JP6111621B2 - Ink discharge timing correction method for ink jet printer and ink jet printer - Google Patents

Description

  The present invention relates to an ink ejection timing correction method for a serial type inkjet printer that performs printing by ejecting ink droplets while moving an inkjet head in the paper width direction with respect to a recording paper on a platen, and the ink ejection timing correction method The present invention relates to an ink jet printer that performs printing by driving an ink jet head at an ink discharge timing corrected by the above.

  The serial type ink jet printer includes a carriage on which an ink jet head is mounted and a carriage moving mechanism that reciprocates the carriage in the paper width direction. The carriage moving mechanism includes a driving pulley and a driven pulley arranged on both sides in the paper width direction with the platen interposed therebetween, a timing belt spanned between the driving pulley and the driven pulley, and a carriage motor as a driving source. The carriage is fixed to the timing belt. When the carriage motor is driven, the driving force is transmitted to the driving pulley, and the timing belt rotates. When the timing belt rotates, the carriage, that is, the ink jet head moves along with the rotation of the timing belt.

  In such a carriage moving mechanism, when the ink jet head is reciprocated in the paper width direction, the ink jet head is moved forward in the direction of approaching the drive pulley from the driven pulley side, and the ink jet head is driven from the drive pulley side. There may be a difference in the moving speed at which the ink-jet head passes on the recording paper depending on whether the ink-jet head is moved backward in the direction of approaching the pulley. Here, when the moving speed at the time of forward movement and the moving speed at the time of backward movement are different when reciprocating the ink-jet head in the paper width direction, the ink-jet head is driven at a reference ink discharge timing preset in the ink-jet printer. When ink droplets are ejected to the target printing position on the recording paper, there is a problem that the landing position of the ink droplet at the time of forward movement and the landing position of the ink droplet at the time of backward movement are deviated, and the printing quality is deteriorated. In order to solve such a problem, in Patent Document 1, by the Bi-d adjustment operation, the landing position and the return position of the ink droplet at the time of forward movement caused by the speed difference between the movement speed at the time of forward movement and the movement speed at the time of backward movement. Corrects the deviation from the landing position of ink droplets during movement.

JP 2002-292959 A

  Some inkjet printers that perform printing on roll paper include a roll paper storage unit that stores the roll paper in a housing of the printer. In addition, in an inkjet printer having a roll paper storage unit in a housing, when the opening / closing lid for loading roll paper into the roll paper storage unit is opened, the roll paper storage unit passes through the platen in conjunction with the opening operation of the opening / closing lid. When the roll paper transport path leading to the paper discharge port is opened and the roll paper is inserted into the roll paper storage section and then the open / close lid is closed, the transport path is partitioned in the housing and the long paper that is fed out of the roll paper There is a structure in which a state in which the recording paper is pulled out along the conveyance path is formed.

  In such a structure, since the platen moves, it is not easy to maintain the posture of the platen, and the platen may be inclined in the paper width direction when the opening / closing lid is closed. When the platen is inclined in the paper width direction, the platen gap between the ink jet head and the platen changes when the ink jet head is moved in the paper width direction.

  If the platen gap changes when the inkjet head is moved in the paper width direction, driving the inkjet head at the reference ink discharge timing while moving the inkjet printer in the paper width direction results from the change in the platen gap. As a result, the landing position of the ink droplet is deviated from the target printing position on the recording paper, and there is a problem that the printing quality is deteriorated.

  In view of such problems, an object of the present invention is to provide an ink discharge timing correction method for an ink jet printer and an ink jet printer that can maintain print quality even when the platen is inclined in the paper width direction. .

In order to solve the above-described problems, the present invention provides an inkjet head that moves in the paper width direction of the recording paper and ejects ink droplets, an opposing position that faces the inkjet head, and an open position that does not face the inkjet head. In the inkjet printer comprising: a moving platen, a reference platen in which a platen gap between the inkjet head and the platen located at the opposite position is constant in the paper width direction, and a central position in the paper width direction on the platen And an inclined platen inclined about an axis extending in the paper feeding direction orthogonal to the paper width direction,
The ink jet head is reciprocated in the paper width direction, and a predetermined print pattern is printed at a corrected ink discharge timing obtained by correcting a preset reference ink discharge timing by a correction time corresponding to an inclination amount of the inclined platen with respect to the reference platen. The pattern printing operation is repeated by changing the inclination amount stepwise,
The correction ink ejection timing of the pattern printing operation in which the ink droplets land on a target printing position on the recording paper is set to the ink ejection timing.

  According to the present invention, a pattern printing operation in which ink droplets have landed on a target printing position on a recording sheet is identified by performing a plurality of pattern printing operations performed while changing the inclination amount of the assumed inclination platen stepwise. By doing so, it is possible to obtain the corrected ink ejection timing corresponding to the actual amount of platen inclination. That is, in a plurality of pattern printing operations performed while changing the correction time stepwise so as to correspond to the inclination amount of the inclination platen, the case where the ink droplets have landed at the target printing position on the recording paper This is a case where the inclination amount of the inclined platen assumed in the pattern printing operation is equal to the actual inclination amount of the platen. Therefore, if the corrected ink discharge timing of the pattern printing operation is set to the ink discharge timing, the deviation of the landing position of the ink droplet due to the change of the platen gap can be corrected in the subsequent printing, and the print quality can be improved. Can be maintained. Here, in the pattern printing operation in which the ink droplets land on the target printing position on the recording paper, a target printing result in which a desired printing pattern is accurately printed is obtained as a printing result. Therefore, it is possible to specify the pattern printing operation in which the ink droplets have landed at the target printing position on the recording paper based on the printing result.

In the present invention, previously said encoder for detecting the movement of the paper width direction of the ink-jet head is installed, the reference period in which the ink jet head is output from the encoder to when you move at the reference speed set in advance T, the gap between T'the real cycle of a predetermined output is Ru signal from the encoder with the position of the inkjet head you move in the paper width direction, the discharge speed of the ink droplet Vi, the inkjet head and the reference platen The correction time Δt corresponding to the amount of inclination of the inclined platen is expressed by the following equation, where PG is the distance between the inclined platen and the reference platen at the predetermined position. Can be.
Δt = T / Vi × {PG × (1 / T−1 / T ′) − ΔPG × 1 / T ′}

  As described above, if the correction time corresponding to the inclination amount of the inclined platen is defined by the mathematical expression, it is easy to drive the inkjet head at the corrected ink discharge timing obtained by correcting the reference ink discharge timing with the correction time. Therefore, it becomes easy to repeat the pattern printing operation while changing the inclination amount of the inclination platen stepwise. Here, if the reference ink ejection timing is corrected using the correction time represented by the above equation, the ink droplet landing position shifts when the moving speed of the ink jet head is changed, and the ink jet head is moved in the paper width direction. It is possible to correct both of the landing position deviations of ink droplets when the platen gap changes when moved to.

In the present invention, before performing the pattern printing operation, have rows Bi-d adjustment operation, when the reference ink ejection timing by driving the ink jet head ejecting ink droplets onto the recording paper on said platen It is desirable to correct the deviation between the landing position during forward movement and the landing position during backward movement. That is, before the pattern printing operation, if the deviation of the landing position due to the speed difference between the moving speed during the forward movement and the moving speed during the backward movement is corrected by the Bi-d adjustment operation, It is possible to avoid the landing position from being shifted due to the speed difference between the moving speed during the forward movement and the moving speed during the backward movement. As a result, the number of repetitions of the pattern printing operation until the target print result is obtained can be reduced, so that the amount of ink consumed for correcting the ink ejection timing can be suppressed. In addition, the printing result of the pattern printing operation does not show a deviation of the landing position due to the difference between the moving speed at the forward movement and the moving speed at the backward movement, and the number of pattern printing operations can be reduced. It becomes easy to select the target print result from the print results.

In the present invention, in the pattern printing operation, it is preferable to perform printing on the paper width direction of at least one end portion of the recording paper. When the platen is inclined, the deviation of the landing position of the ink droplet becomes large at the end portion in the paper width direction of the recording paper. Therefore, if it is confirmed whether or not the ink droplets have landed on the target print position on the recording paper based on the printing result obtained by performing printing on the end portion in the paper width direction of the recording paper in the pattern printing operation, the plurality of printing results can be obtained. It becomes easy to specify the target print result. Here, if only one end portion in the paper width direction of the recording paper is printed in the pattern printing operation, the amount of ink consumed for correcting the ink ejection timing can be suppressed.

Next, the inkjet printer of the present invention is
An inkjet head that ejects ink drops;
A platen that moves between a facing position facing the inkjet head and an open position not facing the inkjet head ;
A head moving mechanism for moving the inkjet head in the paper width direction of the recording paper on the platen;
A transport mechanism for transporting the recording paper in a direction orthogonal to the paper width direction,
A platen gap between the inkjet head and the platen located at the opposite position is constant in the paper width direction, and in a paper feed direction orthogonal to the paper width direction at a central position in the paper width direction on the platen. Assuming an inclined platen inclined around the extending axis,
The ink jet head is reciprocated in the paper width direction, and a predetermined print pattern is printed at a corrected ink discharge timing obtained by correcting a preset reference ink discharge timing by a correction time corresponding to an inclination amount of the inclined platen with respect to the reference platen. The pattern printing operation is repeated by changing the inclination amount stepwise,
The correction ink ejection timing of the pattern printing operation in which the ink droplets land on a target printing position on the recording paper is set to the ink ejection timing.

  According to the present invention, the corrected ink discharge timing corrected with the correction time corresponding to the platen inclination amount is set as the ink discharge timing of the ink jet printer, so the ink on the recording paper generated due to the platen inclination amount The deviation of the landing position of the droplet can be corrected. Accordingly, the print quality can be maintained even when the platen is inclined in the paper width direction.

  According to the present invention, by performing a pattern printing operation for printing a printing pattern a plurality of times and confirming the printing result, it is possible to acquire the corrected ink ejection timing according to the actual platen inclination amount. Further, since the acquired corrected ink discharge timing can be set as the ink discharge timing of the ink jet printer, the print quality can be maintained even when the platen is inclined in the paper width direction.

1 is an external perspective view of an ink jet printer to which the present invention is applied. It is explanatory drawing which shows schematic structure inside an inkjet printer. It is a schematic block diagram which shows the control system of an inkjet printer. 6 is a timing chart schematically showing reference ink ejection timing. FIG. 6 is an explanatory diagram of a deviation in the landing position of an ink droplet depending on a moving speed of a head. It is explanatory drawing of the platen gap when a platen inclines. FIG. 6 is an explanatory diagram of a deviation in the landing position of an ink droplet that occurs due to the inclination of a platen. 6 is a flowchart of an ink discharge timing correction operation. It is an example of the printing result by multiple times pattern printing operation.

  Hereinafter, an inkjet printer to which the present invention is applied will be described with reference to the drawings.

(overall structure)
FIG. 1A is an external perspective view of an ink jet printer to which the present invention is applied, and FIG. 1B is an external perspective view of the ink jet printer with the open / close lid fully opened. In FIG. 1B, the cover case of the opening / closing lid and the lid opening / closing lever are omitted. The ink jet printer 1 of this example is a roll paper printer that prints on a long, constant width recording paper 3 fed out from the roll paper 2.

  As shown in FIG. 1A, the ink jet printer 1 includes a printer main body 5 and an opening / closing lid 6 attached to the front surface of the printer main body 5. A paper discharge port 7 having a predetermined width is formed on the front surface of the outer case 5 a of the printer body 5. A paper discharge guide 8 is discharged forward below the paper discharge port 7, and a lid opening / closing lever 9 is disposed on the side of the paper discharge guide 8. As shown in FIG. 1B, a rectangular shape for loading and unloading the roll paper 2 into and from the roll paper storage unit 10 in the printer body 5 is provided below the paper discharge guide 8 and the lid opening / closing lever 9 in the outer case 5 a. An opening 5b is formed. The opening 5 b is sealed with an opening / closing lid 6.

  When the lid opening / closing lever 9 is operated, the locking of the opening / closing lid 6 is released. When the paper discharge guide 8 is pulled forward after unlocking, as shown in FIG. 1B, the opening / closing lid 6 pivots forward about its lower end and opens until it is almost horizontal. When the opening / closing lid 6 is opened, the roll paper storage unit 10 is opened, and at the same time, a transport path 12 (for the roll paper 2 from the roll paper storage unit 10 via the printing position A by the inkjet head 11 to the paper discharge port 7 ( 2) is opened. Here, the platen 13 is attached to the opening / closing lid 6, and when the opening / closing lid 6 is opened, the platen 13 is exposed to the outside from the opening 5 b. When the opening / closing lid 6 is closed, the platen 13 is disposed at the printing position A and faces the inkjet head 11. As a result, the conveyance path 12 for the roll paper 2 is defined in the printer main body 5.

  FIG. 2 is an explanatory diagram showing a schematic configuration inside the ink jet printer 1. A head unit frame 16 attached horizontally to the upper end of the printer main body frame 15 is disposed above the roll paper storage unit 10. The head unit frame 16 includes an inkjet head 11, a carriage 17 on which the inkjet head 11 is mounted, and a carriage movement mechanism (head movement mechanism) 18 that moves the carriage 17 in the printer width direction. The printer width direction in which the carriage 17 moves is the paper width direction W of the recording paper 3 drawn on the platen 13. The carriage moving mechanism 18 includes a carriage guide shaft 20 that guides the movement of the carriage 17 in the paper width direction W, a carriage motor 21 that serves as a drive source, and a drive that is disposed on both sides of the paper width direction W with the conveyance path 12 interposed therebetween. A pulley 22 and a driven pulley (not shown), and a timing belt 23 spanned between the driving pulley 22 and the driven pulley are provided.

  The carriage guide shaft 20 is stretched horizontally in the paper width direction W with respect to the head unit frame 16. The inkjet head 11 is mounted on the carriage 17 with the ink nozzle surface 11 a facing downward, and the carriage 17 is fixed to the timing belt 23. When the carriage motor 21 is driven, the driving force of the carriage motor 21 is transmitted to the driving pulley 22 and the timing belt 23 rotates. When the timing belt 23 rotates, the carriage 17, that is, the inkjet head 11 moves in the paper width direction W along with this rotation.

  Further, a linear encoder 24 is mounted on the head unit frame 16. The linear encoder 24 includes a linear scale 25 that extends horizontally in parallel with the carriage guide shaft 20 at the upper end portion of the head unit frame 16, and an encoder sensor 26 mounted on the carriage 17. The linear encoder 24 detects the movement of the carriage 17 and the inkjet head 11 in the paper width direction W, and the encoder sensor 26 detects the position, movement speed, and movement direction of the carriage 17 (inkjet head 11) in the paper width direction. A-phase and B-phase signals are output.

  The platen 13 is disposed so as to face the inkjet head 11 and defines a printing position A by the inkjet head 11. A tension guide 30 is attached to the rear end of the platen 13. The tension guide 30 is biased upward by a spring. The recording paper 3 fed out from the roll paper 2 stored in the roll paper storage unit 10 is conveyed along a conveyance path 12 passing through the printing position A in a state where a predetermined tension is applied by the tension guide 30.

  On the rear side of the platen 13, a rear paper feed roller 31 and a rear paper press roller 32 are stretched horizontally in the paper width direction W. A rear paper pressing roller 32 is pressed against the rear paper feeding roller 31 through the recording paper 3 from above with a predetermined pressing force. A front paper feed roller 33 and a front paper press roller 34 are disposed on the front end side of the platen 13. A front paper pressing roller 34 is pressed against the front paper feeding roller 33 through the recording paper 3 from above. The rear paper feed roller 31 and the front paper feed roller 33 are rotationally driven in synchronization by a paper feed motor 35 (see FIG. 3) mounted on the printer main body frame 15. The rear paper feed roller 31, the rear paper press roller 32, the front paper feed roller 33, the front paper press roller 34, and the paper feed motor 35 constitute a transport mechanism 36 that transports the recording paper 3 along the transport path 12. Yes.

  Here, after the opening / closing lid 6 is opened, the roll paper 2 in a state in which the recording paper 3 is pulled out is loaded into the roll paper storage unit 10 and the opening / closing lid 6 is closed. In a state where tension is applied, the sheet extends along the conveyance path 12 via the printing position A on the platen 13 and is set in a state where it is pulled out from the paper discharge port 7. When the recording paper 3 is set in the transport path 12, the paper feed motor 35 is driven, and the cueing is performed in which the printing start position on the recording paper 3 is arranged at the printing position A.

  When print data is supplied from an external device in a state where the recording paper 3 is cued, the ink jet printer 1 performs a printing operation for printing on the recording paper 3 while moving the ink jet head 11 in the paper width direction W. Then, the paper feed motor 35 is driven to print the print data while alternately repeating the paper feed operation of feeding the recording paper 3 by a predetermined paper feed amount.

(Control system)
FIG. 3 is a schematic block diagram showing a control system of the ink jet printer 1. FIG. 4 is a timing chart schematically showing the reference ink discharge timing at which the inkjet head 11 is driven. As shown in FIG. 3, the inkjet printer 1 is configured around a control unit 40 including a CPU. A communication unit 41 including a communication interface and an encoder sensor 26 are connected to the input side of the control unit 40. An inkjet head 11, a carriage motor 21, and a paper feed motor 35 are connected to the output side of the control unit 40 via unillustrated drivers. The communication unit 41 receives print data from an external device and supplies it to the control unit 40. The control unit 40 includes a print control unit 45 and a setting unit 46.

  The print control unit 45 drives the carriage motor 21 to move the ink jet head 11 in the paper width direction W, drives the ink jet head 11 to eject ink droplets onto the recording paper 3 on the platen 13, and paper feed. Print data is printed by alternately repeating a paper feed operation in which the motor 35 is driven to feed the recording paper 3 by a predetermined paper feed amount. Here, when the inkjet head 11 moves in the paper width direction W, the print control unit 45 drives the inkjet head 11 at an ink ejection timing set based on a signal from the encoder sensor 26.

  The setting unit 46 sets the ink discharge timing at which the print control unit 45 drives the inkjet head 11. The setting unit 46 sets the reference ink discharge timing preset in the inkjet printer 1 as the ink discharge timing in the initial state. When an ink discharge timing correction operation described later is performed, the corrected ink discharge timing acquired by the ink discharge timing correction operation is set as the ink discharge timing.

  As shown in FIG. 4, the reference ink ejection timing is, for example, a drive waveform output by the print control unit 45 after the reference time Δt0 has elapsed from the rising point of the B phase among the A phase and B phase signals from the encoder sensor 26. It is what is done. The inkjet head 11 is driven by the output of the drive waveform, and ink droplets are ejected from the inkjet head 11.

(Ink droplet landing position shift)
Here, in the ink jet printer 1, when the print control unit 45 drives the ink jet head 11 at the reference ink discharge timing, the target printing in which the landing positions of the ink droplets discharged from the ink jet head 11 are targeted on the recording paper 3 is performed. It may shift from the position.

  First, in the inkjet printer 1, when the inkjet head 11 is reciprocated in the paper width direction W, the inkjet head 11 is moved forward in the direction of approaching the driven pulley 22 from the driven pulley side, and the inkjet head There may be a difference in the moving speed at which the ink jet head 11 passes over the recording paper 3 when the head 11 is moved backward from the driving pulley 22 toward the driven pulley. If the movement speed at the time of forward movement and the movement speed at the time of backward movement are different, when the ink jet head 11 is driven at the reference ink discharge timing and ink droplets are discharged to the target print position on the recording paper 3, The landing position of the ink droplet and the landing position of the ink droplet during the backward movement are shifted.

  FIG. 5 is an explanatory diagram of the amount of deviation of the ink droplet landing position from the target printing position on the recording paper 3 due to the moving speed of the inkjet head 11. The platen shown in FIG. 5 is an ideal platen 13A in which when the inkjet head 11 is moved in the paper width direction W, the platen gap between the inkjet head 11 and the inkjet head 11 is a constant reference platen gap PG. When the inkjet head 11 is moving at the reference moving speed Vcr as a reference, the landing position of the ink droplets ejected from the inkjet head 11 is the target print on the recording paper 3 as shown in FIG. It becomes a position xVcr. When the moving speed of the inkjet head 11 is an actual moving speed Vcr ′ that is slower than the reference moving speed Vcr, the ink droplet landing position is the target print on the recording paper 3 as shown in FIG. It becomes a rear position x′Vcr behind the position x in the moving direction of the inkjet head 11. Further, when the moving speed of the inkjet head 11 is an actual moving speed Vcr ′ faster than the reference moving speed Vcr, the ink droplet landing position is on the recording paper 3 as shown in FIG. The front position x′Vcr is ahead of the target print position xVcr in the moving direction of the inkjet head 11.

When the moving speed of the inkjet head 11 changes, the deviation amount x′Vcr−xVcr in which the actual landing position of the ink droplet deviates from the target printing position x is set to Vi as the discharging speed at which the ink droplet is discharged. If the actual moving speed obtained by incrementing Δcr by Vcr and the reference moving speed Vcr is Vcr ′, it can be expressed by the following equation (a).
x′Vcr−xVcr = PG / Vi × ΔVcr ·· (a)

  Second, in the inkjet printer 1, the platen 13 is moved by opening and closing the opening / closing lid 6, so that the platen 13 is inclined in the paper width direction W when the opening / closing lid 6 is closed and the platen 13 is disposed at the printing position A. It may be in the state. When the platen 13 is tilted in the paper width direction W, the platen gap is not constant. Therefore, when the ink jet head 11 is driven at the reference ink ejection timing and ink droplets are ejected to the target printing position on the recording paper 3, The landing position deviates from the target printing position.

  FIG. 6 is an explanatory diagram showing the relationship between the current position of the inkjet head 11 in the paper width direction W and the platen gap when the platen 13 is inclined. Each of FIGS. 7A to 7C is an explanatory diagram of a deviation amount in which the landing position of the ink droplet shifts from the target printing position on the recording paper 3 due to the inclination of the platen 13. In FIG. 6, the moving speed of the inkjet head 11 in the paper width direction W is a reference moving speed Vcr, which is constant. In FIG. 6, an inclined platen 13 </ b> B is inclined with respect to the ideal platen 13 </ b> A around the axis L <b> 0 extending in the paper feed direction perpendicular to the paper width direction W at the center position in the paper width direction W on the surface of the platen 13. Assumed.

  FIG. 7A shows a state in which the inkjet head 11 moves in the center in the paper width direction W in FIG. 6, and the platen gap is the reference platen gap PG. In this state, the landing position of the ink droplets ejected from the inkjet head 11 is the target printing position xPG on the recording paper 3. FIG. 7B shows a state in which the inkjet head 11 moves to the right side in the paper width direction W in FIG. 6, and the platen gap is an actual platen gap PG ′ shorter than the reference platen gap PG. . In this state, the landing position of the ink droplet is the rear position x′PG behind the target print position xPG on the recording paper 3 in the moving direction of the inkjet head 11. FIG. 7C shows a state in which the inkjet head 11 moves in FIG. 6 from the left end side in the paper width direction W toward the right side, and the platen gap is an actual platen gap PG ′ longer than the reference platen gap PG. . In this state, the landing position of the ink droplet is a front position x′PG ahead of the target print position xPG on the recording paper 3 in the moving direction of the inkjet head 11.

As shown in FIG. 6, when the platen gap changes linearly with the movement of the inkjet head 11 in the paper width direction W, the deviation amount x′PG− in which the actual landing position of the ink droplet deviates from the target printing position x. xPG is defined as follows, where an ink droplet discharge speed is Vi, and a reference platen gap PG and an actual platen gap obtained by incrementing a separation distance ΔPG between the inclined platen 13B and the ideal platen 13A from the reference platen gap PG is PG ′. It can be represented by the formula (b).
x′PG−xPG = Vcr / Vi × ΔPG (b)

Here, when the moving speed of the inkjet head 11 changes and the platen gap changes in the paper width direction W, the deviation amount (x′−x) by which the actual landing position of the ink droplet deviates from the target printing position x is This is a value obtained by adding the shift amount when the platen gap is changed to the shift amount when the moving speed is changed, and is expressed by the following equation (c). Vcr ′ is the actual moving speed of the inkjet head 11 at the current position in the paper width direction W.
x′−x = 1 / Vi × (PG × ΔVcr + ΔPG × Vcr ′) (c)

(Correction time to correct deviation of ink droplet landing position)
Next, in order to correct the displacement amount (x′−x) of the landing position of the ink droplet represented by the formula (c) to zero or a value close to zero, the timing at which the drive waveform is output by the print control unit 45. And the timing at which the ink droplets are ejected from the inkjet head 11 may be shifted by the time corresponding to the amount of deviation (x′−x). More specifically, the correction time Δt corresponding to the shift amount (x′−x) is added to the reference time Δt0 in FIG. 4, and the timing at which the print control unit 45 outputs the drive waveform is determined from the reference time Δt0. Can be shifted before or after.

Here, the correction time Δt is obtained by converting the shift amount (x′−x) into time. That is, it is obtained by the following equation (d) obtained by dividing the deviation amount (x′−x) by the reference movement speed Vcr.
Δt = (x′−x) / Vcr ·· (d)
Further, if the equation (c) is substituted into the equation (d), the correction time Δt is expressed by the following equation (e).
Δt = 1 / Vi × (PG × ΔVcr + ΔPG × Vcr ′) / Vcr (e)

Furthermore, since ΔVcr is an increment of the actual moving speed Vcr ′ with respect to the reference moving speed Vcr, the correction time Δt is expressed by the following equation (f).
Δt = 1 / Vi
× {PG × (Vcr′−Vcr) + ΔPG × Vcr ′} / Vcr ·· (f)

Here, the reference moving speed Vcr and the actual moving speed Vcr ′ are set so that the resolution of the linear encoder 24 is ES, and the reference period of the signal output from the encoder sensor 26, that is, the inkjet head 11 moves at a preset reference speed. When the reference period output from the encoder sensor 26 is T and the actual period of the signal output from the linear encoder 24 at the current position of the inkjet head 11 moving in the paper width direction W is T ′, (G) and (h).
Vcr = ES / T (g)
Vcr ′ = ES / T ′ (h)

Therefore, by substituting the equations (g) and (h) into the equation (f), the correction time Δt is expressed by the following equation (i).
Δt = 1 / Vi × {PG × (ES / T′−ES / T) + ΔPG × ES / T ′} / (ES / T) (i)

Furthermore, equation (i) can be reduced by the resolution ES. Therefore, the correction time Δt is the reference cycle T of the signal output from the encoder sensor 26, and the actual cycle of the signal output from the linear encoder 24 at the current position of the inkjet head 11 moving in the paper width direction W is T ′. The reference platen gap PG between the ideal platen 13A and the ink jet head 11 and the separation distance ΔPG between the inclined platen 13B and the ideal platen 13A at the current position of the ink jet head 11 moving in the paper width direction W can be expressed. it can. Further, when the actual cycle T ′ is short (the actual moving speed Vcr ′ is fast) from the equation (i), or when the separation distance ΔPG is large (the actual platen gap PG ′ is large), the correction time Δt is large. That is, the timing for outputting the drive waveform is shifted backward. However, as is apparent from FIG. 5C and FIG. 7C, in order to bring the actual landing position of the ink droplet closer to the target printing position x, it is necessary to shift the timing for outputting the drive waveform forward. There is. Therefore, the equation for calculating the correction time Δt is opposite to the sign of equation (i). That is, the correction time Δt is expressed by the following equation (j).
Δt = T / Vi × {PG × (1 / T−1 / T ′) − ΔPG × 1 / T ′} (j)

  As described above, when the corrected ink ejection timing obtained by correcting the reference time Δt0 with the correction time Δt is used, the moving speed of the inkjet head 11 changes and the platen gap changes with the movement of the inkjet head 11 in the paper width direction W. In this case, the deviation amount (x′−x) of the landing position of the ink droplet can be corrected to zero.

(Ink ejection timing correction operation)
FIG. 8 is a flowchart of the ink discharge timing correction operation for correcting the deviation of the landing position of the ink droplet. FIG. 9 is an example of a print result of a predetermined print pattern by a plurality of pattern printing operations. In the ink jet printer 1 of this example, at the final stage of the manufacturing process, the ink discharge timing correction operation shown in FIG. 8 is performed, the reference ink discharge timing preset for the individual is corrected with the correction time Δt, The deviation of the landing position is corrected.

  In the ink ejection timing correction operation, a Bi-d adjustment operation is performed to correct the deviation between the landing position during forward movement and the landing position during backward movement (step ST1).

  In the Bi-d adjustment operation, the ink jet head 11 is driven at the reference ink discharge timing to discharge ink droplets onto the recording paper 3 on the platen 13, and the landing position at the time of forward movement and the landing position at the time of backward movement are determined. This is a well-known technique for correcting the deviation by correcting at least one of the reference ink ejection timing during forward movement and the reference ink ejection timing during backward movement. In this example, the reference ink discharge timing at the backward movement is corrected based on the reference ink discharge timing at the forward movement.

  More specifically, in the Bi-d adjustment operation, the inkjet head 11 is driven at the reference ink discharge timing while moving the inkjet head 11 in the paper width direction W to reach the print target position of the recording paper 3 on the platen 13. The platen 13 is driven by driving the inkjet head 11 at a forward-correction printing operation in which ink droplets are discharged, and at a speed-corrected ink discharge timing in which the reference ink discharge timing is corrected by the speed correction time while moving the inkjet head 11 back in the paper width direction W. A bidirectional printing operation including a backward printing operation for ejecting ink droplets to the printing target position of the upper recording paper 3 is performed. Thereafter, the bidirectional printing operation is repeated a plurality of times while interposing a paper feeding operation for feeding the recording paper 3 in the paper feeding direction and changing the speed correction time stepwise. After that, the speed correction ink ejection timing at the time of backward movement when the printing result in which the landing positions of both the forward printing operation and the backward printing operation coincide with each other is obtained from the plurality of printing results. It is set as the reference ink ejection timing.

  In the Bi-d adjustment operation, the target print position on the recording paper 3 on which the ink droplets are landed is the center position in the paper width direction W, and the print result by the bidirectional print operation is a figure or the like at the center position in the paper width direction W. It is formed. Further, the amount of change for changing the speed correction time and the number of times the bidirectional printing operation is repeated are the difference between the moving speed of the inkjet head 11 in the actual inkjet printer 1 during the forward movement and the movement speed during the backward movement. It is preset based on the distribution. Here, in this example, when the ink jet head 11 is moved in the direction of approaching the driven pulley 22 from the driven pulley side, the ink jet head 11 is moved closer to the driven pulley side from the drive pulley 22 side. The case of moving in the direction is set as the backward movement, but the moving direction during the forward movement and the backward movement may be reversed.

  Next, assuming one inclined platen 13B with respect to the ideal platen 13A, the ink jet head 11 is reciprocated in the paper width direction W, and the reference ink discharge timing corresponds to the inclination amount D (see FIG. 6) of the inclined platen 13B. The pattern printing operation is performed in which the inkjet head 11 is driven at the corrected ink discharge timing corrected with the correction time Δt to discharge the ink droplets onto the recording paper 3 on the platen 13 to print the predetermined print pattern P (step ST2). . The predetermined print pattern P is formed by complementing the ink droplets ejected in the forward movement and the ink droplets ejected in the backward movement to form one figure or the like. In the pattern printing operation, as shown in FIG. 9, a predetermined print pattern M is printed on both end portions of the recording paper 3 in the paper width direction W.

Here, the correction time Δt is obtained by the following equation (j) as described above.
Δt = T / Vi × {PG × (1 / T−1 / T ′) − ΔPG × 1 / T ′} (j)
In Expression (j), T (reference period) and PG (reference platen gap) are preset values. ΔPG (separation distance between the inclined platen 13B and the ideal platen 13A at the current position of the inkjet head 11 moving in the paper width direction W) is based on the assumed inclination amount D of the inclined platen 13B and the encoder sensor 26 during the pattern printing operation. It is a value that can be acquired based on the signal. T ′ (actual cycle) is a value that can be acquired based on a signal from the encoder sensor 26 during the pattern printing operation. Accordingly, the inkjet head 11 can be driven at the corrected ink discharge timing obtained by correcting the reference ink discharge timing with the correction time Δt by determining the inclination amount D assuming one inclination platen 13B.

  When a predetermined printing pattern P is printed, it is confirmed whether or not the pattern printing operation has been repeated a preset number of times (step ST3). If the set number of times has not been reached, the paper feed motor is driven to perform a paper feed operation for feeding the recording paper 3 by a predetermined amount in the paper feed direction (step ST4).

  Thereafter, the pattern printing operation is repeated a predetermined number of times while increasing the inclination amount D of the assumed inclination platen 13B stepwise (steps ST2, ST3, ST4).

  More specifically, the inclination amount D of the inclination platen 13B is increased, and the correction time Δt is changed using the equation (j) so as to correspond to the inclination amount D, and at different correction ink ejection timings for each pattern printing operation. The inkjet head 11 is driven to perform printing.

  Here, since the correction time Δt corresponding to the inclination amount D of the inclined platen 13B can be obtained using the equation (j), it is easy to repeat the pattern printing operation by changing the inclination amount D of the inclined platen 13B. it can. Note that the amount of increase in the tilt amount D (the amount of change in the correction time) to be increased for each pattern printing operation and the number of times the pattern printing operation is repeated depend on the distribution of the tilt amount D of the platen 13 in the actual ink jet printer 1. It is preset based on this.

  If it is determined in step ST3 that the pattern printing operation has been performed a set number of times, a comparative examination operation for comparing and examining a plurality of printing results is performed. The comparison work is performed visually by the operator.

  In the comparative examination work, the one that has obtained the target print result R in which the ink droplets have landed on the target print position on the recording paper 3 is selected from the plurality of print results shown in FIG. Then, the pattern printing operation from which the target printing result R is obtained is specified (step ST5). The target print result R is, for example, a print pattern P with no deviation in the paper width direction W and a higher print density than other print results. Therefore, the target print result R can be selected from a plurality of print results by using the deviation and density as a reference. The comparative study work can be automatically performed using a camera and an image processing apparatus.

  After the pattern printing operation that has obtained the target printing result R is specified, the corrected ink discharge timing in the specified pattern printing operation is input to the setting unit 46 of the control unit 40 by a command or the like, and the corrected ink discharge pattern is input. The ink ejection timing of the ink jet printer 1 is set (step ST6).

  Here, if the corrected ink discharge timing in the pattern printing operation in which the target print result R is obtained is set to the ink discharge timing of the ink jet printer 1, the platen gap between the ink jet head 11 and the platen 13 in the subsequent printing is set. The deviation of the ink droplet landing position from the target printing position due to the change can be corrected. Further, it is possible to correct the deviation of the ink droplet landing position from the target printing position due to the moving speed of the inkjet head 11.

  That is, in a case where the target print result R is obtained as a print result in a plurality of pattern printing operations performed while changing the correction time Δt stepwise so as to correspond to the assumed inclination amount D of the inclination platen 13B, This is a case where the inclination amount D of the inclined platen 13B assumed in each pattern printing operation and the actual inclination amount of the platen 13 are equal (same inclination angle or close inclination angle). Therefore, if the corrected ink discharge timing in the pattern printing operation in which the target print result R is obtained is set to the ink discharge timing of the inkjet printer 1, the ink droplet landing position caused by the change in the platen gap in the subsequent printing is set. Deviation from the target print position can be corrected, and print quality can be maintained.

  Further, in this example, in the ink ejection timing correction operation, the Bi-d adjustment operation is performed before the pattern printing operation, and the landing position caused by the difference between the moving speed at the forward movement and the moving speed at the backward movement is changed. The gap is corrected. As a result, it is possible to avoid the landing position from being shifted due to the difference between the moving speed during the forward movement and the moving speed during the backward movement in the printing result of each pattern printing operation. As a result, the number of times the pattern printing operation is repeated until the target print result R is obtained can be reduced, so that the amount of ink consumed to correct the ink ejection timing can be suppressed. In addition, the printing result of the pattern printing operation does not show a deviation of the landing position due to the difference between the moving speed at the forward movement and the moving speed at the backward movement, and the number of pattern printing operations can be reduced. It becomes easy to select the target print result R from the print results.

  Furthermore, in this example, since printing is performed on the end portion of the recording paper 3 in the paper width direction W in the pattern printing operation, it is easy to specify the target print result R from a plurality of print results. That is, when the platen 13 is inclined, the deviation of the landing position of the ink droplets becomes large at the end portion in the paper width direction W of the recording paper 3, so that the ink droplets are based on the figure formed at such positions. If it is confirmed whether or not the ink has landed at the target print position on the recording paper 3, it is easy to specify the target print result R from a plurality of print results.

(Other embodiments)
The ink jet printer 1 has a configuration in which the platen 13 moves in conjunction with opening / closing of the opening / closing lid 6. However, the present invention may be applied to an ink jet printer in which the platen is fixed to a printer body frame or the like. . In this case, the print quality can be maintained even when the platen 13 is inclined due to component tolerance or the like.

  In the above example, printing is performed on both end portions in the paper width direction W of the recording paper 3 by the pattern printing operation for printing the printing pattern P. However, the recording paper 3 is printed by the pattern printing operation for printing the printing pattern P. If printing is performed on at least one end portion in the paper width direction W, the target print result R can be specified from a plurality of print results. Here, if only one end portion in the paper width direction of the recording paper is printed in the pattern printing operation, the amount of ink consumed for correcting the ink ejection timing can be suppressed.

  In the above example, in the ink ejection timing correction operation, the Bi-d adjustment operation is performed before the pattern printing operation. However, the Bi-d adjustment operation may be omitted.

1 .... Inkjet printer 2 .... roll paper 3 .... recording paper 5 .... printer body 5a ... exterior case 5b ... opening 6 .... opening / closing lid 7, ... output outlet 8, ··· Discharge guide, 9 ·· Cover opening / closing lever, 10 ·· Roll paper storage section, 11 ·· Inkjet head, 11a ·· Ink nozzle surface, 12 ·· Conveyance path, 13 ·· Platen, 13A ·· Ideal platen , 13B ··· Inclined platen, 15 ··· Printer body frame, 16 · · Head unit frame, 17 · · Carriage, 18 · · Carriage moving mechanism (head moving mechanism), 20 · · Carriage guide shaft, 21 · · Carriage motor , 22 · · Drive pulley, 23 · · Timing belt, 24 · · Linear encoder, 25 · · Linear scale, 26 · · Encoder sensor, 0 ... tension guide, 31 ... rear paper feed roller, 32 ... back paper press roller, 33 ... front paper feed roller, 34 ... front paper press roller, 35 ... paper feed motor, 36 ... Conveyance mechanism, 40 ... Control unit, 41 ... Communication unit, 45 ... Print control unit, 46 ... Setting unit, A ... Print position, D ... Tilt amount, L0 ... Center of platen tilt Axis, M ... Print pattern, R ... Target print result, W ... Paper width direction

Claims (5)

In an ink jet printer comprising: an ink jet head that moves in the paper width direction of a recording paper to eject ink droplets; and a platen that moves to a facing position facing the ink jet head and an open position not facing the ink jet head.
A platen gap between the inkjet head and the platen located at the opposite position is constant in the paper width direction, and in a paper feed direction orthogonal to the paper width direction at a central position in the paper width direction on the platen. Assuming an inclined platen inclined around the extending axis,
The ink jet head is reciprocated in the paper width direction, and a predetermined print pattern is printed at a corrected ink discharge timing obtained by correcting a preset reference ink discharge timing by a correction time corresponding to an inclination amount of the inclined platen with respect to the reference platen. The pattern printing operation is repeated by changing the inclination amount stepwise,
An ink discharge timing correction method for an ink jet printer, wherein the correction ink discharge timing of the pattern printing operation in which the ink droplets land on a target print position on the recording paper is set as the ink discharge timing. An encoder that detects movement of the inkjet head in the paper width direction;
When the inkjet head moves at a preset reference speed, the encoder outputs a reference cycle T, the ink droplet ejection speed Vi, and the encoder at a predetermined position of the inkjet head that moves in the paper width direction. T ′ is the actual period of the signal output from PG, PG is the gap between the inkjet head and the reference platen, and ΔPG is the separation distance between the inclined platen and the reference platen at the predetermined position. 2. The ink ejection timing correction method for an ink jet printer according to claim 1, wherein the correction time Δt corresponding to the tilt amount of the tilt platen is represented by the following equation.
Δt = T / Vi × {PG × (1 / T−1 / T ′) − ΔPG × 1 / T ′}   Before performing the pattern printing operation, a Bi-d adjustment operation is performed, and the inkjet head is driven at the reference ink ejection timing to eject ink droplets onto the recording paper on the platen. The ink ejection timing correction method for an ink jet printer according to claim 2, wherein a deviation between the landing position and the landing position at the time of backward movement is corrected.   4. The ink discharge timing correction method for an ink jet printer according to claim 1, wherein printing is performed on at least one end portion of the recording paper in the paper width direction in the pattern printing operation. 5. An inkjet head that ejects ink drops;
A platen that moves between a facing position facing the inkjet head and an open position not facing the inkjet head ;
A head moving mechanism for moving the inkjet head in the paper width direction of the recording paper on the platen;
A transport mechanism for transporting the recording paper in a direction orthogonal to the paper width direction,
A platen gap between the inkjet head and the platen located at the opposite position is constant in the paper width direction, and in a paper feed direction orthogonal to the paper width direction at a central position in the paper width direction on the platen. Assuming an inclined platen inclined around the extending axis,
The ink jet head is reciprocated in the paper width direction, and a predetermined print pattern is printed at a corrected ink discharge timing obtained by correcting a preset reference ink discharge timing by a correction time corresponding to an inclination amount of the inclined platen with respect to the reference platen. The pattern printing operation is repeated by changing the inclination amount stepwise,
An ink jet printer, wherein the corrected ink discharge timing of the pattern printing operation in which the ink droplets land on a target print position on the recording paper is set to the ink discharge timing.