Liquid ejection head and liquid ejection apparatus

Abstract

The invention provides a liquid ejecting head and a liquid ejecting apparatus capable of suppressing the difference in driving time between adjacent nozzles and suppressing the occurrence of concentration unevenness. The liquid ejection head includes an actuator, a nozzle plate, a plurality of electrodes, and a drive circuit. The actuator is formed with a plurality of pressure chambers so that the volumes of the plurality of pressure chambers are variable. The nozzle plate is formed with a plurality of nozzles corresponding to the plurality of pressure chambers. The plurality of electrodes respectively correspond to the plurality of pressure chambers. The drive circuits are electrically and independently connected to the plurality of electrodes, respectively, and generate drive waveforms for driving the pressure chamber for the plurality of electrodes. The driving timing of the driving waveform is set by the sum of the first delay time and the second delay time. The first delay time and the second delay time are in a periodic triangular wave shape relative to the arrangement direction of the nozzles, and the periodic number of nozzles and the delay time are different.

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head and a liquid ejection device. Background Art

[0002] In the existing driving method of the piezoelectric inkjet head, there is a known technology for grouping multiple nozzles so that the driving timing is staggered with different delay times for each group. The driving method of the inkjet head can avoid the concentration of current when driving simultaneously, and can reduce the mutual interference, i.e., crosstalk, between the nozzles on the structure or fluid. In this technology, the delay time is set by the sum of the main delay time and the auxiliary delay time. However, this technology is a discontinuous sawtooth wave with respect to the arrangement direction of the nozzles. Therefore, when applied to an inkjet head with a one-dimensional nozzle configuration, it is easy to produce uneven concentration in discontinuous parts.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-32580 Summary of the Invention

[0004] Technical problem to be solved by the invention

[0005] According to the present invention, it is possible to provide a liquid ejection head and a liquid ejection device that suppress the difference in drive timing between adjacent nozzles and thereby suppress the occurrence of density unevenness.

[0006] Technical solutions to solve problems

[0007] The liquid ejection head involved in the embodiment includes an actuator, a nozzle plate, a plurality of electrodes and a drive circuit. The actuator forms a plurality of pressure chambers so that the volumes of the plurality of pressure chambers are variable. The nozzle plate forms a plurality of nozzles corresponding to the plurality of pressure chambers. The plurality of electrodes respectively correspond to the plurality of pressure chambers. The drive circuit is electrically and independently connected to the plurality of electrodes, and generates a drive waveform for driving the pressure chambers for the plurality of electrodes. The drive timing of the drive waveform is set by the sum of a first delay time and a second delay time. The first delay time and the second delay time are periodic triangular wave-shaped relative to the arrangement direction of the nozzles, and the number of periodic nozzles and the delay time are different. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a perspective view showing the structure of a liquid ejecting head according to the embodiment.

[0009] Figure 2 It is a perspective view showing the main structure of a head body of a liquid ejecting head according to an embodiment.

[0010] Figure 3 It is a cross-sectional view showing the structure of a main part of a head body of a liquid ejecting head according to an embodiment.

[0011] Figure 4 This is a block diagram showing the structure of a circuit board of a liquid ejecting head according to an embodiment.

[0012] Figure 5 It is an explanatory diagram showing an example of the main delay time and the sub delay time according to the embodiment.

[0013] Figure 6 This is an explanatory diagram showing an example of a delay amount using the main delay time and the sub-delay time according to the embodiment.

[0014] Figure 7 This is an explanatory diagram showing an example of the main delay time, the sub-delay time, and the difference between the delay times according to the embodiment.

[0015] Figure 8 This is an explanatory diagram showing an example of the delay amounts of the main delay time and the sub-delay time using a conventional liquid ejection head.

[0016] Figure 9 It is an explanatory diagram schematically showing the structure of a liquid ejecting apparatus using the liquid ejecting head according to the embodiment.

[0017] Description of Reference Numerals

[0018] 1…Liquid ejection head, 2…Liquid ejection device, 11…Head body, 12…Manifold unit, 13…Circuit substrate, 111…Substrate, 112…Frame member, 113…Actuator, 114…Nozzle plate, 115…Electrode, 116…Common liquid chamber, 118…Individual electrode (electrode), 119…Common electrode, 131…Wiring film, 132…Driver IC, 133…Printed wiring substrate, 135…Delay time generation circuit, 136…Drive waveform generation circuit, 137…Print data storage circuit, 139…Drive circuit, 1111…Supply port, 1112…Discharge port, 1131…Pressure chamber, 1132…Air chamber, 1133…Groove, 1134…Piezoelectric body (driving element), 1135…Piezoelectric material, 1136…Liquid-proof wall, 1141…Nozzle, 1142…Nozzle array, 1351… First delay time generating circuit, 1352...Second delay time generating circuit, 1361...Drive waveform generating circuit, 2001...Conveyance path, 2111...Casing, 2112...Media supply unit, 2113...Image forming unit, 2114...Media discharge unit, 2115...Conveyor device, 2116...Temperature control device, 2117...Maintenance device, 2118...Control unit, 2120...Support unit, 2130... …head unit, 2132…supply tank, 2134…pump, 2135…connecting flow path, 21121…paper cassette, 21141…ejection tray, 21161…temperature control water tank, 21162…temperature control circuit, 21201…conveyor belt, 21202…support plate, 21203…belt roller, 21211–21218…guide plate pair, 21221–21228…conveyor rollers, P…paper. DETAILED DESCRIPTION

[0019] Below, refer to Figures 1 to 9 , a liquid ejecting head 1 according to an embodiment and a liquid ejecting apparatus 2 using the liquid ejecting head 1 will be described. Figure 1 is a perspective view showing the structure of a liquid ejecting head 1 according to the embodiment. Figure 2 1 is a perspective view showing the main structure of the head body 11 of the liquid ejecting head 1. Figure 3 1 is a cross-sectional view showing the main structure of the head main body 11 . Figure 4 1 is a block diagram showing the structure of the circuit substrate 13 of the liquid ejecting head 1. Figure 5 is an explanatory diagram showing an example of the main delay time and the sub-delay time, Figure 6 is an explanatory diagram showing an example of a delay amount using a main delay time and a sub-delay time. Figure 7 It is an explanatory diagram showing an example of the main delay time, the sub-delay time, and the difference between the delay times. Figure 8This is an explanatory diagram showing an example of the delay amounts of the main delay time and the sub-delay time using a liquid ejection head according to a comparative example for comparison with the embodiment. Figure 9 1 is an explanatory diagram schematically showing the structure of a liquid ejecting device 2 using a liquid ejecting head 1 according to an embodiment. In addition, in each figure, the structure is appropriately enlarged, reduced, or omitted for the purpose of explanation. Figures 1 to 3 In FIG, X, Y, and Z represent three mutually orthogonal directions.

[0020] The liquid ejection head 1 is, for example, a shared mode inkjet head that ejects ink as a liquid onto a recording medium such as paper. The liquid ejection head 1 is provided at Figure 9 The liquid ejecting apparatus 2 shown is an inkjet recording apparatus. The liquid ejecting head 1 is provided in a head unit 2130 . The head unit 2130 includes a supply tank 2132 as a liquid storage portion provided in the liquid ejecting apparatus 2 .

[0021] The liquid ejection head 1 is supplied with ink, which is a liquid stored in a supply tank 2132. The liquid ejection head 1 may be a non-circulating head that does not circulate the ink, or a circulating head that circulates the ink. Furthermore, the liquid ejection head 1 is connected to a temperature control device 2116 provided in the liquid ejection device 2 and is supplied with a temperature control liquid (temperature-controlled water) for controlling the temperature of the ink.

[0022] like Figure 1 As shown, the liquid ejecting head 1 includes a head body 11, a manifold unit 12, and a circuit board 13. For example, the liquid ejecting head 1 is a side-shooter type four-column integrated head having a pair of head bodies 11 with a pair of actuators 113.

[0023] The head body 11 ejects liquid. Figures 1 to 3 As shown, the head body 11 includes a substrate 111, a frame member 112, an actuator 113 having a plurality of pressure chambers 1131 and a plurality of air chambers 1132, a nozzle plate 114, and electrodes 115 formed on the substrate 111 and the actuator 113. The head body 11 forms a common liquid chamber 116 with the substrate 111, the frame member 112, and the nozzle plate 114. Furthermore, by arranging the actuator 113 in the common liquid chamber 116, the plurality of pressure chambers 1131 and the common liquid chamber 116 are in fluid communication.

[0024] In the example of this embodiment, description is made using an example in which the head body 11 includes a pair of actuators 113 , and both ends of the common liquid chamber 116 communicate with a plurality of pressure chambers 1131 formed in the pair of actuators 113 .

[0025] The substrate 111 is formed into a rectangular plate shape from, for example, a ceramic material. The substrate 111 is formed into, for example, a rectangle that is long in one direction. A wiring pattern that forms a portion of the electrode 115 is formed on one side of the substrate 111. As a specific example, a wiring pattern that forms a portion of a plurality of individual electrodes 118 described later of the electrode 115 and a wiring pattern that forms a portion of a single common electrode 119 are formed on one side of the substrate 111. On one side of the substrate 111, a pair of actuators 113 are arranged in the short side direction of the substrate 111. One side of the substrate 111 is a main surface of the substrate 111. The substrate 111 has, for example, a single or multiple supply ports 1111 and a plurality of discharge ports 1112. The supply port 1111 and the discharge port 1112 are through-holes formed in the substrate 111 between the two main surfaces of the substrate 111.

[0026] The supply port 1111 is the inlet for supplying ink to the common liquid chamber 116. The supply port 1111 is a through-hole formed in the center of the substrate 111 in the short-side direction. The supply port 1111 extends along the long-side direction of the substrate 111. In other words, the supply port 1111 is, for example, an elongated hole extending in one direction along the long-side direction of the actuator 113 and the long-side direction of the common liquid chamber 116. The supply port 1111 is provided between the pair of actuators 113 and opens at a position opposite the common liquid chamber 116.

[0027] The discharge port 1112 is an outlet for discharging ink from the common liquid chamber 116 . A plurality of discharge ports 1112 are provided. Each discharge port 1112 is provided in the common liquid chamber 116 .

[0028] The frame member 112 is fixed to one main surface of the substrate 111 with an adhesive or the like. The frame member 112 surrounds the supply port 1111, the plurality of discharge ports 1112, and the actuator 113 provided on the substrate 111. For example, the frame member 112 has a stepped structure.

[0029] For example, the frame member 112 is formed in a rectangular frame shape, thereby forming an opening that is long in one direction along the long side direction of the frame member 112. A pair of actuators 113, a supply port 1111, and four discharge ports 1112 are arranged in the opening of the frame member 112. In addition, when the liquid ejection head 1 is a circulation type, Figure 2 The discharge port 1112 is shown, but in the case of non-circulation type, no Figure 2 Exhaust port 1112 is shown.

[0030] A pair of actuators 113 are bonded to the mounting surface of substrate 111. A pair of actuators 113 are arranged in two rows on substrate 111, sandwiching supply port 1111 between them. Actuators 113 are formed into a plate shape that is elongated in one direction. Actuators 113 are positioned within the opening of frame member 112 and bonded to the main surface of substrate 111.

[0031] like Figures 1 to 3 As shown, actuator 113 includes: a plurality of pressure chambers 1131 arranged at equal intervals in the longitudinal direction; and a plurality of air chambers 1132 arranged at equal intervals in the longitudinal direction and disposed between adjacent pressure chambers 1131. In other words, in actuator 113, a plurality of pressure chambers 1131 and a plurality of air chambers 1132 are alternately arranged in the longitudinal direction.

[0032] The surface of the actuator 113 opposite the substrate 111 is bonded to the nozzle plate 114. The actuator 113 is formed with multiple grooves 1133 arranged at equal intervals in the longitudinal direction and extending in a direction perpendicular to the longitudinal direction. These grooves 1133 form multiple pressure chambers 1131 and multiple air chambers 1132. Specifically, the grooves 1133 include multiple pressure grooves constituting the multiple pressure chambers 1131 and multiple air grooves constituting the multiple air chambers 1132. In other words, the actuator 113 includes multiple piezoelectric bodies 1134, which are driving elements arranged at equal intervals in the longitudinal direction and form the walls between which the grooves 1133 are formed. These piezoelectric bodies 1134 form multiple pressure chambers 1131 and multiple air chambers 1132 between adjacent piezoelectric bodies 1134. Application of a driving voltage causes the volume of the pressure chambers 1131 to change.

[0033] For example, the width of the actuator 113 in the short-side direction gradually increases from the top side fixed to the nozzle plate 114 toward the substrate 111 side. The cross-sectional shape of the actuator 113, taken along a direction perpendicular to the long-side direction (the short-side direction), is trapezoidal. In other words, the side surfaces of the actuator 113 in the short-side direction are inclined at a predetermined angle.

[0034] As a specific example, Figure 3 As shown, the actuator 113 is formed by a stacked piezoelectric component, which is formed by bonding two rectangular plates of piezoelectric material 1135 that are long in one direction so that their polarization directions are opposite to each other. Here, the piezoelectric material 1135 is, for example, PZT (lead zirconate titanate). The actuator 113 is bonded to the mounting surface of the substrate 111 using, for example, a thermosetting epoxy adhesive. The actuator 113 is formed with an inclined surface, for example, by cutting. In addition, the substrate 111 and the actuator 113 are simultaneously ground, for example, by grinding the surface on which the multiple individual electrodes 118 and the common electrode 119 of the electrode 115 are patterned, to form a ground surface. For example, the ground surface is formed on the inclined surface of the actuator 113 and the substrate 111 that is the base of the inclined surface. The actuator 113 has a plurality of grooves 1133 formed by cutting, for example, to form a plurality of pressure chambers 1131 and a plurality of air chambers 1132 , and also has a piezoelectric body (driving element) 1134 as a side wall separating adjacent grooves 1133 .

[0035] Furthermore, the actuator 113 is provided with wiring patterns that form part of the plurality of individual electrodes 118 and wiring patterns that form part of one or more common electrodes 119 .

[0036] The pressure chamber 1131 deforms during printing or other operations of the liquid ejection head 1, ejecting ink from the nozzle 1141. The pressure chamber 1131 is formed so that the openings in the short-side direction of the actuator 113 each open into the common liquid chamber 116, allowing ink to flow in and out of the pressure chamber 1131.

[0037] Air chamber 1132 is separated from common liquid chamber 116 by blocking both sides of the air groove formed in actuator 113 along its longitudinal direction with resin walls, or liquid-repellent walls 1136, made of a photosensitive resin or the like. Specifically, liquid-repellent walls 1136 of air chamber 1132 are formed by injecting a UV-curable resin into the groove forming air chamber 1132 and then irradiating necessary portions, such as the ends of groove 1133 adjacent to common liquid chamber 116, with UV light using a mask or the like. These liquid-repellent walls 1136 prevent ink from entering air chamber 1132. Furthermore, liquid-repellent walls 1136 are formed on common electrode 119, which is formed within air chamber 1132 of actuator 113. Furthermore, air chamber 1132 is blocked by nozzle plate 114, and nozzles 1141 are not provided. Therefore, ink does not flow into air chamber 1132.

[0038] The nozzle plate 114 is formed in a plate shape. It is fixed to the main surface of the frame member 112 opposite the substrate 111 using an adhesive or the like. The nozzle plate 114 includes a plurality of nozzles 1141 formed at positions opposing the plurality of pressure chambers 1131. In this embodiment, the nozzle plate 114 includes two nozzle arrays 1142, each of which includes a plurality of nozzles 1141 arranged in a single direction. In other words, the liquid ejection head 1 comprises a one-dimensional nozzle arrangement, with a plurality of pressure chambers 1131 and a plurality of nozzles 1141 corresponding to the plurality of pressure chambers 1131 arranged in a single direction relative to a single actuator 113.

[0039] The electrode 115 is an electrode film (metal film) formed of a metal material into a film shape. Figure 2 as well as Figure 3 As shown, the electrode 115 includes, for example, a plurality of individual electrodes 118 connected to the plurality of pressure chambers 1131 , respectively, and a single or a plurality of common electrodes 119 connected to all or some of the plurality of air chambers 1132 .

[0040] The electrodes 115 are formed on the upper surface of the substrate 111 and the inclined surface of the actuator 113 , and are formed on the bottom surfaces and side surfaces of the plurality of pressure chambers 1131 and the plurality of air chambers 1132 .

[0041] The plurality of individual electrodes 118 apply a driving voltage individually to the electrodes 115 formed on the inner surfaces of the plurality of pressure chambers 1131. When the driving voltage is applied, a voltage is generated between the common electrodes 119 formed on the inner surfaces of the adjacent air chambers 1132, and the piezoelectric body 1134 is deformed. In other words, the plurality of individual electrodes 118 deform each pressure chamber 1131 individually. Figure 2 as well as Figure 3 As shown, individual electrodes 118 are formed by wiring patterns formed on substrate 111, wiring patterns formed on the inclined surface of actuator 113, and wiring patterns formed on the inner surface, i.e., bottom and side surfaces, of pressure chamber 1131. Multiple individual electrodes 118 are connected to circuit substrate 13.

[0042] The common electrode 119 is electrically connected to the electrode 115 formed on the inner surface of the air chamber 1132. Figure 2 as well as Figure 3 As shown, common electrode 119 is formed from a wiring pattern formed on substrate 111 and a wiring pattern formed on actuator 113. Common electrode 119 is a wiring pattern formed over a predetermined area on substrate 111 that avoids the area where individual electrodes 118 are formed, the inclined surface of actuator 113 opposite the inclined surface where individual electrodes 118 are formed, and the bottom and side surfaces of air chambers 1132. Common electrode 119 can also be formed on the surface of substrate 111 opposite the surface where actuator 113 is formed, or on the inner circumferential surface of supply port 1111 of substrate 111. Common electrode 119 is connected to circuit board 13.

[0043] The manifold unit 12 includes a manifold, a top plate, an ink supply tube, and an ink discharge tube. By integrating these components, the manifold unit 12 forms a flow path within it. This flow path supplies ink from the primary side via the supply port 1111 to the common liquid chamber 116, and discharges ink from the common liquid chamber 116 to the secondary side via the discharge port 1112.

[0044] like Figure 1 As shown, the circuit board 13 includes a wiring film 131 having one end connected to a connection portion of the substrate 111 , a driver IC 132 mounted on the wiring film 131 , and a printed wiring board 133 mounted on the other end of the wiring film 131 .

[0045] The circuit substrate 13 applies a driving voltage to the wiring pattern of the actuator 113 through a driving circuit such as a driving IC 132 formed in a driving circuit 139 that includes a plurality of individual electrodes (electrodes) 118 that are electrically and independently connected to each other, thereby driving the actuator 113 to increase or decrease the volume of the pressure chamber 1131 and eject droplets from the nozzle 1141.

[0046] The wiring film 131 is connected to the plurality of individual electrodes 118 and the common electrode 119. For example, the wiring film 131 is an ACF (anisotropic conductive film) fixed to the connection portion of the substrate 111 by thermocompression bonding or other means. For example, multiple wiring films 131 are provided for each head body 11. In this embodiment, two wiring films 131 are connected to each actuator 113. For example, the wiring film 131 is a COF (chip on film) with a driver IC 132 mounted thereon.

[0047] The driver IC 132 is connected to the plurality of individual electrodes 118 and the common electrode 119 via the wiring film 131. Alternatively, the driver IC 132 may be connected to the plurality of individual electrodes 118 and the common electrode 119 not via the wiring film 131 but via other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), or NCP (non-conductive paste).

[0048] For example, Figure 4 As shown, as a driving circuit, the driving IC 132 includes: a delay time generating circuit 135, which generates a first delay time and a second delay time for driving multiple pressure chambers 1131 when a printing trigger is input; a driving waveform generating circuit 136, including multiple driving waveform generating circuits 1361 for generating driving waveforms for driving each pressure chamber 1131; a printing data storage circuit 137, which stores printing data; a waveform distribution circuit 138, which can set which of the multiple driving waveforms is to be distributed to the pressure chamber 1131 corresponding to the nozzle 1141; and a driving circuit 139 as a driving signal output circuit, which outputs driving signals for driving multiple pressure chambers 1131. In addition, the delay time generating circuit 135, the drive waveform generating circuit 136, the print data storage circuit 137, the waveform distribution circuit 138 and the drive circuit 139 can be any structure as long as they are arranged on the circuit substrate 13. For example, they can be a structure in which a part is formed on the drive IC 132 and another part is formed on other structures of the circuit substrate 13, such as the printed wiring substrate 133, etc., or they can be a structure in which the entirety is formed on the circuit substrate 13 other than the drive IC 132.

[0049] For example, upon receiving a print trigger signal, the driver IC 132 generates a drive waveform that changes the voltage of the individual electrodes 118 of the actuator 113, thereby deforming the piezoelectric body 1134 of the corresponding pressure chamber 1131. This changes the volume of the pressure chamber 1131, pressurizing the ink within the pressure chamber 1131 and ejecting the ink from the nozzle 1141.

[0050] Furthermore, the plurality of nozzles 1141 (the plurality of pressure chambers 1131) are grouped into a predetermined number of groups of nozzles 1141. Furthermore, the driver IC 132 outputs a drive waveform with a different drive timing for each of the pre-determined grouped nozzles 1141 in response to a print trigger to drive the pressure chamber 1131. For example, if the plurality of nozzles 1141 are grouped into eight groups, the driver IC 132 sets the drive timing (delay amount) for the print trigger using eight different timings and eight nozzle cycles. Furthermore, the drive timing is determined by the number of periodic nozzles and the sum of the main delay time and the sub-delay time, each of which has a different delay time. Furthermore, the number of groups is not limited to eight; as long as it is two or more, it can be an even or odd number.

[0051] In addition, here, when a plurality of nozzles 1141 are grouped into n groups, when the nozzle 1141 at a specified position is set to the first (reference), the nozzle number of the first nozzle 1141 is set to ni, the nozzle number of the second nozzle 1141 is set to ni+1, the nozzle number of the third nozzle 1141 is set to ni+2, and the nozzle number of the nth nozzle 1141 is set to ni+(n-1), the nozzles 1141 whose number (n-1) is 0 or an even number are set to even-numbered nozzles 1141 (even-numbered nozzles), and the nozzles 1141 whose number (n-1) is an odd number are set to odd-numbered nozzles 1141 (odd-numbered nozzles), as described below.

[0052] The main delay time (first delay time) is one type. The main delay time sets the main delay time of the odd-numbered nozzles 1141 for the even-numbered nozzles 1141, for example. The arrangement direction of the nozzles 1141 is set to a triangular wave shape with a period of 2 nozzles. The main delay time sets the pressure propagation time (AL) so that the odd-numbered nozzles are in reverse phase (opposite phase) with respect to the even-numbered nozzles. The pressure propagation time is the time it takes for the pressure wave to propagate from the rear end to the front end of the pressure chamber 1131. The main delay time prevents a decrease in printing quality caused by crosstalk of the fluid between adjacent nozzles 1141. For example, the main delay time is generated by the first delay time generating circuit 1351 of the delay time generating circuit 135 connected to the individual electrode 118 of the pressure chamber 1131 corresponding to the odd-numbered nozzles 1141. For example, the optimal value of the first delay time is the time when the odd-numbered nozzles 1141 and the even-numbered nozzles 1141 are driven simultaneously, and in the example of this embodiment, as Figure 5 as well as Figure 7 As shown, the optimal time difference is 2.0 μs. Here, since the multiple nozzles 1141 are grouped in an alternating arrangement of odd and even numbers, when the time difference (primary delay time) between adjacent nozzles 1141 is 2.0 μs, variations in ejection velocity caused by structural or fluidic crosstalk between nozzles 1141 can be minimized.

[0053] The secondary delay time (second delay time) is set to a periodic triangular wave shape relative to the arrangement direction of the nozzles 1141. As a specific example, Figure 5 As shown in FIG, for mutually adjacent nozzle numbers, a periodic triangular wave shape of more than three nozzles is set. In this embodiment, the triangular wave shape means that, with respect to the minimum and maximum values ​​of the sub-delay time within the cycle, the minimum value increases monotonically to the maximum value via the intermediate value, and the maximum value decreases monotonically to the minimum value via the intermediate value, the intermediate value has a smaller amplitude than the difference between the maximum value and the minimum value, and the minimum value, the maximum value, and the intermediate value between the minimum value and the maximum value are two consecutive identical values. In addition, as shown in FIG. Figure 5 as well as Figure 7 As shown, the sub-delay time is set for two nozzles 1141 adjacent to each other at the minimum value, and similarly, it is set for two nozzles 1141 adjacent to each other at the maximum value. Furthermore, in the sub-delay time between the maximum value and the minimum value, for example, the same sub-delay amount is set for two adjacent nozzles 1141. For example, the sub-delay time is generated by each second delay time generation circuit 1352 of the delay time generation circuit 135 connected to the individual electrode 118 of the pressure chamber 1131 corresponding to each nozzle 1141.

[0054] As a specific example, Figure 5 as well as Figure 7 As shown, the secondary delay time is set to a period of every eight nozzles 1141, and the secondary delay time is set to, for example, four delay timings. Furthermore, these secondary delay times disperse the delay timings of the eight nozzles 1141 from the two delay timings of the primary delay time to eight delay timings. This reduces the number of pressure chambers 1131 corresponding to the multiple nozzles 1141 driven simultaneously, thus reducing instantaneous current, reducing voltage drop, and preventing degradation in print quality.

[0055] like Figure 5 As shown in FIG. 1 , the sub-delay time is set to form a triangular wave shape with respect to the arrangement direction of the nozzles 1141, and the difference between the delay times of adjacent nozzles 1141 is minimized. Specifically, the sub-delay time is set to form a triangular wave shape to prevent the four delay timings from being partially discontinuous with respect to the arrangement direction of the nozzles 1141, forming a sawtooth wave shape and thereby causing density unevenness.

[0056] For example, the secondary delay time is a delay time that is less than 0.1 times the pressure propagation time (AL). Figure 7As shown, for a period of 8 nozzles and a time difference of 0.1 μs in the sub-delay time, the minimum delay time for each nozzle 1141 is 0 μs, and the maximum delay time is 0.3 μs. For example, the sub-delay time (second delay time) for nozzles 1, 9, ..., 1+8n is 0.2 μs, the sub-delay time for nozzles 2, 10, ..., 2+8n is 0 μs, the sub-delay time for nozzles 3, 11, ..., 3+8n is 0 μs, the sub-delay time for nozzles 4, 12, ..., 4+8n is 0.1 μs, the sub-delay time for nozzles 5, 13, ..., 5+8n is 0.1 μs, the sub-delay time for nozzles 6, 14, ..., 6+8n is 0.3 μs, the sub-delay time for nozzles 7, 15, ..., 7+8n is 0.3 μs, and the sub-delay time for nozzles 8, 16, ..., 8+8n is 0.2 μs. Thus, each sub-delay time, from the minimum sub-delay time to the maximum sub-delay time, is set to the same time for two adjacent nozzles 1141. Sub-delay times other than the minimum and maximum values ​​are set by the time difference between the minimum and maximum values, and vice versa. Note that, here, "0.1 times or less" numerically includes 0 μs, but due to the structural reasons of the drive circuit, sub-delay times are used to avoid current concentration and electrical crosstalk during simultaneous driving, and therefore do not include 0. The lower limit is the time required for the current charge and discharge waveforms to fully decrease. Therefore, as an example of the lower limit, 0.05 μs (0.05 times AL) may be used. However, for simplicity of explanation, the lower limit of the sub-delay time is assumed to be 0 μs.

[0057] Furthermore, as the driving timing, the delay time in each nozzle 1141 is set by the sum of the main delay time and the sub-delay time for each group, so that Figure 6 As shown in the figure, the delay time is dispersed into eight timings: 0μs, 0.1μs, 0.2μs, 0.3μs, 2.0μs, 2.1μs, 2.2μs, and 2.3μs. Moreover, the delay time is 2.2μs, 0μs, 2.0μs, 0.1μs, 2.1μs, 0.3μs, 2.3μs, and 0.2μs in the order of nozzle numbers 1 to 8, effectively reducing the concentration of current when driving simultaneously. Moreover, as Figure 7 As shown, the time difference with the adjacent nozzle 1141 is in the range of 1.8μs to 2.2μs. Compared with the main delay time of 2μs of the adjacent nozzle 1141, the sub delay time is -0.2μs to 0.2μs, which can maintain the effect of reducing crosstalk.

[0058] That is, adjacent nozzles 1141 are relative to Figure 7The optimal time difference between even-numbered and odd-numbered nozzles 1141 (main delay time, 2.0 μs) is set within a range of ±0.2 μs to minimize variations in ejection speed caused by crosstalk. Furthermore, since the time difference between adjacent nozzles 1141 does not vary significantly, density variations between adjacent nozzles 1141 are minimized.

[0059] Thus, if a print trigger signal is received, the driver IC 132 including the driver circuit prints each nozzle 1141 in a predetermined group according to the Figure 5 as well as Figure 7 The optimal time difference between the even and odd nozzles 1141 is shown as the main delay time of the triangular wave shape and Figure 5 as well as Figure 7 The triangle-shaped secondary delay time shown in Figure 6 The driver IC 132 generates drive waveforms at different drive timings (delay times) as shown. The driver IC 132 then generates drive waveforms for the individual electrodes 118 corresponding to each nozzle 1141 at different drive timings and applies the drive waveforms to the individual electrodes 118 of the corresponding pressure chambers 1131. Specifically, the driver IC 132 deforms the piezoelectric elements 1134 of the corresponding pressure chambers 1131 at different drive timings, thereby changing the volume of the corresponding pressure chambers 1131 and causing ink to be ejected.

[0060] The printed wiring board 133 is a PWA (Printing Wiring Assembly) on which various electronic components and connectors are mounted.

[0061] In the liquid ejection head 1 thus constructed, the driver IC 132 receives the print trigger signal and prints each nozzle 1141 in a predetermined group according to the Figure 5 as well as Figure 7 The optimal time difference between the even-numbered and odd-numbered nozzles 1141 is shown as the triangular-wave main delay time and the triangular-wave sub-delay time. Figure 6 The drive waveforms based on the print data are generated at different drive timings (delay times) as shown. The driver IC 132 then applies the drive waveforms to the individual electrodes 118 corresponding to the nozzles 1141 at the different drive timings. In this way, as a control method, the driver circuit of the driver IC 132 controls the drive of the pressure chambers 1131 of the actuator 113 at different drive timings.

[0062] That is, the driver IC 132 deforms the piezoelectric body 1134 of the corresponding pressure chamber 1131 at different drive timings, thereby changing the volume of the corresponding pressure chamber 1131 and ejecting the ink. Moreover, the liquid ejection head 1 can minimize the deviation of the ejection speed caused by crosstalk between the nozzles 1141 in the structure or fluid by setting the main delay time between adjacent nozzles 1141 to the optimal time difference. In addition, the liquid ejection head 1 sets the sub-delay time to a triangular wave with a certain period relative to the adjacent nozzle number, and sets the drive timing of the delay time (drive timing) of the adjacent nozzles 1141 within the range of ±0.2μs relative to the main delay time (2.0μs), thereby reducing the deviation of the ejection speed caused by crosstalk. In addition, the time difference between adjacent nozzles 1141 does not change greatly, so the occurrence of uneven concentration between adjacent nozzles 1141 can be suppressed. That is, as Figure 8 As in the prior art shown in FIG, if the delay time is relative to the arrangement direction of the nozzles, a discontinuous portion relative to the arrangement direction of the nozzles 1141 is generated (see FIG. Figure 8 If the range dc) is changed to a sawtooth wave, the time difference between the adjacent nozzles will change greatly, resulting in uneven concentration between adjacent nozzles. Figure 8 Compared with the discontinuous (sawtooth-shaped) delay time of the prior art with respect to the arrangement direction of the nozzles, the delay time of the liquid ejection head 1 with the one-dimensional nozzle arrangement of this embodiment with respect to the arrangement direction of the nozzles 1141 is as shown in FIG. Figure 6 Since the structure shown here is a triangular wave, the liquid ejection head 1 can suppress the occurrence of density unevenness.

[0063] According to the liquid ejection head 1 of the embodiment described above, the pressure chambers 1131 (piezoelectric elements 1134) are driven and controlled for the grouped nozzles 1141 at different drive timings for each group, with the primary delay time set to an optimal time difference and the secondary delay time set to a triangular wave pattern. This allows the liquid ejection head 1 to suppress concentration unevenness by minimizing the difference in delay time between adjacent nozzles 1141.

[0064] Below, refer to Figure 9 The following describes a liquid ejection device 2 having a liquid ejection head 1. The liquid ejection device 2 is an inkjet recording device that ejects ink. The liquid ejection device 2 includes a housing 2111, a medium supply unit 2112, an image forming unit 2113, a medium discharge unit 2114, a transport device 2115 serving as a support device, a temperature control device 2116, a maintenance device 2117, and a control unit 2118. The liquid ejection device 2 also includes a temperature control device that adjusts the temperature of the ink supplied to the liquid ejection head 1.

[0065] The liquid ejection device 2 is an inkjet printer, which performs image formation processing on the paper P by transporting a recording medium such as paper P as the ejection object along a prescribed conveying path 2001 from the medium supply section 2112 through the image forming section 2113 to the medium discharge section 2114 while ejecting liquid such as ink.

[0066] The medium supply unit 2112 includes a plurality of paper cassettes 21121. The image forming unit 2113 includes a support unit 2120 for supporting paper and a plurality of head units 2130 disposed above the support unit 2120 to face each other. The medium discharge unit 2114 includes a discharge tray 21141.

[0067] The support section 2120 includes a conveyor belt 21201 provided in an endless shape in a predetermined area where image formation is performed; a support plate 21202 supporting the conveyor belt 21201 from the back side; and a plurality of belt rollers 21203 provided on the back side of the conveyor belt 21201 .

[0068] The head unit 2130 includes a liquid ejection head 1 as a plurality of inkjet heads, a plurality of supply tanks 2132 as liquid tanks respectively mounted on each of the liquid ejection heads 1, a pump 2134 for supplying ink, and a connecting flow path 2135 connecting the liquid ejection head 1 and the supply tank 2132.

[0069] In this embodiment, the liquid ejecting heads 1 include four colors of cyan, magenta, yellow, and black, and four color supply tanks 2132 for storing inks of these colors. The supply tanks 2132 are connected to the liquid ejecting heads 1 via connection channels 2135 .

[0070] The pump 2134 is a liquid delivery pump composed of, for example, a piezoelectric pump, and is connected to the control unit 2118 and driven and controlled by the control unit 2118 .

[0071] The connecting flow path 2135 includes a supply flow path connected to the ink supply tube of the liquid ejecting head 1. Furthermore, the connecting flow path 2135 includes a recovery flow path connected to the ink discharge tube of the liquid ejecting head 1. For example, if the liquid ejecting head 1 is a non-circulating type, the recovery circuit is connected to the maintenance device 2117, while if the liquid ejecting head 1 is a circulating type, the recovery flow path is connected to the supply tank 2132.

[0072] The transport device 2115 transports paper P along a transport path 2001, from the paper feed cassette 21121 of the medium supply unit 2112, through the image forming unit 2113, to the delivery tray 21141 of the medium delivery unit 2114. The transport device 2115 includes a plurality of guide plate pairs 21211 to 21218 and a plurality of transport rollers 21221 to 21228 arranged along the transport path 2001. The transport device 2115 supports the paper P so that it can move relative to the liquid ejecting head 1.

[0073] The temperature control device 2116 includes a temperature-controlled water tank 21161, a temperature-controlled circuit 21162 for supplying temperature-controlled water, such as piping and tubes, a pump for supplying temperature-controlled water, and a thermostat for adjusting the temperature of the temperature-controlled water. The temperature control device 2116 supplies the temperature-controlled water from the temperature-controlled water tank 21161, which has been adjusted to a predetermined temperature by the thermostat, via the temperature-controlled circuit 21162 to the temperature-controlled water supply pipe of the liquid ejection head 1. Furthermore, the temperature control device 2116 recovers water discharged from the temperature-controlled water discharge pipe via the manifold unit 12 via the temperature-controlled circuit 21162 and returns it to the temperature-controlled water tank 21161. The thermostat is, for example, a heater or a cooler. Alternatively, the temperature control device 2116 may be configured to adjust the temperature of the ink supplied to the liquid ejection head 1.

[0074] The maintenance device 2117, for example, suctions and recovers ink remaining on the outer surface of the nozzle plate 114 during maintenance. Furthermore, if the liquid ejecting head 1 is a non-circulating type, the maintenance device 2117 recovers ink within the head body 11 during maintenance. Such a maintenance device 2117 includes a tray or tank for storing the recovered ink.

[0075] The control unit 2118 includes: a CPU 21181 as an example of a processor; memories such as a ROM (Read Only Memory) for storing various programs, a RAM (Random Access Memory) for temporarily storing various variable data, image data, etc.; and an interface unit for inputting data from the outside and outputting data to the outside.

[0076] According to the liquid ejection device 2 of the embodiment described above, the pressure chamber 1131 is driven and controlled at different drive timings for each group of grouped nozzles 1141, with the primary delay time set to an optimal time difference and the secondary delay time set to a triangular wave shape. As a result, the liquid ejection head 1 can suppress large variations in drive timing between adjacent nozzles 1141, thereby suppressing the occurrence of concentration unevenness.

[0077] Furthermore, the embodiments of the present invention are not limited to the above-described structure. For example, in the above-described example, the liquid ejecting head 1 is provided with a pair of head bodies 11, but the present invention is not limited thereto; a structure having a single head body 11 is also possible. Furthermore, in the above-described example, the actuator 113 of the liquid ejecting head 1 is described as a shared type, but the present invention is not limited thereto; the actuator may also be a stacked type.

[0078] According to at least one embodiment of the liquid ejection head described above, the pressure chambers 1131 (piezoelectric elements 1134) are driven and controlled for the grouped nozzles 1141 at different drive timings for each group, with the primary delay time set to an optimal time difference and the secondary delay time set to a triangular wave pattern. This allows the liquid ejection head 1 to suppress concentration unevenness by minimizing the difference in delay time between adjacent nozzles 1141.

[0079] While several embodiments of the present invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are intended to be within the scope and spirit of the invention and are encompassed by the invention set forth in the claims and their equivalents.

Claims

1. A liquid ejection head, characterized in that: have: an actuator having a plurality of pressure chambers formed therein, wherein the volumes of the plurality of pressure chambers are variable; a nozzle plate formed with a plurality of nozzles corresponding to the plurality of pressure chambers; a plurality of electrodes, corresponding to the plurality of pressure chambers respectively; as well as a driving circuit electrically and independently connected to the plurality of electrodes, generating a driving waveform for driving the pressure chamber for the plurality of electrodes; The driving timing of the driving waveform is set by the sum of the first delay time and the second delay time. The first delay time and the second delay time are periodic triangular wave-shaped with respect to the arrangement direction of the nozzles, and the number of nozzles and the delay time are different in the periodicity.

2. The liquid ejection head according to claim 1, wherein The first delay time is the delay time of the pressure propagation time (AL), and is the cycle of 2 nozzles.

3. The liquid ejection head according to claim 1, wherein The second delay time is a delay time that is 0.1 times or less of the pressure propagation time (AL) and is a cycle of three or more nozzles.

4. A liquid ejection device, characterized in that: A liquid ejecting head according to claim 1 or 2.

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