Patent Description:
In the related art, a liquid discharge apparatus includes a conveyance device that conveys an object in a conveyance direction, a discharge head that discharges a liquid onto the object, and a sensor that detects a positional deviation of the object in a direction orthogonal to the conveyance direction (e.g., <CIT>). In this liquid discharge apparatus, the head unit is moved in the direction orthogonal to the conveyance direction of the object in accordance with the positional deviation detected by the sensor in order to change the position at which the liquid is discharged onto the object. However, the liquid discharge apparatus described in <CIT> includes a dedicated actuator for moving the head unit.

Document <CIT> discloses the preamble of claims <NUM> and <NUM>.

An object of the present disclosure is to provide a liquid discharge apparatus that changes a position of a head unit without a dedicated actuator for moving the head unit.

The invention is defined by a liquid discharge apparatus according to claim <NUM> and by a liquid discharge method according to claim <NUM>.

As a result, the liquid discharge apparatus that changes the position of the head unit without a dedicated actuator for moving the head unit can be provided.

A liquid discharge apparatus, a liquid discharge method, and a control device according to an embodiment of the disclosure is described below with reference to the drawings.

<FIG> is a schematic view of an image forming apparatus <NUM> according to the present embodiment. <FIG> is a block diagram of the image forming apparatus <NUM> according to the present embodiment. The image forming apparatus <NUM> illustrated in <FIG> and <FIG> is an on-demand line head inkjet recording apparatus. The image forming apparatus <NUM> is an example of a liquid discharge apparatus. The image forming apparatus <NUM> includes a sheet supply device <NUM>, a conveyor unit <NUM>, a first image forming device <NUM>, a second image forming device <NUM>, a front-back reverse device <NUM>, a first drying device <NUM>, a second drying device <NUM>, and a sheet collection device <NUM>. The image forming apparatus <NUM> discharges ink onto a sheet S as a recording medium. The ink is an example of a liquid. As illustrated in <FIG>, the image forming apparatus <NUM> includes a controller <NUM>.

The sheet supply device <NUM> includes a supply roller <NUM> around which a long sheet S is wound in a roll shape. The supply roller <NUM> is rotatable in a direction indicated by arrow R1 in <FIG>. As the supply roller <NUM> rotates, the sheet S is fed out. The sheet S is an example of an object. The object may be a paper medium or another medium. The object may be a sheet material and the sheet material may be a cut sheet material. The sheet material may be an oversize sheet material such as wallpaper.

The conveyor unit <NUM> as a conveyor includes multiple conveyance rollers <NUM> to convey the sheet S. The sheet S is stretched over the multiple conveyance rollers <NUM>. The multiple conveyance rollers <NUM> rotate to convey the sheet S. The conveyance roller <NUM> includes a pipe having a circular cross section and a shaft.

The first image forming device <NUM> includes multiple head units <NUM>, 12C, <NUM>, and 12Y that discharge liquid ink onto the sheet S. Each of the head units <NUM>, 12C, <NUM>, and 12Y discharges the ink onto a front side of the sheet S based on image data to be formed on the front side of the sheet S among the image data generated by the controller <NUM> to form an image on the sheet S. The ink may be a liquid containing a colorant, a solvent, and crystalline resin particles dispersed in the solvent. The crystalline resin changes a phase thereof and melts from a crystal to a liquid when heated above a melting point thereof. The head units <NUM>, 12C, <NUM>, and 12Y may be collectively referred to as head units <NUM>, each of which may be referred to as a head unit <NUM> unless distinguished.

The first drying device <NUM> includes a heating drum <NUM> that heats the sheet S. The heating drum <NUM> promotes drying of the ink on the sheet S. The heating drum <NUM> includes a cylindrical component that rotates while the sheet S is wound around the outer circumferential surface thereof. For example, a halogen heater as a heating source is disposed inside the cylindrical component. The heating source is not limited to the halogen heater but may be other heaters.

The heating drum <NUM> faces a back side of the sheet S conveyed in a conveyance path. When the sheet S is conveyed from the first image forming device <NUM>, a lower face (the back side) of the sheet S contacts the outer circumferential surface of the heating drum <NUM>. The heating drum <NUM> conveys the sheet S while heating the sheet S. Thus, the heating drum <NUM> promotes the drying of the ink on the sheet S.

The controller <NUM> controls a rotation speed of the heating drum <NUM>. The controller <NUM> controls the rotation speed of the heating drum <NUM> to substantially the same speed as a conveyance speed in the sheet supply device <NUM>, the sheet collection device <NUM>, and the conveyor unit <NUM>. As a result, the sheet S is conveyed without slipping on the outer circumferential surface of the heating drum <NUM> in a conveyance direction of the sheet S (i.e., a sheet conveyance direction).

A known device that reverses the front side and the back side of the sheet S can be used as the front-back reverse device <NUM>. When the sheet S conveyed from the first drying device <NUM> passes through the front-back reverse device <NUM>, the front and back sides of the sheet S are reversed. The reversed sheet S is conveyed to the second image forming device <NUM>. Thus, the sheet S is conveyed with the front side facing upward, reversed by the front-back reverse device <NUM>, and conveyed with the front side facing downward (with the back side facing upward).

The second image forming device <NUM> basically has the same configuration as the first image forming device <NUM>. The second image forming device <NUM> includes multiple head units <NUM>, 14C, <NUM>, and 14Y that discharge liquid ink onto the sheet S. Each of the head units <NUM>, 14C, <NUM>, and 14Y discharges the ink onto the back side of the sheet S based on image data to be formed on the back side of the sheet S among the image data generated by the controller <NUM> to form an image on the sheet S.

Similarly to the first drying device <NUM>, the second drying device <NUM> includes a heating drum <NUM> that heats the sheet S. The heating drum <NUM> faces the front side of the sheet S conveyed in the conveyance path. When the sheet S is conveyed from the second image forming device <NUM>, a lower face (the front side) of the sheet S contacts the outer circumferential surface of the heating drum <NUM>. The heating drum <NUM> conveys the sheet S while heating the sheet S. Thus, the heating drum <NUM> promotes the drying of the ink on the sheet S. Even if an image is formed (ink is applied) on the front side of the sheet S, the ink has already been dried by the first drying device <NUM> when the heating drum <NUM> contacts the image on the front side. As a result, the image does not deteriorate.

The sheet collection device <NUM> includes a collection roller <NUM> that winds and collects the sheet S. The collection roller <NUM> is rotatable in a direction indicated by arrow R2 in <FIG>. The sheet S is wound in a roll shape around the collection roller <NUM> as the collection roller <NUM> rotates. The sheet collection device <NUM> may include a post-processing unit that performs post-processing such as cutting the sheet S to a predetermined length and aligning the cut sheet S.

The controller <NUM> illustrated in <FIG> may include an information processor such as a personal computer (PC). The controller <NUM> generates image data to be formed on the front side and the back side of the sheet S. The controller <NUM> controls various operations of the sheet supply device <NUM>, the conveyor unit <NUM>, the first image forming device <NUM>, the second image forming device <NUM>, the front-back reverse device <NUM>, the first drying device <NUM>, the second drying device <NUM>, and the sheet collection device <NUM>. For example, the controller <NUM> controls, in addition to the rotation speeds of the supply roller <NUM>, the collection roller <NUM>, and the conveyance rollers <NUM>, the temperatures of the heating sources that heat the heating drums <NUM> and <NUM>.

The image forming device is described below with reference to <FIG> is a schematic bottom view of the image forming device. In <FIG>, the sheet S is indicated by an imaginary line. The image forming device includes the first image forming device <NUM> and the second image forming device <NUM>. The second image forming device <NUM> basically has the same configuration as the first image forming device <NUM>. The first image forming device <NUM> is described below, and the description of the second image forming device <NUM> is omitted.

In the first image forming device <NUM>, the four head units <NUM>, 12C, <NUM>, and 12Y that discharge black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively, are disposed in that order from the upstream side in the direction indicated by arrow A (hereinafter a "conveyance direction A") in which the sheet S is conveyed. The order of arrangement of the head units <NUM>, 12C, <NUM>, and 12Y of the respective colors is not limited to the above example and may be another order. The colors of ink to be used are not limited to yellow, magenta, cyan, and black, and may include other colors. The number of head units <NUM> is not limited to four. The conveyance direction A is an example of a "first direction.

Each of the head units <NUM>, 12C, <NUM>, and 12Y includes multiple liquid discharge heads <NUM>. Hereinafter, the liquid discharge head is abbreviated to a "discharge head. " Each of the head units <NUM>, 12C, <NUM>, and 12Y including the discharge head <NUM> is an example of a liquid discharger. In each of the head units <NUM>, 12C, <NUM>, and 12Y, the number of discharge heads <NUM> may be, for example, four. The number of discharge heads <NUM> is not limited to four. Each of the head units <NUM>, 12C, <NUM>, and 12Y is a line head that is longer than a width of the sheet S. The line head extends in a width direction B intersecting the conveyance direction A. The line head is also called a full-width head.

The discharge head <NUM> has multiple nozzles <NUM>. Ink is discharged from the multiple nozzles <NUM> onto the sheet S. The multiple discharge heads <NUM> are arranged in a staggered manner over the entire width direction B of an image forming area on the sheet S. When the sheet S is conveyed to a position facing each of the head units <NUM>, 12C, <NUM>, and 12Y, the corresponding discharge head <NUM> discharges the ink. Thus, an image is formed on the sheet S.

The discharge head <NUM> includes an ink channel through which ink flows, a drive element for discharging the ink, a pressure chamber for applying pressure to the ink, and a nozzle plate having the nozzles <NUM> from which the ink is discharged. The bottom face of the nozzle plate includes a nozzle face in which the multiple nozzles <NUM> are arranged. The drive element is, for example, a piezoelectric element. As the drive element is driven, the pressure of the ink in the pressure chamber is increased and the ink is discharged from the nozzles <NUM>. The ink droplets discharged from the nozzles <NUM> land on the sheet S as the recording medium.

The "width direction B" of the sheet S may be a direction parallel to a conveyance face on which the sheet S is conveyed and orthogonal to the conveyance direction A. The width direction of the sheet S is indicated by arrow B in <FIG>. The "conveyance face" is a surface through which the sheet S being conveyed passes. For example, the conveyance face is a virtual surface connecting contact portions between the multiple conveyance rollers <NUM> and the sheet S. The "conveyance face" may include a sheet placement surface of a conveyance belt on which the sheet S is placed and conveyed. The width direction B of the sheet S may also be referred to as a "sheet width direction. " The width direction B is an example of a "second direction.

The conveyor unit <NUM> is described below with reference to <FIG> is a schematic side view of the first image forming device <NUM> and the conveyor unit <NUM>. As illustrated in <FIG>, the conveyor unit <NUM> includes the multiple conveyance rollers <NUM>. The multiple conveyance rollers <NUM> include conveyance rollers 17A and 17B. The conveyance roller 17A is disposed on the extreme upstream side in the conveyance direction A among the multiple conveyance rollers <NUM>. The conveyance roller 17B is disposed on the extreme downstream side in the conveyance direction A among the multiple conveyance rollers <NUM>. The conveyance roller 17A includes a pair of drive rollers. The conveyance roller 17B includes a pair of drive rollers. The multiple conveyance rollers <NUM> include a conveyance roller 17C disposed downstream from the conveyance roller 17A.

The multiple conveyance rollers <NUM> include multiple driven rollers 17d to <NUM>. The multiple of driven rollers 17d to <NUM> are disposed between the conveyance roller 17C and the conveyance roller 17B in the conveyance direction A. The driven rollers 17d to <NUM> may be drive rollers.

Multiple liquid discharge positions <NUM>, 10C, <NUM>, and 10Y are illustrated in <FIG>. The head unit <NUM> at the liquid discharge position <NUM> discharges ink to a predetermined position of the sheet S. The head unit 12C at the liquid discharge position 10C discharges ink to a predetermined position of the sheet S. The head unit <NUM> at the liquid discharge position <NUM> discharges ink to a predetermined position of the sheet S. The head unit 12Y at the liquid discharge position 10Y discharges ink to a predetermined position of the sheet S. The liquid discharge positions <NUM>, 10C, <NUM>, and 10Y are examples of a first position. The liquid discharge positions <NUM>, 10C, <NUM>, and 10Y may be collectively referred to as liquid discharge positions <NUM>, each of which may be referred to as a liquid discharge position <NUM> unless distinguished.

The driven rollers 17d and 17e are disposed upstream from and downstream from the liquid discharge position <NUM>, respectively. The driven rollers 17f and <NUM> are disposed upstream from and downstream from the liquid discharge position 10C, respectively. The driven rollers <NUM> and 17i are disposed upstream from and downstream from the liquid discharge position <NUM>, respectively. The driven rollers 17j and <NUM> are disposed upstream from and downstream from the liquid discharge position 10Y, respectively.

As described above, the driven rollers 17d to <NUM> are respectively disposed upstream from and downstream from the corresponding liquid discharge positions <NUM>, 10C, <NUM>, and 10Y, thereby preventing the sheet S from fluttering at the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y. Accordingly, the conveyor unit <NUM> can stably convey the sheet S.

A positional deviation of the sheet S in the width direction B is described below with reference to <FIG> is a plan view of the sheet S meandering in the width direction B. For example, when the conveyance roller <NUM> is eccentric or thermally expanded, the conveyed sheet S may be displaced (deviated) in the width direction B as illustrated in <FIG> (i.e., the positional deviation of the sheet S occurs). As the sheet S is displaced in the width direction B, the sheet S may meander while being conveyed. If the sheet S meanders, the position of the ink landed on the sheet S also deviates from a desired position, causing deterioration of image quality. The image forming apparatus <NUM> can move the head units 12C, <NUM>, and 12Y in the width direction B. In <FIG>, the head units 12C, <NUM>, and 12Y that have been moved in the width direction B are indicated by imaginary lines (two dot chain lines). When the sheet S meanders, the image forming apparatus <NUM> moves the head units 12C, <NUM>, and 12Y in the width direction B to cause the head units 12C, <NUM>, and 12Y to follow the positional deviation of the sheet S in the width direction B.

As illustrated in <FIG>, the image forming apparatus <NUM> includes multiple position sensors <NUM>. The position sensor <NUM> is an example of a position detector. The position sensor <NUM> detects a position of the sheet S in the width direction B. The conveyor unit <NUM> may include the multiple position sensors <NUM>. The position sensor <NUM> can detect, for example, an amount of the positional deviation and a direction of the positional deviation in the width direction B of the sheet S. Thus, the image forming apparatus <NUM> can detect the positional deviation of the sheet S in the width direction B.

The position sensors <NUM> and the head units <NUM>, 12C, <NUM>, and 12Y are disposed on opposite sides of the conveyance path along which the sheet S is conveyed. The position sensor <NUM> may be disposed below the sheet S. The position sensors <NUM> are disposed adjacent to the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y. Specifically, each position sensor <NUM> is disposed between, out of the driven rollers 17d to <NUM>, two driven rollers respectively disposed upstream and downstream from the corresponding one of the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y in the conveyance direction A. The "liquid discharge position" in this specification refers to a liquid discharge position in a state where the sheet S does not meander, that is, a state where the head unit <NUM> does not move in the width direction B and is disposed at a reference position (initial position) set in advance.

The position sensor <NUM> is an optical sensor that detects surface information of the object being conveyed. Examples of the position sensor <NUM> include a charge-coupled device (CCD) camera and a complementary metal oxide semiconductor (CMOS) camera using air pressure, photoelectricity, ultrasonic, or light such as visible light, laser, or infrared light.

A control device <NUM> is described below with reference to <FIG> and <FIG> is a block diagram of the control device <NUM> of the image forming apparatus <NUM>. The control device <NUM> controls operations of the head units <NUM>, 12C, <NUM>, and 12Y and the position sensors <NUM>. As illustrated in <FIG>, the multiple position sensors <NUM> include a first position sensor 30A, a second position sensor 30B, a third position sensor 30C, and a fourth position sensor 30D. The position sensor <NUM> detects the position of the sheet S in the width direction B.

The first position sensor 30A detects the position of the sheet S at a position corresponding to the head unit <NUM> for black. The second position sensor 30B detects the position of the sheet S at a position corresponding to the head unit 12C for cyan. The third position sensor 30C detects the position of the sheet S at a position corresponding to the head unit <NUM> for magenta. The fourth position sensor 30D detects the position of the sheet S at a position corresponding to the head unit 12Y for yellow.

The control of the position sensor <NUM> and the head unit <NUM> is described below with reference to a combination of the first position sensor 30A and the second position sensor 30B as an example. As illustrated in <FIG>, each of the first position sensor 30A and the second position sensor 30B includes an imaging unit <NUM>, an image capture controller <NUM>, and an image storage unit <NUM>. The imaging unit <NUM> includes an imaging device that captures an image of the sheet S being conveyed.

The image capture controller <NUM> includes a shutter control unit <NUM> and an image acquisition unit <NUM>. The shutter control unit <NUM> controls the timing at which the imaging unit <NUM> captures an image. The image acquisition unit <NUM> acquires data of the image captured by the imaging unit <NUM>. The image storage unit <NUM> stores the data of the image acquired by the image capture controller <NUM>.

The sheet S has scattering properties on the surface or inside thereof. Each of the position sensors 30A and 30B includes a laser light source. The laser light source irradiates the sheet S with laser light. When the sheet S is irradiated with the laser light, the laser light is diffusely reflected off the sheet S. The diffuse reflection of the laser light creates a pattern of the sheet S. The pattern is a speckle pattern having spots called "speckles. " The speckle pattern includes surface information. When an image of the sheet S is captured, image data indicating the speckle pattern is acquired.

The position of the pattern is determined from the image data, and the position of a specific portion of the sheet S is detected by the position sensors 30A and 30B. That is, when the sheet S is conveyed, the pattern of the sheet S is also moved. Therefore, by detecting the same pattern at different times by the position sensors 30A and 30B, the movement amount or the movement speed of the sheet S can be obtained.

The controller <NUM> includes a calculation unit <NUM>. The first and second position sensors 30A and 30B transmit the captured images to the calculation unit <NUM>. The calculation unit <NUM> calculates how much the specific portion on the sheet S has moved in the sheet width direction based on the image data transmitted from the first position sensor 30A and the second position sensor 30B.

The controller <NUM> calculates the movement amount of the head unit 12C for cyan in the sheet width direction based on the movement amount (the amount of the positional deviation) of the sheet S calculated by the calculation unit <NUM>. The controller <NUM> causes the head unit 12C to move in the sheet width direction. Thus, the controller <NUM> can control a discharge position of the head unit 12C in the sheet width direction.

In the other combinations of the position sensors <NUM>, the controller <NUM> detects the positional deviation of the sheet S in the same manner and causes the head unit <NUM> for magenta and the head unit 12Y for yellow to move in the sheet width direction based on the detected positional deviation. Thus, the controller <NUM> can control discharge positions of the head units <NUM> and 12Y in the sheet width direction.

The position sensor <NUM> can detect the positional deviation of the sheet S in the sheet conveyance direction. For example, the calculation unit <NUM> calculates how much the specific portion on the sheet S has moved in the conveyance direction A based on the image data transmitted from the first position sensor 30A and the second position sensor 30B. Thus, the calculation unit <NUM> can calculate the positional deviation of the sheet S in the conveyance direction A.

In other combinations of the position sensors <NUM>, the controller <NUM> detects the positional deviation of the sheet S in the conveyance direction A in the same manner. The sheet S may extend in the conveyance direction A when ink permeates through the sheet S. The controller <NUM> controls the discharge timing of each of the head units <NUM>, 12C, <NUM>, and 12Y based on the calculated positional deviation in the conveyance direction A, thereby controlling the discharge position in the conveyance direction A so as to reduce the influence of the positional deviation in the conveyance direction A.

As illustrated in <FIG>, each position sensor <NUM> is disposed between, out of the driven rollers 17d to <NUM>, two driven rollers, thereby enhancing the detection accuracy of each position sensor <NUM>. The conveyance speed of the sheet S is relatively stable between the rollers. Accordingly, in the image forming apparatus <NUM>, the movement amount or the movement speed of the sheet S in at least one direction of the conveyance direction A and the width direction B can be accurately detected.

The position sensors <NUM> are disposed at positions close to the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y at which ink is discharged. The shorter the distance between the position sensor <NUM> and the liquid discharge position <NUM>, the smaller the detection error. Therefore, the positional deviation of the sheet S can be detected with high accuracy.

Further, the position sensor <NUM> is preferably disposed upstream from the liquid discharge position <NUM>. When the position sensor <NUM> is disposed upstream from the liquid discharge position <NUM>, the movement or discharge timing of the head unit <NUM> can be controlled after the position of the sheet S is detected by the position sensor <NUM> and before the sheet S is conveyed to the liquid discharge position <NUM>.

By contrast, when the position sensor <NUM> is disposed directly below the liquid discharge position <NUM>, the landing position of the ink may deviate due to a delay of the control operation. If the control operation is performed quickly, as the position of the position sensor <NUM>, directly below the liquid discharge position <NUM> is preferred to upstream from the liquid discharge position <NUM> for accurately detecting the movement amount of the sheet S directly below the liquid discharge position <NUM>. Alternatively, when the error by the control operation is allowable, the position sensor <NUM> may be disposed downstream from the liquid discharge position <NUM>.

In the present embodiment, intervals D1 to D3 (see <FIG>) between the position sensors <NUM> in the conveyance direction A are set to be an integral multiple of a circumferential length X of the drive roller that conveys the sheet S (for example, the lower drive roller of the pair of drive rollers in the conveyance roller 17B disposed extreme downstream in the conveyance direction A in <FIG>). That is, in <FIG>, the respective distances D1 to D3 from the extreme upstream position sensor 30A to the position sensors 30B to 30D downstream from the position sensor 30A are respectively set to one, two, and three multiples of the circumferential length X of the drive roller (D1 = X, D2 = 2X, D3 = 3X).

Setting the intervals D1 to D3 between the position sensors <NUM> to the integral multiple of the circumferential length X of the drive roller is advantageous as follows. Even if the drive roller is eccentric, this setting can cancel out the speed unevenness of the sheet S due to the eccentricity at the detection positions of the position sensors <NUM>. Accordingly, each position sensor <NUM> can accurately detect the positional deviation of the sheet S.

Similarly, intervals E1 to E3 between the head units <NUM>, 12C, <NUM>, and 12Y in the conveyance direction A are set to one, two, and three multiples of the circumferential length X of the drive roller (E1 = X, E2 = 2X, and E3 = 3X). This setting can cancel out the speed unevenness of the sheet S due to the eccentricity of the drive roller at each of the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y, thereby accurately discharging ink from the head units <NUM>, 12C, <NUM>, and 12Y to the sheet S.

The head unit <NUM> is preferably moved in the width direction B based on the movement amount (amount of the positional deviation) of the sheet S with a good movement accuracy at low cost. For example, in <CIT>, a dedicated actuator or an actuator controller for controlling the actuator is used to have the good movement accuracy, but causes an increase in cost.

<FIG> is a plan view of the liquid discharge head, a position changer, and a cleaning position by a cleaning device. In a typical inkjet recording apparatus, the nozzle <NUM> may be clogged or the nozzle face may be stained while ink is consecutively discharged for recording. For this reason, the discharge head <NUM> is periodically cleaned. The image forming apparatus <NUM> includes a cleaning device <NUM> that cleans the discharge head <NUM>. The cleaning device <NUM> may closely contact the nozzle face to clean the nozzle face of the discharge head <NUM>.

The cleaning device <NUM> may be a maintenance device that maintains a discharge state of the discharge head <NUM>. The image forming apparatus <NUM> performs a cleaning operation to prevent non-discharge, oblique discharge, change in discharge speed, and change in discharge amount due to clogging of the discharge head <NUM> or ink thickening, and to maintain or recover the discharge state.

The cleaning device <NUM> causes the discharge head <NUM> to discharge liquid (e.g., ink) from the nozzles <NUM> to maintain the discharge state of the discharge head <NUM>. In this case, the cleaning device <NUM> may perform a cleaning operation such as purging, dummy discharge, flushing, and wiping. The image forming apparatus <NUM> discharge ink that does not contribute to image formation from the nozzles <NUM> of the discharge head <NUM> to perform the cleaning operation. The cleaning device <NUM> includes, for example, a discharge receiver that receives ink discharged from the discharge head <NUM>. The cleaning device <NUM> is provided for each of the multiple head units <NUM>, 12C, <NUM>, and 12Y.

A cleaning position <NUM> is described below with reference to <FIG>. The cleaning position <NUM> is an example of a second position. The cleaning position may be a position of the head unit <NUM> during the cleaning operation. The cleaning position <NUM> may be, for example, a position above the discharge receiver serving as the cleaning device <NUM>. For example, when the cleaning operation is a wiping operation, the cleaning position <NUM> may be a position of the head unit <NUM> during the wiping operation.

The cleaning position <NUM> is a position of the head unit <NUM> while the cleaning device <NUM> cleans the head unit <NUM>. The cleaning position 43C is a position of the head unit 12C while the cleaning device <NUM> cleans the head unit 12C. The cleaning position <NUM> is a position of the head unit <NUM> while the cleaning device <NUM> cleans the head unit <NUM>. The cleaning position 43Y is a position of the head unit 12Y while the cleaning device <NUM> cleans the head unit 12Y. The cleaning position <NUM> is a position away from the liquid discharge position <NUM> in the width direction B of the sheet S. Specifically, the cleaning positions <NUM>, 43C, <NUM>, and 43Y are separated from the liquid discharge position <NUM>, 10C, <NUM>, and 10Y in the width direction B, respectively. The liquid discharge position <NUM> includes the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y.

The cleaning positions <NUM>, 43C, <NUM>, and 43Y do not overlap the sheet S. In the conveyance direction A of the sheet S, the cleaning positions <NUM>, 43C, <NUM>, and 43Y are arranged at predetermined intervals in correspondence with the head units <NUM>, 12C, <NUM>, and 12Y.

The image forming apparatus <NUM> includes a position changer <NUM> that moves the head unit <NUM> between the cleaning position <NUM> and the liquid discharge position <NUM> in the width direction B. The position changer <NUM> includes position changers <NUM>, 50C, <NUM>, and 50Y. The position changer <NUM> moves the head unit <NUM> in the width direction B. The position changer 50C moves the head unit 12C in the width direction B. The position changer <NUM> moves the head unit <NUM> in the width direction B. The position changer 50Y moves the head unit 12Y in the width direction B.

The position changers <NUM>, 50C, <NUM>, and 50Y may be collectively referred to as position changers <NUM>, each of which may be referred to as the position changer <NUM> unless distinguished.

The position changer <NUM> includes a ball screw <NUM>, a linear guide <NUM>, and a motor <NUM>. The ball screw <NUM> extends in the width direction B and hold the head unit <NUM>. The ball screw <NUM> is disposed at a position shifted downstream from the head unit <NUM> in the conveyance direction A in <FIG>. The ball screw <NUM> may be disposed at a position overlapping the head unit <NUM> in plan view.

The head unit <NUM> is supported by the ball screw <NUM> and the linear guide <NUM>. The motor <NUM> is disposed at one end of the ball screw <NUM>. The motor <NUM> may be disposed at a position close to the cleaning position <NUM> in plan view. The motor <NUM> drives the ball screw <NUM> to move the head unit <NUM> between the cleaning position <NUM> and the liquid discharge position <NUM> in the width direction B.

The linear guide <NUM> extends in the width direction B. The linear guide <NUM> extends from the liquid discharge position <NUM> to the cleaning position <NUM>. The head unit <NUM> is movable along the linear guide <NUM> in the width direction B. The linear guide <NUM> is disposed at a position shifted upstream from the head unit <NUM> in the conveyance direction A. The linear guide <NUM> and the ball screw <NUM> are disposed on opposite sides of the head unit <NUM>. The linear guide <NUM> may be disposed at a position overlapping the head unit <NUM> in plan view. The linear guide <NUM> is an example of a guide. The linear guide <NUM> guides the movement of the head unit <NUM> in the width direction B.

The controller <NUM> controls the motor <NUM> to drive the ball screw <NUM>. The head unit <NUM> is guided by the ball screw <NUM> and the linear guide <NUM> and moves in the width direction B between the liquid discharge position <NUM> and the cleaning position <NUM>. The motor <NUM> is provided for each of multiple ball screws <NUM>. The head units <NUM>, 12C, <NUM>, and 12Y independently move between the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y and the cleaning positions <NUM>, 43C <NUM>, and 43Y, respectively.

The motor <NUM> may be a stepping motor that rotates by a specified number of pulses. The motor <NUM> may be a servo motor including an encoder to detect a rotational position of a rotation shaft of the motor <NUM> to control the rotational position of the rotation shaft. Thus, the image forming apparatus <NUM> can determine the position of the head unit <NUM> in the width direction B with high accuracy. For example, when the sheet S is a copy sheet of a B2 size, the movement amount of the head unit <NUM> between the liquid discharge position <NUM> and the cleaning position <NUM> is, for example, about the <NUM>.

On the other hand, the positional accuracy in the movement of the head unit <NUM> for adjusting the discharge position of ink is, for example, equal to or less than the <NUM>. The position changer <NUM> can perform both the movement of the head unit <NUM> between the liquid discharge position <NUM> and the cleaning position <NUM> and the movement of the head unit <NUM> for adjusting the discharge position of ink. Accordingly, the image forming apparatus <NUM> can adjust the discharge position of ink without a dedicated actuator, which corresponds to the motor <NUM> in the present embodiment, for adjusting the discharge position of ink and an actuator controller for controlling the dedicated actuator. As a result, in the image forming apparatus <NUM>, the increase in cost can be prevented. Further, in the image forming apparatus <NUM>, the head unit <NUM> is moved to adjust the discharge position of ink, thereby preventing the deterioration of the image quality.

A hardware configuration of the image forming apparatus <NUM> is described below with reference to <FIG> is a block diagram illustrating the hardware configuration of the image forming apparatus <NUM> according to the present embodiment. The hardware configuration illustrated in <FIG> may include additional components if desired. The hardware configuration may not include the components illustrated in <FIG> if desired.

The image forming apparatus <NUM> includes the control device <NUM>. The control device <NUM> includes a central processing unit (CPU) <NUM>, a read only memory (ROM) <NUM>, a random access memory (RAM) <NUM>, a non-volatile random access memory (NVRAM) <NUM>, and a hard disk drive (HDD) <NUM>. The CPU <NUM> controls the entire image forming apparatus <NUM>. The ROM <NUM> stores various programs for causing the CPU <NUM> to control the liquid discharge and various data for discharging ink (liquid).

The RAM <NUM> temporarily stores various types of data and the like. The NVRAM <NUM> is a non-volatile memory and can retain data even while a power supply of the image forming apparatus <NUM> is shut off. The control device <NUM> includes a main controller 500A, and the main controller 500A includes the CPU <NUM>, the ROM <NUM>, and the RAM <NUM>. The control device <NUM> includes the controller <NUM> described above.

The control device <NUM> includes an application specific integrated circuit (ASIC) <NUM>. The ASIC <NUM> processes input and output signals for controlling the entire image forming apparatus <NUM>. The ASIC <NUM> performs various kinds of signal processing on the image data. The ASIC <NUM> also performs image processing on the image data input to the control device <NUM>.

The control device <NUM> includes an external interface (I/F) <NUM> for transmitting and receiving data to and from a host <NUM> which is an example of an external device. The host <NUM> includes an information processor such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera. The control device <NUM> receives data transmitted from the host <NUM>. The host <NUM> may include a printer driver <NUM>. The printer driver <NUM> generates dot pattern data for outputting an image from the image forming apparatus <NUM>.

The control device <NUM> further includes an input/output (I/O) unit <NUM> for receiving detection signals output from sensors <NUM>. The sensors <NUM> include the position sensor <NUM>. The sensors <NUM> may include various types of temperature sensors.

The control device <NUM> further includes a head controller <NUM> that controls driving of the discharge head <NUM>. The head controller <NUM> controls the drive element of the discharge head <NUM>. The head controller <NUM> controls the drive element of the discharge head <NUM> to causes the discharge head <NUM> to discharge ink (liquid). The head controller <NUM> executes various types of controls related to the discharge head <NUM>.

The control device <NUM> includes a motor driver <NUM>. The motor driver <NUM> controls driving of a drive motor <NUM> in accordance with a command from the CPU <NUM>. The drive motor <NUM> rotates the conveyance rollers <NUM> of the conveyor unit <NUM>.

The control device <NUM> includes a motor driver <NUM>. The motor driver <NUM> controls driving of the motor <NUM> in accordance with a command from the CPU <NUM>. The motor <NUM> is a motor of the position changer <NUM> to change the positions of the head units <NUM>, 12C, <NUM>, 12Y, <NUM>, 14C, <NUM>, and 14Y.

The image forming apparatus <NUM> may include a control panel <NUM>. The control panel <NUM> is electrically connected to the control device <NUM>. The control panel <NUM> includes a display unit that displays various types of information. A user (operator) can perform an input operation with the control panel <NUM>.

The control device <NUM> receives information based on the input operation by the user from the control panel <NUM>. The control device <NUM> outputs various signals to the control panel <NUM> to display information on the control panel <NUM>. The user may perform the input operation while referring to the information displayed on the control panel <NUM>. The control panel <NUM> is an example of an operation input unit.

The program may be recorded in a computer-readable storage medium such as a compact disc read only memory (CD-ROM) or a flexible disk (FD) as file data in an installable or an executable format, and may be loaded into the image forming apparatus <NUM> via such a storage medium.

Alternatively, the program may be recorded in a computer-readable storage medium such as a compact disc-recordable (CD-R), a digital versatile disc (DVD), a Blu-ray (registered trademark) disc, or a semiconductor memory, and may be loaded into the image forming apparatus <NUM> via such a storage medium. The program to be installed may be downloaded into the image forming apparatus <NUM> via a network such as the Internet. The program may be incorporated in the ROM <NUM> or the like in the image forming apparatus <NUM> in advance.

The control device <NUM> may implement the functions executed by the computer connected to the control device <NUM>. Similarly, the computer connected to the control device <NUM> may implement the functions executed by the control device <NUM>.

In the image forming apparatus <NUM> according to the present embodiment, the head unit <NUM> is moved in the width direction B between the liquid discharge position <NUM> and the cleaning position <NUM>. The controller <NUM> causes the position changer <NUM> to move the head unit <NUM> between the liquid discharge position <NUM> and the cleaning position <NUM>. Accordingly, the head unit <NUM> is moved from the liquid discharge position <NUM> to the cleaning position <NUM>, and the discharge head <NUM> of the head unit <NUM> is cleaned at the cleaning position <NUM>. After the discharge head <NUM> is cleaned, the head unit <NUM> is moved from the cleaning position <NUM> to the liquid discharge position <NUM> to discharge ink onto the sheet S from the head unit <NUM> at the liquid discharge position <NUM>.

In the image forming apparatus <NUM>, the position (i.e., a head position) of the head unit <NUM> is changed in response to the position of the sheet S in the width direction B detected by the position sensor <NUM>. The controller <NUM> causes the position changer <NUM> to change the position of the head unit <NUM> in response to the position of the sheet S in the width direction B detected by the position sensor <NUM>. In other words, in the image forming apparatus <NUM>, the head unit <NUM> is moved by the position changer <NUM> and the controller <NUM> to change the position of the head unit <NUM>. In the image forming apparatus <NUM>, the position of the head unit <NUM> is changed so as to follow the positional deviation of the sheet S without a dedicated position changer for moving the head unit <NUM>.

As a result, a structure of the image forming apparatus <NUM> according to the present embodiment can be simplified as compared with an apparatus including both a position changer for moving the head unit <NUM> to the cleaning position <NUM> and a dedicated position changer for moving the head unit <NUM> so as to follow the positional deviation of the sheet S. As a result, space for the position changer can be reduced. Similarly, in the image forming apparatus <NUM> according to the present embodiment, the system of the controller <NUM> can be simplified as compared with a configuration including multiple controllers that control the operation of the position changers. As a result, the image forming apparatus <NUM> can be manufactured without an increase in manufacturing cost.

In the image forming apparatus <NUM>, the position changer <NUM> includes the linear guide <NUM> along which the head unit <NUM> moves in the width direction B. The image forming apparatus <NUM> having such a configuration can change the position of the head unit <NUM> at a high speed between the liquid discharge position <NUM> and the cleaning position <NUM>. Further, the image forming apparatus <NUM> can change the position of the head unit <NUM> with high accuracy in accordance with the detection result by the position sensor <NUM>.

In the image forming apparatus <NUM>, the position changer <NUM> includes the ball screw <NUM> extending in the width direction B and the motor <NUM> disposed at the end of the ball screw <NUM> to drive the ball screw <NUM>. The image forming apparatus <NUM> having such a configuration can accurately move the head unit <NUM> coupled to the ball screw <NUM> by driving the ball screw <NUM> using the motor <NUM>.

The present disclosure is not limited to the above-described embodiment, and numerous additional modifications and variations are possible without departing from or changing the technical idea of the present disclosure.

In the image forming apparatus <NUM> described above, a configuration including the head units <NUM>, 12C, <NUM>, and 12Y that discharge black, cyan, magenta, and yellow ink has been described, but ink discharged from the head unit <NUM> is not limited thereto. For example, the image forming apparatus <NUM> may include the head unit <NUM> that discharges other special ink. Examples of the special ink include white, silver, gold, and the like.

In the image forming apparatus <NUM> described above, one position changer <NUM> is provided for one head unit <NUM>. However, for example, multiple head units <NUM> may be moved by one position changer <NUM>. For example, in a configuration including five head units <NUM> that discharge black, cyan, magenta, yellow, and silver ink, the position changer <NUM> that moves the head unit <NUM> for black, the position changer <NUM> that moves the head units <NUM> for cyan and magenta, and the position changer <NUM> that moves the head units <NUM> for yellow and silver may be provided. The silver ink is the special ink.

In the above-described embodiment, the position changer <NUM> moves the head unit <NUM> to one side in the width direction B. However, the position changer <NUM> may move the head unit <NUM> to both sides in the width direction B.

In the above-described embodiment, the position changer <NUM> includes the ball screw <NUM>, the linear guide <NUM>, and the motor <NUM>, but the position changer <NUM> is not limited thereto. The position changer <NUM> may include, for example, a power transmission belt, an air cylinder, a gear, or the like.

Each of functions of the above-described embodiments executed by the controller <NUM> can be implemented by one or more processing circuits. The "processing circuit" in the present specification includes a processor programmed to execute each function by software like a processor implemented by an electronic circuit, and a device such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), or a conventional circuit module designed to execute each function described above.

A liquid discharge method according to the present embodiment includes: conveying an object in a first direction; discharging a liquid onto the object, at a first position, from a line head liquid discharger extending in a second direction intersecting the first direction; maintaining a discharge state of the line head liquid discharger at a second position away from the first position in the second direction; moving the line head liquid discharger between the first position and the second position; detecting a position of the object in the second direction; and changing a head position of the line head liquid discharger in response to the position of the object. The image forming apparatus <NUM> according to the present embodiment can execute the liquid discharge method.

Claim 1:
A liquid discharge apparatus (<NUM>) comprising:
a conveyor (<NUM>) configured to convey an object (S) in a first direction (A);
a liquid discharger (<NUM>) configured to discharge a liquid onto the object (S) at a first position (<NUM>), the liquid discharger (<NUM>) including a full-width head extending in a second direction (B) intersecting the first direction (A);
a maintenance device (<NUM>) configured to maintain a discharge state of the liquid discharger (<NUM>) at a second position (<NUM>) away from the first position (<NUM>) in the second direction (B);
a position changer (<NUM>) configured to move the liquid discharger (<NUM>) between the first position (<NUM>) and the second position (<NUM>);
a position detector (<NUM>) configured to detect a position of the object (S) in the second direction (B); and
circuitry (<NUM>) configured to cause the position changer (<NUM>) to change a head position of the liquid discharger (<NUM>) in the second direction in response to the position of the object (S) detected by the position detector (<NUM>);
wherein the position changer (<NUM>) includes a guide (<NUM>) extending in the second direction (B) to guide the liquid discharger (<NUM>) in the second direction (B),
characterized in that
the position changer (<NUM>) further includes:
a ball screw (<NUM>) extending in the second direction (B) and holding the liquid discharger (<NUM>); and
a motor (<NUM>) configured to drive the ball screw (<NUM>) to move the liquid discharger (<NUM>) between the first position (<NUM>) and the second position (<NUM>) in the second direction (B);
wherein the guide (<NUM>) and the ball screw (<NUM>) are disposed on opposite sides of the liquid discharger (<NUM>) in plan view, and
the ball screw (<NUM>) and the guide (<NUM>) guide the liquid discharger (<NUM>) in the second direction (B) between the first position (<NUM>) and the second position (<NUM>).