JP7146302B2 - inkjet printer - Google Patents

Description

The present invention relates to a continuous type ink jet printer, and more particularly to an ink jet printer incorporating a new print distortion correcting means.

Inkjet printers are broadly classified into a continuous type and an on-demand type. In the continuous type inkjet printer, ink is ejected from a nozzle by a pump, and at the position where the ejected ink is separated into ink droplets by vibration of a certain period, the ink droplet is charged by a charging electrode, and furthermore, the ink is separated by a deflection electrode. The trajectory of the droplets is bent so that they collide with predetermined positions on the surface to be printed to form printed dots.

In the above-described continuous type ink jet printer, there is a problem that the printing printed on the surface to be printed is distorted due to the repelling effect of the Coulomb force of the continuously flying ink droplets.

Specifically, when charged ink droplets fly continuously, the subsequent ink droplets have a large amount of charge, so the trajectory of the preceding ink droplets is pushed down by the Coulomb force of the succeeding ink droplets. As a result, the print quality is degraded because the print dots are printed beyond the frame of the character or the outline of the character is distorted.

Japanese Patent Laid-Open No. 2002-200002 mainly describes two means as means for solving the above-described printing distortion. In the first means, uncharged ink droplets are inserted between charged ink droplets to widen the interval between charged ink droplets (see paragraph 0002). On the other hand, in the second means, when there are continuously charged ink droplets, the effect of the Coulomb force is reduced by interposing non-charged ink droplets that are not used for printing between the charged ink droplets ( Paragraph 0020, see Figure 1).

Japanese Patent Application Laid-Open No. 2002-1960

When uncharged ink droplets are inserted between charged ink droplets as in the first means, the printing speed decreases. On the other hand, the second means only shifts the charging timing, so that the printing speed does not decrease.

The present invention has been made in view of such conventional problems, and is an inkjet printer that can reduce print distortion to the extent that it does not affect print quality even when print dots continue in print data. The purpose is to provide a printer.

In order to achieve the above object, an inkjet printer according to the present invention comprises:
a gun that vibrates the ejected ink at a constant frequency to generate continuous ink droplets;
a charging electrode for charging the ink droplets by applying a stepped voltage synchronized with the cycle of the ink droplets;
a deflecting electrode that deflects the ink droplets flying toward the printing material moving in the horizontal direction in the vertical direction according to the degree of electrification so that the ink droplets land on the printing material;
a controller that controls the amount of charge on the ink droplets by changing the voltage applied to the charging electrode;
An inkjet printer that forms characters by printing dots of a plurality of strokes attached to a material to be printed,
The controller reads out print data that determines the positions at which print dots adhere to the material to be printed. While thinning out the number of print dots to be formed, the target print voltage for forming the uppermost and lowermost print dots is maintained, and other print dots are dispersed between the uppermost and lowermost print dots. It is characterized by correcting the target printing voltage so that the

Here, when the number of print dots arranged in succession is A (A is a natural number) and the number of print dots to be thinned is B (B is a natural number), (AB-2) print dots are obtained. , preferably, the target print voltage is corrected so that the dots are evenly arranged between the uppermost and the lowermost print dots.

The controller further comprises a table storing target print voltages for generating (AB-2) print dots evenly arranged between the uppermost and lowermost print dots, wherein the controller Preferably, the target print voltage is read out from the table each time print data for one stroke is processed, and is replaced with the target print voltage of the print data prepared in advance.

By using the print distortion correcting means according to the present invention, the print distortion caused by the Coulomb force between ink droplets can be minimized, and the print quality can be greatly improved.

1 is a diagram showing a schematic configuration of a continuous inkjet printer according to an embodiment of the present invention; FIG. FIG. 2 is a diagram for explaining the operation of printing on a printing material using the inkjet printer of FIG. 1; FIG. 4 is a diagram showing the process of generating ink droplets; FIG. 10 is a diagram showing a printing example when the number “01234” is printed without correcting printing distortion; FIG. 3 is a diagram of extracted blocks related to print distortion correction from among the functional blocks of the controller; 4 is a flow chart showing an algorithm for correcting printing distortion; 7 is a diagram showing print data in main steps of the flowchart of FIG. 6; FIG. FIG. 10 is a diagram showing a comparison of print examples when print distortion is not corrected and when print distortion is corrected;

An inkjet printer according to an embodiment of the present invention will be described below with reference to the drawings.

<Configuration of inkjet printer>
FIG. 1 shows a schematic configuration of a continuous ink jet printer according to the present embodiment. Further, FIG. 2 shows the operation of printing on a printing material using the ink jet printer of FIG.

The ink jet printer 1 comprises a gun 2, a charging electrode 3, a detection electrode 4, a deflection electrode 5, a gutter 6, a pipe 7, pumps 8a and 8b, an ink tank 9 and a controller 10.

The gun 2 is for ejecting ink droplets ID toward the surface of an object to be printed (for example, a packaging box) 11 , and is composed of a gun body 21 , an ultrasonic vibrator 22 and a nozzle 23 . Ink sent from the ink tank 9 by the pump 8 a and supplied to the gun body 21 through the pipe 7 is jetted from the hole of the nozzle 23 while being vibrated by the ultrasonic vibrator 22 .

The ink column IP ejected from the hole of the nozzle 23 is separated into individual ink droplets ID by vibration applied by the ultrasonic vibrator 22, charged by the charging electrode 3, and then deflected by the deflection electrode 5 for printing. Only the ink droplets ID are deflected according to the charge amount and land on the surface of the printing material 11 .

FIG. 2 shows the packaging box 11 moving at a constant speed in the direction indicated by the arrow on a belt conveyor (not shown). When the packaging box 11 is moving in a direction perpendicular to the flight direction of the ink droplets ID, changing the amount of deflection of the ink droplets ID changes the position of the ink droplets that land on the side surface of the packaging box 11 . , when the deflection of the ink droplet ID is repeated in synchronism with the movement of the packing box 11, a character ("A" in the figure) is printed.

On the other hand, the uncharged ink droplet ID and the charged ink droplet ID that is not used for printing are not deflected and jump into the ink collection gutter 6 as they are and are collected in the ink tank 9 . The ink collected by the gutter 6 is transferred to the ink tank 9 through the pipe 7 by the pump 8b and reused.

The controller 10 controls the operation of the ultrasonic transducer 22 of the gun 2, the pulse power source 31 of the charging electrode 3, the detection electrode 4, the DC power source 51 of the deflection electrode 5, and the pumps 8a and 8b. ROM, RAM, etc.), a timer and a display (not shown).

Although the controller 10 and each component to be controlled are connected by signal transmission cables, they are omitted in FIG. 1 except for the cables between the pumps 8a and 8b to avoid complexity. is doing.

The controller 10 applies pressure to the ink contained in the ink tank 9 by driving the pump 8 a to supply the ink to the gun body 21 .

The controller 10 also controls the timing of the pulse voltage applied from the pulse power source 31 to the charging electrode 3 based on the signal detected by the detection electrode 4, thereby adjusting the number and timing of the charged ink droplets ID. . Further, the controller 10 adjusts the amount of deflection of the ink droplets ID deflected by the deflection electrode 5 by controlling the voltage of the DC power supply 51 .

<Correction of printing distortion>
Next, referring to FIGS. 3 to 8, the printing distortion correcting means according to the present embodiment will be described. First, the print distortion to be corrected will be described.

FIG. 3 shows the process of generating an ink droplet ID from the ink column IP ejected from the nozzle 23. As shown in FIG. As shown in FIG. 1, since the gun 2 is grounded, the ink column IP ejected from the nozzle 23 is also held at a potential of 0V. When a positive pulse voltage is applied to the charging electrode 3, a negative charge is induced in the ink column IP. Then, as shown in FIG. 3, when the ink column IP separates into ink droplets ID, a negative charge remains in the ink droplets, and thereafter the ink droplets continue to fly in a charged state.

The flying ink droplets ID are deflected upward according to the charge amount by the DC voltage applied to the deflection voltage 5, and collide with the surface of the printing material 11 to form print dots. In the following description, by changing the voltage applied to the charging electrode 3, a print dot is formed at a target position, so this voltage will be referred to as a "target print voltage".

FIG. 4 shows an example of printing when the number "01234" is printed without correcting the printing distortion. In the drawing, the matrix-shaped frames indicate positions where print dots are formed. The reason why the vertical lines of the matrix are slanted is that the printed material moves by one pitch in the horizontal direction while the ink droplets for one stroke are deflected in the vertical direction.

In the figure, the ◯ mark indicates the position of the print dot specified by the print data, and the ● mark indicates the position of the actually printed print dot.

In FIG. 4, when the print dots are continuous in the vertical direction as indicated by arrow A, the preceding ink droplet is pushed down by the coulomb force due to the large charge amount of the succeeding ink droplet, and the print dot is formed. It protrudes below the print frame. Similarly, as indicated by arrow B, the positions of the printed dots are shifted downward, and the contours of the printed numbers are distorted. As a result of these, print quality is degraded.

In the present embodiment, in order to prevent the deterioration of print quality described above, when the number of print dots in one stroke of print data continues exceeding a predetermined value, the number of print dots formed on the printed material is reduced to thinning out. Furthermore, the target print voltage is maintained to form the highest and lowest print dots, and the target print voltage is set so that other print dots are distributed between the highest and lowest print dots. Correcting.

Print distortion is caused by Coulomb force, air resistance, and various other factors, which affect each other. is not specifically mentioned.

Correction of print distortion according to the present embodiment will be specifically described below with reference to FIGS. 5 to 8. FIG.

FIG. 5 is a diagram in which only blocks related to print distortion correction are extracted from among the functional blocks of the controller 10 described above. The controller 10 includes a control section 11 , a storage section 12 , an input/display section 13 , a D/A conversion section 14 and an amplification section 15 .

Among these, the functions of the control unit 11 are realized by executing a program stored in the storage unit 12 by a CPU (not shown). The input/display unit 13 is implemented by a touch panel type liquid crystal display, and displays input print data and the like.

The target printing voltage set by the control section 11 is converted into an analog signal by the D/A conversion section 14 , amplified by the amplification section 15 , and then applied to the charging electrode 3 .

FIG. 6 is a flow chart showing an algorithm for correcting the print distortion described above. FIG. 7 is a diagram showing print data in main steps of the flow chart of FIG. 6, and FIG. 8 is a diagram showing a comparison of print examples before and after correction.

In the following explanation, it is assumed that the numeral "0" is printed on the surface to be printed. FIG. 7(a) shows the print data of the number "0" stored in the storage unit 12 of the controller 10. As shown in FIG. The print data is represented by a matrix-shaped frame, in which the horizontal axis indicates the horizontal position of the printed material, and the vertical axis indicates the landing position of the deflected ink droplets.

The storage unit 12 stores a set of data on the printing dot formation position shown in FIG. 7A and data on the target printing voltage to be applied to the charging electrode 3. For each deflection (hereinafter referred to as “stroke”), the target printing voltage is read out to generate a stepped voltage signal, which is applied to the charging electrode 3 .

The material to be printed relatively moves at a constant speed in the horizontal direction, and when the first stroke position is reached, the ink droplets ejected from the nozzle 23 are deflected from the bottom to the top according to the amount of charge, and the designated area of the material to be printed is directed. A printed dot marked ● is formed at the position. When print dots for five strokes are formed as shown in FIG. 7A, printing of the number "0" is completed.

FIG. 8(a) shows a print example of the number "0" shown in FIG. 7(a) when printed without correcting the print distortion. As shown in the first and fifth strokes of the print example, when there are five consecutive print dots, the Coulomb force of the succeeding ink drop pushes down the leading ink drop, and the bottom print dot is the target. The contour of the printed number "0" is distorted.

In order to prevent this, in the present embodiment, it is checked whether or not each stroke of the print data contains continuous print dots. Check whether or not the value exceeds the value, and if it exceeds, the number of print dots is thinned out, the target print voltage that forms the highest and lowest print dots is maintained, and the other print dots are the highest and lowest. The target print voltage is corrected so that the dots are evenly arranged between the print dots.

By applying the above-described processing to the print data, it is possible to suppress the pushing down of the preceding ink droplets by the Coulomb force of the succeeding ink droplets, thereby preventing the printed characters from being distorted.

Correction of printing distortion will be specifically described based on the flow chart of FIG. First, the control unit 11 of the controller 10 extracts data of the first stroke from the print data read out from the storage unit 12 (step S1).

Subsequently, the control unit 11 checks whether or not the extracted data contains continuous print dots (step S2). It is determined whether or not the number is greater than or equal to A (step S3).

If it is determined in step S3 that the number of consecutively printed dots is equal to or greater than A (natural number) (Yes), the controller 11 subtracts the parameter B (natural number) from the number of printed dots (step S5).

FIG. 7B shows a state in which print dots are thinned out. In this embodiment, 5 is set as the number A of continuous print dots, and 1 is set as the parameter B. FIG. In the first stroke, since five print dots are continuous, one of them is thinned out as shown in FIG. 7(b).

On the other hand, in step S2, as shown in the second stroke in FIG. 7A, if there is no consecutive print dot number (No), or if the number of consecutive print dots is less than 4 in step S3 (No) , it is determined that the influence of the coulomb force of the succeeding ink droplet is small, and the control unit 11 applies the normal target printing voltage previously stored in the storage unit 12 as the target printing voltage (step S4).

Next, the control unit 11 corrects the printing distortion due to the Coulomb force by correcting the printing positions of the remaining four printing dots of (AB) (steps S6 and S7).

FIG. 7(b) shows remaining print dots excluding the thinned print dots. When printing is executed based on the print data shown in FIG. 7B, the print distortion can be reduced, but the effect is not sufficient because four continuous print dots remain.

Therefore, in the present embodiment, as shown in FIG. 7(c), the position data of the highest and lowest print dots among the four continuous print dots are the highest and lowest of the initial five print data. positional data of the print dots are used. Furthermore, in this embodiment, the remaining two print dots are arranged evenly between the uppermost and lowermost print dots, and the interval between the print dots is widened to minimize the effect of the Coulomb force between the ink droplets. kept to a limit.

In the present embodiment, in order to execute the above-described processing in a short period of time, the print dots of (AB-2) are uniform when the values of the number A of continuous print dots and the interval parameter B are changed. is calculated and stored in the storage unit 12 as a table. Therefore, the control unit 11 only needs to read out the target printing voltage for the print dots corresponding to the numbers A and B from the table and apply the read value to the charging electrode 3 as the target printing voltage each time a stroke is printed.

In the actual process, in the flowchart of FIG. is taken out (step S6). Further, the control unit 11 reads the target print voltage for the remaining two print dots when A=5 and B=1 from the above table, and corrects the target print voltage to the read value (step S7).

Depending on the print data, continuous print dots may exist in two or more locations. In such a case, the process returns to step S2 (No in step S8), and the processes of steps S3 to S7 are repeated for further continuous print dots.

After the processing of steps S2 to S8 has been completed for all print data of one stroke (Yes in step S8), the control unit 11 generates stepped voltage signals based on the data read out in steps S4, S6 and S7. (S9) and applied to the charging electrode 3.

The control unit 11 repeats the processing of steps S1 to S9 for five strokes forming a character (No in step S10), and completes printing on the printing material (Yes in step S10).

FIG. 8(b) shows a printed example of the numeral "0" corrected for printing distortion in this way. Compared to the print example in which print distortion is not corrected shown in FIG. It can be seen that the print quality is improved.

As described above, by using the print distortion correcting means according to the present embodiment, the print distortion caused by the Coulomb force between ink droplets can be minimized, and the print quality can be greatly improved.

In this embodiment, the case of printing the numeral "0" has been described, but the correction of printing distortion is not limited to this. For example, if the printing distortion correcting means according to the present invention is applied to the number "1", a part of the character protrudes below the printing frame as in the printing example shown in FIG. It will not collapse.

Further, in the present embodiment, a case has been described in which the remaining thinned print dots are evenly arranged between the uppermost and lowermost print dots. should be distributed in a small range.

Furthermore, in the present embodiment, print data in which print dots are arranged in a 7×8 frame has been described, but the print distortion correcting means according to the present invention is not limited to this, and a larger matrix or a smaller matrix It can also be applied to print data arranged in The numbers A and B at that time may be appropriately set based on the printing result.

REFERENCE SIGNS LIST 1 inkjet printer 2 gun 3 charge electrode 4 detection electrode 5 deflection electrode 6 gutter 7 pipe 8a, 8b pump 9 ink tank 10 controller 11 control section 12 storage section 13 input/display section 14 D/A conversion section 15 amplification section 21 gun body 22 Ultrasonic transducer 23 Nozzle 31 Pulse power supply 51 DC power supply

Claims (3)

a gun that vibrates the ejected ink at a constant frequency to generate continuous ink droplets;
a charging electrode for charging the ink droplets by applying a stepped voltage synchronized with the cycle of the ink droplets;
a deflecting electrode that deflects the ink droplets flying toward the printing material moving in the horizontal direction in the vertical direction according to the degree of electrification so that the ink droplets land on the printing material;
a controller that controls the amount of charge on the ink droplets by changing the voltage applied to the charging electrode;
An inkjet printer that forms characters by printing dots of a plurality of strokes attached to a material to be printed,
The controller reads out print data that determines the positions at which print dots adhere to the material to be printed. While thinning out the number of print dots to be formed, the target print voltage for forming the uppermost and lowermost print dots is maintained, and other print dots are dispersed between the uppermost and lowermost print dots. and correcting the target print voltage so that the target print voltage is positioned at the Assuming that the number of print dots arranged in succession is A (A is a natural number) and the number of print dots to be thinned out is B (B is a natural number), (AB-2) print dots are the maximum number. 2. An inkjet printer according to claim 1, wherein said target print voltage is corrected so that it is evenly arranged between upper and lower print dots. The controller comprises a table storing target print voltages for generating (AB-2) print dots evenly arranged between the uppermost and lowermost print dots,
3. The inkjet printer according to claim 2, wherein said controller reads out said target print voltage from said table each time print data for one stroke is processed, and replaces said target print voltage with the target print voltage of said print data prepared in advance.

Images