JPH09156102A - Image forming apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of high quality free from density irregularity at a high speed by judging the presence of the emission of emitting orifices related to the formation of pixels present around the pixel formed by an emitting orifice to be corrected and correcting a drive signal for emitting ink corresponding to the pattern of the judged presence of the emitting orifices. SOLUTION: In an image forming apparatus forming an image by using a printing head for emitting ink from a large number of emitting orifices, a change pattern modulating a dot diameter is preliminarily calculated to be stored in an RAM 230 in a table system and, if necessary, a numerical value is drawn out to a gate array 200 having a PWM table from the RAM 230. The numerical value (radom numbers) drawn out of the table of the RAM 230 is added to a fundamental drive table number set in the optimum timing by a CPU 240 and, further, heat pulses are formed on the basis of the data of the PWM of the gate array 200 according to the table number to control a dot diameter.

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 in which ink is ejected onto a print medium for recording and a drive control method for a print head used in the apparatus.

[0002]

2. Description of the Related Art Image forming apparatuses such as printers, copying machines, and facsimiles are configured to print an image of a dot pattern on a print medium such as paper, a plastic thin plate, or cloth based on image information. ing.

The image forming apparatus, depending on the image forming method, is of the ink jet type, wire dot type, thermal type,
Inkjet image forming apparatuses such as inkjet recording devices eject ink droplets as a printing agent from the ejection ports of the printhead and eject the ink droplets onto a print medium to attach an image to the print medium. It is configured to form (print).

In recent years, many printing apparatuses have been used, and high speed printing, high resolution, high image quality, low noise, etc. are required for these printing apparatuses. As a printing device that meets such demands,
Inkjet printing devices are becoming mainstream now. In the inkjet printing apparatus, since printing is performed by ejecting ink from the print head, non-contact printing is possible, and the print head can be manufactured using a manufacturing process similar to that of semiconductors. In addition, since it is possible to mount the ink discharge ports at a high density, and since the ink discharge ports can be driven at a high frequency, it is possible to operate at high speed, so that the above requirements can be satisfied more than enough.

However, in the ink jet printing system, since fluid ink is handled, various hydrodynamic inconvenient phenomena may occur at or above the limit operating speed of the print head. Further, since the ink is generally a liquid, its physical state due to the physical properties of the ink such as its viscosity value (η) and surface tension (γ) always fluctuates depending on the environmental temperature and the time for which the ink is left to cause evaporation. For example, even if normal ejection is possible in the initial state, if the environmental temperature drops or the negative pressure on the storage member side increases due to a decrease in the remaining amount in the ink storage member such as the ink tank. In some cases, the normal discharge state may not be maintained.

In addition, a print head (so-called multi-nozzle head) in which ink discharge ports or liquid paths communicating therewith are integrated is used to discharge ink from a certain discharge port or a group of discharge ports, or into a liquid path thereafter. It is feared that the turbulent flow, the laminar flow, and the like generated by the ink flow accompanying the ink refill operation may adversely affect the surrounding flow due to the nature of the ink as a continuum. In a multi-nozzle head, it is not preferable from the viewpoint of power supply capacity and refill operation to perform ejection operations from all ejection ports at the same time. Therefore, blocks are formed for each predetermined number of nozzle groups. Many are configured to perform time division driving (hereinafter referred to as block driving). However, since the nozzle groups included in one block are driven at the same time within one block, a voltage fluctuation or a change in the ink flow velocity distribution occurs in the nozzle group depending on the image signal, and the ejection state changes accordingly. There is also a risk that the discharge amount will change and the discharge amount will change.

On the other hand, a wide range of image forming apparatuses (printers) for forming monochrome images and color images are stable in various performances such as dot reproducibility, density stability, gradation reproducibility and color reproducibility. It is desired to meet such demand by appropriately selecting a drive control method.

In particular, an ink jet printing method (a bubble jet method proposed by Canon Inc.) in which heat energy is applied to the ink in the liquid path inside the ejection port and the ink is ejected in accordance with the expansion of bubbles generated by the heat energy. Etc.) Since the printer uses heat energy, the ink ejection characteristics (including the ejection amount, ejection speed, bubbling state, refilling state, etc.) due to changes in environmental temperature and self-heating due to printing operation are included. Fluctuates,
In order to maintain the above-mentioned stability, a drive amount control method that employs a drive waveform composed of a plurality of pulses as a drive signal for a print element (electrothermal conversion element) and controls the pulse width appropriately (so-called PWM correction control. Embodiment)).

Further, heads manufactured by mass production have not only different ejection characteristics but also distribution among nozzle groups included in one head. In order to solve these problems, a technique called head shading or , A bitmap correction method has been proposed. Then, a discharge amount control method combined with the correction of the above-mentioned thermal characteristics is also proposed. Further, a method of visually reducing density unevenness by random driving or the like has also been proposed.

[0010]

However, the conventional PWM
In the ejection amount modulation driving method by correction, it is possible to correct the ejection amount fluctuation as an average value of the head based on prediction or the fiber method to make it constant, but Since it is not possible to correct the discharge amount distribution,
There is a problem in that density unevenness occurs during so-called 1-pass printing in which a predetermined print width is printed by only one scan.

The head internal ejection amount distribution correction, in which the ejection amount distribution of each ejection port is measured (head shading) and then bitmap correction is performed, mainly takes into consideration the initial ejection characteristics of the head during production. It could not cope with the change with time.

In recent years, a test pattern is printed when necessary to measure the discharge amount distribution of the discharge port group, and the drive signal is automatically corrected based on this to correct the density unevenness. A technique called so-called AHS (auto head shading) has also been proposed, but this method is a correction based on a static discharge amount distribution under a certain fixed condition, and when printing various image patterns. Discharge status of adjacent discharge ports that occur (fluid influence of discharge status such as whether or not the area around the target discharge port is discharging)
It was not always possible to adequately cope with the dynamic change in the discharge amount, which changes moment by moment due to changes in the ink jet pressure and driving conditions (driving frequency, voltage drop, etc.).

Further, in the density unevenness reducing method by the random driving, the image becomes totally noisy due to the generation of random noise, and there is a risk that the image quality is deteriorated at the cost of reducing the density unevenness.

The present invention takes these problems as technical problems to be solved.

[0015]

To this end, the present invention provides
In an image forming apparatus that forms an image using a print head that has a plurality of ejection ports and ejects ink from the plurality of ejection ports, a unit that controls the ejection amount of ink for each of the plurality of ejection ports. Means for determining the presence / absence of ejection of an ejection port related to the formation of pixels around the pixel formed by the ejection port to be corrected, and ink from the ejection port according to the determined ejection presence / absence pattern. And a correction unit that generates data for correcting the drive signal applied to discharge the ink, and a unit that causes the control unit to control the discharge amount based on the correction data.

Further, the present invention provides an image forming method for forming an image using a print head having a plurality of ejection ports and ejecting ink from the plurality of ejection ports, wherein each of the plurality of ejection ports is formed. A means for controlling the ejection amount of the ink is provided, and the presence or absence of ejection of the ejection port related to the formation of pixels around the pixel formed by the ejection port to be corrected is determined, and the pattern of the presence or absence of the determined ejection is determined. Accordingly, data for correcting a drive signal applied to eject ink from the ejection port is generated, and the control unit controls the ejection amount based on the correction data.

In each of these, a predetermined number of the plurality of energy generating elements provided to generate energy used for ejecting ink from the plurality of ejection ports are provided.
Driven by being divided into multiple blocks as a block,
The correction may be performed according to the driving state of each block.

Alternatively, the correction may be performed in accordance with the presence / absence of ejection from the ejection port related to the formation of pixels around the pixel formed by the ejection port to be corrected.

Here, the surrounding pixels may be formed substantially at the same time as and / or before and after the pixels formed by the ejection ports to be corrected, and further, the surrounding pixels may be formed. The correction can be performed by weighting the information regarding the presence / absence of ejection from the ejection port related to the formation.

Further, in the above, the control of the ejection amount controls the width of the at least one pulse with respect to the drive signal composed of a plurality of pulses including a combination of the pulse directly related to the ejection of the ink and other pulses. You can do it by doing.

Further, the print head serves as a plurality of energy generating elements provided to generate energy used for ejecting ink from the plurality of ejection ports, and heat energy for causing film boiling in the ink. It may have a generating electrothermal conversion element.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings with respect to some examples of embodiments.

(1) First Example (Mechanical Structure of Image Forming Apparatus) FIG. 1 is a perspective view of a mono-color ink jet printer as an example of an image forming apparatus to which the present invention can be applied. The illustrated device IJRA
The carriage HC that engages with the spiral groove 5004 of the lead screw 5005 that rotates via the driving force transmission gears 5011 and 5009 in conjunction with the forward / reverse rotation of the drive motor 5013 has a pin (not shown), and has an arrow. It is reciprocated in the a and b directions. A paper pressing plate 5002 presses the paper against the platen 5000 in the carriage movement direction. Reference numerals 5007 and 5008 denote home position detecting means for confirming the presence of the lever 5006 of the carriage in this area by a photo coupler and switching the rotation direction of the motor 5013. 5016 is a member that supports a cap member 5022 that caps the front surface of the print head.
Reference numeral 5015 denotes a suction means for sucking the inside of the cap to perform suction recovery of the print head through the opening 5023 in the cap. 5017 is a cleaning blade, 5019 is a member that allows the blade to move in the front-rear direction,
These are supported by the main body support plate 5018. It goes without saying that the blade is not limited to this form, and a well-known cleaning blade can be applied to this embodiment. Also, 5012
Is a lever for starting the suction for suction recovery, which moves in accordance with the movement of the cam 5020 that engages with the carriage, and the driving force from the driving motor is movement-controlled by known transmission means such as clutch switching.

The capping, cleaning, and suction recovery are configured so that the desired processing can be performed at their corresponding positions by the action of the lead screen 5005 when the carriage comes to the home position side area. Any desired operation can be applied to this example if desired operation is performed at the timing.

(Configuration Example of Print Head) FIG. 2 shows a configuration example of the print head used in this example. The inkjet printhead IJU of this example is a printhead of a type that has an electrothermal converter that generates thermal energy for causing film boiling in the ink in response to an electrical signal.

In FIG. 2, reference numeral 100 denotes an electrothermal converter (ejection heater) arranged in a plurality of rows on a Si substrate, and electric wiring such as Al for supplying electric power to the electrothermal converter, which is formed by a film forming technique. It is a heater board having the above configuration. 120
Reference numeral 0 denotes a wiring board for the heater board 100, a wiring corresponding to the wiring of the heater board 100 (for example, connected by wire bonding), and a pad 1201 located at an end of the wiring and receiving an electric signal from the main unit. have.

Reference numeral 1300 denotes a grooved top plate provided with partition walls and a common liquid chamber for partitioning a plurality of ink flow paths, and an ink receiving port 1500 for receiving the ink supplied from the ink tank and introducing it into the common liquid chamber. And an orifice plate 400 having a plurality of discharge ports are integrally molded. Polysulfone is preferred as these integral molding materials, but other molding resin materials may be used.

Reference numeral 300 denotes a support body made of, for example, metal that supports the back surface of the wiring board 1200 on a flat surface, and serves as a bottom plate of the ink jet unit. Reference numeral 500 denotes a presser spring, which is M-shaped and presses the common liquid chamber at the center of the M-shape and presses a part of the liquid passage with linear pressure by the front slant portion 501. Heater board 1
00 and the top plate 1300, the foot of the spring is supported by the support member 30.
By engaging with the back surface of the support 300 through the 0 hole 3121 and engaging the two while sandwiching them, the urging force of the pressing spring 500 and the front drooping portion 501 causes the heater board 100 to engage with the heater board 100. The top plate 1300 is fixed by crimping. In addition, the support member 300 has the positioning holes 31 that engage with the two positioning protrusions 1012 and the positioning and heat-fusion holding protrusions 1800 and 1801 of the ink tank.
In addition to 2,1900 and 2000, projections 2500 and 2600 for positioning the apparatus main body with respect to the carriage are provided on the back surface side. In addition, the support 300 is provided with an ink supply pipe 2200 that enables ink supply from the ink tank.
It also has a hole 320 that allows the passage of (described below). The attachment of the wiring board 200 to the support 300 is performed by sticking with an adhesive or the like. The concave portion 240 of the support 300
0 and 2400 are positioning projections 2500 and 2 respectively.
In the assembled ink jet cartridge, which is provided in the vicinity of 600, at the extension point of the head tip region formed by a plurality of parallel grooves 3000 and 3001 on the three sides of the ink jet cartridge, unnecessary objects such as dust and ink are provided. Projection 250
It is located so as not to reach 0,2600. This parallel groove 3000 is formed. The lid member 800 is
While forming the outer wall of the inkjet cartridge,
A space for accommodating the inkjet unit IJU is formed. The ink supply member 600 in which the parallel groove 3001 is formed is the same as the ink supply tube 2200 described above.
A continuous ink conduit 1600 is formed as a fixed cantilever on the supply pipe 2200 side, and a sealing pin 602 for securing a capillary phenomenon between the fixed side of the ink conduit and the ink supply pipe 2200 is inserted. Incidentally, 601 is a packing for connecting and sealing the ink tank IT and the supply pipe 2200, and 700 is a filter provided at the end of the supply pipe on the tank side.

Since the ink supply member 600 is molded, the ink supply member 600 is inexpensive, has a high positional accuracy, and eliminates a decrease in accuracy in forming and manufacturing. In addition, the cantilevered conduit 1600 allows the ink supplying member 600 to be used for mass production. The pressure contact state of 1600 to the ink receiving port 1500 can be stabilized. In this example, a complete communication state can be reliably obtained only by pouring the sealing adhesive from the ink supply member side under the pressure contact state. The ink supply member 600
Is fixed to the support 300 by the holes 19 in the support 300.
01, 1902, the back side pins (not shown) of the ink supply member 600 are
This is easily performed by projecting through the through hole and heat-sealing the portion of the support body 300 projecting to the rear surface side. Since the slightly projected area of the heat-sealed back surface is accommodated in the recess (not shown) in the side wall surface of the ink jet unit IJU mounting surface of the ink tank, the positioning surface of the unit IJU can be accurately obtained.

The ink tank is a cartridge body 100
0, the ink absorber 900, and a lid member 1100 that seals the ink absorber 900 after inserting the ink absorber 900 from the side surface of the cartridge body 1000 opposite to the unit IJU attachment surface.

Reference numeral 900 denotes an absorber for impregnating ink, which is arranged in the cartridge body 1000. 1
220 is a unit IJ composed of the above-mentioned respective parts 100 to 600
It is a supply port for supplying ink to U, and the unit is a part 1 of the cartridge body 1000.
It is also an injection port for performing ink impregnation of the absorber 900 by injecting ink from the supply port 1220 in a process before the arrangement at 010.

In this embodiment, the ink can be supplied to the atmosphere communication port and the supply port, but the rib 2300 in the main body 1000 and the lid member for favorably supplying the ink from the ink absorber. 1100 partial ribs 2500, 2
400, the air presence area in the tank formed by
The ink supply port 12 is continuously connected from the air communication port 1401 side.
Since the configuration is formed over the corner region farthest from 00, it is important that relatively good and uniform ink supply to the absorber is performed from the supply port 1200 side. This method is extremely effective in practice. The rib 1000 has four ribs parallel to the carriage movement direction on the rear surface of the main body 1000 of the ink tank to prevent the absorber from adhering to the rear surface. In addition, the partial ribs 2400 and 2500 are similar to the rib 100.
Although it is provided on the inner surface of the lid member 1100 which is on an extension corresponding to 0, it is in a divided state unlike the rib 1000, so that the presence space of air is larger than the former. Note that the partial ribs 2500 and 2400 are
00 are distributed on a surface that is less than half of the total area of 00. With these ribs, the ink in the corner region farthest from the tank supply port 1200 of the ink absorber could be more stably guided to the supply port 1200 side by capillary force. Reference numeral 1401 denotes an atmosphere communication port provided in the lid member for communicating the inside of the cartridge with the atmosphere. Reference numeral 1400 denotes a liquid-repellent material disposed inside the atmosphere communication port 1401;
This prevents ink from leaking from the air communication port 1400.

Since the ink storage space of the ink tank described above has a rectangular parallelepiped shape and has long sides on its side surfaces, the rib arrangement configuration described above is particularly effective. In the case where the ink absorber 900 has a cubic shape or a cubic shape, it is possible to stabilize the ink supply from the ink absorber 900 by providing a rib on the entire lid member 1100.

(Causes of Occurrence of Mottling Between Nozzles) There are the following seven typical variations as factors that cause unevenness in an image formed by using the print head as described above.

The first point is the variation in the resistance value of the discharge heater. The variation in the resistance value becomes a variation in the heat generation temperature when the ejection heater is driven, and causes a variation in the bubble diameter in the ink, which is the ejection energy. Provoke. When an image is formed by a print head having this variation, the areas and shapes of the dots formed on the print medium vary, which eventually leads to unevenness in the formed image.

The second point is the variation in the surface condition of the heater. Fine irregularities due to the surface roughness of the surface or the degree of contamination with foreign matter cause variations in the foaming start point at the ink foaming start stage, that is, variations in the foaming start time, and cause differences in dot shape and the like. .

The third point is the variation in the shape and diameter of the discharge port. The difference in shape causes variations in the ejection direction and ejection amount, and causes unevenness on the image.

The fourth point is the variation in the position of the heater and the position of the liquid passage in which the heater is arranged. The variation is a difference in impedance between the ejection direction and the non-ejection direction during foaming. The difference in impedance becomes a difference in conversion efficiency that is converted into discharge energy when the bubbles are bubbled, which causes a difference in discharge amount and discharge speed, resulting in image unevenness.

The fifth point is variation in durability. In the print head, the wettability between the ink and the constituent elements of the liquid passage or the ejection port and the energy conversion efficiency change depending on the frequency of use, resulting in a difference in ejection characteristics. That is, since the dot diameter and the landing position differ depending on the frequency of use, unevenness occurs over time on the printed image.

The sixth point is voltage fluctuation. Even when the print head is block driven as described above, the divided block also includes a plurality of electrothermal conversion elements, and a voltage variation occurs in the block due to the print pattern. Therefore, when various patterns are printed, unevenness is dynamically generated on the printed image.

The seventh point is fluid fluctuation. Since the inkjet print head uses an ink that is a fluid as a printing agent, the properties of the fluid affect ejection. The ejection state of the ejection port or the liquid path currently performing the ejection operation is influenced by the past ejection state, and the present ejection state also affects the future ejection state. In addition, the flow of ink also changes depending on the state of ejection of the surrounding ejection ports or liquid paths. That is, unevenness is dynamically generated on the printed image due to the influence of the fluid.

It is very difficult to appropriately suppress the above-mentioned representative image unevenness generating factors and control so that a high-quality image without unevenness can be obtained irrespective of manufacturing variations and temporal changes. It is a problem.

(Structure of Control System) FIG. 3 shows an example of the structure of a control system for the device structure shown in FIG. Here, reference numeral 220 denotes a control unit, which is a CPU 240 in the form of a microcomputer for controlling each unit in accordance with a processing procedure described later, a ROM 250 for storing a program and other fixed data corresponding to the processing procedure, and a work for a required calculation. RAM 230 having an area area, DRAM 6703 having an area for expanding image data related to printing
Further, it has a gate array 200 and the like described later with reference to FIG.

Reference numeral 6705 denotes a head driver for driving a print element (heat generating element or the like) arranged in the head 1 at an appropriate timing, and 6706 and 6707 are drive sources for transporting the print medium 2. Conveyor motor (sub-scanning motor) 6709 and carriage 4
This is a motor driver for driving a carrier motor (main scanning motor) 5013 which is a drive source for moving the. Reference numeral 1600 denotes an operation unit for supplying an image data, and also for an operator to input an instruction for appropriately setting a print mode (high-speed mode, high-definition mode, etc.) and other modes. These data and instructions are interfaced. 670
It is supplied to the control unit 220 via 0. (Logic configuration of inkjet print head used in this example) The print head used in this example has a resolution of 36.
It is an ink jet type print head equipped with 128 discharge ports at 0 DPI. 128 outlets are 16
Each block is allocated to one block, and the discharge control is performed for each same block. An outline of the logic configuration in the head chip of the print head will be described with reference to FIG.

In FIG. 4, reference numeral 100 denotes a print head chip in which the above logic is arranged. Signals for printing, which are roughly classified into three, are input to the logic.

One is a print data signal, which is a signal for selecting the heater of the ejection port to be driven. The signal is DA
When data is input from the TA signal line and serially input to the shift register 101 in the print head, and data for 128 lines corresponding to the discharge heaters corresponding to all discharge ports is stored, the data is latched in synchronization with a latch signal (not shown). It is output to 102 in parallel. Then, the latch 102 outputs an image signal to each AND gate 104 arranged by the number of discharge heaters.

The second is a block selection signal. As described above, since the present print head has an 8-block structure with 16 ejection ports as one block, it is desirable to have a function of selecting 16 ejection ports to be simultaneously driven and controlled in time series. . In the figure, the signal lines of, and have the function, and a 3-bit signal for selecting eight blocks is input to the decoder 103. The signal is applied to the decoder 103
Is decoded into eight signals B1 to B8. Since the blocks of this print head are divided into 16 ejection ports from the top, the B1 signal is output from ejection port # 1 to ejection port #.
It is connected to 16 AND gates up to 16 and the B2 signal is 16 ANDs from outlet # 17 to outlet # 32.
It is connected like a gate (same below).

The third is a heat signal which determines the driving time of the discharge heater. The heat signal is a signal line shown from the inside of the figure, and 16 signal lines corresponding to the number of ejection ports in one block are arranged (however, it is omitted in the figure to be four). The heat signal lines are 1 from the upper part of the discharge port.
Every 6 wires are connected. That is, H1 which is the first heat signal line is AND for discharge ports # 1, # 17, # 33, ....
It is connected to the gate, and H2 is the discharge port # 2, # 18,
# 34, ..., H16 is a discharge port # 16, #
32, ... And 128 gates are respectively connected to AND gates.

Therefore, for example, the discharge heater 105-1 for the discharge port # 1 is turned on because the discharge heater 105-1 is at A
Data signal L connected to ND gate 104-1
It is while the three signals of 1, the block selection signal B1 and the heat signal H1 are on.

(Dot Diameter Modulating Means for Improving Image Quality) The dot diameter modulating means is performed by modulating the pulse width of the heat signal as described above. That is, the pulse pattern of the heat pulse (single pulse, double pulse, etc.)
Or the heat signal lines H1 to H1 controlling the pulse width
The dot diameter control is realized by controlling the pulse signal on 6 for each heat dot. Details of such control will be described below with reference to FIG.

In FIG. 5, the CPU 24 of the printing apparatus
0 transfers data from an address designated by an address bus indicated by a solid line arrow in the drawing through a data bus indicated by a broken line arrow in the drawing. The minimum printing cycle of this printing apparatus is 6 kHz, and the discharge heater corresponding to 128 discharge ports is divided into eight blocks for driving control every 16 lines, and the block interval is 10 μse.
c. During the printing operation, the CPU transfers a trigger pulse every 6 kHz to the gate array 200. Upon receiving the trigger pulse, the gate array 200 receives 10 μs.
It is controlled to input the signal to the print head so that the block selection signal is turned on at the block interval for each ec.

At this time, the data signal for selecting the ejection port to be driven is input in advance from the data signal line to the shift register of the print head, and the data is output from the shift register in response to a latch pulse (not shown). Is latched, and the print data already latched is input to each AND gate 104 connected to each ejection heater.

By determining the block to be selected and the ejection port to be turned on (driving) in the block, and by inputting the heating signal for determining the heating condition to the print head in this state, Energy is applied to the discharge heater of the discharge port.

In the present example, the dot diameter of the ejected ink is modulated to improve the image quality, and the heat pattern for determining the energy applied to the ejection heater is determined and controlled by the processing procedure shown in FIG.

First, when the trigger pulse generated every 6 kHz is input to the gate array 200 (step S
11), the gate array 200 refers to the basic drive pulse at that time. The basic pulse may have a fixed value depending on the print head, but in this example, the CPU sets an optimum basic drive pulse according to the temperature of the print head (step S12). The position to be set is the basic drive table No. in the register group 210 that can set various conditions built in the gate array. The setting register 227. ON / OFF in the register
The PWM table 22 in which various pulse patterns are preset is not set directly.
A table number of 8 is set. 16 types of pulses from table numbers 1 to 16 are set in the PWM table, and pulses are set so that the discharge amount is reduced as the table number becomes smaller.
Specifically, the table is created with a set value such that when the table number is different by 1, the ejection amount is increased or decreased by 1 ng. Here, the temperature of the print head is rising immediately after continuous high-duty printing, so
The discharge amount becomes large. In order to correct this, control is performed so that the basic drive pulse is set by the CPU with a value that narrows down the ejection amount. Although various ejection amount control means have been developed according to the print head temperature, any correction means may be used in this example, or conversely, a print head that cannot be corrected may be used. .

Next, a method of setting the heating condition to be placed on each heating signal line will be described. The heating condition to be placed on each heat signal line, that is, the ejection amount of each ejection port is set to a drive pulse setting corresponding to the voltage variation with respect to the ejection amount when driven by the basic drive pulse. As described above, the PWM table is set so that the discharge amount is modulated at equal intervals. Setting register 2
With respect to the table number set to 27, the table number may be moved back and forth and a pulse may be applied to each heat signal line. In order to move the corresponding basic table number back and forth evenly, it is possible to add a voltage fluctuation amount to the corresponding basic table number and generate a sheet signal to each heat signal line.

However, since the print head has 128 ejection ports and is driven at 6 kHz, it is 166 μse.
The calculation for generating the modulated signal at least 128 times during c and the setting of the PWM value for 128 times must be repeated. Normally, the CPU uses a time-sharing function to control both the engine such as heat interrupt processing and motor drive interrupt processing during printing, and the controller function to analyze print commands and expand them into print data. Processing. With the recent increase in the speed of printing apparatuses, the processing amount of the CPU per unit time has increased dramatically. If the processing overflows during printing where the processing is most concentrated on the CPU, the printing apparatus is operating and the execution of the engine control function cannot be neglected. Therefore, the above division processing is controlled so that the controller function is temporarily stopped and the printing apparatus does not malfunction. However, stopping the controller function temporarily suspends the expansion of the print data of the next line, and after printing one line, the operation of the printing apparatus waits until the expansion of the print data of the next line is completed. Therefore, there is a problem that the printing time per page is not so high even if the printing speed per line is extremely high.

It is obvious that the printing apparatus will be further speeded up in the future, and how to perform high-speed processing of the basic functions of the printing apparatus and how to further reduce the CPU occupancy in additional processing. However, it can be said that this is one of the most important issues in responding to future speed increases.

Dot control in which the dot diameter is modulated for each print dot is effective in improving the image quality by analogy with the future development of the printing apparatus, but it is often difficult to mount a processing function. Although it is easy to assume that this will occur, in this example, the processing load is reduced as follows.

In this example, a change pattern for modulating the dot diameter is calculated in advance and held in the RAM 230 in the form of a table 231. And if necessary, the RAM 23
Numerical values are drawn from 0 to the gate array (step S1
3). Normally, it is necessary to further process the numerical value to generate a pulse, but in this embodiment, the PWM table 228 is provided in the gate array 200 as described above, and the PWM table 228 further modulates the ejection amount for each table number. Since the widths are set to be equal, the numerical value (random number) drawn from the table 231 is added to the basic drive table number preset by the CPU at the optimum timing, and the gate array 200 is further added.
Heat signal table number setting register 211 to
Set the table number for 226 (step S
14) Further, by generating a heat pulse based on the data of the PWM table 228 (step S15), it becomes possible to control the dot diameter. Here, in the present example, the table 231 is a random number table that is digitized in the range of ± 3 with 0 as the center. That is, the basic drive pulse that gives a desired discharge amount in the print head state in consideration of the current temperature rise and the like is ± 3 as the central discharge amount.
The dot diameter is controlled with a modulation width of ng.

Further, since the structure of the print head has the structure of 16 ejection ports in one block as described above, it is necessary to read 16 numerical values in order to perform the printing operation in one block. The width of the numbers in this example is ± 3 as described above and 7 in the range, and the numerical value is stored in 3 bits. That is, a value of 3 word length is extracted for each block of printing operation, but since the CPU used in this example is a 16-bit CPU, it can be executed by three accesses. Further, in the gate array 200, the CPU is the ROM 25
While accessing 0, the gate array 200 is added with a function of creating a desired address and accessing the RAM 230, and the CPU occupation rate required to draw the number to the gate array is virtually zero. Is configured to be possible. In addition, the gate array 20
After the desired value is input to 0, the pulse to be placed on the heat signal line can be calculated and selected only by the addition process that is easy to process as described above, and the desired dot diameter modulation control can be performed with extremely few processes. Becomes In the present embodiment, the ROM 2
Although the number table stored in 50 is expanded and controlled in the RAM 230, the ROM may be directly accessed.

As described above, the number table forming means for preliminarily calculating the numbers and holding them in the form of a table, the PWM table forming means for holding the driving pulse patterns in the form of the table in advance, and the PWM table forming means set in the PWM table The equal discharge amount modulation means is set so that the pulse pattern has the equal discharge amount modulation width, and the DMA means that the gate array creates the desired address and can access the data of the desired address without going through the CPU. By having this, it is possible to obtain the effect of making the density unevenness such as white streaks and black streaks of the printed image less noticeable, but control that suppresses an increase in processing capacity that is an adverse effect of control, that is, an increase in CPU load. Means can be realized.

(Aspect of Discharge Amount Control) Next, a discharge amount control method in this example will be described. In order to control the ejection amount, it is desirable to give a characteristic to the drive waveform of the head, and the divided pulse (plural pulse) drive method is used for the head drive in this example.

FIG. 7 shows a double pulse waveform as a typical pulse waveform thereof. Vop is a driving voltage, P1 is a preheat pulse width, P2 is an interval time (off time), and P3 is a main heat pulse width. ing.
T1, T2, and T3 indicate the times for determining P1, P2, and P3. The voltage VOP is an index of electrical energy required to generate thermal energy, and is determined by the area of the electrothermal conversion element (ejection heater), the resistance value, the film structure, the ejection port of the print head, and the ink path structure. .

The pulse width modulation driving method used in this example is P1
, P2, P3 are applied in this order. P1 indicates the width of the preheat pulse, which is mainly the ink temperature distribution in the nozzle,
Control the viscosity distribution. The width P1 (also controlling P2 and P3 at the same time) is controlled according to the temperature detection using the temperature sensor of the print head. At this time, the width is set so that the ejection heater does not excessively apply thermal energy and pre-foaming or bubble through phenomenon occurs in the ink. The interval time P2 has a function of providing a constant time interval so that the preheat pulse and the main heat pulse do not interfere with each other, and controlling and equalizing the temperature distribution of the ink in the ejection port. The main heat pulse causes a bubbling phenomenon on the ejection heater due to its width P3 to eject ink droplets from the ejection port. These pulse widths are the area of the discharge heater, the resistance value,
It can be determined by the film structure, the ejection port of the head, the ink passage structure, and the physical properties of the ink.

Therefore, when the head structure and ink are determined, and the desired ejection amount: Vd (pl / dot) is determined, P1,
P2 and P3 are arbitrarily determined (the number of combinations of P1, P2 and P3 that generate the same discharge amount is not limited to one).
However, in consideration of the temperature dependency of the discharge amount described later, it is preferable that the interval time P2 is as long as possible in order to widen the control range of the discharge amount with respect to the temperature change.

Next, a discharge amount control method using the preheat pulse P1 (which can also be controlled by P2) will be briefly described.

As shown in FIG. 8, the relationship between the preheat pulse P1 and the discharge amount VD is linear (or non-linear) up to P1LMT with respect to the increase of the pulse width of P1 under the condition that the head temperature (TH) is constant. After that, the pre-foaming phenomenon disturbs the foaming of the main heat pulse P3, and when it exceeds P1MAX, the ejection amount tends to decrease.

Similarly, the head temperature (TH) and P1 /
As shown in FIG. 9, the relationship between the preheat pulse P2 and the ejection amount Vd under the condition that P3 is constant increases up to P2MAX as the pulse width of P2 increases, and thereafter, the ink temperature near the heater increases. The discharge rate tends to decrease when P2MAX is exceeded due to a change in temperature distribution (the main cause is a decrease in temperature). According to the study by the present inventors, P2MAX is dominated by heat conduction determined by the head structure, physical properties of ink, etc.
It is known that almost the same ejection amount can be produced within ± 4 (μsec).

Under the condition that the preheat pulse P1 is constant,
The relationship between the head temperature TH (environmental temperature) and the ejection amount Vd is
As shown in FIG. 10, it tends to increase linearly as the head temperature TH increases. The coefficient of the region showing each linearity is: Preheat pulse dependence coefficient of discharge amount: KP1 = ΔVDP / ΔP1 (ng / μsec ・ dot) Interval time dependence coefficient of discharge amount: KP2 = ΔVDP / ΔP2 (ng / μsec ・ dot ) Head temperature dependence coefficient of ejection amount: Determined as KTH = ΔVDT / ΔTH (ng / C · dot).

By the way, in this example, a head having a structure as shown in FIG. 11 is used.

In FIG. 11, reference numeral 21 is a substrate made of Al or the like and carries a so-called heater board 19 on which an electric wiring pattern, the discharge heater 11 and the like are formed. Reference numeral 22 denotes a top plate joined to the heater board 19, and the discharge heater 11
, A common liquid chamber 15 that communicates with one end of the liquid passage 13 to supply ink, and a discharge for opening the other end of the liquid passage 13 on the surface facing the print medium. It has an outlet 17 and the like. In response to the bubbling on the ejection heater 11, the ink is ejected from the ejection port 17 in the b direction (in this example, it is configured to have a predetermined angle θ with respect to the axis of the liquid passage 13). Accordingly, the ink is refilled from the common liquid chamber 15 into the liquid passage 13 as indicated by the arrow a.

In the head structure shown in FIG. 11, the above coefficient is KPBk = 8.25 (ng / μsec.dot) KTHBk = 0.7 (ng / deg.dot), and these two relationships will be described below. As shown in FIG. 12, the pulse width modulation (PWM) control of P1 or P2 depending on the head temperature can be used effectively so that the environmental temperature changes or the head temperature changes due to self-heating due to the printing operation. It can be seen that the discharge amount can be kept constant even if the occurrence of the above occurs. In this way, an ejection characteristic control method (ejection amount and ejection speed) that can always keep the ink ejection amount constant as a target becomes possible.

In this example, these principles are applied to each ejection port so that the bitmap ejection amount can be corrected for each ejection port.

As for the ejection characteristics of the head which is drive-controlled by using the above-mentioned drive method, in the case of this example, P1 when Vop = 28 (V) in the environment of head temperature TH = 25.0 (° C.) = 2.00 (μsec), P2 = 9.0 ± 3 (μ
sec) and P3 = 4.00 (μsec), optimum driving conditions are obtained and a stable ink ejection state is obtained. The ejection characteristic at this time is that the ink ejection amount Vd = 4.
0.0 (ng / dot), discharge speed V = 14.0 (m /
sec).

Next, the dynamic ejection amount correction method which is a feature of the present invention will be described.

The first example is adapted to cope with dynamic changes in voltage fluctuations. In a print head having a plurality of ejection ports, it is not preferable from the viewpoint of power supply capacity and refill operation to perform ejection operations from all ejection ports at the same time, so a block is formed for each predetermined number of nozzle groups. Then, each block is driven. Therefore, depending on the image signal, the ejection energy changes in the ejection port group due to the voltage fluctuation, and the ejection amount changes. This state is shown in FIGS. 13 (A) and 13 (B). FIG. 13A shows the number of discharge ports (N) for simultaneous discharge and the voltage drop (Vop: voltage fluctuation) generated at that time.
It is shown. FIG. 13B shows the number of ejection ports (N) for simultaneous ejection and the ejection amount fluctuation (Vd) that occurs at that time.

These influences occur when a plurality of ejection ports are ejected simultaneously regardless of the driving method. Therefore, regarding the driving states of the ejection port groups that are present in various ways depending on the image pattern, the data regarding the ejection amount variation due to the predicted voltage variation or the data for correcting it is patterned, and the data of the various tables shown in FIG. This should be reflected in determining the content, or a table for that purpose should be prepared separately. Thus, for example, when receiving or expanding the image data, a table is referred to, the driving state of the ejection port group is determined from the pattern of the image data, and the pulse is generated in the control process as shown in FIG. By performing the width correction (dynamic correction; step S17), it is possible to perform control such that the ejection amount is constant.

That is, according to this example, by performing control equivalent to the PWM drive control, the ejection amount control corresponding to the temperature change due to the environmental temperature change or the head temperature rise and the ejection amount distribution within the head are supported. Ejection amount correction control that also supports dynamic changes in the ejection amount (especially due to the influence of fluid that behaves in various ways when forming various images) while performing a combination of both the above-mentioned bitmap correction Therefore, even when performing high-speed printing (so-called 1-pass printing in which an image is formed in that range by only one scan), there is no density unevenness, and control without density change can be performed reliably, and high-speed and high-quality printing is possible. Image formation becomes possible.

(2) Second Example FIG. 14 shows an example of the configuration of a high speed full color printer used in the second example of the present invention. The printer shown in the drawing has heads Bk1, C1, M1 and Y provided corresponding to four color inks of black, cyan, magenta and yellow.
1, each head is mounted on the carriage 7502 with the ejection port facing downward, and the drive belt 7552
Under the transmission of the driving force by, the reciprocating scanning is performed along the guide rail 7511. On the other hand, the print medium P is the head BK
Conveying rollers 7515, 7516 and 7517, 751 provided in pairs before and after the print area of 1 to Y1
It is nipped and conveyed by 8. A known recovery means is provided outside the print area in the scanning direction of the head.
In this recovery means, reference numeral 7300 denotes a cap unit provided corresponding to each print head, which can be slid horizontally in the drawing as the carriage 7502 is moved, and can be vertically moved up and down. Then, when the carriage 7502 is at the home position, it is joined to the print head portion and capped. In the recovery means, 7401 and 7402
Is a first and second blade as a wiping member, and 7403 is a blade cleaner made of, for example, an absorber for cleaning the first blade 7401. Furthermore, 7500 is a cap unit 730.
A pump unit for absorbing ink or the like from the discharge port of the print head and its vicinity via 0.

The head used in this printer has a resolution of 360 dpi and a driving frequency of 10.8 (kHz).
It has 28 discharge ports.

FIG. 15 is a block diagram showing a configuration example of a control system in the color ink jet printing apparatus.

Here, reference numeral 800 denotes a controller which constitutes a main control unit, for example, a CPU 801 which executes various sequences, a ROM 803 which stores programs and tables corresponding to the procedure, other setting values, and the like. A host device (which may be a reader unit for image reading) serving as a supply source of image data, and image data and other commands, status signals, and the like are transmitted to and received from a controller via an interface (I / F) 812 ( The print pattern is developed in this portion, and the ejection amount correction data for each nozzle is created). Reference numeral 820 denotes a switch group that receives a command input by an operator, such as a power switch 822, a switch 824 for instructing printing start, and a recovery switch 826 for instructing recovery start. Reference numeral 830 is a sensor 832 for detecting the position of the carriage 2 such as a home position sensor and a start position, and a sensor 83 including a leaf switch 530 and used for detecting the pump position.
4 is a sensor group for detecting the state of the device.

Reference numeral 840 is a head driver for driving the electrothermal converter of the print head according to print data and the like. Further, a part of the head driver is also used to drive the heaters 30A and 30B provided to keep the print head at a preferable temperature. Further, the temperature detection values from the temperature sensors 20A and 20B used for controlling the temperature of the print head are the controller 800.
Is input to It should be noted that these heaters and temperature sensors can be simultaneously formed in the heater board manufacturing process as predetermined wiring patterns, etc., one each on each side of the discharge heater arrangement range on the heater board.

Reference numeral 850 is a main scanning motor for moving the carriage 2 in the main scanning direction, and 852 is its driver. A sub-scanning motor 860 is used to convey the print medium.

The fine interlace driving method (driving method corresponding to high-speed printing) with a driving frequency f = 10.8 (kHz) for 128 discharge heaters in this example will be described below in order.

The drive pulse waveform is Vop = 28 for both even-numbered and odd-numbered ejection heaters arranged in a predetermined direction.
(V), P1 = 2 (μsec), P2 = 9 (μse
c), drive at P3 = 4 (μsec). However, the number of blocks is increased from the normal 8 blocks to 9 blocks for driving.

FIG. 16 and FIG. 17 show the waveform of the drive pulse used in this example and the drive state. First, # 1, # 3, # 5, # 7, # 9, # 11, # 13, # 1 of the first block
Double-pulse drive is performed on 16 odd-numbered segments consisting of 5 ejection ports simultaneously.

Next, # 2, # 4, # 6 of the second block.
# 8, # 10, # 12, # 14, # 16, # 18, # 2
0, # 22, # 24, # 26, # 28, # 30, # 32
16 even-numbered segments consisting of
During the double pulses P1 and P3 for driving the odd-numbered segment of the block (hereinafter, those for the odd-numbered segment are expressed as "P1 1B odd" and "P3 1B odd"), the even-numbered segment of the second block is written. Among the double pulses for driving, P1 (hereinafter referred to as "P1 1B even" for even segments) is driven in such a manner that it enters. At this time, P1 1B eve
With respect to n, a delay time of about 8 (μsec) occurs with P1 1B odd.

Next, # 17, # 19, # of the third block
21, # 23, # 25, # 27, # 29, # 31, # 3
3, # 35, # 37, # 39, # 41, # 43, # 4
16 second odd segments consisting of 5 and # 47 simultaneously
Double pulse P1 for even segment of block
The double pulse P1 3B odd for the odd segment of the third block is driven between 2B even and P3 2B even. At this time, P1 2B even has a delay time of about 8 (μsec) with P1 3B odd.

Next, in the same manner, the fourth block # 34,
# 35, # 38, # 40, # 42, # 44, # 46, #
48, # 50, # 52, # 54, # 56, # 58, # 6
16 even segments consisting of 0, # 62, and # 64 are simultaneously driven.

Similarly, by interlacing up to the odd-numbered segment of the eighth block, the pulse opening time (Tblock = P1 + P2 + P3) for each column can be secured for about 15 (μsec) and 128 ejections can be performed. Approximately 1 even if the heater is divided into 8 blocks and the even / odd segment shift drive (shift time: about 8 (μsec))
A high speed drive of 0.8 (kHz) can be achieved.

However, each control parameter at this time is subject to the following conditions.

P1 + P3 <Tdelay (shift time) <P2 Tdelay × 9 + (P1 + P2 + P3) <0.95 × 1000000 /
fop P1: Pre-heat pulse width P2: Interval time (off time) P3: Main heat pulse width Tdelay: Shift time fop: Driving frequency By adopting the above driving method, it is possible to bring out the effect of speeding up refilling, and high speed. In addition, it is possible to print with high image quality.

Next, a discharge amount correction method using a mask pattern, which utilizes the pattern itself of an image related to printing, which is a feature of this example, will be described.

In this example, as shown in FIG. 18, the peripheral ejection ports of the target ejection port for which the ejection amount is to be corrected (for the formation of two pixels in the vertical direction and the formation of three pixels in the horizontal direction). The mask pattern is formed while determining whether or not the ejection operation is performed for such a thing), and the ejection amount of the target ejection port itself is corrected by the pattern.

In this example, the head ejection is performed in the image pattern as shown in FIG. In this case, as in the conventional example, if the drive signal is determined without considering the influence of the surroundings, the result is as follows.

That is, PW based on only the head temperature value
Since the M control is performed, the pre-pulse width P1 is

[0099]

(Equation 1)

Is determined as follows.

On the other hand, in this example, since PWM control is performed by both the head temperature and the pattern,

[0102]

(Equation 2)

Is defined as

Here, a specific example of the above-mentioned method of obtaining ΔP (movement), that is, the method of correcting the meniscus position by ejecting two pixels in the front and rear will be described below.

Generally, the vibration of the meniscus due to the ejection is caused by the vibration wave generated by the ejection of the nozzles around the target pixel. This vibration wave is a two-dimensional function fmeni represented by on / off of the ejection of the surrounding nozzles.
(Xi, tj) (where i: nozzle row direction A, B,
The positions of C, D, E, F, ..., J: time axis direction, present, past (1), past (2), ... Regarding the definition of this function, those obtained from the results of various experiments may be expressed as a function, or this may be tabulated for correction data for simplicity.

Next, a specific example of the function fmeni will be described.

The vibration wave is generated by the long-term influence of ejection. The vibration cycle peculiar to the head: T1 and ejection (foaming) in the vicinity.
Oscillation cycle generated in the short term by: T2 is roughly divided into two. The long term is dominated by past (and future) ejection history (and prediction), and the short term is dominated by current ejection (foaming).

Therefore, the influence of the current (ejection) vibration on the target nozzle is stronger in the neighboring nozzles, and in these nozzles, foaming starts simultaneously with the target nozzle in terms of time, so the position of the meniscus is It moves to the outside (in the direction in which the discharge amount increases) relative to the standard position. Further, vibration due to past (future) ejection history (prediction) occurs as a natural frequency of the head, and as shown in FIG. 28, the meniscus position changes to the plus side (relative to the standard position) with time. It periodically fluctuates from the (discharging amount increasing direction) to the minus side (relative to the standard position (discharging amount decreasing direction) with damping vibration. 28, 1/2 of the cycle: T1 / 2 was about 60 (μsec), and the drive cycle of the head was the drive frequency f (kHz) and the number of blocks (N).
The discharge cycle is about 8 (μsec).
Taking these into consideration, the meniscus vibration function fmeni (x
i, tj) is determined from the image data, and both sizes are symmetrically obtained for the pixel of interest. However, when the cuts of different blocks are the target nozzles, the function (table) must be created in consideration of the time delay of the blocks.

Here, the case of this example will be briefly described. As can be seen from FIG. 18, the past (2) time is 4 dots (A, C, E, G), and the past (1) time is 4 dots (B,
C, D, E), the position variation of the meniscus due to the past influence of each dot is obtained from the natural vibration and its damping curve, and as a result of the experiment, it is slightly ahead of the standard meniscus position, and the ejection amount Tends to increase. In addition, at the present time (ejection), there are 4 dots (A, D, E, G), and the effect of foaming is that the effect of E is the strongest with respect to the target nozzle, and slightly ahead, and the effect of A and G Since the distance is the same and the objects are symmetrical, the effect is twice as large as when only one is used. Therefore, the meniscus position is considerably forward of the standard meniscus position, and the ejection amount is large, so that the correction is performed by narrowing the pulse.

Next, the method of obtaining ΔP (static), that is, the correction of the voltage drop due to the number of simultaneous ejection nozzles in the block is performed as follows.

At the present time (ejection), 4 dots (A, D,
Since it is E, G), it becomes 4/7 for the total number of 7 nozzles in the block, and the voltage drop is also 1-4 / 7 = 3 /
7, the third correction table is selected from the seven stages of correction and the pulse is increased.

Therefore, as a result, the head temperature at this time is 35 (° C.) (change by about 1.0 (μsec) at 10 (° C.))
Then

[0113]

(Equation 3)

It becomes

The above example is an example relating to the head structure in this example, and is not limited to this. In this example, the table is formed based on the data obtained by the experiment, but the pulse correction table may be created by utilizing a fluid simulation or the like. Further, in addition to the dynamic correction and the static correction, as for the ejection amount variation affected by the image pattern, the ejection amount may be corrected and controlled in a range that does not affect the image as necessary. Good.

In this way, considering the past influence of the target ejection port, the meniscus position of the target ejection port changes depending on whether the current drive is immediately after the ejection operation or whether there is a predetermined period. However, the ejection volume varies depending on the meniscus state. In addition, the fluid influence of the surrounding ejection ports or the liquid passages inside the ejection ports also changes the meniscus position of the ejection port of interest. That is, as shown in (i) to (v) of FIG. 19, the meniscus position fluctuates back and forth with respect to the reference position (ii), and the ejection amount fluctuates due to the difference in the amount of ink existing in front of the ejection heater. is there.

Therefore, a meniscus obtained by conducting experiments in advance on various image patterns, that is, various patterns regarding past and future ejection operations in a predetermined range as well as the present ejection port and a plurality of surrounding ejection ports. Various data regarding the position, or various data regarding the ejection volume obtained by the analysis by simulation, and the correction data of the drive signal corresponding thereto are tabulated and stored in, for example, the ROM 803,
By referring to this when the image data is developed, it is possible to perform a so-called dynamic correction based on the image pattern.
That is, in this example, it is possible to perform the optimum ejection amount correction in consideration of the influence of the peripheral ejection ports (driving frequency, pattern), the ink temperature, the head temperature, and the like.

FIG. 20 is a flow chart showing an example of the ejection amount correction procedure used in this example. First, when the head is attached or detached or when the apparatus power is turned on, the correction data for each nozzle that constitutes the head is read. These correction data include ink physical properties (surface tension / ink viscosity), head structure (number of discharge ports, liquid paths or discharge heaters, structure and ink supply method, etc.), drive conditions (drive frequency, drive pulse, drive division). It varies depending on the method, driving order, etc., and the necessary conditions may be selected and tabulated.

The procedure shown in the figure is started, for example, every predetermined time (for example, 50 msec). First, the head temperature is detected in step S101, and step S1 is performed.
At 03, a PWM value corresponding to the temperature is calculated. Next, in step S105, the PWM value is corrected according to the temperature based on the correction data. At this time, the correction amount according to the image pattern is also taken into consideration. The correction amount can be acquired by referring to a required table when the image data is received from the host device 810 or when the image data is developed prior to printing. Then, when the head is actually driven, the drive may be performed using the signal obtained as described above (step S107).

(3) Third Example (Multiple Droplet Multilevel Correction Control) FIG. 21 is a perspective view of a multidroplet type ink jet printing apparatus to which the present invention is applied. The multi-droplet printing method enables gradation expression by allowing a plurality of ink droplets having a small ejection volume to be overlapped in one pixel, and the ejection amount required for one droplet can be reduced. There are more severe requirements for accuracy. Therefore, in this example, a more accurate correction method will be described.

In FIG. 21, reference numeral 1 denotes an ink jet print head (hereinafter simply referred to as a head) in which 128 ejection ports are arranged in the sub-scanning direction. Reference numeral 4 denotes a carriage on which the head 1 is mounted and which moves. The movement of the carriage 4 is slidably engaged at a part thereof and is guided by two guide shafts 5A and 5B extending in the main scanning direction. It is done while being done. 6 is an ink supply tube for supplying ink to the head 1 from an ink tank (not shown), 7
Is a flexible cable for transmitting a drive signal and a control signal based on print data (image signal) from a main body device controller (not shown) to a head drive circuit provided integrally with the head 1. The ink supply tube 6 and the flexible cable 7 are both made of a member that can follow the movement of the carriage 4.

Further, the carriage 4 has guide shafts 5A, 5
It is connected to a part of a belt (not shown) for moving the carriage 4 which is adjusted in parallel with B, and the belt is driven by a carriage motor (main scanning motor) not shown to move in the main scanning direction. It becomes movable. With the movement of the carriage 4, the head 1 can eject ink droplets on the printed surface of the print medium 2 facing the ejection port to perform printing. Reference numeral 3 denotes a roller-shaped platen whose longitudinal direction extends parallel to the guide shafts 5A and 5B, and is used as a print medium 2 (in this specification, paper, plastic film, cloth, etc., liquid such as ink, which is widely used as printing agent). Is used for controlling the print surface of the print medium 2 and for sub-scanning the print medium 2 (hereinafter, also referred to as “paper feed”).

A method of printing 17 gradations on plain paper (a discharge amount is set to be large because the paper bleeding rate is small) using this apparatus will be described. That is, printing is performed by changing the number of ink droplets per pixel within a range of 0 to 16 (ink ejection amount per pixel: within a range of 5 to 80 (ng / dot)).

22 and 23 are conceptual diagrams for explaining the printing method of this example. Reference numeral 1 is a schematic representation of a print head, in which 128 nozzles are arranged in the vertical direction in the figure. For convenience, the numbers of the discharge ports or the discharge heaters are # 1, # 2, ..., # 128 from the bottom to the top of the figure.
And

First, in the first scan, printing is performed while moving the carriage in the main scanning direction at a speed of about 282 mm / sec using only the ejection ports # 1 to # 8. (The state of head drive / control in the main scanning direction at this time will be described in detail in the following drive description). As a result, as shown in FIG. 23A, pixels No. 1 to No. 8 are printed on the print medium with ink droplets 0 or 1 based on the image signal. 8 print media
The pixels are moved upward (in the sub-scanning direction), and printing is performed using the ejection ports # 1 to # 16. As a result, (B) of FIG.
As described above, the # 9 to # 16 ejection ports print the portions of pixels No1 to No8 that were previously printed by the # 1 to # 8 ejection ports, and the # 1 to # 8 ejection ports newly add No9 to N.
O16 pixels will be printed. Therefore, No
Pixels No. 1 to No. 8 are printed with the number of ink droplets 0 to 2 per pixel.

Next, the paper is again moved upward by 8 pixels, and printing is performed using the ejection ports # 1 to # 24. As shown in (C) and (D) of FIG. 23, when the printing is sequentially repeated in the same manner as described above, when the 16th printing is completed, the No. 1 to No. 8 pixels are printed with 0 to 16 drops of ink. That is, a print with 17 gradations can be obtained. When printing is repeated in the same manner as above from the 17th time onward, an image with 17 gradations is obtained over the entire surface. In addition,
Contrary to the start of the printing operation, at the lowermost end of the image, printing may be sequentially stopped from the bottom by eight ejection ports for each scanning to form the image end.

For example, N of the image thus obtained is
Focusing on the pixel of o1, this pixel is
# 9, # 17, # 25, # 33, # 41, # 49, # 5
7, # 65, # 73, # 81, # 89, # 97, # 10
Since 5 or # 113 and # 121 are formed by the ink droplets of 0 or 1 respectively ejected from a total of 16 ejection orifices, the variations in the ink droplet capacities of the ejection orifices are averaged, and an image with no noticeable streaks or unevenness is formed. Will be obtained.

When various images were printed using the above printing method, there were no stripes or unevenness as compared with the conventional printing using a plurality of ink droplets ejecting one pixel from the same ejection port (multi-pass printing method). An extremely high-definition image was obtained. Further, it is preferable because the optimum discharge amount can be set according to the printing material.

In this example, the head having the structure shown in FIGS. 24A to 24C is used.

In FIG. 24, 1-121 is a substrate made of Al or the like, and has an electric wiring pattern and a discharge heater 1-11.
It carries a so-called heater board 1-119 on which 1 and the like are formed. Reference numeral 1-122 denotes a top plate joined to the heater board 1-119, which communicates with the liquid passage 1-113 provided corresponding to the discharge heater 1-111 and one end of the liquid passage 1-113 to communicate the ink. It has a common liquid chamber 1-115 for supply, and a discharge port 1-117 which forms an opening at the other end of the liquid path 1-113 on the surface facing the print medium. Thus, ink is ejected from the ejection port 1-111 in accordance with the bubbling on the ejection heater 1-111.
117, and the common liquid chamber 1-115 accordingly.
Ink is refilled into the liquid path 1-113.

In such a head structure, the head temperature TH =
P when Vop = 15.0 (V) in the environment of 25.0 (° C)
1 = 1.0 (μsec), P2 = 4.0 (μsec),
When a pulse of P3 = 2.0 (μsec) is given, optimum driving conditions are set and a stable ink ejection state is obtained. The ejection characteristics at this time are as follows: ink ejection amount VD = 5.0 (ng / d
ot), discharge speed V = 15.0 ± 0.2 (m / sec)
Met. By the way, the maximum ink ejection amount per pixel is about 80 (ng / dot) for 16 drops, and the maximum drive frequency of the head is fr = 4.0 kHz, which is 360 dp.
With a resolution of i, 128 ejection ports are divided into 16 blocks and are sequentially driven from the first block.

That is, the first block is # 1, # 2, # 3, ..., # 8 The second block is # 9, # 10, # 11, ..., # 16 ..... , # 122, # 123, ...,
Allotment is performed like # 128, and the driving order of the blocks is sequentially driven like the first block, the second block, ..., The 16th block.

In the head structure shown in FIG. 24, KP
= 1.5 (ng / μsec ・ dot) ・ KTH = 0.05
(Ng / deg · dot).

Next, a more accurate ejection amount correction, which is a feature of this example, will be described. In this example, FIG.
As shown in FIG. 5, this is applied to a case where symmetrical discharge weighting is performed on the target ejection port in the left, right, front, and rear, and when the target ejection port is located at the center of the block. Therefore, the ejection amount of the target ejection port can be corrected with the image pattern used in the second example being further multiplied by the weighting coefficient.

The weighting coefficient is adopted. As the distance from the target ejection port and the time interval are longer (farther), the influence on the target ejection port is smaller. Is formed into a table and mapped so that the ejection amount correction data can be created from the ejection amount correction data based on the block number, the ejection port number, and the print pattern signal that comes from the print signal.

(4) Additional Remarks on the Embodiments of the Invention (a) Pattern Mask Weighting Process FIG. 25 shows a case where symmetrical weighting is performed on the target ejection port in the left, right, front, and rear directions. However, the weighting is not limited to the case where the anteroposterior anteroposterior symmetry is applied. FIG. 26 shows a case where left and right are symmetrical with respect to the target ejection port and asymmetrical weighting is performed in the front and rear, which is suitable when the fluid influence is easily influenced by the past state depending on the ejection port structure of the head. FIG. 27 shows a case where asymmetrical weighting is performed on the target ejection port in the left, right, front, and rear directions, and is suitable for the case where the target ejection port is an end of a block or an ejection port with asymmetrical ejection timing such as distributed drive. In addition to the present example, the weighting determination method may be a process generally used in image processing, such as a process for making the density and energy constant.

(B) Processing during multi-pass printing In a printing apparatus that changes the printing state by multi-pass printing according to the print mode (print speed, eg, "fast" / "normal" / "high image quality") or print medium, In the multi-pass printing, the number of passes and the mask pattern applied at that time are taken into consideration to perform the ejection correction by multiplying the actual print pattern (thinning pattern).

(C) Various driving methods As for the driving method of the head, a known method can be applied, and it is optimal for the head from the parameters such as the number of ejection openings, the number of block divisions, the driving frequency, such as the sequential driving method, the forward driving method, and the distributed driving method. The discharge amount may be corrected in consideration of various driving methods and the fluid influence of the target discharge port. Further, the correction method may be changed depending on the position of the ejection port (where the block is driven, etc.).

(D) Variable Driving Frequency In a printing apparatus in which the driving frequency is changed depending on the print mode, the ejection correction condition may be changed according to the driving frequency or the carriage speed.

(E) Control Timing Although it is desirable to perform the ejection amount correction in every ejection cycle, it may be periodically performed in a certain cycle depending on the processing speed of the CPU and the relationship with the desired image.

In addition, it may be changed for each head and for each color, and the ink temperature (when the ink viscosity changes with the ink temperature and the fluid effect changes) and the negative pressure level (when the meniscus vibration changes). Etc.) and other parameters.

(5) Others In the present invention, especially in the ink jet recording system, a means (for example, an electrothermal converter or a laser beam) for generating heat energy as energy used for ejecting ink is used. The present invention provides an excellent effect in the print head and printer of the type in which the thermal energy causes a change in the state of the ink. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

Regarding its typical structure and principle, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. Applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding the nucleate boiling, causing the electrothermal transducer to generate thermal energy, causing film boiling on the heat acting surface of the printhead. This is effective because bubbles can be formed in the liquid (ink) corresponding to this drive signal on a one-to-one basis. Due to the growth and contraction of this bubble, the liquid (ink)
To form at least one droplet. When this drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the liquid (ink) having particularly excellent responsiveness can be obtained.
It is more preferable that the discharge can be achieved. As the pulse-shaped drive signal, US Pat. No. 4,463,359,
The one described in the specification of US Pat. No. 4,345,262 is 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, more excellent recording can be performed.

As the construction of the print head, in addition to the combination construction of the discharge port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which the heat acting portion is arranged in a bending region. In addition, for multiple electrothermal transducers,
Japanese Unexamined Patent Publication No. 59-123670, which discloses a configuration in which a common slit is used as the discharge portion of the electrothermal converter, and Japanese Laid-Open Patent Publication No. 59-63, which discloses a structure in which an opening for absorbing a pressure wave of thermal energy is associated with the discharge portion. The effects of the present invention are effective even with a configuration based on Japanese Patent Laid-Open No. 138461. That is, according to the present invention, recording can be performed reliably and efficiently regardless of the form of the print head.

Furthermore, the present invention can be effectively applied to a full-line type print head having a length corresponding to the maximum width of a recording medium that can be printed by the printer. Such a print head may have a configuration that satisfies the length by combining a plurality of print heads, or a configuration as a single print head that is integrally formed.

In addition, even in the case of the serial type as in the above example, the print head fixed to the apparatus main body or the electrical connection to the apparatus main body and the ink from the apparatus main body by being attached to the apparatus main body The present invention is also effective when a replaceable chip type print head that can be supplied or a cartridge type print head in which an ink tank is integrally provided in the print head itself is used.

Further, it is preferable to add a discharge recovery means for the print head, a preliminary auxiliary means, etc. as the constitution of the printer of the present invention because the effects of the present invention can be further stabilized. Specifically, heating is performed on the print head using capping means, cleaning means, pressurizing or suction means, an electrothermal converter, another heating element, or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type or number of print heads to be mounted is, for example, 1 for a single color ink.
In addition to those provided with only a plurality of inks, a plurality of inks may be provided corresponding to a plurality of inks having different recording colors and densities. That is, for example, the printing mode of the printer is not limited to a printing mode of only a mainstream color such as black, but may be any of a print head integrally formed or a combination of a plurality of print heads. The present invention is also very effective for an apparatus provided with at least one of the full-color recording modes by color mixture.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet system, it is common to control the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change from the solid state of the ink to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the ink jet printer of the present invention is used as an image output terminal of information processing equipment such as a computer, a copying machine combined with a reader or the like, and a facsimile machine having a transmitting / receiving function. It may be one that takes

[0151]

According to the present invention, since the discharge amount correction control can be performed in response to the dynamic change in the discharge amount (particularly due to the influence of the fluid that behaves in various ways when forming various images),
Even when high-speed printing is performed, there is no density unevenness and it is possible to reliably perform control without density change, enabling high-speed and high-quality image formation.

[Brief description of the drawings]

FIG. 1 is a perspective view of an inkjet printer used in a first example of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a print head used in FIG.

3 is a block diagram showing a configuration example of a control system applicable to the printer of FIG.

4 is a block diagram showing an example of a logical configuration in a head chip of the print head of FIG.

FIG. 5 is a block diagram showing a configuration example of a main part of a control system for realizing dot control in the first example.

FIG. 6 is a flowchart illustrating an example of a heat pattern determination procedure in the first example.

FIG. 7 is a schematic waveform diagram showing a print head drive pulse used in the first example.

8 is a diagram showing the relationship between the pre-pulse width P1 and the ejection amount Vd shown in FIG.

FIG. 9 is a diagram showing a relationship between an interval time P2 and a discharge amount Vd.

FIG. 10 is a diagram showing a relationship between environmental temperature and discharge amount.

11A and 11B are a longitudinal sectional view and a front view showing the structure of the print head used in the first example.

FIG. 12 is a diagram showing a state of discharge amount control applied to the first example.

13A and 13B are explanatory diagrams showing states of voltage drop and discharge amount change in the first example.

FIG. 14 is a perspective view of the inkjet printer used in the second example of the embodiment of the present invention.

15 is a block diagram showing a configuration example of a control system applicable to the printer of FIG.

FIG. 16 is an explanatory diagram of a driving method used in the second example.

FIG. 17 is a diagram for explaining details of the driving method used in the second example.

FIG. 18 is a diagram showing an example of a mask pattern using the print pattern in the second example.

FIG. 19 is a diagram schematically showing the ejection state (meniscus position) at each ejection port of the head.

FIG. 20 is a flowchart showing an example of a discharge amount correction procedure of the second example.

FIG. 21 is a perspective view of an inkjet printer used in a third example of the embodiment of the present invention.

FIG. 22 is a diagram for explaining the print operation in the third example.

FIG. 23 is a diagram for explaining the print operation in the third example.

24A, 24B and 24C are a longitudinal sectional view, a plan view and a front view showing the structure of the print head used in the third example.

FIG. 25 is a diagram showing an example of weighting coefficients of the mask pattern used in the third example.

FIG. 26 is a diagram showing another example of the weighting coefficient of the mask pattern.

FIG. 27 is a diagram showing still another example of the weighting coefficient of the mask pattern.

28 is a diagram illustrating vibration of a meniscus with respect to the mask pattern shown in FIG.

[Explanation of symbols]

 1, IJH print head 2, P print medium 4, 502, HC carriage 100 heater board 200 gate array 220, 800 control unit (controller) 240, 801 CPU 230, 805 RAM 250, 803 ROM

Claims (13)

[Claims] 1. An image forming apparatus for forming an image using a print head having a plurality of ejection ports for ejecting ink from the plurality of ejection ports, wherein the ejection amount of ink for each of the plurality of ejection ports. And a means for determining the presence / absence of ejection of an ejection port related to the formation of pixels around the pixel formed by the ejection port to be corrected, and the pattern of the presence or absence of the determined ejection. A correction unit that generates data for correcting a drive signal applied to eject ink from the ejection port; and a unit that causes the control unit to control the ejection amount based on the correction data. A characteristic image forming apparatus. 2. A plurality of energy generating elements provided for generating energy used for ejecting ink from the plurality of ejection ports are divided into a plurality of blocks and driven by a predetermined number of blocks as one block. The image forming apparatus according to claim 1, wherein the correction unit performs the correction according to the driving state of each of the blocks. 3. The image according to claim 1, wherein the peripheral pixels are formed substantially at the same time and / or before and after the pixel formed by the ejection port to be corrected. Forming equipment. 4. The image according to claim 1, wherein the correction unit performs the correction by weighting information regarding the presence / absence of ejection of an ejection port for forming the surrounding pixels. Forming equipment. 5. The control of the ejection amount is performed by controlling the width of the at least one pulse with respect to a drive signal composed of a plurality of pulses including a combination of a pulse directly related to ink ejection and a pulse other than the pulse. The image forming apparatus according to claim 1, which is performed. 6. The print head includes a plurality of energy generating elements provided to generate energy used for ejecting ink from the plurality of ejection ports,
6. An electrothermal conversion element for generating heat energy that causes film boiling in the ink.
The image forming apparatus according to any one of 1. 7. An image forming method for forming an image by using a print head having a plurality of ejection ports for ejecting ink from the plurality of ejection ports, wherein the ejection amount of the ink for each of the plurality of ejection ports. And determining whether or not there is ejection from the ejection port related to the formation of pixels around the pixel formed by the ejection port to be corrected, and according to the determined ejection presence or absence pattern, An image forming method, wherein data for correcting a drive signal applied to eject ink from an ejection port is generated, and the control unit controls the ejection amount based on the correction data. 8. A plurality of energy generating elements provided to generate energy used for ejecting ink from the plurality of ejection ports are divided into a plurality of blocks and driven by a predetermined number of blocks as one block. The image forming method according to claim 7, wherein the correction is performed according to the driving state of each of the blocks. 9. The correction is performed according to the presence / absence of ejection from an ejection port for forming pixels around a pixel formed by the ejection port to be corrected.
2. The image forming method according to 1., 10. The image according to claim 9, wherein the peripheral pixels are formed substantially at the same time and / or before and after the pixel formed by the ejection port to be corrected. Forming method. 11. The image forming method according to claim 9, wherein the correction is performed by weighting the information regarding the presence / absence of ejection of the ejection port relating to the formation of the surrounding pixels. 12. The control of the ejection amount is performed by controlling a width of the at least one pulse for a drive signal composed of a plurality of pulses including a combination of a pulse directly related to ejection of ink and a pulse other than the pulse. The image forming method according to claim 7, wherein the image forming method is performed. 13. The print head serves as a plurality of energy generating elements provided to generate energy used for ejecting ink from the plurality of ejection ports, and generates heat energy for causing film boiling in the ink. 13. The image forming method according to claim 7, further comprising an electrothermal converting element that generates the image.