JP2004017586A - Recorder and method of controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate ununiformity in impact positions of ink drops on a recording medium by controlling an ejection timing of a moving head according to a relative position of a wave made by a waving platen by using the waving platen in order to generate cocklings provided at predetermined intervals. <P>SOLUTION: When the recording is performed by ejecting ink on a recording paper which is waved by ribs provided on the platen, the ink is ejected by reducing the interval of the ejection timing rather than that in a condition without waving in a zone 6 of the recording head moving from the top to the bottom. When the head is moving in a zone 7 from the bottom to the top, the interval of the ejection timing is increased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printing apparatus, and more particularly to a printing apparatus that performs printing by causing a printing head that ejects ink to scan on a printing medium such as printing paper, and a control method thereof.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the development of personal computers, the technology of printer apparatuses has been dramatically improved. The printer device is configured to record an image on a sheet based on image information. Recently, a recording device of a printer apparatus that has been receiving the most attention is a so-called ink jet system in which recording is performed by discharging ink droplets. The advantage is that high-definition images can be recorded at high speed, and are superior to other recording methods in various points such as running cost and quietness.
[0003]
In the ink jet printer as described above, the recording head is caused to scan in a direction (main scanning direction) orthogonal to the conveying direction of the paper (hereinafter referred to as “scanning”) so that the recording head is alternately transported many times. The image is recorded on the paper by performing the rotation. The ejection timing of the recording head includes one generated from a signal read from a linear encoder provided extending in the scanning direction and one generated from a driving pulse of a pulse motor.
[0004]
On the other hand, when the recording head repeatedly ejects ink to the paper, expansion due to water absorption of the ink gathers and the paper has a wavy shape. The phenomenon in which the paper undulates is called cockling.
[0005]
FIG. 2 shows a state of the sheet before printing, and FIG. 3 shows an example in which cockling occurs due to printing. Here, reference numeral 1 denotes a sheet, and reference numeral 2 denotes a sheet base for performing printing called a platen. The problem with the occurrence of cockling is that if the amount of undulation increases, the space between the recording head and the paper becomes narrower, and if the distance between the recording head and the paper is not sufficient, the recording head comes into contact with the paper. On the point. Further, since the interval between the sheet and the recording head is not constant, the ink landing position may deviate from the target position due to the height of the sheet due to cockling.
[0006]
Japanese Patent Laying-Open No. 11-240146 proposes two types of methods. The first proposal is to correct the landing position of ink dots by detecting the distance between the recording head and the paper with a sensor for each scan of printing and delaying the ejection timing based on the amount of cockling. It is. The second is to count the amount of ink ejected in the previous scan, estimate the amount of cockling as an ejection history, and delay the ejection timing based on the count to correct the landing position of the ink dot. Have a suggestion to do.
[0007]
On the other hand, as a method actually used in the existing recording apparatus, several ribs are erected on the platen and cockling is forcibly generated by the ribs, and the cockling cycle is set to a predetermined interval in advance. In order to solve this problem, the amount of change in the position of the sheet due to cockling is reduced. A platen having such a shape is called a waving platen.
[0008]
FIG. 4 shows the state of the sheet by the corrugated platen. Reference numeral 3 denotes a rib for forcibly generating cockling. With respect to such a method of forcibly generating cockling, the effect can be expected most when plain paper such as copy paper which has a small amount of water absorption and is thin and weak in paper strain is used. In other words, by forcibly generating cockling, large cockling due to expansion of the sheet due to ink absorption can be suppressed.
[0009]
Conversely, special paper for high-quality printing (glossy paper, etc.) has excellent water absorption properties, and cockling does not often occur, so there is no need to forcibly generate cockling. . In addition, since such paper itself has a thickness due to coating or the like, the cockling cannot be forcibly generated by the waving platen because the paper is strong, and the paper is placed horizontally with the rib on the platen as a fulcrum. The printing condition is suitable for special paper.
[0010]
[Problems to be solved by the invention]
However, in the first proposal of JP-A-11-240146, a sensor for detecting the distance between the recording head and the sheet is required. At present, ink jet printers are becoming extremely low-priced, and drastic cost reductions are being made. Providing a sensor for detecting the distance between the recording head and the sheet in such a situation is not desirable from the viewpoint of cost in a popular machine having the largest number of units sold.
[0011]
Even if there is a low-cost, high-precision sensor, it is necessary to constantly detect the distance between the recording head and the paper during scanning of the recording head and delay the ejection timing based on the distance. A dedicated IC (for example, an ASIC) is occupied, and the image processing that should be performed is delayed, and as a result, there is a possibility that the printing speed is reduced.
[0012]
The second proposal is a method of counting the ink ejection amount ejected in the previous scan and predicting the cockling amount, but cockling does not always occur as predicted. Further, since this document proposes using a flat platen, various cocklings are generated depending on the influence of the type of paper, temperature, and humidity. For this reason, it is difficult to predict all of them, and the feasibility is low.
[0013]
Further, in the method of forcibly generating cockling by a rib actually used in an existing recording apparatus, the cockling is forcibly generated to reduce and disperse the amount of cockling due to ink absorption. It is possible to suppress cockling that is larger than that of a flat platen. However, on the other hand, there is a problem that the periodic cockling due to the ribs always occurs when a thin sheet of paper, such as plain paper, is used.
[0014]
Since the ejection is performed while scanning the recording head (carriage on which the head is mounted), the ejection speed of the ink dots is a composite speed of the speed in the scanning direction and the ink ejection speed. This is shown in FIG. In the figure, Vcr is the scanning speed (moving speed) of the recording head, and Vdr is the ink ejection speed (flying speed). Thus, Vttl obtained by combining the two actual speeds is the speed of the ink dots actually ejected on the paper. That is, since the speed of the ink dots ejected from the recording head is increased by the speed Vcr in the scanning direction, the position in the scanning direction of the ejected head in the scanning motion and the scanning direction in which the ink lands on the paper are described. Positions do not match.
[0015]
FIG. 6 shows a state in which the recording head is moved at a constant speed in the scanning direction using a flat platen, and ejection is performed at equal intervals. As is clear from the figure, when the recording head is moved at a constant speed and the ink is ejected at equal intervals, the positions of the ink dots landing on the paper are shifted by an amount depending on the scanning speed of the carriage, but the landing of the dots occurs. The position becomes even.
[0016]
On the other hand, FIG. 7 shows a state of ejection when cockling is forcibly generated at the rib position by the wavy platen. As is apparent from the figure, in the section 4 where the paper peaks (parts away from the platen) to valleys (parts near the top of the platen), the scanning direction of the recording head is from right to left in the drawing, so that ink dots The landing interval becomes wider. In the section 5 from the valley to the hill of the paper, a phenomenon occurs that the landing interval of the ink dots becomes narrower.
[0017]
This phenomenon becomes more conspicuous as the scanning speed of the recording head increases. As described above, since high quality and high speed are demanded in the ink jet printer in the future, it is clear that such a problem will become more prominent in the future.
[0018]
Further, when focusing on bidirectional printing, the scanning direction of the recording head is reversed between the forward path and the backward path, and the velocity vector obtained by the combined velocity becomes right and left and reverse. Therefore, the ejection timing in the forward scan and the ejection timing in the backward scan motion must be different according to the difference between the vectors. This alone cannot cope with the case where cockling is forcibly generated by the waving platen. The reason is that the section 4 goes from the peak to the valley on the outward path in FIG. 7, but goes from the valley to the peak on the return path, and the nature of the paper depends on the moving direction when the head is driven. It is.
[0019]
The present invention has been made in view of such a problem, and uses a waving platen to generate cockling provided at a predetermined interval, and adjusts the ejection timing according to the relative position of the wave of the platen of the head during scanning movement. An object of the present invention is to provide a printing apparatus and a control method thereof, which can improve the unevenness of the landing positions of ink on a printing medium by appropriately adjusting the printing apparatus.
[0020]
[Means for Solving the Problems]
In order to solve such a problem, for example, a recording apparatus according to the present invention has the following configuration. That is,
A recording apparatus capable of mounting a head for discharging an ink liquid and performing recording by scanning the head in a direction substantially perpendicular to a conveying direction of a recording medium, the recording apparatus being provided at a position facing the recording head. A wavy platen for generating cockling in the scanning movement direction of the recording medium,
Detecting means for detecting the phase position of the wave of the waving platen of the head during the scanning movement;
Control means for controlling the ejection timing of the ink liquid based on the phase position detected by the detection means.
[0021]
Further, according to a preferred embodiment of the present invention, it has the following configuration. That is,
As described above, when the corrugated platen is used, the ink landing position on the paper is not uniform when the ink is ejected at the same speed and at the same time interval because of the cockling that is forcibly generated. Therefore, in the present invention, in the section from the peak to the valley where the landing interval of the ink dots is wide, the landing interval is not widened by performing the ejection earlier than the reference ejection time interval. Here, the reference ejection time interval is generated from a timing signal read from the encoder, and is generated at the same time when the recording head scans the sheet. To perform ejection earlier than the reference ejection time interval, it is necessary to forcibly perform ejection at a timing earlier than the ejection signal generated from the timing signal read from the encoder. That is, the ejection signal is still generated at a position before the recording head reaches the position where the ejection should be originally performed. As described above, a significant feature of the present invention is that the modulation control for forcibly discharging is performed at a timing earlier than the discharge signal generated from the timing signal read from the encoder. Another significant feature is that the modulation control is performed by the ASIC 10.
[0022]
In the section from the valley to the peak where the landing interval is narrow, the ejection time is delayed so that the landing interval is widened. The delay time is a section from the peak to the valley of the cockling, and the time accumulated by forcibly performing the ejection at a timing earlier than the original ejection timing is used. The accumulated time becomes zero at the position of the peak of the cockling.
[0023]
In this way, by performing modulation control on the ejection signal in accordance with the cockling cycle, correction is performed so that ink dots land on the paper at equal intervals. This is shown in FIG. In section 6 in the drawing, the ejection is performed at a cycle faster than the reference ejection time interval, and in section 7, the control is performed such that the ejection time interval is delayed and returned to the reference ejection time interval. In other words, the reference discharge time interval is the peak position of the peak of the cockling. In the direction toward the valley, since the ejection time interval is advanced, the accumulated time of the advanced time is accumulated. Conversely, in the direction from the valley to the mountain, control is performed such that the accumulated time is reduced by delaying the ejection time in the direction from the valley to the accumulated time at the peak position of the mountain. By this ejection timing modulation control, the ejection intervals of the ink dots on the paper can be made uniform.
[0024]
The reason why the modulation of the ejection time interval can be controlled is that the period of the cockling is uniquely determined by the interval between the ribs. However, since the difference (amplitude) between the peak and the valley of the cockling differs depending on the type of paper, a time for modulating according to the type of paper is prepared. In addition, since the amount of cockling varies depending on the temperature and humidity, the amount of cockling is predicted according to the temperature inside the printer. In addition, special paper or the like, which has a strong paper strain and is thick, does not cause cockling even by the waving platen as described above. Like that.
[0025]
By performing the modulation control of the ejection time interval as described above, it is possible to equalize the landing positions of the ink on the paper with respect to the cockling generated when the waving platen is used. In addition, since the landing positions are uniform, the landing on the forward path and the landing on the return path can be matched even in bidirectional printing.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings.
[0027]
FIG. 1 shows a schematic configuration of a printer engine unit in the embodiment. In FIG. 1, reference numeral 101 denotes an ink cartridge. As shown in the figure, an ink tank is filled with four color inks of Y (yellow), M (magenta), C (cyan), and K (black), and the same print head 102. . On this recording head, there are provided nozzles for discharging a large number of ink liquids along the illustrated Y axis (sub scanning direction), and these nozzles are driven while performing scanning movement in the illustrated X axis (main scanning direction). This makes it possible to store images in band units. Reference numeral 103 denotes a paper feed roller which rotates in the direction of the arrow in the figure while holding down the recording paper P together with the auxiliary roller 104, and feeds the recording paper P in the y direction as needed. Reference numeral 105 denotes a paper feed roller that feeds the recording paper and also plays a role of suppressing the recording paper P as in the case of 103 and 104. A carriage 106 supports the four ink cartridges and moves them together with printing. When printing is not being performed or when the recording head is to be recovered, the home position (h) at the position shown by the dotted line in the drawing is to wait, and a cap mechanism or the like for preventing the recording head from drying. In addition, a suction mechanism for recovering clogging is provided at the same location. However, these are not directly related to the present invention, and thus are omitted. Reference numeral 107 denotes a guide rod having a spiral groove for causing the carriage 106 to perform a scanning motion along the X axis, and for guiding the carriage 106. Since the carriage 106 has a protruding portion (not shown) that fits into the groove in the guide rod 107, after all, rotating the guide rod 107 causes the carriage 106 to move along the X axis. By changing the rotation direction, it is possible to move on the forward path and the return path. Reference numeral 108 denotes a linear encoder, which is provided with a slit in order to generate a print head drive timing signal. The carriage 106 includes a sensor (a linear encoder sensor described later) that optically detects each slit of the linear encoder 108 during the scanning movement.
[0028]
Reference numeral 109 denotes a platen provided at a position facing the recording head 102 so as to sandwich the recording paper P. On the surface of the platen 109, ribs (not shown) for forcibly generating the cockling described above are provided at regular intervals. Therefore, it is also called a wavy platen below. The height of the Z-axis on the upper surface of the rib is set at a position higher than the Z-axis position at which the recording paper P is nipped by the rollers 103 and 104 and the Z-axis position at which the recording paper P is nipped by the roller 105. The P is transported so as to contact the platen 109 with a predetermined pressure.
[0029]
By the way, the recording resolution in the main scanning direction of this type of device is very high at 1200 dpi, and it is difficult to provide a slit in the linear encoder 108 with this accuracy. Therefore, in reality, based on the signal detected by the linear encoder 108, a plurality of drive pulses are generated between the signals to increase the resolution in the main scanning direction.
[0030]
FIG. 9 shows a block diagram of a control system in the embodiment. The configuration shown in the figure will be described below in terms of its processing operation.
[0031]
In the printer device, the CPU 9 reads software (program) stored in the ROM 11 and executes the instruction to perform printing. An ASIC (Application Specific Integrated Circuit) 10 is a hardware that implements a function unique to the printer device, and performs image processing, communication of a host computer via an interface 11, discharge control of a recording head 12, and an LF (paper feed) motor for paper conveyance. The control of the driver 13 and the control of the CR motor driver 14 for scanning movement of the recording head (rotation of the guide rod 107) are performed. The DRAM 15 is used for temporarily storing print data from the host computer, for temporary memory when performing image processing, and for storing print data (image data). Reference numeral 16 denotes a sensor of the linear encoder 108 provided extending in the scanning direction, and controls the position and speed of the recording head using a signal detected by the sensor as a reference signal. Further, the ejection timing of the recording head is controlled based on the reference signal. The ASIC 10 also controls these ejection timings. Further, in the embodiment, a temperature sensor 17 is further provided, and the ejection timing is generated in consideration of data on the temperature.
[0032]
Normally, the scaler (slit interval) used for the linear encoder is about 150 LPI or about 300 LPI, but the actual printing resolution in the scanning direction in printing is 1200 DPI, 2400 DPI, or a higher resolution, that is, the linear encoder. Finer than the scaler resolution. Therefore, the encoder signal is multiplied inside the ASIC 10 and used as the ejection timing. As a method of multiplication, a method of obtaining a desired resolution from both edge signals of the A and B phases of the encoder signal (signal from the sensor 16), and measuring a time between one edge of one phase one cycle before. There is a method of dividing the time to obtain a desired resolution. The former method is simple as a method, but has a problem that the discharge interval is not constant due to the variation of the slider of the encoder scaler. In the latter case, there is little variation as in the former, because the detection is performed with one phase and one edge, but since the signal is divided based on the encoder signal one cycle before, rapid speed fluctuations, especially high speeds, occur. Then, there is a problem that an edge comes before all the ejection signals obtained by dividing the encoder signal of the previous cycle are generated. Generally, the latter method is often used by incorporating a compensation circuit for this problem.
[0033]
In the present embodiment, as shown in FIG. 10, for the cockling of the paper forcibly generated by the waving platen 109, the interval between the ribs is divided into eight sections I to VIII, and the state of the cockling is set in each area. To approximate a straight line. As can be seen from the figure, the state of cockling can be approximately approximated by dividing into eight. However, in the present embodiment, eight divisions are taken as an example. However, an appropriate number n is selected according to the scale of the circuit to be realized, and the number is not necessarily limited to eight. Here, sections I to VIII have different correction times D₁~ D₈have. This correction time is Dn (n = 1 to 8). In order to equalize the landing positions of the ink dots in the sections I to IV (sections indicated by "-" in FIG. 10) from the peak to the valley of the cockling, The time for generating the ejection signal is set at a timing earlier by the correction time. In the sections V to VIII (sections indicated by “+” in FIG. 10) from the valley to the peak, a time for generating the ejection signal is set at a timing later by the correction time.
[0034]
Then, in each section, by generating an ink ejection timing signal, for example, as shown in FIG. 8, in the section 6 from the peak to the valley, the ejection cycle is shorter than the cycle when it is assumed that cockling does not occur. Then, the ink lands on the recording paper at even intervals, and conversely, in the section 7 from the valley to the hill, the cycle is lengthened so that the ink lands on the recording paper.
[0035]
Next, a specific example of how to control the modulation of the ejection timing described in Means for Solving the Problems will be described.
[0036]
In order to simplify the explanation, the intervals in the main scanning direction in the sections I to VIII in FIG. 10 are equal, and in one section, the number of slits of the linear encoder 109 is four, that is, four encoder signals can be obtained. Shall be. Also, an example will be described in which ink is ejected in the main scanning direction at a resolution four times the distance between the slits of the linear encoder 109. Therefore, the distance between the ribs is four slits of the linear encoder. However, in reality, the distance between the ribs is a sufficiently large interval. Note that this is for the sake of simplicity.
[0037]
When the origin of the head 102 (carriage 109) is the home position, the position of the head 102 (also the position of the nozzle) during the scanning movement can be determined by counting the encoder signal output from the linear encoder sensor 16. The positions and intervals of the ribs provided on the platen 109 are known. Therefore, under the above conditions, 32 (= 4 × 8) encoder signals are detected during eight sections from section I to section VIII, and section I to section VIII are repeated alternately.
[0038]
FIG. 11 is a timing chart showing the relationship between the detection signal of the linear encoder 16 and the ejection timing signal in the section I (one of the four sections from the peak to the valley) in FIG.
[0039]
In the figure, reference numeral 16a denotes a detection signal of the linear encoder 16, and reference numeral 16b denotes a result obtained by multiplying the frequency of the detection signal 16a by four (the period is T).₀). In the case of special paper (such as stiff glossy paper) in which cockling does not occur or is difficult, a discharge timing signal (cycle T)₀).
[0040]
The signal 16b 'is an enlarged view of four of the multiplied signals. In the interval I, the period T₀If it is driven as it is, as shown in FIG. 7, the landing interval on the recording paper becomes wide, so that the signal 16b (also 16b ') is directly used as the ejection timing signal (ejection drive signal). Can not.
[0041]
So, T₀For a small time D₁By outputting the drive signal in a short period, the signal 16c is generated. This minute time D_i(I = 1, 2, 3,... 8) is a reference period T₀Is referred to as a correction amount.
[0042]
In the embodiment, as shown in FIG. 10, the interval between the ribs is divided into eight sections, and the undulation due to each cockling is assumed to be linear.₁Is adopted, and the period is constant. Further, in the case of the section IIn, the correction amount D₂Is used to generate a drive timing signal.
[0043]
Here, it should be noted that in the sections I to IV, the driving cycle is equal to the reference cycle T.₀Is shorter in the sections V to VIII. That is, the correction amount Di needs to have a positive or negative sign.
[0044]
In the section I, the reference period T₀The signal 16c generated for D₁Therefore, the accumulated value that advances the timing is n × D1 (n = 4 × 4 = 16 in the embodiment).
[0045]
In addition, since the intervals II to IV are all earlier than the reference period T0, the total accumulated value is n × (D₁+ D₂+ D₃+ D₄).
[0046]
On the other hand, in the sections V to VIII, the reference cycle T₀Needless to say, it is necessary to set the value to a value that offsets the accumulated value in the sections I to IV.
[0047]
Therefore, n × (D₁+ D₂+ D₃+ D₄+ D₅+ D₆+ D₇+ D₈) = 0
It becomes. Where D ₁ ~ D ₄ ≧ 0, D ₅ ~ D₈≦ 0 (in FIG. 11, “T₀-D₁And D₁Is shown as a positive number).
[0048]
The modulation control for generating the drive signal described above is realized by providing a dedicated control circuit inside the ASIC 10, but if a more specific circuit configuration is shown, it is as shown in FIG.
[0049]
In the figure, reference numeral 51 denotes a counter for counting a signal (encoder signal 16a) from the linear encoder 16, and the head 101 (more precisely, the nozzle position of the color component of interest in the head 101) corresponds to any one of the sections I to VIII. This is for calculating whether or not it is located in a section. If the description is made in conformity with the example of the above embodiment, the counter 51 counts up the output value by one every time the four encoder signals 16a are counted. Data that can be expressed). Reference numeral 52 denotes a look-up table (LUT) that inputs the output (3 bits) of the counter 51 as an address and outputs the correction amount Di as output data 52a. 53 is an adder, which is a reference cycle T₀The value 52a from the LUT 52 is added to the value indicating₀'53a is output. Numeral 54 denotes a counter which outputs a sufficiently high-speed clock as a drive signal when the value output from the adder 53 is reached. This can be equivalent to outputting the corrected signal 16c in FIG.
[0050]
The ASIC 10 has a circuit equivalent to the circuit shown in FIG.
[0051]
According to the present embodiment as described above, by performing modulation control of the ejection timing, even when cockling occurs on the sheet due to the wavy platen, the landing positions of the ink dots on the sheet are made uniform. be able to.
[0052]
In the above example, the head has been described with respect to the outward path, but the same control (starting from the section I) may be performed in accordance with the print head scanning direction even in the case of the return path. As a result, the landing in the forward path and the landing in the backward path can be matched even in bidirectional printing.
[0053]
In addition, by storing “0” in all the address positions of the LUT 52, it is possible to deal with a recording sheet in which cockling does not occur. Therefore, it is desirable that the LUT 52 be constituted by a rewritable memory such as a RAM.
[0054]
Further, although the number of sections between the ribs is divided into eight, a more accurate landing position can be realized by dividing the rib into more. Therefore, the correction amount of the landing position may be appropriately switched depending on the scanning movement speed of the recording head, even if the interval is not limited to the eight sections as described above, and even if the rib interval and the recording paper are the same. . This is particularly effective when, for example, the printer can appropriately switch some printing speeds. In addition, the control method also changes depending on the height of the rib (wave height of the recording paper that is wavy).
[0055]
<Explanation of specific example>
Next, based on the above embodiment, a specific example applied to an actual operation of the ink jet printer will be described below.
[0056]
Here, it is assumed that the resolution of the printer is 600 dpi in both the main scanning direction and the sub-scanning direction, and 80 drive signals are generated for one section. The interval between the slits of the linear encoder is 100 dpi. Therefore, six drive signals are output for one encoder signal. Assuming that the number of sections is the same, that is, eight, the distance between the ribs is 80 × 8/600 inches (= about 2.8 cm).
[0057]
Further, assuming that the control start position is the point of the 30th pulse in section III of the section as indicated by reference numeral 130 in FIG. 13, an appropriate cumulative correction time is set as an initial value in accordance with the control start position. The control start position can be set arbitrarily, but is set after the recording head has reached the constant velocity state. For example, it may be set at the start position of the image. In this example, the cumulative correction time at the control start position is as follows.
[0058]
Cumulative correction time at the start of control = − (80 × D₁+ 80 × D₂+ 30 × D₃)
Therefore, at the control start position, the modulated ejection signal is generated at a timing earlier than the reference ejection signal one cycle earlier by the accumulated correction time. Similarly, the next modulated ejection signal is
− (80 × D₁+ 80 × D₂+ 31 × D₃). In this manner, up to the section IV, the modulated ejection signal is generated at a timing earlier than the reference ejection signal one cycle earlier by the accumulated time.
[0059]
In the sections V to VIII, the cumulative time is reduced by adding the correction time integrated to the reference discharge signal one cycle before, and finally, the cumulative correction time at the peak position of the cockling, that is, at the rib position of the platen. Set to zero. This control is continuously performed in accordance with the repetition of cockling.
[0060]
Next, an example of setting the correction time (correction amount) is shown in FIG. The degree of cockling depends on the environment (temperature) in which the device is placed, but as shown, 25 ° C (temperature up to 25 ° C), 30 ° C (temperature higher than 25 ° to 30 ° C), 35 ° C. It was confirmed that most of the situations could be handled by dividing the temperature into three stages of ° C (greater than 30 ° and 35 ° C or less). Which table is used is determined by data detected by the temperature sensor 17 (see FIG. 9). In the case of describing the configuration of FIG. 12, if data from the temperature sensor 17 (three levels in this example, two bits are sufficient) is supplied to the LUT 52 as an address, as a result, It can be equivalent to selecting an appropriate one from a plurality of tables based on data from the temperature sensor 17.
[0061]
In FIG. 14, for example, the correction time in the case of section II and 25 ° C. is D₂= 2, and the ejection timing is advanced by 2 (clk) each time with respect to the reference ejection signal one cycle before. Therefore, at the end of section II,
80 (pulss) × 2 = 160 (clk)
Accumulate time.
[0062]
At the end of the section IV, a total of 320 (clk) accumulated time is generated. Further, in the sections V to VIII, the reference ejection signal of one cycle before is delayed by integrating 1 (clk) each. Therefore, the cumulative correction time from section V to VIII is 332 (clk). Finally, in the regions I to VIII, the sum of the accumulated correction times becomes 302 (clk) -320 (clk) = 0 (clk), and the accumulated correction time becomes zero.
[0063]
The selection of the table selects an appropriate one according to the environmental temperature measured by the thermistor as the temperature sensor 17 installed in the printer at each head of the page and the type of paper. This is because the amount of cockling varies depending on the environmental temperature and the type of paper as described above.
[0064]
The above-described modulation control is performed by the ASIC 10, so that the landing positions of the ink on the paper can be made uniform with respect to the cockling generated when the waving platen is used, and the landing positions become even. Therefore, even in bidirectional printing, landing in the forward path and return path can be matched.
[0065]
As described above, according to the present embodiment, the modulation of the ejection timing is performed so that the landing positions of the ink dots on the paper are uniform with respect to the cockling of the paper that occurs when the wavy platen is used. Perform control. In the control of the discharge timing, the discharge cycle one cycle before in the direction from the peak to the valley of the cockling is sampled, and the discharge is performed at an earlier timing, thereby shortening the discharge cycle. In addition, in the direction from the valley to the peak, the discharge modulation control is performed by discharging at a discharge cycle that is slower than the discharge cycle one cycle before. As a result, the correction is performed using the position of the peak of the cock ring generated by the wavy platen, that is, the rib position on the platen as the reference position.
[0066]
By this ejection modulation control, the landing positions of the ink dots on the paper can be equalized with respect to the cockling of the paper that occurs when the waving platen is used. Further, since the landing positions are uniform, the landing in the forward path and the landing in the return path can be matched even in bidirectional printing.
[0067]
Further, in a printing operation by the scanning movement of the printing head at the head of the page, the ink has not yet penetrated the printing paper. Therefore, in such a state, the influence of cockling is small. Therefore, the table may be changed between the vicinity of the head of the page (during the scanning movement of 1 to n) and thereafter (during the scanning movement after n + 1 times).
[0068]
Further, in the embodiment, the timing which is the basis of the ink ejection is described by adopting the linear encoder, but the present invention is not limited thereto. In particular, if a configuration is provided that can detect a timing equivalent to the actual recording timing, the timing may be appropriately corrected as described above.
[0069]
In the embodiment, the corrugated platen is realized by providing the ribs. However, since the surface shape of the platen may be a corrugated shape, the present invention is not limited to the above embodiment, and the platen also serves as the paper feed roller. You may do it.
[0070]
【The invention's effect】
As described above, according to the present invention, the corrugated platen is used to generate cockling provided at a predetermined interval, and the ejection timing is appropriately adjusted according to the relative position of the wave of the platen of the head during the scanning movement. This makes it possible to improve the unevenness of the landing positions of the ink on the recording medium.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a printer engine according to an embodiment.
FIG. 2 is a diagram illustrating a state of a sheet before printing.
FIG. 3 is a diagram illustrating a state in which cockling occurs due to ink penetration by a printing operation.
FIG. 4 is a diagram illustrating a state in which cockling occurs due to a wavy platen.
FIG. 5 is a diagram showing a vector sum of ink ejection speeds.
FIG. 6 is a diagram illustrating a landing state of ink when printing is performed using a flat platen.
FIG. 7 is a diagram illustrating a landing state when printing is performed using a wavy platen.
FIG. 8 is a diagram showing a state in which a discharge signal is modulated and controlled in order to equalize a landing position.
FIG. 9 is a block diagram schematically illustrating a printer device.
FIG. 10 is a diagram schematically showing a state of cockling.
FIG. 11 is a drive timing chart of a circuit configuration in the embodiment.
FIG. 12 is a diagram illustrating a specific configuration example of a circuit configuration incorporated in an ASIC in the embodiment.
FIG. 13 is a diagram showing a modulation control start position in the embodiment.
FIG. 14 is a diagram showing the contents of a correction time setting table.

Claims (7)

A recording apparatus capable of mounting a head for discharging an ink liquid, and performing recording by scanning the head in a direction substantially perpendicular to a conveying direction of a recording medium,
A waving platen provided at a position facing the recording head, for generating cockling in the scanning movement direction of the recording medium,
Detecting means for detecting the phase position of the wave of the waving platen of the head during the scanning movement;
A control unit for controlling the timing of discharging the ink liquid based on the phase position detected by the detection unit. The control means divides the cockling in the moving direction of the recording head into n areas, starting from the position of the peak of the cockling and extending to the position of the next peak in one cycle, and linearly interpolating each area. 2. The recording apparatus according to claim 1, wherein a correction amount of the ejection timing is generated, and the ejection timing is controlled according to the correction amount determined for each area. The discharge timing is narrower than a reference discharge interval in a case where cockling does not occur in a section from a peak to a valley of cockling, and a discharge time is widened in a section from a valley to a peak. The recording device according to claim 2. The printing apparatus according to claim 1, further comprising a mode in which a printing operation is performed at a reference ejection interval for a printing medium in which cockling does not occur. 3. The recording apparatus according to claim 2, wherein the correction amount for n areas is one set, and the set includes a plurality of sets corresponding to the temperature. The printing apparatus according to claim 1, wherein the detection unit performs detection based on a signal from a linear encoder provided in a scanning movement direction of the print head. It is possible to mount a head for discharging ink liquid, to perform recording by scanning movement of the head in a direction substantially perpendicular to the transport direction of the recording medium, provided at a position facing the recording head, A method of controlling a recording apparatus having a wavy platen for generating cockling in a scanning movement direction,
A detecting step of detecting a phase position of the wave of the waving platen of the head during the scanning movement;
A control step of controlling the ejection timing of the ink liquid based on the phase position detected in the detection step.

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