JP3467666B2 - Drive control method for inkjet printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control method for an ink jet printer, and more particularly, to a method for controlling an ink jet head in an ink jet printer having an ink jet head having a plurality of ink nozzles. The present invention relates to a drive control method suitable for extending the life. 2. Description of the Related Art In general, an ink jet printer has an ink jet head having a large number of ink nozzles arranged in the direction of conveyance of a recording medium in a row direction (a direction orthogonal to the direction of conveyance of the recording medium). It is moved so that printing is performed line by line. The number of ink nozzles of such an ink jet head is generally larger than the number of nozzles (dot number) used for printing one line, and the range of the ink nozzle group used for printing each line is fixed. For example, in an ink jet head having 64 dot ink nozzles, the third to 39 th ink nozzle groups are driven to perform line printing. [0004] For this reason, even though the unused ink nozzles can be used sufficiently, the life of the ink nozzle group that is always used expires before the other ink nozzles. In addition, even among the ink nozzle groups that are always in use, there is a variation in the frequency of use between them, and if the frequency of use of specific ink nozzles is extremely high, they will end their life first. For this reason, it is necessary to shorten the life of the entire inkjet head having the conventional ink nozzle group, which is not economical. In view of this point, for example, Japanese Patent Application Laid-Open No. 5-64
In Japanese Patent No. 891, the range of the used ink nozzle group of the ink nozzle group of the inkjet head is moved stepwise every time one line is printed. For this purpose, the transport amount of the recording medium is switched stepwise every time one line is printed. As described above, by gradually changing the range of the used ink nozzle group among the ink nozzle groups, the difference in the frequency of use of each ink nozzle is reduced, the deterioration of print quality is suppressed, and the life of the inkjet head is extended. Like that. However, in such a method of moving the range of the used ink nozzle group of the ink nozzle groups every time one line is printed, the actual method of using the used ink nozzle groups is not sufficient. No consideration is given to the frequency of use or the total number of times of use of each ink nozzle. Further, after printing one line, the frequency of use or the number of times of use of each ink nozzle by the ink nozzle group used by printing in the next line is not considered. As described above, the conventional method does not consider the actual use frequency of each ink nozzle. For this reason, although there is no unused ink nozzle, it is not expected that a difference in the frequency of use of each ink nozzle is actually suppressed. In this case, it is practically impossible to expect a longer life of the ink jet head and suppression of deterioration of print quality. SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has been made in consideration of the above-described problems, and has been made in view of the fact that the frequency of use of each ink nozzle is made uniform, thereby achieving a long life of an ink jet head. The idea is to propose a method. In order to solve the above-mentioned problems, the present invention is directed to a conveying means for conveying a recording medium, and a recording medium arranged to face the recording medium conveyed by the conveying means. And an inkjet head having a plurality of ink nozzles arranged in the transport direction of the recording medium, and printing while moving the inkjet head in a row direction orthogonal to the transport direction of the recording medium. Inkjet printers that perform the following: Measure the actual use frequency of each ink nozzle in the ink nozzle group; Ink nozzle group used when printing print data that is to be printed after the time when the actual use frequency is measured Calculating the planned use frequency of the print data; based on the actual use frequency and the planned use frequency, at a point in time after the print data is printed. Selecting a range of the used ink nozzle group that is involved in printing the print data from the ink nozzle group so that the use frequency of each of the ink nozzles is uniformed;
The printing of the print data is performed using the selected used ink nozzle group. In the method of the present invention, the frequency of use of each ink nozzle is determined based on the actual frequency of use of each ink nozzle and the expected frequency of use when printing, for example, one line of print data to be printed next. The range of the used ink nozzles in the ink nozzle group is determined so that the directions are averaged. Then, the transport amount for one line by the transport unit is determined so that printing is performed by the determined used ink nozzle group, and the recording medium is transported by the transport amount. Therefore, according to the present invention, since each ink nozzle is used so that the frequency of use of each ink nozzle is substantially uniform, the life of the ink jet head can be extended. A drive control method of an ink jet printer to which the present invention is applied will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an ink jet printer to which the present invention is applied. The overall structure of the ink jet printer 310 of this example is a general structure, and includes a platen roll 300 which is a component of a conveyance unit for conveying the recording paper 105, the inkjet head 10 facing the platen roll 300, A carriage 302 that reciprocates the inkjet head 10 in a row direction (main scanning direction) that is an axial direction of the platen roll 300.
And an ink tank 30 for supplying ink to the inkjet head 10 via an ink tube 306.
One. Reference numeral 303 denotes a pump, which is provided via a cap 304 and a waste ink recovery tube 308 when an ink ejection failure or the like occurs in the inkjet head 10.
It is used to suck ink and collect it in the waste ink reservoir 305. FIG. 2 is a sectional view of the above-described ink-jet head 10, and FIG. 3 is a view taken along line AA of FIG. The ink jet head 10 of this embodiment is of a type in which the volume of an ink chamber communicated with a nozzle is changed by vibrating a vibration plate using electrostatic force to discharge ink droplets. Of course, it is also possible to employ a type in which the volume of the ink chamber communicated with the nozzle is changed using a piezoelectric element or the like to discharge the ink droplets. Furthermore, a type in which the volume of ink is increased by using a heating element to discharge ink droplets may be employed. In the present embodiment, an edge eject type in which ink droplets are ejected from a nozzle hole provided at an end of the substrate is a face eject type in which ink droplets are ejected from a nozzle hole provided in the upper surface of the substrate. Good. The structure of the ink jet head 10 will be described with reference to FIGS. The inkjet head 10 of the present example has a laminated structure in which three substrates 1, 2, and 3 are overlapped. The intermediate substrate 2 is, for example, a silicon substrate, and has a plurality of nozzle grooves formed at equal intervals in parallel from one end on the surface of the substrate 2 so as to form a plurality of ink nozzles 4. A recess for communicating with the bottom wall constituting a discharge chamber 6 (ink chamber) functioning as the diaphragm 5 and an ink inlet for constituting an orifice 7 provided at the rear of the recess. It has a narrow groove and a concave portion that forms a common ink cavity 8 for supplying ink to each discharge chamber 6. Further, a concave portion which forms a vibration chamber 9 for mounting an electrode to be described later is provided in a lower portion of the vibration plate 5. The pitch of the ink nozzles 4 is about 2 mm, and the width thereof is about 40 μm. On the upper surface of the intermediate substrate 2,
A common electrode 17 is formed. The upper substrate 1 bonded to the upper surface of the intermediate substrate 2 is made of, for example, glass or plastic. By bonding the upper substrate 1, the plurality of ink nozzles 4, discharge ports 6, orifices 7, An ink cavity 8 is formed. The upper substrate 1 has an ink cavity 8
Is formed with an ink supply port 14 communicating with the ink supply port. The ink supply port 14 is connected to the ink tank 301 (see FIG. 1) via the connection pipe 16 and the tube 306. Lower substrate 3 joined to the lower surface of intermediate substrate 2
Is made of, for example, glass or plastic. A vibration chamber 9 is formed by joining the lower substrate 3, and individual electrodes 31 are formed at respective positions on the surface of the lower substrate 3 corresponding to the respective vibration plates 5. ing. The individual electrode 31 has a lead portion 32 and a terminal portion 33. Further, the entirety of the electrode 31 and the lead portion 32 except for the terminal portion 33 is covered with an insulating film 34. A lead wire 35 is bonded to each terminal 33. In the ink-jet head 10 having such a structure in which the substrates are overlapped, a driver 220 is further connected between the common electrode 17 formed on the intermediate substrate 2 and the terminal portion 33 of each individual electrode 31. The ink 11 is supplied from the ink tank 301 to the inside of the intermediate substrate 2 through the ink supply port 14, and fills the ink cavity 8, the ejection port 6, and the like. The distance between the electrode 31 and the diaphragm 5 is
It is kept at about 1 μm. In FIG. 2, reference numeral 13 denotes an ink droplet ejected from the nozzle hole 4. The ink to be used is prepared by dissolving or dispersing a surfactant such as ethylene glycol and a dye or pigment in a main solvent such as water, alcohol and toluene. Further, if a heater or the like is attached to the inkjet head, hot melt ink can be used. When, for example, a positive voltage pulse is applied to the individual electrode 31 by the driver 220 and the surface of the electrode 31 is charged to a positive potential, the lower surface of the corresponding diaphragm 5 is charged to a negative potential. . Therefore, the diaphragm 5 is attracted by the electrostatic force and bends downward. Next, when the voltage pulse applied to the electrode 31 is turned off, the diaphragm 5 returns to the original position. By this return operation, the internal pressure of the ejection chamber 6 rises sharply, and the ink droplets 13 are ejected from the nozzle holes 4 toward the recording paper 105. When the vibration plate 5 bends downward, the ink 11 is supplied from the ink cavity 8 to the ejection chamber 6 via the orifice 7. FIG. 4 shows a control system of the ink jet printer of this embodiment. The circuit part which forms the center of this control system can be constituted by, for example, a one-chip microcomputer. In the figure, reference numeral 201 denotes a printer control circuit. The printer control circuit 201 includes internal buses 202, 203, 2 including an address bus and a data bus.
The RAM 205, the ROM 206, and the character generator ROM (CG-ROM) 207 are connected to each other via the terminal 04. A control program is stored in the ROM 206 in advance, and a drive control operation of the inkjet head 10 as described later is executed based on the control program called and activated from the control program. RAM 205
Are used as a working area in drive control.
In the CG-ROM 207, dot patterns corresponding to input characters are developed. Reference numeral 210 denotes a head drive control circuit, which is a printer control circuit 2 connected via an internal bus 209.
Under the control of 01, a drive signal, a clock signal, and the like are output to the head driver 220. Data bus 2
11, print data DATA is supplied. The head driver 220 is composed of, for example, a TTL array, generates drive voltage pulses corresponding to input drive signals, and applies these to the individual electrodes 31 and the common electrodes 17 to be driven. Then, ink droplets are ejected from the corresponding nozzle holes 4. In order to generate the driving voltage pulse signal, the head driver 22
0 is supplied with the ground voltage GND, the drive voltage Vn, and the like. These voltages are the driving voltage Vcc of the power supply circuit 230.
Is generated from Next, the printer control circuit 201 is connected to the carriage motor drive control circuit 23 via the internal bus 231.
2 are connected. Carriage motor drive control circuit 2
32 drives a carriage motor (not shown) for reciprocating a carriage 302 carrying the inkjet head 10 via a motor driver 233, and drives the inkjet head 10 in a row direction indicated by an arrow 234 in the figure. To move. Also, the printer control circuit 2
01 is connected to a transport motor drive control circuit 242 via an internal bus 241. The transport motor drive control circuit 242 drives a transport motor (not shown) via a motor driver 243, so that the platen roller 3 shown in FIG.
The recording paper 105 is transported along the direction 00 in the transport direction indicated by the arrow 244 in the figure. FIG. 5 shows a flowchart of a schematic operation of the ink jet printer 310 having the above-described configuration. FIG. 6A shows a nozzle recovery operation subroutine, and FIG. 6B shows a printing operation subroutine. First, the overall operation will be described.
At T1, initialization of the printer mechanism is executed. Next, in step ST2, a nozzle recovery operation immediately after power-on is performed. This nozzle recovery operation is shown in FIG.
Of steps ST21 to ST23. In this nozzle recovery operation, in step ST21, the ink jet head 1 shown in FIG.
The carriage 302 on which the “0” is mounted is moved from the standby position to the position of the cap 304. Next, in step ST22, a nozzle recovery operation, that is, a preliminary ejection drive is performed. The preliminary ejection driving of the nozzles is a vibration plate corresponding to all nozzles in order to discharge defective ink which causes ink ejection failure, such as ink with increased viscosity in the nozzle hole portion of the inkjet head 10. 5 is driven to eject ink droplets from all nozzles a predetermined number of times. Thereafter, in step ST23, the carriage 302 is returned to the standby position again. Returning to the flowchart of FIG. 5, in step ST3, the time from the previous nozzle recovery operation is counted. This counting is performed using a counter built in the printer control circuit 201 shown in FIG. When the time interval for performing the nozzle recovery operation elapses, step ST
The process proceeds from step 3 to step ST12, and the nozzle recovery operation is performed again. If not, it is determined in step ST4 whether or not to perform printing. If the printing operation is to be performed, the process proceeds to step ST6 after resetting the count value of the nozzle recovery operation period in step ST5, and proceeds to step ST6. A printing operation for printing on the recording paper 105 shown in FIG. 1 is executed. FIG. 6B shows this printing operation. As shown in this figure, first, in step ST61, the count value n is set to "1", and in step ST62, the carriage 302 is moved by one dot in the main scanning direction. In steps ST63 and ST64, by driving the diaphragm 5 of the nozzle corresponding to the designated dot based on the print data DATA, the ink suction and discharge operations of the nozzle are performed. Next, in step ST65, the count value n is incremented by "1", and in step ST66, it is determined whether or not the count value n is the last dot in the row direction (main scanning direction). If it is the last dot, the printing operation is terminated.
Returning to T62, the above operation is repeated. In this example, after the printing operation for one line is completed, the process returns to step ST7 in FIG. 5, and returns the carriage 302 to the initial position. When performing so-called logical seeking, ST7
May not be performed. Next, in step ST8, it is determined whether or not to continue the processing. If the printing is completed, the process proceeds to step ST9 in accordance with the flow of NO, and the paper feeding operation for a predetermined amount of one line, that is, the recording paper 105 is conveyed by one line. After that, the process ends. However, if the printing process is to be continued in step ST8, the process proceeds to step ST10 according to the flow of YES, and the operation of calculating the paper feed amount shown in detail in FIG. 7 is performed. Thereafter, the paper is fed by the amount calculated in step ST11, and the process returns to step ST3. Next, the processing for calculating the paper feed amount will be described with reference to the flowchart of FIG. In this processing routine, first, in step ST71, the frequency of use of each ink nozzle of the inkjet head 10 shown in FIG. The frequency of use of each ink nozzle is updated each time the ink nozzle is driven, and is sequentially stored in the RAM 205. Here, it is assumed that the current frequency of use of each ink nozzle is a distribution curve I as shown in FIG. Further, the ink jet head 10 is provided with a recording paper 105.
It is assumed that a total of 64 ink nozzles are provided from the first ink nozzle located on the leading side in the transport direction to the 64th ink nozzle located on the last end in the transport direction. Furthermore, it is assumed that the dot width (the number of dots in the transport direction) of each print character or the like in normal one-line printing is 24 dots, which is less than half the number of ink nozzles. After the use frequency is read, in step ST72, the expected use frequency of the ink nozzles when the print data is printed is calculated based on the print data for one line to be printed next. . That is, the use frequency of each ink nozzle when the ink nozzle group for 24 dots is used is calculated. FIG. 7C shows an example of the calculated scheduled use frequency (curve II) together with an example of a print character string (ABCD...) In which the use frequency of the nozzle group in the central portion increases like the use frequency. Is shown. Next, in step ST73, 64
A range U of 24 nozzle groups to be used in printing the next one line among the ink nozzles is calculated. Now, the actual use frequency is a curve I as shown in FIG. 7B, and the expected use frequency is a curve II as shown in FIG. 7C. Therefore, the process of this step calculates which range of 24 nozzle groups can be used to minimize the difference Δ between the maximum use frequency MAX and the minimum use frequency MIN of the 64 ink nozzles. . For example, as shown in FIG. 7 (d), when 24 nozzle groups including the nozzle showing the maximum use frequency MAX are selected, the use frequency is superimposed on the curve I and the curve II. A curve III is obtained, and the difference Δ between the maximum use frequency MAX and the minimum use frequency MIN increases as compared to before. In this example, as shown in FIG. 7E, the 24 nozzle groups including the nozzles having the minimum use frequency MIN are selected as the use nozzle groups U, and the obtained use frequency curve IV is the maximum use frequency curve IV. Frequency MAX and minimum usage frequency M
The IN difference Δ is minimized. After the selected nozzle group U is selected in this way, in step ST74, the character string (ABCCD.
The paper feed amount is calculated so that the printing of (.) Can be performed. Thereafter, the process returns to step 11 in FIG. 5, and the paper feeding operation of the calculated amount is executed as described above. As described above, in the driving method of the ink jet printer according to the present embodiment, the actual use frequency of each ink nozzle and the scheduled use of the used nozzle group scheduled by the next printing operation for one line are performed. Based on the frequency, the range of used ink nozzles at the time of printing the next one line is set so that the difference between the maximum value and the minimum value of the use frequency is minimized. Therefore, the difference in the frequency of use of each ink nozzle can be reliably reduced, and the frequency of use of each ink nozzle can be averaged. As a result, the life of the inkjet head can be extended. Further, in the ink jet printer of this embodiment, as shown in the flowchart of FIG. 6A, a preliminary ejection drive is performed periodically to recover the ink nozzles to a state suitable for actual use. I have. Such preliminary ejection drive is performed to eject such defective ink when the ink filled in each ink nozzle is deteriorated due to increased viscosity due to long-term nonuse. In this example, as described above, the use frequency of each ink nozzle can be averaged. Therefore, characteristics such as the viscosity of the ink filled in each ink nozzle can be maintained substantially uniform. For this reason, a situation in which the viscosity of the ink filled therein becomes abnormally high and cannot be recovered even by the above-described preliminary ejection driving does not occur for only a part of the plurality of ink nozzles. Therefore, it is possible to increase the interval of the preliminary ejection drive, thereby improving the efficiency of the printing process. Further, as in the ink jet head of the present embodiment shown in FIG. 2, a voltage pulse is applied between the vibration plate 5 (common electrode 17) and the individual electrode 31, and ink is generated by electrostatic force generated between them. In the type in which the volume of the discharge chamber 6 is changed to discharge the ink droplets, residual charges are generated between them, which may cause a defective discharge of the ink droplets. However, if the driving method of this example is adopted, the frequency of use of each ink nozzle can be averaged, so that some of the ink nozzles are frequently used and a large amount of residual charge is generated in that portion. Can be avoided. For this reason, it is possible to suppress the adverse effects caused by the residual charges. Further, in an ink jet head adopting a driving method in which a voltage pulse of opposite polarity is periodically applied between the vibration plate 5 and the individual electrode 31 to remove the residual charge, the generated residual charge is generated in each ink nozzle. Therefore, by applying a voltage pulse of the opposite polarity, the residual charge in the ink nozzle can be reliably removed. In this case, for example, the cumulative use frequency of each ink nozzle may be cleared each time the preliminary ejection drive is performed, and the use frequency may be measured from the beginning. In the above example, the scheduled use frequency is calculated based on one line of print data to be printed, but the planned use frequency is calculated based on two or more lines of print data. Alternatively, each feed amount for a large number of rows may be calculated. The number of ink nozzles of the ink jet head is not limited to 64 as a matter of course. Further, in order to average the use frequency of each ink nozzle, in the above example, two points of data, the maximum use frequency and the minimum use frequency, are used. The range of the nozzle group to be used may be selected so that the variation in the frequency of use can be suppressed. In any case, various methods can be adopted as a method of averaging the use frequency of each ink nozzle based on the actual use frequency and the expected use frequency. As described above, in the drive control method of the ink jet printer according to the present invention, the actual use frequency of each ink nozzle of the ink nozzle group is measured, and the actual use frequency is measured. Calculated the expected use frequency of the used ink nozzle group when printing the print data scheduled to be printed after the time point, based on the actual use frequency and the scheduled use frequency, the time after the print data was printed Set the range of the used ink nozzle group involved in the printing of the print data so that the usage frequency of each ink nozzle becomes uniform, and using the set used ink nozzle group,
The print data is printed. Therefore,
According to the present invention, the frequency of use or the frequency of use of each ink nozzle can be reliably made uniform, and the life of the inkjet head can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing the overall configuration of an inkjet printer to which the present invention has been applied. FIG. 2 is a schematic sectional view showing an ink jet head mounted on the printer of FIG. FIG. 3 is a view taken in the direction of arrows AA in FIG. 2; FIG. 4 is a schematic block diagram illustrating a control system of an inkjet head in the inkjet printer of FIG. FIG. 5 is a schematic flowchart showing the operation of the inkjet printer of FIG. 1; 6A is a flowchart showing a subroutine of a nozzle recovery operation, and FIG. 6B is a flowchart showing a dot printing operation for one main scanning line. 7A is a flowchart illustrating a subroutine for calculating a paper feed amount, FIG. 7B is a graph illustrating a use frequency curve of each ink nozzle, and FIG. A graph of the expected use frequency curve when printed, (d) a graph showing a change in the use frequency,
(E) is another graph for showing a change in use frequency. [Description of Signs] 4 Ink nozzle 5 Vibration plate 6 Discharge chamber (ink chamber) 10 Ink jet head 13 Ink droplet 17 Common electrode 31 Individual electrode 201 Printer control circuit 210 Head drive control circuit 220 Head driver I Actual of each ink nozzle Use frequency curve II Planned use frequency curve IV of these or one line of print data to be printed Use frequency curve U after actually printing one line of print data U Range of set use nozzle group

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Claims (1)

(57) [Claims 1] Conveying means for conveying a recording medium, and disposed in a state of facing the recording medium conveyed by the conveying means and directed in the conveying direction of the recording medium. A drive control method for an ink jet printer that performs printing while moving the ink jet head in a row direction orthogonal to the recording medium conveyance direction, comprising: Measuring the actual use frequency of each ink nozzle, calculating the expected use frequency of the used ink nozzle group when printing the print data to be printed after the time when the actual use frequency is measured, Based on the actual use frequency and the scheduled use frequency, each of the ink nozzles at a time after the print data is printed In order to make the frequency of use uniform, a range of the used ink nozzle group involved in printing the print data is selected from the ink nozzle group, and printing of the print data is performed using the selected used ink nozzle group. A drive control method for an inkjet printer, comprising: