JP5371724B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a double-sided printing function.

  Conventionally, in an image forming apparatus having a double-sided printing function, if the length of the paper transport path is designed to be small in order to reduce the size of the apparatus, when the paper is reversed, a part of the paper is out of the machine. Exposed to. In particular, in the case of a paper having a long length in the transport direction such as A3 size, since the portion where the paper is exposed to the outside during reversal is large, the user determines that the printing has been completed, and the paper is accidentally pulled out. There is a possibility. For this reason, during double-sided printing, it is known to detect the state of paper withdrawal at a paper reversal standby position and issue a warning to the user to interrupt the drawing (see Patent Document 1).

JP 2006-337548 A

  However, in the prior art, when a part of the paper is exposed to the outside during reversal, the state of the paper being pulled out is detected, and a warning is issued to the user to interrupt the drawing. However, if the user completely pulls out the sheet without noticing the warning, the image forming operation cannot be continued.

  In view of the above-described problems, an image forming apparatus according to the present invention includes a sheet feeding unit that feeds a sheet and a first surface of the sheet fed by the sheet feeding unit. Alternatively, an image forming unit that forms an image on the second surface, and after the image is formed on the first surface of the sheet by the image forming unit, the sheet is exposed in a state where a part of the sheet is exposed to the outside of the image forming apparatus. Reversing means for switching back and reversing the front and back; a refeeding means for refeeding the sheet to the image forming means to form an image on the second surface of the sheet whose front and back are reversed by the reversing means; Detection means for detecting the withdrawal of the sheet that is reversed by the reversing means, and when the detection means detects the withdrawal of the sheet, the image forming means converts the sheet subsequent to the drawn sheet to the image forming means. Ri is a transport control means for waiting a predetermined position upstream, and informing means for the withdrawn sheet to inform the instruction is placed on the paper feed unit, characterized in that it has a.

  According to the present invention, even when the paper is completely pulled out by the user during the paper reversing operation in the image forming apparatus, the image forming operation can be continued with a simple operation.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating an internal configuration of the image forming apparatus. FIG. FIG. 3 is a diagram illustrating an apparatus state during double-sided printing in the image forming apparatus. 6 is a diagram illustrating an example of a warning display in the image forming apparatus. FIG. It is a flowchart which shows the procedure of the process at the time of duplex printing.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an image forming apparatus according to an embodiment.

  In FIG. 1, an image forming apparatus 1 forms an image forming unit 1Y that forms a yellow image, an image forming unit 1M that forms a magenta image, an image forming unit 1C that forms a cyan image, and a black image. Image forming unit 1Bk.

  The image forming units 1Y, 1M, 1C, and 1Bk respectively include photosensitive drums 2a to 2d as image carriers, primary chargers 3a to 3d as primary charging units, developing devices 4a to 4d, and primary transfer units. Transfer rollers 5a to 5d and drum cleaners 6a to 6d are provided. A laser exposure device 7 is provided below the image forming units 1Y, 1M, 1C, and 1Bk, and an endless intermediate transfer belt 8 is provided between the photosensitive drums 2a to 2d and the transfer rollers 5a to 5d.

  The primary chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). The developing devices 4a to 4d develop the toner images (visible images) by attaching toners of the respective colors to the electrostatic latent images formed on the photosensitive drums 2a to 2d. The transfer rollers 5a to 5d are in contact with the photosensitive drums 2a to 2d via the intermediate transfer belt 8 in the primary transfer portions 32a to 32d, respectively. The drum cleaners 6a to 6d have cleaning blades and the like for removing toner remaining on the photosensitive drums 2a to 2d after the primary transfer.

  The exposure apparatus 7 includes a laser light emitting element 7a, a lens 7b, a reflection mirror 7c, and the like. The exposure device 7 irradiates the photosensitive drums 2a to 2d charged by the primary chargers 3a to 3d with laser light corresponding to the image data input from the external device, respectively. As a result, electrostatic latent images of respective colors corresponding to the image data are formed on the photosensitive drums 2a to 2d.

  The image forming apparatus 1 further includes a secondary transfer counter roller 10, a tension roller 11, and a secondary transfer roller 12. The secondary transfer counter roller 10 contacts the secondary transfer roller 12 through the intermediate transfer belt 8 in the secondary transfer unit 34. The tension roller 11 is disposed at a position facing the secondary transfer counter roller 10 with the primary transfer portions 32a to 32d interposed therebetween, and applies tension to the intermediate transfer belt 8.

  The image forming apparatus 1 further includes a sheet feeding cassette 17 that stores a transfer material (sheet) P as a sheet feeding unit, and a manual transfer material tray 20. The image forming apparatus 1 further includes a transport path 18, a registration roller 19, a fixing device 16, a paper discharge roller 21, a paper discharge tray 22, a double-sided path 43, double-sided rollers 40 and 41, and a reverse flapper 44. Is provided.

  The paper feed cassette 17 and the manual transfer material tray 20 feed the transfer material P to the transport path 18. The registration roller 19 conveys the transfer material P in the conveyance path 18. The fixing device 16 includes a fixing roller 16 a and a pressure roller 16 b, which are in contact with each other at the fixing nip portion 31.

  The transfer material P passes through the fixing nip portion, and the paper discharge roller 21 discharges the transfer material P to a paper discharge tray 22 provided on the upper surface of the image forming apparatus 1. When performing double-sided printing, after the trailing edge of the transfer material P reaches the reversal sensor 42, the position of the flapper 44 is switched to the double-sided path 43 side, and the paper discharge roller 21 is rotated in the reverse direction, whereby the transfer material P is double-sided. Send to pass 43. The double-sided rollers 40 and 41 convey the transfer material P in the double-sided path 43. Since the image forming apparatus 1 is designed to have a short paper conveyance path in order to reduce the size of the apparatus, a part of the paper is exposed to the outside when the paper is reversed.

  FIG. 2 is a block diagram showing an internal configuration of the image forming apparatus 1 shown in FIG. The CPU 171 controls the image forming apparatus 1. The ROM 174 stores a control program executed by the CPU 171. The RAM 175 is a work area for the CPU 171 to perform processing. The input / output port 173 is connected to a load 188 such as a motor and a clutch of the image forming apparatus 1, a sensor 189 for detecting a sheet as indicated by 42, 45, and 601 in FIG. The CPU 171 controls input / output of signals through the input / output port 173 in accordance with a control program stored in the ROM 174, and performs an image forming operation.

  The operation unit 172 includes a display unit and a key input unit. The operator instructs the CPU 171 to switch the operation mode and display using the key input means. The CPU 171 displays the state of the image forming apparatus 1 and the operation mode setting by key input on the display unit. The image formation processing unit 200 performs processing for causing the exposure device 7 to emit laser light corresponding to the line image data transferred from the image memory unit 300.

  Hereinafter, the transfer operation of the transfer material during duplex printing in the image forming apparatus 1 will be described with reference to FIG. When the print job is started, the uppermost sheet (transfer material P) of the transfer material bundle placed on the paper feed cassette 17 is separated from the transfer material bundle by the separation roller 80 and directed toward the registration roller 19. Be transported. When the leading edge of the transfer material P is detected by the registration sensor 45, it is transported a predetermined distance and stopped once so that the leading edge of the transfer material P stops at a position where it reaches the registration roller 19. After the registration roller 19 is temporarily stopped, the conveyance is resumed by the registration roller 19 so as to coincide with the image transfer timing in the secondary transfer unit 34, and then conveyed to the fixing device 16 through the secondary transfer unit 34. The transfer paper P is heat-fixed on the toner image by the fixing device 16, conveyed toward the paper discharge roller 21, and further conveyed by the paper discharge roller 21.

  When a plurality of double-sided printings are performed continuously, the feeding operation of the next transfer material (transfer material Q) is started when the trailing edge of the transfer material P passes through the registration sensor 45, and the leading edge of the transfer material Q is set at the registration roller. The conveyance is stopped at the position reaching 19. Further, the paper discharge roller 21 temporarily stops the conveyance when the rear end of the transfer material P reaches the reversal sensor 42. FIG. 3A shows a state in which the transfer material P reaches the reversal position and stops after the image formation on the first side of the duplex printing job is completed. At this time, the exit sensor 601 has detected the transfer material P, and the CPU 171 can recognize that the transfer material P has stopped at the reverse position.

  Next, after the position of the flapper 44 is switched to the double-sided path 43 side, the paper discharge roller 21 rotates in the reverse direction to convey the transfer material P to the double-sided path 43. The double-sided rollers 40 and 41 convey the transfer material P in the double-sided path 43 toward the registration roller 19. On the other hand, the subsequent transfer material Q is resumed while being synchronized with the image transfer timing when the transfer material P is conveyed in the direction of the double-sided path 43 by the paper discharge roller 21 and passes through the reverse sensor 42.

  When the leading edge of the transfer material P reaches the double-sided sensor 55, the transfer material P is temporarily stopped. After waiting for the trailing edge of the transfer material Q to pass through the registration sensor 45, the transfer material P is fed again toward the registration roller 19. After that, similarly to the printing on the front surface, after temporarily waiting at the registration roller 19, the transfer material P is transported again after the rear end of the transfer material Q transported to the double-sided path 43 passes through the reverse sensor 42, and the secondary The toner image transferred onto the intermediate transfer belt 8 in the transfer unit 34 is transferred to the transfer material P. Thereafter, the toner image is heat-fixed on the transfer material P at the fixing nip portion 31, and the transfer material P is discharged onto the paper discharge tray 22 by the paper discharge roller 21, thereby completing a series of image forming operations.

  When the number of printed sheets is three or more, the back side image is formed on the transfer material Q, and when the trailing edge passes through the registration sensor 45, the subsequent sheet feeding operation is started, and the above-described operation is repeated. Become.

  Hereinafter, a process when the transfer material P once stopped at the reversal position during double-sided printing is pulled out by the user will be described.

  When the transfer material P reaches the reverse position and stops, the exit sensor 601 has detected the transfer material P. At this time, if the user accidentally pulls out the transfer material P, the exit sensor 601 enters a non-detection state, and the CPU 171 monitoring the state of the sensor via the input / output port 173 indicates that the transfer material P has been pulled out. Recognize Here, when the image forming operation is temporarily stopped, for the remaining transfer materials existing in the transport path, the transport operation is continued as if the transfer material P was not pulled out. Then, the CPU 171 controls so that the conveyance is temporarily stopped at the position where the leading edge of the subsequent transfer paper Q reaches the registration roller 19. Alternatively, if the succeeding paper Q has already reached the registration roller 19 and has stopped once when the transfer material P is pulled out, control is performed so as to hold the temporarily stopped state.

  FIG. 3B shows a state in which, after the transfer material P at the reverse position is pulled out, the subsequent transfer material Q is conveyed to the position (standby position) of the registration roller 19 that is a predetermined position. This standby position is an upstream position from the position of the secondary transfer portion 34 that is the position of the image forming means. When the transfer material P is pulled out, it is notified that the transferred transfer material P is set on the manual feed tray 20 with the image surface facing up. Specifically, the message is displayed on the display unit of the operation unit 172. In this display method, for example, as shown in FIG. 4, character information is displayed on the operation unit 172 to prompt the user to perform an operation. Moreover, you may make it notify a user with a warning sound or an audio | voice. In the case of a conveyance path configuration in which an image is formed on the upper surface of the transfer material placed on the manual feed tray 20, a display prompting the user to set the image on the manual feed tray is displayed.

  Thereafter, when the transfer paper P pulled out by the user is set on the manual transfer material tray 20, it is detected by the sensor 82 on the manual transfer material tray 20, and the image forming operation is resumed. The image forming operation may be resumed by pressing a copy start key (not shown).

  When the image forming operation is resumed, the transfer of the transfer material Q once stopped by the registration roller 19 is resumed, and the toner image is transferred to the transfer material Q by the secondary transfer portion 34 and then passes through the fixing nip portion 31. Then, it is conveyed toward the paper discharge roller 21. Subsequently, after the rear end of the transfer material Q has passed through the registration sensor 45, the transfer material P is fed from the manual transfer material tray 20 and conveyed toward the registration roller 19. As a result, the same operation as when the transfer material P has not been pulled out is resumed, and a series of image forming operations can be continued without starting over.

  FIG. 5 is a flowchart showing processing during double-sided printing. The processing of this flowchart is executed by the CPU 171. In FIG. 5, the CPU 171 feeds the transfer material P from the paper feed cassette 17 which is the first paper feed means, and performs an image forming operation on the first surface (front surface) (S801). Thereafter, the CPU 171 conveys the transfer material P by the paper discharge roller 21, and determines whether or not the rear end of the transfer material P has reached the reversal position where the reversal sensor 42 is removed (S802). When the rear end of the transfer material P reaches the reverse position, the CPU 171 confirms the state of the sensor 601 and monitors whether the transfer material P has been pulled out (S803). When the presence of the transfer material P is confirmed by the sensor 601, the CPU 171 switches back the transfer material P by reversely rotating the paper discharge roller 21 to perform the front and back reversing operation (S804). Further, the CPU 171 checks the state of the sensor 601 and monitors whether the transfer material P has been pulled out (S805). When the transfer material P is not pulled out, the CPU 171 continues the transport operation as it is, and re-feeds the transfer material P toward the secondary transfer unit 34 via the double-sided rollers 40 and 41 ( S806). That is, the double-sided rollers 40 and 41 function as a refeeding unit. If there is a succeeding sheet on which image formation is to be performed, an image forming operation is performed on the first surface (front surface) of the succeeding sheet (S807). Thereafter, the CPU 171 forms an image on the second surface (back surface) of the transfer material P (S808), and discharges it to the paper discharge tray 22 (S809).

  On the other hand, when the transfer material P at the reverse position is pulled out by the user, the processing is performed according to the following procedure. In step S803 or S805, when it is detected that the transfer material P that should have existed at the reverse position is pulled out by the user because the sensor 601 no longer detects the transfer material, the CPU 171 performs a subsequent sheet retraction process (S810). ). In this process, the CPU 171 causes the leading edge of the subsequent transfer material to contact the registration roller 19 when another transfer material (the sheet subsequent to the pulled-out sheet) existing in the conveyance path has not reached the registration roller 19. Transport until it reaches. When the subsequent transfer material reaches the registration roller 19, the CPU 171 temporarily stops the image forming operation (including the conveying operation) (S811). On the other hand, if the subsequent sheet has already reached the registration roller 19 and stopped, the CPU 171 temporarily stops the image forming operation while maintaining the state. That is, the CPU 171 functions as a conveyance control unit. Next, the CPU 171 displays a message (FIG. 4) prompting the user to set the pulled transfer material P on the manual feed tray 20 as the second paper feeding unit on the operation unit 172 (S812). Thereafter, when the CPU 171 detects that the transfer paper P pulled out by the user is set on the manual feed tray 20 by the sensor 82 on the manual feed tray 20 (S813), the CPU 171 restarts the image forming operation. Specifically, the CPU 171 performs an image forming operation on the first surface (front surface) of the subsequent transfer material so that the order of image formation before the transfer material P is pulled out (S807). Further, the CPU 171 feeds the transfer material P (transfer material P placed on the manual feed tray) which is the preceding paper, forms an image on the second surface (back surface) (S808), and then the subsequent paper. Image formation is performed on the second surface (back surface) (S809). The CPU 171 determines whether or not all the image formation has been completed (S814). If all the image formation has been completed, the CPU 171 ends the processing, and if there is remaining image formation, repeats the processing from S801. .

  By performing the above processing, even if the transfer material on which the image has been formed on the first surface at the reverse position is pulled out by the user, the image formation on the first surface of the transferred transfer material is not performed again. The image formation can be continued while maintaining the page order.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 17 Paper feed cassette 20 Manual transfer material tray 21 Paper discharge roller 171 CPU
172 Operation unit 601 Exit sensor

Claims (4)

In an image forming apparatus that forms an image on both sides of a sheet,
A sheet feeding means for feeding sheets;
Image forming means for forming an image on the first surface or the second surface of the sheet fed by the paper feeding means;
After the image is formed on the first surface of the sheet by the image forming unit, a reversing unit that reverses the front and back by switching back the sheet in a state where a part of the sheet is exposed to the outside of the image forming apparatus;
A refeed unit for refeeding the sheet to the image forming unit to form an image on the second surface of the sheet whose front and back are reversed by the reversing unit;
Detecting means for detecting the withdrawal of the sheet reversed by the reversing means;
A conveyance control unit that waits at a predetermined position upstream of the image forming unit for a subsequent sheet of the extracted sheet when the detection unit detects the extraction of the sheet;
An informing means for informing an instruction to place the pulled sheet on the paper feeding means;
An image forming apparatus comprising:   The conveyance control unit conveys the succeeding sheet to form an image on the first surface of the succeeding sheet waiting at the predetermined position after the pulled sheet is placed on the sheet feeding unit. 2. The image forming apparatus according to claim 1, wherein after that, the pulled sheet is conveyed so as to form an image on the second surface of the pulled sheet.   The paper feeding means includes a first paper feeding means and a second paper feeding means, and when the image is formed on the first surface of the sheet fed from the first paper feeding means, the notification means The image forming apparatus according to claim 1, wherein an instruction to place the pulled sheet on the second sheet feeding unit is notified.   A registration roller configured to temporarily stop the sheet fed from the sheet feeding unit and transport the sheet toward the image forming unit at a predetermined timing; and the predetermined position is a position of the registration roller. The image forming apparatus according to claim 1.

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