JP4613538B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile, or a copying machine that forms an image such as characters and graphics on a recording sheet.

  Conventionally, there are printers, facsimiles, copiers, and the like as image forming apparatuses for recording characters, graphics, and the like on recording paper. FIG. 11 shows an example of an image forming unit of a conventional image forming apparatus. The surface of the photosensitive drum 902 is charged by the charging device 901 to which a predetermined bias voltage is applied, and the LED head 903 is used as the image information. In response to this, the photosensitive drum 902 is selectively exposed to form an electrostatic latent image on the surface of the photosensitive drum 902. A developing device 904 supplies charged toner to the electrostatic latent image to form a toner image, and the toner image is transferred onto a recording sheet by a transfer roller 905 to which a predetermined bias voltage is applied. Thereafter, heat and pressure are applied to the recording paper by the fixing device 906, and the transferred toner image is fixed. On the other hand, after the surface charge of the photosensitive drum 902 to which the toner has been transferred is removed by the charge removal device 907, the toner remaining on the surface is removed by the cleaning device 908 and is charged again by the charging device 901. Yes.

  In the image forming unit as described above, for example, the charging device 901, the photosensitive drum 902, the developing device 904, the charge eliminating device 907, and the cleaning device 908 are accommodated as a process unit 900 in an integrated cartridge that can be attached to and detached from the apparatus main body. . Thus, for example, when the maintenance is performed such that the photosensitive drum 902 is deteriorated or the toner is insufficient, the process unit 900 can be replaced as a unit, and the maintenance work is simplified.

  While the process unit 900 is mounted, the photosensitive drum 902 and the transfer roller 905 on the apparatus main body are in pressure contact with each other, but the process unit 900 is in the radial direction of the photosensitive drum 902 and away from the transfer roller 905. If the toner is removed, that is, if it is removed in the upward direction in the figure, the photosensitive drum 902 and the transfer roller 905 are less likely to rub when the process unit 900 is attached and detached, and the surface of the photosensitive drum 902 is scratched. It ’s hard to follow. In order to remove the process unit 900 in such a direction, an openable / closable cover is provided on the upper surface or side surface of the image forming apparatus, and the process unit 900 is attached and detached by opening the cover. However, so-called OA devices such as printers, facsimiles, and copiers are desired to be compact in consideration of space saving in the office. For example, in order to attach and detach the process unit 900 from the side of the image forming apparatus, It is necessary to secure a space on the side of the. Therefore, in view of space saving and work convenience, a configuration in which the process unit 900 can be accessed from the front side of the apparatus and attached / detached is preferable.

  In order to remove the process unit 900 from the front surface of the image forming apparatus, the process unit 900 is moved in the axial direction of the photosensitive drum 902, that is, toward the front side of the drawing, so that the surface of the photosensitive drum 902 is not damaged. Thus, it is necessary to separate the transfer roller 905 from the photosensitive drum 902 in advance (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-52814

  For example, in order to make the transfer roller 905 detachable in the direction of the arrow, it is conceivable to adopt a configuration in which the transfer guide 909 that supports the transfer roller 905 can be moved in the direction of the arrow. If such a configuration is adopted, the transfer roller 905 needs to be brought into pressure contact with the photosensitive drum 902 when the recording paper is conveyed to form an image. For example, the transfer guide 909 is urged by using a spring or the like. In this case, the transfer guide 909 needs to have strength to withstand a load such as the spring.

  In particular, if the distance that the transfer guide 909 moves when the process unit 900 is inserted / removed, that is, the distance that the transfer roller 905 is separated from the photosensitive drum 902 is long, the spring that acts on the transfer guide 909 in the separated state, etc. Accordingly, the transfer guide 909 is required to have a suitable strength, and the degree of freedom in selecting a material such as a synthetic resin and in designing the size and thickness is reduced, resulting in an increase in cost. On the other hand, if the movement distance of the transfer guide 909 is shortened, the load is reduced. However, if the separation distance between the photosensitive drum 902 and the transfer roller 905 is short, there is a possibility that both of them come into contact with each other when the process unit 900 is inserted and removed.

  In addition, since the biasing force by the elastic body such as a spring is unavoidably caused by a slight difference or changes with time in each apparatus, the nip force between the photosensitive drum 902 and the transfer roller 905 is constant. In addition, it is necessary to adjust the urging force for each device during manufacture and over time.

  Furthermore, since the image forming apparatus itself is desired to be compact, a space for separating the transfer roller 905 is also limited. Further, in terms of cost, a new one is required for the contact and separation of the transfer roller 905. It is preferable to add as few members as possible.

  The present invention has been made to solve such a problem, and in order to insert and remove a process unit including a photosensitive drum from the front side of the apparatus without damaging the photosensitive drum or the like, the transfer roller can be simply and space-saving. It is an object of the present invention to provide a means capable of accurately positioning a transfer roller without contacting or separating from a photosensitive drum and without applying an excessive load to a transfer guide.

The present invention relates to a process unit including a photosensitive drum in an image forming apparatus for forming an image by nipping a recording paper between a photosensitive drum and a transfer roller and transferring a toner image on the surface of the photosensitive drum to the recording paper. Is provided so as to be insertable / removable in the axial direction of the photosensitive drum from the front side of the apparatus, urges the transfer roller to be press-contactable to the photosensitive drum, and rotatably supports it, and constitutes a conveyance path for recording paper The transfer guide is provided so as to be tiltable in a direction in which the transfer roller and the photosensitive drum come into contact with and away from each other, and contacts the transfer guide to hold the transfer guide at a pressure contact position where the transfer roller comes into pressure contact with the photosensitive drum. A holding member is movably provided between the contact position and the release position. The holding member is moved to the release position to release the holding of the transfer guide, and the transfer guide is transferred. Over La operating member for tilting is provided to the retracted position away from the photosensitive drum, the transfer guide is placed at the retracted position side with respect to, urged in the direction of the transfer guide the transfer roller contacts the photosensitive drum Thus, an urging member for preventing the transfer guide from suddenly tilting to the retracted position and for stopping the transfer guide at a position close to the photosensitive drum is provided. And

According to the present invention, in the image forming apparatus, the transfer path extends substantially upward from a paper feed cassette that stores the recording paper, whereby the upper end of the transfer guide is positioned substantially above the lower end. It is arranged by and said Rukoto.

  In the present invention, the holding member holds the transfer guide in a pressure contact position by contacting the vicinity of the tilting tip of the back surface of the guide surface on which the transfer roller is provided in the transfer guide. Further, the present invention is characterized in that it is provided so as to be rotatable in the vicinity of the tilting front end portion on the back surface side and moves between the contact position and the release position.

  Further, the present invention is characterized in that the transfer guide opens and closes with a cover provided on a side surface of the apparatus.

  According to the present invention, an openable / closable shutter that covers the surface of the photosensitive drum as a process unit housing is provided on the transfer guide. The shutter is opened at the press-contact position as the transfer guide tilts, and the shutter is opened at the retracted position. A shutter control member for closing the shutter is provided.

According to the image forming apparatus of the present invention, the process unit including the photosensitive drum is provided so as to be insertable / removable in the axial direction of the photosensitive drum from the front side of the apparatus, and the transfer roller can be pressed against the photosensitive drum. A transfer guide that is urged and rotatably supported is provided so as to be tiltable in a direction in which the transfer roller and the photosensitive drum come in contact with and away from each other, and abuts on the transfer guide so that the transfer roller comes into pressure contact with the photosensitive drum. A holding member that holds the transfer guide at the pressure contact position is movably provided between the contact position and the release position. The holding member is moved to the release position to release the holding of the transfer guide, and the transfer guide is transferred. Since the operating member for tilting the roller to the retracted position away from the photosensitive drum is provided, the transfer roller and the photosensitive drum are separated by tilting the transfer guide, and the photosensitive drum The possible insertion of the process unit in the axial direction of the photosensitive drum without damaging, can realize detachment of the process unit from the front side of the apparatus to easily and space-saving. Further, since the transfer guide is held in the pressure contact position by the holding member so that the transfer roller and the photosensitive drum are in pressure contact with each other, the transfer roller can be accurately positioned without applying an excessive load to the transfer guide. it can. In addition, since the transfer guide constitutes a conveyance path for the recording paper, the process unit can be attached and detached from the front side of the apparatus more easily and with less space. Further, with preventing the said transfer guide is tilted up abruptly retracted position by a biasing member disposed in the retracted position side with respect to the transfer guide, the transfer guide position near the transfer roller is close to the photosensitive drum Since it is stationary, an excessive impact is not applied to the transfer guide.

Further, according to the present invention, the transfer path extends substantially upward from a paper feed cassette that stores the recording paper, whereby the transfer guide constituting a part of the transfer guide is placed at the upper end substantially above the lower end. it can be disposed to position the.

  Further, according to the present invention, the holding member holds the transfer guide in a pressure contact position by contacting the vicinity of the tilting tip on the back side of the guide surface on which the transfer roller is provided in the transfer guide. In addition, the holding member can be configured in a simple and space-saving manner because it is provided so as to be rotatable in the vicinity of the tilting tip portion on the back surface side and moves between the contact position and the release position.

  Further, according to the present invention, since the transfer guide opens and closes with a cover provided on the side surface of the apparatus, for example, the transfer guide can be opened and closed together with a jam access cover for removing a paper jam. In this way, the vicinity of the photosensitive drum can be accessed, and a paper jam removal operation and the like are facilitated.

  According to the invention, an openable / closable shutter that covers the surface of the photosensitive drum as a housing of the process unit is provided on the transfer guide, and the shutter is opened at the press-contact position in accordance with the tilt of the transfer guide, and the retracted position. Since the shutter control member for closing the shutter is provided, the photosensitive drum is protected by the shutter when the process unit is attached or detached, so that it is not accidentally touched or damaged.

  FIG. 1 is a schematic perspective view showing the appearance of a copy / facsimile multifunction peripheral 100 equipped with an image forming apparatus according to an embodiment of the present invention. As shown in FIG. An image reading unit 101 functioning as a bed scanner, an operation panel 102 for inputting image reading and recording start, a main body 103 incorporating an image forming apparatus for forming an image on recording paper, and the recording paper And a paper feed cassette 104 to be supplied. The copier / facsimile multifunction peripheral 100 is provided with a front cover 30 on the front surface of the main body 103, that is, the surface on which the operation panel 102 is provided, and a jam access cover 31 on the right side. By opening, the inside of the main body 103 can be accessed.

  FIG. 2 is a schematic cross-sectional view showing the internal configuration of the main body 103 and the paper feed cassette 104 constituting the image forming apparatus in the copy / facsimile multifunction peripheral 100. As shown in the figure, a paper feed cassette 104 for sequentially supplying recording paper is disposed at the bottom of the apparatus, an image forming unit 105 is disposed above the paper feed cassette 104, and a paper discharge tray is further disposed above it. 106 is arranged. A conveyance path 107 for conveying recording paper from the paper feed cassette 104 to the paper discharge tray 106 extends upward from one end side of the paper feed cassette 104 to the image forming unit 105 and further extends upward. Then, it is formed so as to bend in the horizontal direction and lead to the paper discharge tray 106. Although not shown in the drawing, the image reading unit 101 and the operation panel 102 are disposed above the paper discharge tray 106.

  The paper feed cassette 104 has a box shape capable of storing recording papers of various sizes, and is provided at the bottom of the apparatus so as to be able to be drawn out, so that recording papers can be loaded as needed. Inside the paper feed cassette 104, a guide 40 for holding recording paper of a predetermined size at the paper feed position is disposed. The guide 40 is provided so as to be swingable within a predetermined range, and its bottom plate is biased upward by a spring or the like (not shown), thereby holding a plurality of recording sheets in a stacked state, One end of the uppermost paper is always positioned at the paper feed position. A paper feed roller 41 and a separation pad 42 are provided at the paper feed position, and the uppermost paper positioned at the paper feed position by the guide 40 is in pressure contact with the paper feed roller 41. The paper feed roller 41 is formed by fixing a roller made of silicon and EPDM (Ethylene-Propylene-Diene Methylene Linkage) to a metal roller shaft, for example, and is the top paper. The recording sheet is fed into the conveyance path 107 by rotating while being pressed against the sheet. The separation pad 42 has a friction coefficient with respect to the recording paper that is lower than the friction coefficient with respect to the recording paper of the paper feed roller 41 and higher than the friction coefficient between the recording papers, and can be formed of, for example, urethane resin. Such a separation pad 42 is disposed below the paper feed roller 41 so as to be movable up and down and is urged upward by a spring (not shown). The recording paper that is pressed against the roller surface and passes through the pressed portion is separated and fed one by one by friction.

  As shown in FIGS. 2 and 3, the image forming unit 105 includes a charging device 52, an LED head 53, a developing device 54, a transfer roller 55, and a cleaning device 56 disposed around the photosensitive drum 51, and a photosensitive device. The fixing device 57 is disposed in the conveyance path 107 on the downstream side of the body drum 51. Among these, the photosensitive drum 51, the charging device 52, the developing device 54, and the cleaning device 56 are housed in a cartridge as a process unit 50 and integrated.

  The photoconductive drum 51 has a photoconductive film formed of an organic photoconductor formed on the surface thereof, is rotated at a predetermined speed by a motor, and is charged to a constant voltage by a charging device 52. The charging device 52 is a non-contact corona charging method called a so-called scorotron charger, and although not shown in detail in the drawing, a discharge wire is disposed at substantially the center of a casing electrode forming a half space. In addition, a grid electrode is disposed on the photosensitive drum 51 side, and a corona discharge is generated when a predetermined voltage is applied to the discharge wire, and the amount of ions due to the corona discharge is controlled by the grid electrode. . The charging device 52 may employ another charging device such as a contact roller charging method instead of the non-contact corona charging method.

  The LED head 53 is a so-called self-luminous printer head in which LED arrays are arranged in parallel for the number of recording pixels, and light emitted from the LED array is imaged on the surface of the photosensitive drum 51 by a Selfoc lens array. The surface of the photosensitive drum 51 is selectively exposed to the photosensitive drum 51 based on image information, and an electrostatic latent image is formed on the surface. The surface of the photosensitive drum 51 charged by the charging device 52 is attenuated by being exposed by the LED head 53, and an electrostatic latent image is formed by the potential difference from the unexposed portion. As the image information, for example, an image of a document read by the reading table 101 functioning as a flatbed scanner is transmitted to the LED head 53 as an electrical signal. As the exposure device, a scanning optical system using a semiconductor laser in addition to the LED head 53 may be adopted.

  The developing device 54 includes a supply roller 58, a developing roller 59, and a toner container 60. The toner is generated by a difference in bias voltage applied to the supply roller 58 and the developing roller 59 from an electric circuit (not shown). The toner in the container 60 is supplied to the developing roller 59 through the supply roller 58, and a toner layer is formed on the surface of the developing roller 59. The developing roller 59 on which the toner layer is formed is rotated at a position close to the photosensitive drum 51, and the toner on the developing roller 59 moves to the photosensitive drum 51 due to a potential difference from the electrostatic latent image on the photosensitive drum 51. A toner image is formed on the surface of the photosensitive drum 51 based on the electrostatic latent image. Such a developing device 54 is an example, and selection of magnetic toner or non-magnetic toner, selection of contact development method or non-contact development method, and the like are arbitrary.

  The transfer roller 55 is a roller made of EPDM foam or urethane sponge, and is pressed against the photosensitive drum 51 at a position facing the conveyance path 107 so that a bias voltage is applied from an electric circuit (not shown). Yes. A toner image formed on the surface of the photosensitive drum 51 is applied by applying a bias voltage by nipping the recording paper supplied from the paper feeding cassette 104 through the conveying path 107 by the photosensitive drum 51 and the transfer roller 55. Is transferred to the recording paper.

  The cleaning device 56 is a cleaning blade pressed against the photosensitive drum 51 after transfer, and applies a constant voltage from an electric circuit (not shown) to remove toner and paper dust remaining on the surface of the photosensitive drum 51. The electrostatic latent image is erased while being removed. As a result, the surface of the photosensitive drum 51 is cleaned and continuous use is possible. As the cleaning device, other contact type or non-contact type using a cleaning roller or the like can be adopted, and a cleaningless type without using the cleaning device 56 can be adopted.

  The fixing device 57 includes a heating roller 62 and a pressure roller 63 disposed respectively at positions opposed to the conveyance path 107, and fixes the toner image on the recording paper conveyed through the conveyance path 107 by heating and pressing. is there. The surface of the heating roller 62 is maintained at a predetermined temperature by a heater, and a pressure roller 63 is pressed against the heating roller 62 with a predetermined pressure. The recording sheet on which the toner image has been transferred is nipped between the heating roller 62 and the pressure roller 63 so that the toner on the recording sheet is melted and fixed. The image forming unit 105 configured as described above forms an image of a document read by the reading table 101 on a recording sheet.

  As shown in FIG. 2, the recording sheet is conveyed from the sheet feeding cassette 104 along the conveying path 107 to the image forming unit 105 configured as described above, and the recording sheet on which an image is formed by the image forming unit 105. Is discharged to the discharge tray 106. The conveyance path 107 extends substantially upward from the paper feed cassette 104 to the image forming unit 105, and a pair of registration rollers 70 and 71 for adjusting the conveyance posture of the recording paper is provided in the middle. It has been. The registration rollers 70 and 71 are configured such that a rotation force from a driving source such as a motor is transmitted to a roller shaft, and the pair of registration rollers 70 and 71 are disposed at opposite positions of the conveyance path 107. It is arrange | positioned so that it may press-contact with the roller surface of this. The leading edge of the recording sheet conveyed from the sheet feeding cassette 104 toward the image forming unit 105 comes into contact with the registration rollers 70 and 71. Although not shown in the drawing, a sensor is provided on the upstream side of the registration rollers 70 and 71, and the registration rollers 70 and 71 are rotated after a predetermined time has elapsed since the sensor detected the recording paper. Therefore, since the registration rollers 70 and 71 are stopped when the leading edge of the recording paper comes into contact, the recording paper is bent at the leading edge so that the entire area of the leading edge is in contact with the roller surface of the registration rollers 70 and 71. Abut. Thereby, the skew of the recording sheet is corrected. Thereafter, the recording paper is nipped by the rotation of the registration rollers 70 and 71 and conveyed to the image forming unit 105. A conveyance roller 72 is appropriately provided in the conveyance path 107 between the image forming unit 105 and the paper discharge tray 106, and the recording paper on which an image is formed is conveyed by the conveyance roller 72 and discharged to the paper discharge tray 106. Is done. A C path is formed from the paper feed cassette 104 to the paper discharge tray 106 by such a conveyance path 107.

  As described above, the photosensitive drum 51, the charging device 52, the developing device 54, and the cleaning device 56 are housed and integrated as a process unit 50 in, for example, a synthetic resin cartridge. However, as shown in FIG. 3, the photosensitive drum 51 and the transfer roller 55 are in pressure contact with each other as shown in FIG. In order to prevent the photosensitive drum 51 from being damaged, it is necessary to separate the photosensitive drum 51 and the transfer roller 55 from each other. Hereinafter, a structure for separating the photosensitive drum 51 and the transfer roller 55 will be described in detail.

  The process unit 50 is supported by a frame or the like of the main body 103 and can be held at a predetermined position in the main body 103, and can be inserted and removed in the axial direction of the photosensitive drum 51 from the front side of the main body 103. On the other hand, the transfer roller 55 is rotatably supported by a transfer guide 73 that constitutes a part of the conveyance path 107, and the transfer guide 73 is in a direction in which the photosensitive drum 51 and the transfer roller 55 come into contact with and separate from each other. It can be tilted. That is, in FIG. 3, the process unit 50 can be pulled out and removed from the front side of the figure from the state where it is mounted on the main body 103, and the transfer guide 73 can be tilted to the right side of the figure when the process unit 50 is inserted or removed. The transfer guide 73 is formed from a synthetic resin, a metal plate or the like, and forms a guide surface across the width direction of the transfer path 107 in the transfer path 107 on the opposite side of the process unit 50 as shown in the figure. The support shaft 74 provided on the lower end side thereof is supported by the conveyance guide 75 constituting the conveyance path 107, and the upper end side thereof can be tilted to the side surface side of the main body 103. The transfer guide 73 pivotally supports the transfer roller 55 and one registration roller 70 so as to face the photosensitive drum 51 and the other registration roller 71, respectively, and each bearing portion (not shown). Are provided with springs 76 and 77, respectively, for urging the transfer roller 55 and the registration roller 70 toward the photosensitive drum 51 and the registration roller 71, respectively.

  Further, a C-shaped pin receiving rib 78 that is open on the side of the process unit 50 protrudes from the side surface of the transfer guide 73 that is the front surface side of the main body 103. The pin receiving rib 78 is, as will be described later. It becomes a contact part with the operation lever 86 for tilting the transfer guide 73 to the retracted position. A shutter pushing portion (shutter control member) 79 projects toward the process unit 50 on the upper end side of the side surface of the transfer guide 73. In FIG. 3, for convenience of explanation, the front end side of the shutter pressing portion 79 is omitted. The housing of the process unit 50 is provided with an openable / closable shutter 64 that covers the surface of the photosensitive drum 52. The shutter 64 is biased by a spring (not shown) while the process unit 50 is attached or detached. The photosensitive drum 52 is covered so as to prevent the surface from being touched or damaged by mistake. On the other hand, when the process unit 50 is mounted on the main body 103 and forms an image, the shutter 64 is opened to expose the surface of the photosensitive drum 52, but the shutter pushing portion 79 opens the shutter 64. Is to do.

  4 and 5 show the opening / closing mechanism of the shutter 64, but the operation lever 86 and the like are omitted for convenience of explanation. As shown in FIG. 4, the upper end of the shutter 64 is rotatably supported by a support arm 65, and the support arm 65 is rotatable around a shaft 66. The shaft 66 is provided with an operation arm 67 that contacts the shutter pressing portion 79. As shown in FIG. 4, when the transfer guide 73 is tilted and the photosensitive drum 51 and the transfer roller 55 are separated (retracted position), the shutter pushing portion 79 is also separated from the operation arm 67 of the shutter 64. The shutter 64 is closed by the biasing force of the spring and covers the surface of the photosensitive drum 51. As shown in FIG. 5, when the transfer guide 73 rises in the direction in which the photosensitive drum 51 and the transfer roller 55 are pressed against each other, the shutter pressing portion 79 comes into contact with the operation arm 67 of the shutter 64, and the transfer guide 73 moves. Accordingly, the operating arm 67 is pushed up, whereby the shaft 66 rotates and the support arm 65 rotates around the shaft 66. As a result, the shutter 64 is opened against the urging force of the spring to expose the surface of the photosensitive drum 51, the photosensitive drum 51 and the transfer roller 55 can be pressed against each other, and the transfer guide 73 stands up to be photosensitive. The body drum 51 and the transfer roller 55 are in pressure contact (pressure contact position). In this embodiment, the shutter pushing portion 79 and the operation arm 67 of the shutter 64 are provided on the side surface of the transfer guide 73 on the front side of the main body 103, but may be provided on the back side. .

  Further, as shown in FIG. 3, a contact portion 80 is formed at the tilting tip portion on the back side of the transfer guide 73 and comes into contact with a holding member 81 provided in the vicinity of the contact portion 80. Yes. The holding member 81 protrudes in a radial direction from a rotating shaft 82 supported rotatably on the conveyance guide 75 with the width direction of the transfer guide 73 as an axial direction obliquely above the contact portion 80. Is a flat plate-like member that can be rotated together with the rotary shaft 82. Further, the holding member 81 is urged to a position where the tip abuts against the back surface of the transfer guide 73 by the torsion spring (elastic member) 83, that is, a contact position. By restricting the rotation at the position, it stops at the contact position in a state where no external force is applied, and is rotated clockwise against the urging force of the torsion spring 83 by the external force, and the tip contacts the transfer guide 73. It is possible to move to a position where it does not, that is, a release position. Such a holding member 81 abuts against the abutting portion 80 of the transfer guide 73, whereby the transfer roller 55 can be held in pressure contact with the photosensitive drum 51, that is, the transfer guide 73 can be held in the pressure contact position. Thus, the transfer roller 55 can be accurately positioned without giving a heavy load. Further, unlike the positioning by an elastic body such as a spring, it is not necessary to adjust the urging force at the time of manufacture and over time so that the nip force between the photosensitive drum 51 and the transfer roller 55 is constant, and maintenance can be performed. Etc. are easy.

  Further, as shown in the drawing, a spring (elastic member) 84 is interposed between the transfer guide 73 and the conveyance guide 75, whereby the transfer guide 73 is urged toward the photosensitive drum 51, and an external force is applied. In a state where the transfer roller 55 is not received, that is, in a state where the holding member 81 is not in contact with the contact portion 80, the transfer roller 55 is in a state of being close to the photosensitive drum 51, that is, in a close position. The state in which the transfer roller 55 is close to the photosensitive drum 51 is a state in which the roller surfaces of the transfer roller 55 and the photosensitive drum 51 are in contact with each other without receiving a pressing force, or the transfer roller 55 and the photosensitive drum 51 are in contact with each other. The roller surfaces are not in contact with each other but are in close proximity. The state depends on the relationship between the load of the transfer guide 73 and the biasing force of the spring 84.

  The urging force by the spring 84 is set according to the urging force of the springs 76 and 77 that urge the transfer roller 55 and the registration roller 70 and the distance from the support shaft 74. That is, the urging force of the springs 76 and 77 acts in a direction in which the transfer guide 73 is tilted toward the side surface of the main body 103, so that the transfer guide 55 is brought close to the photosensitive drum 51 by the spring 84. In order to bias 73, the biasing force of the spring 84 needs to be equal to or slightly smaller than the biasing force of the springs 76 and 77. Here, the distances from the support shaft 74 of the transfer guide 73 to the action points of the springs 76, 77, 81 are L1, L2, L3, respectively, and the urging forces of the springs 76, 77, 81 are respectively X, Y, Z. Then, L1: L2: L3 = X: Y: Z, and the urging force of the springs 76 and 77 and the urging force of the spring 84 are balanced. Therefore, the biasing force of the spring 84 may be slightly smaller than the biasing force Z obtained by the above formula. Thereby, when the holding member 81 is rotated from the contact position to the release position, the transfer guide 73 is not suddenly tilted to the retracted position by the urging force of the springs 76 and 77.

  Further, a pin receiving rib 85 projects from the side surface near the lower portion of the contact portion 80 of the transfer guide 73. The pin receiving rib 85 moves the transfer guide 73 from the proximity position to the pressure contact position, as will be described later. It becomes a contact part with the operation lever 86 for tilting.

  As shown in FIG. 3, an operation lever (operation member) 86 for tilting the transfer guide 73 is provided on the front side of the transfer guide 73. The operating lever 86 has an inverted L shape made of steel or synthetic resin, and its bent corner 87 is rotatably fitted to a shaft 88 provided on the main body 103 or the conveyance guide 75. Two arms 89 and 90 that are substantially orthogonal to each other at the bent corner 87 extend substantially downward and horizontally. An operation handle 91 is provided at a lower end portion of the arm 89 extending substantially downward, and a pin 92 projects from the transfer guide 73 side at a substantially central portion thereof so as to be in contact with the pin receiving rib 78. On the other hand, a pin 93 projects from the tip of the arm 90 extending in the substantially horizontal direction toward the transfer guide 73, and can be brought into contact with the pin receiving rib 85 and the holding member 81 by the rotation of the operation lever 86. ing.

  Such an operating lever 86 is provided at a position that can be accessed when the front cover 30 (not shown) of the main body 103 is opened. As shown in FIG. When the holding member 81 and the transfer guide 73 are not operated, the pins 92 and 93 are not in contact with the pin receiving ribs 78 and 85, or even if they are in contact, no load is applied. . Such a position of the operating lever 86 is referred to as a neutral position. As shown in FIG. 6, when the operation lever 86 in the neutral position is operated from the front side of the main body 103 to the side of the operation handle 91, that is, rightward in the figure, the operation lever 86 is rotated rightward. First, the pin 93 of the arm 90 contacts the holding member 81, and the holding member 81 is rotated from the contact position to the release position. Accordingly, the transfer guide 73 is tilted from the press contact position to the proximity position by the urging force of the springs 76 and 77 and the urging force of the spring 84. Specifically, when the transfer guide 73 is positioned by the holding member 81 and is in the pressure contact position, the transfer roller 55 and the registration roller 70 are respectively moved by the urging force of the springs 76 and 77 to the photosensitive drum 51 and the registration roller, respectively. However, when the holding member 81 rotates to the release position, the urging force of the springs 76 and 77 acts on the transfer guide 73 to tilt clockwise. On the other hand, since the spring 84 urges the transfer guide 73 counterclockwise, the transfer guide 73 does not rotate suddenly, and the urging force of the springs 76 and 77 and the urging force of the spring 84 are generated. Tilt to a balanced position, that is, a close position. Although the holding member 81 is biased to the contact position by the torsion spring 83, the holding member 81 comes into contact with the tip end of the transfer guide 73 when the transfer guide 73 tilts to the close position. It does not rotate to the contact position.

  As shown in FIG. 7, when the operation handle 91 is further rotated to the right, the pin 92 of the arm 89 comes into contact with the pin receiving rib 78 of the transfer guide 73, and the transfer guide 73 in the close position is moved to the spring 84. It can be tilted to the retracted position against the urging force. By tilting the transfer guide 73 to the retracted position, the transfer roller 55 can be separated from the photosensitive drum 51, and accordingly, the shutter pressing portion 79 is also separated from the operation arm 67 of the shutter 64 and the shutter 64 is closed. Further, the holding member 81 rotates clockwise against the urging force of the torsion spring 83 while abutting against the tip of the transfer guide 73.

  As described above, the urging force of the spring 84 is not required to the extent that the transfer guide 73 is positioned at the pressure contact position against the urging force of the springs 76 and 77, and it is sufficient that the transfer guide 73 is stopped at the close position. Therefore, even if the transfer guide 73 is tilted so that the transfer roller 55 is sufficiently separated from the photosensitive drum 51, the load received from the spring 84 is not large. Therefore, the transfer guide 73 does not require high strength, and the degree of freedom in designing materials such as synthetic resin and the size and thickness is increased.

  In this manner, the transfer guide 73 is tilted to the retracted position, and the process unit 50 can be pulled out in the axial direction of the photosensitive drum 51, that is, the front side in the figure, with the transfer roller 55 sufficiently separated from the photosensitive drum 51. Therefore, the photosensitive drum 51 or the like is not damaged when the process unit 50 is inserted or removed. In order to prevent the transfer guide 73 from returning from the retracted position to the close position by the biasing force of the spring 84, if a known and arbitrary lock mechanism is provided on the operation lever 86, the transfer guide 73 is operated in a tilted state. This is convenient because the process unit 50 can be inserted and removed by releasing the lever 86.

  After the process unit 50 is replaced, as shown in FIG. 8, the transfer guide 73 is moved by returning the operation lever 86 tilting the transfer guide 73 to the retracted position to the neutral position. The urging force of the springs 76 and 77 and the urging force of the spring 84 return from the retracted position to the close position. The holding member 81 also rotates counterclockwise toward the contact position due to the urging force of the torsion spring 83. However, as described above, the holding member 81 contacts the tilting tip of the transfer guide 73 at the close position. Cannot rotate.

  As shown in FIG. 9, when the operation lever 86 is further rotated leftward from the neutral position, the pin 93 of the arm 90 comes into contact with the pin receiving rib 85 of the transfer guide 73, against the urging force of the springs 76 and 77. Thus, the transfer guide 73 is tilted from the close position to the press contact position. As described above, since the holding member 81 is urged to the contact position by the torsion spring 83, the holding member 81 returns to the contact position by tilting the transfer guide 73 to the pressure contact position, and the tip of the holding member 81 is returned to the contact position. It contacts the contact portion 80 of the transfer guide 73. By operating the operation lever 86 in this manner, the transfer guide 73 can be returned to the press contact position and held by the holding member 81.

  Further, the conveyance guide 75 that supports the transfer guide 73 is supported by the jam access cover 31. As shown in FIG. 10, when the jam access cover 31 is opened, the conveyance guide 75 and the transfer guide 73 are moved to the jam access cover 31. The paper jam near the image forming unit 105 can be removed from the side of the main body 103. As described above, the pin receiving rib 78 of the transfer guide 73 that comes into contact with the pin 92 of the operation lever 86 is C-shaped with the process unit 50 opened, so that when the transfer guide 73 is opened together with the jam access cover 31, There is no interference. Further, when the operation lever 86 is in the neutral position, the pin 93 is not in contact with the pin receiving rib 85 and the holding member 81 of the transfer guide 73, and they interfere when the transfer guide 73 is opened together with the jam access cover 31. There is no need to do. Although not shown in the drawing, the jam access cover 31 can be opened together with the transfer guide 73 even when the transfer guide 73 is in the proximity position. Thus, when the transfer guide 73 is opened, the shutter pushing portion 79 is also separated from the operation arm 67 of the shutter 64, so that the shutter 64 is closed. Accordingly, it is possible to prevent the surface of the photosensitive drum 51 from being accidentally touched when removing a paper jam. Note that the transfer guide 73 may be supported by the frame of the main body 103 instead of the conveyance guide 75. With such a configuration, the frame or the like may be opened together with the jam access cover 31.

  As described above, according to the copy / facsimile multifunction peripheral 100 according to the present embodiment, the process unit 50 is moved in a state in which the transfer guide 73 is tilted by the operation lever 86 and the transfer roller 55 is separated from the photosensitive drum 51. Since the photosensitive drum 51 is inserted and removed in the axial direction, the process unit 50 can be attached and detached from the front side of the main body 103 without damaging the photosensitive drum 51 in a simple and space-saving manner.

  In the present embodiment, the pin 93 of the operation lever 86 is in direct contact with the holding member 81 and is rotated. However, for example, a contact member is provided on the rotating shaft 82 separately from the holding member 81, The contact member and the pin 93 may come into contact with each other and the rotation shaft 82 may be rotated, whereby the holding member 81 may be rotated from the contact position to the release position. In the present embodiment, the transfer guide 73 is returned from the proximity position to the pressure contact position by the operation lever 86. However, if the transfer guide 73 is directly operated to tilt from the proximity position to the pressure contact position, The pin receiving rib 85 can be omitted. In the present embodiment, the embodiment in which the image forming apparatus is implemented as the copy / facsimile multifunction peripheral 100 has been described. However, the image forming apparatus is not limited to the copy / facsimile multifunction peripheral 100, and may be a single machine, a printer, or the like. Of course, the embodiment can be changed without departing from the gist of the invention.

1 is a schematic perspective view showing an external configuration of a copy / facsimile multifunction peripheral 100 according to an embodiment of the present invention. 2 is a schematic cross-sectional view showing a configuration inside a main body 103 of the copy / facsimile multifunction peripheral 100. FIG. FIG. 3 is an enlarged view showing a configuration in the vicinity of a process cartridge 50 in a state where a photosensitive drum 51 and a transfer roller 55 are in pressure contact with each other. 4 is an enlarged view for explaining an opening / closing mechanism of a shutter 64 of a process cartridge 50. FIG. 4 is an enlarged view for explaining an opening / closing mechanism of a shutter 64 of a process cartridge 50. FIG. FIG. 6 is an enlarged view showing a configuration in the vicinity of a process cartridge 50 in a state where a transfer guide 73 is tilted from a pressure contact position to a proximity position. FIG. 6 is an enlarged view showing a configuration in the vicinity of a process cartridge 50 in a state in which a transfer guide 73 is tilted from a close position to a retracted position. FIG. 5 is an enlarged view showing a configuration in the vicinity of a process cartridge 50 in a state where a transfer guide 73 is tilted from a retracted position to a close position. FIG. 4 is an enlarged view showing a configuration in the vicinity of a process cartridge 50 in a state where a transfer guide 73 is tilted from a proximity position to a pressure contact position. FIG. 6 is an enlarged view showing a configuration around a process cartridge 50 in a state where a jam access cover 31 is opened. It is a schematic diagram which shows an example of the conventional image forming apparatus.

Explanation of symbols

50 Process Unit 51 Photosensitive Drum 55 Transfer Roller 64 Shutter 73 Transfer Guide 79 Shutter Pushing Section (Shutter Control Member)
81 Holding member 84 Spring (elastic member)
86 Operation lever (operation member)
100 Copy / facsimile multifunction peripherals (image forming equipment)
107 Transport path

Claims (5)

In an image forming apparatus for forming an image by nipping a recording sheet between a photosensitive drum and a transfer roller and transferring a toner image on the surface of the photosensitive drum to the recording sheet.
A process unit including a photosensitive drum is provided so as to be insertable / removable in the axial direction of the photosensitive drum from the front side of the apparatus,
The transfer roller is urged so as to be in pressure contact with the photosensitive drum and is rotatably supported, and a transfer guide constituting a recording sheet conveyance path can be tilted in a direction in which the transfer roller and the photosensitive drum come into contact with and away from each other. Provided in
A holding member that is in contact with the transfer guide and holds the transfer guide at a pressure contact position where the transfer roller is in pressure contact with the photosensitive drum is provided movably between the contact position and the release position.
An operation member is provided that moves the holding member to a release position to release the holding of the transfer guide, and tilts the transfer guide to a retracted position where the transfer roller is separated from the photosensitive drum,
It is disposed at the retracted position side with respect to the transfer guide, by the transfer guide the transfer roller is urged in the direction of contact with the photosensitive drum, thereby preventing the transfer guide is tilted up abruptly retracted position An image forming apparatus characterized in that an urging member for stopping the transfer guide is provided at a close position where the transfer roller is close to the photosensitive drum.   The transfer guide is disposed with a top end positioned substantially above a lower end by extending the transport path substantially upward from a paper feed cassette that stores the recording paper. Item 2. The image forming apparatus according to Item 1.   The holding member holds the transfer guide in a pressure contact position by contacting the vicinity of the tip end of the back side of the guide surface on which the transfer roller is provided in the transfer guide. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided so as to be rotatable in the vicinity of the front end portion and moves between a contact position and a release position.   The image forming apparatus according to claim 1, wherein the transfer guide opens and closes together with a cover provided on a side surface of the apparatus.   An openable / closable shutter that covers the surface of the photosensitive drum as a housing of the process unit is provided on the transfer guide. A shutter control member that opens the shutter at the press contact position and closes the shutter at the retracted position as the transfer guide is tilted. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided.

Images