JP5743083B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus employing an intermediate transfer system. The image forming apparatus includes various apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions in a complex manner.

  Conventionally, as an image forming apparatus employing an electrophotographic method, each color toner image formed on a photosensitive drum is primarily transferred to an intermediate transfer belt, and a secondary transfer position between the intermediate transfer belt and the secondary transfer roller. A so-called intermediate transfer system is widely used in which a recording material is conveyed to the (secondary transfer nip portion) and toner images superimposed on the intermediate transfer belt are collectively transferred to the recording material.

  In this type of image forming apparatus, although the transfer efficiency of the toner image onto the recording material can be improved, fog toner caused by residual charges other than the toner image is transferred from the photosensitive drum to the secondary transfer roller via the intermediate transfer belt. May adhere. Since the fog toner on the secondary transfer roller causes backside contamination of the recording material, a technique for removing the fog toner on the secondary transfer roller has been conventionally performed. As an example of the removal technique, Patent Document 1 discloses that a positive and negative bias is sequentially applied to the secondary transfer roller, and the fog toner on the secondary transfer roller is reversely transferred to the intermediate transfer belt to be used as a cleaning device for the intermediate transfer belt. The technology to collect them is proposed.

JP 2006-308816 A

  Now, this type of fog toner is generated due to the difference in the output stop timings of the three components, that is, the photosensitive drum, the charging charger, and the developing device, at the time of falling after the end of the printing operation. The fog toner thus generated adheres to a portion of the intermediate transfer belt that faces the photosensitive drum (see FIG. 6A). Thereafter, the intermediate transfer belt is driven to rotate at the start of the printing operation, and the fog toner reaches the secondary transfer position between the intermediate transfer belt and the secondary transfer roller. Then, the fog toner adheres to the secondary transfer roller side, and in the transfer process during printing, the toner moves from the secondary transfer roller side to the back side of the recording material and becomes dirty.

  In this way, the phenomenon of the backside of the recording material due to the fog toner described above occurs in the transfer process during printing. Therefore, the removal of the fog toner (cleaning of the secondary transfer roller) is performed before the transfer stage, that is, the start of the printing operation. It is necessary to do it at the time of raising (initial stage). However, in the above-described conventional configuration, for example, since the secondary transfer roller is cleaned over a long time such that the intermediate transfer belt makes one turn, the time required for cleaning the secondary transfer roller is long until the printing operation starts. There is a problem that the waiting time of the user becomes longer and makes the user wait. That is, there is a problem that the FCOT (first copy time) becomes longer due to an increase in the waiting time. Further, a preparatory operation such as a discharge product removal process for idly rotating the photosensitive drum or an image stabilization process may be performed before the printing operation is performed. Became longer.

  The present invention has been made in view of such a situation, and provides an image forming apparatus capable of appropriately performing cleaning of the secondary transfer roller, and further providing an image forming apparatus capable of improving the FCOT by shortening the standby time. It is a technical issue to do.

The invention according to claim 1 is an intermediate transfer member to which a toner image formed on an image carrier is transferred, a secondary transfer member that transfers a toner image on the intermediate transfer member to a recording material, and the intermediate transfer member. wherein an image forming apparatus includes a cleaning means for removing unwanted deposits brought to the secondary transfer member, and a controller for actuating said cleaning means from the plurality arranged along the intermediate transfer body A monochrome mode in which a single color toner is formed with a single color toner, and a color mode in which a color image is formed with different color toners. the activation of the image forming apparatus based on whether restarting after eliminating jamming, select whether to operate the cleaning means during start-up of the printing operation, the cleaning means during startup of the printing operation In the case of moving, if the previous execution mode is the color mode, the time until the portion of the intermediate transfer member facing the image forming portion farthest from the secondary transfer member moves to the secondary transfer position Is the operation time of the cleaning means, and if the previous execution mode is the monochrome mode, the portion of the intermediate transfer member facing the image forming portion corresponding to the single color toner moves to the secondary transfer position. The time until is the operation time of the cleaning means .

According to a second aspect of the invention, an image forming apparatus according to claim 1, wherein, when the actuating said cleaning means when startup of the printing operation, a plurality of preparatory operation before the start of the printing operation The operation time of the cleaning means is shortened according to the combination of presence and absence.

According to a third aspect of the present invention, there is provided an intermediate transfer member to which a toner image formed on an image carrier is transferred, a secondary transfer member that transfers a toner image on the intermediate transfer member to a recording material, and the intermediate transfer member. An unnecessary adhering matter detecting means for detecting an unnecessary adhering matter on the upper surface, a cleaning means for removing the unnecessary adhering matter brought from the intermediate transfer member to the secondary transfer member, and a control unit for operating the cleaning means; The control unit controls the operation of the cleaning unit based on the detection result of the unnecessary adhering matter detection unit when the printing operation is started up.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect , the unnecessary adhering matter detecting means also serves as a pattern detecting means for detecting a reference pattern of each color on the intermediate transfer member. .

  According to the image forming apparatus according to the first aspect of the present application, the control unit for the cleaning unit that removes the unnecessary deposits brought from the intermediate transfer body to the secondary transfer body, the startup of the image forming apparatus after the jam is resolved Since whether or not to activate the cleaning unit at the start of the printing operation is selected based on whether or not it is restarted, it is necessary to clean the secondary transfer member by the operation of the cleaning unit at the start of the printing operation. It can be performed appropriately. For this reason, when it is not necessary to clean the secondary transfer member, it is possible to shorten the start-up time of the printing operation and to shorten the FCOT. As a result, the waiting time of the user is shortened, and the print productivity can be improved.

  According to the image forming apparatus according to the second aspect of the present application, the control unit for the cleaning unit that removes the unnecessary deposits brought from the intermediate transfer member to the secondary transfer member is used when the printing operation starts. Since the operation of the cleaning unit is controlled based on the detection result of the detection unit, the cleaning timing of the secondary transfer member can be optimized according to the presence or absence of unnecessary deposits on the intermediate transfer belt. For this reason, at the time of starting the printing operation, the secondary transfer member can be more reliably and efficiently cleaned. In addition, there is an advantage that it can contribute to extending the life of consumables such as an image carrier and the intermediate transfer member.

It is a schematic explanatory drawing of a printer. FIG. 4 is an enlarged explanatory view around an intermediate transfer belt and a secondary transfer roller. It is a functional block diagram of a control part. It is a flowchart of process start-up control in the 1st example. It is a flowchart of the secondary transfer roller cleaning control in the second example. (A) is a diagram for explaining the fog toner generated at the time of falling after the end of the printing operation, (b) is a diagram for explaining a mode in which the fog toner is moved by a slight movement of the intermediate transfer belt in the monochrome mode, and (c) is a diagram. FIG. 6 is a diagram illustrating a mode in which fog toner moves by a slight movement of an intermediate transfer belt in a color mode.

  An embodiment in which the present invention is applied to a tandem color digital printer (hereinafter simply referred to as “printer”), which is an example of an image forming apparatus, will be described below with reference to the drawings. In the following description, when using terms indicating a specific direction or position (for example, “left / right”, “up / down”, etc.) as necessary, the direction orthogonal to the paper surface in FIG. ing. These terms are used for convenience of explanation, and do not limit the technical scope of the present invention.

(1). Overview of Printer First, an overview of the printer 10 will be described mainly with reference to FIG. As shown in FIG. 1, the printer 10 forms (prints) an image by a well-known electrophotographic method, and includes an image processing unit 11, a feeding unit 12, a fixing unit 13, a control unit 14, and the like. ing. Although details are not shown, the printer 10 is connected to a network such as a LAN, for example, and receives a print request from an external terminal (not shown) or the like, and consists of yellow, magenta, cyan, and black based on the print request. A multi-color or single-color print job is configured to be executed. In the following description, for convenience, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and reference numerals Y, M, C, and K are used for the numbers of the components related to the reproduction colors. Is added as a subscript.

  The image processing unit 11 includes image forming units 20Y, 20M, 20C, and 20K corresponding to YK colors, an intermediate transfer belt 21 as an intermediate transfer member, and the like. The image forming unit 20Y-20K includes a photosensitive drum 1Y-1K as an image carrier. Around the photosensitive drum 1Y-1K, in order along the clockwise direction of FIG. 1, the charging charger 2Y-2K, the exposure unit 3Y-3K, the developing device 4Y-4K, the primary transfer roller 5Y-5K, and the photosensitive cleaner. 6Y-6K is arranged. YK toner images are formed on the photosensitive drums 1Y-1K by the action of the chargers 2Y-2K, the exposure units 3Y-3K, and the developing units 4Y-4K. The intermediate transfer belt 21 is an endless belt, and is configured to be wound around a driving roller 22 and a driven roller 23 and to be driven to rotate counterclockwise in FIG.

  Developers including toner and carrier are accommodated in the developing devices 4Y-4K of the image forming units 20Y-20K, and the toner is consumed together with printing. Therefore, a TCR sensor 8Y-8K (see FIG. 3) for detecting the internal toner density (ratio of toner in the developer) is attached to the developing devices 4Y-4K. The TCR sensors 8Y-8K in this case are of a type that changes the oscillation frequency in accordance with a change in toner density, which is a mixing ratio of toner and carrier. The detection signal of the TCR sensor 8Y-8K is transmitted to the control unit 14. When the TCR sensor 8Y-8K detects that the toner density in the developing devices 4Y-4K is equal to or lower than a predetermined density, the toner of the corresponding color is supplied from the toner replenishing unit 46Y-46K disposed above the intermediate transfer belt 21. Is supplied to the developing devices 4Y-4K.

  The feeding unit 12 conveys the fed recording material S, the feeding cassette 31 that accommodates the recording material S, the feeding roller 32 that feeds the recording material S in the feeding cassette 31 one by one onto the conveyance path 37, and the feeding material 32. A pair of conveying rollers 33 to perform, a pair of registration rollers 34 that takes a timing to send the recording material S to the secondary transfer position 39, and a secondary transfer that is pressed against the driving roller 22 with the intermediate transfer belt 21 sandwiched at the secondary transfer position 39. A secondary transfer roller 35 as a body is provided. The fixing unit 13 heats and pressurizes the recording material S at a predetermined fixing temperature to fix the unfixed toner image on the recording material S, and includes a fixing roller having a built-in heat source such as a halogen lamp heater, and fixing. And a pressure roller facing the roller.

  The control unit 14 converts an image signal from an external terminal or the like into a YK digital signal, and generates a drive signal for driving the laser diodes of the exposure units 3Y-3K. The laser diode of the exposure unit 3Y-3K is driven by the generated drive signal, and the laser beam is applied from the exposure unit 3Y-3K to the photosensitive drum 1Y-1K uniformly charged by corona discharge of the charging charger 2Y-2K. Is projected. As a result, the photosensitive drum 1Y-1K is exposed and scanned, and an electrostatic latent image is formed on the photosensitive drum 1Y-1K.

  Each electrostatic latent image is developed with toner from the developing devices 4Y-4K. Each color toner image is primarily transferred onto the intermediate transfer belt 21 by an electrostatic force acting between the primary transfer rollers 5Y-5K and the photosensitive drums 1Y-1K. Here, the image forming operation for each color is executed at different timings so that each color toner image overlaps the same position on the intermediate transfer belt 21. The color toner images overlapped on the intermediate transfer belt 21 are moved to the secondary transfer position 39 by the circumferential driving of the intermediate transfer belt 21.

  The recording material S is conveyed from the feeding unit 12 via the registration roller pair 34 in accordance with the timing of the image forming operation. The recording material S is nipped and conveyed between the intermediate transfer belt 21 that is driven to rotate and the secondary transfer roller 35 that is pressed against the intermediate transfer belt 21, and acts between the drive roller 22 and the secondary transfer roller 35. The respective color toner images superimposed on the intermediate transfer belt 21 are secondarily transferred onto the recording material S collectively by the electric power. The recording material S that has passed the secondary transfer position 39 is conveyed to the fixing unit 13. The recording material S is heated and pressurized when passing through the fixing unit 13, and the unfixed toner image is fixed on the recording material S. Thereafter, the recording material S is discharged onto the storage tray 38 by the rotational drive of the discharge roller pair 36.

  The untransferred toner remaining on the photoreceptor drum 1Y-1K is removed from the photoreceptor drum 1Y-1K by the photoreceptor cleaner 6Y-6K. In this case, the photoreceptor cleaner 6Y-6K is a blade member whose tip is in contact with the outer peripheral surface of the photoreceptor drum 1Y-1K, and mechanically scrapes off the untransferred toner, whereby the photoreceptor drum 1Y-1K. The outer peripheral surface of is cleaned. Note that not only untransferred toner but also discharge products generated by charging of the charging charger 2Y-2K adhere to the outer peripheral surface of the photosensitive drum 1Y-1K. These discharge products are also removed by the photoreceptor cleaner 6Y-6K when the photoreceptor drum 1Y-1K rotates. Rotating the photosensitive drum to remove discharge products is called idling.

  On the intermediate transfer belt 21, unnecessary deposits such as untransferred toner and fog toner caused by residual charges other than the toner image may remain. These unnecessary deposits are removed from the intermediate transfer belt 21 by a belt cleaner 24 disposed on the opposite side of the driven roller 23 with the intermediate transfer belt 21 interposed therebetween. The belt cleaner 24 in this case is also a blade member that mechanically scrapes unnecessary deposits in the same manner as the photoconductor cleaner 6Y-6K.

  The above description is a case where a color (multicolor) print job is executed. When a monochrome (single color), for example, black print job is executed, only the image forming unit 20K closest to the secondary transfer roller 35 is driven, and the color photosensitive drums 1Y-1C and the intermediate transfer belt 21 are They are separated from each other by driving of a contact / separation mechanism (not shown). A black toner image is formed on the outer peripheral surface of the photosensitive drum 1 </ b> K, and is primarily transferred to the intermediate transfer belt 21. The black toner image on the intermediate transfer belt 21 is secondarily transferred onto the recording material S at the secondary transfer position 39 and fixed onto the recording material S by the fixing unit 13. When the monochrome print job is completed and the color print job is executed, the contact / separation mechanism is driven to return the photosensitive drum 1Y-1C to the position where it contacts the intermediate transfer belt 21.

  Note that an operation panel 15 is disposed on the front side of the printer 10 at a position where the user can easily operate. The operation panel 15 is provided with keys (buttons) for performing setting of the number of prints, setting of print density, color / monochrome mode switching, and a liquid crystal touch panel, for example.

  As shown in FIG. 2, the secondary transfer roller 35 is connected to a secondary transfer power supply 40 that can be applied by switching between positive and negative biases. The secondary transfer power supply 40 is basically a power supply for generating a secondary transfer bias for transferring the toner image on the intermediate transfer belt 21 to the recording material S at the secondary transfer position 39, and is based on a command from the control unit 14. Control secondary transfer bias. The secondary transfer power supply 40 also functions as a cleaning unit that electrically removes unnecessary deposits brought from the intermediate transfer belt 21 to the secondary transfer roller 35. In other words, a negative cleaning bias and a positive cleaning bias can be applied to the secondary transfer roller 35 alternately. The negative cleaning bias is a bias for returning negatively charged toner (regularly charged toner) among unnecessary deposits to the intermediate transfer belt 21, and the positive cleaning bias is a positively charged toner (reversely charged) among unnecessary deposits. This is a bias for returning the charged toner) to the intermediate transfer belt 21. Unnecessary deposits returned to the intermediate transfer belt 21 are removed by a belt cleaner 24.

  An AIDC sensor 25 serving as a pattern detection unit is disposed on the most downstream side in the circumferential direction of the intermediate transfer belt 21, that is, between the image forming unit 20K closest to the secondary transfer roller 35 and the secondary transfer position 39. Yes. The AIDC sensor 25 uses a reference pattern (also referred to as a test toner image) of each color formed on the intermediate transfer belt 21 during image stabilization processing such as color misregistration, gradation, and image density reproduction correction. It is to detect. The AIDC sensor 25 in this case is a reflective optical sensor having, for example, a light emitting part and a light receiving part, and irradiates the intermediate transfer belt 21 with light from the light emitting part, and receives the reflected light with the light receiving part. The signal is converted into a signal, and the electric signal is transmitted to the control unit 14. A temperature / humidity sensor 26 for detecting the internal temperature / humidity is disposed in the printer 10. The detection signal of the temperature / humidity sensor 26 is transmitted to the control unit 14.

  A manual feed tray 41 that can feed a recording material S of a predetermined size from the outside is provided on one side of the printer 10 so as to be capable of opening and closing. The recording material S on the manual feed tray 41 is fed into the conveyance path 37 by the rotational drive of the manual paper feed roller pair 42 provided on the printer 10 side. On the manual feed tray 41, a push-up plate 43 that pushes the leading end side of the recording material S toward the manual feed roller pair 42 is provided so as to be movable up and down. The push-up plate 43 is configured to move up and down by a push-up plate drive mechanism (not shown) which is a known mechanism such as a gear or a cam. In the vicinity of the push-up plate 43 in the manual feed tray 41, a lift detection sensor 45 that detects the lift posture of the push-up plate 43 is disposed. In this case, the lift detection sensor 45 is turned off in an initial posture in which the push-up plate 43 is separated from the manual feed roller pair 42 and turned on in a push-up posture approaching the manual feed roller pair 42. A detection signal from the elevation detection sensor 45 is transmitted to the control unit 14.

  A plurality of jam sensors 47 to 49 that detect jams (paper jams) of the recording material S are arranged in the conveyance path 37 of the printer 10. The jam sensors 47-49 output a detection signal to the control unit 14 when a jam is detected. If the jam sensor 47-49 detects the front edge of the recording material S and does not detect the rear edge after a predetermined time has elapsed, the control unit 14 determines that a jam has occurred. Further, after a predetermined time has elapsed after the jam sensors 47 and 48 on the upstream side of the conveyance path 37 detect the trailing edge of the recording material S, the downstream side jam sensors 48 and 49 detect the leading edge of the recording material S. Even when not detected, the control unit 14 determines that a jam has occurred. As each jam sensor 47-49, for example, a photo sensor for optically detecting the passage of the recording material S, a contact type limit switch, or the like is employed.

  The photosensitive drums 1Y-1C constituting the color image forming units 20Y-20C are configured to be rotationally driven by these dedicated sub drive motors 29. On the other hand, rotating parts other than the color image forming units 20Y-20C, such as the photosensitive drum 1K, the intermediate transfer belt 21, the feeding roller 32 of the feeding unit 12, the fixing roller of the fixing unit 13, and a push-up plate driving mechanism, etc. Is configured to be rotationally driven by a main drive motor 28. By distributing the drive motors (drive sources) 28 and 29 in this way, the color photosensitive drums 1Y-1C that do not contribute to printing can be stopped during the execution of a monochrome print job, and the photosensitive drums 1Y-1C and Wear due to friction with the photoreceptor cleaner 6Y-6C is prevented. As a result, the life of the photoconductor drum 1Y-1C and the photoconductor cleaner 6Y-6C can be extended.

(2). Next, the configuration of the control unit 14 will be described with reference to FIG. As shown in FIG. 3, the control unit 14 includes, as main components, a communication interface (I / F) unit 101, an image processing unit 102, an image memory 103, a CPU 107, a ROM 108, a RAM 109, a counter 110, a timer 111, and a backup. A memory 112 and the like are provided. These units 101-103 and 107-112 are configured to be able to communicate with each other via a bus 115.

  The communication I / F unit 101 is an interface for connecting to a LAN such as a LAN card or a LAN board, receives print job data from the outside, and transmits the received data to the image processing unit 102. The image processing unit 102 converts print job data from the communication I / F unit 101 into image data of each reproduction color, outputs the image data to the image memory 103, and stores the image data for each reproduction color.

  The CPU 107 reads a necessary program from the ROM 108, converts the image data in the image processing unit 102, writes / reads out the image data in the image memory 103, and takes the timing while processing the image processing unit 11 and the feeding unit. 12 and the like are controlled to execute a smooth print job. In addition, it receives information by pressing a key on the operation panel 15 or touch input on the liquid crystal touch panel, and performs display control and the like. Further, it receives detection signals from the AIDC sensor 25, the temperature / humidity detection sensor 26, the TCR sensor 8Y-8K, the elevation detection sensor 45, the jam sensor 47-49, and the like, and controls the rotation of the main and sub drive motors 28 and 29. Do.

  In the ROM 108, in addition to a control program related to a printing operation, a control program related to a preparatory operation such as a discharge product removal process (idle rotation process), an image stabilization process, a TCR adjustment process, and a toner replenishment process, an image stabilization process Data of a reference pattern for each color to be formed is stored. The RAM 109 is used as a work area for the CPU 107. The counter 110 counts the cumulative number of recording materials S subjected to printing, and stores the cumulative number value in a predetermined storage area of the backup memory 112.

  Here, the TCR adjustment process is an operation of adjusting the parameter reference value so that the ratio of the toner and the carrier becomes the target ratio, and the toner replenishment process is the developing unit 4Y− of toner empty (predetermined density). In this operation, replenishment toner is forcibly replenished within 4K. These preparatory operations can be executed from a state where printing cannot be performed when the device is started up (including when the power is turned on and when returning from the power saving mode that restricts the power consumption although most functions are limited). It can be said that it is an operation to transition to a different state.

  The timer 111 receives power supply from an internal battery (not shown) or the like and measures the drive time of the main drive motor 28. Every time the rotation drive of the main drive motor 28 is started, the time measurement is started from that point, and when the rotation drive is stopped next, the time measurement is ended and reset. The backup memory 112 is a non-volatile storage unit, and preliminarily stores execution conditions for each preparation operation such as idle rotation processing, information indicating the time required for execution, and the like.

(3). First Example of Secondary Transfer Roller Cleaning Control Next, a first example of secondary transfer roller cleaning control by the control unit 14 will be described with reference to FIG. The controller 14 electrically removes unnecessary deposits on the secondary transfer roller 35 by alternately switching positive and negative cleaning biases from the secondary transfer power supply 40 and applying them to the secondary transfer roller 35. It is comprised so that roller cleaning control may be performed. FIG. 4 is a flowchart showing the contents of the process start-up control that is called from the main routine and executed when the apparatus is activated (including when the power is turned on and when returning from the power saving mode). The secondary transfer roller cleaning control is executed as part of the process startup control. The algorithm shown in the flowchart is stored as a control program in the ROM 108 or the like of the control unit 14 and is read by the RAM 109 and executed by the CPU 107.

  As shown in the flowchart of FIG. 4, when the printer 10 is turned on or returned from the power saving mode and started up, the control unit 14 starts process startup control, and jam history information stored in the backup memory 112. (S01), it is determined whether or not there is a jam history, that is, whether or not the current activation is a restart after the jam is resolved (S02). If there is a jam history (S02: YES), the toner image to be transferred to the jammed recording material S may remain on the intermediate transfer belt 21, so the secondary transfer roller cleaning control is set in advance. The specified time is executed (S03). In this case, the intermediate transfer belt 21 is driven to rotate by the rotational drive of the main drive motor 28, and the secondary transfer power supply 40 is applied to the secondary transfer roller 35 for the specified time while alternately switching positive and negative cleaning biases. It will be.

  In the secondary transfer roller cleaning control, switching between the negative polarity cleaning bias and the positive polarity cleaning bias is performed at least once every rotation of the secondary transfer roller 35. Note that the switching timing does not need to completely coincide with the completion timing of one rotation of the secondary transfer roller 35. Switching between the negative polarity cleaning bias and the positive polarity cleaning bias may be performed at an appropriate timing after completion of at least one rotation, for example, every predetermined time. The specified time is preferably longer than the time required for the intermediate transfer belt 21 to make at least one turn. This is because the residual toner on the intermediate transfer belt 21 due to the jam is surely removed by the belt cleaner 24 and the residual toner is prevented from adhering to the secondary transfer roller 35.

  Returning to step S02, if the current activation is not a restart after the jam is cleared and there is no jam history (S02: NO), is the discharge product removal process executed from the detection result of the temperature / humidity sensor 26 or the like? It is determined whether or not (S04). When the discharge product removal process is performed (S04: YES), the main drive motor 28 that is the drive source of the photosensitive drum 1K is driven. Then, since the intermediate transfer belt 21 using the main drive motor 28 as a drive source also rotates by the frequency, the fog toner DT is present at the primary transfer position between the photosensitive drums 1Y-1K and the primary transfer rollers 5Y-5K. (See FIG. 6A.) The fog toner DT moves toward the secondary transfer position 39 by the minute movement of the intermediate transfer belt 21 (see FIGS. 6B and 6C). Therefore, for the purpose of optimizing the time required for cleaning the secondary transfer roller 35 by subtracting the amount of time (driving time T) that the fog toner DT has moved from the predetermined times Tbk and Tcr described later, the main drive motor 28. Is counted and stored (S05), and the process proceeds to step S06. If there is no discharge product removal process (S04: NO), the process proceeds to step S06.

  In step S06, it is determined whether or not the push-up plate 43 is returned to the initial posture from the detection result of the elevation detection sensor 45 or the like. When the push-up plate 43 is returned to the initial position (S06: YES), the main drive motor 28 that is the drive source of the push-up plate drive mechanism is driven. In this case as well, the fog toner DT moves the intermediate transfer belt 21 slightly. It moves toward the secondary transfer position 39 by that amount (see FIGS. 6B and 6C). Therefore, the drive time T of the main drive motor 28 is cumulatively counted and stored (S07), and the process proceeds to step S08. If the push-up plate 43 is in the initial posture (S06: NO), the process proceeds to step S08.

  In step S08, it is determined from the detection result of the TCR sensor 8Y-8K or the like whether or not the TCR adjustment process is executed. When the TCR adjustment process is executed (S08: YES), the main drive motor 28, which is the drive source of the developing devices 4Y-4K, is driven, so that the drive time T is cumulatively counted and stored (S09). The process proceeds to step S10. If there is no TCR adjustment process (S08: NO), the process proceeds to step S10.

  In step S10, it is determined from the detection result of the TCR sensors 8Y-8K or the like whether or not the toner supply process is executed. When the toner replenishment process is executed (S10: YES), the drive time T of the main drive motor 28 that is the drive source of the developing devices 4Y-4K is cumulatively counted and stored (S11), and the process proceeds to step S12. To do. If there is no toner supply process (S10: NO), the process proceeds to step S12.

  In step S12, it is determined whether or not a toner application process for protecting the secondary transfer roller 35 is executed. Here, the toner application process is performed by applying, for example, yellow toner to the secondary transfer roller 35 via the intermediate transfer belt 21 after replacement of the secondary transfer roller 35 or the intermediate transfer belt 21. It is intended to protect. When the toner application process is executed (S12: YES), the drive time T of the main drive motor 28 that is the drive source of the intermediate transfer belt 21 is cumulatively counted and stored (S13), and the process proceeds to step S14. . If there is no toner application process (S12: NO), the process proceeds to step S14. This is the stage “before starting the printing operation”. The discharge product removal process, the initial posture return of the push-up plate 43, the TCR adjustment process, the toner replenishment process, and the toner application process correspond to “preparation operation”.

  In step S14, when a print request is received from an external terminal (not shown) or the like (S14: YES), the presence / absence of a jam history is determined as in step S02 (S15). If there is a jam history (S15: YES), the secondary transfer roller cleaning control has already been executed for a specified time before the start of the printing operation, and it is not necessary to execute the secondary transfer roller cleaning control again. finish. If there is no jam history (S15: NO), then the previous execution mode information stored in the backup memory 112 is acquired (S16), and it is determined whether the previous execution mode is the monochrome mode or the color mode (S17).

  In the monochrome mode (S17: monochrome), the cleaning time TP corresponding to the operation time of the secondary transfer power supply 40 is obtained by subtracting the cumulatively counted driving time T from the preset monochrome predetermined time Tbk. (TP (≧ 0) ← Tbk−T, S18), and the secondary transfer roller cleaning control is executed for the cleaning time TP (S20). In the case of the color mode (S17: Color), a value obtained by subtracting the cumulatively counted driving time T from a preset color default time Tcr is set as the cleaning time TP (TP (≧ 0) ← Tcr -T, S19), the secondary transfer roller cleaning control is executed for the cleaning time TP (S20).

  In the secondary transfer roller cleaning control in step S20, the intermediate transfer belt 21 is driven to rotate by the rotational drive of the main drive motor 28, and the secondary transfer roller 40 is alternately switched between positive and negative cleaning biases from the secondary transfer power source 40. 35 is applied for the cleaning time TP. Thereafter, application of a secondary transfer bias to the secondary transfer roller 35 is started, and a printing operation is executed. The monochrome predetermined time Tbk corresponds to the time until the portion of the intermediate transfer belt 21 that faces the image forming unit 20K corresponding to the single color toner (in this case, black) moves to the secondary transfer position 39. The predetermined color time Tcr corresponds to the time until the portion of the intermediate transfer belt 21 that faces the image forming portion 20Y that is farthest from the secondary transfer roller 35 moves to the secondary transfer position 39. As can be seen from the above description, in the control after step S14, the cleaning time TP of the secondary transfer roller 35 is reduced by subtracting the time T corresponding to the amount of movement of the fog toner DT due to the minute movement of the intermediate transfer belt 21. It is shortened and optimized (see FIGS. 6B and 6C). Note that a time when a print request is received from an external terminal (not shown) or the like (see step S14) corresponds to “at the time of starting the printing operation”.

  According to the above control, whether or not to activate the secondary transfer power supply 40 at the start of the printing operation is selected based on whether or not the printer 10 is restarted after the jam is cleared. The secondary transfer roller 35 can be appropriately cleaned as required by the secondary transfer power supply 40 operation. For this reason, when cleaning of the secondary transfer roller 35 is unnecessary, it is possible to shorten the start-up time of the printing operation, and shorten the FCOT. As a result, the waiting time of the user is shortened, and the printing productivity can be improved.

  Particularly in the first example, when the printer 10 is restarted after the jam is cleared, the secondary transfer power supply 40 is activated before the start of the printing operation and is not activated when the printing operation is started. After startup, the cleaning of the secondary transfer roller 35 is not performed repeatedly, and the start-up time of the printing operation can be shortened.

  Further, when the secondary transfer power supply 40 is activated at the start of the printing operation, the operation time (cleaning time TP) of the secondary transfer power supply 40 is changed according to the previous execution mode, or before the start of the printing operation. Since the cleaning time TP is shortened according to the combination of the presence / absence of a plurality of preparatory operations, the operation time of the secondary transfer power supply 40, in other words, the cleaning time TP of the secondary transfer roller 35 can be optimized according to the startup situation. . For this reason, the cleaning of the secondary transfer roller 35 can be performed reliably and efficiently at the start of the printing operation. In addition, the time for which consumables such as the photosensitive drums 1Y-1K and the intermediate transfer belt 21 are driven wastefully is reduced, which can contribute to extending the life of these consumables.

(4). Second Example of Secondary Transfer Roller Cleaning Control Next, a second example of secondary transfer roller cleaning control by the control unit 14 will be described with reference to FIG. FIG. 5 is a flowchart showing a second example of the secondary transfer roller cleaning control. In the second example, when a print request from an external terminal (not shown) or the like is received, the secondary transfer roller cleaning control is started, and the previous execution mode information stored in the backup memory 112 is acquired (S21). It is determined whether the execution mode is a monochrome mode or a color mode (S22).

  In the monochrome mode (S22: monochrome), measurement of the drive time T of the main drive motor 28 that starts driving upon reception of a print request is started by the timer 111 (S23), and the intermediate transfer belt 21 is detected from the detection result of the AIDC sensor 25. It is determined whether or not there is an unnecessary deposit (S24). If there is no unnecessary deposit (such as fog toner DT) on the intermediate transfer belt 21 (S24: NO), the process proceeds to step S26 described later. If there is an unnecessary deposit (S24: YES), the secondary transfer roller cleaning control is executed at the timing when the unwanted deposit reaches the secondary transfer position 39 (S25). Also in this case, as in the first example, the switching between the negative cleaning bias and the positive cleaning bias is performed at least every rotation of the secondary transfer roller 35. The number of switching is not particularly limited. Next, it is determined whether or not the drive time T of the main drive motor 28 has exceeded a preset monochrome predetermined time Tbk (S26). If the drive time T has not passed the monochrome predetermined time Tbk (S26: NO), the process returns to step S24, and if it has passed (S26: YES), the secondary transfer roller cleaning control is terminated. Thereafter, application of a secondary transfer bias to the secondary transfer roller 35 is started, and a printing operation is executed.

  In the case of the color mode (S22: color), the drive time T of the main drive motor 28 that starts driving upon reception of a print request is started by the timer 111 (S27), and the intermediate transfer belt 21 is detected from the detection result of the AIDC sensor 25. It is determined whether or not there is an unnecessary deposit (S28). If there is no unnecessary deposit on the intermediate transfer belt 21 (S28: NO), the process proceeds to step S30 described later. If there is an unnecessary deposit (S28: YES), the secondary transfer roller cleaning control is executed at the timing when the unwanted deposit reaches the secondary transfer position 39 (S29). Also in this case, switching between the negative polarity cleaning bias and the positive polarity cleaning bias is performed at least every rotation of the secondary transfer roller 35. The number of switching is not particularly limited. Next, it is determined whether or not the drive time T of the main drive motor 28 has passed a preset color predetermined time Tcr (S30). If the drive time T has not passed the color predetermined time Tcr (S30: NO), the process returns to step S28, and if it has passed (S30: YES), the secondary transfer roller cleaning control is terminated. Thereafter, application of a secondary transfer bias to the secondary transfer roller 35 is started, and a printing operation is executed.

  Also in the second example, as in the first example, a time when a print request is received from an external terminal (not shown) or the like corresponds to “at the time of starting the printing operation”. The monochrome default time Tbk and the color default time Tcr are also defined in the same manner as in the first example.

  According to the above control, since the operation of the secondary transfer power supply 40 is controlled based on the detection result of the AIDC sensor 25 as the unnecessary adhering matter detection unit at the time of starting the printing operation, the cleaning timing of the secondary transfer roller 35 is set to an intermediate level. It can be optimized according to the presence or absence of unnecessary deposits on the transfer belt 21. For this reason, the cleaning of the secondary transfer roller 35 can be performed more reliably and efficiently at the start of the printing operation. Further, it can contribute to the extension of the life of consumables such as the photosensitive drums 1Y-1K and the intermediate transfer belt 21. In addition, since the AIDC sensor 25 as the pattern detection means used for the image stabilization process also functions as the unnecessary deposit detection means, the cleaning timing of the secondary transfer roller 35 can be optimized, and the number of parts can be reduced. There is also a merit that the cost can be suppressed by suppressing.

(5). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, a printer has been described as an example of the image forming apparatus. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

1Y-1K photoconductor drum (image carrier)
10 Printer 14 Control unit 20Y-20K Image forming unit 21 Intermediate transfer belt (intermediate transfer member)
28 Main drive motor 35 Secondary transfer roller (secondary transfer body)
40 Secondary transfer power supply (cleaning means)

Claims (4)

An intermediate transfer member to which a toner image formed on the image carrier is transferred; a secondary transfer member that transfers the toner image on the intermediate transfer member to a recording material; and the intermediate transfer member to the secondary transfer member. An image forming apparatus comprising: a cleaning unit that removes the unnecessary extraneous matter brought about; and a control unit that operates the cleaning unit,
A plurality of image forming units arranged along the intermediate transfer member;
The monochrome mode for forming a single color image with a single color toner and the color mode for forming a color image with a plurality of different color toners can be executed.
The control unit selects whether or not to activate the cleaning unit at the start of the printing operation based on whether or not the activation of the image forming apparatus is a restart after the jam is resolved ,
In the case where the cleaning unit is activated at the start of the printing operation,
If the previous execution mode is the color mode, the time required for the portion of the intermediate transfer member facing the image forming portion farthest from the secondary transfer member to move to the secondary transfer position is determined by the cleaning unit. On the other hand, if the previous execution mode is the monochrome mode, the time until the portion of the intermediate transfer member that faces the image forming unit corresponding to the monochrome toner moves to the secondary transfer position is set as the operation time. , The operating time of the cleaning means,
Image forming apparatus. The control unit shortens the operation time of the cleaning unit according to a combination of presence / absence of a plurality of preparatory operations before starting the printing operation when the cleaning unit is activated at the start of the printing operation.
The image forming apparatus according to claim 1 . An intermediate transfer member to which a toner image formed on an image carrier is transferred, a secondary transfer member that transfers the toner image on the intermediate transfer member to a recording material, and unnecessary deposits on the intermediate transfer member are detected. An image forming apparatus comprising: an unnecessary adhering matter detecting unit that performs cleaning, a cleaning unit that removes the unnecessary adhering matter brought from the intermediate transfer member to the secondary transfer member, and a control unit that operates the cleaning unit. Because
The control unit controls the operation of the cleaning unit based on the detection result of the unnecessary adhering matter detection unit when starting up a printing operation.
Image forming apparatus. The unnecessary deposit detection means also serves as a pattern detection means for detecting a reference pattern of each color on the intermediate transfer member.
The image forming apparatus according to claim 3 .

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