JP7085133B2 - Conveyor device, image forming device - Google Patents

Description

The present invention relates to a transport device and an image forming device.

In a transport device for transporting a sheet, positional deviation such as skewing of the sheet or displacement in the width direction during transport becomes a problem. For example, in an image forming apparatus that forms an image on a sheet, there is a problem that the image position formed on the sheet deviates from the ideal position due to the positional deviation during transportation of the sheet.

The invention of a transport device for transporting a sheet while correcting the misalignment of the sheet as described above has already been made. For example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-239348), a drive roller and a nip forming roller are rotatably held on a carriage. Then, the sheet is fed to the nip portion between the rotating drive roller and the nip forming roller, so that the sheet is sandwiched and conveyed to the downstream side. Further, during the sheet transfer, the carriage moves in the width direction of the seat while holding the drive roller and the nip forming roller, so that the positional deviation in the width direction of the seat can be corrected.

As in Patent Document 1, the correction member (carriage and roller) that corrects the misalignment of the seat by moving itself and conveys the sheet returns to the original position after the sheet is conveyed, and conveys the next sheet. And it is necessary to prepare for the correction operation.

At this time, in the case of a transport device that continuously transports sheets at high speed, the interval between the conveyed sheets is shortened. Therefore, unless the movement of the correction member to the reference position is started at an earlier timing, the correction member cannot return to the reference position by the time the next sheet is conveyed, and the position deviation of the sheet is appropriately corrected. There was a problem that it could not be transported to the downstream side. However, on the other hand, while the front sheet is sandwiched between the correction members and conveyed, the correction member cannot be moved to the reference position, and the timing at which the correction member starts to move to the reference position is extremely important. there were.

Under such circumstances, the present invention provides a transport device provided with a correction member capable of quickly moving to a reference position after the sheet correction and transfer operation is completed to prepare for the next sheet transfer operation. It is an object.

In order to solve the above problems, the present invention has a correction member for transporting the sheet and correcting the positional deviation of the sheet, and a downstream side provided on the downstream side of the correction member in the sheet transport direction to transport the sheet. A transport device having a transport member and a detection mechanism for detecting the separation of the correction member from the transport path of the sheet, wherein the correction member is a reference position which is a position facing the transport path of the sheet. By moving from, the position deviation of the sheet can be corrected, and in the correction member, the detection mechanism detects the separation of the correction member, so that the downstream side transport member is transporting the sheet. , It is characterized by moving to the reference position.

In the present invention, by detecting the timing at which the correction member is separated from the seat by the detection mechanism, the correction member can be moved to the reference position without a gap after the correction member is separated. Therefore, it is possible to correct the misalignment of the seat even while continuously transporting the seat at high speed.

It is a schematic block diagram of an image forming apparatus. It is a figure which shows the transport device of this embodiment, (a) is a plan view, (b) is a side view. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a figure explaining the process of transporting a paper by a transporting apparatus. It is a flow diagram explaining the process of transporting a paper by a transporting apparatus. It is a figure which shows the method of calculating the misalignment amount of a paper by CIS. It is a block diagram which shows the structure of the control part which controls each operation of a transfer device. It is a schematic block diagram which shows the image forming apparatus of a different embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

The color image forming apparatus 1 shown in FIG. 1 is provided with an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9K are detachably provided. Each process unit 9Y, 9M, 9C, 9K accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of supporting toner as a developer on the surface, and a charging roller for uniformly charging the surface of the photoconductor drum 10. A developing device, a cleaning device, and the like for supplying toner to the surface of the photoconductor drum 10 are provided.

An exposure unit is arranged above the process unit 9. The exposed unit is configured to emit laser light based on the image data.

The transfer unit 4 is arranged directly below the image-creating unit 2. The transfer unit 4 includes a drive roller, a secondary transfer facing roller 13, a plurality of tension rollers, an endless intermediate transfer belt 16 stretched by these rollers so as to be able to travel around, and a photoconductor drum 10 of each process unit 9. It is composed of a primary transfer roller or the like arranged at a position facing the intermediate transfer belt 16 with respect to the intermediate transfer belt 16. Each primary transfer roller presses the inner peripheral surface of the intermediate transfer belt 16 at each position, and a primary transfer nip is formed at a position where the pressed portion of the intermediate transfer belt 16 and each photoconductor drum 10 come into contact with each other. ing.

Further, the secondary transfer roller 18 is arranged at a position facing the secondary transfer facing roller 13 with the intermediate transfer belt 16 interposed therebetween. The secondary transfer roller 18 presses the outer peripheral surface of the intermediate transfer belt 16, and a secondary transfer nip is formed at a position where the secondary transfer roller 18 and the intermediate transfer belt 16 come into contact with each other.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and is a paper feed cassette 19 as a sheet loading unit that accommodates the paper P as a sheet, and a paper feed roller that carries out the paper P from each paper feed cassette. And so on.

The transport path 6 is a transport path for transporting the paper P carried out from the paper feeding unit 5. A plurality of transport roller pairs are appropriately arranged on the transport path 6 up to the paper ejection unit 8, which will be described later.

On the transport path 6, on the downstream side in the paper transport direction from the paper feed unit 5, and on the upstream side from the secondary transfer nip position, the misalignment of the paper P on the transport path 6 is corrected, and the paper P is moved to the downstream side. A transport device 30 for transport is provided.

The fixing device 7 has a fixing roller 22 heated by a heating source, a pressure roller 23 capable of pressurizing the fixing roller 22, and the like.

The paper ejection unit 8 is provided at the most downstream side of the transport path 6 of the image forming apparatus 1.

A branch portion 6a is provided on the way to the paper discharge portion 8 of the transport path 6, and is branched to the reverse path 6b and the reverse transport path 6c side separately from the path leading to the paper discharge section 8.

Hereinafter, the basic operation of the image forming apparatus 1 will be described with reference to FIG.

When the image forming operation is started in the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9C, 9M, 9K. The image information exposed by the exposure unit on each photoconductor drum 10 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device is supplied to the photoconductor drum 10 by a drum-shaped developing roller, so that the electrostatic latent image is visualized. It is visualized as a toner image (developer image).

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of the arrow A1 in the figure by the rotational drive of the drive roller. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip. As described above, for example, the image forming unit 2, the exposure unit, the transfer unit 4, and the like function as an image forming unit that forms an image on the paper P.

On the other hand, when the image forming operation is started, in the lower part of the image forming apparatus 1, the paper feeding roller of the paper feeding unit 5 is rotationally driven, so that the paper P accommodated in the paper feeding cassette 19 is sent out to the transport path 6. Is done.

The paper P sent out to the transport path 6 is transported to the downstream side by the transport device 30 and the roller pair on the transport path 6, and the misalignment is corrected by the transport device 30, so that the secondary transfer roller 18 and the secondary transfer roller 18 are secondary. It is sent to the secondary transfer nip formed between the transfer facing roller 13. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

The paper P on which the toner image is transferred is conveyed to the fixing device 7, and the paper P is heated and pressed by the fixing roller 22 and the pressure roller 23 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing roller 22 and conveyed to the downstream paper ejection unit 8 and discharged to the outside of the apparatus.

In the case of double-sided printing, after an image is formed on the first surface (front surface) and the image is fixed, the image is conveyed from the branch portion 6a via the inversion path 6b to the inversion transfer path 6c, and then again. , Returned to the transport path 6. Then, the paper is discharged to the paper ejection unit 8 again through the transfer and position correction by the transport device 30, the transfer of the image to the second surface (back surface) by the transfer unit 4, and the fixing operation by the fixing device 7.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9C, 9M, and 9K. It is also possible to use two or three process units 9 to form a two-color or three-color image.

As shown in FIGS. 2 (a) and 2 (b), the transport device 30 of the present embodiment includes a transport roller (upstream transport member) 31, a sandwiching roller (correction member) 32, and a timing roller that transport the paper P. (Downstream side transport member) 33, first CIS (positional deviation detection mechanism) 34 for detecting paper P, second CIS (positional deviation detection mechanism) 35, third CIS (positional deviation detection mechanism) 36, It has a first edge sensor (seat detection mechanism) 37, a second edge sensor (upstream side sheet detection mechanism) 38, a third edge sensor (downstream side sheet detection mechanism) 39, and a fourth edge sensor (detection mechanism) 40. Hereinafter, the transport direction of the paper P is simply referred to as a transport direction, and the upstream side and the downstream side in the transport direction are also simply referred to as an upstream side and a downstream side. Further, the width direction of the paper P is also simply referred to as the width direction.

The transfer roller 31, the sandwiching roller 32, and the timing roller 33 are transfer rollers composed of a pair of rollers. These transport rollers can transport the paper P to the downstream side by rotationally driving each roller pair in a state where the paper P is sandwiched between the nip portions of the rollers. In the transport direction of the paper P, the transport roller 31, the holding roller 32, and the timing roller 33 are arranged from the upstream side to the downstream side in this order, and the paper P transported to the transport device 30 is the same. It is conveyed to the downstream side by each roller in order.

The sandwiching roller 32 is provided so as to be rotatable around the fulcrum 32a in the paper transport surface and movable in the width direction. By these operations, the sandwiched paper P can be rotated or moved in the width direction, and the skewing or the positional deviation in the width direction of the paper P can be corrected. Hereinafter, with respect to the sandwiching roller 32, the rotation of the roller for transporting the paper P is simply referred to as rotation, and the above rotation for skew correction is referred to as rotation in the paper transport surface.

In each CIS of the first CIS34, the second CIS35, and the third CIS36, a contact image in which a plurality of photosensors composed of a light emitting element such as an LED and a light receiving element such as a photodiode are arranged side by side in the width direction of the paper P. It is a sensor.

The first edge sensor 37, the second edge sensor 38, the third edge sensor 39, and the fourth edge sensor 40 are sensors capable of detecting the position of the front end or the rear end of the paper P. As these sensors, for example, a pair of photosensors including a light emitting element and a light receiving element can be used. Each edge sensor is in a detection state when the paper P faces each edge sensor, and is in a non-detection state when the paper P does not face each other, and the detection state changes.

The first edge sensor 37 is provided in the vicinity of the downstream side of the transport roller 31. Further, a second edge sensor 38 and a third edge sensor 39 are provided in the vicinity of the upstream side and the vicinity of the downstream side of the sandwiching roller 32, respectively. The fourth edge sensor 40 is provided in the vicinity of the downstream side of the transport roller 31.

Next, each operation when the paper is continuously passed through the transport device 30 will be described with reference to each operation diagram of FIGS. 2 to 9, a flow diagram of FIG. 10, and FIG.

First, as shown in FIGS. 2A and 2B, the paper P1 conveyed to the transfer device 30 reaches the position of the first CIS34 and then the transfer roller 31. Then, it is sandwiched by the transport roller 31 and transported to the downstream side. At this time, the transport member on the upstream side of the transport device 30 (in this embodiment, the roller pair 50 on the upstream side in FIG. 1) is separated from the paper P.

As shown in FIG. 2B, the holding roller 32 on the downstream side is in a state of being separated from the transport path 6. Of the pair of rollers, only the upper roller is separated, and the lower roller does not move. In the present embodiment, the state in which only the upper roller is separated is referred to as, for example, the separation of the holding rollers 32. Further, the holding roller 32 is arranged at a reference position. The reference position of the holding roller 32 is a position where the holding roller 32 is arranged on the paper transport path 6 facing the transport path 6 as shown in FIG. 2A.

Then, as shown in FIGS. 2A and 2B, the paper P reaches the first edge sensor 37, and the arrival is detected (step S1 in FIG. 10).

After a certain period of time from step S1, the paper P1 reaches the second CIS 35 as shown in FIGS. 3 (a) and 3 (b).

In the present embodiment, t1 seconds have elapsed since the tip of the paper P1 was detected by the first edge sensor 37 in step S1 (step S2), and then the detection by the first CIS34 and the second CIS35 is started. The time t1 is set based on the timing at which the paper P1 reaches the second CIS35. Specifically, the above t1 is set based on the distance between the first edge sensor 37 and the second CIS35 and the transport speed of the paper P1.

Then, based on the detection results of the paper P1 by the first CIS34 and the second CIS35, the skew amount and the position deviation amount in the width direction of the paper P are calculated, and based on the skew amount and the position deviation amount in the width direction. , The pinching roller 32 picks up (step S3). The pick-up operation is an operation of moving the paper P1 in the skewing direction and the position deviation direction in the width direction by the amount of the position deviation. In other words, it is an operation in which the holding roller 32 moves so as to receive the paper P1 which is misaligned in a state of facing the paper P1.

An example of a method of calculating the skew amount and the position deviation amount in the width direction of the paper P1 based on the detection results by the first CIS34 and the second CIS35 will be described with reference to FIG.
As shown in FIG. 11, since the boundary between the paper portion and the non-paper portion can be detected by the first CIS 34 and the second CIS 35, the position in the width direction of the side edge Pa of the paper P1 can be detected. Specifically, the first CIS34 can detect the widthwise position L1 of the point Pa1, and the second CIS35 can detect the widthwise position L2 of the point Pa2. The amount of positional deviation of the paper P1 in the width direction can be obtained, for example, by averaging the position L1 in the width direction and the position L2 in the width direction. Further, the inclination angle (inclination amount) θ of the paper P1 is determined by using the distance M between the first CIS34 and the second CIS35 in the transport direction.
TANθ = (L1-L2) / M ... (1)
It can be expressed as. The skew amount θ of the paper P1 can be obtained from this equation (1). The amount of skew of these sheets P1 is calculated by the sheet position recognition unit 61 (see FIG. 12) of the control unit 60, which will be described later.

As described above, the timing at which the paper reaches the second CIS35 can be estimated by the detection operation of the first edge sensor 37, and the detection operation by the first CIS34 and the second CIS35 is started before the arrival of the paper. Can be done. Therefore, it is possible to reduce the extra detection operation by these CIS, reduce unnecessary energy consumption, and extend the life of the CIS. The detection operation of the first edge sensor 37 is the starting point for starting the correction operation of the paper P1. The (first) correction operation of the paper P1 is the position detection of the paper P1 by the first CIS34 and the second CIS35, the calculation of the misalignment amount, the subsequent pick-up operation of the holding roller 32, and the return operation described later. It refers to a series of operations.

Further, when the paper P1 is conveyed, the tip of the paper P1 reaches the second edge sensor 38 (step S4), as shown in FIGS. 4 (a) and 4 (b). Upon detection by the second edge sensor 38, the roller pair constituting the sandwiching roller 32 begins to shift from the separated state to the pressure contact state.

As shown in FIGS. 5A and 5B, the paper P1 reaches the holding roller 32 after a certain period of time after the paper P1 reaches the second edge sensor 38.

In the present embodiment, after t2 seconds have elapsed from the detection of the paper P1 by the second edge sensor 38 (step S5), the holding roller 32 starts to be rotationally driven (step S6). After that, when the paper P1 reaches the holding roller 32 and is conveyed by the sandwiching roller 32, the conveying roller 31 begins to separate from the conveying path 6 and the sheet P1 (step S7). The time t2 is set at a timing before the paper P1 reaches the holding roller 32, and is determined from the distance between the second edge sensor 38 and the holding roller 32 and the transport speed of the paper P1. Further, the holding roller 32 is in a pressure contact state by the time the paper P1 reaches the holding roller 32.

In this way, the timing at which the paper P1 reaches the holding roller 32 can be estimated by the detection operation of the second edge sensor 38. Then, in accordance with this timing, the holding roller 32 is pressed against the holding roller 32 and driven to rotate as described above, so that the holding roller 32 can convey the paper P1 by the time the paper P1 reaches the holding roller 32. Can be migrated to.

Further, as shown in FIGS. 6A and 6B, after the transport roller 31 is separated from the paper P1, the holding roller 32 that transports the paper P1 while sandwiching the paper P1 performs a return operation, and the position of the paper P1 is displaced. Is corrected (step S8). The return operation is an operation of correcting the misalignment of the paper P1 by rotating the paper P1 in the transport surface and moving the paper P1 in the width direction by the amount of the misalignment of the paper P1 during the transport operation of the paper P1. .. Since the pinching roller 32 has been moved in advance by the amount of the misalignment of the paper P1 due to the above-mentioned picking operation, the pinching roller 32 after the return operation is completed returns to the reference position (from the dotted line portion in FIG. 6a). Move to the solid line). In this way, the transport operation and the correction operation of the holding roller 32 can be started from the detection operation of the second edge sensor 38 as a starting point. In addition, the transport roller 31 shifts to the pressure contact state again at a predetermined timing after the return operation in order to prepare for the next paper transport operation (see FIG. 7b).

After the process of the return operation or the completion of the return operation, the paper P1 reaches the third edge sensor 39, and the arrival is detected (step S9).

Then, as shown in FIGS. 7 (a) and 7 (b), the paper P1 reaches the third CIS 36 after a certain period of time from the arrival at the third edge sensor 39 in step S9. By the time the third CIS 36 is reached, the holding roller 32 completes the return operation, and the first correction operation of the paper P1 is completed.

In the present embodiment, after t3 seconds have elapsed from the arrival of the paper P1 at the third edge sensor 39 (step S10), the detection operation by the second CIS35 and the third CIS36 is started (step S11). This time t3 is set at a timing before the paper P1 is transported to the third CIS 36 in consideration of the distance between the third edge sensor 39 and the third CIS 36 and the transport speed of the paper P1.

By providing the third edge sensor 39 in this way, the timing at which the paper reaches the third CIS36 can be estimated, and the detection operation of the paper P1 by the third CIS36 can be started before the arrival of the third CIS36. ..

The position of the paper P1 whose position deviation has been corrected by the return operation is detected again by the second CIS35 and the third CIS36, and the position deviation amount is calculated. Then, the position shift is corrected again by the holding roller 32. The method of calculating the amount of misalignment of the paper P1 based on the detection results of the second CIS35 and the third CIS36 is the same as the calculation method based on the detection results of the first CIS34 and the second CIS35 described above.

The detection operation by the second CIS35 and the third CIS36 and the correction operation by the holding roller 32 are repeated for t4 seconds after the paper P1 reaches the third edge sensor 39. That is, the detection results by the second CIS35 and the third CIS36 are fed back to the holding roller 32 each time, and the misalignment of the paper P1 is corrected with high accuracy (see steps S11 and S12. Hereinafter, this correction is performed on the paper. Called recorrection operation). Further, the holding roller 32 that has returned to the reference position after the return operation is moved from the reference position by the amount of the correction amount by this re-correction operation, and is moved to a position different from the reference position.

The above re-correction operation is performed until the rear end of the paper P1 passes through the second CIS 35 (step S13). Further, when the paper P1 is conveyed to the downstream side, the paper P1 reaches the timing roller 33 (step S14).

Then, the paper P1 is sandwiched and conveyed by the timing roller 33, the sandwiching roller 32 stops rotating, and is separated from the paper P (step S15). The rotation stop and separation operations of the holding roller 32 are performed at different timings from the detection by the sensor. Specifically, after the sandwiching roller 32 starts the drive rotation in step S6, it rotates by a predetermined rotation speed, then automatically stops the rotation and separates from the paper P1. The predetermined rotation speed is set to a value such that the rotation of the holding roller 32 is stopped after the paper P is nipped into the timing roller 33. That is, based on the distance between the holding roller 32 and the timing roller 33, the rotation speed of the paper P is set to reach the timing roller 33.

The paper P1 is conveyed by the timing roller 33 and reaches the fourth edge sensor 40 as shown in FIGS. 8A and 8B (step S16). After that, the paper P1 is timed by the timing roller 33 and conveyed to the secondary transfer position further downstream, and the transfer of the paper P1 by the transfer device 30 is completed.

At this time, assuming that the number of prints specified for the job of the image forming apparatus is N, it is determined whether or not the paper P1 is the Nth paper (step S17). Then, in the case of the Nth sheet, the transfer operation of the sheet by the transfer device 30 is completed.

When the paper P1 is not the Nth sheet, the transport device 30 shifts to the operation for transporting the next paper P2, as shown in FIGS. 8 (a) and 8 (b). , Paper P2, which is the paper to be printed next to the paper P1, is transported to the upstream side of the transport device 30.

When the new paper P2 is conveyed to the transfer device 30 and the holding roller 32 performs the picking operation again (see step S3), the movement amount of the picking operation of the holding roller 32 is from the reference position of the holding roller 32. Calculated as the amount of movement. Therefore, when starting the picking operation for the new paper P2, it is necessary that the holding roller 32 is arranged at the reference position. In this regard, as described above, since the holding roller 32 is moved from the reference position by the re-correction operation, it is arranged at a position different from the reference position after the re-correction operation of the paper P1 is completed, and the next paper is used. By the time P2 is received, it is necessary to return the holding roller 32 to the reference position. On the other hand, if the pinching roller 32 starts moving to the above-mentioned reference position while the pinching roller 32 is transporting the previous paper P1, the paper P1 will be displaced by that amount. It is necessary to transfer the previous paper P1 to a downstream roller (timing roller 33 in this embodiment) and then start moving to the reference position.

As described above, the movement of the holding roller 32 to the reference position needs to be performed after the transfer operation of the previous sheet P1 is completed and before the next sheet P2 is conveyed. In the present embodiment, the detection operation of the fourth edge sensor 40 is used as the timing of starting the movement of the pinching roller 32 to the reference position. That is, since the fourth edge sensor 40 is arranged near the downstream side of the timing roller 33, when the fourth edge sensor 40 detects the paper P1, the paper P1 is already sandwiched and conveyed by the timing roller 33. , The sandwiching roller 32 is separated from the paper P1 (step S15). Therefore, by starting the movement of the holding roller 32 to the reference position after the paper is detected by the fourth edge sensor 40, the holding roller 32 can be moved to the reference position without causing the position shift of the previous paper P1. ..

By providing the fourth edge sensor 40 in this way, it is possible to determine the timing at which the sandwiching roller 32 moves to the reference position. In particular, by detecting the timing immediately after the pinching roller 32 is separated from the paper P1 by the fourth edge sensor 40, the pinching roller 32 can be returned to the reference position more quickly. Specifically, while the timing roller 33, which is a roller on the downstream side of the holding roller 32, holds and conveys the paper P, the movement of the holding roller 32 to the reference position can be started. Therefore, even in an image forming apparatus capable of high-speed printing in which the distance between the papers to be printed is short, the holding roller 32 can be returned to the reference position until the next paper is conveyed. In other words, the sandwiching roller 32 can carry the paper to the downstream side while correcting the misalignment of each sheet of paper to be printed at high speed, and can support high-speed printing.

In this embodiment, in order to detect the separation of the holding roller 32 from the paper P1, the holding roller is indirectly operated by detecting the arrival of the paper P1 at the fourth edge sensor 40, which is an operation immediately after that. It is assumed that the separation timing of 32 is detected. As described above, the timing of starting the movement of the holding roller 32 to the reference position is not limited to the case where the direct detection of the separation of the holding roller 32 itself is the starting point, and is substantially the same timing or later. By detecting the timing of a specific operation performed at the timing, the separation of the pinching roller 32 can be indirectly detected, and the timing of the start of movement of the pinching roller 32 can be set. As an example of direct detection, the holding roller 32 is provided with a separation detecting mechanism instead of the fourth edge sensor 40, and the holding roller 32 is moved to the reference position by the detection operation of the separation detecting mechanism. May start.

Then, as shown in FIGS. 9 (a) and 9 (b), when the newly conveyed paper P2 reaches the first edge sensor 37, the first CIS 34 and the second CIS 35 detect the paper P2. It is started, and the correction operation of the paper P2 is started (steps S1 to S3).

In the present embodiment, as described above, after the fourth edge sensor 40 detects the paper P1, the first edge sensor 37 detects the new paper P2, so that a new correction operation is started. .. However, in this case, it is necessary to determine whether the detection by the first edge sensor 37 is the detection of the previous paper P1 or the detection of the new paper P2. If the previous paper P1 and the new paper P2 are erroneously detected, the holding roller 32 tries to move to the reference position while the paper P1 is still being conveyed, or the new paper P2 is conveyed. However, a malfunction occurs such that the holding roller 32 has not completed the picking operation, which in turn leads to a misalignment of the paper.

As a specific method for determining that the previous paper P1 has been switched to the new paper P2 depending on the detection state of the first edge sensor 37, for example, the first edge sensor 37 is in the detection state while the paper P1 is being conveyed. Therefore, once the non-detection state is reached and the detection state is reached again, it can be determined that the new paper P2 has been conveyed. That is, it can be determined that this non-detection state has detected the space between the paper P1 and the paper P2, and that the subsequent detection state has been detected by the new paper P2 being conveyed. Because. However, this method causes false positives in the following cases. That is, when the paper P1 is provided with punch holes, the punch holes are temporarily in a non-detection state while the punch holes pass through the first edge sensor 37. Further, when the paper has an image or the like printed on the paper P1 in advance, for example, the black image portion may not be recognized as the paper portion by the first edge sensor 37, and may be temporarily in a non-detection state. be. In this way, even while the paper P1 is being conveyed, it may be temporarily in the non-detection state, and if the above method is adopted, it is erroneously assumed that the paper P1 has passed due to this non-detection state. It is determined that the subsequent detection of the paper P1 is the next paper P2.

From the above circumstances, in the present embodiment, it is determined by steps S18 to S20 of FIG. 10 whether or not the non-detection state of the first edge sensor 37 is between papers. Specifically, after the detection by the fourth edge sensor 40 is performed (after step S16), the monitoring of the detection state of the first edge sensor 37 is started (step S18). Then, when the first edge sensor 37 changes from the detected state to the non-detected state (step S19), if this non-detected state continues for t5 seconds, it is determined that there is a space between papers, and the next paper P2. Move to the correction operation. If the non-detection state does not continue for t5 seconds, the correction operation of the next paper P2 is not performed, and the detection operation by the first edge sensor 37 is continued (step S20).

The above-mentioned t5 is a value provided for determining whether or not the non-detection state is a punched hole portion. Specifically, assuming that the assumed length (hole diameter) of the punch holes in the transport direction is d [mm] and the paper transport speed is v [mm / s], the punch holes pass through the first edge sensor 37. The time to do can be expressed as d / v [s]. That is, when the above-mentioned non-detection state exceeds d / v, t × v> d, and the first edge sensor 37 detects the non-detection portion having a width larger than the punch hole. It can be determined that this non-detection portion is not a punch hole but a space between papers. Therefore, by setting the value of t5 to a value larger than d / v, it is possible to discriminate between paper spaces and punch holes.

Further, assuming that the assumed length between papers is L [mm], the value of t5 needs to be set to a value smaller than L / v. That is, t5 is set so that t × v does not become a value larger than the space between papers. As described above, t5 is set to an arbitrary value larger than d / v and smaller than L / v. In addition, according to the method of this embodiment, it is possible to prevent erroneous detection even in the non-detection state due to the black image or the like passing through the first edge sensor 37. That is, the first edge sensor 37 can detect most of the paper on which a black image or the like is printed as paper, and the first edge sensor 37 is only temporarily in a non-detection state. Therefore, since the non-detection state of the first edge sensor 37 due to the passage of such an image does not continue for more than t5 seconds, the non-detection state due to a black image or the like and the non-detection state due to paper spacing by the above method It is also possible to distinguish it from the state.

The assumed punch hole size d is 5.5 mm to 6.5 mm according to JIS S 6041. However, if there is a hole formed in the sheet other than the punched hole, the distance d can be set according to the length in the transport direction, and the above-mentioned t5 can be set.

When it is determined that the non-detection state by the first edge sensor 37 is between papers, the detection state by the first edge sensor 37 after non-detection is determined to be the next paper P2, and the next paper P2. (Transition to step S2). By repeating the above operation, the transport device 30 can transport N sheets of paper and correct the positional deviation.

In this way, the paper P can be sent out to the secondary transfer position in a state where the positional deviation of each paper with respect to the transport path is corrected, so that an image can be formed at an appropriate position of the paper P. In other words, it is possible to correct the absolute positional deviation of the image formed on the surface of the paper P. When double-sided printing is performed, the inverted paper P is conveyed to the conveying device 30 via the inverted pass 6b and the inverted transfer path 6c (see FIG. 1), the paper position is corrected again, and the paper P is performed. The image position formed on the back surface of the image is corrected. Then, by performing the position correction operation by the transport device 30 before forming the images of the front surface and the back surface, the relative positions of the image of the front surface and the image of the back surface on the paper P are obtained. You can also eliminate the gap.

FIG. 12 is a block diagram showing a configuration of a control unit that controls each operation of the above transport device 30.
As shown in FIG. 12, the control unit 60 includes a paper position recognition unit 61, a first motor control unit 62, a second motor control unit 63, and a transfer motor control unit 64.

The paper position recognition unit 61 calculates the skew amount and the position deviation amount in the width direction of the paper P from the detection information received from each CIS. Then, the paper position recognition unit 61 sends information on the amount of this positional deviation to the first motor control unit 62 and the second motor control unit 63.

The first motor control unit 62 and the second motor control unit 63 are parts that control each movement operation of the holding roller 32 based on the information on the amount of position deviation of the paper P sent from the paper position recognition unit 61.

The first motor control unit 62 is a portion that controls the rotational operation of the sandwiching roller 32 in the transport surface. In response to the signal from the first motor control unit 62, the first motor driver 621 drives the first motor 622 to rotate the sandwiching roller 32 in the transport surface. Then, the rotation amount of the sandwiching roller 32 in the transport surface is detected by the first motor encoder 623.

The second motor control unit 63 is a portion that controls the movement operation of the sandwiching roller 32 in the width direction. In response to the signal from the second motor control unit 63, the second motor driver 631 drives the second motor 632 to move the holding roller 32 in the width direction. Then, the second motor encoder 633 detects the amount of movement of the sandwiching roller 32 in the width direction.

In these first motor 622 and second motor 632, the holding roller 32 is picked up (step S3 in FIG. 10), returned (step S8), re-corrected (step S11), and returned to the reference position. It will be driven at the time of (step S16).

As described above, the detection operation by the first CIS34 and the second CIS35 is performed t1 seconds after the first edge sensor 37 detects the new paper P (see steps S1 to S3). Based on this detection result, the holding roller 32 is picked up and returned. Further, the detection operation by the second CIS35 and the third CIS36 is performed t3 seconds after the third edge sensor 39 detects the paper P (steps S9 to S11). Based on this detection result, the re-correction operation of the sandwiching roller 32 is performed.

When the pinching roller 32 performs the return operation (step S8), it is necessary that the paper P is pinched by the pinching roller 32 and the transport roller 31 (see FIG. 2) on the upstream side is separated (step S7). ). Therefore, the transfer roller separation detection sensor 70 detects the separation of the transfer rollers 31, and this detection signal is transmitted to the first motor control unit 62 and the second motor control unit 63. As a result, the first motor control unit 62 and the second motor control unit 63 can send a signal to each motor driver to start the return operation.

As described above, the operation of returning the holding roller 32 to the reference position is performed after the fourth edge sensor 40 detects the paper P (step S16). That is, the detection information of the fourth edge sensor 40 is sent to the first motor control unit 62 and the second motor control unit 63 to drive each motor, and the holding roller 32 moves to the reference position.

Further, the transfer motor control unit 64 is a part that controls the rotation operation (transfer operation of the paper P) of the holding roller 32. In response to the signal from the transfer motor control unit 64, the transfer motor driver 641 drives the first transfer motor 642, and the holding roller 32 rotates to transfer the paper P.

The rotation operation of the holding roller 32 is performed t2 seconds after the paper P reaches the second edge sensor 38 (steps SS4 to S6). That is, the transfer motor 642 is driven by sending the detection information of the second edge sensor 38 to the transfer motor control unit 64.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

In the above embodiment, the fourth edge sensor 40 is provided on the downstream side of the timing roller 33, and after the detection of the fourth edge sensor 40, the movement of the holding roller 32 to the reference position is started. That is, starting from the time when the paper P reaches the timing roller 33, the holding roller 32 is separated from the transport path 6 and the paper P, and the movement of the holding roller 32 to the reference position is started. However, the present invention is not limited to this, for example, a secondary transfer roller 18 (and a roller pair composed of the secondary transfer opposed rollers 13 facing the secondary transfer roller 18) or another roller pair between the sandwiching roller 32 and the secondary transfer roller 18. If the configuration is provided, a fourth edge sensor may be provided in the vicinity of these rollers, and the rollers may be used as a starting point. However, if the fourth edge sensor 40 is provided near the roller (timing roller 33 in this embodiment) that conveys the paper P next to the pinching roller 32, the pinching roller 32 moves to the reference position at an earlier timing. This is preferable because it can be prepared for the next paper transport and correction operation.

In the above embodiment, the first CIS 34 is arranged upstream of the transfer roller 31, but the first CIS 34 may be arranged downstream of the transfer roller 31.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Further, in the embodiment described above, the present invention has been applied to the transport device 30 installed in the electrophotographic image forming apparatus 1, but to the transport device installed in the inkjet type image forming apparatus. The present invention can also be applied. Hereinafter, an inkjet type image forming apparatus will be described with reference to FIG.

As shown in FIG. 13, the inkjet type image forming apparatus 100 includes a feeding unit 110, a conveying device 120, an image forming unit 130, a drying unit 140, and a paper ejection unit 150.

The paper P sent out from the paper feeding unit 110 is conveyed by the conveying device 120 and sent out to the image forming unit 130.

In the image forming unit 130, the paper P is positioned on the cylindrical drum 131 and is conveyed in the direction of the arrow in the figure by the rotation of the cylindrical drum 131. Then, the paper P is conveyed to the lower part of the ejection head 132 of each color (the position where the image is formed on the paper P) at a predetermined timing, the ink of each color is discharged to the paper P, and the image is formed on the surface of the paper P. ..

The paper P on which the image is formed by the image forming unit 130 is conveyed to the drying unit 140 to evaporate the moisture in the ink, and then is discharged to a position where the operator can take it out by the paper ejection unit 150.

When double-sided printing is performed, after the drying step, the paper P is sent to the reverse transfer path 160, and the paper P is sent to the transfer device 120 again with the front and back sides inverted.

By applying the configuration of the transport device of the present invention described above to the transport device 120 described above, the same effects as those of the present embodiment described above can be obtained. That is, the transport device 120 corrects the skew of the paper P and the positional deviation in the width direction. With the above-described configuration, the transport device 120 can correct the positional deviation of the paper P with respect to the transport path while transporting the paper P at high speed, and the absolute position of the image formed on the paper P with respect to the paper P. The deviation can be corrected. Further, when double-sided printing is performed, it is possible to eliminate the relative positional deviation between the image on the front surface and the image on the back surface by correcting the positional deviation of the image on each surface. Then, the paper P is conveyed to the downstream image forming unit 130 in a state where the positional deviation of the paper P is corrected.

Sheets include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, plastic films, prepregs, copper foil, etc. Is done.

1 Image forming device 6 Transport path 30 Transport device 31 Transport roller (upstream transport member)
32 Holding roller (correction member)
33 Timing roller (downstream transport member)
34 First CIS (Position Misalignment Detection Mechanism)
35 Second CIS (Position Misalignment Detection Mechanism)
36 Third CIS (Position Misalignment Detection Mechanism)
37 First edge sensor (seat detection mechanism)
38 Second edge sensor (upstream sheet detection mechanism)
39 Third edge sensor (downstream sheet detection mechanism)
40 Fourth edge sensor (detection mechanism)
60 Control unit P paper (sheet)

Japanese Unexamined Patent Publication No. 2008-239348

Claims (16)

A correction member that conveys the sheet and corrects the misalignment of the sheet,
A downstream transport member provided on the downstream side of the correction member in the sheet transport direction and transporting the sheet, and a downstream transport member.
A transport device having a detection mechanism for detecting the separation of the correction member from the transport path of the sheet.
The correction member corrects the misalignment of the seat by moving from the reference position on the transport path of the seat.
The compensating member is a transport device characterized in that the detection mechanism detects the separation of the compensating member, so that the downstream transport member moves to the reference position while the sheet is being transported. The transport device according to claim 1, wherein the detection mechanism indirectly detects the separation of the correction member from the transport path of the sheet. Immediately after the downstream transport member starts transporting the sheet, the correction member is separated from the sheet.
The detection mechanism is provided in the vicinity of the downstream side of the downstream side transport member in the sheet transport direction, and by detecting the arrival of the sheet on the downstream side transport member, the correction member is indirectly separated from the sheet. 2. The transport device according to claim 2. The transport device according to claim 1, wherein the detection mechanism directly detects the separation of the correction member from the transport path of the sheet. Further having a sheet detection mechanism for detecting the sheet,
The transport device according to any one of claims 1 to 4, wherein the sheet detection mechanism starts a correction operation of the sheet after detecting the arrival of the sheet. When the non-detection state continues for a predetermined time after the sheet detection mechanism enters the detection state, it is determined that the rear end of the sheet has passed the sheet detection mechanism, and the process proceeds to the correction operation of the next sheet. The transport device according to claim 5. The transport device according to claim 6, wherein the predetermined time is determined by the size of punch holes formed in the sheet. An upstream transport member for transporting the sheet is provided on the upstream side of the correction member in the sheet transport direction.
The transport device according to any one of claims 5 to 7, wherein the sheet detection mechanism is provided in the vicinity of the downstream side of the upstream transport member in the sheet transport direction. An upstream sheet detection mechanism for detecting the arrival of the sheet is further provided on the upstream side of the correction member in the sheet transport direction.
One of claims 1 to 8, after the upstream seat detection mechanism detects the arrival of the seat, the correction member starts an operation for transporting the seat and an operation for correcting the misalignment of the seat. The transport device described in. It also has a plurality of misalignment detection mechanisms for detecting the seat position, and has a plurality of misalignment detection mechanisms.
Claim 1 to calculate the amount of misalignment of the sheet based on the detection result of the misalignment detection mechanism provided on the upstream side of the compensating member in the sheet transport direction, and have the compensating member correct the misalignment of the sheet. To 9 The transport device according to any one of the following items. A downstream sheet detection mechanism for detecting the arrival of the sheet is further provided on the downstream side of the correction member in the sheet transport direction.
The position deviation detection mechanism is provided on the sheet transport downstream side of the downstream side sheet detection mechanism.
After the sheet is detected by the downstream sheet detection mechanism, the position deviation detection mechanism provided on the downstream side of the downstream sheet detection mechanism in the sheet transport direction starts the sheet detection operation, and at least by the position deviation detection mechanism. The transport device according to claim 10, wherein the correction member corrects the positional deviation of the sheet again based on the detection result. The transport device according to any one of claims 1 to 11, wherein the correction member is a pair of rollers that sandwich and transport the sheet. A correction member that conveys the sheet and corrects the misalignment of the sheet,
A downstream transport member provided on the downstream side of the correction member in the sheet transport direction and transporting the sheet, and a downstream transport member.
A transport device provided near the downstream side of the downstream transport member in the sheet transport direction and having a detection mechanism whose detection state changes when the sheet arrives.
The correction member corrects the misalignment of the seat by moving from the reference position on the transport path of the seat.
After the sheet reaches the downstream transport member, the correction member is separated from the sheet.
The compensating member is a transport device characterized in that the downstream transport member is transporting the sheet and moves to the reference position after the detection state of the detection mechanism changes. A correction member that conveys the sheet and corrects the misalignment of the sheet,
A downstream transport member provided on the downstream side of the correction member in the sheet transport direction and transporting the sheet, and a downstream transport member.
A detection mechanism provided near the downstream side of the downstream transfer member in the sheet transport direction and whose detection state changes when the sheet arrives.
A transport device having a control unit that controls the operation of the correction member.
The control unit corrects the misalignment of the seat by moving the correction member from the reference position on the transport path of the seat.
After the sheet reaches the downstream transport member, the control unit separates the correction member from the sheet, the downstream transport member is transporting the sheet, and the detection state of the detection mechanism changes. A transport device, characterized in that the correction member is later moved to the reference position. An image forming apparatus including the transport device according to any one of claims 1 to 14. The image forming apparatus according to claim 15, wherein the downstream transfer member is a transfer roller that transfers an image to the sheet, or a transfer roller provided on the upstream side in the sheet transport direction.

Images