Printer, printing method, and computer program

Abstract

To provide a printer, printing method, and computer program capable of improving printing quality.SOLUTION: A printer that performs printing on a print medium by liquid discharged from nozzles includes: an output unit (amplifier 53 or the like) that outputs a time-division multiplexed signal in which at least a first portion and a second portion subsequent to the first portion of a first drive waveform, and a third portion and a fourth portion subsequent to the third portion of a second drive waveform are arranged such that the third portion is between the first portion and the second portion, and the second portion is between the third portion and the fourth portion; a separation unit (switch group 54) that separates each portion of the one drive waveform from the time-division multiplexed signal output by the output unit at the timing based on the amplitude of each portion; and a drive unit (actuator 88) that discharges the liquid from the nozzles in accordance with the separated waveform signals corresponding to each portion separated by the separation unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a printing apparatus, a printing method, and a computer program.

Background Art

[0002] The printing apparatus described in Patent Document 1 prints on a printing medium with a liquid discharged from a nozzle. An actuator (drive unit) provided in the printing apparatus drives the nozzle, and the liquid is discharged from the nozzle driven by the actuator. An amplifier (output unit) provided in the printing apparatus outputs a time-division multiplexed signal. The time-division multiplexed signal includes at least a first part and a second part of a first drive waveform, and a third part and a fourth part of a second drive waveform. In the first drive waveform, the second part follows the first part, and in the second drive waveform, the fourth part follows the third part. On the other hand, in the time-division multiplexed signal, the first part, the third part, the second part, and the fourth part are arranged in this order.

[0003] A switch (separation unit) provided in the printing apparatus opens and closes a signal line connecting the amplifier and the actuator to each other. For example, when separating each part of the first drive waveform from the time-division multiplexed signal, the switch closes at the start time point of each part of the first drive waveform and opens by the end time point. The actuator discharges the liquid from the nozzle according to a separated waveform signal corresponding to each part of the first drive waveform separated from the time-division multiplexed signal by the switch. By using the time-division multiplexed signal, the standby time of the nozzle can be shortened.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Each part of each drive waveform has a pulse waveform and is arranged at a constant period in the time-division multiplexed signal. However, due to the transient response of the amplifier that outputs the time-division multiplexed signal, waveform distortion can occur in each part of each drive waveform included in the time-division multiplexed signal. In the case of the printing apparatus described in Patent Document 1, each part of each drive waveform is separated at a constant period. Separation at a constant period is simple, but there is a risk that waveform distortion may affect print quality.

[0006] An object of the present disclosure is to provide a printing apparatus, a printing method, and a computer program capable of improving print quality.

Means for Solving the Problems

[0007] A printing apparatus according to the present disclosure is a printing apparatus that prints on a printing medium with a liquid ejected from a nozzle, and at least a first part of a first drive waveform, a second part following the first part, a third part of a second drive waveform, and a fourth part following the third part are arranged such that there is the third part between the first part and the second part, and there is the second part between the third part and the fourth part. An output unit that outputs a time-division multiplexed signal, a separation unit that separates each part of one of the drive waveforms from the time-division multiplexed signal output by the output unit at a timing based on the amplitude of each part, and a drive unit that causes the liquid to be ejected from the nozzle according to a separated waveform signal corresponding to each part separated by the separation unit.

[0008] A printing method according to the present disclosure is a method of printing on a printing medium with a liquid ejected from a nozzle driven according to a separated waveform signal corresponding to each part of one of the drive waveforms separated from a time-division multiplexed signal in which at least a first part of a first drive waveform, a second part following the first part, a third part of a second drive waveform, and a fourth part following the third part are arranged such that there is the third part between the first part and the second part, and there is the second part between the third part and the fourth part. The timing for separating each part of one of the drive waveforms from the time-division multiplexed signal is a timing based on the amplitude of each part.

[0009] A computer program according to the present disclosure is for a printing apparatus that prints on a printing medium with liquid ejected from a nozzle driven according to a separated waveform signal corresponding to each part of one driving waveform separated from a time-division multiplexed signal in which at least a first part of a first driving waveform, a second part following the first part, a third part of a second driving waveform, and a fourth part following the third part are arranged such that the third part is between the first part and the second part, and the second part is between the third part and the fourth part, and is characterized in that the computer is caused to execute a process of obtaining the timing for separating each part of one driving waveform from the time-division multiplexed signal based on the amplitude of each part.

Advantages of the Invention

[0010] According to the printing apparatus, printing method, and computer program of the present disclosure, print quality can be improved.

Brief Description of the Drawings

[0011]

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

[0012] Hereinafter, embodiments of the present disclosure will be described.

[0013] FIG. 1 is a plan view schematically showing a printing apparatus according to an embodiment. In the following description, the front, rear, left, right, top, and bottom shown in FIG. 1 are used. The front-rear direction corresponds to the conveyance direction, the left-right direction corresponds to the scanning direction, and the up-down direction is a direction perpendicular to the paper surface of FIG. 1. The front side of FIG. 1 corresponds to the upper side, and the back side corresponds to the lower side.

[0014] The printing apparatus 1 shown in FIG. 1 includes a platen 2, an ink ejection device 3, and conveyance rollers 4 and 5. On the upper surface of the platen 2, a recording paper 200, which is a printing medium, is placed. The ink ejection device 3 ejects ink (liquid) onto the recording paper 200 placed on the platen 2 to record (print) an image. The ink ejection device 3 includes a carriage 6, a sub-tank 7, and four inkjet heads 8.

[0015] Above the platen 2, two guide rails 11 and 12 for guiding the carriage 6 are provided so as to extend left and right. An endless belt 13 extending left and right is connected to the carriage 6. The endless belt 13 is driven by a carriage drive motor 14. By driving the endless belt 13, the carriage 6 is guided by the guide rails 11 and 12 and reciprocates in the scanning direction in a region facing the platen 2. More specifically, the carriage 6 performs a first movement and a second movement while supporting the four inkjet heads 8. The first movement is to move the inkjet head 8 from one position to another position from left to right in the scanning direction. The second movement is to move the inkjet head 8 from another position to a certain position from right to left in the scanning direction.

[0016] Between the guide rails 11 and 12, a cap 20 and a flushing receiver 21 are provided. The cap 20 and the flushing receiver 21 are arranged below the ink ejection device 3. The cap 20 is arranged at the right end of the guide rails 11 and 12, and the flushing receiver 21 is arranged at the left end of the guide rails 11 and 12. Note that the cap 20 and the flushing receiver 21 may be arranged in reverse left and right.

[0017] The sub-tank 7 and the four ink jet heads 8 are mounted on the carriage 6 and reciprocate in the scanning direction together with the carriage 6. The sub-tank 7 is connected to the cartridge holder 15 via a tube 17. One or more color (four colors in this embodiment) ink cartridges 16 are mounted on the cartridge holder 15. Examples of the four colors include black, yellow, cyan, and magenta. Inside the sub-tank 7, four ink chambers (not shown) are formed. The four colors of ink supplied from the four ink cartridges 16 are respectively stored in the four ink chambers.

[0018] The four ink jet heads 8 are arranged side by side in the scanning direction below the sub-tank 7. While moving in the scanning direction together with the carriage 6, the four ink jet heads 8 eject the four colors of ink supplied from the sub-tank 7 onto the recording paper 200.

[0019] As shown in FIG. 1, the conveyance roller 4 is arranged on the upstream side (rear side) in the conveyance direction from the platen 2. The conveyance roller 5 is arranged on the downstream side (front side) in the conveyance direction from the platen 2. The two conveyance rollers 4 and 5 are driven synchronously by a motor (not shown). The two conveyance rollers 4 and 5 convey the recording paper 200 placed on the platen 2 in the conveyance direction orthogonal to the scanning direction.

[0020] The printing apparatus 1 includes a control device 50. The control device 50 includes a memory 55 such as a non-volatile memory and a RAM. The control device 50 receives a print job and drive waveform data from an external device 100 such as a personal computer or a smartphone, and stores them in the memory 55. The control device 50 controls the driving of an ink ejection device 3, a conveyance roller 4, etc. based on the print job, and executes a printing process.

[0021] FIG. 2 is a schematic partially enlarged cross-sectional view of the inkjet head 8. A plurality of nozzles 80 are formed on the lower surface of each inkjet head 8. One inkjet head 8 corresponds to one color of ink and is connected to one ink chamber of the sub-tank 7. That is, the four inkjet heads 8 respectively correspond to the four colors of ink and are respectively connected to the four ink chambers.

[0022] The inkjet head 8 is provided with an ink supply port and an ink discharge port. The ink supply port and the ink discharge port are connected to the ink chamber via a tube or the like. A circulation pump is interposed between the ink supply port and the ink chamber. The ink sent out from the ink chamber by the circulation pump flows into the inkjet head 8 through the ink supply port and is ejected from the nozzles 80. The ink that is not ejected from the nozzles 80 returns to the ink chamber through the ink discharge port. The ink circulates between the ink chamber and the inkjet head 8.

[0023] The inkjet head 8 includes a plurality of pressure chambers 81. The plurality of pressure chambers 81 constitute a plurality of pressure chamber rows. A diaphragm 82 is formed above the plurality of pressure chambers 81. A layered piezoelectric body 83 (piezoelectric element) is formed above the diaphragm 82. A first common electrode 84 is formed between the piezoelectric body 83 and the diaphragm 82 above each pressure chamber 81.

[0024] A second common electrode 86 is provided inside the piezoelectric body 83. The second common electrode 86 is disposed above each pressure chamber 81 and above the first common electrode 84. The second common electrode 86 is disposed at a position not facing the first common electrode 84. Individual electrodes 85 are formed on the upper surface of the piezoelectric body 83 above each pressure chamber 81. The individual electrodes 85, the first common electrode 84, and the second common electrode 86 face each other vertically with the piezoelectric body 83 interposed therebetween. The diaphragm 82, the piezoelectric body 83, the first common electrode 84, the individual electrodes 85, and the second common electrode 86 constitute an actuator 88 (drive unit). One actuator 88 is provided for one nozzle 80.

[0025] A nozzle plate 87 is provided below each pressure chamber 81. A plurality of nozzles 80 penetrating vertically are formed in the nozzle plate 87. Each nozzle 80 is disposed below each pressure chamber 81. The plurality of nozzles 80 constitute a plurality of nozzle rows extending along the pressure chamber row.

[0026] FIG. 3 is a block diagram of the control device 50. The control device 50 includes a control circuit 51, a D / A converter 52, an amplifier 53, a switch group 54, and a detection unit 56 in addition to the aforementioned memory 55. Drive waveform data is stored in the memory 55. The drive waveform data is data indicating the voltage waveform applied to the individual electrodes 85, that is, the drive waveform for driving the actuator 88, and is data quantized at a predetermined sampling period. In this embodiment, drive waveform data Da, Db, Dc described later is stored in the memory 55.

[0027] The control circuit 51 is a CPU or a logic circuit (e.g., FPGA). The D / A converter 52 converts a digital signal into an analog signal. The amplifier 53 amplifies the voltage of the analog signal. The switch group 54 includes a plurality of nth switches 54(n) (n = 1, 2, …, N). N is the number of actuators 88. The nth switch 54(n) is constituted by, for example, an analog switch IC, and one is provided for each actuator 88. One end of the nth switch 54(n) is connected to the amplifier 53 via a common bus (signal line). The other end of each nth switch 54(n) is connected to the individual electrode 85 in a one-to-one correspondence via a signal line. The detection unit 56 detects the voltage of the analog signal (time-division multiplexed signal) output from the amplifier 53 to the switch group 54.

[0028] The control circuit 51 transmits a selection signal S1 for selecting any one of the nth switches 54(n) and a synchronization signal S2 including any one of the synchronization signals S2a, S2b, S2c described later to the switch group 54. The control circuit 51 transmits the synchronization signal S2 in association with the selection signal S1.

[0029] The first common electrode 84 is connected to the COM terminal, which is the ground (GND) in this embodiment. The second common electrode 86 is connected to the VCOM terminal. The VCOM voltage is higher than the COM voltage. The first capacitor 89a is constituted by the individual electrode 85, the first common electrode 84, and the piezoelectric body 83. The second capacitor 89b is constituted by the individual electrode 85, the second common electrode 86, and the piezoelectric body 83.

[0030] The charge applied to the individual electrode 85 is held by the first capacitor 89a and the second capacitor 89b. Due to the voltages applied to the first capacitor 89a and the second capacitor 89b, the piezoelectric body 83 shown in FIG. 3 deforms, causing the diaphragm 82 to vibrate. Due to the vibration of the diaphragm 82, ink is ejected from the pressure chamber 81 through the nozzle 80. The voltages applied to the first capacitor 89a and the second capacitor 89b are the voltages of the separation waveform signal described later. The higher the voltage of the separation waveform signal, the greater the deformation of the piezoelectric body 83 and the greater the vibration of the diaphragm 82, so a large amount of ink is ejected from the nozzle 80. In other words, when the piezoelectric body 83 is driven according to the separation waveform signal, ink is ejected from the nozzle 80.

[0031] FIG. 4 is an explanatory diagram for explaining an example of a drive waveform. The drive waveforms A, B, and C shown in FIG. 4 are waveforms for deforming the piezoelectric body 83, causing the diaphragm 82 to vibrate, and ejecting the ink in the pressure chamber 81 through the nozzle 80 due to the vibration of the diaphragm 82. For example, the drive waveform A is a waveform for ejecting a large droplet, the drive waveform B is a waveform for ejecting a medium droplet, and the drive waveform C is a waveform for ejecting a large droplet, but the ejection timing is different from that of the drive waveform A.

[0032] In FIG. 4, the right side shows a state in the past compared to the left side. The same applies to FIGS. 5 to 9 described later. The drive waveform data Da shown in FIG. 3 is the quantization data of the drive waveform A, the drive waveform data Db is the quantization data of the drive waveform B, and the drive waveform data Dc is the quantization data of the drive waveform C. The drive waveform data Da has quantized data Ak (k = 0, 1, 2,..., K), the drive waveform data Db has quantized data Bk, and the drive waveform data Dc has quantized data Ck. The quantized data Ak indicates the quantized amplitude of the drive waveform A. Similarly, the quantized data Bk and Ck indicate the quantized amplitudes of the drive waveforms B and C.

[0033] Hereinafter, the quantized data Ak, Bk, and Ck are simply referred to as data Ak, Bk, and Ck. Also, for example, when data Bk is larger than data Ak, it means that the amplitude (or the voltage corresponding to the amplitude) of drive waveform B indicated by data Bk is larger than the amplitude (or the voltage corresponding to the amplitude) of drive waveform A indicated by data Ak. Similarly, when data Bk is equal to data Ak and when data Bk is smaller than data Ak, it means a comparison between the amplitudes (or voltages). The same applies not only to the combination of data Ak and Bk, but also to combinations such as data Ak and Ck, data Bk and Ck, and data Bk and Bk-1.

[0034] FIG. 5 is an explanatory diagram for explaining an example of time-series data, an analog signal, and a time-division multiplexed signal. A, B, and C shown in FIG. 5 indicate that they respectively correspond to drive waveforms A, B, and C. When driving the actuator 88 shown in FIG. 3, the control circuit 51 accesses the memory 55 to obtain drive waveform data Da, Db, and Dc, and creates the time-series data shown in FIG. 5. The time-series data is a digital signal. The time-series data is obtained by arranging data Ak, Bk, and Ck in order with a time interval Δt.

[0035] The time interval Δt is the reciprocal of a predetermined sampling frequency (predetermined sampling period). The predetermined sampling frequency is equal to or higher than the resonance frequency of the inkjet head 8. The resonance frequency of the inkjet head 8 is the resonance frequency when the pressure chamber 81 is not filled with ink, or the resonance frequency when the pressure chamber 81 is filled with ink.

[0036] Data Ak, Bk, and Ck are arranged in the order of A0, B0, C0, A1, B1, C1, …, Ak, Bk, Ck, …, AK, BK, CK for each time (time interval Δt) corresponding to a predetermined sampling period. In other words, the data length of data Ak, Bk, and Ck is equal to or less than the length corresponding to a predetermined sampling period. For example, the sampling frequency is 24 MHz, and the data length of data Ak, Bk, and Ck is approximately 41 nS.

[0037] Also, data Ak and data Bk are continuous, data Bk and data Ck are continuous, and data Ck and data Ak+1 are continuous. That is, there is no data Ck, other quantized data, and data of other waveforms between data Ak and data Bk. Also, there is no data Ak, other quantized data, and data of other waveforms between data Bk and data Ck. Also, there is no data Bk, other quantized data, and data of other waveforms between data Ck and data Ak+1.

[0038] The control circuit 51 shown in FIG. 3 outputs time-series data, which is a digital signal, to the D / A converter 52. The D / A converter 52 converts the time-series data as shown in FIG. 5 into an analog signal and outputs it to the amplifier 53. The analog signal output by the D / A converter 52 is a time-division multiplexed signal before being amplified by the amplifier 53. The amplifier 53 shown in FIG. 3 amplifies the voltage of the input analog signal and outputs it to the switch group 54. The analog signal amplified by the amplifier 53 constitutes a time-division multiplexed signal as shown in FIG. 5.

[0039] That is, the time-division multiplexed signal is not an analog signal corresponding only to data Ak, not an analog signal corresponding only to data Bk, and not an analog signal corresponding only to data Ck. Also, the time-division multiplexed signal is a signal in which a plurality of analog signals corresponding to a set of a total of three data, namely one data Ak, one data Bk, and one data Ck, are continuous in time series. It is preferable that there are three or more sets of this analog signal in one time-division multiplexed signal. That is, it is preferable that data Ak, data Bk, and data Ck are each three or more in one time-division multiplexed signal (K≧2). The reason will be described later.

[0040] There is one time-division multiplexed signal shown in Fig. 5. In Fig. 5, although the analog signal corresponding to data C0 seems to be isolated, it is an analog signal corresponding to a set of a total of three data, namely data A0, data B0, and data C0, and when data A0 and data B0 are in the "0" state, it is the result of being serially continuous with the analog signal corresponding to a set of a total of three data, namely data A1, data B1, and data C1, and when data A1 is in the "0" state. Also, although the analog signal corresponding to the set of data Ak and data Bk where k = 8 seems to be isolated, it is the result of being serially continuous with the analog signal corresponding to a set of a total of three data, namely data Ak-1, data Bk-1, and data Ck-1, and when data Ck-1 is in the "0" state, with the analog signal corresponding to the set of data Ak, data Bk, and data Ck. Also, the reason why the analog signal corresponding to the set of data Ak and data Bk where k = 7 seems to be isolated is the same. Therefore, the analog signal in Fig. 5 can be treated as one time-division multiplexed signal.

[0041] Taking drive waveform data Da as the data of the first drive waveform and the part corresponding to data Ak-1 as the first part, then the part corresponding to data Ak is the second part following the first part. Taking drive waveform data Dc as the data of the second drive waveform and the part corresponding to data Ck-1 as the third part, then the part corresponding to data Ck is the fourth part following the third part. In the above cases, in the time-division multiplexed signal, the first part to the fourth part are arranged such that there is the third part between the first part and the second part, and there is the second part between the third part and the fourth part. That is, the first part to the fourth part are arranged in the order of the first part, the third part, the second part, and the fourth part, and there is the second part next to the third part.

[0042] When the drive waveform data Db is used as the data of the first drive waveform and the portion corresponding to the data Bk-1 is taken as the first portion, the portion corresponding to the data Bk is the second portion following the first portion. When the drive waveform data Da is used as the data of the second drive waveform and the portion corresponding to the data Ak is taken as the third portion, the portion corresponding to the data Ak+1 is the fourth portion following the third portion. In the above cases, in the time-division multiplexed signal, the first to fourth portions are arranged such that there is the third portion between the first portion and the second portion and there is the second portion between the third portion and the fourth portion. That is, the first to fourth portions are arranged in the order of the first portion, the third portion, the second portion, and the fourth portion, and there is the second portion following the third portion.

[0043] When the drive waveform data Dc is used as the data of the first drive waveform and the portion corresponding to the data Ck-1 is taken as the first portion, the portion corresponding to the data Ck is the second portion following the first portion. When the drive waveform data Db is used as the data of the second drive waveform and the portion corresponding to the data Bk is taken as the third portion, the portion corresponding to the data Bk+1 is the fourth portion following the third portion. Also in the above cases, in the time-division multiplexed signal, the first to fourth portions are arranged such that there is the third portion between the first portion and the second portion and there is the second portion between the third portion and the fourth portion. That is, the first to fourth portions are arranged in the order of the first portion, the third portion, the second portion, and the fourth portion, and there is the second portion following the third portion.

[0044] The control circuit 51, the D / A converter 52, and the amplifier 53 constitute an output unit. The amplifier 53 functions as an amplification circuit in the present embodiment. The amplifier 53 amplifies the voltage of the time-division multiplexed signal. One time-division multiplexed signal fits within one ejection drive cycle. For example, if the ejection drive frequency (injection frequency) is 100 kHz, one ejection drive cycle (injection cycle) is 10 μS, and one time-division multiplexed signal has a length of less than 10 μS.

[0045] Ideally, the portion corresponding to the data Ak of the time-division multiplexed signal after amplification by the amplifier 53 is a pulse waveform (the waveform indicated by the broken line in FIG. 5). Similarly, the portions corresponding to the data Bk and Ck of the time-division multiplexed signal after amplification by the amplifier 53 are also pulse waveforms. However, in reality, due to the transient response of the amplifier 53, waveform distortion may occur in the portions corresponding to the data Ak, Bk, and Ck of the time-division multiplexed signal (each portion of each drive waveform included in the time-division multiplexed signal).

[0046] FIG. 6 is an explanatory diagram for explaining waveform distortion. FIG. 6 shows a part of the time-division multiplexed signal after amplification by the amplifier 53. This part is the portion of the time-division multiplexed signal corresponding to the data Ak, Bk, and Ck. In the following description, attention is paid to the portion of the time-division multiplexed signal corresponding to the data Bk. When the data Ak is smaller than the data Bk, as shown in the diagram of "Bk>Ak" in FIG. 6, a waveform distortion occurs such that the voltage of the time-division multiplexed signal gradually increases from the voltage corresponding to the data Ak and reaches the voltage corresponding to the data Bk (hereinafter referred to as the target value).

[0047] Let the start time point and end time point of the portion corresponding to the data Bk of the time-division multiplexed signal be the start time point TB1 and the end time point TB2, and let the time point when the target value is reached (the time point when the waveform distortion converges) be the time point TB3. Then, TB1 < TB3 < TB2. The transient time TB is TB = TB3 - TB1 > 0, and the end time point of the transient time TB is the time point TB3. The start time point TB1 is also the end time point of the portion corresponding to the data Ak of the time-division multiplexed signal, and the end time point TB2 is also the start time point of the portion corresponding to the data Ck of the time-division multiplexed signal. For ease of viewing the figure, the length of the transient time TB is exaggerated.

[0048] When the data Ak is larger than the data Bk, as shown in the diagram of "Bk < Ak" in FIG. 6, a waveform distortion occurs such that the voltage of the time-division multiplexed signal gradually decreases from the voltage corresponding to the data Ak and reaches the voltage corresponding to the data Bk (the target value). Also in this case, the transient time TB is TB = TB3 - TB1 > 0, and the time point TB3 is the end time point of the transient time TB. On the one hand, when data Ak is equal to data Bk, as shown in the diagram of "Bk = Ak" in FIG. 6, no waveform distortion occurs. In this case, TB1 = TB3 < TB2, the transition time TB is TB = TB3 - TB1 = 0, and the end point of the transition time TB is the start point TB1.

[0049] The start point TB1 and the end point TB2 can be obtained by calculation based on the time interval Δt and the value of k of the data Bk. The transition time TB is stored in the memory 55. The transition time TB stored in the memory 55 is, for example, received by the control device 50 from the external device 100 together with the drive waveform data Db. The transition time TB may be obtained experimentally or by calculation. Note that the control circuit 51 of the control device 50 may obtain the transition time TB by calculation during the execution of the printing process.

[0050] The nth switch 54(n) shown in FIG. 3, the first capacitor 89a, and the second capacitor 89b constitute an RC circuit. The response times of the nth switch 54(n) and the piezoelectric body 83 are determined by the electrical resistance value R of the nth switch 54(n) and the capacitance C of the first capacitor 89a and the second capacitor 89b. The nth switch 54(n) with an electrical resistance value R' such that the response times of the nth switch 54(n) and the piezoelectric body 83 are longer than the maximum value of the transition time TB, and the first capacitor 89a and the second capacitor 89b with a capacitance C' such that the response times of the nth switch 54(n) and the piezoelectric body 83 are longer than the maximum value of the transition time TB are selected by the manufacturer, and the printing apparatus 1 of the present embodiment is configured. That is, the maximum value of the transition time TB for the data Bk is shorter than the response times of the nth switch 54(n) and the piezoelectric body 83. Similarly, the maximum values of the transition times for the data Ak and Ck are shorter than the response times of the nth switch 54(n) and the piezoelectric body 83.

[0051] Next, the relationship between the time-division multiplexed signal and the synchronization signal S2 will be described. FIG. 7 is an explanatory diagram for explaining the relationship between an ideal time-division multiplexed signal and a synchronization signal S2. The time-division multiplexed signal shown in FIG. 7 includes a drive waveform signal indicating a drive waveform A, a drive waveform signal indicating a drive waveform B, and a drive waveform signal indicating a drive waveform C.

[0052] Hereinafter, a portion of the drive waveform signal indicating the drive waveform A corresponding to the data Ak is referred to as a drive waveform signal Pak. Since there is no waveform distortion in the ideal drive waveform signal Pak, the voltage of the drive waveform signal Pak is constant (target value) from the start time point to the end time point. The drive waveform signal indicating the drive waveform A includes the drive waveform signals Pak for k = 0, …, K. In order to represent the unevenness of the drive waveform signal indicating the drive waveform A, three or more data Ak are required (K ≧ 2). Similarly, portions of the drive waveform signals indicating the drive waveforms B and C corresponding to the data Bk and Ck are referred to as drive waveform signals Pbk and Pck, respectively. Since there is no waveform distortion in the ideal drive waveform signals Pbk and Pck, the voltage of the drive waveform signals Pbk and Pck is the voltage (target value) corresponding to the data Bk and Ck from the start time point to the end time point.

[0053] The synchronization signal S2 is a pulse wave. The pulse width of the pulse of the synchronization signal S2 is constant at a predetermined time of Δt or less in time interval. Hereinafter, the rising edge / falling edge of the pulse of the synchronization signal S2 is simply referred to as the rising edge / falling edge of the synchronization signal S2. A time interval Δt is provided between the rising edge of the synchronization signal S2a corresponding to the drive waveform signal Pak and the rising edge of the synchronization signal S2b corresponding to the drive waveform signal Pbk. Also, a time interval Δt is provided between the rising edge of the synchronization signal S2b corresponding to the drive waveform signal Pbk and the rising edge of the synchronization signal S2c corresponding to the drive waveform signal Pck. A time interval Δt is provided between the rising edge of the synchronization signal S2c corresponding to the drive waveform signal Pck and the rising edge of the synchronization signal S2a corresponding to the drive waveform signal Pak+1.

[0054] As described above, the data Ak, Bk, and Ck that constitute the time-series data are arranged in order with a time interval Δt. Therefore, when accessing the time-division multiplexed signal at the rising edge of the synchronization signal S2a, the drive waveform signal Pak can be obtained. When accessing the time-division multiplexed signal at the rising edge of the synchronization signal S2b, the drive waveform signal Pbk indicating the drive waveform B can be obtained. When accessing the time-division multiplexed signal at the rising edge of the synchronization signal S2c, the drive waveform signal Pck can be obtained.

[0055] The switch group 54 opens and closes the nth switch 54(n) selected by the selection signal S1 at the opening and closing timing indicated by the synchronization signal S2 (any one of the synchronization signals S2a to S2c) associated with the selection signal S1. In other words, the switch group 54 opens and closes the nth switch 54(n) at a predetermined sampling frequency. The nth switch 54(n) closes at the rising edge of the synchronization signal S2 (the timing when the pulse turns on) and opens at the falling edge of the synchronization signal S2 (the timing when the pulse turns off). The rising edge of the synchronization signal S2 is the start timing for starting the separation of each part of the drive waveform signal, and the falling edge of the synchronization signal S2 is the end timing for ending the separation of each part of the drive waveform signal.

[0056] One type of time-division multiplexed signal and one type of synchronization signal S2 are input to one nth switch 54(n). The nth switch 54(n) separates any one of the drive waveform signal indicating the drive waveform A, the drive waveform signal indicating the drive waveform B, and the drive waveform signal Pc indicating the drive waveform C from the input time-division multiplexed signal by opening and closing according to the input synchronization signal S2. The switch group 54 functions as a separation unit in this embodiment. The nth switch 54(n) functions as a switch in this embodiment.

[0057] FIG. 8 is an explanatory diagram for explaining the drive waveform indicated by the separated waveform signal. For example, when the synchronization signal S2a shown in FIG. 7 is selected, the switch group 54 shown in FIG. 3 keeps the n-th switch 54(n) closed while the pulse of the synchronization signal S2a is at the high level. Also, the switch group 54 keeps the n-th switch 54(n) open while the pulse of the synchronization signal S2a is at the low level. That is, the n-th switch 54(n) closes when starting the separation of any one of the first to fourth parts, and opens when ending the separation of any one of the first to fourth parts. The charge applied to the individual electrode 85 when the n-th switch 54(n) is closed is held by the first capacitor 89a and the second capacitor 89b after the n-th switch 54(n) is opened and until the n-th switch 54(n) is closed next.

[0058] As a result, the actuator 88 is given the separated waveform signal of the drive waveform As shown in FIG. 8. The separated waveform signal of the drive waveform As is a signal corresponding to the drive waveform signals Pak for k = 0, …, K separated by the switch group 54 from the time-division multiplexed signal, and the drive waveform As corresponds to the drive waveform A. The actuator 88 drives according to the separated waveform signal of the drive waveform As and discharges ink from the nozzle 80. Only the period of the drive waveform As is included in one cycle for printing one pixel, and the periods of the drive waveforms Bs and Cs are not included. Therefore, the standby time of the nozzle 80 can be reduced.

[0059] Similarly, when the synchronization signal S2b shown in FIG. 7 is selected, the switch group 54 shown in FIG. 3 opens and closes the n-th switch 54(n) according to the synchronization signal S2b. As a result, the actuator 88 is given the separated waveform signal of the drive waveform Bs shown in FIG. 8. The actuator 88 drives according to the separated waveform signal of the drive waveform Bs and discharges ink from the nozzle 80. Similarly, when the synchronization signal S2c shown in FIG. 7 is selected, the actuator 88 is given the separated waveform signal of the drive waveform Cs shown in FIG. 8. The actuator 88 drives according to the separated waveform signal of the drive waveform Cs and discharges ink from the nozzle 80.

[0060] Hereinafter, drive waveform B is exemplified as one drive waveform to be separated from the time-division multiplexed signal, and the case of separating the drive waveform signal Pbk corresponding to each part of drive waveform B from the time-division multiplexed signal will be described. The same applies when the one drive waveform to be separated from the time-division multiplexed signal is drive waveforms A or C.

[0061] When there is no waveform distortion as in the time-division multiplexed signal shown in FIG. 7, the start timing (the rising edge of the synchronization signal S2b) for starting the separation of the drive waveform signal Pbk is uniformly the start-end point (start-end point TB1 shown in FIG. 6) of the drive waveform signal Pbk. However, if the rising edge of the synchronization signal S2b is uniformly equal to the start-end point TB1 when there is waveform distortion, there is a concern that an appropriate drive waveform Bs cannot be obtained due to the influence of the waveform distortion, and the voltage of the separated waveform signal may become too large or too small. There is a possibility that an appropriate amount of ink may not be ejected from the nozzle 80 driven by the actuator 88 following the inappropriate separated waveform signal.

[0062] If the start timing is uniformly set to the end point TB3 of the transition time TB, the influence of the waveform distortion can be completely eliminated. However, in this case, there is a concern that the pulse width of the drive waveform signal Pbk separated from the time-division multiplexed signal becomes too narrow, and the time for continuously applying the voltage corresponding to the data Bk to the actuator 88 is insufficient. If this time is insufficient, the voltage applied to the piezoelectric body 83 may become too large or too small compared to the voltage corresponding to the data Bk, and there is a possibility that an appropriate amount of ink may not be ejected from the nozzle 80.

[0063] Therefore, the switch group 54 separates the drive waveform signal Pbk from the time-division multiplexed signal output by the amplifier 53 at the timing based on the data Bk. The data Bk corresponds to the target value of the drive waveform signal Pbk. In the time-division multiplexed signal, the drive waveform signal Pbk (second part) corresponding to the data Bk is next to the drive waveform signal Pak (third part) corresponding to the data Ak. If the timing based on data Bk is such that there is no waveform distortion or the influence of waveform distortion can be ignored, the separated waveform signal has an appropriate voltage. An actuator 88 following the appropriate separated waveform signal can eject an appropriate amount of ink from the nozzle 80. As a result, the print quality can be improved.

[0064] As shown in "Bk > Ak" of FIG. 6, when data Bk is larger than data Ak, the start timing TS may be a predetermined timing included between the start point TB1 and the end point TB3 of the transition time TB. In the case of Bk > Ak, since it has been experimentally found that the influence of waveform distortion can be ignored, the start point TB1 is used as the start timing TS in this embodiment. As shown in "Bk = Ak" of FIG. 6, when data Bk is equal to data Ak, there is no waveform distortion, so the start timing TS is the start point TB1.

[0065] As shown in "Bk < Ak" of FIG. 6, when data Bk is smaller than data Ak, the start timing TS may be a predetermined timing included between the start point TB1 and the end point TB3 of the transition time TB. In the case of Bk < Ak, further classification is made according to the magnitude relationship between data Bk, Ak and data Bk-1 corresponding to the drive waveform signal Pbk-1 (the first part).

[0066] FIG. 9 is an explanatory diagram for explaining how to obtain the start timing TS in the case of Bk < Ak. FIG. 9 shows a part of the time-division multiplexed signal after amplification by the amplifier 53. This part is the part of the time-division multiplexed signal corresponding to the drive waveform signals Pbk-1, Pak, Pbk, Pck. For ease of viewing the figure, the illustration of the waveform distortion of the drive waveform signal Pbk-1 and the illustrations of the drive waveform signals Pak-1, Pck-1 located on both sides of the waveform signal Pbk-1 are omitted.

[0067] As shown by "Bk≧Bk-1" in FIG. 9, when Bk < Ak and data Bk is greater than or equal to data Bk-1 (in the case of Ak > Bk≧Bk-1), the start timing TS is the time point TB3 at the end of the transient time TB. The data Bk-1 when k = 0 is treated as "0". Therefore, when k = 0, Bk≧Bk-1 always holds. In the case of Ak > Bk≧Bk-1, if the start timing TS is set to a time point before the time point TB3 which is the end of the transient time TB, there is a possibility that the voltage of the separated waveform signal temporarily becomes excessive due to the influence of waveform distortion (so-called whiskers (noise) occur). Therefore, rather than widening the pulse width of the drive waveform signal Pbk, eliminating the influence of waveform distortion is prioritized.

[0068] As shown by "Bk < Bk-1" in FIG. 9, when Bk < Ak and data Bk is smaller than data Bk-1 (in the case of Ak > Bk-1 > Bk), the start timing TS is the time point TB4 when the detection result of the detection unit 56 becomes equal to or lower than the voltage corresponding to data Bk-1. In other words, separation is started when the voltage of the time-division multiplexed signal output from the amplifier 53 to the switch group 54 drops to be equal to or lower than the voltage corresponding to data Bk-1.

[0069] In the case of Ak > Bk-1 > Bk, if the start timing TS is set to the start point TB1, there is a possibility that so-called whiskers occur in the separated waveform signal due to the influence of waveform distortion. On the other hand, if the start timing TS is set to the time point TB3 which is the end of the transient time TB, there is a possibility that the pulse width of the drive waveform signal Pbk separated from the time-division multiplexed signal becomes too narrow.

[0070] On the other hand, the time point TB4 when the detection result of the detection unit 56 becomes equal to or lower than the voltage corresponding to data Bk-1 is in the middle between the start point TB1 and the time point TB3 which is the end of the transient time TB. The voltage when separation is started at the time point TB4 is lower than the voltage when separation is started at the start point TB1. Also, the pulse width when separation is started at the time point TB4 is wider than the pulse width when separation is started at the time point TB3. As a result, it is possible to achieve both reduction of the influence of waveform distortion and widening of the pulse width of the drive waveform signal Pbk.

[0071] As shown in "Ak < Bk-1" of FIG. 9, when Bk < Ak and data Ak is smaller than data Bk-1 (when Bk-1 > Ak > Bk), the start timing TS is the start point TB1. It has been experimentally found that in the case of Bk-1 > Ak > Bk, the influence of the waveform distortion on the separated waveform signal can be ignored.

[0072] The end timing TE may be a predetermined timing included between the end point TB3 of the transition time TB and the end point TB2 of the drive waveform signal Pbk. In this embodiment, regardless of the magnitude relationship between data Bk and data Ak, the end timing TE is uniformly the end point TB2 (see FIGS. 6 and 9). Therefore, the pulse width of the pulse of the synchronization signal S2b is not constant. When Bk ≧ Ak, the separated drive waveform signal Pbk has the widest pulse width. Also in the case of Bk-1 > Ak > Bk, the separated drive waveform signal Pbk has the widest pulse width.

[0073] Moreover, in the printing apparatus 1, the maximum value of the transition time TB related to data Bk is shorter than the response times of the nth switch 54(n) and the piezoelectric body 83. Therefore, the influence of the waveform distortion is smaller than the influence of the transient response of the nth switch 54(n) and the piezoelectric body 83 on the operation of the actuator 88 (and thus the ink ejection from the nozzle 80).

[0074] In the case of the printing apparatus 1, the control circuit 51 executes a process of obtaining the start timing TS based on data Bk. A program P (computer program) for causing the control circuit 51 to execute the process of obtaining the start timing TS is stored in advance in the memory 55 as shown in FIG. 3. The program P may include a computer program for causing the control circuit 51 to execute a process of obtaining the end timing TE and a process of outputting a pulse of the synchronization signal S2b based on the obtained start timing TS and end timing TE.

[0075] Figure 10 is a flowchart for explaining the arithmetic processing for obtaining the start timing TS. The arithmetic processing is executed for all drive waveform signals Pbk where k = 0, …, K. The control circuit 51 determines whether the data Bk is greater than or equal to the data Ak (S11). When Bk ≥ Ak (S11: YES), the control circuit 51 sets the start point TB1 of the drive waveform signal Pbk as the start timing TS (S12). Also, the control circuit 51 sets the end point TB2 of the drive waveform signal Pbk as the end timing TE (S13), and ends the arithmetic processing.

[0076] When Bk < Ak (S11: NO), the control circuit 51 determines whether the data Bk is greater than or equal to the data Bk-1 (S14). When Bk ≥ Bk-1 (S14: YES), the control circuit 51 sets the point TB3, which is the end point of the transition time TB of the drive waveform signal Pbk, as the start timing TS (S15), and transfers the process to S13.

[0077] When Bk < Bk-1 (S14: NO), the control circuit 51 determines whether the data Bk-1 is less than the data Ak (S16). When Bk-1 < Ak (S16: YES), the control circuit 51 acquires the detection result V of the detection unit 56 (S17), and determines whether the detection result V of the detection unit 56 is less than or equal to the voltage Vb corresponding to the data Bk-1 (S18).

[0078] When V ≤ Vb (S18: YES), the control circuit 51 sets the current time as the start timing TS (S19), and transfers the process to S13. The current time in S19 is equal to the aforementioned time TB4. When V > Vb (S18: NO), the control circuit 51 transfers the process to S17. When Bk-1 > Ak (S16: NO), the control circuit 51 transfers the process to S12.

[0079] After the arithmetic processing shown in FIG. 10 or in parallel with the arithmetic processing, when the current time is the start timing TS obtained at S12, the control circuit 51 turns on the pulse of the synchronization signal S2b. After that, when the current time is the end timing TE obtained at S12, the control circuit 51 turns off the pulse of the synchronization signal S2b. As a result of the above, the separated waveform signal of the drive waveform Bs shown in FIG. 8 can be separated from the time-division multiplexed signal shown in FIG. 5. Although the above-described printing apparatus 1 is a serial printer, it is not limited thereto. For example, the printing apparatus 1 may be a line printer.

[0080] [Summary of the present disclosure] In the present disclosure, an output unit (control circuit 51, D / A converter 52, and amplifier 53) outputs a time-division multiplexed signal. The time-division multiplexed signal includes at least a first drive waveform and a second drive waveform. The first drive waveform includes at least a first portion and a second portion following the first portion. The second drive waveform includes at least a third portion and a fourth portion following the third portion. In the time-division multiplexed signal, the first to fourth portions are arranged such that there is a third portion between the first portion and the second portion, and there is a second portion between the third portion and the fourth portion.

[0081] The separation unit (switch group 54) separates each portion of one drive waveform (for example, either the first or second drive waveform when the time-division multiplexed signal includes only the first and second drive waveforms) from the time-division multiplexed signal output by the output unit. The drive unit (actuator 88) discharges liquid (ink) from the nozzles (nozzles 80) according to the separated waveform signal corresponding to each portion separated by the separation unit. Printing is performed on the printing medium (recording paper 200) by the liquid discharged from the nozzles.

[0082] When separating each part of one drive waveform from a time-division multiplexed signal, the separation unit separates each part at a timing based on the amplitude of each part of the one drive waveform. Therefore, each part of the drive waveform can be separated from the time-division multiplexed signal at a timing where there is no waveform distortion or the influence of waveform distortion on the separated waveform signal can be ignored. Accordingly, the separated waveform signal has an appropriate voltage, and a drive unit following the appropriate separated waveform signal can eject an appropriate amount of liquid from the nozzle. As a result, the print quality can be improved.

[0083] Since the timing for separating each part can be obtained based on the amplitude of each part, each part of one drive waveform is not necessarily separated at a constant period. Also, the timing for separating each part of the first drive waveform and the timing for separating each part of the second drive waveform are not necessarily the same as each other.

[0084] In the present disclosure, the output unit has an amplifier circuit (amplifier 53), and the amplifier circuit amplifies the voltage of the time-division multiplexed signal. Due to the transient response of the amplifier circuit, waveform distortion may occur in each part of each drive waveform included in the time-division multiplexed signal. When there is waveform distortion in each part of the drive waveform included in the time-division multiplexed signal, the transient time of the part is the time from the start point of the part to the point where the waveform distortion of the part converges. When there is no waveform distortion, the transient time is "0".

[0085] The output unit and the drive unit are connected to each other by a signal line (see FIG. 3). The separation unit has a switch (n-th switch 54(n)). The switch opens and closes the signal line. The switch closes when starting to separate each part of the drive waveform and opens when ending the separation of each part of the drive waveform. The drive unit has a piezoelectric element (piezoelectric body 83), and when the piezoelectric element is driven according to the separated waveform signal, liquid is ejected from the nozzle.

[0086] When the switch and the piezoelectric element form an RC circuit in which the closed switch serves as an electrical resistor and the piezoelectric element serves as a capacitor, the response times of the switch and the piezoelectric element are determined by the electrical resistance value R of the switch and the capacitance C of the piezoelectric element, and are proportional to the time constant τ = RC. Since the maximum value of the transient time of each part of the drive waveform is shorter than the response times of the switch and the piezoelectric element, the influence of waveform distortion on the separated waveform signal is smaller than the influence of the transient response of the aforementioned RC circuit on the operation of the drive unit (and thus the ejection of liquid from the nozzle). In other words, by setting the maximum value of the transient time > the response time, the influence of waveform distortion on the separated waveform signal can be relatively reduced.

[0087] In the present disclosure, in the time-division multiplexed signal, the third part and the second part are consecutive in this order. When the amplitude of the second part is greater than the amplitude of the third part (second part > third part), the start timing for starting the separation of the second part from the time-division multiplexed signal is a predetermined time point. The predetermined time point is included between the start time point of the second part and the end time point of the transient time of the second part.

[0088] After the end time point of the transient time of the second part, that is, after the waveform distortion of the second part has converged, the second part is not separated. Therefore, the pulse width of the second part separated from the time-division multiplexed signal can be widened. Thus, there is no inconvenience that the pulse width of the second part separated from the time-division multiplexed signal is too narrow and the time for continuously applying the voltage corresponding to the amplitude of the second part to the drive unit is insufficient. If this time is insufficient, there is a risk that the voltage of the drive unit may become too large or too small compared to the voltage corresponding to the amplitude of the second part.

[0089] In the case of the second part > the third part, it has been experimentally found that the influence of waveform smear on the separated waveform signal can be ignored. Therefore, it is preferable to start separating the second part from the time-division multiplexed signal at the start time point of the second part. In this case, since the separated second part can have the widest possible pulse width, the second part can be separated from the time-division multiplexed signal, and thus a voltage corresponding to the amplitude of the second part can be applied to the driving unit for a sufficient period of time. The start timing in the case of the second part > the third part is not necessarily limited to always being the start time point of the second part. For example, based on the magnitude relationship between the amplitude of the second part and the amplitude of the first part, one start timing may be selected from a plurality of different start timings (for example, the start time point of the second part and the end time point of the transient time of the second part).

[0090] In the present disclosure, in the time-division multiplexed signal, the third part and the second part are consecutive in this order. When the amplitude of the second part is equal to the amplitude of the third part (second part = third part), the timing for separating the second part from the time-division multiplexed signal is the start time point of the second part. In the case of the second part = third part, since no waveform smear occurs, it is optimal to start separating the second part from the time-division multiplexed signal at the start time point of the second part. In this case, since the separated second part can have the widest possible pulse width, the second part can be separated from the time-division multiplexed signal, and thus a voltage corresponding to the amplitude of the second part can be applied to the driving unit for a sufficient period of time.

[0091] In the present disclosure, in the time-division multiplexed signal, the third part and the second part are consecutive in this order. When the amplitude of the second part is smaller than the amplitude of the third part (second part < third part), the start timing for starting to separate the second part from the time-division multiplexed signal is a predetermined time point. The predetermined time point is included between the start time point of the second part and the end time point of the transient time of the second part. Since the separation of the second part does not start after the waveform smear of the second part has converged, there is no disadvantage that the time for continuously applying the voltage corresponding to the amplitude of the second part to the driving unit is insufficient.

[0092] The transition time of the second part may be obtained experimentally or by calculation. The transition time of the second part may be given in advance to the printing apparatus, or for example, may be obtained by calculation during the execution of the printing process by a computer included in the printing apparatus.

[0093] In the present disclosure, when the amplitude of the second part is smaller than the amplitude of the third part and is equal to or greater than the amplitude of the first part (first part ≤ second part < third part), the start timing for starting the separation of the second part from the time-division multiplexed signal is the end point of the transition time of the second part. Since the separation of the second part is not started until the waveform distortion of the second part converges, the separated second part from the time-division multiplexed signal includes only the waveform in which the waveform distortion has converged and reached a steady value. Therefore, there is no possibility that the voltage of the separated waveform signal is affected by the waveform distortion. In the case of first part ≤ second part < third part, if the start timing is set to a time point earlier than the end point of the transition time of the second part (for example, the start point of the second part), there is a possibility that the voltage of the separated waveform signal temporarily becomes excessive due to the influence of the waveform distortion (so-called whiskers (noise) occur).

[0094] In the present disclosure, the detection unit (detection unit 56) detects the voltage of the time-division multiplexed signal output from the output unit to the separation unit. The magnitude of the voltage of the time-division multiplexed signal corresponds to the magnitude of the amplitude of the drive waveform included in the time-division multiplexed signal. When the amplitude of the second part is smaller than the amplitude of the third part, smaller than the amplitude of the first part, and moreover, when the amplitude of the third part is larger than the amplitude of the first part (second part < first part < third part), the start timing for starting the separation of the second part from the time-division multiplexed signal is the time point when the detection result of the detection unit becomes equal to or lower than the voltage corresponding to the amplitude of the first part.

[0095] Incidentally, when the second part < the first part < the third part, if the start timing is set to the start point of the second part, there is a risk that so-called whiskers may occur in the separated waveform signal due to the influence of waveform distortion. On the other hand, if the start timing is set to the end point of the transient time of the second part, the pulse width of the second part separated from the time-division multiplexed signal is too narrow, and there is a risk that the time for continuously applying the voltage corresponding to the amplitude of the second part to the driving unit is insufficient.

[0096] However, in the case of the present disclosure, the start timing is in the middle from the start point of the second part to the point where the waveform distortion of the second part converges. Since the separation of the second part starts after the start point of the second part, the influence of waveform distortion can be reduced, and the occurrence of whiskers in the separated waveform signal can be suppressed. On the other hand, since the separation of the second part starts before the waveform distortion of the second part converges, there is no disadvantage that the time for continuously applying the voltage corresponding to the amplitude of the second part to the driving unit is insufficient.

[0097] Note that in the case of the second part < the first part < the third part, the start timing may be an appropriate point in the middle from the start point of the second part to the point where the waveform distortion of the second part converges (for example, the point when half of the transient time of the second part has elapsed). However, the configuration in which the start timing in the case of the second part < the first part < the third part is set to the point when the detection result of the detection unit becomes equal to or lower than the voltage corresponding to the amplitude of the first part has the advantage that there is no risk of sudden increase or decrease in the voltage of the separated waveform signal.

[0098] When the printing apparatus includes a detection unit, the end point of the transient time of the second part may be the point when the detection result of the detection unit becomes equal to the voltage corresponding to the steady value of the second part. However, it is simpler to obtain the transient time of the second part experimentally or by calculation than to obtain the end point of the transient time of the second part based on the detection result of the detection unit.

[0099] In the present disclosure, when the amplitude of the second part is smaller than the amplitudes of the third part and the first part respectively, and the amplitude of the third part is smaller than the amplitude of the first part (the second part < the third part < the first part), the start timing for starting the separation of the second part from the time-division multiplexed signal is the start point of the second part. In the case of the second part < the third part < the first part, it has been experimentally found that the influence of the waveform distortion on the separated waveform signal can be ignored. Therefore, it is preferable to start the separation of the second part from the time-division multiplexed signal at the start point of the second part. In this case, since the separated second part can be separated from the time-division multiplexed signal so as to have the widest pulse width possible, the voltage corresponding to the amplitude of the second part can be applied to the driving unit for a sufficient period of time.

[0100] In the present disclosure, the end timing for ending the separation of each part of one driving waveform is a predetermined time point. The predetermined time point is included between after the end point of the transient time of each part of one driving waveform and the end point of each part of one driving waveform. When there is no waveform distortion, the end point of the transient time is equal to the start point of each part of one driving waveform. That is, the end timing is in the time zone where each part of one driving waveform has reached a steady value. Therefore, each part of one driving waveform separated from the time-division multiplexed signal necessarily includes a waveform in which the waveform distortion has converged to a steady value. Accordingly, the influence of the waveform distortion on the separated waveform signal can be reduced.

[0101] The end timing may be uniform, or may vary according to the start timing, for example. As the uniform end timing, it is most convenient to use the end point of each part of one driving waveform. When the end timing varies according to the start timing, for example, it is conceivable to set the end timing as the time point when a predetermined time has elapsed from the start timing. However, if the time point when a predetermined time has elapsed from the start timing is before the end point of the transient time of each part of one driving waveform, it is necessary to delay the end timing. On the other hand, if the time point when a predetermined time has elapsed from the start timing is after the end point of each part of one driving waveform, it is necessary to advance the end timing.

[0102] In the present disclosure, when each part of one driving waveform is separated from a time-division multiplexed signal, the part is separated at a timing based on the amplitude of each part. Therefore, each part of one driving waveform can be separated from the time-division multiplexed signal at a timing where there is no waveform distortion or the influence of waveform distortion on the separated waveform signal can be ignored. Accordingly, an appropriate amount of liquid is ejected from the nozzle, so that the printing quality can be improved.

[0103] In the present disclosure, when each part of one driving waveform is separated from a time-division multiplexed signal, the part is separated at a timing based on the amplitude of each part. Since the computer executes the process of obtaining this timing, the user of the printing apparatus does not need to obtain this timing. Therefore, it is possible to achieve both an improvement in printing quality and an improvement in user convenience. The computer that executes the process of obtaining the timing may be provided in the printing apparatus (for example, the control circuit 51), or the calculation result of a computer external to the printing apparatus may be provided to the printing apparatus. A computer-readable storage medium storing the computer program according to the present disclosure is also novel and useful.

[0104] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is not the above-mentioned meaning, but is intended to include the meaning equivalent to the claims and all modifications within the scope of the claims. The independent claims and dependent claims described in the claims can be combined with each other in all possible combinations regardless of the citation format. Further, although the claims use a format (multi-claim format) for describing claims that cite two or more other claims, it is not limited thereto. A format for describing a multi-claim (multi-multi-claim) that cites at least one multi-claim may be used.

Description of Reference Numerals

[0105] 1 Printing apparatus 200 Recording paper (printing medium) 51 Control circuit (output unit, computer) 52 D / A converter (output unit) 53 Amplifier (output unit, amplifier circuit) 54 Switch group (separation unit) 54(n) n-th switch (switch) 56 Detection unit 80 Nozzle 83 Piezoelectric body (piezoelectric element) 88 Actuator (drive unit) P Program (computer program)

Claims

1. A printing apparatus for printing on a printing medium with a liquid ejected from a nozzle, comprising: an output unit that outputs a time-division multiplexed signal in which at least a first portion of a first drive waveform, a second portion following the first portion, a third portion of a second drive waveform, and a fourth portion following the third portion are arranged such that the third portion is between the first portion and the second portion, and the second portion is between the third portion and the fourth portion; a separation unit that separates each portion of one of the drive waveforms from the time-division multiplexed signal output by the output unit at a timing based on the amplitude of each portion; a drive unit that causes the liquid to be ejected from the nozzle according to a separated waveform signal corresponding to each portion separated by the separation unit. The printing apparatus is characterized by comprising the above components.

2. The output unit has an amplification circuit that amplifies the voltage of the time-division multiplexed signal. The separation unit has a switch that opens and closes a signal line connecting the output unit and the drive unit to each other. The switch closes when starting the separation of each portion and opens when ending the separation of each portion. The drive unit has a piezoelectric element that is driven according to the separated waveform signal. The printing apparatus according to claim 1, wherein the maximum value of the transition time of each portion due to the transient response of the amplification circuit is shorter than the response times of the switch and the piezoelectric element.

3. In the time-division multiplexed signal, when the second portion is next to the third portion and the amplitude of the second portion is greater than the amplitude of the third portion, The printing apparatus according to claim 1 or 2, wherein the start timing of separating the second portion from the time-division multiplexed signal is a predetermined timing included between the start time point of the second portion and the end time point of the transition time of the second portion.

4. In the time-division multiplexed signal, when the second portion is next to the third portion and the amplitude of the second portion is equal to the amplitude of the third portion, The printing apparatus according to claim 1 or 2, wherein the start timing of separating the second portion from the time-division multiplexed signal is the start time point of the second portion.

5. In the time-division multiplexed signal, when the second portion is next to the third portion and the amplitude of the second portion is smaller than the amplitude of the third portion, The start timing for starting the separation of the second portion from the time-division multiplexed signal is a predetermined time point included between the start time point of the second portion and the end time point of the transient time of the second portion, according to the printing apparatus of claim 1 or 2.

6. When the amplitude of the second portion is greater than or equal to the amplitude of the first portion, The start timing is the end time point of the transient time of the second portion, according to the printing apparatus of claim 5.

7. The printing apparatus further includes a detection unit that detects the voltage of the time-division multiplexed signal output from the output unit to the separation unit, When the amplitude of the second portion is smaller than the amplitude of the first portion and the amplitude of the third portion is greater than the amplitude of the first portion, The start timing is the time point when the detection result of the detection unit becomes equal to or lower than the voltage corresponding to the amplitude of the first portion, according to the printing apparatus of claim 5.

8. When the amplitude of the second portion is smaller than the amplitude of the first portion and the amplitude of the third portion is smaller than the amplitude of the first portion, The start timing is the start time point of the second portion, according to the printing apparatus of claim 5.

9. The end timing for ending the separation of each portion of one of the drive waveforms is a predetermined time point included between after the end time point of the transient time of each portion and the end time point of each portion, according to the printing apparatus of claim 1 or 2.

10. A method of printing on a printing medium with a liquid ejected from a nozzle driven according to a separation waveform signal corresponding to each portion of one drive waveform separated from a time-division multiplexed signal in which at least a first portion of a first drive waveform, a second portion following the first portion, a third portion of a second drive waveform, and a fourth portion following the third portion are arranged such that there is a third portion between the first portion and the second portion and there is a second portion between the third portion and the fourth portion, The timing for separating each portion of one drive waveform from the time-division multiplexed signal is a timing based on the amplitude of each portion, according to the printing method.

11. A computer program for a printing apparatus that prints on a printing medium with liquid discharged from a nozzle driven according to a separated waveform signal corresponding to each part of one drive waveform separated from a time-division multiplexed signal in which at least a first part of a first drive waveform, a second part following the first part, a third part of a second drive waveform, and a fourth part following the third part are arranged such that the third part is between the first part and the second part, and the second part is between the third part and the fourth part, wherein timing for separating each part of one drive waveform from the time-division multiplexed signal is obtained based on the amplitude of each part, and causing a computer to execute the processing.

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