Print head with dirt detection device, and dirt detection device

Abstract

Detecting the dirt of a print head with a simple device 【Solution means】The print head 1 with a dirt detection device of the present invention is a device for detecting head dirt of a print head of a continuous inkjet printer, and includes a nozzle 12 for ejecting ink droplets, a charging electrode 14 for charging the ink droplets, a deflection electrode 16 for deflecting the charged ink droplets by an electric field, and a gutter 18 for collecting ink droplets not used for printing. A print head 10, and a camera 20 that photographs at least a part of the flight region 102 where the ink droplets ejected from the nozzle 12 fly from the side in the direction in which the ink droplets are ejected from the nozzle 12 and from the side in the direction in which the deflection electrode 16 faces. It is characterized by comprising

Description

Technical Field

[0001] The present invention relates to a print head equipped with a device for detecting dirt of an inkjet printer, and more particularly to a print head with a dirt detection device for detecting dirt on the head of an inkjet printer by photographing with a camera.

Background Art

[0002] Inkjet printers (hereinafter abbreviated as "IJP") are roughly classified into a continuous type and an on-demand type. Among these, the continuous type IJP injects ink from nozzles by a pump, charges the ink droplets by a charging electrode at a position where the injected ink separates into ink droplets, further bends the trajectories of the ink droplets by a deflection electrode, and lands on a predetermined position on the printing surface to form printing dots.

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

[0004] If such a state is left unattended, it will lead to printing defects, so it is necessary to regularly clean the inside of the print head to remove the adhered ink and the like.

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

[0006] Therefore, Patent Document 2 proposes a system for determining whether ink is accumulated on the inner surface of a print head by measuring the degree of decrease in laser light blocked by dirt using an optical sensor.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] However, in the system of Patent Document 2, since laser light is used, it is necessary to emit a large number of laser lights even to detect the dirt on the gutter part, and there is a problem that it is difficult to detect the dirt on parts other than the gutter. The present invention has been made in view of the above-described problems, and an object thereof is to provide a dirt detection device capable of detecting dirt on parts other than the gutter, such as a charging electrode and a deflection electrode. [Means for Solving the Problems]

[0009] An invention made to solve the above problems is a print head with a dirt detection device for detecting ink dirt on a print head of a continuous inkjet printer, the 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 for photographing from a side in a direction in which ink droplets are ejected from the nozzle and from a side in a direction in which the deflection electrodes face each other, and A stain detection device having an information processing unit that processes the image data captured by the camera equipped with The information processing unit includes a storage unit that stores the image data together with the shooting date and time, and a part or all of the area captured by the camera is set as a stain detection target area where the information processing unit detects stains. The stain detection target areas of two image data with different shooting dates and times are compared, and difference image data for identifying different parts of the two image data is created, and a detection unit that detects ink stains from the difference image data characterized by that.

[0010] The print head with a detection device according to the present invention Thus, since ink dirt is photographed by the camera, a wider range of dirt on the print head can be detected compared to the case of detecting ink dirt using laser light. In addition, since the camera photographs from a side in a direction in which ink droplets are ejected from the nozzle and from a side in a direction in which the deflection electrodes face each other, dirt between the deflection electrodes can also be photographed. In addition, it is provided with an information processing unit that processes the image data captured by the camera. The information processing unit includes a storage unit that stores the image data together with the shooting date and time, and a part or all of the area captured by the camera is set as a stain detection target area where the information processing unit detects stains. The stain detection target areas of two image data with different shooting dates and times are compared, and difference image data for identifying different parts of the two image data is created, and a detection unit that detects ink stains from the difference image data. Therefore, head stains can be automatically detected

[0011] The camera preferably photographs at least a part of the flight area where the ink droplets ejected from the nozzle fly. When ink stain enters the flight area of the ink droplets, the ink stain hinders the flight of the ink droplets and suddenly causes printing defects. By photographing the flight area, it is possible to detect that the ink stain has entered the flight area, and thus it is possible to prevent printing defects by stopping printing and cleaning the nozzle or the like.

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

[0014] When the detection unit detects an ink stain, it calculates the speed at which the ink stain grows in a predetermined or predicted stain growth direction using at least one differential image data, and from the ink stain detected in the differential image data and the distance in the stain growth direction of the flight area, it preferably includes a prediction unit that predicts the date and time when the ink stain reaches the flight area. By doing so, it is possible to predict the day when printing defects will occur due to the stain.

[0015] In the print head with a stain detection device according to the present invention, the storage unit stores the date and time when the ink stain reaches the flight area, and the prediction unit preferably predicts a date and time before the date and time when the ink stain reaches the flight area as the date and time when the print head should be cleaned. By doing so, it is possible to perform cleaning before printing defects occur and suppress printing defects caused by ink stains.

[0016] The stain detection target area preferably includes a stain most frequent area including 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, since an important area for detecting head stains is included in the stain detection target area, it is possible to suppress misjudging the cleaning timing.

[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 mounted outside the head cover and photographs the inside of the head cover through a viewing window provided in the head cover. By doing so, there is an effect that it is difficult for head stains to adhere to the camera.

[0018] The present invention is a stain detection device for detecting ink stains on a print head of a continuous inkjet printer. 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. The stain detection device is characterized by including a camera that photographs from the side in the direction in which the ink droplets are ejected from the nozzle and from the side in the direction in which the deflection electrode faces.

Effect of the Invention

[0019] As described above, according to the print head with a detection device according to the present invention, it is possible to detect head stains in a wide range with a simple device.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

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

[0022] (First Embodiment) Using FIGS. 1 to 7, the print head 1 with a dirt detection device according to the first embodiment of the present invention will be described. As shown in FIG. 1, the print head 1 with a dirt detection device mainly includes a print head 10 and a camera 20 (see FIG. 1(b)), and also includes an information processing unit 30 (see FIG. 4) and a display (output device) 40 (see FIG. 6).

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

[0024] The nozzle 12 is fed with ink from an ink tank by a pump and ejects the ink vibrated by an ultrasonic oscillator (neither the pump, the ink tank, nor the ultrasonic oscillator is shown). The ink droplets ejected from the nozzle 12 are charged negatively by a plus pulse voltage applied to the charging electrode 14, and then those used for printing are deflected toward the plus deflection electrode 16A side route toward the position to be printed by the electric field formed by the deflection electrode 16, while those not used for printing fly until they are recovered by the straight-through gutter 18.

[0025] The route along which these ink droplets fly is called a flight route 100 (shown by a dotted line in FIG. 2). A large number of different flight routes 100 are provided for each position to be printed over the area to be printed, and the area formed by these numerous flight routes 100 is called a flight area 102 (shown as a solid-line closed figure in FIG. 2).

[0026] The camera 20 is, for example, a digital camera equipped with an image sensor such as a CCD or CMOS, and includes 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 photographs the inside of the head cover 19 through the viewing window 19a of the head cover 19. By providing the camera 20 outside the head cover 19, there is an effect that the camera 20 is not soiled by ink droplets. However, the camera 20 may be provided inside the head cover 19.

[0027] Alternatively, a wide-angle or fish-eye lens may be attached to the peephole 19a. By doing so, even when the distance between the lens and the subject is short, a sufficiently wide range can be photographed.

[0028] As shown in FIG. 1, the camera 20 performs photographing from the side in the direction in which the ink droplet D is ejected from the nozzle 12 (the rightward direction in FIG. 1(a)), and from the side in the direction in which the deflection electrodes face each other (the vertical direction in FIG. 1(a)). As shown in FIG. 3, the camera 20 photographs an area including the stain detection target area 104 that is the target for the information processing unit 30 to detect stains. The stain detection target area 104 is composed of a part or all of the area photographed by the camera 20, and is the space between the nozzle 12 and the shutter 18, the space between the charging electrodes 14, and the space between the deflection electrodes 16, and is an area including all or part of the peripheral area 103 of the flight area 102.

[0029] In the first embodiment, as shown in FIG. 3, the stain detection target area 104 (the area shown by the dashed-dotted line in FIG. 3) is a rectangular area including between the nozzle 12 and the shutter 18, and between the charging electrode 14, the pair of plus deflection electrodes 16A, and the minus deflection electrode 16B, and is composed of the entire flight area 102 and its peripheral area 103. The stain detection target area 104 also includes a stain most frequent occurrence area 106 where stains are particularly likely to occur. The stain most frequent occurrence area 106 includes a first stain most frequent occurrence area 106a composed of the space between the flight areas 102 and a second stain most frequent occurrence area 106b included in the flight area 102 and adjacent to the entrance of the shutter 18.

[0030] When ink stains occur in the flight area 102, the flight of the ink droplets is hindered by this ink stain, so that printing immediately becomes impaired. Thus, by including the flight area 102 in the stain detection target area 104, it is possible to cope with sudden printing defects.

[0031] In addition, since the dirt detection target area 104 includes the peripheral area 103, it is possible to detect in advance dirt that may affect future printing. By including the most frequent dirt occurrence area 106 where ink dirt grows rapidly, especially the first most frequent dirt occurrence area 106a where ink dirt grows rapidly, in the dirt detection target area 104, it is possible to suppress overlooking dirt generated on the print head 10 compared to the case where the area is not included. However, the dirt detection target area 104 may include only a part of the flight area 102, or may include only a part of the peripheral area 103, and may not include the most frequent dirt occurrence area 106.

[0032] As shown in FIG. 4, the information processing unit 30 includes a storage unit 31, a processing unit 32, a communication unit 33, and an output unit 34. The storage unit 31 stores, together with the image data captured by the camera 20 inside the head and an image database (see FIG. 5) including the shooting date and time, etc., data for specifying the above-described flight area 102, dirt detection target area 104, and most frequent dirt occurrence area 106.

[0033] The processing unit 32 includes 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 reaches the flight area 102 and the date and time when the head should be cleaned.

[0034] The detection unit 321 compares the dirt detection target areas 104 of a plurality of image data with different shooting dates and times, creates difference image data for identifying different parts of the image data, and detects ink dirt from the difference image data. By doing so, the detection unit 321 can automatically detect head dirt based on the difference image data.

[0035] The operation of this detection unit 321 will be specifically described while referring to the image database 311 (illustrated 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, operation time, number of printing times, and the like. As an example, the storage unit 31 stores image data in a washed state, a state with a little dirt attached, a state with medium dirt attached, and a state with considerably dirt attached. The washed state is the state after cleaning the head dirt.

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

[0037] The detection unit 321 compares the image data in the washed state with the image data in the state with a little dirt attached, and creates data (differential 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 differential image data is displayed as a differential image on the display 40 (see FIG. 6).

[0038] The detection unit 321 extracts the head dirt area (hereinafter referred to as the dirty part 108) from the differential image data. It is preferable that the detection unit 321 regards only the area larger than a predetermined area among the dirty parts 108 as the dirty part 108. This is to prevent misrecognizing the noise on the image as the dirty part 108. Also, by predicting the date and time when the head dirt reaches the flight area 102, which will be described later, for a larger head dirt rather than a small head dirt, a more appropriate date and time can be predicted. Further, it is preferable that the detection unit 321 creates a rectangle, a polygon, or a circle surrounding the outer shape of the dirty part 108. By doing so, it becomes easier for the operator to recognize the outer shape of the dirty part 108 (see FIG. 6).

[0039] When the detection unit 321 extracts the soiled part 108, the prediction unit 322 predicts the date and time when the soiled part 108 reaches the flight area 102 (hereinafter referred to as the head soiling arrival date and time). The prediction unit 322 calculates the growth rate of the soiled part 108 growing in the predetermined soiling growth direction 11 using at least one differential image data, and predicts the date and time of reaching the flight area 102 from the soiled part 108 extracted in the differential image data and the distance in the soiling growth direction 11 between the soiled part 108 and the flight area 102. By doing so, the operator can confirm not only the extraction result of the soiled part 108 but also the predicted date and time when the soiled part 108 reaches the flight area 102.

[0040] It is assumed that the soiling growth direction 11 is stored in the storage unit 31 in advance. The storage unit 31 may store a plurality of soiling growth directions 11. By doing so, since a plurality of soiling growth directions 11 can be compared and the soiling growth direction 11 with the fastest soiling progress can be applied, the date when the soiled part 108 invades the flight area 102 can be predicted more accurately.

[0041] FIG. 8 is a diagram schematically showing the soiling growth direction 11, the soiled part 108, and the flight area 102. In FIG. 8, the soiled part 108 adheres to the inner tip of the deflection electrode plus 16A on the inclined part 16A1 provided substantially parallel to the end side 102a on the deflection electrode plus 16A side in the flight area 102.

[0042] First, the prediction unit 322 determines a point S on the boundary line between the soiled part 108 and the inclined part 16A1. Next, the prediction unit 322 calculates the length L in the soiled part 108 from the point S along the soiling growth direction 11 stored in the storage unit 31 in advance. While sequentially moving the point S over the entire length of the boundary line between the soiled part 108 and the inclined part 16A1, the point Smax at which the length L becomes the maximum value Lmax is obtained. Next, the distance Hmax from the point Smax to the flight area 102 is calculated. The prediction unit 322 calculates the speed at which the head soiling grows along the soiling growth direction 11 from the length Lmax and the operating time. Next, the prediction unit 322 calculates the head soiling arrival date and time from the distance Hmax and the speed at which the head soiling grows.

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

[0044] FIG. 9 is a diagram schematically showing a dirt portion 108 with a little dirt attached and a dirt portion 108' with medium dirt attached, which are extracted by the detection unit 321. First, in order to estimate the dirt growth direction 11, the prediction unit 322 finds the maximum dirt adhesion point E (the point farthest from the deflection electrode plus 16A) in the dirt portion 108. The prediction unit 322 finds the maximum dirt adhesion point E' in the dirt portion 108'. Next, the prediction unit 322 predicts the direction connecting the point E and the point E' as the dirt growth direction 11. The processing after predicting the dirt growth direction 11 is the same as the above-described processing method.

[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 a difference between the image data with a little dirt attached and the image data with medium dirt attached. This difference image data shows the head dirt attached from the former to the latter, that is, the region where the head dirt has grown during a predetermined period (the hatched portion in FIG. 9), and is called the dirt growth portion 109. The prediction unit 322 can predict the direction connecting the two points with the widest width in the dirt growth portion 109 in the direction from the inclined portion 16A1 toward the flight region 102 as the dirt growth direction 11.

[0046] As described above, by predicting the head dirt arrival date and time by the prediction unit 322, the operator can recognize not only the presence or absence of head dirt but also the timing when print defects due to head dirt will occur.

[0047] The prediction unit 322 predicts the date and time before the head dirt 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 dirt arrival date and time. The predetermined time may be a fixed time (for example, two days), or the predetermined time may be calculated in consideration of the operating status of the print head 10 and the time required for cleaning. By doing so, the operator can recognize not only the head dirt arrival date and time but also the cleaning date and time, and can automatically clean the print head before the dirt 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, the difference image data as a difference image to the display 40, and also outputs the operation time, the number of printing times, the detection result, and the predicted date and time. The detection result is the presence or absence of head dirt, and the predicted date and time is the head dirt arrival date and time or the cleaning date and time. The output unit 34 preferably outputs the flight area 102, the most frequently soiled area 106, the soiled part 108, and a rectangle surrounding the outer shape of the soiled part 108. By doing so, the operator can confirm the soiled part 108 extracted by the detection unit 321 without overlooking it, and can recognize the positional relationship between the soiled part 108 and the flight area 102 or the most frequently soiled area 106.

[0050] FIG. 7 is a conceptual diagram showing the difference image and the flight area 102 superimposed. FIGS. 7(a), 7(b), and 7(c) are the difference images in the state where a little dirt is attached, the difference image in the state where medium dirt is attached, and the difference image in the state where considerably dirt is attached, respectively. The output unit 34 preferably outputs the difference images in the state where dirt is attached in the order of the shooting date and time. By doing so, it can be seen that the soiled part 108 is growing and approaching the flight area 102.

[0051] Since the ink droplets ejected from the nozzle 12 fly along different flight routes 100 depending on the character size to be printed, the detection unit 321 and the prediction unit 322 may use different flight regions 102 for each character size. By doing so, it is possible to more accurately detect head contamination and predict the date and time of head contamination arrival and cleaning date and time corresponding to the character size to be printed.

[0052] As described above, the present invention is not limited to the above-described embodiments. For example, the camera 20 does not have to photograph the flight region where the ink droplets ejected from the nozzle fly, or it may be mounted inside the head cover 1 9. The print head 10 does not have to include the head cover 19 . The print head 1 with a contamination detection device does not have to include an output device that outputs the image data photographed by the camera . The contamination detection target region for detecting contamination does not have to include the contamination most frequent region, which is a region including at least one of the space between the deflection electrode plus 16A and the flight region 102 or the space inside the flight region 102 adjacent to the entrance of the gutter 18. Yes

Explanation of Signs

[0053] 1: Print head with contamination detection device 10: Print head 100: Flight route 102: Flight region 104: Contamination detection target region 106: Contamination most frequent region 108: Contaminated part 11: Contamination growth direction (direction in which head contamination grows) 12: Nozzle 14: Charging electrode 16: Deflection electrode 16A: Deflection electrode plus 18: Gutter 19: Head cover 20: Camera 30: Information processing unit 31: Storage unit 32: Processing unit 321: Detection unit 322: Prediction unit 33: Communication unit 34: Output unit 40: Display (output device)

Claims

1. Detecting ink stains on the print head of a continuous inkjet printer A print head with a dirt detection device, 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 stain detection device having a camera that takes an image from a side of a direction in which ink droplets are ejected from the nozzle and a side of a direction in which the deflection electrode faces the nozzle, and an information processing unit that processes image data taken by the camera; Equipped with The information processing unit includes a storage unit that stores the image data together with a shooting date and time; a detection unit that detects ink stains from the difference image data by comparing the stain detection target areas of the two image data captured on different shooting dates and times as a stain detection target area for detecting stains from a part or all of the area captured by the camera and creating difference image data that identifies different parts of the two image data; and 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 is provided for outputting image data captured by the camera.

3. A print head with a dirt detection device according to claim 1 or 2.

4. A print head with a stain detection device as described in claim 2, which is provided with 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 ink stain detected in the differential image data, the distance in the stain growth direction of the flight area, and the speed.

5. The memory unit stores a date and time when the ink stain reaches the flight area, 5. The print head with a contamination detection device according to claim 4, wherein the prediction unit predicts a date and time before the ink contamination reaches the flight area as the date and time for cleaning the print head.

6. A print head with a dirt detection device as described in claim 2, wherein the area subject to dirt detection includes an area where dirt occurs most frequently, which is an area including at least one of the space between a deflection electrode positive consisting of the positive pole of the deflection electrode and the flight area, or a space inside the flight area adjacent to the entrance of the gutter.

7. A head cover for covering the print head, The camera is attached to the outside of the head cover and is provided in the head cover.

3. The method according to claim 1 or 2, wherein the inside of the head cover is photographed through a viewing window. Print head with contamination detection device.

8. A stain detection device attached to a print head of a continuous inkjet printer having 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, said stain detection device detecting ink stains on said print head, 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 camera that shoots from an information processing unit that processes image data captured by the camera; Equipped with The information processing unit includes a storage unit that stores the image data together with a shooting date and time; a detection unit that detects ink stains from the difference image data by comparing the stain detection target areas of the two image data captured on different shooting dates and times as a stain detection target area for detecting stains from a part or all of the area captured by the camera and creating difference image data that identifies different parts of the two image data; and A dirt detection device comprising:

Images