JP2020083536A - Sheet carrier and image forming apparatus - Google Patents

Abstract

To provide a sheet carrier adapted to reduce the formation of wrinkles in a sheet and reduce the occurrence of poor transport, and an image forming apparatus comprising the same.SOLUTION: A sheet carrier comprises: a manual tray; a pre-register roller pair; a register roller pair; a pre-register transport motor that drives the pre-register roller pair; a register motor that drives the register roller pair; and a CPU that controls the register motor such that if a job is inputted to feed a sheet from the manual tray, a sheet is fed from the manual tray and a tip of the sheet being transported by the pre-register roller pair is abutted against a nip of the register roller pair in a stopping state, and thereafter the register roller pair is started rotating in timing of register ON. The CPU can execute, in the timing of register ON, a mode of controlling the pre-register transport motor to drive the pre-register roller pair at a lower transport speed than the transport speed of the register roller pair.SELECTED DRAWING: Figure 5

Description

The present invention relates to a sheet conveying device that conveys a sheet and an image forming apparatus including the same.

Generally, in an image forming apparatus such as a printer, a sheet fed from a cassette or the like is abutted against the nip portion of a registration roller pair in a rotation stopped state by a pair of pre-registration rollers, and a loop is formed on the sheet to form a skewed sheet. A configuration for correcting lines is known. The skew-corrected sheet is conveyed by driving the pair of registration rollers and the pair of pre-registration rollers thereafter, but there is a possibility that wrinkles may be formed on the sheet due to the loop formed on the sheet.

For this reason, conventionally, a copying machine has been proposed in which skew feeding of a document is corrected by a document feeding unit, and an image of the document in which skew feeding is corrected is read by an image reading device (see Patent Document 1). The document conveying section feeds the document stacked on the paper feed tray by the pickup roller, and conveys the document to the registration roller pair in the rotation stopped state by the intermediate conveying roller pair. When the leading edge of the original abuts against the nip portion of the pair of registration rollers, a loop is formed and skew is corrected. With the loop formed on the document, the intermediate conveyance roller pair is stopped.

In the mixed loading mode in which originals of different sizes are continuously fed, wrinkles are likely to be formed on the originals. Therefore, the following control is executed so that the originals are not wrinkled. That is, after the loop is formed on the document, only the registration roller pair is driven, and the intermediate conveyance roller pair is not driven. This reduces the document loop and reduces the document wrinkles.

JP, 2013-40019, A

However, in the image reading apparatus described in Patent Document 1, when the skew-corrected sheet is conveyed by the registration roller pair, the leading edge of the sheet may not be nipped by the nip portion of the registration roller pair. When the control in the mixed loading mode is performed, the intermediate conveyance roller pair is not driven, so that the leading edge of the sheet does not enter the nip of the registration roller pair, which may cause conveyance failure such as jam.

Therefore, it is an object of the present invention to provide a sheet conveying device that reduces the formation of wrinkles on a sheet and reduces the occurrence of conveyance defects, and an image forming apparatus including the sheet conveying device.

According to the present invention, in a sheet conveying device, a manual feed tray on which sheets are stacked, a feeding unit that feeds the sheets stacked on the manual feed tray, and a sheet that is sandwiched by the sheets fed by the feeding unit. A first roller pair that is configured to convey in a conveyance direction, a second roller pair that is disposed downstream of the first roller pair in the sheet conveyance direction and that nips and conveys a sheet in a nip portion, and the first roller pair is driven. When a job for feeding a sheet from the manual feed tray is input, a first drive source for driving the second roller pair, a second drive source for driving the second roller pair, and a sheet are fed from the manual feed tray to After the leading edge of the sheet conveyed by the first roller pair is abutted against the nip portion of the second roller pair in the stopped state, the second drive source is set to start the rotation of the second roller pair at a predetermined timing. And a control unit that controls the first drive source so as to drive the first roller pair at a transport speed lower than the transport speed of the second roller pair at the predetermined timing. It is characterized in that it is possible to execute the mode.

Further, the present invention provides, in a sheet conveying device, a sheet supporting means for supporting a sheet, a feeding means for feeding a sheet stacked on the sheet supporting means, and a sheet fed by the feeding means. A first roller pair for nipping and conveying in the sheet conveying direction; a second roller pair arranged downstream of the first roller pair in the sheet conveying direction for nipping and conveying a sheet at a nip portion; A first drive source that drives the roller pair, a second drive source that drives the second roller pair, an acquisition unit that acquires information regarding the basis weight of the sheet supported by the sheet support unit, and the sheet support unit. When a job for feeding a sheet from the first roller pair is fed, the sheet is fed from the sheet supporting means, and the leading end of the sheet conveyed by the first roller pair is stopped. Control means for controlling the second drive source so as to start the rotation of the second roller pair at a predetermined timing after abutting against the sheet. When the amount is the first basis weight, the first drive source and the second drive source are controlled so as to drive the first roller pair and the second roller pair at the same transport speed at the predetermined timing. When the grammage of the sheet acquired by the acquisition unit is the second grammage smaller than the first grammage, the first roller pair is changed to the second roller pair at the predetermined timing. The second mode for controlling the first drive source so as to drive at a transport speed slower than the transport speed of 1 is executed.

According to the present invention, it is possible to reduce wrinkles and conveyance defects of the sheet.

1 is an overall schematic diagram showing a printer according to a first embodiment. The control block diagram which shows a control system. (A) is a schematic diagram showing a state where the leading edge of the sheet has abutted against the nip, and (b) is a schematic diagram showing a state where the sheet is nipped by the nip and conveyed. (A) is a timing chart showing stop registration control in the first mode, and (b) is a timing chart showing non-stop registration control in the first mode. (A) is a timing chart showing stop registration control in the second mode, and (b) is a timing chart showing non-stop registration control in the second mode. The schematic diagram which shows the state which the loop amount of the seat decreased. The flowchart explaining each process in skew feeding correction operation. The flowchart which shows each process of a 2nd mode necessity determination. 9 is a timing chart showing stop registration control in a second mode according to the second embodiment. The flowchart which shows each process of the 2nd mode necessity determination which concerns on 3rd Embodiment.

<First Embodiment>
〔overall structure〕
First, the first embodiment of the present invention will be described. The printer 100 as the image forming apparatus according to the present embodiment is an electrophotographic full-color laser beam printer. As shown in FIG. 1, the printer 100 includes an image reading device 50 that reads an image of a document and a printer body 60. The printer body 60 includes a sheet feeding unit 110 as a sheet conveying device that feeds stacked sheets, an image forming unit 150 that forms an image on the sheet, a fixing device 160 that fixes a toner image on the sheet, and a discharge unit. The transport unit 170 and the double-sided transport unit 190 are provided. When an image forming command is input to the printer 100, an image forming process by the image forming unit 150 is started based on image information input from the image reading device 50 or an external computer connected to the printer 100. ..

The image forming unit 150 as an image forming unit employs a 4-drum full color system. The image forming unit 150 includes a laser scanner 152, four process cartridges 10Y, 10M, 10C, which form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (BK). And 10 BK.

The four process cartridges 10Y, 10M, 10C, and 10BK have the same configuration except that the colors of images to be formed are different. Therefore, only the configuration of the process cartridge 10Y and the image forming process will be described, and the description of the process cartridges 10M, 10C, and 10BK will be omitted.

The process cartridge 10Y includes a photosensitive drum 151, a charging device (not shown), and a developing device 153. The laser scanner 152 irradiates the photosensitive drum 151 with laser light based on the input image information. At this time, the photosensitive drum 151 is charged in advance by the charger, and an electrostatic latent image is formed on the photosensitive drum 151 by being irradiated with the laser beam. After that, the electrostatic latent image is developed by the developing device 153, and a toner image is formed on the photosensitive drum 151.

An intermediate transfer belt 155 is arranged above the process cartridges 10Y, 10M, 10C, and 10BK, and the intermediate transfer belt 155 is rotationally driven in the arrow A direction by the transfer driving roller 142. Inside the intermediate transfer belt 155, four primary transfer rollers 11Y, 11M, 11C, and 11BK that are in contact with the inner surface of the intermediate transfer belt 155 at positions facing the photosensitive drums 151 are provided. Further, a transfer driven roller 143 that comes into contact with the outer surface of the intermediate transfer belt 155 is provided at a position facing the transfer driving roller 142. The transfer driving roller 142 and the transfer driven roller 143 form a transfer roller pair 141 and are in contact with each other to form a transfer nip N2.

In the image forming process, the yellow (Y) toner image formed on each photosensitive drum 151 is transferred and carried on the intermediate transfer belt 155 by applying an electrostatic additional bias to the primary transfer roller 11Y. .. Similarly, the toner images of the respective colors are transferred by the primary transfer rollers 11M, 11C, and 11BK so as to be superposed on the upstream toner images that have already been primarily transferred to the intermediate transfer belt 155. As a result, a full-color toner image is formed on the intermediate transfer belt 155. The full-color toner image is conveyed to the transfer nip N2 by the intermediate transfer belt 155 rotated by the transfer driving roller 142.

In parallel with the image forming process described above, the sheet P is fed from the sheet feeding unit 110. The sheet feeding unit 110 separates the sheets P stacked in a plurality (two in the present embodiment) of cassettes 111 that are formed so as to be pulled out from the printer main body 60 toward the front side by a pickup roller and a separation roller (not shown). Sheets are separated and fed one by one by a roller pair. The sheet P fed by the sheet feeding unit 110 is conveyed to a registration roller pair (hereinafter referred to as a registration roller pair) 131 by a cassette pull-out roller pair 120 and a pre-registration roller pair 121. The registration roller pair 131 as the second roller pair is arranged downstream of the pre-registration roller pair 121 in the sheet conveying direction.

Further, the printer body 60 is provided with a manual feed section 114 having a manual feed tray 113 as a sheet supporting means on which sheets can be manually inserted and stacked. The sheets supported on the manual feed tray 113 are separated and fed one by one by a manual feed roller pair 112 as a feeding unit, and then fed by a manual pull-out roller pair 115 as an intermediate roller pair to a pre-registration roller pair. It is transported to 121. The manual feeding unit 114, the manual pulling-out roller pair 115, the pre-registration roller pair 121, the registration roller pair 131, and the control device 200 described later constitute a sheet conveying device.

The pre-registration roller pair 121 as the first roller pair abuts the leading end of the sheet P against the nip N1 of the registration roller pair 131 in the stopped state to form a loop on the sheet P. As a result, the leading edge of the sheet P follows the nip N1 as the nip portion of the registration roller pair 131, and the skew feeding of the sheet P is corrected. The skewed sheet P is conveyed by the registration roller pair 131 at the transfer timing of the transfer nip N2, and a predetermined transfer current is passed through the transfer roller pair 141 to transfer the toner image on the intermediate transfer belt 155. To be done. The sheet P onto which the toner image has been transferred is subjected to predetermined heat and pressure in the fixing device 160, so that the toner is melted and fixed. The sheet P that has passed through the fixing device 160 is discharged onto a discharge tray 180 by a discharge/conveyance unit 170 including a discharge roller pair 171.

When images are to be formed on both sides of the sheet P, the discharge roller pair 171 is rotated in the forward direction to send the front side of the sheet P on which the toner image is formed on the first side to the outside of the machine, and the rear edge of the sheet P. Reverses when it crosses the branch point 172. As a result, the sheet P is switched back and is transported to the double-sided transport unit 190 in a state in which the front and back and front and back of the sheet are reversed. Then, the sheet P is conveyed again to the transfer nip N2 by the double-sided conveyance section 190, and the toner image is transferred onto the second surface of the sheet P. The sheet P on which the toner images are transferred on the first surface and the second surface is discharged to the discharge tray 180 through the above-described path.

[Control system]
FIG. 2 is a control block diagram showing a control system of the printer 100. A control device 200, which is the control means of the present embodiment, is installed in the main body of the printer 100. The control device 200 includes at least one processor including a central processing unit (CPU) 201, a non-transitory storage device including a read-only memory (ROM) 202, and a random access memory (RAM) 203. Sex storage device. The CPU 201 can read and execute a program stored in the ROM 202 or the like, and controls the operation of the entire image forming apparatus. For example, the CPU 201 sends a command signal to the image forming unit 150 and the fixing device 160 to perform a toner image forming process in the image forming unit 150, temperature control of the fixing device 160, and the like. The storage device such as the ROM 202 and the RAM 203 serves as a storage place for programs and data and also serves as a work space when the CPU 201 executes the programs.

A register motor 133, a pre-register transfer motor 145, and a manual feed motor 146 are connected to the control device 200. The register motor 133 as a second drive source drives a register drive roller 131 a that is a drive roller of the register roller pair 131. To do. The pre-registration transport motor 145 drives the pre-registration driving roller 121a, the cassette pull-out driving roller 120a, and the manual pull-out pulling drive roller 115a, which are the respective driving rollers of the pre-registration roller pair 121, the cassette pull-out roller pair 120, and the manual pull-out roller pair 115. To do. The manual feed motor 146 drives the manual feed drive roller 112 a, which is a drive roller of the manual feed roller pair 112.

The CPU 201 as the control means sends a drive signal for each motor to the motor drive circuit 204, and the motor drive circuit 204 supplies a current to each motor based on the received drive signal to rotate each motor. Thus, the registration roller pair 131, the pre-registration roller pair 121, the cassette pull-out roller pair 120, the manual pull-out roller pair 115, and the manual feed roller pair 112 are driven at desired timing and rotation speed (or conveyance speed).

Further, a registration detection sensor 132 is connected to the sensor output detection circuit 205 of the control device 200, and the registration detection sensor 132 is arranged between the pre-registration roller pair and the registration roller pair in the sheet conveying direction as described later. The leading edge of the conveyed sheet P is detected. As the registration detection sensor 132, for example, a photoelectric sensor is used, and when the sensor output signal indicates that the amount of received light is equal to or more than a threshold value, the sensor output detection circuit 205 outputs a high level signal (ON signal). To do. On the other hand, when the sensor output signal indicates that the amount of received light is less than the threshold value, the sensor output detection circuit 205 outputs a low-level signal (OFF signal). Here, the case where the sensor output detection circuit 205 outputs a binary signal is illustrated, but a multi-valued signal corresponding to the output signal of the sensor may be output. Hereinafter, the signal output from the sensor output detection circuit 205 according to the output signal of the sensor is treated as the detection result of each sensor.

Further, the control device 200 is connected to an operation unit 301 which serves as a user interface of the printer 100. The operation unit 301 includes a display device for displaying information to the user, a physical key capable of inputting information by receiving an input operation by the user, and a touch panel function of the display device. The control device 200 sends a command signal to the operation unit 301 and causes the display device to display information in the form of an image, a text message, or the like. Further, information input to the operation unit 301 (sheet attribute information, print condition setting information, a command for instructing the start of an image forming operation, etc.) is transmitted to the control device 200. The operation unit 301 serves as an acquisition unit for acquiring information about the sheet feed stage that is the sheet feeding source, the sheet basis weight, and the length in the sheet conveyance direction in the present embodiment.

[First mode in skew feeding operation]
Next, the first mode during the skew feeding correction operation by the pre-registration roller pair 121 and the registration roller pair 131 will be described. When a job for feeding the sheet P is input from the manual feed tray 113 (see FIG. 1), the CPU 201 drives the manual feed motor 146 to feed the sheet P by the manual feed roller pair 112. Then, as shown in FIG. 3A, the CPU 201 drives the pre-registration conveyance motor 145 to convey the sheet P by the manual pull-out roller pair 115 and the pre-registration roller pair 121, and the leading end of the sheet P is in the stopped state. Of the registration roller pair 131.

The manual pull-out roller pair 115 has a manual pull-out drive roller 115a driven by a pre-registration conveyance motor 145 as a first drive source and a manual pull-out follower roller 115b that is driven to rotate by the manual pull-out drive roller 115a. The pre-registration roller pair 121 includes a pre-registration driving roller 121a driven by a pre-registration transportation motor 145 and a pre-registration driven roller 121b that is driven and rotated by the pre-registration driving roller 121a. The registration roller pair 131 includes a registration driving roller 131a driven by a registration motor 133 and a registration driven roller 131b that is rotated by the registration driving roller 131a.

A registration detection sensor 132 is arranged upstream of the nip N1 in the sheet conveyance direction. When the leading edge of the sheet P passes the detection position of the registration detection sensor 132, the sensor signal is turned on, and the CPU 201 causes the CPU 201 Can grasp the tip position. After the registration detection sensor 132 is turned on, the CPU 201 drives the pre-registration conveyance motor 145 so as to convey the sheet P by the loop amount D1 in addition to the distance from the detection position of the registration detection sensor 132 to the nip N1. .. As a result, the sheet P having its leading edge hitting the nip N1 has loops formed by the loop amount D1, and skew feeding is corrected.

Then, at a predetermined registration ON timing when the registration roller pair 131 is switched from the stopped state to the driven state, the CPU 201 simultaneously drives the registration motor 133 and the pre-registration transport motor 145, as shown in FIG. 3B. At this time, the registration motor 133 and the pre-registration conveyance motor 145 are driven such that the pre-registration roller pair 121 and the pre-registration roller pair 131 convey the sheet P at the same conveyance speed (peripheral speed). Therefore, the sheet P is conveyed toward the transfer nip N2 while maintaining the loop between the pre-registration roller pair 121 and the registration roller pair 131. The registration ON timing is calculated by a calculation (not shown) from the timing when the toner image formed on the intermediate transfer belt 155 reaches the transfer nip N2.

FIG. 4A is a timing chart showing the drive timing and drive speed of the registration motor 133 and the pre-registration conveyance motor 145 when the time from the sheet P entering the nip N1 to the registration ON timing is long in the first mode. Is. FIG. 4B is a timing chart showing the drive timing and drive speed of the registration motor 133 and the pre-registration transport motor 145 when the time from the sheet P entering the nip N1 to the registration ON timing is short in the first mode. Is. In the following, the driving of the registration motor 133 and the pre-registration transport motor 145 may be changed before being transmitted to the pre-registration roller pair 121 and the registration roller pair 131, respectively. Further, in the following, the driving speeds of the registration motor 133 and the pre-registration transport motor 145 are described as corresponding to the transport speeds (peripheral speeds) of the pre-registration roller pair 121 and the registration roller pair 131.

First, the control shown in FIG. 4A will be described. As shown in FIG. 4A, the CPU 201 drives the pre-registration conveyance motor 145 at the speed V1 at the feeding timing t0 and keeps the registration motor 133 stopped. Then, the CPU 201 drives the pre-registration conveyance motor 145 at the speed V2 at the sensor detection timing t1 when the leading edge of the sheet P is detected by the registration detection sensor 132. The speed V2 is determined based on the elapsed time from the feeding timing t0 to the sensor detection timing t1. Further, the CPU 201 conveys the sheet P by the loop amount D1 from the nip entry timing t2 when the leading edge of the sheet P enters the nip N1, and then stops the pre-registration conveyance motor 145.

Next, the CPU 201 drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V4 at the registration ON timing t3 as a predetermined timing. Then, the CPU 201 drives the registration motor 133 and the pre-registration transport motor 145 at the speed V3 at the shift timing t4 when the leading edge of the sheet P is located upstream of the transfer nip N2 in the sheet transport direction. The speed V3 is substantially equal to the driving speed of the intermediate transfer belt 155 and faster than the speed V4.

Next, the control shown in FIG. 4B will be described. As shown in FIG. 4B, the CPU 201 drives the pre-registration conveyance motor 145 at the speed V1 at the feeding timing t0 and keeps the registration motor 133 stopped. Then, the CPU 201 drives the pre-registration conveyance motor 145 at the speed V2 at the sensor detection timing t1. Further, the CPU 201 conveys the sheet P by the loop amount D1 from the nip entry timing t2, and then stops the pre-registration roller pair 121 without stopping the pre-registration roller pair 121. Drive with. That is, the CPU 201 controls the pre-registration conveyance motor 145 so as not to stop the pre-registration roller pair 121 until the registration ON timing t3.

Then, the CPU 201 drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V3 at the shift timing t4. As described above, when the time from the nip entry timing t2 to the registration ON timing t3 is long, the control for temporarily stopping the pre-registration transport motor 145 as shown in FIG. 4A (hereinafter referred to as stop registration control) is performed. To do. Further, when the time from the nip entry timing t2 to the registration ON timing t3 is short, the control not to stop the pre-registration transport motor 145 as shown in FIG. 4B (hereinafter referred to as non-stop registration control) is performed.

In the above-described first mode, in both of the stop registration control as the first processing and the non-stop registration control as the second processing, the registration motor 133 and the pre-registration conveyance motor 145 are driven at the same speed V4 at the registration ON timing t3. To do. Therefore, the sheet P is conveyed toward the transfer nip N2 while the loop of the sheet P formed by the registration ON timing t3 is maintained.

However, for example, when the sheet P is set on the manual feed tray 113 in a skewed state and the skew amount of the sheet P is large, the sheet P has an asymmetric loop in the width direction orthogonal to the transport direction. .. When the registration roller pair 131 starts to rotate while the sheet P is twisted, the asymmetrically deformed portion may be sandwiched by the registration roller pair 131, and the sheet P may be wrinkled. In particular, when a sheet having a low basis weight and a weak stiffness or a sheet having a long length in the sheet transport direction is transported, wrinkles due to the kink of the sheet P are likely to occur.

This is because when the sheet P before skew correction has skew, the position of the sheet sandwiched by the pre-registration roller pair 121 gradually shifts in the width direction as the pre-registration roller pair 121 rotates. This is to keep going. The deviation between the sheet position of the registration roller pair 131 and the sheet position of the pre-registration roller pair 121 increases as the sheet is conveyed. As a result, the sheet is more likely to be twisted and wrinkles easily occur.

[Second mode in skew feeding operation]
Next, the second mode at the time of skew correction operation by the pre-registration roller pair 121 and the registration roller pair 131 will be described. The second mode is a mode for reducing the wrinkles caused by the above-described twist of the sheet P.

FIG. 5A is a timing chart related to the stop registration control in the second mode, and FIG. 5B is a timing chart related to the non-stop registration control in the second mode. These timing charts are different from the timing charts described in FIGS. 4A and 4B only in the control at the registration ON timing t3, and thus the description of the other portions will be omitted.

In the stop registration control in the second mode, as shown in FIG. 5A, at the registration ON timing t3, the CPU 201 drives the registration motor 133 at the speed V4 and drives the pre-registration conveyance motor 145 at a speed V5 slower than the speed V4. Drive with. Then, the CPU 201 maintains the driving speed of the registration motor 133 and the pre-registration conveyance motor 145 until the shift timing t4, and drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V3 at the shift timing t4. That is, at the shift timing t4 when the first time has elapsed from the registration ON timing t3, the pre-registration roller pair 121 and the registration roller pair 131 are driven at the same speed. The speed relationship described above is set to V5<V4<V3. Further, the speed V5 is calculated by a calculation (not shown) based on how much the loop is resolved by the shift timing t4.

Note that the pre-registration roller pair 121 has a built-in one-way clutch (not shown), and even if the pre-registration roller pair 121 is dragged due to the loop of the sheet P being lost, the one-way clutch will damage the sheet P. Can be reduced.

In the non-stop registration control as the second process in the second mode, as shown in FIG. 5B, the CPU 201 drives the registration motor 133 at the speed V4 at the registration ON timing t3, and drives the pre-registration conveyance motor 145 at the speed. It is driven at a speed V5 slower than V4. Then, the CPU 201 maintains the driving speed of the registration motor 133 and the pre-registration conveyance motor 145 until the shift timing t4, and drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V3 at the shift timing t4.

By such control described in FIGS. 5A and 5B, the pre-registration roller pair 121 is driven at a conveyance speed slower than the conveyance speed of the registration roller pair 131 at the registration ON timing t3. As a result, the sheet P has a reduced loop between the pre-registration roller pair 121 and the registration roller pair 131, as shown in FIG. 6, and wrinkles caused by the kink of the sheet P can be reduced. Further, since the pre-registration conveyance motor 145 is always driven at the registration ON timing t3, even if the leading edge of the sheet P is not pinched by the nip N1 at the registration ON timing t3, the pre-registration roller pair 121 nips the sheet P. It is pushed into N1. As a result, the sheet P does not become unfed, and the conveyance failure can be reduced.

Further, by increasing the speed difference between the pre-registration conveyance motor 145 and the registration motor 133 at the registration ON timing t3, the loop of the sheet P can be quickly eliminated, and the cause of the wrinkle can be avoided faster.

[Skew correction operation flow]
Next, the skew feeding correction operation in this embodiment will be described with reference to the flowchart shown in FIG. As shown in FIG. 7, with the feeding of the sheet P from the manual feed tray 113, the CPU 201 drives the pre-registration conveyance motor 145 at the speed V1 (step S1). The speed V1 is a transportation speed stored in the ROM 202 in advance. Next, the CPU 201 determines whether or not the second mode is necessary to avoid wrinkles on the sheet P (step S2). The determination as to whether or not the second mode is necessary will be described later.

Next, the CPU 201 determines whether or not the registration detection sensor 132 is turned on (step S3). When the registration detection sensor 132 is turned on (step S3: YES), the pre-registration conveyance motor 145 is moved to the speed V2. To drive (step S4). Then, the CPU 201 calculates the registration ON timing t3 by calculation (not shown) from the timing when the toner image formed on the intermediate transfer belt 155 reaches the transfer nip N2 (step S5). Further, since the pre-registration conveyance motor 145 is driven at the speed V2 while the registration motor 133 is stopped, a loop is formed on the sheet P whose leading edge hits the nip N1 (step S6). The loop amount D1 formed on the sheet P is stored in the ROM 202 in advance.

Then, the CPU 201 determines whether or not the registration ON timing t3 has come before the formation of the predetermined loop amount D1 or immediately after the formation of the loop amount D1 (step S7). That is, when the interval between the nip entry timing t2 and the registration ON timing t3 is short (step S7: YES), the process proceeds to step S9. If the interval between the nip entry timing t2 and the registration ON timing t3 is long (step S7: NO), the pre-registration transport motor 145 is stopped (step S8), and the process proceeds to step S9. In step S9, the CPU 201 calculates the speed V4 (step S9), and calculates the shift timing t4 (step S10).

Next, the CPU 201 determines whether or not the registration ON timing t3 is reached (step S11), and when the registration ON timing t3 is reached (step S11: YES), the second mode is required in the second mode necessity determination. It is confirmed whether or not the judgment is made (step S12). When it is determined that the second mode is necessary (step S12: YES), the speed V5 is calculated by calculation (not shown) (step S13). Then, the CPU 201 drives the registration motor 133 at the speed V4 and simultaneously drives the pre-registration conveyance motor 145 at the speed V5 (steps S14 and S15).

When it is determined that the second mode is unnecessary (step S12: NO), the CPU 201 drives the registration motor 133 and the pre-registration transport motor 145 at the speed V4 (step S16). After step S15 or step S16, the CPU 201 determines whether or not the shift timing t4 is reached (step S17). When the shift timing is t4 (step S17: YES), the CPU 201 drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V3 (steps S18 and S19).

Next, the CPU 201 determines whether or not there is a next paper feed request (step S20), and if there is a paper feed request (step S20: YES), returns to step S1 and if there is no paper feed request (step S20: YES). Step S20: NO), and the process ends.

FIG. 8 is a flowchart showing each process of determining whether or not the second mode is necessary. When the second mode necessity determination is started, the CPU 201 determines whether or not the sheet feeding stage that is the sheet feeding source is the manual feed tray 113 (step S31). When the paper feed tray is the manual feed tray 113 (step S31: YES), the CPU 201 determines whether the size of the sheet to be fed is A4 or larger (step S32). When the size of the sheet to be fed is A4 or more (step S32: YES), the CPU 201 determines whether the basis weight of the sheet is 64 g/m ² or less (step S33). The size and basis weight of the paper feed tray and sheets are selected by the operation unit 301.

When the basis weight of the sheet is 64 g/m ² or less (step S33: YES), the CPU 201 determines that wrinkles are likely to occur on the fed sheet P and determines that the second mode needs to be executed. (Step S35), and the process ends. If any one of the following is satisfied: the paper feed tray is not the manual feed tray 113, the size of the sheet is less than A4, and the basis weight of the sheet is greater than 64 g/m ² , the CPU 201 Determines that the second mode is unnecessary (step S34). Then, the second mode necessity determination is completed.

For example, considering only the requirement for the basis weight of the sheet, when the basis weight of the sheet is the first basis weight larger than 64 g/m ² , the first mode is executed, and the pre-registration roller pair 121 and the registration roller at the registration ON timing t3. The pair 131 is driven at the same transport speed. When the basis weight of the sheet is 64 g/m ² or less, that is, when the basis weight is the second basis weight smaller than the first basis weight, the second mode is executed, and the pre-registration roller pair 121 and the registration roller pair 131 are executed at the registration ON timing t3. It is driven at a transport speed lower than the transport speed of.

As described above, in the present embodiment, for example, when feeding a sheet such as a thick paper in which wrinkles are less likely to occur, the sheet P is conveyed toward the transfer nip N2 while maintaining the loop amount of the sheet P. Execute 1 mode. On the other hand, in the case of feeding a sheet having a low basis weight such as thin paper and having a low stiffness, the second mode of carrying the sheet P toward the transfer nip N2 while eliminating the loop of the sheet P is executed.

As a result, wrinkles due to the kink of the sheet P can be reduced. Even if the leading edge of the sheet P is not nipped in the nip N1 at the registration ON timing t3, the sheet P is pushed into the nip N1 by the pre-registration roller pair 121. As a result, the sheet P does not become unfed, and the conveyance failure can be reduced.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. In the second embodiment, the stop registration control in the second mode of the first embodiment is changed. Therefore, the configuration similar to that of the first embodiment will be described by omitting the illustration or by attaching the same reference numeral to the figure.

FIG. 9 is a timing chart of stop registration control in the second mode according to the present embodiment. Note that the timing chart shown in FIG. 9 is different from the timing chart described in FIG. 5A only in the control after the registration ON timing t3, and thus the description of the other portions is omitted.

As shown in FIG. 9, at the registration ON timing t3, the CPU 201 drives the registration motor 133 at a speed V4 and drives the pre-registration conveyance motor 145 at a speed V6 slower than the speed V4. Then, the CPU 201 maintains the drive speed of the registration motor 133 until the shift timing t4, but temporarily stops the pre-registration conveyance motor 145 at the temporary stop timing t5 before the shift timing t4. The shift timing t4 is a timing when a first time has elapsed from the registration ON timing t3, and the temporary stop timing t5 is a timing when a second time shorter than the first time has elapsed from the registration ON timing t3.

After that, the CPU 201 drives the registration motor 133 and the pre-registration conveyance motor 145 at the speed V3 at the shift timing t4. The speed relationship described above is set to V6<V4<V3. The speed V6 may be equal to the speed V5 shown in FIGS. 5A and 5B described in the first embodiment or may be faster than the speed V4. Further, the speed V6 and the temporary stop timing t5 are calculated by calculation (not shown) based on how much the loop is canceled before the shift timing t4.

For example, when the speed difference between the speed V4 and the speed V5 in FIG. 5A is set to be larger than the speed difference between the speed V4 and the speed V6 in FIG. 9, the control described in FIG. Can quickly eliminate the loop of the seat P. On the other hand, as for the non-feed due to the front end of the sheet P not being sandwiched by the nip N1, it is advantageous to reduce the speed difference between the speed V4 and the speed V6 as shown in FIG. The control shown in FIGS. 5(a) and 10 can reduce wrinkles and non-feeding regardless of which method is adopted, but may be appropriately selected depending on the ease of wrinkling and the likelihood of non-feeding. ..

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In the third embodiment, the processing of the second mode necessity judgment of the first embodiment is modified. Therefore, the configuration similar to that of the first embodiment will be described by omitting the illustration or by attaching the same reference numeral to the figure.

FIG. 10 is a flowchart showing each process of the second mode necessity determination according to the third embodiment. When the second mode necessity determination is started, the CPU 201 determines whether or not the sheet feeding stage that is the sheet feeding source is the manual feed tray 113 (step S41). When the paper feed tray is not the manual feed tray 113 (step S41: NO), the CPU 201 determines whether the size of the sheet to be fed is A4 or larger (step S42). When the size of the sheet to be fed is not A4 or more (step S42: NO), the CPU 201 determines whether the basis weight of the sheet is 64 g/m ² or less (step S43). The size and basis weight of the paper feed tray and sheets are selected by the operation unit 301.

When the basis weight of the sheet is not 64 g/m ² or less (step S43: NO), the CPU 201 determines that wrinkles are unlikely to occur on the sheet P to be fed, and determines that it is not necessary to execute the second mode. (Step S45), the process ends. If any one of the following is satisfied: the paper feed tray is the manual feed tray 113, the sheet size is A4 or more, and the basis weight of the sheet is 64 g/m ² or less. , CPU 201 determines that the second mode is necessary (step S44). Then, the second mode necessity determination is completed.

Note that the first to third embodiments may be combined as appropriate. Further, in any of the above-described forms, the speed V6 may be substantially the same as the speed V4 or may be faster than the speed V4.

In each of the above-described embodiments, the case where the sheet P is fed from the manual feed tray 113 has been described as an example. However, even when the sheet P is fed from the cassette 111, the first mode or the second mode is executed. You may.

Further, in any of the above-described embodiments, the electrophotographic printer 100 is used for description, but the present invention is not limited to this. For example, the present invention can be applied to an inkjet type image forming apparatus that forms an image on a sheet by ejecting an ink liquid from a nozzle.

112: feeding unit (manual feeding unit)/113: manual feeding tray, sheet supporting unit/115: intermediate roller pair (manual pulling roller pair)/121: first roller pair (pre-registration roller pair)/131: second Roller pair (registration roller pair)/133: second drive source (registration motor)/145: first drive source, motor (pre-registration conveyance motor)/150: image forming unit (image forming unit)/201: control unit (CPU) /301: Acquisition unit (operation unit)/N1: Nip part (nip)/P: Sheet/t3: Predetermined timing (registration ON timing)

Claims (9)

Bypass tray on which sheets are stacked,
Feeding means for feeding the sheets stacked on the manual feed tray,
A first roller pair that nips the sheet fed by the feeding unit and conveys the sheet in the sheet conveying direction;
A second roller pair arranged downstream of the first roller pair in the sheet transport direction and configured to sandwich and transport the sheet at a nip portion;
A first drive source for driving the first roller pair;
A second drive source for driving the second roller pair;
When a job for feeding a sheet from the manual feed tray is input, the sheet is fed from the manual feed tray, and the leading end of the sheet conveyed by the first roller pair is stopped by the second roller pair. Control means for controlling the second drive source so as to start rotation of the second roller pair at a predetermined timing after abutting against the nip portion,
The control means can execute a mode of controlling the first drive source so as to drive the first roller pair at a transport speed slower than the transport speed of the second roller pair at the predetermined timing.
A sheet conveying device characterized by the above. An acquisition unit that acquires information about the basis weight of the sheet supported by the manual feed tray;
When the basis weight of the sheet acquired by the acquisition means is the first basis weight, the control means may drive the first roller pair and the second roller pair at the same transport speed at the predetermined timing. When the first mode for controlling the first drive source and the second drive source is executed and the basis weight of the sheet acquired by the acquisition unit is the second basis weight smaller than the first basis weight, the predetermined At a timing, a second mode is executed as the mode for controlling the first drive source so as to drive the first roller pair at a transport speed slower than the transport speed of the second roller pair,
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. A sheet supporting means for supporting the sheet,
Feeding means for feeding the sheets stacked on the sheet supporting means,
A first roller pair that nips the sheet fed by the feeding unit and conveys the sheet in the sheet conveying direction;
A second roller pair arranged downstream of the first roller pair in the sheet transport direction and configured to sandwich and transport the sheet at a nip portion;
A first drive source for driving the first roller pair;
A second drive source for driving the second roller pair;
An acquisition unit that acquires information about the basis weight of the sheet supported by the sheet support unit;
When a job for feeding a sheet from the sheet supporting means is input, the sheet is fed from the sheet supporting means, and the leading end of the sheet conveyed by the first roller pair is stopped. Control means for controlling the second drive source so as to start rotation of the second roller pair at a predetermined timing after abutting against the nip portion of
When the basis weight of the sheet acquired by the acquisition means is the first basis weight, the control means may drive the first roller pair and the second roller pair at the same transport speed at the predetermined timing. When the first mode for controlling the first drive source and the second drive source is executed and the basis weight of the sheet acquired by the acquisition unit is the second basis weight smaller than the first basis weight, the predetermined At a timing, a second mode is executed to control the first drive source so as to drive the first roller pair at a transport speed slower than the transport speed of the second roller pair.
A sheet conveying device characterized by the above. The sheet supporting means is a manual feed tray into which sheets are manually fed,
The sheet conveying device according to claim 3, wherein An intermediate roller pair arranged downstream of the feeding unit and upstream of the first roller pair in the sheet conveying direction,
The first driving source is one motor that drives the feeding unit, the intermediate roller pair, and the first roller pair.
The sheet conveying apparatus according to claim 2, wherein the sheet conveying apparatus is a sheet conveying apparatus. In the second mode, the control means drives the first roller pair and the second roller pair at the same transport speed after a first time has elapsed from the predetermined timing, and the first drive source and the second drive source. Controlling the second drive source,
The sheet conveying apparatus according to claim 2, wherein the sheet conveying apparatus is a sheet conveying apparatus. The control means controls the first drive source to stop the first roller pair when a second time shorter than the first time has elapsed from the predetermined timing.
The sheet conveying device according to claim 6, wherein A detection unit that is disposed between the first roller pair and the second roller pair in the sheet conveyance direction and detects the leading edge of the sheet;
The control means controls the first drive source to stop the first roller pair before the predetermined timing, based on the detection means detecting the leading edge of the sheet; And a second process of controlling the first drive source so as not to stop the first roller pair until the predetermined timing.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. A sheet conveying device according to any one of claims 1 to 8,
Image forming means for forming an image on a sheet conveyed by the sheet conveying device,
An image forming apparatus characterized by the above.

Images