JP4378375B2 - Paper reversal transport method - Google Patents

Description

  The present invention relates to a reversal paper feeding method for performing reversal paper feeding of normal paper that is not tab paper and tab paper.

  2. Description of the Related Art Image forming apparatuses such as printers and copying machines have a mode in which a tab sheet is inserted as a work (job) separator between normal printing (copying) processes. As shown in FIG. 12, the tab sheet Pt has a tab portion (ear portion) e so that a part thereof protrudes from one end edge Pa. Usually, a tab or the like is displayed on the tab portion e. It is written or written and used as a slip or the like for organizing materials during filing. In order to transport such tab paper Pt in a copying machine or the like, it is general that the tab portion e is transported with the side without the tab portion e as the leading end so as not to hinder the transport. Further, even when the paper is transported in such a state that the side without the tab portion 3 is set at the leading edge, when used as a slip sheet, it is necessary to reversely discharge the tab paper because of the printing order. Come. Further, when the tab sheet is discharged onto the sheet discharge tray, the tab portion e side is positioned upstream in the sheet conveying direction (rear end side), returned by gravity and brought into contact with a so-called rear end fence, and the sheet conveying direction. When the sheet is aligned, the tab portion e comes into contact with the rear end fence, and the tab portion e protrudes, so that the sheet is inclined. In addition, when the tab portion e is used as a slip sheet, there are many tab positions, so that the tab sheet tilts apart. Therefore, in such a case, it is necessary to reversely discharge the tab sheet, position the tab part e on the downstream side in the sheet conveying direction, and bring the straight line part of the tab sheet into contact with the rear end fence to align the sheet. There is.

  For example, the invention disclosed in Japanese Utility Model Publication No. 3-107454 is known as a technique for reversing and transporting such tab paper Pt. According to the present invention, the paper path is switched by a reversing branch claw swingably provided at a branch portion in the paper transport path of the image forming apparatus, and the transport direction is reversed (reversely fed) so that the paper is fed to a desired transport path. It is designed to be transported. More specifically, the transfer material is sandwiched between a conveying roller and a reversing branch claw arranged in the middle of the reversing path, pressure is applied to the reversing branch claw to generate a conveying force, and the transfer material is conveyed. The transfer material is reversed by moving the reversing branch claw by the pressure applied to the claw, and the reversing branch claw serves as both sheet conveyance and path branching.

  Also known is a further improvement of the above-mentioned technique to improve the transportability of tab paper or the like. In this improved technology, in order to ensure the transportability of the tab paper Pt, the transporting means at the reversing entrance is configured as shown in FIG. That is, as shown in FIG. 13 which is a plan view of the main part of the branching section, a plurality of rollers 17 are provided on the shaft 16 of the conveying roller 10 for feeding the sheet to the reverse conveying tray (switchback section). It arrange | positions adjacent so that the front-end | tip of the inversion branch claw 18 may be pointed in. With this configuration, the tab portion e is always brought into contact with the transport roller 17 so that a transport force in the direction of arrow C is also applied to the tab portion e.

  However, since the dimensions in the width direction Bp of the tab paper Pt and the dimensions and positions of the width Bt of the tab portion e are arbitrary as shown in FIG. 13, there are various types of tab paper Pt. Therefore, in order to cover all of such a wide variety of tab sheets Pt, it is necessary to arrange a large number of conveying rollers 17. Furthermore, when the number of rollers of the conveying roller 17 is increased, there is a concern that the conveying roller 17 may be inadvertently contacted with both ends of the sheet (the leading edge and both sides), and the conveyance reliability may be reduced. Of course, the cost also increases.

  In addition, as a control problem, the reversal timing is delayed by the length of the tab portion e in the transport direction, so that productivity is lowered. That is, as disclosed in Japanese Patent Laid-Open No. 2000-16663, when the detection signal of the trailing edge detection sensor of the sheet is reversed as a trigger, the tab portion e is out of the detection range of the trailing edge detection sensor. Then, the reversal control may be performed before the tab portion e cannot be removed. In order to avoid this, in the invention disclosed in Japanese Patent Laid-Open No. 2000-16663, the sheet is reversed with a margin in timing from the detection timing of the trailing edge detection sensor at least by the length of the tab portion e in the sheet conveyance direction. ing.

  With this configuration, it is possible to avoid a decrease in the transport reliability described above, but even when the rear end of the tab portion e is detected, the reversal timing is further waited by the length in the transport direction of the tab portion e. Therefore, productivity cannot be denied.

  In order to prevent such a decrease in productivity, the front edge and the rear edge of the tab paper are detected, and an accurate inversion timing of the tab paper is obtained by calculation from the detected length between the edges, and the above-described productivity is reduced. Although the decrease can be prevented, the problem of complicated control arises.

  Accordingly, an object of the present invention is to ensure transport reliability in the case of tab paper, and to enable an efficient reversing operation in plain paper that is not tab paper.

In order to achieve the above object, the present invention is provided in a reverse conveyance path for receiving and reversing a sheet on which a single-sided image has been formed, a carry-in means for carrying the sheet into the reverse conveyance path, and the reverse conveyance path. A reversing and conveying means for reversing and carrying out the carried paper, and a reversing and conveying method for reversing and carrying out the paper carried into the reversing and conveying path. The paper is pulled into the reverse conveyance path by the reverse conveyance means, and the paper is reversed when the rear end portion exits the carry-in means. When the paper is not tab paper, the reverse conveyance means is separated a pair of rollers, inverted leave continues driving of the carry-out direction from the conveying path, the trailing end portion conveying rollers and reversing branching claw the unloading the paper at the time of exit of the carrying means of the roller pair Transported across in the roller pair is driven in direction, characterized in that to invert.

According to the above configuration, in the case of tab paper, it is possible to ensure the reliability of conveyance, and in the case of plain paper that is not tab paper, it is possible to reverse the paper when the trailing edge of the paper exits the carry-in means. Therefore, efficient inversion operation is possible .

  According to the present invention, in the case of tab paper, the conveyance reliability is ensured, and in the case of plain paper that is not tab paper, an efficient reversal operation is possible.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts as those in the above-described conventional example are denoted by the same reference numerals, and redundant description is omitted.

<First Embodiment>
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the first embodiment of the present invention. The image forming apparatus PR according to the present embodiment includes an image forming device (photosensitive member, charging device, developing device, transfer device, cleaning device, etc.) 1, a transfer material (recording medium) reverse discharge device 2, a reading device 3, and a writing device. This is an electrophotographic image forming apparatus mainly composed of a device 4, a paper feeding device 8, and a fixing device 9. In this image forming apparatus PR, a document placed on a contact glass (not shown) provided on the upper surface of the reading device 3 is optically read, and the read image is converted into printable image information. Based on this, the writing device 4 performs optical writing on the photosensitive member 6 of the image forming device 1 to form a latent image, and the developing device 7 of the image forming device 1 develops the latent image on the photosensitive member 6 so that the visible toner is visible. Make a statue. On the other hand, the paper P supplied from the paper supply device 8 (hereinafter referred to as “paper” because a paper is used as a transfer material in this embodiment) P is conveyed to the image forming device 1 as shown by an arrow 19 and is made. The transfer device 5 of the image device 1 transfers toner onto the paper P, and the fixing device 9 fixes the image. The paper P on which the image is fixed is discharged to the paper discharge tray 11 or conveyed to the reverse discharge device 2.

  In the reverse discharge device 2, the paper P is directly discharged out of the device, or reversed and conveyed again to the image forming device 1 side. When discharging the paper P straight (normally) out of the image forming apparatus PR, it passes along the path indicated by the arrow 12 when transporting the paper P to the outside of the apparatus through the paper discharge roller 20 as it is. Transport. When the paper is reversed and discharged outside the apparatus, the paper P is conveyed from the reverse discharge apparatus 2 along the path indicated by the arrow 14. When the paper P is reversed in the reverse discharge device 2 and re-supplied to the image forming device 1 to form images on both sides of the paper P, the paper P is conveyed along the path indicated by the arrow 15.

  FIG. 2 is an enlarged view of a main part for explaining details and operation of the reverse discharge device 2 in FIG. In FIG. 2, the reverse discharge device 2 includes a paper discharge branch claw 33, a reverse entrance upper guide plate 25a, a reverse entrance lower guide plate 25b, a paper detection sensor (hereinafter abbreviated as a sensor) 26, and a transport from the upstream side in the paper transport direction. Roller 17, reverse branching claw 18, reverse conveyance guide plate 13, reverse rotation drive roller 21, reverse rotation driven roller 22, position regulation side fence (jogger) 29, double-side drive roller 30, both sides It is mainly composed of the branching claw 28 and the reverse conveyance path 31. In the reversal discharge device 2 constituted by each of these parts, the paper P that has passed through the fixing device 9 and has an image fixed on one side is conveyed to the discharge roller 20 side by switching the discharge branch claw 33. It is selected whether to convey to the reverse discharge device 2 side. That is, the paper P is conveyed to the reverse discharge device 2 by switching the paper discharge branching claw 33 in the direction shown by the solid line in FIG. 2, and the paper P is discharged straight by switching in the direction shown by the broken line in the figure. Is called.

  When the paper discharge branch claw 33 is switched in the direction of the solid line, the paper P enters between the reverse entrance guide plate 25a and the reverse entrance lower guide plate 25b via the path indicated by the arrow 12. A sensor 26 is provided on the reverse entrance guide plate 25a to detect the rear end of the sheet P in the traveling direction. The conveyance roller 17 is provided at a position close to the downstream side in the paper conveyance direction of the sensor 26 provided on the reverse entrance guide plate 25a, and the tip of the reverse branch claw 18 is below the conveyance roller 17 and downstream in the paper conveyance direction. The pressure is applied upward (in the direction of the axis 16 of the conveying roller 17) in the figure by a biasing means (not shown). A plurality of conveyance rollers 17 and reverse branching claws 18 are arranged side by side in a direction perpendicular to the paper surface in FIG. 2, and the leading ends of the reverse branching claws 18 alternately enter between the conveyance rollers 17 as described above. As a result, when the paper P enters between the transport roller 17 and the reverse branch claw 18, the paper P is pressed against the transport roller 17 by the pressure of the reverse branch claw 18, and a transport force is generated to move on the reverse transport guide plate 13. Be transported.

Figure 3 is a conceptual view showing an enlarged around the conveying roller 17 and the inverting branch claw 18 in one embodiment of the reversing apparatus of FIG. 2, FIG. 3 arrow A the carry state of the inverted branching claw 1 8, arrows B indicates the reverse and carry-out state of the reverse branch claw 18 , and the arrow G indicates the carry-in state of the paper P. As shown in these, the paper P at the time of loading is sandwiched between the inverting branch guide 18 and the conveying roller 17, the tip of the inverted branching pawl 18 is pressure in the upward direction is applied, the paper P by the pressure Is pressed against the conveying roller 17, and a conveying force is generated by the frictional force of the conveying roller 17 and is conveyed. When the trailing edge of the sheet P passes through the tip of the reversing branch claw 18, the reverse driven roller 22 descends (swings to the reverse driving roller 21 side), and the paper P is moved to the reverse driven roller 22 and the reverse driving roller 21. The paper P is reversed and conveyed in the reverse direction.

  FIG. 4 is an enlarged conceptual diagram corresponding to FIG. 3 showing a modification of the present embodiment. The difference from the configuration of FIG. 3 is that the reverse drive roller 21 has an independent drive source (conveyance motor 60) and is forward and reverse. It is possible to change the speed. As the transport motor 60, for example, a stepping motor is used. As a result, during the process of entering the reverse conveyance tray 13 when the tab paper Pt is being used, the reverse rotation driving roller 21 is rotated in reverse (rotation in the paper carry-in direction—arrow R direction) and reverse rotation in advance as illustrated. If the driven roller 22 is lowered by turning on the solenoid 61 (in the direction of arrow D in the figure), the sheet P can be drawn and conveyed in the conveying direction (direction C in the figure) while being nipped and conveyed, so the tab portion at the rear end of the sheet It is possible to perform the pull-in conveyance until e passes through the tip of the reverse branch claw 18.

  As a result, as shown in FIG. 5, even in the configuration in which the number of transport rollers 17 is reduced, the ear portion e can surely pass through the tip of the reverse branch claw 18, and the paper P is reliably fed into the reverse transport tray 13. It is. In this embodiment, whether or not the tab portion e has passed through the tip of the reversing branch claw 18 (reversal operation timing) is determined from the sheet trailing edge detection timing at the sensor 26 provided near the entrance of the reversing device 2. Judgment is based on elapsed time. This is because the accuracy is higher when the conveyance time from the detection timing is shorter, which is convenient in controlling a normal sheet that is not the tab sheet Pt.

However, due to the simplification of control and the like, a problem occurs when the timing of the reversal operation is measured in the same sequence regardless of whether the tab sheet is conveyed or not. That is, when the tab portion e is conveyed on the trailing edge side, it is difficult to detect the trailing edge of the sheet. When the number of the sensors 26 is one, in the case of the tab sheet Pt, since the position of the tab portion e in the width direction (direction perpendicular to the transport direction) is unknown, the length Lt of the tab portion e in the transport direction is unknown. In most cases, the detection time is shifted by the minute. Therefore, it is necessary to perform an operation such as a delay of the reversal timing and an increase in the paper interval during conveyance in anticipation of the tab portion e. In order not to perform such an operation of delaying the reversal timing or increasing the paper interval, the sensors 26 are provided at positions corresponding to all the tab portions e and controlled based on the detection outputs of the sensors 26. Although it is possible to cope with this, the number of sensors 26 increases and the control including them becomes complicated, resulting in high costs. Therefore, in the present embodiment, the sheet length L of the tab sheet Pt (including the length Lt of the tab portion e) is input in advance, and the amount of deviation from the passage time t detected by the sensor 26 is overfeed amount δ. It is calculated as (corresponding to Lt of the ear part e), and is transported by that much. That is, if the distance from the sensor 26 to the tip of the reversing branch claw 18 is a predetermined (normal) transport distance K, the feed amount Kt during the tab sheet transport is
Kt = predetermined (normal) transport distance K + excess feed amount δ (1)
It is represented by

  On the other hand, when only the rear end is detected, the length Lt of the tab portion e is input, and the sheet size information (sheet size and conveyance direction) sent from the sheet feeding device 8 is used to determine the sheet conveyance direction. Since the length is known, Lt is added to the length to obtain the sheet length L of the tab sheet Pt.

Further, the actual passing sheet length L ′ detected by the sensor 26 is as follows.
L ′ = V × t (2)
If the length of the tab sheet Pt input in advance is L, the overfeed amount δ corresponding to the length Lt of the ear e is
δ = L−L ′ (3)
Can be calculated. Therefore, if it is determined that the conveyed sheet is tab sheet Pt, more reliable tab sheet inversion control can be realized by controlling the conveyance with the pull-in amount as Kt. Even with a roller configuration, it is possible to reduce costs while improving transport reliability.

  Next, the reverse operation after entering the reverse transport tray 13 will be described. As shown in FIG. 6, the paper once stored in the paper reversing tray 13 is transported in the B direction (paper transport direction) by the forward rotation drive (arrow N direction) of the transport roller 21 and provided downstream thereof. It is delivered to the double-sided drive roller 30. Then, the solenoid 61 is turned OFF to retract the reverse driven roller 22 from the position of the reverse conveyance guide plate 13 and wait for the next paper to enter. Here, assuming that the required transport distance X until a normal sheet that is not a tab sheet is reliably bitten is required, the tab sheet Pt needs to be transported by an excess feed amount calculated previously. That is, it is necessary to send it downstream by the tab portion e. Further, as described above, when entering the reversing conveyance tray 13, the reversing timing is delayed by an excessive feed amount corresponding to the length of the tab portion e of the tab sheet Pt, and thus there is a tendency that there is no room for entering the next sheet. become. This margin becomes smaller as the paper interval is made smaller, and the paper interval control becomes more severe.

Therefore, if the delay corresponding to the excessive feed amount δ is recovered by the speed-increasing control of the reverse drive roller 21, and the same timing as that of the plain paper is realized in the tab paper conveyance, the conveyance reliability can be ensured reliably. At this time, the transport speed when the transport motor 60 is accelerated is calculated using the excess feed amount δ detected from the sensor 26. Here, assuming that the transport distance X is a fixed value, assuming that the normal transport speed is V, the transport speed during acceleration is V ′, and the excess feed amount δ, the necessary speed increase condition is
V ′ ≧ (X + 2δ) / T (4)
Is calculated by Here, T = X / V.

  That is, the excess feed amount at the time of “reverse approach” and “reverse (reverse) transport” is considered (δ × 2), and the loss at 2δ is compensated for by the speed increase at the time of reverse. Here, when the tab sheet Pt that is normally used is determined, the speed increasing condition derived from the previous equation may be fixed.

  Moreover, when comprised in this way, the position control side fence 29 shown in FIG. 2 can also be made to act. The position regulating side fence 29 functions as a so-called jogger fence, is driven by a jogger motor (not shown), and performs an aligning operation in a direction orthogonal to the paper transport direction. In this case, when the pull-in operation is completed, that is, when the rear end (tab portion e) of the sheet passes through the reverse branch claw 18, the pressing state of the reverse driven roller 22 toward the reverse drive roller 21 is once released. At the same time, the position regulating side fence 29 is actuated to perform the aligning operation in the direction orthogonal to the transport direction of the paper Pt, and then the reverse driven roller 22 is again lowered and transported. At this time, there is a slight time lag, but it is sufficient to determine the speed increasing condition in consideration of this amount. When the jogging operation is performed by the position regulating side fence 29 as described above, the position accuracy in the case of performing the post-processing such that the position accuracy of the punching position of the punch hole is improved can be improved.

  When the jogging operation is performed, the tab paper Pt and the normal paper P are operated at different timings depending on the presence or absence of the tab portion e. The normal control (operation) is set with reference to a normal sheet having an overwhelmingly large number of processed sheets, and the control is changed only for the tab sheet Pt. However, the difference is that the tab portion e is reversed by being accelerated by a delay corresponding to the length in the sheet conveyance direction. In this way, the conveyance control from the double-sided drive roller 30 to the image forming unit 1, the image forming control in the image forming unit 1, and the paper discharge control after image forming in the image forming unit 1 are performed as tab sheets. It can be performed at the same timing as that of normal paper P that is not Pt.

  FIG. 7 is a block diagram showing a schematic configuration of a control system of the image forming apparatus PR according to the embodiment of the present invention. The control system of the image forming apparatus PR according to the embodiment of the present invention includes a control device 50 including a microcomputer 51 and various timers 52. The control device 50 includes solenoids 53 and 61, other drive systems, and a conveyance motor. 55, 60, tab sheet size input key 56, sensor 26 and other sensors, and tab sheet insertion mode selection key 27 are connected, and various inputs from the input key, selection key, and sensors are input to microcomputer 51. The microcomputer 51 outputs an instruction signal to the solenoids 53 and 61, the transport motors 55 and 60, and other drive systems.

  The microcomputer 51 includes a CPU, a ROM that stores a program executed by the CPU, a RAM that functions as a work area when the CPU executes the program, an I / O circuit, and the like. . The CPU is set with a tab sheet Pt conveyance mode in which tab sheets are continuously conveyed and a mode in which tab sheets are inserted as a slip sheet during a normal printing process. In the present embodiment, the tab sheet insertion mode selection key 27 is provided on an operation panel (not shown) outside the image forming apparatus. When the tab sheet insertion mode is selected by the tab sheet insertion mode selection key 27, the control device 50 determines the CPU, RAM based on information from the sensor 26, the tab sheet insertion mode selection key 27, the tab sheet size input key, and the like. The microcomputer 51 having a ROM, I / O circuit, etc. performs arithmetic processing to control the operations of various timers and various load devices. Here, the conveyance motor 55 is the conveyance roller 17 and the double-sided drive roller 30, the conveyance motor 60 is the reverse-rotation drive roller 21, the solenoid 61 is moving up and down the reverse-rotation driven roller 22, and the solenoid 53 is oscillating the double-sided branch claw 28. Activate each one.

  FIG. 8 is a flowchart showing a processing procedure of the reverse conveyance processing timing processing of the present invention.

  In this process, the transport motor 60 is driven in the normal direction at a normal linear velocity V (paper carry-out direction—arrow N direction) in advance and waits for the paper to enter (step S1). Next, when the trailing edge of the sheet entering the reverse discharge device 2 is detected by the sensor 26 (step S2), it is further checked whether the detected sheet is a tab sheet Pt (step S3). Whether or not it is tab paper Pt can be determined whether or not the paper being conveyed is tab paper Pt if the tab paper insertion mode is selected by operating the tab paper insertion mode selection key 27 as described above. If it is the paper Pt, the routine proceeds to the routine A, and the excess feed amount δ is set from the equation (3) based on the timing detected by the sensor 26 (step S4). Then, after the paper trailing edge (tab portion e) has passed the sensor 26 and a predetermined time has elapsed (step S5), the transport motor 60 is driven in reverse at the normal linear velocity V (paper loading direction, arrow R direction in FIG. 4), step. At the same time, the solenoid 61 is turned on, the reverse driven roller 22 is lowered (abuts against the reverse drive roller 21) (step S7), and the paper (tab paper Pt) P is drawn and conveyed (conveyed in the direction of arrow C). Move to (Operation). Then, after transporting “predetermined transport distance K + excess feed amount δ” (step S8), the solenoid 61 is turned off to raise the reverse driven roller 22 (separate from the reverse drive roller) (step S9), and the jogger motor A predetermined amount of normal rotation is performed (step S10). As a result, the jogger, that is, the position regulating side fence 29 abuts against the tab paper Pt from the direction orthogonal to the transport direction of the tab paper Pt and pushes in a predetermined amount in the direction orthogonal to the transport direction of the tab paper. The positions are aligned.

  Next, the solenoid 61 is turned on, the reverse drive roller 22 is lowered, the tab paper Pt is sandwiched between the reverse drive roller 21 (step S11), and the transport motor 60 is driven forward (in the direction of arrow N in FIG. 3). Then, it is sent out at a speed higher than the normal speed (speed when carrying out the paper that is not tab paper) (step S12). The transport speed at this time is set to a speed increasing condition V ′ calculated by the CPU based on the equations (3) and (4). When the sheet is conveyed by “predetermined conveyance distance X + overfeed amount δ” so that the sheet is reliably caught by the double-sided drive roller 30 provided further downstream (step 13), the jogger motor is reversed by a predetermined amount to control the position. The side fence 29 is moved to the standby position (step S14), and the solenoid 61 is turned off to retract the reverse driven roller 22 (step S15), and the process returns. In this state, the reverse discharge device 2 switches the conveyance motor 60 to the normal rotation drive at the normal linear velocity V and waits for the next sheet to enter. Note that, because of the speed increasing condition, when the feeding of the tab paper Pt is completed, the timing is the same as that of the paper that is not the tab paper, so the control timing thereafter is exactly the same as that of the normal paper, and the control is complicated. Never do.

  On the other hand, in the case of the normal paper P that is not the tab paper Pt in step S3, the drawing transfer is not performed, and the routine proceeds to the routine B. In the routine B, when the paper P is transported by a predetermined (normal) transport distance K (step S16), the jogger motor is rotated forward by a predetermined amount, and the paper where the position regulating side fence 29 is positioned on the reverse transport guide plate 13 is detected. An alignment operation is performed in the direction perpendicular to the paper transport direction by contacting the side of P (step S17). Next, the solenoid 61 is turned on aiming at the timing when the trailing edge of the paper P passes through the tip of the reverse branching claw 18, the reverse driven roller 21 is lowered (step S18), and the reverse operation is performed. At this time, the reverse rotation driving roller 21 (conveyance motor 60) is driven to rotate forward (in the direction of arrow N in FIG. 6) at a normal speed. When the predetermined distance X is conveyed (step S19), the jogger motor is reversely rotated by a predetermined amount, the position regulating side fence 29 is returned to the standby position (step S20), the solenoid 61 is turned OFF, and the reverse driven roller 21 is retracted ( Step S21) and return.

According to the first embodiment, the inversion timing can be set based on the output of the sensor 26 that detects the trailing edge of the paper, whether it is tab paper or plain paper that is not tab paper. There is no need to do so, and control becomes simple. Further, the control method of the transport roller 21 and the reverse driven roller 22 is changed between the case of tab paper and the case of non-tab paper. In the case of tab paper, the transport to the reverse transport tray 13 is ensured. Can perform a quick reversal operation. Also, in the case of tab paper, the paper is reliably pulled into the reverse transport tray and then reversed at an increased speed, and the timing for unloading from the reverse transport tray is set to be the same as that for normal paper that is not tab paper. The subsequent control timing may be the same as that of the normal paper, and the control is simplified in this respect.

<Second Embodiment>
In the modification of the first embodiment, the rear end portion of the tab paper Pt or the normal paper P is detected by the sensor 26 provided on the upstream side in the paper transport direction of the transport roller 17 of the paper reverse discharge device 2, and this detection is performed. As shown in the flowchart of FIG. 8 described above based on the output, in the process in which the tab sheet Pt enters the reversing conveyance path (reversing conveyance tray 13), until the tab portion e is surely removed from the tip of the branching claw 18, It is configured to be drawn and transported to the back side of the reverse transport tray 13 by a reverse transport means comprising a reverse drive roller 21 and a reverse driven roller 22, simplifying the roller configuration and claw configuration (cost reduction), and reversing ( During reverse conveyance, the reverse conveyance means is driven at an increased speed to absorb the delay loss for the tab portion e conveyance so as not to lower the productivity.

  However, when controlling the reversal timing, there is a limit to simplify the calculation by detecting the trailing edge of both the tab paper and the paper other than the tab paper. Therefore, it is possible to detect and process the passage timing of the leading edge of the sheet by the sensor 26 and to perform simpler control. In this case, the edge of the detection paper is changed depending on whether it is tab paper Pt or normal paper that is not tab paper. In the case of tab paper Pt, the leading edge of the tab paper Pt is changed. The CPU calculates the excess feed amount δ based on the detected output of the detected sensor 26 and the length dimension of the tab sheet Pt input in advance.

  The processing procedure in the second embodiment will be described below with reference to the flowchart of FIG. The configuration and operation of the image forming apparatus are the same as those of the first embodiment described with reference to FIGS.

  In this embodiment, the transport motor 60 is driven in the forward direction (driven in the paper unloading direction) at a normal linear velocity V in advance, and waits for the paper to enter (step S1). Then, it is checked whether the detected paper is a tab paper Pt (step S3). Whether or not it is tab paper Pt is determined by whether or not the tab paper insertion mode is selected by the tab paper insertion mode selection key 27 as described above. If it is a tab sheet Pt, when the sensor 26 detects the leading edge of the sheet (step S2a), the sheet length L including the tab portion e in the case of the tab sheet Pt is determined by the input by the tab sheet size input key 56 described above. Therefore, the process after step S4 is executed after the routine A.

  On the other hand, if the sheet is a normal sheet P that is not a tab sheet Pt in step S3, when the sensor 26 detects the trailing edge of the sheet (step S2b), the routine of B is followed, and the processes after step S16 are executed. .

  In the case of processing in this way, the CPU calculates and processes necessary acceleration conditions based on the above-described equation (4) in accordance with the detection output of the sensor 26. As a result, as in the first embodiment, when the feeding of the tab paper Pt is completed, the timing is the same as that of the paper that is not the tab paper, and the subsequent control timing is exactly the same as that of the normal paper. The control is not complicated.

  Instead of the above-described step S2a, both the leading edge and the trailing edge of the sheet are detected, and the excess feed amount δ is calculated based on the expressions (1) to (4) from the passage of time during the same processing. You can also However, this processing is not preferable because the number of processing steps increases and the control becomes complicated. However, since the passage time is measured, more accurate control is possible.

<Third Embodiment>
This embodiment is an example in which the process of step S4 in the second embodiment is changed and executed at another timing of this process. The processing procedure in the third embodiment will be described below with reference to the flowchart of FIG. The configuration and operation of the image forming apparatus are the same as those of the first embodiment described with reference to FIGS. Moreover, the same code | symbol is attached | subjected to the step equivalent to the flowchart of FIG. 9, and the overlapping description is abbreviate | omitted suitably.

  In this embodiment, the transport motor 60 is driven to rotate forward at a normal linear velocity V in advance, and waits for the paper to enter (step S1). Then, it is checked whether the detected paper is a tab paper Pt (step S3). Whether or not the tab sheet is Pt is determined by whether or not the tab sheet insertion mode is selected as described above. If it is a tab sheet Pt, when the sensor 26 detects the leading edge of the sheet (step S2a), the routine proceeds to the routine A. In this embodiment, instead of step S4 in FIG. 9, step S4 ′ in FIG. Process like this.

  That is, after the leading edge of the tab sheet Pt is detected by the sensor 26, only the transport distance S (= K + L) shown in FIG. 4 is set, and when the transport time corresponding to the transport distance S elapses in step S5, step S6 and subsequent steps. Execute the process. That is, in step S4 'and step S5, the distance S is conveyed so that the rear end of the tab sheet Pt surely passes between the conveying roller 17 and the branching claw 18. Here, L is the length of the tab sheet Pt (including the tab portion e) inputted in advance as described above, and K is the reverse branch claw from the sensor 26 described in relation to the above-described equation (1). 18 is the distance to the tip. Thereby, the passage timing of the paper Pt can be reliably detected regardless of the position of the tab portion e. Next, when a predetermined time has elapsed in step S5 and the conveyance distance conveyance S has been carried, the processes in steps S6 and S7 are executed. In step S8 ′, when the sheet is conveyed by the conveyance distance S set in step S4 ′, the solenoid 61 is turned off (step S9), and the excess feed amount δ is calculated from the input sheet length L (step S4). The feed amount when reversed is set, and the processing after step S10 is executed.

  On the other hand, if the sheet is a normal sheet P that is not a tab sheet Pt in step S3, when the sensor 26 detects the trailing edge of the sheet (step S2b), the routine of B is followed, and the processes after step S16 are executed. .

  According to this embodiment, the tab portion e reliably passes through the sheet nipping portion between the conveyance roller 17 and the branch claw 18 by the conveyance distance S set in step S4 ', so that no jam occurs at this point. Further, since the overfeed amount in step S4 is calculated during the period up to step S9, the operation timing is not delayed by the calculation of the overfeed amount, and efficient processing is possible. The calculation of the excessive feed amount δ in FIG. 10 may be performed between any steps as long as it is completed before the check of the feed amount at the time of reversal in step S13.

<Fourth Embodiment>
In the first to third embodiments, the above-described timing control is performed based on the detection output of the leading edge or the trailing edge of the sheet of the sensor 26 provided on the upstream side of the conveying roller 17 in the sheet conveying direction. Normally, in tip detection, the longer the conveyance distance from the detection position of the sensor, the more a feed error occurs due to slip or the like. In such a case, it is effective in the sense of preventing the occurrence of the error to arrange the sensor in the switchback path and as downstream as possible in the traveling direction. Therefore, in the fourth embodiment, a second sensor 32 that detects the leading edge of the paper (tab paper) is disposed on the downstream side of the reverse rotation driving roller 21 of the reverse conveyance tray 13 in the paper conveyance direction. The control based on the detected output is added to the second embodiment and processed.

  The processing procedure in the fourth embodiment will be described below with reference to the flowcharts of FIGS. 10 and 11. Note that the configuration and operation of the image forming apparatus are the same as those of the first embodiment described with reference to FIGS. Moreover, the same code | symbol is attached | subjected to the step equivalent to the flowchart of FIG. 9 and FIG. 10, and the overlapping description is abbreviate | omitted suitably.

  In this embodiment, the transport motor 60 is driven to rotate forward at a normal linear velocity V in advance, and waits for the paper to enter (step S1). Then, it is checked whether the detected paper is a tab paper Pt (step S3). Whether or not the tab sheet is Pt is determined by whether or not the tab sheet insertion mode is selected as described above. If it is a tab sheet Pt, when the second sensor 32 (FIG. 4) detects the leading edge of the sheet (step S2a '), the routine of FIG. 10A is followed. In the routine A, processing is performed as in step S4 ″ in FIG. 11 instead of step S4 ′ in FIG.

That is, when the tab sheet Pt come enters, the second sensor 32 to set the conveyance distance S (= L-Y) at Step S4 "When the paper leading edge passes, corresponding to the conveyance distance S in step S5 conveying time to execute to the step S6 and subsequent steps course of. that is, between the steps S4 "and S5 in conveyance distance S conveyed tab sheet Pt trailing edge reliably transport rollers 17 and the inverting branch claw 18 It is made to come off (FIG. 4). Here, L is the length of the tab paper Pt (including the length of the tab portion e in the paper conveyance direction), and Y is the distance from the tip of the reverse branching claw 18 to the second sensor 32. Accordingly, it performed leading edge detection in a state in which bite firmly on the inverting transportable octenyl stage by the roller pair of the reverse rotation roller 21 and the reverse rotation driven roller 22 (the state allowing sufficient conveying force), counting the time therefrom (Step S5). As a result, even if there is a slight slip (paper delay) before reaching the nip between the reverse drive roller 21 and the reverse driven roller 22, a more accurate reverse operation is possible regardless of this.

  Next, when a predetermined time has elapsed in step S5 and the conveyance distance conveyance S has been carried, the processes in steps S6 and S7 are executed. In step S8 ′, when the sheet is conveyed by the conveyance distance S set in step S4 ′, the solenoid 61 is turned off (step S9), and the excess feed amount δ is calculated from the input sheet length L (step S4). The feed amount when reversed is set, and the processing after step S10 is executed.

  On the other hand, if the sheet is a normal sheet P that is not a tab sheet Pt in step S3, when the sensor 26 detects the trailing edge of the sheet (step S2b), the routine of B is followed, and the processes after step S16 are executed. .

1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a main part enlarged view showing details of the reverse discharge device of the image forming apparatus of FIG. It is a figure which expands and shows the vicinity of the conveyance roller of the inversion discharge apparatus of FIG. It is a figure which expands and shows the vicinity of the conveyance roller and reverse branch claw of the reverse discharge apparatus in other embodiment of FIG. It is a principal part top view which shows the structure of the inversion entrance part of the inversion discharge apparatus shown in FIG. FIG. 5 is a diagram illustrating a sheet discharge operation of the reverse discharge apparatus illustrated in FIG. 4. It is a block diagram which shows the system configuration | structure of the control system of embodiment shown in FIG. 3 is a flowchart illustrating a control procedure of timing control of the image forming apparatus according to the first exemplary embodiment of the present invention. 10 is a flowchart illustrating a control procedure of timing control of the image forming apparatus according to the second exemplary embodiment of the present invention. 10 is a flowchart illustrating a main part of a control procedure of timing control of an image forming apparatus according to a third embodiment of the present invention. 10 is a flowchart illustrating a main part of a control procedure of timing control of an image forming apparatus according to a fourth embodiment of the present invention. It is a perspective view which shows the tab paper which this invention makes object. It is a principal part top view which shows the structure of the inversion entrance part of the inversion discharge apparatus for conveying the tab paper currently implemented conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper reversal discharge apparatus 3 Reading apparatus 4 Writing apparatus 6 Photoconductor 7 Developing apparatus 8 Paper feed apparatus 9 Fixing apparatus 10 Conveyance roller 13 Reverse conveyance tray 16 Axis 17 Conveyance roller 18 Reverse branching claw 20 Discharge roller 21 Reverse drive roller 22 Reverse driven roller 25a Reverse entrance guide plate 25b Reverse entrance lower guide plate 26 (paper detection) sensor 27 Tab paper insertion mode selection key 28 Double-sided branch pawl 33 Paper discharge branch pawl 50 Controller 51 Microcomputer 53, 61 Solenoid 55, 61 Conveyance motor Pt Tab paper Pa One edge e Tab (ear) part P Paper PR Image forming apparatus

Claims (1)

A reversing conveyance path for receiving and reversing a sheet on which a single-sided image has been formed;
Carrying-in means for carrying the paper into the reverse conveying path;
A reversing and conveying means that is provided in the reversing and conveying path and reverses and carries out the carried paper;
In the reverse conveyance method of the paper that reverses and carries out the paper carried into the reverse conveyance path,
In the case of tab paper, the paper is drawn into the reverse conveyance path by the reverse conveying means, and the paper is reversed when the rear end portion exits the carrying means,
In the case of a sheet that is not a tab sheet, the roller pair of the reverse conveying means is separated at the time of carry-in from the carry-in means, and driving in the carry-out direction from the reverse conveyance path of the roller pair is continued, A method of reversing and conveying a sheet, wherein the sheet is nipped and conveyed by the pair of rollers driven in the carry-out direction when the conveying roller and the reversing branch claw of the carry-in means are removed .

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