JP5130308B2 - Drum unit positioning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a drum unit positioning device that performs positioning between drum units each having photosensitive drums corresponding to four different colors, and an image forming apparatus that includes the positioning device to form a full-color image.

  Conventionally, various so-called quadruple tandem types have been proposed as image forming apparatuses that use yellow, cyan, magenta, and black toners to form full-color images by an electrophotographic process. In this type of image forming apparatus, the four photosensitive drums corresponding to the respective colors are arranged in parallel, and the electrostatic latent image on the photosensitive drum is developed with toner for each color, and then the toner image of each color is transferred to the paper. A full-color image is obtained by sequentially superimposing the images above.

  In such a quadruple tandem type image forming apparatus, in order to prevent color misregistration of the toner images of the respective colors on the paper, the positioning accuracy between the drum units having the respective photosensitive drums can be kept high. Needed. Usually, the drum shaft of each photosensitive drum is supported by a positioning plate having a bearing hole into which each drum shaft fits, and thereby, each drum unit can be positioned with high accuracy.

  By the way, in each drum unit, it is necessary to perform replacement on the user side when the number of printed sheets reaches a predetermined number (for example, tens of thousands) due to the mechanical life. For this reason, it is necessary to make the positioning plate detachable from the apparatus main body so that each drum unit can be replaced.

  In this regard, for example, in the image forming apparatus disclosed in Patent Document 1, a handle is formed on the positioning plate, and the user holds the handle and fits the positioning plate into each drum shaft (the drum shaft is installed in the bearing hole of the positioning plate). It is possible to fit or remove the drum shaft from each drum shaft (cancel the fitting of the drum shaft into the bearing hole). The positioning plate pulled out from each drum shaft is placed at another location outside the apparatus main body and is completely separated from the apparatus main body.

JP-A-7-306566

  However, when the positioning plate is completely separated from the main body of the apparatus after the positioning plate is pulled out from each drum shaft as in Patent Document 1, after the replacement of each drum unit, the positioning plate is inserted into each drum shaft. The user has to search for the fitting position of the positioning plate with a sense of hand, and cannot smoothly fit the positioning plate. For this reason, the workability | operativity at the time of replacement | exchange of each drum unit falls. Further, after the positioning plate is pulled out from each drum shaft, the positioning plate is placed outside the apparatus main body, so that the movement distance when attaching / detaching the positioning plate to / from the apparatus main body is long, and the above workability is further improved. descend.

  Further, when the positioning plate is attached to the apparatus main body, if the fitting direction does not coincide with the drum axis direction, for example, because the fitting direction of the drum shaft into the bearing hole is inclined with respect to the drum axis direction, The resistance and stress increase and the drum shaft does not easily fit into the bearing hole, so-called “squeezing” occurs. Therefore, in the configuration in which the drum shaft is fitted into the bearing hole and positioning is performed, it is desired that the fitting between the bearing hole and the drum shaft can be suppressed and the fitting can be performed smoothly.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to improve workability when replacing each drum unit and to smoothly fit the drum shaft into the bearing hole. It is an object of the present invention to provide a drum unit positioning device that can perform the above and an image forming apparatus including the positioning device.

  The drum unit positioning device according to the present invention is a drum unit positioning device that performs positioning between drum units each having photosensitive drums corresponding to four different colors, and has bearing holes into which the respective drum shafts of the four photosensitive drums are fitted. A positioning plate having a formed flat plate portion; and an opposing wall portion facing the flat plate portion of the positioning plate, and rotating while holding the positioning plate, thereby rotating the drum shaft with respect to the bearing hole. A holder portion that relatively inserts and removes, and a biasing member that biases the flat plate portion in a direction in which the flat plate portion of the positioning plate separates from the opposing wall portion of the holder portion, When the drum shaft is fitted into the bearing hole by turning, the bearing hole and the drum shaft are in contact with each other to resist urging by the urging member. Wherein as the position of said plate with respect to the facing wall portion is changed, it is characterized by holding the positioning plate Te.

  According to the above configuration, the drum shaft is inserted into and removed from the bearing hole of the positioning plate by rotating the holder portion while holding the positioning plate. Thus, if the rotating shaft of the holder unit is supported on the main body side of the image forming apparatus in which each drum unit is loaded, the positioning plate remains on the main body side while being held by the holder unit before and after the replacement of each drum unit. Therefore, compared to a configuration in which the positioning plate is completely separated from the apparatus main body, the moving distance of the positioning plate when attaching / detaching to the apparatus main body is short, and the positioning plate is attached / removed at a position close to the apparatus main body. be able to. In addition, since the rotation trajectory of the holder part is constant, after replacing each drum unit, the positioning part can be attached to the proper position by turning the holder part, and it is necessary to find the attachment position of the positioning part by hand. Nor. Therefore, the positioning plate can be attached / removed smoothly when each drum unit is replaced, compared with the conventional method of completely removing the positioning plate from the main body side and attaching the positioning plate by hand. The workability at the time of replacing each drum unit can be improved.

  Further, as described above, in the configuration in which the positioning plate is attached / removed by rotating the holder portion, the movement locus of the holder portion and the positioning plate is arcuate, and the fitting direction of the drum shaft into the bearing hole is the drum shaft direction. Therefore, when the drum shaft is fitted into the bearing hole, the twisting is likely to occur. However, the holder part is positioned so that the position of the flat plate part changes with respect to the opposing wall part against the biasing by the biasing member due to the contact between the bearing hole and the drum shaft when the positioning plate is fitted by rotation. Holding the board. The change in the position of the flat plate portion includes at least one of a change in the position of the flat plate portion in the urging direction and a change in the inclination of the flat plate portion with respect to the urging direction.

  In this configuration, at the time of contact between the bearing hole and the drum shaft, the flat plate portion approaches the opposing wall portion against the urging by the urging member, or the inclination of the flat plate portion relative to the opposing wall portion changes. The frictional resistance and stress at the time of the contact can be reduced by the relative and continuous position change of the flat plate portion with respect to the opposing wall portion, whereby the twisting of both members can be reduced. Therefore, even if it is the structure which rotates a holder part, the fitting of the drum axis | shaft to a bearing hole can be performed smoothly.

  In the drum unit positioning device of the present invention, the holder portion is fixed to a hook that engages with a device main body in which the drum units are loaded, and a pivot shaft of the hook. And a lever for releasing the engagement with the apparatus main body.

  In this configuration, by operating the lever to rotate the hook, the engagement between the hook and the apparatus main body is released, and the holder portion can be rotated. Further, since the holder portion can be rotated and the positioning plate can be attached / removed by a simple operation such as lever operation, the workability at the time of replacing each drum unit can be further improved.

  In the drum unit positioning device of the present invention, the positioning plate has an insertion portion that is erected on the flat plate portion and has an insertion port through which the rotation shaft of the hook is inserted through a gap. desirable.

  In this configuration, since a gap is formed between the rotation shaft of the hook of the holder portion and the insertion port of the insertion portion of the positioning plate, the flat plate portion of the positioning plate is opposed to the holder portion by this gap. It is supported so that it can be displaced relative to the wall. This makes it possible to reliably change the position of the flat plate portion with respect to the facing wall portion while maintaining the contact when the bearing hole and the drum shaft are brought into contact with each other by the rotation of the holder portion. Therefore, in the configuration in which the holder portion is rotated, the bearing hole and the drum shaft are twisted due to a change in the position of the flat plate portion, although the rotation direction of the holder portion is different from the fitting direction of the drum shaft in the bearing hole. The drum shaft can be surely and smoothly fitted into the bearing hole while reliably reducing the above.

  In the drum unit positioning device of the present invention, it is desirable that the urging member urges a position shifted from the center of the flat plate portion of the positioning plate within a cross section perpendicular to the rotation axis of the holder portion.

  In this case, the urging by the urging member can warp the flat plate portion of the positioning plate within the cross section perpendicular to the rotation axis of the holder portion. As a result, even when there is a slight gap between the two in the state where the insertion of the drum shaft into the bearing hole of the positioning plate has been completed, both of them are surely brought into line contact or surface contact due to the above warpage. Can be reliably adhered. As a result, it is possible to prevent the drum shaft from rattling in the completed positioning state, and to stabilize electrical conduction when the drum shaft and the positioning plate are grounded.

  In the drum unit positioning device of the present invention, the positioning plate further includes a positioning pin that is fitted into a positioning hole of a device main body in which each drum unit is loaded, and the positioning pin is the positioning plate of the positioning plate. It is desirable that the flat plate portion penetrates and is fixed to the flat plate portion, and the biasing member biases the positioning pin from the rear end.

  By positioning the positioning pin in the positioning hole on the apparatus main body side, the positioning plate can be positioned with respect to the apparatus main body. At this time, since the urging member urges the positioning pin provided through the flat plate portion from the rear end, the urging force of the urging member can be efficiently applied to the positioning pin. Thereby, even if it is the structure which rotates a holder part, the positioning pin can be smoothly inserted into the apparatus body side hole part while suppressing the twisting of both, and the positioning plate can be positioned smoothly. Can do.

  In the drum unit positioning device of the present invention, it is desirable that the bearing holes of the positioning plate and the positioning pins are located on the same straight line.

  When the rotation axis of the holder portion is positioned parallel to the direction in which the drum shafts are arranged, the rotation of the holder portion causes each drum shaft to be fitted into each bearing hole of the positioning plate and to the hole on the apparatus main body side. The positioning pin can be fitted at the same time. And since the change of the position of the flat plate part resisting the urging | biasing of the urging | biasing member at the time of a fitting acts similarly with respect to each fitting part, each fitting can be performed smoothly all simultaneously.

  An image forming apparatus of the present invention includes the above-described drum unit positioning device of the present invention and a drum unit having individual photosensitive drums corresponding to four different colors, and performs positioning between the drum units by the drum unit positioning device. A configuration is desirable.

  According to the above configuration, the positioning plate is removed by attaching and detaching the holder unit by rotating the holder unit. An image forming apparatus capable of performing smoothly without causing the occurrence of the problem can be realized.

  The image forming apparatus of the present invention further includes a developing unit provided corresponding to each of the drum units, and developing the electrostatic latent image formed on each of the photosensitive drums with toner, and each of the drum units includes Each has a cleaning device that collects toner remaining after the transfer of the toner image on the photosensitive drum. The image forming device is attached to and detached from the toner disposal opening of each drum unit, and is collected by each cleaning device. The apparatus further includes a waste toner transport device that transports the toner discharged from the toner waste port to a collection container, and the waste toner transport device is provided on the outer side in the drum axial direction of each of the photosensitive drums than the drum unit positioning device. It is desirable that

  When disposing of the waste toner transported by the waste toner transport device and collected in the collection container by positioning the waste toner transport device outside the drum unit positioning device in the drum axial direction (opposite to each drum unit) In addition, it is not necessary to operate the drum unit positioning device. That is, only the collection container can be taken out without operating the drum unit positioning device. As a result, the waste toner can be disposed of efficiently, and the workability can be improved.

  In the image forming apparatus according to the aspect of the invention, the waste toner conveying device has a rotation shaft that is positioned in parallel with a direction in which the toner disposal ports of the drum units are arranged, and the rotation shaft is connected to each drum unit. It is desirable to be positioned below each toner disposal port.

  Since the rotation axis of the waste toner conveying device is located in parallel with the direction in which the toner waste ports are arranged, the rotating waste toner conveying device and the toner waste port are attached to and detached from all the toner waste ports simultaneously. be able to.

  Further, since the rotation shaft of the waste toner conveying device is located below each toner disposal port, the waste toner conveying device opens upward with the rotation shaft as a fulcrum. With such a configuration, when the waste toner transport device is opened (when the connection with each toner waste port is released), the waste toner transport device receives the waste toner falling from each toner waste port. It is possible to prevent the installation surface (floor) of the image forming apparatus from being stained with waste toner.

  In the image forming apparatus according to the aspect of the invention, the rotation shaft of the holder portion of the drum unit positioning device is positioned in parallel to the direction in which the drum shafts of the drum units are arranged, and the rotation shaft is the drum shaft. It is desirable to be located above.

  Since the rotation axis of the holder portion of the drum unit positioning device is located in parallel with the direction in which the drum shafts are arranged, each drum shaft to each bearing hole of the positioning plate is rotated when the drum unit positioning device (holder portion) is rotated. Can be simultaneously inserted.

  Further, since the rotation shaft of the drum unit positioning device (holder part) is positioned above each drum shaft, the drum unit positioning device is opened downward with the rotation shaft as a fulcrum. In this way, the drum unit positioning device and the waste toner transport device are arranged so that the rotation shafts of the drum unit positioning device are opposite to the rotation support points of the waste toner transport device so that the space between the rotation shafts is exposed. Each can be configured to rotate. As a result, even when both the drum unit positioning device and the waste toner conveying device are in the open state, they do not interfere with each other, and a wide space for the drum unit and each development unit (opening / closing opening) is secured. This makes it easy to replace each drum unit and each developing unit.

  The image forming apparatus of the present invention further includes a toner supply unit that is provided corresponding to each of the development units, and that supplies toner from each toner cartridge to each of the development units, and each of the toner supply units includes the development unit. It is desirable to be provided corresponding to the end portion on the opposite side to the waste toner conveying device.

  When each toner supply unit is positioned corresponding to the end of each developing unit on the waste toner transport device side, each toner supply unit has a complicated shape in order to prevent each toner supply unit from interfering with the waste toner transport device. In order to reliably supply toner, it is necessary to provide a toner feed mechanism (for example, a screw) inside each toner supply unit.

  However, since each toner supply unit is positioned corresponding to the end of each developing unit opposite to the waste toner conveyance device, each toner supply unit does not interfere with the waste toner conveyance device. A supply part can be comprised by a simple shape (for example, shape which has a long cylindrical part up and down). Thus, it is possible to supply toner from each toner cartridge to each developing unit without providing a toner feeding mechanism inside each toner supply unit.

  In the image forming apparatus according to the aspect of the invention, it is preferable that each of the toner supply units has a cylindrical part in which toner supplied from each toner cartridge falls due to its own weight.

  In this case, it is possible to supply toner from each toner cartridge to each developing unit via the cylindrical portion without providing a toner feeding mechanism inside each toner supplying unit, thereby simplifying the configuration of each toner supplying unit. can do.

  According to the present invention, as long as the rotating shaft of the holder portion is supported on the apparatus body side, the positioning plate is held by the holder portion even when the drum shaft is pulled out from the bearing hole by the rotation of the holder portion. After the replacement of each drum unit remaining on the main body side, the positioning plate can be attached to the proper position simply by rotating the holder portion in the reverse direction. Therefore, it is not necessary to find the attachment position of the positioning plate by hand every time each drum unit is replaced, and the workability at the time of replacing each drum unit can be improved as compared with the prior art.

  Also, when the drum shaft is fitted into the bearing hole of the positioning plate by turning, the twist caused by the contact between the bearing hole and the drum shaft is reduced by the relative and continuous position change of the flat plate portion with respect to the opposing wall portion. can do. Thereby, even if it is the structure which rotates a holder part, the fitting of the drum axis | shaft to a bearing hole can be performed smoothly.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which expands and shows the image formation part vicinity of the said image forming apparatus. (A) And (b) is a perspective view which shows the other structural example of the said image forming apparatus, (a) is a perspective view in the state before positioning of the drum unit by a positioning device, (b) FIG. 4 is a perspective view of the drum unit after positioning. It is a perspective view which shows the external appearance of the drum unit used as the object of positioning by the said positioning apparatus. It is a perspective view which shows the external appearance of the developing unit used together with the said drum unit. It is a perspective view which shows the schematic structure of the said positioning device. It is a perspective view of the positioning plate of the positioning device in a positioning completed state. It is a perspective view of the said positioning plate in the state inserted in the rotation axis | shaft of the hook of the holder part of the said positioning device. It is a perspective view which expands and shows the insertion part of the said positioning plate. It is a perspective view which shows the schematic structure of the said holder part. (A) And (b) is sectional drawing of the said positioning device, (a) is sectional drawing in the state before positioning completion, (b) is sectional drawing in the positioning completion state. . (A) And (b) is sectional drawing which shows the displacement of the said flat plate part when the front-end | tip of a drum shaft contacts the bearing hole of the flat plate part of the said positioning plate by rotation of the said positioning device, (a) is a cross-sectional view when the flat plate portion is moved in a direction opposite to the biasing direction of the coil spring, and (b) is a cross-sectional view when the inclination of the flat plate portion is changed. (A) And (b) is sectional drawing which shows the displacement of the said flat plate part when the front-end | tip of a positioning pin contacts the hole of the front side board of an apparatus main body by rotation of the said positioning apparatus, ) Is a cross-sectional view when the flat plate portion is moved in a direction opposite to the biasing direction of the coil spring, and (b) is a cross-sectional view when the inclination of the flat plate portion is changed. It is sectional drawing which expands and shows the contact part of the bearing hole of the said flat plate part, and a drum axis | shaft. FIG. 2 is a perspective view illustrating a schematic configuration of a waste toner conveying device of the image forming apparatus. FIG. 4 is a perspective view illustrating a configuration of a conveyance unit of the waste toner conveyance device. FIG. 6 is a perspective view of the waste toner conveying device before being rotated with respect to the apparatus main body. FIG. 3 is a perspective view when the waste toner conveying device is rotated with respect to the apparatus main body. It is a perspective view when the said positioning device is rotated with respect to the apparatus main body. It is a perspective view when the said drum unit is pulled out from the apparatus main body. FIG. 2 is a perspective view illustrating a positional relationship among a developing unit, a toner supply unit, and a toner cartridge of the image forming apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. Before describing the drum unit positioning apparatus of the present invention, first, an image forming apparatus to which the positioning apparatus is applied will be described.

(1. Configuration of entire image forming apparatus)
FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 200 according to an embodiment of the present invention. In this embodiment, the image forming apparatus 200 performs image formation by arranging four photosensitive drums 1a, 1b, 1c, and 1d corresponding to four different colors (yellow, cyan, magenta, and black) in parallel. It consists of a tandem color printer.

  In the apparatus main body of the image forming apparatus 200, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the right side in FIG. These image forming portions Pa to Pd are provided corresponding to images of four different colors (yellow, cyan, magenta, and black), and yellow, cyan, magenta are respectively obtained by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  The image forming portions Pa to Pd are provided with the above-described photosensitive drums 1a to 1d for carrying the visible images (toner images) of the respective colors, and further, an intermediate transfer belt that rotates clockwise in FIG. 8 is provided adjacent to each of the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 8 that moves while contacting the photosensitive drums 1a to 1d. Then, the toner image is transferred onto the sheet P in the fixing device 7 and then discharged from the apparatus main body. An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d counterclockwise in FIG.

  The paper P onto which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is conveyed to the secondary transfer roller 9 via the paper feed roller 12a and the registration roller pair 12b. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a belt in which both ends thereof are overlapped and joined to form an endless shape, or a belt without a seam (seamless) is used. The intermediate transfer belt 8 and the secondary transfer roller 9 are rotationally driven at the same linear speed as the photosensitive drums 1a to 1d by a belt drive motor (not shown). In addition, a belt cleaning device 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed on the upstream side in the moving direction of the intermediate transfer belt 8 as viewed from the image forming portion Pa.

  Next, the image forming units Pa to Pd will be described. Around the photosensitive drums 1a to 1d arranged rotatably, there are charging devices 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d, and the photosensitive drums 1a to 1d. Exposure unit 4 that performs exposure based on image data, development units 3a, 3b, 3c, and 3d that develop electrostatic latent images formed on the photosensitive drums 1a to 1d with toner, and photosensitive drums 1a to 1d Are provided with cleaning devices 5a, 5b, 5c and 5d for collecting and removing the developer (toner) remaining after the transfer of the toner image.

  When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the charging devices 2a to 2d, and then light is irradiated by the exposure unit 4 based on the image data. The electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. Each of the developing units 3a to 3d includes a developing roller (developer carrying member) disposed opposite to the photosensitive drums 1a to 1d, and toners of each color of yellow, cyan, magenta, and black are respectively supplied by a replenishing device (not shown). A predetermined amount is filled. This toner is supplied onto the photosensitive drums 1a to 1d by the developing rollers of the developing units 3a to 3d and electrostatically attached to the toner corresponding to the electrostatic latent image formed by exposure of the exposure unit 4. An image is formed.

  Then, by applying a predetermined transfer voltage to the primary transfer rollers 6 a to 6 d, yellow, cyan, magenta, and black toner images on the photosensitive drums 1 a to 1 d are primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. The primary transfer rollers 6a to 6d are rotationally driven at the same linear speed as the photosensitive drums 1a to 1d and the intermediate transfer belt 8 by a primary transfer drive motor (not shown). Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning devices 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched around a driven roller 10, a drive roller 11, and a tension roller 20. When the intermediate transfer belt 8 starts to rotate clockwise as the drive roller 11 is rotated by the belt drive motor, a sheet is formed. P is conveyed from the registration roller 12b to the nip portion (secondary transfer nip portion) between the secondary transfer roller 9 and the intermediate transfer belt 8 provided adjacent to the intermediate transfer belt 8 at a predetermined timing. A full color image is secondarily transferred on top. The paper P on which the toner image is transferred is conveyed to the fixing device 7.

  The sheet P conveyed to the fixing device 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 13 to fix the toner image on the surface of the sheet P, and a predetermined full color image is formed. It is formed. The paper P on which the full-color image is formed is distributed in the transport direction by the branching section 14 that branches in a plurality of directions. When an image is formed on only one side of the paper P, it is discharged as it is onto the discharge tray 17 by the discharge roller 15.

  On the other hand, when images are formed on both sides of the sheet P, a part of the sheet P that has passed through the fixing device 7 is once projected from the discharge roller 15 to the outside of the apparatus. Thereafter, the paper P is distributed to the paper transport path 18 by the branching section 14 by rotating the discharge roller 15 in the reverse direction, and is transported again to the secondary transfer roller 9 with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred to the surface of the paper P where the image is not formed by the secondary transfer roller 9 and conveyed to the fixing device 7 to fix the toner image, It is discharged to the discharge tray 17.

  A density detection sensor 35 is disposed on the downstream side of the image forming unit Pd and in the immediate vicinity of the upstream side of the secondary transfer roller 9. The density detection sensor 35 irradiates the reference image formed on the intermediate transfer belt 8 in the image forming portions Pa to Pd with measurement light, and detects the amount of reflected light from the reference image. The detection result is transmitted to a control unit (not shown) as a light reception output signal. As the density detection sensor 35, an optical sensor provided with a light emitting element composed of an LED or the like and a light receiving element composed of a photodiode or the like is generally used. When measuring the density of the reference image, when the measurement light is sequentially emitted from the light emitting element to the reference image on the intermediate transfer belt 8, the measurement light is reflected as light reflected by the toner and as light reflected by the belt surface. Is incident on.

  When the toner adhesion amount is large, the reflected light from the belt surface is blocked by the toner, so that the light reception amount of the light receiving element is reduced. On the other hand, when the adhesion amount of toner is small, conversely, the amount of reflected light from the belt surface increases, resulting in an increase in the amount of light received by the light receiving element. Therefore, the toner adhesion amount (image density) of the reference image of each color is detected based on the output value of the received light signal based on the received reflected light amount, and the exposure amount and the development bias characteristic value are compared with a predetermined reference density. By adjusting, density correction is performed for each color.

  Since the density detection sensor 35 needs to strictly define the distance to the reference image, which is a measurement object, as shown in FIG. 1, the density detection sensor 35 is provided with a driving roller 11 having a small distance variation to the surface of the intermediate transfer belt 8. It is arranged at a position facing each other.

  The density detection sensor 35 may be disposed at another position where the reference image on the intermediate transfer belt 8 can be detected. For example, when the density detection sensor 35 is disposed on the downstream side of the secondary transfer roller 9, the image forming units Pa to. There is a possibility that the time from when the reference image is formed by Pd to when the density detection is performed becomes longer, and when the reference image comes into contact with the secondary transfer roller 9, the surface state of the reference image may change. Therefore, as shown in FIG. 1, it is preferable that the intermediate transfer belt 8 is disposed downstream of the image forming portion Pd and upstream of the contact position of the secondary transfer roller 9 with respect to the moving direction of the intermediate transfer belt 8.

(2. Details of the image forming unit)
Next, details of the above-described image forming unit Pa will be described. Since the image forming units Pb to Pd have basically the same configuration as the image forming unit Pa, detailed description thereof is omitted.

  FIG. 2 is an enlarged sectional view showing the vicinity of the image forming portion Pa in FIG. Around the photosensitive drum 1a, the above-described charging device 2a, developing unit 3a, primary transfer roller 6a, and cleaning device 5a are disposed along the drum rotation direction (counterclockwise in FIG. 2). Among these, the primary transfer roller 6a is disposed at a position facing the photosensitive drum 1a with the intermediate transfer belt 8 interposed therebetween.

  The photosensitive drum 1a, the charging device 2a, and the cleaning device 5a are unitized. In the image forming units Pa to Pd, units including the photosensitive drum, the charging device, and the cleaning device are hereinafter referred to as drum units 50a to 50d (see FIG. 3A, FIG. 4, etc.). To do.

  Further, a belt cleaning device 19 including a brush roller 19a facing the driven roller 10 with the intermediate transfer belt 8 interposed therebetween is disposed on the upstream side in the rotation direction of the intermediate transfer belt 8 with respect to the photosensitive drum 1a. The brush roller 19a is rotationally driven in the same direction (forward rotation) at a linear speed that is faster (1.2 times in this case) than the linear speed of the intermediate transfer belt 8 on the contact surface with the intermediate transfer belt 8.

  The charging device 2 a includes a charging roller 21 that contacts the photosensitive drum 1 a and applies a charging bias to the drum surface, and a charging cleaning roller 23 for cleaning the charging roller 21. The developing unit 3a is a touch-down developing type having two agitating and conveying screws 25, a magnetic roller 27, and a developing roller 29, and a developing bias having the same polarity (positive) as the toner charging polarity is applied to the developing roller 29. Applied to cause the toner to fly on the drum surface.

  The cleaning device 5 a includes a rubbing roller (abrasive member) 30, a cleaning blade 31, and a collection spiral 33. The rubbing roller 30 is pressed against the photosensitive drum 1a with a predetermined pressure, and is rotated in the same direction on the contact surface with the photosensitive drum 1a by a color drum cleaning motor (not shown). The linear velocity is controlled to be faster (1.2 times here) than the linear velocity of the photosensitive drum 1a. Examples of the rubbing roller 30 include a structure in which a foam layer made of EPDM rubber and having an Asker C hardness of 55 ° is formed as a roller body around a metal shaft. The material of the roller body is not limited to EPDM rubber, and other materials such as rubber and foamed rubber body may be used, and those having an Asker C hardness of 10 to 90 ° are preferably used.

  In addition, Asker C is one of durometers (spring type hardness testers) defined in the Japan Rubber Association standard, and is a measuring instrument for measuring hardness. Asker C hardness refers to the hardness measured with the above measuring instrument, and the larger the value, the harder the material.

  A cleaning blade 31 is fixed in contact with the photosensitive drum 1a on the surface of the photosensitive drum 1a downstream of the contact surface with the rubbing roller 30 in the rotation direction. As the cleaning blade 31, for example, a polyurethane rubber blade having a JIS hardness of 78 ° is used, and is attached at a predetermined angle with respect to the tangential direction of the photosensitive member at the contact point. The material, hardness, dimensions, the amount of biting into the photosensitive drum 1a, the pressure contact force, and the like of the cleaning blade 31 are appropriately set according to the specifications of the photosensitive drum 1a. The JIS hardness refers to the hardness specified by Japanese Industrial Standards (JIS).

  Residual toner removed from the surface of the photosensitive drum 1a by the rubbing roller 30 and the cleaning blade 31 is discharged to the outside of the cleaning device 5a (see FIG. 2) as the collection spiral 33 rotates. Examples of the toner used in the present invention include those in which an abrasive selected from silica, titanium oxide, strontium titanate, alumina and the like is embedded in the toner particle surface and held so as to partially protrude on the surface. In which the toner is electrostatically attached to the toner surface.

  The surface of the photosensitive drum 1a is polished by the residual toner containing the abrasive by rotating the rubbing roller 30 with respect to the photosensitive drum 1a in this way, and the drum is formed by the rubbing roller 30 and the cleaning blade 31. Remove surface moisture and contaminants along with residual toner.

  The layout inside the apparatus main body can be changed as appropriate. For example, the rotational directions of the photosensitive drums 1a to 1d and the intermediate transfer belt 8 are reversed from the present embodiment, and the positional relationship between the drum units 50a to 50d and the developing units 3a to 3d is reversed from the present embodiment. Of course, it is possible to set the transport path of the paper P in accordance with this.

  For example, FIGS. 3A and 3B are perspective views showing other configuration examples of the image forming apparatus 200. FIG. 3A is a diagram before positioning of the drum units 50a to 50d by the positioning device 60 described later. The perspective view in a state is shown, and Drawing 3 (b) shows the perspective view in the state after positioning of drum units 50a-50d. If the rotation direction of the photosensitive drums 1a to 1d and the intermediate transfer belt 8 and the conveyance path of the paper P can be appropriately set, as shown in FIGS. 3A and 3B, the drum units 50a to 50d and the developing unit are used. Of course, a layout in which the positional relationship with 3a to 3d is reversed from that in FIG. 1 is also possible.

  Here, the drum units 50a to 50d to be positioned by the positioning device 60 to be described later will be supplementarily described. FIG. 4 is a perspective view showing an external appearance of the drum unit 50a to be positioned by the positioning device 60. FIG. The drum unit 50a has a toner disposal port 51a in addition to the photosensitive drum 1a, the cleaning device 5a, and the charging device 2a. The waste toner collected by the cleaning device 5a is discharged from the toner waste port 51a, and is transported to the collection container 120 (see FIG. 16) via the waste toner transport device 110 (see FIG. 15) described later. Similarly, the drum units 50b to 50d also have toner disposal ports 51b to 51d, and the waste toner collected by the cleaning devices 5b to 5d is discharged from the toner disposal ports 51b to 51d and discarded. The toner is transported to the collection container 120 via the toner transport device 110.

  FIG. 5 is a perspective view showing an appearance of the developing unit 3a used in combination with the drum unit 50a. The developing unit 3a includes the above-described two stirring and conveying screws 25, a magnetic roller 27, and a developing roller 29, and a toner supply port 40a connected to a toner supply unit 130a (see FIG. 21) described later. have. Corresponding color toner is supplied into the developing unit 3a through the toner supply port 40a, and is used for developing the electrostatic latent image. Similarly, the developing units 3b to 3d have toner supply ports 40b to 40d, respectively, and corresponding color toners are supplied into the developing units 3b to 3d through the toner supply ports 40a to 40d. Then, it is used for developing an electrostatic latent image.

(3. Drum unit positioning device)
Next, the drum unit positioning device of the present invention will be described. For convenience of explanation below, directions are defined as follows. First, in the above-described image forming apparatus 200, the direction in which the drum axes of the photosensitive drums 1a to 1d are arranged is defined as the X direction, the direction perpendicular to the plane including the drum axes is defined as the Y direction, and the direction perpendicular to the X direction and the Y direction. The direction (drum axis direction) is taken as the Z direction. That is, in the image forming apparatus 200 of FIG. 1, the X direction corresponds to the left-right direction, the Y direction corresponds to the up-down direction, and the Z direction corresponds to the front-rear direction. The directions X, Y, and Z indicate directions in a state where positioning by the drum unit positioning device is completed (hereinafter also referred to as positioning completed state). In addition, the positive / negative direction of each direction of X, Y, and Z is not ask | required here.

  FIG. 6 is a perspective view showing a schematic configuration of the positioning device 60. The positioning device 60 is a drum unit positioning device that positions the drum units 50a to 50d individually having the photosensitive drums 1a to 1d, and includes a positioning plate 70, a holder portion 80, a coil spring 90 (see FIG. 8), and the like. have. Details of each component will be described below.

(3-1. Positioning plate)
FIG. 7 is a perspective view of the positioning plate 70 in a positioning completed state, and FIG. 8 is a perspective view of the positioning plate 70 in a state where the positioning plate 70 is inserted through a rotation shaft 83a of a hook 83 described later of the holder portion 80. The positioning plate 70 includes a flat plate portion 71 and insertion portions 72 and 72.

  As shown in FIG. 6, the flat plate portion 71 is a plate-like flat plate in which bearing holes 73a, 73b, 73c, and 73d, positioning pins 74 and 74, and concave portions 75a, 75b, 75c, and 75d are formed. The bearing holes 73a to 73d are formed in a line at a predetermined interval in the X direction in the flat plate portion 71, and are formed below the center in the Y direction. The concave portions 75a to 75d are formed in the flat plate portion 71 at positions shifted from the bearing holes 73a, 73b, 73c, 73d along the X direction. When the holder portion 80 is rotated, the toner disposal ports 51a to 51d (see FIG. 7) of the drum units 50a to 50d pass through the insides of the recesses 75a to 75d of the flat plate portion 71. Interference with 71 is avoided. As described above, the flat plate portion 71 is formed in a shape that can avoid contact with the toner disposal ports 51a to 51d of the drum units 50a to 50d when the holder portion 80 is rotated.

  The positioning pins 74 and 74 pass through the flat plate portion 71 and are fixed to the flat plate portion 71 so that the bearing holes 73a to 73d and the concave portions 75a to 75d are located between them. Therefore, the positioning pins 74 and 74 are located on the same straight line as the bearing holes 73a to 73d in the X direction. Such positioning pins 74 and 74 are fixed to the flat plate portion 71 with their rear ends caulked to plates 74a and 74a (see FIGS. 11A and 11B), and each drum unit 50a to 50d is loaded. By positioning into the positioning holes 42 and 42 (see FIG. 3A) formed in the front plate 41 of the apparatus main body to be positioned, the apparatus main body is positioned.

  The insertion portions 72 and 72 are formed by bending both ends of the flat plate portion 71 in the X direction in a direction opposite to the contact side with the front plate 41 (see FIG. 7). Therefore, the two insertion portions 72 and 72 are in a positional relationship facing each other with the flat plate portion 71 interposed therebetween.

  Insertion openings 72a and 72a are formed in the insertion portions 72 and 72, respectively. Here, FIG. 9 is an enlarged perspective view showing one insertion portion 72. The rotation shaft 83a of the hook 83 of the holder portion 80 is inserted through the insertion opening 72a through a slight gap t. The same applies to the other insertion portion 72. The average of the gap t is ((inner diameter of insertion port 72a) − (outer diameter of rotating shaft 83a)) / 2.

  That is, when the rotation shaft 83a is inserted through the insertion opening 72a through a gap, there is no uniform gap t between the outer surface of the rotation shaft 83a and the inner surface of the insertion opening 72a. Is positioned so as to be relatively displaced from the center of the insertion port 72a in the radial direction of the insertion port 72a and is in contact with the inner surface of the insertion port 72a, whereby the insertion part 72 is held by the rotating shaft 83a. Therefore, the minimum value of the gap t is 0 (value at the contact point), and the maximum value is (inner diameter of the insertion port 72a) − (outer diameter of the rotation shaft 83a). (Inner diameter of insertion port 72a) − (Outer diameter of rotating shaft 83a)) / 2.

  As described above, since the gap t exists between the inner surface of the insertion opening 72a and the outer surface of the rotation shaft 83a, the positioning plate 70 (particularly, the flat plate portion 71) can be slightly displaced in the holder portion 80. (Especially the pivot shaft 83a). That is, the positioning plate 70 is not completely fixed to the holder portion 80, but is held so that some wobble occurs. The displacement of the flat plate portion 71 includes a parallel movement of the flat plate portion 71 and includes a change in the inclination of the flat plate portion 71.

  Note that the insertion portions 72 and 72 may be configured as a member different from the flat plate portion 71 and fixed to both ends of the flat plate portion 71 in the X direction. In short, the insertion parts 72 and 72 may be provided upright in the Z direction at both ends in the X direction on the flat plate part 71.

(3-2. Holder part)
Next, the holder part 80 is demonstrated based on FIG. 6, FIG. 10 and FIG. 11 (a) (b). FIG. 10 is a perspective view showing a schematic configuration of the holder portion 80. 11 (a) and 11 (b) are sectional views showing a schematic configuration of the positioning device 60. FIG. 11 (a) shows a sectional view before the positioning is completed, and FIG. These show sectional views in a positioning completed state.

The holder portion 80 rotates while holding the positioning plate 70 around the rotation shaft 80a, so that the drum shafts 1a ₁ , 1b ₁ , This is a holding member for relatively inserting and removing 1c ₁ and 1d ₁ . The holder portion 80 is configured by connecting both ends of the rotation shaft 80 a and the main body 81 with connecting portions 82 and 82, and has hooks 83 and 83 and a lever 84.

Pivot shaft 80a is positioned parallel to the X direction the drum shaft 1a ₁ through 1d ₁ of the drum unit 50a~50d lined, and is supported on the apparatus main body so as to be positioned above the drum shaft 1a ₁ through 1d ₁ The The fact that the rotation shaft 80a is positioned above the drum shafts 1a _{1 to} 1d ₁ in FIG. 6 indicates that the rotation shaft 80a is located above the bearing holes 73a to 73d in which the drum shafts 1a _{1 to} 1d ₁ are fitted in the Y direction. It is clear from the location. Therefore, the positioning device 60 can be rotated about the rotation shaft 80a as a fulcrum so as to be opened downward with respect to the front surface of the apparatus main body.

  The main body 81 has a long shape in the X direction as a whole, and a shape in a cross section perpendicular to the rotation shaft 80a is a concave shape in which the side close to the front plate 41 is opened in the positioning completed state. The flat plate portion 71 of the positioning plate 70 described above is located in the opening of the main body 81. However, the flat plate portion 71 is movably held on the rotating shaft 83a via the insertion portions 72 and 72 as described above, and is not fixed to the main body 81. The main body 81 is positioned below the rotation shaft 80a in the Y direction when the positioning is completed.

  Such a main body 81 is configured to include an opposing wall portion 85, a bottom surface portion 86, side surface portions 87 and 87, a top surface portion 88, and hook protection portions 89 and 89.

  The facing wall portion 85 is a wall portion that faces the flat plate portion 71 of the positioning plate 70 via a gap. In the facing wall portion 85, recesses 85a, 85b, 85c, and 85d corresponding to the recesses 75a, 75b, 75c, and 75d of the flat plate portion 71 are formed. As a result, when the holder unit 80 is rotated, the toner disposal ports 51a to 51d of the drum units 50a to 50d pass through the insides of the recesses 85a to 85d of the opposing wall portion 85, and the toner disposal ports 51a to 51d and the opposing wall portion. Interference with 85 is avoided. 11A and 11B, the length (height) in the Y direction of the opposing wall portion 85 is shorter than the length (height) of the flat plate portion 71 in the Y direction. Further, the facing wall portion 85 is provided with a contact portion 85p with which the flat plate portion 71 abuts when the positioning is completed.

  The bottom surface portion 86 is connected to the lower end portion in the Y direction of the opposing wall portion 85 and constitutes the bottom surface of the main body 81. Therefore, the bottom surface portion 86 is a flat plate at the connection portion other than the opposing wall portion 85 and the recesses 85a to 85d, but has a shape having a curved surface along the recesses 85a to 85d at the connection portion with the recesses 85a to 85d. .

  The side surface portions 87 and 87 are vertically connected to the opposing wall portion 85 and the bottom surface portion 86 at both ends in the X direction. The upper surface portion 88 is connected to the upper end portion in the Y direction of the opposing wall portion 85, and the distance from the bottom surface portion 86 is stepped or continuous from the opposing wall portion 85 side toward the opening side (the flat plate portion 71 side). (See FIGS. 11A and 11B). The connecting portions 82 and 82 described above are provided at both ends of the upper surface portion 88 in the X direction.

  The hook protection portions 89 and 89 are respectively provided on the opposite side wall portion 85, the side surface portion 87, and the upper surface portion 88 in the X direction at both ends in the X direction so as to cover the hooks 83 and 83 within a plane perpendicular to the rotation shaft 80a. Is provided so as to protrude slightly in the X direction, and protects the hooks 83 and 83. However, the hook protection portions 89 and 89 are open on the side close to the front side plate 41 in the positioning completed state, and the tips of the hooks 83 and 83 are exposed from this opening.

  The hooks 83 and 83 are engaging members that engage with the apparatus main body (the holes 43 and 43 of the front side plate 41 (see FIG. 3A)) loaded with the drum units 50a to 50d. The rotation shaft 83a is provided at both ends of the rotation shaft 83a, and rotates around the rotation shaft 83a. The hooks 83 and 83 are urged by a spring (not shown) in a rotating direction to engage with the apparatus main body. Note that the rotation shaft 83a of the hooks 83 and 83 is provided in parallel to the rotation shaft 80a of the holder portion 80 (in the X direction when the positioning is completed).

  The lever 84 is fixed to the central portion in the X direction of the rotation shaft 83a of the hook 83/83, and the hook 83/83 is moved in the direction opposite to the rotation direction engaged with the apparatus main body with the rotation shaft 83a as a fulcrum. By rotating, the hooks 83 and 83 are disengaged from the main body.

(3-3. Coil spring)
Next, the coil spring 90 will be described with reference to FIGS. The coil spring 90 is an urging member that urges the flat plate portion 71 in a direction in which the flat plate portion 71 of the positioning plate 70 is separated from the opposed wall portion 85 of the holder portion 80, and between the opposed wall portion 85 and the flat plate portion 71. Is provided. In particular, the coil spring 90 biases a position shifted from the center of the flat plate portion 71 in a cross section perpendicular to the rotation shaft 80 a of the holder portion 80. Specifically, for example, when the positioning is completed in FIG. 11B, the coil spring 90 biases a position shifted downward in the Y direction from the center of the flat plate portion 71. Two coil springs 90 are provided corresponding to the two positioning pins 74 (see FIG. 8), and each of the coil springs 90 biases the positioning pins 74 from the rear end together with the plate 74a.

  The urging member is not limited to the coil spring 90 as long as the urging member can urge the flat plate portion 71 in the direction in which the flat plate portion 71 is separated from the opposing wall portion 85, and may be, for example, a plate spring. However, it may be a rubber-like elastic body.

(3-4. Positioning operation)
Next, an operation for positioning each drum unit 50a to 50d using the positioning device 60 will be described. Hereinafter, the direction in which the positioning device 60 is opened with respect to the apparatus main body, that is, the direction in which the positioning device 60 rotates with respect to the apparatus main body so that the drum units 50a to 50d are exposed is referred to as the A direction. The opposite direction is referred to as the B direction (see FIG. 11A).

First, in the initial state before the replacement of the drum units 50a to 50d, that is, the state in which the drum units 50a to 50d are loaded into the apparatus main body, as shown in FIG. 7, the drum shafts 1a _{1 to} 1d of the drum units 50a to 50d. ₁ is fitted in bearing holes 73a to 73d (see FIG. 6) of the flat plate portion 71 of the positioning device 60, and the drum units 50a to 50d are appropriately positioned. The positioning pins 74 and 74 are fitted in the holes 42 and 42 (see FIG. 3A) of the front plate 41 of the apparatus main body, and the positioning device 60 is appropriately positioned with respect to the apparatus main body. The position of the positioning device 60 with respect to the apparatus main body in such an initial state is the same as the position in the positioning completion state shown in FIG.

  At this time, as shown in FIG. 11 (b), the flat plate portion 71 is in contact with the tip of the contact portion 85 p erected on the opposing wall portion 85 of the holder portion 80, and the opposing wall portion 85 and the flat plate portion 71. Is maintained at the length d (mm) in the Z direction of the contact portion 85p. The flat plate portion 71 is biased in a direction away from the facing wall portion 85 by the coil spring 90, but movement in the biasing direction is restricted by contact with the front plate 41 of the apparatus main body.

Next, when exchanging the drum units 50a to 50d, the user operates the lever 84 of the holder portion 80 to release the positioning by the positioning device 60, and the hook 83. 83 is rotated, and the hooks 83 and 83 are disengaged from the main body (the holes 43 and 43 of the front side plate 41). Thus, the user, by the positioning device 60 is rotated in the direction A rotation shaft 80a of the holder portion 80 as a fulcrum, fitting and hole 42 of the drum shaft 1a ₁ through 1d ₁ into the bearing hole 73a~73d -It becomes possible to cancel | release fitting of the positioning pins 74 and 74 to 42. As shown in FIG. 3A, the user rotates each positioning unit 60 in the A direction until the drum shafts 1a _{1 to} 1d ₁ side of the drum units 50a to 50d are exposed, so that each drum unit 50a is removed from the apparatus main body. ˜50d can be taken out and replaced.

  At this time, the flat plate portion 71 is biased in the direction away from the opposing wall portion 85 by the coil spring 90, but the contact with the front side plate 41 is released, and the restriction on the movement in the bias direction due to the contact is also released. Therefore, as shown in FIG. 11 (a), the distance between the opposing wall portion 85 and the flat plate portion 71 is d + α (mm), and the distance is larger than that in the positioning completed state. The contact with 85p is also released. Α corresponds to the maximum length of the gap t between the insertion port 72a and the rotation shaft 83a (twice the average of the gap t).

After the replacement of the drum units 50a to 50d, the positioning device 60 is rotated in the B direction to position the drum units 50a to 50d. 12A and 12B show a state in which the tip of the drum shaft 1a ₁ is in contact with the bearing hole 73a of the flat plate portion 71 by the rotation of the positioning device 60 in the B direction. Since the drum shaft 1a ₁ extends in the Z direction, the fitting direction of the drum shaft 1a ₁ into the bearing hole 73a is also the Z direction. However, since the rotation direction of the positioning device 60 draws an arc-shaped locus in a cross section perpendicular to the rotation shaft 80a, it is strictly different from the above-described fitting direction. Therefore, it is easy to cause a twist when the drum shaft 1a ₁ is fitted into the bearing hole 73a.

However, the flat plate portion 71, because it is held by a holder part 80 (pivot shaft 83a) through the insertion portion 72, 72 in a displaceable state by the presence of the gap t, and the bearing hole 73a and the drum shaft 1a ₁ 12A, the flat plate portion 71 moves in a direction opposite to the urging direction against the urging of the coil spring 90, as shown in FIG. As shown in FIG. 12B, the flat plate portion 71 itself rotates and the inclination of the flat plate portion 71 with respect to the urging direction changes. Such flat plate portion 71 of the movement, i.e., the relative and and continuous change in position of the flat plate portion 71 with respect to the facing wall portion 85, the frictional resistance and stress at the time of contact with the bearing hole 73a and the drum shaft 1a ₁ alleviation This makes it easy to fit the drum shaft 1a ₁ into the bearing hole 73a. The fitting of the drum shafts 1b _{1 to} 1d ₁ into the bearing holes 73b to 73d is the same as described above.

  13A and 13B show a state in which the tip of the positioning pin 74 is in contact with the hole 42 of the front side plate 41 by the rotation of the positioning device 60 in the B direction. The fitting of the positioning pin 74 into the hole 42 is the same as described above. That is, when the positioning pin 74 and the hole 42 are in contact with each other, as shown in FIG. 13A, the flat plate portion 71 moves in a direction opposite to the biasing direction against the biasing of the coil spring 90. As shown in FIG. 13B, the flat plate portion 71 itself rotates and the inclination of the flat plate portion 71 with respect to the biasing direction changes as shown in FIG. Friction resistance and stress at the time of contact with the positioning pin 74 are reduced, and it becomes easy to fit the positioning pin 74 into the hole 42.

When the fitting of the drum shafts 1a _{1 to} 1d ₁ into the bearing holes 73a to 73d and the fitting of the positioning pins 74 and 74 into the holes 42 and 42 are completed in this way, as shown in FIG. The tip of the contact portion 85p contacts the flat plate portion 71, and positioning is completed. At this time, the tips of the hooks 83 and 83 are fitted and engaged with the holes 43 and 43 of the front side plate 41, and the positioning device 60 is completely fixed to the apparatus main body.

  As described above, according to the positioning device 60 of the present embodiment, if the rotation shaft 80a of the holder portion 80 is supported on the device main body side, the positioning device 60 is on the device main body side before and after the rotation. And is not completely separated from the apparatus body. Thereby, the attaching / detaching operation of the positioning plate 70 can be performed at a position close to the apparatus main body. Further, since the positioning device 60 repeats the rotation with the same trajectory with the rotation shaft 80a as a fulcrum, the positioning plate 70 is securely attached to the proper position by the rotation of the positioning device 60 every time the drum units 50a to 50d are replaced. In addition, it is not necessary to search for the attachment position of the positioning plate 70 for each replacement. Therefore, the operation of attaching / detaching the positioning plate 70 at the time of replacement of the drum units 50a to 50d can be performed smoothly, and the workability at the time of replacement of the drum units 50a to 50d can be significantly improved.

Further, the holder portion 80 of the positioning device 60, when fitted in the drum shaft 1a ₁ through 1d ₁ into the bearing hole 73a~73d by rotation, by contact with the bearing hole 73a~73d and the drum shaft 1a ₁ through 1d _1, The positioning plate 70 is held so that the position of the flat plate portion 71 relative to the opposing wall portion 85 changes relatively against the biasing force of the coil spring 90. Thereby, the frictional resistance and stress at the time of the contact can be reduced by the relative and continuous position change of the flat plate portion 71 with respect to the opposing wall portion 85, and thereby the twisting of both members can be reduced. . Accordingly, even in a configuration in which pivoting the holder portion 80, it is possible to perform the fitting of the drum shaft 1a ₁ through 1d ₁ into the bearing hole 73a~73d smoothly. In addition, since the twisting can be reduced with a simple configuration using the coil spring 90, a configuration in which the positioning plate 70 is attached / detached by the rotation of the holder portion 80 can be easily realized.

  Further, since the holder portion 80 can be rotated and the positioning plate 70 can be attached / removed by a simple operation using the lever 84, the workability at the time of exchanging the drum units 50a to 50d is further improved.

In addition, since a gap t is formed between the insertion port 72a of the insertion portion 72 of the positioning plate 70 and the rotation shaft 83a, the flat plate portion 71 is relative to the opposing wall portion 85 by this gap t. It is supported so that it can be displaced (translatable and rotatable). Thus, while a bearing hole 73a~73d and the drum shaft 1a ₁ through 1d ₁ Tonokojiri reliably reduced by position change of the flat plate portion 71, ensures drum shaft 1a ₁ through 1d ₁ to the bearing hole 73a~73d Can be fitted smoothly.

Further, the coil spring 90 biases a position shifted from the center of the flat plate portion 71 within a cross section perpendicular to the rotation shaft 80a of the holder portion 80 (see FIGS. 11A and 11B). Thereby, some curvature can be given to the flat plate part 71 within the said cross section. Here, FIG. 14 is an enlarged sectional view showing the contact portion between the bearing hole 73a and the drum shaft 1a ₁ of the flat plate portion 71. As shown in the figure, even when there is a slight gap between the bearing hole 73a and the drum shaft 1a ₁ in the positioning completed state, the warpage of the flat plate portion 71 causes the bearing hole 73a and the drum shaft 1a ₁ to be Will surely make line contact or surface contact. The same applies to the contact portions between the bearing holes 73b to 73d and the drum shafts 1b _{1 to} 1d ₁ . As a result, it is possible to prevent rattling of the drum shafts 1a _{1 to} 1d ₁ in the positioning completed state, and to stabilize electrical conduction when the drum shafts 1a _{1 to} 1d ₁ and the positioning plate 70 are grounded. be able to.

  In addition, since the coil spring 90 urges the positioning pin 74 from the rear end, the urging force of the coil spring 90 can be efficiently applied to the positioning pin 74. Thereby, even if it is the structure which rotates the holder part 80, the fitting of the positioning pin 74 to the hole 42 of the front side board 41 of an apparatus main body can be performed smoothly, suppressing both the twists, and a positioning board The positioning of 70 can be performed smoothly.

Further, in the positioning plate 70, the bearing holes 73a to 73d and the positioning pins 74 and 74 are positioned on the same straight line in the X direction, so that the drum shaft to the bearing holes 73a to 73d is rotated by the rotation of the holder portion 80. The fitting of 1a _{1 to} 1d _{1 and} the fitting of the positioning pins 74 and 74 into the holes 42 and 42 can be performed simultaneously. In addition, since the change in the position of the flat plate portion 71 against the bias of the coil spring 90 at the time of fitting acts in the same manner on each fitting portion, each fitting can be performed smoothly all at the same time.

(4. Waste toner transport device)
Next, the waste toner conveying device provided in the image forming apparatus 200 will be described. FIG. 15 is a perspective view illustrating a schematic configuration of the waste toner conveyance device 110. The waste toner conveying device 110 is attached to and detached from the toner waste ports 51a to 51d (see FIG. 7) of the drum units 50a to 50d, and is collected by each cleaning device (corresponding to the cleaning devices 5a to 5d in FIG. 1) to be a toner waste port. This is a device that conveys toner discharged from 51a to 51d to a collection container 120 (see FIG. 16). The waste toner conveying device 110 includes a rotation shaft 110a, connection ports 111a to 111d, a conveying portion 112 (see FIG. 16), a convex portion 113, hooks 114 and 114, and a lever 115. .

  The rotation shaft 110a is supported by the apparatus main body so as to be positioned in parallel with the X direction in which the toner disposal ports 51a to 51d of the drum units 50a to 50d are arranged. The rotation shaft 110a is located below the connection ports 111a to 111d in the Y direction. Therefore, the rotation shaft 110a is located below the toner disposal ports 51a to 51d connected to the connection ports 111a to 111d. doing. By positioning the rotation shaft 110a in this way, the waste toner conveying device 110 can be rotated about the rotation shaft 110a as a fulcrum so as to be opened upward with respect to the front surface of the apparatus main body. .

  The connection ports 111a to 111d are portions that are attached to and detached from the toner disposal ports 51a to 51d of the drum units 50a to 50d. Here, FIG. 16 is a perspective view of the transport unit 112. In FIG. 16, for the sake of convenience, only the drum unit 50d is illustrated among the drum units 50a to 50d. The toner for disposal conveyed to the inside through the connection ports 111a to 111d from the toner disposal ports 51a to 51d is transported along the X direction by the transport unit 112, and via the discharge port 112a (see FIG. 15). And discharged into the collection container 120.

  The protrusion 113 is fitted into the hole 44 (see FIG. 18) of the front plate 41 of the apparatus main body, and positions the waste toner conveying device 110 with respect to the apparatus main body. As shown in FIG. 15, the connection ports 111 a to 111 d and the convex portion 113 are located on the same straight line in the X direction.

  The hooks 114 and 114 are engaging members that engage with the holes 45 and 45 (see FIG. 18) of the front plate 41 of the apparatus main body, and both ends of the rotating shaft 114a that penetrates the side surface of the waste toner conveying device 110. The rotating shaft 114a is used as a fulcrum. The hooks 114 and 114 are biased by a spring (not shown) in a rotating direction to engage with the apparatus main body. The rotating shaft 114a of the hooks 114 and 114 is provided in parallel to the rotating shaft 110a of the waste toner conveying device 110, and is provided above the rotating shaft 110a in the Y direction.

  The lever 115 is provided so as to be interlocked with the hooks 114 and 114, and when the lever 115 is pulled, the hooks 114 and 114 are operated in the direction opposite to the rotation direction engaged with the apparatus main body with the rotation shaft 114 a as a fulcrum. Rotate. Thereby, the engagement of the hooks 114 and 114 with the apparatus main body is released, and the waste toner conveying apparatus 110 can be rotated.

  The waste toner conveying device 110 having the above-described configuration is provided on the opposite side of the drum units 50 a to 50 d with respect to the positioning device 60. That is, the positioning device 60 is located on the outside (front side) in the Z direction of each of the drum units 50a to 50d, and the waste toner conveying device 110 is located on the outside (front side) in the Z direction. Therefore, if the waste toner conveying device 110 is not rotated and opened first, the positioning device 60 cannot be rotated and then opened, and conversely, the positioning device 60 is not rotated and closed first. The waste toner conveying device 110 cannot be rotated and closed.

  Next, a procedure for exchanging the drum units 50a to 50d including the operation of the waste toner conveyance device 110 will be described. FIG. 17 is a perspective view showing the position of the waste toner conveying device 110 in the initial state with respect to the apparatus main body. When replacing the drum units 50a to 50d, first, the front cover (not shown) of the apparatus main body is opened, and then the lever 115 of the waste toner conveying apparatus 110 is pulled to disengage the hooks 114 and 114 from the apparatus main body. Then, the waste toner conveying device 110 is rotated about the rotation shaft 110a. At this time, due to the above-described positional relationship between the rotation shaft 110a and the toner disposal ports 51a to 51d, as shown in FIG. 18, the waste toner conveyance device 110 rotates upward with respect to the front of the apparatus main body. .

When the waste toner conveying device 110 is rotated, the positioning device 60 on the inner side is exposed. Therefore, the positioning device 60 can be rotated, and the positioning device 60 is rotated by the method described above. At this time, from the above-described positional relationship between the rotation shaft 80a and the drum shafts 1a _{1 to} 1d ₁ , as shown in FIG. 19, the positioning device 60 rotates downward with respect to the front surface of the apparatus main body. As a result, the positioning of the drum units 50a to 50d is released. For example, the drum unit 50a can be taken out and replaced as shown in FIG. The developing units 3a to 3d can also be replaced in the state shown in FIG. After the replacement, the normal state can be restored by the reverse procedure.

  As described above, in the image forming apparatus 200, the waste toner conveying device 110 is provided on the opposite side of the positioning units 60 from the drum units 50a to 50d. As described above, the waste toner transport device 110 is positioned outside the positioning device 60 in the drum axial direction, so that the waste toner transported by the waste toner transport device 110 and accumulated in the recovery container 120 is discarded. When removing 120 from the apparatus main body, the positioning device 60 need not be operated. That is, even if the positioning device 60 is not opened, the collection container 120 can be removed from the device main body in the state of FIG. 17, for example. As a result, the waste toner can be disposed of efficiently, and the workability can be improved. In particular, the waste toner disposal operation is often performed simultaneously with, for example, replacement of the toner cartridge, and the frequency thereof is much higher than the replacement frequency of the drum units 50a to 50d. Therefore, the above effect is very high. Become.

The positioning device 60, since it is located inside (the drum unit side) of the waste toner conveying device 110, the deflection caused by the drum shaft 1a ₁ through 1d ₁ becomes longer in each drum unit 50a~50d little relief can do.

  Further, since the rotation shaft 110a of the waste toner transport device 110 is located in parallel with the X direction in which the toner waste ports 51a to 51d are arranged, the rotating waste toner transport device 110 and the toner waste ports 51a to 51d Can be attached and detached at the same time for all of the toner disposal ports 51a to 51d. Further, the rotation shaft 110a is located below the toner disposal ports 51a to 51d, and the waste toner conveyance device 110 is opened upward with the rotation shaft 110a as a fulcrum, so that the waste toner conveyance device 110 is opened. The waste toner falling from the toner disposal ports 51a to 51d toward the installation surface of the image forming apparatus 200 can be received by the waste toner transport device 110, and the installation surface is prevented from being stained with the waste toner. can do.

The rotation shaft 80a of the positioning device 60 is positioned above the drum shafts 1a _{1 to} 1d _{1 of the} drum units 50a to 50d, and the positioning device 60 is opened downward with the rotation shaft 80a as a fulcrum. . In this way, the waste toner transport device 110 and the positioning device 60 are reversed in the opening direction with respect to the apparatus main body, so that the waste toner transport device 110 is rotated about the rotation shaft of the positioning device 60 as in this embodiment. The positioning device 60 can be configured to open the rotating shaft 110a side of the waste toner conveying device 110. That is, the waste toner conveying device 110 and the positioning device 60 can be rotated so that the space between the rotation shaft 110a and the rotation shaft 80a is exposed. In this case, even when both the waste toner conveying device 110 and the positioning device 60 are in the open state, they do not interfere with each other, and the space between the drum units 50a to 50d and the developing units 3a to 3d is wide. Can be secured. As a result, the drum units 50a to 50d and the developing units 3a to 3d can be easily replaced.

(5. About toner supply unit)
Incidentally, the image forming apparatus 200 is provided with a toner supply unit that supplies toner from the toner cartridge to the developing units 3a to 3d. In this embodiment, as described above, the waste toner conveying device 110 is positioned on the front side of the apparatus main body. Similarly, when the toner supply unit is positioned on the front side of the apparatus main body, the toner supply unit is In order to prevent interference with the waste toner conveying device 110, the toner supply unit has to be configured in a complicated shape, and in order to reliably supply the toner, a toner feeding mechanism is provided inside the toner supply unit. (For example, a screw) must be provided. This complicates the configuration of the toner supply unit and the design of the apparatus. Therefore, in this embodiment, the above-described inconvenience is avoided by positioning the toner supply unit on the rear side of the apparatus main body. Details of the arrangement position of the toner supply unit will be described below.

  FIG. 21 is a perspective view showing a positional relationship among the developing unit 3a, the toner supply unit 130a, and the toner cartridge 140a. The same applies to the positional relationships among the developing units 3b to 3d, the toner supply units 130b to 130d, and the toner cartridges 140b to 140d. The above-described intermediate transfer belt 8 (see FIG. 1) is positioned between the toner cartridges 140a to 140d and the developing units 3a to 3d.

  The toner supply units 130a to 130d are provided corresponding to the developing units 3a to 3d, and supply toner of a predetermined color from the toner cartridges 140a to 140d to the developing units 3a to 3d. Each of the toner supply units 130a to 130d is provided corresponding to an end of each developing unit 3a to 3d on the opposite side to the waste toner transport device 110. Accordingly, each of the toner supply units 130a to 130d is positioned on the opposite side of the waste toner conveying device 110 with respect to the intermediate transfer belt 8 (see FIG. 1) in the Z direction. The toner discharge sides of the toner supply units 130a to 130d are connected to toner supply ports 40a to 40d (see FIG. 5) of the developing units 3a to 3d.

  As described above, by positioning the toner supply units 130a to 130d, the toner supply units 130a to 130d do not interfere with the waste toner conveying device 110, and the toner supply units 130a to 130d are configured in a simple shape. It becomes possible to do. For example, in the present embodiment, the toner supply units 130a to 130d are configured to have cylindrical portions 131a to 131d. The cylindrical portions 131a to 131d are cylindrical supply portions that extend straight in the vertical direction so that the toner supplied from the toner cartridges 140a to 140d falls inside due to its own weight, and its design is relatively simple. It is.

  Thus, since each toner supply part 130a-130d can be formed in a simple shape having the cylindrical parts 131a-131d, each toner cartridge can be provided without providing a toner feed mechanism inside each toner supply part 130a-130d. The toner from 140a to 140d can be supplied to the developing units 3a to 3d.

  In particular, since each of the toner supply units 130a to 130d includes the above-described cylindrical portions 131a to 131d, the toner is supplied to each developing unit by utilizing the free fall of the toner inside the cylindrical portions 131a to 131d. Since it can supply to 3a-3d, the structure of each toner supply part 130a-130d can be simplified.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition to the color printer as shown in FIG. 1, the present invention has various functions such as a copying machine, a facsimile machine, and a multifunction machine (copying, facsimile machine, scanner, printer, etc.) and is also called an MFP (Multi Function Peripheral). It is also applicable to other image forming apparatuses such as

  The present invention is applicable to a quadruple tandem type image forming apparatus that forms a color image using an electrophotographic process.

1a to 1d Photosensitive drum 1a _{1 to} 1d ₁ Drum shaft 3a to 3d Developing unit 5a to 5d Cleaning device 42 Hole 50a to 50d Drum unit 51a to 51d Toner waste port 60 Positioning device (drum unit positioning device)
DESCRIPTION OF SYMBOLS 70 Positioning plate 71 Flat plate part 72 Insertion part 72a Insertion hole 73a-73d Bearing hole 74 Positioning pin 80 Holder part 80a Rotating shaft 83 Hook 83a Rotating shaft 84 Lever 85 Opposite wall part 90 Coil spring (biasing member)
DESCRIPTION OF SYMBOLS 110 Waste toner conveying apparatus 110a Rotating shaft 120 Collection container 130a-130d Toner supply part 131a-131d Cylindrical part 140a-140d Toner cartridge 200 Image forming apparatus Pa-Pd Image forming part

Claims (3)

In a drum unit positioning apparatus for positioning between drum units each having a photosensitive drum corresponding to four different colors,
A positioning plate having a flat plate portion formed with a bearing hole into which each drum shaft of the four photosensitive drums is fitted;
A holder portion that has an opposing wall portion that faces the flat plate portion of the positioning plate, and that rotates while holding the positioning plate, thereby allowing the drum shaft to be inserted and removed relative to the bearing hole;
A biasing member that biases the flat plate portion in a direction in which the flat plate portion of the positioning plate separates from the opposing wall portion of the holder portion;
When the drum shaft is fitted into the bearing hole by rotation, the holder portion is in contact with the bearing hole and the drum shaft, and resists urging by the urging member to the flat plate against the opposing wall portion. Holding the positioning plate so that the position of the part changes ,
The holder part is
A hook that engages with an apparatus main body loaded with each drum unit;
A lever that is fixed to the pivot shaft of the hook and releases the engagement of the hook with the device body by rotating the hook;
The positioning plate is
An insertion portion that is erected on the flat plate portion and has an insertion port through which the rotation shaft of the hook is inserted through a gap;
A positioning pin that is fitted into a positioning hole of the apparatus main body in which each drum unit is loaded;
The positioning pin penetrates the flat plate portion of the positioning plate and is fixed to the flat plate portion,
The biasing member biases the positioning pin from the rear end,
The drum unit positioning device, wherein each bearing hole of the positioning plate and the positioning pin are located on the same straight line. 2. The drum unit positioning according to claim 1, wherein the urging member urges a position shifted from a center of the flat plate portion of the positioning plate in a cross section perpendicular to a rotation axis of the holder portion. apparatus. A drum unit having individual photosensitive drums corresponding to four different colors;
An image forming apparatus provided with a drum unit positioning device for positioning between the drum units,
The drum unit positioning device includes:
A positioning plate having a flat plate portion formed with a bearing hole into which each drum shaft of the four photosensitive drums is fitted;
A holder portion that has an opposing wall portion that faces the flat plate portion of the positioning plate, and that rotates while holding the positioning plate, so that the drum shaft is inserted into and removed from the bearing hole;
A biasing member that biases the flat plate portion in a direction in which the flat plate portion of the positioning plate separates from the opposing wall portion of the holder portion;
When the drum shaft is fitted into the bearing hole by rotation, the holder portion is in contact with the bearing hole and the drum shaft, and resists urging by the urging member to the flat plate against the opposing wall portion. Holding the positioning plate so that the position of the part changes,
The image forming apparatus further includes a developing unit that is provided corresponding to each drum unit and that develops an electrostatic latent image formed on each photosensitive drum with toner.
Each of the drum units has a cleaning device that collects toner remaining after the transfer of the toner image on each of the photosensitive drums,
The image forming apparatus includes:
A waste toner transport device that transports the toner that is attached to and detached from the toner waste port of each drum unit and that is collected by the cleaning device and discharged from the toner waste port to a collection container;
The image forming apparatus, wherein the waste toner conveying device is provided on the outer side in the drum axial direction of each of the photosensitive drums with respect to the drum unit positioning device.

Images