JP7775705B2 - Liquid ejection device and liquid ejection method - Google Patents

Description

The present invention relates to a liquid ejection device and a liquid ejection method.

Liquid ejection devices that eject liquid onto a long recording medium as it is transported are known. Such liquid ejection devices are used in applications such as image forming devices that form images on a long recording medium, such as continuous paper, using the ejected liquid.

A liquid ejection device has been disclosed that controls the timing of liquid ejection by multiple liquid ejection units based on the transport distance error in the transport direction of a long recording medium, which is detected by multiple detection units provided corresponding to the positions of each of the multiple liquid ejection units (see, for example, Patent Document 1).

In liquid ejection devices, the accuracy of liquid ejection can sometimes decrease due to the expansion and contraction of the recording medium being transported.

The present invention aims to provide a liquid ejection device with excellent liquid ejection accuracy.

A liquid ejection device according to one aspect of the present invention is a liquid ejection device that ejects liquid onto a long recording medium being transported, and includes: a plurality of liquid ejection means that eject liquid onto the recording medium being transported; a plurality of imaging means that are arranged corresponding to the positions of the liquid ejection means and output captured images of the recording medium being transported; a control means that controls the timing of liquid ejection by the plurality of liquid ejection means based on the effective image area in each of the plurality of captured images output from the plurality of imaging means; and a modification means that changes at least one of the position, shape, and size of the effective image area based on the expansion/contraction state of the recording medium, wherein the number of the plurality of imaging means is less than the number of the plurality of liquid ejection means, and one of the plurality of imaging means is arranged at a position corresponding to the position of the liquid ejection means that is arranged most upstream of the plurality of liquid ejection means in the transport direction .

This invention provides a liquid ejection device with excellent liquid ejection accuracy.

1 is a diagram illustrating a configuration of a liquid ejection device according to an embodiment; FIG. 2 is a block diagram illustrating the configuration of the periphery of a liquid ejection unit according to the embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of a control IC according to an embodiment. 10 is a flowchart of an example of processing by a control IC according to the embodiment. 10A and 10B are diagrams illustrating an example of the relationship between a captured image and an effective image area. FIG. 10 is a diagram illustrating an example of an effective imaging area before a position change. FIG. 10 is a diagram illustrating an example of an effective imaging area after a position change. FIG. 1 is a first diagram showing an example of expansion and contraction of continuous paper in accordance with an ink application area. FIG. 2 is a second diagram showing an example of expansion and contraction of continuous paper depending on the ink application area. 10A and 10B are diagrams illustrating examples of changes in the shape of the effective imaging area according to the expansion and contraction state of the continuous paper. 10A and 10B are diagrams illustrating an example of image data correction according to the expansion and contraction state of continuous paper. FIG. 10 is a diagram illustrating the configuration of a liquid ejection device according to a first modified example. FIG. 10 is a diagram illustrating an example of the configuration of a liquid ejection device according to a second modified example. FIG. 10 is a diagram illustrating an example of the configuration of a liquid ejection device according to a third modified example. FIG. 10 is a diagram illustrating an example of the configuration of a liquid ejection device according to a fourth modified example. FIG. 10 is a diagram illustrating an example of the configuration of a liquid ejection device according to a fifth modified example.

The following describes the embodiments of the invention with reference to the drawings. Note that in each drawing, identical components are designated by the same reference numerals, and duplicate explanations will be omitted where appropriate.

Furthermore, the embodiments shown below are illustrative of a liquid ejection device that embodies the technical concept of the present invention, and the present invention is not limited to the embodiments shown below. Unless otherwise specified, the shapes of the components described below, their relative positions, parameter values, etc. are intended as examples and are not intended to limit the scope of the present invention. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

The liquid ejection device according to the embodiment ejects liquid onto a long recording medium that is being transported. In the embodiment, an inkjet liquid ejection device that ejects ink onto continuous paper, which is a long piece of paper, to form an image is described as an example. Here, continuous paper is an example of a long recording medium, and ink is an example of a liquid. Note that the terms image formation, printing, printing, and recording in the embodiment are all synonymous.

<Configuration example of liquid ejection device 1>
FIG. 1 is a diagram illustrating the configuration of a liquid ejection device 1 according to an embodiment.

In this embodiment, liquid ejection units 210K, 210Y, 210M, and 210C each eject ink and apply the ink to the continuous paper 120 to form an image. Note that when there is no need to distinguish between the liquid ejection units 210K, 210Y, 210M, and 210C, they will be referred to as liquid ejection units 210.

Liquid ejection means 210K ejects black ink, liquid ejection means 210Y ejects yellow ink, liquid ejection means 210M ejects magenta ink, and liquid ejection means 210C ejects cyan ink. A color image is formed on the continuous paper 120 using each color of ink. In the following, for ease of explanation, black may be referred to as K, yellow as Y, magenta as M, and cyan as C.

As shown in FIG. 1, liquid ejection means 210K, 210Y, 210M, and 210C are provided around the continuous paper 120. The liquid ejection means 210K, 210Y, 210M, and 210C eject ink onto the continuous paper 120 as it is transported.

The continuous paper 120 is stretched across a drive roller 230 and eight support rollers 220. The continuous paper 120 moves along conveying direction 2, driven by the drive roller 230. Conveying direction 2 is the direction in which the continuous paper 120 moves as the drive roller 230 rotates.

Eight support rollers 220 arranged opposite the liquid ejection means 210 maintain tension on the continuous paper 120 when ink is ejected from the liquid ejection means 210.

Image capture devices 52A and 52C are provided corresponding to the positions of liquid ejection devices 210K and 210M, and output captured images of the continuous paper 120 being conveyed.

In this embodiment, the imaging device 52A is positioned upstream in the transport direction of the continuous paper 120 from the ejection position where ink is ejected from the liquid ejection device 210K. The imaging device 52C is positioned at a position corresponding to the position of the liquid ejection device 210M. The position corresponding to the position of the liquid ejection device 210M is, for example, immediately below the position where the liquid ejection device 210M ejects ink onto the continuous paper 120.

There are four liquid discharge means 210 and two imaging means 52A and 52B, so the number of imaging means 52A and 52B is fewer than the number of liquid discharge means 210. Furthermore, of the imaging means 52A and 52B, imaging means 52A is located at a position corresponding to the position of liquid discharge means 210K, which is located furthest upstream in the conveying direction 2 among the four liquid discharge means 210. The position corresponding to the position of liquid discharge means 210K is, for example, immediately below the position where liquid discharge means 210K discharges ink onto the continuous paper 120.

Each of the imaging devices 52A and 52C includes an LED (Light Emitting Diode) and an imaging element. The imaging element is a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) containing multiple pixels.

The imaging means 52A and 52C irradiate the continuous paper 120 with light from an LED, capture images of a predetermined imaged area of the continuous paper 120 using an imaging element, and output the captured images Sa and Sc to the control means 520. The predetermined imaged area corresponds to the area on the continuous paper 120 that can be imaged by each of the imaging means 52A and 52C.

The surface of the continuous paper 120 contains a background pattern caused by paper fibers, etc., and the pattern of the background pattern varies depending on the position on the continuous paper 120. The imaging devices 52A and 52C, for example, image this background pattern on the continuous paper 120. However, the object imaged by the imaging devices 52A and 52C is not limited to the background pattern; they may also image marks pre-applied on the continuous paper 120, or the speckle pattern that occurs when laser light is irradiated onto the continuous paper 120.

The control means 520 controls the timing of ink ejection by the liquid ejection means 210K, 210Y, 210M, and 210C based on the effective image areas contained in the captured images Sa and Sc, respectively.

Specifically, the control means 520 detects the transport distance error of the continuous paper 120 in the transport direction 2 based on the effective image area in each of the captured images Sa and Sc, and controls the ink ejection timing of the liquid ejection means 210K, 210Y, 210M, and 210C in accordance with this transport distance error. Here, the effective image area refers to a portion of the image area in each of the captured images Sa and Sc that is used to detect the transport distance error.

In addition to controlling the timing of ink ejection by the liquid ejection means 210Y, 210M, and 210C, the control means 520 can also control the transport of the continuous paper 120, etc.

<Example of the configuration of the liquid ejection unit 210 and its surroundings>
Fig. 2 is a block diagram illustrating an example of the configuration around the liquid discharge unit 210. Note that the liquid discharge units 210K, 210C, 210M, and 210Y all have the same configuration, so Fig. 2 will explain one liquid discharge unit 210 as an example.

As shown in FIG. 2, the liquid ejection means 210 has a head substrate 201, a piezoelectric element support substrate 202, a piezoelectric element driving IC (Integrated Circuit) 203, and multiple piezoelectric elements 204. The piezoelectric element driving IC 203 also has multiple switching circuits 205 that are paired with the multiple piezoelectric elements 204.

The liquid ejection means 210 is communicatively connected to a head drive board 100 that drives the liquid ejection means 210. The head drive board 100 is communicatively connected to an external PC (Personal Computer) 300. In this embodiment, the head drive board 100 is included in the control means 520, but it may also be provided separately from the control means 520.

The liquid ejection means 210 is provided with multiple liquid chambers that contain ink, and each of the multiple liquid chambers is provided with a nozzle that ejects ink. Multiple piezoelectric elements 204 are provided in pairs in the multiple liquid chambers.

The multiple piezoelectric elements 204 expand and contract in response to the drive waveform signal, generating pressure that is applied to the ink in the liquid chamber, causing the ink to be ejected from the nozzle. Each of the multiple switching circuits 205 is an electrical circuit that switches the ink ejection state and non-ejection state of the multiple piezoelectric elements 204.

The head drive board 100 has a control IC 101, drive waveform generation means 102A and 102B, and memory 103. The control IC 101 receives image data Im, which is the basis for image formation by the liquid ejection device 1, from the external PC 300, and transmits this image data Im and an ejection timing signal tt to the liquid ejection means 210. The ejection timing signal tt is a signal that corresponds to the timing of ink ejection by the liquid ejection means 210.

The control IC 101 determines the ink ejection timing based on the captured images Sa and Sc captured by the imaging units 52A and 52C. The control IC 101 outputs an ejection timing signal tt corresponding to the determined ink ejection timing to the liquid ejection unit 210.

The drive waveform generating means 102A outputs a drive waveform signal VcomA generated in accordance with image data Im received via the control IC 101 to the liquid ejection means 210. The drive waveform generating means 102B outputs a drive waveform signal VcomB generated in accordance with image data Im received via the control IC 101 to the liquid ejection means 210.

Memory 103 is a storage device such as a ROM (Read Only Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive).

The multiple switching circuits 205 output drive waveform signals VcomA and VcomB to the piezoelectric elements 204 that are to be put into an ejection state among the multiple piezoelectric elements 204 in response to the image data Im and the ejection timing signal tt. The piezoelectric elements 204 that are put into an ejection state apply pressure to the ink in the liquid chamber in response to the input drive waveform signals VcomA and VcomB, causing ink to be ejected from the nozzle at the ink ejection timing according to the ejection timing signal tt.

<Example of functional configuration of control IC 101>
Fig. 3 is a block diagram illustrating an example of the functional configuration of the control IC 101. As shown in Fig. 3, the control IC 101 has a detection unit 111, a determination unit 112, a communication unit 113, an acquisition unit 114, a change unit 115, a correction unit 116, and an ejection control unit 117. Note that Fig. 3 shows the main components of the control IC 101, but the control IC 101 may have components other than those shown in Fig. 3.

The control IC 101 detects the transport distance error of the continuous paper 120 in the transport direction 2 using the detection unit 111, and determines the ink ejection timing of each of the liquid ejection means 210C, 210M, and 210Y based on the detected transport distance error using the determination unit 112. The control IC 101 causes the liquid ejection means 210K, 210C, 210M, and 210Y to eject ink at the determined ink ejection timing using the ejection control unit 117.

The control IC 101 also receives a print job including image data Im from the external PC 300 via the communication unit 113, and acquires via the acquisition unit 114 information on the internal device temperature constant T1, the drying process temperature constant T2, the humidity constant H1, the continuous paper type constant P1, the ink type constant In1, the ink ejection amount constant In2 onto the front (first side) of the continuous paper 120, and the tension constant Te. Based on the information acquired via the acquisition unit 114, the control IC 101 controls the driving of the movement mechanisms 53A and 53C via the change unit 115, and controls the positions of the imaging means 52A mounted on the movement mechanism 53A and the imaging means 52C mounted on the movement mechanism 53C.

Furthermore, the control IC 101 corrects the image data Im using the correction unit 116 based on the various information acquired by the acquisition unit 114, and then causes the ejection control unit 117 to eject ink from the liquid ejection means 210 based on the corrected image data Im'.

Let's explain in more detail. If the distance between imaging device 52A and imaging device 52C in conveying direction 2 is D [m] and the conveying speed of continuous paper 120 is V [m/s], then a predetermined imaged area of continuous paper 120 will pass the position where imaging device 52A is located, and then after time T (= D/V [s]) has elapsed, it will pass the position where imaging device 52C is located.

However, if there is an error in the amount of transport of the continuous paper 120 by the liquid ejection device 1, this time T will be offset. The control IC 101 captures the imaged area of the continuous paper 120 using the imaging means 52A and outputs the captured image Sa, and then, after the time T has elapsed, captures the imaged area of the continuous paper 120 using the imaging means 52C and outputs the captured image Sc.

If there is an error in the transport distance of the continuous paper 120, the image of the captured area of the continuous paper 120 in the captured image Sc will be shifted along the transport direction 2 relative to the image of the captured area of the continuous paper 120 in the captured image Sa, depending on the transport distance error.

The detection unit 111 performs a cross-correlation calculation between the captured image Sa and the captured image Sc, and calculates the amount of deviation Δ of the captured image Sc relative to the captured image Sa in the conveying direction 2. From the calculated amount of deviation Δ, the detection unit 111 detects the conveying distance error ΔDm of the continuous paper 120 at the position of the liquid ejection means 210M.

Here, with respect to the reference liquid discharger 210K, each of the liquid dischargers 210C, 210M, and 210Y is disposed at a distance y along the transport direction 2. This distance y can be expressed by the following equation (1).
y=a×x+b+T1+T2+H1+P1+I1+I2+Te...(1)

Distance x represents the predetermined distance from liquid discharge means 210K. Multiple liquid discharge means 210 are arranged at equal intervals d. Therefore, ideally, distance xc at the position of liquid discharge means 210C is equal to interval d, distance xm at the position of liquid discharge means 210M is equal to twice the interval d, and distance xy at the position of liquid discharge means 210Y is equal to three times the interval d.

However, due to manufacturing errors in the liquid ejection device 1, the actual positions of the liquid ejection means 210C, 210M, and 210K may deviate from the ideal positions. In this embodiment, the actual positions of the liquid ejection means 210C, 210M, and 210K can be expressed by the above equation (1) using predetermined constants a, b, T1, T2, H1, P1, I1, I2, and Te.

Constant a is the distance ratio error among the multiple liquid ejection means 210. Constant b is the variation error among the multiple liquid ejection means 210. Since the ratio error and variation error occur during the manufacturing process of the liquid ejection device 1, they are measured during the manufacturing process and stored in memory 103. The detection unit 111 detects the transport amount error using the ratio error and variation error stored in memory 103.

The constants T1, T2, H1, P1, I1, I2, and Te represent the amount of expansion and contraction depending on the expansion and contraction state of the continuous paper 120, and are acquired by the acquisition unit 114 (described below) and provided from the acquisition unit 114 to the detection unit 111.

The detection unit 111 calculates the transport amount error ΔDc at the position of the liquid discharger 210C other than the transport amount error ΔDm at the position of the liquid discharger 210M using the following equation (2), and calculates the transport amount error ΔDy at the position of the liquid discharger 210Y using the following equation (3). The detection unit 111 outputs the calculated transport amount errors ΔDc, ΔDm, and ΔDy to the determination unit 112.
ΔDc=a×(ΔDm/2)+b+T1+T2+H1+P1+I1+I2+Te...(2)
ΔDy=a×(3×ΔDm/2)+b+T1+T2+H1+P1+I1+I2+Te...(3)

The determination unit 112 determines the ink ejection timing for each of the liquid ejection units 210C, 210M, and 210Y relative to the ejection from the liquid ejection unit 210K based on the transport distance errors ΔDc, ΔDm, and ΔDy input from the detection unit 111.

For example, the determination unit 112 counts the number of clock pulses of a fixed clock signal output by a rotary encoder attached to the drive roller 230, triggered by the timing when the liquid ejection unit 210K ejects ink. The determination unit 112 determines the timing at which the number of clock pulses reaches the target pulse number corresponding to each of the liquid ejection units 210C, 210M, and 210Y, corrected for the transport distance errors ΔDc, ΔDm, and ΔDy, as the ink ejection timing. The determination unit 112 outputs an ejection timing signal tt corresponding to the determined ink ejection timing to the ejection control unit 117.

The communication unit 113 controls communication between the external PC 300 and the control IC 101. In this embodiment, the control IC 101 receives image data Im, which is the source of the image to be formed on the continuous form 120, from the external PC 300 via the communication unit 113.

The acquisition unit 114 inputs in-device temperature information t1 from the device temperature sensor 54 located within the liquid ejection device 1, inputs drying process temperature information t2 from a drying process temperature sensor 55 located in a drying device provided downstream of the liquid ejection device 1, and inputs humidity information h1 from a humidity sensor 56 located within the liquid ejection device 1. The acquisition unit 114 also inputs tension information te from a tension sensor 57 located within the liquid ejection device 1 that detects the tension applied to the continuous paper 120, and inputs continuous paper type information p1, ink type information in1, and ink ejection amount information in2 onto the second side of the continuous paper 120 from the print job. This information is collectively referred to as expansion/contraction state information U. Based on the input expansion/contraction state information U, the acquisition unit 114 references memory 103, in which correspondence information 130 is stored, to acquire constant information V.

Constant information V is information that represents multiple constants according to the expansion and contraction state of the continuous paper 120. Constant information V includes constant T1, constant T2, constant H1, constant Te, constant P1, constant In1, and constant In2.

The correspondence information 130 includes information indicating the correspondence between internal device temperature information t1 and constant T1, the correspondence between drying process temperature information t2 and constant T2, the correspondence between humidity information h1 and constant H1, and the correspondence between tension information te and constant Te. The correspondence information 130 also includes information indicating the correspondence between continuous paper type information p1 and constant P1, the correspondence between ink type information in1 and constant In1, and the correspondence between ink discharge amount information in2 on the second side of the continuous paper 120 and constant In2. Each correspondence is determined in advance through experiments, simulations, etc.

The meaning of each constant included in the constant information V is shown in Table 1 below.

The acquisition unit 114 outputs the acquired constant information V to the detection unit 111, the change unit 115, and the correction unit 116.

The modification unit 115 is an example of a modification means that modifies at least one of the position, shape, and size of the effective image area on the continuous form 120 based on the expansion/contraction state of the continuous form 120. In this embodiment, the modification unit 115 modifies at least one of the position, shape, and size of the effective image area when the amount of expansion/contraction of the continuous form 120 is equal to or greater than a predetermined expansion/contraction threshold.

In this embodiment, the modification unit 115 drives the moving mechanism 53A that movably mounts the imaging unit 52A in accordance with constant information V based on the expansion/contraction state information U of the continuous form 120, and changes the position of the imaging unit 52A, thereby changing the position of the effective image area in the captured image Sa. Furthermore, the modification unit 115 drives the moving mechanism 53C that movably mounts the imaging unit 52C in accordance with constant information V based on the expansion/contraction state information U of the continuous form 120, and changes the position of the imaging unit 52C, thereby changing the position of the effective image area in the captured image Sc.

The change unit 115 can change the position of each of the imaging devices 52A and 52C in at least one of the conveying direction 2 and the width direction of the continuous paper 120, which intersects with the conveying direction 2.

When the liquid ejection means 210K, 210C, 210M and 210Y eject ink onto the front surface (first side) of the continuous paper 120 and then eject ink onto the back surface (second side) of the continuous paper 120, which is the side opposite the front surface of the continuous paper 120, i.e., when double-sided printing is performed, the modification unit 115 can modify the position of the effective image area based on correspondence information 130 corresponding to the drying state of the continuous paper 120 onto which ink has been ejected onto the front surface of the continuous paper 120, before the liquid ejection means 210K, 210C, 210M and 210Y eject ink onto the back surface of the continuous paper 120.

Note that the change in the effective image area by the change unit 115 is not limited to changing the positions of the imaging devices 52A and 52C, but may also change at least one of the position, shape, and size of the effective image area.

The correction unit 116 corrects the image data Im according to constant information V based on the expansion/contraction state information U of the continuous paper 120, and outputs the corrected image data Im' to the discharge control unit 117. For example, the correction unit 116 can correct the image data Im by performing image processing on the image data Im to reduce the image data according to the reduced state if the continuous paper 120 has been reduced, image processing to expand the image data according to the expanded state if the continuous paper 120 has been expanded, and image processing to shift the image data according to the positional displacement if the continuous paper 120 has been displaced according to the expansion/contraction state.

The ejection control unit 117 ejects ink from each of the multiple liquid ejection means 210 based on the corrected image data Im' and the ejection timing signal tt. The liquid ejection device 1 can form an image on the continuous paper 120 by applying ink ejected from the multiple liquid ejection means 210 to the continuous paper 120.

<Example of processing by control IC 101>
Fig. 4 is a flowchart showing an example of processing by the control IC 101. The control IC 101 starts the processing in Fig. 4 when a print job is received from the external PC 300, or when a user inputs an operation to start image formation using an operation unit of the liquid ejection device 1.

First, in step S41, the control IC 101 inputs the expansion/contraction state information U from the device temperature sensor 54, drying process temperature sensor 55, humidity sensor 56, tension sensor 57, and print job via the acquisition unit 114.

Next, in step S42, the control IC 101 acquires constant information V using the acquisition unit 114, by referencing the correspondence information 130 stored in the memory 103 based on the stretch state information U. The acquisition unit 114 outputs the constant information V to the change unit 115, the correction unit 116, and the detection unit 111.

Next, in step S43, the control IC 101 determines, via the modification unit 115, whether the amount of expansion/contraction of the continuous paper 120 is equal to or greater than a predetermined expansion/contraction threshold.

If it is determined in step S43 that the expansion/contraction threshold is not exceeded (step S43, No), the control IC 101 proceeds to step S45.

On the other hand, if it is determined in step S43 that the expansion/contraction threshold is equal to or greater than the expansion/contraction threshold (step S43, Yes), in step S44, the control IC 101 causes the change unit 115 to drive the movement mechanism 53A that movably mounts the imaging unit 52A in accordance with the constant information V, thereby changing the position of the imaging unit 52A. Furthermore, the control IC 101 causes the change unit 115 to drive the movement mechanism 53C that movably mounts the imaging unit 52C in accordance with the constant information V, thereby changing the position of the imaging unit 52C.

Next, in step S45, the control IC 101 corrects the image data Im according to the constant information V and outputs the corrected image data Im' to the ejection control unit 117.

Note that steps S44 and S45 may be performed in the reverse order, or both steps may be performed in parallel.

Next, in step S46, the control IC 101 inputs the captured images Sa and Sc captured by the imaging units 52A and 52C at the changed positions via the detection unit 111.

Next, in step S47, the control IC 101 detects the conveyance distance errors ΔDc, ΔDm, and ΔDy based on the captured images Sa and Sc using the detection unit 111. The detection unit 111 outputs the detected conveyance distance errors ΔDc, ΔDm, and ΔDy to the determination unit 112.

Next, in step S48, the control IC 101 determines, via the determination unit 112, the ink ejection timing of each of the liquid ejection means 210C, 210M, and 210Y relative to the ejection of the liquid ejection means 210K, based on the transport distance errors ΔDc, ΔDm, and ΔDy input from the detection unit 111. The determination unit 112 outputs an ejection timing signal tt corresponding to the determined ink ejection timing to the ejection control unit 117.

Next, in step S49, the control IC 101 causes the ejection control unit 117 to eject ink from each of the multiple liquid ejection means 210 based on the corrected image data Im' and the ejection timing signal tt.

Next, in step S50, the control IC 101 determines whether to end the process. This determination can be made based on whether all ejection based on the corrected image data Im' has been completed, or whether the user has used the operation unit to input an operation to end image formation.

If it is determined in step S50 that the processing should be terminated (step S50, Yes), the control IC 101 terminates the processing. On the other hand, if it is determined that the processing should not be terminated (step S50, No), the control IC 101 performs the processing from step S41 onwards again.

In this way, the control IC 101 can eject ink onto the continuous paper 120 to form an image.

<Example of changing the position of the effective image area Vc according to the expansion/contraction state of the continuous paper 120>
An example of changing the position of the imaged area 71 in accordance with the expansion/contraction state of the continuous paper 120 will be described with reference to FIGS. 5 to 7. FIG.

Figure 5 is a diagram illustrating the relationship between the captured image Sc and the effective image area Vc. Note that Figure 5 uses the captured image Sc and the effective image area Vc as an example, but the same applies to the captured image Sa and the effective image area Va, so the symbols for the captured image Sa and the effective image area Va are written in parentheses.

As shown in Figure 5, the effective image area Vc is a partial area included in the captured image Sc. When the detection unit 111 performs cross-correlation calculations, the entire captured image Sc is not used, and only this effective image area Vc is used.

The larger the effective image area Vc, the wider the detection range of the transport amount error Dc using cross-correlation calculation, but the lower the detection accuracy of the transport amount error Dc. Therefore, the size of the effective image area Vc is determined in advance as appropriate depending on the required detection accuracy and detection range of the transport amount error Dc.

In addition, in the cross-correlation calculation, the amount of deviation of a characteristic image area of the captured image Sc relative to the characteristic image area of the captured image Sa is mainly detected as the deviation amount Δ. In other words, the characteristic image area affects the accuracy of detecting the transport distance error using the cross-correlation calculation. However, if the characteristic image area is no longer included within the image areas of the captured images Sa and Sc due to expansion or contraction of the continuous paper 120, it may be impossible to detect the deviation amount Δ and therefore the transport distance error D.

Figures 6 and 7 are diagrams illustrating an example of changing the position of the effective imaging area 72 depending on the expansion/contraction state of the continuous paper 120. Figures 6 and 7 show the continuous paper 120 viewed in a plan view from its normal direction. Figure 6 is a diagram illustrating the effective imaging area 72 before the position is changed, and Figure 7 is a diagram illustrating the effective imaging area 72 after the position is changed.

As shown in Figures 6 and 7, on the continuous paper 120, the effective imaging area 72 is included in the imaged area 71. The image of the imaged area 71 corresponds to the captured image Sc, and the image of the effective imaging area 72 corresponds to the effective image area Vc. The feature area 73 is a characteristic area in the imaged area 71, and corresponds to a characteristic image area that affects the accuracy of detecting conveyance amount errors using cross-correlation calculations. Note that Figures 6 and 7 show the feature area 73 in a simplified manner.

As shown in Figure 6, before the change, if the characteristic area 73 is located at the edge of the effective image capture area 72 within the image capture area 71, the characteristic image area may be outside the image area of either the captured image Sa or Sc. In this case, the detection unit 111 cannot detect the image area deviation amount Δ, and therefore cannot detect the transport distance error D.

In this embodiment, the change unit 115 moves the imaging devices 52A and 52C along the movement direction 63 in accordance with the expansion/contraction state of the continuous paper 120, changing the positions of the imaging devices 52A and 52C. This position change allows the feature region 73 to be positioned in an area other than the ends of the effective imaging area 72, for example, in the central area of the effective imaging area 72, as shown in FIG. 7. By positioning the feature region 73 in the central area of the effective imaging area 72, a characteristic image region is included within the image areas of the effective image areas Va and Vc of the captured images Sa and Sc, respectively, making it possible to detect the transport distance error D.

<Example of expansion and contraction of continuous paper 120 according to ink application area>
Figures 8 and 9 are diagrams showing an example of expansion and contraction of the continuous paper 120 depending on the ink application area, with Figure 8 being Figure 1 and Figure 6 being Figure 2. Figures 8 and 9 show the continuous paper 120 as viewed in plan from its normal direction.

In Figures 8 and 9, the ink application area 61 shown by dot hatching represents the area where ink is ejected from the liquid ejection means 210 and applied to the continuous paper 120. The expansion/contraction direction 62 shown by the arrow represents the direction in which the continuous paper 120 expands as a result of the application of ink.

As shown in Figure 8, when ink is applied to the central region of the continuous paper 120, the continuous paper 120 stretches in a substantially uniform direction from the central region where the ink is applied toward the periphery. On the other hand, as shown in Figure 9, when ink is applied to the edge region in the width direction of the continuous paper 120 that intersects with the conveying direction 2, the continuous paper 120 does not stretch uniformly from the edge region where the ink is applied toward the periphery. In other words, it does not stretch in a direction where there is no continuous paper 120 outside the edge region where the ink is applied.

As described above, the elongation state of the continuous paper 120 differs depending on the position of the ink application area on the continuous paper 120. Because the ink application area is determined by image data Im, the liquid ejection device 1 can grasp the difference in the elongation state depending on the position of the ink application area based on the image data Im, and reflect this in changes to at least one of the position, shape, and size of the effective image area by the modification unit 115.

<Example of changing the shape of the effective image area Vc according to the expansion/contraction state of the continuous paper 120>
10 is a diagram showing an example of a change in the shape of the effective image area Vc according to the expansion/contraction state of the continuous paper 120. FIG. 10 shows the continuous paper 120 as viewed in a plan view from the normal direction.

In Figure 10, continuous paper 120a represents continuous paper 120 that has shrunk along conveying direction 2. The modification unit 115 can modify the shape of the effective image area Vc so that the effective imaging area 72a shrinks along conveying direction 2 in accordance with the shrinkage of continuous paper 120a.

The continuous paper 120b represents the continuous paper 120 stretched along the conveying direction 2. The modification unit 115 can modify the shape of the effective image area Vc so that the effective imaging area 72b stretches along the conveying direction 2 in accordance with the stretching of the continuous paper 120b.

The modification unit 115 can also modify the size of the effective image area Vc so that the characteristic image area is included in the effective image area Vc.

<Example of Correction of Image Data Im According to the Expanding/Shrinking State of the Continuous Form 120>
Fig. 11 is a diagram showing an example of image data correction according to the expansion/contraction state of the continuous paper 120. Fig. 11 shows the continuous paper 120 viewed in a plan view from its normal direction, image data Im, and corrected image data Im'.

In Figure 11, continuous paper 120a represents continuous paper 120 that has shrunk along the conveying direction 2, and continuous paper 120b represents continuous paper 120 that has stretched along the conveying direction 2.

When the continuous paper 120 shrinks along the conveying direction 2, as in the case of continuous paper 120a, the correction unit 116 can output corrected image data Ima', which is obtained by correcting the image data Im to expand in the direction corresponding to the conveying direction 2. When the continuous paper 120 expands along the conveying direction 2, as in the case of continuous paper 120b, the correction unit 116 can output corrected image data Imb', which is obtained by correcting the image data Im to shrink in the direction corresponding to the conveying direction 2.

<Modification>
In this embodiment, the liquid ejection device 1 is exemplified as having an imaging means 52A arranged immediately below the liquid ejection means 210K and an imaging means 52C arranged immediately below the liquid ejection means 210M, but this configuration is not limited to this and various modifications are possible.

Figures 12 to 16 are diagrams illustrating the configuration of liquid ejection devices according to various modified examples. Figure 12 shows a first example, Figure 13 shows a second example, Figure 14 shows a third example, Figure 15 shows a fourth example, and Figure 16 shows a fifth example.

As shown in FIG. 12, the liquid ejection device 1a has an imaging unit 52A arranged immediately below the liquid ejection unit 210K, and an imaging unit 52D arranged immediately below the liquid ejection unit 210Y. The imaging unit 52D outputs an image Sd obtained by capturing an image of the continuous paper 120 at a position corresponding to the liquid ejection unit 210Y.

As shown in FIG. 13, liquid ejection device 1b has imaging means 52A arranged immediately below liquid ejection means 210K and imaging means 52B arranged immediately below liquid ejection means 210C. Imaging means 52B outputs an image Sb obtained by capturing an image of continuous paper 120 at a position corresponding to liquid ejection means 210C.

As shown in FIG. 14, liquid ejection device 1c has imaging means 52A positioned immediately below liquid ejection means 210K, imaging means 52B positioned immediately below liquid ejection means 210C, and imaging means 52C positioned immediately below liquid ejection means 210M. Imaging means 52B outputs an image Sb of continuous paper 120 captured at a position corresponding to liquid ejection means 210C, and imaging means 52C outputs an image Sc of continuous paper 120 captured at a position corresponding to liquid ejection means 210M.

As shown in FIG. 15, liquid ejection device 1d has imaging means 52A arranged immediately below liquid ejection means 210K, imaging means 52B arranged immediately below liquid ejection means 210C, and imaging means 52D arranged immediately below liquid ejection means 210Y. Imaging means 52B outputs an image Sb of continuous paper 120 taken at a position corresponding to liquid ejection means 210C, and imaging means 52D outputs an image Sd of continuous paper 120 taken at a position corresponding to liquid ejection means 210Y.

As shown in FIG. 16, liquid ejection device 1e has imaging means 52A arranged immediately below liquid ejection means 210K, imaging means 52C arranged immediately below liquid ejection means 210M, and imaging means 52D arranged immediately below liquid ejection means 210Y. Imaging means 52C outputs an image Sc obtained by capturing an image of continuous paper 120 at a position corresponding to liquid ejection means 210M, and imaging means 52D outputs an image Sd obtained by capturing an image of continuous paper 120 at a position corresponding to liquid ejection means 210Y.

The liquid ejection devices 1a, 1b, 1c, 1d, and 1e described above also achieve the same effects as liquid ejection device 1.

<Effects of the liquid ejection device 1>
As described above, the liquid ejection device 1 ejects ink (liquid) onto the transported continuous paper 120 (long recording medium). The liquid ejection device 1 includes liquid ejection units 210K, 210C, 210M, and 210Y (plurality of liquid ejection units) that eject ink onto the transported continuous paper 120, and imaging units 52A and 52C (plurality of imaging units) that are provided corresponding to the positions of the liquid ejection units 210K, 210C, 210M, and 210Y and that output captured images Sa and Sc of the transported continuous paper 120. The liquid ejection device 1 also includes control unit 520 that controls the ink ejection timing (liquid ejection timing) of the liquid ejection units 210K, 210C, 210M, and 210Y based on the effective image areas Va and Vc of the captured images Sa and Sc (plurality of captured images) output from the imaging units 52A and 52C, respectively. Furthermore, the liquid ejection device 1 has a change unit 115 (change means) that changes at least one of the position, shape, and size of the effective image areas Va and Vc based on the expansion and contraction state of the continuous paper 120 .

The liquid ejection device 1 changes at least one of the position, shape, and size of the effective image areas Va and Vc based on the expansion/contraction state of the continuous paper 120. Therefore, even if the continuous paper 120 expands or contracts, the characteristic image areas that affect the detection accuracy by cross-correlation calculation are included in the effective image areas Va and Vc, making it possible to detect errors in the transport amount of the continuous paper 120. In this embodiment, by making it possible to detect errors in the transport amount of the continuous paper 120, it is possible to provide a liquid ejection device 1 that has excellent control accuracy of the ink ejection timing and excellent ink ejection accuracy.

In addition, in this embodiment, the number of imaging devices 52A and 52C is fewer than the number of liquid ejection devices 210K, 210C, 210M, and 210Y. Of the imaging devices 52A and 52C, imaging device 52A is positioned at a position corresponding to the position of liquid ejection device 210K, which is positioned most upstream in the conveying direction 2, among liquid ejection devices 210K, 210C, 210M, and 210Y. In this embodiment, the number of imaging devices 52A and 52C is reduced, which simplifies the configuration of the liquid ejection device 1. It also reduces device costs.

Furthermore, in this embodiment, when the amount of expansion or contraction of the continuous paper 120 is equal to or greater than a predetermined expansion or contraction threshold, at least one of the position, shape, and size of the effective image areas Va and Vc is changed. The liquid ejection device 1 performs changes using the change unit 115 only when the amount of expansion or contraction of the continuous paper 120 is equal to or greater than a predetermined expansion or contraction threshold, thereby reducing the processing load for changes by the change unit 115.

Furthermore, in this embodiment, the expansion/contraction state of the continuous paper 120 includes an expansion/contraction state corresponding to at least one of the following: the amount of ink ejected onto the continuous paper 120, the humidity around the continuous paper 120, the type of continuous paper 120, the type of ink, the dryness state of the ink ejected onto the continuous paper 120, and the tension applied to the continuous paper 120. Because the expansion/contraction information includes this information, the liquid ejection device 1 can detect an error in the transport amount of the continuous paper 120 even if the continuous paper 120 expands or contracts due to various factors.

In addition, in this embodiment, the modification unit 115 modifies at least one of the position, shape, and size of the effective image areas Va and Vc based on predetermined correspondence information 130 that indicates the correspondence between the expansion/contraction state of the continuous paper 120 and at least one of the position, shape, and size of the effective image areas Va and Vc. The liquid ejection device 1 does not need to calculate the above-mentioned equation (1) using the modification unit 115 every time the expansion/contraction state of the continuous paper 120 changes, thereby reducing the computational load.

In addition, in this embodiment, the liquid ejection devices 210K, 210C, 210M, and 210Y eject ink onto the front (first side) of the continuous paper 120, and then eject ink onto the back (second side) of the continuous paper 120. Before the liquid ejection devices 210K, 210C, 210M, and 210Y eject ink onto the back side, the modification unit 115 modifies at least one of the position, shape, and size of the effective image areas Va and Vc based on correspondence information 130 corresponding to the drying state of the continuous paper 120 onto which the ink has been ejected onto the front side of the continuous paper 120. Because the modification unit 115 modifies the effective image areas Va and Vc based on correspondence information 130 corresponding to the drying state of the continuous paper 120 onto which the ink has been ejected onto the front side of the continuous paper 120, the liquid ejection device 1 can detect transport amount errors of the continuous paper 120 even if the continuous paper 120 expands or contracts due to the ink applied to the front side during double-sided printing.

In addition, in this embodiment, the modification unit 115 modifies at least one of the position, shape, and size of the effective image areas Va and Vc by changing the position of the imaging means 52A and 52C in at least one of the conveyance direction 2 and the width direction of the continuous paper 120. Because the liquid ejection device 1 uses the modification unit 115 to change the positions of the imaging means 52A and 52C in both the conveyance direction 2 and the width direction of the continuous paper 120, it is possible to detect errors in the conveyance amount of the continuous paper 120 even if the continuous paper 120 expands or contracts in both the conveyance direction 2 and the width direction of the continuous paper 120.

Furthermore, in this embodiment, the liquid ejection means 210K, 210C, 210M, and 210Y eject ink onto the continuous paper 120 based on image data Im' corrected in accordance with the expansion and contraction state of the continuous paper 120. If an image is formed on the continuous paper 120 while the continuous paper 120 is in a temporarily expanded or contracted state, the image formed on the continuous paper 120 may be distorted if the continuous paper 120 subsequently returns to its pre-expansion state. The liquid ejection device 1 corrects the image data in accordance with the expansion and contraction state of the continuous paper 120, thereby preventing deformation of the image formed on the continuous paper 120.

Although the embodiments have been described above, the present invention is not limited to the specifically disclosed embodiments above, and various modifications and variations are possible without departing from the scope of the claims.

In the embodiments, the terms image formation, recording, printing, copying, and printing are all synonymous. Recording media include media such as paper, recording paper, recording sheet, plain paper, glossy paper, film, and cloth. Recording media may be made of paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or other materials that can accept liquid even temporarily. Recording media are not limited to sheet-like shapes, and may also be structures such as walls and ceilings, or the sides, bottom, or top of cardboard. The surface of a three-dimensional object fixed to the ground or a facility may also be used as a recording medium.

The liquid may have a viscosity and surface tension that allows it to be ejected from the liquid ejection unit, and is not particularly limited. However, it is preferable that the viscosity of the liquid be 30 mPa·s or less at room temperature and pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, etc. containing a solvent such as water or an organic solvent; a colorant such as a dye or pigment; a functionalizing material such as a polymerizable compound, resin, or surfactant; a biocompatible material such as DNA, amino acids, proteins, or calcium; or an edible material such as a natural dye. These may be used, for example, in inkjet inks, surface treatment solutions, components of electronic elements and light-emitting elements, and solutions for forming electronic circuit resist patterns.

The liquid ejection unit is a functional component that ejects and sprays liquid from a nozzle. Energy sources for ejecting liquid include piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a vibration plate and opposing electrodes.

Embodiments also include a liquid ejection method. For example, the liquid ejection method is a liquid ejection method using a liquid ejection device that ejects liquid onto a long recording medium being transported, in which the liquid ejection device ejects liquid onto the recording medium being transported using multiple liquid ejection units, multiple imaging units provided corresponding to the positions of the liquid ejection units capture images of the recording medium being transported and output them, a control unit controls the timing of liquid ejection by the multiple liquid ejection units based on the effective image area in each of the multiple captured images output by the multiple imaging units, and a modification unit modifies at least one of the position, shape, and size of the effective image area based on the expansion/contraction state of the recording medium. This liquid ejection method can achieve the same effects as the liquid ejection device described above.

Furthermore, all ordinal numbers, quantitative numbers, etc. used above are merely examples used to specifically explain the technology of the present invention, and the present invention is not limited to these examples. Furthermore, the connections between the components are merely examples used to specifically explain the technology of the present invention, and the connections that realize the functions of the present invention are not limited to these examples.

Furthermore, each function of the embodiments described above can be realized by one or more processing circuits. Here, the term "processing circuit" as used herein includes processors programmed to perform each function by software, such as processors implemented by electronic circuits, as well as devices such as ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and conventional circuit modules designed to perform each of the functions described above.

REFERENCE SIGNS LIST 1 Liquid ejection device 2 Transport direction 52A, 52B, 52C, 52D Imaging means 53A, 53C Moving mechanism 61 Ink application area 62 Expanding/contracting direction 63 Moving direction 71 Imaged area 72 Effective imaging area 73 Feature area 100 Head driving board 101 Control IC
102A, 102B Drive waveform generating means 103 Memory 111 Detecting unit 112 Determining unit 113 Communication unit 114 Acquiring unit 115 Changing unit (changing means)
116 Correction unit 117 Discharge control unit 120 Continuous paper (long recording medium)
130 Corresponding information 201 Head substrate 202 Piezoelectric element support substrate 203 Piezoelectric element driving IC
204 Piezoelectric element 205 Switching circuit 210, 210K, 210C, 210M, 210Y Liquid discharge means 220 Support roller 300 External PC
520 Control means Im Image data Im' Corrected image data tt Ejection timing signals Sa, Sc Captured image U Stretch state information V Constant information Vc, Va Effective image area t1 Temperature information inside device t2 Drying process temperature information h1 Humidity information p1 Continuous paper type information in1 Ink type information in2 Information on amount of ink ejected onto surface te Tension information a, b, T1, T2, H1, P1, I1, I2, Te Constants

JP 2017-170889 A

Claims (8)

A liquid ejection device that ejects liquid onto a long recording medium being conveyed,
a plurality of liquid ejection means for ejecting liquid onto the recording medium being conveyed;
a plurality of image capturing means provided corresponding to the positions of the liquid ejection means, the image capturing means capturing an image of the recording medium being conveyed, and outputting the captured image;
a control unit that controls the timing of liquid ejection by the plurality of liquid ejection units based on an effective image area in each of the plurality of captured images output from the plurality of imaging units;
a change unit that changes at least one of the position, shape, and size of the effective image area based on the expansion/contraction state of the recording medium ,
the number of the plurality of imaging means is less than the number of the plurality of liquid ejection means,
A liquid ejection device, wherein one of the plurality of imaging means is arranged at a position corresponding to the position of the liquid ejection means that is arranged most upstream in the transport direction among the plurality of liquid ejection means. 2. The liquid ejection device according to claim 1 , wherein the change unit changes at least one of the position, shape, and size of the effective image area when the amount of expansion or contraction of the recording medium is equal to or greater than a predetermined expansion or contraction threshold. 3. The liquid ejection device according to claim 1, wherein the expansion/contraction state of the recording medium includes an expansion/contraction state corresponding to at least one of the amount of the liquid ejected onto the recording medium, the humidity around the recording medium, the type of the recording medium, the type of the liquid, the dryness state of the liquid ejected onto the recording medium, and the tension applied to the recording medium . A liquid ejection device described in any one of claims 1 to 3, wherein the modification means modifies at least one of the position, shape and size of the effective image area based on predetermined correspondence information indicating the correspondence between the expansion/contraction state of the recording medium and at least one of the position, shape and size of the effective image area. the plurality of liquid ejection means eject the liquid onto a first surface of the recording medium, and then eject the liquid onto a second surface of the recording medium, the second surface being an opposite surface to the first surface;
5. The liquid ejection device according to claim 4, wherein the modification means modifies at least one of the position, shape, and size of the effective image area based on the correspondence information corresponding to the dryness state of the recording medium onto which the liquid has been ejected onto the first surface before the plurality of liquid ejection means eject the liquid onto the second surface. A liquid ejection device described in any one of claims 1 to 5, wherein the change means changes at least one of the position, shape, and size of the effective image area by changing the position of each of the multiple imaging means in at least one of the transport direction of the recording medium and the width direction of the recording medium that intersects the transport direction. 7. The liquid ejection device according to claim 1 , wherein the plurality of liquid ejection devices eject the liquid onto the recording medium based on image data corrected in accordance with the expansion/contraction state of the recording medium. A liquid ejection method using a liquid ejection device that ejects liquid onto a long recording medium being conveyed, the liquid ejection device comprising:
A plurality of liquid ejection means eject liquid onto the recording medium being conveyed;
outputting captured images of the recording medium being conveyed by a plurality of imaging means provided corresponding to the positions of the liquid discharge means;
a control unit that controls timings of liquid ejection by the plurality of liquid ejection units based on effective image areas in each of the plurality of captured images output from the plurality of imaging units;
a change unit that changes at least one of the position, shape, and size of the effective image area based on the expansion/contraction state of the recording medium;
the number of the plurality of imaging means is less than the number of the plurality of liquid ejection means,
A liquid ejection method, wherein one of the plurality of imaging means is arranged at a position corresponding to the position of the liquid ejection means arranged most upstream in the transport direction among the plurality of liquid ejection means.