JP2011207214A - Image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem wherein there is a risk of soiling a belt if an idle ejection region is enlarged when carrying out idle ejection to suction holes while productivity is lowered if the idle ejection region is narrowed.SOLUTION: A plurality of arrays A1-A8, B1-B8 of suction holes 201 with a plurality of suction holes 201 arranged in the arranged direction of nozzles are arranged at required spaces and in a predetermined cycle in a conveyor belt 43. When idle ejection is performed to the suction holes 201, a region (the number of nozzles) used as the idle ejection region on one suction hole 201 is changed to a region k2 or k according to ejection accuracy.

Description

  The present invention relates to an image forming apparatus and a program, and more particularly to an image forming apparatus including a recording head that ejects droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . 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, ceramics, or the like. In addition, “image formation” means not only that an image having a meaning such as a character or a figure is imparted to the medium but also an image having no meaning such as a pattern is imparted to the medium (simply liquid. It also means that a droplet hits the medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials and the like are also included.

  In such an image forming apparatus (hereinafter, also simply referred to as “inkjet recording apparatus”), the recording head is caused by the evaporation of the solvent from the nozzle because of recording by discharging ink from the nozzle onto the paper. There is a problem in that a recording failure occurs due to a discharge failure due to an increase in ink viscosity, solidification of ink, adhesion of dust, and mixing of bubbles.

  Therefore, in order to maintain the ink droplet ejection state from the recording head satisfactorily, a so-called idle ejection operation is performed in which droplets that do not contribute to image formation (empty ejection droplets) are ejected during the printing operation.

  In the serial type image forming apparatus, since the recording is performed while moving the recording head, the position where the idle ejection is performed is set in an area outside the sheet conveying path by the conveying means for conveying the sheet, and the recording head reciprocates. Since idle ejection can be performed outside the transport path as a process of the operation, the interruption time of the printing operation is short, and there is almost no problem that the printing speed is lowered.

  On the other hand, in a line type image forming apparatus that forms an image without moving the recording head (fixed state), if an empty ejection position is set outside the paper conveyance path, the printing operation is interrupted. Since it is necessary to move the recording head to the idle ejection position outside the conveyance path, there is a problem that considerable time loss occurs and continuous printing and high-speed printing are not realized.

  Therefore, as described in Patent Document 1, conventionally, air is sucked from a plurality of suction holes formed in the conveyance belt to adsorb the sheet material, and the conveyance of the conveyance belt conveys the sheet material to the printing unit. As a configuration, for all the nozzles of each ink jet head, any one of the suction holes provided in the transport belt passes through the print position of each nozzle, and the nozzle and the suction hole are provided between the recording media. It is known that the ink receiving member receives the ink through the suction hole by discharging the ink from the nozzle after the alignment.

JP 2007-168277 A

  By the way, as described above, when idle ejection is performed with respect to the suction holes, the suction holes are formed by shifting the positions in the nozzle arrangement direction, so that all the nozzles do not correspond to the suction holes at the same time. Here, if the idle ejection is performed for all the nozzles corresponding to one suction hole, the number of nozzles that can be ejected at one time increases, but if the droplet ejection accuracy is low, the nozzles land on the conveyor belt. There is a risk of soiling the conveyor belt and the printed matter. On the other hand, if the number of nozzles that perform idle ejection corresponding to one suction hole is reduced, the number of rows of suction holes that are necessary for performing idle ejection for all nozzles increases, and as a result, a wide space between the sheets must be obtained. In this case, there is a problem that the printing speed is lowered (productivity is lowered).

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain optimum productivity while avoiding contamination of the conveyor belt.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head in which a plurality of nozzles for discharging droplets are arranged;
A plurality of suction holes are formed, and an endless conveyance belt that conveys a sheet in a direction crossing the nozzle arrangement direction of the recording head;
Control means for controlling an idle ejection operation for ejecting droplets that do not contribute to image formation from the recording head toward the suction hole of the transport belt when there is no paper;
And a means for changing the number of nozzles discharged to one suction hole during the idle discharge operation.

  Here, the number of nozzles ejected to the one suction hole may be changed according to the ejection accuracy of the recording head.

  In this case, a means for determining whether or not the discharge accuracy at the current idle discharge operation has changed with respect to the discharge accuracy at the previous idle discharge operation, and the discharge accuracy when it is determined that the discharge accuracy has changed. And a means for changing the number of nozzles discharged to the one suction hole and setting the number of nozzles in the previous idle discharge operation when it is determined that the discharge accuracy has not changed. And can.

  In addition, a productivity priority mode and an image quality priority mode are provided, and the number of nozzles discharged to the one suction hole can be changed according to each mode.

The program according to the present invention is:
From the recording head to a suction hole formed in an endless conveying belt that conveys a sheet from a recording head in which a plurality of nozzles for discharging droplets are arranged in a direction intersecting the nozzle arrangement direction of the recording head. A program for causing a computer to perform a process for controlling an empty ejection operation for ejecting droplets that do not contribute to image formation when there is no paper.
The computer is configured to perform a process of changing the number of nozzles discharged to one suction hole during the idle discharge operation.

  The image forming apparatus according to the present invention includes means for changing the number of nozzles discharged to one suction hole during the idle discharge operation, so that optimum productivity can be obtained while avoiding contamination of the conveyor belt. Can be.

  According to the program of the present invention, since the number of nozzles discharged to one suction hole is changed during the idle discharge operation, it is possible to obtain optimum productivity while avoiding contamination of the conveyor belt. it can.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to the present invention. It is a schematic plane explanatory drawing similarly. It is explanatory drawing which shows an example of a head module. It is typical explanatory drawing with which it uses for description of the overlapping part of a head. It is block explanatory drawing which shows the outline | summary of a control part. It is explanatory drawing with which it uses for description of arrangement | positioning of the suction hole of a conveyance belt, and an idle discharge area | region. It is explanatory drawing with which it uses for description in the case of the idle discharge area | region 2k per one suction hole. It is explanatory drawing with which it uses for description in the case of the idle discharge area | region k per one suction hole. It is a flowchart with which it uses for description of the process which determines the idle discharge area | region (nozzle number) with respect to one suction hole in 1st Embodiment of this invention. It is a flowchart with which it uses for description of the process which determines the idle discharge area | region (nozzle number) with respect to one suction hole in 2nd Embodiment of this invention. It is explanatory drawing similarly used for description of calculation of an idle discharge area | region. It is explanatory drawing with which it uses for description of the head arrangement | positioning used for description of 3rd Embodiment of this invention. It is explanatory drawing similarly used for description of calculation of an idle discharge area | region. It is a flowchart with which it uses for description of 4th Embodiment of this invention. It is explanatory drawing which shows an example of a mode setting screen similarly. It is explanatory drawing which similarly shows the other example of a mode setting screen. It is a flowchart with which it uses for description of 5th Embodiment of this invention. It is a flowchart with which it uses for description of 6th Embodiment of this invention. It is a flowchart with which it uses for description of the area | region calculation process of FIG. It is a flowchart with which it uses for description of 7th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram for explaining the overall configuration of the image forming apparatus, and FIG. In FIG. 2, the nozzles of the recording head are shown in a transmissive state.
The image forming apparatus 1 is a line-type image forming apparatus, and includes a paper feed unit 2 that stacks and feeds paper P, a paper discharge unit 3 that discharges and stacks printed paper P, and paper P. A transport unit 4 that transports the paper from the unit 3 to the paper discharge unit 3 and an image forming unit 5 that discharges droplets onto the paper P transported by the transport unit 4 to form an image are provided.

  The paper feed unit 2 is configured to carry a paper feed tray 21 on which the paper P is stacked, a paper feed roller pair 22 that feeds paper P from the paper feed tray 21 one by one, a registration roller pair 23, and transport of the paper P The guide member 24 etc. which guide these are provided.

  The paper discharge unit 3 has a paper discharge tray 31 for stacking and holding the paper P fed by a jump table 32 for guiding and smoothly feeding the lower surface of the paper P conveyed from the conveyance belt 43.

  The conveyance unit 4 performs air suction from an endless conveyance belt 43 that is wound between a driving roller (conveyance roller) 41 and a driven roller 42 and a suction hole 201 of the conveyance belt 43 to convey the paper P. A suction means 44 such as a suction fan to be adsorbed on 43, a platen member (deflection prevention member) 45 that supports the conveying belt 43 from the back surface at a position facing the image forming unit 5, and idle discharged droplets (waste liquid). ) And the like, and the conveyance belt 43 orbits in the direction indicated by the arrow in FIG. 1 to adsorb the paper P and convey it from the left to the right in the drawing.

  The image forming unit 5 discharges droplets of four colors of ink (yellow Y, magenta M, cyan C, black K) onto the paper P that is sucked and held on the transport belt 43 and transported. Head type array 50 including line type recording heads 51Y, 51M, 51C, 51K (hereinafter referred to as “recording head 51” when colors are not distinguished), and each recording head 51 from an ink tank such as a sub tank (not shown). And a branching member 52 that distributes and supplies ink.

  Here, the head module array 50 of the image forming unit 5 conveys a plurality of heads 101 having a nozzle row 103 in which a plurality of nozzles 102 are arranged on a common base member 53 as shown in FIGS. The recording heads 51 of each color are configured by a plurality of (in this example, 10) heads 101 in a zigzag array in two rows. . Note that the entire arrangement of a plurality of nozzles arranged in a direction intersecting the paper conveyance direction constituted by a plurality of heads 101 is referred to as a “nozzle row in a recording head”. The head module array 50 is not limited to the above configuration.

  As shown in FIG. 4, the heads 101 are arranged so that one or a plurality of nozzles 102 at the ends of two adjacent heads 101 overlap (overlap) in the nozzle arrangement direction (head arrangement direction). Thereby, recording can be performed at the same recording position (dot position) by the nozzles 102 of the two heads 101.

  1 and 2, on the upstream side of the registration roller pair 23 in the paper conveyance direction (hereinafter simply referred to as “upstream side”), a pair of paper feed rollers 22 that separate and feed the paper P one by one. A first paper detection unit 11 for controlling the drive timing and for reading the position and size of the paper P is disposed, and for determining the droplet discharge timing from the recording head 51 and for the paper upstream of the image forming unit 5. A recording position detection unit 12 for detecting the trailing edge is disposed, a second sheet detection unit 13 for reading the position of the sheet P is disposed on the downstream side of the image forming unit 5, and a drive roller (conveyance roller) 41 is disposed above the drive roller 41. A paper end detection unit 14 for determining whether the paper P is jammed or the supply timing of the next paper P is provided.

  Further, as shown in FIG. 2, a belt reference hole row recognition mark (marker) 17 is provided on the transport belt 43, and as shown in FIGS. 1 and 2, the belt for detecting the belt reference hole row recognition mark 17 is provided. A reference hole row detection sensor 16 is arranged.

Next, an outline of the control unit in this image forming apparatus will be described with reference to the block explanatory diagram of FIG.
This control unit is a main control unit (system controller) composed of a microcomputer, an image memory, a communication interface, and the like that also serve as control means and control means for performing control relating to idle ejection in the present invention, which controls the entire image forming apparatus. 501. The main control unit 501 sends print data to the print control unit 502 in order to form an image on a sheet based on image data transferred from an external information processing apparatus (host side) and various command information. The main control unit 501 stores and holds a program in the present invention in order to perform control related to idle ejection, and is executed by the CPU in the main control unit 501.

  Based on the print data signal received from the main control unit 501, the print control unit 502 generates data for driving pressure generation means for ejecting droplets from the nozzles 102 of the recording head 51. Transfer and various signals necessary for transfer confirmation, etc. to the head driver 503, a storage unit as drive waveform data storage means, a D / A converter and a voltage amplifier for D / A conversion of drive waveform data And a drive waveform generation unit composed of a current amplifier and the like, and a selection means for selecting a drive waveform to be given to the head driver 503, a drive composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) A waveform is generated and output to the head driver 503 to drive-control the recording head 51.

  Further, the main control unit 501 drives and controls a sheet feed motor 505 that rotates the transport belt 43 and a motor that drives the suction fan 44 via the motor driver 504. The main control unit 501 also performs drive control of a paper feed motor that feeds the paper P from the paper feed unit 2, but is not illustrated.

  In addition, the main control unit 501 receives detection signals from the sensor group 506 including the above-described various detection units, the detection sensors 11 to 16, and other various sensors, and receives various information from the operation unit 507. Exchange input / output and display information.

Next, an image forming operation in this image forming apparatus will be described.
Image data to be printed is input from the information processing apparatus via a communication interface in the main control unit 501 and stored in an internal image memory. The main control unit 501 drives the paper feed roller pair 22 by a paper feed drive unit (not shown), separates the uppermost paper P on the paper feed tray 21 and feeds the paper toward the registration roller pair 23, and at a predetermined timing. The circular movement of the conveyor belt 43 is started.

  When the main control unit 501 receives a paper detection signal from the paper detection unit 11, after a predetermined timing, the main control unit 501 drives the registration roller pair 22 to send the paper P onto the transport belt 43.

  Thereafter, when the main control unit 501 detects that the leading end of the sheet P has reached the sensor unit of the recording position detection unit 12, the main control unit 501 performs an image on the sheet P conveyed from each recording head 51 at a predetermined timing. An image is formed by ejecting droplets according to data. That is, image data stored in an image memory (not shown) is transferred to the print control unit 502 and converted into dot data for each color, and the recording head 51 is driven via the head driver 503 in accordance with the dot data. Thus, a required droplet is ejected from the nozzle 102.

  The recording head 51 controls the droplet discharge timing in synchronization with the conveyance speed of the paper P based on the detection result from the recording position detection unit 12, and the image on the paper P without stopping the conveyance of the paper P. Can be formed.

  Then, the paper P on which the image is formed is continuously conveyed by the conveying belt 43 and discharged onto the paper discharge tray 31 of the paper discharge unit 3.

Next, a configuration relating to idle ejection in the image forming apparatus will be described.
First, referring to FIG. 2, the transport belt 43 is provided with a plurality of suction holes 201 arranged so as to pass through positions facing the nozzles 102 for all the nozzles 102 of the recording head 51. Here, the arrangement of the suction holes 201 in the nozzle arrangement direction is referred to as a “suction hole row”. In this example, the suction hole arrays A1 to A8 (referred to as “suction hole array A” when not distinguished) and the suction hole arrays B1 to B8 (referred to as “suction hole array B” when not distinguished) are provided in the paper transport direction. They are repeatedly arranged from the downstream side toward the upstream side, that is, from right to left in FIG.

  As shown in FIG. 2, both the suction hole arrays A and B are arranged so that the center of the suction hole 201 is positioned on a virtual line segment having a predetermined angle θ with respect to the paper transport direction, and the virtual In the hole arrangement of the next suction hole array A1, the center A1c of the suction holes 201 provided in the middle of the pair of suction holes 201 corresponding to the nozzles 102a corresponding to the overlapping portions generated by the staggered arrangement of the heads 101 The angle θ is set so as to pass.

  As a result, out of a total of 16 rows of suction hole rows A1 to A8 and B1 to B8, 9 rows pass through the positions facing all the nozzles 102 of each recording head 51 no matter which row starts empty ejection, It is possible to complete empty discharge.

  Since the suction holes 201 have the same size (hole diameter), the number of nozzles ejected to one suction hole 201 is set to a predetermined continuous constant number. Nozzles 102a corresponding to overlapping portions (overlapping portions in the nozzle arrangement direction) generated by the staggered arrangement of the heads 101 and 101, and nozzles 102b at the end of the nozzle row in the recording head 51 that is less frequently used (nozzles 102b are the recording head 51). Nozzles at the end of the nozzle row) is set to be about half the number of nozzles. Here, the number of the nozzles 102a and 102b is not limited to one, and when two or more nozzles 102 are stacked in the nozzle arrangement direction, both are the nozzles 102a. Similarly, the nozzle 102b at the end in the nozzle row direction is also one. Not only the number but also handling two or more nozzles 102 as nozzles 102b in relation to idle ejection is included.

  That is, the number of nozzles discharged to the suction holes 201 corresponding to the overlapping portions of the heads 101 is determined as a result of empty discharge from half the number of nozzles 102 in each head 101 on the upstream side in the transport direction and the downstream side in the transport direction. As shown, the number of nozzles to be ejected other than the overlapping portion is almost the same.

  Further, of the suction hole arrays A and B, the nozzle 102a corresponding to the overlapping part of the two heads 101 generated by the staggered arrangement of the heads 101 in the suction hole array A1 and the end portion in the nozzle arrangement direction (recording head) The center of one suction hole 201 is provided on each of the line segments C and D that pass through the nozzle 102b at the edge 51) and are parallel to the paper conveyance direction. In FIG. 2, the corresponding suction hole 201 is indicated by a bold line.

  Then, the suction hole array A1 having the suction holes 201 that pass through the end portions of the recording head 51 and the overlapping nozzles 102a in the nozzle arrangement direction of the two heads 101 is referred to as a reference suction hole array (reference hole array). In order to detect the position of the reference hole row A1, the belt reference hole row recognition mark 17 described above is provided at the side end portion (end portion in the nozzle arrangement direction) of the conveying belt 43 and is detected by the belt reference hole row detection sensor 16. Like to do. The belt reference hole array recognition mark 17 is periodically and similarly provided for the suction hole array (reference hole array) A1 that is repeatedly formed and arranged over the entire circumference of the transport belt 43. .

  In the present embodiment, due to the arrangement of the suction holes 201, the arrangement of the suction holes 201 in the suction hole array B4 is the same as the arrangement of the suction holes 201 in the suction hole array A1, and is similarly indicated by a thick line. . Here, the suction holes 201 provided in the conveying belt 43 are provided for sucking and conveying the paper P, and the arrangement of the suction holes 201 is made uniform. The suction hole row such as the suction hole row B4 is not particularly required to be used as a suction hole for performing idle ejection, and can be used only as a suction hole for sucking paper, or the suction hole row B4 can be used as a suction hole. Of these holes 201, the second idle discharge is performed also on the nozzles 102 a corresponding to the head overlapping portions and the suction holes 201 facing the nozzles 102 b at the end of the nozzle arrangement direction where the frequency of use is low. It is also possible to keep the discharge state of the nozzle 102 better.

Next, the idle ejection operation in this image forming apparatus will be described.
During printing or standby, when a specific nozzle 102 is used less frequently and ink droplets are not ejected for a certain period of time, a phenomenon occurs in which the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, even if the actuator means (not shown) of the head 101 is operated, ink droplets cannot be ejected from the nozzle 102. Before this state is reached, the head 101 is driven to operate the actuator means within the range of the viscosity that can be discharged, and empty discharge is performed to discharge the deteriorated ink (ink in the vicinity of the nozzle having increased viscosity). It is to be noted that control is performed so that the idle ejection is performed after a predetermined non-operating nozzle elapsed time or the number of recordings has elapsed.

  That is, when the recording operation is continuously performed until the predetermined time or the predetermined number of times is reached, the main control unit 501 (system controller) causes the first paper detection unit 11 to set the leading end Psa of the paper Ps to be transported next. After detection, after the trailing edge Pfb of the currently transported paper Pf passes the detection position of the recording position detection unit 12, the print control unit 502 transfers drive data according to the idle ejection drive pattern to the driver 503, Liquid droplets (empty ejection droplets) that do not contribute to recording are ejected from the nozzles 102 in the recording head 51Y.

  As a result, using the transport interval between the rear end of the sheet P currently being transported and the front end of the sheet P to be transported next, there is a mutual gap (between sheets) of the sheet P at a position facing the recording head 51. When positioned, the ejected droplets are ejected from the nozzles of the recording head 51 </ b> Y toward the suction holes 201 arranged so as to pass through the position between the conveyance belt 43 between the sheets and the nozzles 102 of the recording head 51. Let

  The empty discharge droplets discharged toward the suction hole 201 of the transport belt 43 in this way pass through the suction holes 201 of the transport belt 43 and the through holes provided in the deflection preventing member 45, and are further provided therebelow. Land on the empty ink receiver 46. As a result, unused dried ink or defective ink whose viscosity has changed is removed from the nozzles 102 of the recording head 51.

  Next, after the idle ejection from the nozzles 102 of the recording head 51 is performed, the suction holes 201 of the transport belt 43 are sequentially moved to positions facing the nozzles 102 of the recording heads 51M, 51C, and 51K. Accordingly, the ejection droplets are ejected from the respective recording heads 51M, 51C, 51K.

  At this time, the main control unit 501 discharges empty discharge droplets from the other recording heads 51M, 51C, and 51K in substantially the same place as the suction holes 201 on the conveyance belt 43 where the empty discharge is performed by the recording head 51Y. The droplet discharge timing is controlled as described above. That is, on the basis of the detection result of the recording position detection unit 10, the adjacent recording heads 51M, 51C, Ejection is performed sequentially from each of 51K. Note that the timing of the recording heads 51 during idle ejection is exactly the same as the timing of the recording heads 51 during normal printing. The difference is that, during normal printing, the detection signal at the leading edge of the paper P by the recording position detector 12 is used as a reference, while during the idle ejection operation, the detection signal at the trailing edge of the paper P is used as a reference. .

Next, the arrangement of the suction holes of the conveyor belt and the idle ejection area will be described with reference to FIG.
In the following, for the sake of simplicity, it is assumed that there is no difference between the suction hole arrays A and B, nozzle misalignment in the sub-scanning direction (paper transport direction) due to the staggered arrangement, and nozzle misalignment for each YMCK color. Further, here, for the sake of simplicity, there are two types of empty discharge areas (areas used as empty discharge areas) for one suction hole 201, that is, areas k and 2k, that is, the upper limit of the empty discharge possible area. Although it is set as the empty discharge area | region 2k and the arrangement | positioning of the suction hole 201 according to it, it is possible to use other methods.

  Here, since the number of nozzles corresponding to the area set as the idle ejection area is the number of nozzles that can be idle ejected into the suction hole at once, the idle ejection can be performed in one suction hole by changing the size of the idle ejection area. The number of nozzles will be changed.

  First, the suction holes 201 are arranged on the conveyor belt 43 at a specified interval. Here, as shown in FIG. 6, they are arranged at regular intervals of 2k + (N × 2k) in the main scanning direction (nozzle arrangement direction). R is the radius of the suction hole 201 and T is the distance between lines in the sub-scanning direction. Line group (suction hole array group) A (one suction hole array) is denoted as Am, and line group (suction hole array) B (one suction hole array) is denoted as Bm (m = 1, 2,... N + 1). Then, the line group B starts after the (N + 1) th line of the line group A.

  At this time, if the area used for idle ejection in each suction hole 201 is the idle ejection area 2k, idle ejection can be performed only with a nozzle corresponding to 2k × (number of line Am suction holes) in the line Am. . Therefore, in the line Am + 1 that is a distance T away from the line Am in the sub-scanning direction, the nozzles that have not been able to perform idle ejection in the line Am are ejected idle.

  As described above, when the idle discharge possible region is 2k, it is necessary to use the suction holes 201 for N + 1 lines of the line group A in order to perform the idle discharge of all the nozzles in one line in the main scanning direction. At this time, if the idle ejection of all the nozzles for one line in the main scanning direction is performed between the sheets, it is necessary to widen at least the space between the sheets as shown in FIG.

  Similarly, if the idle discharge possible area for each suction hole 201 is k, the line group A alone cannot perform the idle discharge of all the one line in the main scanning direction, and the suction holes for N + 1 lines of the line group B. 201 must be used. At this time, if the idle ejection of all the nozzles for one line in the main scanning direction is performed between the sheets, it is necessary to widen at least the distance between the sheets by 2 × T × N or more as shown in FIG.

Next, a process for determining an empty discharge region (number of nozzles) for one suction hole in the first embodiment of the present invention will be described with reference to the flowchart of FIG.
First, when a condition for performing the idle ejection is satisfied, the idle ejection area determination process is started, and it is determined whether the ejection accuracy satisfies the maximum area condition.

  Here, it is assumed that the paper interval is the same as that used in the description of FIG. 5 and is determined by the system and printing conditions such as productivity specifications. Further, as described above, the condition for performing the idle discharge is determined by the elapsed time or temperature from the previous idle discharge.

  In addition, regarding the discharge accuracy, the conditions under which the discharge accuracy is lowered are low ambient temperature (environmental temperature), high ink viscosity, continuous white images, discharge after narrow paper width, etc. For example, it is assumed that the discharge accuracy satisfies the “maximum region condition” when the discharge accuracy deterioration factor does not occur.

  When the discharge accuracy satisfies the maximum region condition, the empty dischargeable region (number of nozzles) for one suction hole 201 is 2k (note that 2k is the maximum number of nozzles that can be discharged). . In this way, by setting the empty dischargeable area (the number of nozzles) to 2k, the possibility of empty discharge droplets landing other than the suction holes 201 becomes higher than when the empty discharge area is set to k. Since the gap can be minimized, productivity is maximized.

  On the other hand, when the discharge accuracy does not satisfy the maximum region condition, the empty dischargeable region (number of nozzles) for one suction hole 201 is set to k. At this time, it is possible to avoid landing of empty ejection droplets other than the suction hole 201.

  As described above, by performing the process of changing the number of nozzles discharged to one suction hole during the idle discharge operation, it is possible to obtain optimum productivity while avoiding contamination of the conveyor belt.

Next, a process for determining an empty discharge area (number of nozzles) for one suction hole in the second embodiment of the present invention will be described with reference to the flowchart of FIG.
First, when a condition for performing the idle ejection is satisfied, the idle ejection area determination process is started, and it is determined whether the ejection accuracy satisfies the maximum area condition.

  When the discharge accuracy satisfies the maximum region condition, the empty dischargeable region (number of nozzles) for one suction hole 201 is set to be the maximum, and the gap between the sheets is set to the minimum. This maximizes productivity.

  On the other hand, when the discharge accuracy does not satisfy the maximum region condition, the idle discharge possible region (number of nozzles) is calculated according to the discharge accuracy, and then the sheet interval is calculated.

For example, it is conceivable that the accuracy in the transport direction is deteriorated when the viscosity of the ink is increased. As shown in FIG. 11, it is assumed that the ejection accuracy of the ejected ink is the transport direction distance Y. Since the radius R of the suction hole 201 is known by design, the ejection region 2X can be obtained geometrically. Specifically, it is known from the three square theorem that X ² + Y ² = R ^2, and it is obtained by the following equation (1).

  Further, when the maximum discharge area is 2k, the space between the sheets can be calculated as the distance between the sheets = (2k / 2X) × the minimum sheet space.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 12 is an explanatory diagram for explaining the arrangement of the recording head according to the embodiment, and FIG. 13 is an explanatory diagram for explaining calculation of an empty ejection region in one suction hole.
In this embodiment, the recording head 51 is disposed obliquely. By arranging the recording head 51 at an angle, the apparent nozzle density at a unit distance in the main scanning direction (paper transport direction) increases, so that the resolution can be increased without changing the number of nozzles and the nozzle density of the recording head 51. it can.

As described above, an example will be described in which an empty ejection area is calculated in accordance with the accuracy in the main scanning direction and the conveyance direction when the nozzle row 103 is inclined due to the recording head 51 being arranged obliquely.
When calculating the empty dischargeable region 2r passing through the center of the suction hole 201 having the radius R, the angle θ1 of the nozzle row 103 is known by design. From the trigonometric ratio, sin θ1 = y / r and cos θ1 = x / r. Therefore, when the discharge accuracy x is in the main scanning direction, the discharge region 2r can be calculated from r = x / cos θ1. Further, when the discharge accuracy y in the transport direction is, the discharge region 2r can be calculated from r = y / sin θ.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 14 is a flowchart for explaining the embodiment, and FIGS. 15 and 16 are explanatory diagrams for explaining different examples of the mode setting screen.
Here, a mode setting screen as shown in FIG. 15 is displayed when the user operates an operation unit (not shown) to set printing conditions, or on the printer driver on the host side. Alternatively, a mode setting screen as shown in FIG. 16 is displayed on a setting screen for a machine administrator (not shown) so that the administrator can set the mode. Note that the productivity priority mode (prioritizing speed over image quality) is a mode in which the printing speed is at least faster than the image quality priority mode (prioritizing image quality over speed), and the image quality priority mode is higher than the productivity priority mode. In this mode, at least the printing speed is reduced.

  Then, as shown in FIG. 14, when the user sets the image quality priority mode, the empty dischargeable area is set to k as described above, and when the productivity priority mode is set, the empty dischargeable area is set to 2k as described above. Set.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 17 is a flowchart for explaining the embodiment.
Here, when “automatic mode” is selected on the mode setting screen shown in FIG. 16 described above, it is determined whether or not the printing condition corresponds to the image quality priority mode. The printing condition corresponding to the image quality priority mode is a condition in which ejection failure is likely to occur, for example, when the temperature is low or when the leaving time until the start of printing is long. When the image quality priority mode is applicable, the operation is performed in the image quality priority mode. In other cases, the operation is performed in the productivity priority mode.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 18 is a flowchart for explaining the embodiment.
First, this process is entered when conditions for performing idle discharge such as the elapsed time and temperature from the previous idle discharge are satisfied, and whether or not the discharge accuracy has changed with respect to the discharge accuracy at the previous idle discharge. Determine. As described above, the conditions under which the discharge accuracy decreases include when the viscosity of the ink is increasing, when a white image continues, when the discharge time is long, such as after passing through a narrow paper width, and the ambient temperature. When is low.

  Here, when the discharge accuracy is changing, a calculation process of an empty dischargeable region (number of nozzles) corresponding to the discharge accuracy for one suction hole is performed. On the other hand, when the discharge accuracy has not changed, the previous area setting value is used.

  Thereafter, the paper interval is calculated using the calculation or the previous area. The paper gap is determined by the system and printing conditions such as productivity specifications.

Next, the region calculation processing of FIG. 18 will be described with reference to the flowchart of FIG.
First, the discharge accuracy is acquired. Here, the discharge accuracy can be determined by the elapsed time from the previous discharge time, the ambient temperature, and the like. For example, the accuracy may be reduced by 1% every time one minute elapses, the accuracy may be reduced by 1% each time the temperature drops, or a combination thereof may be determined.

  Then, an empty dischargeable area corresponding to the acquired discharge accuracy is calculated. For example, if the maximum empty discharge area is k and the acquired discharge accuracy is reduced by t%, the area can be obtained as (100−t) k / 100.

  Thereafter, the number of nozzles is determined from the calculated idle discharge possible region. For example, if the number of nozzles corresponding to the maximum empty dischargeable area is 10 and the discharge accuracy is reduced by 10%, the number of nozzles at this time is (100% −10%) × 10/100% = 9 Is required.

Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 20 is a flowchart for explaining the embodiment.
First, when a condition for performing idle ejection is satisfied, a type of a preset mode is determined. At this time, as described in the fourth embodiment, the mode is set to any one of the productivity priority mode, the image quality priority mode, and the automatic setting mode.

  Here, when the set mode is the productivity priority mode, the idle discharge possible area is set to 2k, which is the maximum idle discharge possible area described above. In this case, since the gap between the sheets can be minimized, the productivity is maximized.

  Further, when the set mode is the image quality priority mode, the idle ejection possible region is set to k described above. In this case, the sheet interval is extended twice as compared with the case of 2k, but the risk of being discharged onto the conveyor belt is reduced, and belt contamination can be avoided.

  Further, when the set mode is the automatic setting mode, it is determined whether or not the discharge accuracy has changed. Similarly to the above-described sixth embodiment, when the discharge accuracy has changed, the discharge to one suction hole is determined. The calculation process of the empty dischargeable area (number of nozzles) according to the accuracy is performed, and when the discharge accuracy is not changed, the previous area setting value is used.

  The sheet interval is calculated using the empty dischargeable area determined as described above.

DESCRIPTION OF SYMBOLS 4 ... Conveyance unit 5 ... Image forming unit 43 ... Conveyance belt 51, 51Y, 51M, 51C, 51K ... Recording head 101 ... Head 102 ... Nozzle 201 ... Suction hole A1-A8, B1-B8 ... Suction hole row

Claims (5)

A recording head in which a plurality of nozzles for discharging droplets are arranged;
A plurality of suction holes are formed, and an endless conveyance belt that conveys a sheet in a direction crossing the nozzle arrangement direction of the recording head;
Control means for controlling an idle ejection operation for ejecting droplets that do not contribute to image formation from the recording head toward the suction hole of the transport belt when there is no paper;
An image forming apparatus comprising: means for changing the number of nozzles ejected to one suction hole during the idle ejection operation.   The image forming apparatus according to claim 1, wherein the number of nozzles ejected to the one suction hole is changed in accordance with ejection accuracy of the recording head. Means for determining whether or not the discharge accuracy at the current idle discharge operation has changed with respect to the discharge accuracy at the previous idle discharge operation;
When it is determined that the discharge accuracy has changed, the number of nozzles discharged to the one suction hole is changed according to the discharge accuracy, and when it is determined that the discharge accuracy has not changed, the previous idle discharge operation The image forming apparatus according to claim 2, further comprising a unit that sets the number of nozzles.   4. The image forming apparatus according to claim 1, further comprising a productivity priority mode and an image quality priority mode, wherein the number of nozzles discharged to the one suction hole is changed according to each mode. From the recording head to a suction hole formed in an endless conveying belt that conveys a sheet from a recording head in which a plurality of nozzles for discharging droplets are arranged in a direction intersecting the nozzle arrangement direction of the recording head. A program for causing a computer to perform a process for controlling an empty ejection operation for ejecting droplets that do not contribute to image formation when there is no paper.
A program for causing the computer to perform a process of changing the number of nozzles discharged to one suction hole during the idle discharge operation.

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