JP5196841B2 - Image forming apparatus - Google Patents

Description

  The present invention provides an image for forming an image on a recording medium by detachably mounting a plurality of process cartridges (image forming units) having an image carrier and image forming process means acting on the image carrier on an apparatus main body. The present invention relates to a forming apparatus.

  Examples of the image forming apparatus as described above include a tandem type color electrophotographic apparatus using a plurality of process cartridges for forming respective color component images such as yellow, magenta, cyan, and black. The color electrophotographic apparatus is a color electrophotographic copying machine, a color electrophotographic printer (color laser printer, color LED printer, etc.) and the like.

  In the case of an electrophotographic system, the process cartridge is an electrophotographic photosensitive member as an image carrier and an image forming process means that acts on the electrophotographic photosensitive member, and is integrally formed into a cartridge. It can be attached to and detached from the apparatus main body. The image forming process means includes, for example, a charging means for uniformly charging the photoconductor, a developing means for developing an electrostatic image formed on the photoconductor as a toner image, and a toner remaining on the photoconductor after the toner image is transferred. At least one of the cleaning means to be removed. The apparatus main body is an image forming apparatus portion excluding the process cartridge.

  The process cartridge can be attached to and detached from the apparatus main body by the user himself. Therefore, the maintenance of the image forming apparatus can be performed by the user himself / herself without depending on the service person.

Patent Document 1 describes the following configuration as a configuration in which four process cartridges (photosensitive unit) are attached to and detached from the apparatus main body. That is, all four process cartridges are supported by a common holding member that can move up and down in conjunction with the turning operation of the operation lever. Then, all four process cartridges are moved to the image forming position in the apparatus main body and held in the positioning state by the downward movement of the holding member interlocked with the rotation operation of the operation lever in one direction. Further, all four process cartridges are moved from the image forming position to the mounting position with respect to the apparatus main body by the upward movement of the holding member interlocked with the rotation operation of the operation lever in the reverse direction.
JP 2002-62782 A

  However, if the process cartridge is, for example, compatible with A3 size, only one process cartridge weighs 2-3 kg. Therefore, a large force is required to move the common holding member that supports all four process cartridges as in the above configuration. Therefore, as in Patent Document 1, the configuration of moving by a manual operation lever requires a large operation force, and there is a problem that the burden on the user (user) increases. Even in the case of a configuration that moves with a driving source such as a motor, it is necessary to use a motor with a high driving force or to configure a driving means using a driving gear train with a high reduction ratio. There was a problem that the cost would be increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing a load when a process cartridge is moved.

Typical configuration of an image forming apparatus according to the present invention for achieving the above object, a first image forming unit detachably mountable to the apparatus main body of a chromatic image forming apparatus an image bearing member, an image bearing a second image forming units have a body detachably attached to the apparatus main body, comprising the said first image forming unit and said second image forming unit is removable portion to the device body to the image forming position when the image is formed from the mounting position when mounted in the apparatus main body, an image forming apparatus having a moving means for moving from the image forming position in the opposite to the mounting position, and the first image forming unit and the second image forming unit, wherein is positioned in contact with the abutting portion of the frame of the apparatus main body when moved into the image forming position, the abutment when in the mounting position Spaced apart from, the moving means is driven by one driving source, the start timing of the movement from the mounting position of the second image forming unit and the first image forming unit to the image forming position Further , the start timing of the movement from the image forming position to the mounting position is made different .

  According to the present invention, in a configuration in which a plurality of image forming units are moved, it is possible to reduce a load when moving the image forming units.

<< Overall Configuration of Image Forming Apparatus >>
The image forming apparatus in this embodiment is an electrophotographic full-color printer having a plurality of image forming units, here, four image forming units. FIG. 1 is a schematic front sectional view of the image forming apparatus. FIG. 2 is an external perspective view of the image forming apparatus. FIG. 3 is an external perspective view of the image forming apparatus showing a state where the open / close door is opened and one image forming unit is being inserted or removed.

  The image forming apparatus 1 records a full-color image or a monochrome image corresponding to electrical image information input from an external host apparatus B that is communicably connected to a control circuit unit (CPU) A that is a control unit of the apparatus. Can be formed and output on a recording material P. The host device B is a computer image reader or the like. The control circuit unit A performs image forming sequence control by exchanging electrical signals with the host apparatus B and exchanging electrical signals with the image forming process equipment.

  Here, with respect to the image forming apparatus 1, the front side or the front side (front side) is the side on which the open / close door 2 is provided. The back side (rear side) is the opposite side. Left and right are left or right when the device is viewed from the front. The apparatus main body is an image forming apparatus part excluding the image forming unit.

  In FIG. 1, reference numeral 4 denotes an intermediate transfer belt unit (belt-shaped transfer means, transfer conveying means). The unit 4 includes a secondary transfer inner roller 5 disposed on the right side of the apparatus, a driven roller 6 disposed on the left side of the apparatus, a tension roller 7 disposed near the driven roller, and the three rollers. And an intermediate transfer belt 8 wound between rollers. An intermediate transfer belt (hereinafter abbreviated as a belt) 8 is a flexible endless belt made of a dielectric material. The three rollers 5, 6, 7 are arranged in parallel with the rotational axis direction being the front-rear direction. The tension roller 7 is urged to move upward to give tension to the belt 8. The belt 8 is driven to rotate at a predetermined speed in the counterclockwise direction indicated by the arrow as the secondary transfer inner roller 5 is driven to rotate. On the inner side of the belt portion on the descending side between the driven roller 6 and the secondary transfer inner roller 5, four first to fourth ones are sequentially spaced from the left side to the right side in the belt moving direction. A next transfer roller (primary transfer means) 9 is disposed in parallel with the rotational axis direction being the front-rear direction. A belt cleaner 10 for cleaning the outer surface of the belt 8 is disposed outside the belt suspension portion of the driven roller 6.

  A plurality of image forming units are arranged in parallel below the belt 8. In the apparatus of this embodiment, four image forming units 11Y, 11M, 11C, and 11K are arranged in order from the left side to the right side along the moving direction of the belt portion on the lower side between the driven roller 6 and the secondary transfer inner roller 5. It is arranged.

  The image forming unit 11Y is a first image forming unit, the image forming unit 11M is a second image forming unit, the image forming unit 11C is a third image forming unit, and the image forming unit 11K is a fourth image forming unit. Each image forming unit has an image carrier on which a toner image is formed, and is a process cartridge that can be attached to and detached from the image forming apparatus main body. Hereinafter, it is abbreviated as a cartridge. A configuration for attaching and detaching each cartridge to the apparatus main body 3 will be described later.

  The intermediate transfer belt unit 4 is arranged across the first, second, third, and fourth cartridges 11Y, 11M, 11C, and 11K, and is in contact with the image carriers of the cartridges 11Y, 11M, 11C, and 11K. The belt-like transfer means for transferring the image. Each of the cartridges 11Y, 11M, 11C, and 11K is disposed below the intermediate transfer belt unit 4 in the vertical direction of the image forming apparatus.

  Each cartridge is an electrophotographic process mechanism having the same configuration, and has a drum-type electrophotographic photosensitive member (hereinafter abbreviated as a drum) 12 as an image carrier (image forming medium). The image forming apparatus also includes a primary charger 13, a developing device 14, and a drum cleaning device 15, which are image forming process units that act on the drum 12. The primary charger 13 is a charging unit that uniformly charges the surface of the drum 12 to a predetermined polarity and potential, and uses a charging roller. The developing device 14 is a developing unit that visualizes an electrostatic image formed on the drum surface by supplying a developer to the drum 12 as a toner image. The drum cleaner 15 is a cleaning unit that cleans the surface of the drum 12 and uses a cleaning blade.

  The first cartridge 11Y forms a yellow (Y) toner image on the drum 12, and the developer 14 stores Y toner as a developer. The second cartridge 11M forms a magenta (M) toner image on the drum 12, and the developing device 14 contains M toner as a developer. The third cartridge 11 </ b> C forms a cyan (C) toner image on the drum 12, and the developer 14 contains C toner as a developer. The fourth cartridge 11K forms a black (K) toner image on the drum 12, and the developer 14 contains K toner as a developer.

  Each cartridge is arranged in parallel with the rotation axis direction of the drum 12 in the front-rear direction, and the upper surface of the drum 12 is the descending side of the belt 8 between the driven roller 6 and the secondary transfer inner roller 5. In contact with the lower surface of the belt portion. Each of the first to fourth primary transfer rollers 9 is opposed to the upper surface of the drum 12 of the corresponding cartridge with the belt portion on the downstream side of the belt 8 interposed therebetween. In each cartridge, a contact portion between the drum 12 and the belt 8 is a primary transfer portion T1.

  Below the first to fourth cartridges 11Y, 11M, 11C, and 11K, a laser scanner unit 16 that is an exposure unit for the drum 12 of each cartridge is disposed. This unit 16 includes laser light emitting means for performing modulated light emission corresponding to time-series electric digital pixel signals of image information, a polygon mirror, an imaging optical system, a reflection mirror, and the like.

  Below the laser scanner unit 16, a paper cassette 17 in which recording materials P are stacked and stored is disposed. The paper cassette 17 is inserted and removed from the front side of the image forming apparatus (front loading). Reference numeral 17 a (FIG. 2) denotes a handle for cassette insertion / removal operation provided on the front plate of the paper cassette 17.

  A secondary transfer outer roller (secondary transfer means) 22 is disposed outside the belt suspension portion of the secondary transfer inner roller 5. A contact portion between the belt 8 and the secondary transfer outer roller 22 is a secondary transfer portion T2.

  The operation for forming a full-color image is as follows. An electrical recording image signal relating to a full-color image is input from the host device B to the control circuit unit A. The control circuit unit A performs necessary image processing on the input recording image signal, and drives the first to fourth cartridges 11Y, 11M, 11C, and 11K at a predetermined control timing. As a result, each drum 12 is driven to rotate at the same predetermined speed in the clockwise direction indicated by the arrow. A charging roller 13 as a primary charger rotates following the rotation of the drum 12. The belt 8 is rotated at the same speed as the rotation speed of the drum 12 in the counterclockwise direction of the arrow by the rotational drive of the secondary transfer inner roller 5 as a driving roller. The surface of the rotating drum 12 is uniformly charged to a predetermined polarity and potential by the charging roller 13. The charged surface of the drum 12 is image-exposed by the laser scanner unit 16. The unit 16 outputs a laser beam L modulated in response to the image-processed recording image signal input from the control circuit unit A, and scans and exposes the charged surface of the drum 12. As a result, an electrostatic image corresponding to the scanning exposure pattern is formed on the drum surface. The formed electrostatic image is developed as a toner image by the developing roller 14a (FIG. 5) of the developing device 14.

  By the electrophotographic process as described above, in the first cartridge 11Y, a Y color toner image corresponding to the Y color component image of the full color image is formed on the surface of the drum 12 at a predetermined control timing. In the second cartridge 11M, an M color toner image corresponding to the M color component image of the full color image is formed on the surface of the drum 12 at a predetermined control timing. In the third cartridge 11C, a C toner image corresponding to the C color component image of the full color image is formed on the surface of the drum 12 at a predetermined control timing. In the fourth cartridge K, a K toner image corresponding to the K color component image of the full color image is formed on the surface of the drum 12 at a predetermined control timing.

  Then, at the primary transfer portion T1 of the first cartridge 11Y, the Y color toner image formed on the drum 12 of the cartridge 11Y is primarily transferred onto the belt 8 being rotationally driven. Next, at the primary transfer site T1 of the second cartridge 11M, the M color toner image formed on the drum 12 of the cartridge 11M is superimposed and superimposed on the Y color toner image on the belt 8. In the same manner, the M toner image and the K toner image are sequentially primary transferred onto the belt 8 at the primary transfer portions T1 of the third cartridge 11C and the fourth cartridge 11K. That is, four color toner images of Y color + M color + C color + K color are sequentially superimposed and transferred (superimposed transfer / multiple transfer) on the belt 8 to form a full-color unfixed toner image. The The order of forming the color toner images to be superimposed and transferred on the belt 8 is not limited to the above color order.

  In each primary transfer portion T1, the primary transfer of the toner image from the drum 12 to the belt 8 is performed by applying a predetermined primary transfer bias from the power supply unit to each primary transfer roller 9 and from the drum 12 to the belt. The toner image is electrostatically transferred to 8.

  Further, in each cartridge, the surface of the drum 12 after passing through the primary transfer portion is cleaned by the removal of the primary transfer residual toner by the drum cleaner 15 and repeatedly used for image formation.

  The unfixed toner image of the full-color image synthesized and formed on the belt 8 as described above is conveyed by the subsequent rotation of the belt 8 and reaches the secondary transfer portion T2.

  On the other hand, the pickup roller 18 is driven at a predetermined control timing, and the recording material P is separated and fed from the cassette 17 in cooperation with the separation pad 19. The fed recording material P is guided upward by the conveying path 20 in the vertical direction and reaches the registration roller 21. Then, after being aligned with the toner image on the belt 8 by the registration roller 21, it is conveyed to the secondary transfer portion T2. In the process in which the recording material P is nipped and conveyed through the secondary transfer portion T2, a predetermined secondary transfer bias is applied from the power supply unit to the secondary transfer outer roller 22, and the full color unfixed toner on the belt 8 is applied. The image is secondarily transferred to the recording material P at once.

  The recording material P that has exited the secondary transfer portion T2 is separated from the belt 8, guided by the conveyance guide 23, and introduced into the fixing unit 24. The fixing unit 24 in this embodiment is a heat and pressure fixing device having a roller pair of a heat roller 24a and a pressure roller 24b as basic constituent members, and the recording material P is introduced into a fixing nip portion which is a pressure contact portion of the roller pair. By being sandwiched and conveyed, it receives heat and pressure. As a result, the toner of each color toner image is melted and mixed to be fixed on the surface of the recording material as a full-color print image (fixed image formation).

  The recording material P that has exited the fixing unit 24 passes through the first discharge roller pair 25, the conveyance path 26, and the second discharge roller pair 27, and then passes from the discharge port 28 to the discharge tray 29 on the upper surface of the apparatus. Discharged.

  Further, the surface of the belt 8 after separation of the recording material is cleaned by removing the secondary transfer residual toner by the belt cleaner 10 in the subsequent rotation process of the belt 8 to prepare for the next image forming process.

  In the monochrome print mode, only the fourth cartridge 11K that forms a K-color toner image is controlled for image formation. In the first to third cartridges 11Y, 11M, and 11C, the drum 12 is driven to rotate, but the image forming operation is not performed.

  In the image forming apparatus according to the present exemplary embodiment, the first to fourth cartridges 11Y, 11M, 11C, and 11K are disposed below the intermediate transfer belt unit 4, so that the K color toner is compared with the case where the cartridges are disposed above. The distance between the primary transfer site T1 and the secondary transfer site T2 of the image is shortened. This shortens the time from picking up the recording material P to discharging it.

《Cartridge and cartridge holding configuration》
As each of the first to fourth cartridges 11Y, 11M, 11C, and 11K mounted on the apparatus main body is used for image formation, the developer (toner) contained in the developing device 14 is consumed. The Therefore, for example, a detection unit (not shown) for detecting the remaining amount of developer in each cartridge is provided in the cartridge. In the control circuit unit A, the remaining amount value detected by the detecting means is compared with a preset threshold value for cartridge life warning or life warning. Then, for a cartridge whose developer has decreased to a remaining amount value that is less than the threshold value, the display unit 30 displays a life warning or a life warning for the cartridge. As a result, the user is urged to prepare a cartridge for replacement or to replace the cartridge, thereby maintaining the quality of the output image.

  In the image forming apparatus according to the present embodiment, the cartridge is replaced by a method in which the opening / closing door 2 provided on the front side of the image forming apparatus is opened as shown in FIG. Reference numeral 2 a denotes a handle for opening / closing operation provided on the opening / closing door 2.

  Each of the first to fourth cartridges 11Y, 11M, 11C, and 11K has the same configuration and shape. 4A is a perspective view of the cartridge as viewed from the non-driving side, and FIG. 4B is a perspective view of the cartridge as viewed from the driving side. The cartridge is an assembly having the longitudinal direction O-O of the drum 12 as a longitudinal axis, and in the cartridge frame 31, as shown in FIGS. 1 and 5, the drum 12, a charging roller 13 as a primary charger, and a developing device. 14. A predetermined drum cleaner 15 is incorporated. The drum 12 is rotatable between one end side and the other end side in the longitudinal direction between bearing portions 32 and 33 disposed on one end side (non-driving side) and the other end side (driving side) of the cartridge frame 31. It is arranged to be supported. A drum drive coupling 34, a development drive coupling 35, and first and second electrical contact portions 36 and 37 are provided on the drive side end face of the cartridge frame 31. The drum drive coupling 34 is a drum drive force receiving portion that receives a drive force for rotating the drum 12 from the apparatus main body side. The developing drive coupling 35 is a developing roller driving force receiving portion that receives a driving force for rotating the developing roller 14a (FIG. 5) of the developing device 14 from the apparatus main body side. The first electrical contact portion 36 is an electrical contact that receives a charging bias supplied from the apparatus main body side to the charging roller 13. The second electrical contact portion 37 is an electrical contact that receives a developing bias supplied from the apparatus main body side to the developing roller 14a. On the bottom surface of the cartridge frame 31, a slit opening 38 (FIG. 5) is formed as a laser light incident opening portion along the longitudinal direction of the bottom surface at a substantially central portion in the short side direction of the bottom surface.

  The first to fourth cartridges 11Y, 11M, 11C, and 11K are first to fourth trays 41Y, 41M, and 41C as holding members (holding frames) that individually hold the cartridges in the apparatus main body, respectively. -It is mounted on 41K.

  Each tray is moved to a first position where the cartridge is positioned at an image formable portion (image forming position) with respect to the apparatus main body by a tray lifting mechanism (drive means) 50 which is a moving means described below. Moved up. In addition, the cartridge is retracted (separated) from the image formable portion and moved downward to a second position positioned at the detachable portion (mounting position) with respect to the apparatus main body. That is, the tray moves from the mounting position when the cartridge is mounted to the apparatus main body to the image forming position when image formation is performed, and conversely from the image forming position to the mounting position.

  7 is a perspective view of the first to fourth trays 41Y, 41M, 41C, and 41K and the tray lifting mechanism 50, and FIG. 8 is a perspective view of only the tray lifting mechanism 50 with the tray omitted from FIG.

  Each of the trays 41Y, 41M, 41C, and 41K is a plate-like member having a shape and size substantially corresponding to the shape of the bottom surface of the cartridge, and is parallel to the lower side of the intermediate transfer belt unit 4 with the longitudinal direction being the front-rear direction. Are arranged horizontally. Each of the trays 41Y, 41M, 41C, and 41K is disposed so as to be movable in parallel in a vertical direction along a vertical guide member (not shown).

  In each tray, reference numeral 42 denotes a slit opening as a laser beam incident opening formed along the tray longitudinal direction at a substantially central portion in the short side direction of the tray surface. In a state where the cartridge is placed on the tray in a predetermined manner, the slit opening 38 on the bottom surface side of the cartridge frame 31 is positioned corresponding to the slit opening 42 on the tray side as shown in FIG. Then, the laser beam L emitted upward from the laser scanner unit 16 below the tray enters the cartridge through the slit openings 42 and 38 from the bottom to the top.

  In each tray, reference numerals 43 and 44 denote urging members (urging means) which are disposed on the front side and the back side of the upper surface of the tray and elastically receive and support the cartridge. As shown in FIG. 6, the urging members 43 and 44 on the front side and the rear side are obtained by inserting a coil spring 46 and a pusher 47 in this order into a vertical hole 45 formed in the tray. The upper part of the pusher 47 protrudes from the upper surface of the tray. The cartridge placed on the tray is lifted elastically from the upper surface of the tray by the elastic force of the coil spring 46 of the biasing members 43 and 44 on the front side and the back side and the pusher 47 on the front side and the back side of the bottom surface, respectively. It is supported by the state.

  Below the trays 41Y, 41M, 41C, and 41K, the first to fourth rotating shafts (link shafts) 51Y, 51M, 51C, and 51K are arranged in parallel with the axial direction being the front-rear direction. Yes. Each rotating shaft is rotatably supported via a bearing member (not shown) between a front frame 61 (FIG. 13) and a back frame 62 of the main body frame forming the skeleton of the apparatus main body 3. Further, tray raising / lowering cams (eccentric cams) 52 and 53 are fixedly disposed on the front side and the rear side of each rotating shaft, respectively. Each elevating cam has the same shape and size, and the elevating cam 52 on the front side and the elevating cam 53 on the back side are fixed to the rotating shaft in the same phase.

  The front and back cam follower portions 47 are provided on the front side elevating cam 52 and the rear side elevating cam 53 of each rotating shaft so as to protrude downward on the lower surface side of the corresponding tray. 48 (Fig. 9) is in contact. Therefore, each tray is moved up by the large bulge portion (large diameter portion) of the elevating cams 52 and 53 and is moved down by the small bulge portion (small diameter portion) by rotating the corresponding rotation shaft. The

  In the present embodiment, the aforementioned front side and back side biasing members 43 and 44 on the upper surface side of the tray are disposed inside the front and back cam follower portions 47 and 48 described above. Yes (Figure 9).

  First to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K are disposed at the front ends of the first to fourth rotating shafts 51Y, 51M, 51C, and 51K, respectively. Each of these electromagnetic clutches is turned on when energized, and a clutch gear 55 coaxial with the rotating shaft is integrally connected to the rotating shaft. Further, when the power is cut off, the clutch is turned off, and the connection of the clutch gear 55 to the rotating shaft is released. As a result, the clutch gear 55 can idle (rotate free) with respect to the rotation shaft.

The clutch gear 55 of the first electromagnetic clutch 54Y is engaged with the output gear 56 of the drive motor M, which is a drive source (one drive source), via an idler gear 57a. The clutch gear 55 of the first electromagnetic clutch 54Y and the clutch gear 55 of the second electromagnetic clutch 54M are engaged via an idler gear 57b. The clutch gear 55 of the second electromagnetic clutch 54M and the clutch gear 55 of the third electromagnetic clutch 54C are engaged via an idler gear 57c. The clutch gear 55 of the third electromagnetic clutch 54C and the clutch gears 55 of the fourth electromagnetic clutch 54K are meshed via idler gears 57d.
Thus, the rotational force of the output gear 56 of the drive motor M is transmitted through the idler gear 57a~57d from the first to the clutch gear 55 of the fourth respective electromagnetic clutches 54Y · 54M · 54C · 54 K . When the drive motor M is turned on, if any of the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K is energized, it corresponds to the electromagnetic clutch that is clutch-on by energization. The rotating shaft, that is, the lifting cams 52 and 53 rotate. When the electromagnetic clutch is de-energized, the clutch gear 55 is free to rotate even when the drive motor M is turned on, and the rotary shafts corresponding to the electromagnetic clutch, that is, the lifting cams 52 and 53 stop rotating. . In this way, the rotation shaft, that is, the lifting cams 52 and 53 is controlled to rotate by the rotational force transmitted from the drive motor M via the electromagnetic clutch. Each clutch gear 55 has the same diameter and the same number of teeth. The idler gears 57a to 57d have the same diameter and the same number of teeth.

  As shown in FIG. 11, the first to fourth trays 41Y, 41M, 41C, and 41K stop the rotary shafts 51Y, 51M, 51C, and 51K with the large raised portions of the elevating cams 52 and 53 facing upward. The maximum ascending movement position in the state of being in operation is the first position. With the tray moved upward to the first position, the cartridge placed on the tray is held in the mounted state positioned at the image forming position with respect to the apparatus main body.

  That is, the upper portions of the non-drive side and drive side bearings 32 and 33 of the cartridge are the abutting portions of the frames 61 and 62 (FIG. 13) on the front side and the back side of the main body frame forming the skeleton of the apparatus main body, respectively. It hits 63 and 64 and is received. The abutting parts 63 and 64 as positioning parts are angled cutout concave parts, and the upper parts of the bearing parts 32 and 33 as positioning parts are arcuate convex parts. When the above-mentioned convex part fits into the above-mentioned concave part, it contacts mutually at two points of the abutting surface. Then, the bearing portions 32 and 33 are elastically pressed against the abutting portions 63 and 64 by the urging force F (FIG. 6) of the urging members 43 and 44 provided on the tray. As a result, the cartridge is positioned and fixed with respect to the frames 61 and 62, and the upper surface of the drum 12 is positioned at the image forming position in contact with the belt 8. Further, on the drive side of the cartridge in this mounted state, a first drive output unit (not shown) on the apparatus main body side is mechanically coupled to the drum drive coupling 34 (FIG. 4). A second drive output unit (not shown) on the apparatus main body side is mechanically coupled to the development drive coupling 35. Further, the first and second main body electric contact portions on the apparatus main body side are electrically coupled to the first and second electric contact portions 36 and 37.

  The intermediate transfer belt unit 4 is positioned and arranged with respect to the frames 61 and 62. That is, the belt 8 is positioned and arranged with respect to the frames 61 and 62 of the apparatus main body. Therefore, the cartridges 11Y, 11M, 11C, and 11K are abutted against the abutting portions 63 and 64 of the frames 61 and 62 as described above, so that the drum 11 is fixed to the belt 8. It is positioned and fixed at a predetermined position in contact. That is, each of the cartridges 11Y, 11M, 11C, and 11K is positioned in contact with the abutting portions 63 and 64 of the frames 61 and 62 when moved to the image forming position.

  In addition, the rotary shafts 51Y, 51M, 51C and 51K are driven half-turn from the state shown in FIG. 11, and as shown in FIG. 12, the small raised portions of the elevating cams 52 and 53 are directed upward to stop the rotary shaft. The lowermost movement position of each tray in the state of being in the state is the second position. With the tray moved down to the second position, the cartridge placed on the tray is retreated (separated) from the image forming position and held in a state of being positioned at the mounting position with respect to the apparatus main body. That is, the cartridge is lowered with the lowering of the tray, the positioning by pressing the bearing portions 32, 33 against the abutting portions 63, 64 is released, and the drum 12 is positioned at the mounting position where the upper surface of the drum 12 is separated from the belt 8. It is done. Thus, the cartridges 11Y, 11M, 11C, and 11K are separated from the abutting portions 63 and 64 when moved to the mounting position.

  Here, in order to reduce the size, the image forming apparatus according to the present embodiment uses the first to fourth cartridges 11Y, 11M, 11C, and 11K as adjacent cartridges while narrowing the interval Pdrm between the drums of each cartridge. The arrangement is overlapped so as to be stacked. That is, the first to fourth cartridges 11Y, 11M, 11C, and 11K are overloaded with respect to the direction of moving from the image forming position (FIG. 11) to the mounting position (FIG. 12) in order from one side to the other side of the arrangement. It is arranged to wrap. In the present embodiment, a part of the first cartridge 11Y overlaps with a part of the second cartridge 11M in the vertical direction of the image forming apparatus. A part of the second cartridge 11M overlaps with a part of the third cartridge 11C so as to be positioned upward in the vertical direction of the image forming apparatus. A part of the third cartridge 11C overlaps with a part of the fourth cartridge 11K in the vertical direction of the image forming apparatus so as to be positioned above.

<< Tray lifting control >>
In this embodiment, a door switch D-SW (FIGS. 3 and 10) is provided as a door opening / closing means for detecting that the opening / closing door 2 provided on the front side of the image forming apparatus is opened and closed. It is set up. The door switch D-SW is turned on when the door 2 is closed, and a close signal is input to the control circuit A. Further, the door switch D-SW is turned off when the door 2 is closed, and an open signal is input to the control circuit A.

  Then, based on the input of the open signal, the control circuit A sequentially sets the four trays that are all held at the first position as shown in FIG. 11 with a time difference between the trays (between the holding members). The tray elevating mechanism is controlled so as to start moving from the first position to the second position. Further, the control circuit A sequentially sets the four trays, which are all held at the second position, with a time difference between the trays (between the holding members) based on the input of the close signal, as shown in FIG. The tray elevating mechanism is controlled to start moving from the second position to the first position. That is, the control circuit unit A controls the first to fourth electromagnetic clutches Y, 54M, and the tray elevating mechanism 50 so that the first to fourth trays 41Y, 41M, 41C, and 41K move up and down as described above. 54C and 54K are linked and released in a coordinated manner at different timings. That is, the start timing of movement (lifting / lowering operation) is made different between the cartridges.

  This will be described in detail below. When the open / close door 2 is closed, the first to fourth trays 41Y, 41M, 41C, and 41K are all moved up to the first position and held in the stopped state as shown in FIG. Yes. That is, all of the first to fourth cartridges 11Y, 11M, 11C, and 11K are held at the image forming position with respect to the apparatus main body. The motor M of the tray lifting mechanism is held in the off state, and the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K are all held in the clutch-off state. In this state, the image forming apparatus can execute image formation.

  When the open / close door 2 is opened from the above state and an open signal is input, the control circuit A includes a drum drive coupling 34 on the drive side of each cartridge and a first drive output unit on the apparatus main body side for the development drive coupling 35. An operation of releasing the coupling of the second drive output unit is executed. Further, the control circuit A executes an operation of releasing the coupling of the first and second main body electrical contact portions on the apparatus main body side to the first and second electrical contact portions 36 and 37 on the driving side of each cartridge.

  Further, the control circuit A turns on the motor M of the tray lifting mechanism. Even if the motor M is turned on, as long as the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K are all kept in the clutch-off state, the clutch gear 55 of each electromagnetic clutch only idles. is there. Accordingly, the first to fourth rotary shafts 51Y, 51M, 51C, and 51K are not rotationally driven.

  Next, the control circuit A corresponds to the fourth cartridge 11K which is the lowermost cartridge of the first to fourth cartridges 11Y, 11M, 11C, and 11K that are sequentially overlapped as described above. The fourth electromagnetic clutch 54K is energized for 0.5 seconds. Here, in the tray elevating mechanism of this embodiment, when each electromagnetic clutch is energized for 1 second, that is, when the clutch is turned on for only 1 second, the corresponding rotating shaft, that is, the cams 52 and 53 make one rotation (360 degree rotation). The design configuration is as follows. Therefore, when the fourth electromagnetic clutch 54K is energized for 0.5 seconds, the fourth rotating shaft 51K is rotated half a turn (180 degrees) and stopped. As a result, the fourth tray 41K is moved from the first position to the second position as shown in FIG. That is, the fourth cartridge 11K is retracted from the image forming position and is held in a state of being positioned at a mounting position where it can be attached to and detached from the apparatus main body.

  Next, the control circuit A energizes the third electromagnetic clutch 54C corresponding to the third cartridge 11C for 0.5 seconds. Therefore, the third rotating shaft 51C is rotated halfway and stopped. As a result, the third tray 41C is moved from the first position to the second position as shown in FIG. That is, the third cartridge 11C is retracted from the image forming position and is held in a state of being positioned at the mounting position with respect to the apparatus main body.

  Next, the control circuit A energizes the second electromagnetic clutch 54M corresponding to the second cartridge 11M for 0.5 seconds. Therefore, the second rotation shaft 51M stops half a turn. Thereby, the second tray 41M is moved from the first position to the second position as shown in FIG. That is, the second cartridge 11M is retracted from the image forming position and is held in a state of being positioned at the mounting position with respect to the apparatus main body.

  Next, the control circuit A energizes the first electromagnetic clutch 54Y corresponding to the first cartridge 11Y for 0.5 seconds. Therefore, the first rotating shaft 51Y is rotated halfway and stopped. As a result, the first tray 41Y is moved from the first position to the second position. That is, the first cartridge 11Y is retracted from the image forming position and is held in a state of being positioned at the mounting position with respect to the apparatus main body. Thereafter, the motor M is turned off.

  Thus, the energization is performed for 0.5 seconds in the order of the fourth electromagnetic clutch 51K → the third electromagnetic clutch 51C → the second electromagnetic clutch 51M → the first electromagnetic clutch 51Y. That is, the movement start timing at which each cartridge descends is delayed in the order of cartridges 11K → 11C → 11M → 11Y. As a result, in about 2 seconds, the cartridges are sequentially moved downward one by one, and finally, the operation of moving all the cartridges from the image forming position in FIG. 11 to the mounting position in FIG. 12 is completed.

  FIG. 17 is a control flowchart executed by the control circuit unit A based on the input of the open signal as described above.

  As shown in FIG. 12, the first to fourth cartridges held in the mounted position are on the non-driving side (near side) on the near side exposed when the open / close door 2 is opened. It faces the outside from the opening 61a (FIGS. 3 and 13) of the frame 61. FIG. Therefore, the old cartridge to be replaced is pulled out from the tray on which the old cartridge is placed to the outside. The cartridge can be easily taken out because the positioning (pressing) of the cartridge with respect to the apparatus main body is released. Then, the new cartridge is placed on the tray after the old cartridge is taken out. The cartridge is placed on the tray with the cartridge driving side first, and is slid along the front and rear guide ribs (side walls) 41a provided on the tray and pushed into the back of the apparatus. That is done. The cartridge is sufficiently pushed in until the back side is received by the back side stopper rib (back wall) 41b of the tray and further pushing is prevented.

  After the replacement of the cartridge to be replaced as described above, the door 2 is closed. When the close signal is input, the control circuit A turns on the motor M of the tray lifting mechanism. Even if the motor M is turned on, as long as the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K are all kept in the clutch-off state, the clutch gear 55 of each electromagnetic clutch only idles. is there. Accordingly, the first to fourth rotary shafts 51Y, 51M, 51C, and 51K are not rotationally driven.

  Next, the control circuit A performs the first electromagnetic to the cartridge 11Y which is the uppermost cartridge of the first to fourth cartridges 11Y, 11M, 11C, and 11K that are sequentially overlapped as described above. Energization of the clutch 54Y is started for 0.5 seconds. Therefore, the first rotating shaft 51Y is rotated halfway and stopped. Thereby, the first tray 41Y is moved from the second position to the first position as shown in FIG. That is, the first cartridge 11Y is held in a state where it is positioned from the mounting position to the image forming position with respect to the apparatus main body.

  Next, the control circuit A starts energizing the second electromagnetic clutch 54M corresponding to the second cartridge 11M for 0.5 seconds earlier than the other cartridges. Therefore, the second rotation shaft 51M stops half a turn. Accordingly, the second tray 41M is moved from the second position to the first position as shown in FIG. That is, the second cartridge 11M is held in a state of being positioned from the mounting position to the image forming position with respect to the apparatus main body.

  Next, the control circuit A starts energization for 0.5 second to the third electromagnetic clutch 54C corresponding to the third cartridge 11C. Therefore, the third rotating shaft 51C is rotated halfway and stopped. As a result, the third tray 41C is moved from the second position to the first position as shown in FIG. That is, the third cartridge 11C is held in a state of being positioned from the mounting position to the image forming position with respect to the apparatus main body.

  Next, the control circuit A starts energization for 0.5 second to the fourth electromagnetic clutch 54K corresponding to the fourth cartridge 11K. Therefore, the fourth rotation shaft 51K is rotated halfway and stopped. As a result, the fourth tray 41K is moved from the second position to the first position. That is, the fourth cartridge 11K is held in a state of being positioned from the mounting position to the image forming position with respect to the apparatus main body. Thereafter, the motor M is turned off.

  In this way, the energization is performed for 0.5 seconds by shifting the energization start timing in the order of the first electromagnetic clutch 51Y → the second electromagnetic clutch 51M → the third electromagnetic clutch 51C → the fourth electromagnetic clutch 51K. That is, the movement start timing at which each cartridge rises is faster in the order of cartridges 11Y → 11M → 11C → 11K. Thus, in about 2 seconds, the cartridges are sequentially raised and moved one by one, and finally, the operation of moving all the cartridges from the mounting position in FIG. 12 to the image forming position in FIG. 11 is completed.

  Next, the control circuit A executes an operation of coupling the first drive output unit and the second drive output unit on the apparatus main body side with respect to the drum drive coupling 34 and the development drive coupling 35 on the drive side of each cartridge. Further, the control circuit A executes an operation of coupling the first and second main body electrical contact portions on the apparatus main body side to the first and second electrical contact portions 36 and 37 on the driving side of each cartridge. As a result, the image forming apparatus is ready to execute image formation.

  FIG. 21 is a control flow diagram executed by the control circuit unit A based on the input of the closing signal as described above.

  Here, the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K are cumulative because there is a minute connection error of several milliseconds in the clutch connection time, and the first to fourth rotating shafts 51Y, 51M are cumulative. -There is a possibility that the phase of the lifting cam is shifted between 51C and 51K. Further, the impact of the device may cause the lift cam phase to shift between the first to fourth rotating shafts 51Y, 51M, 51C, and 51K. Therefore, by providing a flag (not shown) on the first to fourth rotating shafts 51Y, 51M, 51C, 51K or the lift cam and detecting the flag position by a sensor (not shown), the first to fourth rotations are performed. The phase of the lifting cam among the shafts 51Y, 51M, 51C, and 51K may be prevented from shifting. Also, intermittent half-rotation clutches can be used for the first to fourth electromagnetic clutches 54Y, 54M, 54C, and 54K.

  In order to achieve both a reduction in the size of the image forming apparatus and a reduction in time required for forming a toner image on the intermediate transfer belt 8 (high productivity), it is desirable to shorten the interval Pdrm between the drums of each cartridge as much as possible. However, since it is necessary to arrange the developing means / charging means on the upstream side in the drum rotation direction and the cleaning means on the downstream side of the cartridge with the primary transfer portion interposed therebetween, a predetermined arrangement space is provided on the left and right sides of the cartridge with respect to the drum. Is required. In order to shorten the interval Pdrm while securing the left and right arrangement spaces, in the present embodiment, as described above, the adjacent process cartridges are overlapped so as to be stacked.

  Therefore, when moving the tray of the cartridge in the overlap arrangement from the second position to the first position, the tray 41Y → 41M → 41C → 41K with a time difference from the tray 41Y holding the cartridge 11Y on the upper side of the overlap. It is moved in the order. That is, the movement start timing is varied. On the contrary, when the tray of the overlapped cartridge is moved from the first position to the second position, the tray 41K is changed by adding a time difference of the movement start from the tray 41K holding the cartridge 11K on the lower side of the overlap. It is moved in the order of 41C → 41M → 41Y. That is, the tray 41Y starts to move late.

  When the cartridges are moved from the mounting position to the image forming position in the order of cartridges 11Y → 11M → 11C → 11K, the drum 12 and the belt 8 of the first cartridge 11Y first come into contact with each other. The belt 8 is sandwiched between the drum 12 and the first primary transfer roller 9. Subsequently, the drum 12 of the second cartridge 11M comes into contact with the belt 8 in a state where a predetermined tension is applied. The belt 8 is sandwiched between the drum 12 and the second primary transfer roller 9. Therefore, the state of the belt 8 between adjacent drums is stabilized, and the slack of the belt 8 is suppressed. This has the effect of preventing rubbing with the drum when the wrinkles of the belt 8 and the slack of the belt 8 are eliminated. The same effect is exhibited between the drums of the second and third cartridges 11M and 11C and between the drums of the third and fourth cartridges 11C and 11K.

  In the first embodiment of the present invention, since the cartridges overlap, the cartridges are moved in the order of cartridges 11Y → 11M → 11C → 11K. However, as long as the configurations do not overlap, the order may be 11M → 11C → 11K → 11Y, 11C → 11M → 11Y → 11K, 11C → 11K → 11M → 11Y, or the like.

  Compared with the case where four cartridges are moved up and down at once, the driving force can be greatly reduced.

  FIG. 22 shows the torque of the drive motor M necessary to move and fix the first to fourth cartridges 11Y, 11M, 11C, and 11K from the mounting positions with respect to the apparatus main body to the image forming positions with or without time difference. It is a comparison. It can be seen that the maximum torque can be reduced by ΔT1 (N · m) as compared to the case where four cartridges are moved at a time.

  The positioning of the cartridge by the abutment adopted in this embodiment is a highly accurate positioning with less play of the cartridges 11Y, 11M, 11C, and 11K with respect to the frames 61 and 62 as compared with the positioning by fitting with holes. Is possible. The relative positional deviations of the cartridges 11Y, 11M, 11C, and 11K are directly connected to the deviation of the image that is primarily transferred, so that the color image quality is greatly affected. Therefore, it can be said that positioning with little play by abutment is a very effective means for improving color image quality.

  Further, since the positioning is based on the two points of the abutting surface and the urging force F of the urging members 43 and 44, the cartridge can be separated from the positioning portion by retracting the tray provided with the urging members 43 and 44. . By arranging the biasing members 43 and 44 under the cartridge as in this embodiment, a wide opening of the apparatus main body when the cartridge is replaced can be secured, and the usability without an obstacle at the time of insertion / extraction can be achieved. An excellent arrangement is possible.

  In the present embodiment, the configuration in which the cartridges 11Y, 11M, 11C, and 11K are arranged below the belt 8, and the cartridges are moved upward to abut against the frames 61 and 62 for positioning is described. The present invention is not limited to this configuration, and can be widely applied as long as it is a configuration in which the cartridge is moved to a predetermined position of the frame and abutted. For example, a configuration in which the cartridge is disposed above the belt 8 and the cartridge is moved downward and abuts against the frame may be employed.

  Although the present embodiment has been described with the configuration in which the adjacent cartridges overlap each other, the order in which the cartridges abut against the frames 61 and 62 may be arranged in order from either one even when the cartridges are not overlapped. Is applicable. Further, when the cartridges are arranged so as not to overlap, the order of the upward movement or the downward movement of each cartridge can be arbitrarily set.

  This embodiment shows another example of the tray lifting mechanism (drive mechanism). FIG. 23 is a perspective view of a main part of the tray lifting mechanism 70 in the present embodiment. Reference numerals 71 and 72 denote a pair of slide rails as reciprocating members that are reciprocated and disposed horizontally in parallel on the front side and the back side with the longitudinal direction being the left-right direction. Each of the slide rails 71 and 72 is held by a guide member (not shown) and is slidable in the left-right direction. Rack gears 73 and 73 are provided on the right end side of the slide rails 71 and 72, respectively. The rack gears 73 and 73 are engaged with rail drive gears 74 and 74 fixed to the output shaft of the drive motor M, respectively. Therefore, when the drive motor M is driven to rotate forward, the slide rails 71 and 72 on the near side and the far side move together to the left (one direction). In this embodiment, the leftward movement of the rail is referred to as forward movement. In addition, when the drive motor M is driven in reverse, the front and back slide rails 71 and 72 move together to the right (reverse direction). In this embodiment, the rightward movement of the rail is referred to as a backward movement.

  On the upper surfaces of the slide rails 71 and 72 on the front side and the rear side, the first to fourth trays corresponding to the first to fourth trays 41Y, 41M, 41C, and 41K are mirror-symmetrical along the length, respectively. Cam-shaped portions 75Y, 75M, 75C, and 75K are provided. Each of the cam-shaped portions includes a first holding surface a that holds the tray at the first position, a second holding surface c that holds the tray at the second position, and a first holding surface a. And a slope b connecting the second holding surface c. That is, each cam-shaped part is an elevating part that moves the tray up and down.

  Further, on the lower surface side of the first to fourth trays 41Y, 41M, 41C, and 41K, rotatable rollers 76 (FIG. 24) are disposed on the front side and the back side, respectively. The front and back rollers 76 are on the front and back slide rails 71 and 72, respectively.

  In the course of the forward movement of the slide rails 71 and 72, the roller 76 moves up the slope b from the second holding surface c of the cam-shaped portion to the first holding surface a. Accordingly, the tray moves from the second position to the first position. Further, in the backward movement process of the slide rails 71 and 72, the roller 76 moves from the first holding surface a of the cam-shaped portion down the inclined surface b to the second holding surface c. Accordingly, the tray moves from the first position to the second position.

  In this case, in the forward movement process of the rail, each tray moves sequentially from the second position to the first position with a time difference, and in the backward movement process, each tray sequentially adds the time difference to the first position. Each cam shape portion is configured to move from the first position to the second position.

  This will be described in detail below. When the open / close door 2 is closed, the slide rails 71 and 72 are stopped at the forward movement end positions, and the trays 41Y, 41M, 41C, and 41K are all in the first position as shown in FIG. It is moved up and held in a stopped state. That is, the rollers 76 of all trays are on the first holding surface a of the corresponding cam-shaped portion, and all the cartridges 11Y, 11M, 11C, and 11K are mounted at the image forming positions with respect to the apparatus main body. Held in a state.

  When the open / close door 2 is opened, the slide rails 71 and 72 are stopped at the backward movement end positions, and all of the trays 41Y, 41M, 41C, and 41K are in the second position as shown in FIG. Is moved down to the position and held in a stopped state. That is, the rollers 76 of all trays are on the second holding surface c of the corresponding cam-shaped portion, and all the cartridges 11Y, 11M, 11C, and 11K are positioned at the mounting positions with respect to the apparatus main body. Is retained.

  When the open / close door 2 is opened from the state of FIG. 24 and an open signal is input, the control circuit portion A receives the first drive output on the apparatus main body side with respect to the drum drive coupling 34 and the development drive coupling 35 on the drive side of each cartridge. The operation of releasing the coupling between the unit and the second drive output unit is executed. Further, the control circuit A executes an operation of releasing the coupling of the first and second main body electrical contact portions on the apparatus main body side to the first and second electrical contact portions 36 and 37 on the driving side of each cartridge.

  Next, the control circuit unit A drives the motor M in the reverse direction at a predetermined rotation speed by a predetermined rotation angle. As a result, the slide rails 71 and 72 move backward by a predetermined stroke from the forward movement end point position and stop at the predetermined backward movement end point position.

  In the backward movement process of the slide rails 71 and 72, first, the rollers 76 of the fourth tray 41K first descend the slope b from the first holding surface a of the corresponding cam-shaped portion 75K, and the second holding surface. Move to c. As a result, the fourth tray 41K is moved from the first position to the second position as shown in FIG. That is, the fourth cartridge 11K is retracted from the image forming position and is held in a state of being positioned at the mounting position with respect to the apparatus main body. Next, the roller 76 of the third tray 41C moves from the first holding surface a of the corresponding cam-shaped portion 75C down the slope b to the second holding surface c. As a result, the third tray 41C is moved from the first position to the second position as shown in FIG. That is, the third cartridge 11 </ b> C is retracted from the image forming position and is held in the mounting position with respect to the apparatus main body. Next, the roller 76 of the second tray 41M moves from the first holding surface a of the corresponding cam-shaped portion 75M down the slope b to the second holding surface c. As a result, the second tray 41M is moved from the first position to the second position as shown in FIG. That is, the second cartridge 11M is retracted from the image forming position and is held in the mounting position with respect to the apparatus main body. Finally, the roller 76 of the first tray 41Y moves from the first holding surface a of the corresponding cam-shaped portion 75Y down the slope b to the second holding surface c. As a result, the first tray 41Y is moved from the first position to the second position. That is, the first cartridge 11Y is retracted from the image forming position and is held in the mounting position with respect to the apparatus main body.

  In this way, in the backward movement process of the slide rails 71 and 72, the cartridges are sequentially moved downward at different movement start timings one by one. Finally, the operation of moving all the cartridges from the image forming position in FIG. 24 to the mounting position in FIG. 25 is completed.

  When the open / close door 2 is closed and a close signal is input from the state of FIG. 25, the control circuit unit A drives the motor M to rotate forward at a predetermined rotational speed by a predetermined rotational angle. As a result, the slide rails 71 and 72 move forward by a predetermined stroke from the backward movement end point position and stop at the predetermined forward movement end point position.

  In the forward movement process of the slide rails 71 and 72 described above, first, the rollers 76 of the first tray 41Y first move upward from the second holding surface c of the corresponding cam-shaped portion 75Y up the inclined surface b to perform the first holding. Transition to plane a. Thereby, the first tray 41Y is moved from the second position to the first position as shown in FIG. That is, the first cartridge 11Y is held in a state of being positioned from the mounting position to the image forming position. Next, the roller 76 of the second tray 41M moves up the slope b from the second holding surface c of the corresponding cam-shaped portion 75M to the first holding surface a. Accordingly, the second tray 41M is moved from the second position to the first position as shown in FIG. That is, the second cartridge 11M is held in a state of being positioned from the mounting position to the image forming position. Next, the roller 76 of the third tray 41C moves up the slope b from the second holding surface c of the corresponding cam-shaped portion 75C to the first holding surface a. As a result, the third tray 41C is moved from the second position to the first position as shown in FIG. That is, the third cartridge 11C is held in a state of being positioned from the mounting position to the image forming position. Finally, the roller 76 of the fourth tray 41K moves up the slope b from the second holding surface c of the corresponding cam-shaped portion 75K to the first holding surface a. As a result, the fourth tray 41K is moved from the second position to the first position. That is, the fourth cartridge 11K is held in a state of being positioned from the mounting position to the image forming position.

  In this way, in the forward movement process of the slide rails 71 and 72, the cartridges are sequentially moved upward with different movement start timings one by one. Finally, the operation of moving all the cartridges from the mounting position in FIG. 25 to the image formable portion in FIG. 24 is completed.

  After the completion of this operation, the control circuit unit A performs an operation of coupling the first drive output unit and the second drive output unit on the apparatus main body side with respect to the drum drive coupling 34 and the development drive coupling 35 on the drive side of each cartridge. Run. Further, the control circuit A executes an operation of coupling the first and second main body electrical contact portions on the apparatus main body side to the first and second electrical contact portions 36 and 37 on the driving side of each cartridge. As a result, the image forming apparatus is ready to execute image formation.

  The roller 76 rotates when the slide rails 71 and 72 move forward to reduce the friction load.

  The first to fourth cam-shaped portions (elevating portions) 75Y, 75M, 75C, and 75K provided on the slide rails 71 and 72 in correspondence with the respective trays have predetermined start and end timings of the slope b. Designed to be different. Moreover, the length of the 1st holding surface a and the length of the 2nd holding surface c are designed so that it may mutually differ predetermined. Thus, in the backward movement process of the slide rails 71 and 72, the four trays can be moved from the first position to the second position with a time difference in the order of 11K → 11C → 11M → 11Y. In the forward movement process of the slide rails 71 and 72, the four trays can be moved from the second position to the first position with a time difference in the order of 11Y → 11M → 11C → 11K.

  FIG. 32 shows the driving torque of the rail driving gear 74 necessary for sequentially moving the four cartridges from the mounting position relative to the apparatus main body to the image forming position in the forward movement process of the slide rails 71 and 72. The comparison is based on the presence or absence of a time difference. It can be seen that the maximum torque can be reduced by ΔT2 (N · m) compared to the case where four cartridges are moved at a time.

  In this embodiment, the slide rails 71 and 72 are used to sequentially raise and lower the trays with a difference in start time. Compared with the tray lifting mechanism of the first embodiment, this tray lifting mechanism eliminates the electromagnetic clutch and makes the control simple by only forward / reverse rotation control of the rail drive gear 74, thereby further reducing the cost. doing. However, since a sufficient time difference cannot be provided in a space-saving manner, the torque reduction rate is lower than that in the first embodiment.

The rail drive gear 74 is controlled to rotate by the drive motor M, but this is not particularly limited as long as it is a mechanism that rotates the rail drive gear 74 forward and backward such as forward / reverse rotation control using a motor or control by a crank. . A mechanism for manually rotating the rail drive gear 74 forward and reverse using a lever may be used. In the case of manual operation, torque reduction contributes to improvement in user operability because it reduces user operation force.

  In the above embodiment, the image forming unit partially overlaps in the vertical direction of the image forming apparatus. However, the same effect can be obtained even if the image forming unit has a structure that does not overlap.

  The image forming process of the image forming apparatus is not limited to the electrophotographic process. An electrostatic recording process using a dielectric as an image carrier, a magnetic recording process using a magnetic as an image carrier, or the like may be used.

  Further, the number of cartridges as the image forming unit is not limited to four in the embodiment. The present invention can be applied to an image forming apparatus in which at least a first cartridge and a second cartridge are installed and used.

1 is a schematic front view of an image forming apparatus according to a first embodiment. External perspective view of image forming apparatus External perspective view of the image forming apparatus showing a state in the middle of opening / closing the door and inserting or removing one of the cartridges (A) is the external appearance perspective view which looked at the cartridge from the non-drive side, (b) is the external appearance perspective view which looked at the cartridge from the drive side Explanatory drawing of a slit opening as a laser beam incident opening provided on the cartridge side and tray side Explanatory drawing of the urging member provided on the tray side A perspective view of the first to fourth trays and the tray lifting mechanism 7 is a perspective view of only the tray lifting mechanism without the tray from FIG. Perspective view of the bottom side (back side) of the tray Block diagram of control system Diagram of a state where all trays are moved to the first position and held Diagram of a state where all trays are moved to the second position and held Perspective view of the front frame and back frame of the main body frame First, the fourth tray is moved from the first position to the second position. Next, a diagram showing a state in which the third tray is moved from the first position to the second position. Next, the second tray is moved from the first position to the second position. Flow chart of control executed by the control circuit unit based on the opening signal when the door is opened First, the first tray is moved from the second position to the first position. Next, the second tray is moved from the second position to the first position. Next, a diagram showing a state in which the third tray is moved from the second position to the first position. Flow chart of control executed by the control circuit unit based on the closing signal when the door is closed Required torque diagram The perspective view of the slide rail part of the tray raising / lowering mechanism in Example 2. Diagram of a state where all trays are moved to the first position and held Diagram of a state where all trays are moved to the second position and held First, the fourth tray is moved from the first position to the second position. Next, a diagram showing a state in which the third tray is moved from the first position to the second position. Next, the second tray is moved from the first position to the second position. First, the first tray is moved from the second position to the first position. Next, the second tray is moved from the second position to the first position. Next, a diagram showing a state in which the third tray is moved from the second position to the first position. Required torque diagram

Explanation of symbols

  4. Intermediate transfer belt unit (belt-shaped transfer means), 11 (Y, M, C, K), Process cartridge, 12. Electrophotographic photosensitive drum (image carrier), 13-15. Forming process means, 41 (Y, M, C, K), Process cartridge tray (holding member), 50, 70, Drive mechanism, 52, 53, Elevating cam, 54 (Y, M, C, K) ..Electromagnetic clutch, 71.72..Slide rail (reciprocating member), 75 (Y.M.C.K) .. Cam-shaped portion, a..first holding surface, b..slope, c. .Second holding surface, 61.62..Main body frame, 63.64..Cartridge abutting portion

Claims (6)

A first image forming unit detachably mountable to the apparatus main body of a chromatic image forming apparatus an image bearing member, a second image forming unit detachably mountable to the apparatus main body have a image bearing member, wherein image forming position at which the image is formed from the mounting position when mounted in the apparatus main body a removable portion and said second image forming unit and the first image forming unit relative to the apparatus main body to, an image forming apparatus having moving means from said image forming position in the reverse is moved to the mounting position, and
The first image forming unit and the second image forming unit are positioned in contact with the abutting portion of the frame of the apparatus main body when moved to the image forming position, and abutted when in the mounting position. Apart from the part,
Said moving means is driven by a single drive source, said at different start timing of the movement to the image forming position from the mounting position of the the first image forming unit a second image forming unit and the image An image forming apparatus, wherein a start timing of movement from a forming position to the mounting position is varied .   The part of the first image forming unit overlaps with the part of the second image forming unit in the vertical direction of the image forming apparatus so as to be positioned above. The image forming apparatus according to 1. Start timing of the movement to the image forming position from the mounting position of the first image forming unit earlier than the start timing of the movement to the image forming position from the mounting position of the second image forming unit, wherein The start timing of the movement of the first image forming unit from the image forming position to the mounting position is later than the start timing of the movement of the second image forming unit from the mounting position to the image forming position. The image forming apparatus according to claim 2. The image forming apparatus according to claim 1, wherein the driving source is a motor. The image forming apparatus according to claim 1, wherein the driving source is a manual operation member. The abutting portion is a notch-shaped concave portion, the positioned portion of the image forming unit is a convex portion of a circular arc surface, and the convex portion becomes the concave portion when the image forming unit moves to the image forming position. 6. The image forming apparatus according to claim 1, wherein the image forming unit is positioned by being fitted to each other at two points on the abutting surface.