Print head with contamination detection apparatus, and contamination detection apparatus

Abstract

To detect contamination of a print head with a simple apparatus.SOLUTION: A print head 1 with a contamination detection apparatus according to the present invention is an apparatus for detecting head contamination of a print head of a continuous-type inkjet printer, includes: a print head 10 that includes a nozzle 12 that ejects ink droplets, a charging electrode 14 that charges the ink droplets, a deflection electrode 16 that deflects the charged ink droplets by an electric field, and a gutter 18 that collects ink droplets not used for printing; and a camera 20 that captures at least a part of a flight region 102 in which ink droplets ejected from the nozzle 12 fly, from a lateral side in a direction of ejection of the ink droplets from the nozzle 12 and from a lateral side in a direction facing the deflection electrode 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a print head provided with a device for detecting dirt on an inkjet printer, and more particularly to a print head provided with a dirt detection device that detects dirt on the head of an inkjet printer by taking pictures with a camera. [Background technology]

[0002] Inkjet printers (hereafter abbreviated as "IJP") are broadly divided into continuous and on-demand types. Of these, continuous IJPs use a pump to eject ink from a nozzle, a charging electrode charges the ink droplets at the point where the ejected ink separates into ink droplets, and a deflection electrode deflects the trajectory of the ink droplets, causing them to land at a predetermined position on the printing surface, forming a print dot.

[0003] In the above-mentioned continuous IJP, repeated printing causes ink stains to adhere to the inside of the print head, such as the surfaces of the deflection electrodes and gutter.

[0004] Leaving this state unattended can lead to poor printing, so the inside of the print head must be periodically cleaned to remove any ink or other contaminants.

[0005] For example, Patent Document 1 discloses a print head cleaning device, but the operator must remove the cover of the print head to check for dirt.

[0006] Therefore, Patent Document 2 proposes a system that uses an optical sensor to measure the degree of reduction in laser light blocked by dirt, thereby determining whether ink has accumulated on the inner surface of the print head. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-171651 [Patent Document 2] WO2015 / 187926 publication Summary of the Invention [Problem to be solved by the invention]

[0008] However, the system in Patent Document 2 uses laser light, so it is necessary to emit a large number of laser beams just to detect dirt in the gutter area, which makes it difficult to detect dirt on parts other than the gutter. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a dirt detection device that can detect dirt on parts other than the gutter, such as the charging electrode and the deflection electrode. [Means for solving the problem]

[0009] The invention made to solve the above problems is a print head with a stain detection device that detects ink stains on the print head of a continuous inkjet printer, characterized in that it comprises a print head that has a nozzle that ejects ink droplets, a charging electrode that charges the ink droplets, a deflection electrode that deflects the charged ink droplets by an electric field, and a gutter that collects ink droplets that are not used for printing, and a camera that takes pictures from the side of the direction in which the ink droplets are ejected from the nozzle and from the side of the direction in which the deflection electrode faces.

[0010] In this way, since the ink stains are photographed with a camera, it is possible to detect stains over a wider area of ​​the print head than when detecting ink stains using laser light. Also, since the camera photographs from the side of the direction in which ink droplets are ejected from the nozzles and the side of the direction in which the deflection electrodes face, it is possible to photograph stains between the deflection electrodes as well.

[0011] The camera preferably captures an image of at least a portion of the flight area through which ink droplets ejected from the nozzles fly. If ink stains enter the flight area of ​​the ink droplets, the ink stains will interfere with the flight of the ink droplets, causing sudden printing defects. By capturing an image of the flight area, it is possible to detect that ink stains have entered the flight area, which can lead to preventing printing defects by stopping printing and cleaning the nozzles, for example.

[0012] The print head with a detection device according to the present invention preferably includes an output device that outputs the image data captured by the camera as an image, allowing a person to check the degree of contamination of the print head by looking at the image displayed on the output device, such as a monitor or printer.

[0013] The print head with detection device according to the present invention preferably includes an information processing unit that processes image data captured by a camera, and the information processing unit preferably includes a storage unit that stores the image data together with the date and time of capture, and a detection unit that compares part or all of the area captured by the camera as a dirt detection target area in which the information processing unit detects dirt, compares the dirt detection target areas of two image data captured on different dates and times, creates differential image data that identifies the different parts of the two image data, and detects ink dirt from the differential image data. This allows head dirt to be detected automatically.

[0014] It is preferable to provide a prediction unit that, when the detection unit detects an ink stain, calculates the speed at which the ink stain will grow in a predetermined or predicted stain growth direction using at least one differential image data, and predicts the date and time at which the ink stain will reach the flight area based on the distance in the stain growth direction between the ink stain detected in the differential image data and the flight area. In this way, it is possible to predict the day on which printing defects will occur due to the stain.

[0015] In the print head with a contamination detection device according to the present invention, it is preferable that the memory unit stores the date and time when the ink contamination will reach the flight area, and the prediction unit predicts a date and time before the ink contamination reaches the flight area as the date and time when the print head should be cleaned. This makes it possible to perform cleaning before print defects occur and prevent print defects caused by ink contamination.

[0016] The dirt detection target area preferably includes a dirt most frequently occurring area that includes at least one of the space between the deflection electrode plus and the flight area, or the space inside the flight area adjacent to the entrance of the gutter. By doing so, an area important for detecting head dirt is included in the dirt detection target area, thereby preventing mistakes in timing for cleaning.

[0017] The print head with a detection device according to the present invention preferably includes a head cover that covers the print head, and the camera is attached to the outside of the head cover and takes pictures of the inside of the head cover through a viewing window provided in the head cover, which has the effect of preventing head dirt from adhering to the camera.

[0018] The present invention provides a stain detection device for detecting ink stains on the print head of a continuous inkjet printer, wherein the print head is equipped with a nozzle that ejects ink droplets, a charging electrode that charges the ink droplets, a deflection electrode that deflects the charged ink droplets using an electric field, and a gutter that collects ink droplets that are not used for printing, and the stain detection device is equipped with a camera that takes images from the side of the direction in which the ink droplets are ejected from the nozzle and from the side of the direction in which the deflection electrode faces. [Effects of the Invention]

[0019] As described above, the print head with a detection device according to the present invention can detect a wide range of head contamination with a simple device. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are a front view and a side view, respectively, schematically illustrating the configuration of a print head according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic front view showing the flight area of ​​the print head shown in FIG. 1. [Figure 3] FIG. 2 is a schematic front view showing a stain detection target area and a stain most frequently occurring area of ​​the print head shown in FIG. 1. [Figure 4] FIG. 2 is a functional block diagram of an information processing unit according to the first embodiment. [Figure 5] 3 is an image database stored in a storage unit of an information processing unit according to the first embodiment. [Figure 6] 4 is a display example on a display according to the first embodiment. [Figure 7] 10 is an example showing how dirt detected from differential image data invades the flight area over time. [Figure 8] FIG. 10 is an explanatory diagram showing a method for predicting the date and time when head dirt will reach the flight area. [Figure 9] FIG. 10 is an explanatory diagram showing another method for predicting the date and time when head dirt will reach the flight area. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and appropriate modifications can be made without departing from the spirit and scope of the present invention.

[0022] (First embodiment) A print head 1 with a dirt detection device according to a first embodiment of the present invention will be described using Figures 1 to 7. As shown in Figure 1, the print head 1 with a dirt detection device mainly comprises a print head 10 and a camera 20 (see Figure 1(b)), as well as an information processing unit 30 (see Figure 4) and a display (output device) 40 (see Figure 6).

[0023] As shown in Figure 1, the print head 10 comprises a nozzle 12 that ejects ink droplets D, a charging electrode 14 that negatively charges the ink droplets, a deflection electrode 16 that deflects the charged ink droplets using an electric field, a gutter 18 that collects ink droplets not used for printing, and a head cover 19. The deflection electrode 16 forms an electric field with a positive deflection electrode 16A and a negative deflection electrode 16B that face each other across the flying ink droplets. Reference numeral 18a denotes the entrance of the gutter 18.

[0024] Nozzle 12 ejects ink that has been delivered from an ink tank by a pump and vibrated by an ultrasonic vibrator (the pump, ink tank, and ultrasonic vibrator are not shown). The ink droplets ejected from nozzle 12 are negatively charged by a positive pulse voltage applied to charging electrode 14, and those to be used for printing are deflected by the electric field formed by deflection electrode 16 to a route on the positive deflection electrode 16A side toward the printing position, while those not to be used for printing fly straight until they are collected in gutter 18.

[0025] The route along which the ink droplets fly is called flight route 100 (shown by dotted lines in Figure 2). A number of flight routes 100 are provided across the printing range, with each different route being set for each printing position, and the area formed by these flight routes 100 is called flight area 102 (shown by a closed solid line in Figure 2).

[0026] The camera 20 is, for example, a digital camera equipped with an image sensor such as a CCD or CMOS, and is equipped with an LED light that illuminates the inside of the head cover 19. As shown in FIG. 1(b), the camera 20 is provided outside the head cover 19 and takes pictures of the inside of the head cover 19 through a viewing window 19a in the head cover 19. By providing the camera 20 outside the head cover 19, there is an advantage that the camera 20 is not soiled by ink droplets. However, the camera 20 may also be provided inside the head cover 19.

[0027] A wide-angle or fisheye lens may be attached to the viewing window 19a, allowing a sufficiently wide range to be photographed even when the distance between the lens and the subject is short.

[0028] As shown in FIG. 1, the camera 20 captures images from the side of the direction in which the ink droplets D are ejected from the nozzles 12 (toward the right in FIG. 1(a)) and from the side of the direction in which the deflection electrodes face (up and down in FIG. 1(a)). As shown in FIG. 3, the camera 20 captures an image of an area including a dirt detection target area 104 in which the information processing unit 30 detects dirt. The dirt detection target area 104 consists of part or all of the area captured by the camera 20, and is an area that includes the space between the nozzles 12 and the gutter 18, the space between the charging electrodes 14, and the space between the deflection electrodes 16, and includes all or part of a peripheral area 103 of the flight area 102.

[0029] In the first embodiment, as shown in Fig. 3, the dirt detection target area 104 (the area shown by the dashed line in Fig. 3) is a rectangular area that includes the area between the nozzle 12 and the gutter 18, the charged electrode 14, and the area between the pair of deflection electrodes 16A and 16B, and is made up of the entire flight area 102 and its surrounding area 103. The dirt detection target area 104 also includes a most frequent dirt area 106 where dirt is particularly likely to occur. The most frequent dirt area 106 includes a first most frequent dirt area 106a that consists of the space between the flight areas 102, and a second most frequent dirt area 106b that is included in the flight area 102 and adjacent to the entrance of the gutter 18.

[0030] If ink stains occur in the flight area 102, the ink stains will interfere with the flight of ink droplets, immediately causing problems in printing. In this way, by including the flight area 102 in the stain detection target area 104, it is possible to deal with sudden printing defects.

[0031] Furthermore, by including the peripheral region 103 in the stain detection target region 104, stains that may affect future printing can be detected in advance. By including the stain detection target region 104 in the most frequent stain region 106 where ink stains grow quickly, particularly the first most frequent stain region 106a where ink stains grow quickly, it is possible to reduce the likelihood of stains occurring on the print head 10 being overlooked compared to when that region is not included. However, the stain detection target region 104 may include only a portion of the flight region 102, or only a portion of the peripheral region 103, or it may not include the most frequent stain region 106.

[0032] 4, the information processing unit 30 is composed of a memory unit 31, a processing unit 32, a communication unit 33, and an output unit 34. The memory unit 31 stores image data of the inside of the head photographed by the camera 20 together with an image database (see FIG. 5) including the date and time of photographing, and also stores the data specifying the flight area 102, the dirt detection target area 104, and the area 106 where dirt most frequently occurs.

[0033] The processing unit 32 is made up of a detection unit 321 and a prediction unit 322. The detection unit 321 performs head dirt detection processing, and the prediction unit 322 predicts the date and time when the head dirt will reach the flight area 102 and the date and time when the head should be cleaned.

[0034] The detection unit 321 compares the stain detection target areas 104 of multiple pieces of image data captured at different times and creates differential image data that identifies the different parts of the image data, and detects ink stains from the differential image data. In this way, the detection unit 321 can automatically detect head stains based on the differential image data.

[0035] The function of this detection unit 321 will be specifically described with reference to the image database 311 (shown in FIG. 5) stored in the storage unit 31. The image database 311 is a database that manages image data, and is composed of image data, differential image data, shooting date and time, operating time, number of prints, etc. As an example, the storage unit 31 stores image data for each of the following states: cleaned, slightly soiled, medium soiled, and heavily soiled. The cleaned state refers to the state after the head has been cleaned.

[0036] The output unit 34 outputs the image data as an image and the differential image data as a differential image to the display 40, and also outputs the operating time, the number of prints, the detection result, and the predicted date and time.

[0037] The detector 321 compares the image data of the washed state with the image data of the slightly soiled state, and generates data (difference image data) for displaying the parts included in both in black and the parts included in the latter but not in the former in white. This difference image data is displayed as a difference image on the display 40 (see FIG. 6).

[0038] The detection unit 321 extracts the area of ​​head dirt (hereinafter referred to as the dirty area 108) from the differential image data. It is preferable that the detection unit 321 only identifies areas of the dirty area 108 that are larger than a predetermined area as the dirty area 108. This is to prevent noise on the image from being mistakenly recognized as the dirty area 108. Furthermore, by targeting large head dirt rather than small head dirt and predicting the date and time when the head dirt, described below, will reach the flight area 102, a more accurate date and time can be predicted. It is also preferable that the detection unit 321 create a rectangle, polygon, or circle that surrounds the outline of the dirty area 108. This makes it easier for the operator to recognize the outline of the dirty area 108 (see FIG. 6).

[0039] When the detection unit 321 extracts the stain portion 108, the prediction unit 322 predicts the date and time when the stain portion 108 will reach the flight area 102 (hereinafter referred to as the head stain arrival date and time). The prediction unit 322 uses at least one differential image data to calculate the growth speed of the stain portion 108 in a predetermined stain growth direction 11, and predicts the date and time when the stain portion 108 will reach the flight area 102 from the distance in the stain growth direction 11 between the stain portion 108 extracted in the differential image data and the flight area 102. This allows the operator to confirm not only the extraction result of the stain portion 108 but also the predicted date and time when the stain portion 108 will reach the flight area 102.

[0040] The dirt growth direction 11 is assumed to be stored in advance in the memory unit 31. The memory unit 31 may store a plurality of dirt growth directions 11. In this way, the plurality of dirt growth directions 11 can be compared and the dirt growth direction 11 in which the dirt progresses the fastest can be applied, thereby more accurately predicting the day when the dirt portion 108 will enter the flight area 102.

[0041] 8 is a diagram showing a schematic representation of the dirt growth direction 11, the dirt portion 108, and the flight area 102. In Fig. 8, the dirt portion 108 is attached to an inclined portion 16A1 provided at the inner tip of the positive deflection electrode 16A and substantially parallel to the edge 102a of the flight area 102 on the side of the positive deflection electrode 16A.

[0042] First, the prediction unit 322 provisionally determines point S on the boundary between the stained portion 108 and the inclined portion 16A1. Next, the prediction unit 322 calculates the length L from point S within the stained portion 108 along the stain growth direction 11, which has been previously stored in the memory unit 31. Point S is repeatedly moved sequentially over the entire length of the boundary between the stained portion 108 and the inclined portion 16A1, and a point Smax at which length L is at its maximum value Lmax is found. Next, the prediction unit 322 calculates the distance Hmax from point Smax to the flight area 102. The prediction unit 322 calculates the speed at which the head dirt grows along the dirt growth direction 11 from the length Lmax and the operating time. Next, the prediction unit 322 calculates the date and time at which the head dirt will arrive from the distance Hmax and the speed at which the head dirt grows.

[0043] Next, a method for predicting the head dirt arrival date and time after predicting the dirt growth direction 11 in a case where the dirt growth direction 11 is not stored in advance in the storage unit 31 will be described.

[0044] FIG. 9 is a diagram showing a schematic representation of a stained area 108 with a slight amount of staining and a stained area 108' with a moderate amount of staining, both extracted by the detection unit 321. First, the prediction unit 322 finds the maximum staining point E (the point farthest from the deflection electrode plus 16A) in the stained area 108 to estimate the stain growth direction 11. The prediction unit 322 finds the maximum staining point E' in the stained area 108'. Next, the prediction unit 322 predicts the direction connecting points E and E' as the stain growth direction 11. The processing after predicting the stain growth direction 11 is the same as the processing method described above.

[0045] The method by which the prediction unit 322 predicts the dirt growth direction 11 is not limited to this. For example, the prediction unit 322 creates the difference between image data in a state where there is a little dirt and image data in a state where there is a moderate amount of dirt. This difference image data indicates the head dirt that has accumulated from the former to the latter, that is, the area where the head dirt has grown over a predetermined period (the shaded area in FIG. 9), and is called the dirt growth area 109. The prediction unit 322 can predict, as the dirt growth direction 11, the direction from the inclined portion 16A1 toward the flight area 102 and the direction connecting the two widest points in the dirt growth area 109.

[0046] As described above, by the prediction unit 322 predicting the date and time when head contamination will occur, the operator can recognize not only whether head contamination exists, but also when printing defects due to head contamination will occur.

[0047] The prediction unit 322 predicts the date and time before the head contamination arrival date and time as the date and time when the print head 10 should be cleaned (hereinafter referred to as the cleaning date and time). Specifically, the prediction unit 322 sets the cleaning date and time to a predetermined time before the head contamination arrival date and time. The predetermined time may be a fixed time (for example, two days), or it may be calculated taking into account the operating status of the print head 10 and the time required for cleaning. This allows the operator to recognize not only the head contamination arrival date and time but also the cleaning date and time, and also enables the print head to be automatically cleaned before the contamination reaches the flight area 102.

[0048] The communication unit 33 communicates with the camera 20, the display 40, and a production management system (not shown).

[0049] As shown in FIG. 6, the output unit 34 outputs the image data as an image and the differential image data as a differential image to the display 40, and also outputs the operating time, number of prints, detection results, and predicted date and time. The detection results indicate the presence or absence of head contamination, and the predicted date and time indicate the date and time of head contamination arrival and cleaning. The output unit 34 preferably outputs the flight area 102, the most frequently occurring contamination area 106, the contaminated area 108, and a rectangle surrounding the outline of the contaminated area 108. This allows the operator to check the contaminated area 108 extracted by the detection unit 321 without missing it and to recognize the positional relationship between the contaminated area 108 and the flight area 102 or the most frequently occurring contamination area 106.

[0050] FIG. 7 is a conceptual diagram showing the difference image and the flight area 102 superimposed on each other. FIGS. 7(a), (b), and (c) are difference images with a slight amount of dirt, a moderate amount of dirt, and a considerable amount of dirt, respectively. The output unit 34 preferably outputs the difference images with dirt in the order of the date and time of capture. This makes it clear that the dirt area 108 is growing and approaching the flight area 102.

[0051] Since ink droplets ejected from the nozzles 12 fly along flight routes 100 that differ depending on the character size to be printed, the detection unit 321 and prediction unit 322 may use different flight regions 102 for each character size. This makes it possible to more accurately detect head contamination and predict the date and time when head contamination will arrive and when it will be cleaned, depending on the character size to be printed.

[0052] As described above, the present invention is not limited to the above-described embodiment. For example, the camera 20 does not need to capture the flight area where ink droplets ejected from the nozzles fly, and may be attached inside the head cover 19. The print head 10 does not need to include the head cover 19. The print head 1 with a contamination detection device does not need to include an output device that outputs image data captured by the camera, or an information processing unit that processes image data captured by the camera. The contamination detection target area where contamination is detected does not need to include the most frequently occurring contamination area, which is an area that includes at least one of the space between the deflection electrode plus 16A and the flight area 102, or the space inside the flight area 102 adjacent to the entrance of the gutter 18. [Explanation of symbols]

[0053] 1: Print head with dirt detection device 10: Print head 100: Flight route 102:Flight area 104: Dirt detection target area 106: Area where dirt occurs most frequently 108: Dirt area 11: Dirt growth direction (direction in which head dirt grows) 12: Nozzle 14: Charged electrode 16: Deflection electrode 16A: Deflection electrode positive 18: Gutter 19: Head cover 20: Camera 30: Information Processing Department 31: Storage section 32: Processing section 321:Detection unit 322: Prediction Department 33: Communications Department 34: Output section 40: Display (output device)

Claims

1. A print head equipped with a contamination detection device for detecting ink contamination of a print head of a continuous inkjet printer, a print head including a nozzle for ejecting ink droplets, a charging electrode for charging the ink droplets, a deflection electrode for deflecting the charged ink droplets by an electric field, and a gutter for collecting ink droplets not used for printing; a camera that takes an image from a side of the direction in which ink droplets are ejected from the nozzle and a side of the direction in which the deflection electrode faces; A print head with a dirt detection device, comprising:

2. 2. The print head with a contamination detection device according to claim 1, wherein the camera captures an image of at least a part of a flight area in which ink droplets ejected from the nozzle fly.

3. an output device that outputs image data captured by the camera; 3. The print head with the contamination detection device according to claim 1 or 2.

4. an information processing unit that processes image data captured by the camera; The information processing unit includes a storage unit that stores the image data together with the date and time of shooting; a detection unit that compares the stain detection target areas of the two image data captured on different dates and times with a part or all of the area captured by the camera as a stain detection target area in which the information processing unit detects stains, creates differential image data that identifies different parts of the two image data, and detects ink stains from the differential image data; The print head with a dirt detection device according to claim 1 or 2, comprising:

5. A print head with a stain detection device as described in claim 4, which, when the detection unit detects ink stains, uses at least one differential image data to calculate the speed at which the ink stains will grow in a predetermined or predicted stain growth direction, and is further provided with a prediction unit that predicts the date and time at which the ink stains will reach the flight area based on the ink stains detected in the differential image data, the distance in the stain growth direction to the flight area, and the speed.

6. the storage unit stores the date and time when the ink stain reaches the flight area; 6. The print head with a contamination detection device according to claim 5, wherein the prediction unit predicts a date and time before the ink contamination reaches the flight area as the date and time when the print head should be cleaned.

7. 5. A print head with a contamination detection device as described in claim 4, wherein the contamination detection target area includes a contamination most frequently occurring area that includes at least one of the space between the deflection electrode plus and the flight area, or the space inside the flight area adjacent to the entrance of the gutter.

8. a head cover for covering the print head; 3. The print head with a dirt detection device according to claim 1, wherein the camera is attached to the outside of the head cover and takes an image of the inside of the head cover through an observation window provided in the head cover.

9. A stain detection device for detecting ink stains on a print head of a continuous inkjet printer, comprising: the print head includes a nozzle for ejecting ink droplets, a charging electrode for charging the ink droplets, a deflection electrode for deflecting the charged ink droplets by an electric field, and a gutter for collecting ink droplets not used for printing; A stain detection device comprising a camera for taking images from a side of the direction in which ink droplets are ejected from the nozzle and from a side of the direction in which the deflection electrode faces.

Images