JPH04208468A - Ink jet printer - Google Patents

Abstract

PURPOSE:To determine whether a fill-in is present or not by ejecting ink drops directly on a sheet-like matter for testing from ink jet nozzles and reading the printed state with an image sensor optically. CONSTITUTION:In an ink jet printer 1, print liquid is ejected from ink jet nozzles 9, 10, 11, 12 on a sheet-like matter 2 such as cloths to be conveyed by a conveyer 3 based on an image data so as to print desired patterns. On a side part of the sheet-like matter 2 on which printing will be actually performed, a fill-in detecting area where a sheet-like matter 18 for testing is to be arranged is provided. The ink is ejected also on the sheet-like matter 18 for testing from the ink jet nozzles. Also, a sensor 20 for detecting optically the printed state of the sheet-like matter 18 for testing and a fill-in detecting device for detecting fill-in of also the nozzles based on a difference in quantity of light between a printing part and a non-printing part in the output of the sensor 20 are provided. Thus, fill-in of the nozzles can be detected regardless of type of head and kind of ink.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inkjet printing device that prints a desired pattern on a sheet-like object such as cloth or paper by jetting ink from a nozzle, and particularly relates to an inkjet printing device that prints a desired pattern on a sheet-like object such as cloth or paper. The present invention relates to an inkjet printing device that can detect the presence or absence of clogging.

[Prior Art] In an inkjet printing device that prints a pattern by disposing a plurality of inkjet nozzles on a sheet-like object such as cloth and ejecting ink droplets, if even one nozzle becomes clogged, the desired horizontal pattern cannot be obtained. Therefore, various clogging detection devices have been proposed that detect whether or not ink droplets are ejected from the nozzle tip.

For example, a liquid pressure sensing element is installed in the nozzle head to detect the ink pressure inside the head, and an inkjet pressure sensing element is installed at the location where unnecessary ink droplets are ejected. A device for detecting clogging by detecting abnormalities in
No. 974), a device in which a dummy ejection head is provided in addition to the actual printing head and the amount of ink flowing into both heads is compared to detect clogging (Japanese Patent Laid-Open No. 57-20361), and In a device that drives a piezoelectric element to eject ink droplets from the tip of a nozzle, a charging electrode and an ink droplet adhering body are configured on the same insulating substrate surface, and the induced current generated in the adhering body as the charged ink droplets fly and adhere. A device (Japanese Unexamined Patent Publication No. 71261/1983) has been proposed that detects the presence or absence of ink ejection by detecting the presence or absence of ink.

[Problems to be Solved by the Invention] Among the above-mentioned inkjet nozzle clogging detection devices, the one described in Japanese Patent Application Laid-open No. 158974/1983 has a high density detection device because a liquid pressure detection element is provided for each nozzle head. However, there was a problem in that it could not be used in a multi-nozzle head. Further, the method described in Japanese Patent Application Laid-open No. 57-20361 has a problem that the structure is complicated due to the provision of a dummy ejection head, and that detection becomes difficult when the number of nozzles increases. Furthermore, the method described in JP-A No. 60-71261 has the problem that detection becomes impossible when insulating ink such as oil-based ink is used, and an M source of several hundred V is required as a charging power source. Therefore, there was a problem that there was a risk of sparks and the like.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inkjet printing apparatus that can detect nozzle clogging regardless of the type of head or type of ink (and without causing the risk of sparks or the like).

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following configuration.

That is, the inkjet printing device according to the present invention prints on a sheet-like object such as a fabric conveyed by the conveyance device.
In an inkjet printing device that prints a desired pattern by ejecting printing fluid from an inkjet nozzle based on image data, a test sheet is placed next to the sheet that will actually be printed to detect clogging. a sensor for optically detecting the printing state of the test sheet, and a print portion in the output of the sensor. The present invention is characterized in that it is provided with a clogging detection device having means for determining whether the nozzle is clogged based on the difference in the amount of light between the nozzle and the non-printing portion.

[Operation] Ink droplets are directly ejected from an inkjet nozzle onto a test sheet, and the printed state is optically read by an image sensor. In areas where the nozzles are clogged, ink will not adhere to the test sheet, and
Since a line is drawn in the background color of the test sheet, the presence or absence of clogging can be determined by optically detecting the difference in the amount of light between this line and the area to which the ink has adhered.

[Embodiment] Figure 2 is a perspective view showing the configuration of an inkjet printing device 1 which is an embodiment of the present invention.
This is a device that prints on the sheet-like material 2 by sequentially conveying it to a printing position by driving the drum 5. The drum 5 is driven by a servo motor 6 (sub-scanning section).

The print section that sprays ink dots onto the sheet-like material 2 carries yellow, magenta, cyan, black, etc. inkjet nozzle heads 9, 10, 11° 12, each having a plurality of nozzle holes arranged in a row, on the carriage 1.
3. The carriage 13 is moved along guide rails 15 and 16 by a carriage drive belt 17.
The drive timing for each nozzle head moves back and forth in a direction perpendicular to the direction in which the sheet-like object 2 is conveyed, and is moved to a predetermined position of the sheet-like object 2 that is intermittently conveyed (main scanning section). Control is performed by a control device (not shown), and desired ink dots are sprayed onto the sheet-like material based on print data, and a duplicate image is printed.

As mentioned above, the sheet-like material 2 is carried by a belt 3 which is a conveying device.
A clogging detection area is provided on the side of the actual printing line described above, and a test sheet 18 is also placed on the belt 3 and conveyed to the printing position. It is designed to be transported to a blockage detection area.

In the clogging detection area, ink droplets are sprayed onto the test sheet 18 by all nozzles of the nozzle head every time the carriage 13 scans. The surface of the test sheet 18 onto which the ink has been sprayed is optically read by an image sensor 20 provided in the clogging detection area.

The image sensor 20 is composed of a CCD camera 21 and a light source 22, as shown in FIG. The image sensor 20 includes a light receiving element so as to be able to optically scan each of the yellow ink adhesion area 24y, the magenta ink adhesion area 24m, the cyan ink adhesion area 24c, and the black ink adhesion area 24b printed on the test sheet 18. are arranged in four columns. The test sheet 18 is preferably of relatively high brightness, such as white.

As shown in FIG. 3, each row of light receiving elements 26 has 2048 elements arranged in a row at a pitch of 13 μm. This means that when each nozzle head has 256 nozzle rows, 7 bits of the light receiving element corresponds to 1 nozzle, and 128 spare bits are assigned to the front and rear, resulting in 128+7X25
6+128=2048. Each light-receiving element is configured to convert light energy into electric charge and accumulate it when reflected light from a printed sheet-like object is incident thereon, and the electric charge is accumulated in accordance with the intensity of the light. The accumulated charges are instantaneously transferred to the analog register 27 in response to instructions from a control device (not shown), and then sequentially transferred to the output gate 28. From the output gate 28, a video output with a voltage level (analog value) proportional to the amount of charge of the light receiving element is outputted in order from the lower bit to the upper bit (1→2048), and the determination section 29 performs the determination described below.

As shown in FIG. 4, the imaging positions 26y, 26m, 26c, and 26b by the image sensor in which the light receiving elements are arranged in four rows are set to be slightly larger than the print width W printed on the test sheet 18. ing. The print width W is determined by each large nozzle 30 of the inkjet head 9, 10, 11, 12,
The reason why the imaging position of the image sensor, which is sequentially printed by the printing width W as the sheet material 2 is fed intermittently, is slightly larger than the printing width corresponds to the nozzle hole of the inkjet head as described above. This is because a light-receiving element is provided at the front and rear of the light-receiving element, and spare bits are allocated before and after the light-receiving element. When the test sheet 18 onto which ink droplets have been sprayed from all the nozzles of each head is optically scanned by the image sensor, each imaging position 26y is detected.

At 26m, 26c, and 26b, the video output is output in order from the lower bit to the upper bit as described above. FIGS. 5(a), (b), and (c) are diagrams showing examples of video output,
If the nozzle is not clogged, the output will be as shown in (a) of the same figure. In other words, at the imaging position corresponding to the lower 1 to 128 bits of the light receiving element, ink has not yet been printed on the test sheet, and the amount of reflected light is large due to the background color of the test sheet, and the charging output is large. The voltage level of the video output increases. 12, which corresponds to the print width W where ink is sprayed from all nozzles and the ink adheres.
Imaging positions of 9 to 1920 bits and 1921 to 204 where ink has already been attached during the previous carriage scan
The amount of reflected light at the 8-bit imaging position is reduced because of the ink attached, and the voltage level of the video output becomes low.

Additionally, if the large nozzle is clogged somewhere, as shown in Figure (b), ink will not be sprayed in the clogged area between 128 and 1920 bits, and the amount of reflected light will increase, resulting in video output. The location where is large will be detected as a peak. In addition, abnormalities may occur in the conveyance of sheet-like materials,
If a gap or the like occurs in the print in the main scanning direction, the amount of reflected light will increase in the areas where ink is not attached between the 1920 and 2048 bits, as shown in Figure (c).
Points with large video output will be detected. The clock for transferring the charge of the light receiving element to the shift register is set to 2.
If the frequency is 5 MHz, the corresponding bits of each light receiving element can be expressed using the transfer time axis as a reference, as shown in FIG.

As described above, since the video output from the image sensor 20 is determined based on the difference in the amount of light reflected from the ink adhesion location and the background color of the sheet-like object, if this determination level THR is set appropriately, the nozzle of the inkjet nozzle head Clogging of holes can be easily detected. Moreover, since multiple light-receiving elements correspond to one nozzle of the multi-nozzle head and detect clogging, the nozzle where the clogging has occurred can be identified, and the clogging removal work can be carried out appropriately and easily. be able to. In addition, since detection is performed by actually depositing ink, there are no restrictions depending on the type of ink, and unlike conventional methods, a charging power source is not required for clogging detection, so there is no risk of sparks, etc. , we did not specifically explain the type of nozzle head, but as is clear from the above explanation, it does not matter whether it is a continuous type or an on-demand type nozzle head, and even a high-density multi-nozzle head. I can handle it. still,
A means for applying an appropriate adhesive on the belt 3 is provided, and the sheet-like material 2 is placed on the belt 3 coated with the appropriate adhesive to increase the degree of adhesion between the belt 3 and the sheet-like material 2. This makes it possible to print with higher precision.

In the above embodiment, an apparatus for printing a sheet material that is intermittently conveyed in the horizontal direction has been described, but the present invention can also be applied to a cylindrical scanning type printer as shown in FIG. This apparatus is provided with a test printing drum 42 coaxially with a drum 40 to which a sheet-like material 41 is attached, and before starting printing on the sheet-like material 41, the test sheet-like material attached to the test printing drum 42 is Yellow, cyan, magenta, arranged on the carriage 43,
Ink dots may be sprayed by the inkjet heads 45 for four colors of black, optical scanning may be performed by the image sensor 50, and the video output signal may be processed in the same manner as described above.

In addition, in order to avoid the waste of conveying the test sheet material using the same conveyor belt as the sheet material to be printed, a configuration as shown in FIG. Installation, ink adhesion part 2431.
24m, 24c, and 24b are subjected to a test using the cleaning mechanism 61 provided on the rotary table before the 0th order scanning is performed in which optical scanning is performed at the imaging positions 26y, 26m, and 26c126b of the image sensor in the same manner as above. By erasing the ink adhering to the sheet material and sequentially performing clogging detection, it is possible to save on the test sheet material.

[Effects of the Invention] As is clear from the above description, according to the inkjet printing apparatus according to the present invention, nozzle clogging can be easily and accurately detected without being affected by the type of ink used, the type of head, etc. Since clogging can be easily removed, duplicate images can be printed evenly, and the reliability of the apparatus can be improved.

Furthermore, since the clogging removal work only needs to be performed when clogging occurs, it is possible to improve the operating rate of the inkjet printing apparatus.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention, and FIG.
The figure shows the configuration of the main parts, Figure 3 is a block diagram showing the configuration of the optical scanning unit centering on the image sensor, and Figure 4 shows the actual state of printing on sheet materials and test sheet materials. Plan views schematically shown in FIGS. 5(a), (b), and (c).
) is a diagram illustrating a video output waveform, and FIGS. 6 and 7 are diagrams illustrating modified embodiments. 1... Inkjet printing device 2... - Sheet-like material 3... Conveyor belt 9.10
．． 11, 12... Inkjet nozzle head
18...Test sheet-like object 20...Image sensor

Claims (1)

[Claims] (1) A sheet-like object that is actually printed in an inkjet printing device that prints a desired pattern on a sheet-like object such as a cloth that is transported by a transport device by jetting printing liquid from an inkjet nozzle based on image data. A clogging detection area in which a test sheet is placed is provided on the side of the test sheet, and ink is sprayed from an inkjet nozzle onto the test sheet, and the test sheet is printed. A clogging detection device is provided, which includes a sensor that optically detects the state, and a means for determining whether the nozzle is clogged based on the difference in the amount of light between the printed part and the non-printed part in the output of the sensor. Inkjet printing equipment.