JP2016151621A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image disturbance occurring in a transfer unit when a rear end of a recording medium pulls out of a guide member, and prevent reduction in conveyance quality of the recording medium.SOLUTION: An image formation device comprises: an intermediate transfer belt 10; a secondary transfer roller 24 that forms a secondary transfer nip N for transferring an image of the intermediate transfer belt 10 to a recording medium; an entrance guide plate 210 that is provided upstream of the secondary transfer roller 24 in a recording medium conveyance direction, and guides the recording medium; and a resist roller pair 49 that is provided upstream of the entrance guide plate 210, and sends out the recording medium toward the transfer nip. The entrance guide plate 210 includes an upstream end 210a and a downstream end 210b that extend in a direction crossing the recording medium conveyance direction, and comprises: an eccentric cam 241 that changes an amount of protrusion of the downstream end 210b with respect to the upstream end 210a of the guide plate; a motor 244; and motor drive control means 245 that causes the downstream end to protrude from the upstream end after a rear end of the recording medium pulls out of the resist roller pair and before the rear end thereof pulls out of the guide plate.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus.

  In the electrophotographic image forming apparatus, the toner image formed in the image forming unit is transferred to a recording medium in the transfer unit. At this time, the recording medium is guided by the guide member and conveyed to the transfer unit. When transported by the guide member, an impact occurs when the trailing edge of the recording medium passes through the guide member, and the impact may cause image disturbance in the transfer portion. In order to prevent such image disturbance, the rigidity of the guide member is lowered, or the tip shape of the guide member is devised.

  The shape of the guide member in the conventional image forming apparatus will be described. FIG. 9 is a cross-sectional view showing a schematic structure of a secondary transfer portion in a conventional image apparatus, FIG. 10 shows an inlet guide plate arranged in the secondary transfer portion in the conventional image apparatus, and FIG. FIG. 4B is a cross-sectional view of the next transfer portion, FIG. 5B is a plan view of the inlet guide plate, and FIG.

  As shown in FIG. 9, in the secondary transfer unit 500, the intermediate transfer belt 10 is sandwiched between the secondary transfer roller 24 and the secondary transfer counter roller 16 to form a secondary transfer nip N. On the upstream side of the recording medium conveyance in the secondary transfer nip N, a lower inlet guide plate 240 and an inlet guide plate 550 are provided as guide members. Here, the lower entrance guide plate 240 is fixed to the side plate of the secondary transfer unit, and the entrance guide plate 550 is fixed to the side plate of the intermediate transfer unit.

  The secondary transfer roller 24 includes a cylindrical cored bar 24b and an elastic layer 24a made of an elastic material fixed to the peripheral surface thereof. The secondary transfer counter roller 16 includes a metal counter roller shaft 16a and a coating layer 16b. A power supply 29 that supplies a DC voltage or a DC voltage and an AC voltage is connected to the opposed roller shaft 16a, and transfer can be performed by superimposing only the DC voltage or the AC voltage and the DC voltage. In the secondary transfer roller 24, the periphery of the cored bar 24b is covered with an elastic layer 24a. In the secondary transfer unit 500, a downstream guide plate 570 and a guide roller 37 of the intermediate transfer belt 10 are disposed. The guide roller 37 is fixed to the intermediate transfer unit.

  As shown in FIGS. 10A and 10B, the entrance guide plate 550 includes a rigid holding portion 551, and a sheet member 552 disposed so as to protrude from the holding portion 551 toward the secondary transfer roller 24. 553. In this example, there are two sheet members 552 and 553, but there may be three to five sheet members.

  10B, the end edge 550a of the inlet guide plate 550 on the secondary transfer roller 24 side has an angle α with respect to a straight line L perpendicular to the conveyance direction of the intermediate transfer belt 10. Yes. Accordingly, a sudden change in the posture of the recording medium that occurs when the recording medium passes through the entrance guide plate 550 is suppressed, and image distortion at the transfer portion is prevented.

  The material of the sheet members 552 and 553 is composed of a flexible sheet such as PC (polycarbonate), PET (polyethylene terephthalate), and high density PE (polyethylene). Each of the sheet members 552 and 553 may be conductive or non-conductive. The holding portion 551 and the sheet members 552 and 553 are bonded to each other by bonding their surfaces with a double-sided tape, for example.

  As described above, when the edge 550a of the entrance guide plate 550 is angled with respect to the direction perpendicular to the conveyance direction of the intermediate transfer belt 10, an impact is generated when the rear end of the recording medium passes through the entrance guide plate 550. It does not occur, and image disturbance during image transfer can be prevented. However, depending on the recording medium, skew occurs due to contact resistance with the entrance guide plate 550, and the quality of the recording medium conveyance is deteriorated.

  In Patent Document 1, a flexible sheet member is attached so as to protrude from the leading end of the rigid holding portion in order to suppress a sudden change in posture of the trailing end of the recording medium at the end of the guide of the trailing end of the recording medium. There is described one having three or more flexible portions in which the bending rigidity per unit area of the projecting portion from the holding portion of the member is different from each other and becomes smaller toward the downstream side in the guide member direction.

  Japanese Patent Application Laid-Open No. 2004-228561 has a shape in which one end of a guide member in the conveyance path protrudes in the conveyance direction from the other in order to prevent image defects caused by the trailing edge of the recording medium hitting the image carrier. What is changed according to the type of is described.

  However, in the conventional technique described above, since the guide plate is always in the same position with a constant shape, the load on the recording medium differs depending on the type of the recording medium when the recording medium is conveyed, and this is called skew. The transport quality deteriorates. Similarly, those described in Patent Document 1 and Patent Document 2 also cause a decrease in conveyance quality of the recording medium by the guide member.

  Accordingly, the present invention provides an image forming apparatus capable of preventing image disturbance at the transfer portion due to an impact when the trailing edge of the recording medium passes through the guide member, and preventing deterioration in conveyance quality of the recording medium. For the purpose.

  An image forming apparatus according to the present invention includes an image carrier, a transfer member that forms a transfer nip for transferring an image carried on the image carrier to a recording medium, and a recording medium conveyance direction relative to the transfer member. A guide member provided on the upstream side for guiding the recording medium; and a conveyance member provided on the upstream side in the recording medium conveyance direction with respect to the guide member and feeding the recording medium toward the transfer nip. The member includes one end portion and the other end portion arranged along a direction intersecting the conveyance direction of the recording medium, and a protrusion amount changing means for changing the protrusion amount of the other end portion with respect to the one end portion of the guide member. And a protrusion amount control means for controlling the operation of the protrusion amount changing means to protrude the other end portion after the rear end of the recording medium has passed through the conveying member and before the guide member is removed. And equipped with It is characterized in.

  According to the present invention, it is possible to prevent image disturbance that occurs at the transfer portion when the trailing edge of the recording medium passes through the guide member, and to prevent deterioration in the conveyance quality of the recording medium.

1 is a cross-sectional view illustrating an overall structure of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a secondary transfer unit of the image apparatus. It is a figure which shows the entrance guide plate arrange | positioned at the secondary transfer part of the image apparatus with a protrusion amount change means. It is a figure which shows the protrusion amount change state of the entrance guide plate arrange | positioned at the secondary transfer part of the image apparatus. It is a timing chart which shows the example of operation of the guide board. It is a timing chart which shows the example of operation of the guide board. It is a timing chart which shows the example of operation of the guide board. It is a timing chart which shows the example of operation of the guide board. It is sectional drawing which shows the structure of the secondary transfer part in the conventional image device. 1 shows an inlet guide plate disposed in a secondary transfer portion in a conventional image apparatus, wherein (a) is a sectional view of the secondary transfer portion, (b) is a plan view of the inlet guide plate, and (c) is an inlet. It is a front view of a guide plate.

  An image forming apparatus according to an embodiment for carrying out the present invention will be described. In the present invention, the image forming apparatus prevents the image disturbance occurring at the transfer portion when the rear end of the recording medium has passed through the guide member, and prevents the recording medium from being deteriorated in conveyance quality. It is assumed that the position can be changed depending on the type of the recording medium. This prevents image disturbance that occurs at the transfer portion when the trailing edge of the recording medium passes through the guide member, and prevents deterioration in conveyance quality.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described. First, the overall structure of the image forming apparatus will be described. FIG. 1 is a cross-sectional view showing the overall structure of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to the present embodiment is a tandem type color copier. The image forming apparatus 100 includes a printer unit 110, a paper feeding unit 120, a scanner unit 130, and an automatic document feeder (ADF) 140.

  The printer unit 110 includes an endless belt-shaped intermediate transfer belt 10 as an image carrier. The intermediate transfer belt 10 is wound around the driving roller 14, the driven roller 15, and the secondary transfer counter roller 16 in such a posture that the side view is an inverted triangle shape. Is moved endlessly in the clockwise direction in the figure. Above the intermediate transfer belt 10, four image forming units 18Y, 18M, 18C, and 18K for forming toner images of Y (yellow), M (magenta), C (cyan), and K (black) are provided. It arrange | positions so that it may line up along a belt moving direction.

  The image forming units 18Y, 18M, 18C, and 18K include photoreceptors 20Y, 20M, 20C, and 20K, developing units 61Y, 61M, 61C, and 61K, and photoreceptor cleaning devices 63Y, 63M, 63C, and 63K. Yes. The photoreceptors 20Y, 20M, 20C, and 20K are rotationally driven in the counterclockwise direction in the figure by the driving means while abutting the intermediate transfer belt 10 to form primary transfer nips for Y, M, C, and K, respectively. The The developing units 61Y, 61M, 61C, and 61K develop the electrostatic latent images formed on the photoreceptors 20Y, 20M, 20C, and 20K with Y, M, C, and K toners. Further, the photoconductor cleaning devices 63Y, 63M, 63C, and 63K clean the transfer residual toner adhering to the photoconductors 20Y, 20M, 20C, and 20K after passing through the primary transfer nip. In this printer, a tandem image forming unit is configured by the four image forming units 18Y, 18M, 18C, and 18K arranged in the belt moving direction.

  In the printer unit 110, an optical writing unit 21 is disposed above the tandem image forming unit. The optical writing unit 21 performs an optical writing process by optical scanning on the surfaces of the photoconductors 20Y, 20M, 20C, and 20K that are driven to rotate counterclockwise in the drawing to form an electrostatic latent image. Is. Prior to the optical writing process, the surfaces of the photoreceptors 20Y, 20M, 20C, and 20K are uniformly charged by the uniform charging means of the image forming units 18Y, 18M, 18C, and 18K, respectively.

  The transfer unit including the intermediate transfer belt 10 has primary transfer rollers 62Y, 62M, 62C, and 62K inside the loop of the intermediate transfer belt 10. These primary transfer rollers 62Y, 62M, 62C, and 62K press the intermediate transfer belt 10 toward the photoreceptors 20Y, 20M, 20C, and 20K on the back side of the primary transfer nip for Y, M, C, and K. A secondary transfer portion 70 is formed below the intermediate transfer belt 10. A secondary transfer roller 24, which is a transfer member, is disposed in the secondary transfer unit 70, and the secondary transfer roller 24 is driven to rotate by a motor. The secondary transfer roller 24 is in contact with a portion of the intermediate transfer belt 10 that is wound around the secondary transfer counter roller 16 from the belt surface side to form a secondary transfer nip N. A sheet-like recording medium such as recording paper is fed into the secondary transfer nip N from the registration roller pair 49 at a predetermined timing. Then, the four-color superimposed toner images on the intermediate transfer belt 10 are secondarily transferred collectively onto the recording medium at the secondary transfer nip N.

  The paper feeding unit 120 includes a paper feeding roller 42 that feeds a recording medium from paper feeding cassettes 44 arranged in multiple stages in the paper bank 43, a separation roller 45 that separates the sent recording medium and guides it to a paper feeding path 46, a printer A conveyance roller 47 that conveys the recording medium is provided in the paper feed path 48 of the unit 110. Regarding the supply of the recording medium, manual feeding is possible in addition to the paper feeding unit 120, and the recording medium on the manual feeding tray 51 and the recording medium on the manual tray 51 are directed to the manual feeding path 53. Separation rollers 52 are provided to separate each one. In the printer unit 110, the manual paper feed path 53 joins the paper feed path 48.

  Near the end of the paper feed path 48, a registration roller pair 49 is arranged as a conveying means. The registration roller pair 49 sandwiches the recording medium conveyed in the paper feed path 48 between the rollers and then feeds it toward the secondary transfer nip N at a predetermined timing. The registration roller pair 49 is rotationally driven by a motor.

  The scanner unit 130 reads the image information of the document placed on the contact glass 32 by the reading sensor 36 and sends the read image information to the control unit of the printer unit 110. Based on the image information received from the scanner unit 130, the control unit controls a light source such as a laser diode or an LED (light emitting diode) in the optical writing unit 21 of the printer unit 110, so that Y, M, C, K Writing light is emitted, and the photoconductors 20Y, 20M, 20C, and 20K are optically scanned. By this optical scanning, electrostatic latent images are formed on the surfaces of the photoreceptors 20Y, 20M, 20C, and 20K, and the latent images are developed into Y, M, C, and K toner images through a predetermined development process. The ADF 140 conveys the document placed on the document table 30 to the scanner unit 130.

  In the image forming apparatus 100 according to the embodiment, when a color image is copied, an original is set on the original table 30 of the ADF 140 or the original is set on the contact glass 32 of the scanner unit 130 by opening the ADF 140. Close ADF 140 and hold down the document. Then press the start switch. Then, when the document is set on the ADF 140, the document is conveyed onto the contact glass 32. Thereafter, the scanner unit 130 starts driving, and the first traveling body 33 and the second traveling body 34 start traveling along the document surface. Then, the light emitted from the light source by the first traveling body 33 is emitted on the original surface, and the obtained reflected light is folded and directed to the second traveling body 34. The folded light is further folded by the mirror of the second traveling body 34 and then enters the reading sensor 36 through the imaging lens 35. Thereby, the content of the original is read.

  When the printer unit 110 receives image information from the scanner unit 130, the printer unit 110 feeds a recording medium having a size corresponding to the image information to the paper feed path 48. Along with this, the drive roller 14 is rotationally driven by the drive motor to move the intermediate transfer belt 10 endlessly in the clockwise direction in the drawing. At the same time, after starting rotation of the photoconductors 20Y, 20M, 20C, and 20K of the image forming units 18Y, 18M, 18C, and 18K, uniform charging processing and optical writing processing for the photoconductors 20Y, 20M, 20C, and 20K, Perform development processing. The Y, M, C, and K toner images formed on the surfaces of the photoreceptors 20Y, 20M, 20C, and 20K by these processes are sequentially overlapped at the primary transfer nips for Y, M, C, and K, and are intermediate. Primary transfer is performed on the transfer belt 10 to form a four-color superimposed toner image.

  In the paper supply unit 120, one of the paper supply rollers 42 is selectively rotated according to the recording medium size, and the recording medium is sent out from one of the three paper supply cassettes 44. The fed recording medium is separated one by one by the separation roller 45 and then introduced into the paper feed path 46, and then sent to the paper feed path 48 in the printer unit 110 via the transport roller 47. When the manual feed tray 51 is used, the paper feed roller 42 of the tray is driven to rotate, and the recording medium on the tray is fed to the manual paper feed path 53 while being separated by the separation roller 52. Near the end. In the vicinity of the end of the paper feed path 48, the recording medium stops by abutting the leading edge against the registration roller pair 49. Thereafter, when the registration roller pair 49 is rotationally driven at a timing that can be synchronized with the four-color superimposed toner image on the intermediate transfer belt 10, the registration roller pair 49 is fed into the secondary transfer nip N and is in close contact with the four-color superimposed toner image on the belt. To do. Then, secondary transfer is collectively performed on the recording medium due to the influence of the nip pressure and the transfer electric field.

  The recording medium on which the four-color superimposed toner image is secondarily transferred at the secondary transfer nip N is sent into the fixing device 25 by the paper transport belt 22. When the fixing device 25 sandwiches the fixing nip between the pressure roller 27 and the fixing belt 26, the four-color superimposed toner image is fixed on the surface by pressure or heat treatment. The recording medium on which the color image is formed in this manner is stacked on a discharge tray 57 outside the apparatus via the discharge roller pair 56. When an image is also formed on the other surface of the recording medium, the recording medium is discharged from the fixing device 25 and then sent to the sheet reversing device 28 by the path switching by the switching claw 55. Then, after being turned upside down, it is returned to the registration roller pair 49 again, and then passes through the secondary transfer nip N and the fixing device 25 again.

  In the secondary transfer unit 70, after passing through the secondary transfer nip N, the surface of the intermediate transfer belt 10 before entering the primary transfer nip for Y where the primary transfer process is the most upstream among the four colors is placed on the surface of the belt. The cleaning device 17 is in contact.

  Next, the secondary transfer unit 70 of the printer unit 110 according to the embodiment will be described. FIG. 2 is a cross-sectional view showing a secondary transfer portion of the image apparatus according to the embodiment of the present invention. In the secondary transfer unit 70, as described above, the secondary transfer nip N is formed with the intermediate transfer belt 10 sandwiched between the secondary transfer counter roller 16 and the secondary transfer roller 24. On the upstream side of the secondary transfer nip N in the recording medium conveyance direction, an inlet guide plate 210 as a guide member and a lower inlet guide plate 250 are arranged. The secondary transfer roller 24 includes a cylindrical cored bar 24b and an elastic layer 24a made of an elastic material fixed to the peripheral surface thereof, and is grounded. As the metal constituting the metal core 24b, stainless steel, aluminum or the like can be used, but is not limited to these materials.

  The elastic layer 24a preferably has a JIS-A hardness of 70 [°] or less. When the cleaning blade is brought into contact with the secondary transfer roller 24, various problems are caused if the elastic layer 24a is too soft. For this reason, it is desirable that the elastic layer 24a has a JIS-A hardness of 40 [°] or more. When the secondary transfer roller 24 is not cleaned, the elastic layer 24a can be softened, thereby reducing an abnormal image due to an impact when the recording medium enters and exits the secondary transfer unit 70.

  The elastic layer 24a is preferably about 35 to 65 [deg.] In Asker-C hardness in consideration of mass production capability. The elastic layer 24a of the secondary transfer roller 24 is made of conductive epichlorohydrin rubber, EPDM or Si rubber in which carbon is dispersed, NBR having an ion conductive function, urethane rubber, or the like as a rubber material exhibiting conductivity. Also good. The elastic layer 24a fixed on the peripheral surface of the core metal 24b is made of a conductive rubber material whose resistance value is adjusted so as to exhibit a resistance of about 6.5 to 7.5 [LogΩ]. . The reason why the electric resistance of the elastic layer 24a is adjusted within a predetermined range is that the recording medium in the secondary transfer nip N is used when a recording medium having a relatively small size in the roller axial direction such as A5 size is used. Therefore, it is possible to prevent the transfer current from being concentrated at a position where the belt and the roller are in direct contact without any intervention.

  The secondary transfer roller 24 having such a configuration is pressed toward the intermediate transfer belt 10 that is wound around the secondary transfer counter roller 16 and the like. The secondary transfer counter roller 16 includes a counter roller shaft 16a and a coating layer 16b. The member of the opposed roller shaft 16a is made of metal, and a power supply 29 for applying a DC voltage or a DC voltage and an AC voltage is connected to the opposed roller shaft 16a. A guide roller 37 for the intermediate transfer belt 10 is provided on the upstream side of the secondary transfer counter roller 16.

  As described above, in the present embodiment, in the secondary transfer unit 70, the inlet guide plate 210 and the lower inlet guide plate 250 are arranged on the upstream side of the secondary transfer nip N. The entrance guide plate 210 and the lower entrance guide plate 250 are fixed to the intermediate transfer side plate. A registration roller pair 49 is disposed on the upstream side of the recording medium conveyance of the entrance guide plate 210 as a conveyance member that feeds the recording medium toward the secondary transfer nip N.

  In the present embodiment, the secondary transfer roller 24 can be provided with bias cleaning. Further, a secondary transfer belt can be provided instead of the secondary transfer roller 24, or a cleaning blade can be provided.

  Next, the inlet guide plate 210 will be described. FIG. 3 is a view showing an entrance guide plate arranged in the secondary transfer portion of the image apparatus according to the embodiment of the present invention together with the protrusion amount changing means, and FIG. It is a figure which shows the protrusion amount change state of a board.

  The inlet guide plate 210 includes a substrate 211, a first sheet member 212, a second sheet member 213, and a variable guide member 214. That is, the entrance guide plate 210 is configured by arranging the first sheet member 212 and the second sheet member 213 on the substrate 211 via the variable guide member 214. In the inlet guide plate 210, the upstream end of the substrate 211 is an upstream end 210 a that is one end of the inlet guide plate 210, and the downstream end of the second sheet member 213 is a downstream end 210 b that is the other end of the inlet guide plate 210. And a protrusion amount changing means for changing the protrusion amount of the downstream end 210b with respect to the upstream end 210a. The substrate 211 and the variable guide member 214 are made of metal, and the first sheet member 212 and the second sheet member 213 are made of a flexible sheet such as PC (polycarbonate), PET (polyethylene terephthalate), and high-density PE (polyethylene). Configure.

  FIG. 3 is a view showing an entrance guide plate disposed in the secondary transfer portion of the image apparatus together with the protrusion amount changing means, and FIG. FIG. As shown in FIG. 3, the variable guide member 214 is disposed on the substrate 211 of the inlet guide plate 210 so as to be rotatable about the shaft member 231. A pin 232 is formed on the variable guide member 214, and the pin 232 is inserted into an elongated hole 234 formed in the variable guide member 214. For this reason, the variable guide member 214 can rotate to the predetermined angle β around the shaft member 231 with respect to the substrate 211. The shaft member 231 and the pin 232 are configured by a rigid body, for example, a metal step screw.

  A contact piece 235 is formed on the variable guide member 214 on the long hole 234 side, and the eccentric cam 241 contacts the contact piece 235. The eccentric cam 241 is driven to rotate about the rotation shaft 242. By rotating the eccentric cam 241, the variable guide member 214, the first sheet member 212 and the second sheet member 213 attached to the variable guide member 214 move, and the protrusion amount of the downstream end 210b with respect to the upstream end 210a is increased. Be changed. In addition, a coil spring 243 is disposed in a tensioned state between the protrusion 236 of the substrate 211 and the contact piece 235. In a state where the eccentric cam 241 does not contact the contact piece 235, the upstream end 210a and the downstream end 210b of the inlet guide plate 210 are parallel to each other.

  The eccentric cam 241 and the motor 244 that rotationally drives the eccentric cam 241 constitute a protrusion amount changing means. The drive of the motor 244 is controlled by motor drive control means 245 that is a protrusion amount control means. By performing drive control of the motor 244 with the motor drive control means 245, the timing at which the eccentric cam 241 starts rotating, the rotation amount, and the rotation speed can be set to desired values. Thereby, the angle, movement timing, and movement speed of the variable guide member 214 can be set.

  In a state where the recording medium is sandwiched between both the secondary transfer roller 24 and the registration roller pair 49, the recording medium is stably conveyed between the two. In this state, in order to maintain the conveyance quality, it is preferable that the inlet guide plate 210 is less inclined in the front-rear direction. For this reason, during the conveyance of the recording medium, the motor drive control means 245 is driven by the motor drive control means 245 so that the eccentric cam 241 does not contact the contact piece 235 in order to ensure the conveyance quality of the recording medium. As a result, the variable guide member 214 of the inlet guide plate 210 is pulled by the coil spring 243 to the state shown in FIG. 3, and the downstream end 210b is parallel to the upstream end 210a.

  On the other hand, if the upstream end 210a and the downstream end 210b of the entrance guide plate 210 remain parallel to each other, the posture of the recording medium changes suddenly when it exits the entrance guide plate 210, so that image disturbance occurs during transfer. End up.

  Therefore, in the present embodiment, the variable guide member 214 is driven after the trailing edge of the recording medium has passed through the registration roller pair 49 and before the entrance guide plate 210, so that the entrance guide plate 210 The amount of protrusion of the downstream end 210b from the upstream end 210a is changed. Thereby, the downstream end 210b is inclined with respect to the upstream end 210a. As a result, the state is inclined by a predetermined angle β with respect to the straight line L intersecting at right angles to the transport direction of the 210b recording medium. For this reason, the motor drive control means 245 drives the motor 244 and presses the contact piece 235 with the eccentric cam 241. As a result, as shown in FIG. 4, the variable guide member 214 is inclined and the downstream end 210b protrudes from the upstream end 210a and is inclined by a predetermined angle β.

  The timing at which the variable guide member 214 is driven, that is, the timing at which the motor drive control means 245 drives the motor 244 to drive the variable guide member 214 is after the trailing edge of the recording medium has passed through the registration roller pair 49. And before the entrance guide plate 210 is removed. Preferably, it is immediately before the rear end of the recording medium passes through the entrance guide plate 210. “Timing immediately before” is, for example, when the entrance guide plate 210 is in contact within an area within 5 mm from the rear end of the recording medium.

  The configuration of the entrance guide plate 210 is not limited to the above-described example. The drive mechanism of the variable guide member 214 is not limited to a structure including the motor 244, the eccentric cam 241 and the coil spring 243, and may be another drive mechanism using a solenoid or other actuator.

  In this embodiment, after the recording medium passes, the state of the inlet guide plate 210 is returned to a state corresponding to the passage of the next recording medium. Further, the motor drive control means 245 can set whether or not to set the position on the inlet guide plate 210 by external support.

  In this embodiment, the movement start time of the entrance guide plate 210 at the rear end of the recording medium can be changed depending on the type of the recording medium. For example, when the entrance guide plate 210 is arranged in a direction perpendicular to the conveyance direction of the recording medium, the entrance guide plate 210 may be inclined due to a dimensional error of parts of the apparatus. In this case, the guide angle during paper feeding can be adjusted. In this example, the upstream end 210a of the inlet guide plate 210 is inclined, but the upstream end 210a can be inclined.

  Next, the operation timing and operation change of the entrance guide plate 210 in the image forming apparatus 100 according to the present embodiment will be described. 5, 6, 7 and 8 are timing charts showing examples of the operation of the guide plate. In the image forming apparatus according to the embodiment, the entrance guide plate 210 is driven immediately before the rear end of the recording medium is removed from the downstream end 210 b of the entrance guide plate 210.

  In the example shown in FIG. 5, it is optimal to transport the recording medium in a horizontal state where there is no difference in the protruding amount before and after the entrance guide plate 210. The upstream end 210a and the downstream end 210b of the entrance guide plate 210 are held in parallel from the front end of the recording medium, and the inclination of the downstream end 210b of the entrance guide plate 210 is controlled immediately before the rear end of the recording medium is removed from the front end of the entrance guide plate. . In the example shown in FIG. 5, the inclination amount of the downstream end 210 b when the recording medium rear end passes through the downstream end 210 b of the inlet guide plate 210 is shown in two patterns (solid line and broken line). This amount of inclination can be arbitrarily set by controlling. In addition to moving the downstream end 210b of the inlet guide plate 210, the upstream end 210a can also be moved.

  In the example shown in FIG. 6, the downstream end 210 b of the inlet guide plate 210 is inclined by a predetermined amount, and the inclination is increased immediately before the rear end of the recording medium comes out of the downstream end 210 b of the inlet guide plate 210. In the example shown in FIG. 6, two patterns of change in the tilt amount (solid line and broken line) are shown, but this tilt amount can be arbitrarily set by controlling the rotation amount of the eccentric cam 241. In addition to moving the downstream end 210b of the inlet guide plate 210, the upstream end 210a can also be moved.

  The example shown in FIG. 7 shows a case where the downstream end 210b is inclined at a predetermined timing corresponding to the type of the recording medium. In this example, the operation indicated by the solid line is started at an earlier timing than the operation indicated by the broken line. In the example shown in FIG. 7, the operation timing is changed to an early timing, but can be changed to a later timing.

  The example shown in FIG. 8 shows a case where the user changes the speed of the tilting operation of the downstream end 210b for each type of recording medium. In this example, the operation indicated by the solid line is changed later than the operation indicated by the broken line. The operation speed can be changed later. Further, the change of the operation start timing shown in FIG. 7 and the operation speed shown in FIG. 8 can be controlled independently, and the change of the start timing and the change of the speed can be controlled simultaneously. Furthermore, the angle control shown in FIG. 5 and the movement amount control shown in FIG. 6 can be performed together.

10: Intermediate transfer belt (image carrier)
16: Secondary transfer counter roller 16a: Counter roller shaft 24: Secondary transfer roller (transfer member)
24a: elastic layer 49: registration roller pair (conveying member)
70: Secondary transfer unit 100: Image forming apparatus 210: Entrance guide plate (guide member)
210a: upstream end 210b: downstream end 211: substrate 212: first sheet member 213: second sheet member 214: variable guide member 231: rotating shaft 232: pin 234: elongated hole 235: contact piece 236: protrusion 241: eccentricity Cam (Projection amount changing means)
244: Motor (projection amount changing means)
245: Motor drive control means (projection amount control means)
250: Lower entrance guide plate

JP 2010-61060 A JP 2008-58593 A

Claims (5)

An image carrier;
A transfer member that forms a transfer nip for transferring the image carried on the image carrier to a recording medium;
A guide member that is provided upstream of the transfer member in the recording medium conveyance direction and guides the recording medium;
A conveyance member that is provided upstream of the guide member in the recording medium conveyance direction, and that feeds the recording medium toward the transfer nip;
With
The guide member includes one end and another end arranged along a direction intersecting the conveyance direction of the recording medium,
A protrusion amount changing means for changing the protrusion amount of the other end portion relative to the one end portion of the guide member;
A protrusion amount control means for controlling the operation of the protrusion amount changing means to protrude the other end portion after the rear end of the recording medium has passed through the conveying member and before the guide member is removed; ,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the protrusion amount control unit can change an operation start timing of the guide member at a rear end of the recording medium of the guide member.   The image forming apparatus according to claim 1, wherein the protrusion amount control unit can change a moving speed for changing the protrusion amount by the protrusion amount changing unit.   The protrusion amount control means sets the guide member according to the next recording medium before the leading edge of the next recording medium comes after the change of the position of the guide member at the rear end of the recording medium by the protrusion amount changing means. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to a position.   The image forming apparatus according to claim 1, wherein the protrusion amount control unit can set whether or not to change a protrusion amount of the guide member.