JP6968611B2 - Sheet transfer device - Google Patents

Description

The present invention relates to a sheet transport device for transporting sheets.

Some sheet transport devices used in image forming devices and the like correct the skew of a sheet by abutting the tip of the sheet against a nip portion of a roller pair or an abutting portion such as a shutter member and bending the sheet. Further, in order to cope with the diversification of sheets used as a recording medium, a sheet transporting device is required to transport various types of sheets having different rigidity.

Patent Document 1 describes a configuration in which a sheet is conveyed to a pair of registration rollers via a curved transfer path, and a transfer unit having a transfer belt is arranged at a curved portion of the transfer path. In this configuration, the tip of the sheet bends along the rotation direction of the transfer belt to bring the sheet into surface contact with the transfer belt, thereby improving the transfer performance of a sheet having high rigidity such as thick paper.

Japanese Unexamined Patent Publication No. 2008-105805

By the way, in the configuration in which the tip of the sheet is abutted against the contact portion such as the nip portion of the registration roller pair as in the sheet transport device described in Patent Document 1, in the vicinity of the registration roller pair due to the skew correction. Out-of-plane deformation may occur on the sheet. When the registration roller pair starts transporting the sheet while the sheet is out-of-plane deformation, the deformed portion may be sandwiched between the nip portions and wrinkles may occur.

An object of the present invention is to provide a sheet transfer device capable of reducing the occurrence of wrinkles while ensuring the stability of sheet transfer operation for various types of sheets having different rigidity.

The sheet transfer device according to one aspect of the present invention includes a transfer roller pair that sandwiches and conveys a sheet, an upstream side transfer roller pair arranged upstream of the transfer roller pair in the sheet transfer direction, and a sheet transfer direction. provided on the downstream of the conveying roller pair, a registration roller pair for conveying by nipping the sheet, the registration roller pair to correct the skew of the sheet by the tip of the sheet over bets are brought into contact with , a pre-Symbol registration roller conveyance guide for guiding the sheet towards the pair, when viewed from the width direction perpendicular to the sheet conveying direction, inclined upward toward the downstream of the sheet conveyance direction, and A transport guide that forms a curved sheet transport path that increases its inclination with respect to the horizontal direction as it approaches the registration roller pair, a first state in which the transport roller pair is brought into contact with each other, and a more than the first state. a second state that causes a large contact with each other the transport roller pair in contact pressure, the third state to separate the pair of conveying rollers, and switchable switching means the transport roller pair, said first state The first mode in which the sheet is conveyed toward the registration roller pair by the transfer roller pair, the second mode in which the sheet is conveyed toward the registration roller pair by the transfer roller pair in the second state, and the transfer. The control means includes a control means capable of carrying out a third mode in which the roller pair is set as the third state and the sheet is conveyed toward the registration roller pair by the upstream transfer roller pair , and the control means is the first. When transporting a sheet having a basis weight of, the first mode is executed, and when transporting a sheet having a second basis weight larger than the first basis weight, the second mode is executed . When transporting a sheet having a third basis weight smaller than that of the first basis weight sheet, the third mode is executed .

According to the sheet transport device according to the present invention, it is possible to reduce the occurrence of wrinkles while ensuring the stability of the sheet transport operation for various types of sheets having different rigidity.

The schematic diagram of the image forming apparatus which concerns on this disclosure. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (low pressure state) which concerns on Example 1. FIG. The perspective view which shows the pressurizing mechanism of the roller pair before a cash register which concerns on Example 1. FIG. The perspective view which shows the pressurizing mechanism of the roller pair before a cash register which concerns on Example 1. FIG. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (high pressure state) which concerns on Example 1. FIG. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (separation state) which concerns on Example 1. FIG. The block diagram which shows the control composition of the pre-registration transport apparatus which concerns on Example 1. FIG. The flowchart which shows the control method of the pre-registration transfer apparatus which concerns on Embodiment 1. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (low pressure state) which concerns on Example 2. FIG. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (high pressure state) which concerns on Example 2. FIG. The schematic diagram of the roller pair before the cash register and the pressurizing mechanism (separation state) which concerns on Example 2. FIG.

Hereinafter, the image forming apparatus according to the present disclosure will be described with reference to the drawings. The image forming apparatus includes a printer, a copying machine, a facsimile, and a multifunction device, and 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 manuscript. Sheets used as recording media include paper and paper such as envelopes, plastic films for overhead projectors, and cloth.

As shown in FIG. 1, the image forming apparatus 100 includes an apparatus main body 100A accommodating an image forming unit 150 and an image reading apparatus 300 arranged above the apparatus main body 100A and reading image information from a document. The image forming unit 150, which is an example of the image forming means, includes an intermediate transfer tandem system configuration including four image forming units PY, PM, PC, PK and an intermediate transfer belt 155. The image forming unit 150 transfers the toner image formed by the image forming units PY to PK to the sheet S via the intermediate transfer belt 155. Since the configurations of the image forming units PY to PK are basically the same except that the colors of the toners used for development are different, the configuration of the image forming unit and the formation operation of the toner image are performed by taking the yellow image forming unit PY as an example. Will be explained.

When the image forming unit PY is required to form a toner image, the photosensitive drum 151, which is a photoconductor, is rotationally driven, and the charging device uniformly charges the surface of the photosensitive drum 151. The exposure apparatus 152 provided at the lower part of the apparatus main body 100A irradiates the photosensitive drum 151 with a laser beam based on image information to expose the surface of the drum, and forms an electrostatic latent image on the photosensitive drum 151. Then, the electrostatic latent image is visualized (developed) by the toner supplied from the developing device 153, so that the toner image is formed on the surface of the photosensitive drum 151.

Similarly, in the image forming units PM, PC, and PK, a toner image of the corresponding color is formed on the photosensitive drum. The toner images formed by the image forming units PY to PK are primarily transferred from the photosensitive drum 151 to the intermediate transfer belt 155, which is an intermediate transfer body, by the primary transfer roller 154. Adhesions such as toner remaining on the photosensitive drum 151 are removed by cleaning devices provided in the image forming units PY to PK.

The intermediate transfer belt 155 is wound around a secondary transfer inner roller 156, a tension roller 157, and a tension roller 158, and is rotationally driven in the counterclockwise direction in the figure. The toner image supported on the intermediate transfer belt 155 is secondarily transferred to the sheet S in the secondary transfer portion formed between the secondary transfer roller 159 facing the secondary transfer inner roller 156 and the intermediate transfer belt 155. NS. Adhesions such as toner remaining on the intermediate transfer belt 155 are removed by a belt cleaning device. The sheet S to which the toner image is transferred is delivered to the fixing device 160. The fixing device 160 has a fixing roller pair for sandwiching and transporting the sheet S and a heat source for heating the sheet S, and applies heat and pressure to the toner image while transporting the sheet S. As a result, the toner melts and sticks and is fixed to the sheet S.

In parallel with such an image forming process, a feeding operation of feeding the sheet S from the cassette feeding unit 110 or the manual feeding unit 115 toward the sheet S is executed. The cassette feeding unit 110 includes a feeding cassette 111 as a seat supporting means, and a feeding unit 112 that feeds the sheet S from the feeding cassette 111. Further, the manual feed feeding unit 115 includes a manual feed tray 116, which is another example of the seat support means, and a feed unit 117 for feeding the sheet S set in the manual feed tray 116. The feeding units 112, 117 include feeding rollers 112a, 117a for feeding the sheet S, and separating rollers 112b, 117b for separating the sheet S conveyed by the feeding rollers 112a, 117b from other sheets. The feeding units 112 and 117 are examples of the seat feeding means for feeding the seat S, and may be replaced with other feeding mechanisms such as a separation pad method and an air feeding method.

The sheet S fed by the feeding units 112 and 117 is conveyed to the skew correction device 130 via the drawing roller pair 113. The skew correction device 130 corrects the skew of the sheet S, as will be described in detail later, and sends the sheet S to the secondary transfer unit at a timing in accordance with the progress of the image formation process by the image forming unit 150.

The sheet S on which an image is formed by passing through the secondary transfer unit and the fixing device 160 is passed to the discharge path 172 of the sheet discharge unit 170, and the device main body 100A and the image reading device 300 are connected by the discharge roller pair 171. It is discharged to the discharge tray 180 provided between them. When double-sided printing is performed, the sheet S is switchback-transported by the discharge roller pair 171 which is a pair of reversing rollers and delivered to the double-sided transport unit 190, and is conveyed by the transport roller pair 193 via the double-sided pass 192. Then, the sheet S that has reached the skew correction device 130 again is discharged to the discharge tray 180 by the discharge roller pair 171 after the image is formed on the back surface by the image forming unit 150.

Next, the configuration and operation of the skew correction device 130 according to the first embodiment will be described. As shown in FIG. 1, the skew correction device 130 is a sheet transfer device including a registration roller pair (hereinafter referred to as a registration roller pair) 131 and a pre-registration roller pair 132 arranged upstream thereof. Hereinafter, the direction in which the sheets move in order via the pre-registration roller pair 132 and the registration roller pair 131 is defined as the sheet transport direction.

The pre-registration roller pair 132 corresponds to a first transport means capable of sandwiching and transporting a sheet between a rotatable first transport member and a second transport member. The register roller pair 131 corresponds to a second transport means capable of correcting the skew of the sheet by abutting on the front end of the sheet, that is, the downstream end in the sheet transport direction, and capable of sandwiching and transporting the sheet.

The image forming apparatus 100 according to the present embodiment has a vertical conveying type (see FIG. 1) that forms an image with respect to the sheet S that is conveyed upward inside the apparatus main body 100A. Then, the sheet S fed from the manual feed feeding section 115 arranged on the side surface of the apparatus main body 100A is conveyed toward the secondary transfer section via the curved sheet transport path 133. That is, the sheet transport path 133 has a shape curved from a substantially horizontal direction to a substantially vertical direction as it approaches the register roller pair 131 when viewed from the width direction orthogonal to the sheet transport direction.

By the way, with the diversification of sheets used as recording media, it is required that the sheet conveying device used for the image forming apparatus can stably convey various types of sheets having different rigidity. Since a sheet with high rigidity such as thick paper tends to have a large transfer resistance, the nip pressure of the roller-to-132 in front of the cash register is set high to increase the force for holding the sheet to assist the transfer of the sheet by the roller-to-register roller to 131. It is possible to make it.

However, when the nip pressure of the pre-registration roller pair 132 is configured to be always high, there is a concern that wrinkles of the seat S may occur when the registration roller pair 131 starts transporting the sheet S. That is, in the state before the registration roller pair 131 starts rotating, the front end of the seat S is abutted against the nip portion of the registration roller pair 131, and the seat S is placed in the loop space between the registration roller pair 132 and the registration roller pair 131. Form a loop. In this state, out-of-plane deformation of the sheet S may occur in the vicinity of the register roller pair 131, and when the register roller pair 131 starts rotating, the portion where the out-of-plane deformation occurs is sandwiched between the register roller pair 131. The sheet S may be wrinkled. Such wrinkles on the sheet are of great concern when transporting a sheet having a relatively low rigidity, which is prone to out-of-plane deformation.

Therefore, in the present embodiment, the force of the pre-registration roller pair 132 to hold the sheet S can be switched according to the type of the sheet, so that wrinkles occur when the register roller pair 131 starts to convey the sheet S. Is reduced. Hereinafter, the configuration of the pressurizing mechanism of the pre-registration roller pair 132 will be described with reference to FIGS. 2 to 6. FIG. 2 is a schematic view showing a pre-registration roller pair 132 and a pressurizing mechanism 121 in a state of being nipped at a low pressure, and FIGS. 3 and 4 are perspective views showing a pre-registration roller pair 132 and a pressurizing mechanism 121. Further, FIGS. 5 and 6 are schematic views showing a pre-registration roller pair 132 and a pressurizing mechanism in a state of being nipped at a high pressure and a state of being separated from each other, respectively.

The pressurizing mechanism 121 can change the contact pressure when the drive roller 134 and the driven roller 135 are in contact with each other. That is, in the pressurizing mechanism 121, the first transport member is in contact with the first transport member in a first state in which the first transport member and the second transport member are in contact with each other, and the first transport member and the second transport member are in contact with each other higher than in the first state. This is an example of a switching means capable of switching between the second state of contact with pressure. Further, the pressurizing mechanism 121 can switch the pre-registration roller pair 132 to a separated state (third state) in which the driving roller 134 and the driven roller 135 are separated from each other.

As shown in FIG. 2, the pressurizing mechanism 121 includes a roller shaft 136 of the driven roller 135, a roller support member 140, a tension spring 137, and a return spring 145. As shown in FIG. 3, the driven roller 135 is arranged so as to be exposed to the sheet transport path through the opening 141 formed in the plate-shaped roller support member 140 extending in the width direction. The roller support member 140 is a swing member that can swing around the swing shaft 142 with respect to the transport guides 133a and 133b constituting the seat transport path 133. The roller shaft 136 is supported by the roller support member 140 by hooking the central portion of the tension spring 137 whose both ends are held on the roller support member 140, and the drive roller 134 rotates as the roller support member 140 swings. It is possible to relative to the axis. The return spring 145 is stretched between the fixing member integrated with the transport guide 133a and the roller support member 140, and urges the roller support member 140 in a direction in which the driven roller 135 is separated from the drive roller 134.

Further, as shown in FIG. 4, the pressurizing mechanism 121 includes a cam 144 which is a cam member and an arm 143 which swings integrally with the roller support member 140. In the pressurizing mechanism 121, when the arm 143 is pressed by the cam 144, the roller support member 140 swings against the urging force of the return spring 145.

As shown in FIG. 5, when the roller support member 140 swings in a direction closer to the drive roller 134 as compared with the first state (see the broken line) in which the pre-registration roller pair 132 is nipped at a low pressure, the pre-registration roller pair 132 is moved. It is in the second state of being niped at high pressure. At this time, since the tension spring 137, which is an elastic member, is stretched as compared with the first state, the driven roller 135 is pressed against the drive roller 134 with a stronger elastic force than the first state according to the amount of deformation of the tension spring 137.

On the other hand, as shown in FIG. 6, when the roller support member 140 swings in a direction away from the drive roller 134 as compared with the first state (see the broken line), the roller-front roller pair 132 is separated from each other in the third state. That is, the roller support member 140 is released from the pressing force of the cam 144 and swings according to the urging force of the return spring 145, so that the driven roller 135 is separated from the drive roller 134.

As shown in FIG. 7, the cam 144 of the pressurizing mechanism 121 and the drive roller 134 of the pre-registration roller pair 132 are connected to the pre-registration drive motor 202 which is a common drive source. The drive transmission unit 203 that transmits the driving force of the pre-registration drive motor 202 to the cam 144 and the drive roller 134 is transferred to either the cam 144 or the drive roller 134 according to the rotation direction of the pre-registration drive motor 202 capable of forward / reverse rotation. Transmits the driving force. That is, when the pre-registration drive motor 202 rotates in the first direction (normal rotation), the driving force is transmitted to the drive roller 134 to rotationally drive the pre-registration roller pair 132, while the pressurizing mechanism 121 It doesn't work. On the contrary, when the pre-registration drive motor 202 rotates in the second direction (reverse rotation), the cam 144 rotates and the pre-registration roller pair 132 switches between the first to third states, while the pre-registration is performed. The roller pair 132 is not driven to rotate. The drive transmission unit 203 achieves such a function by disposing a one-way clutch corresponding to each of the drive roller 134 and the cam 144, for example.

Further, in the pre-registration transport unit composed of the pre-registration roller pair 132 and the pressurizing mechanism 121, the cam angle for detecting the rotation angle of the cam 144 as a detecting means capable of detecting the pressurizing state of the pre-registration roller pair 132. A detection sensor 204 is provided. As the cam angle detection sensor 204, for example, a transmissive photoelectric sensor that detects a flag member that swings integrally with the roller support member 140 can be used.

Hereinafter, a method of controlling the sheet transfer operation by the skew correction device 130 will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7, the image forming apparatus 100 is equipped with a CPU circuit unit 201, which is an example of control means. The CPU circuit unit 201 includes a memory 206 for temporarily or permanently storing a program and data, and a central processing unit (CPU) 205 as an arithmetic unit capable of executing the program. The CPU circuit unit 201 receives an input signal from an operation unit 200 that includes a liquid crystal panel and various buttons and functions as a user interface. The CPU circuit unit 201 controls the operation of the skew correction device 130 by driving and controlling the pre-registration drive motor 202 and other actuators.

The CPU 205 realizes the functions of each process in the flowchart shown in FIG. 8 by executing the program read from the memory 206. The CPU 205 continues the standby state until a print job instructing the image forming apparatus 100 to output an image is input (S1). At this time, the pre-registration roller pair 132 is held in a separated state.

When the execution instruction of the print job is detected with the basis weight of the sheet S used as the recording medium input via the operation unit 200 (S2). Control (S3 to S10) according to the basis weight N of the sheet S is started. When the basis weight N is smaller than the first reference value (N <N1), it is determined to maintain the pre-registration roller pair 132 in a separated state (S3). On the other hand, in the case of a sheet in the intermediate region where the basis weight N is equal to or more than the first reference value and less than the second reference value (N1 ≦ N <N2), it is determined that the roller pair 132 in front of the register is nipped at a low pressure ( S4: Yes). Further, when the basis weight N is equal to or greater than the second reference value (N ≧ N2), it is determined that the pre-registration roller pair 132 is niped at a high pressure (S4: No). Then, the pre-registration drive motor 202 rotates in the forward direction in response to the detection signal from the cam angle detection sensor 204, so that the pre-registration roller pair 132 is in a state of being nipated at low pressure or high pressure (S5, S6).

In other words, when transporting a sheet having a first basis weight, the first transport means is set to the first mode and the sheet having a second basis weight larger than the first basis weight is conveyed. If this is the case, the first transport means will be in the second mode set to the second state. Further, when transporting a sheet having a third basis weight smaller than the first basis weight, the first transfer means is set to the third mode in the third mode. The sheet having the first basis weight is, for example, plain paper in the range of 60 gsm to 300 gsm, in which case the second basis weight corresponds to thick paper of 300 gsm or more and the third basis weight corresponds to thin paper of less than 60 gsm. ..

When the pressurizing state of the pre-registration roller pair 132 is appropriately set by the pressurizing mechanism 121, the pre-registration drive motor 202 starts reverse rotation and the pre-registration roller pair 132 is rotationally driven (S7). The seat S that has passed through the nip portion of the pre-registration roller pair 132 abuts on the stopped register roller pair 131 to form a loop, and the skew of the seat S is corrected (S8 to S10). Specifically, after the front end of the seat S is detected by the detection sensor arranged near the registration roller pair 131, the driving of the registration front roller pair 132 or the transport unit on the upstream side thereof is continued for a certain period of time. A loop of sheet S is formed.

At this time, when the pre-registration roller pair 132 is in the separated state, the sheet S is additionally conveyed as compared with the case where the pre-registration roller pair 132 is in the contact state (S10), so that a relatively large loop is performed. Is formed. In other words, in the first mode or the second mode, a loop of the sheet is formed by the sheet being conveyed by the first conveying means with the first conveying amount after the sheet is brought into contact with the second conveying means. On the other hand, in the third mode, after the sheet comes into contact with the second transport means, the sheet is transported by the upstream transport means with a second transport amount larger than the first transport amount, thereby forming a loop of the sheet. .. However, the upstream transport means is a transport roller equivalent that is arranged upstream from the first transport means and transports the sheet toward the first transport means. For example, the feed unit 117 or the extraction roller pair 113 in FIG. 1 is used. Corresponds to this. As a result, even in the third mode in which the distance between the roller pairs sandwiching the seat S is widened, it is possible to secure a loop between the pre-registration roller pair 132 and the registration roller pair 131, which is effective for skew correction, and the first mode and Oblique correction can be realized with the same accuracy as the second mode.

After that, by starting the rotation of the register roller pair 131, the sheet S in a state where the skew is corrected is sent out to the secondary transfer unit (S11). At this time, in the second mode in which the roller pair 132 in front of the register is strongly in contact with each other, the seat S is strongly sandwiched as compared with the first mode in which the contact pressure is relatively low, so that the transport force is stronger than in the first mode. Is given to the sheet S. Then, after the image is transferred in the secondary transfer unit, the sheet S is discharged to the discharge tray, and the print job is completed (S12).

After the print job is completed, if there is no new job input and the standby state continues and the sheet is not conveyed by the skew correction device 130 for a predetermined time, the pre-registration drive motor 202 rotates in the forward direction and the pre-registration roller. The pair 132 is switched to a separated state. After that, when a new print job is submitted, the above flow is repeated. If the next job is executed continuously after the print job is completed, such as when multiple print jobs are stacked, the state of the rollers before the checkout to 132 according to the basis weight of the sheet of the next job. Should be changed.

In this way, the pre-registration roller pair 132 is configured to be switchable between a low pressure niped state, a high pressure niped state, and a separated state by the pressurizing mechanism 121. In other words, the first transport means according to the present embodiment can be switched to a first state in which the sheet is weakly sandwiched, a second state in which the sheet is strongly sandwiched, and a third state in which the sheet is released. Then, it is possible to perform a switching operation for appropriately switching the state of the first transport means according to the type of the sheet, and it is possible to achieve both stability of the sheet transport operation and reduction of wrinkles.

Specifically, for a sheet such as thick paper, which has high rigidity and tends to have a large transfer resistance, the transfer of the sheet by the register roller pair 131 is started in the second state in which the pre-registration roller pair 132 is nipped at a high pressure. The mode (second mode) is selected. As a result, the sheet transfer by the register roller pair 131 (second transfer means) is assisted by the register front roller pair 132 (first transfer means), reducing the possibility of sheet non-feeding and improving the stability of the sheet transfer operation. Can be improved.

For a sheet such as thin paper having low rigidity and prone to out-of-plane deformation, a mode (third mode) in which the transfer of the sheet by the register roller pair 131 is started in the third state in which the pre-registration roller pair 132 is separated is selected. .. As a result, the transfer of the sheet by the register roller pair 131 is started in a state where the out-of-plane deformation of the sheet in the vicinity of the register roller pair 131 is alleviated, so that the occurrence of wrinkles can be suppressed.

For sheets such as plain paper with medium rigidity, the mode (first mode) in which the transfer of the sheet by the register roller pair 131 is started in the first state in which the register roller pair 132 is nipped at a low pressure is selected. Will be done. As a result, the transfer of the sheet by the register roller pair 131 (second transfer means) is assisted by the register front roller pair 132 (first transfer means). Here, since the pressing force of the pre-registration roller pair 132 is weaker than that in the second state, slipping of the sheet is allowed to some extent even if the rigidity is as high as that of plain paper. Therefore, the stress caused by the asymmetric loop in the width direction formed by the skew correction is released by the slip of the sheet with respect to the pre-registration roller pair 132, and the inclination of the sheet sent out from the register roller pair 131 (skew return). ) Is prevented. That is, by switching between the first mode and the second mode, the first conveying means can hold the sheet with an appropriate holding force according to the rigidity of the sheet. It is possible to achieve both reduction of the acting stress.

Further, in this embodiment, after the print job is completed with the pre-registration roller pair 132 niped at low pressure or high pressure, the operation of switching the pre-registration roller pair 132 to a separated state after a certain period of time elapses (S13). Will be done. As a result, the load on the pre-registration roller pair 132 and the pressurizing mechanism 121 in the standby state can be reduced, and the durability of the apparatus can be improved. For example, even when a strong tension spring 137 that realizes a high-pressure nip state is used, it is possible to prevent creep deformation of the drive roller 134 or the roller support member 140 due to the elastic force of the tension spring 137. be.

(Modification example)
In this embodiment, the pressurizing state of the pre-registration roller pair 132 is switched to three stages, but the pressing force in the contact state may be controlled more finely. Further, it is not limited to the configuration in which the pressurizing state of the roller pair 132 in front of the cash register is changed according to the basis weight of the sheet S, for example, whether or not the surface is processed such as coated paper and whether or not the sheet has a special shape such as an envelope. The pressurization state may be changed by.

Further, in this embodiment, the skew of the seat S is corrected by abutting the front end of the seat S against the nip portion of the registration roller pair 131, but the front end of the seat S is applied to the shutter member arranged near the registration roller pair. It may be configured to hit. In that case, the shutter member is retracted and the seat S is sandwiched between the registration roller pairs, so that the seat S can be conveyed by the registration roller pair.

Next, the skew correction device, which is the sheet transfer device according to the second embodiment, will be described with reference to FIGS. 9 to 11. The skew correction device according to the present embodiment is different from the first embodiment in the configuration of the pressurizing mechanism of the roller pair in front of the register. Other elements common to the first embodiment are designated by the same reference numerals as those of the first embodiment, and the description thereof will be omitted.

As shown in FIG. 9, the bearing member 146 that rotatably supports the driven roller 135 of the pre-registration roller pair 132 is movably supported by the regulating surfaces 147 and 147 in the directions of approaching and separating from the driving roller 134. ing. The driven roller 135 comes into contact with and separates from the drive roller 134 when the bearing member 146 is moved by the pressurizing mechanism 122, which is another example of the switching means.

The pressurizing mechanism 122 includes a roller support member 149, a stopper 148, and a compression spring 138. The roller support member 149 is a swing member that can swing around the swing shaft 142 by the same cam mechanism (see FIG. 4) as in the first embodiment. The bearing member 146 has a protrusion 146a that extends away from the rotation axis of the drive roller 134 and penetrates the roller support member 149, and the compression spring 138 is arranged on the outer peripheral side of the protrusion 146a. As a result, the compression spring 138, which is an elastic member, is arranged between the roller support member 149 and the bearing member 146 in a state where the expansion / contraction direction is aligned with the moving direction of the bearing member 146 regulated by the regulation surface 147. .. Further, a stopper 148 is attached to the tip of the protrusion 146a, and the roller support member 149 swings clockwise in the drawing so that the bearing member 146 is pulled via the stopper 148.

The pre-registration roller pair 132 shown in FIG. 9 is in a state of being nipated at a low pressure (first state), and the compression spring 138 exerts a reaction force on the roller support member 149 to press the bearing member 146. As a result, the driven roller 135 is pressed against the drive roller 134 by the elasticity of the compression spring 138 and the pressing force determined by the position of the roller support member 149.

As shown in FIG. 10, when the roller pair 132 in front of the register is nipped at a high pressure (second state), the roller support member 149 is closer to the bearing member 146 than in the first state (see the broken line). Swing. As a result, the compression spring 138 is compressed as compared with the first state, so that the driven roller 135 is pressed against the drive roller 134 with a stronger pressing force. Therefore, the force (nip pressure in the nip portion N1) of the front roller pair 132 holding the seat S is stronger than that in the first state.

As shown in FIG. 11, when the roller pair 132 in front of the register is separated (third state), the roller support member 149 swings in the direction separated from the bearing member 146 as compared with the first state (see the broken line). Move. As a result, the bearing member 146 is pulled away from the rotation axis of the drive roller 134 via the stopper 148, and the driven roller 135 is separated from the drive roller 134. Then, the nip portion of the pre-registration roller pair 132 is opened, and the pre-registration roller pair 132 is in a state of not sandwiching the seat S.

The skew correction device provided with the pressurizing mechanism 122 according to the present embodiment can be controlled by the same control method as that of the first embodiment. That is, for a sheet of plain paper or the like having a medium rigidity, the mode (first mode) in which the transfer of the sheet by the register roller pair 131 is started in the first state in which the register roller pair 132 is nipped at a low pressure is selected. Will be done. For a sheet of thick paper or the like having high rigidity, a mode (second mode) in which the transfer of the sheet by the registration roller pair 131 is started in the second state in which the registration roller pair 132 is nipped at a high pressure is selected. For a sheet of thin paper or the like having low rigidity, a mode (third mode) in which the transfer of the sheet by the register roller pair 131 is started in the third state in which the register roller pair 132 is separated from each other is selected.

As described above, also in this embodiment, the pre-registration roller pair 132 corresponding to the first transport means is switched between the state of being nipped at low pressure, the state of being niped at high pressure, and the state of being separated by the pressurizing mechanism 121. Possible to be configured. As a result, the state of the first transport means can be appropriately switched according to the type of the sheet, and the stability of the sheet transport operation and the reduction of wrinkles can be achieved at the same time.

Further, in this embodiment, unlike the configuration in which the driven roller 135 is pressed against the drive roller 134 by using the tension spring as in the first embodiment, the driven roller 135 is pressed against the drive roller 134 by using the compression spring 138. In this configuration, the pressing force of the roller pair 132 in front of the register can be adjusted by the roller support member 149 arranged at a position farther from the seat transfer path than the roller shaft 136 of the driven roller 135. Therefore, compared to the arrangement of the first embodiment (see FIG. 2) in which the roller support member 140 is closer to the rotation axis of the drive roller 134 than the roller shaft 136, the movable range of the roller support member 149 by the transport guide 133a or the like is increased. The restrictions are loosened. Therefore, for example, by setting the stroke of the roller support member 149 corresponding to the switching between the first state and the second state to be large, it is possible to accurately control the nip pressure of the roller to 132 in front of the register.

(Other embodiments)
In Examples 1 and 2 above, the skew correction device arranged upstream of the secondary transfer unit has been described as an example of the sheet transfer device, but this technique may be applied to other sheet transfer devices. For example, it can be used as a device for transporting a sheet while correcting the skew of the sheet in a sheet processing device that performs a process such as drilling a sheet discharged from the device main body of the image forming apparatus. Further, the intermediate transfer tandem type image forming unit 150 (see FIG. 1) is an example of an image forming means, and for example, the present technology may be applied to a sheet transporting device in an inkjet type image forming apparatus.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100, 130 ... Sheet transport device (image forming device, skew correction device) / 113,117 ... Upstream transport means (pulling roller pair, feeding unit) / 121, 122 ... Switching means (pressurizing mechanism) / 131 ... 2nd transport means (registration roller pair) / 132 ... 1st transport means (roller pair before registration) / 134 ... 1st transport member (drive roller) / 135 ... 2nd transport member (driven roller) / 137,138 ... Elastic member (tension spring, compression spring) / 140,149 ... Swing member (roller support member) / 144 ... Cam member (cam) / 150 ... Image forming means (image forming unit) / 201 ... Control means (CPU circuit unit) ) / 202 ... Drive motor (drive motor before registration) / S3 to S6 (switching operation)

Claims (4)

A pair of transport rollers that sandwich and transport the sheet,
An upstream transfer roller pair arranged upstream of the transfer roller pair in the sheet transfer direction,
Wherein provided in the sheet conveyance direction downstream of the transport roller pair, a registration roller pair for conveying by nipping the sheet, the leading end of the sheet over bets to correct the skew of the sheet by being abutted With a pair of registration rollers,
A conveyance guide for guiding the sheet toward the front Symbol registration roller pair, when viewed from the width direction perpendicular to the sheet conveying direction, inclined upward toward the downstream of the sheet conveyance direction, and, A transport guide that forms a curved sheet transport path so that the inclination in the horizontal direction increases as it approaches the registration roller pair.
A first state in which the transport roller pairs are brought into contact with each other, a second state in which the transport roller pairs are brought into contact with each other with a contact pressure larger than that in the first state, and a third state in which the transport roller pairs are separated from each other. With a switching means capable of switching the transfer roller pair,
A first mode in which the sheet is conveyed toward the registration roller pair by the transfer roller pair in the first state, and a first mode in which the sheet is conveyed toward the registration roller pair by the transfer roller pair in the second state. A control means capable of executing two modes and a third mode in which the sheet is conveyed toward the registration roller pair by the upstream transfer roller pair with the transfer roller pair in the third state.
Equipped with
The control means executes the first mode when transporting a sheet having a first basis weight, and when transporting a sheet having a second basis weight larger than the first basis weight, the first mode is described. When executing the two modes and transporting a sheet having a third basis weight smaller than the sheet having the first basis weight, the third mode is executed .
A sheet transfer device characterized by this. The transport roller pair has a drive roller and a driven roller that follows the rotation of the drive roller.
Further equipped with a drive motor that can rotate in the first direction and the second direction opposite to the first direction.
When the drive motor rotates in the first direction, the drive roller is rotationally driven.
When the drive motor rotates in the second direction, the state of the transport roller pair is switched by the switching means.
The sheet transport device according to claim 1, wherein the sheet transport device is characterized by the above. The switching means has a rotatable cam member, a swing member that swings by the cam member, and an elastic member that connects the swing member and the driven roller, and the swing member swings. By doing so, the driven roller is brought into contact with and separated from the driving roller, and in a state where the driving roller and the driven roller are in contact with each other, the driven roller is driven by an elastic force corresponding to the position of the swinging member to the elastic member. The contact pressure of the transport roller pair is changed by pressing the roller toward the drive roller.
The sheet transport device according to claim 2 , wherein the sheet transport device is characterized by the above. An image forming means for forming an image on a sheet sent out from the registration roller pair is provided.
The sheet transport device according to any one of claims 1 to 3, wherein the sheet transport device is characterized by the above.

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