JP2006182523A - Sheet carrying mechanism and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrying mechanism for carrying sheets to a target unit while suppressing the number of sensors arranged on a carrying passage to reduce the occurrence of carrying jam and detecting the condition of carrying the sheets about their treatment. <P>SOLUTION: The sheet carrying mechanism comprises a main carrying passage S and a switch-back carrying passage S' via which the sheet is carried, a branch pawl 43 located on the carrying passages S, S', one part of which abuts on the sheet, rocks from an initial position H to a rocking position A and returns to the initial position H with its dead weight to serve as a carrying passage changing portion 43a for changing the carrying passages S, S' and the other part of which serves as a detected portion 43b, and a photo sensor 46 and a control part 50 for detecting the condition of the carrying passage changing portion 43a from the detected portion 43b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a paper transport mechanism for transporting paper and an image forming apparatus including the paper transport mechanism.

  In recent years, with the diversification of image forming apparatuses, the main unit is equipped with a double-sided printing function, optional stapling and punching processes, a shifter function for sorting discharged paper, and an image forming unit such as a multi-bin sorter. An increasing number of units have been connected or connected.

In such an image forming apparatus, it is necessary to switch the transport path in order to transport the paper being transported to a target unit or the like according to the requested image formation processing content, and the transport path is branched. Many have been developed. In addition, an image forming apparatus having a branched conveyance path includes a conveyance path for conveying a sheet, and whether the sheet is accurately conveyed to a target unit or the like and is processed on the conveyance path. A plurality of sensors (mechanism sensors, optical sensors, etc.) that are means for detecting the conveyance state of the paper, and a branch claw that is located at a position where the conveyance path branches and navigates the leading edge of the paper in a desired conveyance direction A paper transport mechanism is provided (see, for example, Patent Document 1).
JP 2001-335217 A

  However, in the configuration of the above-described Patent Document 1, a plurality of sensors and branching claws arranged on the conveyance path cause paper conveyance JAM. This is because the sheet being conveyed is caught by being in contact with a sensor or branch claw located on the conveyance path. In addition, the shape of the transport path must be matched to the sensor or branch pawl arrangement shape, etc., in order to properly display the functions of the sensor and branch claws, so the transport path does not become a smooth shape. Has become complicated.

  The object of the present invention is to suppress the number of sensors and the like on the conveyance path and reduce the occurrence of conveyance JAM, while conveying the sheet such as whether the sheet is conveyed to the target unit and processed. It is an object of the present invention to provide a paper transport mechanism and an image forming apparatus that can detect the above.

  In order to solve the above problems, the present invention has the following configuration.

(1) A branching claw positioned on a transport path through which a sheet is transported, a part of which is brought into contact with the sheet on the transport path to move from an initial position, and returns to the initial position by its own weight. A branch claw that is a transport path changing unit that changes the transport path, and the other part is a detected part that moves in conjunction with the transport path changing unit;
A position detection unit that detects a position of the detected portion and a state detection unit that detects a state of the transport path changing unit based on a detection result of the position detection unit.

  In this configuration, the transport path changing unit switches the transport path by moving by the contact of the sheet at the initial position, and switches the transport path by returning to the initial position by its own weight when the contact of the sheet disappears, and A branching claw having a detected portion that moves together with the conveyance path changing unit and is detected by the position detection means is arranged on the conveyance path. Further, the state of the transport path changing unit is detected based on the detection result detected by the position detecting unit by the state detecting unit.

  Therefore, from the state of the transport path changing unit detected by the state detection unit, the transport direction of the paper, the timing at which the paper has passed, and the transport state of the paper such as the paper transport JAM are detected.

  Further, since the detected portion of the position detecting means is provided in the branching claw, it is not necessary to provide the detected portion separately on the transport path. In addition, since a part of the transport path is changed and a part of the detected part is a branch claw, the transport path change part and the part to be detected are not configured in the same region, and the structure of the branch claw is complicated. do not become.

  (2) The branching claw is supported by an axis whose axis direction is orthogonal to the conveyance path so as to be swingable, and the conveyance path changing unit is an area on the side through which the paper on the conveyance path passes from the axis. The detected portion is in a region on the side where the sheet on the transport path does not pass from the shaft.

  In this configuration, the branching claw is supported so as to be swingable on an axis whose axial direction is orthogonal to the conveyance path. For this reason, the conveyance path changing unit swings about the axis by the contact of the paper on the conveyance path. Further, since the detected part is located in the region where the sheet on the transport path does not pass from the shaft, the detected part always swings to a position facing the transport path changing part by swinging of the branching claw.

  Therefore, since the state of the transport path changing unit is detected based on the detected part that swings as the transport path changing unit swings, the configuration of the branch claw and the configuration of detecting the state of the transport path changing unit are complicated. In addition, there is no need to expose the detected portion on the conveyance path.

(3) The detected parts are two detected members that pass through the position detecting unit according to the state of the corresponding transport path changing unit and have different widths in the direction of passing through the position detecting unit.
The state detection unit detects a time during which the two detected members pass based on a detection result of the position detection unit, and detects a state of the transport path changing unit according to the detected time. To do.

  In this configuration, one of the two detected members having different widths in the direction of passing through the position detecting unit passes through the position detecting unit with the movement of the conveyance path changing unit. Further, the state detection means detects the time that the detected member passes based on the detection result of the position detection means, and detects which detected member has passed by the difference in the passing time. Therefore, the state of the transport path changing unit is easily detected based on the time that the detected unit passes.

  (4) The position detecting means includes a photo sensor.

  In this configuration, the position detection means includes a photosensor. Therefore, the configuration of the detected portion and the position detection means is simply configured.

(5) an opening / closing door that opens the inside of the main body mechanism;
A stopper that supports the branching claw at the initial position when the door is completely closed and interrupts the support when the door is open,
The transport path changing unit swings downward from the initial position by its own weight when the support is interrupted.

  In this configuration, a stopper is provided that interrupts the support of the branching claw at the initial position while the open / close door is open. Further, while the opening / closing door is opened, the conveyance path changing unit swings downward from the initial position by its own weight, and one of the two detected members passes through the position detecting means. Therefore, since the transfer path changing unit swings according to the state of the open / close door, the open / close state of the open / close door is also detected by the position detecting unit and the state detecting unit.

(6) Provided with a display means for displaying the conveyance status of the paper on the conveyance path,
The state detection means passes through a predetermined arrangement position of the branching claw on a maximum size sheet that can be conveyed on the conveyance path, when the conveyance path changing unit is in contact with the sheet. When the passage time elapses, the paper conveyance JAM is displayed on the display means.

  In this configuration, the conveyance JAM is generated when the state detection unit continuously detects the state in which the conveyance path changing unit is in contact with the sheet and moves even after a predetermined passage time has elapsed. The display means displays that the conveyance JAM has occurred.

(7) The paper transport mechanism according to any one of (1) to (6) is provided,
An image is formed on a sheet conveyed on the conveyance path.

  In this configuration, the paper transport mechanism according to any one of (1) to (6) is provided, and image formation is performed on the paper transported on the transport path.

(8) The paper transport mechanism according to any one of (1) to (6) is provided,
The conveyance path includes a main conveyance path from an image forming unit that forms a toner image on a sheet to a sheet discharge unit that discharges the sheet to the outside via a fixing device that fixes the toner image, and the discharge route. A switchback transport path for switchback transporting the paper on which one side is imaged from the paper section to the image forming section,
The transport path changing unit switches between the main transport path and the switchback transport path.

  In this configuration, the paper transport mechanism according to any one of (1) to (6) is provided, and after the paper is image-formed on one surface and transported to the paper discharge unit, the paper is transported by the transport path changing unit. The main transport path and the switchback transport path included in the path are switched, switchback transport is performed, and image formation is performed on the other surface.

  According to the present invention, the following effects can be obtained.

  (1) By detecting the state of a part of the transport path changing part of the branching claw based on the detected part of the other part, it is not necessary to separately provide the detected part on the transport path. The configuration is not complicated, and the sheet conveyance state can be detected while reducing the occurrence of sheet conveyance JAM. Further, since a part of the transport path changing unit and another part of the detected part constitute a branch claw, the structure of the branch claw can be simplified.

  (2) By disposing the transport path changing unit in an area on the side where the paper on the transport path passes from the axis, and disposing the detected part in an area on the side where the paper on the transport path does not pass from the axis, Since the state of the transport path changing unit can be detected based on the detected part that swings with the swing of the transport path changing unit, the configuration of the branching claw and the state of detecting the state of the transport path changing unit can be simplified. In addition, since it is not necessary to expose the detected portion on the transport path, the configuration of the transport path is not complicated, and the occurrence of paper transport JAM can be further reduced.

  (3) By making the detected portion two detected members having different widths in the direction of passing through the position detecting means, the state of the transport path changing portion can be easily detected by the difference in time passing through the position detecting means. With the simple configuration, it is possible to detect the states of the three transport path changing units including the initial position.

  (4) By including a photo sensor in the position detection means, the configuration of the detected part and the position detection means can be simply configured.

  (5) By providing a stopper that interrupts the support of the branching claw at the initial position while the open / close door is opened, the conveyance state of the paper on the conveyance path is detected using the position detection unit and the state detection unit. In addition, the open / closed state of the door can be detected.

  (6) By displaying that the transport JAM has occurred, it is possible to immediately notify the user of the abnormality.

  (7) Since the paper transport mechanism according to any one of (1) to (6) is provided, it is not necessary to separately provide the detected part on the transport path, so that the configuration of the transport path becomes complicated. Therefore, it is possible to detect the sheet conveyance state while reducing the occurrence of sheet conveyance JAM.

  (8) By including the paper transport mechanism according to any one of (1) to (6), switching between the main transport path and the switchback transport path in double-sided image formation also includes a transport path changing unit and a detected unit. Since it can be performed using a branching claw, it is not necessary to provide the detected part separately on the transport path, so that the structure of the transport path does not become complicated, and also in an image forming apparatus that forms images on both sides. It is possible to detect the sheet conveyance state while reducing the occurrence of sheet conveyance JAM.

  Hereinafter, an image forming apparatus having a sheet conveyance path according to the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 as the main body apparatus of the present invention has a copier mode, a printer mode, and a FAX mode as image forming modes for forming an image on a sheet (including a recording medium such as an OHP). It is selected and image formation on both sides is possible.

  The image forming apparatus 100 includes a document reading unit 10, a paper feeding unit 20, an image forming unit 30, a paper transport mechanism 40, a paper discharge unit 50, an operation panel unit (not shown), and the like. The document reading unit 10 is disposed on the upper part of the apparatus main body, and includes a platen glass 11, an automatic document feeder 12, a first scanning body 13, a second scanning body 14, a reading optical unit 15, and the like. The document reading unit 10 scans one or both sides of the document placed on the platen glass 11 via the document transport path R and the switchback document transport path R ′ to read image information. A platen glass 11 disposed below the automatic document feeder 12 is made of transparent glass, and a document is placed so that the document surface faces the upper surface. The automatic document feeder 12 automatically feeds the document stored on the document set tray 12 a onto the platen glass 11. When a plurality of documents are placed on the document set tray 12a, the documents are fed onto the platen glass 11 one by one.

  The first scanning body 13 includes an exposure lamp 13a, a first reflecting mirror 13b, and the like. The exposure lamp 13 a exposes a document surface of a document placed on the platen glass 11 or a document fed on the platen glass 11 by the automatic document feeder 12. The first reflecting mirror 13b causes the image light reflected on the document surface to enter a second reflecting mirror described later.

  The second scanning body 14 includes a second reflection mirror 14a, a third reflection mirror 14b, and the like. The second reflection mirror 14a reflects the image light incident from the first reflection mirror 13b and causes the image light to enter the third reflection mirror 14b. The third reflection mirror 14 b reflects the image light incident from the second reflection mirror 14 a and causes the image light to enter the imaging lens 15 a constituting the reading optical unit 15. The reading optical unit 15 includes an imaging lens 15a, a CCD (Charge Coupled Device) 15b, and the like, and reads image light from the document surface. The imaging lens 15a focuses the image light incident from the third reflecting mirror 14b on the CCD 15b. The CCD 15b photoelectrically converts the received image light.

  When the original surface of the original placed on the platen glass 11 is read, the first scanning body 13 is moved at a predetermined moving speed V along the surface direction of the platen glass 11 by a driving means (not shown), and exposure is performed. The lamp 13a exposes the document surface. At this time, the second scanning body 14 is moved along the surface direction of the platen glass 11 at the moving speed V / 2 in conjunction with the movement of the first scanning body 13 and the original surface incident from the first scanning body 13. Is incident on the imaging lens 15a. The reason why the moving speed of the second scanning body 14 is set to V / 2 with respect to the moving speed V of the first scanning body 13 is that the optical path length of the optical path M from the document surface to the CCD 15b is kept constant and the image light is accurately transmitted. This is for receiving light.

  On the other hand, when reading a document stored in the document placement tray 12a of the automatic document feeder 12, the first scanning body 13 is stationary at the position shown in FIG. The original surface of the original fed on the platen glass 11 facing the first scanning body 13 is exposed. The exposed document is placed on the paper discharge tray 12b. At this time, the image light from the first scanning body is incident on the imaging lens 15a while the second scanning body 14 is also stationary at the position shown in FIG.

  The paper feed unit 20 is disposed at the lower part of the apparatus main body, and includes a paper feed tray 21, a manual feed tray 22, a paper feed roller 23, a separating member 24, and the like. The paper feed tray 21 and the manual feed tray 22 place paper fed to the main transport path S during image formation. The paper feed roller 23 rotates and conveys the paper stored in the paper feed tray 21 and the like to the separating member 24. The separating member 24 conveys one sheet at a time to the main conveying path S when the sheets conveyed by the sheet feeding roller 23 are conveyed in a superimposed manner.

  The image forming unit 30 is disposed on the side of the manual feed tray 22 below the document reading unit 10, and includes a laser scanning unit (hereinafter referred to as LSU) 37, a photoconductor 31 that is an image carrier of the present invention, and a fixing device 36. A charger 32, a developing device 33, a transfer device 34, and a cleaning unit 35 are arranged around the photoconductor 31 in this order along the arrow Y direction that is the rotation direction of the photoconductor 31. .

  The paper transport mechanism 40 includes a transport roller 41, a registration roller 42, a branch claw 43, and the like, and transports paper on the main transport path S and the switchback transport path S ′. The main transport path S guides the paper from the paper supply unit 20 to the paper discharge unit 50 via the image forming unit 30. The switchback conveyance path S ′ guides the paper on which one side has been image-formed from the paper discharge roller 51 to the registration roller 42 while reversing the paper when the double-sided image is formed. The transport roller 41 is positioned on the main transport path S and the switchback transport path S ′, and rotates to transport the paper.

  The registration roller 42 is formed on the outer peripheral portion of the photoreceptor 31 by chucking the leading end portion of the sheet in the sheet conveying direction (hereinafter referred to as the leading end portion of the sheet) so as to be parallel to the axial direction. The toner image is conveyed again between the photosensitive member 31 and the transfer device 34 so that the toner image is aligned. The branch claw 43 switches between the main transport path S and the switchback transport path S ′.

  The paper discharge unit 50 is disposed above the paper feed tray 21 and includes a paper discharge roller 51, a paper discharge tray 52, and the like. The paper discharge roller 51 discharges the paper transported on the main transport path S to the paper discharge tray 52. Further, the paper discharge roller 51 is capable of reversible rotation, and when performing image formation on both sides of the paper, after chucking the paper on which the image formation on the front surface that has been transported on the main transport path S is finished, It rotates in the direction opposite to the rotation direction to be discharged and is conveyed to the switchback conveyance path S ′. As a result, the front and back surfaces of the sheet are reversed so that the back surface faces the photoreceptor 31 and image formation is performed on the back surface. The paper discharge tray 52 stores the paper on which image formation has been completed, which has been discharged from the paper discharge roller 51.

  FIG. 2 is an enlarged view of a dotted line portion shown in FIG. FIG. 2A shows an initial position H in which the sheet being conveyed does not pass through the branch claw 43 from the image forming unit 30. FIG. 2B shows the swing position A in a state where the conveyed paper passes from the image forming unit 30 through the branching claw 43. FIG. 2C shows a swing position B that is a state when an unillustrated opening / closing door provided on the front surface of the image forming apparatus 100 is opened. FIG. 3 is an enlarged view of the stopper 45 and the branch claw 43.

  As shown in FIG. 2, the branching claw 43 is swingably supported by a shaft 44 whose axial direction is perpendicular to the paper transport direction, and the paper transported by the swing is placed in an appropriate transport path S or S ′. Lead. Further, the branching claw 43 is supported by the stopper 45 so as to be positioned at the initial position H as shown in FIG. Further, the branching claw 43 includes a conveyance path changing unit 43a, a detected unit 43b, and the like.

  As shown in FIG. 3B, the conveyance path changing unit 43a is located at a position exposed on the conveyance paths S and S ′ with respect to the shaft 44, and is in an area on the side through which the conveyed sheet passes. The transport path changing unit 43a switches the transport paths S and S ′ of the transported paper. For example, when the paper is image-formed at the image forming unit 30 at the initial position H and is transported to the paper discharge unit 50, the transport path changing unit 43a comes into contact with the transported paper and is shown in FIG. It swings to the swing position A shown. As a result, the paper is guided to the paper discharge unit 50. After the sheet passes through the branching claw 43, the branching claw 43 returns to the initial position H shown in FIG.

  One end of the stopper 45 is fixed to the open door, and is pulled out to the front side by opening the open / close door. Therefore, while the open door is opened, the branching claw 43 supported by the stopper 45 at the initial position H is moved from the initial position H shown in FIG. 2A to the swing position shown in FIG. Swing to B.

  Since the stopper 45 is inclined at the other end as shown in FIG. 3 (A), when the door is completely closed, a part of the stopper 45 that is inclined is in the swing position B. 43 and rocks to the initial position H.

  As shown in FIG. 3B, the detected portion 43 b is in a region where the paper does not pass through the shaft 44 and is a region detected by the photosensor 46. The detected portion 43b is composed of detected members 43ba, 43bb and the like, and swings with the swing of the transport path changing portion 43a. When the branching claw 43 is at the initial position H, the photosensor 46 is positioned between the detected members 43ba and 43bb as shown in FIG. The photosensor 46 included in the position detecting means of the present invention detects whether or not the detected members 43ba and 43bb have passed through a detection unit (not shown), and detects the positions of the detected members 43ba and 43bb.

  When the branching claw 43 swings from the initial position H to the swinging position A, the detected member 43bb passes through the detection portion of the photosensor 46 as shown in FIG. Conversely, when the branching claw 43 returns from the swing position A to the initial position H due to its own weight, the detected member 43bb passes through the detection portion of the photosensor 46.

  Further, when the open door is opened and the branching claw 43 swings from the initial position H to the swinging position B, the detected member 43ba passes through the detection portion of the photosensor 46. Conversely, when the open door is completely closed and the branching claw 43a swings from the swing position B to the initial position H, the detected portion 43ba passes through the detection portion of the photosensor 46.

  Further, the detected members 43ba and 43bb are formed so that the widths in the direction of passing through the detection portion of the photosensor 46 are different from each other. The photosensor 46 outputs the detection results of the detected members 43ba and 43bb to the connected control unit 50.

  The control unit 50 included in the state detection unit of the present invention controls the operation of the entire image forming apparatus 100, and from the detection time of the detected members 43ba and 43bb detected based on the detection result received from the photosensor 46, It is detected which of the detected members 43ba and 43bb has passed through the photosensor 46 based on data stored in advance in a memory or the like (not shown). Further, the control unit 50 detects whether the transport path changing unit 43a is in the initial position H or the swinging positions A and B from the detected members 43ba and 43bb that have passed.

  As a result, the state of the transport path changing unit 43a can be easily detected, and the states of the three transport path changing units 43a of the initial position H and the swing positions A and B can be detected with a simple configuration. Further, the open / closed state of the door can be detected by the photo sensor 46. In this embodiment, the contactless photosensor 46 is used, but a contact sensor or the like may be used.

  FIG. 4 is a flowchart showing a procedure for forming an image on both sides of a sheet. When an image formation start input is received via the operation panel unit, it is first determined whether or not the image formation conditions are appropriately input (S1). Image forming conditions include monochrome printing or full-color printing setting, single-sided or double-sided image forming setting, and the like. If it is determined in S1 that all input of image forming conditions have not been accepted, display is performed on a display unit (not shown) (for example, a liquid crystal display device) to prompt the user to input (S2). Wait until it is accepted. In the present embodiment, a procedure for performing image formation (copying) of a double-sided image of a document placed on the document placement tray 12a will be described.

  When it is determined in S1 that an input of image forming conditions has been accepted, a process of reading image information on both sides of the document, such as a process of conveying a document placed on the document placing tray 12a and reading it by the document reading unit 30 (S3).

  Thereafter, based on the read image information and image formation conditions, a paper feed process is performed in which paper of an appropriate size is fed from the paper feed tray 21 and the manual feed tray 22 to the image forming unit 30 via the main transport path S. (S4). Next, a process of forming an image on one side of the paper such as transferring the toner image and fixing the toner image by the fixing device 36 is performed (S5).

  Thereafter, it is determined whether or not the leading edge of the sheet has passed through the fixing device 36 (S6), and the apparatus waits until it passes. The determination as to whether or not the sheet has passed is made, for example, based on the detection result of the presence or absence of sheet passing by a sensor (not shown) provided immediately after the fixing device 36 in the sheet transport direction.

  If it is determined in S6 that the leading edge of the sheet has passed through the fixing device 36, it is determined whether or not the branch claw 43 has swung from the initial position H to the swing position A (S7). For example, since the time for reaching the branching claw 43 from the time when the leading edge of the sheet passes the fixing device 36 is constant, at least a time longer than the arrival time is set in advance as the arrival time, and the branching claw is reached within this arrival time. When it is detected that 43 has swung to the swing position A, it is determined that the branch claw 43 has swung to the swing position A.

  If it is determined in S7 that the branch claw 43 has not swung to the swing position A, it is determined that the transport JAM has occurred, and the image forming operation of the apparatus is stopped (S8), and the display means that the transport JAM has been performed. (S9) The user is prompted to remove the sheet. As a result, the user can be immediately notified of the abnormality. Thereafter, it waits until a request for image formation is received again.

  On the other hand, if it is determined in S7 that the branch claw 43 has swung to the swing position A, it is determined whether or not the branch claw 43 has returned from the swing position A to the initial position H (S10). For example, with respect to the maximum size sheet that can be conveyed by the image forming apparatus 100, at least the leading edge of the sheet passes the arrangement position of the branching claw 43, and the trailing edge of the sheet in the sheet conveying direction (hereinafter referred to as the trailing edge of the sheet). ) Is a passage time or more, and when it is detected that the branching claw 43 has returned to the initial position H within this passage time, it is determined that the branching claw 43 has returned to the initial position H.

  If it is determined in S10 that the branching claw 43 has not returned to the initial position H, it is determined that the transport JAM has occurred on the main transport path S where the branching claw 43 is located, and the process proceeds to S8.

  On the other hand, if it is determined in S10 that the branching claw 43 has returned to the initial position H, it is determined whether or not the trailing edge of the paper has reached the paper discharge roller 51 (S11) and waits until it is determined that it has reached. For example, the determination is made based on whether or not the trailing edge of the sheet has been detected by a sensor (not shown) located upstream of the sheet discharge direction of the sheet discharge roller.

  If it is determined in S11 that the trailing edge of the paper has reached the paper discharge roller 51, the rotation (forward rotation) of discharging the paper to the paper discharge tray 52 by the paper discharge roller 51 is stopped (S12). The roller 51 is caused to chuck the paper. Note that the paper discharge roller 51, the conveyance roller 41, and the like have started to rotate forward when an image formation request is received.

  Thereafter, the paper discharge roller 51 and the conveyance roller 41 are rotated in the reverse direction (S13), and the sheet is switched back and conveyed to the image forming unit 30 via the switchback conveyance path S '. Next, it is determined whether or not the sheet has been switched back and conveyed to the image forming unit 30 (S14). For example, in the maximum size sheet that can be conveyed by the image forming apparatus 100, at least the time from the start of switchback conveyance until the leading edge of the sheet is chucked by the registration roller 42 positioned immediately before the image forming unit 30 in the sheet conveyance direction. This time is set as the switchback conveyance time, and when it is not detected that the leading edge of the sheet is chucked by the registration roller 42 within the switchback conveyance time, it is determined that the sheet is not switched back and conveyed to the image forming unit 30.

  If it is determined in S14 that the image forming unit 30 has not been switched back and conveyed, it is determined that the sheet has jammed on the switchback conveyance path S ′, and the process proceeds to S8. On the other hand, if it is determined in S14 that the image has been switched back to the image forming unit 30, the image forming process is performed on the other side of the sheet in the same manner as in S5 (S15). In S15, the rotation of the transport roller 41 and the paper discharge roller 51 is returned to the normal rotation.

  Thereafter, similarly to the process of S6, it is determined whether or not the leading edge of the sheet has passed the fixing device 36 (S16), and the process waits until it passes. If it is determined in S16 that the leading edge of the sheet has passed through the fixing device 36, it is determined whether or not the branching claw 43 has swung from the initial position H to the swinging position A in the same manner as in S7 (S17). .

  If it is determined in S17 that the branching claw 43 does not swing to the swinging position A, it is determined that the transport JAM has occurred, and the process proceeds to S8. On the other hand, if it is determined in S17 that the branch claw 43 has swung to the swing position A, it is determined whether or not the branch claw 43 has returned from the swing position A to the initial position H in the same manner as in S10 (S18). .

  If it is determined in S18 that the branching claw 43 has not returned to the initial position H, it is determined that a transport JAM has occurred on the main transport path S where the branching claw 43 is located, and the process proceeds to S8.

  On the other hand, if it is determined in S18 that the branching claw 43 has returned to the initial position H, it is determined whether or not the trailing edge of the paper has reached the paper discharge roller 51 as in S11 (S19). stand by.

  On the other hand, if it is determined in S19 that the trailing edge of the sheet has reached the paper discharge roller 51, it is determined whether or not a new image is to be formed next from the image forming conditions (S20). Shifts to the process of S3. If it is determined that no new image formation is to be performed, the process ends.

  As described above, the image forming apparatus 100 according to the present invention includes the paper conveyance mechanism 40 having the branching claw 43 provided with the detected portion 43b, so that the detected portion 43b is separately provided on the conveyance paths S and S ′. Since there is no need, the configuration of the transport paths S and S ′ does not become complicated, and it is possible to detect the paper transport state while reducing the occurrence of paper transport JAM. Further, since a part of the conveyance path changing unit 43a and the other part of the detected part 43b form a branch claw, the configuration of the branch claw 43 can be simplified.

  Further, since the transport path changing unit 43a is arranged in the area where the paper passes from the shaft 44, and the detected part 43b is arranged in the area where the paper does not pass from the shaft 44, the transport path changing unit Since the state of the transport path changing unit 43a can be detected based on the detected part 43b that swings with the swinging of 43a, the configuration of the branch claw 43 and the configuration of detecting the state of the transport path changing unit 43a can be simplified. . Further, since it is not necessary to expose the detected portion 43b on the transport paths S and S ′, the configuration of the transport paths S and S ′ is not complicated, and the occurrence of paper transport JAM can be further reduced. it can.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 2 is an enlarged cross-sectional view of a part of the image forming apparatus. FIG. FIG. 3 is an enlarged view showing a simple configuration of a stopper and a branch claw provided in the image forming apparatus. 4 is a flowchart illustrating a procedure for forming an image on both sides of a sheet in the image forming apparatus.

Explanation of symbols

40-paper conveyance mechanism 43-branching claw 43a-conveyance path changing unit 43b-detected unit 43ba, bb-detected member 44-shaft 45-stopper 46-photo sensor 50-control unit 100-image forming apparatus A, B- Swing position H-Initial position S-Main transport path S '-Switchback transport path

Claims (8)

A branching claw positioned on a transport path along which the paper is transported, wherein a part of the pawl is brought into contact with the paper on the transport path to move from the initial position, and returns to the initial position by its own weight. A branching claw that is a transport path changing unit to be changed, and the other part is a detected part that moves in conjunction with the transport path changing unit;
A sheet conveyance mechanism comprising: a position detection unit that detects a position of the detected portion; and a state detection unit that detects a state of the conveyance path changing unit based on a detection result of the position detection unit. .   The branching claw is swingably supported on an axis whose direction is perpendicular to the conveyance path, and the conveyance path changing unit is in a region on the side through which the paper on the conveyance path passes from the axis. The paper transport mechanism according to claim 1, wherein the detected portion is in a region where the paper on the transport path does not pass through the shaft. The detected part is two detected members that pass through the position detecting unit according to the state of the corresponding transport path changing unit and have different widths in the direction of passing through the position detecting unit.
The state detection unit detects a time during which the two detected members pass based on a detection result of the position detection unit, and detects a state of the transport path changing unit according to the detected time. The paper transport mechanism according to claim 1.   The paper conveyance mechanism according to claim 1, wherein the position detection unit includes a photo sensor. An open / close door that opens the interior of the main body mechanism;
A stopper that supports the branching claw at the initial position when the door is completely closed and interrupts the support when the door is open,
The paper transport mechanism according to claim 3, wherein the transport path changing unit swings downward from the initial position by its own weight when the support is interrupted. Display means for displaying the conveyance status of the paper on the conveyance path;
The state detection means passes through a predetermined arrangement position of the branching claw on a maximum size sheet that can be conveyed on the conveyance path, when the conveyance path changing unit is in contact with the sheet. 2. The paper transport mechanism according to claim 1, wherein when the passage time is detected, the paper transport JAM is displayed on the display means. A sheet transport mechanism according to any one of claims 1 to 6,
An image forming apparatus that forms an image on a sheet conveyed on the conveyance path. A sheet transport mechanism according to any one of claims 1 to 6,
The conveyance path includes a main conveyance path from an image forming unit that forms a toner image on a sheet to a sheet discharge unit that discharges the sheet to the outside via a fixing device that fixes the toner image, and the discharge route. A switchback transport path for switchback transporting the paper on which one side is imaged from the paper section to the image forming section,
The image forming apparatus, wherein the conveyance path changing unit switches between the main conveyance path and the switchback conveyance path.

Images