Image forming apparatus

Abstract

The image forming apparatus includes an image bearing member, a belt, an outer roller, an inner roller, a tension roller, a transport roller pair, a guide member including a convex portion, a belt driving motor configured to drive the belt, a torque sensor configured to detect a torque of the belt driving motor, and a control unit, and a control unit configured to execute conveyance control for controlling a rotation speed of the conveyance roller pair based on a detection result of the torque sensor after the sheet has reached the transfer nip portion such that a first conveyance speed of the sheet conveyed by the transfer nip portion becomes faster than a second conveyance speed of the sheet conveyed by the conveyance roller pair.

Description

Technical Field

[0001] This disclosure relates to an imaging apparatus for forming an image on a sheet. Background Technology

[0002] Typically, imaging equipment transfers a toner image formed on an intermediate transfer belt or photosensitive drum onto a sheet at a transfer section, and then fixes the toner image to the sheet by applying heat and pressure. A registration roller pair is positioned upstream of the transfer section, and the sheet is positioned straddling both the transfer section and the registration roller pair. It is generally known that if the sheet is positioned straddling the two rollers, the sheet is pulled or pushed by the registration roller pair due to slight differences in the rotational speeds of the rollers. As a result, the sheet's posture at the upstream position of the transfer section may become unstable, which can lead to image defects. For example, the speed at which the sheet is conveyed by the registration roller pair and from the transfer section may vary due to tolerances in the outer diameter of the registration roller pair.

[0003] Therefore, Japanese Patent Application Publication No. 2011-081347 discloses an imaging device in which a set torque of the secondary transfer roller is stored in a memory when the sheet is transported solely by the transfer section. The imaging device obtains the torque deviation by subtracting the measured torque of the secondary transfer roller when the sheet is transported by both the registration roller pair and the transfer section from the set torque, and controls the rotational speed of the registration roller pair to make the torque deviation zero. Thus, the proposed imaging device attempts to suppress pulling or pushing of the sheet by the registration roller pair.

[0004] However, especially when using sheets with low stiffness, the speed difference between the sheet's transport in the transfer section and the registration roller pair can affect the sheet's posture. However, when the sheet is being pushed into the transfer section, this speed difference is less likely to cause a change in the driving torque of the secondary transfer rollers. This is because a loop forms on the sheet when it is pushed into the transfer section. Therefore, even when the rotational speed of the registration roller pair is controlled to make the torque deviation zero, as taught in Japanese Patent Application Publication No. 2011-081347, the sheet's posture may not be sufficiently stabilized, especially when the sheet has low stiffness. Summary of the Invention

[0005] According to a first aspect of this disclosure, an imaging apparatus includes: an image carrier member configured to carry a toner image; a belt on which the toner image is transferred from the image carrier member to the belt as the belt rotates in a rotational direction; an outer roller configured to contact an outer peripheral surface of the belt; an inner roller arranged opposite the outer roller and with the belt between the inner and outer rollers, the inner roller configured to contact an inner peripheral surface of the belt and form a transfer clamping portion with the outer roller; a tension roller configured to contact an inner peripheral surface of the belt and disposed upstream of the inner roller in the rotational direction; a pair of conveyor rollers configured to convey a sheet toward the transfer clamping portion; and a guide member configured to guide the sheet conveyed by the pair of conveyor rollers. The sheet is guided toward the transfer clamping portion, the guiding member including a protrusion projecting toward the outer peripheral surface of the belt and disposed between an imaginary line passing through the clamping portion of the conveyor roller pair and the transfer clamping portion and an imaginary line extending along the outer peripheral surface of the belt stretched between the tension roller and the inner roller; a belt drive motor configured to drive the belt; a torque sensor configured to detect the torque of the belt drive motor; and a control unit configured to perform conveying control based on the detection result of the torque sensor after the sheet has reached the transfer clamping portion, the conveying control controlling the rotational speed of the conveyor roller pair such that a first conveying speed of the sheet conveyed by the transfer clamping portion becomes faster than a second conveying speed of the sheet conveyed by the conveyor roller pair.

[0006] According to a second aspect of this disclosure, an imaging apparatus includes: an image carrier member configured to carry a toner image; a belt on which the toner image is transferred from the image carrier member to the belt as the belt rotates in a rotational direction; an outer roller configured to contact an outer peripheral surface of the belt; an inner roller arranged opposite the outer roller and with the belt between the inner and outer rollers, the inner roller configured to contact an inner peripheral surface of the belt and form a transfer clamping portion with the outer roller; a tension roller configured to contact an inner peripheral surface of the belt and disposed upstream of the inner roller in the rotational direction; a pair of conveyor rollers configured to convey a sheet toward the transfer clamping portion; and a guide member configured to guide the sheet conveyed by the pair of conveyor rollers. The sheet is guided toward the transfer clamping portion. The guiding member includes a protrusion that projects toward the outer peripheral surface of the belt and is arranged between an imaginary line passing through the clamping portion of the conveyor roller pair and the transfer clamping portion and an imaginary line extending along the outer peripheral surface of the belt stretched between the tension roller and the inner roller; a belt drive motor configured to drive the belt; a torque sensor configured to detect the torque of the belt drive motor; and a control unit configured to perform conveying control, which controls the rotational speed of the conveyor roller pair such that the torque detected by the torque sensor when the sheet is clamped by the conveyor roller pair and the transfer clamping portion becomes greater than the torque detected by the torque sensor when the sheet is clamped and conveyed only by the transfer clamping portion.

[0007] The features of this disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of the embodiments is by way of example. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the overall cross-sectional structure of the imaging device.

[0009] Figure 2 This is a schematic diagram of the peripheral structure of the transfer clamping part.

[0010] Figure 3 This is a block diagram of the control block of the control unit located in the imaging device.

[0011] Figure 4 It is a graph showing the torque fluctuations of a driven motor.

[0012] Figure 5A This is a schematic diagram of the sheet's behavior.

[0013] Figure 5B yes Figure 5A Enlarged image.

[0014] Figure 6 This is a flowchart of the printing control process.

[0015] Figure 7 This is a flowchart of the printing control process.

[0016] Figure 8A This is a schematic diagram of the guide component based on the modified example.

[0017] Figure 8B It is based on the modified example. Figure 8A Enlarged image. Detailed Implementation

[0018] Overall structure

[0019] Figure 1 This is an overall schematic diagram of the cross-sectional structure of the imaging device 100 according to this embodiment. The imaging device 100 includes an imaging unit 140 for forming an image on a sheet P used as a recording material, a sheet feeding unit 117, a fixing unit 150, a sheet ejection device 200, and an image reading device 102. Furthermore, the imaging device 100 includes a device body 101, which is a housing that houses the imaging unit 140.

[0020] An imaging device is a device that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from a document, and includes printers, copiers, fax machines, and multifunction devices. Furthermore, in addition to the main body having imaging capabilities, an imaging device may also have auxiliary devices connected to it (e.g., optional feeders, image reading devices, or sheet handling devices), and in this case, the entire system including the connected auxiliary devices is identified as an imaging device.

[0021] Imaging unit 140 is an intermediate transfer tandem electrophotographic unit, wherein imaging stations Y, M, C and Bk for forming toner images of four colors are arranged along intermediate transfer belt 145.

[0022] Sheet P is housed in a box 116 located at the lower part of the device body 101, and the sheets are fed one by one by a sheet feeding unit 117. The sheet feeding unit 117 includes, for example, a feed roller for feeding the sheet P, and a separation roller, which is arranged in contact with the feed roller and separates the sheet P fed by the feed roller from other sheets P by applying a frictional force to the sheet P. Various types of sheets with different sizes and materials can be used as sheet P for recording materials, such as paper (including plain paper and thick paper), plastic film, cloth, surface-treated sheet materials (e.g., coated paper), and sheet materials with special shapes (e.g., envelopes and index paper).

[0023] The sheet P fed by the sheet feeding unit 117 is conveyed from the pre-registration roller pair 110 to the registration roller pair 120. Then, the skew of the sheet P is corrected by the registration roller pair 120, which serves as the transport roller pair, and the sheet P is conveyed toward the transfer clamping part 130 at a timing synchronized with the toner image forming process performed by the imaging unit 140.

[0024] Imaging unit 140 includes an intermediate transfer belt 145 on which a toner image is transferred from a photosensitive drum 141, and an outer peripheral surface 145b (see reference) serving as a junction between the intermediate transfer belt 141 and the photosensitive drum 141. Figure 2 The imaging unit 140 includes a secondary transfer outer roller 132 that contacts the outer roller of the secondary transfer outer roller 132. Furthermore, the imaging unit 140 includes a drive roller 131 arranged to face the secondary transfer outer roller 132 with an intermediate transfer belt 145 interposed therebetween, contacting the inner circumferential surface 145c of the intermediate transfer belt 145, and forming a transfer clamping portion 130 together with the secondary transfer outer roller 132. The transfer clamping portion 130 clamps and transports the sheet. Additionally, the imaging unit 140 includes a tension roller 147 that contacts the inner circumferential surface 145c of the intermediate transfer belt 145 (see reference). Figure 2 It contacts and is arranged upstream of drive roller 131 in the direction of arrow A.

[0025] The intermediate transfer belt 145 is wound around the drive roller 131, tension roller 146, multiple primary inner rollers 144, and tension roller 147, and stretched with a predetermined tension. By driving the drive roller 131, the intermediate transfer belt 145 rotates in the direction of arrow A. Thus, the intermediate transfer belt 145 forms a belt inclined surface 145a, which is located between the tension roller 147 and the drive roller 131 in the direction of arrow A, and guides the sheet P toward the transfer clamping portion 130. The belt inclined surface 145a is part of the outer peripheral surface 145b. The tension roller 147 is located upstream of the drive roller 131 in the direction of arrow A.

[0026] In parallel with the transport process described above, which transports the sheet P to the transfer clamping unit 130, the imaging unit 140 performs a toner image forming process. The imaging stations Y, M, C, and Bk of the imaging unit 140 each include a photosensitive drum 141 serving as a drum-shaped image carrier (i.e., an electrophotographic photosensitive component), a charging unit such as a charging roller, and a developing unit 143 serving as a developing unit. The imaging unit 140 also includes an exposure unit 142 arranged below the four photosensitive drums 141. In the toner image forming process, the charging unit uniformly charges the surface of the photosensitive drums 141, and the exposure unit 142 exposes the photosensitive drums 141 based on a signal corresponding to the image information of the image to be formed, thereby forming an electrostatic latent image on the surface of the photosensitive drums 141. The electrostatic latent image is developed by toner supplied from the developing unit 143, forming a monochrome toner image. Thus, four colors (yellow, magenta, cyan, and black) of toner images are formed on the surfaces of the four photosensitive drums 141.

[0027] The intermediate transfer belt 145, used as a belt, is driven along... Figure 1 The image rotates in the direction indicated by arrow A. The toner image carried on the four photosensitive drums 141 is sequentially transferred, one at a time, by the inner rollers 144 in a stacked manner, onto the intermediate transfer belt 145. As a result, a full-color toner image is formed on the intermediate transfer belt 145, which is then conveyed to the transfer clamping section 130. By applying pressure and a transfer bias at the transfer clamping section 130, the toner image is transferred a second time from the intermediate transfer belt 145 onto the sheet P. During the second transfer of the toner image onto the sheet P, a secondary transfer voltage is applied from a high-voltage power supply to either the drive roller 131 or the secondary transfer outer roller 132.

[0028] The sheet P, which has passed through the transfer clamping section 130, is conveyed to the fixing unit 150. The fixing unit 150 includes a fixing roller 155 in which a heater is disposed, and a pressure roller 156 that contacts the fixing roller 155 with a predetermined pressing force. The fixing roller 155 is powered by a fixing motor 154 (see below). Figure 3 The fixing unit 150 is driven to rotate, and the pressure roller 156 follows the fixing roller 155. While the fixing unit 150 clamps and transports the sheet P through the fixing clamping part 157, which is formed by the fixing roller 155 and the pressure roller 156 and serves as the fixing section, it applies pressure and heat to the toner image on the sheet P. As a result, the toner melts and solidifies after passing through the fixing clamping part, thereby obtaining an image fixed onto the sheet P.

[0029] The sheet P, having passed through the fixing unit 150, is guided by the first guide member 151 to either the first sheet discharge channel 230 leading to the first sheet discharge roller pair 160 or the second sheet discharge channel 240 leading to the second sheet discharge roller pair 161. When images are formed on both sides of the sheet P, the sheet P with the image formed on the first side is guided by the first guide member 151 toward the second sheet discharge roller pair 161 and conveyed to the outside of the equipment by the second sheet discharge roller pair 161. When the trailing edge of the sheet P in the conveying direction passes the second guide member 152, the second sheet discharge roller pair 161 reverses the conveying direction of the sheet P and feeds the sheet P into the double-sided conveying path 180. During the reversal operation performed by the second sheet discharge roller pair 161, the portion of the sheet P protruding outside the equipment body 101 is supported by the second sheet discharge tray 171. The sheet P, which has arrived again at the registration roller pair 120 via the double-sided transport path 180, forms an image on the second surface after skew correction and timing correction, by passing through the transfer clamping part 130 and the fixing unit 150.

[0030] A sheet discharge device 200 for discharging sheet P to the outside of the equipment (i.e., the outside of the equipment body 101) is arranged downstream of the fixing unit 150 in the sheet conveying direction. The sheet discharge device 200 includes a first sheet discharge roller pair 160, a second sheet discharge roller pair 161, a first sheet discharge tray 170, and a second sheet discharge tray 171.

[0031] When sheet P is discharged, the sheet P delivered from the fixing unit 150 is guided by the first guide member 151 to the first sheet discharge roller pair 160, and discharged by the first sheet discharge roller pair 160 to the outside of the equipment body 101. The first sheet discharge tray 170 is arranged on the upper part of the equipment body 101, and the sheet P discharged by the first sheet discharge roller pair 160 is supported or stacked on the first sheet discharge tray 170. The sheet P supported on the first sheet discharge tray 170 or the second sheet discharge tray 171 slides on the inclined surface of the first sheet discharge tray 170 or the second sheet discharge tray 171 by its own weight, and is aligned by bringing the trailing edge of the sheet against the alignment surface of the equipment body 101.

[0032] Imaging device 100 includes an image reading device 102 disposed on the upper part of device body 101. Image reading device 102 includes a platen glass on which documents are placed, and an image sensor that reads images from the documents through the platen glass. Furthermore, image reading device 102 includes an automatic document feeder that feeds documents placed on a document tray one at a time for image sensor to read images. According to this embodiment, imaging device 100 employs a so-called in-body sheet discharge configuration, wherein an in-body sheet discharge space 190 of sheet P is arranged vertically between imaging unit 140 and image reading device 102. The advantage of the in-body sheet discharge configuration is that, compared to an arrangement where the first sheet discharge tray 170 is disposed on the side of device body 101 and the sheet discharge space is disposed on the side of device body 101, the area occupied by imaging device 100 when viewed from above can be smaller.

[0033] Furthermore, the imaging unit 140 described above is an example of an imaging unit, and a direct transfer type electrophotographic unit can be used to transfer a toner image formed on a photosensitive element to a sheet without inserting an intermediate transfer body. Additionally, the sheet P can be fed from a multi-purpose tray 113 arranged in an openable / closable manner on the side surface of the device body 101. The sheet P supported on the multi-purpose tray 113 is conveyed by a pair of transport rollers 114 to a pair of traction rollers 115. The sheet P is then conveyed by the traction rollers 115 to a pair of registration rollers 120, where a toner image is formed as described above.

[0034] Peripheral structure of the transfer clamp

[0035] Next, we will refer to Figure 2 The peripheral structure of the transfer clamping part 130 is described in more detail. Figure 2 This is a schematic diagram of the peripheral structure of the transfer clamping part 130. (See diagram below.) Figure 2 As shown, a pre-registration sensor 111 is arranged between the pre-registration roller pair and the registration roller pair 120. By bringing the leading edge of the sheet P conveyed by the pre-registration roller pair 110 against and aligning it with the clamping portion of the registration roller pair 120 in a stopped state, the skewness of the sheet P is corrected. Based on the timing of the pre-registration sensor 111 detecting the leading edge of the sheet P, the registration roller pair 120 is driven at a timing that matches the transfer of the toner image onto the sheet.

[0036] A guide member 301 is provided between the registration roller pair 120 and the transfer clamping part 130 to guide the sheet P conveyed by the registration roller pair 120 toward the transfer clamping part 130. The guide member 301 includes a protrusion 301a protruding toward the belt inclined surface 145a of the intermediate transfer belt 145. The protrusion 301a is provided in the region AR between virtual lines L1 and L2. Virtual line L1 passes through the clamping part 120a and the transfer clamping part 130 of the registration roller pair 120, and virtual line L2 extends along the belt inclined surface 145a. Virtual line L2 is also the common tangent of the drive roller 131 and the secondary transfer outer roller 132 at the transfer clamping part 130.

[0037] The guide member 301 is arranged on the side opposite to the drive roller 131, i.e., the non-imaging surface side, relative to the virtual line L2. As described below, the sheet P held by the transfer clamp 130 and the registration roller pair 120 is conveyed to move in a sliding motion relative to the protrusion 301a of the guide member 301. Therefore, the guide member 301 serves as a conveying load when conveying the sheet P. Furthermore, a fixing ring sensor 153 that detects the deflection amount (hereinafter also referred to as the ring) of the sheet P is arranged between the transfer clamp 130 and the fixing unit 150.

[0038] control block

[0039] Figure 3 This is a block diagram showing the control block of the control unit 210 disposed in the imaging device 100. (Example) Figure 3 As shown, the control unit 210 includes a CPU 211, a memory 212, and an interface unit 213.

[0040] The central processing unit (CPU) 211 is the element that performs arithmetic processing. The memory 212 includes read-only memory (ROM) and random access memory (RAM). RAM stores information input to the control unit 210, information detected by various sensors, and arithmetic results. ROM stores pre-acquired data and control programs. The CPU 211 and memory 212 can transfer and retrieve data from each other. The interface unit (I / F) 213 controls the signal input / output between the control unit 210 and devices connected to the control unit 210.

[0041] Various units of the imaging device 100 (such as the imaging unit 140, the intermediate transfer belt 145, and the drive devices for components related to the transport of the sheet P, as well as various power supplies) are connected to the control unit 210. For example, various high-voltage power supplies (such as charging voltage, developing voltage, primary transfer voltage, and secondary transfer voltage, not shown) with drive motor 133 are connected to the control unit 210. In addition, signals indicating the detection results (i.e., output values) of the current values ​​of various drive motors are input to the control unit 210 and stored in the memory 212.

[0042] Furthermore, the pre-registration drive motor 112, the registration drive motor 121, and the fixing motor 154 are connected to the control unit 210. The pre-registration drive motor 112 drives the pre-registration roller pair 110. The registration drive motor 121, acting as a transport motor, drives the registration roller pair 120. The fixing motor 154 drives the fixing roller 155. Additionally, the pre-registration roller pair 110 and the registration roller pair 120 each include a drive roller and a driven roller that rotates in response to the rotation of the drive roller, and the drive rollers are each driven by the pre-registration drive motor 112 and the registration drive motor 121. The pressure roller 156 of the fixing unit 150 rotates in response to the rotation of the fixing roller 155. Alternatively, the fixing motor 154 can be configured to drive the pressure roller 156, and the fixing roller 155 can rotate in response to the rotation of the pressure roller.

[0043] The drive motor 133 drives the drive roller 131 so that the intermediate transfer belt 145 moves in the direction of arrow A. Figure 1 The drive motor 133 rotates. Furthermore, the drive motor 133 includes a torque sensor 134 capable of continuously detecting the drive load (i.e., torque) of the drive motor 133 at arbitrary time intervals. In this embodiment, a current detection unit that detects the current flowing through the drive motor 133 is used as an example of the torque sensor 134. The torque fluctuation information of the drive motor 133 collected by the torque sensor 134 is stored in the memory 212.

[0044] The operation unit 220 is connected to the control unit 210. The operation unit 220 includes a display unit (such as a display panel) for displaying information and an input unit for inputting information into the control unit 210 through operations performed by an operator (such as a user or service personnel). The operation unit 220 may consist of a touch panel that functions as both a display unit and an input unit. Furthermore, the image reading device 102 or an external device (such as a personal computer) connected to the imaging device 100 may be connected to the control unit 210.

[0045] The control unit 210 controls various units of the imaging device 100 to form an image based on the job information. The job information, in addition to information about the sheet feeder, start commands (i.e., start signals), and image information input from the operation unit 220 or external devices, may also include information related to the printing operation, such as the properties of the sheet P, i.e., command signals. The information related to the properties of the sheet P (hereinafter referred to as "sheet-related information") includes any information used to identify the sheet, such as sheet type (including plain paper, high-quality paper, glossy paper, coated paper, and embossed paper, i.e., so-called paper type categories), numerical values ​​or ranges of values ​​such as basis weight, thickness, and dimensions, and brand names such as manufacturer names or product numbers.

[0046] According to this embodiment, information related to the properties of sheet P may include information related to the stiffness of sheet P, such as the basis weight information of sheet P. When information related to printing operation conditions is input from the operation unit 220, the operation unit 220 is used to input information related to the basis weight of the sheet P to which the toner image is to be transferred to the input unit of the control unit 210. Furthermore, when information related to printing operation conditions is input from an external device such as a personal computer, the interface unit 213 is used to input information related to the basis weight of the sheet P to which the toner image is to be transferred to the input unit of the control unit 210.

[0047] Imaging device 100 executes a job (i.e., a printing job) initiated based on a start command. This job is a series of operations related to forming an image on one or more sheets P and outputting it. The job typically includes imaging processing (i.e., printing and imaging operations), pre-rotation processing, sheet spacing processing in the case of forming images on multiple sheets P, and post-rotation processing. Imaging processing is the process of forming an electrostatic latent image of the image to be actually formed and output on the sheet P, forming a toner image, and performing primary and secondary transfers of the toner image; the term "during imaging" refers to this processing interval. Pre-rotation processing is the process of performing preparatory operations before imaging processing, from the input of the start command until the actual start of image formation. Sheet spacing processing is the process corresponding to the interval between sheet P and subsequent sheets P in the case of continuously imaging multiple sheets P (i.e., during continuous imaging). Post-rotation processing is the process of performing preparatory operations (i.e., preparation operations) after imaging processing. The non-imaging timing (i.e., the non-imaging interval) is the interval other than the formation of an image, and includes pre-rotation processing, sheet spacing processing, post-rotation processing, and multiple pre-rotation processing, which is a preparation process when the imaging device 100 is powered on or when it resumes from a dormant state.

[0048] The sleep state (i.e., the dormant state) is a state in which the power supply to all parts of the imaging device 100, except for the control unit 210 or a portion thereof, is stopped and power consumption is reduced compared to the standby state. According to this embodiment, the current value of the drive motor 133 is always stored during imaging processing. The current value is stored in the memory 212 as torque fluctuation data, i.e., as fluctuation data of the torque Tq of the drive motor 133.

[0049] Torque fluctuation with drive motor

[0050] Next, we will refer to Figure 4 This describes the torque fluctuations detected by the torque sensor 134, which drives the motor 133. Figure 4 This is a graph showing the torque fluctuation of the drive motor 133. The times t1 to t5 described below are calculated based on the time t0 when the sheet P arrives at the transfer clamping part 130, the distance between each roller, the length of the sheet P in the conveying direction, and the rotational speed of each roller.

[0051] like Figure 4As shown, the belt drive motor 133 experiences torque fluctuations due to the load fluctuations from the sheet P passing through the transfer clamping section 130 and the load fluctuations from the intermediate transfer belt 145 and the drive roller 131. The torque Tq of the belt drive motor 133 varies depending on which section of the transport path the sheet P is passing through. According to this embodiment, time t0 to time t2 is referred to as section A, and time t2 to time t4 is referred to as section B. Section A is the section from when the leading edge of the sheet P reaches the transfer clamping section 130 (i.e., time t0) to when it reaches the fixing clamping section 157 (i.e., time t2). Section B is the section from when the leading edge of the sheet P reaches the fixing clamping section 157 (i.e., time t2) to when the trailing edge of the sheet P reaches the clamping section of the registration front roller pair 110 (i.e., time t4). In interval B, after time t3 when the leading edge of sheet P reaches the fixing ring sensor 153, control unit 210 controls fixing motor 154 to perform ring control for controlling the amount of circulation of sheet P between transfer clamping part 130 and fixing clamping part 157.

[0052] Figure 4 Starting from the top paragraph, the rotational speed of the fuser motor 154, the transport period of the sheet P by the registration pre-roller pair 110, the transport period of the sheet P by the registration roller pair 120, the transport period of the sheet P by the transfer clamp 130, the transport period of the sheet P by the fuser roller 155, and the torque fluctuation of the drive motor 133 are shown in the order of naming.

[0053] exist Figure 4 In this context, the fixed torque value at time (t0-Δt) (which is Δt earlier than time t0, i.e., before the leading edge of the sheet P reaches the transfer clamping part 130) is called the idle torque value Tq_ST. In other words, the idle torque value Tq_ST is the drive load (i.e., torque) when the sheet P is not clamped by the transfer clamping part 130 and the belt drive motor 133 is driven.

[0054] After the leading edge of the sheet P reaches the transfer clamping section 130 at time t0, the torque Tq shifts at a value lower than the idle torque value Tq_ST during interval A. This is because, by feeding the sheet P to the transfer clamping section 130, the conveying force from the registration roller pair 120 is added to the belt drive motor 133 as the torque driving the intermediate transfer belt 145, and the torque Tq decreases accordingly.

[0055] In interval B following interval A, the conveying resistance increases as the leading edge of sheet P reaches the fixing clamp 157, and conveying sheet P requires greater torque. Therefore, the torque Tq of the drive motor 133 increases and moves by a value that is approximately greater than the idle torque value Tq_ST.

[0056] Then, when the trailing edge of sheet P passes the registration front roller pair 110 at time t4, it loses the conveying force applied by the registration front roller pair 110 that conveys sheet P, causing the torque Tq of the drive motor 133 to increase. Next, the trailing edge of sheet P passes sequentially through the protrusion 301a of guide member 301 (see reference). Figure 2 The registration roller pair 120, i.e., time t5, and the torque Tq increases. Thereafter, at time t6 when the trailing edge of the sheet P passes through the transfer clamping part 130, the torque Tq of the drive motor 133 takes a fixed idle torque value Tq_ST'.

[0057] As described above, fluctuations in the torque Tq of the drive motor 133 occur when the leading edge of the sheet P reaches the clamping portion of each roller pair along the conveying path, and when the trailing edge of the sheet P passes through the clamping portion of each roller pair. Furthermore, the torque Tq typically varies depending on the properties of the conveyed sheet P (e.g., weight or stiffness). By subtracting the idle torque value Tq_ST from the torque Tq of the drive motor 133, forces other than those caused by the sheet P (e.g., the sliding load on the rollers) can be eliminated, and in the following description, this torque is referred to as the sheet conveying torque Tq_p. In other words, the sheet conveying torque Tq_p is the value obtained by subtracting the idle torque value Tq_ST from the torque Tq.

[0058] The sheet behavior before the transfer clamping section

[0059] Next, we will refer to Figure 5A and Figure 5B Describe the behavior of sheet P before it reaches the transfer clamping section 130. Figure 5A This is a schematic diagram illustrating the behavior of sheet P. Figure 5B yes Figure 5A An enlarged image. For example... Figure 5A As shown, the guide member 301 is arranged between the registration roller pair 120 and the transfer clamping part 130, and serves as the transport load during the transport of the sheet P by causing the sheet P to move relative to the guide member 301 in a sliding motion. The sheet P is transported while being guided by the guide member 301 to form a loop and approach the intermediate transfer belt 145.

[0060] For example, if the outer diameter of the registration roller pair 120 is equal to the nominal size (i.e., the design size value), the sheet P conveyed across the registration roller pair 120 and the transfer clamping part 130 is conveyed in posture P1. However, if the outer diameter of the registration roller pair 120 is smaller than the nominal size, the sheet P is conveyed in posture P2 when the registration roller pair 120 rotates at the nominal speed. The circulation of the sheet P is smaller in posture P2 than in posture P1. This is because the conveying speed of the sheet P through the registration roller pair 120 is reduced due to the smaller outer diameter of the registration roller pair 120 than the nominal size.

[0061] Furthermore, if the outer diameter of the registration roller pair 120 is larger than the nominal size, then when the registration roller pair 120 rotates at the nominal speed, the sheet P is conveyed in posture P3. The circulation of the sheet P is greater in posture P3 than in posture P1. This is because the conveying speed of the sheet P through the registration roller pair 120 is increased due to the outer diameter of the registration roller pair 120 being larger than the nominal size.

[0062] In this state, the distance between the sheet P and the inclined surface 145a of the intermediate transfer belt 145 in sliding contact is called the distance X, such as... Figure 5B As shown, when the sheet P is in postures P1, P2, and P3, the distances X will be X1, X2, and X3, respectively. Distance X2 is shorter than distance X1, and distance X3 is longer than distance X2.

[0063] According to this embodiment, the appropriate distance X is equal to or greater than distance X2 and equal to or less than distance X3. If distance X is less than distance X2, the sheet P may not be aligned along the inclined surface 145a. Consequently, the load on the secondary transfer power supply that applies the secondary transfer voltage to the secondary transfer outer roller 132 will decrease, potentially causing the secondary transfer voltage to increase above the assumed value. If the secondary transfer voltage increases above the assumed value, image defects such as image degradation may occur, for example, due to abnormal discharge to the sheet P. Simultaneously, if distance X becomes greater than distance X3, the sheet P may slide beyond what is necessary relative to the inclined surface 145a, and image defects such as image rubbing may occur.

[0064] In the following description, when the sheet conveying speed of the registration roller pair 120 is slower than that of the transfer clamping section 130, it is assumed that the sheet P is in a pulled state. Furthermore, when the sheet conveying speed of the registration roller pair 120 is faster than that of the transfer clamping section 130, it is assumed that the sheet P is in a pushed state. Generally, if the sheet P is in a pulled state, the conveying resistance of the sheet P increases, causing the sheet conveying torque Tq_p to increase. Simultaneously, if the sheet P is in a pushed state, the conveying force from the registration roller pair 120 is added as torque to the belt drive motor 133 to drive the intermediate transfer belt 145, causing the sheet conveying torque Tq_p to decrease.

[0065] Compared to sheets with low stiffness, sheets with high stiffness (e.g., thick paper) experience greater reaction forces to the conveying forces received from the registration roller pair 120 and the transfer clamping section 130, as well as greater reaction forces when rings are formed on the sheet. Therefore, even if the conveying speed of the sheet P transported by the registration roller pair 120 changes from the nominal conveying speed due to tolerances in the outer diameter of the registration roller pair 120, the sheet with high stiffness does not easily change its orientation, and the fluctuation range of distance X is small. In other words, the sensitivity of the sheet conveying torque Tq_p to the difference in conveying speed between the registration roller pair 120 and the transfer clamping section 130 remains unchanged regardless of whether the sheet is in a pulled or pushed state.

[0066] Meanwhile, when the sheet has low rigidity (e.g., thin paper), the sheet posture may easily change due to the tolerance of the outer diameter of the registration roller pair 120. Furthermore, especially when the sheet is in a pushed state, the sensitivity of the sheet transport torque Tq_p to the difference in transport speed between the registration roller pair 120 and the transfer clamping section 130 will be low. This is because a ring is formed on the sheet by pressing it with the registration roller pair 120, and the transport force of the registration roller pair 120 transporting the sheet is transmitted to the belt drive motor 133 in a damped state.

[0067] Therefore, in sheets with relatively low stiffness, the distance X must fall within a fixed range to avoid causing image defects. The ideal range for distance X is determined by factors such as the material of the intermediate transfer belt 145 or the voltage applied to the sheet.

[0068] Therefore, according to this embodiment, the control unit 210 executes... Figure 6 The conveying control shown ensures that the posture of the upstream of the transfer clamp 130 is stable within a range that does not result in image defects, even for sheets with low rigidity.

[0069] Registration speed control

[0070] Next, we will refer to Figure 6 and Figure 7 The description includes a registration speed control used for conveying control, which controls the rotational speed of the registration roller pair 120 via a control unit 210. Figure 6 and Figure 7 Each is a flowchart illustrating a print control system including registration speed control. According to this embodiment, the registration speed is controlled at... Figure 4 The process is performed within the interval B shown, from time t0 to time t4, but the technique is not limited thereto. In other words, it is preferable to perform registration speed control for at least a portion of the time period from time t0 when the leading edge of the sheet P reaches the transfer clamping part 130 to time t4 when the trailing edge of the sheet P passes through the registration front roller 110.

[0071] The following description illustrates an example of an operator instructing the imaging device 100 to perform a print job from the operation unit 220. Figure 6 and Figure 7 The diagram shows the print control that focuses on registration speed control according to this embodiment, and omits many other operations that are typically required to perform the job and output the image.

[0072] like Figure 6 As shown, the operator inputs information such as the size and weight of the sheet P to be used through the operation unit 220 of the imaging device 100 (S1). The operator then executes a printing job from the operation unit 220 (S2). The job information sent to the control unit 210 includes information related to the properties of the sheet P. According to this embodiment, the information related to the properties of the sheet P includes at least the weight and size information of the sheet P.

[0073] When a print job is executed, the control unit 210 retrieves from memory 212 the registration speed correction value v1(n-1) up to the sheet preceding the sheet that serves as the registration speed control target, and the target torque T, which will be described later. Loop (S3). The sheet used as the registration speed control target is the nth sheet, and the sheet that precedes the nth sheet is the (n-1)th sheet. Memory 212 stores information related to the sheet properties and the corresponding target torque T. Loop The table. Furthermore, the control unit 210 sets pre-determined printing operation conditions for each property of the sheet P.

[0074] Next, after the skewness of sheet P has been corrected by the registration roller pair 120, the control unit 210 begins to rotate the registration roller pair 120 (S4). In this state, the time is... Figure 4 The time t1 is recorded, and the registration roller pair 120 rotates at a speed V1 + v1(n-1). The speed V1 is the nominal rotational speed of the registration roller pair 120.

[0075] Next, the control unit 210 drives the drive motor 133, causing the intermediate transfer belt 145 to move at a speed VPS (S5). Furthermore, the control unit 210 begins to acquire the torque Tq of the drive motor 133 via the torque sensor 134 (S6).

[0076] Next, the control unit 210 determines whether time t0-Δt has been reached (S7). If it is determined that time t0-Δt has been reached (S7: Yes), the control unit 210 acquires the idle torque value Tq_ST (S8) when the sheet P is not held by the transfer clamping part 130. Then, at time t0, the sheet P reaches the transfer clamping part 130 (S9).

[0077] Next, as Figure 7As shown, the control unit 210 determines whether time t2 has been reached (S10). At time t2, the leading edge of the sheet P reaches the fixing clamp 157. When it is determined that time t2 has been reached (S10: Yes), the control unit 210 performs registration speed control, wherein the target torque T, which was invoked in step S3, is used as the reference. Loop The idling torque value Tq_ST obtained in step S8 and the torque Tq obtained in step S11 are used to control the registration speed, which is the rotational speed of the registration roller pair 120.

[0078] First, the sheet transport torque Tq_p is obtained based on the idle torque value Tq_ST and the torque Tq detected by the torque sensor 134. The sheet transport torque Tq_p, used as the transport torque, is obtained by subtracting the idle torque value Tq_ST from the torque Tq. Torque Tq is the first torque used to drive the drive motor 133 when the sheet is held by the transfer clamping part 130. The idle torque value Tq_ST is the second torque used to drive the drive motor 133 when the sheet is not held by the transfer clamping part 130.

[0079] The target torque T will be described below. Loop Target torque T Loop The registration speed is controlled according to this embodiment. Figure 4 The ideal value of the sheet conveying torque Tq_p in section B. Target torque T Loop This is a positive value that keeps the sheet P in a stretched state between the registration roller pair 120 and the transfer clamping part 130. In other words, the target torque is the torque of the drive motor 133 set so that the conveying speed of the sheet transported by the transfer clamping part 130 (i.e., the first conveying speed) is faster than the conveying speed of the sheet transported by the registration roller pair 120 (i.e., the second conveying speed). However, the target torque T Loop The set value allows the sheet P to be in a moderately stretched state that will not cause damage to the sheet P, and this value can be set to different values ​​depending on the type and size of the sheet.

[0080] Then, the control unit 210 determines whether the sheet conveying torque Tq_p is greater than the target torque T. Loop (S11). If the sheet conveying torque Tq_p is greater than the target torque T... Loop (S11: Yes), then the rotational speed of the registration roller 120 is reduced by, for example, a predetermined value f (S12). Simultaneously, if the sheet conveying torque Tq_p is equal to or less than the target torque T... Loop (S11: Yes), then the rotational speed of the registration roller pair 120 is increased by this value f (S13). The value f used to accelerate or decelerate the registration speed is not necessarily fixed, and the value used to decelerate the registration speed (f1) may be different from the value used to accelerate the registration speed (f2).

[0081] Next, the control unit 210 determines whether time t4 has been reached (S14). If it is determined that time t4 has not been reached (S14: No), the process returns to step S11. That is, the sheet conveying torque Tq_p and the target torque T are compared. Loop Until time t4 is reached, feedback control of the registration speed (which is the rotational speed of the registration roller pair 120) is performed. As a result, the sheet P is controlled to be in a stretched state between the registration roller pair 120 and the transfer clamping part 130.

[0082] When the sheet P is in a stretched state, the non-imaging surface of the sheet P (i.e., the surface opposite to the side to which the toner image is transferred) contacts the protrusion 301a of the guide member 301. Thus, the sheet P is supported at three points: the registration roller pair 120, the protrusion 301a, and the transfer clamping part 130. In other words, the registration speed is controlled such that the sheet P is supported at these three points: the registration roller pair 120, the protrusion 301a, and the transfer clamping part 130. Specifically, in the registration speed control, the rotational speed of the registration roller pair 120 is controlled based on the detection result of the torque sensor 134, such that the first conveying speed of the sheet transported by the transfer clamping part 130 is faster than the second conveying speed of the sheet transported by the registration roller pair 120. In this state, the protrusion 301a is arranged such that the aforementioned distance X (where the sheet P slides in contact with the inclined surface 145a of the intermediate transfer belt 145) falls within the range of distance X2 to distance X3.

[0083] According to this embodiment, if the protrusion 301a is arranged in the region AR between the virtual line L1 that passes through the clamping part 120a of the registration roller pair 120 and the transfer clamping part 130 and the virtual line L2 that extends along the inclined surface 145a, then the distance X is set to fall within the range of distance X2 to distance X3.

[0084] like Figure 8A and Figure 8B As shown in the modified example, the guide member 401 includes a protrusion 401a, and the protrusion 401a can be arranged such that the distance X between the sheet P and the inclined surface 145a of the intermediate transfer belt 145 is set to an ideal distance X1. In this state, the posture of the sheet P between the protrusion 401a and the transfer clamping part 130 is approximately posture P1.

[0085] return Figure 6 When it is determined that time t4 has been reached (S14: Yes), the control unit 210 stores the registration speed correction value v1(n) in the memory 212. For example, the registration speed correction value v1(n) is calculated by the following formula (1).

[0086] v1(n)=(-f·m1+f·m2) / (m1+m2)...(1)

[0087] m1: The number of times deceleration is performed in step S12 based on registration speed control.

[0088] m2: The number of times acceleration is performed in step S13 based on registration speed control.

[0089] When the next sheet (i.e., the (n+1)th sheet) is fed, in step S3, the control unit 210 retrieves the registration speed correction value v1(n) from the memory 212. Then, the control unit 210 determines whether all the number of sheets specified in the print job have been printed (S16). If it is determined that not all the number of sheets specified in the print job have been printed (S16: No), the process returns to step S3.

[0090] If it is determined that all the required number of sheets specified in the print job have been printed (S16: Yes), the control unit 210 stops the rotation of each roller (S17) and ends the print job (S18). As described above, print control ends.

[0091] As described above, according to this embodiment, a target torque T is set to keep the sheet P in a stretched state between the registration roller pair 120 and the transfer clamping part 130. Loop Therefore, the sheet P is supported by three points: the registration roller pair 120, the protrusion 301a, and the transfer clamping part 130, and the posture of the sheet conveyed by the transfer clamping part 130 is stabilized.

[0092] Furthermore, even with relatively low-stiffness sheets (e.g., thin paper), by setting the sheet to a stretched state, registration speed control can be performed within a range that is highly sensitive to the difference in conveying speed between the registration roller pair 120 and the transfer clamping section 130. Therefore, the responsiveness of the registration speed acceleration or deceleration to the sheet posture is improved, and the sheet can be conveyed in an appropriate posture. Consequently, the distance X between the sheet P and the inclined surface 145a of the intermediate transfer belt 145 in sliding contact can be set to fall within an appropriate range that will not cause image defects. Thus, image defects can be suppressed.

[0093] Furthermore, when the sheet P is in a sliding motion relative to the protrusion 301a of the guide member 301, the aforementioned distance X will fall within a suitable range where image defects will not occur, thereby suppressing image defects. Moreover, the imaging device 100 can be manufactured while allowing tolerances in the outer diameter dimensions of the registration roller pair 120, enabling the suppression of image defects and reducing costs. Furthermore, even for thin paper with low stiffness, image defects can be suppressed, allowing for an increase in the number of corresponding media and improved usability.

[0094] Other embodiments

[0095] According to the above embodiment, a current detection unit that measures the current value of the driven motor 133 has been used as the torque sensor 134, but the technology is not limited to this. For example, a strain gauge that detects the torque of the driven motor 133 or an electrostatic capacitive torque sensor can also be used.

[0096] Furthermore, the torque sensor 134 can detect the torque of any component along the drive transmission path between the drive motor 133 and the drive roller 131, rather than the torque of the drive motor 133.

[0097] Furthermore, according to the above embodiment, in the registration speed control, the rotation speed of the registration roller pair 120 is controlled based on the detection result of the torque sensor 134, so that the first conveying speed of the transfer clamping part 130 conveying the sheet becomes faster than the second conveying speed of the registration roller pair 120 conveying the sheet. However, this technology is not limited to this. That is, the torque detected by the torque sensor 134 (called the reference torque) when the sheet is only clamped and conveyed by the transfer clamping part 130 can be stored in advance in the memory 212. Then, in the registration drive control, the rotation speed of the registration roller pair 120 can be controlled so that the torque detected by the torque sensor 134 when the sheet is clamped by the registration roller pair 120 and the transfer clamping part 130 is greater than the reference torque.

[0098] Furthermore, according to the above embodiment, the registration roller pair 120 is driven by a registration drive motor 121 independent of the drive motor 133, but the technology is not limited thereto. For example, instead of the registration drive motor 121, a transmission mechanism can be used, which can change the rotational speed of the registration roller pair 120 by changing the speed of the drive from the drive motor 133 and transmitting it to the registration roller pair 120.

[0099] Furthermore, according to the above embodiments, examples of performing registration speed control regardless of the properties of the sheet have been shown, but the technology is not limited thereto. For example, a configuration can be adopted in which registration speed control is not performed on sheets with a first stiffness (e.g., thick paper), but on sheets with a second stiffness (e.g., thin paper) that are less than the first stiffness.

[0100] Embodiments of this disclosure can also be implemented by a computer of a system or device that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transitory computer-readable storage medium") to implement the functions of one or more of the above embodiments, and / or the computer includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for implementing the functions of one or more of the above embodiments. Embodiments of this disclosure can also be implemented by means of a computer of the system or device through methods such as reading and executing computer-executable instructions from a storage medium to implement the functions of one or more of the above embodiments and / or controlling the one or more circuits to implement the functions of one or more of the above embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessor unit (MPU)) and may include a network of individual computers or individual processors to read and execute computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or storage medium. The storage medium may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), the memory of a distributed computing system, an optical disk (e.g., a compact optical disk (CD), a digital versatile disk (DVD), or a Blu-ray disc (BD)). TM One or more of the following: flash memory devices, memory cards, etc.

[0101] Other embodiments

[0102] Embodiments of the present invention can also be implemented by providing software (including computer program products of computer programs) that performs the functions of the above embodiments to a system or device via a network or various storage media, and the computer (central processing unit (CPU) or microprocessor unit (MPU) of the system or device) reads and executes the computer program.

[0103] Although this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An imaging device, comprising: An image carrier component configured to carry a toner image; A toner image is transferred from the image carrier member to the tape as the tape rotates in the rotational direction; An outer roller, the outer roller being configured to contact the outer peripheral surface of the belt; An inner roller is arranged to face the outer roller and the belt is located between the inner roller and the outer roller. The inner roller is configured to contact the inner circumferential surface of the belt and form a transfer clamping portion with the outer roller. The tension roller is configured to contact the inner circumferential surface of the belt and is arranged upstream of the inner roller in the direction of rotation. A pair of conveyor rollers configured to convey a sheet toward the transfer clamping portion; A guide member configured to guide a sheet conveyed by the conveyor roller pair toward the transfer clamping portion, the guide member including a protrusion projecting toward the outer peripheral surface of the belt and arranged between an imaginary line passing through the clamping portion of the conveyor roller pair and the transfer clamping portion and an imaginary line extending along the outer peripheral surface of the belt stretched between the tension roller and the inner roller. A belt drive motor is configured to drive the belt; A torque sensor configured to detect the torque of the driven motor; and A control unit is configured to perform transport control based on the detection result of the torque sensor after the sheet has arrived at the transfer clamping part. The transport control is used to control the rotational speed of the transport roller pair, such that a first transport speed of the sheet transported by the transfer clamping part becomes faster than a second transport speed of the sheet transported by the transport roller pair.

2. The imaging device according to claim 1, wherein, The protrusion of the guide member is configured to slide in contact with the sheet held by the conveyor rollers and the transfer clamp when the conveying control is performed.

3. The imaging device according to claim 1, wherein, The control unit is configured such that: (i) Obtain the target torque of the belt drive motor set such that the first conveying speed becomes faster than the second conveying speed, and the conveying torque obtained by subtracting the second torque of the belt drive motor when the sheet is not held by the transfer clamp from the first torque of the belt drive motor when the sheet is held by the transfer clamp. (ii) In the conveying control, the rotational speed of the conveying roller pair is controlled such that the second conveying speed is decelerated when the conveying torque is greater than the target torque; as well as (iii) Controlling the rotational speed of the conveying roller pair such that the second conveying speed is accelerated when the conveying torque is less than the target torque.

4. The imaging device according to claim 3, wherein, The target torque is set based on the properties of the sheet being conveyed.

5. The imaging apparatus according to any one of claims 1 to 4, wherein, The torque sensor includes a current detection unit configured to detect the current flowing to the driven motor.

6. The imaging apparatus according to any one of claims 1 to 4, wherein, The control unit performs the conveying control for at least a portion of the time period from when the sheet has arrived at the transfer clamp to when the sheet passes through the conveying roller pair.

7. The imaging apparatus according to any one of claims 1 to 4, further comprising a conveying motor configured to drive the conveying roller pair, in, The control unit is configured to control the rotational speed of the conveyor roller pair by controlling the conveyor motor.

8. An imaging device, comprising: An image carrier component configured to carry a toner image; A toner image is transferred from the image carrier member to the tape as the tape rotates in the rotational direction; An outer roller, the outer roller being configured to contact the outer peripheral surface of the belt; An inner roller is arranged to face the outer roller and the belt is located between the inner roller and the outer roller. The inner roller is configured to contact the inner circumferential surface of the belt and form a transfer clamping portion with the outer roller. The tension roller is configured to contact the inner circumferential surface of the belt and is arranged upstream of the inner roller in the direction of rotation. A pair of conveyor rollers configured to convey a sheet toward the transfer clamping portion; A guide member configured to guide a sheet conveyed by the conveyor roller pair toward the transfer clamping portion, the guide member including a protrusion projecting toward the outer peripheral surface of the belt and arranged between an imaginary line passing through the clamping portion of the conveyor roller pair and the transfer clamping portion and an imaginary line extending along the outer peripheral surface of the belt stretched between the tension roller and the inner roller. A belt drive motor is configured to drive the belt; A torque sensor configured to detect the torque of the driven motor; and A control unit configured to perform conveying control, the conveying control being used to control the rotational speed of the conveying roller pair such that the torque detected by the torque sensor when the sheet is held by the conveying roller pair and the transfer clamp becomes greater than the torque detected by the torque sensor when the sheet is held and conveyed only by the transfer clamp.

9. The imaging device according to claim 8, wherein, The protrusion of the guide member is configured to slide in contact with the sheet held by the conveyor rollers and the transfer clamp when the conveying control is performed.

10. The imaging device according to claim 8, wherein, The torque sensor includes a current detection unit configured to detect the current flowing to the driven motor.

11. The imaging device according to claim 8, wherein, The control unit performs the conveying control for at least a portion of the time period from when the sheet has arrived at the transfer clamp to when the sheet passes through the conveying roller pair.

12. The imaging apparatus according to any one of claims 8 to 11, further comprising a conveying motor configured to drive the conveying roller pair, in, The control unit is configured to control the rotational speed of the conveyor roller pair by controlling the conveyor motor.

Images