JP2009001400A - Paper sheet conveying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper sheet conveying device capable of constantly reliably conveying a narrow and thick paper sheet such as a postcard straight toward an object such as an image carrier of an image forming device. <P>SOLUTION: The paper sheet conveying device comprises upstream side roller pairs 30 for nipping and conveying a postcard P1 and resist roller pairs 40 which are arranged immediately on the downstream side of the upstream side roller pairs while the installation position is set so that a fore end of the postcard P1 reaches while the conveying state of the postcard P1 by the upstream side roller pairs 30 is continued (in other words, the distance to the upstream side roller pairs 30 is smaller than the longitudinal dimension (the first length) of the postcard P1). The upstream side roller pairs 30 are set to be shorter than the width (the second length) of the postcard P1 while the resist roller pairs 40 are set to be longer than the width of the postcard P1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paper transport device devised so as to be able to transport straight special paper (narrow and thick paper) such as a postcard having a small width and a narrow width. The present invention relates to a paper conveying apparatus that can be suitably applied to an image forming apparatus such as a facsimile apparatus.

  2. Description of the Related Art Conventionally, a sheet conveying apparatus (sheet conveying apparatus in Patent Document 1) for narrow-thick and thick sheets such as postcards as described in Patent Document 1 is known. This sheet conveying device is provided in an image forming apparatus such as a copying machine, a printer, or a facsimile machine, for example, immediately upstream of a photosensitive drum as an image carrier. Such a sheet conveying device is constituted by a pair of conveying rollers (usually called a pair of registration rollers) as rotating bodies arranged in parallel with each other in a state where the circumferential surfaces are pressed against each other. Such a narrow and thick paper is devised so as to be directed straight to the photosensitive drum without being inclined.

  Specifically, each of the conveying rollers has a pair of roller shafts arranged so as to extend in the same direction, and a width that is concentrically fitted to each central portion of the pair of roller shafts so as to be integrally rotatable. A pair of central rollers that are shorter than the width of the narrow paper, and a pair of outer rollers that are fitted in a symmetrical state on the outer sides in the axial direction of the pair of central rollers. One roller shaft is provided with springs at both ends thereof, and the peripheral surfaces of the respective conveying rollers are pressed against each other by the urging force of the springs.

According to the sheet conveying apparatus having such a configuration, when the narrow and thick sheet is fed into the center part of the pair of conveying rollers, the narrow and thick sheet is nipped only by the pair of center part rollers. Each of the pair of outer rollers outside the central roller is in a state where the peripheral surfaces thereof are in contact with each other by the biasing force of the spring, so that the narrow thick paper sandwiched between the pair of central rollers is The application of a force that causes the sheet to be inclined is alleviated, and this prevents the occurrence of inconvenience that the narrow and thick sheet is conveyed obliquely.
JP 2000-355435 A

  However, in the paper transport device described in Patent Document 1, when the narrow and thick paper is being nipped by the central roller and being transported, the force that the paper receives at both ends in the paper width direction is unbalanced. Since the oblique transport caused by this problem is eliminated by only a pair of transport rollers, there are limits to measures to prevent the oblique transport, and narrow and thick paper is always directed straight to the photosensitive drum in a stable state. It had a problem that it could not be delivered.

  That is, although the thing of patent document 1 can prevent that a narrow and thick paper will become diagonal after reaching a pair of center part roller, it has already been conveyed diagonally by the time it reaches the center part roller. It is not possible to straighten the existing paper. However, in practice, for example, when narrow and thick paper is fed out from a predetermined paper cassette, it is often skewed already, and if this oblique conveyance reaches the paper conveyance device, it will be an actual problem. As useless.

  SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and is capable of always transporting a narrow and thick paper such as a postcard straightly toward an object such as an image carrier of an image forming apparatus. An object of the present invention is to provide a possible paper transport device.

  The first aspect of the present invention is arranged in a conveyance path for conveying a first sheet having a first length in the conveyance direction and having a second length in a direction orthogonal to the conveyance direction. A pair of conveyance rollers that nip and convey the sheet, and a pair of registration rollers that are arranged in parallel to the pair of conveyance rollers at a position shorter than the first length on the downstream side in the sheet conveyance direction from the pair of conveyance rollers. The length of the conveyance roller pair is set shorter than the second length, and the length of the registration roller pair is set longer than the second length. Is.

  According to this configuration, the length of the conveyance roller pair is set to be shorter than the second length, which is the width dimension of the first sheet, while the length of the registration roller pair is longer than the second length. Therefore, when the first sheet hits the registration roller pair in the oblique conveyance, the first sheet rotates around one end of the conveyance roller pair to correct the oblique conveyance. Accordingly, the first sheet that has passed the registration roller pair is always conveyed straight along the conveyance direction.

  The invention according to claim 2 is the invention according to claim 1, wherein the first sheet is of a postcard size.

  According to this configuration, the postcard is prevented from being conveyed in a skewed state. Therefore, for example, when the paper transport device is employed as the pre-stage of postcard printing processing for postcard transport processing, proper printing that does not skew the postcard is performed. Further, for example, when the postcard transport processing is performed for reading characters and symbols written on the postcard, it contributes to proper reading processing.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the distance between the nip portion of the transport roller pair and the nip portion of the registration roller pair is L, and the paper width dimension of the narrow and thick paper Is D, and the length of the transport roller is W,
L <(D−W)
The value of L is set so as to satisfy the above.

  According to this configuration, by setting the distance L between the nip portion of the conveying roller pair and the nip portion of the registration roller pair so as to satisfy “L <(D−W)”, the narrow and thick paper Is properly rotated around the rotation fulcrum on the conveying roller pair in a state where there is no inconvenience that the skew is not corrected and the skew is not corrected, and the skew state is corrected.

  Incidentally, when the distance between the pair of conveyance rollers and the pair of registration rollers increases and the value of L, which is the distance between the two, becomes larger than “(D−W)”, it is conveyed obliquely by the driving of the pair of conveyance rollers and the tip angle. The narrow and thick paper whose portion hits the nip portion of the registration roller pair is prioritized by elastic deformation by bending rather than turning around the turning fulcrum in the carrying roller pair, and this makes it difficult to correct the oblique feeding.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the narrow and thick paper is transported by the pair of transport rollers and the narrow and thick paper is transported by the pair of registration rollers. The formed angle is set to 10 ° or less.

  According to this configuration, when the angle formed by the conveyance direction of the narrow and thick paper by the pair of conveyance rollers and the conveyance direction of the narrow and thick sheet by the pair of registration rollers (hereinafter referred to as the delivery angle) exceeds 10 °, The narrow and thick paper that has reached the registration roller pair from the transport roller pair hits the peripheral surface of one roller of the registration roller pair before the tip reaches the nip part of both rollers, and damages the leading edge. However, if the delivery angle is as small as 10 ° or less, the narrow and thick paper that has reached the registration roller pair from the conveyance roller pair will be transferred to the nip part of the registration roller pair. Immediately, the nip is properly captured and reliably conveyed downstream.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the transport path has a third length that is longer than the second length in a direction orthogonal to the transport direction. A pair of side rollers is provided on both sides of the pair of transport rollers and capable of transporting the second sheet by niping the second sheet.

  According to such a configuration, when a second sheet whose width direction orthogonal to the conveying direction is longer than the first sheet is conveyed by the conveying device, the center of the second sheet is nipped by the conveying roller pair. Since both sides are conveyed while being nipped by the pair of side rollers, they are conveyed in a stable state. As described above, by arranging the side roller pairs at the outer positions on both sides of the conveying roller pair, not only the first narrow paper but also the second wide paper can be stably conveyed. The versatility of the paper transport device is improved.

  According to the paper transport device of the present invention, the length of the transport roller pair is set shorter than the second length, which is the width of the first paper, while the length of the registration roller pair is Since the length is set to be longer than the second length, even if the first sheet reaches the registration roller pair by oblique conveyance, the mechanical force between the pair of conveyance rollers and the registration roller pair via the first sheet is set. The first sheet that has passed through the registration roller pair can be transported straightly along the transport direction, and the first sheet is transported obliquely. Can be prevented.

  FIG. 1 is an external perspective view showing an embodiment of an image forming apparatus 10 to which a paper conveying device 20 according to the present invention is applied, and shows a state where a front cover is removed. FIG. 2 is a front sectional view illustrating the outline of the internal structure of the image forming apparatus 10. 1 and 2, the XX direction is referred to as the left-right direction, and the Y-Y direction is referred to as the front-rear direction. In particular, the -X direction is leftward, the + X direction is rightward, the -Y direction is frontward, and the + Y direction is rearward. That's it.

  First, as shown in FIG. 1, an image forming apparatus 10 according to the present embodiment is a so-called in-body discharge type copying machine, and an apparatus main body 11 includes an image forming unit 12, a fixing unit 13, A paper storage unit 14, a paper discharge unit 15, an image reading unit 16, and an operation unit 17 are formed. In the image forming apparatus 10, the paper discharge unit 15 is formed by recessing a part of the apparatus main body 11 below the image reading unit 16, whereby the image forming apparatus 10 is configured to be in-body discharge type. It is called. As shown in FIG. 2, the sheet transport apparatus 20 according to the present embodiment has a sheet (second sheet) P or a postcard (first post) between the left end of the sheet storage unit 14 and the left end of the image forming unit 12. 1 sheet) P1 is provided in a vertical conveyance posture for conveying P1 in the vertical direction.

  The apparatus main body 11 includes a lower casing 111 that has a rectangular parallelepiped shape in appearance, an upper casing 112 that has a flat rectangular parallelepiped shape disposed above the lower casing 111, and the upper casing 112. And a connecting portion 113 interposed between the lower casing 111 and the lower casing 111. The connecting portion 113 is a structure for connecting the paper discharge portion 15 between the lower housing 111 and the upper housing 112 to each other, and stands from the left portion of the lower housing 111. It is installed. The upper housing 112 is supported on the upper end portion of the connecting portion 113 on the left side.

  The lower casing 111 includes an image forming unit 12, a fixing unit 13, and a sheet storage unit 14, and the upper casing 112 is equipped with an image reading unit 16 and an operation unit 17. . In the present embodiment, the operation unit 17 is attached to the upper casing 112 in a state of projecting forward from the front edge of the upper casing 112.

  The paper storage unit 14 includes a paper cassette 141 formed in two stages that can be inserted into and removed from the apparatus main body 11. A sheet bundle P0 of normal sheets P is stored in the lower sheet cassette 141, and a postcard (first sheet) formed of thick sheets with a narrow sheet width is stored in the upper sheet cassette 141. A bundle of P1 (postcard bundle P0 ′) is stored. When the image forming process is performed, the sheet P or the postcard P1 is fed out from the sheet bundle P0 or the postcard bundle P0 ′ one by one and sent to the image forming unit 12 to perform the printing process on the sheet P or the postcard P1. Is done.

  The paper discharge unit 15 is formed between the lower housing 111 and the upper housing 112. The paper discharge unit 15 has an in-body paper discharge tray 151 formed on the upper surface of the lower casing 111, and the paper P onto which the toner image from the image forming unit 12 has been transferred is The paper is discharged toward the in-body discharge tray 151.

  The image reading unit 16 includes a contact glass 161 mounted on the upper surface opening of the upper housing 112 for placing a document, and an openable / closable document pressing cover 162 for pressing the document placed on the contact glass 161. And an optical system 163 having a scanning mechanism for scanning the image of the document placed on the contact glass 161.

  Then, the analog information of the document image read by the optical system 163 is converted to a digital signal and then output to an exposure unit 123 described later, and is subjected to image forming processing.

  The operation unit 17 is used to input processing information related to image forming processing. The operation unit 17 is used to input the number of sheets P to be processed, the numeric keypad 171 and other various operation keys, and further to perform touch input. An LCD (Liquid crystal display) 172 and the like are provided.

  Further, a manual feed tray 18 is provided on the right surface of the lower housing 111 at a position directly above the paper storage unit 14. The lower side of the manual feed tray 18 is pivotally supported around the support shaft 181, and is positioned between a closed posture that stands up to close the manual feed port and an open posture that protrudes 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.

  A relay unit 184 and a transport unit 185 connected to the downstream end (left end) of the relay unit 184 are provided between the manual feed tray 18 and a later-described photosensitive drum 121 of the image forming unit 12. It has been. The sheet P (FIG. 2) manually fed from the manual feed tray 18 is directed toward a nip portion between the photosensitive drum 121 and a transfer roller 125 described later via the relay unit 184 and the transport unit 185. Sent out.

  The lower surface of the lower casing 111 is provided with a maintenance door 19 for maintenance that can be opened and closed by pivoting forward and backward around the door shaft 191. In addition, an out-of-body discharge tray 152 that can be opened and closed is provided immediately above 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.

  As shown in FIG. 2, the image forming unit 12 is provided with a photosensitive drum 121 at a substantially central portion thereof. The photosensitive drum 121 is uniformly charged on its peripheral surface by a charging unit 122 provided immediately to the right while rotating clockwise around the drum center. Then, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 121 by the laser beam from the exposure unit 123 based on the image information of the original image read by the image reading unit 16. Toner is supplied from the developing unit 124 provided below the photosensitive drum 121 toward the electrostatic latent image, whereby a toner image is formed on the peripheral surface of the photosensitive drum 121.

  On the peripheral surface of the photosensitive drum 121 on which the toner image is formed, the paper P or the postcard P1 sent out from any one of the paper cassettes 141 of the paper storage unit 14 or the paper P manually fed from the manual tray 18 is conveyed by the transport unit 185. And it is fed through the registration roller pair 40.

  The registration roller pair 40 includes a unit-side registration roller 41 as a driving roller that is driven and rotated by driving of a drive motor (not shown), and a peripheral surface on the left side that abuts on the peripheral surface of the unit-side registration roller 41 and rotates in a driven manner. The cover side registration roller 42 is a driven roller. The unit-side registration roller 41 is provided on the apparatus main body 11 side, whereas the cover-side registration roller 42 is provided on a cover member 195 side described later that can be opened and closed with respect to the sheet conveying apparatus 20.

  The sheet P fed to the photosensitive drum 121 via the registration roller pair 40 is subjected to electrostatic action of the transfer roller 125 disposed on the left side of the photosensitive drum 121 and facing the photosensitive drum 121. The toner image on the peripheral surface of the photosensitive drum 121 is transferred. The sheet P on which the toner image is transferred is separated from the photosensitive drum 121 and sent to the fixing unit 13.

  The photosensitive drum 121 that has completed the transfer process of the toner image on the paper P or the postcard P1 is continuously rotated in the clockwise direction, so that the peripheral surface thereof is cleaned by the cleaning device 126 provided immediately above the photosensitive drum 121. Then, it goes to the charging unit 122 for the next image forming process.

  The fixing unit 13 includes a fixing roller 131 provided with an energization heating element such as a halogen lamp inside, and a pressure roller 132 disposed opposite to the fixing roller 131 on the left side. The sheet P fed from the image forming unit 12 is subjected to a fixing process of the toner image by obtaining heat from the fixing roller 131 while passing through the nip portion between the fixing roller 131 and the pressure roller 132. The

  When the sheet P or postcard P1 after the fixing process is for single-sided printing, the body of the paper discharge unit 15 is selectively selected via a paper discharge conveyance path 102 provided above the fixing unit 13. It is discharged to the inner discharge tray 151 or discharged to the outer discharge tray 152.

  On the other hand, when the sheet P or the postcard P1 after the fixing process is for double-sided printing in which the single-sided printing process is completed, the first half is passed through the reciprocating conveyance path 103 provided above the discharge conveyance path 102. After being discharged into a temporary evacuation space 153 formed above the in-body discharge tray 151, it is reversely fed through the reverse feed path 104, and is supplied to the image forming unit 12 again with the front and back sides reversed, and the back side. Printing processing is performed on the side. The paper P or postcard P1 for which double-sided printing has been completed is discharged to the paper discharge tray 151 or the out-body discharge tray 152.

  In such an image forming apparatus 10, the lower casing 111 is provided with a cover member 195 that can be opened and closed with respect to the image forming unit 12 immediately inside the maintenance door 19. The cover member 195 is disposed in a state of being held on the right surface side of the closed maintenance door 19. The cover member 195 is pivotally supported around a support shaft 195 a supported by the lower housing 111 with the lower end portion positioned slightly above the lower end portion of the maintenance door 19. . Such a cover member 195 rotates forward and backward around the support shaft 195a, thereby closing the left surface of the image forming unit 12 (indicated by a solid line in FIG. 2) and opening the left surface open. The posture can be changed between the postures (indicated by a two-dot chain line in FIG. 2).

  Then, in a state where the cover member 195 is set to the closed posture, the paper vertical transport path for transporting the paper P and the postcard P1 fed from the paper cassette 141 or the manual feed tray 18 to the right surface side of the cover member 195. (Conveyance path) 101 is formed.

  The cover member 195 is provided when the paper P is jammed by changing the posture of the cover member 195 to the open posture when a paper jam occurs in the vertical paper conveyance path 101 corresponding to the left side of the image forming unit 12. Is to be exposed to the outside and removed.

  In addition, when performing double-sided printing on the paper P between the right side of the maintenance door 19 set in the closed posture and the left side of the cover member 195 set in the closed posture, only one side is printed. A reverse conveyance path 104 is formed for reversely feeding the sheet P on which has been applied. The paper P that has been reversely fed along the reverse feed path 104 is introduced into a vertical paper feed path 101 formed between the left side of the transport unit 185 and the right side of the cover member 195 with the front and back sides reversed. Subsequently, the printing process (transfer process) by the photosensitive drum 121 is performed on the back side of the paper P. 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.

  In the present embodiment, the paper P that is manually fed from the manual feed tray 18 is fed leftward by the driving of the feed roller 182 provided at the back (left side) of the manual feed tray 18. Then, the sheet is conveyed toward the registration roller pair 40 in the sheet vertical conveyance path 101 via the conveyance roller pair 183, the relay unit 184, and the conveyance unit 185, and continues to the photosensitive drum 121 and the transfer roller 125 via the registration roller pair 40. Is supplied to the nip portion.

  FIG. 3 is a partially enlarged view of FIG. 2 for explaining an embodiment of the paper transport device 20 according to the present invention, and FIG. 4 is a perspective view of the paper transport device 20 shown in FIG. 3 and 4 are the same as those in FIG. 1 (X is the left-right direction (-X: leftward, + X: rightward), Y is the front-rear direction (-Y: forward, + Y: backward)).

  First, as shown in FIG. 3, the sheet conveying device 20 is formed immediately upstream (directly below) the photosensitive drum 121 and between the left surface of the conveying unit 185 and the right surface of the cover member 195. It is provided facing the vertical paper conveyance path 101.

  On the other hand, the transport unit 185 includes a unit main body 185a that is detachably interposed between a downstream end of the relay unit 184 (FIG. 2) and a right surface of a substantially lower half of the cover member 195, and the unit main body. And a guide member 185b that is detachably attached to 185a. A manual feed path 185c is formed between the unit main body 185a and the guide member 185b with the downstream end facing the vertical paper path 101, and is sent from the manual tray 18 to the transport unit 185 via the relay unit 184. The paper P thus fed is introduced into the vertical paper conveyance path 101 through the manual conveyance path 185c.

  The sheet transport device 20 is located above the upstream roller pair 30 disposed on the left side of the unit main body 185 a of the transport unit 185 and the guide member 185 b of the transport unit 185, and on the photosensitive drum 121. And a registration roller pair 40 disposed immediately below.

  The upstream roller pair 30 includes a unit-side transport roller 301 as one side provided on the left side of the unit body 185a and a cover-side transport roller 302 as the other side provided on the right side of the cover member 195. It has become. Each of these transport rollers 301 and 302 is formed of an elastomer such as synthetic rubber or soft synthetic resin.

  The unit-side transport roller 301 is fitted around the unit-side roller shaft 303 provided between the front and rear side walls of the transport unit 185 so as to be concentrically and integrally rotatable. The cover-side transport roller 302 is externally fitted so as to be concentrically rotatable around a cover-side roller shaft 304 provided between the front and rear side walls of the cover member 195. A unit-side lower gear 33 (FIG. 4) is externally fitted to the right end of the unit-side roller shaft 303 so as to be rotatable integrally therewith, and a cover-side lower gear 34 is attached to the right end of the cover-side roller shaft 304. Are fitted concentrically and integrally rotatable. The cover side lower gear 34 is meshed with the unit side lower gear 33.

  On the other hand, a drive motor 50 is provided at an appropriate position in the apparatus main body 11, and the driving force of the drive motor 50 is transmitted to the unit-side lower gear 33 via a predetermined first gear mechanism 51.

  Therefore, by closing the cover member 195 and driving the drive motor 50 in a state where the peripheral surface of the cover-side transport roller 302 is pressed against and in contact with the peripheral surface of the unit-side transport roller 301, the driving force is reduced to the first gear. This is transmitted to the cover-side lower gear 34 via the mechanism 51 and the unit-side lower gear 33, whereby the unit-side conveyance roller 301 and the cover-side conveyance roller 302 rotate in opposite directions, respectively. As a result, the sheet P or the postcard P1 is conveyed while being securely nipped between the conveying rollers 301 and 302 (that is, the upstream roller pair 30).

  As shown in FIG. 4, the upstream roller pair 30 has a central roller pair (conveying roller) formed by concentrically fitting the central rollers 311 and 312 to the roller shafts 303 and 304, respectively. Pair) 31 and a total of two sets of side roller pairs 32 formed by externally fitting the side rollers 321 and 322 to the respective roller shafts 303 and 304 on both outer sides of the central roller pair 31. I have.

  Incidentally, the central roller 311, 312 is a unit body side central roller 311 which is concentrically and integrally fitted around the unit side roller shaft 303 and rotates concentrically around the cover side roller shaft 304. A cover member-side central roller 312 is externally fitted.

  The registration roller pair 40 includes a unit-side registration roller 41 that is one side registration roller disposed immediately above the guide member 185 b of the transport unit 185, and a cover member 195 side facing the unit-side registration roller 41. And a cover side registration roller 42 which is the other side registration roller.

  The unit-side registration roller 41 is externally fitted so as to be concentrically and integrally rotatable around a main body-side roller shaft 411 provided between predetermined frames provided at appropriate positions in the front and rear of the apparatus main body 11. On the other hand, the cover-side registration roller 42 is rotatably supported around a cover-side roller shaft 421 provided between the front and rear side plates of the cover member 195. The peripheral surface of the cover-side registration roller 42 is brought into contact with the peripheral surface of the unit-side registration roller 41 with the cover member 195 being closed.

  A unit-side upper gear 43 (FIG. 4) is externally fitted to the rear end portion of the main body side roller shaft 411 so as to rotate integrally therewith, and at the rear end portion of the cover side roller shaft 421, a cover side upper portion. A gear 44 is concentrically fitted so as to be integrally rotatable. The cover side upper gear 44 is meshed with the unit side upper gear 43. The driving force of the driving motor 50 is transmitted to the unit-side upper gear 43 via a predetermined second gear mechanism 52.

  Therefore, by closing the cover member 195 and driving the drive motor 50 in a state where the peripheral surface of the cover-side registration roller 42 is pressed against the peripheral surface of the unit-side registration roller 41, the driving force is reduced to the second gear. This is transmitted to the cover-side upper gear 44 via the mechanism 52 and the unit-side upper gear 43, whereby the unit-side registration roller 41 and the cover-side registration roller 42 rotate in opposite directions, respectively. As a result, the paper P or the postcard P1 is conveyed while being securely nipped between the registration rollers 41 and 42 (that is, the registration roller pair 40).

  Each of the registration rollers 41 and 42 is formed of an elastomer such as a synthetic rubber or a soft synthetic resin material like the upstream roller pair 30 and is compressed and elastically deformed with the cover member 195 closed. As a result, the sheet P can be reliably registered. Such a pair of registration rollers 40 is set to have substantially the same length as the outer dimension between the front and rear side roller pairs 32.

  The central roller pair 31 has a length dimension extending in the front-rear direction set to be shorter than a width dimension D (second length: 100 mm) of the postcard P1. The inner dimension between the pair of front and rear side rollers 32 is set longer than the width dimension of the postcard P1. Therefore, a normal sheet P having a third length that is longer than the second length according to the present invention, such as A4 size and B5 size, in the direction orthogonal to the conveyance direction is transferred from the lower sheet cassette 141. When the sheet P is fed out and reaches the upstream roller pair 30, the sheet P is nipped at the center roller pair 31 and both widths are also nipped by the front and rear side roller pairs 32. Will be transported.

  On the other hand, when the postcard P1 fed out from the upper paper cassette 141 reaches the upstream roller pair 30, the postcard P1 is not nipped by the front and rear side roller pairs 32, but the central roller pair 31. It is conveyed in a state where it is nipped only in the area.

  In this embodiment, as shown in FIG. 3, a straight line connecting the nip portion N1 of the upstream roller pair 30 and the nip portion N2 of the registration roller pair 40 and the paper P or postcard P1 by the registration roller pair 40. The angle γ formed by the transport direction (vertical direction in the example shown in FIG. 3) is set to 10 ° or less.

  This is because when the angle γ exceeds 10 °, the sheet P or the postcard P1 conveyed toward the registration roller pair 40 by the upstream roller pair 30 directly enters the nip portion N2 of the registration roller pair 40. Instead, the paper P and the postcard P1 cannot be properly conveyed because they head toward the nip portion N2 after once colliding with the peripheral surface of one of the rollers (in the example shown in FIG. 3, the unit side registration roller 41). This is because there is a fear.

  FIG. 5 is an explanatory diagram for explaining the correction action of the transport posture of the postcard P1 when the postcard P1 is being transported by the paper transport device 20, and FIG. 5 (A) is a paper transport device shown in FIG. FIG. 5B is an exploded view of the force received by the upper left corner of the postcard P1 from the nip portion N2 of the registration roller pair 40. FIG. In FIG. 5, in order to facilitate the explanation, X and Y are not used for the direction display, and the left and right of each member are defined according to the left and right sides of the paper. That is, in FIG. 5, the front in FIGS. 1-4 is a left side, and the back is the right side.

  5A, the distance between the nip portion N1 of the upstream roller pair 30 and the nip portion N2 of the registration roller pair 40 (distance between the nip portions) is L, and the length dimension of the central roller pair 31 is shown. Let (central roller length) be W. The distance L between the nip portions is set shorter than the vertical dimension (first length) of the postcard P1. In FIG. 5 (A), as an example, the postcard P1 reaches the registration roller pair 40 by the oblique conveyance inclined upward to the left, whereby the upper left corner P2 of the postcard P1 is the nip of the registration roller pair 40 being stopped. The state at the moment when it hits the portion N2 is indicated by a solid line, and the state rotated counterclockwise around the rotation center O is indicated by a two-dot chain line. The rotation center O is formed at the left end portion of the nip portion N1 in the central roller pair 31 of the upstream roller pair 30.

  At the moment when the corner of the postcard P1 hits the registration roller pair 40, the distance (skew (skew) amount) between the upper right corner P3 of the postcard P1 and the nip N2 of the registration roller pair 40 is d. To do.

  Further, at this moment, since the registration roller pair 40 is stopped, if the conveying force for the postcard P1 by the central roller pair 31 is F, the postcard P1 includes the central roller pair 31. Only this conveying force F is acting. When the moment around the rotation center O due to the conveying force F is taken into consideration, the point of action on the postcard P1 is the central portion in the left-right direction in FIG. 5 along the nip portion N1 in the central roller pair 31 (that is, the rotation center). As a result, the postcard P1 has a moment M in the following formula (1) in the counterclockwise direction around the rotation center O. It is working.

In the rotation around the rotation center O of the postcard P1, the distance between the rotation center O and the upper left corner P2 of the postcard P1 (that is, the rotation radius) gradually increases as the rotation amount increases. However, since the increase amount is very small, it is ignored in the following formulas (1) to (7).
M = (W / 2) × F (1).

  Due to the moment shown in the formula (1), the postcard P1 rotates counterclockwise around the rotation center O, so that the skew posture of the postcard P1 is corrected to a straight posture. In this case, the leading edge (upper edge) of the skewed postcard P1 indicated by the solid line in FIG. 5A rotates around the rotation center O and overlaps the nip portion N2 as indicated by the two-dot chain line. To be corrected.

  Then, after the time required for this correction (an extremely short time of 1 second or less) has elapsed, the registration roller pair 40 starts driving. Thereafter, the postcard P1 is sent out toward the photosensitive drum 121 in a straight posture as the registration roller pair 40 continues to be driven, so that the toner image on the peripheral surface of the photosensitive drum 121 is not inclined on the postcard P1. Is properly transferred.

On the other hand, when the upper left corner portion P2 of the postcard P1 comes into contact with the nip portion N2 of the registration roller pair 40, the upper left corner portion P2 receives a reaction force (reaction force) from the nip portion N2, as shown in FIG. Force) f. Then, on the postcard P1, a moment m of the following expression (2) acting counterclockwise around the rotation center O caused by the reaction force f acts.
m = ((D−W) / 2) × f (2).

The moment m calculated by the equation (2) and the moment M calculated by the equation (1) are equal to each other (that is, ((D−W) / 2) × f = (W / 2) As a result, the following expression (3) is derived.
f = (W / (D−W)) × F (3).

  FIG. 6 shows the relationship between W and f / F when the central roller length W that is the length dimension of the central roller pair 31 is set on the horizontal axis and “f / F” is set on the vertical axis. It is a graph based on (3) Formula. 100 mm is adopted as the width dimension D of the postcard P1.

  As is apparent from the graph of FIG. 6, until the central roller length W reaches 50 mm, the value of f / F gradually increases so as to be approximately proportional to the increase in the central roller length W. Until it reaches 70 mm, the gradient is slightly steeper than before. And when the center roller length W exceeds 70 mm, it turns out that the value of f / F increases rapidly.

  An increase in the value of f / F means that the value of the reaction force f acting on the upper left corner P2 of the postcard P1 is increased because the conveyance force F is a predetermined constant value. When the reaction force f increases, the upper left corner P2 of the postcard P1 fits between the registration rollers 41 and 42 of the resist roller pair 40 that is stopped (that is, rubs through the nip portion N2). The postcard P1 is bent.

  Then, if the postcard P1 is fitted or bent between the registration rollers 41 and 42 of the registration roller pair 40 in which the postcard P1 is stopped, there is a disadvantage that the skew of the postcard P1 is not corrected. In order to avoid such inconvenience, the central roller length W may be set to 70 mm or less.

  However, if the central roller length W is too short, the frictional force with respect to the postcard P1 at the nip portion N1 of the central roller pair 31 becomes small, and the postcard P1 cannot be conveyed well. When setting the roller length W, it is determined after performing various tests, but it is practically preferable to set the roller length W to about 50 mm.

Next, as shown in FIG. 5B, the reaction force f acting downward on the upper left corner P2 of the postcard P1 is divided into a component force f ″ along the line segment O-P2 and this component force f ″. When it is broken down into the orthogonal component force f ′, it is based on the premise that the skew angle β of the postcard P1 is sufficiently small, between the straight line connecting the rotation center O and the upper left corner P2 and the nip N2. Is approximately equal to an angle α formed between a straight line connecting the tip of the component force f ′ and the tip of the component force f ″ and an arrow indicating the component force f ′.
α≈θ (4).

Since tan α = f ″ / f ′, as a result, f ″ / f′≈tan θ (5)
Is established.

  FIG. 7 is a graph of the equation (5). That is, in FIG. 7, the horizontal axis sets the angle θ between the straight line connecting the rotation center O of the postcard P1 and the upper left corner P2 and the nip N2, and the vertical axis indicates “f ″ / f ′”. It is a graph which shows the relationship between both which set the value of.

  As can be seen from this graph, the value of “f ″ / f ′” initially increases gradually as the angle θ increases from “0”. Increases rapidly. The component force f ′ is a force acting so as to rotate the postcard P1 around the rotation center O, whereas the component force f ″ is a force of the postcard P1 from the upper left corner P2 to the rotation center O. This is a force acting to bend the postcard P1 in the direction of the head. Therefore, when the component force f ″ increases (that is, when the value of “f ″ / f ′” increases), the force to deflect the postcard P1. As a result, the postcard P1 bends, and the skew of the postcard P1 is not corrected.

  Here, the relationship between “f ″ / f ′” and the angle θ is as shown in the graph of FIG. It can be seen that the value of “f ″ / f ′” increases rapidly when θ exceeds about 70 °. The value of “f ″ / f ′” at that time is about 2.

  Here, the distance L between the nips, the width D of the postcard P1, the central roller length W of the upstream roller pair 30 and the angle θ are approximately (that is, the skew angle β is expressed as “ The relationship shown in the following formula (6) exists.

L / ((D−W) / 2) ≈tan θ (6).

  Then, when tan θ in the equation (6) is arranged as 2 or less, the following inequality (7) can be obtained.

L <(D−W) (7).

  The expression (7) indicates that the distance between the nip portions L should be set shorter than the difference between the width D of the postcard P1 and the central roller length W. For example, when the width dimension D of the postcard P1 is 100 mm and the central roller length W is 50 mm, the distance L between the nip portions is 50 mm or less.

In order to preferentially rotate the postcard P1 without bending, it is desirable that the value of the component force f ″ is set to be equal to or less than the value of the component force f ′. Then
L <(D−W) / 2 (8).

  The expression (8) shows that the distance between the nip portions L should be set shorter than the value obtained by dividing the difference between the width dimension D of the postcard P1 and the central roller length W by “2”. is there. For example, when the width D of the postcard P1 is 100 mm and the central roller length W is 50 mm, the distance L between the nip portions is 25 mm or less.

  FIG. 8 illustrates how the front end of the skewed postcard P1 moves in the axial direction of the registration roller pair 40 when it reaches the nip portion N2 (registration position) of the registration roller pair 40. It is explanatory drawing of. In FIG. 8, as in the case of FIG. 5, the left and right of each member are defined in accordance with the left and right sides of the paper without using X and Y for the direction display in order to facilitate the explanation. That is, in FIG. 8, the front in FIGS. 1-4 is a left side, and the back is the right side.

  When the postcard P1 reaches the nip portion N2 at an angle β with respect to the direction in which the nip portion N2 extends, the postcard P1 is corrected to the correct posture by rotating around the rotation center O by the angle β. At this time, the postcard P1 is slightly rotated in the axial direction of the registration roller pair 40 (that is, the extending direction of the nip portion N2) after the upper left corner P2 contacts the nip portion N2 of the registration roller pair 40 by the rotation. Slide.

In this case, the slide amount of the upper left corner portion P2 of the postcard P1 is m, the distance between the rotation center O and the upper left corner portion P2 of the postcard P1 is R, and the perpendicular line dropped from the rotation center O to the nip portion N2. When the tip of the γ is an angle formed between the upper left corner P2 of the postcard P1 that has reached the nip portion N2 in a skewed state and the straight line connecting the rotation center O,
m = R × sin β × cos γ (9)
Is established.

Here, when the width of the postcard P1 is 100 mm, the width of the conveyance roller is W, and the distance between the registration roller and the conveyance roller is L, the distance in the registration axis direction between the rotation center O and the upper left corner P2 is M (M = If (100−W) / 2), β is a minute angle and can be approximated as “sin β≈d / 100”, and from cos γ = M / R, m≈√ (L ² × M ² ) × (d / 100) × L / √ (L 2 × M 2)
= (L / 100) × d (10)
Is established.

  Therefore, when the distance L between the nip portions is 30 mm, the slide amount m is 0.3d according to the equation (10), and when the skew amount d is 3 mm, the slide amount m is 0.9 mm (m = 0.3d = 0.3 × 3 mm = 0.9 mm).

  As indicated by a dotted line in FIG. 8, when the distance L between the nip portions is 60 mm, the slide amount m is 1.8 mm (m = (L / 100) × d = (60/100) × 3 mm = 1). .8 mm).

  If the upper left corner P2 of the postcard P1 is in contact with the nip portion N2 of the registration roller pair 40 and slides in the extending direction of the nip portion N2, the upper left corner P2 of the postcard P1 may be broken or damaged. . Therefore, it is preferable to keep the slide amount m as small as possible. From this point of view, it is desirable that the central roller pair 31 in the upstream roller pair 30 be as close to the registration roller pair 40 as possible.

  5 and FIG. 8, the postcard P1 takes as an example a case where the postcard P1 is skewed so that the upper left corner P2 first hits the nip portion N2 of the registration roller pair 40. As described above, even when the postcard P1 is skewed so that the upper right corner hits first, the postcard P1 is corrected to the correct posture by the same mechanism in a bilaterally symmetrical manner.

  As described above in detail, the paper transport device 20 according to the present embodiment transports the postcard P1 that is a thick, narrow, thick paper whose width in the direction perpendicular to the transport direction is equal to or smaller than a predetermined dimension straightly and properly. The upstream roller pair 30 that nips and conveys the postcard P1 and the upstream roller pair 30 of the postcard P1 that is disposed immediately downstream of the upstream roller pair 30 and that is conveyed by the upstream roller pair 30 Is set so that the leading edge of the postcard P1 reaches the position (that is, the distance between the upstream roller pair 30 is shorter than the vertical dimension (first length) of the postcard P1). The registration roller pair 40 is provided.

  According to such a configuration, the thick postcard P1 having a narrow width less than or equal to the predetermined dimension in the paper width direction orthogonal to the transport direction is first transported while being nipped by the upstream roller pair 30, and the nip state is not resolved. The leading end reaches the resist roller pair 40 that is stopped. When the leading edge of the postcard P1 reaches the registration roller pair 40, the registration roller pair 40 is driven and rotated after a short timing, and thereafter the postcard P1 is conveyed while being nipped by the driving of the registration roller pair 40. The

  The upstream roller pair 30 is set shorter than the paper width dimension orthogonal to the paper conveyance direction of the postcard P1, and the registration roller pair 40 is set longer than the paper width dimension. When the postcard P1 is conveyed obliquely by driving 30, one corner of the tip of the postcard P1 hits the nip portion of the resist roller pair 40 in a stopped state. At this time, the postcard P1 has an upstream side. Since the roller pair 30 is in a driving state, the corner portion is the point of action from the nip portion of the registration roller pair 40, and the opposite direction of the sheet conveyance direction is the corner portion side end portion of the upstream roller pair 30 as a fulcrum. A moment in the direction is generated. As a result, the postcard P1 is quickly rotated around the fulcrum in the direction in which the oblique conveyance is eliminated. By this rotation, the oblique conveyance state is eliminated and the postcard P1 is directed straight to the registration roller pair 40. Since the registration roller pair 40 is driven after this state, the postcard P1 can be conveyed straight by driving the registration roller pair 40 thereafter.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the paper conveying device 20 according to the present invention is applied to the image forming apparatus 10. However, the present invention is limited to applying the paper conveying device 20 only to the image forming apparatus 10. However, the present invention can be applied to an apparatus that handles various types of paper, such as a normal printing press or a staple machine that staples a bundle of sheets into a booklet.

  (2) In the above embodiment, a copying machine has been described as an example of the image forming apparatus 10 to which the paper conveyance device 20 is applied. However, the present invention is limited to the image forming apparatus 10 being a copying machine. However, it may be a printer or a facsimile machine.

  (3) In the above embodiment, the postcard P1 has been described as an example of the first paper targeted by the paper transport device 20, but the present invention is limited to the first paper being the postcard P1. Instead, the paper conveyance device 20 can be applied to various types of narrow and thick paper such as Christmas cards and information cards for the time of celebration.

  (4) In the above embodiment, the paper transport device 20 is applied to the case where the paper P is vertically transported. However, the present invention applies the paper transport device 20 only to the vertical transport of the paper P. The present invention is not limited, and the present invention may be applied to so-called lateral conveyance in which the paper P is conveyed horizontally.

1 is an external perspective view showing an embodiment of an image forming apparatus to which a paper conveying apparatus according to the present invention is applied, and shows a state where a front cover is removed. FIG. FIG. 2 is a front sectional view for explaining an outline of an internal structure of the image forming apparatus shown in FIG. 1. FIG. 3 is a partially enlarged perspective view of FIG. 2 for explaining an embodiment of the sheet conveying apparatus according to the present invention. FIG. 4 is a perspective view of the paper transport device shown in FIG. 3. FIG. 5 is an explanatory diagram for explaining an action of correcting a postcard conveyance posture when a postcard is being conveyed by the paper conveyance device, and (A) is an explanatory diagram of a right side view of the paper conveyance device shown in FIG. ) Is an exploded view of the force that the upper left corner of the postcard receives from the nip portion of the registration roller pair. It is a graph which shows the relationship between W and f / F when the center part roller length W which is the length dimension of a center part roller pair is set to a horizontal axis, and "f / F" is set to the vertical axis | shaft. Both the angle θ between the straight line connecting the rotation center O of the postcard P1 and the upper left corner P2 and the nip N2 is set on the horizontal axis, and the value “f ″ / f ′” is set on the vertical axis. It is a graph which shows the relationship. FIG. 10 is an explanatory diagram for explaining how much the front end of the skewed postcard moves in the axial direction of the registration roller pair when it reaches the nip portion (registration position) of the registration roller pair.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 101 Paper vertical conveyance path (conveyance path)
DESCRIPTION OF SYMBOLS 102 Paper discharge conveyance path 103 Reciprocating conveyance path 104 Reverse conveyance path 11 Apparatus main body 111 Lower housing | casing 112 Upper housing | casing 113 Connection part 12 Image formation part 121 Photosensitive drum 122 Charging unit 123 Exposure unit 124 Development unit 125 Transfer roller 126 Cleaning Device 13 Fixing portion 131 Fixing roller 132 Pressure roller 14 Paper storage portion 141 Paper cassette 15 Paper discharge portion 151 In-body discharge tray 152 Out-body discharge tray 153 Temporary retraction space 16 Image reading portion 161 Contact glass 162 Document pressing cover 163 Optical system 17 Operation unit 171 Numeric keypad 172 LCD
18 Manual feed tray 181 Support shaft 182 Feeding roller 183 Conveying roller pair 184 Relay unit 185 Conveying unit 185a Unit main body 185b Conveying path for guide member 185c 19 Maintenance door 191 Door shaft 195 Cover member 195a Support shaft 20 Paper conveying device 30 Upstream roller pair 301 Unit-side conveying roller 302 Cover-side conveying roller 303 Unit-side roller shaft 304 Cover-side roller shaft 31 Center roller pair (conveying roller pair)
311 Unit body side center roller 312 Cover member side center roller 32 Side roller pair 321 Side roller 40 Registration roller pair 41 Unit side registration roller 411 Body side roller shaft 412 Cover side roller shaft 42 Cover side registration roller D Width dimension f Reaction force F Conveying force N1 Nip part N2 of conveying roller pair Nip part O of registration roller pair Center roller pair left end position P Paper (second paper)
P0 paper bundle P1 postcard (first paper)
P0 'Postcard bundle P2 Upper left corner of postcard P3 Upper right corner of postcard L Distance between nips W Center roller length

Claims (5)

A transport having a first length in the transport direction and arranged in a transport path for transporting a first sheet having a second length in a direction orthogonal to the transport direction, and transporting the first sheet in a nip. With Laura pair,
A registration roller pair disposed in parallel with the transport roller pair at a position shorter than the first length on the downstream side in the paper transport direction from the transport roller pair;
The conveying roller pair is set to have a length dimension shorter than the second length,
The sheet conveying apparatus, wherein the registration roller pair is set to have a length dimension longer than the second length.   2. The paper conveying apparatus according to claim 1, wherein the first paper is of a postcard size. When the distance between the nip portion of the conveying roller pair and the nip portion of the registration roller pair is L, the paper width dimension of the narrow and thick paper is D, and the length dimension of the conveying roller is W,
L <(D−W)
The sheet conveying apparatus according to claim 1, wherein a value of L is set so as to satisfy the above.   2. The angle formed by the conveyance direction of narrow and thick paper by the pair of conveyance rollers and the conveyance direction of narrow and thick paper by the pair of registration rollers is set to 10 ° or less. 4. The paper conveying device according to any one of 3 to 3. The transport path is capable of transporting a second sheet having a third length that is longer than the second length in a direction orthogonal to the transport direction;
5. The sheet conveying apparatus according to claim 1, further comprising a pair of side rollers capable of conveying the second sheet while nipping the second sheet on both sides of the pair of conveying rollers.

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