JP2019119551A - Conveyance device and image formation device - Google Patents

Abstract

To correct a position of a sheet with high accuracy even when abnormality occurs in any of detection means installed on each of the upstream side and the downstream side of a sandwiching roller pair.SOLUTION: When abnormality of a downstream detection part 36 (downstream detection means) is detected by abnormality detection means, before a sheet P is conveyed to a position of a sandwiching roller pair 31, "first correction" similar to normal time is performed based on a detection result of an upstream side detection part 35, then the position of the sandwiching roller pair 31 is continuously changed from a reference position on the basis of a continuous detection result by the upstream side detection part 35 while the sheet P is conveyed by the sandwiching roller pair 31. On the contrary, when abnormality of the upstream side detection part 35 (upstream detection means) is detected by the abnormality detection means, the position of the sandwiching roller pair 31 is continuously changed from the reference position on the basis of the continuous detection result by the downstream side detection part 36 while the sheet P is conveyed by the sandwiching roller pair 31.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a conveying apparatus for conveying a sheet, and an image forming apparatus such as an electrophotographic or inkjet copying machine provided with the same, a printer, a facsimile, or a compound machine thereof, an offset printing machine, etc. It is a thing.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, detection means such as a plurality of CISs (contact image sensors) are provided at intervals in the transport direction on the transport path, and based on the detection results thereof The sheet is corrected for skew in the rotational direction in the sheet conveyance plane, or is referred to as “lateral resist” as appropriate at a position in the sheet width direction (a direction orthogonal to the conveyance direction). There is known a technique for correcting the deviation of) to a normal position (see, for example, Patent Documents 1 and 2).

Specifically, in the image forming apparatus in Patent Documents 1 and 2, a pinching roller pair configured to be able to pivot in the pivoting direction or move in the width direction in the transport surface while pinching and transporting the sheet It is provided. Further, two CISs (first detection means) are arranged in parallel along the transport path on the upstream side of the pinching roller pair, and one CIS (second sensing means) is installed on the downstream side of the pinching roller pair It is done. Each of these CISs detects the attitude of the sheet passing through the position in the rotational direction and the width direction.
Then, while holding and conveying the sheet, the holding roller pair rotates in the rotation direction to perform skew correction (skew correction) based on the detection result detected by the two upstream CIS. It moves in the width direction and performs horizontal registration correction. Thereafter, the pinching roller pair pinches and conveys the sheet subjected to the skew correction and the lateral registration correction, based on the detection result detected by the CIS on the upstream side and the CIS on the downstream side with respect to the pinching roller pair. In addition to skew correction by rotating in the rotational direction, lateral registration correction is performed by moving in the width direction.

The above-described conventional conveyance device corrects the position (orientation) of the sheet with high accuracy because the position in the rotational direction and the width direction of the sheet is corrected a plurality of times while the sheet is nipped and conveyed by the nipping roller pair. The effect to be corrected can be greatly expected.
However, the conventional conveyance device includes any one of the detection means (CIS) installed upstream of the holding roller pair and the detection means (CIS) installed downstream of the holding roller pair. If an abnormality occurs in the sheet, it is impossible to correct the position of the sheet with high accuracy.

  The present invention has been made to solve the above-described problems, and an abnormality occurs in the upstream detection means among the detection means installed on the upstream side and the downstream side with respect to the pinch roller pair. In the case where the sheet has slipped, or when an abnormality has occurred in the downstream detection means among the detection means installed respectively on the upstream side and the downstream side with respect to the nipping roller pair, the position of the sheet is high An object of the present invention is to provide a conveying device and an image forming apparatus capable of correcting the accuracy.

  The conveyance device according to the present invention is a conveyance device that conveys a sheet in a conveyance path, and a pinching roller pair that pinches and conveys the sheet in the conveyance path, and a position upstream of the pinching roller pair in the conveyance direction. Upstream detection means for detecting the position of the sheet in the width direction and / or the rotational direction in the conveyance surface, and the sheet in the width direction or the position downstream of the pinch roller pair in the conveyance direction And / or downstream side detection means for detecting the position in the rotational direction, variable means for changing the position in the width direction or / and rotational direction of the pinch roller pair, the upstream side detection means, and the downstream side detection means When there is no abnormality in the upstream side detection means by the abnormality detection means and a state in which the downstream side detection means has an abnormality is detected. The position of the nipping roller pair is changed from the reference position corresponding to the position of the sheet detected by the upstream side detection unit before the sheet is conveyed to the position of the pair, and the sheet is nipped thereafter The position of the pinching roller pair in the state is changed to the reference position, and thereafter, while the sheet is conveyed by the pinching roller pair, the sheet continuously detected by the upstream side detection means The position of the holding roller pair is continuously changed from the reference position so as to be corrected based on the position.

  According to the present invention, when an abnormality occurs in the upstream detection means among the detection means respectively installed on the upstream side and the downstream side with respect to the nipping roller pair, or in the upstream with respect to the nipping roller pair A conveying device capable of correcting the position of the sheet with high accuracy even if an abnormality occurs in the downstream detection means among the detection means respectively installed on the side and the downstream side; An image forming apparatus can be provided.

FIG. 1 is an overall configuration diagram showing an image forming apparatus in Embodiment 1 of the present invention. It is the schematic which shows a conveying apparatus. It is a top view which shows a part of conveyance apparatus. It is a perspective view which shows the principal part of a conveying apparatus. It is a control flow which shows the 1st amendment. It is a block diagram showing a control part. It is a control flow which shows the 2nd amendment. It is the schematic which shows operation | movement of a conveying apparatus when there is no abnormality in an upstream detection part and a downstream detection part. FIG. 9 is a schematic view showing the operation of the transfer device following FIG. 8; It is the schematic which shows the operation | movement of a reference | standard board. It is a graph which shows the output level of CIS. It is a graph which shows the output level of CIS as another form. It is the schematic which shows operation | movement of a conveying apparatus in, when there exists abnormality in a downstream detection part. FIG. 14 is a schematic view showing the operation of the transfer device following FIG. 13; It is the schematic which shows operation | movement of a conveying apparatus in, when there exists abnormality in an upstream detection part. FIG. 16 is a schematic view showing the operation of the transfer device following FIG. 15; FIG. 13 is a schematic view showing the operation of the transport apparatus in the case where there is an abnormality in the upstream side detection unit as a modification example 1; FIG. 18 is a schematic view showing the operation of the transfer device following FIG. 17; It is a top view which shows a part of conveyance apparatus in Embodiment 2 of this invention. FIG. 18 is a top view showing a part of the transfer device in a second modification. It is a side view which shows the line sensor as a downstream detection means in the conveying apparatus of FIG. FIG. 10 is an overall configuration diagram showing an image forming apparatus in Embodiment 3 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the redundant description will be appropriately simplified or omitted.

Embodiment 1
Embodiment 1 of the present invention will be described in detail with reference to FIGS.
First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a copying machine as an image forming apparatus, 2 is an original reading unit for optically reading image information of an original D, and 3 is a photosensitive member based on image information read by the original reading unit 2 An exposure unit for irradiating the surface of the drum 5 and an image forming unit 4 for forming a toner image (image) on the surface of the photosensitive drum 5 as an image carrier.
Further, 7 is a transfer roller as a transfer unit for transferring the toner image formed on the surface of the photosensitive drum 5 onto the sheet P, 10 is a document conveyance unit for conveying the set document D to the document reading unit 2, 14 is a sheet feeding cassette (sheet feeding unit) in which sheets P such as sheets are stored; 20 is a fixing device for fixing an unfixed image on the sheet P; 21 is a fixing roller installed in the fixing device 20; The pressure roller installed in the apparatus 20 is shown.
A conveying device 30 conveys the sheet P along a conveying path, and a pair of pinching rollers (horizontal resist 31 functions as a registration roller (timing roller) 31 conveying the sheet P toward the transfer roller 7 (transfer nip portion)・ Screw correction roller)

With reference to FIG. 1, an operation at the time of normal image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). The exposure unit 3 emits exposure light L (laser light) based on the image information of the electrical signal toward the surface of the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated clockwise in FIG. 1 and passes through predetermined image forming processes (charging step, exposing step, developing step) to form image information on the photosensitive drum 5. An image (toner image) corresponding to the image is formed.
Thereafter, the image formed on the surface of the photosensitive drum 5 is transferred onto the sheet P conveyed by the nipping roller pair 31 functioning as a registration roller at the transfer nip portion where the transfer roller 7 and the photosensitive drum 5 abut. Be done.

On the other hand, referring to FIGS. 1 and 2, the sheet P conveyed to the position of the transfer roller 7 (transfer nip portion) operates as follows.
First, one sheet feeding cassette is automatically or manually selected from the plurality of sheet feeding cassettes 12 to 14 of the image forming apparatus main body 1 (for example, the sheet feeding cassette 12 installed in the apparatus main body 1 is selected) Shall be
Then, the uppermost sheet of the sheet P stored in the sheet feeding cassette 12 is fed by the sheet feeding roller 41 toward the curved conveyance path in which the first conveyance roller pair 42 and the second conveyance roller pair 43 are installed. Will be sent.

Thereafter, the sheet P passes through the position of the merging portion X (a portion where the transport paths from the two sheet feeding cassettes 13 and 14 installed outside the apparatus main body 1 merge) from the curved transport path. The sheet passes through the linear conveyance path in which the third conveyance roller pair 44 (upstream conveyance roller pair) and the alignment unit 51 are installed, and reaches the position of the pinch roller pair 31 constituting the alignment unit 51. Then, a skew correction and a lateral registration correction are performed by the pinching roller pair 31 constituting the matching unit 51, and the transfer roller is adjusted in timing to align with the image formed on the photosensitive drum 5. The sheet is conveyed toward the position 7 (transfer nip).
The transfer roller 7 and the photosensitive drum 5 are rotated along the conveyance direction indicated by the arrows, and are disposed downstream of the pair of holding rollers 31 in the conveyance direction to nip and convey the sheet P. It also functions as a downstream conveyance roller pair.

Then, the sheet P after the transfer process passes the position of the transfer roller 7 (transfer nip portion), and then reaches the fixing device 20 through the conveyance path. The sheet P having reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, and the image is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22. . The sheet P on which the image is fixed is discharged from between the fixing roller 21 and the pressure roller 22 (which is a nip portion), and then discharged from the image forming apparatus main body 1.
Thus, a series of image forming processes (image forming operations) are completed.

Here, referring to FIG. 2, the image forming apparatus 1 according to the first embodiment can feed the sheet P from the three sheet feeding cassettes 12 to 14 to the position of the transfer roller 7 (transfer nip portion). Is configured as.
Further, each of the conveying roller pairs 42 to 44 (including the conveying roller pair not having reference numerals) installed in the conveying device 30 is a driving roller (a roller rotationally driven by a driving mechanism). The roller pair includes a driven roller (a roller that is driven to rotate due to a frictional resistance with a drive roller), and configured to be able to convey the sheet P while holding it by two rollers. Further, the transfer roller 7 abuts against the photosensitive drum 5 at the transfer nip portion in a state where a predetermined transfer bias is applied, and rotates in the counterclockwise direction in FIG. The image carried on the photosensitive drum 5 is transferred to the sheet P while the sheet P is being conveyed.

  Here, the position of the transfer roller 7 (transfer nip portion) from the joining portion X where the conveyance path from the first sheet feeding cassette 12 and the conveyance paths from the second and third cassettes 13 and 14 merge. As a conveyance path up to, a linear conveyance path formed substantially linearly along the conveyance direction of the sheet P is provided. The straight conveyance path is formed by a straight conveyance guide plate (guide plates disposed so as to sandwich the front and back surfaces of the sheet P being conveyed), and the third conveyance roller pair 44 (along the conveyance direction) An upstream conveyance roller pair), an upstream detection unit 35 (upstream detection unit), a pinch roller pair 31 (alignment unit 51), and a downstream detection unit 36 (downstream detection unit) are installed. Each of the third conveyance roller pair 44 and the pinching roller pair 31 is a roller pair including a drive roller and a driven roller, and conveys the sheet P while nipping the sheet P with two rollers. Then, the pinching roller pair 31 performs an alignment operation of skew feeding correction (correction for positional deviation in the rotation direction in the sheet conveyance surface) and lateral registration correction (correction for positional deviation in the width direction). Functions as a matching unit 51 for performing the process, which will be described in detail later.

Next, the conveyance device 30 will be described in detail with reference to FIGS.
Hereinafter, the configuration in the conveyance path from the merging portion X to the transfer roller 7 (transfer nip portion) and the operation performed there will be described.
Referring to FIGS. 2 and 3, the conveyance device 30 includes a third conveyance roller pair 44 (upstream) along a straight conveyance path of the sheet P (a conveyance path from the junction X to the transfer roller 7). Side conveyance roller pair), upstream detection unit 35 (upstream first CIS 35A and upstream second CIS 35B) as upstream detection means, pinching roller that functions as an alignment unit 51 and also functions as a registration roller A pair 31, a downstream detection unit 36 (a downstream first CIS 36A and a downstream second CIS 36B) as downstream detection means are installed.
A plurality of four CISs 35A, 35B, 36A, 36B (contact image sensors) are arranged side by side in the width direction (the vertical direction of FIG. 2 corresponds to the vertical direction of FIG. 2). A line sensor composed of a photo sensor, which optically detects a side edge Pa (edge portion) of the sheet P passing through the position.
As described above, in the conveyance device 30 according to the first embodiment, the detection units 35 and 36 including two line sensors that detect the side edge Pa of the sheet P conveyed in the predetermined conveyance direction in the conveyance path, They are respectively installed on the upstream side and the downstream side of the pinching roller pair 31.

Here, the pinching roller pair 31 is a roller pair having a plurality of roller portions divided in the width direction, and is driven by a first drive motor 59 (refer to FIG. 4) as a drive unit (first drive unit). The drive roller 31a is driven to rotate, and the driven roller 31b rotates to follow the rotation of the drive roller 31a. The pinching roller pair 31 is formed so as to be capable of conveying the sheet P by rotating in a state in which the sheet P is pinched.
In the first embodiment, a roller pair having a plurality of roller portions divided in the width direction is used as the pinching roller pair 31. However, a roller portion extending in the width direction is provided without being divided in the width direction. A roller pair can also be used.

Here, in the transport device 30 according to the first embodiment, a variable unit that changes the position in the width direction or the rotation direction of the pinch roller pair 31, and a control unit 90 (see FIG. 6) that controls the variable unit. Is provided. The variable means comprises a moving means configured to move the pinching roller pair 31 in the width direction, and a pivoting means configured to pivot the pinching roller pair 31 in the pivoting direction.
That is, the pinching roller pair 31 is formed to be able to pivot in the pivoting direction (the pivoting in the direction of the double arrow W in FIGS. 3 and 4) and at the same time in the width direction (broken line in FIGS. It is formed to be movable in the direction of the double arrow S.

Specifically, referring to FIG. 4, the pinching roller pair 31 (driving roller 31a and driven roller 31b) is rotationally driven by a first drive motor 59 as a driving means (first driving means) to pinch the sheet P. Transport in the state of
Specifically, the first drive motor 59 (first drive means) is fixed to the frame of the conveyance device 30 (image forming apparatus 1). In the first drive motor 59, the gear portion 76a (in the width direction of the frame side rotation shaft 76 in which the drive gear 59a installed on the motor shaft is rotatably held by the rising portion 71b of the base portion 71 (frame) And the frame side rotation shaft 76 is rotationally driven in the direction of the arrow Q in FIG. Then, when the frame side rotation shaft 76 is rotationally driven, the rotation driving force is transmitted to the rotation shaft of the drive roller 31a via the coupling 75 and the drive roller 31a is rotated, and the driven roller is driven thereby. 31b will also rotate.
Here, the coupling 75 interposed between the rotation shaft of the drive roller 31a and the frame side rotation shaft 76 held by the frame is a coupling (shaft joint) such as a constant velocity joint or a universal joint. Even if the holding roller pair 31 is rotated together with the holding member 72 by the drive of the second drive motor 62, which will be described later, even if the axial angle between the rotation shaft of the drive roller 31a and the frame side rotation shaft 76 changes The rotational drive force is transmitted without any change.

The pinching roller pair 31 is rotatably held by the substantially rectangular frame-like holding member 72 (movable member) and is also held movable in the width direction. Specifically, the drive roller 31a and the driven roller 31b are rotatably held by the holding member 72 via bearings (fixed to the holding member 72) at both widthwise end portions of the rotation shaft. ing. The driving roller 31 a and the driven roller 31 b are each held movably in the width direction (rotational axis direction) by the holding member 72. In particular, a sufficient gap is provided between the support portion 72b on one end side of the holding member 72 and the gear portion 72a, and even if the drive roller 31a and the driven roller 31b slide to one end in the width direction, The rotation axes of these components are configured not to interfere with the gear portion 72a.
Further, the holding member 72 is rotatably supported around a shaft portion 71 a with respect to a base portion 71 which functions as a part of a frame of the conveyance device 30 (image forming apparatus 1). Further, a second drive motor 62 (rotational motor) as a rotation means (variable means) is fixedly installed at one end side in the width direction of the base portion 71. The motor shaft 62a of the second drive motor 62 The gear formed on the rear side is formed to mesh with a gear portion 72 a formed on one end side in the width direction of the holding member 72. As a result, by the rotational drive of the second drive motor 62 in the forward and reverse directions, the holding roller pair 31 as well as the holding member 72 pivots about the shaft portion 71a (by the pivoting in the double arrow W direction in FIGS. 3 and 4). There will be. The second drive motor 62 (turning means) is configured to be able to turn the holding member 72 in the turning direction together with the pinch roller pair 31 based on the detection results of the detection units 35 and 36 described later. . A known encoder is installed on the motor shaft of the second drive motor 62 (rotation motor), and the amount of rotation and the direction of rotation of the holding roller pair 31 relative to the reference position are detected indirectly It is configured to be. As a result, skew correction can be performed by the holding roller pair 31 based on the detection results of the detection units 35 and 36.
Thus, the constituent members such as the second drive motor 62 and the holding member 72 function as a rotation means (variable means) for rotating the pinch roller pair 31 in the rotation direction inclining with respect to the transport direction. Become.
In the first embodiment, the pinching roller pair 31 (holding member 72) is configured to rotate around the center position in the width direction, but the pinching roller pair 31 (holding member 72) is in the width direction. It can also be configured to rotate about the position on the end side.

The motor shaft 63a of the third drive motor 63 (shift motor) as moving means (variable means) is provided on the other end side in the width direction of the frame side rotary shaft 76 rotatably held by the base portion 71 (frame). A rack gear portion 78 that meshes with the pinion gear formed in the above is installed so as to be rotatable relative to the frame side rotation shaft 76. The rack gear portion 78 is held by the frame so as to slide along the guide rail formed in the frame in the non-rotational width direction (the direction of the double arrow S in FIG. 4) with the frame side rotation shaft 76. ing. Here, like the first and second drive motors 59 and 62, the third drive motor 63 (moving means) is fixed to the frame of the conveyance device 30 (image forming apparatus 1) and installed.
On the other hand, between the coupling 75 and the support portion on the other end side of the holding member 72, the drive roller 31a and the driven roller 31b move in the width direction in conjunction with each other, so that both rollers 31a and 31b. And a connecting member 73 that rotatably connects the two. Specifically, the connecting member 73 is held by a snap ring 81 installed in a groove formed respectively by the rotation shaft of the drive roller 31a and the rotation shaft of the driven roller 31b, and the drive roller 31a moves in the width direction Then, in conjunction with that, the driven roller 31b is also moved in the width direction by the same distance.
With such a configuration, the nipping roller pair 31 is in the width direction (rotational direction of the arrow S in FIG. 4, vertical direction in FIG. 2, up and down in FIG. 3) by rotational driving of the third drive motor 63 in forward and reverse directions. Will be moving). As described later, the third drive motor 63 (moving means) is configured such that the pinch roller pair 31 can be moved in the width direction together with the frame side rotation shaft 76 based on the detection results of the detection units 35 and 36. It is.
A known encoder is installed on the motor shaft of the third drive motor 63 (shift motor) so that the amount of movement and the direction of movement of the pinch roller pair 31 relative to the reference position can be detected indirectly. Is configured. Thus, lateral registration correction can be performed by the pinching roller pair 31 based on the detection results of the detection units 35 and 36.
As described above, moving members (such as the third drive motor 63, the rack gear portion 78, the frame side rotation shaft 76, the coupling 75, the connecting member 73, and the holding member 72) move the pinching roller pair 31 in the width direction. Functions as a variable means).

Then, the pair of holding rollers 31 rotates in the rotation direction together with the holding member 72 based on the detection results of the two detection units 35 and 36 while conveying the sheet P in the holding state, thereby the position of the sheet P. Will be corrected several times. That is, the pinching roller pair 31 functions as means for performing skew correction of the sheet P by displacing the sheet P conveyed in the conveyance path in the rotational direction.
Furthermore, while the pinching roller pair 31 transports the sheet P in the pinching state, the pinching roller pair 31 moves in the width direction based on the detection results of the two detection units 35 and 36, thereby multiple times the position of the sheet P in the width direction It will be corrected over the That is, the pinching roller pair 31 also functions as means for displacing the sheet P conveyed in the conveyance path in the width direction to correct the lateral registration of the sheet P.

  Here, the third conveyance roller pair 44 is installed at a position upstream (upstream side in the conveyance direction) with respect to the pinching roller pair 31. The third conveyance roller pair 44 is formed so as to be able to convey the sheet P by rotating in a state in which the sheet P is held, and is formed so as to be separable so as to switch between the state in which the sheet P is held and the state not held A transport roller pair. Then, when the sheet P reaches the position of the pinching roller pair 31 and is in a pinching / conveying state by the pinching roller pair 31, the third feeding roller pair 44 is switched from the pinching state to the pinching state. become.

Further, in the first embodiment, the pinching roller pair 31 is disposed at the upstream side of the conveyance path with respect to the transfer roller 7 (and the photosensitive drum 5) as the downstream side conveyance roller pair, and the resist is A conveying roller pair that also functions as a roller, and is rotated in a state in which the sheet P is held, and the sheet P (the sheet P after being subjected to skew correction and lateral registration correction by the holding roller pair 31 itself) Is conveyed toward the transfer nip portion.
Here, the first drive motor 59 for rotationally driving the pinching roller pair 31 (drive roller 31a) is a rotation speed variable drive motor, and is formed so as to be able to change the transport speed of the sheet P. . Then, when the timing when the sheet P is conveyed to the position of the pinching roller pair 31 is detected by the sheet detection sensor (photosensor) (the sheet P is conveyed to the position of the pinching roller pair 31 and the sheet is When the pinched state of P is detected, the desired lateral registration correction and skew correction are performed by the pinching roller pair 31, and the pinching roller pair 31 is further based on the detection result (detection timing) of the sheet detection sensor. Transport speed is changed. That is, the conveyance by the pinching roller pair 31 is performed so that the timing when the sheet P is conveyed to the transfer roller 7 by the pinching roller pair 31 and the timing when the image formed on the photosensitive drum 5 reaches the transfer roller 7 are matched. The speed is changed (the conveyance timing of the sheet P conveyed to the transfer nip portion is adjusted). Thus, the image can be transferred to a desired position of the sheet P while the lateral registration correction and the skew feeding correction of the sheet P are performed without stopping the conveyance of the sheet P by the holding roller pair 31.
The pinching roller pair 31 does not cause distortion in the image transferred onto the sheet P due to a difference in linear velocity with the photosensitive drum 5 immediately after the leading edge of the sheet P reaches the transfer nip portion. The transport speed is changed (the transport speed is changed so that the linear velocity ratio to the photosensitive drum 5 is 1).

  Further, the pinching roller pair 31 is a transport roller pair formed so as to be separable so as to switch between the pinching state and the non pinching state of the sheet P. Then, when the sheet P reaches the position of the transfer nip portion (transfer roller 7) and is in a state of being nipped and conveyed by the transfer roller 7 and the photosensitive drum 5, the pinching roller pair 31 starts gripping the sheet P It will be switched to the state which does not hold it.

With reference to FIG. 3, an upstream detection unit 35 (upstream detection unit) that optically detects the position (posture) of the sheet P at a position upstream of the pinch roller pair 31 in the transport direction. Two CISs (an upstream first CIS 35A and an upstream second CIS 35B) are provided. The upstream first CIS 35 </ b> A is disposed upstream of the pinch roller pair 31 and downstream of the third transport roller pair 44. The upstream second CIS 35B is disposed upstream of the pinch roller pair 31 and downstream of the upstream first CIS 35A.
In addition, two CIS as a downstream detection unit 36 (downstream detection unit) that optically detects the position (posture) of the sheet P at the position downstream of the holding roller pair 31 in the conveyance direction. (The downstream side first CIS 36A and the downstream side second CIS 36B are provided.) The downstream first CIS 36 </ b> A is disposed downstream of the nipping roller pair 31 and upstream of the transfer roller 7. The downstream second CIS 36B is disposed upstream of the transfer roller 7 and downstream of the downstream first CIS 36A.
Each of the CISs 35A, 35B, 36A, 36B as these four line sensors is composed of a plurality of photosensors (consisting of a light emitting element such as an LED and a light receiving element such as a photodiode) juxtaposed in the width direction. The position of the side end portion Pa (edge portion) at one end side in the width direction of the sheet P is detected.

In the first embodiment, the upstream detection unit 35 detects the position (the amount of positional deviation) of the sheet P conveyed in the conveyance path of the conveyance device 30 in the width direction. Then, based on the detection result, the lateral registration correction is performed while the sheet P is nipped and conveyed by the nipping roller pair 31.
As a specific example, with reference to FIG. 3, the sheet P is at the one end side in the width direction (downward in FIG. 3) with respect to the normal position indicated by the one-dot chain line When the upstream side detection unit 35 detects that the position is shifted by a distance α, the control unit 90 (see FIG. 6) sets the displacement amount α as a correction amount, and the sheet is held by the pinching roller pair 31. In a state in which P is nipped and transported, the nipping roller pair 31 (holding member 72) is moved by the distance α to the other end side (upper side in FIG. 3) in the width direction (shift control is performed).

  More specifically, the average value of the positional displacement amount M1 of the sheet P in the width direction detected by the upstream first CIS 35A and the positional displacement amount M2 of the sheet P in the width direction detected by the upstream second CIS 35B ((M1 + M2 The position (displacement) of the sheet P in the width direction is detected based on 2.). Then, with the sheet P nipped and conveyed by the nipping roller pair 31 so as to offset the value α as the correction amount α to be corrected, the nipping roller pair 31 (the average value ((M1 + M2) / 2) described above The holding member 72) is shifted (shift control is performed).

More specifically, in the calculation unit (control unit), the positional deviation amount α in the width direction is calculated based on the detection results of the upstream first CIS 35A and the upstream second CIS 35B, and The count number p2 (shift motor encoder count number) in the encoder (shift motor encoder) of the 3-drive motor 63 is calculated. Then, the count number p2 is stored as the “target transport encoder count number p2” of the third drive motor 63 (shift motor). The motor driver is controlled by the controller (shift controller) to perform the third drive while detecting the shift position by the shift motor encoder (while performing feedback control) based on the “target transport encoder count number p2” described above. The motor 63 (shift motor) is driven.
In the calculation of the “target transport encoder counter number”, the correction amount (conveyance amount) per one count (one pulse) is checked in advance by calculation from a design value or the like, and stored in the operation unit deep.

Furthermore, in the first embodiment, the position (displacement amount) of the sheet P conveyed in the conveyance path of the conveyance device 30 by the upstream first CIS 35A and the upstream second CIS 35B (the upstream detection unit 35). Is detected. Then, based on the detection result, skew correction (skew correction) is performed while the sheet P is nipped and conveyed by the nipping roller pair 31.
As a specific example, with reference to FIG. 3, the sheet P is only at an angle β in the positive direction (the positive direction of the rotation direction) with respect to the normal position (the normal position without skew) indicated by the one-dot chain line. When the skewed state is detected by the upstream first CIS 35A and the upstream second CIS 35B, the control unit 90 uses the skew amount β as a correction amount to hold the sheet P by the holding roller pair 31. The pair 31 (the holding member 72) is rotated in the reverse direction (the opposite direction of the rotation direction, that is, the clockwise direction in FIG. 3) by the angle β (rotation control is performed).

More specifically, the difference between the positional displacement amount M1 of the sheet P in the width direction detected by the upstream first CIS 35A and the positional displacement amount M2 of the sheet P in the width direction detected by the upstream second CIS 35B (M2-M1 Of the sheet P in the rotational direction of the sheet P based on the value ((M2-M1) / H) obtained by dividing the distance of the upstream first CIS 35A and the upstream second CIS 35B by the separation distance H in the transport direction. Detect Then, the correction angle β to be corrected is obtained by setting the value ((M2−M1) / H) described above as tan β, and the sheet P is nipped and conveyed by the nipping roller pair 31 so as to offset the angle β. The pinching roller pair 31 (holding member 72) is pivoted to the opposite side (the pivoting control is performed).
Note that the positional displacement amounts M1 and M2 in the width direction described above are both displacement amounts from the normal position (a normal position without positional displacement in the width direction).

  More specifically, the calculation unit (control unit) calculates the positional displacement amount β in the rotational direction based on the detection results of the upstream first CIS 35A and the upstream second CIS 35B, and based on the positional displacement amount β The count number p1 (rotational motor encoder count number) in the encoder (rotational motor encoder) of the second drive motor 62 is calculated. Then, the count number p1 is stored as the “target transport encoder count number p1” of the second drive motor 62 (rotational motor). Then, the motor driver is controlled by the controller (rotational controller) while detecting the rotational position by the rotational motor encoder (while performing feedback control) based on the above-mentioned “target transport encoder count number p1”. The second drive motor 62 (rotational motor) is driven.

As described above, in the first embodiment, the holding roller pair 31 holds the sheet P without stopping conveyance of the sheet P, and based on the detection result of the upstream side detection unit 35 in the rotation direction. The positional displacement (oblique feeding) of the sheet P in the rotational direction is corrected by rotating, and the positional displacement (horizontal resist) of the sheet P in the width direction is corrected by moving in the width direction.
As a result, the productivity of the apparatus can be significantly improved as compared with the case where the sheet P is stopped and the skew correction and the lateral registration correction are separately performed. In addition, when performing skew correction or lateral registration correction, a difference in linear velocity does not occur between the plurality of roller portions installed in the width direction in the pinch roller pair 31, so a thin sheet or a sheet P having a low surface friction coefficient Even if the sheet P is passed, the sheet P is neither bent nor slipped.

Further, in the first embodiment, in addition to the upstream detection unit 35 (upstream detection unit) disposed on the upstream side of the nipping roller pair 31, the downstream side of the nipping roller pair 31 is disposed along the transport path. By using the downstream side detection unit 36 (downstream side detection means), the positional deviation correction (the skew correction and the lateral registration correction) of the sheet P is performed by the holding roller pair 31 in two steps.
Specifically, before the pinching roller pair 31 pinches and conveys the sheet P, the upstream detection unit 35 detects the skew amount and the lateral registration amount of the sheet P, and the pinching roller pair 31 is detected based on the detection result. Thus, the skew feeding correction of the sheet P is performed while holding and transporting the sheet P, and the horizontal registration correction of the sheet P is performed at substantially the same timing (these corrections are appropriately referred to as “first correction”). ). Furthermore, after the “first correction” is performed, the skew amount and width of the sheet P are measured by the upstream detection unit 35 and the downstream detection unit 36 in a state in which the pinch roller pair 31 nips and transports the sheet P. The resist amount is further detected, and the skew feed correction of the sheet P is performed based on the detection result, and the horizontal registration correction of the sheet P is performed at substantially the same timing (these corrections are appropriately performed It is called “correction (re-correction)”.
In the “second correction (re-correction)”, the leading end of the sheet P is a correction operation that corrects the posture of the sheet P in the rotation direction and the width direction based on the detection results of the two detection units 35 and 36. The process is repeated as much as possible just before reaching the transfer nip, which will be described in detail later.

  Here, in the first embodiment, a state in which there is no abnormality in the upstream detection unit 35 (upstream detection unit) and the downstream detection unit 36 (downstream detection unit) is detected by the abnormality detection unit described later. The position of the pinching roller pair 31 corresponds to the position of the sheet P detected by the upstream sensing unit 35 (upstream sensing unit) before the sheet is conveyed to the position of the pinching roller pair 31 from the reference position. The position is changed to the reference position so as to correct the position of the nipping roller pair 31 in the state of nipping the sheet P after that (a first correction). After that, while the sheet P is being conveyed by the pinching roller pair 31, the sheet continuously detected by the upstream detection unit 35 and the downstream detection unit 36 (upstream detection unit and downstream detection unit) The position of the pinching roller pair 31 is continuously changed from the reference position so as to be corrected based on the position of P (a second correction).

Specifically, before the sheet P is conveyed to the position of the pinching roller pair 31, the second sheet P is made to face the sheet P in accordance with the skew amount of the sheet P based on the detection result of the upstream side detection unit 35. The pinching roller pair 31 is pivoted from the pivoting reference position (a position corresponding to the normal position without positional deviation in the pivoting direction) by the drive motor 62 (pivoting means), and the sheet P in the width direction The third driving motor 63 (moving means) moves the nipping roller pair 31 in the width direction from the movement reference position (a position corresponding to the normal position without positional deviation in the width direction) corresponding to the positional shift amount. There is.
Thereafter, the pair of holding rollers 31 holding the sheet P is pivoted back to the pivot reference position by the second drive motor 62 (pivoting means) so as to correct skew, and the width The third drive motor 63 (moving means) is moved to return to the movement reference position so that the position of the direction is corrected.
This is the “first correction”.

Then, after that, the “second correction (re-correction)” is repeated in the range where the re-correction operation is possible.
That is, the position (the positional deviation in the width direction and the rotational direction) of the sheet P after the position (the positional deviation in the width direction and the rotational direction) of the sheet P is corrected by the holding roller pair 31 The two detectors 35, 36 detect the position until the trailing edge of the sheet P passes. Then, the position of the sheet P (positional displacement in the width direction and the rotational direction) is further corrected based on the detection result.
That is, at the time of the recorrection (at the time of the second correction), the holding roller pair 31 holds the sheet P so as to further correct the skew of the sheet P based on the detection results of the two detection units 35 and 36 In the state, the sheet P is rotated from the above-described rotation reference position, and is moved in the width direction from the above-described movement reference position in a state in which the sheet P is nipped to further correct the position of the sheet P in the width direction.
At the time of re-correction (at the time of the second correction), the position (width direction and rotation direction) of the sheet P based on the detection results of the two detection units 35 and 36 (four CISs 35A, 35B, 36A, and 36B) Method of calculating the position shift of the sheet P, based on the detection result of the upstream side detection unit 35 (the two CISs 35A and 35B) described above, calculates the position (position shift of the width direction and the rotational direction) of the sheet P And the number of detection results is increased from two to four.

As described above, based on the detection result before the sheet P is nipped by the nipping roller pair 31, the lateral registration correction and the skew feeding correction are performed once while the sheet P is nipped and conveyed by the nipping roller pair 31, 2 The sheet P is held in the nip of the pinching roller pair 31 to perform the lateral registration correction and the skew feeding correction again while pinching and conveying the sheet P by the pinching roller pair 31 based on the detection results of the two detection units 35 and 36. There is a possibility that slight displacement in the width direction or skewing may occur due to a shock when rushing in, and the width direction may be slight if the roller portion of the pinching roller pair 31 has eccentricity or defective assembly. It is because there is a possibility that the position shift and the skewing may occur.
On the other hand, in the first embodiment, based on the detection result before being pinched by the pinching roller pair 31, the lateral registration correction and the skew feeding correction are performed while the sheet P is pinched and conveyed by the pinching roller pair 31. After performing once, based on the detection results of the detection units 35 and 36 after being nipped by the nipping roller pair 31, the lateral registration correction and the skew feeding correction are again performed while nipping and conveying the sheet P by the nipping roller pair 31. Since this is performed, the above-described possibility is limited, and lateral resist correction and skew correction can be performed with higher accuracy.

Here, in the first embodiment, when the second correction is performed, the width direction and the rotation of the sheet P are feedback controlled based on the detection results of the two detection units 35 and 36 detected almost continuously. Correct the position of the direction. That is, in the second correction, the position information of the sheet P is detected every moment by the two detection units 35 and 36. Then, the position (displacement amount) in the width direction and the rotation direction of the sheet P is calculated based on the position information and is fed back to the control unit 90, and the displacement amount of the sheet P in the width direction and the rotation direction is corrected. The (encoder count number) is corrected every moment, and drive control of the second and third drive motors 62 and 63 is performed based on the correction amount. Such re-correction operation is repeated within the possible range until immediately before the leading edge of the sheet P reaches the transfer nip portion and until the sheet P passes the position of the two detection units 35 and 36.
By performing feedback control in this manner, positional deviation of the sheet P that occurs at the time of recorrection (at the time of the second correction), correction error at the time of the second correction, and the like can be corrected with high responsiveness. Accurate horizontal registration correction and skew correction can be performed.

In the first embodiment, the “second correction” is performed using the upstream detection unit 35 and the downstream detection unit 36. However, the “second correction” is performed using only the downstream detection unit 36. Can be configured to perform “correction of
In that case, the method of calculating the position (the positional deviation in the width direction and the rotational direction) of the sheet P based on the detection result of the downstream side detection unit 36 (four CISs 36A and 36B) is the upstream side detection described above It is substantially the same as the method of calculating the position (positional deviation in the width direction and the rotational direction) of the sheet P based on the detection result of the part 35 (two CISs 35A and 35B).

Hereinafter, the “first correction” will be further supplemented and described with reference to FIGS. 5 and 6.
FIG. 5 is a flowchart showing a control flow until “first correction” is performed, and FIG. 6 is a block diagram showing a control unit 90 regarding the first correction (or the second correction).
As shown in FIG. 5, first, the upstream detection unit 35 (two CISs 35A and 35B) detects the sheet P (step S21), and the positional deviation amount α and the skew amount β in the width direction of the sheet P are detected. (Step S22). Then, based on these detection results, the correction amount α ′ in the width direction and the skew correction amount β ′ are calculated (step S23), and the correction amount in the first correction is determined.
Then, based on the correction amount, the encoder count number is calculated by each encoder (see FIG. 6) (step S24). Then, the calculated encoder count number is input to a controller for driving the pinching roller pair 31. Then, according to the input encoder count number, the second drive motor 62 and the third drive motor 63 are driven by the respective motor drivers, and the pinching roller pair 31 rotates and slides to move the pick-up operation. Is performed (step S25). Then, after the pinching roller pair 31 pinches the sheet P, the pinching roller pair 31 is rotated to slide back to the reference position by the driving of the second and third drive motors 62 and 63, and is slid. Correction is performed (step S26).

FIG. 7 is a flowchart showing a control flow of the “second correction (recorrection)”.
As shown in FIG. 7, in the second correction, first, the sheet P is detected by the two detection units 35 and 36 (four CISs 35A, 35B, 36A, and 36B) (step S31). The positional deviation amount and the skew amount are detected (step S32). Then, based on these detection results, the correction amount in the width direction and the skew correction amount are calculated (step S33), and the encoder count number is calculated (step S34). Then, the second drive motor 62 and the third drive motor 63 are driven by the respective motor drivers according to the calculated encoder count number (step S35). The flow of steps S31 to S35 is repeated while the sheet P is detected by the first CIS 36 (while the upstream detection unit 35 can detect the position of the sheet P) (step S36).
In the second correction, the position information of the sheet P is detected every moment by the two detection units 35 and 36 after the correction start. Then, the amount of positional deviation in the width direction of the sheet P and the amount of skew are calculated based on the positional information, and are fed back to the control unit 90, and the encoder count number (the amount of positional deviation correction in the width direction of the sheet P The correction amount is corrected every moment. By performing feedback control as described above, it is possible to correct positional deviation of the sheet P generated at the time of the second correction, an error of the correction at the time of the second correction, and the like, and perform correction with higher accuracy. Can.

Hereinafter, in FIG. 8 and FIG. 9, the operation of the transport apparatus 30 configured as described above is normal (when no abnormality is detected in the detection units 35 and 36 by the abnormality detection unit described later). An example will be described in detail.
8 (A1) to (C1) and FIGS. 9 (A1) to (C1) are top views showing the operation of the transfer device 30 in the order, and FIGS. 8 (A2) to (C2). 9 (A2) to 9 (C2) are side views of the transfer device 30 corresponding to the operations of FIGS. 8 (A1) to 8 (C1) and FIGS. 9 (A1) to 9 (C1), respectively.
First, as shown in FIGS. 8A1 and 8A2, the sheet P fed from the sheet feeding cassette 12 is nipped and conveyed toward the position of the nipping roller pair 31 by the third conveying roller pair 44. (Conveying in the direction of the white arrow). At this time, the pinching roller pair 31 is located at the pivoting reference position (which is a normal position corresponding to the sheet P without skew) in the pivoting direction, and the position in the width direction is the displacement reference position (width direction). Position corresponding to the sheet P with no positional deviation.
Then, when the sheet P reaches the upstream side detection unit 35 (when it passes the position of the upstream first CIS 35A and reaches the position of the upstream second CIS 35B), the upstream side detection unit 35 shifts the lateral resist of the sheet P α is detected. Further, the skew amount β of the sheet P is detected by the upstream side detection unit 35.

Thereafter, as shown in FIGS. 8B1 and 8B, the holding roller pair 31 together with the holding member 72 is pivoted in the same rotational direction according to the skew amount β detected by the upstream side detection unit 35. While rotating from the rotation reference position by an angle β and shifting from the movement reference position by the distance α in the same width direction in accordance with the positional deviation amount α detected by the upstream side detection unit 35.
Then, as shown in FIGS. 8 (C1) and (C2), immediately before the leading end of the sheet P reaches the pinch roller pair 31, the rotational drive of the pinch roller pair 31 (the rotational drive in the arrow direction in the figure) is performed. When the sheet P is started and nipped and conveyed by the nipping roller pair 31, the third conveyance roller pair 44 moves apart in a direction (the solid arrow direction) in which the conveyance path is opened and the sheet P is not nipped. The timing when the leading end of the sheet P reaches the pinching roller pair 31 is the timing when the leading end of the sheet P is detected by the CIS 35B, 35B, the conveyance speed of the sheet P, and the position of the pinching roller pair 31 from the position of the CIS 35A, 35B. It can also be determined by the calculation unit (control unit) based on the distance to the position, and the like.

Then, as shown in FIGS. 9A1 and 9A2, the pinching roller pair 31 is an axial portion so as to offset the skew amount β detected by the upstream side detection unit 35 while pinching and conveying the sheet P. The rotation is performed so as to return to the rotation reference position centering on 71a, and is moved in the width direction so as to return to the movement reference position so as to offset the positional deviation amount α detected by the upstream side detection unit 35. Thus, the "first correction" is completed.
Then, as shown in FIGS. 9 (B1) and (B2), while the sheet P after the first correction is nipped and conveyed toward the transfer nip portion by the nipping roller pair 31, the upstream side detection portion 35 The skew amount β of the sheet P is detected almost continuously by the downstream side detection unit 36. Further, the positional deviation amount α of the lateral resist of the sheet P is detected almost continuously by the upstream side detection unit 35 and the downstream side detection unit 36 for the sheet P after the first correction. The holding roller pair 31 and the holding member 72 have shaft portions in different rotation directions (reverse directions) in accordance with the skew amount β detected almost continuously by the upstream side detection unit 35 and the downstream side detection unit 36. While rotating from the rotation reference position by an angle β centering on 71a from the reference position, different width directions (reverse direction according to the positional shift amount α detected almost continuously by the upstream side detection unit 35 and the downstream side detection unit 36 ) Is shifted from the movement reference position by a distance α. Thus, the "second correction" is performed.
Thus, the sheet P is conveyed toward the transfer roller 7 (transfer nip portion) while the skew correction and the lateral registration correction are performed every moment again. At this time, the number of rotations of the pinching roller pair 31 (the transport speed of the sheet P until it reaches the transfer roller 7) is changed so as to adjust the timing to the image on the photosensitive drum 5.

  Then, as shown in (C1) and (C2) in FIG. 9, the sheet P is conveyed toward the transfer roller 7 (image transfer portion), and the image is transferred to a desired position on the sheet P. . At this time, when the sheet P is nipped and conveyed by the transfer roller 7 (and the photosensitive drum 5), the nipping roller pair 31 is in the separated state, and the skew correction and lateral direction of the sheet P conveyed next are corrected. In preparation for registration correction, the rotation reference position and the movement reference position are returned. Then, after the rear end of the sheet P passes the position of the nipping roller pair 31, the nipping roller pair 31 is returned to the contact state. Further, the third conveyance roller pair 44 which has been in the separated state is returned to the contact state, and prepares for the conveyance operation of the sheet P conveyed next.

Here, in the transport apparatus 30 according to the present embodiment, abnormality detection means 90, 94 and so on for detecting abnormalities in the upstream side detection unit 35 (upstream side detection means) and the downstream side detection unit 36 (downstream side detection means) 96 are provided.
Specifically, as shown in FIG. 10, in the transfer device 30, a reference plate moving mechanism composed of a reference plate 94, a connecting rod 95, a crank disk 96, etc. is provided for each of the four CISs 35A, 35B, 36A, 36B. is set up. The reference plate moving mechanisms 94 to 96 and the control unit 90 function as abnormality detection means for detecting an abnormality in the detection units 35 and 36. In FIG. 10, reference plate moving mechanisms 94 to 96 for detecting an abnormality in the upstream first CIS 35A are illustrated, and reference plate moving mechanisms for detecting an abnormality in the other CISs 35B, 36A, 36B are illustrated. The description is omitted.
As shown in FIG. 10, of the straight conveyance guide plates 91 and 92 installed so as to sandwich the front and back surfaces of the sheet P to be conveyed, the straight conveyance guide plate 91 facing the upstream first CIS 35A In order to enable optical detection by the CIS 35A, a window 93 made of a transparent material such as glass is provided. And as shown to FIG. 10 (A), the recessed part for accommodating the reference | standard board 94 in the position adjacent to the window part 93 is formed. The reference plate 94 has a white surface and is formed to face the entire width of the CIS 35A, and is connected to one end of the connecting rod 95. The other end side of the connecting rod 95 is connected to a crank disk 96 (connected to the motor).
With such a configuration, the crank disk 96 is rotated about the rotation axis by the control of the motor by the control unit 90, whereby the reference plate 94 is at the retracted position shown in FIG. , CIS 35A) and the facing position shown in FIGS. 10 (B) and 10 (C) (moving over the slope 91a and contacting the window 93). .

Then, at the time of the normal image forming operation described earlier with reference to FIG. 1 and the like, the reference plate 94 is stored at the retracted position shown in FIG.
On the other hand, at the time of warming up (at the time of non-image formation) before the image forming operation is started, the crank disk 96 is rotationally driven, and the reference plate 94 is moved to the position of FIG. Shading correction of the CIS 35A (correction for equalizing the output for each pixel) is performed.
Further, at the time of warming up, the crank disk 96 is further rotationally driven, the reference plate 94 is moved to the position of FIG. 10C, and the control unit 90 determines whether or not there is an abnormality in the CIS 35A according to the output of the CIS 35A at that time. Will be judged.

The abnormality detection of the CIS by the abnormality detection units 90 and 94 to 96 is performed for all of the four CISs 35A, 35B, 36A, and 36B.
Then, the abnormality detection means 90, 94 to 96 make the movable movable reference plate 94 opposite to the position facing the upstream side detection unit 35 and the position facing the downstream side detection unit 36 so as to detect the upstream side. Of the unit 35 and the downstream side detection unit 36, one whose output value does not reach the reference value V0 as a whole is detected as an abnormal state. That is, in each CIS, a state in which all the output values of the plurality of photosensors (pixels) do not reach the reference value is detected as an abnormal state. As a cause of occurrence of such an abnormality of the aspect, for example, there is a case where one light emitting element (light source) itself common to a plurality of light receiving elements in the CIS is broken.
Specifically, when the white reference plate 94 is made to face all four CISs 35A, 35B, 36A, 36B as shown in FIG. As shown in (A), when it exceeds the reference value V0, the control unit 90 determines that both of the two detection units 35 and 36 are normal.
On the other hand, when the white reference plate 94 is made to face all the four CISs 35A, 35B, 36A, 36B as shown in FIG. 10C, as shown in FIG. 11B. When there is a CIS whose output level falls below the reference value V0, the control unit 90 determines that there is an abnormality in the detection unit in which the CIS is installed. For example, among the four CISs 35A, 35B, 36A, 36B, only the output level of the upstream first CIS 35A does not reach the reference value V0 as shown in FIG. 11B, and the other three CISs 35B, 36A, 36B When the output level of the signal reaches the reference value V0 as shown in FIG. 11A, it is determined that the upstream detection unit 35 has an abnormality and the downstream detection unit 36 has no abnormality. .

Further, in the present embodiment, the abnormality detection units 90 and 94 to 96 have the reference plates 94 movable to a position facing the upstream detection unit 35 and a position facing the downstream detection unit 36 respectively. Then, among the upstream side detection unit 35 and the downstream side detection unit 36, one whose output value of a part of the plurality of photosensors (pixels) does not reach the reference value V0 is detected as an abnormal state. As a cause of occurrence of such an abnormality in the aspect, for example, there may be a case where paper dust or the like adheres to a reading position corresponding to a part of pixels among a plurality of pixels (light receiving elements) in CIS.
Specifically, when the white reference plate 94 is opposed to all four CISs 35A, 35B, 36A, 36B as shown in FIG. 10C, the output levels of all pixels in all CISs However, as shown in FIG. 12A, when it exceeds the reference value V0, the control unit 90 determines that both of the two detection units 35 and 36 are normal.
On the other hand, when the white reference plate 94 is made to face all the four CISs 35A, 35B, 36A, 36B as shown in FIG. 10C, as shown in FIG. 12B. When there is a CIS whose output level at a part of the pixels (in the example shown, the sixth pixel from one end in the width direction) falls below the reference value V0, the detection unit in which the CIS is installed has abnormality The control unit 90 determines that there is a certain one.

  In the present embodiment, when an abnormality as shown in FIG. 11B or 12B is detected in one of the two detection units 35 and 36, the image forming operation is performed. Control so that the image forming operation can be continued while performing skew correction and lateral registration correction using another detection unit that does not cause abnormality in the apparatus and cause no downtime of the apparatus. There is.

  More specifically, if no abnormality is detected in the upstream detection unit 35 (upstream detection unit) and the downstream detection unit 36 (downstream detection unit) by the abnormality detection units 90 and 94 to 96, the process proceeds to the end. The skew feed correction and the lateral registration correction are performed in the procedure as described with reference to FIGS. 8 and 9 ("first correction" and "second correction" are performed).

On the other hand, when there is no abnormality in the upstream side detection unit 35 by the abnormality detection means 90 and 94 to 96 and a state in which the downstream side detection unit 36 has an abnormality is detected, as shown in FIGS. Thus, the position of the pinching roller pair 31 is changed from the reference position corresponding to the position of the sheet P detected by the upstream side detection unit 35 before the sheet P is conveyed to the position of the pinching roller pair 31, and then The position of the nipping roller pair 31 in the state of nipping the sheet P is changed to the reference position. That is, the skew correction and the lateral registration correction are performed in the same procedure as the “first correction” in the normal state described earlier with reference to FIGS. 8 and 9.
After that, while the sheet P is being conveyed by the pinching roller pair 31, the position of the pinching roller pair 31 is corrected based on the position of the sheet P continuously detected by the upstream side detection unit 35. Is continuously changed from the reference position. That is, the “second correction” in the normal state described above with reference to FIGS. 8 and 9 is a skew correction or a lateral registration correction by feedback control based on the detection results of the two detection units 35 and 36. On the other hand, when the downstream side detection unit 36 is abnormal, as the “second correction”, the skew correction or the lateral registration correction by feedback control based only on the detection result of the upstream side detection unit 35 which is normal. It will be done.

On the other hand, when there is an abnormality in the upstream side detection unit 35 by the abnormality detection means 90, 94 to 96 and a state in which there is no abnormality in the downstream side detection unit 36 is detected, as shown in FIGS. While the sheet P is conveyed by the nipping roller pair 31, the position of the nipping roller pair 31 is continuously from the reference position so that the position is corrected based on the position of the sheet P continuously detected by the downstream side detection unit 36. Change.
That is, when the upstream side detection unit 35 is abnormal, the correction corresponding to the “first correction” in the normal state described above with reference to FIGS. 8 and 9 is not performed, and FIGS. The skew correction and the horizontal registration correction by the feedback control corresponding to the “second correction” at the normal time described above are performed based on only the detection result of the normal downstream side detection unit 36.

Specifically, when the upstream side detection unit 35 is abnormal, first, as shown in FIGS. 15A1 and 15A2, the sheet P fed from the sheet feeding cassette 12 is a third conveyance roller pair 44. Thus, the sheet is nipped and conveyed toward the position of the nipping roller pair 31 (conveyance in the direction of the white arrow). At this time, the position in the rotation direction of the pinching roller pair 31 is at the rotation reference position, and the position in the width direction is at the movement reference position.
Thereafter, as shown in FIGS. 15 (B1) and (B2), the sheet P passes through the upstream side detection unit 35, but the detection by the upstream side detection unit 35 and the rotation and movement of the nipping roller 31 are performed. I can not. That is, the position in the rotation direction of the pinching roller pair 31 is at the rotation reference position, and the position in the width direction is at the movement reference position.
Then, as shown in FIGS. 15 (C1) and (C2), immediately before the leading end of the sheet P reaches the pinch roller pair 31, the rotational drive of the pinch roller pair 31 (rotation drive in the arrow direction in the figure) is performed. When the sheet P is started and nipped and conveyed by the nipping roller pair 31, the third conveyance roller pair 44 moves apart in a direction (the solid arrow direction) in which the conveyance path is opened and the sheet P is not nipped.

Then, as shown in FIGS. 16A1 and 16A2, the holding roller pair 31 holds and conveys the sheet P. Also at this time, the position in the rotation direction of the pinching roller pair 31 is at the rotation reference position, and the position in the width direction is at the movement reference position.
Then, as shown in FIG. 16 (B1) and (B2), the skew amount β of the sheet P is detected by the downstream side detection unit 36 while the sheet P is nipped and conveyed toward the transfer nip portion by the nipping roller pair 31. Is detected almost continuously. Further, the positional deviation amount α of the lateral resist of the sheet P is detected almost continuously by the downstream side detection unit 36. Then, the holding roller pair 31 and the holding member 72 are only at an angle β around the shaft 71a in different rotational directions (reverse directions) in accordance with the skew amount β substantially continuously detected by the downstream side detection unit 36. While rotating from the rotation reference position, shift movement is performed from the movement reference position by a distance α in a different width direction (reverse direction) in accordance with the positional shift amount α substantially continuously detected by the downstream side detection unit 36.
Thus, the sheet P is conveyed toward the transfer roller 7 (transfer nip portion) while the skew correction and the lateral registration correction are performed every moment again.

  Then, as shown in (C1) and (C2) of FIG. 16, the sheet P is conveyed toward the transfer roller 7 (image transfer portion), and the image is transferred to a desired position on the sheet P. . At this time, when the sheet P is nipped and conveyed by the transfer roller 7 (and the photosensitive drum 5), the nipping roller pair 31 is in the separated state, and the skew correction and lateral direction of the sheet P conveyed next are corrected. In preparation for registration correction, the rotation reference position and the movement reference position are returned. Then, after the rear end of the sheet P passes the position of the nipping roller pair 31, the nipping roller pair 31 is returned to the contact state. Further, the third conveyance roller pair 44 which has been in the separated state is returned to the contact state, and prepares for the conveyance operation of the sheet P conveyed next.

As described above, in the first embodiment, the upstream detection unit 35 installed upstream of the holding roller pair 31 and the downstream detection unit 36 installed downstream of the holding roller pair 31. The position of the sheet P can be corrected with high accuracy without causing a down time in the apparatus, even if an abnormality occurs in any of the above.
In particular, in the first embodiment, since the upstream detection unit 35 and the downstream detection unit 36 are both configured by two line sensors (CIS) arranged in parallel at distant positions in the transport direction. Even when the position of the sheet P is corrected using only the upstream side detection unit 35 as shown in FIGS. 13 and 14, only the downstream side detection unit 36 as shown in FIGS. 15 and 16. Even in the case of correcting the position of the sheet P, highly accurate correction is possible.

When any one of the upstream detection unit 35 and the downstream detection unit 36 detects an abnormality by the abnormality detection units 90 and 94 to 96, the display panel (in the image forming apparatus main body 1) Installed on the exterior part). Then, the user sees the display on the display panel and makes a serviceman call, but there is no downtime before the maintenance by the serviceman, and the positional deviation correction of the sheet P is performed. The image forming operation can be continued in the possible state.
Further, in the present embodiment, when the abnormality detecting means 90 and 94 to 96 detect an abnormality in both the upstream side detection unit 35 and the downstream side detection unit 36, the display panel displays that effect. At the same time, the user can select whether to interrupt the image forming operation until maintenance is performed or to continue the image forming operation in a state in which the positional displacement of the sheet P may occur. ing.

In the first embodiment, as shown in FIG. 12B, the abnormality detection units 90 and 94 to 96 do not output the output values of a part of the plurality of photosensors (pixels) to the reference value V0. When the detection result of the photosensor (pixel) is used, it can also be detected as an abnormal state.
That is, the detection result of the pixel having an abnormality in the output value (in the example of FIG. 12B, the sixth pixel from one end side in the width direction) is used for the calculation for detecting the position of the sheet P. In the case where there is an abnormality in the detection unit related to the pixel only when the detection result is not used in the calculation for detecting the position of the sheet P, it is determined that the detection unit related to the pixel does not have abnormality. The positional deviation of the sheet P is corrected in accordance with any one of the procedures shown in FIGS. 8 and 9, 13 and 14, 15 and 16. For example, when the output level of the upstream first CIS 35A becomes as shown in FIG. 12B, when the sixth pixel data is used in the arithmetic processing, the abnormality in FIGS. The positional deviation correction of the sheet P is performed in the procedure of time), and the positional deviation correction of the sheet P is performed in the procedure of FIG. 8 and FIG. 9 (when normal) when the sixth pixel data is not used for arithmetic processing.
By performing such control, it is possible to reduce the frequency of switching of the positional deviation correction procedure.

<Modification 1>
FIGS. 17 and 18 are schematic diagrams showing the operation of the transport apparatus 30 when there is an abnormality in the upstream side detection unit 35 as the first modification, and a diagram corresponding to FIGS. 15 and 16 in the present embodiment. It is.
As shown in FIGS. 17 and 18, in the first modification, when the upstream detection unit 35 has an abnormality and the downstream detection unit 36 has no abnormality detected by the abnormality detection units 90 and 94 to 96. Abuts the leading end of the sheet P conveyed toward the holding roller pair 31 in a state in which the rotational drive is stopped, and corrects the skew of the sheet P. After that, while the sheet P is nipped and conveyed by the nipping roller pair 31, the position of the sheet P continuously detected by the downstream side detection unit 36 is corrected so as to be corrected. The position is continuously changed from the reference position.
That is, when the upstream side detection unit 35 is abnormal, the correction corresponding to the “first correction” in the normal state described above with reference to FIGS. 8 and 9 is not performed, and the leading end of the sheet P Abuts against the nipping portion of the pair 31 to perform skew correction, and thereafter, the skew correction by feedback control corresponding to the “second correction” in the normal state described earlier with reference to FIGS. 8 and 9. The lateral registration correction is performed based only on the detection result of the downstream side detection unit 36 that is normal. Therefore, skew correction is performed in two steps.

Specifically, in the first modification, when the upstream side detection unit 35 is abnormal, first, as shown in FIGS. 17A1 and 17A2, the sheet P fed from the sheet feeding cassette 12 is: The sheet is nipped and conveyed toward the position of the nipping roller pair 31 by the third conveying roller pair 44 (conveyance in the direction of the white arrow). At this time, the position in the rotation direction of the pinching roller pair 31 is at the rotation reference position, and the position in the width direction is at the movement reference position.
Thereafter, the sheet P passes through the upstream side detection unit 35, but the detection by the upstream side detection unit 35 and the rotation and movement of the nipping roller 31 are not performed. That is, the position in the rotation direction of the pinching roller pair 31 is at the rotation reference position, and the position in the width direction is at the movement reference position.
Then, as shown in FIGS. 17B1 and 17B2, the leading end of the sheet P abuts against the nip portion of the holding roller pair 31 in the rotation stop state, and the third conveyance roller pair 44 is kept for a short time thereafter. Holding and transportation are performed. Thereby, a part of the sheet P is curved as shown in FIG. 17 (B2), and the leading end thereof abuts against the nip portion of the holding roller pair 31 across the width direction, whereby the first skew correction is performed. Will be done.
Thereafter, as shown in (C1) and (C2) of FIG. 17, rotational driving of the pinch roller pair 31 (rotation drive in the direction of the arrow in the figure) is started, and the sheet P is pinched and conveyed by the pinch roller pair 31. Then, the third conveyance roller pair 44 separates and moves in a direction in which the sheet P is not held by opening the conveyance path (a solid arrow direction).
The subsequent operation shown in FIG. 18 is substantially the same as that of FIG. 16 described above.
When such control is performed, the accuracy of the skew correction is further enhanced as compared with those performed in FIG. 15 and FIG.

As described above, the conveyance device 30 according to the first embodiment has no abnormality in the upstream detection unit 35 (upstream detection unit) by the abnormality detection units 90 and 94 to 96, and the downstream detection unit 36 (downstream When a state in which there is an abnormality in the detecting means is detected, the pinching roller corresponding to the position of the sheet P detected by the upstream side detection unit 35 before the sheet P is conveyed to the position of the pinching roller pair 31 The position of the pair 31 is changed from the reference position, and then the position of the nipping roller pair 31 in the state of nipping the sheet P is changed to the reference position, and thereafter, the sheet P is nipped and conveyed by the nipping roller pair 31 In the meantime, the position of the pinching roller pair 31 is continuously changed from the reference position so that the position of the sheet P continuously detected by the upstream side detection unit 35 is corrected. On the other hand, when a state in which the upstream side detection unit 35 has an abnormality and the downstream side detection unit 36 has no abnormality is detected by the abnormality detection units 90 and 94 to 96, the sheet P is held by the pinching roller pair 31. While being nipped and conveyed, the position of the nipping roller pair 31 is continuously changed from the reference position so that the position of the sheet P continuously detected by the downstream side detection unit 36 is corrected.
As a result, even if an abnormality occurs in any of the detection units 35 and 36 (detection means) respectively installed on the upstream side and the downstream side with respect to the pinching roller pair 31, the position of the sheet P is highly accurate. Can be corrected.

Second Embodiment
Second Embodiment A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 19 is a top view showing a part of the transfer apparatus 30 in the second embodiment, which corresponds to FIG. 3 in the first embodiment.
The conveyance apparatus 30 according to the second embodiment has the point that one area sensor is used as the downstream side detection means, while the two line sensors (CIS 36A, 36B) as the downstream side detection means are used. This is different from the form 1 of
As shown in FIG. 19, the conveyance device 30 according to the second embodiment uses one area sensor 37 as a downstream detection unit (downstream detection unit) installed downstream of the pinch roller pair 31. .
The area sensor 37 as the downstream side detection means is a plurality of photosensors arranged in parallel in the width direction and the transport direction, and in the same manner as the plurality of line sensors arranged in the transport direction, It is possible to optically detect the position in the width direction and the rotational direction of the sheet P. Therefore, even when the area sensor 37 is used as the downstream side detection means, the position of the sheet P can be corrected with high accuracy as in the first embodiment. In the first embodiment, when any one of the area sensor 37 (downstream detection means) and the upstream detection unit 35 (upstream detection means) detects an abnormality by the abnormality detection means 90, 94 to 96, Similar to the above, switching of the correction operation can be performed.
In the second embodiment, although the area sensor 37 is used as the downstream side detection means, an area sensor can be used as the upstream side detection means, and both the upstream side detection means and the downstream side detection means are areas Sensors can also be used.

Here, in the second embodiment, based on the conveyance speed of the sheet P detected by the area sensor 37, the rotational speed of the pinching roller pair 31 is corrected.
The area sensor 37 can detect the conveyance speed of the sheet P from the detection timing of the sheet P by the photosensors arranged in parallel in the conveyance direction because the plurality of photosensors are arranged in parallel in the conveyance direction. Therefore, when the sheet P is nipped and conveyed by the nipping roller pair 31 (at the time of the second correction), the conveyance speed of the sheet P is aimed while the conveyance speed of the sheet P is detected by the area sensor 37. The rotational speed of the first drive motor 59 is variably controlled so as to be the value of.
As a result, the timing when the sheet P is conveyed to the transfer nip portion by the pinching roller pair 31 and the timing when the image formed on the photosensitive drum 5 reaches the transfer roller 7 are accurately matched. The image can be accurately transferred to a desired position.
In the second embodiment, the rotational speed of the pinching roller pair 31 is corrected based on the conveyance speed of the sheet P detected by the area sensor 37 and the leading end position of the sheet P detected by the area sensor 37. You can also The area sensor 37 can detect the leading end position of the sheet P in addition to the transport speed of the sheet P. Therefore, by detecting the leading end position of the sheet P, the timing at which the sheet P is nipped and conveyed by the nipping roller pair 31 is accurately grasped by the nipping roller pair 31, and the image is accurately transferred to the desired position of the sheet P. Effect will be exhibited further.

<Modification 2>
FIG. 20 is a top view showing a part of the transfer device 30 in the second modification, corresponding to FIG. 19 in the second embodiment. FIG. 21 is a side view showing a color CIS 38 (line sensor) as the downstream side detection means (downstream side detection unit) in the transport apparatus.
As shown in FIG. 20, in the second modification, one CIS 38 for color is used as the downstream side detection means. The color CIS 38 is one line sensor that splits the light reflected by the object into three colors (RGB) and receives the light. As shown in FIG. 21, the color CIS 38 includes one common light source 38a and three photodiode arrays 38dR, 38dG and 38dB corresponding to three colors (each of a plurality of light receiving elements are arranged in parallel in the width direction And a lens array 38b, a color filter 38c for RGB, and the like. Then, when detecting the position of the sheet P (when optically detecting the side edge Pa of the sheet P), the light emitted from the light source 38 a is reflected by the sheet P, and the lens array 38 b and the color filter 38 c The light separated into three colors via the three photodiode arrays 38dR, 38dG, and 38 dB is received.
As described above, even if the CIS 38 for color is a single line sensor in form, a plurality of photosensors are substantially parallelly arranged in the width direction and the transport direction, and is similar to the area sensor It is a thing. Therefore, even when the color CIS 38 is used as the downstream side detection means, the position of the sheet P can be corrected with high accuracy as in the second embodiment. In the second embodiment, when any one of the color CIS 38 (downstream side detection means) and the upstream side detection unit 35 (upstream side detection means) detects an abnormality by the abnormality detection means 90, 94 to 96, Similar to the above, switching of the correction operation can be performed.
In the second modification, the CIS 38 for color is used as the downstream side detection means, but the CIS for color may be used as the upstream side detection means, or both for the upstream side detection means and the downstream side detection means. CIS can also be used.

As described above, the conveyance device 30 (image forming apparatus 1) according to the second embodiment has no abnormality in the upstream detection unit 35 (upstream detection unit) by the abnormality detection units 90 and 94 to 96, and thus the area sensor When a state where there is an abnormality in 37 (downstream detection means) is detected, the position of the sheet P detected by the upstream detection unit 35 before the sheet P is conveyed to the position of the pinching roller pair 31 Then, the position of the nipping roller pair 31 is changed from the reference position, and then the position of the nipping roller pair 31 in the state of nipping the sheet P is changed to the reference position, and then the sheet P is transferred by the nipping roller pair 31 The position of the pinch roller pair 31 is continuously changed from the reference position so that the position of the sheet P continuously detected by the upstream side detection unit 35 is corrected while being pinched and conveyed. To have. On the other hand, when the abnormality detection means 90, 94 to 96 detect that the upstream side detection unit 35 has an abnormality and the area sensor 37 has no abnormality, the sheet P is held by the holding roller pair 31. While being conveyed, the position of the pinching roller pair 31 is continuously changed from the reference position so that the position of the sheet P continuously detected by the area sensor 37 is corrected.
As a result, even if an abnormality occurs in any of the detection units 35 and 36 (detection means) respectively installed on the upstream side and the downstream side with respect to the pinching roller pair 31, the position of the sheet P is highly accurate. Can be corrected.

Embodiment 3
Third Embodiment A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 22 is an entire configuration view showing the image forming apparatus 100 in the third embodiment. The image forming apparatus 100 according to the third embodiment is different from those of the above-described embodiments, which are of the electrophotographic type, in that they are of the inkjet type.
22, an ink jet printer 100 as an image forming apparatus, a conveyance drum 102 for conveying a sheet P, conveyance rollers 103 and 104 for conveying a sheet P, and a clipper 105 for holding the sheet P on the conveyance drum 102 Indicates
A separation member 106 separates the sheet P from the conveyance drum 102. A conveyance belt 107 conveys the sheet P separated from the conveyance drum 102. A discharge tray 108 discharges and stacks the sheet P after printing. Indicate.
Reference numerals 110Y, 110M, 110C, and 110K denote recording heads (printing modules) in which an image forming unit for printing and printing by an inkjet method is unitized.
Further, also in the inkjet type image forming apparatus 100 according to the third embodiment, a characteristic transport device 30 is installed as in the case of each of the embodiments.

Here, the image forming apparatus 100 according to the third embodiment is for forming a color image, and as shown in FIG. 22, the recording head 110 K for black and the three colors for color (yellow, The recording heads 110Y, 110M and 110C of magenta and cyan) are provided. The four recording heads 110Y, 110M, 110C, and 110K are disposed in parallel to be opposed to the conveyance drum 102 and to be parallel to the rotation direction of the conveyance drum 102.
The four recording heads 110Y, 110M, 110C, and 110K have substantially the same structure except that the colors (types) of the inks used for printing are different. The recording heads 110Y, 110M, 110C, and 110K are mainly composed of piezoelectric actuators, thermal actuators, etc., and have nozzles for discharging ink as droplets, an ink tank filled with ink, a control substrate ( Control unit etc. are provided.

The operation of the image forming apparatus 1 will be briefly described with reference to FIG.
First, when a print command is input from the personal computer or the like to the control unit of the image forming apparatus 100 together with image information, the sheet P is fed from the sheet feeding cassette 12 by the sheet feeding roller. The sheet P fed from the sheet feeding cassette 12 is conveyed by the conveyance device 30 toward the conveyance drum 102. At this time, in the transport device 30, as in the embodiments described above, depending on the presence / absence of abnormality of the two detection units 35 and 36, based on the detection result by the normal detection unit, the holding roller pair 31 The positional deviation of the sheet P in the width direction and the rotational direction is corrected.
On the other hand, the recording heads 110Y, 110M, 110C, and 110K of each color are converted into writing information of each color based on the input image information.
Then, the sheet P conveyed to the conveyance drum 102 is positioned on the conveyance drum 102 while being held by the clipper 105, and conveyed along the rotation of the conveyance drum 102 in the counterclockwise direction.
Then, ink as droplets is sequentially sprayed from the recording heads 110Y, 110M, 110C, and 110K of the respective colors on the sheet P conveyed in the arrow direction of FIG. 22 by the rotation of the conveyance drum 102, based on the writing information. A desired color image is formed on the sheet P.
Thereafter, the sheet P on which the desired image has been formed is separated from the transport drum 102 by the separation member 106. Then, the sheet P separated from the conveyance drum 102 is conveyed by the conveyance belt 107 and discharged onto the sheet discharge tray 108.

As described above, the conveyance device 30 (image forming apparatus 100) according to the third embodiment includes the upstream side detection unit 35 (the upstream side) by the abnormality detection units 90 and 94 to 96 as in the embodiments described above. When there is no abnormality in the side detection means and a state in which there is an abnormality in the downstream side detection unit 36 (downstream side detection means) is detected, the upstream side is conveyed before the sheet P is conveyed to the position of the pinching roller pair 31 The position of the nipping roller pair 31 is changed from the reference position corresponding to the position of the sheet P detected by the detection unit 35, and then the position of the nipping roller pair 31 in the state of nipping the sheet P is changed to the reference position. After that, while the sheet P is nipped and conveyed by the nipping roller pair 31, the nipping roller pair 3 is configured such that the position of the sheet P continuously detected by the upstream side detection unit 35 is corrected. It is continuously changed from the reference position to position. On the other hand, when a state in which the upstream side detection unit 35 has an abnormality and the downstream side detection unit 36 has no abnormality is detected by the abnormality detection units 90 and 94 to 96, the sheet P is held by the pinching roller pair 31. While being nipped and conveyed, the position of the nipping roller pair 31 is continuously changed from the reference position so that the position of the sheet P continuously detected by the downstream side detection unit 36 is corrected.
Thereby, when an abnormality occurs in the detection unit 35 on the upstream side among the detection units 35 and 36 (detection means) installed respectively on the upstream side and the downstream side with respect to the pinching roller pair 31, or When an abnormality occurs in the detection unit 36 on the downstream side of the detection units 35 and 36 respectively installed on the upstream side and the downstream side with respect to the roller pair 31, the position of the sheet P is highly accurate Can be corrected. In particular, even if an abnormality occurs in any of the detection units 35 and 36 (detection means) respectively installed on the upstream side and the downstream side with respect to the pinching roller pair 31, the position of the sheet P can be made with high accuracy. It can be corrected.

In the first and second embodiments, the present invention is applied to the conveyance device 30 which causes the pinching roller pair 31 functioning as the lateral registration and skew feeding correction roller to also function as the registration roller. The transport apparatus that can be used is not limited to this, and the present invention can be applied to transport apparatuses having other configurations. For example, the present invention can of course be applied to a conveyance device in which a registration roller is installed downstream of the pinching roller pair 31 functioning as a lateral registration and skew feeding correction roller.
Further, in the first and second embodiments, the present invention is applied to the transport device 30 installed in the monochrome image forming apparatus 1, but it is needless to say that the transport device installed in the color image forming apparatus. The present invention can be applied to
In each of the above-described embodiments, the present invention is applied to the conveyance device 30 that performs skew correction and lateral registration correction of a transfer sheet as a sheet P on which an image is formed. The present invention can also be applied to a transport apparatus that performs row correction and lateral registration correction.
In each of the above-described embodiments, the present invention is applied to the conveyance device 30 installed in the electrophotographic image forming apparatus 1 or the inkjet image forming apparatus 100. The present invention is not limited to this, and the present invention can also be applied to a transport apparatus installed in an image forming apparatus of another type (for example, an offset printing machine or the like). Furthermore, the present invention can of course be applied to a transport apparatus installed in a post-processing apparatus that performs post-processing such as binding processing and folding processing on a sheet after image formation.
In each of the above-described embodiments, the present invention is applied to the transport device 30 that performs both the skew correction and the lateral registration correction. However, the transport that performs either the skew correction or the lateral registration correction The present invention can also be applied to an apparatus.
In each of the above embodiments, the mechanism for moving the reference plate 94 is used as the abnormality detection means for detecting the abnormality of the detection units 35 and 36, but the abnormality detection means is not limited to this. It is also possible to use a detection unit that detects a change in output of the detection units 35 and 36 when a dummy sheet is conveyed.
And, even in such cases, the same effects as those of the respective embodiments can be obtained.

  It is to be noted that the present invention is not limited to the present embodiment, and it is apparent that the present embodiment can be appropriately modified within the scope of the technical idea of the present invention other than suggested in the present embodiment. is there. Further, the number, the position, the shape, and the like of the constituent members are not limited to the present embodiment, and the number, the position, the shape, and the like suitable for practicing the present invention can be set.

In the present specification and the like, “sheet” is defined to include all sheet-like recording media such as coated paper, label paper, OHP sheet, film and the like in addition to ordinary paper (paper).
In the specification and the like of the present application, the “width direction” is defined as a direction orthogonal to the sheet conveyance direction.
In the present specification and the like, the description “A or / and B” is defined as being synonymous with “at least one of A and B”.

1 Image forming device (image forming device main body),
5 Photosensitive drum (downstream conveyance roller pair),
7 Transfer roller (downstream conveyance roller pair),
30 transport devices,
31 nipping roller pair (registration roller),
35 upstream detector (upstream detector),
35A upstream first CIS (line sensor),
35B upstream second CIS (line sensor),
36 downstream detection unit (downstream detection unit),
36A downstream first CIS (line sensor),
36B downstream second CIS (line sensor),
37 area sensors,
CIS for 38 colors,
59 first drive motor,
62 second drive motor (variable means, rotation means),
63 third drive motor (variable means, moving means),
90 control unit (error detection means),
94 Reference plate (error detection means),
P sheet (recording medium).

JP, 2016-175776, A JP, 2016-108152, A

Claims (12)

A conveyance device for conveying a sheet in a conveyance path
A pinching roller pair that pinches and conveys a sheet in the conveyance path;
Upstream detection means for detecting the position of the sheet in the width direction or / and the rotation direction in the conveyance surface at a position upstream of the holding roller pair in the conveyance direction;
Downstream detection means for detecting the position in the sheet width direction or / and the rotation direction at a position downstream in the conveyance direction with respect to the pair of holding rollers;
Variable means for changing the position in the width direction or / and the rotational direction of the pinch roller pair;
Abnormality detection means for detecting an abnormality between the upstream side detection means and the downstream side detection means;
Equipped with
When the abnormality detection means detects that the upstream side detection means has no abnormality and the downstream side detection means has an abnormality, the upstream side is detected before the sheet is conveyed to the position of the pinch roller pair. The position of the nipping roller pair is changed from the reference position according to the position of the sheet detected by the detecting means, and then the position of the nipping roller pair in the state of nipping the sheet is changed to the reference position And after that, while the sheet is being conveyed by the nipping roller pair, the nipping roller pair is corrected based on the position of the sheet continuously detected by the upstream side detection means. A transport apparatus characterized by continuously changing the position from the reference position. A conveyance device for conveying a sheet in a conveyance path
A pinching roller pair that pinches and conveys a sheet in the conveyance path;
Upstream detection means for detecting the position of the sheet in the width direction or / and the rotation direction in the conveyance surface at a position upstream of the holding roller pair in the conveyance direction;
Downstream detection means for detecting the position in the sheet width direction or / and the rotation direction at a position downstream in the conveyance direction with respect to the pair of holding rollers;
Variable means for changing the position in the width direction or / and the rotational direction of the pinch roller pair;
Abnormality detection means for detecting an abnormality between the upstream side detection means and the downstream side detection means;
Equipped with
When the abnormality detection means detects that the upstream side detection means has an abnormality and the downstream side detection means has no abnormality, the downstream side is conveyed while the sheet is being conveyed by the pinching roller pair. The conveyance device characterized by continuously changing the position of the pinch roller pair from the reference position so as to be corrected based on the position of the sheet continuously detected by the side detection means.   When the abnormality detection means detects that the upstream side detection means has an abnormality and the downstream side detection means does not have an abnormality, it is conveyed toward the pinching roller pair in a state in which the rotational drive is stopped. The leading end of the sheet is abutted to correct the skew of the sheet, and thereafter, the sheet is continuously detected by the downstream side detection means while the sheet is conveyed by the nipping roller pair. 3. The conveyance device according to claim 2, wherein the position of the pinch roller pair is continuously changed from the reference position so as to be corrected based on the position of the sheet.   When the abnormality detection means detects that the upstream side detection means has no abnormality and the downstream side detection means has an abnormality, the upstream side is detected before the sheet is conveyed to the position of the pinch roller pair. The position of the nipping roller pair is changed from the reference position according to the position of the sheet detected by the detecting means, and then the position of the nipping roller pair in the state of nipping the sheet is changed to the reference position And after that, while the sheet is being conveyed by the nipping roller pair, the nipping roller pair is corrected based on the position of the sheet continuously detected by the upstream side detection means. The transport apparatus according to claim 2 or 3, wherein the position is continuously changed from the reference position.   When the abnormality detecting unit detects that there is no abnormality in the upstream detecting unit and the downstream detecting unit, the upstream detecting unit detects the sheet before being conveyed to the position of the pinch roller pair. The position of the nipping roller pair is changed from the reference position according to the detected position of the sheet, and then the position of the nipping roller pair in the state of nipping the sheet is changed to the reference position, and then While the sheet is being conveyed by the pinching roller pair, based on the position of the sheet continuously detected by the upstream detection unit and the downstream detection unit, or by the downstream detection unit. The transport apparatus according to any one of claims 1 to 4, wherein the position of the holding roller pair is continuously changed from the reference position so as to be corrected.   The abnormality detection means causes the movable reference plate to face the position facing the upstream side detection means and the position facing the downstream side detection means, and the upstream side detection means and the downstream side detection The conveyance device according to any one of claims 1 to 5, wherein among the means, one in which the entire output value does not reach a reference value is detected as an abnormal state. The upstream side detection means and the downstream side detection means are respectively provided with a plurality of photosensors arranged in parallel in the width direction,
The abnormality detection means causes the movable reference plate to face the position facing the upstream side detection means and the position facing the downstream side detection means, and the upstream side detection means and the downstream side detection The method according to any one of claims 1 to 5, characterized in that among the means, one whose output value of a part or all of the plurality of photosensors does not reach a reference value is detected as an abnormal state. Transport device.   The abnormality detection means is characterized as detecting an abnormal state when the output value of a part of the plurality of photosensors does not reach the reference value and the detection result of the photosensor is used. The conveying apparatus according to claim 7, wherein   The upstream detection means and the downstream detection means may each be any one of two line sensors, one area sensor, and one line sensor arranged in parallel at distant positions in the transport direction. The transport apparatus according to any one of claims 1 to 8, which is characterized by the following. The variable means is
Moving means configured to move the pinch roller pair in the width direction;
Rotation means configured to be able to rotate the holding roller pair in the rotation direction;
The transport apparatus according to any one of claims 1 to 9, wherein   The control apparatus which controls the said variable means was provided, The conveyance apparatus in any one of the Claims 1-10 characterized by the above-mentioned.   An image forming apparatus comprising the conveyance device according to any one of claims 1 to 11.

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