JP6123255B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus.

  An image forming apparatus such as a printer or a copying machine prints an image on the surface of a sheet fed and conveyed from a sheet tray or the like by a sheet feeding and conveying unit, and discharges the sheet on which the image has been printed out of the apparatus. In such an image forming apparatus, it is common to monitor the position of a sheet conveyed based on the outputs of a plurality of sheet detection sensors provided in the sheet conveyance path and control the operation of the conveying unit. .

  For example, when printing is performed by an electrophotographic image forming apparatus, the sheet is temporarily stopped by a registration roller provided upstream of the transfer unit, and then the sheet is conveyed to the transfer unit in accordance with the transfer timing. The conveying means is controlled. Further, when the sheet is temporarily stopped by the registration roller in continuous printing on a plurality of sheets, the transport unit is controlled so that the subsequent sheet is also stopped in the transport path.

  Here, when the leading edge or trailing edge of the paper transport direction stops at the detection position of the paper detection sensor when the paper is stopped as described above, the paper detection is affected by the curl of the paper edge or the vibration of the device. The sensor output may become unstable, causing erroneous detection of the presence or absence of paper and causing a conveyance error.

  Therefore, in order to prevent erroneous detection of the paper detection sensor in such an image forming apparatus, the next paper detection start timing by the paper detection sensor arranged in the paper conveyance path corresponds to the time that can be detected by the paper detection sensor. A paper conveying apparatus that sets the distance to the specified distance is disclosed (for example, see Patent Document 1). According to the paper conveyance device according to Patent Document 1, it is possible to reduce the influence of erroneous detection by bringing the next paper detection start timing closer to the leading edge of the next paper to be conveyed.

  However, since the paper detection start timing is early, if there is even a slight delay in the conveyance of the next paper, the paper detection sensor may not detect the paper at a predetermined timing and may erroneously detect that the paper has not passed. In addition, in order to increase the number of printed sheets per unit time, when the sheet interval is narrowed, the next sheet detection start timing may not be set to a predetermined distance.

  The present invention has been made in view of the above, and provides a sheet conveying apparatus capable of preventing erroneous detection by a detection unit that detects passage of a conveyed sheet and conveyance abnormality caused by erroneous detection. With the goal.

  According to the sheet conveying apparatus of one aspect of the present invention, a conveying unit that conveys a sheet along a conveying path, a first detecting unit that detects an end of the sheet conveyed in the conveying direction by the conveying unit, A second detection unit that is provided upstream of the first detection unit in the conveyance path and detects an end portion of the sheet conveyed in the conveyance direction, and controls conveyance of the sheet by the conveyance unit. And when the length L in the conveyance direction of the sheet satisfies the following expression when stopping the conveyance of the sheet by the conveyance unit: After the first detection unit detects the leading end in the sheet conveyance direction, the conveyance unit starts conveyance stop processing after the conveyance unit conveys the sheet by a predetermined distance.

B + Ls ≧ L ≧ B + Ls−Lm
Here, B is a distance from when the conveyance stop process is started until the conveyance unit stops conveying the sheet, Ls is a distance between the first detection unit and the second detection unit in the conveyance path, Lm is a preset margin.

  According to the embodiment of the present invention, it is possible to provide a sheet conveying apparatus capable of preventing erroneous detection by a detection unit that detects passage of a conveyed sheet and conveyance abnormality caused by erroneous detection.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating a schematic configuration of a sheet conveying device in the image forming apparatus according to the embodiment. FIG. 5 is a diagram illustrating a paper conveyance stop position in the paper conveyance device. FIG. 6 is a diagram illustrating the posture of a sheet conveyed along a conveyance path. 6 is a diagram illustrating a time chart of a conveyance roller pair and a sheet detection sensor in the sheet conveying apparatus according to the embodiment. FIG. FIG. 6 is a diagram illustrating a flowchart of a paper transport process in the paper transport device according to the embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<Configuration of image forming apparatus>
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 100 according to the embodiment.

  As shown in FIG. 1, an image forming apparatus 100 according to the present embodiment includes a plurality of image forming units provided along an intermediate transfer belt that is an endless belt, and prints and outputs a color image on a sheet. An electrophotographic tandem color image forming apparatus.

  The image forming apparatus 100 includes four image forming units 1a, 1b, 1c, and 1d that are disposed along the traveling direction of the intermediate transfer belt 10. The image forming unit 1a includes a photosensitive drum 2a as an image carrier, a drum charger 3a, an exposure device 4a, a developing device 5a, a transfer device 6a, a cleaning device 7a, and the like. The image forming units 1b to 1d have the same configuration as the image forming unit 1a. Each image forming unit 1 forms toner images of different colors, for example, the image forming unit 1a is yellow, the image forming unit 1b is magenta, the image forming unit 1c is cyan, and the image forming unit 1d is black.

  The operation of the image forming unit 1a will be described below, but the operations of the other image forming units 1b to 1d are the same.

  The photosensitive drum 2a of the image forming unit 1a rotates in the direction B in the drawing when receiving a start instruction signal for an image forming operation from a print control device (not shown), and continues to rotate until the image forming operation ends. When the photosensitive drum 2a starts rotating, a high voltage is applied to the drum charger 3a, and the surface of the photosensitive drum 2a is uniformly charged to a negative charge.

  Next, when image data such as characters and figures converted into dot images is sent from the print control apparatus to the image forming apparatus 100 as an on / off signal of the exposure apparatus 4a, the exposure apparatus 4a performs photosensitivity based on the image data. The surface of the drum 2a is irradiated with laser light to form an electrostatic latent image.

  When the electrostatic latent image formed on the photosensitive drum 2a reaches the position facing the developing device 5a by the laser light irradiated from the exposure device 4a, the toner charged in the negative charge stored in the developing device 5a is discharged. The toner image is formed on the photosensitive drum 2a by being attracted to and attached to the electrostatic latent image.

  When the toner image formed on the photosensitive drum 2a reaches the transfer device 6a as the primary transfer means, the toner image formed on the intermediate transfer belt 10 rotates in the direction of arrow A in the figure by the action of a high voltage applied to the transfer device 6a. Is transcribed. Untransferred toner remaining on the photosensitive drum 2a without being transferred onto the intermediate transfer belt 10 is removed by the cleaning device 7a, and the photosensitive drum 2a is prepared for the next image forming operation.

  Similarly, in the image forming units 1 b to 1 d, toner images of respective colors are formed and transferred onto the intermediate transfer belt 10 so that a full color toner image is formed on the intermediate transfer belt 10.

  The paper P is conveyed in the direction of arrow C in the figure from the paper supply device 17 in accordance with the timing at which the full color toner image formed on the intermediate transfer belt 10 reaches the paper transfer device 9 as the secondary transfer means. A full color toner image is secondarily transferred onto the surface of the toner. The transfer residual toner remaining on the intermediate transfer belt 10 is removed by the belt cleaning mechanism 12.

  The sheet P on which the full color toner image is transferred is conveyed to the fixing device 11 by the conveying belt 18. The paper P is heated and pressed by the fixing device 11, so that the full color toner image on the paper P is melted and fixed on the paper P.

  When performing double-sided printing, the paper P that has passed through the fixing device 11 passes through the fixing device 11 and is then reversely conveyed in the apparatus to reach the conveying roller pair 14g, and again to the paper transfer device 9 for backside printing. It is conveyed toward. The sheet P on which single-sided printing or double-sided printing has been performed passes through the fixing device 11 and is then conveyed in the direction of arrow E in the figure, and is discharged from the image forming apparatus 100.

  The paper supply device 17 includes paper stacking units 19a and 19b and paper supply units 20a and 20b including a calling roller pair, a paper supply roller pair, a separation roller pair, and a grip roller pair. The paper supply device 17 can store and transport paper of various sizes, thicknesses, and types.

  When the paper feeding unit 20a receives a paper feeding start instruction signal from a printing control device (not shown), the paper feeding unit 20a starts to rotate the calling roller pair, the paper feeding roller pair, the separation roller pair, and the grip roller pair. The calling roller pair of the paper stacking unit 19a feeds the paper P and transports it to the paper feed roller pair and the separation roller pair in the previous transport path. The paper P fed out from the call roller pair is fed by the paper feed roller pair and conveyed to the grip roller pair.

  The separation roller pair rotates in the reverse direction to the paper feed roller pair and pushes back the lower sheet P fed from the calling roller pair to the sheet stacking portion 19a. The paper P fed by the paper feed roller pair is transported to the transport roller pair 14a, 14b provided on the downstream side by the grip roller pair.

  The transport roller pairs 14a and 14b transport the paper P to the transport roller pair 14c located on the downstream side of the transport path. When there is a sheet P on the downstream side of the conveyance path, or when there is a sheet P that reaches the conveyance roller pair 14g for backside printing and stops at the sheet stop point 16b, At the paper stop point 16a, the paper is temporarily stopped and waited.

  Upon receiving a paper feed start instruction signal from a print control device (not shown), the paper feed unit 20b feeds the paper P from the paper stacking unit 19b and transports it to the transport roller pair 14c. Similarly to the sheet P conveyed from the paper supply unit 20a, the conveyance roller pair 14c stops the sheet conveyance at the sheet stop point 16a as necessary and waits.

  The transport roller pair 14c transports the paper P to the transport roller pair 14d at a predetermined transport timing. The transport roller pair 14d transports the paper P in the direction of arrow C in the figure, and when the paper P transported in advance stops at the paper stop point 16d, the transport of the paper P at the paper stop point 16c. Stop and wait.

  When the conveyance roller pair 14d receives the conveyance resumption instruction signal, the conveyance roller pair 14d resumes conveyance of the paper P stopped at the paper stop point 16c, and conveys the paper P to the conveyance roller pair 14e. The transport roller pair 14e transports the paper P together with the downstream transport roller pair 14f, and when the paper P transported first stops at the paper stop point 16e, the paper P is temporarily stopped at the paper stop point 16d. Stop transport and wait. When the conveyance roller pair 14 f receives the conveyance resumption instruction signal, the conveyance roller pair 14 f resumes conveyance of the paper P and conveys the paper P to the registration entrance roller pair 22.

  The timing roller pair 15 conveys the paper P to the registration roller pair 13 at the paper stop point 16e and temporarily stops. The registration roller pair 13 conveys the paper P to the paper transfer device 9 in accordance with the timing when the full-color toner image transferred onto the intermediate transfer belt 10 reaches the paper transfer device 9. The transfer timing roller pair 23 adjusts the conveyance timing of the paper P by adjusting the acceleration timing of the rotation speed, and finely adjusts the paper transfer position of the full-color toner image on the intermediate transfer belt 10.

  In the image forming apparatus 100, as described above, the transport roller pairs 14a to 14f, the registration roller pair 13, the transfer timing roller pair 23, and the like are used for the transport state of another sheet P in the transport path or the transfer timing to the sheet P. At the same time, control is performed so that the front end of the sheet P in the transport direction stops at the sheet stop points 16a to 16e.

  The image forming apparatus 100 includes temperature / humidity sensors 21a, 21b, and 21c that detect the temperature and humidity of each unit, and can monitor the temperature and humidity.

  Note that the image forming apparatus 100 according to the present embodiment is an electrophotographic tandem type color image forming apparatus, but is a monochrome image forming apparatus or an image forming apparatus employing another image forming method such as an ink jet method. It may be present and is not limited to the present embodiment.

<Configuration of paper transport device>
Next, a schematic configuration of the sheet conveying apparatus 200 that conveys the sheet P in the image forming apparatus 100 will be described.

  FIG. 2 is a diagram illustrating a schematic configuration of the sheet conveying device 200 in the image forming apparatus 100 according to the embodiment.

  As shown in FIG. 2, the paper transport apparatus 200 includes transport roller pairs 14d to 14f, paper detection sensors 24a to 24e, paper guides 31a and 31b, driving means 50, control means 51, and the like.

  Each of the conveyance roller pairs 14d to 14f includes a driving roller that is rotationally driven and a driven roller that is driven to rotate while sandwiching the paper P between the driving rollers, and conveys the paper P along the conveyance path.

  The paper detection sensors 24a to 24e are detection means for detecting that the end portion in the transport direction of the paper P transported by the transport roller pairs 14d to 14f and the like pass, and are, for example, optical sensors.

  The paper guides 31a and 31b are guide means for guiding the paper P transported by the transport roller pairs 14d to 14f from both sides. The paper guide 31a guides one side of the paper P and the other side of the paper P. And a paper guide 31b for guiding. Note that the interval Lpass between the paper guide 31a and the paper guide 31b is substantially constant in the transport path.

  The drive unit 50 is controlled by the control unit 51, and rotates the drive roller of the transport roller pair 14f to transport the paper P to the transport roller pair 14f.

  The control unit 51 controls the conveyance of the paper P by the conveyance roller pair 14f by controlling the operation of the driving unit 50 according to the detection result of the paper P by the paper detection sensor 24c, the conveyance state of the preceding paper P, and the like. To do. The control unit 51 includes, for example, a CPU, a ROM, a main memory, and the like. Various functions of the control unit 51 are realized by a control program recorded in the ROM or the like being read into the main memory and executed by the CPU. . However, part or all of the control means 51 may be realized only by hardware. Further, the control means 51 may be physically configured by a plurality of devices.

  The conveyance rollers 14d and 14e, the registration roller pair 13, the timing roller pair 15, and the registration entrance roller pair 22 are connected to the driving means (not shown) controlled by the control means 51 or the control means (not shown), respectively. Is driven to rotate in a state in which the conveyance timing and the like are controlled.

<Paper transport stop position>
FIG. 3 is a diagram illustrating a conveyance stop position of the paper P in the paper conveyance device 200. In the following, the conveyance stop position by the conveyance roller pair 14f will be described, but the same applies to other conveyance roller pairs and the like.

  As shown in FIG. 3A, the paper transport apparatus 200 includes a transport roller pair 14e, a paper detection sensor 24b on the upstream side of the transport roller pair 14f, and a paper detection sensor 24c on the downstream side of the transport roller pair 14f.

  Here, the length of the sheet P in the conveyance direction is L, the distance between the sensors between the sheet detection sensor 24b and the sheet detection sensor 24c in the conveyance path is Ls, and the sheet is conveyed after the control unit 51 starts the conveyance stop process. Let B be the paper conveyance distance until the operation is stopped. Further, the control unit 51 monitors the transport position of the paper P based on the detection result by the paper detection sensor 24c, and starts the transport stop process when the leading end in the transport direction of the paper P reaches a predetermined position.

  As shown in FIG. 3A, for example, when the control unit 51 performs the conveyance stop processing of the paper P simultaneously with the detection of the leading edge of the paper P by the paper detection sensor 24c (the detection position of the paper detection sensor 24c and the arrival of the paper). Consider the case where the point R1 is at the same position). In this case, if the length L in the transport direction of the paper P satisfies the following formula (1), the rear end of the transport direction of the paper P is detected by the upstream paper detection sensor 24b when the transport of the paper P is stopped. It will stop at the position.

L = B + Ls (1)
When the conveyance of the paper P is stopped in the state shown in FIG. 3A, the output of the paper detection sensor 24b becomes unstable due to the influence of the curling of the rear end of the paper P, the vibration of the apparatus, and the like. There is a possibility that the presence or absence of P is erroneously detected to cause a conveyance abnormality.

  Therefore, when the length L in the transport direction of the paper P satisfies the above equation (1), the control means 51 transports the paper P when it reaches the paper arrival point R2, as shown in FIG. Set to start the stop process. The timing at which the paper P reaches the paper arrival point R2 can be obtained from the elapsed time after the leading edge of the paper P is detected by the paper detection sensor 24c and the transport speed of the paper P by the transport roller pair 14f.

  With such a setting, when the paper P reaches the paper arrival point R2, the control unit 51 starts the conveyance stop process, and as shown in FIG. Stopping at the detection position 24b is eliminated. Therefore, it is possible to prevent erroneous detection of the paper P by the paper detection sensor 24b and conveyance abnormality due to erroneous detection.

  Here, as illustrated in FIG. 4, when the paper P is conveyed in a bent state between the paper guides 31 a and 31 b (FIG. 4 (a)) or in the case of duplex printing, the paper P is curled. In some cases, it is transported in the state (FIG. 4B). Therefore, in the example shown in FIG. 3B, for example, when the length L in the transport direction of the paper P satisfies the following expression (2), the control unit 51 selects the paper arrival point R2 to select the paper. It is preferable to control so as to stop the conveyance.

B + Ls ≧ L ≧ B + Ls−Lm1 (2)
Here, Lm1 is a margin set in consideration of expansion and contraction, conveyance delay, and the like, and is set to a value between 5% and 10% of the length L in the conveyance direction of the paper P, for example. Further, the length L in the transport direction of the paper P is the length of the paper P in the transport direction regardless of the transport state such as a bent state or a curled state as shown in FIG.

  When the length L in the transport direction of the paper P satisfies the above equation (2), for example, when the transport of the paper P is stopped in the configuration illustrated in FIG. To stop the transfer. By performing the conveyance stop process when the leading edge of the paper P reaches the paper arrival point R2, the trailing edge of the paper P does not stop at the detection position of the paper detection sensor 24b. Accordingly, it is possible to reliably prevent erroneous detection of the paper P by the paper detection sensor 24b, conveyance abnormality caused by the erroneous detection, and the like.

  In this way, a plurality of paper arrival points R are provided in each pair of conveyance rollers of the paper conveyance device 200, and the control unit 51 appropriately selects the paper arrival point R according to the length in the conveyance direction of the paper P when the paper conveyance is stopped. By performing the conveyance stop process, it is possible to prevent erroneous detection of paper by the paper detection sensor. Note that three or more paper arrival points R may be provided, and may be set as appropriate according to the length L in the transport direction of the paper P when the paper transport is stopped.

  Further, the distance A between the paper arrival point R1 and the paper arrival point R2 in the conveyance path of the paper P takes into account slack between the paper guides 31a and 31b of the paper P and the paper guide 31a and the paper guide 31b. It is preferable that it is more than the space | interval Lpass (Formula (3)).

A ≧ Lpass (3)
The distance A is preferably equal to or greater than the distance Lpass between the sheet guides plus a push amount Lpt and a margin Lm2 in consideration of sheet expansion / contraction, conveyance delay, and the like (formula (4)).

A ≧ Lpass + Lpt + Lm2 (4)
Here, the push-in amount Lpt is a distance by which the conveyance roller pair 14f conveys and pushes the paper P so that the paper P does not stop at the detection position of the paper detection sensor 24b.

  FIG. 5 is a diagram illustrating a time chart of the transport roller pairs 14e and 14f and the paper detection sensors 24b and 24c in the paper transport apparatus 200 according to the embodiment.

  In the paper transport device 200, when the transport roller pair 14e, 14f transports the paper P, first, the transport roller motor as driving means is excited at time T1, and the transport roller pair 14e, 14f rotates at time T2. After starting the operation, a constant rotational speed is reached at time T3.

  After the leading end of the paper P passes through the transport roller pair 14e, the paper detection sensor 24b detects the paper P at time T4. The paper P is transported to the transport roller pair 14e and then transported by the transport roller pair 14f, and the leading end is detected by the paper detection sensor 24c at time T5.

  Here, when the conveyance of the paper P is stopped and the length in the conveyance direction of the paper P satisfies, for example, the above equation (2), the paper detection sensor 24c detects the leading end of the paper P, When the paper P is transported by the distance A, the control means 51 executes a transport stop process. When the conveyance stop process is executed by the control means 51, the conveyance roller motor stops at time T6, and conveyance of the paper P by the conveyance roller pair 14e, 14f stops.

  When the conveyance is stopped, the trailing edge of the paper P does not stop at the detection position of the paper detection sensor 24b, and erroneous detection of the paper P by the paper detection sensor 24b can be prevented when the conveyance of the paper P is resumed.

<Paper transport processing>
FIG. 6 illustrates a flowchart of a paper transport process in the paper transport apparatus 200.

  First, in step S1, the control means 51 determines whether or not there is a sheet P being conveyed in the sheet conveying apparatus 200. If the sheet P is being conveyed, an event being conveyed is confirmed in step S2. The event during conveyance is information regarding the operation of each conveyance roller pair in accordance with the stop position of the paper P or the like. Next, in step S3, it is confirmed whether or not the sheet P is stopped by, for example, the transport roller pair 14f in the transport event.

  When stopping the paper P by the conveyance roller pair 14f, in step S4, the control unit 51 prepares paper data including the length L in the conveyance direction of the paper P being conveyed, and in step S5, the conveyance is performed. The paper arrival point R is selected according to the length L in the transport direction of the medium paper P. Here, for example, when the length L in the transport direction of the paper P satisfies the above equation (2), the paper arrival point R2 is selected, and when the equation (2) is not satisfied, the paper arrival point R1 is selected. To do. Alternatively, the paper arrival point R2 may be selected when the length L in the transport direction of the paper P satisfies the above formula (1) or formula (2).

  In this embodiment, the control unit 51 acquires a preset size of the paper P to be transported. For example, the control unit 51 detects the leading edge and the trailing edge of the paper P in the paper detection sensor on the upstream side of the transport path. A result of detecting the length of the paper P in the transport direction may be acquired based on the passage time interval. It becomes possible to control the conveyance stop position according to the length in the conveyance direction of the paper P actually being conveyed.

  If the control means 51 has selected the paper arrival point R1 in step S6, then in step S7, it waits for the paper detection sensor 24c to detect the leading edge of the paper P in the transport direction. . When the leading edge of the paper P is detected by the paper detection sensor 24c, the control means 51 executes a conveyance stop process in step S8, and in step S9, the control means 51 determines the paper P as the next in-conveyance event. The waiting for resumption of transport is set and the processing is terminated.

  If the control means 51 has selected the paper arrival point R2 in step S6, first, in step S10, the distance A from the paper detection sensor 24c to the paper arrival point R2 is calculated. Next, in step S11, a time TA during which the paper P is transported by the distance A by the transport roller pair 14f is calculated.

  Next, in step S12, it waits for the paper detection sensor 24c to detect the leading edge of the paper P in the transport direction. When the paper detection sensor 24c detects the leading edge of the paper P, in step S13, The control means 51 starts counting time t (t = 0).

  Even after the leading edge of the sheet P is detected by the sheet detection sensor 24c, the sheet P is continuously conveyed by the conveying roller pair 14f, and when the time t reaches the time TA in step S14, the control means in step S11. 51 performs the conveyance stop process of the conveyance roller 14f.

  Next, in step S12, the control means 51 sets the waiting for resumption of conveyance of the paper P as the next conveyance event, and ends the processing.

  Although the case where the conveyance of the paper P is stopped by the conveyance roller pair 14f has been described above, the same conveyance stop is also performed for the other conveyance roller pairs, the registration roller pair 13, the timing roller pair 15, the registration entrance roller pair 22, and the like. It is preferable to carry out the treatment.

  When the conveyance of the paper P is stopped, the paper arrival point R is appropriately selected according to the length L in the conveyance direction of the paper P by the above processing, and the paper P reaches the selected paper arrival point R. At the time, the control means 51 executes a conveyance stop process. In this manner, since the paper stop point is changed according to the length L in the transport direction of the paper P, the rear end portion of the paper P does not stop at the detection position of the paper detection sensor 24. Therefore, according to the paper transport apparatus 200 and the image forming apparatus 100 according to the present embodiment, it is possible to prevent erroneous paper detection by the paper detection sensor 24 and abnormal transport due to erroneous detection.

  The sheet conveying apparatus and the image forming apparatus according to the embodiments have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made within the scope of the present invention.

14f Conveying roller pair (conveying means)
24b Paper detection sensor (first detection sensor)
24c Paper detection sensor (second detection sensor)
31a, 31b Paper guide (guide means)
51 Control Unit 100 Image Forming Apparatus 200 Paper Conveying Device (Sheet Conveying Device)
P paper

JP 2010-70375 A

Claims (5)

Conveying means for conveying the sheet along the conveying path;
First detection means for detecting an end portion of the sheet in the conveyance direction conveyed by the conveyance means;
A second detection unit that is provided on the upstream side of the first detection unit in the conveyance path and detects an end of the sheet conveyed in the conveyance direction by the conveyance unit;
Control means for controlling the conveyance of the sheet by the conveyance means,
When the length L in the sheet conveyance direction satisfies the following expression when stopping the conveyance of the sheet by the conveyance unit, the control unit causes the first detection unit to perform the sheet conveyance direction. A sheet conveying apparatus which starts conveyance stop processing after the conveying unit conveys the sheet for a predetermined distance after detecting the leading edge of the sheet .
B + Ls ≧ L ≧ B + Ls−Lm
Here, B is a distance from when the conveyance stop process is started until the conveyance unit stops conveying the sheet, Ls is a distance between the first detection unit and the second detection unit in the conveyance path, Lm is a preset margin. Guide means for guiding the sheet conveyed along the conveyance path from both sides,
The sheet conveying apparatus according to claim 1, wherein the predetermined distance at which the control unit starts the conveyance stop process is equal to or greater than an interval of the guide unit. The conveying means includes a driving roller that is rotationally driven by a driving means, and a driven roller that is driven to rotate while sandwiching the sheet between the driving rollers, and the first detecting means and the first roller in the conveying path. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is provided between the two detecting units. A sheet length detection unit that detects a length in the conveyance direction of the sheet on the upstream side of the first detection unit in the conveyance path;
4. The sheet according to claim 1, wherein the control unit controls the conveyance unit based on a length of the sheet in a conveyance direction detected by the sheet length detection unit. 5. Conveying device.   An image forming apparatus comprising the sheet conveying device according to claim 1.

Images