JP2010274449A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recorder small in density difference among a plurality of heads. <P>SOLUTION: The ink jet recorder 1 in which a plurality of heads 2 are arranged in a main scan direction to constitute one line can form a test pattern 25 for all combinations of a pair of two heads selected from the plurality of heads. Two heads of each combination print respective predetermined printing patterns adjacent to each other on a printing paper, whereby the test pattern 25 is formed. When a maintenance person inputs a comparison result by an equality sign or a sign of inequality for two heads of each combination from a visual recognition result, a density rank is calculated and displayed for all heads. Moreover, a reference head with a correction voltage value of 0 is selected, and + or - correction voltage values are suitably inputted with regards to other heads. Hence, printing small in density difference among the heads becomes possible by driving voltages after corrected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a line-type ink jet recording apparatus in which a plurality of ink jet head modules are arranged in the main scanning direction to form one line, and particularly includes density adjusting means for making the density between the plurality of ink jet head modules uniform. The present invention relates to an inkjet recording apparatus.

  The ink jet recording apparatus includes an ink jet head module (hereinafter, abbreviated as a head module or simply a head if necessary) that forms a desired image with ink droplets ejected according to a driving voltage. In a line-type inkjet recording apparatus in which the inkjet head modules are arranged in the main scanning direction to form one line, there is a difference in ejection characteristics for each inkjet head module, and thus a density difference appears between the head modules. Therefore, it is necessary to make adjustments so as to reduce such a density difference. As the method, a method using an automatic image reading device such as a scanner is proposed as disclosed in Patent Document 1 below. Has been.

  However, there are some sites where no automatic image reading device is installed. At that time, the maintenance staff must manually adjust the density difference between the head modules. In addition, when adjusting the density difference between the head modules using an automatic image reader, it is necessary for maintenance personnel to carry one automatic image reader at a time, or to have at least several units at the maintenance site. is there. Therefore, the cost increases in proportion to the number of maintenance personnel or bases. Further, when the maintenance staff carries the automatic image reading apparatus to the site, transportation means and transportation costs are required so as not to damage the apparatus. Furthermore, when using an automatic image reader, if the accuracy of the processing algorithm is low, manual correction will eventually be required, or conversely, increasing the accuracy will require a complicated algorithm and a large number of development steps. There are issues such as.

  Therefore, in order to avoid such a problem, there is a method in which a maintenance person manually adjusts the density between the head modules without using an automatic image reading apparatus. Conventionally, manual density adjustment has been performed by the following method. That is, when printing is performed using a solid pattern as shown in FIG. 2A, a printed matter having a density difference between head modules is output as shown in FIG. 2B due to a characteristic difference between the heads. The density reference head is determined by the printed matter, and the voltage adjustment of the head module is performed until the density of the head module adjacent to the density of the reference head module is equal. Meanwhile, solid pattern printing and voltage adjustment are repeated many times. Next, the voltage of the head module is adjusted by comparing the density of the head module with the adjusted voltage as a new reference and comparing it with the density of the adjacent head module. Similarly, the printing of the solid pattern and the voltage adjustment of the head module are repeated until the density adjustment between all the head modules is completed.

  As another method, a head module to be used as a density reference is determined on the printed solid pattern, and it is determined whether the density of the other head module is higher or lower than the density of the head module. There is also a method of adjusting the voltage of each head module in accordance with this determination.

JP 2002-269543 A

  According to the first conventional method in which the maintenance staff manually adjusts the density of the head module by looking at the actually printed solid pattern, the density is adjusted for each head module. There has been a problem that it takes a long time because of an increase in labor and maintenance. Further, according to this method, since the density is compared only between the adjacent head modules, the density difference may be greatly different between the non-adjacent head modules. It was difficult to perform adjustment with high accuracy.

  Further, in the case of the second method in which the density adjustment is performed by comparing the density difference between the head modules that are not adjacent to each other, there is another head around the pattern printed by the head module for which the density adjustment is to be performed. There are other patterns with different densities printed by the module, and when observing the pattern density by the head module that is going to adjust the density, the person who makes the adjustment uses the optical density illusion at the time of observation from the density of the surrounding pattern. In some cases, the concentration adjustment work is difficult.

  FIG. 3 illustrates such an optical illusion. The density of the small gray square at the center to be observed is actually the same in both the left and right diagrams in FIG. 3, but it affects the surrounding density. Since the optical illusion occurs, the right figure with a lower density appears darker. As described above, in the second method in which the density adjustment is performed by comparing the density differences between the head modules that are not adjacent to each other, an optical illusion occurs when observing the print result, so that accurate determination is difficult. For this reason, there is a problem that the density difference between the head modules cannot be adjusted to be small regardless of the number of adjustments, the number of times of printing a solid pattern increases, and the number of adjustments also increases.

  The present invention has been made in order to solve the above-described problem. Even if there is no device capable of measuring density, a plurality of head modules are not only adjacent to each other but also adjacent to each other. A test pattern that does not cause the optical illusion is generated, and the test pattern can be used to make accurate adjustments to reduce the density difference between the head modules. The first purpose is to reduce the labor of the staff.

  A second object of the present invention is to adjust the density difference between the head modules at a small number of adjustments by simultaneously adjusting the density difference between the head modules in a plurality of head modules.

An ink jet recording apparatus according to claim 1 is:
In an inkjet recording apparatus in which a plurality of inkjet head modules are arranged in the main scanning direction to form one line,
Drive voltage storage means for storing a drive voltage for defining the ink discharge amount of each inkjet head module for each inkjet head module;
Drive voltage setting means for setting the drive voltage for each of the inkjet head modules in the drive voltage storage means;
An inkjet head module controller that drives each inkjet head module with the drive voltage stored in the drive voltage storage;
For all combinations of two selected from a plurality of inkjet head modules, each of the two inkjet head modules included in each combination has a predetermined printing pattern adjacent to each other on one printing sheet. Test pattern generating means for driving the inkjet head module so as to form a printed test pattern;
By operating the drive voltage setting unit according to the observation result of the test pattern formed by the test pattern generation unit, and setting the drive voltage of the drive voltage storage unit, between the head modules at the time of printing The feature is that the density difference can be adjusted.

The inkjet recording apparatus according to claim 2 is the inkjet recording apparatus according to claim 1,
Comparison result input means for inputting a comparison result of the density of the print pattern in each combination of the inkjet head modules based on the observation result of the test pattern;
A print density rank calculating unit that calculates the rank of the print density of the inkjet head module from each comparison result input by the comparison result input unit;
Display means for displaying the density of each inkjet head module according to the calculation result of the print density rank calculation unit;
Reference head module selection means for selecting the ink jet head module having a reference print density based on the density of each ink jet head module displayed on the display means in setting the drive voltage by the drive voltage setting means; ,
It is characterized by having.

The inkjet recording apparatus according to claim 3 is the inkjet recording apparatus according to claim 2,
The display means includes
For input by the comparison result input means, the two inkjet head modules included in each combination are displayed, and the relationship of the density of each print pattern by the two displayed inkjet head modules is indicated by a comparison symbol. Display for input,
For the input by the reference head module selection means, the respective inkjet head modules and their densities are displayed in order of density according to the calculation result of the print density rank calculation unit, and the inkjet head module to be selected is designated. It is characterized by being displayed so that it can be selected by a symbol.

The inkjet recording apparatus according to claim 4 is the inkjet recording apparatus according to claim 3,
The display means includes
For the input by the drive voltage setting means, the drive voltage of the inkjet head module selected by the reference head module selection means is corrected on the screen in which the inkjet head modules and their densities are arranged and displayed in order of density. The correction voltage value is displayed as 0, and other correction voltage values for correcting the drive voltage of the inkjet head module are displayed so as to be input according to the density.

  According to the invention of claim 1, in the plurality of head modules forming a line, a plurality of head modules including a set of two adjacent head modules and a set of two head modules not adjacent to each other With respect to all the combinations of two sets selected from the above, a test pattern can be generated in which two head modules of each combination print a predetermined print pattern on a single print sheet so as to be adjacent to each other. That is, it is possible to print a test pattern printed on one print sheet so that the print patterns are adjacent to each other for all head module combinations. For this reason, in observing the test pattern, when observing the print pattern of the head module for which the density adjustment is to be performed, the print pattern is not affected by the density of other print patterns around it. Since it is only necessary to perform density comparison (one density is larger, smaller or equal to the other) with respect to the printed pattern by the two head modules formed, the mechanical structure of the apparatus is a head that is actually at a remote position. Even between modules, the optical illusion is less likely to occur when comparing the density of printed patterns, and it is possible to set the drive voltage of each head module so that the density difference during printing is small. It is possible to make adjustments so that quality printed matter can be output.

  According to the second aspect of the present invention, the print density rank calculation unit can be used for the ink jet head module only by observing the test pattern and inputting the comparison result of the print pattern density in each combination of the ink jet head modules by the comparison result input means. The order of printing density is calculated, and the display means displays the head modules in order of density according to their numbers. For this reason, when the drive voltage is set by the drive voltage setting means, the reference head module selection means selects the ink jet head module having the reference print density based on the density of each ink jet head module displayed on the display means. can do. As described above, since the head modules are displayed on the display means in order of density, if a head module having a density determined to be appropriate is selected as a reference, the density state for the reference head module is displayed. Therefore, it is possible to see at a glance how dark or lighter the other head module is compared to the reference head module, so that it is possible to determine how much higher or lower the current voltage value should be. Become a material. Further, since the density balance of all the head modules can be known at a glance, the drive voltages of a plurality of head modules can be adjusted at a time, and the density difference between the head modules can be adjusted with a small number of times.

  According to the ink jet recording apparatus of the third aspect, after the test pattern is observed, when the comparison result of the density of each print pattern of the two head modules is input by the comparison result input means, it is displayed on the display means. It is only necessary to input a comparison symbol (for example, inequality sign or equal sign) indicating the relationship between the density of the two ink jet head modules. Further, in order to set the drive voltage by the drive voltage setting means, when the ink jet head module having the reference print density is selected by the reference head module selecting means, the respective ink jet heads displayed in order of density on the display means. All you have to do is select a module with the designation symbol.

  According to the ink jet recording apparatus of the fourth aspect, when the driving voltage of each ink jet head module is input by the driving voltage setting means, the display means displays the ink jet head modules and their densities in order of density. In addition, since the correction voltage of the driving voltage of the ink jet head module serving as the reference selected by the reference head module selecting means is displayed as 0, the correction voltage of the driving voltage of the other ink jet head module is displayed in the order of density. Can be entered as appropriate.

(A) is a plan view and a cross-sectional view showing configurations of an inkjet head module, a transport system, and the like in the line-type inkjet recording apparatus according to the embodiment of the invention, and (b) is an electrical connection of main components in the embodiment. It is the block diagram shown. (A) is a figure which shows the solid chart for performing the density difference adjustment between several head modules, (b) is the solid chart of the figure (a) actually printed with the line-type inkjet recording device. This is an example of printing when a density difference occurs between a plurality of head modules. It is the comparison figure which showed the example in which the optical illusion is caused by the surrounding density. It is a figure which shows the production method of the test pattern performed with the line type inkjet recording device which concerns on embodiment of this invention. It is a figure which shows the example of the test pattern in the line type inkjet recording device which concerns on embodiment of this invention. 5 is a flowchart showing an operation from printing a test pattern to adjusting a density difference between head modules in the line type ink jet recording apparatus according to the embodiment of the present invention. It is a figure which shows the example of a display of the display means in the line type inkjet recording device which concerns on embodiment of this invention. 6 is a flowchart showing a procedure for calculating density ranking in the line-type inkjet recording apparatus according to the embodiment of the present invention. It is a figure which shows the example of a display of the display means in the line type inkjet recording device which concerns on embodiment of this invention. In the embodiment of the present invention, when the drive voltage is adjusted a plurality of times, the setting value oscillates (a) and the state (b) converges without oscillating. In the embodiment of the present invention, it is a schematic diagram showing the procedure of operation for calculating the density order and replacing the density level order of each head for each comparison result.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1A shows a head configuration in a line-type ink jet recording apparatus and a printing paper conveyance system.
The ink jet recording apparatus 1 of this example is a so-called line type apparatus in which a plurality of ink jet head modules are arranged in the main scanning direction to form one line, and the heads are cyan (C), black (K), magenta (M ) And 6 for each color of yellow (Y). In FIG. 1, for each color, six heads from No. 1 head to No. 6 head are in the main scanning direction (vertical direction in the drawing) orthogonal to the sub-scanning direction (horizontal direction in the drawing) in which the printing paper is conveyed. ) In a staggered manner, and constitutes one line in the main scanning direction for each color, and the driving timing of each head is adjusted according to the position in the sub-scanning direction on the printing paper in the main scanning direction. One line parallel to the print can be printed. In the present specification, the reference numerals of the inkjet head module 2 (head 2) collectively refer to the heads of each color, No. 1 to No. 6.

  As shown in FIG. 1A, the ink jet recording apparatus 1 includes a transport conveyor 4 and rollers 8 as transport means for transporting the printing paper 3 below the head 2 described above. The conveyor 4 has a driving roller 5 and a driven roller 6 having axes parallel to the main scanning direction (vertical direction in the drawing), and a conveyor belt 7 wound around these rollers 5 and 6. The roller 8 is provided for each head 2 on the upstream side in the transport direction of each head 2 so as to be substantially in contact with the transport belt 7 of the transport conveyor 4, and holds the printing paper 3 on the upper surface of the transport belt 7. The printing paper 3 can be transported in cooperation with the transport conveyor 4 while maintaining the distance from each head 2 at a predetermined value.

FIG. 1B is a block diagram showing electrical connections of main components in the ink jet recording apparatus 1 of the present example.
The CPU 10 that is a control unit includes a ROM 11 that stores various programs executed by the CPU 10, a RAM 12 that functions as a work area of the CPU 10, an inkjet head module 2 that is a control target, and various types of controls for controlling the head 2. An input / output device 13 for inputting / outputting information is connected.

  As will be described later, the RAM 12 connected to the CPU 10 stores density comparison result storage means 14 for storing data on the print density comparison results of the respective heads inputted to the CPU 10 by the maintenance personnel by looking at the test pattern, and this density comparison. Based on the data about the result, there is a head order storage means 15 for storing data about the order of each head relating to the print density determined by the CPU 10. Further, the RAM 12 includes a drive voltage storage unit 16 that stores a drive voltage that defines the ink discharge amount of the inkjet head module 2 for each head 2.

  The input means of the input / output device 13 connected to the CPU 10 includes two drive voltage setting means 17 for setting the drive voltage for each head 2 in the drive voltage storage means 16 of the RAM 12 and two comparisons made by observation of the test pattern. When the drive voltage is set by the comparison result input means 18 for inputting the comparison result (large, small or equal) of the print patterns of the head 2 and the drive voltage setting means 17, the head 2 having a reference print density. And a reference head module selecting means 19 for selecting.

  Further, a display means 20 such as an LCD is provided as an output device of the input / output device 13. This display means 20 looks at the print results of the two heads 2 printed on the test pattern and inputs the comparison result of the density, as will be described in detail later, as shown in FIG. All the combinations of the two heads 2 and 2 selected from among them can be displayed, and an input screen can be displayed so that the comparison result of the print density can be input with equal signs or inequality signs for each set. Although the details will be described later, the display unit 20 can display the head 2 density and the head 2 number calculated by the CPU 10 according to the input data in a list in order of density, as shown in FIG. The head 2 serving as a reference when adjusting the drive voltage for density correction above can be specified, and correction voltages of other heads 2 can be input to the specified reference head 2.

  The CPU 10 serving as a control unit includes respective components that function as described below by software. First, the CPU 10 includes an inkjet head module control unit 21 that controls the driving of the inkjet head module 2. The ink jet head module control unit 21 drives each head 2 with the driving voltage for each head 2 stored in the driving voltage storage means 16 of the RAM 12. Further, the ink jet head module control unit 21 has a test pattern generating means 22 for printing a test pattern which becomes a reference when adjusting the driving voltage of the head 2. The test pattern generation means 22 will be described in detail later with reference to FIG. 4 or FIG. 5, but all the combinations of two sets selected from the plurality of heads 2 are included in each combination. It is possible to generate a test pattern 25 in which each of the heads 2 and 2 prints a predetermined printing pattern 24 on a single printing paper 3 adjacent to each other.

  Further, the CPU 10 has a print density rank calculation unit 27. The print density rank calculation unit 27 is used by the maintenance person to input the visual comparison results of the print patterns 24 and 24 of the two heads 2 and 2 printed adjacent to each other on the test pattern 25 by the comparison result input unit 18. In the case of input, the print density rank of the inkjet head module is calculated from the input comparison result.

  FIG. 4 illustrates the procedure or operation when the ink jet head module control unit 21 of the CPU 10 generates the test pattern 25 on the printing paper 3 by the test pattern generating means 22 in the ink jet recording apparatus 1 of this example. In the test pattern 25, two print patterns 24 are printed adjacent to each other not only between the head modules 2 and 2 adjacent to each other in the plurality of head modules 2, but also about the head modules 2 not adjacent to each other.

  First, the printing paper 3 having a predetermined size is conveyed in a portrait orientation, and cyan (which is the most upstream in the conveyance direction of the printing paper 3 in the present example (vertical arrow “printing” direction in FIG. 4)) in this example. C) The width of the paper in the horizontal direction in which the positions in the sub-scanning direction (the same direction as the vertical arrow “printing” direction in FIG. 4) coincide with each other for the 1st to 6th heads. Printing is performed so that a predetermined interval occurs in the main scanning direction, and this printing operation is performed at six positions with a predetermined interval in the sub-scanning direction according to the conveyance of the printing paper 3. As a result, six print patterns 24 having the same shape from the first head to the sixth head are printed in six at a total of 6 × 6 = 36 locations on one printing paper 3 (FIG. 4, first time: vertical) Direction paper).

  Next, a printing operation similar to that of the first printing is performed while the printing paper 3 is conveyed in a horizontally long state with the printing surface as it is. When the printing paper 3 is placed sideways and the short side direction coincides with the vertical arrow “printing” direction (sub-scanning direction) in FIG. 4, each of the six print patterns 24 in six rows parallel to the sub-scanning direction is number 1. The head No. 6 prints from the head. On the other hand, if the heads 1 to 6 print the print pattern 24 in the main scanning direction at six positions at predetermined intervals in the sub-scanning direction, all the heads are printed. The two print patterns 24 and 24 can be printed adjacent to each other (FIG. 4, second time: lateral paper passing).

  FIG. 5 is a detailed view of the test pattern 25 printed by the procedure of FIG. The numbers shown in each print pattern 24 in the figure indicate the numbers of the head modules 2, and two adjacent head modules 2, 2 and two head modules 2, 2 not adjacent to each other are included. FIG. 9 shows a state in which printing patterns 24 and 24 are printed adjacent to each other on a common printing paper 3.

  According to the above-described configuration of the inkjet recording apparatus 1 of this example, the print patterns 24 and 24 in which the two heads 2 and 2 are adjacent to each other as shown in FIG. Can generate a test pattern 25 that is printed on a common sheet of printing paper 3, so that the maintenance staff can hardly see the illusion of the entire set of two heads 2 and 2 by looking at this. The print density can be compared directly.

  Then, when the result is input to the CPU 10 by the head comparison result input means 18, the CPU 10 displays a list of the head 2 and its density on the display means 20 in order of density. The head 2 can be selected by the reference head module selection means 19, and the correction voltage for the other head 2 can be set by the drive voltage setting means 17. Thereby, the drive voltage of the drive voltage storage means 16 of the RAM 12 can be set to a corrected value, and the density difference between the heads 2 and 2 at the time of printing is adjusted.

Next, a more detailed procedure of the density adjustment operation of the head 2 in the ink jet recording apparatus 1 of this example will be described with reference to FIGS.
FIG. 6 is a flowchart showing a procedure (S10 to S16) from the start of the adjustment of the density difference between the head modules 2 and 2 to the end of the adjustment of the density difference in the present embodiment.

  As shown in FIG. 6, the maintenance staff prints the test pattern 25 by the method of FIG. 4 described above (S10, S11). The maintenance staff looks at the test pattern 25 printed as shown in FIGS. 4 to 5, and visually evaluates whether there is a difference in density between the head modules 2 and 2 (S12). Therefore, when it is evaluated that there is no density difference between the head modules 2 and 2, the adjustment is finished without adjusting the density (S13). When it is evaluated that there is a density difference between the head modules 2 and 2, the density adjustment between the head modules 2 and 2 is performed according to the display on the display means 20 (S14 to S16).

  The maintenance staff looks at the test pattern 25 printed, and in accordance with the display contents of the display means 20 shown in FIG. 7, the density difference between the heads 2 and 2 for each combination of two different head modules 2 and 2. The judgment result is input with a comparison symbol. Specifically, an inequality sign or an equal sign as a comparison symbol is selected and input in a blank space between two fields where the numbers of the two heads 2 displayed on the screen of the display means 20 are shown (FIG. 6, S14).

  Next, as shown in FIG. 6, the density ranking of the head 2 is calculated based on the input inequality sign or equal sign (S15). FIG. 8 is a flowchart showing a density ranking calculation method (S20 to S29).

  As shown in FIG. 8, the head comparison result table which is the density comparison result stored in the density comparison result storage means 14 is referred to (S20), and the densities of the head module 2 of interest and the comparison head module 2 are compared (see FIG. 8). S21). Here, the comparison of the density of the print pattern 24 by the target head 2 (the nth head 2) and the comparison head 2 is started from n = 1.

  As shown in FIG. 8, regarding the density of the print pattern 24, when the target head module 2 is smaller than the comparative head module 2 (target head <comparative head in S 21), the comparative head module 2 is one level higher than the target head module 2. (S22). If the target head module 2 is approximately the same level as the comparison head module 2 (the target head in FIG. 21 is a comparison head), the target head module 2 and the comparison head module 2 are set to the same level (S23). If the target head module 2 is larger than the comparison head module 2 (target head> comparison head in S21), nothing is done (S24).

  FIG. 11 shows a comparison of the respective densities of the target head 2 and the comparison head 2 as shown in the steps S21 to S24 in FIG. 8 when the target head 2 is the first head and the comparison head 2 is the second head. It is the figure which showed typically the control content in the case of changing or maintaining the density | concentration level order of each head 2 according to the comparison result at the time of doing.

  Next, as shown in FIG. 8, it is determined whether all comparison head modules 2 have been compared with the head module 2 of interest (S25). If NO, the next comparison head module that has not been compared yet is determined. 2 is compared (from S26 to S21). If YES in S25, it is determined whether or not the head number n of the head module 2 of interest is 6. If NO, the head number starting from n = 1 has still reached the last number. Since there is no head, the head 2 of the next head number n + 1 obtained by adding 1 to the current head number n is set as the head of attention 2 and the next comparison is made (return from S28 to S21). In the case of YES in S27, the number of heads of interest starting from n = 1 has reached 6, and the comparison of all the heads of attention 2 with all the comparison heads 2 has been completed, so the processing is terminated (S29). ).

  As described above, the density comparison between all the head modules 2 of interest and the comparison head module 2 is performed, and as a result, the print density rank calculation unit 27 of the CPU 10 changes the density of the head module 2 from the higher density level to the lower density level. By arranging the numbers, each head 2 is given a density order corresponding to the head module 2 having the highest density to the head module 2 having the lowest density. The head order relating to the density is stored in the density comparison result storing means 14 of the RAM 12.

  Next, as shown in FIG. 9, the CPU 10 displays the calculated density ranking of the head module 2 on the display screen of the display means 20. The maintenance staff manually inputs the correction voltage value of the head module 2 according to the displayed order. At this time, the maintenance staff first determines the reference head module 2 as a reference for density, and inputs a specified designation symbol (a black triangle symbol in the illustrated example) in the reference column. The correction voltage value of the head module 2 (head number 1 in FIG. 9) designated as the reference is set to zero. Next, the maintenance staff corrects the correction voltage in the positive direction for the head module 2 having a lower density than the head module 2 (head number 1) as a reference for density (2, 3, 5 in descending order of density in the head number). A value is set and input, and the correction voltage value is set and input in the minus direction for the dark head module 2 (4 and 6 in descending order of density in the head number).

  When the setting or input up to this point is completed, the test pattern 25 is printed again, the density difference between the head modules 2 and 2 is visually evaluated, and the same operation is performed for the density difference between the head modules 2 and 2. Repeat until it runs out.

  In this way, the printing of the test pattern 25 and the operation of inputting the correction voltage based on the result of actual visual evaluation of the printed test pattern 25 by the maintenance staff, thereby adjusting the driving voltage of each head 2, The following problems are expected when it is repeated several times. That is, when the correction voltage value is input again to correct the drive voltage corrected by the correction voltage value of the head module 2 input for the first time, two test patterns 25 on the printing paper 3 are used. Although the print patterns 24 and 24 by the heads 2 and 2 are printed adjacent to each other for easy comparison, the density difference is difficult to judge in some cases. The correction voltage value to be input even if this is visually judged. There may be a case where the (adjustment amount of the drive voltage) cannot be determined.

  In such a case, if an incorrect correction voltage value that deviates from the target density (density by the selected reference head module 2) is input, as shown in FIG. The drive voltage value (voltage set value) may oscillate every set time and may not converge to the drive voltage corresponding to the target concentration.

  Therefore, in the input of the correction voltage value at this time, if the voltage value of the adjustment amount smaller than the correction voltage value input last time is input, the correction voltage value input as shown in FIG. As a result of this, the drive voltage value set converges to the drive voltage value corresponding to the target density. Therefore, when the correction voltage value is input again in this way, if the correction voltage value smaller than the previously input correction voltage value is input, the set drive voltage value vibrates in the vicinity of the target value. Concentrates to the target value, and the density when printing with this drive voltage approaches the target density, so the density difference between the heads 2 and 2 can be adjusted with fewer adjustments. It becomes.

  The method of setting the correction voltage value input after the second time to a value smaller than the previous correction voltage value may be regularly executed as a method for adjusting the concentration in maintenance work by maintenance personnel. As an apparatus configuration in the inkjet recording apparatus 1 of the example, a correction voltage value that has been input previously is stored, and a correction voltage value that is input after that cannot be input beyond the previous correction voltage value. Or it may be realized as a software configuration.

DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus 2 ... Inkjet head, head 10 ... CPU as control means
11 ... ROM
12 ... RAM
DESCRIPTION OF SYMBOLS 13 ... I / O amount apparatus 14 ... Concentration comparison result storage means 15 ... Head order storage means 16 ... Drive voltage storage means 17 ... Drive voltage setting means 18 ... Comparison result input means 19 ... Reference head module selection means 20 ... Display means 21 ... Inkjet Head module control unit 22 ... Test pattern generating means 24 ... Print pattern 25 ... Test pattern 26 ... Input / output device control unit 27 ... Print density order calculation unit

Claims (4)

In an inkjet recording apparatus in which a plurality of inkjet head modules are arranged in the main scanning direction to form one line,
Drive voltage storage means for storing a drive voltage for defining the ink discharge amount of each inkjet head module for each inkjet head module;
Drive voltage setting means for setting the drive voltage for each of the inkjet head modules in the drive voltage storage means;
An inkjet head module controller that drives each inkjet head module with the drive voltage stored in the drive voltage storage;
For all combinations of two selected from a plurality of inkjet head modules, each of the two inkjet head modules included in each combination has a predetermined printing pattern adjacent to each other on one printing sheet. Test pattern generating means for driving the inkjet head module so as to form a printed test pattern;
By operating the drive voltage setting unit according to the observation result of the test pattern formed by the test pattern generation unit, and setting the drive voltage of the drive voltage storage unit, between the head modules at the time of printing An ink jet recording apparatus characterized in that a density difference can be adjusted. Comparison result input means for inputting a comparison result of the density of the print pattern in each combination of the inkjet head modules based on the observation result of the test pattern;
A print density rank calculating unit that calculates the rank of the print density of the inkjet head module from each comparison result input by the comparison result input unit;
Display means for displaying the density of each inkjet head module according to the calculation result of the print density rank calculation unit;
Reference head module selection means for selecting the ink jet head module having a reference print density based on the density of each ink jet head module displayed on the display means in setting the drive voltage by the drive voltage setting means; ,
The inkjet recording apparatus according to claim 1, comprising: The display means includes
For input by the comparison result input means, the two inkjet head modules included in each combination are displayed, and the relationship of the density of each print pattern by the two displayed inkjet head modules is indicated by a comparison symbol. Display for input,
For the input by the reference head module selection means, the respective inkjet head modules and their densities are displayed in order of density according to the calculation result of the print density rank calculation unit, and the inkjet head module to be selected is designated. 3. The ink jet recording apparatus according to claim 2, wherein the display is made so that it can be selected by a symbol. The display means includes
For the input by the drive voltage setting means, the drive voltage of the inkjet head module selected by the reference head module selection means is corrected on the screen in which the inkjet head modules and their densities are arranged and displayed in order of density. 4. The inkjet according to claim 3, wherein a value of the correction voltage is displayed as 0 and a value of a correction voltage for correcting the drive voltage of the other inkjet head module is displayed so as to be input according to the density. Recording device.