JP4939151B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image by transferring a toner image formed on a photoreceptor onto a transfer sheet, and in particular, even when there is a print request including a mixture of color pages and monochrome pages, the print request is satisfied. The present invention relates to an image forming apparatus capable of extending the life of the image forming unit, reducing the printing cost, shortening the printing time, and reducing noise while outputting in the order of pages.

In image forming apparatuses capable of switching between a conventional color print mode and a monochrome print mode, a method in which a printer controller identifies the color and monochrome of an image and switches the print mode for each page is often employed. This is referred to as an automatic color selective printing (ACS) mode.
In other words, the black image forming unit and the yellow, magenta, and cyan image forming units can be driven independently, and the contact between the photoconductor and the intermediate transfer belt in the image forming unit is independent. In the color printing mode, the black, yellow, magenta and cyan image forming units are driven, and the primary transfer roller is pressed against each photoconductor and the intermediate transfer belt. In the monochrome printing mode, only the black image forming unit is driven, and only the black photoconductor is brought into contact with the intermediate transfer belt.
The purpose of the above control is to prevent these image forming units from reaching the replacement time early by driving the other three color image forming units that are not required for monochrome printing. This is effective when color printing or monochrome printing continues to some extent in the printing request.

As a prior art, as disclosed in Patent Document 1, the color print system checks whether there is a color image in the print data, and if there is a color image, the print prediction cost and print prediction at the time of ACS printing and non-ACS printing. The time is calculated and displayed, and it is checked whether or not the initial value set in the non-ACS mode is changed. The color print system performs the system ACS and non-ACS change processing depending on whether there is a change instruction. A technique for performing ACS printing when ACS printing is selected and performing non-ACS printing when non-ACS printing is selected is disclosed.
As Patent Document 2, a first paper discharge sensor and a second paper discharge sensor that detect transfer paper are provided on a reverse conveyance path between a fixing device and a paper discharge roller, and the first paper discharge sensor. And a technique of increasing the linear speed of the paper discharge roller to be higher than the linear speed of the fixing roller at a predetermined timing after one of the second paper discharge sensor detects the transfer paper.

As Patent Document 3, image data is divided into a single color page group and a multicolor page group so as to be divided into a single color page group that does not include a color image and a multicolor page group that includes a color image, and passes through an intermediate tray. The pages to be discharged to the page and the discharge tray are determined, the pages are rearranged in the order of image formation, image formation mode information is added to the rearranged image data, and image formation and discharge are performed based on the image data information. Technology is disclosed.
Patent Document 4 discloses a switchback conveyance path for reversing a sheet having an image writing unit (image forming position) on a sheet fed to a first conveyance path by a sheet feeding unit and having an image formed on one side. A discharge path for discharging the paper on which the image is formed on both sides, the switchback conveyance path and the discharge path are provided adjacent to each other on the same side with respect to the image forming position, and the switchback means and the discharge means A first driving state driven by a common driving means, in which the switchback means operates in the direction of discharging the paper, the switchback means operates in the direction of receiving the paper, and the discharging means operates in the direction of discharging the paper And a second driving state is disclosed.

As disclosed in Patent Document 5, the paper discharged from the discharge means of the paper discharge unit is stacked on the receiving tray T of the paper discharge unit, and the receiving tray is provided with a paper stopper that restricts movement in the paper discharge direction. The stopper is formed integrally with a cover that is removed from the image forming apparatus main body in advance so as to be removable when the paper discharge unit is mounted, and a technique for attaching the stopper to the receiving tray after the cutting is disclosed.
JP 2003-308201 A JP 2003-182907 A JP 2005-175537 A JP 2001-63892 A Japanese Patent Laid-Open No. 2002-20021

  However, the conventional technology has a drawback that the frequency of switching between the color printing mode and the monochrome printing mode increases when color printing and monochrome printing are alternately mixed in a small number of pages in one printing request. . When the color printing mode and the monochrome printing mode are switched, the contact operation of the primary transfer roller with respect to the photosensitive member is required. At this time, the image forming unit is also driven, so that the yellow, magenta, and cyan image forming units are driven. While the drive time is reduced, the drive time of the black image formation unit is increased, and the effect of preventing the image formation unit, which is the target effect for the entire system, from reaching the replacement time early is not fully exhibited, or It may be counterproductive.

Further, if the number of times of switching is large, the switching operation takes time, so that the entire printing time becomes long, and further, there is a disadvantage that the operation sound during the switching operation leads to noise. This phenomenon is more conspicuous when the total number of print requests at one time is small and the number of times of switching between the color print mode and the monochrome print mode is large.
In order to solve the above-described problem, conventionally, a color print system, a color print program, and a recording in which a user appropriately selects automatic color selection printing (ACS) and non-automatic color selection printing (non-ACS) and performs print processing. A medium has been proposed (Patent Document 1: JP 2003-308201 A).

However, in this non-ACS mode, when there are a large number of monochrome pages sandwiched between color pages in one print request, these monochrome prints are performed in the color print mode. Since the magenta and cyan image forming units are driven without actually forming an image, the life of the image forming unit is shortened, and no image is formed even when either the ACS mode or the non-ACS mode is selected. There are cases where the image forming unit is driven for a long time and is inefficient.
The present invention has been made to solve the above-described conventional problems, and its purpose is to create an image while outputting in the order of pages according to the print request even when there is a print request in which color pages and monochrome pages are mixed. An object of the present invention is to provide an image forming apparatus capable of extending the life of a unit, reducing the printing cost, shortening the printing time, and reducing noise.

In order to achieve the above-described object, the invention described in claim 1 includes an exposure unit that forms latent images on a plurality of photoconductors, a plurality of developing units that visualize the formed latent images with toner, An intermediate transfer unit that sequentially superimposes and holds toner images formed by a plurality of developing units, and a sheet stacked on a sheet stacking unit in synchronization with the toner image formed by the intermediate transfer unit. A sheet feeding / conveying means for conveying, a transferring means for transferring the toner image to the paper, and a fixing means for fixing and discharging the toner image transferred to the paper. All the first transfer rollers of the intermediate transfer unit are in pressure contact with the photosensitive member with the intermediate transfer belt interposed therebetween, and in the case of monochrome printing, only the black first transfer roller is in pressure contact with the photosensitive member with the intermediate transfer belt interposed therebetween. Image formation A switching device provided on a paper transport path between fixing and paper discharge, and downstream of the switching device so that the printed paper is discharged from either of them by the selection control of the switching device. A first paper discharge port and a second paper discharge port respectively provided in the lower and upper paper transport paths, a rear end of the paper discharged from the second paper discharge port, and the first discharge port. Provided in the vicinity of the first and second paper discharge ports so as to stack the rear end of the paper discharged from the second paper discharge port in order to maintain a gap with the paper discharged from the paper port. The color printing and the monochrome printing are performed so that the number of times of switching between the color printing mode and the monochrome printing mode is minimized in a printing process in which the partition member and the color printing page and the monochrome printing page are mixed. And control Controller means for controlling the switching device for discharging the printed sheets from one of the first and second discharge ports so that the printed sheets are stacked in the requested page order. The partition member is movable, and the controller means moves the partition member to thereby adjust the trailing edge of the sheet discharged from the stacked second discharge port. It is characterized by being placed on the paper discharged from the first paper discharge port .

According to a second aspect of the present invention, the controller means performs one of the color printing and the monochrome printing together in a printing process in which the color printing page and the monochrome printing page are mixed, The other one of the color printing and the monochrome printing is performed together, and the printed paper is placed in any of the first and second discharge ports so that the printing paper is stacked in the order of the pages requested for printing. It is characterized by controlling the switching device for discharging the water.
According to a third aspect of the present invention, the image forming apparatus is further provided on a paper transport path between the fixing and paper discharge so as to stop the paper discharged from the first and second paper discharge ports. A paper stopper is provided.

According to a fourth aspect of the invention, the paper stopper is movable in the paper transport direction in accordance with the size of the paper to be printed.
According to a fifth aspect of the present invention, an upper limit value is set for the number of sheets discharged and stacked on the second discharge port by the controller means, and the second number of sheets exceeding the upper limit value is set. Discharging to the paper discharge port is prohibited.
The invention according to claim 6 is characterized in that the upper limit value of sheets discharged and stacked at the second discharge port is variable .

According to the present invention, even when there is a print request in which a color page and a monochrome page are mixed, the switching between the color print mode and the monochrome print mode is reduced to the minimum number of times, and the image forming unit actually forms an image. Since the driving time can be reduced, the life of the image forming unit can be extended, the printing cost can be reduced, the printing time can be shortened, and the noise can be reduced.
Further, according to the present invention, regardless of whether or not the optional automatic duplex unit is installed, a paper branching mechanism and first and second discharge ports are provided between fixing and discharging of the apparatus main body. Therefore, the apparatus of the present invention can be realized without a large structural change. In addition, even when the automatic duplex unit is installed, the duplex discharge operation is not impaired by using the second discharge port for the switchback of the sheet.

In addition, according to the present invention, since the stopper that the front end of the paper abuts is provided on the paper ejection stacker, the paper ejected from the second paper ejection port is overrun and the paper that should be originally stacked on the partition plate It is possible to prevent the rear end from dropping from the partition member and the page order being out of order.
Further, according to the present invention, since the stopper is configured to be movable in the paper transport direction, the second paper discharge can be performed regardless of the length of the paper by adjusting according to the length of the paper. The paper discharged from the mouth overruns and the trailing edge of the paper that should be originally stacked on the partition plate falls down from the partition member, thereby preventing the page order from being out of order.
In addition, according to the present invention, an upper limit is set for the number of sheets discharged to the second sheet discharge port in response to a single print request, so that the sheet discharged from the first sheet discharge port is already in the second state. Therefore, it is possible to prevent a problem that the paper cannot be inserted due to the weight of the paper loaded in the paper discharge port.

Further, according to the present invention, the upper limit value of the number of sheets discharged to the second discharge port can be changed in response to a single print request by operating the operation panel or the like. Since it can be set to an optimum value depending on the environment or the like, the effect of the present invention can be exhibited to the maximum while preventing a paper jam.
Further, according to the present invention, the paper stacked on the second paper discharge port can be dropped onto the paper discharge stacker by rotating the partition member and changing its position or angle. It is possible to reduce the ratio of the number of times of switching even for a printing request that is frequently (4 times or more) switched between the printing mode and the monochrome printing mode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of an embodiment of an image forming apparatus according to the present invention.
As shown in FIG. 1, in this image forming apparatus, latent images are exposed to the photoreceptors 8a to 8d in the four image forming units 2a to 2d by exposure from the exposure unit 1 based on an image signal from a controller 20 described later. An image is formed, developed, and visualized as a toner image. Here, in the case of color printing, toner images formed by a plurality of image forming units 2a to 2d of yellow, magenta, and cyan (Y, M, and C) are sequentially superimposed and transferred onto the intermediate transfer belt 3a. In the case of printing, only the toner image formed by the black image forming unit 2a is transferred to the intermediate transfer belt 3a.
In the primary transfer roller 4 provided inside the intermediate transfer belt 3a, in the color printing mode, the four primary transfer rollers 4a to 4d are in pressure contact with the photoconductors 8a to 8d with the intermediate transfer belt 3a interposed therebetween. In the printing mode, only the black primary transfer roller 4a is pressed against the photoreceptor 8a with the intermediate transfer belt 3a interposed therebetween.

In synchronization with the toner image, the sheets stacked on the sheet feeding unit 7 are separated and conveyed one by one, and the toner image is transferred onto the sheet by the second transfer roller 5. The toner image transferred to the paper is fixed by applying heat and pressure in the fixing unit 6.
Further, a switching device 10 is provided on the paper conveyance path between fixing and paper discharge, and the first paper discharge port 11 and the second paper discharge path are respectively provided on the lower and upper paper conveyance paths downstream of the switching device 10. A paper port 12 is provided, and the printed paper is discharged to one of the first and second paper discharge ports 11, 12 under the control of the switching device 10. A partition member 15 is provided in the vicinity.
Thus, the sheet discharged from the upper second discharge port 12 is discharged from the lower first discharge port 11 by stacking the rear end on the partition member 15 under the control of the switching device 10. The paper is stacked with a gap between the paper and the printed paper.

In addition, the size of the paper discharged from the first and second paper discharge ports 11 and 12 is set in the paper discharge stacker 25 in the paper conveyance path downstream of the first and second paper discharge ports 11 and 12. A sheet stopper 17 is provided that moves together and stops the sheets discharged from the first and second sheet discharge ports 11 and 12 (see FIG. 5).
Here, as shown in FIG. 2, an image signal from an external device such as a personal computer or an image reading device is input to a controller 20 including a CPU 21, a RAM 22, a ROM 23, and the like. The number of pages of the entire print request, whether each page is color printing or monochrome printing, the required number of times of switching the printing mode, etc. are detected in advance. Based on the detection results, the controller 20 controls the image formation and conveys the paper. The path switching device 10 is controlled. FIG. 2 is a block diagram of the controller 20 shown in FIG.
Further, here, regardless of whether or not the optional automatic duplex unit is installed, a sheet branching mechanism and first and second discharge ports are provided between fixing and discharging of the apparatus main body. It is possible to realize the device of the present invention without a large structural change. In addition, even when the automatic duplex unit is installed, the duplex discharge operation is not impaired by using the second paper discharge port for the switchback of the sheet.

Next, operations of the sheet transport path switching device 10 and the first and second paper discharge ports 11 and 12 embodying the present invention will be described with reference to the flowchart of FIG. FIG. 3 is an operation flowchart of the image forming processing and paper transport path switching device 10 and the first and second paper discharge ports 11 and 12 embodying the present invention.
If the print request is a total of four pages, the first page is color printing, the second page is monochrome printing, the third page is color printing, and the fourth page is monochrome printing, in step 101 of FIG. , It is detected that the print request is a total of 4 pages, the first page is color printing, the second page is monochrome printing, the third page is color printing, and the fourth page is monochrome printing. The unit is switched to the color printing mode, and the first and third pages, which are color printing, are printed together (step 102).

The controller 20 then switches the switching device 10 upward so that the first-page color-printed sheet is discharged from the first discharge port 11 below. ) Is printed from the first paper discharge port 11 (step 103), and then the switching device 10 causes the second paper discharge port 12 on the upper side of the color-printed third page of paper. The sheet is switched downward so as to be discharged from the second sheet, and the third-page (second sheet) color-printed sheet is discharged from the second discharge port 12 (step 104).
At this time, as shown in FIG. 4, the trailing edge of the third page is stacked on the partition member 15, and there is a gap between the trailing edge of the first page and the trailing edge of the third page. In the example shown in FIG. 4, the case where there is no paper stopper 17 is shown.

Thereafter, the image forming unit and the intermediate transfer unit are switched from the color printing mode to the monochrome printing mode by the controller 20, and the second and fourth pages, which are monochrome printing, are printed together (step 105).
The controller 20 then switches the switching device 10 upward so that the second-page paper printed in monochrome is discharged from the lower first discharge port 11, and the second page (third sheet). ) Is printed from the first paper discharge port 11 and inserted between the first printed page and the third page (step 106), and then the switching device 10 is printed in monochrome. The fourth page (fourth sheet) of monochrome printed paper is discharged from the second paper discharge port 12 so that the fourth page is discharged from the upper second paper discharge port 12. And overlaid on the already printed three pages (step 107).

By operating as described above, printing is performed according to the page order of the print request, and color printing and monochrome printing need only be switched once.
According to the present embodiment, if the switching between the color print mode and the monochrome print mode is three times or less in response to one print request in the ACS mode, the prints in the respective print modes are integrated into one mode. Printing can be performed by switching.

FIG. 8 shows a print mode according to the present invention when the print request is a total of four pages, the first page is color print, the second page is monochrome print, the third page is color print, and the fourth page is monochrome print. Graph showing the driving / stopped state and the number of color / monochrome switching of a plurality of image forming units 2a to 2d of yellow, magenta, and cyan (Y, M, C) in ACS mode and non-ACS mode, and their evaluation FIG.
The above operation is achieved by the controller 20 detecting in advance the number of pages of the entire print request, whether each page is color printing or monochrome printing, and the required number of times of switching the print mode, and controlling based on the detection results. It is like that.
For example, when printing is performed in response to a print request from a personal computer, printing is started after spooling the print request from the personal computer to the controller 20. Further, a storage device such as a memory card or a hard disk drive may be added as necessary.

Next, the paper stopper 17 that prevents paper overrun will be described.
As shown in FIG. 5, the paper stopper 17 for preventing paper overrun provided on the paper discharge stacker 25 has a length L from the rear end of the partition member 15 at least as long as the paper length matches the paper length. It is set at a position shorter than the length of.
That is, since a stopper is provided on the paper discharge stacker 25 so that the front end of the paper hits, the paper discharged from the second paper discharge port 12 overruns and the rear end of the paper that should be originally stacked on the partition member 15 is detected. It is possible to prevent a problem that the page order falls from the partition member 15 and the page order is out of order.
The paper stopper 17 is movable in the paper transport direction on the paper discharge stacker 25 in the paper transport path, and can be adjusted to an optimum position according to the length of the paper to be printed under the control of the controller 20. (See FIG. 5 and FIG. 6).

Note that the position for adjusting the paper stopper 17 may be set in advance at several fixed positions in accordance with the standard size of the paper, or may be configured to be finely adjusted regardless of the standard size of the paper.
Also, for example, when the first page is color printed, the second page is monochrome printed, and the third to twentieth pages are printed in color, the second discharge port 12 is loaded with 18 sheets from the third page to the 20th page. There is a possibility that the second page of paper discharged to the first paper discharge port 11 cannot be inserted after the paper is stacked.

That is, there is a possibility that the paper discharged from the first paper discharge port 11 cannot be inserted due to the weight of the paper already stacked in the second paper discharge port 12 and becomes a paper jam.
Therefore, if the upper limit value of the number of sheets discharged from the second discharge port 12 is set to 10 sheets, in the case of such a print request, all sheets in the ACS mode or the non-ACS mode are all printed in the first mode. The sheets can be discharged in the order of pages to one sheet discharge port 11.
Accordingly, it is possible to prevent a problem that the paper discharged from the first paper discharge port 11 cannot be inserted due to the weight of the paper already stacked in the second paper discharge port and becomes a paper jam.

Note that the operation panel and the controller 20 can be changed and set so that the initial value of the upper limit value set in advance can be increased or decreased depending on the installation environment of the apparatus, the type of paper, and the like.
Accordingly, the upper limit value of the number of sheets can be changed by an operation using the operation panel, and can be set to an optimum value depending on the type of paper to be printed, the use environment of the apparatus, and the like.
Further, as shown in FIG. 7, the partition member 15 is configured to be rotatable, and sheets stacked on the partition member 15 at the second discharge port 12 are controlled by the controller 20 under the control of the controller 20. It can also be configured to drop onto the paper discharge stacker on the mouth 11 side.

In other words, the partition member 15 is configured to be freely selectable by the control of the controller 20 between the position where the sheets are stacked and the position where the stacked sheets are dropped onto the paper discharge stacker.
As a result, by rotating the partition member 15 and changing the position of the partition member 15, the paper stacked on the second paper discharge port 12 can be dropped onto the paper discharge stacker 25, and thus in the ACS mode. It is possible to repeat the operation shown in FIG. 3 even for a print request that is frequently (4 times or more) switched between the color print mode and the monochrome print mode, so that the ratio of the number of times of switching can be reduced. become.

1 is a schematic view of an embodiment of an image forming apparatus according to the present invention. It is a block diagram of the controller 20 shown in FIG. 3 is an operation flowchart of an image forming process and paper transport path switching device 10 and first and second paper discharge ports 11 and 12 embodying the present invention. FIG. 6 is an explanatory diagram showing a state where there is a gap between a color print sheet rear end and a monochrome print sheet rear end at the first and second paper discharge ports 11 and 12. FIG. 4 is an explanatory diagram showing a state in which large-size sheets stopped by a sheet stopper 17 are stacked on first and second sheet discharge ports 11 and 12. FIG. 6 is an explanatory diagram showing a state in which small-size sheets stopped by a sheet stopper 17 are stacked on first and second sheet discharge ports 11 and 12. FIG. 10 is an explanatory diagram illustrating a state in which a partition member 15 rotates and sheets stacked on a second sheet discharge port are dropped on a sheet discharge stacker. Drive / stop states of a plurality of image forming units 2a to 2d of yellow, magenta, and cyan (Y, M, and C) in the print mode, the ACS mode, and the non-ACS mode according to the present invention, and the number of times of color / monochrome switching It is a graph which shows evaluation of.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Exposure unit, 2a-2d ... Image formation unit, 3 ... Intermediate transfer belt, 4a-4d ... Primary transfer roller, 5 ... 2nd transfer roller, 6 ... Fixing unit, 7 ... Paper feed part, 8a-8d ... Photoreceptor, 10... Switching device, 11... First discharge port, 12... Second discharge port, 15... Partition member, 17. ROM, 25 ... discharge stacker

Claims (6)

An exposure unit that forms latent images on a plurality of photoconductors, a plurality of developing units that visualize the formed latent images with toner, and a toner image formed by the plurality of developing units are sequentially superimposed and transferred. Intermediate transfer means for holding, paper feed conveying means for separating and conveying the paper stacked on the paper stacking unit one by one in synchronization with the toner image formed by the intermediate transfer means, and transferring the toner image to the paper And a fixing unit that fixes and discharges the toner image transferred to the sheet, and when performing color printing, all the first transfer rollers of the intermediate transfer unit sandwich the intermediate transfer belt. And an image forming apparatus in which only the black first transfer roller is in pressure contact with the photoconductor across the intermediate transfer belt in monochrome printing.
A switching device provided on the paper transport path between fixing and paper discharge;
A first paper discharge port and a second paper discharge path respectively provided on the lower and upper paper transport paths downstream of the switching device so that the printed paper is discharged from either one by the selection control of the switching device. The paper exit and
In order to maintain a gap between the trailing edge of the sheet discharged from the second discharge port and the sheet discharged from the first discharge port, the sheet discharged from the second discharge port A partition member provided in the vicinity of the first and second discharge ports so as to stack a rear end;
In the printing process in which the color printing page and the monochrome printing page are mixed, the color printing and the monochrome printing are controlled so as to minimize the number of times of switching between the color printing mode and the monochrome printing mode. Controller means for controlling the switching device for discharging the printed sheets from one of the first and second discharge ports so that the printing sheets are stacked in the order of pages of the print request. and, the equipped,
The partition member is movable, and by moving the partition member by the controller means, the rear end of the sheet discharged from the stacked second discharge port is changed to the first discharge sheet. An image forming apparatus, wherein the image forming apparatus is placed on a sheet discharged from a mouth .   In the printing process in which the color printing page and the monochrome printing page coexist, the controller means collectively performs one of the color printing and the monochrome printing, and then combines the other of the color printing and the monochrome printing. And the switching device for discharging the printed paper from one of the first and second discharge ports so that the printing paper is stacked in the order of the pages of the print request. The image forming apparatus according to claim 1, wherein control is performed.   The image forming apparatus further includes a paper stopper on a paper conveyance path between the fixing and paper discharge to stop the paper discharged from the first and second paper discharge ports. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 3, wherein the paper stopper is movable in a conveyance direction of the paper according to a size of the paper to be printed.   The controller means sets an upper limit value for the number of sheets discharged and stacked on the second discharge port, and discharge of sheets exceeding the upper limit value to the second discharge port is prohibited. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 5, wherein an upper limit value of sheets discharged and stacked at the second discharge port is variable.

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