JP2013163333A - Method for controlling line inkjet printer, line inkjet printer and method for manufacturing line inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method suitable for a line inkjet printer, capable of simplifying the circuit configuration of a printing control unit, and also, improving quality of printing on a recording paper.SOLUTION: A line inkjet printer includes: an inkjet head 3; a paper feed motor 12; a first encoder 31 configured to perform a feedback control of the paper feed motor 12; a second encoder 34 configured to control the ejection timing of ink from the inkjet head 3; and a rotating shaft 20 to which a first encoder scale 32 of the first encoder 31 and a second encoder scale 35 of the second encoder 34 are fixed. When printing on the recording paper, a first output signal S1 from the first encoder 31 and a second output signal S2 from the second encoder 34 are corrected such that the rotating speed of the paper feed motor 12 calculated based on the first output signal S1 may match with the rotating speed of the paper feed motor 12 calculated based on the second output signal S2.

Description

  The present invention relates to a method for controlling a line inkjet printer, a line inkjet printer, and a method for manufacturing the line inkjet printer.

  Conventionally, as an inkjet printer, a line inkjet that performs printing on recording paper by performing a paper feeding operation for feeding recording paper to a printing position by a stopped inkjet head and an ink ejection operation from the inkjet head in parallel. A printer is known (for example, see Patent Document 1). A line inkjet printer described in Patent Document 1 includes a transport mechanism having a transport roller for transporting recording paper and a transport motor that drives the transport roller, and an encoder that outputs a pulse signal as the transport roller rotates. And a control device for controlling the transport motor and the inkjet head. The control device includes a first low-pass filter and a second low-pass filter to which a pulse signal output from the encoder is input. The first low-pass filter is configured to pass a pulse signal having a frequency equal to or lower than the first frequency, and the second low-pass filter is configured to pass a pulse signal having a frequency lower than the second frequency higher than the first frequency. . This control device controls the transport motor based on the pulse signal that has passed through the first low-pass filter, and controls the ink ejection timing of the inkjet head based on the pulse signal that has passed through the second low-pass filter.

JP 2009-83401 A

  In the line inkjet printer described in Patent Document 1, a first low-pass filter that passes a pulse signal having a frequency equal to or lower than the first frequency is used for the control system of the transport mechanism, and the control system for the inkjet head has a first higher frequency than the first frequency. Since the second low-pass filter that passes a pulse signal of two frequencies or less is used, the pulse signal from the encoder can be filtered with an optimum frequency characteristic in each control system. Therefore, in this line inkjet printer, it is possible to stably convey recording paper with good followability to the speed command by a feed motor controlled by feedback, and to improve the recording accuracy by the inkjet head. As a result, it is possible to improve the printing quality on the recording paper. However, in the line inkjet printer described in Patent Document 1, the first low-pass filter and the second low-pass filter are used, so that the circuit configuration of the control device is complicated.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a line inkjet that can improve the print quality on recording paper while simplifying the circuit configuration of a print control unit that controls a paper feed motor for transporting the recording paper and an inkjet head. The object is to propose a control method for a line inkjet printer suitable for a printer. Another object of the present invention is to propose a line inkjet printer controlled by such a control method and a method for manufacturing the line inkjet printer.

  In order to solve the above-described problems, a control method for a line inkjet printer according to the present invention includes an inkjet head that ejects ink toward a recording sheet, and the recording sheet along a conveyance path that passes through a printing position by the inkjet head. A paper feed roller for conveying, a paper feed motor for rotating the paper feed roller, a first encoder for detecting the rotational speed of the paper feed motor and feedback-controlling the paper feed motor, and the inkjet head The second encoder for controlling the ink ejection timing in the printer, the first encoder scale constituting the first encoder, and the second encoder scale constituting the second encoder are fixed and rotated by the power of the paper feed motor A rotating shaft, and a line having And a rotation speed of the paper feed motor calculated based on a first output signal output from the first encoder during printing on the recording paper, and a control method of the second jet encoder. At least one of the first output signal and the second output signal is corrected so as to match the rotation speed of the paper feed motor calculated based on the output second output signal. .

  In the line inkjet printer of the present invention, a first encoder for detecting the rotational speed of the paper feed motor and performing feedback control of the paper feed motor and a second encoder for controlling ink ejection timing in the inkjet head are separately provided. In preparation. Therefore, an encoder suitable for paper feed control can be used as the first encoder, and an encoder suitable for ink ejection control can be used as the second encoder. In the line inkjet printer of the present invention, the first encoder scale constituting the first encoder and the second encoder scale constituting the second encoder are fixed to a common rotating shaft, and the first encoder scale and the second encoder scale are The encoder scale rotates as a unit. Therefore, even if the first encoder and the second encoder are provided separately, the temporal deviation between the first output signal output from the first encoder and the second output signal output from the second encoder is suppressed. can do.

  In this way, in the present invention, an encoder suitable for paper feed control can be used as the first encoder, and an encoder suitable for ink ejection control can be used as the second encoder, and the first encoder can output the first encoder. The time difference between the first output signal and the second output signal output from the second encoder can be suppressed. Therefore, feedback control is performed even if the first and second low-pass filters are not provided in the print control unit that controls the paper feed motor and the inkjet head as in the line inkjet printer described in Patent Document 1. With the paper feed motor, it is possible to carry a stable recording paper with good follow-up to the speed command and to improve the recording accuracy by the ink jet head. As a result, printing on the recording paper is possible. It becomes possible to improve the quality. That is, it is possible to improve the print quality on the recording paper while simplifying the circuit configuration of the print control unit.

  Here, generally, the target rotational speed of the paper feed motor during printing on recording paper varies as shown in FIG. That is, the paper feed motor during printing accelerates from a stopped state to a predetermined speed at a constant acceleration, then rotates at a constant speed for a predetermined time, and then decelerates and stops at a constant acceleration. In the present invention, the actual rotation speed of the paper feed motor is calculated based on the first output signal output from the first encoder. Ideally, the paper feed roller is not loaded. The rotation speed of the paper feed motor calculated based on the first output signal substantially matches the target rotation speed. However, in practice, for example, at a constant speed at which the paper feed motor rotates at a constant speed even if the paper feed roller is not loaded due to the distortion or eccentricity of the first encoder scale fixed to the rotating shaft. In the region, as shown by the solid line in FIG. 5, the rotation speed of the paper feed motor calculated based on the first output signal periodically fluctuates with a period of one rotation of the first encoder scale with respect to the target rotation speed. There are things to do. Further, the paper feed motor is feedback-controlled based on the actual rotational speed that varies as shown by the solid line in FIG. 5, for example.

  In the present invention, since the second encoder scale is fixed to the rotating shaft that is rotated by the power of the paper feed motor, the actual rotation speed of the paper feed motor is based on the second output signal output from the second encoder. However, as with the rotation speed of the paper feed motor calculated based on the first output signal, the paper is affected by the distortion or eccentricity of the second encoder scale fixed to the rotation shaft. Even if no load is applied to the feed roller, for example, in the constant speed region where the paper feed motor rotates at a constant speed, as shown by the dotted line in FIG. 5, the paper feed motor calculated based on the second output signal The rotation speed may periodically change with a period of one rotation of the second encoder scale with respect to the target rotation speed. Further, the ink ejection timing of the ink jet head is controlled so as to correspond to the actual rotational speed that fluctuates as shown by the dotted line in FIG. 5, for example.

  Even when the rotation speed calculated based on the first output signal and the rotation speed calculated based on the second output signal fluctuate with respect to the target rotation speed in a state where no load is applied to the paper feed roller, If the rotation speed calculated on the basis of the first output signal matches the rotation speed calculated on the basis of the second output signal, the feedback control is performed even when printing on the recording paper in which the paper feed roller is loaded. It is possible to improve the print quality on the recording paper by synchronizing the transport speed and transport amount of the recording paper by the paper feed motor and the ink ejection timing by the ink jet head. However, generally, as shown in FIG. 5, since the rotational speed calculated based on the first output signal is different from the rotational speed calculated based on the second output signal, recording by the paper feed motor is performed. There is a possibility that the printing speed on the recording paper is deteriorated due to the deviation of the paper conveyance speed and conveyance amount from the ink ejection timing by the inkjet head.

  In the present invention, at the time of printing on the recording paper, the rotation speed of the paper feed motor calculated based on the first output signal is matched with the rotation speed of the paper feed motor calculated based on the second output signal. At least one of the first output signal and the second output signal is corrected. For this reason, in the present invention, even if the rotation speed calculated based on the first output signal and the rotation speed calculated based on the second output signal are deviated from each other, It is possible to improve the print quality on the recording paper by synchronizing the transport speed and transport amount with the ink ejection timing by the ink jet head.

  In the present invention, when printing on the recording paper, the rotation speed of the paper feed motor calculated based on the second output signal is the rotation speed of the paper feed motor calculated based on the first output signal. It is preferable to correct the second output signal so as to match. If comprised in this way, control of a line inkjet printer will become easy compared with the case where both the 1st output signal and the 2nd output signal are correct | amended. Further, if configured in this way, the first output signal for feedback control of the paper feed motor is not corrected, so that feedback control of the paper feed motor can be stabilized. As a result, the conveyance of the recording paper by the paper feed roller can be stabilized.

  In the present invention, a speed difference that is a difference between a rotation speed of the paper feed motor calculated based on the first output signal and a rotation speed of the paper feed motor calculated based on the second output signal is calculated. And calculating and storing a correction value for eliminating the speed difference, and at least one of the first output signal and the second output signal based on the correction value when printing on the recording paper. It is preferable to correct one. With this configuration, if there is an abnormality in the first encoder, the second encoder, etc., the speed difference becomes large, and therefore it is possible to detect an abnormality in the first encoder, the second encoder, etc. based on the speed difference. . Further, with this configuration, the line inkjet printer itself can calculate the speed difference and the correction value. For example, when the first encoder scale or the second encoder scale is replaced by repairing the line inkjet printer, The correction value can be calculated and stored on the spot.

  In the present invention, it is preferable that the speed difference is calculated and the correction value is calculated and stored when the line inkjet printer is turned on. With this configuration, the first output is based on the correction value reflecting the influence of the rotational speed calculated based on the first output signal and the temporal change in the rotational speed calculated based on the second output signal. At least one of the signal and the second output signal can be corrected. Therefore, printing on the recording paper caused by the change over time is suppressed by suppressing the deviation caused by the change over time between the recording paper conveyance speed and conveyance amount by the paper feed motor and the ink ejection timing by the inkjet head. It becomes possible to suppress deterioration in quality.

  The line inkjet printer of the present invention is controlled by the above-described line inkjet printer control method. The line inkjet printer includes a speed reduction mechanism that reduces the rotation of the paper feed motor and transmits the speed to the paper feed roller, the speed reduction mechanism includes the rotation shaft, and the rotation shaft includes the paper feed motor. It is preferable that the rotation speed is lower than that of the paper feed roller. With this configuration, the first and second encoder scales are attached to the rotation shaft of the paper feed roller because the first and second encoder scales are attached to the rotation shaft that rotates faster than the paper feed roller. As compared with, it is possible to reduce the diameters of the first and second encoder scales while ensuring the resolution of the first and second encoders.

  In this case, since the rotation shaft to which the first encoder scale is attached is different from the rotation shaft of the paper feed roller, the paper feed motor calculated based on the first output signal output from the first encoder is used. Even if the rotation speed is controlled, it is difficult to appropriately control the rotation speed of the paper feed roller, and the print quality on the recording paper tends to be lowered. However, in the present invention, as described above, the recording paper conveyance speed and conveyance amount by the feedback-controlled paper feed motor and the ink ejection timing by the inkjet head are synchronized with each other to improve the print quality on the recording paper. It becomes possible.

  When manufacturing the line inkjet printer of the present invention, the rotation speed of the paper feed motor calculated based on the first output signal and the rotation speed of the paper feed motor calculated based on the second output signal are calculated. It is preferable to calculate a correction value for matching and store the correction value in a print control unit that controls the paper feed motor and the inkjet head. In this case, it is possible to eliminate the need to calculate and store the correction value when using the line inkjet printer, and thus it is possible to simplify the control when using the line inkjet printer. In this case, the rotation speed of the paper feed motor calculated based on the first output signal and the rotation speed of the paper feed motor calculated based on the second output signal when the line inkjet printer is manufactured. When the speed difference is calculated, it is possible to detect an abnormality in the first encoder, the second encoder, etc. based on the calculated speed difference.

1 is a schematic longitudinal sectional view showing an overall configuration of a printer according to an embodiment of the present invention. The schematic plan view which looked at the inkjet head from the nozzle surface side. Explanatory drawing of the control system which controls a deceleration mechanism and printing operation. The figure which shows an example of the target rotational speed of a paper feed motor. The figure which shows an example of the rotational speed of the paper feed motor calculated based on the 1st output signal, and the rotational speed of the paper feed motor calculated based on the 2nd output signal.

  A line inkjet printer control method and a line inkjet printer to which the present invention is applied will be described below with reference to the drawings.

(Overall configuration of line inkjet printer)
FIG. 1 is a schematic longitudinal sectional view showing the overall configuration of a line inkjet printer 1 according to an embodiment of the present invention. FIG. 2 is a schematic plan view of the inkjet head 3 viewed from the ink nozzle surface side. The line inkjet printer 1 (hereinafter referred to as “printer 1”) performs printing on a long recording paper P using a plurality of types of color inks. A roll paper loading unit 2 is provided at the rear portion of the printer 1, and the recording paper P drawn from the roll paper Q loaded therein is a platen 4 that defines a printing position A by the ink jet head 3. It is transported along a transport path 5 that passes through the surface.

  A paper guide 6 for preventing skew of the recording paper P is disposed above the roll paper loading unit 2. Behind the paper guide 6, a feeding roller 7 for pulling out the recording paper P from the roll paper Q is disposed. The feeding roller 7 is rotated in the forward and reverse directions by a feeding motor (not shown).

  The recording paper P is drawn obliquely rearward from the roll paper Q toward the feeding roller 7, and is then wound around the feeding roller 7. The recording paper P drawn forward through the feed roller 7 passes through the load roller 8 disposed behind the paper guide 6 and then the paper guide 6 and the paper feed roller pair 9 disposed in front thereof. Is set so as to pass through the surface of the platen 4 via. The paper feed roller pair 9 includes a paper feed roller 10 that comes into contact with the recording paper P from below, and a pressing roller 11 that is urged from above to the paper feed roller 10 side. A paper feed motor 12 for rotating the paper feed roller 10 in the forward and reverse directions is disposed below the paper feed roller pair 9. Between the paper feed motor 12 and the paper feed roller 10, a speed reduction mechanism 13 that decelerates the rotation of the paper feed motor 12 and transmits it to the paper feed roller 10 is configured.

  Above the platen 4, the inkjet head 3 mounted on the carriage 14 is disposed. An ink cartridge mounting portion 15 is provided below the platen 4. The ink cartridge mounting unit 15 is mounted with ink cartridges that store inks of four colors, cyan, magenta, yellow, and black. When the ink cartridge is mounted in the ink cartridge mounting portion 15, the ink supply pump mechanism (not shown) is connected to the ink tank in the ink cartridge, and ink can be supplied to the inkjet head 3. Become.

  As shown in FIG. 2, the ink jet head 3 is a composite head including a first head 3A and a second head 3B. The first head 3A is formed with an ink nozzle row B that ejects black ink and an ink nozzle row C that ejects cyan ink, and the second head 3B has an ink nozzle row that ejects magenta ink. M and an ink nozzle row Y for discharging yellow ink are formed. The first and second heads 3A and 3B are formed wider than the recording paper P. Each of the ink nozzle rows B, C, M, and Y extends in the recording sheet width direction (printer width direction) of the recording sheet P, and is arranged in an area having a width that can cover the entire printing area of the recording sheet P.

  The ink-jet head 3 is mounted on the carriage 14 so as to reciprocate between a printing position A shown in FIG. 1 and a home position (not shown) deviated from the conveyance path 5 to the outside in the printer width direction. It is configured. The ink jet head 3 performs printing on the recording paper P that is transported through the transport path 5 while stopped at the printing position A. When printing is completed, the ink jet head 3 is retracted to the home position and stands by. During standby, a maintenance operation for preventing or eliminating clogging of the ink nozzles of the inkjet head 3 is performed.

  When the printer 1 receives a print command from an external device with the recording paper P drawn from the roll paper Q being set in the transport path 5, the printer 1 moves the inkjet head 3 from the home position toward the print position A. Then, it is positioned at the printing position A and stopped. In this state, the paper feeding roller 10 is rotated to convey the recording paper P, and the ink ejection operation for ejecting ink from the inkjet head 3 toward the recording paper P is performed in parallel. Printing is performed on the recording paper P passing through the position A.

(Configuration of deceleration mechanism and control system)
FIG. 3 is an explanatory diagram of the speed reduction mechanism 13 and a control system that controls the printing operation. The speed reduction mechanism 13 includes an intermediate shaft (rotating shaft) 20 disposed in parallel with the paper feed roller 10. The speed reduction mechanism 13 includes a first pulley 21 that is attached to the output shaft of the paper feed motor 12, a second pulley 22 that is larger in diameter than the first pulley 21 and attached to the intermediate shaft 20, and more than the second pulley 22. A third pulley 23 having a small diameter and attached to the intermediate shaft 20 and a fourth pulley 24 having a diameter larger than that of the paper feed roller 10 and the third pulley 23 and attached to the rotation shaft of the paper feed roller 10 are provided. The second pulley 22 is fixed to the central portion of the intermediate shaft 20 in the axial direction, and the third pulley 23 is fixed to one shaft end portion of the intermediate shaft 20. The fourth pulley 24 is fixed to one shaft end portion of the rotation shaft of the paper feed roller 10. A first endless belt 25 is bridged between the first pulley 21 and the second pulley 22, and a second endless belt 26 is bridged between the third pulley 23 and the fourth pulley 24. ing. In the speed reduction mechanism 13, the intermediate shaft 20 rotates at a lower speed than the paper feed motor 12 and at a higher speed than the paper feed roller 10.

  A first encoder 31 for detecting the rotational speed of the paper feed motor 12 and performing feedback control of the paper feed motor 12 is controlled at the other shaft end portion of the intermediate shaft 20 and the ink ejection timing in the inkjet head 3 is controlled. A second encoder 34 is provided. The first encoder 31 includes a first encoder scale 32 formed in a disk shape and an optical sensor 33. The second encoder 34 includes a second encoder scale 35 formed in a disk shape and an optical sensor 36.

  The first encoder scale 32 and the second encoder scale 35 are fixed to the intermediate shaft 20 with a predetermined interval in the axial direction of the intermediate shaft 20. Slits are formed at equiangular intervals in the outer peripheral edge portions of the first encoder scale 32 and the second encoder scale 35. The sensor 33 includes a light emitting element and a light receiving element that are arranged so as to sandwich the slit portion of the first encoder scale 32. The sensor 36 includes a light emitting element and a light receiving element that are arranged so as to sandwich the slit portion of the second encoder scale 35. The resolution of the first encoder 31 is higher than the resolution of the second encoder 34. In this embodiment, the first encoder 31 has a resolution four times that of the second encoder 34.

  The first encoder 31 is connected to a print control unit 40 that controls the printing operation of the printer 1, and the first output signal S <b> 1 output from the first encoder 31 is input to the print control unit 40. The print control unit 40 is an electronic circuit that includes a CPU and a ROM equipped with firmware. Based on the first output signal S1, the print control unit 40 calculates the rotation speed and rotation amount of the paper feed motor 12 (that is, the conveyance speed and the paper feed amount of the recording paper P by the paper feed roller 10). Based on the calculation result, the paper feed motor 12 is controlled to control the conveyance speed and the paper feed amount of the recording paper P by the paper feed roller 10.

  Similar to the first encoder 31, the second encoder 34 is connected to the print control unit 40, and the second output signal S <b> 2 output from the second encoder 34 is input to the print control unit 40. The second encoder 34 outputs a predetermined number of pulse signals (a number depending on the resolution) while the intermediate shaft 20 makes one rotation (that is, while the paper feed amount by the paper feed roller 10 reaches a predetermined amount). Output as the second output signal S2. The print controller 40 generates a drive waveform for ejecting ink from the ink nozzles B, C, M, and Y of the ink jet head 3 based on the second output signal S2. In addition, the print control unit 40 drives a piezoelectric element mounted on the inkjet head 3 based on the generated drive waveform to eject ink from the inkjet head 3.

  The speed reduction mechanism 13 includes a detection mechanism (not shown) for detecting the origin position in the rotation direction of the intermediate shaft 20. Alternatively, the paper feed motor 12 is provided with an encoder, and the origin position in the rotation direction of the intermediate shaft 20 can be detected based on an output signal from the encoder.

(Control of line inkjet printer)
The actual rotation speed of the paper feed motor 12 is calculated based on the first output signal S1. As described above, when the paper feed roller 10 is not loaded, ideally, the rotational speed of the paper feed motor 12 calculated based on the first output signal S1 substantially matches the target rotational speed. Actually, even if no load is applied to the paper feed roller 10 due to the distortion or eccentricity of the first encoder scale 32 fixed to the intermediate shaft 20, for example, as shown by the solid line in FIG. The rotation speed of the paper feed motor 12 calculated based on the one output signal S1 may fluctuate with respect to the target rotation speed. In this embodiment, since the second encoder scale 35 is fixed to the intermediate shaft 20, the rotation speed of the paper feed motor 12 can be calculated based on the second output signal S2. If the paper feed roller 10 is not loaded, ideally, the rotational speed of the paper feed motor 12 calculated based on the second output signal S2 also coincides with the target rotational speed. Even if no load is applied to the paper feed roller 10 due to the influence of the distortion or eccentricity of the second encoder scale 35 fixed to 20, it is based on the second output signal S2, for example, as shown by the dotted line in FIG. The rotational speed of the paper feed motor 12 calculated in this way may vary with respect to the target rotational speed.

  In general, as shown in FIG. 5, the rotational speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotational speed of the paper feed motor 12 calculated based on the second output signal S2. It is off. That is, the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 used for feedback control of the paper feed motor 12 and the paper feed motor 12 used for controlling the ink discharge timing of the inkjet head 3 are used. The rotational speed is off. Therefore, the recording paper P is in a state where the rotational speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotational speed of the paper feed motor 12 calculated based on the second output signal S2 are deviated. When printing on the recording paper P is performed, the transport speed and transport amount of the recording paper P by the paper feed motor 12 and the ink ejection timing by the ink jet head 3 are shifted, and the print quality on the recording paper P deteriorates.

  Therefore, in this embodiment, when printing on the recording paper P, the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 and the paper feed motor 12 calculated based on the second output signal S2. The print control unit 40 corrects the second output signal S2 so as to match the rotation speed. That is, when printing on the recording paper P, the rotational speed of the paper feed motor 12 calculated based on the second output signal S2 is matched with the rotational speed of the paper feed motor 12 calculated based on the first output signal S1. As described above, the print control unit 40 corrects the second output signal S2.

  Specifically, the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 when the paper feed motor 12 is rotated in a state where no load is applied to the paper feed roller 10, and the second The print control unit 40 calculates a speed difference D, which is a difference from the rotation speed of the paper feed motor 12 calculated based on the output signal S2, for each predetermined rotation angle of the paper feed motor 12, and the speed difference D is calculated. The print control unit 40 calculates in advance a correction value to be eliminated for each predetermined rotation angle of the paper feed motor 12, and stores it in a table. Further, when printing on the recording paper P, the print control unit 40 corrects the second output signal S2 based on the correction value. In the present embodiment, the print control unit 40 calculates the speed difference D and calculates and stores the correction value in the factory when the printer 1 is manufactured. Further, in the printer 1 after being installed by the user, when the power is turned on, the print control unit 40 calculates the speed difference D and calculates and stores the correction value.

(Main effects of this embodiment)
As described above, the printer 1 according to this embodiment includes the first encoder 31 for feedback control of the paper feed motor 12 and the second encoder 34 for controlling the ink ejection timing in the inkjet head 3 separately. I have. Therefore, an encoder suitable for paper feed control can be used as the first encoder 31, and an encoder suitable for ink ejection control can be used as the second encoder. In the present embodiment, the first encoder scale 32 and the second encoder scale 35 are fixed to the common intermediate shaft 20, and the first encoder scale 32 and the second encoder scale 35 rotate integrally. Therefore, even if the first encoder 31 and the second encoder 34 are provided separately, it is possible to suppress a time lag between the first output signal S1 and the second output signal S2. Therefore, in this embodiment, unlike the line inkjet printer described in Patent Document 1, even if the first and second low-pass filters are not provided in the print control unit 40, the speed is controlled by the paper feed motor 12 that is feedback-controlled. It becomes possible to convey the recording paper P with good followability with respect to the command, and to improve the recording accuracy by the inkjet head 3, and as a result, the printing quality on the recording paper P can be improved. It becomes possible to increase. That is, it is possible to improve the print quality on the recording paper P while simplifying the circuit configuration of the print control unit 40.

  In this embodiment, when printing on the recording paper P, the rotational speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotational speed of the paper feed motor 12 calculated based on the second output signal S2. The print control unit 40 corrects the second output signal S2 so as to match. Therefore, even if the rotational speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotational speed of the paper feed motor 12 calculated based on the second output signal S2 are different, the paper feed motor Therefore, the print quality on the recording paper P can be improved by synchronizing the transport speed and transport amount of the recording paper P by 12 and the ink ejection timing by the ink jet head 3. In this embodiment, since the second output signal S2 is corrected, the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 and the paper calculated based on the second output signal S2. As compared with the case where both the first output signal S1 and the second output signal S2 are corrected so as to match the rotation speed of the feed motor 12, the control of the printer 1 becomes easier. Further, since the first output signal S1 for feedback control of the paper feed motor 12 is not corrected, the feedback control of the paper feed motor 12 can be stabilized, and as a result, the recording paper P of the recording paper P by the paper feed roller 10 can be stabilized. It becomes possible to stabilize conveyance.

  In the present embodiment, a print control is performed for a speed difference D between the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotation speed of the paper feed motor 12 calculated based on the second output signal S2. The print control unit 40 calculates and stores a correction value for eliminating the speed difference D while the unit 40 calculates. That is, the printer 1 itself has a function of calculating the speed difference D and the correction value. Therefore, for example, when the first encoder scale 32 or the second encoder scale 35 is replaced by repairing the printer 1, it is possible to calculate and store the correction value on the spot. In this embodiment, the printing control unit 40 calculates the speed difference D, and if the first encoder 31 or the second encoder 34 is abnormal, the speed difference D increases. When the power of 1 is turned on, it is possible to detect an abnormality in the first encoder 31 and the second encoder 34 based on the speed difference D.

  In this embodiment, when the printer 1 is turned on, the print control unit 40 calculates the speed difference D and calculates and stores the correction value. Therefore, the second output signal S2 is based on the correction value reflecting the influence of the rotational speed calculated based on the first output signal S1 and the temporal change in the rotational speed calculated based on the second output signal S2. Can be corrected. Therefore, the recording paper P caused by the change with time is suppressed by suppressing the deviation caused by the change with time of the conveyance speed and conveyance amount of the recording paper P by the paper feed motor 12 and the ink ejection timing by the inkjet head 3. It is possible to suppress a decrease in print quality on P.

  In this embodiment, the first and second encoder scales 32 and 35 are attached to the intermediate shaft 20 that rotates at a higher speed than the paper feed roller 10. Therefore, as compared with the case where the first and second encoder scales 32 and 35 are attached to the rotation shaft of the paper feed roller 10, the first and second encoders 31 and 34 are secured while maintaining the resolution. The diameters of the encoder scales 32 and 35 can be reduced. Therefore, even when the printer 1 is downsized, the inkjet that moves in the apparatus width direction on the transport path 5 when the inkjet head 3 is reciprocated between the printing position A and the home position with the carriage 14 mounted. Interference between the head 3 and the carriage 14 and the first and second encoder scales 32 and 35 can be prevented.

(Other embodiments)
In the embodiment described above, when printing on the recording paper P, the print control unit 40 calculates the rotation speed of the paper feed motor 12 calculated based on the second output signal S2 based on the first output signal S1. The second output signal S2 is corrected so as to match the rotation speed of the paper feed motor 12. However, the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 is changed to the second output signal S2. The first output signal S1 may be corrected so as to match the rotation speed of the paper feed motor 12 calculated based on this. In this case, for example, similarly to the above-described embodiment, the print control unit 40 may calculate the speed difference D and calculate and store a correction value for eliminating the speed difference D.

  Further, the print control unit 40 matches the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 and the rotation speed of the paper feed motor 12 calculated based on the second output signal S2. In addition, the first output signal S1 and the second output signal S2 may be corrected. In this case, for example, the difference between the rotation speed of the paper feed motor 12 calculated based on the first output signal S1 and the target rotation speed is calculated, and a correction value for eliminating this difference is calculated, Based on the correction value, the first output signal is corrected, and the difference between the rotation speed of the paper feed motor 12 calculated based on the second output signal S2 and the target rotation speed is calculated, and this difference is eliminated. A correction value may be calculated and the second output signal may be corrected based on the correction value.

  In the above-described embodiment, when the printer 1 is turned on, the print control unit 40 calculates the speed difference D and calculates and stores the correction value. However, the rotation speed calculated based on the first output signal S1 and the correction value are stored. Since the rotational speed calculated based on the second output signal S2 does not vary greatly over time, the speed difference D is calculated and the correction value only when the printer 1 is manufactured or maintained. May be calculated and stored. In this case, control when the printer 1 is turned on can be simplified. In this case, the speed difference D and the correction value may be calculated by a predetermined device provided separately from the printer 1. That is, the printer 1 itself does not have to have the function of calculating the speed difference D and the correction value. In the above-described embodiment, the speed difference D is calculated and the correction value is calculated and stored in the factory when the printer 1 is manufactured. However, the speed difference D and the correction value are calculated when the printer 1 is manufactured. It is not necessary.

  In the embodiment described above, the first encoder scale 32 and the second encoder scale 35 are formed separately, but the radially inner portion of one disk-shaped member becomes the second encoder scale 35, and this circle A radially outer portion of the plate-like member may be the first encoder scale 32. In the above-described form, the speed reduction mechanism 13 includes one intermediate shaft 20, but a plurality of intermediate shafts are provided, and the rotation of the paper feed motor 12 is reduced stepwise through the plurality of intermediate shafts. Then, it may be transmitted to the paper feed roller 10. In this case, if the first and second encoder scales 32 and 35 are attached to the same intermediate shaft, the first and second encoder scales 32 and 35 are attached to any intermediate shaft of the plurality of intermediate shafts. May be.

  In the embodiment described above, the speed reduction mechanism 13 includes the intermediate shaft 20, but may not include the intermediate shaft 20. In this case, an endless belt may be bridged between the first pulley 21 of the paper feed motor 12 and the fourth pulley 24 of the paper feed roller 10. In this case, the first and second encoder scales 32 and 35 may be attached to the rotation shaft of the paper feed roller 10. Further, when the speed reduction mechanism 13 includes the intermediate shaft 20, the first and second encoder scales 32 and 35 may be attached to the rotation shaft of the paper feed roller 10.

  DESCRIPTION OF SYMBOLS 1 ... Printer (line inkjet printer), 3 ... Inkjet head, 5 ... Conveyance path, 10 ... Paper feed roller, 12 ... Paper feed motor, 13 ... Deceleration mechanism, 20. ..Intermediate shaft (rotating shaft), 31 ... first encoder, 32 ... first encoder scale, 34 ... second encoder, 35 ... second encoder scale, 40 ... print control unit , A ... print position, D ... speed difference, P ... recording paper, S1 ... first output signal, S2 ... second output signal

Claims (7)

An inkjet head that ejects ink toward the recording paper;
A paper feed roller for transporting the recording paper along a transport path passing through a printing position by the inkjet head;
A paper feed motor for rotating the paper feed roller;
A first encoder for detecting a rotation speed of the paper feed motor and feedback-controlling the paper feed motor;
A second encoder for controlling the ejection timing of ink in the inkjet head;
A control method for a line inkjet printer, comprising: a first encoder scale constituting the first encoder and a second encoder scale constituting the second encoder, and a rotating shaft fixed by the power of the paper feed motor. And
Based on the rotation speed of the paper feed motor calculated based on the first output signal output from the first encoder and the second output signal output from the second encoder during printing on the recording paper. A control method for a line inkjet printer, wherein at least one of the first output signal and the second output signal is corrected so as to match the calculated rotation speed of the paper feed motor.   At the time of printing on the recording paper, the rotation speed of the paper feed motor calculated based on the second output signal is matched with the rotation speed of the paper feed motor calculated based on the first output signal. The method of controlling a line inkjet printer according to claim 1, wherein the second output signal is corrected. Calculating a speed difference that is a difference between a rotation speed of the paper feed motor calculated based on the first output signal and a rotation speed of the paper feed motor calculated based on the second output signal; Calculate and store a correction value for eliminating the speed difference,
3. The line inkjet printer according to claim 1, wherein at least one of the first output signal and the second output signal is corrected based on the correction value when printing on the recording paper. 4. Control method.   4. The method of controlling a line inkjet printer according to claim 3, wherein the speed difference is calculated and the correction value is calculated and stored when the line inkjet printer is turned on.   A line inkjet printer controlled by the method for controlling a line inkjet printer according to any one of claims 1 to 4. A deceleration mechanism that decelerates the rotation of the paper feed motor and transmits it to the paper feed roller
The speed reduction mechanism has the rotating shaft,
The line inkjet printer according to claim 5, wherein the rotation shaft rotates at a lower speed than the paper feed motor and at a higher speed than the paper feed roller.   7. The paper feed motor calculated based on the rotation speed of the paper feed motor calculated based on the first output signal and the second output signal when manufacturing the line inkjet printer according to claim 5 or 6. A method for manufacturing a line ink jet printer, comprising: calculating a correction value for matching the rotation speed of the paper and storing the correction value in a print control unit that controls the paper feed motor and the ink jet head.

Images