JP5716083B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a positioning mechanism between drum units mounted on the image forming apparatus.

  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 is fitted, thereby positioning each drum unit with high accuracy.

  By the way, in each drum unit, due to the life of the photosensitive drum, it is necessary to replace the drum unit when the number of printed sheets reaches a predetermined number (for example, tens of thousands). 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.

  Further, when exchanging the drum unit, it is necessary to retract the developing roller disposed in contact with or close to each photosensitive drum from the photosensitive drum. For example, in Patent Document 2, the developing roller is brought into contact with the photosensitive drum in accordance with the mounting operation of the developing device to the image forming apparatus body or the closing operation of the opening / closing unit, and the developing device is removed or the opening / closing unit is opened. Accordingly, a developing device having a roller contact / separation mechanism for retracting the developing roller from the photosensitive drum is disclosed.

JP-A-7-306566 JP 2007-94386 A

  However, when the positioning plate is completely separated from the apparatus main body after the positioning plate is pulled out from each drum shaft as in Patent Document 1, after replacing 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.

  Accordingly, a method of inserting and removing the drum shaft relative to the bearing hole of the positioning plate by providing a holder member that is rotatably supported by the image forming apparatus main body while holding the positioning plate can be considered. In such a configuration, a spring member is provided to hold the holder member in an open state so as not to hinder the replacement operation of each drum unit and the developing unit disposed adjacent thereto.

  On the other hand, as described in Patent Document 2, when the shaft member for separating and contacting the developing roller with respect to the photosensitive drum protrudes from the front surface of the developing unit, the developing roller is pushed by pushing the shaft member with the positioning plate. The developing roller is retracted from the photosensitive drum by approaching the photosensitive drum and opening the positioning plate. However, since the reaction force of the shaft member acts when the positioning member is mounted by rotating the holder member, a certain amount of force is required for mounting the positioning plate. Furthermore, when the biasing force of the spring member for holding the holder member in the open state is applied in addition to the reaction force of the shaft member, there is a problem that the operability of the holder member holding the positioning plate is deteriorated.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of improving workability when replacing a drum unit and a developing unit.

  In order to achieve the above object, a first configuration of the present invention includes an image forming apparatus including a plurality of drum units, a plurality of developing units, a positioning plate, a roller contact / separation mechanism, a holder member, and a holding unit. Device. The plurality of drum units individually have photosensitive drums on which electrostatic latent images corresponding to different colors are formed, and are detachably disposed on the apparatus main body. The plurality of developing units are disposed so as to be close to or retractable from the respective photosensitive drums, have individual developing rollers for supplying toner on the respective photosensitive drums, and are detachably disposed adjacent to the respective drum units. . The positioning plate positions each drum unit. The roller contact / separation mechanism includes a shaft member provided so as to be able to protrude and retract from each developing unit surface facing the positioning plate, and a first urging member that urges the shaft member in a direction protruding from the developing unit surface. Each developing roller approaches or retracts from each photosensitive drum. The holder member is rotatably supported with respect to the apparatus main body, and a positioning plate is attached to the holder member. The holding means holds the holder member in a first position where the shaft member is pushed into the developing unit against the urging force of the first urging member and each drum unit is positioned by the positioning plate. The holder member is rotated by a predetermined amount from the first position and the first position. The shaft member protrudes from the developing unit by the first biasing member, and the positioning of each drum unit by the positioning plate is released. The position is selected and arranged.

  According to the first configuration of the present invention, each drum unit can be reliably positioned in a state in which the holder member is mounted at the first position. Further, the shaft member protrudes from the surface of each developing unit by the first urging member only by rotating the holder member from the first position to the second position, and each developing roller is retracted from each photosensitive drum. Can do. Therefore, the drum unit and the developing unit can be attached and detached in an arbitrary order, and workability at the time of replacement and maintenance of the drum unit and the developing unit is improved.

1 is a schematic cross-sectional view showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. Enlarged sectional view of the vicinity of the image forming portion Pa in the figure External perspective view of drum unit detachably mounted on image forming apparatus External perspective view of developing unit used with drum unit Schematic side view of roller contact / separation mechanism Schematic view of the relationship between the roller contact / separation mechanism, the developing roller, and the photosensitive drum as viewed from the right in FIG. The perspective view which looked at the positioning device from the positioning plate side The perspective view which looked at the positioning device from the holder member side The perspective view which shows the positional relationship of the positioning plate and drum unit in the positioning completion state Side sectional view of the positioning device cut at the position of the positioning pin The perspective view which looked at the waste toner conveyance apparatus mounted in an image forming apparatus from the drum unit side The perspective view which shows the structure of the conveyance part of a waste toner conveyance apparatus. The perspective view which shows the state before rotating a waste toner conveying apparatus with respect to an apparatus main body. The perspective view which shows the state which rotated the waste toner conveyance apparatus with respect to the apparatus main body The side view which looked at the position (1st position) of the initial state of a development unit and a positioning device from the left direction of FIG. The front view which shows the state which open | released the positioning device to the 2nd position Side view of developing unit and positioning device viewed from the left in FIG. The front view which shows the state which open | released the positioning device to the 3rd position FIG. 17 is an enlarged view of the vicinity of the drum unit and the developing unit. Side view of developing unit and positioning device viewed from the left in FIG. The perspective view which shows the state which pulled out the drum unit from the apparatus main body.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 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.

  In the image forming portions Pa to Pd, the above-described photosensitive drums 1a to 1d for carrying visible images (toner images) of the respective colors are arranged, respectively, and further intermediate transfer that rotates counterclockwise in FIG. A belt 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 13 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 clockwise 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 dielectric resin is used for the intermediate transfer belt 8, and a (seamless) belt mainly having no seam 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). A blade-like belt cleaner 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed downstream of the secondary transfer roller 9.

  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 5 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 7a, 7b, 7c and 7d for collecting and removing the developer (toner) remaining after the transfer of the toner image.

  When image data is inputted 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 5 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 so as to face the photosensitive drums 1a to 1d, and a predetermined amount of two-component developer containing toners of cyan, magenta, yellow, and black colors, respectively. Filled.

  In addition, when the ratio of the toner in the two-component developer filled in each developing unit 3a to 3d falls below a specified value due to the formation of a toner image described later, the developing devices 3a to 3d are transferred from the toner containers 4a to 4d. Toner is replenished. This toner is supplied onto the photosensitive drums 1a to 1d by the developing units 3a to 3d and electrostatically attached to form a toner image corresponding to the electrostatic latent image formed by exposure of the exposure unit 5. Is done.

  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 7a to 7d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched over a driven roller 10 and a drive roller 11, and when the intermediate transfer belt 8 starts to rotate counterclockwise as the drive roller 11 is rotated by the belt drive motor, the sheet P is registered. The roller 12b is conveyed at a predetermined timing to a secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 and a nip portion (secondary transfer nip portion) between the intermediate transfer belt 8 and full color on the paper P at the nip portion. The image is secondarily transferred. The sheet P on which the toner image is transferred is conveyed to the fixing device 13.

  The sheet P conveyed to the fixing device 13 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 13a 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 forming images on both sides of the paper P, a part of the paper P that has passed through the fixing device 13 is once protruded from the discharge roller 15 to the outside of the device. 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 sheet P where the image is not formed by the secondary transfer roller 9 and conveyed to the fixing device 13 to fix the toner image, It is discharged to the discharge tray 17.

  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 7a are arranged 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 7a 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 40a to 40d (see FIG. 4).

  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 so-called touch-down developing type that includes two agitating and conveying screws 25, a magnetic roller 27, and a developing roller 29, and the developing roller 29 has the same polarity (positive) as the toner charging polarity. A bias is applied to cause the toner to fly on the drum surface.

  The cleaning device 7 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 driven to rotate in the same direction on the contact surface with the photosensitive drum 1a by a drum cleaning motor (not shown). The speed is controlled to be faster (1.2 times here) than the linear speed 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).

  The 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 7a (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 appropriately changed as long as the rotation directions 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. For example, the rotation 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 40a to 40d 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.

  FIG. 3 is a perspective view showing the appearance of the drum unit 40a. Note that the drum units 40b to 40d have basically the same configuration as the drum unit 40a, and a description thereof will be omitted. The drum unit 40a has a toner disposal port 41a in addition to the photosensitive drum 1a, the charging device 2a, and the cleaning device 7a. The waste toner collected by the cleaning device 7a is discharged from the toner waste port 41a and is transported to the collection container 110 (see FIG. 12) via the waste toner transport device 100 (see FIG. 11) described later.

  FIG. 4 is a perspective view showing an appearance of the developing unit 3a used in combination with the drum unit 40a. Since the developing units 3b to 3d have basically the same configuration as the developing unit 3a, description thereof is omitted. The developing unit 3a includes the above-described two agitating and conveying screws 25, a magnetic roller 27, and a developing roller 29, and is connected to a toner supply unit (not shown) that supplies toner from the toner container 4a. The toner supply port 50a is provided. Corresponding color (here, cyan) toner is supplied into the developing unit 3a through the toner supply port 50a, and is used for developing the electrostatic latent image.

  Further, the developing units 3a to 3d include a roller contact / separation mechanism 51 (see FIG. 5) that moves the developing roller 29 (see FIG. 2) closer to or away from the photosensitive drums 1a to 1d. An abutting portion 53a of a shaft member 53 constituting the roller contacting / separating mechanism 51 protrudes from the front surface of the developing units 3a to 3d facing the positioning plate 70 (see FIG. 7) of the apparatus 60. Further, a duct connecting portion 50b connected to a suction duct for sucking the floating toner in the developing units 3a to 3d is formed in the vicinity of the contact portion 53a. Further, a fitting hole 50c into which positioning bosses 86a to 86d (see FIG. 7) of the positioning device 60 are fitted is formed below the contact portion 53a and the duct connecting portion 50b.

  FIG. 5 is a schematic side view of the roller contact / separation mechanism, and FIG. 6 is a schematic view of the relationship between the roller contact / separation mechanism, the developing roller, and the photosensitive drum as viewed from the axial direction (right direction in FIG. 5). The approach and retraction mechanism of the developing roller 29 to the photosensitive drums 1a to 1d by the roller contact / separation mechanism 51 will be described with reference to FIGS. Here, the roller contact / separation mechanism 51 of the developing unit 3a will be described, but the description is omitted because the same applies to the developing units 3b to 3d. The roller contact / separation mechanism 51 includes arm members 52a and 52b, a shaft member 53, a compression spring 54, and a bearing member 55.

  The arm members 52a and 52b abut against the shaft member 53 from below, and are biased upward by a biasing means (not shown) such as a spring in a free state. The shaft member 53 is formed of a material having a predetermined rigidity and is a rod-like member disposed along the longitudinal direction of the developing unit 3a. The shaft member 53 is disposed so as to be movable in the axial direction (arrow AA ′ direction). Yes. The shaft member 53 has an abutting portion 53a that can abut on the positioning plate 70 (see FIG. 7) at an end portion on the front side in the axial direction, and on the outer peripheral surface of the shaft member 53, arm members 52a and 52b Two ribs 53b having a trapezoidal shape in side view are formed at corresponding positions.

  The compression spring 54 biases the shaft member 53 axially forward (in the direction of arrow A ′) so that the contact portion 53a of the shaft member 53 protrudes from the front side of the developing unit 3a in a free state. The bearing member 55 is formed integrally with the arm members 52a and 52b, and receives links at both ends of the rotary shafts 27a and 29a of the magnetic roller 27 and the developing roller 29 (see FIG. 2) to connect the rollers 27 and 29. It functions as a member, and rotates integrally around the rotation axis of the magnetic roller 27. Accordingly, when the bearing member 55 rotates about the rotation shaft 27a, the developing roller 29 rotates together with the bearing member 55 about the magnetic roller 27 to approach or retract from the photosensitive drum 1a. The bearing member 55 may be a separate member from the arm members 52a and 52b.

  As shown in FIGS. 5 and 6, in a state where the contact portion 53a of the shaft member 53 protrudes from the developing unit 3a, the arm members 52a and 52b ride on the rib 53b and are pushed downward, and the developing roller 29 is It is in a position retracted from the photosensitive drum 1a. When the contact portion 53a is pushed into the developing unit 3a from this state, the arm member 52a, 52b is detached from the rib 53b by the shaft member 53 moving in the axially inner side (arrow A direction), and the arm member 52a and 52b rotate in the direction of arrow B. The bearing member 55 together with the arm members 52a, 52b also rotates in the direction of arrow B about the rotation shaft 27a, so that the developing roller 29 approaches the photosensitive drum 1a.

  Further, when the pressing of the contact portion 53a is released again, the shaft member 53 moves forward in the axial direction (arrow A ′ direction) by the urging force of the compression spring 54, so that the arm members 52a and 52b ride on the ribs 53b. The arm members 52a and 52b rotate in the arrow B ′ direction. The bearing member 55 as well as the arm members 52a and 52b rotate in the direction of the arrow B ′ about the rotation shaft 27a, so that the developing roller 29 is retracted from the photosensitive drum 1a.

  Here, the shaft member 53 is configured such that the front side arm member 52a and the back side arm member 52b are simultaneously pushed downward by the ribs 53b. However, the rotation timings of the arm members 52a and 52b are different. May be. For example, the rear arm member 52b may be pushed down first, and then the front arm member 52a may be pushed down.

  Next, a drum unit positioning device used in the image forming apparatus 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.

  7 and FIG. 8 are perspective views of the positioning device 60 as viewed from the drum unit side and the outside of the device, respectively. FIG. 9 is a perspective view of the positioning plate 70 in the positioning completed state as viewed from the outside of the device. It is side surface sectional drawing which cut | disconnected the apparatus at the position of the positioning pin. The positioning device 60 is a drum unit positioning device that positions the drum units 40 a to 40 d each having the photosensitive drums 1 a to 1 d, and includes a positioning plate 70 and a holder member 80. Details of each component will be described below.

  As shown in FIG. 7, the positioning plate 70 has bearing holes 73a, 73b, 73c, 73d, positioning pins 74, 74, recesses 75a, 75b, 75c, 75d, and openings 76a, 76b, 76c, 76d. A flat plate portion 71 is provided. 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 positioning pins 74 and 74 are fixed to the flat plate portion 71 so that the bearing holes 73a to 73d, the concave portions 75a to 75d, and the openings 76a to 76d are positioned therebetween. That is, the positioning pins 74 and 74 are located on the same straight line in the X direction as the bearing holes 73a to 73d. The positioning pins 74 and 74 are positioned with respect to the apparatus main body by being fitted into positioning holes (not shown) formed in the front side plate 41 of the apparatus main body in which the drum units 40a to 40d are loaded.

  The recesses 75a to 75d are formed in the flat plate portion 71 at positions shifted from the bearing holes 73a to 73d in the X direction. When the holder member 80 is rotated, the toner disposal ports 41a to 41d (see FIG. 9) of the drum units 40a to 40d pass inside the recesses 75a to 75d of the flat plate portion 71, and the toner disposal ports 41a to 41d and the flat plate portion Interference with 71 is avoided.

  Duct connecting portions 50b (see FIG. 4) formed on the front surfaces of the developing units 3a to 3d overlap the openings 76a to 76d. Thereby, the duct connection part 50b and the suction duct (not shown) formed in the holder member 80 are communicated.

  The positioning plate 70 is fixed with a grounding spring 90 that comes into contact with the front plate 41 of the apparatus body when the positioning device 60 is closed. The photosensitive drums 1a to 1d are grounded through the grounding spring 90 and the positioning plate 70.

  As shown in FIG. 9, the insertion portion 72 is 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. The insertion portion 72 has an insertion port 72a through which the rotation shaft 83a of the hook 83 of the holder member 80 is inserted through a slight gap.

  Thus, the presence of a gap between the inner surface of the insertion opening 72a and the outer surface of the rotation shaft 83a allows the positioning plate 70 (particularly the flat plate portion 71) to be able to be slightly displaced in the holder member 80 ( In particular, it is held on a rotating shaft 83a). That is, the positioning plate 70 is not completely fixed to the holder member 80, but is held so that some wobble (displacement) occurs with respect to the holder member 80. The displacement of the flat plate portion 71 includes a parallel movement of the flat plate portion 71 in the direction of the rotation shaft 83a, and also includes a change in the inclination of the flat plate portion 71 having the rotation shaft 83a as the swing axis.

The holder member 80, by rotating while holding the positioning plate 70 about the rotary shaft 80a, the bearing hole 73a~73d of the positioning plate 70, the drum shaft _{1a 1, 1b 1, 1c 1} , 1d A holding member for relatively inserting and removing ₁ . The holder member 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.

  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. As described above, the positioning plate 70 is held on the rotating shaft 83a via the insertion portions 72 and 72 so as to be displaceable.

  In the main body 81, recesses 85a, 85b, 85c, and 85d corresponding to the recesses 75a to 75d of the flat plate portion 71 are formed. As a result, when the holder member 80 is rotated, the toner disposal ports 41a to 41d of the drum units 40a to 40d pass through the insides of the recesses 85a to 85d of the main body 81, and the toner disposal ports 41a to 41d, the holder member 80, and the like. Interference can be avoided. Positioning bosses 86a to 86d that fit into the fitting holes 50c of the developing units 3a to 3d are projected from the lower end of the main body 81.

Pivot shaft 80a is positioned parallel to the X direction the drum shaft 1a ₁ through 1d ₁ of the drum unit 40a~40d 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. 7 indicates that the rotation shaft 80a is located above the bearing holes 73a to 73d into 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 of the apparatus main body.

  The hook protectors 89 and 89 are provided so as to slightly protrude in the X direction from the main body 81 so as to cover the hooks 83 and 83 in a plane perpendicular to the rotation shaft 80a. doing. The hook protection portions 89 and 89 are open on the side close to the front plate 41 so that the hooks 83 and 83 can be engaged with the front plate 41.

  The hooks 83 and 83 are engaging members that engage with holes (not shown) of the apparatus main body (front side plate 41) in which the drum units 40a to 40d are loaded, and the rotation shaft 83a supported by the main body 81. It is provided at both ends, and rotates integrally with the rotation shaft 83a as a fulcrum. The hooks 83 and 83 are urged by a spring (not shown) in a rotating direction to engage with the apparatus main body. The rotation shaft 83a of the hooks 83 and 83 is provided in parallel (X direction) with the rotation shaft 80a of the holder member 80.

  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.

  One end of a tension spring 91 is connected to one of the rotation shafts 83a of the hooks 83 and 83, and the other end of the tension spring 91 is fixed in the apparatus main body. And the fixed position of the tension spring 91 and the rotation fulcrum of the positioning device 60 (the rotation shaft 80a of the holder member 80) so that the urging force of the tension spring 91 acts in the direction of assisting the rotation operation of the positioning device 60. The relationship is determined. Specifically, the tension spring 91 is urged in the opening direction when the rotation angle of the positioning device 60 is greater than or equal to a predetermined angle in the apparatus body, and the rotation angle of the positioning device 60 is greater than the predetermined angle. When it is small, the positioning device 60 is fixed at a position where it is biased in the closing direction. Details of the fixing position of the tension spring 91 will be described later.

  Further, as shown in FIG. 10, a coil spring 92 that biases the flat plate portion 71 in a direction in which the flat plate portion 71 of the positioning plate 70 is separated from the main body 81 of the holder member 80 is formed between the inner wall surface of the main body 81 and the flat plate portion 71. It is provided in between. The coil spring 92 urges a position shifted from the center of the flat plate portion 71 in a cross section perpendicular to the rotation shaft 80 a (see FIG. 8) of the holder member 80. Specifically, two coil springs 92 are provided corresponding to the two positioning pins 74, respectively, and each positioning pin 74 is urged together with the plate 74a from the rear end to the front plate 41 side.

  In addition, as long as the flat plate part 71 can be urged in a direction in which the flat plate part 71 is separated from the main body 81, the plate spring 71 is not limited to a coil spring, and may be a plate spring or a rubber-like elastic body. Also good.

  Next, the waste toner conveying device provided in the image forming apparatus 200 will be described. FIG. 11 is a perspective view showing the configuration of the waste toner transport device 100 as viewed from the lower side on the drum unit side, and FIG. 12 shows the waste toner transport mechanism including the waste toner transport device 100 and the toner collection container from the upper front side of the device. FIG. In FIG. 12, only the connection ports 101a to 101d and the conveyance unit 102 of the waste toner conveyance device 100 are illustrated.

  The waste toner transport device 100 is attached to and detached from the toner waste ports 41a to 41d of the drum units 40a to 40d, and collects the toner collected by the cleaning devices 7a to 7d (see FIG. 1) and discharged from the toner waste ports 41a to 41d. This is a device for transporting to a collection container 110 (see FIG. 12). The waste toner conveying apparatus 100 includes a rotation shaft 100a, connection ports 101a to 101d, a conveying unit 102, a convex portion 103, hooks 104 and 104, and a lever 105.

  The rotation shaft 100a is supported by the apparatus main body so as to be positioned in parallel with the X direction in which the toner disposal ports 41a to 41d of the drum units 40a to 40d are arranged. The rotation shaft 100a is located on the lower side in the Y direction than the connection ports 101a to 101d. Therefore, the rotation shaft 100a is located on the lower side in the Y direction than the toner disposal ports 41a to 41d connected to the connection ports 101a to 101d. doing. Since the rotation shaft 100a is positioned in this manner, the waste toner conveying device 100 can be rotated about the rotation shaft 100a as a fulcrum so as to be opened upward with respect to the front surface of the apparatus main body. .

  The connection ports 101a to 101d are portions that are attached to and detached from the toner disposal ports 41a to 41d of the drum units 40a to 40d. In FIG. 12, only the drum unit 40a is illustrated among the drum units 40a to 40d for convenience. The waste toner conveyed from the toner disposal ports 41a to 41d to the inside through the connection ports 101a to 101d is conveyed along the X direction by the conveyance unit 102 and is transferred to the collection container 110 through the discharge port 102a. Discharged.

  The convex portion 103 is fitted into the hole 44 (see FIG. 14) of the front plate 41 of the apparatus main body, and positions the waste toner conveying device 100 with respect to the apparatus main body. As illustrated in FIG. 11, the connection ports 101 a to 101 d and the convex portion 103 are located on the same straight line in the X direction.

  The hooks 104 and 104 are engaging members that engage with the holes 45 and 45 (see FIG. 14) of the front plate 41 of the apparatus main body, and both ends of the rotating shaft 104a that penetrates the side surface of the waste toner conveying device 100. It rotates integrally with this rotating shaft 104a as a fulcrum. The hooks 104 and 104 are urged by a spring (not shown) in a rotation direction to engage with the apparatus main body. In addition, the rotation shaft 104a of the hooks 104 and 104 is provided in parallel to the rotation shaft 100a of the waste toner conveying device 100, and is provided above the rotation shaft 100a in the Y direction.

  The lever 105 is provided so as to be interlocked with the hooks 104 and 104. When the lever 105 is pulled, the hook 105 is hooked in the direction opposite to the rotation direction engaged with the holes 45 and 45 with the rotation shaft 104a as a fulcrum. 104 and 104 rotate. As a result, the hooks 104 and 104 are disengaged from the apparatus main body, and the waste toner conveying apparatus 100 can be rotated.

  The waste toner conveying device 100 having the above-described configuration is provided on the opposite side of each of the drum units 40a to 40d with respect to the positioning device 60. That is, the positioning device 60 is positioned on the outer side in the Z direction (the front side of the device) of each of the drum units 40a to 40d, and the waste toner conveying device 100 is positioned on the outer side in the Z direction. Therefore, if the waste toner conveying device 100 is not rotated and opened first, then the positioning device 60 cannot be rotated and opened, and conversely, the positioning device 60 must be first rotated and closed. The waste toner conveying device 100 cannot be rotated and closed.

  Next, a procedure for replacing the developing units 3a to 3d and the drum units 40a to 40d, including operations of the positioning device 60 and the waste toner conveying device 100, will be described. FIG. 13 is a perspective view showing positions of the positioning device 60 and the waste toner conveying device 100 with respect to the apparatus main body in an initial state.

In the state of FIG. 13, that is, in the state where the developing units 3 a to 3 d and the drum units 40 a to 40 d are loaded in the apparatus main body, as shown in FIG. 9, the drum shafts 1 a _{1 to 1} d ₁ of the drum units 40 a to 40 d. Is fitted in the bearing holes 73a to 73d of the flat plate portion 71 of the positioning device 60, and the drum units 40a to 40d are appropriately positioned. Further, the positioning pins 74 and 74 of the positioning device 60 are fitted in the holes of the front plate 41 of the apparatus main body, and the convex portion 103 of the waste toner conveying device 100 is also engaged with the holes 44 of the front plate 41. Therefore, the positioning device 60 and the waste toner conveying device 100 are appropriately positioned with respect to the apparatus main body.

  When replacing the developing units 3a to 3d and the drum units 40a to 40d from this state, first, a front cover (not shown) of the apparatus main body is opened, and then the lever 105 of the waste toner conveying device 100 (see FIG. 11). Is pulled to release the engagement between the hooks 104 and 104 and the holes 45 and 45 of the front side plate 41, and the waste toner conveying device 100 is rotated about the rotating shaft 100a.

  At this time, due to the above-described positional relationship between the rotation shaft 100a and the toner disposal ports 41a to 41d, the waste toner conveyance device 100 is rotated upward with respect to the front of the apparatus main body. When the waste toner conveying device 100 is rotated, as shown in FIG. 14, the positioning device 60 on the inner side is exposed.

  FIG. 15 is a side view of the initial positions of the developing unit and the positioning device as viewed from the left in FIG. In the following FIGS. 15, 17, and 20, the relationship between the developing unit 3a and the positioning device 60 will be described, but the relationship between the developing units 3b to 3d and the positioning device 60 will be described in exactly the same manner. .

  As shown in FIG. 15, in the positioning device 60, the positioning plate 70 is disposed at a position (first position) facing the front surface of the developing units 3a to 3d, and separates the developing roller 29 of each developing unit 3a to 3d. The contact portion 53 a of the shaft member 53 to be contacted is pushed into the developing units 3 a to 3 d by the flat plate portion 71 of the positioning plate 70. As a result, the developing rollers 29 (see FIG. 2) of the developing units 3a to 3d are arranged close to the photosensitive drums 1a to 1d in the corresponding drum units 40a to 40d, respectively.

  Further, when the positioning device 60 is in the first position, the straight line L passing through the fulcrum 93 on the main body side of the tension spring 91 and the rotation shaft 80a of the holder member 80 is positioned above the tension spring 91. The position of the fulcrum 93 is set. Therefore, the urging force in the direction in which the positioning units 60 are pressed against the developing units 3a to 3d (in the direction of white arrows in the figure) is acting.

  The urging force acting from the tension spring 91 acts in a direction to relieve the urging force in the opening direction acting from the compression spring 54 (see FIG. 5) via the contact portion 53a, so that the load applied to the hooks 83 and 83 is reduced. It is reduced. Therefore, deformation and breakage can be suppressed without increasing the strength of the hook 83.

  Next, the lever 84 provided on the holder member 80 of the positioning device 60 is operated to rotate the hooks 83 and 83 with the rotation shaft 83a as a fulcrum, and the hooks 83 and 83 and the apparatus main body (front plate 41) Release the engagement. 16 is a front view of the developing unit and the positioning device with the hooks of the positioning device being released, and FIG. 17 is a side view of the developing unit and the positioning device as viewed from the left in FIG.

The urging force of the compression spring 54 (see FIG. 5) acting on the shaft member 53 is stronger than the urging force of the tension spring 91 acting on the positioning member 60 when the urging forces of the developing units 3a to 3d are combined. Therefore, when the engagement between the hooks 83 and 83 and the apparatus main body is released, the contact portion 53a of the shaft member 53 protrudes from the front surface of the developing units 3a to 3d by the urging force of the compression spring 54, as shown in FIG. In addition, the positioning device 60 is held at a position (second position) rotated upward by a predetermined angle (counterclockwise in FIG. 17) from the position in FIG. At this time, 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 front side plate 41 are also released.

  Even in this second position, since the straight line L passing through the fulcrum 93 on the main body side of the tension spring 91 and the rotation shaft 80a of the holder member 80 is located above the tension spring 91, the positioning device 60 Is applied with a biasing force in a direction in which the developing units 3a to 3d are pressed against each other (in the direction of white arrows in the figure). Therefore, there is no need to worry that the positioning device 60 opens vigorously and hits the hand.

  Since the angle formed between the straight line L and the tension spring 91 is smaller at the second position than at the first position, the urging force in the white arrow direction acting on the positioning device 60 from the tension spring 91 is greater than that at the first position. Is also getting smaller. Therefore, when the positioning device 60 is rotated to a third position to be described later, there is no possibility that the load on the hand becomes too large.

  Next, with the rotation shaft 80a of the holder member 80 as a fulcrum, the positioning device 60 is released from the second position to a position (third position) that is further rotated upward by a predetermined angle. 18 is a front view showing a state in which the positioning device is opened to the third position, FIG. 19 is an enlarged view of the vicinity of the drum unit and the developing unit in FIG. 18, and FIG. 20 shows the developing unit and the positioning device on the left side of FIG. It is the side view seen from the direction.

  By opening the positioning device 60 to the third position, the front of the developing units 3a to 3d and the drum units 40a to 40d is widely opened as shown in FIG. Since the developing rollers 29 of the developing units 3a to 3d are retracted from the photosensitive drums 1a to 1d, for example, the drum unit 40d can be taken out and replaced as shown in FIG. Further, the other drum units 40a to 40c and the developing units 3a to 3d can be similarly replaced in the state shown in FIG.

  In this third position, as shown in FIG. 20, a straight line L passing through the fulcrum 93 on the main body side of the tension spring 91 and the rotation shaft 80a of the holder member 80 is located below the tension spring 91. Therefore, a biasing force acting in a direction away from the developing units 3a to 3d (in the direction of the white arrow in the figure) is applied to the positioning device 60. As a result, the positioning device 60 is held at the third position against the force of gravity by the urging force of the tension spring 91, so that it is not necessary to support the positioning device 60 by hand, and the drum units 40a to 40d and the developing unit 3a. -3d replacement workability is improved.

  After replacement of the developing units 3a to 3d or the drum units 40a to 40d, the positioning device 60 is shown in FIG. 18 by rotating the positioning device 60 downward from the state of FIG. Arranged at the second position. At this time, as described above, the urging force in the closing direction (the white arrow direction in FIG. 18) acts on the positioning device 60, and the positioning device 60 is held in contact with the contact portion 53a. The hand holding the member 60 can be released and easily moved to a position where force can be easily applied.

  Then, by applying force to the positioning device 60 from the state of FIG. 18 and pushing it to the first position shown in FIG. 15, the contact portion 53a is pushed into the developing units 3a to 3d, and again, each developing unit 3a to The 3d developing roller 29 is pressed against the photosensitive drums 1a to 1d. Here, since the urging force of the tension spring 91 acts in the closing direction, the load applied to the hand when the positioning device 60 is mounted can be reduced. Finally, the waste toner conveying device 100 can be returned to the state shown in FIG. 13 by rotating it upward and closing it.

  As described above, according to the configuration of the present embodiment, the pressing of the photosensitive drums 1a to 1d and the developing roller 29 of the developing devices 3a to 3d is released only by opening the waste toner conveying device 100 and the positioning device 60. can do. Therefore, any of the developing units 3a to 3d or the drum units 40a to 40d can be extracted or inserted in any order, and the developing units 3a to 3d and the drum units 40a to 40d can be replaced. Workability can be greatly improved.

  Further, by adjusting the position of the fulcrum 93 of the tension spring 91, the urging force acting on the positioning device 60 at the second position in contact with the contact portion 53a of the shaft member 53 is set in the closing direction. There is no worry that the positioning device 60 will open violently and hit the hand when 83 is released, and the load when mounting the positioning device 60 from the second position to the first position can be reduced.

  Further, since the biasing force of the tension spring 91 acts in the closing direction at the first position, the load in the opening direction applied to the hook 83 from the contact portion 53a can be reduced, and the durability of the hook 83 is also improved. Furthermore, since the urging force of the tension spring 91 acts in the opening direction at the third position, the developing units 3a to 3d and the drum units 40a to 40d can be easily replaced with both hands.

  The magnitude of the urging force of the tension spring 91 in the first to third positions can be adjusted as well as the position of the changing point where the direction of the urging force changes depending on the position of the fulcrum 93 of the tension spring 91. The magnitude of the urging force of the tension spring 91 can also be adjusted by selecting the elastic coefficient of the tension spring 91.

As shown in FIG. 19, the contact portion 53a of the shaft member 53 is provided on a straight line passing through the drum shafts 1a _{1 to} 1d ₁ (the same height as the drum shafts 1a _{1 to} 1d ₁ ). When the hooks 83 are released, the positioning plate 70 is pressed at the same height as the drum shafts 1a _{1 to} 1d ₁ (positioning pins 74) by the contact portion 53a.

As shown in FIG. 10, the positioning plate 70 is urged away from the holder member 80 by a coil spring 92, and the positioning pins 74 are in contact with the bearing holes 73a to 73d (drum shafts 1a _{1 to} 1d ₁ ) in the X direction. It is provided on the same straight line. Therefore, the direction of the pressing force acting on the positioning plate 70 from the contact portion 53a and the direction of the urging force acting on the positioning plate 70 from the coil spring 92 are just opposite directions. Accordingly, the pressed positioning plate 70 is less likely to tilt with respect to the drum axis 1a ₁ through 1d _1, since the drum shaft 1a ₁ through 1d ₁ and the bearing hole 73a~73d Tonokojiri can be suppressed, smooth positioning device 60 Can be opened.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, 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 can be used in an image forming apparatus including a plurality of drum units and developing units that can be attached to and detached from the apparatus main body, and a positioning plate that positions each drum unit. By using the present invention, it is possible to provide an image forming apparatus that is easy to mount and remove the positioning plate and excellent in workability at the time of unit replacement.

1a to 1d Photosensitive drum 1a _{1 to} 1d ₁ Drum shaft 3a to 3d Developing unit 40a to 40d Drum unit 41a to 41d Toner disposal port 51 Roller contact / separation mechanism 52a, 52b Arm member 53 Shaft member 53a Contact portion 54 Compression spring (first spring 1 biasing member)
55 Bearing member 60 Positioning device 70 Positioning plate 80 Holder member 80a Rotating shaft 83 Hook (holding means)
91 Tension spring (second biasing member)
92 Coil spring (third biasing member)
DESCRIPTION OF SYMBOLS 100 Waste toner conveying apparatus 100a Rotating shaft 110 Toner collection container 200 Image forming apparatus Pa-Pd Image forming part

Claims (5)

A plurality of drum units each having a photosensitive drum on which electrostatic latent images corresponding to different colors are formed and arranged detachably with respect to the apparatus main body;
A plurality of developing units disposed so as to be close to or retractable from the respective photosensitive drums, each having a developing roller for supplying toner onto the respective photosensitive drums, and detachably disposed adjacent to the respective drum units. Unit,
A positioning plate for positioning each drum unit;
A pair of bearing members that rotatably support both end portions of the rotation shaft of the developing roller and are rotatably supported with respect to the developing unit, a pair of arm members fixed to the bearing member, and the positioning A shaft member provided so as to be able to project and retract from the surface of each developing unit facing the plate, and reciprocating while contacting each arm member , and the shaft member is pivoted from the surface of the developing unit. A first urging member that urges in the protruding direction, and the shaft member is pushed into the developing unit to bring the developing rollers closer to the photosensitive drums , and the shaft member. A roller contacting / separating mechanism for retracting each developing roller with respect to each photosensitive drum by protruding from the developing unit ;
In an image forming apparatus comprising:
A holder member that is rotatably supported with respect to the apparatus main body and on which the positioning plate is mounted, and the shaft member is placed in the developing unit against the urging force of the first urging member. Holding means that is pushed in and holds each drum unit in a first position positioned by the positioning plate;
A second urging member that urges the holder member in a predetermined rotation direction;
Is provided,
The holder member rotates by a predetermined amount from the first position and the first position, and the shaft member protrudes from the developing unit by the first biasing member, and each drum unit by the positioning plate Are selectively disposed at a second position where the positioning is released, and a third position where the drum unit and the front surface of the developing unit are opened by a predetermined amount from the second position .
The second urging member urges the holder member in a direction to rotate in the first position direction when the holder member is in the first position and the second position, and the holder member When the second biasing member is rotated by a predetermined angle from the second position to the third position, the biasing force of the second biasing member changes in a direction in which the holder member is rotated in the third position direction. An image forming apparatus.   The positioning plate is formed with a plurality of bearing holes into which the drum shafts of the respective photosensitive drums are fitted, and when the holder member is disposed at the first position, the drum shafts are inserted into the bearing holes. 2. The image forming apparatus according to claim 1, wherein the drum unit is positioned by being fitted in the first and second drum units. 3. The second urging member is a tension spring having one end fixed to the holder member and the other end fixed to the apparatus main body, and when the holder member is in the second position, the main body of the tension spring The image forming apparatus according to claim 1 , wherein a straight line passing through a fulcrum on the side and a rotation axis of the holder member is located on the third position side with respect to the tension spring . Said second biasing member, the image forming apparatus according to any one of claims 1 to 3, characterized in that it is capable of holding the holder member to the third position. The positioning plate is supported so as to be able to swing with respect to the holder member, and is biased between the positioning plate and the holder member in a direction away from the holder member on a straight line passing through the bearing hole of the positioning plate. And a contact portion of the shaft member that contacts the positioning plate is provided at substantially the same height as each drum shaft of each drum unit. the image forming apparatus according to any one of claims 1 to 4.