Nozzle unit control method and inkjet recording apparatus

Abstract

To provide a nozzle unit control method and an inkjet recording apparatus capable of achieving appropriate viscosity of ink before being ejected from a nozzle.SOLUTION: A processor 81 times a capped time that is a duration time of a capped state of a nozzle unit 31 when the ink is not being ejected, and an open time that is a duration time of an open state of the nozzle unit 31 when the ink is not being ejected (S7, S8). The processor 81 sets a number-of-times parameter relating to the number of times that a meniscus of the ink in a plurality of nozzles 32 of the nozzle unit 31 is oscillated according to the capped time and the open time (S4). The processor 81 generates the meniscus oscillation of the ink the number of times corresponding to the number of times parameter from when a request for image formation is received until when the image formation is started (S11).SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a nozzle unit control method and an inkjet recording apparatus for realizing appropriate viscosity of ink before being ejected from a nozzle.

Background Art

[0002] An inkjet recording apparatus includes a nozzle unit having a plurality of nozzles and a plurality of piezoelectric elements. Each of the plurality of nozzles forms an image on the sheet by ejecting ink onto the sheet.

[0003] Each of the plurality of piezoelectric elements pressurizes the ink supplied to each of the plurality of nozzles. The plurality of piezoelectric elements are provided corresponding to the plurality of nozzles.

[0004] When the moisture of the ink volatilizes, the viscosity of the ink increases. When the viscosity of the ink supplied to each nozzle is high, the ejection performance of the ink from each nozzle when each piezoelectric element operates deteriorates.

[0005] In addition, the inkjet recording apparatus may include a cap that covers the plurality of nozzles. Also, it is known to set the number of times of the micro driving operation of the plurality of piezoelectric elements according to the time from the start of the decapping state of the nozzle unit to the start of printing (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Incidentally, the viscosity of the ink changes even when the plurality of nozzles are covered by the cap.

[0008] An object of the present invention is to provide a nozzle unit control method and an inkjet recording apparatus capable of realizing an appropriate viscosity of ink before being ejected from a nozzle.

Means for Solving the Problems

[0009] A nozzle unit control method according to one aspect of the present invention is a method for controlling a nozzle unit. The nozzle unit includes a plurality of nozzles capable of ejecting ink and a plurality of piezoelectric elements for pressurizing the ink supplied to the plurality of nozzles. The nozzle unit is selectively switched between a cap state in which the plurality of nozzles are covered by a cap and an open state in which the plurality of nozzles are opened by removing the cap. The nozzle unit control method includes the processor setting a count parameter related to the number of times of meniscus oscillation of the ink in the plurality of nozzles according to a cap time that is a duration of the cap state of the nozzle unit and an open time that is a duration of the open state of the nozzle unit in a situation where ink ejection is not performed. Further, the nozzle unit control method includes the processor generating the meniscus oscillation of the ink a number of times corresponding to the count parameter by vibrating the plurality of piezoelectric elements after receiving a request for image formation by ink ejection and before the image formation is started.

[0010] An inkjet recording apparatus according to another aspect of the present invention includes one or more of the nozzle units and a processor that realizes the nozzle unit control method.

Advantages of the Invention

[0011] According to the present invention, it becomes possible to provide a nozzle unit control method and an inkjet recording apparatus capable of realizing an appropriate viscosity of ink before being ejected from a nozzle.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] 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.

[0014] [First Embodiment] The inkjet recording apparatus 10 according to the first embodiment is a printer, a facsimile apparatus, a copying machine, a multifunction peripheral, or the like that can execute printing processing by an inkjet method.

[0015] The printing process is a process of forming an image on the sheet 9. The sheet 9 is a sheet-like image forming medium such as paper or a resin film.

[0016] [Configuration of Inkjet Recording Apparatus 10] The inkjet recording apparatus 10 includes a sheet storage unit 12, a sheet conveyance device 2, an inkjet unit 3, an ink supply unit 4, a cap unit 6, a unit moving device 60, and a control device 8. The inkjet unit 3 has a plurality of nozzle units 31.

[0017] The sheet conveyance device 2, the inkjet unit 3, the ink supply unit 4, the cleaning unit 5, the cap unit 6, and the control device 8 are housed in the main body 11 of the inkjet recording apparatus 10.

[0018] The sheet conveyance device 2 conveys the sheets 9 stored in the sheet storage unit 12 one by one along the sheet conveyance path 20. Further, the sheet conveyance device 2 sends out the sheet 9 on which an image has been formed from the sheet conveyance path 20. For example, the sheet conveyance device 2 sends out the sheet 9 from the sheet conveyance path 20 to a discharge tray or another device in the subsequent stage.

[0019] The sheet conveyance device 2 includes a sheet sending unit 21, a plurality of sets of conveyance roller pairs 22, a first belt conveyance unit 23, a second belt conveyance unit 24, and a sending roller pair 25. The sheet sending unit 21 sends out the sheets 9 from the sheet storage unit 12 one by one to the sheet conveyance path 20.

[0020] The plurality of sets of conveyance roller pairs 22 take over the conveyance of the sheet 9 from the sheet sending unit 21 and convey the sheet 9 toward the first belt conveyance unit 23.

[0021] The first belt conveyance unit 23 is disposed below the inkjet unit 3. The first belt conveyance unit 23 conveys the sheet 9 in a predetermined conveyance direction D0 while facing the surface of the sheet 9 toward the inkjet unit 3.

[0022] The direction orthogonal to the conveyance direction D0 is the main scanning direction D1, and the direction along the conveyance direction D0 is the sub-scanning direction D2 (see FIGS. 1 and 3).

[0023] In the first belt conveyance unit 23, a plurality of tension rollers 231 rotate while supporting the endless first conveyance belt 230. Thereby, the first belt conveyance unit 23 places the sheet 9 on the first conveyance belt 230 and conveys it in the conveyance direction D0. Further, the first belt conveyance unit 23 feeds out the sheet 9 to the second belt conveyance unit 24.

[0024] The first belt conveyance unit 23 is disposed at a conveyance position or a belt retracted position. FIG. 1 shows a state in which the first belt conveyance unit 23 is disposed at the conveyance position, and FIG. 3 shows a state in which the first belt conveyance unit 23 is disposed at the belt retracted position. In the present embodiment, the belt retracted position is a position vertically below the conveyance position.

[0025] The first belt conveyance unit 23 forms a sheet conveyance path 20 between itself and a plurality of nozzle units 31 when disposed at the conveyance position. The belt retracted position is a position farther from the plurality of nozzle units 31 than the conveyance position.

[0026] The first belt conveyance unit 23 is disposed at the conveyance position when the printing process is performed. The second belt conveyance unit 24 is disposed on the downstream side in the conveyance direction D0 with respect to the first belt conveyance unit 23 located at the conveyance position.

[0027] In the second belt conveyance unit 24, a plurality of tension rollers 241 rotate while supporting the endless second conveyance belt 240. Thereby, the second belt conveyance unit 24 places the sheet 9 on which an image is formed on the second conveyance belt 240 and conveys it, and further sends out the sheet 9 to the pair of delivery rollers 25.

[0028] The pair of delivery rollers 25 is disposed on the downstream side in the conveyance direction D0 with respect to the second belt conveyance unit 24. The pair of delivery rollers 25 sends out the sheet 9 on which an image is formed to the outside of the main body 11.

[0029] The inkjet unit 3 includes a plurality of nozzle units 31 and a nozzle unit support 30 that supports the plurality of nozzle units 31. The plurality of nozzle units 31 forms an image on the sheet 9 by ejecting inks of a plurality of colors toward the sheet 9 being conveyed by the first belt conveyance unit 23.

[0030] In the example shown in FIG. 1, the plurality of nozzle units 31 are divided into four line heads 300 corresponding to black, cyan, magenta, and yellow inks. The ink supply unit 4 supplies inks of respective colors to the plurality of nozzle units 31.

[0031] The four line heads 300 are arranged side by side in the sub-scanning direction D2. It is also conceivable that the number of line heads 300 included in the inkjet unit 3 is three or five or more.

[0032] The plurality of nozzle units 31 each have an ink ejection portion 31A facing the upper surface of the first conveyance belt 230. The ink ejection portion 31A includes a plurality of nozzles 32 each capable of ejecting the ink (see FIG. 2). Further, the ink ejection portion 31A includes a plurality of piezoelectric elements 33, a plurality of pressure chambers 35, and a plurality of diaphragms 34 (see FIG. 2).

[0033] The plurality of piezoelectric elements 33, the plurality of pressure chambers 35, and the plurality of diaphragms 34 are provided corresponding to the plurality of nozzles 32, respectively.

[0034] The plurality of pressure chambers 35 communicate with the plurality of nozzles 32 respectively. The plurality of pressure chambers 35 form passages for the ink supplied to the plurality of nozzles 32. The ink in the plurality of pressure chambers 35 is supplied to the plurality of nozzles 32 respectively.

[0035] 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.

[0036] The drive signal is a continuous pulse signal with pulse width modulation. The drive signal is supplied from the control device 8 to each piezoelectric element 33.

[0037] That is, each piezoelectric element 33 pressurizes the ink supplied to the plurality of nozzles 32 respectively when the drive signal is supplied from the control device 8.

[0038] The piezoelectric element 33 to which the drive signal is supplied vibrates with the energy for the ink to be ejected from the corresponding nozzle 32. That is, each piezoelectric element 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.

[0039] 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. The plurality of nozzles 32 form an image on the sheet 9 by ejecting the ink onto the sheet 9.

[0040] In the example shown in FIG. 1, the plurality of nozzle units 31 are divided into four line heads 300 corresponding to black, cyan, magenta, and yellow inks. The ink supply unit 4 supplies the inks of respective colors to the plurality of nozzle units 31.

[0041] The four line heads 300 are arranged side by side in the sub-scanning direction D2 and are fixed in a predetermined positional relationship (see FIGS. 1 and 2). Note that the number of line heads 300 provided in the inkjet unit 3 may be three or five or more.

[0042] The cap unit 6 is selectively arranged at one of the cap retracted position and the cap position. FIG. 1 shows a state where the cap unit 6 is arranged at the cap retracted position. FIG. 2 shows a state where the cap unit 6 is arranged at the cap position.

[0043] The cap unit 6 has a plurality of caps 61 and a cap support 62. When the cap unit 6 is arranged at the cap position, the plurality of caps 61 cover the plurality of nozzles 32 of each nozzle unit 31.

[0044] The unit moving device 60 moves the first belt conveyance unit 23 and the cap unit 6. The unit moving device 60 executes a first unit arrangement process or a second unit arrangement process.

[0045] The first unit arrangement process is a process of arranging the cap unit 6 at the cap standby position and arranging the first belt conveyance unit 23 at the conveyance position. The second arrangement process is a process of arranging the first belt conveyance unit 23 at the belt retracted position and arranging the cap unit 6 at the cap position.

[0046] The unit moving device 60 executes the first unit arrangement process before the printing process is executed. Further, when the printing process corresponding to the print request has ended and no new print request is received, the unit moving device 60 executes the second unit arrangement process.

[0047] In the following description, the state of each nozzle unit 31 covered by each cap 61 is referred to as the cap state. Further, the state of each nozzle unit 31 from which each cap 61 has been removed is referred to as the open state.

[0048] By executing the first unit arrangement process, each nozzle unit 31 becomes the open state. By executing the second unit arrangement process, each nozzle unit 31 becomes the cap state. Each nozzle unit 31 is selectively switched to either the cap state or the open state.

[0049] When each nozzle unit 31 is in the cap state, the rate at which the viscosity of the ink in the plurality of nozzles 32 in each nozzle unit 31 increases is alleviated.

[0050] [Control device 8] The control device 8 executes various data processing and controls devices provided in the inkjet recording apparatus 10. The control device 8 is an example of a control unit that controls a plurality of piezoelectric elements 33 and other devices.

[0051] As shown in FIG. 4, 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 drive circuit 86.

[0052] 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.

[0053] The RAM 82 is a computer-readable volatile memory device. The RAM 82 primarily stores the computer program executed by the CPU 81 and the data output and referenced by the CPU 81 during the execution of various processes.

[0054] The secondary storage device 83 is a computer-readable non-volatile memory device. The secondary storage device 83 can store and update the computer program and various data. For example, one or both of a flash memory and a hard disk drive are employed as the secondary storage device 83.

[0055] 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.

[0056] 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.

[0057] For example, the CPU 81 receives a print job from the host device through the communication device 85. The inkjet unit 3 forms an image specified by the print job on the sheet 9.

[0058] The drive circuit 86 inputs the control signal from the CPU 81 through the signal interface 84. The drive circuit 86 outputs the drive signal to each of the plurality of piezoelectric elements 33 according to the input control signal.

[0059] The drive circuit 86 generates the drive signal corresponding to each of the plurality of piezoelectric elements 33 according to the content of the control signal and supplies the generated drive signal to the plurality of piezoelectric elements 33. Each nozzle 32 discharges an amount of ink corresponding to the drive signal.

[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 conveyance control unit 8b, a print control unit 8c, and the like.

[0061] The main control unit 8a executes control to start various processes according to operations on an operation device (not shown), control of a display device (not shown), and the like.

[0062] The conveyance control unit 8b controls the sheet conveyance device 2 and the unit moving device 60. The print control unit 8c causes the inkjet unit 3 to execute the printing process in synchronization with the conveyance of the sheet 9 by the sheet conveyance device 2.

[0063] The print control unit 8c outputs the control signal to the drive circuit 86 through the signal interface 84. The print control unit 8c causes the inkjet unit 3 to execute the printing process by controlling a plurality of piezoelectric elements 33 via the drive circuit 86.

[0064] When the temperature of the ink drops, the viscosity of the ink increases. When the viscosity of the ink supplied to each nozzle 32 is high, the ejection performance of the ink from each nozzle 32 when each piezoelectric element 33 operates deteriorates.

[0065] In the present embodiment, each nozzle unit 31 includes a heater 36 that heats the ink ejection portion 31A and a temperature sensor 37 (see FIG. 2). That is, the heater 36 and the temperature sensor 37 are arranged in each nozzle unit 31.

[0066] Furthermore, the control device 8 includes a heater power supply circuit 87 that supplies power to the heater 36 (see FIG. 4).

[0067] Furthermore, the plurality of processing modules in the CPU 81 include a heater control unit 8d (see FIG. 4). The heater control unit 8d controls the heater 36 through the heater power supply circuit 87.

[0068] By operating the heater 36 by the heater control unit 8d, the first print time is shortened. The first print time is the time from when the inkjet recording apparatus 10 receives a print request until the start of the print process.

[0069] The temperature sensor 37 detects the temperature of the ink ejection unit 31A. That is, the temperature sensor 37 detects the temperature of the nozzle unit 31. For example, the temperature sensor 37 is a thermistor.

[0070] The heater control unit 8d controls the heater 36 by feedback control based on the detected temperature of the temperature sensor 37 and the target temperature.

[0071] Incidentally, the viscosity of the ink changes even under the situation where the plurality of nozzles 32 are covered with the cap 61.

[0072] Therefore, the print control unit 8c executes pre-ink ejection control described later. The pre-ink ejection control is control for realizing an appropriate viscosity of the ink before being ejected from each of the nozzles 32 without ejecting the ink to each of the nozzle units 31.

[0073] [Ink Oscillation Control] As described later, the print control unit 8c executes ink oscillation control in the pre-ejection control (step S11 in FIG. 5). The print control unit 8c supplies an ink oscillation signal to the plurality of piezoelectric elements 33 through the drive circuit 86 in the ink oscillation control.

[0074] The print control unit 8c vibrates the plurality of piezoelectric elements 33 by supplying the ink oscillation signal to the plurality of piezoelectric elements 33. When the plurality of piezoelectric elements 33 vibrate in response to the ink oscillation signal, meniscus oscillation of the ink occurs in the plurality of nozzles 32.

[0075] The ink oscillation signal is a signal that vibrates a plurality of piezoelectric elements 33 with energy sufficient to cause the meniscus oscillation of the ink. Specifically, the ink oscillation signal is a continuous pulse signal with a lower frequency and smaller energy than the drive signal.

[0076] When the ink oscillation control is being executed, the meniscus oscillation of the ink occurs inside the pressure chamber 35 and the nozzle 32 without the ink being ejected from the nozzle 32. As a result, the temperature of the ink rises and the viscosity of the ink decreases inside the pressure chamber 35 and the nozzle 32.

[0077] In the pre-ejection control, the print control unit 8c sets a count parameter related to the number of times of the meniscus oscillation of the ink (see steps S1 to S10 in FIG. 5). Further, the print control unit 8c executes the ink oscillation control from when a request for image formation by ejection of the ink is received until the image formation is started (see steps S6 and S11 in FIG. 5).

[0078] In the ink oscillation control, the print control unit 8c supplies an ink oscillation signal corresponding to the count parameter to the plurality of piezoelectric elements 33, thereby generating the meniscus oscillation of the ink the number of times corresponding to the count parameter.

[0079] [Pre-ink ejection control] Hereinafter, an example of the procedure of the pre-ink ejection control will be described with reference to the flowchart shown in FIG. 5.

[0080] The pre-ink ejection control is an example of a process for realizing a nozzle unit control method for controlling each nozzle unit 31. The CPU 81 that executes the pre-ink ejection control is an example of a processor for realizing the nozzle unit control method.

[0081] When the CPU 81 is activated, the print control unit 8c starts the pre-ink ejection control. The print control unit 8c executes the pre-ink ejection control in a situation where the ink is not ejected by the plurality of nozzles 32.

[0082] The print control unit 8c also starts the pre-ink ejection control when the print process corresponding to the print request is completed.

[0083] In the following description, S1, S2,... represent identification codes of a plurality of steps in the pre-ink ejection control. In the pre-ink ejection control, first, the process of step S1 is executed.

[0084] <Step S1> In step S1, the print control unit 8c determines the nozzle unit state, which is the state of each nozzle unit 31, and then sets an initial value of the state continuation time.

[0085] In the present embodiment, the print control unit 8c determines either the cap state or the open state as the nozzle unit state. The state continuation time is the cap time or the open time.

[0086] The cap time is the continuation time of the cap state of each nozzle unit 31 in a situation where the ink is not ejected. The open time is the continuation time of the open state of each nozzle unit 31 in a situation where the ink is not ejected.

[0087] When the nozzle unit state at the time of executing the process of step S1 is the cap state, the print control unit 8c sets the initial value of the continuation time of the cap state as the initial value of the state continuation time.

[0088] When the nozzle unit state at the time of executing the process of step S1 is the open state, the print control unit 8c sets the initial value of the continuation time of the open state as the initial value of the state continuation time.

[0089] When the print control unit 8c starts the pre-ink ejection control in response to the end of the print process corresponding to the print request, the print control unit 8c sets the initial value of the state duration to 0.

[0090] On the other hand, when the print control unit 8c starts the pre-ink ejection control in response to the startup of the CPU 81, the print control unit 8c sets the initial value of the state duration based on the update status data DT1 recorded in the secondary storage device 83.

[0091] The update status data DT1 and the method for setting the initial value of the state duration based on the update status data DT1 will be described later.

[0092] After executing the process of step S1, the print control unit 8c executes the process of step S2.

[0093] <Step S2> In step S2, the print control unit 8c selects a parameter setting rule corresponding to the nozzle unit state from among a plurality of predetermined candidate rules.

[0094] The parameter setting rule is a rule for deriving the number parameter corresponding to the state duration. That is, the parameter setting rule represents the correspondence between the state duration and the number parameter.

[0095] For example, each of the candidate rules is set as a lookup table representing the correspondence between the state duration and the number parameter. Also, each of the candidate rules may be set as a calculation formula for calculating the number parameter from the state duration.

[0096] In the present embodiment, the plurality of candidate rules include a first candidate rule R1 adopted when the nozzle unit state is the open state and a second candidate rule R2 adopted when the nozzle unit state is the cap state (see FIG. 6).

[0097] FIG. 6 is a graph showing an example of two candidates for the parameter setting rule. In FIG. 6, a part of each of the first candidate rule R1 and the second candidate rule R2 is omitted.

[0098] In FIG. 6, the time T1 on the horizontal axis is the state duration time, and the number of times N1 on the vertical axis is the number of times parameter.

[0099] In the present embodiment, the number of times parameter is the number of times of the meniscus oscillation that the print control unit 8c generates in a plurality of piezoelectric elements 33 in the ink oscillation control.

[0100] Note that the number of times parameter may be a value representing the oscillation frequency of the ink oscillation signal. In each of the nozzle units 31, the meniscus oscillation of the corresponding number of times occurs according to the oscillation frequency of the ink oscillation signal.

[0101] As shown in FIG. 6, regardless of the nozzle unit state, the larger the number of times parameter is set as the state duration time is longer. Also, when the nozzle unit state is the cap state, the increase rate of the number of times parameter according to the elapse of the state duration time is smaller than when the nozzle unit state is the open state.

[0102] After executing the process of step S2, the print control unit 8c executes the process of step S3.

[0103] <Step S3> In step S3, the print control unit 8c determines the nozzle unit state. As described above, the nozzle unit state is the open state or the cap state.

[0104] When the determined nozzle unit state has not changed from the state determined last time, the print control unit 8c executes the process of step S4. Even when the process of the first step S3 after the start of the pre-discharge control is executed, the print control unit 8c executes the process of step S4 following the process of step S3.

[0105] On the other hand, when the determined nozzle unit state has changed from the previously determined state, the print control unit 8c executes the process of step S9.

[0106] When the process of step S3 is executed following the processes of steps S1 and S2, the print control unit 8c skips step S3 and executes the process of step S4.

[0107] <Step S4> In step S4, the print control unit 8c sets the number parameter corresponding to the state duration according to the parameter setting rule (see FIG. 6).

[0108] When the number parameter has already been set, the process of step S4 is a process of updating the number parameter.

[0109] As described above, the state duration when the nozzle unit state is the cap state is the cap time, and the state duration when the nozzle unit state is the open state is the open time.

[0110] After executing the process of step S4, the print control unit 8c executes the process of step S5.

[0111] <Step S5> In step S5, the print control unit 8c records update status data DT1 including the data of the update result DT11 and the data of the update time DT12 in the secondary storage device 83 (see FIGS. 4 and 7).

[0112] In the present embodiment, the update result DT11 represents the number parameter updated in step S4.

[0113] The CPU 81 always measures the current time. The data representing the time when the process of step S4 is executed is included in the update status data DT1 as the data of the update time DT12.

[0114] Note that the data of the update result DT11 may be data representing the state duration corresponding to the number parameter updated in step S4. In this case, the state duration corresponding to the update result DT11 is the initial value of the state duration set in step S1 or the state duration updated in step S8 described later.

[0115] After executing the process of step S5, the print control unit 8c executes the process of step S6.

[0116] <Step S6> In step S6, the print control unit 8c selects the following process according to the presence or absence of a request for image formation by the ejection of the ink. In the present embodiment, the request for image formation is the reception of the print job.

[0117] When there is no request for image formation, the print control unit 8c executes the process of step S7. On the other hand, when there is a request for image formation, the print control unit 8c executes the process of step S11.

[0118] <Step S7> In step S7, the print control unit 8c waits until a predetermined unit time has elapsed since the process of step S3 was executed.

[0119] When the unit time has elapsed, the print control unit 8c executes the process of step S8.

[0120] <Step S8> In step S8, the print control unit 8c updates the state duration. The processes of steps S7 and S8 of the pre-ink ejection control are an example of the process of measuring the cap time and the release time.

[0121] After executing the process of step S8, the print control unit 8c executes the processes after step S3 again.

[0122] <Step S9> In step S9, the print control unit 8c switches the parameter setting rule to a rule corresponding to the new nozzle unit state.

[0123] In the present embodiment, the switching of the parameter setting rule is a switch from one of the first candidate rule R1 and the second candidate rule R2 to the other.

[0124] After executing the process of step S9, the print control unit 8c executes the process of step S10.

[0125] <Step S10> In step S10, the print control unit 8c performs an initial setting of the state duration.

[0126] For example, the print control unit 8c sets, as the initial value of the new state duration, the state duration associated with the latest count parameter in the switched parameter setting rule.

[0127] In FIG. 6, the count N11 is the value of the latest count parameter. Also, the first duration TX1 is the state duration associated with the count N11 in the first candidate rule R1. The second duration TX2 is the state duration associated with the count N11 in the second candidate rule R2.

[0128] When the switched parameter setting rule is the first candidate rule R1, the print control unit 8c sets the first duration TX1 as the initial value of the new state duration. On the other hand, when the switched parameter setting rule is the second candidate rule R2, the print control unit 8c sets the second duration TX2 as the initial value of the new state duration.

[0129] After executing the process of step S10, the print control unit 8c executes the processes after step S4 again.

[0130] Here, the setting of the initial value of the state duration based on the update status data DT1 in step S1 will be described. The update status data DT1 referred to in step S1 is data recorded in the secondary storage device 83 by the process of step S5.

[0131] When a power outage or a transition to the power saving mode occurs, the CPU 81 shifts from the operating state to the standby state, and the pre-ink ejection control is interrupted once. Then, when the CPU 81 starts up from the standby state, the print control unit 8c executes the pre-ink ejection control.

[0132] In the above case, in step S1, the print control unit 8c sets the initial value of the state duration based on the update status data DT1, the startup time of the CPU 81, and the state of the nozzle unit 31 at startup.

[0133] Specifically, the print control unit 8c selects the parameter setting rule at startup corresponding to the nozzle unit state at startup. Further, the print control unit 8c derives a standby time that is the difference between the current time and the update time DT12 of the update status data DT1.

[0134] Furthermore, the print control unit 8c specifies, as the pre-standby duration, the state duration associated with the number parameter represented by the update result DT11 of the update status data DT1 in the parameter setting rule at startup. The process of specifying the pre-standby duration is the same as the process of specifying the first duration TX1 or the second duration TX2 based on the number N11 in step S10 (see FIG. 6).

[0135] Furthermore, the print control unit 8c sets, as the initial value of the state duration, the time obtained by adding the standby time to the specified pre-standby duration. By reflecting the initial value set in this way in the state duration, in step S4, the change in the viscosity of the ink during the period when the CPU 81 was in the standby state is reflected in the number parameter.

[0136] In step S5, data representing the update result of the state duration may be included in the update status data DT1 as the data of the update result DT11. In this case, in step S1 in response to the activation of the CPU 81, the print control unit 8c sets, as the initial value of the state duration, the time obtained by adding the pause time to the time represented by the update result DT11.

[0137] The state of the nozzle unit does not change during the pause state of the CPU 81. Therefore, the state of the nozzle unit when the CPU 81 is activated from the pause state is the state of the nozzle unit during the pause of the CPU 81.

[0138] Therefore, when the state of the nozzle unit when the CPU 81 is activated is the cap state, the initial value of the state duration set in step S1 is the initial value of the cap time. On the other hand, when the state of the nozzle unit when the CPU 81 is activated is the open state, the initial value of the state duration set in step S1 is the initial value of the open time.

[0139] As described above, the print control unit 8c sets the count parameter according to the cap time and the open time (see steps S1 to S10).

[0140] <Step S11> In step S11, the print control unit 8c executes the ink oscillation control to generate meniscus oscillations corresponding to the count parameter in each ink ejection unit 31A of the nozzle unit 31.

[0141] The print control unit 8c executes the process of step S11 after receiving the image formation request and before the image formation is started.

[0142] After executing the process of step S11, the print control unit 8c ends the pre-ink ejection control. After ending the pre-ink ejection control, the print control unit 8c causes the inkjet unit 3 to execute the print process corresponding to the image formation request.

[0143] By executing the pre-ink ejection control, the meniscus oscillation control is executed so that the meniscus oscillation occurs the number of times considering both the opening time and the cap time. As a result, appropriate viscosity of the ink before being ejected from the ink ejection unit 31A is realized.

[0144] [Second Embodiment] Next, an inkjet recording apparatus 10A according to the second embodiment will be described with reference to FIG. 8.

[0145] The inkjet recording apparatus 10A includes a configuration in which a humidifying device 7 is added to the inkjet recording apparatus 10. The humidifying device 7 humidifies the inside of the cap 61 when each of the nozzle units 31 is in the cap state. The humidifying device 7 generates moist air and supplies the moist air into the cap 61 through a hose 70.

[0146] The print control unit 8c in the present embodiment determines the cap state of the nozzle unit state as a first cap state and a second cap state in the steps S1 and S3 of the pre-ink ejection control.

[0147] That is, the print control unit 8c in the present embodiment determines one of the open state, the first cap state, and the second cap state as the nozzle unit state.

[0148] The first cap state is a state in which the inside of the cap 61 is not humidified by the humidifying device 7. The second cap state is a state in which the inside of the cap 61 is humidified by the humidifying device 7.

[0149] When the nozzle unit state is the second cap state, the viscosity of the ink in the ink ejection unit 31A improves over time.

[0150] On the other hand, after the operation of the humidifying device 7 starts, it takes time until the inside of the cap 61 is humidified enough to affect the viscosity of the ink.

[0151] The print control unit 8c determines that the nozzle unit state is the first cap state during a period when the humidifying device 7 is not operating in the cap state. Further, the print control unit 8c also determines that the nozzle unit state is the first cap state during a period from when the operation of the humidifying device 7 starts in the cap state until a predetermined reference time elapses.

[0152] Furthermore, the print control unit 8c determines that the nozzle unit state is the second cap state during a period after the reference time has elapsed since the operation of the humidifying device 7 started in the cap state.

[0153] The print control unit 8c in the present embodiment measures the first cap time, the second cap time, or the open time as the state continuation time in the ink ejection pre-control steps S7 and S8.

[0154] The first cap time is the continuation time of the first cap state. The second cap time is the continuation time of the second cap state.

[0155] In step S9 in the present embodiment, the selection candidates of the parameter setting rules include three candidate rules. The three candidate rules include a first candidate rule R1, a second candidate rule R2, and a third candidate rule.

[0156] The first candidate rule R1 is adopted when the nozzle unit state is the open state (see FIG. 6). The second candidate rule R2 is adopted when the nozzle unit state is the first cap state (see FIG. 6). The third candidate rule is adopted when the nozzle unit state is the second cap state.

[0157] As shown in FIG. 6, the first candidate rule R1 and the second candidate rule R2 are rules that increase the value of the count parameter in accordance with the passage of the state duration. On the other hand, the third candidate rule is a rule that decreases the value of the count parameter in accordance with the passage of the state duration.

[0158] In the print control unit 8c in the present embodiment, in step S9, the parameter setting rule is switched from one of the three candidate rules to another. That is, the print control unit 8c in the present embodiment sets the count parameter in accordance with the first cap time, the second cap time, and the release time.

[0159] Even when the inkjet recording apparatus 10A is employed, the same effects as those obtained when the inkjet recording apparatus 10 is employed can be obtained.

[0160] Note that, in the present embodiment, the print control unit 8c may determine that the nozzle unit state is the second cap state during the period from when the operation of the humidifying device 7 starts until the humidifying device 7 stops. In this case, the third candidate rule is a rule that slightly increases or does not change the value of the count parameter during the period until the state duration reaches the reference time.

[0161] [Third Embodiment] Next, an inkjet recording apparatus according to the third embodiment will be described with reference to FIGS. 9 and 10.

[0162] The inkjet recording apparatus according to the present embodiment includes the same configuration as the inkjet recording apparatus 10 (see FIGS. 1 to 4).

[0163] In the present embodiment, the print control unit 8c executes the pre-ink ejection control according to the procedure shown in FIG. 9. Hereinafter, differences from the procedure shown in FIG. 5 in the procedure of the pre-ink ejection control shown in FIG. 9 will be described.

[0164] The pre-ink ejection control shown in FIG. 9 is an example of a process for implementing the nozzle unit control method. The CPU 81 that executes the pre-ink ejection control shown in FIG. 9 is an example of a processor for implementing the nozzle unit control method.

[0165] In the present embodiment, the print control unit 8c executes the pre-ink ejection control according to a procedure in which step S4a is added to the procedure shown in FIG. 5. Hereinafter, differences from the procedure shown in FIG. 5 among the procedures of the pre-ink ejection control shown in FIG. 9 will be described.

[0166] In the first candidate rule R1 in the present embodiment, a temperature correction width W1 of the value of the number parameter is set for each state duration (see FIG. 10). Similarly, in the second candidate rule R2 in the present embodiment, a temperature correction width W2 of the value of the number parameter is set for each state duration (see FIG. 10).

[0167] The lower and upper limits of the temperature correction widths W1 and W2 of the number parameter correspond to a first reference temperature and a second reference temperature, which are the detected temperatures of the temperature sensor 37, respectively. The first reference temperature is higher than the second reference temperature.

[0168] That is, the first candidate rule R1 and the second candidate rule R2 are rules for setting a larger value of the number parameter when the detected temperature of the temperature sensor 37 is lower than when it is higher for each state duration.

[0169] The print control unit 8c in the present embodiment executes the process of step S4a before the process of step S4.

[0170] <Step S4a> In step S4a, the print control unit 8c acquires the detected temperature of the temperature sensor 37. The temperature sensor 37 is an example of a temperature detection unit that detects the temperature of the nozzle unit 31.

[0171] <Step S4> In step S4, the print control unit 8c sets the count parameter according to the state duration in accordance with the parameter setting rule, and corrects the count parameter according to the detected temperature of the temperature sensor 37.

[0172] In the present embodiment, the print control unit 8c sets the corrected count parameter by performing linear interpolation based on the detected temperature of the temperature sensor 37 with respect to the temperature correction width W1 or the temperature correction width W2 in the parameter setting rule.

[0173] By adopting the present embodiment, the count parameter reflecting the influence of the mounting state of the cap 61 and the temperature of the ink on the viscosity of the ink is set. As a result, an appropriate viscosity of the ink before being ejected in the ink ejection unit 31A is realized.

[0174] In the present embodiment, an in-machine temperature sensor for detecting the temperature inside the main body 11 may be disposed inside the main body 11. The in-machine temperature sensor is an example of a temperature detection unit that detects the temperature around the nozzle unit 31.

[0175] In the above case, the detected temperature of the in-machine temperature sensor may be used for correcting the count parameter instead of the detected temperature of the temperature sensor 37.

[0176] [First Modified Example] Next, a first modified example, which is a modified example of the third embodiment, will be described.

[0177] In this modified example, the inkjet recording apparatus 10 includes a humidity sensor that detects the humidity inside the main body 11. The humidity sensor is an example of a humidity detection unit that detects the humidity around the nozzle unit 31.

[0178] In the print control unit 8c in this application example, in step S4a of the pre-ink ejection control, the detected humidity of the humidity sensor is acquired.

[0179] Furthermore, in this application example, the print control unit 8c corrects the number parameter according to the detected humidity of the humidity sensor in the step S4 of the pre-ink ejection control.

[0180] For example, in the first candidate rule R1 and the second candidate rule R2 in this application example, a humidity correction width of the value of the number parameter is set for each state duration. The humidity correction width is set in the same manner as the temperature correction widths W1 and W2 (see FIG. 10).

[0181] In this application example, the first candidate rule R1 and the second candidate rule R2 are rules that set the number parameter to a larger value when the detected humidity of the humidity sensor is lower than when it is higher for each state duration.

[0182] Furthermore, in step S4, the print control unit 8c sets the number parameter corresponding to the state duration according to the parameter setting rule, and corrects the number parameter according to the detected humidity of the humidity sensor.

[0183] In this application example, both the correction of the number parameter based on the detected temperature of the temperature sensor 37 and the correction of the number parameter based on the detected humidity of the humidity sensor may be executed.

[0184] For example, the average value of the number parameter corrected based on the detected temperature of the temperature sensor 37 and the number parameter corrected based on the detected humidity of the humidity sensor is set as the number parameter.

[0185] Also, the one with the larger number of times among the number parameter corrected based on the detected temperature of the temperature sensor 37 and the number parameter corrected based on the detected humidity of the humidity sensor may be set as the number parameter.

[0186] Further, one or both of the correction of the number parameter based on the detected temperature of the temperature sensor 37 and the correction of the number parameter based on the detected humidity of the humidity sensor may be applied to the inkjet recording apparatus 10A.

[0187] [Second Modified Example] Next, a second modified example, which is a modified example of the third embodiment, will be described.

[0188] In this modified example, the print control unit 8c controls by dividing the plurality of piezoelectric elements 33 of each nozzle unit 31 into a plurality of element groups. The plurality of element groups are divided according to the distance from the heater 36.

[0189] In this modified example, the print control unit 8c individually executes the correction of the number parameter based on the detected temperature of the temperature sensor 37 for the plurality of element groups.

[0190] For example, in this application example, the temperature correction widths W1 and W2 of the first candidate rule R1 and the second candidate rule R2 are set corresponding to each of the plurality of element groups.

[0191] Further, the print control unit 8c may correct the detected temperature of the temperature sensor 37 using a correction coefficient set corresponding to the plurality of element groups. In this case, the print control unit 8c uses the corrected detected temperature for the correction of the number parameter correction.

[0192] In each nozzle unit 31, the influence that the ink in the plurality of nozzles 32 receives from the heat of the heater 36 may vary depending on the positions of the plurality of nozzles 32. Even in such a case, by adopting this application example, the number parameter correction corresponding to the position of each nozzle 32 is performed.

[0193] [Third Modified Example] Next, a third modified example, which is a modified example of the inkjet recording apparatus 10, will be described.

[0194] In the inkjet recording apparatus 10, the characteristics of the change in viscosity are different for each of the inks having different colors.

[0195] In this application example, different first candidate rules R1 and second candidate rules R2 are set for each color of the ink.

[0196] [Fourth Modification Example] Next, a fourth modification example, which is a modification example of the inkjet recording apparatus 10, will be described.

[0197] In this modification example, the inkjet recording apparatus 10 includes an ink recovery device that recovers the ink discharged into the cap 61 when the nozzle unit state is the cap state.

[0198] In this application example, each time the cap time reaches a predetermined upper limit time, the print control unit 8c supplies the drive signal to the plurality of piezoelectric elements 33 to discharge ink from the plurality of nozzles 31.

[0199] In this application example, in the pre-ink discharge control, when ink is discharged into the cap 61, the state duration is initialized to 0, and then the processing after step S3 is executed (see FIG. 5).

[0200] [Supplementary Note of the Invention] Hereinafter, a summary of the invention extracted from the above-described embodiments will be appended. Note that each configuration and each processing function described in the following supplementary note can be arbitrarily combined by making selections.

[0201] <Supplementary Note 1> A nozzle unit control method for controlling a nozzle unit that includes a plurality of nozzles capable of discharging ink and a plurality of piezoelectric elements that pressurize the ink supplied to the plurality of nozzles, and that selectively switches between a cap state in which the plurality of nozzles are covered by a cap and an open state in which the plurality of nozzles are opened by removing the cap, The processor measures a cap time, which is the duration of the cap state of the nozzle unit in a situation where the ink is not being ejected, and an open time, which is the duration of the open state of the nozzle unit in a situation where the ink is not being ejected. The processor sets a count parameter related to the number of times of meniscus oscillation of the ink in the plurality of nozzles according to the cap time and the open time. The processor causes the plurality of piezoelectric elements to vibrate to generate the meniscus oscillation of the ink the number of times corresponding to the count parameter from when a request for image formation by ink ejection is received until the image formation is started. A nozzle unit control method including this.

[0202] <Appendix 2> The processor sets the count parameter according to a first cap time, which is the cap time when the inside of the cap covering the plurality of nozzles is not humidified by a humidifying device, a second cap time, which is the cap time when the inside of the cap covering the plurality of nozzles is humidified by the humidifying device, and the open time. The nozzle unit control method according to Appendix 1.

[0203] <Appendix 3> The processor corrects the count parameter according to the detection temperature of a temperature detection unit that detects the temperature of the nozzle unit or the temperature around the nozzle unit. The nozzle unit control method according to Appendix 1 or Appendix 2.

[0204] <Appendix 4> The nozzle unit includes a heater. When the temperature detection unit is arranged in the nozzle unit. The processor divides the plurality of piezoelectric elements into a plurality of element groups and individually corrects the count parameter based on the detection temperature of the temperature detection unit for the plurality of element groups. The nozzle unit control method according to Appendix 3.

[0205] <Appendix 5> The nozzle unit control method according to any one of Appendices 1 to 4, wherein the processor corrects the number parameter according to the detected humidity of a humidity detection unit that detects the humidity around the nozzle unit.

[0206] <Appendix 6> The processor records update status data including data of the update result of the cap time or the opening time, or data of the update result of the number parameter, and data of the update time, in a non-volatile storage device. The nozzle unit control method according to any one of Appendices 1 to 5, including: when the processor starts up from a standby state, setting an initial value of the cap time or the opening time based on the update status data recorded in the non-volatile storage device, the startup time, and the state of the nozzle unit at startup.

[0207] <Appendix 7> An inkjet recording apparatus including a plurality of nozzles capable of discharging ink and a plurality of piezoelectric elements for pressurizing the ink supplied to the plurality of nozzles, and one or more nozzle units that selectively switch between a capped state in which the plurality of nozzles are covered by a cap and an open state in which the plurality of nozzles are opened by removing the cap. A processor that implements the nozzle unit control method according to any one of Appendices 1 to 6.

Explanation of Reference Numerals

[0208] 6: Cap unit 7: Humidifying device 8: Control device 10, 10A: Inkjet recording apparatus 30: Nozzle unit support 31: Nozzle unit 31A: Ink discharge part 32: Nozzle 33: Piezoelectric element 34: Diaphragm 35: Pressure chamber 36: Heater 37: Temperature sensor 60: Unit moving device 61: Cap 62: Cap support

Claims

1. A nozzle unit control method for controlling a nozzle unit including a plurality of nozzles capable of discharging ink and a plurality of piezoelectric elements for pressurizing the ink supplied to the plurality of nozzles, which selectively switches between a cap state in which the plurality of nozzles are covered by a cap and an open state in which the plurality of nozzles are opened by removing the cap, comprising: a processor measuring a cap time that is a duration of the cap state of the nozzle unit in a situation where ink discharge is not performed and an open time that is a duration of the open state of the nozzle unit in a situation where ink discharge is not performed; the processor setting a count parameter related to the number of times of meniscus oscillation of the ink in the plurality of nozzles according to the cap time and the open time; the processor generating the meniscus oscillation of the ink a number of times according to the count parameter by vibrating the plurality of piezoelectric elements after receiving a request for image formation by ink discharge and before the image formation is started. The nozzle unit control method includes the above steps.

2. The processor sets the count parameter according to a first cap time that is the cap time in a state where the inside of the cap covering the plurality of nozzles is not humidified by a humidifying device, a second cap time that is the cap time in a state where the inside of the cap covering the plurality of nozzles is humidified by the humidifying device, and the open time. The nozzle unit control method according to Claim 1.

3. The processor corrects the count parameter according to a detection temperature of a temperature detection unit that detects a temperature of the nozzle unit or a temperature around the nozzle unit. The nozzle unit control method according to Claim 1 or Claim 2.

4. The nozzle unit includes a heater. When the temperature detection unit is disposed in the nozzle unit. The processor divides the plurality of piezoelectric elements into a plurality of element groups and individually corrects the count parameter based on the detection temperature of the temperature detection unit for the plurality of element groups. The nozzle unit control method according to Claim 3.

5. The nozzle unit control method according to claim 1 or claim 2, wherein the processor corrects the number parameter according to the detected humidity of a humidity detection unit that detects the humidity around the nozzle unit.

6. The processor records update status data including the update result of the cap time or the open time, or the data of the update result of the number parameter, and the data of the update time, in a non-volatile memory device. The nozzle unit control method according to claim 1 or claim 2, wherein when the processor starts up from a standby state, it sets an initial value of the cap time or the open time based on the update status data recorded in the non-volatile memory device, the startup time, and the state of the nozzle unit at startup.

7. An inkjet recording apparatus including a plurality of nozzles capable of discharging ink and a plurality of piezoelectric elements that pressurize the ink supplied to the plurality of nozzles, and one or more nozzle units that selectively switch between a capped state in which the plurality of nozzles are covered by a cap and an open state in which the plurality of nozzles are opened by removing the cap. An inkjet recording apparatus comprising a processor that implements the nozzle unit control method according to claim 1 or claim 2.

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