JP7000687B2 - Liquid discharge device and liquid discharge system - Google Patents

Description

The present invention relates to a device for discharging a liquid and a system for discharging a liquid.

Conventionally, there are known methods of performing various processes using a head unit. For example, a method of forming an image by a so-called inkjet method of ejecting ink from a print head is known. A method of improving the print quality of an image printed on a print medium by this image formation is known.

For example, a method of adjusting the orientation of a print head is known in order to improve print quality. Specifically, first, the position fluctuation in the lateral direction of the web (web), which is a printing medium passing through the continuous paper printing system, is detected by the sensor. A method of adjusting the position of the print head in the lateral direction so as to compensate for the position variation detected by this sensor is known (see, for example, Patent Document 1).

However, for example, in order to further improve the image quality of the image to be formed, it may be required to improve the landing position of the discharged liquid. For example, if the landing position shifts, the image quality of the image deteriorates. On the other hand, in the conventional technique, there is a problem that the accuracy of the processing position such as the landing position of the discharged liquid may not be further improved in the transport direction.

One aspect of the present invention is to provide a device for discharging a liquid that can further improve the accuracy of a processing position such as a landing position of the liquid to be discharged in the direction in which the object to be transported is conveyed.

In order to solve the above-mentioned problems, a device having a plurality of liquid discharge head units, which is one aspect of the present invention, is to discharge liquid to a transported object by the liquid discharge head unit. A first unit in which the liquid discharge head unit is provided on the upstream side of the landing position where the liquid can be discharged with respect to a predetermined position of the object to be transported in the transport direction of the object to be transported, and supports the object to be transported. A support member, a second support member provided on the downstream side of the landing position in the transport direction of the object to be transported, and a second support member for supporting the object to be transported, and a liquid discharge head unit are installed for each of the objects to be transported. Is transported at a timing based on the detection result of the detection unit and a detection unit that outputs a detection result indicating the position, movement speed, movement amount, or a combination thereof in the transportation direction in which the is transported. The liquid to be conveyed is provided with a control unit for discharging the liquid to a plurality of liquid discharge head units while conveying the object to be conveyed, and the detection unit includes the first support member and the first support member. It is characterized in that it is installed between the support member 2 and on the side opposite to the liquid discharge head unit with respect to the object to be transported.

In the direction in which the object to be conveyed is conveyed, the accuracy of the processing position such as the landing position of the discharged liquid can be further improved.

It is a schematic diagram which shows an example of the apparatus which discharges a liquid which concerns on one Embodiment of this invention. It is a schematic diagram which shows the whole structure example of the apparatus which discharges a liquid which concerns on one Embodiment of this invention. It is a figure which shows an example of the external shape of the liquid discharge head unit which concerns on one Embodiment of this invention. It is a block diagram which shows the hardware configuration example which realizes the detection part which concerns on one Embodiment of this invention. It is an external view which shows an example of the detection apparatus which concerns on one Embodiment of this invention. It is a functional block diagram which shows an example of the functional structure using the detection part which concerns on one Embodiment of this invention. It is a block diagram which shows an example of the hardware composition of the control part which concerns on one Embodiment of this invention. It is a block diagram which shows an example of the hardware composition of the data management apparatus which the control part which concerns on one Embodiment of this invention has. It is a block diagram which shows an example of the hardware composition of the image output apparatus which the control part which concerns on one Embodiment of this invention has. It is a block diagram which shows an example of the correlation calculation method which concerns on one Embodiment of this invention. It is a figure which shows an example of the search method of the peak position in the correlation calculation which concerns on one Embodiment of this invention. It is a figure which shows the calculation result example of the correlation calculation which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the whole processing by the apparatus which discharges a liquid which concerns on one Embodiment of this invention. It is a timing chart and a conceptual diagram which shows an example of the whole processing by the apparatus which discharges a liquid which concerns on one Embodiment of this invention. It is a functional block diagram which shows an example of the functional structure of the apparatus which discharges a liquid which concerns on one Embodiment of this invention. It is a schematic diagram which shows the whole structure example of the apparatus which concerns on a comparative example. It is a figure which shows an example of the deviation of the landing position in the apparatus which concerns on a comparative example. It is a figure which shows an example of the influence which the eccentricity of a roller has on the deviation of the landing position. It is a schematic diagram which shows the 1st modification of the hardware structure which realizes the detection part which concerns on one Embodiment of this invention. It is a schematic diagram which shows the 2nd modification of the hardware structure which realizes the detection part which concerns on one Embodiment of this invention. It is a schematic diagram which shows the 3rd modification of the hardware structure which realizes the detection part which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the plurality of image pickup lenses used for the detection part which concerns on one Embodiment of this invention. It is a schematic diagram which shows the modification of the apparatus which discharges a liquid which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the present specification and the drawings, the components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<Overall configuration example>
Hereinafter, a case where the head unit included in the transport device is a liquid discharge head unit that discharges liquid will be described as an example.

FIG. 1 is a schematic view showing an example of a device for discharging a liquid according to an embodiment of the present invention. For example, the device that discharges the liquid is an image forming device as shown in the figure. In such an image forming apparatus, the discharged liquid is a recording liquid such as ink which is water-based or oil-based. Hereinafter, an example will be described in which the device for discharging the liquid is the image forming apparatus 110.

The object to be transported is, for example, a recording medium or the like. In the illustrated example, the image forming apparatus 110 ejects a liquid to the web 120, which is an example of a recording medium conveyed by a roller 130 or the like, to form an image. Further, the web 120 is a so-called continuous paper printing medium or the like. That is, the web 120 is a roll-shaped sheet or the like that can be wound up. As described above, the image forming apparatus 110 is a so-called production printer. In the following description, an example will be described in which the roller 130 adjusts the tension of the web 120 and the web 120 is conveyed in the direction shown in the drawing (hereinafter referred to as “transport direction 10”). Further, in this example, the image forming apparatus 110 ejects inks of four colors of black (K), cyan (C), magenta (M), and yellow (Y) to an image at a predetermined position on the web 120. Is an inkjet printer that forms.

FIG. 2 is a schematic view showing an overall configuration example of a device for discharging a liquid according to an embodiment of the present invention. As shown in the figure, the image forming apparatus 110 has four liquid ejection head units for ejecting inks of four colors.

Each liquid discharge head unit discharges each liquid of each color to the web 120 transported in the transport direction 10. Further, it is assumed that the web 120 is conveyed by two pairs of nip rollers, rollers 230 and the like. Hereinafter, of the two pairs of nip rollers, the nip roller installed on the upstream side of each liquid discharge head unit is referred to as "first nip roller NR1". On the other hand, the nip roller installed on the downstream side of the first nip roller NR1 and each liquid discharge head unit is referred to as "second nip roller NR2". As shown in the figure, each nip roller rotates with an object to be transported such as a web 120 sandwiched between them. As described above, each nip roller and roller 230 is a mechanism or the like that conveys the web 120 or the like in a predetermined direction.

Further, it is desirable that the recording medium of the web 120 is long. Specifically, it is desirable that the length of the recording medium is longer than the distance between the first nip roller NR1 and the second nip roller NR2. Furthermore, the recording medium is not limited to the web. That is, the recording medium may be a sheet that is folded and stored, so-called "Z paper" or the like.

In the overall configuration example shown below, each liquid discharge head unit is installed in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side to the downstream side. do. That is, the liquid discharge head unit (hereinafter referred to as "black liquid discharge head unit 210K") installed on the most upstream side is used for black (K). The liquid discharge head unit (hereinafter referred to as "cyan liquid discharge head unit 210C") installed next to the black liquid discharge head unit 210K is used for cyan (C). Further, the liquid discharge head unit (hereinafter referred to as "magenta liquid discharge head unit 210M") installed next to the cyan liquid discharge head unit 210C is used for the magenta (M). Subsequently, the liquid discharge head unit (hereinafter referred to as "yellow liquid discharge head unit 210Y") installed on the most downstream side is used for yellow (Y).

Each liquid ejection head unit ejects ink of each color to a predetermined portion of the web 120 based on image data or the like. The position where this ink is ejected (hereinafter referred to as “landing position”) is substantially equal to the position where the liquid ejected from the liquid ejection head unit lands on the recording medium, that is, the landing position is directly under the liquid ejection head unit or the like. Is. Hereinafter, an example will be described in which the processing position where the processing is performed by the liquid discharge head unit is set as the landing position.

In this example, the black ink is ejected to the landing position of the black liquid ejection head unit 210K (hereinafter referred to as “black landing position PK”). Similarly, the cyan ink is ejected to the landing position of the cyan liquid ejection head unit 210C (hereinafter referred to as “cyan landing position PC”). Further, the magenta ink is ejected to the landing position of the magenta liquid ejection head unit 210M (hereinafter referred to as “magenta landing position PM”). Further, the yellow ink is ejected to the landing position of the yellow liquid ejection head unit 210Y (hereinafter referred to as “yellow landing position PY”).

The timing at which each liquid ejection head unit ejects ink is controlled by the controller 520 connected to each liquid ejection head unit. Further, the controller 520 controls the timing based on the detection result and the like.

Further, a plurality of rollers are installed for each liquid discharge head unit. As shown in the figure, for example, the plurality of rollers are installed on the upstream side and the downstream side, respectively, with each liquid discharge head unit interposed therebetween. In the illustrated example, a roller (hereinafter referred to as “first roller”) is installed on the upstream side of each liquid discharge head unit for each liquid discharge head unit. Further, a roller (hereinafter referred to as "second roller") is installed separately from the first roller on the downstream side of each liquid discharge head unit. When the first roller and the second roller are installed in this way, so-called "fluttering" can be reduced at each landing position. The first roller and the second roller are driven rollers, respectively. Further, the first roller and the second roller may be rollers that are rotationally driven by a motor or the like.

The first roller, which is an example of the first support member, and the second roller, which is an example of the second support member, do not have to be a rotating body such as a driven roller. That is, the first roller and the second roller may be support members that support the object to be transported. For example, the first support member and the second support member may be a pipe or a shaft having a circular cross section. In addition, the first support member and the second support member may be a curved plate or the like whose portion in contact with the object to be transported has an arc shape. Hereinafter, an example will be described in which the first support member is the first roller and the second support member is the second roller.

Specifically, in order to eject black ink at a predetermined position on the web 120, a black first roller CR1K for transporting the web 120 to the black landing position PK is installed. On the other hand, a second roller CR2K for black that conveys the web 120 from the black landing position PK to the downstream side is installed. Similarly, the first roller CR1C for cyan and the second roller CR2C for cyan are installed on the cyan liquid discharge head unit 210C, respectively. Further, a first roller CR1M for magenta and a second roller CR2M for magenta are installed on the magenta liquid discharge head unit 210M, respectively. Further, a first roller CR1Y for yellow and a second roller CR2Y for yellow are installed on the yellow liquid discharge head unit 210Y, respectively.

An example of the outer shape of the liquid discharge head unit will be described with reference to FIG. First, FIG. 3A is a schematic plan view showing an example of four liquid discharge head units 210K to 210Y of the image forming apparatus 110 according to the embodiment of the present invention.

As shown in FIG. 3A, the liquid discharge head unit is a line type head unit in this embodiment. That is, the image forming apparatus 110 has four liquid discharge head units 210K, 210C corresponding to black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side in the transport direction 10 of the recording medium. 210M and 210Y are arranged.

Further, in the present embodiment, the black (K) liquid discharge head unit 210K staggers four heads 210K-1, 210K-2, 210K-3 and 210K-4 in a direction orthogonal to the transport direction 10 of the web 120. Arrange in a shape. As a result, the image forming apparatus 110 can form an image in the entire width direction (direction orthogonal to the conveying direction) of the image forming area (printing area) of the web 120. Since the configurations of the other liquid discharge head units 210C, 210M and 210Y are the same as the configurations of the black (K) liquid discharge head unit 210K, the description thereof will be omitted.

In this example, the example in which the liquid discharge head unit is configured by four heads has been described, but the liquid discharge head unit may be configured by a single head.

<Example of detection unit>
For each liquid discharge head unit, a sensor for detecting the position, moving speed, moving amount, or a combination thereof of the recording medium, which is an example of the detection unit, is installed. As this sensor, it is desirable to use an optical sensor or the like that uses light such as a laser or infrared rays. The optical sensor may be, for example, a CCD (Charge Coupled Device) camera, a CMOS (Complementary Metal Oxide Sensor) camera, or the like. Further, the optical sensor is preferably a global shutter. With the global shutter, even if the moving speed is high, the optical sensor can reduce the so-called image deviation caused by the deviation of the shutter timing as compared with the rolling shutter or the like. Further, the sensor is preferably configured as described below, for example.

FIG. 4 is a block diagram showing an example of a hardware configuration that realizes a detection unit according to an embodiment of the present invention. For example, the detection unit is realized by hardware such as a detection device 50, a control device 52, a storage device 53, and an arithmetic unit 54 as shown in the figure.

First, the detection device 50 is, for example, the following device.

FIG. 5 is an external view showing an example of a detection device according to an embodiment of the present invention.

When detection is performed by the detection device shown in the figure, the speckle pattern formed by shining light from a light source on an object to be transported such as a web is imaged. Specifically, the detection device first has an optical system such as a semiconductor laser light source (LD) and a collimating optical system (CL). Further, the detection device has a CMOS image sensor for capturing an image in which a speckle pattern or the like is captured, and a telecentric imaging optical system (OL) for condensing and imaging the speckle pattern on the CMOS image sensor.

In the illustrated configuration example, the CMOS image sensor captures an image in which the speckle pattern is captured a plurality of times at each of the time “TM1” and the time “TM2”, for example. Then, based on the image captured at the time "TM1" and the image captured at the time "TM2", an arithmetic unit such as an FPGA (Field-Programmable Gate Array) circuit performs processing such as cross-correlation calculation. .. Next, based on the movement of the correlation peak position calculated by the correlation calculation or the like, the detection device or the like outputs the movement amount or the like that the transported object has moved from the time "TM1" to the time "TM2". In the illustrated example, the size of the detection device is width W × depth D × height H is 15 × 60 × 32 [mm]. The details of the correlation calculation will be described later.

The CMOS image sensor is an example of hardware that realizes an image pickup unit, and the FPGA circuit is an example of an arithmetic unit.

Returning to FIG. 4, the control device 52 controls the detection device 50 and the like. Specifically, the control device 52 outputs, for example, a trigger signal to the detection device 50 to control the timing at which the CMOS image sensor releases the shutter. Further, the control device 52 controls so that a two-dimensional image can be acquired from the detection device 50. Then, the control device 52 takes an image of the detection device 50 and sends the generated two-dimensional image to the storage device 53 or the like.

The storage device 53 is a so-called memory or the like. It is desirable that the two-dimensional image sent from the control device 52 or the like can be divided and stored in different storage areas.

The arithmetic unit 54 is a microcomputer or the like. That is, the arithmetic unit 54 performs an arithmetic operation for realizing various processes using the image data and the like stored in the storage apparatus 53.

The control device 52 and the arithmetic unit 54 are, for example, a CPU (Central Processing Unit), an electronic circuit, or the like. The control device 52, the storage device 53, and the arithmetic unit 54 do not have to be different devices. For example, the control device 52 and the arithmetic unit 54 may be one CPU or the like.

<Example of functional configuration of detection unit>

FIG. 6 is a functional block diagram showing an example of a functional configuration using the detection unit according to the embodiment of the present invention. Hereinafter, as shown in the figure, a combination of the black liquid discharge head unit 210K and the cyan liquid discharge head unit 210C will be described as an example among the detection units installed for each head unit. Further, as shown in the figure, the detection unit 52A for the black liquid discharge head unit 210K outputs the detection result related to the "A position", and the detection unit 52B for the cyan liquid discharge head unit 210C detects the "B position". An example of outputting the result will be described. First, the detection unit 52A for the black liquid discharge head unit 210K is composed of, for example, an image pickup unit 16A, an image pickup control unit 14A, an image storage unit 15A, and the like. In this example, the detection unit 52B for the cyan liquid discharge head unit 210C has, for example, the same configuration as the detection unit 52A, and is composed of an image pickup unit 16B, an image pickup control unit 14B, an image storage unit 15B, and the like. Hereinafter, the detection unit 52A will be described as an example.

As shown in the figure, the image pickup unit 16A images the web 120 transported in the transport direction 10. The image pickup unit 16A is realized by, for example, a detection device 50 or the like (FIG. 4 or the like).

The image pickup control unit 14A includes a shutter control unit 141A and an image capture unit 142A. The image pickup control unit 14A is realized by, for example, a control device 52 or the like (FIG. 4).

The image capture unit 142A acquires an image captured by the image pickup unit 16A.

The shutter control unit 141A controls the timing at which the image pickup unit 16A takes an image.

The image storage unit 15A stores the image captured by the image pickup control unit 14A. The image storage unit 15A is realized by, for example, a storage device 53 or the like (FIG. 4).

The calculation unit 53F can calculate the position of the pattern possessed by the web 120, the movement speed at which the web 120 is conveyed, and the movement amount at which the web 120 is conveyed, based on the respective images stored in the image storage units 15A and 15B. .. Further, the calculation unit 53F outputs the data of the time difference Δt indicating the shutter timing to the shutter control unit 141A. That is, the calculation unit 53F indicates the shutter timing to the shutter control unit 141A so that the image indicating the “A position” and the image indicating the “B position” are imaged with a time difference Δt, respectively. Further, the calculation unit 53F may control a motor or the like that conveys the web 120 so as to have a calculated moving speed. The calculation unit 53F is realized by, for example, a controller 520 or the like (FIG. 2).

The web 120 is a member having a scattering property on the surface or inside. Therefore, when the web 120 is irradiated with the laser beam, the reflected light is diffusely reflected. Due to this diffuse reflection, a pattern is formed on the web 120. That is, the pattern is a spot called "speckle", a so-called speckle pattern. Therefore, when the web 120 is imaged, an image showing a speckle pattern is obtained. Since the position of the speckle pattern can be known from this image, it is possible to detect where the predetermined position of the web 120 is. It should be noted that this speckle pattern is generated because the irradiated laser beam interferes with the uneven shape formed on the surface or the inside of the web 120.

Further, the light source is not limited to the device using the laser beam. For example, the light source may be an LED (Light Emitting Diode), an organic EL (Electro-Luminescence), or the like. The pattern does not have to be a speckle pattern depending on the type of light source. Hereinafter, an example in which the pattern is a speckle pattern will be described.

Therefore, when the web 120 is conveyed, the speckle pattern of the web 120 is also conveyed. Therefore, if the same speckle pattern is detected at different times, the amount of movement in the transport direction can be obtained. That is, when the same speckle pattern is detected and the movement amount of the pattern is obtained, the calculation unit 53F can obtain the movement amount of the web 120 in the transport direction. When the obtained movement amount is converted per unit time, the calculation unit 53F can obtain the movement speed at which the web 120 in the transportation direction is conveyed.

As shown in the figure, image pickup units are installed at regular intervals in the transport direction 10. Then, the web 120 is imaged at each position by each imaging unit.

Assuming that the time difference is Δt, the shutter control unit 141A causes the image pickup unit 16A to image the web 120 at intervals of the time difference Δt. Based on the speckle pattern shown by the image generated by this imaging, the calculation unit 53F obtains the movement amount of the web 120. Specifically, assuming that the moving speed is V [mm / s] and the relative distance is L [mm], which is the interval installed in the transport direction 10, the time difference Δt can be expressed by the following equation (1).

Δt = L / V (1)
In the above equation (1), the relative distance L [mm] is the distance between the “A position” and the “B position” and can be obtained in advance. Therefore, once the time difference Δt is determined, the calculation unit 53F can obtain the moving speed V [mm / s] based on the above equation (1). As described above, based on the speckle pattern, the image forming apparatus can accurately determine the position, the moving amount and the moving speed in the transport direction, or a combination thereof. The image forming apparatus may output a combination of any one of the position, the moving amount, and the moving speed in the transport direction.

The sensor may detect a position or the like in a direction orthogonal to the transport direction. That is, the sensor may also be used to detect the positions in the transport direction and the positions orthogonal to the transport direction. When used in this way, the cost can be reduced in each direction. In addition, since the number of sensors can be reduced, space can be saved.

Further, the calculation unit 53F performs a cross-correlation calculation on the image data D1 (n) and D2 (n) indicating the respective images captured by the detection units 52A and 52B. Hereinafter, the image generated by the cross-correlation operation is referred to as a “correlation image”. For example, the calculation unit 53F calculates the deviation amount ΔD (n) based on the correlation image.

For example, the cross-correlation calculation is a calculation shown by the following equation (2).

D1 ★ D2 * = F-1 [F [D1] ・ F [D2] *] (2)
In the above equation (2), the image data D1 (n), that is, the image data indicating the image captured at the "A position" is referred to as "D1". Similarly, in the above equation (2), the image data D2 (n), that is, the image data indicating the image captured at the “B position” is referred to as “D2”. Further, in the above equation (2), the Fourier transform is indicated by "F []" and the inverse Fourier transform is indicated by "F-1 []". Furthermore, in the above equation (2), the complex conjugate is indicated by "*" and the cross-correlation operation is indicated by "★".

As shown in the above equation (2), when the cross-correlation calculation "D1 ★ D2" is performed on the image data D1 and D2, the image data showing the correlated image is obtained. When the image data D1 and D2 are two-dimensional image data, the image data showing the correlated image is the two-dimensional image data. Further, when the image data D1 and D2 are one-dimensional image data, the image data showing the correlated image is one-dimensional image data.

In the correlated image, for example, when a broad luminance distribution becomes a problem, a phase-limited correlation method may be used. The phase-limited correlation method is, for example, a calculation shown by the following equation (3).

D1 ★ D2 * = F-1 [P [F [D1]] ・ P [F [D2] *]] (3)
In the above equation (3), "P []" indicates that only the phase is extracted in the complex amplitude. Further, all the amplitudes are set to "1".

In this way, the calculation unit 53F can calculate the deviation amount ΔD (n) based on the correlation image even if the luminance distribution is broad.

The correlation image shows the correlation between the image data D1 and D2. Specifically, the higher the degree of coincidence between the image data D1 and D2, the steeper the peak, that is, the luminance that becomes the so-called correlation peak is output at the position closer to the center of the correlated image. Then, when the image data D1 and D2 match, the positions of the center and the peak of the correlated image overlap.

Based on the timing calculated by such calculation, the black liquid discharge head unit 210K and the cyan liquid discharge head unit 210C each discharge liquid. The timing of discharging the liquid is controlled by the first signal SIG1 for the black liquid discharge head unit 210K and the second signal SIG2 for the cyan liquid discharge head unit 210C output by the controller 520.

Returning to FIG. 2, in the following description, a device such as a detection device installed on the black liquid discharge head unit 210K is referred to as a “black sensor SENK”. Similarly, a device such as a detection device installed on the cyan liquid discharge head unit 210C is referred to as a "cyan sensor SENC". Further, a device such as a detection device installed on the magenta liquid discharge head unit 210M is referred to as a "magenta sensor SENM". Furthermore, a device such as a detection device installed on the yellow liquid discharge head unit 210Y is referred to as a "yellow sensor SENY". Further, in the following description, the black sensor SENK, the cyan sensor SENC, the magenta sensor SENM, and the yellow sensor SENY may be collectively referred to as a “sensor”.

Further, in the following description, the "position where the sensor is installed" refers to a position where detection or the like is performed. Therefore, it is not necessary to install all the devices such as the detection device at the "position where the sensor is installed", and the devices other than the sensor may be installed at other positions by being connected by a cable or the like. The black sensor SENK, the cyan sensor SENC, the magenta sensor SENM, and the yellow sensor SENY shown in FIG. 2 show examples of positions where the sensors are installed.

As described above, it is desirable that the position where the sensor is installed is close to each landing position. If the sensor is installed at a position close to each landing position, the distance between each landing position and the sensor becomes short. Then, when the distance between each landing position and the sensor becomes short, the error in detection can be reduced. Therefore, the image forming apparatus can accurately detect the position of the recording medium by the sensor.

The position close to each landing position is specifically between each first roller and each second roller. That is, in the illustrated example, it is desirable that the position where the black sensor SENK is installed is INTK1 between the black rollers as shown in the figure. Similarly, the position where the cyan sensor SENC is installed is preferably the cyan roller-to-roller INTC1 as shown in the figure. Further, it is desirable that the position where the magenta sensor SENM is installed is the magenta roller-to-roller INTM1 as shown in the figure. Furthermore, it is desirable that the position where the yellow sensor SENY is installed is INTY1 between the yellow rollers, as shown in the figure.

In this way, when the sensor is installed between the rollers, the sensor can detect the position of the recording medium or the like at a position close to each landing position. In many cases, the moving speed is relatively stable between the rollers. Therefore, the image forming apparatus can accurately detect the position of the recording medium.

It is desirable that the position where the sensor is installed is closer to the first roller than the landing position between the rollers. That is, it is desirable that the position where the sensor is installed is on the upstream side of each landing position.

Specifically, the position where the black sensor SENK is installed is from the black landing position PK to the position where the black first roller CR1K is installed toward the upstream side (hereinafter referred to as "black upstream section INTK2"). .) Is desirable. Similarly, the position where the cyan sensor SENC is installed is from the cyan landing position PC to the position where the cyan first roller CR1C is installed toward the upstream side (hereinafter referred to as "cyan upstream section INTC2"). Is desirable. Further, the position where the magenta sensor SENM is installed is from the magenta landing position PM to the position where the magenta first roller CR1M is installed toward the upstream side (hereinafter referred to as "magenta upstream section INTM2"). It is desirable to have it. Furthermore, the position where the yellow sensor SENY is installed is from the yellow landing position PY to the position where the first yellow roller CR1Y is installed toward the upstream side (hereinafter referred to as "yellow upstream section INTY2"). Is desirable.

When sensors are installed in the upstream section INTK2 for black, the upstream section INTC2 for cyan, the upstream section INTM2 for magenta, and the upstream section INTY2 for yellow, the image forming apparatus can accurately detect the position of the recording medium.

When the sensor is installed at such a position, the sensor is installed on the upstream side of each landing position. Therefore, the image forming apparatus can accurately detect the position of the recording medium in the orthogonal direction, the transport direction, or both directions by the sensor on the upstream side. Therefore, the image forming apparatus can calculate the timing at which each liquid discharge head unit discharges the liquid, the amount of movement of the head unit, or both. That is, when the web 120 is conveyed to the landing position after the position is detected on the upstream side, the ejection timing is calculated or the head unit is moved during that time, so that the image forming apparatus changes the landing position with high accuracy. can do.

If the position where the sensor is installed is located directly under each liquid discharge head unit, color shift may occur due to a delay in the control operation or the like. Therefore, when the position where the sensor is installed is on the upstream side of each landing position, the image forming apparatus can reduce the color shift and improve the image quality. Further, it may be restricted to set the position near each landing position or the like as the position where the sensor or the like is installed. Therefore, it is desirable that the position where the sensor is installed is closer to each first roller than each landing position.

Further, the position of the sensor may be, for example, directly below each of the liquid discharge head units. In the following description, an example in which the sensor is directly under each liquid discharge head unit will be illustrated and described. As in this example, when the sensor is directly underneath, the exact amount of movement underneath can be detected by the sensor. Therefore, if the control operation or the like can be performed quickly, it is desirable that the sensor is located closer to the position directly under each liquid discharge head unit. On the other hand, the sensor does not have to be directly under each liquid discharge head unit, and even if it is not directly under it, the same calculation is performed.

If the error is acceptable, the position of the sensor is directly under each liquid discharge head unit or between each first roller and each second roller, and downstream from directly below each liquid discharge head unit. It may be a position or the like.

Further, the image forming apparatus may further include a measuring unit such as an encoder. Hereinafter, an example in which the measuring unit is realized by the encoder will be described. Specifically, the encoder is installed, for example, with respect to the rotation axis of the roller 230. In this way, the amount of movement in the transport direction can be measured based on the amount of rotation of the roller 230. When this measurement result is used together with the detection result by the sensor, the image forming apparatus can discharge the liquid to the web 120 with higher accuracy.

<Example of control unit>
The controller 520 (FIG. 2), which is an example of the control unit, has, for example, the configuration described below.

FIG. 7 is a block diagram showing an example of the hardware configuration of the control unit according to the embodiment of the present invention. For example, the controller 520 has a host device 71 such as an information processing device and a printer device 72. In the illustrated example, the controller 520 causes the printer device 72 to form an image on the recording medium based on the image data and the control data input from the host device 71.

The host device 71 is, for example, a PC (Personal Computer) or the like. Further, the printer device 72 has a printer controller 72C and a printer engine 72E.

The printer controller 72C controls the operation of the printer engine 72E. First, the printer controller 72C transmits / receives control data to / from the host device 71 via the control line 70LC. Further, the printer controller 72C transmits / receives control data to / from the printer engine 72E via the control line 72LC. By transmitting and receiving the control data, various printing conditions and the like indicated by the control data are input to the printer controller 72C, and the printer controller 72C stores the printing conditions and the like by the registers and the like. Next, the printer controller 72C controls the printer engine 72E based on the control data, and performs image formation according to the print job data, that is, the control data.

The printer controller 72C has a CPU 72Cp, a print control device 72Cc, and a storage device 72Cm. The CPU 72Cp and the print control device 72Cc are connected by a bus 72Cb and communicate with each other. Further, the bus 72Cb is connected to the control line 70LC via a communication I / F (interface) or the like.

The CPU 72Cp controls the operation of the entire printer device 72 by a control program or the like. That is, the CPU 72Cp is an arithmetic unit and a control unit.

The print control device 72Cc transmits / receives data indicating a command, status, or the like to / from the printer engine 72E based on the control data transmitted from the host device 71. As a result, the print control device 72Cc controls the printer engine 72E. Further, the image storage units 15A and 15B shown in FIG. 6 are realized by, for example, a storage device 72Cm or the like. Further, the calculation unit 53F shown in FIG. 6 is realized by, for example, a CPU 72Cp or the like. The image storage units 15A and 15B and the calculation unit 53F may be realized by other arithmetic units and storage devices.

Data lines 70LD-C, 70LD-M, 70LD-Y and 70LD-K, that is, a plurality of data lines are connected to the printer engine 72E. Then, the printer engine 72E receives the image data from the host device 71 via the plurality of data lines. Next, the printer engine 72E forms an image of each color based on the control by the printer controller 72C.

The printer engine 72E has data management devices 72EC, 72EM, 72EY and 72EK, that is, a plurality of data management devices. Further, the printer engine 72E has an image output device 72Ei and a transfer control device 72Ec.

FIG. 8 is a block diagram showing an example of the hardware configuration of the data management device included in the control unit according to the embodiment of the present invention. For example, a plurality of data management devices have the same configuration. Hereinafter, an example in which each data management device has the same configuration will be described, and the data management device 72EC will be described as an example. Therefore, duplicate description will be omitted.

The data management device 72EC has a logic circuit 72ECl and a storage device 72ECm. As shown in the figure, the logic circuit 72ECl is connected to the host device 71 via the data line 70LD-C. Further, the logic circuit 72ECl is connected to the print control device 72Cc via the control line 72LC. The logic circuit 72ECl is realized by an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or the like.

The logic circuit 72ECl stores the image data input from the host device 71 in the storage device 72ECm based on the control signal input from the printer controller 72C (FIG. 7).

Further, the logic circuit 72ECl reads out the image data Ic for cyan from the storage device 72ECm based on the control signal input from the printer controller 72C. Next, the logic circuit 72ECl sends the read image data Ic for cyan to the image output device 72Ei.

It is desirable that the storage device 72ECm has a capacity of storing about 3 pages of image data. When the image data of about 3 pages can be stored, the storage device 72ECm can store the image data input from the host device 71, the image data during image formation, and the image data for next image formation.

FIG. 9 is a block diagram showing an example of the hardware configuration of the image output device included in the control unit according to the embodiment of the present invention. As shown in the figure, the image output device 72Ei includes an output control device 72Eic, a black liquid discharge head unit 210K, a cyan liquid discharge head unit 210C, a magenta liquid discharge head unit 210M, and a yellow liquid discharge head, which are liquid discharge head units of each color. It has a unit 210Y.

The output control device 72Eic outputs image data of each color to the liquid discharge head unit of each color. That is, the output control device 72Eic controls the liquid discharge head unit of each color based on the input image data.

The output control device 72Eic controls a plurality of liquid discharge head units simultaneously or individually. That is, the output control device 72Eic receives the input of the timing and controls to change the timing of discharging the liquid to each liquid discharge head unit. The output control device 72Eic may control any of the liquid discharge head units based on the control signal input from the printer controller 72C (FIG. 7). Further, the output control device 72Eic may control any of the liquid discharge head units based on an operation by the user or the like.

The printer device 72 shown in FIG. 7 has a different route for inputting image data from the higher-level device 71 and a route used for transmission / reception between the higher-level device 71 and the printer device 72 based on the control data. This is an example.

Further, the printer device 72 may be configured to form an image with, for example, one black color. In the case of performing image formation with one black color, in order to increase the speed of image formation, for example, a configuration having one data management device and four black liquid discharge head units may be used. In this way, the black ink is ejected by each of the plurality of black liquid ejection head units. Therefore, faster image formation can be performed as compared with the configuration in which one black liquid discharge head unit is used.

The transport control device 72Ec (FIG. 7) is a motor, a mechanism, a driver device, and the like for transporting the web 120. For example, the transport control device 72Ec controls a motor or the like connected to each roller or the like to transport the web 120.

<Correlation operation example>
FIG. 10 is a block diagram showing an example of a correlation calculation method according to an embodiment of the present invention. For example, the detection unit can calculate the relative position of the web at the position of the sensor, the movement amount, the movement speed, or a combination thereof, etc. by performing the correlation calculation according to the configuration as shown in the figure.

Specifically, as shown in the figure, the detection unit includes a first two-dimensional Fourier transform unit FT1, a second two-dimensional Fourier transform unit FT2, a correlation image data generation unit DMK, a peak position search unit SR, and a calculation unit CAL. And a configuration having a conversion result storage unit MEM.

The first two-dimensional Fourier transform unit FT1 converts the first image data D1. Specifically, the first two-dimensional Fourier transform unit FT1 has a configuration including a Fourier transform unit FT1a for the orthogonal direction and a Fourier transform unit FT1b for the transport direction.

The Fourier transform unit FT1a for the orthogonal direction performs a one-dimensional Fourier transform on the first image data D1 in the orthogonal direction. Then, the Fourier transform unit FT1b for the transport direction performs one-dimensional Fourier transform of the first image data D1 in the transport direction based on the conversion result by the Fourier transform unit FT1a for the orthogonal direction. In this way, the Fourier transform unit FT1a for the orthogonal direction and the Fourier transform unit FT1b for the transport direction perform one-dimensional Fourier transform in the orthogonal direction and the transport direction, respectively. The first two-dimensional Fourier transform unit FT1 outputs the conversion result converted in this way to the correlation image data generation unit DMK.

Similarly, the second two-dimensional Fourier transform unit FT2 transforms the second image data D2. Specifically, the second two-dimensional Fourier transform unit FT2 has a configuration including a Fourier transform unit FT2a for the orthogonal direction, a Fourier transform unit FT2b for the transport direction, and a complex conjugate unit FT2c.

The Fourier transform unit FT2a for the orthogonal direction performs a one-dimensional Fourier transform on the second image data D2 in the orthogonal direction. Then, the Fourier transform unit FT2b for the transport direction performs one-dimensional Fourier transform of the second image data D2 in the transport direction based on the conversion result by the Fourier transform unit FT2a for the orthogonal direction. In this way, the Fourier transform unit FT2a for the orthogonal direction and the Fourier transform unit FT2b for the transport direction perform one-dimensional Fourier transform in the orthogonal direction and the transport direction, respectively.

Next, the complex conjugate unit FT2c calculates the complex conjugate of the conversion result by the Fourier transform unit FT2a for the orthogonal direction and the Fourier transform unit FT2b for the transport direction. Then, the second two-dimensional Fourier transform unit FT2 outputs the complex conjugate calculated by the complex conjugate unit FT2c to the correlation image data generation unit DMK.

Subsequently, the correlated image data generation unit DMK has the conversion result of the first image data D1 output from the first two-dimensional Fourier transform unit FT1 and the second image output from the second two-dimensional Fourier transform unit FT2. Correlated image data is generated based on the conversion result of the data D2.

The correlation image data generation unit DMK has a configuration including an integration unit DMKa and a two-dimensional inverse Fourier transform unit DMKb.

The integration unit DMKa integrates the conversion result of the first image data D1 and the conversion result of the second image data D2. Then, the integration unit DMKa outputs the integration result to the two-dimensional inverse Fourier transform unit DMKb.

The two-dimensional inverse Fourier transform unit DMKb performs a two-dimensional inverse Fourier transform on the integration result by the integration unit DMKa. When the two-dimensional inverse Fourier transform is performed in this way, the correlated image data is generated. Then, the two-dimensional inverse Fourier transform unit DMKb outputs the correlated image data to the peak position search unit SR.

The peak position search unit SR searches for a peak position having a peak luminance (peak value) that has the steepest (that is, a steep rise) in the generated correlated image data. First, a value indicating the intensity of light, that is, the magnitude of brightness is input to the correlated image data. The brightness is input in a matrix.

In the correlated image data, the luminance is arranged at the pixel pitch interval of the area sensor, that is, the pixel size interval. Therefore, it is desirable that the search for the peak position is performed after performing so-called subpixel processing. In this way, when the sub-pixel processing is performed, the peak position can be searched with high accuracy. Therefore, the detection unit can accurately output the position, the movement amount, the movement speed, and the like.

For example, the search by the peak position search unit SR is performed as follows.

FIG. 11 is a diagram showing an example of a method for searching for a peak position in a correlation calculation according to an embodiment of the present invention. In the figure, the horizontal axis indicates the position in the transport direction in the image indicated by the correlated image data. On the other hand, the vertical axis indicates the brightness of the image indicated by the correlated image data.

Hereinafter, among the brightnesses indicated by the correlated image data, three data of the first data value q1, the second data value q2, and the third data value q3 will be described as an example. That is, in this example, the peak position search unit SR (FIG. 10) searches for the peak position P on the curve k connecting the first data value q1, the second data value q2, and the third data value q3.

First, the peak position search unit SR calculates each difference in the brightness of the image indicated by the correlated image data. Then, the peak position search unit SR extracts a combination of data values having the largest difference value among the calculated differences. Next, the peak position search unit SR extracts a combination adjacent to the combination of data values having the largest difference value. In this way, the peak position search unit SR can extract three data as shown in the illustrated first data value q1, second data value q2, and third data value q3. Then, when the curve k is calculated by connecting the three extracted data, the peak position search unit SR can search for the peak position P. By doing so, the peak position search unit SR can search for the peak position P at a higher speed by reducing the amount of calculation such as sub-pixel processing. The position of the combination of data values having the largest difference value is the steepest position. Further, the sub-pixel processing may be processing other than the above processing.

As described above, when the peak position search unit SR searches for the peak position, for example, the following calculation result can be obtained.

FIG. 12 is a diagram showing an example of a calculation result of a correlation calculation according to an embodiment of the present invention. The figure shows the correlation intensity distribution of the cross-correlation function. In the figure, the X-axis and the Y-axis indicate the serial numbers of the pixels. A peak position such as the illustrated "correlation peak" is searched by the peak position search unit SR (FIG. 10).

In the figure, an example in which there is a fluctuation in the Y direction has been described, but when there is a fluctuation in the X direction, the peak position is generated at a position shifted in the X direction as well.

Returning to FIG. 10, the calculation unit CAL calculates the relative position, movement amount, movement speed, and the like of the web. For example, the calculation unit CAL can calculate the relative position and the amount of movement by calculating the difference between the center position of the correlated image data and the peak position searched by the peak position search unit SR.

Further, the calculation unit CAL can calculate the movement speed by dividing the movement amount by time, for example.

As described above, the detection unit can detect the relative position, the movement amount, the movement speed, and the like by the correlation calculation. The detection method of relative position, movement amount, movement speed, etc. is not limited to this. For example, the detection unit may detect a relative position, a movement amount, a movement speed, or the like as follows.

First, the detection unit binarizes the brightness of each of the first image data and the second image data. That is, the detection unit sets "0" if the luminance is equal to or less than the preset threshold, and "1" if the luminance is larger than the threshold. The detection unit may detect the relative position by comparing the first image data and the second image data binarized in this way.

Further, the detection unit may detect a relative position, a movement amount, a movement speed, or the like by another detection method. For example, the detection unit may detect a relative position from each pattern reflected in each image data by so-called pattern matching processing or the like.

<Overall processing example>
FIG. 13 is a flowchart showing an example of overall processing by the device for discharging the liquid according to the embodiment of the present invention. For example, it is assumed that image data showing an image formed on the web 120 (FIG. 1) is input to the image forming apparatus 110 in advance. Next, the image forming apparatus 110 performs the whole processing shown in FIG. 13 based on the image data, and forms the image shown by the image data on the web 120.

Note that FIG. 13 shows the processing for one liquid discharge head unit. That is, FIG. 13 is, for example, in the example shown in FIG. 2, the process relating to the black liquid discharge head unit 210K. Further, for the liquid discharge head units of other colors, for example, the processes shown in FIG. 13 are separately performed in parallel or before and after.

In step S01, the image forming apparatus detects the position, the moving speed, the moving amount, or a combination thereof. That is, in step S01, the image forming apparatus detects the position, the moving speed, the moving amount, or a combination thereof of the web 120 by the sensor.

For example, in step S01, the image forming apparatus detects a position, a moving speed, a moving amount, or a combination thereof according to the configuration shown in FIG.

In step S02, the image forming apparatus calculates the time required for the portion to be image-formed on the web 120 to be conveyed to the landing position.

For example, first, a sensor on the upstream side, that is, a black sensor SENK (FIG. 2) or the like, detects the time required for the web 120 to be transported by a specified amount. Based on this detection result, the timing at which the black liquid discharge head unit 210K discharges is generated. When the timing for discharging the black liquid discharge head unit 210K is generated, the detection result by the black sensor SENK is integrated in the detection by the downstream sensor, that is, the cyan sensor SENC (FIG. 2) or the like. For example, the cyan sensor SENC or the like detects the time required for the web 120 to be conveyed by a predetermined amount, as in the case of black. Based on this detection result, the timing at which the cyan liquid discharge head unit 210C discharges is corrected. Hereinafter, the same applies to magenta and yellow, which are further downstream.

In addition, the time may be calculated by the following method or the like. First, it is assumed that the distance from the position where the sensor is installed to the landing position is input in advance. Further, it is assumed that the predetermined portion is determined by the image data or the like. Next, the image forming apparatus detects the moving speed in step S01. By doing so, the time required for the predetermined location to be transported to the landing position can be calculated by calculating "distance ÷ moving speed = time".

In steps S01 and S02, processing is performed based on the timing at which the liquid is discharged by the liquid discharge head unit in front (for example, black with respect to cyan). Subsequently, step S03 is a process performed at a position where a sensor installed downstream from the previous landing position (for example, a cyan sensor SENC (FIG. 2)) is installed. Hereinafter, the timing at which the liquid is discharged by the previous liquid discharge head unit is referred to as "first timing T1". On the other hand, the timing at which the liquid is discharged by the next (cyan in this example) liquid discharge head unit is referred to as "second timing T2". Further, the timing at which the detection is performed by the sensor between the first timing T1 and the second timing T2 is referred to as "third timing T3".

In step S03, the image forming apparatus detects a predetermined location. The step S03 is performed at the third timing T3.

In step S04, the image forming apparatus calculates the amount of deviation based on the detection result in step S03, and adjusts the timing at which the liquid is discharged at the next landing position, that is, the second timing T2, based on the amount of deviation. do.

The above processing can be described by, for example, the following timing chart and conceptual diagram.

FIG. 14 is a timing chart and a conceptual diagram showing an example of overall processing by an apparatus for discharging a liquid according to an embodiment of the present invention. In the illustrated example, the first timing T1 is the timing at which the black liquid is discharged, and the second timing T2 is the timing at which the cyan liquid is discharged. Further, in this example, the timing at which the cyan sensor SENC installed between the black liquid discharge head unit 210K and the cyan liquid discharge head unit 210C performs detection is set as the third timing T3.

In this example, the position where the cyan sensor SENC performs detection is hereinafter referred to as "detection position PREN". As shown in the figure, the detection position PREN is assumed to be a position "installation distance D" from the landing position of the cyan liquid discharge head unit 210C. Further, in the following example, it is assumed that the interval at which each sensor is installed is the same as the installation interval (relative distance L) of each liquid discharge head unit.

First, at the first timing T1, the image forming apparatus turns the first signal SIG1 “ON” so as to discharge the liquid to the black liquid discharge head unit 210K. Then, the image forming apparatus acquires the image data at the timing when the first signal SIG1 is turned “ON”. In the illustrated example, the image acquired at the first timing T1 is represented by the first image signal PA, and the image data corresponds to the image data D1 (n) at the “A position” shown in FIG.

When the image data D1 is acquired, the image forming apparatus can detect the position of a predetermined position, the moving speed V to which the web 120 is conveyed, and the like (step S01 shown in FIG. 13). Further, when the moving speed can be detected, the image forming apparatus divides the relative distance L by the moving speed V (L ÷ V), and determines the time required for the predetermined location to be transported to the next landing position. It can be calculated (step S02 shown in FIG. 13).

Next, at the third timing T3, the image forming apparatus acquires image data. In the illustrated example, the image acquired at the third timing T3 is represented by the second image signal PB, and the image data corresponds to the image data D2 (n) at the “B position” shown in FIG. 8 (FIG. 13). Step S03 shown. Next, the image forming apparatus performs a cross-correlation operation on the image data D1 (n) and D2 (n). In this way, the image forming apparatus can calculate the deviation amount ΔD (0).

In a state where the roller has no thermal expansion and there is no slip between the roller and the web 120, that is, in a so-called ideal state, the image forming apparatus moves a relative distance L at a predetermined position of the web 120. It takes time of "L ÷ V" to convey at the speed V.

Therefore, the "imaging cycle T" shown in FIG. 10 is set to, for example, "imaging cycle T = imaging time difference = relative distance L / moving speed V". In the illustrated example, the sensors of the black sensor SENK and the cyan sensor SENC are installed at intervals of the relative distance L. If it is in an ideal state, the predetermined portion of the web 120 detected by the black sensor SENK is conveyed to the position of the detection position PREN after "L ÷ V" time.

On the other hand, in reality, there are many cases where thermal expansion occurs in the rollers or slippage occurs between the rollers and the web 120. In the correlation calculation method shown in FIG. 10, when "imaging cycle T = relative distance L / moving speed V" is set, the timing at which the image data D1 (n) is imaged by the black sensor SENK and the cyan sensor SENC. The time difference from the timing at which the image data D2 (n) is captured is “L ÷ V”. In this way, the image forming apparatus may calculate the deviation amount ΔD (0) with “L ÷ V” as the “imaging period T”. Hereinafter, an example of the third timing illustrated will be described.

At the third timing T3, the image forming apparatus calculates the deviation amount ΔD (0) which is an example of the second distance. Then, the image forming apparatus adjusts the timing at which the cyan liquid discharge head unit 210C discharges the liquid, that is, the second timing T2, based on the installation distance D, the deviation amount ΔD (0), and the moving speed V (FIG. 13). Step S04) shown in.

In an ideal state such as no thermal expansion of the rollers, the image forming apparatus takes a time of "D ÷ V" to convey the installation distance D at the moving speed V. Therefore, in step S02, the time of “D ÷ V” is calculated based on “L ÷ V”, and the second timing T2 is determined. On the other hand, in reality, the position where the liquid is to be discharged is a position where the amount of deviation ΔD (0) is from the position where the cyan liquid discharge head unit 210C discharges the liquid due to thermal expansion of the roller or the like. Therefore, it takes a time of "ΔD (0) ÷ V" for the predetermined position to be conveyed to the position where the cyan liquid discharge head unit 210C discharges the liquid. Therefore, the image forming apparatus deviates from the second timing T2, that is, the timing (for the ideal state) in which the timing for setting the second signal SIG2 to “ON” is determined based on “L ÷ V”, by the amount of deviation ΔD (0). ) Adjust the timing so that the liquid can be discharged.

Specifically, the adjustment amount of the adjustment timing is "(ΔD (0) −D) / V". In this way, the image forming apparatus adjusts the second timing T2 so as to shift by “(ΔD (0) −D) / V”. By doing so, even if the rollers have thermal expansion or the like, the image forming apparatus adjusts based on the deviation amount ΔD (0), the installation distance D, and the moving speed V, so that the object to be transported is in the direction of being conveyed. , The accuracy of the landing position of the discharged liquid can be further improved.

The timing of detection, that is, the third timing T3, is, for example, the minimum time during which the object to be transported is conveyed to the position where the liquid discharge head unit discharges the liquid (hereinafter, simply referred to as "minimum time"). It is desirable to determine based on. That is, since the thermal expansion and the like of the rollers differ depending on the situation and the like, the time required for the web 120 to be conveyed to the position where the liquid discharge head unit discharges the liquid varies. Therefore, the user or the like measures a plurality of times required for transportation in advance. Then, the minimum time, which is the shortest time among the measured times, is determined. In this way, first, the minimum time is predetermined.

Next, assuming that a predetermined location is conveyed to the detection position in the minimum time, the image forming apparatus sets a timing earlier than the time in which the predetermined location is conveyed to the detection position in the minimum time as the third timing T3. To. The web 120 may be transported in the shortest amount of time. Therefore, if the detection is not performed at an earlier timing than the transportation in the minimum time, a predetermined location may be overlooked. Therefore, when the image forming apparatus determines the third timing T3 based on the minimum time, the image forming apparatus can perform the detection with high accuracy.

In addition, the image forming apparatus may be preset with an ideal moving speed for each mode. The ideal moving speed is the moving speed in the absence of thermal expansion or the like. Further, "D" is predetermined in design. Then, the image forming apparatus first sets the ideal moving speed as "V", calculates "D / V", and determines the timing of discharging the liquid in the ideal state. After that, when the deviation amount is known, the image forming apparatus can adjust the timing in the ideal state based on the deviation amount and determine the timing for discharging the liquid to the liquid discharge head unit.

As described above, when the signal is transmitted at the timing adjusted in step S04, the image forming apparatus discharges the liquid at the timing indicated by the signal. In this way, when one or more liquids are ejected, the image indicated by the image data is formed on the web 120.

In the above, an example of adjusting and determining the timing has been described, but the image forming apparatus directly calculates and determines the timing of discharging the liquid to the liquid discharge head unit from the deviation amount and “V” and “D”. Is also good.

<Function configuration example>
FIG. 15 is a functional block diagram showing an example of the functional configuration of the device for discharging the liquid according to the embodiment of the present invention. As shown in the figure, the image forming apparatus 110 includes a plurality of liquid discharge head units, a detection unit 110F10 for each liquid discharge head unit, and a control unit 110F20. Further, the image forming apparatus 110 includes a calculation unit 53F.

As shown in the figure, the detection unit 110F10 is installed for each liquid discharge head unit. Specifically, in the example shown in FIG. 2, the number of detection units 110F10 is four as shown in the figure. Further, the detection unit 110F10 detects the position of the web 120 in the transport direction, the moving speed, the moving amount, or a combination thereof. The detection unit 110F10 is realized by, for example, the hardware configuration shown in FIG. 4 or FIG. Further, the detection unit 110F10 corresponds to the detection units 52A and 52B in FIG.

The calculation unit 53F calculates the time for the transported object to be transported to the landing position where the liquid discharge head unit can discharge the liquid based on the plurality of detection results. That is, the calculation unit 53F outputs the calculation result used for determining the timing at which the control unit 110F20 discharges the liquid based on the deviation amount and the like.

The control unit 110F20 discharges the liquid to a plurality of liquid discharge head units at a timing determined by adjustment based on the detection result by the detection unit 110F10 or the like. The control unit 110F20 is realized by, for example, the hardware configuration shown in FIG.

Further, preferably, the position where the detection unit 110F10 performs detection, that is, the position where the sensor is installed, is preferably a position close to the landing position such as the black landing position PK such as INTK1 between the black rollers. That is, when the detection is performed by the black roller-to-roller INTK1 or the like, the image forming apparatus 110 can accurately detect the position, the moving speed, the moving amount, and the like in the transport direction.

Further, preferably, the position where the detection unit 110F10 detects, that is, the position where the sensor is installed, is the position on the upstream side of the landing position among the rollers, such as the black upstream section INTK2 and the like. good. That is, when the detection is performed in the black upstream section INTK2 or the like, the image forming apparatus 110 can accurately detect the position, the moving speed, the moving amount, and the like in the transport direction. Moreover, the image forming apparatus 110 can generate a calculation and a timing based on the detection result by the detection unit 110F10 to discharge the liquid to each liquid discharge head unit.

Further, as shown in the figure, the image forming apparatus 110 is preferably configured to include the measuring unit 110F30. With the measuring unit 110F30, the image forming apparatus 110 can more reliably detect the position of the recording medium and the like. For example, it is assumed that a measuring device such as an encoder is installed on the rotating shaft of the roller 230. Then, the measuring unit 110F30 measures the movement amount of the recording medium by an encoder or the like. As described above, when the measurement result measured by the measurement unit 110F30 is further input, the image forming apparatus 110 can more reliably detect the position of the recording medium in the transport direction and the like.

<Comparison example>
FIG. 16 is a schematic view showing an overall configuration example of the apparatus according to the comparative example. The image forming apparatus 110A shown in the figure is different from the example shown in FIG. 2 in that the sensor is not installed and the encoder 240 is installed. Further, in FIG. 16, rollers 220 and 230 carry the web 120. It is assumed that the encoder 240 is installed with respect to the rotation axis of the roller 230.

In the image forming apparatus 110A, each liquid discharge head unit is arranged at a position obtained by multiplying the peripheral length of the roller 230 by an integer. In this way, the deviation due to the eccentricity of the roller synchronized with the rotation cycle of the roller is canceled. Further, the deviation of the position where each liquid discharge head unit is installed may be canceled by correcting the timing of each liquid discharge head unit to discharge the liquid by a test print or the like.

Further, in the image forming apparatus 110A, each liquid discharge head unit discharges liquid based on the encoder signal output by the encoder 240.

FIG. 17 is a diagram showing an example of a deviation of the landing position in the device according to the comparative example. The figure shows an example of the deviation of the landing position of the liquid discharged from each liquid discharge head unit in the image forming apparatus 110A shown in FIG.

The first graph G1 shows the actual position of the web. On the other hand, the second graph G2 is the position of the web calculated based on the encoder signal from the encoder 240 (FIG. 16). That is, if there is a difference between the first graph G1 and the second graph G2, the position where the web is actually located and the calculated position of the web are different in the transport direction, so that the landing position is likely to be displaced. ..

For example, this is an example in which a deviation amount σ occurs in the liquid discharge by the black liquid discharge head unit 210K. Further, the amount of deviation may differ depending on the liquid discharge head unit. That is, in the discharge other than black, each deviation amount is often different from the deviation amount σ.

The amount of deviation is caused by, for example, eccentricity of the roller, thermal expansion of the roller, slippage between the web and the roller, expansion and contraction of the recording medium, and a combination thereof.

FIG. 18 is a diagram showing an example of the influence of the eccentricity of the roller and the like on the deviation of the landing position. The illustrated graph shows an example of the effects of roller thermal expansion, eccentricity and slippage between the roller and the web. That is, each graph shows the difference between the position of the web calculated based on the encoder signal from the encoder 240 (FIG. 16) and the actual position by the “deviation amount” on the vertical axis. Further, FIG. 18 shows an example in which the roller has an outer diameter of “φ60” and the material of the roller is aluminum.

The third graph G3 shows the deviation amount when the roller has an eccentricity amount of "0.01 mm". As shown in the third graph G3, the amount of deviation due to eccentricity is often a cycle synchronized with the rotation cycle of the roller. In addition, the amount of deviation due to eccentricity is often proportional to the amount of eccentricity, but it is often not cumulative.

The fourth graph G4 shows the amount of deviation when the roller has eccentricity and thermal expansion. The thermal expansion is an example when there is a temperature change of "-10 ° C.".

The fifth graph G5 shows the amount of deviation when the roller has an eccentricity and a slip generated between the web and the roller. The slip generated between the web and the roller is an example when it is "0.1%".

Further, in order to reduce meandering of the web, so-called tension may be applied to pull the web in the transport direction. Depending on this tension, the web may stretch or contract. Further, the expansion and contraction of the web may differ depending on the thickness, width, coating amount and the like of the web.

<Summary>
The device for discharging a liquid according to an embodiment of the present invention obtains a detection result such as a position in a transport direction, a moving speed, or a moving amount for each liquid discharging head unit. Therefore, the device for discharging the liquid according to the embodiment of the present invention can determine the timing and the like for discharging the liquid for each liquid discharge head unit based on the amount of displacement and the like. Therefore, as compared with the comparative example shown in FIG. 16, the device for discharging the liquid according to the embodiment of the present invention can accurately compensate for the deviation generated at the landing position of the liquid in the transport direction.

Further, in the device for discharging the liquid according to the embodiment of the present invention, it is less necessary to arrange each liquid discharge head unit at a position obtained by multiplying the peripheral length of the roller by an integer, as compared with the comparative example shown in FIG. , It is possible to reduce the restrictions on installing each liquid discharge head unit.

Further, in the device for discharging the liquid according to the embodiment of the present invention, the movement amount is not calculated based on the rotation amount of the rollers as in the comparative example shown in FIG. 16, but the position of the web is directly detected. Therefore, the influence of thermal expansion of the roller can be canceled with high accuracy. In addition, in the device for discharging the liquid according to the embodiment of the present invention, if the detection is performed at a position close to the liquid discharge head unit, the influence of the expansion and contraction of the web can be canceled with high accuracy.

As described above, if the influence of the eccentricity of the roller, the thermal expansion of the roller, the slip generated between the web and the roller, the expansion and contraction of the recording medium, and the combination thereof can be reduced, the device for discharging the liquid can be used in the transport direction. In, the accuracy of the landing position of the discharged liquid can be further improved.

Further, in the case of ejecting a liquid to form an image on a recording medium, the device for ejecting the liquid according to the embodiment of the present invention causes color shift when the landing position of the discharged liquid of each color becomes accurate. The number is reduced, and the image quality of the formed image can be improved.

Further, each detection unit detects the position, moving speed, or moving amount of the transported object for each liquid discharge head unit based on the patterns of the transported object at two or more different timings. In this way, the timing at which each liquid discharge head unit discharges the liquid is controlled based on the respective detection results, so that the device for discharging the liquid is displaced at the landing position of the liquid in the transport direction. Can be compensated more accurately.

<Modification example>
When adjusting the timing at which multiple liquid discharge head units discharge liquid, the device that discharges the liquid corresponds to the sensor corresponding to each liquid discharge head unit and the liquid discharge head unit located at the most upstream position. Each timing may be adjusted based on the detection result with the sensor.

Specifically, as shown in FIG. 2, it is assumed that the liquid discharge head unit is installed in the order of black, cyan, magenta, and yellow from the upstream. That is, in this example, the black sensor SENK is a sensor corresponding to the liquid discharge head unit located at the most upstream.

Then, in this example, the device for discharging the liquid adjusts the timing at which the cyan liquid discharge head unit 210C discharges the liquid based on the detection result by the black sensor SENK and the detection result by the cyan sensor SENC. Further, the device for discharging the liquid adjusts the timing at which the magenta liquid discharge head unit 210M discharges the liquid based on the detection result by the black sensor SENK and the detection result by the magenta sensor SENM. Similarly, the timing at which the yellow liquid discharge head unit 210Y discharges the liquid is adjusted based on the detection result by the black sensor SENK and the detection result by the yellow sensor SENY.

As described above, when the detection result by the sensor located at the most upstream is used, it is difficult to integrate the error. Therefore, the device for discharging the liquid can more accurately compensate for the deviation generated at the landing position of the liquid.

However, the combination of detection results does not have to be as described above as long as the error is within an acceptable range. That is, while the magenta liquid discharge head unit 210M adjusts the timing at which the liquid is discharged, the device that discharges the liquid adjusts based on the detection result by the cyan sensor SENC and the detection result by the magenta sensor SENM. You may go.

The detection device 50 shown in FIG. 4 may be realized by the following hardware, for example.

FIG. 19 is a schematic view showing a first modification of a hardware configuration that realizes a detection unit according to an embodiment of the present invention. In the following description, the same devices as those described above will be designated by the same reference numerals, and the description thereof will be omitted.

Compared with the hardware configuration described above, the detection device is different in that it has a plurality of optical systems. That is, the hardware configuration described above is a so-called "monocular", whereas the hardware configuration of the first modification is a "compound eye".

Further, in the following modification, the position of the compound eye for detection using the first image pickup lens 12A on the upstream side is defined as the "A position", and the second image pickup lens 12B located downstream of the first image pickup lens 12A is used. The position where the detection is performed by using is referred to as "B position". Further, in the following modification, "L" is read as the distance between the first image pickup lens 12A and the second image pickup lens 12B.

The web 120, which is an example of the detection target, is irradiated with laser light or the like from the first light source and the second light source, respectively. The position where the first light source irradiates the light is defined as the "A position", and similarly, the position where the second light source irradiates the light is defined as the "B position".

The first light source and the second light source include a light emitting element that emits laser light and a collimated lens that makes the laser light emitted from the light emitting element substantially parallel light. Further, the first light source and the second light source are installed at positions where the surface of the web 120 is irradiated with the laser beam from an oblique direction.

The detection device 50 has an area sensor 11, a first image pickup lens 12A at a position facing the "A position", and a second image pickup lens 12B at a position facing the "B position".

The area sensor 11 is, for example, a sensor having a configuration in which an image pickup device 112 is formed on a silicon substrate 111. It is assumed that the image sensor 112 has an "A region 11A" and a "B region 11B" that can acquire a two-dimensional image, respectively. Further, the area sensor 11 is, for example, a CCD sensor, a CMOS sensor, a photodiode array, or the like. The area sensor 11 is housed in the housing 13. Further, the first image pickup lens 12A and the second image pickup lens 12B are held by the first lens barrel 13A and the second lens barrel 13B, respectively.

In this example, as shown, the optical axis of the first imaging lens 12A coincides with the center of the "A region 11A". Similarly, the optical axis of the second imaging lens 12B coincides with the center of the "B region 11B". Then, the first image pickup lens 12A and the second image pickup lens 12B form an image of light in the "A region 11A" and the "B region 11B", respectively, to generate a two-dimensional image.

In addition, the detection device 50 may have a configuration or the like described below.

FIG. 20 is a schematic view showing a second modification of the hardware configuration that realizes the detection unit according to the embodiment of the present invention. Hereinafter, the points different from FIG. 19, that is, the hardware configuration of the detection device 50 are excerpted and illustrated. Compared with the configuration shown in FIG. 19, the configuration of the detection device 50 is different in that the first image pickup lens 12A and the second image pickup lens 12B are integrated into the lens 12C. On the other hand, the area sensor 11 and the like have the same configuration as shown in FIG. 19, for example.

Further, in this example, it is desirable that the aperture 121 or the like is used so that the images of the first image pickup lens 12A and the second image pickup lens 12B do not interfere with each other to form an image. As described above, when the aperture 121 or the like is used, the regions for forming the images of the first image pickup lens 12A and the second image pickup lens 12B can be limited respectively. Therefore, it is possible to reduce the interference between the respective images, and the detection device 50 can calculate the moving speed at the position of the sensor upstream based on the images generated at the "A position" and the "B position". Then, the moving speed can be calculated in the same manner by the position of the sensor installed downstream. In this way, the image forming apparatus may control the timing of discharging the liquid based on the speed difference between the moving speeds calculated on the upstream side and the downstream side.

FIG. 21 is a schematic view showing a third modification of the hardware configuration that realizes the detection unit according to the embodiment of the present invention. Compared with the configuration shown in FIG. 20, the configuration of the detection device 50 shown in FIG. 21 (A) is different in that the area sensor 11 is the second area sensor 11'. On the other hand, the configurations of the first image pickup lens 12A, the second image pickup lens 12B, and the like are the same as those in FIG. 20, for example.

The second area sensor 11'has, for example, the configuration shown in FIG. 21 (B). Specifically, as shown in FIG. 21B, a plurality of image pickup devices b are formed on the wafer a. Next, the image pickup device as shown in FIG. 21B is cut out from the wafer a, respectively. The first image sensor 112A and the second image sensor 112B, which are the plurality of image pickup elements to be cut out, are each formed on the silicon substrate 111. On the other hand, the positions of the first image pickup lens 12A and the second image pickup lens 12B are determined according to the distance between the first image pickup element 112A and the second image pickup element 112B.

The image pickup device is often manufactured for imaging. Therefore, the ratio in the X direction and the Y direction of the image sensor, that is, the aspect ratio is often a ratio that matches the image format, such as square, "4: 3" or "16: 9". In the present embodiment, images are taken at two or more points separated by a certain interval. Specifically, an image is taken at each point separated by a certain interval in the X direction, which is one direction in two dimensions, that is, in the transport direction 10 (FIG. 2). On the other hand, the image sensor has an aspect ratio that matches the image format. Therefore, when imaging two points separated by a certain interval in the X direction, the image sensor in the Y direction may not be used. Further, when the pixel density is increased, the cost may be increased because the image sensor having a high pixel density is used in either the X direction or the Y direction.

Therefore, with the configuration shown in FIG. 21, the first image sensor 112A and the second image sensor 112B that are separated from each other at regular intervals can be formed on the silicon substrate 111. Therefore, the number of image pickup elements in which the image pickup element in the Y direction is not used can be reduced. Therefore, the waste of the image sensor can be reduced. Further, since the first image sensor 112A and the second image sensor 112B are formed by a semiconductor process with high accuracy, the distance between the first image sensor 112A and the second image sensor 112B can be made accurate.

FIG. 22 is a schematic view showing an example of a plurality of image pickup lenses used in the detection unit according to the embodiment of the present invention. A lens array as shown may be used to implement the detector.

The illustrated lens array has a configuration in which two or more lenses are integrated. Specifically, the illustrated lens array is an example having 3 rows and 3 columns in the vertical and horizontal directions and having a total of 9 imaging lenses A1 to C3. When such a lens array is used, an image showing nine points can be captured. In this case, an area sensor having nine imaging regions is used.

In this way, for example, operations on two imaging regions are likely to be executed simultaneously, that is, executed in parallel. Next, when each calculation result is averaged or error elimination is performed, the detection device calculates accurately and improves the stability of the calculation as compared with the case where one calculation result is used. can do. In addition, the calculation may be executed based on the application software whose speed fluctuates. Even in this case, since the area where the correlation calculation can be performed is expanded, it becomes easy to obtain a highly accurate speed calculation result.

The first support member and the second support member may also be used. For example, the first support member and the second support member may have the following configurations.

FIG. 23 is a schematic view showing a modified example of the device for discharging the liquid according to the embodiment of the present invention. As compared with FIG. 2, in the illustrated configuration, the arrangement of the first support member and the second support member is different. As shown in the figure, the first support member and the second support member may be realized by, for example, the first member RL1, the second member RL2, the third member RL3, the fourth member RL4, and the fifth member RL5. .. That is, the second support member provided on the upstream side of each liquid discharge head unit and the first support member provided on the downstream side of each liquid discharge head unit may be shared. The first support member and the second support member may be combined with a roller or a curved plate.

The device for discharging the liquid according to the present invention may be realized by a system for discharging the liquid having one or more devices. For example, the black liquid discharge head unit 210K and the cyan liquid discharge head unit 210C are devices having the same housing, and the magenta liquid discharge head unit 210M and the yellow liquid discharge head unit 210Y are devices having the same housing, both of which are included. It may be realized by a system that discharges a liquid.

Further, in the liquid ejection device and the liquid ejection system according to the present invention, the liquid is not limited to ink, but may be another type of recording liquid, fixing treatment liquid, or the like. That is, the liquid ejection device and the liquid ejection system according to the present invention may be applied to a liquid ejection device other than ink.

Therefore, the device for discharging the liquid and the system for discharging the liquid according to the present invention are not limited to forming an image. For example, the formed object may be a three-dimensional model or the like.

Further, the object to be transported is not limited to a recording medium such as paper. The transported object may be made of a material to which a liquid can adhere. For example, the material to which the liquid can be attached may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, or a combination thereof, as long as the liquid can be attached even temporarily.

Further, in the embodiment of the present invention, it may be realized by a program for executing a part or all of the methods of discharging the liquid to a computer such as an image forming apparatus, an information processing apparatus, or a combination thereof.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are made within the scope of the gist of the present invention described in the claims. Or it can be changed.

110 Image Forming Device 120 Web 210K Black Liquid Discharge Head Unit 210C Cyan Liquid Discharge Head Unit 210M Magenta Liquid Discharge Head Unit 210Y Yellow Liquid Discharge Head Unit SENK Black Sensor SENC Cyan Sensor SENM Magenta Sensor SENY Yellow Sensor 520 Controller

Japanese Unexamined Patent Publication No. 2015-13476

Claims (16)

A device having a plurality of liquid discharge head units and discharging liquid to a transported object by the liquid discharge head unit.
A first unit in which the liquid discharge head unit is provided on the upstream side in the transport direction of the transported object with respect to a predetermined position of the transported object from the landing position where the liquid can be discharged, and supports the transported object. Support members and
A second support member provided on the downstream side in the transport direction of the object to be transported from the landing position and supporting the object to be transported, and a second support member.
A detection unit installed for each liquid discharge head unit and outputting a detection result indicating the position, moving speed, moving amount, or a combination thereof in the transport direction in which the transported object is transported.
A control unit that discharges the liquid to a plurality of liquid discharge head units while transporting the transported object to the transported object that is transported at a timing based on the detection result of the detection unit. Prepare,
The detection unit discharges a liquid characterized by being installed between the first support member and the second support member and on the side opposite to the liquid discharge head unit with respect to the object to be transported. Device to do. The control unit determines the timing based on the detection result.
The timing determined by the control unit is at least the timing at which the liquid discharge head unit corresponding to the detection unit on the downstream side in the transport direction of the object to be transported discharges the liquid. The device for discharging the liquid according to claim 1. The first or second aspect of the present invention, wherein the control unit determines the timing at which the liquid discharge head unit discharges the liquid for each liquid discharge head unit based on the detection result. A device that discharges liquid. Based on the detection result, the control unit calculates the time required for the transported object to be transported to the landing position where the liquid discharge head unit can discharge the liquid, and determines the timing. The device for discharging the liquid according to any one of claims 1 to 3, which is characteristic. The device for discharging a liquid according to any one of claims 1 to 4, wherein the detection unit uses an optical sensor. The device for discharging the liquid according to any one of claims 1 to 5, wherein the detection unit obtains the detection result based on the pattern of the transported object. The pattern is generated by the interference of light applied to the uneven shape formed on the object to be transported.
The device for discharging the liquid according to claim 6, wherein the detection unit obtains the detection result based on an image obtained by capturing the pattern. The device for discharging a liquid according to any one of claims 1 to 7 , wherein the position of the detection unit is installed at a position closer to the first support member than the landing position . The device for discharging a liquid according to any one of claims 1 to 8 , wherein an image is formed on the object to be transported when the liquid is discharged. The device for discharging a liquid according to any one of claims 1 to 9 , wherein the transported object is a sheet that is long and continuous along the transport direction . Further equipped with a measuring unit for measuring the amount of movement of the object to be transported,
The device for discharging the liquid according to any one of claims 1 to 10 , wherein the control unit discharges the liquid based on the movement amount measured by the measuring unit and the detection result. .. In the control unit, the installation distance from the detection position where the detection unit detects is to the landing position where the liquid discharge head unit can discharge the liquid, and the detection target to be detected at the detection position in the ideal state are real. 1 _ A device for discharging the liquid according to item 1. The liquid according to any one of claims 1 to 12 , wherein the detection unit detects between the liquid discharge head units at a timing determined based on the minimum time for the transported object to be transported. A device that discharges. The device for discharging a liquid according to any one of claims 1 to 13 , wherein the detection unit is installed directly below the liquid discharge head unit . The detection unit has a light source and has a light source.
The device for discharging a liquid according to any one of claims 1 to 14, wherein the light source is an LED . A system that includes a plurality of liquid discharge head units and has one or more devices for discharging liquid by the plurality of liquid discharge head units to a transported object.
A first unit in which the liquid discharge head unit is provided on the upstream side in the transport direction of the transported object with respect to a predetermined position of the transported object from the landing position where the liquid can be discharged, and supports the transported object. Support members and
A second support member provided on the downstream side in the transport direction of the object to be transported from the landing position and supporting the object to be transported, and a second support member.
A detection unit installed for each liquid discharge head unit and outputting a detection result indicating the position, moving speed, moving amount, or a combination thereof in the transport direction in which the transported object is transported.
A control unit that discharges the liquid to a plurality of the liquid discharge head units while transporting the transported object to the transported object that is transported at the timing based on the detection result of the detection unit.
Equipped with
The detection unit discharges a liquid characterized by being installed between the first support member and the second support member and on the side opposite to the liquid discharge head unit with respect to the object to be transported. System to do.

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