JP2008201513A - Medium conveying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve inconvenience that correction is completely performed when a recording medium is largely skewed and unnecessary abutment is performed to damage the medium when skewing is contrarily less in a medium conveying device used for an image forming device or the like and provided with function for correcting the skewing of the recording medium. <P>SOLUTION: The medium conveying device is provided with a pair of conveying rollers 308 extending in a direction approximately perpendicular to a conveying direction of the recording paper and abutted with a leading end of the conveying recording paper; a feed roller 203 and a retard roller 204 for conveying the recording paper toward the pair of conveying rollers 308; a paper sensor unit 302 for detecting passing of both ends in a width direction of the conveying recording paper; and a means for controlling these. After passing of both ends of the recording paper is detected by the paper sensor unit 302, the recording paper is conveyed by a predetermined amount and is abutted on a nip part of the pair of conveying rollers to correct the skewing of the recording paper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a medium conveying device of an image forming apparatus such as a printer, a copying machine, and a facsimile.

  2. Description of the Related Art Conventionally, image forming apparatuses such as printers, copiers, and facsimiles mainly form images by the following process. That is, after the photosensitive member as an image carrier is charged, optical writing according to an image signal is performed by a laser scanning optical system or an LED light writing optical system to form an electrostatic latent image on the photosensitive member. Next, the electrostatic latent image is converted into a toner image by toner adhesion by a developing device, and the toner image is transferred to a transfer material such as transfer paper or a film directly or via an intermediate transfer member. Then, the transferred transfer material is conveyed to a fixing device, and the toner image is fixed on the transfer material by this fixing device to obtain an image.

  Such an image forming apparatus is provided with a medium transport device that transports the recording paper fed out from the paper cassette. As an image recording apparatus provided with a recording paper medium transport device, for example, a paper feed roller that feeds a recording paper from a paper cassette, a pair of registration rollers provided downstream of the paper feed roller in the paper transport direction, An upstream side immediately before the roller, and a sheet sensor provided in the center of the direction orthogonal to the sheet conveyance direction, and when the leading edge of the sheet conveyed by the sheet feeding roller is detected by the sheet sensor, From that point on, there is a type in which a certain amount of paper is transported by the paper feed roller, the paper is abutted against the stopped registration roller, the paper skew is corrected, and then the registration roller is driven to transport the paper downstream. (For example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-352448 (page 7, FIG. 1)

  However, in this conventional configuration, since the sheet sensor detects the center of the leading edge of the medium that has been conveyed while being inclined, the skew cannot be completely corrected when the amount of inclination of the medium is large. In addition, assuming that the amount of tilt of the medium is large, if the abutment amount is set large, the load on the medium increases when the amount of tilt of the medium is small, causing damage such as bending of the medium. There was a fear.

  The object of the present invention is to eliminate these problems and correct skew even when the amount of tilt of the medium is large. Further, even when the amount of tilt of the medium is small, the skew is not caused to damage the transported medium. It is an object of the present invention to provide a medium transport device and an image forming apparatus that can correct the above.

A medium conveying apparatus according to the present invention is a medium conveying apparatus having a function of correcting skew of a medium,
An abutting means that extends in a direction substantially perpendicular to the conveying direction of the medium and abutted against a leading end of the medium to be conveyed; a medium conveying means that conveys the medium toward the abutting means; A medium detecting means disposed between the abutting means and the medium transporting means for detecting the passage of both ends of the transported medium in the width direction, and the passage of the both ends detected by the medium detecting means. And a control unit that transports the medium by a predetermined amount by the medium transport unit and corrects the skew by abutting the medium against the abutting unit.

An image forming apparatus according to the present invention includes:
The image forming apparatus includes: the medium conveying device; and an image forming unit that forms an image on the conveyed medium.

  According to the present invention, even when the skew amount of the medium to be transported is greatly different for each medium, it is possible to always correct the skew by performing the minimum necessary butting.

Embodiment 1 FIG.
FIG. 1 is a main part configuration diagram of the main part configuration of the image forming apparatus according to the first embodiment of the present invention as viewed from the front.

  The image forming apparatus 1000 shown in the figure has a configuration as a color electrophotographic printer capable of printing four colors of black (K), yellow (Y), magenta (M), and cyan (C). In the drawing, a paper feed tray 100 is detachably attached to the main body of the image forming apparatus 1000 and accommodates a recording paper 101 as a recording medium stacked therein. Inside the paper feed tray 100, a paper placement plate 102 is rotatably provided on the support shaft 102a, and more than half of the recording paper 101 on the feeding side is placed on the paper placement plate 102. The paper feed tray 100 is provided with a guide member (not shown) that regulates the stacking position of the recording paper 101, and the paper feeding direction and the paper feeding direction orthogonal to the feeding direction of the recording paper 101 (arrow E direction in the figure). The side of the paper is regulated in the direction, and the stacking position of the recording paper 101 to be stored is kept constant.

  On the feeding side of the paper feed tray 100, a lift-up lever 103 that is rotatably provided on the support shaft 103a is provided. The support shaft 103a is engaged with the motor 104 so as to be able to contact and separate. When the paper feed tray 100 is mounted on the main body of the image forming apparatus 1000, the lift-up lever 103 and the motor 104 are engaged, and a control unit (not shown) drives the motor 104. When the motor 104 rotates and the lift-up lever 103 rotates, the tip of the lift-up lever 103 pushes up the bottom of the paper stacking plate 102 and the recording paper 101 loaded on the paper stacking plate 102 rises. When the recording sheet 101 rises to a certain height, a control unit (not shown) obtains information from the rise detection unit 201 that detects this rise, detects this, and stops the motor 104.

  A paper feeding unit 200 that feeds the recording paper 101 one by one is provided on the feeding side of the paper feed tray 100. The paper feeding unit 200 includes a pickup roller 202 provided so as to press-contact the recording paper 101 raised to a certain height, a feed roller 203 for separating the recording paper 101 fed by the pickup roller 202 one by one, and a retard A roller pair of rollers 204, a paper presence / absence detection unit 205 for detecting the presence / absence of the recording paper 101, and a paper remaining amount detection unit 206 for detecting the remaining amount of paper are provided.

  The recording sheet 101 fed out by one roller pair of the feed roller 203 and the retard roller 204 is sent to the sheet conveying unit 300. The fed recording sheet 101 passes through the sheet sensor unit 302 and is sent to a conveying roller pair 308 including a driving roller 309 and a driven roller 310. As will be described later, the conveyance roller pair 308 starts to rotate under the control of a control unit 320 (FIG. 5), which will be described later, at a timing delayed by a predetermined time from the time when the recording paper 101 has passed the paper sensor unit 302. As a result, the recording paper 101 is pushed into the nip portion of the conveying roller pair 308 whose rotation is stopped in a slightly bent state, and the skew is corrected.

  The recording paper 101 sent out from the transport roller pair 308 is sent to the transport roller pair 311. The conveyance roller pair 311 is rotated by the conveyance motor 326 (FIG. 5) from the time point when the recording paper 101 is detected by the paper sensor unit 302, and sends the recording paper 101 without stopping. The recording paper 101 sent out by the conveying roller pair 311 passes through the writing sensor 315 and is sent to the image forming unit 400. Power is transmitted to these conveying roller pairs 308 and 311 via drive transmission means (not shown).

  The image forming unit 400 uses four process units 430K, 430Y, 430M, and 430C (collectively referred to simply as 430) arranged in series and a toner image formed by the process unit 430 on the upper surface of the recording paper 101. And a transfer portion 460 for transferring by the Coulomb force. The four toner image forming units 430 arranged in series have the same configuration, and only the colors of the toners used, that is, black (K), yellow (Y), magenta (M), and cyan (C) are used. Here, in this order from the upstream side in the paper conveyance direction, a black (K) process unit 430K, a yellow (Y) process unit 430 (Y), a magenta (M) process unit 430 (M), In addition, process units 430 (C) for cyan (C) are arranged.

  Accordingly, for the sake of simplicity, only the black (K) process unit 430 (K) is shown in its configuration, and description of the other process units is omitted.

  The process unit 430 (K) includes a photosensitive drum 431 that carries a toner image, a charging roller 432 that charges the surface of the photosensitive drum 431, and an LED array that forms an electrostatic latent image on the surface of the charged photosensitive drum 431. An LED head 433, a developing roller 434 that forms a toner image on an electrostatic latent image by frictional charging, a toner supply unit 436 that supplies toner, a cleaning blade 435 that scrapes off residual toner remaining on the surface of the photosensitive drum 431 after transfer, and the like. Is provided. The drums or rollers used in each of these devices rotate by receiving power from a drive source (not shown) via gears.

  The transfer unit 460 is paired with a transfer belt 461 that electrostatically attracts and conveys a sheet, a drive roller 462 that is rotated by a drive unit (not shown) to drive the transfer belt 461, and a drive roller 462. The tension roller 463 to be stretched and the respective photosensitive drums 431 of the process unit 430 are arranged to face each other and press-contact with each other, and a voltage is applied to transfer the toner image onto the recording paper 101 formed by conductive rubber or the like. The image forming apparatus includes a transfer roller 464 to be applied, a cleaning blade 465 for scraping and cleaning the toner adhering to the transfer belt 461, and a toner box 466 for depositing toner scraped off by the cleaning blade 465.

  The process unit 430 and the transfer belt 461 are driven in synchronization, and the toner images of the respective colors are sequentially superimposed and transferred onto the recording paper 101 electrostatically attracted to the transfer belt 461. The recording paper 101 to which the image is transferred by the image forming unit 400 in this way is sent to the fixing unit 500 that fuses the toner image to the recording paper 101 with heat and pressure.

  The fixing unit 500 includes a halogen lamp 503a serving as a heat source therein, an upper roller 501 having a surface formed of an elastic body, and a halogen lamp 503b serving as a heat source therein, and a lower roller 502 having a surface formed of an elastic body. The toner image is melted and fixed on the recording paper 101 by applying heat and pressure to the toner image on the recording paper 101 sent out from the image forming unit 400. Thereafter, the recording sheet 101 is discharged to the stacker unit 505 by the discharge roller pairs 504a, 504b, and 504c.

  Note that the XYZ coordinates in the figure are the X-axis in the transport direction when the recording paper 101 passes through the process unit 430, the Y-axis in the rotational axis direction of the photosensitive drum 431, and are orthogonal to these two axes. The Z axis is taken in the direction. Further, when XYZ coordinates are shown in other drawings to be described later, the axial directions of these coordinates indicate a common direction. In other words, the XYZ axes in each figure indicate the arrangement direction when the depicted portion of each figure constitutes the image forming apparatus 1000 shown in FIG.

  Next, the configuration of the medium conveyance device 301 including the feed roller 203, the retard roller 204, the paper sensor unit 302, and the conveyance roller pair 308 shown in FIG. 1 will be further described. FIG. 2 is a perspective view showing a main part configuration of the medium transport apparatus 301 according to the first embodiment of the present invention, and FIG. 3 is a main part configuration diagram of the medium transport apparatus 301 viewed from the paper feed tray 100 side. FIG. 4 is a main part configuration diagram of the medium transport device 301 as viewed from the rotation axis direction of the photosensitive drum 431 (the front side of the drawing in FIG. 1).

  As shown in FIG. 2, the medium conveying device 301 includes a feed roller 203 and a retard roller 204 as medium conveying means, arranged in order from the upstream side in the medium conveying direction indicated by arrow A in FIG. A sheet sensor unit 302 as a means and a medium transport roller pair 308 as an abutting means are configured. The paper sensor unit 302 is arranged in parallel substantially perpendicular to the medium transport direction, and is provided with two arm members 303 and 304 serving as displacement members that come into contact with the paper to be transported. The lever member 305 that swings by the operation of 303, 304, the lever support shaft 307 that is the axis of operation when the lever member 305 swings, and compression between the lever member 305 and the lever support shaft 307 The spring 351 (FIG. 3) hung in this state and a switch 306 as detection means for detecting that the lever member 305 is displaced to a predetermined position.

  As shown in FIG. 3, the feed roller 203 and the retard roller 204 are paired in parallel with each other in the direction in which each rotation axis is substantially orthogonal to the medium conveyance direction indicated by the arrow A (the rotation axis direction of the photosensitive drum 431). As shown in FIG. 4, the recording paper 101 is disposed at a position where the recording paper 101 can be conveyed toward the conveyance roller pair 308 downstream in the medium conveyance direction.

  The arm members 303 and 304 are for pressing down the paper contact portions 336 and 337 for contacting the paper leading edge 101a (FIG. 3), the rotation shafts 318 and 319 parallel to the rotation shaft of the feed roller 203, and the lever member 305, respectively. Lever pressing portions 338 and 339 are provided. The lever pressing portions 338 and 339 are located on the opposite side of the paper contact portions 336 and 337 with respect to the shaft centers of the rotation shafts 318 and 319. As shown in FIG. 3, the arm members 303 and 304 have a center plane in the width direction of the recording sheet 101 (a plane that includes the assumed sheet width center position when the recording sheet 101 is conveyed and is perpendicular to the sheet width direction). ) Are arranged symmetrically with respect to 600.

As shown in FIG. 3, the arm members 303 and 304 are disposed at positions where the sheet contact portions 336 and 337 are separated from the center plane 600 in the width direction of the sheet by a distance L, respectively. In the image forming apparatus 1000 including the medium transport device 301, the paper contact portions 336 and 337 are set according to the distance L of the recording paper 101 set to be transportable and having the minimum width W. ,
W> 2L
Is satisfied, and it is determined to be an appropriate position close to both ends of the sheet front end 101a.

  For example, if the short side of an A4 size recording sheet is the smallest sheet size that can be conveyed, the minimum sheet width W is 210 mm. At this time, if the distance L is set to 100 mm, the skew angle of the medium can be corrected to about 18 ° as will be described later. Usually, the skew angle of the medium does not exceed 5 ° at the maximum, so that the margin is sufficient. Since the arm members 303 and 304 are in contact with the paper leading edge 101a, as shown in FIG. 4, the rotation of the arm members 303 and 304 is performed under the above conditions so that the paper contact portions 336 and 337 are on the paper transport path. The shafts 318 and 319 are rotatably supported by the image forming apparatus 1000 main body.

  As shown in FIG. 3, the lever member 305 has a symmetrical shape with respect to the center surface 600 in the width direction, and is a length in the width direction that can contact either of the lever pressing portions 338 and 339 of the arm members 303 and 304. Have A hanging part 341 is formed at the center of the lever member 305, and a long hole 340 having a long axis in the height direction perpendicular to the width direction is formed in the hanging part 341. A lever support shaft 307 fixed to the main body of the image forming apparatus 1000 is fitted into the elongated hole 340 having a predetermined thickness. Accordingly, the lever member 305 is held by the lever support shaft 307 so as to be rotatable and slidable. A spring 351 for urging the lever member 305 upward is stretched between the lever support shaft 307 and the lever member 305 in a compressed state. Therefore, the lever member 305 is maintained in a state where the lower end portion of the elongated hole 340 is in contact with the lever support shaft 307 as shown in FIG.

  The lever support shaft 307 is on the center surface 600 in the width direction of the sheet, is substantially parallel to the X axis, and both end portions of the lever member 305 to be held are respectively the lever pressing portions 338 and 339 of the arm members 303 and 304. It is fixed at a position where it can be contacted below.

  As shown in FIG. 3, the switch 306 has the switch lever 306 a drooping on the switch lever 306 a so that the rotation plane of the switch lever 306 a is parallel to the slide plane (YZ plane) of the lever member 305. Further, the lever member 305 is pushed down in the vertical direction (Z-axis minus direction) against the biasing force of the spring 351 as described later, so that the tip end of the portion 341 can be brought into contact with it. The switch 306 is disposed at a position where the switch 306 is switched from the off state to the on state when reaching the position.

  The conveying roller pair 308 includes a driving roller 309 and a driven roller 310. The drive roller 309 includes a shaft 316, and a friction material 317 such as rubber is wound around the outer periphery. The shaft 316 receives a rotational force from a conveyance motor 326 (FIG. 5) described later, and is in the direction of arrow B in FIG. It is comprised so that it may rotate. The driven roller 310 is disposed opposite to and parallel to the driving roller 309, and is rotatably held. A peripheral surface of the driven roller 310 is provided on the peripheral surface of the driving roller 309 by springs (not shown) provided at both ends of the rotating shaft. The formed friction material 317 is evenly biased. As a result, the drive roller 309 is driven to rotate in the direction of arrow C in the figure, and the recording paper 101 to be sandwiched is conveyed in the direction of arrow A.

  FIG. 5 is a block diagram showing a main configuration of a control system that controls the operation of the medium transport apparatus 301 related to the present invention.

  In the figure, the control unit 320 has a main control unit 321 serving as a control center, and the main control unit 321 incorporates a CPU composed of a control unit and a calculation unit, a RAM and ROM of a program memory, a timer counter, and the like. Based on the detection signal from the paper sensor unit 302 input from the input port, each unit is activated and control is switched. In addition, a paper feed motor control unit 322, a transport motor control unit 323, and a clutch control unit 324 are connected to the main control unit 321. The transport motor control unit 323 sends an operation signal to the transport motor 326 to control the operation, the paper feed motor control unit 322 sends an operation signal to the paper feed motor 325 to control the operation, and the clutch control unit 324 An operation signal is sent to the clutch 327 to control the operation of the clutch.

  The conveyance motor 326 directly drives the conveyance roller pair 311 and indirectly drives the conveyance roller pair 308 via a clutch 327 that turns on and off the transmission state. The feed roller 203 is driven to rotate.

  Each of these motors is, for example, a two-phase excitation pulse motor. The motor rotation is accelerated or decelerated by passing a constant current through each motor and switching the phase current direction at the rising edge of the clock signal or changing the clock frequency. To control. For example, a micro electromagnetic clutch or the like is used as the clutch. A magnetic field is generated by a current flowing through a coil in the clutch, and power is transmitted to the drive roller 309 by attracting and contacting the armature and rotor in the clutch. By turning off the current flowing through the coil, the armature and the rotor are released, and the power to the drive roller 309 is cut off.

  The operations of the image forming apparatus 1000 and the medium transport apparatus 301 in the above configuration will be described.

  First, an outline of the operation of the entire image forming apparatus 1000 will be described with reference to FIG. The recording paper 101 stored in a stacked state on the paper tray 100 is separated one by one from the top by the paper feeding unit 200 including the pickup roller 202, the feed roller 203, and the retard roller 204, and contributes to the paper conveyance path. Is done. The recording paper 101 passes through the paper sensor unit 302 and is sent to the conveyance roller pair 308. The conveyance roller pair 308 sends out the recording paper 101 at a predetermined timing described later based on the passage time of the medium through the paper sensor unit 302. At this time, the conveyed recording paper 101 is abutted between the roller nips of the conveying roller pair 308 whose rotation is stopped, and the skew is corrected. The operation of the sheet sensor unit 302, the operation of the transport roller pair 308, and the control for rotationally driving the transport roller pair 308 will be described in detail later.

  The recording paper 101 sent out by the transport roller pair 308 is sent to the transport roller pair 311. The conveyance roller pair 311 is rotationally driven from the time point when the recording paper 101 is detected to be passed by the paper sensor unit 302, and feeds the recording paper 101 without stopping. The recording sheet 101 sent out by the pair of conveying rollers 311 passes through the writing sensor 315 and is sent to the image forming unit 400.

  Here, the recording paper 101 is conveyed by the transfer belt 461 and is conveyed between the photosensitive drum 431 and the transfer roller 464 of the black (K) process unit 430K. Thereafter, the recording sheet 101 is sandwiched between the photosensitive drum 431 and the transfer roller 464, and the toner image is transferred onto the recording surface.

  Similarly, the recording paper 101 sequentially passes through the process units 430Y to 430C, and in the passing process, the electrostatic latent images formed by the respective exposure devices 433 are developed as the respective color toner images by the developing roller 434. Sequentially transferred and superposed on the recording surface. After the toner images of the respective colors are superimposed on the recording surface, the recording paper 101 on which the toner image is fixed by the fixing unit 500 is recorded on the outside of the image forming apparatus by the discharge roller pairs 504a, 504b, and 504c. The paper is discharged to the paper stacker unit 505. A color image is formed on the recording paper 101 through the above process.

  Next, operations of the sheet sensor unit 302 and the conveyance roller pair 308 of the medium conveyance device 301 will be described in detail with reference to the operation explanatory diagrams of FIGS.

  The operation explanatory diagrams of FIGS. 6 to 9 schematically show the process in which the skewed recording paper 101 passes through the medium conveying device 301 in time series. In each figure, (a) is a view seen from the paper feed tray 100 (FIG. 1) side, and (b) is a view seen from the rotation axis direction of the pickup roller 202 (the front side of the drawing in FIG. 1). In each figure (a), for simplicity, the driving roller 309 and the driven roller 310 are not shown, and only the nip portion 610 is indicated by a dotted line. The recording medium 101 that has passed through the paper sensor unit 302 is normally abutted against the nip portion 610 of the conveying roller pair 308 that is stopped from rotating to correct skewing. In each of FIGS. In order to avoid complications, the nip portion 610 is shown as it is for the sake of convenience.

  As described above, when the recording sheet 101 is sent out from the medium conveying apparatus 301 toward the conveying roller pair 308 by the sheet feeding unit 200 (FIG. 1) on the upstream side in the medium conveying direction indicated by the arrow A, the recording sheet is eventually obtained. The leading end 101 a of 101 reaches the paper sensor unit 302. FIG. 6 shows the state at this time, and it is assumed that the recording paper 101 sent out as described above is inclined with respect to the medium conveyance direction, that is, is skewed by a predetermined amount.

  As shown in FIG. 6, at this time, for example, in the case of a skew that is sent out with the one end side end 101b of the paper leading end 101a positioned ahead of the other end side end 101c in the medium conveying direction of the arrow A, First, the end portion 101 b on one end side of the recording sheet 101 conveyed comes into contact with the sheet contact portion 337 of the arm member 304. Thereafter, when the recording paper 101 further moves, as shown in FIG. 7, the paper contact portion 337 is pushed against the one end portion 101 b of the recording paper 101, whereby the arm member 304 is moved around the rotation shaft 319 with an arrow. It rotates in the B direction (FIG. 7B).

  6 to 9, “□” indicates the position on the conveyance path of the one end portion 101 b of the recording paper 101, and “●” indicates the other end portion 101 c of the recording paper 101. The position on the conveyance path is shown. Here, the one end side end portion 101 b refers to a portion of the leading end 101 a of the recording paper 101 that contacts the paper contact portion 337 of the arm member 304, and the other end side end portion 101 c refers to the leading end of the recording paper 101. 101a is a portion that contacts the paper contact portion 336 of the arm member 303. The rotational position before the arm members 303 and 304 contact the recording paper 101 and rotate in the direction of arrow B is hereinafter referred to as a reference position, and the rotational position after the arm member 303 and 304 rotates by a predetermined amount in the direction of arrow B is hereinafter referred to as a detection position. .

  As shown in FIG. 7, when the paper contact portion 337 is pushed up by the one end 101b of the paper leading edge 101a and the arm member 304 rotates in the direction of arrow B from the reference position to the detection position, the arm member 304 is accompanied by this rotation. The lever pressing portion 339 comes into contact with one end portion 305a of the lever member 305 and pushes the contact portion 305a downward. At this time, the lever member 305 rotates in the direction of arrow F with the other end 305b of the lever member 305 contacting the arm member 303 at the reference position as a substantial rotation center. That is, the end 305a on one end side of the lever member 305 is in a position pushed down by the lever pressing portion 339 of the arm member 304, and the drooping portion 341 biased by the spring 351 slightly lowers against the biasing force. Moved.

  Thereafter, when the recording paper 101 is further conveyed, as shown in FIG. 8, the one end 101b and the other end 101c of the leading edge 101a are moved in the medium conveying direction of the arrow A from the state of FIG. The paper advances and the central portion of the paper leading edge 101a reaches the nip portion 610 formed by the stopped conveying roller pair 308. On the other hand, the other end portion 101c of the paper leading end 101a is conveyed to a position where it contacts the paper contact portion 336 of the arm member 303 and pushes up the arm member 303, whereby the arm member 303 moves its rotating shaft 318. It rotates in the direction of arrow B at the center. FIG. 8 shows a state immediately after the arm member 303 starts to rotate in the B direction. By this rotation, the lever pressing portion 338 of the arm member 303 pushes down the other end 305b of the lever member 305 that is in contact with the lever member 305.

  At this time, the lever member 305 rotates in the direction of the arrow G with the one end side end portion 305a of the lever member 305 in contact with the arm member 304 at the detection position as a substantial rotation center. That is, the other end 305b of the lever member 305 is in a position pushed down by the lever pressing portion 338 of the arm member 303, and the drooping portion 341 biased by the spring 351 further moves downward against the biasing force. Moved. However, at this time, the switch 306 is still in the OFF state, and the conveyance roller pair 308 is not driven and is kept stopped as will be described later.

  Thereafter, when the recording paper 101 is further conveyed, as shown in FIG. 9, the one end side end portion 101b and the other end side end portion 101c of the sheet leading end 101a move forward in the medium conveying direction from the state of FIG. One end 101b of the leading end 101a of the sheet is in a state of being abutted against the nip 610 formed by the stopped conveying roller pair 308. On the other hand, the other end 101c of the paper leading end 101a further pushes up the paper contact portion 336 of the arm member 303 and rotates the arm member 303 to the detection position. FIG. 9 shows a state after the arm member 303 has rotated to the detection position. By this rotation, the lever pressing portion 338 of the arm member 303 further pushes down the other end 305b of the lever member 305 that is in contact with the lever member 305.

  At this time, the lever member 305 further rotates in the direction of the arrow G with the one end side end 305a of the lever member 305 in contact with the arm member 304 at the detection position as a substantial rotation center. As a result, the other end 305b of the lever member 305 becomes a position pressed down by the lever pressing portion 338 of the arm member 303 rotated to the detection position, that is, a position pressed to the same level as the one end 305a. The hanging portion 341 biased by the spring 351 moves further downward against the biasing force, and reaches a predetermined position where the switch 306 is switched from the off state to the on state.

  After the other end 101c of the leading edge 101a passes through the opposing arm member 303 and the switch 306 is turned on, the recording paper 101 continues to be conveyed by a predetermined amount of movement D1. The leading end 101 a is abutted against the nip portion 610 formed in the conveying roller pair 308. Thereafter, the conveyance roller pair 308 is driven by driving from a driving source (not shown), whereby the recording paper 101 is taken in by the conveyance roller pair 308 that has been rotated, and is moved in the medium conveyance direction A by the conveyance roller pair 308. Be transported.

The predetermined movement amount D1 is determined as follows. That is, as shown in FIG. 9, when the switch 306 is turned on, the positions of the paper contact portions 336 and 337 of the arm members 303 and 304 on the paper transport path (see FIG. The distance on the conveyance path from the nip portion 610 to the nip portion 610 is L1, and the distance on the conveyance path set as the predetermined abutting amount is R1, the predetermined movement amount D1 is the sum of these,
D1 = L1 + R1 (1)
Defined by

As described above, according to the medium transport apparatus 301 of the present embodiment, when the paper leading end 101a is skewed as shown in FIG. 9, the other end of the both ends of the paper leading end 101a transported with a delay. The switch 306 is turned on only when the side end 101c contacts the arm member 303 and the arm member 303 is rotated to the detection position, and the passage of the sheet is detected. Accordingly, when the switch 306 is turned on, the distance S1 from the other end side corner portion 101e located at the tail end of the sheet leading end 101a to the nip portion 610 is substantially equal to the distance L1, and depends on the skew state of the sheet 101. The variation amount of the distance S1 is small. Therefore, it is not necessary to adjust the abutting distance R1 according to the skew state of the sheet 101, and the minimum necessary amount can be fixedly set as the predetermined movement amount D1.
In FIG. 9, L1> S1 due to a problem in the drawing, but actually L1 <S1.

  Next, the overall operation of the medium transport apparatus 301 according to the present embodiment will be further described with reference to FIGS.

  The main control unit 321 issues a paper feed start instruction to the paper feed motor control unit 322 (step S1), drives the paper feed motor 325 to rotate the pickup roller 202 and the feed roller 203, and prints paper from the paper tray 100. 101 is fed, and the fed recording paper 101 is conveyed in one sheet (step S2). The paper sensor unit 302 watches the passage of the paper leading edge 101a of the paper 101 conveyed by the feed roller 203 and the retard roller 204, and detects the passage by turning on the switch 306 by the above-described mechanism (step). S3).

  When the paper sensor unit 302 detects the passage of the paper leading edge 101a, the main control unit 321 instructs the carry motor control unit 323 to drive the carry motor 326. As a result, the conveyance roller pair 311 is rotated by the rotation driving force of the conveyance motor 326 being transmitted. On the other hand, since the transmission state of the clutch 327 controlled by the clutch control unit 324 is off at this time, the pair of conveyance rollers 308 are stopped without transmitting the power of the conveyance motor 326 (step S4). After the paper sensor unit 302 detects the passage of the paper leading edge 101a, the paper sensor unit 302 is further transported toward the nip 610 (FIG. 6) of the transport roller pair 308 by the predetermined movement amount D1 (step S5). At this time, as described in the description accompanying the above equation (1), the trailing edge of the paper 101a (if the recording paper is skewed, the one of the one end 101b and the other end 101c is followed. Is pointed to the nip 610 and further conveyed by a predetermined abutting distance R1.

  By this abutting operation, a skew correction operation is performed on the recording sheet 101, and the feed roller control unit 322 stops the feed roller 203 (step S6). The main control unit 321 issues an instruction to the clutch control unit 324, applies a current to the clutch 327, and transmits the drive of the transport motor 326 to the transport roller pair 308 (step S7). The drive roller 309 to which the drive is transmitted conveys the recording paper 101 with the driven roller 310 that is driven and rotated, and conveys the recording paper 101 to the downstream conveyance roller pair 311. At this time, the feed roller 203 whose driving is stopped sends the recording paper 101 by being driven, but the driving of the feed roller 203 is resumed in synchronization with the driving of the conveying roller pair 308 so as to convey the recording paper 101. You may comprise.

  The sheet sensor unit 302 detects that the trailing edge of the sheet has passed through the sheet detection area by the switch 306 being turned off again after the conveying roller pair 311 starts conveying the recording sheet 101 (step S100). S8). The paper sensor unit 302 is also for detecting an abnormal conveyance of the recording paper 101. The main control unit 321 detects an abnormal paper conveyance when the leading edge or the trailing edge of the recording paper 101 is not detected by the paper sensor unit 302. Judge.

  The conveyance motor 326 is driven by a predetermined amount even after the switch 306 returns to the OFF state, and the conveyance roller pair 308 and the conveyance roller pair 311 are thereby rotated by a predetermined amount (step S9). Thereafter, the main control unit 321 issues an instruction to the clutch control unit 324 to stop the current applied to the clutch 327 and turn off the transmission state of the clutch 327 so that no power is transmitted to the pair of conveying rollers 308 ( Step S10). When continuous printing is performed (step S11, Yes), the main control unit 321 newly instructs to start paper feeding and conveyance, and the control from step S1 is repeated again. If there is no (No in step S11), the operation is terminated.

  Next, as a comparative example, a medium conveyance device 1301 shown in FIG. 11 will be described.

  This medium conveying device 1301 is configured by a feed roller 203, a retard roller 204, a paper sensor unit 372, and a medium conveying roller pair 1308, which are arranged in order from the upstream side in the medium conveying direction indicated by arrow A in FIG. Is done.

  The feed roller 203 and the retard roller 204 are arranged such that their rotation axes are paired in parallel in a direction substantially orthogonal to the medium conveyance direction indicated by the arrow A, and directed toward a conveyance roller pair 1308 downstream in the conveyance direction. Thus, the recording paper 101 is disposed at a position where it can be conveyed.

  The paper sensor unit 372 includes a sensor lever 329 and a photo sensor 330. The sensor lever 329 includes a lever portion 332 that detects the leading edge of the paper, a rotation shaft 331 that is parallel to the rotation shaft of the feed roller 203, and a shielding portion 333 that shields the photosensor. Further, the sensor lever 329 is disposed so that the lever portion 332 is in contact with the central portion in the width direction of the sheet conveyed on the conveyance path. The photo sensor 330 is a sensor of a type in which a light emitting element surface and a light receiving element surface are disposed to face each other, and an object passes between them and detects the object by blocking light, and the center of the sheet is conveyed to a specified position. The shielding portion 333 of the sensor lever 329 is disposed at a position where the photosensor 330 is shielded from light.

  The conveying roller pair 1308 includes a driving roller 328 and a driven roller 310. The drive roller 328 includes a shaft 334, and a friction material 335 such as rubber is wound around the outer periphery. The shaft 334 receives a rotational force from a drive source (not shown) and rotates in the direction of arrow B in the figure. ing. The driven roller 310 is disposed opposite to and parallel to the drive roller 328, and is rotatably held. The peripheral surface of the driven roller 310 is rotated by a spring (not shown) provided at both ends of the rotation shaft. The friction material 335 formed is equally biased. As a result, the drive roller 328 is driven to rotate in the direction of arrow C in the figure, and the recording paper 101 to be sandwiched is conveyed in the direction of arrow A.

  In the medium conveying apparatus 1301 of the comparative example, the recording sheet 101 fed from the sheet feeding unit 200 (FIG. 1) is conveyed by the medium conveying similarly to the operation in the medium conveying apparatus 301 (FIG. 2) according to this embodiment. When transported along the direction A to the paper sensor unit 372, the lever portion 332 is contacted and pushed up. In the sensor lever 329, the lever portion 332 is lifted by the paper leading edge 101a (FIG. 12), rotates in the direction of arrow B around the rotation shaft 331, and the shielding portion 333 moves downward. As a result, when the paper leading edge 101a reaches a specified position, the shielding portion 333 is rotationally moved to a position where the photosensor 330 is shielded, and the passage of the paper is detected.

  Thereafter, similarly to the medium conveying apparatus 301 according to the present embodiment, the recording paper 101 is further conveyed by a predetermined amount by the feed roller 203 and abuts against the nip portion of the conveying roller pair 1308 to correct the skew. Thereafter, after the feed roller 203 is temporarily stopped, the driving roller 328 is rotated by a driving source (not shown), and the recording paper 101 is nipped and conveyed by the conveying roller pair 1308.

  Next, operations of the sheet sensor unit 372 and the conveyance roller pair 1308 in the medium conveyance device 1301 will be described in detail with reference to the operation explanatory diagrams of FIGS.

  The operation explanatory diagrams of FIGS. 12 to 14 schematically show the process in which the skewed recording paper 101 passes through the medium conveying device 1301 in time series. In each figure, (a) is a view seen from the paper feed tray 100 (FIG. 1) side, and (b) is a view seen from the rotation axis direction of the pickup roller 202 (the front side of the drawing in FIG. 1). In each drawing (a), for the sake of simplicity, the driving roller 328 and the driven roller 310 are not shown, and only the nip portion 610 is indicated by a dotted line. The recording medium 101 that has passed through the paper sensor unit 372 is normally abutted against the nip portion 610 to correct skewing. However, in each of FIGS. Is shown in a state of passing through the nip portion 610 as it is.

  As described above, when the recording sheet 101 is fed out from the medium conveying apparatus 1301 toward the conveying roller pair 308 by the sheet feeding unit 200 (FIG. 1) on the upstream side in the medium conveying direction indicated by the arrow A, the recording sheet is eventually collected. The leading end 101 a of 101 reaches the paper sensor unit 372. FIG. 12 shows the state at this time, and it is assumed that the recording sheet 101 sent out as described above is inclined with respect to the medium conveying direction, that is, skewed by a predetermined amount.

  As described above, when the conveyed paper 101 is largely skewed, the paper sensor unit 372 and the recording paper 101 of the comparative example are in a state as shown in FIG. If the recording paper 101 continues to be conveyed as it is, a state as shown in FIG. At this time, the one end 101b of the paper leading edge 101a reaches a position where it abuts against the nip 610 of the pair of conveying rollers 308. Further, the central portion of the paper leading edge 101a contacts the lever portion 332 and pushes it up. The pushed sensor lever 329 rotates around the rotation shaft 331, the shielding part 333 is pushed down, and the shielding part 333 shields the photosensor 330 from light. As a result, the paper sensor unit 372 detects that the front end 101a (center portion) of the paper has reached a predetermined position of the paper sensor unit 372.

  12 to 14, “□” indicates the position of one end 101 b of the recording paper 101, and “●” indicates the position of the other end 101 c of the recording paper 101. Show.

As the sheet sensor unit 372 detects the leading edge 101a, the recording sheet 101 is further conveyed by a predetermined movement amount D1. This predetermined movement amount D1 is on the conveyance path from the position of the lever portion 332 on the sheet conveyance path (see FIG. 13B) to the nip 610 when the sheet sensor unit 372 detects light shielding and is turned on. Is a distance L1, and a distance on the conveyance path set as a predetermined abutting amount is R1, the predetermined movement amount D1 is the sum of these,
D1 = L1 + R1
Defined by

  The delay distance S2 shown in FIG. 13 is a nip portion 610 formed by the conveyance roller pair 1308 from the other end side corner portion 101e corresponding to the tail end of the paper leading end 101a when the paper sensor unit 372 detects the recording paper 101. Represents the distance to.

FIG. 14 shows a state immediately after the recording sheet 101 is further conveyed by a predetermined movement amount D1 from the state of FIG. As is clear from the figure, the delay distance S2 of the skewed sheet 101 is
S2> D1 = L1 + R1
In this case, as shown in FIG. 14, in addition to the distance L1, when the sheet 101 is conveyed by the butting distance R1 for the butting operation, the other end side corner 101e corresponding to the tail end of the sheet leading edge 101a is It is not transported to the position of the nip portion 610 formed by the transport roller pair 308. In this case, the sheet 101 is conveyed in the medium conveying direction A by starting the driving roller 328 while leaving a large skew.

  FIG. 15 shows a comparison of the range in which the skew of the recording paper can be corrected in the medium conveying apparatus 301 according to the present embodiment and the medium conveying apparatus 1301 in the comparative example. As shown in FIG. 6A, θ represents the amount of inclination of the recording paper when the recording paper 101 is skewed in the conveyance direction indicated by the arrow A. In the medium transport apparatus of the present embodiment and the comparative example, the abutting distance R1 is set to 4 mm, and the recording paper to be transported is an A4 size paper as an example.

  In the case of the medium conveying apparatus 1301 of the comparative example, as shown in FIG. 4B, the abutting distance R1 is 4 mm, so that one side has a skew of 4 [mm] = 105 sin θ [mm], that is, an inclination angle θ = Corrections can only be made up to a skew of about 2 °.

On the other hand, in the medium transport apparatus 301 of the present embodiment, as shown in FIG. 5C, for example, as described above, from the center surface 600 in the width direction of the recording paper for the purpose of detecting A4 size paper. Assuming that the distance L between the sheet contact portions 336 and 337 is 100 mm, the one-side skew amount capable of correcting the skew is
100 tan θ + 4 [mm] (2)
It becomes.

On the other hand, as shown in FIG. 4D, the detection unit (paper contact portions 336 and 337) is set at a position of L = 100 mm from the center surface 600 in the width direction of the recording paper. If the tip corner is inclined more than the inclination angle θm that is inclined until it reaches the position of 100 mm from the center plane 600 in the width direction, the recording sheet does not contact the detection unit. Therefore, the maximum inclination angle θm of the paper that can be corrected is
105 cos θm = 100
Is satisfied, that is, θm = 18 °.

At this time, from the above equation (2),
100 tan (18 °) + 4≈36
Therefore, even when the skew amount is set to about 36 mm at the maximum, the correction can be made.

  As described above, according to the medium transport apparatus of the present embodiment, even when the skew amount of the medium to be transported is greatly different for each medium, the skew is always performed by performing the minimum necessary abutment. Can be corrected. Therefore, it is possible to prevent inconveniences such as the case where the medium cannot be corrected completely when the medium is skewed greatly, or the medium is damaged by performing an abutment more than necessary when the skew is small. In addition, since the minimum butting is sufficient, it is possible to reduce the running noise caused by the deflection of the paper that occurs during the operation of hitting the paper.

Embodiment 2. FIG.
FIG. 16 is a perspective view showing a main configuration of a medium transport apparatus 701 according to the second embodiment of the present invention. FIG. 17 is a view of the medium transport apparatus 701 as viewed from the paper feed tray 100 (FIG. 1). FIG. 18 is a main part configuration diagram of the medium conveying device 701 as viewed from the rotation axis direction of the photosensitive drum 431 (the front side of the drawing in FIG. 1).

  The main difference between the medium conveying apparatus 701 and the medium conveying apparatus 301 of the first embodiment shown in FIG. 2 is the configuration of the paper sensor unit 702. Accordingly, in this medium transport apparatus 701, parts common to the medium transport apparatus 301 (FIG. 2) of the first embodiment described above are denoted by the same reference numerals, or the description thereof is omitted here by omitting the drawings. Focus on the differences. Note that an image forming apparatus that employs the medium conveying apparatus 701 is exactly the same as the image forming apparatus 1000 (except for the medium conveying apparatus 301) described in the first embodiment except for the medium conveying apparatus 701. Will be omitted, and FIG. 1 will be referred to if necessary.

  A sheet sensor unit 702 as a medium detecting unit is arranged in parallel substantially perpendicular to the medium conveyance direction indicated by an arrow A in the drawing, and detection levers 740 as two displacement members that come into contact with the conveyed sheet. 741 and a photo sensor 742 as a detecting means attached to the image forming apparatus main body for detecting that the detection levers 740 and 741 are rotated to a predetermined rotation position as will be described later. Here, the photosensor 742 is composed of, for example, a reflective photosensor, and a light emitting element and a light receiving element are incorporated in one case. In this reflection type photosensor, as described later, the detection target is on a predetermined optical path, the light irradiated from the light emitting element is reflected by the detection target, and the light receiving element receives the reflected light; The output signal is changed to detect the passage of the detected object when the detected object is not on the predetermined optical path and the light receiving element cannot receive the light emitted from the light emitting element.

  As shown in FIG. 17, the feed roller 203 and the retard roller 204 are parallel to the direction in which the respective rotation axes are substantially orthogonal to the medium conveyance direction indicated by the arrow A (the rotation axis direction of the photosensitive drum 431 (FIG. 1)). As shown in FIG. 18, the recording paper 101 is disposed at a position where the recording paper 101 can be conveyed toward the conveyance roller pair 308 downstream in the medium conveyance direction.

  FIG. 19A is an external perspective view of the detection lever 740, and FIG. 19B is an external perspective view of the detection lever 741. As shown in FIGS. 4A and 4B, the detection levers 740 and 741 are rotational axes that are rotatably held by the main body of the image forming apparatus 1000 at predetermined positions, which will be described later, parallel to the rotational axis of the feed roller 203. 745, 746, paper contact portions 743, 744 for contacting the paper leading edge 101a, and reflecting portions 747, 748 for reflecting the light emitted from the photosensor 742. The reflecting portions 747 and 748 are located on the opposite sides of the paper contact portions 743 and 744 with respect to the axes of the rotation shafts 745 and 746, respectively, and are emitted from the light emitting element 742a of the photosensor 742 as shown in FIG. The optical path opening portions 749 and 750 are provided at positions where the light is reflected toward the light receiving element 742b, and further pass through when the light reaches a predetermined position by rotating around the rotation shafts 745 and 746. .

As shown in FIG. 17, the detection levers 740 and 741 are disposed substantially symmetrically with respect to the center plane 600 in the width direction of the recording paper 101 so that the reflection portions 747 and 748 overlap each other. The positions in the width direction where the arm portions 753 and 754 of the detection levers 740 and 741 are disposed are the positions where the sheet contact portions 743 and 744 are separated from the sheet width direction center plane 600 by a distance L, respectively. In the image forming apparatus 1000 including the medium conveying apparatus 701, the sheet contact portions 743 and 744 are set according to the distance L of the recording sheet 101 that is set so as to be able to be conveyed. And
W> 2L
Meet.
That is, the detection levers 740 and 741 are such that the respective paper contact portions 743 and 744 are at appropriate positions close to both ends of the paper front end 101a satisfying the above formula, and are on the conveyance path that can contact the paper front end 101a. Placed in.

  As shown in FIGS. 17 and 18, the photosensor 742 has a pair of light emitting elements 742a and light receiving elements 742b on a substantially central surface 600 in the width direction, and detection levers 740 and 741 are arranged at the leading edge of the paper as will be described later. The optical path opening portions 749 and 750 face each other and light is reflected by the reflection portions 747 and 748 when both of them reach the predetermined rotation position in contact with 101a and rotate in the direction of arrow B (FIG. 18). The optical path of the photosensor 742 is opened, and the output state is disposed at a position where the output state is switched from the off state to the on state.

  In the present embodiment, the above-described reflective type is used as the photosensor 742. However, the sending element and the light receiving element are arranged at positions facing each other via the reflecting portions 747 and 748 of the detection levers 740 and 741. The light receiving element may receive light that goes straight without being shielded. In this case, the light output from the light emitting element passes through the optical path opening portions 749 and 750 and is received by the light receiving element, thereby changing the output signal and detecting the passage of the detected object.

  FIG. 20 is a block diagram showing the main configuration of a control system that controls the operation of the medium transport apparatus 701 related to the present invention. This control system differs from the control system of the medium transport apparatus 301 in the first embodiment described with reference to FIG. 5 only in the configuration of the paper sensor unit 702 (the paper sensor unit 302 in FIG. 5). It is. Therefore, the main control unit 321 performs the same control as the control system of the medium transport apparatus 301 in the first embodiment described above with reference to FIG. 5 based on the output of the photosensor 742. The overlapping description here regarding the configuration is omitted.

  Next, the operations of the paper sensor unit 702 and the conveyance roller pair 308 of the medium conveyance device 701 will be described in detail with reference to the operation explanatory diagrams of FIGS.

  The operation explanatory diagrams of FIGS. 21 to 24 schematically show the process in which the skewed recording sheet 101 passes through the medium conveying device 701 in time series. In each figure, (a) is a view of the medium conveying device 701 as viewed from the direction of the rotation axis of the pickup roller 202 (the front side of the paper surface in FIG. 1), and (b) is an arrow D in FIG. It is the figure seen from the direction. Note that the direction of arrow D is substantially perpendicular to the front surface of the photosensor 742 (the surface facing the reflection portions 747 and 848 of the detection lever and to which the light emitting element 742a and the light receiving element 742b belong).

  In each drawing (b), for simplicity, the driving roller 309 and the driven roller 310 are not shown, and only the nip portion 610 is indicated by a dotted line as necessary. The recording medium 101 that has passed through the paper sensor unit 302 is normally abutted against the nip portion 610 of the conveying roller pair 308 whose rotation is stopped, and corrects the skew. In each of FIGS. In order to avoid complications, the nip portion 610 is shown as it is for the sake of convenience.

  As described above, when the recording sheet 101 is sent out from the medium conveying apparatus 701 toward the conveying roller pair 308 by the sheet feeding unit 200 (FIG. 1) on the upstream side in the medium conveying direction indicated by the arrow A, the recording sheet is eventually collected. The leading end 101a of 101 reaches the paper sensor unit 702. FIG. 21 shows the state at this time, and it is assumed that the recording sheet 101 sent out as described above is inclined with respect to the medium conveyance direction, that is, skewed by a predetermined amount.

  As shown in FIG. 21, at this time, for example, in the case of a skew that is sent out with the one end 101b of the leading end 101a positioned forward in the medium conveying direction with respect to the other end 101c, the skew is first transported. One end 101 b of the recording sheet 101 that comes in contact with the sheet contact portion 744 of the detection lever 741. Thereafter, when the recording paper 101 further moves, as shown in FIG. 22, the paper contact portion 744 is pushed by the one end 101 b of the recording paper 101, whereby the detection lever 741 is moved to the arrow about the rotation shaft 746. It rotates in the B direction (FIG. 22 (a)).

  21A to 24, “□” indicates the position on the conveyance path of the one end portion 101 b of the recording paper 101, and “●” indicates the other end portion 101 c of the recording paper 101. The position on the conveyance path is shown. Here, the one end 101b refers to a portion of the leading end 101a of the recording paper 101 that contacts the paper contact portion 744 of the detection lever 741, and the other end 101c refers to the leading end of the recording paper 101. 101a is a portion that contacts the paper contact portion 743 of the detection lever 740. The rotation position before the detection levers 740 and 741 contact the paper and rotate in the arrow B direction is hereinafter referred to as a reference position, and the rotation position after the predetermined amount of rotation in the arrow B direction is hereinafter referred to as a detection position.

  Thereafter, when the recording paper 101 is further conveyed, as shown in FIG. 23, the one end 101b and the other end 101c of the paper leading edge 101a move forward in the conveying direction from the state of FIG. The central portion of the tip 101a reaches the nip portion 610 formed by the conveying roller pair 308. At this time, the rotation of the detection lever 741 in the direction of the arrow B has been completed and has reached the detection position, and the optical path opening portion 750 of the detection lever 741 has reached a position where the optical path of the photosensor 742 is opened. On the other hand, the other end 101c of the paper leading edge 101a is conveyed to a position where it contacts the paper contact portion 743 of the detection lever 740, and the detection lever 740 also starts to rotate in the direction of arrow B from the reference position.

  However, since the detection lever 340 has not reached the detection position at this time, the path opening part 749 provided in the reflection part 747 does not reach the position where the optical path of the photosensor 742 is opened. Accordingly, the light emitted from the light emitting element 742a (FIG. 18) of the photosensor 742 is reflected by the reflecting portion 747 serving as a detection body and detected by the light receiving element 742b, so that the output signal is kept off. For this reason, the conveyance roller pair 308 is not driven yet and remains stopped.

  Thereafter, when the recording paper 101 continues to be further conveyed, as shown in FIG. 24, the one end 101b and the other end 101c of the paper leading edge 101a move forward in the conveying direction from the state of FIG. One end 101b of 101a is in a state of being abutted against a nip portion 610 formed by the conveying roller pair 308 (at this time, the conveying roller pair 308 has not yet rotated). On the other hand, the other end 101c of the paper leading edge 101a further pushes up the paper contact portion 743 of the detection lever 740 and rotates the detection lever 740 to the detection position. FIG. 24 shows a state after the detection lever 740 has rotated to the detection position.

  By this rotation, the optical path opening part 749 of the detection lever 740 and the optical path opening part 350 of the detection lever 741 reach the position where the optical path of the photosensor 742 is simultaneously opened, and the light emitted from the light emitting element 742a is not reflected. Accordingly, the light emitted from the light emitting element 742a of the photosensor 742 is not reflected by the reflecting portions 747 and 748 and is not received by the light receiving element 742b, so that the signal output from the photosensor 742 changes to the on state. Accordingly, the main control unit 321 determines that the paper leading edge 101a has reached a predetermined position in the medium detection unit 702.

  Since the operation after the recording paper 101 is detected by the paper sensor unit 702 is the same as that in the first embodiment, the description thereof is omitted here.

  Next, the overall operation of the medium transport apparatus 701 of this embodiment will be further described based on the flowchart of FIG.

  The process of the flowchart shown in the figure is exactly the same as the process of the flowchart shown in FIG. 10 in the first embodiment except for the processes of steps S3 ′ and S8 ′ related to the operation of the paper sensor unit 702. It is. In step S3 ′, the paper sensor unit 702 watches the passage of the paper leading edge 101a of the paper 101 conveyed by the feed roller 203 and the retard roller 204, and the passage of the output is output from the photosensor 742 by the above-described mechanism. In step S8 ′, the sheet sensor unit 702 turns off the sheet sensor unit 702 again after the conveyance roller pair 311 starts conveying the recording sheet 101, so that the trailing edge of the sheet is detected. It is detected that the paper has passed through the paper detection area. Other operation steps are exactly the same as the process of the flowchart shown in FIG. 10 described in the first embodiment, and a description thereof is omitted here.

  Note that the skew correction capability of the medium transport apparatus 701 according to the present embodiment is such that the position where the paper contact portions 743 and 744 of the detection levers 740 and 741 are disposed is the arm of the medium transport apparatus 301 according to the first embodiment. When the arrangement positions of the paper contact portions 336 and 337 of the members 304 and 305 are the same, the skew correction capability of the medium conveyance device 301 described in the first embodiment is equivalent.

  As described above, according to the medium transport apparatus of the second embodiment, even when the skew feeding amount of the transported medium is greatly different for each medium, as in the case of the first embodiment described above. It is always possible to correct skew by performing the minimum necessary butting. Therefore, it is possible to prevent inconveniences such as the case where the medium cannot be corrected completely when the medium is skewed greatly, or the medium is damaged by performing an abutment more than necessary when the skew is small. In addition, since the minimum butting is sufficient, it is possible to reduce the running noise caused by the deflection of the paper that occurs during the operation of hitting the paper.

  Furthermore, since the medium conveying device 701 in the present embodiment is simple and has a smaller number of parts constituting the medium detecting unit than the medium conveying device 301 in the first embodiment, Cost reduction can be expected by reducing the number of manufacturing processes and simplifying parts management.

  In each of the above-described embodiments, the lever member is used. However, the present invention is not limited to this, and the same effect can be obtained even when the shape of the actuator is different.

  In the second embodiment, an example using a reflection type photosensor has been described. However, the present invention is not limited to this. For example, a photo interrupter, a regression reflection type photosensor, an actuator type photosensor, or the like is used instead. It is also possible.

  In each of the above-described embodiments, an example in which the paper sensor and the transport roller are arranged immediately after the paper feed roller has been described. However, the present invention is not limited to this. For example, two sets of paper sensors that are not paper feed rollers are used. The medium conveyance device to be combined and the place of use can take various forms, such as being arranged in the middle of the pair of conveyance rollers.

  In each of the above-described embodiments, the A4 size is taken as an example of the minimum sheet width W, and as an example of disposing the sheet sensor, the distance L from the center in the sheet width direction of the sheet contact portion is L = 100 mm. However, the present invention is not limited to this, and the paper size and the distance L are appropriately set.

  In this embodiment, an example is shown in which the medium conveyance device is applied to an image forming apparatus of a type that directly transfers a toner image onto a print medium using four process units. However, the present invention is not limited to this. In addition, a device that performs image processing on a conveyed medium, such as a color image forming device using an intermediate transfer belt, a single color image forming device using one process unit, a copying machine using them, an automatic document reading device, etc. It can be implemented.

  Furthermore, in the present embodiment, the example in which the recording paper is abutted for the skew correction by the conveyance roller while the rotation is stopped has been described, but the present invention is not limited to this, and a recording plate such as an abutting plate is used. Various aspects can be taken, such as using a different one.

1 is a main part configuration diagram of a main part configuration of an image forming apparatus according to a first embodiment of the present invention as viewed from the front; It is a perspective view which shows the principal part structure of the medium conveying apparatus of Embodiment 1 by this invention. FIG. 3 is a main part configuration diagram of the medium conveying apparatus according to the first embodiment as viewed from a sheet feeding tray side. FIG. 2 is a main part configuration diagram of the medium conveyance device according to the first embodiment when viewed from the rotation axis direction of the photosensitive drum (the front surface side of FIG. 1). FIG. 3 is a block diagram illustrating a configuration of a main part of a control system that controls operations related to the present invention of the medium conveyance device according to the first embodiment. FIG. 6 is an operation explanatory diagram for explaining operations of a paper sensor unit and a conveyance roller pair in the medium conveyance device according to the first embodiment. FIG. 6 is an operation explanatory diagram for explaining operations of a paper sensor unit and a conveyance roller pair in the medium conveyance device according to the first embodiment. FIG. 6 is an operation explanatory diagram for explaining operations of a paper sensor unit and a conveyance roller pair in the medium conveyance device according to the first embodiment. FIG. 6 is an operation explanatory diagram for explaining operations of a paper sensor unit and a conveyance roller pair in the medium conveyance device according to the first embodiment. 3 is a flowchart showing the flow of the overall operation of the medium carrying device according to the first embodiment. It is a perspective view which shows the principal part structure of the medium conveying apparatus mention | raise | lifted as a comparative example of this invention. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair of a medium conveyance device of a comparative example. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair of a medium conveyance device of a comparative example. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair of a medium conveyance device of a comparative example. 2A and 2B are diagrams for explaining a skew correction capability in the medium conveying apparatus according to the first embodiment and a medium conveying apparatus of a comparative example, and FIG. FIG. 4 is a diagram for explaining the correction capability of the comparative example, and FIGS. 4C and 4D are diagrams for explaining the correction capability of the medium conveying apparatus of the first embodiment. It is a perspective view which shows the principal part structure of the medium conveying apparatus of Embodiment 2 by this invention. FIG. 5 is a main part configuration diagram of a medium transport device according to a second embodiment as viewed from a sheet feeding tray side. FIG. 6 is a configuration diagram of a main part of a medium transport device according to a second embodiment as viewed from the rotation axis direction of the photosensitive drum (the front side in FIG. 1). (A) is an external appearance perspective view of one detection lever, (b) is an external perspective view of the other detection lever. FIG. 10 is a block diagram illustrating a configuration of a main part of a control system that controls operations related to the present invention of the medium transport device according to the second embodiment. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair in the medium conveyance device of the second embodiment. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair in the medium conveyance device of the second embodiment. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair in the medium conveyance device of the second embodiment. FIG. 10 is an operation explanatory diagram for explaining operations of a sheet sensor unit and a conveyance roller pair in the medium conveyance device of the second embodiment. 6 is a flowchart illustrating an overall operation flow of the medium carrying device according to the second embodiment.

Explanation of symbols

  100 paper feed tray, 101 recording paper, 101a paper front end, 101b one end side end, 101c other end side end, 101e other end side corner, 102 paper placing plate, 102a support shaft, 103 lift up lever, 103a support Shaft, 104 motor, 200 paper feeding unit, 201 rise detection unit, 202 pickup roller, 203 feed roller, 204 retard roller, 205 paper presence / absence detection unit, 206 paper remaining amount detection unit, 300 paper conveyance unit, 301 medium conveyance device, 302 Paper sensor unit, 303, 304 Arm member, 305 Lever member, 305a One end side end, 305b Other end side end, 306 Switch, 306a Switch lever, 307 Lever support shaft, 308 Conveying roller pair, 309 Driving roller, 310 driven roller, 311 transport roller pair, 315 writing sensor, 316 shaft, 317 friction material, 318, 319 rotating shaft, 320 control unit, 321 main control unit, 322 paper feed motor control unit, 323 transport motor control unit , 324 Clutch control unit, 325 Paper feed motor, 326 Conveyance motor, 327 Clutch, 328 Drive roller, 329 Sensor lever, 330 Photo sensor, 331 Rotating shaft, 332 Lever unit, 333 Shielding unit, 334 Shaft, 335 Friction material, 336 , 337 Paper contact part, 338, 339 Lever pressing part, 340 slot, 341 hanging part, 351 spring, 372 Paper sensor unit, 400 image forming part, 430 process unit, 431 photoconductor Ram, 432 charging roller, 433 LED head, 434 developing roller, 435 cleaning blade, 436 toner supply unit, 460 transfer unit, 461 transfer belt, 462 drive roller, 463 tension roller, 464 transfer roller, 465 cleaning blade, 466 toner box , 500 fixing unit, 501 upper roller, 502 lower roller, 503a, 503b halogen lamp, 504a, 504b, 504c discharge roller pair, 505 stacker portion, 600 width direction center plane, 610 nip portion, 620 detection position, 701 medium transport device, 702 Paper sensor unit, 740 detection lever, 741 detection lever, 742 photo sensor, 742a light emitting element, 742b light reception Element, 743 Paper contact part, 744 Paper contact part, 745 Rotating shaft, 746 Rotating shaft, 747 Reflecting part, 748 Reflecting part, 749 Optical path opening part, 750 Optical path opening part, 753 Arm part, 754 Arm part, 1000 Image forming apparatus 1301 Medium conveying device, 1308 A pair of conveying rollers.

Claims (10)

A medium transport apparatus having a function of correcting skew of a medium,
An abutting means that extends in a direction substantially perpendicular to the conveyance direction of the medium, and abutting the leading end of the medium to be conveyed;
Medium conveying means for conveying the medium toward the abutting means;
A medium detecting means disposed between the abutting means and the medium transporting means for detecting passage of both ends in the width direction of the transported medium;
Control means for correcting a skew by abutting the medium against the abutting means after the medium detecting means detects passage of the both ends and detecting the passage of the medium by the medium conveying means. A medium conveying apparatus characterized by the above. The medium detection means includes
A plurality of displacement members each having a contact portion that is movable in the transport direction by contact with the medium being transported;
The medium according to claim 1, further comprising: a single detection unit configured to detect that all the contact portions of the displacement member have been moved in the transport direction by a predetermined amount due to contact with the medium. Conveying device. The detection means includes
A light emitting unit that emits light toward the displacement member;
A light receiving portion for receiving the light emitted by the displacement member,
The displacement member is disposed so as to be displaced on the optical path of the emitted light, and all the contact portions of the displacement member are moved in the transport direction by a predetermined amount based on a change in the light receiving level of the light in the light receiving portion. The medium conveying device according to claim 2, wherein the medium conveying device is detected.   The medium transporting apparatus according to claim 3, wherein the light receiving unit receives light emitted by the light emitting unit and reflected by the displacement member.   4. The medium conveying apparatus according to claim 3, wherein the light receiving unit receives light emitted by the light emitting unit and traveling straight without being blocked by the displacement member.   The plurality of displacement members each include an opening through which light can pass, and when all the contact portions of the displacement member are moved in the transport direction by a predetermined amount, all the openings overlap, 6. The medium conveying apparatus according to claim 4, wherein the light emitted from the light emitting section is allowed to pass.   A swingable arrangement is provided between the displacement member and the detection means, and the distance from the detection means as all the contact portions of the displacement member are moved in the transport direction by a predetermined amount. The medium conveying apparatus according to claim 2, further comprising a lever member that changes by more than a predetermined amount and changes the output of the detection unit from the first state to the second state. The abutting means is
A driving roller;
The medium conveyance device according to claim 1, wherein the medium conveyance device is a pair of conveyance rollers configured to be a driven roller that is in contact with the driving roller. The controller is
9. The medium conveyance according to claim 8, wherein after the medium is brought into contact with the pair of conveyance rollers in the stopped state and the skew feeding is corrected, the medium is conveyed in the conveyance direction by driving the conveyance roller pair. apparatus. A medium carrying device according to any one of claims 1 to 9;
An image forming apparatus comprising: an image forming unit that forms an image on the conveyed medium.

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