JP3120618B2 - Thermal inkjet recording device - Google Patents

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 in which a current pulse is applied to a heater, bubbles are generated in ink by heat, and ink is ejected by the pressure to form dots.

[0002]

2. Description of the Related Art In a thermal ink jet recording apparatus, a nozzle is provided in a print head, a current pulse is applied to a heater section provided in an ink flow path communicating with the nozzle, and bubbles are rapidly generated in the ink by heat. This is a recording apparatus of a method of forming dots by ejecting ink droplets toward a recording medium by the pressure of generated bubbles.

In such a thermal ink jet recording apparatus, the temperature of the print head rises because bubbles are generated by heat. Further, the ink supply pressure decreases due to the decrease in the remaining amount of ink. 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, peeling or fading occurs.

[0004] When the temperature of the print head rises, the amount of ink droplets to be ejected increases, and the amount of ink consumed increases. On the other hand, the ink supply pressure decreases, and ink supply is not sufficient. In addition, the recovery of the ink meniscus after the ink discharge does not follow the discharge frequency, and the discharge becomes unstable. Furthermore, if the ink meniscus after the ejection is not recovered at the ejection frequency, air is entrapped in the nozzle. For this reason, missing dots or the like in a printed image occur.

In order to solve these problems, in the conventional ink jet recording apparatus, a sufficient margin was anticipated, and the driving frequency was fixed at a stable low frequency which did not cause deterioration in image quality. Therefore, printing speed is limited,
Alternatively, when a solid-color image is printed, there is a problem that a low-density pattern in which dots are thinned out must be used instead.

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

However, in these conventional techniques, the driving conditions are changed by changing the voltage and the pulse width. This technique aims to suppress the change in the diameter of the dot by changing the driving conditions, or to adjust the dot to some extent so that the ink droplet can be properly ejected. For this reason, it was not possible to correct a large image defect such as dropping of an ink droplet or directional bending. Also, in order to correct the driving frequency, the driving voltage, the driving pulse width, and the like as in the related art,
There is a disadvantage that the control circuit is complicated.

Further, these conventional techniques do not solve the problem of a decrease in ink supply pressure caused by a decrease in the amount of remaining ink.

[0009]

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

[0010]

According to a first aspect of the present invention, there is provided a thermal ink jet recording apparatus for performing printing by supplying ink from an ink storage section to a print head.
An ink supply pressure detector for detecting the ink supply pressure, and a number of print scans for printing one scan of image data based on the ink supply pressure data detected by the ink supply pressure detector. When the number of print scans is one, the image data for one scan is controlled so as to form an image by one print scan. When the number of selected print scans is plural, the number of print scans is one. The image processing apparatus further includes a print control unit that divides the image data into a plurality of pieces and controls to form an image by performing a plurality of print scans.

According to a second aspect of the present invention, in a thermal ink jet recording apparatus for performing printing by supplying ink from an ink storage unit to a print head, a head temperature detecting means for detecting a head temperature, and the head temperature detecting means The number of print scans for printing one scan of image data is selected based on the detected head temperature data,
When the number of selected print scans is one, control is performed such that image data for one scan is formed by one print scan, and when the number of selected print scans is plural, one scan is performed. The image processing apparatus further comprises a print control unit that divides the image data into a plurality of pieces, and controls so that an image is formed by a plurality of print scans.

[0012]

According to the first aspect of the present invention, the number of print scans for printing one scan of image data based on the ink supply pressure data detected by the ink supply pressure detecting means for detecting the ink supply pressure is determined. When the number of the selected print scans is one, the image data for one scan is formed by one print scan. When the number of the selected print scans is plural, Since the image data for one scan is divided into a plurality of parts and an image is formed by a plurality of print scans, even if the ink supply pressure to the nozzle part decreases, the amount of ink consumption per scan can be reduced. Thus, it is possible to avoid a phenomenon that the ink meniscus after ejection does not recover at the ejection frequency and the ejection becomes unstable.

According to the present invention, the number of print scans for printing one scan of image data is selected based on the head temperature data detected by the head temperature detecting means for detecting the head temperature. When the number of selected print scans is one, the image data of one scan is formed by one print scan, and when the number of selected print scans is plural, one scan is performed. Is divided into a plurality of parts, and an image is formed by performing a plurality of print scans. Therefore, even if the ink consumption of each nozzle becomes large due to an increase in the ejection drop amount due to an increase in the head temperature. The ink consumption per scan can be reduced, and the recovery of the ink meniscus after the discharge does not follow the discharge frequency and the phenomenon that the discharge becomes unstable is recovered. It can be.

A control circuit for performing a plurality of print scans is usually provided in a recording apparatus, and this circuit can be used in common. Therefore, such a control circuit is used as in the conventional correction of the drive frequency, drive voltage and drive pulse width. It is not necessary to provide a complicated control circuit.

[0015]

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

The CPU 1 controls each part of the ink jet printing apparatus in accordance with control software and data stored in the ROM 2. CPU1
Is connected to the head temperature detection unit 3 and the ink supply pressure detection unit 4 and captures head temperature data and ink supply pressure data. Further, the CPU 1 controls the print control signal generator 9 to generate signals 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 calculates the head temperature data, the remaining ink amount data, and the image data taken from the head temperature detection unit 3 and the ink supply pressure detection unit 4,
A print control signal generator 9 is generated by generating a signal for controlling whether print data is printed by a single printing device or by printing a plurality of print scans.

The ROM 2 holds control software for operating the CPU 1, setting values, and the like. A part of the ROM 2 may be configured by a readable and writable RAM, and the set values and the like may be configured to be rewritable. Furthermore, work R
An AM or a nonvolatile RAM may be provided.

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

Image data input interface unit 5
Receives image data provided from the host computer, for example, 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. The mask data generating unit 8 is controlled based on a signal for controlling whether to print the print data sent from the CPU 1 by one printing device or to print by dividing the print data into a plurality of print scans. The mask data generator 8 generates mask data used for the image data according to the control of the print control signal generator 9 and sends it to the data converter 7.
The data converter 7 reads out the image data stored in the image memory 6 and masks the image data according to the mask data input from the mask data generator 8. Then, the masked image data is converted into serial data in accordance with the timing signal generated by the print control signal generator 9 and sent to the head via the head drive controller 10.

The head drive control unit 10 includes a data conversion unit 7
Receives the serial image data sent from the printer, and receives the timing signal sent from the print control signal generator 9 to drive the head to perform printing. Carriage drive controller 11 and paper feed motor drive controller 12
Performs the drive control of the carriage and the 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 position of the recording paper and the position of the head can be relatively moved in a direction perpendicular to the operation direction of the carriage.

FIG. 2 is a schematic structural view of the vicinity of a head cartridge showing one embodiment of the ink jet recording apparatus of the present invention. In the figure, 21 is a print module, 22 is a porous body, 23 is a print head nozzle, 24a and 24b are ink tubes, 25 is a head temperature detector, 26 is an ink supply pressure detector, and 27 is an ink supply pressure detector. This is the 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
Has absorbed the ink for printing. The ink absorbed by the porous body 22 is the ink tube 24a.
Flows into the ink chamber 27 for detecting the ink supply pressure.
The ink that has flowed into the ink flow path 27 having the ink chamber for detecting the ink supply pressure further flows into the print head nozzle section 23 via the ink tube 24b. The print head nozzle unit 23 is provided with a heater for each nozzle,
By the heating of the heater, the ink flowing into the print head nozzle portion 23 is discharged, adheres to the recording medium, and printing is performed. The head temperature detecting section 25 is arranged at a position where the temperature of the print head nozzle section 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 supply pressure detection ink chamber 27. For example, an elastic body provided with a resistance strain gauge is attached to a through hole provided in a part of the wall of the ink supply pressure detecting ink chamber 27, the resistance value is detected, and the ink pressure is detected. Can be configured.

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

The outputs of the head temperature detecting section 25 and the ink supply pressure detecting section 26 are amplified if necessary, converted into digital signals, and read into 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,
Next, how the number of pixels for printing counted by the image data input / output interface unit 5 in FIG. 1 affects printing will be described. FIG. 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 shows 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 temperature of the head is increased, the ink supply pressure is reduced, and printing is performed in a portion having a high printing density, image defects occur when the tendency exceeds a certain level, and the image quality is reduced. descend. FIG. 3 shows the relationship between these parameters and the highest frequency at which stable printing can be performed without causing image defects, that is, the image defect limit frequency.
5 to FIG. In the figure, the frequency indicated by the solid line is the image defect limit frequency, and the frequency indicated by the dotted line is the printing frequency in a normal state. 3 and 4, an image having a print image density of 70% is used as a 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 printing frequency, for example, a printing frequency indicated by a dotted line, in response to the temperature rise of the head, when the head temperature exceeds a certain temperature, the image defect limit frequency is increased. , And the head is driven to cause image defects.

As shown in FIG. 4, when the printing use time elapses and the remaining amount of ink decreases and the ink supply pressure decreases, the image defect limit frequency decreases. Therefore, when the head is driven at a constant printing frequency, for example, the printing frequency indicated by the dotted line, the head is driven beyond the image defect limit frequency from a certain time, so that an image defect occurs. Become.

Further, as shown in FIG. 5, even at the same head temperature and ink supply pressure, the difference in image density causes a difference in the ink flow rate, and thus a difference in the image defect limit frequency appears. Therefore, when an image having a high image density is printed at a high printing frequency, an image defect occurs.

As described above, when the head is driven at a constant printing frequency, an image defect may occur due to an increase in the head temperature, a decrease in the ink supply pressure, or printing of a portion having a high image density. However, even if the head temperature, the ink supply pressure, or the image density causes image defects, any of these image defects can be avoided by using a printing method that reduces the ink flow rate.
Therefore, the printing state such as the head temperature, the ink supply pressure, and the image density is detected, and in accordance with the state, an image to be recorded by one printing scan is printed by dividing the printing into two or more printing scans. As a result, it is possible to reduce the amount of ink required for one print scan, and to perform stable driving 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 generator 9 is provided with the CPU 1
From, a reference clock serving as a reference for control timing, a print start signal indicating start and end of printing, a print end signal,
A mode selection signal indicating a print mode is received. The mode selection signal can include information indicating how many print scans the image of the band area to be printed is divided into and printed. On the basis of these signals, the print control signal generator 9 generates 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, and ink Enable signal ENABLE as a timing signal for ejecting
Is output.

The address signals A15-A0 are input to the image memory 6 and the mask data generator 8.
The image memory 6 stores the input address signals A15-A0.
Is output to the shift register 31. The shift register 31 takes in the image data into the shift register 31 according to the latch signal RATCH output from the print control signal generator 9. Shift register 3
Numeral 1 outputs image data DATA1 of one bit at a time in accordance with a bit shift signal BIT SHIFT output from the print control signal generator 9 for the fetched data.

On the other hand, an address signal A15-A0 input to the image memory 6, a scan signal FSCAN indicating what number of divisional recordings are being performed, and a data output for each bit are supplied to the mask data generator 8. A bit shift signal BIT SHIFT for performing the operation is input. Based on these signals, a mask signal MASK OUT corresponding to image data for each bit is output.

The AND circuit 32 outputs image data DATA 1 of 1 bit output from the shift register 31.
Mask signal MAS output from mask data generator 8
KOUT, a timing signal MASK output from the print control signal generator 9 is input, and a mask signal MASK O
The print data DAT masked by the UT is output to the head drive control unit 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. This example shows a case where an image is formed by two print scans using periodic mask data composed of 8 bits.

In the mask data setting section 44, mask data is set. The mask data can be set by a DIP switch, a jumper switch, or the like, or can be configured by a ROM to store data in advance, or can be configured by a RAM to be settable by the CPU 1. The mask data set in the mask data setting section 44 is 8
The data is input to the bit shift register 41. The mask data stored in the 8-bit shift register 41 corresponds to the bit shift signal B sent from the print control signal generator 9.
It is output one bit at a time by IT SHIFT. The mask data for each bit is returned to the 8-bit shift register 41 and circulates. 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 signal A15-A0 and the scan signal F sent from the print control signal
SCAN is input to the arithmetic circuit 45, and a select signal is output. The data selector 43 selects mask data or its inverted data according to the select signal, and outputs the selected data as a mask signal MASK OUT signal.

In the above example, 8-bit cyclic data is used as the mask data. However, longer or shorter cyclic data can be used. Further, it is of course possible to configure so that all the mask data is read from the mask data setting unit 44. It is also possible to configure so that an image is formed by three or more printing scans. 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 data selector 43 may be configured to input and select mask data for the number of times of print scanning.

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 printing scans will be described. First, the head temperature is detected by the head temperature detector 3 every time the carriage performs one scan of printing. The detected head temperature data is A / D converted and sent to the CPU 1.
Further, every time the printing operation for one page is completed, the ink supply pressure is detected by the ink supply pressure detector 4. The detected ink supply pressure data is A / D converted, and is taken into the CPU 1.

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

As the image data, the amount of data to be printed by one ordinary carriage scan, that is, image data for one band is read. For example, 300s
When printing in A3 size with pi (Spot per inch), if the margins on both sides are 8 mm each, the printing width is about 281 mm, and 3328 dots are printed. Accordingly, the drive of the head is performed by 3328.
Times. In addition, nozzles are arranged on 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, for example, in 8-bit parallel.

The number of pixels of the image data is detected by connecting an 8-bit 1-bit signal line to each of the 156-bit counters, detecting the transferred image data, and increasing the number of ejections to eight. 156 bit counter. Then, each upper 4 bits are assigned to CPU1.
And add it. 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 integrated, and when it is determined that a state in which an image defect can occur is determined,
Printing is performed in two scans.

Based on the head temperature data, ink remaining amount data, and print image density data, the CPU 1
The threshold value is compared with each threshold data stored in the ROM 2. FIG. 8 shows head temperature data, ink remaining amount data,
FIG. 7 is an explanatory diagram of an example of a division of print image density data and an example of a print operation at that time. Head temperature threshold is 35 ° C, 45 ° C
And T1, 35 ° C. when the head temperature is lower than 35 ° C.
The case where the temperature is 45 ° C. or lower is indicated as T2, and the case where the temperature is 45 ° C. or higher is indicated as T3. The threshold value of the ink supply pressure is the ink supply pressure when the available ink amount becomes 10% of the initial available ink amount, and the available ink amount is the initial available ink amount. The ink supply pressure when the amount becomes 2% of the amount. The ink supply pressure when the ink remaining amount is 10% or more is P1, the ink supply pressure when the ink remaining amount is less than 10% and 2% or more is P2, and the ink supply pressure when the ink remaining amount is less than 2% is P1. It is shown as P3. The threshold value of the print image density is 70%. D1 is when the print image density is less than 70%, and D2 when the print image density is 70% or more. These thresholds can be set as appropriate.

Based on the threshold values and the levels of the detected head temperature, ink supply pressure, and print image density, as shown in FIG. 8, a printing operation, that is, whether or not printing is performed in two printings is performed. Is determined. In FIG. 8, "yes" indicates that an image is formed by two printing scans, and "no" indicates that an image is formed by one printing.
In FIG. 8, when the head temperature is T3, the print image density is D2, the head temperature is T2, the print image density is D2, the ink supply pressure is P3 or P2, and the head temperature is T1. And the ink supply pressure is P3,
When the print image density is D2, a mode in which an image is formed in two print scans is selected.

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

When data for one band is printed twice, there are various combinations of which pixels are printed first and which pixels are printed second, but the image density is reduced. Therefore, 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
FIG. 4 is an explanatory diagram of a relationship between a mask pattern and a printed image when an image is formed by two printing scans. In the figure, in the upper row of (A), 1 indicates a pixel to be printed in the first print scan, and 2 indicates a pixel to be printed in the second print scan. (B) is the first printing 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. For example, a printed image in the case of printing a solid image by using such a mask is shown in the lower part. (C) is the second printing scan, and as in (B), the upper row shows the mask data, and the lower row shows the printing image at that time. White circles indicate the pixels printed by the first printing scan. Is shown. (D) is an example of the mask data used for the first and second print scans. Here, a case where two mask data of 128 bits are used alternately is shown. Since the mask data of A and B are mutually inverted patterns, as shown in FIG. 7, it is possible to use one pattern, create an inverted signal thereof, and select either one. It is. Further, as shown in FIG. 7, an 8-bit mask pattern may be circulated and used.

FIG. 9 shows an example in which pixels printed by the first and second printing scans are arranged in a staggered pattern. FIG. 10 shows an example in which printing is performed alternately one line at a time. FIG. 11 shows an example in which printing is performed alternately one line at a time. As shown in FIG. 10, when printing is performed simultaneously in one column, a large amount of ink is consumed at one time, but nothing is printed at the next timing, so that time for supplying ink can be secured. There is no occurrence of missing dots or the like. In addition, when printing one line as shown in FIG. 11, a certain nozzle is driven at a high driving frequency, but an adjacent nozzle is not driven and ink is not ejected. Consumption is halved,
Smooth ink supply is performed. FIG.
When printing is performed in a zigzag pattern, the number of driving nozzles in one row is halved, ink consumption is halved, and each nozzle is driven evenly. Can be performed.

As described above, when a predetermined pixel is selectively printed in the first printing and the second printing, the data conversion unit 7 adjusts the printing control signal in accordance with the printing control signal generated by the printing control signal generation unit 9. Reads image data from the image memory 6,
When the data is converted to serial data and transferred 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, and the image data is masked. Head drive controller 1
Send it to 0.

FIG. 12 is a timing chart for explaining an operation example when an image is formed by two printing scans. Here, it is assumed that 128 nozzles are arranged in the head, and that image data to be printed is data for ejecting by all nozzles. At this time, the head drive control unit 1 is multiplied by the mask data shown in FIG.
It is assumed that a signal is sent to 0 and two printing scans are performed.

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

The print control signal generator 9 is triggered by the rise of the reference clock input from the CPU 1 to
A head drive signal is output so that one nozzle scan can be performed. First, a clear signal FCLR is generated, and the head drive control unit 10 is initialized. Next, address signals A15-A0 are set, image data is read from the image memory 6 by 8 bits, and a latch signal LATCH is read.
Is generated, and the read image data is stored in the shift register 31 of the data conversion unit 7. Here, among the address signals A15-A0, A15-A4 indicate the number of head scan in one carriage scan, and A3
-A0 indicates the order of the data of the 16 sections when the 128 nozzles are divided into 8 bits.

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

Such a driving operation of the head is repeated with the movement of the carriage, and the first printing scan is performed. Then, a second print scan is performed in the same manner,
It is necessary to switch mask data, such as inverting the logic of the mask used. To switch the mask data, the mask data generator 8 receives an address signal A15-A0 and a scan signal FSCAN. From these signals, the arithmetic circuit 45 outputs a selection signal for selecting the mask data A or the inverted mask data B, and the data selector 43 selects either of them based on the output signal. For example, FIG. 9 and FIG.
In the example of 0, the mask A is selected at the time of the odd-numbered head scan in the first print scan and at the time of the even-numbered head scan in the second print scan, and the mask B is selected at other times. The determination of whether the head scan is odd or even is based on addresses A15-A4
Can be determined by the level of the least significant bit A4. for that reason,
For example, in the examples of FIGS. 9 and 10, the address signal to be input to the mask data generating section 8 is only A4, and FIG.
In the example, the input of the address signal is not required.

While performing such mask data switching, two printing scans are performed. After two print scans, one paper feed operation is performed. This allows
The printing operation for one band is completed. The printing operation as described above is repeated to print one page. When printing of one page is completed, the recording medium is discharged, 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, when it is determined that an image can be formed by one print scan as a result of referring to FIG. By a normal printing operation, an operation is performed such that an image is formed by one printing scan. This switching can be performed for each printing 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 driving have been described on the premise that the carriage scanning in the same direction is repeated twice as a method of divided recording. However, it can be realized with a similar configuration.

Further, an image may be formed by performing three or more printing scans. In this case, 3
Hold more than one mask data,
It is sufficient to switch the mask data by inputting the head scan number and use it. At this time, there is basically no need to change the configuration of masking the serially converted image data.

[0059]

As is apparent from the above description, according to the present invention, an image free from printing defects can be formed stably even in an environment where the temperature of the head is increased and the ink supply pressure is reduced. . Further, the ink in the ink cartridge can be used up to the end without waste.

[Brief description of the drawings]

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

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.

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

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

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

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

FIG. 7 is a block diagram illustrating an example of a mask data generation unit.

FIG. 8 is a diagram illustrating an example of classification of head temperature data, remaining ink data, and print image density data, and an example of a printing operation at that time.

FIG. 9

FIG. 11 is an explanatory diagram of a relationship between a mask pattern and a printed image when an image is formed by two printing 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 detector, 5 image data input interface, 6 image memory, 7 data converter, 8 mask data generator, 9 print control signal generator, 10 head drive controller, 11 carriage drive controller, 12
Paper feed motor drive control unit, 21 print modules,
22 porous body, 23 print head nozzle part, 24a,
24b ink tube, 25 head temperature detector, 26
Ink supply pressure detector, 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.

Claims (2)

(57) [Claims] An ink supply pressure detecting means for detecting an ink supply pressure in an ink jet recording apparatus for printing by supplying ink from an ink storage unit to a print head, and an ink detected by the ink supply pressure detecting means. The number of print scans for printing one scan of image data is selected based on the supply pressure data. When the number of selected print scans is one, the image data for one scan is printed by one print scan. Print control means for controlling to form an image and, when the number of selected print scans is plural, dividing image data for one scan into a plurality of parts and controlling to form an image by plural print scans; A thermal inkjet recording apparatus comprising: 2. A thermal ink jet recording apparatus for printing by supplying ink from an ink storage unit to a print head, wherein a head temperature detecting means for detecting a head temperature, and a head temperature data detected by the head temperature detecting means. The number of print scans for printing one scan of image data is selected based on the number of print scans. When the number of selected print scans is one, an image is formed by one print scan of one scan of image data. When the number of selected print scans is a plurality of times, print control means for dividing image data for one scan into a plurality of pieces and forming an image by a plurality of print scans is provided. Characteristic thermal inkjet recording device.