JP2005111770A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an improvement in productivity compatible with a reduction in mechanical deterioration by controlling switching timing from a color printing mode to a black-and-white printing mode, in a tandem color image forming apparatus capable of doing the black-and-white printing in the color printing mode. <P>SOLUTION: While image data is received in the present color printing mode, in the case where the next page to be printed is a black-and-white image and where the number of continuous black-and-white images up to the present is a reference number or above, it is predicted that the black-and-white image continues from this time, so that switching to the black-and-white printing mode can be performed. After the reception of the image data is completed in the present color printing mode, the switching to the black-and-white printing mode is performed when the number of the black-and-white images, which prove to be continued from this time, is a second reference number or above. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing and a monochrome printing mode capable of monochrome printing only.

  A color image forming apparatus such as a color copier or a color printer forms a color image by superimposing yellow (Y), magenta (M), cyan (C), and black (K) images. Yes. For example, in a tandem color image forming apparatus using an electrophotographic process, image forming units including a photosensitive drum, a charging device, a scanning optical device, a developing device, and the like are prepared for each of Y, M, C, and K colors. These are arranged along an endless belt-like intermediate transfer belt, and a color image is formed by superimposing images of the respective colors on the circulating intermediate transfer belt. Since the length of the intermediate transfer belt extends over a plurality of pages, the image forming operation for a plurality of pages is performed in parallel during continuous printing.

  Such a color image forming apparatus has a color printing mode for executing color printing and a monochrome printing mode for executing monochrome printing, and these printing modes are switched according to the type of image. In the monochrome printing mode, only monochrome printing is possible, but in the color printing mode, monochrome printing is possible by using only K colors.

  When switching from the color printing mode to the black and white printing mode, the Y, M, and C color photosensitive drums are separated from the intermediate transfer belt and the detachment operation is performed to stop the rotation thereof. When switching from the black-and-white printing mode to the color printing mode, the rotation of the Y, M, and C photoconductor drums is resumed, and the advancing work is performed such that these advancing toward the intermediate transfer belt. The above-described operation is performed after the image forming process and the transfer process to the transfer paper of all pages that are proceeding in parallel on the intermediate transfer belt are completed.

  Since the above operations are involved, it takes a long time to switch the print mode. For this reason, if the print mode is switched each time depending on whether the image is color or black and white, the productivity of image formation is reduced. On the other hand, if black and white printing is performed in the color printing mode without switching the printing mode, the photosensitive drum, intermediate transfer belt, and developer of unused colors are deteriorated, and the mechanical life is shortened.

  Therefore, a color image forming apparatus has been proposed in which the timing for switching from the color printing mode to the black and white printing mode is determined according to the printing status so as to reduce mechanical deterioration while improving productivity. For example, when the number of continuous black and white images up to a certain point has reached a certain level, it is determined that there is a high probability that black and white images will continue thereafter, and the color print mode is switched to the black and white print mode (for example, patents). Reference 1). Further, there is a configuration in which the color printing mode is switched to the monochrome printing mode when the number of continuous monochrome images in the future is equal to or greater than a certain value (see, for example, Patent Document 2).

JP 2001-305818 A Japanese Patent Laid-Open No. 11-34438

  If the switching determination from the color printing mode to the monochrome printing mode is performed based on only the continuous number of monochrome images up to the present time, the determination of the switching time may be delayed. For example, if the above criterion is used until a page to be printed in the future is already known as a color image or a black and white image, the switching time is unnecessarily delayed.

  On the other hand, in the case of determining the timing for switching from the color printing mode to the monochrome printing mode based on only the continuous number of monochrome images in the future, a printing operation is performed in which printing is advanced one after another from the page where image data has been captured. In some cases, there is a problem that an appropriate switching time is missed.

  The present invention aims to solve the above problem, and in a color image forming apparatus capable of black and white printing in a color printing mode, the timing for switching from the color printing mode to the black and white printing mode is controlled. The purpose of this is to achieve both the improvement of property and the reduction of mechanical deterioration.

The invention according to claim 1 is a color image forming apparatus provided with a color printing mode capable of both color printing and monochrome printing and a monochrome printing mode capable of monochrome printing only as a printing mode.
A print mode determining means (103) for determining whether the print mode is a color print mode or a monochrome print mode;
A print mode switching means (46) for switching the print mode according to the determination of the print mode determination means (103);
An image memory (112) for storing image data to be printed;
In the case of printing a plurality of copies, print control means (101) for storing one part of image data in the image memory (112) and performing at least the second and subsequent copies by reading the image data from the image memory (112). When,
Determination means (102) for determining whether the image data input to the image memory (112) is a color image to be printed in color or a monochrome image to be printed in black and white;
The print mode determining means (103) is a continuous print until the present page is a monochrome image when the current print mode is the color print mode and the image data is being taken into the image memory (112). When the number of monochrome images being processed is equal to or greater than the first reference number, switching from the color printing mode to the monochrome printing mode is determined, the current printing mode is the color printing mode, and the image memory (112) for image data After completion of the capture, the color image forming apparatus is characterized in that switching from the color printing mode to the monochrome printing mode is determined when the number of continuous monochrome images is equal to or greater than the second reference number in the future.

  According to the above invention, during the capture of the image data, the timing for switching from the color print mode to the monochrome print mode is determined based on the number of monochrome images that have been continuously printed up to now, and after the capture of the image data is completed, The timing for switching from the color printing mode to the monochrome printing mode is determined based on the number of continuous monochrome images in the future. When printing is proceeding one after another from the page that has been captured during the capture of the image data, it is not known whether the future page is color or black and white. Therefore, if the number of continuous black and white images up to the current time is equal to or greater than the first reference number, it is determined that there is a high probability that black and white images will continue thereafter, and switching to the black and white printing mode is determined. On the other hand, when the capture of the image data has already been completed as in the case of printing the second copy of a plurality of copies, it is possible to grasp how many pages of monochrome images will continue in the future. Therefore, the switching to the monochrome printing mode is determined at an early stage by determining the switching to the monochrome printing mode based on the continuous number of monochrome images in the future.

  In this way, the judgment criteria for switching from the color printing mode to the monochrome printing mode are different between the reception of the image data and the completion of the reception of the image data. To switch to the monochrome printing mode.

The invention according to claim 2 is a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing and a monochrome printing mode capable of monochrome printing only as a printing mode.
A print mode determining means (103) for determining whether the print mode is a color print mode or a monochrome print mode;
A print mode switching means (46) for switching the print mode according to the determination of the print mode determination means (103);
Determining means (102) for determining whether the image data to be printed is a color image to be printed in color or a monochrome image to be printed in black and white;
The print mode determining means (103) knows that the current print mode is the color print mode and the next page is a black and white image based on the determination result of the determination means (102) and the subsequent appearance of the color image When the time is unknown, when the number of monochrome images continuously printed up to now is equal to or more than the first reference number, it is determined to switch from the color printing mode to the monochrome printing mode, and the current printing mode is the color printing mode. If the appearance time of the next color image is known on the basis of the determination result of the determination means (102), the monochrome printing is started from the color printing mode when the number of continuous monochrome images is equal to or greater than the second reference number. A color image forming apparatus characterized by determining switching to a mode.

  According to the above invention, when the appearance time of the next color image is not known, switching from the color print mode to the black and white print mode is determined based on the number of black and white images that have been continuously printed until now, and the next color image is determined. When the appearance time of the image is known, switching from the color printing mode to the monochrome printing mode is determined based on the number of continuous monochrome images in the future. In the case where several pages of image data are read ahead of the page currently being printed, the appearance time of the next color image may be found during the reception of the image data. If the appearance time of the next color image is known, the continuity of black and white images is determined up to that page. Therefore, black and white printing can be performed even during reception of image data by using the determined continuous number of black and white images as a reference. Switching to the mode can be determined early.

According to a third aspect of the present invention, there is provided a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing and a monochrome printing mode capable of monochrome printing only as a printing mode.
A print mode determining means (103) for determining whether the print mode is a color print mode or a monochrome print mode;
A print mode switching means (46) for switching the print mode according to the determination of the print mode determination means (103);
Determination means (102) for determining whether the image data to be printed is a color image to be printed in color or a monochrome image to be printed in black and white;
The print mode determining means (103) knows that the current print mode is the color print mode and the next page is a black and white image based on the determination result of the determination means (102) and the subsequent appearance of the color image When the time is unknown, the color print mode is changed to black and white when the total number of black and white images that have been continuously printed up to now and the number of black and white images that are known to be continuous in the future is equal to or greater than the first reference number. When it is decided to switch to the print mode and the current print mode is the color print mode and the appearance time of the next color image is known on the basis of the determination result of the determination means (102), In the color image forming apparatus, the switching from the color printing mode to the monochrome printing mode is determined when the number of sheets is equal to or more than the second reference number.

  According to the above invention, when the appearance time of the next color image is unknown, the total number of black and white images that have been continuously printed up to now and the number of black and white images that have been found to be continuous in the future is used as a reference. Switching from the color printing mode to the monochrome printing mode is determined. If the image data can be prefetched from the page currently being printed, it is determined whether or not the prefetched page is a monochrome image even during reception of the image data. Therefore, the decision to switch to the monochrome printing mode is made at an earlier stage by making a judgment based on the total number of monochrome images that have been continuously printed up to now and the number of monochrome images that are known to be continuous in the future. can do.

The invention according to claim 4 is the color image forming apparatus according to claim 1, 2 or 3, wherein the first reference number and the second reference number can be set independently.

  The configuration may be such that the user can change the setting of each reference number, or may be configured to be automatically set on the apparatus side. Even if both the first reference number and the second reference number can be changed, only one of them can be changed. For example, the tendency of the mixed state of color images and black and white images may be grasped from the print history, and the first reference number of sheets may be set automatically or manually based on this tendency.

According to a fifth aspect of the present invention, when the print mode determining means (103) finds that the current print mode is the color print mode and the monochrome image continues from the next page to the last page of the current print job. 5. The color image forming apparatus according to claim 1, wherein switching from the color printing mode to the monochrome printing mode is determined when the continuous number is equal to or greater than the third reference number. .

  According to the above invention, when it is found that the monochrome image continues from the next page to the final page of the current printing operation, it is determined to switch to the monochrome printing mode based on the third reference number. When the condition that the black and white image continues until the end of the printing operation is determined, the optimum reference number of sheets is set under the condition, so that a fine response corresponding to the printing situation becomes possible. For example, the third reference number of sheets is set without taking into account the mechanical deterioration when returning to the color printing mode.

In the invention according to claim 6, the magnitude of the mechanical deterioration caused by printing n (n is a positive integer) number of black and white images in the color print mode is caused by changing from the color print mode to the black and white print mode. Each reference number of sheets is set to a minimum number n or more within a range that is equal to or greater than the sum of the magnitude of mechanical deterioration and the magnitude of mechanical deterioration caused by changing from the monochrome printing mode to the color printing mode. A color image forming apparatus according to claim 1, 2, 3, 4 or 5.

  According to the above invention, the reference number of sheets is set within a range in which mechanical deterioration is less when the mode is switched to the monochrome printing mode. For example, the second reference number is compared with the number of black and white images that are known to be continuous in the future, so that switching to the black and white printing mode is performed only when it is clear that the mechanical deterioration is reduced. As described above, the second reference number may be set.

  According to the color image forming apparatus of the present invention, during the capture of the image data, the timing for switching from the color printing mode to the monochrome printing mode is determined based on the number of monochrome images that have been continuously printed up to now, and the image data After the completion of capturing, the timing for switching from the color printing mode to the monochrome printing mode is determined based on the number of continuous monochrome images. As a result, the color print mode is switched to the black and white print mode at an appropriate time at any time regardless of the state of capturing the image data, and it is possible to efficiently improve productivity and reduce mechanical deterioration.

  Also, if you do not know when the next color image appears, determine whether to switch from the color print mode to the monochrome print mode based on the number of monochrome images that have been continuously printed up to now, and the next color image appears Is determined, switching from the color printing mode to the monochrome printing mode is determined based on the number of continuous monochrome images in the future. Thereby, even when image data is being received, if there is a pre-read color page, it is possible to determine whether or not it is possible to switch to the monochrome printing mode at an earlier time.

  Furthermore, when the next color image appearance time is unknown, the color printing mode is based on the total number of black and white images that have been continuously printed up to now and the number of black and white images that have been found to be continuous in the future. To switch to the monochrome printing mode. As a result, even when the image data is being received, the pre-read black and white page is included in the determination, so that switching to the black and white printing mode can be determined at an earlier time.

  If the reference number for determining whether to switch to the monochrome printing mode can be set independently for each determination method, an optimum reference number can be set according to each determination method and the printing mode of the user.

  If the standard number of black and white images is found to be continuous from the next page to the final page of the current print job, the standard number of prints can be set independently of the other standard number. By independently setting the reference number of sheets in consideration of the special condition of termination, a fine response according to the printing situation becomes possible.

  In the case of setting the reference number of sheets within a range in which mechanical deterioration is less when switching to the monochrome printing mode, the significance of switching to the monochrome printing mode is ensured. In other words, since switching the printing mode always causes a decrease in productivity, the purpose of satisfying both the improvement of productivity and the reduction of mechanical deterioration by satisfying the condition that the mechanical deterioration is smaller than the case without switching. Is achieved.

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

  FIG. 2 shows a cross-sectional configuration of the color image forming apparatus 10 according to the embodiment of the present invention. The color image forming apparatus 10 is an apparatus called a color digital copying machine. The color image forming apparatus 10 includes an automatic document feeder 20, a reading unit 30, and a printer unit 40. The automatic document feeder 20 has a function of feeding the originals 2 stacked on the original placement tray 21 one by one to the reading portion of the reading unit 30 and discharging the read originals to the paper discharge tray 27. A double-sided document has a function of reversing the front and back and sending it to the reading unit 30 again after single-sided scanning.

  The automatic document feeder 20 includes a paper feed roller 22 that sequentially feeds the documents stacked on the document placing tray 21 from the top, and a contact roller for allowing the document to pass while contacting the contact glass 31 that is a document reading position. 23 and a guide roller 24 for guiding the original fed by the paper feed roller 22 along the contact roller 23. Further, a switching claw 25 for switching the advancing direction of the document that has passed through the contact glass 31, a reversing roller 26 for reversing the front and back of the double-sided document, and a paper discharge tray 27 for discharging the document that has been read are provided. Yes.

  The reading unit 30 has a function of reading a document in color. The reading unit 30 includes an exposure scanning unit 35 including a light source 33 and a mirror 34, a color line image sensor 36 that receives reflected light from a document and outputs an electrical signal corresponding to the light intensity, and a document. A condenser lens 37 that condenses the reflected light from the line image sensor 36, and various mirrors 38 that form an optical path for guiding the reflected light from the mirror 34 of the exposure scanning unit 35 to the line image sensor 36. ing.

  When reading a document fed by the automatic document feeder 20, the exposure scanning unit 35 moves to a reading position below the contact glass 31, stops, and reads a moving document conveyed by the contact roller 23 thereon. It is like that. When reading a document placed on the platen glass 32, the exposure scanning unit 35 moves from left to right along the lower surface of the platen glass 32 to read a stationary document.

  The printer unit 40 is referred to as a tandem color image forming apparatus, and includes an endless belt-shaped intermediate transfer belt 41 and a plurality of image forming units 50Y that form single-color images on the intermediate transfer belt 41, respectively. 50M, 50C, and 50K, a paper feeding unit 70 that feeds transfer paper, a transport unit 80 that transports the fed transfer paper, and a fixing device 42 are provided.

  The image forming unit 50Y forms a yellow (Y) color image on the intermediate transfer belt 41, and the image forming unit 50M forms a magenta (M) color image on the intermediate transfer belt 41. The image forming unit 50 </ b> C forms a cyan (C) color image on the intermediate transfer belt 41, and the image forming unit 50 </ b> K forms a black (K) color image on the intermediate transfer belt 41.

  The image forming unit 50Y includes a photosensitive drum 51Y as a cylindrical electrostatic latent image carrier on which an electrostatic latent image is formed, a charging device 52Y disposed around the photosensitive drum 51Y, a developing device 53Y, and a cleaning device. Device 54Y. In addition, a laser unit 55Y including a laser diode, a polygon mirror, various lenses, a mirror, and the like is provided.

  The photosensitive drum 51Y is driven by a drive unit (not shown) and rotates in a certain direction (the direction of arrow A in the figure), and the charging device 52Y uniformly charges the photosensitive drum 51Y. The laser unit 55Y functions to repeatedly scan the surface of the photosensitive drum 51Y with the laser light in the width direction (main scanning direction) by reflecting the laser light emitted from the laser diode with a rotating polygon mirror. An electrostatic latent image is formed on the photosensitive drum 51Y by scanning the uniformly charged surface of the photosensitive drum 51Y with a laser beam that is turned ON / OFF according to yellow image data. The developing device 50Y visualizes the electrostatic latent image on the photosensitive drum 51Y with yellow toner. The toner image formed on the surface of the photosensitive drum 51 </ b> Y is transferred to the intermediate transfer belt 41 at a location where it contacts the intermediate transfer belt 41. The cleaning device 54Y functions to remove and collect the toner remaining on the surface of the photosensitive drum 51Y after the transfer by rubbing with a blade or the like.

  The image forming unit 50M, the image forming unit 50C, and the image forming unit 50K are different from each other in the color of the toner and the image forming unit 50Y except that the laser light is turned on / off with the image data corresponding to each color. The description is omitted here. Note that the same constituent elements have the same numerals and are denoted by M, C, and K instead of the subscript Y.

  The intermediate transfer belt 41 is rotatably supported by winding a plurality of rollers. The intermediate transfer belt 41 circulates in a direction indicated by an arrow B by a driving unit (not shown). In the course of rotation, images of the respective colors are formed on the intermediate transfer belt 41 in the order of (Y), (M), (C), and (K) by the image forming units 50Y, 50M, 50C, and 50K to form a color image. Is synthesized. This color image is transferred from the intermediate transfer belt 41 to the transfer paper at the secondary transfer location C provided at the lower end of the circulation path of the intermediate transfer belt 41. The toner remaining on the intermediate transfer belt 41 after the transfer is removed by the cleaning device 44.

  The paper feed means 70 has a plurality of paper feed cassettes 71 and normally accommodates transfer papers of different sizes and paper types. The transfer paper accommodated in each paper feed cassette 71 is sent out one by one from the top to the conveying means 80 by the first paper feed roller 72. The conveying unit 80 passes the secondary transfer point C and the fixing device 42 through the secondary transfer portion C and the fixing device 42 and discharges the transfer paper from the paper feeding cassette 71 to the discharge tray outside the apparatus, and the transfer paper passing through the fixing device 42. After reversing the display, the reversing path 80b is formed upstream of the secondary transfer location C and joined again to the normal path 80a. Each of the paths 80a and 80b has a large number of conveying rollers 81 at an interval shorter than the transfer direction size of the minimum size transfer paper.

  The color image forming apparatus 10 includes a color printing mode in which both color printing and monochrome printing are possible and a monochrome printing mode in which only monochrome printing is possible. In the monochrome printing mode, the Y, M, and C photoconductor drums 51Y, 51M, and 51C are separated from the intermediate transfer belt 41, and only the K photoconductor drum 51K is in contact with the intermediate transfer belt 41 to form an image. It has become. When black and white printing is executed in the color printing mode, only the K color is formed while keeping all the photosensitive drums 51Y, 51M, 51C, and 51K at the same positions as when performing color printing.

  When switching from the color printing mode to the monochrome printing mode, the Y, M, and C photoconductor drums 51Y, 51M, and 51C are separated from the intermediate transfer belt 41, and the detachment operation is performed to stop the rotation thereof. This separation operation is performed after completion of image formation and transfer onto the transfer paper relating to all pages proceeding in parallel on the intermediate transfer belt 41. When switching from the monochrome printing mode to the color printing mode, the rotation of the Y, M, and C photoconductor drums 51Y, 51M, and 51C is resumed, and the advancing work for advancing them to the intermediate transfer belt 41 and bringing them into contact with each other is performed. Done.

  FIG. 3 shows a schematic electrical configuration of the color image forming apparatus 10. The color image forming apparatus 10 includes a control unit 100 that performs overall control of the operation of the apparatus. The control means 100 is composed of a circuit having a CPU (Central Processing Unit), ROM (Read Only Memory) and RAM (Random Access Memory) as main parts. Various devices in addition to the automatic document feeder 20, the reading unit 30, and the printer unit 40 are connected to the control unit 100 through a bus. Among these, the print controller 111 performs a function of receiving print data from an external device such as a personal computer and expanding the received data into image data.

  The image memory 112 has a function of storing image data corresponding to a document read by the reading unit 30 and image data developed by the print controller 111. When printing a plurality of copies, at least one portion of image data is stored. As the image memory 112, a large-capacity auxiliary storage device such as a hard disk device is used in addition to a semiconductor memory. The image processing unit 113 performs a function of enlarging / reducing the image, a function of rotating the image, and the like. The compression unit 114 functions to compress the image data stored in the determination unit 102, and the expansion unit 115 functions to expand the compressed image data read from the determination unit 102 to the original state.

  The display operation unit 116 includes a liquid crystal display having a touch panel on the surface and various operation switches, and has a function of performing various guidance displays and status displays to the user and receiving various operations from the user. The printer unit 40 includes a printing mode switching unit 46 that moves the photosensitive drums 51Y, 51M, and 51C forward and backward to execute a separation operation and an advancement operation for switching the printing mode. The print mode switching means 46 includes an advancing / retreating mechanism that drives the photoreceptor drums 51Y, 51M, and 51C back and forth, a driving motor, and the like.

  The control unit 100 functions as a print control unit 101, a determination unit 102, and a print mode determination unit 103. The print control unit 101 controls job execution and image data flow. When printing the first copy of a plurality of copies, the image data is printed while being stored in the image memory 112, and the second and subsequent copies are sequentially read from the image memory 112 and printed. The determination unit 102 has a function of determining whether the image data input to the image memory 112 or the image data developed by the print controller 111 is a color image to be printed in color or a monochrome image to be printed in black and white.

  The image data is read from the reading unit 30 in a user designation mode in which the user designates whether the captured image is to be printed in color or in black and white, and in an automatic discrimination mode in which the apparatus automatically determines whether to perform color printing or monochrome printing. Performed in either mode. In the user designation mode, color printing or monochrome printing can be designated in units of the entire document. Further, by adding and reading the originals, it is possible to switch between color printing and black-and-white printing at the cuts of the originals. In addition, the document may be read after presetting for each page whether to perform color printing or monochrome printing before reading the document.

  The user designation mode is used when a color original is to be printed in black and white. When color printing or monochrome printing is specified in units of the entire document or by a preset, it is determined whether all pages are printed in color or monochrome at the start of reading the document. In the case of additional reading, every time a document is read, whether color printing or black-and-white printing is sequentially determined for the page according to the user's specification.

  In the automatic determination mode, the reading unit 30 captures a document as a color image. The determination unit 102 analyzes the captured image data and determines whether the image is a color image or a monochrome image. Here, when any one of Y, M, and C color components is included, it is determined as a color image. In the automatic determination mode, every time a page of image data is captured, it is determined whether the page is a color image or a monochrome image. Therefore, during the capture of image data, each page is printed in color according to the progress of the capture operation. Whether to print will be determined sequentially. The determination result is stored in the image memory 112 together with the image data.

  For print data received from an external device, it is determined whether to perform color printing or monochrome printing based on the header information. The header information may be added to the print data for each page in addition to being added to the head of the entire print data. When the header information is added to the head of the entire print data, it becomes clear when all the pages related to the current printing are to be printed in color or black and white when the header information is received. When header information is added to each page, it is sequentially determined whether color printing or monochrome printing should be performed each time header information of each page is received.

  The printing mode determination unit 103 has a function of determining whether the printing mode is a color printing mode or a monochrome printing mode. Here, whether or not to switch from the color printing mode to the monochrome printing mode is determined based on whether or not the continuous number of monochrome images up to the present time is equal to or more than the first reference number during the reception of the image data. Further, after the reception of the image data is completed, the determination is made based on whether or not the number of continuous black and white images is equal to or greater than the second reference number in the future.

  The first reference number and the second reference number can be set independently. These settings may be fixedly determined as values unique to the apparatus, or may be configured to be changed according to the usage status of the user.

  Each reference number is set to a value that satisfies the following conditions. Let D1 be the magnitude of mechanical degradation caused by printing one monochrome image in the color printing mode. Let D2 be the magnitude of mechanical deterioration caused by changing from the color printing mode to the monochrome printing mode. Let D3 be the magnitude of mechanical deterioration caused by changing from the monochrome printing mode to the color printing mode. At this time, each reference number is set to a minimum value n or more that satisfies D2 + D3 <D1 × n (n is a positive integer).

  That is, the reference number of sheets is set within a range in which the mechanical deterioration is less when the monochrome printing mode is switched to the monochrome printing mode than when the monochrome printing is continued in the color printing mode. When the print mode is switched, the productivity is always lowered with the switch, so there is no point in switching to the monochrome print mode when the mechanical deterioration is the same or large. Therefore, the switching condition is that at least mechanical deterioration is reduced.

  The magnitude of the mechanical deterioration may be obtained by observing the deterioration when the target operation is performed many times such as several thousand times. For example, it may be determined based on the number of scratches generated on the intermediate transfer belt, the degree of surface degradation, and the like. Alternatively, the degree of mechanical deterioration can be determined from the idle time of the developing device. When the monochrome printing is performed in the color printing mode, T1 is the idling time of the developer of a color other than black per print, T2 is the idling time when switching from the color printing mode to the monochrome printing mode, and the color from the monochrome printing mode to the color. The degree of mechanical deterioration can be compared by comparing T1 × n (n is the number of black and white prints in the color print mode) and T2 + T3, where T3 is the idling time when switching to the print mode. Alternatively, it is also obtained by actually performing the operation several thousand times so as to obtain the degree of deterioration of the intermediate transfer belt and comparing the deterioration state of the developer or the like. The degree of mechanical deterioration of some parts is calculated, and it is determined which part is to be given specific gravity to determine the degree of mechanical deterioration as a whole.

  FIG. 1 shows a flow of operations related to switching of print modes. This operation is repeated for each page. The print mode determination unit 103 checks whether the next page is a color image to be color-printed with reference to the determination result of the determination unit 102 (step S201). In the case of a color image (step S201; Y), it is checked whether or not the current print mode is the color print mode (step S202). In the case of the color printing mode (step S202; Y), it is determined that it is not necessary to switch the printing mode, and the processing is ended as it is. If the current print mode is the monochrome print mode (step S202; N), the print mode is switched to the color print mode prior to the start of printing the next page (step S203).

  If the next page is a black and white image to be printed in black and white (step S201; N) and the current print mode is the black and white print mode (step S204; N), it is determined that there is no need to switch the print mode, and the process is terminated. . If the next page is a black and white image to be printed in black and white (step S201; N) and the current print mode is the color print mode (step S202; Y), it is checked whether image data is currently being received (step S202). S205). Receiving image data includes not only receiving print data from an external device but also reading a document from the reading unit 30.

  When receiving (step S205; Y), the number of continuous prints of black and white images up to the present time is checked, and if this is greater than a predetermined first reference number (step S206; Y), the print mode is changed to the black and white print mode. Switching (step S208). If it is less than the first reference number (step S206; N), monochrome printing is continued in the color printing mode. When the reception of the image data is completed (step S205; N), the future continuous printing number of black and white images is checked, and if this is equal to or greater than the predetermined second reference number (step S207; Y), the printing mode Is switched to the monochrome printing mode (step S208). If it is less than the second reference number (step S207; N), monochrome printing is continued in the color printing mode (end).

  FIG. 4 shows the difference in switching timing to the monochrome printing mode depending on whether image data is being received or after reception is completed. The upper part of the figure shows the original, the middle part shows the output state during reception of the image data, and the lower part shows the output state after completion of the image data reception. Here, the first reference number is set to four and the second reference number is set to three.

  The original shown in FIG. 4 has six monochrome pages after the first page is colored, the second page is black and white, and the third page is colored. Since the third page 300 is in color, the color print mode is set during printing of the page 300. While the image data is being received, since the black and white pages 301 to 304 are continuously the first reference number (four) and the next page 305 is also a black and white page, the black and white printing mode is set between the pages 304 and 305. It has switched to. After the completion of the reception of the image data, when printing up to the third page, it is already known that the monochrome pages 311 to 313 continue for the second reference number (three) or more after the fourth page. And the monochrome page 311 are switched to the monochrome print mode.

  For example, when only one copy is printed or when the first copy of a plurality of copies is printed, the operation shown in the middle of FIG. 4 is performed. Further, when printing the second and subsequent copies of a plurality of copies, the operation is as shown in the lower part of FIG.

  It should be noted that the cut of the section is not relevant in the determination of the continuous number of monochrome images in the future. As shown in FIG. 5, even if only two pages of black and white pages 321 and 322 continue after the color page 320 in the same part, the second page is combined with the black and white pages 323 to 325 after the first page of the next part. If the number is equal to or larger than the reference number of sheets, switching to the monochrome printing mode is executed.

  In addition, when the current print mode is the color print mode and it is known that the black and white image is continuous from the next page to the last page of the current printing operation, the continuous number is equal to or greater than the third reference number. In this case, the color printing mode may be switched to the monochrome printing mode. If the black and white image continues to the end, the color print mode is not restored in the middle, and the third reference number can be set without taking into account the mechanical deterioration. For example, the third reference number may be set to a value not less than the minimum m that satisfies D2 + D3 <D1 × m (m is a positive integer), and can be set to a number smaller than the second reference number. Become.

  Next, a case will be described in which switching to the monochrome printing mode is determined based on whether or not a page to be color-printed next is known regardless of whether or not image data is being received. Even when image data is being received, if the document is pre-read prior to printing, it is determined whether the pre-read page should be color-printed. Similarly, in the case of print data, it is determined whether or not color printing should be performed for a page received prior to printing even during data reception. Also, in the user designation mode, when it is designated whether or not to perform color printing in units of the entire document, or when designated by a preset, it is determined whether or not each page is already color-printed before the reading of the document is started. Therefore, by adding a preceding page, which is already determined whether or not color printing is being performed, to the determination material regardless of whether image data is being received, switching to the black and white printing mode is determined earlier. ing.

  FIG. 6 shows the flow of the print mode switching operation when it is determined to switch to the monochrome print mode based on whether or not the next page to be color-printed is known. Steps S401 to S404 are the same as those shown in FIG. If the next page to be printed is a monochrome image (step S401; N) and the current print mode is the color print mode (step S404; Y), it is checked whether or not the next color image page is known (step S404; Y). Step S405).

  If it is determined by the prefetching of the image data or the like that the page of the next color image will appear (step S405; Y), whether the continuous number of future black and white images is greater than the second reference number Whether or not is checked (step S408). When the number is equal to or greater than the second reference number (step S408; Y), the mode is switched to the monochrome printing mode (step S409). When the number is equal to or smaller than the second reference number (step S408; N), monochrome printing in the color printing mode is continued (end).

  When it is not known how many pages ahead of the next color image will appear (step S405; N), the total number of continuous black-and-white images up to now and the number of continuous black-and-white images already known in the future are added up. (Step S406). When the total number is equal to or greater than the first reference number (step S407; Y), the mode is switched to the monochrome printing mode (step S409). When the total number is equal to or less than the first reference number (step S407; N), the color printing mode is selected. Continue black and white printing (end).

  FIG. 7 shows an output when the appearance time of the next color image is not known and the sum of the continuous number of black-and-white images up to the present and the continuous number of future black-and-white images is less than the first reference number. An example of a state is shown. The first reference number of sheets is four. In the figure, the monochrome page 502 next to the color page 501 is currently being printed, and it is found by prefetching that the next page 503 and the next page 504 are monochrome images. The page 504 is receiving image data, and it is not known whether the next page 505 is color or monochrome.

  At this time, the total number of continuous black-and-white images (one page 502) and the subsequent continuous black-and-white images (two pages 503 and 504) is three, which is less than the first reference number. The monochrome printing in the color printing mode is continued.

  FIG. 8 shows an output when the appearance time of the next color image is not known and the sum of the continuous number of black and white images up to the present and the continuous number of future black and white images is equal to or greater than the first reference number. An example of a state is shown. In the figure, the monochrome page 512 next to the color page 511 is currently being printed, and it is found by prefetching that the next page 513 to the page 515 two pages ahead are monochrome images. The page 515 is receiving image data, and it is not known whether the next page 516 is color or monochrome.

  At this time, the total number of continuous black-and-white images (one page 512) and the subsequent continuous black-and-white images (three from page 513 to 515) is four, which is greater than the first reference number. Therefore, the monochrome print mode is switched between the page 512 and the page 513.

  FIG. 9 shows an example of the output state when the appearance time of the next color image is known. The second reference number is set to four. In the figure, the color page 521 is currently being printed, and by prefetching, three consecutive pages from the next page 522 to the page 524 are black and white images, and the next page 525 is a color image. It turns out. Since the number of continuous black and white images up to the next color page 525 is three and less than the second reference number, black and white printing in the color printing mode is continued.

  FIG. 10 shows another example of the output state when the appearance time of the next color image is known. In the figure, a color page 531 is currently being printed, and by prefetching, four consecutive pages from the next page 532 to page 535 are black and white images, and the next page 536 is a color image. It turns out. Since the number of continuous monochrome images up to the next color page 536 is four or more than the second reference number, the monochrome print mode is switched between page 531 and page 532.

  As described above, even when image data is being received, whether or not to switch to the monochrome printing mode can be determined at an early stage by including the pre-read page in the determination material. When the next color page is not known, the monochrome print mode is set on the condition that the continuous number of monochrome images up to now is equal to or more than the first reference number and the next page is a monochrome image. You may comprise so that it may switch to. In this case, the advantage of prefetching occurs when the appearance time of the next color page is known.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention. For example, in the embodiments, a full-color image forming apparatus has been described as an example, but a color image forming apparatus capable of expressing only a limited number of colors such as two colors may be used.

3 is a flowchart showing an operation related to switching of a print mode performed by a color image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the cross-sectional structure of the color image forming apparatus concerning embodiment of this invention. 1 is a block diagram illustrating a schematic electrical configuration of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows an example of the switching timing to the black-and-white printing mode during reception of image data and after completion of reception. It is explanatory drawing which shows an example of the printed matter with which a monochrome image continues between the present part and the following part. 6 is a flowchart showing an operation when the color image forming apparatus according to the embodiment of the present invention controls the switching to the black and white printing mode by adding the pre-read page during the reception of the image data to the determination material. An example of the output state when the appearance time of the next color image is not known and the sum of the continuous number of black and white images up to the present and the continuous number of future black and white images is less than the first reference number It is explanatory drawing shown. An example of the output state when the appearance time of the next color image is not known and the sum of the continuous number of black and white images up to the present and the continuous number of future black and white images is equal to or greater than the first reference number It is explanatory drawing shown. It is explanatory drawing which shows an example of the output state when the appearance time of the next color image is known. It is explanatory drawing which shows another example of the output state when the appearance time of the next color image is known.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Color image forming apparatus 20 ... Automatic document feeder 30 ... Reading part 40 ... Printer part 46 ... Print mode switching means 100 ... Control means 101 ... Print control means 102 ... Judgment means 103 ... Print mode determination means 111 ... Print controller 112 ... Image memory 113 ... Image processing means 114 ... Compression means 115 ... Expansion means 116 ... Display operation unit

Claims (6)

In a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing, and a monochrome printing mode capable of monochrome printing only, as printing modes.
Print mode determining means for determining whether the print mode is a color print mode or a monochrome print mode;
Print mode switching means for switching the print mode according to the determination of the print mode determination means;
An image memory for storing image data to be printed;
Print control means for storing one part of image data in the image memory and printing at least the second and subsequent copies by reading the image data from the image memory in the case of printing a plurality of copies;
Determining means for determining whether the image data input to the image memory is a color image to be color-printed or a monochrome image to be monochrome-printed;
The print mode determination unit is configured to select a monochrome image which is a monochrome image which is continuously printed up to the present time when a page to be printed next is a monochrome image while the current print mode is the color print mode and the image data is being taken into the image memory. When the number of sheets is equal to or more than the first reference number, it is decided to switch from the color printing mode to the monochrome printing mode, and after the current printing mode is the color printing mode and the image data is taken into the image memory, it will continue in the future. A color image forming apparatus, wherein switching from a color printing mode to a monochrome printing mode is determined when the number of monochrome images to be performed is equal to or greater than a second reference number. In a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing, and a monochrome printing mode capable of monochrome printing only, as printing modes.
Print mode determining means for determining whether the print mode is a color print mode or a monochrome print mode;
Print mode switching means for switching the print mode according to the determination of the print mode determination means;
Determining means for determining whether the image data to be printed is a color image to be printed in color or a monochrome image to be printed in black and white;
The print mode determining means determines that the current print mode is a color print mode and the next page is a black and white image based on the determination result of the determination means and the subsequent appearance time of the color image is not known. Determining whether to switch from the color printing mode to the monochrome printing mode when the number of monochrome images continuously printed to date is equal to or more than the first reference number, the current printing mode being the color printing mode, and the determination unit If the next color image appearance time is known based on the result of the determination, it is decided to switch from the color printing mode to the monochrome printing mode when the number of continuous monochrome images is equal to or larger than the second reference number in the future. A characteristic color image forming apparatus. In a color image forming apparatus having a color printing mode capable of both color printing and monochrome printing, and a monochrome printing mode capable of monochrome printing only, as printing modes.
Print mode determining means for determining whether the print mode is a color print mode or a monochrome print mode;
Print mode switching means for switching the print mode according to the determination of the print mode determination means;
Determining means for determining whether the image data to be printed is a color image to be printed in color or a monochrome image to be printed in black and white;
The print mode determining means determines that the current print mode is a color print mode and the next page is a black and white image based on the determination result of the determination means and the subsequent appearance time of the color image is not known. When the total number of monochrome images that have been continuously printed up to now and the number of monochrome images that are known to be continuous in the future is greater than or equal to the first reference number, the color printing mode is switched to the monochrome printing mode. If the current print mode is the color print mode and the appearance time of the next color image is known based on the determination result of the determination means, the number of continuous black and white images will be greater than or equal to the second reference number in the future. In this case, the color image forming apparatus determines whether to switch from the color printing mode to the monochrome printing mode. The color image forming apparatus according to claim 1, 2, or 3, wherein the first reference number and the second reference number can be set independently. The print mode determining means determines that when the current print mode is the color print mode and the black and white image is continuous from the next page to the last page of the current printing operation, the continuous number is equal to or greater than the third reference number. 5. The color image forming apparatus according to claim 1, wherein switching from the color printing mode to the monochrome printing mode is determined in the case of The magnitude of the mechanical degradation caused by printing n (n is a positive integer) number of black and white images in the color printing mode is the same as the magnitude of the mechanical degradation caused by changing from the color printing mode to the black and white printing mode. The reference number of sheets is set to a minimum number of sheets n or more within a range that is equal to or greater than the sum of the magnitude of mechanical deterioration caused by changing from the mode to the color printing mode. The color image forming apparatus according to 4 or 5.

Images