JP4732220B2 - Sheet-like medium guiding method, sheet-like medium guiding device, sheet-like medium path switching device, and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet-like medium guiding method, a sheet-like medium guiding device, and a sheet-like medium path switching device, which are applied to a conveying path having a portion for conveying a sheet-like medium (hereinafter also referred to as paper) by bending it. The present invention also relates to an image forming apparatus that is an object of these methods and apparatuses.

  An image forming apparatus having a branching unit that switches conveyance of a sheet to two conveyance paths is known (for example, see Patent Document 1). In such an image forming apparatus, the branching claw that guides the sheet at the branching unit is switched to one of the first and second positions corresponding to the desired branched conveyance path, and the sheet is guided. Since the path changes in the branching direction at the branching portion, the sheet is bent and conveyed. In addition, in the image forming apparatus, a curved portion whose direction of travel changes in the paper conveyance path other than the branch portion.

  Bending of these paths in the paper conveyance path becomes a factor that impedes paper conveyance. In addition, the curvature of the bend must be increased if the device is to be reduced in size, and if the curve becomes tight, the contact angle between the front end of the paper and the guide surface with which the front end of the paper contacts (on the guide surface) The angle between the surface downstream of the contact position and the leading edge increases, and the leading edge of the paper tends to stagnate. In the case of paper curled due to the influence of the transport process, humidity, or the passage of the heat fixing device, the curl direction may be opposite to the curving direction of the transport path. In such a case, the leading edge of the paper is nearly perpendicular to the guide surface. In particular, the transportability is impaired due to contact at an angle.

2. Description of the Related Art Some image forming apparatuses for double-sided image formation are configured to arbitrarily select whether the fixed paper is discharged to a paper discharge unit or conveyed to a double-sided image forming unit by a branching claw having a function of switching a path. However, with the miniaturization of the machine, the curvature of bending at the guide surface of the branching claw tends to increase. As the curvature increases, the leading edge of the curled paper comes into contact with the turn section (guide surface) at an angle close to vertical, and the leading edge breaks due to the stagnation of the leading edge of the paper that is pushed during the turn by the branching claw. There is a problem that it is easy to cause a breakage of the ears, a broken ear or a jam.
On the other hand, in the conventional image forming apparatus, the guide member that guides the sheet conveyed through these curved portions in the sheet conveyance path is configured such that its posture (position) is not changed until the sheet passes.

JP 2005-178554 A

  The present invention has been made in view of the above problems, and a sheet-like medium guiding method, sheet-like medium guiding device, sheet-like medium path switching device, which has improved sheet-like medium transportability in a curved portion of a conveying path, It is an object to provide an image forming apparatus.

In order to achieve the above-mentioned object, the invention according to claim 1 is a method for guiding a sheet-like medium in a conveying path having a curved portion in which the traveling direction of the sheet-like medium changes, and the leading edge of the sheet-like medium that has approached the curved portion Receiving the portion with a guide member previously disposed in the curved portion, and displacing and guiding the guide member while maintaining a small contact angle of the sheet-like medium with respect to the guide surface according to the advance of the tip portion; did.
The invention according to claim 2 is the sheet medium guide method according to claim 1, wherein the guide surface of the sheet medium formed on the guide member is inclined along the transport direction on the upstream side of the curved portion. When the leading edge of the sheet-like medium reaches the guide surface, the guide surface is moved along the conveying direction on the downstream side of the curved portion as the leading edge advances. The leading end portion of the sheet-like medium is guided while being displaced so as to be in the position.
According to a third aspect of the present invention, there is provided a sheet-like medium guiding device for use in a conveyance path having a curved portion in which the traveling direction of the sheet-like medium changes, and a guide surface arranged on the curved portion for guiding the sheet-like medium. And a guide direction of the sheet-like medium along the transport direction on the upstream side of the curved portion, and the transport direction on the downstream side of the curved portion in accordance with the progress of the position of the leading end portion of the sheet-like medium. Displacement means for displacing the guide member so as to be displaced to a position along the position is provided.
According to a fourth aspect of the present invention, in the sheet-like medium guiding apparatus according to the third aspect, the displacing means includes a means for swingably supporting the guiding member, a driving means for driving the guiding member, Control means for controlling the drive means was provided.
According to a fifth aspect of the present invention, in the sheet-like medium guiding apparatus according to the fourth aspect, the control means receives the detection information from the sheet-like medium detecting means for detecting the sheet-like medium being conveyed, and the driving means. It was decided to control the drive.
According to a sixth aspect of the present invention, in the sheet medium guiding apparatus according to any one of the third to fifth aspects, the guide surface has a position along the conveying direction of the sheet medium on the upstream side of the curved portion. The home position of the guide member is provided, and home position detecting means for detecting the home position is provided.
The invention according to claim 7 is the sheet medium guide device according to claim 6, further comprising home position detecting means for detecting that the guide member is located at a home position, wherein the control means is Receiving detection information from the home position detection means, the driving means sets the guide member to the home position, and receiving the detection information from the sheet medium detection means, the leading end of the sheet medium is the guide surface. The guide member is displaced by driving the driving means at the timing of contact with the guide member.
According to an eighth aspect of the present invention, in the sheet-like medium guiding apparatus according to the seventh aspect, the control means returns the guide member to the home position after the sheet-like medium passes through the guide surface.
The invention according to claim 9 is a path switching device for switching a plurality of paths of the sheet-like medium at a branching portion of the conveyance path through which the sheet-like medium is conveyed, and has a plurality of guide surfaces for guiding the sheet-like medium. A switching member that switches the path of the sheet-like medium by switching the position of these guide surfaces by displacement and a switching means that displaces the switching member are provided, and at least one of the guide surfaces (hereinafter referred to as a displacement guide surface). In accordance with the position of the leading end of the sheet-like medium, the displacement guide surface moves from the standby position along the conveyance direction on the upstream side of the branching portion to the conveyance state along the conveyance direction on the downstream side of the branching portion. The leading end portion of the sheet-like medium is guided while being displaced by the switching means.
According to a tenth aspect of the present invention, in the path switching device for the sheet-like medium according to the ninth aspect, the standby position and the conveyance position are both downstream in the conveyance direction of the displacement guide surface in the conveyance position. The side end portion is in a state where it protrudes to the inside of the conveyance path from the guide surface constituting the conveyance path, and the upstream end portion in the conveyance direction of the displacement guide surface does not protrude from the guide surface constituting the conveyance path in the standby state. It was decided to become.
According to an eleventh aspect of the present invention, in the sheet medium path switching device according to the ninth or tenth aspect, the switching means includes a means for swingably supporting the switching member, and a drive for driving the switching member. And control means for controlling the driving means.
According to a twelfth aspect of the present invention, in the route switching device for the sheet-like medium according to the eleventh aspect, the control means receives the detection information from the sheet-like medium detecting means for detecting the sheet-like medium being conveyed and receives the detection information. The driving of the means was controlled.
According to a thirteenth aspect of the present invention, there is provided the sheet medium path switching device according to the twelfth aspect, wherein the sheet medium detecting means is a sensor provided in the switching member or a sensor provided in the conveyance path upstream of the branching section. It was decided that.
According to a fourteenth aspect of the present invention, in the sheet medium path switching device according to any one of the tenth to thirteenth aspects, the displacement guide surface is along the conveying direction of the sheet medium upstream of the branch path. A home position detecting means for detecting the home position is provided as the home position of the switching member.
According to a fifteenth aspect of the present invention, there is provided the sheet medium path switching device according to the fourteenth aspect, further comprising home position detecting means for detecting that the switching member is located at the home position, and the control means. Receives the detection information from the home position detection means, sets the switching member to the home position by the drive means, receives the detection information from the sheet medium detection means, and the leading end of the sheet medium is The switching means is displaced by driving the driving means at the timing of contact with the displacement guide surface.
According to a sixteenth aspect of the present invention, in the route switching device for a sheet-like medium according to the fifteenth aspect, the control means returns the switching member to the home position after the sheet-like medium passes through the displacement guide surface. .
According to a seventeenth aspect of the present invention, there is provided an image forming apparatus including a conveyance path having a curved portion in a traveling direction of the sheet-like medium. Prepared for the department. Here, it is effective to apply to an image forming apparatus in which a fixing device is provided upstream of the curved portion.
The invention according to claim 19 is an image forming apparatus comprising a transport path having a branching section for branching and transporting the sheet-like medium, and the sheet-form medium path switching device according to any one of claims 9 to 16. Was provided in the branching section. Here, it is effective to apply to an image forming apparatus in which a fixing device is provided upstream of the branch portion. Furthermore, it is effective to apply to an image forming apparatus in which the branching unit is divided into a conveyance path toward the paper discharge unit and a conveyance path toward the reverse refeeding unit for double-sided image formation.

  By transporting the curved portion of the transport path while keeping the contact angle small by the guide surface that is displaced and guided according to the progress of the sheet-shaped medium, the transportability of the sheet-shaped medium can be improved.

[1] First Embodiment An image forming apparatus with a double-sided transport device to which the present invention is applied is set forth with reference to FIG. The image forming apparatus of this embodiment is a full-color printer that employs a so-called tandem method.
Inside the image forming apparatus 100, there are four latent images as image forming means for forming images of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Drum-shaped photoconductors 2Y, 2M, 2C, and 2Bk, which are carriers, are arranged in parallel at equal intervals in the left-right direction in the drawing. During operation of the image forming apparatus 100, the image forming apparatus 100 is rotated in the direction of the arrow by a drive source (not shown). Around these photoreceptors, members and devices necessary for an electrophotographic image forming apparatus such as a developing device are arranged to form image forming units 1Y, 1C, 1M, and 1Bk. The four image forming units 1Y, 1C, 1M, and 1Bk all have the same configuration.

  In each of the image forming units 1Y, 1C, 1M, and 1Bk, image forming members such as a charging device, a developing device, and a cleaning device are sequentially arranged around the photosensitive member as means for performing an electrophotographic process. .

  Below the photoreceptors 2Y, 2C, 2M, and 2Bk, laser light corresponding to image data for each color is scanned on the surface of each photoreceptor that has been uniformly charged by a charging device to form an electrostatic latent image. The exposure apparatus 8 is provided. The exposure device 8 is a laser scanning type exposure device using a laser light source, a polygon mirror, etc., and beam light 8Y, 8C, 8M modulated from four semiconductor lasers (not shown) according to image data to be formed. Issue 8Bk.

  The yellow (Y), cyan (C), magenta (M), and black (Bk) toners are consumed by the developing devices arranged corresponding to the photoreceptors 2Y, 2M, 2C, and 2Bk that handle the respective colors. From the toner cartridges 40Y, 40C, 40M, and 40Bk, which are detected by a toner detection unit (not shown) and store toner of each color provided in the upper part of the image forming apparatus 100, to each developing device by a supply unit (not shown). Supplied.

  The electrostatic latent image for each color formed on the surface of each of the photoconductors 2Y, 2C, 2M, and 2Bk by the light beams 8Y, 8C, 8M, and 8Bk is developed by a developing device arranged corresponding to each photoconductor. , Become a visible image.

  An intermediate transfer unit 6 is disposed above the photoreceptors 2Y, 2C, 2M, and 2Bk. In the intermediate transfer unit 6, an intermediate transfer belt 6a as an image carrier that is supported and stretched by a plurality of belt support rollers 6b, 6c, 6d, and 6e is disposed so as to run in the arrow direction. The intermediate transfer belt 6a is endless, and is stretched and arranged so that a part of each of the photoreceptors 2Y, 2C, 2M, and 2Bk after the developing process comes into contact.

  A toner image carried by each of the photoreceptors 2Y, 2C, 2M, and 2Bk is transferred to the intermediate transfer belt 6a. In this transfer, a bias is applied to the primary transfer roller 7, and the bias is electrostatically transferred to the belt surface.

  A cleaning device 6h is provided on the outer peripheral portion of the intermediate transfer belt 6a at a position facing the roller 6e. The cleaning device 6h wipes off unnecessary toner remaining on the surface of the intermediate transfer belt 6a and foreign matters such as paper dust. The roller 6e facing the cleaning device 6h includes a mechanism that applies tension to the belt 6a.

  A secondary transfer roller 14a is provided in the vicinity of the support roller 6b on the outer periphery of the intermediate transfer belt 6a. The secondary transfer roller 14a is applied with a transfer bias from a power supply 14b. The toner image carried by the intermediate transfer belt 6a is electrostatically transferred onto the sheet S by applying a bias while passing the sheet S between the intermediate transfer belt 6a and the secondary transfer roller 14a. The intermediate transfer belt 6a and the secondary transfer roller 14a constitute a secondary transfer portion 14.

  Below the exposure device 8, two stages of paper feed cassettes 9A and 9B are arranged so that they can be drawn out. Further, another sheet feeding device 50 is provided below. The paper feeding device 50 includes two paper feeding cassettes 9C and 9D. The paper S stored in these paper feed cassettes is selectively sent out by the rotation of the corresponding paper feed roller 10A, and sent to the transport path P1 by the separating means 11A and the transport roller pair 12A. A pair of registration rollers 13 is provided in the transport path P1. The registration roller 13 feeds the sheet S to the secondary transfer unit 14 at a feeding timing.

  A manual paper feeder 25 is provided on the right side of the figure. The uppermost sheet S stored in the manual sheet feeding device 25 is fed by the sheet feeding roller 26 and separated by the separating unit 27, and the pair of registration rollers is passed by the driving roller 22 and the conveying roller 24 through the conveying path P1. 13.

  A fixing device 15 having a heating unit is provided on the downstream side (upper side) of the secondary transfer unit 14 via a conveyance path P2. The fixing device 15 includes a fixing roller 15a with a built-in heater and a pressure roller 15b.

The conveyance path P3 on the downstream side of the fixing device 15 is branched into two. One branched conveyance path P4a reaches a pair of paper discharge rollers 16. The other branched conveyance path P4b reaches the reverse refeeding section for duplex image formation on the downstream side. Here, the reverse refeeding unit is a general term for a mechanism for reversing the paper and a conveyance path for guiding the paper after the reversal to the secondary transfer unit 14.
The branching section is provided with a first switching guide G1 as a switching member for switching the path of the sheet S that has been fixed.

  The first switching guide G1 is rotatable. In the state shown in the drawing, the sheet S after fixing is guided to the transport path P4a, and is discharged to the paper discharge unit T above the image forming apparatus 100 by the pair of paper discharge rollers 16. Stack paper.

The image forming apparatus 100 is provided with a reverse refeed unit including a transport path and rollers for reversing and refeeding paper so that images can be automatically formed on both sides of the paper downstream of the transport path P4b. Have
The reverse refeed unit includes a switchback path P5 and a refeed path P6 that continue from the conveyance path P4b inside the frame F, and forms an image on the other side of the sheet S on which image formation has been completed on one side. A first switching guide G1, a second switching guide G2, a reversible drive roller 18a, a reversible drive roller 22 and other rollers are provided so as to be conveyed again to the paper path P1.

  Conveying rollers 23 and 24 are in contact with the driving roller 22, and when the conveying roller 22 rotates in the clockwise direction, paper is conveyed from the manual sheet feeding device 25 in cooperation with the conveying roller 24. When rotating in the counterclockwise direction, the sheet S is fed again in the direction of the registration roller 13 in cooperation with the transport roller 23.

  When the first switching guide G1 is rotated clockwise about the shaft 107 from the state shown in the drawing, the sheet S after the fixing is guided to the conveyance path P7 by the roller pair 17 and the third switching guide G3, and the second switching guide G1. It is conveyed to the driving roller 18a and the driven roller 18b through the guide G2, and once sent to the switchback path P5.

  The drive roller 18a rotates counterclockwise with the trailing edge of the sheet held in, and the second switching guide G2 rotates counterclockwise from the illustrated state, so that the sheet S is re-feeded. It is sent to the road P6. The sheet S conveyed by the roller pairs 15c, 20 and 14c, 21 provided in the refeed path P6 is further conveyed by the pair of the driving roller 22 and the conveying roller 23 and reaches the registration roller 13.

  The third switching guide G3 above the fixing device 15 and downstream of the conveying direction of the roller pair 17 conveys the fixed paper to the paper discharge path P8 and transfers it to another paper discharge device (not shown). It is for discharging.

In this image forming apparatus, image formation on only one side of the paper S (single-sided mode) and image formation on both sides (double-sided mode) can be performed by the operator's selection.
In the single-sided mode, first, an electrostatic latent image is obtained by irradiating the uniformly charged surface of the photoconductor 2Y with laser light 8Y corresponding to image data for yellow emitted from the semiconductor laser by the operation of the exposure device 8. Is formed.

  This electrostatic latent image is developed with yellow toner by a developing device, becomes a visible image, and is primarily transferred to the surface of the intermediate transfer belt 6a that moves in synchronization with the photoreceptor 2Y by the transfer action of the primary transfer roller 7Y. Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner on the photoconductors 2C, 2M, and 2Bk.

  As a result, yellow Y, cyan C, magenta M, and black Bk toner images are carried on the surface of the intermediate transfer belt 6a as sequentially overlapping four-color toner images in the direction of the arrow together with the intermediate transfer belt 6a. Moved. On the other hand, the surface of each photoconductor is cleaned of residual toner and foreign matter by a cleaning device.

  The four-color toner image formed on the intermediate transfer belt 6a is transferred onto the sheet S conveyed in synchronization with the intermediate transfer belt 6a by receiving a transfer action by the secondary transfer roller 14a. Then, on the intermediate transfer belt 6a side, the surface is cleaned by a belt cleaning device 6h to prepare for the next image forming / transfer process. The sheet S on which the image has been transferred is subjected to a fixing action by the fixing device 15, and is discharged from the conveyance path P4a to the sheet discharge unit T through the sheet discharge roller 16 with the image surface facing downward (face down).

  In the duplex mode, by the operation as described above, first, the image is transferred from the intermediate transfer belt 6a to one side of the sheet S by the secondary transfer unit 14, and the sheet that has passed through the fixing device 15 is transferred by the first switching guide G1. The course is guided toward the roller pair 17.

  The sheet S that has exited the roller pair 17 passes through a third switching guide G3 and a conveyance path P7 provided downstream of the conveyance path of the roller pair 17, and is reversed with a driving roller 18a, a driven roller 18b, a switchback path P5, and the like. Proceed to the refeed section. In the reversing and refeeding section, the sheet S that travels sideways on the upper part of the second switching guide G2 at the rotation position in FIG. 1 is conveyed toward the conveying path P5 by the driving roller 18a and the driven roller 18b. The possible drive roller 18a rotates in a clockwise direction. The roller pair 19 provided in the conveyance path P5 is also a roller capable of forward and reverse rotation, and once the sheet is received in the switchback conveyance path P5, the sheet is reversely rotated to reversely feed the sheet. At that time, the second switching guide G2 rotates counterclockwise from the posture shown in the drawing, and is conveyed by the roller pairs 15c and 20 and the roller pairs 14c and 21 with the one that has been the rear edge of the paper as the leading edge. It is conveyed toward the path P1.

  The paper P transported on the transport path P1 is fed again to the registration roller 13. The sheet S having an image on one side is transported again toward the secondary transfer unit 14 having the secondary transfer roller 14a at the timing of the registration roller 13, thereby the toner on the intermediate transfer belt 6a. The image is transferred to the other side of the paper S.

  The sheet S on which the full-color toner images are transferred on both sides in this way is subjected to the fixing process 15 by the fixing device 15 again, the path is switched to the transport path P4a by the first switching guide G1, and the sheet discharge stack 16 discharges the sheet stack. The paper is discharged onto the section T. Although the illustrated image forming apparatus 100 is a so-called in-body discharge type, the present invention is not limited to this.

[2] Second embodiment
A sheet medium path switching apparatus according to the present invention will be described with reference to FIGS.
2a, 2b, and 2c show the first switching guide G1 in FIG. 1 and the upstream and downstream conveying paths in an enlarged manner. A conveyance path P3 located downstream of the fixing device 15 is branched at a branching portion 60 into a conveyance path P4a toward the paper discharge roller 16 and a conveyance path P4b toward the counter roller 17. These transport paths are composed of opposing guide plates that regulate and guide the path of the paper S. A paper discharge unit T is provided downstream of the paper discharge roller 16, and a reverse refeeding unit is provided downstream of the counter roller 17.

  There is not much change in the path of the paper S between the transport path P3 and the transport path P4b with the branching section 60 therebetween, but on the other hand, the paper path is between the transport path P3 and the transport path P4a with the branching section 60 in between. The course of S has changed and bent.

  A first switching guide G1 (hereinafter referred to as a branching claw G1) as a switching member for switching the path of the sheet S from the transport path P3 to the transport path P4a or the transport path P4b is disposed in the branch section 60. Has been. The branch claw G1 has a configuration in which a plurality of claw members are coaxially arranged on the shaft 107 as shown in FIG.

  The branch claw G1 has a substantially triangular shape as shown in FIG. 2 when viewed from the axial direction, and has two guide surfaces 61 and 62 for guiding the paper to portions corresponding to two sides of the triangle. The guide surface 60 is for guiding the paper S from the transport path P3 to the transport path P4b, and the guide surface 61 is for guiding the paper S from the transport path P3 to the transport path P4a.

  The branch claw G1 can swing around the shaft 107, and after swinging, the position of each guide surface is changed by control to stop in a predetermined position, and the path of the sheet S is changed from the transport path P3 to Switch to the transport path P4a or the transport path P4b.

In the switching state in which the sheet is guided from the conveyance path P3 to the conveyance path P4a, a dynamic element is included, and the guide surface is displaced according to the progress of the leading edge of the sheet. Basically, as shown in FIGS. 2a and 2b, the branch claw G1 blocks the conveyance path P4b, and the guide surface 61 is located across the conveyance path P3 and the conveyance path P4a, so that the sheet S is an arrow. As shown by, the guide surface 61 guides the transport path P3 to the transport path P4a.
More specifically, in FIG. 2 a, the guide surface 61 is in a standby state that takes a posture along the transport direction in the transport path P <b> 3 on the upstream side of the branching portion 60, and is stationary in this standby state. Wait for the paper S.

  However, when the sheet S arrives at the branching portion 60, the rotation of the branching claw G1 about the shaft 107 starts to rotate counterclockwise according to the position of the leading end of the sheet S, and the guide surface 61 is displaced while the leading end of the sheet S is displaced. The sheet is guided and finally stopped in the conveying position shown in FIG. In this transport position, the guide surface 61 takes a posture along the transport direction on the transport path P4a on the downstream side of the branch portion 60. Thus, the guide surface 61 is guided while being displaced according to the position of the leading end of the sheet S. In this sense, the guide surface 61 is dynamic and is also referred to as a displacement guide surface.

  Another switching state is a state in which the branching claw G1 blocks the transport path P4a and the guide surface 62 is located across the transport path P3 and the transport path P4b as shown in FIG. As indicated by an arrow, the guide surface 62 guides the transport path P3 and guides it to the transport path P4b. In this switching state, the guide surface 62 is static because it is fixed in one posture, and the position of the guide surface 62 is referred to as a fixed state.

  The guide surface 60, which is a guide surface to the transport path P4b, has a small degree of course change from the transport path P3 to the transport path P4b. The guide surface 61, which is a guide surface, has a large degree of course change from the transport path P3 to the transport path P4a, and is curved with a curvature corresponding to this.

  In this example, when guiding from the conveyance path P3 constituting the curved portion having a large degree of course change to the conveyance path P4a, the guide surface 61 is changed from the standby position [FIG. 2a] to the conveyance position according to the position of the front end of the sheet. Although the displacement is performed up to [FIG. 2 b], with this displacement, the contact angle of the leading edge of the sheet S with respect to the guide surface 61 is kept small as the leading edge of the sheet S advances.

  In the stand-by position [FIG. 2a], the guide surface 61 is in a position along the transport direction (arrow direction) of the transport path P3 on the upstream side of the branch portion 60 (curved portion). ], The guide surface 61 is in a position along the conveyance direction (arrow direction) in the conveyance path P4a on the downstream side of the branch portion 60 (curved portion). Simultaneously with the advancement of the paper leading edge, the guide surface 61 is displaced from the standby position to the transporting position, and the paper leading edge is guided while the contact angle of the paper leading edge with respect to the guide surface 61 is small.

  Here, as a comparative example, a case will be described in which the paper is guided in a manner according to the prior art in which the guide surface 61 is kept static while the paper S is guided and is not displaced. Assume that a sheet S ′ having an unfavorable condition is conveyed to the guide surface 61 fixed in the standby position shown in FIG. 3A, curled in the direction opposite to the curving direction of the guide surface 61. In this case, the contact angle θ1 of the leading edge of the sheet S ′ with respect to the guide surface 61 is relatively small as shown in FIG. This is because in the standby state, the guide surface 61 is in a state along the transport direction of the transport path P3, and it can be said that the front end portion is difficult to jam. However, the sheet S ′, which is pushed forward by the fixing unit 15 and is conveyed by being regulated by the guide plate 63 that constitutes the conveyance path, is deformed so that the leading end thereof rises with respect to the guide surface 61. It is considered that the contact angle θ1 becomes large and the leading edge of the sheet is prevented from proceeding and jammed easily. Since the guide surface 61 is statically fixed by assumption, there is a risk that the tip portion will jam as a result.

  On the other hand, suppose that the guide surface 61 fixed by the guide surface 61 in the transport position shown in FIG. 4A is curled in the direction opposite to the curving direction of the guide surface 61 as in FIG. Assume that a badly conditioned sheet S ′ has been conveyed. In this case, the contact angle θ2 of the leading end of the sheet S ′ with respect to the guide surface 61 is relatively large from the beginning as shown in FIG. This is because the guide surface 61 is set to a position along the transport direction of the transport path P4a so as to be suitable for guiding the portion after the leading end of the sheet under the transport position. When the leading end of the sheet S ′ contacts the guide surface under the state of the state, the leading end jam of the sheet is likely to occur.

  As described above, when the paper is guided in a static manner in which the guide surface 61 is not displaced according to the position of the leading edge of the paper, there is a possibility of jamming. On the other hand, in the dynamic configuration in which the guide surface 61 is displaced according to the position of the leading end of the sheet as in this example, the sheet is waited in the standby state and the leading end of the sheet comes into contact with the guiding surface. The guide surface 61 starts to move toward the conveyance position from the beginning, and the displacement is continued as the leading edge of the paper advances. Therefore, the leading edge of the paper always has a relatively small contact angle θ1 with respect to the guiding surface 61. The tip can be guided while maintaining the degree. When the leading edge portion is guided in this way, the leading edge portion of the sheet S ′ is deformed as indicated by a two-dot chain line in FIG. 4A in the transporting position, and the contact angle becomes a relatively small θ1. Thereafter, it is smoothly guided to the transport path P4a.

  In the fixing device 15 illustrated in FIG. 1, the pressure roller 15b made of a hard material is pressed against the fixing roller 15a made of a relatively soft material. Therefore, as shown in FIG. The sheet S ′ passing through the nip portion tends to curl toward the pressure roller 15b, and this curl tendency is shown in FIGS. 3 and 4 because of the layout of various apparatuses for image formation. However, in the present embodiment, it is possible to obtain good conveyance performance even with respect to the sheet S ′ which is unfavorable in terms of the conveyance performance.

  As shown in FIG. 2a, in the stand-by position, the upstream end 61a in the transport direction of the guide surface 61 serving as the displacement guide surface does not protrude from the guide surface (inner surface) of the guide plate 64 constituting the transport path. Further, as shown in FIG. 2b, in the transport position, the downstream end 61b in the transport direction of the guide surface 61 serving as the displacement guide surface protrudes from the guide surface (inner side surface) of the guide plate 65 constituting the transport path to the inside of the transport path. State. This is because a step that hinders the conveyance of the leading end of the sheet is not created.

  Displacement of the guide surfaces 61 and 62 to the standby position, the transport position, and the fixed position described above is performed by the displacement of the branch claw G1, and the switching means performs the displacement of the branch claw G1. In FIG. 6, the switching means includes a shaft 107 that is supported by a bearing (not shown) and supports the branch claw G1 so as to be swingable, a drive means that drives the branch claw G1, and a control means that controls the drive means. The leading end side of the branching claw G1 can be fitted into a hole (which may be a concave shape) provided in the guide plates 63 and 64, so that the conveyance direction of the paper S is branched.

  Driving means for driving the branch claw G1 includes a pulley 106 fixed to the shaft 107, a stepping motor 105, a pulley 108 fixed to the rotation shaft of the stepping motor 105, a timing belt 109 wound around the pulleys 106 and 108, and the like. Become. The branching claw G1 is displaced by the driving force of the stepping motor 105.

A shutter 102 for detecting the rotational position is fixed to the shaft 107, and the guide surface of the branching claw G1 is detected by detecting the edge of the shutter 102 with a photo sensor 103 as home position detecting means for detecting the home position of the branching claw G1. It is possible to detect that 61 is in the standby position.
The stepping motor 105 is driven at the timing when the leading edge of the sheet S comes into contact with the guide surface 61 of the branching claw G1 in the standby position as the home position, and the branching claw G1 is moved from the standby position toward the transporting position.
Detection that the leading edge of the sheet S abuts (or approaches) the guide surface 61 of the branch claw G1 is performed by a reflective sensor 101 embedded in the middle of the guide surface 61 of the branch claw G1. The control means, which will be described later, that has received the detection information of the sensor 101 can calculate the point in time when the tip portion contacts the guide surface 61 and set the displacement timing of the branch claw G1.
Alternatively, instead of embedding the sensor in the guide surface 61 as in the above example, the leading edge of the sheet S is detected by an appropriate sensor such as a jam detection sensor provided in the conveyance path on the upstream side of the branching portion 60, and this detection time point Then, the timing of the displacement of the branch claw G1 can be set by calculating the time point when the leading end abuts the guide surface 61 from the required time from the sensor to the guide surface 61.
Since the branch claw G1 can be switched by using the registration start of the sheet S waiting at the registration roller 13 as a trigger, the registration sensor 110 is located immediately upstream of the nip portion of the registration roller 13 as shown in FIG. In the configuration in which the sheet is arranged, it is possible to know the timing at which the sheet reaches the guide surface G1 based on the registration roller driving start timing instead of the registration roller 13.

  In FIG. 7, the control means 111 including a CPU or the like drives the stepping motor 105 to displace the branching claw G1 based on the output information from the sensor 101, the operation unit 112, registration roller driving start information, and the like. The operation unit 112 is an operation unit of the image forming apparatus 100. If the instruction given by the operator at the operation unit 112 is image formation on only one side of the paper S (single-sided mode), the guide surface 61 is brought into the standby state of FIG. In the case of image formation on both sides (double-sided mode), the guide surface 62 is set to the fixed state shown in FIG. 2c when the one-sided image ends, and the guide surface 61 is set to the standby state shown in FIG. return.

  Normally, the standby position shown in FIG. 2a is set as the home position, but when the sheet is branched to the transport path P4a, the stepping motor 105 is started to start when the leading end of the sheet comes into contact with the guide surface 61. Rotate for a predetermined number of pulses as the tip of the head advances, and then stop. This stopping position is the conveying state of FIG. When branching the sheet to the transport path P4b, the stepping motor 105 is started and rotated by a predetermined pulse to stop in a fixed state.

  The photo sensor 103 is home position detecting means for detecting that the branch claw G1 is located at the home position, and the control means 111 receives the detection information from the photo sensor 103, and the stepping motor 105 moves the branch claw G1 to the home position. In a standby position, the detection information from the sensor 101 is received, and the stepping motor 105 is driven at the timing when the leading edge of the sheet S comes into contact with the guide surface 61 to displace the branching claw G1 to the transport position. The control unit 111 returns the branching claw G1 to the standby position after the trailing edge of the sheet has passed the guide surface 61.

[3] Third Embodiment In the second embodiment, the transportability of the paper S in the curved portion of the transport path in the branching section 60 is improved. It improves the transportability at the part where the transport path is bent.

  For example, in the switchback path P5 of the image forming apparatus 100 shown in FIG. 1, the section between the driving roller 18a and the roller 19 has a curved portion 120 in which the paper path changes from the horizontal direction to the vertical direction. . In the curved portion 120, the paper transportability is lowered.

  Therefore, in the present embodiment, as shown in FIGS. 8 and 9, the guide member G1 ′ provided with the guide surface 61 ′ that guides the paper S disposed on the curved portion 120 and the position of the leading end of the paper S are provided. The guide member G1 ′ is moved so that the guide surface 61 is displaced from the position along the conveyance direction on the upstream side of the curved portion 120 to the position along the conveyance direction on the downstream side of the curved portion 120 as the travel of the curved portion 120 progresses. A guide device for the sheet S in the curved portion 120 is configured by the displacement means for displacing.

  In the present embodiment, the sheet guide mode in the curved portion 120 is the same as the guide mode from the transport path P3 to the transport path P4a in the second embodiment. That is, the guide member G <b> 1 ′ corresponds to the branch claw G <b> 1 and the guide surface 61 ′ corresponds to the guide surface 61.

  As shown in FIG. 8, the guide surface 61 ′ waits for the leading edge of the paper S in a standby position that is a position along the paper conveyance direction on the upstream side of the curved portion 120. Then, from the time when the leading edge of the sheet S comes into contact with the guide surface 61 ′, the displacement of the inclination of the guiding surface 61 ′ is started according to the progress of the position of the leading edge of the sheet S, and as shown in FIG. Displacement is performed until 'is in a transport state that is a position along the transport direction on the downstream side of the curved portion 120. This displacement is performed by the rotation of the guide member G1 'about the shaft 107'. In the process of displacement, the contact angle with the guide surface 61 'is maintained so as not to increase.

  Displacement means for displacing the guide member G1 ′ includes a means for supporting the guide member G1 in a swingable manner, such as a shaft 107 ′ to which the guide member G1 ′ is fixed, a bearing, and a drive means (first step) for driving the guide member G1 ′. And a control unit (corresponding to the control unit 111 in the second embodiment) for controlling the driving unit. The stepping motor 105, the pulleys 106 and 108, the timing belt 109, etc. . This control means receives the detection information from the paper detection means (reflection type sensor 101 ′ embedded in the guide surface 61 ′, registration sensor 110, etc.) for detecting the paper being conveyed, and drives the stepping motor as the drive means. Control to perform displacement between the standby position and the transport position.

  The standby position (FIG. 8) in which the guide surface 61 ′ is in the position along the conveyance direction of the sheet-like medium on the upstream side of the curved portion 120 is defined as the home position of the guide member G <b> 1 ′. The home position detecting means for detecting the home position is a member corresponding to the shutter 102 and the photosensor 103 in FIG. 6, and the guide member C1 ′ is set to the home position in accordance with the contents described in the third embodiment. In response to the detection information from the sheet detecting means such as the sensor 101 ′, the driving means is driven at the timing when the leading end of the sheet comes into contact with the guide surface 61 ′ to displace the guide member C1 ′ between the standby position and the transport position. Let The control means returns the guide member G1 'to the home position after the sheet passes through the guide surface 61'.

  In the present embodiment, the curved portion 120 in the image forming apparatus in FIG. 1 is shown as an example of the curved portion to which the guide device for the paper S is applied. The present invention can be applied when there is a risk of partial jam. In this example, in relation to the fixing device 15, the curl tendency by the fixing device 15 and the bending tendency in the curved portion 120 are in the same direction, and it can be said that the leading edge jam hardly occurs, but it is at a position away from the fixing device. As a result, the curl tendency may change to be unfavorable for the conveyance of the curved part during the conveyance process, and in fact, the risk of the occurrence of a jam at the tip part due to the balance between the degree of curl and the degree of bending. In such a case, it is better to apply.

1 is a front view of an image forming apparatus. It is a figure explaining the state of the branching nail | claw in a standby position. It is a figure explaining the state of the branch nail | claw in a conveyance position. It is a figure explaining the state of the branch nail | claw in a fixed state. (A) is the figure explaining the contact angle of the sheet | seat with respect to the guide surface in a stand-by state, (b) is the elements on larger scale of the contact angle part. (A) is the figure explaining the contact angle of the sheet | seat with respect to the guide surface in a conveyance state, (b) is the elements on larger scale of the contact angle part. FIG. 6 is a diagram illustrating a paper curl tendency in a fixing device section. It is the perspective view which showed the principal part of the course switching apparatus. It is the block diagram which established the control system of the stepping motor. It is a figure explaining the state of the guide member in a stand-by position. It is a figure explaining the state of the guide member in a conveyance state.

Explanation of symbols

60 Branching portions 61, 61 ′, 62 Guide surface 100 Image forming apparatus 101, 101 ′ Sensor 102 Shutter 103 Photosensor 105 Stepping motor 110 Registration sensor 111 Control means 120 Curved portion G1 First switching guide (switching member, branching claw)
G1 'guide members P3, P4a, P4b Transport path P5 Switchback path P6 Refeed path S Paper (sheet-like medium)

Claims (21)

A method for guiding a sheet-like medium in a conveyance path having a curved portion in which the traveling direction of the sheet-like medium changes,
The leading end of the sheet-like medium that has reached the curved portion is received by a guide surface of a guide member that is provided in advance in the curved portion, and the contact angle of the sheet-like medium with respect to the guiding surface is reduced as the leading end advances. A guide method for a sheet-like medium, wherein the guide member is displaced and guided while maintaining. The sheet-like medium guiding method according to claim 1,
The guide surface of the sheet-like medium formed on the guide member is placed in an inclined position along the conveying direction on the upstream side of the curved portion, and waits for the arrival of the sheet-like medium.
When the leading end of the sheet-like medium reaches the guide surface, the guide surface is displaced so as to be in a position along the conveying direction on the downstream side of the curved portion as the leading end advances. A method for guiding a sheet-like medium, characterized by guiding a leading end. A sheet medium guide device used in a conveyance path having a curved portion in which the traveling direction of the sheet medium changes.
A guide member provided with a guide surface arranged in the curved portion for guiding the sheet-like medium;
The guide surface is displaced from a position along the conveying direction on the upstream side of the curved portion to a position along the conveying direction on the downstream side of the curved portion according to the progress of the position of the leading end portion of the sheet-like medium. As described above, a sheet medium guide apparatus comprising a displacement means for displacing the guide member. The sheet-like medium guiding device according to claim 3,
The apparatus for guiding a sheet-like medium, wherein the displacing means includes means for swingably supporting the guide member, drive means for driving the guide member, and control means for controlling the drive means. The sheet-like medium guiding apparatus according to claim 4,
An apparatus for guiding a sheet-like medium, wherein the control means receives detection information from a sheet-like medium detection means for detecting a sheet-like medium being conveyed, and controls driving of the driving means. The sheet-like medium guiding device according to any one of claims 3 to 5,
The sheet is provided with a home position detecting means for detecting a home position of the guide member, wherein the guide surface is in a position along the conveying direction of the sheet medium on the upstream side of the curved portion. -Shaped medium guide device. The sheet-like medium guiding device according to claim 6,
Home position detection means for detecting that the guide member is located at a home position, and the control means receives detection information from the home position detection means and moves the guide member to the home position by the drive means. And receiving the detection information from the sheet-like medium detecting means, and driving the driving means at a timing when the leading end of the sheet-like medium comes into contact with the guide surface to displace the guide member. Sheet-like medium guiding device. The sheet-like medium guiding device according to claim 7,
The control unit is configured to return the guide member to the home position after the sheet medium has passed through the guide surface. A path switching device that switches a plurality of paths of a sheet-like medium at a branch portion of a conveyance path through which the sheet-like medium is conveyed,
A switching member that has a plurality of guide surfaces for guiding the sheet-shaped medium and switches the path of the sheet-shaped medium by switching the position of the guide surfaces by displacement; and a switching means for displacing the switching member,
With respect to at least one of the guide surfaces (hereinafter referred to as a displacement guide surface), the displacement guide surface is in a standby state along the transport direction on the upstream side of the branch portion, depending on the position of the leading end of the sheet-like medium that travels. An apparatus for switching a path of a sheet-like medium, wherein the leading end of the sheet-like medium is guided while being displaced by the switching means from a position to a conveying position along a conveying direction on the downstream side of the branching section. In the route switching device for a sheet-like medium according to claim 9,
With respect to both the standby state and the transport state, in the transport state, the downstream end of the displacement guide surface in the transport direction is in a state of protruding from the guide surface constituting the transport path to the inside of the transport path, and In the standby state, the upstream end portion in the transport direction of the displacement guide surface does not protrude from the guide surface constituting the transport path. In the route switching device for a sheet-like medium according to claim 9 or 10,
The switching means includes means for swingably supporting the switching member, driving means for driving the switching member, and control means for controlling the driving means. apparatus. In the route switching device for a sheet-like medium according to claim 11,
An apparatus for switching a path of a sheet-like medium, wherein the control means receives detection information from a sheet-like medium detection means for detecting a sheet-like medium being conveyed and controls driving of the driving means. In the route switching device for a sheet-like medium according to claim 12,
The sheet-like medium path switching device, wherein the sheet-like medium detecting means is a sensor provided on the switching member or a sensor provided on a conveyance path upstream of the branching section. The route switching device for a sheet-like medium according to any one of claims 9 to 13,
The displacement guide surface is provided with home position detecting means for detecting the home position by setting the position along the conveying direction of the sheet-like medium on the upstream side of the branch path as the home position of the switching member. A path switching device for sheet media. The route switching device for a sheet-like medium according to claim 14,
Home position detecting means for detecting that the switching member is located at the home position, and the control means receives detection information from the home position detecting means and causes the switching member to move the switching member to the home position. And setting the position to receive the detection information from the sheet-like medium detecting means, and driving the driving means at a timing when the leading end of the sheet-like medium comes into contact with the displacement guide surface to displace the switching member. A sheet-type medium path switching device. The route switching device for a sheet-like medium according to claim 15,
The path switching device for a sheet-like medium, wherein the control means returns the switching member to the home position after the sheet-like medium passes through the displacement guide surface. In the image forming apparatus provided with a conveyance path having a curved portion in the traveling direction of the sheet-like medium,
9. An image forming apparatus comprising the sheet-shaped medium guiding device according to claim 3 in the curved portion. The image forming apparatus according to claim 17.
An image forming apparatus, wherein a fixing device is provided upstream of the curved portion. In an image forming apparatus provided with a conveyance path having a branching section that branches and conveys a sheet-like medium,
17. An image forming apparatus comprising the sheet medium path switching device according to claim 9 at the branching portion. The image forming apparatus according to claim 19.
An image forming apparatus, wherein a fixing device is provided upstream of the branch portion. The image forming apparatus according to claim 20, wherein
2. The image forming apparatus according to claim 1, wherein the branching unit is divided into a conveyance path toward the paper discharge unit and a conveyance path toward the reverse refeeding unit for double-sided image formation.

Images