JP5786455B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink from a recording head mounted on a carriage.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a composite machine of these, for example, a liquid discharge recording type image forming apparatus using a recording head for discharging ink droplets is known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid ejection method is an apparatus that forms an image by ejecting liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramics. In addition, “image formation” not only applies an image having a meaning such as a character or a figure to a medium, but also applies an image having no meaning such as a pattern to a medium (simply a liquid). It also means that a droplet hits the medium). The “ink” is not limited to what is called ink, and is not particularly limited as long as it becomes a liquid when ejected. For example, a DNA sample, a resist, a pattern material, etc. Is also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  By the way, for example, an image forming apparatus using such a liquid has a plurality of image forming units, and an image is formed by a plurality of image forming units to improve productivity.

  Patent Document 1 aims to provide a parallel processing printer that can discharge paper in order of pages without causing collision of paper on the discharge path at low cost, and a plurality of printing means for printing an image on paper, A printing control unit that is provided for each printing unit and controls the printing unit; a paper discharge unit that discharges a print page printed by the printing unit; and a main control unit that allocates print data to each printing control unit. When the print data is allocated from the main control unit, each print control unit obtains the print time based on the allocated print data and the state of the print unit, and notifies the main control unit. Based on the print time, the print start timing or the adjustment print time is set and input to each print control means, and each print control means performs printing at the input print start timing or print time. It discloses a parallel processing printer for controlling the printing means.

  However, when an image is formed by a plurality of image forming units in order to improve productivity, idle discharge and cleaning of maintenance ink other than image formation for normally discharging ink are performed in each of the plurality of image forming units. Necessary and waste liquid increases.

  Accordingly, the present invention provides an image forming apparatus having a plurality of image forming units, which minimizes the unnecessary ejection and cleaning of maintenance ink other than image formation by the image forming unit to the minimum necessary, and improves productivity and waste liquid. It aims at realizing reduction of.

According to the present invention, there is provided, according to the present invention, a paper feeding unit that stores a recording medium, a plurality of image forming units that form an image by discharging droplets to the recording medium supplied from the paper feeding unit, In the image forming apparatus having a paper discharge unit that discharges the recording medium on which the image has been formed by the image forming means , the plurality of image forming means can process image formation on the recording medium in parallel and are initially set. Until the predetermined number of image planes is exceeded, the problem is solved by performing image formation after performing idle ejection maintenance with only one of the plurality of image forming means selected first.

In addition, after the predetermined number of image planes is exceeded, it is preferable to perform image formation after performing idle ejection maintenance also in other image forming units.
It is preferable that a stop time storage unit that stores stop time information of the plurality of image forming units is provided, and an image forming unit to be used first is selected from the plurality of image forming units based on the stop time information.

It is preferable that an operation time storage unit that stores operation time information of the plurality of image forming units is provided, and an image forming unit to be used first is selected from the plurality of image forming units based on the operation time information.
Further, it is preferable to select an image forming unit having a shorter operating time as an image forming unit to be used first.

In addition, it is preferable to select an image forming unit that has a longer continuous stop time and stops beyond a predetermined continuous stop time as an image forming unit to be used first regardless of the operation time.
Further, it is preferable to change the initially set predetermined number of image planes of the image forming means to be selected to a smaller number of image planes.

In addition, in place of or in addition to the operating time storage means, ink consumption amount storage means for storing ink consumption amount information of the plurality of image forming means is provided, and ink consumption amount information instead of or in addition to the operating time information. Based on the above, it is preferable to select an image forming unit to be used first from the plurality of image forming units.
Even if the number of image planes in the image forming unit selected first does not reach the predetermined number of image planes, when print data exceeding the predetermined number of image planes is accumulated in the print data buffer unit, another image formation is performed. It is preferable to perform image formation after performing idle discharge maintenance by means.

  In addition, even if the number of image planes in the image forming unit selected first exceeds a predetermined number of image planes, depending on the number of remaining image planes to be printed, first, without using other image forming units. It is preferable to continue the image formation by the selected image forming means.

  According to the present invention, the plurality of image forming units are evenly formed by performing image formation using only one of the plurality of image forming units that is initially selected until the initially set number of image planes is exceeded. Used to reduce the waste liquid by minimizing the empty discharge and cleaning of ink for maintenance other than image formation at the image forming means, and prevent the ink from thickening inside the recording head due to standing for a long period of time. Can be improved.

1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention including a plurality of recording head units. 3 is a flowchart showing control of a recording head unit in the image forming apparatus according to the present invention.

First, an example of an image forming apparatus 10 according to the present invention having a plurality of recording head units will be described with reference to FIG. FIG. 1 is an overall configuration diagram of the image forming apparatus 10.
The image forming apparatus 10 includes recording head units (image forming units) 101 and 102 as image forming units that form droplets by ejecting droplets onto a sheet 100 that is a recording medium, and a conveyance belt 106 that conveys the sheet 100. 112, a paper feed tray 103 that stores the paper 100, and a processing liquid coating apparatus 200 that is also a coating means for coating the processing liquid 201 on the paper 100 that is a member to be coated on the upstream side of the recording head unit 101 in the paper transport direction. And a paper discharge tray 104 for discharging the paper 100 on which an image is formed.

The recording head unit 101 is composed of a line type liquid discharge head having a nozzle row in which a plurality of nozzles for discharging droplets are arranged in a length corresponding to the paper width. Yellow (Y), magenta (M), cyan (C) and recording heads 101y, 101m, 101c, and 101k that discharge ink droplets of each color of black (K) are provided. Note that the serial type image forming apparatus may be configured to mount the recording head on a carriage that can reciprocate in the conveyance direction and the orthogonal direction. In the case of the serial type, the carriage uses a reciprocating mechanism (not shown) to eject ink droplets while moving in a direction perpendicular to the paper conveyance direction, and the conveyance belts 106 and 112 change the line feed (moves a predetermined conveyance distance). (Stop) is repeated to form an image.
The recording head unit 102 has the same configuration as this, and recording heads 102y, 102m, which discharge ink droplets of yellow (Y), magenta (M), cyan (C), and black (K), respectively. 102c and 102k.

The conveyor belt 106 is an endless belt, and is configured to circulate between the conveyor roller 121 and the tension roller 122. The paper 100 can be held on the transport belt 106 by, for example, a configuration that performs electrostatic suction, suction by air suction, or other known transport means. Further, a conveying means using a roller pair can also be used.
The conveyor belt 112, the conveyor roller 123, and the tension roller 124 have the same configuration. The conveyor belt 112 is an endless belt and is stretched between the conveyor roller 124 and the tension roller 123. It is configured to go around.

  The paper feeding unit 20 can be inserted and removed from the front side of the apparatus main body 10, and separates and feeds the paper feeding cassette 103 that loads and stores a large number of paper sheets 100 and the paper sheets 100 in the paper feeding cassette 103 one by one. A pickup roller 131 and a conveying roller pair 132 are provided.

  Further, the image forming apparatus 10 includes, as separate paper feeding units, a straight manual feed tray 105 that manually feeds the paper 100, a pickup roller 141 and a transport roller for feeding the paper 100 one by one from the straight manual feed tray 105. A pair 142 is provided.

  The processing liquid coating apparatus 200 includes a processing liquid container (not shown) in which a deformable PET film, for example, containing the processing liquid 201 is formed into a bag shape, and a pump (not illustrated) that pumps the processing liquid 201 supplied from the processing liquid container. And a coating unit 210 that coats the processing liquid 201 onto the paper 100 as a recording medium. The processing liquid 201 in the processing liquid container (not shown) is sucked up by a pump (not shown) and supplied to the liquid chamber 202 in the coating unit 210 through a supply path (not shown) to prepare for coating.

  The processing liquid 201 supplied to the liquid chamber 202 is confirmed by a liquid level detection sensor (not shown) provided in the liquid chamber 202 that the liquid level and the liquid level angle are within a predetermined range. The liquid level detection sensor uses, for example, an electrode pin method. Since the electrode pin method is a known technique, it will not be described in detail here, but the liquid level is detected by passing electricity through the electrode pins and conducting electricity between the electrode pins via the liquid. By this method, it is possible to prevent insufficient supply of the processing liquid 201 and supply of a predetermined amount or more to the liquid chamber 202.

  The application unit 210 includes a conveyance roller 234 that conveys the paper 100, an application roller 232 that applies the treatment liquid 201 to the paper 100 so as to face the conveyance roller 234, and supplies the treatment liquid 201 to the application roller 232 to form a liquid film. A squeeze roller 233 for reducing the thickness is provided.

  These rollers are arranged so that the application roller 232 is in contact with the conveyance roller 234 and the squeeze roller 233 is in contact with the application roller 232. Then, a liquid film layer of the processing liquid 201 supplied by the squeeze roller 233 and the application roller 232 is formed, transferred to the transport roller 234 side by the rotation of the application roller 232, and applied to the paper 100 as a recording medium. .

  Here, the treatment liquid 201 is a modifying material that modifies the surface of the paper 100 by being applied to the surface of the paper 100. For example, the treatment liquid 201 is applied in advance to the paper 100 (not limited to paper as a material as described above) without unevenness, so that moisture of the ink can quickly permeate the paper 100 and increase the color component. Fixing agent (setting agent) that prevents bleeding (feathering, bleeding, etc.) and back-through by increasing viscosity and further drying, and increases productivity (number of images output per unit time). is there.

  The composition of the treatment liquid 201 is, for example, a cellulose (any one of anionic, cationic, nonionic, or a mixture of two or more thereof) that promotes moisture permeation ( Hydroxypropyl cellulose etc.) and a solution to which a base such as talc fine powder is added. Furthermore, the treatment liquid 201 can contain fine particles.

  The paper 100 stored in the paper feed tray 103 is separated and fed one by one by the pickup roller 131 and sent to the registration roller pair 133 by the conveyance roller pair 132, and the conveyance roller pair 134 is sent from the registration roller pair 133 at a predetermined timing. Is sent to the processing liquid coating apparatus 200 via the transport path 300, and the processing liquid 201 is applied by the processing liquid coating apparatus 200.

  The paper 100 coated with the treatment liquid 201 is separated into the conveyance path 301 by the separation claw 400 indicated by a solid line, and the conveyance path is switched. The paper 100 separated into the conveyance path 301 is sent and held on the conveyance belt 106 via the conveyance path 301 by the conveyance roller pair 135. Then, the ink is transported by the circular movement of the transport belt 106 and droplets of each color are ejected from the recording head unit 101 to form an image.

  The paper 100 on which the image is formed is conveyed by the circular movement of the conveying belt 106 and conveyed to the paper discharge unit 30 as a paper discharge unit via the conveyance paths 302 and 309 by the conveyance roller pairs 136, 150, 143, and 144. Is done.

An image forming method in the recording head unit 102, which is another image forming unit, will be described.
The paper 100 coated with the treatment liquid 201 is separated into the conveyance path 305 by the separation claw 400 indicated by a broken line, and the conveyance path is switched. The paper 100 separated into the conveyance path 305 is sent and held on the conveyance belt 112 by the conveyance roller 141 via the conveyance path 305. Then, it is conveyed by the circular movement of the conveyor belt 112 and droplets of each color are ejected from the head unit 102 to form an image.

The sheet 100 on which the image is formed is conveyed by the circular movement of the conveyance belt 112 and conveyed to the paper discharge unit 30 via the conveyance path 306 by the conveyance roller pairs 142 and 143.
The downstream side of the conveying roller pair 143 is a common discharge path for paper on which an image is formed by the recording head units 102 and 101.

  When discharging the paper 100 with the image surface facing upward, the paper 100 transported to the paper discharge unit 30 is sent to the transport path 309 by switching the transport path by the separation claw 403, and discharged by the paper discharge roller pair 156. The paper is discharged to the tray 104.

  The paper discharge tray 104 is provided with a paper discharge end fence 107 for abutting the front end of the discharged paper and aligning the front end of the discharged paper. The paper discharge end fence 107 is provided so as to be movable in the arrow direction according to the paper size by a moving means (not shown). A plurality of sheets conveyed by the sheet discharge end fence 107 can be stacked without being disturbed on the sheet discharge tray.

  When the sheet 100 is discharged with the image surface facing downward, the sheet 100 conveyed to the sheet discharge unit 30 is sent to the switchback conveyance path 307 by switching the conveyance path by the separation claw 403. The sheet 100 sent to the switchback conveyance path 307 is conveyed by the reverse roller pair 155. Below the reverse roller pair 155, a reverse end fence 310 is provided that can be moved in the direction of the arrow by a moving means (not shown) so that at least the entire surface of the sheet does not go below the reverse roller pair 155. Even when a plurality of sheets are overlapped by the reverse end fence 310 and conveyed by the reverse roller pair 155, the entire surface of the previously conveyed sheet is prevented from falling out of the reverse roller pair 155 and falling down. Can do.

  When the rear end of the most downstream sheet 100 passes through the separation claw 404, the sheet 100 is switched back by the reverse roller pair 155, separated to the conveyance path 308 by the separation claw 404, and the sheet discharge tray 104 by the sheet discharge roller pair 156. The paper is discharged.

  When the sheet 100 is fed from the straight manual feed tray 105, the sheet 100 is conveyed toward the recording head unit 102 in the conveyance path 311 by the pickup roller 141 and the conveyance roller pair 142, and an image is formed on the sheet. Then, it passes through the paper discharge unit 30 and is discharged to a paper discharge tray 104 provided thereon.

Next, a case where images are formed on both sides of a sheet will be described.
The paper 100 stored in the paper feed tray 103 is separated and fed one by one by the pickup roller 131 and sent to the registration roller pair 133 by the conveyance roller pair 132, and the conveyance roller pair 134 is sent from the registration roller pair 133 at a predetermined timing. Is sent to the processing liquid coating apparatus 200 via the transport path 300, and the processing liquid 201 is applied by the processing liquid coating apparatus 200.

  The paper 100 coated with the treatment liquid 201 is separated into the conveyance path 301 by the separation claw 400 indicated by a solid line, and the conveyance path is switched. The paper 100 separated into the conveyance path 301 is sent and held on the conveyance belt 106 via the conveyance path 301 by the conveyance roller pair 135. Then, the ink is transported by the circular movement of the transport belt 106 and droplets of each color are ejected from the recording head unit 101 to form an image on the first surface.

  The sheet 100 on which the image of the first surface is formed is conveyed by the circumferential movement of the conveying belt 106 and is conveyed through the conveying path 302 by the conveying roller pair 136. The sheet 100 conveyed through the conveyance path 302 is separated by the separation claw 402 indicated by a solid line and separated into the switchback conveyance path 303. Next, the sheet 100 is conveyed from a reverse roller pair 137 for reversing and feeding the separated sheet 100 to the switchback conveyance path 303, and to the refeed path 304 by the separation claw 401 indicated by a solid line. The transport path is switched, and the transport roller pair 138, 139, 140 is transported again to the registration roller pair 133 via the refeed path 304.

  The paper 100 sent to the registration roller pair 133 is sent from the registration roller pair 133 to the processing liquid coating apparatus 200 via the transport path 300 by the transport roller 134 at a predetermined timing, and the processing liquid coating is applied to the second surface of the paper 100. The processing liquid 201 is applied by the apparatus 200.

  The sheet 100 coated with the treatment liquid 201 on the second surface is separated into the conveyance path 305 by the separation claw 400 indicated by a broken line, and the conveyance path is switched. The paper 100 separated into the conveyance path 305 is sent and held on the conveyance belt 112 by the conveyance roller 141 via the conveyance path 305. Then, it is transported by the circular movement of the transport belt 112 and droplets of each color are ejected from the head unit 102 to form an image on the second surface.

The sheet 100 on which the image on the second surface is formed is conveyed by the circular movement of the conveyance belt 112 and conveyed to the paper discharge unit 30 via the conveyance path 306 by the conveyance roller pair 142 and 143.
The paper 100 transported to the paper discharge unit 30 is switched to a transport path by the separation claw 403 and sent to the transport path 309, and is discharged to the paper discharge tray 104 by the paper discharge roller pair 156.

Next, control of the recording head unit in the image forming apparatus of the present invention will be described.
The image forming apparatus 10 functions as an input system for image data (print data) formed by the recording head units 101 and 102, an information processing apparatus such as an external personal computer, an image reading apparatus such as an image scanner, a digital camera, etc. Print data including image data can be received from a host such as an image pickup apparatus via a cable or a network, and the received print data can be processed and printed.

  When an image formation input signal is input to the image forming apparatus 10, a paper feed motor (not shown) and a paper feed clutch (not shown) are driven to separate the paper 100 one by one from the paper feed cassette 103 and feed the paper 20. Are fed to an arbitrary recording head unit 101 or 102. When there is a print on the next page, a paper edge detection sensor (not shown) and a paper transport distance are calculated to detect the rear edge position of the previous page, and the distance between the paper and the previous page is predetermined. Is determined (for example, 60 mm), and when a predetermined sheet-to-sheet distance is reached, paper is fed and conveyed to the printing start position of the recording head unit 101 or 102, whereby predetermined paper is Paper is continuously fed to the printing start position at a distance, and paper feeding is repeated until the last page.

  At this time, as a characteristic control of the present invention, the paper 100 is continuously conveyed to one of the recording head units 101 and 102 selected first up to a predetermined number of image planes, and the recording head selected first. Image formation is performed only by the unit. This recording head unit prepares for image formation and performs idle discharge for maintenance toward an empty discharge port (not shown). In order to increase the productivity when the predetermined number of image planes or the predetermined number of sheets is exceeded, the other recording head unit similarly prepares for image formation and performs idle discharge for maintenance toward an empty discharge port (not shown). After the predetermined number of image planes, images are formed simultaneously by both recording head units 101 and 102.

  Here, the predetermined number of image planes is one index for saving ink, and the user may set the predetermined number of image planes from a display unit (not shown) of the image forming apparatus 10 or the image forming apparatus. 10 may be set from a personal computer connected to the network.

  Further, the image forming apparatus includes a stop time storage unit that stores stop time information of a plurality of recording head units, and selects an image forming unit to be used first from the plurality of recording head units based on the stop time information. To do. For example, in the case of continuous stop for one week, regardless of the operation time of the recording head unit, one unit having a longer continuous stop time is selected as the image forming means to be used first, and the predetermined number of image planes of this unit is selected. Change the setting to 1. Therefore, when the number of image surfaces is two or more, the other unit, that is, both the recording head units 101 and 102, are prepared for image formation, and the ink for maintenance is discharged to the empty discharge port (not shown). The recording head unit forms an image. As a result, both recording head units can perform idle discharge maintenance for a long period of time.

  The one-week continuous stop in this case is a time before the ink in the recording head becomes unrecoverable by maintenance with normal idle discharge because the ink in the recording head becomes thickened due to drying and cannot be discharged. The continuous stop time is not limited to weekly continuous stop, and may be any continuous stop time that can be recovered only by normal idle discharge. When this continuous stop time is exceeded to some extent, maintenance by suction using a suction cap (not shown) is required, which causes more waste liquid compared to normal idle discharge. In order to avoid this, if the image is left for a long period of time, the predetermined number of image planes is set to 1, and idle recording maintenance is performed in both recording head units so that images are formed in both recording head units. desirable.

  In addition, the image forming apparatus includes an operation time storage unit that stores operation time information of a plurality of recording head units, and selects a recording head unit having a shorter operation time based on the operation time information or a plurality of recording head units. One recording head unit to be used first may be selected so that the head units have substantially the same operating time. As a result, it is possible to prevent only one of the recording head units from being used and deteriorate and to extend its life.

  Next, using FIG. 2, one of the recording head units 101 and 102 is selected based on the stop time information and the operation time information of the recording head unit, and printing is performed up to a predetermined number of image planes by the selected unit. A series of sequence control in the image forming apparatus of the present invention in which printing is performed in other units after the number of pages will be described.

  As described above, the image forming apparatus includes the stop time storage unit that stores the stop time information of the plurality of print head units and the operation time storage unit that stores the operation time information. The unit 101 or 102 is selected to form an image first.

  First, when an image formation input signal is input to the image forming apparatus 10 (S1), the continuous stop time of the recording head unit 101 is that of the recording head unit 102 based on the stop time information of the stop time storage means of the recording head units 101 and 102. It is determined whether it is longer (S2). If Yes (if longer), it is determined from the stop time information in the stop time storage means whether the stop time of the recording head unit 101 is equal to or longer than a predetermined continuous stop time (S3). In the case of No here, it is determined from the operation time information stored in the operation time storage means whether the operation time of the recording head unit 101 is shorter than that of the recording head unit 102 (S5). In the case of Yes, the recording head unit 101 is selected as an image forming unit to be used first, and printing is performed by the recording head unit 101 without using another recording head unit 102 having a longer operating time (S6). . Next, it is determined whether a predetermined number of image planes have been printed in the recording head unit 101 (S7). In the case of No here, printing is continued only by the recording head unit 101. Thereafter, when the predetermined number of image planes is exceeded in S7, printing is performed also in the other recording head units 102 until printing is completed, that is, printing is performed simultaneously in the recording head units 101, 102 (S8, S9, S10).

  On the other hand, in the flow from S3 to S5, in the case of No in S5, the recording head unit 102 having the shorter operating time is selected as the image forming unit to be used first, and the recording head unit 101 having the longer operating time is not used. Then, printing is performed by the recording head unit 102 (S13). Thereafter, printing is performed by the recording head unit 102 until a predetermined number of image planes are printed.

  In the case of Yes in S3, since it is necessary to operate the recording head unit 101 that has been stopped for the continuous stop time or longer, the image forming unit to be used first is not selected by the determination of the length of the operation time (S5). In addition, the predetermined number of image faces of the recording head unit 101 is set to 1 (S4), and after performing idle discharge maintenance, printing is performed by the recording head unit 101 (S6). Thereafter, the sequence control from S7 to S10 is performed.

  If No in S2 (if it is short), it is determined from the stop time information in the stop time storage means whether the stop time of the recording head unit 102 is equal to or longer than a predetermined continuous stop time (S11). In the case of No here, it is determined from the operation time information stored in the operation time storage means whether the operation time of the recording head unit 101 is shorter than that of the recording head unit 102 (S5). In the case of No, the recording head unit 102 is selected as an image forming unit to be used first, and printing is performed by the recording head unit 102 without using the recording head unit 101 having a longer operating time (S13). Next, it is determined whether a predetermined number of image planes have been printed in the recording head unit 102 (S14). In the case of No here, printing is continued by the recording head unit 102. Thereafter, when the predetermined number of image planes is exceeded in S14, printing is also performed in the recording head unit 101 until printing is completed, that is, printing is performed simultaneously in the recording head units 101 and 102 (S15, S16, and S17).

  On the other hand, in the flow from S11 to S5, in the case of Yes in S5, the recording head unit 101 having the shorter operating time is selected as the image forming unit to be used first, and the recording head unit 102 having the longer operating time is not used. Then, printing is performed by the recording head unit 101 (S6). Thereafter, printing is performed by the recording head unit 101 until a predetermined number of image planes are printed.

  In the case of Yes in S11, since it is necessary to operate the recording head unit 102 that has been stopped for the continuous stop time or longer, the image forming means to be used first is not selected by the determination of the length of the operation time (S5). In addition, the predetermined number of image surfaces of the recording head unit 102 is set to 1 (S12), and after performing idle discharge maintenance, printing is performed by the recording head unit 102 (S13). Thereafter, the sequence control from S14 to S17 is performed.

  Here, the image forming apparatus includes an ink consumption amount storage unit that stores information about the ink consumption amount of the recording head unit instead of or in addition to the operation time storage unit. The amount may be used as an index. In this case, instead of or in addition to S5, control may be performed so that printing is performed with a recording head unit that consumes less ink.

  As described above, after receiving the image input signal, the recording head unit to be used first is selected based on the stop time information and the operating time information of the recording head unit, and the selected recording head unit selects a predetermined number of image planes or a predetermined number. Printing is performed until the number is exceeded. Then, after the predetermined number of image planes or the predetermined number of sheets, other recording head units are used simultaneously. As a result, a plurality of recording head units can be used evenly, thickening of the ink inside the recording head due to standing for a long time can be prevented, and productivity can be improved and waste liquid can be reduced.

  Further, even if the number of image planes for which printing has been completed in one recording head unit has not reached the predetermined number of image planes, a print data buffer section (not shown) of the image forming apparatus 10 has a predetermined number of image planes or more. It may be set to use another recording head unit when the print data is accumulated. Thereby, the printing time can be shortened.

In addition, the predetermined number of image planes is given a certain width (for example, 5 to 10 sheets), that is, even if the number of image planes of one selected recording head unit exceeds the predetermined number of image planes, the remaining number of image planes remains. When the number is small, the image formation may be continued by the selected image forming means without using another unit.
For example, if the number of remaining images to be printed is less than the predetermined number of sheets (5 sheets) even if the predetermined number of image planes (5 sheets) is exceeded, only one recording head unit is used without using another recording head unit. Also good. This is because even if other recording head units are in a printable state, the effect of improving productivity is small when the number of printed sheets is small.

  Further, the predetermined number of image planes may be set by the user selecting a print mode such as a saving mode, a standard mode, or a high-speed mode. In the saving mode, for example, only one recording head unit among a plurality of recording head units is used. In the standard mode, for example, only one recording head unit is used up to 30 image planes, and the other recording head units are used simultaneously for 31-60 image planes. In the high-speed mode, for example, only one recording head unit is used up to 4 image planes, and the other recording head units are used simultaneously for 5-8 image planes.

  Further, the total printing time may be employed instead of the predetermined number of image planes as the switching timing for using a plurality of recording head units. For example, when it takes 1 minute or more to complete the printing of the image data in one recording head unit, a plurality of recording head units may be used. At this time, another recording head unit may be used after one minute has actually passed since printing, or the image forming apparatus is provided with a printing time calculation device, and the printing time calculation device is determined from the data stored in the print data buffer unit. A plurality of recording head units may be used when it is determined that it takes longer than a predetermined printing time.

Also, different predetermined image planes may be used for double-sided printing and single-sided printing. Specifically, in the case of double-sided printing, since it takes a relatively long time to form an image, the predetermined number of image surfaces may be set smaller than that of single-sided printing.
In this way, by using only one recording head unit up to a predetermined number of image planes, it is possible to reduce the amount of idle ejection of maintenance ink and to reduce waste liquid.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the configuration of each part of the image forming apparatus is arbitrary, and three or more recording head units can be applied.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Paper feed part 30 Paper discharge unit (paper discharge part)
100 paper (recording medium)
101, 102 Recording head unit (image forming means)

JP 2005-153261 A

Claims (10)

An image is formed by a paper feeding unit that stores a recording medium, a plurality of image forming units that form an image by ejecting droplets onto the recording medium supplied from the paper feeding unit, and the plurality of image forming units. In an image forming apparatus having a paper discharge unit for discharging the recording medium,
The plurality of image forming means can process image formation on the recording medium in parallel,
An image forming apparatus that performs image formation after performing idle ejection maintenance with only one of the plurality of image forming units that is initially selected until a predetermined number of image planes is initially set. 2. The image forming apparatus according to claim 1, wherein after the predetermined number of image surfaces is exceeded , image formation is performed after idle discharge maintenance is performed in another image forming unit.   A stop time storage unit that stores stop time information of the plurality of image forming units is provided, and an image forming unit to be used first is selected from the plurality of image forming units based on the stop time information. The image forming apparatus according to claim 1.   An operating time storage unit that stores operating time information of the plurality of image forming units is provided, and an image forming unit to be used first is selected from the plurality of image forming units based on the operating time information. The image forming apparatus according to claim 1.   5. The image forming apparatus according to claim 4, wherein an image forming unit having a shorter operating time is selected as an image forming unit to be used first.   6. The image forming means that is initially used as an image forming means to be used first is an image forming means that has a longer continuous stop time regardless of the operation time and has stopped after a predetermined continuous stop time. The image forming apparatus according to claim 1.   7. The image forming apparatus according to claim 6, wherein the predetermined number of image planes initially set for the image forming means to be selected is changed to a smaller number of image planes.   Instead of or in addition to the operating time storage means, an ink consumption storage means for storing ink consumption information of the plurality of image forming means is provided, and based on the ink consumption information instead of or in addition to the operating time information. 6. The image forming apparatus according to claim 4, wherein an image forming unit to be used first is selected from the plurality of image forming units. Even when the number of image planes in the image forming unit selected first does not reach the predetermined number of image planes, when the print data more than the predetermined number of image planes is stored in the print data buffer unit, another image forming unit 9. The image forming apparatus according to claim 1 , wherein image formation is performed after performing idle discharge maintenance .   Even if the number of image planes in the image forming means selected first exceeds the predetermined number of image planes, it is selected first without using other image forming means depending on the number of remaining image planes to be printed. The image forming apparatus according to claim 1, wherein image formation is continued by the image forming unit.

Images