Inkjet control method and inkjet recording device

Abstract

To prevent each of nozzles from getting clogged in a period of time during which a print request is made and then print processing is completed.SOLUTION: A processor 81 sets one or more specific numbers in accordance with achievements of actual discharging of ink by a nozzle unit 30 at the time when a precedent sheet preceding a target sheet is conveyed by a belt conveying device 23, for each target sheet to be conveyed by a precedent conveying device 22x (S304). The processor 81 makes the nozzle unit 30 execute an opening-flushing process for discharging ink toward subsequent opening portions corresponding to the specific numbers passing on a print position following the precedent sheet of a plurality of opening portions 233 of the conveying belt 231 (S305). The processor 81 makes the precedent conveying device 22x execute a process for conveying the target sheet to the belt conveying device 23, at a timing after the timing at which ink is discharged toward the subsequent opening portions corresponding to the specific numbers (S306).SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an inkjet control method and an inkjet recording apparatus for performing flushing control to prevent nozzle clogging.

Background Art

[0002] An inkjet recording apparatus executes a printing process for forming an image on a sheet by an inkjet method. In the inkjet recording apparatus, it is necessary to prevent clogging of each of a plurality of nozzles. For example, it is known that flushing control is performed when a predetermined time has elapsed since the previous printing process (see, for example, Patent Document 1).

[0003] The flushing control is control for causing the inkjet recording apparatus to execute a flushing process of ejecting ink regardless of the printing process. For example, the flushing control is executed in a situation where the plurality of nozzles are covered with a cap.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, even during the period from when a print request occurs until the printing process ends, it is required to appropriately maintain the viscosity of the ink supplied to each of the nozzles and prevent clogging of each of the nozzles.

[0006] An object of the present invention is to provide an inkjet control method and an inkjet recording apparatus capable of preventing clogging of each nozzle during the period from when a print request occurs until the printing process ends.

Means for Solving the Problem

[0007] An inkjet control method according to one aspect of the present invention is a method for controlling an inkjet recording apparatus including a belt conveyance device, a pre-stage conveyance device, and a nozzle unit. The belt conveyance device has an endless conveyance belt in which a plurality of openings each formed of one or more through-holes are formed at intervals in the circumferential direction, and conveys a sheet on the conveyance belt by rotating the conveyance belt. The pre-stage conveyance device conveys the sheet to the belt conveyance device. The nozzle unit has a plurality of nozzles arranged to face a print position on the upper surface of the conveyance belt and a plurality of piezoelectric elements that pressurize ink supplied to the plurality of nozzles to eject the ink from the plurality of nozzles, and is capable of performing a print process of forming an image on the sheet by ejecting ink onto the sheet conveyed on the conveyance belt. The inkjet control method includes a processor setting one or more specific numbers for each target sheet to be conveyed by the pre-stage conveyance device according to the ink ejection record of the nozzle unit when the previous sheet before the target sheet was conveyed by the belt conveyance device. Further, the inkjet control method includes the processor causing the nozzle unit to perform an opening flushing process of ejecting ink toward the subsequent openings corresponding to the specific number among the plurality of openings that pass through the print position following the previous sheet. Further, the inkjet control method includes the processor causing the pre-stage conveyance device to perform a process of conveying the target sheet to the belt conveyance device at a timing following the subsequent openings corresponding to the specific number.

[0008] An inkjet recording apparatus according to another aspect of the present invention includes the belt conveyance device, the pre-stage conveyance device, the nozzle unit, and the processor that realizes the inkjet control method.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide an inkjet control method and an inkjet recording apparatus that can prevent clogging of each nozzle during the period from when a print request occurs until the print process ends.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are an example of embodying the present invention and do not limit the technical scope of the present invention.

[0012] [Configuration of Inkjet Recording Apparatus 10] The inkjet recording apparatus 10 according to the embodiment is a printer capable of performing printing processing by an inkjet method.

[0013] The printing process is a process of forming an image on the sheet 9 by ejecting ink onto the sheet 9. The sheet 9 is a sheet-like image forming medium such as paper or a resin film.

[0014] Note that the inkjet recording apparatus 10 may be a facsimile apparatus, a copying machine, or a multifunction machine capable of performing the printing process by an inkjet method.

[0015] As shown in FIG. 1, the inkjet recording apparatus 10 includes a sheet storage unit 1, a sheet conveyance device 2, a printing unit 3, a plurality of ink supply units 4, and a control device 8.

[0016] The sheet storage unit 1, the sheet conveyance device 2, the printing unit 3, the plurality of ink supply units 4, and the control device 8 are arranged inside the main housing 11. The inkjet recording apparatus 10 further includes an operation device 801 and a display device 802.

[0017] The sheet conveyance device 2 feeds out the sheets 9 stored in the sheet storage unit 1 one by one to the conveyance path 20, and further conveys the sheets 9 along the conveyance path 20.

[0018] The sheet conveyance device 2 includes a feeding mechanism 21, a plurality of pairs of conveyance rollers 22, a belt conveyance device 23, a discharge roller pair 24, and the like. The feeding mechanism 21 feeds out the sheets 9 from the sheet storage unit 1 to the conveyance path 20. The plurality of pairs of conveyance rollers 22 convey the sheets 9 along the conveyance path 20, and further convey the sheets 9 to the belt conveyance device 23.

[0019] A plurality of pairs of conveying rollers 22 may convey cut paper supplied from a roll paper supply device connected to the front stage of the inkjet recording apparatus 10 to the belt conveying device 23. The roll paper supply device feeds out a roll paper wound in a roll shape, and generates the cut paper by cutting the fed-out paper at a preset length. Further, the roll paper supply device supplies the cut paper to the inkjet recording apparatus 10. The cut paper is an example of the sheet 9.

[0020] The belt conveying device 23 is disposed below the printing unit 3. The belt conveying device 23 includes an endless conveying belt 231 and a plurality of tension rollers 232.

[0021] The plurality of tension rollers 232 rotatably support the conveying belt 231. A motor (not shown) rotates one of the plurality of tension rollers 232 to rotate the conveying belt 231. The belt conveying device 23 conveys the sheet 9 in the conveying direction D0 on the conveying belt 231 by rotating the conveying belt 231.

[0022] The direction orthogonal to the conveying direction D0 is the main scanning direction D1, and the direction along the conveying direction D0 is the sub-scanning direction D2 (see FIG. 1).

[0023] The plurality of pairs of conveying rollers 22 includes a registration roller pair 22a disposed in the front stage of the belt conveying device 23. The registration roller pair 22a is disposed upstream in the conveying direction D0 with respect to the belt conveying device 23.

[0024] The sheet conveying device 2 includes a registration motor 22b that rotates the registration roller pair 22a, and a sheet detection device 220 disposed in the front stage of the registration roller pair 22a.

[0025] The resist roller pair 22a and the resist motor 22b constitute a pre-stage conveyance device 22x that conveys the sheet 9 to the belt conveyance device 23. The sheet detection device 220 detects the sheet 9 at a position upstream of the resist roller pair 22a in the conveyance path 20 in the conveyance direction D0.

[0026] The pre-stage conveyance device 22x can temporarily stop the conveyance of the sheet 9 according to the detection timing of the sheet 9 by the sheet detection device 220, and then convey the sheet 9 to the belt conveyance device 23 at an arbitrary timing.

[0027] The printing unit 3 forms an image on the sheet 9 by discharging inks of a plurality of colors toward the sheet 9 conveyed by the belt conveyance device 23.

[0028] The discharge roller pair 24 is disposed downstream of the belt conveyance device 23 in the conveyance direction D0. The discharge roller pair 24 discharges the sheet 9 with an image formed thereon to the outside of the main housing 11. For example, the discharge roller pair 24 sends out the sheet 9 from the main housing 11 to a discharge tray or a post-stage device disposed adjacent to the inkjet recording apparatus 10.

[0029] The plurality of ink supply units 4 supply inks of predetermined colors to the printing unit 3 respectively. For example, the colors of the inks are black, cyan, magenta, and yellow. In this case, the inkjet recording apparatus 10 includes four ink supply units 4.

[0030] [Printing unit 3] The printing unit 3 forms an image on the sheet 9 by discharging ink onto the sheet 9 conveyed by the belt conveyance device 23. The printing unit 3 includes a plurality of nozzle units 30 corresponding to a plurality of ink colors.

[0031] The printing unit 3 includes a plurality of nozzle units 30 corresponding to a plurality of ink colors. The plurality of ink supply units 4 supply ink to the plurality of nozzle units 30.

[0032] In this embodiment, the printing unit 3 includes four nozzle units 30 corresponding to black, cyan, magenta, and yellow inks.

[0033] Each nozzle unit 30 has an ink ejection unit 31 (see FIG. 1). The ink ejection unit 31 includes a plurality of nozzles 32 disposed to face the upper surface of the conveyance belt 231 (see FIG. 2). The plurality of nozzles 32 each form an image on the sheet 9 by ejecting ink onto the sheet 9.

[0034] Furthermore, the ink ejection unit 31 includes a plurality of piezoelectric elements 33, a plurality of pressure chambers 35, and a plurality of diaphragms 34. The plurality of piezoelectric elements 33, the plurality of pressure chambers 35, and the plurality of diaphragms 34 are respectively provided corresponding to the plurality of nozzles 32.

[0035] The plurality of pressure chambers 35 each communicate with the plurality of nozzles 32. The plurality of pressure chambers 35 each form a passage for the ink supplied to the plurality of nozzles 32. The ink in the plurality of pressure chambers 35 is respectively supplied to the plurality of nozzles 32.

[0036] The plurality of diaphragms 34 each form a part of the partition wall of the plurality of pressure chambers 35. Each piezoelectric element 33 pressurizes the ink in the pressure chamber 35 via each diaphragm 34 when a drive signal is supplied.

[0037] The drive signal is a signal whose waveform is adjusted according to the size of the ink droplets to be ejected. The drive signal is supplied from the control device 8 to each piezoelectric element 33.

[0038] That is, each piezoelectric element 33 pressurizes the ink supplied to the plurality of nozzles 32 by being supplied with the drive signal from the control device 8.

[0039] The piezoelectric element 33 to which the drive signal is supplied vibrates with the energy for ink to be ejected from the corresponding nozzle 32. That is, each of the piezoelectric elements 33 pressurizes the ink in the pressure chamber 35 to such an extent that the ink is ejected from the nozzle 32 when the drive signal is supplied.

[0040] The ink pressurized by the piezoelectric element 33 to which the drive signal is supplied flows from the pressure chamber 35 into the corresponding nozzle 32 and is further ejected from the nozzle 32.

[0041] That is, the plurality of piezoelectric elements 33 eject ink from the plurality of nozzles 32 by pressurizing the ink supplied to the plurality of nozzles 32. Each of the nozzle units 30 can execute the printing process by ejecting ink onto the sheet 9 conveyed on the conveyance belt 231.

[0042] Each of the nozzle units 30 further includes a unit heater 36 and a unit temperature sensor 37 (see FIG. 2). The unit heater 36 and the unit temperature sensor 37 are arranged at the ink ejection part 31 of each of the nozzle units 30.

[0043] That is, the inkjet recording apparatus 10 includes a plurality of unit heaters 36 and a plurality of unit temperature sensors 37 corresponding to the plurality of nozzle units 30.

[0044] The unit heater 36 heats the ink ejection part 31. The unit temperature sensor 37 detects the temperature of the ink ejection part 31. That is, the unit temperature sensor 37 detects the temperature of the nozzle unit 30 on the nozzle unit 30. For example, the unit temperature sensor 37 is a thermistor.

[0045] The unit temperature sensor 37 is an example of an internal temperature sensor that detects the internal temperature of the inkjet recording apparatus 10.

[0046] When the temperature of the ink decreases, the viscosity of the ink increases. When the viscosity of the ink supplied to each of the nozzles 32 is high, the ejection performance of the ink from each of the nozzles 32 when each of the piezoelectric elements 33 operates deteriorates.

[0047] The unit heater 36 maintains the viscosity of the ink supplied to each of the nozzles 32 in an appropriate state by heating the ink in the ink ejection unit 31.

[0048] Before the printing process is started, the unit heater 36 heats the ink in the ink ejection unit 31, thereby shortening the first print time. The first print time is the time from when the inkjet recording apparatus 10 receives a print request until the start of the printing process.

[0049] The power supplied to the unit heater 36 is adjusted by feedback control based on the detected temperature of the unit temperature sensor 37.

[0050] The operation device 801 receives a human operation. For example, the operation device 801 includes one or both of a touch panel and one or more operation buttons. The display device 802 can display various types of information. For example, the display device 802 is a panel display device such as a liquid crystal panel unit.

[0051] [Control device 8] The control device 8 executes various data processes and controls the devices included in the inkjet recording apparatus 10.

[0052] As shown in FIG. 3, the control device 8 includes a CPU (Central Processing Unit) 81 and peripheral devices such as a RAM (Random Access Memory) 82, a secondary storage device 83, and a signal interface 84. Further, the control device 8 includes a communication device 85 and a heater power supply circuit 86.

[0053] The CPU 81 is a processor that executes various data processing and controls by executing a computer program. The CPU 81 is an example of a processor that controls a plurality of piezoelectric elements 33 and other devices.

[0054] The RAM 82 is a volatile storage device readable by a computer. The RAM 82 primarily stores the computer program executed by the CPU 81 and the data output and referenced during the execution of various processes by the CPU 81.

[0055] The secondary storage device 83 is a non-volatile storage device readable by a computer. The secondary storage device 83 can store and update the computer program and various data. For example, one or both of a flash memory or a hard disk drive are adopted as the secondary storage device 83.

[0056] The signal interface 84 converts the signals output by various sensors into digital data and transmits the converted digital data to the CPU 81. Further, the signal interface 84 converts the control commands output by the CPU 81 into control signals and transmits the control signals to the devices to be controlled.

[0057] The communication device 85 can communicate with a host device (not shown) and other devices. The host device is an information processing device such as a personal computer or a smartphone operated by a user.

[0058] For example, the CPU 81 receives a print job from the host device through the communication device 85. The printing unit 3 forms an image specified by the print job on the sheet 9.

[0059] The heater power supply circuit 86 supplies a unit heater 36 with an amount of power corresponding to an input power command.

[0060] The CPU 81 includes a plurality of processing modules realized by executing the computer program. The plurality of processing modules include a main control unit 8a, a print control unit 8b, a temperature control unit 8c, and the like.

[0061] The main control unit 8a executes control to start various processes in response to a processing request input through the operation device 801 or the communication device 85, and control of the display device 802. The processing request includes a print request for requesting execution of the print process.

[0062] The print control unit 8b controls the sheet conveyance device 2. That is, the print control unit 8b controls the supply of the sheet 9 by the feeding mechanism 21, the conveyance of the sheet 9 by the plurality of pairs of conveyance rollers 22 and the belt conveyance device 23, and the discharge of the sheet 9 by the discharge roller pair 24.

[0063] Furthermore, the print control unit 8b causes the print unit 3 to execute the print process in synchronization with the conveyance of the sheet 9 by the sheet conveyance device 2. The print control unit 8b causes the print unit 3 to execute the print process by controlling the plurality of piezoelectric elements 33.

[0064] The temperature control unit 8c controls the power supplied to the unit heater 36 by outputting the signal of the power command to the heater power supply circuit 86 through the signal interface 84.

[0065] Each nozzle unit 30 includes a drive circuit 300 that supplies the drive signal to each piezoelectric element 33 (see FIG. 1).

[0066] The drive circuit 300 outputs the drive signal to each piezoelectric element 33 according to the input pressurization command signal. Each nozzle unit 30 forms an image on the sheet 9 with the ink ejected from the plurality of nozzles 32 by supplying the drive signal to the plurality of piezoelectric elements 33 from the drive circuit 300.

[0067] The print control unit 8b outputs a signal of the pressurization command corresponding to the size of the ink droplets to be ejected from each of the nozzles 32 to the drive circuit 300 through the signal interface 84. The print control unit 8b controls each of the piezoelectric elements 33 through the drive circuit 300.

[0068] Incidentally, it is required to appropriately maintain the viscosity of the ink supplied to each of the nozzles 32 and prevent clogging of each of the nozzles 32 during the period from when the print request occurs until the print process ends.

[0069] The print control unit 8b executes first opening flushing control, sheet flushing control, and second opening flushing control, which will be described later (see FIGS. 5 to 7). The first opening flushing control, the sheet flushing control, and the second opening flushing control include processes for preventing clogging of each of the nozzles 32 during the period from when the print request occurs until the print process ends.

[0070] A plurality of openings 233 each composed of one or more through-holes 234 are formed at intervals in the circumferential direction on the conveyor belt 231 of the belt conveyor device 23 (see FIG. 4).

[0071] When a plurality of nozzles 32 eject ink when each of the openings 233 passes through the print position facing the ink ejection part 31 of each of the nozzle units 30, the ejected ink passes through each of the openings 233.

[0072] The inkjet recording apparatus 10 further includes an ink recovery mechanism 5 that recovers the ink that has passed through each of the openings 233 of the conveyor belt 231 (see FIG. 1).

[0073] For example, the ink recovery mechanism 5 includes an ink tray, a pump, and an ink tank. The ink tray receives the ink that has passed through each of the openings 233. The pump conveys the ink that has fallen into the ink tray by sucking it through a tube. The ink tank stores the ink conveyed by the pump.

[0074] The inkjet recording apparatus 10 further includes a belt position sensor 6 used for detecting the rotational position of the conveyance belt 231. For example, the belt position sensor 6 is a photosensor or a microswitch that detects a detected portion 230 formed on the conveyance belt 231. The photosensor is a reflective or transmissive sensor.

[0075] When the belt position sensor 6 is the photosensor, the detected portion 230 is a through hole or a mirror surface portion formed on the conveyance belt 231. Also, when the belt position sensor 6 is the microswitch, the detected portion 230 is a protrusion formed on the conveyance belt 231.

[0076] The print control unit 8b measures the belt rotation time, which is the rotation time of the conveyance belt 231, starting from the point in time when the detected portion 230 is detected by the belt position sensor 6.

[0077] Furthermore, the print control unit 8b specifies the proximal end passing timing according to the belt rotation time.

[0078] The proximal end passing timing is the timing when each of the openings 233 passes through the proximal end of the region on the conveyance belt 231 that conveys the sheet 9. The proximal end is the start position of the conveyance of the sheet 9 on the conveyance belt 231.

[0079] The print control unit 8b controls the loading of the sheet 9 onto the belt conveyor 23 so that the leading end of the sheet 9 reaches the base end on the conveyor belt 231 following the base end passing timing. The print control unit 8b controls the loading of the sheet 9 onto the belt conveyor 23 by controlling the preceding conveyor device 22x.

[0080] Also, the print control unit 8b specifies the nozzle passing timing according to the belt rotation time. The nozzle passing timing is the timing at which each opening 233 passes through the print position facing the ink ejection part 31 of each nozzle unit 30.

[0081] Here, one or more of the plurality of nozzle units 30 that face any of the plurality of openings 233 at the nozzle passing timing are referred to as target nozzle units. The print control unit 8b causes the target nozzle units to execute an opening flushing process at the nozzle passing timing.

[0082] The opening flushing process is a process of ejecting ink toward each opening 233 in the region of the conveyor belt 231 where the sheet 9 does not exist. The opening flushing process is, for example, referred to as a line flushing process or the like.

[0083] Furthermore, the print control unit 8b can also cause each nozzle unit 30 to execute a sheet flushing process while the sheet 9 is being conveyed by the belt conveyor 23.

[0084] The sheet flushing process is a process of ejecting ink onto the non-drawing area of the sheet 9 that is not drawn on the sheet 9 in parallel with the print process on the sheet 9. The sheet flushing process is, for example, referred to as an in-sheet flushing process or an in-paper flushing process or the like.

[0085] The print control unit 8b causes each nozzle unit 30 to execute the sheet flushing process so that a plurality of ink dots are formed in a dispersed manner over a wide area of the sheet 9. As a result, the plurality of ink dots are formed on the sheet 9 so as to be as inconspicuous as possible.

[0086] When the opening flushing process or the sheet flushing process is executed, highly viscous ink is ejected from the plurality of nozzles 32 of each nozzle unit 30, and the ink is newly filled. As a result, the viscosity of the ink in the plurality of nozzles 32 is appropriately maintained.

[0087] Note that the inkjet recording apparatus 10 may include a rotary encoder that detects the rotational position of one of the plurality of tension rollers 232. In this case, the print control unit 8b counts the number of encoder pulses, which is the number of output pulses of the rotary encoder, starting from the time when the detected portion 230 is detected by the belt position sensor 6.

[0088] The print control unit 8b can specify the proximal end passing timing according to the number of encoder pulses. Similarly, the print control unit 8b can specify the nozzle passing timing according to the number of encoder pulses.

[0089] The first opening flushing control and the second opening flushing control are processes for causing each nozzle unit 30 to execute the opening flushing process. The sheet flushing control is a process for causing each nozzle unit 30 to execute the sheet flushing process.

[0090] After receiving the print request, the print control unit 8b executes the first opening flushing control before starting the print process corresponding to the print request in the print unit 3. Further, the print control unit 8b executes the sheet flushing control in parallel with the control for causing the print unit 3 to execute the print process.

[0091] Further, for each print process on one sheet 9, the print control unit 8b executes the second opening flushing control before the print process on the next sheet 9.

[0092] The first opening flushing control, the sheet flushing control, and the second opening flushing control are each an example of a process for realizing an inkjet control method for controlling the inkjet recording apparatus 10. The CPU 81 including the print control unit 8b is an example of a processor for realizing the inkjet control method.

[0093] [First Opening Flushing Control] Hereinafter, an example of the procedure of the first flushing control will be described with reference to the flowchart shown in FIG. 5.

[0094] When the main control unit 8a receives the print request through the operation device 801 or the communication device 85, the main control unit 8a causes the print control unit 8b to execute the first opening flushing control.

[0095] In the following description, S101, S102,... are codes for identifying each of a plurality of steps in the first opening flushing control. In the first opening flushing control, first, the process of step S101 is executed.

[0096] <Step S101> In step S101, the print control unit 8b derives the rest time of each nozzle unit 30. The rest time is the duration of the state in which the ink of each nozzle unit 30 does not eject until the print control unit 8b receives the print request.

[0097] For example, the print control unit 8b records information on the print end time, which is the time when the print process corresponding to the print request ends, in the secondary storage device 83. Further, the print control unit 8b derives the difference between the time when the print request is received and the print end time recorded in the secondary storage device 83 as the rest time.

[0098] After executing the process of step S101, the print control unit 8b executes the process of step S102.

[0099] <Step S102> In step S102, the print control unit 8b acquires the unit temperature, which is the detected temperature of the unit temperature sensor 37 of each nozzle unit 30.

[0100] After executing the process of step S102, the print control unit 8b executes the process of step S103.

[0101] <Step S103> In step S103, the print control unit 8b sets the number of flushing times according to the pause time and the unit temperature.

[0102] The print control unit 8b sets the number of flushing times to be more when the pause time is long than when the pause time is short. Also, the print control unit 8b sets the number of flushing times to be more when the unit temperature is low than when the unit temperature is high.

[0103] For example, a reference setting table representing the correspondence between the pause time and the reference number of times when the unit temperature is the reference temperature is set in advance. The print control unit 8b derives the reference number of times by applying the pause time to the reference setting table.

[0104] Furthermore, the print control unit 8b corrects the reference number of times according to the difference between the unit temperature and the reference temperature, and sets the corrected number of times as the number of flushing times. In this case, when the unit temperature is higher than the reference temperature, the print control unit 8b corrects the reference number of times in a decreasing direction. On the other hand, when the unit temperature is lower than the reference temperature, the print control unit 8b corrects the reference number of times in an increasing direction.

[0105] After executing the process of step S103, the print control unit 8b executes the process of step S104.

[0106] Note that the inkjet recording apparatus 10 may include a peripheral temperature sensor that detects the temperature around a plurality of nozzle units 30. In this case, the detected temperature of the peripheral temperature sensor may be used for setting the number of flushing times instead of the unit temperature. The peripheral temperature sensor is an example of the internal temperature sensor.

[0107] After executing the process of step S103, the print control unit 8b executes the process of step S104.

[0108] <Step S104> In step S104, the print control unit 8b causes each nozzle unit 30 to execute the opening flushing process for the number of flushing times set in step S103.

[0109] For example, the print control unit 8b operates the belt conveyance device 23 and causes each nozzle unit 30 to execute the opening flushing process for the number of flushing times in a situation where the belt conveyance device 23 is operating. In this case, the print control unit 8b causes each nozzle unit 30 to execute the opening flushing process at each of the nozzle passing timings of the number of flushing times.

[0110] Further, the print control unit 8b may stop the belt conveyance device 23 at the nozzle passing timing after operating the belt conveyance device 23. In this case, the print control unit 8b causes each nozzle unit 30 to execute the opening flushing process for the number of flushing times in a situation where the belt conveyance device 23 is stopped.

[0111] After executing the process of step S104, the print control unit 8b ends the first opening flushing control.

[0112] Following the first opening flushing control, the print control unit 8b causes the sheet conveyance device 2 and the print unit 3 to execute the conveyance of the sheet 9 corresponding to the print request and the print process.

[0113] Furthermore, the print control unit 8b executes the sheet flushing control in parallel with the print process.

[0114] [Sheet Flushing Control] Next, an example of the procedure of the sheet flushing control will be described with reference to the flowchart shown in FIG. 6.

[0115] As described above, the print control unit 8b executes the sheet flushing control in parallel with the control for causing the print unit 3 to execute the print process.

[0116] In the following description, S201, S202,... are codes for identifying each of a plurality of steps in the sheet flushing control. In the sheet flushing control, first, the process of step S201 is executed.

[0117] <Step S201> In step S201, the print control unit 8b acquires sheet length information representing the length of the target sheet in the conveyance direction D0. The target sheet in the sheet flushing control is the sheet 9 to be conveyed by the belt conveyance device 23.

[0118] For example, the print control unit 8b acquires the sheet information included in the print request as the sheet length information. The sheet information includes sheet size information representing the vertical size and the horizontal size of the target sheet and orientation information representing the orientation of the target sheet. The size information may be information representing the standard size of the sheet 9.

[0119] In the above case, the print control unit 8b specifies one of the vertical size information and the horizontal size information of the target sheet as the sheet length information according to the orientation information.

[0120] After executing the process of step S201, the print control unit 8b executes the process of step S202.

[0121] <Step S202> In step S202, the print control unit 8b acquires the unit temperature for each of the nozzle units 30.

[0122] After executing the process of step S202, the print control unit 8b executes the process of step S203.

[0123] <Step S203> In step S203, the print control unit 8b corrects a preset reference length based on the unit temperature.

[0124] The reference length is a length to be compared with the length of the sheet length information. For example, the reference length before correction is generally the interval between a plurality of openings 233 in the conveyance belt 231. FIG. 8 shows a state in which the sheet 9 having the reference length before correction is conveyed by the belt conveyance device 23. FIG. 9 shows a state in which a sheet 9 longer than the reference length before correction is conveyed by the belt conveyance device 23.

[0125] When the sheet 9 having the reference length before correction is conveyed under the situation where the unit temperature is the reference temperature, the viscosity of the ink in the plurality of nozzles 32 is appropriately maintained only by the opening flushing process.

[0126] When the unit temperature is higher than the reference temperature range based on the reference temperature, the print control unit 8b corrects the reference length to be longer. On the other hand, when the unit temperature is lower than the reference temperature range, the print control unit 8b sets the reference length to 0.

[0127] After executing the process of step S203, the print control unit 8b executes the process of step S204.

[0128] In addition, when the inkjet recording apparatus 10 includes the ambient temperature sensor, the detected temperature of the ambient temperature sensor may be used for correcting the reference length instead of the unit temperature.

[0129] <Process S204> In process S204, the print control unit 8b compares the length of the sheet length information with the reference length. The print control unit 8b selects the following process according to whether the length of the sheet length information is longer than the reference length.

[0130] When the length of the sheet length information is not longer than the reference length, the print control unit 8b executes the process of step S207. In this case, the processes of steps S205 and S206 are not performed. On the other hand, when the length of the sheet length information is longer than the reference length, the print control unit 8b executes the process of step S205.

[0131] <Process S205> In process S205, the print control unit 8b sets a target area to be subjected to the sheet flushing process in the entire area in the conveyance direction D0 of the target sheet according to the sheet length information.

[0132] The target area is a series of areas extending from the rear end to the front end side of the target sheet. The target area is a part or all of the area of the target sheet.

[0133] For example, the print control unit 8b sets the target area that is longer in the conveyance direction D0 when the length of the sheet length information is long than when it is short.

[0134] After executing the process of step S205, the print control unit 8b executes the process of step S206.

[0135] <Process S206> In process S206, the print control unit 8b causes each nozzle unit 30 to execute the sheet flushing process.

[0136] In step S206, the print control unit 8b causes each nozzle unit 30 to execute the sheet flushing process in parallel with the print process corresponding to the print request.

[0137] In step S206, the print control unit 8b causes each nozzle unit 30 to execute the sheet flushing process for the target area of the target sheet.

[0138] After executing the process of step S206, the print control unit 8b executes the process of step S207.

[0139] <Step S207> In step S207, the print control unit 8b selects the next process according to whether the print process corresponding to the print request has ended.

[0140] When the print process corresponding to the print request has not ended, the print control unit 8b executes the processes after step S201 for the next target sheet. On the other hand, when the print process corresponding to the print request has ended, the print control unit 8b ends the sheet flushing control.

[0141] As described above, in steps S204 to S206, the print control unit 8b selectively executes one of the first unit control and the second unit control for each sheet 9. The first unit control is a process of causing each nozzle unit 30 to execute the sheet flushing process. The second unit control is a process of not causing each nozzle unit 30 to execute the sheet flushing process.

[0142] [Second Opening Flushing Control] Next, an example of the procedure of the sheet flushing control will be described with reference to the flowchart shown in FIG. 7.

[0143] As described above, for each print process on one sheet 9, the print control unit 8b executes the second opening flushing control before the print process on the next sheet 9.

[0144] In the following description, S301, S302,... are codes for identifying each of a plurality of steps in the second opening flushing control. In the second opening flushing control, first, the process of step S301 is executed.

[0145] <Step S301> In step S301, the print control unit 8b derives the non-ejection time corresponding to each nozzle unit 30 during the print period for the previous sheet before the target sheet.

[0146] The target sheet in the second opening flushing control is the sheet 9 to be conveyed by the front-stage conveying device 22x. The non-ejection time is the duration of the ink non-ejection state for each of a plurality of nozzles 32 from the start point or from the middle to the end point of the print process for the previous sheet.

[0147] For example, the print control unit 8b derives the plurality of durations of the ink non-ejection state corresponding to the plurality of nozzles 32 in each nozzle unit 30, and derives the representative value of the plurality of durations as the non-ejection time for each nozzle unit 30.

[0148] For example, the maximum value of the plurality of durations in each nozzle unit 30 is derived as the non-ejection time for each nozzle unit 30.

[0149] After executing the process of step S301, the print control unit 8b executes the process of step S302.

[0150] <Step S302> In step S302, the print control unit 8b acquires the unit temperature for each nozzle unit 30.

[0151] After executing the process of step S302, the print control unit 8b executes the process of step S303.

[0152] <Step S303> In step S303, the print control unit 8b corrects a preset reference duration based on the unit temperature. The reference duration is a time to be compared with the non-discharge time.

[0153] When the non-discharge time does not exceed the reference duration under the situation where the unit temperature is the reference temperature, the viscosity of the ink in each of the nozzles 32 is appropriately maintained only by one opening flushing process.

[0154] When the unit temperature is higher than a reference temperature range with the reference temperature as a reference, the print control unit 8b corrects the reference duration to be longer. On the other hand, when the unit temperature is lower than the reference temperature range, the print control unit 8b corrects the reference duration to be shorter.

[0155] After executing the process of step S303, the print control unit 8b executes the process of step S304.

[0156] When the inkjet recording apparatus 10 includes the ambient temperature sensor, the detected temperature of the ambient temperature sensor may be used for correcting the reference duration instead of the unit temperature.

[0157] <Step S304> In step S304, the print control unit 8b sets a specific number by comparing the non-discharge time derived in step S301 with the reference duration. The specific number is an integer of 1 or more.

[0158] For example, when the non-discharge time of each of the nozzle units 30 does not exceed the reference duration, the print control unit 8b sets the specific number to 1.

[0159] On the other hand, when the non-discharge time of each nozzle unit 30 exceeds the reference continuous time, the print control unit 8b sets the specific number to 2. Note that when the non-discharge time of each nozzle unit 30 exceeds the reference continuous time, the print control unit 8b may set the specific number to a number of 3 or more according to the non-discharge time.

[0160] After executing the process of step S304, the print control unit 8b executes the process of step S305.

[0161] <Step S305> In step S305, the print control unit 8b causes each nozzle unit 30 to execute the opening flushing process for the specific number of times set in step S304.

[0162] Here, one or more of the plurality of openings 233 of the conveyor belt 231 that pass through the print position following the previous sheet are referred to as subsequent openings.

[0163] In step S305, the print control unit 8b causes each nozzle unit 30 to execute the opening flushing process a specific number of times directed at the specific number of subsequent openings.

[0164] For example, when the specific number is 1, the print control unit 8b causes each nozzle unit 30 to execute one opening flushing process directed at one subsequent opening. When the specific number is 2, the print control unit 8b causes each nozzle unit 30 to execute two opening flushing processes directed at two subsequent openings.

[0165] After executing the process of step S305, the print control unit 8b executes the process of step S306.

[0166] <Step S306> In step S306, the print control unit 8b causes the pre-stage conveyor device 22x to execute a process of conveying the target sheet to the belt conveyor device 23 at a timing following the specific number of subsequent openings.

[0167] In other words, the print control unit 8b causes the pre-stage conveying device 22x to execute a process of conveying the target sheet to the belt conveying device 23 at a timing when the specified number of subsequent openings that are the targets of the opening flushing process have passed the proximal end of the conveying belt 231.

[0168] For example, when the specified number is 1, the print control unit 8b causes the pre-stage conveying device 22x to execute a process of conveying the target sheet to the belt conveying device 23 at a timing when one subsequent opening is interposed between the target sheet and the previous sheet.

[0169] Also, when the specified number is 2, the print control unit 8b causes the pre-stage conveying device 22x to execute a process of conveying the target sheet to the belt conveying device 23 at a timing when two subsequent openings are interposed between the target sheet and the previous sheet.

[0170] After executing the process of step S306, the print control unit 8b executes the process of step S307.

[0171] <Step S307> In step S207, the print control unit 8b selects the next process according to whether or not the print process corresponding to the print request has ended.

[0172] When the print process corresponding to the print request has not ended, the print control unit 8b executes the processes after step S301 for the next target sheet.

[0173] That is, the print control unit 8b executes the processes of steps S301 to S306 for each target sheet to be conveyed by the pre-stage conveying device 22x. The non-discharge time of each nozzle unit 30 is an example of the ink discharge record of each nozzle unit 30 when the previous sheet is conveyed by the belt conveying device 23.

[0174] On the other hand, when the printing process corresponding to the printing request is completed, the print control unit 8b ends the second opening flushing control.

[0175] By executing each of the first opening flushing control, the sheet flushing control, and the second opening flushing control, the viscosity of the ink supplied to each nozzle 32 of the nozzle unit 30 is properly maintained during the period from when the printing request occurs until the printing process ends. As a result, clogging of each nozzle 32 is prevented.

[0176] [First Modification Example] Next, a first modification example of the inkjet recording apparatus 10 will be described.

[0177] In this modification example, the inkjet recording apparatus 10 includes a humidity sensor that detects the humidity inside the main housing 11. The humidity sensor is an example of an internal humidity sensor that detects the internal humidity of the inkjet recording apparatus 10.

[0178] In the print control unit 8b in this modification example, in the step S202 of the sheet flushing control, the environmental humidity, which is the detected humidity of the humidity sensor, is acquired.

[0179] Furthermore, in the step S203 of the sheet flushing control, the print control unit 8b in this modification example corrects the reference length according to the environmental humidity.

[0180] For example, in this modification example, when the environmental humidity is higher than a reference humidity range with respect to the reference humidity, the print control unit 8b corrects the reference length to be longer. On the other hand, when the environmental humidity is lower than the reference humidity range, the print control unit 8b sets the reference length to 0.

[0181] In the print control unit 8b in this modification example, in the step S302 of the second opening flushing control, the environmental humidity is acquired.

[0182] Furthermore, in this modification example, the print control unit 8b corrects the reference duration according to the environmental humidity in the second opening flushing control step S303.

[0183] For example, in this modification example, when the environmental humidity is higher than the reference humidity range, the print control unit 8b corrects the reference duration to be longer. On the other hand, when the environmental humidity is lower than the reference humidity range, the print control unit 8b corrects the reference duration to be shorter.

[0184] In this modification example, the print control unit 8b may perform both the correction based on the unit temperature and the correction based on the environmental humidity with respect to the correction of the reference length and the reference duration. Also, the print control unit 8b may perform only one of the correction based on the unit temperature and the correction based on the environmental humidity.

[0185] [Second Modification Example] Next, a second modification example of the inkjet recording apparatus 10 will be described.

[0186] In this modification example, the main control unit 8a can set one of two candidate modes as the operation mode according to the mode setting information input through the operation device 801 or the communication device 85.

[0187] The two candidate modes include a first operation mode in which one or both of the opening flushing process and the sheet flushing process are automatically selected as the target flushing process, and a second operation mode in which only the opening flushing process is preferentially selected as the target flushing.

[0188] In this modification example, when the first operation mode is set as the operation mode, the print control unit 8b executes the sheet flushing control according to the procedure shown in FIG. 5.

[0189] On the other hand, when the second operation mode is set as the operation mode, the print control unit 8b does not execute the sheet flushing control.

[0190] Even when this modified example is adopted, the same effects as those when the embodiment is adopted can be obtained. Note that this modified example may be applied to the first modified example.

[0191] [Third Modified Example] Next, a third modified example of the inkjet recording apparatus 10 will be described.

[0192] In this modified example, the print control unit 8b executes specific number setting processing shown below instead of the processing in steps S301 to S304 in the second opening flushing control.

[0193] In this modified example, the specific number setting processing sets the specific number according to whether or not the sheet flushing process for the previous sheet was executed.

[0194] For example, when the sheet flushing process for the previous sheet was executed, the print control unit 8b sets the specific number to 1. Also, when the sheet flushing process for the previous sheet was not executed, the print control unit 8b sets the specific number to 2.

[0195] In this modified example, the execution or non - execution of the sheet flushing process for the previous sheet is an example of the ink ejection record of each nozzle unit 30 when the previous sheet is conveyed by the belt conveyance device 23.

[0196] Even when this modified example is adopted, the same effects as those when the embodiment is adopted can be obtained. Note that this modified example may be applied to the first modified example or the second modified example.

[0197] [Supplementary Note of the Invention] The following is an appendix on the outline of the invention extracted from the above embodiments. Note that each configuration and each processing function described in the following appendix can be arbitrarily selected and combined as needed.

[0198] <Appendix 1> An inkjet recording apparatus having an endless conveyor belt in which a plurality of openings each formed of one or more through-holes are formed at intervals in the circumferential direction, and conveying a sheet on the conveyor belt by rotating the conveyor belt, a belt conveyor device, A pre-stage conveyor device for conveying the sheet to the belt conveyor device, A nozzle unit having a plurality of nozzles arranged to face a printing position on the upper surface of the conveyor belt and a plurality of piezoelectric elements for discharging ink from the plurality of nozzles by pressurizing the ink supplied to the plurality of nozzles, and capable of performing a printing process of forming an image on the sheet by discharging ink onto the sheet conveyed on the conveyor belt. An inkjet control method for controlling the inkjet recording apparatus, comprising: The processor sets one or more specific numbers for each target sheet to be conveyed by the pre-stage conveyor device according to the ink discharge record of the nozzle unit when the previous sheet before the target sheet was conveyed by the belt conveyor device. The processor causes the nozzle unit to perform an opening flushing process of discharging ink toward the subsequent openings corresponding to the specific number among the plurality of openings that pass through the printing position following the previous sheet. The processor causes the pre-stage conveyor device to perform a process of conveying the target sheet to the belt conveyor device at a timing following the subsequent openings corresponding to the specific number. An inkjet control method including this.

[0199] <Appendix 2> The inkjet control method according to Appendix 1, wherein the processor sets the specific number according to the duration of the ink non-discharge state of each of the plurality of nozzles from the start point or during to the end point of the printing process for the previous sheet.

[0200] <Appendix 3> When the inkjet recording apparatus includes one or both of an internal temperature sensor that detects the internal temperature and an internal humidity sensor that detects the internal humidity, The processor corrects a reference time according to a detection result of one or both of the internal temperature sensor and the internal humidity sensor, and sets the specific number by comparing the duration of the ink non-ejection state with the corrected reference time. The inkjet control method according to Appendix 2.

[0201] <Appendix 4> The processor selectively executes one of a first unit control for causing the nozzle unit to perform a sheet flushing process of ejecting ink to a non-drawing area not drawn on the sheet in parallel with the printing process for each sheet, and a second unit control for not causing the nozzle unit to perform the sheet flushing process, The processor sets the specific number according to whether or not the sheet flushing process for the previous sheet was executed. The inkjet control method according to Appendix 1.

[0202] <Appendix 5> Having an endless conveyor belt in which a plurality of openings each formed of one or more through holes are formed at intervals in the circumferential direction, and a belt conveyor device that conveys a sheet on the conveyor belt by rotating the conveyor belt, A pre-stage conveyor device that conveys the sheet to the belt conveyor device, A nozzle unit having a plurality of nozzles arranged to face a printing position on the upper surface of the conveyor belt and a plurality of piezoelectric elements that eject ink from the plurality of nozzles by pressurizing the ink supplied to the plurality of nozzles, and capable of performing a printing process of forming an image on the sheet by ejecting ink onto the sheet conveyed on the conveyor belt An inkjet recording apparatus comprising a processor that realizes the inkjet control method according to any one of Appendices 1 to 4.

Explanation of Signs

[0203] 2: Sheet conveying device 3: Printing section 4: Ink supply section 5: Ink recovery mechanism 6: Belt position sensor 8: Control device 10: Inkjet recording apparatus 22: Pair of conveying rollers 22a: Pair of registration rollers 22b: Registration motor 22x: Front-stage conveying device 23: Belt conveying device 30: Nozzle unit 31: Ink ejection section 32: Nozzle 33: Piezoelectric element 36: Unit heater 37: Unit temperature sensor 86: Heater power supply circuit 220: Sheet detection device 230: Detection target 231: Conveying belt 232: Tensioning roller 233: Opening 234: Through hole

Claims

1. A belt conveyor device having an endless conveyor belt formed with a plurality of openings each consisting of one or more through holes at intervals in the circumferential direction, and conveying a sheet on the conveyor belt by rotating the conveyor belt, A pre-stage conveyor device for conveying the sheet to the belt conveyor device, A nozzle unit having a plurality of nozzles arranged to face a printing position on the upper surface of the conveyor belt and a plurality of piezoelectric elements for discharging ink from the plurality of nozzles by pressurizing the ink supplied to the plurality of nozzles, and capable of executing a printing process for forming an image on the sheet by discharging ink onto the sheet conveyed on the conveyor belt, An inkjet control method for controlling an inkjet recording apparatus including: The processor sets one or more specific numbers for each target sheet to be conveyed by the pre-stage conveyor device according to the ink discharge record of the nozzle unit when the previous sheet before the target sheet was conveyed by the belt conveyor device, The processor causes the nozzle unit to execute an opening flushing process of discharging ink toward the subsequent openings corresponding to the specific number that pass through the printing position following the previous sheet among the plurality of openings, The processor causes the pre-stage conveyor device to execute a process of conveying the target sheet to the belt conveyor device at a timing following the subsequent openings corresponding to the specific number. An inkjet control method including:

2. The inkjet control method according to claim 1, wherein the processor sets the specific number according to the duration of the ink non-discharge state of each of the plurality of nozzles from the start point or from the middle to the end point of the printing process for the previous sheet.

3. When the inkjet recording apparatus includes one or both of an internal temperature sensor for detecting the internal temperature and an internal humidity sensor for detecting the internal humidity, The inkjet control method according to claim 2, wherein the processor corrects a reference time according to a detection result of one or both of the internal temperature sensor and the internal humidity sensor, and sets the specific number by comparing the duration of the ink non-discharge state with the corrected reference time.

4. a first unit control for causing the processor to execute, for each sheet, a sheet flushing process of discharging ink to a non-drawing area that is not drawn on the sheet in parallel with the printing process by the nozzle unit, and a second unit control for not causing the nozzle unit to execute the sheet flushing process, and selectively executing one of them; The inkjet control method according to claim 1, wherein the processor sets the specific number according to whether or not the sheet flushing process for the previous sheet has been executed.

5. a belt conveyor having an endless conveyor belt formed with a plurality of openings each consisting of one or more through holes at intervals in the circumferential direction, and conveying a sheet on the conveyor belt by rotating the conveyor belt; a pre-stage conveyor for conveying the sheet to the belt conveyor; a nozzle unit having a plurality of nozzles disposed to face a printing position on the upper surface of the conveyor belt and a plurality of piezoelectric elements for discharging ink from the plurality of nozzles by pressurizing ink supplied to the plurality of nozzles, and capable of executing a printing process of forming an image on the sheet by discharging ink onto the sheet conveyed on the conveyor belt; an inkjet recording apparatus comprising: a processor that realizes the inkjet control method according to any one of claims 1 to 4.

Images