JP2011126203A - Recording position correcting device, and recording apparatus - Google Patents

Abstract

When a recording medium is transported out of the original transport position, the relative position between the recording medium and the head unit is not constant, and an image cannot be formed on an intended portion of the recording medium. .
SOLUTION: Head units 10 and 20 for ejecting liquid onto a recording medium P transported on a transport surface 50, detection units S1 to S4 for detecting the position of the transported recording medium P, and detection units S1 to S1. A conveyance information calculation unit 91 that calculates conveyance information indicating the conveyance state of the recording medium P based on the position of the recording medium P detected in S4 is provided. And the control part 90 which moves the head units 10 and 20 in the direction parallel to the conveyance surface 50 based on conveyance information is provided.
[Selection] Figure 2

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 for detecting a position of the recording medium conveyed on the conveying surface; a moving unit for moving the head unit in a direction parallel to the conveying surface; and the head unit perpendicular to the conveying surface. A rotation unit that rotates about an axis in a certain direction, a conveyance information calculation unit that calculates conveyance information indicating a conveyance state of the recording medium based on the position of the recording medium detected by the detection unit, and the conveyance information Control means for moving the head unit by controlling the moving means and the rotating means based on the conveyance information calculated by the calculating means; And the conveyance information calculation means is configured as the conveyance information based on the position of the recording medium detected before the recording on the recording medium is started by the detection means with respect to the conveyance direction of the recording medium. Calculating the inclination of the reference direction of the recording medium set for the recording medium and the moving speed of the recording medium in a direction orthogonal to the reference direction of the recording medium, and the control means Before the recording is started, the rotation unit is controlled based on the inclination of the recording medium in the reference direction calculated by the conveyance information calculation unit, so that the recording medium matches the inclination of the reference direction of the recording medium. The moving unit is controlled based on the moving speed of the recording medium calculated by the conveyance information calculating unit during the execution of recording on the recording medium by rotating the head unit. It allows at the same speed as the moving speed of the recording medium, and wherein the moving the head unit in a direction perpendicular to the reference direction of the recording medium.

According to this recording position correction apparatus, the conveyance information calculation unit calculates conveyance information indicating the conveyance state of the recording medium based on the position of the recording medium detected by the detection unit. Based on the transport information, the control unit moves the head unit in a direction parallel to the transport surface and rotates the head unit about an axis perpendicular to the transport surface.
Since the head unit is moved based on the conveyance information indicating the conveyance state of the recording medium, the head unit is moved according to the conveyance information when the relative position between the recording medium being conveyed and the head unit is not constant. The relative position of 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 conveyance information calculation unit includes a movement speed V of the recording medium in a direction orthogonal to a reference direction of the recording medium, a conveyance speed v of the recording medium, and the recording medium. It is desirable to calculate according to the equation V = v · sin θ based on the skew amount θ of the medium.
According to this recording position correction apparatus, the conveyance information calculation means can calculate the moving speed of the recording medium in the direction orthogonal to the reference direction of the recording medium. Therefore, the control unit can move the head unit based on the calculated moving speed of the recording medium. 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 offset by the movement of the head unit.

[Application Example 3]
In the recording position correction apparatus according to the application example described above, the detection unit includes two detection units that detect positions of ends of the recording medium in a direction orthogonal to a reference direction of the recording medium. The conveyance information calculation means is provided apart from the conveyance direction of the medium, and the reference of the recording medium detected by the two detection means is an inclination of the reference direction of the recording medium with respect to the conveyance direction of the recording medium. It is desirable to calculate based on the position of the end in the direction orthogonal to the direction.
According to this recording position correction apparatus, the conveyance information calculation unit can calculate the inclination of the recording medium in the reference direction with respect to the recording medium conveyance direction. For this reason, the control unit can rotate the head unit around an axis in a direction perpendicular to the conveyance surface based on the calculated inclination of the reference direction of the recording medium with respect to the conveyance direction of the recording medium. 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 rotation of the head unit.

[Application Example 4]
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. It is explanatory drawing of the moving speed of the paper in the paper width direction. Explanatory drawing of the movement state of a paper. The figure which shows the example of the correction | amendment presence or absence with respect to a head unit. The figure which shows the example of the presence or absence of correction | amendment with respect to a head unit in 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 rows are capable of ejecting inks of different colors, and in this embodiment, black (K), cyan (C), magenta (M), yellow in order 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.
Referring back to FIGS. 1 and 2, two edge sensors S <b> 1 and S <b> 2 are disposed in the transport direction of the paper P at the upstream side in the transport direction X of the head unit 10. In addition, two edge sensors S3 and S4 are arranged in the transport direction of the paper P so as to be upstream of the head unit 20 in the transport direction X. These edge sensors S1 to S4 are sensors serving as detection units that detect the position of the end in the width direction of the paper P. For example, the reflective sensors have a structure in which a light emitting element and a light receiving element face the direction of the conveyance surface 50. It is an image sensor. The end in the width direction of the paper P is the end of the paper P in the direction perpendicular to the reference direction x of the paper P, that is, the end in the paper width direction y. 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.

Note that these edge sensors S1 to S4 may be automatically moved to a position where the position of the end in the width direction can be detected according to the size of the sheet P in the sheet width direction y.
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 conveyance information includes the positional deviation amount and skew amount of the paper P.

  The conveyance information calculation unit 91 determines the positional deviation amount and skew of the sheet P based on the position of the end in the width direction detected when the sheet P conveyed on the conveyance surface 50 passes through each of the edge sensors S1 to S4. Calculate the amount. The misregistration amount here is a misregistration amount from a predetermined reference position in the transport width direction Y of the paper P, and represents an interval from the reference position to the position of the end portion in the width direction of the paper P. The skew amount represents the amount of inclination of the reference direction x of the paper P with respect to the transport direction X. When the paper P is viewed from above, a positive value is obtained when the reference direction x of the paper P is inclined counterclockwise with respect to the transport direction X, and a negative value is obtained when the paper P is inclined clockwise. It becomes.

Further, the control unit 90 is configured to move the head units 10 and 20 in the longitudinal direction based on the positional deviation amount and the skew amount calculated by the conveyance information calculation unit 91 and the θ rotation shaft 13 as a center. A movement amount calculation unit 92 for calculating the rotation amount 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 calculate the positional deviation amount and the skew amount of the paper P based on the detection results of the upstream edge sensors S1 and S2 in step S10. Specifically, the positional deviation amount and the skew 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 causes the conveyance information calculation unit 91 to calculate the moving speed of the paper P in the paper width direction y based on the skew amount calculated in step S20. Specifically, as shown in FIG. 7, the moving speed of the paper P in the paper width direction y is calculated according to the following equation (1) based on the transport speed of the paper P and the skew amount of the paper P.
V = v · sinθ (1)
Here, V is the moving speed of the paper P in the paper width direction y, v is the transport speed of the paper P, and θ is the skew amount of the paper P.

In step S40, the control unit 90 uses the movement amount calculation unit 92 to calculate the movement amount in the longitudinal direction of the head unit 10 and the θ rotation shaft 13 based on the positional deviation amount and the skew amount calculated in step S20. Calculate the amount of rotation centered.
In step S50, 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 S40. 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 S60, the control unit 90 starts the constant speed movement correction for the head unit 10 based on the movement speed of the paper P in the paper width direction y calculated in step S30. Specifically, driving of the Y-axis motor 14 is started, and the head unit 10 is continuously moved in the paper width direction y by the calculated movement speed of the paper P in the paper width direction y. The continuous movement of the head unit 10 in the sheet width direction y is continued until the ejection time for the sheet P1 has elapsed, that is, until the operation of the recording position correction apparatus proceeds to step S90 described later.

FIG. 8 is an explanatory diagram of the movement state of the paper P, and is a view of the paper P and the head unit 10 as viewed from above. Note that the upstream side in the transport direction X across the head unit 10 shows the paper P before passing under the head unit 10, and the downstream side shows the paper P after passing under the head unit 10. A white arrow indicates a direction in which the paper P is conveyed.
In FIG. 8, the paper P is transported in the transport direction X in a skewed state. Therefore, in the state in which the head unit 10 is rotationally corrected and placed at a position parallel to the paper width direction y of the paper P, the paper P moves in the longitudinal direction of the head unit 10 at a speed v in the paper width direction y of the paper P. Move to. Therefore, the relative position between the paper P and the head unit 10 can be kept constant by continuously moving the head unit 10 in the paper width direction y at the moving speed v.
That is, conventionally, in such an ink jet printer, when the movement correction and the rotation correction are performed on the head unit 10 according to the positional deviation amount and the skew feeding amount of the paper P, complicated calculation and high-speed control are required. Therefore, it has been difficult to improve the image position accuracy.

  Therefore, in the ink jet printer 100 of the present embodiment, when the paper P is conveyed in a skewed posture, the head unit 10 is rotationally corrected and placed at a position parallel to the paper width direction y, and then the paper Printing was performed while moving the head unit 10 at the same speed as the movement speed of P in the paper width direction y. For this reason, the relative position of the paper P and the head unit 10 can be made constant during printing. As a result, the image position accuracy can be increased without complicated calculations and high-speed control, and the print image can be printed on the paper P in the correct orientation.

In step S80, 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 S90, 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 S80, instead of determining whether or not the ejection time has elapsed, a sensor that detects 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 S80 that the ejection time has not elapsed, printing for one sheet P is being continued and the sheet P is being conveyed, so this determination is repeated.

  Next, specific examples of movement correction and rotation correction for the head units 10 and 20 will be described. FIG. 9 is a diagram illustrating an example of whether or not the head unit 10 is corrected. FIGS. 9A1 and 9B1 show printing examples when no correction is performed, and FIGS. 9A2 and 9B2 show printing examples 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 will be described here, the same applies to the head unit 20.

  In FIG. 9A1, 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), the head unit 10 is corrected for movement in the transport width direction Y only before printing is started, and neither movement correction nor rotation correction is performed during printing. 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. 9B1, the paper P is conveyed in the conveyance 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), before starting printing, the head unit 10 is subjected to movement correction and rotation correction so that the longitudinal direction of the head unit 10 is parallel to the paper width direction y. The sheet P is moved in the direction opposite to the direction y at the same speed as the sheet width direction. Thereby, the relative position of the paper P and the head unit 10 can be made constant during printing. 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 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 conveyance information calculation unit 91 in FIG. 2 and steps S20 and S30 in FIG. 6 constitute a conveyance information calculation unit. The control unit 90, the movement amount calculation unit 92 in FIG. 2, and steps S40 to S60 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 positional deviation amount and skew amount of the paper P calculated based on the detection results of the edge sensors S1 to S4. I do. For this reason, for example, even when the paper P is transported in a skewed posture, the movement correction, the rotation correction, and the combination of the movement correction and the rotation correction are performed according to the transport state, and printing is performed. Sometimes, the relative position between the paper P and the head units 10 and 20 can be made constant. 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.
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.

  In the inkjet printer 100 of the present embodiment, when the paper P is transported in a skewed posture, the head unit 10 is rotationally corrected and placed at a position parallel to the paper width direction y, and then the paper Printing was performed while moving the head unit 10 at the same speed as the movement speed of P in the paper width direction y. For this reason, the relative position of the paper P and the head unit 10 can be made constant during printing. As a result, the image position accuracy can be increased without complicated calculations and high-speed control, and the print image can be printed on the paper P in the correct orientation.

(Modification)
In the above embodiment, as shown in FIG. 9, when the paper P is conveyed in a skewed posture, the head unit 10 is rotationally corrected and placed at a position parallel to the paper width direction y. Printing is performed while moving the head unit 10 in the longitudinal direction at a constant speed. However, the present invention is not limited to this. For example, as shown in FIG. 10, the paper P maintains the correct posture. However, during the conveyance, the paper P moves in the conveyance width direction Y at a constant speed va, and the conveyance direction X When the paper P is transported in an oblique direction, printing may be performed while moving the head unit 10 in the transport width direction Y at the speed va. Here, the moving speed of the head unit 10 in the conveyance width direction Y is set manually based on the result of the test print, for example.

  FIG. 10 is a diagram illustrating an example of whether or not the head unit 10 is corrected in a modified example. FIG. 10A1 shows a printing example when no correction is performed, and FIG. 10A2 shows a printing example 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.

  In FIG. 10A1, 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 (a1), 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 (a2), printing is performed while moving the head unit 10 in the transport width direction Y. As a result of this correction printing, in (a2), the correct rectangular print image G is printed in the correct posture on the central portion of the paper P.

  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. 11, 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.
In addition, although the longitudinal direction of the head unit 10 is set to be parallel to the paper width direction y by the rotation correction with respect to the head unit 10, the present invention is not limited to this. For example, the longitudinal direction of the head unit 10 is the paper width direction y. It may be slightly shifted from the parallel direction.

  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, 90 ... Control unit, 91 ... transport information calculation unit, 92 ... movement amount calculation unit, 100 ... inkjet printer, 300 ... inkjet printer according to modification, S1 to S4 ... edge sensor

Claims (4)

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 conveyed on the conveying surface;
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;
A conveyance information calculation unit that calculates conveyance information indicating a conveyance state of the recording medium based on the position of the recording medium detected by the detection unit;
Control means for moving the head unit by controlling the movement means and the rotation means based on the conveyance information calculated by the conveyance information calculation means,
The conveyance information calculation unit is configured to determine, as the conveyance information, the conveyance direction of the recording medium based on the position of the recording medium detected before the detection unit starts recording on the recording medium. Calculating the inclination of the reference direction of the recording medium set in the recording medium and the moving speed of the recording medium in a direction orthogonal to the reference direction of the recording medium;
The control unit controls the rotation unit based on the inclination of the recording medium in the reference direction calculated by the conveyance information calculation unit before recording on the recording medium is started, thereby The moving unit is rotated based on the moving speed of the recording medium calculated by the conveyance information calculating unit during execution of recording on the recording medium by rotating the head unit according to the inclination of the medium in the reference direction. A recording position correcting apparatus, wherein the head unit is moved in a direction orthogonal to a reference direction of the recording medium at the same speed as the moving speed of the recording medium by controlling. The transport information calculating means calculates the moving speed V of the recording medium in a direction orthogonal to the reference direction of the recording medium based on the transport speed v of the recording medium and the skew amount θ of the recording medium using the formula V The recording position correcting apparatus according to claim 1, wherein the recording position correcting apparatus calculates according to v = sin θ. The detection means includes two detection units that detect positions of ends of the recording medium in a direction orthogonal to a reference direction of the recording medium, separated from each other in the conveyance direction of the recording medium,
The conveyance information calculation unit is configured to determine an inclination of the reference direction of the recording medium with respect to the conveyance direction of the recording medium at an end portion in a direction orthogonal to the reference direction of the recording medium detected by the two detection units. The recording position correction apparatus according to claim 1, wherein the recording position correction apparatus calculates the position based on the position. A recording apparatus comprising the recording position correction apparatus according to claim 1 and performing recording on a recording medium.

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