Driving device

Abstract

To provide a driving device that can reduce a differences in discharge speed among a plurality of drops.SOLUTION: A driving device according to an embodiment comprises a driving part that applies, to an actuator, a driving signal for driving a pressure chamber communicated with a nozzle that discharges liquid. A waveform of the driving signal is a multi-drop waveform having a plurality of drop waveforms which can make the pressure chamber discharge one liquid droplet through an extended state, a steady state and a contracted state. At least one or more drop waveforms are adjusted drop waveforms whose state is brought from the contracted state into an auxiliary contracted state where contraction amounts are smaller than in the contracted state.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a drive device. [Background technology]

[0002] Multi-drop driving is known as one of the ejection control methods for liquid ejection devices such as inkjet heads. In multi-drop driving, in order to improve printing performance, it is required to reduce the difference in ejection speed for each drop, and there is a method of increasing the ejection speed by adding a micro-vibration pulse before the ejection waveform. However, the micro-vibration pulse added before ejection has a large effect on the first drop, and it is difficult to adjust the ejection speed from the second drop onwards. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,661,785 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a driving device capable of reducing the difference in ejection speed between a plurality of drops. [Means for solving the problem]

[0005] The driving device according to the embodiment includes a driving unit that applies to an actuator a driving signal that drives a pressure chamber that communicates with a nozzle that ejects liquid. The waveform of the driving signal is a multi-drop waveform that has a plurality of drop waveforms that cause the pressure chamber to eject one droplet by passing through an expansion state, a steady state, and a contraction state. At least one of the drop waveforms is an adjustment drop waveform that causes the pressure chamber to enter an auxiliary contraction state in which the contraction amount is smaller than that of the contraction state after the expansion state. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram illustrating a configuration of a liquid ejection device according to a first embodiment. [Diagram 2] FIG. 1 is a perspective view showing a configuration of a liquid ejection head according to a first embodiment. [Diagram 3] FIG. 4 is a waveform diagram showing a multi-drop waveform according to the embodiment. [Figure 4] 6 is a waveform diagram showing the ejection waveforms of a plurality of drops in the embodiment; [Diagram 5] FIG. 4 is a waveform diagram showing a standard drop waveform in the embodiment. [Figure 6] FIG. 4 is a waveform diagram showing an adjusted drop waveform in the embodiment. [Figure 7] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment. [Figure 8] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment. [Figure 9] 5 is a graph showing the pulse width of each drop in a multi-drop waveform according to an embodiment. [Figure 10] 11 is a graph showing the ejection speed in the case of full driving in a multi-drop waveform according to the embodiment. [Figure 11] FIG. 11 is a waveform diagram showing a multi-drop waveform according to another embodiment. [Figure 12] 6 is a waveform diagram showing the ejection waveforms of a plurality of drops in the embodiment; [Figure 13] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment; [Figure 14] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment; [Figure 15] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment; [Figure 16] 11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment; [Figure 17]11 is a graph showing measurement results of the ejection speed of each drop using a multi-drop waveform according to the embodiment; [Figure 18] 6 is a graph showing the pulse width of each drop in a multi-drop waveform according to the embodiment; [Figure 19] 11 is a graph showing the ejection speed in the case of full driving in a multi-drop waveform according to the embodiment. [Figure 20] FIG. 11 is a waveform diagram showing a multi-drop waveform according to another embodiment. [Figure 21] 6 is a waveform diagram showing the ejection waveforms of a plurality of drops in the embodiment; [Figure 22] FIG. 11 is a waveform diagram showing a multi-drop waveform according to a comparative example. [Figure 23] 13 is a graph showing the measurement results of the ejection speed of each drop using a multi-drop waveform according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A liquid ejection head 1 according to a first embodiment and a liquid ejection device 2 using the liquid ejection head 1 will be described below with reference to Figs. 1 to 3. Fig. 1 is an explanatory diagram showing the configuration of the liquid ejection device 2 according to the first embodiment, and Fig. 2 is a perspective view showing the configuration of the liquid ejection head 1. Fig. 3 is a waveform diagram showing a multi-drop waveform in the first embodiment, and Fig. 4 is a waveform diagram showing the ejection waveform for a plurality of drops. Note that in each figure, the configuration is enlarged, reduced, or omitted as appropriate for the purpose of explanation.

[0008] A liquid ejection device 2 having a liquid ejection head 1 will be described with reference to Fig. 1. The liquid ejection device 2 includes a housing 2111, a medium supply unit 2112, an image forming unit 2113, a medium ejection unit 2114, a conveying device 2115 which is a supporting device, and a control unit 2118.

[0009] The liquid ejection device 2 is an inkjet printer that performs an image formation process on paper P by ejecting liquid such as ink while transporting the paper P as a recording medium, which is the object of ejection, along a predetermined transport path 2001 from a medium supply section 2112 through an image forming section 2113 to a medium ejection section 2114.

[0010] The medium supply unit 2112 includes a plurality of paper feed cassettes 21121. The image forming unit 2113 includes a support unit 2120 that supports paper, and a plurality of head units 2130 that are disposed above and facing the support unit 2120. The medium discharge unit 2114 includes a paper discharge tray 21141.

[0011] The support section 2120 includes a conveyor belt 21201 provided in a loop shape in a predetermined area where image formation is performed, a support plate 21202 supporting the conveyor belt 21201 from the rear side, and a plurality of belt rollers 21203 provided on the rear side of the conveyor belt 21201.

[0012] The head unit 2130 includes liquid ejection heads 1 which are multiple inkjet heads, multiple supply tanks 2132 as liquid tanks mounted on each liquid ejection head 1, a pump 2134 which supplies ink, and a connection flow path 2135 which connects the liquid ejection heads 1 and the supply tanks 2132.

[0013] The liquid ejection head 1 is supplied with ink as liquid stored in a supply tank 2132. The liquid ejection head 1 may be a non-circulation type head that does not circulate ink, or may be a circulation type head that circulates ink.

[0014] In this embodiment, the liquid ejection heads 1 are provided with four colors, cyan, magenta, yellow, and black, and four supply tanks 2132 for storing ink of each color. The supply tanks 2132 are connected to the liquid ejection heads 1 by connection flow paths 2135.

[0015] As shown in FIG. 2, the liquid ejection head 1 is an inkjet head, and includes a nozzle plate 21 having a plurality of nozzles 211, an actuator substrate 22, a manifold 23 joined to the actuator substrate 22, and a drive circuit 24 (drive unit).

[0016] The actuator substrate 22 is disposed opposite the nozzle 211 and includes an actuator 25 as a liquid ejection section having a plurality of pressure chambers 26 communicating with the nozzle 211 and a drive element section adjacent to the plurality of pressure chambers 26. The actuator substrate 22 is configured in a predetermined shape that forms a predetermined flow path including the plurality of pressure chambers 26 between the actuator substrate 22 and the nozzle plate 21.

[0017] An electrode connected to the drive circuit 24 is formed on the drive element portion adjacent to the pressure chamber 26 of the actuator 25. The electrode is connected to the control unit 2118 via a driver of the drive circuit 24 (described later) by wiring connected to the drive circuit 24, for example, and is configured to be drive-controllable by control by a processor.

[0018] The drive circuit 24 includes a driver IC 241 and various wiring boards 242. The drive circuit 24 drives the actuator 25 by applying a drive voltage to the wiring pattern of the actuator 25 by the driver IC 241, thereby increasing or decreasing the volume of the pressure chamber 26 and causing droplets to be ejected from the nozzles 211 arranged opposite to the actuator 25.

[0019] The liquid ejection head 1 comprises a nozzle plate 21, an actuator substrate 22, and a manifold 23, and defines a predetermined flow path having a pressure chamber 26 therein. The flow path of the liquid ejection head 1 is connected to a connection flow path 2135 of a liquid ejection device. For example, the liquid ejection head 1 is a share mode type inkjet head.

[0020] The pump 2134 is a liquid-sending pump constituted by, for example, a piezoelectric pump. The pump 2134 is connected to the control unit 2118, and is drive-controlled by the control unit 2118.

[0021] The connection flow path 2135 includes a supply flow path that is connected to an ink supply pipe of the liquid ejection head 1. The connection flow path 2135 also includes a recovery flow path that is connected to an ink discharge pipe of the liquid ejection head 1. For example, if the liquid ejection head 1 is of a non-circulation type, the recovery flow path is connected to a maintenance device, and if the liquid ejection head 1 is of a circulation type, the recovery flow path is connected to a supply tank 2132.

[0022] The transport device 2115 transports the paper P along a transport path 2001 that runs from a paper feed cassette 21121 of the medium supply unit 2112 through the image forming unit 2113 to a paper discharge tray 21141 of the medium discharge unit 2114. The transport device 2115 includes a plurality of guide plate pairs 21211-21218 and a plurality of transport rollers 21221-21228 that are arranged along the transport path 2001. The transport device 2115 supports the paper P so that it can move relative to the liquid ejection head 1.

[0023] The control unit 2118 is, for example, a control board, and includes a processor, a read only memory (ROM), a random access memory (RAM), an I / O port which is an input / output port, and an image memory.

[0024] The processor is a processing circuit such as a CPU (Central Processing Unit) that is a controller. The processor controls the head unit 2130, the drive motor, the operation unit, various sensors, and the like provided in the liquid ejection device 2 through an I / O port. The processor transmits the print data stored in the image memory to the drive circuit 24 in the drawing order.

[0025] Furthermore, the control unit 2118 determines an adjusted drop waveform based on the adjustment data, for example, selecting an adjusted drop waveform to be applied from among adjusted drop waveforms that can be set in multiple stages.

[0026] The ROM stores various programs, etc. The RAM temporarily stores various variable data, image data, etc. The I / O port is an interface unit that inputs data from the outside and outputs data to the outside. Print data from an externally connected device is sent to the control unit 2118 through the I / O port and saved in the image memory.

[0027] The print data is data converted from image data including color and density image information for each area and input to the head for ejecting liquid. The liquid ejection head 1 selects a drive waveform based on the print data and applies the drive waveform to the actuator 25.

[0028] The characteristics of the liquid ejection head 1 used in the liquid ejection device 2 according to the embodiment and the drive waveform of the drive signal generated by the drive circuit 24 of the liquid ejection head 1 will be described below. For example, the liquid ejection head 1 is multi-drop driven, and can be driven in multiple gradations by combining multiple drop waveforms including a standard drop waveform and an adjusted drop waveform. In other words, the drive circuit 24 drives with a multi-gradation drive waveform by multiple patterns (multiple types) of multi-drop signals.

[0029] The control unit 2118 sets a drive waveform to be applied to each drive element based on the print data. For example, the control unit 2118 sets a combination of an adjusted drop waveform and a standard drop waveform based on the print data. As a specific example, the control unit 2118 selects a drive pattern for each element from a plurality of patterns that are set and stored in advance. In addition, the control unit 2118 sets an adjustment amount of the adjusted drop waveform for each nozzle.

[0030] For example, the control unit 2118 drives a plurality of drive elements corresponding to each nozzle of the liquid ejection unit with a plurality of multi-waveform patterns including a standard drop waveform, an adjusted drop waveform, and a non-ejection waveform, based on print data.

[0031] Fig. 3 is a graph showing an example of a drive waveform. In this embodiment, the drive waveform has five drop waveforms (elements) in one printing cycle. Fig. 4 is a drive waveform showing the ejection waveform of each drop. Fig. 5 shows a standard drop waveform, and Fig. 6 shows an adjusted drop waveform. In Figs. 3 to 6, the vertical axis shows voltage [V] and the horizontal axis shows time [μs].

[0032] For example, a multi-drop waveform WW as a drive waveform has a plurality of drop waveforms, and is configured by a combination of a standard drop waveform WA and an adjusted drop waveform WB.

[0033] In the multi-drop waveform WW according to this embodiment, the first and second drops are adjusted drop waveforms WB, and the third to fifth drops are standard drop waveforms WA.

[0034] Here, the standard drop waveform WA has an expansion element PA (expansion portion), a steady element PB (steady portion), and a contraction element PC (contraction portion), each of which is a pulse waveform, as shown in Fig. 5. In other words, the standard drop waveform WA is a waveform that ejects one droplet from the pressure chamber through an expansion state, a steady state, and a contraction state.

[0035] The pulse width TA of the expansion element PA in the standard drop waveform WA is set to an acoustic length AL, which is half the time of the natural vibration period of the pressure chamber 26 of the liquid ejection head 1 .

[0036] As an example, the standard drop waveform WA is a waveform that produces an ejection volume of 4 pL. For example, the maximum ejection volume is 20 pL for 5 drops.

[0037] The adjusted drop waveform WB has an expansion element PA, a steady element PB, an auxiliary contraction element PD, and a contraction element PC. That is, the adjusted drop waveform WB is a waveform that ejects one droplet from the pressure chamber through an expansion state, an auxiliary contraction state, a steady state, and a contraction state. Here, the period TS of the multiple drop waveforms WA and WB is constant.

[0038] 3 to 6, the standard drop waveform WA includes an expansion element PA, which is a pulse waveform that expands the pressure chamber 26 by lowering the voltage from the intermediate voltage Vb to the expansion voltage Va and then returns to the intermediate voltage Vb after a certain time has passed, to eject ink, a steady element PB that maintains the intermediate voltage Vb for a certain time, and a contraction element PC, which is a pulse waveform that increases the voltage from the intermediate voltage Vb to a contraction voltage Vc that is higher than the expansion voltage Va and the intermediate voltage Vb, to contract the pressure chamber 26 and then returns the voltage to the intermediate voltage Vb again. For example, the intermediate voltage Vb=0V.

[0039] As an example, the standard drop waveform WA shown in Figures 3 to 5 is a step waveform in which the voltage is raised and lowered in stages when increasing and decreasing the voltage during expansion and contraction, but the invention is not limited to this and may be a waveform in which the voltage is raised and lowered all at once.

[0040] The adjusted drop waveform WB includes an expansion element PA, which is a pulse waveform that expands the pressure chamber 26 by lowering the voltage from the intermediate voltage Vb to the expansion voltage Va, and then returns to the intermediate voltage Vb after a certain time has passed, to eject ink; an auxiliary contraction element PD, which is a pulse waveform that raises the voltage from the intermediate voltage Vb to an auxiliary contraction voltage Vd, which is higher than the expansion voltage Va and the intermediate voltage Vb, to cause the pressure chamber 26 to vibrate slightly, and then returns to the intermediate voltage Vb after a certain time has passed; a stationary element PB that maintains the intermediate voltage Vb for a certain time; and a contraction element PC, which is a pulse waveform that raises the voltage to a contraction voltage Vc, which is higher than the expansion voltage Va and the intermediate voltage Vb, to contract the pressure chamber 26, and then returns to the intermediate voltage Vb again. For example, the intermediate voltage Vb=0V. Here, the contraction amount of the auxiliary contraction element PD is smaller than the contraction amount of the contraction element. For example, the auxiliary contraction voltage Vd is smaller than the contraction voltage Vc, and is about 1 / 2 of the contraction voltage Vc. For example, the auxiliary contraction element PD starts after the expansion element PA, but may be increased to the auxiliary contraction voltage Vd after returning from the expansion voltage to the intermediate voltage Vb and then remaining at Vb for a certain period of time.

[0041] The adjusted drop waveform WB is obtained by adding a pulse that contracts by about half the contraction element PC immediately after the end of the expansion state at the steady state timing provided between the expansion and contraction of the standard drop waveform WA. In the adjusted drop waveform WB, the pulse width TA of the expansion element PA is set to AL (Acoustic Length), which is half the time of the natural vibration period of the pressure chamber 26 of the liquid ejection head 1.

[0042] As an example, the adjustment drop waveform WB shown in Figures 3 to 6 is a step waveform that raises and lowers the voltage in stages when increasing and decreasing the voltage during expansion and contraction, but the present invention is not limited to this and may be a waveform that raises and lowers the voltage all at once.

[0043] For example, the adjusted drop waveform WB can adjust the amount of contraction in multiple stages. For example, the control unit 2118 adjusts the pulse width or height (amplitude) of each element of the adjusted drop waveform in multiple stages to adjust the ejection volume. That is, the control unit 2118 can adjust the ejection volume of droplets ejected from the nozzle by selecting and setting each element pulse width or height of the adjusted drop waveform WB in multiple stages for each nozzle, as well as selecting a combination pattern of the adjusted drop waveform WB, standard drop waveform WA, and non-ejection waveform according to the print data.

[0044] The control unit 2118 sets the width of the auxiliary contraction element PD (auxiliary contraction pulse) to be smaller as the number of drops increases. That is, the contraction amount of the auxiliary contraction state in the drop ejection waveform of the multi-drop waveform WW is smaller the later the drop is in the order of drops. Specifically, the pulse width TD of the auxiliary contraction element PD of the adjusted drop waveform WB of the second drop is smaller than the pulse width TD of the auxiliary contraction element PD of the adjusted drop waveform WB of the first drop.

[0045] Here, the larger the width of the auxiliary contraction element PD, the greater the increase in the ejection speed. Furthermore, if the auxiliary contraction element PD is not inserted, the ejection speed increases with an increase in the number of drops. For this reason, if the ejection speed of each drop is to be constant, the pulse width required to keep the speed constant decreases as the number of drops increases. Therefore, in order to reduce the difference in the ejection speeds of multiple drops, the speed difference can be reduced by reducing the width of the pulse that contracts by half as the number of drops increases.

[0046] Therefore, in this embodiment, the contraction amount of the auxiliary contraction is reduced as the drop is placed later by adjusting the pulse width TD of the auxiliary contraction element PD. Note that in this embodiment, at least one drop including the final drop has a standard drop waveform WA that does not include the auxiliary contraction element PD.

[0047] In the multi-drop waveform WW, the time TS of the multiple drop waveforms is constant. Also, the pulse width TA of the expansion state is set to AL. Also, in the multi-drop waveform WW, the total TU of the pulse widths of the auxiliary contraction state and the steady state of the multiple drop waveforms is within a certain range. For example, the time of the expansion state and the time of the contraction state are each constant, and the total time of the auxiliary contraction state and the steady state is constant. In other words, by setting the time so that when the pulse width TD of the auxiliary contraction state is increased, the pulse width of the steady state is correspondingly smaller, and conversely, when the pulse width TD of the auxiliary contraction state is decreased, the pulse width of the steady state is correspondingly larger, the overall time is set so that it does not change.

[0048] 7 and 8 are graphs showing the measurement results of the ejection speed when multiple nozzles are driven by the multi-drop waveform WW. The horizontal axis shows the number of drops (drop order), and the vertical axis shows the ejection speed. In each graph, the ejection speed is shown for four different nozzle drive conditions: when one nozzle out of multiple nozzles is driven (e.g., driven nozzle: #013, measured at #013), when multiple nozzles are driven simultaneously (e.g., driven nozzles: #007, #010, #013 #016 #019 measured at #013), when multiple nozzles are driven consecutively (e.g., driven nozzles: #010, #011, #012, #013, #014, #015, #016 measured at #013), and when all nozzles are driven (e.g., driven nozzles: all nozzles measured at #013). In all cases, the same nozzle was measured (e.g., #013). As shown in Figures 7 and 8, it can be seen that the ejection speed differs depending on the drive conditions. In addition, the conditions for making the ejection speed of each drop almost constant are not unique and have a certain range, so several measurement results with different drive conditions are shown. Figures 7 and 8 show the measurement results when the drive condition is changed to change the pulse width TA of the expansion element, that is, the pulse width TD of the auxiliary contraction element PD relative to AL.

[0049] FIG. 7 shows a case where the pulse width TD of the auxiliary contraction element PD for the first drop is 0.34AL, and the pulse width TD of the auxiliary contraction element PD for the second drop is 0.11AL, and FIG. 8 shows a case where the pulse width TD of the auxiliary contraction element PD for the first drop is 0.4AL, and the pulse width TD of the auxiliary contraction element PD for the second drop is 0.15AL. Moreover, Fig. 9 is a graph showing the pulse width TD of the auxiliary contraction element PD at this time. The horizontal axis shows the number of drops, and the vertical axis shows the pulse width TD of the auxiliary contraction element PD for each drop. Fig. 10 shows a comparison of the ejection speeds when all nozzles are driven. As shown in Fig. 10, it can be seen that the difference in ejection speeds is reduced by adjusting the pulse width TD.

[0050] According to this embodiment, in the driving waveform for each gradation, an adjusted drop waveform WB including an auxiliary contraction element PD is combined after expansion, and the auxiliary contraction element PD is made smaller for the rear drop, thereby reducing the difference in ejection speed.

[0051] For example, as shown in FIG. 22 as a comparative example, when the standard drop waveform WA is used, the ejection speed is smaller as the number of first drops is smaller, as shown in FIG. 23. Also, as the number of drops increases and the order of the drops increases, the ejection speed increases, and finally it is saturated at a certain ejection speed. Also, a technology is conceivable in which a short pulse (micro-vibration pulse) that contracts the actuator is inserted before the drive waveform to increase the ejection speed of droplets immediately after the micro-vibration pulse, but the droplets that are affected by the micro-vibration pulse are mainly the first droplet, and there is not much effect on the second drop and after. Furthermore, depending on the period of the pressure wave, the ejection speed of the second drop may be reduced due to the influence of residual vibration. As another method, the ejection speed of the second drop and after may be suppressed by adjusting the insertion timing of the contraction part of the drive waveform and the pulse width TD to suppress the vibration generated by the drive waveform, and as a result, the ejection speed difference between multiple drops may be suppressed. However, adjusting the drive waveform in this way leads to an increase in the drive voltage, and the power consumption required for ejection per unit volume increases.

[0052] In contrast, according to the present embodiment, by applying an auxiliary pulse while reducing the auxiliary pulse of the subsequent drop, it is possible to reduce power consumption while increasing the ejection speed of the low drop and further control the difference in ejection speed between each drop to be very small.

[0053] Moreover, by using the standard drop waveform for at least one drop including the final drop, power consumption can be reduced.

[0054] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications and improvements are possible as appropriate.

[0055] For example, in the above embodiment, the first two drops out of the five drops are set as the adjusted drop waveform WB, and the third drop to the fifth drop are set as the standard drop waveform WA, but the present invention is not limited to this.

[0056] Fig. 11 is a graph showing a multi-drop waveform according to another embodiment. Fig. 12 is a waveform diagram showing the ejection waveform for each drop. For example, as shown in Figs. 11 and 12, in a multi-drop waveform WW2 according to another embodiment, the first three drops are adjusted drop waveforms WB, and the fourth and fifth drops are standard drop waveforms WA.

[0057] In the multi-drop waveform WW2 in this embodiment, the pulse width TD of the auxiliary contraction of the second drop is smaller than the pulse width TD of the auxiliary contraction of the first drop, and the pulse width TD of the auxiliary contraction of the third drop is smaller than the pulse width TD of the auxiliary contraction of the first drop.

[0058] In this embodiment, the contraction amount of the auxiliary contraction is reduced as the drop becomes later by adjusting the pulse width TD of the auxiliary contraction element PD. Also, at least one or more drops including the final drop, for example, the fourth drop and the fifth drop, are standard drop waveforms WA that do not include the auxiliary contraction element PD.

[0059] In the multi-drop waveform WW2, the time TS of each drop is also constant, and the pulse width TA of the expansion state is set to AL. In the multi-drop waveform WW2, the sum TU of the pulse widths in the auxiliary contraction state and the steady state is within a certain range for the multiple drop waveforms. For example, when the steady state is reached immediately after the expansion element and then the auxiliary contraction state is reached after a certain time has elapsed, i.e., when the auxiliary contraction element is inserted in the middle of the steady element, the total time of the steady state before and after the auxiliary contraction state is set to the pulse width of the steady state.

[0060] 13 to 17 are graphs showing the measurement results of the ejection speed when multiple nozzles are driven by the multi-drop waveform WW2. The horizontal axis shows the number of drops, and the vertical axis shows the ejection speed. In each graph, the ejection speed is shown for four different nozzle drive conditions: when one nozzle out of multiple nozzles is driven (e.g., driven nozzle: #013, measured at #013), when multiple nozzles are driven simultaneously (e.g., driven nozzles: #007, #010, #013 #016 #019 measured at #013), when multiple nozzles are driven consecutively (e.g., driven nozzles: #010, #011, #012, #013, #014, #015, #016 measured at #013), and when all nozzles are driven (e.g., driven nozzles: all nozzles measured at #013). In all cases, the same nozzle was measured (e.g., #013).

[0061] FIG. 13 shows the case where the pulse widths TD of the auxiliary contraction elements PD for the first drop to the third drop are set to 0.34AL, 0.15AL, and 0.06AL, respectively.

[0062] FIG. 14 shows the case where the pulse widths TD of the auxiliary contraction elements PD for the first drop to the third drop are set to 0.4AL, 0.18AL, and 0.06AL, respectively.

[0063] FIG. 15 shows the case where the pulse widths TD of the auxiliary contraction elements PD for the first drop to the third drop are set to 0.45AL, 0.22AL, and 0.06AL, respectively.

[0064] FIG. 16 shows the case where the pulse widths TD of the auxiliary contraction elements PD for the first drop to the third drop are set to 0.51AL, 0.25AL, and 0.06AL, respectively.

[0065] FIG. 17 shows the case where the pulse widths TD of the auxiliary contraction elements PD for the first drop to the third drop are set to 0.57AL, 0.28AL, and 0.06AL, respectively.

[0066] Figure 18 is a graph showing the pulse width TD of the auxiliary contraction element PD at this time. The horizontal axis shows the number of drops, and the vertical axis shows the pulse width TD of the auxiliary contraction element PD for each drop. Figure 19 shows a comparison of the ejection speeds when all nozzles are driven. As shown in Figure 19, it can be seen that the difference in ejection speeds is reduced by adjusting the pulse width TD.

[0067] In this embodiment as well, in the drive waveform for each gradation, an adjusted drop waveform WB including an auxiliary contraction element PD is combined after expansion, and the auxiliary contraction element PD is made smaller for the drop that is later in the sequence, thereby reducing the difference in ejection speed.

[0068] Furthermore, the specific conditions of the standard drop waveform and the adjusted drop waveform are not limited to those in the above embodiment. For example, the adjusted drop waveform may be any waveform that allows adjustment of the ejection volume, and it goes without saying that other conditions may be applied.

[0069] For example, in the above embodiment, an example of five-drop driving is shown, but the present invention is not limited to this, and the number of drops may be four or less, or six or more. Furthermore, the number of drop waveforms is not limited to two types, and a combination of three types, four or more types may be used.

[0070] For example, in the above embodiment, the multi-drop waveform WW has multiple adjusted drop waveforms WB and the pulse width of the auxiliary contraction element PD of the subsequent drop is small, but this is not limited to the above. For example, there may be only one adjusted drop waveform WB. That is, for example, in a two-drop drive, only the first drop may be an adjusted drop waveform WB including an auxiliary contraction element PD, and the second drop may be a standard drop waveform WA. Also, in the case of three or more drops, only the first drop may be an adjusted drop waveform WB including an auxiliary contraction element PD, and the second drop and after may be a standard drop waveform WA.

[0071] Also, for example, at least some of the drop waveforms in a multi-drop waveform may be non-ejection waveforms.

[0072] In addition, in the above embodiment, an example was shown in which the ejection speed was adjusted by the pulse width TD of the auxiliary contraction element PD, but this is not limited to this, and it is also possible to vary the ejection volume by, for example, the voltage value or the pulse width of another element.

[0073] Fig. 20 is a waveform diagram of a multi-drop waveform WW3 according to another embodiment. Fig. 21 is a waveform diagram showing the ejection waveform for each drop of the multi-drop waveform WW3. As shown in Figs. 20 and 21, in the multi-drop waveform WW3, the amplitude, i.e., the voltage value, of the auxiliary contraction pulse of the drop ejection waveform is smaller for the later drop, i.e., the larger the drop number. That is, in this embodiment, the height, not the width, of the auxiliary contraction element PD is made different.

[0074] For example, in the multi-drop waveform WW3, the first and second drops are adjusted drop waveforms WB having an auxiliary contraction element PD, and the third to fifth drops are standard drop waveforms WA not including an auxiliary contraction element PD. Here, the auxiliary contraction element PD of the first drop and the auxiliary contraction element PD of the second drop have the same pulse width TD but different voltage values. Specifically, the voltage value of the auxiliary contraction element PD of the adjusted drop waveform WB of the first drop is the same as the voltage value in the contraction state, and the voltage value of the auxiliary contraction element PD of the second drop is about half the voltage value in the contraction state. The auxiliary contraction element PD has a smaller pulse width and a smaller contraction amount than the contraction element and PC.

[0075] In this embodiment as well, the difference in ejection speed can be reduced by combining an adjusted drop waveform WB including an auxiliary contraction element PD after expansion in the drive waveform and reducing the contraction amount of the auxiliary contraction element PD for the rear drop.

[0076] In the above embodiment, the standard drop waveform WA is applied to at least the final drop, but the present invention is not limited to this. For example, the adjusted drop waveform WB may be applied to all drops up to the final drop.

[0077] In addition, the voltage value applied to each piezoelectric element can be adjusted appropriately 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 a voltage to both of the piezoelectric elements.

[0078] The drive waveform is not limited to a pull-shooting waveform, but may be a push-shooting waveform or a push-pull-shooting waveform.

[0079] For example, the configuration of the liquid ejection head 1 is not limited to the above example, and may be used for other types of heads. For example, the liquid ejection head may be configured to drive the liquid ejection unit by vibrating a vibration plate provided between the pressure chamber and the drive element unit through deformation of the drive element unit.

[0080] The liquid ejection device 2 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 be, for example, a 3D printer, industrial manufacturing machinery, or medical machinery, and may be one that forms a three-dimensional object by ejecting, for example, a material substance or a binder for solidifying the material from an inkjet head.

[0081] In the above embodiment, the control operation is performed by the control unit 2118, but the present invention is not limited to this. For example, the liquid ejection head 1 may be provided with a drive circuit for driving an actuator, and the liquid ejection head 1 itself may be a drive device, or may be equipped with a drive device.

[0082] According to at least one of the embodiments described above, by combining an adjusted drop waveform WB including an auxiliary contraction element PD after expansion in a drive waveform and reducing the contraction amount of the auxiliary contraction element PD for the rear drop, it is possible to reduce the difference in ejection speed of multiple drops.

[0083] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0084] 1...liquid ejection head, 2...liquid ejection device, 21...nozzle plate, 22...actuator substrate, 23...manifold, 24...driving circuit, 25...actuator, 26...pressure chamber, 211...nozzle, 242...wiring substrate, 2001...transport path, 2111...housing, 2112...medium supply section, 2113...image forming section, 2114...medium discharge section, 2115...transport device, 2118...control section, 2120...support section, 2130...head unit, 2132...supply tank, 2134...pump, 2135...connection flow path, 21121...paper feed cassette, 21141...paper discharge tray, 21201...transport belt, 21202...support plate, 21203...belt roller, 21211~21218...guide plate pair, 21221~21228...conveyor rollers, IC241...driver, WA...standard drop waveform, WB...adjusted drop waveform, WW2...multidrop waveform, WW3...multidrop waveform, PA...expansion element, PB...steady element, PC...contraction element, PD...auxiliary contraction element.

Claims

1. a drive unit that applies a drive signal to the actuator to drive a pressure chamber that communicates with a nozzle that ejects liquid; The waveform of the drive signal is a multi-drop waveform having a plurality of drop waveforms that cause the pressure chamber to eject one droplet through an expansion state, a steady state, and a contraction state, and a drive device, wherein at least one of the drop waveforms is an adjusted drop waveform having an auxiliary contraction element that, after the expanded state, causes the pressure chamber to enter an auxiliary contraction state with a smaller contraction amount than the contraction state.

2. A plurality of the regulated drop waveforms; The adjusted drop waveforms each have a contraction amount in the auxiliary contraction state of a later adjusted drop waveform that is smaller than a contraction amount in the auxiliary contraction state of an earlier adjusted drop waveform. The drive device according to claim 1 .

3. the voltage of the assisted contraction state is greater than the voltage of the steady state and less than or equal to the voltage of the contraction state; The drive device according to claim 1 , wherein the sum of the pulse widths of the auxiliary contraction state and the steady state of the plurality of drop waveforms is within a certain range.

4. The multi-drop waveform has three or more drops, The drop waveform of at least a first drop has an auxiliary contraction element that sets the auxiliary contraction state, The drive arrangement of claim 1 , wherein one or more of the drop waveforms, including at least a final drop, do not have the auxiliary contraction element.

5. A plurality of the regulated drop waveforms; The drive apparatus of claim 1 , wherein the adjusted drop waveforms have a pulse width or amplitude of the auxiliary contraction element of a later adjusted drop waveform that is smaller than the pulse width or amplitude of the auxiliary contraction element of an earlier adjusted drop waveform.

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