JP4623101B2 - Liquid ejecting apparatus and control method thereof - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus that ejects liquid from a nozzle opening in the form of droplets, and a control method therefor, and more particularly, to a device that finely vibrates a meniscus to prevent liquid thickening.

  One type of liquid ejecting apparatus that can eject liquid in the form of droplets is an image recording apparatus such as a printer or a plotter. In this image recording apparatus, characters and images are recorded by ejecting (ejecting) liquid ink from an ejection head and landing on a print recording medium such as recording paper. Recently, application to various devices has been studied taking advantage of the ability to land a very small amount of liquid with high accuracy. For example, a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming an electrode such as an organic EL (Electro Luminescence) display or FED (surface emitting display), a chip for manufacturing a biochip (biochemical element) Manufacturing equipment has been proposed.

In this type of liquid ejecting apparatus, the liquid to be ejected is exposed at the nozzle opening to form a meniscus (liquid free surface). The solvent component may evaporate through the meniscus, and the viscosity of the liquid may increase near the nozzle opening.
In order to prevent this increase in viscosity, the liquid is agitated by slightly vibrating the meniscus to the extent that droplets are not discharged. One type of this micro-vibration operation is a micro-vibration operation within a period during which droplets can be ejected. The fine vibration operation is performed, for example, by including a fine vibration pulse in a drive signal for driving the pressure generating element and selectively supplying the fine vibration pulse to the pressure generating element (for example, Patent Documents). 1).

  In this case, the drive signal generation circuit generates a series of drive signals when receiving the generation timing signal. For example, as shown in FIG. 10, in an ink jet printer which is a kind of liquid ejecting apparatus, a series of drive signals COM are generated over a signal generation period every time a generation timing signal PTS is received. This is to accurately define the landing position of the droplet. That is, the generation timing signal is generated by multiplying the encoder output from the linear encoder indicating the carriage position (increasing the frequency several times). Thereby, the deviation between the scanning position of the recording head and the signal generation timing can be reduced as much as possible, and the accuracy of the landing position can be improved. The signal generation cycle is defined so that the droplet discharge gradation (recording gradation in the printer) is one unit. Therefore, the above-described printer generates a generation timing signal every time a one-dot area arrives.

Japanese Patent Laid-Open No. 10-81013 (pages 6-7, FIG. 4)

By the way, in this type of liquid ejecting apparatus, high-frequency ejection of droplets is required.
This is because the processing speed can be increased and the landing density can be improved. For example, in an ink jet printer, if the ejection frequency of ink droplets can be increased, the scanning speed of the recording head can be increased correspondingly while maintaining the resolution of the image. In addition, the resolution of the image can be increased while maintaining the scanning speed of the recording head.

  Here, in order to realize high-frequency ejection of droplets, it is necessary to shorten the generation interval between the preceding and succeeding ejection pulses with respect to ejection pulses for ejecting droplets. However, the above-described micro-vibration pulse is only for vibrating the meniscus and is not involved in the discharge of the droplet. For this reason, in the conventional structure which puts a fine vibration pulse in each discharge period, the time for a fine vibration pulse is needed. Accordingly, the droplet discharge interval is extended by the minute vibration pulse, which becomes an obstacle to high-frequency droplet discharge.

Further, the necessary degree of the fine vibration operation differs depending on the type of liquid to be ejected.
That is, some liquids require frequent fine vibrations during the non-ejection period, and some liquids do not. Therefore, it is not efficient to carry out uniformly regardless of the type of liquid.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a liquid ejecting apparatus capable of ejecting droplets at a higher frequency and a control method thereof.

The present invention has been proposed in order to achieve the above object, the jet head is create a pressure variation to the liquid in the pressure chamber Ri by the operation of the pressure generating element to eject liquid droplets from the nozzle openings,
Drive signal generating means for generating a series of drive signals each including an ejection pulse for ejecting a droplet and a micro-vibration pulse for micro-vibrating a meniscus each time a generation timing signal is received ;
In a liquid ejecting apparatus comprising: a pulse supply unit that selects a pulse included in the drive signal according to a discharge gradation of a droplet, and supplies the selected pulse to the pressure generating element.
The drive signal includes a first unit periodic signal having a fine vibration pulse and an ejection pulse, and a second unit periodic signal having no fine vibration pulse and having only an ejection pulse ,
The type and order of occurrence of ejection pulse included in the first unit period signal, the type and order of occurrence of ejection pulse included in the second subsignal, but are the same,
The drive signal has at least one second unit period signal at a head portion .

  According to the present invention, the mixed drive signal has a plurality of unit periods as a repetition period, and includes a first unit period signal and a second unit period signal. Since the second unit cycle signal does not include the micro-vibration pulse, the unit cycle can be made shorter than the first unit cycle signal by the amount of no micro-vibration pulse. Thereby, it is possible to shorten the signal generation cycle as much as possible while adding necessary fine vibrations. In other words, the generation period of one unit can be shortened as much as possible for the drive signal. As a result, high-frequency ejection of droplets can be realized.

In the above invention, the mixed drive signal includes N (N is an integer of 2 or more) unit period signals set according to the type of liquid to be ejected in one signal generation period. It is preferable that one of the unit cycle signals is the first unit cycle signal, and the frequency of the minute vibrations in the signal generation cycle is 1 / N times.
According to the present invention, the execution frequency of the fine vibration in the mixed drive signal is defined by the type of liquid. Thereby, the execution frequency of the fine vibration is optimized according to the type of liquid. Accordingly, the droplet ejection frequency can be increased as much as possible while giving the liquid a necessary and sufficient fine vibration.

  In the above invention, the mixed drive signal has at least one second unit cycle signal at the head of the signal generation cycle, and can perform micro-vibration by the micro-pulses in the middle of the signal generation cycle. The structure which does is preferable.

In the above invention, the pulse supply means includes a selection timing signal output means for outputting a selection timing signal for defining a pulse selection timing, and a pulse selection data output means for outputting pulse selection data every time the selection timing signal is received. Preferably, the selection timing signal output means includes a selection timing signal for the second unit periodic signal including a dummy selection timing signal corresponding to the minute vibration pulse of the first unit periodic signal for output.
According to the present invention, the number of bits of the pulse selection data of the first unit periodic signal having the fine vibration pulse and the number of bits of the pulse selection data of the second unit periodic signal not having the fine vibration pulse can be made uniform. . Thereby, the pulse selection data of the first unit periodic signal and the pulse selection data of the second unit periodic signal can be handled in the same way, the processing can be simplified and suitable for high-speed processing.

In the above invention, it is preferable that the time width of the drive signal is set to be equal to or less than the minimum value of the generation interval variation of the generation timing signal.
Also, there is provided a latch signal output means for periodically outputting a latch signal that defines the latch timing of the ejection gradation, and the time width of the unit cycle signal is set to be equal to or less than the minimum value of the interval variation of the latch signal. Is preferred.
According to these configurations, the time width of the drive signal is determined based on the variation in the generation interval of the generation timing signal, and the time width of the unit cycle signal is determined based on the variation in the generation interval of the latch signal. The trouble that the generation timing signal occurs during the generation of the drive signal of the next period and the generation of the latch signal during the generation of the unit period signal and the generation of the unit period signal of the next period are ensured. Can be prevented.

In the above invention, the ejection pulse is composed of a small droplet ejection pulse capable of ejecting a small amount of droplets and a medium droplet ejection pulse capable of ejecting a medium amount of droplets, and the first unit period signal is a pair of A medium droplet discharge pulse, one small droplet discharge pulse generated between these medium droplet discharge pulses, and the micro-vibration pulse are included in a unit cycle, and the second unit cycle signal is a pair of signals. A configuration in which a medium droplet discharge pulse and one small droplet discharge pulse generated between these medium droplet discharge pulses are included in a unit cycle is preferable.
Further, the ejection pulse is constituted by a small droplet ejection pulse capable of ejecting a small amount of droplets, and the first unit period signal includes a plurality of the small droplet ejection pulses and the micro vibration pulses generated at equal intervals. In the unit cycle, and the second unit cycle signal preferably includes a plurality of small droplet ejection pulses generated at equal intervals in the unit cycle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, an image recording apparatus which is one form of the liquid ejecting apparatus, and more specifically, an ink jet printer (hereinafter referred to as a printer) will be described as an example.

  FIG. 1 is a perspective view illustrating the basic configuration of the printer. As shown in FIG. 1, a printer includes a carriage 4 to which a recording head 1 (a kind of the liquid ejecting head of the present invention) is attached and a cartridge holding portion 3 that detachably holds an ink cartridge 2, and the carriage. 4 includes a head scanning mechanism that moves the recording paper 5 along the paper width direction (main scanning direction) of the recording paper 5, and a paper feeding mechanism that moves the recording paper 5 along the paper feeding direction (sub-scanning direction).

  The head scanning mechanism is connected to a guide shaft 6 installed in the paper width direction, a pulse motor 7 disposed on one side of the main scanning direction in the printer, and a rotation shaft of the pulse motor 7, and is rotated by the pulse motor 7. The drive pulley 8 to be driven, the idle pulley 9 disposed on the other side in the main scanning direction opposite to the drive pulley 8, and the drive pulley 8 and the idle pulley 9 are stretched over the carriage 4 And a linear encoder 11 for outputting position information of the carriage 4 (recording head 1), and a control unit 12 (see FIG. 6) for controlling the rotation of the pulse motor 7. The paper feed mechanism includes a paper feed motor 13 as a drive source, a paper feed roller 14 that is rotationally driven by the paper feed motor 13, and a control unit 12 that controls the operation of the paper feed motor 13. .

  For example, as shown in FIG. 2, the recording head 1 includes a case 21, a vibrator unit 22 housed in the case 21, a flow path unit 23 joined to the front end surface of the case 21, and the like. Has been. The case 21 is, for example, a block-like member molded from a thermosetting resin such as an epoxy resin, and is provided with a storage space 24 that can store the vibrator unit 22. The vibrator unit 22 includes a vibrator group 25 including a comb-like piezoelectric vibrator 25a, a fixing plate 26 to which the vibrator group 25 is joined, and the like, and each piezoelectric vibrator 25a is a cantilever beam. Support in the state. The piezoelectric vibrator 25a is a kind of pressure generating element in the present invention, and is a kind of electromechanical conversion element, and a free end portion expands and contracts in the longitudinal direction of the element according to the vibrator potential.

  The flow path unit 23 has a configuration in which the nozzle plate 28 is bonded to one surface of the flow path forming substrate 27 and the elastic plate 29 is bonded to the other surface of the flow path forming substrate 27. The flow path unit 23 is provided with a reservoir 30, an ink supply port 31, a pressure chamber 32, a nozzle communication port 33, and a nozzle opening 34. Each of these portions forms a plurality of ink flow paths corresponding to the nozzle openings 34 from the ink supply ports 31 through the pressure chambers 32 and the nozzle communication ports 33 to the nozzle openings 34.

  The elastic plate 29 is provided with a diaphragm portion. This diaphragm part is a part that divides a part of the pressure chamber 32, and is provided around the island part (thick part) 35 to which the tip surface of the piezoelectric vibrator 25a is joined, and around the island part 35, and has elasticity. And having a thin portion 36. And if the piezoelectric vibrator 25a expand | extends, the island part 35 will be pushed by the pressure chamber 32 side, and will be displaced. The displacement of the island portion 35 reduces the pressure chamber volume. On the other hand, when the piezoelectric vibrator 25 a contracts, the island portion 35 is pulled away from the pressure chamber 32. The displacement of the island portion 35 increases the pressure chamber volume.

As the volume of the pressure chamber 32 changes, the pressure in the ink in the pressure chamber 32 varies. Therefore, ink droplets can be ejected from the nozzle openings 34 by controlling the pressure fluctuation. For example, an ink droplet can be ejected by contracting the piezoelectric vibrator 25a in the longitudinal direction of the element and then rapidly expanding the piezoelectric vibrator 25a. In this case, the pressure chamber 32 expands due to the contraction of the piezoelectric vibrator 25 a, and the ink stored in the reservoir 30 flows into the pressure chamber 32. Thereafter, the pressure chamber 32 abruptly contracts due to the rapid expansion of the piezoelectric vibrator 25a and the ink in the pressure chamber 32 is pressurized, so that an ink droplet is ejected from the corresponding nozzle opening 34.
Note that by changing the pressure fluctuation pattern applied to the ink in the pressure chamber 32, the amount of ejected ink droplets can be changed, and the meniscus can be vibrated slightly.

  Next, the linear encoder 11 will be described. The linear encoder 11 includes a scale 41 (see FIGS. 3 and 4) stretched in parallel with the main scanning direction on the housing side of the printer, and a photo interrupter 42 (see FIG. 5) attached to the back surface of the carriage 4. I have.

  The scale 41 is a band-shaped (band-shaped) member made of a transparent resin, and a plurality of black stripes 41a that cross the band width direction are formed at a constant pitch in the band longitudinal direction. In the present embodiment, each stripe 41a is printed at a pitch corresponding to 180 dpi. Locking holes 41b and 41c are formed at both ends of the scale 41, respectively. These locking holes 41b and 41c are locked by hooks, respectively. That is, as shown in FIG. 3, one locking hole 41 b is locked to a first hook 43 attached to the idler pulley 9 side on the back plate surface of the housing. The first hook 43 pulls the scale 41 outward in the longitudinal direction due to its elasticity. The other locking hole 41c is locked to a second hook 44 provided on the side plate on the pulse motor 7 side, as shown in FIG.

  The photo interrupter 42 is configured by attaching a pair of a light emitting element 45 and a light receiving element 46 to the inner side surface of a U-shaped frame 47 in an opposed state. The scale 41 is disposed between the light emitting element 45 and the light receiving element 46. For this reason, the output level of the detection signal (encoder output) from the light receiving element 46 is different between the state where the light from the light emitting element 45 is transmitted through the scale 41 and the state where the stripe 41a blocks the light from the light emitting element 45. . The encoder output is input to the control unit 12 as shown in FIG.

Accordingly, in this linear encoder 11, when the carriage 4 (recording head 1) moves in the main scanning direction, the light from the light emitting element 45 is intermittently blocked by the stripe 41a. Is output. Since the stripes 41a are provided at regular intervals, the control unit 12 can recognize the scanning position of the carriage 4 based on the encoder output.
The linear encoder 11 is not limited to this configuration as long as an encoder output corresponding to the movement of the carriage 4 can be obtained. For example, the scale 41 may be formed of a light-shielding band member, and light-transmitting slits may be provided at regular intervals.

Next, the electrical configuration of the printer will be described based on the block diagram of FIG.
The illustrated printer includes a printer controller 51 and a print engine 52. The printer controller 51 includes an interface (external I / F) 53 for receiving print data from a host computer (not shown), a RAM 54 for storing various data, and a ROM 55 for storing various data processing routines. A control unit 12 including a CPU, an oscillation circuit 56 that generates a clock signal (CK), a drive signal generation circuit 57 that generates a drive signal (COM) to be supplied to the recording head 1, and print data ( And an interface (internal I / F) 58 for transmitting drive signals and the like to the print engine 52.

  The external I / F 53 receives, for example, print data including any one or more of character code, graphic function, and image data from a host computer or the like. The external I / F 53 outputs a busy signal (BUSY), an acknowledge signal (ACK), and the like to the host computer. The RAM 54 is used as a reception buffer, an intermediate buffer, an output buffer, a work memory (not shown), or the like. Print data from the host computer received by the external I / F 53 is temporarily stored in the reception buffer. The intermediate buffer stores the intermediate code data converted by the control unit 12. Print data serially transmitted to the recording head 1 is developed in the output buffer. The ROM 55 stores various control routines executed by the control unit 12, font data and graphic functions, various procedures, and the like.

  The control unit 12 functions as data expansion means and expands print data into print data. In this case, the control unit 12 reads the print data in the reception buffer, converts it into intermediate code data, and stores this intermediate code data in the intermediate buffer. Then, the control unit 12 analyzes the intermediate code data read from the intermediate buffer, and expands the intermediate code data into print data for each dot with reference to font data, graphic functions, and the like in the ROM 55. In the present embodiment, this print data is composed of 2-bit data. The expanded print data is stored in the output buffer, and when one line of print data corresponding to one main scan is obtained, this one line of print data (SI) is recorded through the internal I / F 58. Serially transmitted to the head 1. When one line of print data is transmitted from the output buffer, the contents of the intermediate buffer are erased and conversion to the next intermediate code data is performed.

  The control unit 12 also functions as a generation timing signal output unit that outputs a generation timing signal (PTS). Here, the generation timing signal is a signal that determines the generation start timing of the drive signal generated by the drive signal generation circuit 57. That is, the drive signal generation circuit 57 outputs a series of drive signals over the signal generation period each time the generation start timing signal is received. In the present embodiment, this generation start timing signal is output at an interval corresponding to 720 dpi. And the control part 12 outputs a generation | occurrence | production timing signal by multiplying the encoder output from the linear encoder 11 4 times. For example, the output interval of the generation timing signal is obtained by 1/4 of the immediately preceding cycle, and the generation timing signal is output based on this output interval.

  Further, the control unit 12 also functions as a latch signal output unit and a selection timing signal output unit, and selects a latch signal (LAT) that defines the latch timing of print data and a selection timing of pulses included in the drive signal. A prescribed channel signal (CH, a kind of selection timing signal of the present invention) is output. As will be described later, the latch signal of the present embodiment is generated for the first time upon receipt of the generation start timing signal, and then generated for the second time on the condition that the specified time has elapsed. For this reason, the control part 12 functions also as a time measuring means which time-measures the elapsed time after generating the 1st latch signal. In other words, the latch signal output means defines the generation timing of the second latch signal based on the generation timing of the first latch signal.

The drive signal generation circuit 57 is a kind of drive signal generation means in the present invention, and includes a plurality of ejection pulses (SP, MP1, MP2) and micro vibration pulses (VP) as illustrated in FIG. A series of drive signals (COM) is generated over a signal generation period. This drive signal will be described in detail later.
Further, the drive signal generation circuit 57 in the present embodiment acquires change amount information (information indicating the change amount of voltage) from the control unit 12 in a timely manner, and adds the acquired change amount information in units of extremely short update cycles. It has a configuration. Then, at the end of the signal generation cycle, change amount information of the value [0] is given from the control unit 12. Therefore, during the period from the end of the signal generation cycle to the start of the next signal generation cycle, a constant signal is output at the intermediate potential Vm although the control by the control unit 12 is released.

  The print engine 52 includes the pulse motor 7 provided in the head scanning mechanism, the paper feed motor 13 provided in the paper feed mechanism, the recording head 1 and the like. The pulse motor 7 functions as a drive source that moves the recording head 1. That is, by operating this pulse motor 7, the recording head 1 is moved in the width direction of the recording paper 5 (that is, the main scanning direction). The paper feed motor 13 functions as a drive source for sequentially feeding the recording paper 5 in the paper feed direction (that is, the sub-scanning direction). The pulse motor 7 and the paper feed motor 13 operate in cooperation with each other under the control of the control unit 12.

  Next, the electrical configuration of the recording head 1 will be described. The recording head 1 includes a shift register circuit including a first shift register 61 and a second shift register 62, a latch circuit including a first latch circuit 63 and a second latch circuit 64, a decoder 65, a control logic 66, A level shifter 67, a switch circuit 68, and a piezoelectric vibrator 25a are provided. A plurality of shift registers 61 and 62, latch circuits 63 and 64, decoder 65, level shifter 67, switch circuit 68, and piezoelectric vibrator 25 a are provided corresponding to each nozzle opening 34 of the recording head 1. .

The recording head 1 ejects ink droplets based on print data (SI) from the printer controller 51. Specifically, it is as follows.
Print data from the printer controller 51 is serially transmitted from the internal I / F 58 to the first shift register 61 and the second shift register 62 in synchronization with the clock signal (CK) from the oscillation circuit 56. This print data is 2-bit data as described above. In this embodiment, the print data is a level representing four levels of recording gradation (a kind of ejection gradation) consisting of non-recording, small dots, medium dots, and large dots. It is composed of key information. Specifically, non-recording is gradation information [00], small dots are gradation information [01], medium dots are gradation information [10], and large dots are gradation information [11]. It is.

  This print data is set for each nozzle opening 34. The lower bit (L) data of all the nozzle openings 34 is input to the first shift register 61, and the upper bit (H) data is the second. Input to the shift register 62. A first latch circuit 63 is electrically connected to the first shift register 61, and a second latch circuit 64 is electrically connected to the second shift register 62. When the latch signal (LAT) from the printer controller 51 is input to each latch circuit, the first latch circuit 63 latches the lower bit data of the print data, and the second latch circuit 64 the upper bit of the print data. Latch the data. The set of the first shift register 61 and the first latch circuit 63 and the set of the second shift register 62 and the second latch circuit 64 that perform such an operation constitute a storage circuit and are input to the decoder 65. The previous print data is temporarily stored.

  The print data latched by each latch circuit is input to the decoder 65. The decoder 65 functions as a translation unit, translates 2-bit print data, and generates pulse selection data. The decoder 65 of this embodiment includes a waveform selection table that defines the relationship between print data and drive pulses, and generates pulse selection data based on this waveform selection table. The pulse selection data is configured by associating each bit with each pulse constituting the drive signal (COM). In the present embodiment, 4-bit pulse selection data is generated. Then, supply or non-supply of the drive pulse to the piezoelectric vibrator 25a is selected according to the contents of each bit (for example, [0], [1]). The drive pulse supply control will be described in detail later.

  The decoder 65 also receives a timing signal from the control logic 66. The control logic 66 generates a timing signal based on the latch signal (LAT) and the channel signal (CH). That is, the control logic 66 generates a timing signal when receiving a latch signal or a channel signal. The decoder 65 also functions as pulse selection data output means, and outputs pulse selection data every time a timing signal is received.

  In this case, the pulse selection data translated by the decoder 65 is input to the level shifter 67 every time the timing signal reception timing comes in order from the higher bit side. For example, at the first timing in the unit cycle (for example, at the start of the periods t1 and t1 ′ shown in FIG. 7), the most significant bit data of the pulse selection data is input to the level shifter 67 and the second timing (the start of the period t2). The second bit data in the pulse selection data is input to the level shifter 67. Thereafter, data is similarly input, and the data of the least significant bit in the pulse selection data is input to the level shifter 67 at the fourth timing (at the start of the period t4). The level shifter 67 functions as a voltage amplifier. When the pulse selection data is [1], the level shifter 67 outputs an electric signal boosted to a voltage capable of driving the switch circuit 68, for example, a voltage of about several tens of volts. [1] pulse selection data boosted by the level shifter 67 is supplied to a switch circuit 68 functioning as a switch means. A drive signal (COM) is supplied from the drive signal generation circuit 57 to the input side of the switch circuit 68, and the piezoelectric vibrator 25a is connected to the output side of the switch circuit 68.

  The pulse selection data controls the operation of the switch circuit 68, that is, the supply of pulses to the piezoelectric vibrator 25a. For example, during a period in which the pulse selection data applied to the switch circuit 68 is [1], the switch circuit 68 is in a connected state and a drive pulse is supplied to the piezoelectric vibrator 25a, and the piezoelectric vibrator 25a follows this drive pulse. The potential level changes. On the other hand, while the pulse selection data applied to the switch circuit 68 is [0], the level shifter 67 does not output an electrical signal for operating the switch circuit 68. For this reason, the switch circuit 68 is disconnected and no driving pulse is supplied to the piezoelectric vibrator 25a. In addition, since the piezoelectric vibrator 25a behaves like a capacitor, when the switch circuit 68 is in a disconnected state, it continues to hold the potential immediately before the disconnection.

  The decoder 65, the control logic 66, the level shifter 67, the switch circuit 68, and the control unit 12 that perform such operations function as a kind of pulse supply means in the present invention, and are driven from the drive signals based on the print data. A pulse is selected and supplied to the piezoelectric vibrator 25a.

  Next, the drive signal COM generated by the drive signal generation circuit 57 (a kind of drive signal generation means) will be described.

  As shown in FIG. 7, the drive signal COM of the present embodiment can be divided into a first half part and a second half part based on the latch signal (LAT). The first half part is the front unit period signal PD1, and the second half part. Is the rear unit periodic signal PD2. The front unit period signal PD1 and the rear unit period signal PD2 are generated over a unit period defined by one dot (gradation information). In other words, this drive signal COM is a signal generation cycle (the time width of the drive signal COM, specifically, the time width of the drive signal COM), which is generated over the unit cycle defined by the recording gradation. The time until the end of the second medium dot ejection pulse MP2 in the side unit period signal PD2) can be said to be included.

  The front unit period signal PD1 and the rear unit period signal PD2 are different in the included pulses. That is, the front unit period signal PD1 includes the first medium dot ejection pulse MP1 (a kind of medium droplet ejection pulse), the small dot ejection pulse SP (a kind of small droplet ejection pulse), and the second middle dot ejection pulse MP2. The rear unit period signal PD2 is composed of the three ejection pulses SP, MP1, MP2 and the micro-vibration pulse VP. . In short, the front unit period signal PD1 and the rear unit period signal PD2 are different in the presence or absence of the micro-vibration pulse VP, and the types and generation order of the included ejection pulses are the same.

  Therefore, the front unit periodic signal PD1 corresponds to a kind of the second unit periodic signal of the present invention, and the rear unit periodic signal PD2 corresponds to a kind of the first unit periodic signal of the present invention. In the drive signal COM, the front unit period signal PD1 and the rear unit period signal PD2 are mixed. For this reason, the exemplified drive signal COM can be said to be a kind of the mixed drive signal COM of the present invention.

  Hereinafter, each pulse will be described. As described above, the front unit period signal PD1 and the rear unit period signal PD2 differ only in the presence or absence of the micro-vibration pulse VP, and the types of included pulses are the same. Each pulse included in the unit cycle signal PD2 will be described.

  First, the fine vibration pulse VP will be described. As shown in FIG. 8, the fine vibration pulse VP is a trapezoidal pulse composed of a fine vibration expansion element P1, a fine vibration hold element P2, and a fine vibration contraction element P3. The micro-vibration expansion element P1 is a waveform element that increases the potential with a relatively gentle gradient that does not cause ink droplets to be ejected from the intermediate potential (reference potential) Vm to the micro-vibration potential Va. When this fine vibration expansion element P1 is supplied to the piezoelectric vibrator 25a, the piezoelectric vibrator 25a is slightly contracted in the longitudinal direction of the element, and the volume of the pressure chamber 32 is slightly increased. The fine vibration hold element P2 is an element that holds the fine vibration potential Va. The contracted state of the piezoelectric vibrator 25a is maintained over the supply period of the fine vibration hold element P2, and the pressure chamber 32 maintains the previous expanded state. The fine vibration contraction element P3 is a waveform element that lowers the potential with a relatively gentle gradient that does not cause ink droplets to be ejected from the fine vibration potential Va to the intermediate potential Vm. When this fine vibration expansion element P1 is supplied to the piezoelectric vibrator 25a, the piezoelectric vibrator 25a slightly extends in the longitudinal direction of the element, and the volume of the pressure chamber 32 returns to the reference volume.

  Next, the first medium dot ejection pulse MP1 and the second medium dot ejection pulse MP2 will be described. These medium dot ejection pulses MP1 and MP2 are pulses for ejecting a medium amount (for example, 7.5 pl) of ink droplets, and all have the same waveform shape in the present embodiment. That is, the expansion element P4 that raises the potential with a constant gradient that does not eject ink droplets from the intermediate potential Vm to the maximum potential Vh, the expansion hold element P5 that maintains the maximum potential Vh for a predetermined time, and the minimum potential Vg from the maximum potential Vh. The discharge element P6 is configured to suddenly lower the potential to the maximum, the vibration suppression hold element P7 that maintains the minimum potential Vg for a predetermined time, and the expansion vibration suppression element P8 that increases the potential from the minimum potential Vg to the intermediate potential Vm.

  When the medium dot ejection pulses MP1 and MP2 are supplied to the piezoelectric vibrator 25a, the piezoelectric vibrator 25a and the pressure chamber 32 operate as follows. That is, with the supply of the expansion element P4, the piezoelectric vibrator 25a contracts greatly, and the pressure chamber 32 expands from the steady state to the maximum volume. With this expansion, the pressure chamber 32 is depressurized, and the meniscus is drawn to the pressure chamber 32 side. The expansion state of the pressure chamber 32 is maintained over the supply period of the expansion hold element P5, and the meniscus vibrates freely during the maintenance period. Subsequently, the discharge element P6 is supplied, the piezoelectric vibrator 25a is greatly expanded, and the pressure chamber 32 is rapidly contracted to the minimum volume. Along with the contraction, the ink in the pressure chamber 32 is pressurized and an ink droplet is ejected from the nozzle opening 34. The damping hold element P7 is supplied following the ejection element P6, and the contracted state of the pressure chamber 32 is maintained. At this time, the meniscus vibrates greatly due to the influence of ink droplet ejection. Thereafter, the expansion damping element P8 is supplied at a timing at which the vibration of the meniscus can be canceled, and the pressure chamber 32 expands and returns to the reference state. That is, in order to cancel out the ink pressure in the pressure chamber 32, the pressure chamber 32 is expanded to reduce the ink pressure. Thereby, the vibration of the meniscus is suppressed.

  Next, the small dot ejection pulse SP will be described. The small dot ejection pulse SP is a pulse for ejecting a small amount (for example, 3.5 pl) of ink droplets. The small dot ejection pulse SP of the present embodiment includes a pulling element P9 that increases the potential with a relatively steep gradient from the lowest potential Vg to the maximum potential Vh, a pulling hold element P10 that maintains the maximum potential Vh for an extremely short time, A discharge element P11 that lowers the potential with a steep gradient from the potential Vh to a discharge potential Vf that is slightly lower than the maximum potential Vh, a discharge hold element P12 that maintains the discharge potential Vf for an extremely short time, and a minimum potential Vg from the discharge potential Vf. A contraction damping element P13 that lowers the potential to a minimum, a damping control element P14 that maintains the minimum potential Vg for a predetermined time, and an expansion damping element P15 that increases the potential from the minimum potential Vg to the intermediate potential Vm.

When this small dot ejection pulse SP is supplied to the piezoelectric vibrator 25a, the piezoelectric vibrator 25a and the pressure chamber 32 operate as follows. That is, the piezoelectric vibrator 25a contracts greatly with the supply of the retracting element P9, and the pressure chamber 32 rapidly expands from the minimum volume to the maximum volume. Along with this expansion, the pressure chamber 32 is greatly depressurized, and the meniscus is largely drawn toward the pressure chamber 32 side. At this time, the central portion of the meniscus, that is, the vicinity of the center of the nozzle opening 34, is once drawn largely, and then rises into a convex shape due to reaction. Next, the pull-in hold element P10 and the discharge element P11 are continuously supplied, the pressure chamber 32 is slightly contracted as the discharge element P11 is supplied, and the ink is slightly pressurized, and the central portion of the meniscus is formed as an ink droplet. Discharged.
As the ink droplets are ejected, the meniscus vibrates greatly, but the volume of the pressure chamber 32 fluctuates due to the contraction damping element P13, the damping hold element P14, and the expansion damping element P15 that are supplied thereafter. Meniscus vibration after droplet ejection is suppressed.

In the rear unit period signal PD2, the fine vibration pulse VP, the first medium dot ejection pulse MP1, the small dot ejection pulse SP, and the second middle dot ejection pulse MP2 are generated in this order from the start side of the rear unit period. . That is, the minute vibration pulse VP is generated in the period t1 ′, and the first medium dot ejection pulse MP1 is generated in the period t2. Further, the small dot ejection pulse SP is generated in the period t3, and the second medium dot ejection pulse MP2 is generated in the period t4.
On the other hand, the front unit period signal PD1 does not have the fine vibration pulse VP. For this reason, as shown in FIG. 7, the first medium dot ejection pulse MP1, the small dot ejection pulse SP, and the second middle dot ejection pulse MP2 are generated in this order from the start side of the front unit period. That is, the first medium dot ejection pulse MP1 is generated in the period t2, the small dot ejection pulse SP is generated in the period t3, and the second medium dot ejection pulse MP2 is generated in the period t4. In the front unit period signal PD1, the period t1 is set before the period t2. This period t1 is an extremely short period set for simplification of control, and the function thereof will be described later.

  When comparing the front unit period signal PD1 and the rear unit period signal PD2, the generation period (that is, the time width) of the signal is equal to that of the front unit period signal PD1 by the amount not including the micro-vibration pulse VP. Shorter. Specifically, the generation period of the front unit period signal PD1 is the end of the second medium dot ejection pulse MP2 (the end of the expansion damping element P8) from the rising edge of the first latch signal (LAT), and the rear side The generation period of the unit cycle signal PD2 is the end of the second medium dot ejection pulse MP2 from the rising edge of the second latch signal. Therefore, if the front unit cycle signal PD1 and the rear unit cycle signal PD2 are mixed to form the drive signal COM, the signal generation cycle can be shortened as much as possible while adding necessary fine vibrations. In other words, the generation period of one unit can be shortened as much as possible for the drive signal COM. As a result, high frequency ejection of ink droplets can be realized.

Further, in the present embodiment, a unit period signal (corresponding to the first unit period signal of the present invention) having the minute vibration pulse VP is generated in the second half of the signal generation period, and the unit period signal (without the minute pulse VP) ( (Corresponding to the second unit period signal of the present invention) is generated in the first half of the signal generation period. This is in order to enhance the effect of the fine vibration by causing the fine vibration in the non-ejection state of the ink droplet (fine vibration in printing) to be performed during the signal generation cycle.
In other words, since the micro-vibration pulse VP is generated at the head part of the unit period, if it is generated in the first half of the signal generation period, the micro-oscillation pulse VP cannot be vibrated until the next signal generation period arrives. The meniscus is left unattended over this period. Also, at the beginning of the signal generation cycle, there is a high possibility that ink thickening has not progressed due to ink droplet ejection in the immediately preceding cycle.
Therefore, as in the present embodiment, if a unit period signal that does not have the micro-vibration pulse VP is generated before the unit period signal that has the micro-vibration pulse VP, the micro-vibration occurs in the middle of the signal generation period. The operation is performed, and the ink thickening in the vicinity of the nozzle opening 34 can be efficiently prevented.
From this point of view, the fine vibration pulse VP is preferably generated at a timing close to the middle of the signal generation cycle. This is because the time from the end of the immediately preceding signal generation cycle to the generation timing of the fine vibration pulse VP is equal to the time from the generation timing of the fine vibration pulse VP to the start of the next signal generation cycle.
As a result, the meniscus leaving time is less varied before and after the minute vibration pulse VP, and the effect of the minute vibration can be further enhanced.

  By the way, the drive signal COM is generated every time the drive signal generation circuit 57 receives the generation timing signal (PTS). As described above, the generation timing signal is generated by the control unit 12 multiplying the encoder output from the linear encoder 11. For this reason, the generation timing signal may be generated with some variation rather than complete equal intervals. Then, the time width per cycle of the drive signal COM without considering the variation of the generation timing signal (in the example of FIG. 7, the time until the end of the expansion damping element P8 of the second medium dot ejection pulse MP2 corresponds). ), There is a possibility that the generation of the drive signal COM is not completed at the time of reception of the next generation timing.

  In view of this point, in the present embodiment, the time width per cycle of the drive signal COM is set to be equal to or less than the minimum value of the variation in the generation interval T of the generation timing signal. In this case, for example, the variation in the generation interval T is acquired based on the manufacturing accuracy of the scale 41. Specifically, it is calculated from the dimensional tolerance of the formation pitch in the stripe 41a. Further, the minimum value of the encoder output is obtained by, for example, actually detecting the formation pitch in the stripe 41a by the photo interrupter 42. Then, the minimum value of the generation interval variation of the generation timing signal is acquired from the minimum value of the encoder output.

  Then, if the time width per cycle of the drive signal COM is set to be equal to or less than the minimum value of the generation interval variation of the generation timing signal, the generation of the drive signal COM is surely ended at the reception time of the next generation timing. The reliability of the printer can be improved.

  Similarly, in the present embodiment, the time widths of the front unit periodic signal PD1 and the rear unit periodic signal PD2 are defined in consideration of variations in the generation intervals T1 and T2 between successive latch signals (LAT). Yes. That is, the time width per cycle of each of the unit cycle signals PD1 and PD2 is set to be equal to or less than the minimum value of the variation in generation interval of the latch signal. By configuring in this way, each unit cycle signal has been generated at the next generation timing of the latch signal, so that the problem that the next latch signal is received during the generation can be prevented. The reliability of the printer can be improved.

  Next, recording control by the printer having the above configuration will be described. As shown in FIG. 7, in this embodiment, the front unit period signal PD1 is composed of three ejection pulses SP, MP1, and MP2, and the rear unit period signal PD2 is composed of three ejection pulses SP, MP1, and MP2, and one It is constituted by a fine vibration pulse VP. Here, since it is sufficient to assign one pulse selection data to one pulse, 3 bits are sufficient for the pulse selection data corresponding to the front unit period signal PD1. In this regard, in this embodiment, the pulse selection data is 4 bits. In other words, dummy pulse selection data is provided before the first medium dot ejection pulse MP1, and control based on this pulse selection data is performed by a dummy channel signal CH ′ (ie, dummy selection timing signal). Yes.

  The reason for this configuration is to align the number of bits of the pulse selection data corresponding to the front unit period signal PD1 and the pulse selection data corresponding to the rear unit period signal PD2. As described above, the decoder 65 (translation means) translates the print data (gradation information) to generate pulse selection data. At this time, if the number of data bits differs between the pulse selection data corresponding to the front unit cycle signal PD1 and the pulse selection data corresponding to the rear unit cycle signal PD2, the decoder 65 translates the print data. It is necessary to recognize whether the print data for the front unit cycle signal PD1 or the print data for the rear unit cycle signal PD2. In a device such as a printer that requires high-speed translation processing, it is preferable not to perform such recognition operation as much as possible because it causes processing delay. Then, if the number of bits of the pulse selection data for the front unit period signal PD1 and the pulse selection data for the rear unit period signal PD2 are aligned, the decoder 65 only needs to translate the latched print data. Processing can be simplified and speeded up.

By arranging the number of bits of the pulse selection data in this way, the data for the micro-vibration pulse VP (the most significant bit in this example) remains in the pulse selection data for the front unit period signal PD1. This extra data must be invalidated in some way. This is because the consistency between the pulse selection data and the selected pulse cannot be obtained. In this embodiment, this invalidation is performed by providing a dummy channel signal CH ′.
Specifically, in the front unit cycle, the dummy channel signal CH ′ is output immediately after the LAT signal is generated and the drive signal COM is at the intermediate potential Vm. With this configuration, in the fine vibration gradation information [00], the switch circuit 68 is turned on in the period t1 from the generation timing of the latch signal to the generation timing CH ′ of the dummy channel signal, and the drive signal COM is the piezoelectric vibration. It is supplied to the child 25a. However, during this period t1, the drive signal COM is constant at the intermediate potential Vm, and since this intermediate potential Vm is the same potential as the terminal potential of each pulse, the piezoelectric vibrator 25a maintains the previous state. Therefore, the pulse selection data can be invalidated without any trouble.

  In addition, when this piezoelectric vibrator 25a is used over a long period of time or is used in a high humidity environment, there is a possibility that the potential may drop due to natural discharge. When the intermediate potential Vm is supplied to the piezoelectric vibrator 25a using a dummy channel signal as in the present embodiment, even if the vibrator potential is lowered by natural discharge, the intermediate potential Vm is returned to the intermediate potential Vm. For this reason, when supplying the ejection pulse and the micro-vibration pulse VP, these pulses can be supplied smoothly (that is, with the potential gap reduced). As a result, problems such as erroneous ejection of ink droplets can be prevented.

  Next, gradation control in this printer will be described. In this printer, recording for two dots is performed by the drive signal COM of one repetition unit. Each dot is recorded with 4 gradations. For this reason, two latch signals (PTS) are generated for one generation timing signal (PTS). Further, as described above, since control in one unit cycle is performed by 4-bit pulse selection data, three channel signals are generated in one unit cycle. The decoder 65 outputs the most significant bit of the pulse selection data at the reception timing of the latch signal, and outputs the second bit of the pulse selection data at the reception timing of the first channel signal. Similarly, the decoder 65 outputs the third bit in the pulse selection data at the reception timing of the second channel signal, and outputs the least significant bit in the pulse selection data at the reception timing of the third channel signal.

  Then, the decoder 65 generates 4-bit pulse selection information by translating the print data (gradation information). Specifically, the decoder 65 generates the pulse selection data [1000] by translating the non-ejection tone information [00], and the pulse selection data [0010] by translating the small dot tone information [01]. Generate. Further, the pulse selection data [0100] is generated by translating the medium dot gradation information [10], and the pulse selection data [0101] is generated by translating the large dot gradation information [11].

  Thereby, ink droplet ejection control as illustrated in FIG. 9 is performed. That is, in the front unit period, the switch circuit 68 is turned on in the period t1 by the non-ejection gradation information [00], and the intermediate potential Vm is supplied to the piezoelectric vibrator 25a as described above. Ink droplets are not ejected by the supply of the intermediate potential Vm. Then, the switch circuit 68 is turned on in the period t3 by the small dot gradation information [01], the small dot ejection pulse SP is supplied to the piezoelectric vibrator 25a, and a small ink droplet is ejected. Further, the switch circuit 68 is turned on in the period t2 by the medium dot gradation information [10], the first medium dot ejection pulse MP1 is supplied to the piezoelectric vibrator 25a, and the medium ink droplet is ejected. Furthermore, the switch circuit 68 is turned on in the periods t2 and t4 by the large dot gradation information [11], and the first medium dot ejection pulse MP1 and the second medium dot ejection pulse MP2 are continuously supplied to the piezoelectric vibrator 25a. Then, the middle ink droplet is ejected twice in succession.

  Further, in the rear unit period, the switch circuit 68 is turned on in the period t1 ′ by the non-ejection gradation information [00], and the micro vibration pulse VP is supplied to the piezoelectric vibrator 25a. In other recording gradations, the same operation as the front unit period is performed. Briefly, small ink droplets are ejected by gradation information [01] of small dots, and medium ink droplets are ejected once by gradation information [10] of medium dots. Also, medium ink droplets are ejected twice in succession by the large dot gradation information [11].

As described above, in the present embodiment, the rear unit period signal PD2 having the minute vibration pulse VP and the minute vibration pulse VP in the signal generation period which is the time width per unit period of the drive signal COM. Since the front unit period signal PD1 that does not include the signal is mixed, the time width of the drive signal COM can be shortened by the amount of the minute vibration pulse VP. Also, considering the signal generation period, the frequency of microvibration is reduced, so that power consumption can be reduced accordingly.
Further, by generating a unit cycle signal having a micro-vibration pulse VP in the second half of the signal generation cycle and generating a unit cycle signal not having the micro-vibration pulse VP in the first half of the signal generation cycle, the micro-vibration pulse VP is generated. Since it is generated approximately in the middle of the cycle, the fine vibration can be optimized as described above.
Further, since the types and generation order of the ejection pulses are the same for the first half unit cycle signal and the second half unit cycle signal, the decoder 65 translates the print data without distinguishing between the first half unit cycle signal and the second half unit cycle signal. Can be done. This simplifies the processing and is suitable for high-speed processing.

  By the way, the present invention is not limited to the above embodiment, and various modifications can be made based on the description of the scope of claims. For example, in the above-described embodiment, two (N = 2) unit cycle signals are included in one signal generation cycle, and one unit cycle has a unit cycle signal (second cycle) that does not have the fine vibration pulse VP. Although the example comprised by the unit period signal) was demonstrated, you may include the unit period signal of 3 or more (N> = 3) in one signal generation period.

Further, since the degree of viscosity increase of the ink (liquid) differs depending on the type, the number (N) of unit cycle signals included in one signal generation cycle is made different according to the type of ink to be ejected. One unit period signal is a unit period signal having a minute vibration pulse VP (first unit period signal in the present invention), and the other unit period signal is a unit period signal having no minute vibration pulse VP (in the present invention). (Second unit periodic signal). For example, in the case of a pigment ink that has a higher degree of solvent evaporation than a dye ink and tends to thicken, two unit cycle signals are included in one signal generation cycle as in the above embodiment. On the other hand, in the dye ink which is hard to thicken, for example, 6 to 8 unit cycle signals are included in one signal generation cycle. With this configuration, the execution frequency of the fine vibration becomes 1 / N times based on the unit cycle, and the generation time of the drive signal COM is made possible while giving the necessary and sufficient fine vibration to the type of ink to be ejected. Can be shortened.
In consideration of the effect of fine vibration, N is finite and is a number that can sustain the effect of fine vibration. Experimentally, it has been confirmed that it is possible to set up to about N = 16 if the liquid is hard to thicken.

Further, the ejection pulse is not limited to the one having the above shape, and various ejection pulses can be used. For example, all the ejection pulses within one recording cycle may have the same shape.
Specifically, the ejection pulse is constituted by a small dot ejection pulse SP (a kind of small droplet ejection pulse) that can eject a small amount of droplets, and the first unit cycle signal includes a plurality of small dots that are generated at equal intervals. The ejection pulse SP and the micro-vibration pulse VP are included in the unit cycle, and the second unit cycle signal includes only a plurality of small dot ejection pulses SP generated at equal intervals in the unit cycle.

  Further, the pressure generating element is not limited to the piezoelectric vibrator 25a. For example, it may be a flexural vibration mode piezoelectric vibrator or a magnetostrictive element. Furthermore, an electrostatic actuator may be used.

  The present invention can also be applied to a liquid ejecting apparatus other than a printer and a control method thereof. For example, a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode manufacturing apparatus for forming electrodes such as an organic EL (Electro Luminescence) display and FED (surface emitting display), and a chip for manufacturing a biochip (biochemical element) The present invention can also be applied to a manufacturing apparatus and a liquid ejecting apparatus such as a micropipette that supplies an accurate amount of a sample solution.

FIG. 2 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view illustrating the structure of a recording head. It is a figure explaining a linear encoder, and is a figure explaining the fastening part by the side of an idle pulley. It is a figure explaining a linear encoder, and is a figure explaining the fastening part by the side of a drive pulley. It is a figure explaining a linear encoder and a figure explaining a photo interrupter. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a figure explaining a drive signal and discharge control of an ink drop. It is a figure explaining a rear unit period signal. FIG. 6 is a diagram for explaining recording gradation and ejection control. It is a figure explaining the drive signal and the discharge control of an ink drop in a conventional apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Recording head, 2 ... Ink cartridge, 3 ... Cartridge holding part, 4 ... Carriage, 5 ... Recording paper, 6 ... Guide shaft, 7 ... Pulse motor, 8 ... Drive pulley, 9 ... Sliding pulley, 10 ... Timing belt , 11 ... Linear encoder, 12 ... Control unit, 13 ... Paper feed motor, 14 ... Paper feed roller, 21 ... Case, 22 ... Vibrator unit, 23 ... Flow path unit, 24 ... Storage empty part, 25 ... Vibrator group 25a ... piezoelectric vibrator, 26 ... fixing plate, 27 ... channel forming substrate, 28 ... nozzle plate, 29 ... elastic plate, 30 ... reservoir, 31 ... ink supply port, 32 ... pressure chamber, 33 ... nozzle communication port, 34 ... Nozzle opening, 35 ... Island part, 36 ... Thin part, 41 ... Scale, 42 ... Photo interrupter, 43 ... First hook, 44 ... Second hook, 45 ... Light emitting element, 46 ... Light receiving element, 5 ... Printer controller, 52 ... Print engine, 53 ... External I / F, 54 ... RAM, 55 ... ROM, 56 ... Oscillator circuit, 57 ... Drive signal generating circuit, 58 ... Internal I / F, 61 ... First shift register, 62 ... second shift register, 63 ... first latch circuit, 64 ... second latch circuit, 65 ... decoder, 66 ... control logic, 67 ... level shifter, 68 ... switch circuit.

Claims (8)

An ejection head that causes pressure fluctuations in the liquid in the pressure chamber by the operation of the pressure generating element and ejects droplets from the nozzle opening;
Drive signal generating means for generating a series of drive signals each including an ejection pulse for ejecting a droplet and a micro-vibration pulse for micro-vibrating a meniscus each time a generation timing signal is received;
In a liquid ejecting apparatus comprising: a pulse supply unit that selects a pulse included in the drive signal according to a discharge gradation of a droplet, and supplies the selected pulse to the pressure generating element.
The drive signal includes a first unit periodic signal composed of a fine vibration pulse and an ejection pulse generated after the fine vibration pulse, and a second unit periodic signal having only the ejection pulse without the fine vibration pulse,
The type and generation order of the ejection pulses included in the first unit periodic signal are the same as the type and generation order of the ejection pulses included in the second unit periodic signal,
The drive signal has at least one second unit periodic signal at a leading portion ;
The liquid ejecting apparatus, wherein a generation period of the second unit periodic signal is shorter than a generation period of the first unit periodic signal . The drive signal includes N (N is an integer of 2 or more) unit cycle signals in one signal generation cycle, and one of the N unit cycle signals is used as the first unit cycle signal. ,
The liquid ejecting apparatus according to claim 1, wherein an execution frequency of the minute vibration within the signal generation period is set to 1 / N times. The pulse supply means includes a selection timing signal output means for outputting a selection timing signal for determining a pulse selection timing, and a pulse selection data output means for outputting pulse selection data every time the selection timing signal is received,
The selection timing signal output means includes a selection timing signal for the second unit periodic signal including a dummy selection timing signal corresponding to the minute vibration pulse of the first unit periodic signal for output. The liquid ejecting apparatus according to any one of claims 1 to 3.   5. The liquid ejecting apparatus according to claim 1, wherein a time width of the drive signal is set to be equal to or less than a minimum value of variation in generation interval of the generation timing signal. Latch signal output means for periodically outputting a latch signal for determining the latch timing of the ejection gradation is provided,
5. The liquid ejecting apparatus according to claim 1, wherein a time width of the unit periodic signal is set to be equal to or less than a minimum value of variation in generation interval of the latch signal. The ejection pulse is composed of a small droplet ejection pulse capable of ejecting a small amount of droplets and a medium droplet ejection pulse capable of ejecting a medium amount of droplets,
The first unit cycle signal includes a pair of medium droplet discharge pulses, one small droplet discharge pulse generated between the medium droplet discharge pulses, and the micro-vibration pulse within a unit cycle. ,
The second unit cycle signal includes a pair of medium droplet ejection pulses and one small droplet ejection pulse generated between the medium droplet ejection pulses within a unit cycle. The liquid ejecting apparatus according to any one of claims 1 to 6. The ejection pulse is constituted by a small droplet ejection pulse capable of ejecting a small amount of droplets,
The first unit period signal includes a plurality of small droplet ejection pulses and micro-vibration pulses generated at equal intervals in a unit period.
7. The liquid according to claim 1, wherein the second unit cycle signal includes a plurality of small droplet discharge pulses generated at equal intervals in a unit cycle. Injection device. An ejection head that causes pressure fluctuations in the liquid in the pressure chamber by the operation of the pressure generating element and ejects droplets from the nozzle opening;
Drive signal generating means for generating a series of drive signals each including an ejection pulse for ejecting a droplet and a micro-vibration pulse for micro-vibrating a meniscus each time a generation timing signal is received;
In a liquid ejecting apparatus comprising: a pulse supply unit that selects a pulse included in the drive signal according to a discharge gradation of a droplet, and supplies the selected pulse to the pressure generating element.
The drive signal includes a first unit periodic signal composed of a fine vibration pulse and an ejection pulse generated after the fine vibration pulse, and a second unit periodic signal having only the ejection pulse without the fine vibration pulse,
The type and generation order of the ejection pulses included in the first unit periodic signal are the same as the type and generation order of the ejection pulses included in the second unit periodic signal,
The drive signal has at least one second unit periodic signal at a leading portion ;
The method of controlling a liquid ejecting apparatus, wherein a generation period of the second unit periodic signal is shorter than a generation period of the first unit periodic signal .

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