal roller, is rotatably supported at the opening of the cleaning box 46, and is in contact with the surface (lower surface) of the lower portion of the transport belt 38. The cleaning roller 47 is rotationally driven in the direction opposite to the moving direction of the conveying belt 38 at the position of contact with the conveying belt 38 (counterclockwise in the figure) during the cleaning operation. A cleaning bias is applied to the cleaning roller 47 from a cleaning bias line 94 described later.

  The toner adhering to the conveying belt 38 due to contact with the photosensitive drum 25 and the adhering matter such as paper dust adhering to the conveying belt 38 due to contact with the paper 3 are moved to the cleaning roller 47 when the conveying belt 38 is moved. It is electrically captured by the cleaning roller 47. Then, the trapped deposits are removed from the cleaning roller 47 in the cleaning box 46 and stored in a removed matter storage section in the cleaning box 46.

The fixing unit 19 is disposed behind the transfer unit 18. The fixing unit 19 includes a heating roller 48 and a pressure roller 49.
The heating roller 48 is made of a metal base tube having a release layer formed on the surface thereof, and a halogen lamp is provided along the axial direction thereof. Then, the surface of the heating roller 48 is heated to the fixing temperature by the halogen lamp. The pressure roller 49 is provided so as to press the heating roller 48.

Then, the color image transferred onto the paper 3 is then conveyed to the fixing unit 19 and thermally fixed while the paper 3 passes between the heating roller 48 and the pressure roller 49.
The paper discharge unit 6 includes a paper discharge side U-shaped path 50, a paper discharge roller 51 as a discharge unit, and a paper discharge tray 52.
The discharge-side U-shaped path 50 has an upstream end adjacent to the fixing unit 19 at the lower side and a downstream end at the upper side so that the sheet 3 is fed rearward. Is formed as a substantially U-shaped paper 3 conveyance path so that the paper 3 is discharged forward.

The paper discharge roller 51 is provided as a pair of rollers at the downstream end of the paper discharge side U-shaped path 50.
The discharge tray 52 is formed on the upper surface of the main casing 2 as an inclined wall that is inclined downward from the front to the rear.
The sheet conveyed from the fixing unit 19 is fed rearward to the upstream end of the discharge side U-shaped path 50, and the conveyance direction is reversed in the discharge side U-shaped path 50. The paper is ejected forward onto a paper ejection tray 52 by a paper ejection roller 51.

  In this color laser printer 1, the transfer unit 18, the pickup roller 10, the paper feed roller 11, the rear conveyance roller 13 and the pair of registration rollers 14 are integrally held by a belt unit frame 61 as a unit frame. Thus, a belt unit 60 that can be attached to and detached from the main body casing 2 in the horizontal direction from the front side is configured. In addition, the paper tray 9 and the front transport roller 13 are integrally held by the paper feed unit frame 71, so that the paper feed as a recording medium accommodation unit that can be attached to and detached from the main body casing 2 in the horizontal direction from the front side. A unit 70 is configured.

  As shown in FIG. 5, the belt unit frame 61 includes a left side plate 65 and a right side plate 66 that are opposed to each other with a gap in the width direction, a bottom plate 62 that is laid between them, and a front end of the bottom plate 62. A sheet guide member 64 that is swingably mounted between the left side plate 65 and the right side plate 66 and guides the sheet 3 conveyed on the paper feeding side U-shaped path 12 onto the conveying belt 38 above the section. It has.

  In this belt unit frame 61, between the left side plate 65 and the right side plate 66, the pickup roller 10, the paper feed roller 11, the rear conveyance roller 13, the pair of registration rollers 14, the drive roller 36, and the driven roller 37 is installed rotatably. Further, bearings 43 (see FIG. 6) at both ends of the roller shaft 41 of the transfer roller 39 are supported by the left side plate 65 and the right side plate 66, respectively, so that the transfer is performed between the left side plate 65 and the right side plate 66. A roller 39 is rotatably installed. Further, the bottom plate 62 is formed with a concave portion 103 which is recessed one step lower than the front and rear portions thereof in a portion facing the portion excluding the vicinity of the driven roller 37 of the conveying belt 38, and a belt is formed on the front side in the concave portion 103. A cleaning device 40 is arranged.

The lower end portions of the left side plate 65 and the right side plate 66 are bent inward in the width direction to form a paper feed unit guide 67 for guiding the movement when the paper feed unit 70 (paper feed unit frame 71) is attached or detached. ing.
The sheet feeding unit frame 71 includes a left side plate 72 and a right side plate 73 that are opposed to each other with a space therebetween in the width direction, and a front plate 74 (see FIG. 1) that is installed between these front end portions. Yes. The sheet feeding unit frame 71 holds the sheet tray 9 between the left side plate 72 and the right side plate 73 behind the front plate 74.

  Further, the left side plate 72 and the right side plate 73 are opposed to the left side plate 65 and the right side plate 66 of the belt unit frame 61 with a predetermined interval, respectively. The left side plate 72 and the right side plate 73 are provided with a protruding portion 75 so as to protrude from each upper end portion toward the outside in the width direction and extend in the front-rear direction. The sheet feeding unit frame 71 has both overhang portions 75 engaged with the sheet feeding unit guide 67 of the belt unit frame 61 from above, so that the sheet feeding unit guide 67 is moved away from the sheet feeding unit guide 67. Along the horizontal direction, it is slidably held.

The main body casing 2 is a left main body side plate that is disposed to face the left side plate 65 and the right side plate 66 of the belt unit frame 61 with a predetermined interval on the outer side in the width direction with the belt unit 60 mounted. 81 and a right main body side plate 82 are provided.
A belt unit guide 83 is formed at each lower end of the left main body side plate 81 and the right main body side plate 82 as a guide member that protrudes inward in the width direction and extends long in the front-rear direction. A guide portion 85 is formed at the upper end portion of each belt unit guide 83 by cutting out a portion closer to the inside in the width direction into a rectangular shape in front view over the entire length direction. Then, the lower end portions of the left side plate 65 and the right side plate 66 of the belt unit frame 61 are fitted into these guide portions 85, so that the belt unit frame 61 is guided to the guide casing 85 (belt unit) with respect to the main body casing 2. It is slidably mounted in the horizontal direction along the guide 83).

  Further, as shown in FIG. 1, the main body casing 2 includes an electrode holder 86 disposed opposite to the belt unit frame 61 on the rear side in a state where the belt unit frame 61 is attached to the main body casing 2. Yes. As shown in FIG. 6, the electrode holder 86 holds a plurality (six) of electrodes 92 arranged in the width direction so as to extend forward. Further, a positioning convex portion 101 having a substantially rectangular shape in bottom view extending toward the front is formed on the front surface of the electrode holder 86 at the center in the width direction.

FIG. 6 is a view as seen from below the belt unit 60 (belt unit frame 61).
The rear end portion of the belt unit frame 61 is provided with a plurality of terminals 91 as a plurality of power supply terminals that are respectively connected to the electrodes 92 when mounted on the main casing 2. Each terminal 91 extends in the vertical direction along the rear end surface of the recess 103, is bent rearward, and is formed in a substantially L shape in side view protruding rearward from the rear end surface of the recess 103. Each terminal 91 is arranged such that the electrode 92 contacts the lower surface of the portion protruding from the belt unit frame 61 in a state where the belt unit frame 61 is mounted on the main casing 2. Further, when the belt unit 60 is attached to the main casing 2, the terminals 91 and the electrodes 92 are connected to the photosensitive belts at the same time or after the terminals 91 and the electrodes 92 are connected. 25 are arranged in such a positional relationship as to contact 25.

  Further, in the rear end portion of the belt unit frame 61 that protrudes rearward from the recess 103, the electrode holder 86 is positioned in a state where the belt unit frame 61 is mounted on the main casing 2 on the lower surface. A positioning groove 102 into which the convex portion 101 is fitted is formed. The belt unit frame 61 can be positioned in the width direction with respect to the main body casing 2 by fitting the positioning convex portions 101 into the positioning groove portions 102. Further, since the positioning convex portion 101 is formed on the electrode holder 86, the belt unit frame 61 is positioned in the width direction with respect to the main body casing 2 with the positioning convex portion 101 as a reference, thereby the belt. A displacement in the width direction between each terminal 91 provided in the unit frame 61 and each electrode 92 held by the electrode holder 86 can be prevented. Therefore, reliable connection between each terminal 91 and each electrode 92 can be achieved.

  The belt unit frame 61 includes four transfer bias lines 93 for supplying a transfer bias to the transfer roller 39, a cleaning bias line 94 for supplying a cleaning bias to the cleaning roller 47, and the inside of the conveyor belt 38. , A neutralizing bias line 96 for supplying a neutralizing bias to the neutralizing needle 95 extending along each transfer roller 39 is provided.

Each transfer bias line 93 has one end connected to the terminal 91, extends in the front-rear direction, bends in the middle and extends in the width direction, and the other end compresses a compression spring 44 that biases one (left side) bearing 43 (see FIG. 7).
One end of the cleaning bias line 94 is connected to the terminal 91, extends in the front-rear direction, bends in the middle and extends in the width direction, and the other end is connected to one end of the cleaning roller 47.

  One end of the static elimination bias line 96 is connected to the terminal 91 and extends in the front-rear direction. As shown in FIG. 8, each static elimination needle 95 is formed with an insertion hole through which the static elimination bias line 96 is inserted. The static elimination bias line 96 is inserted into the insertion hole of each static elimination needle 95 and is made of solder or the like. Each static elimination needle 95 is connected by a connecting material 97. Further, the upper end portion of each static elimination needle 95 is formed in a shape in which a large number of mountain-shaped protrusions are connected, and is in contact with the back surface of the upper portion of the conveyor belt 38.

  According to the above configuration, by sliding the belt unit frame 61 along the guide portion 85 (belt unit guide 83), the belt unit 60 is a straight line extending horizontally from the front side with respect to the main body casing 2. It is possible to attach and detach along the attachment / detachment path 100 (see FIG. 3). Further, by sliding the paper feed unit frame 71 along the paper feed unit guide 67, the paper feed unit 70 can be attached to and detached from the main body casing 2 and the belt unit 60 in the horizontal direction from the front side.

  Thereby, as shown in FIG. 2, only the paper feeding unit 70 can be attached to and detached from the main casing 2. As shown in FIG. 3, the belt unit 60 can be attached to and detached from the main casing 2 in the same direction as the attaching / detaching direction of the sheet feeding unit 70 integrally with the sheet feeding unit 70. Therefore, the belt unit 60 and the paper feeding unit 70 can be attached and detached with a single operation. As a result, it is possible to improve the operability when the belt unit 60 and the paper feeding unit 70 are attached and detached.

Moreover, if both the belt unit 60 and the paper feeding unit 70 are detached from the main casing 2, a large space is formed below the image forming unit 5 as shown in FIG. When a jam of the paper 3 occurs, it is possible to easily remove the jammed paper 3 by putting a hand in the large space from the front side.
In this color laser printer 1, the attachment / detachment path 100 does not bend and extends in a straight line along the horizontal direction, and the belt unit 60 is removed from the main casing 2 along the attachment / detachment path 100. It can be moved in a straight line until the departure is completed. Further, the belt unit 60 can be moved along the attachment / detachment path 100 in a straight line from the start of attachment to the main body casing 2 to the completion of attachment. Therefore, the attaching / detaching operation of the belt unit 60 with respect to the main body casing 2 can be performed very easily.

  Further, by detaching the belt unit 60 from the main casing 2, as shown in FIG. 4, the paper guide member 64 is rotated, and the conveying belt 38 and the belt cleaning device 40 are moved upwardly or integrally. The belt unit frame 61 can be lifted and taken out. Therefore, the conveyance belt 38 and the belt cleaning device 40 can be easily replaced or maintained.

  The upper portion of the conveyor belt 38 has an angle formed by the movement direction of the upper portion of the drive roller 36 and a horizontal direction, which is a detachment direction of the belt unit 60 described later, by the separation of the belt unit 60. Since the surface is inclined so that the contact between the photosensitive drums 25 and the photosensitive drums 25 is released, when the belt unit 60 is detached along the linear attachment / detachment path 100, the conveyance belt 38 is associated with the separation. The contact between the surface and the photosensitive drum 25 is released. Therefore, the operation of moving the belt unit 60 in the direction intersecting the horizontal direction in order to separate the belt from the photosensitive drum 25 can be eliminated, and the operability when the belt unit 60 is detached from the main body casing 2 is improved. Can be achieved.

  On the other hand, when the belt unit 60 is attached to the main casing 2, if the belt unit 60 is attached along the linear attachment / detachment path 100, the surface of the conveyance belt 38 comes into contact with each photosensitive drum 25 along with the attachment. . Therefore, after the belt unit 60 is moved in the direction along the attachment / detachment path, the operation of moving the belt unit 60 in the direction intersecting the horizontal direction in order to bring the conveyance belt 38 into contact with the photosensitive drum 25 can be eliminated. The operability when the belt unit 60 is attached to the main casing 2 can be improved.

In addition, when the belt unit 60 is attached to and detached from the main casing 2, it is not necessary to move the belt unit 60 in a direction that intersects with the direction along the attachment / detachment path 100, thereby simplifying the configuration for guiding the movement of the belt unit 60. And cost can be reduced.
Furthermore, the belt unit 60 can be easily detached from the main casing 2 because the belt unit 60 is separated from the main body casing 2 in a substantially horizontal direction. For this reason, the detachability operability of the belt unit 60 can be further improved.

  Further, since the belt unit 60 is detached in the direction orthogonal to the rotation axis of the photosensitive drum 25, the contact between the surface of the conveyor belt 38 and each photosensitive drum 25 is released immediately after the belt unit 60 moves in the separation direction. be able to. Therefore, it is possible to prevent the rubbing between the transport belt 38 and each photosensitive drum 25. Therefore, damage to each photosensitive drum 25 or the conveyance belt 38 due to sliding friction between the conveyance belt 38 and each photosensitive drum 25 can be prevented.

Further, since the movement of the belt unit 60 is guided by the belt unit guide 83, the belt unit 60 can be easily detached from the main body casing 2. For this reason, the detachability operability of the belt unit 60 can be further improved.
Further, as shown in FIG. 1, since the belt unit 60 and the paper feeding unit 70 are arranged so as to overlap in the detaching direction of the belt unit 60, that is, in the horizontal direction, the size of the color laser printer 1 in the vertical direction. Can be reduced.

  Furthermore, since each terminal 91 is provided at the end (rear end) on the downstream side in the mounting direction of the belt unit 60, it is not exposed until the belt unit 60 is completely detached from the main body casing 2. Therefore, it is possible to prevent the user from touching the terminal 91. Moreover, since the electrode 92 connected to each terminal 91 is arrange | positioned with respect to the belt unit 60 in the mounting direction downstream (back side), it can also prevent that a user touches the electrode 92. FIG. As a result, contamination of each terminal 91 and each electrode 92 can be prevented.

Further, since the terminals 91 are arranged side by side in the width direction, when the belt unit 60 is attached to the main casing 2, the connection between the plurality of terminals 91 and the electrodes 92 can be achieved simultaneously.
Further, when the belt unit 60 is attached to the main casing 2, the terminals 91 and the electrodes 92 are connected to the photosensitive belts at the same time or after the terminals 91 and the electrodes 92 are connected. Therefore, it is not necessary to slide the belt unit 60 for connecting the terminal 91 and the electrode 92 after the conveying belt 38 contacts each photosensitive drum 25. In addition, it is possible to prevent sliding between the conveyor belt 38 and each photosensitive drum 25. Therefore, damage to each photosensitive drum 25 or the conveyance belt 38 due to sliding friction between the conveyance belt 38 and each photosensitive drum 25 can be prevented.

Further, in this color laser printer 1, the mounting position of the process cartridge 21 is set by a predetermined amount between the adjacent process units 17 in the order of the black process unit 17K, the cyan process unit 17C, the magenta process unit 17M, and the yellow process unit 17Y. It is set to be high.
More specifically, the compression spring 44 (see FIG. 7) urges the transfer roller 39 (bearing 43) upward, and the movement direction at the start of detachment of the belt unit 60 depends on the compression spring 44. Since the horizontal direction is perpendicular to the urging direction of the transfer roller 39, as shown in FIG. 3, when the belt unit 60 is detached from the main casing 2, the photosensitive drums 25 are pressed with the conveying belt 38 interposed therebetween. Each transfer roller 39 is moved upward by the elastic force of the compression spring 44, and the conveyor belt 38 is lifted upward (in the urging direction by the compression spring 44). In consideration of the lifting of the transport belt 38, the shift amount A of the mounting position of the process unit 17 adjacent in the front-rear direction (the shift amount of the lower end position of the photosensitive drum 25) A is the lift amount of the transport belt 38 from the shift amount A. A value C obtained by subtracting B is set to be larger than zero.

From another viewpoint, when the belt unit 60 is detached from the main casing 2, the belt unit 60 has a process unit 17 in which the lift amount B of the transport belt 38 (transfer roller 39) is adjacent in the front-rear direction. The transfer roller 39 is supported so as to be less than the deviation amount A of the mounting position.
Therefore, when the belt unit 60 is detached from the main casing 2, even if the conveyance belt 38 is lifted, it is possible to reliably prevent the conveyance belt 38 and each photosensitive drum 25 from rubbing. As a result, it is possible to prevent damage to the photosensitive drum 25 or the conveyance belt 38 due to sliding between the conveyance belt 38 and each photosensitive drum 25.

  In FIG. 3, the deviation amount between the mounting position of the process cartridge 21 in the black process section 17K and the mounting position of the process cartridge 21 in the cyan process section 17C is shown as A, but the process cartridge 21 in the cyan process section 17C is shown in FIG. The deviation amount between the attachment position and the attachment position of the process cartridge 21 in the magenta process unit 17M is also A, and this deviation amount A has a value C obtained by subtracting the lift amount B of the conveying belt 38 from the deviation amount A. It is set to be larger. Similarly, the deviation amount between the mounting position of the process cartridge 21 in the magenta process section 17M and the mounting position of the process cartridge 21 in the yellow process section 17Y is A, and this deviation amount A is changed from the deviation amount A to the transport belt 38. Is set so that the value C obtained by subtracting the floating amount B is greater than zero.

  Further, in this color laser printer 1, the pickup roller 10 in the paper feeding unit 4 is opposite in the pickup direction of the paper 3 toward the front and the conveyance direction of the paper 3 in the rear at each image forming position. Direction, and the conveyance direction of the sheet 3 toward the rear at each image forming position is opposite to the discharge direction of the sheet 3 toward the front of the sheet discharge roller 51 in the sheet discharge unit 6. It is arranged to be. Therefore, it is possible to reduce the size of the apparatus while securing the conveyance path for the sheet 3.

In the color laser printer 1, in each process unit 17, the process cartridge 21 is inclined in the front-rear direction and the vertical direction (the thickness direction of the paper 3), that is, from the upper side to the lower side. It is attached and detached along the direction in which it is inclined. Therefore, the operability of attaching / detaching the process cartridge 21 can be improved.
Furthermore, in the color laser printer 1, a plurality of process cartridges 21 and a plurality of scanner units 20 corresponding thereto are alternately arranged in the front-rear direction. Therefore, the apparatus can be reduced in size by these efficient arrangements.

  In the above description, the tandem color laser printer 1 that directly transfers from the photosensitive drums 25 to the paper 3 has been exemplified. However, the present invention is not limited to this, and for example, toner for each color. An image can also be configured as an intermediate transfer type color laser printer in which an image is temporarily transferred from each photoconductor to an intermediate transfer belt and then transferred to a sheet at once. In this case, the belt of the present invention is an intermediate transfer belt. May be. It can also be configured as a monochrome laser printer.

  Further, the terminal 91 includes a terminal for supplying a transfer bias, a terminal for supplying a cleaning bias, and a terminal for supplying a neutralizing bias. A terminal may be included.

1 is a side sectional view showing an embodiment of a color laser printer as an image forming apparatus of the present invention. FIG. 2 is a side sectional view showing a state where a paper feeding unit of the color laser printer shown in FIG. 1 is detached. FIG. 2 is a side sectional view showing a state where a paper feeding unit and a belt unit of the color laser printer shown in FIG. 1 are detached. FIG. 4 is a side cross-sectional view showing a state where a conveyor belt and a belt cleaning device 40 are taken out from the belt unit frame shown in FIG. 3. FIG. 2 is a front sectional view of the color laser printer shown in FIG. 1. It is a bottom view of the belt unit shown in FIG. FIG. 7 is a perspective view of the vicinity of the shaft end portion of the transfer roller shown in FIG. 6. It is a perspective view of the connection part of the static elimination bias line and static elimination needle shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color laser printer 3 Paper 10 Pickup roller 25 Photosensitive drum 36 Drive roller 37 Driven roller 38 Conveyor belt 51 Paper discharge roller 60 Belt unit 61 Belt unit frame 70 Paper feed unit 83 Belt unit guide 91 Terminal 92 Electrode 100 Attachment / detachment path

Claims (18)

A belt unit comprising a plurality of rollers and a belt supported by the plurality of rollers so as to be capable of rotating around;
An image forming apparatus including a plurality of photoconductors arranged along a circumferential movement direction of the belt and contacting a surface of the belt;
The belt unit is detachably attached to the image forming apparatus along a linear attachment / detachment path,
The belt is in contact with each photoconductor in a state where the belt unit is detached from the image forming apparatus due to an elastic force of a compression spring, as compared with a state where the belt unit is attached to the image forming apparatus. Is configured to float in a direction orthogonal to the direction of separation of the belt unit and the direction of the rotation axis of the roller,
The plurality of photosensitive members are arranged so that positions in a direction perpendicular to the belt unit detachment direction and the rotation axis direction of the roller are shifted by a predetermined amount sequentially from the upstream side of the belt unit detachment direction. ,
The image forming apparatus according to claim 1, wherein the predetermined amount is set to be equal to or more than a lift amount of the belt when the belt unit is detached from the image forming apparatus.   The image forming apparatus according to claim 1, wherein a direction in which the belt unit is detached is a substantially horizontal direction. The photoconductor is rotatable about an axis extending in the rotation axis direction of the roller,
The image forming apparatus according to claim 1, wherein a direction in which the belt unit is detached is a direction orthogonal to an axis of the photoconductor.   4. The image forming apparatus according to claim 1, further comprising a guide member that guides movement of the belt unit when the belt unit is detached from the image forming apparatus. A recording medium storage unit that stores the recording medium and is detachably attached to the image forming apparatus;
5. The image forming apparatus according to claim 1, wherein a direction in which the recording medium accommodation unit is detached and a direction in which the belt unit is detached are the same direction.   6. The image forming apparatus according to claim 5, wherein the belt unit and the recording medium accommodation unit are detachably attached to the image forming apparatus.   The image forming apparatus according to claim 5, wherein a part of the belt unit is disposed so as to overlap the recording medium accommodation unit in a direction in which the belt unit is detached.   The belt unit is provided at an end of the belt unit on the downstream side in the mounting direction with respect to the image forming apparatus, and includes a power supply terminal for supplying power to the belt unit. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 8, wherein a plurality of the power supply terminals are provided along a rotation axis direction of the roller. In a state where the belt unit is mounted on the image forming apparatus, the belt unit includes electrodes connected to the power supply terminals.
The contact of the belt with the photoconductor when the belt unit is attached to the image forming apparatus is achieved after the connection between the power supply terminals and the electrodes. Image forming apparatus.   The power supply terminal extends toward the downstream side in the mounting direction of the belt unit with respect to the image forming apparatus, along the bottom surface of the belt unit.
  The image forming apparatus according to claim 10, wherein the electrode extends toward an upstream side in a mounting direction of the belt unit with respect to the image forming apparatus. The feeding terminal, said characterized in that it comprises a terminal for supplying a transfer bias for the developer image carried on the photosensitive member onto a recording medium, according to any one of claims 8 to 11 Image forming apparatus. The power supply terminal includes at least one of a terminal for supplying a cleaning bias for cleaning the belt, a terminal for supplying a bias for discharging the belt, and a terminal for ground connection of the belt unit. The image forming apparatus according to claim 12 , comprising any one of them. Before Symbol belt unit, by the movement to the withdrawal direction, characterized in that the contact between the plurality of the photosensitive member is released at the same time, the image forming apparatus according to any one of claims 1 to 13.   15. The image forming apparatus according to claim 1, wherein the belt is a conveyance belt for conveying a recording medium. In an image forming apparatus provided with a process cartridge provided with the photoreceptor for each color,
A supply means for picking up and supplying the recording medium; and a discharging means for discharging the recording medium,
The process cartridges of the respective colors are arranged between the supply unit and the discharge unit in the conveyance path of the recording medium,
The pickup direction of the recording medium picked up by the supply means and the conveyance direction of the recording medium at the image forming position where images are sequentially formed by the process cartridges of the respective colors are opposite directions,
16. The recording medium according to claim 1, wherein the recording medium is disposed such that a conveyance direction of the recording medium at the image forming position is opposite to a discharge direction of the recording medium discharged by the discharge unit. The image forming apparatus according to any one of the above.   17. The process cartridge according to claim 16, wherein the process cartridge is attached / detached along a direction inclined with respect to a conveyance direction of the recording medium at the image forming position and a thickness direction of the recording medium orthogonal thereto. The image forming apparatus described. A plurality of exposure apparatuses are provided corresponding to the process cartridges of the respective colors,
18. The process cartridge according to claim 16, wherein the process cartridge of each color and a plurality of exposure apparatuses corresponding to the process cartridge are alternately arranged in a conveyance direction of the recording medium at the image forming position. Image forming apparatus.

Images