JP2010228901A - Medium conveying apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a medium conveying device capable of correcting the skew of a printing medium conveyed in a conveyance passage and an image forming device having the medium conveying device. <P>SOLUTION: The medium conveying device includes the conveyance passage for conveying the medium, a detecting means (a line sensor 203) for detecting the skew amount of the medium, a conveyance means (a drive roller 201 and an idle roller 202) positioned opposing the conveyance passage and movable in the direction vertical to the conveyance passage for conveying the medium, a control means for calculating the position of the conveyance means on the detected result of the detecting means, and a driving means (a cam gear 212) for moving the conveyance means through instructions from the control means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a medium conveying apparatus including a medium skew feeding correction mechanism that corrects skew (oblique feeding) of a printing medium conveyed on a conveying path, and an image forming apparatus having the medium conveying apparatus.

  2. Description of the Related Art Conventionally, as a medium transport apparatus including a medium skew correction mechanism included in an image forming apparatus such as an electrophotographic printer, for example, as disclosed in Patent Document 1, a print medium stacked on a medium stacking unit is supplied by a pickup roller. The print medium separated by the feed roller and the retard roller is conveyed by the feed roller, and the print medium is arranged to face the stopped registration roller and the registration roller. The print media skew is corrected by making the print media bend by abutting against the abutting part (nip) of the installed pinch roller and by making the tip of the print media parallel to the registration rollers. A paper feeding device has been proposed.

Japanese Patent Laid-Open No. 2003-201045

  However, in the paper feeding device, if the cutting accuracy of the printing medium is low and the leading end portion of the printing medium is cut obliquely, or if the assembling accuracy of the registration roller is low, the printing medium There is a problem that the skew of the print medium cannot be corrected only by making the front end parallel to the registration roller.

  In view of the above problems, an object of the present invention is to provide a medium transport apparatus capable of correcting a skew of a print medium transported along a transport path and an image forming apparatus having the medium transport apparatus.

The present invention adopts the following configuration in order to solve the above points.
<Configuration 1>
The medium transport apparatus of the present invention includes a transport path for transporting a medium, detection means for detecting a skew amount of the medium, and a medium provided at a position facing the transport path and movable in a direction perpendicular to the transport path. It is characterized by comprising conveying means for conveying, control means for calculating the position of the conveying means based on the detection result of the detecting means, and driving means for moving the conveying means in accordance with instructions from the control means.

<Configuration 2>
An image forming apparatus according to the present invention includes the medium conveying device described in Configuration 1.

  According to the present invention, the detecting means for detecting the skew amount of the medium conveyed on the conveying path, and the conveying means for conveying the medium provided at a position facing the conveying path and movable in the direction perpendicular to the conveying path. And a control unit that calculates the position of the transport unit based on the detection result of the detection unit and a drive unit that moves the transport unit in accordance with an instruction from the control unit, so that the skew of the medium transported on the transport path is corrected. Can do.

1 is a perspective view of a medium skew correction mechanism according to a first embodiment of the invention. It is a figure which shows the arrangement | positioning position of the medium skew feeding correction mechanism of Example 1 which concerns on this invention. It is a front view of the medium skew feeding correction mechanism according to the first embodiment of the present invention. It is a figure which shows the structure which can adjust the load with respect to the drive roller of the idle roller in the medium skew feeding correction mechanism of Example 1 which concerns on this invention. FIG. 3 is an exploded view (part 1) of the medium skew correction mechanism according to the first embodiment of the invention. FIG. 6 is an exploded view (part 2) of the medium skew feeding correcting mechanism according to the first embodiment of the present invention. It is a top view of the medium skew feeding correction mechanism according to the first embodiment of the present invention. It is a figure which shows the image of the inclination of the idle roller with respect to the drive roller of Example 1 which concerns on this invention, and the press balance between both rollers. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus according to the first exemplary embodiment of the present invention. 6 is a flowchart illustrating an operation in a medium skew correction mechanism of the image forming apparatus according to the first exemplary embodiment of the present invention. It is a figure which shows the arrangement | positioning position of the medium skew feeding correction mechanism of Example 2 which concerns on this invention. It is a figure which shows the structure of the image forming apparatus of Example 2 which concerns on this invention. It is a block diagram which shows the control structure of the image forming apparatus of Example 2 which concerns on this invention. 6 is a flowchart (part 1) illustrating an operation of the medium skew correction mechanism of the image forming apparatus according to the second exemplary embodiment of the present invention. 7 is a flowchart (part 2) illustrating the operation of the medium skew correction mechanism of the image forming apparatus according to the second exemplary embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Configuration of Example 1>
FIG. 9 is a diagram illustrating a configuration of the image forming apparatus 100 according to the first embodiment of the present invention.
As shown in FIG. 9, the image forming apparatus 100 includes a paper cassette 11 for stacking and holding the print medium 1, a paper feed roller 12, a separation frame 13, a registration roller pair 14, and a medium that is a medium conveyance device. The skew correction mechanism 200 includes image forming units 15K, 15Y, 15M, and 15C, a transfer belt unit 16, an image fixing unit 17, a discharge roller 18, and a driven roller 19. In this embodiment, the case where the image forming apparatus 100 is a printer will be described as an example. However, the present invention is not limited thereto, and an MFP (Multi Function Peripheral) having a printer function may be used.

  The entire image forming apparatus 100 is controlled by the apparatus control unit 101. The device control unit 101 is connected to a host device (not shown) such as a PC (Personal Computer) via the I / F unit 102 via a network. The apparatus control unit 101 includes a microcomputer and the like, and a voltage is applied to each unit by a power supply unit 108 (to be described later), print control is performed based on information from each sensor, and the like.

  The image forming unit 15K is a mechanism for forming a black (K) developer image that is black, and is supplied from a toner storage unit 151 that contains toner that is a black developer, as shown in FIG. A developer image is formed on the photosensitive drum 152 using the black toner.

  The image forming unit 15Y is a mechanism for forming a yellow (Y) developer image. The toner storage unit accommodates yellow toner and forms a yellow developer image on the photosensitive drum. Except for the above, the configuration of the image forming unit 15K is the same.

  The image forming unit 15M is a mechanism for forming a magenta (M) developer image. The toner storage unit stores magenta toner and forms a magenta developer image on the photosensitive drum. Except for the above, the configuration of the image forming unit 15K is the same.

  The image forming unit 15C is a mechanism for forming a cyan (C) developer image. The toner storage unit accommodates cyan toner and forms a cyan developer image on the photosensitive drum. Except for the above, the configuration of the image forming unit 15K is the same.

  The transfer belt unit 16 is a mechanism for transferring the developer images of the respective colors formed on the photosensitive drums of the image forming units 15K, 15Y, 15M, and 15C onto the print medium 1, as shown in FIG. Further, the transfer belt 161, the belt driving roller 162, the driven roller 163, and the transfer belts arranged to face the photosensitive drums of the image forming units 15 K, 15 Y, 15 M, and 15 C via the transfer belt 161. It comprises rollers 164K, 164Y, 164M, 164C. The transfer belt 161 is wound around a belt driving roller 162 and a driven roller 163 and travels by driving the belt driving roller 162 to convey the print medium 1 adsorbed by static electricity.

  The image fixing unit 17 is a mechanism for fixing the developer image transferred onto the printing medium 1 to the printing medium 1, and is in contact with the heating roller 171 and the heating roller 171 as shown in FIG. The pressure roller 172 is provided. Here, the heating roller 171 has a heater (not shown) for heating the heating roller 171 in the roller.

FIG. 10 is a block diagram showing a control configuration of the image forming apparatus 100 according to the first embodiment of the present invention.
As shown in FIG. 10, the image forming apparatus 100 includes a device control unit 101 that controls the entire device, an I / F (Inter Face) unit 102, a temporary configuration, and the like. A storage unit 103, a reading unit 104, an image memory 105, a motor control unit 106, a high voltage control unit 107, and a power supply unit 108 are provided.

  As shown in FIG. 10, the motor control unit 106 has a fixing motor 109 for rotating the heating roller 171 and a sheet feeding for rotating the sheet feeding roller 12 based on a program preset in a memory (not shown). A motor 110, a registration motor 111 for rotating the registration roller pair 14, a belt driving motor 112 for rotating the belt driving roller 162 for running the transfer belt 161, and a drum for rotating the photosensitive drum 152 The motor 113 is controlled.

  As shown in FIG. 10, the high-pressure control unit 107 is based on each transfer roller 164 (164K, 164Y, 164M, 164C) and the power supply unit 108 to the heating roller 171 based on a program preset in a memory (not shown). The voltage application is controlled.

  The overall control configuration of the image forming apparatus 100 according to the first embodiment of the present invention will be described below.

  The device control unit 101 receives print data from a host device (not shown) via the I / F unit 102. Here, the I / F unit 102 is a serial interface such as USB (Universal Serial Bus) or a parallel interface such as IEEE1284, and is connected to a host device using a predetermined protocol of each interface.

  The apparatus control unit 101 converts print data received from the host apparatus into image data, and stores the image data in the image memory 105.

  After storing the image data, the apparatus control unit 101 instructs the motor control unit 106 to drive the paper feed motor 110, the belt drive motor 112, and the drum motor 113.

  Upon receiving an instruction to drive the paper feed motor 110, the motor control unit 106 applies the voltage of the power supply unit 108 to the paper feed motor 110 to drive the paper feed motor 110.

  The paper feed roller 12 is rotated by driving the paper feed motor 110. Here, the motor control unit 106 controls and drives the paper feed motor 110 so that the rotational speed of the paper feed roller 12 becomes a specified rotational speed preset in a memory (not shown).

  When the sheet feeding roller 12 starts rotating, the sheet feeding roller 12 feeds the uppermost printing medium 1 held by the sheet cassette 11 and conveys the printing medium 1. Here, the print medium 1 held by the paper cassette 11 of the present embodiment is plain paper such as A4 size, but is not limited thereto, and may be long paper.

  The separation frame 13 is used to separate and stop the print medium 1 positioned below the second sheet conveyed by the paper feed roller 12 from the first print medium 1. Accordingly, only one print medium 1 that has passed through the separation frame 13 is conveyed. For separating the print medium 1, a retard roller may be used instead of the separation frame 13.

  The print medium 1 that has passed through the separation frame 13 is conveyed to the registration roller pair 14.

  The entrance sensor 20 of the image forming apparatus 100 shown in FIG. 9 has a registration roller pair so that the leading edge of the printing medium 1 conveyed from the paper supply roller 12 is in contact with the nip between both rollers of the registration roller pair 14. 14 is a sensor used to stop the printer 14, and when the leading edge of the print medium 1 is detected, an entrance detection signal is generated and transmitted to the apparatus control unit 101.

  Upon receiving the inlet sensor signal, the apparatus control unit 101 instructs the motor control unit 106 to temporarily stop the registration motor 111.

  Upon receiving a temporary stop instruction, the motor control unit 106 stops applying the voltage of the power supply unit 108 to the drive motor, and stops driving the drive motor. Accordingly, the print medium 1 stops in a state where the leading end hits the nip of the registration roller pair 14 under the control of the apparatus control unit 101. The bending of the printing medium 1 is formed, and the ridge line at the front end in the conveyance direction of the printing medium 1 abuts against the entire nip portion of the registration roller pair 14 by the restoring force of the printing medium 1 and becomes parallel. By driving, even when the printing medium 1 is skewed, this skewing is corrected.

  When the drive of the drive motor is stopped for a predetermined time set in a memory (not shown) in the motor control unit 106, the apparatus control unit 101 instructs the motor control unit 106 to re-drive the drive motor and performs motor control. The unit 106 is instructed to drive the registration motor 111.

  Upon receiving an instruction to drive the registration motor 111, the motor control unit 106 applies the voltage of the power supply unit 108 to the registration motor 111 to drive the registration motor 111.

  Since the paper feed roller 12 has a one-way gear, when the printing medium 1 is conveyed by the registration roller pair 14, it is rotated by the conveyed printing medium 1.

  On the other hand, the registration roller pair 14 is rotated by the driving of the registration motor 111. Here, the motor control unit 106 controls and drives the registration motor 111 so that the rotation speed of the registration roller pair 14 becomes a specified rotation speed preset in a memory (not shown).

  Thus, the printing medium 1 that has been stopped is conveyed toward the medium skew correction mechanism 200 by the registration roller pair 14.

  The medium skew correction mechanism 200 corrects a skew generated in the process of transporting the print medium 1, particularly the print medium 1, transported from the registration roller pair 14 according to a control configuration described later. Transport in the direction.

  On the other hand, upon receiving an instruction to drive the belt drive motor 112 and the drum motor 113, the motor control unit 106 applies the voltage of the power supply unit 108 to the belt drive motor 112 and the drum motor 113, and the belt drive motor 112 and the drum motor 113 The motor 113 is driven.

  When the belt driving roller 162 is rotated by driving the belt driving motor 112, the transfer belt 161 starts running. Here, the motor control unit 106 controls the belt driving motor 112 to rotate the belt driving roller 162 so that the traveling speed of the transfer belt 161 becomes a predetermined traveling speed preset in a memory (not shown).

  On the other hand, when the photosensitive drum 152 is rotated by driving the drum motor 113, the surface of the photosensitive drum 152 is charged by a charging roller (not shown).

  When the writing sensor 21 of the image forming apparatus 100 detects the leading edge of the print medium 1 conveyed from the medium skew correction mechanism 200, the apparatus control unit 101 instructs an exposure unit (not shown) of the image forming apparatus 100 to perform exposure. The write-out sensor has a start position of each color developer image on each photosensitive drum in order to form each color developer formed on each photosensitive drum of each image forming unit 15K to 15C on the print medium 1. , And used to match the writing start position of each color developer image on the printing medium 1.

  The exposure unit is composed of, for example, arranged LEDs (Light Emitting Diodes), and emits light based on the instruction of the exposure, and for each color based on the image data stored in the image memory 105 on the surface of the photosensitive drum 152 to be charged. In addition, an electrostatic latent image is formed on each color photosensitive drum.

  When an electrostatic latent image is formed on the surface of the photosensitive drum 152, the black toner supplied from the toner storage unit 151 is controlled on the surface of the developing roller via a supply roller (not shown) under the control of the device control unit 101. After that, the film is formed to have a uniform thickness by a layer forming blade (not shown) and developed into the electrostatic latent image on the photosensitive drum 152. As a result, a black developer image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 152.

  Similarly, yellow, magenta, and cyan developer images corresponding to the electrostatic latent image are formed on the surface of each photosensitive drum of each image forming unit by image forming processing in the image forming units 15Y, 15M, and 15C. It is formed.

  On the other hand, when the belt driving roller 162 rotates, the transfer belt 161 made of, for example, an endless belt wound around the belt driving roller 162 and the driven roller 163 travels in the y direction as shown in FIG. The print medium 1 is electrostatically attracted to the transfer belt 161 and conveyed. As a result, the developer image formed on the surface of the photosensitive drum 152 is transferred onto the print medium 1 by the transfer roller 164K to which a high voltage is applied from the power supply unit 108 via the high voltage control unit 107 under the control of the apparatus control unit 101. Is transcribed. Here, as shown in FIG. 9, the x, y, and z directions are defined.

  Similarly, the developer images of the respective colors formed in the image forming units 15Y, 15M, and 15C are transferred to each transfer roller to which a high voltage is applied from the power supply unit 108 via the high voltage control unit 107 under the control of the apparatus control unit 101. Transferred onto the print medium 1 by 164Y, 164M, 164C.

  Under the control of the apparatus control unit 101, the surface of the heating roller 171 of the image fixing unit 17 is heated to a preset specified temperature by a heater (not shown) disposed in the heating roller 171. Here, the heater generates heat by applying a current from the power supply unit 108 under the control of the apparatus control unit 101.

  When the print medium 1 to which the image has been transferred is sandwiched and conveyed between a heating roller 171 heated to a specified temperature and a pressure roller 172 disposed in pressure contact with the heating roller 171, the print medium The developer image 1 is heated and pressed by the heating roller 171 and the pressure roller 172 and fixed on the print medium 1.

  As shown in FIG. 9, the print medium 1 subjected to the fixing process is sandwiched between a discharge roller 18 that rotates by being driven by a fixing motor 109, and a driven roller 19 that is disposed to face the discharge roller 18. And is discharged from the discharge port. Thereby, the printing process for one print medium 1 in the image forming apparatus 100 ends.

  Next, the configuration of the medium skew correction mechanism 200 according to the first embodiment of the present invention will be described in detail.

FIG. 1 is a perspective view of a medium skew correction mechanism 200 according to the first embodiment of the present invention.
As shown in FIG. 1, the medium skew correction mechanism 200 includes a drive roller 201 disposed below the medium conveyance path, a medium facing the drive roller 201 and perpendicular to the conveyance direction of the print medium 1. It has an idle roller 202 disposed on the upper side of the conveyance path, a line sensor 203, and side frames 204A and 204B.

FIG. 2 is a diagram illustrating an arrangement position of the medium skew feeding correction mechanism 200 according to the first embodiment of the present invention.
As shown in FIG. 2, the medium skew correction mechanism 200 is disposed downstream of the registration roller pair 14 in the transport direction of the print medium 1 and upstream of the transfer belt unit 16 in the transport direction of the print medium 1 as shown in FIG. 2. (See FIG. 9).

FIG. 3 is a front view of the medium skew feeding correction mechanism 200 according to the first embodiment of the present invention.
The front view in the present embodiment is a view of the image forming apparatus 100 viewed from the y direction.
Both ends of the shaft of the drive roller 201 are rotatably supported by the side frames 204A and 204B via bearings (not shown).

  As shown in FIG. 3, a drive gear 205 is attached to the end of the shaft 2011 of the drive roller 201 outside the side frame 204B. The drive gear 205 rotates upon receiving the driving force of the drive gear drive motor 114 (see FIG. 10).

  As shown in FIG. 3, bearings 206A and 206B are attached to both ends of the idle roller 202, respectively. These bearings 206A and 206B are attached to the long holes 2041A and 2041B of the side frames 204A and 204B so as to be movable up and down.

  The surface layer of the drive roller 201 and the idle roller 202 is made of rubber, for example, and the surface of the roller corresponds to the pressing force of the idle roller 202 against the drive roller 201 at the contact portion (nip) of both rollers. And deform. The same material for the surface layers of both rollers is preferable because it is easy to adjust the nip amount of the nip portion, but different materials may be used.

  As shown in FIG. 3, annular grooves 20211 </ b> A and 20211 </ b> B are formed at both ends of the shaft 2021 protruding from bearings 206 </ b> A and 206 </ b> B that support the idle roller 202. The annular grooves 20211A and 20211B are engaged with the upper ends of idle roller springs 207A and 207B used for adjusting the interaxial distance of the idle roller 202 relative to the drive roller 201, that is, the pressing force.

  As shown in FIG. 3, the lower end of the idle roller spring 207B is engaged with an annular groove 2081 formed at the end of a post 208 attached to the side frame 204B.

FIG. 4 is a diagram illustrating a configuration in which the load on the drive roller 201 of the idle roller 202 of the medium skew correction mechanism 200 according to the first embodiment of the present invention can be adjusted.
As shown in FIG. 4, the lower chord of the idle roller spring 207 </ b> A is engaged with an annular groove 2101 formed at the end of the post 210 attached to the L-shaped cam bracket 209.

  The L-shaped cam bracket 209 is engaged with a guide portion 2042 (see FIG. 5) having a U-shaped cross section formed on the side frame 204A so as to be movable up and down. The bent portion 2091 at the lower end of the L-shaped cam bracket 209 is supported by a support spring 211 on a base portion 2043 formed below the side frame 204A.

  With the above configuration, as shown in FIG. 3, in the idle roller 202, one end of the roller is always attracted to the drive roller 201 by the idle roller spring 207B and the other end is variable in load by the idle roller spring 207A. It is attracted to the drive roller 201 in a state. The drive roller 201 and the idle roller 202 are conveying units that correct skew of the conveyed printing medium 1.

5 and 6 are exploded views of the medium skew correction mechanism 200 according to the first embodiment of the present invention.
As shown in FIGS. 5 and 6, the side frame 204A has two screw holes 2044a and 2044b for attaching a cam gear drive motor 213 for rotating the cam gear 212 rotatably supported by the post 210. Has been. As shown in FIG. 5, the cam gear drive motor 213 is incorporated in a mounting plate 2131 in which two screw holes 2132 and 2133 are processed, and has a shape covered with an upper plate 2134. The cam gear drive motor 213 is fixed to the two screw holes 2044a and 2044b processed in the side frame 204A by the two screws 220a and 220b in the two screw holes 2132 and 2133 processed in the mounting plate 2131. And attached to the side frame 204A.

  As shown in FIG. 5, a drive pulley 214 that transmits the drive of the cam gear drive motor 213 to the idle gear 215 is attached to the shaft portion 2135 of the cam gear drive motor 213. As shown in FIG. 5, a post portion 2136 for rotatably mounting the idle gear 215 is formed at the end portion of the upper plate 2134 of the cam gear drive motor 213. As shown in FIG. 5, the post portion 2136 is passed through a through hole 2151 formed at the center of the idle gear 215, and the idle gear 215 is provided to be rotatable with respect to the post portion 2136. The drive pulley 214 is configured to mesh with an idle gear 215 attached to the post portion 2136.

  Further, a cam follower post 216 is attached above the side frame 204A as shown in FIG. A cam follower 217 is rotatably supported by the cam follower post 216.

  As shown in FIG. 6, the cam gear 212 includes a cam portion 2121 formed with a cam curve that increases the distance from the through hole 2125 to the radial end when rotated clockwise, and the gear portion 2122. . The cam portion 2121 is fixed to the gear portion 2122 together with the slit disk 218 by screws 221 and is rotatably attached to the post 210. As shown in FIG. 3, the cam portion 2121 is configured to contact the outer periphery of the cam follower 217. Here, since the cam bracket 209 is always pushed upward by the action of the support spring 211, the rotating cam portion 2121 and the outer periphery of the cam follower 217 always come into contact with each other. The gear portion 2122 is configured to mesh with the idle gear 215.

  As shown in FIG. 6, the cam gear 212 includes a through-hole for screwing a screw 221 for fixing the slit disk 218 (a screw hole 2123 for screwing with the screw 221 of the cam portion 2121; A long hole 2124) through which the screw 221 of the portion 2122 passes.

  Further, as shown in FIG. 6, the cam gear 212 has a through hole (a through hole 2125 of the cam portion 2121 and a through hole 2126 of the gear portion 2122) through which the post 210 passes in the center. On the other hand, the slit disk 218 has a through hole 2181 for allowing the post 210 to pass through, as shown in FIG. The cam gear 212 and the slit disk 218 are rotatably mounted on the post 210 through the through holes 2125, 2126, and 2181. Since the tooth surfaces of the gear portion 2122 of the idle gear 215 and the cam gear 212 are engaged with each other, when the cam gear drive motor 213 is driven, the cam gear 212 rotates via the drive pulley 214 and the idle gear 215. As described above, since the cam gear 212 and the slit disk 218 are screwed together, when the cam gear 212 rotates, the slit disk 218 rotates simultaneously.

  Since the cam portion 2121 rotates while contacting the cam follower 217 when the cam gear 212 is rotated, the cam bracket 209 to which the cam gear 212 is attached, that is, the post 210, according to the position of the cam portion 2121 contacting the cam follower 217. The position in the Z-axis direction varies. Corresponding to the change in the position of the post 210 in the Z-axis direction, the idle roller spring 207A expands and contracts because one end is engaged with the post 210 and the other end is engaged with the shaft 2021 of the idle roller 202. The pressing force applied to the roller 201 and the idle roller 202 changes, and the distance between the axes of the idle roller 202 with respect to the drive roller 201 also varies.

  Next, as described above, when the cam gear 212 rotates, the slit disk 218 also rotates simultaneously. At this time, the photocoupler sensor 219 detects the slit hole 2182 of the slit disk 218 and calculates the rotation angle of the slit disk 218. Thus, the cam gear 212 can be rotated by an arbitrary rotation angle. As shown in FIG. 5, the photocoupler sensor 219 is attached to the upper surface of the bent portion 2091 at the lower end of the L-shaped cam bracket 209 via a support plate 222, and matches the vertical movement of the cam bracket 209. To move up and down. Thereby, the photocoupler sensor 219 can always detect the slit hole 2182 of the slit disk 218 that moves in accordance with the movement of the cam bracket 209. The slit disk 218 and the photocoupler sensor 219 constitute drive amount detection means for detecting the drive amount of the cam gear drive motor 213.

  The photocoupler sensor 219 photoelectrically converts light emitted from the light emitting element (photodiode), light receiving element (phototransistor), and light emitted from the light emitting element through the plurality of slit holes 2182, and It comprises a pulse shaping circuit that pulses the obtained electrical signal and outputs a pulse signal. The number of pulse signals output from the photocoupler sensor 219 is used to detect an arbitrary rotation angle of the cam gear 212.

FIG. 7 is a plan view of the medium skew feeding correction mechanism 200 according to the first embodiment of the present invention.
The plan view in this embodiment is a view of the image forming apparatus 100 as viewed from above (−z direction).
As shown in FIG. 7, the line sensor 203 that detects the skew of the print medium 1 is disposed in the vicinity of the positions where the drive roller 201 and the idle roller 202 are disposed and upstream of the both media rollers in the medium conveyance path. As shown in FIG. 7, the line sensor 203 is disposed at a position where the right end of the conveyed print medium 1 is detected, that is, a position where the right end of the various defined sizes of the print medium 1 can always be detected. The Here, the line sensor 203 is a reflective line sensor including, for example, a plurality of LEDs (Light Emitting Diode) (not shown), a plurality of light receiving elements, and an internal control circuit unit, and has an accuracy of at least 0.1 mm. To detect the position of the medium.

  When the line sensor 203 detects the position of the right end of the print medium 1 being conveyed, the line sensor 203 outputs a medium position signal indicating the position of the right end of the print medium 1. Based on the medium position signal output from the line sensor 203, the skew amount calculation unit 115 (see FIG. 10), which will be described later, calculates the skew amount of the print medium 1. The device control unit 101 drives the cam gear drive motor 213 based on the calculated skew amount, and sets the distance between the left and right axes (pressing force) of the idle roller 202 with respect to the drive roller 201.

  A control configuration that is a feature of the image forming apparatus 100 according to the first embodiment of the present invention will be described below.

  In addition to the above configuration, the image forming apparatus 100 includes a skew amount calculation unit 115 as shown in FIG.

  In addition to the above configuration, the motor control unit 106 controls the drive gear drive motor 114 for rotating the drive roller 201 via the drive gear 205 and the cam gear 212 as shown in FIG. The cam gear drive motor 213 is driven and controlled.

  When the line sensor 203 detects the right end of the print medium 1 conveyed from the registration roller pair 14, the line sensor 203 outputs a medium position signal. In this embodiment, the skew amount calculation unit 115 calculates the amount of change in the right end position of the medium, that is, the skew amount from the amount of reflected light received by the line sensor 203 when transporting one medium. When the position of the medium moves more than the amount of skew, it is determined that skew has occurred on the medium. The allowable skew amount may be set at the time of manufacture, or may be configured so that the operator can arbitrarily set it.

  As another method of detecting the skew amount, when the line sensor 203 is arranged at a position where a medium without skew is not detected, that is, outside the allowable skew range, and the line sensor 203 outputs a medium position signal, the device control unit 101 The medium position signal may be transferred to the skew amount calculation unit 115.

  When the skew amount calculation unit 115 receives the medium position signal, the skew amount calculation unit 115 calculates the skew amount from the amount of change in the right end position of the print medium 1 indicated by the signal.

  The skew amount may be calculated as a medium conveyance speed that is the traveling speed of the transfer belt 161 by using a skew feeding rate calculated from a predetermined traveling speed preset in a memory (not shown) and the length of the medium. it can. Alternatively, the traveling speed of the transfer belt 161 may be calculated from the drive control of the belt drive motor 112 controlled by the motor control unit 106. The line sensor 203 and the skew amount calculation unit 115 are detection units that detect the skew amount of the conveyed printing medium 1.

  When the skew amount calculation unit 115 calculates the skew amount of the print medium 1, the apparatus control unit 101 transfers the skew amount to the motor control unit 106.

  When the motor control unit 106 receives the skew amount, ± 0.5 mm is stored as a permissible skew amount in a memory (not shown), and the skew of the print medium 1 when the skew amount is 0.5 mm or more. Therefore, if the skew amount is, for example, greater than -0.5 mm and less than 0.5 mm, the cam gear drive motor 213 is not driven, that is, the skew correction is not performed and the drive gear is not driven. Only the drive motor 114 is driven.

FIG. 8 is an explanatory diagram showing an image of the inclination of the idle roller 202 with respect to the drive roller 201 and the inter-axial balance between both rollers according to the first embodiment of the present invention.
A, A ′, B, B ′, C, and C ′ in FIG. 8 indicate the inter-axis distance between the drive roller 201 and the idle roller 202, and A = B = C. The hatched portions between the drive roller 201 and the idle roller 202 in FIGS. 8A, 8B, and 8C indicate the pressing amount (nip amount) between the two rollers. A, B, and C represent the left end of each roller, and A ′, B ′, and C ′ represent the distance between the axes of the right end of each roller.
When the cam gear drive motor 213 is not driven, the cam gear 212 does not rotate in either the positive or negative direction and is in a stopped state. At this time, in order to prevent the rotation of the cam gear 212, a holding current for controlling the drive of the cam gear 212 may be supplied to the cam gear drive motor 213. When the cam gear 212 is stopped in the initial state, the idle roller 202 has almost equal pressing forces applied to the idle roller springs 207A and 207B, that is, both ends of the idle roller 202. Set to be in parallel. Therefore, as shown in FIG. 8B, the pressure balance between both rollers is generally balanced on both the left and right sides. At this time, the left-end inter-axis distance B and the right-end inter-axis distance B ′ between the two rollers are substantially the same, and therefore B = B ′. When the inter-axis distance (pressing force) between the drive roller 201 and the idle roller 202 is balanced in this way, as shown in FIG. 8B, the pressing force in the direction perpendicular to the medium conveyance direction between the rollers is equalized. Therefore, since the medium conveyance speed in the pressing unit is also equalized, the conveyed print medium 1 is conveyed while being conveyed between both rollers.

  On the other hand, when the received skew amount is larger than the allowable skew amount, for example, 0.5 mm (the print medium 1 is skewed to the right), the motor control unit 106 sets the cam gear drive motor 213 to a negative value. It is driven in the direction (counterclockwise) and the drive gear drive motor 114 is driven. When the cam gear drive motor 213 is driven in the negative direction, the cam gear 212 and the slit disk 218 fixed to the cam gear 212 rotate in the negative direction.

  When the slit disk 218 rotates in the negative direction, the photocoupler sensor 219 outputs a pulse signal every time it detects the slit hole 2182 of the slit disk 218.

  The cam gear drive motor 213 is a stepping motor and controls the amount of rotation of the cam gear 212 in the positive direction or the negative direction based on the number of pulse signals output from the photocoupler sensor 219. That is, the cam gear drive motor 213 rotates the cam gear 212 by a predetermined angle using the pulse signal output from the photocoupler sensor 219. That is, the cam gear 212 is a drive unit that moves the transport unit (moves the position of the right end of the idle roller 202 with respect to the drive roller 201) in accordance with an instruction from the control unit (motor control unit 106).

  When the cam gear 212 rotates by a predetermined angle in the negative direction, the cam portion 2121 increases the distance between the cam follower post 216 and the post 210, so that the pressing force of the idle roller spring 207A to the right end of the idle roller 202 increases. Therefore, the tension of the idle roller spring 207A increases, the pressing force generated at the right end of the idle roller 202 increases, and the nip amount on the right end side of the idle roller 202 becomes larger than the nip amount on the left end side. That is, the idle roller 202 inclines the shaft 2021 so as to move the right end portion downward with respect to the drive roller 201, and thereby the pressing force is increased at the right end portion. At this time, the left-end inter-axis distance A and the right-end inter-axis distance A ′ between the drive roller 201 and the idle roller 202 are A> A ′ because the right end portion moves downward. In this way, when the pressing force between the drive roller 201 and the idle roller 202 is increased at the right end, as shown in FIG. 8A, when the print medium 1 being conveyed passes between both rollers, the right end portion is at the left end. Since it is transported more than the portion, the print medium 1 is skewed leftward as indicated by the solid line to the dotted line in the figure. By adjusting the amount of rotation of the cam gear 212 in accordance with the amount of skew of the print medium 1 at the right end pressing amount at this time, the skew of the print medium 1 can be corrected. The rotation amount of the cam gear 212 may be calculated according to the skew amount. In this case, the skew can be corrected quickly, but the rotation amount of the cam gear 212 corresponding to the skew amount needs to be determined in advance from an experiment or the like. On the other hand, the cam gear 212 may be rotated by a fixed amount regardless of the skew amount. However, in this case, it may take time to correct the skew or may not be corrected when the skew is large.

  When the received skew amount is, for example, an allowable skew amount of −0.5 mm or less (the print medium 1 is skewed leftward), the motor control unit 106 moves the cam gear drive motor 213. While driving in the forward direction, the drive gear drive motor 114 is driven. When the cam gear drive motor 213 is driven in the forward direction, the cam gear 212 and the slit disk 218 fixed to the cam gear 212 rotate in the forward direction.

  When the cam gear 212 rotates in the forward direction by a predetermined angle, the idle roller 202 tilts the shaft 2021 so that the right end portion moves upward with respect to the drive roller 201. As a result, the pressing force at the right end portion becomes smaller than that at the left end portion. At this time, the left-end inter-axis distance C and the right-end inter-axis distance C ′ between the drive roller 201 and the idle roller 202 are C <C ′ because the right end portion moves upward. As described above, when the right end of the pressing force between the drive roller 201 and the idle roller 202 is weakened, as shown in FIG. 8C, when the print medium 1 being conveyed passes between both rollers, the right end portion is the left end. Since it is transported less than the portion, the print medium 1 is skewed rightward from the solid line to the dotted line in the figure. The skew of the print medium 1 can be corrected by adjusting the amount of rotation of the cam gear 212 according to the amount of skew of the print medium 1 at the right end pressing amount at this time.

  Note that the amount of change in the medium conveyance speed is set to about ± 1% at the maximum so that the skew of the print medium 1 can be corrected without causing wrinkles in the print medium 1.

  As described above, the motor control unit 106 controls the application or stop of the voltage to the cam gear drive motor 213 based on the skew amount of the print medium 1 calculated by the skew amount calculation unit 115, and controls the drive roller 201. The distance between the axes of the idle roller 202 is adjusted. With the above control configuration, the print medium 1 is conveyed between the drive roller 201 and the idle roller 202.

<Operation of Example 1>
Next, the operation of the medium skew correction mechanism 200 of the image forming apparatus 100 according to the first embodiment of the present invention will be described with reference to the flowchart of FIG.

FIG. 11 is a flowchart showing the operation of the medium skew correction mechanism 200 according to the first embodiment of the invention.
The drive gear drive motor 114 is driven to transport the print medium 1 (step S101). When the line sensor 203 detects the right end of the print medium 1 conveyed from the registration roller pair 14, the line sensor 203 outputs a medium position signal (step S102). When the line sensor 203 outputs a medium position signal, the apparatus control unit 101 transfers the medium position signal to the skew amount calculation unit 115.

  When the skew amount calculation unit 115 receives the medium position signal, the skew amount calculation unit 115 calculates the skew amount from the amount of change in the right end position of the print medium 1 indicated by the signal (step S103).

  When the skew amount calculation unit 115 calculates the skew amount of the print medium 1, the apparatus control unit 101 transfers the skew amount to the motor control unit 106.

  Upon receiving the skew amount, the motor control unit 106 determines whether the skew amount is within the allowable skew amount range (± 0.5 mm in this embodiment), that is, whether skew has occurred. Is determined (step S104).

  When the cam gear drive motor 213 is not driven, the cam gear 212 does not rotate in either the positive or negative direction and is in a stopped state. When the cam gear 212 is stopped, the idle roller 202 is in a parallel state with respect to the drive roller 201 without changing from the initial state, so as shown in FIG. Keep both left and right in balance. In this way, when the inter-axis distance (pressing force) between the drive roller 201 and the idle roller 202 is balanced, as shown in FIG. 8B, the conveyed printing medium 1 remains in the conveyed state. Be transported.

  On the other hand, if the received skew amount is larger than 0.5 mm, which is the allowable skew amount (the print medium 1 is skewed to the right) (step S105), the motor control unit 106 drives the cam gear. It is determined that the rotation direction of the motor 213 is driven in the negative direction (counterclockwise) (step S106). When the cam gear drive motor 213 is driven in the negative direction, the cam gear 212 and the slit disk 218 fixed to the cam gear 212 rotate in the negative direction.

  When the slit disk 218 rotates in the negative direction, the photocoupler sensor 219 outputs a pulse signal every time it detects the slit hole 2182 of the slit disk 218.

  The cam gear drive motor 213 stops when the cam gear 212 is rotated by the rotation amount of the cam gear 212 calculated from the skew amount using the pulse signal output from the photocoupler sensor 219 (step S107).

  When the cam gear 212 rotates in the negative direction, the idle roller 202 tilts the shaft 2021 so as to move the right end portion downward with respect to the drive roller 201. As a result, the pressing force is increased at the right end portion. When the right end of the pressing force between the drive roller 201 and the idle roller 202 is strengthened, as shown in FIG. 8A, the conveyed print medium 1 is conveyed with a large amount at the right end when passing between both rollers. Therefore, the skew is corrected straight like the dotted line in the figure.

  In addition, when the received skew amount is, for example, an allowable skew amount of −0.5 mm or less (the print medium 1 is skewed leftward), the motor control unit 106 sets the cam gear drive motor 213. It is determined that the rotation direction is driven in the positive direction (step S108). When the cam gear drive motor 213 is driven in the forward direction, the cam gear 212 and the slit disk 218 fixed to the cam gear 212 rotate in the forward direction.

  When the cam gear 212 rotates in the forward direction, the idle roller 202 tilts the shaft 2021 so that the right end portion moves upward with respect to the drive roller 201. As a result, the pressing force is reduced at the right end portion. When the right end of the pressing force between the drive roller 201 and the idle roller 202 is weakened, as shown in FIG. 8C, the transported print medium 1 is transported with less right end when passing between both rollers. Therefore, the skew is corrected straight like the dotted line in the figure.

<Effect of Example 1>
According to the image forming apparatus 100 of the first embodiment, the line sensor 203 outputs a medium position signal indicating the position of the right end of the printing medium 1 conveyed from the registration roller pair 14, and the skew amount calculation unit 115 is output. The skew amount is calculated from the change amount of the right end position of the print medium 1 based on the medium position signal, and the cam gear drive motor 213 is rotated in the positive direction or the negative direction based on the calculated skew amount, and the cam gear 212 is moved. By rotating a predetermined amount and adjusting the balance of the pressing force of the idle roller 202 against the registration roller 201, the distance (pressing force) between the axes of the idle roller 202 and the registration roller 201 is adjusted. The left and right pressing force between the two rollers can be adjusted while being stabilized, so that the print medium 1 conveyed toward the transfer belt unit 16 can be scanned. It is possible to correct the over.

  Further, the image forming apparatus 100 according to the first exemplary embodiment is configured to adjust the left and right pressing force between both rollers by using an idle roller 202 formed of a single roller that is not divided with respect to the drive roller 201. The conveyance force is gradually adjusted from the right end to the left end of the print medium 1 to be performed. Therefore, for example, in contrast to a mechanism in which two independent rollers are arranged to face the drive roller 201 instead of the idle roller 202 and the skew feeding of the medium is adjusted by a difference in rotational speed between the two rollers, the medium conveyance speed is uneven. The generation of wrinkles can be reduced and the generation of wrinkles on the print medium 1 can be prevented.

<Configuration of Example 2>
According to the case where the drive roller 201 and the idle roller 202 of the skew feeding correction mechanism 200 of the image forming apparatus 100 according to the first exemplary embodiment are configured by two rollers that are elastic bodies, or when the assembly accuracy of the rollers is low. In some cases, it is not possible to execute the skew correction of the medium as expected due to wear of the ink. In the image forming apparatus 100a according to the second exemplary embodiment of the present invention, in order to detect whether or not the skew correction is reliably performed, the print medium 1 after the skew correction is provided on the downstream side of the transfer belt unit 16 in the medium transport direction. A second line sensor 223 (see FIG. 12) for outputting a corrected medium position signal indicating the medium position is further provided.

  Further, in this embodiment, the corrected medium position signal output from the second line sensor 223 is added to the function of calculating the skew amount included in the skew amount calculation unit 115 of the image forming apparatus 100 according to the first embodiment. A skew amount calculation unit 115a to which a function for calculating a skew amount after correction is added is added.

  Furthermore, in this embodiment, the image forming apparatus 100 according to the first embodiment includes a skew amount storage unit 116 that stores the skew amount of the print medium 1 calculated by the skew amount calculation unit 115a and the skew amount after correction. to add. In other words, in this embodiment, the motor control unit 106a assumes the skew amount of the print medium 1 of the previous page stored in the skew amount storage unit 116 and the skew amount corrected from the skew amount. The drive motor 213a is driven and controlled, and the correction value for the rotation amount of the cam gear 212 is determined.

FIG. 13 is a diagram showing the configuration of the image forming apparatus 100a according to the second embodiment of the present invention.
As shown in FIG. 13, the image forming apparatus 100 a includes a paper cassette 11, a paper feed roller 12, a separation frame 13, a registration roller pair 14, a medium skew feeding correction mechanism 200 a that is a medium conveyance device, and an image formation. Units 15K, 15Y, 15M, and 15C, a transfer belt unit 16, an image fixing unit 17, a discharge roller 18, and a driven roller 19 are included.

  The entire image forming apparatus 100a is controlled by the apparatus control board 101a. The device control unit 101a is connected to a host device (not shown) such as a PC via a network via the I / F unit 102. The apparatus control unit 101a includes a microcomputer and the like, and the application of voltage by the power supply unit 108 to each unit and printing control based on information from each sensor are performed.

FIG. 12 is a diagram illustrating an arrangement position of the medium skew feeding correction mechanism 200a according to the second embodiment of the present invention.
The medium skew correction mechanism 200a uses the first line sensor 203 to check the state of the print medium after skew correction, as shown in FIG. 12, with respect to the medium skew correction mechanism 200 of the first embodiment. A second line sensor 223 is additionally disposed downstream of the medium conveyance direction, in the present embodiment, downstream of the transfer belt unit 16 and upstream of the image fixing unit 17.

  When the skew correction is completed and the second line sensor 223 detects the position on the right side of the print medium 1 conveyed by the transfer belt 161, the second line sensor 223 outputs a corrected medium position signal indicating the right end position of the print medium 1. . Based on the corrected medium position signal output from the second line sensor 223, the skew amount calculation unit 115a (see FIG. 14) performs the corrected skew indicating the skew amount of the print medium 1 at the position of the second line sensor 223. The line amount is calculated. The motor control unit 106a drives the cam gear drive motor 213a based on the calculated corrected skew amount to readjust the inter-axis distance (pressing force) between the drive roller 201 and the idle roller 202.

  The other configuration of the image forming apparatus 100a according to the second embodiment is the same as that of the image forming apparatus 100 according to the first embodiment.

  Hereinafter, the control configuration of the image forming apparatus 100a will be described in detail.

FIG. 14 is a block diagram illustrating a control configuration of the image forming apparatus 100a according to the second embodiment of the present invention.
As shown in FIG. 14, the image forming apparatus 100a has a device control unit 101a that controls the entire device, an I / F unit 102, a temporary storage unit 103, and the like. Reading unit 104, image memory 105, motor control unit 106a, high voltage control unit 107, power supply unit 108, line sensor 203, skew amount calculation unit 115a, second line sensor 223, skew A quantity storage unit 116.

  As shown in FIG. 14, the motor control unit 106 a includes a fixing motor 109 for rotating the heating roller 171, a paper feeding motor 110 for rotating the paper feeding roller 12, and a resist roller pair 14. A registration roller 111, a belt driving motor 112 for rotating the belt driving roller 162 for running the transfer belt 161, a drum motor 113 for rotating the photosensitive drum 152, and a drive roller 201 via a drive gear 205. A drive gear drive motor 114 for rotating the cam gear 212 and a cam gear drive motor 213a for rotating the cam gear 212 are controlled.

  When the line sensor 203 detects the right end of the print medium 1 conveyed from the registration roller pair 14, the line sensor 203 outputs a medium position signal. In this embodiment, the skew amount calculation unit 115a calculates the amount of change in the right end position of the print medium 1, that is, the skew amount based on the amount of reflected light received by the line sensor 203 when transporting one print medium 1. When the calculated position of the print medium 1 is moved beyond the allowable skew amount, it is determined that skew has occurred in the print medium 1.

  In addition, as a method of detecting the skew amount, as in the first embodiment, when the line sensor 203 outputs a medium position signal, the apparatus control unit 101a transfers the medium position signal to the skew amount calculation unit 115a. Also good.

  When the skew amount calculation unit 115a receives the medium position signal, the skew amount calculation unit 115a calculates the skew amount based on the medium conveyance speed from the change amount of the right end position of the print medium 1 indicated by the signal.

  When the skew amount calculation unit 115a calculates the skew amount of the print medium 1, the apparatus control unit 101a transfers the skew amount to the motor control unit 106a and stores it in the skew amount storage unit 116. The skew amount storage unit 116 is a storage unit that stores the skew amount of the print medium 1.

  When the motor control unit 106a receives the skew amount, the motor control unit 106a sets in a memory (not shown) that the skew of the print medium 1 needs to be corrected when the allowable skew amount is ± 0.5 mm or more. Therefore, when the correction skew amount is, for example, above -0.5 mm and less than 0.5 mm, the cam gear drive motor 213a is not driven. When the cam gear drive motor 213a is not driven, as described in the first embodiment, the pressing balance between both rollers is generally balanced on both the left and right sides in the initial state. As described above, when the axial distance between the drive roller 201 and the idle roller 202, that is, the pressing force is balanced, the transported print medium 1 is transported while being transported.

  On the other hand, the motor control unit 106a moves the cam gear drive motor 213a in the negative direction when the skew amount is larger than, for example, the allowable skew amount of 0.5 mm (the print medium 1 is skewed to the right). To drive. When the cam gear drive motor 213a is driven in the negative direction, as described in the first embodiment, the cam gear 212 rotates in the negative direction by a predetermined angle. When the cam gear 212 rotates by a predetermined angle in the negative direction, the idle roller 202 inclines the shaft 2021 so that the right end portion moves downward with respect to the drive roller 201, thereby increasing the pressing force at the right end portion. . As described above, when the pressing force between the drive roller 201 and the idle roller 202 is increased at the right end, the print medium 1 is conveyed in a large amount at the right end portion.

  In addition, when the received skew amount is, for example, an allowable skew amount of −0.5 mm or less (the print medium 1 is skewed leftward), the motor control unit 106a moves the cam gear drive motor 213a. Drive in the positive direction. When the cam gear drive motor 213a is driven in the forward direction, the cam gear 212 rotates in the forward direction by a predetermined angle as described in the first embodiment. When the cam gear 212 rotates in the forward direction by a predetermined angle, the idle roller 202 inclines the shaft 2021 so that the right end portion moves upward with respect to the drive roller 201, thereby reducing the pressing force at the right end portion. . As described above, when the pressing force between the drive roller 201 and the idle roller 202 is weakened at the right end, the print medium 1 is conveyed with a small right end portion.

  As described above, the motor control unit 106a controls the application or stop of the voltage to the cam gear drive motor 213a based on the calculated skew amount, and adjusts the balance of the pressing force of the idle roller 202 against the drive roller 201. By adjusting the distance between the axes. The print medium 1 passes between the drive roller 201 and the idle roller 202 and is conveyed to the transfer belt 161. Even after the trailing edge of the print medium 1 passes between the drive roller 201 and the idle roller 202, the motor control unit 106a determines that both rollers have the current inter-axis distance based on the skew amount stored in the skew amount storage unit 116. The drive of the cam gear drive motor 213a is controlled so as to maintain the above.

  When the second line sensor 223 detects the right end of the print medium 1 conveyed from the transfer belt 161, the second line sensor 223 outputs a corrected medium position signal. When the second line sensor 223 outputs the corrected medium position signal, the apparatus control unit 101a transfers the signal to the skew amount calculation unit 115a.

  When the skew amount calculation unit 115a receives the corrected medium position signal, the skew amount of the print medium 1 at the position where the second line sensor 223 is disposed, based on the change amount of the right end position of the print medium 1 indicated by the signal. The corrected skew amount is calculated. The second line sensor 223 and the skew amount calculation unit 115a are post-correction skew amount detection means for detecting the skew amount of the print medium 1 after correction.

  When the skew amount calculation unit 115a calculates the corrected skew amount of the print medium 1, the apparatus control unit 101a transfers the corrected skew amount to the motor control unit 106a and also calculates the corrected skew amount. This is stored in the skew amount storage unit 116. The skew amount storage unit 116 is a storage unit that stores the corrected skew amount of the print medium 1.

  When the motor control unit 106a receives the corrected skew amount, the medium skew correction is performed as expected by the skew correction by the first line sensor 203, that is, the skew correction is successful. If it can be determined, the cam gear drive motor 213a is driven and controlled in the current state.

  On the other hand, in the motor control unit 106a, the skew correction of the print medium 1 is greatly acting on the medium skew assumed by the skew correction by the first line sensor 203, that is, the skew correction is strong. When it can be determined that it is acting too much, a skew correction amount correction value that is a correction value of the skew correction amount of the first line sensor 203 calculated from the second line sensor 223 is calculated, and the cam gear drive motor The drive of 213a is controlled to rotate the cam gear 212 in the negative direction by the skew correction amount correction value.

  Further, the motor control unit 106a has a small skew correction of the print medium 1 with respect to the medium skew assumed by the skew correction by the first line sensor 203, that is, the skew correction is weak. When it can be determined that the action is insufficient, a skew correction amount correction value that is a correction value of the skew correction amount of the first line sensor 203 calculated from the second line sensor 223 is calculated, and the cam gear drive motor 213a is calculated. And the cam gear 212 is rotated in the forward direction by the skew correction amount correction value.

  The shaft distance between the drive roller 201 and the idle roller 202 is readjusted by the control of the cam gear drive motor 213a based on the post-skew correction amount stored in the skew amount storage unit 116 of the motor control unit 106a. The motor control unit 106a makes the skew correction of the print medium 1 of the next page smoother, and the inter-axis distance in which both rollers are adjusted based on the corrected skew amount stored in the skew amount storage unit 116. The drive of the cam gear drive motor 213a is controlled so as to maintain the above.

  The other control configuration of the image forming apparatus 100a according to the second embodiment is the same as the control configuration of the image forming apparatus 100 according to the first embodiment.

<Operation of Example 2>
Next, the operation of the medium skew correction mechanism 200a of the image forming apparatus 100a according to the second embodiment of the present invention will be described with reference to the flowcharts of FIGS.

15 and 16 are flowcharts showing the operation of the medium skew correction mechanism 200a according to the second embodiment of the present invention.
The drive gear drive motor 114 is driven to transport the print medium 1 (step S201). When the line sensor 203 detects the right end of the print medium 1 conveyed from the registration roller pair 14, the line sensor 203 outputs a medium position signal (step S202). When the line sensor 203 outputs the medium position signal, the apparatus control unit 101a transfers the medium position signal to the skew amount calculation unit 115a.

  When the skew amount calculation unit 115a receives the medium position signal, the skew amount calculation unit 115a calculates the skew amount from the amount of change in the right end position of the print medium 1 indicated by the signal (step S203).

  When the skew amount calculation unit 115a calculates the skew amount of the print medium 1, the apparatus control unit 101a transfers the skew amount to the motor control unit 106a and stores it in the skew amount storage unit 116 (step S204). ).

  When the motor controller 106a receives the skew amount described above, if the corrected skew amount is, for example, above the allowable skew amount of −0.5 mm and less than 0.5 mm (step S205), the cam gear drive motor 213a. Do not drive. When the cam gear drive motor 213a is not driven, the inter-axis distance (pressing force) between the drive roller 201 and the idle roller 202 is substantially balanced, so that the transported print medium 1 is transported while being transported. .

  On the other hand, when the skew amount is larger than the allowable skew amount, for example, 0.5 mm (the print medium 1 is skewed to the right) (step S206), the motor control unit 106a determines the cam gear drive motor. 213a is driven in the negative direction (step S207). The cam gear drive motor 213a stops when the cam gear 212 is rotated by the rotation amount of the cam gear 212 calculated from the skew amount (step S208). When the cam gear 212 rotates in the negative direction, the idle roller 202 tilts the shaft 2021 so as to move the right end portion downward with respect to the drive roller 201. As a result, the pressing force is increased at the right end portion. When the pressing force between the drive roller 201 and the idle roller 202 is increased at the right end, the right end portion of the printing medium 1 is conveyed more than the left end portion.

  In addition, when the received skew amount is, for example, an allowable skew amount of −0.5 mm or less (the print medium 1 is skewed leftward), the motor control unit 106a moves the cam gear drive motor 213a. Drive in the forward direction (step S209). When the cam gear drive motor 213a is driven in the forward direction, the cam gear 212 rotates in the forward direction. When the cam gear 212 rotates in the forward direction, the idle roller 202 tilts the shaft 2021 so that the right end portion moves upward with respect to the drive roller 201. As a result, the pressing force is reduced at the right end portion. When the right end of the pressing force between the drive roller 201 and the idle roller 202 is weakened, the print medium 1 is conveyed with a right end portion less than a left end portion.

  The print medium 1 passes between the drive roller 201 and the idle roller 202 and is conveyed to the transfer belt 161. Even after the trailing edge of the print medium 1 passes between the drive roller 201 and the idle roller 202, the motor control unit 106a determines that both rollers have the current inter-axis distance based on the skew amount stored in the skew amount storage unit 116. The drive of the cam gear drive motor 213a is controlled so as to maintain the above.

  When the second line sensor 223 detects the right end of the print medium 1 conveyed from the transfer belt 161 (step S210), the second line sensor 223 outputs a corrected medium position signal. When the second line sensor 223 outputs the corrected medium position signal, the apparatus control unit 101a transfers the signal to the skew amount calculation unit 115a.

  When the skew amount calculation unit 115a receives the corrected medium position signal, the skew amount of the print medium 1 at the position where the second line sensor 223 is disposed, based on the change amount of the right end position of the print medium 1 indicated by the signal. The corrected skew feed amount is calculated (step S211).

  When the skew amount calculation unit 115a calculates the corrected skew amount of the print medium 1, the apparatus control unit 101a transfers the corrected skew amount to the motor control unit 106a and also calculates the corrected skew amount. This is stored in the skew amount storage unit 116 (step S212).

  When the motor control unit 106a receives the corrected skew amount, the medium skew correction is performed as expected by the skew correction by the first line sensor 203, that is, the skew correction is successful. If it can be determined (step S213), the cam gear drive motor 213a is driven and controlled in the current state.

  On the other hand, in the motor control unit 106a, the skew correction of the print medium 1 is greatly acting on the medium skew assumed by the skew correction by the first line sensor 203, that is, the skew correction is strong. If it can be determined that it is acting too much (step S214), a skew correction amount correction value that is a correction value of the skew correction amount of the first line sensor 203 calculated from the second line sensor 223 is calculated. Then, the drive of the cam gear drive motor 213a is controlled to rotate the cam gear 212 in the negative direction by the skew correction amount correction value (step S215).

  Further, the motor control unit 106a has a small skew correction of the print medium 1 with respect to the medium skew assumed by the skew correction by the first line sensor 203, that is, the skew correction is weak. When it can be determined that the action is insufficient, a skew correction amount correction value that is a correction value of the skew correction amount of the first line sensor 203 calculated from the second line sensor 223 is calculated, and the cam gear drive motor 213a is calculated. And the cam gear 212 is rotated in the positive direction by the skew correction amount correction value (step S216).

  The shaft distance between the drive roller 201 and the idle roller 202 is readjusted by the control of the cam gear drive motor 213a based on the post-skew correction amount stored in the skew amount storage unit 116 of the motor control unit 106a. The motor control unit 106a makes the skew correction of the print medium 1 of the next page smoother, and the inter-axis distance in which both rollers are adjusted based on the corrected skew amount stored in the skew amount storage unit 116. The drive of the cam gear drive motor 213a is controlled so as to maintain the above.

<Effect of Example 2>
According to the image forming apparatus 100a of the second embodiment, since the second line sensor 223 is disposed at a position downstream of the first line sensor 203 in the medium conveyance direction, the medium of the print medium 1 after skew correction is performed. The position can be detected. Thereby, it is determined whether or not the medium skew correction as expected by the skew correction by the first line sensor 203 is surely performed. If not, the skew correction amount correction value is set. Since the calculation and the drive control of the cam gear drive motor 213a are performed to rotate the cam gear 212 by the skew correction amount correction value, the skew of the print medium 1 can be corrected more accurately than in the image forming apparatus 100 of the first embodiment. it can.

  Further, according to the image forming apparatus 100a, the skew amount calculation unit 115a after the correction indicates the skew amount of the print medium 1 after the skew correction based on the corrected medium position signal output from the second line sensor 223. Calculate the skew amount. Thus, during the printing process for the next page, the skew correction amount correction value can be applied to adjust the rotation amount of the cam gear 212, so that the print medium 1 can be smoother than the image forming apparatus 100 of the first embodiment. It is possible to perform the skew correction.

  In the first and second embodiments, the medium skew correction mechanisms 200 and 200a are described as independent mechanisms disposed between the registration roller pair 14 and the transfer belt unit 16, but the drive roller 201 and the idle roller Instead of 202, the registration roller pair 14 may be incorporated in the medium skew feeding correction mechanisms 200 and 200a.

  In the first and second embodiments, the line sensor 203 monitors the skew of the printing medium 1 that is always conveyed and outputs a medium position signal. However, the line sensor 203 is not limited to this and is preset in a memory (not shown). A configuration may be adopted in which the skew of the printing medium 1 conveyed at regular intervals is detected and a medium position signal is output.

  Further, in the first and second embodiments, the apparatus control units 101 and 101a transfer the skew amount to the motor control units 106 and 106a every time the skew amount calculation units 115 and 115a calculate the skew amount. However, the present invention is not limited to this, and the configuration may be such that the skew transfer amount is transferred to the motor control units 106 and 106a only when a predetermined amount (threshold value) preset in a memory (not shown) is exceeded.

  In the first and second embodiments, the medium skew correction mechanisms 200 and 200a are configured to adjust the left and right pressing force between the two rollers by moving one end of the idle roller 202 up and down relative to the drive roller 201. However, the present invention is not limited to this, and the left and right pressing force between both rollers may be adjusted by moving both ends of the roller up and down.

  In the first embodiment, the medium skew correction mechanism 200 is configured to perform skew correction on the print medium 1 of one page. However, in consideration of the case where a plurality of pages of the print medium 1 are conveyed, the skew amount is considered. The skew amount calculated by the calculation unit 115 is stored in a storage unit (not shown), and when the skew correction of the print medium 1 of the next page is performed, the skew amount of the previous page stored in the storage unit is assumed. A configuration may be adopted in which the inter-axis distance (pressing force) between the registration roller 201 and the idle roller 202 is adjusted.

  In the first and second embodiments, a stepping motor is employed as the cam gear drive motor 213. However, depending on the detection accuracy of the slit disk 218, the stepping motor can be changed to a DC motor.

  In the above-described embodiments, an example in which the image forming apparatus of the present invention is applied as a color printer has been described. However, the present invention is not limited to this, and can be applied to, for example, a monochrome printer, a copying machine, a facsimile machine, and an MFP.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Apparatus control part 106 Motor control part 114 Drive gear drive motor 115 Skew amount calculation part 116 Skew amount storage part 200 Medium skew correction mechanism 201 Drive roller 202 Idle roller 203 Line sensors 204A and 204B Side frame 205 Drive gear 207A, 207B Idle roller spring 209 Cam bracket 211 Support spring 212 Cam gear 213 Cam gear drive motor 214 Drive pulley 215 Idle gear 217 Cam follower 218 Slit disk 2182 Slit hole 219 Photocoupler sensor 223 Second line sensor

Claims (8)

A transport path for transporting the medium;
Detecting means for detecting a skew amount of the medium;
Transport means for transporting a medium provided at a position facing the transport path and movable in a direction perpendicular to the transport path;
Control means for calculating the position of the conveying means based on the detection result of the detecting means;
A medium conveying apparatus comprising: a driving unit that moves the conveying unit in accordance with an instruction from the control unit.   The medium conveying apparatus according to claim 1, wherein the driving unit that moves the conveying unit is a cam. A post-correction skew amount detecting means for detecting the skew amount of the medium after the skew correction;
Storage means for storing the detected skew amount and the skew amount after skew correction;
2. The medium transport apparatus according to claim 1, wherein the control unit calculates the position of the transport unit based on the skew amount stored in the storage unit and the skew amount after skew correction.   The medium conveying apparatus according to claim 1, wherein the detection unit is an optical sensor.   The medium conveying apparatus according to claim 4, wherein the optical sensor is a line sensor. The driving means includes
The medium conveying apparatus according to claim 1, further comprising a driving amount detecting unit for detecting a driving amount of the driving unit. The drive amount detection means includes
A slit disk that rotates in response to the drive means;
The medium conveying apparatus according to claim 6, further comprising an optical sensor corresponding to the slit disk.   An image forming apparatus comprising the medium conveying device according to claim 1.

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