JP2006235066A - Color image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus capable of preventing the lowering of throughput in double-sided printing, where a printing mode for the front surface of recording material is different from a printing mode for the back surface of the recording material as a color image forming apparatus, whose image forming speed is different with respect to the printing mode. <P>SOLUTION: The color image forming apparatus decides (s37) at which image forming speed, either the first or second speed an image is to be formed on a side for which monochrome printing is designated, based on the printing data (s32 and s35) when the printing mode for the front surface of the recording material is different from the printing mode for the back surface of the recording material, and controls to form the image on a side, for which the monochrome printing is designated at the image forming speed (s39) decided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is a color image forming apparatus, such as a printer or a copier, capable of duplex printing and having a different image forming speed in the case of only full-color printing and an image forming speed in the case of only monocolor (monochrome or monochrome) printing. In particular, the present invention relates to improvement in productivity (throughput) of the image output.
It is about.

  In recent years, the demand for color image output has been increasing year by year, and in some cases, color copiers and color printers have been introduced as full-color and mono-color combined machines in the office, and color image output is becoming common. .

  On the other hand, in general offices, there are usually many monocolor images such as documents and documents for copying and printing, and there are many cases where the ratio of color image output is smaller than that for monocolor image output. Under such circumstances, when a color copying machine or a color printer is used as a mono-color combined machine, since the frequency of mono-color output is high, high productivity of mono-color image output is required. .

  In conventional color copying machines and color printers, the image forming speed for forming a full color image and the image forming speed for forming a monocolor image are generally the same. Therefore, in order to increase the productivity of monocolor image output, a copying machine and a printer that increase the productivity of monocolor image output by increasing the monocolor image formation speed from the full color image formation speed have been proposed.

  By the way, when changing the image forming speed, it is necessary to change the speed of the latent image, development, transfer, conveyance, fixing and the like. For example, by changing the speed of the scanner motor for changing the laser irradiation speed, changing the speed of the drum motor for changing the rotational speed of the photosensitive drum, or changing the speed of the main motor for changing the conveyance, transfer, and fixing speed, etc. A lot of time is required for processing necessary for switching the forming speed.

  Therefore, the switching of the image forming speed does not occur in the case of outputting only a monocolor image or outputting only a full color image. However, when a mono-color image and a full-color image are mixed, it is necessary to change the image forming speed.

  However, when switching output from a monocolor image to a full-color image, or from a full-color image to a monocolor image, if the control is performed so that the image formation speed is simply switched in response to the output switching, it is necessary to switch the image formation speed as described above. Since a long process is required, there is a case where the throughput when mono-color / full-color images are mixed decreases.

  Therefore, in order to prevent a decrease in throughput, Patent Document 1 proposes a technique of performing printing at an image formation speed of a full-color image having a slow image formation speed when performing mixed output of a monocolor image and a full-color image.

Patent Document 2 proposes a technique for determining the timing for switching the image forming speed from the first part of job contents or the contents of all image data. Patent Document 3 proposes a technique for determining whether to switch to a full-color image formation speed or a mono-color image formation speed from the print completion time or the number of continuous mono-color pages when switching from full-color printing to mono-color printing. Has been.
JP 2002-139878 A JP 2002-268500 A JP 2003-054080 A

  However, when double-sided printing is performed with print data in which the front side print mode and the back side print mode are different in an image forming apparatus in which the image formation speed in the mono color print mode and the image formation speed in the full color print mode are different, the following problems occur. appear.

  Here, description will be made assuming double-sided printing when print data is registered in the order of recording material ID1 (table: full color) → recording material ID2 (table: full color) → recording material ID1 (back: monocolor). To do. The state of the conveyance path of the image forming apparatus at that time is shown in FIG.

  First, image formation of ID1 (table: full color) is performed (B1). Then, the recording material passes through the fixing device and is conveyed to the double-sided conveyance path (C1, D1). In parallel with the reversing operation, the feeding operation of ID2 (table: full color) is started (D1). The ID1 recording material is conveyed through the double-sided conveyance path to the double-sided refeed standby position, and the ID2 recording material is image-formed (E1). The recording material of ID1 is scheduled to perform backside: monocolor image formation next in the order of reservation. However, since the image forming speed is different between full color and mono color, it is necessary to perform a speed switching operation such as shifting the scanner motor. Further, when the recording material on which image formation is performed is present in the image forming unit, the speed switching cannot be performed, and therefore the recording material of ID1 is waiting at the refeed standby position (F1 to H1). Even if the ID2 recording material passes through the fixing device and the image forming apparatus starts the speed switching, the ID1 recording material continues to stand by at the refeed standby position until the speed switching ends (I1). The recording material of ID2 also keeps waiting at the second standby position until the speed switching is completed (I1). After the speed switching is completed, the ID1 recording material is fed from the duplex conveyance path, and the ID2 recording material is conveyed to the refeed standby position (J1 to K1).

  As described in this example, since the speed switching control cannot be started until the ID2 recording material passes through the fixing device, the ID1 recording material must continue to stand by in the double-sided conveyance path, resulting in a decrease in throughput. It is clear that this is done. Further, since the ID2 recording material waits at the second sheet standby position until feeding of the ID1 recording material is started when the speed is switched, it takes a long time to expose a part of the recording material outside the apparatus. Therefore, there is a risk that the user pulls out the recording material, and there is a problem in operability.

  In this example, the image forming apparatus capable of waiting for two sheets of recording material on the duplex conveyance path has been described. However, an image forming apparatus that can wait for only one sheet of recording material in the double-sided conveyance path cannot wait for two sheets in the double-sided conveyance path when performing speed switching, and cannot switch the print mode during duplex printing. It will be.

  The present invention has been made under such circumstances, and in a color image forming apparatus having different image forming speeds in the printing mode, both the printing mode for the surface of the recording material and the printing mode for the back surface of the recording material are different. It is an object of the present invention to provide a color image forming apparatus capable of preventing a decrease in throughput for a printing case.

  In order to solve the above problems, in the present invention, a color image forming apparatus is configured as described in (1) below.

(1) Monocolor print data comprising image forming means capable of forming an image in the full color printing mode or the monocolor printing mode on the front and back surfaces of the recording material according to the printing data, and a control means for controlling the image forming means. In the color image forming apparatus, the second image forming speed when the full color printing is performed only according to the full color printing data is slower than the first image forming speed when the mono color printing is performed according to the above.
When the printing mode for the front surface of the recording material is different from the printing mode for the back surface of the recording material, the control unit forms an image on the surface designated for monocolor printing at the first or second image forming speed. A color image forming apparatus that determines whether to perform monochromatic printing at a determined image forming speed and performs image formation on a surface on which the monochrome printing is designated.

  According to the present invention, in an image forming apparatus having different image forming speeds in a printing mode, speed switching is limited for a case of duplex printing in which the printing mode for the front surface of the recording material and the printing mode for the back surface of the recording material are different. As a result, a decrease in throughput can be prevented. In addition, the time during which a part of the recording material is exposed outside the apparatus in the double-sided conveyance path can be reduced, leading to improvement in operability.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to an embodiment of a color image forming apparatus. The present invention is not limited to the form of the apparatus, and can be implemented in the form of a method supported by the description of the embodiments.

A “color image forming apparatus” that is Embodiment 1 will be described.
The present embodiment is an example relating to speed control during double-sided printing in which the front surface of the recording medium is designated as a full color printing mode and the back surface is designated as a monochrome printing mode.

First, the mechanism of the color image forming apparatus will be described.
In FIG. 1, the color image forming apparatus includes a main body 101, a cassette sheet supply unit 202b for storing a recording material 213, a multi-sheet supply tray 202a into which the recording material 213 is manually fed by a user, and a recording material 213 supplied to the main body 101. A sheet supply unit 219 for supplying from the unit 202b and the multi-sheet supply tray 202a, an image forming unit 218 for performing image processing, and the like are provided.

  In this color image forming apparatus, the image forming unit 218 uniformly distributes the surfaces of the four photosensitive drums 215a, 215b, 215c, and 215d corresponding to the respective colors of magenta, cyan, yellow, and black, and the photosensitive drums 215. Charging units 217a, 217b, 217c, and 217d for charging; optical units 117a, 117b, 117c, and 117d as exposure units that irradiate a laser beam to form an electrostatic latent image on the photosensitive drum 215; Developing devices 216 a, 216 b, 216 c, and 216 d that make toner images appear by attaching toner to the image, and transfer rollers 208 a and 208 b as transfer means for transferring the toner image on the photosensitive drum 215 to the recording material 213, 208c, 208d, etc. The charging device 217 and the developing device 216 are sequentially arranged around the photosensitive drum 215 in accordance with the rotation direction of the photosensitive drum 215.

  Here, the photosensitive drum 215, the charging device 217, and the developing device 216 are integrally formed as a cartridge to form process cartridges 206a, 206b, 206c, and 206d.

The recording material 213 supplied by the sheet supply unit 219 is conveyed from the upstream side (downward in the figure) to the downstream side (upward in the figure) in the recording material conveyance direction.
During this time, the recording material 213 is appropriately detected by the registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112 disposed in the conveyance path.

  Each image forming process of the image forming unit 218 operates in synchronization with the timing at which the recording material 213 is detected by each sensor, and the recording material 213 is processed in the order of magenta, cyan, yellow, and black by the process cartridge 206. The color toner images are sequentially superimposed and transferred to form a color image. The color toner image superimposed and transferred onto the recording material 213 is heated and pressurized by the fixing device 214 and melted and fixed on the surface of the recording material 213. Thereafter, the recording material 213 is discharged to the discharge tray 210.

  If an image is also formed on the other surface of the recording material 213, the paper discharge roller pair 209 is reversed in synchronization with the timing at which the rear end of the recording material 213 is detected by the paper discharge sensor 112. The recording material 213 is guided to the reverse path. The recording material 213 guided to the reversing path is transported in the reversing path by the reversing transport rollers 211a and 211b, and is transported to the image forming unit 218 again.

  A color toner image is formed on the opposite surface of the recording material 213 by the image forming unit 218, the color toner image is melted and fixed on the recording material 213 by the fixing device 214, and the recording material 213 is discharged to the discharge tray 210.

  Next, an image forming operation of the color image forming apparatus will be described. In this embodiment, the image forming mode includes a color printing mode for performing color printing and a monocolor printing mode for performing monochromatic printing of only one color.

  This type of image forming apparatus has a full-color print mode in which a full-color image is formed using four color toners and a mono-color print mode in which a mono-color image is formed using only Bk toner. In the printing mode, the developing roller 216 is brought into contact with the photosensitive drum 215, respectively.

  On the other hand, in the monocolor printing mode, only the developing roller 216d is brought into contact with the photosensitive drum 215d. Accordingly, when a monocolor image is formed, the rotation can be stopped without bringing the color developing rollers 216a, 216b, and 216c into contact with the photosensitive drums 215a, 215b, and 215c. Since the life of the developing device is governed by the number of rotations of the developing roller, stopping the rotation of the color developing rollers 216a, 216b, 216c shortens the life of the color developing device for forming a monocolor image. Can be prevented. Further, since the color developing rollers 216a, 216b, and 216c are separated from the photosensitive drums 215a, 215b, and 215c, it is not necessary to charge the photosensitive drums 215a, 215b, and 215c. In general, the surface of the photosensitive drum is scraped by electric discharge during charging. Therefore, in the mono color printing mode, the photosensitive drums 215a, 215b, and 215c can be extended while being rotated while being charged.

  The dominant item that determines the image forming speed of this type of image forming apparatus is the fixing property of the fixing device. In the monocolor printing mode, the amount of toner transferred to the recording material is larger than that in the full color printing mode. Therefore, the speed of the recording material passing through the fixing device can be increased. Therefore, taking advantage of this characteristic, as described above, the mono-color image forming speed is set higher than the full-color image forming speed.

FIG. 2 is a control block diagram of the color image forming apparatus of this embodiment.
The color image forming apparatus main body 101 is connected to the host computer 104 directly or via a network. The print data created by the host computer 104 is received by the controller 103 and converted into an image signal. The controller 103 inquires of the control unit 102 about the state, confirms that it is in a printable state, and then issues an instruction to start printing to the control unit 102. Upon receiving the print start instruction, the control unit 102 controls the transport control unit 105, the fixing device drive control unit 106, the optical units 117a, 117b, 117c, and 117d, the drum drive control unit 108, and the paper feed control unit 107 that are connected. To start printing such as activating each load.

  The conveyance control unit 105 controls the driving of the transfer rollers 208a, 208b, 208c, and 208d and the reverse conveyance rollers 211a and 211b by driving the conveyance motor 113.

  The fixing device drive control unit 106 controls the driving of the fixing device 214 and the discharge roller pair 209 by driving the fixing motor 114.

  The paper feed control unit 107 drives the paper feed motor 115 to control the drive of the paper feed pickup rollers 203 a and 203 b, the paper feed transport rollers 204 a and 204 b, and the registration roller 205.

  The drum drive control unit 108 controls the driving of the process cartridges 206a, 206b, 206c, and 206d by driving the drum motors 116a, 116b, 116c, and 116d.

  When the printing preparation is completed, the control unit 102 issues a paper feed instruction to the paper feed control unit 107, whereby the sheet supply unit 219 starts feeding the recording material 213. At this time, the control unit 102 changes to the image forming state and notifies the controller 103 that the image forming state has changed.

  When the registration sensor 110 detects the leading edge of the fed recording material 213, the control unit 102 sends a print start signal to the controller 103 after a predetermined time. The controller 103 that has received the print start signal outputs an image signal in synchronization with the print start signal.

  The image signal output from the controller 103 is modulated into an on / off signal of a laser beam by the optical unit 117 and exposed on the photosensitive drum 215.

  As the recording material 213 is conveyed along the conveyance path, the image forming unit 218 is controlled to form a color image on the recording material 213.

  When the image forming process is normally completed and the trailing edge of the recording material 213 is detected by the paper discharge sensor 112, the control unit 102 determines that the printing has been normally completed, and the image forming process is enabled again. Is notified to the controller 103.

  In addition, since the image formation speed is different between the full-color printing mode and the mono-color printing mode, when the image formation speed is switched after the print start signal for the previous print data, the control unit 102 sends the print start signal to the controller 103. Before sending the image, the clock frequency at the time of image formation is notified.

  FIG. 3 shows a print data pattern order at the time of duplex printing of a general image forming apparatus. Print data patterns at the time of duplex printing are roughly divided into two types shown in FIG. 3 as (1) and (2). (1) is a pattern in which the printing data of the front and back surfaces of one recording material are registered alternately. In the pattern (1), for example, when the recording material of ID1 has finished printing on the front surface and is transporting through the double-sided transport path, the image forming unit of the image forming apparatus does not contribute to image formation. Productivity is reduced. Therefore, normally, as shown in (2), the recording material is registered on the double-sided conveyance path by registering print data as ID1 (front) → ID2 (front) → ID1 (back) → ID3 (front). In this state, the pattern in which the image forming unit is activated is used.

  The difference in the conditions in which the print data order is set in the pattern (1) and the pattern (2) is due to the difference in the paper size limit that can be scheduled and the rendering processing (raster expansion processing of drawing objects) of the scheduling target page. This is due to the difference in time spent.

  In the color image forming apparatus of the present embodiment, in the double-sided printing in which the full-color printing mode and the mono-color printing mode have different image forming speeds, the recording material is double-sided in the pattern (1) even when the front and back side printing modes are different. Since the time for performing the speed switching operation is shorter than the time for transporting along the transport path, even if the speed switching is performed, the throughput is not reduced. However, the speed control described later is also applied to an image forming apparatus in which the time for performing the speed switching operation is shorter than the time during which the double-sided conveyance path is conveyed.

  FIG. 4 shows a conventional timing chart (no speed limitation) when double-sided printing data is registered according to the pattern (2) with the front side designated in full-color printing mode and the back side designated in mono-color printing mode. Show. Throughput switching operation is performed between ID2 (table: full color) → ID1 (back: monocolor), ID1 (back: monocolor) → ID3 (table: full color), and each print data, resulting in a significant decrease in throughput. Resulting in.

  Therefore, in this embodiment, when the print data is switched from ID2 (front: full color) to ID1 (back: monocolor), the next print data content of ID1 (back: monocolor) is printed at the full color image formation speed. Determine whether or not to do.

  A flowchart relating to this determination is shown in FIG. In FIG. 5, it is assumed that the back side mono-color page is designated for the target print data.

  As a first step T10, it is checked whether the target print data is a back monocolor page and the front page of the corresponding data is full color page print data. If it is not suitable, it is determined that the speed switching accompanying the printing mode switching from full color to mono color is performed. If this step T10 is met, the process proceeds to the next step T11. In the next step T11, it is determined whether or not the next print data of the back monochrome page is full color. If the next print data is full color, it is determined that the downtime associated with speed switching is large, the speed switching is omitted, it is determined that the back side monocolor should be formed at full color speed, and the back side page is full color. It is set to carry at the image forming speed (T12). If the next print data is monochrome, it is determined that the downtime is smaller when the speed is switched, and the speed is switched as usual. If it is determined in steps T10 and T11 that the speed is switched, the process proceeds to step T15 and the speed is switched. After T12 and T15 are completed, a process (T13) related to a printing mode change such as development, charging, and other high voltage application is performed for full color image formation. Then, the back side sheet feeding operation is started (T14).

  In summary, if the next print data is full-color printing, it is determined that printing is performed at the full-color image formation speed to improve the throughput, and only the print mode is switched, and the speed is not switched. Continue. If the next print data is print data for monochrome printing, it is determined to switch the speed as usual. FIG. 6 shows a timing chart when the same image forming process as that in FIG. 4 is executed according to the present embodiment without switching the speed. It can be seen from FIG. 4 that the throughput is improved.

  FIG. 7 shows an exchange sequence between the engine (corresponding to the control unit 102 in FIG. 2) and the controller 103 when it is determined not to execute speed switching from full color to mono color. The engine receives a full-color print mode print reservation and paper feed start instruction from the controller (s32, s33). This print reservation corresponds to ID2 (table: full color) s21 in FIG. Next, the engine starts conveying the recording material and notifies the controller of a print start signal at a predetermined timing (s33). Upon receiving the print start signal, the controller transfers image data corresponding to the print data to the engine (s34), and an image is formed on the recording material. During this image formation, the controller transmits a monochrome print mode print reservation (s35) and a paper feed start instruction to the engine as the next print data (s36). Here, the engine determines the conveyance speed according to the above procedure. Here, if it is determined that full-color image formation is performed at the image formation speed in the full-color print mode, the engine next determines that the controller performs image formation at the image formation speed in the full-color print mode. In order to notify, the image clock in the next print data is notified (s39). Then, paper feeding is started, and a print start signal is notified as in the case of the preprint data (s40).

  The above is the embodiment of this example. By adopting this embodiment, it is possible to reduce the downtime from the full-color printing mode to the mono-color printing mode, and to prevent a decrease in throughput.

  A “color image forming apparatus” that is Embodiment 2 will be described. In this embodiment, an example of speed control at the time of double-sided printing in which the front surface of the recording material is designated as a monochrome printing mode and the rear surface is designated as a full-color printing mode will be described.

  Since the configuration of the color image forming apparatus of the present embodiment is almost the same as that of the first embodiment, description of common parts is omitted.

  FIG. 8 shows a conventional timing chart when printing data for double-sided printing is registered with the front side designated as a mono-color printing mode and the back side designated as a full-color printing mode. Since the speed switching operation is executed between ID2 (front: monocolor) → ID1 (back: full color),... And each print data, the throughput is significantly reduced.

  Therefore, in this embodiment, before the start of image formation of ID1 (table: monocolor), if the back side print mode is different from the front side and is recognized as the full color print mode, ID1 (table: monocolor) is recognized. It is determined that printing should be performed at a full color image forming speed.

A flowchart regarding this determination is shown in FIG.
In a first step T20, it is determined whether the front side print data is a monochromatic page. If not, the driving is started at the monochromatic image forming speed (T25). If it matches, the process proceeds to the next step T21. In the next step T21, it is determined whether the back side print data is already known at this point and the back side print data is in the full-color print mode. If not, the driving is started at the monochromatic image forming speed (T25). If the back page is full color, speed switching will be sandwiched, it will be determined that downtime is large, and in order to omit speed switching, it will be determined that the front mono color should be imaged at full color speed, It is set that the front monochrome page is conveyed in full color at the image forming speed (T22). Then, as set, driving is started at the full-color image forming speed (T23). After T23 and T25 are finished, the front side sheet feeding operation is started (T24).

  FIG. 10 shows a timing chart when it is determined that the speed switching is not performed according to the present embodiment in the case of FIG. It can be seen from FIG. 8 that the throughput is improved.

  FIG. 11 shows an exchange sequence between the engine and the controller when it is determined that image formation is performed at the full-color image formation speed according to the information on the back surface. Mono-color print mode print reservation (front), mono-color print mode print reservation (front), full-color print mode print reservation (back), and a paper feed start instruction are received (s74, s62, s63, s64). At this point, the color printing mode on the front and back sides of the first recording material is different and the back side is in full-color printing mode, so it is determined that mono-color printing data on the front side is to be imaged at full-color image formation speed. Then, the driving is started at the full-color image forming speed (s65).

  Next, since the engine is different from the designated image forming speed, the engine notifies the image clock (s66). Next, the recording material conveyance is started, and a printing start signal / TOP is notified to the controller at a predetermined timing (s67). When receiving the / TOP, the controller transfers the image data corresponding to the print data to the engine (s69), and an image is formed on the recording material.

  The above is the embodiment of the second embodiment. By adopting this embodiment, when it has been found that the print mode is switched from the mono color to the full color, the mono color print mode is executed by executing the image formation in the mono color print mode at the full color image forming speed. Can reduce downtime from full-color printing mode to prevent a drop in throughput.

  A “color image forming apparatus” that is Embodiment 3 will be described. In the present embodiment, an example will be described in which whether or not the speed is switched is determined from the contents of the subsequent print data during double-sided printing in which the front side of the recording material is designated as a full color printing mode and the back side is designated as a monochromatic printing mode.

  Since the configuration of the color image forming apparatus of the present embodiment is almost the same as that of the first embodiment, description of common parts is omitted.

  FIG. 12 shows a conventional timing chart when double-sided printing data is registered. Since the speed switching operation is executed between each printing mode of ID2 (front: full color) → ID1 (back: monochromatic),..., The throughput is significantly reduced.

  Therefore, in this embodiment, when the print data is switched from ID2 (table: full color) to ID1 (back: monocolor), the image forming apparatus determines a full color image from the next print data content of ID1 (back: monocolor). It is determined whether printing should be performed at the formation speed.

  A flowchart regarding this determination is shown in FIG. In FIG. 13, the target print data is designated as a monochrome page on the back side.

  As a first step T30, it is checked whether the back side is a monochromatic page and the front page of the corresponding data is print data of a full color page. If it is not suitable, it is determined that the speed switching accompanying the printing mode switching from full color to mono color is performed. If this step T30 is met, the process proceeds to the next step T31. In the next step T31, the print data that follows the mono-color page on the back side is referred to, and the number of continuous mono-color pages until the full-color print data appears after the mono-color page is counted. Next, at T32, it is determined whether or not the number of continuous monochromatic pages calculated at T31 is greater than a predetermined value. If the number of continuous monochromatic pages is smaller than the predetermined number, it is determined that the downtime associated with speed switching is large, speed switching should be omitted, and continuous pages from the back monocolor should be formed at full color speed. Judgment is made and it is set to transport the back page at the full-color image forming speed (T32). When the number of continuous monochromatic pages is larger than the predetermined number, it is determined that the speed switching is performed with a smaller downtime, and it is determined that the speed switching is performed as usual. If it is determined in steps T30 and T32 that speed switching is performed, the process proceeds to step T36, and speed switching is performed. After the processing of T33 and T36 is completed, processing (T34) such as development, charging, and other high voltage application is performed for full color image formation. Then, the back side sheet feeding operation is started (T35).

  FIG. 14 shows a timing chart in the case where the same print mode and print data as shown in FIG. It can be seen from FIG. 12 that the throughput is improved.

  The predetermined value to be compared with the continuous number of monochromatic pages is set to an optimum value from parameters such as the image forming speed of the image forming apparatus and the switching time of the image forming speed. Alternatively, the predetermined number may be set from an external device such as a host computer.

  FIG. 15 shows an exchange sequence between the engine and the controller when it is determined not to execute speed switching from full color to mono color. The engine receives full color print mode reservation, mono color print mode reservation, mono color print mode reservation, mono color print mode reservation, full color print mode reservation, and feed start instruction from the controller (s102, s103, s104, s105, s107). .

  Here, the engine determines the conveyance speed according to the above procedure (s108). Here, it is determined that full-color image formation is performed at the image formation speed in the full-color print mode, and then the engine notifies the controller that image formation is performed at the image formation speed in the full-color print mode. Therefore, the image clock in the next print data is notified.

  Next, the engine starts recording material conveyance (s109), and notifies the controller of a print start signal / TOP at a predetermined timing. Upon receiving the print start signal, the controller transfers image data corresponding to the print data to the engine (s110), and an image is formed on the recording material. During this image formation, the controller transmits a paper feed start instruction (s111).

  The above is the embodiment of the third embodiment. By adopting this embodiment, it becomes possible to make more efficient determination, the downtime from the full-color printing mode to the mono-color printing mode can be reduced, and a reduction in throughput can be prevented.

  A “color image forming apparatus” that is Embodiment 4 will be described. In the present embodiment, an example will be described in which whether or not the speed is switched is determined from the number of recording materials waiting on both sides during double-sided printing in which the front surface of the recording material is designated as a full color printing mode and the back surface is designated as a monochromatic printing mode.

  Since the configuration of the color image forming apparatus of the present embodiment is almost the same as that of the first embodiment, description of common parts is omitted.

  As described with reference to FIG. 16 in the disclosure of the invention, the print data of the front side print mode and the back side print mode are different in the image forming apparatus in which the image forming speed in the mono color printing mode and the image forming speed in the full color printing mode are different. When double-sided printing is performed, the recording material must continue to wait in the double-sided conveyance path until the speed switching is completed, and throughput is reduced. Further, the recording material waits at the second standby position in the double-sided conveyance path, and a part of the recording material is exposed outside the apparatus.

  Due to the drive configuration of the duplex conveying section of the color image forming apparatus, an image forming apparatus that can wait for only one recording material in the duplex conveying path cannot wait for two sheets in the duplex conveying path when performing speed switching. This means that the print mode cannot be switched during duplex printing.

  Therefore, in this embodiment, the color image forming apparatus waits in the double-sided conveyance path by switching data when switching the print data of ID2 (front: full color) → ID1 (back: monocolor). The number of recording materials is calculated, and it is determined from the calculated number whether or not printing should be performed at the full color image forming speed.

  A flowchart relating to this determination is shown in FIG. In FIG. 17, the target print data is designated as a monochrome page on the back side.

  In a first step T40, it is checked whether the back side is a monochromatic page and the front page of the corresponding data is print data of a full color page. If it is not suitable, it is determined that the speed switching accompanying the printing mode switching from full color to mono color is performed. If this step T40 is met, the process proceeds to the next step T41. In the next step T41, when the speed switching associated with the monochrome page on the back side is executed, the number of recording materials waiting in the duplex conveyance path is counted at the speed switching end timing. Next, at T42, it is determined whether the standby number of recording materials in the double-sided conveyance path calculated at T41 is larger than a predetermined value. If the number is smaller than the predetermined number, the speed switching is omitted, it is determined that the continuous page from the back monocolor should be image-formed at the full-color speed, and the back-side page is set to be conveyed at the full-color image forming speed (T42). ). When the standby number of recording materials is larger than the predetermined number, it is determined that the speed is switched as usual. If it is determined in steps T40 and T42 that the speed is switched, the process proceeds to step T46, and the speed is switched. After the processing of T43 and T46 is completed, processing (T44) such as development, charging, and other high voltage application is performed for full color image formation. Then, the back side sheet feeding operation is started (T45).

  The predetermined value to be compared with the standby number of recording materials in the duplex conveyance path is set to an optimum value from the parameters of the drive configuration of the image forming apparatus.

  The above is the embodiment of the fourth embodiment. By adopting this embodiment, in a color image forming apparatus in which the number of standby sheets is limited by the configuration of the double-sided conveyance unit, it is possible to execute switching from full color to monocolor without any problem in conveying the recording material.

1 is a diagram illustrating a schematic configuration of a color image forming apparatus that is Embodiment 1. FIG. Control block diagram in the first embodiment Diagram explaining the registration order of print data for duplex printing Timing chart when speed limit is not performed according to the first embodiment The flowchart which shows the process of Example 1. Timing chart in the case of speed limitation according to the first embodiment Sequence diagram of controller and control unit for speed limit according to embodiment 1 Timing chart when speed limit is not performed according to the second embodiment The flowchart which shows the process of Example 2. Timing chart in case of speed limitation according to embodiment 2 Sequence diagram of controller and control unit for speed limit according to embodiment 2 Timing chart when speed limit is not performed according to the third embodiment The flowchart which shows the process of Example 3. Timing chart in case of speed limitation according to embodiment 3 Sequence diagram of controller and control unit for speed limitation according to embodiment 3 Diagram showing how the recording material is conveyed during duplex printing with speed switching The flowchart which shows the process of Example 4.

Explanation of symbols

102 control unit 103 controller 218 image forming unit

Claims (7)

An image forming unit capable of forming an image in the full color printing mode or the mono color printing mode on the front and back surfaces of the recording material according to the print data, and a control unit for controlling the image forming unit. In a color image forming apparatus in which the second image forming speed when performing full color printing according to only the full color printing data is slower than the first image forming speed when performing color printing.
When the printing mode for the front surface of the recording material is different from the printing mode for the back surface of the recording material, the control unit forms an image on the surface designated for monocolor printing at the first or second image forming speed. A color image forming apparatus that determines whether to perform monochromatic printing at a determined image forming speed and performs image formation on a surface for which mono-color printing is designated. The color image forming apparatus according to claim 1.
When the designated print mode for the front surface of the recording material is a full-color print mode and the designated print mode for the back surface of the recording material is a monocolor print mode, the control means performs an image on the back surface before forming the back surface image of the recording material. A color image forming apparatus that judges whether or not to form an image at the second image forming speed. The color image forming apparatus according to claim 1.
In the case where it is found that the designated printing mode for the front surface of the recording material is a monocolor printing mode and the designated printing mode for the back surface of the recording material is a full color mode before the surface image of the recording material is formed. In addition, the color image forming apparatus is characterized in that the image forming speed on the surface is controlled to form an image at the second image forming speed. The color image forming apparatus according to claim 1.
The control means calculates the number of printing surfaces in a continuous monocolor printing mode from the printing surface designated by the monocolor printing mode, which is a target for determining whether the image is formed at the first or second image forming speed. When the calculated number of printing surfaces is equal to or less than a predetermined number, the color image forming apparatus determines that the target mono color print mode print data is formed at the second image forming speed. The color image forming apparatus according to claim 4.
The color image forming apparatus, wherein the predetermined number can be set from outside the color image forming apparatus. An image forming unit capable of forming an image in the full color printing mode or the mono color printing mode on the front and back surfaces of the recording material according to the print data, and a control unit for controlling the image forming unit. An image forming method in a color image forming apparatus in which a second image forming speed is lower when full color printing is performed only in accordance with full color print data than a first image forming speed when performing color printing,
Print data indicating whether the first or second image forming speed is used to form an image on the surface designated for mono-color printing when the printing mode for the front surface of the recording material is different from the printing mode for the back surface of the recording material. And forming an image on the surface on which the mono-color printing is designated at the determined image forming speed. The color image forming apparatus according to claim 1.
Switching the print mode from the front full color print mode to the back mono color print mode Before the image formation of the print data in the mono color print mode, the speed is switched from the second image forming speed to the first image forming speed. When doing
A calculating means for calculating the number of recording materials to be waiting in the double-sided conveyance path at the end of the speed switching;
The control means calculates the recording material standby number in the double-sided conveyance path at the time of speed switching by the calculation means, and when the calculation result is equal to or less than a predetermined value,
A color image forming apparatus, wherein it is determined that the print data in the mono color print mode should be formed at the second image forming speed.

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