Image formation device and image formation method

Abstract

To enable securing printing throughput as high as possible while avoiding deterioration in quality of printing, as well as, lowering the running cost of a toner cartridge.SOLUTION: An image formation device of the present disclosure comprises: a plurality of image formation units; a transfer unit provided opposite the plurality of image formation units; a fixation unit fixing images transferred by the transfer unit onto a medium; and a control part controlling image formation processing. At least two of the plurality of image formation units perform image formation using developers of the same color, and the control part causes an image formation unit that is provided downstream in a conveyance direction, of the at least two image formation units performing the image formation using the developers of the same color, to form images based upon information on the medium.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus and an image forming method.

Background Art

[0002] For example, as a general method for producing printed matter in an electrophotographic printer, after transferring an image formed on an image drum to a sheet while transporting the sheet with a belt, the image transferred to the medium is thermally fixed to the sheet while transporting the sheet through a fuser. This method is widely known.

[0003] The apparatus described in the prior art also uses this method, and is configured such that the transport speed of the fuser is slightly faster than the transport speed of the belt (see Patent Document 1).

[0004] When printing using thick or long sheets in an apparatus with this configuration, if the leading sheet straddles the fuser and the belt and the image is being transferred onto the trailing sheet on the belt, the transport speed of the trailing sheet fluctuates slightly at the moment the leading sheet passes the end of the belt. Then, since the transport speed of the trailing sheet fluctuates at a time when the image should be transferred while transporting the trailing sheet at a constant speed, a problem occurs in that the image transfer to the trailing sheet becomes disrupted.

[0005] In the prior art, in order to avoid this problem, when the conditions of the sheet thickness and sheet length are such that image transfer disruption occurs due to speed fluctuations, the distance between the leading sheet and the trailing sheet is increased so that it becomes the distance from the position where the speed fluctuation occurs to the position in front of the most upstream image drum, so that the trailing sheet is not in the relationship of having the image transferred to it at the moment the leading sheet passes the position where the speed fluctuation occurs.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] In conventional technology, image transfer disturbance to subsequent sheets was prevented by widening the space between sheets to the distance from the position where speed fluctuation occurs to the position in front of the most upstream image drum, but when images are output only from the most downstream image drum, for example, image transfer disturbance can be prevented even if the space between sheets is narrowed to the distance from the position where speed fluctuation occurs to the position in front of the most downstream image drum, and in this way, image disturbance can be prevented while minimizing the decrease in throughput.

[0008] Incidentally, a typical configuration of the image output section of an image forming device is that it is separated into an image drum that outputs the image and a toner cartridge that supplies toner to it, and when the toner runs out, the toner is replenished by replacing the toner cartridge with a new one.

[0009] In image forming devices with this type of configuration, although the image drums and toner cartridges are separate as mentioned above, some devices have a configuration in which N image drums are integrated and cannot be separated individually, and N toner cartridges are also integrated and cannot be separated individually. For example, in a color printer with three colors, C, M, and Y, all the image drums are integrated and cannot be separated individually into C, M, and Y, and all the toner cartridges are also integrated and cannot be separated individually into C, M, and Y. This is called an all-color integrated device. In such an all-color integrated device, when any one image drum reaches the end of its life, all the image drums for all colors are replaced together. Furthermore, when any one toner cartridge is depleted, all the toner cartridges for all colors are replaced together.

[0010] In some cases, the toner of such an all-in-one color printer may be used as either full-color toner or black toner to convert it into a monochrome printer. In that case, if an image is output from any one of the image drums, a monochrome printing result desired by the user can be obtained. Therefore, it is possible to arbitrarily select from which image drum the image is output on the image forming apparatus side. When making this selection, if the most downstream image drum is selected, as described above, the distance between sheets can be reduced to the distance from the position where speed variation occurs to the position in front of the most downstream image drum, so that it is possible to minimize the decrease in throughput while preventing image distortion.

[0011] However, if only the most downstream image drum, which is advantageous for throughput, is selected for printing, only the most downstream toner cartridge will quickly run out. When replacing the toner cartridge to replenish the toner at such a time, since it is an all-in-one color toner cartridge, it is necessary to replace even the upstream toner cartridges that still have a lot of toner left. Then, the toner in the upstream toner cartridges will be wasted. In addition, if the apparatus is continued to be used without replacing the toner cartridge to replenish the toner and the image drum that is not replenished with toner continues to rotate, the image drum will be damaged. Therefore, it is common to make it impossible to print until the toner cartridge is replaced and the toner is replenished after the toner runs out.

[0012] In view of the above-described problems, the present disclosure aims to provide an image forming apparatus and an image forming method capable of ensuring the printing throughput as much as possible while avoiding a decrease in the quality of printed matter, and also avoiding the situation where only a specific toner cartridge quickly runs out, so that the toner in the toner cartridges that have not run out can be used without waste when replacing the toner cartridge, and the running cost can be reduced.

Means for Solving the Problems

[0013] To solve such problems, the image forming apparatus according to the first disclosure includes: (1) a plurality of image forming units that form an image on a medium using a developer and are arranged in the conveyance direction of the medium; (2) a transfer unit that is provided facing the plurality of image forming units and transfers the image formed by each image forming unit onto the medium while conveying the medium; (3) a fixing unit that fixes the image transferred by the transfer unit onto the medium; and (4) a control unit that controls the image forming process. Among (5) the plurality of image forming units, at least two image forming units form an image using a developer of the same color. (6) The control unit causes an image forming unit provided on the downstream side in the conveyance direction among at least two image forming units that form an image using a developer of the same color to form an image based on information of the medium.

[0014] The image forming method according to the second disclosure is an image forming method of an image forming apparatus including a plurality of image forming units that form an image on a medium using a developer and are arranged in the conveyance direction of the medium, a transfer unit that is provided facing the plurality of image forming units and transfers the image formed by each of the image forming units onto the medium while conveying the medium, a fixing unit that fixes the image transferred by the transfer unit onto the medium, and a control unit that controls the image forming process. Among the plurality of image forming units, at least two image forming units form an image using a developer of the same color, and the control unit causes an image forming unit provided on the downstream side in the conveyance direction among at least two image forming units that form an image using a developer of the same color to form an image based on information of the medium.

Advantages of the Invention

[0015] According to the present disclosure, by providing the above-described technical solution, it is possible to ensure the printing throughput as much as possible while avoiding a decrease in the quality of printed matter, and it is also possible to prevent only a specific toner cartridge of the integrated toner cartridge from being quickly depleted. Therefore, it is not necessary to waste the toner in the toner cartridge that has not been depleted by replacing the toner cartridge, and the running cost can be reduced.

Brief Description of the Drawings

[0016]

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Figure 12

Embodiment for Carrying Out the Invention

[0017] (A) Main Embodiment Hereinafter, embodiments of the image forming apparatus and the image forming method according to the present disclosure will be described in detail with reference to the drawings.

[0018] This embodiment exemplifies a case where the image forming apparatus according to the present invention is applied to an electrophotographic printer that forms an image on a roll paper. However, the image forming apparatus according to the present disclosure is not limited to the printer according to the embodiment, and the medium is not limited to roll paper, and may be copy paper (PPC: Plain Paper Copier), etc.

[0019] The image forming apparatus according to the embodiment is an image forming apparatus configured to be able to arbitrarily select an image drum for image output (that is, image formation). When the thickness and length of the paper used for printing meet the conditions for the occurrence of image transfer disorder, an image drum that can avoid image transfer disorder and shorten the paper interval is selected for image output.

[0020] Also, when selecting an image drum for image output, in order to prevent the toner cartridge that supplies toner to that image drum from being quickly depleted by only outputting images from a specific image drum, the image drum for image output is selected according to the remaining toner amount of the toner cartridge.

[0021] (A-1) Configuration of the Embodiment FIG. 1 is a configuration diagram showing the configuration of the image forming apparatus according to the embodiment. FIG. 2 is a configuration diagram showing the configuration of the control system of the image forming apparatus according to the embodiment.

[0022] In FIG. 1, an image forming apparatus 10 according to an embodiment includes a roll paper 100, a paper end sensor 101, a first conveyance roller 102, a reflection sensor 103, a cutter 104, a second conveyance roller 105, a writing sensor 106, an integrated ID (Image Drum) unit 107 (107-1 to 107-3), an integrated TC (Toner Cartridge) unit 108 (108-1 to 108-3), a belt unit 109 as a transfer unit, a fixing device 110, a discharge sensor 111, a conveyance motor 112, a conveyance clutch 113, a cutter clutch 114, an ID motor 116, a belt motor 117, and a fixing motor 118.

[0023] The paper end sensor 101 detects the setting of the roll paper 100.

[0024] The conveyance motor 112 is a drive source for the first conveyance roller 102, the second conveyance roller 105, the cutter 104, and the cutter 104.

[0025] The conveyance clutch 113 transmits the motor driving force to the first conveyance roller 102. The first conveyance roller 102 conveys the set roll paper 100 by the driving force supplied from the conveyance motor 112. The reflection sensor 103 detects the presence or absence of the roll paper 100 and black marks.

[0026] The cutter clutch 114 transmits the motor driving force to the cutter 104. The cutter 104 cuts the roll paper 100.

[0027] The second conveyance roller 105 conveys the cut paper. The writing sensor 106 detects the leading edge / rear end of the paper to generate the image output timing and generate between papers.

[0028] The ID motor 116 is a drive source for the integrated ID unit 107. The integrated ID unit 107 performs image output. The integrated TC unit 108 supplies a developer (for example, toner) to the corresponding ID.

[0029] The integrated ID unit 107 has three IDs, ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3), which are arranged along the paper transport direction.

[0030] Each of ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3) forms an image on one side of a sheet of paper using a developer (for example, toner).

[0031] In this embodiment, for the sake of convenience, it is assumed that the toner used in ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3) is all black toner.

[0032] A belt motor 117 is a drive source for a belt unit 109, and the belt unit 109 transports paper and transfers an image onto the paper.

[0033] The belt unit 109 is installed opposite ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3), and while transporting the paper, transfers the images formed by ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3) onto one side of the paper.

[0034] A fixing motor 118 is a drive source for the fixing unit 110, and the fixing unit 110 fixes the transferred image onto the paper.

[0035] The ejection sensor 111 monitors the ejection of the paper and detects the ejection of the paper.

[0036] 1, when cutter 104 cuts the roll paper, the paper downstream of the cutting position that has reached the desired paper length is transported by second transport roller 105, belt unit 109, and fuser 110, and is then ejected outside the device. The leading edge of the roll paper upstream of the cutting position waits at standby position 115 until the next paper feed begins.

[0037] The integrated ID unit 107 is composed of three IDs: ID#1 (107-1), ID#2 (107-2), and ID#3 (107-3), and is configured such that each of the IDs #1 to #3 cannot be separated individually. Therefore, when any one of the IDs #1 to #3 reaches the end of its life, the entire integrated ID unit 107 will be replaced.

[0038] Similarly, the integrated TC unit 108 is composed of three TCs: TC#1 (108-1), TC#2 (108-2), and TC#3 (108-3), and is configured such that each of the TCs #1 to #3 cannot be separated individually. Therefore, when the toner contained inside any one of the TCs #1 to #3 runs out, the entire integrated TC unit 108 will be replaced to replenish the toner.

[0039] Hereinafter, the set of ID#1 (107-1) and TC#1 (108-1) that supplies toner to it will be referred to as "ST1 (ST: Station)", the set of ID#2 (107-2) and TC#2 (108-2) that supplies toner to it will be referred to as "ST2", and the set of ID#3 (107-3) and TC#3 (108-3) that supplies toner to it will be referred to as "ST3".

[0040] Here, each of ST1, ST2, and ST3 is referred to as one "image forming unit", and ST1, ST2, and ST3 arranged along the paper conveyance direction are collectively referred to as a plurality of image forming units.

[0041] Next, the configuration of the control system of the image forming apparatus 10 according to the embodiment will be described.

[0042] In FIG. 2, the image forming apparatus 10 includes, as a control system configuration, an interface unit 200, a print control unit 201, a sensor control unit 210, a media conveyance control unit 220, an image control unit 230, and a fixing control unit 240.

[0043] The hardware of the image forming apparatus 10 is, for example, a device having a CPU, a RAM, a ROM, an EEPROM, an input / output interface, etc. A processing program (such as an image forming processing program) is stored in the ROM, and by executing the processing program with the CPU, various functional units of the image forming apparatus 10 can be made to function.

[0044] The interface unit 200 communicates with a host device (not shown). It mainly receives print instructions and transmits the device status.

[0045] When the print control unit 201 receives a print instruction from a host device through the interface unit 200, it executes print processing in an integrated manner for each control unit (print control unit 201, sensor control unit 210, medium conveyance control unit 220, image control unit 230, fixing control unit 240).

[0046] The sensor control unit 210 controls the operations of various sensors. The sensor control unit 210 includes a paper end sensor control unit 211 that reads the paper end sensor 101, a reflection sensor control unit 212 that reads the reflection sensor 103, a writing sensor control unit 213 that reads the writing sensor 106, and a discharge sensor control unit 214 that reads the discharge sensor 111.

[0047] The medium conveyance control unit 220 controls the conveyance of paper, and includes a medium conveyance unit 221, a medium position detection unit 222, and a cutter control unit 223.

[0048] The medium conveyance unit 221, under the control of the medium conveyance control unit 220, drives the conveyance motor 112, the conveyance clutch 113, the belt motor 117, and the fixing motor 118 to rotate the first conveyance roller 102, the second conveyance roller 105, the belt unit 109, and the fixing unit 110 to control the conveyance of the medium.

[0049] The medium position detection unit 222 monitors sensor changes to detect the position of the medium.

[0050] The cutter control unit 223 controls the cutter 104 by driving the cutter clutch 114.

[0051] The image control unit 230 includes an image forming unit 231 that drives the ID motor 116 to form an image, a transfer control unit 232 that transfers the formed image to a medium, and a toner remaining amount management unit 233 that manages the remaining amount of toner.

[0052] The fixing control unit 240 includes a heater control unit 241 that controls the heater of the fixing device 110 and a temperature detection unit 242 that detects the temperature of the fixing device 110.

[0053] (A-2) Operations of the Embodiment Next, the operations of the image forming apparatus 10 according to the embodiment will be described with reference to the drawings.

[0054] (A-2-1) Method for Avoiding Image Transfer Disturbance First, the image transfer disturbance occurring in the image forming apparatus 10 of the embodiment will be described.

[0055] FIG. 3 is a diagram showing the relationship between the paper thickness of the printing paper and the paper length at which image transfer disturbance occurs in the embodiment. FIG. 4 is an explanatory diagram for explaining the occurrence of image transfer disturbance in the image forming apparatus 10 according to the embodiment.

[0056] Here, a case where the image output station is "ST3 (combination of ID#3 (107-3) and TC#3 (108-3))" will be described.

[0057] In FIG. 4, the side where the roll paper 100 is set is defined as "upstream", and the side where the conveyed paper is discharged to the outside of the apparatus is defined as "downstream". Among the continuously conveyed papers, the paper on the downstream side is referred to as "preceding paper 400", and the paper on the upstream side is referred to as "subsequent paper 401".

[0058] Assume that the relationship between the paper thickness and the paper length (paper cut length in the case of the embodiment) of the printing paper conforms to the conditions of FIG. 3. In this example, when the leading sheet 400 passes through the belt unit 109 (i.e., when the trailing edge of the leading sheet 400 passes through the downstream end of the belt unit 109), and the leading edge of the trailing sheet 401 reaches the contact point between ID#3 (107-3) and the belt unit 109 and image transfer is in progress, the conveyance speed of the trailing sheet 401 fluctuates slightly, resulting in image transfer distortion in the trailing sheet 401.

[0059] Similar to the above-described example, when outputting an image from ST1, image transfer distortion occurs when the leading edge of the trailing sheet 401 reaches the contact point between ID#1 (107-1) and the belt unit 109 and image transfer is in progress. Further, when outputting an image from ST2, image transfer distortion occurs when the leading edge of the trailing sheet 401 reaches the contact point between ID#2 (107-2) and the belt unit 109 and image transfer is in progress.

[0060] Next, with reference to FIGS. 5 to 7, a method for avoiding image transfer distortion in the image forming apparatus 10 of the embodiment will be described.

[0061] Note that the distance between the contact position of ID#1 and the belt unit 109 in ST1 and the contact position of ID#2 and the belt unit 109 in ST2 is defined as "L1". The distance between the contact position of ID#2 and the belt unit 109 in ST2 and the contact position of ID#3 and the belt unit 109 in ST3 is defined as "L2". The distance between the contact position of ID#3 and the belt unit 109 in ST3 and the position of the downstream end of the belt unit 109 is defined as "L3".

[0062] FIG. 5 is an explanatory diagram for explaining a method of avoiding image transfer distortion when outputting an image from ST1. If the distance between sheets is set to "L1 + L2 + L3 + margin" or more, the trailing sheet 401 will not be in the middle of image transfer when the leading sheet 400 passes through the belt unit 109, so image transfer distortion can be avoided.

[0063] 6 is an explanatory diagram illustrating a method for avoiding image transfer disturbances when outputting an image from ST2. If the distance between sheets is set to at least "L2 + L3 + margin," the following sheet 401 will not be in the middle of image transfer the moment the preceding sheet 400 leaves the belt unit 109, and image transfer disturbances can be avoided.

[0064] 7 is an explanatory diagram illustrating a method for avoiding image transfer disturbances when outputting an image from ST3. If the gap between sheets is set to "L3 + margin" or more, the following sheet 401 will not be in the middle of image transfer the moment the preceding sheet 400 leaves the belt unit 109, and image transfer disturbances can be avoided.

[0065] The aforementioned "margin" is provided to prevent image transfer from occurring on the following sheet 401 at the moment the preceding sheet 400 leaves the belt unit 109, even if the timing at which the preceding sheet 400 leaves the belt unit 109 is slightly delayed compared to the expected timing due to slack in the sheet or a slight slippage in transport. The value of this margin may be a fixed value stored in advance in the device program, or may be externally configurable.

[0066] (A-2-2) Image formation processing Next, the operation of the image forming apparatus 10 of the embodiment will be described in detail with reference to the drawings.

[0067] Hereinafter, the term "priority ST" refers to a priority image forming unit (ST) that is preferentially selected as a candidate for image formation among multiple image forming units that form images using the same color developer (in this embodiment, this corresponds to multiple STs (ST1, ST2, ST3) that use black toner). The priority ST is also called the priority image forming unit.

[0068] In addition, an "used ST" is an image forming unit that is determined to perform image formation by checking the usage status of each of multiple image forming units that form images using the same color developer in order to level out the remaining amount of developer. If the remaining amount of developer is kept level, the priority ST becomes the used ST, and if not, another ST is switched to the used ST. An used ST is also called a used image forming unit.

[0069] (A-2-2-1) Overall processing FIG. 8 is a flowchart showing the overall process of the printing operation in the image forming apparatus 10 of the embodiment.

[0070] When a user sends print data, the print control unit 201 receives the print instruction via the interface unit 200, and the print control unit 201 notifies the medium transport unit 221 of a paper feed instruction for each page.

[0071] When the medium transport unit 221 receives the paper feed instruction, the one-page paper feed start process is started, and the process proceeds to S600 in FIG.

[0072] [S600] The medium conveying unit 221 checks whether the relationship between the paper thickness and the paper length satisfies the image transfer disturbance condition exemplified in FIG. 3 (S600), and proceeds to S601.

[0073] [S601] The medium transport unit 221 determines whether this is the first print after power-on (S601). If this is the first print (S601 / Yes), the process proceeds to S604, and if this is not the first print (S601 / No), the process proceeds to S602.

[0074] Here, at the first printing after power-on, the process of determining the ST to be used and the paper spacing has never been performed, so the process of determining the ST to be used and the paper spacing should be performed forcibly. Therefore, the medium transport unit 221 performs the judgment in this step.

[0075] [S602] The media conveyance unit 221 determines whether the applicability / non-applicability to the image transfer disturbance condition has changed between the previous print instruction and the current print instruction (S602). If it has changed (S602 / Yes), the process proceeds to S604. If it has not changed (S602 / No), the process proceeds to S603.

[0076] Here, when the applicability / non-applicability to the image disturbance condition changes, the ST to be preferentially used changes. Therefore, since it is necessary to forcibly perform the determination of the ST to be used and the determination process between sheets, the determination in this step is being performed.

[0077] [S603] The media conveyance unit 221 acquires the TC remaining amount of the ST to be used from the toner remaining amount management unit 233 and determines whether the value of the TC remaining amount of the ST to be used has reached the ST usage limit value (S603). If the value of the TC remaining amount has reached the ST usage limit value (S603 / YES), the process proceeds to S604. If the value of the TC remaining amount has not reached the ST usage limit value (S603 / No), the process proceeds to S605.

[0078] When performing the determination of the ST to be used and the determination process between sheets, which will be described later, a "ST usage limit value" indicating up to what value of the TC remaining amount of the ST used for image output is allowed to output images from that ST will be set. However, since there is no need to switch the ST to be used as long as the value of the TC remaining amount of the ST to be used has not reached the ST usage limit value, the determination in this step is being performed.

[0079] [S604] The media conveyance unit 221 performs the determination of the ST to be used and the determination process between sheets (S604). A detailed explanation of the determination of the ST to be used and the determination process between sheets will be described later with reference to FIG. 9.

[0080] [S605] The media conveyance unit 221 performs the inter-sheet generation process using the information regarding the sheet position from the sheet position detection unit 222 (S605). A detailed explanation of the inter-sheet generation process will be described later with reference to FIG. 11.

[0081] [S606] The media conveyance unit 221 drives the conveyance motor 112 and the conveyance clutch 113 to rotate the first conveyance roller 102, starts the paper feeding of the roll paper waiting at the standby position 115 (S606), and ends the process.

[0082] (A-2-2-2) Determination of the ST to be used and determination process between sheets FIG. 9 is a flowchart showing the determination of the ST to be used and the determination process between sheets in the image forming apparatus 10 of the embodiment.

[0083] [S620] The media conveyance unit 221 refers to the result of whether it meets the image transfer disturbance condition performed in S600. If the result of whether it meets the image transfer disturbance condition is "Yes", that is, if it meets the image transfer disturbance condition (S620 / YES), the process proceeds to process S621. Thereafter, the process proceeds so that the ST as far downstream as possible is used as the ST for image output (ST for image output). This is because when the image transfer disturbance condition is met, using the downstream ST can shorten the paper interval.

[0084] On the other hand, if the result of whether it meets the image transfer disturbance condition is "No", that is, if it does not meet the image transfer disturbance condition (S620 / NO), the process proceeds to S632, and thereafter, the process proceeds so that the ST as far upstream as possible is used as the ST for image output (ST for image output). This is because when the image transfer disturbance condition is not met, the paper interval can be made the same regardless of which ST is used. In order to prevent the remaining TC amount of the downstream ST from becoming too small in case printing that meets the image transfer disturbance condition is performed in the future.

[0085] [S621] The media conveyance unit 221 sets the priority ST to the most downstream ST (for example, ST3 in this embodiment) (S621) and proceeds to S622.

[0086] [S622] The medium conveying unit 221 acquires the remaining TC amount information from the remaining toner amount management unit 233, compares the remaining TC amount value of the priority ST with the remaining TC amount values of other STs located upstream of the priority ST (S622), and proceeds to S623. In other words, the remaining TC amount of the priority ST is compared with the remaining TC amount of other STs located upstream of the priority ST.

[0087] [S623] The medium conveying unit 221 refers to the comparison result made in S622 and determines whether the TC remaining amount value of the priority ST is the smallest value compared with the TC remaining amount values of other STs located upstream (S623).

[0088] If the TC remaining value of the priority ST is not the smallest (S623 / Yes), the TC remaining value of the priority ST still has a margin compared to the TC of other STs upstream, so the process transitions to S629. In other words, if the TC remaining value of the priority ST is not less than the TC remaining value of other STs upstream of the priority ST, the process transitions to S629, and the priority ST is designated as the ST to be used (S629).

[0089] On the other hand, if the TC remaining value of the priority ST is the smallest (S623 / NO), the process proceeds to S624 because the TC remaining value of the priority ST is the smallest. In other words, if the TC remaining value of the priority ST is smaller than the TC remaining value of other STs located upstream of the priority ST, the process proceeds to S624.

[0090] [S624] The medium conveying unit 221 refers to the TC remaining amount information obtained from the toner remaining amount management unit 233, calculates the maximum value among the TC remaining amount values of other STs upstream of the priority ST, sets this value as "Umax" (S624), and transitions to S625.

[0091] [S625] The medium conveying unit 221 determines whether "Umax - TC remaining amount value of the priority ST" is smaller than the threshold value Th1 (S625). That is, the difference between Umax, which is the TC with the largest amount of toner among the TCs upstream of the priority ST, and the TC remaining amount value of the priority ST is calculated, and the difference value is determined whether it is smaller than the threshold value Th1.

[0092] If the "Umax-priority ST TC remaining amount value" is equal to the threshold value Th1 (S625 / YES), the process proceeds to S629, and if the "Umax-priority ST TC remaining amount value" is not equal to the threshold value Th1 (S625 / NO), the process proceeds to S626.

[0093] In S625, since the TC remaining value of the priority ST is the smallest compared to the TC remaining values of other STs upstream of it, it is desirable to switch the used ST to the upstream ST in order to prevent the TC of the priority ST from running out.

[0094] However, since using the ST that is as downstream as possible can shorten the gap between sheets, depending on the device operation, there may be cases where it is desired to improve throughput by allowing printing from the TC of the priority ST even if the TC remaining value of the priority ST is the smallest.

[0095] Therefore, a threshold value Th1 is set so that even if the TC remaining value of the priority ST is the smallest, the priority ST can be used if the difference between the TC remaining value of the priority ST and the TC remaining value of the upstream ST is less than the threshold value Th1. In other words, when the TC remaining amount of the priority ST is greater than the TC remaining amount of the other STs and the difference between the TC remaining amount of the other STs and the TC remaining amount of the priority ST is less than the threshold value Th1, the priority ST is set as the ST to be used.

[0096] The threshold value Th1 may be set arbitrarily by the user.

[0097] [S626] The medium transport unit 221 updates the priority ST to the ST immediately upstream of the current priority ST (S626), and proceeds to S627.

[0098] In S626, the current priority ST is not used, and the next best ST, which is one ST upstream, is set as the priority ST.

[0099] [S627] The medium transport unit 221 determines whether the priority ST has become the most upstream ST (for example, in this embodiment, this corresponds to "ST1" located at the most upstream position) (S627).

[0100] If the priority ST is the most upstream ST (S627 / Yes), the process proceeds to S628, and if the priority ST is not the highest priority ST (S627 / No), the process proceeds to S622.

[0101] [S628] The medium transport unit 221 designates the most upstream ST as the ST to be used (S628). The medium transport unit 221 notifies the image control unit 230 of the determined ST to be used via the print control unit 201, and the process proceeds to S630. Thereafter, the image control unit 230 outputs an image from the notified ST to be used.

[0102] [S629] The medium conveying unit 221 sets the priority ST as the use ST (S629). The medium conveying unit 221 notifies the image control unit 230 of the determined use ST via the print control unit 201, and the process proceeds to S630. Thereafter, the image control unit 230 outputs an image from the notified use ST.

[0103] [S630] The medium conveying unit 221 performs a paper spacing setting process according to the ST used (S630), and then the process proceeds to S631. Details of the paper spacing setting process will be described later with reference to FIG.

[0104] [S631] The medium conveying unit 221 sets the ST use limit value to "the TC remaining amount value of the used ST--limit value Lmt1" (S631), and ends the process.

[0105] This ST usage limit value (ST usage limit) is set to prevent the ST to be used from being changed frequently after it has been determined.

[0106] For example, suppose print data that meets the image transfer disturbance condition is sent and the threshold value Th1 at that time is 3%. In this example, if the ST usage limit is not used, the ST in use may change every time the remaining amount changes by 1%, as shown below. (Printing start): TC1 = 99%, TC2 = 97%, TC3 = 97% ··· Use ST = ST3 (TC1 - TC3 ≤ 3%) (Change in remaining amount of TC3): TC1 = 99%, TC2 = 97%, TC3 = 96% ··· Use ST = ST2 (TC1 - TC3 > 3%) (Change in remaining amount of TC2): TC1 = 99%, TC2 = 96%, TC3 = 96% ··· Use ST = ST1 (TC1 - TC2 > 3%) (Change in remaining amount of TC1): TC1 = 98%, TC2 = 96%, TC3 = 96%, ··· Use ST = ST3 (TC1 - TC3 ≤ 3%)

[0107] That is, at the start of printing, assume TC1 = 99%, TC2 = 97%, TC3 = 97%, and the ST used at this time is "ST3". The "TC remaining amount of Umax - priority ST (= TC1 - TC3 = 2%)" is below the threshold value (3%).

[0108] After that, assume the TC remaining amount of ST3, which is the ST used, changes by 1%. That is, it changes to TC1 = 99%, TC2 = 97%, TC3 = 96%. At this time, the ST used switches to "ST2", and the "TC remaining amount of Umax - priority ST (= TC1 - TC3 = 3%)" becomes larger than the threshold value (3%).

[0109] Also, assume the TC remaining amount of ST2, which is the ST used, changes by 1%. That is, it changes to TC1 = 99%, TC2 = 96%, TC3 = 96%. At this time, the ST used switches to "ST1", and the "TC remaining amount of Umax - priority ST (= TC1 - TC2 = 3%)" becomes larger than the threshold value (3%).

[0110] Furthermore, assume the TC remaining amount of ST1, which is the ST used, changes by 1%. That is, it changes to TC1 = 98%, TC2 = 96%, TC3 = 96%. At this time, the ST used switches to "ST3", and the "TC remaining amount of Umax - priority ST (= TC1 - TC3 = 3%)" is below the threshold value (3%).

[0111] In this way, if the used ST is frequently switched, the paper will also be frequently switched accordingly. Therefore, it becomes difficult to grasp the time from the start to the end of printing, which may be an obstacle when constructing a system that displays, for example, the estimated time until the end of printing.

[0112] Therefore, in S631, the "TC remaining amount value of the used ST - limit value Lmt1" is calculated to set the "ST usage limit value", and the used TC is not switched as long as the TC remaining amount value of the used ST is less than the ST usage limit.

[0113] Note that by adjusting the value of the limit value Lmt1, the effect of the ST usage limit can be adjusted. Therefore, the value of this limit value Lmt1 may be set arbitrarily by the user.

[0114] By adjusting the value of the limit value Lmt1, it is possible to prevent the ST for image output (i.e., the ST for image formation) from being biased towards a specific ST. Therefore, when performing continuous printing, in order to prevent bias towards a specific ST, for example, the value of the limit value Lmt1 may be varied according to the number of printed sheets.

[0115] [S632] If the result of whether or not it meets the image transfer disorder condition is "No", that is, if it does not meet the image transfer disorder condition (S620 / NO), the medium conveyance unit 221 sets the priority ST to the uppermost ST (corresponding to "ST1" in this embodiment) (S632) and transitions to S633.

[0116] [S633] The medium conveyance unit 221 acquires the TC remaining amount information from the toner remaining amount management unit 233, compares the TC remaining amount value of the priority ST with the TC remaining amount values of other STs downstream of the priority ST (S633), and transitions to S633.

[0117] [S634] The medium conveyance unit 221 refers to the comparison result performed in S632 and determines whether or not the TC remaining amount value of the priority ST is not the minimum value compared to the TC remaining amount values of other STs on the downstream side (S634).

[0118] And when the TC residual value of the priority ST is not the minimum (S634 / Yes), since the TC remaining amount value of the priority ST still has a margin compared to the TC of other STs on the downstream side, the process transitions to S639.

[0119] On the other hand, when the TC residual value of the priority ST is the minimum (S634 / NO), since the TC remaining amount value of the priority ST is the minimum value, the process transitions to S634.

[0120] [S635] The medium conveyance unit 221 refers to the TC remaining amount information acquired from the toner remaining amount management unit 233, calculates the maximum value among the TC remaining amount values of other STs downstream from the priority ST, sets that value as "Dmax" (S635), and transitions to S636.

[0121] [S636] The medium conveyance unit 221 determines whether "Dmax - the TC remaining amount value of the priority ST" is smaller than the threshold Th2 (S636).

[0122] And if "Dmax - the TC remaining amount value of the priority ST" is smaller than the threshold Th2 (S636 / YES), the process transitions to S639, and if "Dmax - the TC remaining amount value of the priority ST" is not smaller than the threshold Th2 (S636 / No), the process transitions to S637.

[0123] In S636, the TC remaining amount value of the priority ST is the minimum compared to the TC remaining amount values of other STs on the downstream side. Therefore, in order to prevent the TC of the priority ST from running out, it is desirable to switch the used ST to the downstream ST.

[0124] However, in preparation for the case where printing corresponding to the image transfer disturbance condition is performed, if the TC remaining amount of the downstream ST is prevented from decreasing, the apparatus can always exhibit high throughput.

[0125] Therefore, a threshold value Th2 is provided here. Even if the TC remaining amount value of the priority ST is the minimum, if the difference value from the TC remaining amount value of the ST downstream of it is less than the threshold value Th2, the priority ST can be used. This threshold value Th2 may be arbitrarily set by the user.

[0126] [S637] The medium conveyance unit 221 updates the priority ST to an ST one downstream of the current priority ST (S637), and transitions to S638.

[0127] In S637, the current priority ST is not used, and an ST one downstream, which is the next best ST, is set as the priority ST.

[0128] [S638] The medium conveyance unit 221 determines whether the priority ST has become the most downstream ST (corresponding to "ST3" located most downstream in this embodiment) (S638).

[0129] If the priority ST is the most downstream ST (S638 / Yes), the process transitions to S640. If the priority ST is not the most downstream ST (S638 / NO), the process transitions to S633.

[0130] [S639] The medium conveyance unit 221 uses the priority ST as the ST to be used (S639). The medium conveyance unit 221 notifies the determined ST to be used to the image control unit 230 via the print control unit 201, and transitions to S641. After that, the image control unit 230 outputs an image from the notified ST to be used. That is, the ST to be used is the station (ST) of the image drum (ID) for forming an image.

[0131] [S640] The medium conveyance unit 221 uses the most downstream ST as the ST to be used (S640). The medium conveyance unit 221 notifies the determined ST to be used to the image control unit 230 via the print control unit 201, and transitions to S641. After that, the image control unit 230 outputs an image from the notified ST to be used.

[0132] [S641] The medium transport unit 221 sets the standard paper spacing for the device as the paper spacing (S641).

[0133] If the image transfer disturbance conditions are not met, the paper spacing can be the same regardless of which ST is used, so the standard paper spacing for the device is set.

[0134] [S642] The medium conveying unit 221 sets the ST use limit value to "the remaining TC amount of the used ST--limit value Lmt2" (S642), and ends the process.

[0135] If the image transfer disturbance conditions are not met, the paper spacing can be the same regardless of which ST is used, so the behavior of frequent paper switching as described above does not occur. Therefore, if the image transfer disturbance conditions are not met, it is not necessarily necessary to use the ST usage limit value.

[0136] However, if the limit value Lmt2 is set to "0", the effect of the ST use limit value can be disabled, so that control using the ST use limit value can be performed even when the image transfer disturbance conditions are not met. This limit value Lmt2 may be set arbitrarily by the user.

[0137] FIG. 12 is a diagram illustrating an example of a process for determining a used ST and a paper gap according to the embodiment.

[0138] For example, the parameter values of the threshold value Th1, the limit value Lmt1, the threshold value Th2, and the limit value Lmt2 are all set to 3%.

[0139] The threshold value Th1, limit value Lmt1, threshold value Th2, and limit value Lmt2 may be set to different values depending on the operation mode. For example, decreasing each value will help to equalize the remaining toner amounts of each TC, while increasing each value will reduce the frequency of switching the ST in use and improve throughput.

[0140] Based on this, when the toner remaining amount in the TC is large, these respective numerical values are increased to prioritize throughput. On the other hand, when the toner remaining amount in the TC starts to decrease, these respective numerical values are decreased to prioritize toner remaining amount leveling. Thus, the numerical values of the threshold Th1, limit value Lmt1, threshold Th2, and limit value Lmt2 may be varied according to the situation.

[0141] Also, in this embodiment, the units of the toner remaining amount value, threshold Th1, limit value Lmt1, threshold Th2, and limit value Lmt2 are percentages (%), but it is not limited to this. For example, other units that can control the toner remaining amount value, such as the number of dots, may be used.

[0142] (A-2-2-3) Inter-sheet setting process FIG. 10 is a flowchart showing the operation of the inter-sheet setting process according to the embodiment.

[0143] Here, in S630 of FIG. 9, the medium conveyance unit 221 will be described in detail for the inter-sheet setting process of setting the distance length between the trailing edge of the preceding sheet 400 and the leading edge of the succeeding sheet 401 according to the used ST. Here, the description will be made with reference to FIGS. 5 to 7.

[0144] [S650] The medium conveyance unit 221 determines whether the used ST is ST3 (S650). If the used ST is ST3 (S650 / YES), the process transitions to S651, and if the used ST is not ST3 (S650 / NO), the process transitions to S652.

[0145] [S651] When the used ST is ST3 (S650 / YES), the medium conveyance unit 221 sets the distance length between the sheets to "L3 + margin" (S651), and ends the inter-sheet setting process according to the used ST.

[0146] [S652] When the used ST is not ST3 (S650 / NO), the media conveyance unit 221 determines whether the used ST is ST2 (S652). If the used ST is ST2 (S652 / Yes), the process proceeds to S653, and if the used ST is not ST2 (S652 / NO), the process proceeds to S654.

[0147] [S653] When the used ST is ST2 (S652 / YES), the media conveyance unit 221 sets the distance length between sheets to "L2 + L3 + margin" (S653) and ends the sheet - to - sheet setting process according to the used ST.

[0148] [S654] When the used ST is not ST2 (S652 / NO), the media conveyance unit 221 sets the distance length between sheets to "L1 + L2 + L3 + margin" (S654) and ends the sheet - to - sheet setting process according to the used ST.

[0149] (A - 2 - 2 - 4) Inter - sheet generation process FIG. 11 is a flowchart showing the operation of the inter - sheet generation process according to the embodiment.

[0150] Here, in S605 of FIG. 8, the media conveyance unit 221 will be described in detail about the inter - sheet generation process of generating a distance between sheets.

[0151] [S660] The media position detection unit 222 determines whether there is a preceding sheet 400 that has not been completely discharged in front of the roll paper 100 from which paper feeding is about to start (S660).

[0152] If there is a preceding sheet 400 that has not been completely discharged in front of the roll paper 100 (S660 / Yes), the process proceeds to S661. On the other hand, if there is no preceding sheet 400 (S660 / No), since paper feeding can start immediately, the media position detection unit 222 notifies the media conveyance unit 221 of the completion of inter - sheet generation and ends the process.

[0153] [S661] The media position detection unit 222 determines whether the preceding sheet 400 has passed through the writing sensor 106 (S661). For example, when the writing sensor 106 outputs an OFF signal when detecting a sheet and outputs an ON signal when not detecting a sheet, the media position detection unit 222 detects that the sheet has passed through when the signal from the writing sensor 106 switches from an OFF signal to an ON signal.

[0154] If the preceding sheet 400 has passed through the writing sensor 106 (S661 / Yes), the process transitions to S664. If the preceding sheet 400 has not passed through the writing sensor 106 (S661 / No), the process transitions to process S662.

[0155] [S662] When the preceding sheet 400 has not passed through the writing sensor 106 (S661 / NO), the media position detection unit 222 checks the state of the writing sensor 106 (S662) and the process transitions to S663. That is, the media position detection unit 222 monitors the detection signal from the writing sensor 106.

[0156] [S663] The media position detection unit 222 monitors the detection signal from the writing sensor 106 and determines whether the preceding sheet 400 has passed through the writing sensor 106 (S663). For example, it monitors for the detection signal from the writing sensor 106 to switch from an OFF signal to an ON signal, and when it becomes an ON signal, the media position detection unit 222 determines that the preceding sheet 400 has passed through.

[0157] If it is determined that the preceding sheet 400 has passed through the writing sensor 106 (S663 / YES), the process transitions to S664. If it is determined otherwise (S663 / NO), the process transitions to S662.

[0158] [S664] After the preceding sheet 400 has passed through the writing sensor 106, the media position detection unit 222 confirms the rear end position of the preceding sheet 400 based on the drive amount of the conveyance motor 112 (S664) and transitions to S665.

[0159] [S665] The medium position detection unit 222 determines whether the distance from the rear end position of the preceding paper 400 to the standby position 105 (the position where the leading edge of the roll paper 100, which will soon start feeding, is waiting) is equal to or greater than the distance between the papers (S665).

[0160] In other words, the medium position detection unit 222 temporarily waits for the start of feeding of the following paper 401, and determines whether the distance between the rear end position of the preceding paper 400 and the leading end position of the waiting following paper 401 is equal to or greater than the set distance between the papers.

[0161] Then, when the distance between the rear end position of the preceding paper 400 and the standby position 115 becomes equal to or greater than the distance between the papers (S665 / YES), the media position detection unit 222 notifies the media conveying unit 221 that the paper spacing generation is complete, and the process ends.

[0162] On the other hand, if the distance between the rear end position of the preceding sheet 400 and the standby position 115 is not equal to or greater than the distance between the sheets (S665 / No), the process returns to S664 and the process is repeated.

[0163] (A-3) Effects of the embodiment As described above, according to the embodiment, when printing is performed under conditions that correspond to image transfer disturbance conditions, image transfer disturbance is avoided according to the ST used, and printing is performed by setting the shortest possible paper spacing, thereby maintaining print quality while suppressing a decrease in printing throughput.

[0164] In addition, in a device that has an integrated ID and an integrated TC and can determine the ST to be used for image output on the device side, the ST to be used is determined by referring to the remaining TC amount of each ST so that the remaining TC amount is not biased, so that when one of the TCs in the integrated TC runs out and the integrated TC is replaced for toner replenishment, the amount of toner wasted in the other TCs can be reduced.

[0165] (B) Other embodiments Although various modified embodiments have been mentioned in the above-described embodiments, the present invention can also be applied to the following modified embodiments.

[0166] (B-1) In the above-described embodiment, an example of an apparatus having an integrated ID and an integrated TC has been described.

[0167] However, the image forming apparatus of the present disclosure can also be applied to an apparatus having a separable ID and TC instead of an integrated type. In the case of such an apparatus configuration, even if toner remaining amounts are uneven and a lot of toner remains in other TCs when one of the TCs runs out, only the TC that has run out of toner needs to be replaced, so toner in other TCs will not be wasted due to TC replacement.

[0168] On the other hand, if the used ST is biased towards a certain ST (specific ST) and other STs are not used for a long period, the toner in the unused ST may deteriorate, and there may be a problem that print quality cannot be guaranteed when it comes to using it. By applying the present disclosure in such a case, the used ST can be switched according to the toner remaining amount, and it is possible to prevent the toner in a certain ST from deteriorating due to not being used for a long period.

[0169] (B-2) In the above-described embodiment, an example of an apparatus that performs monochrome printing by putting black toner (black developer) in all three STs has been described, but the image forming apparatus of the present disclosure can also be applied to an apparatus having a plurality of color toners.

[0170] For example, there is an apparatus for the purpose of printing a monochrome document in black and printing only the seal and stamp part in red, and it is assumed that the apparatus can be equipped with four STs.

[0171] For example, when two black STs and two red STs are installed, arrange them in the order of ST1 = red, ST2 = black, ST3 = red, ST4 = black along the conveyance direction from upstream.

[0172] At this time, let ST1 and ST2 (one set of STs is referred to as "Set 1") be at least two image forming units that perform image formation using a developer of the same color (red). Similarly, let ST3 and ST4 (one set of STs is referred to as "Set 2") be at least two image forming units that perform image formation using a developer of the same color (black).

[0173] And in the image forming apparatus, when performing printing that meets the image transfer disturbance condition, if the downstream Set 2 is used, it is possible to suppress a decrease in printing throughput while maintaining print quality.

Explanation of Reference Numerals

[0174] 10…Image forming apparatus, 100…Roll paper, 101…Paper end sensor, 102…First conveyance roller, 103…Reflection sensor, 104…Cutter, 105…Second conveyance roller, 106…Writing sensor, 107…Integrated ID unit, 107-1~107-3)…ID, 108…Integrated TC unit, 108-1~108-3…TC, 109…Belt unit, 110…Fuser, 111…Discharge sensor, 112…Conveyance motor, 113…Conveyance clutch, 114…Cutter clutch, 115…Standby position, 116…ID motor, 117…Belt motor, 118…Fuser motor, 200…Interface unit, 201…Print control unit, 210…Sensor control unit, 211…Paper end sensor control unit, 212…Reflection sensor control unit, 213…Writing sensor control unit, 214…Discharge sensor control unit, 220…Media conveyance control unit, 221…Media conveyance unit, 222…Media position detection unit, 223…Cutter control unit, 230…Image control unit, 231…Image forming unit, 232…Transfer control unit, 233…Toner remaining amount management unit,

Claims

1. A plurality of image forming units that form images on a medium using a developer and are arranged in the conveyance direction of the medium, A transfer unit provided opposite to the plurality of image forming units, and while conveying the medium, transfers the images formed by the respective image forming units onto the medium, A fixing unit that fixes the images transferred by the transfer unit onto the medium, A control unit that controls image forming processing and is provided with, Among the plurality of image forming units, at least two image forming units perform image formation using a developer of the same color, The control unit, Based on the information of the medium, causes an image to be formed on the image forming unit provided on the downstream side in the conveyance direction among the at least two image forming units that perform image formation using a developer of the same color. An image forming apparatus characterized by the above.

2. When the medium length of the medium for which a print instruction has been given is equal to or greater than a predetermined length, the control unit causes an image to be formed on the image forming unit that is the most downstream in the conveyance direction among the at least two image forming units that perform image formation using a developer of the same color. The image forming apparatus according to claim 1, characterized by this.

3. When the medium length of the medium for which a print instruction has been given is less than a predetermined length, the control unit causes an image to be formed on an image forming unit other than the image forming unit that is the most downstream in the conveyance direction among the at least two image forming units that perform image formation using a developer of the same color. The image forming apparatus according to claim 1 or 2, characterized by this.

4. The control unit, When the medium length of the medium for which a print instruction has been given is equal to or greater than a predetermined length, Compares the developer remaining amount value of the priority image forming unit that preferentially determines image formation among the at least two image forming units that perform image formation using a developer of the same color, with the developer remaining amount value of another image forming unit upstream of the priority image forming unit. When the developer remaining amount of the priority image forming unit is less than the developer remaining amount of the other image forming unit, the priority image forming unit is set as the used image forming unit for image formation. The image forming apparatus according to claim 1, characterized by this.

5. The control unit, When the medium length of the medium for which a print instruction has been given is equal to or greater than a predetermined length, Of the at least two image forming units that perform image formation using a developer of the same color, when the remaining amount value of the developer in the priority image forming unit that preferentially determines image formation is greater than the remaining amount value of the developer in another image forming unit upstream of the priority image forming unit, and the difference between the remaining amount of the developer in the other image forming unit and the remaining amount of the developer in the priority image forming unit is less than a threshold value, the priority image forming unit is set as the used image forming unit for image formation. The image forming apparatus according to claim 1, characterized in that.

6. The control unit, Of the at least two image forming units that perform image formation using a developer of the same color, the image forming apparatus according to claim 5, characterized in that the control unit sets the distance between the medium conveyed first and the medium conveyed later according to the position of the used image forming unit.

7. The control unit, Of the at least two image forming units that perform image formation using a developer of the same color, the image forming apparatus according to claim 5, characterized in that the control unit sets a predetermined limit value for the remaining amount value of the developer in the used image forming unit.

8. An image forming method for an image forming apparatus, comprising: a plurality of image forming units that form an image on a medium using a developer and are arranged in the conveyance direction of the medium; A transfer unit provided opposite to the plurality of image forming units and transferring the images formed by the respective image forming units onto the medium while conveying the medium; A fixing unit that fixes the image transferred by the transfer unit onto the medium; A control unit that controls an image forming process Among the plurality of image forming units, at least two image forming units perform image formation using a developer of the same color, Based on the information of the medium, the control unit causes an image forming unit provided on the downstream side in the conveyance direction among the at least two image forming units that perform image formation using a developer of the same color to form an image. The control unit, The image forming method, characterized in that. ​

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