JPH06238916A - Thermal ink-jet recording device - Google Patents

Abstract

PURPOSE:To provide a thermal ink-jet recording device which is free from missing image or blur and can perform printing having a favorable image quality. CONSTITUTION:A head temperature is detected by a head temperature detecting part 3 and ink supply pressure is detected by an ink supply pressure detecting part 4, which are taken in a CPU 1. Althogh an image data is stored in an image memory 6 through an interface 5, at that time a printing number of dots are calculated and sent to the CPU 1. In the CPU 1, whether or not an image is formed by dividing into two time printing scanning is decided based on those data and a mask data generating part 8 is controlled through a printing control signal generating part 9. The image data read out from the image memory 6 is converted into a serial data by a data conversion part 7, masked with mask data from a mask data generating part 8 and a printing data is sent out to a head driving control part 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal ink jet recording apparatus for forming a dot by applying a current pulse to a heater to generate bubbles in the ink by heat and ejecting the ink by the pressure.

[0002]

2. Description of the Related Art A thermal ink jet recording apparatus is provided with a nozzle in a print head, and a current pulse is applied to a heater portion provided in an ink flow path communicating with the nozzle to rapidly generate bubbles in the ink by heat. A recording device of a type in which ink droplets are ejected toward a recording medium by the pressure of generated bubbles to form dots.

In such a thermal ink jet recording apparatus, since bubbles are generated by heat, the temperature of the print head rises. In addition, the ink supply pressure decreases due to the decrease in the remaining ink amount. Due to the increase in the temperature of the print head and the decrease in the ink supply pressure, there is a problem that, particularly when a print pattern having a high print image density is printed, missing or blurring occurs.

When the temperature of the print head rises, the drop amount of ejected ink drops increases and the amount of ink consumed increases, whereas the ink supply pressure decreases and the ink supply is not sufficient. However, the recovery of the ink meniscus after the ink is discharged does not follow the discharge frequency, and the discharge becomes unstable. Furthermore, if the recovery of the ink meniscus after ejection does not follow the ejection frequency, air will be trapped in the nozzle. As a result, missing dots in the printed image occur.

In order to solve these problems, in the conventional ink jet recording apparatus, the drive frequency is fixed to a stable low frequency which does not cause the deterioration of the image quality with a sufficient margin. Therefore, the printing speed is restricted,
Alternatively, when printing a solid image, there is a problem that a low density pattern with thinned dots must be used instead.

In order to solve such a problem, for example,
In Japanese Patent Laid-Open No. 61-237651, the ambient temperature is detected, the drive frequency is determined based on the detected temperature data, and the density data is converted into an optimum drive voltage according to the temperature data. The technique for printing is described.
According to this conventional technique, it is possible to reduce density fluctuation due to increase in drop amount due to increase in head temperature and bleeding on recording paper. Further, Japanese Patent Application Laid-Open No. 61-242850 discloses a technique of adjusting the driving energy according to the environmental temperature to prevent the generation of satellites and mists due to the temperature rise.

However, in these conventional techniques, the driving conditions are changed by changing the voltage and the pulse width. This was a technique aimed at appropriately ejecting ink droplets by suppressing changes in the diameter of the dots by changing the driving conditions or adjusting the dots to some extent. Therefore, it is not possible to correct a large image defect such as ink dropout or directional bending. Further, like the conventional technique, in order to correct the drive frequency, drive voltage, drive pulse width, etc.,
It has the drawback of complicating the control circuit.

Further, these conventional techniques have not solved the problem of the drop in ink supply pressure caused by the decrease in the ink remaining amount.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and thermal ink jet recording capable of performing high-quality printing without image loss or blurring by simple control. The purpose is to provide a device.

[0010]

According to a first aspect of the present invention, in a thermal ink jet recording apparatus, a detecting means for detecting the state of the thermal ink jet recording apparatus and a detection output from the detecting means. It is characterized by including print control means for dividing the image data for one scan into a plurality of portions based on the signal and controlling so as to form an image by a plurality of print scans.

According to the second aspect of the invention,
In a thermal inkjet recording device that performs printing by supplying ink from an ink storage unit in which an absorber is impregnated with ink to a print head, a detection unit that detects the ink supply pressure and an ink supply pressure detected by the detection unit Based on the above, the image data for one scan is divided into a plurality of pieces, and a print control means is provided for controlling to form an image by a plurality of print scans.

[0012]

According to the present invention, since the image data for one scan is divided into a plurality of print scans for printing, it is possible to reduce the ink consumption amount for each scan. As a result, the ink consumption of each nozzle increases due to the increase in the ejection drop amount due to the rise in the head temperature, and even if the ink supply pressure to the nozzle portion decreases due to the decrease in the ink remaining amount, the ejection amount decreases. It is possible to avoid the phenomenon that the recovery of the ink meniscus afterwards does not follow the ejection frequency and the ejection becomes unstable.

Further, since the ink supply pressure is detected and the printing is controlled a plurality of times on the basis of the detected ink supply pressure, even if the print pattern has a high print image density, the print pattern can be reliably printed. Moreover, it is possible to prevent slipping out and fading. At this time, when the ink supply pressure is high, the number of scans can be reduced, or control can be performed so that printing is performed by one scan, and the printing speed is not unnecessarily reduced.

A control circuit for performing a plurality of print scans is usually provided in a recording apparatus, and since this circuit can be shared, it is possible to perform the conventional correction of drive frequency, drive voltage, and drive pulse width. In addition, it is not necessary to provide a complicated control circuit.

[0015]

1 is a block diagram showing an embodiment of an ink jet recording apparatus of the present invention. In the figure, 1 is a CPU,
Reference numeral 2 is a ROM, 3 is a head temperature detection unit, 4 is an ink supply pressure detection unit, 5 is an image data input interface unit, and 6 is an image data input interface unit.
Is an image memory, 7 is a data conversion unit, 8 is a mask data generation unit, 9 is a print control signal generation unit, 10 is a head drive control unit, 11 is a carriage drive control unit, and 12 is a paper feed motor drive control unit.

The CPU 1 controls each section of the ink jet recording apparatus according to the control software and data stored in the ROM 2. Also, CPU1
Is connected to the head temperature detection unit 3 and the ink supply pressure detection unit 4, and takes in the head temperature data and the ink supply pressure data. Further, the CPU 1 controls the print control signal generator 9 to generate a signal for driving the head drive controller 10, the carriage drive controller 11, and the paper feed motor drive controller 12. In particular, the CPU 1 follows the head temperature data, the remaining ink amount data, and the image data fetched from the head temperature detecting unit 3 and the ink supply pressure detecting unit 4,
A signal is generated to control whether the print data is printed by the printing device once or divided into a plurality of print scans, and the print control signal generator 9 is controlled.

The ROM 2 holds control software for operating the CPU 1 and set values. A part of the ROM 2 may be composed of a readable / writable RAM so that the set value and the like can be rewritten. Furthermore, work R
An AM or a non-volatile RAM may be equipped.

The head temperature detecting section 3 detects the head temperature using, for example, a thermistor and sends the temperature data to the CPU 1 via an internal A / D converter. The ink supply pressure detection unit 4 detects the ink pressure in the ink flow path by using, for example, a resistance line strain gauge or a pressure sensor using a piezoelectric element, and the ink remaining amount is detected via an internal A / D converter. Quantity data C
Send to PU1. The head temperature detection unit 3 and the ink supply pressure detection unit 4 can be provided near the print head and the ink tank.

Image data input interface section 5
Receives, for example, image data given from the host computer and writes it in the image memory 6. At this time, the image data input interface unit 5 counts the number of pixels to be printed from the transferred image data and sends this information to the CPU 1.

The print control signal generator 9 generates signals for driving the head drive controller 10, the carriage drive controller 11, and the paper feed motor drive controller 12 in accordance with instructions from the CPU 1. Further, the mask data generation unit 8 is controlled based on a signal for controlling whether the print data sent from the CPU 1 is printed by one printing device or is divided into a plurality of print scans. Under the control of the print control signal generation unit 9, the mask data generation unit 8 generates mask data used for the image data and sends it to the data conversion unit 7.
The data conversion unit 7 reads the image data stored in the image memory 6 and masks the image data according to the mask data input from the mask data generation unit 8. Then, in accordance with the timing signal generated by the print control signal generator 9, the masked image data is converted into serial data and sent to the head via the head drive controller 10.

The head drive controller 10 includes a data converter 7
In response to the serial image data sent from the printer and the timing signal sent from the print control signal generator 9, the head is driven and printing is performed. Carriage drive controller 11 and paper feed motor drive controller 12
Respectively perform drive control of the carriage and drive control of the paper feed motor in accordance with the timing signal sent from the print control signal generator 9. The head is scanned by driving the carriage. Further, by the paper feeding operation, the positions of the recording paper and the head can be relatively moved in the direction perpendicular to the movement direction of the carriage.

FIG. 2 is a schematic configuration diagram of the vicinity of a head cartridge showing an embodiment of the ink jet recording apparatus of the present invention. In the drawing, 21 is a print module, 22 is a porous body, 23 is a print head nozzle section, 24a and 24b are ink tubes, 25 is a head temperature detection section, 26 is an ink supply pressure detection section, and 27 is an ink supply pressure detection section. It is an ink chamber. The head temperature detector 25 and the ink supply pressure detector 26 shown in FIG. 2 correspond to the head temperature detector 3 and the ink supply pressure detector 4 shown in FIG. 1, respectively.

The porous body 22 in the print module 21
The ink for printing is absorbed in the. The ink absorbed in the porous body 22 is the ink tube 24a.
Through the ink supply pressure detecting ink chamber 27.
The ink flowing into the ink flow path 27 having the ink supply pressure detecting ink chamber further flows into the print head nozzle portion 23 via the ink tube 24b. The print head nozzle unit 23 is provided with a heater for each nozzle,
The ink that has flowed into the print head nozzle portion 23 due to the heating of the heater is ejected, adheres to the recording medium, and printing is performed. The head temperature detection unit 25 is arranged at a position where the temperature of the print head nozzle unit 23 at this time can be measured, and for example, a thermistor can be used. The ink supply pressure detector 26 detects the ink pressure in the ink chamber 27 for detecting ink supply pressure. For example, an elastic body with a resistance line strain gauge is attached to a through hole provided in a part of the wall of the ink supply pressure detecting ink chamber 27, and the resistance value is detected to detect the ink pressure. Can be configured.

Further, in the ink jet recording apparatus of the type having the ink sub tank chamber, a part of the wall of the ink sub tank chamber may be made thin to have elasticity, and a resistance wire strain gauge may be attached to the portion. Ink supply pressure detector 2
In addition to the resistance wire strain gauge, a semiconductor strain gauge, a diaphragm type pressure sensor, or a pressure sensor using a piezoelectric element can be used as the element 6.

The outputs of the head temperature detecting section 25 and the ink supply pressure detecting section 26 are amplified as required, converted into digital signals, and read by the CPU 1.

The head temperature detected by the head temperature detector 25, the ink supply pressure detected by the ink supply pressure detector 26,
Then, how the number of pixels to be printed counted by the image data input / output interface unit 5 in FIG. 1 affects printing will be described. 3 is a graph showing the relationship between the head temperature and the image defect limit frequency, FIG. 4 is a graph showing the relationship between the print use time and the image defect limit frequency, and FIG. 5 is a graph showing the relationship between the image density and the image defect limit frequency. It is a graph.

As mentioned in the description of the prior art, when the head temperature is increased, the ink supply pressure is decreased, and printing is performed on a portion having a high print density, an image defect occurs when the tendency exceeds a certain level, and the image quality is deteriorated. descend. FIG. 3 shows the relationship between these parameters and the maximum frequency at which stable printing can be performed without causing image defects, that is, the image defect limit frequency.
Through FIG. In the figure, the frequency shown by the solid line is the image defect limit frequency, and the frequency shown by the dotted line is the printing frequency in the normal state. Further, in FIGS. 3 and 4, an image having a print image density of 70% is used as the print pattern.

As shown in FIG. 3, as the head temperature increases due to continuous printing, the image defect limit frequency decreases. As can be seen from FIG. 3, when the head is driven at a constant print frequency, for example, the print frequency shown by the dotted line with respect to the head temperature rise, when the head temperature exceeds a certain temperature, the image defect limit frequency The head is driven over the distance, which causes an image defect.

Further, as shown in FIG. 4, when the printing use time elapses and the ink remaining amount decreases and the ink supply pressure decreases, the image defect limit frequency decreases. Therefore, if the head is driven at a constant printing frequency, for example, the printing frequency shown by the dotted line, the head will be driven beyond the image defect limit frequency for a certain period of time, causing an image defect. Become.

Further, as shown in FIG. 5, even at the same head temperature and ink supply pressure, the image defect limit frequency is different because the ink flow rate is different due to the difference in image density. Therefore, when an image having a high image density is printed at a high printing frequency, an image defect will occur.

As described above, when the head is driven at a constant printing frequency, an image defect may occur due to an increase in head temperature, a decrease in ink supply pressure, printing of a portion having a high image density, and the like. However, even if the head temperature, the ink supply pressure, or the image density that causes an image defect is reached, a printing method that reduces the ink flow rate can avoid any of these image defects.
Therefore, the print state such as the head temperature, the ink supply pressure, the image density, etc. is detected, and the image to be recorded by one print scan is printed in two or more print scans according to the detected print state. As a result, the ink flow rate required for one print scan can be reduced, and stable driving can be performed without causing image defects.

FIG. 6 is a block diagram showing an example of the periphery of the data conversion unit. In the figure, 31 is a shift register and 32 is an AND circuit. The print control signal generation unit 9 includes the CPU 1
, A reference clock that serves as a reference for control timing, a print start signal indicating the start and end of printing, a print end signal,
A mode selection signal indicating the print mode is received. As the mode selection signal, it is possible to include information indicating how many print scans the image of the band-shaped area to be printed is divided and printed. Based on these signals, the print control signal generator 9 creates and outputs various signals. For the head drive control unit 10, a clear signal FCLR for initializing the head drive control unit 10, a bit shift signal BIT SHIFT serving as a timing signal for receiving print data DAT for each bit to be printed, an ink Signal ENABLE which is a timing signal for discharging
Is output.

Address signals A15-A0 are also input to the image memory 6 and the mask data generator 8.
The image memory 6 receives the input address signals A15-A0.
The image data corresponding to is output to the shift register 31. The shift register 31 fetches the image data into the shift register 31 by the latch signal RATCH output from the print control signal generator 9. Shift register 3
1 outputs the image data DATA1 bit by bit in accordance with the bit shift signal BIT SHIFT output from the print control signal generator 9 for the captured data.

On the other hand, the mask data generator 8 is supplied with the address signals A15-A0 input to the image memory 6, the scan signal FSCAN indicating how many times the divided recording is being performed, and the data output for each bit. A bit shift signal BIT SHIFT for performing is input. Based on these signals, the mask signal MASK OUT corresponding to the image data for each bit is output.

The AND circuit 32 outputs the image data DATA1 for each bit output from the shift register 31,
Mask signal MAS output from the mask data generator 8
KOUT and the timing signal MASK output from the print control signal generator 9 are input, and the mask signal MASK O
The print data DAT masked by the UT is output to the head drive controller 10 and printed.

FIG. 7 is a block diagram showing an example of the mask data generator. In the figure, 41 is an 8-bit shift register, 42 is an inverter, 43 is a data selector, 44 is a mask data setting unit, and 45 is an arithmetic circuit. In this example, a case is shown in which an image is formed by two print scans using periodic mask data composed of 8 bits.

Mask data is set in the mask data setting section 44. The mask data can be set by using a DIP switch, a jumper switch, or the like, a ROM to store data in advance, or a RAM to be settable by the CPU 1. The mask data set in the mask data setting unit 44 is 8
It is input to the bit shift register 41. The mask data stored in the 8-bit shift register 41 is the bit shift signal B sent from the print control signal generator 9.
It is output bit by bit by IT SHIFT. The mask data for each 1 bit is returned to the 8-bit shift register 41 and circulates. Further, the mask data for each bit is input to the data selector 43 as it is and the data inverted by the inverter 42.

On the other hand, the address signals A15-A0 and the scan signal F sent from the print control signal generator 9 are sent.
The SCAN is input to the arithmetic circuit 45 and a select signal is output. The data selector 43 selects the mask data or its inverted data by this select signal and outputs it as the mask signal MASK OUT signal.

In the above example, 8-bit cyclic data is used as the mask data, but it is also possible to use longer or shorter cyclic data. Further, it is of course possible to read all the mask data from the mask data setting unit 44. It is also possible to form the image by printing scanning three or more times. In that case, the mask data for each time can be selected by, for example, the scan signal FSCAN and set in the shift register. Alternatively, the mask data may be input to the data selector 43 by the number of print scans and selected.

The operation of one embodiment of the ink jet recording apparatus of the present invention will be described with reference to FIG. Here, a case where an image is formed by two print scans will be described. First, each time the carriage prints for one scan, the head temperature detection unit 3 detects the head temperature. The detected head temperature data is A / D converted and sent to the CPU 1.
In addition, the ink supply pressure detection unit 4 detects the ink supply pressure each time the printing operation for one page is completed. The detected ink supply pressure data is A / D converted and taken into the CPU 1.

When the image data is sent from the host computer, it is written in the image memory 6 via the image data input interface section 5. The image data input interface unit 5 counts the number of pixels to be printed at the time of transferring the image data and sends it to the CPU 1.
The detection of the number of pixels can also be performed by the controller in the image memory 6. The CPU 1 detects the print image density from the number of pixels to be printed.

As the image data, the amount of data to be printed by one normal carriage scan, that is, the image data for each band is read. For example, 300s
When A3 size printing is performed by pi (Spot per inch), if the margins on both sides are set to 8 mm, the printing width is about 281 mm, and 3328 dots are printed. Therefore, drive the head 3328
It will be done once. Further, nozzles are arranged in the head so that, for example, 128 dots are printed in a direction substantially perpendicular to the scanning direction of the carriage. Therefore, the image data for one band is 3328 × 12.
8-bit data will be transferred. This amount of image data is transferred in 8-bit parallel, for example.

The number of pixels of the image data is detected by connecting each 8-bit 1-bit signal line to a 156-bit counter, detecting the transferred image data, and discharging eight times. It counts with the 156-bit counter. Then, the upper 4 bits of each are set to the CPU 1
Transfer to and add. For example, when the value transferred to the CPU 1 and added is 72, the ratio to 3328 × 128 pixels is about 70%. Based on the image density measured in this way, the head temperature data and the ink supply pressure data are combined, and when it is determined that an image defect may occur,
Printing is divided into two scans.

The CPU 1 uses the head temperature data, the ink remaining amount data, and the print image density data that have been taken in as a basis.
The respective threshold value data stored in the ROM 2 are compared. FIG. 8 shows head temperature data, ink remaining amount data,
FIG. 6 is an explanatory diagram of an example of the classification of the print image density data and the printing operation at that time. Head temperature threshold is 35 ℃, 45 ℃
And when the head temperature is lower than 35 ℃, T1, 35 ℃
The time below 45 ° C is indicated as T2, and the time above 45 ° C is indicated as T3. The threshold of the ink supply pressure is the ink supply pressure when the remaining amount of ink that can be used reaches 10% of the initial remaining amount of ink that can be used, and the remaining amount of usable ink that is initially used. The ink supply pressure is 2% of the amount. The ink supply pressure when the remaining ink amount is 10% or more is P1, the ink supply pressure when the remaining ink amount is less than 10%, 2% is P2, and the ink supply pressure when the remaining ink amount is less than 2%. It is shown as P3. The print image density threshold is 70%. The case where the print image density is less than 70% is shown as D1, and the case where it is 70% or more is shown as D2. These thresholds can be set as appropriate.

Based on the threshold value, the detected head temperature, the ink supply pressure, and the print image density level, as shown in FIG. 8, it is determined whether or not the printing operation is performed, that is, whether or not the printing is performed twice. Is judged. In FIG. 8, the case where the image is formed by dividing the printing scan twice is shown as “yes”, and the case where the image is formed by the printing once is shown as “no”.
In FIG. 8, when the head temperature is T3 and the print image density is D2, the head temperature is T2, the print image density is D2, and the ink supply pressure is P3 or P2, and the head temperature is T1. And the ink supply pressure is P3,
In addition, when the print image density is D2, the mode in which the image is divided into two print scans to form an image is selected.

When the ink supply pressure is P3, that is, when the remaining amount of ink is less than 2%, the lamp for warning the ink shortage is turned on to prompt the user to replace the ink cartridge. At this time, a sound warning means such as a buzzer may be provided. In FIG. 8, “(alar
m) ”.

When the data for one band is printed twice, there are various possible combinations of which pixels are printed first and which pixels are printed second, but the image density is reduced. In order to achieve this, it is better to disperse and print as much as possible. For example, three patterns as shown in FIGS. 9 to 11 can be considered. 9 to 11 show
FIG. 7 is an explanatory diagram of a relationship between a mask pattern and a print image when forming an image by two print scans. In the figure, the numbers shown in the upper part of (A) indicate the pixels printed by 1 in the first print scan, and the pixels printed by 2 in the second print scan. (B) is the first print scan, and the upper row is the mask data used at that time, where 1 indicates a pixel to be printed and 0 indicates a pixel not to be printed. A print image when a solid image is printed by such a mask is shown in the lower stage. (C) is the second print scan, and similarly to (B), the upper row shows the mask data and the lower row shows the print image at that time, but the white circles indicate the pixels printed by the first print scan. Shows. (D) is an example of the mask data used for the first and second print scans, and here shows a case where two 128-bit mask data are alternately used. Since the mask data of A and B are patterns which are inverted to each other, as shown in FIG. 7, it is possible to use one pattern, create an inverted signal thereof, and select either one. Is. Further, as shown in FIG. 7, an 8-bit mask pattern may be circulated and used.

FIG. 9 shows an example in which the pixels printed by the first and second printing scans are arranged in a staggered pattern. Further, FIG. 10 shows an example in which printing is alternately performed for each column. Further, FIG. 11 shows an example in which printing is alternately performed line by line. As shown in FIG. 10, when printing is performed in one column at the same time, a large amount of ink is consumed at one time, but since nothing is printed at the next timing, it is possible to secure a time for supplying ink, No missing dots will occur. Further, as shown in FIG. 11, when printing one line, a certain nozzle is driven at a high driving frequency, but the adjacent nozzle is not driven and ink is not ejected, so that the ink is not ejected as a whole. Consumption is halved,
Smooth ink supply will be performed. Figure 9
When staggered printing is performed, the number of drive nozzles in one row is half, ink consumption is halved, and each nozzle is evenly driven, so that well-balanced drive control is performed. Can be done.

As described above, when the predetermined pixels are selectively printed by the first printing and the second printing, the data conversion unit 7 matches the print control signal generated by the print control signal generation unit 9 with each other. Read the image data from the image memory 6,
When converting to serial data and transferring to the head drive control unit 10, mask data as shown in FIGS. 9 to 11 is generated in synchronization with the image data converted to serial data to mask the image data. Head drive control unit 1
You can send it to 0.

FIG. 12 is a timing chart for explaining an operation example when an image is formed by two print scans. Here, it is assumed that 128 nozzles are arranged in the head and that the image data to be printed is the data for ejecting with all the nozzles. At this time, by applying the mask data shown in FIG.
It is assumed that a signal is sent to 0 to perform two print scans.

First, when the power supply for printing is turned on or before printing is started, the print control signal generator 9
Sends a reset signal to the mask data generation unit 8 and inputs the mask data set in advance in the mask data setting unit 44 to the 8-bit shift register 41. Alternatively, after detecting the state of the device, a mask pattern according to the state of the device may be selected or set.

The print control signal generator 9 uses the rising edge of the reference clock input from the CPU 1 as a trigger to set 1
A head drive signal is output so that one scan of 28 nozzles can be performed. First, the clear signal FCLR is generated to initialize the head drive controller 10. Next, the address signals A15-A0 are set, the image data is read from the image memory 6 by 8 bits, and the latch signal LATCH is set.
Is generated and the read image data is stored in the shift register 31 of the data conversion unit 7. Here, of the address signals A15-A0, A15-A4 indicates which head scan in one carriage scan, and A3
-A0 indicates the number of the 16th division data when 128 nozzles are divided into 8 bits.

Next, the bit shift signal BIT SHIFT
When T is sent to the data conversion unit 7, the shift register 31
The image data stored in is output as serial data DATA1. At this time, the same bit shift signal BI
T SHIFT is also input to the mask data generation unit 8,
Mask signal M whose mask data is synchronized with image data
It is output as ASK OUT. Then, the serial data DATA1 is input to the AND circuit 32 together with the mask signal MASK OUT and the timing signal MASK, and is sent to the head drive controller 10 as masked print data DAT. The head drive control unit 10 outputs the input print data DAT to the bit shift signal BIT S
Captured at the rising edge of HIFT, one block of four nozzles is driven by the enable signal ENABLE.

Such a head driving operation is repeated with the movement of the carriage to perform the first print scan. Then, similarly, the second print scan is performed,
It is necessary to switch the mask data, such as inverting the logic of the mask used. The address signals A15-A0 and the scan signal FSCAN are input to the mask data generator 8 for switching the mask data. Based on these signals, the arithmetic circuit 45 outputs a selection signal for selecting the mask data A or the inverted mask data B, and the output signal causes the data selector 43 to select either one. For example, FIG. 9 and FIG. 1 described above.
In the example of 0, the mask A is selected at the odd-numbered head scan in the first print scan and the even-numbered head scan in the second print scan, and the mask B is selected at other times. Whether the head scan is an odd number or an even number is determined by the addresses A15-A4.
It can be determined by the level of the least significant bit A4. for that reason,
For example, in the example of FIGS. 9 and 10, only the address signal input to the mask data generator 8 is A4.
In the above example, it is not necessary to input the address signal.

While switching the mask data as described above, the print scan is performed twice. After two print scans, one paper feed operation is performed. This allows
The printing operation for one band is completed. The above printing operation is repeated to print one page. When the printing of one page is completed, the recording medium is ejected, and if there is image data to be printed, the next recording medium is fed and the image data is printed by the same printing operation.

The above-described recording operation has been described for the case where an image is formed by two print scans. However, as a result of referring to FIG. 8, when it is determined that the image can be formed by one print scan, The normal printing operation operates so as to form an image by one printing scan. This switching can be performed for each print of one band. for that reason,
One or two print scans are selected according to the print data of each band.

The above-described embodiments of image data transfer and head drive have been described on the premise that the carriage scanning in the same direction is repeated twice as a method of division recording. However, when recording is performed by reciprocating carriage scanning. However, it can be realized with a similar configuration.

It is also possible to form an image by printing scanning three times or more. In this case, 3
Holds more than one mask data,
The mask data may be switched by inputting the number of the head scan and used. At this time, there is basically no need to change the configuration of masking the image data converted into serial data.

[0059]

As is apparent from the above description, according to the present invention, there is no print defect even in an environment such as head temperature rise, ink supply pressure reduction, and printing of a portion having many pixels for printing. An image can be stably formed. In addition, the ink in the ink cartridge can be used up to the end without waste. Further, for example, even when the ink supply pressure is reduced, a low-density image such as a text pattern is printed at high speed, and even in a graphic pattern with many pixels to be printed, there is no image dropout or blurring and the image quality is good. There is an effect that printing can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an inkjet recording apparatus of the present invention.

FIG. 2 is a schematic configuration diagram in the vicinity of a head cartridge showing an embodiment of the inkjet recording apparatus of the present invention.

FIG. 3 is a graph showing the relationship between head temperature and image defect limit frequency.

FIG. 4 is a graph showing the relationship between the print use time and the image defect limit frequency.

FIG. 5 is a graph showing the relationship between image density and image defect limit frequency.

FIG. 6 is a block diagram showing an example of the periphery of a data conversion unit.

FIG. 7 is a block diagram showing an example of a mask data generator.

FIG. 8 is an explanatory diagram of an example of head temperature data, ink remaining amount data, and print image density data, and an example of the printing operation at that time.

FIG. 9

FIG. 11 is an explanatory diagram of a relationship between a mask pattern and a print image when an image is formed by two print scans.

FIG. 12 is a timing chart for explaining an operation example when an image is formed by two print scans.

[Explanation of symbols]

1 CPU, 2 ROM, 3 head temperature detector, 4
Ink supply pressure detection unit, 5 image data input interface unit, 6 image memory, 7 data conversion unit, 8 mask data generation unit, 9 print control signal generation unit, 10 head drive control unit, 11 carriage drive control unit, 12
Paper feed motor drive controller, 21 Print module,
22 porous body, 23 print head nozzle section, 24a,
24b ink tube, 25 head temperature detector, 26
Ink supply pressure detection unit, 27 ink supply pressure detection ink chamber, 31 shift register, 32 AND circuit, 418
Bit shift register, 42 inverter, 43 data selector, 44 mask data setting unit, 45 arithmetic circuit.

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Claims (2)

[Claims] 1. A detection means for detecting a state of a thermal ink jet recording apparatus, and image data for one scan is divided into a plurality of pieces based on a detection signal outputted from the detection means, and an image is formed by a plurality of print scans. A thermal ink jet recording apparatus having a print control means for controlling the above. 2. In a thermal ink jet recording apparatus for performing printing by supplying ink from an ink storage unit in which an absorber is impregnated with ink to a print head, a detection unit for detecting an ink supply pressure and a detection unit for detecting the ink supply pressure. A thermal ink jet recording apparatus comprising a print control unit that divides image data for one scan into a plurality of pieces based on the ink supply pressure and controls so as to form an image by a plurality of print scans.