JP2003103780A - Head driving unit for ink-jet printer, and driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head driving unit for an ink-jet printer capable of improving the printing quality at the time of black color printing in a simple configuration, and to provide a head driving method. SOLUTION: The head driving unit 10 for an ink-jet printer comprises a driving voltage setting circuit for setting a driving signal at the optimum voltage for a piezoelectric element for a black color printing nozzle (black color printing optimum driving voltage) at the time a black color printing operation is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention drives a piezoelectric element provided corresponding to a nozzle of each color for ejecting ink droplets of each color based on one head drive circuit in a head of an ink jet printer. The present invention relates to a technique for driving the head of the ink jet printer.

[0002]

2. Description of the Related Art Conventionally, as an output device of a computer, an ink jet type color printer of a type that ejects ink of several colors from a recording head has been widely used, and an image processed by a computer or the like is printed in multiple colors and multiple gradations. It is widely used to For example, in an ink jet printer using a piezoelectric element as a driving element for ejecting ink, each piezoelectric element provided corresponding to a plurality of nozzles of a print head is selectively driven to generate each piezoelectric element. Ink droplets are ejected from the nozzles based on the dynamic pressure of the element, and the ink droplets are made to adhere to the printing paper, thereby forming dots on the printing paper and performing printing.

Here, each piezoelectric element is provided corresponding to a nozzle for ejecting an ink droplet, and the driver I
It is driven by a drive signal supplied from C (head drive circuit) to eject ink droplets.

[0004]

By the way, in the low-priced ink jet printer, in order to reduce the cost, the piezoelectric element corresponding to the nozzle row of each color is driven based on one driving circuit. Has been done. On the other hand, in the nozzle rows of the respective colors, variations in the nozzle shape, the characteristics of the piezoelectric elements, and the like cause variations in the ejection amount of ink droplets with respect to the driving voltage of the piezoelectric elements.

For this reason, information about the drive voltage (drive voltage information) according to each drive waveform mode (drive voltage information) is held in the control unit of the printer main body at the time of assembly of each ink jet printer. The drive voltage information is read when the power of the inkjet printer is turned on or when printing is started, and the piezoelectric elements are drive-controlled by the optimum drive voltage for all the nozzles. As a result, the ink droplet ejection amounts of the nozzle rows of each color are averaged, and the color print quality is improved.

However, when the piezoelectric elements corresponding to such nozzle rows are driven and controlled by the optimum drive voltage, the piezoelectric elements corresponding to the nozzle rows for black printing also become
In the same manner, the drive is controlled by the optimum drive voltage of all the nozzles.

Therefore, especially in the case of printing only in black, the optimum driving voltage of the piezoelectric element corresponding to the nozzle row for black printing is larger than the optimum driving voltage for color due to the variation in the nozzle row for black printing. In the case of deviation, the ejection amount of black ink droplets may increase or decrease from the optimum amount. Therefore, when the ejection amount of the black ink droplets is small, white streaks occur in the printing, and when the ejection amount of the black ink droplets is large, the printing bleeding occurs and the print quality is deteriorated. There was a problem that it would decrease.

SUMMARY OF THE INVENTION An object of the present invention is to provide a head driving device and a head driving method for an ink jet printer, which has a simple structure to improve print quality during black printing.

[0009]

In order to solve the above problems, in the present invention, at the time of black printing, the piezoelectric element corresponding to the nozzle row for black printing is driven and controlled with a drive voltage most suitable for black printing. did.

That is, in the head drive device of the ink jet printer according to the first aspect, the piezoelectric element for applying pressure to the ink provided corresponding to each of the plurality of nozzles is provided.
A head drive device for an inkjet printer, which is driven by a drive signal from one head drive circuit selectively at a predetermined print timing to eject ink droplets from a corresponding nozzle to perform recording. A drive voltage setting circuit for setting a drive signal to an optimum drive voltage (black print optimum drive voltage) for the piezoelectric element of the black printing nozzle is characterized by being provided.

According to another aspect of the present invention, there is provided a head driving method for an ink jet printer in which a piezoelectric element that applies pressure to ink provided corresponding to each of the plurality of nozzles is selectively used as a head at a predetermined printing timing. A method for driving a head of an inkjet printer, which is driven by a drive signal from a drive circuit, and ejects ink droplets from a corresponding nozzle to perform recording. During black printing, the drive signal is black-printed by a drive voltage setting circuit. A method for driving a head of an ink jet printer, comprising setting an optimum drive voltage for a piezoelectric element of a cleaning nozzle.

According to this structure, during black printing,
The drive signal is set by the drive voltage setting circuit to an optimum drive voltage for the piezoelectric element of the black printing nozzle. As a result, the piezoelectric element of the black printing nozzle is Since the drive is controlled with the optimum drive voltage for the nozzle, the black ink droplets are ejected from this nozzle at the optimum ejection amount and printed, so that white stripes and bleeding do not occur during black printing The quality will be improved.

According to another aspect of the present invention, in the head drive device, the drive voltage setting circuit detects a black print and sets an optimum black print drive voltage when the print mode is the black print mode. To do.

According to a ninth aspect of the present invention, in the head driving method, the driving voltage setting circuit detects black printing and sets an optimum black printing driving voltage when the printing mode is the black printing mode. To do.

According to this structure, the drive voltage setting circuit is
Since the drive voltage is set to the optimum drive voltage for black printing in the black print mode, the piezoelectric element of the black printing nozzle is drive-controlled at the optimum drive voltage for this nozzle.

Therefore, in the black printing mode, the black ink droplets are ejected from this nozzle at the optimum ejection amount,
Since printing is performed, white lines and bleeding do not occur during black printing, and print quality is improved.

According to another aspect of the present invention, the drive voltage setting circuit detects black printing and sets an optimum black printing driving voltage when the print data for one scan is only black. Is characterized by.

According to a tenth aspect of the present invention, in the head driving method, the driving voltage setting circuit detects black printing and sets an optimum black printing driving voltage when print data for one scan is only black. Is characterized by.

According to this structure, the drive voltage setting circuit is
When the print data for one scan is black print only, the drive voltage is set to the optimum drive voltage for black print, so the piezoelectric element of the black print nozzle is drive-controlled with the optimum drive voltage for this nozzle. become. Therefore,
Print data for one scan is black print only In the black print mode, black ink droplets are ejected and printed from this nozzle at an optimum discharge amount, so white stripes and blurring occur during black print during this one scan. Without increasing the print quality.

According to another aspect of the present invention, the drive voltage setting circuit sets the black print optimum drive voltage based on the drive voltage information set for each color.

According to the eleventh aspect of the present invention, in the head driving method, the driving voltage setting circuit sets the optimum black printing driving voltage based on the driving voltage information set for each color.

According to this configuration, when the driving voltage information is set for each color, the driving voltage setting circuit determines the optimum black printing driving voltage based on the driving voltage information set for black printing. By setting, the piezoelectric element of the black printing nozzle is drive-controlled with an optimum drive voltage for this nozzle.

According to a fifth aspect of the present invention, in the head drive device, the drive voltage setting circuit sets the optimum black print drive voltage based on the drive voltage information set for each column.

According to a twelfth aspect of the present invention, in the head driving method, the driving voltage setting circuit sets the optimum black printing driving voltage based on the driving voltage information set for each column.

According to this configuration, when the drive voltage information is set for each column, the drive voltage setting circuit is configured to optimize the black printing based on the drive voltage information set for the nozzle column for black printing. By setting the drive voltage, the piezoelectric element of the black printing nozzle is drive-controlled with the optimum drive voltage for this nozzle.

According to another aspect of the present invention, there is provided a plurality of black printing nozzles in the head drive device, and the drive voltage setting circuit sets the black of each line based on the drive voltage information set for each line. The black printing optimum driving voltage is set as an average value of the printing optimum driving voltage.

In the head driving method according to the thirteenth aspect, a plurality of nozzles for black printing are provided in a plurality of columns, and the drive voltage setting circuit sets the black of each column based on the drive voltage information set for each column. The black printing optimum driving voltage is set as an average value of the printing optimum driving voltage.

According to this structure, when a plurality of black printing nozzles are provided and the driving voltage information is set for each row, the driving voltage setting circuit causes the black printing nozzles to be arranged for each nozzle row. Based on the drive voltage information set in, by setting the average value of the black print optimum drive voltage of each nozzle row as the black print optimum drive voltage, the piezoelectric element of the black printing nozzle of each nozzle row,
Drive control is performed with an optimum drive voltage for this nozzle.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. The embodiment described below is
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

FIG. 1 is a diagram showing a hardware configuration of an ink jet printer according to an embodiment of the present invention. In FIG. 1, the printer controller 2 is a control board mounted in the printer, and causes the print engine 3 to execute a printing operation according to the data input from the interface device 4. CPU (Central Processi
ng Unit: central processing unit, ROM (Read On)
By executing a program stored in a ly memory (read-only storage element) 21, each unit in the printer controller 2 is controlled. The main bus of the printer controller 2 has a RAM serving as a main storage device of the CPU 23.
(Random Access Memory) 22
And PROM (Progra
mable ReadOnly Memory: a rewritable read-only memory element) 24 is connected.

Custom IC in the printer controller 2
The chip 26 actually sends various signals to the print engine 3 according to the print command interpreted by the CPU 23 to operate it. That is, the custom IC chip 26 plays a role as an engine control unit that controls the printing drive of the printer.

The motor drive signal sent from the custom IC chip 26 via the signal line 28 causes the motor 29 to feed the printing paper, and moves the carriage 30 on which the head unit 31 is mounted.

The transmission path 32 is a bus line having a bit width corresponding to the number of nozzles mounted on the print head, and based on the image buffer data developed in the RAM 23, ink ejection or ejection of each nozzle is performed. A stop signal is sent to the print head. At this time, the drive voltage of the print head follows the analog voltage waveform generated by the D / A converter 33.

The analog signal for determining the size of the ink particle is once sent to the D / A converter 33 in the form of a collection of digital vector data. Here, the digital signal is converted into an analog trapezoidal wave, an example of which is shown in FIG. 2, and then sent to the ink nozzle driving switching element 35.

FIG. 3 shows, as an example of a typical ink jet printer, a system in which ink is ejected from a nozzle by utilizing the expansion action of a piezoelectric element.
The structure of the head drive circuit is shown. In FIG. 3, each switching element 35 (n of 35 to 1 to 35) has two inputs of digital and analog, and an analog drive signal according to these inputs is provided to the piezoelectric element 37 (1 to 37 of 37).
To n). One of the input signal lines of each switching element 35 is a digital input signal line 3 which represents the state of ink ejection and ejection stoppage at the nozzle.
It is 2. The digital input signal line 32 is connected to the input from the custom IC chip 26 (see FIG. 1). Data serially input from the custom IC chip 26 is continuously transferred to each shift register 41 (n of 41 to 41), latched at a predetermined timing, and input to each switching element 35.

The other input signal line of the input signal lines of each switching element 35 is input from the transistor 34 (see FIG. 1) and is an analog waveform for determining the size of ink particles to be ejected. It is an input signal line.

FIG. 4 shows the structure of a head drive device in an ink jet printer according to an embodiment of the present invention. In FIG. 4, the head driving device 100 includes a piezoelectric element 37 and a piezoelectric element 37, each of which is provided corresponding to a nozzle row of, for example, four colors of an inkjet printer.
7, a head drive circuit 112 for supplying a drive signal to one of the electrodes 37a of the seven electrodes, and a current amplifier circuit 11 provided between the head drive circuit 112 and each piezoelectric element 37.
3, switching circuit 135 and drive voltage setting circuit 12
It is composed of 0 and 0.

Here, in FIG. 4, the piezoelectric element 37 is used.
In fact, in the head of the inkjet printer, as described above, one nozzle row is provided for each color, and a plurality of piezoelectric elements 37 (1 to 37 of 37) are provided for each nozzle row. n) are provided. That is, for the black printing nozzle row B shown in FIG. 5, the piezoelectric element 37B (n of 37B 1 to 37B [not shown]) is used, and for the cyan printing nozzle row C, the piezoelectric element 3B is used.
7C (n of 1 to 37C of 37C [not shown]), and the piezoelectric element 37M (37M) in the nozzle row M for magenta printing.
1-37M n (not shown)), the piezoelectric element 37Y (1-37 of 37Y) in the yellow printing nozzle row Y.
N (not shown) of Y) are provided respectively. still,
In the case of FIG. 5, only one black printing nozzle row B is provided.

The head drive circuit 112 is configured as a driver IC and generates a drive signal COM for the head of the ink jet printer, and is arranged, for example, in the printer body.

The current amplification circuit 113 is composed of two transistors 115 and 116. Of these, the collector of the first transistor 115 is connected to the constant voltage power source, and the base is connected to the output of the head drive circuit 112. As a result, it becomes conductive based on the signal from the head drive circuit 112 and is supplied to each piezoelectric element 37 via the switching circuit 135.

The emitter of the second transistor 116 has each switching element 3 of the switching circuit 135.
5, the base is connected to the output of the head drive circuit 112, and the collector is connected to the other electrode 37b of each piezoelectric element 37 as described later. As a result, the piezoelectric element 37 becomes conductive based on the signal from the head drive circuit 112, and the piezoelectric elements 37 are discharged through the switching circuit 135.

When the control signal is input, the switching circuit 135 is turned on at the drive timing of the corresponding piezoelectric element 37, and outputs the drive signal COM to each piezoelectric element 37. This switching circuit 13
Reference numeral 5 is actually configured as a so-called transmission gate 135a for turning on / off each piezoelectric element 37.

The drive voltage setting circuit 120 reads the drive voltage information for each color recorded in the printer head or the printer main body when the power is turned on or when printing is started, and the drive voltage information is supplied to the head drive circuit 112. Transmit to set drive voltage. At that time, when the print mode of the ink jet printer is set to the color print mode, the drive voltage setting circuit 120 calculates the average value of the drive voltage determined by the drive voltage information for each color, and The drive voltage average value is set as the drive voltage and output to the head drive circuit 112.

When the print mode of the ink jet printer is set to the black print mode, the drive voltage setting circuit 120 outputs the drive voltage information among the above drive voltage information.
The drive voltage set by the drive voltage information for black printing is set as the black print optimum drive voltage and is output to the head drive circuit 112.

The head drive device 100 according to one embodiment of the present invention is configured as described above, and operates as follows according to the flowchart of FIG. 6 based on the head drive method according to the present invention.

First, in step A1, when a print command is input from the printer body, the drive voltage setting circuit 120
Determines in step A2 whether the black print mode is selected in the print command.

When the black print mode is selected (Yes in step A2), the drive voltage setting circuit 120 determines the drive voltage (black) determined by the drive voltage information for black printing in step A3. The optimum print driving voltage) is set as the driving voltage and output to the head driving circuit 112.

After that, in step A4, printing is performed, and the piezoelectric element 37B of the black nozzle array is applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135. Black printing is performed by being driven and controlled by the driving voltage.

On the other hand, if the black print mode is not selected in step A2, that is, the color print mode is selected (No in step A2), the drive voltage setting circuit 120 proceeds to step A5. Then, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Then, in step A4, printing is executed and the piezoelectric elements 37B, 37C, 37 of the nozzle rows of each color are printed.
M and 37Y are connected to the switching circuit 13 from the head drive circuit 112 through the current amplification circuit 113, respectively.
Color printing is performed by being driven and controlled by the drive voltage applied via 5 (the average value of the drive voltage determined by the drive voltage information of each color).

In this way, in the case of black printing, printing is performed using the drive voltage (optimal black printing drive voltage) determined by the drive voltage information of the nozzle row for black printing as the drive voltage, and printing is performed. Since black printing is performed with the optimum discharge amount of ink drops,
No white lines or bleeding will occur.

On the other hand, in the case of color printing, printing is performed using the average value of the drive voltage determined by the drive voltage information of the nozzle row for each color as the drive voltage, as in the conventional ink jet printer. As a result, color printing with good color balance is performed.

FIG. 7 shows the structure of the nozzles of the head drive unit according to the second embodiment of the present invention. In FIG. 7, the head drive device 300 has substantially the same configuration as the head drive device 100 shown in FIG. 4, and is different only in the following points.

That is, in the head drive device 300,
The printing nozzles are provided with a plurality (three in the figure) of nozzle rows B1, B2, B3 for black printing, and each nozzle for color printing has one nozzle row, namely, A cyan printing nozzle array C, a magenta printing nozzle array M, and a yellow printing nozzle array Y are provided, and each nozzle array B1, B2, B3, C,
Plural piezoelectric elements (not shown) for M and Y
Is provided.

Then, when the print mode of the ink jet printer is set to the color print mode, the drive voltage setting circuit 120 calculates the average value of the drive voltage determined by the drive voltage information for each color. , The average value of the drive voltage is set as the drive voltage, and the head drive circuit 1
Output to 12.

When the print mode of the ink jet printer is set to the black print mode, the drive voltage setting circuit 120 outputs the drive voltage information among the above drive voltage information.
The average value of the driving voltage set by the driving voltage information of each nozzle row for black printing is set as the optimum black printing driving voltage and is output to the head driving circuit 112.

According to the head driving device 300 having such a configuration, the head driving method according to the present invention is used, and the head driving method shown in FIG.
It operates as follows according to the flowchart in FIG.

First, in step B1, when a print command is input from the printer body, the drive voltage setting circuit 120
Determines in step B2 whether the black print mode is selected in the print command.

When the black print mode is selected (Yes in step B2), the drive voltage setting circuit 120 determines in step B3 the drive voltage information regarding each nozzle row for black printing. The average value of each drive voltage (optimum drive voltage for black printing) is set as a drive voltage and output to the head drive circuit 112.

After that, in step B4, printing is executed and the plurality of piezoelectric elements 37B1 and 37B of the black nozzle row are printed.
B2 and 37B3 (not shown) are the head drive circuit 112.
The black printing is performed by being driven and controlled by the black printing optimum driving voltage applied from the current amplification circuit 113 through the switching circuit 135.

On the other hand, if the black print mode is not selected in step B2, that is, if the color print mode is selected (No in step B2), the drive voltage setting circuit 120 proceeds to step B5. Then, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Then, in step B4, printing is executed and the piezoelectric elements 37 (B1, B2, B
3), 37C, 37M, and 37Y are applied to the drive voltage from the head drive circuit 112 via the current amplification circuit 113 and the switching circuit 135 (average drive voltage determined by the drive voltage information of each color). value)
The color printing is performed by being driven and controlled by.

Thus, in the case of black printing, printing is performed with the average value of the drive voltages (black drive optimum drive voltage) determined by the drive voltage information of each nozzle row for black printing as the drive voltage. As a result, black printing is performed with an almost optimal ejection amount of black ink droplets, so that white stripes and bleeding do not occur.

On the other hand, in the case of color printing, printing is performed using the average value of the drive voltage determined by the drive voltage information of the nozzle row for each color as the drive voltage, as in the conventional ink jet printer. As a result, color printing with good color balance is performed.

FIG. 9 shows the structure of the nozzles of the head drive unit according to the third embodiment of the present invention. In FIG. 9, the head drive device 400 and its nozzle have the same configuration as the head drive device 100 shown in FIG.
The configuration is different only in the following points.

That is, in this embodiment, the drive voltage setting circuit 120 does not set the drive voltage according to the print mode of the ink jet printer, but sets the drive voltage for each scan of the printer head during the printing operation. It is supposed to be set. Then, the drive voltage setting circuit 120
If the print data for one scan includes data for color printing, calculate the average value of the drive voltage determined by the drive voltage information for each color and use this drive voltage average value as the drive voltage. It is set and output to the head drive circuit 112.

If the print data for one scan consists only of black print data, the drive voltage setting circuit 120 sets the drive voltage set by the drive voltage information for black printing in the above drive voltage information. Is set as a black printing optimum drive voltage and is output to the head drive circuit 112.

According to the head driving apparatus 400 having such a structure, the head driving method according to the present invention is used, and the head driving method shown in FIG.
According to the flowchart of No. 0, it operates as follows.
First, when a print command is input from the printer body in step C1, the drive voltage setting circuit 120 causes
In step 2, it is determined whether the print data for one scan is only black print data.

If only the black print data is present, the drive voltage setting circuit 120 drives the drive voltage (black print optimum drive voltage) determined by the drive voltage information for black printing in step C3. It is set as a voltage and output to the head drive circuit 112.

Then, in step C4, printing for one scan is executed, and the piezoelectric element 37B of the black nozzle row is
Black printing is performed by being drive-controlled by the black printing optimum drive voltage applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135.

If color printing data is included in step C2, the drive voltage setting circuit 120
In step C5, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Then, in step C4, printing is executed, and the piezoelectric elements 37B, 37C, 37 of the nozzle rows of each color are printed.
M and 37Y are connected to the switching circuit 13 from the head drive circuit 112 through the current amplification circuit 113, respectively.
Color printing is performed by being driven and controlled by the drive voltage applied via 5 (the average value of the drive voltage determined by the drive voltage information of each color).

After printing with the print data for one scan, at step C6, if there is the next print data, the process returns to step C2 again, and the process is repeated for the print data for the next one scan. If there is no next print data in C6, the printing ends.

In this way, when the print data for one scan is only black print data, the drive voltage (black print optimum drive voltage) determined by the drive voltage information of the nozzle row for black printing is driven. Since printing is performed as a voltage, black printing is performed with an optimum discharge amount of black ink droplets, so that white stripes and bleeding do not occur.

On the other hand, when the print data for one scan includes the data for color printing, the drive voltage determined by the drive voltage information of the nozzle array for each color is the same as in the conventional ink jet printer. By performing the printing with the average value of (1) as the driving voltage, color printing with good color balance is performed.

FIG. 11 shows the structure of the nozzles in the head driving device according to the fourth embodiment of the present invention. In FIG. 11, the head drive device 500 and its nozzle have the same configuration as the head drive device 300 shown in FIG. 7, but differ only in the following points.

That is, in this embodiment, the drive voltage setting circuit 120 sets the drive voltage for each scan of the printer head during the printing operation. And
When the print data for one scan includes data for color printing, the drive voltage setting circuit 120 calculates the average value of the drive voltage determined by the drive voltage information for each color, and the average drive voltage is calculated. The value is set as a drive voltage and output to the head drive circuit 112.

When the print data for one scan consists only of black print data, the drive voltage setting circuit 120 sets the drive voltage information based on the drive voltage information of each nozzle row for black printing. The average value of the generated driving voltage is set as the black printing optimum driving voltage and is output to the head driving circuit 112.

According to the head driving device 500 having such a configuration, the head driving method according to the present invention is used, and the head driving method shown in FIG.
According to the flow chart of No. 2, it operates as follows.
First, in step D1, when a print command is input from the printer body, the drive voltage setting circuit 120 causes
In step 2, it is determined whether the print data for one scan is only black print data.

If only the black print data is present, the drive voltage setting circuit 120 determines in step D3 the average value of each drive voltage determined by the drive voltage information of each nozzle row for black printing (( The optimum driving voltage for black printing is set as the driving voltage, and the head driving circuit 112 is set.
Output to.

Thereafter, in step D4, printing for one scan is executed, and the piezoelectric element 37 (B
1, B2, B3) from the head drive circuit 112 via the current amplification circuit 113 and further to the switching circuit 135.
The black printing is performed by being driven and controlled by the black printing optimum driving voltage applied via the.

If color printing data is included in step D2, the drive voltage setting circuit 120
In step D5, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Then, in step D4, printing is executed, and the piezoelectric elements 37 (B1, B2, B) of the nozzle rows of each color are printed.
3), 37C, 37M, and 37Y are applied to the drive voltage from the head drive circuit 112 via the current amplification circuit 113 and the switching circuit 135 (average drive voltage determined by the drive voltage information of each color). value)
The color printing is performed by being driven and controlled by.

After the printing with the print data for one scan is completed, if there is the next print data in step D6, the process returns to step D2 again, and the process is repeated for the print data for the next one scan. If there is no next print data in D6, the printing ends.

In this way, when the print data for one scan is only black print data, the average value of each drive voltage determined by the drive voltage information of each nozzle row for black printing (black print optimum By performing the printing with the (driving voltage) as the driving voltage, the black printing is performed with an almost optimal ejection amount of the black ink droplets, so that white stripes and bleeding do not occur.

On the other hand, when the print data for one scan includes color print data, the drive voltage determined by the drive voltage information of the nozzle array for each color is the same as in the conventional ink jet printer. By performing the printing with the average value of (1) as the driving voltage, color printing with good color balance is performed.

Here, a configuration in which the head driving methods by the head driving devices 100 and 400 according to the first and third embodiments of the present invention are combined is also possible. in this case,
The head drive of the head drive device is performed as follows according to the flowchart shown in FIG.

That is, in FIG. 13, first, step E
When a print command is input from the printer body at 1, the drive voltage setting circuit 120 determines at step E2 whether the black print mode is selected in the print command.

When the black print mode is selected (Yes in step E2), the drive voltage setting circuit 120 determines the drive voltage (black) determined by the drive voltage information for black printing in step E3. The optimum print driving voltage) is set as the driving voltage and output to the head driving circuit 112.

After that, in step E4, printing is executed, and the black printing optimum in which the piezoelectric element 37B of the black nozzle row is applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135. Black printing is performed by being driven and controlled by the driving voltage.

If the color print mode is selected in step E2, the drive voltage setting circuit 120 is selected.
Determines in step E5 whether the print data for one scan is only black print data.

If only the black print data is present, the drive voltage setting circuit 120 drives the drive voltage (black print optimum drive voltage) determined by the drive voltage information for black print in step E6. It is set as a voltage and output to the head drive circuit 112.

Thereafter, in step E7, printing for one scan is executed, and the piezoelectric element 37B of the black nozzle row is
Black printing is performed by being drive-controlled by the black printing optimum drive voltage applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135.

If color printing data is included in step E5, the drive voltage setting circuit 120
In step E8, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Then, in step E7, printing is performed and the piezoelectric elements 37B, 37C, 37 of the nozzle rows of each color are printed.
M and 37Y are connected to the switching circuit 13 from the head drive circuit 112 through the current amplification circuit 113, respectively.
Color printing is performed by being driven and controlled by the drive voltage applied via 5 (the average value of the drive voltage determined by the drive voltage information of each color).

After the printing with the print data for one scan is completed, if there is the next print data in step E9, the process returns to step E5 again, and the process is repeated for the print data for the next one scan, and the step is repeated. If there is no next print data at E9, the printing ends.

As described above, in the black printing mode, printing is performed by using the driving voltage determined by the driving voltage information of the nozzle row for black printing (black printing optimum driving voltage) as the driving voltage. Since black printing is performed with the optimum discharge amount of black ink droplets, white stripes and bleeding do not occur.

On the other hand, in the color printing mode, when the print data for one scan is only the black print data, the driving similarly determined by the driving voltage information of the nozzle row for black printing is performed. Printing is performed with the voltage (black drive optimum drive voltage) as the drive voltage,
When the color print data is included, printing is performed using the average value of the drive voltage determined by the drive voltage information of the nozzle row for each color as the drive voltage, as in the case of the conventional ink jet printer, thereby performing color balance. Good color printing is performed.

On the other hand, it is possible to combine the head driving methods of the head driving devices 100 and 400 according to the second and fourth embodiments of the present invention. In this case, the head drive of the head drive device is performed as follows according to the flowchart shown in FIG.

That is, in FIG. 14, first, step F
When the print command is input from the printer main body at 1, the drive voltage setting circuit 120 determines at step F2 whether the black print mode is selected in the print command.

When the black print mode is selected (Yes in step F2), the drive voltage setting circuit 120 determines the drive voltage information of each nozzle row for black printing in step F3. The average value of each drive voltage (optimum drive voltage for black printing) is set as a drive voltage and output to the head drive circuit 112.

Thereafter, in step F4, printing is performed, and the black nozzle array piezoelectric element 37B is applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135 to optimize black printing. Black printing is performed by being driven and controlled by the driving voltage.

On the other hand, if the black print mode is not selected in step F2, that is, if the color print mode is selected (No in step F2), the drive voltage setting circuit 120 proceeds to step F5. Then, it is determined whether the print data for one scan is only black print data.

If only the black print data is present, the drive voltage setting circuit 120 determines in step F6 the average value of each drive voltage (the drive voltage information determined by the drive voltage information of each nozzle row for black printing). The optimum drive voltage for black printing is set as the drive voltage, and the head drive circuit 112 is set.
Output to.

Then, in step F7, printing for one scan is executed, and the piezoelectric element 37B of the black nozzle row is
Black printing is performed by being drive-controlled by the black printing optimum drive voltage applied from the head drive circuit 112 through the current amplification circuit 113 and further through the switching circuit 135.

If color printing data is included in step F5, the drive voltage setting circuit 120
In step F8, the average value of the drive voltage determined by the drive voltage information for each color is set as the drive voltage and output to the head drive circuit 112.

Thereafter, in step F7, printing is executed, and the piezoelectric elements 37B, 37C, 37 of the nozzle rows of each color are printed.
M and 37Y are connected to the switching circuit 13 from the head drive circuit 112 through the current amplification circuit 113, respectively.
Color printing is performed by being driven and controlled by the drive voltage applied via 5 (the average value of the drive voltage determined by the drive voltage information of each color).

After the printing with the print data for one scan is completed, if there is the next print data in step F9, the process returns to the above step F5 again, and the process is repeated for the print data for the next one scan. If there is no next print data in F9, the printing ends.

As described above, in the black print mode, printing is performed by using the drive voltage determined by the drive voltage information of the nozzle row for black printing (black print optimum drive voltage) as the drive voltage. Since black printing is performed with the optimum discharge amount of black ink droplets, white stripes and bleeding do not occur.

On the other hand, in the color printing mode, when the print data for one scan is only the black print data, the driving similarly determined by the driving voltage information of the nozzle row for black printing is performed. Printing is performed with the voltage (black drive optimum drive voltage) as the drive voltage,
When the color print data is included, printing is performed using the average value of the drive voltage determined by the drive voltage information of the nozzle row for each color as the drive voltage, as in the case of the conventional ink jet printer, thereby performing color balance. Good color printing is performed.

Therefore, according to the head driving method described with reference to the flow charts of FIGS. 13 and 14, when the printing mode of the ink jet printer is the black printing mode, the driving voltage is always set to the black printing mode. By setting the drive voltage determined based on the drive voltage information of the nozzle row or the average value thereof, it is not necessary to reset the drive voltage during printing, and printing can be performed easily and in a short time. Become.

When the print mode of the ink jet printer is the color print mode, the drive voltage is set to the nozzle row for black printing only when the print data for one scan is only the data for black printing. It is possible to improve the quality of black printing by setting the drive voltage determined based on the drive voltage information of 1 or its average value.

In the above-described embodiment, the piezoelectric element 3
For example, a piezo element is used as 7, but the piezoelectric element is not limited to this, and other piezoelectric elements such as an electrostrictive element and a magnetostrictive element may be used. Further, in the above-described embodiment,
Although the ink jet printer that performs so-called four-color printing has been described, it is obvious that the present invention can be applied to, for example, an ink jet printer that performs four or more color printing.

Further, in the above-described embodiment, when color printing is performed, the average value of the drive voltage of each color is used as the drive voltage. However, the optimum drive voltage for all nozzles is stored in advance in a memory or the like, and The same effect can be obtained by reading the optimum driving voltage and performing color printing. Further, the value of the driving voltage for each color may be divided and the ratio may be stored in a memory or the like.

[0115]

As described above, according to the present invention, at the time of black printing, the driving signal is set to the optimum driving voltage for the piezoelectric element of the black printing nozzle by the driving voltage setting circuit. As a result, as compared with the conventional case where the piezoelectric element of the black printing nozzle is driven and controlled by the optimum driving voltage of the piezoelectric element of each color nozzle for color printing, the piezoelectric element of the black printing nozzle is Since this nozzle is driven and controlled with an optimum drive voltage, black ink droplets are ejected from this nozzle at an optimum ejection amount and printed, so white stripes and bleeding do not occur during black printing, Print quality is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a hardware configuration of an inkjet printer according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a trapezoidal waveform for driving a head in the form of a graph.

FIG. 3 is a diagram for explaining how to generate the waveform shown in FIG. 2 using both a digital signal and an analog signal.

FIG. 4 is a block diagram showing a configuration of a first embodiment of a head drive device according to the present invention.

5 is a schematic diagram showing a configuration of a nozzle row in the head drive device of FIG.

6 is a flowchart showing the operation of the head drive device of FIG.

FIG. 7 is a schematic diagram showing the configuration of a nozzle row in a second embodiment of the head drive device according to the present invention.

8 is a flowchart showing the operation of the head drive device of FIG.

FIG. 9 is a schematic diagram showing the configuration of a nozzle row in a third embodiment of the head drive device according to the present invention.

10 is a flowchart showing the operation of the head drive device of FIG.

FIG. 11 is a schematic diagram showing a configuration of a nozzle row in a fourth embodiment of the head drive device according to the present invention.

12 is a flowchart showing the operation of the head drive device of FIG.

FIG. 13 is a flowchart showing an operation by a combination of the head drive devices of FIGS. 4 and 9.

FIG. 14 is a flowchart showing an operation by a combination of the head drive devices of FIGS. 7 and 11.

[Explanation of symbols]

10, 30, 40, 50 Head drive device 37 Piezoelectric element 37a One electrode 37b Ground side electrode 112 head drive circuit 113 Current amplification circuit 135 switching circuit 120 drive voltage setting circuit

Claims (13)

[Claims] 1. A piezoelectric element for applying pressure to ink provided corresponding to each of a plurality of nozzles is selectively driven at a predetermined printing timing by a drive signal from one head drive circuit, and the corresponding nozzle is driven. An inkjet printer head drive that ejects ink droplets for recording. When black print is detected, the drive signal is set to the optimum drive voltage (black print optimum drive voltage) for the piezoelectric element of the black print nozzle. A head drive device for an ink jet printer, comprising: a drive voltage setting circuit for 2. The inkjet according to claim 1, wherein the drive voltage setting circuit detects black printing and sets a black print optimum drive voltage when the print mode is the black print mode. Drive device for digital printer. 3. The drive voltage setting circuit detects black printing and sets an optimum drive voltage for black printing when print data for one scan is only black printing. A head drive device for an ink jet printer according to item 1. 4. The driving voltage setting circuit according to claim 1, wherein the driving voltage setting circuit sets a black printing optimum driving voltage based on driving voltage information set for each color. Head drive device for inkjet printer. 5. The driving voltage setting circuit according to claim 1, wherein the driving voltage setting circuit sets a black printing optimum driving voltage based on driving voltage information set for each column. Head drive device for inkjet printer. 6. A plurality of rows of black printing nozzles are provided, and the drive voltage setting circuit calculates the average value of the optimum black printing drive voltage of each row based on the drive voltage information set for each row. The head driving device for an inkjet printer according to claim 5, wherein an optimum driving voltage for black printing is set. 7. An inkjet printer comprising the head drive device according to claim 1. Description: 8. A piezoelectric element for applying pressure to ink provided corresponding to each of the plurality of nozzles is selectively driven at a predetermined printing timing by a drive signal from one head drive circuit, and the corresponding nozzle is driven. A method for driving a head of an ink jet printer that ejects ink droplets for recording, wherein during black printing, the drive voltage setting circuit sets the drive signal to the optimum drive voltage for the piezoelectric element of the black printing nozzle. A method for driving a head of an inkjet printer, comprising: 9. The inkjet according to claim 8, wherein the drive voltage setting circuit detects black printing and sets an optimum drive voltage for black printing when the print mode is a black print mode. Method for driving heads of digital printers. 10. The drive voltage setting circuit detects black printing and sets an optimum drive voltage for black printing when print data for one scan is only black printing. 7. A method for driving a head of an ink jet printer according to item 1. 11. The black printing optimum drive voltage is set on the basis of the drive voltage information set for each color by the drive voltage setting circuit, according to claim 8. A method for driving a head of an inkjet printer. 12. The driving voltage setting circuit according to claim 8, wherein the driving voltage setting circuit sets a black printing optimum driving voltage based on driving voltage information set for each column. A method for driving a head of an inkjet printer. 13. A plurality of rows of black printing nozzles are provided, and the drive voltage setting circuit calculates the average value of the optimum black printing drive voltage of each row based on the drive voltage information set for each row. The method for driving a head of an ink jet printer according to claim 12, wherein an optimum driving voltage for black printing is set.