JP2011126204A - Recording position correcting device, and recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that an image cannot be formed at an intended part of a recording medium because a relative position between the recording medium and a head unit becomes not constant when the recording medium is transferred by being deviated from an original transfer position. <P>SOLUTION: The recording position correcting device includes head units 10 and 20 which jet liquids to the recording medium P transferred on a transfer surface 50, detecting parts S1-S4 which detect positions of the transferred recording medium P, and a transfer information calculating part 91 which calculates transfer information that shows the transfer state of the recording medium P on the basis of the positions of the recording medium P detected by the detecting parts S1-S4. A control part 90 is provided which moves the head units 10 and 20 in a direction parallel to the transfer surface 50 on the basis of the transfer information. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a recording position correction apparatus and a recording apparatus.

Conventionally, in a recording apparatus such as an ink jet printer, various techniques have been proposed for ejecting a liquid from a head unit to an accurate position with respect to a transported recording medium.
For example, in the ink jet printer described in Patent Document 1 below, in order to land droplets at an accurate position even in a print medium region where the transport speed is not constant, the transport speed of the print medium is detected and the discharge timing is set. I am trying to correct it.
In addition, in the inkjet printer described in Patent Document 2 below, the alignment adjustment of the line head is automatically performed with high accuracy in order to prevent printing defects such as oblique lines due to the alignment failure of the line head. Yes.

JP-A-8-230194 JP 2008-12712 A

However, the ink jet printer described in Patent Document 1 cannot cope with a change in the behavior in the width direction of the print medium during printing.
Further, it cannot cope with a case where the print medium is transported in an oblique transport direction, or when the print medium is transported out of the original transport position. As described above, when the relative position between the print medium and the head unit is not constant, an image cannot be formed on an intended portion of the print medium.
In addition, in the case of the above-mentioned Patent Document 2, it is a proposal related to the alignment method of the line head of the ink jet printer, and as in the case of the above-described Patent Document 1, the relative position between the print medium and the head unit during printing is changed. I cannot respond to it.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Application Example 1]
A recording position correction apparatus according to this application example moves a head unit that ejects liquid with respect to a recording medium conveyed on a conveying surface, and corrects the recording position of the ejected liquid on the recording medium. A detecting unit that detects a position of the recording medium with respect to the head unit; a moving unit that moves the head unit in a direction parallel to the conveying surface; and the head unit that is perpendicular to the conveying surface. The head by controlling the moving means and the rotating means based on the position of the recording medium relative to the head unit detected by the detecting means; And a control means for moving the unit.

According to this recording position correction apparatus, the detecting means detects the position of the recording medium with respect to the head unit. Based on the detection result, the control unit moves the head unit in a direction parallel to the transport surface, and rotates the head unit around an axis perpendicular to the transport surface.
Since the head unit is moved based on the position of the recording medium with respect to the head unit, when the relative position between the recording medium being conveyed and the head unit is not constant, the head unit is moved according to this position. These relative positions can be made constant. As a result, it is possible to form an image on the intended portion of the recording medium from the head unit.

[Application Example 2]
In the recording position correction apparatus according to the application example, the detection unit is disposed upstream of the head unit in the recording medium conveyance direction, and detects the position of the recording medium conveyed on the conveyance surface. 1 detection unit, a second detection unit that is disposed in the head unit and detects the position of the recording medium conveyed on the conveyance surface, and the position of the recording medium detected by the first detection unit And calculating means for calculating the position of the recording medium relative to the head unit based on the position of the recording medium detected by the second detection unit.

  According to this recording position correction apparatus, the calculating means calculates the position relative to the head unit based on the position of the recording medium detected by the first detection unit and the position of the recording medium detected by the second detection unit. The position of the recording medium can be calculated. Therefore, the control unit can move the head unit based on the calculated position of the recording medium with respect to the head unit, and can rotate the head unit around an axis in a direction perpendicular to the transport surface. As a result, when the skew occurs in the recording medium, the displacement of the relative position between the recording medium and the head unit due to the skew can be canceled by the movement and rotation of the head unit.

[Application Example 3]
In the recording position correction apparatus according to the application example, the detection unit is disposed in an upstream portion of the head unit in the transport direction of the recording medium, and detects the position of the recording medium transported on the transport surface. A first detection unit; a second detection unit that is disposed in a downstream portion of the head unit in a conveyance direction of the recording medium and detects a position of the recording medium conveyed on the conveyance surface; Calculation means for calculating the position of the recording medium relative to the head unit based on the position of the recording medium detected by one detection unit and the position of the recording medium detected by the second detection unit It is desirable to provide According to this recording position correction apparatus, the calculating means calculates the position relative to the head unit based on the position of the recording medium detected by the first detection unit and the position of the recording medium detected by the second detection unit. The position of the recording medium can be calculated. Therefore, the control unit can move the head unit based on the calculated position of the recording medium with respect to the head unit, and can rotate the head unit around an axis in a direction perpendicular to the transport surface. As a result, when the skew occurs in the recording medium, the displacement of the relative position between the recording medium and the head unit due to the skew can be canceled by the movement and rotation of the head unit.

[Application Example 4]
In the recording position correction apparatus according to the application example described above, the recording position correction apparatus includes a detection unit moving unit that moves each of the first detection unit and the second detection unit in a direction crossing a direction in which the recording medium is conveyed. desirable.
According to this recording position correcting apparatus, the detection moving unit can move each of the first detection unit and the second detection unit in a direction crossing the direction in which the recording medium is conveyed. For this reason, the positions of the first detection unit and the second detection unit can be adjusted so that the recording medium is located in an area where the recording medium can be detected by the first detection unit and the second detection unit. Accordingly, even when the size of the recording medium is changed and the position in the direction intersecting the conveyance direction of the recording medium is changed, the position of the recording medium is appropriately detected by the first detection unit and the second detection unit. be able to.

[Application Example 5]
In the recording position correction apparatus according to the application example, the control unit is configured to determine a relative position between the recording medium and the head unit based on the position of the recording medium with respect to the head unit detected by the detection unit. It is desirable to move the head unit by controlling the head unit moving means and the head unit rotating means by PID control so as to be constant.
According to this recording position correcting apparatus, the control means can make the relative position between the recording medium and the head unit constant by PID control.

[Application Example 6]
A recording apparatus according to this application example includes the recording position correction apparatus described above, and performs recording on a recording medium.
According to this recording apparatus, when the relative position between the recording medium being conveyed and the head unit is not constant, the relative position between the recording medium and the head unit is made constant by the recording position correction apparatus, and the recording medium is intended. It becomes possible to form and record an image on the part.

1 is a side sectional view schematically showing an outline of an ink jet printer. FIG. 2 is a plan view schematically showing an outline of an ink jet printer. Explanatory drawing of the arrangement | sequence of each discharge head. Explanatory drawing of the mechanism and operation | movement which concern on the movement and rotation of a head unit. Explanatory drawing of the cam mechanism and operation | movement which concern on the movement and rotation of a head unit. 6 is a flowchart showing the operation of the recording position correction apparatus during printing. The figure which shows the example of the correction | amendment presence or absence with respect to a head unit. The top view which shows typically the outline of the inkjet printer which concerns on a modification. The top view which shows typically the outline of the inkjet printer which concerns on a modification. The top view which shows typically the outline of the inkjet printer which concerns on a modification. The top view which shows typically the outline of the inkjet printer which concerns on a modification. The top view which shows typically the outline of the inkjet printer which concerns on a modification. 1 is a side sectional view schematically showing an outline of a tandem type ink jet printer.

  Hereinafter, as an example of a recording apparatus that includes a recording position correction apparatus and performs recording on a recording medium, an ink jet printer according to the present embodiment that prints (discharges) a liquid such as ink and prints an image or the like on a recording medium such as paper. Will be described. The ink jet printer here includes two head units in which a plurality of ink jet heads (ejection heads) are arranged in a direction intersecting the paper transport direction, and is a line head type ink jet printer capable of printing in a so-called one pass. It is.

  FIG. 1 is a side sectional view schematically showing an outline of an ink jet printer 100 according to the present embodiment. FIG. 2 is a plan view schematically showing the outline of the inkjet printer 100. In the ink jet printer 100 shown in FIGS. 1 and 2, printing is performed on a transport unit 1 that holds and transports a rectangular paper P to be printed, and the paper P that is held and transported by the transport unit 1. A printing unit 2 to be executed is provided. The operations of the transport unit 1 and the printing unit 2 are controlled by a control unit 90 shown in FIG. In the following description, the normal conveyance direction of the paper P in the inkjet printer 100 is the conveyance direction X, and the direction from the left side to the right side of the direction orthogonal to the conveyance direction X is the conveyance width direction Y. Called. In addition, the longitudinal direction of the paper P in the paper P is referred to as a reference direction x, and the direction from the left to the right facing the reference direction x out of the directions orthogonal to the longitudinal direction is referred to as a paper width direction y.

The conveyance unit 1 includes a gate roller 31 constituted by a pair of upper and lower nip rollers shown in FIG. 1, a driven roller 32 disposed on the upstream side in the conveyance direction X, and a drive roller disposed on the downstream side in the conveyance direction X. 34, a tension roller 33 disposed below the driven roller 32 and the drive roller 34, and an endless belt 35 that winds between the three rollers 32, 33, 34 in a loop.
The drive roller 34 is a roller for applying a transport force in the transport direction X to the endless belt 35. As shown in FIG. 2, a conveyance drive motor 36 for transmitting power to the drive roller 34 is directly connected to one end in the conveyance width direction Y. On the other hand, the driven roller 32 is a roller having the same height as that of the driving roller 34 and arranged to face each other in parallel at a certain distance.

  The endless belt 35 is an endless belt-shaped member formed of a material having elasticity such as a synthetic rubber or a resin film. As shown in FIG. 2, the endless belt 35 has a large number of air holes 37 formed therein. The suction and holding action of the paper P by a suction device (not shown) is executed through the vent hole 37 so that the paper P is sucked and held on the transport surface 50 of the endless belt 35 that transports the paper P. Here, as a suction method of the suction device, for example, suction by negative pressure or electrostatic suction can be employed. Further, the suction device sucks the paper P onto the endless belt 35 so that the reference direction x of the paper P is aligned with the transport direction of the paper P.

  On the other hand, the printing unit 2 includes a head unit 10 disposed on the upstream side in the transport direction X, a head unit 20 disposed on the downstream side, and the like. Each head unit 10, 20 includes a plurality of ejection heads 11 that eject ink droplets, as shown in FIG. These ejection heads 11 are divided (separated) in the transport direction X by each of the head units 10 and 20, and four are arranged in the head unit 10 row and three in the head unit 20 row. The ejection heads 11 in each row are also divided (separated) in the transport width direction Y so that the entire ejection heads 11 are staggered in plan view, that is, transported along the transport width direction Y. They are alternately arranged upstream and downstream in the direction X.

The head units 10 and 20 can be reciprocated in the transport width direction Y and rotated around the θ rotation shaft 13 by the Y-axis motor 14 and the θ-axis motor 15 provided therein. Details of the movement and rotation of the head units 10 and 20 will be described later.
FIG. 3 is an explanatory diagram of the arrangement of the ejection heads 11 and is a view of the head units 10 and 20 as viewed from below. As shown in the figure, on the surface (nozzle surface) of each ejection head 11 facing the transport surface 50, a number of nozzles that eject ink droplets are formed. Specifically, on each nozzle surface, four rows of nozzle rows composed of a plurality of nozzles arranged along the transport width direction Y are formed apart from each other in the transport direction X. These four nozzle arrays can eject inks of different colors. In this embodiment, black (K), cyan (C), magenta (M), yellow are sequentially arranged from the upstream side in the transport direction X. (Y) ink is ejected. In addition, each ejection head 11 is superposed in the transport direction X with the nozzle at the transport width direction Y end of the adjacent ejection head 11 that is separated in the transport direction X or the opposite direction. It is arranged. Then, for each color, that is, for each nozzle row, a necessary amount of ink droplets are simultaneously ejected from the nozzles at the necessary locations, thereby forming minute ink dots on the paper P. The ink jet printer 100 repeats this operation while transporting the paper P in the transport direction X. Then, only by sending the paper P in the transport direction X in one pass, an image having a width corresponding to the distance between the nozzles at both ends in the transport width direction Y of the head units 10 and 20 can be printed.

  The method for ejecting ink from the nozzles is not limited to a specific method, and various methods such as an electrostatic method, a piezo method, and a film boiling ink jet method can be employed. The electrostatic method is a method in which a drive pulse is applied to the electrostatic gap to displace the diaphragm in the cavity, and ink droplets are ejected by a pressure change in the cavity caused by the displacement. The piezo method is a method in which a drive pulse is applied to a piezo element to displace a diaphragm in a cavity, and ink droplets are ejected by a pressure change in the cavity caused by the displacement. The film boiling ink jet method is a method in which ink is heated by a micro heater provided in a cavity, and ink droplets are ejected by a pressure change accompanying generation of bubbles.

  Further, each head unit 10, 20 can be reciprocated in the longitudinal direction of the head unit 10, 20 which is parallel to the transport surface 50. The longitudinal direction of the head units 10 and 20 is the direction in which the ejection heads 11 are arranged in each head unit 10 and 20. Further, each of the head units 10 and 20 can be rotated clockwise and counterclockwise about a θ rotation shaft 13 that is an axis perpendicular to the conveyance surface 50 shown in FIG. That is, the head units 10 and 20 can be rotated in a direction parallel to the transport surface 50. Here, the θ rotation axis 13 is an axis that extends along a direction perpendicular to the conveyance surface 50 and does not move relative to the conveyance unit 1.

  FIG. 4 is an explanatory diagram of a mechanism and an operation related to the movement and rotation of the head unit 10. The head unit 10 shown in the figure includes a Y-axis motor 14 that transmits power for reciprocating the head panel 12 in the longitudinal direction, a slide rail (not shown) that extends along the longitudinal direction of the head unit 10, and a head. A θ-axis motor 15 that transmits power for rotating the panel 12 around the θ-rotating shaft 13 is attached. As with the head unit 10, the head unit 20 is also provided with a Y-axis motor 14, a slide rail, and a θ-axis motor 15. The head unit 20 can be reciprocated in the longitudinal direction and rotated clockwise and counterclockwise about the θ rotation shaft 13. In this embodiment, as the Y-axis motor 14 and the θ-axis motor 15 attached to the head units 10 and 20, for example, a linear ultrasonic motor capable of controlling a minute displacement is used.

FIG. 4A shows an example in which the head unit 10 has moved by Ya in the transport width direction Y from the reference position. This is a result of driving the Y-axis motor 14 based on the control of the control unit 90 and moving the head panel 12 by Ya in the longitudinal direction along the slide rail.
FIG. 4B shows an example in which the head unit 10 is rotated clockwise from the reference position by the angle θa around the θ rotation shaft 13. This is a result of driving the θ-axis motor 15 and rotating the head panel 12 about the θ rotation shaft 13 clockwise by an angle θa based on the control of the control unit 90.

  Here, as a combination of FIGS. 4A and 4B, as shown in FIG. 4C, the Y-axis motor 14 is driven to move the head panel 12 in the longitudinal direction, and then the θ-axis. The motor 15 can be driven to rotate the head panel 12 around the θ rotation axis 13. Conversely, after the θ-axis motor 15 is driven to rotate the head panel 12 around the θ-rotation axis 13, the Y-axis motor 14 is driven to move the head panel 12 in the longitudinal direction. Also good. Of course, the movement and rotation of the head panel 12 may be performed simultaneously.

On the other hand, as shown in FIG. 5, by attaching a Y-axis cam 16 and a θ-axis cam 17 to the head unit 10, the head unit 10 is reciprocated in the longitudinal direction, and the θ rotation shaft 13 is also centered. And may be rotated clockwise and counterclockwise.
FIG. 5A shows an example in which the head unit 10 has moved by Ya in the longitudinal direction from the reference position in accordance with the rotation of the Y-axis cam 16. FIG. 5B shows an example in which the head unit 10 is rotated clockwise from the reference position by the angle θa around the θ rotation shaft 13 in accordance with the rotation of the θ axis cam 17. FIG. 5C shows that the head unit 10 moves from the reference position in the longitudinal direction of the head unit 10 according to the rotation of the Y-axis cam 16, and the head unit 10 moves to the reference position according to the rotation of the θ-axis cam 17. In the example shown in FIG. 4, the angle is rotated clockwise around the θ rotation axis 13 by an angle θa.

The positions of the θ rotation shaft 13, the Y axis motor 14, the θ axis motor 15, the Y axis cam 16, and the θ axis cam 17 are not limited to the positions shown in FIGS.
Returning to FIG. 1 and FIG. 2, the edge sensor S <b> 1 is disposed on the upstream side in the transport direction X of the head unit 10. The head unit 10 is provided with an edge sensor S2. Similarly, an edge sensor S3 is disposed upstream of the head unit 20 in the transport direction X. The head unit 20 is provided with an edge sensor S4. These edge sensors S1 to S4 are sensors that detect the position of the end in the width direction of the paper P. For example, the edge sensors S1 to S4 are reflective image sensors having a structure in which a light emitting element and a light receiving element face the transport surface 50 direction. . The end in the width direction of the paper P is an end of the end of the paper P in the paper width direction y of the paper P. Each edge sensor S1-S4 detects the position of the width direction edge part of the paper P on the conveyance surface 50 by irradiating the light from a light emitting element to the conveyance surface 50 direction, and receiving reflected light with a some light receiving element. can do. In the present embodiment, for example, a CCD image sensor or a CMOS image sensor is used as the edge sensors S1 to S4.

A control unit 90 shown in FIG. 2 includes a CPU, a ROM, a RAM, and the like (not shown), and controls the entire units and mechanisms of the inkjet printer 100. The control unit 90 includes a conveyance information calculation unit 91 that calculates conveyance information indicating the conveyance state of the paper P on the conveyance surface 50. This transport information includes the relative position and relative tilt amount of the paper P.
The conveyance information calculation unit 91 determines the relative position and the relative inclination amount of the sheet P based on the positions of the end portions in the width direction detected when the sheet P conveyed on the conveyance surface 50 passes through the edge sensors S1 to S4. Is calculated. Here, the relative position is a relative position of the paper P from the predetermined reference position in the head unit 10 and represents an interval from the reference position to the position of the end portion in the width direction of the paper P. The relative inclination amount represents the amount of inclination of the paper P in the paper width direction y with respect to the longitudinal direction of the head unit 10.

Further, the control unit 90 includes the amount of movement in the longitudinal direction of each head unit 10, 20 and the θ rotation shaft 13 based on the relative position and relative tilt amount of the paper P calculated by the conveyance information calculation unit 91. A movement amount calculation unit 92 for calculating the rotation amount at the center is included.
For example, when a displacement occurs when the transported paper P passes under the head units 10 and 20, the movement amount calculated by the movement amount calculation unit 92 causes the head units 10 and 20 to be displaced. By moving in the opposite direction, the amount of movement cancels out the positional deviation. Further, when the paper P is skewed when the paper P passes under the head units 10 and 20, the rotation amount calculated by the movement amount calculation unit 92 causes the head units 10 and 20 to skew. The amount of rotation cancels the skew by rotating to match the inclination. That is, when the paper P passes under the head units 10 and 20, the rotation amount for making the head units 10 and 20 orthogonal to the width direction ends of the paper P is calculated.

The above-described edge sensors S1 to S4, the Y-axis motor 14, the θ-axis motor 15, the control unit 90 including the conveyance information calculation unit 91 and the movement amount calculation unit 92 constitute a recording position correction device, and the conveyance state of the paper P And a function of correcting printing on the paper P according to the above.
Note that the number and arrangement positions of the edge sensors to be arranged are not limited to the above. For example, the position of the paper P is detected by arranging only one edge sensor or three or more edge sensors on the upstream and downstream sides of each head unit 10 and 20. You may make it do. Alternatively, the edge sensor may be disposed only on either the upstream side or the downstream side of the head units 10 and 20.

Next, the operation of the recording position correction apparatus during printing will be described.
FIG. 6 is a flowchart showing the operation of the recording position correction apparatus during printing. The operation shown in the figure is started when the paper P to be printed is transported onto the transport surface 50. Although the operation in the head unit 10 will be described here, the same applies to the head unit 20.

First, in step S05, the control unit 90 controls the edge sensors S1 to S4 disposed on the upstream side and the downstream side of the head unit 10, and starts detection operations in the edge sensors S1 to S4.
In step S <b> 10, the control unit 90 determines whether or not the edge direction of the paper P is detected by the edge sensors S <b> 1 and S <b> 2 disposed on the upstream side of the head unit 10.
If both the edge sensors S1, S2 detect the width direction edge of the paper P, the process proceeds to the next step S20.

  On the other hand, if none of the edge sensors S1, S2 detects the width direction end of the paper P, the process proceeds to step S11, and the control unit 90 performs a specified time after the paper P is transported onto the transport surface 50. It is determined whether or not elapses. The specified time here is a time exceeding the allowable time until the paper P conveyed on the conveyance surface 50 passes through both the edge sensors S1 and S2. Therefore, when the specified time has elapsed, the control unit 90 determines that the paper P is in a jammed state or is transported with a large deviation that cannot be detected by the edge sensors S1 and S2.

  Here, if the specified time has elapsed, the process proceeds to step S12, and the control unit 90 takes measures such as paper jam. When the handling of the paper jam or the like in step S12 is completed, the process returns to step S10, and the determination of the detection of the edge in the width direction of the paper P is repeated. For example, the control unit 90 displays a message indicating that a jam or the like has occurred on the paper P on an operation screen (not shown) and accepts a user operation.

On the other hand, if the specified time has not elapsed, the process returns to step S10, and the determination of detection of the edge in the width direction of the paper P is repeated.
In step S20, the control unit 90 causes the conveyance information calculation unit 91 to determine the relative position of the paper P based on the detection results of the upstream edge sensor S1 and the edge sensor S2 provided in the head unit 10 in step S10. And the relative inclination amount is calculated. Specifically, the relative position and the relative inclination amount of the paper P are calculated based on the positions of the end portions in the width direction of the paper P detected by the edge sensors S1 and S2.
In step S30, the control unit 90 uses the movement amount calculation unit 92 to move the head unit 10 in the transport direction Y based on the relative position and relative inclination amount of the paper P calculated in step S20, and θ rotation. The amount of rotation about the axis 13 is calculated.

In step S40, the control unit 90 performs movement correction and rotation correction on the head unit 10 based on the movement amount and rotation amount of the head unit 10 calculated in step S30. Specifically, the Y-axis motor 14 is driven, and the head unit 10 is moved in the longitudinal direction according to the calculated movement amount. Further, the θ-axis motor 15 is driven, and the head unit 10 is rotated around the θ-rotation shaft 13 according to the calculated rotation amount. Accordingly, the positional deviation between the paper P and the head unit 10 is canceled, the longitudinal direction of the head unit 10 is parallel to the paper width direction y, and the inclination between the paper width direction y of the paper P and the head unit 10 is canceled. To do.
Here, when the calculated movement amount is 0 and the rotation amount is 0, that is, when neither the positional deviation nor the skew is generated for the paper P, the movement correction and the head unit 10 are corrected. None of the rotation correction is performed and the state is left as it is.

  On the other hand, when the movement amount is other than 0 and the rotation amount is 0, that is, when only the positional deviation occurs and the skew does not occur with respect to the paper P, for example, as shown in FIG. 10 is only corrected for movement in the longitudinal direction. As a result, the paper width direction y of the paper P and the head unit 10 are held in a parallel state, and the paper width direction y of the paper P and the head unit 10 are not inclined, and the paper P and the head unit 10 are held. Offset the misalignment.

  On the other hand, when the amount of movement is 0 and the amount of rotation is other than 0, that is, when only the skew is generated with no positional deviation for the paper P, for example, as shown in FIG. 10, only rotation correction is performed around the θ rotation axis 13. As a result, a state in which there is no positional deviation between the paper P and the head unit 10 is maintained, the longitudinal direction of the head unit 10 is parallel to the paper width direction y, and the inclination between the paper width direction y of the paper P and the head unit 10 is set. cancel.

  On the other hand, when the movement amount is other than 0 and the rotation amount is other than 0, that is, when both the positional deviation and the skew are generated with respect to the paper P, for example, as shown in FIGS. As shown in FIG. 4C, which is a combination, the head unit 10 is subjected to rotation correction around the θ rotation axis 13 together with movement correction in the longitudinal direction. Accordingly, the positional deviation between the paper P and the head unit 10 is canceled, the longitudinal direction of the head unit 10 is parallel to the paper width direction y, and the inclination between the paper width direction y of the paper P and the head unit 10 is canceled. To do.

In step S50, the control unit 90 starts ejecting ink droplets onto the paper P from the head unit 10 that has been subjected to movement correction and rotation correction in step S40. As a result, printing on the paper P is started.
In step S <b> 60, the conveyance information calculation unit 91 calculates the relative position and the relative inclination angle of the paper P based on the detection results of the upstream edge sensor S <b> 1 and the edge sensor S <b> 2 disposed in the head unit 10.

  In step S70, the control unit 90 calculates the movement amount of the head unit 10 in the transport direction Y based on the relative position of the paper P calculated in step S60 by the movement amount calculation unit 92. Specifically, the amount of movement of the head unit 10 in the transport direction Y is calculated by PID control so that the relative position between the paper P and the head unit 10 is constant. PID control is control which consists of a combination of proportional control (Proportional Control), integral control (Integral Control), and differential control (Derivative Control). Proportional control is control that changes the amount of movement of the head unit 10 in the transport direction Y in proportion to the relative position of the paper P. The integral element is control for changing the amount of movement of the head unit 10 in the transport direction Y in proportion to the time integration of the relative position of the paper P. Further, the differential element is control for changing the amount of movement of the head unit 10 in the transport direction Y in proportion to the differential of the relative position of the paper P.

  Further, the control unit 90 calculates a rotation amount around the θ rotation axis 13 of the head unit 10 based on the relative inclination amount of the paper P calculated in step S60 by the movement amount calculation unit 92. Specifically, the rotation amount around the θ rotation axis 13 is calculated by PID control so that the relative inclination amount of the paper P becomes constant zero. The PID control here includes proportional control, integral control, and differential control. Proportional control is control in which the amount of rotation about the θ rotation axis 13 of the head unit 10 is changed in proportion to the relative tilt amount of the paper P. The integral control is a control for changing the rotation amount of the head unit 10 around the θ rotation axis 13 in proportion to the time integration of the relative inclination amount of the paper P. Further, the differential control is control for changing the rotation amount of the head unit 10 around the θ rotation axis 13 in proportion to the differential of the relative inclination amount of the paper P.

In step S80, the control unit 90 performs movement correction and rotation correction on the head unit 10 based on the movement amount and rotation amount of the head unit 10 calculated in step S70. Specifically, the Y-axis motor 14 is driven, and the head unit 10 is moved in the longitudinal direction according to the calculated movement amount. Further, the θ-axis motor 15 is driven, and the head unit 10 is rotated around the θ-rotation shaft 13 according to the calculated rotation amount.
In step S90, the control unit 90 determines whether or not the ejection time for one sheet of paper P has elapsed.

When the ejection time has elapsed, the process proceeds to the next step S100, and the control unit 90 determines whether or not printing of all sheets P to be printed has been completed. When the printing of all the sheets P is finished, the printing process is finished. If the sheet P to be printed remains, the process returns to step S10 to determine whether to detect the end of the next sheet P in the width direction.
In step S90, instead of determining whether or not the ejection time has elapsed, a sensor for detecting the end of the sheet P1 is provided to determine whether or not printing for the sheet P1 has been completed. You may do it.

On the other hand, if it is determined in step S90 that the discharge time has not elapsed, printing for one sheet P1 is being continued and the sheet P is being conveyed, so the process returns to step S60, and detection of the edge sensors S1 and S2 Based on the result, the relative position and the relative tilt amount of the paper P are calculated.
That is, every time a predetermined time elapses, the position of the end in the width direction of the sheet P conveyed along with printing is detected in real time, and the relative position and the relative tilt amount of the sheet P are detected in real time based on the detected position. The movement correction and the rotation correction are performed on the head unit 10 in real time according to the calculated relative position and relative inclination amount. As a result, the positional relationship between the paper P and the head unit 10 can always be kept correctly during printing.

  Next, specific examples of movement correction and rotation correction for the head units 10 and 20 will be described. FIG. 7 is a diagram illustrating an example of whether or not the head unit 10 is corrected. FIGS. 7 (a1), (b1), (c1), (d1), and (e1) show printing examples when no correction is performed, and (a2), (b2), (c2), and (d2) , (E2) shows an example of printing when correction is performed. In each figure, the paper P before printing is shown on the upstream side in the transport direction X across the head unit 10, and the paper P after printing is shown on the downstream side. A white arrow indicates a direction in which the paper P is conveyed. Although an example of correction by the head unit 10 is described here, the same applies to the head unit 20.

  In FIG. 7A1, the paper P is transported in the transport direction X while maintaining the correct posture, but the entire paper P is displaced in the transport width direction Y. For this reason, in the case where no correction is performed (a1), the entire rectangular print image G is printed biased toward the edge of the paper P. On the other hand, in (a2), printing is performed with the head unit 10 moved and corrected in the transport width direction Y. As a result of this correction printing, in (a2), a rectangular print image G is printed at the correct position in the central portion of the paper P.

  In FIG. 7B1, the paper P is transported in the transport direction X in a skewed posture. For this reason, when correction is not performed (b1), the entire rectangular print image G is printed on the paper P with an inclination. On the other hand, in (b2), printing is performed while moving the head unit 10 in the direction opposite to the conveyance width direction Y in a state where the head unit 10 is rotationally corrected and placed at a position orthogonal to the widthwise end of the paper P. ing. As a result of this correction printing, in (b2), the rectangular print image G is printed in the correct posture on the central portion of the paper P.

  In FIG. 7C1, the sheet P is maintained in the correct posture, but is conveyed in an oblique direction with respect to the conveyance direction X. For this reason, when correction is not performed (c1), the print image G that should be a rectangular shape is printed on the paper P in a parallelogram shape and an inclined shape on the paper P due to the deviation of the image G at the time of printing. Yes. On the other hand, in (c2), printing is performed while moving the head unit 10 in the transport width direction Y. As a result of this correction printing, in (c2), the correct rectangular print image G is printed in the correct posture on the central portion of the paper P.

  In FIG. 7D 1, the paper P is transported in an oblique direction with respect to the transport direction X in a skewed posture. For this reason, when correction is not performed (d1), the print image G that should be a rectangular shape is printed in a parallelogram shape on the paper P instead of a rectangular shape due to the deviation of the image G at the time of printing. On the other hand, in (d2), printing is performed in a state where the head unit 10 is rotationally corrected and placed at a position orthogonal to the width direction end of the paper P. As a result of this correction printing, a correct rectangular print image G is printed on the central portion of the paper P in (d2).

  In FIG. 7 (e1), the paper P is meandering in the transport direction X and being transported. For this reason, when correction is not performed (e1), the print image G that should be a rectangular shape is printed in a distorted shape including a curve instead of a rectangular shape on the paper P due to the deviation of the image G at the time of printing. Yes. On the other hand, in (e2), printing is performed in a state where the head unit 10 is placed at a position orthogonal to the width direction end portion of the paper P while being rotationally corrected. As a result of this correction printing, a correct rectangular print image G is printed on the central portion of the paper P in (e2).

  In the present embodiment, the paper P in FIGS. 1 and 2 constitutes a recording medium. Similarly, the edge sensors S1 to S4 in FIGS. 1 and 2 constitute detection means. Further, the Y-axis motor 14 in FIG. 2 constitutes a moving means. Further, the θ-axis motor 15 in FIG. 2 constitutes a rotating means. Further, the control unit 90, the conveyance information calculation unit 91, the movement amount calculation unit 92, and steps S20 to S40 and S60 to S80 in FIG. 6 constitute a control unit.

As described above, according to the ink jet printer 100 of the present embodiment, the following effects can be obtained.
In the ink jet printer 100 of the present embodiment, movement correction and rotation correction are performed on the head units 10 and 20 according to the relative position and relative inclination amount of the paper P calculated based on the detection results of the edge sensors S1 to S4. Do. For this reason, for example, when the paper P is displaced in the transport width direction Y, in a skewed posture, transported in an oblique direction, or transported in a meandering state, etc. Even in this case, the movement correction, the rotation correction, and the combination of the movement correction and the rotation correction are performed according to the conveyance state, and the relative position between the paper P and the head units 10 and 20 can be made constant during printing. it can. As a result, an image can be formed on the intended portion of the paper P, and an image with high resist accuracy and less visible unevenness can be formed.

  Further, since printing is performed in a state where the head unit 10 is rotationally corrected and placed at a position orthogonal to the widthwise end of the paper P, ink droplets are always ejected from the head units 10 and 20 onto the paper P. It is possible to maintain the ideal positional relationship orthogonal. As a result, for example, when image data matched with ejection characteristics generated in advance by image processing or image data in which unevenness is difficult to see due to error dispersion or the like is printed, the effect of these images is not impaired.

Further, by performing the above-described movement correction and rotation correction on each head unit 10 and 20 at high speed and with high accuracy, the eccentricity and vibration of each roller of the transport unit 1 that changes every time during transport of the paper P. It is possible to cope with a minute (several tens of μm level) posture change of the paper P caused by the above.
In addition, since it is not necessary to correct the position, posture, etc. of the paper P in front of each head unit 10, 20, a skew correction mechanism and a leading edge alignment mechanism for the paper P become unnecessary. Thereby, the effect of the cost reduction of the inkjet printer 100 can be acquired.

  Further, in the inkjet printer 100 of the present embodiment, when the paper P is conveyed in a skewed posture, each head unit 10, based on the relative position of the paper P with respect to the head unit 10. 20 is subjected to movement correction and rotation correction. For this reason, the relative position of the paper P and the head unit 10 can be made constant during printing. Thereby, the correction of the ink landing position can be performed with high accuracy without performing complicated calculation and high-speed control.

(Modification)
In the above embodiment, as shown in FIG. 2, the edge sensor S <b> 1 is disposed upstream of the head unit 10 in the transport direction X, and the edge sensor S <b> 2 is disposed in the head unit 10. However, the present invention is not limited to this. For example, as shown in FIG. 8, the head unit 10 may be provided with both edge sensors S <b> 1 and S <b> 2. Specifically, the edge sensor S1 is disposed on the upstream side surface of the head unit 10 in the transport direction X, and the edge sensor S2 is disposed on the downstream side surface. Similarly, the edge sensor S3 may be disposed on the upstream side surface in the transport direction X of the head unit 20, and the edge sensor S4 may be disposed on the downstream side surface.
In this modification, the edge sensors S1 and S3 in FIG. 8 constitute a first detection unit. Further, the edge sensors S2 and S4 in FIG. 8 constitute a second detection unit.

  For example, as shown in FIG. 9, the edge sensor S <b> 1 may be movable in the transport width direction Y, and the edge sensor S <b> 2 may be movable in the longitudinal direction of the head unit 10. Specifically, a motor 71 for transmitting power for reciprocating the edge sensor S1 in the transport width direction Y and a slide rail 72 extending along the transport width direction Y are provided. Further, a motor 73 for transmitting power for reciprocating the edge sensor S2 in the longitudinal direction of the head unit 10 and a slide rail 74 extending along the longitudinal direction of the head unit 10 are provided. Then, the control unit 90 controls the motor 71 to detect the region irradiated with light from the light emitting element of the edge sensor S1, that is, the position of the edge in the width direction of the paper P by the edge sensor S1. The edge sensor S1 is moved in the transport width direction Y so that the end of the paper P in the transport width direction enters the region. In addition, the control unit 90 controls the motor 73 so that the region irradiated with light from the light emitting element of the edge sensor S2, that is, the position of the edge in the width direction of the paper P is detected by the edge sensor S2. The edge sensor S2 is moved in the longitudinal direction of the head unit 10 so that the end portion in the conveyance width direction of the paper P enters the region. The edge sensor S3 is also provided with a motor 71 and a slide rail 72 as in the edge sensor S1. Similarly to the edge sensor S2, the edge sensor S4 is provided with a motor 73 and a slide rail 74. Then, the control unit 90 controls the motor 71 to move the edge sensor S3 in the transport width direction so that the end portion in the transport width direction of the paper P enters the region irradiated with light from the light emitting element of the edge sensor S3. Move to Y. In addition, the control unit 90 controls the motor 73 to move the edge sensor S4 to the head unit 10 so that the end portion in the conveyance width direction of the paper P enters the region irradiated with light from the light emitting element of the edge sensor S4. Is moved in the longitudinal direction. Thereby, even when the size of the paper P is changed and the position of the paper P in the paper width direction y is changed, the position of the end portion in the width direction of the paper P can be appropriately detected by the edge sensors S1 to S4.

Note that the method of setting the movement amount of the edge sensors S1 to S4 is not limited to a specific method, and various methods can be employed. For example, when the paper P is fed to the center of the transport surface 50 in the transport width direction, the position of the paper P in the transport width direction can be predicted based on the size of the paper P in the paper width direction y. Therefore, the user operates an input device (not shown), causes the user to input the size of the paper P in the paper width direction y, and calculates the predicted position of the end of the paper P in the paper width direction based on the input size. Then, the movement amount of the edge sensors S1 to S4 can be set so that the region irradiated with light from the light emitting element is located at the calculated predicted position.
In this modification, the edge sensors S1 and S3 in FIG. 9 constitute a first detection unit. Further, the edge sensors S2 and S4 in FIG. 9 constitute a second detection unit. Furthermore, the motors 71 and 73 and the slide rails 72 and 74 in FIG. 9 constitute detection unit moving means.

For example, as shown in FIG. 10, when both the edge sensors S <b> 1 and S <b> 2 are arranged in the head unit 10, the edge sensors S <b> 1 and S <b> 2 may be movable in the longitudinal direction of the head unit 10. . Specifically, a motor 75 for transmitting power for reciprocating the edge sensor S1 in the longitudinal direction of the head unit 10 and a slide rail 76 extending along the longitudinal direction of the head unit 10 are provided. In addition, a motor 77 for transmitting power for reciprocating the edge sensor S2 in the longitudinal direction of the head unit 10 and a slide rail 78 extending along the longitudinal direction of the head unit 10 are provided. Then, the control unit 90 controls the motor 75 so that the region irradiated with light from the light emitting element of the edge sensor S1, that is, the position of the edge in the width direction of the paper P is detected by the edge sensor S1. The edge sensor S1 is moved in the longitudinal direction of the head unit 10 so that the end of the sheet P in the transport width direction enters the region. Further, the control unit 90 controls the motor 77 to detect the region irradiated with light from the light emitting element of the edge sensor S2, that is, the position of the edge portion in the width direction of the paper P by the edge sensor S2. The edge sensor S1 is moved in the longitudinal direction of the head unit 10 so that the end of the sheet P in the transport width direction enters the region. The edge sensor S3 is also provided with a motor 75 and a slide rail 76 as in the edge sensor S1. Similarly to the edge sensor S2, the edge sensor S4 includes a motor 77 and a slide rail 78. Then, the control unit 90 controls the motor 75 to move the edge sensor S3 to the head unit 10 so that the end portion in the conveyance width direction of the paper P enters the region irradiated with light from the light emitting element of the edge sensor S3. Is moved in the longitudinal direction. In addition, the control unit 90 controls the motor 77 to move the edge sensor S4 to the head unit 10 so that the end portion in the conveyance width direction of the paper P enters the region irradiated with light from the light emitting element of the edge sensor S4. Is moved in the longitudinal direction. Thereby, even when the size of the paper P is changed and the position of the paper P in the paper width direction y is changed, the position of the end portion in the width direction of the paper P can be appropriately detected by the edge sensors S1 to S4.
In this modification, the edge sensors S1 and S3 in FIG. 10 constitute a first detection unit. Further, the edge sensors S2 and S4 in FIG. 10 constitute a second detection unit. Furthermore, the motors 75 and 77 and the slide rails 76 and 78 in FIG. 10 constitute detection unit moving means.

  Further, for example, when only the paper P having a predetermined size such as A4 and A5 is to be printed, the position of the end portion in the paper width direction of the paper P can be predicted in advance. Therefore, the edge sensors S <b> 1 to S <b> 4 may be provided so that the irradiation region of the light from the light emitting element is located at each of the predicted positions in the paper width direction. Specifically, for example, as shown in FIG. 11, a plurality of edge sensors S <b> 1 are provided upstream of the head unit 20 and separated from each other in the transport width direction Y. A plurality of edge sensors S2 are provided in the head unit 10 so as to be separated from each other in the longitudinal direction of the head unit 10. Each of the edge sensors S1 and S2 is arranged so that the irradiation region of the light from the light emitting element is positioned at each of the predicted positions of the end of the paper P in the paper width direction. Similarly, a plurality of edge sensors S3 are provided on the upstream side of the head unit 20 so as to be separated in the transport width direction Y. A plurality of edge sensors S4 are provided in the head unit 20 so as to be separated from each other in the longitudinal direction of the head unit 20. Each of the edge sensors S3 and S4 is arranged so that the irradiation region of the light from the light emitting element is positioned at each of the predicted positions of the end of the paper P in the paper width direction. Thereby, even when the size of the paper P is changed and the position of the paper P in the paper width direction y is changed, the position of the end portion in the width direction of the paper P can be appropriately detected by the edge sensors S1 to S4. Further, it is not necessary to move the edge sensors S1 to S4.

  For example, as shown in FIG. 12, when both the edge sensors S <b> 1 and S <b> 2 are arranged in the head unit 10, the plurality of edge sensors S <b> 1 are arranged on the upstream side surface of the head unit 20. 10 apart from each other in the longitudinal direction. Further, the plurality of edge sensors S <b> 2 are provided on the downstream side surface of the head unit 10 so as to be separated from each other in the longitudinal direction of the head unit 10. Each of the edge sensors S1 and S2 is arranged so that the irradiation region of the light from the light emitting element is positioned at each of the predicted positions of the end of the paper P in the paper width direction. Similarly, a plurality of edge sensors S <b> 3 are provided on the side surface on the upstream side of the head unit 20 so as to be separated in the longitudinal direction of the head unit 20. A plurality of edge sensors S4 are provided on the side surface on the downstream side of the head unit 20 so as to be separated from each other in the longitudinal direction of the head unit 20. The edge sensors S3 and S4 are arranged so that the irradiation region of the light from the light emitting element is positioned at the predicted position of the end of the paper P in the paper width direction. Thereby, even when the size of the paper P is changed and the position of the paper P in the paper width direction y is changed, the position of the end portion in the width direction of the paper P can be detected appropriately. Further, it is not necessary to move the edge sensors S1 to S4.

Moreover, in the said embodiment, as shown in FIG. 1 etc., it was set as the structure which provides the common conveyance part 1 with respect to the two head units of the head units 10 and 20. As shown in FIG. However, the present invention is not limited to this. For example, as shown in a side sectional view schematically showing the outline of the ink jet printer 300 in FIG. 13, a tandem type in which a transport unit 1 is provided as an independent mechanism for each head unit 10, 20. It may be configured as follows.
In addition, the plurality of ejection heads 11 are divided and arranged by the two head units 10 and 20, but the invention is not limited to this. The inkjet printer includes only one head unit, and all the ejection units are disposed in the head unit. A configuration in which the heads are arranged may be employed.

  DESCRIPTION OF SYMBOLS 1 ... Conveyance part, 2 ... Printing part, 10, 20 ... Head unit, 11 ... Discharge head, 12 ... Head panel, 13 ... θ rotation axis, 14 ... Y axis motor, 15 ... θ axis motor, 16 ... Y axis cam , 17 ... θ-axis cam, 31 ... gate roller, 32 ... driven roller, 33 ... tension roller, 34 ... drive roller, 35 ... endless belt, 36 ... transport drive motor, 37 ... vent hole, 50 ... transport surface, 71 ... Motor, 72 ... slide rail, 73 ... motor, 74 ... slide rail, 75 ... motor, 76 ... slide rail, 77 ... motor, 78 ... slide rail, 90 ... control unit, 91 ... transport information calculation unit, 92 ... amount of movement Calculation unit, 100 ... inkjet printer, 300 ... inkjet printer according to modification, S1 to S4 ... edge sensor

Claims (6)

A recording position correction apparatus that corrects a recording position of the ejected liquid in the recording medium by moving a head unit that ejects the liquid with respect to the recording medium conveyed on the conveying surface,
Detecting means for detecting a position of the recording medium with respect to the head unit;
Moving means for moving the head unit in a direction parallel to the transport surface;
Rotating means for rotating the head unit around an axis perpendicular to the transport surface;
Control means for moving the head unit by controlling the moving means and the rotating means based on the position of the recording medium relative to the head unit detected by the detecting means. A recording position correction apparatus characterized by the above. The detection means includes
A first detection unit that is disposed upstream of the head unit in the conveyance direction of the recording medium and detects the position of the recording medium conveyed on the conveyance surface;
A second detection unit that is disposed in the head unit and detects a position of the recording medium conveyed on the conveyance surface;
Based on the position of the recording medium detected by the first detector and the position of the recording medium detected by the second detector, the position of the recording medium relative to the head unit is calculated. The recording position correction apparatus according to claim 1, further comprising a calculation unit. The detection means includes
A first detection unit that is disposed in a portion of the head unit on the upstream side in the conveyance direction of the recording medium and detects the position of the recording medium conveyed on the conveyance surface;
A second detection unit that is disposed in a portion of the head unit on the downstream side in the conveyance direction of the recording medium and detects the position of the recording medium conveyed on the conveyance surface;
Based on the position of the recording medium detected by the first detector and the position of the recording medium detected by the second detector, the position of the recording medium relative to the head unit is calculated. The recording position correction apparatus according to claim 1, further comprising a calculation unit.   The detection unit moving means for moving each of the first detection unit and the second detection unit in a direction crossing a direction in which the recording medium is conveyed is provided. Recording position correction device.   The control means is based on the position of the recording medium with respect to the head unit detected by the detecting means, and the head unit by PID control so that the relative position between the recording medium and the head unit is constant. The recording position correcting apparatus according to claim 1, wherein the recording unit corrects the moving unit and the head unit rotating unit. A recording apparatus comprising the recording position correcting apparatus according to claim 1 and performing recording on a recording medium.

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