JP2024077980A - Liquid discharge device, liquid discharge method, and program - Google Patents

Abstract

To improve impact position accuracy of liquid to a sheet material by adjusting deviation of discharge timing of nozzle arrays due to thickness of the sheet material on a rotating member.SOLUTION: A liquid discharge device includes: a rotating member which holds a sheet material on a peripheral surface and conveys the sheet material; a discharge section which arranges a plurality of nozzle arrays in which a plurality of nozzles for discharging liquid to the sheet material are arranged in a direction orthogonal to a conveyance direction of the sheet material; a sheet material position detection section which detects the position of the sheet material; a timing signal generation section which generates a timing signal according to rotation amount of the rotating member; a discharge timing generation section which generates discharge timing of each nozzle array of the discharge section on the basis of a detection result of the position of the sheet material and the generated timing signal; and a discharge timing adjustment section which adjusts discharge timing of other nozzle arrays with respect to a reference nozzle array on the basis of thickness of the sheet material on the rotating member.SELECTED DRAWING: Figure 6

Description

This disclosure relates to a liquid ejection device, a liquid ejection method, and a program.

Liquid ejection devices that eject liquid onto a sheet material are known. Also known are liquid ejection methods using liquid ejection devices and programs that cause a computer of the liquid ejection device to execute the liquid ejection methods.

Patent document 1 describes a method of holding a sheet material on a rotating member and determining the ejection timing of ejection units arranged at multiple positions along the conveying direction of the sheet material.

However, with conventional methods for determining ejection timing, the ejection timing can differ between multiple nozzle rows arranged along the conveying direction of the sheet material depending on the thickness of the sheet material on the rotating member.

In view of the above problems, the technology disclosed herein aims to improve the accuracy of the landing position of liquid on the sheet material by adjusting the deviation in the ejection timing of the nozzle array due to the thickness of the sheet material on the rotating member.

In order to solve the above problem, according to one aspect of the present disclosure,
A rotating member that holds and conveys the sheet material on its circumferential surface;
an ejection section in which a plurality of nozzle rows are arranged in a conveying direction of the sheet material, the nozzle rows including a plurality of nozzles for ejecting liquid onto the sheet material, the nozzle rows being aligned in a direction perpendicular to the conveying direction of the sheet material;
a sheet material position detection unit that detects the position of the sheet material;
a timing signal generating unit that generates a timing signal according to an amount of rotation of the rotating member;
a discharge timing generating section that generates a discharge timing of the nozzle array of each of the discharge sections based on a detection result of the position of the sheet material and the generated timing signal;
a discharge timing adjustment unit that adjusts the discharge timing of the other nozzle arrays relative to the reference nozzle array based on a thickness of the sheet material on the rotating member;
A liquid ejection device is provided, comprising:

According to the present disclosure, it is possible to improve the accuracy of the landing position of liquid on the sheet material by adjusting the deviation in the ejection timing of the nozzle array due to the thickness of the sheet material on the rotating member.

1 is a schematic configuration diagram of a liquid ejection device according to an embodiment. FIG. 2 is a plan view of a discharge section according to an embodiment. FIG. 2 is a side view of a rotating member and its surroundings according to an embodiment. FIG. 2 is a plan view of a discharge section and a timing signal generation section according to an embodiment. FIG. 2 is a diagram illustrating a hardware configuration of a liquid ejection device according to an embodiment. FIG. 2 is a functional configuration diagram of a liquid ejection device according to an embodiment. 6 is a flowchart showing a processing procedure of a liquid ejection device according to an embodiment. 4 is a timing chart of a liquid ejection device according to an embodiment. 5A and 5B are diagrams illustrating distances between nozzle rows of a liquid ejection head according to an embodiment. FIG. 13 is a diagram showing a distance between discharge units according to an embodiment. 11A and 11B are diagrams illustrating a deviation in landing positions between an upstream head and a downstream head according to an embodiment.

Embodiments of the present disclosure will now be described in detail with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicate descriptions will be omitted as appropriate.

(Overall configuration and main configuration of liquid ejection device)
Fig. 1 is a schematic diagram of a liquid ejection device according to an embodiment of the present invention, and Fig. 2 is a plan view of an ejection section according to the embodiment of the present invention.

The inkjet printer 1 is an example of a liquid ejection device, for example a line-type inkjet printer. The inkjet printer 1 comprises an input section 10, a printing section 20, a drying section 30, and an output section 40. The inkjet printer 1 prints on a sheet material P, such as paper, which is a sheet-like member, input from the input section 10 by applying a liquid such as ink in the printing section 20, dries the liquid adhering to the sheet material P in the drying section 30, and then discharges the sheet material P to the output section 40.

The loading section 10 includes an input tray 11 on which multiple sheets of material P are stacked, a feeding device 12 that separates and sends out the sheet materials P one by one from the input tray 11, and a pair of registration rollers 13 that sends the sheet materials P to the printing section 20.

The feeding device 12 can be any one of a device using rollers or a device using air suction. The sheet material P sent out from the input tray 11 by the feeding device 12 is sent to the printing unit 20 after the leading edge of the sheet material P reaches the pair of registration rollers 13, which are driven at a predetermined timing.

The printing unit 20 includes a transport drum 21 that holds and transports the sheet material P on its circumferential surface, and a liquid ejection unit 22 that ejects liquid toward the sheet material P held by the transport drum 21. The transport drum 21 is an example of a rotating member.

The printing section 20 also includes a transfer cylinder 24 that receives the fed sheet material P and passes it to the transport drum 21, and a transfer cylinder 25 that passes the sheet material P transported by the transport drum 21 to the drying section 30.

The sheet material P transported from the loading section 10 to the printing section 20 has its leading edge gripped by a sheet gripper provided on the surface of the transfer cylinder 24, and is transported as the transfer cylinder 24 rotates. The sheet material P transported by the transfer cylinder 24 is handed over to the transport drum 21 at a position opposite the transport drum 21.

A sheet gripper is also provided on the surface of the transport drum 21, and the leading edge of the sheet material P is gripped by the sheet gripper. A number of suction holes are formed and distributed on the surface of the transport drum 21. An adsorption device 26 generates a suction airflow that flows inward from the suction holes of the transport drum 21.

Then, the sheet material P transferred from the transfer drum 24 to the transport drum 21 has its leading edge gripped by the sheet gripper and is adsorbed onto the transport drum 21 by the suction airflow of the suction device 26, and is transported as the transport drum 21 rotates.

The liquid discharge section 22 is equipped with six color discharge units 23, from the first discharge unit 23A to the sixth discharge unit 23F. The first discharge unit 23A discharges, for example, a cyan (C) liquid, and the second discharge unit 23B discharges, for example, a magenta (M) liquid. The third discharge unit 23C discharges, for example, a yellow (Y) liquid, and the fourth discharge unit 23D discharges, for example, a black (K) liquid. The fifth discharge unit 23E and the sixth discharge unit 23F are used to discharge one of the special liquids such as white, gold, silver, and fluorescent colors. The liquid discharge section 22 can further be provided with a discharge unit 23 that discharges a treatment liquid such as a surface coating liquid.

As shown in FIG. 2, the ejection unit 23 for each color is a full-line head array in which multiple liquid ejection heads 100 that eject liquid are arranged in a direction perpendicular to the transport direction of the sheet material P. The multiple liquid ejection heads 100 are arranged on a base member 102. The liquid ejection heads 100 are arranged in the transport direction in multiple nozzle rows 101, each of which has multiple nozzles arranged in a direction perpendicular to the transport direction of the sheet material P, and print by shifting the timing of ejecting liquid from each nozzle row 101. The liquid ejection heads 100 are an example of an ejection section.

The ejection operation of each color ejection unit 23 is controlled by a drive signal corresponding to the printing information. When the sheet material P held on the transport drum 21 passes through the area facing the liquid ejection section 22, liquid of each color is ejected from each color ejection unit 23, and an image corresponding to the printing information is printed.

The drying unit 30 includes a drying mechanism unit 31 for drying the liquid adhering to the sheet material P in the printing unit 20, and a suction transport mechanism unit 32 for transporting the sheet material P transported from the printing unit 20 under suction.

The sheet material P transported from the printing unit 20 is received by the suction transport mechanism 32, then transported through the drying mechanism 31 and delivered to the discharge unit 40.

When the sheet material P passes through the drying mechanism 31, the liquid adhering to the sheet material P is subjected to a drying process. The drying process causes the water content in the liquid and other liquid components to evaporate, the colorant contained in the liquid adhering to the sheet material P to be fixed, and curling of the sheet material P is suppressed.

The discharge section 40 includes a discharge tray 41 on which multiple sheet materials P are stacked. The sheet materials P conveyed from the drying section 30 are stacked and held in the discharge tray 41 in sequence.

In addition, in the inkjet printer 1, for example, a pre-processing unit that performs pre-processing on the sheet material P can be disposed upstream of the printing unit 20. Also, for example, a post-processing unit that performs post-processing on the sheet material P to which liquid has been attached can be disposed between the drying unit 30 and the discharge unit 40.

Examples of the pre-treatment section include a section that performs a pre-coating process in which a treatment liquid that reacts with the liquid to suppress bleeding is applied to the sheet material P. Examples of the post-treatment section include a section that performs a sheet reversal and transport process in which the sheet material P printed in the printing section 20 is reversed and sent back to the printing section 20 to print on both sides of the sheet material P, and a section that performs a process of binding multiple sheets of the sheet material P.

Next, the configuration for controlling the ejection timing in the liquid ejection device will be described with reference to Figures 3 and 4.

Figure 3 is a side view of the rotating member and its surroundings according to one embodiment, and Figure 4 is a plan view of the ejection section and timing signal generation section according to one embodiment. For simplicity of explanation, only one ejection unit 23 is shown in Figure 4.

Although not shown, each color ejection unit 23 shown in FIG. 3 is provided with a lifting mechanism that raises and lowers the ejection unit 23 in the radial direction of the transport drum 21. The lifting mechanism raises and lowers the ejection unit 23 in the radial direction of the transport drum 21, thereby maintaining a constant gap between the surface of the sheet material P and the nozzle surface of the ejection unit 23 according to the thickness of the sheet material P.

An encoder wheel 202 is provided on the shaft 21a of the transport drum 21, and a first encoder sensor 203 is disposed to read the encoder wheel 202. The encoder wheel 202 and the first encoder sensor 203 constitute a first encoder 201. The first encoder 201 is a rotary encoder, and generates a first timing signal of a pulse wave corresponding to the amount of rotation (amount of rotational drive) of the transport drum 21.

As shown in FIG. 4, an encoder scale 212 is provided on the circumferential surface of the transport drum 21, and a second encoder sensor 213 is disposed to read the encoder scale 212. The encoder scale 212 and the second encoder sensor 213 constitute a second encoder 211. The second encoder 211 is a linear encoder, and generates a second timing signal of a pulse wave corresponding to the amount of movement of the circumferential surface of the transport drum 21. The second timing signal is a signal that correlates with the amount of movement of the sheet material P on the circumferential surface of the transport drum 21.

Here, the second encoder sensor 213 constituting the second encoder 211 is disposed near the discharge unit 23 of each color. For example, the second encoder sensor 213 is attached to the base member 102 of the discharge unit 23 of each color. Therefore, the second encoder 211 is constituted by the second encoder sensor 213 of the discharge unit 23 of each color and the encoder scale 212 of the transport drum 21. The first encoder 201 and the second encoder 211 are an example of a timing signal generating unit that generates a timing signal according to the amount of rotation of the rotating member. Note that instead of using two types of encoders, the first encoder 201 and the second encoder 211, either one of them may be used.

Furthermore, as shown in FIG. 3, a sheet material position sensor 220 that detects the leading edge of the sheet material P is disposed upstream of the first ejection unit 23A, which is the most upstream in the conveying direction. The sheet material position sensor 220 is an example of a sheet material position detection unit.

The sheet material position sensor 220 detects the leading edge of the sheet material P, but may also be configured to read a mark (such as a registration mark) attached to the sheet material P. By configuring it to read a mark, it can be used not only with cut sheet material, but also with continuous media such as continuous paper.

(Example of Hardware Configuration of Liquid Ejection Apparatus)
Next, the hardware configuration of the liquid ejection device will be described with reference to Fig. 5. Fig. 5 is a diagram showing the hardware configuration of the liquid ejection device according to one embodiment. The inkjet printer 1 includes a central processing unit (CPU) 301, a read only memory (ROM) 302, and a random access memory (RAM) 303. The inkjet printer 1 also includes a non-volatile random access memory (NVRAM) 304.

The inkjet printer 1 also includes an external device connection I/F 308, a network I/F 309, and a bus line 310. The inkjet printer 1 also includes a sheet transport section 311, a transport driver 312, and an operation panel 330. The ejection unit 23 for each color includes a liquid ejection head driver 322 and multiple liquid ejection heads 100.

The CPU 301 controls the overall operation of the inkjet printer 1. The ROM 302 stores programs such as IPL used to drive the CPU 301. The RAM 303 is used as a work area for the CPU 301. The NVRAM 304 stores various data such as programs, and preserves the various data even when the power to the inkjet printer 1 is cut off.

The external device connection I/F 308 is connected to a PC (Personal Computer) via a USB (Universal Serial Bus) cable or the like, and communicates control signals and print data with the PC. The network I/F 309 is an interface for data communication using a communication network such as the Internet. The bus line 310 is an address bus, a data bus, or the like for electrically connecting each component such as the CPU 301.

The sheet transport unit 311 is, for example, a roller and a motor that drives the roller, and transports the sheet material P in the transport direction along a transport path within the inkjet printer 1. The transport driver 312 controls the movement of the sheet transport unit 311 in the transport direction.

The liquid ejection head 100 has multiple nozzle rows 101 in which multiple nozzles that eject liquid are aligned in a direction perpendicular to the transport direction. The liquid ejection head 100 is disposed on a base member 102 so that the ejection surface (nozzle surface) faces the sheet material P. The liquid ejection head 100 forms an image on the sheet material P by ejecting liquid at a predetermined position on the sheet material P that is transported intermittently in the transport direction. The liquid ejection head driver 322 is a drive circuit that controls the drive of the liquid ejection head 100.

The operation panel 330 is configured with a touch panel that displays the current setting values or a selection screen, etc., and accepts input from the operator, as well as an alarm lamp, etc.

The liquid ejection head driver 322 may be configured not to be mounted on the ejection unit 23 of each color, but to be arranged outside the ejection unit 23 and connected to a bus line. Also, the transport driver 312 and the liquid ejection head driver 322 may be configured by functions realized by commands of the CPU 301 according to a program.

(Example of functional configuration of liquid ejection device)
Next, a functional configuration relating to ejection timing control of the liquid ejection device will be described with reference to Fig. 6. Fig. 6 is a functional configuration diagram of the liquid ejection device according to one embodiment.

The inkjet printer 1 includes various functional parts, such as an ejection start timing determination unit 501, an ejection timing generation unit 502, an ejection timing adjustment unit 503, and a head drive control unit 504. These functional parts are realized, for example, by a program that causes a processor, such as the CPU 301, to execute various functions.

When the detection result of the sheet material position sensor 220 detects the leading edge position of the sheet material P, the ejection start timing determination unit 501 starts counting the number of pulses of the first timing signal of the first encoder 201. When the count value of the number of pulses of the first timing signal of the first encoder 201 reaches a predetermined value, the ejection start timing determination unit 501 determines the ejection start timing of the ejection units 23 of each color. The ejection start timing determination unit 501 notifies the ejection timing generation unit 502 and the head drive control unit 504 of the ejection start timing of the ejection units 23.

When the sheet material P reaches the position of the ejection start timing, the ejection timing generation unit 502 starts counting the number of pulses of the second timing signal of the second encoder 211. The ejection timing generation unit 502 generates the ejection timing of each nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 based on the count value of the number of pulses of the second timing signal of the second encoder 211.

The rotation radius from the center of the shaft 21a of the transport drum 21 to the surface of the sheet material P on the transport drum 21 varies depending on the thickness of the sheet material P. Therefore, even if the count value of the number of pulses of the second timing signal of the second encoder 211 reaches a predetermined value, the actual movement amount of the surface of the sheet material P does not match the expected target movement amount.

The ejection timing adjustment unit 503 adjusts the ejection timing of the other nozzle rows 101 relative to the reference nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 based on the thickness of the sheet material P. The thicknesses of the various sheet materials P are stored in a non-volatile memory such as the NVRAM 304 or a storage such as a HD (Hard Disk). The thicknesses of the sheet materials P may also be stored in the storage of an external device capable of communicating with the inkjet printer 1.

The head drive control unit 504 sends an ejection start timing signal to the liquid ejection head driver 322 of the ejection unit 23 of each color at the determined ejection start timing. The head drive control unit 504 also sends an ejection timing signal to the liquid ejection head driver 322 of the ejection unit 23 of each color at the adjusted ejection timing.

The liquid ejection head driver 322 ejects liquid from each nozzle row 101 in accordance with the ejection timing signal for each nozzle row 101 of each liquid ejection head 100.

(Example of Processing Procedure of Liquid Ejection Apparatus)
Next, the flow of the process of the ejection timing control will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the process procedure of the liquid ejection device according to an embodiment. The flowchart shown in Fig. 7 is realized by a program that causes the CPU 301 to execute various processes.

<Step S001>
In the inkjet printer 1, after the transfer drum 24 transfers the sheet material P to the transport drum 21, the suction device 26 starts to adsorb the sheet material P, and the sheet material P is transported by the rotation of the transport drum 21.

<Step S002>
The inkjet printer 1 detects the leading edge position of the sheet material P by the sheet material position sensor 220 .

<Step S003>
When the inkjet printer 1 detects the leading edge position of the sheet material P by the ejection start timing determination unit 501, it starts counting the number of pulses of the first timing signal of the first encoder 201. When the count value of the number of pulses of the first timing signal of the first encoder 201 reaches a predetermined value, the inkjet printer 1 determines the ejection start timing of the ejection units 23 of each color by the ejection start timing determination unit 501. The inkjet printer 1 notifies the ejection timing generation unit 502 and the head drive control unit 504 of the ejection start timing of the ejection units 23 of each color by the ejection start timing determination unit 501.

<Step S004>
When the sheet material P reaches the position of the ejection start timing, the inkjet printer 1 starts counting the number of pulses of the second timing signal of the second encoder 211 by the ejection timing generation unit 502. The inkjet printer 1 generates the ejection timing of each nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 by the ejection timing generation unit 502.

<Step S005>
The inkjet printer 1 adjusts the ejection timing of the other nozzle rows 101 with respect to the reference nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 by the ejection timing adjustment section 503 based on the thickness of the sheet material P. The inkjet printer 1 notifies the head drive control section 504 of the adjusted ejection timing by the ejection timing adjustment section 503. The inkjet printer 1 sends the ejection timing signal of each nozzle row 101 to the liquid ejection head driver 322 of the ejection unit 23 of each color by the head drive control section 504.

(Discharge timing)
Here, a detailed description will be given of the ejection start timing of the ejection units 23 of each color using the first encoder 201, and the ejection timing of each nozzle row 101 of each liquid ejection head 100 using the second encoder 211, with reference to Fig. 8. Fig. 8 is a timing chart of a liquid ejection device according to one embodiment.

When the CPU 301 detects a falling edge of the position detection signal PS of the sheet material position sensor 220, which indicates the leading edge position of the sheet material P, the inkjet printer 1 starts counting the number of pulses of the first timing signal ES1 of the first encoder 201.

When the count value of the number of pulses of the first timing signal ES1 of the first encoder 201 reaches a predetermined value, the inkjet printer 1 determines the ejection start timing of the ejection unit 23 of each color by the CPU 301. The inkjet printer 1 sends the ejection start timing signal determined by the CPU 301 to the liquid ejection head driver 322 of the ejection unit 23 of each color.

The ejection start timing signal includes one of the Y print signal YS, M print signal MS, C print signal CS, K print signal KS, 5ST print signal 5STS, and 6ST print signal 6STS.

When the count value of the number of pulses of the first timing signal ES1 of the first encoder 201 reaches a predetermined value, the inkjet printer 1 starts counting the number of pulses of the second timing signal ES2 of the second encoder 211 by the CPU 301. The inkjet printer 1 generates the ejection timing of each nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 based on the count value of the number of pulses of the second timing signal ES2 of the second encoder 211 by the CPU 301.

The inkjet printer 1 also uses the CPU 301 to adjust the ejection timing of the other nozzle rows 101 relative to the reference nozzle row 101 of each liquid ejection head 100 in the ejection unit 23 based on the thickness of the sheet material P. The inkjet printer 1 uses the CPU 301 to send the adjusted ejection timing signal to the liquid ejection head driver 322 of the ejection unit 23 for each color.

The inkjet printer 1 forms an image on the sheet material P by ejecting liquid from each nozzle row 101 of the liquid ejection head 100 using the liquid ejection head driver 322 of each color ejection unit 23.

As described above, the overlay accuracy of each color is controlled by the number of pulses of the first timing signal ES1 of the first encoder 201. In addition, the spacing between dots in the transport direction and the positional accuracy of the dots are controlled by the number of pulses of the second timing signal ES2 of the second encoder 211.

After the ejection start timing signal for each color is sent to the liquid ejection head driver 322 for each color, the ejection of liquid from each liquid ejection head 100 is performed by an ejection timing signal generated from the number of pulses of the second timing signal ES2 of the second encoder 211.

As a result, the ejection accuracy between the same colors, which requires high accuracy, can be determined by the position of the sheet material P on the transport drum 21, which is obtained from the number of pulses of the second timing signal ES2 of the second encoder 211. The second encoder 211 detects the amount of movement of the surface of the transport drum 21, and can cancel errors due to the rotation accuracy of the transport drum 21 and the component accuracy of the transport drum 21. Therefore, even if a high-precision encoder is not used for the first encoder 201, high-precision liquid landing position accuracy can be obtained, improving print quality.

(Method of Adjusting Ejection Timing of Nozzle Array)
A method for adjusting the ejection timing of the nozzle array 101 will be described in detail below.

The inkjet printer 1 prints by adsorbing the sheet material P to the transport drum 21, so the radius of rotation from the center of the shaft 21a of the transport drum 21 to the surface of the sheet material P on the transport drum 21 is larger than the radius R of the transport drum 21 by the thickness t of the sheet material P. Therefore, the actual amount of movement of the surface of the sheet material P obtained from the second timing signal ES2 of the second encoder 211 varies depending on the thickness t of the sheet material P.

The inkjet printer 1 therefore adjusts the ejection timing according to the thickness of the sheet material P so that there is no deviation in the ejection timing of each nozzle row 101 of each liquid ejection head 100 in the ejection unit 23. The ejection timing is adjusted based on the reference thickness t0 of the sheet material P.

However, when printing on an actual sheet material P, the difference in the rotation radius to the surface of the sheet material P on the transport drum 21 between the reference thickness t0 of the sheet material P and the actual thickness t of the sheet material P causes a discrepancy in the ejection timing.

Therefore, the inkjet printer 1 further adjusts the deviation in ejection timing by the difference between the reference thickness t0 of the sheet material P and the actual thickness t of the sheet material P.

Figure 9 is a diagram showing the distance between nozzle rows 101 of a liquid ejection head 100 according to one embodiment. Figure 10 is a diagram showing the distance between ejection units 23 according to one embodiment.

As shown in FIG. 9, the liquid ejection head 100 has, for example, eight lines of nozzle rows 101, that is, the first nozzle row L1 to the eighth nozzle row L8. Also, as shown in FIG. 10, the multiple liquid ejection heads 100 are arranged on the base member 102, shifted by 1200 dpi in a direction perpendicular to the conveying direction of the sheet material P.

As shown in FIG. 9, the distance between the reference first nozzle row L1 and the other second nozzle row L2 is a distance L12, and the distance between the reference first nozzle row L1 and the other third nozzle row L3 is a distance L13. The distance between the reference first nozzle row L1 and the other fourth nozzle row L4 is a distance L14, and the distance between the reference first nozzle row L1 and the other fifth nozzle row L5 is a distance L15.

Furthermore, the distance between the reference first nozzle row L1 and the other sixth nozzle row L6 is the distance L15+L16, and the distance between the reference first nozzle row L1 and the other seventh nozzle row L7 is the distance L15+L17. Furthermore, the distance between the reference first nozzle row L1 and the other eighth nozzle row L8 is the distance L15+L18.

First, the inkjet printer 1 uses the 8-line nozzle array 101 to eject liquid onto a reference sheet material P at ideal distances L12 to L18. The inkjet printer 1 corrects the ejection timing of the other nozzle arrays, second nozzle array L2 to eighth nozzle array L8, based on the difference between the result printed by the reference first nozzle array L1 and the result printed by any one of the other nozzle arrays, second nozzle array L2 to eighth nozzle array L8. This correction is called "inter-nozzle array timing correction." Inter-nozzle array timing correction is performed, for example, before the inkjet printer 1 is shipped.

By correcting the timing between nozzle rows, the distance error from the reference first nozzle row L1 to any one of the other nozzle rows L2 to L8 is calculated as the first adjustment value. The first adjustment value is stored in a non-volatile memory such as NVRAM 304 or a storage such as a HD (Hard Disk). The first adjustment value may also be stored in the storage of an external device capable of communicating with the inkjet printer 1.

Inter-nozzle array timing correction simultaneously corrects distance errors between nozzle arrays, fluctuations in the gap between the nozzle face of the ejection unit 23 and the surface of the reference sheet material P, and differences in liquid ejection speed between nozzle arrays.

The inkjet printer 1 then adjusts the ejection timing of the nozzle row 101 based on the thickness t of the actual sheet material P. After the timing between the nozzle rows is corrected, the thickness of the reference sheet material P changes from t0 to the thickness t of the actual sheet material P, so the radius of rotation to the surface of the actual sheet material P adsorbed to the transport drum 21 is the radius R of the transport drum 21 plus the thickness t of the actual sheet material P.

On the other hand, the rotation radius to the surface of the reference sheet material P used for printing when correcting the timing between the nozzle rows is the radius R of the transport drum 21 plus the thickness t0 of the reference sheet material P. Therefore, the ratio of the rotation radius during actual printing to the rotation radius during correcting the timing between the nozzle rows is (R+t)/(R+t0).

When the distance from the reference first nozzle row L1 to any one of the other second nozzle row L2 to eighth nozzle row L8 is adjusted using the rotation angle obtained from the second encoder 211, the sheet material P is conveyed by the conveying drum 21 with a deviation of the rotation radius ratio (R+t)/(R+t0).

Therefore, when correcting the distance L12 from the reference first nozzle row L1 to the other second nozzle row L2, for example, the inkjet printer 1 calculates the distance error ΔL12 calculated by the following formula (1) as the second adjustment value. The second adjustment value is stored in a non-volatile memory such as NVRAM 304 or a storage such as an HD (Hard Disk). The second adjustment value may also be stored in the storage of an external device capable of communicating with the inkjet printer 1.

The inkjet printer 1 then adds the second adjustment value calculated by formula (1) to the first adjustment value used during timing correction between the nozzle arrays, thereby adjusting the ejection timing of the second nozzle array L2 relative to the reference first nozzle array L1 according to the actual thickness of the sheet material P.

Similarly, the inkjet printer 1 calculates the distance errors ΔL13 to ΔL18 as second adjustment values for the distances L13 to L18 from the reference first nozzle row L1 to any one of the other nozzle rows, the third nozzle row L3 to the eighth nozzle row, and adds the second adjustment value to the first adjustment value. By adding the second adjustment value to the first adjustment value, it becomes possible to adjust the ejection timing for all other nozzle rows L2 to L8 according to the thickness of the sheet material P.

Normally, the inkjet printer 1 performs timing correction between nozzle rows for each color, and adjusts the ejection timing for each color according to the thickness of the sheet material P. By applying ejection timing adjustment according to the thickness of the sheet material P to the timing correction between nozzle rows for all colors, high quality printing is possible.

In this example, the inkjet printer 1 uses a lifting mechanism to raise and lower the ejection unit 23 in the radial direction of the transport drum 21 for each color according to the thickness of the sheet material P, and maintains a constant distance between the surface of the sheet material P and the nozzle surface of the ejection unit 23.

In other words, the rotation angle of the transport drum 21 relative to the ejection unit 23 of each color does not vary according to the thickness of the sheet material P. Therefore, the inkjet printer 1 does not need to adjust the ejection timing according to the thickness of the sheet material P between the reference first nozzle rows L1 of the multiple liquid ejection heads 100 in the ejection unit 23 of each color.

(Method of Adjusting Ejection Timing Between Upstream Head and Downstream Head)
A method for adjusting the ejection timing between the upstream head and the downstream head will be described in detail below.

As shown in FIG. 10, the multiple liquid ejection heads 100 in the ejection unit 23 of each color are aligned with a shift in both the transport direction of the sheet material P and the width direction of the sheet material P. In other words, the odd-numbered liquid ejection heads 100 from the upstream side of the sheet material P and the even-numbered liquid ejection heads 100 from the upstream side of the sheet material P are aligned with a shift in both the transport direction and the width direction of the sheet material P.

In such a head array configuration, the landing position of the liquid on the sheet material P may be misaligned between the upstream liquid ejection head 100 (upstream head) and the downstream liquid ejection head 100 (downstream head) in one ejection unit 23.

Figure 11 shows the deviation in landing position between the upstream head and downstream head in one embodiment.

In this example, the discharge unit 23 has an upstream liquid discharge head 100 (upstream head) and a downstream liquid discharge head 100 (downstream head) arranged at an angle to the lifting direction of the discharge unit 23. The inkjet printer 1 uses a lifting mechanism to lift the discharge unit 23 in the radial direction of the transport drum 21, based on the center between the upstream head and the downstream head.

In the inkjet printer 1, the lifting mechanism expands or contracts the reference distance g0 of the gap between the nozzle face of the discharge unit 23 and the surface of the sheet material P during timing correction between the nozzle rows to a distance g according to the actual thickness t0 of the sheet material P. When the discharge unit 23 is raised or lowered by the lifting mechanism, the position of the liquid landing on the sheet material P is shifted by having a predetermined angle θ between the lifting direction of the discharge unit 23 and the discharge direction of the liquid discharge head 100.

In other words, if there is a certain angle θ between the ascending and descending direction of the discharge unit 23 and the discharge direction of the liquid discharge head 100, and the discharge directions of the upstream head and the downstream head are different, the landing distance of the liquid between the upstream head and the downstream head changes when the discharge unit 23 ascends and descends.

In such a head array configuration, the inkjet printer 1 further adjusts the ejection timing of the nozzle rows between the upstream head and the downstream head when the lifting mechanism raises and lowers the ejection unit 23 in accordance with the thickness of the sheet material P.

For example, consider the case where the gap between the nozzle face of the ejection unit 23 and the surface of the reference sheet material P during inter-nozzle array timing correction is expanded from the reference distance g0 to the distance g during lifting and lowering. The landing positions of the liquid on the sheet material P from the nozzle arrays 101 of both the upstream head and the downstream head are shifted inward.

The deviation amount ΔLg of the landing position is calculated from the following formula (2). That is, the deviation amount ΔLg of the landing position is calculated based on the lifting displacement amount of the discharge unit 23 (the distance g of the gap between the nozzle face and the surface of the sheet material P - the reference distance g0) and the angle θ between the lifting direction of the discharge unit 23 and the discharge direction of the liquid discharge head 100. The reference distance g0 and the angle θ are stored in a non-volatile memory such as the NVRAM 304 or a storage such as a HD (Hard Disk). The reference distance g0 and the angle θ may also be stored in the storage of an external device that can communicate with the inkjet printer 1.

In this embodiment, the ejection direction of the upstream head and the ejection direction of the downstream head are inclined at the same angle θ with respect to the ascending and descending direction of the ejection unit 23, so the same landing position deviation amount ΔLg occurs for both the upstream head and the downstream head.

Therefore, the correction value for correcting the first adjustment value for timing correction between nozzle rows of the downstream head with reference to the upstream head is twice the deviation amount ΔLg of the landing position. The inkjet printer 1 uses the ejection timing adjustment unit 503 to subtract this correction value (2 x ΔLg) from the distances between nozzle rows L12 to L18 of each downstream head.

Conversely, if the gap between the nozzle face and the surface of the reference sheet material P during nozzle row timing correction is reduced from the reference distance g0 to distance g', the landing positions of the liquid on the sheet material P from the nozzle rows 101 of both the upstream head and the downstream head will shift outward. Therefore, the inkjet printer 1 adds this correction value (2 x ΔLg) to the nozzle row distances L12 to L18 of each downstream head by the ejection timing adjustment unit 503.

The inkjet printer 1 also adjusts the ejection timing according to the thickness of the sheet material P by substituting the nozzle row distances L12 to L18 corrected by the correction value (2 x ΔLg) into equation (1) using the ejection timing adjustment unit 503.

As a result, the inkjet printer 1 can produce high-quality images even when the gap between the ejection unit 23 and the surface of the sheet material P is changed.

(Effects of this embodiment)
According to the above embodiment, the ejection timing (distances between nozzle rows L12 to L18) of the other nozzle rows L2 to L8 relative to the reference nozzle row L1 is adjusted according to the thickness of the sheet material P on the transport drum 21, thereby improving the accuracy of the landing position of the liquid on the sheet material P.

In addition, when there is a predetermined angle θ between the ascending and descending direction of the discharge unit 23 and the discharge direction of the liquid discharge head 100 and the discharge directions of the upstream head and the downstream head are different, the discharge timing between the upstream head and the downstream head is corrected when the discharge unit 23 ascends and descends. Therefore, a high-quality image can be formed even if the gap between the discharge unit 23 and the surface of the sheet material P is changed.

The various functions of the embodiments described above can be realized by one or more processing circuits. In this specification, the term "processing circuit" includes a processor programmed to execute each function by software, such as a processor implemented in an electronic circuit. The term "processing circuit" also includes any device, such as an ASIC or DSP (Digital Signal Processor), designed to execute each function. The term "processing circuit" also includes devices such as an FPGA (Field Programmable Gate Array) and conventional circuit modules.

式（３）により前記第２調整値ΔＬを算出する、前記＜３＞に記載の液体吐出装置。
＜５＞ 前記吐出部が３列以上の前記ノズル列を備える場合、前記吐出タイミング調整部は、前記搬送方向で最も上流側の前記ノズル列と他の前記ノズル列のいずれか一つとの間の距離に基づいて他の前記ノズル列の前記第２調整値を算出する、前記＜３＞または＜４＞に記載の液体吐出装置。
＜６＞ 前記液体吐出装置は、前記回転部材の回転方向に複数の前記吐出部を備え、
前記吐出タイミング調整部は、各々の前記吐出部の前記搬送方向で最も上流側の前記ノズル列同士の間では、前記シート材の厚みに応じた前記吐出タイミングの調整を実行せず、各々の前記吐出部の基準の前記ノズル列と他の前記ノズル列との間で前記シート材の厚みに応じた前記吐出タイミングの調整を実行する、前記＜１＞から＜５＞のいずれか一項に記載の液体吐出装置。
＜７＞ 前記液体吐出装置は、前記回転部材の回転方向に複数の前記吐出部と、複数の前記吐出部を前記回転部材の半径方向に同時に昇降させる昇降機構と、を備え、
前記吐出タイミング調整部は、前記昇降機構の昇降方向と、複数の前記吐出部のうちの少なくとも一つの液体吐出方向と、が平行でない場合に、
前記昇降方向と前記液体吐出方向との間の角度と、
前記吐出部のノズル面と基準の前記シート材の表面との間の隙間の距離と、前記吐出部のノズル面と実際の前記シート材の表面との間の隙間の距離との間の差分と、
に基づいて基準の前記ノズル列に対する他の前記ノズル列の前記吐出タイミングをさらに補正する、前記＜１＞から＜６＞のいずれか一項に記載の液体吐出装置。
＜８＞ 前記吐出タイミング調整部は、前記昇降方向と前記液体吐出方向との間の角度をθとし、前記吐出部の前記ノズル面と基準の前記シート材の表面との間の隙間の距離をｇ０とし、前記吐出部の前記ノズル面と実際の前記シート材の表面との間の隙間の距離をｇとした場合に、

式（４）により、基準の前記ノズル列に対する他の前記ノズル列の前記吐出タイミングを補正する、前記＜７＞に記載の液体吐出装置。
＜９＞ 液体吐出装置により実行される液体吐出方法であって、前記液体吐出装置が、
シート材を回転部材の周面に保持して搬送するステップと、
複数のノズルが前記シート材の搬送方向と直行する方向に並んだノズル列を前記搬送方向に複数配置した吐出部から液体を前記シート材に吐出するステップと、
前記シート材の位置を検知するステップと、
前記回転部材の回転量に応じたタイミング信号を生成するステップと、
前記シート材の前記位置の検知結果と、生成された前記タイミング信号と、に基づいて前記吐出部の各々の前記ノズル列の吐出タイミングを生成するステップと、
前記回転部材上の前記シート材の厚みに基づいて基準の前記ノズル列に対する他の前記ノズル列の前記吐出タイミングを調整するステップと、
を実行する、液体吐出方法。
＜１０＞ 液体吐出装置のコンピュータに、
シート材を回転部材の周面に保持して搬送する指令を行うステップと、
複数のノズルが前記シート材の搬送方向と直行する方向に並んだノズル列を前記搬送方向に複数配置した吐出部から液体を前記シート材に吐出する指令を行うステップと、
前記シート材の位置を検知するステップと、
前記回転部材の回転量に応じたタイミング信号を生成するステップと、
前記シート材の前記位置の検知結果と、生成された前記タイミング信号と、に基づいて前記吐出部の各々の前記ノズル列の吐出タイミングを生成するステップと、
前記回転部材上の前記シート材の厚みに基づいて基準の前記ノズル列に対する他の前記ノズル列の前記吐出タイミングを調整するステップと、
を実行させる、プログラム。 Aspects of the present disclosure are, for example, as follows.
<1> A rotating member that holds and conveys a sheet material on a peripheral surface thereof;
an ejection section in which a plurality of nozzle rows are arranged in a conveying direction of the sheet material, the nozzle rows including a plurality of nozzles for ejecting liquid onto the sheet material, the nozzle rows being aligned in a direction perpendicular to the conveying direction of the sheet material;
a sheet material position detection unit that detects the position of the sheet material;
a timing signal generating unit that generates a timing signal according to an amount of rotation of the rotating member;
a discharge timing generating section that generates a discharge timing of the nozzle array of each of the discharge sections based on a detection result of the position of the sheet material and the generated timing signal;
a discharge timing adjustment unit that adjusts the discharge timing of the other nozzle arrays relative to the reference nozzle array based on a thickness of the sheet material on the rotating member;
A liquid ejection device comprising:
<2> The liquid ejection device described in <1>, wherein the ejection timing adjustment unit adjusts the ejection timing of the other nozzle rows relative to the reference nozzle row based on the distance between the reference nozzle row and one of the other nozzle rows, the thickness of the sheet material, and the radius of the rotating member.
<3> The liquid ejection device described in <2>, wherein the ejection timing adjustment unit calculates a first adjustment value of the ejection timing based on a reference thickness of the sheet material, and calculates a second adjustment value of the ejection timing based on the reference thickness of the sheet material and an actual thickness of the sheet material.
<4> When a distance between the reference nozzle row and any one of the other nozzle rows is L, a reference thickness of the sheet material is t0, an actual thickness of the sheet material is t, and a radius of the rotating member is R, the ejection timing adjustment unit

The liquid ejection apparatus according to <3>, wherein the second adjustment value ΔL is calculated by equation (3).
<5> The liquid ejection device described in <3> or <4>, wherein, when the ejection unit has three or more nozzle rows, the ejection timing adjustment unit calculates the second adjustment value of the other nozzle rows based on the distance between the nozzle row most upstream in the transport direction and any one of the other nozzle rows.
<6> The liquid ejection device includes a plurality of the ejection units in a rotation direction of the rotating member,
The liquid ejection device described in any one of <1> to <5>, wherein the ejection timing adjustment unit does not adjust the ejection timing in accordance with the thickness of the sheet material between the nozzle rows that are most upstream in the transport direction of each of the ejection units, but adjusts the ejection timing in accordance with the thickness of the sheet material between the reference nozzle row of each of the ejection units and the other nozzle rows.
<7> The liquid ejection device includes a plurality of the ejection units in a rotation direction of the rotating member, and a lifting mechanism that simultaneously lifts and lowers the plurality of ejection units in a radial direction of the rotating member,
When a direction in which the lifting mechanism is raised and lowered is not parallel to a liquid ejection direction of at least one of the plurality of ejection units,
an angle between the lifting direction and the liquid ejection direction;
a difference between a gap distance between a nozzle surface of the discharge portion and a reference surface of the sheet material and a gap distance between the nozzle surface of the discharge portion and an actual surface of the sheet material;
The liquid ejection device according to any one of <1> to <6>, further correcting the ejection timing of the other nozzle arrays with respect to the reference nozzle array based on a difference between the ejection timing of the other nozzle arrays and the ejection timing of the reference nozzle array.
<8> When an angle between the lifting direction and the liquid ejection direction is θ, a gap distance between the nozzle face of the ejection unit and a reference surface of the sheet material is g0, and a gap distance between the nozzle face of the ejection unit and an actual surface of the sheet material is g, the ejection timing adjustment unit

The liquid ejection apparatus according to <7>, wherein the ejection timing of the other nozzle arrays is corrected with respect to the reference nozzle array by using equation (4).
<9> A liquid ejection method performed by a liquid ejection device, the liquid ejection device comprising:
A step of conveying a sheet material while holding it on a circumferential surface of a rotating member;
ejecting liquid onto the sheet material from an ejection section having a plurality of nozzle rows arranged in a conveying direction of the sheet material, the nozzle rows being each formed in a direction perpendicular to the conveying direction of the sheet material;
sensing the position of the sheet material;
generating a timing signal corresponding to an amount of rotation of the rotary member;
generating ejection timings for the nozzle arrays of each of the ejection sections based on a detection result of the position of the sheet material and the generated timing signal;
adjusting the ejection timing of the other nozzle arrays relative to a reference nozzle array based on a thickness of the sheet material on the rotating member;
A liquid ejection method comprising:
<10> A computer of the liquid ejection device,
issuing a command to convey the sheet material while holding it on a circumferential surface of a rotating member;
issuing a command to eject liquid onto the sheet material from an ejection unit having a plurality of nozzle rows arranged in a conveying direction of the sheet material, the nozzle rows being each formed in a direction perpendicular to the conveying direction of the sheet material;
sensing the position of the sheet material;
generating a timing signal corresponding to an amount of rotation of the rotary member;
generating ejection timings for the nozzle arrays of each of the ejection sections based on a detection result of the position of the sheet material and the generated timing signal;
adjusting the ejection timing of the other nozzle arrays relative to a reference nozzle array based on a thickness of the sheet material on the rotating member;
A program that executes.

REFERENCE SIGNS LIST 1 Inkjet printer 10 Carry-in section 11 Carry-in tray 12 Feeding device 13 Pair of registration rollers 20 Printing section 21 Transport drum 21a Shaft 22 Liquid ejection section 23 Ejection unit 24 Transfer cylinder 25 Transfer cylinder 26 Suction device 30 Drying section 31 Drying mechanism section 32 Suction transport mechanism section 40 Carry-out section 100 Liquid ejection head 101 Nozzle row 102 Base member 201 First encoder 202 Encoder wheel 203 First encoder sensor 211 Second encoder 212 Encoder scale 213 Second encoder sensor 220 Sheet material position sensor 301 CPU
302 ROM
303 RAM
304 NVRAM
308 External device connection interface
309 Network I/F
310 Bus line 311 Sheet transport section 312 Transport driver 330 Operation panel 322 Liquid ejection head driver 501 Ejection start timing determination section 502 Ejection timing generation section 503 Ejection timing adjustment section 504 Head drive control section P Sheet material PS Position detection signal ES1 First timing signal ES2 Second timing signal YS Y print signal MS M print signal CS C print signal KS K print signal 5STS 5ST print signal 6STS 6ST print signal

JP 2019-155794 A

Claims (10)

A rotating member that holds and conveys the sheet material on its circumferential surface;
an ejection section in which a plurality of nozzle rows are arranged in a conveying direction of the sheet material, the nozzle rows including a plurality of nozzles for ejecting liquid onto the sheet material, the nozzle rows being aligned in a direction perpendicular to the conveying direction of the sheet material;
a sheet material position detection unit that detects the position of the sheet material;
a timing signal generating unit that generates a timing signal according to an amount of rotation of the rotating member;
a discharge timing generating section that generates a discharge timing of the nozzle array of each of the discharge sections based on a detection result of the position of the sheet material and the generated timing signal;
a discharge timing adjustment unit that adjusts the discharge timing of the other nozzle arrays relative to the reference nozzle array based on a thickness of the sheet material on the rotating member;
A liquid ejection device comprising: The liquid ejection device according to claim 1, wherein the ejection timing adjustment unit adjusts the ejection timing of the other nozzle rows relative to the reference nozzle row based on the distance between the reference nozzle row and one of the other nozzle rows, the thickness of the sheet material, and the radius of the rotating member. The liquid ejection device according to claim 2, wherein the ejection timing adjustment unit calculates a first adjustment value of the ejection timing based on a reference thickness of the sheet material, and calculates a second adjustment value of the ejection timing based on the reference thickness of the sheet material and the actual thickness of the sheet material. When a distance between the reference nozzle row and any one of the other nozzle rows is L, a reference thickness of the sheet material is t0, an actual thickness of the sheet material is t, and a radius of the rotating member is R, the ejection timing adjustment unit

The liquid ejection device according to claim 3 , wherein the second adjustment value ΔL is calculated by using equation (3). The liquid ejection device according to claim 3 or 4, wherein when the ejection section has three or more nozzle rows, the ejection timing adjustment section calculates the second adjustment value for the other nozzle rows based on the distance between the nozzle row furthest upstream in the transport direction and any one of the other nozzle rows. the liquid ejection device includes a plurality of ejection portions arranged in a rotational direction of the rotating member,
A liquid ejection device as described in any one of claims 1 to 4, wherein the ejection timing adjustment unit does not adjust the ejection timing in accordance with the thickness of the sheet material between the nozzle rows that are most upstream in the transport direction of each of the ejection units, but adjusts the ejection timing in accordance with the thickness of the sheet material between the reference nozzle row of each of the ejection units and the other nozzle rows. the liquid ejection device includes a plurality of ejection units in a rotational direction of the rotating member, and a lifting mechanism that simultaneously lifts and lowers the plurality of ejection units in a radial direction of the rotating member,
When a direction in which the lifting mechanism is raised and lowered is not parallel to a liquid ejection direction of at least one of the plurality of ejection units,
an angle between the lifting direction and the liquid ejection direction;
a difference between a gap distance between a nozzle surface of the discharge portion and a reference surface of the sheet material and a gap distance between the nozzle surface of the discharge portion and an actual surface of the sheet material;
The liquid ejection device according to claim 1 , further correcting the ejection timing of the other nozzle arrays with respect to the reference nozzle array based on a difference between the ejection timing of the other nozzle arrays and the ejection timing of the reference nozzle array. When an angle between the ascending/descending direction and the liquid ejection direction is θ, a gap distance between the nozzle face of the ejection unit and a reference surface of the sheet material is g0, and a gap distance between the nozzle face of the ejection unit and an actual surface of the sheet material is g,

The liquid ejection device according to claim 7 , wherein the ejection timing of the other nozzle arrays is corrected with respect to the reference nozzle array by using equation (4). A liquid ejection method performed by a liquid ejection device, the liquid ejection device comprising:
A step of conveying a sheet material while holding it on a circumferential surface of a rotating member;
ejecting liquid onto the sheet material from an ejection section having a plurality of nozzle rows arranged in a conveying direction of the sheet material, the nozzle rows being each formed in a direction perpendicular to the conveying direction of the sheet material;
sensing the position of the sheet material;
generating a timing signal corresponding to an amount of rotation of the rotary member;
generating ejection timings for the nozzle arrays of each of the ejection sections based on the detection result of the position of the sheet material and the generated timing signal;
adjusting the ejection timing of the other nozzle arrays relative to a reference nozzle array based on a thickness of the sheet material on the rotating member;
A liquid ejection method comprising: A computer of the liquid ejection device
issuing a command to convey the sheet material while holding it on a circumferential surface of a rotating member;
issuing a command to eject liquid onto the sheet material from an ejection unit having a plurality of nozzle rows arranged in a conveying direction of the sheet material, the nozzle rows being each formed in a direction perpendicular to the conveying direction of the sheet material;
sensing the position of the sheet material;
generating a timing signal corresponding to an amount of rotation of the rotary member;
generating ejection timings for the nozzle arrays of each of the ejection sections based on the detection result of the position of the sheet material and the generated timing signal;
adjusting the ejection timing of the other nozzle arrays relative to a reference nozzle array based on a thickness of the sheet material on the rotating member;
A program to execute.

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