JP5241659B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a cover member that opens and closes a process control sensor with respect to an image carrier.

  In an image forming apparatus that forms an image on a sheet through an electrophotographic image forming process, there is a process control performed during non-execution of an image forming process for forming an image on the sheet, and the driving state of the image forming unit Some of them include a detection unit that detects the density of a toner image on the image carrier during execution of process control for controlling the image (see, for example, Patent Document 1). The detection unit is disposed in the vicinity of the image carrier.

  If the toner scattered from the image carrier adheres to the detection unit, the detection accuracy of the detection unit is lowered. Therefore, the image carrier is moved in the moving direction so that the closed position covering the detection unit and the detection unit are exposed to the image carrier. It is conceivable to provide the image forming apparatus with a cover member that is displaced to the open position displaced in the direction along the direction.

JP 2002-148897 A

  However, a sheet conveyance path is provided in the vicinity of the image carrier. A pre-transfer charging device that adjusts the charge of the toner image may be provided in the vicinity of the image carrier. For this reason, if a region for the displacement of the cover member is newly provided in the vicinity of the image carrier, the size in the direction along the moving direction of the image carrier in the vicinity of the image carrier must be widened, and image formation is performed. There arises a problem that the apparatus is enlarged and the first copy time, which is the time from the start of the image forming process to the end of the first image forming process, is extended.

  An object of the present invention is to provide an image forming apparatus capable of preventing the enlargement of the image forming apparatus and the extension of the first copy time.

  The image forming apparatus of the present invention includes an image forming unit, an image carrier, a region constituting member, a detecting unit, and a cover member. The image forming unit forms a toner image based on the image data through an electrophotographic image forming process. The image carrier rotates while carrying the toner image formed by the image forming unit. The area constituent member is an area constituent member arranged so as to form a predetermined working area with the image carrier, and is only applied to the image carrier during execution of an image forming process for forming an image on a sheet. Acts through the working area. The detection unit is disposed in the vicinity of the image carrier, and is a process control performed during non-execution of the image forming process for forming an image on the sheet, and during the execution of the process control for controlling the driving state of the image forming unit The density of the toner image carried on the image carrier is detected. The cover member is displaced to a closed position covering the detection unit with respect to the image carrier and an open position displaced in a direction along the moving direction of the image carrier so as to expose the detection unit. At least a part of the cover member is arranged in the working area in the open position.

  In this configuration, the area constituent member acts on the image carrier via the action area only during execution of the image forming process. For this reason, the action area is used for the image carrier only during execution of the image forming process. On the other hand, since the cover member is disposed in the open position while the process control is being performed and the image forming process is not being performed, the active region is not used when the cover member is disposed in the open position. . For this reason, even if at least a part of the cover member is arranged in the action region in the open position, it does not hinder the image forming process. On the other hand, since at least a part of the cover member is disposed in the operation region in the open position, there is no need to newly provide a region for the displacement of the cover member in the vicinity of the image carrier. The dimension in the direction along the direction does not widen.

  In the above-described configuration, the region constituent member is a side wall that forms a sheet conveyance path for supplying a sheet to the surface of the image carrier so that the toner image carried by the image carrier is transferred, and at least a part of the cover member is In the open position, it can be arranged in the sheet conveyance path. Since the cover member is disposed at the open position while the process control is being performed and the image forming process is not being performed, the sheet is not conveyed to the sheet conveyance path when the cover member is disposed at the open position. For this reason, even if at least a part of the cover member is disposed in the sheet conveyance path in the open position, it does not hinder the image forming process. On the other hand, since at least a part of the cover member is disposed in the sheet conveyance path in the open position, there is no need to newly provide a region for the cover member to be displaced in the vicinity of the image carrier. The dimension along the moving direction does not increase.

  Further, the cover member can constitute a part of the side wall of the sheet conveying path in the closed position. Since the cover member is also used as a part of the side wall of the sheet conveyance path, the space in the direction along the moving direction of the image carrier is smaller than when the cover member and the side wall of the sheet conveyance path are provided adjacent to each other. can do. Further, at least a part of the cover member is disposed in the sheet conveyance path in the open position, but it is not necessary to move the side wall of the sheet conveyance path in order to displace the cover member. In addition, since it is not necessary to provide a notch in the side wall of the sheet conveyance path, the manufacturing process can be simplified.

  Further, the area constituting member is a pre-transfer charging device that adjusts the charge of the toner image carried on the image carrier, and at least a part of the cover member is located between the pre-transfer charging device and the image carrier in the open position. It can be constituted so that it may be arranged. Since the cover member is disposed at the open position while the process control is being performed and the image forming process is not being performed, the pre-transfer charging device is not driven when the cover member is disposed at the open position. For this reason, even if at least a part of the cover member is disposed between the pre-transfer charging device and the image carrier in the open position, it does not hinder the image forming process. On the other hand, since the length of the pre-transfer charging device in the direction along the moving direction of the image carrier is larger than that of the detection unit, it is sufficient to place a cover member between the pre-transfer charging device and the image carrier. There is a lot of space. For this reason, at least a part of the cover member is disposed between the pre-transfer charging device and the image carrier in the open position, so that a region for displacing the cover member needs to be newly provided in the vicinity of the image carrier. Therefore, the dimension in the direction along the moving direction of the image carrier is not widened.

  In addition, a plurality of detection units are provided in the rotation axis direction of the image carrier, and the cover member can be configured to extend in the rotation axis direction to a length that covers all of the plurality of detection units in the closed position. Since one cover member has only to be displaced in order to open and close the plurality of detection units, the drive control can be simplified.

  Further, a plurality of detection units are provided in the rotation axis direction of the image carrier, and a plurality of cover members are provided corresponding to the detection units, and the plurality of cover members are interlocked with each other between the closed position and the open position. It can be configured to be displaced. If one cover member is displaced in order to open and close a plurality of detection parts, all the cover members are displaced, so that the drive control can be simplified.

  According to the present invention, the enlargement of the image forming apparatus and the extension of the first copy time can be prevented.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the relationship between the process in execution and the state of each part. 1 is a diagram illustrating a partial configuration of an image forming apparatus. FIG. 2 is an enlarged view showing a partial configuration of the image forming apparatus. FIG. 6 is a diagram illustrating a partial configuration of an image forming apparatus according to another embodiment. FIG. 10 is a diagram illustrating a partial configuration of an image forming apparatus according to another embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  As illustrated in FIG. 1, the image forming apparatus 10 forms a multicolor or single color image on a sheet, which is an example of a sheet, based on image data. The image forming apparatus 10 includes image forming stations (image forming units) 21, 22, 23, 24, an intermediate transfer belt unit 31, a plurality of primary transfer rollers 32A to 32D, a secondary transfer belt 33, a fixing device 34, a sheet conveyance path. (Sheet transport path) 35, paper feed tray 36, paper discharge tray 37, pre-transfer charging device 38, process control sensor (detection unit) 39, and control unit 100. The control unit 100 comprehensively controls the image forming apparatus 10.

  The image forming apparatus 10 uses an image data corresponding to four hues of black, cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of a color image. The image forming process is performed. In the image forming stations 21 to 24, toner images of respective hues are formed. The image forming stations 21 to 24 are arranged in a row in the horizontal direction along the intermediate transfer belt unit 31.

  Hereinafter, the image forming station 21 will be mainly described. The image forming stations 22 to 24 are configured in substantially the same manner as the image forming station 21. The black image forming station 21 includes a photosensitive drum 41, a charging device 42, an exposure device 43, a developing device 44, and a cleaning unit 45, and forms a black toner image through an electrophotographic image forming process.

  The photosensitive drum 41 is an electrostatic latent image carrier, has a cylindrical shape, and rotates when a driving force is transmitted from a first driving source (not shown). The photosensitive drum 41 has a cylindrical conductive substrate and a photosensitive layer provided on the peripheral surface of the conductive substrate.

  The charging device 42 is disposed along the axial direction of the photosensitive drum 41 so as to face the peripheral surface of the photosensitive drum 41. The charging device 42 is a non-contact type charging device, and uniformly charges the peripheral surface of the photosensitive drum 41 to a predetermined potential.

  The exposure device 43 has a semiconductor laser, and irradiates the photosensitive drum 41 with a laser beam modulated by black image data. An electrostatic latent image based on black image data is formed on the peripheral surface of the photosensitive drum 41.

  The developing device 44 contains a black developer. As the developer, for example, a two-component developer composed of a toner and a carrier is used. The developing device 44 charges the toner by stirring the toner and the carrier. The developing device 44 develops the electrostatic latent image into a toner image by supplying toner to the peripheral surface of the photosensitive drum 41 on which the electrostatic latent image is formed.

  The developing devices 44 of the image forming stations 22 to 24 contain developers of cyan, magenta, and yellow, and the photosensitive drums 41 store cyan, magenta, and yellow. A toner image of each color is formed.

  The intermediate transfer belt unit 31 includes an intermediate transfer belt 311, a driving roller 312, and a driven roller 313. As the intermediate transfer belt 311, for example, a film having a predetermined thickness in the range of 100 to 150 μm is used. The intermediate transfer belt 311 constitutes an image carrier, is stretched between a driving roller 312 and a driven roller 313, and moves around in one direction. The intermediate transfer belt 311 is stretched and rotated by a drive roller 312 and a driven roller 313, and there is no member that serves as a rotation shaft. However, the rotation axis direction of the intermediate transfer belt 311 is different from that of the drive roller. This is substantially the same as the rotation axis direction 312.

  The outer peripheral surface of the intermediate transfer belt 311 faces the respective photosensitive drums 41 of the image forming stations 21 to 24. As an example, the driving roller 312 is disposed on the downstream side of the image forming stations 21 to 24 in the moving direction 91 of the intermediate transfer belt 311, and the driven roller 313 is disposed on the upstream side of the image forming stations 21 to 24.

  The primary transfer rollers 32 </ b> A to 32 </ b> D are arranged to face the respective photosensitive drums 41 of the image forming stations 21 to 24 with the intermediate transfer belt 311 interposed therebetween. The primary transfer rollers 32B to 32D are configured in substantially the same manner as the primary transfer roller 32A. The primary transfer roller 32A has a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm, and a conductive elastic material that covers the peripheral surface of the shaft. A high voltage is uniformly applied to the intermediate transfer belt 311 by the conductive elastic material. A position where the intermediate transfer belt 311 faces the respective photosensitive drums 41 of the image forming stations 21 to 24 is a primary transfer position.

  In the primary transfer rollers 32A to 32D, in order to primarily transfer the toner image carried on the peripheral surface of the photosensitive drum 41 onto the intermediate transfer belt 311, the polarity (for example, minus) of the toner is opposite to the polarity (for example, minus). (Plus) primary transfer bias is applied by constant voltage control. As a result, the toner images of the respective colors formed on the respective photosensitive drums 41 of the image forming stations 21 to 24 are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 311 and transferred to the outer peripheral surface of the intermediate transfer belt 311 in full color. A toner image is formed.

  However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, only part of the four photosensitive drums 41 corresponding to the hue of the input image data is input. An electrostatic latent image and a toner image are formed. For example, during the monochrome image forming process, the electrostatic latent image and the toner image are formed only on the photosensitive drum 41 corresponding to the black hue, and only the black toner image is formed on the outer peripheral surface of the intermediate transfer belt 311. Transcribed.

  The cleaning unit 45 removes and collects toner remaining on the peripheral surface of the photosensitive drum 41 after development and primary transfer.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 311 at each primary transfer position is conveyed to a predetermined secondary transfer position by the circumferential movement of the intermediate transfer belt 311. The secondary transfer belt 33 is disposed so as to be in pressure contact with the driving roller 312 with the intermediate transfer belt 311 interposed therebetween. The secondary transfer belt 33 is in pressure contact with the intermediate transfer belt 321 with a predetermined nip pressure. A position where the secondary transfer belt 33 faces the driving roller 312 with the intermediate transfer belt 311 interposed therebetween is a secondary transfer position. The secondary transfer belt 33 can be replaced with a secondary transfer roller.

  A pre-transfer charging device 38 is disposed between the image forming station 24 disposed on the most downstream side in the moving direction 91 of the intermediate transfer belt 311 and the secondary transfer position. The pre-transfer charging device 38 is a non-contact type charging device, and is disposed close to the outer peripheral surface of the intermediate transfer belt 311. A counter roller 53 is disposed so as to face the pre-transfer charging device 38 with the intermediate transfer belt 311 interposed therebetween.

  The pre-transfer charging device 38 is driven only during the image forming process. The pre-transfer charging device 38 is driven to give the toner image carried on the outer peripheral surface of the intermediate transfer belt 311 a charge having the same polarity (for example, minus) as the toner charging polarity (for example, minus). As a result, the charge of the toner image is adjusted, and the performance of secondary transfer for transferring the toner image from the outer peripheral surface of the intermediate transfer belt 311 to the sheet at the secondary transfer position is improved.

  The paper feed tray 36 stores paper. When the paper fed from the paper feed tray 36 passes between the secondary transfer belt 33 and the intermediate transfer belt 311, the secondary transfer belt 33 has a polarity opposite to the toner charging polarity (for example, minus) ( For example, a positive high voltage is applied. As a result, the toner image is secondarily transferred from the outer peripheral surface of the intermediate transfer belt 311 to the sheet.

  Of the toner primarily transferred from one or all of the four photosensitive drums 41 to the intermediate transfer belt 311, the toner remaining on the intermediate transfer belt 311 without being transferred to the paper prevents color mixing in the next step. Therefore, the intermediate transfer belt cleaning unit 51 collects the toner.

  The fixing device 34 includes a heating roller 341 and a pressure roller 342. The sheet on which the toner image has been transferred is guided to the fixing device 34 and is heated and pressed by passing between the heating roller 341 and the pressure roller 342. As a result, the toner image is firmly fixed on the paper. The sheet on which the toner image is fixed is discharged onto the discharge tray 37 by the discharge roller pair 52.

  In the image forming apparatus 10, the sheet stored in the sheet feed tray 36 is sent to the sheet discharge tray 37 between the secondary transfer belt 33 and the intermediate transfer belt 32 and via the fixing device 34. A conveyance path 35 is provided. The paper transport path 35 extends in a substantially vertical direction.

  In the paper conveyance path 35, a pickup roller, conveyance roller pairs 54A, 54B, 54C, a registration roller pair 55, and the above-described paper discharge roller pair 52 are arranged. The pickup roller feeds the paper in the paper feed tray 36 to the paper transport path 35 one by one. The conveyance roller pairs 54A, 54B, and 54C convey the fed paper along the paper conveyance path 35. The registration roller pair 55 guides the conveyed sheet between the secondary transfer belt 33 and the intermediate transfer belt 311 at a predetermined timing.

  The registration roller 55 stops rotating when the photosensitive drum 41 and the intermediate transfer belt 311 start to operate. The sheet fed prior to the rotation of the intermediate transfer belt 311 stops in a state where the front end is abutted against the registration roller 55. Thereafter, the registration roller 55 is a position where the secondary transfer belt 33 and the intermediate transfer belt 311 are in pressure contact with each other, at a timing when the front end portion of the sheet and the front end portion of the toner image carried on the intermediate transfer belt 311 face each other. Start spinning.

  In the full color image forming process in which the image forming process is performed in all of the image forming stations 21 to 24, the four primary transfer rollers 32A to 32D press the intermediate transfer belt 311 against all the photosensitive drums 41. On the other hand, at the time of monochrome image forming processing in which image forming processing is performed only at the image forming station 21, only the primary transfer roller 32 </ b> A facing the image forming station 21 presses the intermediate transfer belt 311 against only the photosensitive drum 41 of the image forming station 21. Let

  The process control sensor 39 is disposed between the pre-transfer charging device 38 and the secondary transfer position and close to the pre-transfer charging device 38. The process control sensor 39 is also close to the intermediate transfer belt 311. In this embodiment, one process control sensor 39 is provided between the center portion and the end portion in the rotation axis direction of the drive roller 312.

  The image forming apparatus 10 performs process control for controlling the driving states of the image forming stations 21 to 24 during the non-execution of the image forming process for forming an image on a sheet. As an example, the process control is executed when the image forming apparatus 10 is activated and every predetermined number of image forming processes. The process control is not executed during the execution of the image forming process, and the image forming process is not executed during the execution of the process control.

  In the process control, a toner image having a predetermined pattern is formed on the outer peripheral surface of the intermediate transfer belt 311. The process control sensor 39 detects the density of the toner image carried on the outer peripheral surface of the intermediate transfer belt 311 during execution of the process control, and outputs the detected density to the control unit 100.

  The control unit 100 compares the detected density input from the process control sensor 39 with a reference value stored in advance, and controls the driving state of the image forming stations 21 to 24 based on the comparison result. Examples of driving states of the image forming stations 21 to 24 include a developing bias voltage (V) and an exposure condition of the exposure device 43, that is, a laser duty (%).

  By executing the process control, the maximum density and halftone density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 311 in the image forming process can be accurately expressed.

  As shown in FIG. 2, the state of paper conveyance, driving of the pre-transfer charging device 38, and detection or non-detection of the process control sensor 39 are different between the execution of the image forming process and the execution of the process control. Specifically, the conveyance of the paper in the paper conveyance path 35 is performed during the execution of the image forming process, but is not performed during the execution of the process control. The pre-transfer charging device 38 is driven while the image forming process is being executed, but is not driven while the process control is being executed. Further, the process control sensor 39 does not perform detection during the execution of the image forming process, but performs detection during execution of the process control.

  As shown in FIG. 3, the process control sensor 39 is disposed so as to face the intermediate transfer belt 311 from below. In order to prevent the detection accuracy of the process control sensor 39 from deteriorating due to the toner scattered from the intermediate transfer belt 311 adhering to the process control sensor 39, the image forming apparatus 10 includes a cover member 61. The cover member 61 can be displaced to a closed position where the intermediate transfer belt 311 covers the process control sensor 39 and an open position where the process control sensor 39 is exposed. The control unit 100 places the cover member 61 in the open position during the execution of the process control, and places the cover member 61 in the closed position during the non-execution of the process control, that is, during the execution of the image forming process.

  The cover member 61 includes a cover portion 611 that can cover the process control sensor 39, and a support portion 612 that supports the cover portion 611, and is formed in an L-shaped cross section as an example. The support portion 612 is pivotally supported so as to be displaceable in a direction along the moving direction 91 of the intermediate transfer belt 311 at a position that does not overlap the process control sensor 39 in the rotation axis direction of the driving roller 312. The cover portion 611 extends in the direction of the rotation axis of the drive roller 312 to a length that can cover the process control sensor 39.

  The cover member 61 follows the moving direction 91 of the intermediate transfer belt 311 so that the process control sensor 39 is exposed to the intermediate transfer belt 311 from a closed position where the process control sensor 39 is covered with the intermediate transfer belt 311. By being displaced in the direction, it is placed in the open position. In FIG. 3, the cover member 61 in a state of being placed at the closed position is indicated by a two-dot chain line, and the cover member 61 in a state of being placed at the open position is indicated by a solid line.

  The shaft for rotating the cover member 61 extends to the outside of the image forming area in the rotation axis direction of the driving roller 312, and acts on the outside of the image forming area in a direction to rotate with respect to the axis of the cover member 61. A solenoid and a spring (not shown) are arranged.

  The cover member 61 is displaced from the closed position to the open position when the solenoid is turned on. Further, the cover member 61 is urged by a spring in the direction of displacement from the open position to the closed position, and when the solenoid is turned off, the cover member 61 returns from the open position to the closed position. Note that a stopper is provided at a predetermined position so that the cover member 61 is not further displaced from the open position beyond the closed position.

  In addition to the registration roller pair 55, the driving roller 312, the secondary transfer belt 33, and the fixing device 34, the sheet conveyance path 35 that passes through the secondary transfer position includes side walls 351, 352, and 353 that function as sheet guides. ing. The side wall 352 is disposed in the vicinity of the intermediate transfer belt 311 and the process control sensor 39. The side wall 352 constitutes a paper conveyance path 35 between the intermediate transfer belt 311. The side wall 352 acts on the intermediate transfer belt 311 via the sheet conveyance path 35 only during execution of the image forming process. That is, the side wall 352 supplies the sheet so as to pass through the sheet conveyance path 35 to the intermediate transfer belt 311 only during the execution of the image forming process. The paper transport path 35 is an operation area that supplies paper to the intermediate transfer belt 311 only during execution of the image forming process. The side wall 352 functions as a region constituting member that constitutes the paper conveyance path 35.

  In this embodiment, at least a part of the cover member 61 is disposed in the paper conveyance path 35 in the open position. A part of the side wall 351 of the paper transport path 35 is cut out so as not to prevent displacement between the closed position and the open position of the cover member 61. The cutout of the paper transport path 35 is smaller than the width of the paper transported through the paper transport path 35 in the rotation axis direction of the drive roller 312 so as not to cause a paper jam.

  In FIG. 4, the cover member 61 </ b> A disposed in the closed position is indicated by a solid line, and the cover member 61 </ b> A disposed in the open position is indicated by a two-dot chain line.

  As shown in FIG. 4, at least a part of the cover member 61 is disposed in the sheet conveyance path 35 in the open position, so that the upstream of the cover member 61 disposed in the closed position in the moving direction 91 of the intermediate transfer belt 311. The interval L1 between the side end portion and the pre-transfer charging device 38 and the interval L2 between the downstream end portion of the cover member 61 disposed at the closed position and the side wall 351 of the sheet conveying path 35 are respectively closed. It is smaller than the displacement dimension L3 between the position and the open position. This is because the cover member 61 can be displaced so that the process control sensor 39 is exposed to the intermediate transfer belt 311 even if the distances L1 and L2 are smaller than the displacement dimension L3 of the cover member 61.

  In the moving direction 91 of the intermediate transfer belt 311, the distance L1 between the upstream end of the cover member 61 disposed at the closed position and the pre-transfer charging device 38 and the downstream end of the cover member 61 disposed at the closed position. Since each of the distances L2 between the cover member 61 and the side wall 351 of the paper transport path 35 is smaller than the displacement dimension L3 between the closed position and the open position of the cover member 61, at least a part of the cover member 61 is at the paper transport path in the open position. The process control sensor 39 can be opened and closed without increasing the distance between the image forming station 24 arranged on the most downstream side and the secondary transfer position.

  Since the cover member 61 is disposed at the open position while the process control is being performed and the image forming process is not being performed, the sheet is transported to the sheet transport path 35 when the cover member 61 is disposed at the open position. Not. For this reason, even if at least a part of the cover member 61 is disposed in the paper conveyance path 35 in the open position, it does not hinder the image forming process. On the other hand, since at least a part of the cover member 61 is disposed in the sheet conveyance path 35 in the open position, there is no need to newly provide an area for the cover member 61 to be displaced in the vicinity of the intermediate transfer belt 311. The dimension along the moving direction 91 of the intermediate transfer belt 311 does not increase. Specifically, it is not necessary to newly provide an area for the cover member 61 to be displaced between the image forming station 24 arranged on the most downstream side in the moving direction 91 of the intermediate transfer belt 311 and the secondary transfer position. Therefore, the interval between the image forming station 24 arranged on the most downstream side and the secondary transfer position does not increase.

  Accordingly, this is the time from the start of the image forming process to the end of the first image forming process after the enlargement of the image forming apparatus 10 and the cover forming member 61 that opens and closes the process control sensor 39. The extension of the first copy time can be prevented.

  When a plurality of (for example, two) process control sensors 39 are provided in the direction of the rotation axis of the drive roller 312, the cover member 61 rotates to a length that covers all of the plurality of process control sensors 39 in the closed position. It can be configured to extend in the direction. Since one cover member 61 has only to be displaced in order to open and close the plurality of process control sensors 39, control of driving for displacing the cover member 61 can be simplified.

  When a plurality of process control sensors 39 are provided in the direction of the rotation axis of the drive roller 312, a plurality of cover members 61 are provided corresponding to each of the process control sensors 39, and the plurality of cover members 61 are opened and closed. It can be configured to be displaced in conjunction with each other. As an example, the plurality of cover members 61 are fixed to a single shaft that is rotatably supported at a predetermined position, and all the cover members 61 are configured to be displaced together by rotating the shaft. it can. Since all the cover members 61 can be displaced by displacing one cover member 61 in order to open and close the plurality of process control sensors 39, control of driving for displacing the cover members 61 is simplified. it can.

  Further, the displacement of the cover member 61 in the direction along the moving direction 91 of the intermediate transfer belt 311 is not limited to the configuration of rotating about the axis, and may be configured to slide, for example. Further, the cover member 61 is not limited to the L-shaped cross section, and may be formed, for example, by bending the support portion 612 in the middle.

  As shown in FIG. 5, at least a part of the cover member 61 </ b> A may be configured to be disposed between the pre-transfer charging device 38 and the intermediate transfer belt 311 in the open position. In FIG. 5, the cover member 61 </ b> A placed in the closed position is indicated by a two-dot chain line, and the cover member 61 </ b> A placed in the open position is indicated by a solid line.

  The pre-transfer charging device 38 is disposed so as to form a region 381 between the intermediate transfer belt 311. The pre-transfer charging device 38 applies a charge to the toner image on the intermediate transfer belt 311 via the region 381 only during the image forming process.

  A region 381 between the pre-transfer charging device 38 and the intermediate transfer belt 311 is used as an operation region. The pre-transfer charging device 38 functions as a region constituting member that constitutes an action region.

  Since the cover member 61A is disposed at the open position while the process control is being performed and the image forming process is not being performed, the pre-transfer charging device 38 is not driven when the cover member 61A is disposed at the open position. For this reason, even if at least a part of the cover member 61A is disposed between the pre-transfer charging device 38 and the intermediate transfer belt 311 in the open position, the image forming process is not hindered.

  On the other hand, since the length of the pre-transfer charging device 38 in the direction along the moving direction 91 of the intermediate transfer belt 311 is larger than that of the process control sensor 39, the pre-transfer charging device 38 is not between the pre-transfer charging device 38 and the intermediate transfer belt 311. There is sufficient space for placing the cover member 61A. For this reason, at least a part of the cover member 61A is disposed between the pre-transfer charging device 38 and the intermediate transfer belt 311 in the open position, so that the cover member 61A is disposed on the most downstream side in the moving direction 91 of the intermediate transfer belt 311. There is no need to newly provide an area for the displacement of the cover member 61A between the image forming station 24 and the secondary transfer position, and the distance between the image forming station 24 arranged on the most downstream side and the secondary transfer position is the same. Does not spread.

  As shown in FIG. 6, the cover member 61 </ b> B can constitute a part of the side wall 351 of the paper transport path 35 in the closed position. In FIG. 6, the cover member 61 </ b> B arranged at the closed position is indicated by a solid line, and the cover member 61 arranged at the open position is indicated by a two-dot chain line.

  Since the cover member 61B is also used as a part of the side wall 31 of the paper conveyance path 35, the moving direction 91 of the intermediate transfer belt 311 is more than that when the cover member 61B and the side wall 351 of the paper conveyance path 35 are provided adjacent to each other. The space along the direction can be reduced. Further, at least a part of the cover member 61B is disposed in the paper transport path 35 in the open position, but it is not necessary to move the side wall 351 of the paper transport path 35 in order to displace the cover member 61B, so that the driving means or the like An increase in the number of parts can be prevented, and it is not necessary to provide a notch in the side wall 351 of the paper transport path 35, so that the manufacturing process can be simplified.

  In the embodiment shown in FIG. 6, at least a part of the cover member 61 </ b> B is disposed in the paper conveyance path 35 in the open position, but is disposed between the pre-transfer charging device 38 and the intermediate transfer belt 311 in the open position. It can also be configured to be.

  Note that the present invention can also be applied to an image forming apparatus having only one image forming station of any hue, for example, a black image forming station 21. In this embodiment, the photosensitive drum 41 constitutes an image carrier. The pre-transfer charging device 38 and the process control sensor 39 are disposed close to the photosensitive drum 41 and close to each other. The cover member 61 has a closed position that covers the process control sensor 39 with respect to the photosensitive drum 21 and an open position that is displaced in a direction along the rotation direction of the photosensitive drum 21 so as to expose the process control sensor 39. Displace.

  The sheet conveyance path through which the sheet for transferring the toner image from the photosensitive drum 41 is conveyed toward the photosensitive drum 41 is an operation for supplying the sheet to the photosensitive drum 41 only during the image forming process. Configure the area. The side walls constituting the paper transport path function as region constituting members constituting the action region. At least a part of the cover member 61 is disposed in the sheet conveyance path in the open position.

  Further, the area between the pre-transfer charging device 38 and the photosensitive drum 41 can constitute an action area for applying a charge to the toner image on the photosensitive drum 41 only during the execution of the image forming process. The pre-transfer charging device 38 can function as a region constituting member that constitutes the working region. At least a part of the cover member 61 may be disposed between the pre-transfer charging device 38 and the photosensitive drum 41 in the open position.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

10 Image forming apparatus 21-24 Image forming station (image forming unit)
311 Intermediate transfer belt (image carrier)
312 Driving roller 313 Driven roller 32A to 32D Primary transfer roller 33 Secondary transfer belt 35 Paper transport path (sheet transport path)
351 Side wall (regional component)
38 Pre-transfer charging device (regional component)
39 Process control sensor (detector)
61, 61A, 61B Cover member 100 Control unit

Claims (1)

An image forming unit that forms a toner image based on image data through an electrophotographic image forming process;
An image carrier that rotates and carries a toner image formed by the image forming unit;
An area constituting member arranged so as to form a predetermined working area with the image carrier, and the working area for the image carrier only during execution of an image forming process for forming an image on a sheet. A region component acting via
Arranged in the vicinity of the image carrier and carried by the image carrier during execution of process control for controlling the driving state of the image forming unit, which is performed during non-execution of the image forming process. A detection unit for detecting the density of the toner image,
A cover member that is displaced to a closed position that covers the detection unit with respect to the image carrier and an open position that is displaced in a direction along the moving direction of the image carrier so as to expose the detection unit;
The area constituting member is a sheet conveying path that supplies a sheet to the surface of the image carrier in order to transfer a toner image carried by the image carrier, and is a side wall that constitutes the sheet conveying path that is the working area. Yes,
At least a part of the cover member is disposed in the sheet conveyance path at the open position,
The cover member constitutes a part of the side wall in the closed position;
A plurality of the detection units are provided in the rotation axis direction of the image carrier,
The image forming apparatus includes a plurality of cover members corresponding to the detection units, and the plurality of cover members are displaced in conjunction with each other between the closed position and the open position .

Images