JP2014059516A - Image forming device and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fixation failure or paper jam during overwrite printing, to prevent reduction in usability.SOLUTION: An image forming device includes: a transfer part 15 which forms an image on a recording material; a document reading part 100 which reads a document; acquisition processing (S1102) acquiring information on a color material used in forming a document image or an image forming device which has formed the document image from document image data read by the document reading part 100; a program memory 803 which stores information on the image forming device; and a CPU 801 which permits (S1106, S1107) the transfer part 15 to perform overwrite printing on the document when the information acquired by the acquisition processing (S1102) has been stored in the program memory 803 (S1151-S1153).

Description

  The present invention relates to an original reading apparatus represented by an auto document feeder unit (ADF), an image forming apparatus such as a copying machine or a laser beam printer provided with an ADF, and a control method of the image forming apparatus.

  Conventionally, in this type of image forming apparatus, a document conveyance path to a document conveyance type document reading unit and a recording material conveyance path of an image forming unit with respect to a recording material are configured independently of each other. That is, for each of the document and the recording material, a paper feed unit, a guide member that constitutes a predetermined conveyance path, a plurality of conveyance rollers, a motor that drives the conveyance roller, a paper discharge unit, and the like are disposed independently of each other. ing. For this reason, the overall mechanism of the image forming apparatus is complicated, the cost is increased, and the apparatus size is inevitably increased. Therefore, in Patent Document 1, for example, a document reading unit is disposed in a recording material conveyance path from a paper feeding unit to a paper discharge unit, and the document conveyance path and the recording material conveyance path are used in common, thereby conveying a conveyance mechanism. Proposal of simplification, cost reduction and size reduction.

  For example, Patent Document 2 discloses a technique for reading an image printed on a document, creating an overwrite image based on the image, and performing overwrite printing on the read document. By using the document conveyance path and the recording material conveyance path in common, the document after reading can be used as it is as a recording material, and it is easy to perform overwrite printing.

JP 2000-158881 A Japanese Patent Laid-Open No. 10-129071

  When overwriting printing is performed, a toner image is newly transferred onto a document on which a color material such as toner has already been formed, and fixing is performed. For this reason, if the color material on the original and the newly transferred toner have different characteristics, the fixing unit of the image forming apparatus does not support the color material on the original. There are cases where jamming occurs due to adhesion and winding. In addition, when overwriting printing is performed on a document in which toner is used, if the toner amount limit value defined for each image forming apparatus is exceeded by overwriting, there is a possibility that fixing failure or jamming may occur. is there. For this reason, the occurrence of a failure in the image forming apparatus and a decrease in usability due to jam processing are problems.

  The present invention has been made under such circumstances, and it is an object of the present invention to suppress fixing failure and jam when overwriting is performed, and to prevent deterioration of usability.

  In order to solve the above-described problems, the present invention is configured as follows.

  (1) Image forming means for forming an image on a recording material, reading means for reading an original, and an image on which color material used for image formation of the original or original image is formed from original image data read by the reading means An acquisition unit that acquires information about the forming apparatus; a storage unit that stores information about the image forming apparatus; and the information that is acquired by the acquisition unit is stored in the storage unit. An image forming apparatus comprising: a control unit that permits overwriting printing on the document.

  According to the present invention, it is possible to suppress the occurrence of fixing failure or jamming when executing overwrite printing, and prevent usability from being lowered.

Sectional drawing which shows the structure of the image forming apparatus of Example 1, and explanatory drawing of a double-sided printing process FIG. 6 is a diagram for explaining operations of duplex reading of a document and duplex printing of a recording material according to the first embodiment. FIG. 6 is a diagram for explaining operations of duplex reading of a document and duplex printing of a recording material according to the first embodiment. FIG. 6 is a diagram for explaining operations of duplex reading of a document and duplex printing of a recording material according to the first embodiment. The block diagram which shows the structure of the control part and host computer in Examples 1-3. FIG. 3 is a block diagram illustrating a circuit configuration of a document reading unit according to the first to third embodiments. FIG. 6 is a diagram for explaining the overwrite printing operation in the first to third embodiments. 6 is a flowchart illustrating a control sequence for overwriting printing according to the first exemplary embodiment, and a flowchart illustrating a control sequence for determining whether or not to continue overwriting printing. FIG. 6 is a diagram for explaining document image data, overwrite image data, and output image data according to the first to third embodiments. 10 is a flowchart illustrating a control sequence of overwriting printing continuation permission determination processing according to the second embodiment. 10 is a flowchart illustrating a control sequence of toner amount calculation processing according to the second exemplary embodiment. 10 is a flowchart showing a control sequence of the overprinting continuation determination process in Example 3, and a graph showing the relationship between the toner amount and the fixing temperature at which fixing is possible.

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

[Image Forming Process in Image Forming Apparatus]
First, the image forming process will be described. FIG. 1A is a cross-sectional view of the image forming apparatus of this embodiment. 1A, in the center of the image forming apparatus 1, a rotatable photosensitive drum 10 that is an image carrier and a developing roller 11 that is in parallel with the photosensitive drum 10 and rotates while holding toner are arranged. Yes. When receiving the image formation instruction, the light emitting unit 21 included in the optical unit 2 irradiates the surface of the rotating photosensitive drum 10 with laser light. A latent image is formed on the surface of the photosensitive drum 10 irradiated with the laser light. When development is performed by attaching toner held by the developing roller 11 to the latent image on the surface of the photosensitive drum 10, a toner image is formed on the surface of the photosensitive drum 10.

  The first sheet feeding unit 30 stores a recording material S that is transported through a transport path for image formation, which is a first transport path formed between the transport roller 40 and the discharge roller 60, and on which image formation is performed. Has been. When an image formation instruction is received, the recording material S is conveyed to the conveying roller 40 one by one by a cassette (hereinafter referred to as “CST”) pickup roller 31 and a separating member 32. The conveyance roller 40 adjusts the conveyance timing so that the toner image on the photosensitive drum 10 is transferred to a predetermined position of the recording material S, and conveys the recording material S to the transfer unit 15.

  The toner image on the photosensitive drum 10 is transferred to the recording material S by the transfer voltage and pressure applied to the transfer unit 15, and the recording material S is conveyed to the fixing unit 50. In the fixing unit 50, the toner image is fixed on the recording material S by the heat of the heating roller 51 and the pressure of the pressure roller 52 facing the heating roller 51. The recording material S on which the toner image is fixed is conveyed to the paper discharge roller 60.

  In the case of single-sided printing, the paper discharge roller 60 conveys the recording material S as it is, and the recording material S is stacked on the first paper discharge unit 70. In the case of duplex printing, the paper discharge roller 60 transfers the recording material S until the trailing end of the recording material S in the transport direction passes through the double-sided flapper 61. When the double-sided flapper 61 detects that the recording material S has passed through the double-sided flapper 61, the double-sided flapper 61 uses the common conveyance as the second conveyance path through which the recording material S and the original G are conveyed together. Switch to the road 80 side. The paper discharge roller 60 rotates in the reverse direction and transports the recording material S to the common transport path 80. As shown in FIG. 1B, the recording material S that has been switched back is conveyed to the document reading unit 100 by the conveyance roller 41. Further, the recording material S is conveyed again to the transfer unit 15 by the conveying rollers 42 and 40, and the toner image is transferred to the other surface of the recording material S, and the toner image is fixed to the recording material S by the fixing unit 50. The paper is stacked on the first paper discharge unit 70 by the paper discharge roller 60.

[Operations for duplex scanning of originals and duplex printing of recording materials]
Next, a process for reading an image of a document and performing double-sided printing on a recording material will be described. FIG. 2A is an explanatory diagram showing a state when reading of the surface of the original G is started. The original G stored in the second paper supply unit 90 provided upstream in the conveyance direction of the common conveyance path 80 is conveyed to the conveyance roller 41 one by one by the original pickup roller 91 and the separation member 92. The document reading unit 100 stands by at a position facing the white reference member 101 when the document reading is not performed. The document reading unit 100 provided in the image forming apparatus emits light to the white reference member 101 before starting to read the first surface, which is the surface of the document G conveyed from the second sheet feeding unit 90. And the white reference value is corrected, and then rotated to a position facing the common conveyance path 80. The conveyance roller 41 conveys the document G to the document reading unit 100. The document reading unit 100 is already in a position facing the common transport path 80, and when the leading end of the document G in the transport direction is detected, the image on the document G is read. The image read by the document reading unit 100 is stored in an image memory 804 described later as document image data on the first side of the document. Note that the white reference member 101 is disposed downward, and consideration is given to dust adhesion. Further, here, the white reference member 101 is used as the reference member, but it is not limited to white.

  FIG. 2B is an explanatory diagram showing a state when reading of the first surface, which is the surface of the original G, is completed. The document G that has passed through the document reading unit 100 is transported to the transport roller 42. The conveyance roller 42 stops when the trailing edge of the document G passes through the switchback flapper 82, and the document G is stopped while being sandwiched between the conveyance rollers 42.

  FIG. 2C is an explanatory diagram showing a state when reading of the second side, which is the back side of the original G, is started. When the switchback flapper 82 switches the conveyance path of the document G from the common conveyance path 80 side to the document conveyance path 81 side which is the third conveyance path, the document reading unit 100 is positioned to face the document conveyance path 81. Rotate to. The conveyance roller 42 rotates in the reverse direction, and the document G is conveyed to the document reading unit 100 along the document dedicated conveyance path 81. When the document reading unit 100 detects the leading end of the document G in the conveyance direction, the document reading unit 100 reads an image of the second surface, which is the back surface of the document G, and stores it in the image memory 804 as document image data of the second document surface. When reading the back side of the document G is not performed, the document G is transported along the document transport path 81 by the transport rollers 43 and 44 and is stacked on the second paper discharge unit 110.

  The recording material S fed from the first paper feeding unit 30 is transported to the transport roller 40 one by one. At substantially the same time, the latent image based on the original image data on the second side, which is the back side of the original G stored in the image memory 804, is first generated by the laser light from the light emitting unit 21 to the photosensitive drum 10. Formed on top. Next, after the toner image formed by developing the latent image in the transfer unit 15 is transferred to the recording material S, the recording material S is conveyed to the fixing unit 50, and the image formation on the second surface of the document G is completed. In FIG. 2-2 (c), the feeding of the recording material S is started at the same time as the reading of the image on the second surface, which is the back surface of the document G, is started. After reading, feeding of the recording material may be started.

  FIG. 2D is an explanatory diagram showing a state when reading of the back side of the original G is finished. When the document reading is finished, the document G is transported by the transport rollers 43 and 44 and stacked on the second paper discharge unit 110. The switchback flapper 82 moves the conveyance path from the document-dedicated conveyance path 81 to the common conveyance path so that the recording material S conveyed along the common conveyance path 80 is conveyed in the direction of the conveyance roller 40 when the trailing edge of the document G passes. Switch to 80. The recording material S on which the image formation on the second side of the document has been completed is the common conveyance path 80 switched by the double-sided flapper 61 by the reverse rotation of the paper discharge roller 60 provided in the conveyance direction downstream portion of the conveyance path of the recording material S. To be transported.

  FIG. 2-3E is an explanatory diagram illustrating a state in which the recording material S is conveyed to the image forming unit in order to form an image on the first surface of the document G. The recording material S conveyed to the common conveyance path 80 passes through the document reading unit 100 whose sensor unit faces the document dedicated conveyance path 81 side, and is conveyed to the conveyance roller 40 by the conveyance roller 42, and is indicated by a broken line. The recording material S is conveyed to the transfer unit 15 again as shown. A toner image is formed on the recording material S on which the image formation for the second side of the original G has already been completed, based on the original image data for the first side of the original G stored in the image memory 804, and the recording is performed. The material S is stacked on the first paper discharge unit 70.

[Overview of control unit of image forming apparatus]
FIG. 3 is a block diagram illustrating a configuration of a control unit 800 including a CPU 801 that controls the image forming apparatus 1 and a host computer 850. In FIG. 3, a light emitting unit 21 having a rotating polygon mirror, a motor, a laser light emitting element, and the like is connected to an ASIC (Application Specific Integrated Circuit) 802. The CPU 801 outputs a control signal to the ASIC 802 to control the light emitting unit 21 provided in the optical unit 2 in order to scan the photosensitive drum 10 with laser light and draw a desired latent image. At this time, the ASIC 802 creates a control signal based on the image data received from the CPU 801. The optical unit 2 forms a latent image on the photosensitive drum 10 by driving a laser signal based on a control signal from the ASIC 802. The main motor 830 drives the CST pickup roller 31, the conveyance roller 40, the photosensitive drum 10, the transfer unit 15, the heating roller 51, and the pressure roller 52 in order to convey the recording material S. The double-sided drive motor 840 is turned on at the start of driving of the paper feed roller for feeding the recording material S, and the CST paper feed solenoid 822 for driving the CST pickup roller 31, the document pickup roller 91, and the transport rollers 41 to 44. Drive. The CPU 801 controls drive systems such as the main motor 830 and the double-sided drive motor 840 via the ASIC 802.

  Further, the CPU 801 controls a high voltage power source 810, a low voltage power source 811, and a fixing unit 50 that control a charging voltage, a developing voltage, and a transfer voltage necessary for the electrophotographic process. Further, the CPU 801 detects the temperature by a thermistor (not shown) provided in the fixing unit 50 and performs control to keep the temperature of the fixing unit 50 constant.

  The program memory 803 is connected to the CPU 801 via a bus (not shown). The program memory 803 stores a program and data for executing processing performed by the CPU 801, and the CPU 801 controls the operation of the image forming apparatus 1 based on the program and data stored in the program memory 803.

  The ASIC 802 performs speed control of the motor inside the light emitting unit 21 and speed control of the main motor 830 and the double-sided drive motor 840 based on an instruction from the CPU 801. The ASIC 802 detects a tack signal output from a motor (not shown) (a pulse signal output from the motor each time the motor is rotated), and sends the tack signal to the motor so that the output interval of the tack signal is a predetermined time. On the other hand, an acceleration or deceleration signal is output to control the motor speed. As described above, the control load of the CPU 801 can be reduced by controlling the motor and the like with a hardware circuit like the ASIC 802.

  In the host computer 850, the CPU 851 executes various controls based on application programs and printer drivers stored in the program memory 853, and operates according to instructions from the user via the input / output device 856. The host computer 850 communicates with the CPU 801 via the external IF (interface) 852 and the external IF 805 of the control unit 800. The host computer 850 receives the document read image from the CPU 801 and stores it in the image memory 854 and the external storage device 855. Further, the host computer 850 stores overwritten image data created by the user while referring to the original read image in the image memory 854 or the external storage device 855.

  When the user gives an overwrite print instruction, the host computer 850 transmits an overwrite print command to the CPU 801, receives read image data of the original G from the CPU 801, and stores it in the image memory 854 and the external storage device 855. The host computer 850 generates overwrite image data while referring to the read image data of the original G as necessary, and stores it in the image memory 854 or the external storage device 855. Thereafter, the host computer 850 notifies the CPU 801 that overwrite printing is continued, and transmits overwrite image data.

  Next, the control operation of the control unit 800 when printing a recording material will be described. When the user issues a print instruction, the host computer 850 transmits a print command and image data to the CPU 801. When the CPU 801 receives a print command instructing printing on the recording material from the host computer 850, the CPU 801 drives the main motor 830, the double-sided drive motor 840, and the CST paper feed solenoid 822 via the ASIC 802 to convey the recording material S. . After the toner image formed on the photosensitive drum 10 is transferred by the transfer unit 15 to the recording material S, the toner image is fixed to the recording material by the fixing unit 50, and the recording material S serves as a recording material stacking unit by the paper discharge roller 60. The paper is discharged to the first paper discharge unit 70. In order to improve the alignment of the recording materials, the first paper discharge unit 70 is provided with a gradual upward gradient from the vicinity of the paper discharge outlet toward the recording material discharge direction. Here, the CPU 801 supplies predetermined power from the low voltage power source 811 to the fixing unit 50, generates a desired amount of heat in the fixing unit 50, and heats the recording material S, whereby a toner image on the recording material S is displayed. It is fused and fixed to the recording material S.

  Next, the control operation of the control unit 800 when reading a document will be described. When the user gives a scan instruction, the host computer 850 transmits a scan command to the CPU 801. When the CPU 801 receives a scan command instructing reading of the original G from the host computer 850, the CPU 801 drives the double-side flapper solenoid 820 and the double-sided drive motor 840 via the ASIC 802 to operate the original feed solenoid 823. As a result, the torque of the duplex drive motor 840 is transmitted to the document pickup roller 91, and the document G is conveyed. The document reading unit 100 reads the document G based on the CISSTART signal 902, the CISLED signal 903, the Sl_in signal 912, the Sl_select signal 913, and the SYSCLK signal 914 that are control signals from the ASIC 802. Details of these control signals will be described later. Then, the CPU 801 stores the read document image data output as the Sl_out signal 910 from the document reading unit 100 in the image memory 804 connected to the ASIC 802 by control via the ASIC 802. Further, the CPU 801 transmits the read document image data to the host computer 850 via the external IF 805. Thereafter, the CPU 801 operates the switchback solenoid 821 to tilt the switchback flapper 82 toward the original document conveying path 81, reverse the double-sided drive motor 840, and convey the original G to the second paper discharge unit 110.

[Outline of document scanning unit]
Next, details of the document reading unit 100 will be described with reference to FIG. FIG. 4 is a block diagram illustrating a circuit configuration of the document reading unit 100. In FIG. 4, a CIS (Contact Image Sensor) sensor unit 901 is a contact image sensor portion. For example, photodiodes for 10368 pixels are arranged in an array at a specific main scanning density (for example, 1200 dpi). The CISSTART signal 902 is a document reading start pulse signal input to the CIS sensor, and the CISLED signal 903 is a control signal for controlling the light emitting element 907. The current amplifying unit 906 controls the current supplied to the light emitting element 907 based on the CISLED signal 903, and the light emitting element 907 uniformly irradiates the document G. The timing generator 917 receives the SYSCLK signal 914 and generates an ADCLK signal 916 and a CISCLK signal 915. The SYSCLK signal 914 is a system clock that determines the operation speed of the document reading unit 100, and the ADCLK signal 916 is a sampling clock that determines the sampling speed of the A / D converter 908. The CISCLK signal 915 is used as a transfer clock for the CISSNS signal 918 that is an output signal of the shift register 905.

  Next, the document reading operation will be described. When the CISSTART signal 902 becomes active, the CIS sensor unit 901 starts accumulating charges based on the light irradiated from the light emitting element 907 and reflected by the original G, and sequentially stores the charge data accumulated in the output buffer 904. Set. The timing generator 917 outputs a CISCLK signal 915 having a clock frequency of about 500 kHz to 1 MHz, for example, to the shift register 905. The shift register 905 outputs the charge data set in the output buffer 904 to the A / D converter 908 as the CISSNS signal 918 in synchronization with the input CISCLK signal 915. Since the CISSNS signal 918 has a predetermined data guarantee area, the A / D converter 908 needs to sample the CISSNS signal 918 after a predetermined time has elapsed from the rising timing of the CISCLK signal 915 that is the transfer clock. The CISSNS signal 918 is output from the shift register 905 in synchronization with both the rising edge and the falling edge of the CISCLK signal 915 that is a transfer clock. Therefore, the ADCLK signal 916 that is a clock for sampling the CISSNS signal 918 is generated by the timing generator 917 so that the frequency thereof is twice that of the CISCLK signal 915. CISSNS signal 918 is then sampled on the rising edge of ADCLK signal 916. The timing generator 917 divides the SYSCLK signal 914 that is the input system clock to generate an ADCLK signal 916 and a CISCLK signal 915 that is the transfer clock. The phase of the ADCLK signal 916 is delayed by the above-described data guarantee area as compared with the CISCLK signal 915 of the transfer clock.

  The CISSNS signal 918 is digitally converted by the A / D converter 908 and output to the output interface circuit 909 as the CISSNS_D signal 919. The output interface circuit 909 outputs the CISSNS_D signal 919 as serial data S1_out signal 910 at a predetermined timing. At this time, an analog output reference voltage is output from the CISSTART signal 902 which is a start pulse to the CISSNS_D signal 919 for a predetermined pixel, and cannot be used as an effective pixel.

  Also, the control circuit 911 controls the A / D conversion gain of the A / D converter 908 via the ASIC 802 based on the Sl_in signal 912 and the Sl_select signal 913 from the CPU 801. For example, when the contrast of the image of the read document cannot be obtained, the CPU 801 increases the contrast by increasing the A / D conversion gain of the A / D converter 908, and always reads the document with the best contrast. It can be carried out.

  Here, the description has been given using the device configuration in which the image information of all the pixels is output as a CISSNS_D signal 919 which is one output signal. However, for high-speed reading of a document, the pixels are divided into areas, A configuration in which A / D conversion is simultaneously performed on a plurality of areas may be employed. Further, although the description has been given in the embodiment using the CIS sensor for the document reading unit 100, the CIS sensor can be replaced with a CMOS sensor, a CCD sensor, or the like.

[Overwrite printing process]
(1) Single-sided overwrite printing Next, a process for performing overwrite printing will be described. FIG. 5A is an explanatory diagram of single-side overwrite printing. As described with reference to FIGS. 2A and 2B, when the user gives an overwrite print instruction to the original G, the host computer 850 transmits an overwrite print command to the CPU 801. Then, under the control of the CPU 801, first, the first side of the document G stored in the second paper feeding unit 90 is read by the document reading unit 100, and when the document reading is completed, the document G is sandwiched between the conveyance rollers 42. Stop in state.

  When the original reading is completed and the host computer 850 next notifies the CPU 801 of the continuation of the overwrite printing, the original G is conveyed to the conveying roller 40 under the control of the CPU 801. The conveyance roller 40 adjusts the timing so that the toner image on the photosensitive drum 10 is transferred to a predetermined position of the original G, and conveys the original G to the transfer unit 15. As a result, the original G can be used as the recording material S, and an image is formed on the first surface of the original G by the same method as in FIG. After the image formation, the original G is conveyed to the paper discharge roller 60 and stacked on the first paper discharge unit 70.

(2) Duplex overwrite printing (part 1)
Next, a process for performing double-sided overwriting will be described. First, as an operation order, the first side of the original G is read, then the second side is read, and then the both sides are executed by the procedure of overwriting printing on the first side of the original G and overwriting printing on the second side. The overwriting process will be described. FIG. 5B is a diagram for explaining double-sided overwrite printing. As described with reference to FIGS. 2-1 (a), (b), and 2-2 (c), first, the first side and the second side of the original G stored in the second paper feed unit 90 are read. After being read by the unit 100, the original G is stopped while being held between the conveyance rollers 43.

  When the original reading is completed and the host computer 850 next notifies the CPU 801 of the continuation of overwriting printing, the original G is conveyed from the conveying roller 43 to the conveying roller 40 under the control of the CPU 801. The conveyance roller 40 adjusts the timing so that the toner image on the photosensitive drum 10 is transferred to a predetermined position of the original G, and conveys the original G to the transfer unit 15. When the document G is conveyed from the conveyance roller 43 to the conveyance roller 40, the document G passes through the document reading unit 100 again. Since the document reading unit 100 reads the document G during passage and detects the document end of the document G when the image forming unit enters, the deviation of the document G generated in the switchback operation after the document reading is accurately corrected. be able to. As a result, the original G can be used as the recording material S, and an image is formed on the first surface of the original G by the same method as in FIG. Also, image formation is performed on the second side of the original G by the same method as in FIG. After the overwriting printing operation on the first side of the original G is completed, the original G passes through the original reading unit 100 again in order to perform the overwriting printing operation on the second side as shown in FIG. The document reading unit 100 reads the document G during passage to detect the document edge, and image formation on the second side is performed in accordance with the position of the document edge. After the image formation, the original G is conveyed to the paper discharge roller 60 and stacked on the first paper discharge unit 70.

(3) Duplex overwrite printing (part 2)
Next, a description will be given of a double-sided overwriting process executed in the order of overwriting printing on the first side after reading the first side as an operation sequence, and then overwriting on the second side after reading the second side. To do. That is, the original G performs an operation of repeating the single-sided overwriting operation described with reference to FIG. After the one-side overwriting operation is completed, the original G is switched back using the double-sided flapper 61 as in FIG. 1B, the second side is read by the original reading unit 100, and then the overwriting printing operation is performed. Can be realized.

[Overwrite printing operation overview]
When the CPU 801 receives an overwrite print command from the host computer 850, the CPU 801 drives the duplex flapper solenoid 820 and the duplex drive motor 840 via the ASIC 802 to operate the document feed solenoid 823. As a result, the torque of the duplex drive motor 840 is transmitted to the document pickup roller 91, and the document G is conveyed. Then, the CPU 801 stores the document image data read by the document reading unit 100 in the image memory 804 connected to the ASIC 802 by control via the ASIC 802. Further, the read document image data is transmitted by the CPU 801 to the host computer 850 via the external IF 805. At this time, in the case of single-sided overprinting or double-sided overprinting that repeats the single-sided overprinting procedure twice after single-sided reading of the original G, the original G is once held between the transport rollers 42 after single-sided reading. Stop. On the other hand, when double-sided overwrite printing is performed after reading both sides of the original G, the original G is temporarily held between the conveyance rollers 43 after the double-sided reading.

  The host computer 850 saves the original image data received from the CPU 801 in the image memory 854, and performs a process for determining whether or not to continue overwriting, which will be described later, based on the received original image data, and determines whether or not to continue overwriting. To do. If the host computer 850 determines that the overwriting printing can be continued, the host computer 850 creates overwriting image data based on the received document image data, notifies the CPU 801 of overwriting of the overwriting and also creates the overwriting image data. Send. When the host computer notifies the continuation of overwrite printing, the CPU 801 drives the main motor 830 and the double-sided drive motor 840 to convey the document G to the image forming unit, and receives the document G using it as a recording material. Overwrite printing of the first surface is performed using the overwrite image data. In the case of double-sided overprinting, overwriting printing is also performed on the second side of the original G. On the other hand, if it is determined that continuation of overwrite printing is not possible, the host computer 850 notifies the CPU 801 of cancellation of overwrite printing, and the CPU 801 that is notified of cancellation of overwrite printing does not perform image formation, and does not perform document G as it is. Eject paper.

  By the overwrite printing process described above, an image printed on a document can be read, and an overwrite image created based on the image can be overwritten on the document. Since the document conveyance path and the recording material conveyance path are used in common, the process of switching the document to the recording material can be automatically performed in the image forming apparatus without human intervention.

[Overwrite printing control sequence]
When overprinting is performed, since the original G on which a color material such as toner has already been formed is used as the recording material S, a toner image is further transferred to the original G and fixing is performed. Since the original G is created using various image forming apparatuses, there are various color materials used for original printing, such as toner and ink. Even with the same color material, the toner may have different characteristics such as the melting temperature. Therefore, for example, when the fixing unit 50 of the image forming apparatus 1 does not correspond to the color material on the document G, a fixing failure occurs or the document G used as the recording material S adheres to the fixing unit 50. There is a case where jamming occurs due to winding.

  Therefore, in this embodiment, the host computer 850 performs a determination process as to whether or not to continue overwrite printing based on the document image data. In the following, with reference to FIG. 6, the continuation determination process for overprinting according to the present embodiment will be described. FIG. 6A is a flowchart showing a control sequence for overwrite printing according to the present embodiment.

  In step 1101 (hereinafter referred to as S1101), upon receiving an overwrite print command from the host computer 850, the CPU 801 reads the document G by the document reading unit 100 under the control of the ASIC 802. The CPU 801 transmits the read document image data to the host computer 850 via the external IF 805. When the host computer 850 receives the document image data from the CPU 801, the host computer 850 stores the document image data in the image memory 854 or the external storage device 855.

  In step S <b> 1102, the host computer 850 acquires image forming apparatus information that specifies the image forming apparatus that has printed the original G, which is print information of the original G, from the original image data stored in the image memory 854. FIG. 7A is an example of document image data read from the document G. In the figure, an image indicated by reference numeral 1201 is image forming apparatus information. As shown in FIG. 7A, image forming apparatus information that can specify the image forming apparatus used for document printing is printed in advance on a document to be overwritten. Here, in order to indicate that the original G has been printed by the image forming apparatus “ENGINE-A”, a character string “ENGINE-A” is encoded with a barcode in the CODE39 format and printed on the original G, for example. ing. The host computer 850 detects a barcode from the document image data stored in the image memory 854, decodes the barcode, and acquires information on the image forming apparatus on which the document G is printed.

  By the way, in the present embodiment, an image encoded with a barcode is used as the image forming apparatus information. However, other information formats, for example, an image encoded with a two-dimensional barcode, or a digital watermark using minute dots are used. An image may be used. Further, when the original G is a color original, an additional information image for specifying the printing apparatus added at the time of printing may be used. In this embodiment, information that can identify the image forming apparatus used for printing the original document is used as the image forming apparatus information. However, information that can identify the color material used for printing the original document may be used. For example, a character string “TONAR-D” or “INK-E” is displayed on the bar to indicate that the original G has been printed with the color material “TONAR-D” (toner D) or “INK-E” (ink E). It may be encoded with a code and printed on the original G.

  In step S1103, the host computer 850 determines whether image forming apparatus information has been acquired from the document image data. If the host computer 850 succeeds in acquiring the image forming apparatus information, the host computer 850 proceeds to S1104 and acquires the image forming apparatus information because the barcode is not printed on the document image data or the barcode cannot be decoded successfully. If unsuccessful, the process advances to S1108.

  In step S <b> 1104, the host computer 850 determines whether or not overwriting printing can be continuously performed based on the acquired image forming apparatus information and whether or not overwriting printing can be continued. Details of the processing of S1104 will be described later. In step S1105, the host computer 850 determines whether or not overwriting printing can be continued. If it is determined that overwriting printing can be continued, the process proceeds to step S1106. If it is determined that overwriting printing cannot be continued, the process proceeds to step S1108.

  In step S1106, the host computer 850 notifies the CPU 801 of the continuation of overwrite printing, and transmits overwrite image data for the document G shown in FIG. In step S1107, the CPU 801 notified of the continuation of overwrite printing overwrites the overwrite image data (FIG. 7B) received from the host computer 850 on the document G shown in FIG. A document G that is an output image shown in FIG.

  In step S <b> 1108, the host computer 850 notifies the CPU 801 to cancel overwriting. In step S <b> 1109, the CPU 801 that is notified by the host computer 850 to cancel the overwrite printing discharges the document G as it is without performing the overwrite printing on the document G, and ends the overwrite printing.

[Determining whether to continue overwriting]
Next, the determination process for determining whether or not to continue overwriting in S1104 in FIG. 6A will be described in detail with reference to FIGS. FIG. 6B is a flowchart showing a control sequence of the overwrite printing continuation determination process in S1104.

  In step S1151, the host computer 850 identifies the image forming apparatus that has printed the document G based on the image forming apparatus information obtained by decoding the barcode. The host computer 850 decodes the barcode of the image forming apparatus information 1201 in the original image data shown in FIG. 7A and obtains a character string “ENGINE-A”, whereby the original G becomes the image forming apparatus. It is detected that “ENGINE-A” has been printed.

  In step S1152, the host computer 850 determines whether the original G printed by the image forming apparatus or color material specified in the processing in step S1151 can be overwritten. Therefore, the host computer 850 stores in the program memory 853 a permission list that lists image forming apparatuses and color materials that have been printed on the original G that can be overwritten by the image forming apparatus 1. FIGS. 7D and 7E show examples of the first permission list and the second permission list, respectively. FIG. 7D shows a list of image forming apparatuses that use toner that permits overprinting and toner that allows overprinting. On the other hand, FIG. 7E shows a list of image forming apparatuses that use a color material (for example, ink) other than the toner permitted to be overwritten or a color material other than the toner permitted to be overwritten. In the first permission list and the second permission list, a color material having good fixability to the document G to be overwritten and an image forming apparatus using the color material are set. That is, the first permission list and the second permission list are lists of image forming apparatuses and color materials on which the document G is printed, overwriting by the image forming apparatus 1 is permitted. For example, the overwriting printing is executed. An apparatus of the same type as the image forming apparatus 1 and a color material having the same characteristics are set. Then, the host computer 850 continues the overwriting printing on the original G depending on whether the image forming apparatus or the color material specified by decoding the barcode is in the first permission list or the second permission list. Determine if it is possible. If the image forming apparatus or the color material used for printing the original G is included in the permission list, the host computer 850 determines that overwriting printing can be continued and proceeds to S1153, and if not included. In step S1154, it is determined that overwriting cannot be continued. In step S1153, the host computer 850 determines that the determination result can be overwritten and ends the process. In step S1154, the host computer 850 determines that the determination result cannot be overwritten and ends the process.

  In the present embodiment, the host computer 850 has performed the determination process of whether or not to continue overprinting, but may be executed by another configuration, for example, the CPU 801, or all or part of the processing may be executed by the ASIC 802. . In this case, the CPU 801 and the ASIC 802 execute the image forming apparatus information acquisition process in S1102 in FIG. 6A and the image forming apparatus specifying process and determination process in S1151 and 1152 in FIG. 6B. . Further, in the case of this configuration, the first permission list and the second permission list are stored in the program memory 803. In the above description, the host computer 850 stores the first permission list and the second permission list in the program memory 853. However, the host computer 850 may store the first permission list and the second permission list in the external storage device 855, for example.

  Further, in the process of S1152 of FIG. 6B, it is determined that overwriting printing can be continued only for the document printed by the image forming apparatus or the color material set in the first permission list and the second permission list. For example, when it is possible to continue overprinting only for a document printed using toner, the first permission list made up of color materials other than toner is not necessary. Only the second permission list needs to be targeted. Similarly, when it is possible to continue overprinting only for a document printed using a color material other than toner, the second permission list made up of toner is not necessary, and therefore whether or not it is possible in the processing of S1152 is determined. Only the first permission list needs to be targeted.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of fixing failure and jam when overwriting printing is performed, and it is possible to prevent a decrease in usability. In other words, an image forming apparatus or a color material that has good fixability when performing overwriting printing is set in the permission list, and only for documents printed with the image forming apparatus or the color material set in the permission list. Overwrite printing is possible. Thereby, even if overwrite printing is performed, fixing failure and jam occurrence can be suppressed, and deterioration in usability can be prevented.

  In the first exemplary embodiment, an image forming apparatus or a color material on which a document is printed is identified based on image forming apparatus information read from the document, and whether or not overwriting printing can be continued is determined. Was suppressed. When overwrite printing is performed, an overwrite image is formed on a document on which a toner image has already been formed, and an output image is completed. As a result, the toner amount of each pixel of the output image is obtained by adding the toner amount used for the corresponding pixel of the overwrite image to the toner amount used for the corresponding pixel of the original image. The image forming device can be used for each pixel of the image formed on the recording material so that the recording material will not be poorly fixed and the recording material will not adhere and wrap around the fixing part due to the excessive amount of toner used. A limit value for the toner amount is provided. However, when overprinting is performed, the toner amount limit value may be exceeded. As a result, the toner may be poorly fixed on the recording material, or the document used as the recording material may adhere to the fixing unit. May wrap and jam. Therefore, in the second embodiment, in addition to the image forming apparatus information in the first embodiment, a new determination criterion for suppressing occurrence of fixing failure and jam when overwriting printing is continued will be described.

[Determining whether to continue overwriting]
In this embodiment, the host computer 850 changes the determination criterion when toner is used for printing the document G, and after the overwrite printing calculated from the toner amount on the document G and the toner amount of the overwrite image. The toner amount of the pixel of the output image is used for the determination process of whether or not to continue overprinting. Hereinafter, with reference to FIGS. 8A and 8B, the determination process of whether or not to continue overwriting according to this embodiment will be described. In this embodiment, as the process of S1104 in the flowchart at the time of overwrite printing shown in FIG. 6A of Embodiment 1, the determination process of whether or not to continue overwriting shown in FIG. 8-1A is performed.

  FIG. 8A is a flowchart illustrating a control sequence of the overwrite printing continuation determination process in the present embodiment. FIG. 8A is a flowchart obtained by adding the processes of S1303 to S1305 to the process of the flowchart illustrated in FIG. 6B of the first embodiment. Since S1301, S1302, S1306, and S1307 in FIG. 8-1 (a) are the same processes as S1151, S1152, S1153, and S1154 in FIG. 6 (b), detailed description of the processing contents is omitted.

  In S1301 and S1302, as in S1151 and S1152 of the first embodiment, the host computer 850 places the image forming apparatus or color material specified based on the document image data in the first permission list or the second permission list. Determine if it is included. The host computer 850 proceeds to S1307 when it is not included in the permission list, and proceeds to S1303 when it is included in the permission list. In step S1303, the host computer 850 determines whether the color material of the original G is toner or whether the original G is printed by an image forming apparatus that uses toner as the color material. That is, the host computer 850 determines whether or not the specified image forming apparatus and color material are included in the first permission list of FIG. As described above, the first permission list in FIG. 7D includes an image forming apparatus using toner and toner as a color material. If the image forming apparatus and the color material specified in S1301 are included in the first permission list in FIG. 7D, it can be determined that the document G has been printed using toner. If it is not included, it can be determined that printing is performed with a color material other than toner. If the original G is printed with a color material other than toner, the host computer 850 proceeds to step S1306. In step S1306, as in the first embodiment, the host computer 850 processes the determination result indicating whether or not overwriting can be continued as overwriting. finish. On the other hand, if the host computer 850 determines that the document G has been printed using toner, the process advances to step S1304. In step S <b> 1304, the host computer 850 performs a toner amount calculation process (details will be described later) of each pixel of the output image in which the document G is overwritten with the overwrite image. In step S <b> 1305, the host computer 850 continues overwriting printing based on a new determination criterion whether the calculated toner amount of each pixel of the output image is within the limit value range of the toner amount that can be used by the image forming apparatus. A determination process of availability is performed. The host computer 850 proceeds to S1306 if the calculated toner amount of each pixel of the output image is within the toner amount limit value range of the image forming apparatus, and proceeds to S1307 if there is a pixel exceeding the toner amount limit value. In step S <b> 1307, the host computer 850 sets the determination result of whether or not to continue overprinting as overprinting is impossible, and ends the process.

[Calculation of toner amount of output image after overwrite printing]
Next, the toner amount calculation processing of each pixel of the output image in S1304 in FIG. 8-1 (a) will be described with reference to FIG. 8-1 (b). FIG. 8B illustrates a processing sequence for calculating the amount of toner used in each pixel of the output image after overwrite printing. In step S <b> 1311, the host computer 850 calculates the amount of toner used in the original G for each pixel of the original G based on the original image data. In step S1312, the host computer 850 calculates the amount of toner used in the overwritten image for each pixel of the overwritten image based on the overwritten image data overwritten on the document G. In step S <b> 1313, the host computer 850 adds the toner amount used in the overwrite image to the toner amount used in the document G, and calculates the toner amount used in the output image formed on the document G. Calculation is performed for each pixel of the output image. In step S1314, the host computer 850 determines whether or not the calculation process of the toner amount to be used has been completed for all the pixels of the output image. If the calculation has not been completed, the process returns to step S1311. finish.

[Calculation of toner amount of original image]
Next, the toner amount calculation processing of the original image in S1311 of FIG. 8-1 (b) will be described with reference to FIGS. 8-2 (c) and 7 (a). FIG. 8C is a flowchart illustrating a processing sequence for calculating the amount of toner used in the original G. FIG. 7A shows document image data read from the document G by the document reading unit 100. When the CPU 801 reads the document G, the CPU 801 transmits the document image data to the host computer 850. When the host computer 850 receives the document image data from the CPU 801, the CPU 801 stores the document image data in the image memory 854.

  In the original image data (FIG. 7A) received from the CPU 801, the RGB gradation values of each pixel are stored in the image memory 854 as raster data. Since the RGB gradation values are device-dependent colors expressed in a color space depending on the color characteristics of the CIS sensor unit 901 that reads the document G, in the image forming apparatus (FIG. 7A) where the document G is printed, This value is unrelated to ENGINE-A). In step S1401, the host computer 850 converts the color space of the document image data from a CIS color space that is dependent on the color characteristics of the CIS sensor unit 901 to a device-independent color space. As the device-independent color space, for example, a CIE L * a * b * space or a CIE XYZ space can be used. Further, as an example of conversion, a known conversion method can be used according to an ICC (International Color Consortium) profile of the CIS sensor unit 901.

  In step S1402, the host computer 850 converts the color space of the document image data from the device-independent color space to the color space of the image forming apparatus (ENGINE-A) that printed the document G. In the processing of S1301, the host computer 850 has already detected from the image forming apparatus information printed on the original G that the original G has been printed by the image forming apparatus “ENGINE-A”. Therefore, the host computer 850 uses the ICC profile of the image forming apparatus “ENGINE-A” to convert the color space of the document image data from the device-independent color space to the color space of the image forming apparatus that printed the document G. . Although the ICC profile of the image forming apparatus that printed the original G is used here, the ICC profile of the color material used for printing the original G may be used. That is, when it is detected that the original G is printed with “TONAR-D” (toner D), the color space of the original image data is made device-independent by using the ICTON profile of “TONAR-D”. The color space may be converted to the color space of the toner on which the document G is printed.

  In step S1403, the host computer 850 separates the original image data from RGB gradation values to CMYK gradation values. At this time, the host computer 850 refers to the color separation table of the image forming apparatus “ENGINE-A”. The above-described ICC profile and color separation table are stored in advance in the program memory 853 and the external storage device 855. Through the processing described above, the color information of the document image data depends on the image forming apparatus (ENGINE-A in FIG. 7A) that printed the document G from the device-dependent RGB gradation values of the CIS sensor unit 901. It can be converted into CMYK gradation values.

  In step S <b> 1404, the host computer 850 calculates the toner amount on the original G from the CMYK gradation values of the original image data. Here, the total amount of CMYK gradation values is used as the toner amount used in the original G.

  Next, taking the color of the area 1202 in FIG. 7A as an example, the amount of toner used in the document G shown in FIG. 8-1B based on the flowchart in FIG. A process (S1311) of calculating for each pixel will be described. First, it is assumed that (R, G, B) = (157, 187, 97) as RGB gradation values of the document image data for a certain pixel in the area 1202 in FIG. Since this value is the RGB gradation value of the color space depending on the CIS sensor unit 901, it is converted into a device-independent color space in the processing of S1401, and after conversion using the CIE L * a * b * space (L *, a *, b *) = (71, −27, 44) is obtained as the value of. In step S1402, the apparatus-independent color space is converted into the color space of the image forming apparatus on which the document G is printed. The converted values are (R, G, B) = (170, 220, 81). ) Is obtained. Next, color separation is performed from RGB gradation values to CMYK gradation values by the processing of S1403, and CMYK gradation values corresponding to (R, G, B) = (170, 220, 81) are set as (C, M , Y, K) = (55%, 16%, 71%, 0%). Finally, when the toner amount used in the original G is calculated from the CMYK gradation values by the processing of S1404, the toner amount calculated for a certain pixel in the area 1202 is 142% (= 55% + 16% + 71% + 0%). )

[Calculation of toner amount of overwritten image data]
Next, the processing for calculating the toner amount of the overwritten image in S1312 of FIG. 8-1 (b) will be described with reference to FIGS. 8-2 (d) and 7 (b). FIG. 8D is a flowchart illustrating a processing sequence for calculating the toner amount of the overwritten image. FIG. 7B shows image data to be overwritten on the original G. The overwritten image data is created by an application program running on the host computer 850 and stored in the image memory 854.

  In the overwrite image data (FIG. 7B), the RGB gradation values of each pixel are stored in the image memory 854 as raster data. Normally, the RGB gradation values are expressed in an sRGB color space that can be processed by an application program operating on the host computer 850. Therefore, in S1411, the host computer 850 converts the color space of the overwritten image data from the sRGB color space to a device-independent color space. Here, the CIE L * a * b * space described above is used as the device-independent color space.

  In step S1412, the host computer 850 converts the color space of the overwrite image data from the device-independent color space to the color space of the image forming apparatus 1 that performs overwrite printing. Unlike the document image described above, the host computer 850 uses the ICC profile of the image forming apparatus 1 that performs overwriting printing to perform overwriting printing of the color space of the overwriting image data from the device-independent color space. Convert to 1 color space. For example, when the image forming apparatus 1 is “ENGINE-B”, the ICC profile of the image forming apparatus “ENGINE-B” is used.

  In step S <b> 1413, the host computer 850 separates the overwrite image data from RGB gradation values to CMYK gradation values. At this time, the host computer 850 refers to the color separation table of the image forming apparatus “ENGINE-B”. The above-described ICC profile and color separation table are stored in advance in the program memory 853 and the external storage device 855. Through the above-described processing, the color information of the overwritten image data is converted from the gradation value of the sRGB color space that can be processed on the host computer 850 to the CMYK gradation value depending on the image forming apparatus 1 that performs overprinting on the original G. be able to.

  In step S1414, the host computer 850 calculates the toner amount of the overwrite image from the CMYK gradation values of the overwrite image data. Here, the total value of CMYK gradation values is used as the toner amount used in the overwritten image.

  Next, taking the color of the area 1210 in FIG. 7B as an example, the toner amount used in the overwritten image shown in FIG. 8-1B based on the above-described flowchart in FIG. A process (S1312) for calculating each pixel will be described. First, it is assumed that (R, G, B) = (40, 94, 166) is set as the RGB gradation value of the overwritten image data for a certain pixel in the region 1210 in FIG. Since this value is a gradation value in the sRGB color space, it is converted into a device-independent color space in the processing of S1411, and (L *, a *, b *) = (39, 2, -45). In step S1412, the apparatus-independent color space is converted to the color space of the image forming apparatus overwritten on the original G. As converted values, (R, G, B) = (35, 148, 202) is obtained. Next, color separation is performed from RGB gradation values to CMYK gradation values by the processing of S1413, and CMYK gradation values corresponding to (R, G, B) = (35, 148, 202) are (C, M , Y, K) = (92%, 63%, 23%, 0%). Finally, when the toner amount used in the overwritten image is calculated from the CMYK gradation values by the processing of S1414, the toner amount calculated for a certain pixel in the area 1210 is 178% (= 92% + 63% + 23% + 0%). )

[Calculation of toner amount of output image]
In step S <b> 1313, the host computer 850 calculates the amount of toner used in the output image. Since the output image is formed by printing the overwrite image on the document G, the toner amount used in a certain pixel of the output image is the same as the toner amount used in the same pixel of the document G as the same pixel of the overwrite image. It can be calculated by adding the amount of toner used.

  FIG. 7C is an output image obtained by overwriting the original image data in FIG. 7A with the overwrite image data in FIG. 7A to 7C, the region 1220 shown in FIG. 7C is a portion where the region 1202 in FIG. 7A and the region 1210 in FIG. 7B overlap. I understand. As described above, the toner amount of a pixel in the original image area 1202 is 142%, and the toner amount of a pixel in the overwrite image area 1210 is 178%. Accordingly, if a certain pixel in the original image area 1202 and a certain pixel in the overwrite image area 1210 are the same pixel, the toner amount of the same pixel in the output image area 1220 is 320% (= 142% + 178%).

[Determining whether to continue overwriting]
Next, in step S1305 of FIG. 8A, the host computer 850 determines whether the toner amount used in each pixel of the output image is within the usable toner amount limit range. The host computer 850 determines whether or not the overwriting can be continued depending on whether or not the maximum toner amount out of the toner amount used in each pixel of the output image exceeds the limit value of the usable toner amount. Accordingly, the host computer 850 determines that overwriting printing can be continued if the maximum amount of toner used in the pixel of the output image is within the limit value range, and proceeds to the processing of S1306. On the other hand, if there is even one pixel that exceeds the limit value of the toner amount, the host computer 850 determines that overwriting printing cannot be continued, and proceeds to the processing of S1307.

  For example, when the limit value of the usable toner amount of the image forming apparatus 1 is 200%, the calculated toner amount 320% of a certain pixel in the area 1220 of the output image exceeds this limit value, and the host computer In step 850, it is determined that it is impossible to continue overwriting. As a result, an overwritten image exceeding the toner amount limit value is not formed, and it is possible to prevent the occurrence of fixing failure and the occurrence of jamming due to the original G being attached to the fixing portion and being wound.

  In this embodiment, the host computer 850 executes determination processing for determining whether or not to continue overwriting, but may be executed by another configuration, for example, the CPU 801, or all or part of the processing may be executed by the ASIC 802. Good. In this case, the ICC profile and the color separation table are stored in the program memory 803.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of fixing failure and jam when overwriting printing is performed, and it is possible to prevent a decrease in usability. In particular, when toner is used for printing an original, whether or not to continue overprinting is determined. The amount of toner used in the output image calculated from the amount of toner used in the original image and the overwritten image is determined by the image forming apparatus. Judgment is made based on whether the amount of toner that can be used during printing is within the limit value range. Thereby, even if overwrite printing is performed, fixing failure and jam occurrence can be suppressed, and deterioration in usability can be prevented.

  In the second embodiment, in addition to the image forming apparatus information and the color material information, whether or not the toner amount of each pixel of the output image calculated from the toner amount on the document and the toner amount of the overwrite image is within the toner amount limit value range. Judgment was made on whether or not to continue overprinting, and fixing failure and jamming were suppressed. When overwriting printing is performed, the toner image already formed on the original is overwritten and printed, so the toner amount limit value stipulated for each image forming apparatus is likely to be exceeded, and as a result, overwriting cannot be continued. The frequency of becoming will increase. For this reason, for example, the toner amount limit value can be changed by increasing the fixing temperature of the fixing unit 50. However, if the fixing temperature is always increased during overwriting printing, the power consumption of the image forming apparatus increases. Resulting in. Therefore, in the third embodiment, a new determination criterion that suppresses occurrence of fixing failure and jam that is used when the toner amount of the output image exceeds the toner amount limit value of the image forming apparatus in the second embodiment will be described.

[Determining whether to continue overwriting]
In this embodiment, when the toner amount of each pixel of the output image exceeds the toner amount limit value of the image forming apparatus, the host computer 850 changes the fixing temperature of the fixing unit 50 to perform overwrite printing. Determine if continuation is possible. Hereinafter, with reference to FIG. 9, the determination process of whether or not to continue overwriting according to this embodiment will be described. In this embodiment, as the process of S1104 in the flowchart at the time of overwrite printing shown in FIG. 6A of the first embodiment, the process for determining whether or not to continue overwriting shown in FIG. 9A is performed.

  FIG. 9A is a flowchart showing a control sequence of the overwrite printing continuation determination process in this embodiment. FIG. 9A is a flowchart in which the processes of S1508 and S1509 are added to the process of the flowchart shown in FIG. 8-1A of the second embodiment. Since S1501 to S1507 in FIG. 9A are the same processes as S1301 to S1307 in FIG. 8-1A, detailed description of the processing contents is omitted.

  In step S1505, the host computer 850 determines whether the toner amount used in each pixel of the output image is within the limit value range of the usable toner amount, and determines that overwriting printing can be continued if the toner amount is within the limit value range. Then, the process proceeds to S1506, and if not, the process proceeds to S1508.

  In step S <b> 1508, the host computer 850 increases the fixing temperature of the fixing unit 50 from the normal fixing temperature, and uses whether or not the output image printed by overwriting on the document can be fixed satisfactorily as a new criterion. Determine whether printing can be continued. FIG. 9B is a graph showing the relationship between the toner amount and the fixable fixing temperature in the fixing unit 50 of the image forming apparatus 1, and the vertical axis indicates the fixable temperature (unit: ° C.) in the fixing unit 50. The horizontal axis indicates the toner amount (unit:%). In the image forming apparatus 1, the fixing temperature is set to 180 ° C. as a normal fixing temperature condition, and the temperature of the fixing unit 50 is controlled so that the toner can be satisfactorily fixed up to 200% as shown in FIG. 9B. Yes. As shown in FIG. 9B, when the fixing temperature of the fixing unit 50 is increased to the upper limit of 200 ° C., it is possible to fix the toner image satisfactorily up to a toner amount of 300%. As a result, the limit value of the usable toner amount can be changed from 200% to 300%, and the host computer 850 determines that fixing is possible if the toner amount of each pixel of the output image is within 300%. Proceed to processing. On the other hand, if there is a pixel whose toner amount exceeds 300% among the pixels of the output image, the host computer 850 determines that fixing is not possible and proceeds to the processing of S1507. This determination result is regarded as being incapable of overwriting printing, and the process ends.

  In step S1509, the host computer 850 notifies the CPU 801 to change the fixing temperature of the fixing unit 50, and the process advances to step S1506. Upon receiving the notification, the CPU 801 changes the temperature control of the fixing unit 50 to increase the fixing temperature from a predetermined temperature of 180 ° C. to 200 ° C. to perform overwriting printing. Return to 180 ° C. In step S <b> 1506, the host computer 850 determines that the overwrite printing continuation determination result can be overwritten, and ends the process.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of fixing failure and jam when overwriting printing is performed, and it is possible to prevent a decrease in usability. In particular, if there are pixels in the output image where the amount of toner used exceeds the toner amount limit value, it is determined whether or not overwrite printing is possible by changing the fixing temperature of the fixing unit, and overwriting is performed. If printing is possible, overwrite printing is performed by changing the fixing temperature. As a result, overwriting can be performed even when the toner amount of the pixel of the output image exceeds the toner amount limit value, but the fixing temperature can be changed only when the toner amount limit value is exceeded. Even if printing is performed, a significant increase in power consumption of the image forming apparatus can be suppressed. Furthermore, since fixing failure and jam can be suppressed, it is possible to prevent a decrease in usability.

[Other Examples]
In the above-described embodiment, the image forming apparatus or the color material on which the original is printed is detected and specified based on the image forming apparatus information acquired from the original image data. However, it can be detected and specified by other methods. For example, the user of the image forming apparatus inputs image forming apparatus information using the input / output apparatus 856, and the host computer 850 prints an original from the image forming apparatus information acquired from the input / output apparatus 856. May be detected and identified.

  In the above-described embodiment, the program of the host computer 850 or the CPU 801 that realizes the functions of the embodiment is stored in the program memories 853 and 803 in advance. For example, a program that realizes the functions of the above-described embodiments may be stored in a computer-readable storage medium, and the host computer 850 or the CPU 801 may read the program code from the storage medium and execute it. As a storage medium for supplying the program code, for example, a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, DVD, or the like is used. it can.

  In the above-described embodiments, the description has been made on the assumption that the image forming apparatus forms a monochrome image. However, the present invention can also be applied to a color image forming apparatus. As a color image forming apparatus, a photosensitive drum as an image carrier for forming an image of each color of yellow, magenta, cyan, and black is arranged side by side, and an image is transferred from each photosensitive drum to a recording material or an intermediate transfer member. The present invention can be applied to a color image forming apparatus of a system for transferring the image. Further, the present invention can be applied to a color image forming apparatus in which images of respective colors are sequentially formed on one image carrier (photosensitive drum), a color image is formed on an intermediate transfer member, and transferred to a recording material.

  As described above, similarly to the above-described embodiment, in this embodiment, it is possible to suppress the occurrence of fixing failure and jam when overwriting printing is performed, and to prevent a decrease in usability.

15 Transfer unit 100 Document reading unit 801 CPU
803 Program memory

Claims (8)

Image forming means for forming an image on a recording material;
Reading means for reading an original;
Obtaining means for obtaining information relating to a color material used for image formation of a document or an image forming apparatus that has performed image formation of the document from document image data read by the reading unit;
Storage means for storing information about the image forming apparatus;
If the information acquired by the acquisition unit is stored in the storage unit, a control unit that permits overprinting on the document by the image forming unit;
An image forming apparatus comprising:   The control means is such that the color material used for image formation of the document is toner, and the amount of toner used for the output image is a predetermined limit value in each pixel of the output image obtained by overprinting the document. The image forming apparatus according to claim 1, wherein overprinting is not permitted when there are more pixels than. A fixing means for fixing an image formed on a recording material;
The predetermined limit value can be changed by changing a fixing temperature of the fixing unit,
The control unit permits overprinting when the amount of toner used in each pixel of the output image does not exceed the predetermined limit value changed by increasing the fixing temperature of the fixing unit. The image forming apparatus according to claim 2.   The amount of toner used for each pixel of the output image is the amount of toner used for image formation of the corresponding pixel of the document and the toner used for image formation of the corresponding pixel of the overwrite image used for overwriting printing on the document. The image forming apparatus according to claim 2, wherein the image forming apparatus is calculated based on the amount.   5. The image forming apparatus according to claim 4, wherein the amount of toner used for image formation of the original is calculated based on original image data read by the reading unit.   The image forming apparatus according to claim 4, wherein the toner amount used for image formation of the overwrite image is calculated based on image data of the overwrite image.   The predetermined limit value is a toner amount limit value for preventing a fixing failure on a recording material due to an excessive amount of toner and an adhesion winding of the recording material to a fixing unit due to an excessive amount of toner. The image forming apparatus according to claim 2. A control method for an image forming apparatus that performs image formation,
A reading step in which the reading means reads the document;
An acquisition step of acquiring information relating to a color material used for image formation of a document or an image forming apparatus that has performed image formation of the document from the document image data read by the reading step;
An image forming method comprising: a control step of permitting overwriting printing on the document when the information acquired by the acquiring step is stored in a storage unit of the image forming apparatus. Control method of the device.

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