JP2002211011A - Ink jet recorder and printer driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that variation in the ejection characteristics due to individual difference of ink jet head must be corrected because the head has variation in the dimensions of channel or the actuator characteristics, and to provide an ink jet recorder producing a high quality image by high ink drop ejection characteristics through a simple arrangement. SOLUTION: The ink jet recorder for forming a combined and enlarged one pixel dot D3 on the surface of a sheet by ejecting a plurality of ink drops I3 from a nozzle 44 comprises means for correcting the size of one pixel dot by correcting the number of a plurality of ink drops being ejected. A plurality of kinds of combined and enlarged one pixel dot having different size can be formed on the surface of a sheet by ejecting a plurality of micro ink drops of substantially the same size from the nozzle and differentiating the number of drops being ejected. Preferably, the volume of the ink drop does not exceed 5p1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus and a printer driver.

[0002]

2. Description of the Related Art An ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, and a plotter includes a nozzle for discharging ink droplets and an ink chamber (ink flow path) communicating with the nozzle. , Discharge chamber, pressure chamber, pressurized liquid chamber, liquid chamber, etc.)
An energy generating means for generating energy for pressurizing the ink in the ink liquid chamber, and an ink jet head for discharging the ink droplets from the nozzles by pressing the ink in the ink liquid chamber by driving the energy generating means, By driving the energy generating means in accordance with the recorded image, the ink in the ink liquid chamber is pressurized and ink droplets are ejected from the nozzles to record the image.

In an ink jet head used in this ink jet recording apparatus, as a means for generating energy for pressurizing ink in an ink liquid chamber, a vibration plate forming a wall surface of the ink liquid chamber is deformed using a piezoelectric element. A so-called piezo-type device that ejects ink droplets by changing the volume of an ink liquid chamber (Japanese Patent Laid-Open No. 2-51)
No. 734), or a so-called bubble type in which an ink droplet is ejected by pressure generated by heating ink in an ink liquid chamber using a heating resistor to generate air bubbles (Japanese Patent Application Laid-Open No. 61-59911). ), The diaphragm and the electrode forming the wall surface of the ink liquid chamber are arranged in parallel, and the diaphragm is deformed by electrostatic force generated between the diaphragm and the electrode, thereby changing the volume of the ink liquid chamber. There is known an electrostatic type in which ink droplets are ejected (see JP-A-6-71882).

In the conventional ink jet recording apparatus, an image is represented by a binary value based on ON / OFF of a dot of a fixed size, and this method does not require much gradation of characters and line drawings. Although there was no particular problem with images, it cannot be applied to images that require gradation such as photographs.

Therefore, in order to enable multi-valued printing (halftone printing), a density modulation method in which the density is changed by having a plurality of inks of the same color having different densities, and minute dots are shot many times at the same position. A dot number modulation method that changes the size of dots formed by changing the size of dots formed by ejecting ink droplets of a plurality of volumes (drop volumes) is adopted. ing.

Among these three methods, the dot diameter modulation method has an advantage that an image having high gradation can be formed without lowering the printing speed. In this case, the ink droplet volume can be changed by increasing or decreasing the drive voltage in the PZT method using a piezoelectric element, and by mounting a plurality of heaters in the valve method using film boiling. However, in these means, in the case of ink jet recording, the capacity of the ejected ink droplet and the nozzle diameter, the configuration of the liquid chamber to be pressurized, the drive pulse waveform, and the like are complicatedly related to each other.
If the optimum combination is not satisfied, there is a possibility that the ejection stability of the ink droplets may be remarkably reduced, so that the ink capacity cannot be changed much.

Therefore, as disclosed in JP-A-59-207265 and JP-A-60-157875, ink droplets generated in response to the first pressure pulse are:
Before separating from the meniscus surface, the second, third,. . . In some cases, a plurality of ink droplets connected to each other are ejected by applying the pressure pulse to make the total amount of the ink droplets variable, thereby enabling gradation control by dots.

Further, the ink jet head used in the ink jet recording apparatus has a variation in the dimensions of the flow path including the ink liquid chamber and the characteristics of the actuator (the characteristics of the energy generating means). Although the ink amount is uniform, it is necessary to correct the ink amount between different heads, and it is necessary to ship the recording device after correcting the driving conditions according to the head.

In view of this, conventionally, Japanese Patent Application Laid-Open No. H11-277737
As described in Japanese Unexamined Patent Application Publication No. H11-133, in order to eliminate fluctuations in ink ejection characteristics due to manufacturing dimensional variations, at the shipping stage, the maximum value of ink ejection amount is obtained.
One that determines a set value of a pulse signal width of a drive voltage is known.

Further, even when the amount of the ejected ink is optimized at room temperature, the amount of the ejected ink varies depending on the operating temperature under the influence of the viscosity of the ink. Therefore, as described in, for example, U.S. Pat. No. 4,352,114, the drive voltage of the actuator is changed in accordance with the operating temperature, the drive voltage is set higher than room temperature in a low temperature range, and the drive voltage is set lower in a high temperature range. Such an ink jet head is known.

In order to cope with the change in the ink droplet ejection characteristics due to the temperature, see Japanese Patent Laid-Open No. 6-182.
As described in Japanese Patent Application Laid-Open No. Hei 8-156248, a method of arbitrarily setting a voltage amplitude of a pulse voltage based on temperature information detected by a temperature detecting unit, as described in Japanese Patent Application Laid-Open No. 8-156248, The adjustment of the maximum applied voltage value for the characteristic correction by environmental temperature and the adjustment of the rise and fall time of the applied voltage can be performed independently.
As described in Japanese Patent Application Laid-Open No. 10-202883, in an electrostatic ink jet head, a head ambient temperature is detected, a pulse width of a driving voltage is adjusted according to the ambient temperature, and a temperature compensation control of ink ejection characteristics is performed. Such is known.

[0012]

However, as described above, since the ink jet head has variations in the dimensions of the flow path and the actuator characteristics, it is necessary to correct the variations in the ejection characteristics due to the head individual differences as described above. At the same time, in order to obtain a more accurate image, it is necessary to correct the driving conditions according to all the nozzles to correct the variation in the ejection characteristics caused by the difference between the nozzles.

When the voltage of the driving waveform applied to the ink jet head is corrected to correct the ejection characteristics between the heads or the nozzles and the ink droplet amount is changed,
The following inconveniences occur. That is, generally speaking, it is considered that the volume change amount of the ink liquid chamber increases and decreases in proportion to the voltage of the driving waveform, and the drop volume of the ink droplet to be ejected also increases and decreases substantially in proportion to the voltage. In fact, it has been confirmed that even if the driving voltage is increased, the droplet volume does not increase in proportion to the voltage, and the voltage must be increased more than necessary to increase the droplet volume of the ink droplet. . On the other hand, it has been confirmed that when the driving voltage is increased, the droplet speed of the ejected ink droplet increases substantially in proportion to the voltage.

That is, it is usually important to always keep the volume of the ejected ink droplets at an appropriate value in order to ensure print quality. Therefore, when the drive voltage is corrected in order to optimize the droplet volume of the ejected ink droplets or to make the droplet volume uniform regardless of the operating temperature, the increase in the droplet volume is small. Even if the speed is greatly increased or the volume of the droplet is slightly reduced, the droplet speed will be greatly reduced. Such an excessive increase in the drop velocity means an increase in the positive and negative ink pressures in the ink liquid chamber, which significantly deteriorates the ejection stability, and a large drop in the drop velocity impedes the straightness of the flying ink drops. become.

As described above, when the droplet volume of the ejected ink droplet is to be corrected by the voltage value of the drive waveform, the drive voltage must be largely corrected for the correction of the small droplet volume. The drop velocity will change greatly. Conversely, after setting the driving conditions of the inkjet head in advance, it is difficult to correct the droplet volume to an appropriate value due to restrictions such as a driving voltage, a droplet speed, and crosstalk.

As for the operating temperature, when the droplet volume is to be kept within a certain range, both the driving voltage and the droplet velocity increase in a low temperature range, and both the driving voltage and the droplet velocity decrease in a high temperature range. If there are restrictions on voltage and crosstalk, a drop volume may not be secured in a low temperature range.

Therefore, as described above, not only the drive voltage of the drive waveform, but also the pulse width, the rise time constant or the fall time constant is controlled alone or in combination, or a complicated pulse waveform is applied to control. However, even with these methods, there are problems that the above-mentioned problems cannot be satisfactorily improved, and that control becomes complicated and cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an ink jet recording apparatus capable of obtaining a high quality image with high ink droplet ejection characteristics with a simple configuration, and controls the driving of the ink jet recording apparatus. It is an object to provide a printer driver for the purpose.

[0019]

In order to solve the above-mentioned problems, an ink jet recording apparatus according to the present invention forms one pixel dot which is connected and enlarged on paper by discharging a plurality of ink droplets from a nozzle. An ink jet recording apparatus comprising a dot diameter correcting means for correcting the number of ejected droplets of a plurality of ink droplets to correct the size of one pixel dot.

Here, by discharging a plurality of minute ink droplets having substantially the same size from the nozzles and varying the number of the discharged droplets, a plurality of types of one-pixel dots having different sizes, which are combined and enlarged on the paper surface, can be formed. Can be formed. In this case, it is preferable that the volume of the ink droplet does not exceed 5 pl.

A plurality of ink droplets having different sizes are ejected from the nozzles, and a plurality of ink droplets having different sizes are combined and enlarged on a paper surface by combining the plurality of ink droplets having different sizes. Can be formed. In this case, it is preferable that the dot diameter correction means corrects the minimum number of ink droplets among a plurality of types of ink droplets of different sizes, and that the volume of the minimum ink droplet does not exceed 5 pl. preferable.

Further, it is preferable that the dot diameter correcting means corrects the number of ejection pulses by correcting the number of driving pulses applied to the ink jet head.

Further, the dot diameter correcting means can correct the number of ejected droplets based on the variation of the ejection characteristics of the ink droplets between the heads. Further, the dot diameter correction means can correct the number of ejected droplets based on the variation in the ejection characteristics of the ink droplets between the nozzles of the inkjet head. Still further, the dot diameter correcting means may correct the number of ejected droplets based on the result of the density adjustment. Further, the dot diameter correction means may correct the number of ejected droplets based on the detection result of the surrounding environment.

Further, it is preferable that an ejection characteristics control unit for controlling the ejection characteristics of the ink droplets is provided together with the dot diameter correction unit. In this case, it is preferable that the dot diameter correction means corrects the number of drive pulses applied to the inkjet head, and the ejection characteristic control means corrects the waveform parameters of the drive pulse.

A nozzle for discharging ink droplets, an ink chamber communicating with the nozzle, a diaphragm forming a wall surface of the ink chamber, and an electrode facing the diaphragm;
It is preferable to mount an electrostatic ink jet head that ejects ink droplets from nozzles by deforming the vibration plate by electrostatic force. Further, the inkjet head for ejecting ink droplets may be configured such that one head is configured by arranging a plurality of head modules.

A printer driver according to the present invention is a printer driver for driving and controlling an ink jet recording apparatus which forms a single pixel dot by discharging a plurality of ink droplets, and corrects the number of the plurality of discharged ink droplets. And / or table information in which the correspondence between the correction values and the head rank is tabulated and / or the correspondence between the correction values and the surrounding environment is tabulated.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of the mechanism.

This ink jet recording apparatus includes a carriage movable in the main scanning direction inside the recording apparatus main body 1, a recording head including an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. The paper feed cassette 4 or the manual feed tray 5 takes in the paper 3, and records the required image by the print mechanism 2, and then the output tray mounted on the rear side. 6 is discharged.

The printing mechanism 2 slides the carriage 13 in the main scanning direction (the direction perpendicular to the paper surface in FIG. 2) by a main guide rod 11 and a sub guide rod 12, which are guide members which are laterally mounted on left and right side plates (not shown). This carriage 1
3 is provided with a head 14 composed of an ink jet head for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet discharge direction facing downward. Above 13, each ink tank (ink cartridge) 15 for supplying each color ink to the head 14 is exchangeably mounted.

The ink cartridge 15 has an upper air port communicating with the atmosphere, a lower supply port for supplying ink to the ink jet head 14, and a porous body filled with ink inside. The ink supplied to the inkjet head 14 by the capillary force of the body is maintained at a slight negative pressure. The ink is supplied from the ink cartridge 15 into the head 14.

Here, the carriage 13 is slidably fitted on the main guide rod 11 on the rear side (downstream side in the paper conveyance direction), and the slave guide rod 1 on the front side (upstream side in the paper conveyance direction).
2 slidably mounted. The main scanning motor 1 is moved to scan the carriage 13 in the main scanning direction.
7, a timing belt 20 is stretched between a driving pulley 18 and a driven pulley 19, which are driven to rotate, and the timing belt 20 is fixed to the carriage 13. When the main scanning motor 17 rotates forward and backward, the carriage 13 is rotated. It is driven back and forth.

Although the recording heads 14 of the respective colors are used here, a single head having nozzles for ejecting ink droplets of the respective colors may be used. Furthermore, head 1
As described later, the electrostatic type 4 includes a diaphragm forming at least a part of a wall surface of an ink liquid chamber and an electrode facing the diaphragm, and deforms and displaces the diaphragm by electrostatic force to pressurize ink. An inkjet head is used.

On the other hand, the paper 3 set in the paper cassette 4
Roller 21 and a friction pad 22 for separating and feeding the paper 3 from the paper feed cassette 4 and a guide member 23 for guiding the paper 3
A transport roller 24 that reverses and transports the fed paper 3, a transport roller 25 that is pressed against the peripheral surface of the transport roller 24, and a tip roller 26 that defines an angle at which the paper 3 is fed from the transport roller 24. Is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.

Further, there is provided a printing receiving member 29 which is a paper guide member for guiding the paper 3 fed from the transport roller 24 below the recording head 14 in accordance with the moving range of the carriage 13 in the main scanning direction. I have. On the downstream side of the printing receiving member 29 in the sheet conveying direction, a conveying roller 31 and a spur 32, which are driven to rotate in order to send out the sheet 3 in the sheet discharging direction.
And a paper discharge roller 33 and a spur 34 for feeding the paper 3 to the paper discharge tray 6 and guide members 35 and 36 for forming a paper discharge path.

At the time of recording, the recording head 14 is driven in accordance with an image signal while moving the carriage 13 so that ink is ejected onto the stopped paper 3 to record one line, and the paper 3 is moved by a predetermined amount. After transport, the next line is recorded. Upon receiving a recording end signal or a signal indicating that the rear end of the sheet 3 has reached the recording area, the recording operation is terminated and the sheet 3 is discharged.

At a position outside the recording area on the right end side of the carriage 13 in the moving direction, a recovery device 37 for recovering from the ejection failure of the head 14 is disposed. Recovery device 3
7 has a cap means, a suction means and a cleaning means. The carriage 13 is moved to the recovery device 37 side during the printing standby, the head 14 is capped by the capping means, and the ejection opening (nozzle hole) is kept in a wet state, thereby preventing ejection failure due to ink drying.
In addition, by ejecting (purging) ink that is not related to printing during printing or the like, the ink viscosity of all the ejection ports is kept constant, and stable ejection performance is maintained.

When a discharge failure occurs, the discharge port (nozzle) of the head 14 is sealed by capping means, bubbles and the like are sucked out of the discharge port by suction means through a tube, and ink adhering to the discharge port surface is sucked. The dust and the like are removed by the cleaning means, and the ejection failure is recovered. The sucked ink is discharged to a waste ink reservoir (not shown) provided at a lower portion of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

Next, an ink jet head constituting the head 14 of the ink jet recording apparatus will be described with reference to FIGS. 3 is an exploded perspective view of the ink-jet head, FIG. 4 is a cross-sectional explanatory view of the head along the diaphragm longitudinal direction, FIG. 5 is an enlarged cross-sectional explanatory view of main parts of the same head along the diaphragm longitudinal direction, and FIG. FIG. 3 is an enlarged sectional view of a main part of the head along the transverse direction of the diaphragm.

The ink jet head 40 includes a flow path substrate 41 which is a first substrate using a silicon substrate such as a single crystal silicon substrate and an SOI substrate, and a silicon substrate provided below the flow path substrate 41, Pyrex ( (Registered trademark) An electrode substrate 42, which is a second substrate using a glass substrate, a ceramic substrate, or the like, and a nozzle plate 43, which is a third substrate provided above the flow path substrate 41, eject a plurality of ink droplets. The nozzle 44, a pressurizing chamber 46 which is an ink liquid chamber to which each nozzle 44 communicates, a common liquid chamber flow path 48 which communicates with each pressurizing chamber 46 via a fluid resistance part 47 also serving as an ink supply path, and the like are formed. ing.

In the flow path substrate 41, a concave portion is formed to form a pressurizing chamber 46 and a diaphragm 50 which also serves as a first electrode serving as a bottom which is a wall surface of the pressurizing chamber 46, and a fluid resistance is formed in the nozzle plate 43. A groove for forming the portion 47 is formed, a penetrating portion for forming a common liquid chamber flow channel 48 is formed in the flow channel substrate 41, and an ink supply port 4 for introducing ink into the common liquid chamber flow channel 48 is formed in the electrode substrate 42.
9 are formed.

Here, for example, when a single crystal silicon substrate is used as the flow path substrate 41, boron is injected in advance to the diaphragm thickness to form a high-concentration boron layer serving as an etching stop layer. After bonding, the concave portion serving as the pressurizing chamber 46 is anisotropically etched using an etching solution such as a KOH aqueous solution, whereby the high-concentration boron layer serves as an etching stop layer and the diaphragm 50 is formed with high precision. Is done. When an SOI substrate in which an active layer substrate is bonded to a base substrate via an oxide layer is used, the diaphragm 50 is formed using the active layer substrate.

Although an electrode film may be separately formed on the diaphragm 50, the diaphragm also serves as an electrode by diffusion of impurities as described above. Further, the diaphragm 50
An insulating film can be formed on the surface on the electrode substrate 42 side. As this insulating film, an oxide-based insulating film such as SiO ₂
A nitride insulating film such as i ₃ N ₄ can be used.
For the formation of the insulating film, the surface of the diaphragm can be thermally oxidized to form an oxide film, or a film forming technique can be used. Further, the flow path substrate 1 is provided with a common electrode. The common electrode is provided by sputtering a metal such as Al and performing sintering (thermal diffusion) to ensure conduction with the flow path substrate 1 and to form an ohmic contact with the flow path substrate 1 made of a semiconductor substrate. Is taking.

Further, a single crystal silicon substrate is used as the electrode substrate 42, and the oxide film layer 4 is formed on the silicon substrate by a thermal oxidation method or the like.
2a, an electrode forming groove 54 is formed in the portion of the oxide film layer 42a, and an electrode 15 which is a second electrode facing the diaphragm 50 is provided on the bottom surface of the electrode forming groove 54. A predetermined gap 56 (having a gap of 0.2 μm) is formed between the vibration plate 5 and the electrode 55.
0 and the electrode 55 constitute an actuator unit. Note that an electrode protection film 57 made of an oxide insulating film such as a SiO ₂ film and a nitride insulating film such as a Si ₃ N ₄ film is formed on the surface of the electrode 55.

The bonding between the flow path substrate 41 and the electrode substrate 42 can be performed by an adhesive, but a more reliable physical bonding, for example, when the electrode substrate 42 is formed of silicon, A direct bonding method via an oxide film can be used. This direct bonding is performed at a high temperature of about 1000 ° C. When the electrode substrate 42 is made of glass, anodic bonding can be performed. When the electrode substrate 42 is formed of silicon and anodic bonding is performed, Pyrex glass may be formed between the electrode substrate 42 and the flow path substrate 41, and anodic bonding may be performed via this film. Furthermore, the flow path substrate 41 and the electrode substrate 42 can be bonded by eutectic bonding in which a binder such as gold is interposed between bonding surfaces using a silicon substrate.

The electrodes 55 of the electrode substrate 42 include:
A commonly used in the process of forming a semiconductor element
Metal materials such as l, Cr, and Ni, high melting point metals such as Ti, TiN, and W, and polycrystalline silicon materials whose resistance has been reduced by impurities can be used. When the electrode substrate 42 is formed of a silicon wafer, it is necessary to form an insulating layer (the above-described oxide film layer 42a) between the electrode substrate 42 and the electrode 55. When an insulating material such as glass is used for the electrode substrate 42, there is no need to form an insulating layer between the electrode 55 and the electrode 55.

When a silicon substrate is used as the electrode substrate 42, an impurity diffusion region can be used as the electrode 55. In this case, an impurity used for diffusion is an impurity having a conductivity type opposite to the conductivity type of the substrate silicon, a pn junction is formed around the diffusion region, and the electrode 55 and the electrode substrate 42 are formed.
Are electrically insulated from each other.

The nozzle plate 43 is formed by arranging a large number of nozzles 44 in two rows, and has a discharge surface subjected to a water-repellent treatment. Here, the nozzle plate 43 is manufactured by the Ni electroforming method, but a nozzle having a multilayer structure of a resin and a metal layer can also be used. This nozzle plate 43
Are bonded to the flow path substrate 41 with an adhesive.

The adhesive bonding between the flow path substrate 41 and the nozzle plate 43 will be described. First, an adhesive is applied to the upper surface of the flow path substrate 41. In this case, since the protrusion of the adhesive affects the ejection characteristics, the applied film thickness of the adhesive needs to be about 1 μm. In order to apply the adhesive to the thin film as described above, it is preferable to apply the adhesive by a transfer method. In this transfer method, for example, the adhesive is thinned to a roller with a doctor blade, and the adhesive is transferred from the roller to a transfer pad.
Further, the adhesive is transferred from the transfer pad to the upper surface of the flow path substrate 1.

Next, in order to determine the nozzle plate 43 and the flow path substrate 41, an ultraviolet-curing adhesive or a flash adhesive for temporary bonding is applied to the corners of the flow path substrate 41,
And the flow path substrate 41 to which the adhesive has been applied is aligned, and temporary pressurization is performed. Here, in the case of an ultraviolet curable adhesive,
After the adhesive is cured by irradiating ultraviolet rays, the pressure is applied and the adhesive is cured by heating. When performing the heat bonding, the flow path substrate 4
If 1 (actuator) is long, the head is warped due to a difference in linear expansion coefficient between silicon forming the flow path substrate 41 and Ni or SUS forming the nozzle plate 43, and the actuator is destroyed by internal stress. Because
It is better that the curing temperature of the adhesive is low. As the adhesive for joining the flow path substrate 41 and the nozzle plate 43, a two-component mixed type (room temperature curing type) epoxy adhesive is preferable. The lower the better, the better, the temperature is preferably 40C to 100C.

In the ink jet head 40, the nozzles 44 are arranged in two rows, and the pressurizing chamber 46, the vibration plate 50, the electrodes 55, etc. are arranged in two rows corresponding to the nozzles 44, respectively. A configuration in which a liquid chamber flow path 48 is arranged to supply ink to the left and right pressurizing chambers 46 is adopted. This makes it possible to configure a multi-nozzle head having a large number of nozzles with a simple head configuration.

The electrode 55 of the ink-jet head 40 is extended outside to form a connection portion (electrode pad portion) 55a, on which an FPC cable 61 on which a driver IC 60 as a head drive circuit is mounted is connected to an anisotropic conductive film or the like. Connected through. At this time, the electrode substrate 42 and the nozzle plate 43
As shown in FIG. 4, airtight sealing is performed with a gap sealing agent 62 using an adhesive such as an epoxy resin.

Further, the entire ink jet head 40 is joined on the frame member 65 with an adhesive. The frame member 65 has an ink supply hole 66 for supplying ink from outside to the common liquid chamber flow path 48 of the inkjet head 40, and the FPC cable 61 and the like have holes 67 formed in the frame member 65. Is stored in.

The gap between the frame member 65 and the nozzle plate 43 is sealed with a gap sealing agent 68 using an adhesive such as an epoxy resin as shown in FIG. The ink is applied to the electrode substrate 42 and the FPC cable 6
It is prevented from going around to 1st mag.

The frame member 6 of the head 14
5 includes a joint member 70 with the ink cartridge 15.
Are connected to the common liquid chamber flow path 48 through the ink supply hole 66 from the ink cartridge 15 via the filter 71.
Is supplied with ink.

In the ink-jet head 40, the diaphragm 50 is used as a common electrode, the electrode 55 is used as an individual electrode, and a driving voltage is applied between the diaphragm 50 and the electrode 55, so that the diaphragm 50 and the electrode 55 are connected to each other. The diaphragm 50 is deformed and displaced toward the electrode 55 due to the electrostatic force generated during the period, and the electric charge between the diaphragm 50 and the electrode 55 is discharged from this state. By changing the internal volume (volume) / pressure of
Ink droplets are ejected from the nozzles 44.

That is, when a pulse voltage is applied to the electrode 55 serving as an individual electrode, a potential difference occurs between the diaphragm 50 serving as a common electrode and an electrostatic force is generated between the individual electrode 55 and the diaphragm 50. As a result, the diaphragm 50 is displaced according to the magnitude of the applied voltage. After that, the applied pulse voltage falls, whereby the displacement of the diaphragm 50 is restored, and the restoring force increases the pressure in the pressurizing chamber 46, thereby ejecting ink droplets from the nozzles 44. In this case, the diaphragm 50
The method of displacing the diaphragm 50 until it comes into contact with the electrode 55 (actually, the surface of the insulating protective film 57) is called a contact driving method, and the method of displacing the diaphragm 50 to a position where it does not contact the electrode 55 is called a non-contact driving method.

Next, an outline of a control section of the ink jet recording apparatus will be described with reference to FIG. This control unit is a microcomputer (hereinafter referred to as “C”) that controls the entire recording apparatus also serving as a dot diameter correction unit according to the present invention.
PU ”. ) 80, a ROM 81 storing necessary fixed information such as a program, a table of a head rank and a pulse number correction value of a drive pulse, various tables such as a table of an ambient temperature and a pulse number correction value of a drive pulse, and a working memory. , A RAM 82 for storing data obtained by processing image data transferred from the host, a parallel input / output (PIO) port 84, an input buffer 85, and a parallel input / output (PI
O) Ports 86 and 87, a waveform generation circuit 88, a head drive circuit (driver IC) 89, a driver 90, and the like.

Here, the host HS is connected to the PIO port 84.
Various information such as image data is input from the printer driver PD side via a cable or a network, and various instruction information such as reliability recovery instruction information from an operation panel (not shown), a sheet for detecting the start and end of the sheet. A detection signal from the presence / absence sensor, a signal from various sensors such as a home position sensor for detecting the home position (reference position) of the carriage 13 and the like are input.
Necessary information is transmitted to the host HS and the operation panel via the IO port 84.

The waveform generating circuit 88 generates a pulse-like drive waveform (drive pulse) applied between the diaphragm 50 and the electrode 55 of the ink jet head 40 based on drive waveform data supplied from the CPU 80 via the PIO port 87. ) Is generated and output. Head drive circuit (driver I
C) 89, each of the nozzles 44 of the head 14 based on various data and signals given through the PIO port 87.
Energy generating means (diaphragm 50 and electrode 5
A drive pulse is applied to 5).

Further, the driver 90 is connected to the PIO port 8
By controlling the driving of the main scanning motor 17 and the sub-scanning motor 27 according to the driving data given via the
The carriage 13 is moved and scanned in the main scanning direction, and the transport roller 24 is rotated to transport the sheet 3 by a predetermined amount.

The control section has a head rank detection circuit 92 connected to rank identification means 91 provided on the head 14 (inkjet head 40) to detect the head rank of the inkjet head 40. The rank identification means 91 is formed on the surface of the substrate of the inkjet head 40, and based on the actual ink droplet ejection characteristics of the inkjet head 40 measured at the time of shipment of the inkjet head 40, the optimal pulse number initial value Pwn of the driving pulse. Is a means for setting.

The head rank identification means 91 has, for example, a 4-bit resistor connection pattern, and the resistance value changes depending on whether each pattern is cut (open) or not (close / short). Therefore, the rank detection circuit 92 is connected to the resistance connection pattern of the head rank identification means 92, and the resistance of the head rank identification means 92 is detected to detect the head rank of the mounted inkjet head 40.

The control unit has a temperature detecting circuit 94 for detecting an ambient temperature, which is one of the ambient environments, based on a detection signal of a temperature sensor 93 provided on the head 14 (inkjet head 40). . As the temperature sensor 93, a thermistor as a temperature detecting element provided on the surface of the substrate of the ink jet head 40 is used. Then, the temperature detection circuit 94 detects a change in the resistance value of the temperature sensor 93, performs A / D conversion with an internal A / D converter, and performs P / O conversion on the PIO port 87.
To the CPU 80 via

Next, details of the head drive control section in this control section will be described with reference to FIG. This head drive control unit includes the CPU 80, ROM 81, RA
M82 and a main control unit 101 including peripheral circuits, a waveform generation circuit 88, an amplifier 102, and a drive circuit (driver I
C) 103, rank detection circuit 92, temperature detection circuit 94
And the like.

The main control unit 101 supplies data for generating a drive pulse Pv to the waveform generation circuit 88, and print signal (serial data) SD, shift clock CLK, and latch signal LAT to the driver IC 103.
Give etc. The waveform generation circuit 88 includes a D / A converter and the like, and generates and outputs a drive pulse Pv in time series by performing D / A conversion of voltage value data provided from the main control unit 101.

The driver IC 103 selects a drive pulse Pv given from the waveform generation circuit 88 in accordance with the print signal and gives it to each individual electrode 55 of the ink jet head 40 constituting the head 14.

That is, the driver IC 103 is provided with the shift register 10 for inputting the serial clock CLK from the main control unit 101 and the serial data SD as a print signal.
5 and the register value of the shift register 105
Latch circuit 1 that latches with latch signal LAT from 01
06, a level conversion circuit 107 that changes the level of the output value of the latch circuit 106, and an analog switch array 108 whose on / off is controlled by the level conversion circuit 107. The analog switch array 108 includes analog switches AS1 to AS connected to m individual electrodes 55 of the inkjet head 40 (the number of nozzles is m).
m. The diaphragm 50 serving as a common electrode of the inkjet head 40 is grounded.

Then, serial data (print signal) SD is fetched into the shift register 105 according to the shift clock, and the latch circuit 106 latches the serial data SD fetched into the shift register circuit 105 by the latch signal LAT, and the level conversion circuit Input to 107. The level conversion circuit 107 turns on / off the analog switch ASn (n = 1 to m) connected to the individual electrode 55 of each actuator according to the content of the data.

This analog switch ASn (m = 1 to
m), the drive pulse Pv is given from the waveform generation circuit 88 via the amplifier 102, so that the analog switch AS
When n (m = 1 to m) is turned on, the drive pulse Pv is applied to the corresponding individual electrode 55.

Next, the operation of the ink jet recording apparatus thus configured will be described with reference to FIGS. First, the ink droplet ejection characteristics (ejection droplet speed Vj and ejection droplet volume M
The dependence of the drive waveform (drive pulse) of j) on the pulse width PW will be described with reference to FIG.

When a pulse voltage is applied to the electrode 55 of the ink jet head 40 and the diaphragm 50 is attracted, a negative pressure is generated in the pressurizing chamber 46. Since the pressure oscillates at the natural frequency of the pressurizing chamber 46, the pressure at the time of falling of the pulse is a combination of the residual pressure vibration at the time of rising of the pulse and the restoring pressure.

Therefore, in the electrostatic type ink jet head 40, a difference occurs in the ink droplet ejection characteristics depending on the pulse width PW of the applied pulse voltage. That is, for example, as shown in FIG. 9, the ejection characteristics (ejection droplet speed Vj, ejection droplet mass Mj) vary depending on the timing of superposition of the pressures based on the pulse width PW, so that the pulse width PW of the drive pulse Pv varies. By doing so, the droplet ejection characteristics (ejection droplet speed Vj, ejection droplet mass Mj) can be changed.

If the pulse falling time of the drive pulse Pv is lengthened (the falling time constant is lengthened), the vibration plate 5
Since the recovery of the displacement of 0 becomes slower and the droplet volume Mj and the droplet speed Vj change, the droplet discharge characteristics can be changed also by this.

Next, the formation of one pixel dot by a plurality of droplets in the head drive control unit of the ink jet recording apparatus will be described with reference to FIGS. As shown in FIG. 10A, the head drive control unit controls the main drive unit 101 and the waveform generation circuit 88 within one drive cycle.
It repeatedly generates and outputs, for example, 17 drive pulses Pv. The 17 drive pulses Pv output from the waveform generation circuit 88 for each drive cycle are supplied to the analog switches AS1 to ASm of the driver IC 103 via the amplifier 102. Has been given to.

Here, the print signal SD is sent from the main control unit 101.
, The analog switch ASn (n) of the driver IC 103 as shown in FIG.
= 1 to m) is turned on or off, and the analog switch ASn
Is selected while the drive pulse Pv is being supplied to the individual electrode 55n of the inkjet head 40 corresponding to the switch ASn, as shown in FIG.

FIG. 9C shows an example of different numbers of pulses applied to the individual electrodes 55 corresponding to one nozzle. In the driving cycle (T1 to T2), one analog switch ASn is provided. Since it is in the ON state for the duration of the pulse, one drive pulse Pv is applied to the head 40,
In the driving cycle (T2 to T3), since the analog switch ASn is in the ON state for the time of three pulses, three driving pulses Pv are applied to the head 40, and the driving cycle (T
In 3 to T4), since the analog switch ASn is in the ON state for a time corresponding to seven pulses, the seven drive pulses P
v is applied to the head 40, and in the drive cycle (T4 to T5), the analog switch ASn is in the ON state for a time corresponding to 14 pulses. Therefore, 14 drive pulses Pv are applied to the head 40, and the drive cycle ( In T5 to T6), the driving pulse Pv is not applied to the head because printing is not performed.

Thus, for example, as shown in FIG. 11A, when one drive pulse Pv is given, one ink droplet (this is the minimum ink droplet) is ejected, and this ink droplet I1 is left as it is. Land on the paper 3 to form one pixel dot D1 by one drop. When three drive pulses Pv are given as shown in FIG. 3B, three ink droplets I1 are sequentially ejected and united during flight to form one ink droplet I3 on the paper 3. And landed on 3 drops 1
Pixel dots D3 (D3> D1) are formed.

Similarly, when seven drive pulses Pv are given as shown in FIG. 9C, seven ink droplets I1 are sequentially discharged and united during flight to form one ink droplet I7. And landed on the paper 3 to make one pixel dot D7
(D7> D3) is formed. When 14 drive pulses Pv are given as shown in FIG. 3D, 14 ink drops I1 are sequentially ejected and united during flight to form one ink drop D14 on the paper 3. And one pixel dot D14 (D14> D7) is formed by 14 drops.

As described above, in this ink jet recording apparatus, a plurality of minute ink droplets I1 having substantially the same size are ejected from the nozzles, and the number of the ejected ink droplets is made different, so that the ink droplets are combined and expanded on the paper surface. A plurality of types of one pixel dots having different sizes can be formed. In this case, each minute ink droplet can be ejected separately, or each minute ink droplet can be ejected continuously. In this case, the ink droplets are united into one ink droplet during flight, and Although they land on the paper, they can land on the paper surface and be joined almost simultaneously.

That is, by forming one pixel dots of different sizes, it is possible to express an image of intermediate gradation, and it is easy to form pixel dots of different sizes by changing the number of ink droplets to be ejected. Can be. in this case,
Usually, the smallest dot is often formed by a single ejection droplet.

The number of ink droplets to be ejected can be made different by changing the number of drive pulses applied as a drive waveform. When a minute ink droplet is ejected from the nozzle of the head in response to a plurality of pulses, the minute droplet group merges during flight before reaching the surface of the paper to form one pixel dot, or on the paper. Since one pixel dot is formed by combining and enlarging, a pixel dot having a different size is printed as a pixel dot to be printed on a sheet.

Here, the droplet volume of a single minute ink droplet is set to about 2 pl. In this example, when forming an image at 600 dpi, the ink droplet ejection amount required for filling an image with a solid is 28 pl. Therefore, one pixel dot is typically formed by overlapping 14 drops. When a multi-valued gradation image is used, the number of drops to be overlapped is, for example, 14 drops / 7 drops / 3 drops / 1, as described above.
The amount of ink per pixel dot at that time is 28 pl / 14 pl /
6 pl / 2 pl.

Next, a description will be given of the correction of variations among the ink jet heads 40 in the ink jet recording apparatus. As described above, the inkjet head 40 (head 14) is provided with the rank identification means 91, and the rank detection circuit 92 detects the rank of the mounted head 14.

For example, here, as shown in FIG.
The head rank is classified into eight stages of ranks A to H, and 600
The correspondence between the standard ink droplet amount necessary for forming an image at dpi and the optimum pulse number initial value Pwn of the driving pulse Pv is set. This correspondence is tabulated and stored in the ROM 81 in advance. FIG. 13 shows an example of the ejection droplet volume Mj with respect to the initial pulse number Pwn of the drive pulse Pv in the inkjet heads of head ranks B, D, and F. In this example, based on the head rank D, when 14 drive pulses Pv are applied, that is, when 14 minimum ink droplets are combined, an ink droplet volume of 28 pl is obtained.

Therefore, the ink droplet ejection characteristics are actually measured at the time of shipment of the ink-jet head, the head rank of the ink-jet head is determined based on the result, and the initial pulse number of the driving pulse Pv required to obtain a certain characteristic is obtained. Initialize the value Pwn. At this time, the disconnection processing is performed so that the resistance connection pattern (4 bits in this configuration) of the head rank identification means 91 corresponds to the determined rank.

Thus, the head drive control section corrects the initial pulse number Pwn of the drive pulse Pv according to the head rank of the ink jet head 40 mounted in the rank detection circuit 92. That is, the rank detection circuit 9
Based on the detection result of the head rank of the inkjet head 40 from No. 2, the initial pulse number Pwn of the drive pulse Pv corresponding to the determined head rank stored in the ROM 81 in advance is developed in the RAM 82, and With the initial pulse number Pwn of the developed drive pulse Pv as an initial value, the on-time of the analog switch ASn is controlled as described above to control the pulse number Pn of the drive pulse Pv to be applied.

For example, when the ink jet head 40 of the head rank D is mounted, the initial value Pwn (= 14) of the number of drive pulses Pv for obtaining a standard ink droplet volume of 28 pl is set to the ink jet head 40 as an initial value. The pulse number Pn of the drive pulse Pv to be applied is determined, and the ink droplet corresponding to the pulse number Pn is ejected.
In this case, when performing multi-value recording, the number of pulses is increased or decreased with respect to the pulse number Pn set as the initial value.

On the other hand, for example, when an ink jet head of head rank B is mounted, the pulse number Pn of the drive pulse Pv for obtaining a standard ink droplet volume of 28 pl is changed to the initial pulse number of the drive pulse Pv of rank B. Pwn (= 12), and the pulse number initial value P
The pulse number Pn of the drive pulse Pv applied to the inkjet head 40 is determined with wn (= 12) as an initial value, and ink droplets corresponding to the pulse number Pn are ejected. Also in this case, when performing multi-value recording, the number of pulses is increased or decreased with respect to the pulse number Pn set as the initial value.

Similarly, when an ink jet head having a head rank F is mounted, the pulse number Pn of the drive pulse Pv for obtaining a standard ink droplet volume of 28 pl is changed to the pulse number initial value Pwn (= Pwn of the drive pulse Pv of the rank F). 1
7), and the pulse number initial value Pwn (= 17)
Is determined as an initial value, and the number of pulses Pn of the drive pulse Pv applied to the inkjet head 40 is determined, and ink droplets corresponding to the number of pulses Pn are ejected. Also in this case, when performing multi-value recording, the number of pulses is increased or decreased with respect to the pulse number Pn set as the initial value.

That is, in the present embodiment, the dot diameter correction means corrects the number of ejected droplets by correcting the reference pulse number itself based on the variation in the ejection characteristics of ink droplets between the heads. Of course, for example, data of the number of correction pulses is provided for each of the head ranks A to H, and the initial value of the number of pulses for the inkjet head is determined by adding or subtracting the number of correction pulses to or from the reference number of pulses. You can also

As described above, by providing the means for correcting the size of one pixel dot by correcting the number of ink droplets to be ejected in accordance with the variation of the ink droplet ejection characteristics between the heads, Discharge characteristics can be corrected with a simple configuration, and variations due to individual differences between heads are reduced, so that high-quality images can be formed.

Here, a plurality of different micro ink droplets having substantially the same size are overlapped with each other, that is, a plurality of droplets are combined during flight and combined, or combined on the paper surface.
By forming a plurality of types of pixel dots having different sizes by forming pixel dots, the same pulse shape as the drive waveform (drive pulse) can be used, and the configuration of the head drive control unit is simplified, Correction control of the number of drops can be performed with a simple configuration.

Further, the number of ejected droplets can be corrected with a simple structure by performing the correction control of the number of ejected droplets by the number of drive pulses.

Next, a description will be given of the correction of the variation in the ejection characteristics due to the fluctuation of the surrounding environment. As described above, the detection signal of the temperature sensor 93 provided in the inkjet head 40 is input to the temperature detection circuit 94, and a change in the ambient temperature around the inkjet head 40 can be detected as a change in the resistance value of the temperature sensor 93 using a thermistor. . The change in the resistance value detected by the temperature detection circuit 94 is A / D-converted by the temperature detection circuit 94 and then supplied to the CPU 80 via the PIO port 87.

The main control unit 101 detects (determines) the ambient temperature of the ink jet head 40 by sampling the detection signal from the temperature detection circuit 94 at a sampling cycle of, for example, about 2 seconds, and drives based on the detected temperature. The pulse number initial value Pwn of the pulse Pv is corrected. in this case,
By changing the initial number of pulses during the printing process and not changing the initial value of the number of pulses at the time of printing the next process after the end of the printing pass, it is possible to prevent the image quality from deteriorating due to pixel disturbance.

That is, as shown in FIG. 13, for example, if the pulse number initial value Pwn of the same drive pulse Pv, the droplet volume of the ink droplet ejected from the ink jet head varies due to a change in the ambient temperature. In this example (the head of the head rank D described above), when the initial pulse number Pwn of the drive pulse Pv is 14, a standard drop volume of 28 pl is obtained at an ambient temperature of 22 ° C.
At 2 ° C., the drop volume will be 32 pl, while at 7 ° C. the drop volume will be 24 pl.

Therefore, in order to obtain a constant droplet volume, the pulse number initial value Pwn may be changed according to the ambient temperature. For example, in the case of the head having the above-mentioned head rank D, when the ambient temperature is 22 ° C., 14 pulse number initial values Pwn, 32
12 ° pulse number initial value Pwn at 0 ° C., 1 at 7 ° C.
By setting the initial number of pulses Pwn to eight, the droplet volume becomes 2
It becomes 8 pl constant.

Therefore, in the ROM 81, a correspondence table in which the correspondence between the ambient temperature of the ink jet head and the initial pulse number Pwn of the drive pulse Pv is stored in advance.

As a result, the CPU 8 of the head drive control section
0 indicates that the pulse number initial value Pwn corresponding to the detected temperature is retrieved and output from the correspondence table and developed in the RAM 82, and the developed pulse number initial value Pwn is used as an initial value to determine the pulse number Pn of the drive pulse Pv. By ejecting the required number of ink droplets, the size of the pixel dot is corrected.

In this case, when the pulse number initial value is frequently changed near the switching temperature when correcting the pulse number initial value with respect to the temperature change, the print density becomes conspicuous, so that the hysteresis characteristic is provided at the time of correction. It is also possible to obtain better printing results. It is also possible to perform an interpolation operation from the correction table to perform a smooth gradation correction.
Printing results with higher printing quality can be obtained.

As described above, by correcting the number of driving pulses of the ink jet head based on the ambient temperature of the ink jet head to correct the size of the pixel dot, the fluctuation of the ink ejection characteristics due to the temperature change is compensated. As a result, stable ink ejection characteristics can always be obtained,
This improves image quality.

Of course, for example, data of the number of correction pulses is provided for each ambient temperature, and the number of correction pulses is added to or subtracted from the reference number of pulses, and the initial value of the number of pulses for the ink jet head is set. It can also be decided.

Next, a description will be given of the correction of the variation of the ejection characteristics due to the variation of the ejection characteristics between the heads and the fluctuation of the ambient temperature. In this case, for example, the pulse number initial value Pw for each ambient temperature for each head rank A to H described above
For example, as shown in FIG. 16, n is determined and tabulated, and eight types of temperature compensation correspondence tables (ambient temperature and pulse number initial value Pwn) corresponding to the head ranks A to H are set.
Is stored in the ROM 81. Then, a pulse number initial value Pwn corresponding to the detected head rank and the ambient temperature is read and developed in the RAM 82, and the pulse number Pn of the driving pulse Pv is determined using the pulse number initial value Pwn as an initial value to determine the required droplet number. Discharge ink droplets.

As described above, by providing a correspondence table for temperature compensation of the initial pulse number Pwn of the driving pulse with respect to the head rank and the ambient temperature for each head rank, the discharge between heads and the fluctuation of the operating temperature can be achieved with a simple configuration. Variations in characteristics can be reduced.

FIG. 17 shows the basic characteristics of the ejection speed among the ink droplet ejection characteristics.
Here, the ejection droplet speed with respect to the pulse number initial value Pwn of the driving pulse in the case of the head ranks B, D, and F shown in FIG. 13 is shown. As can be seen from this figure, even if the initial pulse number Pwn of the drive pulse is corrected, the ejection droplet speed does not change significantly. In the ink jet head of this embodiment, the set value of the discharge droplet speed is set to 7 ± 1.5 m /
s. Therefore, if the ink jet head has a head rank of B to F, the discharge droplet speed can be used as it is.

However, in the case of the head rank A, the speed is higher, and in the case of the head ranks G and H, the speed is lower. Therefore, it is preferable to correct the ejection droplet speed.
In order to correct such a droplet speed, the voltage value of the drive pulse (drive voltage), pulse width, pulse rise time constant or pulse fall time constant (however, in the case of the electrostatic type, the pulse rise time The change of the constant does not affect the droplet ejection speed.

That is, for example, when correction is performed using the voltage value of the drive pulse, when the drive voltage of the drive pulse is increased,
The ink droplet ejection amount does not increase in proportion to the voltage, and the ejection ink droplet speed increases substantially in proportion to the voltage. Therefore, the increase in the ink droplet ejection amount is small and the speed is greatly increased. The speed can be greatly reduced by only slightly reducing the ink droplet ejection amount.)

Accordingly, the correction of the ink droplet ejection amount is mainly performed by the number of pulses having a large effect of correcting the ink droplet ejection amount (drop volume), and the pulse waveform (driving voltage) having a large ink droplet speed correction effect is used. Is a very effective means. In other words, the present invention is implemented by using both the means for correcting the number of ink droplets to be ejected and the special characteristic control means for controlling the ejection speed of each droplet.

In the above-described head drive control section, the ejection characteristic control means generates a drive pulse by performing D / A conversion of the drive pulse data using a D / A converter (waveform generation circuit 88). Therefore, in order to change the waveform parameter of the drive pulse, a plurality of types of drive pulse data of necessary waveform parameters are stored in the ROM 81 in advance, and the necessary drive pulse data is read out and given to the waveform generation circuit 88. By doing so, the parameters of the pulse waveform of the drive pulse can be changed and controlled with a simple configuration.

In the above embodiment, the case of the largest pixel dot among the different pixel dots used for expressing the image of the intermediate gradation has been described. However, the same can be applied to other pixel dots. In addition, as for the minimum dot, the dot diameter itself is often not visually recognizable, and is often used in a highlight portion of an image. Therefore, even if correction for this is not performed, there may be no practical problem. .

Further, the volume of one ejected droplet for correcting the number of droplets is preferably 5 pl or less, which is an appropriate value for suitably performing the correction control. That is, although it depends on the required pixel dot diameter, usually, 300 dpi which is frequently used for printing is used.
For a 360 dpi image, the amount of drops forming dots is ± 5
Not exceeding pl is an allowable value. In this embodiment,
The permissible value is ± 3 pl for the pixel dots of the 600 dpi image. In the present invention, since correction control is performed based on the number of drops,
Basically, digital correction is performed in accordance with the volume of one discharged droplet, and the resolution of correction is the volume of one discharged droplet. Therefore, it is preferable that the volume of one discharged droplet does not exceed 5 pl.

In other words, to have a resolution of 1/10 or less of the volume of a discharged droplet for forming a required pixel dot, that is, to form a pixel dot requiring a volume of one discharged droplet. Is preferably 1/10 or less of the volume of the ejected droplet. This is a method of forming a plurality of types of dot diameters by superimposing a single minute ink discharge droplet, or a plurality of types of dots by combining a plurality of different size droplets or a plurality of different size droplets. It is possible to adapt to the minimum ejection volume of the ejection droplet in the formation method. Also in the case of a method in which a plurality of types of pixel dots are formed by combining a plurality of droplets of different sizes, it is preferable to control the modulation of the minimum number of discharged droplets in consideration of the resolution of correction.

Here, in order to eject a plurality of ejection droplets of different sizes by applying different pulse waveforms and to form one pixel dots of different sizes by this combination, as shown in FIG. Since the ejection droplet volume Mj changes by changing the pulse width PW of the pulse, drive pulses Pv having a plurality of pulse widths PW are generated. For example, data of drive pulses of each pulse width is stored in the ROM 81 in advance, This is read out and D / A-converted by the waveform generation circuit 88 to generate and output a drive pulse having a plurality of pulse widths within one drive cycle. What should be done is to select.

Further, as for the recording apparatus, there is a case where the discharge characteristics of the ink jet head change with the elapse of a long period of time. Further, depending on the user's preference, the density may be changed from the set printing state. Also in this case, the density of the printing quality of the ink recording apparatus can be adjusted by using the correcting means of the present invention. This can be easily implemented by changing the condition setting of the printing apparatus driver from the host computer connected to the printing apparatus, installing an external switch that can normally operate the recording apparatus main body, or installing an internal switch corresponding to a maintenance service person.

Further, the printer driver P of the host HS
D stores a correspondence table between the correction values such as the pulse number initial value described above and the head rank, and a correspondence table between the correction values such as the pulse number initial value and the surrounding environment, and stores necessary table information on the inkjet recording apparatus side. Transfer to RAM
It can also be used by storing it in such as. The printer driver PD may be stored in a storage medium such as an FDD, or may be downloaded to a host via a network.

In general, the manufacturing accuracy of a large number of nozzles varies to some extent. Therefore, even if a drive pulse having the same waveform is applied, the size of the ink droplets to be ejected does not always become the same, and the inter-nozzle sizes are not always the same. , There is a variation in the discharge characteristics. To correct this variation, it is necessary to perform correction control according to the ejection characteristics of each nozzle. Usually, the variation in the ejection characteristics between the nozzles in the head is smaller than the variation in the ejection characteristics between the heads. However, when high-precision printing quality is required, correction between nozzles may need to be corrected. Also in this case, performing the correction control according to the present invention makes it possible to relatively easily correct the variation relatively easily without changing the drive circuit or the like simply by storing the correction information in the ROM in advance.

Further, the present invention can be applied to an ink jet recording apparatus equipped with a piezo type ink jet head or a bubble type ink jet head other than the electrostatic type ink jet head, but is particularly effective when the electrostatic type ink jet head is mounted. It is a target.

That is, in the electrostatic ink jet head, manufacturing variations in the main dimensions such as the thickness and width of the diaphragm, which affect the behavior until the diaphragm comes into contact with the counter electrode, are always allowed. When adjusting and correcting the peak value of the drive voltage to secure stable ink ejection characteristics and maintain print quality above a certain level, when the diaphragm is deformed by electrostatic force and comes into contact with the counter electrode side, Since the displacement of the plate is restricted by the counter electrode and cannot be displaced beyond a certain limit, and the compliance of the ink liquid chamber becomes small, when the value of the driving voltage is changed, the compliance changes and the natural vibration of the ink liquid chamber is changed. The number also changes, making it difficult to control for maintaining stable ink ejection characteristics. In addition, since there is an upper limit to the volume fluctuation of the ink liquid chamber, a sufficient compensation effect cannot be expected by a control method in which the voltage value of the driving voltage is changed to compensate for the fluctuation of the ink ejection characteristics caused by the change of the ink viscosity. The same state is obtained by controlling the pulse waveform such as the pulse width of the drive voltage pulse, the pulse rise time constant, and the pulse fall time constant, so that it is difficult to perform sufficient compensation control. Effective stabilization is required.

In the case where the correction control is performed by the number of ejected droplets according to the present invention, there is no problem peculiar to the head using the electrostatic force. Therefore, the present invention can be applied as a preferable correction unit in an ink jet recording apparatus equipped with an electrostatic ink jet head.

Further, the present invention is particularly effective for inter-module compensation when a large number of heads in a full multi-head configuration using a line head are used in combination as a module. That is, when forming a line head, it is very difficult to manufacture a full-line head with a high yield. Therefore, as shown in FIG. 18, a head is configured by arranging a plurality of head modules HM for one line. In this case, variations in the ink droplet ejection characteristics between the head modules HM inevitably occur. Therefore, by correcting the drive waveform for each head module HM, variations in the ink droplet ejection characteristics between the head modules HM are reduced. As a result, a line head having excellent ink droplet ejection characteristics can be configured at low cost.

In each of the above-described embodiments, the example in which the planar shape of the diaphragm and the electrodes of the electrostatic ink jet head is rectangular is described. However, the planar shape may be trapezoidal or triangular. Further, in each of the above-described embodiments, the vibration plate and the liquid chamber are formed of the same member as the flow path substrate in the ink jet head. However, the vibration plate and the liquid chamber forming member may be formed of different members and joined. .

Further, the shapes, arrangements, and forming methods of the nozzles, the pressurizing chambers, the fluid resistance portions, and the common flow path liquid chambers of the ink jet head that are driven and controlled in the present invention can be appropriately changed. For example, in the above embodiment, the nozzle is a side shooter type ink jet head formed so that ink droplets are ejected in the direction of displacement of the diaphragm. An edge shooter type inkjet head formed so as to discharge may be used.

[0123]

As described above, according to the ink jet recording apparatus of the present invention, since the means for correcting the number of ejected droplets of a plurality of ink droplets to correct the size of one pixel dot is provided, it is simple. With such a configuration, high ink droplet ejection characteristics and image quality can be obtained.

Here, by discharging a plurality of minute ink droplets having substantially the same size from the nozzles and making the number of the discharged droplets different, a plurality of types of one-pixel dots having different sizes which are combined and enlarged on the paper surface can be obtained. The formation facilitates correction of the number of drops. In this case, when the volume of the ink droplet does not exceed 5 pl, the resolution of correction is improved.

Further, a plurality of ink droplets having different sizes are ejected from the nozzles, and a plurality of ink droplets having different sizes are combined and expanded on the paper surface by combining the plurality of ink droplets having different sizes. Is formed, it is easy to correct the number of drops. In this case, the dot diameter correction unit corrects the smallest number of ink droplets among a plurality of types of ink droplets having different sizes, thereby improving the resolution of correction. At this time, since the minimum volume of the ink droplet does not exceed 5 pl, the resolution of correction is further improved.

Furthermore, the dot diameter correcting means corrects the number of ejected droplets by correcting the number of drive pulses applied to the ink jet head, thereby simplifying the structure for correcting the number of ejected droplets.

The dot diameter correcting means corrects the number of ejected droplets based on the variation in the ejection characteristics of the ink droplets between the heads, thereby reducing the variation in the ejection characteristics between the heads and improving the high ejection characteristics. can get. Further, the dot diameter correction means corrects the number of ejected droplets based on the variation in the ejection characteristics of the ink droplets between the nozzles of the inkjet head, thereby reducing the variation in the ejection characteristics between the nozzles in the same head. It is possible to obtain uniform and high discharge characteristics by reducing the amount.

Further, the dot diameter correcting means corrects the number of ejected droplets based on the result of the density adjustment, so that the variation of the ejection characteristics over time is reduced and stable ejection characteristics are obtained over a long period of time. be able to. In addition, the dot diameter correction means corrects the number of ejected droplets based on the detection result of the surrounding environment, thereby reducing variations in the ejection characteristics due to fluctuations in the surrounding environment and obtaining high ejection characteristics.

Further, the provision of the ejection characteristic control means for controlling the ejection characteristics of the ink droplets together with the dot diameter correction means makes it possible to suppress fluctuations in the droplet speed and to perform more accurate correction. it can. In this case, the dot diameter correction means corrects the number of drive pulses applied to the ink jet head, and the ejection characteristics control means corrects the waveform parameters of the drive pulses, so that the number of drops can be corrected and the ejection characteristics can be corrected with a simple configuration. Corrections can be made.

Further, it has a nozzle for discharging ink droplets, an ink chamber with which the nozzle communicates, a diaphragm forming the wall surface of the ink chamber, and an electrode facing the diaphragm.
Equipped with an electrostatic inkjet head that ejects ink droplets from nozzles by deforming the vibration plate by electrostatic force, high-precision, high-density recording can be performed without being affected by the type of ink. Furthermore, a line head that can obtain uniform ink droplet ejection characteristics with a simple configuration can be obtained by arranging a plurality of head modules and arranging one head as an inkjet head that ejects ink droplets. .

According to the printer driver of the present invention,
A configuration having table information in which the correspondence between a correction value for correcting the number of ejected drops of a plurality of ink droplets and a head rank is tabulated and / or table information in which the correspondence between the correction value and the surrounding environment is tabulated. Therefore, it is easy to control the number of ink droplets to be ejected in an ink jet recording apparatus that ejects a plurality of ink droplets to form one pixel dot.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of a mechanism section of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory side view of the mechanism.

FIG. 3 is an exploded perspective view of a head of the recording apparatus.

FIG. 4 is an explanatory cross-sectional view of the head in the longitudinal direction of the diaphragm.

FIG. 5 is an enlarged cross-sectional explanatory view of the head in the longitudinal direction of the diaphragm.

FIG. 6 is an enlarged sectional explanatory view of a main part of the head in the transverse direction of the diaphragm.

FIG. 7 is a block diagram illustrating an example of a control unit of the recording apparatus.

FIG. 8 is a block diagram illustrating a head drive control unit of the control unit.

FIG. 9 is an explanatory diagram for explaining a relationship between a pulse width of a driving waveform of the head, a droplet speed, and a droplet volume.

FIG. 10 is an explanatory diagram for explaining the operation of the head drive control unit;

FIG. 11 is an explanatory diagram for explaining formation of one pixel dot by combining a plurality of ink droplets;

FIG. 12 is an explanatory diagram illustrating a table of a head rank and a pulse number initial value of a drive pulse.

FIG. 13 is an explanatory diagram for describing a head rank, a pulse number initial value of a driving pulse, and a discharged droplet volume;

FIG. 14 is an explanatory diagram for explaining the ambient temperature, the initial value of the number of drive pulses, and the volume of ejected droplets;

FIG. 15 is an explanatory diagram illustrating a table of an ambient temperature and a pulse number initial value of a drive pulse.

FIG. 16 is an explanatory diagram illustrating a table of a head rank, an ambient temperature, and a pulse number initial value of a drive pulse.

FIG. 17 is an explanatory diagram for explaining a relationship between a head rank, the number of driving pulses, and a discharge droplet speed.

FIG. 18 is an explanatory diagram for explaining a line head including a plurality of head modules;

[Explanation of symbols]

13: carriage, 14: head, 24: transport roller,
33: paper ejection roller, 40: ink jet head, 41
... channel substrate, 42 ... electrode substrate, 43 ... nozzle plate, 44 ...
Nozzle, 46 ... Pressure chamber, 47 ... Fluid resistance part, 48 ... Common flow path liquid chamber, 50 ... Vibration plate, 55 ... Electrode, 56 ... Gap, 88 ... Waveform generation circuit, 91 ... Head rank identification means, 92 ... Head rank detection circuit, 93 ... temperature sensor,
94: temperature detection circuit, 101: main control unit, 103: driver IC.

Claims (16)

[Claims] 1. An ink jet recording apparatus for forming one pixel dot which is joined and enlarged on a paper surface by ejecting a plurality of ink droplets from a nozzle, wherein the number of ejected droplets of the plurality of ink droplets is corrected by correcting the number of the ejected droplets. An ink jet recording apparatus comprising a dot diameter correcting means for correcting the size of a pixel dot. 2. The ink jet recording apparatus according to claim 1, wherein a plurality of minute ink droplets having substantially the same size are ejected from the nozzles, and the number of ejected droplets is made different from each other, thereby increasing the size of the ink on the paper. An ink jet recording apparatus for forming a plurality of types of one-pixel dots having different sizes. 3. The ink jet recording apparatus according to claim 2, wherein the volume of the ink droplet does not exceed 5 pl. 4. The ink jet recording apparatus according to claim 1, wherein a plurality of ink droplets having different sizes are ejected from the nozzles, and the plurality of ink droplets having different sizes are combined so as to be combined and expanded on a paper surface. An ink jet recording apparatus, wherein a plurality of types of one pixel dots having different sizes are formed. 5. The ink jet recording apparatus according to claim 4, wherein said dot diameter correction means corrects the smallest number of ink droplets among said plurality of different size ink droplets. Inkjet recording device. 6. The ink jet recording apparatus according to claim 5, wherein the minimum volume of the ink droplet does not exceed 5 pl. 7. The ink jet recording apparatus according to claim 1, wherein the dot diameter correction means corrects the number of ejection droplets by correcting the number of drive pulses applied to the ink jet head. Characteristic inkjet recording device. 8. The ink jet recording apparatus according to claim 1, wherein the dot diameter correction unit corrects the number of the discharged droplets based on a variation in the discharge characteristics of the ink droplets between the heads. Inkjet recording apparatus. 9. The ink jet recording apparatus according to claim 1, wherein the dot diameter correction unit corrects the number of the ejected droplets based on a variation in the ejection characteristics of the ink droplets between nozzles of the inkjet head. An ink jet recording apparatus comprising: 10. The ink jet recording apparatus according to claim 1, wherein said dot diameter correcting means corrects the number of ejected droplets based on a result of density adjustment. 11. An ink jet recording apparatus according to claim 1, wherein said dot diameter correcting means corrects the number of ejected droplets based on a detection result of a surrounding environment. . 12. An ink jet recording apparatus according to claim 1, further comprising an ejection characteristic control unit for controlling an ejection characteristic of an ink droplet, together with said dot diameter correction unit. Recording device. 13. An ink jet recording apparatus according to claim 12, wherein said dot diameter correction means corrects the number of drive pulses applied to the ink jet head, and said ejection characteristic control means corrects a waveform parameter of said drive pulse. An ink jet recording apparatus comprising: 14. The ink jet recording apparatus according to claim 1, wherein: a nozzle for discharging ink droplets; an ink chamber to which the nozzle communicates; a diaphragm forming a wall surface of the ink chamber; An ink jet recording apparatus, comprising: an electrode facing the vibration plate; and an electrostatic ink jet head for discharging the ink droplet from the nozzle by deforming the vibration plate by electrostatic force. 15. An ink jet recording apparatus according to claim 1, wherein said ink jet head for ejecting ink droplets comprises a plurality of head modules arranged to form one head. Inkjet recording device. 16. A printer driver for driving and controlling an ink jet recording apparatus for forming one pixel dot which is combined and expanded on a paper surface by discharging a plurality of ink droplets, wherein the number of discharged droplets of the plurality of ink droplets is corrected. A printer driver having table information in which the correspondence between the correction values and the head ranks is tabulated and / or table information in which the correspondence between the correction values and the surrounding environment is tabulated.