Patent Application
20140253620
This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application No. 2013-045789, filed on Mar. 7, 2013; No. 2013-077194, filed on Apr. 2, 2013; No. 2013-097982, filed on May 7, 2013; and No. 2013-109261, filed on May 23, 2013 in the Japan Patent Office, the entire disclosures of which are hereby incorporated by reference herein.
1. Technical Field
The present invention relates to an image recording apparatus, image recording method, and recording medium storing a program for recording an image.
2. Background Art
In image recording apparatuses, e.g., inkjet recording apparatuses, a recording head that consists of multiple driven nozzles that discharge ink droplets (ink discharging nozzles) is mounted on a carriage. Images are formed by moving (main scanning) the carriage in the direction perpendicular to the recording medium carrying direction and discharging ink droplets.
If the number of nozzles that discharge ink droplets simultaneously changes, since load to drive the nozzles (capacitance) changes too, rise time and fall time of the driving waveform changes and discharging velocity of the ink droplets becomes unstable. There then arise problems such as increasing satellites (mist) due to overshoot and undershoot in the driving waveform.
In the driving waveforms shown in
To solve this issue, a technology that includes multiple driving circuits, selects a driving circuit to be used in accordance with the number of driven nozzles, and adjusts driving capability is well known. The image recording apparatus described in JP-2008-254204-A includes a driving circuit that drives a recording head that includes recording elements. In the recording head driving circuit, multiple driving circuits are connected to one recording element in parallel. The recording head driving circuit includes an output circuit block that converts voltage supplied from a power supply into driving voltage that has a predetermined waveform, a recorded data integrator that integrates the number of the recording elements based on recorded data, and a driving circuit selector that selects at least one driving circuit from the multiple driving circuits so that on resistance of the output circuit block becomes less than a predetermined value in accordance with the integrated value calculated by the recorded data integrator.
However, such an approach entails an increase in cost due to the presence of multiple driving circuits.
An example embodiment of the present invention provides an image recording apparatus that includes a recording head controller that transfers image data and a driving waveform to a recording head in conjunction with position information of the recording head. The recording head controller includes a driving waveform storage unit that stores multiple driving waveform data, a number of driven nozzles calculator that calculates the number of nozzles driven simultaneously from the image data, and a driving waveform selector that selects one driving waveform data from the multiple driving waveform data based on the calculated number of driven nozzles and a predetermined threshold value of the number of driven nozzles.
An example embodiment of the present invention include a recording method of using the image recording apparatus, and a non-transitory recording medium storing a program that causes a computer to implement the recording method of using the image recording apparatus.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result.
In the following example embodiment, in outputting driving waveform in an image recording apparatus, driving waveform can be prevented from being unstable due to variation of load of recording head depending on the number of driven nozzles without using conventional complicated driving circuit.
A carriage 1 is held by a guide rod 2 and scans in the main scanning direction via a belt 4 hanged between a main scanning motor 3. The carriage 1 includes a recording head 9 that discharges ink droplets in colors such as yellow (Y), cyan (C), magenta (M), and black (K) for example, and ink droplets are discharged from driven nozzles 10 (ink discharging nozzles) laid out on the recording head 9. An image is formed on a recording medium by moving the carriage 1 in the main scanning direction and discharging ink droplets at necessary positions.
The position information of the carriage 1 can be acquired by reading patterns recorded at even intervals on an encoder sheet 5 mounted on a case by an encoder sensor 6 mounted on the carriage 1 and adding/subtracting counts.
An image for a band whose width is the same as length of nozzle row is formed by moving the carriage 1 in the main scanning direction and discharging ink droplets once. After finishing forming the image for one band, an image can be formed at any place on the recording medium by repeating moving the recording medium in the sub-scanning direction by driving a sub-scanning motor 7 and performing the image forming operation for one band.
A recording head controller 25 transfers the image data stored in the RAM 23, the recording head driving waveform stored in the ROM 22, and a control signal to a recording head driver 11 in conjunction with position information of the carriage 1 acquired from a main scanning encoder 3a (i.e., position information of the recording head 9).
The recording head driver 11 drives the recording head 9 based on the data transferred from the recording head controller 25 and discharges ink droplets.
In
The recording head controller 25 transfers image data (serial data) SD for the number of nozzles of the recording head 9 (that equals the number of actuators) to a shift register 111 for image data in the recording head driver 11 by using the image data transfer clock SCK (t1 in
After finishing transferring, the image data (serial data) SD is stored in a latch 112 for each image data for each driven nozzle 10 by using the image data latch signal SLn (t2 in
After latching the image data, the recording head controller 25 outputs the head driving waveform Vcom to instruct the nozzles to discharge ink droplets at each gradation value (t3 in
That is, logical operation is performed with the gradation control signal from MN(0) to MN(3) and the latched image data SD in the recording head driver 11, and that results in generating the head driving waveform VoutN after decoding gradation depending on each driving nozzle 10. The actuator 91 in the recording head 9 discharges ink droplets based on the image data by opening/closing the analog switch 115.
Main scanning consists of accelerated stage that the carriage 1 accelerates until the carriage 1 reaches constant velocity, constant velocity stage, decelerated stage that the carriage 1 decelerates after the carriage 1 passes position where printing is finished, and halt stage during performing linefeed etc.
In addition, from timing A in the constant velocity stage and the accelerated stage to timing B in the constant velocity stage and the decelerated stage, printing stage that an image is formed on the recording sheet by discharging ink droplets is included. Depending on printing modes, it is determined whether the accelerated stage and the decelerated stage are included in the printing stage or the printing stage consists of the constant velocity stage only.
In
If the carriage discharges an ink droplet at the velocity Vj from the recording head 9 with moving at the velocity Vc, the ink droplet lands at the landing position Xj.
The landing position Xj can be calculated using following equation:
Xj=(Hj÷Vj)×Vc
From Equation 1, if the carriage velocity Vc changes to Vc2, the ink droplet landing position Xj also changes to Xj2, and that results in misaligning landing positions.
Similarly, changes of Hj (distance between the recording head and the recording medium) and Vj (discharging velocity of ink droplets from the recording head to the recording medium) also affect the ink droplet landing position Xj.
The common head driving waveform Vcom input into the recording head 9 consists of multiple driving pulses, and sizes of discharged ink droplets corresponding to image data for each nozzle are determined by the combination of the driving pulses. In
Regarding upper bit and lower bit of two bits for the image data, if the upper bit is 0 and the lower bit is 0, no droplet is discharged. If the upper bit is 0 and the lower bit is 1, small droplet is discharged. If the upper bit is 1 and the lower bit is 0, medium droplet is discharged. If the upper bit is 1 and the lower bit is 1, large droplet is discharged. Consequently, it is necessary to determine the two bit data to determine the size of droplets.
Load of actuator (capacitance) varies depending on the number of driven nozzles. If the load varies, rising time and fall time of the head driving waveform Vcom vary. If the rising time and the fall time of the head driving waveform Vcom vary, width of low tL of the driving pulse varies. If the width of low of the driving pulse tL varies, discharging velocity Vj of the ink droplet from the recording head to the recording medium varies. If the discharging velocity Vj varies, the landing position Xj of the ink droplets fluctuates as described in
In
The threshold of the number of driven nozzles storage unit 253 stores at least more than one threshold value, and preferably, that value is variable such as a register configuration.
The driving waveform selector 254 selects one waveform from multiple waveforms a and b stored in the driving waveform storage unit 251 and output it based on the number of driven nozzles sent from the number of driven nozzles calculator 252, threshold of the number of driven nozzles, and information sent from the head driving mask pattern output unit 250.
After being performed digital/analog conversion by the D/A converter 256, the selected driving waveform is input into the recording head driver 11.
Taking the waveform shown in
That is, the numbers of driven nozzles that affect the rising time and the fall time of the driving waveform pulses are different for each of the driving pulses from (1) to (4).
Accordingly, a unit of timing of selecting the driving waveform is preferably a unit of the driving pulse (a unit of one MN period).
In
In the driving waveform data appropriate if the number of driven nozzles is large (i.e., the driving waveform b here), for example, the rising time and the fall time of the driving pulse become long (i.e., they become dull) due to the large capacitance. Consequently, with considering this point, the rising time and the fall time of the driving waveform b are set shorter than the driving waveform a preliminarily as shown in
In
The driving waveform is selected by using a table for each of the driving pulses from (1) to (4). A driving waveform selection table is described below.
In
In the first example of the setting table shown in
For example, if the combination of the target droplet sizes is “large droplet, medium droplet, and small droplet”, the threshold value of the number of driven nozzles is set to 700 nozzles. Similarly to the case in
In the head driving waveform Vcom, the driving waveform data is different depending on the print mode, and the ink droplet discharging velocity Vj is also different. Taking that point into account, in the third example configuration, different threshold values of the number of driven nozzles can be configured corresponding to the print modes (“high speed, fast, fine, and high quality”) preliminarily.
For example, in the case of “high speed”, the threshold value of the number of driven nozzles is set to 100 nozzles. Similarly to the cases in
In some cases, the ink droplet discharging velocity varies depending on temperature of the recording head. Taking that point into account, in the fourth example configuration, different threshold values for the number of driven nozzles can be configured corresponding to the detected temperature of the recording head 9.
For example, setting temperature in 10° C. increments, the threshold value of the number of driven nozzles is set to 100 nozzles if the temperature is less than 10° C. Similarly to the cases in
As shown in
For example, if the main scanning velocity is less than 500 mm/s, the threshold value of the number of driven nozzles is set to 100 nozzles. Similarly to the cases in
In the fifth example configuration shown in
For example, the threshold value of the number of driven nozzles is set to 100 nozzles in the acceleration stage. Similarly to the cases in
In selecting the driving waveform in cases shown in
As described above, in the inkjet recording apparatus in this embodiment, the most appropriate driving waveform output can be realized in accordance with the number of driven nozzles without increasing costs significantly. In addition, the driving waveform can be prevented from becoming unstable due to fluctuation of the recording head load depending on the number of driven nozzles unlike the conventional techniques.
The recording head controller 25 in this embodiment calculates driving waveform data appropriate for the number of driven nozzles and outputs the calculated result to use it for a head driving waveform Vcom by a recording head driver 11 that drives multiple nozzles using a common driving pulse waveform. For that purpose, the recording head controller 25 in this embodiment includes a driving waveform storage unit (first storage unit) 251 that stores standard driving waveform data, a number of driven nozzles calculator 252 that calculates the number of nozzles driven simultaneously from the image data, a correction data for driving waveform storage unit (second storage unit) 257 that stores driving waveform correction data to correct the standard driving waveform data, and a driving waveform calculator 258 as a driving waveform compensator that corrects the standard driving waveform data by using the driving waveform correction data acquired based on the number of driven nozzles. The driving waveform calculator 258 corrects and calculates driving waveform data appropriate for the number of driven nozzles from the standard waveform data and the driving waveform correction data acquired based on the number of driven nozzles and outputs the calculated result to use it for a head driving waveform Vcom. Here, the driving waveform data from which the head driving waveform Vcom is made is generated by correcting operation. However, it is possible to perform the correction by a process other than operation.
An image data transmitter 255 in the recording head controller 25 transfers image data to be recorded stored in the RAM 23 as a print job and passes serial data SD in the image data to the number of driven nozzles calculator 252.
A head driving mask pattern output unit 250 outputs the head driving mask pattern MN to the recording head driver 11.
The standard driving waveform data stored in the driving waveform storage unit 251 is used for generating a driving waveform that can discharge stable ink droplets regardless of the fluctuation in the number of driven nozzles by correcting the standard driving waveform data in accordance with the number of driven nozzles that varies depending on the image data to be recorded. The reason of correcting the standard driving waveform data is to make storage size of driving waveform data prepared in advance in the driving waveform storage unit 251 small.
In the standard driving waveform prepared in this embodiment, the standard driving waveform is stored by memorizing waveform values at each data point assuming generating a driving waveform by reading at predetermined sampling rate. In particular, the standard driving waveform data is a group of waveform values at each data point that digitizes the head driving waveform Vcom shown in
The method of correcting the standard driving waveform data can also be used for stabilizing discharging the ink droplet for change of condition in operating characteristic of the recording head 9.
In addition, the method of correcting the standard driving waveform data can also make the storage area to store driving waveform data small. Consequently, it is possible to make the size of hardware resources such as storage unit that stores the driving waveform data relatively small.
The standard driving waveform data can be prepared by calculating data that can minimize processing load in correcting data and prevent image quality from deteriorating experimentally and adopting the acquired experiential values.
The number of driven nozzles calculator 252 includes counters for each size of discharged droplets and counts the number of nozzles driven simultaneously based on serial data SD received from the image data transmitter 255 in transferring the image data.
The reason to include the counter for each ink droplet size is because the combination of driving pulses is different depending on the ink droplet sizes (as shown in
The correction data for driving waveform storage unit 257 stores the driving waveform correction data to be used for correcting the standard driving waveform data that stabilizes discharging velocity that becomes unstable in case of keep driving by using the same driving waveform data. The driving waveform correction data includes data such as the correction value used for correcting operation in accordance with the number of driven nozzles performed by the driving waveform calculator 254, applicable condition for the correcting value, and the threshold values of the number of driven nozzles that determines whether or not the correction is necessary (shown in FIGS from 13 to 18 later). It should be noted that the correction value includes correction coefficient (described later).
Regarding the driving waveform correction data, it is preferable to manage it in the form of a correction table for driving waveform for example so that it is possible to refer to the correction values, applicable condition for the correcting value, and the threshold values of the number of driven nozzles that determines whether or not the correction is necessary associated with the number of driven nozzles and to be able to change values of data and information by setting register etc.
After inputting the number of driven nozzles and the driving waveform correction data managed in the correction table for driving waveform, the driving waveform calculator 258 operates on the standard driving waveform and outputs driving waveform data (digital) appropriate for the number of driven nozzles.
After being digital/analog converted by the D/A converter 256, the operated driving waveform data is input to the recording head driver 11 as the head driving waveform Vcom (analog).
The recording head controller 25 can be constructed by using the computer that consists of components such as the CPU 21, ROM 22, and RAM 23 etc. in the functional block configuration shown in
In this case, the ROM 22 stores a control program and control data etc. that the CPU 21 uses to control driving of the recording head 9. The RAM 23 is used as memory that stores data etc. generated by the control program temporarily or a work area that stores data necessary for operation of a software program. In addition, nonvolatile memory devices such as NVRAM (not shown in figures) normally included in the computer can be used for storing a part of control data needed to be modified.
If the recording head controller 25 is constructed by the computer, programs including and control data for controlling the recording head driver 11 are installed in the computer via various storage media. The CPU 21 can perform the intended operation by running the installed programs and using the installed control data.
Next, a process of correcting a driving waveform executed by the recording head controller 25 is described below.
After receiving a request for outputting a driving waveform from the CPU 21 that accepted a print job, the recording head controller 25 starts the process for correcting the driving waveform shown in
After starting the process, first, the recording head controller 25 inputs standard driving waveform data to be processed into the driving waveform calculator 254 from the driving waveform storage unit 251 in S101.
The driving waveform data input from the driving waveform storage unit 251 is the standard driving waveform data. The standard driving waveform data consists of a group of digitized sampling values, that is, waveform values at each data point in the square waveform e.g., shown in
In addition, the target waveform values to be corrected are in rising period and fall period in the square waveform, and period of low with tL shown in
Next, the recording head controller 25 checks whether or not the waveform value currently input is the same as the waveform value at the adjacent data point (stored in the driving waveform calculator 254 already) in S102. After comparing the input waveform value with the waveform value at the adjacent data point, it is determined that they are the same waveform values if the difference of the waveform values does not exceed predefined value. For example, assuming the predetermined value as ±1, it is determined that they are the same waveform values if the absolute value of the difference does not exceed 1. In another case, assuming the past three data points as adjacent data points and subtracting each waveform value from the input waveform value, it can be determined that the waveform values are the same if the difference does not exceed the predetermined value at any of three data points.
By performing the process described above, it is determined whether or not the input waveform value is within the nontarget low width tL period. As in the example case described above, it is determined whether or not the waveform value is within the low width tL period by using the threshold value ±1 on waveform values for three data points. However, the number of waveform values used for that purpose is not limited to three, and the configured threshold value used for that purpose is not limited to ±1. For example, the number of waveform values and the threshold value can be modified arbitrarily by using a register configuration. In that case, the modified configuration values etc. are stored in the correction data for driving waveform storage unit 257.
If it is necessary to set more than a certain period for the low width tL period, it is possible to prepare a configuration value for the low width tL period in the correction data for driving waveform storage unit 257 and assure that period.
In S102, if it is determined that the input waveform value and the waveform value at the adjacent data point are the same and the input waveform value is nontarget (YES in S102), the correction operation is not performed, and the process ends.
Alternatively, after comparing the input waveform value with the waveform values at adjacent three data points, if all of those differences exceed the predetermined value, it is determined that they are not the same waveform values. Accordingly, the waveform value at the input data point is the waveform value in the rising time or the fall time that is the target to be corrected.
In S102, if it is determined that the waveform value at the input data point is not the same as the waveform value at the adjacent data point (NO in S102) and the waveform value at the input data point is the target to be corrected, the correcting operation of the driving waveform appropriate for the number of driven nozzles is performed in S103. The driving waveform calculator 258 performs the correcting operation in S103.
In S103, the driving waveform calculator 258 performs steps from (i) to (iv) shown below as the correcting operation for the driving waveform.
The purpose of correcting the driving waveform data is to stabilize the discharging velocity that become unstable due to the fluctuation in the number of nozzles driven simultaneously. Therefore, the number of driven nozzles that the number of driven nozzles calculator 252 calculates from the image data to be processed is acquired as information necessary for correcting.
The rising period and the fall period of the waveform currently input is the target to be corrected, and correction value applied in accordance with the slope of the waveform is configured. Therefore, the difference X between the waveform value at the data point currently input and the waveform value at the adjacent data point (already stored through this operation) is acquired. It should be noted that the difference X can be either plus (+) values or minus (−) values, and the plus values correspond to the rising period, and the minus values correspond to the fall period. In addition, since the difference X has already been calculated in S102, this difference X can be used for that purpose.
Subsequent data and information is acquired from the correction data for driving waveform storage unit 257.
In determining whether or not it is necessary to correct in (iv) described below, threshold value of the number of driven nozzles is set, and waveform whose number of driven nozzles is less than the threshold value is eliminated from the target to be corrected. Since the threshold value of the number of driven nozzles is changed in accordance with condition regarding operational characteristic of the recording head 9, the threshold value of the number of driven nozzles is acquired from a table that indicates their correspondence relationship (with reference to
In selecting correction value in accordance with applicable condition in (v) described later, the correction value is modified depending on the number of driven nozzles and waveform in the rising period and the fall period of the driving waveform. Therefore, the correction value applied to the input waveform is acquired from the table that indicates correspondence relationship between the X that corresponds to the number of driven nozzles and the slope of the rising period and the fall period of the waveform and the correction value.
In performing correction operation in (vi) described later, the correction operation is performed by using predetermined operation expression. The predetermined expression is indicated in the acquired table described above in combination with the selected correction value.
In this embodiment, the threshold value of the number of driven nozzles is configured to the waveform value to be corrected determined in S102. If the number of driven nozzles is less than the threshold value, the waveform value is eliminated from the correction target since it is difficult to achieve a significant effect of the correction. The threshold value of the number of driven nozzles can be configured in accordance with condition regarding operational characteristic in the recording head 9, and performance can be enhanced much more by modifying the configuration in accordance with the change of the condition.
In determining whether or not it is necessary to correct by using the threshold value of the number of driven nozzles, it is checked whether or not the number of driven nozzles acquired from the number of driven nozzles calculator 252 exceeds threshold value of the number of driven nozzles applied to the waveform to be corrected and acquired from the correction data for driving wave form storage unit 257 (described in (iii) Acquire correction data above). That is, if it does not exceed the threshold value of the number of driven nozzles, it is determined that it is unnecessary to correct, and the waveform value is eliminated from the target to be corrected. Alternatively, if it exceeds the threshold value of the number of driven nozzles, it is determined that it is necessary to correct, and the waveform value is considered as the target to be corrected. it should be noted that an example that modifies the threshold value of the number of driven nozzles depending on the change of condition regarding the operational characteristic of the recording head 9 will be described in detail later with reference to
After determining whether or not it is necessary to correct by using the threshold value of the number of driven nozzles, if it is determined that it is necessary to correct, it is necessary to modify the applied correction value in accordance with the changes of the difference X that corresponds to the slope of the waveform and the number of driven nozzles and to configure the correction value that accommodates to those changes.
The accommodating correction value is acquired with reference to a table that associates the number of driven nozzles for the waveform to be corrected and the difference X with the correction values. In the referred table acquired from the correction data for driving waveform storage unit 257, the number of driven nozzles either equal to or larger than the threshold value of the number of driven nozzles is changed at appropriate levels, the difference |X| (absolute value of the difference X) is partitioned at appropriate values in accordance with the changed number of nozzles, and the correction values applied in each zone are associated. The example table will be described in detail later with reference to FIGS. 21 and 22.
Since the waveform values in the rising period and the fall period are targets to be corrected, the driving waveform calculator 258 determines the rising period and the fall period and performs the correcting operation by using the correction value (correction coefficient) configured in accordance with the difference X that corresponds to the number of driven nozzles and the slope of the waveform. Regarding the correction value configured in accordance with the number of driven nozzles and the difference X, the value acquired in (iii) Acquire correction data described above is used for that purpose.
Regarding operational expression for the correcting operation, either multiplication or addition/subtraction can be used for that purpose. Equation 2 uses multiplication of correction coefficient, and Equation 3 uses addition/subtraction of correction value:
|N−1th driving waveform data)−(Nth driving waveform data)|×Correction coeffic
|N−1th driving waveform data)−(Nth driving waveform data)|±Correction value
In the equations described above, “Nth driving waveform data” is the waveform value at the data point currently input. In addition, “N−1th driving waveform data” is the waveform data at the data point adjacent to the data point currently input and stored in the driving waveform calculator 258 already after performing the correcting operation. Consequently, |(N−1th driving waveform data)−(Nth driving waveform data)| indicates the difference X that corresponds to the slope of the waveform.
The correcting operation is performed using the value calculated by the equations described above. Minus correction is performed on the waveform values in the fall period, and plus correction is performed on the waveform values in the rising period.
Getting back to the flowchart shown in
After finishing the correcting operation of the driving waveform data, the process ends.
Here, regarding cycle of correcting the driving waveform in accordance with the flowchart shown in
In the case of the driving pulse cycle, cycle information is input from the head driving mask pattern output unit 250 (shown in
The number of driven nozzles that is driven simultaneously calculated by the driving nozzle operation unit 258 is used for selecting the correction value for the correcting operation and determining whether or not it is necessary to correct in the process of correcting the driving waveform shown in
Next, a table that indicates correspondence relationship between the number of driven nozzles and the difference X and the correction value stored in the correction data for driving waveform storage unit 257 is described below.
In the table shown in
The correction coefficient is the correction value in the case of using the multiplication operational expression (Equation 2 described above) for the correcting operation.
In correcting the driving waveform, the driving waveform data whose difference |X| is less than 1 is out of the target to be corrected, and the driving waveform data whose difference |X| is either equal to or larger than 1 is the target to be corrected.
The number of driven nozzles shown in the table in
If the interval of the number of driven nozzles in the table shown in
The example table shown in
Regarding correction of the driving waveform, the driving waveform data whose difference |X| is less than 1 is nontarget for the correction, and the difference |X| either equal to or larger than 1 is the target for the correction.
The number of driven nozzles in the table shown in
If the interval of the number of driven nozzles in the table shown in
In the first example and second example described above, it is assumed that the waveform during the rising period and the fall period is the target to be corrected, and the waveform during the low width time tL is nontarget.
However, even with the waveform during the rising period and the fall period to be corrected, range of the number of driven nozzles that hardly affects to the discharging operation depending on the condition regarding the operational characteristic of the recording head 9 even if it is excluded from the correcting target exists.
Therefore, in this embodiment, even with the waveform during the rising period and the fall period to be corrected, threshold values of the number of driven nozzles that correspond to each condition regarding the operational characteristic of the recording head 9 are configured, and it is considered as nontarget to be corrected in case of not exceeding the threshold value to enhance performance much more.
As a configuration example of a table stored in the correction data for driving waveform storage unit 257 preliminarily to be used for the correcting operation, a table that includes the threshold value of the number of driven nozzles configured in accordance with the condition regarding the operational characteristic of the recording head 9 is described below.
In correcting the driving waveform, the driving waveform data less than the threshold value of the number of driven nozzles shown for each of the driving pulse number is nontarget to be corrected. For example, since the threshold value of the number of driven nozzles is configured as 100 for the driving pulse (2) used for driving the large droplet only, the number of nozzles either equal to or larger than 100 is the target to be corrected.
It is determined whether or not it is necessary to perform the correction with reference to the threshold value of the number of driven nozzles in the correction table shown in
Only if it is determined that it is necessary to perform the correction, the driving waveform is corrected in accordance with the number of driven nozzles. Regarding the method of correcting the waveform, the first example (shown in
The correcting operation cycle is the same as the converting cycle of the D/A converter 256, and the operation described above can be performed each time the driving waveform data is updated. However, the correcting operation cycle can be the cycle of the driving pulses from (1) to (4). In case of using the cycle of the driving pulses from (1) to (4), the cycle information is input from the head driving mask pattern output unit 250 (shown in
In correcting the driving waveform, the driving waveform data less than the threshold value of the number of driven nozzles shown for each of the printing modes is nontarget to be corrected. Therefore, for example, since the threshold value of the number of driven nozzles is configured as 200 for the printing mode “fast” in
Consequently, it is determined whether or not it is necessary to perform the correction with reference to the threshold value of the number of driven nozzles 200 in the correction table shown in
Only if it is determined that it is necessary to perform the correction, the driving waveform is corrected in accordance with the number of driven nozzles. Regarding the method of correcting the waveform, the first example (shown in
The correcting operation cycle is the same as the converting cycle of the D/A converter 256, and the operation described above is performed each time the driving waveform data is updated.
The temperature of the recording head 9 is condition regarding the operational characteristic of the recording head 9, and the discharging velocity varies depending on the temperature of the recording head 9. Therefore, the correction is performed to cope with the temperature change.
In
In correcting the driving waveform, the driving waveform data less than the threshold value of the number of driven nozzles shown for each of the recording head temperatures is nontarget to be corrected. For example, if the temperature of the recording head 9 detected by the sensor in correcting is 15° C., since the threshold value of the number of driven nozzles is configured as 200 for the range from 10° C. to 20° C. in
Consequently, it is determined whether or not it is necessary to perform the correction with reference to the threshold value of the number of driven nozzles 200 in the correction table shown in
Only if it is determined that it is necessary to perform the correction, the driving waveform is corrected in accordance with the number of driven nozzles. Regarding the method of correcting the waveform, the first example (shown in
The correcting operation cycle is the same as the converting cycle of the D/A converter 256, and the operation described above is performed each time the driving waveform data is updated.
As shown in
In
The main scanning velocity of the recording head 9 is the component velocity of the discharging velocity of the ink droplets, and the discharging velocity varies depending on the main scanning velocity of the recording head 9. Therefore, the correction is performed to cope with the main scanning velocity change.
In
In correcting the driving waveform, the driving waveform data less than the threshold value of the number of driven nozzles shown for each of the main scanning velocity of the recording head 9 is nontarget to be corrected. For example, if the main scanning velocity of the recording head 9 acquired from the velocity profile in correcting is 800 mm/s, since the threshold value of the number of driven nozzles is configured as 300 for the range from 700 mm/s to 900 mm/s in
Consequently, it is determined whether or not it is necessary to perform the correction with reference to the threshold value of the number of driven nozzles 300 in the correction table shown in
Only if it is determined that it is necessary to perform the correction, the driving waveform is corrected in accordance with the number of driven nozzles. Regarding the method of correcting the waveform, the first example (shown in
The correcting operation cycle is the same as the converting cycle of the D/A converter 256, and the operation described above is performed each time the driving waveform data is updated.
In the sixth example described above with reference to the correction table shown in
In
In
In correcting the driving waveform, the driving waveform data less than the threshold value of the number of driven nozzles shown for each of the main scanning velocity of the recording head 9 is nontarget to be corrected. For example, if the main scanning position of the recording head 9 acquired in controlling velocity in accordance with the velocity profile is deceleration stage, since the threshold value of the number of driven nozzles is configured as 200 for the deceleration stage in
Consequently, it is determined whether or not it is necessary to perform the correction with reference to the threshold value of the number of driven nozzles 200 in the correction table shown in
Only if it is determined that it is necessary to perform the correction, the driving waveform is corrected in accordance with the number of driven nozzles. Regarding the method of correcting the waveform, the first example (shown in
The correcting operation cycle is the same as the converting cycle of the D/A converter 256, and the operation described above is performed each time the driving waveform data is updated.
Next, another method of correcting the driving waveform is described below.
In the method of correcting the driving waveform described above, the standard driving waveform data is corrected using the number of driven nozzles and the difference |X| that corresponds to the slope of the waveform acquired from the correction table in the first example (shown in
However, in the standard correcting method, the value calculated using Equation 2 or Equation 3 described above with the correction value selected from the correction table does not change if the number of driven nozzles and the difference |X| that corresponds to the slope of the waveform. Therefore, the value deviates from expectation value (with reference to
To cope with this issue, additional correction is performed to make the deviation small.
Assuming that the waveform of the driving pulse waveform to be corrected during the rising period and the fall period has linear characteristic, in this additional correction, correction value is added to the values calculated by the standard correcting method described above at each data point of the driving waveform.
In
In
The correction values in the correction value (α) table makes the deviation that cannot be coped with the correction value in accordance with the difference |x| and the number of the driven nozzles at data points of the driving waveform using the standard correcting method described above small.
The table shown in
Here, the above deviation is described below with reference to
As shown in
In case of successive waveform data whose slope is the same, i.e., driving waveform data that has linear characteristic, it is possible to make the deviation smaller by performing the correction using “the correction value+α” (i.e., the correction value by the standard correcting method described above+the additional correction value α).
In particular, if the expected driving waveform data in the periods A, B, C, and D is 100→90→80→70, the actual driving waveform is like 100→95→90→85. In this case, by performing the correction using “the correction value+α” that makes the deviation from the expectation value small, considering the correction value 5 as the reference value, in accordance with the successive number of consecutive periods B→C→D (F→G→H), the correction that takes easiness of the waveform into account by adding the correction value (α) in the table shown in
Load of actuator 91 (capacitance) varies depending on the number of driven nozzles. If the load varies, rising time tp and fall time td of the head driving waveform Vcom vary. If the rising time tp and the fall time td of the head driving waveform Vcom vary, width of low tL (tL1 and tL2) of the driving pulse vary. If the width of low of the driving pulse tL (tL1 and tL2) vary, discharging velocity Vj of the ink droplet from the recording head 9 to the recording medium 8 varies. If the discharging velocity Vj varies, the landing position Xj of the ink droplets fluctuates as described in
That is, due to the change of the number of nozzles 10 driven simultaneously, the rising time tp, the fall time td, and the width of low of the driving pulse vary. That is, the driving waveform Vcom that consists of the group of multiple driving pulses varies, and that results in deteriorating printing quality.
In this embodiment, both the issue described above and a problem to minimize the increase of hardware resource such as memory capacity and an arithmetic circuit are solved at the same time. For that purpose, here, timing of transferring the driving waveform to the D/A convertor 30 connected to the recording head controller 25 is corrected using delay data in accordance with the number of nozzles 10 driven simultaneously (delay correction). Accordingly, D/A converting cycle of each driving pulse in the D/A convertor 30 is corrected, and that can minimize the fluctuation in the driving waveform that consists of the group of driving pulses. The delay data can be both plus (extension) and minus (reduction).
The driving waveform timing generator 260 selects the most appropriate delay data in accordance with the number of driven nozzles based on the threshold value of the number of driven nozzles used for selecting the delay data and outputs the selected delay data from the common driving circuit.
In
The driving waveform timing generator 260 selects one delay data from multiple delay data a and b stored in the delay data storage unit 261 based on the number of driven nozzles acquired from the number of driven nozzles calculator, the threshold value of the number of driven nozzles, and information from the driving mask pattern output unit 250. The driving waveform timing generator 260 corrects the timing of transferring the driving waveform data (digital data: DA_DAT signal) to the D/A convertor 256 (periodic fluctuation of the driving waveform) based on the selected delay data a or b.
The number of driven nozzles calculator 252 includes counters for each size of discharged droplets and counts the number of nozzles driven simultaneously from the image data (serial data) SD in transferring the image data.
The threshold of the number of driven nozzles storage unit 253 stores at least more than one threshold value, and preferably, that value is variable such as a register configuration.
Next, correction of the timing of transferring the driving waveform data by the driving waveform timing generator is described below.
For example, the D/A convertor 256 in this embodiment fetches DA_DAT signal at the rising edge of DA_CK signal (a clock signal for transferring driving waveform data DA_DAT signal) and outputs the driving waveform (Vcom) converted to an analog signal at the next rising edge of DA_CK signal. That is, the D/A convertor 256 converts the received driving waveform as the digital signal into the driving waveform (Vcom) as the analog signal.
DA_CK(1) signal in
The driving waveform data (DA_DAT signal) stored in the delay data storage unit 261 is generated assuming that the D/A converting cycle tCL is constant for each of the multiple driving pulses that consist of the driving waveform data stored in the delay data storage unit 261. The delay data a and b described above are delay amount for the D/A converting cycle tCK.
In
If it is unnecessary to perform the correction, the driving waveform (data) Vcom becomes equivalent to the driving waveform (data) stored in the driving waveform storage unit 251 by making all delay amount 0.
In case of performing the delay correction, the driving waveform data DA_DAT signal also delays just like the clock DA_CK signal.
As described above, in the recording head controller 25, one delay data is selected from the stored delay data based on the number of nozzles driven simultaneously. The timing of driving waveform for correcting the timing of transferring the driving waveform to the D/A convertor based on the selected delay data, and the timing of transferring the driving waveform data to the D/A convertor based on the selected delay data is corrected. In addition, the D/A converting cycle in the D/A converter is modified by correcting the timing of transferring the driving waveform data, and the fluctuation of the driving waveform due to the fluctuation of the number of nozzles driven simultaneously is minimized. The units that perform steps described above such as the driving waveform timing generator 260 can be realized by executing a program by the computer in the inkjet recording apparatus.
Taking the waveform shown in
That is, the numbers of driven nozzles that affect the rising time and the fall time of the driving waveform pulses are different for each of the driving pulses from (1) to (4).
Accordingly, a unit of timing of selecting the driving waveform is preferably a unit of the driving pulse (a unit of one MN period).
In
Here, in the delay data b appropriate if the number of driven nozzles is large, for example, the rising time and the fall time of the driving pulse become long (i.e., they become dull) due to the large capacitance. Consequently, with considering this point, the delay data b is used for correcting the timing of transferring the driving waveform data to the D/A converter 256 preliminarily so that the rising period and the fall period of the driving pulse become shorter.
In
Here, since the delay data is selected in the unit of the driving pulse (unit of 1 MN period), it is preferable that the grand total of the delay data a is the same as the grand total of the delay data b.
In
In addition, in the driving pulses from (1) to (4), the delay data a is selected if the number of driven nozzles is less than the threshold value of the number of driven nozzles, and the delay data b is selected if the number of driven nozzles is either equal to or larger than the threshold value of the number of driven nozzles.
In the first example of the setting table shown in
Here, in a unit of mask signal values of the driving pulse, the target droplet sizes are categorized as (i) large droplet, medium droplet, and small droplet, (ii) large droplet and medium droplet, (iii) large droplet and small droplet, (iv) large droplet, (v) medium droplet and small droplet, (vi) medium droplet, and (vii) small droplet. On that basis, the threshold values are configured for each of the droplet sizes.
That is, in the case of (i) large droplet, medium droplet, and small droplet, the threshold value of the number of driven nozzles is set to 700 nozzles. In the case of (ii) large droplet and medium droplet, the threshold value of the number of driven nozzles is set to 600. In the case of (iii) large droplet and small droplet, the threshold value of the number of driven nozzles is set to 400. In the case of (iv) large droplet, the threshold value of the number of driven nozzles is set to 300. In the case of (v) medium droplet and small droplet, the threshold value of the number of driven nozzles is set to 500. In the case of (vi) medium droplet, the threshold value of the number of driven nozzles is set to 200. In the case of (vii) small droplet, the threshold value of the number of driven nozzles is set to 100.
Similarly to the case in
In the head driving waveform Vcom, the driving waveform data is different depending on the print mode, and the ink droplet discharging velocity Vj is also different. Taking that point into account, in the third example configuration, different threshold values of the number of driven nozzles can be configured corresponding to the print modes
As shown in
Similarly to the cases in
In some cases, the ink droplet discharging velocity varies depending on temperature of the recording head 9. Taking that point into account, in the fourth example configuration, different threshold values for the number of driven nozzles can be configured corresponding to the detected temperature of the recording head 9.
In this fourth example, the temperature of the recording head 9 is categorized as (i) less than 10° C., (ii) either equal to or more than 10° C. and less than 20° C., (iii) either equal to or more than 20° C. and less than 30° C., and (iv) either equal to or more than 30° C. The number of categories can be modified.
Here, in the case of (i) less than 10° C., the threshold value of the number of driven nozzles is set to 100 nozzles. In the case of (ii) either equal to or more than 10° C. and less than 20° C., the threshold value of the number of driven nozzles is set to 200 nozzles. In the case of (iii) either equal to or more than 20° C. and less than 30° C., the threshold value of the number of driven nozzles is set to 300 nozzles. In the case of (iv) either equal to or more than 30° C., the threshold value of the number of driven nozzles is set to 400 nozzles. zzles is set to 100 nozzles if the temperature is less than 10° C.
Similarly to the cases in
As shown in
If the printing stage includes not only the constant velocity stage of the carriage 1 but also the acceleration stage and the deceleration stage, the landing position Xj is corrected by adjusting timing of driving the head basically. In this case, degree of influence of the ink droplet discharging velocity to the landing position Xj depending on the number of driven nozzles is different in the constant velocity stage, the acceleration stage, and the deceleration stage.
Taking that point into account, in the fifth example configuration, different threshold values for the number of driven nozzles can be configured corresponding to the main scanning velocity.
In
Similarly to the cases in
In the fifth example configuration shown in
In
Similarly to the cases in
In selecting the delay data in cases shown in
As described above, in the image recording apparatus in this embodiment, delay amount added to the D/A converting cycle is included in the correction table, the threshold values of the number of discharging nozzles are parameterized, it is determined whether or not it is necessary to correct the driving waveform, and the D/A converting cycle is corrected if necessary. Consequently, in this embodiment, the necessary arithmetic circuit is small, the increase of hardware resources such as memory capacity and the arithmetic circuit can be minimized, and it is possible to perform the correction in accordance with the number of driven nozzles.
The driving waveform storage unit 251 stores multiple driving waveform data. The number of driven nozzles calculator 252 calculates the number of nozzles driven simultaneously from the image data. The driving waveform selector 254 selects one driving waveform data from multiple driving waveform data based on the number of driven nozzles. The threshold of number of driven nozzles storage unit 253 stores threshold values used for selecting the driving waveform in a storage area whose value is changeable such as a register. The history storage unit 270 stores a history of the past number of driven nozzles and the driving wave form selected in past times. The driving waveform storage unit 251 stores two driving waveforms a and b. The driving waveform selector 254 selects one driving waveform from the two driving waveform data based on the number of driven nozzles calculated by the number of driven nozzles calculator 252. The number of driven nozzles calculator 252 includes counters for each size of discharged droplets and counts the serial data SD in transferring the image data. The threshold of the number of driven nozzles storage unit 253 stores at least more than one threshold value, and preferably, that value is variable such as a register configuration. The driving waveform selector 254 selects one waveform from the multiple waveforms stored in the driving waveform storage unit 251 and output it based on the number of driven nozzles sent from the number of driven nozzles calculator 252, threshold of the number of driven nozzles, and information sent from the head driving mask pattern output unit 250 and the history storage unit 270. The D/A converter 256 performs analog conversion on the driving waveform selected by the driving waveform selector 254 and outputs it as a head driving waveform Vcom.
While it is still possible to suppress, for example, minimize the deviation of the landing positions of the ink droplets if the number of driven nozzles is large, the deviation of the landing positions due to the switch of the driving waveform also occurs.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
As can be appreciated by those skilled in the computer arts, this invention may be implemented as convenient using a conventional general-purpose digital computer programmed according to the teachings of the present specification. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software arts. The present invention may also be implemented by the preparation of application-specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the relevant art.
Each of the functions of the described embodiments may be implemented by one or more processing circuits. A processing circuit includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC) and conventional circuit components arranged to perform the recited functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-045789 | Mar 2013 | JP | national |
| 2013-077194 | Apr 2013 | JP | national |
| 2013-097982 | May 2013 | JP | national |
| 2013-109261 | May 2013 | JP | national |
