JP6273810B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses employing an electrophotographic system such as a printer, a copying machine, and a facsimile have been widely used. This type of image forming apparatus is provided with a bending correction mechanism for correcting the bending of the sheet conveyed to the image forming unit with respect to the traveling direction. The bending correction mechanism includes a registration roller and a loop roller, and corrects the bending of the sheet by forming a loop by abutting the leading end of the sheet against the registration roller by conveying the sheet with the loop roller.

  Examples of the image forming apparatus having a function of correcting the paper skew include the following patent documents. For example, Patent Document 1 discloses image formation in which a slip correction coefficient is calculated based on a required time for paper conveyance between two conveyance sensors, and the rotation speed of the conveyance roller is finely adjusted using the calculated slip correction coefficient. An apparatus is described. In Patent Document 2, the contact state with a pressure roller or the like is variable based on the conveyance state of a sheet material detected by a displacement member such as an actuator or a non-contact type sheet material detection sensor such as a reflection type photosensor. An image forming apparatus is described in which the pressure applied to the sheet material is changed.

JP 2010-215345 A JP 2008-13352 A

  However, the paper bending correction described in Patent Documents 1 and 2 has the following problems. That is, in Patent Document 1, although it is possible to predict the slip amount with respect to the paper roller, the roller provided between the two points must be driven to rotate. It is not possible to cope with the paper bending correction in which the loop roller on the side is rotated to generate a loop.

  In the method using the sensor and the actuator described in the cited document 2, only a decrease or increase in the loop amount of the sheet with respect to a certain height can be confirmed. Further, the appropriate loop shape differs for each paper size, basis weight, and paper type. Therefore, the conventional method using a sensor or the like can determine only the appropriate loop shape of a specific type of paper, and cannot sufficiently cope with an image forming apparatus using a plurality of types of paper. Furthermore, when a sensor or the like is used, only one point of the paper loop can be detected. Therefore, when the loop shape is greatly deformed such as an abnormal loop, the state of the paper loop shape can be accurately confirmed. Can not.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of accurately confirming the loop shape of a sheet at the time of correcting the sheet skew.

The image forming apparatus according to the present invention is provided on the upstream side of the first roller pair that conveys paper and the first roller pair in the paper traveling direction, and abuts the paper against the first roller pair. A second roller pair that forms a loop, an imaging unit that acquires an image showing a loop shape on a side surface in the loop of the paper formed by the second roller pair, and acquired by the imaging unit A control unit that adjusts a loop shape of the paper based on the image, and the control unit is orthogonal to the loop shape of the image acquired by the imaging unit and the paper traveling direction and orthogonal to the paper width direction. Whether the loop shape of the image acquired by the imaging unit is an abnormal loop shape is determined based on whether or not there are a plurality of intersections with the reference line.

  According to the present invention, since the image indicating the loop shape on the side surface of the paper is acquired by the imaging unit, the accurate state of the paper loop shape can be obtained without depending on the paper type of the paper, and as a result. The paper can be adjusted to a proper loop shape.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. It is a perspective view which shows the structural example of a resist unit. It is a side view which shows the structural example of a resist unit. 2 is a block diagram illustrating an example of a functional configuration of the image forming apparatus. FIG. It is a figure for demonstrating abnormal loop shape. It is a figure for demonstrating a small loop shape. It is a figure for demonstrating a large loop shape. 6 is a flowchart illustrating an operation example of the image forming apparatus at the time of paper skew correction. It is a flowchart which shows the operation example of life extension control mode.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Configuration example of image forming apparatus]
First, the image forming apparatus 100 according to the present invention will be described. FIG. 1 shows an example of the configuration of an image forming apparatus 100 according to the present invention. As shown in FIG. 1, the image forming apparatus 100 is called a tandem type image forming apparatus, and includes an automatic document feeder 80 and an apparatus main body 102. The automatic document conveyance unit 80 is attached to the upper part of the apparatus main body 102 and sends out the paper set on the conveyance table to the image reading unit 90 of the apparatus main body 102 by a conveyance roller or the like.

  The apparatus main body 102 includes an operation display unit 70, an image reading unit 90, an image forming unit 10, an intermediate transfer belt 8, a paper feeding unit 20, a registration unit 200, a fixing unit 44, and an automatic paper reversing and conveying unit. 60 (Auto Duolex Unit: hereinafter referred to as ADU).

  The operation display unit 70 is configured by a touch panel in which an operation unit and a display unit are combined. The operation display unit 70 displays an input screen (menu screen) for receiving image forming conditions such as paper size, basis weight, and paper type, and receives position information selected on the input screen.

  The image reading unit 90 scans and exposes the document placed on the document table or the document transported by the automatic document transport unit 80 by the optical system of the scanning exposure device, and the image of the scanned document is CCD (Charge Coupled Devices). ) Photoelectric conversion is performed by an image sensor to generate an image information signal. The image information signal is output to the image forming unit 10 after being subjected to analog processing, analog / digital (hereinafter referred to as A / D) conversion processing, pseudo correction, image compression processing, and the like by an image processing unit (not shown).

  The image forming unit 10 forms an image by electrophotography, and includes an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, The image forming unit 10C forms a cyan (C) color image, and the image forming unit 10K forms a black (K) color image. In this example, common function names, for example, Y, M, C, and K indicating colors to be formed are added to the back of the reference numeral 10.

  The image forming unit 10Y includes a photosensitive drum 1Y, a charger 2Y, an exposure unit (optical writing unit) 3Y, a developing unit 4Y, and a cleaning unit 6Y arranged around the photosensitive drum 1Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 6M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charger 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 6C disposed around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 6K disposed around the photosensitive drum 1K.

  Respective photosensitive drums (image carriers) 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, chargers 2Y, 2M, 2C, and 2K, exposure units 3Y, 3M, 3C, and 3K, development The devices 4Y, 4M, 4C, and 4K and the cleaning units 6Y, 6M, 6C, and 6K have the same configuration. In the following description, Y, M, C, and K are not used unless particularly distinguished.

  The charger 2 charges the surface of the photosensitive drum 1 almost uniformly. The exposure unit 3 is composed of, for example, an LPH (LED Print Head) having an LED array and an imaging lens, or a polygon mirror type laser exposure scanning device, and the photosensitive drum 1 is irradiated with laser light based on an image information signal. Scan to form an electrostatic latent image. The developing device 4 develops the electrostatic latent image formed on the photosensitive drum 1 with toner. As a result, a toner image which is a visible image is formed on the photosensitive drum 1.

  The intermediate transfer belt 8 is stretched by a plurality of rollers and is rotatably supported. The intermediate transfer belt 8 is provided with a cleaning unit 9 for cleaning the intermediate transfer belt 8. Along with the rotation of the intermediate transfer belt 8, the primary transfer roller 7 and the photosensitive drum 1 rotate, and a predetermined voltage is applied between the primary transfer roller 7 and the photosensitive drum 1, whereby the photosensitive member. The toner image formed on the drum 1 is transferred onto the intermediate transfer belt 8 (primary transfer).

  The paper feed unit 20 has a plurality of paper feed trays 20A and 20B in which paper P such as A3 and A4 is accommodated. The paper P transported from the paper feed trays 20A, 20B by the transport rollers 22, 24, 26, 28, etc. is transported to the registration unit 200. Note that the number of paper feed trays is not limited to two. Further, a single or a plurality of large-capacity paper feeders that can accommodate a large-capacity paper P may be connected as necessary.

  The registration unit 200 includes a loop roller pair 30 and a registration roller pair 32. The paper P conveyed to the registration unit 200 is abutted by the pair of loop rollers 30 to form a loop, thereby correcting the bending (for example, skew) of the paper P with respect to the paper traveling direction D. The paper P in which the bending of the paper P is corrected is conveyed to the secondary transfer roller 34 at a predetermined timing. In the secondary transfer roller 34, the Y, M, C, and K color toner images transferred onto the intermediate transfer belt 8 are collectively transferred onto the surface of the paper P conveyed by the resist roller pair 32 ( Secondary transfer). The second-transferred sheet P is conveyed to the fixing unit 44 on the downstream side in the sheet traveling direction D.

  The fixing unit 44 includes a pressure roller and a heating roller. The fixing unit 44 fixes the toner image on the surface of the paper P to the paper P by performing pressure and heat treatment on the paper P on which the toner image has been transferred by the secondary transfer roller 34.

  A transport path switching unit 48 for switching the transport path of the paper P to the paper discharge path side or the ADU 60 side is provided downstream of the fixing unit 44 in the paper travel direction D. The transport path switching unit 48 performs transport path switching control based on the selected print mode (single-sided print mode, double-sided print mode, or the like).

  The paper P on which single-sided printing has been completed in the single-sided printing mode or the paper P on which double-sided printing has been completed in the double-sided printing mode is discharged onto the paper discharge tray by the paper discharge roller 46.

  Further, when the paper P on which the image is formed on the front side is re-fed to the image forming unit 10 in the double-sided printing mode, the paper P on which the image is formed on the front side is switched between the transport paths. It is conveyed to the ADU 60 via the unit 48. The paper P transported to the ADU 60 is transported to the switchback path via the transport roller 62 and the like. In the switchback path, the ADU roller 64 is reversely controlled to be transported to the U-turn path section with the trailing edge of the paper P as the head, and to the registration roller pair 32 by the transport rollers 66 and 68 provided in the U-turn path section. The paper P is fed again in a state where the front and back sides are reversed. The paper P that has been re-fed to the registration roller pair 32 is subjected to the same image forming process as that on the front side of the paper P. The sheet P on which the image has been transferred to the back surface by the image forming unit 10 is subjected to a fixing process by the fixing unit 44, and is then discharged onto the paper discharge tray via the conveyance path switching unit 48 and the paper discharge roller 46.

[Configuration example of resist unit]
Next, a configuration example of the resist unit 200 will be described. 2 is a perspective view showing an example of the configuration of the resist unit 200, and FIG. 3 is a side view showing an example of the configuration of the resist unit 200.

  2 and 3, the registration unit 200 includes a loop roller pair 30, a registration roller pair 32, an imaging unit 110, a pressurizing unit 120, a spring 122, guide members 160, 162, and 164. have.

  The loop roller pair 30 includes a roller 30a and a roller 30b disposed to face the roller 30a. The loop roller pair 30 forms a loop by bending the paper P by abutting the leading end portion of the paper P sandwiched between the rollers 30 a and 30 b against the registration roller pair 32.

  The registration roller pair 32 is provided on the downstream side of the loop roller pair 30 in the sheet traveling direction D, and includes a roller 32a and a roller 32b disposed to face the roller 32a. The registration roller pair 32 corrects the paper bending by forming a loop of the paper P, and conveys the paper P to the secondary transfer roller 34 at a predetermined timing after the correction of the paper P bending.

  The imaging unit 110 is provided on one side (side surface side of the sheet P) in the width direction orthogonal to the sheet traveling direction D of the sheet P, and is provided on the side surface side of the sheet P formed by the loop roller pair 30 and the registration roller pair 32. Imaging the loop shape. For the imaging unit 110, for example, a camera composed of a CCD, a CMOS (Complementary Metal-Oxide Semiconductor), or the like is used.

  The guide member 160 is disposed so as to straddle between the loop roller pair 30 and the registration roller pair 32. The guide member 162 is disposed so as to be inclined obliquely upward from the registration roller pair 32 and functions as an auxiliary member or the like when forming a loop of the paper P. The guide member 164 is provided so as to be inclined obliquely upward on the inner surface side of the guide member 160 and on the registration roller pair 32 side, and functions as an auxiliary member or the like that efficiently forms a loop of the paper P.

  The pressurizing unit 120 includes, for example, a motor or a solenoid, and changes the pressure (pressing force) applied to the paper P (roller 30b) by the roller 30a. One end of a spring 122 is attached to the pressure unit 120, and a roller 30 a is attached to the other end of the spring 122.

  When the spring 122 is pressed to the roller 30 a side by the pressing unit 120, the roller 30 a is pressed to the roller 30 b side by the urging force of the spring 122. Thereby, the pressurizing force with respect to the roller 30b of the roller 30a in contact with the roller 30b is increased. On the other hand, when the pressure applied to the spring 122 of the pressurizing unit 120 is reduced, the pressure applied to the roller 30b of the roller 30a is reduced.

[Block Configuration Example of Image Forming Apparatus]
Next, a block configuration example of the image forming apparatus 100 according to the present invention will be described. FIG. 4 is a block diagram illustrating an example of a functional configuration of the image forming apparatus 100. As shown in FIG. 4, the image forming apparatus 100 includes a control unit 50 that controls the operation of the entire apparatus. The control unit 50 includes a CPU (Central Processing Unit) 52, a ROM (Read Only Memory) 54, and a RAM (Random Access Memory) 56. The CPU 52 executes software (program) read from the ROM 54 to control each unit of the image forming apparatus 100 and realize functions related to image formation including paper skew correction control.

  An operation display unit 70, a memory 72, an imaging unit 110, a pressure unit 120, a roller driving unit 130, and a roller driving unit 140 are connected to the control unit 50, respectively. The operation display unit 70 displays an operation screen for setting image forming conditions such as paper type based on an instruction from the control unit 50, or generates input information based on the image forming conditions received on the operation screen. Or supplied to the controller 50.

  The memory 72 includes a nonvolatile semiconductor memory or an HDD (Hard Disk Drive). The memory 72 stores a database in which an image indicating an appropriate loop shape of the paper P is stored, an image indicating an appropriate loop shape of the paper P transported before the current paper P, and the like. The proper loop shape is a loop shape that serves as a reference when determining the state of the loop shape of the paper P, and means a loop shape that can reliably perform the paper bending correction. It is set for each size, basis weight, paper type, and environmental conditions.

  The imaging unit 110 generates image information (image data) indicating the loop shape of the paper P captured from the side surface of the paper P and supplies the image information to the control unit 50. The pressurizing unit 120 controls the pressure applied to the paper P of the loop roller pair 30 by adjusting the pressing force applied to the spring 122 based on an instruction from the control unit 50.

  The roller driving unit 130 is configured by, for example, a stepping motor, and is driven based on a driving signal supplied from the control unit 50 to control the driving speed and driving timing of the loop roller pair 30 (for example, the roller 30b). When the current loop shape is a small loop shape or a large loop shape, which will be described later, the drive signal (pressing force) is calculated based on a difference value between the vertex of the current loop shape and the vertex of the appropriate loop shape.

  The roller driving unit 140 is composed of a stepping motor, for example, and is driven based on a driving signal supplied from the control unit 50 to control the driving speed and driving timing of the registration roller pair 32.

[Example of loop pattern]
Next, a loop-shaped pattern of the paper P will be described. FIG. 5 is a diagram for explaining an example of an abnormal loop shape. In FIG. 5, the solid line shows an example of the abnormal loop shape, and the broken line shows the appropriate loop shape PS. 6 and 7 shown below, it is assumed that the appropriate loop shape PS is common.

  For example, when the feeding of the paper P by the loop roller pair 30 is excessive, as shown in FIG. 5, the loop shape P1 of the paper P has a shape that is significantly different from the chevron shape of the appropriate loop shape PS. In this example, such a loop shape P1 of the paper P is called an abnormal loop shape. When the loop shape P1 of the paper P is an abnormal loop shape, it is difficult to normally perform the paper skew correction.

  FIG. 6 is a diagram for explaining an example when the loop shape of the paper P is smaller than the appropriate loop shape PS (hereinafter referred to as a small loop shape). In FIG. 6, a solid line shows an example of a small loop shape, and a broken line shows an appropriate loop shape PS. For example, when the loop roller pair 30 deteriorates over time or paper dust adheres to the roller surface, slippage occurs between the loop roller pair 30 and the paper P, and the nip force by the loop roller pair 30 decreases. The loop shape P2 of the paper P becomes a mountain-shaped loop shape lower than the appropriate loop shape PS. In this example, such a loop shape P2 of the paper P is called a small loop shape. When the loop shape P2 of the paper P is a small loop shape, a mountain-shaped loop is formed temporarily, so that it does not correspond to the abnormal loop shape, and it is possible to correct the paper skew.

  FIG. 7 is a diagram for explaining an example of a shape in which the loop shape of the paper P is larger than the appropriate loop shape PS (hereinafter referred to as a large loop shape). In FIG. 7, the solid line indicates an example of the large loop shape P3, and the broken line indicates the appropriate loop shape PS. When the feeding amount of the paper P by the loop roller pair 30 slightly increases (the feeding amount is smaller than that in the case of FIG. 5), as shown in FIG. 7, the mountain shape in which the loop shape P3 of the paper P is larger than the appropriate loop shape PS. It becomes a loop shape. In this example, such a loop shape P3 of the paper P is referred to as a large loop shape. When the loop shape P3 of the paper P is a large loop shape, a mountain-shaped loop is formed temporarily, so that it does not correspond to the abnormal loop shape P1, and it is possible to correct the paper skew.

[Operation example of image forming apparatus]
Next, an operation example of the image forming apparatus 100 according to the present invention will be described. FIG. 8 is a flowchart illustrating an example of the operation of the image forming apparatus 100 when correcting the bending of the paper P. When the image forming process is started, for example, the paper P is taken out from the paper supply unit 20, and the taken-out paper P is conveyed to the loop roller pair 30 by the rollers 22, 24, 26, and 28. The paper P is looped by the leading end of the paper P being abutted against the registration roller pair 32 and being bent by the conveyance by the loop roller pair 30.

  As shown in FIG. 8, in step S <b> 10, the imaging unit 110 captures the loop shape on the side surface side of the paper P formed by abutting against the registration roller pair 32 and generates image data. For example, the control unit 50 controls the imaging timing based on a sheet detection result such as a sensor provided in the registration unit 200. The control unit 50 acquires image data indicating the loop shape on the side surface side of the paper P imaged by the imaging unit 110.

  In step S20, the control unit 50 determines whether or not the loop shape of the sheet P of the acquired image is an abnormal loop shape. As an example of a method for determining whether the loop shape is abnormal, for example, as shown in FIG. 5, a reference line (reference information) L orthogonal to the sheet traveling direction D is matched with the loop shape of the acquired image. In this case, there is a method of determining whether there are two or more intersections between the loop shape of the paper P and the reference line L. Note that the determination of the presence or absence of the abnormal loop shape is not limited to the above method, and other known methods may be employed.

  When the loop shape of the sheet P of the acquired image is the loop shape P1 shown in FIG. 5, the control unit 50 has two or more intersections between the loop shape P1 of the sheet P and the reference line L (three points in this example: C1, C2, C3), it is determined that the loop shape P1 of the paper P is an abnormal loop shape, and the process proceeds to step S120. On the other hand, the control unit 50 determines that the loop shape of the paper P of the acquired image is not an abnormal loop shape when the intersection of the loop shape of the paper P of the acquired image and the reference line L is one point. Proceed to S30.

  When the loop shape of the paper P is an abnormal loop shape, the control unit 50 controls the drive timing of the loop roller pair 30 in step S120. The control unit 50 controls the operation of the roller driving unit 130 to control the stop timing of the loop roller pair 30 to be faster than the stop timing of the paper P before (previous) the previous time. As a result, excessive feeding of the paper P by the loop roller pair 30 can be suppressed, and the paper P can be prevented from having an abnormal loop shape. When the control of the drive timing of the loop roller pair 30 is completed, the control unit 50 proceeds to step S50.

  In addition to the control of the driving timing of the loop roller pair 30, it is also possible to control the pressurizing force and the conveyance speed of the loop roller pair 30 as will be described later. In addition, when the abnormal loop is not resolved even by these controls, it is preferable to perform a guidance display on the screen of the operation display unit 70 for urging the replacement of the loop roller pair 30.

  On the other hand, if the loop shape of the paper P is not an abnormal loop shape, in step S30, the control unit 50 determines whether or not the loop shape of the paper P of the acquired image is smaller than the appropriate loop shape PS of the paper P stored in the database in advance. Determine whether. The appropriate loop shape PS corresponding to the size, basis weight, and paper type of the paper P to be used is read from the database. As an example of a technique for determining whether the shape is a small loop shape, a vertex is acquired from the loop shape of the current paper P, and the value of the acquired loop shape of the paper P is greater than the value of the vertex of the appropriate loop shape PS in the database. There is a method for determining whether the value is small or not. At this time, a certain range is provided on the apex side of the apex of the appropriate loop shape PS, and when the value of the apex of the loop shape of the current paper P is less than the lower limit value Th1 of the range, it is determined that the loop shape is small. Can do.

  As shown in FIG. 6, when the loop shape of the current paper P is the loop shape P2, the control unit 50 determines that the value of the vertex P2T of the loop shape P2 is less than the lower limit value Th1 of the appropriate loop shape PS. It is determined that the loop shape is a small loop shape, and the process proceeds to step S70. Further, the control unit 50 calculates a difference value between the vertex P2T of the loop shape of the current sheet P and the vertex PST of the appropriate loop shape PS, and stores the calculated difference value in the memory 72. On the other hand, if the value of the apex of the loop shape of the current paper P is equal to or greater than the lower limit value Th1 of the appropriate loop shape PS, the control unit 50 proceeds to step S40.

  In the above example, the image of the appropriate loop shape PS stored in advance in the database is used. However, the present invention is not limited to this. For example, when the loop shape of the paper P conveyed before the current paper P, for example, the previous paper P is an appropriate loop shape, the current paper is used by using the loop shape image of the paper P. It can also be determined whether the loop shape of P is smaller than the appropriate loop shape PS.

  When it is determined that the loop shape of the paper P is a small loop shape, in step S70, the control unit 50 determines whether or not the pressing force (pressing force) of the spring 122 can be increased. This is because if the pressure applied by the spring 122 is too large, the nip pressure of the loop roller pair 30 becomes strong and the paper P may be damaged. Therefore, the upper limit value of the pressure applied by the spring 122 is limited to a certain value. If the controller 50 determines that the pressure applied by the spring 122 can be increased, for example, the upper limit has not been reached, the process proceeds to step S80. In step S80, the control unit 50 increases the pressure of the spring 122 by controlling the operation of the pressurizing unit 120 based on the difference value calculated in step S30. At this time, the pressing force of the spring 122 can be increased stepwise according to the difference value.

  As a result, the pressing force (nip pressure) of the loop roller pair 30 also increases, so that the slip of the paper P can be suppressed and the paper P can be sent out reliably. As a result, the amount of decrease (difference value) in the loop of the paper P can be restored, so that the current loop shape of the paper P can be adjusted to an appropriate loop shape. Even when the loop amount is close to zero, it is possible to adjust to the appropriate loop shape by adjusting the pressing force of the spring 122. When the control of the pressing force by the spring 122 is completed, the process proceeds to step S50.

  On the other hand, when it is judged that the control part 50 cannot increase the pressurizing force of the spring 122, it progresses to step S90. In step S90, the control unit 50 determines whether or not the speed of the loop roller pair 30 can be changed. If the speed of the loop roller pair 30 can be changed, the control unit 50 proceeds to step S100. In step S100, the control unit 50 controls the operation of the roller driving unit 130 based on the calculated difference value, thereby reducing the rotational speed of the loop roller pair 30.

  Thereby, since the resistance value (frictional force) with respect to the paper P of the loop roller pair 30 can be increased, the slip of the loop roller pair 30 with respect to the paper P can be prevented. As a result, the amount of decrease (difference value) in the loop of the paper P can be restored, so that the current loop shape of the paper P can be adjusted to an appropriate loop shape. When the control by changing the speed of the loop roller pair 30 is completed, the process proceeds to step S50.

  On the other hand, when it is determined that the speed change of the loop roller pair 30 is impossible, the control unit 50 proceeds to step S110. For example, when the rotation speed of the loop roller pair 30 has reached the lower limit value, the speed of the loop roller pair 30 cannot be changed (decelerated) any more. to decide. In step S110, the control unit 50 executes the life extension control mode. Details of the life extension control mode will be described later.

  On the other hand, if it is determined that the loop shape of the paper P is not smaller than the appropriate loop shape PS, in step S40, the control unit 50 determines that the current paper P loop shape of the acquired image is stored in advance in the database. It is determined whether or not it is larger than the appropriate loop shape PS. As an example of a method for determining whether the shape is a large loop shape, a vertex is obtained from the loop shape of the current paper P, and the obtained vertex value of the loop shape of the current paper P is the vertex PST of the appropriate loop shape PS in the database. There is a method of judging by whether or not it is larger than the value of. At this time, when a certain range is provided on the ± side of the apex PST of the appropriate loop shape PS, and the value of the apex of the loop shape of the current paper P exceeds the upper limit value Th2 (see FIG. 7), the large loop It can be determined that the shape.

  As shown in FIG. 7, when the loop shape of the current paper P is the loop shape P3, the control unit 50 determines that the value of the vertex P3T of the loop shape P3 exceeds the upper limit value Th2 of the appropriate loop shape PS. It is determined that the current loop shape is a large loop shape, and the process proceeds to step S60. Further, the control unit 50 calculates a difference value between the vertex P2T of the loop shape of the current sheet P and the vertex PST of the appropriate loop shape PS, and stores the calculated difference value in the memory 72. On the other hand, when the value of the apex of the loop shape of the current paper P is equal to or less than the upper limit value Th2 of the appropriate loop shape PS, the control unit 50 determines that the loop shape of the paper P is the proper loop shape RS, and step S50. Proceed to

  In the above example, the image of the appropriate loop shape PS stored in advance in the database is used. However, the present invention is not limited to this. For example, when the loop shape of the paper P conveyed before the current paper P, for example, the previous paper P is an appropriate loop shape, the current paper is used by using the loop shape image of the paper P. It can also be determined whether the loop shape of P is smaller than the appropriate loop shape PS.

  If it is determined that the loop shape of the paper P is a large loop shape, the control unit 50 controls the drive timing of the loop roller pair 30 in step S60. The control unit 50 controls the operation of the roller driving unit 130 based on the difference value calculated in step S40 so that the stop timing of the loop roller pair 30 is slightly faster than the previous stop timing of the paper P. To do. As a result, excessive feeding of the paper P by the loop roller pair 30 can be suppressed, and the paper P can be prevented from having a large loop shape.

  In addition, when the pressing force (pressing force) of the spring 122 can be reduced, the control unit 50 controls the operation of the pressing unit 120 based on the difference value calculated in step S40. The applied pressure may be decreased. As a result, the pressing force (nip pressure) of the loop roller pair 30 also decreases, so that the excessive delivery of the paper P can be eliminated and the loop shape RS can be adjusted.

  In step S50, the control unit 50 determines whether the job is completed. If the control unit 50 determines that the job has been completed, the process of correcting the bending of the paper P is terminated. On the other hand, when determining that the job is not completed, the control unit 50 returns to step S10, acquires an image showing the loop shape after the next sheet P in the job being executed, and the loop shape after the next sheet is determined. It is determined whether or not the shape is an abnormal loop.

(Example of operation in life extension control mode)
Next, a life extension control mode for extending the life of a job without stopping the job or shortening the job stop time will be described. The life extension control mode is executed when the paper P has a small loop shape and the pressure applied to the loop roller pair 30 cannot be changed or the speed of the loop roller pair 30 cannot be changed. .

  FIG. 9 is a flowchart illustrating an example of the operation in the life extension control mode. As shown in FIG. 9, in step S <b> 200, the control unit 50 displays guidance (warning) information for prompting the user to replace the loop roller pair 30 on the screen of the operation display unit 70. The guidance information may be voice or a combination with display on the screen. At this stage, since the service person has not arrived at the site, the loop roller pair 30 is not replaced.

  In step S210, the control unit 50 determines whether or not the acquired loop shape of the paper P has returned to an appropriate loop shape. If the control unit 50 determines that the loop shape of the current paper P has returned to the proper loop shape, the control unit 50 proceeds from the life extension control mode to step S50 for performing normal paper bending correction control shown in FIG. On the other hand, if the control unit 50 determines that the loop shape of the current paper P has not returned to the appropriate loop shape PS, the control unit 50 proceeds to step S220.

  In step S220, the control unit 50 determines whether or not the loop amount of the paper P is “0 (or an amount close to zero loop)” based on the loop shape of the acquired image. For example, the control unit 50 determines whether the loop amount is “0” from the top of the loop shape. This is because, for example, when paper dust or the like adheres to the loop roller pair 30, slippage of the paper P with respect to the loop roller pair 30 may occur, and the loop amount of the paper P may become “0”. Because there is. When the control unit 50 determines that the loop amount of the paper P is “0”, the process proceeds to step S250, and when it determines that the loop amount of the paper P is not “0”, the control unit 50 proceeds to step S230.

  When the loop amount of the paper P is “0”, the control unit 50 controls the roller driving unit 130 to temporarily stop driving the loop roller pair 30 in step S250. Subsequently, in step S <b> 260, the control unit 50 displays guidance information for prompting the user to clean the loop roller pair 30 on the screen of the operation display unit 70. The guidance information may be voice or a combination with display on the screen.

  In step S270, the control unit 50 determines whether or not the cleaning of the loop roller pair 30 has been completed. For example, the control unit 50 determines whether or not cleaning has been completed by selecting a signal for detecting insertion / removal of the loop roller pair 30 or a button indicating completion of cleaning on the operation display unit 70. When it is determined that the cleaning of the loop roller pair 30 has been completed, the control unit 50 proceeds to step S230. On the other hand, when it is determined that the cleaning of the loop roller pair 30 has not been completed, the control unit 50 returns to step S260 and continues to prompt the cleaning of the loop roller pair 30.

  In step S230, the control unit 50 determines whether the job is completed. When the control unit 50 determines that the job has been completed, the process of correcting the curvature of the series of sheets P ends. On the other hand, if the control unit 50 determines that the job is not completed, the process proceeds to step S240.

  In step S240, the control unit 50 determines whether or not an image indicating the loop shape of the next sheet P has been acquired. If acquisition of the image has been completed, the control unit 50 acquires an image indicating the loop shape of the next sheet P. The process returns to step S210. On the other hand, if the image acquisition has not been completed, the process returns to step S230.

  In step S210, the control unit 50 determines again whether or not the loop shape of the paper P has returned to the appropriate loop shape PS. This is because, for example, the conditions such as moisture contained in the paper P may differ depending on each paper, and the moisture contained in the subsequent paper and the like is normal, and the loop of the paper P may return to the appropriate loop shape PS. Because. Further, when the job is, for example, a mixture of thin paper and thick paper, the paper P may return to the proper loop shape PS by changing the paper type of the paper P from, for example, thick paper to thin paper. Furthermore, there is a case where the paper P can be normally sent out by cleaning the loop roller pair 30. If the sheet P does not return to the proper loop shape PS even by these life extension controls, it is preferable to replace the loop roller pair 30.

  When the loop shape of the paper P returns to the appropriate loop shape PS, the control unit 50 proceeds to step S50 where normal paper bending correction control shown in FIG. 8 is performed from the life extension control mode. On the other hand, when the control unit 50 determines that the loop shape of the current sheet P has not returned to the appropriate loop shape, the control unit 50 repeatedly executes the processes of steps S220 to S270 described above.

  As described above, according to the present embodiment, since the image showing the loop shape on the side surface of the paper P imaged by the imaging unit 110 is used, two-dimensional information (vertex and Posture). As a result, even when the loop shape is an abnormal loop or the position of the vertex changes like a small loop shape or a large loop shape, an appropriate correction amount (difference value amount) can be calculated. By feeding back this correction value to the loop roller pair 30, an appropriate loop amount can be ensured.

  Further, in the present embodiment, even when the paper P has a small loop shape and the proper loop shape PS cannot be secured due to the control limit such as the pressure of the spring 122, the loop roller pair 30 A life extension control mode is executed in which cleaning is performed or whether the proper loop is determined based on the image of the next sheet. Thereby, since the replacement of the loop roller pair 30 can be avoided, the cost due to the replacement of the loop roller pair 30 and the occurrence of downtime due to the job stop when the loop roller pair 30 is replaced can be suppressed.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. For example, the abnormal loop shape, the small loop shape, and the large loop shape described in the above embodiment are examples, and other various shapes are also included. Moreover, in the said embodiment, when the pressurization control of the spring 122 was difficult, the speed control of the loop roller pair 30 was performed, However, these controls may be reverse. Furthermore, the order of determining whether the loop shape of the paper P is a small loop shape and the determination of whether it is a large loop shape may be reversed.

30 Loop roller pair (second roller pair)
32 Registration roller pair (first roller pair)
50 control unit 70 operation display unit 100 image forming apparatus 110 imaging unit 120 pressure unit 130 roller driving unit (driving unit)
200 Registration unit P Paper PS Appropriate loop shape

Claims (8)

A first pair of rollers for conveying paper;
A second roller pair provided upstream of the first roller pair in the paper traveling direction and forming a loop by abutting the paper against the first roller pair;
An imaging unit that acquires an image showing a loop shape on a side surface in a loop of the paper formed by the second roller pair;
A control unit that adjusts a loop shape of the paper based on the image acquired by the imaging unit,
Based on whether there are a plurality of intersections between the loop shape of the image acquired by the imaging unit and a reference line orthogonal to the paper traveling direction and orthogonal to the paper width direction, the control unit An image forming apparatus comprising: determining whether a loop shape of the acquired image is an abnormal loop shape. A drive unit that rotationally drives the second roller pair;
When the control unit determines that the loop shape of the image is the abnormal loop shape based on a comparison result between the image acquired by the imaging unit and set reference information, the control unit controls the drive unit. The image forming apparatus according to claim 1, wherein a rotation speed of the second roller pair is controlled. A pressure unit that adjusts the pressing force of the second roller pair;
When the loop shape of the image acquired by the imaging unit is not the abnormal loop shape and smaller than a reference appropriate loop shape, the control unit controls the pressurizing unit to control the second roller. The image forming apparatus according to claim 1, wherein the pressure of the pair is increased. A drive unit that rotationally drives the second roller pair;
The control unit controls the driving unit to control the second roller pair when the loop shape of the image acquired by the imaging unit is not the abnormal loop shape and is smaller than a reference appropriate loop shape. The image forming apparatus according to claim 1, wherein the speed of the image forming apparatus is reduced. When the pressure control or the speed control of the second roller pair cannot be performed and the paper loop is not formed, the control unit transmits information for prompting the cleaning of the second roller pair. The image forming apparatus according to claim 3, wherein the image forming apparatus is notified. If the control unit cannot perform pressure control or speed control of the second roller pair, the control unit acquires an image indicating a loop shape of the next sheet, and the acquired loop shape of the next sheet becomes an appropriate loop shape. The image forming apparatus according to claim 3, wherein it is determined whether or not it has returned. A drive unit that rotationally drives the second roller pair;
The control unit controls the driving unit to control the second roller pair when the loop shape of the image acquired by the imaging unit is not the abnormal loop shape and is larger than a reference appropriate loop shape. The image forming apparatus according to claim 1, wherein a rotation speed of the image forming apparatus is controlled. The image forming apparatus according to claim 1, wherein the imaging unit is provided on one side in a width direction orthogonal to a sheet traveling direction of the sheet.

Images