JP2009217072A - Image forming apparatus, its method, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that detects one-side printed sheet of paper (called as a back sheet hereinafter) without increasing the cost, and also to provide its method, program, and recording medium. <P>SOLUTION: The image forming apparatus is provided with: a back sheet detecting means disposed on a paper conveyance path between a paper feed section and an image transfer section and used to detect a back sheet on the one-side of which printing has been already carried out; and an image formation control means for controlling image formation on the sheet based on the detection result of the back paper detecting means. A sensor 21 provided for the back sheet detecting means also detects a pattern used for process control. That is, based on an output value of the same sensor 21, both the process control and the detection of the back of the sheet 15 are carried out. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, and a facsimile machine that performs printing processing by reusing paper on which an image has already been printed (printed), a method, a program, and a recording medium.

  In recent years, in order to prevent environmental destruction and resource reduction, and to reduce costs, an image of a sheet (hereinafter referred to as a backing paper) on which an image has been formed (printed) once on one side is formed in an image forming apparatus. It is becoming possible to form a desired image on a non-exposed surface.

However, when printing is performed using the backing paper, there is a problem that double printing is performed on the surface on which an image is already formed. In view of this, a technique has been proposed in which whether or not an image is formed on the surface of a sheet by a sensor during conveyance to improve prevention of double printing (for example, Patent Document 1).
JP 2003-316206 A

  However, the technique disclosed in Patent Document 1 has a problem in that it is necessary to newly provide a sensor, which increases costs. SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus, a method, a program, and a recording medium that can detect the back side of a sheet without increasing the cost. .

  An image forming apparatus according to the present invention is provided on a paper conveyance path between a paper feed unit and an image transfer unit, and detects a back paper that has already been printed, and a detection result of the back paper detection unit And an image formation control means for controlling image formation on the paper based on the above, and the back paper detection means also detects a pattern when performing process control.

  In the image forming apparatus of the present invention, the backing paper detection unit includes a reflection type photosensor that focuses on the transfer belt, and the reflection type photosensor passes the conveyance sheet between the reflection type photosensor and the transfer belt. The output value of the reflection type photosensor is used as a reading value of the process control pattern when the process control is executed, and is used as a reading value of the paper surface when transporting the paper.

  The image forming apparatus of the present invention further includes a paper passage detection unit that detects whether or not the paper passes through the reflection type photosensor, and the paper passage detection unit reflects the paper based on the time when the paper passes through the registration sensor. The back paper detection means detects whether the paper is passing by the paper passage detection means, and detects whether the paper is passing or not.

  The image forming apparatus of the present invention is characterized in that the backing paper detection means performs backing paper detection based on the change amount of the reflection type photosensor output value.

  In the image forming apparatus of the present invention, the backing paper detection means further includes a plurality of reflection type photosensors, and detects that the paper is backing paper when the difference between the output values of the plurality of reflection type photosensors is a certain value or more. It is characterized by.

  In the image forming apparatus of the present invention, the back paper detecting means detects the back paper only when printing on the first side during double-sided printing, and the image forming control means is detected as being back paper by the back paper detecting means. In this case, printing on the second surface in double-sided printing is prohibited.

  The image forming apparatus of the present invention is characterized in that the image forming control unit stops the subsequent printing when the back paper detecting unit detects that the paper is the back paper.

  The image forming apparatus of the present invention further includes a paper reversing unit that reverses the paper, and a double-sided detection unit that detects whether both sides of the paper have been printed by passing the reflective photosensor twice through the paper reversing unit. And when the double-sided detection means detects that no image is formed on the paper transfer surface, image formation is performed.

  The image forming method of the present invention is provided on a paper conveyance path between a paper feeding unit and an image transfer unit, and detects a back paper that has already been printed, and a detection result of the back paper detection step And an image formation control step for controlling the image formation on the paper based on the above, and the back paper detection step detects a pattern in the case of performing process control.

  In the image forming method of the present invention, in the backing paper detection step, the conveyance paper is passed between the reflective photosensor and the transfer belt, and the output value of the reflective photosensor focused on the transfer belt is measured. The process control pattern is used as a reading value when the process control is executed, and is used as a reading value of the paper surface when the paper is transported.

  The image forming method of the present invention further includes a paper passage detection step for detecting whether or not the paper passes through the reflection type photosensor, and the paper passage detection step reflects the time based on the time when the paper passes through the registration sensor. The back paper detection step detects whether the paper is passing by the paper passage detection step, and detects whether the paper is passing or not.

  In the image forming method of the present invention, in the back paper detection step, the back paper is detected based on the amount of change in the reflection photosensor output value, and the difference between the maximum value and the minimum value of the reflection photosensor output value while the paper is passing When the value is equal to or greater than a certain value, it is detected that the paper is a backing paper.

  In the image forming method of the present invention, the backing paper detection step performs the backing paper detection using a plurality of reflective photosensors, and when the difference between the output values of the plurality of reflective photosensors is a predetermined value or more, the backing paper It is detected that it is.

  In the image forming method of the present invention, the back paper detection step detects the back paper only at the time of printing on the first side during double-sided printing, and the image formation control step is detected as the back paper by the back paper detection step. In this case, printing on the second surface in double-sided printing is prohibited.

  The image forming method of the present invention is characterized in that the image forming control step stops the subsequent printing when the back paper detecting step detects that the paper is a back paper.

  The image forming method of the present invention further includes a paper reversing step for reversing the paper, and a double-sided detecting step for detecting whether both sides of the paper are printed by passing the reflective photosensor twice through the paper reversing step. And when the double-sided detection step detects that an image is not formed on the sheet transfer surface, image formation is performed.

  The program of the present invention is provided on a paper conveyance path between the paper feeding unit and the image transfer unit, and detects a back paper that has already been printed, and an image on the paper based on the detection result of the detecting process. The process of controlling the formation is executed by the computer, and the process of detecting is executed by the computer to detect the pattern for process control based on the output value of the reflective photosensor focused on the transfer belt. Let

  The recording medium of the present invention is a computer-readable recording medium on which the program is recorded.

  According to the present invention, since the process control and the detection of the back of the paper are performed by the same sensor, it is possible to detect the back of the paper without increasing the cost.

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

(Embodiment 1)
FIG. 1 shows an example of a schematic configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, an image forming apparatus 1 according to an embodiment of the present invention is provided with AIO cartridges (image forming units) 2 </ b> A, 2 </ b> B, 2 </ b> C, and 2 </ b> D for each color arranged along a transfer belt 12. The transfer belt 12 is an endless belt wound around a secondary transfer driving roller 3 and a transfer belt tension roller 4 that are rotationally driven. The AIO cartridge 2A includes a photoconductor 5A, a charger 6A disposed around the photoconductor 5A, an exposure device 7, a developing device 8A, a cleaner blade 9A, and the like. The plurality of AIO cartridges 2A, 2B, 2C, and 2D have the same internal configuration except that the color of the toner image to be formed is different. The exposure unit 7 is configured to irradiate laser beams 10A, 10B, 10C, and 10D that are exposure lights corresponding to image colors formed by the AIO cartridges 2A, 2B, 2C, and 2D.

  Also formed on the paper feed tray 14 for stacking the paper 15, the paper feed roller 16, the registration roller 17, the registration sensor 22, the paper discharge roller 19, the double-sided roller 20, and the transfer belt 12 for transporting the paper 15. The image forming apparatus includes a secondary transfer roller 13 for transferring an image onto a sheet, and a fixing unit 18 that fixes the toner on the sheet onto which the toner has been transferred. Further, a sensor 21 for reading the pattern formed by the process control and the surface of the sheet being conveyed is close to the transfer belt 12.

  FIG. 2 shows a configuration example of the sensor 21 according to the embodiment of the present invention. As shown in FIG. 2, the sensor 21 includes three reflective photosensors 21 </ b> A, 21 </ b> B, and 21 </ b> C. The reflective photosensor 21 includes an LED (Light Emitting Diode) light emitting unit, a regular reflection light receiving unit, and a diffuse reflection light receiving unit. The light emitted from the LED light emitting unit hits the transfer belt 12 or the paper 15 being conveyed, and the reflected light is detected by the regular reflection light receiving unit and the diffuse reflection light receiving unit and converted into a voltage.

  FIG. 3 shows an example of a schematic configuration of a control system of the image forming apparatus 1 according to the embodiment of the present invention. As shown in FIG. 3, the control system of the image forming apparatus 1 according to the embodiment of the present invention includes a control unit 28 using, for example, a CPU (Central Processing Unit), and a plurality of prints input from communication means and transfer means. An image is formed on an image memory 23 for storing an image, an image forming unit 24 for forming a visible image from a print image stored in the image memory 23, a process control unit 25 for adjusting toner density, and a sheet being conveyed. A memory 26 that stores a control program that controls the entire image forming apparatus in addition to controlling the entire image forming apparatus with the backing paper detection unit 27 and the control unit 28. And comprising.

  Next, a general operation of the image forming apparatus 1 according to the embodiment of the present invention will be described. When a print image is acquired in the image memory 23, the outer peripheral surface of the photoconductor 5A is uniformly charged by the charger 6A in the dark during image formation, and then exposed by the laser light 10A from the exposure device 7, An electrostatic latent image is formed. The developing unit 8A visualizes the electrostatic latent image with toner, and a toner image is formed on the photoreceptor 5A.

  This toner image is transferred onto the transfer belt 12 by the action of the primary transfer roller 11A at a position (primary transfer position) where the photoreceptor 5A and the transfer belt 12 are in contact with each other. By this transfer, a toner image is formed on the transfer belt 12. After the toner image has been transferred, the photoreceptor 5A waits for the next image formation after the unnecessary toner remaining on the outer peripheral surface is wiped off by the cleaning blade 9A.

  As described above, the transfer belt 12 to which the toner image is transferred by the AIO cartridge 2A is conveyed to the next AIO cartridge 2B. In the AIO cartridge 2B, the image is superimposed and transferred onto the image formed on the transfer belt 12 by the same process as the image forming process in the AIO cartridge 2A.

  The transfer belt 12 is further conveyed to the next AIO cartridges 2C and 2D, and is transferred onto the transfer belt 12 in a similar manner by the same operation. Thus, a full-color image is formed on the transfer belt 12. The transfer belt 12 on which the full-color superimposed image is formed is conveyed to the position of the secondary transfer roller 13.

  During the paper transport operation during image formation, the paper 15 stored in the paper feed tray 14 is sequentially sent out by rotating the paper feed roller 16 clockwise from the top. The driving of the registration roller 17 is started at a timing at which the toner image and the paper 15 are overlapped on the toner image conveyed by the transfer belt 12 and the secondary transfer roller 13. At this time, the registration roller 17 is rotated counterclockwise to feed out the paper 15.

  The paper 15 sent out by the registration roller 17 transfers the toner image on the transfer belt 12 to the paper 15 by the secondary transfer roller 13, and then the toner image is fixed by heat and pressure by the fixing device 18. The paper is discharged out of the image forming apparatus 1 by a paper discharge roller 19 that is driven to rotate counterclockwise.

  When performing duplex printing, the paper discharge roller 19 is driven to rotate clockwise before the paper 15 passes through the paper discharge roller 19, and the paper 15 is conveyed to the double-sided conveyance path. The sheet 15 conveyed to the duplex conveyance path is conveyed again to the registration roller 17 via the duplex roller 20. The sheet 15 that has reached the registration roller 17 is again fed from the registration roller 17, and after the toner image is transferred to the opposite side of the sheet surface by the secondary transfer roller 13, the toner image is The paper is fixed by pressure and discharged to the outside of the image forming apparatus by a paper discharge roller 19 that is driven to rotate counterclockwise.

  On the other hand, as described above, the image forming apparatus 1 forms a toner image and transfers the toner image to the paper 15. However, the toner density transferred to the paper 15 varies due to deterioration of parts and environmental (temperature / humidity) changes. To do. For this reason, the toner density adjustment operation is performed in the process control unit 25 at the timing of toner image creation and environmental change.

  FIG. 4 shows the relationship between the toner adhesion amount and the output voltage of the image forming apparatus 1 according to the embodiment of the present invention. An example of the toner density adjustment operation will be described in detail with reference to FIG. First, the charging bias to the photoconductors 5A, 5B, 5C, and 5D is kept constant, and exposure is performed from the exposure unit 7. At that time, the development biases of the development units 8A, 8B, 8C, and 8D are made variable to change the toner image. Form. The formed toner image is read by the sensor 21. As shown in the graph of FIG. 4, the output value of the specularly reflected light from the sensor 21 can be converted into the toner density, and the smaller the voltage, the higher the toner density. Next, the process control unit 25 calculates a developing bias that achieves the target toner density of the image forming apparatus 1. The calculated development bias value is used in the image forming unit 24 to create a toner image having a stable density.

  FIG. 5 illustrates sensor reading at the time of process control, color misalignment correction, and backing paper detection of the image forming apparatus 1 according to the embodiment of the present invention. As shown in FIG. 5A, during the process control, the pattern of the toner image drawn on the transfer belt 12 is read and the process control is performed. On the other hand, at the time of printing, as shown in FIG. 5B, the sheet 15 fed from the sheet feeding tray 14 passes through between the sensor 21 and the transfer belt 12 with the same sensor as the process control. It is read by a certain sensor 21 to detect whether an image has been printed.

  By using the same sensor at the time of process control and at the time of backing paper detection, it is possible to suppress an increase in cost due to the additional sensor. The sensor 21 is installed at a position so that the focal length matches the transfer belt 12. As a result, it is possible to judge with the regular reflection light at the time of process control and to accurately determine the density, and at the time of detecting the back paper, it is possible to obtain a sensor output value with sufficient accuracy for detecting the back paper because the judgment is based on the diffuse reflection light. .

  FIG. 6 shows the sensor output of diffusely reflected light in one reflective photosensor 21A provided in the sensor 21 when the sensor reading surface of the image forming apparatus 1 according to the embodiment of the present invention passes the blank paper 15. Represents a value. FIG. 7 shows sensor output values of diffuse reflected light in the reflective photosensor 21A of the sensor 21 when the sheet 15 having an image is passed through the sensor reading surface of the image forming apparatus 1 according to the embodiment of the present invention. . Image detection will be described in detail with reference to the graphs shown in FIGS.

  As shown in FIG. 6, when a blank sheet passes, the sensor output value hardly changes. On the other hand, as shown in FIG. 7, when the paper 15 on which the image exists is passed, the sensor output value increases. The backing paper detection unit 27 measures the maximum sensor output value Smax and the minimum sensor output value Smin when the paper is passed, and if the difference between Smax and Smin is equal to or greater than a certain value Dv, an image is printed on the paper. to decide. Here, Dv = 0.3. The reflective photosensors 21B and 21C also perform image detection in the same manner as the reflective photosensor 21A.

  Further, the backing paper detection unit 27 monitors the difference between the sensor output values of the three reflective photosensors 21A, 21B, and 21C while the paper 15 is passing. If the difference is greater than or equal to a certain value Dh, it is determined that an image is printed on the paper. Here, Dh = 0.3. Thereby, it can be determined from the density difference in both the sub-scanning direction and the main-scanning direction, and the accuracy of backing paper detection is improved.

  FIG. 8 shows an example of the operation flow of the control unit 28 of the image forming apparatus 1 according to the embodiment of the present disclosure. An example of the operation of the control unit 28 based on the control program according to the embodiment of the present invention will be described in detail with reference to the flowchart shown in FIG.

  First, the control unit 28 determines whether or not to execute process control from environmental information (temperature, humidity), the number of printed sheets, and the like (step S801). If it is determined that the process control is to be executed (step S801 / YES), the process control unit 25 executes the process control (step S802). On the other hand, if it is determined in step S801 that the process control is not executed (step S801 / NO), it is determined whether or not the top of the sheet has passed the registration sensor 22 (step S803). If the top of the sheet has not passed the registration sensor 22 (step S803 / NO), the process returns to step S801. However, if the leading edge of the sheet has passed the registration sensor 22 (step S803 / YES), the time measurement from the passage of the registration sensor 22 is started (step S804).

  Next, it is determined whether or not the time from passing through the registration sensor 22 has passed the time T (step S805). This is for determining whether the head of the paper has reached the position of the sensor 21. By determining the passage of the paper 15 using time, it is possible to improve the accuracy of the range for detecting the back paper. The time T is determined by the paper conveyance speed determined by the paper type, printing mode, and the like. If it is determined in step S805 that the time from passing through the registration sensor 22 has not elapsed time T (NO in step S805), the process returns to step S805. On the other hand, when it is determined that the time T from the registration sensor 22 has passed the time T (step S805 / YES), it is detected whether the image is printed on the paper 15 by the above-described image detection method (step S805 / YES). Step S806). Then, the toner image formed on the transfer belt 12 is transferred and fixed on the paper 15 and printed (step S807).

  Next, it is determined whether or not double-sided printing is performed (step S808). When duplex printing is not performed (step S808 / NO), the paper 15 is discharged out of the image forming apparatus 1. On the other hand, when performing duplex printing (step S808 / YES), it is determined whether or not the paper 15 is a backing paper (step S809). In the case of the backing paper (step S809 / YES), the paper is discharged out of the image forming apparatus 1 without printing (step S811). On the other hand, if it is not the back paper (step S809 / NO), printing is performed on the second side on which the paper 15 is not printed, and the paper is discharged out of the image forming apparatus 1 (step S811).

  According to the present embodiment, the sensor 21 is used for both process control, color misregistration correction and paper image detection, thereby preventing double printing due to double-sided printing when using the backing paper without increasing costs. It becomes possible to do. In addition, since the sensor 21 is provided at a position where the focal length matches the transfer belt 12, the density can be accurately determined because the determination is performed using the regular reflection light during the process control. On the other hand, at the time of backing paper detection, it is possible to obtain a sensor output value with sufficient accuracy for backing paper detection because it is determined by diffuse reflected light.

  Further, since it is determined whether or not the paper has reached the position of the sensor 21 based on the time from the passage of the registration sensor 22, the reading value of the paper surface when the paper 15 passes through the reflective photosensor 21. Even when there is no difference between the sensor output values of the transfer belt 12 and the transfer belt 12, it is possible to detect the backing paper. Further, since the backing paper is determined from the amount of change in the output value of the reflection type photosensor 21, it is possible to detect the backing paper even in special paper such as colored paper.

  In addition, since a plurality of reflection type photosensors 21 are installed in the main scanning direction and the difference between the output values of the reflection type photosensors 21 is equal to or larger than a predetermined value, it is determined as a backing paper. Even when there is no change in the output value, it is possible to detect the back paper.

  Further, since the backing paper detection process is executed only on the first surface during duplex printing, it is possible to prevent meaningless backing paper detection in printing on the second surface of the paper 15 in duplex printing. Furthermore, since double-sided printing is not performed when it is detected that the paper is a back paper, double-sided printing on the already printed surface can be prevented when double-sided printing is performed on the back paper.

(Embodiment 2)
FIG. 9 shows an example of the operation flow of the control unit 28 of the image forming apparatus 1 according to the embodiment of the present disclosure. In the present embodiment, an example of a processing flow in the case where it is determined that the back paper is detected by the back paper detection will be described in detail using the flowchart shown in FIG. The schematic configuration of the image forming apparatus 1 according to the present embodiment is the same as the configuration of the image forming apparatus 1 according to the first embodiment described above, including a control system including the sensor 21 and the control unit 28, and detailed description thereof is omitted. In the present embodiment, the contents of the control program are partially different from those of the first embodiment described above, and the differences will be described in detail below.

  First, the control unit 28 determines whether or not to execute process control from environmental information (temperature, humidity), the number of printed sheets, and the like (step S901). If it is determined that the process control is to be executed (step S901 / YES), the process control unit 25 executes the process control (step S902). On the other hand, if it is determined in step S901 that process control is not to be executed (step S901 / NO), it is determined whether or not JOB exists as a print request (step S903). If there is no print request (step S903 / NO), the process returns to step S901. If there is a print request (step S903 / YES), it is determined whether or not it is determined to be the back paper as a result of the back paper detection in the preceding JOB (step S904).

  If it is determined in step S904 that the paper is a backing paper as a result of the knowledge detection (step S904 / YES), it is determined whether or not the current job is duplex printing (step S905). In the case of duplex printing (step S905 / YES), the paper 15 is discharged out of the image forming apparatus 1 (step S915). On the other hand, if it is not double-sided printing (step S905 / NO), an image is printed on the sheet 15, and the sheet 15 is discharged out of the image forming apparatus 1 (step S915).

  If it is not determined in step S904 that the paper is the back paper (step S904 / NO), it is determined whether the head of the paper has passed the registration sensor 22 (step S907). If it is determined that the top of the sheet has not passed the registration sensor 22 (step S907 / NO), the process returns to step 907. If it is determined that the leading edge of the sheet has passed the registration sensor 22 (step S907 / YES), the subsequent processing is the same as the processing after step S804 in the flowchart of FIG. 8 described in the first embodiment, and detailed description thereof is omitted. To do.

  According to the present embodiment, when printing is detected as a backing paper, the subsequent printing is stopped. Therefore, in a job for performing double-sided printing of a plurality of sheets, it is detected that the first sheet is backing paper, and the sensor position is detected on the second sheet. Even if it is not detected that the paper is a backing paper, double printing can be prevented.

(Embodiment 3)
FIG. 10 shows an example of the operation flow of the control unit 28 of the image forming apparatus 1 according to the embodiment of the present disclosure. In the present embodiment, an example of the flow of processing for detecting whether both sides of the paper 15 have been printed will be described in detail with reference to the flowchart shown in FIG. The schematic configuration of the image forming apparatus 1 according to the present embodiment is the same as the configuration of the image forming apparatus 1 according to the first embodiment described above, including a control system including the sensor 21 and the control unit 28, and detailed description thereof is omitted. In the present embodiment, the contents of the control program are partially different from those of the first embodiment described above, and the differences will be described in detail below.

  First, the control unit 28 determines whether or not to execute process control from environmental information (temperature, humidity), the number of printed sheets, and the like (step S1001). If it is determined that the process control is to be executed (step S1001 / YES), the process control unit 25 executes the process control (step S1002). If it is determined in step S1001 that the process control is not executed (step S1001 / NO), it is determined whether or not JOB exists as a print request (step S1003). If there is no print request (step S1003 / NO), the process returns to step S1001. On the other hand, when there is a print request (step S1003 / YES), paper conveyance is started (step S1004).

  Next, it is determined whether or not the top of the sheet has passed the registration sensor 22 (step S1005). If it is determined that the top of the sheet has not passed the registration sensor (step S1005 / NO), the process returns to step S1005. On the other hand, when it is determined that the top of the sheet has passed the registration sensor 22 (step S1005 / YES), time measurement from the passage of the registration sensor 22 is started (step S1006).

  Subsequently, it is determined whether or not the time T from the registration sensor 22 has passed (step S1007). If the time from passing through the registration sensor 22 has not passed the time T (step S1007 / NO), the process returns to step S1007. On the other hand, when the time from the registration sensor 22 has passed the time T (step S1007 / YES), image detection is performed as to whether an image is printed on the paper by the above-described image detection method (step S1008). The sheet is conveyed to the double-sided conveyance path (step S1009).

  It is determined whether the image detection on the transfer surface of the paper 15 has been completed (step S1010). If the image detection on the transfer surface has not been completed (step S1010 / NO), the process returns to step S1005. On the other hand, if the image detection on the transfer surface has been completed (step S1010 / YES), it is determined whether or not the image is printed on the transfer surface (step S1011). The determination in step S1011 is that the sensor 21 can detect only the surface opposite to the transfer surface of the paper 15, so that the paper 15 is passed through the double-sided conveyance path and passed through the sensor 21 twice. This is determined by performing image detection.

  If an image is printed on the transfer surface in step S1011 (step S1011 / YES), the sheet 15 is discharged out of the image forming apparatus 1 without printing (step S1016). On the other hand, if no image is printed on the transfer surface (step S1011 / NO), it is determined whether the print job is double-sided printing (step S1012). In the case of double-sided printing (step S1012 / YES), double-sided printing is executed (step S1015), and the paper is discharged out of the image forming apparatus 1 (step S1016). If it is not double-sided printing (step S1012 / NO), it is determined whether printing has already been performed on the second side of the paper 15 (step S1013). If printing has been completed on the second side of the sheet 15 (step S1013 / YES), the sheet 15 is discharged out of the image forming apparatus 1 (step S1016). On the other hand, if not printed (NO in step S1013), an image is printed on the transfer surface (step S1014), and the paper 15 is discharged out of the image forming apparatus 1 (step S1016).

  According to the present embodiment, since it is detected whether or not both sides of the paper 15 have been printed, it is possible to prevent double printing by double-sided printing on the back paper. Further, even when the back paper is mistakenly set on the paper feed tray 14, the double printing can be prevented.

  Note that a program for the CPU to execute the processing shown in the flowcharts of the respective drawings constitutes a program according to the present invention. As a computer-readable recording medium for recording the program, a semiconductor storage unit, an optical and / or magnetic storage unit, or the like can be used. By using such a program and a recording medium in a system having a configuration different from that of each of the above-described embodiments and causing the CPU to execute the program, substantially the same effect as the present invention can be obtained.

  Although specifically described based on the preferred embodiments, the present invention is not limited to the above-described image forming apparatus, method, program, and recording medium, and various modifications can be made without departing from the scope of the invention. It goes without saying that there is.

1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the structural example of the sensor 21 which concerns on embodiment of this invention. 2 is a diagram illustrating an example of a schematic configuration of a control system of the image forming apparatus 1 according to the embodiment of the present invention. FIG. FIG. 3 is a graph showing a relationship between the toner adhesion amount and the output voltage of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating sensor reading at the time of process control, color misregistration correction, and detection of a backing paper of the image forming apparatus 1 according to the embodiment of the present invention. The graph showing the sensor output value of the diffuse reflected light in one reflective photosensor 21A provided in the sensor 21 when the sensor reading surface of the image forming apparatus 1 according to the embodiment of the invention passes the blank paper 15. It is. 6 is a graph showing the sensor output value of diffuse reflected light in the reflective photosensor 21A of the sensor 21 when a sheet 15 having an image is passed through the sensor reading surface of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a flow of operation of a control unit 28 of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a flow of operation of a control unit 28 of the image forming apparatus 1 according to the embodiment of the present invention. 6 is a diagram illustrating an example of a flow of operations of a control unit 28 of the image forming apparatus 1 according to the embodiment of the present disclosure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2A, 2B, 2C, 2D AIO cartridge 3 Secondary transfer drive roller 4 Transfer belt tension roller 5A, 5B, 5C, 5D Photoconductor 6A, 6B, 6C, 6D Charger 7 Exposure unit 8A, 8B, 8C , 8D Developer 9A, 9B, 9C, 9D Cleaner blade 10A, 10B, 10C, 10D Laser light 11A, 11B, 11C, 11D Primary transfer roller 12 Transfer belt 13 Secondary transfer roller 14 Paper feed tray 15 Paper 16 Paper feed roller DESCRIPTION OF SYMBOLS 17 Registration roller 18 Fixing device 19 Paper discharge roller 20 Double-sided roller 21 Sensor 21A, 21B, 21C Reflective type photo sensor 22 Registration sensor 23 Image memory 24 Image imaging unit 25 Process control unit 26 Memory (control program)
27 Backing paper detection unit 28 Control unit

Claims (18)

A backing paper detection means provided on a paper transport path between the paper feeding section and the image transfer section, for detecting a backing paper that has already been printed;
Image formation control means for controlling image formation on paper based on the detection result of the backing paper detection means,
The image forming apparatus according to claim 1, wherein the backing paper detection means also detects a pattern when process control is performed. The backing paper detection means includes a reflective photosensor that focuses on the transfer belt,
The reflection type photosensor is provided such that a conveyance sheet passes between the reflection type photosensor and the transfer belt,
2. The image according to claim 1, wherein the output value of the reflection type photosensor is used as a reading value of a process control pattern when executing process control, and is used as a reading value of a sheet surface when conveying a sheet. Forming equipment. Paper passing detection means for detecting whether or not the paper is passing through the reflective photosensor;
The paper passage detection means detects whether the paper is passing through the reflective photosensor based on the time when the paper passes through the registration sensor,
The image forming apparatus according to claim 2, wherein the back paper detection unit detects the back paper when the paper passage detection unit detects that the paper is passing.   The image forming apparatus according to claim 2, wherein the back paper detecting unit performs back paper detection based on a change amount of the output value of the reflective photosensor.   The back paper detection means further comprises a plurality of reflection type photosensors, and detects that the paper is a back paper when a difference between the output values of the plurality of reflection type photosensors is a predetermined value or more. 5. The image forming apparatus according to 4. The backing paper detection means performs the backing paper detection only at the time of printing on the first side during duplex printing,
6. The image forming control unit according to claim 1, wherein the image forming control unit prohibits printing on the second side in double-sided printing when the back sheet detecting unit detects that the sheet is a back sheet. 2. The image forming apparatus according to item 1.   7. The image formation according to claim 1, wherein the image formation control unit stops the subsequent printing when the back paper detection unit detects that the paper is a back paper. 8. apparatus. Paper reversing means for reversing the paper;
A double-sided detection unit for detecting whether both sides of the paper have been printed by passing the reflective photosensor twice by the paper reversing unit;
8. The image forming apparatus according to claim 1, wherein an image is formed when an image is not formed on the sheet transfer surface by the double-sided detection unit. 9. A back paper detection step for detecting a back paper that is already printed and is provided on a paper transport path between the paper feed unit and the image transfer unit;
An image formation control step for controlling the image formation on the paper based on the detection result of the backing paper detection step,
The image forming method according to claim 1, wherein the back paper detecting step also detects a pattern in the case of performing process control.   The backing paper detecting step is configured such that a conveyance sheet passes between the reflection type photo sensor and the transfer belt, and an output value of the reflection type photo sensor focused on the transfer belt is controlled by a process control. The image forming method according to claim 9, wherein the image forming method is used as a reading value of a process control pattern at the time of execution, and is used as a reading value of a paper surface at the time of paper conveyance. A paper passage detection step for detecting whether or not the paper has passed through the reflective photosensor;
The paper passage detection step detects whether or not the paper is passing through the reflective photosensor based on the time when the paper passes through the registration sensor.
The image forming method according to claim 10, wherein the back paper detection step performs back paper detection when the paper passage detection step detects that the paper is passing.   The backing paper detection step performs backing paper detection based on a change amount of the reflection type photosensor output value, and a difference between a maximum value and a minimum value of the reflection type photosensor output value while the paper is passing is a certain value or more. 12. The image forming method according to claim 10, wherein the image is detected as a backing paper.   The backing paper detection step detects the backing paper using a plurality of reflection type photosensors, and detects that the paper is a backing paper when a difference between the output values of the plurality of reflection type photosensors is a predetermined value or more. The image forming method according to claim 12. The back paper detection step performs the back paper detection only at the time of printing on the first side during duplex printing,
The image forming control step prohibits printing on the second side in double-sided printing when the backside paper detecting step detects that the paper is a backside paper. 2. The image forming method according to item 1.   The image formation according to any one of claims 9 to 14, wherein the image forming control step stops the subsequent printing when the back paper detecting step detects that the paper is a back paper. Method. A paper reversing step for reversing the paper;
A double-sided detection step of detecting whether both sides of the paper have been printed by passing the reflective photosensor twice through the paper reversing step,
The image forming method according to claim 9, wherein when the double-sided detection step detects that an image is not formed on the sheet transfer surface, the image is formed. A process for detecting a backing paper that has been printed on a paper conveyance path between the paper feeding unit and the image transfer unit;
A process for controlling image formation on a sheet based on a detection result of the process to be detected;
The detecting process is a program that causes a computer to detect a pattern in the case of performing process control based on an output value of a reflection type photosensor focused on a transfer belt.   A computer-readable recording medium on which the program according to claim 17 is recorded.

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