JP5352715B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing a risk that a rotary guide member rotates by a rotation torque generated when a sheet hits a guide path. <P>SOLUTION: An image forming apparatus performs: entrance timing holding processing that holds a rotation position of a stepping motor 51 by supplying an excitation current of a first current value to the stepping motor 51 at a timing when a leading edge of paper P enters a receiving opening in a state that an ejecting opening of a guide path 320 is oriented to either a top edge conveyance path 101a or a reciprocating conveyance path 103; and passage timing holding processing that reduces the excitation current to a second current value which is smaller than the first current value when the leading edge of paper P passes through the guide path 320. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus including a sheet carry-out direction switching device that switches a conveyance direction of a sheet being conveyed.

  2. Description of the Related Art Conventionally, a sheet carry-out direction switching device (a sheet carry-out processing device in Patent Document 1) used in a sheet conveyance system of an image forming apparatus as described in Patent Document 1 is known. In this sheet carry-out direction switching device, an image is formed in an image forming apparatus, and a sheet carry-out destination on which a toner image is formed is placed between a discharge tray and a switchback conveyance path for duplex printing processing. The rotary guide member (switching gate in Patent Document 1) provided at the branch point of the discharge destination is provided.

  In this rotary guide member, four guide plates are installed between a pair of opposing circular side plates that are spaced apart and slightly longer than the width of the sheet, and each circular side plate is directed in the opposite direction from the center position. It is formed by providing a projecting rotary shaft.

  Different guide passages (straight-ahead guide passages at the center and reverse guide passages on both sides) are provided between the guide plates. Then, according to the amount of rotation from the reference phase of the rotary guide member, it is determined which guide path the sheet conveyed toward the rotary guide member passes through, so that the sheet is sent to a preset delivery destination. It will be discharged towards.

  The rotary guide member is configured to rotate integrally around the rotation axis by a stepping motor that is driven and rotated according to the number of pulses of the pulse signal. As a result, the position of the rotary guide member is set (that is, the destination of the conveyed sheet is set).

JP-A-9-86759

  By the way, when the stepping motor is brought into a non-excited state by setting the current flowing in the coil to zero, so-called detent torque is generated as a holding torque that works to fix the rotational position. Therefore, after setting the position of the rotary guide member by the stepping motor as described above, if the stepping motor is brought into a non-excited state, the rotary guide member is fixed by the detent torque.

  However, the rotary guide member is bent when the leading edge of the conveyed sheet collides with the guide plate of the guide path at the entrance of the rotary guide, so that the sheet conveying direction is bent. A large rotational torque exceeding the torque is generated, and there is a possibility that the rotary guide member rotates and the sheet cannot be conveyed correctly.

  The present invention has been made in view of such circumstances, and is a sheet carry-out direction switching device capable of reducing the possibility that the rotary guide member will be rotated by the rotational torque generated when the sheet collides with the guide passage. An object of the present invention is to provide an image forming apparatus including

  An image forming apparatus according to the present invention is an image forming apparatus including a sheet carry-out direction switching device and an image forming unit that forms an image on the sheet based on predetermined image data, the sheet carry-out direction switching device. Is provided with a guide passage through which the conveyed sheet can pass, and rotates around a support shaft extending in the width direction of the sheet orthogonal to the conveyance direction to exit at least one of the two conveyance destinations. A rotary guide member capable of changing its attitude so as to face it, a stepping motor for changing the attitude of the rotary guide member, and a motor control unit for controlling the rotation of the stepping motor by supplying a coil exciting current to the stepping motor And a leading edge entrance timing acquisition unit that acquires the timing at which the leading edge of the sheet enters the entrance of the guide passage. In the state where the exit of the guide passage is directed to one of the at least two transport destinations, the motor control unit is configured to perform the first operation at a timing when the leading edge of the sheet acquired by the leading edge input timing acquiring unit enters the inlet. An input timing holding process for holding the rotational position of the stepping motor by supplying an exciting current having a current value to the stepping motor, and when the leading edge of the sheet passes through the guide path, the excitation current is converted to the first current. A passage timing holding process for reducing the current value to a second current value smaller than the value, and a rear end timing acquisition unit that acquires a timing at which the rear end of the sheet is discharged from the exit of the guide passage, The motor control unit further sets the exit of the guide passage toward one of the at least two transport destinations. And supplying an exciting current having a third current value larger than the second current value to the stepping motor at a timing when the trailing edge of the sheet acquired by the trailing edge output timing acquisition unit is discharged from the exit. An exit timing holding process for holding the rotational position of the stepping motor is executed.

  According to this configuration, the leading edge entry timing acquisition unit acquires the timing at which the leading edge of the sheet enters the entrance of the guide path and the sheet may collide with the guiding path and the rotational torque may be applied to the rotary guide member. Then, since the motor control unit performs the entering timing holding process for holding the rotational position of the stepping motor by supplying the exciting current having the first current value to the stepping motor at the timing when the leading edge of the sheet enters the entrance. As a result of the holding force of the motor being larger than the detent torque, it is possible to reduce the possibility that the rotary guide member rotates with the rotational torque generated when the sheet collides with the guide path. Here, if the excitation current continues to flow while the stepping motor is stopped, the stepping motor may be heated. Further, when the leading edge of the sheet passes through the guide passage, the rotational torque applied to the rotary guide member decreases. Therefore, when the leading end of the sheet passes through the guide path, the motor control unit executes a passing timing holding process for reducing the excitation current to a second current value smaller than the first current value, thereby exciting the stepping motor excitation current. This can reduce the risk of heating of the stepping motor.

  According to this configuration, the timing at which the rear end of the sheet is discharged from the exit of the guide passage, and the rotational torque may be applied to the rotary guide member with the force that the sheet bent in the guide passage rebounds. Is acquired by the rear end timing acquisition unit. Then, the rotational position of the stepping motor is adjusted by supplying an excitation current having a third current value larger than the second current value to the stepping motor at a timing when the rear end of the sheet is discharged from the exit of the guide passage. Since the exit timing holding process for holding is performed, the holding force of the stepping motor becomes larger than the detent torque. As a result, it is possible to reduce the possibility that the rotary guide member rotates due to the rebounding force of the sheet to return.

  Further, it is preferable that the third current value is a value less than the first current value.

Since the force at which the sheet rebounds and rebounds is weaker than the force at which the front end of the sheet collides with the guide path, the third current that flows through the stepping motor at the timing when the rear end of the sheet is discharged from the exit of the guide path By making the excitation current of the value smaller than the excitation current of the first current value that flows to the stepping motor at the timing when the leading edge of the sheet enters the entrance of the guide passage, heat generation of the stepping motor can be reduced.

  Further, the apparatus further includes a elasticity information acquisition unit that acquires information relating to the elasticity of the sheet as elasticity information, and the motor control unit is configured such that the elasticity information acquired by the elasticity information acquisition unit is preset with the elasticity of the sheet. In the case where it is indicated that the elasticity is equal to or greater than the first elasticity, it is preferable to execute the entry timing holding process.

  The rotational torque that acts on the rotary guide member when the sheet collides with the guide passage increases as the elasticity of the sheet increases. Therefore, according to this configuration, when the elasticity information acquired by the elasticity information acquisition unit is greater than or equal to the first elasticity set in advance, the rotary guide member is likely to rotate due to the collision of the sheet. The on-timing holding process is executed by the motor control unit. On the other hand, if the elastic force of the sheet is weak and less than the first elastic force, there is little possibility that the rotary guide member will rotate due to the collision of the sheet. Therefore, the heat generation of the stepping motor is not performed without executing the exciting current increasing process by the input timing maintaining process. Can be reduced.

  Further, the apparatus further includes a elasticity information acquisition unit that acquires information relating to the elasticity of the sheet as elasticity information, and the motor control unit is configured such that the elasticity information acquired by the elasticity information acquisition unit is preset with the elasticity of the sheet. In the case of indicating that the elasticity is equal to or greater than the first elasticity, the entrance timing holding process and the exit timing holding process are executed, and the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is weaker than the first elasticity. In the case where it is indicated that the second elasticity is greater than or equal to the second elasticity indicating an elasticity that is weaker than the first elasticity, it is preferable to execute the entry timing holding process without executing the output timing holding process.

  According to this configuration, when the elasticity information acquired by the elasticity information acquisition unit is greater than or equal to the first elasticity set in advance, and the rotary guide member is highly likely to rotate due to the collision of the sheet, the motor The control unit executes an incoming timing holding process and an outgoing timing holding process. When the elasticity of the sheet is weak, the rotational torque applied to the rotary guide member by the sheet decreases, so the timing at which the rear end of the sheet is discharged from the exit of the guide passage, that is, the leading end of the sheet enters the entrance of the guide passage. At the timing when the rotational torque applied to the rotary guide member becomes smaller than the timing, the rotational torque applied to the rotary guide member synergistically decreases. Therefore, when the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the seat is weaker than the first elasticity and is equal to or higher than the second elasticity indicating the elasticity less than the first elasticity, the motor control unit By not performing the timing holding process and increasing the excitation current, it is possible to reduce the heat generation of the stepping motor as compared with the case where the output timing holding process is executed regardless of the elasticity of the sheet.

  The motor control unit may further include the entry timing holding process and the exit timing holding process when the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is weaker than the second elasticity. It is preferable not to execute any of the above.

  Since the elastic force of the sheet is weaker than that of the second elastic force, the motor control unit is activated when there is little possibility that the rotary guide member will rotate due to the collision of the sheet even when the leading edge of the sheet enters the entrance of the guide passage. Since neither the timing holding process nor the outgoing timing holding process is executed, the excitation current does not increase in the incoming timing holding process and the outgoing timing holding process. As a result, the incoming timing holding process is performed when the elasticity of the sheet is weaker than the second elastic force. The heat generation of the stepping motor can be reduced as compared with the case of executing the above.

  The elasticity information acquisition unit that acquires information on the elasticity of the sheet as elasticity information; and the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is strong, and the first current value is It is preferable to further include an exciting current setting unit for increasing.

  The rotational torque that acts on the rotary guide member when the sheet collides with the guide passage increases as the elasticity of the sheet increases. Therefore, according to this configuration, as the elasticity of the sheet is increased by the excitation current setting unit, the excitation current value in the on-timing holding process is increased and the holding power of the stepping motor is increased, so the sheet collided with the guide path. The possibility that the rotary guide member rotates due to the rotational torque that is sometimes generated can be reduced.

  In addition, the elasticity information acquisition unit acquires a sheet type as to whether the sheet is plain paper or cardboard as the elasticity information, and the elasticity of the cardboard is set as the first elasticity. Is preferred.

  According to this configuration, when a thick paper having a higher elasticity than that of the plain paper is conveyed, the holding timing holding process is executed to increase the holding power of the stepping motor. Even when a larger rotational torque is generated than when the collision occurs in the guide passage, the possibility that the rotary guide member rotates can be reduced.

  The elasticity information acquisition unit acquires the type of the sheet as the elasticity information, whether the sheet is plain paper, thick paper, or a resin sheet, and the elasticity of the resin sheet is the first elasticity. And the elasticity of the cardboard may be set as the second elasticity.

  According to this configuration, when a resin sheet that is more elastic than plain paper or thick paper is conveyed, both the entry timing holding process and the exit timing holding process are executed, so that both the timing when the resin sheet enters the guide path and the timing when it exits. Since the holding power of the stepping motor is increased, the possibility that the rotary guide member rotates due to the collision or rebound of the resin sheet can be reduced. Further, when the thick paper having a lower elasticity than the resin sheet is conveyed, the exit timing holding process is not executed, so that the rotational torque applied to the rotary guide member becomes weaker than when the thick paper enters the guide passage. As a result of the excitation current at the timing being reduced from the resin sheet, the heat generation of the coil is reduced.

  In the image forming apparatus having such a configuration, the leading edge entry timing acquisition unit acquires the timing at which the leading edge of the sheet enters the entrance of the guide path and the sheet may collide with the guiding path and rotational torque may be applied to the rotary guide member. Is done. Then, since the motor control unit performs the entering timing holding process for holding the rotational position of the stepping motor by supplying the exciting current having the first current value to the stepping motor at the timing when the leading edge of the sheet enters the entrance. As a result of the holding force of the motor being larger than the detent torque, it is possible to reduce the possibility that the rotary guide member rotates with the rotational torque generated when the sheet collides with the guide path.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory front sectional view for explaining an outline of an embodiment of an image forming apparatus to which a sheet carry-out direction switching device according to the present invention is applied. FIG. 2 is an enlarged explanatory view showing a mechanism part of a carry-out direction switching device formed in the apparatus main body of the image forming apparatus shown in FIG. 1. FIG. 3 is a partially cutaway perspective view showing an embodiment of a carry-out direction switching unit shown in FIG. 2, showing a state viewed obliquely from above. It is a perspective view which shows the state which looked at the carrying-out direction switching part shown in FIG. 3 from diagonally downward. It is the VV sectional view taken on the line of the carrying out direction switching part shown in FIG. It is explanatory drawing of the front sectional view for demonstrating the paper guide attitude | position of a rotary guide member, (A) is the state in which the rotary guide member was set to the reference | standard attitude | position, (B) is a standing attitude of the rotary guide member. Each of these shows a state in which the posture is set. It is explanatory drawing of front sectional view for demonstrating the paper guide attitude | position of a rotary guide member, (A) is the state in which the rotary guide member was set to the inclination attitude | position for in-body discharge trays, (B) The rotary guide member is shown in a state where the posture is set to the posture for the reverse feed path. FIG. 2 is a block diagram illustrating an example of an electrical configuration of the image forming apparatus illustrated in FIG. 1. FIG. 9 is a circuit diagram illustrating an example of an excitation current switching circuit illustrated in FIG. 8. FIG. 10 is a circuit diagram showing a modification of the exciting current switching circuit shown in FIG. 9. 3 is a flowchart illustrating an example of an operation of the image forming apparatus illustrated in FIG. 1. 3 is a flowchart illustrating an example of an operation of the image forming apparatus illustrated in FIG. 1. 3 is a flowchart illustrating an example of an operation of the image forming apparatus illustrated in FIG. 1.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is an explanatory front sectional view for explaining an outline of a configuration of an image forming apparatus 10 including a sheet carry-out direction switching device 20 according to an embodiment of the present invention. 2 is an enlarged explanatory view around the carry-out direction switching unit 109, which is a mechanism part of the carry-out direction switching device 20 shown in FIG. The carry-out direction switching unit 109 is formed in the apparatus main body 11 of the image forming apparatus 10. 1 and 2, the XX direction is referred to as the left-right direction, and in particular, the -X direction is referred to as the left, and the + X direction is referred to as the right.

  An image forming apparatus 10 shown in FIG. 1 is a so-called in-body discharge type copying machine, and includes an image forming unit 12, a fixing unit 13, a sheet storage unit 14, and a discharge unit 15 in an apparatus main body 11. In addition, an image reading unit 16 and an operation unit 17 are provided. A part of the paper discharge unit 15 (an in-body paper discharge tray 151 to be described later) is formed by recessing a part of the apparatus main body 11 below the image reading unit 16. 10 is referred to as an in-body discharge type.

  The apparatus main body 11 includes a lower main body 111 having a rectangular parallelepiped shape in appearance, an upper main body 112 having a flat rectangular shape opposed to the upper portion of the lower main body 111, and the upper main body 112 and the lower main body 111. And a connecting portion 113 interposed therebetween. The connecting portion 113 is a structure for connecting the in-body discharge tray 151 of the discharge portion 15 between the lower main body 111 and the upper main body 112 to each other.

  The lower body 111 includes an image forming unit 12, a fixing unit 13, and a sheet storage unit 14, and an image reading unit 16 is mounted on the upper body 112. The operation unit 17 is provided at the front edge portion of the upper main body 112.

  The operation unit 17 receives an operation input related to the image forming process, and includes a numeric keypad for inputting the number of sheets P to be processed and other various operation keys 171, and an LCD (Liquid) for touch input. A touch panel 172 having a crystal display is provided.

  Further, the operation unit 17 determines whether the paper P (sheet) stored in a paper storage unit such as the paper storage unit 14 or the manual feed tray 18 is plain paper, cardboard, or OHP (OverHead Projector). Sheet type information related to the elasticity of the paper P (sheet), such as whether it is a transparent resin sheet, is received as elasticity information. In this case, the operation unit 17 corresponds to an example of a elasticity information acquisition unit. In the following description, a sheet member other than paper such as an OHP sheet is also described as paper P.

  The sheet storage unit 14 includes a detachable sheet cassette 141 provided immediately below the image forming unit 12 in the lower main body 111 and a large amount of detachable sheets provided further below the sheet cassette 141. And a large-capacity deck 142 that can store sheets P. In the present embodiment, the paper cassette 141 is provided in two stages, and the large capacity deck 142 is provided in two rows.

  When the image forming process is performed, the sheets P are fed out one by one from the sheet bundle P1 stored in the sheet cassette 141 or the large-capacity deck 142, and sent to the image forming unit 12 to the sheet P. An image forming process (printing process) is executed.

  The paper discharge unit 15 includes an in-body discharge tray (switchback tray) 151 formed between the lower main body 111 and the upper main body 112, and an out-body discharge tray (external tray) formed outside the apparatus main body 11. ) 152 and an in-cylinder finisher 153 provided at a position directly above the in-cylinder discharge tray 151. The toner image-transferred paper P sent from the image forming unit 12 passes through a carry-out direction switching unit 109 provided in the connecting unit 113, and the in-cylinder paper discharge tray 151, the discharge destination outside the cylinder, The paper is discharged toward either the paper tray 152 or the in-body finisher 153. The in-body finisher 153 performs post-processing such as punching and stapling on the discharged paper P.

  The in-body discharge tray 151 is used not only for discharging the paper P, but also when the paper P is subjected to the double-sided printing process, printing on the back side of the paper P for which the front side printing process has been completed. It is also used as a switchback tray for turning the paper P upside down for processing. In other words, the paper P on which the front side printing process has been completed is once discharged onto the in-body discharge tray 151, and then switched back with the latest leading edge so far, to the image forming unit 12. Returned. The paper P for which single-sided printing has been completed is subjected to a printing process on the back side by the image forming unit 12 and is discharged to the in-cylinder discharge tray 151 or the out-cylinder discharge tray 152.

  The image reading unit 16 includes a contact glass 161 mounted on the upper surface opening of the upper body 112 for placing a document, an openable / closable document pressing cover 162 for pressing the document placed on the contact glass 161, An automatic document reading unit 163 mounted on the document pressing cover 162 and a scanning mechanism 164 that scans an image of the document placed on the contact glass 161 are provided.

  An image of a document placed on the contact glass 161 or supplied onto the contact glass 161 by the automatic document reading unit 163 is read as analog information by the scanning mechanism 164 and then converted into a digital signal, which will be described later. The data is output toward the exposure unit 123 and used for image forming processing.

  Further, a manual feed tray 18 is provided at a position directly above the sheet storage unit 14 on the right surface of the lower main body 111. The lower side of the manual feed tray 18 is pivotally supported around a support shaft 181 and is positioned between a closed posture standing to close the manual feed port and an open posture protruding rightward. It can be changed. The manual feed tray 18 is used to manually feed the paper P one by one in a state where the posture is set to the open posture. The sheet P manually fed from such a manual tray 18 is sent out toward a nip portion between a photosensitive drum 121 and a transfer roller 125, which will be described later, via a sheet vertical conveyance path 101.

  A maintenance door 19 for maintenance that can be opened and closed is provided on the left surface of the lower main body 111. The out-body discharge tray 152 is provided at an upper position of the maintenance door 19. The paper P for which printing processing has been completed in the image forming unit 12 is selectively discharged to either the out-body discharge tray 152 or the in-body discharge tray 151.

  The image forming unit 12 is provided with a photosensitive drum 121 at a substantially central portion in the vertical direction and on the left side. The photosensitive drum 121 is uniformly charged on its peripheral surface by a charging unit 122 provided at a right position while rotating clockwise around the drum center.

  An exposure unit 123 that irradiates the peripheral surface of the photosensitive drum 121 with a laser beam based on the image information of the original image read by the image reading unit 16 is provided on the right side of the photosensitive drum 121. Then, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 121 by irradiation of the laser beam from the exposure unit 123. Toner is supplied from the developing unit 124 provided below the photosensitive drum 121 toward the electrostatic latent image, whereby a toner image along the electrostatic latent image is formed on the peripheral surface of the photosensitive drum 121. .

  On the photosensitive drum 121 on which the toner image is formed, the sheet P conveyed from the sheet cassette 141 or the large-capacity deck 142 moves up the sheet vertical conveyance path 101 extending in the vertical direction, and a resist for timing. It is fed through the roller pair 143. Then, the toner image on the peripheral surface of the photosensitive drum 121 is transferred to the sheet P that has reached the photosensitive drum 121 by the action of the transfer roller 125 arranged to face the photosensitive drum 121 on the left side. The sheet P on which the toner image is transferred is separated from the photosensitive drum 121 and sent to the fixing unit 13.

  After the transfer of the toner image to the paper P is completed, the photosensitive drum 121 continues to rotate in the clockwise direction, so that the peripheral surface is cleaned by the cleaning device 126 provided immediately above the photosensitive drum 121. It goes to the charging unit 122 for the image forming process.

  The fixing unit 13 includes a heating roller 131 having an energization heating element such as a halogen lamp therein, a fixing roller 132 disposed opposite to the heating roller 131 on the left side, and a tension between the fixing roller 132 and the heating roller 131. The fixing belt 133 is provided, and a pressure roller 134 is provided on the left side so as to face the surface of the fixing belt 133. The sheet P fed from the image forming unit 12 receives the heat of the heating roller 131 through the fixing belt 133 while passing through the nip portion between the fixing belt 133 and the pressure roller 134, thereby A fixing process of the toner image to the paper P is executed.

  The sheet P after the fixing process passes through the sheet discharge conveyance path 102 via the unloading direction switching unit 109 above the fixing unit 13 when the sheet P is for single-sided printing. In-cylinder discharge tray that is discharged to 152, discharged to the in-cylinder discharge tray 151 through the reciprocating conveyance path 103, and further used as a switchback tray through the reciprocating conveyance path 103 for duplex printing. 151 is temporarily discharged.

  In the case of double-sided printing, the single-sided printed paper P, the first half of which has been discharged to the in-body discharge tray 151 via the reciprocating conveyance path 103, is the reverse of the up-down direction provided in the maintenance door 19. The paper is reversely fed through the feeding / conveying path 104 and supplied again to the image forming unit 12 in a state where the front and back sides are reversed, and printing processing is performed on the back side. The paper P for which double-sided printing has been completed is discharged to the in-body discharge tray 151 or the out-body discharge tray 152.

  The maintenance door 19 is provided with a cover member 191 whose right surface is opposed to the left surface of the image forming unit 12 on the right side of the reverse feed path 104. The cover member 191 is held on the right side of the maintenance door 19. In the state where the maintenance door 19 is set to the closed posture, the paper is fed from the paper cassette 141, the large capacity deck 142, and the manual feed tray 18 between the right side of the cover member 191 and the left side of the image forming unit 12. A part of the vertical paper conveyance path 101 for conveying the paper P is formed.

  As shown in FIG. 2, the carry-out direction switching unit 109 is set in a space directly above the housing 135 of the fixing unit 13 and on the left side of the left side wall 151 a of the in-body discharge tray 151. On the upper right side of the carry-out direction switching unit 109, a first concave circular arc guide plate is provided below the upper edge of the left side wall 151a of the in-cylinder sheet discharge tray 151 and extending into the in-cylinder sheet discharge tray 151. 108 a is provided, and in the upper left part of the carry-out direction switching unit 109, a sheet P is formed in a concave arc shape so as to pass through the left side of the fixing unit 13 toward the lower reverse conveyance path 104. A second arc guide plate 108b is provided.

  A gap is formed between the left end portion of the first arc guide plate 108a and the right end portion of the second arc guide plate 108b so as to receive the paper P discharged upward from the fixing portion 13, and this gap An upper end conveyance path 101a as a part of the vertical sheet conveyance path 101 extending upward is formed at the top of the sheet.

  A switching guide member 107 having a substantially isosceles triangular shape is provided at a position immediately above the upper end conveying path 101a. The switching guide member 107 switches the discharge destination of the paper P sent out from the upper end conveyance path 101a between the in-cylinder finisher 153 and the out-cylinder discharge tray 152, and a portion corresponding to the apex of the isosceles triangle is downward. The posture is set so as to face.

  Then, the switching guide member 107 rotates in the clockwise direction around the guide shaft 107a that pivotally supports the approximate center of gravity, thereby guiding the paper P to the in-body finisher 153 along the right surface. Then, by rotating counterclockwise around the guide shaft 107a, the posture of the outer case discharge tray 152 can be changed between the posture toward the outer case discharge tray to guide the paper P along the left surface. Yes.

  That is, since the image forming process in the image forming unit 12 is completed and the sheet subjected to the fixing process in the fixing unit 13 is once led out to the carry-out direction switching unit 109 and then discharged to various places according to the purpose. is there. The carry-out direction switching unit 109 includes a rotary guide member 30 instead of the conventional triangular switching guide.

  A plurality of conveyance rollers are provided around the rotary guide member 30, and the paper P smoothly enters and exits the rotary guide member 30 by these conveyance rollers. As such a conveyance roller, a fixing unit outlet roller 106a provided at a position immediately before the rotary guide member 30 (a position immediately below) at the outlet position of the fixing unit 13 and a position below the first arc guide plate 108a (that is, a reciprocating conveyance). On the path 103) and immediately below the in-cylinder discharge tray 151 and below the first discharge roller 106b and the second arc guide plate 108b, which are responsible for discharging the paper P to the in-cylinder discharge tray 151. A reverse transfer path conveying roller 106c that is provided and handles the conveyance of the paper P toward the reverse transfer path 104, and a switching guide member 107 provided at a position immediately below the switching guide member 107 at the downstream end of the upper end conveying path 101a. A conveying roller 106d for a switching guide member that carries the sheet P toward the conveyance, and a second discharge roller 10 provided at the upstream end of the out-body discharge tray 152. And e, and a third discharge roller 106f is employed which is provided on the inlet side of the cylinder in the finisher 153.

  Various paper sensors are provided around the rotary guide member 30 in order to detect the conveyance state of the paper P via the rotary guide member 30. As such a sheet sensor, an upper fixing sensor 105a (front end timing acquisition unit, rear end timing acquisition unit) provided at the downstream end of the fixing unit 13 (upper part of the casing of the fixing unit 13), and in-body discharge A first discharge sensor 105 b provided at the inlet portion of the tray 151, a reverse feed sensor 105 c provided at the upstream end position of the reverse feed path 104, and a second discharge roller 106 e at the upstream end of the outside-body discharge tray 152. And a third discharge sensor 105e provided near the third discharge roller 106f on the inlet side of the in-body finisher 153.

  The sheet P sent out from the fixing unit 13 by the detection of the sheet P by these sensors and the preset operation of the carry-out direction switching unit 109 and the switching guide member 107 based on the detection result is directed toward a predetermined position. It will be carried out.

  Hereinafter, the carry-out direction switching unit 109 will be described with reference to FIGS. FIGS. 3 and 4 are partially cutaway perspective views showing an embodiment of the carry-out direction switching unit 109. FIG. 3 shows a state seen from diagonally above, and FIG. 4 shows a state seen from diagonally below. Show. FIG. 5 is a cross-sectional view taken along the line VV of the carry-out direction switching unit 109 shown in FIG. 3, in which the rotary guide member 30 is set to the reference posture S1 with a two-dot chain line, and the rotary guide member 30 with a solid line. Indicates the state in which the posture is set to the standing posture S2. 3 to 5, the X direction is referred to as the left-right direction, and the Y direction is referred to as the front-rear direction. In particular, -X is referred to as the left, + X is the right, -Y is the front, and + Y is the rear.

  First, as shown in FIG. 3, the carry-out direction switching unit 109 receives the paper P sent from the fixing unit 13 (FIG. 2) via the fixing unit outlet roller 106a, and moves the paper P toward a predetermined position. A rotary guide member 30 that guides the discharge of the paper P, a guide pulley 40 that is attached to the rotary guide member 30 and guides the toner image formed on the paper P so as not to be adversely affected, and the rotary guide member 30 A posture changing means 50 for changing the posture of the rotary guide member 30 by rotating forward and backward around a guide shaft (support shaft) 34, and a reference rotation position of the rotary guide member 30 whose posture is changed by the posture changing means 50 And a reference position detection unit 60 for detection.

  The rotary guide member 30 is fixed to the left arc guide plate 32 in a state where the rotary guide member 30 is juxtaposed in the front-rear direction, and a pair of left-right arc guide plates 32 laid between the side plates 31 in the front-rear direction. A plurality of guide fins 33, a pair of front and rear guide shafts 34 projecting concentrically from the approximate center of gravity of the front and rear side plates 31 in opposite directions, and the upper edges of the pair of side plates 31. Cover body 35.

  Each side plate 31 is formed by deforming each square-shaped portion after the basic shape in a front view is set to be substantially square. By installing the left and right arc guide plates 32 between the pair of side plates 31, the pair of arc guide plates 32 serve as a structural material, and the rotary guide member 30 is structurally formed firmly.

  The pair of arc guide plates 32 are formed such that their opposing surfaces bulge in an arc shape in the opposing direction when viewed from the front. The pair of arc guide plates 32 is set so that the distance in the left-right direction between the lower edge portions gradually decreases as it goes upward. Between the pair of arc guide plates 32, a guide passage 320 for guiding the paper P sent from the fixing unit 13 is formed.

  A receiving opening 321 (inlet) for receiving the paper P led out from the fixing unit 13 is formed between the lower edge portions of the pair of arc guide plates 32, and a discharge opening for discharging the paper P between the upper edge portions. 322 (exit) is formed. Then, the paper P led out from the fixing unit 13 is introduced between the pair of arc guide plates 32 from the receiving opening 321 via the fixing upper sensor 105a, and a discharge opening described later provided in the discharge opening 322 and the cover body 35. It is discharged upward through 351 (exit). Where the paper P discharged from the discharge port 351 through the guide passage 320 of the rotary guide member 30 is directed thereafter is determined in advance according to the attitude of the rotary guide member 30, This will be described in detail later.

  The guide fins 33 are reversely conveyed from the in-body discharge tray 151 temporarily stored in a state in which the rotary guide member 30 is set in a posture S4 (refer to FIG. 7B) for a reverse conveyance path, which will be described later. This is for receiving and guiding the double-sided printing paper P to be printed on the back side toward the path 104. The guide fins 33 are formed in a circular arc shape whose upper edge surface is convex upward in the same manner as the upper edge surface of the side plate 31 in the state set in the posture S4 for the reverse feed path (FIG. 7B). Thus, an upstream end portion of the reverse feed path 104 is formed between the second arc guide plate 108b formed in a concave arc shape below.

  A pair of guide shafts 34 concentrically projecting in opposite directions from the pair of side plates 31 are supported by an unillustrated frame of the apparatus body 11, and are rotated about the axis by driving the posture changing means 50. The guide member 30 can be rotated forward and backward integrally.

  The cover body 35 is for preventing foreign matters such as dust from entering the rotary guide member 30, and covers the upper portion of the rotary guide member 30 as shown in FIG. 31 between the upper edges in FIG. A discharge port 351 (exit) extending in the front-rear direction for discharging the paper P is provided at the top of the cover body 35 at a position facing the discharge opening 322 of the pair of arc guide plates 32.

  A plurality of pairs of guide pulleys 40 are provided on the front and rear sides of the pair of left and right arc guide plates 32. The plurality of pairs of guide pulleys 40 rotate around a pair of left and right pulley shafts 41 installed between the pair of side plates 31 in a state of penetrating each guide fin 33 at positions on the left and right sides of the pair of left and right arc guide plates 32. It is supported freely.

  On the other hand, the left and right arc guide plates 32 are provided with through windows 323 as shown in FIG. 4 at positions corresponding to the respective guide pulleys 40. A part of each of the pair of guide pulleys 40 enters the guide passage 320 between the pair of arc guide plates 32 through a part of the through windows 323, whereby the peripheral surface of each guide pulley 40 is guided to the guide passage. 320 are in a state of facing each other.

  Accordingly, the sheet P led out from the fixing unit 13 is introduced between the pair of arc guide plates 32 through the receiving opening 321, and the image forming surface of the sheet P contacts the pair of arc guide plates 32. Without passing between the peripheral surfaces of the left and right guide pulleys 40. At this time, even if the image forming surface of the paper P contacts the peripheral surface of the guide pulley 40, the guide pulley 40 rotates around the pulley shaft 41 due to this contact, so the original forming surface of the paper P becomes the arc guide plate. No sliding contact with the inner surface of 32 occurs. Therefore, it is possible to effectively prevent the occurrence of inconvenience that the image is disturbed when the document forming surface of the paper P is brought into sliding contact.

  The posture changing means 50 is for setting the posture of the rotary guide member 30 based on a control signal from the control unit 200 described later. The posture changing means 50 is fixed to the stepping motor 51, the drive gear 52 that is concentrically and externally fitted to the drive shaft 511 of the stepping motor 51, and the rear guide shaft 34 so as to be integrally rotatable. In addition, a sect gear 53 that meshes with the drive gear 52 is provided.

  Since the stepping motor 51 is configured such that the rotation angle is set according to the number of pulses of the pulse signal, the stepping motor 51 supplies the stepping motor 51 with a signal having a pulse number set in advance according to the purpose. The rotation angle of the motor 51, that is, the attitude of the rotary guide member 30 is controlled very precisely.

  Therefore, when the stepping motor 51 is used, as in the conventional case, for example, when the guide destination is changed by changing the posture of the predetermined guide member by turning on / off the power supply to the solenoid. In comparison with this, the posture can be changed with extremely high accuracy, and there is no inconvenience that abnormal noise occurs.

  The stepping motor 51 is installed horizontally on the rear upper portion of the rotary guide member 30 so that the drive shaft 511 faces forward. The driving force of the stepping motor 51 is transmitted to the rotary guide member 30 via the drive gear 52 and the sect gear 53. Accordingly, when the stepping motor 51 is driven forward / reversely, the rotary guide member 30 is rotated forward / reversely around the guide shaft 34 to change its posture.

  The reference position detection unit 60 is set to a reference position S1 (FIG. 6A) in which the light shielding piece 61 projecting radially outward from the sect gear 53 and the rotary guide member 30 is the home position. And a light sensor 62 disposed on a rotation locus around the guide shaft 34 of the light shielding piece 61 so as to face the light shielding piece 61 in the state where the light shielding piece 61 is opposed.

  The optical sensor 62 is a so-called photointerrupter configured by arranging a light emitting element 623 and a light receiving element 624 to face each other on a bifurcated support case 621 having a pair of element support arms 622.

  In the support case 621, each element support arm 622 sandwiches the rotation locus of the light shielding piece 61, and the light shielding piece 61 is positioned between the pair of element support arms 622 in a state where the rotary guide member 30 is set to the reference posture S1. The installation position is set so as to. The light emitting element 623 is provided on one element support arm 622, and the light receiving element 624 is provided on the other element support arm 622 and is disposed to face the light emitting element 623.

  Therefore, when the rotary guide member 30 is not set to the reference posture S1, the light emitted from the light emitting element 623 is received by the light receiving element 624, and thus the rotary guide member 30 is not set to the reference posture S1. Can be detected.

  On the other hand, when the rotary guide member 30 is set to the reference posture S1, the light shielding piece 61 is positioned between the pair of element support arms 622, and the light from the light emitting element 623 is shielded by the light shielding piece 61. Therefore, the light receiving element 624 is turned off. Accordingly, it can be detected that the rotary guide member 30 is set to the reference posture S1.

  In addition, with the rotation position of the stepping motor 51 when the light receiving element 624 is turned off as a reference position, an excitation pulse is supplied from the reference position to the stepping motor 51, so that only a desired rotation angle is obtained according to the number of excitation pulses. The stepping motor 51 can be rotated to bring the rotary guide member 30 into a desired posture.

  Hereinafter, the sheet guide posture of the rotary guide member 30 will be described with reference to FIGS. 6 and 7. 6 and 7 are explanatory views in front sectional view of the rotary guide member 30 for explaining the sheet guide posture of the rotary guide member 30. FIG. 6A shows a state in which the rotary guide member 30 is set to the reference posture S1, and FIG. 6B shows a state in which the rotary guide member 30 is set to the standing posture S2.

  7A shows a state in which the rotary guide member 30 is set in the inclined posture S3 for the in-body discharge tray, and FIG. 7B shows the rotary guide member 30 in the posture S4 for the reverse feed path. Each state in which the posture is set is shown. 6 and 7 is the same as that shown in FIG. 1 (−X: leftward, + X: rightward).

  First, as shown in FIG. 6A, when the rotary guide member 30 is set to the reference posture S1, the rotary guide member 30 guides the guide passage 320 between the pair of arc guide plates 32 from the vertical position. It rotates about 30 ° counterclockwise around the shaft 34, and is tilted leftward.

  In this state, the light shielding piece 61 fixed to the sect gear 53 is positioned between the pair of element support arms 622 of the optical sensor 62, and light from the light emitting element 623 (FIG. 3) is shielded and incident on the light receiving element 624. It is gone. Accordingly, it is detected that the rotary guide member 30 is set to the reference posture S1, and the reference position of the stepping motor is detected.

  As shown in FIG. 6B, when the rotary guide member 30 is set in the standing posture S2, the discharge port 351 is positioned at a position facing the upper end conveyance path 101a. In the standing posture S2, the sheet P led out from the fixing unit 13 is introduced into the guide passage 320 of the rotary guide member 30 from the receiving opening 321 through the upper fixing sensor 105a, passes between the pair of guide pulleys 40, and is discharged. It is discharged from the outlet 351 toward the upper upper end conveying path 101a.

  Thereafter, the paper P is directly discharged to the outside-cylinder discharge tray 152 or once discharged to the in-cylinder finisher 153 and subjected to post-processing such as stapling, and then discharged to the outside-cylinder discharge tray 152 as a sheet bundle. Or

  Further, as shown in FIG. 7A, when the rotary guide member 30 is set to the inclined posture S3 for the in-body discharge tray, the discharge port 351 is positioned at a position facing the discharge roller 106b. In the inclining posture S3 for the in-body discharge tray, the paper P led out from the fixing unit 13 passes through the guide passage 320 of the rotary guide member 30, passes through the discharge port 351, and is guided to the first arc guide plate 108a. The paper is discharged to the in-body discharge tray 151. The inclining posture S3 for the in-body discharge tray is also used when performing switchback for reversing the paper P when the double-sided printing is performed on the paper P.

  As shown in FIG. 7B, when the rotary guide member 30 is set to the posture S4 for the reverse feed path, the guide fins 33 are provided between the first discharge roller 106b and the reverse feed path 104. Arranged so as to span. As a result, in the switchback when performing double-sided printing, the paper P that has been reversely fed from the in-body paper discharge tray 151 side by the first discharge roller 106b is guided by the guide fins 33 and conveyed to the reverse conveyance path 104. Has been made possible.

  FIG. 8 is a block diagram showing an example of the electrical configuration of the image forming apparatus 10 shown in FIG. The image forming apparatus 10 includes a control unit 200 and an excitation current switching circuit 400 in addition to the above-described mechanism unit. In FIG. 8, various rollers for transporting paper, switching guides, and the like are collectively described as a transport mechanism 120.

  The control unit 200 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And a timer circuit and peripheral circuits thereof. The control unit 200 is connected to the image reading unit 16, the image forming unit 12, the fixing unit 13, the transport mechanism 120, and the operation unit 17.

  Various sensors such as the optical sensor 62 and the upper fixing sensor 105a are connected to the control unit 200. Further, a stepping motor 51 is connected to the control unit 200 via an exciting current switching circuit 400. The control unit 200 functions as a copy control unit 201, a motor control unit 202, an excitation current setting unit 203, and a sheet type storage unit 204 by executing a control program stored in a ROM, for example.

  In this case, the carry-out direction switching unit 109, the excitation current switching circuit 400, the operation unit 17, the upper fixing sensor 105a, the motor control unit 202, the excitation current setting unit 203, and the sheet type storage unit 204 are examples of the carry-out direction switching device 20. Is configured. The motor control unit 202 may be configured using, for example, an ASIC (Application Specific Integrated Circuit).

  The fixing upper sensor 105a has a lever shape. When the sheet P is discharged from the fixing unit 13 by the fixing unit exit roller 106a, the upper fixing sensor 105a is pushed up by the sheet P, the upper fixing sensor 105a is turned on, and the sheet P is detected. When the paper P is transported and the trailing edge of the paper P exceeds the position of the upper fixing sensor 105a, the upper fixing sensor 105a returns to the original position and turns off.

  Thus, the fixing sensor 105a is turned on while the sheet P passes through the position of the fixing upper sensor 105a, that is, the position where the sheet P that has come out of the fixing unit 13 enters the receiving opening 321 of the guide passage 320. Therefore, the timing at which the fixing upper sensor 105a changes from OFF to ON indicates the timing at which the leading edge of the paper P enters the receiving opening 321, and the timing at which the fixing upper sensor 105a changes from ON to OFF is at the trailing edge of the paper P. The timing for entering the receiving opening 321 is shown.

  The fixing upper sensor 105a is not necessarily a lever type sensor, and may be a paper sensor using, for example, an optical sensor or an electrostatic sensor.

  A copy control unit 201 controls the operation of each unit in the apparatus and executes copying of a document image. Specifically, the copy control unit 201 transports the paper P by the transport mechanism 120 and transmits image data read from the original by the image reading unit 16 to the image forming unit 12. Image formation on P is executed.

  The sheet type storage unit 204 is configured using, for example, a RAM. Then, the user uses the operation unit 17 to select the type of paper P accommodated in the manual feed tray 18, each paper cassette 141, and each large capacity deck 142, for example, the paper P is plain paper or thick paper. If the sheet type information related to the elasticity of the paper P (sheet) such as OHP (OverHead Projector) transparent resin sheet (hereinafter referred to as OHP sheet) is input, this type information is stored in the sheet type. It is stored in the unit 204 as elasticity information.

  In this case, the elasticity of the OHP sheet corresponds to an example of the first elasticity, and the elasticity of the thick paper corresponds to an example of the second elasticity.

  The exciting current setting unit 203 obtains an exciting current value I1 (first current value), an exciting current value I2 (second current value), and an exciting current value I3 (third current value) for exciting the coil of the stepping motor. The setting is made based on the elasticity information stored in the sheet type storage unit 204. Specifically, when the paper P accommodated in the paper accommodating portion to be used for printing is a transparent resin sheet, the exciting current setting unit 203 sets the exciting current values I1, I3, and I2 to the largest currents. Set to value.

  Thereafter, the excitation current setting unit 203 sets the excitation current values I1, I3, and I2 so that the current value gradually decreases in the order of thick paper and plain paper, and the current value becomes the smallest on plain paper. The excitation current values I1, I3, and I2 are set by the excitation current setting unit 203 so that I1> I3> I2. The exciting current value I2 may be set to zero.

  In this case, since the transparent resin sheet has the strongest (stiff) elasticity, then the thick paper has the strongest elasticity, and the plain paper has the weakest (soft) elasticity, the elasticity information stored in the sheet type storage unit 204 is The stronger the elasticity of P is, the more exciting current values I1, I3, and I2 are increased by the exciting current setting unit 203.

  FIG. 9 is a circuit diagram showing an example of the excitation current switching circuit 400 shown in FIG. The excitation current switching circuit 400 shown in FIG. 9 includes a motor driver 401 and an analog / digital (A / D) converter 402.

  The motor driver 401 is a general-purpose driver IC (Integrated Circuit) for driving a stepping motor, for example, and A, B, A ′, B in the stepping motor 51 according to pulse control signals SA and SB output from the control unit 200. The stepping motor 51 is rotated by the rotation angle corresponding to the number of pulses of the pulse control signals SA and SB by outputting the excitation current of each phase of 'in the form of pulses.

  Specifically, the motor driver 401 outputs the A phase excitation current in the stepping motor 51 and the A ′ phase that is the reverse phase of the A phase in response to the pulse control signal SA. In addition, the motor driver 401 outputs an excitation current of the B phase in the stepping motor 51 and a B ′ phase that is an inverted phase of the B phase in response to the pulse control signal SB. Further, the motor driver 401 sets the excitation current values of the A phase, the B phase, the A ′ phase, and the B ′ phase so as to be proportional to the reference voltage Vref, for example, according to the reference voltage Vref input to the Vref terminal 403. To do.

  The analog-digital converter 402 outputs a voltage corresponding to the control signal output by the motor control unit 202 to the Vref terminal 403 of the motor driver 401 as the reference voltage Vref.

  Returning to FIG. 8, the motor control unit 202 increases the holding power of the stepping motor 51 by increasing the excitation current at the timing when the leading edge of the paper P enters the receiving opening 321 of the rotary guide member 30 according to the elasticity of the paper P. An input timing holding process, a passing timing holding process for reducing the excitation current while the leading edge of the paper P passes through the guide path 320, and a timing at which the trailing edge of the paper P is discharged from the discharge port 351 of the rotary guide member 30. An output timing holding process for increasing the holding power of the stepping motor 51 by increasing the excitation current is executed.

  Specifically, the motor control unit 202 determines that the leading edge of the paper P enters the receiving opening 321 and stops the stepping motor 51 when the upper fixing sensor 105a changes from OFF to ON in the input timing holding process. The excitation current of the excitation current value I1 is supplied to the stepping motor 51 by outputting the reference voltage Vref corresponding to the excitation current value I1 from the analog-digital converter 402 for the preset on / hold time t1. As a result, the holding force of the stepping motor 51 increases.

  The on-holding time t1 is, for example, 0.1 second, for example, from the time when the upper fixing sensor 105a is turned on until the leading edge of the paper P hits the arc guide plate 32 in the receiving opening 321 and is guided to the guide passage 320 Is preset.

  In the passage timing holding process, the motor control unit 202 keeps the leading edge of the sheet P passing through the guide path 320 until the upper fixing sensor 105a is turned off after the entry holding time t1 in the entry timing holding process has elapsed. The analog-digital converter 402 outputs the reference voltage Vref corresponding to the excitation current value I2 to supply the excitation current having the excitation current value I2 to the stepping motor 51. If it does so, the exciting current which flows into the coil of the stepper motor 51 will decrease, and the heat_generation | fever of a stepper motor will reduce.

  Then, when the upper fixing sensor 105a changes from on to off in the exit timing holding process, the motor control unit 202 determines that the rear end of the paper P is immediately before being discharged from the discharge port 351, and the stepping motor 51, the reference voltage Vref corresponding to the excitation current value I3 is output from the analog-digital converter 402 for a preset output holding time t2, while the excitation current of the excitation current value I3 is supplied to the stepping motor 51. Supply. As a result, the holding force of the stepping motor 51 increases. In this case, the output holding time t2 is slightly longer than the time required for the trailing edge of the paper P to be conveyed from the position of the upper fixing sensor 105a and exit the discharge port 351, and is given as a time with some allowance, for example. 0.3 seconds is preset.

  Note that a reference voltage generation circuit 404 may be provided instead of the analog-digital converter 402 as in the excitation current switching circuit 400a shown in FIG. In the excitation current switching circuit 400a, the control unit 200a does not include the excitation current setting unit 203, and accordingly, the excitation current values I1, I3, and I2 are fixedly set.

  The reference voltage generation circuit 404 shown in FIG. 10 includes resistors R1 to R8 and transistors Q1 and Q2. Then, the DC 5V voltage is divided by a series circuit of a resistor R1 and a resistor R2, and the divided voltage is input to the Vref terminal 403 as a reference voltage Vref. The Vref terminal 403 is connected to the ground via the resistor R3 and the transistor Q1. The base and emitter of the transistor Q1 are connected by a resistor R6, and the base of the transistor Q1 is connected to the controller 200a via a resistor R5. When the motor control unit 202 sets the pulse control signal K1 to the high level, the transistor Q1 is turned on.

  The Vref terminal 403 is connected to the ground via the resistor R4 and the transistor Q2. The base and emitter of the transistor Q2 are connected by a resistor R8, and the base of the transistor Q1 is connected to the control unit 200 via a resistor R7. When the motor control unit 202 sets the pulse control signal K2 to a high level, the transistor Q2 is turned on.

  For example, the resistor R1 is 1 kΩ, and the resistors R2 to R4 are 4 kΩ. In this case, when the motor control unit 202 sets the pulse control signals K1 and K2 to the low level, the transistors Q1 and Q2 are turned off and 5V is divided by 1 kΩ and 4 kΩ, so that the reference voltage Vref becomes 4V. . Similarly, when the motor control unit 202 sets the pulse control signal K1 to the high level and the pulse control signal K2 to the low level, the transistor Q1 is turned on, the transistor Q2 is turned off, and 5V is divided by 1 kΩ and 2 kΩ. The reference voltage Vref is 3.3V. When the motor control unit 202 sets the pulse control signals K1 and K2 to the high level, the transistors Q1 and Q2 are turned on and 5V is divided by 1 kΩ and 4/3 kΩ, so that the reference voltage Vref is 2. 9V.

  In this case, the excitation current of the stepping motor 51 output from the motor driver 401 when the transistors Q1 and Q2 are turned off is set to the excitation current value I1, and from the motor driver 401 when one of the transistors Q1 and Q2 is turned on. The output current of the stepping motor 51 is set to the excitation current value I3, and the resistance of the stepping motor 51 output from the motor driver 401 when the transistors Q1 and Q2 are turned on becomes the excitation current value I2. Resistance values of R1 to R4 are set.

  Accordingly, the reference voltage Vref can be generated by the reference voltage generation circuit 404 using a resistor or a transistor without providing the analog-digital converter 402, so that the cost can be reduced.

  Next, the operation of the image forming apparatus 10 configured as described above will be described. 11, 12, and 13 are flowcharts showing an example of the operation of the image forming apparatus 10 shown in FIG. First, for example, when the user depresses the operation key 171 to copy the document, the copy control unit 201 controls the operations of the image reading unit 16, the image forming unit 12, the fixing unit 13, and the transport mechanism 120 to form an image. Is started (step ST1).

  Next, the number of pulses required for positioning the rotary guide member 30 by the motor control unit 202 in a posture corresponding to the discharge destination of the paper P and the job setting contents such as single-sided printing or double-sided printing. Pulse control signals SA and SB are output to the motor driver 401. Then, the excitation current of each phase of the stepping motor 51 is output from the motor driver 401 in response to the pulse control signals SA and SB, and the stepping motor 51 is driven. As a result, the rotary guide member 30 corresponds to the job setting content. Positioned to the posture (step ST2).

  Next, whether or not the posture of the rotary guide member 30 is set to any one of the standing posture S2 and the inclined posture S3 for the in-body discharge tray by the motor control unit 202, that is, the discharge port 351 is the upper end conveyance path. It is confirmed whether or not it faces either 101a or the reciprocating conveyance path 103 (step ST3).

  If the posture of the rotary guide member 30 is neither the standing posture S2 nor the inclined posture S3 for the in-body discharge tray (NO in step ST3), the process is terminated. On the other hand, if the posture of the rotary guide member 30 is one of the standing posture S2 and the inclining posture S3 for the in-body discharge tray (YES in step ST3), it is stored in the sheet type storage unit 204 by the motor control unit 202. The type information of the current sheet is confirmed (steps ST4 and ST5).

  If the paper P stored in the paper storage unit used for image formation is an OHP sheet (YES in step S4), the stepping motor 51 should be held with a holding force corresponding to the most elastic sheet. If the paper P stored in the paper storage unit used for image formation is a thick paper (NO in step ST4 and YES in step ST5), the process proceeds to step ST21, and the sheet P is held according to a medium elastic sheet. The process proceeds to step ST31 to hold the stepping motor 51 by force. If the paper P stored in the paper storage unit used for image formation is plain paper (NO in step ST4, NO in step ST5), the stepping motor 51 has a holding force corresponding to the sheet having the smallest elasticity. To step ST6.

  First, when the paper P stored in the paper storage unit used for image formation is an OHP sheet (YES in step S4), in step ST21, the excitation current setting unit 203 causes the excitation current values I1, I3, I2 is set to current values I1max, I3max, and I2max, respectively.

  The current value I1max is the same even when the strong OHP sheet is discharged from the fixing unit 13 by the fixing unit exit roller 106a and the leading end of the OHP sheet hits the arc guide plate 32 in the receiving opening 321. An exciting current value is set that can cause the stepping motor 51 to generate a holding force that can prevent the rotary guide member 30 from rotating due to the rotational torque caused by being pressed.

  The current value I3max is set as follows. That is, since the paper P is bent by the rotary guide member 30 so as to change the conveyance direction, when the rear end of the paper P comes out of the discharge port 351, the rear end of the paper P tries to return to its original state due to its elasticity. Rebound. The current value I3max is a rotational torque caused by being pushed by the OHP sheet, even when the trailing end of the strongly elastic OHP sheet pushes the discharge port 351 with a force of coming out of the discharge port 351 and returning straight. An exciting current value that can cause the stepping motor 51 to generate a holding force that can prevent the rotary guide member 30 from rotating is set.

  In this case, the rotational torque generated in the rotary guide member 30 when the leading end of the OHP sheet hits the circular arc guide plate 32 in the receiving opening 321 is greater than the rotational torque generated in the rotary guide member 30 when the OHP sheet returns straight. Since it is larger, the current value I1max is set to a current value larger than the current value I3max.

  The current value I2max is a rotation that is applied to the rotary guide member 30 by rotating the guide pulley 40 when the elastic OHP sheet passes through the guide path 320 or by the sheet contacting the arc guide plate 32. An exciting current value that can cause the stepping motor 51 to have a holding force that can prevent the rotary guide member 30 from rotating by torque is set.

  In this case, since the rotational torque generated when passing through the guide passage 320 is smaller than the torque generated when the sheet enters the receiving opening 321 or exits from the discharge port 351, the current value I2max is the current value I1max and the current value I3max. A smaller current value is set.

  Next, it is confirmed by the motor control unit 202 whether or not the upper fixing sensor 105a is turned on (step ST22). When the upper fixing sensor 105a is turned on (YES in step ST22), it means the timing immediately before the leading edge of the sheet P hits the position of the upper fixing sensor 105a, that is, the arc guide plate 32 in the receiving opening 321. Thus, the pulse control signals SA and SB are output so as to flow the excitation current of the phase that can hold the stepping motor 51 at the current position, and the excitation current switching circuit is used to set the excitation current of the stepping motor 51 to the excitation current value I1. An instruction signal is output to 400.

  Then, the excitation current switching circuit 400 outputs the excitation currents of the A, B, A ′, B ′ phases so as to hold the stepping motor 51 in the stopped state, and the excitation current value of the phase through which the current flows becomes the excitation current value. The current value I1 is set (step ST23).

  As a result, the holding torque can be increased by increasing the excitation current of the stepping motor 51 to the excitation current value I1 at the timing when the rotational torque is applied to the rotary guide member 30 when the leading edge of the paper P hits the arc guide plate 32. Therefore, the possibility that the rotary guide member 30 rotates can be reduced.

  Next, the motor control unit 202 outputs an instruction signal to the excitation current switching circuit 400 to reduce the excitation current of the stepping motor 51 to the excitation current value I2 after the on-holding time t1 has elapsed since the upper fixing sensor 105a is turned on. (Step ST24). Then, the excitation current switching circuit 400 reduces the excitation current value of the phase through which the current flows to the excitation current value I2.

  When the on-holding time t1 elapses after the upper fixing sensor 105a is turned on, the paper P is guided by the arc guide plate 32 and passes through the guide passage 320. As a result, the rotational torque acting on the rotary guide member 30 is reduced. Therefore, by reducing the excitation current of the stepping motor 51 to the excitation current value I2, heat generation of the stepping motor 51 is reduced while maintaining the posture of the rotary guide member 30. can do.

  Next, whether or not the upper fixing sensor 105a is turned off is confirmed by the motor control unit 202 (step ST25). When the upper fixing sensor 105a is turned off (YES in step ST25), the rear end of the sheet P is immediately before the position of the upper fixing sensor 105a, that is, immediately before the receiving opening 321, and a slight time passes through the guide passage 320. Later, it means that the trailing edge of the paper P exits the discharge port 351.

  Therefore, the motor control unit 202 outputs the pulse control signals SA and SB so as to flow the excitation current of the phase that can hold the stepping motor 51 at the current position, and increases the excitation current of the stepping motor 51 to the excitation current value I3. An instruction signal is output to the exciting current switching circuit 400 in order to do this. Then, the exciting current switching circuit 400 increases the exciting current value of the phase through which the current flows to the exciting current value I3 (step ST26).

  As a result, the exciting current of the stepping motor 51 is increased to the exciting current value I3 at the timing when the trailing edge of the strong elastic OHP sheet pushes the discharging port 351 with the force of going out from the discharging port 351 and returning straight. Since the holding torque can be increased, the possibility that the rotary guide member 30 rotates can be reduced.

  Next, the motor control is performed after the elapse of the holding time t2 after the fixing upper sensor 105a is turned off, that is, at the timing when the paper P comes out of the discharge port 351 and the rear end of the paper P does not press the rotary guide member 30. The unit 202 sets the pulse control signals SA and SB to the low level. Then, the excitation current of each phase of the stepping motor 51 is made zero by the motor driver 401, and the stepping motor 51 is held with the detent torque (step ST27).

  In this case, when there is no possibility that the rotational torque due to the conveyance of the paper P acts on the rotary guide member 30, the excitation current is set to zero and the stepping motor 51 is held with the detent torque. While maintaining this posture, the heat generation of the stepping motor 51 can be reduced.

  Next, the operation when the paper P stored in the paper storage unit used for image formation is thick paper will be described. In this case, in step ST31, the excitation current setting unit 203 sets the excitation current values I1, I3, and I2 to the current values I1mid, I3mid, and I2mid, respectively.

  The current value I1mid is determined even when the thick paper having a medium elasticity is discharged from the fixing unit 13 by the fixing unit outlet roller 106a and the leading end of the thick paper hits the arc guide plate 32 in the receiving opening 321. An exciting current value is set that can cause the stepping motor 51 to generate a holding force that can prevent the rotary guide member 30 from rotating due to the rotational torque caused by being pressed.

  The current value I3mid is a rotational torque caused by being pushed with thick paper even when the trailing edge of the thick paper having a moderately strong elasticity pushes the discharge port 351 with a force of coming out from the discharge port 351 and returning straight. Thus, an exciting current value that can cause the stepping motor 51 to have a holding force that can prevent the rotary guide member 30 from rotating is set.

  In this case, the rotational torque generated in the rotary guide member 30 when the leading end of the thick paper hits the arc guide plate 32 in the receiving opening 321 is larger than the rotational torque generated in the rotary guide member 30 when the thick paper tries to return straight. The current value I1mid is set to be larger than the current value I3mid.

  The current value I2mid is added to the rotary guide member 30 by rotating the guide pulley 40 when the thick elastic paper having a moderate elasticity passes through the guide passage 320 or the sheet contacts the arc guide plate 32. An exciting current value that can cause the stepping motor 51 to have a holding force that can prevent the rotary guide member 30 from rotating by the generated rotational torque is set.

  In this case, since the rotational torque generated when passing through the guide passage 320 is smaller than the torque generated when the sheet enters the receiving opening 321 or exits from the discharge port 351, the current value I2mid is the current value I1mid and the current value I3mid. A smaller current value is set.

  Since the elasticity of the cardboard is smaller than that of the OHP sheet, the current values I1mid and I3mid are set such that the current value I1mid is smaller than the current value I1max, the current value I3mid is smaller than the current value I3max, and the current value I2mid is smaller than the current value I2max. , I2mid is set.

  Hereinafter, steps ST32 to ST34 are the same as steps ST22 to ST24, and thus the description thereof is omitted. Here, since the current values I1mid, I3mid, and I2mid are set to current values smaller than the current values I1max, I3max, and I2max, the excitation current values I1, I3, and I2 in steps ST32 to ST34 are set in steps ST22 to ST24. It becomes smaller than exciting current values I1, I3, and I2. Therefore, the excitation current can be reduced while reducing the possibility that the rotary guide member 30 rotates according to the elasticity of the paper P.

  Next, steps ST35 and ST36 similar to steps ST25 and ST27 are executed.

  Here, the rotational torque that acts on the rotary guide member 30 at the timing when the paper P exits from the discharge port 351 is smaller than the rotational torque that acts on the rotary guide member 30 at the timing when the paper P enters the receiving opening 321. When the paper P is a thick paper, the rotational torque acting on the rotary guide member 30 is smaller than when the paper P is an OHP sheet. Therefore, when the paper P is a thick paper, the output timing holding process for increasing the excitation current at the timing when the paper P exits from the discharge port 351 is not executed, and the rotary current can be maintained even if the excitation current is maintained at the excitation current value I2. The guide member 30 may not be rotated.

  In such a case, the excitation current can be reduced while reducing the possibility that the rotary guide member 30 rotates by executing steps ST35 and ST36 without executing the output timing holding process corresponding to step ST26. it can.

  Of course, the same processing as step ST26 may be executed after step ST35. Even when the same processing as in step ST26 is executed, the excitation current value I3 in this case is smaller than the excitation current value I3 in step ST26. Therefore, the excitation current can be reduced while reducing the possibility that the rotary guide member 30 rotates according to the elasticity of the paper P.

  Next, the operation when the paper P stored in the paper storage unit used for image formation is plain paper will be described. In this case, in step ST6, the excitation current setting unit 203 sets the excitation current values I1, I3, and I2 to the current values I1min, I3min, and I2min, respectively.

  The current value I1min is the same even when the plain paper having low elasticity is discharged from the fixing unit 13 by the fixing unit exit roller 106a and the leading edge of the plain paper hits the arc guide plate 32 in the receiving opening 321. An exciting current value is set that can cause the stepping motor 51 to generate a holding force that can prevent the rotary guide member 30 from rotating due to the rotational torque caused by being pressed.

  The current value I3min is a rotational torque caused by being pressed with plain paper even when the trailing edge of the plain paper with weak elasticity pushes the discharge port 351 with a force of coming out of the discharge port 351 and returning straight. An exciting current value that can cause the stepping motor 51 to generate a holding force that can prevent the rotary guide member 30 from rotating is set.

  In this case, the rotational torque generated in the rotary guide member 30 when the leading edge of the plain paper hits the circular arc guide plate 32 in the receiving opening 321 is greater than the rotational torque generated in the rotary guide member 30 as the plain paper tries to return straight. Since it is large, the current value I1min is set to a current value larger than the current value I3min.

  The current value I2min is a rotation applied to the rotary guide member 30 by rotating the guide pulley 40 when plain paper having weak elasticity passes through the guide path 320 or the sheet contacts the arc guide plate 32. An exciting current value that can cause the stepping motor 51 to have a holding force that can prevent the rotary guide member 30 from rotating by torque is set.

  In this case, since the rotational torque generated when passing through the guide passage 320 is smaller than the torque generated when the sheet enters the receiving opening 321 or exits from the discharge port 351, the current value I2min is the current value I1min and the current value I3min. A smaller current value is set.

  Further, since the elasticity of plain paper is smaller than that of OHP sheets and thick paper, the current value I1min is smaller than the current values I1max and I1mid, the current value I3min is smaller than the current values I3max and I3mid, and the current value I2min is smaller than the current values I2max and I2mid. The current values I1min, I3min, and I2min are set so that

  Next, step ST7 similar to step ST22 is executed. Here, when the paper P is plain paper, the rotational torque acting on the rotary guide member 30 is smaller than when the paper P is an OHP sheet or thick paper. Therefore, when the paper P is plain paper, the entrance timing holding processing for increasing the excitation current at the timing when the leading edge of the paper P enters the receiving opening 321 and the excitation current at the timing when the paper P exits from the discharge port 351. Even if none of the output timing holding processing is executed and the exciting current is maintained at the exciting current value I2, there is a case where the rotary guide member 30 may not rotate.

  In such a case, the motor control unit 202 outputs the pulse control signals SA and SB so that the excitation current of the phase that can hold the stepping motor 51 at the current position flows, and the excitation current of the stepping motor 51 is set to the excitation current value I1. By outputting an instruction signal to the excitation current switching circuit 400 to set the excitation current switching circuit 400, the excitation current switching circuit 400 causes the excitation currents of the phases A, B, A ′, and B ′ to be held in the stopped state. In addition to the output, the excitation current value of the phase through which the current flows may be set to the excitation current value I2 (step ST8).

  Hereinafter, by performing steps ST9 and ST10 corresponding to steps ST25 and ST27 without executing the processing corresponding to steps ST24 and ST26, the excitation current is reduced while reducing the possibility that the rotary guide member 30 rotates. can do.

  Of course, it is possible to execute the same processing as steps ST23 and ST24 after step ST7 and the same processing as step ST26 after step ST9. Even when processing similar to steps ST23, ST24, ST26 is executed, the excitation current values I1, I3 in this case are smaller than the excitation current values I1, I3 in steps ST23, ST6. Therefore, the excitation current can be reduced while reducing the possibility that the rotary guide member 30 rotates according to the elasticity of the paper P.

  As described above, the carry-out direction switching device 20 controls the excitation current of the stepping motor 51 to reduce the heat generation of the stepping motor 51 while rotating the rotation torque generated when the paper P collides with the guide path 320. Since the possibility that the guide member 30 rotates can be reduced, it is not necessary to separately provide a brake mechanism for the rotary guide member 30, and the cost can be easily reduced.

  Further, if the holding force is generated while the exciting current is continuously supplied to the stepping motor 51, the coil may generate heat and damage the stepping motor 51. However, the carry-out direction switching device 20 shown in FIG. Since the exciting current is increased and the holding force of the stepping motor 51 is increased only at the timing when the increase of the rotational torque accompanying the conveyance of the paper P is expected, the heat generation of the coil is reduced and the stepping motor 51 is damaged. The fear can be reduced.

  If the rotary guide member 30 is held only by the detent torque of the stepping motor 51 when transporting the paper P, the rotary guide member 30 guides one sheet P each time the rotary guide member 30 is guided. Since the rotational position of the member 30 may be shifted, it is necessary to reposition the rotary guide member 30 every time one sheet P is guided.

  At this time, the stepping motor 51 cannot control the rotation angle with an absolute value, and needs to control with the relative rotation angle from the reference position. Therefore, each time the sheet P is guided, the reference posture S1. It is necessary to perform the positioning again after detecting the reference position by the reference position detection unit 60 or to provide the same position detection sensor as the reference position detection unit 60 corresponding to each posture position.

  However, when the sheet P is returned to the reference orientation S1 each time one sheet P is guided, it takes time for the positioning process, so that the printing time increases when a plurality of images are formed. In addition, if a plurality of position detection sensors are provided corresponding to each posture position, the cost of the sensors increases.

  On the other hand, the carry-out direction switching device 20 can reduce the possibility that the rotary guide member 30 will be rotated by the rotational torque generated when the paper P collides with the guide passage 320. Therefore, each time the paper P is guided one sheet, the positioning is performed. There is no risk of increasing the printing time because there is no need to redo. Further, since the carry-out direction switching device 20 does not need to include a plurality of positioning sensors for the stepping motor 51, there is no possibility that the cost of the positioning sensor increases.

  Although the example in which the type information of the paper P is used as the elasticity information is shown, the elasticity information is not limited to the type information of the paper P. For example, the data obtained by quantifying the thickness of the paper P and the elasticity of the paper P May be used as elasticity information. Further, although an example in which the input of the type information of the paper P, which is elasticity information, is acquired by the operation unit 17, the elasticity information acquisition unit automatically measures the thickness of the paper P, for example, or increases the strength of the elasticity. The elasticity information may be acquired by measuring the length.

  Moreover, although the elasticity information has shown the example which is 3 steps | paragraphs of an OHP sheet, a cardboard, and a plain paper, elasticity information may show a elasticity in 2 steps | paragraphs and may be 4 steps | paragraphs or more. Further, the configuration may be such that the elasticity information is not used and the excitation current setting unit 203 and the sheet type storage unit 204 are not provided, and the motor control unit 202 performs steps ST22 to ST27 and ST32 to ST36 regardless of the elasticity information. It may be configured to execute either one.

  Further, although an example in which the upper fixing sensor 105a is used as a leading end timing acquisition unit and a trailing end timing acquisition unit has been shown, the rear fixing sensor 105a, for example, near the discharge opening 322 in the guide passage 320, for example, A sensor may be provided as the end timing acquisition unit.

  Further, the front end timing acquisition unit and the rear end timing acquisition unit are not necessarily limited to examples using sensors. For example, the timing at which the leading edge of the paper P enters the receiving opening 321 and the timing at which the trailing edge of the paper P is discharged from the discharge port 351 are calculated based on the elapsed time since the image is formed on the paper P. May be.

  Further, although the example in which the carry-out direction switching device 20 is applied to the image forming apparatus 10 has been shown, the carry-out direction switching device 20 is connected to various devices that handle sheets (for example, downstream from the image forming apparatus 10 and discharged). The present invention can be applied to a post-processing apparatus that performs post-processing such as stapling on a sheet that has been processed.

  Further, although a copying machine is employed as the image forming apparatus 10, the image forming apparatus is not limited to the copying machine, and may be a printer or a facsimile apparatus.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming part 13 Fixing part 14 Paper storage part 15 Paper discharge part 17 Operation part 20 Unloading direction switching device 30 Rotary guide member 32 Circular guide plate 34 Guide shaft 40 Guide pulley 50 Posture changing means 51 Stepping motor 60 Reference Position detection unit 101 Paper vertical conveyance path 101a Upper end conveyance path 102 Paper discharge conveyance path 103 Reciprocation conveyance path 104 Backward conveyance path 105a Upper fixing sensor 106a Fixing section outlet roller 106b First discharge roller 106c Reverse conveyance path conveyance roller 106d Switching Conveying roller for guide member 109 Unloading direction switching unit 120 Conveying mechanism 151 In-body discharge tray 152 Out-body discharge tray 153 In-body finisher 171 Operation key 172 Touch panel 200, 200a Control unit 201 Copy control unit 202 Motor control unit DESCRIPTION OF SYMBOLS 203 Excitation current setting part 204 Sheet | seat classification memory | storage part 320 Guide path 321 Reception opening 322 Discharge opening 351 Discharge opening 400,400a Excitation current switching circuit 401 Motor driver 402 Analog digital converter 404 Reference voltage generation circuit P Paper

Claims (8)

An image forming apparatus comprising: a sheet carry-out direction switching device; and an image forming unit that forms an image on the sheet based on predetermined image data,
The sheet carry-out direction switching device is
A guide path that allows the conveyed sheet to pass therethrough is provided, and rotates around a support shaft that extends in the width direction of the sheet perpendicular to the transport direction to direct the exit of the guide path to at least two transport destinations. A rotary guide member that can change its orientation as much as possible,
A stepping motor for changing the posture of the rotary guide member;
A motor controller for controlling the rotation of the stepping motor by supplying a coil exciting current to the stepping motor;
A leading edge entry timing acquisition unit that acquires a timing at which the leading edge of the sheet enters the entrance of the guide passage;
The motor controller is
In a state where the exit of the guide passage is directed to one of the at least two transport destinations,
An input timing holding process for holding the rotational position of the stepping motor by supplying an excitation current having a first current value to the stepping motor at a timing when the leading edge of the sheet acquired by the leading edge input timing acquisition unit enters the inlet. When,
When the leading edge of the sheet passes through the guide path, a passing timing holding process for reducing the excitation current to a second current value smaller than the first current value is performed.
A rear end timing acquisition unit for acquiring a timing at which the rear end of the sheet is discharged from the exit of the guide passage;
The motor control unit further includes:
In a state where the exit of the guide passage is directed to one of the at least two transport destinations,
The stepping motor is supplied with an excitation current having a third current value larger than the second current value at the timing when the trailing edge of the sheet acquired by the trailing edge output timing acquisition unit is discharged from the exit. An image forming apparatus that performs an output timing holding process for holding a rotational position of a motor. The image forming apparatus according to claim 1, wherein the third current value is a value less than the first current value. A elasticity information acquisition unit that acquires information on the elasticity of the sheet as elasticity information;
The motor controller is
The entry timing holding process is executed when the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is equal to or greater than a preset first elasticity. Or the image forming apparatus of 2. A elasticity information acquisition unit that acquires information on the elasticity of the sheet as elasticity information;
The motor controller is
When the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is equal to or higher than a preset first elasticity, the entry timing holding process and the exit timing holding process are executed,
When the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is weaker than the first elasticity and equal to or greater than the second elasticity indicating an elasticity that is weaker than the first elasticity, the output timing holding process The image forming apparatus according to claim 1, wherein the input timing holding process is executed without executing the process. The motor control unit further includes:
When the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is weaker than the second elasticity, neither the entry timing holding process nor the exit timing holding process is executed. The image forming apparatus according to claim 4. A elasticity information acquisition unit that acquires information on the elasticity of the sheet as elasticity information;
6. An excitation current setting unit that increases the first current value as the elasticity information acquired by the elasticity information acquisition unit indicates that the elasticity of the sheet is stronger. The image forming apparatus according to any one of the above. The elasticity information acquisition unit
Obtaining the sheet type as the elasticity information, whether the sheet is plain paper or cardboard,
The image forming apparatus according to claim 3, wherein the elasticity of the cardboard is set as the first elasticity. The elasticity information acquisition unit
The sheet type of whether the sheet is plain paper, cardboard or resin sheet is acquired as the elasticity information,
6. The image forming apparatus according to claim 4, wherein the elasticity of the resin sheet is set as the first elasticity, and the elasticity of the cardboard is set as the second elasticity.

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