JPH0939275A - Ink jet recording method and recorder therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a smooth printing without reversing the gradation and discharge amount. SOLUTION: A ROM 521 stores a predetermined number of ink droplet discharges of each nozzle required to obtain the set maximum ink dot diameter. A record controller 511 determines the number of discharging ink droplets to the same pixel of the nozzle corresponding to the pixel of the printing data from the stored content and the gradation data of the printing data to be input from an external unit, and performs multiple ink ejection to express the gradation of the image.

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 method and recording apparatus applied to a facsimile, a copying machine, a printer and the like.

[0002]

2. Description of the Related Art In recent years, an ink jet recording apparatus for ejecting ink droplets from a recording head nozzle to print on a sheet has been put into practical use. On the other hand, there is an increasing demand for a recording device that can express gradation, and in the inkjet recording device described above, a method of controlling the ejection amount of ink droplets can be considered in order to express gradation for each pixel. In addition, there is proposed a method in which a small ink droplet is overlaid on the same pixel on a sheet to express gradation (Japanese Patent Laid-Open No. 6-26).
No. 2773).

[0003]

However, although it is possible to change the ejection amount of the ink droplets, the range is limited to about 1/2 at the minimum, so that the gradation can be varied over a wide range. Difficult to describe, not practical.

On the other hand, when gradations are expressed by repeatedly striking the same pixel with a small ink droplet as described in Japanese Patent Laid-Open No. 6-262773, the ink droplet ejection amount of each nozzle may vary due to variations in nozzle diameter. If there is a variation, the variation in the ejection amount is enlarged by repeatedly ejecting the ink droplets. Therefore, depending on the degree of variation, for example, the discharge amount of a nozzle with a deep gradation is smaller than the discharge amount of a nozzle with a small gradation.
There is a possibility that the gradation and the ink droplet ejection amount may be reversed.

The present invention solves the above problems and provides an ink jet recording method and a method for obtaining a smooth printed image without reversing the gradation and the ejection amount when the gradation is expressed by repeatedly ejecting ink drops. It is an object to provide a recording device.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a plurality of nozzles arranged at a constant pitch are caused to eject ink droplets a required number of times so that recording pixels having different ink dot diameters in a stepwise manner can be formed. In the obtained ink jet recording method, the predetermined number of ejections required to obtain the set maximum ink dot diameter is obtained for each nozzle, and the gradation data of the recording pixel and the predetermined number of ejections of the nozzle corresponding to the recording pixel are obtained. From the above, the number of ink droplets ejected from each nozzle is determined according to the gradation data, and the ink droplets are ejected the number of times (claim 1).

Further, it is set in an ink jet recording apparatus which obtains recording pixels having stepwise different ink dot diameters by causing each of a plurality of nozzles arranged at a constant pitch to eject ink droplets a required number of times. And the number of discharges of each nozzle required to obtain the maximum ink dot diameter and the number of discharges of ink droplets of the nozzle corresponding to the recording pixel from the gradation data of the recording pixel, and each nozzle. And an ejection control means for ejecting the ink droplets the number of times of ejection determined from (Claim 2).

According to this structure, the number of ink droplet ejections of the nozzle corresponding to the recording pixel is determined from the predetermined number of ejections of each nozzle required to obtain the set maximum ink dot diameter and the gradation data of the recording pixel. Then, ink droplets are ejected by the number of ejections determined from each nozzle, and recording pixels having different ink dot diameters are obtained, and the gradation of the recording pixels is expressed.

Further, in the ink jet recording apparatus according to the second aspect, the maximum gradation of the recording pixel is the predetermined number of times of ejection, and the number of times of ink droplet ejection and the gradation data are associated and stored as table data for each nozzle. The ejection number determining means refers to the table data and selects the ejection number of the nozzle corresponding to the recording pixel according to the gradation data of the recording pixel (claim 3). ).

According to this structure, the number of ink droplet ejections and the gradation data of the recording pixels are associated with each other and stored in the storage means as table data for each nozzle, and the maximum ink dot diameter for which the maximum gradation is set is obtained. The predetermined number of discharges from each nozzle is required. Then, the ejection number determining means determines the ejection number of each nozzle by referring to the table data and selecting the ejection number of the nozzle corresponding to the recording pixel according to the gradation data of the recording pixel.

[0011]

FIG. 2 is a perspective view showing a configuration around a printing position in an embodiment of an ink jet recording apparatus according to the present invention. FIG. 3 is a diagram schematically showing the nozzles of the recording head 1 and the conveyed paper P. This ink jet recording apparatus prints an image by ejecting ink droplets from a nozzle arranged in the recording head 1 onto a recording medium such as a paper P.

The recording head 1 has nozzles 11 arranged in a line, for example.
Are arranged at predetermined intervals, each nozzle communicates with a pressurizing chamber (not shown), and each pressurizing chamber communicates with an ink liquid chamber (not shown) in which ink is further stored.

The recording head 1 is formed in, for example, a rectangular parallelepiped shape, and is supported by two support shafts 12 and 13 fixed to the main body of the apparatus.

In the ink ejection direction from the nozzles 11 of the recording head 1, the conveyor belt 2 is located at a position separated by a predetermined dimension.
1 is provided. The transport belt 21 is arranged such that the belt surface is orthogonal to the ink ejection direction and the paper transport direction indicated by the arrow in FIG. 2 is orthogonal to the nozzle array direction, and the width dimension is the dimension in the nozzle array direction of the recording head 1. The same endless shape as the driving roller 22 and the driven roller 23.
It is stretched over and is used to adsorb paper by electrostatic force and convey it.

The shafts of the driving roller 22 and the driven roller 23 are rotatably supported by side plates 24 and 25 fixed to the main body of the apparatus. A gear 26 is fixed on the shaft of the drive roller 22 near the side plate 24, and the gear 26 is meshed with a gear 28 fixed to the motor shaft of the conveyor belt motor 27.

The conveyor belt motor 27 is composed of, for example, a pulse motor, and the drive roller 22 is provided via gears 28 and 26.
The drive roller 22 is rotated by rotationally driving the shaft of, and the transport belt 21 is rotationally driven.

Further, the conveyor belt 2 with respect to the paper conveying direction.
A sheet feeding system 211 (FIG. 1) is arranged outside the drawing on the upstream side of 1, while a sheet discharging system 212 (FIG. 1) is arranged outside the drawing on the downstream side.

Then, the paper P is a paper feed system 211 (FIG. 1).
Is conveyed to the conveying belt 21 by the conveying belt 21, and ink droplets are ejected from the nozzles 11 of the recording head 1 to be printed while being conveyed by the conveying belt 21. Is discharged.

FIG. 1 is a block diagram showing the control arrangement of an embodiment of an ink jet recording apparatus according to the present invention. In the present embodiment, the recording head 1, the paper transport unit 2, the operation unit 3, the display unit 4, the control unit 5, and the like are configured, and based on operation data and print data input from an external device such as a personal computer or an image reading device. The operation of each part is performed.

The recording head 1 includes a piezoelectric element 14 that pressurizes the pressurizing chamber and a drive circuit 15 that drives each piezoelectric element 14.
It has.

The piezoelectric element 14 is made of, for example, PZT,
Each of the nozzles is disposed on one side wall of the pressurizing chamber corresponding to each nozzle, and a pair of electrodes are respectively disposed, and a voltage signal is applied between the electrodes to deform the pressurizing chamber. .

The drive circuit 15 is composed of a power source, various circuit elements, etc., and applies a voltage signal between the electrodes of each piezoelectric element 14 to deform the piezoelectric element 14. Further, the drive circuit 15 is disposed at a proper position in the recording head 1 and has a latch portion, which temporarily latches input multi-valued print data of, for example, one line of paper, and converts it into parallel signals. It is what is output.

The drive circuit 15 is provided with a circuit for forming a voltage signal to be applied to the piezoelectric elements 14 individually corresponding to each piezoelectric element 14. Then, the ink droplets filled from the ink liquid chamber are ejected toward the paper from each nozzle of the recording head 1 by the pressurization of the pressure chamber.

The drive circuit 15 may be provided in a matrix so that the time-division drive can be performed.

The paper transport unit 2 includes a transport belt motor 27,
It comprises a paper feed system 211, a paper discharge system 212, a drive circuit 213 and the like. The drive circuit 213 is composed of a power source, various circuit elements, and the like, and supplies a drive current to the conveyor belt motor 27, the paper feed system 211, and the paper discharge system 212. Driving and stopping are controlled by the controller 5.

The operation unit 3 includes a start key for starting the printing operation, a number setting key for setting the number of printed sheets, and the like, and is operated by the user. The display unit 4 is composed of an LED, an LCD or the like, and displays the set number of prints, the size of the printed paper, and the like.

The control unit 5 comprises a CPU 51, a storage unit 52, an interface (I / F) unit 53, etc.
The operation of the entire apparatus is controlled in synchronization with the internal clock 1. The CPU 51 includes a recording control unit 511, a mechanism control unit 512, a display control unit 513, and the like, and the recording control unit 511 and the mechanism control unit 512 perform control operations in synchronization with each other. The display control unit 513 controls the display content of the display unit 4.

The storage unit 52 includes a ROM 521 and a RAM 5
22. The ROM 521 stores a control program and fixed data, and also stores data of each nozzle described later. The RAM 522 temporarily stores data and the like.

The I / F section 53 receives a signal input from an external device, and print data is recorded in the recording control section 511.
In addition, operation data such as paper size is output to the mechanism control unit 512.

The recording control unit 511 serially transmits the input print data to the drive circuit 15 of the recording head 1. The recording control unit 511 outputs the parallel signal converted by the drive circuit 15 to the corresponding piezoelectric element 14 as a pulse drive signal to control the ink droplet ejection timing.

Further, the recording control section 511 determines the number of ejections of each nozzle to the same recording pixel from the gradation data of the print data corresponding to each pixel and the data of each nozzle stored in the ROM 521. It is a thing. Then, the recording control unit 511 repeatedly transmits the voltage application signal to the piezoelectric element corresponding to each nozzle the determined number of times of ejection.

The cycle of ink droplet ejection by the recording controller 511, that is, the cycle of signal output to each piezoelectric element 14 is set within the range of the capability of the recording head 1.

The mechanism control section 512 drives the sheet feeding system 211 via the drive circuit 213 based on the input operation data to convey the sheet to the conveying belt 21. Further, the mechanism control unit 512 drives the paper discharge system 212 to discharge the printed paper to the outside of the apparatus main body.

Further, the mechanism control section 512 has the drive circuit 21.
A drive pulse is supplied to the conveyor belt motor 27 via 3 to drive the motor.

Then, the paper conveyance is stopped during the ink droplet ejection, and the paper conveyance is performed by a predetermined distance each time the ink droplet ejection for one pixel of each nozzle, that is, for one line of the paper is completed. In this case, when the ink droplet ejection from all nozzles on one line of the sheet is completed, the sheet may be conveyed by a predetermined distance and the ink droplet ejection on the next line may be started.

The paper may be continuously conveyed at a predetermined speed without stopping. In this case, the ink drop ejection of each line is started in a predetermined cycle, and even if the ink drop ejection of all nozzles on one line of the paper is completed, the ink drop ejection of the next line is started until the predetermined cycle elapses. If this is not done, printing can be performed at a predetermined line interval.

Next, the data of each nozzle stored in the ROM 521 will be described with reference to FIGS. 4 and 5. FIG.
FIG. 6 is a diagram illustrating a set value of a diameter of an ink dot ejected on a sheet.

In FIG. 4, the ink droplet ejection interval in the nozzle array direction and the paper transport direction is D, and the resolutions in both directions are the same. In this case, the optimum value of the maximum ink dot diameter when the gradation is 1 is √ (2) × D where the diagonal ink dots are in contact with each other. Then, in the present embodiment, the number of ejections is set so that the maximum ink dot diameter becomes this value when the gradation is 1.

FIG. 5 is a diagram showing a state where the ink dot diameter is different due to the variation of the nozzles. The recording head 1 is set so as to be capable of expressing 5 gradations including non-ejection of ink droplets, and the nozzle 11b has an ink dot diameter of one set of ejected ink droplets that is equal to the set value and ink of four times. The droplet discharge reaches the optimum diameter, and 5 gradations can be expressed as set.

On the other hand, the nozzle 11a has an ink dot diameter of less than a set value for one ink droplet ejection due to variations in the nozzle diameter and the ejection force of the piezoelectric element, and has reached the optimum diameter after five ink droplet ejections. Therefore, 6 gradations can be expressed.

Further, the nozzle 11c has an ink dot diameter exceeding a set value by one ink droplet ejection due to variations in the nozzle diameter and the ejection force of the piezoelectric element, and the optimum diameter is obtained by three ink droplet ejections. Therefore, only 4 gradations can be expressed.

Then, in the ROM 521, for each nozzle,
The predetermined number of ink droplet ejection times of each nozzle required to obtain the set maximum ink dot diameter as described above is stored. From the stored contents and the gradation data of the print data, the recording control unit 511 determines the number of ink droplet ejection times of the nozzle corresponding to the pixel of the print data.

For example, if the gradation of the print data corresponding to the nozzles 11a, 11b and 11c is 1, the number of ink droplet ejections is 5, 4 and 3, respectively. The nozzle 11
The gradation of the print data corresponding to a, 11b, and 11c is 0.
If the number is 5, the number of ink droplet ejections is, for example, 3, 2,
2 times.

Next, the procedure of the printing operation will be described with reference to the flowchart of FIG. When the print data is input (step S1), the print operation is started, and the predetermined number of ink droplet discharges stored in the ROM 521 of the nozzle corresponding to the print data is compared with the gradation data of the print data. Then, the number of ink droplets ejected from each nozzle is determined (step S3), and the ink droplets are ejected from each nozzle by the determined number of ejections to perform printing (step S4).

In this way, the number of ink droplet ejections of each nozzle required for the diameter of the ink dot ejected on the paper to reach the optimum diameter is stored in the ROM 521, and the ink is ejected for each nozzle according to the gradation data of the print data. Since the number of droplet ejections is determined, the gradation of the print data and the ink dot diameter do not reverse, and smooth gradation and stable image quality printing can be performed.

Further, when the gradation of an image is expressed by changing the ink droplet ejection amount, the driving circuit 15 has a complicated circuit structure, but the ejection amount for one ink droplet ejection is constant. Since they are overlaid, the gradation of the image can be expressed by the drive circuit 15 having a simple structure.

Further, since the optimum diameter of the ink dots can be made constant and the gradation of the image is expressed by overlapping ejection of ink drops regardless of the presence or absence of ink drops, white streaks between ink dots can be expressed. And black streaks can be made inconspicuous.

The number of ejections corresponding to the gradation data is obtained in advance for each nozzle from the predetermined number of ejections of each nozzle required for the ink dot diameter to reach the optimum diameter.
In M521, the number of ink droplet ejections corresponding to the gradation of print data may be stored in a table format for each nozzle. In this case, the recording control unit 511 sets R for each nozzle.
By referring to the table of the OM 521 and setting the number of ink droplet ejections corresponding to the gradation data of the print data as the number of ejections of the nozzle, it is possible to easily determine the number of ink droplet ejections of each nozzle with a simple configuration. it can.

Further, a predetermined number of patterns are classified according to a predetermined number of ejections of each nozzle required for the ink dot diameter to reach the optimum diameter, and the ROM 521 stores each pattern and which pattern each nozzle belongs to. You may do it. For example, in this embodiment, the nozzle 11 of FIG.
The three types of patterns a, 11b, and 11c and which pattern each nozzle belongs to are stored. In this case, the printing control unit 511 refers to the ROM 521 for each nozzle to determine which pattern it belongs to, and determines the number of ink droplet ejections corresponding to the gradation data in the pattern as the number of ejections of the nozzle. By doing so, it is possible to easily determine the number of ink droplet ejections of each nozzle with a simple configuration.

Further, the ROM 521 may store a mathematical formula for calculating the number of ink droplet ejections for the gradation data for each nozzle. In this case, the recording control unit 511 can determine the number of ink droplet ejections of each nozzle by calculating the number of ink droplet ejections from the gradation data of the print data using the formula of the ROM 521 for each nozzle. .

Next, using the flowchart of FIG. 7, RO
An example of a procedure for obtaining the data of each nozzle stored in M521 will be described.

First, for example, ink droplets are ejected from all nozzles toward the paper by shifting the timing so that the ink dots from the adjacent nozzles do not overlap on the paper, and an image analyzer such as a microscope equipped with a CCD is used. Then, the diameter of the ink dot that is ejected once from each nozzle is measured (step S11). Next, the predetermined number of ejections required for the ink dot diameter to reach the optimum diameter is calculated for each nozzle from the obtained measurement data (step S12).

With this procedure, the data stored in the ROM 521 can be obtained for each nozzle.

In step S12, the ink dot diameter is measured every time the ink droplet is ejected, the ink droplet is ejected until the ink dot diameter reaches the optimum diameter, and the number of times is counted. You may do it.

[0055]

As described above, according to the first aspect of the invention, the predetermined number of ejections required to obtain the set maximum ink dot diameter is obtained for each nozzle, and the gradation data of the recording pixel is obtained. The number of ink droplets ejected from each nozzle is calculated from the predetermined number of ejections of the nozzle corresponding to the recording pixel in accordance with the gradation data, and the ink droplets are ejected by that number of times. It is possible to print with stable image quality with smooth gradation without the ink dot diameter reversing.

According to the second aspect of the invention, the ink of the nozzle corresponding to the recording pixel is determined from the predetermined number of ejections of each nozzle required to obtain the set maximum ink dot diameter and the gradation data of the recording pixel. Since the number of droplet ejections is determined and the ink droplets are ejected by the number of ejections determined from each nozzle, the gradation of the recording pixel and the ink dot diameter do not reverse, and a stable image with smooth gradation is obtained. Quality printing can be performed. Further, since the ejection amount in one ejection of the ink droplets is constant and the gradation is expressed by the overlapping ejection of the ink droplets, the configuration for ejecting the ink droplets can be simplified.

According to the third aspect of the present invention, the maximum gradation of the recording pixel is the predetermined number of discharges, and the number of ink droplet discharges and the gradation data are associated and stored as table data for each nozzle. Since the number of ejections of the nozzle corresponding to the recording pixel is selected according to the gradation data of the recording pixel with reference to the table data, the number of ink droplet ejections of each nozzle can be easily determined with a simple configuration. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control configuration of an embodiment of an inkjet recording apparatus according to the present invention.

FIG. 2 is a perspective view showing a configuration around a printing position in an embodiment of the inkjet recording apparatus according to the present invention.

FIG. 3 is a diagram schematically showing the nozzles of the recording head 1 and a conveyance paper P.

FIG. 4 is a diagram illustrating a set value of a diameter of an ink dot ejected on a sheet.

FIG. 5 is a diagram showing a state where ink dot diameters are different due to nozzle variations.

FIG. 6 is a flowchart showing a procedure of a printing operation.

FIG. 7 is a flowchart showing an example of a procedure for obtaining data of each nozzle stored in a ROM 521.

[Explanation of symbols]

 1 Recording Head 14 Piezoelectric Element 15 Drive Circuit 2 Paper Conveying Section 27 Conveying Belt Motor 3 Operating Section 4 Display Section 5 Control Section 51 CPU 511 Recording Control Section 512 Mechanism Control Section 52 Storage Section 521 ROM 522 RAM

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Motoyuki Fukuda 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Mita Industrial Co., Ltd. (72) Seiji Hata 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Within Mita Engineering Co., Ltd.

Claims (3)

[Claims] 1. An inkjet recording method for obtaining recording pixels in which ink dot diameters are changed stepwise by causing each of a plurality of nozzles arranged at a constant pitch to eject ink droplets a required number of times. The predetermined number of ejections required to obtain the maximum ink dot diameter is obtained for each nozzle, and the number of ink droplet ejections of each nozzle is calculated from the gradation data of the recording pixel and the predetermined number of ejections of the nozzle corresponding to the recording pixel. Is calculated according to the gradation data,
An ink jet recording method, characterized in that ink droplets are ejected the number of times. 2. An ink jet recording apparatus, wherein a plurality of nozzles arranged at a constant pitch are caused to eject ink droplets a required number of times to obtain recording pixels having stepwise different ink dot diameters. And the number of discharges of each nozzle required to obtain the maximum ink dot diameter and the number of discharges of ink droplets of the nozzle corresponding to the recording pixel from the gradation data of the recording pixel, and each nozzle. An ink jet recording apparatus, comprising: an ejection control unit that ejects ink droplets the number of times of ejection determined from the above. 3. The ink jet recording apparatus according to claim 2, wherein the maximum gradation of a recording pixel is the predetermined ejection number, and the ink droplet ejection number and gradation data are associated and stored as table data for each nozzle. The discharge number determining means refers to the table data and selects the discharge number of the nozzle corresponding to the recording pixel according to the gradation data of the recording pixel. Inkjet recording device.