JP2010160324A - Image forming apparatus and method for controlling the same - Google Patents

Abstract

An image forming apparatus capable of reliably discharging paper P remaining in the image forming apparatus.
An image forming apparatus includes: a discharge / reverse roller that discharges paper P to the outside of the apparatus or reverses the paper into the apparatus; a feed path for feeding the paper to a secondary transfer unit; A single-sided conveyance path 43 composed of a conveyance path for conveying the paper P that has passed through the next transfer section 34 to the discharge / reverse roller 21, and a sheet P reversed by the discharge / reverse roller 21 for conveying to the single-sided conveyance path 43. A double-sided conveyance path 44, and when the image forming apparatus 100 is activated or restarted after a jam is detected, if the paper P remaining on the single-sided conveyance path 43 is not detected by the detection sensors 53, 54, 55, the conveyance roller After the conveying operation in the double-sided conveyance path 44 is started by the rotation of the rollers 40 and 41 and the registration roller 19, the discharge operation in the single-sided conveyance path 43 is performed by the rotation of the discharge / reverse roller 21. Is Nawa.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus that forms an image on a second surface by conveying a sheet via a duplex conveyance path for forming an image on a second surface after forming an image on a first surface of the sheet.

  2. Description of the Related Art Image forming apparatuses capable of forming images on both sides of a sheet as a recording medium are known as image forming apparatuses such as copying machines, laser printers, and facsimiles that form an image on a recording medium using an electrophotographic method. ing.

  According to this image forming apparatus, when an image is formed on the first side, which is one side of the sheet, the sheet fed from the sheet feeding unit is conveyed to the image forming unit, and one of the sheets of the sheet is conveyed by the image forming unit. The sheet with the image formed on the surface is discharged out of the apparatus as it is. When images are formed on both sides (first side and second side) of the paper, the paper on which the image is formed on one side by the image forming unit is reversed by the reversing unit and re-conveyed to the image forming unit. Then, an image is formed on the other side of the sheet by the image forming unit, and then discharged outside the apparatus.

  In such an image forming apparatus, a jam may occur when an image is formed on both sides of a sheet. In this case, since there is a possibility that the paper may remain in the transport path for transporting the paper, the user simply and quickly determines in which position of the transport path the paper remains, and uses the paper in the apparatus. It is necessary to discharge outside.

  On the other hand, there is an image forming apparatus provided with a plurality of sensors for detecting paper in the conveyance path. According to this image forming apparatus, at least one of the plurality of sensors detects the sheet in the conveyance path, and it is possible to determine in which position of the conveyance path the sheet remains by specifying the detected sensor. it can.

  However, in such an image forming apparatus, in order to reliably detect the paper remaining in the conveyance path, the single-sided conveyance path until the fed paper is discharged out of the apparatus, and the reversed paper are images. It is necessary to provide sensors evenly on the double-sided conveyance path until it is conveyed to the forming unit. For this reason, it is difficult to reduce the cost and size of the product of the image forming apparatus.

  Therefore, an image forming apparatus has been proposed in which a sensor is provided only on the single-sided conveyance path, the elapsed time after the sensor at a predetermined position detects the paper is measured, and the position of the paper is determined based on the elapsed time. (See Patent Document 1). According to this image forming apparatus, the elapsed time from the time when the rear end in the paper transport direction passes the sensor is measured, and the current paper position is determined based on the elapsed time and the transport speed of the image forming apparatus. Based on this determination, the driving of the reversing unit is controlled. Therefore, even if the sheet remains in the duplex conveyance path and is not detected by the sensor, the current position of the sheet can be determined.

Japanese Patent Laid-Open No. 2007-93930

  However, in the image forming apparatus that determines the current position of the sheet based on the elapsed time from when the trailing edge of the sheet is detected, when the conveyance speed or the like changes due to wear of the conveyance roller that conveys the sheet, or the like. There is a risk of erroneous determination of the current paper position. Also, the actual conveyance speed, etc., may differ from the conveyance speed, etc., that the image forming apparatus recognizes based on the settings due to a mistake in the paper size setting or material setting by the user. There is a risk of mistakes. If the current determination of the position of the sheet is wrong, the reversing unit or the like is driven based on the erroneous determination, so that the sheet remaining in the apparatus cannot be reliably discharged out of the apparatus.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reliably discharging the paper remaining in the image forming apparatus and a control method therefor.

  In order to achieve the above object, an image forming apparatus according to claim 1 includes an image forming unit that forms an image on a sheet, and a reversing unit that reverses the sheet on which the image is formed by the image forming unit, In the image forming apparatus that forms images on both front and back sides of the paper, the reversing unit is a discharge / reverse unit that also serves as a discharge unit that discharges the paper to the outside of the apparatus, and feeds the paper to the image forming unit. A single-sided conveying path comprising a feeding path and a conveying path for conveying the sheet having passed through the image forming unit to the discharging / reversing unit, and the sheet reversed by the discharging / reversing unit as the single-sided conveying path. A double-sided conveyance path for conveying, a paper detection unit that is arranged in the single-sided conveyance path and detects the paper, and when the image forming apparatus is activated or restarted after jam detection based on the output of the paper detection unit , The paper detection unit Therefore when the sheet is not detected, after starting the paper transport operation in the two-sided conveyance path, characterized in that it comprises a control means for controlling to perform the paper discharge operation in the one-sided conveyance path.

  8. The image forming apparatus control method according to claim 7, wherein an image forming unit that forms an image on a sheet, and a discharge / reversing unit that discharges the sheet on which the image has been formed by the image forming unit to the outside of the apparatus or inverts the sheet into the apparatus. A single-sided conveyance path including a feeding path for feeding the sheet to the image forming unit and a conveyance path for conveying the sheet that has passed through the image forming unit to the discharge / reverse unit, and the discharge A control method of an image forming apparatus, comprising: a double-sided conveyance path for conveying the paper reversed by a reversing unit to the single-sided conveyance path, and forming images on both front and back sides of the paper. When the apparatus is activated or restarted after the paper jam is detected, a paper detection step for detecting whether or not the paper remains in the one-sided conveyance path, and when the paper is not detected in the paper detection step, Double-sided A transfer step of initiating the paper transporting operation in the road, after the transfer step, characterized by having a, a discharge step of the paper discharge operation in the one-sided conveyance path.

  According to the present invention, when the remaining of the paper in the single-sided conveyance path is not detected at the time of starting the image forming apparatus or restarting after detecting the jam of the paper, Since the paper discharge operation is performed in the conveyance path, the paper remaining in the image forming apparatus can be reliably discharged.

1 is a cross-sectional view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a cross-sectional view schematically illustrating a configuration around a conveyance path of the image forming apparatus according to the exemplary embodiment. FIG. FIG. 2 is a block diagram schematically showing a control configuration in the image forming apparatus according to the present embodiment. It is a block diagram which shows the structure of an image memory part roughly. It is a block diagram which shows the structure of an external I / F process part roughly. 6 is a flowchart illustrating a procedure of residual paper discharge processing executed by the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically showing a state of residual paper in the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically showing a state of residual paper in the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically showing a state of residual paper in the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically showing a state of residual paper in the image forming apparatus according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, an image forming apparatus 100 is a tandem type color image forming apparatus using an electrophotographic system, and includes four image forming units 1Y, 1M, 1C, and 1Bk that form an image forming unit, and an intermediate transfer belt 8. And a laser exposure unit 7.

  The image forming unit 1Y is a unit for forming a yellow toner image. The image forming unit 1M is a unit for forming a magenta toner image. The image forming unit 1C is a unit for forming a cyan toner image. The image forming unit 1Bk is a unit for forming a black toner image. The image forming units 1Y, 1M, 1C, and 1Bk are arranged in a line at a constant interval.

  In each of the image forming units 1Y, 1M, 1C, and 1Bk, drum-type electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) 2a, 2b, 2c, and 2d are arranged. Around each photosensitive drum 2a, 2b, 2c, 2d, there are primary chargers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and a drum cleaner device 6a. , 6b, 6c, 6d are respectively arranged.

  Each of the photosensitive drums 2a, 2b, 2c, and 2d is a negatively charged OPC photosensitive member, and has a photoconductive layer on an aluminum drum base. A clockwise rotation indicated by an arrow in the drawing by a driving device (not shown). Rotate at a given process speed in the direction. An electrostatic latent image of a corresponding color is formed on each of the photosensitive drums 2a, 2b, 2c, and 2d by a laser exposure unit 7 described later.

  Each primary charger 3a, 3b, 3c, 3d uniformly charges the surface of each photosensitive drum 2a, 2b, 2c, 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). .

  The developing devices 4a, 4b, 4c, and 4d store yellow toner, cyan toner, magenta toner, and black toner, respectively. Each developing device 4a, 4b, 4c, 4d is made visible by attaching each color toner to each electrostatic latent image formed on each photosensitive drum 2a, 2b, 2c, 2d and developing it as a toner image. Image.

  The transfer rollers 5a, 5b, 5c, and 5d are arranged so as to be in contact with the photosensitive drums 2a, 2b, 2c, and 2d via the intermediate transfer belt 8 at the primary transfer portions 32a, 32b, 32c, and 32d. Yes. Each of the transfer rollers 5a, 5b, 5c, and 5d sequentially transfers the toner images on the corresponding photosensitive drums 2a, 2b, 2c, and 2d on the intermediate transfer belt 8 in a superimposed manner.

  The drum cleaners 6a, 6b, 6c and 6d respectively remove residual toner remaining on the photosensitive drums 2a, 2b, 2c and 2d from the corresponding photosensitive drums 2a, 2b, 2c and 2d. The surfaces of the photosensitive drums 2a, 2b, 2c, and 2d are cleaned by scraping them off.

  The intermediate transfer belt 8 is disposed on the upper surface side of each photosensitive drum 2a, 2b, 2c, 2d in FIG. 1 so as to be in contact with each photosensitive drum 2a, 2b, 2c, 2d. It is stretched between the tension roller 11. The primary transfer surface 8b formed on the surface of the intermediate transfer belt 8 that faces the photosensitive drums 2a, 2b, 2c, and 2d is inclined with the secondary transfer counter roller 10 side facing downward. In other words, the intermediate transfer belt 8 is disposed so that the primary transfer surface 8b is inclined so that the secondary transfer portion 34 described later is on the lower side. This inclination angle is set to about 15 °, for example. The intermediate transfer belt 8 is made of a dielectric resin such as polycarbonate, polyethylene terephthalate resin film, polyvinylidene fluoride resin film, or the like.

  The secondary transfer counter roller 10 is a drive roller for driving the intermediate transfer belt 8, and is disposed in the secondary transfer portion 34 so as to be in contact with the secondary transfer roller 12 via the intermediate transfer belt 8. . The secondary transfer roller 12 functions as a transfer unit of the present invention.

  The tension roller 11 is disposed on the opposite side across the primary transfer portions 32a, 32b, 32c, and 32d of the secondary transfer counter roller 10, and applies tension to the intermediate transfer belt 8. A belt cleaning device 13 that removes and collects residual toner remaining on the surface of the intermediate transfer belt 8 is installed near the tension roller 11 and outside the endless intermediate transfer belt 8.

  The laser exposure device 7 is disposed below each image forming unit 1Y, 1M, 1C, 1Bk in FIG. The laser exposure device 7 is composed of laser light emitting means, a polygon lens, a reflecting mirror, and the like that emit light corresponding to time-series electric digital pixel signals of given image information. The laser exposure device 7 exposes the photosensitive drums 2a, 2b, 2c, and 2d to expose the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d charged by the primary chargers 3a, 3b, 3c, and 3d. Then, an electrostatic latent image corresponding to each color corresponding to the image information is formed.

  The image forming apparatus 100 also includes a paper feed cassette 17, a manual feed tray 20, a registration roller 19, a fixing unit 16, a discharge / reverse roller 21, double-sided rollers 40 and 41, a single-sided conveyance path 43, and a double-sided conveyance path 44. The registration roller 19 and the double-sided rollers 40 and 41 function as a conveyance roller of the present invention, and the discharge / reverse roller 21 functions as a discharge / reverse unit of the present invention.

  A paper P of a predetermined size is stored in the paper feed cassette 17. A paper P of a predetermined size is stacked on the manual feed tray 20. The paper P stored in the paper feed cassette 17 or the paper P stacked on the manual feed tray 20 is supplied one by one to the registration roller 19 via the paper feed path 18.

  The registration roller 19 corrects the skew of the paper P, and feeds the paper P after the skew correction to the secondary transfer unit 34 in accordance with the image forming timing in the secondary transfer unit 34 described above. .

  The fixing unit 16 has a fixing roller 16a, a pressure roller 16b, and a fixing nip portion (not shown) between the fixing roller 16a and the pressure roller 16b, and is downstream of the secondary transfer portion 34 in the paper P conveyance direction. Are arranged in a vertical path configuration. The fixing roller 16a incorporates a heater such as a ceramic heater for heating the paper P, and the pressure roller 16b is pressed against the fixing roller 16a with a predetermined pressing force.

  A discharge / reverse roller 21 serving as a discharge unit and a reversing unit is disposed on the downstream side of the fixing unit 16 in the conveyance direction of the paper P. The discharge / reverse roller 21 is capable of normal rotation and reverse rotation, and the paper P conveyed from the fixing unit 16 by normal rotation is discharged onto the paper discharge tray 22 or is reversed and conveyed toward the double-sided roller 40. To do. The duplex roller 40 conveys the sheet P conveyed from the discharge / reverse roller 21 toward the duplex roller 41, and the duplex roller 41 conveys the sheet P conveyed from the duplex roller 40 toward the registration roller 19.

  The single-sided conveyance path 43 includes a feeding path that is a path of the sheet P when the sheet P is fed from the registration roller 19 to the secondary transfer unit 34, and a discharge / discharge path from the secondary transfer unit 34 via the fixing unit 16. The conveyance path is a path of the paper P when being conveyed to the reverse roller 21. The double-sided conveyance path 44 is a path of the paper P until the paper P reversed by the discharge / reverse roller 21 is conveyed to the registration roller 19 via the double-sided rollers 40 and 41. Moreover, each edge part of the single-sided conveyance path 43 and the double-sided conveyance path 44 is connected, respectively, and forms one annular conveyance path. In the single-sided conveyance path 43, a paper discharge sensor 53, a fixing loop sensor 54, and a registration sensor 55 that detect the presence or absence of the paper P remaining on the single-sided conveyance path 43 are arranged. These sensors 53 to 55 function as a sheet detection unit of the present invention.

  As shown in FIG. 2, the discharge / reverse roller 21, the fixing roller 16 a, and the pressure roller 16 b are connected to the fixing motor 50. The registration roller 19 and the double-sided rollers 40 and 41 are connected to a paper feed motor 51. The secondary transfer counter roller 10 is connected to the drum motor 52. The sheet feeding motor 51 functions as the first roller driving unit of the present invention, and the fixing motor 50 functions as the second roller driving unit.

  The fixing motor 50 rotationally drives the discharge / reverse roller 21, the fixing roller 16a, and the pressure roller 16b in the paper discharge direction so that the paper P is sent out of the apparatus from the fixing unit 16. Further, the fixing motor 50 rotationally drives the discharge / reverse roller 21 in the paper reverse direction so that the paper P is sent from the discharge / reverse roller 21 toward the double-sided roller 40. The paper feed motor 51 moves the registration roller 19 and the double-sided rollers 40 and 41 in the paper transport direction so that the paper P reversed by the discharge / reverse roller 21 is sent out toward the secondary transfer unit 34 (see FIG. 1). Rotating drive. The drum motor 52 rotationally drives the secondary transfer counter roller 10 so that the paper P fed to the secondary transfer unit 34 is sent out toward the fixing unit 16.

  Here, in FIG. 2, the paper discharge direction is the direction in which the discharge / reverse roller 21 rotates in the direction of the arrow, and the paper reverse direction is the direction in which the discharge / reverse roller 21 rotates in the direction opposite to the arrow. is there. The paper conveyance direction is a direction in which the registration roller 19 and the double-sided rollers 40 and 41 rotate in the direction of the arrow. In the image forming apparatus 100, even when the sheet P remains across the discharge / reverse roller 21 and the duplex rollers 40 and 41, the sheet feeding motor 50 rotates the duplex rollers 40 and 41. The paper P can be pulled out.

  Next, the control configuration of the image forming apparatus 100 according to the present embodiment will be described with reference to FIGS.

  FIG. 3 is a block diagram schematically showing a control configuration in the image forming apparatus 100 according to the present embodiment.

  In FIG. 3, a ROM 174 in which a control program is written, a RAM 175 as a work area for the CPU 171 to perform processing, and an input / output port 173 are connected to the CPU 171 via an address bus and a data bus, respectively. The CPU 171 controls the entire image forming apparatus 100 by reading and executing the control program in the ROM 174.

  In the input / output port 173, various loads (not shown) such as a fixing motor 50, a paper feed motor 51, a drum motor 52, and other clutches that control each part of the image forming apparatus 100, and paper on the single-sided conveyance path 43 are provided. Inputs such as a paper discharge sensor 53 for detecting P, a fixing loop sensor 54, and a registration sensor 55 are connected. The CPU 171 controls input / output of each unit via the input / output port 173 in accordance with the contents of the control program stored in the ROM 174, and executes an image forming operation.

  An operation unit 172 is connected to the CPU 171 and controls the display and keys of the operation unit 172. The user instructs an image forming operation mode such as image formation on both sides and image formation on one side and display switching to the CPU 171 via the input from the key, and the CPU 171 indicates the state of the image forming apparatus 100 and the key input. Displays the operation mode setting by.

  The CPU 171 also includes an image processing unit 200 that performs processing for exposing the line image data transferred from the image memory unit 300 to the exposure device 7, an image memory that performs image expansion processing, temporary image storage processing, and the like. The unit 300 and an external I / F processing unit 400 that transmits and receives image data, processing data, and the like from an external device such as a PC are connected.

  As illustrated in FIG. 4, the image memory unit 300 includes a page memory 301, a memory controller 302, and a compressed data expansion processing unit 303.

  The memory controller 302 arbitrates access to the page memory 301 for generation of a DRAM refresh signal of the page memory 301, writing of data from the image I / F processing unit 400, and reading of data to the image forming unit 200. Further, in accordance with an instruction from the CPU 171, the write address to the page memory 301, the read address from the page memory 301, and the read direction are controlled.

  That is, for example, the memory controller 302 determines whether the image data received from the external I / F processing unit 400 from the external device is compressed data. When the memory controller 302 determines that the data is compressed data, the compressed data decompression processing unit 303 performs the decompression process on the compressed data, and then the write process is performed on the page memory 301 formed of a memory such as a DRAM. Thereafter, the memory controller 302 performs image input / output access such as image reading to the image forming unit 200.

  As illustrated in FIG. 5, the external I / F processing unit 400 includes a USB I / F 401, a Centro I / F 402, and a network I / F 403.

  The external I / F processing unit 400 receives image data and print command data transmitted from the external device 500 via any of the USB I / F 401, the Centro I / F 402, and the network I / F 403. Further, the image forming apparatus status information determined by the CPU 171 is transmitted to the external apparatus 500. Here, the external device 500 is a computer, a workstation, or the like.

  That is, print command data received from the external device 500 via any of the USB I / F unit 401, the Centro I / F unit 402, and the network I / F unit 403 is transmitted to the CPU 171. The CPU 171 that has received the print command data generates settings and timings for executing a print operation using the image processing unit 200, the input / output port 173, and the like. Further, image data received from the external device 500 via any of the USB I / F 401, the Centro I / F 402, and the network I / F 403 is transmitted to the image memory unit 300 according to the timing based on the print command data.

  Next, an image forming operation in the image forming apparatus 100 according to the present embodiment will be described. First, an operation for forming an image on one side of the paper P will be described.

  When the image forming apparatus 100 transmits an image formation start signal, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk are rotationally driven at a predetermined process speed. The photosensitive drums 2a, 2b, 2c, and 2d that are driven to rotate are uniformly charged negatively by the primary chargers 3a, 3b, 3c, and 3d, respectively. Next, the exposure device 7 emits color-separated image signals input from the outside from the laser light emitting element, and passes the polygon lenses, reflection mirrors, etc. to the respective colors on the photosensitive drums 2a, 2b, 2c, 2d. A corresponding electrostatic latent image is formed.

  Next, in the image forming unit 1Y, the developing device 4a to which a developing bias having the same polarity as the negative polarity which is the charging polarity of the photosensitive drum 2a is applied to the electrostatic latent image formed on the photosensitive drum 2a by yellow toner. To make a visible image as a toner image. This yellow toner image is intermediate transfer driven by a transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied in a primary transfer portion 32a between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the belt 8. The intermediate transfer belt 8 onto which the yellow toner image has been transferred is moved to the image forming unit 1M side.

  Next, in the image forming unit 1M, the magenta toner image formed on the photosensitive drum 2b is superimposed on the yellow toner image on the intermediate transfer belt 8 by the primary transfer unit 32b by the same operation as the image forming unit 1Y. It is transferred together. Similarly, cyan and black toner images formed by the photosensitive drums 2c and 2d are sequentially superimposed on the yellow and magenta toner images superimposed and transferred on the intermediate transfer belt 8 by the primary transfer portions 32c and 32d, respectively. A full-color toner image is formed on the intermediate transfer belt 8. At this time, the residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d is scraped off and collected by a cleaning blade or the like provided in the drum cleaner devices 6a, 6b, 6c, and 6d.

  The paper P fed from the paper feed cassette 17 or the manual feed tray 20 is secondarily transferred by the registration roller 19 in accordance with the timing at which the leading edge of the toner image on the intermediate transfer belt 8 is moved to the secondary transfer unit 34. It is fed to the section 34. A full-color toner image is collectively transferred to the sheet P fed to the secondary transfer unit 34 by the secondary transfer roller 12 to which a secondary transfer bias having a positive polarity opposite to that of the toner is applied. Is done. The residual toner remaining on the intermediate transfer belt 8 is removed and collected by the belt cleaning device 13.

  The paper P on which the full-color toner image is formed is conveyed to the fixing unit 16 and heated and pressed at the fixing nip portion between the fixing roller 16a and the pressure roller 16b. The toner image is fixed. The sheet P having the toner image fixed on one side is conveyed to the discharge / reverse roller 21 and discharged onto the discharge tray 22 on the upper surface of the main body outside the apparatus by the discharge / reverse roller 21 to complete a series of image forming operations. .

  Next, an operation of forming images on both the front and back sides of the paper P in the image forming apparatus 100 according to the present embodiment will be described. Since the image forming operation during this operation is basically the same as the image forming operation during the operation for forming an image on one side described above, description of the overlapping operation will be omitted, and different operations will be described below.

  The paper P on which the toner image is formed on one side by the same operation as described above is conveyed to the paper discharge tray 22 on the upper surface of the main body by the discharge / reverse roller 21 until most of the paper P is discharged outside the apparatus. Is done. When most of the paper P is discharged out of the apparatus, the discharge / reverse roller 21 stops. At this time, the rear end portion with respect to the transport direction of the paper P is located at the reversible position 42.

  The stopped discharge / reverse roller 21 starts to rotate in the direction opposite to the rotation direction so far, and feeds the paper P to the double-sided conveyance path 44. By the reverse rotation of the discharge / reverse roller 21, the rear end portion of the paper P located at the reverse position 42 is sent to the double-sided conveyance path 44 as a front end portion in the conveyance direction. The sheet P conveyed to the double-sided roller 40 along with the reverse rotation of the discharge / reverse roller 21 is conveyed to the double-sided roller 41 by the double-sided roller 40 and further conveyed to the registration roller 19 by the double-sided roller 41. During this transport operation, the next image formation start signal is transmitted.

  Subsequently, the sheet P is subjected to the secondary transfer by the registration roller 19 in accordance with the timing at which the full-color toner image formed on the intermediate transfer belt 8 is moved to the secondary transfer unit 34 by the same operation as described above. It is conveyed to the section 34. Then, the paper P having the toner image fixed on the other surface by the same operation as described above is discharged onto the paper discharge tray 22 by the discharge / reverse roller 21, and the series of image forming operations is completed.

  Next, a residual paper discharge process as a control method of the image forming apparatus 100 according to the present embodiment will be described with reference to FIG.

  FIG. 6 is a flowchart showing a procedure of residual paper discharge processing executed by the image forming apparatus 100 according to the present embodiment. This flowchart is executed by the CPU 171 based on a program stored in the ROM 174.

  In FIG. 6, when the power of the image forming apparatus 100 is turned on (when starting up), or when the door of the apparatus main body is opened and closed due to the occurrence of a jam (when restarting after detecting a jam), the CPU 171 Start the discharge process. First, the CPU 171 determines whether or not there is paper P remaining in the single-sided conveyance path 43 based on the outputs of the paper discharge sensor 53, the fixing loop sensor 54, and the registration sensor 55 (step S601).

  When all of the paper discharge sensor 53, the fixing loop sensor 54, and the registration sensor 55 have not detected the paper P (NO in step S601), the CPU 171 rotates the registration roller 19 and the double-sided rollers 40 and 41 to the paper feed motor 51. Driving is started (step S606). As a result, the registration roller 19 and the double-sided rollers 40 and 41 rotate, and a carrying operation as a paper carrying operation for carrying the paper P remaining on the double-sided carrying path 44 to the single-sided carrying path 43 is started.

  If the registration sensor 55 detects the paper P after the conveyance operation is started (YES in step S607), the CPU 171 causes the drum motor 52 and the fixing motor 50 to start driving each roller (step S608). As a result, the discharge / reverse roller 21, the fixing roller 16 a, the pressure roller 16 b, and the secondary transfer counter roller 10 rotate and serve as a sheet discharge operation for discharging the sheet P remaining on the single-sided conveyance path 43 to the outside of the apparatus. The discharge operation (discharge step) is started. Next, the process proceeds to step S603.

  In step S607, if the registration sensor 55 does not detect the paper P (NO in step S607) and the predetermined time T2 has elapsed (YES in step S609), the CPU 171 drives the drum motor 52 and the fixing motor 50 to drive each roller. Start (step S608). Next, the process proceeds to step S603.

  Here, the predetermined time T2 is required for the sheet P remaining on the duplex conveying path 44 and in the vicinity of the discharge / reverse roller 21 having the longest distance from the registration roller 19 to be conveyed to the registration roller 19. It's over time. Preferably, the time is sufficiently longer than the time required for the paper P in the vicinity of the discharge / reverse roller 21 to be conveyed to the registration roller 19.

  On the other hand, when at least one of the paper discharge sensor 53, the fixing loop sensor 54, and the registration sensor 55 detects the paper P (YES in step S601), the CPU 171 simultaneously controls the paper feeding motor 51, the drum motor 52, and the fixing motor 50. The rotation drive of each roller is started (step S602). As a result, the discharge / reverse roller 21, the fixing roller 16a, the pressure roller 16b, the registration roller 19, the double-sided rollers 40 and 41, and the secondary transfer counter roller 10 rotate, and the discharge operation is started. In this process, the discharge / reverse roller 21 rotates to discharge the paper P. Next, the process proceeds to step S603.

  When the process proceeds to step S603 and the elapsed time since the drum motor 52 and the fixing motor 50 start to rotate has passed the predetermined time T1 (YES in step S603), the CPU 171 rotates each roller to each motor 50, 51, 52. The drive is stopped (step S604). Here, the predetermined time T1 is a sufficient time from when the registration sensor 55 detects the paper P until the paper P is discharged out of the apparatus. When the paper feed motor 51, the drum motor 52, and the fixing motor 50 stop the respective rollers, this processing is completed.

  According to the present embodiment, for example, when the paper P remains at the position indicated by the thick line in FIG. 7A, the paper discharge sensor 53 and the fixing loop sensor 54 detect the paper P. Based on the detection result, each roller starts to rotate as shown in FIG. Thereby, the paper P on the single-sided conveyance path 43 can be reliably discharged out of the apparatus.

  Further, not only the paper P positioned only on the single-sided conveyance path 43 but also, for example, the paper P straddling the double-sided conveyance path 44 and the single-sided conveyance path 43 is also detected by the registration sensor 55, so Can be discharged.

  Further, for example, when the paper P remains at the position indicated by the thick line in FIG. 8A, the sensors 53, 54, and 55 do not detect the paper P, and based on the detection result, FIG. As shown in FIG. 8B, the double-sided rollers 40 and 41 and the registration roller 19 start to rotate. Thus, the paper P remaining on the double-sided conveyance path 44 is sent out to the single-sided conveyance path 43 and straddles the double-sided conveyance path 44 and the single-sided conveyance path 43. The sheet P straddling both transport paths is detected by the registration sensor 55, and based on the detection result, as shown by the arrow in FIG. P can be reliably discharged out of the apparatus.

  In addition, for example, it is assumed that the paper P remains at the position indicated by the thick line in FIG. In this case, since the sensors 53, 54, and 55 do not detect the paper P, the double-sided rollers 40 and 41 and the registration roller 19 start to rotate. Even if the double-sided rollers 40 and 41 and the registration roller 19 start to rotate, the sheet P does not exist in the double-sided conveyance path 44. Therefore, even after the double-sided rollers 40 and 41 and the registration roller 19 start to rotate, the sensors 53, 54 and 55 do not detect the paper P. However, according to the present embodiment, even if the sensors 53, 54, and 55 do not detect the paper P, after a predetermined time (T2) has elapsed since the double-sided rollers 40 and 41 and the registration roller 19 started to rotate. The discharge / reverse roller 21 also starts to rotate. Therefore, even the paper P remaining at the position shown in FIG. 9 can be reliably discharged out of the apparatus.

Furthermore, for example, even when the paper P remains at the position indicated by the thick line in FIG. 10, the discharge / reverse roller 21 starts rotating after the predetermined time T2 has elapsed, so that Even the remaining paper P can be reliably discharged out of the apparatus.
As described above, according to the present embodiment, even during the conveyance of the paper P, the paper P remains in the apparatus due to the occurrence of a jam, for example, and in which state the paper P remains in the apparatus. The sheet P can be reliably discharged out of the apparatus.

  The present invention supplies a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU, MPU, etc.) of the system or apparatus stores the storage medium in the storage medium. This can also be realized by reading out and executing the program code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the program code and the storage medium storing the program code constitute the present invention.

  Examples of the computer-readable storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, an optical disk such as a CD-ROM, a CD-R, and a CD-RW, A DVD-ROM, a DVD-RAM, a DVD-RW, a DVD + RW, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used. Alternatively, the program code may be downloaded via a network.

  In addition to executing the program code read by the computer, an OS (operating system) operating on the computer performs part or all of the actual processing based on an instruction of the program code, and the processing This includes the case where the functions of the above-described embodiment are realized.

  Furthermore, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the expanded function is based on the instruction of the program code. This includes a case where a CPU or the like provided on the expansion board or the expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

DESCRIPTION OF SYMBOLS 10 Secondary transfer counter roller 12 Secondary transfer roller 16 Fixing unit 19 Registration roller 21 Discharge / reversing rollers 40 and 41 Double-sided conveyance roller 43 Single-sided conveyance path 44 Double-sided conveyance path 50 Fixing motor 51 Paper feed motor 52 Drum motor 53 Paper discharge sensor 54 Fixing loop sensor 55 Registration sensor

Claims (7)

In an image forming apparatus that includes an image forming unit that forms an image on a sheet, and a reversing unit that reverses the sheet on which the image is formed by the image forming unit, and forms an image on both the front and back sides of the sheet.
The reversing unit is a discharging / reversing unit that also serves as a discharging unit that discharges the paper out of the apparatus,
A single-sided conveyance path comprising a feeding path for feeding the sheet to the image forming unit and a conveyance path for conveying the sheet that has passed through the image forming unit to the discharge / reverse unit;
A double-sided conveyance path for conveying the paper reversed by the discharge / reversing unit to the single-sided conveyance path;
A paper detection unit that is disposed on the one-sided conveyance path and detects the paper;
When the sheet detection unit does not detect the sheet at the time of starting up the image forming apparatus or restarting after jam detection based on the output of the sheet detection unit, after starting the sheet conveyance operation in the double-sided conveyance path And an image forming apparatus comprising: a control unit that performs control so as to perform a sheet discharging operation in the one-sided conveyance path.   The image forming apparatus according to claim 1, wherein the control unit performs control so that the paper discharge operation is performed after a predetermined time has elapsed from the start of the paper transport operation.   The image forming apparatus according to claim 1, wherein the control unit starts the paper transport operation and controls the paper discharge operation after the paper detection unit detects the paper.   When the sheet is detected by the sheet detection unit at the time of starting the image forming apparatus or at the time of restart after detecting a jam based on the output of the sheet detection unit, the control unit 4. The image forming apparatus according to claim 1, wherein the sheet discharge operation is controlled to start at the same time. 5.   3. The predetermined time is equal to or longer than a time required for the paper remaining in the double-sided conveyance path in the vicinity of the reversing unit to be conveyed to the single-sided conveyance path by the paper conveyance operation. Image forming apparatus. The discharge / reverse unit has a discharge / reverse roller that rotates forward and reverse,
The image forming apparatus further includes:
A conveyance roller provided in the double-sided conveyance path and the feeding path;
First roller driving means for driving the conveying roller;
A second roller driving means for driving the discharge / reverse roller,
The control unit controls the first roller driving unit to rotate the conveyance roller in the normal direction to rotate in the sheet conveying direction in the sheet conveying operation, and to drive the second roller in the sheet discharging operation. 6. The image forming apparatus according to claim 1, wherein the unit controls the discharge / reverse roller to rotate in the reverse direction by rotating the discharge / reverse roller. An image forming unit that forms an image on a sheet, a discharge / reversing unit that discharges or reverses the sheet on which the image is formed by the image forming unit, and feeds the sheet to the image forming unit. A single-sided conveyance path comprising a feeding path for conveying and a conveyance path for conveying the sheet having passed through the image forming unit to the discharge / reversing unit, and the single-sided conveyance of the sheet reversed by the discharging / reversing unit A double-sided conveyance path for conveying to the path;
A paper detection step for detecting whether or not the paper remains in the one-sided conveyance path at the time of starting up the image forming apparatus or restarting after detecting the paper jam;
If the paper is not detected in the paper detection step, a transport step for starting a paper transport operation in the double-sided transport path;
And a discharging step of performing a sheet discharging operation on the one-sided conveying path after the conveying step.

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