Liquid discharge apparatus and control method of liquid discharge apparatus

Abstract

The present application relates to a liquid ejecting apparatus and a control method of a liquid ejecting apparatus. The liquid ejecting apparatus includes a plurality of ejecting portions each including a nozzle, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts a pressure variation to a liquid in the pressure chamber in accordance with a drive signal including a first ejection pulse including a first ejection element whose potential is changed from a first potential to a second potential to drive the piezoelectric element in a manner that a volume of the pressure chamber is contracted to eject the liquid from the nozzle, the piezoelectric element having a displacement characteristic in which, in a case where a potential changed from the first potential to the second potential is applied, a unit displacement amount is smaller than in a case where a potential changed from the first potential to a potential at a center of the first potential and the second potential is applied, and an absolute value of a change amount of the potential of the first ejection element per 1 μsec is 0.35 times or less of a first potential difference.

Description

Technical Field

[0001] This invention relates to a liquid ejection device and a control method for the liquid ejection device. Background Technology

[0002] Liquid ejection devices for printing images are known, which use piezoelectric elements to eject liquids such as ink from multiple nozzles. For example, a liquid ejection device may have a liquid ejection head comprising multiple ejection sections. Each ejection section includes a nozzle for ejecting ink, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variations to the ink within the pressure chamber according to a drive signal. For example, Patent Document 1 discloses a liquid ejection device in which a piezoelectric element is displaced according to an applied voltage, and liquid is ejected from a nozzle by the displacement of the piezoelectric element.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2012-171266

[0004] Furthermore, the voltage supplied to the piezoelectric element is set to the voltage required to eject a desired amount of liquid from the nozzle. Depending on the set voltage, if the voltage supplied to the piezoelectric element fluctuates due to circuitry or other factors, the ejection characteristics, such as the amount and speed of liquid ejected, may change, resulting in a decrease in print quality. Therefore, in a liquid ejection device, it is desirable to suppress changes in the liquid ejection characteristics caused by fluctuations in the voltage supplied to the piezoelectric element. Summary of the Invention

[0005] To address the above-mentioned issues, the liquid ejection device of the present invention comprises: a liquid ejection head having a plurality of ejection portions, each of which includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit that generates the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element to eject liquid from the nozzle by causing the volume of the pressure chamber to contract. The piezoelectric element has the following displacement characteristics: when a potential changing from the first potential to the second potential is applied, compared to when a potential changing from the first potential to the center of the first potential and the second potential is applied, the displacement of the piezoelectric element, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount, and the absolute value of the change in potential of the first ejection element per 1 μs is less than 0.35 times the absolute value of the potential difference between the first potential and the second potential, i.e., the first potential difference.

[0006] Additionally, other liquid ejection devices according to the present invention include: a liquid ejection head having a plurality of ejection portions, each of which includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit that generates the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element such that the volume of the pressure chamber is contracted and liquid is ejected from the nozzle, the potential difference from the first potential to the second potential is set such that the deviation of the amount of liquid ejected when the potential difference deviates is within a predetermined allowable amount, and the amount of potential change of the first ejection element per unit time is set such that the amount of liquid ejected is a desired amount.

[0007] Furthermore, the control method for the liquid ejection device according to the present invention is as follows: the liquid ejection device comprises: a liquid ejection head having a plurality of ejection portions, each of the plurality of ejection portions including a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element for imparting pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit for generating the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element to eject liquid from the nozzle by causing the volume of the pressure chamber to contract. When a potential changing from the first potential to the second potential is applied, compared to when a potential changing from the first potential to the center of the first potential and the second potential is applied, the displacement of the piezoelectric element, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount. The absolute value of the change in potential of the first ejection element per 1 μs is set to be less than or equal to 0.35 times the absolute value of the potential difference between the first potential and the second potential, i.e., the first potential difference.

[0008] In addition, another control method for a liquid ejection device according to the present invention is as follows: the liquid ejection device includes: a liquid ejection head having a plurality of ejection portions, each of the plurality of ejection portions including a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit that generates the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element such that the volume of the pressure chamber is contracted and liquid is ejected from the nozzle, the potential difference from the first potential to the second potential is set such that the deviation of the amount of liquid ejected when the potential difference deviates is within a predetermined allowable amount, and the amount of potential change of the first ejection element per unit time is set such that the amount of liquid ejected is a desired amount. Attached Figure Description

[0009] Figure 1 This is a block diagram illustrating an example of the structure of a liquid ejection device according to an embodiment of the present invention.

[0010] Figure 2 It is a schematic diagram showing the structure of a liquid ejection device.

[0011] Figure 3 This is an explanatory diagram used to illustrate the general structure of the header unit.

[0012] Figure 4 This is an explanatory diagram used to illustrate the relationship between the driving voltage of a piezoelectric element and the amount of ink ejected.

[0013] Figure 5 This is a block diagram illustrating an example of the structure of a head unit.

[0014] Figure 6 This is a timing diagram illustrating an example of the operation of a liquid ejection device within a unit of time.

[0015] Figure 7 This is a timing diagram illustrating an example of the operation of the liquid ejection device involved in the first variation.

[0016] Explanation of reference numerals in the attached figures

[0017] 1…Liquid ejection device, 2…Control unit, 3…Head unit, 4…Drive signal generation unit, 5…Storage unit, 7…Transportation unit, 8…Maintenance unit, 30…Recording head, 31…Switching circuit, COM…Drive signal, CV…Pressure chamber, D…Ejection section, N…Nozzle, PZ…Piezoelectric element. Detailed Implementation

[0018] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions and proportions of the various parts are appropriately made different from the actual dimensions. Furthermore, the embodiments described below are preferred examples of the present invention, and therefore various technically preferred limitations are included. However, unless otherwise specified in the following description, the scope of the present invention is not limited to these embodiments.

[0019] [1. Implementation Method]

[0020] First, refer to Figure 1 The structure of the liquid ejection device 1 according to this embodiment will be described. In this embodiment, as an example, the liquid ejection device 1 is envisioned as an inkjet printer that ejects ink to a medium to form an image. Furthermore, in this embodiment, ink refers to an example of "liquid". Additionally, in this embodiment, the medium is envisioned as something described later. Figure 2 The recording paper shown is PP.

[0021] Figure 1 This is a block diagram illustrating an example of the structure of the liquid ejection device 1 according to an embodiment of the present invention.

[0022] In the liquid ejection device 1, for example, printing data IMG representing an image to be formed by the liquid ejection device 1 is supplied from a host computer or digital camera. The liquid ejection device 1 performs printing processing to form the image represented by the printing data IMG supplied from the host computer onto a medium.

[0023] The liquid ejection device 1 includes: a control unit 2 for controlling various parts of the liquid ejection device 1; a head unit 3 for providing an ejection section D for ejecting ink; and a drive signal generation unit 4 for generating multiple drive signals COM for driving the ejection section D. Furthermore, the liquid ejection device 1 includes a storage unit 5 for storing various information such as printing data IMG and the control program of the liquid ejection device 1. Moreover, the liquid ejection device 1 includes: a transport unit 7 for changing the relative position of the recording paper PP with respect to the head unit 3; and a maintenance unit 8 for performing maintenance processing on the ejection section D provided on the head unit 3. The head unit 3 is an example of a "liquid ejection head," and the drive signal generation unit 4 is an example of a "drive signal generation unit."

[0024] Furthermore, in this embodiment, it is envisioned that the head unit 3 and the drive signal generation unit 4 correspond to each other. For example, the liquid ejection device 1 may have multiple head units 3 and multiple drive signal generation units 4 corresponding one-to-one with the multiple head units 3. Alternatively, the liquid ejection device 1 may have one head unit 3 and one drive signal generation unit 4 corresponding to the one head unit 3.

[0025] In this embodiment, it is envisioned that the liquid ejection device 1 has four head units 3 and four drive signal generation units 4 corresponding one-to-one with the four head units 3. However, for ease of explanation below, as Figure 1 As illustrated, sometimes the explanation will focus on one of the four head units 3 and one of the four drive signal generation units 4 that corresponds to one of the head units 3.

[0026] The control unit 2 is configured to include one or more CPUs (Central Processing Units). Alternatively, the control unit 2 may replace the CPU or, in addition to the CPU, include a programmable logic device such as an FPGA (Field-Programmable Gate Array). Furthermore, the control unit 2 operates according to the control program stored in the storage unit 5, generating signals such as the printed signal SI and the waveform specification signal dCOM for controlling the operation of various parts of the liquid ejection device 1.

[0027] Here, the waveform specification signal dCOM is a digital signal that specifies the waveform of the drive signal COM. Additionally, the drive signal COM is an analog signal used to drive the ejector section D. Furthermore, the printing signal SI is a digital signal used to specify the type of operation of the ejector section D. Specifically, the printing signal SI is a signal that specifies the type of operation of the ejector section D by specifying whether to supply each drive signal COM to the ejector section D.

[0028] The drive signal generation unit 4 includes, for example, a DAC (Digital Analog Converter) and generates multiple drive signals COM based on a waveform specification signal dCOM supplied from the control unit 2. For example, each of the multiple drive signals COM generated by the drive signal generation unit 4 includes a waveform specified by the waveform specification signal dCOM. The drive signal generation unit 4 outputs the multiple drive signals COM generated based on the waveform specification signal dCOM to the switching circuit 31 included in the head unit 3.

[0029] The storage unit 5 is configured to include one or both of the following: volatile memory such as RAM (Random Access Memory), non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory). Alternatively, the storage unit 5 may also be included in the control unit 2.

[0030] The head unit 3 has a recording head 30 and a switching circuit 31.

[0031] The recording head 30 has M ejection sections D. Furthermore, the value M is one or more natural numbers. Hereinafter, the m-th ejection section D among the M ejection sections D provided in the recording head 30 is sometimes referred to as ejection section D[m]. Here, the variable m is a natural number satisfying "1≤m≤M". Additionally, hereafter, when a structural element or signal of the liquid ejection device 1 corresponds to an ejection section D[m] among the M ejection sections D, the suffix [m] is sometimes added to the symbol used to represent that structural element or signal.

[0032] The switching circuit 31 switches whether to supply each drive signal COM to the ejector section D[m] based on the printing signal SI. Furthermore, as will be described below... Figure 5 As shown, the drive signal COM supplied to the ejector section D [m] is sometimes referred to as the individual drive signal Vin [m].

[0033] As described above, in this embodiment, the liquid ejection device 1 performs the printing process. During the printing process, the control unit 2 generates signals such as a printing signal SI based on the printing data IMG to control the head unit 3. Additionally, during the printing process, the control unit 2 generates signals such as a waveform specification signal dCOM to control the drive signal generation unit 4. Furthermore, during the printing process, the control unit 2 generates signals to control the transport unit 7. Thus, during the printing process, the control unit 2 controls the transport unit 7 in a manner that changes the relative position of the recording paper PP with respect to the head unit 3, and adjusts the presence or absence of ink ejection from the ejection section D[m], the amount of ink ejected, and the ink ejection timing. In this way, the control unit 2 controls each part of the liquid ejection device 1 to form an image corresponding to the printing data IMG on the recording paper PP.

[0034] In addition, the conveying unit 7 includes: a carriage conveying mechanism 72 for reciprocating the carriage 721; and a media conveying mechanism 71 for conveying recording paper PP. Regarding the carriage 721, [further details will be provided later]. Figure 2 This will be discussed later.

[0035] Furthermore, as described above, in this embodiment, the liquid ejection device 1 performs maintenance procedures. For example, the maintenance procedures include: rinsing to discharge ink from the ejection section D; wiping to remove foreign matter such as ink adhering to the nozzle N of the ejection section D using a wiper; and pumping to draw ink from the ejection section D using a tubular pump or the like. Regarding the nozzle N, in Figure 3 This will be discussed later.

[0036] The maintenance unit 8 includes: an ink discharge receiving section for receiving ink discharged from the ejector section D during rinsing; a wiper for wiping away foreign matter such as ink adhering to the nozzle N of the ejector section D; and a pump for suctioning ink, air bubbles, etc., from the ejector section D. The ink discharge receiving section, wiper, and pump are not shown in the figures.

[0037] Next, refer to Figure 2 The general overall structure of the liquid ejection device 1 will be described.

[0038] Figure 2 This is a schematic diagram illustrating the structure of the liquid ejection device 1. (For example...) Figure 2 As shown, in this embodiment, the liquid ejection device 1 is assumed to be a serial printer as an example.

[0039] like Figure 2 As shown, the liquid ejection device 1, in addition to having the ability to eject liquids in the form of liquids, also has the ability to eject liquids in the form of liquids. Figure 1 In addition to the elements described herein, it also includes a liquid container 14 for storing ink. The liquid container 14 can be, for example, a box that can be detached from the liquid dispensing device 1, a bag-shaped ink pouch formed of a flexible membrane, or an ink canister that can be refilled with ink. Furthermore, the type of ink stored in the liquid container 14 is not particularly limited, but can be arbitrary.

[0040] Under the control of the control unit 2, the media transport mechanism 71 transports the recording paper PP in the Y2 direction along the Y-axis. Hereinafter, the Y1 direction and the Y2 direction (opposite to the Y1 direction) will be collectively referred to as the direction along the Y-axis. Similarly, the X1 direction (intersecting the Y-axis) and the X2 direction (opposite to the X1 direction) will be collectively referred to as the direction along the X-axis. Furthermore, the Z1 direction (intersecting both the X-axis and Y-axis) and the Z2 direction (opposite to the Z-axis) will be collectively referred to as the direction along the Z-axis. In this embodiment, as an example, the X-axis, Y-axis, and Z-axis are assumed to be orthogonal to each other. However, the present invention is not limited to this configuration. The X-axis, Y-axis, and Z-axis may simply intersect each other. In this embodiment, the Z2 direction corresponds to the ink ejection direction from the ejection section D [m].

[0041] Under the control of the control unit 2, the carriage conveying mechanism 72 causes the head unit 3 to reciprocate in the X1 and X2 directions. Figure 2 As shown, the carriage conveying mechanism 72 has a generally box-shaped carriage 721 that houses the head unit 3, and an annular belt 722 to which the carriage 721 is fixed. Furthermore, the liquid container 14 can also be housed together with the head unit 3 in the carriage 721.

[0042] Next, refer to Figure 3 The general structure of head unit 3 is described below.

[0043] Figure 3 This is an explanatory diagram used to illustrate the general structure of head unit 3. Figure 3 The upper layer diagram is an exploded 3D view of the head unit 3. Figure 3 The lower layer of the diagram is a sectional view of line aa as shown in the exploded perspective. Section aa is parallel to the XZ plane and passes through the inlet 364, which will be described later.

[0044] like Figure 3 As shown, the head unit 3 includes a wiring board 20 housing an electronic component EC, a flow channel board 33, a pressure chamber board 34, a vibrating plate 35, M piezoelectric elements PZ, a housing 36, a sealing plate 37, a nozzle board 38, and a vibration absorber 39. The electronic component EC includes, for example, a switching circuit 31. For example, the recording head 30 is electrically connected to the switching circuit 31 via the wiring board 20. Figure 3 As shown in the exploded perspective view, the recording head 30 includes, for example, a flow channel substrate 33, a pressure chamber substrate 34, a vibrating plate 35, M piezoelectric elements PZ, a housing 36, a sealing plate 37, a nozzle substrate 38, and a vibration absorber 39.

[0045] Here, in the region located on the flow channel substrate 33 in the Z1 direction, a pressure chamber substrate 34, a vibrating plate 35, M piezoelectric elements PZ, a housing 36, and a sealing plate 37 are provided. On the other hand, in the region on the flow channel substrate 33 in the Z2 direction, a nozzle substrate 38 and a vibration absorber 39 are provided. In addition, a wiring substrate 20 is provided, for example, on the Z1 direction surface of the vibrating plate 35. The elements of the head unit 3 are generally long, plate-shaped parts in the Y-axis direction, which are joined together by adhesive, for example.

[0046] like Figure 3 As shown in the exploded perspective view, the nozzle substrate 38 is a plate-shaped component having a nozzle array Ln comprising M nozzles N arranged along the Y-axis. Each nozzle N is a through-hole for ink to pass through. Furthermore, the flow channel substrate 33, pressure chamber substrate 34, and nozzle substrate 38 are formed, for example, by processing a single-crystal silicon substrate using semiconductor manufacturing techniques such as etching. However, the materials and manufacturing methods of each element of the head unit 3 are arbitrary. The direction of the Y-axis can also be expressed as the direction in which the M nozzles N are arranged.

[0047] The flow channel substrate 33 is a plate-shaped component used to form the flow channels of ink. For example... Figure 3 As shown, the flow channel substrate 33 has an opening 332, M supply channels 334, and M connecting channels 336. The opening 332 is a continuous through-hole spanning the M nozzles N along the Y-axis when viewed from above along the Z-axis. That is, the opening 332 is an elongated through-hole extending along the Y-axis. The supply channels 334 and connecting channels 336 are through-holes formed independently for each nozzle N. Furthermore, as... Figure 3 As shown in the cross-sectional view, a relay channel 338 spanning M supply channels 334 is formed on the surface of the channel substrate 33 in the Z2 direction. The relay channel 338 is a channel that connects the opening 332 with the M supply channels 334.

[0048] The pressure chamber substrate 34 is a plate-shaped component having M pressure chambers CV corresponding to M nozzles N. Each pressure chamber CV is a space, referred to as a cavity, located between the flow channel substrate 33 and the vibrating plate 35, used to apply pressure to the ink filled within it. The M pressure chambers CV are divided by partitions WL of the pressure chamber substrate 34 and arranged in the direction along the Y-axis. Each pressure chamber CV is formed by holes opening on two surfaces of the pressure chamber substrate 34 and is elongated in the direction along the X-axis. The X2 end of each pressure chamber CV communicates with a corresponding supply flow channel 334 among the M supply flow channels 334. On the other hand, the X1 end of each pressure chamber CV communicates with a corresponding connecting flow channel 336 among the M connecting flow channels 336.

[0049] A vibrating plate 35 is disposed on a surface of the pressure chamber substrate 34 facing the opposite direction to the surface of the flow channel substrate 33. The vibrating plate 35 is a plate-shaped component that can be elastically deformed. Figure 3 As shown in the cross-sectional view, the vibrating plate 35 includes an insulating film 352 and an elastic film 351 stacked along the Z-axis. Viewed from the elastic film 351, the insulating film 352 is located in the opposite direction to the pressure chamber substrate 34. The elastic film 351 is formed, for example, of silicon oxide. The insulating film 352 is formed, for example, of zirconium oxide.

[0050] According to Figure 3 As understood, the flow channel substrate 33 and the vibrating plate 35 are spaced apart from each other on the inner side of each pressure chamber CV. The vibrating plate 35 forms part of the wall of the pressure chamber CV. The ink stored in the liquid storage chamber RS ​​(described later) is supplied and filled into the M pressure chambers CV in parallel from the relay flow channel 338 to the branches of each supply flow channel 334.

[0051] like Figure 3 As shown, on the surface of the vibrating plate 35 in the direction opposite to that of the pressure chamber substrate 34, M piezoelectric elements PZ are provided, each corresponding to one of the M nozzles N. For example, in any m from 1 to M, nozzle N [m] corresponds to piezoelectric element PZ [m]. The nozzle N corresponding to the piezoelectric element PZ refers to the nozzle N that communicates with the pressure chamber CV that partially or completely overlaps with the piezoelectric element PZ when viewed from above in the Z2 direction. Each piezoelectric element PZ is an actuator that deforms upon the supply of a drive signal COM, and is elongated in the direction along the X-axis. The M piezoelectric elements PZ are arranged in the direction along the Y-axis in a manner corresponding to the M pressure chambers CV. When the drive signal COM is supplied to the piezoelectric element PZ, and the vibrating plate 35 vibrates in conjunction with the deformation of the piezoelectric element PZ, the pressure in the pressure chamber CV changes. Due to the pressure change in the pressure chamber CV, the ink filled in the pressure chamber CV is ejected through the communication channel 336 and the nozzle N. That is, the piezoelectric element PZ is a driving element that causes the ink in the pressure chamber CV to be ejected from the nozzle N by vibrating the vibrating plate 35.

[0052] like Figure 3 As shown in the cross-sectional view, the piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric element Zm disposed between the upper electrode Zu and the lower electrode Zd. For example, a drive signal COM is supplied to the upper electrode Zu, and a drive signal COM (described later) is supplied to the lower electrode Zd. Figure 5 The constant potential bias voltage signal VBS is shown. Additionally, a pressure chamber CV is provided in the Z2 direction of the piezoelectric element PZ.

[0053] In addition, Figure 3In the cross-sectional view, to avoid complicating the drawings, the wiring connected to the upper electrode Zu and supplying the drive signal COM to the upper electrode Zu, and the wiring connected to the lower electrode Zd and supplying the bias voltage signal VBS to the lower electrode Zd, are omitted. Furthermore, in this embodiment, the case of supplying the drive signal COM to the upper electrode Zu and the bias voltage signal VBS to the lower electrode Zd is envisioned, but it is also possible to supply the bias voltage signal VBS to the upper electrode Zu and the drive signal COM to the lower electrode Zd.

[0054] In this embodiment, as an example, it is envisioned that the piezoelectric element PZ is displaced in the Z2 direction by changing the potential of the individual drive signal Vin [m] supplied to the ejector section D [m] from a low potential to a high potential. That is, in this embodiment, it is envisioned that when the potential of the individual drive signal Vin [m] supplied to the ejector section D [m] is high, the volume of the pressure chamber CV of the ejector section D [m] is smaller compared to the case of a low potential.

[0055] like Figure 3 As shown, the housing 36 is a structure manufactured, for example, by injection molding of resin material, and is fixed to the surface of the flow channel substrate 33 in the Z1 direction. Figure 3 As shown in the cross-sectional view, a receiving portion 362 and an inlet 364 are formed in the housing 36. The receiving portion 362 is a recessed portion with a shape corresponding to the opening 332 of the flow channel substrate 33. The inlet 364 is a through hole communicating with the receiving portion 362. The space formed by the opening 332 of the flow channel substrate 33 and the receiving portion 362 of the housing 36 functions as a liquid storage chamber RS, which stores ink supplied to the M pressure chambers CV. Ink supplied from the liquid container 14 and passing through the inlet 364 is stored in the liquid storage chamber RS.

[0056] The sealing plate 37 is a structure that strengthens the mechanical strength of the pressure chamber substrate 34 and the vibrating plate 35 while protecting the M piezoelectric elements PZ from the influence of external gas. The sealing plate 37 is fixed to the surface of the vibrating plate 35, for example, by an adhesive. Figure 3 As shown in the cross-sectional view, the sealing plate 37 has a recess on the surface opposite to the vibrating plate 35. A sealing space 372 is formed by fixing the sealing plate 37 to the surface of the vibrating plate 35. M piezoelectric elements PZ are enclosed within the sealing space 372.

[0057] The vibration absorber 39 absorbs pressure fluctuations within the liquid storage chamber RS. That is, the vibration absorber 39 absorbs vibrations from the ink stored in the liquid storage chamber RS. For example, the vibration absorber 39 includes a flexible sheet member capable of elastic deformation. Specifically, the vibration absorber 39 is disposed on the surface of the flow channel substrate 33 in the Z2 direction, such that it closes the opening 332, the relay flow channel 338, and the plurality of supply flow channels 334 to form the bottom surface of the liquid storage chamber RS.

[0058] Next, refer to Figure 4 An example illustrating the relationship between the driving voltage v of the piezoelectric element PZ and the amount of ink ejected will be provided. Furthermore, in this embodiment, the driving voltage v of the piezoelectric element PZ, for example, corresponds to the following... Figure 6 The waveform element Pa3 shown is defined by the potential difference Va1h between the starting potential VLa and the ending potential VHa. Waveform element Pa3 is a component of the drive signal COM and is also an ejection component that causes ink to be ejected from nozzle N.

[0059] Figure 4 This is an explanatory diagram used to illustrate the relationship between the driving voltage v of the piezoelectric element PZ and the amount of ink ejected. Figure 4 The horizontal axis represents the driving voltage v of the piezoelectric element PZ, and the vertical axis represents the amount of ink ejected.

[0060] like Figure 4 As shown, increasing the driving voltage v of the piezoelectric element PZ increases the ink ejection volume. However, when the driving voltage v of the piezoelectric element PZ is large, the change in ink ejection volume (i.e., the unit change) is smaller when the driving voltage v of the piezoelectric element PZ is small compared to when the driving voltage v of the piezoelectric element PZ is small. Figure 4 For ease of understanding, let's assume the unit change in ink ejection volume is the change in ink ejection volume when the driving voltage v of the piezoelectric element PZ changes by a predetermined amount Ru. For example, the unit change in ink ejection volume when the driving voltage v of the piezoelectric element PZ changes from voltage v1 to voltage v2, which is a predetermined amount Ru greater than voltage v1, is denoted as change amount DW1. Conversely, the unit change in ink ejection volume when the driving voltage v of the piezoelectric element PZ changes from voltage v4, which is greater than voltage v1, to voltage v5, which is a predetermined amount Ru greater than voltage v4, is denoted as change amount DW2, which is smaller than change amount DW1.

[0061] Thus, when the driving voltage v of the piezoelectric element PZ varies within the range of voltage v4 to voltage v5, the change in ink ejection volume is less sensitive to changes in the driving voltage v of the piezoelectric element PZ compared to when the driving voltage v of the piezoelectric element PZ varies within the range of voltage v1 to voltage v2. That is, as according to... Figure 4 As understood, when the driving voltage v of the piezoelectric element PZ is large, the change in ink ejection volume is less sensitive to the change in the driving voltage v of the piezoelectric element PZ compared to the case where the driving voltage v of the piezoelectric element PZ is small.

[0062] Therefore, in this embodiment, the driving voltage v of the piezoelectric element PZ is set within a range where the sensitivity of the ink ejection amount to changes in the driving voltage v is low. For example, the driving voltage v of the piezoelectric element PZ is set such that the deviation of the ink ejection amount when the driving voltage v deviates within a predetermined range is within a specified allowable range. Specifically, for example, when the deviation of the ink ejection amount is set to be within ±10% or less of the desired ejection amount, it is preferable to set the driving voltage v of the piezoelectric element PZ such that the deviation of the ejection amount when the driving voltage v deviates within a predetermined range is within approximately ±4% of the desired ejection amount. Furthermore, it is preferable that, at a driving voltage v set in a manner that makes the deviation of the ink ejection amount within a specified allowable range, the potential change rate of the waveform element Pa3, which is the ejection element that causes ink to be ejected from the nozzle N, is set such that the ink ejection amount becomes the desired ejection amount. In addition, the potential change rate is the amount of potential change per unit time. Thus, in this embodiment, since the driving voltage v of the piezoelectric element PZ is set within a range where the sensitivity of the ink ejection amount to the change in driving voltage v is low, the change in ink ejection amount when the driving voltage v of the piezoelectric element PZ changes can be suppressed.

[0063] Furthermore, the relationship between the driving voltage v of the piezoelectric element PZ and the ink ejection velocity is the same as the relationship between the driving voltage v of the piezoelectric element PZ and the ink ejection volume. For example, the ink ejection velocity increases with an increase in the driving voltage v of the piezoelectric element PZ. Additionally, when the driving voltage v of the piezoelectric element PZ is large, the change in ink ejection velocity (i.e., the unit change) when the driving voltage v of the piezoelectric element PZ changes by a unit amount is smaller compared to when the driving voltage v of the piezoelectric element PZ is small. In other words, when the driving voltage v of the piezoelectric element PZ is large, the sensitivity of the ink ejection velocity to changes in the driving voltage v of the piezoelectric element PZ is lower compared to when the driving voltage v of the piezoelectric element PZ is small. Therefore, by setting the driving voltage v of the piezoelectric element PZ to suppress changes in the ink ejection volume when the driving voltage v of the piezoelectric element PZ changes, changes in the ink ejection velocity when the driving voltage v of the piezoelectric element PZ changes can also be suppressed. That is, in this embodiment, it is possible to suppress changes in ink ejection characteristics such as ejection volume and ejection speed when the driving voltage v of the piezoelectric element PZ changes.

[0064] Here, the ink ejection amount varies substantially linearly with respect to the displacement of the piezoelectric element PZ. Therefore, the relationship between the driving voltage v of the piezoelectric element PZ and its displacement is the same as the relationship between the driving voltage v of the piezoelectric element PZ and the ink ejection amount. For example, the displacement of the piezoelectric element PZ increases with an increase in the driving voltage v. Furthermore, when the driving voltage v of the piezoelectric element PZ is large, the displacement of the piezoelectric element PZ by a unit change in driving voltage v becomes smaller compared to when the driving voltage v is small. In other words, when the driving voltage v of the piezoelectric element PZ is large, the displacement of the piezoelectric element PZ is less sensitive to changes in driving voltage v compared to when the driving voltage v is small. Thus, the piezoelectric element PZ has the following displacement characteristic: when the driving voltage v of the piezoelectric element PZ is large, the displacement per unit is smaller compared to when the driving voltage v is small.

[0065] Next, refer to Figure 5 A summary of head unit 3 is provided.

[0066] Figure 5 This is a block diagram illustrating an example of the structure of head unit 3.

[0067] As in Figure 1 As described above, the head unit 3 has a recording head 30 and a switching circuit 31. In addition, the head unit 3 has: wiring La, from which a drive signal COM is supplied from the drive signal generation unit 4; wiring Li [m], which supplies a separate drive signal Vin [m] to the ejection section D [m]; and wiring Ld, which supplies a bias voltage signal VBS.

[0068] The switching circuit 31 has M switches Wa[1] to Wa[M] corresponding one-to-one with the M ejector sections D[1] to D[M], and a connection state specifying circuit 310. The connection state specifying circuit 310 specifies the connection state of each of the M switches Wa. For example, the connection state specifying circuit 310 generates a connection state specifying signal Qa[m] that specifies the on / off state of the switch Wa[m] based on at least a portion of the printing signal SI and latching signal LAT supplied from the control unit 2.

[0069] The switch Wa[m] switches the conduction and deconduction of the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] disposed on the ejector section D[m] based on the connection state specification signal Qa[m]. That is, the switch Wa[m] switches the conduction and deconduction of the wiring La and the wiring Li[m] connected to the upper electrode Zu[m] based on the connection state specification signal Qa[m]. In this embodiment, the switch Wa[m] is turned on when the connection state specification signal Qa[m] is high and turned off when it is low. When the switch Wa[m] is turned on, the drive signal COM supplied to the wiring La is supplied as a separate drive signal Vin[m] to the upper electrode Zu[m] of the ejector section D[m] via the wiring Li[m].

[0070] Next, refer to Figure 6 The operation of the liquid ejection device 1 in Tu during a unit period will be explained.

[0071] Figure 6 This is a timing diagram illustrating an example of the operation of the liquid ejection device 1 within a unit period Tu. In this embodiment, when the liquid ejection device 1 performs printing processing, a printing processing period including one or more unit periods Tu is set as the operating period of the liquid ejection device 1. The liquid ejection device 1 according to this embodiment can drive each ejection section D for printing processing within each unit period Tu. The unit period Tu is, for example, the driving cycle of M ejection sections D. Furthermore, in this embodiment, it is envisioned that one cycle of the drive signal COM is a unit period Tu.

[0072] Control unit 2 outputs a latch signal LAT with a pulse PlsL. Thus, control unit 2 defines the unit period Tu as the period from the rising edge of pulse PlsL to the rising edge of the next pulse PlsL.

[0073] The printing signal SI includes, for example, M individually designated signals Sd[1] to Sd[M], which correspond one-to-one with the M ejector sections D[1] to D[M]. The individually designated signal Sd[m] specifies the driving method of the ejector section D[m] in each unit period Tu when the liquid ejection device 1 performs the printing process.

[0074] Before each unit period Tu of the printing process, the control unit 2 supplies the printing signal SI, which includes individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in sync with the clock signal CL. Furthermore, during each unit period Tu, the connection state designation circuit 310 generates a connection state designation signal Qa[m] based on the individual designation signal Sd[m].

[0075] For example, during a unit period Tu of printing processing, the ejector section D[m] is designated by a separate signal Sd[m] as either a dot-forming ejector section D or a non-dot-forming ejector section D. In the dot-forming ejector section D, the piezoelectric element PZ of the ejector section D is driven to eject ink from the nozzle N of the ejector section D. For example, the dot-forming ejector section D[m] is supplied with... Figure 6 The drive signal COM shown is used as a separate drive signal Vin[m].

[0076] The drive signal COM includes: a pulse PA that causes ink to be ejected from nozzle N; a waveform element Ps preceding the pulse PA; and a waveform element Pe following the pulse PA. The pulse PA is an example of a "first ejection pulse". The waveform element Ps, the pulse PA, and the waveform element Pe are supplied to wiring La, for example, via the drive signal COM, and Tu is supplied to wiring La during a unit period.

[0077] For example, waveform element Ps is the element that maintains the potential of the drive signal COM at the reference potential Vref from the beginning of the unit period Tu to the beginning of the pulse PA. Similarly, waveform element Pe is the element that maintains the potential of the drive signal COM at the reference potential Vref from the end of the pulse PA to the end of the unit period Tu.

[0078] The pulse PA is a pulse whose potential, originating from the reference potential Vref, passes through potentials VLa and VHa and returns to the reference potential Vref. Potential VLa is lower than the reference potential Vref and is the lowest potential of the pulse PA. Potential VHa is higher than the reference potential Vref and is the highest potential of the pulse PA. That is, the reference potential Vref is the potential between potentials VLa and VHa. Potential VLa is an example of a "first potential," and potential VHa is an example of a "second potential." Furthermore, the reference potential Vref is an example of a "third potential." The reference potential Vref, potential VLa, and potential VHa are defined, for example, based on the ejection characteristics of the ink in the ejection section D. For example, as in... Figure 4 As explained, the potentials VLa and VHa are specified in such a way that the potential difference Va1h between VLa and VHa is within a range where the sensitivity of the ink ejection volume to changes in the potential difference Va1h is low. Furthermore, the rate of change of the potential of the waveform element Pa3 included in the pulse PA is specified in such a way that the ink ejection volume is the desired ejection volume. In addition, in Figure 6 In the example shown, the pulse PA includes waveform elements Pa1, Pa2, Pa4, and Pa5 in addition to waveform element Pa3.

[0079] Waveform element Pa1, following waveform element Ps, is an expansion element used to displace the piezoelectric element PZ in the Z1 direction. In the expansion element, the potential of the drive signal COM changes in the way that the volume of the pressure chamber CV expands. For example, in waveform element Pa1, to drive the piezoelectric element PZ to expand the volume of the pressure chamber CV, the potential of the drive signal COM changes from the reference potential Vref to the potential VLa. When the volume of the pressure chamber CV expands, the surface of the ink in the nozzle N is pulled in the Z1 direction, which is opposite to the ejection direction. Hereinafter, the situation where the surface of the ink in the nozzle N is pulled in the opposite direction to the ejection direction is sometimes referred to as "pulling in." Furthermore, waveform element Pa1 is an example of a "first expansion element."

[0080] Waveform element Pa2 follows waveform element Pa1 and is used to maintain the position of the piezoelectric element PZ along the Z-axis. For example, in waveform element Pa2, in order to drive the piezoelectric element PZ in a manner that maintains the volume of the pressure chamber CV that expands through waveform element Pa1, the potential of the drive signal COM is maintained. Therefore, in waveform element Pa2, the potential of the drive signal COM is maintained at the potential VLa at the end of waveform element Pa1. For example, waveform element Pa2 maintains the potential of the drive signal COM at potential VLa from the end of waveform element Pa1 to the beginning of waveform element Pa3. Furthermore, waveform element Pa2 is an example of a "first expansion maintenance element".

[0081] Waveform element Pa3, following waveform element Pa2, is a contraction element used to displace the piezoelectric element PZ in the Z2 direction. In the contraction element, the potential of the drive signal COM changes in a way that causes the volume of the pressure chamber CV to contract. For example, in waveform element Pa3, in order to drive the piezoelectric element PZ in a way that causes the volume of the pressure chamber CV to contract, the potential of the drive signal COM changes from potential VLa to potential VHa. When the volume of the pressure chamber CV contracts, the surface of the ink in the nozzle N is pushed out in the ejection direction, i.e., the Z2 direction. Thus, ink is ejected from the nozzle N. Therefore, waveform element Pa3 is an element that changes the potential of the drive signal COM from potential VLa to potential VHa, driving the piezoelectric element PZ in a way that causes the volume of the pressure chamber CV to contract and ink to be ejected from the nozzle N. Hereinafter, the surface of the ink pushed out in the ejection direction is sometimes referred to as pushing. Furthermore, waveform element Pa3 is an example of a "first ejection element".

[0082] Waveform element Pa4 is a sustaining element following waveform element Pa3. For example, in waveform element Pa4, in order to drive the piezoelectric element PZ in a manner that maintains the volume of the pressure chamber CV that contracts through waveform element Pa3, the potential of the drive signal COM is maintained at the potential VHa at the end of waveform element Pa3. For example, from the end of waveform element Pa3 to the beginning of waveform element Pa5, the potential of the drive signal COM is maintained at potential VHa. Furthermore, waveform element Pa4 is an example of a "first contraction sustaining element".

[0083] Waveform element Pa5 is an expansion element following waveform element Pa4. For example, in waveform element Pa5, in order to expand the volume of the pressure chamber CV maintained by waveform element Pa4 and thus attenuate the residual vibration of the ink within the pressure chamber CV, the potential of the drive signal COM changes from potential VHa to the reference potential Vref. Furthermore, the volume of the pressure chamber CV maintained by waveform element Pa4 is equivalent to the volume of the pressure chamber CV that contracts by waveform element Pa3. Thus, waveform element Pa5 is an element that changes the potential of the drive signal COM from potential VHa to the reference potential Vref, causing the volume of the pressure chamber CV to expand and thus attenuating the vibration of the ink within the pressure chamber CV. Furthermore, waveform element Pa5 is an example of a "first vibration damping element".

[0084] Thus, the pulse PA is a so-called pull / push / pull waveform. However, the pulse PA is not limited to a pull / push / pull waveform. For example, the pulse PA can also be a so-called pull / push waveform.

[0085] Next, examples of setting the various elements of the pulse PA will be explained. The values ​​in the following examples are mainly calculated based on experiments.

[0086] For example, as in Figure 4 As explained, the piezoelectric element PZ exhibits a displacement characteristic where the larger the potential difference VA1h, which is the driving voltage v of the piezoelectric element PZ, the smaller the unit displacement. Therefore, for example, when a potential that changes from potential VLa to potential VHa is applied, the unit displacement of the piezoelectric element PZ becomes smaller compared to the case where a potential that changes from potential VLa to a potential VCa, which is the center of potentials VLa and VHa, is applied.

[0087] For example, preferably, the potentials VLa and VHa are set such that the first unit displacement when the potential applied to the piezoelectric element PZ changes from potential VLa to potential VHa is 75% or less of the second unit displacement when the potential applied to the piezoelectric element PZ changes from potential VLa to potential VCa. More preferably, the potentials VLa and VHa are set such that the first unit displacement is 50% or less of the second unit displacement.

[0088] Alternatively, the potentials VLa and VHa are preferably set such that the first displacement of the piezoelectric element PZ per 1V when a potential change from VLa to VHa is applied to the piezoelectric element PZ is 75% or less of the second displacement of the piezoelectric element PZ per 1V when a potential change from VLa to a potential 1V higher than VLa is applied to the piezoelectric element PZ. More preferably, the potentials VLa and VHa are set such that the first displacement is 50% or less of the second displacement.

[0089] Alternatively, the potentials VLa and VHa are preferably set such that when a potential ranging from a predetermined amount within the range including potential VHa is applied to the piezoelectric element PZ, the third displacement of the piezoelectric element PZ becomes 75% or less of the fourth displacement of the piezoelectric element PZ when a potential ranging from that predetermined amount within the range including potential VLa is applied to the piezoelectric element PZ. More preferably, the potentials VLa and VHa are set such that the third displacement becomes 50% or less of the fourth displacement.

[0090] As in the example above, by setting potentials VLa and VHa, the potential difference VaLh between potentials VLa and VHa, i.e., the driving voltage v of the piezoelectric element PZ, can be used within a range where the sensitivity of changes in ink ejection characteristics to changes in driving voltage v is reduced. As a result, in this embodiment, changes in ink ejection characteristics can be suppressed when the driving voltage v supplied to the piezoelectric element PZ changes.

[0091] In addition, such as in Figure 4As explained, when using a pulse PA of the driving voltage v in a range where the sensitivity of the ink ejection amount to the change of the driving voltage v is low, the ink ejection amount is greater than that in a range where the sensitivity of the ink ejection amount to the change of the driving voltage v is high. Therefore, if the driving voltage v of the piezoelectric element PZ is simply set within a range where the sensitivity of the ink ejection amount to the change of the driving voltage v is low, there is a possibility that the ink ejection amount becomes greater than the desired amount. Furthermore, the inventors of this application have experimentally confirmed that by setting the absolute value of the change in potential per 1 μs of the waveform element Pa3 that causes ink ejection to be less than 0.35 times the absolute value of the potential difference Va1h between potentials VLa and VHa, i.e., the first potential difference, the possibility of the ink ejection amount becoming greater than the desired amount can be suppressed. Therefore, it is preferable that the absolute value of the change in potential per 1 μs of the waveform element Pa3 is less than 0.35 times the absolute value of the potential difference Va1h between potentials VLa and VHa, i.e., the first potential difference. In this case, it is possible to prevent the ink ejection amount from becoming greater than the desired amount. For example, even when the desired ejection amount is small, in this embodiment, the driving voltage v of the piezoelectric element PZ can be used within the range of deviation of the displacement amount of the piezoelectric element PZ when the driving voltage v changes, and the desired amount of ink can be ejected. Hereinafter, the absolute value of the potential difference Va1h, i.e., the first potential difference, will also be simply referred to as the potential difference Va1h.

[0092] Furthermore, it is preferable that the interval TIVa from the beginning of waveform element Pa1 to the beginning of waveform element Pa3 is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejector D. The natural vibration period of the ejector D is, for example, the natural vibration period representing the natural vibration periods of M ejector Ds. For example, the natural vibration period representing the natural vibration periods of M ejector Ds could also be the natural vibration period of one of the M ejector Ds. Alternatively, the natural vibration period representing the natural vibration periods of M ejector Ds could be the average of the natural vibration periods of K ejector Ds, or it could be the maximum or minimum value among the natural vibration periods of K ejector Ds. Furthermore, the value K is a natural number satisfying "2 ≤ K ≤ M". In this embodiment, by setting the interval TIVa within a range that is 0.5 times longer and 0.75 times shorter than the natural vibration period of the ejector section D, the waveform element Pa3 can be supplied to the piezoelectric element PZ at a timing after the peak of the natural vibration of the pressure fluctuation of the liquid in the pressure chamber CV generated by the waveform element Pa1 has passed. As a result, for the pressure fluctuation of the liquid in the pressure chamber CV generated by the waveform element Pa1, the waveform element Pa3 is intentionally supplied at a timing when the ejection efficiency is not optimal to suppress the amount of ink ejected, and the desired amount of ink can be ejected.

[0093] Furthermore, it is preferable that the absolute value of the potential difference Va1r between the reference potential Vref and the potential VLa is less than 0.55 times the potential difference Va1h, and the absolute value of the potential change of the waveform element Pa1 per 1 μ second is less than 0.25 times the potential difference Va1h. In addition, the lower limit of the absolute value of the potential change of the waveform element Pa1 per 1 μ second is, for example, 0.15 times the potential difference Va1h. In this way, by reducing the potential difference Va1r between the start and end points of the waveform element Pa1, which is an expansion element, and the rate of potential change, it is possible to suppress the ink ejection amount from becoming greater than desired.

[0094] Furthermore, it is preferable that the period Ta from the start to the end of the waveform element Pa2 is longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection section D. In this case, it is possible to prevent the amount of ink ejected from becoming more than desired.

[0095] Furthermore, the operation of the liquid ejection device 1 is not limited to... Figure 6 The example shown. For example, in Figure 6 The example illustrates a single drive signal COM for ejecting ink from nozzle N, but the invention is not limited to this approach. For instance, multiple drive signals COM, corresponding to the size of the dot, can be used as the drive signal COM for ejecting ink from nozzle N. Even in this case, the multiple drive signals COM for ejecting ink from nozzle N are each determined in such a way that the drive voltage v of the piezoelectric element PZ is within a range where the sensitivity of the ink ejection amount to changes in the drive voltage v is low. Alternatively, multiple drive signals COM, including one or both of a drive signal COM having a micro-vibration waveform for preventing ink thickening and a drive signal COM having a micro-vibration waveform for generating residual vibrations for evaluating the ejection state, can be used.

[0096] In this embodiment, the liquid ejection device 1 includes: a head unit 3 having a plurality of ejection sections D, each of which includes a nozzle N for ejecting ink, a pressure chamber CV communicating with the nozzle N, and a piezoelectric element PZ that imparts pressure variation to the ink in the pressure chamber CV according to a drive signal COM; and a drive signal generation unit 4 that generates the drive signal COM. The drive signal COM includes a pulse PA. The pulse PA includes a waveform element Pa3, the potential of which changes from potential VLa to potential VHa, and drives the piezoelectric element PZ such that the volume of the pressure chamber CV contracts, thereby ejecting ink from the nozzle N. The piezoelectric element PZ has the following displacement characteristic: when a potential change from potential VLa to potential VHa is applied, compared to when a potential change from potential VLa to a potential VCa at the center of potential VLa and potential VHa is applied, the displacement of the piezoelectric element PZ, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount. The absolute value of the change in potential of waveform element Pa3 per 1 μ second is less than 0.35 times the absolute value of the potential difference between potential VLa and potential VHa, i.e., the first potential difference.

[0097] Thus, in this embodiment, the potential VLa at the start point and the potential VHa at the end point of the waveform element Pa3, which causes ink to be ejected from the nozzle N, are set such that the unit displacement of the piezoelectric element PZ is smaller compared to the case where the piezoelectric element PZ is driven by a potential that changes from potential VLa to potential VCa. Therefore, in this embodiment, changes in the ink ejection characteristics can be suppressed when the potential applied to the piezoelectric element PZ to eject ink from the nozzle N changes. Furthermore, in this embodiment, since the absolute value of the potential change of the waveform element Pa3 per 1 μs is less than 0.35 times the first potential difference, it is possible to prevent the ink ejection amount from exceeding the desired amount. That is, in this embodiment, a driving voltage v determined by the potential VLa at the start point and the potential VHa at the end point of the waveform element Pa3 can be used within a small range of unit displacement of the piezoelectric element PZ, and the desired amount of ink can be ejected.

[0098] Alternatively, in this embodiment, the pulse PA may also include a waveform element Pa1, which is an element preceding waveform element Pa3. The potential of Pa1 changes from a reference potential Vref to a potential VLa, driving the piezoelectric element PZ in a manner that expands the volume of the pressure chamber CV. The interval TIVa from the start of waveform element Pa1 to the start of waveform element Pa3 is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejection section D. In this case, waveform element Pa3 can be supplied to the piezoelectric element PZ at a timing when the peak of the natural vibration period of the pressure variation of the liquid in the pressure chamber CV generated by waveform element Pa1 has passed. This allows for the supply of waveform element Pa3 at a timing when the ejection efficiency is not optimal, thus suppressing the amount of ink ejected and thereby ejecting the desired amount of ink.

[0099] Alternatively, in this embodiment, the absolute value of the potential difference Va1r between the reference potential Vref and the potential VLa may be 0.55 times or less of the first potential difference, and the absolute value of the potential change of the waveform element Pa1 per 1 μ second may be 0.25 times or less of the first potential difference. In this case, since the potential difference Va1r between the reference potential Vref at the starting point and the potential VLa at the ending point of the waveform element Pa1 (which is an expansion element) and the potential change of the waveform element Pa1 per 1 μ second are reduced, it is possible to suppress the ink ejection amount from becoming more than desired.

[0100] Alternatively, in this embodiment, the pulse PA may also include a waveform element Pa2, which maintains a potential at potential VLa from the end point of waveform element Pa1 to the start point of waveform element Pa3. The period Ta from the start point to the end point of waveform element Pa2 is longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection section D. In this case, it is possible to prevent the amount of ink ejected from becoming more than desired.

[0101] Furthermore, in this embodiment, the potential difference Va1h from potential VLa to potential VHa is set such that the deviation in the amount of ink ejected when the potential difference Va1h deviates is within a specified allowable amount, and the change in potential per unit time of waveform element Pa3 is set such that the amount of ink ejected is the desired amount. Therefore, in this embodiment, changes in the ink ejection characteristics can be suppressed when the potential applied to the piezoelectric element PZ to eject ink from nozzle N changes.

[0102] [2. Variations]

[0103] The above methods can be modified in a variety of ways. Specific modifications are illustrated below. Two or more methods selected from the following examples can be appropriately combined without contradiction. Furthermore, in the following examples of modifications, elements with equivalent functions, effects, and implementation methods are represented by the same symbols used in the above description, and their detailed explanations are appropriately omitted.

[0104] [First variation]

[0105] In the above embodiments, the driving signal COM includes a single pulse PA that causes ink to be ejected from the nozzle N, but the invention is not limited to this approach. For example, the driving signal COM may also have multiple pulses that cause ink to be ejected from the nozzle N.

[0106] Figure 7 This is a timing diagram illustrating an example of the operation of the liquid ejection device 1 involved in the first modified example. Figure 7 The timing diagram shown, except that the drive signal COM includes pulse PB after pulse PA, is similar to... Figure 6 The timing diagrams shown are the same. Figure 7 The explanation will focus on the pulse PB.

[0107] The drive signal COM includes pulses PA and PB that cause ink to be ejected from nozzle N, waveform element Ps preceding pulse PA, waveform element Pe following pulse PB, and waveform element Pab connecting pulses PA and PB. Pulse PB is an example of a "second ejection pulse," and waveform element Pab is an example of a "pulse connection element." Waveform element Ps, pulse PA, waveform element Pab, pulse PB, and waveform element Pe are supplied to wiring La, for example, via drive signal COM, while in unit period Tu, wiring La is supplied to wiring La.

[0108] For example, waveform element Ps and Figure 6 The waveform element Ps shown is the same. Additionally, waveform element Pe is the element that maintains the potential of the drive signal COM at the reference potential Vref from the end of pulse PB to the end of unit period Tu. Furthermore, waveform element Pab maintains the potential at the reference potential Vref from the end of waveform element Pa5 of pulse PA to the beginning of waveform element Pb1 of pulse PB (described later). Moreover, in this modified example, the reference potential Vref is an example of a "third potential" and a "fourth potential".

[0109] Pulse PB is the pulse following pulse PA, and it has the same pull / push / pull waveform as pulse PA. For example, pulse PB includes waveform elements Pb1, Pb2, Pb3, Pb4, and Pb5, which correspond to the waveform elements Pa1, Pa2, Pa3, Pa4, and Pa5 of pulse PA, respectively. Detailed explanations of elements identical to those in pulse PA are omitted.

[0110] The pulse PB is a pulse from the reference potential Vref, through potentials VLb and VHb, back to the reference potential Vref from the potential of the drive signal COM. Potential VLb is lower than the reference potential Vref and is the lowest potential of pulse PB. Potential VHb is higher than the reference potential Vref and is the highest potential of pulse PB. That is, the reference potential Vref is the potential between potentials VLb and VHb. Potential VLb is an example of a "fifth potential," and potential VHb is an example of a "sixth potential." Potentials VLb and VHb, like potentials VLa and VHa, are determined based on the ink ejection characteristics of the ejection section D. For example, as in... Figure 4 As explained, the potentials VLb and VHb are determined in a way that makes the potential difference VBlh between VLb and VHb a range where the sensitivity of the ink ejection amount to changes relative to changes in the potential difference VBlh is low. Furthermore, the rate of change of the potential of the waveform element Pb3 contained in the pulse PB is determined in a way that makes the ink ejection amount the desired ejection amount.

[0111] Waveform element Pb1 is an expansion element following waveform element Pab. For example, in waveform element Pb1, in order to drive the piezoelectric element PZ in a manner that causes the volume of pressure chamber CV to expand, the potential of the drive signal COM changes from the reference potential Vref to the potential VLb. Furthermore, waveform element Pb1 is an example of a "second expansion element".

[0112] Waveform element Pb2 is a sustaining element following waveform element Pb1. For example, in waveform element Pb2, in order to drive the piezoelectric element PZ in a manner that sustains the volume of the pressure chamber CV that expands through waveform element Pb1, the potential of the drive signal COM is maintained. Therefore, in waveform element Pb2, the potential of the drive signal COM is maintained at the potential VLb at the end of waveform element Pb1. For example, from the end of waveform element Pb1 to the beginning of waveform element Pb3, waveform element Pb2 maintains the potential of the drive signal COM at potential VLb. Furthermore, waveform element Pb2 is an example of a "second expansion sustaining element".

[0113] Waveform element Pb3 is a contraction element following waveform element Pb2. For example, in waveform element Pb3, in order to drive the piezoelectric element PZ by causing the volume of pressure chamber CV to contract, the potential of the drive signal COM changes from potential VLb to potential VHb. This causes ink to be ejected from nozzle N. Thus, waveform element Pb3 is an element that drives the piezoelectric element PZ by causing the potential of the drive signal COM to change from potential VLb to potential VHb, thereby causing the volume of pressure chamber CV to contract and ink to be ejected from nozzle N. Furthermore, waveform element Pb3 is an example of a "second ejection element".

[0114] Waveform element Pb4 is a sustaining element following waveform element Pb3. For example, in waveform element Pb4, in order to drive the piezoelectric element PZ in a manner that maintains the volume of the pressure chamber CV that contracts through waveform element Pb3, the potential of the drive signal COM is maintained at the potential VHb at the end of waveform element Pb3. For example, from the end of waveform element Pb3 to the beginning of waveform element Pb5, the potential of the drive signal COM is maintained at potential VHb in waveform element Pb4.

[0115] Waveform element Pb5 is an expansion element following waveform element Pb4. For example, in waveform element Pb5, the potential of the drive signal COM changes from potential VHb to reference potential Vref, causing the volume of the pressure chamber CV maintained by waveform element Pb4 to expand, thereby attenuating the residual vibration of the ink within the pressure chamber CV. Furthermore, the volume of the pressure chamber CV maintained by waveform element Pb4 is equivalent to the volume of the pressure chamber CV that contracts by waveform element Pb3. Thus, waveform element Pb5 is the element that causes the potential of the drive signal COM to change from potential VHb to reference potential Vref, causing the volume of the pressure chamber CV to expand and attenuating the vibration of the ink within the pressure chamber CV.

[0116] Next, examples of setting the various elements of pulse PB will be explained.

[0117] In this modified example, the potentials VLb and VHb are also set in a manner similar to that of potentials VLa and VHa, such that the sensitivity of the displacement of the piezoelectric element PZ to changes in the driving voltage v of the piezoelectric element PZ is set to a lower range. For example, when a potential changing from VLb to VHb is applied, the unit displacement of the piezoelectric element PZ is smaller compared to the case where a potential changing from VLb to VCb, the center of potentials VLb and VHb, is applied.

[0118] For example, preferably, the potentials VLb and VHb are set such that the third unit displacement when the potential applied to the piezoelectric element PZ changes from potential VLb to potential VHb is 75% or less of the fourth unit displacement when the potential applied to the piezoelectric element PZ changes from potential VLb to potential VCb. More preferably, the potentials VLb and VHb are set such that the third unit displacement is 50% or less of the fourth unit displacement.

[0119] Alternatively, the potentials VLb and VHb are preferably set such that the fifth displacement of the piezoelectric element PZ per 1V when a potential change from VLb to VHb is applied to the piezoelectric element PZ is 75% or less of the sixth displacement of the piezoelectric element PZ per 1V when a potential change from VLb to a potential 1V higher than VLb is applied to the piezoelectric element PZ. More preferably, the potentials VLb and VHb are set such that the fifth displacement is 50% or less of the sixth displacement.

[0120] Alternatively, the potentials VLb and VHb are set such that when a potential ranging from a predetermined amount within the range including potential VHb is applied to the piezoelectric element PZ, the seventh displacement of the piezoelectric element PZ becomes 75% or less of the eighth displacement of the piezoelectric element PZ when a potential ranging from that predetermined amount within the range including potential VLb is applied to the piezoelectric element PZ. More preferably, the potentials VLb and VHb are set such that the seventh displacement becomes 50% or less of the eighth displacement.

[0121] By setting the potentials VLb and VHb as described in the example above, the potential difference VBlh between potentials VLb and VHb, i.e., the driving voltage v of the piezoelectric element PZ, can be used within a range where the sensitivity of changes in ink ejection characteristics to changes in driving voltage v is relatively low. As a result, in this embodiment, changes in ink ejection characteristics when the driving voltage v supplied to the piezoelectric element PZ changes can be suppressed.

[0122] Furthermore, similar to the waveform element Pa3 of the pulse PA, it is preferable that the absolute value of the potential change per 1 μ second of the waveform element Pb3 is less than or equal to the absolute value of the potential difference VBlh between potential VLb and potential VHb, i.e., the second potential difference. In this case, it is possible to prevent the ink ejection amount from becoming greater than the desired ejection amount. For example, even when the desired ejection amount is small, in this modified example, the driving voltage v of the piezoelectric element PZ can be used within the range of the deviation of the displacement amount of the piezoelectric element PZ when the driving voltage v changes, and the desired amount of ink can be ejected. Hereinafter, the absolute value of the potential difference VBlh, i.e., the second potential difference, will also be simply referred to as the potential difference VBlh.

[0123] Furthermore, the interval TIVb from the start of waveform element Pb1 to the start of waveform element Pb3 is, for example, longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejection section D. Therefore, waveform element Pb3 can be supplied to the piezoelectric element PZ at a timing after the peak of the natural vibration of the pressure fluctuation of the liquid in the pressure chamber CV generated by waveform element Pb1 has passed. As a result, for the pressure fluctuation of the liquid in the pressure chamber CV generated by waveform element Pb1, waveform element Pb3 is intentionally supplied at a timing when the ejection efficiency is not optimal to suppress the ink ejection volume, and the desired amount of ink can be ejected.

[0124] Furthermore, the absolute value of the potential change of waveform element Pb1 per 1 μ second is, for example, less than 0.25 times the potential difference VBlh. Additionally, the lower limit of the absolute value of the potential change of waveform element Pb1 per 1 μ second is, for example, less than 0.15 times the potential difference VBlh. In this way, by reducing the potential change rate of waveform element Pb1 as an expansion element, it is possible to suppress the ink ejection amount from becoming greater than desired. Furthermore, the absolute value of the potential difference VBlr between the reference potential Vref and the potential VLb can also be less than 0.55 times the potential difference VBlh.

[0125] Furthermore, the period Tb from the start to the end of waveform element Pb2 can be longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection section D. In this case, it is possible to prevent the amount of ink ejected from becoming more than desired.

[0126] Furthermore, it is preferable that the interval TIVab from the beginning of waveform element Pa3 to the beginning of waveform element Pb3 is at least 4.15 times the natural vibration period of the ejection section D. Additionally, the upper limit of the interval TIVab is, for example, 6 times the natural vibration period of the ejection section D. When the interval TIVab is at least 4.15 times the natural vibration period of the ejection section D, it is possible to suppress the influence of residual vibration caused by waveform element Pa3 on the ejection characteristics of the ink ejected through waveform element Pb3.

[0127] Furthermore, it is preferable that the period Tab from the start to the end of the waveform element Pab is at least twice the natural vibration period of the ejection section D. Additionally, the upper limit of the period Tab is, for example, four times the natural vibration period of the ejection section D. When the period Tab is at least twice the natural vibration period of the ejection section D, it is possible to suppress the influence of residual vibration caused by the pulse PA on the ejection characteristics of the ink ejected by the pulse PB. For example, it is possible to suppress the effect of residual vibration caused by the pulse PA, preventing the amount of ink ejected by the pulse PB from becoming more than the desired ejection amount.

[0128] Thus, in this modified example, pulses PA and PB are set such that the driving voltage v of the piezoelectric element PZ falls within a range where the sensitivity of ink ejection characteristics to changes in driving voltage v is relatively low. Therefore, in this modified example, it is possible to suppress deviations in the amount of ink ejected when the driving voltage v deviates, while simultaneously setting the desired amount of ink ejected per unit period Tu.

[0129] Furthermore, the operation of the liquid ejection device 1 in this modified example is not limited to... Figure 7 The example shown. For example, the pulse PB is not limited to a pull / push / pull waveform. Specifically, for example, the pulse PB can also be a pull / push waveform. Additionally, for example, the drive signal COM can also have three or more pulses ejecting ink from the nozzle N. Additionally, for example, multiple pulses, including pulses PA and pulse PB, can also be pulses used to form dots of different sizes ejected from the nozzle N. Furthermore, for example, the potential at the end of waveform element Pa5 of pulse PA and the potential at the beginning of waveform element Pb1 of pulse PB can also be potentials different from the reference potential Vref.

[0130] Furthermore, for example, the potential VLb can be the same as the potential VLa, or it can be a different potential from the potential VLa. Similarly, the potential VHb can be the same as the potential VHa, or it can be a different potential from the potential VHa. Additionally, the absolute value of the potential difference Va1h between potentials VLa and VHa, i.e., the first potential difference, can be the same as, or different from, the absolute value of the potential difference VBlh between potentials VLb and VHb, i.e., the second potential difference. However, it is preferable that the first potential difference is smaller than the second potential difference. When the first potential difference is smaller than the second potential difference, compared to when the first potential difference is greater than the second potential difference, residual vibrations generated by the pulse PA can be suppressed. As a result, the amount of ink ejected by the pulse PB can be suppressed to be greater than the desired ejection amount.

[0131] In this modified example, the drive signal COM further includes a pulse PB after the pulse PA. The pulse PB includes: waveform element Pb1, where the potential changes from a reference potential Vref to a potential VLb, driving the piezoelectric element PZ by expanding the volume of the pressure chamber CV; waveform element Pb3, where the potential changes from a potential VLb to a potential VHb, driving the piezoelectric element PZ by contracting the volume of the pressure chamber CV and ejecting ink from the nozzle N; and waveform element Pb2, which maintains the potential at potential VLb from the end of waveform element Pb1 to the beginning of waveform element Pb3. When a potential change from potential VLb to potential VHb is applied, the unit displacement of the piezoelectric element PZ is smaller compared to when a potential change from potential VLb to a potential VCb, the center of potentials VLb and VHb, is applied. The absolute value of the potential change per 1 μsecond of waveform element Pb1 is less than or equal to the absolute value of the potential difference VBlh between potentials VLb and VHb, i.e., less than 0.25 times the second potential difference. The interval TIVb from the start of waveform element Pb1 to the start of waveform element Pb3 is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejector D. The absolute value of the potential change per 1 μs of waveform element Pb3 is less than 0.35 times the second potential difference.

[0132] Thus, in this modified example, the drive signal COM includes a pulse PB after the pulse PA. Furthermore, the waveform element Pb3 of pulse PB is similarly set to be such that the drive voltage v, defined by the potential VLb at the start point and the potential VHb at the end point of waveform element Pb3, falls within a range where the unit displacement of the piezoelectric element PZ is relatively small. Therefore, in this modified example, while suppressing deviations in the ink ejection amount when the drive voltage v of the ejection section D deviates, the ink ejection amount in one drive cycle, i.e., one unit period Tu, of the ejection section D can be set to the desired ejection amount.

[0133] Furthermore, in this modified example, the interval TIVab from the beginning of waveform element Pa3 to the beginning of waveform element Pb3 can also be more than 4.15 times the natural vibration period of the ejection section D. This can suppress the influence of residual vibration caused by waveform element Pa3 on the ejection characteristics of the ink ejected through waveform element Pb3.

[0134] Furthermore, in this modified example, the period Tab from the start to the end of the waveform element Pab can also be more than twice the natural vibration period of the ejection section D. In this case, the effect of residual vibration caused by the pulse PA on the ejection characteristics of the ink ejected by the pulse PB can be suppressed.

[0135] Furthermore, in this modified example, the first potential difference may be less than the second potential difference. In this case, compared to the case where the first potential difference is greater than or equal to the second potential difference, residual vibrations caused by the pulse PA can be suppressed. As a result, the amount of ink ejected by the pulse PB can be suppressed to a greater extent than desired.

[0136] [Second variation]

[0137] In the above embodiment, the liquid ejection device 1 is illustrated with four head units 3, but the present invention is not limited to this configuration. For example, the liquid ejection device 1 may have one or more but no more than three head units 3, or it may have five or more head units 3. In this modified example, the same effects as in the above embodiment can also be obtained.

[0138] [Third variation]

[0139] In the above embodiments and modifications, the liquid ejection device 1 is exemplified as a serial printer, but the present invention is not limited to this. For example, the liquid ejection device 1 may also be a so-called line printer in which multiple nozzles N in the head unit 3 are arranged to extend wide relative to the width of the recording paper PP. In this modification, the same effects as in the above embodiments and modifications can also be obtained.

[0140] [Fourth variation]

[0141] In the above-described embodiments and modifications, the piezoelectric element PZ is displaced in the Z2 direction by changing the potential of the individual drive signal Vin[m] from a low potential to a high potential. However, the present invention is not limited to this method. For example, a piezoelectric element PZ that is displaced in the Z2 direction by changing the potential of the individual drive signal Vin[m] from a high potential to a low potential can also be used. In this case, for example, the potential of the drive signal COM changes from a low potential to a high potential in the portion corresponding to the expansion element and from a high potential to a low potential in the portion corresponding to the contraction element. In this modification, the drive voltage v of the piezoelectric element PZ is also set to a range where the unit displacement of the piezoelectric element PZ is small. Therefore, in this modification, the same effects as in the above-described embodiments and modifications can also be obtained.

[0142] [3. Postscript]

[0143] Based on the examples above, for instance, understand the following structure.

[0144] The liquid ejection device according to preferred embodiment 1 comprises: a liquid ejection head having a plurality of ejection portions, each of which includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit that generates the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element whose potential changes from a first potential to a second potential, and drives the piezoelectric element to eject liquid from the nozzle by causing the volume of the pressure chamber to contract. The piezoelectric element has the following displacement characteristics: when a potential change from the first potential to the second potential is applied, compared to when a potential change from the first potential to the center of the first potential and the second potential is applied, the displacement of the piezoelectric element, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount, and the absolute value of the change in potential of the first ejection element per 1 μs is less than 0.35 times the absolute value of the potential difference between the first potential and the second potential, i.e., the first potential difference.

[0145] According to method 1, a driving voltage defined by the first potential at the start of the first ejection pulse and the second potential at the end of the first ejection pulse can be used within a small range of unit displacement of the piezoelectric element, and the desired amount of ink can be ejected.

[0146] In the liquid ejection device according to Method 2, which is a specific example of Method 1, the first ejection pulse further includes a first expansion element, which is an element preceding the first ejection element. The potential changes from a third potential to the first potential to drive the piezoelectric element in such a way that the volume of the pressure chamber expands. The interval from the start of the first expansion element to the start of the first ejection element is longer than 0.5 times and shorter than 0.75 times the inherent vibration period of the ejection portion.

[0147] According to method 2, residual vibrations caused by the driving signal can be suppressed.

[0148] In the liquid ejection device according to Method 3, which is a specific example of Method 1 or 2, the absolute value of the potential difference between the third potential and the first potential is less than 0.55 times the first potential difference, and the absolute value of the potential change of the first expansion element per 1 μs is less than 0.25 times the first potential difference.

[0149] According to method 3, it is possible to prevent the amount of liquid ejected from becoming more than desired.

[0150] In the liquid ejection device according to embodiment 4, which is a specific example of embodiments 1 to 3, the first ejection pulse further includes a first expansion sustaining element, which maintains the potential at the first potential from the end point of the first expansion element to the start point of the first ejection element. The period from the start point to the end point of the first expansion sustaining element is longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection portion.

[0151] Method 4 ensures the stability of liquid ejection.

[0152] In the liquid ejection device of method 5, which is a specific example of any of methods 1 to 4, the drive signal further includes a second ejection pulse after the first ejection pulse. The second ejection pulse includes: a second expansion element, the potential of which changes from a fourth potential to a fifth potential, driving the piezoelectric element to expand the volume of the pressure chamber; a second ejection element, the potential of which changes from the fifth potential to a sixth potential, driving the piezoelectric element to contract the volume of the pressure chamber and eject liquid from the nozzle; and a second expansion sustaining element, which maintains the potential at the fifth potential from the end point of the second expansion element to the beginning point of the second ejection element, and, when a potential change from the fifth potential to the sixth potential is applied, maintains the potential at the fifth potential in relation to the potential change from the fifth potential. Compared to the case where the potential reaches the center of the fifth and sixth potentials, the unit displacement of the piezoelectric element is smaller, the absolute value of the potential change of the second expansion element per 1 μs is less than 0.25 times the absolute value of the potential difference between the fifth and sixth potentials, i.e., the second potential difference, the interval from the start of the second expansion element to the start of the second ejection element is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejection portion, and the absolute value of the potential change of the second ejection element per 1 μs is less than 0.35 times the second potential difference.

[0153] According to method 5, it is possible to suppress the deviation of the liquid ejection amount when the driving voltage of the ejector is deviated, and to increase the liquid ejection amount in one driving cycle of the ejector.

[0154] In the liquid ejection device according to Method 6, which is a specific example of Method 5, the interval from the start of the first ejection element to the start of the second ejection element is more than 4.15 times the inherent vibration period of the ejection portion.

[0155] According to method 6, it is possible to suppress the influence of residual vibration caused by the first ejection element on the ejection characteristics of the liquid ejected through the second ejection element.

[0156] In the liquid ejection device according to embodiment 7, which is a specific example of embodiment 5 or 6, the first ejection pulse further includes: a first contraction sustaining element that maintains the potential at the second potential from the end point of the first ejection element; and a first damping element that is an element following the first contraction sustaining element, wherein the potential changes from the second potential to the fourth potential, causing the volume of the pressure chamber to expand and thus attenuating the vibration of the liquid in the pressure chamber. The drive signal further includes a pulse connection element that maintains the potential at the fourth potential from the end point of the first damping element to the start point of the second expansion element, wherein the period from the start point to the end point of the pulse connection element is more than twice the natural vibration period of the ejection portion.

[0157] According to method 7, it is possible to suppress the influence of residual vibration caused by the first ejection pulse on the ejection characteristics of the liquid ejected by the second ejection pulse.

[0158] In the liquid ejection device of method 8, which is a specific example of any of methods 5 to 7, the first potential difference is smaller than the second potential difference.

[0159] According to method 8, it is possible to prevent the amount of liquid ejected by the second ejection pulse from becoming more than the desired amount.

[0160] Furthermore, in the liquid ejection device according to embodiment 9, which is a preferred alternative, the device includes: a liquid ejection head having a plurality of ejection portions, each of which includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit that generates the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element such that the volume of the pressure chamber is contracted and liquid is ejected from the nozzle, the potential difference from the first potential to the second potential is set such that the deviation of the amount of liquid ejected when the potential difference deviates is within a predetermined allowable amount, and the amount of potential change of the first ejection element per unit time is set such that the amount of liquid ejected is a desired amount.

[0161] According to method 9, it is possible to suppress the change in the amount of liquid ejected when the potential applied to the piezoelectric element in order to eject the liquid from the nozzle changes.

[0162] Furthermore, the control method of the liquid ejection device according to preferred embodiment 10 is as follows: the liquid ejection device comprises: a liquid ejection head having a plurality of ejection portions, each of the plurality of ejection portions including a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element for imparting pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit for generating the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element to eject liquid from the nozzle by causing the volume of the pressure chamber to contract. When a potential changing from the first potential to the second potential is applied, compared to when a potential changing from the first potential to the center of the first potential and the second potential is applied, the displacement of the piezoelectric element, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount. The absolute value of the potential change of the first ejection element per 1 μs is set to be less than or equal to 0.35 times the absolute value of the potential difference between the first potential and the second potential, i.e., the first potential difference.

[0163] Method 10 can achieve the same effect as method 1.

[0164] In the control method of the liquid ejection device according to Method 11, which is a specific example of Method 10, the first ejection pulse further includes a first expansion element, which is an element preceding the first ejection element. The potential changes from a third potential to the first potential to drive the piezoelectric element in such a way that the volume of the pressure chamber expands. The interval from the start of the first expansion element to the start of the first ejection element is longer than 0.5 times and shorter than 0.75 times the inherent vibration period of the ejection portion.

[0165] Method 11 can achieve the same effect as method 2.

[0166] In the control method of the liquid ejection device according to embodiment 12, which is a specific example of embodiment 10 or 11, the absolute value of the potential difference between the third potential and the first potential is less than 0.55 times the first potential difference, and the absolute value of the change in potential of the first expansion element per 1 μs is less than 0.25 times the first potential difference.

[0167] Method 12 can achieve the same effect as method 3.

[0168] In the control method of the liquid ejection device according to embodiment 13, which is a specific example of embodiments 10 to 12, the first ejection pulse further includes a first expansion sustaining element, which maintains the potential at the first potential from the end point of the first expansion element to the start point of the first ejection element, and the period from the start point to the end point of the first expansion sustaining element is longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection portion.

[0169] Method 13 can achieve the same effect as method 4.

[0170] In the control method of the liquid ejection device according to method 14, which is a specific example of any of methods 10 to 13, the drive signal further includes a second ejection pulse after the first ejection pulse. The second ejection pulse includes: a second expansion element, the potential of which changes from a fourth potential to a fifth potential, driving the piezoelectric element in such a way as to expand the volume of the pressure chamber; a second ejection element, the potential of which changes from the fifth potential to a sixth potential, driving the piezoelectric element in such a way as to contract the volume of the pressure chamber and eject liquid from the nozzle; and a second expansion sustaining element, which maintains the potential at the fifth potential from the end point of the second expansion element to the start point of the second ejection element, when applied from the... When the potential changes from the fifth potential to the sixth potential, compared to the case where a potential is applied that changes from the fifth potential to the center of the fifth and sixth potentials, the unit displacement of the piezoelectric element is smaller, the absolute value of the potential change of the second expansion element per 1 μs is less than 0.25 times the absolute value of the potential difference between the fifth and sixth potentials, i.e., the second potential difference, the interval from the start of the second expansion element to the start of the second ejection element is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejection portion, and the absolute value of the potential change of the second ejection element per 1 μs is less than 0.35 times the second potential difference.

[0171] Method 14 can achieve the same effect as method 5.

[0172] In the control method of the liquid ejection device according to method 15, which is a specific example of method 14, the interval from the start of the first ejection element to the start of the second ejection element is more than 4.15 times the inherent vibration period of the ejection part.

[0173] Method 15 can achieve the same effect as method 6.

[0174] In the control method of the liquid ejection device according to method 16, which is a specific example of method 14 or 15, the first ejection pulse further includes: a first contraction maintenance element that maintains the potential at the second potential from the end point of the first ejection element; and a first damping element that is an element after the first contraction maintenance element, wherein the potential changes from the second potential to the fourth potential, causing the volume of the pressure chamber to expand and thus attenuating the vibration of the liquid in the pressure chamber. The drive signal further includes a pulse connection element that maintains the potential at the fourth potential from the end point of the first damping element to the start point of the second expansion element, wherein the period from the start point to the end point of the pulse connection element is more than twice the natural vibration period of the ejection portion.

[0175] Method 16 can achieve the same effect as method 7.

[0176] In the control method of the liquid ejection device according to method 17, which is a specific example of any of methods 14 to 16, the first potential difference is smaller than the second potential difference.

[0177] Method 17 can achieve the same effect as method 8.

[0178] Furthermore, as a preferred alternative, the control method of the liquid ejection device according to method 18 is as follows: the liquid ejection device comprises: a liquid ejection head having a plurality of ejection portions, each of the plurality of ejection portions including a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric element for imparting pressure variation to the liquid in the pressure chamber according to a drive signal; and a drive signal generation unit for generating the drive signal, the drive signal including a first ejection pulse, the first ejection pulse including a first ejection element, the potential of the first ejection element changing from a first potential to a second potential, and driving the piezoelectric element in such a way as to cause the volume of the pressure chamber to contract and eject liquid from the nozzle, the potential difference from the first potential to the second potential being set such that the deviation of the amount of liquid ejected when the potential difference deviates is within a predetermined allowable amount, and the amount of potential change of the first ejection element per unit time being set such that the amount of liquid ejected is a desired amount.

[0179] Method 11 can achieve the same effect as method 9.

Claims

1. A liquid ejection device, characterized in that, have: A liquid ejector head has multiple ejection sections, each of which includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal. as well as The drive signal generation unit generates the drive signal. The driving signal includes a first ejection pulse. The first ejection pulse includes a first ejection element whose potential changes from a first potential to a second potential, driving the piezoelectric element in a manner that causes the volume of the pressure chamber to contract, thereby ejecting liquid from the nozzle. The piezoelectric element has the following displacement characteristics: when a potential change from the first potential to the second potential is applied, compared to when a potential change from the first potential to the center of the first and second potentials is applied, the displacement of the piezoelectric element, i.e., the unit displacement, is smaller when the applied potential changes by a unit amount. The absolute value of the change in potential of the first ejected element per 1 μ second is less than or equal to the absolute value of the potential difference between the first potential and the second potential, i.e., less than 0.35 times the first potential difference.

2. The liquid ejection device according to claim 1, characterized in that, The first ejection pulse also includes a first expansion element, which is an element preceding the first ejection element, wherein the potential changes from a third potential to the first potential to drive the piezoelectric element by causing the volume of the pressure chamber to expand. The interval from the start of the first expansion element to the start of the first ejection element is longer than 0.5 times and shorter than 0.75 times the inherent vibration period of the ejection portion.

3. The liquid ejection device according to claim 2, characterized in that, The absolute value of the potential difference between the third potential and the first potential is less than 0.55 times the first potential difference. The absolute value of the change in potential of the first expansion element per 1 μ second is less than 0.25 times the first potential difference.

4. The liquid ejection device according to claim 2, characterized in that, The first ejection pulse further includes a first expansion sustaining element, which maintains the potential at the first potential from the end point of the first expansion element to the start point of the first ejection element. The period from the start point to the end point of the first expansion sustaining element is longer than 0.25 times and shorter than 0.43 times the inherent vibration period of the ejection portion.

5. The liquid ejection device according to claim 1, characterized in that, The drive signal further includes a second ejection pulse after the first ejection pulse. The second ejection pulse includes: The second expansion element, whose potential changes from the fourth potential to the fifth potential, drives the piezoelectric element by causing the volume of the pressure chamber to expand. The second ejection element, whose potential changes from the fifth potential to the sixth potential, drives the piezoelectric element by causing the volume of the pressure chamber to contract and eject liquid from the nozzle; and The second expansion sustaining element maintains the potential at the fifth potential from the end point of the second expansion element to the start point of the second ejection element. When a potential that changes from the fifth potential to the sixth potential is applied, compared to when a potential that changes from the fifth potential to the center of the fifth and sixth potentials is applied, the unit displacement of the piezoelectric element becomes smaller. The absolute value of the potential change of the second expansion element per 1 μs is less than or equal to the absolute value of the potential difference between the fifth and sixth potentials, i.e., less than 0.25 times the second potential difference. The interval from the start of the second expansion element to the start of the second ejection element is longer than 0.5 times and shorter than 0.75 times the natural vibration period of the ejection portion. The absolute value of the change in potential of the second ejected element per 1 μ second is less than 0.35 times the second potential difference.

6. The liquid ejection device according to claim 5, characterized in that, The interval from the start of the first ejection element to the start of the second ejection element is more than 4.15 times the inherent vibration period of the ejection portion.

7. The liquid ejection device according to claim 5, characterized in that, The first ejection pulse also includes: The first contraction sustaining element maintains the potential at the second potential from the end point of the first ejection element; and The first damping element, which follows the first contraction maintenance element, changes its potential from the second potential to the fourth potential, causing the volume of the pressure chamber to expand and thus attenuating the vibration of the liquid within the pressure chamber. The drive signal further includes a pulse connection element that maintains the potential at the fourth potential from the end point of the first damping element to the start point of the second expansion element. The period from the start point to the end point of the pulse connection element is more than twice the natural vibration period of the ejection portion.

8. The liquid ejection device according to claim 5, characterized in that, The first potential difference is smaller than the second potential difference.

9. A liquid ejection device, characterized in that, have: A liquid ejector head has multiple ejection sections, each of which includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal. as well as The drive signal generation unit generates the drive signal. The driving signal includes a first ejection pulse. The first ejection pulse includes a first ejection element whose potential changes from a first potential to a second potential, driving the piezoelectric element in a manner that causes the volume of the pressure chamber to contract, thereby ejecting liquid from the nozzle. The potential difference from the first potential to the second potential is set such that the deviation in the amount of liquid ejected when the potential difference deviates is within a specified tolerance. The change in potential of the first ejection element per unit time is set to make the ejection amount of liquid reach the desired amount.

10. A control method for a liquid ejection device, characterized in that, The liquid ejection device includes: A liquid ejector head has multiple ejection sections, each of which includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal. as well as The drive signal generation unit generates the drive signal. The driving signal includes a first ejection pulse. The first ejection pulse includes a first ejection element whose potential changes from a first potential to a second potential, driving the piezoelectric element in a manner that causes the volume of the pressure chamber to contract, thereby ejecting liquid from the nozzle. When a potential that changes from the first potential to the second potential is applied, compared to the case where a potential that changes from the first potential to the center of the first and second potentials is applied, the displacement of the piezoelectric element, i.e., the unit displacement, becomes smaller when the applied potential changes by a unit amount. The absolute value of the change in potential of the first ejected element per 1 μ second is set to be less than 0.35 times the absolute value of the potential difference between the first potential and the second potential, i.e., the first potential difference.

11. A control method for a liquid ejection device, characterized in that, The liquid ejection device includes: A liquid ejector head has multiple ejection sections, each of which includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and a piezoelectric element that imparts pressure variation to the liquid in the pressure chamber according to a drive signal. as well as The drive signal generation unit generates the drive signal. The driving signal includes a first ejection pulse. The first ejection pulse includes a first ejection element whose potential changes from a first potential to a second potential, driving the piezoelectric element in a manner that causes the volume of the pressure chamber to contract, thereby ejecting liquid from the nozzle. The potential difference from the first potential to the second potential is set such that the deviation in the amount of liquid ejected when the potential difference deviates is within a specified tolerance. The change in potential of the first ejection element per unit time is set to make the ejection amount of liquid reach the desired amount.

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