JP2007293218A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a secondary transfer roll and an intermediate transfer body cleaning unit contact and leave with respect to an intermediate transfer body are performed in fixed timing in a predetermined area without reference to variation in torque of a motor that a conventional contacting/leaving mechanism has. <P>SOLUTION: A timing information acquiring unit acquires, as timing information, a time that the secondary transfer roll requires to contact and leave the intermediate transfer belt after the image forming apparatus is powered on. Based upon the information, an operation indication timing setting unit sets timing wherein the secondary transfer roll contacts and leaves the intermediate transfer belt always in the predetermined area. Further, a timing where the intermediate transfer body cleaning unit contacts and leaves the intermediate transfer belt is also set based upon the timing information. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that transfers a toner image formed on the surface of a photosensitive drum based on image data onto a recording sheet via an intermediate transfer member.

  An image forming apparatus that forms an image on a recording sheet based on input image data includes, for example, a color image using four colors of cyan (C), magenta (M), yellow (Y), and black (K). There is something that forms.

  An image forming apparatus that forms a color image forms, for example, a cyan toner image on a photosensitive drum as an image carrier, and transfers (primary transfer) the cyan toner image formed on the photosensitive drum to an intermediate transfer member. . Next, a magenta toner image is formed on the image bearing member and transferred to an intermediate transfer member on which the cyan toner image is transferred.

  This operation is also performed for yellow and black, and a color image is formed by transferring each color in a multiple manner onto the intermediate transfer member.

  The image is transferred from the intermediate transfer member to the recording paper by sandwiching the recording paper between the intermediate transfer member and the secondary transfer roll, and the secondary transfer roll applies a predetermined potential between the recording paper and the toner. (Secondary transfer).

  By the way, since it is necessary to sequentially correspond to the developing unit (developing roll) containing the toner of each color for the image carrier, each developing roll and the photosensitive drum are mechanically or electrically operated when facing each other or when retracted. In particular, unnecessary toner (toner that is not necessary for image formation) may adhere to the photosensitive drum in a node shape (main scanning direction). This toner is transferred to the intermediate transfer member during the primary transfer.

  When such a nodular toner is present and the secondary transfer roll is in contact with and separated from the intermediate transfer member, if it is on the upstream side of the secondary transfer roll, it is transferred to the surface of the secondary transfer roll, The back side of the recording paper becomes dirty.

The secondary transfer roll is configured to be in contact with and separated from the intermediate transfer member. Patent Document 1 discloses that the intermediate transfer member is separated from the intermediate transfer member by a contact / separation mechanism unit that uses a DC motor until the toner image is carried and rotated until a color image is formed. ing. The contact / separation operation of the secondary transfer roll by the contact / separation mechanism unit is performed in the predetermined range of the interimage, which is a section of pages formed on the intermediate transfer member, that is, an area between images (FIG. 7). See).
JP 2003-140512 A

  However, the current contact / separation mechanism has been designed with a relatively rough timing of operation and the like from the viewpoint that the secondary transfer roll may be contacted / separated in a relatively wide range within the range of the interimage. For this reason, the direct current of the contact / separation mechanism section is caused by machine differences of the image forming apparatus, installation environment of the image forming apparatus, aging of the image forming apparatus including replacement parts (CRU), changes in internal temperature of the image forming apparatus, and the like. The motor torque varies, and the time required for the secondary transfer roll and the intermediate transfer member cleaning unit to contact or separate from the intermediate transfer member varies.

  In this case, if the moving speed of the intermediate transfer member is slow, the change in the time required for contact and separation hardly affects the quality of the image formed on the recording paper by the image forming apparatus. This is because the time margin for the secondary transfer roll to contact the intermediate transfer member is sufficient within the range of the inter image.

  However, when the moving speed of the intermediate transfer member is increased in order to improve the processing speed, the contactable time of the secondary transfer roll for avoiding the above-described toner band is gradually reduced, and in the current contact / separation mechanism, The problem of not being able to cope occurs.

  The same problem can be applied to the intermediate transfer member cleaning unit disposed with the contact / separation mechanism portion with respect to the intermediate transfer member.

  In the present invention, in consideration of the above facts, even if the contact / separation mechanism is designed with relatively rough operation timing, the contact operation of the secondary transfer roll to the intermediate transfer member can be performed mainly at a desired timing. An object of the present invention is to obtain an image forming apparatus capable of avoiding transfer of a defective toner image onto a recording sheet.

According to the present invention, a toner image is formed by forming an electrostatic latent image on an image carrier with a toner supply developing roller sequentially facing the image carrier, and this toner image is intermediately transferred at a primary transfer portion. The primary transfer to the body is repeated at least twice with the developing roll changed, and two or more toner images are transferred onto the intermediate transfer body, and the toner image is secondary transferred from the intermediate transfer body. An image forming apparatus for transferring the toner image to a predetermined region of the intermediate transfer body based on a position signal detected from the intermediate transfer body in an image forming process for secondary transfer onto a recording sheet via a roll. ,
A contact / separation mechanism for bringing the secondary transfer roll into contact with and separating from the intermediate transfer member, and an operation instruction to the contact / separation mechanism after the secondary transfer roll contacts the intermediate transfer member Timing information acquisition means for acquiring contact timing information that is time based on actual operation of the contact / separation mechanism section, and the contact / separation mechanism based on contact timing information acquired by the timing information acquisition means And an operation instruction timing setting means for setting a contact operation instruction timing for instructing a contact operation to the part.

  According to the present invention, the contact timing information, which is the time from when the operation instruction is given to the contact / separation mechanism of the secondary transfer roll to when the secondary transfer roll contacts the intermediate transfer member, is based on the actual operation. The timing information acquisition means acquires. Based on the acquired contact timing information, the operation instruction timing setting means sets the contact operation instruction timing for instructing the contact operation to the contact / separation mechanism. Thereby, the secondary transfer roll can be brought into contact with the intermediate transfer member at a desired timing.

  In the present invention, the timing information acquisition unit further acquires a separation timing which is a time from when the operation instruction is given to the contact / separation mechanism unit until the secondary transfer roll and the intermediate transfer member are separated. The operation instruction timing setting means further sets a separation operation timing for instructing a separation operation to the contact / separation mechanism unit based on the separation timing information.

  The timing information acquisition unit acquires separation timing information that is a time required for the secondary transfer roll to separate from the intermediate transfer member, and the operation instruction timing setting unit performs the separation operation to the contact / separation mechanism unit based on the separation timing information. Set the instructed separation operation timing. Thereby, the secondary transfer roll can be separated from the intermediate transfer member at a desired timing.

  Furthermore, in the present invention, the setting of the operation instruction timing by the operation instruction timing setting means is set in consideration of a transition period when the secondary transfer roll is energized.

  Thereby, the operation timing setting means is applied to the contact / separation mechanism unit with respect to the secondary transfer roll in consideration of the time from the voltage non-application to reaching the predetermined voltage value and the time from the predetermined voltage value to the voltage non-application. The timing for instructing the contact and separation operation can be set.

  In the present invention, at least one of the contact timing information and the separation timing information is acquired after the image forming apparatus is turned on.

  Thereby, the timing information acquisition unit can obtain the contact timing information and the separation timing information according to the temporal change of the image forming apparatus.

  Even with a contact / separation mechanism designed with relatively rough operation timing, the contact operation of the secondary transfer roll to the intermediate transfer body can be performed mainly at a desired timing, and a defective toner image can be recorded on the recording paper. It is possible to obtain an image forming apparatus that can avoid the transfer of the image.

(First embodiment)
FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention.

  The image forming apparatus 10 includes a photosensitive drum 14 that is an image carrier, a charging roll 16, an exposure device 18, and a developing device 20 in order to form a toner image based on input image data.

  The photosensitive drum 14 is uniformly charged by the charging roll 16 in contact with the photosensitive drum 14, and rotates in the A direction, which is clockwise in FIG.

  The exposure device 18 is provided on the lower side of the image forming apparatus 10 in FIG. 1 and forms an electrostatic latent image on the surface of the charged photosensitive drum 14 using laser light based on the image data.

  The developing device 20 includes a cyan color developing device 20C, a magenta color developing device 20M, a yellow color developing device 20Y, and a black color developing device 20K.

  The developing device 20 is in contact with the photosensitive drum 14 and rotates in the B direction, which is counterclockwise in FIG. 1, in synchronization with the photosensitive drum 14 around the development rotary center 20 o of the developing device 20.

  The cyan developing device 20C is provided with a cyan developing roll 20Ca.

  The magenta color developing device 20M is provided with a magenta color developing roll 20Ma.

  The yellow color developing device 20Y is provided with a yellow color developing roll 20Ya.

  The black color developing device 20K is provided with a black color developing roll 20Ka.

  The toner of each color charged by stirring is discharged from each developing roll, and the toner of each color is electrostatically adsorbed to the electrostatic latent image on the surface of the photosensitive drum 14 to obtain a toner image.

  Further, the image forming apparatus 10 includes an endless intermediate transfer belt 26 that is an intermediate transfer member and a primary transfer roll 24.

  The intermediate transfer belt 26 is supported by an upper support roll 30 provided on the upper side of the image forming apparatus 10 in FIG. 1 and a lower support roll 32 provided on the lower side of the image forming apparatus 10 in FIG.

  Further, the intermediate transfer belt 26 is driven to rotate in the direction C in FIG. 1 by a frictional force by being in close contact with the photosensitive drum 14 in a lap region between the wrap-in roll 34 and the wrap-out roll 36.

  The primary transfer roll 24 is disposed between the wrap-in roll 34 and the wrap-out roll 36. The primary transfer roll 24 sandwiches the intermediate transfer belt 26 between the photosensitive drum 14 and primarily transfers the toner image to the intermediate transfer belt 26.

  The toner image transferred to the intermediate transfer belt 26 is secondarily transferred to the recording paper 38 by the secondary transfer roll 40.

  The secondary transfer roll 40 includes a backup roll 42 with the intermediate transfer belt 26 interposed therebetween. The intermediate transfer belt 26 and the recording paper 38 are sandwiched between the secondary transfer roll 40 and the backup roll 42. The secondary transfer roll 40 applies a charge to the recording paper 38 to electrostatically transfer the toner image to the recording paper 38 due to a potential difference between the toner image and the recording paper 38.

  The recording paper 38 is accumulated in the paper feed cassette 44, and is taken out from the paper feed cassette 44 one by one by the feed roll 46 and the retard roll 48 and conveyed in the direction D in FIG.

  Before the recording sheet 38 is transferred by the secondary transfer roll 40, the size in the feeding direction is detected by the registration sensor 72, and the toner transferred to the recording sheet 38 and the intermediate transfer belt 26 by the registration roll 50 based on the detection signal. The conveyance timing is controlled so that the leading edge matches the image.

  The recording paper 38 onto which the toner image has been transferred by the secondary transfer roll 40 is sent to the fixing device 52.

  The fixing device 52 includes a heat roll 54 and a pressure roll 56, and fixes the toner onto the recording paper 38 by heat from the heat roll 54 and pressure from the pressure roll 56.

  The recording paper 38 on which the toner is fixed is discharged to the upper part of the image forming apparatus 10 in FIG.

  Further, the image forming apparatus 10 includes a photoconductor cleaning blade 60 in order to remove the toner remaining on the photoconductor drum 14. Residual toner removed by the photoreceptor cleaning blade 60 is collected in a waste toner box 62.

  Further, the toner remaining on the intermediate transfer belt 26 is removed by the intermediate transfer member cleaning unit 64.

  The intermediate transfer member cleaning unit 64 includes a scraper 66 and a charging brush 68. The scraper 66 scrapes the residual toner on the intermediate transfer belt 26, and the charging brush 68 holds the intermediate transfer belt 26 between the backup roll 70 and charges the residual toner to the reverse polarity. As a result, the residual toner is transferred to the photosensitive drum 14 by the primary transfer roll 24 and removed by the photosensitive member cleaning blade 60.

  Next, with reference to FIG. 2, the configuration of the main part of the control system of the image forming apparatus 10 will be described.

  The image forming apparatus 10 includes a microcomputer 200 that performs overall control.

  The microcomputer 200 is connected to a network interface 204, an HDD 206, a power supply control unit 208, and an image formation processing control unit 210 via a bus 202 such as a control bus or a data bus.

  The network interface 204 is connected to a personal computer (not shown) via a network, and accepts input of image data from the personal computer.

  The HDD 206 stores image data input from the network interface 204.

  The power control unit 208 performs control related to power supply of the image forming apparatus 10.

  The image formation processing control unit 210 performs control for forming image data as an image on the recording paper 38 based on an image processing signal from the microcomputer 200.

  The image forming process control unit 210 is connected to an exposure apparatus control unit 212, a voltage control unit 214, a fixing device control unit 216, and a drive system control unit 218.

  The exposure apparatus control unit 212 controls the exposure apparatus 18.

  For example, the voltage control unit 214 controls the voltage applied to the charging roll 16, the secondary transfer roll 40, and the charging brush 68.

  The fixing device control unit 216 performs temperature control of the heat roll 54 constituting the fixing device 52 and pressure control by the pressure roll 56.

  The drive system control unit 218 controls drive parts such as the photosensitive drum 14, the developing device 20, and the feed roll 46 that takes out the recording paper 38 from the paper feed cassette 44.

  The drive system controller 218 also controls the operation in which the secondary transfer roll 40 and the intermediate transfer member cleaning unit 64 come into contact with and separate from the intermediate transfer belt 26.

  Here, the structure of the contact / separation mechanism for bringing the secondary transfer roll 40 and the intermediate transfer member cleaning unit 64 into contact with and away from the intermediate transfer belt 26 will be described.

  FIG. 3 shows a contact / separation mechanism unit 300 for bringing the secondary transfer roll 40 into and out of contact with the intermediate transfer belt 26.

  The contact / separation mechanism unit 300 includes an L-shaped secondary transfer roll support unit 302, a compression coil spring 304, and an eccentric cam 306.

  The secondary transfer roll 40 is disposed on the left surface of the upper end of the secondary transfer roll support 302 in FIG.

  The secondary transfer roll support unit 302 includes a shaft 308 at an L-shaped bent portion, and rotates about the shaft 308 as a central axis.

  The compression coil spring 304 is provided on the right surface of the secondary transfer roll support 302 near the top end of FIG. 3 and is connected to the internal support 310 on the right side of FIG.

  The eccentric cam 306 is provided so as to be in contact with the upper surface of the secondary transfer roll support portion 302 near the front end of the right portion in FIG.

  The eccentric cam 306 is rotated around the axis E by a DC motor (not shown). As the eccentric cam 306 rotates about the axis E, the secondary transfer roll support portion 302 rotates about the axis 308, and the secondary transfer roll 40 contacts or separates from the intermediate transfer belt 26.

  More specifically, when the eccentric cam 306 rotates in a direction in contact with the secondary transfer roll support 302 at a point F that is the minimum radius position of the eccentric cam 306, the compression coil spring 304 that has been in a compressed state is biased. Is stretched by. The secondary transfer roll support 302 is rotated in the direction G in FIG. 3 by the action of the compression coil spring 304 extending, and the secondary transfer roll 40 contacts the intermediate transfer belt 26.

  On the other hand, when the eccentric cam 306 rotates in a direction in contact with the secondary transfer roll support 302 at a point H that is the maximum radial position of the eccentric cam 306, the secondary transfer roll support 302 is compressed by the action of the rotation. The coil spring 304 is rotated in the direction I in FIG. 3 while being contracted against the urging force. As a result, the secondary transfer roll 40 is separated from the intermediate transfer belt 26.

  FIG. 4 shows the structure of the contact / separation mechanism portion 300A of the intermediate transfer member cleaning unit 64 with respect to the intermediate transfer belt 26. Since this structure has the same configuration as that of the contact / separation mechanism unit 300 shown in FIG. 3, an A is added to the end of each symbol, and the description of the configuration is omitted.

  FIG. 5 shows the relationship between the rotation angle of the eccentric cams 306 and 306A and the eccentric cam torque characteristic O, and the relationship between the rotation angle of the eccentric cams 306 and 306A and the eccentric cam radius P.

  From FIG. 5, it can be seen that the eccentric cam torque characteristic O varies with the variation of the eccentric cam radius P.

  However, the eccentric cam torque characteristics O of the eccentric cams 306 and 306A do not fluctuate only by the influence of the cam radius.

  The torque of the DC motor itself that rotates the eccentric cams 306 and 306A varies depending on various environmental factors such as machine differences of the image forming apparatus 10, installation environment, aging including replacement parts (CRU), and internal temperature changes. The fluctuation of the torque of the DC motor due to the environmental factor directly becomes the fluctuation of the torque of the eccentric cams 306 and 306A.

  Torque fluctuations due to environmental factors cause a shift in the timing at which the secondary transfer roll 40 and the intermediate transfer member cleaning unit 64 contact and separate from the intermediate transfer belt 26. The timing shift becomes relatively prominent when the image forming apparatus 10 is speeded up and downsized.

  As a result, the quality of an image formed on the recording paper 38 by the image forming apparatus 10 may be deteriorated due to a variation in torque due to environmental factors.

  For this reason, it is necessary to prevent a deviation in the timing at which the secondary transfer roll 40 and the intermediate transfer body cleaning unit 64 come into contact with and separate from the intermediate transfer belt 26 even if torque fluctuations due to environmental factors occur.

  FIG. 6 is a functional block diagram functionally showing details of the image forming process control unit 210 provided in the image forming apparatus 10.

  The image formation processing control unit 210 includes a timing information acquisition unit 500 that is a timing information acquisition unit, a timing information acquisition setting unit 502, and an operation instruction timing setting unit 504 that is an operation instruction timing setting unit.

  The timing information acquisition unit 500 has completed the contact with the contact drive start signal indicating that the drive of the motor is started to bring the secondary transfer roll 40 into contact with the intermediate transfer belt 26 from the drive system control unit 218. A contact drive completion signal indicating this is received, and the time required for the secondary transfer roll 40 to contact the intermediate transfer belt 26 is obtained as contact timing information.

  In addition, the timing information acquisition unit 500 has completed the separation drive start signal indicating that the drive of the motor has started in order to separate the secondary transfer roll 40 from the intermediate transfer belt 26 from the drive system control unit 218 and the separation. And a time required for the secondary transfer roll 40 to be separated from the intermediate transfer belt 26 is obtained as separation timing information.

  Timing information related to contact and separation acquired by the timing information acquisition unit 500 is transmitted to the operation instruction timing setting unit 504.

  The timing information acquisition setting unit 502 sets the timing at which the timing information acquisition unit 500 acquires timing information related to contact and separation. The set time is transmitted to the timing information acquisition unit 500 and the drive system control unit 218.

  The operation instruction timing setting unit 504 contacts the secondary transfer roll 40 and the intermediate transfer member cleaning unit 64 to the intermediate transfer belt 26 based on the timing information transmitted from the timing information acquisition unit 500 regarding contact and separation. , The timing for separating is set. The set timing is transmitted to the drive system control unit 218 and the voltage control unit 214.

  Based on the set timing, the drive system controller 218 drives the secondary transfer roll contact / separation motor 508 and rotates the eccentric cam 306 to bring the secondary transfer roll 40 into contact with and separate from the intermediate transfer belt 26. . Further, the drive system controller 218 drives the cleaning unit contact / separation motor 510 and rotates the eccentric cam 306A based on the set timing, thereby bringing the intermediate transfer member cleaning unit 64 into contact with and separating from the intermediate transfer belt 26. Let

  Further, the drive system control unit 218 controls the developing device rotation motor 512 for rotating the developing device 20. The developing device 20 is rotationally driven by the developing device rotating motor 512, and can sequentially supply the CMYK color toners to the photosensitive drum.

  Further, the drive system control unit 218 moves the secondary transfer roll 40 to the intermediate transfer belt while the photosensor 506 reads the positioning mark of the intermediate transfer belt 26 twice at the time set in the timing information acquisition setting unit 502. 26, a predetermined signal is transmitted to the timing information acquisition unit 500.

  Based on the timing set by the operation instruction timing setting unit 504, the voltage control unit 214 controls the secondary transfer roll 40 and the charging brush 68 according to output of voltage or current and stop of output.

  The operation according to the first embodiment of the present invention will be described below.

  With reference to FIG. 7, an inter-image between the images formed on the intermediate transfer belt 26 will be described.

  The intermediate transfer belt 26 moves from right to left in FIG. 7 in the Q direction.

  An inter-image 602 is formed between the image forming regions 600 formed on the intermediate transfer belt 26.

  In the image forming area 600, toners of CMYK colors are transferred from the photosensitive drum 14 in a multiplexed manner, and a toner image is formed as a color image. When the formation of the color image is completed in the image forming area 600, the secondary transfer roll 40 comes into contact with the intermediate transfer belt 26 in a predetermined area in the inter image 602, and the color image is transferred to the recording paper 38.

  The intermediate transfer belt 26 includes not only the image forming area 600 but also the inter image 602 as a toner band 604A generated when the intermediate transfer body cleaning unit is separated, and a toner band 604B generated when the developing device 20 is opposed to the photosensitive drum 14. Toner adheres.

  When the toner bands 604A and 604B adhere to the secondary transfer roll 40, the secondary transfer roll 40 adheres to the back surface of the recording paper 38 as dirt when the toner image is transferred from the intermediate transfer belt 26 to the recording paper 38.

  Therefore, the secondary transfer roll 40 must abut on the upstream side of the intermediate transfer belt in the advancing direction Q in FIG. 7 with respect to the toner band 604B.

  A voltage is applied to the secondary transfer roll 40 in order to form a potential difference between the recording paper 38 and the toner.

  The voltage applied to the secondary transfer roll 40 takes time to reach a predetermined voltage value. Before the secondary transfer roll 40 transfers the toner image from the intermediate transfer belt 26 to the recording paper 38, a predetermined voltage value is required. The voltage value must be reached. If the transfer is performed before the secondary transfer roll 40 reaches a predetermined voltage value, a transfer failure of the toner image onto the recording paper 38 occurs.

  When the distance that the intermediate transfer belt 26 moves in the time from when the voltage is applied to the secondary transfer roll 40 until the predetermined voltage value is reached is R, the timing of applying the voltage to the secondary transfer roll is shown in FIG. A straight line S is shown.

  From the above, the secondary transfer roll 40 must come into contact with the intermediate transfer belt 26 in the contact area 606 between the toner band 604B and the straight line S in FIG.

  Further, the separation of the secondary transfer roll 40 from the intermediate transfer belt 26 is performed immediately after the transfer of the toner image onto the recording paper 38 is completed.

  Here, when the speed and size of the image forming apparatus 10 are increased, the speed at which the intermediate transfer belt 26 moves in the Q direction in FIG. 7 increases. Accordingly, the time width for contacting the secondary transfer roll 40 in the contact area 606 is shortened, and the timing at which the secondary transfer roll 40 contacts the intermediate transfer belt 26 in the contact area 606 may be shifted. is there.

  Therefore, the operation instruction timing setting unit 504 shown in FIG. 6 sets the timing at which the secondary transfer roll contact / separation motor 508 operates so that the secondary transfer roll 40 contacts the intermediate transfer belt 26 in the contact area 606. Set.

  With reference to FIG. 8, a flow of image formation accompanied by setting processing for timing at which the secondary transfer roll 40 contacts and separates from the intermediate transfer belt 26 will be described.

  In step 800, the image forming apparatus 10 is turned on.

  Next, in step 802, the secondary transfer roll 40 is moved away from the intermediate transfer belt 26. Further, in the positioning operation, the intermediate transfer member cleaning unit 64 is brought into contact with the intermediate transfer belt 26.

  Next, in step 804, an initialization operation sequence is executed, the image forming apparatus 10 is initialized, and input of a print signal is awaited.

  In step 806, it is determined whether a print signal is input to the image forming apparatus 10. If a print signal is input, the determination is affirmative, and the process proceeds to step 808. On the other hand, if the print signal is not input, the determination is negative, and the waiting state is maintained until the print signal is input.

  In step 808, the timing information acquisition unit 500 acquires timing information of the time required for the secondary transfer roll 40 to contact and separate from the intermediate transfer belt 26.

  In step 810, toner development processing is performed based on the print signal.

  Next, in step 812, the timing at which the secondary transfer roll 40 comes into contact with and separates from the contact region 606 of the intermediate transfer belt 26 based on the timing information acquired by the timing information acquisition unit 500 at the operation instruction timing setting unit 504. Set. The timing at which the intermediate transfer body cleaning unit 64 contacts and separates from the intermediate transfer belt 26 is also set based on the timing information acquired by the timing information acquisition unit 500.

  In step 814, the secondary transfer roll contact / separation motor 508 operates at the set timing, and the secondary transfer roll 40 contacts the intermediate transfer belt 26.

  In step 816, the voltage control unit 214 starts applying voltage to the secondary transfer roll 40 at the contact timing set in step 812.

  Next, at step 818, the recording paper 38 is conveyed between the secondary transfer roll 40 and the intermediate transfer belt 26, and transfer of the image formed with toner on the surface of the intermediate transfer belt 26 to the recording paper 38 is started. .

  Next, at step 820, it is determined whether or not the transfer of the image onto the recording paper 38 has been completed. If the transfer is completed, the determination is affirmative and the process proceeds to step 824. On the other hand, when the transfer is not completed, the determination is negative, and the transfer is continued until the transfer is completed.

  In step 822, since the transfer to the recording paper 38 has been completed, the application of voltage to the secondary transfer roll 40 is stopped at the timing when the secondary transfer roll 40 set in step 812 starts to separate from the intermediate transfer belt 26.

  Next, in step 824, the secondary transfer roll 40 is separated from the intermediate transfer belt 26 based on the separation timing set in step 812.

  Next, at step 826, the intermediate transfer body cleaning unit 64 contacts the intermediate transfer belt 26 based on the timing set at step 812 and removes the toner remaining on the intermediate transfer belt 26.

  In the flow described with reference to FIG. 8, the timing information acquisition unit 500 acquires timing information related to the time during which the secondary transfer roll 40 contacts and separates from the intermediate transfer belt 26, and after the image forming apparatus 10 is turned on, Performed at the beginning of the formation process.

  However, the present invention is not limited to this, and the acquisition of timing information by the timing information acquisition unit 500 may be performed immediately before setting the operation instruction timing for contact and separation.

  Further, the acquisition of timing information by the timing information acquisition unit 500 may be performed by the operation of the secondary transfer roll 40 during the positioning operation and the initialization operation.

  FIG. 9 shows an operation sequence of each mechanism unit based on the flow of FIG.

  An abutment pulse for abutting the secondary transfer roll 40 against the secondary transfer roll contact / separation motor 508 while reading the positioning mark signal A and the positioning mark signal B at the start of image forming processing. A separation pulse S2 for separation from S1 is input to the secondary transfer roll contact / separation motor 508.

  The width of the contact pulse S1 and the width of the separation pulse S2 are time widths required for the secondary transfer roll 40 to contact and separate from the intermediate transfer belt 26, and the timing information acquisition unit 500 acquires these time widths. To do. The time width changes as the torque of the secondary transfer roll contact / separation motor 508 fluctuates due to machine differences in the image forming apparatus 10, installation environment of the image forming apparatus, changes with time, changes in internal temperature, and the like.

  When transferring an image to the recording paper 38, the secondary transfer roll 40 must abut on the abutting region 606 of the intermediate transfer belt 26 during the time width α1, and the time width α1 is always constant. is there.

  The operation instruction timing setting unit 504 obtains a time width T1 that is a difference between the time width α1 and the time width of the contact pulse S1. After the time width T1 obtained by the operation instruction timing setting unit 504 from the positioning mark E, the timing for inputting the contact pulse S1 to the secondary transfer roll contact / separation motor is reached.

  In addition, the secondary transfer roll 40 must be separated from the intermediate transfer belt 26 during the time width α2, and the time width α2 is always constant. The operation instruction timing setting unit 504 obtains a time width T2 that is the difference between the time width α2 and the time width of the separation pulse S2.

  The timing at which the separation pulse S2 is input to the secondary transfer roll contact / separation motor 508 is after the time width T2 from the stop of the operation signal U of the registration sensor 72 (see FIG. 1).

  A signal for applying a voltage to the secondary transfer roll 40 is a secondary transfer roll power output signal Z, and the timing at which the voltage application to the secondary transfer roll 40 is started is performed by the secondary transfer roll 40 to the intermediate transfer belt 26. After contact. On the other hand, the timing at which the voltage application is stopped is before the separation pulse S2 is input to the secondary transfer roll contact / separation motor 508.

  Further, the intermediate transfer body cleaning unit 64 is in contact with the secondary transfer belt in the positioning operation (see step 802 in FIG. 8). For this reason, the intermediate transfer member cleaning unit 64 must be separated from the intermediate transfer belt 26 during the time width β2. The time width required for the cleaning unit contact / separation motor 510 to separate the intermediate transfer member cleaning unit 64 is the width of the separation pulse Y2.

  The operation instruction timing setting unit 504 assumes that the time width of the separation pulse Y2 and the time width of the pulse S2 acquired by the timing information acquisition unit 500 are the same, and determines the time from the difference between the time width β2 and the time width of the separation pulse S2. The width X2 is obtained.

  After the time width X2 from the positioning mark signal B, the timing for separating the intermediate transfer body cleaning unit 64 from the intermediate transfer belt 26 is reached. The power output signal W is input to the charging brush 68 until just before the intermediate transfer member cleaning unit 64 is separated from the intermediate transfer belt 26.

  Further, the intermediate transfer member cleaning unit 64 must be brought into contact with the intermediate transfer belt 26 during the time width β1. The time width required to bring the intermediate transfer member cleaning unit 64 into contact with the cleaning unit contact / separation motor 510 is the width of the contact pulse Y1.

  The operation instruction timing setting unit 504 assumes that the time width of the contact pulse Y1 and the time width of the contact pulse S1 acquired by the timing information acquisition unit 500 are the same, and the time width between the time width β1 and the contact pulse S1. The time width X1 is obtained from the difference between the two.

  The timing after the time width X1 from the positioning mark signal E is the timing at which the intermediate transfer body cleaning unit 64 is brought into contact with the intermediate transfer belt 26. A power output signal W is input to the charging brush 68 at the timing when the intermediate transfer member cleaning unit 64 comes into contact with the intermediate transfer belt 26.

As described above, according to the present embodiment, the time required for the secondary transfer roll 40 to contact and separate from the intermediate transfer belt 26 after the power is supplied to the image forming apparatus 10 is used as timing information. Acquired by the information acquisition unit 500. Based on this, the operation instruction timing setting unit 504 sets the timing at which the secondary transfer roll 40 always contacts and separates in a predetermined region of the intermediate transfer belt 26. The timing at which the intermediate transfer member cleaning unit 64 contacts and separates from the intermediate transfer belt 26 is also set based on the timing information.
(Second embodiment)
In the first embodiment, the timing at which the intermediate transfer member cleaning unit 64 contacts and separates from the intermediate transfer belt 26 is obtained from the time required for the contact and separation of the secondary transfer roll 40 acquired by the timing information acquisition unit 500. ing.

  However, the secondary transfer roll 40 is disposed closer to the fixing device 22 than the intermediate transfer member cleaning unit 64 (see FIG. 1). Therefore, the temperature around the secondary transfer roll 40 and the temperature around the intermediate transfer member cleaning unit 64 may be different.

  Accordingly, the timing information acquisition unit 500 acquires the time required for the intermediate transfer body cleaning unit 64 to contact and separate from the intermediate transfer belt 26 as timing information, and based on the timing information, the operation instruction timing setting unit 504 acquires the intermediate transfer body. The timing at which the cleaning unit 64 contacts and separates from the intermediate transfer belt 26 is set.

  Further, the input / output timing of the voltage to the charging brush 68 is also determined based on the time required for the intermediate transfer body cleaning unit 64 to contact and separate from the intermediate transfer belt 26 obtained by the timing information acquisition unit 500. Set at 504.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a diagram illustrating a main configuration of a control system of the image forming apparatus according to the present embodiment. It is a figure which shows the structure of the contact-separation mechanism part of the secondary transfer roll which concerns on this Embodiment. FIG. 4 is a diagram showing a structure of an approach / separation mechanism portion of an intermediate transfer member cleaning unit according to the present embodiment. It is a figure which shows the relationship between the rotation angle of an eccentric cam, and an eccentric cam torque characteristic, and the relationship between the rotation angle of an eccentric cam, and an eccentric cam radius. 3 is a functional block diagram functionally showing details of an image forming process control unit included in the image forming apparatus. FIG. FIG. 4 is a diagram necessary for explaining an interimage between images formed on an intermediate transfer belt. 10 is a flowchart of image formation accompanied by a setting process of an operation time for the secondary transfer roll. It is a figure which shows the operation | movement sequence of each mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Photosensitive drum (image carrier)
26 Intermediate transfer belt (intermediate transfer member)
40 Secondary transfer roll 64 Intermediate transfer member cleaning unit 300 Contact / separation mechanism unit 500 Timing information acquisition unit (timing information acquisition unit)
504 Operation instruction timing setting unit (operation instruction timing setting means)

Claims (4)

A toner image is formed by forming an electrostatic latent image on the image carrier with the toner supply developer roll sequentially facing the image carrier, and the toner image is primarily transferred to the intermediate transfer member at the primary transfer portion. This is repeated at least twice with the developing roll changed, and two or more toner images are transferred onto the intermediate transfer member, and the toner image is transferred from the intermediate transfer member via the secondary transfer roll. An image forming apparatus for transferring the toner image to a predetermined region of the intermediate transfer body based on a position signal detected from the intermediate transfer body in an image forming process for secondary transfer onto a recording sheet,
A contact / separation mechanism for contacting and separating the secondary transfer roll from the intermediate transfer member;
Based on the actual operation of the contact / separation mechanism unit, the contact timing information, which is the time from when the operation instruction to the contact / separation mechanism unit is performed until the secondary transfer roll contacts the intermediate transfer member, is obtained. Timing information acquisition means for acquiring;
Based on the contact timing information acquired by the timing information acquisition unit, an operation instruction timing setting unit that sets a contact operation instruction timing for instructing the contact operation to the contact / separation mechanism unit;
An image forming apparatus comprising:   The timing information acquisition unit further acquires a separation timing that is a time from when the operation instruction is given to the contact / separation mechanism unit until the secondary transfer roll and the intermediate transfer member are separated from each other, and the operation instruction timing setting is performed. The image forming apparatus according to claim 1, wherein the unit further sets a separation operation timing for instructing the separation / separation mechanism unit to perform a separation operation based on the separation timing information.   3. The image according to claim 1, wherein the setting of the operation instruction timing by the operation instruction timing setting means is set in consideration of a transition period when the secondary transfer roll is energized. Forming equipment.   The image forming apparatus according to claim 1, wherein at least one of the contact timing information and the separation timing information is acquired after the image forming apparatus is powered on.

Images