Drive unit, liquid discharge unit, and drive method

Abstract

To provide a drive device, a liquid discharge device, and a drive method that can adjust the discharge speed to an appropriate range. [Solution] The drive device according to the embodiment has a plurality of discharge waveforms that include a discharge pulse having an expansion element that expands a pressure chamber communicating with a nozzle for discharging droplets and a contraction element that contracts the pressure chamber, when discharging n drops (where n is an integer of 2 or more), and has an intermediate time between the discharge waveform that discharges the droplet of one drop and the discharge waveform that discharges the droplet of the next drop, and the intermediate time is set according to the discharge speed for a predetermined discharge amount, within a range of 0.2 to 2 times the half-period of the natural vibration period of the pressure chamber. The drive device drives the liquid discharge unit with a multi-drop drive waveform.

Description

Technical Field

[0001] Embodiments of the present invention relate to a driving device, a liquid ejection device, and a driving method.

Background Art

[0002] As a liquid ejection device, an inkjet head mounted on an inkjet printer is known. An inkjet printer ejects ink droplets from an inkjet head to form an image or the like on the surface of a recording medium. The inkjet head ejects ink droplets from a nozzle communicating with a pressure chamber by changing the volume of the pressure chamber with a piezoelectric actuator. The operation of the actuator is controlled by a drive waveform input to the actuator.

[0003] In a liquid ejection device, multi-drop drive in which ink droplets are ejected and driven a plurality of times is adopted because it can expand the gradation expression range and ensure the stability of ejection. In such a liquid ejection device, it is required to set the ejection volume and ejection speed to appropriate values. For example, when the acoustic length (AL), which is half of the natural vibration period of the pressure chamber, changes according to the dimensions and structure of the pressure chamber of the liquid ejection head, the ejection speed at the same ejection volume changes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a driving device, a liquid ejection device, and a liquid driving method capable of adjusting the ejection speed to an appropriate range.

Means for Solving the Problems

[0006] The drive device according to this embodiment has multiple discharge waveforms that include a discharge pulse having an expansion element that expands a pressure chamber communicating with a nozzle for discharging droplets and a contraction element that contracts the pressure chamber, when discharging n drops (where n is an integer of 2 or more), and has an intermediate time between the discharge waveform for discharging one drop of droplets and the discharge waveform for discharging the next drop of droplets, and the intermediate time is set according to the discharge speed for a predetermined discharge amount, within a range of 0.2 to 2 times the half-period of the natural vibration period of the pressure chamber. The drive device drives the liquid discharge unit with a multi-drop drive waveform. [Brief explanation of the drawing]

[0007] [Figure 1] An explanatory diagram showing the configuration of a liquid dispensing device according to the first embodiment. [Figure 2] An explanatory diagram showing the configuration of a liquid dispensing head according to an embodiment. [Figure 3] An explanatory diagram showing the basic discharge waveform in the drive waveform according to the same embodiment. [Figure 4] This diagram shows the drive waveform of Example 1 of the same embodiment. [Figure 5] This diagram shows the drive waveform of Example 2 of the same embodiment. [Figure 6] An explanatory diagram showing the relationship between AL and discharge speed. [Figure 7] An explanatory diagram showing the configuration of a liquid dispensing device according to another embodiment. [Figure 8] An explanatory diagram showing the drive waveform of Comparative Example 1. [Modes for carrying out the invention]

[0008] The liquid discharge head 10 (drive device) and liquid discharge device 100 according to the first embodiment will be described below with reference to Figures 1 to 5. Figure 1 is a block diagram showing the configuration of the liquid discharge device 100 according to the first embodiment, and Figure 2 is a perspective view of the liquid discharge head 10. Figure 3 is an explanatory diagram showing the basic discharge waveform Wa in the drive waveform according to the embodiment. Figure 4 is a waveform diagram of the drive waveform WW1 of Example 1 of the embodiment, and Figure 5 is a waveform diagram of the drive waveform WW2 of Example 2. Figure 6 is an explanatory diagram showing the relationship between AL and discharge speed.

[0009] As shown in Figure 1, the liquid dispensing device 100 includes a liquid dispensing head 10, a liquid supply unit 21, a transport unit 22, an operation unit 25, a display unit 26, and a control unit 30.

[0010] The liquid ejection device 100 is an inkjet printer that performs image formation processing on a medium such as paper by ejecting a liquid such as ink from the liquid ejection head 10 while transporting the medium, such as paper, along a predetermined transport path that passes through a printing position opposite the liquid ejection head 10.

[0011] The liquid ejection head 10 shown in Figure 2 is, for example, a shear-mode, sheared-wall type inkjet head. The liquid ejection head 10 may be a non-circulating head that does not circulate ink, or it may be a circulating head that circulates ink. In this embodiment, the liquid ejection head 10 will be described using an example of a non-circulating head.

[0012] For example, the liquid discharge head 10 includes an actuator 11 having a plurality of piezoelectric elements communicating with a nozzle, and a drive circuit 12 that drives the actuator 11.

[0013] For example, the liquid ejection head 10 has a flow path that includes a plurality of nozzles 111 for ejecting liquid, a plurality of pressure chambers communicating with the nozzles, and a common chamber communicating with the plurality of pressure chambers. The flow path of the liquid ejection head 10 is connected to a liquid supply unit 21, and ink is supplied from the liquid supply unit to the flow path of the liquid ejection head 10. The actuator 11 applies a voltage to the electrodes of piezoelectric elements provided in each pressure chamber, causing the piezoelectric elements to deform and thereby increasing or decreasing the volume of the pressure chamber, which in turn causes ink to be ejected from the nozzle.

[0014] The drive circuit 12 drives the actuator 11 by applying a drive voltage to the electrodes of the piezoelectric element. The drive circuit 12 generates control signals and drive signals for operating the piezoelectric elements. The drive circuit 12 generates control signals for control purposes, such as selecting the timing for discharging the liquid and the piezoelectric element from which to discharge the liquid, according to the image signal input from the control unit 30 of the liquid discharging device 100. The drive circuit 12 also generates the voltage to be applied to the electrodes of each piezoelectric element, i.e., the drive signal (electrical signal), according to the control signal. When the drive circuit 12 applies a drive signal to the piezoelectric element, the piezoelectric element is driven to change the volume of its pressure chamber. In other words, the actuator 11 is configured to be controllable by the control unit 30.

[0015] As shown in Figure 1, the drive circuit 12 comprises a data buffer 13, a decoder 14, and a driver 15. The data buffer 13 stores print data in chronological order for each piezoelectric element of the actuator 11. The decoder 14 controls the driver 15 for each piezoelectric element based on the print data stored in the data buffer 13. Based on the control of the decoder 14, the driver 15 outputs a drive signal to operate each piezoelectric element. The drive signal is a voltage applied to the electrodes of each piezoelectric element.

[0016] The liquid supply unit 21 is connected to the primary side of the flow path of the liquid discharge head 10 and supplies liquid to the flow path of the liquid discharge head 10. For example, the liquid supply unit 21 includes a tank for storing liquid, a connecting flow path that connects the tank and the flow path of the liquid discharge head 10, and a liquid pump that sends the liquid from the tank to the liquid discharge head 10.

[0017] The conveyance unit 22 conveys a medium such as a sheet of paper along a predetermined conveyance path and supplies it to the printing position. The conveyance unit 22 includes, for example, a plurality of conveyance rollers and conveyance guides arranged along the conveyance path. The conveyance unit 22 supports the medium so as to be relatively movable with respect to the liquid ejection head 10.

[0018] The operation unit 25 includes function keys such as a power key, a paper feed key, and an error reset key.

[0019] The display unit 26 has a display capable of displaying various states of the image printing apparatus.

[0020] The control unit 30 is, for example, a control board and includes a processor 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, an image memory 34, and an I / O port 35 which is an input / output port.

[0021] The processor 31 is a processing circuit such as a CPU (Central Processing Unit) which is a controller. The processor 31 corresponds to the central part of the computer. The processor 31 controls each part in order to realize various functions as a printer according to an operating system and an application program. For example, the processor 31 controls the operations of the liquid ejection head 10 provided in the liquid ejection device 100, the liquid supply unit 21, and the conveyance unit 22. Also, at the time of printing, the processor 31 transmits the print data stored in the image memory 34 to the drive circuit 12 in the order of drawing.

[0022] The ROM 32 corresponds to the read-only main storage part of the computer. The ROM 32 stores the above-mentioned operating system and application program. The ROM 32 may store data necessary for the processor 31 to execute processes for controlling each part.

[0023] RAM33 corresponds to the rewritable main memory portion of the computer described above. RAM33 stores the data necessary for the processor 31 to execute processing. RAM33 is also used as a work area, where information is rewritten as needed by the processor 31. The work area may include image memory where print data is displayed.

[0024] The image memory 34 stores, for example, print data from an externally connected device 200.

[0025] The I / O port 35 is an interface unit that inputs data from the externally connected device 200 and outputs data to the outside. Print data from the externally connected device 200 is transmitted to the control unit 30 via the I / O port 35 and stored in the image memory 34.

[0026] The print data is data input to the liquid discharge head 10, and is converted from image data, including color and density image information for each region, in order to discharge the liquid. For example, the AL information of the liquid discharge head 10 may be included as part of the print data as an indicator of the discharge speed at a predetermined discharge volume. For example, the AL of the liquid discharge head 10 is input by an external device 200, input as part of the information for setting the drive waveform, and recorded.

[0027] The liquid discharge head 10 then sets the drive waveform based on the printed data including AL and applies the drive waveform to the actuator 11. In other words, in this embodiment, the liquid discharge head 10 becomes a drive device that adjusts the intermediate time of the drive waveform based on AL.

[0028] In the liquid dispensing device 100 configured in this way, the control unit 30 inputs a signal to the liquid dispensing head 10, applies a drive voltage to the drive circuit 12, generates a potential difference in the piezoelectric elements acting as actuators 11, selectively deforms the piezoelectric elements, and increases or decreases the volume of the pressure chamber, thereby dispensing liquid from the nozzle 111. For example, when the volume of the pressure chamber expands or contracts during operation, pressure oscillations occur within the pressure chamber. These pressure oscillations increase the pressure within the pressure chamber, causing ink droplets to be dispensed from the nozzle 111 communicating with the pressure chamber. For example, a signal input from the control unit 30 causes the driver 15 to apply a drive voltage to the electrodes of the pressure chamber via electrodes, generating a potential difference in the piezoelectric elements, selectively deforming the piezoelectric elements, and changing the volume of the pressure chamber. For example, when a voltage that acts as an expansion element is applied, the piezoelectric element deforms, increasing the volume of the corresponding pressure chamber and decreasing the pressure, allowing ink from the common chamber to flow into that pressure chamber. Then, with the volume of the pressure chamber increased, when a reverse potential driving voltage is applied to the electrodes of the piezoelectric element, the piezoelectric element deforms, decreasing the volume of the pressure chamber and increasing the pressure. As a result, the ink in the pressure chamber is pressurized and ejected from the nozzle 111.

[0029] In the liquid dispensing device 100, as shown in Figure 7, when the liquid is dispensed while the liquid dispensing head 10 is moved relative to the medium PP along the transport direction, multiple dots are formed on the medium PP.

[0030] The following describes the characteristics of the liquid discharge head 10 used in the liquid discharge device 100 according to this embodiment, and the drive waveform generated by the drive signal in the drive circuit 12 of the liquid discharge head 10. For example, the liquid discharge head 10 is multidrop driven and can be driven in multiple gradations by combining multiple drop waveforms. That is, the drive circuit 12 is driven by multiple patterns (multiple types) of multidrop signals to produce multi-gradation drive waveforms. Specifically, the conditions for the drive waveform are set for each piezoelectric element. When setting the drive waveform, the drive pattern may be selected for each element from a plurality of pre-set and stored patterns. In the driving method of the liquid discharge device according to this embodiment, the liquid discharge unit is driven by the drive waveform WW1 to discharge n drops (n is an integer of 2 or more).

[0031] The drive waveform generated by the drive signal in the drive circuit 12 of the liquid discharge head 10 will be described with reference to Figures 3, 4, 5, and 6. Figure 3 shows the basic discharge waveform Wa used for the drive waveform WW1 of Embodiment 1. Figure 4 shows the drive waveform WW1 of Embodiment 1. Figure 5 shows the drive waveform WW2 of Embodiment 2. Figure 6 is a graph showing the discharge speed at a predetermined discharge amount when the intermediate time is changed. Figure 8 shows the drive waveform WW0 of Comparative Example 1. In each waveform diagram, the horizontal axis represents time and the vertical axis represents voltage.

[0032] Figure 4 shows the drive waveform WW1 according to this embodiment. The drive waveform WW1 shows an example of a multidrop drive waveform that ejects ink n times (where n is an integer of 2 or more) within one drive cycle to form one dot. The waveform data of the drive waveform WW1 is stored, for example, in the memory of the drive circuit 12.

[0033] The drive waveform input to the actuator 11 may be set or selected by the driver 15 of the drive circuit 12 based on the grayscale data sent from the control unit 30. For example, in this embodiment, the drive waveform is set based on AL data as one of the data for setting the drive waveform. AL can be acquired, for example, by measurement, and is pre-inputted and stored. The natural vibration period λ that determines AL can be measured by detecting the change in the impedance of the actuator while it is filled with ink.

[0034] The drive waveform WW1 of Example 1 is a multi-drop drive and comprises multiple ejection waveforms. The drive waveform WW1 is a 4-drop waveform and has four ejection waveforms W1 to W4, each containing an expansion element and a contraction element. That is, the drive waveform WW1 is a drive waveform that has a maximum of 4 drop waveforms (elements) in one printing cycle and is a waveform that drives with multiple grayscale levels, for example, 5 grayscale levels. Here, as an example, a multi-drop drive waveform (n=4) with 4 ejection cycles within one drive cycle is given, but it is not limited to this. The periodic length T of each ejection waveform W1, W2, W3 from 1 to (n-1) is equal.

[0035] For example, when a single pixel is composed of multiple n drops (n>1), the drive waveform WW1 is a multi-drop waveform in which the first to (n-1) drops are output with a first output waveform, the basic output waveform Wa, and the final drop, the nth drop, is output with a second output waveform, the final output waveform. For example, the drive waveform WW1 has a basic output waveform Wa from the first drop to the n-1th drop, and a second output waveform, the final output waveform Wb, which is the output waveform for the nth drop. That is, in the drive waveform WW1, the basic output waveform Wa is repeated n-1 times, and after an intermediate time Tm, the final output waveform Wb is provided.

[0036] Figure 3 is an explanatory diagram showing an example of a basic discharge waveform Wa. The basic discharge waveform Wa is a so-called pull-drive waveform. The basic discharge waveform Wa includes discharge pulses D (D1 to D3) which have, for example, an expansion element that expands the pressure chamber and a contraction element that contracts the pressure chamber. Specifically, the discharge pulse D expands the pressure chamber by lowering the voltage from a first voltage Vb, which is an intermediate voltage, to a second voltage Va, which is lower than the first voltage Vb (expansion element), and after maintaining the second voltage Va for a predetermined time, it increases the voltage to contract (contraction element). In addition, the basic discharge waveform Wa has a contraction waveform element S that keeps the chamber in a contracted state for a predetermined time after contraction by the discharge pulse D. For example, in the contracted waveform elements S(S1~S3) after returning to the intermediate voltage with the discharge pulse D, the voltage may be maintained at the intermediate voltage, which is the first voltage Vb, for a predetermined time, or, as shown by the dashed line in Figure 3, after contracting to the first voltage Vb, the voltage may be further increased to a third voltage Vc which is higher than the intermediate voltage, and then returned to its original state after a predetermined time has elapsed, resulting in a waveform with a stepwise voltage change.

[0037] Therefore, the drive waveform WW1 has discharge pulses D(D1~D3) having an expansion element that expands the pressure chamber and a contraction element that returns to an intermediate voltage after expansion, and contraction waveform elements S(S1~S3) after the discharge pulses D(D1~D3), and in the contraction waveform elements S(S1~S3) there is a damping pulse Pd that contracts to a voltage higher than the intermediate voltage and returns to the intermediate voltage after contraction.

[0038] In addition, in the basic discharge waveform Wa, the pulse width of the discharge pulse D may be set to be narrower than AL, as shown by the dashed line.

[0039] For example, each ejection waveform Wa is set to a time width twice that of AL, which is half a period of the natural vibration period λ determined by the ink characteristics and the internal structure of the print head. The width of the ejection pulse D in the basic ejection waveform Wa is the width of AL (Acoustic Length). For example, the intermediate voltage is, for example, 0V, and is also called the reference voltage. For example, a rectangular pulse waveform is shown as an example, but it is not limited to this, and a trapezoidal waveform may also be used.

[0040] In the basic output waveforms Wa from 1 to (n-1), excluding the fourth and final drop, the width of each pulse is the same, and is set to, for example, AL. The width (time) of each pulse may be AL (Acoustic Length), or it may be a shorter time than AL.

[0041] AL is half a period of the natural vibration period λ, which is determined by the ink characteristics and the internal structure of the print head. Note that the length of the ejection waveform may be set to be longer than 2AL.

[0042] In the drive waveform WW1, an intermediate time Tm is provided between the discharge waveform of one drop and the discharge waveform of the next drop. For example, it is between the discharge waveform that discharges the i-th drop (i≧1) and the discharge waveform that discharges the i+1th drop, and is set between Si and D(i+1). In this embodiment, as an example, an intermediate time Tm is provided between the final discharge waveform Wb of the last drop and the basic discharge waveform Wa of the (n-1)th drop. Here, the intermediate time Tm is set to a time longer than the interval between discharge waveforms from the first drop to the (n-1)th drop. For example, the intermediate time Tm is set to a range of 0.2 times or more and 2 times or less than 0.2 times or more and less than 2 times AL.

[0043] Furthermore, the drive waveform WW1 according to Embodiment 1 of this embodiment may have a boost pulse PB immediately before the final drop discharge pulse D4 at the intermediate time Tm. The boost pulse PB is a pulse waveform having a contraction element that sets the voltage to a higher voltage than the intermediate voltage and an expansion element that returns the voltage to the intermediate voltage after contraction. Specifically, the boost pulse PB raises the voltage from a first voltage Vb, which is the intermediate voltage, to a third voltage Vc that is higher than the first voltage Vb, and then returns to the first voltage Vb after a predetermined time has elapsed. For example, the pulse width of the boost pulse PB is preferably AL, but it may be set to a time shorter than AL.

[0044] The final discharge waveform Wb is a so-called pull-drive waveform. The final discharge waveform Wb includes a discharge pulse D (D4) which has, for example, an expansion element that expands the pressure chamber and a contraction element that contracts the pressure chamber. Specifically, the discharge pulse D expands the pressure chamber by lowering the voltage from a first voltage Vb, which is an intermediate voltage, to a second voltage Va, which is lower than the first voltage Vb (expansion element), and after maintaining the second voltage Va for a predetermined time, it increases the voltage to contract (contraction element). Furthermore, the final discharge waveform Wb has a contraction waveform element S4 after the discharge pulse D4. The final discharge waveform Wb is a waveform in which the voltage changes in steps, with the contraction waveform element S4, which is contracted by returning to the first voltage Vb, which is an intermediate voltage, further increasing the voltage to a third voltage Vc, which is higher than the intermediate voltage, after a predetermined time has elapsed, and then returning to the original voltage.

[0045] In other words, the final discharge waveform Wb includes a discharge pulse D (D4) having an expansion element that expands the pressure chamber and a contraction element that brings the voltage back to the intermediate voltage after expansion, and a damping pulse Pd (Pd4) that contracts to a voltage higher than the intermediate voltage and returns to the intermediate voltage after contraction. This final discharge waveform Wb is a discharge waveform with a longer pulse width (duration) than the basic discharge waveform Wa.

[0046] Here, the pulse widths of the first drop damping pulse (Pd1) and the nth drop damping pulse (Pdn) satisfy Pdn > Pd1 ≥ 0.

[0047] For example, in the drive waveform WW1, a damping pulse Pd is provided in the discharge waveform W1 for the first drop that ejects the first droplet, and in the discharge waveform W4 for the last, fourth drop. The pulse width of the damping pulse Pd is Pd4 > Pd1, and the width of the damping pulse Pd4 in discharge waveform W4 is larger than the pulse width of the damping pulse Pd1 in discharge waveform W1. Therefore, in the drive waveform WW1, the discharge waveform Wn for the last drop, the nth drop, has a longer pulse width (duration) than the discharge waveforms Wn from the 1st to the (n-1st)th drop.

[0048] In this embodiment, the discharge waveform Wa from the second drop up to the (n-1)th drop does not have a damping pulse Pd, and after the discharge pulse D contracts, the waveform remains at the first voltage Vb for a predetermined time. In this case, the pulse width of the damping pulse in the discharge waveform W from the second drop to the n-1th drop is zero.

[0049] As an example, as shown in Figure 4, in the discharge waveform up to (n-1), which is the basic discharge waveform Wa, the pulse width of the discharge pulse D and the pulse width of the contracted waveform element S in the contracted state after the discharge pulse D are both AL. For example, the pulse width of the damping pulse in the contracted state waveform of the first drop is 0.55AL. Also, the pulse width of the discharge pulse D4 of the final drop is AL. In the contracted state of the discharge waveform of the last drop, the pulse width of the damping pulse Pd4 is 1.6AL, and the holding time before the damping pulse Pd4 is 0.23AL.

[0050] In the drive waveform WW1, the intermediate time Tm is when the discharge rate at a predetermined discharge rate reaches a predetermined appropriate value. The value is set to be such that the discharge speed is affected by an indicator. For example, the intermediate time Tm is set to a value corresponding to the AL value of the liquid discharge head 10. For example, the length of the intermediate time Tm can be set or adjusted by the drive circuit 12 or the control unit 30. That is, Tm is adjusted so that the longer AL is, the higher the discharge speed, and the shorter AL is, the lower the discharge speed.

[0051] Here, the volume Vd of the discharged droplet is defined by the integral of the flow rate through the nozzle, which has a circular cross-section of radius r, from the time the fluid ejects the droplet toward the nozzle until the time the flow stops or reverses. The relationship between the discharge volume Vd and the droplet ejection velocity vj is given by the following equation.

number

[0052] For example, Figure 5 shows the drive waveform WW2 according to Example 2 of this embodiment. The drive waveform WW2 is a waveform with an intermediate time Tm of 2 AL, a damping pulse Pd4 of 2.1 AL, and a holding time of 0.45 AL. For example, the graph in Figure 6 shows the discharge rate for a predetermined discharge amount in the drive waveform WW0 of Example 1 with an intermediate time Tm of 1.5 AL, Example 2 with an intermediate time Tm of 2.0 AL, and Comparative Example 1 which has no intermediate time. The vertical axis shows the discharge rate with 1.0 as the target value. The horizontal axis shows AL (μs). The graph plots the discharge rate for each waveform at three different points on the horizontal axis where AL is different. For example, in the range of AL from (II) to (III), the waveform with an intermediate time of 1.5 AL is close to the target value. In this case, by applying the waveform with an intermediate time set to 1.5 AL, a discharge rate that suppresses satellite droplets and trailing mist after discharge can be achieved. On the other hand, when AL is around (I), it can be seen that the intermediate time is close to the target value when it is between 1.5AL and 2.0AL. Therefore, when AL is (I), a waveform with an intermediate time Tm of approximately 1.8AL is applied. In other words, in this embodiment, the shorter AL, the longer the intermediate time Tm is set and adjusted, and conversely, the longer AL, the shorter the intermediate time is set and adjusted.

[0053] According to the liquid discharge head 10 and liquid discharge device 100 of this embodiment, it is possible to maintain an appropriate discharge speed while suppressing satellite mist. In other words, if the discharge speed is affected by changes in AL due to changes in the dimensions or structure of the pressure chamber, the shorter AL is, the longer the intermediate time Tm is set, and conversely, the longer AL is, the shorter the intermediate time is set and adjusted to maintain an appropriate discharge speed.

[0054] It should be noted that the embodiments of the present invention are not limited to the configuration described above. In the above embodiment, an example was shown in which an intermediate time Tm is set between the discharge waveform that discharges the nth drop, which is the final drop, and the discharge waveform that discharges the (n-1)th drop, but it is not limited to this. For example, it may be between waveform element S1 and discharge pulse D2, or between waveform element S2 and discharge pulse D3. In other words, the intermediate time Tm is set between any two discharge waveforms. Note that the intermediate time Tm is longer than the length between other discharge waveforms for which no intermediate time Tm is provided.

[0055] For example, the above embodiment shows an example where the intermediate time Tm is set based on AL, but it is not limited to this. For example, the intermediate time may be adjusted based on an indicator other than AL. In another embodiment, the liquid discharge head 10 and liquid discharge device 100 shown in Figure 7 have the intermediate time Tm set for each row of nozzles 111 based on the difference in impact distance. For example, in this embodiment, the drive circuit 12 or control unit 30 adjusts the intermediate time Tm of the drive waveform for each nozzle 111 or for each row of nozzles 111 based on the distance to the medium.

[0056] For example, as shown in Figure 7, in the liquid ejection device 100, when the medium is placed on a curved surface such as a roll surface, the distance from the surface to which the droplets land differs for each nozzle row and for each nozzle. For example, the further the nozzle is from the surface to which the droplets land, the more susceptible it is to the influence of airflow, and the more the landing accuracy tends to deteriorate. Therefore, locally increasing the ejection speed for nozzles that are further away from the surface to which the droplets land improves the landing accuracy, but since the ejection volume increases in conjunction with the ejection speed, unevenness occurs in the diameter of the landed dots. Accordingly, in this embodiment, the intermediate time Tm is set and adjusted so that the ejection speed for a predetermined ejection amount increases as the distance between the landing surface and the nozzle surface of the inkjet head increases, or so that the ejection speed for a predetermined ejection amount decreases as the distance between the landing surface and the nozzle surface decreases.

[0057] As a specific example, the liquid discharge head 10 or liquid discharge device 100 according to this embodiment is equipped with a detection sensor SS for detecting the distance to the medium, such as a laser scan, and is configured to detect the distance to the medium for each nozzle row or for each nozzle. The liquid discharge head 10 or liquid discharge device 100 drives the actuator 11 with a drive waveform WW1 having an intermediate time Tm corresponding to the distance detected by the detection sensor SS. For example, the intermediate time Tm in the drive waveform WW1 is set and adjusted to reduce the effect of changes in discharge volume that occur when the discharge speed is adjusted. Note that the detection means is not limited to the detection sensor SS, and the distance may be detected by means of visual inspection, for example.

[0058] According to this embodiment, by using a drive waveform WW1 with an intermediate time Tm that corresponds to the distance, when the distance to the printing surface to which the droplet will land differs depending on the nozzle 111, the ejection speed for a predetermined ejection volume can be set to an appropriate value, thereby improving print quality. For example, the intermediate time Tm in the drive waveform is set according to the distance to the target to which the droplet will land, such that the ejection speed for a predetermined ejection volume is faster when the distance is greater, and slower when the distance is smaller. For example, when the surface to which the droplet will land is far from the ejection surface of the nozzle 111, in addition to adjusting to increase the ejection speed, the intermediate time Tm in the drive waveform can be adjusted for each nozzle row or for each nozzle to output a waveform that maintains a predetermined ejection volume.

[0059] Furthermore, in the above embodiment, for example, a drive circuit 12 for driving the actuator 11 is provided on the liquid discharge head 10, and an example is shown where the liquid discharge head 10 itself becomes the drive device. However, for example, the liquid discharge head 10 or the liquid discharge device 100 may be configured to have a drive device mounted on it. The drive waveform input to each actuator 11 may be set by the control unit 30, for example, by setting the waveform in multiple grayscale levels for each nozzle.

[0060] For example, the method for adjusting the intermediate time in each of the above embodiments may be configured to select from a plurality of pre-stored waveform patterns according to the AL and distance. Alternatively, it may be configured to be user-configurable according to the AL and distance. In other words, the setting and adjustment of the drive waveform, including the adjustment of the intermediate time, may be performed in the liquid discharge head 10, or it may be configured to be set and adjusted in the control unit or other device.

[0061] In other embodiments, the control unit 30 may be a drive device that adjusts the intermediate time of the drive waveform. For example, the control unit 30 or processor 31 sets the intermediate time Tm of the drive waveform based on the AL of the liquid discharge head 10. Alternatively, the intermediate time of the drive waveform is set for each nozzle or for each row of nozzles based on the distance to the medium. In other words, the control unit 30 is configured to select and set the waveform in multiple levels for each nozzle, and to adjust the discharge speed of the droplets discharged from the nozzle by increasing or decreasing the intermediate time based on AL and distance information.

[0062] For example, the above embodiment shows an example of 4-drop drive, but it is not limited to this, and the number of drops may be 3 or less, or 5 or more. Furthermore, the drop waveform is not limited to 2 types, but may be a combination of 3 or 4 or more types.

[0063] For example, the above embodiment was described using a drive waveform that discharges a maximum of 4 drops, but it is not limited to this, and may also use a drive waveform that discharges a maximum of 3 drops or less, or a maximum of 5 drops or more.

[0064] For example, the above embodiment shows an example in which a boost pulse PB is provided at an intermediate time Tm, but it is not limited to this. Also, the specific conditions of each waveform can be changed as appropriate, for example, the pulse widths may be different. Furthermore, intermediate damping pulses Pdm may be provided in discharge waveforms W2 and W3 other than the first and last damping pulses Pd1 and Pdn, which are smaller than the damping pulses Pd1 and Pdn of the first and last. In that case, the pulse widths of the damping pulse (Pd1) of the first drop, the intermediate damping pulses (Pdm) from the second drop to the (n-1)th drop, and the damping pulse (Pdn) of the nth drop satisfy Pdn > Pd1 > Pdm ≥ 0. Also, damping pulses Pd1 and Pd4 may not be present in the first and last discharge waveforms W1 and W4.

[0065] This does not exclude the possibility of setting a delay time shorter than the intermediate time Tm in the waveform up to the (n-1)th drop.

[0066] Furthermore, while the example shown illustrates multiple output pulses having the same pulse width and being rectangular waves, this is not the only possible configuration. For example, the waveform could be a step waveform that switches voltage in stages, or it could be a trapezoidal waveform.

[0067] Furthermore, the voltage values ​​applied to each piezoelectric element can be adjusted as appropriate according to various conditions. For example, a potential difference may be generated by grounding one of adjacent piezoelectric elements and applying a voltage to the other, or a potential difference may be generated by applying voltages to both of them separately.

[0068] For example, in the above embodiment, a liquid ejection head 10 having a driver 15 was given as an example of a drive device, but it is not limited to this. Various control devices may be used as drive devices, such as a control device for an inkjet recording device connected to the liquid ejection head 10 and provided outside the liquid ejection head 10.

[0069] The configuration of the liquid discharge head 10 is not limited to the example described above, and may be used for other types of heads. For example, it is not limited to a configuration in which a diaphragm provided between the pressure chamber and the drive element is vibrated by the deformation of the drive element, but can be applied to various other configurations, such as a type in which a pressure chamber is formed between multiple columnar drive element sections.

[0070] Furthermore, the inkjet head may be a non-circulating head that does not circulate ink, or a circulating head that does circulate ink.

[0071] Each potential of the drive waveform can be changed, and the voltage value applied to each piezoelectric element can be adjusted as appropriate according to various conditions. Furthermore, the piezoelectric element may be configured to expand when the voltage is increased and contract when the voltage is decreased, or to expand when the voltage is decreased and contract when the voltage is increased. The order of expansion and contraction in each discharge pulse can also be set as appropriate according to various conditions.

[0072] The drive waveform may be not limited to pull-driven driving, but may also be a push-driven driving or push-pull driving waveform. For example, the configuration of the liquid ejection head 10 is not limited to the example described above and may be used with other types of heads. For example, the configuration may involve driving the liquid ejection unit by vibrating a diaphragm provided between the pressure chamber and the drive element unit through deformation of the drive element unit. Alternatively, the structure may involve deforming the diaphragm with static electricity to eject ink, or using a heating element type structure that utilizes thermal energy from a heater or the like to eject ink from the nozzle. In these cases, the diaphragm or heater acts as an actuator to apply pressure vibration inside the pressure chamber.

[0073] The liquid ejection device 100 is exemplified as an inkjet printer that forms a two-dimensional image using ink on an image-forming medium, but is not limited to this, and may also be a 3D printer, industrial manufacturing machine, or medical machine, for example. The liquid ejection device may be a 3D printer, industrial manufacturing machine, or medical machine, and may, for example, form a three-dimensional object by ejecting a material or a binder for solidifying the material from an inkjet head.

[0074] According to at least one embodiment described above, it is possible to achieve both high accuracy and reduced satellite mist.

[0075] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0076] 10...Liquid discharge head, 11...Actuator, 12...Drive circuit, 13...Data buffer, 14...Decoder, 15...Driver, 21...Liquid supply unit, 22...Transport unit, 25...Operation unit, 26...Display unit, 30...Control unit, 31...Processor, 32...ROM, 33...RAM, 34...Image memory, 35...I / O port, 100...Liquid discharge device, 111...Nozzle, 200...External connection device, D4...Discharge pulse, Pd1, Pd4...Damping pulse, S4...Contraction waveform element, W1~W4...Discharge waveform, WW1, WW2...Drive waveform.

Claims

1. A drive device that drives a liquid dispensing unit by a multi-drop drive waveform, which has multiple dispensing waveforms that include a dispensing pulse having an expansion element that expands a pressure chamber communicating with a nozzle for dispensing droplets and a contraction element that contracts the pressure chamber, and has an intermediate time between the dispensing waveform for dispensing one drop of droplets and the dispensing waveform for dispensing the next drop of droplets, and the intermediate time is set according to the dispensing speed for a predetermined dispensing amount, within a range of 0.2 to 2 times the half-period of the natural vibration period of the pressure chamber.

2. At least one of the discharge waveforms includes a damping pulse that, after the discharge pulse, contracts the pressure chamber with a voltage higher than the intermediate voltage, and then reduces the voltage after contraction. The drive device according to claim 1, wherein the intermediate time in the drive waveform can be set based on AL, which is half a period of the natural vibration period of the pressure chamber.

3. The drive device according to claim 1, wherein the intermediate time in the drive waveform is adjusted for each row of nozzles or for each nozzle, depending on the distance from the nozzle to the target to which the droplet lands, such that the discharge speed for a predetermined discharge amount is faster when the distance is greater, or slower when the distance is smaller.

4. A liquid dispensing device comprising the drive device according to any one of claims 1 to 3.

5. When discharging n droplets (where n is an integer of 2 or more), the liquid discharging unit is driven by a multi-drop drive waveform using a drive waveform that has multiple discharge pulses, each having an expansion element that expands the pressure chamber provided in the liquid discharging unit and a contraction element that contracts after expansion, and having an intermediate time between the discharge waveform discharging the (n-1)th droplet and the discharge waveform discharging the (n-1)th droplet that is longer than the interval between the discharge waveforms from the 1st drop to the (n-1)th drop, and the intermediate time is in the range of 0.2 times or more and 2 times or less of the half-period of the natural vibration period of the pressure chamber. A driving method in which the intermediate time in the driving waveform is set according to the discharge speed for a predetermined discharge amount.

Images