Cartridge and bearing member

On a projection plane orthogonal to an axial line of a developing agent bearing member, forming an imaginary region surrounded by a plurality of straight lines and edges of electric contacts, while satisfying first, second, and third conditions, disposes the entirety of a positioning region inside an imaginary region. The first condition is that each of the ends of the plurality of straight lines is situated at an edge of the electric contacts or at the center of the developing agent bearing member. The second condition is that the center of the developing agent bearing member is situated at an intersection of the plurality of straight lines, or upon one of the straight lines. The third condition is that each of the straight lines is stipulated so that the area of the imaginary region is maximal, within the constrictions of the first and second conditions.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an electrophotographic image forming apparatus (also referred to as an “image forming apparatus”), and to a cartridge detachably mounted to the apparatus main unit of the image forming apparatus.

An image forming apparatus forms images on a recording medium using an electrophotographic image forming process. Examples of image forming apparatuses include electrophotographic copiers, electrophotographic printers (e.g., laser beam printers, LED printers, etc.), facsimile apparatuses, word processors, and so forth.

A cartridge is an arrangement where at least one of an electrophotographic photosensitive drum (also referred to as “photosensitive drum”) that is an image bearing member and a process unit (e.g., developing agent bearing member (also referred to as “developing roller”)) that acts upon the photosensitive drum has been formed into a cartridge. The cartridge is detachably mounted to the image forming apparatus. Both the photosensitive drum and the developing roller may be integrally formed into a single cartridge, or separately formed as different cartridges. The former, where both the photosensitive drum and developing roller are included, is referred to as a “process cartridge. In the latter, the arrangement including the photosensitive drum is referred to as a “drum cartridge”, and the arrangement including the developing roller is referred to as a “developing cartridge”. The term “image forming apparatus main unit” refers to the remainder of the image forming apparatus after removal of the cartridge(s).

Description of the Related Art

Conventionally, image forming apparatuses have used the cartridge system where process cartridges, drum cartridges, and developing cartridges are detachably mounted to the main unit of the image forming apparatus. According to these cartridge systems, maintenance of the image forming apparatus can be performed by the user him/herself, without having to depend on a field engineer for service, which has markedly improved ease of use. Accordingly, these cartridge systems are in widespread use in image forming apparatuses.

Positioning portions are provided to the cartridge, to position the cartridge in the image forming apparatus. There also are provided cartridges having memory for communicating with a power supply portion that supplies power from the image forming apparatus and with the image forming apparatus to record information of the cartridge, in order to control the image forming process (e.g., Japanese Patent Laid-Open No. 2014-119505).

The positions of a process unit and electric contacts provided to the cartridge, serving as an interface portion with the image forming apparatus are preferably highly precise, from the perspective of image quality stability and reducing the size of the image forming apparatus and cartridge. For example, the cartridge includes the photosensitive drum, and multiple electric communication units such as electric contacts and memory, as interface portions with the image forming apparatus.

Inside the main unit of the apparatus the cartridge is positioned by being pressed upwards by a cartridge lifter provided to the main unit of the apparatus so as to press the cartridge against an abutment portion of a deep-side frame. A positioned portion provided to the cartridge, that is abutted against the deep-side frame by being pressed upwards is provided near the photosensitive drum. That is to say, the positioning portion is at a position away from the electric contacts and memory. This tends to result in larger error in the position of the electric contacts and memory within the main unit of the apparatus. Conventionally, stable electric communication has been realized by forming a mechanism that can follow positional error of the electric contacts of the cartridge. This has been performed by managing the dimensions of parts making of the cartridge at a high level of precision, and forming units of multiple parts at the electric contact portion of the main unit of the apparatus.

SUMMARY OF THE INVENTION

A cartridge detachably mountable to an apparatus main unit of an image forming apparatus, the cartridge includes: a developing agent bearing member; a plurality of electric contacts each electrically connecting to the apparatus main unit; and a positioning region where the cartridge is positioned in a mounting direction of being mounted to the apparatus main unit, by coming into contact with the apparatus main unit. On an a projection plane orthogonal to an axial line of the developing agent bearing member, forming an imaginary region surrounded by a plurality of straight lines and edges of the electric contacts, while satisfying first, second, and third conditions, disposes the entirety of the positioning region is disposed inside the imaginary region. The first condition is that each of the ends of the plurality of straight lines is situated at an edge of the electric contacts or at the center of the developing agent bearing member. The second condition is that the center of the developing agent bearing member is situated at an intersection of the plurality of straight lines, or upon one of the straight lines. The third condition is that each of the straight lines is stipulated so that the area of the imaginary region is maximal, within the constrictions of the first and second conditions.

DESCRIPTION OF THE EMBODIMENTS

A cartridge and electrophotographic image forming apparatus according to the present invention will be described with reference to the drawings. The electrophotographic image forming apparatus will be described exemplified by a laser beam printer main unit, and a drum cartridge and developing cartridge detachably mounted to the laser beam printer main unit. In the following description, the longitudinal direction of the drum cartridge and developing cartridge is a direction generally parallel with a rotation axis L1of a photosensitive drum and a rotation axis L0of a developing roller. The rotation axis L1of the photosensitive drum and rotation axis L0of the developing roller are directions orthogonal to a conveyance direction of a recording medium. A transverse direction of the drum cartridge and the developing cartridge is a direction generally orthogonal to the rotation axis L1of the photosensitive drum and rotation axis L0of the developing roller. The direction in which the drum cartridge and developing cartridge are mounted to and detached from the laser beam printer main unit is the transverse direction of the cartridges in the embodiment. Note that reference symbols in the description are for referencing the drawings, and do not restrict the configuration.

First Embodiment

Description will proceed in the following order.

(1) Overall description of image forming apparatus

(2) Description of electrophotographic image forming process

(3) Configuration description of cleanerless system

(4) Configuration description of drum cartridge C

(5) Configuration description of developing cartridge B1

(6) Configuration description of positioning developing cartridge B1as to apparatus main unit A1

(7) Configuration description of contact/separation of developing cartridge B1to/from drum cartridge C

(8) Description of positioning portion of developing cartridge B1and interface portions

(1) Overall Description of Image Forming Apparatus

First, the overall configuration of an image forming apparatus to which an embodiment of the present invention has been applied will be described with reference toFIG. 2.FIG. 2is a side cross-sectional explanatory diagram of the image forming apparatus. The image forming apparatus illustrated inFIG. 2forms images by developing agent t on a recording medium2by electrophotographic image forming processing, in accordance with image information communicated from an external device such as a personal computer or the like. The developing cartridge B1and drum cartridge C are provided so as to be attachable and detachable to and from an apparatus main unit A1by the user. Examples of the recording medium2include recording paper, label sheets, OHP sheets, cloth, and so forth. The developing cartridge B1also has a developing roller13serving as a developing agent bearing member, and so forth. The drum cartridge C has a photosensitive drum10serving as an image bearing member, a charging roller11, and so forth.

The surface of the photosensitive drum10is uniformly charged by the charging roller11, by voltage applied from the apparatus main unit A1. The surface of the photosensitive drum10that has been charged is then irradiated by a laser beam L from an optical unit1in accordance with image information, and an electrostatic latent image is formed on the photosensitive drum10in accordance with the image information. This electrostatic latent image is developed by the developing agent t, by a later-described developing unit, thereby forming a developed image on the surface of the photosensitive drum10.

The recording medium2accommodated in a sheet feed tray4is separated and fed one sheet at a time, being regulated by a feed roller3aand a separating pad3bin contact therewith, synchronously with formation of the developed image. The recording medium2then is conveyed by a conveyance guide3dto a transfer roller6serving as a transfer unit. The transfer roller6is urged so as to come into contact with the surface of the photosensitive drum10.

Next, the recording medium2passes a transfer nip6aformed by the photosensitive drum10and the transfer roller6. Voltage of opposite polarity as the developed image is applied to the transfer roller6at this time, thereby transferring the developed image formed on the surface of the photosensitive drum10onto the recording medium2.

The recording medium2onto which the developed image has been transferred is regulated by a conveyance guide3fand conveyed to a fixing unit5. The fixing unit5has a drive roller5aand a fixing roller5cinto which is built in a heater5b. Heat and pressure are applied to the recording medium2when passing through a nip5dformed by the drive roller5aand fixing roller5c, thereby fixing the developed image transferred into the recording medium2. Accordingly, an image is formed on the recording medium2. Thereafter, the recording medium2is conveyed by a discharge roller pair3gand discharged at a discharge unit3h.

(2) Description of Electrophotographic Image Forming Process

Next, an electrophotographic image forming process to which an embodiment of the present invention has been applied will be described with reference toFIG. 3.FIG. 3is a cross-sectional explanatory diagram of the developing cartridge B1and drum cartridge C. As illustrated inFIG. 3, the developing cartridge B1includes the developing roller13serving as a developing unit, a developing blade15, and so forth, in a developer container16. The drum cartridge C has the photosensitive drum10, charging roller11, and so forth, in a cleaning frame21.

The developing agent t accommodated in a developing agent storage unit16aof the developer container16is fed from an opening16bof the developer container16into a developing chamber16c, by a developing agent conveying member17, rotatably supported in the developer container16, rotating in the direction indicated by the arrow X17. The developing roller13, in which a magnet roller12is built in, is provided in the developer container16.

Specifically, the developing roller13is configured including a shaft portion13eand rubber portion13d. The shaft portion13eis a slender electroconductive cylinder of aluminum or the like, and the middle portion thereof in the longitudinal direction is covered by the rubber portion13d(seeFIGS. 7A and 7B). The rubber portion13dcovers the shaft portion13eso that the outer shape thereof is coaxial with the shaft portion13e. The developing roller13attracts the developing agent t in the developing chamber16cto the surface of the developing roller13by the magnetic force of the magnet roller12. Thus, the developing roller13bears the developing agent. That is to say, the developing roller13serves as a developing agent bearing member that bears developing agent on the surface thereof.

The developing blade15is configured including a support member15amade up of a metal plate, and an elastic member15bmade from urethane rubber, a stainless steel plate, or the like, and is provided so that the elastic member15belastically comes into contact with the developing roller13with a constant contact pressure. Rotation of the developing roller13in a rotation direction X5regulates the amount of the developing agent t adhering to the surface of the developing roller13, and imparts a triboelectric charge to the developing agent t. Accordingly, a developing agent layer is formed on the surface of the developing roller13. Rotation in the rotation direction X5of the developing roller13, to which voltage has been applied from the apparatus main unit A1and that is in contact with the photosensitive drum10, supplies the developing agent t to a developing region on the photosensitive drum10.

In a case of a contact developing system such as in the present embodiment, maintaining a state where the developing roller13is constantly in contact with the photosensitive drum10as illustrated inFIG. 3may deform the rubber portion13dof the developing roller13. The developing roller13is preferably separated from the photosensitive drum10when not developing.

The charging roller11is provided in contact with the outer peripheral surface of the photosensitive drum10, rotatably supported by the cleaning frame21and urged toward the photosensitive drum10. A detailed configuration will be described later. The charging roller11uniformly charges the surface of the photosensitive drum10by application of voltage from apparatus main unit A1. The voltage to be applied to the charging roller11is set to a value so that the potential difference between the surface of the photosensitive drum10and the charging roller11is equal to or greater than discharge start voltage. Specifically, DC voltage of −1300 V is applied as the charging bias. The surface of the photosensitive drum10at this time is uniformly charged by contact charging to a charged potential (dark potential) of −700 V. The charging roller11performs driving rotation as to rotation of the photosensitive drum10in the present example (described later). The laser beam L from the optical unit1forms the electrostatic latent image on the surface of the photosensitive drum10. The developing agent t is subsequently transferred in accordance with the electrostatic latent image on the photosensitive drum10to form a visible image of the electrostatic latent image, thereby forming a developed image on the photosensitive drum10.

(3) Configuration Description of Cleanerless System

Next, the cleanerless system according to the present example will be described. An example of a so-called cleanerless system, where no cleaning member is provided to remove from the surface of the photosensitive drum10transfer residual developing agent t2remaining on the photosensitive drum10without being transferred, is illustrated in the present embodiment.

The photosensitive drum10is rotationally driven in the direction of the arrow C5, as illustrated inFIG. 3. A void (upstream void11b) is formed on the upstream side of a charging nip11athat is the contact portion of the charging roller11and photosensitive drum10, when viewed from the rotation direction C5of the photosensitive drum10. The transfer residual developing agent t2remaining on the surface of the photosensitive drum10after the transfer step is negatively charged, the same as the photosensitive drum10, by discharge at this upstream void11b. The surface of the photosensitive drum10is charged to −700 V at this time. The transfer residual developing agent t2charged to negative polarity passes through the charging nip11awithout adhering to the charging roller11, due to the relationship in potential difference (surface potential of photosensitive drum10=−700 V, potential of charging roller11=−1300 V).

The transfer residual developing agent t2that has passed the charging nip11areaches a laser irradiation position d. The amount of the transfer residual developing agent t2is not enough to shield the laser beam L of the optical unit, and accordingly does not influence the step of image formation of the electrostatic latent image on the photosensitive drum10. The transfer residual developing agent t2that has passed the laser irradiation position d and is at unexposed portions (the surface of the photosensitive drum10not subjected to irradiation of laser) is recovered by the developing roller13under electrostatic force, at a developing nip13kthat is the contact portions of the developing roller13and photosensitive drum10. On the other hand, the transfer residual developing agent t2at exposed portions (the surface of the photosensitive drum10subjected to irradiation of laser) is not recovered by electrostatic force and continues to remain on the photosensitive drum10. Still, there are cases where some of the transfer residual developing agent t2is recovered by physical force due to peripheral speed difference between the developing roller13and the photosensitive drum10.

Such transfer residual developing agent t2remaining on the photosensitive drum10without being transferred to the paper is generally recovered to the developer container16. The transfer residual developing agent t2recovered at the developer container16is mixed with the developing agent t remaining in the developer container16and used.

The following two configurations are employed in the present embodiment for the transfer residual developing agent t2to pass the charging nip11awithout adhering to the charging roller11. The first is that an optical electrostatic charge removal member8is provided between the transfer roller6and charging roller11. The optical electrostatic charge removal member8is situated at the upstream side of the charging nip11ain the direction of rotation of the photosensitive drum10(arrow C5), and performs optical electrostatic charge removal of surface potential of the photosensitive drum10that has passed the transfer nip6a, so that stable discharge can be performed at the upstream void11b. The potential of the photosensitive drum10before charging is set to around −150 V over the entire region in the longitudinal direction by this optical electrostatic charge removal member8, so uniform discharge can be performed when charged, and the transfer residual developing agent t2can be uniformly negatively charged.

The second is that a predetermined peripheral speed difference is provided to the driving rotation of the charging roller11as to the photosensitive drum10. As described above, almost all of the toner is of negative polarity due to discharging, but there is a certain amount of transfer residual developing agent t2that was not completely negatively charged, and this transfer residual developing agent t2may adhere to the charging roller11at the charging nip11a. Providing the predetermined peripheral speed difference to the driving rotation of the charging roller11and the photosensitive drum10enables such transfer residual developing agent t2to be imparted negative polarity by rubbing between the photosensitive drum10and charging roller11. This serves to suppress adhesion of the transfer residual developing agent t2to the charging roller11. A charging roller gear69is provided to one end of the charging roller11in the longitudinal direction thereof, and the charging roller gear69engages a drive side flange24provided to the same longitudinal-direction end of the photosensitive drum10. Thus, the charging roller11is rotationally driven by rotational driving of the photosensitive drum10. The peripheral speed of the surface of the charging roller11is set to as to be around 105 to 120% of the peripheral speed of the surface of the photosensitive drum10.

Next, the configuration of the drum cartridge C and developing cartridge B1to which an embodiment of the present invention has been applied will be described. Note that in the following direction, the side with relation to the longitudinal direction that rotary force is transmitted from the apparatus main unit A1to the drum cartridge C and developing cartridge B1will be referred to as “drive side”. The other side thereof is the other end of the drum cartridge C and developing cartridge B1, and will be referred to as “nondrive side”.

(4) Configuration Description of Drum Cartridge C

Next, the configuration of the drum cartridge C will be described with reference toFIGS. 4A and 4B.FIG. 4Ais a perspective explanatory diagram viewing the drum cartridge C from the nondrive side.FIG. 4Bis a perspective explanatory diagram from which the cleaning frame21, a drum bearing30, a drum shaft54, and so forth, have been omitted from illustration for description of around the photosensitive drum10and charging roller11. It can be seen inFIGS. 4A and 4Bthat the drum cartridge C has the photosensitive drum10and charging roller11. The charging roller11is rotatably borne by a charging roller bearing67aand a charging roller bearing67b, and is urged toward the photosensitive drum10by a charging roller urging member68aand a charging roller urging member68b.

The drive side flange24is integrally fixed to a drive side end portion10aof the photosensitive drum10, and a nondrive side flange28is integrally fixed to a nondrive side end portion10bof the photosensitive drum10. The drive side flange24and nondrive side flange28are coaxially fixed to the photosensitive drum10by a technique such as swaging, adhesion, or the like. At both end portions in the longitudinal direction of the cleaning frame21, the drum bearing30is fixed to the drive side end portion and the drum shaft54to the nondrive side end portion, by a technique such as screwing, adhesion, press-fitting, or the like. The drive side flange24integrally fixed to the photosensitive drum10is rotationally borne by the drum bearing30, and the nondrive side flange28is rotationally borne by the drum shaft54.

The charging roller gear69is provided to one end of the charging roller11in the longitudinal direction, the charging roller gear69meshing with a gear portion24gof the drive side flange24. A drive side end portion24aof the drive side flange24has a configuration (omitted from illustration) where rotary force is transmitted from the apparatus main unit A1side. As a result, the charging roller11is also rotationally driven long with the rotational driving of the photosensitive drum10. As described above, the peripheral speed of the surface of the charging roller11is set to as to be around 105 to 120% of the peripheral speed of the surface of the photosensitive drum10.

(5) Configuration Description of Developing Cartridge B1

FIG. 5is a perspective explanatory diagram viewing the developing cartridge B1from the drive side.FIG. 6is a perspective explanatory diagram viewing the developing cartridge B1from the nondrive side.FIGS. 7A and 7Bare disassembled views of the developing cartridge B1with the drive side disassembled,FIG. 7Abeing from the drive side andFIG. 7Bfrom the nondrive side, andFIGS. 8A and 8Bare disassembled views of the developing cartridge B1with the nondrive side disassembled,FIG. 8Abeing from the drive side andFIG. 8Bfrom the nondrive side.

Overall Configuration of Developing Cartridge B1

A configuration relating to the overall configuration of the developing cartridge B1will be described with reference toFIGS. 5 through 8B. The developing roller13and developing blade15are provided to the developing cartridge B1. The developing blade15has a drive side end portion15a1and a nondrive side end portion15a2in the longitudinal direction of a support member15afixed to the developer container16by a screw51and a screw52.

A drive side developer bearing36and nondrive side developer bearing46are provided at the ends of the developer container16in the longitudinal direction. The drive side developer bearing36and nondrive side developer bearing46are bearing members that rotatably bear the respective ends of the shaft of the developing roller13. A drive side end portion13afits into a hole36aof the drive side developer bearing36, and a nondrive side end portion13cfits into a support portion46fof the nondrive side developer bearing46, so that the developing roller13is rotatably borne. A developing roller gear29is disposed coaxially with the developing roller13, on the drive side end portion13aof the developing roller13further outward in the longitudinal direction from the drive side developer bearing36, and is engaged so that the developing roller13and the developing roller gear29can integrally rotate.

Configuration of Drive Side of Developing Cartridge B1

The configuration relating to the drive side of the developing cartridge B1will be described with reference toFIGS. 5, 7A, and 7B. The drive side developer bearing36of the developing cartridge B1rotatably supports a drive input gear27at the outer side thereof in the longitudinal direction, and the drive input gear27meshes with the developing roller gear29. A coupling member180is provided coaxially with the drive input gear27. A developing side cover34is provided at the outermost end portion of the drive side of the developing cartridge B1so as to cover the drive input gear27and so forth from the outer side in the longitudinal direction. The coupling member180protrudes to the outside in the longitudinal direction through a hole34ain the developing side cover34. The coupling member180is configured to engage a main unit side drive member100provided to the apparatus main unit A1, so that rotary force is transmitted.

The configuration is such that the rotary force thereof is transmitted to a rotary force transmission-receiving portion (omitted from illustration) of the drive input gear27, via rotary force transmission portions180c1and180c2of the coupling member180. As a result, the configuration is such that the rotary force input to the coupling member180is transmitted to the developing roller13serving as a rotary member via the drive input gear27and developing roller gear29, and the developing roller13rotates on the rotation axis L0in the rotation direction X5.

A coupling spring185is formed of a torsion coil spring, and a positioning portion185aof the coupling spring185is supported by a spring supporting portion34hof the developing side cover34. One end portion185bof the coupling spring185is fixed to a spring engaging portion (omitted from illustration) of the developing side cover34, and an other end portion185cof the coupling spring185is in contact with a guided portion180dof the coupling member180. Thus, in a state where the developing cartridge B1is alone, i.e., in a state where the developing cartridge B1is not mounted to the apparatus main unit A1, a rotation axis L2of the coupling member180is inclined as to a rotation axis L3of the drive input gear27. The coupling member180is held in a state where the guided portion180dthereof is in contact with an inclination regulating portion34kat a portion of the hole34aof the developing side cover34.

The drive side developer bearing36is provided with a drive side contact/separation lever70serving as a lever main unit, and a drive side developing pressurizing spring71serving as an elastic member. Details will be described later.

Configuration of Nondrive Side of Developing Cartridge B1

The configuration relating to the nondrive side of the developing cartridge B1will be described with reference toFIGS. 6, 8A, and 8B. A memory board47and a contact portion47aserving as an exposed face, are provided as a contact point portion (electric contact) at the nondrive side end portion of the developing cartridge B1. The manufacturing lot and property information of the developing cartridge B1are recorded in the memory board47, and used when forming images at the apparatus main unit A1. The memory board47is provided with the contact portion47amade of a metal such as iron or copper or the like, and when performing image forming, electrically connects to the apparatus main unit A1via the contact point portion47aand performs communication. The memory board47is fixed to the nondrive side developer bearing46by a technique such as press-fitting, adhesion, or the like. A developing roller contact portion13fand developing blade contact portion15fare further provided to the nondrive side developer bearing46as a contact point portion (electric contact) at the nondrive side end portion of the developing cartridge B1. In a state where the developing roller13, to which voltage is applied from the apparatus main unit A1, is in contact with the photosensitive drum10, as described above, the developing roller13is rotated and developing agent t is supplied from the photosensitive drum10to the developing region. Specifically, in the present configuration, −300 V is applied to the developing roller13and −600 V to the developing blade for uniform contact charging, as bias of voltage applied from the apparatus main unit A1. Conduction is secured from the developing roller13to the developing roller contact portion13fand from the developing blade15to the developing blade contact portion15fby electroconductive resin, coming into contact with contacts disposed on the apparatus main unit A1, whereby voltage is applied to the developing roller13and developing blade15. The contact portion47ais an electric contact for electric communication, and the developing roller contact portion13fand developing blade contact portion15fare electric contacts for application of voltage (electric power supply).

The nondrive side developer bearing46is configured by double-shot injection molding, where two types of resin material are integrally molded. A bearing base portion46gthat is a first molded member is molded using an insulating polystyrene material, and the developing roller contact portion13fand developing blade contact portion15fare molded using an electroconductive polyacetal resin including carbon black. Thus, the above-described conduction can be secured. Note that the method of conduction, resin materials, and molding methods may be selected taking into consideration functionality such as strength and so forth, cost, and the like, and the above is not restrictive. Details of the contact position relationship between the contacts of the nondrive side end portion and the apparatus main unit A1will be described in detail later.

The nondrive side developer bearing46is provided with a nondrive side contact/separation lever72serving as a lever main unit, and a nondrive side developing pressurizing spring73serving as an elastic member. Details will be described later.

(6) Configuration Description of Positioning Developing Cartridge B1as to Apparatus Main Unit A1

Next, positioning of the developing cartridge B1as to the apparatus main unit A1will be described with reference to the drawings.FIG. 9is a perspective explanatory diagram viewing the apparatus main unit A1from the nondrive side, andFIG. 10is a perspective explanatory diagram viewing the apparatus main unit A1from the drive side.FIGS. 11A through 11Dare explanatory diagrams illustrating the process of the developing cartridge B1being mounted to the apparatus main unit A1, as viewed from the drive side.

The developing cartridge B1is provided with a guided portion46dhaving a positioning portion46band a rotation stopping portion46con the nondrive side developer bearing46, as illustrated inFIG. 9. Also, the developing side cover34is provided with a guided portion34dhaving a positioning portion34band a rotation stopping portion34c, as illustrated inFIG. 10. The positioning portion46bof the nondrive side developer bearing46and the positioning portion34bof the developing side cover34are portions that position the developing cartridge B1in the mounting direction (the direction in which the developing cartridge B1is mounted to the apparatus main unit) in the present embodiment. The rotation stopping portion46cof the nondrive side developer bearing46and the rotation stopping portion34cof the developing side cover34are portions that position the rotational posture at the time of insertion into the image forming apparatus.

Provided on a drive-side side-plate90making up the housing of the apparatus main unit A1is a drive side guide member92, and further a drive side swing guide80that integrally moves with the developing cartridge B1inside of the apparatus main unit A1, as illustrated inFIG. 9. The drive side guide member92further is provided with a first guide portion92a, a second guide portion92b, and a third guide portion92c. Grooves following a mounting/detaching path X1of the developing cartridge B1are formed in the first guide portion92aand second guide portion92b, and a groove following a mounting/detaching path X3of the drum cartridge C is formed in the third guide portion92c. A guide portion80ais provided to the drive side swing guide80. The guide portion80ais an extension of the first guide portion92aof the drive side guide member92, and a groove is formed following a mounting/detaching path X2of the developing cartridge B1.

Similarly, at the nondrive side of the apparatus main unit A1, provided on a nondrive-side side-plate91making up the housing of the apparatus main unit A1is a nondrive side guide member93, and further a nondrive side swing guide81that moves in the same way as the drive side swing guide80, as illustrated inFIG. 10. The nondrive side guide member93further is provided with a first guide portion93aand a second guide portion93b. Grooves following a mounting/detaching path X1of the developing cartridge B1are formed in the first guide portion93a, and a groove following a mounting/detaching path X3of the drum cartridge C is formed in the second guide portion93b. A guide portion81ais provided to the nondrive side swing guide81. The guide portion81ais an extension of the first guide portion93aof the nondrive side guide member93, and a groove is formed following a mounting/detaching path X2of the developing cartridge B1.

The present configuration uses a configuration of a swing guide that moves integrally with the developing cartridge B1inside the apparatus main unit A1, Whereby contact/separation of the contact state of the developing roller13of the developing cartridge B1as to the photosensitive drum10in the drum cartridge C can be selectively controlled. In a case of a contact developing system such as in the present embodiment, keeping the developing roller13constantly in contact with the photosensitive drum10as illustrated inFIG. 3can result in the rubber portion13dof the developing roller13deforming, as described above. Accordingly, the developing roller13is preferably separated from the photosensitive drum10when not developing. The contact/separation configuration will be described later.

The method of mounting the developing cartridge B1to the apparatus main unit A1will be described. Inside of the apparatus main unit A1is exposed by pivoting a main unit cover94, disposed at the tip of the apparatus main unit A1so as to be capable of being opened and closed, in an opening direction D1, as illustrated inFIGS. 9 and 10. Thereafter, the guided portion46dof the nondrive side developer bearing46of the developing cartridge B1is engaged with the first guide portion93aof the nondrive side guide member93of the apparatus main unit A1. Also, the guided portion34dof the developing side cover34of the developing cartridge B1is engaged with the first guide portion92aof the drive side guide member92of the apparatus main unit A1. Accordingly, the developing cartridge B1is inserted into the apparatus main unit A1following the mounting/detaching path X1formed by the first guide portion92aof the drive side guide member92and the first guide portion93aof the nondrive side guide member93.

The developing cartridge B1inserted into the apparatus main unit A1following the mounting/detaching path X1is then inserted into the apparatus main unit A1following the mounting/detaching path X2. The mounting/detaching path X2is formed by a guide portion80aof the drive side swing guide80and a guide portion81aof the nondrive side swing guide81.

In further detail, the guided portion34dprovided to the developing side cover34is first guided by the first guide portion92aprovided on the drive side guide member92of the apparatus main unit A1. The guided portion34dis then handed from the first guide portion92ato the guide portion80ain this configuration, in conjunction with the mounting processing thereof. The guide portion80ais provided to the drive side swing guide80of the apparatus main unit A1.

Similarly, at the nondrive side, the guided portion46dprovided to the nondrive side developer bearing46is first guided by the first guide portion93aprovided on the nondrive side guide member93of the apparatus main unit A1. The guided portion46dis then handed to the guide portion81ain this configuration, in conjunction with the mounting processing thereof. The guide portion81ais provided to the nondrive side swing guide81of the apparatus main unit A1.

Positioning of Developing Cartridge B1as to Swing Guide

Next, the configuration where the developing cartridge B1is positioned by the drive side swing guide80and nondrive side swing guide81of the apparatus main unit A1will be described. Note that the basic configurations are the same between the drive side and the nondrive side, so description will be made below by way of example of the drive side of the developing cartridge B1.FIGS. 11A through 11Dillustrate the state of the developing cartridge B1and the drive side swing guide80in the process of the developing cartridge B1being mounted to the apparatus main unit A1.FIG. 11Aillustrates a state where the guided portion34dprovided to the developing side cover34of the developing cartridge B1is guided by the first guide portion80aof the drive side swing guide80, and the developing cartridge B1is on the mounting/detaching path X2.FIG. 11Billustrates a state where mounting of the developing cartridge B1has further been advanced from the state inFIG. 11A, and the positioning portion34bof the guided portion34dof the developing side cover34abuts a positioning portion82aof a drive side pressing member82provided to the drive side swing guide80at a point P1.

The drive side pressing member82also has, in addition to the positioning portion82a, a hole82b, a seating face82c, and further a regulating portion82d, as illustrated inFIGS. 11A through 11D. The hole82bengages a boss80cof the drive side swing guide80, and is rotatably supported centered on the boss80c. One end of a drive side pressing spring83, that is a compression spring, is in contact with the seating face82c. The other end of the drive side pressing spring83is in contact with a seating face80dof the drive side swing guide80. Accordingly, the drive side pressing member82is configured to receive pressing force rotating in the clockwise direction (direction of arrow Ra1) centered on the boss80cof the drive side swing guide80. Note that the position of the drive side pressing member82is regulated by the regulating portion82dthereof abutting a rotation regulating portion80eprovided on the drive side swing guide80.

FIG. 11Cillustrates a state where mounting of the developing cartridge B1has further been advanced from the state inFIG. 11A, with the guided portion34dof the developing side cover34pressing the drive side pressing member82down. Describing in further detail, the guided portion34dof the developing side cover34presses the drive side pressing member82. Accordingly, the drive side pressing member82pivots in the counterclockwise direction (direction of arrow Ra2) centered on the boss80cof the drive side swing guide80against the pressing force of the drive side pressing spring83.FIG. 11Cillustrates a state in which the positioning portion34bof the developing side cover34and an upper edge portion82eof the drive side pressing member82are in contact.

FIG. 11Dillustrates a state where mounting of the developing cartridge B1has further been advanced from the state inFIG. 11C, with the positioning portion34bof the developing side cover34and the positioning portion82eof the drive side pressing member82in contact. An urging force F4of the drive side pressing member82acts upon the positioning portion34bof the developing side cover34, and the positioning portion34bcomes into contact with a positioning portion80fof the drive side swing guide80at a point P3. Accordingly, the drive side of the developing cartridge B1is positioned as to the drive side swing guide80.

The configuration of positioning of the positioning portion46bof the nondrive side developer bearing46as to the nondrive side swing guide81is the same as at the drive side. The nondrive side swing guide81, a nondrive side pressing member84, and a nondrive side pressing spring85, are respectively provided corresponding to the drive side swing guide80, drive side pressing member82, and drive side pressing spring83. Accordingly, the positioning portion46bof the nondrive side developer bearing46is positioned and fixed as to the nondrive side swing guide81.

This will be described in further detail with reference toFIG. 1. The position of the developing cartridge B1in the mounting direction of mounting to the image forming apparatus main unit is positioned by the positioning portion46bprovided to the developing cartridge B1and the nondrive side swing guide81coming into contact. When the developing cartridge B1is mounted to the apparatus main unit, the positioning portion46bis pressed by the nondrive side pressing member84, and thus receives force in a direction of arrow Fy at point Fp. A region (contact region, positioning region) Uy of the positioning portion46bis pressed against the nondrive side swing guide81. As a result, the positioning region Uy of the positioning portion46bis positioned in a state of being in contact with the nondrive side swing guide81. Accordingly, the developing cartridge B1is regulated from moving toward the downstream side in the mounting direction. That is to say, the developing cartridge B1is in a state of not moving in the mounting direction (a state of having been positioned in the mounting direction). According to the above-described configurations, the developing cartridge B1is positioned and fixed to the swing guides at the drive side and the nondrive side, and is positioned within the apparatus main unit.

(7) Configuration Description of Contact/Separation of Developing Cartridge B1to/from Drum Cartridge C

Next, the pressurized state of the developing roller13as to the photosensitive drum10and the separated state thereof will be described. In the present embodiment, the contact state of the developing roller13of the developing cartridge B1as to the photosensitive drum10of the drum cartridge C, and the separated state thereof, are selectively controlled.

The drive side swing guide80is supported as to the drive-side side-plate90of the apparatus main unit A1so as to be capable of pivotal movement in the directions of arrow N5and arrow N6, as illustrated inFIGS. 12A through 13D. The drive side swing guide81also is supported as to the nondrive-side side-plate91of the apparatus main unit A1so as to be capable of pivotal movement in the directions of arrow N5and arrow N6. The developing cartridge B1is positioned as to the drive side swing guide80and nondrive side swing guide81. Accordingly, the developing cartridge B1is in a state capable of pivotal movement in the directions of arrow N5and arrow N6inside the apparatus main unit A1.

Further, a drive side apparatus pressing member150and nondrive side apparatus pressing member151attached to the apparatus main unit A1are configured to receive driving force from an unshown motor, and to be movable in the direction of arrow N7and arrow N8, and in the direction of arrow NH7and arrow NH8.

The drive side apparatus pressing member150has a configuration of being capable of engaging the drive side contact/separation lever70, and the nondrive side apparatus pressing member151with the nondrive side contact/separation lever72. The drive side contact/separation lever70and nondrive side contact/separation lever72each have a pressed face (first contact surface70aand72a) and a separating face (second contact surface70gand72g). Pressing faces (second contact surfaces150band151b) and separating faces (150aand151a) respectively of the drive side apparatus pressing member150and nondrive side apparatus pressing member151act thereupon. Accordingly, the contact state and separated state of the photosensitive drum10and developing roller13can be selected as necessary, by the respectively singular parts that are the drive side contact/separation lever70and nondrive side contact/separation lever72. Hereinafter, a pressure mechanism serving as a contact state, and a separating mechanism serving as a separated state, will be described in detail.

Pressure Mechanism for Contact State

FIGS. 12A and 12Bare explanatory diagrams illustrating the contact state of the developing cartridge B1where the developing roller13and photosensitive drum10are in contact. The contact pressure mechanism is the same configuration for the drive side and nondrive side, so description will be made in detail regarding the drive side. The second contract surface150bof the drive side apparatus pressing member150and the first contact surface70aof the drive side contact/separation lever70are in contact, as illustrated inFIGS. 12A and 12B. Accordingly, the drive side contact/separation lever70is in a state of having rotated in the direction of arrow N9inFIG. 12B, against the biasing force of the drive side developing pressurizing spring71.

The third contact surface70cof the drive side contact/separation lever70then compresses the drive side developing pressurizing spring71, and receives biasing force F10afrom the drive side developing pressurizing spring71. As a result moment M10in the direction of the arrow N10acts upon the drive side contact/separation lever70.

At this time, the second contact surface150bof the drive side apparatus pressing member150and the first contact surface70aof the drive side contact/separation lever70are in contact. Accordingly, the first contact surface70aof the drive side contact/separation lever70receives force F11from the second contact surface150bof the drive side apparatus pressing member150so that a moment balanced with the moment M10acts upon the drive side contact/separation lever70. Accordingly, this means that external force of the force F11is acting upon the developing cartridge B1. Also, a drive side urging unit76is provided between a protrusion80hof the drive side swing guide80and protrusion90dof the drive-side side-plate90, urging in the direction of arrow N12. Accordingly, this means that external force of the force F12is acting upon the developing cartridge B1, positioned by the drive side swing guide80, in the direction of arrow N12.

That is to say, the developing cartridge B1receives moment M6in the direction of the developing roller13and photosensitive drum10coming closer (direction of arrow N6) by the force F11due to the drive side developing pressurizing spring71and the force F12due to the drive side urging unit76. The rubber portion13dof the developing roller13can be pressed into contact with the photosensitive drum10at a predetermined pressure by this moment M6.

As illustrated inFIGS. 13A and 13C, the second contact surface151bof the nondrive side apparatus pressing member151and the first contact surface72aof the drive side contact/separation lever72are in contact. In the same way as with the drive side, moment MH10in the direction of arrow NH10acts upon the nondrive side contact/separation lever72by receiving force urging FH10from the nondrive side developing pressurizing spring73. The first contact surface72areceives force FH11from the second contact surface151bof the nondrive side apparatus pressing member151, meaning that external force of force FH11is acting on the developing cartridge B1.

Also, a nondrive side urging unit77is provided between the nondrive side swing guide81and the nondrive-side side-plate91(omitted from illustration inFIGS. 13A through 13D), urging in the direction of arrow NH12, meaning that external force of force FH12is acting on the developing cartridge B1in the direction of arrow NH12. Accordingly, the developing roller13and photosensitive drum10receive the moment M6in the direction of arrow N6, and is pressed into contact at a predetermined pressure along with the drive side.

Separating Mechanism for Separated State

FIG. 13Bis an explanatory diagram illustrating a separated state of the developing cartridge B1, where the developing roller13and photosensitive drum10are separated. The separating mechanism is the same configuration at the drive side and nondrive side, so description will be made in detail regarding the nondrive side.

As illustrated inFIGS. 13B and 13D, the first contact surface151aof the nondrive side apparatus pressing member151and the second contact surface72gof the nondrive side contact/separation lever72are in contact. Accordingly, the nondrive side contact/separation lever72is in a state of having rotated in the direction of arrow NH10inFIG. 13Dagainst the urging force of the nondrive side urging unit77. Further, the third contact surface72cof the nondrive side contact/separation lever72receives urging force FH10from the nondrive side developing pressurizing spring73. As a result, the moment MH10in the direction of arrow NH10acts upon the nondrive side contact/separation lever72. At this time, the first contact surface151aof the nondrive side apparatus pressing member151and the second contact surface72gof the nondrive side contact/separation lever72are in contact. Accordingly, the second contact surface72gof the nondrive side contact/separation lever72receives force FH11from the first contact surface151aof the nondrive side apparatus pressing member151, so that a moment balanced with the moment MH10acts upon the nondrive side contact/separation lever72. Accordingly, this means that external force of the force FH11is acting on the developing cartridge B1. Thus, the developing cartridge B1pivots in the direction of arrow N5due to the nondrive side apparatus pressing member151moving in the direction of arrow N8. At this time, the developing roller13and the photosensitive drum10are in a state separated by a gap of a distance δ8.

(8) Description of Positioning Portion of Developing Cartridge B1and Interface Portions

The configuration for positioning interface portions that the developing cartridge B1has with high precision will be described next. Note that the interface portions that the developing cartridge B1illustrated in the present embodiment has are the functional procession that function by coming into contact with or by engaging the apparatus main unit A1or drum cartridge C. Examples of interfaces regarding which particularly highly precise positioning is desirable include the developing roller13, the coupling member180, the contact portions that are electric contacts (memory board47, developing roller contact portion13f, and developing blade contact portion15f), and so forth.

The positions of the interface portions of the developing cartridge B1as to the apparatus main unit A1and drum cartridge C are preferably highly precise, from the perspective of image quality stability and reducing the size of the image forming apparatus and cartridge. For example, the position of the developing roller13that the developing cartridge B1has as to the photosensitive drum10that the drum cartridge C has, having been positioned in the image forming apparatus, is positioned with high precision. Accordingly, information can be printed with high precision, without misregistration as to the recording medium2when forming images.

Also, the contact portions of the developing cartridge B1(memory board47, developing blade contact portion15f, and developing roller contact portion13f) a positioned with high precision as to the power supply portions of the image forming apparatus. Accordingly, maximum reduction in size can be realized while taking into consideration the shape tolerance and position tolerance of the contact portions and the power supply portions, thereby enabling the size of the image forming apparatus and the cartridge to be reduced.

As described above, the nondrive side developer bearing46according to the present embodiment has an interface portion regarding which highly precision positioning is desired. Included are a developing roller contact portion13f1and developing blade contact portion15f1to apply voltage to the memory board47, developing roller13, and developing blade15, as illustrated inFIGS. 1, 8A, and 8B. The interface portions will be described in further detail.

Description will be made regarding the developing roller contact portion13fand developing blade contact portion15f. The developing roller contact portion13fand developing blade contact portion15fare integrally formed of the electroconductive resin of the nondrive side developer bearing46. Due to having been integrally formed of electroconductive resin, a back surface portion13f1of the developing roller contact portion13fand a support portion46fare connected. Further, a back surface portion15f1and a developing blade contact portion15f2of the developing blade contact portion15fare in contact. Accordingly, the nondrive side end portion13cof the developing roller13being rotatably fit to the support portion46fof the nondrive side developer bearing46secures conduction. Fitting or gluing a developing blade conducting portion15f3with the developing blade contact portion15f2, and re-injecting electroconductive resin to the contact portions after having assembled the developing cartridge B1, secures conductivity. Note that methods for conduction are not restricted to the above method.

Conduction between a first power supply portion81b1of the nondrive side swing guide81and the developing roller contact portion13f1, and conduction between a second power supply portion81b2of the nondrive side swing guide81and the developing blade contact portion15f, will be described with reference toFIGS. 9, 10, and 13A. The developing cartridge B1mounted within the apparatus main unit A1is positioned and held by the drive side swing guide80and nondrive side swing guide81, as described above. The first power supply portion81b1and second power supply portion81b2are configured on the nondrive side swing guide81as power supply portions corresponding to the developing roller contact portion13fand developing blade contact portion15f, as illustrated inFIGS. 9 and 10. These first and second power supply portions are for applying applied voltage from the apparatus main unit A1to the developing cartridge B1.

The developing cartridge B1held by the nondrive side swing guide81is in a contact state where the developing roller13and the photosensitive drum10are in contact when forming images, as illustrated inFIG. 13A. The first power supply portion81b1and second power supply portion81b2of the nondrive side swing guide81are provided with power supply contacts (omitted from illustration) formed of leaf springs or the like and having spring properties are disposed at the portions indicated by dotted lines, protruding toward the nondrive side developer bearing46.

Accordingly, power can be supplied in a stable manner to the developing cartridge B1positioned and held by the nondrive side swing guide81. The reason is that, when forming images, contact pressure between the first power supply portion81b1and the developing roller contact portion13f, and contact pressure between the second power supply portion81b2and the developing blade contact portion15f, are secured. Note that the contact range of the developing roller contact portion13fand developing blade contact portion15fof the nondrive side developer bearing46, when the developing cartridge B1is mounted, needs to be decided taking into consideration part tolerance and so forth, so that contact with the power supply portions of the nondrive side swing guide81can be made in a sure manner.

Further, description will be made regarding conduction with a power supply portion120provided at a position facing the contact portion47aof the memory board47. Power is supplied from the power supply portion120of the apparatus main unit A1provided at a position facing the contact portion47aof the memory board47fixed to the nondrive side developer bearing46when forming images, as illustrated inFIG. 13A.

As described above, the developing cartridge B1positioned and held by the nondrive side swing guide81is subject to pressure on the nondrive side contact/separation lever72of the developing cartridge B1from the nondrive side apparatus pressing member151, and is in a contact state. In this configuration, the contact portion47apresses the power supply portion120of the apparatus main unit A1in by a predetermined amount by this pressure, from the state before the mounting of the developing cartridge B1.

The power supply portion120has a power supply contact120A, formed of a wire spring or leaf spring or the like and having spring properties, protruding from the power supply portion120. Contact pressure between the power supply portion120and the contact portion47ais secured by external force of the force FH12in the contact state of the developing cartridge B1, so stable power supply can be realized. Note that the conduction method is not restricted to this method. Note that the contact range needs to be decided taking part tolerance and so forth in to consideration, so that contact of the contact portion47aof the memory board47fixed to the nondrive side developer bearing46and the power supply portion120of the apparatus main unit A1can be made in a sure manner, when the developing cartridge B1is mounted.

In the present embodiment, the developing roller13and the interface portions of electric contacts are formed as parts with positional precision and dimensional tolerance guaranteed, with the positioning portion46bof the nondrive side developer bearing46as a dimensional reference. The positioning portion46bof the nondrive side developer bearing46is positioned within a region surrounded by straight lines connecting the interface portions and a developing roller center13zregarding which highly precise positioning is desired, as illustrated inFIGS. 1, 8A, and 8B.

That is to say, positioning the positioning portion46bin an imaginary region U1that is a generally polygonal shape surrounded by the straight lines S1, S2, S3, and S4, and edges of the electric contacts, as illustrated inFIG. 1, enables the positioning precision as to the interfacing portions at the image forming apparatus side to be raised to a high level. More specifically, the positions of the portions are set so that the entire positioning region Uy of the positioning portion46bcoming into contact with the nondrive side swing guide81is contained within the imaginary region U1.

The effects of situating the positioning portion46b(positioning region Uy, seeFIG. 1) in the imaginary region U1will be described below.FIG. 14is a simulated diagram illustrating the positioning portion and the interface portions from a cross-sectional direction. Schematically illustrated here are four interface portions regarding which high-precision positioning with positioning portions of the image forming apparatus in the insertion direction is desired, in the same way as the nondrive side developer bearing46. The four interface portions represent the developing roller13, the contact portion47aof the memory board47, the developing roller contact portion13f, and the developing blade contact portion15f.

InFIG. 14, the center points of interface portions Ja, Jb, Jc, and Jd are represented by Ta, Tb, Tc, and Td, respectively. If a center point of a certain positioning portion is T1, T2, the external tolerance range of the interface portions is Ka1, Kb1, Kc1, Kd1, Ka2, Kb2, Kc2, Kd2.

The interface portion Ja represents the developing roller13, the interface portion Jb represents the contact portion47aof the memory board47, interface portion Jc represents the developing roller contact portion13f, and the interface portion Jd represents the developing blade contact portion15f. The interface portions are drawn as circles, having the same outer diameters, to facilitate understanding of the description.

Each interface portion is formed as a part46T, and the positional dimensions are defined with the center points T1and T2of the positioning portion as the dimensional reference. Here, center point T1is situated within a generally polygonal imaginary region U2of which the range has been set so that the maximum area is formed by the outer shape of the center point Ta of the interface portion Ja and the interface portions Jb, Jc, and Jd. The developing roller13that the interface portion Ja represents is required to have high precision regarding the center position, since the developing roller13is fit and supported by the nondrive side developer bearing46. Accordingly, the center position of the interface portion Ja should be defined with high precision. The interface portions Jb, Jc, and Jd represent the contact portions, so the relative position as to the interfacing portions at the image forming apparatus side is required to be highly precise. Accordingly, the outer shape ranges of the interface portions Jb, Jc, and Jd should be set with high precision.

A generally polygonal imaginary region, formed by the center point Ta of the interface portion Ja, and the outer shapes (edges) of the interface portions Jb, Jc, and Jd, so as to have the largest area, is set as U2. Due to the above-described reason, setting the center point T1within the imaginary region U2enables the distance tolerance from the center point T1to the interface portions to be reduced. Here, the center point T1is situated at a position where the distance R from the center point T1to each interface portion is equidistant. A center point T2has been set at a position outside of the range of the imaginary region U2and close to the interface portion Ja, for the sake of comparison with the center point T1.

The fact that using the center point T1of the positioning portion as a reference enables the range tolerance of each interface portion to be reduced and precision to be raised inFIG. 14will be described in further detail. The dimensional range tolerance of each interface portion described here will be described regarding distance tolerance dependent on the distance from the center points T1and T2to the center points Ta, Tb, Tc, and Td of the interface portions. The center point T1is situated at an equal distance R from the center point of each interface portion, and the tolerance depends on the distance R, so an equal tolerance range K1is obtained.
K1=Ka1=Kb1=Kc1=Kd1

The center point T2is defined near the position of the interface portion Ja. The distance from the center point T2to the center point Ta is distance La, the distance from the center point T2to the center point Tb is distance Lb, and the distance from the center point T2to the center point Tc is distance Lc. Comparing the distance tolerances Ka2, Kb2, KC2, and Kd2to each interface portion in the case of the center point T2with the distance tolerance K1from the center point T1to each interface portion finds
Ka2=La/R×K1
Kb2=Kc2=Lb/R×K1
Kd2=(La+R)/R×K1=(Ka2+1)×K1
so
Tu1<Tu2
where a region connecting the outer dimension ranges of the interfaces is Tu1for a region according to T1and Tu2for a region according to T2.

Accordingly, using the center point T1of the positioning portion as a reference enables the positional tolerance of the interface portions to be more highly precise, and the formed part46T can be reduced in size to region Tu1, as compared to region Tu2. The interfacing portion at the image forming apparatus size also can be reduced in size.

Note thatFIG. 14according to the present embodiment illustrates a case of the center point T1of the positioning portion to be an equal distance R from each interface portion. However, the center point T1of the positioning portion can be selected by designing the precision of part position tolerance, from the perspective of function, placement, and cost, of each interface portion within the imaginary region U2. That is to say, in a case where there is leeway regarding design placement of the interface portion Jd, the center point T1of the positioning portion can be decided according to the remaining interface portions Ja, Jb, and Jc, regarding which high precision is desired.

Further, although the center point Te of the rotation stopping portion is situated in the imaginary region U2in the same way as with the nondrive side developer bearing46, generally, the longer the distance between the center points T1and T2of the positioning portions is, the smaller the tolerance for deciding posture is. That is to say, the precision can be raised further. Accordingly, the center point Te is preferably decided taking into consideration the outer dimensions of the entire part, and part functionality.

As described above, the center point T1of the positioning portion is defined within the imaginary region U2of a range formed by the center point Ta of the interface portion Ja, and the outer shapes of the interface portions Jb, Jc, and Jd, so as to have the largest area. Accordingly, the positions of multiple interface portions can be positioned with precision, and reduction in size of the image forming apparatus and cartridge, and stable image quality can be realized.

Returning toFIG. 1, the imaginary region is strictly defined as follows. The developing roller, positioning portion (positioning region), and multiple electric contacts are projected on a projection plane orthogonal to the axial line of the developing roller. On this projection plane, an imaginary region formed by multiple straight lines (S1, S2, S3, and S4) and the edges of the electric contacts (15f,13f, and47a), so that first, second and third conditions are satisfied, is the imaginary region U1.

The first condition is that each of the ends of the multiple straight lines (S1, S2, S3, and S4) forming the imaginary region U1is situated at one of the center13zof the developing roller and edges of the electric contacts (developing blade contact portion15f, developing roller contact portion13f, and contact portion47a).

The second condition is that center13zof the developing roller (center of support portion) is situated at an intersection of different straight lines, or upon one of the straight lines. That is to say, the center13zof the developing roller is situated on the edge of the imaginary region U1.

The third condition is that each of the straight lines is stipulated so that the area of the imaginary region U1is maximal, within the constrictions of the first and second conditions.

In the present embodiment, the straight line S1is a straight line of which both ends are at the center13zof the developing roller and the edge of the developing blade contact portion15f. The straight line S2is a straight line of which both ends connect the edge of the developing blade contact portion15fand the edge of the developing roller contact portion13f. The straight line S3is a straight line of which both ends connect the edge of the developing roller contact portion13fand the edge of the contact portion47a. The straight line S4is a line connecting the edge of the contact portion47aand the center13zof the developing roller. Note that on the projection plane, the position of the center13zof the developing roller is the same as the position of the center of the support portion46f(seeFIG. 8B) that fits (in contact) with the shaft of the developing roller13(nondrive side end portion13c) and supports the shaft.

Connecting the different straight lines by the edges of the electric contacts forms the region U1. The edge of the developing blade contact portion15fconnects between the edge of the straight line S1and the edge of the straight line S2. The edge of the developing roller contact portion13fconnects between the edge of the straight line S2and the edge of the straight line S3. The contact portion47aconnects between the edge of the straight line S3and the edge of the straight line S4.

Both ends of the straight lines S1, S2, S3, and S4are situated at positions where the area of the imaginary region U1is maximal, within the constrictions of the first and second conditions. All of the positioning portion46b(positioning region Uy) is included within this imaginary region U1.

A positional relationship suitable for multiple members (the interface portions) in a cartridge has been described above in the present embodiment as an example of a configuration where a developing cartridge is mounted to an apparatus main unit. However, the above-described suitable positional relationship among the various types of interface portions holds even in a case where a process cartridge is mounted to the image forming apparatus main unit and not a developing cartridge. That is to say, the cartridge detachably mountable to the apparatus main unit may be a process cartridge having both a photosensitive drum and developing roller, or a developing cartridge having, of the two, only the one developing roller.

This application claims the benefit of Japanese Patent Application No. 2015-183147, filed Sep. 16, 2015, which is hereby incorporated by reference herein in its entirety.