JPH0245153A - Ink-jet recorder - Google Patents

Abstract

PURPOSE:To detect the abnormality of a head by generating bubbles by electrolysis in a liquid in a liquid chamber between a pair of electrodes installed into the liquid chamber, applying voltage so as to change the volume of bubbles by discharge and detecting the currents of the electrodes. CONSTITUTION:Voltage pulses are applied to one of at least a pair of electrodes 10, 11 of a recording head 1 from a driver 2 in response to a recording signal from a CPU 7, and currents flowing between the electrodes at that time are detected by a current detecting means 4, and transmitted to a voltage comparator 5 as a voltage signal. The voltage signal from the current detecting means 4 and predetermined comparison voltage (one or the plural) from a comparison voltage source 6 are compared by the voltage comparator 5, and the result is transmitted to the CPU 7 and a signal 8 is emitted in accordance with a comparison result with the voltage of the comparison voltage source 6. Accordingly, since the presence of a residual bubble 13 can be detected, the bubble may be discharged only when there is the bubble, thus eliminating the unnecessary stand-by time and also preventing the waste of ink.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to abnormality detection in an inkjet recording apparatus.

Enmaihanisaki Utility Model Publication No. 61-122840 discloses a gas generating means that generates gas by electrolyzing water, which is the main component of ink, and a gas generating means that generates gas by electrolyzing water, which is the main component of ink, and that the generated gas decomposes the ink into small droplets. An inkjet ejecting apparatus that ejects an inkjet using the pressure of the gas when it expands has been disclosed, in which an alternating current signal voltage is superimposed subsequent to the recording voltage of the gas generating means.

Further, U.S. Pat. No. 3,179,042 discloses a recording device that ejects ink using Joule heat (I"R loss) when electricity is applied to conductive ink. Although it is not explicitly stated in this U.S. patent specification, when electricity is applied to conductive ink, bubbles are generated on the electrode surface due to electrolysis (this may not occur in the case of consumable electrodes, but it is not practical). ), bubbles that are generated when the ink evaporates due to Joule heat or thermal energy during discharge disappear when the electricity is turned off.However, it is difficult for the bubbles generated due to electrolysis to immediately dissolve in the ink. In addition, it is not always possible to completely release the lubricant from the nozzle, etc. Also, due to temperature changes when left for a long time, dissolved l in the ink may
Gas often turns into bubbles in inkjet recording, and for this reason, most inkjet recording apparatuses (especially on-demand type) have a bubble discharge means. Moreover, since it is difficult to detect the presence or absence of air bubbles, most ink is discharged at a predetermined timing regardless of the presence or absence of air bubbles. This requires unnecessary waiting time and wasteful discharge of ink. Also, if air bubbles remain on or near the electrode surface,
Even if a voltage pulse is applied, the current value decreases. As a result, the necessary energy cannot be obtained, and ink ejection becomes unstable.

The present invention was made in view of the above-mentioned circumstances.
In particular, a voltage pulse is applied to one of a pair of electrodes in contact with the conductive ink, and bubbles due to electrolysis or Joule heat (
In inkjet recording devices that eject ink using ink evaporation due to ink evaporation (I2R loss) or discharge in gas, the change in current value due to the presence or absence of air bubbles is detected, and only if it is abnormal. This was done for the purpose of detecting abnormalities in the head by issuing a signal to take countermeasures.

In order to achieve the above object, the present invention provides a discharge port for discharging a liquid, a liquid chamber communicating with the discharge port, a pair of electrodes provided in the liquid chamber, and a pair of electrodes provided in the liquid chamber. a voltage applying means for applying a voltage to change the volume of the bubbles by electric discharge after generating bubbles in the liquid in the liquid chamber between the electrodes; and a current detecting means for detecting the current of the electrodes. It is characterized by having the following. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a block diagram for explaining one embodiment of the present invention, in which 1 is a recording head, 2 is a driver 3 is a power supply, 4 is a current detection means, 5 is a voltage comparator, and 6 is a comparison A voltage source, 7 a CPU, and 8 a signal for notifying an abnormality or for operating a countermeasure. A voltage pulse is applied from the driver 2 to one of at least one pair of electrodes of the recording head 1 in response to a recording signal from the CPU 7, and the current flowing between the electrodes at that time is detected by the current detection means 4, and the current is detected as a voltage signal by a voltage comparator. Send to 5. The voltage comparator 5 compares the voltage signal from the current detection means 4 with a predetermined comparison voltage (one or more) from the comparison voltage source 6, and sends the result to the CPU.
The signal 8 is sent to the current detecting means 7 and outputs a signal 8 according to the comparison result with the voltage of the comparison voltage source 6.The current detecting means 4 and the subsequent ones may perform the signal 8 at all times, or at the time the power is turned on and thereafter, the signal 8 is output at necessary intervals or as necessary recording signals. You may do this for each number.

In addition, there are various conventional means for performing this using the signal 8. For example, there are methods for displaying an abnormality to notify the operator, and methods for discharging the ink in the head under pressure or by suctioning under negative pressure (when newly supplied ink is discharged). The ink is a deaerated ink that dissolves residual air bubbles), etc.

FIG. 2 is a diagram for explaining an example of a recording head.
is an injection port, 10.11 is an electrode, 12 is a conductive ink, 1
3 is residual air bubbles.

Figure 3 is a diagram for explaining an example of ink jetting using Joule heat (I''R41t), where (a) shows the voltage pulse applied to the electrode, and (b) shows the current waveform during normal operation. Converted to voltage, (C) shows residual bubble 1 as shown in Figure 2.
3 is an example of a current waveform (converted to voltage).

In the waveform of FIG. 3(b), the peak value Vp is higher than Vs (comparison voltage 1), and sufficient Joule heat is applied to the electrode 10 (the area is smaller than the electrode 11, and the current density is higher near the other electrode 10). bubbles are generated near the electrode 10.
(If the electrode 10 is an anode, it is difficult to discharge) and the current is almost zero at the falling edge of the voltage pulse. In the waveform of FIG. 3 (Q), the electrode surface area (effective) becomes smaller due to the residual bubbles 13, and the current peak VP is smaller than Vsl, resulting in insufficient Joule heat, so the generated bubbles cannot cover the electrode. Even at the falling part of a), vI! A current equivalent to is flowing.

In such a state, the volume of bubbles generated is insufficient, so that the speed of the ink to be ejected may be reduced or may not be ejected at all. Therefore, the voltage comparator 5 (a) Vp) Vs.

(b) Vx<Vsz (c) Vp>Vs1&Vll<V8゜[V S, t
V s, , V s is the output of the comparison voltage WX6], it is determined to be normal, and any other result is determined to be abnormal.

As is clear from the above description, the present invention provides a recording device that ejects ink by applying a voltage pulse to one of at least a pair of electrodes that are in contact with conductive ink. means for detecting a current value flowing between the electrodes when a pulse is applied;

The presence or absence of residual air bubbles can be detected in an inkjet recording device that has a means for comparing the detected value with a predetermined value and a means for generating a signal that indicates an abnormality when the comparison result is outside the predetermined range. ,
It is only necessary to discharge air bubbles when necessary (when there are bubbles), and there is no need to periodically discharge air bubbles regardless of whether they are necessary, as is the case in the past.Therefore, unnecessary waiting time can be avoided. This also eliminates wasted ink.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining one embodiment of the present invention, FIG. 2 is a detailed view of the head portion, and FIG. 3 is a drive pulse waveform diagram. DESCRIPTION OF SYMBOLS 1... Recording head, 2... Driver, 3... Power supply, 4... Current detection means, 5... Voltage comparator, 6...
...Comparison voltage source, 7...CPU, 8...Signal notifying abnormality, 9...Injection port, 10.11...Electrode, 1
2... Conductive ink. 13...Residual bubbles.

Claims (1)

[Claims] 1. A discharge port for discharging liquid, a liquid chamber communicating with the discharge port, a pair of electrodes provided within the liquid chamber, and bubbles caused by electrolysis in the liquid in the liquid chamber between the pair of electrodes. 1. An inkjet recording apparatus comprising: a voltage applying means for applying a voltage so as to change the volume of the bubbles by discharge after generating the bubbles; and a current detecting means for detecting the current of the electrode.