JP7692855B2 - INKJET PRINTER AND METHOD FOR CONTROLLING INKJET PRINTER - Google Patents

Description

The present invention relates to an inkjet printer and a method for controlling an inkjet printer.

Industrial inkjet printers atomize ink, give these ink particles an amount of charge corresponding to the characters to be printed, and then deflect the ink particles according to the amount of charge to fly toward the print target (such as a product) to print. In such inkjet printers, when the ink particles are charged (electrified) in accordance with the print pattern that constitutes the print characters, it is known that fluctuations in the Coulomb force that occurs between the flying ink particles can cause the ink particles to land on the print target and shift in position, resulting in a deterioration in print quality. Various technologies have been proposed in the past to prevent this deterioration in print quality. For example, JP 2005-35210 A (Patent Document 1) discloses one technology for solving this problem.

This patent document 1 describes that "the device includes a charge amount correction means for reading, from the printing information stored in the storage means, the number a of landable ink particles A to be charged among the landable ink particles that are ejected immediately before the ejection of the ink particles to be charged and that are within a set reference number from the ink particles to be charged, and the number b of uncharged landable ink particles B that are present between the ink particles to be charged and the landable ink particles A to be charged immediately before the ink particles to be charged, and correcting the charge amount of the charge information of the ink particles to be charged based on correction data corresponding to the numbers a and b that are stored in advance in the storage means."

JP 2005-35210 A

According to the technology of Patent Document 1 mentioned above, the amount of charge is corrected based on the correction data stored in correspondence with the number of charged ink particles and the number of non-charged ink particles from the stored printing information, so high quality printing can be obtained.

However, even if high quality printing was achieved initially, as the operation time of the inkjet printer increases, the state of the ink may change due to foreign matter being mixed into the ink during use or the ink itself deteriorating over time, causing a change in the charge rate. In addition, ink droplets may adhere to the device, making it impossible to maintain stable high quality printing. To prevent this deterioration in print quality that occurs over long periods of operation, maintenance personnel have periodically checked the ink for discoloration and whether the ink has been used for a specified period of time, and have replaced the ink. However, it is difficult for maintenance personnel to accurately detect the deterioration state of the ink through maintenance inspections, and it is also difficult to carry out regular maintenance inspections.

The object of the present invention is to provide an inkjet printer and an inkjet printer control method that can automatically detect changes in the ink state over time based on the actual printed state.

To solve the above problems, the present invention provides an inkjet printer that includes, as an example, an ink nozzle that atomizes ink and ejects the ink particles, a charging electrode that imparts a charge amount corresponding to a printed character to the ink particles, a deflection electrode that deflects the ink particles that have passed through the charging electrode according to the charge amount and causes them to fly toward a printed object, and a gutter that collects non-charged ink particles that are not used for printing, and a control unit that stores printed character information, calculates a charging voltage for imparting the charge amount based on a character pattern corresponding to the printed character information, and controls the charging electrode, and is provided with an inspection device that captures the results of printing on the printed object as an image and inspects the printing condition using the image, and the inspection device calculates the dot position deviation between the printed dot position of a target dot determined for each printed character and the target position of the target dot, stores the dot position deviation in chronological order, and judges the ink condition of the ink based on the stored dot position deviation.

As another example of the present invention, the control method of an inkjet printer includes a print head including an ink nozzle that atomizes ink and ejects the ink particles, a charging electrode that imparts an amount of charge corresponding to a printed character to the ink particles, a deflection electrode that deflects the ink particles that have passed through the charging electrode according to the amount of charge and causes them to fly toward a printed object, and a gutter that collects non-charged ink particles not used for printing, and stores printed character information, calculates a charging voltage for imparting the amount of charge based on a character pattern corresponding to the printed character information, and controls the charging electrode, and captures the results of printing on the printed object as an image, determines the dot position of a target dot determined for each printed character from the image, calculates a dot position deviation, which is the deviation between the dot position and a target dot position for the target dot, stores the dot position deviation in chronological order, and judges the ink condition of the ink based on the stored dot position deviation.

The present invention provides an inkjet printer and a method for controlling an inkjet printer that makes it possible to estimate the state of ink during use from the actual printing state.

FIG. 1 is a diagram showing the appearance of an inkjet printer. FIG. 1 is a diagram illustrating a schematic configuration of an inkjet printer. 1 is a diagram showing a configuration of an inkjet printer according to a first embodiment of the present invention. 10 is an example of an operational flowchart for determining a dot of interest in the first embodiment. FIG. 2 is a diagram for explaining main functions in the first embodiment. 11 is an example of statistical information of variation for determining the ink condition. FIG. 11 is a diagram showing a configuration of an inkjet printer according to a second embodiment of the present invention. FIG. 11 is a diagram showing a configuration of an inkjet printer according to a third embodiment of the present invention. 13 is an example of an operational flowchart for determining a dot of interest in the third embodiment. FIG. 13 is a diagram showing the configuration of an inkjet printer according to a fourth embodiment of the present invention.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that the present invention is not to be interpreted as being limited to the contents of the embodiments described below. Those skilled in the art will easily understand that the configuration can be changed without departing from the technical idea or intent of the present invention. In addition, in the configurations of the embodiments described below, the same symbols are used in common between the drawings for the same devices or parts having similar functions, and duplicated descriptions may be omitted. In addition, the position, size, shape, range, etc. of each component shown in the drawings do not represent the actual position, size, shape, range, etc., in order to make the invention easier to understand. Therefore, the present invention is not limited to the position, size, shape, range, etc. of the component devices disclosed in the drawings.

Example 1
First, a first embodiment of the present invention will be described with reference to Figs. 1 to 6. Fig. 1 is an external view of the entire inkjet printer. Fig. 2 is a diagram showing a schematic configuration of the inkjet printer. Fig. 3 is a diagram showing the entire system configuration of the inkjet printer in the first embodiment of the present invention. Fig. 4 is an example of an operational flowchart for determining a dot of interest. Fig. 5 is a diagram showing the main functions in the first embodiment. Fig. 6 is an example of statistical information on variation for determining the ink condition.

First, the schematic configuration and print control of the inkjet printer in the first embodiment of the present invention will be described with reference to Figures 1 and 2.

In FIG. 1, the inkjet printer comprises a print head 2 that receives a supply of ink and prints, and a device main body 1 that delivers the ink for printing to the print head 2 and collects the ink not used for printing from the print head 2. A cable 5 connects the device main body 1 and the print head 2. The device main body 1 also comprises an internal control unit 3. This control unit 3 controls the ink supply of the device main body 1 and the printing control (charge control) of the print head 2. The operation and display unit 4 is disposed on the front of the device main body 1, and has the function of displaying information related to printing and inputting information such as printed characters to the control unit 3. A touch panel or the like is used for the operation and display unit 4.

The print head 2 prints a predetermined pattern (print data previously stored in the control unit 3) on a print object 10, such as a product moving on a transport device 6, such as a belt conveyor. The arrow in the figure indicates the direction in which the print object 10 moves. When the print object 10 reaches the printing position, the control unit 3 controls the print head 2, which then prints on the print object 10.

Next, the printing principle of an inkjet printer will be explained with reference to Figure 2. In Figure 2, the same devices as those in Figure 1 are designated by the same reference numerals. First, the device main body 1 is equipped with an ink container 11 that stores (holds) ink a, an ink supply pump 12 for supplying ink a to the print head 2, and an ink recovery pump 13 for recovering ink not used for printing back into the ink container 11.

The print head 2 is equipped with an ink nozzle 21 for atomizing and ejecting the ink delivered from the device main body 1. The ink nozzle 21 is equipped with a vibrator (piezoelectric element), and the ink in the ink nozzle 21 is excited by applying a periodic voltage to the piezoelectric element. This causes the ink to be ejected from the ink nozzle 21 as an ink column b, and then ejected as ink particles. The print head 2 is also equipped with a charging electrode 22 that imparts a charge corresponding to the printing content to the passing ink particles, a deflection electrode 23 that deflects the charged ink particles c according to the amount of charge, causing them to fly toward the printing target 10, and a gutter 24 for collecting ink particles d that are not used for printing.

The deflection electrode 23 generates an electrostatic field between the positive and negative electrodes, deflecting the ink particles that pass through. As a result, the charged ink particles c used for printing fly toward the print target 10 and land (land), thereby executing the printing. Meanwhile, the uncharged ink particles d that are not used for printing travel straight through the deflection electrode 23 and are collected by the gutter 24. The ink collected by the gutter 24 is collected by the ink recovery pump 13 into the ink container 11. The collected ink is reused for printing.

The control unit 3 has a function of supplying a charging voltage to the charging electrode 22 of the print head 2 to perform printing control (charging control), and a main body control function of controlling the operation of the pump and the like within the device main body 1. The following mainly describes the printing control in the print head 2, and the configuration and operation of inputting the printed results (printing results) and performing ink condition judgment.

Next, the configuration and operation of a first embodiment of the present invention having a function of determining the state of ink based on the print result will be described with reference to FIG.
First, in Fig. 3, the devices with the same reference symbols (numbers) as those in Fig. 1 and Fig. 2 indicate the same devices as those in Fig. 1 and Fig. 2. Therefore, the operation description of the devices already described may be omitted. In addition, the control unit 3 and the inspection device 7 in the first embodiment of the present invention can be realized by hardware having the functions of a computer, but in order to facilitate understanding of the first embodiment, the internal configurations of the control unit and the inspection device are described here by displaying them in block diagrams.

In FIG. 3, the control unit 3 inputs the contents (print data) to be printed on the printing object 10 from the operation/display unit 4, and stores it in an internal memory (not shown). The target dot determination unit 32 of the control unit 3 determines the target dot based on the print data 31 stored in this memory.

Here, the "notable dot" is a dot selected from among the M rows x N columns of print dots that make up the printed character. Basically, one notable dot is sufficient for each character, but multiple dots are also acceptable. In the following explanation, the number of notable dots is assumed to be one for each character. As for the notable dot in this embodiment 1, a dot that is less affected by the Coulomb force acting on the ink particles in flight is selected as described below, but the present invention is not limited to this, and any dot can be selected as the notable dot. Also, in embodiment 1, the print data is imported and the notable dot is determined online, but once the print data (characters to be printed) is determined, a dot that has been determined in advance for each character may be determined (selected) as the notable dot.

In FIG. 3, the charging voltage control unit 33 of the control unit 3 is provided to control the amount of charge applied to the ink particles for each dot that constitutes the print, and supplies the charging voltage to be applied to the flying ink particles to the charging electrode 22. The dot sharing unit 34 is provided to share information about the target dot determined by the target dot determination unit 32 with the inspection device 7. The correction information input unit 35 is provided to input correction information (charge control correction value) determined by the inspection device 7. Based on this correction information, the charging voltage control unit 33 executes correction control of the charging voltage to impart charge to the moving ink particles.

The inspection device 7 is provided to capture the print result printed on the print object 10 by the print head 2 as an image and inspect the print condition based on this image (determine whether the print condition is acceptable or not), but in this embodiment 1 also has a function to determine the ink condition and a correction value calculation function. The camera 70 takes an image of the print object 10 after printing as it is transported by the transport device 6, and supplies the image to the inspection device 7.

The inspection device 7 is provided with an image processing unit 71, which takes in the image captured by the camera 70 and outputs the printing status through image processing. The image processing unit 71 processes the image so that the printing status can be determined on a print dot basis. Note that image processing is a process that removes noise and the like from the image and performs image feature extraction and image recognition, but these are well-known matters and detailed explanations will be omitted here.

The dot position deviation acquisition unit 72 is provided to obtain the print position deviation (dot position deviation) between the dot position of the target dot obtained from the print result by image processing by the image processing unit 71 and the planned print position (target dot position) of the target dot.

The correction information calculation unit 73 calculates correction information (correction value) to eliminate (reduce) the deviation based on the dot position deviation from the dot position deviation acquisition unit 72.

Specifically, the correction value is determined from the difference between the planned landing coordinates of the dot of interest (target dot position) and the acquired absolute position of the dot. When determining the correction value, the effect of relative coordinates is taken into consideration. Relative coordinates are necessary to correct the misalignment of the entire character. In inkjet printers, the entire character may be misaligned due to misalignment of the object to be printed or misalignment of the timing of the image capture by the inspection device. In this case, a deviation in the absolute value also occurs, but since this is not due to deterioration of the ink, the effect of this is excluded from the judgment. The correction value is mainly performed in the form of a correction to the added voltage value. If the charging rate decreases due to deterioration of the ink, the landing position will be lower than expected even if the expected charge is added. To correct this, it is necessary to add more charging voltage to the ink.

As already explained, this calculated correction information is supplied to the charging voltage control unit 33 via the correction information input unit 35 of the control unit 3 and is used to control the correction of the charging voltage.

The dot position deviation for the target dot obtained by the dot position deviation acquisition unit 72 is supplied to the ink condition determination unit 74. The ink condition determination unit 74 stores the input dot position deviation for the target dot position in chronological order, and determines the state of the ink in use based on the stored dot position deviation. That is, it determines whether the state of the ink in use has deteriorated due to long-term use, etc., and is in a state where the ink should be replaced. Specifically, in this embodiment 1, the dot position deviations for the past N times stored in chronological order are statistically processed to determine the ink condition. For example, if there is a large variation, it is determined that the ink is deteriorating, and the ink condition is determined.

If the ink condition determination unit 74 determines that the ink condition has deteriorated to the point where ink replacement is required, or that the ink condition is approaching a state where ink replacement is required, it outputs warning information via the warning output unit 75. The warning information is displayed on a display unit (not shown) provided in the inspection device, or is sent (output) to the outside for transmission to a monitoring center (not shown) or the like.

Next, a specific example of a method for determining a dot of interest in the dot of interest determination unit 32 will be described with reference to FIG. 4. Note that the method for determining a dot of interest is not limited to the method described here.

In FIG. 4, when print data 31 is input, steps S01 to S08 are performed to determine the dot of interest in each print character. In step S01, one character is selected from the print data, and in step S02, one of the dots that make up the selected character is selected.

In step S03, the dot position score of the selected dot is obtained. By determining a score in advance for each dot that constitutes each printed character, the dot position score of each dot can be obtained. For example, the score is determined as follows. That is, in order for the print head to print upper dots, it is necessary to apply a larger charging voltage and greatly change the flight path of the ink particles. For this reason, the upper dots are characterized by being weak and easily disturbed by external disturbances. Therefore, in order to eliminate the influence of external disturbances and extract only changes due to aging, an algorithm is used that makes it more likely that lower dots will be selected as the dot of interest. Specifically, the dot position score is determined so that the score of the lower dots is higher. For example, if the height direction of the print is 10 dots, the score is determined so that 1 point from the top row...10 points. In addition, normalization is performed at the end so that the influence contributing to the dot of interest is equal for each score part. In the case of the previous example, a division by 10 is performed at the end.

Next, in step S04, a score is given that takes into account the effects of merge scatter. Merge scatter is a phenomenon in which the flight path of flying ink particles changes due to the Coulomb force between them. When dots to be printed are continuous vertically, they are susceptible to the effects of merge scatter, reducing the stability of the printed dots. Therefore, a point deduction process is performed on dots that have dots before and after them. In theory, all flying ink particles affect each other, but in this embodiment, only the three dots before and after are considered. If there are dots immediately before and after, -3 points are added for each, and -2 points and -1 point are added for each dot that is one dot apart. Finally, a standardization process is performed.

Next, in step S05, a score is assigned based on the relative position of the dot of interest in the previous (first printed) printed character. Relative position information for each dot of interest is required to detect the deviation of the dot of interest. Since the larger the relative position, the greater the amount of information that can be obtained, points are added according to the magnitude of the relative position. In this embodiment, one point is added each time the relative position is off by one dot. Finally, normalization is performed.

In step S06, it is determined whether the processing in steps S03 to S05 has been completed for all dots that make up the character selected in step S01. If there are dots that have not yet been processed (if NO), the process returns to step S02 and repeats until processing of all dots has been completed. If processing of all dots in the character selected in step S01 has been completed (if YES), the process proceeds to step S07.

In step S07, the scores of all dots in the character selected in step S01 are totaled, the dot with the highest score is determined, and this dot with the highest score is selected (determined) as the "dot of interest" for that character.

In step S08, it is determined whether or not the selection of the focus dot for all characters in the printed text has been completed. If the selection of the focus dot for all characters has not been completed (if NO), the process returns to step S01, a remaining character is selected, and the above-described processing of steps S02 to S07 is performed on the newly selected character.

Then, in step S08, when the selection of the focus dot for all characters is completed, this operation ends. In this way, one focus dot can be selected for each printed character.

In FIG. 4, the dot position score, merge scatter score, and previous character relative position score for each dot that makes up the printed character are calculated, and the sum of these is used to determine the dot of interest, but it is also possible to use some of these scores to determine the dot of interest. For example, it may be the sum of the dot position score and the merge scatter score. The dot of interest determination unit 32 in FIG. 3 determines one dot of interest for each character to be printed using the method described above.

Next, the main functions of the inspection device 7 shown in FIG. 3 will be described with reference to FIG. 5. The dot position deviation acquisition function 100 is a function of the dot position deviation acquisition unit 72 in FIG. 3. The position deviation of the target dot obtained by the dot position deviation acquisition function 100 is input to the correction information determination function 110, which calculates a correction value, and the ink state determination function 130. The correction information determination function 110 determines the correction value and outputs it to the correction control function 120. The correction control function 120 executes correction control in the charge control. The ink state determination function 130 stores the dot position deviation of the target dot in chronological order, and determines the state of the ink being used based on the stored dot position deviation data. Specifically, for example, the ink state is determined by looking at the degree of variation in the dot position deviation for the past N times. Then, if it is determined that ink replacement is necessary as a result of this ink state determination, the determination result is given to the ink replacement warning function 140. As a result, the ink replacement warning function 140 issues a warning.

Next, a specific example of the ink condition determination method in the ink condition determination unit 74 in FIG. 3 will be described with reference to FIG. 6. This determination is made using the dot position deviation of a dot of interest stored in chronological order in the past. That is, the dot position deviations stored in chronological order are referenced, for example, for the past 10 times, and if the number of dot position deviations that exceed a threshold is counted, it is determined that the ink should be replaced and a warning is issued. Of course, there are multiple methods for determining the ink condition, and methods other than this one may also be used. That is, this can be realized by determining ink deterioration using known statistical methods using the dot position deviation of a dot of interest stored in chronological order.

As described above, according to the first embodiment of the present invention, a dot of interest is determined for each printed character, a dot position deviation is obtained, which is the deviation between the dot position of the dot of interest extracted from the character actually printed on the printing target and the target dot position, and a correction value for charge control is obtained based on this dot position deviation to perform printing correction control. This dot position deviation is also stored in chronological order, and the state of ink deterioration can be judged based on this stored dot position deviation. Furthermore, if the judged ink condition has reached a level requiring ink replacement (including when approaching a level requiring ink replacement), a warning can be issued to encourage ink replacement. This can reduce the work of ink maintenance and inspection.

Example 2
Next, a second embodiment of the present invention will be described with reference to Fig. 7. Fig. 7 is a diagram showing the overall system configuration of an inkjet printer in the second embodiment of the present invention.

First of all, this Example 2 and Example 1 shown in FIG. 3 have basically the same functions and are also almost the same in configuration. Therefore, a detailed explanation of Example 2 will be omitted, and the explanation will focus on the differences from Example 1.

In the first embodiment, an inspection device 7 was provided, which determined the dot position deviation of the target dot, calculated the correction value, and determined the ink condition.

In contrast, Example 2 in FIG. 7 differs from Example 1 in that the inspection device 7 is not provided, and all of the arithmetic processing functions that were performed by the inspection device 7 are performed within the control unit 3.

This second embodiment of the present invention has the same effects as the first embodiment. Furthermore, in this second embodiment, the functions performed by the inspection device are executed within the printing control unit 3, making it possible to make the overall configuration compact.

Example 3
Next, a third embodiment of the present invention will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a diagram showing the overall system configuration of an inkjet printer in the third embodiment of the present invention. Fig. 9 is a flowchart explaining a method of determining a dot of interest in the third embodiment.

First, the configuration of Example 3 shown in FIG. 8 is almost the same as Example 1 (FIG. 3), but there are some differences. When the reference numerals (numbers) given to the devices constituting FIG. 8 are the same as the reference numerals (numbers) given to the devices in FIG. 3, those devices have the same functions. Therefore, detailed explanations of those devices will be omitted. Similarly, in the flowchart for determining a dot of interest shown in FIG. 9, the same reference numerals are given to the same processing operations as in FIG. 4, and explanations thereof will be omitted. Below, the differences between Example 3 and Example 1 will be mainly explained.

In this embodiment 3, even when printing is relatively stable, it is possible to discover and correct degradation in print quality due to dot position deviation of the dot of interest. That is, in the first embodiment, when selecting the dot of interest, a stable dot that is less susceptible to disturbances is selected. However, for example, when the printing speed is slow, the influence of disturbances is small, and selecting a stable dot may make it difficult to capture the effects of ink deterioration and the like. Therefore, in this embodiment 3, the print stability is input from the outside, and the score algorithm is corrected based on that.

In FIG. 8, the difference from the configuration of Example 1 is that print stability 36 is stored in a memory (not shown) in the control unit 3. In this Example 3, print stability 36 is set from the operation/display unit 4. In addition to this method, it is also possible to input parameters such as the line speed and create a parameter called print stability from them.

Figure 9 shows a flowchart for determining the dot of interest using print stability. Compared to Figure 4, which is the flowchart for the first embodiment, step S10, which uses print stability, has been added to the calculations of steps S03 to S05. Based on this, the method of adding points for each score section is changed. For example, in step S03, which determines the dot position score, the dot position that will have the highest score is changed according to the print stability. In the first embodiment, the lowest dot was set to have the highest score, but here, the upper dot is set to have the highest score according to stability, and an algorithm is used in which the score is added so that one point is reduced for every dot that is one dot away from that. Similarly, in steps S04 and S05, a score is set that takes print stability into consideration, and the score for each dot is determined based on that.

According to the third embodiment described above, it is possible to obtain the same effect as the first embodiment, and it is also possible to detect and correct deterioration in print quality by using the target dot even when printing is stable.

Example 4
Next, a fourth embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a diagram showing the overall system configuration of an inkjet printer in the fourth embodiment of the present invention.
The fourth embodiment has a configuration similar to that of the first embodiment shown in FIG. 3, but is different in that a print image transmission unit 76 for transmitting a print image to the outside is provided. The other configurations and functions are similar to those of the first embodiment. The following description will focus on the configurations that are different from the first embodiment.

In FIG. 10, the inspection device 7 determines the dot position deviation of the target dot, calculates a correction value, judges the ink condition, and outputs warning information if the ink has deteriorated beyond a certain level. Furthermore, the inspection device 7 in Example 4 has a function of outputting the image captured by the print image transmission unit 76 from the camera 70, or image information obtained by processing this image in the image processing unit 71, to an external system such as a service center.

This eliminates the need for maintenance personnel to report printing conditions, allowing for more rapid maintenance response. In many cases, the parts that need to be replaced on an inkjet printer can be determined from disturbances in the printing, and by sending this information in advance, more efficient maintenance is possible. Additionally, by sending internal information about the inkjet printer, it is also possible to improve the accuracy of maintenance.

The fourth embodiment described above has the same effects as the first embodiment, and enables more efficient maintenance.

1...Device body, 2...Print head, 3...Control unit, 4...Operation and display unit, 5...Cable, 6...Transportation device, 7...Inspection device, 10...Printing object, 11...Ink container, 12...Ink supply pump, 13...Ink recovery pump, 21...Ink nozzle, 22...Charging electrode, 23...Deflection electrode, 24...Gutter, 31...Printing data, 32...Target dot determination unit, 33...Charging voltage control unit, 34...Dot sharing unit, 35...Correction information input unit, 36...Printing stability, 70...Camera, 71...Image processing unit, 72...Dot position deviation acquisition unit, 73...Correction information calculation unit, 74...Ink state determination unit, 75...Warning output unit, 76...Printing image transmission unit

Claims (14)

an inkjet printer comprising: a print head including an ink nozzle which atomizes ink and ejects the ink particles, a charging electrode which imparts an amount of charge corresponding to a printed character to the ink particles, a deflection electrode which causes the ink particles which have passed through the charging electrode to be deflected according to the amount of charge and fly toward a print target, and a gutter which collects non-charged ink particles not used for printing; and a control unit which stores print character information, calculates a charging voltage for imparting the amount of charge based on a character pattern corresponding to the print character information, and controls the charging electrode,
providing an inspection device that captures the result of printing on the printing object as an image and inspects the printing condition using the image;
The inspection device calculates a dot position deviation between a printed dot position of a dot of interest determined for each printed character and a target position of the dot of interest, stores the dot position deviation in chronological order, and judges the ink condition of the ink based on the stored dot position deviation. The inkjet printer according to claim 1, characterized in that the inspection device calculates correction information for reducing the dot position deviation based on the dot position deviation, and the control unit inputs the correction information and corrects and controls the charging electrode. The inkjet printer according to claim 1 or 2, characterized in that the inspection device issues a warning to encourage ink replacement when the ink condition indicates that the ink should be replaced. An inkjet printer according to claim 1 or 2, characterized in that the inspection device calculates the dot position deviation, stores the dot position deviation in chronological order, and the control unit judges the state of the ink based on the stored dot position deviation. The inkjet printer according to claim 1, wherein the inspection device transmits image information obtained from the image to an external device. The inkjet printer according to claim 1, characterized in that the dot of interest is determined for each printed character based on the total value of one or more of the following points: a dot position score for each dot constituting a printed character, a merge scatter score, and a previous character relative position score. The inkjet printer according to claim 6, characterized in that the dot position score, the merge scatter score, and the previous character relative position score are changed according to the printing stability. The inkjet printer according to claim 1, characterized in that the ink condition is determined based on the variation in the dot position deviations stored for the past N times. A control method for an inkjet printer comprising: a print head including an ink nozzle which atomizes ink and ejects the ink particles, a charging electrode which imparts an amount of charge corresponding to a printed character to the ink particles, a deflection electrode which causes the ink particles which have passed through the charging electrode to be deflected according to the amount of charge and fly toward a print target, and a gutter which collects non-charged ink particles not used for printing; and storing print character information, and calculating a charging voltage for imparting the amount of charge based on a character pattern corresponding to the print character information, and controlling the charging electrode, the method comprising:
A control method for an inkjet printer, which captures the result of printing on the printing target as an image, obtains a dot position of a focus dot determined for each printed character from the image, calculates a dot position deviation which is the deviation between the dot position and a target dot position of the focus dot, stores the dot position deviation in chronological order, and judges the ink condition of the ink based on the stored dot position deviation. The inkjet printer control method according to claim 9, further comprising: calculating correction information for reducing the dot position deviation based on the dot position deviation; and correcting and controlling the charging electrode based on the correction information. The inkjet printer control method according to claim 9, characterized in that if the ink state indicates that the ink should be replaced, a warning is issued to encourage the user to replace the ink. The inkjet printer control method according to claim 9, further comprising transmitting image information obtained from the image to an external device. A method for controlling an inkjet printer as described in claim 9, characterized in that the dot of interest is determined for each printed character based on the total value of one or more of the following points: a dot position score for each dot constituting a printed character, a merge scatter score, and a previous character relative position score. The inkjet printer control method according to claim 9, characterized in that the ink state is determined based on the variation in the dot position deviations stored for the past N times.

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