JPH06122199A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To properly hold the emission amt. of ink by generating a signal driving each nozzle on the basis of the signal prescribing the drive timing of a recording head according to stored pattern data. CONSTITUTION:When serial image data VD is transmitted from an external device 19 such as a host computer, the drive signal necessary for driving a recording head part 11 is formed in a head control signal forming part 13 by the command from a CPU 12. Processing such as mirror processing is performed with respect to the image data VD in the head control signal forming part 13. The signals BE0-3 driving a heater 16 in the drive signal outputted from the head control signal forming part 13 are divided in waveform in a heater driving signal dividing part 14 to be outputted to the heater 16 of the recording head part 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image using an ink jet recording system.

[0002]

2. Description of the Related Art Various products have been announced as printers that perform recording by ejecting ink from nozzles (recording elements) provided in a recording head, that is, a so-called inkjet recording method. Among them, several heaters are installed in the nozzle in which the ink is immersed, and by applying a pulse signal to the heaters, the heaters are heated to boil the ink, and the bubble pressure generated thereby causes the ink to be ejected from the nozzles. A method of discharging is also known. When an image forming apparatus such as an inkjet printer is configured using a recording head that employs such a method, a plurality of nozzles are arranged in the recording head, and the recording head is scanned to form an image. .

An example of a conventional control circuit for driving such a recording head is shown in FIGS. FIG. 10 (A)
, The image data VD is transferred as serial binary data, and the serial-parallel converter 901-0.
After the serial signal is converted into the parallel signal by 901-n, the data is latched corresponding to each nozzle by the latch (LAT) signal. Further, a plurality of nozzles of the print head are divided into a plurality of blocks, and heater driving pulse signals BE0 to BE are given to the blocks (the pulse signals are at a high level for a certain period of time as shown in FIG. 10B). Signal). As a result, only the heater corresponding to the nozzle whose image data is latched at the high level is turned on, and ink is controlled to be ejected from the corresponding nozzle. In this case, the heater driving pulse signals BE0 to BE were applied to the head only during recording.

[0004]

When forming an image by the above-mentioned ink jet method, the recording head is scanned once in the main scanning direction, and after the scanning, the recording head is returned to its original position and the recording medium is sub-scanned. The method of moving the scanning direction by the recording width of the recording head and then performing the next scanning is adopted. For this reason, particularly in the case of printing on large-sized paper and continuous enlargement, etc., the temperature of the heater of the print head decreases in the print time interval from the first scan to the next scan.
As a result, there is a problem that the amount of ink ejected from the ink head is reduced at the start of the next scan, resulting in uneven density.

Further, as in the case of half-edge feeding or printing of a reduced image, only the nozzles of a part of the print head are used in the first scan, and the nozzles not used in the first scan are used in the second scan. Even when the recording is performed by using the recording medium, similarly to the above, there is a problem that the ink discharge amount is changed due to the temperature decrease of the heater and the uneven density occurs. Further, there is a similar problem when recording an image recorded by using a specific nozzle in the recording head with high frequency.

The present invention has been made in view of the above-mentioned conventional example, in which the drive signal of the recording head is an arbitrary pulse signal,
An object of the present invention is to provide an image forming apparatus capable of maintaining an appropriate ink ejection amount.

The present invention has been made in view of the above conventional example, and it is an object of the present invention to provide an image forming apparatus capable of suppressing an increase in temperature of a recording head due to image data and maintaining an appropriate ink ejection amount. To aim.

[0008]

In order to achieve the above object, the image forming apparatus of the present invention has the following constitution. That is, in an image forming apparatus that forms an image using a recording head of an inkjet recording system, a storage unit that stores pulse pattern data and a storage unit that stores the pulse pattern data in the storage unit based on a signal that defines a drive timing of the recording head. Pulse generating means for generating a drive signal for driving each nozzle of the recording head according to the pattern data.

Further, in order to achieve the above object, the image forming apparatus of the present invention has the following configuration. That is, in an image forming apparatus that forms an image using a recording head of an inkjet recording system, a counting unit that counts the number of consecutive image data that eject ink and whether the count value by the counting unit is a predetermined value or more is determined. It has a judging means for judging, and a thinning means for thinning out a predetermined amount of image data to be recorded when it is judged from the judgment result by the judging means that the value is not less than a predetermined value.

[0010]

In the above structure, a drive signal for driving each nozzle of the print head is generated in accordance with the pattern data stored in the storage means for storing the pulse pattern data, based on the signal defining the drive timing of the print head. Works like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the schematic arrangement of the ink jet printer of this embodiment. As shown in FIG. 1, the inkjet printer of this embodiment is roughly composed of two elements. That is, the head control unit 10 that generates a signal necessary for controlling the interface with the external device 19 and driving the head, and the head control unit 10
In accordance with a control signal from the recording paper 17 which is a recording medium.
And a recording head unit 11 for forming an image.

The head controller 10 includes a CPU 12, a head control signal generator 13, a heater drive signal divider 14, another load unit 18, and the like. The CPU 12 controls the interface with the external device 19 to which the serial image data VD is transferred, and also controls the operation of the entire head controller 10. When the serial image data VD is transferred from the external device 19 such as a host computer, the head control signal generation unit 1 is instructed by the CPU 12
At 3, a drive signal necessary for driving the recording head unit 11 is generated. Further, in the head control signal generation unit 13, processing such as mirror processing is performed on the image data VD. In this way, among the drive signals output from the head control signal generation unit 13, the signals BE0 to BE0 for driving the heater 16 are output.
3 (in the present embodiment, the print head unit 11 has 256 nozzles arranged therein, these nozzles are divided into 4 blocks, and the heater drive signal BE (BE0
To BE3) are output), the heater drive signal division unit 1
Waveform division (pulse pattern generation) is performed in step 4,
It is output to the heater 16 of the recording head unit 11.

The serial image data VD output from the head control signal generator 13 is converted from serial data to parallel data by the serial-parallel converter 15, and the parallel data is temporarily stored by the latch signal LAT. Retained. The heater of each nozzle of the print head is heated and driven by the image data VD thus held and the heater drive signals BEO0 to BEO3 generated by the heater drive signal division unit 14. In this way, the image is formed by ejecting the ink from the nozzle and adhering the ink to the recording paper 17.

FIG. 2 is a diagram for explaining the manner of waveform division (pulse generation) performed by the heater drive signal divider 14.

As shown in FIG. 2, with respect to the heater drive signals BE0 to BE3 output from the head control signal generator 13, the residual heat of the heater 16 is removed only while the heater drive signals BE0 to BE3 are at a high level. When performing, the signal is divided into signals having a pulse width that is short enough not to eject ink, and during actual recording, a signal for ejecting ink is applied to the heater 16. By this preheat treatment, the heater 16
It is possible to keep the temperature constant and to suppress the fluctuation of the ink ejection amount from the nozzle. Also, the heater drive signal division unit 14
Then, it is possible to generate several types of pulse patterns, such as a heater drive signal (pulse pattern) for actual recording and a heater drive signal (pulse pattern) for preheating the heater. In each case, Accordingly C
Which pulse pattern is to be output can be switched by the output signal from the PU 12 or the sensor of the other load unit 18.

Next, the pulse signal BE for driving the heater
Details of the heater drive signal division unit 14 that controls the fine division of O0 to O3 will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the heater drive signal division unit 14.

The heater drive signal dividing section 14 is composed of a heater drive signal data setting section (for preheating) 30, a heater drive signal data setting section (for recording) 31, and a heater drive signal selecting section 32. The heater drive signal data setting unit (for preheating) 30 is set with pattern data such that a pattern signal generated by dividing the heater drive signal to the extent that ink is not ejected is generated before recording is started. Further, in the heater drive signal data setting unit (for recording) 31, pulse pattern data for actual recording is C
When the heater 12 is set by the PU 12, the recording operation is actually started, and the heater drive signals BE0 to 3 are input, the drive signal is output to the block of each nozzle to heat the heater 16. There is.

FIG. 4 is a diagram for explaining the switching between the area for ejecting ink and the preheating area as the recording head 11 scans.

As shown in FIG. 4, the sensors 41 to 44 are arranged in the scanning path of the recording head 11, and ink is ejected from the nozzles of the recording head 11 in the area 45 defined by the sensors 41 and 42 ( Preliminary discharge) is performed and the sensor 4
The area between 3 and the sensor 44 is set as an area 46 in which recording is actually performed. The signal PBVE indicates a switching signal that is generated based on detection signals from these sensors and switches between preheating of the recording head 11 and heating for ejecting ink.
The switching signal PBVE has a high level in an area where the heater 16 is heated to eject ink, and has a low level in areas 47 and 48 where ink is not ejected. That is, the sensor 4
After detecting the passage of the recording head 11 by No. 1 until the sensor 42 detects the recording head 11, it is judged that the area 45 is for preventing the clogging of the nozzles, and the signal PBV
It is determined that the areas 47 and 48 where E is at a low level are preheating areas, and the period from when the sensor 43 detects the recording head 11 to when the sensor 44 detects it is the actual recording area 46. This PBVE signal is input to the above-mentioned heater drive signal selector 32, whereby the heater drive signal selector 32 switches the pulse width of the heater drive pulse signal between preheating and recording by hardware. .

The recording head 11 is also used for half-end feeding and reduction.
When printing is performed using only some of the nozzles, the nozzles of the recording head 11 can be freely divided into blocks by setting by the CPU 12 in order to preheat unused nozzles. It is also possible to switch the driving mode of the heater 16.

Next, with reference to FIG. 5, the control method of the heater drive signal data setting sections 30 and 31 will be described in detail.
Note that FIG. 5 shows the control circuit for generating pulse data of only BE0 of the heater drive signals BE0 to 3 for simplification of description, but other heater drive signals BE1,
Since the same applies to 2 and 3, these explanations are omitted.

In FIG. 5, each of 500 to 505 is an 8-bit latch circuit, and each of 510 to 515 is an 8-bit shift register circuit. Prior to the start of recording, pulse data (for example, data for determining the BEO0 signal as shown in FIG. 2) is latched by the CPU 12 through the data bus in the 8-bit latch circuits 500 to 505. After that, when the recording operation is started and the BE0 signal is input and becomes high level, the pulse pattern data is loaded in parallel from the respective latch circuits to the corresponding 8-bit shift register circuits 510 to 515. After that, in synchronization with the clock signal 520, the shift register 515 →
The pulse pattern data is sequentially shifted in each shift register and output as a serial signal in the order of 514 → 513 → 512 → 511 → 510.

In the present embodiment, the period during which the heater drive signal BE0 is at high level is 16 μsec, which is 3 MHz.
The clock signal 520 is shifted to a maximum of 48 clock signals. Therefore, six 8-bit latch circuits 500 are set so that 48 pulse pattern data can be set.
˜505, six 8-bit shift register circuits 510
˜515. Since the serial input terminal of the 8-bit shift register 515 at the final stage is grounded, the serial output of the shift register 510 automatically becomes low level after the output of 48 pulse pattern data is completed. By performing the control as described above, it is possible to output the BEO0 signal obtained by dividing the heater drive signal BE0 into a plurality of pulse signals while the BE0 signal is at the high level, as shown in FIG.

The clock signal 52 used in this embodiment is
Since the frequency of 0 is 3 MHz, the maximum number of divided pulses is 48, but the present invention is not limited to this. That is, more pulses can be generated by setting the frequency of the clock signal 520 higher and increasing the number of latch circuits and shift register circuits. This enables more accurate preheating.

Next, the control method of the heater drive signal selector 32 will be described in detail with reference to FIG.

The heater drive signal selection section 32 is composed of selectors 60 to 64, 66 and latch circuits 65, 67. The selector 60 uses the recording-preheating switching signal PBVE based on the signals from the sensors 41 to 44 of FIG. 4 to generate the heater drive signal B generated in the above three blocks.
EA0-3 (for preheating), BEB0-3 (for actual recording)
Is selected and output. That is, the selector 6
1 to 64 are signal B depending on the set value of the latch circuit 65.
Any one of EA0-3 and BEB0-3 is selected and output. Here, since the nozzles of the recording head 11 are divided into four blocks, the four selectors 61 to 64 are used to select in block units. This is to enable the other nozzles to be preheated when recording is performed using only one part of the nozzles of the recording head 11.

Then, the CPU 12 sets which heater drive signal to use for which block in the latch circuit 65 through the data bus, and the selector 6 is set according to the set value.
1 to 64 select the BEA signal or BEB. Further, in the final stage selector 66, of the signals output from the two types of selectors 60 and the selectors 61 to 64,
The CPU 12 selects which is to be output to the recording head 11 based on the data set in the latch circuit 67. That is, the selector 60 outputs a heater driving signal corresponding to recording-preheating, the selectors 61 to 64 output heater driving signals corresponding to the nozzle blocks of the recording head 11, and these are output to the latch circuit 67. It is appropriately switched according to the content and output to the heater 16.

FIG. 7 is a flow chart showing the control of the CPU 12 of the ink jet printer of this embodiment, and the control program for executing this processing is stored in the ROM in the CPU 12. The process shown in the flowchart of FIG.
The recording head 11 is activated at the timing of recording, and at this time, the data to be recorded next is the recording head 1.
It is assumed that the serial-to-parallel converter 15 is set to 1.

First, in step S1, it is determined whether the time is a preheat timing or a timing for actually recording, and if it is a preheat timing (the signal PBPBVE is at a low level), the process proceeds to step S2, and the head control signal generator BE0-B of the heater drive signal data setting unit 30 of 13
Latch circuit (500 to 50) corresponding to each E3
In 5), the pulse pattern of BEA0 to 3 is determined 48.
Set the bit data. On the other hand, at the recording timing, the process proceeds to step S3, and the latch circuits (500 to 505) corresponding to BE0 to BE3 of the heater drive signal data setting unit 31 of the head control signal generation unit 13 are
The 48-bit data that determines the pulse pattern of BEA0 to 3 is set.

Thus, the pulse pattern (BEO0 in FIG. 2 is
When the pulse signal of 3) is determined, the process proceeds to step S4, and at the time of the next recording, it is determined whether the heater drive signal is switched for each block. As described above, this is for preheating the heater 16 corresponding to an unused nozzle when printing is performed using only a part of the nozzles of the recording head, such as half-end feeding or reduction printing. used. When the switching for each block is not performed, the process proceeds to step S5, and the selector 66 sets information for selecting the output of the selector 60 in the latch circuit 67. As a result, the heater driving signals BEO0 to 3 output are switched according to the preheating timing or the recording timing (the signal level of the signal PBVE).

On the other hand, if the block-by-block switching is performed in step S4, the process proceeds to step S6, in which the selector 66 sets the data in the latch circuit 67 so as to select the output from the selectors 61 to 64, and the latch circuit 65 next. The data for selecting the block (one of the selectors 61 to 64) is set. In this way, when recording in one block is completed in step S7, the process returns to step S6, and if the next selector (for example, the selector 61 before that is selected,
This time, the latch circuit 65 is selected so that the selector 62) is selected.
Set the data to. In this way, steps S6 to S8 are repeated until the recording by the nozzles of the four blocks of the recording head is completed.

By performing the above-described processing, the change in the ink ejection amount caused by the recording of a large-sized sheet or the cooling of the heater by the continuous enlargement recording, and the cooling of the heater by the recording of the half-edge feed / reduced image. It is possible to prevent uneven density due to. <Second Embodiment> Next, a second embodiment of the present invention will be described.

In the first embodiment described above, the pulse pattern data is created using a plurality of 8-bit latch circuits and 8-bit shift register circuits, but it is also possible to use a RAM.

FIG. 8 shows the configuration of a pulse pattern data generation circuit when a RAM is used.

A pulse pattern data generation circuit using a RAM is composed of a 256 counter 70, a RAM 71, a selector 73, a gate circuit 72, and latch circuits 74 and 75. If the registration signal 801 is set to the low level before the start of recording, the selector 73 causes the address bus (A
BUS) is selected, and the content of the data bus (DBUS) is selected in the gate circuit 72. In this state, the CPU
The pulse pattern data is stored in the lower address 0000 to 00FF (hexadecimal number) of the RAM 71 through the data bus and the address bus.

At this time, when two or more types of pulse pattern data for recording and for preheating are required, or when only one part of several blocks of the recording head is used for recording and other blocks are used. When the nozzle of is used for preheating,
By making the upper address of the RAM 71 variable by the latch circuit 75, several types of pulse pattern data are RA
Can be written to M71.

When the setting of the pulse pattern data in the RAM 71 is completed in this way and the recording operation is started, the register signal 801 is set to the high level, the selector 73 selects the output of the counter 70, and the gate circuit 72 is closed. Next, when the heater drive signal BE0 is input, the counter 70 is counted up. Thus R
By changing the lower bits of the address of the AM 71, the pulse pattern data stored in the RAM 71 before the start of recording is read from the ROM 71 and output. Here, the counter 70 outputs a maximum of "256" different addresses corresponding to the number of nozzles in each block of the recording head 11.

Further, the switching between recording and preheating is performed by the above-mentioned FIG.
Like the latch circuit 67, the setting value of the latch circuit 75 can be changed to change the high-order address (read address) of the RAM 71 and change the output pulse pattern data (BEO0 to 3).

By carrying out the above processing, it is possible to prevent the occurrence of density unevenness, as in the above-mentioned embodiment.

In the above-described second embodiment, the pulse signal is generated by writing the pulse pattern data in the RAM 71 in advance before the recording is started.
By using M to write the pulse pattern data of several patterns in advance in this ROM, it can be realized as in the case of the RAM 71.

In the above-described embodiment, the nozzles of the recording head having a plurality of nozzles are divided into a plurality of blocks and the heater drive signal is supplied to each block. However, as shown in FIG. Heater drive signal (BE
It is also possible to realize more accurate preheating by supplying 0 to BE256) and further dividing the heater driving signal.

As described above, according to this embodiment, when the nozzles to be used are limited even during a period in which the recording head is not driven at recording time intervals, or during recording, the recording head By adding a heater drive signal to the heater of each nozzle to such an extent that ink is not ejected, it is possible to prevent the temperature of the heater from decreasing and to make the ejection amount of ink proper, thereby preventing uneven density.

Next, a third embodiment of the present invention will be described with reference to FIGS.

In the third embodiment, while the recording head is scanning to perform recording, the temperature gradient of the heater of the recording head varies depending on the ejection conditions of the recording head. Changes and it becomes impossible to make fine density adjustments. This solves the problem that density unevenness occurs in the recorded image.

FIG. 11 is a block diagram showing the schematic arrangement of an ink jet printer according to the third embodiment of the present invention. The parts common to those in FIG. 1 described above are designated by the same reference numerals, and their description will be omitted.

Reference numeral 10a denotes a head controller, 11a denotes a recording head, which responds to a control signal from the head controller 10a.
The head unit 24 is driven to eject ink to form an image on recording paper. The CPU 21 controls the entire head controller 10a. Now, when the serial binary image data VD is sent from the external device 19, the head control signal generation unit 22 generates a drive signal necessary for the head unit 24 to eject ink. The image data VD output from the head control signal generation unit 22 is the main scanning AHS.
The conversion is performed by the unit 23 so as to prevent the occurrence of density unevenness due to the increase in the ink ejection amount due to the temperature rise of the heater in the nozzle of the head unit 24. That is, the main scanning AHS unit 2
3 is the number of high-level image data corresponding to each nozzle in the main scanning direction (in this embodiment, ink ejection is performed when the image data is high level, and ink is ejected when the image data is low level). Control) so that when the count value reaches a predetermined value, the image data of several dots is forcibly set to the low level and the number of discharges is reduced at the point where the ink discharge amount increases. is doing.

The image data VD thus controlled,
By supplying the head drive signal to the head unit 24, in the head unit 24, only the corresponding nozzle for which the image data VD is at the high level is driven and ink is ejected. This ink is attached to the recording paper to form an image.

Next, details of the main scanning AHS section 23 in which ink ejection control in the main scanning direction is performed will be described with reference to FIG.

The main scanning AHS section 23 is a main scanning AHS.
Parts 2001 to 2256 (for 1 to 256 nozzles), 256
A latch circuit 2257 and a 256-bit parallel input-serial output shift register 2258 are provided.
Each of the main scanning AHS units 2001 to 2256 counts the high level number of the image data corresponding to each nozzle with respect to the image data input as serial binary data, and the count value reaches a predetermined value. When this is done, processing is performed to force the image data for several dots to a low level. Thereafter, the 256 latch circuit latches 256 bits of the image data corresponding to each nozzle to which these processes have been applied. The image data latched by the latch 2257 is sent to the 256 shift register 2258, converted again into serial binary data, and supplied to the head unit 24.

In this embodiment, the head portion 24 has 256
Since it consists of one nozzle, 256 main scans A
The HS unit is composed of a 256-bit latch circuit and a 256-bit shift register. However, when it is composed of more nozzles, it is necessary to increase the circuit structure by that amount.

Next, referring to FIG. 13, the main scanning AHS unit 2
3 will be described in detail.

Reference numeral 51 is a main scanning direction image data detecting section for detecting the state of the image data VD corresponding to each nozzle. A counter 52 counts the number of high level image data corresponding to each nozzle. Reference numeral 53 is a comparison unit, which compares the count value of the counter 52 with the value set by the CPU 21, and when the count value becomes larger than the set value, the comparison output is set to the low level. One of the comparison output signals is input to the delay unit 54, which delays it by several dots. This delayed signal resets the counter 52 and clears the count value to "0". An AND circuit 55 takes the logical product of the comparison output of the comparison unit 53 and the serial binary image data VD. As a result, when the count value of the counter 52 is smaller than the value set by the CPU 21, the input image data VD remains as it is in the AND circuit 55.
When it is larger than the set value, the AND circuit 55 is closed, and the image data is forcibly set to the low level and output.

The set value by the CPU 21 at this time is as shown in FIG.
As shown in FIG. 4, the ink discharge amount is set to be high at a place where the discharge amount is small and low at a place where the discharge amount is large. In this way, several dots and image data are thinned according to the ink ejection state. The delay unit 34 has a function of delaying the reset timing of the counter 52 in order to thin out the dots to be thinned out when the number of ink ejection data exceeds a predetermined value.

FIG. 15 is a circuit diagram showing a specific circuit example of the main scanning AHS section 23, and the portions common to FIG. 12 are indicated by the same numbers.

In FIG. 15, reference numeral 2001 shows the main scanning AHS circuit for the first nozzle, and reference numeral 2002 shows the main scanning AHS circuit for the second nozzle. The latch circuit 401 enables the enable signal P indicating the effective component of the image data VD.
VE is latched in synchronization with the clock (CLK), and a timing signal for detecting the image data of the first nozzle is generated. Further, using the timing signal, the latch circuit 450 of the processing circuit 2002 of the second nozzle adds a delay of one clock to generate the detection timing of the image data of the second nozzle. Similarly, the third nozzle,
4th nozzle ... Image data of 256th nozzle is detected.

In the AHS circuit 2001, the latch circuit 402 latches the image data VD by using the detection timing signal of the image data of each nozzle. The AND gate 403 detects an edge. The number of high-level counters 404 is counted using the edge signal of the image data VD. Further, the CPU 21 sets the maximum count value in the latch circuit 405.

The comparator 406 compares the output value of the counter 404 with the setting value of the CPU 21, and when the output value of the counter 404 is larger than the setting value of the CPU 21, the comparison output of the comparator 406 becomes low level, and this signal The image data is delayed by a high level edge signal.
Further, the AND gate 411 resets the counter 404 with a signal obtained by taking the logical product of the output signal of the latch circuit 402 and the comparison output latched by the latch circuit 410,
Clear the count. Further, the AND gate 40
7, the logical product of the comparison output that has become low level and the input image data VD is obtained, and the output image data is forced to be low level.

In this embodiment, since the delay is applied only by the latch circuit 410, only one dot of image data can be thinned out. However, when it is desired to thin out several dots, the number of latch circuits (delay amount) should be increased. Can be realized by

On the contrary, from the set value of the CPU 21 to the counter 4
When the output value of 04 is smaller, the output signal of the comparator 406 becomes high level, and the input image data VD is output as it is through the AND gate 407. The operation of the main scanning AHS circuit 2001 for the second nozzle is also executed in the same manner.

Such control is performed for all the nozzles of the head section 24, and the latch circuit 2257 latches the image data VD at the trailing edge of the signal PVE. The latched image data VD (256 bits) is parallel-serial converted by the shift register 2258 and output.

By the above processing, the temperature of each heater of the nozzle in the head portion 24 rises, and at a point where a change in the ink ejection amount is expected, the image data VD is set to a low level at several places and is not output. By doing so, it is possible to prevent the temperature of the heater from rising and prevent the occurrence of density unevenness due to fluctuations in the ink ejection amount.

In the above-described embodiment, the AHS circuit in the main scanning direction is used only in the printer. However, a circuit for counting the number of high level image data is provided and the counted value is used. By changing the threshold level when binarizing multi-valued data on the reader side,
realizable.

FIG. 16 is a block diagram showing the schematic arrangement of a copying machine according to the fourth embodiment of the present invention.

In the reader unit 601, the document image is transferred to the CCD 6
The signal is read by 03, the read signal is amplified by an amplifier, and then converted by an A / D converter 605 into a digital signal. After that, the image processing unit 606 performs various image processing such as shading, input masking, output masking, and sharpness processing. The image data subjected to such various image processing is converted into binary data by the binarizing unit 607. In the printer unit 602, similarly to the above-described embodiment, the head control signal generation unit 608 generates a control signal necessary for driving the head 610, and the head 610 ejects ink. The main scanning AHS unit 609 is
The number of times the image data output from the head control signal generation unit 608 is continuously turned on is counted. According to the count value, the threshold level at the time of binarization is changed as shown in FIG. This controls the image data to be turned off when ink is ejected continuously.

Referring to FIG. 18, main scanning AHS unit 609
Will be described in detail. 800 is AHS for the first nozzle
The number of circuits corresponding to the number of nozzles of the head 610 is provided, such as a circuit, a second nozzle 801 and a third nozzle 802.

The latch circuit 81 latches the PVE signal indicating the effective area of the image data in synchronization with the clock signal (CLK), and generates the timing signal 85 for detecting the image data of the first nozzle. Using this timing signal,
The image data corresponding to the nozzle is latched in the latch circuit 82. Next, the AND gate 83 calculates the logical product of the latched image data and the timing signal 85.
The output of the AND circuit 83 obtained by this logical product becomes high level when the image data becomes high level, and the counter 74 is counted up by this signal. Further, the counter 84 is reset when the output of the latch circuit 82 becomes low level. As a result, the counter 84 counts when the image data is continuously turned on.

As described above, it is possible to prevent the occurrence of uneven density, as described above.

In the above-described embodiment, when the image data is continuously at the high level, the threshold for binarization is controlled to be changed. On the other hand, a subtraction circuit may be provided to perform level conversion when the image data continuously has a high level.

Further, the printer side is provided with means for counting the number of high level image data, but the number of high level of the binarized image data on the reader side is counted and binarized. Level conversion or 2 for the previous multi-valued data
This can be realized by changing the threshold value for digitization.

As described above, according to this embodiment, when ink is ejected continuously in the main scanning direction, the temperature rise of the heater is prevented by thinning out the image data of several dots to prevent the ink ejection amount. Can be properly done.

The present invention brings excellent effects particularly in an ink jet type recording head and a recording apparatus for recording by forming flying droplets by utilizing thermal energy among the ink jet recording systems.

With regard to its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, liquid (ink)
By applying at least one drive signal to the electrothermal transducer arranged corresponding to the sheet or liquid path in which is stored, which corresponds to the recorded information and gives a rapid temperature rise exceeding nucleate boiling. Since the electrothermal converter is caused to generate heat energy to cause film boiling on the heat-acting surface of the recording head, as a result, bubbles in the liquid (ink) corresponding to the drive signal in a one-to-one relationship can be formed. It is valid. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make this drive signal in a pulse shape, because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be achieved.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, A configuration using US Pat. No. 4,558,333 or US Pat. No. 4,459,600, which discloses a configuration in which the heat-acting surface is arranged in a bending region, may be used. In addition, Japanese Unexamined Patent Application Publication No. Sho 5-5 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters.
Japanese Patent Application Laid-Open No. 9-123670 and Japanese Patent Application Laid-Open No. Sho 5 (1993) -58
A configuration based on Japanese Patent Publication No. 9-138461 may also be used.

Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used.

In addition, by being attached to the apparatus main body, it can be electrically connected to the apparatus main body and can be supplied with ink from the apparatus main body by a replaceable chip type recording head or the recording head itself. Alternatively, a cartridge type recording head provided with an ink tank may be used.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus of the present invention, because the effect of the present invention can be further stabilized. . Specific examples thereof include capping means, cleaning means, pressurizing or suctioning means for the recording head, preheating means using an electrothermal converter or another heating element or a combination thereof, and recording. It is also effective to perform a stable recording by performing a preliminary discharge mode in which another discharge is performed.

Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrally configured or a plurality of combinations may be used. Alternatively, the device may be provided with at least one of full-color mixed colors.

In the embodiments of the present invention described above, the ink is described as a liquid, but it is an ink that solidifies at room temperature or lower and that softens at room temperature, or is a liquid, or the above-mentioned liquid. In the inkjet method, it is common to control the temperature of the ink itself within a range of 30 ° C to 70 ° C to control the temperature of the ink so that the viscosity of the ink is within a stable ejection range. It is sufficient that the ink is liquid.

In addition, the temperature rise due to the thermal energy is positively prevented by using it as the energy for the state change of the ink from the solid state to the liquid state, or the ink is solidified in the standing state for the purpose of preventing the evaporation of the ink. In some cases, such as ink that is liquefied by applying heat energy according to a recording signal and ejected as a liquid ink, or one that has already started to solidify when it reaches a recording medium. The use of an ink having a property of being liquefied only by heat energy is also applicable to the present invention. In such a case, the ink is disclosed in JP-A-54-5684.
No. 7 or JP-A-60-71260, a mode in which the porous sheet is opposed to the electrothermal converter in the state of being held as a liquid or solid in the recess or through hole of the porous sheet. May be In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, as a form of the recording apparatus according to the present invention, in addition to the one provided integrally or separately as an image output terminal of the information processing equipment such as the word processor and the computer as described above, it is combined with a reader or the like. It may be in the form of a copying machine or a facsimile machine having a transmission / reception function.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program for implementing the present invention to a system or an apparatus.

[0084]

As described above, according to the present invention, the ejection amount of ink can be properly maintained by using the drive signal of the recording head as an arbitrary pulse signal.

According to another aspect of the invention, it is possible to suppress the temperature rise of the recording head due to the image data and to keep the ink ejection amount proper.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an inkjet printer according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the manner of waveform division (pulse generation) performed in the heater drive signal division unit of the first embodiment.

FIG. 3 is a block diagram showing a configuration of a heater drive signal division unit of the first embodiment.

FIG. 4 is a diagram illustrating switching between an ink ejection area and a preheating area, which accompanies scanning of the recording head according to the present exemplary embodiment.

FIG. 5 is a block diagram showing a circuit configuration of a heater drive signal data setting unit of the first embodiment.

FIG. 6 is a block diagram showing a circuit configuration of a heater drive pulse selection unit of the first embodiment.

FIG. 7 is a flowchart showing the control of the CPU of the inkjet printer of this embodiment.

FIG. 8 is a block diagram showing a configuration of a pulse pattern data generation circuit when a RAM according to a second embodiment of the present invention is used.

FIG. 9 is a diagram showing an energization circuit and energization timing for each nozzle heater of the recording head.

FIG. 10 is a diagram showing a conventional heater drive circuit and its timing.

FIG. 11 is a block diagram showing a schematic configuration of an inkjet printer according to a third embodiment of the present invention.

12 is a block diagram showing details of a main scanning AHS unit in FIG.

13 is a block diagram showing details of main scanning AHS corresponding to each nozzle of FIG.

FIG. 14 is a diagram showing a relationship between an ink ejection amount and a setting value by a CPU in the third embodiment.

15 is a circuit diagram showing a specific circuit example of a main scanning AHS unit in FIG.

FIG. 16 is a block diagram showing a schematic configuration of a copying machine according to a fourth embodiment of the present invention.

FIG. 17 is a diagram showing a relationship between a count value and a threshold value in the fourth embodiment.

FIG. 18 is a block diagram showing details of a main scanning AHS unit in a fourth embodiment.

[Explanation of symbols]

 12, 21 CPU 13, 22 Head control signal generation unit 14 Heater drive signal division unit 16 Heater 23 Main scan AHS unit 24 Head unit 30, 31 Heater drive signal data set unit 32 Heater drive pulse select unit 51 Main scan direction image data detection Section 52 counter section 53 comparison section

Claims (5)

[Claims] 1. An image forming apparatus for forming an image using a recording head of an inkjet recording system, wherein the storage means stores pulse pattern data, and the storage means based on a signal defining a drive timing of the recording head. An image forming apparatus comprising: pulse generating means for generating a drive signal for driving each nozzle of the recording head according to the pattern data stored in the image forming apparatus. 2. The storage means stores first pulse pattern data for ejecting ink and second pulse pattern data for not ejecting ink, and stores the first or second pulse pattern data according to a driving state of the recording head. The image forming apparatus according to claim 1, further comprising a selection unit that selects any of the second pulse pattern data. 3. A drive unit for driving the nozzles of the recording head in a divided manner, and reading of the pulse pattern data stored in the storage unit is controlled according to the division of the nozzles by the drive unit, and each nozzle block is controlled. The image forming apparatus according to claim 1, further comprising a unit that generates a drive signal corresponding to. 4. An image forming apparatus for forming an image using a recording head of an ink jet recording system, a counting means for counting the number of continuous image data for ejecting ink, and a count value by the counting means is a predetermined value or more. An image forming apparatus comprising: a determining unit that determines whether or not the image forming apparatus includes a determining unit that determines whether or not a predetermined value is exceeded based on a determination result of the determining unit. 5. The recording head is a recording head for ejecting ink by utilizing thermal energy, and is an inkjet recording head provided with a thermal energy converter for generating thermal energy given to the ink. The image forming apparatus according to claim 1 or 4, characterized in that