WO2010043118A1

WO2010043118A1 - Ink-jet printer and printing method thereof

Info

Publication number: WO2010043118A1
Application number: PCT/CN2009/001156
Authority: WO
Inventors: 刘志红; 陈�峰
Original assignee: 北大方正集团有限公司; 北京大学; 北京北大方正电子有限公司
Priority date: 2008-10-17
Filing date: 2009-10-19
Publication date: 2010-04-22
Also published as: CN101402282A; CN101402282B

Abstract

An ink-jet printer and a printing method thereof for improving the quality of printing. The method includes: according to the time for spraying ink droplets to the medium and moving velocity of the medium, obtaining the time error of time intervals between the time taken for ink droplets arriving at the medium when the medium moving velocity is variable and constant; adjusting jet moment of the ink droplets based on the time error; jetting the ink droplets according to the adjusted jet moment. Adjusting the jet moment of the ink droplets can improve the quality of printing by avoiding positional error which is brought when the ink droplets fall on the medium which moves in a variable velocity, eliminating accumulative error when multiple ink droplets are jetted, and adjusting the arriving positions of the ink droplets arriving at the medium.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of inkjet printing, and more particularly to an inkjet printer and a printing method thereof. Background technique

The principle of inkjet imaging is: The ink is ejected from the fine nozzle onto the medium at a certain speed, and the image is reproduced by the interaction of the ink and the substrate. An inkjet printhead typically consists of several nozzles, and an inkjet printer contains several inkjet printheads. At present, in a high-speed inkjet printing apparatus, an inkjet print head fixing and a medium moving method are generally used to complete the printing of the entire image. In this method, the nozzle of the inkjet print head covers the entire print width, and the inkjet head ejects once to form a line of images. After printing one line, the medium is moved to the print position of the next line, and the inkjet head prints the next line of images. This cycle, until the printing of an image is completed. As shown in Fig. 1, the ink jet head ejects ink droplets onto the medium at a certain speed in a certain manner, and the encoder shaft rotates to drive the medium to move. In this printing mode, the inkjet control system needs to accurately calculate the moment when the media moves to the next line of printing position, otherwise the position of the ink droplets on the substrate will be inconsistent with the ideal position, thus affecting the quality of the photocopying.

In the prior art, an ink jet control system generally employs an encoder as a measuring tool to calculate the distance traveled by the medium, and the timing of the encoder pulse to control the timing of the ink jet head ejection. In the device shown in Figure 1, the encoder is usually mounted on a high-precision shaft. For example, an encoder with a rotational speed of 2000 rpm and a shaft circumference of 160 mm will produce 2000 pulses while rotating the encoder. The speed of motion is 0.4m/s, so the encoder produces a pulse with an average period of 1/((0.4/0.16) *2000) = 0.0002s, or 200us. Therefore, if the inkjet controller ejects at the edge of each encoder, it can achieve a resolution of 2000/(160/25.4) = 317.5dpi.

However, in the prior art, the time difference between the ink jet head ejecting ink droplets and the ink droplets falling on the medium is generally not considered, and the timing at which the ink jet head ejects the ink droplets is equivalent to the timing at which the ink droplets fall on the medium, the ink jetting There is a certain distance between the head and the medium, which causes a certain amount of time for the ink droplets to fall on the medium. In theory, The mass movement can be in a uniform motion state. At this time, when the ink droplet reaches the medium over a period of time, it can still accurately reach the printing position of the line; but in reality, the medium moves at a small time. The inside (such as in milliseconds) is always changing. Therefore, when the ink jet head ejects ink droplets, the moving speed of the medium is different from the speed of the medium when the ink droplets fall on the medium shield. The position and ideal of the ink droplets falling on the medium are ideal. The location is also different, which affects the print quality. The following details:

The movement of the medium is usually driven by the motor, and the rotation speed of the motor usually changes periodically, such as an upward trend for a period of time, and a downward trend for another period of time. Therefore, the running speed of the medium cannot be an absolute hook speed. Therefore, the pulse width of the encoder is sinusoidal fluctuation within a certain range. In the prior art, the ink jet control system controls the ink jet head to eject at the rising or falling edge of each pulse of the encoder.

As an example, assuming that the apparatus shown in Fig. 1 is used, the distance between the inkjet head and the medium is 2 mm, and the initial movement speed of the ink droplet is set to 10 m/s, then the first ink droplet is ejected from the inkjet head to the ink droplet. The time on the medium is 200us; the inkjet control system calculates that each encoder pulse represents a medium moving distance of one line, as shown in Figure 2, in this example, a total of 9 encoder pulse signals are sent, respectively, 200us. 201 us, 202us, 203us, 204us, 205us, 206us, 207us, 208us; and preset inkjet control system controls the inkjet head to eject at the rising edge of each encoder pulse. Taking the first ink droplet and the second ink droplet as an example, in the prior art, the interval between the two ink jets is 200 us. In fact, when the first ink dot passes through the 200us time and then falls on the medium, The moving speed of the medium has changed to a distance of 201us to move 1 line. Therefore, the position of the second ink dot on the medium is not exactly at the printing position, and the relatively accurate printing position is moved forward a little. One ink drop is 200us, not the ideal arrival time, ie 201us, so the distance between the first ink droplet and the second ink droplet will be smaller than the ideal value, and the amplitude is about (201 - 200) / 201 = 0.5 %.

Similarly, the distance between the second ink droplet and the third ink droplet is also smaller than the ideal value... the eighth ink droplet and the first

The spacing of the nine ink drops is also less than the ideal value. Therefore, the time error of the first ink drop to the ninth ink drop is the accumulated value of the time error of every two ink drops, as shown in Fig. 2, the time error of the second line is 401-400 = lus, the first The time error of 3 lines is 603-601=2us, and the time error of the 4th line is 806-803=3us. The time error of the 5th line is 1010-1006=4us, the time error of the 6th line is 1215-1210=5us, the time error of the 7th line is 1421-1415=6us, and the time error of the 8th line is 1628-162 l =7us, the error of the ink droplet on the 9th line is the largest, and the difference from the ideal value reaches 1836-1828 = 8us, which is about 4% of the line distance.

The inventors have also found that in the case where the distance between the ink jet head and the medium is increased and the medium moving speed fluctuates greatly, the accumulated time error is higher, and the print quality cannot be guaranteed. Summary of the invention

Embodiments of the present invention provide a printing method of an inkjet printer for improving print quality. The method includes:

According to the time required for the ink droplets to be ejected to the medium and the moving speed of the medium, the time error at the moment when the ink droplets fall onto the medium and the time when the ink droplets fall onto the medium when the ink moving speed is constant is obtained;

Adjusting the injection timing of the ink droplet according to the time error;

The ink droplet ejection is performed at the adjusted injection timing.

Preferably, the time required for the ink droplets to be ejected to the medium is determined by the speed of the ink droplet ejection of the ink jet printer, the distance between the nozzle and the medium.

Preferably, the time error obtained according to the time required for the ink droplets to be ejected to the medium and the moving speed of the medium comprises:

According to the time required for the ink droplets to be ejected into the medium and the average pulse period, the number of hysteresis periods at which the ink droplets fall on the medium at the timing of the ejection of the ink droplets is obtained, and the average pulse period is based on the moving speed of the medium and the circumference of the encoder connecting shaft. The number of pulses per revolution of the encoder and the encoder is determined;

The time error is obtained from the difference between the pulse periods separated by the number of lag cycles. Preferably, the number of hysteresis cycles is not less than the minimum integer value of the time required for the ink drops to fall on the medium divided by the average pulse period.

Preferably, adjusting the injection timing of the ink droplet according to the time error comprises: Obtaining a compensation value required to adjust an injection timing of the ink droplet according to the time error;

The injection timing of the ink droplets is adjusted according to the compensation value.

Preferably, adjusting the injection timing of the ink droplet according to the compensation value comprises:

Obtaining a time interval from the pulse edge to the injection timing of the adjusted ink droplet according to the default injection delay and the compensation value;

The ejection timing of the ink droplets is adjusted according to the time interval.

Preferably, the default injection delay is set to be one quarter of the average pulse period.

Preferably, the adjusting the ejection timing of the ink droplets means that the ejection timing of the ink droplets is delayed from the encoder pulse by the time interval.

An embodiment of the present invention further provides an inkjet printer for improving print quality, the apparatus comprising: an error determining unit for obtaining a medium movement according to a time required for an ink droplet to eject from the ink to the medium and a moving speed of the medium The time error at the moment when the ink droplet falls onto the medium when the speed changes, and the time when the ink droplet falls on the medium when the moving speed of the medium is constant;

An adjusting unit, configured to adjust an injection timing of the ink droplet according to the time error;

The ink jet unit is configured to perform ink droplet ejection at the adjusted injection timing.

Preferably, the error determining unit further includes:

An average pulse period determining subunit for determining an average pulse period according to a moving speed of the medium, a circumference of the encoder connecting shaft, and a number of pulses per revolution of the encoder;

a hysteresis period number determining sub-unit for obtaining a lag period of the time at which the ink droplet falls on the medium relative to the ejection timing of the ink droplet according to the time required for the ink droplet to be ejected to the medium and the average pulse period;

The error discriminating subunit is configured to obtain the time error based on a pulse period separated by the number of hysteresis periods.

Preferably, the adjusting unit further includes:

a compensation value calculation subunit, configured to obtain a compensation value required to adjust an injection timing of the ink droplet according to the time error;

And a adjusting subunit, configured to adjust an injection timing of the ink droplet according to the compensation value. In the embodiment of the present invention, according to the time required for the ink droplets to be ejected to the medium and the moving speed of the medium, the time when the ink droplet falls onto the medium when the movement speed of the shield changes and the time when the ink droplet falls to the medium when the moving speed of the medium is constant is obtained. The time error is adjusted by the timing error to adjust the ejection timing of the ink droplets, and the ink droplet ejection is performed according to the adjusted ejection timing, so that the position of the ink droplet falling on the medium when the movement speed of the medium changes can be avoided, so that the ink droplet falls accurately At the target position of the medium, the influence of the time error on the print quality is eliminated, and when a plurality of ink droplets are ejected, the cumulative error of the position where the ink drops fall onto the medium is not formed, and the print quality is greatly improved. DRAWINGS

Figure 1 is a schematic view of an ink jet printer jet in the background art;

Figure 2 is a schematic view showing the cumulative time error of the ink droplet sequence ejected by the ink jet printer in the background art;

3 is a schematic flow chart of a printing method of an inkjet printer according to an embodiment of the present invention;

4 is a schematic diagram of eliminating accumulation time errors generated by ink droplet sequences ejected by an inkjet printer in accordance with an embodiment of the present invention;

FIG. 5 is a schematic structural view of an inkjet printer according to an embodiment of the present invention; FIG.

6 is a schematic structural view of an error determining unit of an inkjet printer according to an embodiment of the present invention; and FIG. 7 is a schematic structural view of an adjusting unit of an inkjet printer according to an embodiment of the present invention. detailed description

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

As shown in FIG. 3, in an embodiment of the present invention, a printing method of an inkjet printer includes: Step 301: According to a time required for ink droplets to be ejected to a medium and a moving speed of the medium, the ink droplets fall to the medium when the moving speed of the medium changes. The time error at the moment when the upper moment and the moving speed of the medium are constant when the ink droplet falls onto the medium;

Step 302: Adjust an injection timing of the ink droplet according to the time error; Step 303: Perform ink droplet ejection according to the adjusted injection timing.

In one embodiment, when step 301 is performed, since the nozzle of the ink jet printer has a certain distance from the medium, it takes a certain time for the ink droplet to fall onto the medium after the ink droplet is ejected. When implemented, there are various methods for determining the time required for the ink droplets to fall onto the medium, such as using a timer, etc.; preferably, depending on the ink droplet ejection speed of the ink jet printer, the distance between the nozzle and the medium, The time required for the ink droplets to be ejected to the medium is determined, and the time required for the ink droplets to be ejected to the medium is equal to the distance between the nozzle and the medium divided by the speed at which the ink jet head ejects. As an example: Let the ink droplets obtain a certain ejection velocity V at the time of ejection, and the distance between the inkjet head and the medium is s, and the time required for the ink droplets to reach the medium is t=s/v.

During the time required for the ink droplet to fall onto the medium, the change of the moving speed of the medium is further represented by a change of the pulse period, and the pulse period is inversely proportional to the moving speed of the medium. In order to facilitate the determination of the time error and the accumulated time difference, the pulse period is The change replaces the change in the speed of movement of the medium. In the implementation, each pulse cycle is clocked and the cycle duration is recorded.

In one embodiment, if the medium passes a complete pulse period while moving, the medium is just running to a printing position of one line, so that the position of the ink drop on the medium is only at the moment when the ink drops on the medium. The pulse period is related to the pulse period at the injection timing of the ink droplets, regardless of the pulse period that passes through the middle. Therefore, the time error can also be obtained only by the pulse period at the time when the ink drops on the medium and the pulse period of the ink droplet ejection timing, and the time error of one ink droplet is the time when the ink droplet falls on the medium. The difference between the pulse period and the pulse period of the ejection timing of the ink droplets.

In the implementation, there are various methods for determining the time error of the ink droplets, for example, using a timer, and preferably, the two pulse periods can be judged by the number of hysteresis periods of the ejection timing of the ink droplets at the time when the ink drops on the medium. The difference. The number of the hysteresis pulse periods has various judging methods, for example, the pulses are manually counted in the time required for the ink droplets to be ejected into the medium, preferably, according to the time required for the ink droplets to be ejected to the medium and the average pulse period. That is, the average pulse period of how many encoders are included in the time required for the ink droplets to fall on the medium, and the number of hysteresis pulse periods is not less than the minimum integer value of the time required for the ink droplets to fall on the medium divided by the average pulse period. for example:

Set the running speed of the medium V, the circumference of the encoder connecting shaft is 1, then the time required for each revolution of the encoder is And because the number of pulses per revolution of the encoder is m, the average pulse period T of the encoder is ( ) / m, that is, T = 1 / ( VX m );

Then, within a time t required for the ink droplet to fall onto the medium, at least an integer period of t/T is taken, that is, the number of pulse periods n is delayed.

In an embodiment, when the step 302 is implemented, the injection timing of the ink droplets is adjusted according to the time error. For example, the injection timing of the ink droplets may be directly advanced or delayed according to the time error, or may be The time error obtains a compensation value required to adjust the ejection timing of the ink droplet, and adjusts the ejection timing of the ink droplet according to the compensation value.

The compensation value required to adjust the injection timing of the ink droplet based on the time error will now be described as an example.

In the implementation, before the first ink droplet reaches the medium, the inkjet control system does not adjust the timing of the inkjet because it cannot predict the time error formed by the ink droplet falling on the medium, so the first ink droplet reaches the medium. The compensation value of the ink droplets to be ejected in time is 0. According to the recorded pulse period of the encoder, the time error corresponding to one ink droplet is obtained. Because there are multiple ink droplets in one sequence, and the time error of the ink droplets will have a cumulative effect, the basis of adjustment of the previous ink droplet is The timing of the ejection of the ink droplet is adjusted. for example:

Let the compensation value be Di, each pulse period of the encoder is TEi, for any one of the injection sequences I (i>n+l), D1 to _Dn+1 are 0; set the time error of one ink droplet to Ti, Bay ' J Ti = TEi-TE^; then the compensation value of the ink droplet Di = Ti + Dw.

Because the moving speed of the medium is usually sinusoidal, the position where the ink drops fall on the medium will be delayed or advanced. Correspondingly, the adjustment of the injection timing of the ink droplet may be to advance the injection timing. It may be that the injection timing is delayed. To facilitate control of the timing of the ejection of the ink droplets, in one embodiment, a default injection delay Tdmax is provided to delay the injection timing of the ink droplets from the pulse edge.

The shield movement speed does not change, so the compensation value is usually small, generally less than one tenth of the average pulse period. Therefore, Tdmax is usually set to one quarter of the average pulse period. At this point, the ink drops The injection timing is delayed by a certain time with respect to the pulse edge, and it is difficult to control the injection timing until the injection timing advances to the front of the pulse edge.

According to Tdmax and the compensation value, the ejection timing of the ink droplet is adjusted, and the time interval from the pulse edge to the ink jet head ejection is the sum of the Tdmax and the compensation value, which is denoted as Fi = Tdmax + Di.

In one embodiment, step 303 is implemented from the beginning of the pulse edge, and after the duration of Fi, the ink droplets are ejected, that is, the ejection is performed at a hysteresis time.

An example is given to illustrate:

For convenience in comparison with the background art, the same conditions as in the example shown in Fig. 2 are employed in this example, that is, the time required for the ink droplets to reach the medium is 200 us, and the average pulse period of the encoder is 200 us, and the ink droplets are obtained according to the above conditions. The time at which the medium falls on the medium is delayed by one cycle with respect to the ink droplet ejection timing, the Tdmax is set to 50 us, and the injection timing is delayed by the upper or lower edge of the encoder pulse, as shown in FIG. Since the first ink droplet and the second ink droplet are ejected, no ink droplets reach the medium, and the time error of the formation is not known. Therefore, the first ink droplet and the second ink droplet are not adjusted, but only The ejection timing is delayed by Tdmax, and the first ink droplet and the second ink droplet are ejected at 50 us and 250 us, respectively. When the third ink droplet is ejected, T3 = TE3-TE2 = lus according to TE3=202 and TE2 = 201, because the first ink droplet and the second ink droplet are not adjusted, so the third ink The injection timing of the drops is adjusted to the sum of the delays Tdmax and T3 after the rising or falling edge of the encoder, ie 51us.

Similarly, T4 = lus can be obtained because the third ink droplet has adjusted the time error lus. Therefore, the fourth ink droplet is adjusted based on the adjustment of the third ink droplet, that is, the ejection of the fourth ink droplet. The time is adjusted to 52us after the rising or falling edge of the encoder. Similarly, the injection timing of the fifth ink drop to the ninth ink drop in Fig. 4 can be adjusted to the encoder rise or fall lag 53us, 54us, 55us, 57us, 57us. It can be calculated from the calculation that the spacing of the second row to the ninth row in Fig. 4 remains consistent with the ideal value, and the error accumulation is eliminated.

Based on the same inventive concept, an embodiment of the present invention further provides an inkjet printer. As shown in FIG. 5, the device includes:

The error determining unit 501 is configured to: according to the time and medium shift of the ink droplet from the ejection to the falling onto the medium The moving speed, the time error at the moment when the ink drop falls onto the medium when the moving speed of the medium changes, and the time when the ink drop falls onto the medium when the moving speed of the medium is constant;

The adjusting unit 502 is configured to adjust an injection timing of the ink droplet according to the time error;

The ink jet unit 503 is configured to perform ink droplet ejection at the adjusted injection timing.

In an embodiment, as shown in FIG. 6, the error determining unit 501 shown in FIG. 5 may further include: an average pulse period determining subunit 601, configured to adjust the speed of the medium, the circumference of the encoder connecting shaft, and the encoder. The number of revolution pulses determines the average pulse period;

The hysteresis period number determining sub-unit 602 is configured to obtain, according to the time required for the ink droplets to be ejected into the medium and the average pulse period, the number of hysteresis periods at which the ink droplets fall on the medium at the timing of the ejection of the ink droplets;

The error discriminating sub-unit 603 is configured to obtain the time error based on a pulse period separated by the number of hysteresis periods.

In one embodiment, as shown in FIG. 7, the adjusting unit 502 shown in FIG. 5 further includes: a compensation value calculating sub-unit 701, which obtains a compensation value required to adjust an injection timing of the ink droplet according to the time error;

The adjustment subunits 702, 4 adjust the injection timing of the ink droplets according to the compensation value.

In the embodiment of the present invention, according to the time required for the ink droplets to be ejected to the medium and the moving speed of the medium, the timing at which the ink droplet falls onto the medium when the moving speed of the medium changes and the time when the ink droplet falls onto the medium when the moving speed of the medium is constant is obtained. Error, adjusting the ejection timing of the ink droplet according to the timing error, and performing ink droplet ejection according to the adjusted ejection timing, which can avoid an error in the position where the ink droplet falls onto the medium when the moving speed of the medium changes, so that the ink droplet falls accurately on the medium. At the target position, the influence of the time error on the print quality is eliminated, and when a plurality of ink droplets are ejected, the cumulative error of the position where the ink drops fall onto the medium is not formed, and the print quality is greatly improved.

In the implementation, the default injection delay can also be set, and the injection timing is postponed to accurately detect the arrival of the pulse edge. It may be necessary to convert the injection before the pulse edge into the injection after the pulse edge, which is easy to implement. The spirit and scope of the Ming. Thus, it is intended that the present invention cover the modifications and the modifications of the invention

Claims

Claim

A printing method for an inkjet printer, the method comprising:

According to the time required for the ink droplets to be ejected to the medium and the moving speed of the medium shield, the time error of the moment when the ink droplets fall onto the medium and the moment when the ink droplets fall onto the medium when the moving speed of the medium shield is constant is obtained;

Adjusting an injection timing of the ink droplet according to the time error;

The ink droplet ejection is performed at the adjusted injection timing.

The method according to claim 1, wherein the time required for the ink droplets to be ejected to the medium is determined according to a droplet ejection speed of the ink jet printer, a distance between the nozzle and the medium.

3. The method according to claim 1, wherein the obtaining the time error according to the time required for the ink droplet to be ejected to the medium and the moving speed of the medium comprises:

The time error is obtained from the difference between the pulse periods separated by the number of lag cycles.

4. The method of claim 3, wherein the number of hysteresis cycles is not less than a minimum integer value of the time required for the ink drops to fall on the medium divided by the average pulse period.

5. The method according to claim 1, wherein the adjusting an injection timing of the ink droplet according to the time error comprises:

Obtaining a compensation value required to adjust an injection timing of the ink droplet according to the time error;

6. The method according to claim 5, wherein the adjusting the injection timing of the ink droplet according to the compensation value comprises:

The timing of the ejection of the ink droplets is adjusted according to the time interval.

7. The method of claim 6 wherein said default injection delay is set to one quarter of said average pulse period.

8. The method according to claim 6, wherein the adjusting the ejection timing of the ink droplets means delaying the ejection timing of the ink droplets from the pulse edge by the time interval.

9. An ink jet printer, characterized in that the device comprises:

The error determining unit is configured to select a time required for the ink droplet to eject from the ink to the medium and a moving speed of the medium, and obtain a time when the ink droplet falls on the medium shield when the moving speed of the medium changes, and the ink droplet falls to the medium when the moving speed of the medium is constant. Time error at the moment of time;

10. The inkjet printer according to claim 9, wherein the error determining unit further comprises:

a hysteresis period number determining subunit for obtaining a number of hysteresis periods of the time at which the ink droplets fall on the medium relative to the ejection timing of the ink droplets according to the time required for the ink droplets to be ejected to the medium and the average pulse period;

The inkjet printer according to claim 9, wherein the adjusting unit further comprises:

And a adjusting subunit, configured to adjust an injection timing of the ink droplet according to the compensation value.