JP2020131516A - Ink jet printer, ejection timing correction method of ink jet printer and program - Google Patents

Abstract

To properly correct ejection timing of ink.SOLUTION: An ink jet printer ejects ink on the basis of an encoder pulse showing a rotational position of an endless conveyance belt drive shaft, and comprises: a belt reference position detection part which detects that the conveyance belt rotates around; a drive shaft reference position detection part which detects that the belt drive shaft rotates around; and a control part which can set ejection timing between a signal of the encoder pulse and an ejection operation, in which the control part comprises at least a first correction function for correcting the ejection timing by a first correction table on the basis of a signal from the belt reference position detection part, generates a plurality of test patterns on the same medium with heads at different ejection timings, at a position spaced apart for N rotations (N is an integer, and N≥1) of the belt drive shaft by using a signal from the drive shaft reference position detection part as a reference position, and creates profile data for one rotation of the conveyance belt to determine the first correction table on the basis of a result by reading the test patterns.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inkjet printer capable of correcting the ejection timing of a nozzle, a ejection timing correction method and a program of the inkjet printer.

In an inkjet printer that prints on a medium such as paper, the medium is belt-conveyed, and ink is ejected from the nozzle to the medium in synchronization with the pulse signal output from the encoder attached to the drive shaft that carries the belt. I am printing. FIG. 19 shows a simplified configuration of a general inkjet printer.
In the ink jet printer 1A, an endless transport belt 12 for transporting a medium is hung on transport rollers 10 and 11, and an encoder 13 is attached to the belt drive shaft 10A to detect rotation of the belt drive shaft 10A. .. Heads of each color 15K (for black), 15C (cyan), 15M (magenta), and 15Y (yellow) are installed on the transport belt 12 at predetermined intervals. Each color 15K, 15C, 15M, 15Y is provided with a line-shaped ejection head (not shown), and a desired color is ejected from an ink tank (not shown), and a print on the medium P conveyed by the conveying belt 12 is printed. Will be done. The encoder pulse generated by the output of the encoder 13 is used for ink ejection at the heads 15K, 15C, 15M, and 15Y of each color.

By the way, in general, the drive shaft and the encoder mounted on the drive shaft have a fluctuation component called an eccentric component, which is synchronized with a rotation cycle, due to reasons such as mounting accuracy, memory accuracy, and variation in the radius of the shaft. As a means of suppressing color shift due to an eccentric component, a method of measuring the amount of eccentricity in advance, creating a correction table, and correcting the pulse interval of the encoder according to the value of the correction table is known and used. There is.

Further, the thickness of the transport belt is not uniform, and errors with respect to the thickness are ubiquitous. Especially in the case of a steel transport belt, the error becomes large because there is a joint.
If the thickness of the conveyor belt is not uniform, the radius of gyration fluctuates at the joint with the drive shaft, so the amount of belt movement per unit angular velocity also fluctuates, and there is a deviation between the encoder pulse and the actual amount of movement. Occurs. Normally, one rotation of the shaft and one rotation of the belt are asynchronous, so in order to make a more accurate correction, it is necessary to measure both the eccentric component of the shaft and the fluctuation component of the belt thickness separately. Therefore, it is necessary not only to correct the eccentric component of the drive shaft, but also to obtain the profile of the variable component for one round of the belt and correct it.
That is, in order to perform eccentric correction with high accuracy, two types of correction tables, an eccentric correction table for the drive shaft and a correction table based on the profile of the entire belt, are required, and it is necessary to execute the correction based on the combined result. ..

For example, Patent Document 1 proposes a technique of measuring the eccentric component of the drive shaft and the thickness variation of the belt with a displacement variation detector, determining the correction amount from the measurement result, and performing the correction.
Further, in Patent Document 2, there is a technique of measuring speed fluctuation with a laser Doppler, dividing the result of Fourier transform into an eccentric component of a drive shaft or a thickness fluctuation component of a belt, and setting a correction value in a corresponding correction table. Proposed.

Japanese Unexamined Patent Publication No. 2008-44767 Japanese Unexamined Patent Publication No. 2011-68065

However, the method of Patent Document 1 cannot remove the eccentric component due to the mounting error of the encoder and the error component of the encoder itself. Further, there is a problem that the displacement fluctuation detector becomes expensive when trying to improve the accuracy.

The problem to be solved is to efficiently acquire two types of fluctuation components, the eccentricity correction amount and the profile of the entire belt.
The deviation between the encoder pulse and the actual amount of movement is mainly caused by the eccentric component of the drive shaft and the variation component of the belt thickness. In general, it is difficult to strictly synchronize between one rotation of the belt and one rotation of the drive shaft (even if the ratio is set to be an integer ratio, the position gradually shifts due to a small amount of deviation). Eventually it will be treated asynchronously.
Therefore, in order to create a correction table for correcting the deviation of the movement amount, it is necessary to separate the measured deviation amount into an eccentric component of the shaft and a component due to the variation in the thickness of the belt and hold them as independent values.
In Patent Document 2, an actual belt speed is measured using a laser Doppler sensor, Fourier transform is performed to obtain a frequency component, and the frequency is separated into a shaft component and a belt component. However, this method has the disadvantage that it cannot be separated well when the ratio of the circumference of the belt to the circumference of the shaft is close to an integral multiple, and because the laser Doppler sensor is expensive, it is difficult to mount it on the device and only at the time of installation. There is a drawback that it cannot cope with aging because it is an adjustment of.
There is also the idea of measuring the physical displacement amount that combines the fluctuation of the belt thickness and the fluctuation of the shaft diameter in real time with the completely opposite idea, and performing the correction from there, but in this case, the eccentric component of the encoder itself, There are drawbacks that it cannot handle error components and that high measurement accuracy is required.

The present invention has been made in the context of the above circumstances, and an object of the present invention is to separately measure both the eccentric component of the drive shaft and the stacking fluctuation of the belt without requiring a particularly expensive device. ..

Among the inkjet printers of the present invention, the first embodiment is determined based on an encoder pulse indicating the rotation position of the belt drive shaft from a single-color or a plurality of-color ink ejection nozzle with respect to a medium conveyed by an endless transfer belt. An inkjet printer that prints on the medium by ejecting ink at the ejection timing.
A belt reference position detection unit that detects that the transport belt has made one revolution, and
A drive shaft reference position detection unit that detects that the belt drive shaft has made one rotation, and
It has a control unit that can set the discharge timing between the signal of the encoder pulse and the discharge operation.
The control unit has at least a first correction function for correcting the discharge timing by the first correction table based on the signal from the belt reference position detection unit.
Further, the control unit is a head having different discharge timings with the signal from the drive shaft reference position detection unit as a reference position, and N rotations of the belt drive shaft depending on the physical distance between the discharge nozzles of the head ( N is an integer, and a plurality of test patterns are generated on the same medium at positions N ≧ 1) apart, and the variation in the distance between the test patterns is obtained based on the reading result of reading the test patterns. It is characterized in that profile data for one round of the transport belt is created and the first correction table is determined.

In the invention of the other form of the inkjet, in the invention of the above-described embodiment, the control unit corrects the ejection timing by at least a second correction table based on a signal from the drive shaft reference position detecting unit. Has a second correction function,
The control unit uses the signal from the drive shaft reference position detection unit as a reference position, and due to the discharge at different discharge timings, a plurality of control units are placed on the same medium at positions separated by at least one rotation of the belt drive shaft. A test pattern is generated, the variation of the distance between the test patterns is obtained based on the reading result of reading the test pattern, profile data for one rotation of the drive shaft is created, and the second correction table is defined. It is characterized by that.

In the invention of the other form, in the invention of the above-described embodiment, the control unit is in a state where the first correction function by the first correction table is enabled, and the test is performed for the second correction table. It is characterized by generating a pattern.

In the invention of the other form, in the invention of the above-mentioned embodiment, the control unit uses the first correction table based on the content of creating profile data for one round of the drive shaft. It is characterized in that a correction table is obtained.

In the invention of the other form, in the invention of the above-described embodiment, the control unit corrects the ejection timing by the first correction table and the second correction table, and executes job printing. It is characterized by.

Another form of the invention of the inkjet is characterized in that, in the invention of the above form, the test pattern is formed by a straight line inclined with respect to the transport direction of the medium.

In the invention of the other form of the inkjet, in the invention of the above-mentioned embodiment, the control unit first determines either the first correction table or the second correction table.

In the invention of the other form of the inkjet, in the invention of the above-described embodiment, the control unit determines the first correction table, so that the signal from the belt reference position detection unit and the signal from the drive shaft reference position detection unit are used. Based on this, it is characterized in that the timing of placing the medium on the transport belt is controlled.

In the invention of the other form, in the invention of the above-described embodiment, the control unit sets a plurality of test patterns for determining the first correction table by ejecting from the ejection nozzle of the same head to the drive shaft reference position. It is characterized in that two or more rotations are created based on the signal of the detection unit, and the variation of the distance between the test patterns at the relative positions separated by one rotation is obtained.

In the invention of the other form of the inkjet, in the invention of the above-described embodiment, the control unit simultaneously creates profile data by creating the test pattern and measures by the laser Doppler sensor, and obtains the measurement result by the laser Doppler sensor. It is separated into an eccentric component and a variable component of the thickness of the belt.

In the ejection timing correction method of the inkjet printer of the present invention, the ejection timing is adjusted based on the encoder pulse indicating the rotation position of the belt drive shaft from the ejection nozzle of single color or multiple color ink for the medium conveyed by the endless conveying belt. It is a discharge timing correction method to correct,
At least, the first correction for correcting the discharge timing can be performed by the first correction table based on the signal from the belt reference position.
With the signal from the drive shaft reference position as the reference position, heads with different discharge timings are separated by N rotations of the belt drive shaft (N is an integer, N ≧ 1) depending on the physical distance between the discharge nozzles of the head. At the same position, a plurality of test patterns are generated on the same medium, the variation of the distance between the test patterns is obtained based on the reading result of reading the test patterns, and the profile data for one round of the transport belt is obtained. It is characterized in that the first correction table is prepared and defined.

The invention of the ejection timing correction method of the other form of the inkjet printer is the second aspect of the invention of the said embodiment, in which the ejection timing is corrected by at least the second correction table based on the signal from the drive shaft reference position. Can be corrected,
Using the signal from the drive shaft reference position as the reference position, a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by discharging at different discharge timings, and the test patterns are read. Based on the reading result, the variation of the distance between the test patterns is obtained, profile data for one rotation of the drive shaft is created, and the second correction table is defined.

In the invention of the ejection timing correction method of the other form of the inkjet printer, either the first correction table or the second correction table is defined first in the invention of the above form.

In the programming of the present invention, ink is ejected from a single-color or multiple-color ink ejection nozzle to a medium conveyed by an endless conveyor belt at an ejection timing determined based on an encoder pulse indicating the rotation position of the belt drive shaft. This is programming executed by the control unit of the inkjet printer that prints on the medium.
The programming enables at least a second correction to correct the discharge timing by a second correction table based on the signal from the drive shaft reference position detector.
A reading result in which a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by ejection with different discharge timings with the drive shaft reference position as a reference position, and the test patterns are read. Based on the above, the variation in the distance between the test patterns is obtained, profile data for one round of the drive shaft is created, and the control unit is made to execute so as to determine the second correction table.

In the invention of the other form, the program further corrects the discharge timing by at least a second correction table based on a signal from the drive shaft reference position detection unit. Allows correction of 2
A reading result in which a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by ejection with different discharge timings with the drive shaft reference position as a reference position, and the test patterns are read. Based on the above, the variation of the distance between the test patterns is obtained, profile data for one rotation of the drive shaft is created, and the control unit is made to execute so as to determine the second correction table.

As described above, according to the present invention, by measuring the variation in the distance between the landing positions separated by the perimeter of the drive shaft, if there is no variation in the thickness of the belt, the landing positions separated by the perimeter are separated. The distance of is always the same because the eccentric component of the shaft cancels out. It can be used as a correction value for the fluctuation component of the belt thickness.
Further, in the invention of another form, it is possible to measure the fluctuation amount of the interval of the landing position for each predetermined number of encoder pulses. The former fluctuation amount and the latter fluctuation amount make it possible to measure the belt thickness fluctuation component and the shaft eccentric component separately.

It is a figure which shows the schematic structure of the inkjet printer of one Embodiment of this invention. Similarly, it is a figure which shows the test pattern for the 1st correction table printed on the medium. Similarly, it is a schematic configuration diagram of an inkjet printer that explains the operation when performing normal printing. Similarly, it is a schematic block diagram of an inkjet printer explaining the operation when creating profile data. Similarly, it is a schematic block diagram of an inkjet printer explaining the operation when creating a test chart for the first correction table. It is also a figure which shows the test chart for the 1st correction table. Similarly, it is a schematic block diagram of the inkjet printer explaining the operation when storing the 1st correction table. Similarly, it is a schematic block diagram of an inkjet printer explaining the operation when creating a test chart for a second correction table. It is also a figure which shows the test chart for the 2nd correction table. Similarly, it is the schematic block diagram of the inkjet printer explaining the operation when storing the 2nd correction table. It is a schematic block diagram of the inkjet printer explaining the operation when creating the test chart for the 1st correction table in another form. It is also a figure which shows the test chart for the 1st correction table. Similarly, it is a schematic block diagram of an inkjet printer explaining the operation when creating a test chart for a second correction table. Similarly, it is the schematic block diagram of the inkjet printer explaining the operation when storing the 2nd correction table. It is also a figure which shows the test chart for the 2nd correction table. Similarly, it is a schematic block diagram of the inkjet printer explaining the operation when storing the 1st correction table. It is a schematic block diagram of the inkjet printer explaining the operation at the time of performing the medium transfer timing in still another form. It is a figure which shows the example of the test chart in still another form. It is a figure which shows the schematic structure of a general inkjet printer.

Hereinafter, the constitution and action of the ink jet to which the present invention is applied will be described with reference to the accompanying drawings.
In the ink jet printer 1, as shown in FIG. 1, an endless transport belt 12 for transporting a medium is hung on transport rollers 10 and 11. An encoder 13 is attached to the belt drive shaft 10A, and detects the rotation of the belt drive shaft 10A.
Heads of each color 15K (for black), 15C (cyan), 15M (magenta), and 15Y (yellow) are installed on the transport belt 12 at predetermined intervals. Each color 15K, 15C, 15M, 15Y is provided with a line-shaped ejection head (not shown), and a desired color is ejected from an ink tank (not shown), and a print on the medium P conveyed by the conveying belt 12 is printed. Will be done.

During the output of the encoder 13, the Z-phase pulse is transmitted to the print data generation unit 20, and the encoder pulse generated by the output of the encoder 13 is used for ink ejection at the heads 15K, 15C, 15M, and 15Y of each color.

FIG. 2 is a diagram showing a test pattern printed on a medium for the first correction table of the present invention.
A plurality of test patterns 150K linearly formed by the discharge nozzle of the head 15K are printed on the paper P with a predetermined interval in the transport direction. Further, in the direction orthogonal to the transport direction, a plurality of test patterns 150M are printed at the same transport direction interval as the test pattern with an interval.
The test pattern 150K and the test pattern 150M are formed so that the corresponding lines are separated from each other by a distance L1 ... Ln corresponding to one rotation of the belt drive shaft.
These test patterns 150K and 150M are read by an image reading device such as an in-line sensor, and the fluctuation of the distance Ln (n = 1 ...) Is measured.

In the above, the line ejection (thinning out the line interval if necessary) is performed in the direction orthogonal to the medium transport direction in synchronization with the encoder pulse for one rotation based on the Z phase. Discharge different colors in the same way. However, it is assumed that the line is discharged at a timing delayed by one rotation or more from the above line discharge due to the difference in physical position between the heads. It may be discharged at a plurality of rotations N (integer; N ≧ 1).
The distance between the lines corresponding to the Z phase is measured between the above two colors. Since the distances between the corresponding lines described above are deviated by exactly the circumference of the drive shaft, they should be evenly spaced if the eccentric components of the drive shaft are offset and there is no change in the thickness of the belt. That is, if there is a variation in the distance between the corresponding lines, that becomes a variation component in the thickness of the belt.

According to the above principle, first, the fluctuation data of the thickness for one week of the belt can be acquired, and the first correction table corresponding to one round of the belt can be created.
Further, the discharge distance between the lines with the same color is acquired for one rotation of the drive shaft, and a second correction table which is an eccentric component of the drive shaft is created. The second correction table may be obtained by applying a correction process using the correction values in the first correction table, and the second correction table may be obtained by using the above-mentioned correction contents and the first correction table. You may want to get a correction table.
For actual printing, the composite result of the first correction table and the second correction table is applied.

The detailed operation in the inkjet printer 1 will be described.
First, normal printing will be described with reference to FIG.
The inkjet printer 1 has the following configurations in addition to the configurations described with reference to FIG.
The head drive signal generation unit 21 generates a drive signal for each head and transmits it to each head. The head drive signal generation unit 21 receives the output of the print data generation unit 20.

Further, the first correction table 41 and the second correction table 42 are readable and stored in the memory 40. An encoder correction logic 30 is connected to the memory 40, and the encoder correction logic 30 notifies the memory 40 of the address to cause the correction value 1 in the first correction table or the correction value 1 in the second correction table. The correction value 2 is stored or acquired. Further, the output of the drive shaft reference position detection unit 14A provided on the transfer roller 10 is sent to the encoder correction logic 30, and information on the A phase and the Z phase in the encoder 13 can be obtained. Further, the output of the belt reference position detection unit 14B arranged in the vicinity of the conveyor belt 12 is output to the encoder correction logic 30. Reference numeral 10B is a drive motor for rotationally driving the transport roller 10.

The encoder correction logic 30 is connected to the discharge clock generation logic 22, and the corrected A phase is output from the encoder correction logic 30 to the discharge clock generation logic 22. In the discharge clock generation logic 22, the detection result of the medium passage sensor 14C for detecting the passage of the medium is sent, the discharge clock is generated, and the discharge clock is sent to the head drive signal generation unit 21.
The head drive signal generation unit 21 generates a head drive signal based on the print data and the ejection clock, and ejects ink at each of the heads 15K, 15C, 15M, and 15Y.

In normal printing, the correction data 1 for correcting the belt thickness component is read from the first correction table 41 based on the signal of the belt reference position detection unit 14B that detects one circumference of the belt, and Z is output by one rotation of the encoder. Based on the phase, the correction data 2 for correcting the eccentric component of the drive shaft is read from the second correction table 42, and the A-phase signal input from the encoder is based on the correction data obtained by combining the correction data 1 and the correction data 2. The interval is corrected and printing is performed.
The encoder correction logic 30 and the discharge clock generation logic 22 in the above configuration function as a part of the configuration of the control unit of the present invention.

Next, the procedure for creating profile data will be described with reference to FIG.
In order to realize this embodiment, the in-line sensor 16 that reads the image formed on the medium in synchronization with the discharge clock and the image from the in-line sensor 16 are analyzed to calculate the correction value. Image analysis + correction value calculation The logic 25 and the media transfer timing control unit 26 that controls the medium transfer timing based on the signal of the belt reference position detection unit 14B and the Z phase are additionally mounted in order to efficiently print the test chart. And.
At this time, a signal from the belt reference position detection unit 14B is input to the correction value calculation logic 25, and the calculated correction value and the positional relationship on the conveyor belt 12 are associated with each other.
Further, the discharge clock generation logic 22 has a function of inputting a Z-phase signal and waiting for both the medium transfer and the Z-phase to start printing.

Next, a procedure for acquiring the first correction table 41 and the second correction table 42 will be described. The following procedure can be achieved by a control program executed by the control unit.

[Procedure 1]
As shown in FIG. 5, the correction process is disabled and a test chart for detecting the thickness of the belt is printed.
As shown in FIG. 6, the test chart 1 is basically a parallel line for one rotation of the drive shaft (magenta and black pattern in this example), and its physical discharge timing is separated by one rotation of the drive shaft. Moreover, it is assumed that printing of each color is started after waiting for both the detection of the medium and the Z phase.
Further, the medium transfer timing control unit 26 controls the transfer timing of the medium, and adjusts the transfer timing so that the test chart fits on the medium even if the Z phase is waited for and printing is performed.
The discharged data is read by the in-line sensor 16, and the image analysis + correction value calculation logic 25 measures the amount of variation in the interval between the corresponding lines between the colors to calculate the correction value due to the thickness of the belt.

[Procedure 2]
As shown in FIG. 7, the medium transfer timing control unit 26 determines which part of the transfer belt 12 the correction value calculated from the output of the belt reference position detection unit 14B is, and cooperates with the medium transfer timing control unit 26. Then, the correction data covering one round of the transport belt is acquired.
When the acquisition of one round of the transport belt is completed, the correction value is set in the first correction table 41 in the memory 40.

[Procedure 3]
As shown in FIG. 8, in the correction logic, only the correction value 1 is enabled and the correction process is performed, and the test chart 2 for measuring the eccentric component is printed as shown in FIG. (In this example, a single color test pattern 150K with only K color is printed)
Also at this time, the discharge clock generation logic 22 waits for both the media detection and the Z-phase signals to print the test chart. Further, the medium transfer timing control unit controls the transfer timing of the medium, and adjusts the transfer timing so that the test chart fits on the medium even if the Z phase is waited for and printing is performed.
The discharged data is read by the in-line sensor 16, and the image analysis + correction value calculation logic 25 measures the fluctuation between individual lines and calculates the correction value of the eccentric component.

[Procedure 4]
As shown in FIG. 10, the correction value measured in step 3 is set as a correction value in the second correction table 42 of the memory 40.
This completes the setting of the values of the two correction tables 41 and 42, and the normal printing operation can be performed thereafter.

As explained above, the fluctuation of the distance between the landing positions separated by the circumference of the shaft is measured (if there is no fluctuation of the thickness of the belt, the distance between the landing positions separated by the circumference is the eccentric component of the shaft. Since they are offset, they are always the same value. This is used as the correction value for the fluctuation component of the belt thickness, and the correction data for one circumference of the belt is first obtained and this correction is performed, and then the landing position for each predetermined number of encoder pulses. By measuring the amount of variation in the interval between the belts and measuring the correction value of the eccentric component of the shaft, the component of the thickness variation of the belt and the eccentric component of the shaft can be measured separately.

Specifically, the Z phase of the drive shaft is set as the start position, and a straight line perpendicular to the medium transport direction is drawn around the drive shaft (encoder) in synchronization with the encoder signal attached to the drive shaft. Perform the same drawing with different colors. At this time, it is essential that the physical distance between the heads of these two colors is at least the circumference of the drive shaft. The physical distance between the straight lines corresponding to each color fluctuates (because the radius of gyration changes) due to fluctuations in the thickness of the belt. By applying this principle and measuring the fluctuation of the interval of the corresponding straight line for one round of the belt, profile data of the fluctuation of the thickness of the belt is created. Next, with the correction based on the belt profile information, the Z phase of the drive shaft is set as the start position again, and in synchronization with the encoder signal attached to the drive shaft, the straight line perpendicular to the medium transport direction is set as the drive shaft (encoder). 1) Draw for one lap. By measuring the fluctuation of the interval of each straight line with respect to this drawing result, the amount of eccentricity for one round of the encoder can be measured. As a result, the variation component of the belt thickness and the eccentric component of the drive shaft can be measured separately, and highly accurate correction is possible based on the combined result.

Next, the procedure of another embodiment will be described.
[Procedure 1]
As shown in FIG. 11, the correction process is disabled, and the test chart 3 capable of extracting only the eccentric component of the drive shaft is printed.
As shown in FIG. 12, the test chart 3 is basically a parallel line for one rotation of the drive shaft (in this example, the test patterns 150C and 150K of cyanata and black), and the physical discharge timing thereof is one rotation of the drive shaft. It is assumed that the colors are separated from each other and printing is started by waiting for both the detection of the medium and the Z phase.

In the test chart 3, by comparing the measured values of g1, g2, g3, g4, ... gN with the theoretical values, it is possible to calculate a correction value in which both factors of the eccentricity of the shaft and the thickness of the belt are combined. ..
Further, by comparing the measurement results of d1, d2, d3, d4, .... DN with the theoretical values, the correction component due to the thickness of the belt can be calculated. By subtracting this value from the correction value in which both the eccentricity of the shaft and the thickness of the belt are combined, the correction value consisting of only the eccentricity component of the shaft can be calculated.

Further, the medium transfer timing control unit 26 controls the transfer timing of the medium, and adjusts the transfer timing so that the test chart fits on the medium even if the Z phase is waited for and printing is performed.
The discharged data is read by the in-line sensor 16, and the image analysis + correction value calculation logic 25 measures the amount of variation in the interval between the corresponding lines between the colors to calculate the correction value due to the thickness of the belt.
At the same time, the correction value (combined factors of both the eccentricity of the shaft and the thickness of the belt) is calculated by measuring the fluctuation of the interval between the lines in the same color (black in this case). From there, the correction value calculation result due to the thickness of the belt is removed, and the second correction value consisting of only the eccentric component of the shaft is calculated.

[Procedure 2]
A second correction value composed of only the eccentric component of the shaft calculated in step 1 is set in the second correction table 42 as shown in FIG.

Step 3]
As shown in FIG. 14, the correction logic enables only the correction value 2 to perform the correction process, and prints a test chart 4 for measuring the amount of fluctuation due to the thickness of the transport belt 12. (In this example, a single color test pattern 150K with only K color is printed)
Also at this time, the discharge clock generation logic 22 prints the test chart based on the detection of the medium and the delay amount from the belt reference position detection signal. As shown in FIG. 15, it is assumed that the test chart includes a reference mark based on the amount of delay with respect to the belt reference position.
Further, the medium transfer timing control unit 26 controls the medium transfer timing, and prints the test chart so that the test chart efficiently covers the entire belt.
The discharged data is read by an in-line sensor, the image analysis + correction value calculation logic measures the fluctuation between individual lines, and the correction value is calculated due to the fluctuation of the belt thickness.

[Procedure 4]
As shown in FIG. 16, the correction value measured in step 3 is set as the correction value in the first correction table.
This completes the setting of the values of the two correction tables, and the normal printing operation can be performed thereafter.

Next, another embodiment will be described with reference to FIG.
The medium transfer timing control unit 26 controls the rotation of the transfer roller 50A and the abutting roller 50B.
The medium conveyed by rotating the transfer roller 50A is conveyed to the position of the abutting roller 50B (usually not rotating) and stops at the position of the abutting roller 50B.
When the medium transfer timing control unit 26 determines that the timing is appropriate based on the signal from the belt reference position detection unit 14B and the Z-phase signal from the encoder 13, the medium transfer timing control unit 26 rotates the abutting roller 50B to use the medium as a medium. Control to push out onto the transport belt.

Next, still another embodiment will be described.
FIG. 18 shows an example of the test chart 5 used in this embodiment. The test chart 5 is a pattern corresponding to the number of encoder pulses for two laps, and is a pattern in which the print position of the second lap is shifted by the distance K so that the first lap and the second lap can be easily determined.
In this test chart as well, the medium transfer timing control unit 26 controls the transfer timing with reference to the Z phase so that the print result fits in the medium.
By measuring the distance of the horizontal lines that are separated by one circumference from the print result of the test chart, the correction value due to the fluctuation of the thickness component of the conveyor belt can be calculated.

In a device that can measure the amount of belt movement with a laser Doppler sensor and measure the amount of fluctuation of the amount of belt movement with respect to the pulse interval of the encoder attached to the drive shaft, the measured amount of fluctuation is biased by the drive shaft. The value is a combination of the core component and the variable component of the belt thickness. By simultaneously performing the measurement with the laser Doppler sensor and the test pattern printing of the present embodiment, the measurement result with the laser Doppler sensor can be accurately separated into the eccentric component and the variation component of the belt thickness.

Although the present invention has been described above based on the above-described embodiment, the scope of the present invention is not limited to the description of the above-described embodiment, and the present invention is defined as long as it does not deviate from the scope of the present invention. Appropriate changes are possible.

1 Inkjet printer 10 Conveying roller 11 Conveying roller 10A Belt drive shaft 12 Conveying belt 13 Encoder 14A Drive shaft reference position detection unit 14B Belt reference position detection unit 14C Medium passage sensor 16 In-line sensor 20 Printing data generation unit 21 Head drive signal generation unit 22 Discharge clock generation logic 25 Correction value calculation logic 26 Media transfer timing control unit 30 Encoder correction logic 40 Memory 41 First correction table 42 Second correction table 50A Transfer roller 50B Butting roller

Claims (15)

By ejecting ink from a single-color or multiple-color ink ejection nozzle to the medium conveyed by the endless transfer belt at an ejection timing determined based on an encoder pulse obtained by measuring the rotation of the belt drive shaft, the medium is ejected. An inkjet printer that prints
A belt reference position detection unit that detects that the transport belt has made one revolution, and
A drive shaft reference position detection unit that detects that the belt drive shaft has made one rotation, and
It has a control unit that can set the discharge timing between the signal of the encoder pulse and the discharge operation.
The control unit has at least a first correction function for correcting the discharge timing by the first correction table based on the signal from the belt reference position detection unit.
Further, the control unit is a head having different discharge timings with the signal from the drive shaft reference position detection unit as a reference position, and N rotations of the belt drive shaft depending on the physical distance between the discharge nozzles of the head ( N is an integer, and a plurality of test patterns are generated on the same medium at positions N ≧ 1) apart, and the variation in the distance between the test patterns is obtained based on the reading result of reading the test patterns. An inkjet printer characterized in that profile data for one round of the transport belt is created and the first correction table is determined. The control unit has at least a second correction function for correcting the discharge timing by a second correction table based on a signal from the drive shaft reference position detection unit.
The control unit uses the signal from the drive shaft reference position detection unit as a reference position, and due to the discharge at different discharge timings, a plurality of control units are placed on the same medium at positions separated by at least one rotation of the belt drive shaft. A test pattern is generated, the variation of the distance between the test patterns is obtained based on the reading result of reading the test pattern, profile data for one rotation of the drive shaft is created, and the second correction table is defined. An inkjet printer that features that. The inkjet according to claim 2, wherein the control unit generates the test pattern for the second correction table in a state where the first correction function by the first correction table is enabled. Printer. The inkjet according to claim 2, wherein the control unit obtains the second correction table using the first correction table based on the content of creating profile data for one round of the drive shaft. Printer. According to any one of claims 2 to 4, the control unit corrects the ejection timing by the first correction table and the second correction table and executes job printing. The described inkjet printer. The inkjet printer according to any one of claims 1 to 5, wherein the test pattern is formed by a straight line inclined with respect to the transport direction of the medium. The inkjet printer according to any one of claims 2 to 6, wherein the control unit defines one of the first correction table and the second correction table. In order to determine the first correction table, the control unit controls the timing of placing the medium on the conveyor belt based on the signal from the belt reference position detection unit and the signal from the drive shaft reference position detection unit. The inkjet printer according to any one of claims 1 to 7. The control unit creates a plurality of test patterns for determining the first correction table for two or more rotations based on the signal of the drive shaft reference position detection unit by discharging from the discharge nozzle of the same head. The inkjet printer according to any one of claims 1 to 8, wherein the variation in the distance between the test patterns at the relative positions separated by rotation is obtained. The control unit simultaneously creates profile data by creating the test pattern and measures by the laser Doppler sensor, and separates the measurement result by the laser Doppler sensor into an eccentric component and a variation component of the belt thickness. The inkjet printer according to any one of claims 1 to 9. A discharge timing correction method that corrects the discharge timing based on an encoder pulse that measures the rotation of the belt drive shaft from a single-color or multi-color ink discharge nozzle for a medium conveyed by an endless transfer belt.
At least, the first correction for correcting the discharge timing can be performed by the first correction table based on the signal from the belt reference position.
With the signal from the drive shaft reference position as the reference position, heads with different discharge timings are separated by N rotations of the belt drive shaft (N is an integer, N ≧ 1) depending on the physical distance between the discharge nozzles of the head. At the same position, a plurality of test patterns are generated on the same medium, the variation of the distance between the test patterns is obtained based on the reading result of reading the test patterns, and the profile data for one round of the transport belt is obtained. A method for correcting ejection timing of an inkjet printer, which comprises creating and defining the first correction table. At least, the second correction table for correcting the discharge timing can be performed by the second correction table based on the signal from the drive shaft reference position.
Using the signal from the drive shaft reference position as the reference position, a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by discharging at different discharge timings, and the test patterns are read. The inkjet printer according to claim 11, wherein the variation in the distance between the test patterns is obtained based on the reading result, profile data for one rotation of the drive shaft is created, and the second correction table is determined. Discharge timing correction method. The ejection timing correction method for an inkjet printer according to claim 12, wherein either the first correction table or the second correction table is defined first. By ejecting ink from a single-color or multiple-color ink ejection nozzle to the medium conveyed by the endless transfer belt at an ejection timing determined based on an encoder pulse obtained by measuring the rotation of the belt drive shaft, the medium is ejected. Programming executed by the control unit of the printing ink printer.
The programming enables at least a second correction to correct the discharge timing by a second correction table based on the signal from the drive shaft reference position detector.
A reading result in which a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by ejection with different ejection timings with the drive shaft reference position as a reference position, and the test patterns are read. Based on the above, a program that obtains the variation of the distance between the test patterns, creates profile data for one rotation of the drive shaft, and causes the control unit to execute the second correction table. The program further
At least, the second correction table based on the signal from the drive shaft reference position detection unit enables the second correction for correcting the discharge timing.
A reading result in which a plurality of test patterns are generated on the same medium at positions separated by at least one rotation of the drive shaft by ejection with different discharge timings with the drive shaft reference position as a reference position, and the test patterns are read. Based on the above, a variation in the distance between the test patterns is obtained, profile data for one rotation of the drive shaft is created, and the control unit is made to execute so as to determine the second correction table. 14. The inkjet printer according to 14.

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