JP5927162B2 - Image forming unit and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image forming unit and an image forming apparatus including the same, and more particularly, to a mechanism for bringing a process roller into contact with and retracting from an object.

  In an electrophotographic image forming apparatus, the surface of a photosensitive drum is charged by a nip by a charging roller, and a charged toner drum surface is exposed and developed to form a toner image, and the toner image is formed on a recording sheet. Image formation is performed by transferring and fixing. In recent years, the product has been required to have a long life. In the case of the above-described configuration, if the charging roller is deteriorated due to contamination, the product may have a short life.

  Therefore, a mechanism for preventing the charging roller from being contaminated by cleaning the charging roller by niping a cleaning roller made of a foaming roller has been proposed. However, if the cleaning roller or the charging roller is permanently deformed by the pressure received by the nips, charging abnormality occurs, and the formed image is adversely affected. For this reason, a technique has been proposed in which each roller receiving pressure during nip is separated to release each roller from the pressure to avoid permanent deformation.

  Japanese Patent Application Laid-Open No. 2004-151561 discloses a mechanism for separating a charging roller that is pressed against a photosensitive drum from the photosensitive drum. Japanese Patent Application Laid-Open No. 2004-228561 discloses a mechanism for separating a transfer roller that is in pressure contact with a photosensitive drum from the photosensitive drum. Further, Patent Document 3 discloses a mechanism for moving a backup roller that presses a belt to be cleaned against a cleaning roller from a state in which the belt is pressed into contact with the cleaning roller.

JP 2006-267399 A JP 2008-151867 A JP 2007-1680 A

  In the case of the image forming apparatus having the charging roller and the cleaning roller described above, when the charging roller is nipped with respect to the photosensitive drum, the cleaning roller is also nipped with this charging roller. Therefore, in order to prevent roller deformation due to pressurization, both the nip of the photosensitive drum and the charging roller and the nip of the charging roller and the cleaning roller are released, and the charging roller and the cleaning roller are released from both nips. There is a need to. However, in the techniques disclosed in the above patent documents, each pair of rollers can be separated from each other and released from the pressurization. Therefore, even when these techniques are used, the charging roller and the cleaning roller are removed from both the nips. It is difficult to release.

  Moreover, it is preferable that the charging roller and the cleaning roller are released from the nip according to the operation of the image forming apparatus.

  The present invention has been made in order to solve the above-described problem. In a mechanism in which a plurality of nips between rollers are present, the release of both rollers forming each nip from the pressurization can be performed by a simple mechanism. It is intended to be performed according to the operation of the device.

An image forming unit according to an aspect of the present invention includes a first process roller that nips an object, a second process roller that is nipable with respect to the first process roller, and the first process roller. A bushing member having a first shaft support portion that supports the shaft, a second shaft support portion that supports the second process roller in a state where the first process roller is placed, and is supported by the first shaft support portion. The first process roller includes a moving mechanism that moves the bush member in a direction in which the first process roller contacts and separates from the object, and a driving mechanism that drives the moving mechanism according to an image forming operation. The shaft support portions are arranged side by side in the contact / separation direction, and the first shaft support portion has a relief shape portion that allows the first process roller to be displaced in the contact / separation direction within the first shaft support portion. In a state where the first process roller is not nipped with the object, the first process roller is pivotally supported with play in the contact / separation direction by the relief shape portion, and the first process roller is In a state of being nipped with the object, the first shaft support part is configured to displace the position in the first shaft support part to the second process roller side when the first process roller is pressed by the object. The first process roller is pivotally supported, and the moving mechanism presses the bush member toward the object in the contact / separation direction, and a support portion that slidably supports the bush member in the contact / separation direction. Provided on the side of the pressing member and the bush member housed in the support portion, and guides the movement of the bushing member in the contact / separation direction by the pressing of the pressing member The bush member has an engaging portion extending toward a lower surface portion of the support portion facing the bush member, and the engaging portion includes a columnar base and a tip of the base The lower end portion is formed with a receiving hole that passes through the base portion of the engagement portion, and the bush member is disposed on the lower surface portion. A position restricting member that is movable in a direction orthogonal to the contact / separation direction is disposed on the back surface side of the lower surface portion that is opposite to the side, and the position restricting member penetrates from the receiving hole. A locking hole through which the base portion passes is formed, and the locking hole has a first locking hole having a width equivalent to the diameter of the base portion of the engaging portion and a diameter equivalent to the diameter of the tip portion. A second locking hole that is integrally formed and extends in the orthogonal direction. And when the position restricting member moves to a locking position where the first locking hole is locked to the distal end portion in the orthogonal direction, and the second locking hole is the base and the distal end portion. When the position restricting member moves to a non-locking position that matches the position, the engaging portion protrudes from the receiving hole to the position restricting member side with a different amount of protrusion, and the position restricting member moves to the locking position. When the member moves, the pressing member contracts in the contact / separation direction, and the position of the bushing member in the contact / separation direction remains at a position where the first process roller is not nipped with the object, When the position restricting member moves to the non-locking position, the pressing member presses the bushing member toward the object in the contact / separation direction, and the first process roller nips the object. In a state Ri, the drive mechanism is an image forming unit for moving the position regulating member between the locking position and the unlocked position.

  According to the present invention, the first and second process rollers are arranged side by side with respect to the object by the bush member, and the first shaft support portion of the bush member is niped by the first process roller to the object. In the state where it is not, the first process roller is relieved and is pivotally supported by the shape portion with play in the contact / separation direction. For this reason, in a state where the first process roller does not receive pressure toward the second process roller in the contact / separation direction, the first and second process rollers do not receive pressure from the other roller.

  Then, when the moving mechanism is driven by the driving mechanism, the first process roller is pressed from the object when the bush member moves in the contact / separation direction and the first process roller is nipped from the object. In response, the position in the first shaft support is displaced toward the second process roller. For this reason, if the 1st process roller will be in the state which receives a press from the above-mentioned subject, it will be in the state where it nipped in both the subject and the 2nd process roller.

  Further, when the moving mechanism is driven by the drive mechanism and the bush member moves in the contact / separation direction, and the first process roller and the object are switched from the nip state to the nip release state, the object and Both the nip of the first process roller and the nips of the first and second process rollers are released, and both the first and second process rollers can be released from pressure.

  Further, the drive mechanism moves the bush member in accordance with the image forming operation to switch the state where the first process roller is nipped to the object or the state where the first process roller is not nipped to the object. Therefore, the first process roller and the second process roller can be released from the nip according to the operation of the image forming apparatus. When it is not necessary for image formation, the first process roller and the second process roller can be released from the nip, so that roller deformation due to pressurization can be suppressed.

  Moreover, according to the said structure, it is possible to implement | achieve switching of the nip of the said roller and the release of a nip with a comparatively simple mechanism, without requiring a complicated mechanism.

  According to the present invention, in a mechanism in which a plurality of nips between rollers are present, release of both rollers forming each nip from pressure can be performed by a simple mechanism in accordance with the operation of the image forming apparatus.

1 is a front sectional view showing the structure of an image forming apparatus having an image forming unit according to an embodiment of the present invention. FIG. 3 is a perspective view illustrating a mechanism around a photosensitive drum and a charging device. FIG. 3 is a perspective view illustrating a mechanism around a photosensitive drum and a charging device, and a diagram illustrating a state in which the charging device is pulled out. FIG. 3 is a perspective view showing a charging device in a state where a photosensitive drum, a charging roller, and a cleaning roller are taken out. FIG. 3 is a side cross-sectional view of the photosensitive drum and the charging device when viewed from the direction of arrow A in FIG. 2, in which (A) shows a state where the charging roller is nipped on the surface of the photosensitive drum, The state where it is separated from the surface of the photosensitive drum is shown. FIGS. 3A and 3B are perspective views showing a state where the photosensitive drum and the charging device are viewed from below in FIG. 2, in which FIG. 3A shows a state where the charging roller is nipped on the surface of the photosensitive drum, and FIG. The state where it is separated from the surface of the photosensitive drum is shown. 4A and 4B are diagrams showing a drive mechanism for sliding the position regulating member, where FIG. 5A shows a state where the charging roller is nipped on the surface of the photosensitive drum, and FIG. Indicates the state. 2 is a functional block diagram schematically showing a main internal configuration of the image forming apparatus. FIG. It is a flowchart which shows the operation | movement which switches the nip of a charging roller and a cleaning roller concerning embodiment, or the release of a nip. 10 is a flowchart showing an operation of switching between the nip of the charging roller and the cleaning roller according to Modification 2 or the release of the nip. FIG. 9 is a side cross-sectional view of a photosensitive drum and a charging device according to Modification 3 as viewed from the direction of arrow A in FIG. 2, and (A) shows a state where a charging roller is nipped on the surface of the photosensitive drum; ) Shows a state where the charging roller is separated from the surface of the photosensitive drum.

  Hereinafter, an image forming unit and an image forming apparatus including the image forming unit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front sectional view showing the structure of an image forming apparatus having an image forming unit according to an embodiment of the present invention.

  The image forming apparatus 1 according to an embodiment of the present disclosure is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus body 11 including an operation unit 40, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, a document reading unit 5, and the like.

  When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 optically reads a document fed by the document feeding unit 6 or a document placed on the document placing glass 161, Generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD or a network-connected computer.

  When the image forming apparatus 1 performs an image forming operation, the image forming unit 12 is supplied from the paper supply unit 14 based on the image data generated by the document reading operation or the image data stored in the built-in HDD. A toner image is formed on a recording paper P as a recording medium to be paper. The image forming units 12M, 12C, 12Y, and 12Bk of the image forming unit 12 include a photosensitive drum 121, a charging device 123, an exposure device 124, a developing device 122, and a primary transfer roller 126, respectively. .

  Each developing device 122 of the image forming units 12M, 12C, 12Y, and 12Bk contains toner for developing an electrostatic latent image. The developing device 122 supplies the toner to the surface of the photosensitive drum 121 that has been charged by the charging device 123 and exposed by the exposure device 124.

  When performing color printing, the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12 each receive image data. A toner image is formed on the photosensitive drum 121 by charging, exposure, and development processes based on the image composed of each color component, and the toner image is driven by the primary transfer roller 126 by the driving roller 125a and the driven roller 125b. The image is transferred onto the intermediate transfer belt 125 that is stretched around the belt.

  The intermediate transfer belt 125 is driven by a driving roller 125 a in a state where an image carrying surface on which a toner image is transferred is set on the outer peripheral surface thereof and in contact with the peripheral surface of the photosensitive drum 121. The intermediate transfer belt 125 travels endlessly between the driving roller 125a and the driven roller 125b while being synchronized with each photosensitive drum 121.

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to become a color toner image. The secondary transfer roller 210 conveys the color toner image formed on the surface of the intermediate transfer belt 125 from the sheet feeding unit 14 through the conveyance path 190 at the nip N between the intermediate transfer belt 125 and the driving roller 125a. The recording sheet P is transferred. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  Next, mechanisms around the photosensitive drum 121 and the charging device 123 in the image forming units 12M, 12C, 12Y, and 12Bk will be described. Since the mechanisms around the photosensitive drum 121 and the charging device 123 in the image forming units 12M, 12C, 12Y, and 12Bk are the same, in the following description, the image forming unit for which color is specified. Without explaining.

  FIG. 2 is a perspective view showing a mechanism around the photosensitive drum 121 and the charging device 123. FIG. 3 is a perspective view showing a mechanism around the photosensitive drum 121 and the charging device 123, and shows a state where the charging device 123 is pulled out. FIG. 4 is a perspective view showing the charging device 123 with the photosensitive drum 121, the charging roller 22 and the cleaning roller 23 taken out.

  In the image forming unit, a charging device 123 is disposed below the photosensitive drum 121. The charging device 123 includes a charging case 21, a charging roller 22, a cleaning roller 23, a bush member 24, and a moving mechanism 25.

  The charging case 21 is composed of a housing whose surface facing the photosensitive drum 121 is open. Inside the charging case 21, a charging roller 22, a cleaning roller 23, a bush member 24, and a moving mechanism 25 are disposed.

  The charging roller (an example of a first process roller) 22 is a roller that contacts the photosensitive drum (an example of an object) 121 and applies a charging bias to the drum surface to charge the surface of the photosensitive drum 121. The charging roller 22 is formed, for example, by a conductive rubber layer in which an ionic conductive material is mixed with epichlorohydrin. A bias is applied to the charging roller 22 from a charging bias applying unit (not shown).

  The cleaning roller (an example of a second process roller) 23 is a roller that cleans the charging roller 22. The cleaning roller 23 is, for example, a sponge (foaming) roller. The cleaning roller 23 is disposed so as to be in contact with the charging roller 22. For example, the circumferential surface of the cleaning roller 23 rotates in the same direction with a circumferential speed difference with respect to the circumferential surface of the charging roller 22. The dirt adhering to the peripheral surface of 22 is removed.

  As shown in FIG. 4, the rotation axes of the photosensitive drum 121, the charging roller 22, and the cleaning roller 23 are arranged side by side on a virtual straight line. The bush member 24 is a member that pivotally supports the charging roller 22 and the cleaning roller 23. The bush member 24 is formed with a first shaft support portion 241 that rotatably supports the rotation shaft 221 of the charging roller 22 and a second shaft support portion 242 that rotatably supports the rotation shaft 231 of the cleaning roller 23. ing.

  A moving mechanism 25 is attached to the lower part of the bush member 24. The moving mechanism 25 includes a push spring 251 and a guide portion 26 described later. The push spring 251 presses the bush member 24 in a state where the charging roller 22 and the cleaning roller 23 are pivotally supported from the lower side to the upper side in FIG. 4, that is, in the direction in which the charging roller 22 approaches the photosensitive drum 121. On the other hand, when pressure is applied to the charging roller 22 from the upper side to the lower side in FIG. 4, that is, in a direction away from the photosensitive drum 121, the pressing spring 251 contracts itself, thereby causing the bush member 24 to move toward the charging roller 22. Move down. Therefore, the push spring 251 moves the bush member 24 in the contact / separation direction in which the charging roller 22 contacts / separates with respect to the photosensitive drum 121.

  The charging case 21 houses a bush member 24 in a state where the charging roller 22 is pivotally supported by the first shaft support portion 241 and the cleaning roller 23 is pivotally supported by the second shaft support portion 242.

  Next, a mechanism for releasing the nip or the nip of the charging roller 22 from the photosensitive drum 121 by moving the bush member 24 will be described. FIG. 5 is a side sectional view of the photosensitive drum 121 and the charging device 123 viewed from the direction of arrow A in FIG. 2, and (A) shows a state in which the charging roller 22 is nipped on the surface of the photosensitive drum 121. (B) shows a state in which the charging roller 22 is separated from the surface of the photosensitive drum 121.

The support portion 27 supports the bush member 24. The charging case 21 of the charging device 123 includes a support portion 27 and a guide portion 26. The support portion 27 includes a side surface portion 271 and a lower surface portion 272, and is configured by a part of the charging case 21. The guide part 26 is a guide rail provided on the inner wall surface of the side part 271 of the support part 27. The guide rail as the guide portion has a recess that extends in the contact / separation direction and guides the movement of the bush member 24 in the contact / separation direction. The recess is formed at the position of the charging case 21 facing the protrusions 243 formed on both sides of the bush member 24. The guide portion supports the protruding portion 243 fitted in the concave portion so as to be slidable in the contact / separation direction.

  One end of the push spring 251 is attached to the lower part of the bush member 24, and the other end is attached to the lower surface part 272 of the support part 27 facing the lower part. Accordingly, the push spring 251 moves the bush member 24 and the charging roller 22 and the cleaning roller 23 pivotally supported by the bush member 24 in the direction of approaching the surface of the photosensitive drum 121 by the pressing force of the bush member 24 and the cleaning roller 23. It is moved in a direction away from the surface of the photosensitive drum 121 by contracting in response to a force resisting the pressing force from the outside.

  The first shaft support portion 241 provided in the bush member 24 has a relief shape portion 245 that allows the charging roller 22 to be displaced in the first shaft support portion 241 in the contact / separation direction. As shown in FIGS. 5A and 5B, the relief shape portion 245 has a long hole shape in which the diameter in the contact / separation direction is longer than the diameter in the direction orthogonal to the direction. The diameter of the relief shape portion 245 in the orthogonal direction is set to be slightly longer than the diameter of the charging roller 22 or close to this. The relief-shaped portion 245 has a lower surface portion 245 a formed in an arc shape along the peripheral surface shape of the rotation shaft 221 of the charging roller 22, and an upper portion has an opening 245 b that faces the photosensitive drum 121. The first shaft support portion 241 supports the charging roller 22 with play in the contact / separation direction by the relief shape portion 245. The relief shape portion 245 guides the direction of displacement of the charging roller 22 in the contact / separation direction.

  The first shaft support portion 241 includes a displacement restricting portion 245c that restricts the displacement of the charging roller 22 in the first contact portion 241 in the contact / separation direction to a constant amount. The front end of the opening 245b on the photosensitive drum 121 side extends in a direction (inward direction) in which the diameter of the long hole is reduced to form a displacement restricting portion 245c. As a result, when the charging roller 22 is displaced to the photosensitive drum 121 side, when the charging roller 22 moves to a position where it comes into contact with the displacement restricting portion 245c, the movement is restricted due to interference by the displacement restricting portion 245c.

  The charging roller 22 that is pivotally supported by the first pivotal support 241 is placed on the cleaning roller 23 that is pivotally supported by the second pivotal support 242. The distance between the first shaft support portion 241 and the second shaft support portion 242 is in a state of being supported by the first shaft support portion 241 with play when the charging roller 22 is placed on the cleaning roller 23. Is set to For this reason, the charging roller 22 is not pressed in the direction away from the photosensitive drum 121 in the contact / separation direction, for example, as shown in FIG. In a state where the member 24 is not pressed against the photosensitive drum 121, the charging roller 22 is simply placed on the cleaning roller 23, and does not enter a nip state where the cleaning roller 23 is pressed. In this state, the rotation shaft 221 of the charging roller 22 is pivotally supported by the first shaft support portion 241 with a space between the lower surface portion 245 a of the first shaft support portion 241.

  The bush member 24 has an engaging portion 246 that protrudes and extends toward the lower surface portion 272 (not shown in FIG. 4). A receiving hole 2721 for receiving and penetrating the engaging portion 246 is formed in the lower surface portion 272 that is positioned opposite the lower portion of the bush member 24. The engaging portion 246 has, for example, a columnar base portion 2461, and this base portion 2461 penetrates the receiving hole 2721 and protrudes below the lower surface portion 272 regardless of the expansion / contraction state of the push spring 251. However, the amount of protrusion of the base portion 2461 from the lower surface portion 272 increases or decreases according to the amount of expansion / contraction of the push spring 251. In the base portion 2461, a tip end portion 2462 on the lower surface portion 272 side is formed in a disk shape having a larger diameter than the base portion 2461.

  A position regulating member 29 that is movable in a direction orthogonal to the contact / separation direction is disposed on the back surface side of the lower surface portion 272. The position regulating member 29 has a width equal to the width of the lower surface portion 272 and is attached to the support portion 27 so as to be slidable along the back surface. The position regulating member 29 is slid by a drive mechanism 30 (see FIG. 7) described later.

  6 is a perspective view showing a state where the photosensitive drum and the charging device are viewed from below in FIG. 2. FIG. 6A shows a state where the charging roller is nipped on the surface of the photosensitive drum, and FIG. The charging roller is separated from the surface of the photosensitive drum.

  As shown in FIGS. 6A and 6B, the position restricting member 29 is formed with a locking hole 291 protruding from the lower surface portion 295 of the position restricting member 29. The locking hole 291 has a width equivalent to the diameter of the base portion 2461 of the engaging portion 246 and extends in the orthogonal direction, and a second engagement having a diameter equivalent to the diameter of the distal end portion 2462. It consists of a stop hole 291b. The first locking hole 291a and the second locking hole 291b are integrally formed to form a locking hole 291 that is one hole. The height of the contact hole 291 in the contact / separation direction is such that the pressing spring 251 is contracted in the contact / separation direction to such an extent that the charging roller 22 supported by the first shaft support 241 is separated from the photosensitive drum 121. Is a possible dimension.

  When the push spring 251 contracts in the contact / separation direction and the base portion 2461 of the engagement portion 246 of the bush member 24 protrudes from the lower surface portion 272, the first locking hole 291a is formed in the orthogonal direction. When the position restricting member 29 is slid to the position where it is locked to the front end portion 2462, the contact direction of the bush member 24 is moved to a position where the charging roller 22 is separated from the photosensitive drum 121 by the locking. It is possible to keep the position.

  In addition, when the position restricting member 29 is slid to the position where the second locking hole 291b matches the base portion 2461 and the distal end portion 2462 in the orthogonal direction, the distal end portion 2462 is unlocked from the locking hole 291. The At this time, the pressing spring 251 is released from the suppression by the locking, and presses and moves the bush member 24 toward the photosensitive drum 121 in the contact / separation direction.

  When the charging roller 22 in a state where the first locking hole 291a and the distal end portion 2462 are not locked and is supported by the first shaft support portion 241 by the pressing by the pressing spring 251 moves to the photosensitive drum 121 side, the charging is performed. When the roller 22 comes into contact with the photosensitive drum 121, the movement due to the pressing is suppressed by the contact with the photosensitive drum 121. The pressing force of the pressing spring 251 is set to a value that allows the charging roller 22 to contact the photosensitive drum 121 with a pressure equal to or higher than a predetermined pressing force. For this reason, in a state where the first locking hole 291 a and the tip end portion 2462 are not locked, the charging roller 22 is nipped with the photosensitive drum 121.

  Next, the drive mechanism 30 that slides the position regulating member 29 will be described with reference to FIG. In FIG. 7, the charging case 21 is not shown for convenience of explanation.

  The drive mechanism 30 includes a restriction wall 31 that restricts movement of the position restriction member 29, a solenoid 33 that operates according to an image forming operation of the image forming apparatus 1, and an arm that connects the solenoid 33 with one end of the restriction wall 31. 32.

  The position restricting member 29 is constantly pressed in a direction (arrow B direction in the drawing) perpendicular to the contact / separation direction by a pressing member (not shown). A restriction wall 31 is provided on the position restriction member 29 on the arrow B direction side. The restriction wall 31 restricts the movement of the position restricting member 29 in the arrow B direction. The restriction wall 31 is supported in the image forming unit 12 so as to be movable in a direction orthogonal to the arrow B direction.

  Here, the width of the regulating wall 31 in the arrow B direction differs depending on the position in the direction orthogonal to the arrow B direction. As shown in FIG. 7B, in the state where the position restricting member 29 is in contact with the wide portion 311 having a wide width in the arrow B direction in the restricting wall 31, the distal end portion 2462 of the engaging portion 246 is the first engagement. It is locked to the stop hole 291a. Therefore, in this state, the charging roller 22 is separated from the surface of the photosensitive drum 121.

  On the other hand, as shown in FIG. 7A, in the state where the position restricting member 29 is in contact with the narrow portion 312 having a narrow width in the arrow B direction in the restricting wall 31, the second locking hole 291b is the base portion 2461. In addition, the leading end portion 2462 of the engaging portion 246 is unlocked from the first locking hole 291a. Accordingly, in this state, the charging roller 22 is nipped with the photosensitive drum 121.

  In this way, by moving the regulating wall 31 in a direction perpendicular to the arrow B direction, the charging roller 22 and the cleaning roller 23 are nipped, and the charging roller 22 and the cleaning roller 23 are released from the nip. You can switch between

As shown in FIGS. 6A and 6B, an inclination for guiding the distal end portion 2462 of the engaging portion 246 is provided between the first locking hole 291a and the second locking hole 292b. Yes. The distal end portion 2462 of the engaging portion 246 moves along this inclination, so that the distal end portion 2462 is locked in the first locking hole 291a, or between the distal end portion 2462 and the first locking hole 291a. Switch to the unlocked state.

  As shown in FIGS. 7A and 7B, one end of the restriction wall 31 is connected to the solenoid 33 via the arm 32. When the solenoid 33 operates, the arm 32 rotates about the fulcrum shaft 321, and a force is applied to the restriction wall 31 in a direction perpendicular to the arrow B direction. Thereby, the regulation wall 31 moves in the direction orthogonal to the arrow B direction.

  The solenoid 33 is connected to the wiring 34 and operates based on a signal transmitted through the wiring 34. This signal is generated by a control unit 100 (see FIG. 8) described later, and the solenoid 33 operates in accordance with the image forming operation of the image forming apparatus 1.

  Next, the electrical configuration of the image forming apparatus 1 will be described. FIG. 8 is a functional block diagram schematically showing the main internal configuration of the image forming apparatus 1.

  The image forming apparatus 1 includes a control unit 10, a document reading unit 5, a document feeding unit 6, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, an operation unit 40, and the like.

  The control unit 10 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like, and controls overall operation of the image forming apparatus 1. The control unit 10 includes a control unit 100. The control unit 100 is connected to the document reading unit 5, the document feeding unit 6, the image forming unit 12, the fixing unit 13, the sheet feeding unit 14, the operation unit 40, and the like, and performs drive control of these units. In particular, the control unit 100 generates a signal for controlling the driving of the solenoid 33 of the image forming unit 12 in accordance with the image forming operation of the image forming apparatus 1. The solenoid 33 operates based on this signal. As a result, the image forming apparatus 1 nips the charging roller 22 and the cleaning roller 23 of the image forming unit 12 and releases the charging roller 22 and the cleaning roller 23 from the nip according to the image forming operation. You can switch between states. Further, the control unit 100 includes a counter 110. The counter 110 counts a continuous time during which the image forming apparatus 1 is not performing an image forming operation.

  The operation unit 40 includes a touch panel unit and operation key units that receive instructions from the user regarding various operations and processes that can be executed by the image forming apparatus 1. The touch panel unit is provided in a display part of a display unit 400 such as an LCD (Liquid Crystal Display) provided in the operation unit 40. For example, the operator can input a power-on instruction or a power-off instruction for the image forming apparatus 1 using the operation unit 40.

  Next, the operation of the image forming apparatus 1 having the above configuration will be described. FIG. 9 is a flowchart showing an operation for switching the nip of the charging roller and the cleaning roller or the release of the nip.

  When the image forming apparatus 1 is powered on (YES in step S1), the control unit 100 activates a control system that controls the image forming operation and the like of the image forming apparatus 1 (step S2).

  After starting the control system, the control unit 100 drives the solenoid 33 to nip the charging roller 22 and the cleaning roller 23 from the state where the charging roller 22 and the cleaning roller 23 of the image forming unit 12 are released from the nip. (Step S3).

  Thereafter, the control unit 100 monitors whether or not a power-off instruction for the image forming apparatus 1 is input by the operation unit 40 (step S4). When an instruction to turn off the image forming apparatus 1 is input from the operation unit 40 (YES in step S4), the control unit 100 drives the solenoid 33 to nip the charging roller 22 and the cleaning roller 23 of the image forming unit 12. The charging roller 22 and the cleaning roller 23 are switched from the nip state to the nip state released from the nip (step S5).

  After releasing the nip, the control unit 100 ends the control system that controls the image forming operation of the image forming apparatus 1 (step S6).

  As described above, the control unit 100 switches the nip between the charging roller 22 and the cleaning roller 23 or the release of the nip, using the power-on instruction and the power-off instruction of the image forming apparatus 1 as triggers. When the power is turned off when the image forming operation is not performed, the charging roller 22 and the cleaning roller 23 are released from the nip, so that deformation due to the pressure of the charging roller 22 and the cleaning roller 23 can be suppressed.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. Below, the modification 1, said modification 2, and the modification 3 of said embodiment are demonstrated.

<Modification 1>
In the above-described embodiment, the case where the nip between the charging roller 22 and the cleaning roller 23 or the release of the nip is switched using the power-on instruction and the power-off instruction of the image forming apparatus 1 as triggers has been described. However, the present invention is not necessarily limited to this case. The present invention only needs to switch the nip between the charging roller 22 and the cleaning roller 23 or the release of the nip according to the image forming operation of the image forming apparatus 1.

  FIG. 10 is a flowchart illustrating an operation of switching the nip or the nip release of the charging roller and the cleaning roller according to the first modification.

  The counter 110 of the control unit 100 counts the continuous time during which the image forming apparatus 1 is not performing an image forming operation (step S10). When the continuous time during which the image forming operation is not performed has elapsed for a predetermined time or longer (YES in step S10), the control unit 100 drives the solenoid 33 to charge the charging roller 22 and the cleaning roller 23 of the image forming unit 12. The charging roller 22 and the cleaning roller 23 are switched from the nip state to the nip state (step S11).

  After switching to the state of releasing from the nip, the control unit 100 determines whether or not an instruction to execute image formation is given by the operation unit 40 (step S12). When an instruction to perform image formation is given (YES in step S12), the control unit 100 drives the solenoid 33 to charge the charging roller 22 and the cleaning roller 23 of the image forming unit 12 from the nip. The roller 22 and the cleaning roller 23 are switched to a nip state (step S13). After switching the charging roller 22 and the cleaning roller 23 to the nip state, the control unit 100 executes an image forming process (step S14).

  As described above, when the image forming operation is not performed for a certain period of time or longer, the charging roller 22 and the cleaning roller 23 are released from the nip, so that deformation due to pressurization of the charging roller 22 and the cleaning roller 23 can be suppressed.

  The control unit 100 releases the charging roller 22 and the cleaning roller 23 from the nip when the image forming apparatus 1 shifts to a mode (so-called power saving mode) in which standby power is smaller than normal. Also good.

<Modification 2>
In the above-described embodiment, in a device in which a plurality of nips between rollers exist, a mechanism for switching both rollers forming each nip between the nip state and the nip release state is provided between the photosensitive drum 121 and the charging roller 22, and the charging roller 22. The mechanism for switching between the cleaning roller 23 and the cleaning roller 23 is described as an example, but the mechanism is not limited to this. The present invention can also be applied to switching between nips or nip release states between other rollers. In addition to the image forming apparatus 1, the mechanism can be applied to other apparatuses having a plurality of nips between rollers.

<Modification 3>
In the above embodiment, a case has been described in which the rotation axes of the photosensitive drum 121, the charging roller 22, and the cleaning roller 23 are arranged side by side on a virtual straight line (see FIGS. 4 and 5). However, the present invention is not necessarily limited to this case.

  11 is a side cross-sectional view of the photosensitive drum and the charging device according to the third modification as seen from the direction of arrow A in FIG. 2, and FIG. 11A shows a state where the charging roller is nipped on the surface of the photosensitive drum. (B) shows a state where the charging roller is separated from the surface of the photosensitive drum.

  As shown in FIGS. 11A and 11B, in the example shown in the third modification, the cylindrical axes of the photosensitive drum 121, the charging roller 22, and the cleaning roller 23 are arranged side by side on a common virtual straight line. Not. On the other hand, the first shaft support portion 241 that supports the charging roller 22 and the second shaft support portion 242 that supports the cleaning roller 23 are arranged side by side in the contact / separation direction as in the example described in the above embodiment. It is installed.

  Here, in the above-described embodiment and modification, the “contacting / separating direction” and “contacting / separating direction” are states in which the charging roller 22 is in contact with the photosensitive drum 121 from a state in which it is in contact. Or the direction of switching from the contacted state to the separated state. In Modification 3 shown in FIGS. 11A and 11B, the “contacting / separating direction” is the vertical direction of the paper surface.

  As shown in FIG. 11B, in a state where the charging roller 22 is not nipped with the photosensitive drum 121, the first shaft support portion 241 has play in the contact / separation direction due to the charging roller 22 being released. It is pivotally supported.

  As shown in FIG. 11A, in a state where the charging roller 22 is nipped to the photosensitive drum 121, the first shaft support portion 241 is moved in the first shaft support portion 241 by the charging roller 22 being pressed by the photosensitive drum 121. The charging roller 22 is pivotally supported so as to displace the position at the cleaning roller 23 side.

  For this reason, even if it is an example shown in the modification 3, the effect similar to said embodiment is acquired.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control unit 100 Control part 110 Counter 12Bk, 12C, 12M, 12Y Image forming unit 121 Photoconductor drum 123 Charging device 21 Charging case 22 Charging roller 23 Cleaning roller 24 Bush member 241 1st axis support part 242 2nd axis Supporting portion 245 Escape shape portion 245c Displacement restricting portion 246 Engaging portion 2461 Base portion 2462 Tip portion 25 Moving mechanism 251 Pushing spring 26 Guide portion 27 Supporting portion 2721 Receiving hole 29 Position restricting member 291 Locking hole 291a First locking hole 291b Second Locking hole 30 Drive mechanism 31 Restriction wall 311 Wide portion 312 Narrow portion 32 Arm 321 Support shaft 33 Solenoid 34 Wiring 40 Operation portion

Claims (7)

A first process roller that nips the object;
A second process roller provided to be nipable with respect to the first process roller;
A bushing member having a first shaft support portion that supports the first process roller, and a second shaft support portion that supports the second process roller in a state where the first process roller is placed;
A moving mechanism for moving the bush member in a direction in which the first process roller pivotally supported by the first pivotal support portion contacts and separates from the object;
A drive mechanism for driving the moving mechanism according to an image forming operation,
The first and second shaft support portions are arranged side by side in the contact / separation direction,
The first shaft support portion has a relief shape portion that allows the first process roller to be displaced in the contact / separation direction within the first shaft support portion, and the first process roller is not nipped to the object. In the state, the first process roller is pivotally supported by the relief shape portion with play in the contact / separation direction,
In a state where the first process roller is nipped to the object, the first shaft support portion is positioned in the first shaft support portion by the first process roller being pressed by the object. The first process roller is pivotally supported so as to be displaced toward the roller side ,
The moving mechanism is housed in the support part, a support part that slidably supports the bush member in the contact / separation direction, a pressing member that presses the bush member toward the object in the contact / separation direction, and the support part. A guide portion that is provided on a side of the bush member in a state of being in a state of guiding the movement of the bush member in the contact / separation direction by the pressing of the pressing member,
The bush member has an engaging portion extending toward a lower surface portion of the support portion facing the bush member,
The engaging portion has a columnar base and a disk-shaped tip having a larger diameter than the base formed at the tip of the base,
A receiving hole is formed in the lower surface portion to receive the base portion of the engaging portion.
A position regulating member that is movable in a direction orthogonal to the contact / separation direction is disposed on the back surface side of the lower surface portion that is opposite to the side on which the bush member is disposed,
The position restricting member is formed with a locking hole through which the base portion penetrating from the receiving hole passes.
The locking hole is integrally formed with a first locking hole having a width equivalent to the diameter of the base portion of the engaging portion and a second locking hole having a diameter equivalent to the diameter of the tip portion. A single hole extending in the orthogonal direction,
In the orthogonal direction, when the position restricting member moves to a locking position where the first locking hole locks to the tip portion, and when the second locking hole matches the base portion and the tip portion. When the position restricting member moves to the locking position, the engaging portion protrudes from the receiving hole to the position restricting member side with a different amount of protrusion.
When the position regulating member moves to the locking position, the pressing member contracts in the contact / separation direction, and the bushing member is moved to a position where the first process roller is not nipped with the object. When the contact / separation direction position remains and the position regulating member moves to the non-locking position, the pressing member presses the bush member toward the object in the contact / separation direction, and the first process roller Is nipped to the object,
The drive mechanism is an image forming unit that moves the position regulating member between the locking position and the non-locking position . The guide portion has a recess that extends in the contact / separation direction and guides the movement of the bush member in the contact / separation direction, and the recess is filled with protrusions formed on both sides of the bush member. The image forming unit according to claim 1, wherein the protruding portion is slidably supported in the approaching / separating direction in a state of being inserted. The position regulating member is pressed toward a direction orthogonal to the contact / separation direction,
The drive mechanism includes a solenoid that operates according to an image forming operation, and a restriction wall that restricts movement of the position restricting member in the pressing direction.
The regulating wall has a width in the pressing direction that differs depending on a position in a direction orthogonal to the pressing direction, and is movable in a direction orthogonal to the pressing direction by the operation of the solenoid.
The position regulating member, by the regulating wall is moved in a direction perpendicular to the pressing direction, the image forming according to claim 1 or claim 2 moves between the locking position and the unlocked position unit. The driving mechanism drives the moving mechanism to switch the first process roller to a position where the image forming apparatus is nipped with the object when the image forming apparatus is turned on, and when the image forming apparatus is turned off, the first process The image forming unit according to claim 1, wherein a roller is switched to a position where the roller is not nipped with the object. 3. The image formation according to claim 1 , wherein the drive mechanism switches the first process roller to a position where the object is not nipped with the object when an image forming operation is not performed for a predetermined time or longer. unit. The object is a photosensitive drum;
The first process roller is a charging roller that contacts the surface of the photosensitive drum and charges the surface,
The second process roller is a cleaning roller for cleaning the charging roller;
An exposure unit that exposes the surface of the photosensitive drum charged by the charging roller to form an electrostatic latent image; and
A developing unit that supplies toner to the electrostatic latent image formed by the exposure unit to form a toner image;
The image forming unit according to claim 1, further comprising: a transfer unit that transfers the toner image formed by the developing unit onto a recording medium or an intermediate transfer belt. An image forming unit according to claim 6 ;
An image forming apparatus comprising: a fixing unit that fixes the toner image transferred to the recording medium directly or indirectly by the image forming unit to the recording medium.