JP7028026B2 - Liquid discharge device - Google Patents

Description

The present invention relates to a liquid discharge device.

Conventionally, there has been known a liquid discharge device that discharges a liquid from a nozzle of a liquid discharge head by supplying a drive signal having a predetermined waveform to the liquid discharge head in each of continuous recording cycles. In this liquid discharge device, when the interval of the discharge timing for discharging the liquid from the nozzle is constant, if one recording cycle is longer than the length of the drive signal, the desired amount of liquid is discharged from the nozzle in each recording cycle. Can be made to.

On the other hand, there is a liquid discharge device of this type configured so that the discharge timing can be adjusted. For example, Patent Document 1 describes the following inkjet printer.

In the inkjet printer of Patent Document 1, printing is performed on recording paper (recorded medium) by ejecting ink from an inkjet head (liquid ejection head) mounted on the carriage while reciprocating the carriage along the scanning direction. ing. In this inkjet printer, the recording paper is pressed against the surface of a platen having a plurality of ribs arranged at equal intervals in the scanning direction by a plurality of corrugated plates or a plurality of corrugated spurs, so that the recording paper is placed on the inkjet head side. The protruding peaks and the recessed valleys on the opposite side of the inkjet head form a wavy shape that alternates along the scanning direction.

Therefore, in Patent Document 1, if the ink is ejected at the same ejection timing as when the recording paper does not have a wavy shape, the ink landing on the recording paper is displaced in the landing position, which leads to deterioration of image quality. Further, at this time, the amount of ink landing position deviation differs for each part of the recording paper. Therefore, in Patent Document 1, in order to land the ink at an appropriate landing position on the recording paper, the ejection timing is adjusted according to the gap between the ejection surface and each peak portion and valley portion of the recording paper. ..

In order to adjust the discharge timing in this way, it is necessary to further secure a period for adjusting the discharge timing within each recording cycle.

Japanese Unexamined Patent Publication No. 2013-223961

By the way, in order to enable multi-gradation image recording, it is necessary to provide a plurality of types of drive signals in which the discharge amounts of the liquids discharged from the nozzles are different from each other as the drive signals. Here, in general, it is necessary to lengthen the drive signal in order to increase the discharge amount of the liquid. Therefore, if the drive signal is lengthened in order to increase the discharge amount of the liquid, the period during which the discharge timing can be adjusted becomes short in each recording cycle, which limits the adjustment of the discharge timing. As a result, the image quality of the image may deteriorate. For example, in solid printing or the like, if the amount of liquid discharged in each of a predetermined number or more continuous recording cycles is large, the ejection timing cannot be sufficiently adjusted in each recording cycle, and the dots in each recording cycle cannot be sufficiently adjusted. If the formation position deviates from the ideal formation position, the distance between adjacent dots may widen. In this case, the area of the portion where the dots are not formed on the recording medium is expanded, and the portion becomes conspicuous. It is conceivable to lengthen the recording cycle in order to sufficiently adjust the ejection timing in each recording cycle, but if the length of the recording cycle is lengthened, the processing time required for image recording becomes long. Occurs.

An object of the present invention is to provide a liquid ejection device capable of suppressing deterioration of the image quality of an image recorded on a recording medium.

In order to solve the above problems, the liquid discharge device of the present invention has a liquid discharge head having a discharge surface on which a nozzle for discharging liquid is formed, and the liquid discharge head has the discharge surface with respect to a recording medium. A moving mechanism that moves at least one of the recording medium and the liquid discharge head so as to move relative to each other in a relative movement direction parallel to the data, and a liquid discharged from the nozzle for each of a continuous predetermined recording cycle. A storage unit for storing image data in which a discharge amount is set and a control unit are provided, and the control unit has a signal length for driving the liquid discharge head to discharge liquid from the nozzle. A first drive signal having a plurality of types of drive signals different from each other and having a discharge amount of more than zero, and a second drive signal having a larger discharge amount and longer than the first drive signal as compared with the first drive signal. A plurality of types of drives including a drive signal and a third drive signal having a larger discharge amount than the first drive signal and the second drive signal and longer than the first drive signal and the second drive signal. A signal can be generated, and when an image is recorded on a recording medium, one drive signal is selected from the plurality of types of drive signals for each of the recording cycles based on the image data. Then, while the liquid discharge head is relatively moved in the relative movement direction with respect to the recording medium by the movement mechanism, the drive signal selected for the recording cycle is discharged to the liquid in each of the recording cycles. The discharge timing of supplying the data to the head and selectively discharging the liquid from the nozzles and discharging the liquid from each of the nozzles in the recording cycle is set to the predetermined period within the recording cycle and the recording cycle. On the other hand, when the driving signal selected is determined at any timing within a predetermined period in which the longer the driving signal is, the shorter the driving signal is, and when the driving signal is selected for each of the recording cycles, the recording is performed in the image data. When the discharge amount set for the cycle is the first discharge amount, the first drive signal is selected, and in the image data, the discharge amount set for the recording cycle is the first. When the second discharge amount is larger than the discharge amount, the recording cycle satisfies a predetermined condition belonging to a specific recording cycle group in which the recording cycle in which the second discharge amount is set is continuous by a predetermined number or more. When, the third drive signal is selected for the recording cycle, and when the predetermined condition is not satisfied, the second drive signal is selected for the recording cycle.

In the recording cycle in which the second drive signal is selected, the discharge timing can be adjusted for a shorter period than in the recording cycle in which the first drive signal is selected, so that the discharge timing may not be sufficiently adjusted. Therefore, when the second drive signal is selected for each recording cycle belonging to the specific recording cycle group, the dot formation position formed in each recording cycle deviates from the ideal formation position, so that the dots are formed on the recording medium. The area of the part where is not formed is widened, and that part may be conspicuous. Therefore, in the present invention, when the recording cycle belongs to the specific recording cycle group in which the recording cycle in which the second discharge amount is set is continuous for a predetermined number or more, the third discharge amount is larger than that of the second drive signal. Select the drive signal. As a result, the dots formed in the recording cycle belonging to the specific recording cycle group can be increased, so that even if the dot formation position deviates from the ideal formation position, the dot is not formed on the recording medium. The area of can be reduced. As a result, deterioration of image quality can be suppressed. On the other hand, even when the second discharge amount is set for the recording cycle, the second drive signal is selected when it does not belong to the specific recording cycle group. Since the second drive signal is shorter than the third drive signal, the predetermined period in which the discharge timing can be adjusted is long. Therefore, the difference between the formation position of the dots formed in the recording cycle and the ideal formation position can be reduced.

It is an external perspective view of an inkjet printer. It is a top view of the recording part of FIG. (A) is a sectional view taken along line IIIA-IIIA of FIG. 2, and FIG. 2 (b) is a view of FIG. 2 as viewed from the direction of arrow IIIB. (A) is a sectional view taken along line IVA-IVA of FIG. 2, and (b) is a sectional view taken along line IVB-IVB of FIG. (A) is a block diagram showing an electrical configuration of an inkjet printer, (b) is a diagram showing image data, and (c) is a diagram illustrating a drive signal to be selected for each recording cycle. It is a flowchart which shows the flow of the process at the time of recording. (A) is a plan view of an inkjet head, (b) is an enlarged view of part A of (a), and (c) is a sectional view taken along line BB of (b). It is a figure which shows 5 kinds of drive signals. It is a figure explaining the adjustment of the discharge timing. (A) is a flowchart showing the flow of a selection process for selecting a drive signal, and (b) is a flowchart showing the flow of a discharge timing determination process for determining a discharge timing. (A) is a diagram for explaining a partial region, and (b) is a flowchart showing the flow of selection processing according to the second embodiment. (A) is a diagram for explaining a drive signal to be selected for each recording cycle according to the third embodiment, and (b) is a flowchart showing a flow of selection processing according to the third embodiment. It is a flowchart which shows the flow of the selection process which concerns on 4th Embodiment. (A) is a diagram showing a medium ball discharge signal, (b) is a diagram showing an adjustment discharge signal 1, (c) is a diagram showing an adjustment discharge signal 2, and (d) is a diagram showing a large ball discharge signal. It is a figure which shows the signal, (e) is a figure explaining the selection process of the drive signal which concerns on modification 1. (A) is a flowchart showing the flow of the selection process according to the modification of the third embodiment, and (b) is the flowchart showing the flow of the discharge timing determination process according to the modification of the third embodiment. It is a flowchart which shows the flow of the discharge timing determination process which concerns on the modification of 1st Embodiment.

(First Embodiment)
<Overall configuration of printer>
The printer 1 (“liquid ejection device” of the present invention) according to the first embodiment can record an image on the paper S (“recorded medium” of the present invention) and can also read an image. It is a so-called multifunction device. As shown in FIG. 1, the printer 1 includes a recording unit 2 (see FIG. 2), a feeding unit 3, a discharging unit 4, a reading unit 5, an operating unit 6, a display unit 7, and the like. Further, the operation of the printer 1 is controlled by the control device 50 (see FIG. 5A).

The recording unit 2 is provided inside the printer 1 and records an image on the paper S. The recording unit 2 will be described in detail later. The feeding unit 3 is a part for feeding the paper S to the recording unit 2. The feeding unit 3 can accommodate a plurality of types of paper S having different sizes, and selectively feeds any one of the plurality of types of paper S to the recording unit 2. The ejection unit 4 is a portion where the paper S on which the image is recorded by the recording unit 2 is ejected. The reading unit 5 is a scanner or the like, and reads a document. The operation unit 6 includes buttons and the like, and the user performs necessary operations on the printer 1 by operating the buttons of the operation unit 6. The display unit 7 is a liquid crystal display or the like, and displays information necessary for using the printer 1.

Next, the recording unit 2 will be described. As shown in FIGS. 2 to 4, the recording unit 2 includes a carriage 11, an inkjet head 12 (“liquid discharge head” of the present invention), a transport roller pair 13, nine plate 14, platen 15, and eight discharge roller pairs. It is equipped with 16, 9 spurs 17, an encoder 18, and the like. However, in FIG. 2, in order to make it easier to see the plate 14, the rib 20 described later, and the like, the carriage 11 is shown by a two-dot chain line, and is actually arranged below the carriage 11 which is hidden behind the carriage 11 and cannot be seen. The members are shown by solid lines. Further, in FIG. 2, the guide rails and the like that support the carriage 11 are not shown.

The carriage 11 (“moving mechanism” of the present invention) is movably supported along a scanning direction (left-right direction) by a guide rail (not shown). The carriage 11 is connected to a carriage motor 56 (see FIG. 5A) via a belt or the like (not shown), and when the carriage motor 56 is driven, the carriage 11 reciprocates with the left-right direction as the scanning direction.

The inkjet head 12 is mounted on the carriage 11 and reciprocates in the scanning direction together with the carriage 11. Further, the inkjet head 12 ejects ink from a plurality of nozzles 10 formed on the ink ejection surface 12a which is the lower surface thereof. The plurality of nozzles 10 form a nozzle row 9 by being arranged along a transport direction (front-back direction) orthogonal to the scanning direction. Further, the inkjet head 12 has four nozzle rows 9 arranged in the scanning direction. Then, black, yellow, cyan, and magenta inks are ejected from the plurality of nozzles 10 in order from the one forming the nozzle row 9 on the right side. The inkjet head 12 is connected to an ink cartridge (not shown) via a tube (not shown) or the like, and the ink stored in the ink cartridge is supplied to the inkjet head 12. The ink ejection surface 12a is a horizontal plane parallel to the scanning direction and the conveying direction. The detailed configuration of the inkjet head 12 will be described later.

The transport roller pair 13 is arranged on the upstream side in the transport direction with respect to the inkjet head 12. The transport roller pair 13 has an upper roller 13a and a lower roller 13b, and these rollers nip the paper S fed from the feeding unit 3 from the vertical direction and transport the paper S in the transport direction. The upper roller 13a is a drive roller driven by a transfer motor 57 (see FIG. 5A). The lower roller 13b is a driven roller that rotates in conjunction with the rotation of the upper roller 13a.

The nine plates 14 extend from a position overlapping the transport roller pair 13 to a position downstream of the transport roller pair 13 in the transport direction, and are arranged at equal intervals in the scanning direction. Each plate 14 has a pressing portion 14a at an end on the downstream side in the transport direction, and the paper S is pressed from above by the pressing portion 14a.

The platen 15 is arranged on the downstream side of the transport roller pair 13 in the transport direction so as to face the ink ejection surface 12a. The platen 15 extends in the scanning direction over the entire length of the movement range of the carriage 11 when recording an image. Eight ribs 20 are formed on the upper surface of the platen 15. The eight ribs 20 are evenly spaced so that each extends in the transport direction and is located between adjacent plates 14 in the scanning direction. The rib 20 supports the paper S from below.

Here, the upper end of the rib 20 is located above the pressing portion 14a. As a result, the rib 20 supports the paper S from below at a position above the position where the holding portion 14a holds the paper S.

The eight sets of discharge roller pairs 16 are arranged on the downstream side in the transport direction with respect to the inkjet head 12. Further, the position of the discharge roller pair 16 in the scanning direction is substantially the same as that of the rib 20. Each discharge roller pair 16 has an upper roller 16a and a lower roller 16b, and these rollers receive the paper S from the transport roller pair 13, nip the paper S from the vertical direction, and further transport the paper S in the transport direction. do. Further, the discharge roller pair 16 discharges the paper S toward the paper discharge tray 31b. The lower roller 16b is a drive roller driven by a transfer motor 57 (see FIG. 5A). The upper roller 16a is a spur, and is a driven roller that rotates in conjunction with the rotation of the lower roller 16b. Here, the upper roller 16a comes into contact with the recording surface of the paper S after recording the image, but the upper roller 16a is not a roller having a flat outer peripheral surface but a spur, so that ink on the paper S is less likely to adhere. ..

The nine spurs 17 are arranged on the downstream side of the discharge roller pair 16 in the transport direction and hold the paper S from above. Further, the positions of the nine spurs 17 in the scanning direction are substantially the same as the holding portions 14a of the nine plates 14. Further, since the spur 17 is not a roller having a flat outer peripheral surface but a spur, ink on the paper S is unlikely to adhere to the spur 17.

The number of plates 14 and discharge roller pairs 16 and the number of ribs 20 and spurs 17 are examples, and these numbers may be different from the above. The number of plates 14 and discharge roller pairs 16, as well as ribs 20 and spurs 17 may be at least one each.

Then, the paper S is supported from below by eight ribs 20 and eight lower rollers 16b, and is bent by being pressed from above by the holding portions 14a of the nine plates 14 and the nine spurs 17, and is bent in FIG. 3 (a). ) And (b), it has a wave shape along the scanning direction.

Further, in the corrugated paper S, the position where each rib 20 and the discharge roller pair 16 are arranged is a mountain peak Pt having a maximum height in the scanning direction. Further, on the paper S, the position where the holding portion 14a and the spur 17 of each plate 14 are arranged is the valley apex Pb where the height is the minimum in the scanning direction. That is, in the paper S, the mountain portion protruding toward the ink ejection surface 12a centering on the peak Pt and the valley portion recessed from the peak portion centered on the valley vertex Pb and recessed away from the ink ejection surface 12a alternate. It has a wave shape that is lined up. In the present embodiment, the combination of eight ribs 20, eight lower rollers 16b, nine plates 14, and spurs 17 corresponds to the "wave shape generation mechanism" of the present invention.

The encoder 18 is mounted on the carriage 11 and outputs a signal indicating the position of the carriage 11 (inkjet head 12) in the scanning direction to the control device 50.

Next, the electrical configuration of the printer 1 will be described. The operation of the printer 1 is controlled by the control device 50. As shown in FIG. 5A, the control device 50 includes an ASIC (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a flash memory 54, and various control circuits. Application Specific Integrated Circuit) 55 and the like are provided. An inkjet head 12, a carriage motor 56, a transfer motor 57, and the like are electrically connected to the ASIC 55.

The ROM 52 stores programs executed by the CPU 51, various fixed data, and the like. The RAM 53 temporarily stores data necessary for executing the program, image data IM to be recorded, and the like. The delay time information GI, which will be described later, is stored in the flash memory 54.

The control device 50 controls the inkjet head 12, the feeding unit 3, the carriage motor 56, the transport motor 57, and the like to perform various processes. In the control device 50, only the CPU 51 may perform various processes, only the ASIC 55 may perform various processes, or the CPU 51 and the ASIC 55 cooperate with each other to perform various processes. It may be a thing. Further, the control device 50 may be one in which one CPU 51 performs processing independently, or may be one in which a plurality of CPUs 51 share the processing. Further, in the control device 50, one ASIC 55 may perform the processing independently, or a plurality of ASICs 55 may share the processing.

Hereinafter, the processing performed by the control device 50 when recording an image on the paper S will be described.

As shown in FIG. 6, the control device 50 controls the feeding unit 3 to execute a paper feeding process for supplying the paper S to the recording unit 2 (S1). In this paper feed process, the paper S is conveyed to the recording start position. The recording start position is a position where the first region of the paper S on which an image is recorded and the ink ejection surface 12a of the inkjet head 12 face each other. Subsequently, the control device 50 executes the recording process (S2). In the recording process, the control device 50 controls the carriage motor 56 to move the carriage 11 in the scanning direction, and controls the inkjet head 12 to eject ink from a plurality of nozzles 10 at a predetermined ejection timing. By doing so, the image is recorded on the paper S. In this embodiment, the moving speed of the carriage 11 in the recording path is a constant speed. Further, in the following, for convenience, in the recording process, ink is ejected from a plurality of nozzles 10 only when the carriage 11 is moved to one side in the scanning direction (in the present embodiment, the right side) to perform the recording pass. It is described as a thing, but is not limited to this. That is, when moving the carriage 11 to either one side or the other side in the scanning direction, ink may be ejected from a plurality of nozzles 10 to perform the recording pass.

Subsequently, the control device 50 executes the transfer process (S3). In the transport process, the control device 50 controls the transport motor 57 to cause the transport roller pair 13 and the discharge roller pair 16 to perform a transport operation of transporting the paper S by a predetermined transport amount. Then, when the recording of the image on the paper S is not completed (S4: NO), the process returns to S2. As a result, the recording path and the conveying operation are alternately repeated until the recording of the image on the paper S is completed.

When the recording of the image on the paper S is completed (S4: YES), the control device 50 executes the paper ejection process (S5). In the paper ejection process, the control device 50 controls the conveyor motor 57. , The paper S is discharged to the paper discharge unit 4 by the transport roller pair 13 and the discharge roller pair 16.

(Detailed configuration of inkjet head)
Next, the inkjet head 12 will be described in detail. As shown in FIG. 7A, the inkjet head 12 includes a flow path structure 81 in which a plurality of nozzles 10 and a plurality of pressure chambers 83 communicating with the plurality of nozzles 10 are formed, and a flow path structure 81. It is provided with a piezoelectric actuator 86 arranged on the upper surface.

As shown in FIG. 7 (c), the flow path structure 81 has a structure in which four plates are laminated. A plurality of nozzles 10 are formed on the lower surface of the flow path structure 81. As shown in FIG. 7A, the plurality of nozzles 10 are arranged in the transport direction, forming four rows of nozzles corresponding to the four colors of ink, respectively. The plurality of pressure chambers 83 are arranged in four rows like the plurality of nozzles 10.

Further, as shown in FIGS. 7A and 7B, four manifolds 84 extending in the transport direction are formed in the flow path structure 81, respectively. The four manifolds 84 supply four colors of ink to each of the four rows of pressure chambers. Further, the four manifolds 84 are connected to four ink supply holes 85 formed on the upper surface of the flow path structure 81. Ink of four colors is supplied to each of the four ink supply holes 85 from an ink cartridge (not shown). From the above configuration, a plurality of individual flow paths branching from each manifold 84 to the nozzle 10 via the pressure chamber 83 are formed in the flow path structure 81.

As shown in FIG. 7 (c), the piezoelectric actuator 86 corresponds to the diaphragm 87 covering the plurality of pressure chambers 83, the piezoelectric layer 88 arranged on the upper surface of the diaphragm 87, and the plurality of pressure chambers 83. It is provided with a plurality of individual electrodes 89. The plurality of individual electrodes 89 located on the upper surface of the piezoelectric layer 88 are electrically connected to the driver IC 90 that drives the piezoelectric actuator 86, respectively.

The diaphragm 87 located on the lower surface of the piezoelectric layer 88 is made of a metal material and serves as a common electrode facing a plurality of individual electrodes 89 with the piezoelectric layer 88 interposed therebetween. The diaphragm 87 is connected to the driver IC 90 and is always held at the ground potential. Then, the driver IC 90 switches the potential of the individual electrode 89 between a predetermined positive potential (whether) and the ground potential, and ejects ink droplets from the nozzle 10 corresponding to the individual electrode 89.

The operation of the above-mentioned piezoelectric actuator 86 when ejecting ink from the nozzle 10 is as follows. When a predetermined positive potential is applied to a certain individual electrode 89 by the driver IC 90, the vibration plate 87 as a common electrode held at the ground potential with the individual electrode 89 to which the positive potential is applied is 87. A potential difference is generated between the two, and the piezoelectric layer 88 sandwiched between the individual electrode 89 and the vibrating plate 87 is subjected to piezoelectric deformation. The piezoelectric deformation of the piezoelectric layer 88 causes a volume change in the pressure chamber 83, and pressure (discharge energy) is applied to the ink in the pressure chamber 83. At this time, ink droplets are ejected from the nozzle 10 communicating with the pressure chamber 83.

In this embodiment, a predetermined positive potential is applied to the individual electrode 89 in advance, a ground potential is once applied to the individual electrode 89 each time there is a discharge request, and then the positive potential is applied again at a predetermined timing. It is configured to be applied to the individual electrode 89. In this case, the pressure of the ink in the pressure chamber 83 drops at the timing when the individual electrode 89 reaches the ground potential, and the ink is sucked from the manifold 84 into the individual flow path. After that, at the timing when the individual electrode 89 becomes a positive potential again, the pressure of the ink in the pressure chamber 83 rises, and the ink droplets are ejected from the nozzle 10.

Further, the driving of the piezoelectric actuator 86 by the driver IC 90 will be described in detail. When the inkjet head 12 moves in the scanning direction together with the carriage 11, the driver IC 90 has a predetermined waveform for each of the plurality of individual electrodes 89 of the piezoelectric actuator 86 in each of the temporally continuous recording cycles. By supplying the drive signal, the potential of the individual electrode 89 described above is switched. The recording cycle is the time required for the inkjet head 12 to move by a unit distance corresponding to the resolution in the scanning direction.

Here, in the present embodiment, the types of ink ejection amount (ink droplet volume) that can be ejected from the nozzle 10 within one recording cycle are "non-ejection" in which the ejection amount is zero and "non-ejection" in which the ejection amount is zero. There are five types, "extra large ball", "large ball", "medium ball" and "small ball". "Extra large ball", "large ball", "medium ball", and "small ball" have the largest discharge amount in this order.

The driver IC 90 can generate five types of drive signals corresponding to the above five types of discharge amounts as drive signals. Then, the drive signal supplied to the individual electrode 89 in each recording cycle is selected from five types of drive signals. As shown in FIG. 8, the five types of drive signals are composed of a non-discharge signal (a) having no discharge pulse P and four types of discharge signals (b) to (e) having each discharge pulse P. In the recording cycle in which the non-ejection signal is applied to the individual electrode 89, the potential of the individual electrode 89 does not change, so that the ink droplets are not ejected from the nozzle 10.

The four types of discharge signals (b) to (e) are a small ball discharge signal including one discharge pulse P, a medium ball discharge signal including two discharge pulses P, a large ball discharge signal including three discharge pulses P, and a discharge pulse. It consists of an oversized ball ejection signal containing four Ps. The pulse widths of the discharge pulses P of each discharge signal are equal to each other. Further, for the discharge signals having a plurality of discharge pulses P, the intervals between the two consecutive discharge pulses P are equal to each other.

Here, when the ejection pulse P is applied, pressure is applied to the ink in the pressure chamber 83, and the ink droplets are ejected from the nozzle 10. Therefore, the larger the number of ejection pulses P, the larger the ejection amount of ink ejected from the nozzle 10. That is, the amount of ink ejected from the nozzle 10 is large in the order of the extra large ball ejection signal, the large ball ejection signal, the medium ball ejection signal, and the small ball ejection signal.

Further, the lengths of the four types of ejection signals are set to be shorter than the length of the recording cycle. The length of the ejection signal is a sum of the length of time for applying the ejection pulse P and the length of time for suppressing the pressure fluctuation of the ink in the pressure chamber 83 after the output of the ejection pulse P. In the present embodiment, the larger the number of discharge pulses P, the longer the signal length. That is, the length of the signal is longer in the order of the extra large ball discharge signal, the large ball discharge signal, the medium ball discharge signal, and the small ball discharge signal.

In each of the recording cycles, the additional signal having no discharge pulse P is equal to the selected drive signal by subtracting the length of the drive signal from the length of the recording cycle (FIG. 8). It is supplied to the individual electrode 89 with the addition of a one-dot chain line (shown by a chain line). Further, as described above, since the non-discharge signal is a signal having no discharge pulse P, it is a drive signal having a signal length of zero. That is, the non-discharge signal is a signal having only an additional signal. The medium ball discharge signal and the small ball discharge signal correspond to the "first drive signal" of the present invention, the large ball discharge signal corresponds to the "second drive signal", and the extra large ball discharge signal corresponds to the "third drive signal". do.

Next, the configuration of the ASIC 55 of the control device 50 for driving the piezoelectric actuator 86 in the recording process will be described. As shown in FIG. 5A, the ASIC 55 incorporates a waveform data storage circuit 61, a head control circuit 62, and a transfer control circuit 63. The waveform data storage circuit 61 stores waveform data related to each pulse waveform of the above-mentioned five types of drive signals (see FIG. 8) output by the driver IC 90. The head control circuit 62 controls the driver IC 90 of the inkjet head 12 and the carriage motor 56, respectively, based on the image data IM in the recording process of recording an image on the paper S. Similarly, in the recording process, the transfer control circuit 63 controls the transfer motor 57 to transfer the paper S in the transfer direction. Hereinafter, the head control circuit 62 will be described in detail.

The head control circuit 62 performs a selection process for selecting one type of drive signal from five types of drive signals for each nozzle 10 (individual electrode 89) for each recording cycle based on the image data IM. Further, the head control circuit 62 transmits the selection data indicating the drive signal selected in the selection process and the waveform data stored in the waveform data storage circuit 61 to the driver IC 90, and sends the selection data and the waveform data to the driver IC 90. Based on the above, a drive signal generation process for generating a drive signal having a predetermined drive waveform is performed. By supplying this drive signal to the plurality of individual electrodes 89 of the piezoelectric actuator 86, ink is selectively ejected from the plurality of nozzles 10 corresponding to the plurality of individual electrodes 89 in each recording cycle.

Hereinafter, prior to explaining the selection process of the head control circuit 62 in detail, first, the image data IM will be described. As shown in FIG. 5B, the image data IM has a plurality of dot elements D corresponding to a plurality of dots (including non-ejection dots on which the ink does not land) formed on the paper S. Specifically, the image data IM is formed by a plurality of dot elements D arranged in the X and Y directions orthogonal to each other. The X direction and the Y direction correspond to the scanning direction and the transport direction, respectively.

In each dot element D, the amount of ink ejected from the nozzle 10 when forming the corresponding dot is set. Specifically, for each dot element D, among the above-mentioned five types (extra-large ball, large ball, medium ball, small ball, non-ejection) that can be ejected from the nozzle 10 within one recording cycle, the extra-large ball is selected. One of the four types of discharge amount excluding is set. In the image data IM shown in FIG. 5B, each of the four types of discharge amounts set for each dot element D is shown as "00", "01", "10", and "11". There is. "00" corresponds to "non-discharge", "01" corresponds to "small ball", "10" corresponds to "medium ball", and "11" corresponds to "large ball". The "small ball" and "medium ball" set in the dot element D of the image data IM correspond to the "first discharge amount" of the present invention, and the "large ball" corresponds to the "second discharge amount".

Further, the image data IM has raster data L for a plurality of lines. The raster data L for one line means that the plurality of dot elements D for the plurality of dots arranged along the scanning direction on the paper S are the scanning directions of the plurality of dots corresponding to the plurality of dot elements D. It is a dot element sequence arranged in the order according to the arrangement order along. Then, each raster data L corresponds to one nozzle 10. That is, the plurality of dot elements D of the raster data L are dot elements D corresponding to the dots formed by the ink ejected from the corresponding nozzle 10 in each of the continuous recording cycles in the recording process. Therefore, in other words, the raster data L is data in which the ejection amount of the ink ejected from the nozzle 10 is set in each of the continuous recording cycles in the recording process. In FIG. 5 (b) and FIG. 5 (c) to be referred to later, the number attached to the upper side of the raster data L indicates the number of the recording cycle corresponding to the dot element D from the start of the recording process. ing.

In the selection process, the head control circuit 62 selects a drive signal for each of the continuous recording cycles based on the raster data L of the image data IM. Specifically, the head control circuit 62 selects a non-discharge signal for a recording cycle in which the set discharge amount is “non-discharge”, and the head control circuit 62 selects a non-discharge signal for a recording cycle in which the set discharge amount is “small ball”. Selects a small ball ejection signal, and selects a medium ball ejection signal for a recording cycle in which the set ejection amount is "medium ball". Further, the head control circuit 62 basically selects a large ball discharge signal for a recording cycle in which the set discharge amount is “large ball”. However, although the details will be described later, when a predetermined condition is satisfied, an extra-large ball discharge signal is exceptionally selected for a recording cycle in which the set discharge amount is “large ball”. As described above, in the present embodiment, basically, for each recording cycle, one type of drive signal is selected from four types of drive signals: non-discharge signal, small ball discharge signal, medium ball discharge signal, and large ball discharge signal. Select a drive signal.

By the way, in the recording process, since the ink is ejected from the nozzle 10 while the carriage 11 is moving, an inertial force acts on the ink ejected from the nozzle 10. Therefore, the flight direction of the ink is not the direction directly below, but the direction including the component in the moving direction of the carriage 11. Therefore, when attempting to form dots at a certain dot forming position on the paper S, it is necessary to eject ink from the nozzle 10 before the inkjet head 12 reaches directly above the dot forming position. Here, when the carriage 11 moves at a constant speed and the interval between the ejection timings of the ink ejected from the nozzle 10 is constant, when the paper S does not have a wavy shape, the ink landing on the paper S. The positions are evenly spaced.

However, in the present embodiment, as described above, the paper S conveyed to the recording start position has a wavy shape in which the mountain portions and the valley portions are alternately arranged in the scanning direction. Therefore, the distance between the ink ejection surface 12a and the paper S in the vertical direction differs depending on the position of the inkjet head 12 (carriage 11) in the scanning direction. Therefore, in the present embodiment, when the carriage 11 is moved at a constant speed and the ejection timing interval is made constant, as shown in FIG. 9A, the interval between the ink landing positions on the paper S varies. .. That is, the spacing between dots on the paper S varies. Specifically, in the paper S, a downward slope region from the mountain apex Pt of the mountain portion to the valley apex Pb of the valley portion adjacent to the mountain portion on the downstream side in the moving direction of the carriage 11 (the "first" of the present invention. The dot forming region ”) is a region in which the vertical distance between the ink ejection surface 12a and the paper S gradually decreases. Then, the dot spacing in the scanning direction in this downhill slope region is wider than the dot spacing corresponding to the scanning direction resolution (dot spacing when the paper S is not wavy). On the other hand, in the paper S, an ascending slope region from the valley apex Pb of the valley portion to the mountain apex Pt of the mountain portion adjacent to the valley portion on the downstream side in the moving direction of the carriage 11 (the "second dot" of the present invention. The “forming region”) is a region in which the vertical distance between the ink ejection surface 12a and the paper S gradually increases. Then, the spacing between the dots in the scanning direction in this ascending slope region is narrower than the spacing between the dots corresponding to the resolution in the scanning direction.

Therefore, in the present embodiment, the head control circuit 62 also adjusts the ejection timing for ejecting ink from the nozzle 10 so that the intervals between the dots on the paper S are equal. The discharge timing is the timing at which the start point of the drive signal is supplied to the individual electrode 89 when the drive signal is supplied to the individual electrode 89. In each recording cycle, the head control circuit 62 determines the time point at which a predetermined delay time is added to the start time point of the recording cycle as the discharge timing. This delay time adjustment is based on the output of the encoder 18.

Hereinafter, the adjustment of the delay time when forming dots in the downward slope region will be described. In the downhill slope region, the distance between the ink ejection surface 12a and the paper S in the vertical direction becomes longer as the valley apex Pb is approached, and the ink flying time becomes longer. Therefore, when forming dots in the downward slope region, the closer the dot formation position is to the valley apex Pb, the longer the delay time. For example, as shown in FIG. 9B, when dots are formed at each position closer to the valley apex Pb in the order of positions P1, P2, P3, P4 in the downhill slope region, the delay time related to the position P1 is formed. To be the longest. Then, the delay time is gradually shortened in the order of position P2, position P3, and position P3.

On the other hand, the head control circuit 62 shortens the delay time as it approaches the mountain peak Pt in the uphill slope region. As a result, even if the paper S has a wavy shape, dots can be formed at intervals corresponding to the resolution in the scanning direction. This delay time can be determined, for example, based on the reading result when a predetermined test pattern recorded by the recording unit 2 is read by the reading unit 5. The flash memory 54 stores delay time information GI indicating the relationship between each position of the inkjet head 12 in the scanning direction and the determined delay time. Although the details will be described later, the head control circuit 62 determines the ejection timing in each recording cycle based on the position information of the inkjet head 12 output from the encoder 18 and the delay time information GI.

Here, in order to eject a desired amount of ink from the nozzle 10 in each recording cycle, both the start point and the end point of the drive signal supplied to the individual electrode 89 need to be within the recording cycle. Therefore, the maximum time that can be set as the delay time is the time obtained by subtracting the length of the drive signal from the recording cycle (hereinafter referred to as the buffer time). In other words, it is necessary to determine the discharge timing within the period from the start time of the recording cycle to the time when the buffer time has elapsed (hereinafter, the adjustable period). As shown in FIG. 7, the buffer time becomes shorter as the length of the drive signal supplied to the individual electrode 89 becomes longer.

On the other hand, when the paper S has a wavy shape, in order to form dots at intervals corresponding to the scanning direction resolution, the length of the adjustable period, that is, when each drive signal is supplied to the individual electrodes 89, is used. The buffer time must be longer than the required time. As described above, in the present embodiment, basically, one of four types of drive signals, a non-discharge signal, a small ball discharge signal, a medium ball discharge signal, and a large ball discharge signal, is supplied to the individual electrode 89. .. Then, among these four types of drive signals, the buffer time is the shortest when the large ball discharge signal is supplied to the individual electrode 89. Therefore, if the recording cycle is set to be equal to or longer than the length obtained by adding the length of the large ball ejection signal and the required time, it is possible to form dots at intervals corresponding to the scanning direction resolution. However, if the recording cycle is lengthened, the time required for the recording process becomes long, and the throughput decreases.

Therefore, in the present embodiment, in order to improve the throughput, the recording cycle is less than the length obtained by adding the length of the large ball ejection signal and the required time, and the length of the medium ball ejection signal and the required time. It is set to be longer than the length obtained by adding time. Therefore, in the recording cycle in which the large ball ejection signal is supplied to the individual electrodes 89, the adjustment of the ejection timing (adjustment of the delay time) is restricted. As a result, dots cannot be formed at the ideal forming position on the paper S, and the image quality of the image may deteriorate. The ideal formation position is a position where the distance between the dots formed in the previous recording cycle and the dots formed in the current recording cycle corresponds to the scanning direction resolution.

Here, when solid printing or the like is performed, as shown in FIG. 5C, the recording cycle in which the discharge amount of the “large ball” of “11” is set is a predetermined number or more (3 or more in this embodiment). There will be a continuous group of specific recording cycles. If a large ball ejection signal is selected for each of the recording cycles belonging to these specific recording cycle groups, the ejection timing cannot be sufficiently adjusted in these recording cycles, and the dot formation positions formed in each recording cycle are formed. May deviate from the ideal formation position and the spacing between adjacent dots may widen. In this case, the area of the portion where the dots are not formed on the paper S is expanded, and the portion becomes conspicuous. That is, although the image data represents a solid image, the image recorded on the paper S may not be a solid image but may be partially a white background. On the other hand, even in the recording cycle in which the discharge amount of the "large ball" is set, if it does not belong to the specific recording cycle group, even if the formation position of the dots formed in the recording cycle deviates from the ideal formation position. That part is inconspicuous.

Therefore, in the present embodiment, as shown in FIG. 5C, in the raster data L, the head control circuit 62 uses a “large ball” discharge amount of “11” as the discharge amount set for the recording cycle. In some cases, when the recording cycle belongs to the specific recording cycle group, the extra-large ball ejection signal is selected without selecting the large ball ejection signal for the recording cycle. As a result, the size of the dots formed in each recording cycle belonging to the specific recording cycle group can be increased as compared with the case where the large ball ejection signal is selected. Therefore, even if the dot formation position deviates from the ideal formation position, the area of the portion on the paper S where the dots are not formed can be reduced. As a result, deterioration of image quality can be suppressed. On the other hand, even when the discharge amount set for the recording cycle is the discharge amount of the "large ball", when the discharge amount does not belong to the specific recording cycle, the large ball discharge signal is selected. Since the large ball ejection signal has a shorter length than the extra large ball ejection signal, the adjustable period is long, so that the difference between the dot formation position and the ideal formation position formed in the recording cycle can be reduced.

When the discharge amount set for the recording cycle immediately before the specific recording cycle group is zero, the dots formed by the earliest recording cycle among the recording cycles belonging to the specific recording cycle group are the dots of the image. It is likely that the dots form the edges. When the discharge amount set for the recording cycle immediately after the specific recording cycle group is zero, the dots formed by the recording cycle having the latest order among the recording cycles belonging to the specific recording cycle group are the dots of the image. It is likely that the dots form the edges. If the formation position of these dots deviates from the ideal formation position, a step may be generated in the image and the deterioration of the image quality may be noticeable. Therefore, even when the recording cycle belongs to the specific recording cycle group, the head control circuit 62 has a discharge amount set for the recording cycle immediately before the recording cycle and a recording cycle one after the recording cycle. When any of the discharge amounts set for is zero, the large ball discharge signal is selected for the recording cycle.

Hereinafter, the drive signal selection process according to one individual electrode 89 performed by the head control circuit 62 will be described with reference to FIG. 10A. First, the head control circuit 62 sets the variable N to 1 (A1). After that, the head control circuit 62 extracts the discharge amount set for the Nth recording cycle from the raster data L assigned to the nozzle 10 corresponding to the individual electrode 89 (A2). Then, the head control circuit 62 determines whether or not the extracted discharge amount is a "large ball" of "11" (A3). When it is determined that it is not a "large ball" (A3: NO), the drive signal corresponding to the extracted discharge amount is selected for the Nth recording cycle (A4). That is, a non-discharge signal when it is "00" "non-discharge", a small ball discharge signal when it is "01" "small ball", and a medium ball when it is "10" "middle ball". Select each discharge signal. When the processing of A4 is completed, the processing of A9 is started.

When it is determined in the process of A3 that the extracted discharge amount is a "large ball" (A3: YES), the head control circuit 62 has the Nth recording cycle as the specific recording cycle based on the raster data L. It is determined whether or not it belongs to the group (A5). When it is determined that the Nth recording cycle belongs to the specific recording cycle group (A5: YES), it is set for the N-1st recording cycle and the N + 1st recording cycle based on the raster data L. It is determined whether or not any of the discharge amounts is zero (non-discharge) (A6). When it is determined that none of the discharge amounts is zero (A6: NO), the head control circuit 62 selects an oversized ball discharge signal for the Nth recording cycle (A7), and processes A9. Move.

On the other hand, when it is determined in the processing of A5 that the Nth recording cycle does not belong to the specific recording cycle group (A5: NO), or in the processing of A6, the N-1th recording cycle and the N + 1th recording cycle When it is determined that any of the discharge amounts set for is zero (A6: YES), the head control circuit 62 selects a large ball discharge signal for the Nth recording cycle (A8). ), Move on to the processing of A9.

In the process of A9, the head control circuit 62 determines whether or not the selection of the drive signal is completed for all the recording cycles of the raster data L. When it is determined that the selection of the drive signal is not completed (A9: NO), the variable N is updated to [N + 1] (A10), and the process returns to A2. On the other hand, when it is determined that the selection of the drive signal is completed (A9: YES), the selection process is terminated.

Next, the ejection timing determination process for determining the ink ejection timing in a certain recording cycle (hereinafter, attention recording cycle) performed by the head control circuit 62 will be described with reference to FIG. 10B. In the present embodiment, the discharge timing determination process is performed during the recording process.

The head control circuit 62 determines whether or not the drive signal selected for the attention recording cycle is an oversized ball ejection signal (B1). When it is determined that it is an oversized ball ejection signal (B1: YES), the head control circuit 62 determines the ejection timing in the attention recording cycle as the reference ejection timing (B2). The reference discharge timing is a predetermined timing, for example, the start time of the recording cycle. When the processing of B2 is completed, the discharge timing determination processing is completed.

On the other hand, when it is determined in the processing of B1 that the signal is not an oversized ball ejection signal (B1: NO), the head control circuit 62 sets the ejection timing in the attention recording cycle to the dot formation position formed in the attention recording cycle. The adjustment discharge timing is determined by adjusting the reference discharge timing so that the difference between the ideal formation position and the ideal formation position is smaller than the reference discharge timing (B3). Specifically, the head control circuit 62 is formed in the attention recording cycle within the adjustable period of the attention recording cycle based on the position information of the inkjet head 12 output from the encoder 18 and the delay time information GI. The timing at which the dot formation position is closest to the ideal formation position is determined as the adjustment discharge timing. More specifically, the head control circuit 62 extracts the delay time corresponding to the position of the inkjet head 12 output from the encoder 18 from the delay time information GI. When the length of the adjustable period of the attention recording cycle is equal to or longer than the extracted delay time, the time when the extracted delay time elapses from the start time of the recording cycle is determined as the adjustment discharge timing. On the other hand, when the length of the adjustable period of the attention recording cycle is less than the extracted delay time, the end point of the adjustable period is determined to be the adjusted discharge timing. When the processing of B3 is completed, the discharge timing determination processing is completed.

As described above, according to the first embodiment, when the discharge amount set for the recording cycle is the discharge amount of the "large ball" and the recording cycle belongs to the specific recording cycle group, the discharge amount is for the recording cycle. Select the oversized ball ejection signal without selecting the large ball ejection signal. As a result, the size of the dots formed in each recording cycle belonging to the specific recording cycle group can be increased as compared with the case where the large ball ejection signal is selected. Therefore, even if the dot formation position deviates from the ideal formation position, the area of the portion where the dots are not formed on the paper S can be reduced, and as a result, the deterioration of the image quality can be suppressed. Can be done. On the other hand, even when the discharge amount set for the recording cycle is the discharge amount of the "large ball", when the discharge amount does not belong to the specific recording cycle, the large ball discharge signal is selected. Since the large ball discharge signal has a shorter length than the oversized ball discharge signal, the adjustable period is long. Therefore, the difference between the formation position of the dots formed in the recording cycle and the ideal formation position can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. As described above, in the first embodiment, when the recording cycle is a recording cycle in which the discharge amount of the “large ball” is set, the recording cycle is determined with respect to the recording cycle depending on whether or not the recording cycle belongs to the specific recording cycle group. The drive signal to be selected was switched between the large ball ejection signal and the oversized ball ejection signal. On the other hand, in the second embodiment, when the recording cycle is a recording cycle in which the ejection amount of the "large ball" is set, the partial region of the paper S to which the dots formed by the recording cycle belong is the partial region. Depending on whether or not the ratio of dots (hereinafter, also referred to as large ball dots) formed by the recording cycle in which the discharge amount of "large balls" is set to all the dots formed in (hereinafter, large ball ratio) is equal to or higher than a predetermined value. Then, the drive signal selected for the recording cycle is switched between the large ball ejection signal and the extra large ball ejection signal.

The partial area is an area obtained by dividing an image forming area, which is the entire area on which dots are formed on the paper S, into a plurality of areas. That is, the image forming region is composed of a plurality of partial regions. When a solid image or the like is recorded in such a partial region, the proportion of large balls in the partial region becomes large. Here, when the large ball ratio in the partial region is large and the distance between the large ball dots is narrow, such as when the large ball dots are in contact with each other, when the formation position of the large ball dots deviates from the ideal formation position, the paper S is used. Since the distance between the large dots formed in the image looks wider than the distance between the large dots represented on the image data IM, the deterioration of the image is easily noticeable. On the other hand, when the proportion of large balls in the partial region is small and the distance between the large ball dots is wide, even if the formation position of the large ball dots deviates from the ideal formation position, the large balls formed on the paper S. It is difficult to see that the distance between the dots is wider than the distance between the large dots represented on the image data IM, and the deterioration of the image is not noticeable. Therefore, in the second embodiment, when the large ball ratio is equal to or more than a predetermined value (for example, 70% or more), an extra large ball ejection signal is selected, and when it is less than a predetermined value, a large ball ejection signal is selected. Hereinafter, the partial region will be described as being a region formed by 25 dots in 5 rows and 5 columns, but the region is not particularly limited thereto.

Hereinafter, the drive signal selection process performed by the head control circuit 62 according to the second embodiment will be described with reference to FIG. 11 (b). First, the head control circuit 62 calculates the large ball ratio for each of the partial regions based on the image data IM (C1). Specifically, the head control circuit 62 extracts the dot element group PD (see FIG. 11A) corresponding to each partial region from the image data IM. The dot element group PD is a dot element group composed of 25 dot elements D in 5 rows and 5 columns. Then, the head control circuit 62 counts the number of dot elements D for which the discharge amount of the "large ball" is set based on the extracted dot element group PD, and divides the count value by 25 to obtain the large ball ratio. And.

Next, the head control circuit 62 executes the same processing of C2 to C5 as the processing of A1 to A4 described above. Then, when the head control circuit 62 determines in the processing of C4 that the discharge amount set for the Nth recording cycle is a "large ball" (C4: YES), the head control circuit 62 is in the Nth recording cycle. It is determined whether or not the large ball ratio calculated by the processing of C1 is equal to or more than a predetermined value with respect to the partial region to which the formed dots belong (C6). When it is determined that the large ball ratio is equal to or higher than a predetermined value (C6: YES), the head control circuit 62 selects an oversized ball discharge signal for the Nth recording cycle (C7), and processes C9. Move. On the other hand, when it is determined that the large ball ratio is less than the predetermined value (C6: NO), the head control circuit 62 selects the large ball discharge signal (C8) for the Nth recording cycle, and C9. Move on to processing. After that, the head control circuit 62 executes the same processing of C9 and C10 as the above-mentioned A9 and A10.

According to the second embodiment described above, when the discharge amount set for the recording cycle is the discharge amount of "large ball", and the large ball ratio of the partial region to which the recording cycle belongs is equal to or more than a predetermined value, the said The oversized ball ejection signal is selected without selecting the large ball ejection signal for the recording cycle. As a result, in the partial region where the large ball ratio is equal to or higher than the predetermined value, the size of the dots formed in the recording cycle in which the discharge amount of the "large ball" is set can be increased as compared with the case where the large ball discharge signal is selected. can. As a result, even if the formation position of the dots formed by the recording cycle in which the discharge amount of the "large ball" is set deviates from the ideal formation position, by increasing the size of the dots, the "large ball" can be formed. It is possible to make it difficult to see that the distance between the dots formed by the set recording cycle is wide. As a result, deterioration of image quality can be suppressed. On the other hand, even when the discharge amount set for the recording cycle is the discharge amount of "large ball", when the large ball ratio of the partial region to which the recording cycle belongs is less than a predetermined value, the large ball discharge signal is selected. As a result, the difference between the formation position of the dots formed in the recording cycle and the ideal formation position can be reduced.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. Unlike the first embodiment, the third embodiment does not include the oversized ball ejection signal in the types of drive signals that can be supplied to the individual electrodes 89. Then, when the recording cycle is a recording cycle in which the discharge amount of the "large ball" is set, and the recording cycle belongs to the specific recording cycle group, as shown in FIG. 12 (a), it is selected for the recording cycle. The drive signal to be driven is not a large ball discharge signal but a medium ball discharge signal.

Hereinafter, the drive signal selection process performed by the head control circuit 62 according to the third embodiment will be described with reference to FIG. 12 (b). The head control circuit 62 executes the processing of D1 to D5 similar to the processing of A1 to A5 described above. Then, when the head control circuit 62 determines in the process of D5 that the Nth recording cycle belongs to the specific recording cycle group (D5: YES), the head control circuit 62 sends a middle ball ejection signal to the Nth recording cycle. Select (D6) and move on to the processing of D8. Further, when it is determined in the processing of D5 that the Nth recording cycle does not belong to the specific recording cycle group (D5: NO), the head control circuit 62 selects a large ball ejection signal for the Nth recording cycle. Then (D7), the process of D8 is started. After that, the head control circuit 62 executes the same processing of D8 and D9 as the processing of A8 and A9.

In the third embodiment, in the discharge timing determination process, the head control circuit 62 uses the difference between the dot formation position and the ideal formation position formed in the recording cycle as the reference for the discharge timing in each recording cycle. Determine the adjusted discharge timing by adjusting the reference discharge timing so that it is smaller than the discharge timing.

As described above, according to the third embodiment, when the discharge amount set for the recording cycle is the discharge amount of the "large ball" and the recording cycle belongs to the specific recording cycle group, the discharge amount is for the recording cycle. Select the medium ball ejection signal without selecting the large ball ejection signal. As a result, the adjustable period in which the ejection timing can be adjusted in the recording cycle can be lengthened, so that the difference between the dot formation position formed in the recording cycle and the ideal formation position can be reduced. As a result, it is possible to suppress an increase in the area of the portion where dots are not formed on the paper S, so that deterioration of image quality can be suppressed. On the other hand, even when the discharge amount set for the recording cycle is the discharge amount of the "large ball", when the discharge amount does not belong to the specific recording cycle, the large ball discharge signal is selected. Thereby, the size of the dots formed in the recording cycle can be set to a desired size based on the image data.

(Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, when the recording cycle is a recording cycle in which the ejection amount of "large balls" is set, the ratio of large balls in the partial region on the paper S to which the dots formed by the recording cycle belong is equal to or higher than a predetermined value. Sometimes a medium ball discharge signal is selected, and when it is less than a predetermined value, a large ball discharge signal is selected.

Hereinafter, the drive signal selection process performed by the head control circuit 62 according to the fourth embodiment will be described with reference to FIG. The head control circuit 62 executes the processing of E1 to E6 similar to the processing of C1 to C6 described above. Then, in the processing of E6, when it is determined that the large ball ratio calculated by the processing of E1 is equal to or more than a predetermined value with respect to the partial region to which the dots formed in the Nth recording cycle belong (E6: YES). The head control circuit 62 selects the middle ball discharge signal for the Nth recording cycle (E7), and proceeds to the process of E9. On the other hand, when it is determined that the large ball ratio is less than the predetermined value (E6: NO), the head control circuit 62 selects the large ball discharge signal for the Nth recording cycle (E8), and E9. Move on to processing. After that, the head control circuit 62 executes the same processing of E9 and E10 as the above-mentioned A9 and A10.

In the fourth embodiment as well, as in the third embodiment, in the discharge timing determination process, the head control circuit 62 sets the discharge timing in each recording cycle to the ideal position of the dots formed in the recording cycle. The adjustment discharge timing is determined by adjusting the reference discharge timing so that the difference from the formation position becomes smaller than the reference discharge timing.

As described above, according to the fourth embodiment, when the discharge amount set for the recording cycle is the discharge amount of "large ball", and the large ball ratio of the partial region to which the recording cycle belongs is equal to or more than a predetermined value, the said The medium ball ejection signal is selected without selecting the large ball ejection signal for the recording cycle. As a result, the adjustable period in which the ejection timing can be adjusted in the recording cycle can be lengthened, so that the difference between the dot formation position formed in the recording cycle and the ideal formation position can be reduced. On the other hand, even when the discharge amount set for the recording cycle is the discharge amount of "large ball", when the large ball ratio of the partial region to which the recording cycle belongs is less than a predetermined value, the large ball discharge signal is selected. Thereby, the size of the dots formed in the recording cycle can be set to a desired size based on the image data.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made as long as it is described in the claims. Hereinafter, a modified example will be described.

First, before explaining the modified example of the third embodiment, the premise matters will be described. As described with reference to FIG. 9A, when the carriage 11 moves at a constant speed and the interval between the ejection timings of the ink ejected from the nozzle 10 is constant, the interval between dots in the ascending slope region becomes. , The dot spacing is narrower than the dot spacing corresponding to the scanning direction resolution, and the dot spacing is wider than the dot spacing corresponding to the scanning direction resolution in the downhill slope region. Therefore, in the uphill slope region, even if the ejection timing is not sufficiently adjusted, it is unlikely that the area of the portion where the dots are not formed on the paper S will increase. On the other hand, in the downhill slope region, it is necessary to adjust the ejection timing in order to suppress the area of the portion where the dots are not formed on the paper S from expanding. Here, even in the downward slope region, the delay time required to make the dot spacing corresponding to the scanning direction resolution differs depending on the dot formation position. Specifically, as shown in FIG. 14 (e), dots are provided at the position K1 of the mountain apex Pt in the downhill region, the position K2 near the intermediate position of the downhill slope, and the position K3 near the valley apex Pb of the downhill slope. When forming, it is necessary to increase the delay time for forming dots at each position in the order of position K1, position K2, and position K3. Therefore, in the recording cycle in which the dots are formed at the position K1, it is necessary to set the drive signal to the middle ball discharge signal in order to lengthen the delay time. On the other hand, in the recording cycle in which dots are formed at positions K2 and K3, it is not necessary to lengthen the delay time as compared with the recording cycle in which dots are formed at position K1, so the drive signal is longer than the middle ball ejection signal. It may be a drive signal.

Therefore, in this modification, the driver IC 90 individually separates the adjustment discharge signal 1 and the adjustment discharge signal 2 in addition to the four types of drive signals of non-discharge signal, small ball discharge signal, medium ball discharge signal, and large ball discharge signal. It is configured to be able to supply to the electrode 89. As shown in FIGS. 14A and 14B, the adjustment discharge signal 1 has two discharge pulses P as in the middle ball discharge signal, but the discharge pulse P is higher than that of the middle ball discharge signal. The pulse width is long. Therefore, the adjustment ejection signal 1 has a larger amount of ink ejected from the nozzle 10 and a longer signal length than the medium ball ejection signal. Further, as shown in FIGS. 14 (c) and 14 (d), the adjustment discharge signal 2 has three discharge pulses P as in the large ball discharge signal, but the discharge pulse P is higher than that of the large ball discharge signal. The pulse width of is short. Therefore, the adjustment ejection signal 2 has a smaller ejection amount of ink ejected from the nozzle 10 and a shorter signal length than the large ball ejection signal. From the above, in the medium ball ejection signal, the adjusting ejection signal 1, the adjusting ejection signal 2, and the large ball ejection signal, the amount of ink ejected from the nozzle 10 increases in this order, and the length of the signal becomes long.

Then, in the head control circuit 62, when the recording cycle is a recording cycle in which the discharge amount of the “large ball” is set, even when the recording cycle belongs to the specific recording cycle group, the dots formed by the recording cycle When the formation position is in the uphill slope region, the large ball ejection signal is selected without selecting the medium ball ejection signal for the recording cycle. On the other hand, when the recording cycle is a recording cycle in which the discharge amount of the "large ball" is set, the recording cycle belongs to the specific recording cycle group, and the formation position of the dots formed by the recording cycle is a downward slope. In the case of a region, one of the middle ball discharge signal, the adjustment discharge signal 1, and the adjustment discharge signal 2 is selected for the recording cycle according to the position where the dot is formed. .. Specifically, as shown in FIG. 14 (e), the downhill slope region is divided into a first region, a second region, and a third region along the scanning direction. Then, the middle ball discharge signal is selected for the recording cycle in which the dots are formed in the first region closest to the peak Pt. The adjustment discharge signal 1 is selected for the recording cycle in which dots are formed in the second region. Then, when forming a dot in the third region closest to the valley apex Pb, the adjustment discharge signal 2 is selected.

Hereinafter, the drive signal selection process performed by the head control circuit 62 according to this modification will be described with reference to FIG. 15 (a). The head control circuit 62 executes the processing of F1 to F6 similar to the processing of A1 to A6 described above. Then, when the head control circuit 62 determines in the processing of F6 that neither the N-1st recording cycle nor the discharge amount set for the N + 1st recording cycle is zero (F6: NO). Turns on the change flag corresponding to the Nth recording cycle stored in the RAM 53 (F7). Here, the change flag is stored in the RAM 53 for each recording cycle. Then, when the change flag is in the ON state and the formation position of the dots formed by the corresponding recording cycle is within the downward slope region, the large ball ejection signal is not selected for the corresponding recording cycle. It is a flag instructing to select any one of the middle ball discharge signal, the adjustment discharge signal 1, and the adjustment discharge signal 2. That is, in this modification, for the recording cycle in which the corresponding change flag is ON, the drive signal is selected in the discharge timing determination process without selecting the drive signal in this selection process. When the processing of F7 is completed, the process proceeds to the processing of F9.

On the other hand, when it is determined in the processing of F5 that the Nth recording cycle does not belong to the specific recording cycle group (F5: NO), or in the processing of F6, the N-1st recording cycle and the N + 1th recording cycle are set. When it is determined that any of the set discharge amounts is zero (F6: YES), the head control circuit 62 selects a large ball discharge signal for the Nth recording cycle (F8). Move on to the processing of F9. After that, the head control circuit 62 executes the same processing of F9 and F10 as the processing of A9 and A10.

Next, the discharge timing determination process according to this modification will be described with reference to FIG. 15 (b). The head control circuit 62 determines whether or not the change flag corresponding to the attention recording cycle stored in the RAM 53 is in the ON state (G1). If it is determined that the change flag is in the OFF state (G1: NO), the process proceeds to G5. On the other hand, when it is determined that the change flag is in the ON state (G1: YES), the head control circuit 62 sets the dot formation position formed in the attention recording cycle on the ascending slope based on the output of the encoder 18. It is determined whether it is in the area or the downhill slope area (G2). When it is determined that the dot formation position is within the uphill slope region (G2: YES), the large ball ejection signal is selected for the attention recording cycle (G3), and the process proceeds to G5. On the other hand, when it is determined that the dot formation position is within the downward slope region (G2: NO), the middle ball discharge signal and the adjustment discharge signal 1 are determined according to the dot formation position formed in the attention recording cycle. , And any one of the adjustment discharge signals 2 is selected for the attention recording cycle (G4). When the processing of G4 is completed, the process proceeds to the processing of G5. In the process of G5, the head control circuit 62 executes the same process as B3 described above.

As described above, in this modification, the size of each dot can be brought closer to a desired size based on the image data while suppressing the area of the portion where the dots are not formed on the paper S from expanding. As a result, deterioration of image quality can be suppressed. In this modification, the "adjustment discharge signal 1" and the "adjustment discharge signal 2" also correspond to the "first drive signal" of the present invention.

In this modification, the downhill slope region is divided into three regions, a first region, a second region, and a third region along the scanning direction, but the region is not particularly limited to this, and may be divided into a plurality of regions. It suffices if it is divided. For example, when it is divided into four regions, the adjustment discharge signal 3 can be supplied to the individual electrode 89 in addition to the adjustment discharge signal 1 and the adjustment discharge signal 2. Then, in the four regions of the downward slope region, the closer to the peak Pt, the shorter the signal length among the middle ball discharge signal, the adjustment discharge signal 1, the adjustment discharge signal 2, and the adjustment discharge signal 3. Assign a drive signal. When the set discharge amount is a "large ball" and the position where the dots are formed is within the downhill slope region when the drive signal is selected for the recording cycle belonging to the specific recording cycle group, the dot is formed. The drive signal assigned to the area to which the position belongs may be selected.

Next, an example of modification of the first embodiment will be described. Also in this modification, when the recording cycle is the recording cycle in which the discharge amount of the “large ball” is set, as in the modification of the third embodiment described above, when the recording cycle belongs to the specific recording cycle group. However, when the formation position of the dots formed by the recording cycle is within the uphill slope region, the large ball ejection signal is selected for the recording cycle. Therefore, as in the modification of the third embodiment described above, the RAM 53 stores the change flag corresponding to each recording cycle. Then, also in this modification, the head control circuit 62 performs the same processing as the selection process described with reference to FIG. 15A in the modification of the third embodiment described above. However, the change flag stored in the RAM 53 sends a large ball ejection signal to the corresponding recording cycle when the formation position of the dots formed by the corresponding recording cycle is within the downhill slope region in the ON state. It is a flag instructing to select an oversized ball ejection signal without selecting it.

Hereinafter, the discharge timing determination process according to this modification will be described with reference to FIG. The head control circuit 62 determines whether or not the change flag corresponding to the attention recording cycle stored in the RAM 53 is in the ON state (H1). When it is determined that the change flag is in the OFF state (H1: NO), the process proceeds to H4. On the other hand, when it is determined that the change flag is in the ON state (H1: YES), the head control circuit 62 raises the slope region where the dots formed in the attention recording cycle are formed based on the output of the encoder 18. It is determined whether it is inside or within the downhill slope area (H2). When it is determined that the dot formation position is within the uphill slope region (H2: YES), the large ball ejection signal is selected for the attention recording cycle (H3), and the process proceeds to H4. Then, the head control circuit 62 executes the same process as the above-mentioned B3 in the process of H4, and ends the present process. On the other hand, when it is determined that the dot formation position is within the downhill slope region (H2: NO), the head control circuit 62 selects an oversized ball ejection signal for the attention recording cycle (H5). After that, the head control circuit 62 determines the discharge timing in the recording cycle as the reference discharge timing (H6), and ends this process.

As described above, also in this modification, it is possible to make the size of each dot close to a desired size based on the image data while suppressing the area of the portion where the dots are not formed on the paper S from expanding. As a result, deterioration of image quality can be suppressed.

Hereinafter, other modification examples will be described.

In the first embodiment and the second embodiment, the extra-large ball ejection signal is a drive signal having a larger number of ejection pulses P than the medium ball ejection signal, but the present invention is not particularly limited to this, and the medium ball ejection signal is not limited thereto. Any signal may be used as long as the amount of ink ejected from the nozzle 10 is larger than that of the ejection signal and the length of the signal is longer. Therefore, for example, the extra-large ball discharge signal may be a drive signal in which the number of the medium ball discharge signal and the discharge pulse P is the same, but the pulse width of the discharge pulse P is long.

Further, in the first embodiment, the oversized ball ejection signal may be uniformly selected for each of the recording cycles belonging to the specific recording cycle group. Further, in the first embodiment and the second embodiment, in the recording cycle for selecting the oversized ball ejection cycle, the ejection timing is set as the reference ejection timing, but the present invention is not limited to this, and the reference ejection timing is adjusted. It may be adjusted discharge timing.

Further, the wave shape generation mechanism that causes the wave shape on the paper S is a mechanism that combines the rib 20, the discharge roller pair 16, the holding portion 14a of the plate 14, and the spur 17, but the mechanism is not particularly limited to this. do not have. For example, the spur 17 may not be provided, and the paper S may be pressed from above only by the plate 14. In this way, even when the paper S is pressed from above only by the plate 14, the paper S can have a wavy shape.

Further, it does not have to be provided with a wave shape generation mechanism. Even a printer that does not have a wave shape generation mechanism may need to adjust the ejection timing. For example, when ink is ejected onto paper, expansion due to water absorption of the ink gathers, which may cause the paper to undulate along the scanning direction, that is, so-called cockling. Even when recording an image on a paper having such a cock ring, it is necessary to adjust the ejection timing as in the above-described embodiment. Further, even when the speed of the carriage 11 fluctuates, it is necessary to adjust the discharge timing.

Further, in the above-described embodiment, the printer 1 is a so-called serial printer that records an image on the paper S while moving the inkjet head 12 in a direction intersecting the transport direction of the paper S, but the inkjet head 12 is used. It may be a line type printer that records an image on the paper S conveyed by the conveying device in a fixed state. Even in such a line-type printer, if the transport speed of the paper S fluctuates, it is necessary to adjust the ejection timing.

The actuator that ejects ink from the nozzle 10 is a piezoelectric actuator that ejects ink from the nozzle 40 by utilizing the piezoelectric deformation of the piezoelectric layer, but the actuator is not limited to this. For example, it may be an actuator having a heating element that heats ink to cause film boiling.

Further, in the above, an example in which the present invention is applied to a printer that ejects ink from a nozzle and records on paper S has been described, but the present invention is not limited thereto. Of course, it can also be applied to a liquid ejection device that ejects a liquid other than ink, for example, a liquefied resin or metal, cures and forms a model, or ejects a metal or the like to a recording medium. It can also be applied to a liquid ejection device that records an image by ejecting ink from a nozzle onto a recording medium other than the paper S, for example, a case of a mobile terminal such as a smartphone or a corrugated cardboard. A liquid ejection device that records images by ejecting black, yellow, cyan, and magenta inks from the head after printing with white ink as a base on a recording medium made of a transparent resin such as a transparent film. Can also be applied to.

Further, in the above, the transport mechanism for transporting the recorded medium is a roller transport mechanism using a transport roller, but the present invention is not limited to this. For example, it may be a transport mechanism in which the recorded medium is placed on a belt and the recorded medium is conveyed by running the heald. The recorded medium may be placed on a table and the table may be placed on a ball screw or the like. It may be a transport mechanism that transports the recording medium by moving it by a moving means.

1 Printer 10 Nozzle 11 Carriage 12 Inkjet head 13 Conveyor roller vs. 16 Discharge roller vs. 50 Control device

Claims (16)

A liquid discharge head having a discharge surface on which a nozzle for discharging liquid is formed,
A moving mechanism that moves at least one of the recorded medium and the liquid discharge head so that the liquid discharge head moves relative to the recorded medium in a relative moving direction parallel to the discharge surface.
A storage unit that stores image data in which the amount of liquid discharged from the nozzle is set for each of the continuous predetermined recording cycles.
Control unit and
Equipped with
The control unit
A first drive signal having a plurality of types of drive signals having different signal lengths for driving the liquid discharge head to discharge the liquid from the nozzle and having a discharge amount of more than zero, and the first drive signal. The second drive signal, which has a larger discharge amount and is longer than the first drive signal, has a larger discharge amount than the first drive signal, and the second drive signal has a larger discharge amount than the first drive signal and the second drive signal. It is possible to generate a plurality of types of drive signals including one drive signal and a third drive signal longer than the second drive signal.
When recording an image on a recording medium
Based on the image data, one drive signal is selected from the plurality of types of drive signals for each of the recording cycles.
While the liquid discharge head is relatively moved in the relative movement direction with respect to the recording medium by the movement mechanism, the drive signal selected for the recording cycle is transmitted to the liquid discharge head in each of the recording cycles. It is supplied to selectively discharge the liquid from the nozzle, and
The discharge timing for discharging the liquid from each of the nozzles in the recording cycle is any of the predetermined periods within the predetermined period in which the longer the drive signal selected for the recording cycle, the shorter the discharge timing. Decided at that timing,
When selecting the drive signal for each of the recording cycles,
In the image data, when the discharge amount set for the recording cycle is the first discharge amount, the first drive signal is selected.
In the image data, when the discharge amount set for the recording cycle is a second discharge amount larger than the first discharge amount, the second discharge amount is set for the recording cycle. When the predetermined condition belonging to the specific recording cycle group in which the recording cycle is continuous for a predetermined number or more is satisfied, the third drive signal is selected for the recording cycle, and when the predetermined condition is not satisfied, the third drive signal is selected. A liquid discharge device characterized in that the second drive signal is selected with respect to a recording cycle. The control unit
When selecting the drive signal for each of the recording cycles
Even when the discharge amount set for the recording cycle is the second discharge amount and the predetermined condition is satisfied, the image data is set to the recording cycle one before the recording cycle. When either the discharge amount set with respect to the discharge amount or the discharge amount set with respect to the recording cycle one after the recording cycle is zero, the second drive is performed with respect to the recording cycle. The liquid discharge device according to claim 1, wherein a signal is selected. A liquid discharge head having a discharge surface on which a nozzle for discharging liquid is formed,
A moving mechanism that moves at least one of the recorded medium and the liquid discharge head so that the liquid discharge head moves relative to the recorded medium in a relative moving direction parallel to the discharge surface.
A storage unit that stores image data in which the amount of liquid discharged from the nozzle is set for each of the continuous predetermined recording cycles.
Control unit and
Equipped with
The control unit
A first drive signal having a plurality of types of drive signals having different signal lengths for driving the liquid discharge head to discharge the liquid from the nozzle and having a discharge amount of more than zero, and the first drive signal. The second drive signal, which has a larger discharge amount and is longer than the first drive signal, has a larger discharge amount than the first drive signal, and the first drive signal has a larger discharge amount than the first drive signal and the second drive signal. It is possible to generate a plurality of types of drive signals including a drive signal and a third drive signal longer than the second drive signal.
When recording an image on a recording medium
Based on the image data, one drive signal is selected from the plurality of types of drive signals for each of the continuous recording cycles.
While the liquid discharge head is relatively moved in the relative movement direction with respect to the recording medium by the movement mechanism, the drive signal selected for the recording cycle is transmitted to the liquid discharge head in each of the recording cycles. It is supplied to selectively discharge the liquid from the nozzle, and
The discharge timing for discharging the liquid from each of the nozzles in the recording cycle is any of the predetermined periods within the predetermined period in which the longer the drive signal selected for the recording cycle, the shorter the discharge timing. Decided at that timing,
When selecting the drive signal for each of the recording cycles,
In the image data, when the discharge amount set for the recording cycle is the first discharge amount, the first drive signal is selected.
In the image data, when the discharge amount set for the recording cycle is a second discharge amount larger than the first discharge amount,
Of the plurality of partial regions constituting the image forming region on which the dots are formed on the recording medium, the partial regions to which the dots formed in the recording cycle belong are for all the dots formed in the partial region. When the ratio of dots formed by the recording cycle in which the second discharge amount is set in the image data satisfies a predetermined condition of being equal to or more than a predetermined value, the third drive signal is transmitted to the recording cycle. A liquid discharge device, characterized in that the second drive signal is selected for the recording cycle when the predetermined condition is not satisfied. The control unit
When determining the discharge timing for each of the recording cycles
When the third drive signal is selected for the recording cycle, the discharge timing for the recording cycle is determined to be a predetermined reference discharge timing within the predetermined period.
When the second drive signal is selected for the recording cycle, the difference between the ejection timing for the recording cycle and the dot formation position formed in the recording cycle and the predetermined ideal formation position is the difference. The invention according to any one of claims 1 to 3, wherein the reference discharge timing is determined to be an adjusted discharge timing adjusted within the predetermined period so as to be smaller than the case of the reference discharge timing. Liquid discharge device. The control unit
When determining the discharge timing for each of the recording cycles
The liquid discharge device according to claim 4, wherein when the first drive signal is selected for the recording cycle, the discharge timing for the recording cycle is determined to be the adjusted discharge timing. Each of the plurality of types of drive signals is a pulse signal.
The liquid discharge device according to any one of claims 1 to 5, wherein the third drive signal has a larger number of pulses than the first drive signal and the second drive signal. Each of the plurality of types of drive signals is a pulse signal.
The liquid discharge device according to any one of claims 1 to 6, wherein the third drive signal has a pulse width longer than that of the first drive signal and the second drive signal. A liquid discharge head having a discharge surface on which a nozzle for discharging liquid is formed,
A moving mechanism that moves at least one of the recorded medium and the liquid discharge head so that the liquid discharge head moves relative to the recorded medium in a relative moving direction parallel to the discharge surface.
A storage unit that stores image data in which the amount of liquid discharged from the nozzle is set for each of the continuous predetermined recording cycles.
Control unit and
Equipped with
The control unit
A first drive signal having a plurality of types of drive signals having different signal lengths for driving the liquid discharge head to discharge the liquid from the nozzle and having a discharge amount of more than zero, and the first drive signal. It is possible to generate a plurality of types of drive signals including a second drive signal having a larger discharge amount than the first drive signal and longer than the first drive signal.
When recording an image on a recording medium
Based on the image data, one drive signal is selected from the plurality of types of drive signals for each of the recording cycles.
While the liquid discharge head is relatively moved in the relative movement direction with respect to the recording medium by the movement mechanism, the drive signal selected for the recording cycle is transmitted to the liquid discharge head in each of the recording cycles. It is supplied to selectively discharge the liquid from the nozzle, and
The discharge timing for discharging the liquid from each of the nozzles in the recording cycle is any of the predetermined periods within the predetermined period in which the longer the drive signal selected for the recording cycle, the shorter the discharge timing. Decided at that timing,
When selecting the drive signal for each of the recording cycles,
In the image data, when the discharge amount set for the recording cycle is the first discharge amount, the first drive signal is selected.
In the image data, when the discharge amount set for the recording cycle is a second discharge amount larger than the first discharge amount, the second discharge amount is set for the recording cycle. When the predetermined condition belonging to the specific recording cycle group in which the recording cycle is continuous for a predetermined number or more is satisfied, the first drive signal is selected for the recording cycle, and when the predetermined condition is not satisfied, the first drive signal is selected. A liquid discharge device characterized in that the second drive signal is selected with respect to a recording cycle. A liquid discharge head having a discharge surface on which a nozzle for discharging liquid is formed,
A moving mechanism that moves at least one of the recorded medium and the liquid discharge head so that the liquid discharge head moves relative to the recorded medium in a relative moving direction parallel to the discharge surface.
A storage unit that stores image data in which the amount of liquid discharged from the nozzle is set for each of the continuous predetermined recording cycles.
Control unit and
Equipped with
The control unit
A first drive signal having a plurality of types of drive signals having different signal lengths for driving the liquid discharge head to discharge the liquid from the nozzle and having a discharge amount of more than zero, and the first drive signal. It is possible to generate a plurality of types of drive signals including a second drive signal having a larger discharge amount and longer than the first drive signal as compared with the first drive signal.
When recording an image on a recording medium
Based on the image data, one drive signal is selected from the plurality of types of drive signals for each of the continuous recording cycles.
While the liquid discharge head is relatively moved in the relative movement direction with respect to the recording medium by the movement mechanism, the drive signal selected for the recording cycle is transmitted to the liquid discharge head in each of the recording cycles. It is supplied to selectively discharge the liquid from the nozzle, and
The discharge timing for discharging the liquid from each of the nozzles in the recording cycle is any of the predetermined periods within the predetermined period in which the longer the drive signal selected for the recording cycle, the shorter the discharge timing. Decided at that timing,
When selecting the drive signal for each of the recording cycles,
In the image data, when the discharge amount set for the recording cycle is the first discharge amount, the first drive signal is selected.
In the image data, when the discharge amount set for the recording cycle is a second discharge amount larger than the first discharge amount,
Of the plurality of partial regions constituting the image forming region on which the dots are formed on the recording medium, the partial regions to which the dots formed in the recording cycle belong are for all the dots formed in the partial region. When the ratio of dots formed by the recording cycle in which the second discharge amount is set in the image data satisfies a predetermined condition of being equal to or higher than a predetermined value, the first drive signal is transmitted to the recording cycle. A liquid discharge device, characterized in that the second drive signal is selected for the recording cycle when the predetermined condition is not satisfied. The control unit
When determining the discharge timing for each of the recording cycles
The difference between the dot formation position formed in the recording cycle and the predetermined ideal formation position is smaller than that in the case where the discharge timing for the recording cycle is set to a predetermined reference discharge timing within the predetermined period. The liquid discharge device according to claim 8 or 9, wherein the reference discharge timing is determined to be an adjusted discharge timing adjusted within the predetermined period. The liquid discharge device according to any one of claims 1 to 10, wherein the moving mechanism is a carriage that mounts the liquid discharge head and can reciprocate along the relative moving direction. The recording medium is formed with a predetermined wave shape in which a mountain portion protruding toward the discharge surface side and a valley portion recessed away from the discharge surface from the mountain portion are lined up along the relative movement direction. The liquid discharge device according to claim 11, further comprising a wave shape generation mechanism. The recording medium is formed with a predetermined wave shape in which a mountain portion protruding toward the discharge surface side and a valley portion recessed away from the discharge surface from the mountain portion are lined up along the relative movement direction. It also has a wave shape generation mechanism,
The moving mechanism is a carriage that reciprocates the liquid discharge head with respect to the recording medium in the relative moving direction.
The control unit
When selecting the drive signal for each of the recording cycles
In the image data, when the discharge amount set for the recording cycle is the second discharge amount and the predetermined condition is satisfied.
In the recording cycle, when a dot is formed in the first dot forming region from the apex of the mountain portion to the apex of the valley portion adjacent to the mountain portion on the downstream side in the moving direction of the carriage, the dot is formed. The first drive signal is selected for the recording cycle, and the first drive signal is selected.
In the recording cycle, when a dot is formed in the second dot forming region from the apex of the valley portion to the apex of the mountain portion adjacent to the valley portion on the downstream side in the moving direction of the carriage, the dot is formed. The liquid discharge device according to claim 8 or 9, wherein the second drive signal is selected without selecting the first drive signal with respect to the recording cycle. The control unit
When determining the discharge timing for each of the recording cycles
In the image data, when the discharge amount set for the recording cycle is the second discharge amount and the predetermined condition is satisfied.
The recording cycle is a recording cycle in which dots are formed in the first dot forming region, and the dot forming position formed in the recording cycle is higher than the first forming position in the first dot forming region. When the second forming position is close to the apex of the mountain portion, the ejection timing for the recording cycle is compared with the ejection timing when forming dots at the first forming position, from the start time of the recording cycle. The liquid discharge device according to claim 13, wherein the liquid discharge device is determined at a distant timing. There are a plurality of types of the first drive signal having different signal lengths.
The control unit
When selecting the drive signal for each of the recording cycles
In the image data, when the discharge amount set for the recording cycle is the second discharge amount and the predetermined condition is satisfied.
The recording cycle is a recording cycle in which dots are formed in the first dot forming region, and the dot forming position formed in the recording cycle is higher than the first forming position in the first dot forming region. When the second formation position is close to the apex of the mountain portion, the first one selected when forming a dot at the first formation position among the plurality of types of the first drive signals for the recording cycle. The liquid discharge device according to claim 13, wherein a first drive signal having a shorter signal length than the drive signal is selected. The recording medium is formed with a predetermined wave shape in which a mountain portion protruding toward the discharge surface side and a valley portion recessed away from the discharge surface from the mountain portion are lined up along the relative movement direction. It also has a wave shape generation mechanism,
The moving mechanism is a carriage that reciprocates the liquid discharge head with respect to the recording medium in the relative moving direction.
The control unit
When selecting the drive signal for each of the recording cycles
In the image data, when the discharge amount set for the recording cycle is the second discharge amount and the predetermined condition is satisfied.
In the recording cycle, when a dot is formed in the dot forming region from the apex of the valley portion to the apex of the mountain portion adjacent to the valley portion on the downstream side in the moving direction of the carriage, the third. The liquid discharge device according to any one of claims 1 to 7, wherein the second drive signal is selected without selecting a drive signal.

Images