JPH02239943A - Clog detector for ink jet printer - Google Patents

Abstract

PURPOSE:To detect clog of a nozzle of an ink jet printer by colliding an ink droplet to be injected from the nozzle to a vibration sensor and measuring the amplitude of a vibration at the time of collision. CONSTITUTION:A pulse generator 25 is operated to inject an ink droplet 31 from the end 26 of a nozzle toward paper 32. The injected droplet 31 is collided with the paper 32. A vibration sensor 28 detects a vibration when the droplet 31 is collided with the paper 32, and generates a voltage in response to the degree of the vibration. An amplifier 29 amplifies the voltage value of the sensor 28, and outputs it to a discriminator 31. A discriminator 30 judges a normal injection of the droplet 31 if the signal from the amplifier 29 exceeds a predetermined value, and judges clog of the nozzle if the amplified signal does not become a predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device that detects clogging of an inkjet printer using a vibration sensor instead of using optical means.

[Conventional technology]

This type of inkjet printer is a non-impact type printer that prints arbitrary characters or figures by ejecting ink droplets from a nozzle to form ink dots on a printing surface. This inkje notebook printer has advantages such as being able to be miniaturized, producing low operating noise, high printing speed, and being able to print on non-flat surfaces and color printing, and its uses are increasing. It is.

This printer uses a continuous ink ejection method. There are on-demand methods, electric field control methods, ink mist methods, bubble jet methods, etc. In either method, the nozzle that ejects ink is extremely small, with a diameter of several tens of μm to about 100 μm.
Depending on the type of ink, there is a problem in that nozzles are easily clogged due to crystallization of ink components or the presence of large particles.

In addition, in on-demand printer heads, ink is supplied by balancing the capillary suction force of the ink flow path with the restoring force of the diaphragm in the ink chamber, so if air bubbles get mixed into the ink, the ink will no longer be ejected. The problem is that this is no longer done. Naturally, when the nozzle becomes clogged,
This causes printing defects. Furthermore, since this printing defect is discovered after printing on the substrate, there is a drawback that defective products are generated due to the printing defect.

Therefore, conventionally, as shown in FIGS. 6 and 7, for example, nozzle clogging has been monitored using optical detection means. The prior art shown in FIG. 6 is the technology described in US Pat. No. 4,323,908. In this prior art, the pulse generator 1
The piezoelectric element 3 of the head body 2 is converted into mechanical vibration by the pulse signal from the ink chamber 4, and the ink is transferred to the nozzle tip 5.
The ink Wj6 is extruded from the ink to form ink Wj6, and this is adhered to the printing material. Nozzle clogging is detected by using a photoelectric detector 7 to detect ink droplets 6 ejected from the nozzle tip 5.

Furthermore, the prior art shown in FIG.
This is the technique described in Publication No. G. In this conventional technology,
When the piezoelectric element 3 of the head body 2 is vibrated to eject ink droplets 9 from the nozzle tip surface 8, the ink meniscus (curved surface formed by the liquid surface due to capillary action) 10 of the nozzle tip surface 8 is By detecting the movement of
It is designed to detect nozzle clogging. That is, when a voltage is applied to the piezoelectric element 3 from the state shown in FIG. 3A, the piezoelectric element 3 expands and contracts, and the pressure in the ink chamber 4 becomes reduced. Therefore, the ink meniscus 10 is drawn inward from the nozzle tip surface 8, as shown in the figure (bl).At this time, the ink that was blocking the light from the light source 11 moves, so it In this way, by detecting the movement of the ink meniscus 10 by the optical detection means, clogging of the nozzle is detected.In addition, in this conventional technology, When the piezoelectric element 3 returns to its original state, the pressure in the pressure chamber 4 increases, so that the ink passes through the state shown in Figure Cl in the same figure, and then forms an ink droplet 9 as shown in Figure fdl in the same figure.
and is ejected onto the printing material.

[Problem to be solved by the invention]

As described above, all conventional means for detecting nozzle clogging are based on optical methods. Here, the size of the ink droplet is approximately 5 μm at most because the diameter of the nozzle injection hole is extremely thin, about several tens of micrometers, as described above.
It is about 0 to 200 μm. Therefore, in order to detect such minute ink droplets by optical means, the installation position accuracy and detection accuracy of the detector must be high.

Therefore, there was a drawback that the overall mechanism and the configuration of the discrimination circuit of the optical detection device became complicated. Another disadvantage is that the larger the number of nozzles in an inkjet printer, the more difficult it becomes to install an optical detection device. Furthermore, there is a drawback that a slight positional shift of the optical detection device causes detection failure, resulting in a lack of reliability.

[Means to solve the problem]

The present invention has been made to improve and eliminate the above-mentioned problems of the conventional art, and it is an object of the present invention to provide a clogging detection device with a simple configuration, high reliability, and low cost.

The means adopted by the present invention to solve the above problem includes a vibration sensor disposed opposite to the nozzle tip of an inkjet printer, and a discriminator that discriminates the output signal of this vibration sensor. It constitutes a clogging detection device for inkjet printers.

[For production]

When ink droplets are ejected to a vibration sensor disposed opposite the nozzle tip of an inkjet printer, a voltage is generated in the vibration sensor due to the vibration caused by the collision of the ink droplets. By measuring this voltage value and comparing it with a determination circuit, it is possible to determine whether the ink droplets have been ejected normally.

That is, it is possible to detect whether or not the nozzle is clogged.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An explanation will be given below with reference to the drawings based on an embodiment in which the configuration of the present invention is applied to an on-demand type inkjet printer.

FIG. 1 is a block diagram showing the entire embodiment of the apparatus. The inkjet printer 20 is configured to supply ink from an ink container 21 to an ink chamber 23 of a hexagonal main body 22. The ink in the ink chamber 23 is ejected from the nozzle tip 26 by applying a voltage to the piezoelectric element 24 attached to the head body 22 and vibrating it through the pulse generator 25, thereby varying the pressure in the ink chamber 23. It is supposed to be done. This configuration is basically the same as the conventional case.

The clogging detection device 27 of this embodiment has a vibration sensor 28 disposed opposite the nozzle tip 26 of the inkjet printer 20. This vibration sensor 2
The output signal of 8 is amplified by an amplifier 29, and the amplified signal is further discriminated by a discriminator 30. Also, on the inkjet printer 20 side of the vibration sensor 28,
A paper 32 is provided to which ink droplets 31 are attached.

To detect clogging, first turn on and off the pulse generator 25.
F operation is performed to eject ink droplets 31 from the nozzle tip 26 toward the paper 32. The ejected ink droplets 31 are
It collides with the paper 32. The vibration sensor 28 detects the vibration when the ink droplet 31 collides with the paper 32, and generates a voltage depending on the degree of vibration. amplifier 29
amplifies the voltage value of the vibration sensor 28, and the discriminator 3
Output to 0. Discriminator 30 compares whether the signal from amplifier 29 exceeds a predetermined value. If the amplified signal exceeds a predetermined value, ink drop 3
1 is determined to be injecting normally, and if the amplified signal is less than a predetermined value, it is determined that nozzle clogging has occurred. If necessary, the output signal of the discriminator 30 may be displayed by voice or by a CRT display or the like.

This makes it possible to detect whether or not the nozzle is clogged.

The reason why the paper 32 is arranged is to repeatedly detect clogging, and if this paper 32 is not present, ink droplets 31 will adhere to and accumulate on the vibration sensor 28, reducing the detection sensitivity of the vibration sensor 28. Because it does. Of course, it is also possible to detect the clogging state by directly colliding the ink droplets 31 with the vibration sensor 28.

[Experiment example]

Figure 2 shows the actual production of an inkjet printer.
1 is a diagram showing the entire experimental apparatus in which the effects of the present invention were confirmed. The experiment was conducted by manufacturing a stemme-type printing head 40 having two chambers with a nozzle diameter of 50 μm. and,
Diameter 5N and thickness Q. A piezoelectric element 41 made by Fuji Ceramisox with a diameter of 5 ++ n and a thickness Q of 4 mm was adhered to a stainless steel disc 42 having a diameter of 5 + n and a thickness of Q, and this was attached to the print head 40 as a diaphragm 43.

On the other hand, a vibration sensor 44 made by Fuji Ceramics was placed opposite the print head 40, and a collision plate 46 for ink droplets 45 was fixed to the vibration sensor 44. In this case, the distance t between the collision plate 46 and the nozzle tip surface was set to 2 mm. The ink used was Seiko Epson ink for inkjet printers.

In the experiment, in this setting state, the diaphragm 43 was
A square wave pulse voltage of 140 V and 60 μs was applied by the pulse generator 47, and an ink droplet 45 was ejected from the nozzle hole 48. Then, the vibration when the ink droplet 45 collided with the collision plate 46 was converted into a voltage value, and this was recorded with a storage scope 49.

3 to 5 show the recording results of the storage scope 49. FIG. FIG. 3 shows a voltage waveform in a normal state in which the nozzle hole 48 is not clogged.

Further, FIG. 4 shows a voltage waveform in a state where the nozzle hole 48 is forcibly heated and dried using a dryer, and the nozzle hole 48 is slightly clogged. Further, FIG. 5 shows the voltage waveform when the nozzle hole 48 is heated and dried in the same manner to cause complete clogging.

According to the voltage waveform shown in FIG. 3 when ink is normally ejected, when the ink droplet 45 collides with the collision plate 46, a large vibration is generated, which gradually attenuates and returns to an almost steady state after 400 μs. ing. However, in the slightly clogged state shown in FIG. 4, the amount of ink droplets 45 ejected is small, so the vibration caused by collision is small.

Furthermore, in the completely clogged state shown in FIG. 5, as a matter of course, no ink droplets 45 are ejected and no vibration occurs at all. As is clear from these results, by measuring the vibration when the ink droplets 45 collide with the collision plate 46, it is possible to detect nozzle clogging in an inkjet printer. Note that in the case where a plurality of nozzles are provided, ink droplets may be ejected from each nozzle to detect a clogging state.

By the way, the present invention is not limited to the above-described embodiments, and can be modified as appropriate. For example, a commercially available small condenser microphone may be used as the vibration sensor, and the clogging state may be detected by measuring the loudness of the sound of ink droplets colliding.

〔Effect of the invention〕

As explained above, in the present invention, ink droplets ejected from a nozzle collide with a vibration sensor, and by measuring the magnitude of vibration at the time of collision, nozzle clogging of an inkjet printer is detected. Is possible. Therefore, clogging can be detected simply by causing ink droplets to collide with the vibration sensor, and the installation accuracy of the detection device can be made rough. That is, since there is no need to optically detect extremely fine ink droplets as in the conventional method, there are no detection errors and highly reliable detection can be obtained.

Furthermore, the overall configuration of the detection device is extremely simple, allowing for miniaturization and cost reduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the entirety of a detection device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the entire experimental device for confirming the effects of the present invention, and FIGS. 3 to 5 6 is a voltage waveform diagram showing experimental results, FIG. 6 is a block diagram showing a conventional clogging detection device, and FIG. 7 (al to FD) explains the operation mode of another conventional clogging detection device. It is a drawing. 20... Inkjet printer 22... Hesod body 23... Ink 26...
・Nozzle tip surface 27...Clogging detection device 28...
Vibration sensor 3o...Discriminator 31...Ink droplet Patent applicant Inax Co., Ltd. Agent Patent attorney Toshihiko Uchida-ku C Tsumi-ku Kumi-H Sho-ku α) Taste

Claims (1)

[Claims] 1. A clogging detection device for an inkjet printer, comprising a vibration sensor disposed opposite to the tip of a nozzle of the inkjet printer, and a discriminator that discriminates the output signal of the vibration sensor.