JP7463171B2 - Inspection system for inspecting circulation state of liquid ejection head, liquid circulation device, and liquid ejection device - Google Patents

Description

The present invention relates to an inspection system for inspecting the circulation state of a liquid ejection head, a liquid circulation device, and a liquid ejection device.

As a recording device for recording characters and images on a recording medium, there is a liquid ejection device that ejects liquid toward the recording medium to perform recording. Such a liquid ejection device has a liquid ejection head that is equipped with an ejection port for ejecting liquid.

It is known that when the ejection port is exposed to the atmosphere, the volatile components in the liquid evaporate from the ejection port into the atmosphere over time, causing the viscosity of the liquid inside the ejection port to increase. When the viscosity of the liquid inside the ejection port increases, the ejection speed of the ejected droplets slows down when the liquid is ejected, which can affect the landing accuracy. In particular, when there is a long period of time during which the liquid is not ejected (hereinafter referred to as rest time), the increase in the viscosity of the liquid becomes significant, and the ejection port may experience ejection problems.

As one measure against this phenomenon of thickening of the liquid, Patent Document 1 discloses a method of suppressing thickening of the liquid in the ejection port by circulating the liquid in the pressure chamber between the pressure chamber and the outside (hereinafter, sometimes referred to as liquid circulation).

As a method for checking whether the liquid is circulating normally, a method of printing a pattern such as a straight line after a long rest period and evaluating the pattern to check the state of circulation is considered. A specific explanation will be given with reference to FIG. 8. FIG. 8(a) shows the print result obtained when the circulation is normal, and the liquid ejected from each ejection port forms a substantially straight line. On the other hand, FIG. 8(b) shows an example of the print result obtained when the liquid circulation is defective in the center of the ejection port row. When the liquid circulation is not normal, the viscosity of the liquid in the ejection port increases, and the ejection speed of the liquid ejected from the ejection port decreases. Therefore, the liquid ejected from the ejection port located in the center of the poor circulation lands on the rear side (rear side in the X direction) in the relative movement direction between the liquid ejection head and the recording medium. The difference in the landing position due to the delay in the landing of the liquid is used to check the state of circulation.

JP 2017-177437 A

However, if there is an abnormality in the liquid circulation throughout the entire nozzle row, and the ejection speed of the liquid ejected from each nozzle decreases uniformly, the printed result will be a roughly straight line pattern similar to that shown in Figure 8(a). Therefore, if there is an abnormality in the liquid circulation throughout the entire nozzle row, there is a risk that the liquid circulation will be erroneously determined to be normal.

In view of the above problems, the present invention aims to provide an inspection system that can prevent erroneous inspection of the circulation state when an abnormality occurs in the liquid circulation throughout the entire ejection port array.

The above problem is solved by the present invention described below. That is, the present invention provides an inspection system for inspecting the circulation state of a liquid ejection head that has an ejection port array consisting of a plurality of ejection ports that eject liquid, and a pressure chamber that communicates with the ejection ports and has a pressure generating element that generates pressure to eject liquid from the ejection ports, and that circulates the liquid in the pressure chamber between the outside of the pressure chamber and controls the viscosity of the liquid in the ejection port. The ejection port array has a first group of ejection ports and a second group of ejection ports, and the system includes a viscosity adjustment process for increasing the viscosity of the liquid in the ejection port of the second group to be higher than the viscosity of the liquid in the ejection port of the first group, a circulation process for circulating the liquid in the pressure chamber that communicates with the ejection port of the second group between the outside of the pressure chamber, and an inspection process for inspecting the circulation state of the liquid ejection head based on the difference between the landing position of the liquid ejected from the ejection port of the first group and the landing position of the liquid ejected from the ejection port of the second group.

The present invention provides an inspection system that can properly inspect the state of circulation without erroneous judgment, even when an abnormality occurs in the liquid circulation throughout the entire ejection port array.

FIG. 2 is a perspective view showing a liquid ejection head and an element substrate. FIG. 11 is a flowchart showing a flow of a liquid circulation inspection. FIG. 4 is a diagram showing a test pattern according to the first embodiment; 5 is a flowchart showing a flow of evaluating a test pattern according to the first embodiment. FIG. 4 is a diagram showing image processing of a test pattern. 10A to 10C are views showing image processing of a test pattern according to the second embodiment. FIG. 13 is a diagram showing a conventional inspection pattern.

The embodiment of the present invention will be described with reference to the drawings. Note that in each drawing, parts having the same function are given the same reference numerals, and their description may be omitted.

(Liquid ejection head)
FIG. 1 is a diagram showing an example of a liquid ejection head 10 that can be inspected by the present invention. FIG. 1(a) is a perspective view showing the liquid ejection head 10. As shown in the figure, the liquid ejection head 10 has a support member 1 and a plurality of element substrates C that eject liquid such as ink, and the support member 1 supports the element substrates C. The plurality of element substrates C are bonded to the support member 1 via an adhesive layer (not shown). In the liquid ejection head 10, eight element substrates C1 to C8 are linearly arranged on the same surface of the support member 1 as the element substrates C. The element substrates C1 to C8 may each have the same or approximately the same shape, or may have different shapes. In FIG. 1(a), the element substrates C1 to C8 have the same shape and are rectangular when viewed from above, but may have a parallelogram or trapezoid shape. The number of element substrates C is not limited to eight, and may be any number.

Figure 1(b) is an enlarged perspective view of one element substrate C. As shown in Figure 1(b), the element substrate C has a plurality of ejection ports 3 for ejecting liquid. The ejection ports 3 are arranged in four rows, 3a to 3d, approximately parallel to the longitudinal direction (Y direction) of the element substrate C. Each of the ejection port rows 3a to 3d is actually composed of an array of 512 ejection ports 3, but the number of ejection ports is omitted in Figure 1(b). Furthermore, the number of ejection port rows is not limited to four and may be any number of rows.

Although not shown, the element substrate C is equipped with a pressure chamber that communicates with the ejection port 3, a supply port for supplying liquid to the pressure chamber, and a pressure generating element that generates pressure to eject the liquid. The ejection port 3 and the pressure generating element are arranged facing each other with the pressure chamber in between, and the liquid in the pressure chamber is ejected from the ejection port 3 by the pressure generated by the pressure generating element. In addition, in order to suppress the increase in viscosity of the liquid due to evaporation of the liquid (water, etc.) from the ejection port 3, the liquid in the pressure chamber is circulated between the outside of the pressure chamber. In other words, the liquid ejection head 10 is configured to circulate the liquid in order to control the viscosity of the liquid in the ejection port.

(Circulation inspection device)
FIG. 2 is a diagram showing a circulation inspection device 20 for inspecting the state of circulation in the liquid ejection head 10. In the circulation inspection device 20 shown in FIG. 2, a horizontal beam 23 is installed between two supports 22 on a base plate 21, and a camera 25 for reading the liquid ejection head 10 to be inspected and an inspection pattern is attached to the beam 23 facing downward. On the base plate 21, a Y stage 26 that can move between the supports 22 in the Y direction is mounted, and an X stage 27 that can move in the X direction (the direction in which the recording medium 28 moves relative to the liquid ejection head 10 (relative movement direction)) is mounted thereon. The recording medium 28 is adsorbed and fixed on the X stage 27. In addition, a liquid tray 29 for receiving the liquid that is ejected from the liquid ejection head 10 and is not to land on the recording medium 28 is fixed to the X stage 27. The liquid that is not to land on the recording medium 28 refers to the liquid that is ejected in the process in step S3 described later.

When inspecting the circulation state of the liquid ejection head 10, the Y stage 26 is moved below the liquid ejection head 10, and an inspection pattern is printed on the recording medium 28 while driving the X stage 27 and ejecting liquid by the liquid ejection head 10 in conjunction with each other. The Y stage 26 and the X stage 27 are then driven so that the inspection pattern is positioned below the camera 25. The camera 25 then reads the inspection pattern printed on the recording medium 28, and the inspection pattern read by an image processing device (not shown) is evaluated to inspect the circulation state.

First Embodiment
A first embodiment of an inspection system for inspecting the state of circulation will be described with reference to Figs. 3 to 6. Hereinafter, among the ejection ports constituting the ejection port array, the ejection ports belonging to the area not to be inspected will be referred to as the first group of ejection ports, and the ejection ports belonging to the area to be inspected will be referred to as the second group of ejection ports. Fig. 3 is a flowchart showing a method for inspecting the state of circulation in this embodiment. In this embodiment, the inspection of odd-numbered element substrates C1, C3, C5, and C7 among the eight element substrates C1 to C8 arranged in the liquid ejection head 10 shown in Fig. 1(a) will be described. At this time, even-numbered element substrates C2, C4, C6, and C8 are element substrates having ejection ports not to be inspected.

First, the liquid ejection head 10 to be inspected is mounted on the circulation inspection device 20, and then the recording medium 28 is mounted on the X-stage 27 (step S1).

Next, the X-stage 27 and the Y-stage 26 are moved to a predetermined initial position (step S2). The initial position is a position where the ink tray 29 fixed to the X-stage 27 is directly below the liquid ejection head 10.

Next, droplets are continuously ejected from all the ejection ports (step S3). At this time, the droplets ejected from each ejection port 3 are collected in the ink receiving tray 29 and do not land on the recording medium 28. By performing step S3, all the ejection ports can be made to eject liquid normally. This is because, even if an ejection port is defective, by continuously ejecting liquid from the ejection port, the thickened liquid in the ejection port is ejected into the ink receiving tray 29, and fresh liquid is refilled into the ejection port. In other words, by performing step S3, only liquid with a viscosity that allows normal ejection is present in the ejection port. In step S3, low-viscosity liquid is present in the ejection port (viscosity control process). In this way, the circulation inspection device has a viscosity control means that can perform step S3.

In step S3, liquid is continuously ejected from all the ejection ports in order to make the ejection ports capable of ejecting normally, but this embodiment is not limited to this. In other words, any process that can make the ejection ports capable of ejecting normally can be step S3. Therefore, for example, a cap member (not shown) may be attached to the element substrate C to suck the inside of the element substrate and release the liquid in the ejection ports to the outside, thereby lowering the viscosity of the liquid in the ejection ports and making the ejection ports capable of ejecting normally. In addition, in step S3, an example in which liquid is ejected from all the ejection ports has been described, but this embodiment is not limited to this. In other words, in step S3, liquid may be ejected only from the first group of ejection ports. This makes it possible to reduce the amount of liquid ejected from the ejection ports.

After that, when a predetermined time has elapsed, while continuing to discharge liquid from the non-tested discharge ports, only the discharge from the test-target discharge port 3 (the discharge ports of the odd-numbered element substrate) is stopped, and a period of suspension of discharge is provided (step S4, viscosity adjustment process). In this process, the test-target discharge port 3 enters a suspension period during which no discharge is performed, and the liquid in the discharge port increases in viscosity as the volatile components in the liquid evaporate. That is, by performing step S4, the viscosity of the liquid in the second group of discharge ports increases more than the viscosity of the liquid in the first group of discharge ports. The suspension period varies depending on the diameter of the discharge port and the components of the liquid, but in this embodiment, the suspension period is set to 2 minutes. In order to shorten this suspension period, air is blown toward the discharge port 3 using an air blow nozzle (not shown), which promotes the evaporation of the volatile components in the liquid. In this way, the circulation inspection device has a viscosity adjustment means that can perform step S4.

Then, the liquid in the pressure chamber connected to the ejection port 3 to be inspected is circulated (step S5, circulation process). At this time, if the liquid circulation function is normal, even if the ejection of liquid from the ejection port 3 is stopped, the liquid in the pressure chamber connected to the ejection port 3 is circulated to the outside of the pressure chamber, so the degree of thickening of the liquid in the ejection port 3 is minor. In the above, it has been described that the circulation process is performed after the viscosity adjustment process, but the present invention is not limited to this. That is, step S3 (viscosity control process) and step S4 (viscosity adjustment process) may be performed while constantly circulating the liquid. The circulation means for circulating the liquid by the circulation process is, for example, a pump. In this embodiment, the liquid ejection device (not shown) that ejects liquid using the liquid ejection head 10 has the circulation means, but the present invention is not limited to this. That is, the liquid ejection head 10 may have the circulation means (even in this case, since the circulation inspection device 20 has the liquid ejection head 10 equipped with the circulation means, the circulation inspection device 20 is said to have the circulation means). In addition, if the liquid ejection device has a circulation means, when inspecting the liquid circulation, only the liquid ejection head 10 is attached to the circulation inspection device 20, so the circulation inspection device 20 has the circulation means instead of the liquid ejection device.

Next, ejection of liquid from the ejection ports not subject to inspection is stopped, thereby stopping ejection from all ejection ports 3 (step S6), and the liquid ejection head 10 is moved onto the recording medium 28. After that, the test pattern is printed without any time delay from the cessation of ejection (step S7). The reason for performing steps S5 and S6 without any time delay is to ensure that the test pattern is printed properly even if the ejection ports 3 not subject to inspection (the ejection ports of the even-numbered element substrates) have poor liquid circulation. In other words, the ejection ports 3 not subject to inspection continue to eject liquid until just before the printing of the test pattern, so that they remain in a normal ejection state when the test pattern is printed, regardless of the circulation state of the ejection ports 3 not subject to inspection.

Next, the Y-stage 26 and the X-stage 27 are driven, the printed test pattern is read by the camera 25 (step S8), the read test pattern is evaluated (step S9), and the evaluation result is displayed (step S10), and the process ends. The evaluation of the test pattern will be described in detail later.

Up to this point, we have explained the inspection of odd-numbered element substrates C1, C3, C5, and C7, but the procedure is the same when inspecting even-numbered element substrates C2, C4, C6, and C8, except that the element substrate C that stops ejection in step S4 is the even-numbered one.

The test pattern printed in step S7 and the test pattern evaluation in step S9 will be described with reference to FIGS. 4 to 6. FIG. 4 is a schematic diagram of the entire printed test pattern. By ejecting one droplet at a time from each of the ejection port rows 3a to 3d of all element substrates C, straight lines 5a to 5d composed of droplets ejected from each ejection port row are formed. The test pattern evaluation is performed by image processing the pattern printed from the ejection port rows of the same row of two adjacent element substrates. FIG. 5 is a flowchart for evaluating the test pattern. FIG. 6 is a schematic diagram of the image processing procedure according to the flowchart of FIG. 5, and illustrates the test pattern printed by ejecting from the ejection port rows 3a of the element substrates C1 and C2. For the sake of explanation, FIG. 6 will be used below, but the evaluation procedure is similar for other element substrates C and other ejection port rows. In addition, since each ejection port row has 512 ejection ports 3 arranged, the same number of droplets land on the recording medium, but the number is omitted in FIG. 6 and the schematic diagrams following FIG. 6. Below, we will explain a flow for evaluating the liquid circulation function of the ejection port array 3a of the element substrate C1 as an example of the evaluation.

First, in step S21, an area to be image-processed is set from within the entire test pattern. In order to evaluate the ejection port array 3a of element substrate C1, the test pattern to be image-processed is 5a. Furthermore, since the element substrate to be evaluated is element substrate C1, the image processing area is set to area 7, which includes the straight lines printed by element substrates C1 and C2 in test pattern 5a, as shown in FIG. 6(a).

Next, in step S22, the image processing area 7 is divided into small sections. As shown in FIG. 6(b), the image processing area 7 is divided into a number of sections K (each section is numbered from the right end, such as K1, K2, K3, etc.). It is preferable that the width of section K is equal to or less than the diameter of one drop of the landed liquid (hereinafter also referred to as the landed droplet), and the vertical width is 5 to 10 times the diameter of the landed droplet. Here, the diameter of the landed droplet of the liquid ejection head 10 to be inspected is approximately 40 micrometers, and the width of section K is 30 micrometers and the vertical width is 200 micrometers.

The reason why the width of the section K is set to be less than the diameter of one droplet of the landed liquid is to allow for sensitive detection of changes in the landing position in the transport direction of the recording medium. For example, if the width is set large enough to accommodate multiple landing droplets within one section, and the landing positions of the multiple droplets that land within one section are scattered in the recording medium paper transport direction (X direction), the center of gravity position in the recording medium transport direction within one section will be near the average position of the multiple droplets. This is because, as will be described in detail later, the minimum and maximum values of the center of gravity position in the recording medium transport direction are used in the inspection here, making one section smaller allows for more accurate detection of the center of gravity positions of the minimum and maximum values. However, making it too small simply increases the number of sections without changing the results much, so a diameter of about one drop is appropriate.

The vertical width of each section K is set to 5 to 10 times the diameter of the landing droplet because we want the liquid droplets to land within the area of section K even if the circulation state is poor and the ejection speed is slow. If the vertical width of each section K is small and the area of section K is small, the liquid may land outside the area of section K if the ejection speed of the liquid is slow, and this may be treated as another defective form in which "liquid was not ejected." To avoid this, in this embodiment, the vertical width of each section K is set to 5 to 10 times the diameter of the landing droplet so that the droplets can land reliably in section K even if the ejection speed is somewhat slow.

Next, in step S23, whether or not part of the inspection pattern, i.e., the landed droplets, are present within each section K is detected from the pixel density, and if landed droplets are present, the area of the landed droplets is calculated. If the area of the landed droplets is less than a preset area, the section K is stored as having no landed droplets. If the landed droplets are equal to or greater than the set area, the center of gravity position in the X direction is calculated and stored for each section K. Figure 6(c) is a schematic diagram of section K2 when step S23 is executed, and the position indicated by the arrow in the figure is the center of gravity position in the X direction.

Next, in step S24, the presence or absence of any sections stored in step S23 as having no landed droplets is confirmed. If the liquid circulation is normal in all of the ejection ports 3 in the ejection port array 3a of the element substrate C1, then there are landed droplets of a predetermined area or more in the sections K other than the section K1 at the end of the straight line 5a. Therefore, if there is even one section in all sections other than the section K1 at the end that does not have landed droplets of a predetermined area or more, it is determined that there is an abnormality in the liquid ejection head 10, and the test pattern evaluation is terminated without evaluating the circulation.

If it is confirmed in step S24 that the landing droplets exist in all the sections K except the ends, the difference between the largest value (maximum value) and the smallest value (minimum value) of the center of gravity positions in the X direction determined for each section K in S23 is calculated in the next step S25. This difference represents the difference between the largest and smallest ejection speeds (ejection speed difference) of the liquid ejected from the ejection port. If this difference is greater than a predetermined value, it means that the liquid ejection head 10 has an ejection port 3 in which the liquid circulation is not functioning normally, and the liquid ejection head 10 is detected as an abnormal head (step S26, inspection process). On the other hand, if the difference is equal to or less than a predetermined value, it is determined that the liquid circulation of the liquid ejection head 10 is normal (step S26, inspection process). Then, the evaluation flow of the inspection pattern is terminated. In other words, the state of circulation is evaluated (inspected) based on the difference in the landing positions of the liquid. It is preferable that the predetermined value compared with the difference between the maximum and minimum values of the center of gravity positions in the X direction is any value within the range of 1.5 to 2.5 times the diameter of the landing droplet. If the specified value is less than 1.5 times, there is a risk that even if the liquid circulation is normal, the difference in the center of gravity position will be greater than the specified value due to an error, etc., and the circulation will be determined to be poor. Also, if the specified value is more than 2.5 times, there is a risk that even if the liquid circulation is poor, the difference in the center of gravity position will be less than the specified value, and the circulation will be determined to be normal.

For example, if the predetermined value is set to 2.0 times, and the difference between the maximum value and the minimum value is greater than 2.0 times the diameter of the landing droplet, it is determined that the liquid circulation is poor. If the difference between the maximum value and the minimum value is equal to or less than 2.0 times the diameter of the landing droplet, it is determined that the liquid circulation is normal. In this embodiment, the predetermined value is 80 micrometers. In this manner, the circulation inspection device has an inspection means capable of performing step S26. In this embodiment, the diameter of the landing droplet for calculating the predetermined value is set to the average value of the diameters of the droplets that land in each section K. However, the present invention is not limited to this, and the predetermined value may be a predetermined value.

If the difference in the liquid landing positions is greater than a predetermined value, the inspection system may display a message indicating that the liquid is not circulating normally, and if the difference in the liquid landing positions is equal to or less than the predetermined value, the inspection system may display a message indicating that the liquid is circulating normally.

Figure 6 (d) shows an example of the landing state when a small section is assigned to the image processing area 7 in step S22 of Figure 5, and there is a problem with the liquid circulation of all the ejection ports 3 of the ejection port row 3a of the element substrate C1, and the ejection speed is uniformly slow overall. Since the ejection speed of the landing droplets from C1 is uniformly slow, the landing state of the droplets ejected only from C1 is approximately a straight line. On the other hand, since the element substrate C2 is composed only of ejection ports that can eject liquid normally, the ejection speed of the landing droplets from the element substrate C2 is not slower than that of the element substrate C1. Therefore, even if the landing droplets from C1 land uniformly on the rear side of the recording medium transport direction, a liquid circulation abnormality can be detected by evaluating the difference between the maximum and minimum values of the X-direction center of gravity position of each section K, including the landing droplets from C2. When a test pattern such as that shown in FIG. 6(d) is obtained, the maximum value of the X-direction center of gravity position used in the calculation of step S24 is any value in the printing area by element substrate C2, and the minimum value of the X-direction center of gravity position is any value in the printing area by element substrate C1.

So far, the liquid circulation function evaluation of the nozzle array 3a of the element substrate C1 has been described, but other element substrates and nozzle arrays can be evaluated in the same way. To summarize the above, the nozzles that make up the nozzle array are divided into a first group and a second group that is the target of the inspection of the circulation state. The nozzles of the first group are made to be in a state where they can normally eject liquid, and the nozzles of the second group are made to have an increased viscosity of the liquid. In this state, liquid is ejected from the first and second groups to print and evaluate the inspection pattern. If the circulation of the nozzles of the second group is normal, the viscosity of the liquid in the nozzles of the second group increases only slightly at most. Therefore, there is no large difference between the landing position of the liquid from the nozzles of the first group and the landing position of the liquid from the nozzles of the second group, and the difference is equal to or less than a predetermined value. If the circulation of the nozzles of the second group is not normal, the difference in the landing position will be greater than a predetermined value. The state of the liquid circulation is inspected based on such differences.

In this manner, in this embodiment, even if poor liquid circulation occurs throughout a certain nozzle row on a certain element substrate, causing a uniform slowdown in the ejection speed, a test pattern is printed from an adjacent element substrate at a normal ejection speed, and these are combined and evaluated as a single pattern. This makes it possible to properly inspect the state of circulation without erroneously determining that poor circulation has occurred throughout a certain nozzle row.

In the above description, the circulation inspection device 20 shown in FIG. 2 was used as a device for inspecting the state of liquid circulation, but the present invention is not limited to using such an inspection device. That is, if a liquid ejection device having a liquid ejection head 10, such as an inkjet printer, is capable of performing the inspection flow shown in FIG. 3, the present invention can be suitably applied to the liquid ejection device. If the liquid ejection device has the functions of the present invention (viscosity adjustment means, circulation means, inspection means), the user of the liquid ejection device can easily check the liquid circulation state when he or she has doubts about the recording quality. Then, if it is determined that the liquid circulation is the cause of the deterioration of the recording quality, it is possible to suppress operations such as unnecessary recovery processing. If the liquid ejection device does not have a camera 25 (inspection means), the user can visually check the inspection pattern printed on the recording medium to inspect the state of liquid circulation. At this time, in order to make it easier for the user to determine whether the difference in the landing positions of the above-mentioned liquid is greater than a predetermined value, it is preferable to print a straight line having a predetermined length beside the inspection pattern.

Second Embodiment
A second embodiment will be described. Note that the same reference numerals as in the first embodiment are used to represent the same parts as in the first embodiment. Also, the description of the same contents as in the first embodiment will be omitted.

The liquid ejection head to be inspected in this embodiment is not a so-called page-wide head that corresponds to the width of the recording medium as shown in FIG. 1(a), but a head (not shown) equipped with only one element substrate C. Therefore, in the first embodiment, the element substrates C were inspected separately for odd and even numbers, but in this embodiment, which has only one element substrate, the ejection port arrays are inspected separately for odd and even numbers. Also, the inspection flow of this embodiment is largely similar to the flow of FIG. 3 described in the first embodiment, but there are some differences due to the difference in the number of element substrates C mounted, and the differences are described below.

In step S4, the ejection of liquid from the test object is stopped, but in this embodiment, the test object or non-object differs depending on the ejection port row within the same element substrate. Therefore, if the test object is an odd-numbered ejection port row, the ejection of liquid from the ejection port rows 3a and 3c is stopped, and if the test object is an even-numbered ejection port row, the ejection of liquid from the ejection port rows 3b and 3d is stopped.

The test pattern to be printed is the same as the pattern in the first embodiment (Figure 4), with straight lines 5a to 5d printed from each of the ejection port rows 3a to 3d. Note that since the liquid ejection head to be inspected in this embodiment is equipped with only one element substrate C, the straight lines 5a to 5d are short.

The flow for evaluating the inspection pattern read by the camera 25 is almost the same as the flow for the first embodiment (Figure 5), but after step S26, step S27 is added, which evaluates the distance between the odd-numbered straight line and the adjacent (even-numbered) straight line. The image processing for evaluating the straight lines 5a and 5b in step S27 will be described with reference to Figure 7.

Figure 7 is a schematic diagram of the process for evaluating the distance between two straight lines 5a and 5b. Each of the straight lines 5a and 5b is divided into small sections K, and the X-direction center of gravity position within each section is determined. After that, the difference in the X-direction center of gravity positions is calculated based on the X-direction center of gravity positions of sections with the same section number, for example, K2a and K2b, K3a and K3b, etc. Then, if even one of the differences between the sections K is outside a preset range (a point larger than a specified value), it is determined that the discharge speed is slow, in other words, that there is poor circulation of the liquid.

In this embodiment, even if poor liquid circulation occurs across an entire nozzle row on an element substrate, causing the ejection speed to slow down uniformly, a test pattern is printed from an adjacent nozzle row at the normal ejection speed, and the relative distance between them is evaluated. This makes it possible to properly inspect the state of liquid circulation without erroneously determining that poor circulation has occurred across an entire nozzle row.

Third Embodiment
A third embodiment of the present invention will be described. When describing the same parts as those in the first and second embodiments, the same reference numerals as those in the first and second embodiments will be used. Also, the description of the same contents as those in the first and second embodiments will be omitted.

The liquid ejection head to be inspected in this embodiment is a head (not shown) equipped with only one element substrate C, as in the second embodiment. However, the element substrate C has only one row of ejection ports, not four as in FIG. 1(b). The inspection flow in this embodiment is similar to the flow in FIG. 3 described in the first embodiment, but there are some differences due to the difference in the number of element substrates C mounted and the number of ejection ports 3 to be inspected. Therefore, the differences will be described below.

In this embodiment, one row (512 outlets) of outlets 3 is divided in half in the middle into two groups of 256 outlets each, with one group being the one not to be inspected (first group) and the other being the one to be inspected (second group). After that, the groups to be inspected and the non-tested groups are reversed and inspected in the same way, allowing the entire row to be inspected.

In step S4 (FIG. 3), ejection from the ejection ports being inspected is stopped by stopping ejection from the 256 ejection ports 3 belonging to the group being inspected. The printed inspection pattern is the same as the pattern in the first embodiment, and straight lines are printed from all the ejection ports 3 in the ejection port row.

The flow for evaluating the read test pattern is the same as that of the first embodiment (Figure 5), except that the length of the test pattern is different. That is, the test pattern is evaluated based on the presence or absence of a section K where no droplets are present, and the difference in the liquid landing position (center of gravity position in the X direction). Even if poor circulation occurs throughout the entire ejection port row, the liquid circulation can be properly inspected without erroneous judgment.

3: ejection port 3a to 3d: ejection port array 10: liquid ejection head

Claims (20)

an ejection port array including a plurality of ejection ports for ejecting liquid;
a pressure chamber communicating with the ejection port and having a pressure generating element that generates pressure for ejecting liquid from the ejection port;
having
1. An inspection system for inspecting a state of circulation in a liquid ejection head that controls a viscosity of the liquid in the ejection port by circulating the liquid in the pressure chamber between the pressure chamber and an outside of the pressure chamber, comprising:
the nozzle array includes a first group of nozzles and a second group of nozzles,
a viscosity adjusting step of increasing the viscosity of the liquid in the second group of ejection ports to be greater than the viscosity of the liquid in the first group of ejection ports;
a circulation step of circulating the liquid in the pressure chamber communicating with the second group of ejection ports between the pressure chamber and an outside of the pressure chamber;
an inspection step of inspecting a state of circulation in the liquid ejection head based on a difference between a landing position of liquid ejected from the ejection ports of the first group and a landing position of liquid ejected from the ejection ports of the second group;
An inspection system comprising: if a difference between a landing position of the liquid ejected from the ejection port of the first group and a landing position of the liquid ejected from the ejection port of the second group is greater than a predetermined value, it is determined that the circulation is poor and a message to that effect is displayed;
2. The inspection system according to claim 1, wherein, when the difference is equal to or smaller than the predetermined value, the circulation is determined to be normal and a message to that effect is displayed. The liquid discharged from the discharge port lands on a recording medium,
the recording medium moves relative to the liquid ejection head;
3. The inspection system according to claim 2, wherein the landing position of the liquid is set to a position of a center of gravity of the liquid that has landed on the recording medium in a relative movement direction of the recording medium, and the inspection step inspects a state of circulation in the liquid ejection head. The inspection system according to claim 3, wherein the predetermined value is any value within a range of 1.5 to 2.5 times the diameter of the liquid that has landed on the recording medium. The inspection system according to any one of claims 1 to 4, wherein the viscosity adjustment process increases the viscosity of the liquid in the second group of nozzles to be greater than the viscosity of the liquid in the first group of nozzles by ejecting liquid from the first group of nozzles and not ejecting liquid from the second group of nozzles. The inspection system according to any one of claims 1 to 4, wherein the viscosity adjustment step comprises discharging liquid from the first group of nozzles and blowing air into the second group of nozzles, thereby increasing the viscosity of the liquid in the second group of nozzles to be greater than the viscosity of the liquid in the first group of nozzles. The inspection system according to any one of claims 1 to 6, further comprising a step of continuously ejecting liquid from the first group of ejection ports prior to the viscosity adjustment step. The inspection system according to any one of claims 1 to 6, further comprising a step of aspirating liquid from the first group of outlets prior to the viscosity adjustment step. the liquid ejection head includes a plurality of element substrates each including the ejection port, the pressure generating element, and the pressure chamber;
9. The inspection system according to claim 1, wherein the first group of ejection ports and the second group of ejection ports are ejection ports formed on different element substrates. the liquid ejection head includes an element substrate including the ejection port, the pressure generating element, and the pressure chamber;
9. The inspection system according to claim 1, wherein the first group of ejection ports and the second group of ejection ports are formed in different ejection port rows of the same element substrate. the liquid ejection head includes an element substrate including the ejection port, the pressure generating element, and the pressure chamber;
9. The inspection system according to claim 1, wherein the first group of ejection ports and the second group of ejection ports are formed in the same ejection port row of the same element substrate. an ejection port array including a plurality of ejection ports for ejecting liquid;
a pressure chamber communicating with the ejection port and having a pressure generating element that generates pressure for ejecting liquid from the ejection port;
having
1. A circulation inspection device for inspecting a state of circulation in a liquid ejection head that controls a viscosity of the liquid in the ejection port by circulating the liquid in the pressure chamber between the pressure chamber and an outside of the pressure chamber,
the nozzle array includes a first group of nozzles and a second group of nozzles,
a viscosity adjusting means for increasing the viscosity of the liquid in the second group of ejection ports to be greater than the viscosity of the liquid in the first group of ejection ports;
a circulation means for circulating the liquid in the pressure chamber communicating with the second group of ejection ports between the pressure chamber and the outside of the pressure chamber;
an inspection means for inspecting a state of circulation in the liquid ejection head based on a difference between a landing position on a recording medium of the liquid ejected from the ejection ports of the first group and a landing position on the recording medium of the liquid ejected from the ejection ports of the second group;
A circulation inspection device comprising: if a difference between a landing position of the liquid ejected from the ejection port of the first group and a landing position of the liquid ejected from the ejection port of the second group is greater than a predetermined value, it is determined that the circulation is poor and a message to that effect is displayed;
13. The circulation inspection device according to claim 12, wherein when the difference is equal to or smaller than the predetermined value, the circulation is judged to be normal and a message to that effect is displayed. The liquid discharged from the discharge port lands on a recording medium,
the recording medium moves relative to the liquid ejection head;
14. The circulation inspection device according to claim 12 or 13, wherein the landing position of the liquid is set to the position of the center of gravity of the liquid that has landed on the recording medium in the direction of relative movement of the recording medium, and the inspection means inspects the state of circulation in the liquid ejection head. The circulation inspection device according to claim 13, wherein the predetermined value is any value within a range of 1.5 to 2.5 times the diameter of the liquid that has landed on the recording medium. an ejection port array including a plurality of ejection ports for ejecting liquid;
a pressure chamber communicating with the ejection port and having a pressure generating element that generates pressure for ejecting liquid from the ejection port;
having
A liquid ejection device capable of inspecting a state of circulation of a liquid ejection head that controls a viscosity of the liquid in the ejection port by circulating the liquid in the pressure chamber between the pressure chamber and the outside, comprising:
the nozzle array includes a first group of nozzles and a second group of nozzles,
a viscosity adjusting means for increasing the viscosity of the liquid in the second group of ejection ports to be greater than the viscosity of the liquid in the first group of ejection ports;
a circulation means for circulating the liquid in the pressure chamber communicating with the second group of ejection ports between the pressure chamber and the outside of the pressure chamber;
an inspection means for inspecting a state of circulation in the liquid ejection head based on a difference between a landing position on a recording medium of the liquid ejected from the ejection ports of the first group and a landing position on the recording medium of the liquid ejected from the ejection ports of the second group;
A liquid ejection device comprising: if a difference between a landing position of the liquid ejected from the ejection port of the first group and a landing position of the liquid ejected from the ejection port of the second group is greater than a predetermined value, it is determined that the circulation is poor and a message to that effect is displayed;
The liquid ejection device according to claim 16, wherein, when the difference is equal to or smaller than the predetermined value, the circulation is determined to be normal and a message to that effect is displayed. The liquid discharged from the discharge port lands on a recording medium,
the recording medium moves relative to the liquid ejection head;
A liquid ejection device according to claim 16 or 17, wherein the landing position of the liquid is defined as the position of the center of gravity of the liquid that has landed on the recording medium in the direction of relative movement of the recording medium, and the inspection means inspects the state of circulation in the liquid ejection head. The liquid ejection device according to claim 17, wherein the predetermined value is any value within a range of 1.5 to 2.5 times the diameter of the liquid that has landed on the recording medium. The liquid ejection device according to any one of claims 16 to 19, wherein the viscosity adjustment means ejects liquid from the ejection ports of the first group and does not eject liquid from the ejection ports of the second group, thereby increasing the viscosity of the liquid in the ejection ports of the second group to be higher than the viscosity of the liquid in the ejection ports of the first group.

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