JP7567458B2 - LIQUID EJECTION APPARATUS, LIQUID EJECTION METHOD, AND LIQUID EJECTION PROGRAM - Google Patents

Description

The present invention relates to a liquid ejection device, a liquid ejection method, and a liquid ejection program for use in an image recording device such as an inkjet printer.

A printer described in Patent Document 1 is known in the past. Patent Document 1 describes that the platen gap, which is the distance from the nozzle surface of the head from which ink droplets are ejected to the landing position of the ink droplets on the medium, can change due to changes in the medium, etc. Also, in a printer, the ink exposed from the nozzle hole is prone to drying and thickening, and as the viscosity increases, the ink ejection characteristics are affected. Therefore, in order to diffuse the thickened ink into the ink inside the head, it is known to implement control (non-ejection vibration control) that slightly vibrates the ink exposed from the nozzle hole so as not to eject it.

JP 2010-142978 A

When the distance from the nozzle surface to the medium becomes relatively large, it is necessary to apply a higher voltage to the actuator to eject ink droplets in order to make the ink droplets reach the medium. However, if non-ejection vibration control is performed while the actuator is being driven with such a high voltage, the ink will not merely vibrate slightly, but may leak out of the nozzle hole, soiling the medium or the surrounding area of the printer.

The present invention has been made to solve these problems, and aims to provide a liquid ejection device, a liquid ejection method, and a liquid ejection program that can prevent liquid from leaking due to non-ejection vibrations when the liquid ejection voltage is changed according to the distance from the nozzle face to the medium.

The present invention has been made to solve the above-mentioned problems, and the liquid ejection device according to the present invention includes an ejection head having a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to the liquid in the pressure chamber, a waveform generation circuit that generates a waveform of a drive signal for driving the actuator, and a control device, the drive signal including an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate the meniscus of the nozzle without ejecting the droplets from the nozzle, and the control device executes a mode determination process that determines which of a plurality of print modes corresponding to the gap between the nozzle and the ejection medium is the print mode, an ejection signal generation process that causes the waveform generation circuit to generate a waveform as the ejection drive signal with a larger amplitude as the gap is larger in the print mode, and a non-ejection signal generation process that causes the waveform generation circuit to generate a waveform as the non-ejection drive signal with a different timing for the actuator to apply pressure to the liquid from other print modes, based on the determined print mode.

With this configuration, by changing the amplitude of the waveform of the ejection drive signal depending on the gap between the nozzle and the receiving medium, proper landing of droplets can be achieved regardless of the gap during printing, while the timing of pressure application by the non-ejection drive signal is also varied depending on the gap, preventing droplets from unintentionally leaking out of the nozzle when preventing thickening of the meniscus. In other words, according to the present invention, proper printing and proper prevention of thickening of the meniscus can be achieved regardless of the gap between the nozzle and the receiving medium.

The present invention provides a liquid ejection device, a liquid ejection method, and a liquid ejection program that can achieve proper printing and prevent the meniscus from thickening properly, regardless of the gap between the nozzle and the ejected medium.

FIG. 1 is a schematic diagram showing a schematic configuration of a liquid ejection device according to a first embodiment. FIG. 2 is a cross-sectional view showing the configuration of the ejection head of FIG. FIG. 3 is a block diagram showing the configuration of an image recording apparatus equipped with the liquid ejection apparatus of FIG. FIG. 4 is a flowchart showing the liquid ejection method according to the first embodiment. FIG. 5 is a schematic diagram for explaining the non-ejection drive signal generated by the waveform generating circuit in the high gap printing mode. FIG. 6 is a block diagram showing the configuration of an image recording apparatus including a liquid ejection device according to the second embodiment. FIG. 7 is a flowchart showing a liquid ejection method according to the second embodiment.

(Embodiment 1)
A liquid ejection device, a liquid ejection method, and a liquid ejection program according to an embodiment of the present invention will be described with reference to the drawings. Note that the liquid ejection device, the liquid ejection method, and the liquid ejection program described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the gist of the present invention.

[Liquid ejection device]
1, a liquid ejection device 10 of this embodiment ejects ink as an example of a liquid, and includes a storage tank 12, a carriage 16, an ejection head 20, a pair of transport rollers 15, a pair of guide rails 17, and a sub-tank 18. In the liquid ejection device 10, paper 14 is placed on a platen (not shown).

The carriage 16 is equipped with an ejection head 20. The carriage 16 extends in a main scanning direction perpendicular to the transport direction of the paper 14, and is supported by a pair of guide rails 17 arranged parallel to the transport direction. The carriage 16 is driven by a carriage motor 33 (see FIG. 3) to reciprocate in the main scanning direction along the guide rails 17. This causes the ejection head 20 to reciprocate in the main scanning direction. In addition, the carriage 16 is equipped with, for example, four sub-tanks 18. Each sub-tank 18 is connected to a corresponding storage tank 12 via a tube.

The pair of transport rollers 15 are arranged with their axes aligned along the main scanning direction and parallel to each other in the transport direction. The transport rollers 15 rotate about their axes when driven by a transport motor 31 (see FIG. 3), thereby transporting the paper 14 on the platen in the transport direction. The carriage 16 is located between the pair of transport rollers 15. Therefore, the ejection head 20 moves in the main scanning direction together with the carriage 16, ejecting ink onto the paper 14 on the platen, and the paper 14 is transported in the transport direction by the transport rollers 15, allowing an image to be printed on the entire surface of the paper 14.

Ink is stored in the storage tank 12. The storage tank 12 is connected to a sub-tank 18 mounted on the carriage 16 via an ink flow path to supply ink to the ejection head 20, and ink is supplied from the sub-tank 18 to the ejection head 20. Furthermore, the storage tanks 12 and sub-tanks 18 are provided for each type of ink. For example, four storage tanks 12 and four sub-tanks 18 are provided, and each storage tank 12 and each sub-tank 18 stores black, yellow, cyan, and magenta ink.

As shown in FIG. 2, the ejection head 20 has multiple nozzles 21 that eject ink. The ejection head 20 has a flow path forming body made of a laminate. A liquid flow path is formed inside the flow path forming body, and multiple nozzle holes 21a are opened on its lower surface, the ejection surface 40a. In addition, an actuator 60 is laminated on the flow path forming body via a vibration plate 55, and when this actuator 60 is driven, the volume of the liquid flow path changes. At this time, the meniscus vibrates in the nozzle hole 21a and ink is ejected. The configuration of the ejection head 20 will be described below.

[Discharge head]
2, the flow path forming body of the ejection head 20 is composed of a laminate of multiple plates, and a vibration plate 55 and an actuator (piezoelectric element) 60 are further laminated on the flow path forming body. An insulating film 56 is connected on the vibration plate 55, and a common electrode 61 (described later) is connected on the insulating film 56.

The multiple plates include a nozzle plate 46, a spacer plate 47, a first flow path plate 48, a second flow path plate 49, a third flow path plate 50, a fourth flow path plate 51, a fifth flow path plate 52, a sixth flow path plate 53, and a seventh flow path plate 54, which are stacked in this order from the bottom up.

Each plate has holes and grooves of various sizes. Inside the flow path forming body where the plates are stacked, the holes and grooves are combined to form multiple nozzles 21, multiple individual flow paths 64, and manifolds 22 as liquid flow paths.

The nozzles 21 are formed penetrating the nozzle plate 46 in the stacking direction. On the ejection surface 40a of the nozzle plate 46, multiple nozzle holes 21a, which are the tips of the nozzles 21, are aligned in the arrangement direction to form a nozzle row. The above-mentioned arrangement direction is perpendicular to the stacking direction.

The nozzle plate 46 is disposed below the spacer plate 47. The spacer plate 47 is formed, for example, from stainless steel. The spacer plate 47 has a recess 45 in which a thin portion constituting the damper portion 47a and a damper space 47b are formed by being recessed in the thickness direction of the spacer plate 47 from the surface on the nozzle plate 46 side, for example by half etching. With this configuration, a damper space 47b is formed as a buffer space between the manifold 22 and the nozzle plate 46.

The manifold 22 communicates with a number of pressure chambers 28 (described later) to which a liquid ejection pressure is applied, and stores the liquid to be supplied to each pressure chamber 28. That is, the manifold 22 extends in the arrangement direction, is connected to one end of each of the individual flow paths 64, and functions as a common flow path for the liquid flowing through each individual flow path 64. Such a manifold 22 is formed above the spacer plate 47. Specifically, through holes that penetrate the first flow path plate 48 to the fourth flow path plate 51 in the stacking direction and a recess recessed from the lower surface of the fifth flow path plate 52 are formed overlapping each other in the stacking direction.

The manifold 22 is also connected to a supply port 22a. The supply port 22a is formed, for example, in a cylindrical shape and is provided at one end in the arrangement direction (the longitudinal direction of the manifold 22). The manifold 22 and the supply port 22a are connected by a flow path (not shown) that penetrates the upper part of the fifth flow path plate 52, the sixth flow path plate 53, and the seventh flow path plate 54, respectively.

The multiple individual flow paths 64 are each connected to the manifold 22. The upstream end of each individual flow path 64 is connected to the manifold 22, and the downstream end is connected to the base end of the nozzle 21. Each individual flow path 64 is composed of a first communication hole 25, a supply throttle path 26 which is an individual throttle path, a second communication hole 27, a pressure chamber 28, and a descender 29, and these components are arranged in this order.

The first communication hole 25 is formed by a through hole in the stacking direction formed in the fifth flow path plate 52. The upstream end (lower end) of the first communication hole 25 opens and is connected to the upper part of the manifold 22. The upstream end of the supply throttle path 26 is connected to the downstream side (upper end) of the first communication hole 25. The supply throttle path 26 is formed by half etching, for example, and is formed by a groove recessed from the lower surface of the sixth flow path plate 53.

The second communication hole 27 is formed by a through hole formed in the sixth flow path plate 53 in the stacking direction. The upstream end (lower end) of the second communication hole 27 is connected to the downstream end of the supply throttle path 26. The pressure chamber 28 is formed as an opening that penetrates the seventh flow path plate 54 in the stacking direction. The upstream end of the pressure chamber 28 is connected to the downstream end (upper end) of the second communication hole 27.

The descender 29 is formed by penetrating the multiple plates 47-53 in the stacking direction, and is provided near the manifold 22 in the width direction (short side direction of the manifold 22). The upstream end of the descender 29 is connected to the downstream end of the pressure chamber 28, and the downstream end of the descender 29 is connected to the base end of the nozzle 21. The nozzle 21 overlaps the descender 29 in the stacking direction, for example, and is disposed in the center of the descender 29 in the direction perpendicular to the stacking direction (width direction).

The vibration plate 55 is laminated on the seventh flow path plate 54 and covers the upper end opening of the pressure chamber 28.

The actuator 60 includes a common electrode 61, a piezoelectric layer 62, and an individual electrode 63, which are arranged in this order from the bottom. The common electrode 61 covers the entire surface of the vibration plate 55 via an insulating film 56. The piezoelectric layer 62 is provided for each pressure chamber 28, and is arranged on the common electrode 61 so as to overlap the pressure chamber 28. The individual electrode 63 is provided for each pressure chamber 28, and is arranged on the piezoelectric layer 62. One actuator 60 is composed of one individual electrode 63, the common electrode 61, and the portion of the piezoelectric layer 62 sandwiched between the two electrodes.

The individual electrodes 63 are electrically connected to a head driver IC 74 (see FIG. 3). The head driver IC 74 receives a control signal from a control device 71 (see FIG. 3) and generates a drive signal (voltage signal) to apply to the individual electrodes 63. In contrast, the common electrode 61 is always held at ground potential. In this configuration, the active portion of the piezoelectric layer 62 expands and contracts in the planar direction together with the two electrodes 61, 63 in response to the drive signal. In response, the vibration plate 55 deforms in cooperation with the drive signal, changing in a direction that increases or decreases the volume of the pressure chamber 28. This applies an ejection pressure to the pressure chamber 28 that ejects liquid from the nozzle 21.

In the ejection head 20 as described above, the supply port 22a is connected to the subtank 18 via a pipe. When a pressure pump provided on the pipe is driven, liquid flows from the subtank 18 through the pipe and into the manifold 22 via the supply port 22a. The liquid then flows from the manifold 22 into the supply throttle passage 26 via the first communication hole 25, and from the supply throttle passage 26 into the pressure chamber 28 via the second communication hole 27. The liquid then flows through the descender 29 and into the nozzle 21. When an ejection pressure is applied to the pressure chamber 28 by the actuator 60, the liquid is ejected from the nozzle hole 21a.

[Image Recording Device]
Next, an image recording apparatus 1, such as an inkjet printer, that includes the liquid ejection apparatus 10 of the present embodiment will be described with reference to the drawings.

As shown in FIG. 3, in addition to the liquid ejection device 10, the image recording device 1 includes a network interface (I/F) 70, a control device 71 consisting of a CPU and the like, a RAM 72, a storage 73, a head driver IC 74, a temperature sensor 75, a waveform generating circuit 76, a recording medium reading device 77, motor driver ICs 30 and 32, a conveying motor 31, and a carriage motor 33.

The RAM 72 temporarily stores print jobs received from an external device 200, such as a personal computer, via the network interface 70, and operation information input by a user via the external device 200. The storage 73 is, for example, an SSD, and stores the liquid ejection program of this embodiment, a control program for performing various data processing, and various data required to execute the control program.

The waveform generating circuit 76 generates a waveform of a drive signal for driving the actuator 60. For example, the waveform generating circuit 76 generates a desired waveform of a drive signal based on a voltage corresponding to one power supply circuit selected from a plurality of power supply circuits (not shown) each having a different supply voltage, and a plurality of pulse signals of different waveforms stored in advance in the storage 73 or the like, or a modified signal obtained by modifying the same. In this embodiment, the drive signal includes an ejection drive signal that applies pressure to the liquid in the pressure chamber 28 so as to eject droplets from the nozzle 21, a non-ejection drive signal that applies pressure to the liquid in the pressure chamber 28 so as to vibrate the meniscus of the nozzle 21 without ejecting droplets from the nozzle 21, and a non-vibration signal that does not change the pressure of the liquid in the pressure chamber 28. In addition, the operation mode of the meniscus that vibrates without ejecting droplets from the nozzle 21 due to the non-ejection drive signal is referred to as non-ejection vibration below.

The head driver IC 74 drives the ejection head 20 in response to an instruction from the control device 71, causing the nozzle 21 to eject droplets, or vibrates the meniscus of the nozzle 21 for non-ejection. The motor driver IC 30 controls the drive of the transport motor 31 in response to an instruction from the control device 71. As a result, the transport motor 31 operates the transport roller 15, which transports the paper 14 in the transport direction. In addition, the other motor driver IC 32 controls the drive of the carriage motor 33 in response to an instruction from the control device 71. As a result, the carriage motor 33 operates the carriage 16, which moves the ejection head 20 in the main scanning direction.

The recording medium reading device 77 is a device that reads out a liquid ejection program from a computer-readable recording medium 80, such as a flexible disk, CD (CD-ROM, CD-R, CD-RW, etc.), DVD (DVD-ROM, DVD-RAM, DVD-R, DVD+R, DVD-RW, DVD+RW, etc.), Blu-ray disk, magnetic disk, optical disk, and magneto-optical disk. This recording medium reading device 77 may be a device that reads out a liquid ejection program from a recording medium, such as a USB flash memory. The read liquid ejection program is stored in the storage 73 and executed by the control device 71. The liquid ejection program of this embodiment may be stored in the storage 73 from the external device 200 via the network interface 70, or may be downloaded from the Internet and stored in the storage 73.

The control device 71 constitutes a computer according to the present invention. The control device 71 has, as its functional configuration, a mode determination unit 71a, an ejection signal generation unit 71b, and a non-ejection signal generation unit 71c. Each of these functions is realized by the control device 71 executing a predetermined program. Therefore, the mode determination unit 71a causes the computer constituting the control device 71 to function as a mode determination means, and similarly, the ejection signal generation unit 71b causes the computer to function as an ejection signal generation means, and the non-ejection signal generation unit 71c causes the computer to function as a non-ejection signal generation means.

Of these, the mode determination unit 71a executes a mode determination process to determine which of a plurality of printing modes corresponding to the gap between the nozzle 21 and the ejection receiving medium such as the paper 14 is the printing mode. As an example, the image recording device 1 according to this embodiment has two printing modes, a low gap printing mode in which the distance between the nozzle 21 and the ejection receiving medium is a low gap GL as shown in FIG. 2, and a high gap printing mode in which this distance is a high gap GH that is larger than the low gap GL. Information specifying the printing mode is included, for example, in the printing job. Therefore, the mode determination unit 71a receives a printing job sent from the external device 200 and determines the printing mode based on the information included in this printing job.

It should be noted that there may be three or more printing modes depending on the distance between the nozzle 21 and the ejection medium. One or more types of printing modes may be included in one print job. For example, different printing modes may be set for different print areas in one print job. In this case, the mode determination unit 71a determines which printing mode should be used for each print area. The information specifying the printing mode is not limited to the form included in the print job. For example, when a print job is executed, the user may input information specifying the printing mode from the external device 200, etc., and the mode determination unit 71a may determine the printing mode to be used when executing this print job based on this information input via the network interface 70.

The ejection signal generating unit 71b executes an ejection signal generating process in which the waveform generating circuit 76 generates an ejection drive signal waveform whose amplitude increases as the gap increases based on the print mode determined by the mode determining unit 71a. In other words, the waveform generating circuit 76 generates an ejection drive signal waveform (voltage waveform) whose amplitude increases when the print mode is the high gap print mode compared to when the print mode is the low gap print mode.

Based on the print mode determined by the mode determination unit 71a, the non-ejection signal generation unit 71c executes a non-ejection signal generation process, which causes the waveform generation circuit 76 to generate a waveform as a non-ejection drive signal, in which the timing at which the actuator 60 applies pressure to the ink in the pressure chamber 28 differs from that of other print modes. The specific manner in which the non-ejection signal generation unit 71c generates the waveform will be described later.

[Liquid ejection method]
Next, the operation of the image recording apparatus 1, that is, the liquid ejection method executed by the liquid ejection apparatus 10 included in the image recording apparatus 1, will be described with reference to the flowchart of FIG.

As shown in FIG. 4, the control device 71 determines whether a print job has been received (step S1). When a print job is received (S1: YES), the control device 71 determines the print mode in which to execute the print job (step S2). In this embodiment, the control device 71 determines whether the print mode is the high gap print mode or the low gap print mode.

Here, if the control device 71 determines in step S2 that the printing mode is the high gap printing mode (S2: YES), the control device 71 causes the waveform generation circuit 76 to generate a waveform with a large amplitude (applied voltage VH) as the ejection drive signal (step S3), and also causes the waveform generation circuit 76 to generate a non-ejection drive signal for the high gap (step S4). On the other hand, if the control device 71 determines in step S2 that the printing mode is the low gap printing mode (S2: NO), the control device 71 causes the waveform generation circuit 76 to generate a waveform with a small amplitude (applied voltage VL; VL < VH) as the ejection drive signal (step S5), and also causes the waveform generation circuit 76 to generate a non-ejection drive signal for the high gap (step S6).

In this way, the larger the gap in the print mode, the greater the amplitude (potential difference) of the waveform generated by the waveform generation circuit 76 as the ejection drive signal (steps S3 and S4). The signal amplitude determined in steps S3 and S4 according to the print mode is also applied to the amplitude of the waveform of the non-ejection drive signal generated in steps S5 and S6. In contrast, the non-ejection drive signal generated in steps S5 and S6 has a different timing at which the actuator 60 of the ejection head 20 applies pressure to the ink (for example, the on/off timing of the pulse wave) depending on the print mode. This point will be described later with reference to FIG. 5.

As described above, when the ejection drive signal and non-ejection drive signal corresponding to the printing mode are generated by the waveform generation circuit 76 (steps S3 to S6), the first one pass of printing is executed (step S7). That is, in the high gap printing mode, the control device 71 drives the actuator 60 with the ejection drive signal having the amplitude of the voltage VH generated in step S3, ink is ejected from the nozzle 21, and an image for one pass is formed on the ejection medium. On the other hand, in the low gap printing mode, the control device 71 drives the actuator 60 with the ejection drive signal having the amplitude of the voltage VL generated in step S5, ink is ejected from the nozzle 21, and an image for one pass is formed on the ejection medium. This allows ink to be ejected at a speed corresponding to the gap, and ink to land at an appropriate position on the ejection medium.

Next, it is determined whether printing for one pass is complete (step S8). If it is determined that printing is not complete (S8: NO), the process of step S8 is repeated and the process waits until printing for one pass is complete. If it is determined that printing for one pass is complete (S8: YES), non-ejection drive is started (step S9). In this non-ejection drive, in the case of high gap printing mode, the control device 71 drives the actuator 60 with the non-ejection drive signal for high gap generated in step S4, and vibrates the meniscus without ejecting ink from the nozzle 21. On the other hand, in the case of low gap printing mode, the control device 71 drives the actuator 60 with the non-ejection drive signal for low gap generated in step S6, and vibrates the meniscus without ejecting ink from the nozzle 21.

In parallel with the execution of the non-ejection drive (step S9), the control device 71 determines whether printing of all passes included in the print job has been completed (step S10). If it is determined that printing has been completed (S10: YES), the control device 71 ends the non-ejection drive started in step S9 and ends the printing process in FIG. 4. Specifically, the carriage 16 is moved to a predetermined standby position, and the ejection surface 40a of the ejection head 20 is capped to prevent the meniscus from drying. At the same time, the non-ejection drive is also ended.

If it is determined that printing of all passes has not been completed (S10: NO), it is determined whether printing of the next pass has started (step S11), and if it has started (S11: YES), the non-ejection drive is ended (step S12) and the process is executed again from step S7. Note that the order of steps S1 to S12 is not limited to that shown in FIG. 4; for example, the generation of the non-ejection drive signal in steps S4 and S6 only needs to be completed before step S9, which starts the non-ejection drive, and therefore may be performed while printing one pass is being performed using the ejection drive signal (steps S7 and S8).

[Non-ejection drive signal]
The non-ejection drive signal that the non-ejection signal generating section 71c of the control device 71 causes the waveform generating circuit 76 to generate in steps S4 and S6 described above will be described with reference to FIG.

Figure 5 shows waveforms representing five types of pulse signals PS1 to PS5. Of these, pulse signal PS1 at the top of the page is an example of a non-ejection drive signal generated by the waveform generation circuit 76 in low gap printing mode. Pulse signal PS2 is a comparative example, in which only the amplitude of pulse signal PS1 is increased. Pulse signals PS3 to PS5 are examples of non-ejection drive signals generated by the waveform generation circuit 76 in high gap printing mode. Hereinafter, pulse signal PS1 will also be referred to as low gap non-ejection signal PS1, and pulse signals PS3 to PS5 will also be referred to as high gap non-ejection signals PS3 to PS5. Each of signals PS1 to PS5 will be described in detail.

The low gap non-ejection signal PS1 has multiple pulse waves PW1 during the ejection period T0, which is the period during which the ejection head 20 ejects ink from the nozzle 21 once. In the example of FIG. 5, four pulse waves PW1 are included during the ejection period T0. Therefore, the period T1 of the pulse wave PW1 is one-fourth of the ejection period T0. The pulse wave PW1 also has a pulse P1 that is defined by the amplitude of the voltage VL relative to the reference potential Vref and the pulse width of time T11 (T11<T1). Such a pulse P1 displaces the actuator 60 inwardly into the pressure chamber 28, applying pressure to the ink.

As described above, the amplitude of the waveform of the low gap non-ejection signal PS1 is the same as the amplitude (voltage VL) applied to the ejection drive signal in the low gap printing mode in step S5 of FIG. 4. In other words, in the low gap printing mode, the ejection drive signal and the non-ejection drive signal have the same waveform amplitude (voltage VL). Similarly, in the high gap printing mode, the ejection drive signal and the non-ejection drive signal (high gap non-ejection signals PS3 to PS5) have the same waveform amplitude (voltage VH). However, the high gap non-ejection signals PS3 to PS5 have different pulse wave on/off timing compared to the low gap non-ejection signal PS1.

To explain the relationship between the low gap non-ejection signal PS1 and the high gap non-ejection signals PS3 to PS5, the pulse signal PS2 is shown in Figure 5 as a comparative example. The pulse signal PS2 has a waveform in which only the amplitude of the low gap non-ejection signal PS1 is modified from the voltage VL corresponding to the low gap printing mode to the voltage VH corresponding to the high gap printing mode. Therefore, this pulse signal PS2 has four pulse waves PW2 during the ejection period T0, the period T2 of these pulse waves PW2 is the same as the period T1, and the pulse width T21 of the pulse P2 of the pulse wave PW2 is also the same as the above pulse width T11.

When ejecting ink to form an image, the larger the gap between the nozzle 21 and the receiving medium, the larger the amplitude of the waveform of the ejection drive signal (the voltage applied) must be in order to ensure that the ink lands properly on the receiving medium. Therefore, in this embodiment, an ejection drive signal is generated in high gap printing mode with an amplitude of a voltage VH that is larger than that in low gap printing mode (steps S3 and S5 in FIG. 4).

However, if a non-ejection drive signal with a large amplitude is applied to the actuator 60 even during non-ejection drive, the pressure applied to the ink may become too large, causing ink to unintentionally leak out of the nozzle 21. In other words, if the pulse signal PS2 in FIG. 5 is used as the non-ejection drive signal, the meniscus cannot be vibrated for non-ejection, and ink may be ejected.

The liquid ejection device 10 according to this embodiment therefore generates a waveform in which the timing at which the actuator 60 applies pressure to the ink is different from that in the low gap printing mode, thereby preventing ink leakage when the meniscus is vibrated for non-ejection in the high gap printing mode. The high gap non-ejection signals PS3 to PS5 shown in FIG. 5 are examples of non-ejection drive signals in the high gap printing mode, in which the timing is different from that in the low gap printing mode.

The high gap non-ejection signal PS3 has a waveform in which the pulse width T21 of the pulse P2 in the pulse signal PS2 of the comparative example is shortened. That is, the high gap non-ejection signal PS3 has a waveform with a larger amplitude than the low gap non-ejection signal PS1, while having a smaller duty ratio, which is the ratio of the pulse width to the period of the pulse wave. Specifically, the high gap non-ejection signal PS3 has four pulse waves PW3 during the ejection period T0, and the period T3 of this pulse wave PW3 is the same as the period T1 of the low gap non-ejection signal PS1. The pulse wave PW3 also has a pulse P3 that is defined by the amplitude of the voltage VH and the pulse width of the time T31. And this pulse width T31 is shorter by ΔT31 than the pulse width T11 of the low gap non-ejection signal PS1.

In this way, the high gap non-ejection signal PS3 has a larger amplitude than the low gap non-ejection signal PS1, but the pulse width is shorter and the duty ratio of the pulse wave is smaller. This makes it possible to prevent the pressure applied to the ink during non-ejection drive from becoming excessive, and to prevent ink ejection when the meniscus is vibrated for non-ejection.

The high gap non-ejection signal PS4 has a waveform in which some of the pulse waves PW2 in the pulse signal PS2 of the comparative example have been thinned out. In other words, the high gap non-ejection signal PS4 has a waveform in which the amplitude is larger than that of the low gap non-ejection signal PS1, while the number of pulse waves included in the ejection period T0 is small. Specifically, the high gap non-ejection signal PS4 has two pulse waves PW4 during the ejection period T0, and therefore the period T4 of this pulse wave PW4 is longer than the period T1 of the low gap non-ejection signal PS1, being twice the period T1. In addition, the pulse wave P4 has a pulse P4 that is defined by the amplitude of the voltage VH and the pulse width of the time T41. Of these, the pulse width T41 is the same as the pulse width T11 of the pulse P1 of the low gap non-ejection signal PS1.

In this way, the high gap non-ejection signal PS4 has a larger amplitude than the low gap non-ejection signal PS1, while the number of pulses during the ejection period T0 is reduced. This makes it possible to prevent the pressure applied to the ink during non-ejection driving from becoming excessive, and to prevent ink ejection when the meniscus is vibrated for non-ejection.

The high gap non-ejection signal PS5 has a waveform in which the interval between two consecutive pulses P2 is changed according to a predetermined rule, compared to the pulse signal PS2 of the comparative example. A specific explanation will be given. The interval from the end of the voltage application of the previous pulse wave PW5 (i.e., after the previous pulse P5 switches from on to off) to the start of the voltage application of the next pulse wave PW5 (i.e., the next pulse P5 turns on) is T52. Note that this interval T52 is expressed as T52 = T5 - T51, where T5 is the period T5 of the pulse wave PW5 of the high gap non-ejection signal PS5 and the pulse width T51 of the pulse P5 of the pulse wave PW5. Also, AL is the acoustic length corresponding to the portion of the individual flow path 64 of the ejection head 20 from the pressure chamber 28 to the nozzle 21. At this time, the high gap non-ejection signal PS5 has a waveform that is larger in amplitude than the low gap non-ejection signal PS1, while the difference ΔT52 between the interval T52 and the acoustic length AL is larger than in the case of the low gap non-ejection signal PS1.

In this way, the high gap non-ejection signal PS5 has a waveform in which the difference ΔT52 between the interval T52 between two successive pulses P5 and the acoustic length AL is larger. This makes it possible to prevent the pressure applied to the ink during non-ejection drive from becoming excessive, and to prevent ink ejection when the meniscus is vibrated for non-ejection. Note that in the example of Figure 5, when increasing the difference ΔT52, this is achieved by changing the waveform in the direction of making the interval T52 larger relative to the acoustic length AL.

The amount of deformation of the waveform of each of the high gap non-ejection signals PS3 to PS5 from the waveform of the low gap non-ejection signal PS1 can be set arbitrarily. However, the greater the amplitude (voltage VH) of the waveform of the ejection drive signal in the high gap printing mode, the smaller the ratio of the increase in deformation of the waveform of the high gap non-ejection signals PS3 to PS5 to the increase in amplitude is preferably set.

Specifically, for the high gap non-ejection signal PS3, the greater the amplitude (voltage VH) of the waveform of the ejection drive signal in the high gap printing mode, the smaller the ratio of the decrease in the duty ratio of the high gap non-ejection signal PS3 to the increase in amplitude. For the high gap non-ejection signal PS4, similarly, the greater the amplitude (voltage VH), the smaller the ratio of the decrease in the wave number of the high gap non-ejection signal PS4 to the increase in amplitude. For the high gap non-ejection signal PS5, similarly, the greater the amplitude (voltage VH), the smaller the ratio of the increase in the difference of the high gap non-ejection signal PS5 to the increase in amplitude.

This prevents ink from being ejected during non-ejection driving while also preventing the non-ejection vibrations applied to the meniscus from becoming too small.

As an example of reducing the ratio of the change in each parameter (i.e., the decrease in duty ratio, the decrease in wave number, and the increase in difference) to the increase in amplitude described above, a logarithm can be applied more specifically. For example, when the change in a parameter is Y, Y can be defined as the logarithm of a number greater than 1, with base a, and the increase in amplitude (voltage VH) as the antilogarithm X.

(Embodiment 2)
The ease with which ink comes out of the nozzles 21 during non-ejection drive varies depending on the viscosity of the ink, and one of the factors that determine the viscosity of the ink is the temperature of the ink. Therefore, the image recording device 1A according to the second embodiment is configured to correct the waveform of the high gap non-ejection signal in the high gap print mode depending on the temperature of the ink. Such an image recording device 1A will be described below.

The image recording device 1A shown in FIG. 6 differs from the image recording device 1 shown in FIG. 3 in that it includes a temperature sensor 75 and that the control device 71 includes a temperature acquisition unit 71d and a non-ejection signal correction unit 71e, but the rest of the configuration is substantially the same. In this embodiment, the control device 71 and temperature sensor 75 are provided in the liquid ejection device 10. Therefore, the differences between the image recording devices 1 and 1A correspond to the differences between the liquid ejection devices 10 that they each include.

The temperature sensor 75 is provided, for example, on the carriage 16, and moves in the main scanning direction together with the ejection head 20 when the ejection head 20 moves in the main scanning direction. The temperature sensor 75 detects the ambient temperature near the carriage 16 as the ambient temperature of the ejection head 20.

The temperature acquisition unit 71d executes a temperature acquisition process to acquire the temperature around the ejection head 20. Since the image recording device 1 of this embodiment is equipped with a temperature sensor 75 mounted on the carriage 16, the temperature acquisition unit 71d acquires the temperature detected by this temperature sensor 75 as the temperature around the ejection head 20. Note that the acquisition of temperature by the temperature acquisition unit 71d is not limited to from the temperature sensor 75 equipped in the image recording device 1, and the temperature around the ejection head 20 may be acquired based on the temperature detected by an external temperature sensor. Alternatively, the temperature around the ejection head 20 may be predicted based on the operating state of the ejection head 20 (for example, the continuous printing time, in other words the continuous driving time of the actuator 60) without relying on a temperature sensor.

The non-ejection signal correction unit 71e performs a non-ejection signal correction process in which, in the high gap printing mode, the waveform of the non-ejection drive signal generated by the non-ejection signal generation unit 71c is corrected to a different waveform depending on the temperature acquired by the temperature acquisition unit 71d.

Such an image recording device 1A operates according to the flow of each process as shown in the flowchart of FIG. 7. That is, the control device 71 provided in the image recording device 1A executes the operations of steps S1 to S12 described in the first embodiment with reference to FIG. 4. However, among these, between steps S4 and S7, correction of the waveform of the non-ejection drive signal according to temperature is executed (steps S20, S21).

Specifically, when the control device 71 determines that the printing mode is the high gap printing mode (step S2: YES), it generates an ejection drive signal with a large amplitude (step S3) and generates a non-ejection drive signal for the high gap (high gap non-ejection signal) (step S4). Next, the temperature acquisition unit 71d acquires the temperature around the ejection head 20 from the temperature detected by the temperature sensor 75 (step S20). Then, the non-ejection signal correction unit 71e corrects the high gap non-ejection signal generated in step S4 based on this temperature (step S21). Thereafter, the operations from step S7 onwards described in FIG. 4 are executed.

Here, in correcting the high gap non-ejection signal in step S21, the same idea as in generating the high gap non-ejection signal in step S4 can be applied. In that case, the increase in amplitude of the waveform of the ejection drive signal can be replaced with a high temperature.

Specifically, the waveform of the high gap non-ejection signal is corrected so that the higher the acquired temperature, the smaller the duty ratio, which is the ratio of the pulse width to the pulse wave period. Alternatively, the waveform of the high gap non-ejection signal is corrected so that the higher the acquired temperature, the smaller the number of pulse waves included in the ejection period. Alternatively, the waveform of the high gap non-ejection signal is corrected so that the higher the acquired temperature, the larger the difference between the interval between two successive pulses and the acoustic length. In other words, the waveform of the high gap non-ejection signal is corrected to a waveform different from the high gap non-ejection signal before correction, depending on the acquired temperature.

As a result, even if the temperature around the ejection head 20 rises and the ink becomes less viscous and more fluid, the pressure applied by the actuator 60 to the ink in the pressure chamber 28 can be suppressed, preventing the ink from being unintentionally ejected during non-ejection driving.

(Embodiment 3)
Incidentally, the liquid ejection device 10 according to the above-mentioned first and second embodiments prevents ink ejection during non-ejection driving in the high gap printing mode by changing the timing at which the actuator 60 applies pressure to the ink in the pressure chamber 28. In contrast to this, ink ejection during non-ejection driving in the high gap printing mode may be prevented by adjusting the amplitude of the non-ejection driving signal (high gap non-ejection signal) applied to the actuator 60.

In this case, the configurations of the liquid ejection device and image recording device shown in Figures 1 to 3 can be applied, and the operation of the image recording device is explained by the flowchart shown in Figure 4. However, since there are some differences in the configuration and operation of the liquid ejection device 10 according to the third embodiment from the explanation given with reference to Figures 1 to 4, this point will be mainly explained below.

The control device 71 of the liquid ejection device 10 according to the third embodiment has a mode determination unit 71a, an ejection signal generation unit 71b, and a non-ejection signal generation unit 71c, as in the first embodiment (see FIG. 3). Of these, the mode determination unit 71a determines whether the printing mode is low gap printing mode or high gap printing mode (see step S2 in FIG. 4). In addition, the ejection signal generation unit 71b causes the waveform generation circuit 76 to generate an ejection drive signal with a waveform having a larger amplitude in the high gap printing mode than in the low gap printing mode.

On the other hand, the non-ejection signal generating unit 71c differs from that in embodiment 1. Specifically, the non-ejection signal generating unit 71c causes the waveform generating circuit 76 to generate a waveform as the non-ejection drive signal that has a larger amplitude in the high gap printing mode than in the low gap printing mode, and also causes the waveform generating circuit 76 to generate a waveform as the non-ejection drive signal in which ΔV1 is larger than ΔV2 when the amplitude difference between the ejection drive signal in the high gap printing mode and the low gap printing mode is ΔV1 and the amplitude difference between the non-ejection drive signal in the high gap printing mode and the low gap printing mode is ΔV2.

That is, in high gap printing mode, the signal amplitudes of both the ejection drive signal and the non-ejection drive signal are made larger than in low gap printing mode. However, regarding the difference in amplitude between high gap printing mode and low gap printing mode, the non-ejection signal ΔV2 has a smaller waveform than the ejection drive signal difference ΔV1. This makes it possible to suppress the pressure that the actuator 60 applies to the ink in the pressure chamber 28, and to prevent ink from being unintentionally ejected during non-ejection driving.

The present invention can be applied to a liquid ejection device, a liquid ejection method, and a liquid ejection program.

REFERENCE SIGNS LIST 1 Image recording device 10 Liquid ejection device 20 Ejection head 21 Nozzle 28 Pressure chamber 60 Actuator 71 Control device 71a Mode determination unit 71b Ejection signal generation unit 71c Non-ejection signal generation unit 71d Temperature acquisition unit 71e Non-ejection signal correction unit 75 Temperature sensor 76 Waveform generation circuit

Claims (13)

an ejection head including a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber;
a waveform generating circuit for generating a waveform of a drive signal for driving the actuator;
A control device,
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
The control device includes:
a mode determination process for determining which of a plurality of printing modes is selected according to a gap between the nozzles and the ejection receiving medium;
an ejection signal generation process for causing the waveform generation circuit to generate, as the ejection drive signal, a waveform having a larger amplitude as the gap is larger in the print mode based on the determined print mode;
a non-ejection signal generation process for causing the waveform generation circuit to generate, as the non-ejection drive signal, a waveform in which the timing at which the actuator applies pressure to the liquid is different from that in other printing modes, based on the determined printing mode;
A liquid ejection device. The liquid ejection device according to claim 1, wherein the control device causes the waveform generation circuit to generate a pulse wave having a smaller duty ratio, which is the ratio of the pulse width to the period, as the non-ejection drive signal in the non-ejection signal generation process, the larger the amplitude of the waveform of the ejection drive signal generated in the ejection signal generation process. The liquid ejection device according to claim 2, wherein the ratio of the decrease in the duty ratio of the non-ejection drive signal to the increase in the amplitude is decreased as the amplitude of the waveform of the ejection drive signal increases. The liquid ejection device according to any one of claims 1 to 3, wherein the control device, in the non-ejection signal generation process, causes the waveform generation circuit to generate a waveform as the non-ejection drive signal having a smaller number of waves included in one ejection cycle, which is a cycle for ejecting one liquid droplet, as the amplitude of the waveform of the ejection drive signal generated in the ejection signal generation process is larger. The liquid ejection device according to claim 4, wherein the ratio of the number of decreases in the wave number in the non-ejection drive signal to the amount of increase in the amplitude is decreased as the amplitude of the waveform of the ejection drive signal increases. The liquid ejection device according to any one of claims 1 to 5, wherein the control device causes the waveform generation circuit to generate, as the non-ejection drive signal, a waveform in which the difference between the acoustic length and the interval from the end of voltage application of the previous pulse wave to the start of voltage application of the next pulse wave is greater the greater the amplitude of the waveform of the ejection drive signal generated in the ejection signal generation process. The liquid ejection device according to claim 6, wherein the ratio of the increase in the difference in the non-ejection drive signal to the increase in the amplitude is decreased as the amplitude of the waveform of the ejection drive signal increases. the printing modes include a low gap printing mode in which the distance between the nozzles and the ejection receiving medium is a low gap , and a high gap printing mode in which the distance is a high gap that is larger than the low gap;
The control device includes:
A temperature acquisition process for acquiring a temperature around the ejection head;
a non-ejection signal correction process is executed in the high gap printing mode to correct the waveform of the non-ejection drive signal generated in the non-ejection signal generation process to a different waveform in accordance with the acquired temperature.
The liquid ejection device according to any one of claims 1 to 7. an ejection head including a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber;
a waveform generating circuit for generating a waveform of a drive signal for driving the actuator;
A control device,
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
The control device includes:
a mode determination process for determining which printing mode is the current printing mode, either a low gap printing mode in which the distance between the nozzle and the ejection medium is a low gap, or a high gap printing mode in which the distance is a high gap that is larger than the low gap;
an ejection signal generation process for causing the waveform generation circuit to generate a waveform having a larger amplitude as the ejection drive signal in the high gap printing mode than in the low gap printing mode;
a non-ejection signal generation process for causing the waveform generation circuit to generate, as the non-ejection drive signal, a waveform having a larger amplitude in the high gap printing mode than in the low gap printing mode, and causing the waveform generation circuit to generate, as the non-ejection drive signal, a waveform in which ΔV1 is larger than ΔV2, when an amplitude difference between the high gap printing mode and the low gap printing mode is ΔV1 and an amplitude difference between the non-ejection drive signal is ΔV2;
A liquid ejection device. A liquid ejection method using a liquid ejection device including an ejection head having a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber, a waveform generating circuit that generates a waveform of a drive signal for driving the actuator, and a control device, comprising:
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
a mode determination step of determining which of a plurality of printing modes is selected according to a gap between the nozzles and the ejection receiving medium;
an ejection signal generating step of causing the waveform generating circuit to generate, as the ejection drive signal, a waveform having a larger amplitude as the gap increases in the printing mode determined based on the print mode;
a non-ejection signal generating step of causing the waveform generating circuit to generate, as the non-ejection drive signal, a waveform having a timing at which the actuator applies pressure to the liquid that is different from that in other printing modes based on the determined printing mode;
Liquid dispensing method. A liquid ejection program to be executed by a computer in a liquid ejection device including an ejection head having a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber, a waveform generating circuit that generates a waveform of a drive signal for driving the actuator, and a control device, the program comprising:
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
The computer,
a mode determination means for determining which of a plurality of printing modes is selected according to a gap between the nozzles and the ejection receiving medium;
an ejection signal generating means for causing the waveform generating circuit to generate, as the ejection drive signal, a waveform having a larger amplitude as the gap in the print mode is larger, based on the determined print mode;
based on the determined print mode, causes the waveform generation circuit to generate a waveform having a different timing for applying pressure to the liquid by the actuator from that of other print modes;
Liquid dispensing program. A liquid ejection method using a liquid ejection device including an ejection head having a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber, a waveform generating circuit that generates a waveform of a drive signal for driving the actuator, and a control device, comprising:
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
a mode determination step of determining which printing mode is the current printing mode, either a low gap printing mode in which the distance between the nozzle and the ejection medium is a low gap, or a high gap printing mode in which the distance is a high gap that is larger than the low gap;
an ejection signal generating step of causing the waveform generating circuit to generate, as the ejection drive signal, a waveform having a larger amplitude in the high gap printing mode than in the low gap printing mode;
a non-ejection signal generating step of causing the waveform generating circuit to generate, as the non-ejection drive signal, a waveform having a larger amplitude in the high gap printing mode than in the low gap printing mode, and causing the waveform generating circuit to generate, as the non-ejection drive signal, a waveform in which ΔV1 is larger than ΔV2, when an amplitude difference between the high gap printing mode and the low gap printing mode is ΔV1 and an amplitude difference between the non-ejection drive signal is ΔV2.
Liquid dispensing method. A liquid ejection program to be executed by a computer in a liquid ejection device including an ejection head having a nozzle, a pressure chamber communicating with the nozzle, and an actuator that applies pressure to liquid in the pressure chamber, a waveform generating circuit that generates a waveform of a drive signal for driving the actuator, and a control device, the program comprising:
the drive signals include an ejection drive signal that applies pressure to the liquid in the pressure chamber so as to eject droplets from the nozzle, and a non-ejection drive signal that applies pressure to the liquid in the pressure chamber so as to vibrate a meniscus of the nozzle without ejecting the droplets from the nozzle,
The computer,
a mode determination means for determining which printing mode is the current printing mode, either a low gap printing mode in which the distance between the nozzle and the ejection medium is a low gap, or a high gap printing mode in which the distance is a high gap that is larger than the low gap;
an ejection signal generating means for causing the waveform generating circuit to generate a waveform having a larger amplitude as the ejection drive signal in the high gap printing mode than in the low gap printing mode;
a non-ejection signal generating means for causing the waveform generating circuit to generate, as the non-ejection drive signal, a waveform having a larger amplitude in the high gap printing mode than in the low gap printing mode, and for causing the waveform generating circuit to generate, as the non-ejection drive signal, a waveform in which ΔV1 is larger than ΔV2, when an amplitude difference between the ejection drive signal in the high gap printing mode and the low gap printing mode is ΔV1 and an amplitude difference between the non-ejection drive signal in the high gap printing mode and the low gap printing mode is ΔV2;
Liquid dispensing program.

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