JPH03270941A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To enable an end of ink to be detected accurately during an ordinary printing or a recovery operation by a method wherein the ink jet recorder outputs by detecting variation in resistance exceeding a set value between an electrode coming in contact with a porous material and an electrode in an ink chamber and besides a set value in recovery operation of a printing head is made less than a set value in ordinary printing. CONSTITUTION:An electrode S1 is provided to an inner wall surface of an ink tank 8, and an electrode S2 is provided in an interconnecting hole 13 at a lower part of the ink tank 8. Reference voltage Vcc is applied to either electrode, for instance, to the electrode S1, and the other electrode S2 is earthed. Resistance between both electrodes S1, S2 is small and stable under a condition wherein ink is enough stored in a foam 7 in the ink tank 8. When the ink in the foam 7 decreases and an area of a connection part of ink between both electrodes starts decreasing, the resistance steeply increases. It is detected with a differentiating circuit 16, and is compared with a set value with a comparator 17. When it exceeds the set value, at alarm lamp or the like are lighted, and running out of ink is displayed. Further, a set value changing means 20 is established. In recovery operation of a printing head 3, said means receives a recovery operation signal from a panel, and changes automatically the set value to a lower value than that in printing.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an inkjet recording device that records characters, etc. on a recording medium by ejecting ink droplets from a nozzle, and particularly relates to an ink end detection device in an ink tank provided in the device. . [Prior art 1] In an inkjet recording device that ejects ink droplets from a nozzle to write characters or the like on a recording medium according to recording information, when the ink in the ink tank is exhausted and the supply is cut off, Not only will it become impossible to record and write, but the data that should be saved may be lost, or air may get into the pipe leading to the nozzle, making it very difficult to record and write even if you replenish the ink. Problems arise in that ink is consumed and it takes time.

[Problems to be Solved by the Invention] In order to deal with such problems, it is sufficient to install a level detector in the tank, but in particular, it is possible to mount the ink tank on the print head and 6 on the carriage. In such an inkjet recording apparatus, it is necessary to prevent air bubbles generated in the ink in the ink tank from entering the pipe portion leading to the nozzle due to vibrations such as when the carriage returns. For this reason, measures have been taken to house a porous foam such as urethane foam in the ink tank and impregnate the ink, but this method has the problem of not being able to directly detect the end of the ink. Ta. Furthermore, in this type of inkjet recording apparatus, when a print head is clogged with dust or the like and a printing defect occurs, a recovery operation is performed by pump suction from a nozzle or the like. Since a larger amount of ink is consumed during this recovery operation than during normal printing, there is a problem in that it becomes even more difficult to detect when the ink runs out. An object of the present invention is to detect the end of ink very accurately during normal printing and during recovery operation even in such an inkjet recording device in which the porous material in the ink tank is impregnated with ink. be. [Means for Solving the Problems J] In order to achieve the above object, the present invention provides an inkjet recording device that records on a recording medium by ejecting ink droplets from a nozzle. A porous material impregnated with a water-soluble ink is housed in an ink tank communicating with the ink tank, and an electrode that contacts the porous material and an electrode located within the ink chamber are disposed, and when the temperature exceeds a set value, An ink end detection circuit that detects and outputs a resistance change between electrodes is provided, and the set value during a recovery operation of the print head is set smaller than the set value during normal printing. . [Function 1] With this configuration, the gap between the ink in the porous material and the ink in the ink chamber, which occurs immediately before the ink in the porous material is depleted, occurs depending on the recovery operation of the print head and during normal printing. A decrease in the communication area of the ink can be detected as a change in electrical resistance, which indicates the ink end. Therefore, the state in which ink cannot be supplied to the print head can be detected in advance during the recovery operation and during normal printing. [Example] The illustrated example will be described below, but prior to that, the state before and after depletion of the ink impregnated into the porous material and the change in electrical resistance will be described with reference to FIGS. 3 and 4. At the top of the ink chamber A, whose top end serves as the ink outlet,
When a porous material B such as polyurethane foam is compressed, the water-soluble ink i impregnated into the porous material B is sequentially supplied into the ink chamber A by capillary action in the amount corresponding to the consumed amount. (Fig. 3(a))
), under this condition, the resistance between the two electrodes S-, S, arranged in the porous material B and ink chamber A, is kept small and almost constant (as shown in Fig. 4). Area a),
On the other hand, as the ink in the porous material B gradually depletes, a part of the gas g that has entered the porous material B to replace the ink i flows through the porous material B while experiencing great resistance. When it reaches the bottom and a part of the ink outlet appears, the ink i in the porous material B that was in communication with this part
A partial break occurs between the ink l in the ink chamber A and the ink l in the ink chamber A (Fig. 3(b)), and the resistance between the fractional amounts tis, s, which corresponds to a decrease in the communication area of the ink, increases. (Region b in Figure 4) Furthermore, as the ink l in the porous material B becomes depleted, the ink communication area further decreases, and finally the ink i in the porous material B and the ink chamber A The ink i is divided, and the resistance between the picture electrodes S, , S, becomes maximum (region tic in Fig. 4). Therefore, by detecting the resistance between the picture electrodes S, , S, It is possible to detect ink end. 1.2 shows an embodiment of the present invention specifically constructed based on the above-mentioned ink end detection principle, and FIG. FIG. 2 is a block diagram showing an ink end detection circuit. A print head 3 is integrally provided in the vicinity of the platen 1 on a carriage 2 that reciprocates along the platen 1. Further, an ink tank 8 is provided behind the head 3 and is filled with a foam 7 made of a porous material such as polyurethane foam. This ink tank 8
A vent hole 10 is provided in the lid 9 to allow atmospheric air to be taken in. Also on the bottom is Form 7.
A table-shaped protrusion 11 is formed to ensure close contact with the foam 7, and an ink chamber 12 for accommodating and holding the water-soluble ink 7 in the foam 7 is formed downward from the center of the protrusion 11. Further, this ink chamber 12 has a communication hole 13 extending from its lower end in the direction of the head 3. The end of this communication hole 13 is sealed with a rubber plug 14.
The water-soluble ink contained in the ink tank 8 is supplied to the print head 3 by inserting a hollow needle 5 communicating with the print head 3 through the filter chamber 4. The symbols S, , S in the figure are the electrodes for detecting the end of the ink described above. One electrode s1 is provided on the inner wall surface of the ink tank 8 so as to contact the form 7, and the other electrode S8 extends into the communication hole 13 through the rubber stopper 14 so as to come into contact with the water-soluble ink. There is. Then, these electrodes S, , S, and the glue also have one of the electrodes, for example, the electrode S,
A reference voltage Vcc is applied to as shown in FIG.
The other electrode St is grounded. A resistance change detection circuit including a differentiation circuit 16 and a comparison circuit 17 is connected to the electrode Sl on the side to which the reference voltage Vcc is applied. The ink end detection is performed based on an output signal when the amount of resistance change exceeds a preset partial level (ie, a set value). Furthermore, the set value is changed by the set value changing means 20, and is set smaller during the recovery operation than during normal printing. Next, the ink end detection operation performed by the above-described apparatus will be explained. When enough ink is stored in the form 7 in the ink tank 8 and the one picture electrodes S, , S, are connected via water-soluble ink, the picture electrodes S, , S, are connected via water-soluble ink.
The resistance between S and S is small and stable. This state continues as long as the foam 7 is wet even if the ink decreases and the electrode S1 is no longer in direct contact with the ink. Due to the subsequent recording/writing operation of the inkjet recording device, the ink in the form 7 further decreases, and the gas that has entered the form 7 reaches the upper open end of the ink chamber 12, forming an ink communication section connecting the form 7 and the ink chamber 12. When the area of starts decreasing. Along with this, the resistance increases rapidly as shown in the area shown in FIG. This resistance change is immediately detected as a change amount by the differentiating circuit 16. When this amount of change exceeds the set value input to the comparison circuit 7, the output signal from the comparison circuit 17 lights up a warning lamp, etc., and displays the end state on the panel surface, etc. . Further, a sequence is set in the recording apparatus to immediately stop the printing operation when the carriage 2 returns to the home position. Note that the above-mentioned detection circuit can be constructed in an analog or digital manner using well-known circuits. Furthermore, the electrode s3 on the side of the ink chamber 12 can also serve as the hollow needle 5. When ink is consumed from the ink tank 8 containing the form 7, the fourth
It has been found through experiments that the characteristics shown in the figure change slightly, and the region a in FIG. 4 becomes narrower as the amount of ink consumed per unit time increases. During normal printing, the amount of change described above is so small that it does not pose a practical problem. However, during recovery operations such as pump suction from the nozzles, which is performed when the print head 3 has a printing defect due to dirt, dust, etc., the amount of ink consumed per unit time is extremely large compared to normal printing. becomes. For this reason, the movement of air within the form 7 becomes intense, and the state of (b) in Fig. 3 not only becomes narrower in the area a in Fig. 4, but also becomes closer to area C in the form 7. It was also found that air started to enter the ink chamber 12 from the form 7. In the configuration of the inkjet recording device, the setting values shown in FIG. 4 can be determined in conjunction with the above-mentioned recovery operation of the print head 3. The remaining amount of ink at the time of detection increases, resulting in extremely poor ink consumption efficiency.Therefore, in this embodiment, the setting value changing means 20 changes the setting value for normal printing by 1 to change the setting value to the above-mentioned setting value. is now set to be in the first half of the area.

【Effect of the invention】

As described above, according to the present invention, an electrode that contacts the porous material inside the ink tank and an electrode located inside the ink chamber provided at the bottom of the ink tank are provided, and the resistance generated between these electrodes is reduced. Since an ink end detection circuit is provided that detects and outputs when the change exceeds a set value, it is now possible to detect the end state of the ink in the ink tank. Furthermore, the setting value for ink end detection during print head recovery operation has been made smaller than during normal printing, making it possible to reliably detect ink end before air enters the tube leading to the nozzle in all usage conditions. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main parts of an inkjet recording apparatus according to an embodiment of the present invention, FIG. 2 is a configuration diagram of an ink end detection circuit, and FIG. 3(a). (b) and (c) are explanatory diagrams showing states before and after running out of ink, and FIG. 4 is a diagram showing the relationship between ink consumption and electrical resistance.・Platen・Print head・Hollow needle・Form・Ink tank・Ink chamber・Electrode Figure 1 Figure 3 jli 4 Figure

Claims (1)

[Claims] In an inkjet recording device that records on a recording medium by ejecting ink droplets from a nozzle, an ink tank communicating with a print head via an ink chamber provided at a lower end houses a porous material impregnated with water-soluble ink, An electrode in contact with the porous material and an electrode located in the ink chamber are provided, and an ink end detection circuit is provided to detect and output a resistance change between the two electrodes exceeding a set value, and An inkjet recording apparatus characterized in that the setting value during a recovery operation of the print head is smaller than the setting value during normal printing.