Recording apparatus

A recording head having a plurality of recording elements arranged thereon is scanned in a direction different from the direction of arrangement of the recording elements to effect a main scan. The scan is started when one scan of print data is stored in a buffer memory. Further, when a predetermined time has elapsed before one scan of print data is stored in the buffer memory, the scan is started without waiting for the storage of one scan of data and the data currently stored in the buffer memory is recorded. After the scan, a sheet is fed in accordance with the amount of print data recorded. The buffer memory can be effectively utilized without regard to a processing speed and a data transfer rate of a host apparatus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a recording apparatus for recording an 
image on a recording medium in accordance with print data. 
2. Related Background Art 
A serial type recording apparatus which prints data transferred from a host 
apparatus on a recording medium has been known. Such a recording apparatus 
records on the recording medium in accordance with a print command from 
the host apparatus. Accordingly, when a print speed of the recording 
apparatus is sufficiently high, a processing speed of the host apparatus 
becomes critical. 
In the serial type recording apparatus, the printing is not started unless 
one line of data along a scan direction is stored. As a result, if a print 
data transfer rate changes line by line, a data buffer in the recording 
apparatus may not be effectively used. 
In a color output recording apparatus which has recently been becoming 
popular rapidly, print data is of huge volume and the low processing speed 
of the host apparatus and the low data transfer rate are raising a serious 
problem. 
In a recording head having a plurality of recording elements integrally 
arranged (hereinafter referred to as a multi-head) to improve a recording 
speed, it is common to provide a plurality of integrally arranged ink 
discharge orifices and liquid paths, and to arrange a plurality of such 
multi-heads to comply with a color requirement. 
In printing a high resolution monochromatic image or color image, various 
factors such as coloration, tonality (or gradation) and uniformity should 
be considered. As to the uniformity, a slight variation from nozzle to 
nozzle which is caused during the manufacturing process of the multi-head 
may affect the amount of discharge of ink by the nozzle and the direction 
of discharge and it finally appears as a scatter of the density of the 
printed image, which results in the degradation of the image quality. To 
solve the problem of scatter of density, it has been proposed to print a 
print area, which may normally be printed in one scan, in a plurality of 
scans and feed a sheet for each scan (for example, U.S. Pat. No. 
4,967,203). 
For example, the printing in a first scan is effected while a lower half of 
a print head is used for a predetermined print area on a record sheet and 
a mask of zig-zag pattern (or checker flag pattern) is applied to the 
print data. Then, the sheet is fed by one half of the print head. Then, 
the printing in a second scan is effected while an upper half of the print 
head is used and a mask of a complementary zig-zag pattern (or reverse 
checker flag pattern) is applied with the print data (hereinafter referred 
to as split recording). By this recording, the affect by the nozzle to 
produce nozzle scatter of the print head at the designated print area is 
minimized. 
However, since the recording is effected by discharging the ink in the ink 
jet recording apparatus, the tint may differ between the recording on a 
dry record sheet and the printing on a wet record sheet. Particularly in 
the split recording as described above in which one print area is printed 
in a plurality of scans, the ink is discharged on the wet sheet ink in a 
second scan. 
The recording apparatus usually records on a recording medium by a print 
command from the host apparatus. Accordingly, when the print speed of the 
recording apparatus is sufficiently high, the processing speed of the host 
apparatus becomes critical. If the print data processing speed and the 
data transfer speed of the host apparatus are lowered in the course of 
printing, the ink printed in the previous scan is dried and the tint may 
differ from that of the printing effected before drying and the scatter of 
density appears in the print and high quality printing is not attained. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved recording 
apparatus in view of the problems described above. 
It is another object of the present invention to provide a recording 
apparatus which can effectively utilize storage means for storing print 
data irrespective of a processing speed and a data transfer rate of a host 
apparatus. 
It is still another object of the present invention to provide a recording 
apparatus which can attain high quality recording irrespective of the 
processing speed and the transfer rate of the host apparatus. 
It is still another object of the present invention to provide a recording 
apparatus which effects the recording of a predetermined amount of data 
when the predetermined amount of data is stored in storage means, and 
effects the recording of a smaller amount of data than the predetermined 
amount even before the storage of the predetermined amount of data if a 
predetermined time has elapsed so that the storage means for storing the 
print data is effectively utilized. 
If is a further object of the present invention to provide a recording 
apparatus which effects the printing without waiting for the storage of a 
predetermined amount of data even if the transfer of print data is delayed 
in the split recording so that the scatter of density due to the change in 
the time between the record scans is prevented and a high quality of image 
is attained. 
The above and other objects of the present invention will be apparent from 
the drawings and the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Embodiment 
FIG. 1 shows a construction of a color ink jet recording apparatus which 
has an electro-thermal transducer as discharge energy generation means and 
causes a change of state of ink by using a thermal energy generated by the 
electro-thermal transducer to discharge the ink. 
In FIG. 1, a recording medium 1 such as a paper or plastic sheet is 
supported by a pair of transport rollers 2 and 3 arranged above and below 
a record area and it is transported in a direction of an arrow A by the 
transport roller 2 driven by a sheet feed motor 4. A guide shaft 5 is 
provided in front of the transport rollers 2 and 3 in parallel thereto. A 
carriage 6 is reciprocally moved in a direction of an arrow B along the 
guide shaft by an output of a carriage motor 7 through a wire 8. 
A recording head 90 which is an ink jet head of a type which discharges ink 
by using the thermal energy is mounted on the carriage 6 which serves as 
head drive means. The recording head 90 is for color image recording and 
arranged in a scan direction of the carriage, and comprises four recording 
heads 9 provided for each of colors cyan (C), magenta (M), yellow (Y) and 
black (Bk), that is, a black head 9A, a cyan head 9B, a magenta head 9C 
and a yellow head 9D. An ink discharge unit having a plurality of (for 
example, 48 or 64) ink discharge orifices arranged in a vertical line 
which traverses the direction of scan of the carriage is provided on a 
front plane of each of the recording heads 9, that is, the plane facing a 
record plane of the recording medium 1 with a predetermined spacing (for 
example, 0.8 mm) therebetween. 
FIG. 2 shows a longitudinal sectional view of a portion of the ink 
discharge unit of the recording heads 9 (the recording heads 9A-9D being 
of the same construction). 
In FIG. 2, a plurality of ink discharge orifices 10 are formed vertically 
at a predetermined pitch on a plane facing the recording medium 1, and an 
electro-thermal transducer (such as a heat generating resistor) 11 
provided for each ink discharge orifice 10 is driven (energized) in 
accordance with record information to cause a film boiling phenomenon in 
the ink to generate bubbles 11A, and the ink is discharged by a resulting 
pressure to form flying ink droplets 12 so that the ink droplets are 
deposited on the recording medium 1 in a predetermined pattern to attain 
recording by a dot pattern. 
A heat driver 13 for energizing and deenergizing the electro-thermal 
transducer is provided for each of the recording heads 9A-9D, and a 
circuit board for a driver 29 therefor is provided on the carriage 6. 
Numeral 10A denotes a liquid path and numeral 10B denotes a common liquid 
chamber. 
A control unit including an engine control circuit (CPU) of the recording 
apparatus and associated ROM and RAM receives a command signal and a data 
signal (record information) from a controller 14 of a host apparatus, and 
applies a drive power supply (heat power supply) for the electro-thermal 
transducer to the respective recording heads 9A to 9D through a drive 
circuit 29 and the heat driver 13, together with drive sources for various 
motors in accordance with the received signals. 
Keys including an on-line/off-line selection switch 16A, a line feed key 
16B, a form feed key 16C and a record mode selection key 16D and a display 
unit including an alarm lamp 16E and a power lamp 16F are provided on a 
console panel 160 (FIG. 1) mounted on an outer case (not shown) of the 
recording apparatus. 
FIG. 3 shows a block diagram of a control unit of the color ink jet 
recording apparatus shown in FIG. 1. 
In FIG. 3, a CPU 21 in a form of a microprocessor is connected to the host 
apparatus 14 through an interface 22 and controls the recording operation 
in accordance with a command signal and a record information signal read 
into a data memory (buffer) 23 from the controller of the host apparatus 
14 and a program and print command data stored in a program memory 24 in a 
form of ROM and a working memory 25 in a form of RAM. 
The CPU 21 controls the carriage motor 7 and the sheet feed motor 4 through 
an output port 26 and a motor driver 27, and controls the recording head 9 
through a head control circuit 29 in accordance with the record 
information stored in the data memory 23 to record the data. 
The outputs from the keys 16A to 16D (FIG. 1) on the console panel 160 are 
sent to the CPU 21 through an input port 32, and control signals are 
supplied through an output port 36 for the alarm lamp 16E and the power 
lamp 16F. 
Numeral 33 denotes a timer arranged on the control circuit board and it is 
connected to an interrupt port of the CPU 21 through an input port 34. 
In FIG. 3, a power supply circuit 28 outputs a logic drive voltage VCC 
(e.g. 5 volts), a motor drive voltage VM (e.g. 30 volts), a reset voltage 
RESET, a heat voltage VH (e.g. 25 volts) for energizing the 
electro-thermal transducer 11 of the recording head 9 for generating a 
heat, and a back-up voltage VDDH for protecting the recording head 9. 
The heat voltage VH is applied to the recording head 9, and the back-up 
voltage VDDH to the head control circuit 29 and the recording head 9. 
Numeral 15 denotes an ink cartridge for storing ink to be supplied to the 
respective recording heads 9A-9D, numeral 41 denotes a sensor for 
detecting the presence or absence of the ink in the ink cartridge 15, and 
numeral 42 denotes a sensor for detecting the presence or absence of the 
ink cartridge 15. 
The present invention is now explained in detail by using the ink jet 
recording apparatus of the above construction. 
FIG. 5 shows a printout printed by a prior art printing method. Print data 
is sent from the host apparatus 14 through the interface 22. In the print 
data of FIG. 5, a first scan is for character data, a second scan, a third 
scan and a portion of a fourth scan are for graphic image, and the 
remaining portion of the fourth scan to a portion of a sixth scan are is 
for character image. 
In the host apparatus, the data processing of the graphic data usually 
takes a longer time for data processing and development than the data 
processing of the character image. On the other hand, in the recording 
apparatus, the processing time and the printing time for the received 
image data are same for the characters and the graphics. 
Noticing to the fourth scan, a portion thereof is for the graphic image 
data which requires a long time to transfer the data and the remaining 
portion is for the character data which does not take a long time. By 
printing the graphic image data of the fourth scan first and releasing the 
data memory 23 for the subsequently transmitted data, the data memory 23 
can be effectively utilized for the character data which is transmitted at 
a higher rate so that rapid printing can be attained. 
FIG. 6 shows a printout printed by the printing method in accordance with 
the present invention. The print data sent from the host apparatus is same 
as the print data of FIG. 5. In the present method, when the transmission 
time of one scan of print data from the host apparatus exceeds a 
predetermined time which is monitored by a timer 33, the printing is 
effected without waiting for the storage of one scan of print data. 
In FIG. 6, the first scan of character data is printed without regard to 
the timer 33 because the host apparatus rapidly transfer the print data. 
However, since the host apparatus takes a long time for the image 
development and the transfer of the graphic image data of the second scan 
to the seventh scan, the printing is automatically effected when the time 
set by the timer has elapsed regardless of the storage of one scan of data 
in the data memory 23. As a result, the character image data which is 
relatively rapidly sent in the eighth scan can be effectively developed in 
the data memory 23 which has been released from the previously printed 
graphic image data, and the print processing time of the overall recording 
apparatus is reduced. 
The print control of the present invention is explained with reference to a 
control flow chart of FIG. 4. After the initialization of the recording 
apparatus, an interface data receive routine shown in FIG. 4 is started. 
In the interface data receive routine, the print data sent from the host 
apparatus 14 through the interface 22 is received (F1) and the print data 
is developed into the data memory 23 by the CPU 21 (F2). The number of 
lines stored of the developed print data is stored in the working memory 
25 (memory area LINE) (F3). Then, whether the developed data has been 
stored by one scan (60 lines in the present embodiment) or not is 
determined (F4), and if one scan of data has been stored, it is printed by 
one scan (F6). After the printing, the sheet is fed by the number of 
printed lines, that is, by one scan (F7) to be ready for the next 
printing. Since the printing is effected earlier than the time set in the 
timer 33, the timer is cleared (F8) and the predetermined time is set 
again (F9) (10 seconds in the present embodiment). 
When a predetermined signal is applied from the timer 33 to the interrupt 
port, the CPU 21 executes a timer routine. In the time routine, a time-out 
flag is set when the preset time (10 seconds) is elapsed (F10). When the 
flag is set during the reception of the data from the interface (F5), the 
printing is effected for the received lines even if the received print 
data does not reach one scan (60 lines) (F6). After the printing, the 
sheet is fed by the number of printed lines to be ready for the next 
printing. The timer is cleared (F8), the time-out flag is reset and the 
timer is set again to the predetermined time (F9). 
By the above operation, the data buffer of the recorder can always be 
released for reuse without regard to the speed of the processing time and 
the print data transfer time of the host apparatus. 
Embodiment 2 
A second embodiment of the present invention is now explained by using a 
control flow chart of FIG. 7. In the present embodiment, the printing is 
effected at a constant time interval by a timer interruption without 
regard to the transfer rate of the host apparatus but the sheet feed is 
effected after the printing of one scan. 
First, when the initialization of the recording apparatus is completed, an 
interface data receive routine shown in FIG. 7 is started as it is in the 
embodiment 1. In the interface data receive routine, the print data sent 
from the host apparatus 14 through the interface 22 is received (F11) and 
the print data is developed into the data memory 23 by the CPU 21 (F12). 
The number of lines of the developed print data is stored in the working 
memory 25 and the number of lines printed before the sheet feed is stored 
in a S.sub.-- LINE (F13). Whether the developed data has reached one scan 
(60 lines in the present embodiment) or not is determined (F14), and if it 
reaches one scan, the one scan is printed (F16). After the printing, 
whether the printing has been effected for the number of lines printed 
after the previous sheet feed, that is, 60 lines or one scan as stored in 
the S.sub.-- LINE or not is determined (F17), and if one scan has been 
printed, the sheet is fed by 60 lines (F18) and the number of printed 
lines LINE is cleared (F19). Since the printing is effected earlier than 
the time set in the timer 33, the timer is cleared and the predetermined 
time is set again (10 seconds in the present embodiment) (F20). 
When a predetermined signal is applied from the timer 33 to the interrupt 
port, the CPU 21 executes a timer routine. In the timer routine, when the 
preset time (10 seconds) is elapsed, a time-out flag is set (F21). If the 
flag is set during the reception of the data from the interface (F15), the 
received lines are printed even if the received lines of the print data do 
not reach one scan (F16). If the sheet was not fed in the previous 
printing, the print data for the ink discharge unit of the recording head 
9 is staggered accordingly so that the printing is made in the correct 
area. This may be attained by controlling the print data to the head 9. 
After the printing, the sheet is not fed because the number of printed 
lines S.sub.-- LINE after the previous sheet feed does not reach one scan 
(F17). The timer is cleared, the time-out flag is reset and the timer is 
set again to the predetermined time (F20). 
By the above operation, the data buffer of the recording apparatus may 
always be released for reuse without regard to the speed of the processing 
time and the data transfer rate of the host apparatus and without 
increasing the number of times of sheet feed. 
Embodiment 3 
A third embodiment of the present invention is now explained. In the 
present embodiment, the recording is completed in a plurality of scans by 
using different record areas of the recording head for a predetermined 
area on the recording sheet and sequentially using masks of complementary 
thinning patterns for the print data. A timer is provided in the recording 
apparatus, and if the transfer of the print data from the host apparatus 
takes a longer time than a predetermined time, the printing is effected 
without waiting for the transmission of one line of data, and the 
subsequent sheet feed is determined in accordance with the amount of print 
and the printing is effected without regard to the speed of the processing 
and development of the print data and the data transfer rate of the host 
apparatus so that the print interval between the first scan and the second 
scan is always kept constant and the degree of dry of the sheet at the 
printing in the second scan is kept constant. In this manner, the scatter 
of density in the printout is eliminated. 
The present embodiment is explained in detail. The construction of the 
recording apparatus in the present embodiment is same as that of FIGS. 1 
and 2 and the construction of the control unit is same as that of FIG. 3, 
and the explanation thereof is omitted. 
FIG. 8 shows a block diagram of an electrical configuration of a head 
driver and a head for effecting zig-zag and complementary zig-zag thinning 
printing. FIGS. 9(a) through 9(i) show waveforms of signals on a circuit 
of FIG. 8. 
In the present embodiment, a head having an eight-nozzle ink discharge port 
is used as a recording head. 
A head unit 100 loads print data Si into an 8-bit shift register 101 by a 
print data synchronous clock CLKi and sets signals BEi1*, BEi2*, BEi3* and 
BEi4* to ON conditions, respectively, to drive a transistor array 103 of 
the head unit 100 and cause a heater 104 to generate heat for effecting 
the printing. A signal LATCH* is a control signal to latch the print data 
to a latch circuit 102, and a signal CARESi* is a reset signal to clear 
the latch. One heating is started by a signal Heat Trigger and a pulse 
generator 106 generates the signals BEi1*, BEi2*, BEi3* and BEi4*. Those 
signals may be staggered in time but they are shown to be outputted 
simultaneously for simplification purpose. 
In order to effect the thinning, an output of a flip-flop 105 is switched 
by an input timing of the signal Heat Trigger so that the masking signal 
is alternately changed (for example, BEi1* and BEi3*) for each heating. As 
shown in a timing chart of FIG. 9, it is switched by High/Low of an output 
signal DATA ENB of the flip-flop 105. When the signal Heat Trigger is 
applied, the unmasked signal of the signals BEi1*, BEi2*, BEi3* and BEi4* 
is rendered low and the heater provided for the corresponding nozzle is 
energized so that the ink droplet is discharged. A broken line shows a 
mask timing which corresponds to the signal DATA ENB. Both EVEN signal and 
ODD signal are for initialization of the mask pattern. When the printing 
in the zig-zag pattern (or check flag pattern) is desired, the EVEN signal 
is sent prior to the printing of one line so that the flip-flop 105 is 
preset to enable the zig-zag printing. When the printing in the 
complementary zig-zag pattern (or reverse checker flag pattern) is 
desired, the ODD signal is sent so that the flip-flop 105 is set and the 
signals BEi2* and BEi4* are first turned on to allow the complementary 
zig-zag printing. 
An actual print method is explained with reference to FIGS. 10(a) and (b). 
In FIGS. 10(a) and (b), one scan is represented by 12 vertical nozzles for 
simplification purpose. In an n-th scan, the zig-zag printing is effected 
in areas 1 and 2 by using the above circuit and the entire record area of 
the recording head in accordance with the print data transferred from the 
host apparatus. After the printing, the sheet is fed by one area, that is, 
one half of one scan width (6 nozzles). Then, the complementary zig-zag 
printing is effected in areas 2 and 3 by using the entire record area of 
the recording head in accordance with the print data. As a result, high 
grade printing is attained in the area 2 without the affect by the nozzle 
by nozzle scatter of the recording head. 
A recording operation in the actual printing is shown in FIG. 11. In FIG. 
11, character image data and graphic image data are mixedly present. When 
this image is to be printed in the above print method, one half of the 
character image data is first zig-zag printed by using an upper half 
record area of the recording head (scan 1). Then, the character image data 
is complementary zig-zag printed by using the entire record area of the 
recording head (scan 2). Then, the zig-zag printing and the complementary 
zig-zag printing are alternately effected while the sheet is sequentially 
fed by one half of the scan width (scans 3 to 12). Finally, the zig-zag 
printing is effected by using a lower half recording area of the recording 
head (scan 13). In this manner, the print data is recorded on the record 
sheet. 
However, in the host apparatus which transfers the print data, the graphic 
image data usually takes a longer time to process, develop and transfer 
than the character data. In the scans 1 and 2 of FIG. 11, the print data 
is transferred relatively quickly but the transfer of one scan of print 
data is delayed during the period in which the graphic image data is 
transferred (scans 3 to 7). As a result, in the scans 3 to 7, the ink 
discharged in one scan is dried on the sheet and the ink is discharged in 
the next scan on the dried ink. On the other hand, in the scans 1 and 2 
and 8 to 13, the ink is discharged before the ink discharged in the 
previous scan is not yet dried. As a result, the density of the ink is 
different from that of the scans 3 to 7. 
In the present embodiment, if one scan of print data is not sent from the 
host apparatus in the predetermined time, the printing is effected even if 
one scan of data is not stored so that the printing is effected in the 
same dry condition of ink discharged in the previous scan to keep the 
constant print density. 
An actual printout in the present embodiment is explained with reference to 
FIG. 12. 
In FIG. 12, the scans 1 and 2 are identical to those of FIG. 11. In the 
transfer of the graphic image data, if the transfer time of the host 
apparatus is longer than the predetermined time, the printing is started 
before one scan of print data is stored in the data memory 23 by the 
function of the timer 33. In this case, the print sequence of the zig-zag 
(or checker flag) and complementary zig-zag (or reverse checker flag) is 
maintained and the sheet feed width is one half of the print width. From 
the scan 15, the print data is the character image data and one scan of 
data is stored in the predetermined time. Thus, the print width is 
expanded. 
A control for effecting the above recording operation is explained with 
reference to flow charts of FIGS. 13A and 13B. After the initialization of 
the recording apparatus, the recording apparatus waits for the print data 
from the host apparatus. When it receives the print data from the host 
apparatus (F31), it determines whether it is the first line data or not 
(F32), and if it is, the content of a memory area Pre-LINE which is set in 
the working memory 25 for storing the number of lines previously developed 
is set to zero (F35). If it is not the first line data, it determines 
whether it is the last line data or not (F33), and if it is, a last line 
flag in the working memory 25 is set (F34). If it is not the last line 
data, the process proceeds to F36. In F36, the print data is developed 
into the data memory 23. The number of lines developed is stored in the 
memory area LINE in the working memory 25 (F37). When the developed print 
data reaches one half of scan (30 lines in FIG. 13A) (F38), the zig-zag 
print pattern (or checker flag pattern) or the complementary zig-zag 
pattern (or reverse checker flag pattern) is set in accordance with the 
zig-zag BIT in the working memory 25 (F40) and the printing is effected 
(F41). The printing covers the area not completed in the previous scan. 
The zig-zag BIT sets the zig-zag pattern or the complementary zig-zag 
pattern which is set at the start of the printing of the scan. 
After the scan, whether the last line flag is set or not is determined 
(F42). If it is not set, the sheet is fed by the number of lines stored in 
the memory area Pre-LINE in the working area 25 (F43). Thus, in the next 
printing, the printing may be effected from the point of current 
development. The timer 33 which monitors the time interval of the print 
data sent from the host apparatus is cleared and the timer is set to a 
predetermined time (F44) (10 seconds in the present embodiment), and a 
thinning pattern for the next printing is set in accordance with the 
content of the Pre-LINE (F45, F46). 
If the content of the Pre-LINE is even, the zig-zag BIT is flipped to 
effect the next printing with the different thinning pattern from the 
current one, and if it is odd, the zig-zag BIT is kept unchanged to effect 
the next printing with the same thinning pattern as the current one. For 
example, if the current printing is by the zig-zag, the next printing is 
by the complementary zig-zag. 
The number of print lines developed is stored in the Pre-LINE and the LINE 
is cleared (F47). 
If the last line flag is set in F42, a counter in the working memory 25 is 
incremented by one (F48), whether the content of the counter is 2 or not 
is determined (F49), and if it is not, the process proceeds to F43 to 
conduct the same operation as that described above. If the content of the 
counter is equal to 2, the sheet is ejected (F50) and the last line flag 
and the counter are reset (F51). 
When the predetermined signal is applied from the timer 33 to the interrupt 
port, the CPU 21 executes a timer routine. In the timer routine, when the 
preset time (10 seconds) is elapsed, a timeout flag is set (F30). If the 
flag is set during the reception of the data from the interface (F39), the 
printing of the received lines is effected even if the received data does 
not reach one scan (F41). In this case, the lines not printed in the 
previous scan are also printed. Then, whether it is the last line or not 
is determined as it is for the first scan printing (F42), and if it is not 
the last line, the sheet is fed by the number of print lines previously 
developed stored in the memory area Pre-LINE (F43) to be ready for the 
next printing. In this case, the timer is cleared, the time-out flag is 
reset and the timer is set again to the predetermined time (F44). Whether 
the number of lines previously developed is odd or even is determined 
(F45), and if it is odd, the zig-zag BIT is remained unchanged, and if it 
is even, the zig-zag BIT is flipped so that the printing of the newly 
developed print area is completed in the next printing. 
If it is the last line, one scan is made as described above, the sheet is 
ejected (F50) and the last line flag and the counter are reset. 
By the above operation, the dry condition of the ink previously printed is 
constant in the overprinting of the zig-zag and complementary zig-zag 
printing without regard to the speed of the processing time and the print 
data transfer rate of the host apparatus. As a result, the print density 
is kept constant and high grade image quality is attained. 
Embodiment 4 
A fourth embodiment of the present invention is now explained. In the 
present embodiment, a 4.times.4 mask pattern instead of the zig-zag and 
complementary zigzag patterns is used as a mask pattern in effecting the 
multi-pass printing. FIGS. 14(a) and (b) an example of the 4.times.4 mask 
pattern. This mask pattern is printed in four scans to attain a normal 
printout as shown in the bottom. An electric circuit which allows the 
printing with this mask pattern is shown in FIG. 15. 
In this circuit, an 8-nozzle unit which is controlled by 4 rows by 2 
columns diode matrix drive is used as a head unit. The head unit 110 is 
controlled by a combination of two row signals and four column signals and 
heaters 110-1 to 110-8 are energized by the respective combination to 
cause state change in the ink so that the ink is discharged to print data. 
For example, in order to energize all of the eight nozzles, the print data 
(1111) is set in a print data register 114 and a mask data register 113 
and a signal Row1 is sent. When the heaters 110-1 to 110-7 corresponding 
to the nozzles are energized, a signal Row2 is sent without updating the 
data in the print data register 114. In this manner, the heaters 110-5 to 
110-8 are energized. 
Any mask data may be set in the mask data register 113. The mask status is 
explained with reference to a timing chart of FIGS. 16(a) through 16(h). 
First, (1000) is written into the mask register 113. "1" represents data 
to be printed and "0" represents data to be masked. After the data has 
been written into the print register 114, the signals Row1 and Row2 are 
sent out in staggered manner. When different masks are to be applied to 
Row1 and Row2, it is necessary to update the setting of the mask data 
before the signal Row2 is sent. Thereafter, the mask data is written into 
the mask data register and the heaters are sequentially energized to 
attain the mask patterns MASK 1 and MASK 2 as shown below the arrow. 
Similarly, mask patterns MASK 3 and MASK 4 are attained by modifying the 
mask data. 
An example in which the present invention is applied to the 4.times.4 
multi-pass printing described above is explained with reference to flow 
charts of Figs. 17A and 17B. After the initialization of the recording 
apparatus, the recording apparatus waits for the print data from the host 
apparatus. When it receives the print data from the host apparatus (F61), 
it determines whether it is first line data or not (F62), and if it is, a 
flag 1 in the working memory 25 is set (F64). If it is not the first line 
data, it determines if it is the last line data or not (F63). If it is, a 
flag 2 in the working memory 25 is set (F65). If it is neither the first 
line data nor the last line data, the process proceeds to F66. 
In F66, the print data is developed into the data memory 23. The number of 
lines developed is stored in the memory area LINE in the working memory 25 
(F67). When the developed lines in the data memory reach one quarter of 
scan (15 lines in FIG. 17A) (F68) mask array A.sub.-- MASK is changed in 
accordance with the number of lines stored in the LINE, a mask pattern to 
be written into the mask data register 113 is determined in accordance 
with the mask pattern P.sub.-- MASK and the mask array A.sub.-- MASK 
(F71), and the scan is made to print the image (F72). The printing covers 
the area not completed in the previous scan. The mask pattern includes the 
MASK 1, MASK 2, MASK 3 and MASK 4 shown in FIG. 14, and the mask 
arrangement includes the mask arrays 1, 2, 3 and 4 of FIG. 14. 
The scan is made in accordance with the mask pattern and the mask array 
determined in F71 to print the image (F72). Then, whether the flag 1 is 
set or not is determined (F73), and if it is, the content of the counter 
in the predetermined area in the working memory 25 is incremented by one 
and whether the content of the counter is 4 or not is determined (F75, 
F77). Before the content of the counter reaches 4, the sheet is not fed 
and the timer 33 which monitors the time interval of the print data sent 
from the host appratus is cleared and the predetermined time (10 seconds 
in the present embodiment) is set again (F80). The number of print lines 
developed in the latest three times is stored in the predetermined area in 
the working area 25 and the content of the memory area LINE is cleared 
(F81). The mask pattern P.sub.-- MASK is incremented to set to the next 
one (F82) and the process returns to F61. When the count reaches 4, the 
flag 1 and the counter are reset (F78), and the sheet is fed by the number 
of lines developed in the three previous scans (F79). Then, the process 
proceeds to F80 and the same process as that described above is effected. 
If the flag 1 is not set in F73, whether the flag 2 is set or not is 
determined (F74). If the flag 2 is not set, the sheet is fed by the number 
of lines developed in the previous three scans stored in the working 
memory 25 (F79). Then, the process proceeds to F80 et seq to conduct a 
similar process to that described above. 
If the flag 2 is set in F74, the counter is incremented and whether the 
count is 4 or not is determined (F76, F83). Before it reaches 4, the 
process proceeds to F79 to conduct the same process as that described 
above. When the count reaches 4, it is decided that the recording is over 
and the flag 2 and the counter are reset (F84) and the sheet is ejected 
(F85). 
When the predetermined signal is applied from the timer 33 to the interrupt 
port, the CPU 21 executes the timer routine. In the timer routine, when 
the preset time (10 seconds) is elapsed, the time-out flag is set (F60). 
When this flag is set during the reception of the data from the interface 
(F69), the received lines are printed even if the received print data does 
not reach one scan (F72). In this case, it is necessary to modify the 
content of the mask array A.sub.-- MASK by the number of print lines 
developed. In the printing, the lines not completed in the previous scan 
are covered by setting the mask register by the contents of A.sub.-- MASK 
and P.sub.-- MASK (F71). After the printing, the process proceeds to F73 
et al. and the sheet is fed by the print area developed in the three 
previous scans to be ready for the next printing. In this case, the timer 
is cleared, the time-out flag is reset, and the timer is set again to the 
predetermined time. 
The operation of the mask array A.sub.-- MASK may be eliminated by printing 
four lines at a time. 
As described above, the scatter of density is avoided in the split 
recording without regard to the processing speed of the host apparatus and 
high grade image is attained. 
In the above embodiments, the ink jet recording apparatus which utilizes 
the thermal energy to form the flying droplets to record the data has been 
described. A typical configuration thereof and a principle are disclosed 
in U.S. Pat. No. 4,723,129 and U.S. Pat. No. 4,740,796. The present system 
is applicable to either an on-demand type or a continuous type. In the 
on-demand type, at least one drive signal which causes a rapid temperature 
rise over a nuclear boiling point in accordance with recording information 
is applied to electro-thermal converters arranged on sheets by which 
liquid (ink) is held in order to generate the thermal energy in the 
electro-thermal converters to cause film boiling on a thermal acting plane 
of a recording head. As a result, bubbles of ink which directly correspond 
to the drive signal are formed. To form the bubbles, the liquid (ink) is 
discharged by contraction thorough the discharging orifice to form at 
least one droplet. When the drive signal is a pulse signal, the formation 
and the contraction of the bubble can be attained instantly and properly 
and highly responsible discharge of liquid (ink) is attained. 
The drive by the pulse signal is disclosed in U.S. Pat. No. 4,463,359 and 
U.S. Pat. No. 4,345,262. When a condition disclosed in U.S. Pat. No. 
4,313,124 relating to a temperature rise factor on the thermal acting 
plane is adopted, better recording can be attained. 
The recording head may be a combination of discharge orifices, a liquid 
path and electro-thermal converters (linear liquid flow path or orthogonal 
liquid flow path) disclosed in the above patents, or a construction shown 
in U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600 which discloses to 
arrange the thermal acting portion in a curved area. 
Further, it may be a construction as disclosed in Japanese Laid-Open Patent 
Application No. 59-123670 in which a common slit to a plurality of 
electro-thermal converters is used as a discharge portion of the 
electro-thermal converters or Japanese Laid-Open Patent Application No. 
59-138461 in which an aperture for absorbing a pressure wave of thermal 
energy is formed for the discharge portion. 
The present invention is also applicable to a full line type recording head 
having a length equal to a maximum width of a recording medium on which 
the recording apparatus can print. Such a recording head may meet the 
length requirement by a combination of a plurality of recording heads or a 
single integral recording head. 
The present invention is also applicable to a replaceable chip type 
recording head which, when it is mounted on the apparatus, permits the 
electrical connection with the apparatus and the supply of ink from the 
apparatus, or a cartridge type recording head having an ink tank 
integrally provided in the recording head. 
It is preferable in further stabilizing the effect of the present invention 
to add recovery means and preliminary auxiliary means to the recording 
head. Specific examples are capping means for the recording head, cleaning 
means, pressurizing or suction means, preliminary heating means including 
a electro-thermal transducer, a separate heating element or a combination 
thereof, and preliminary discharge mode for discharging separately from 
the discharge for recording. 
The record mode of the recording apparatus is not limited to one in which 
black is a principal color but multi-color of different colors or full 
color by the mixture of colors may be used by the combination of a 
plurality of integral recording heads. 
In the embodiments of the present invention, the ink is described as liquid 
although it may be solidified at or below a room temperature, or softened 
or liquid at the room temperature. In the ink jet system, the ink may be 
temperature controlled in a range of 30.degree.-70.degree. C. to bring the 
viscosity of the ink to a stable discharge range. Accordingly, it is only 
necessary that the ink is in liquid state when the recording signal is 
applied. 
In addition, the temperature rise by the thermal energy may be prevented by 
using it as the energy to change the state of the ink from solid to liquid 
or the ink which is solidified when it is left may be used to prevent the 
evaporation of the ink. In any case, the ink may have a property that it 
is liquidified by the thermal energy, for example, it is liquidified by 
the application of the recording signal of the thermal energy and 
discharged as the liquid ink or it starts to be liquidified when it 
reaches the recording medium. In this case, the ink may be held in 
recesses or via-holes of a porous sheet in solid state to face the 
electro-thermal transducer as disclosed in Japanese Laid-Open Patent 
Application No. 54-56847 or Japanese Laid-Open Patent Application No. 
60-71260. In the present invention, the most effective way to the inks 
described above is to execute the film boiling system. 
Further, the recording apparatus of the present invention may be a combined 
or stand-alone image output terminal of an information processing 
apparatus such as a word processor or a computer, or a copying machine 
combined with a reader, or a facsimile apparatus having a receive/transmit 
function. 
The present invention is not limited to the ink jet system which uses the 
thermal energy but it is also applicable to an ink jet system which uses a 
piezo-electric element.