JPH02147345A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To maintain stable printing invariably by detecting a peak current value by impressing an image electric signal between electrodes in a pair provided in a liquid chamber, and by varying an impression voltage so that said value be converged to a predetermined reference value. CONSTITUTION:A recording head is constructed of one ink inlet 7 and liquid chambers partitioned by partition walls 6, and a recording electrode 1, a common electrode 2 and further one jetting port 5 are provided in each liquid chamber. By impressing a voltage between the electrodes in a pair, a bubble is generated by electrolysis and jetting is made from the jetting port 5. An image electric signal Vp is impressed between the electrodes of a head electrode 15, and a current peak value of Ip is detected by a current detecting circuit 16 and compared with Vref of a reference value generating circuit 18 by a comparator 17. When the Ip does not reach a reference value, a signal is given by a control device 11 so that the Vp increased by DELTAVp be outputted from a programmable power source 12, the voltage is impressed again between the electrodes of the head electrode 15, and this operation is repeated until the Ip reaches the reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus using an on-demand recording head.

As a prior art related to the present invention, for example, Utility Model Application No. 61-1
There are methods described in Japanese Patent Publication No. 22840 and Japanese Patent Publication No. 54-35773, but the method described in Japanese Utility Model Application Publication No. 122840/1983 electrolyzes the injected liquid and uses the pressure when the gas expands. This type uses a jet to fire, and an alternating current signal voltage is superimposed on the recording voltage. Furthermore, the device described in Japanese Patent Publication No. 54-35773 has a discharge chamber and a discharge path for discharging ink therein, circulates the ink in the discharge chamber and discharges it, and causes an impact volume change. It ejects ink. Furthermore, as an application that has already been filed, the current value flowing between the electrodes is detected and compared with a predetermined value,
There are some that have a means to notify you that there is an abnormality when it is out of range.

However, the prior art is an example in which electricity is applied between two electrodes both provided in the liquid chamber,
The method described in Publication No. 0 is intended to remove substances adhered to the electrode surface by superimposing an alternating current signal, but the application of the alternating current signal inevitably generates bubbles. In addition, the method described in Japanese Patent Publication No. 54-35773 uses forced circulation to remove generated air bubbles and deteriorated ink, and to maintain fresh ink at all times, but the device becomes larger, etc. There are drawbacks.

In addition, as a method to maintain the function of on-demand inkjet, methods such as forcibly pressurizing the liquid chamber or forcibly suctioning from the orifice are generally used, but since a large amount of ink is discharged, it is difficult to maintain the ink level. There are disadvantages such as high cost and long waiting time for a series of operations.

In the previously proposed system, self-recovery was not possible with the abnormality detection means, so a recovery means as shown in the conventional example had to be provided. If air bubbles remain on or near the electrode surface, the current value between the electrodes will decrease even if an image electrical signal is applied, making normal printing impossible.

-15 The present invention was made in view of the above-mentioned circumstances,
Applying an image electrical signal between a pair of electrodes installed in the liquid chamber,
This is a means of detecting the peak current value, comparing it with a predetermined reference value, and converging to that value.Convergence is achieved by changing the applied voltage to the reference value, thus ensuring stable printing at all times. This was done for the purpose of providing an inkjet recording device that can be maintained.

In order to achieve the above object, the present invention provides an inkjet recording device that ejects a conductive liquid from an ejection port in response to an image electric signal (Vp), which includes two electrodes disposed in a liquid chamber, and the electrodes. Potential difference applying means for applying a potential difference between
a current detection means that detects a current peak value when the power is turned on and/or at every fixed time, or every time a page is changed in printing, and a comparison circuit that compares the detected current peak value with a reference value. , the difference obtained from the comparison circuit (image electrical signal V
The present invention is characterized by comprising a convergence circuit that increases or decreases the current value (p) and converges it to a reference current value. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a configuration diagram for explaining one embodiment of a recording head of an inkjet recording apparatus according to the present invention.
2 is a recording electrode, 2 is a common electrode, 3 is an upper plate, 4 is a lower plate, 5 is an injection port, 6 is a partition wall, and 7 is an ink inlet. The recording head is composed of an ink lower portion and a liquid chamber partitioned by a partition wall 6. Each liquid chamber has a recording electrode 1 and a common electrode 2.
, and one injection port 5 is further provided. By applying a voltage between a pair of electrodes, bubbles are generated by electrolysis, and by further applying electricity, the electrical resistance of the fluid decreases rapidly due to temperature rise, so that the current increases. At the same time, the bubbles coalesce and rapidly expand as merged bubbles, and the injection port 5
Inject from.

FIG. 2 is a detection/control block diagram of the inkjet recording apparatus according to the present invention, FIG. 3 is a diagram showing another embodiment of the comparison circuit 19 of FIG. 2, and FIG. 4 is a diagram showing another embodiment of the comparison circuit 19 of FIG.

This is a diagram showing a current waveform when a voltage is applied between electrodes, and in the diagram, 11 is a control device, 12 is a programmable power supply, and 13
14 is a switch control circuit, 14 is a switching circuit, 15 is a head electrode, 16 is a current detection circuit, 17 is a comparator, 18
19 is a reference value generation circuit, 19 is a comparison circuit, 2o is an A/D converter, and 21 is a peak hold circuit.

The current peak value is detected by the current detection means when the power is turned on or during subsequent printing. As shown in Fig. 4(a), when an image electrical signal is applied in the form of a pulse, the current (
Ip) reaches I5T as shown in Fig. 4(b), and normal droplet ejection is performed, but as shown in Fig. 4(c), if it is I, the ejection energy is small and the ejected droplet becomes small. Or,
There may be times when it is not possible to spray all the water. This is a phenomenon that occurs when a long stop period continues or when air bubbles are present in or near the electrode itself.

In order to improve the above-mentioned problem, as shown in FIG. 2, a printing operation is performed by determining whether the current value is good or bad.

The operation sequence is as follows: First, one image electric signal Vp is applied between the electrodes of the head electrode 15, the current peak value of IP is detected by the current detection circuit 16, and the detected current peak value Ip is set as Vi. The comparator 17 compares Ip with Vref of the reference value generation circuit 18, and if Ip does not reach the reference value, the control device 11 issues a signal to output VP increased by ΔVp from the programmable power supply 12, and then outputs the signal again. , a voltage is applied between the electrodes of the head electrode 15, and Ip
This is repeated until it reaches the reference value. Figure 3 shows
This is configured to shorten the time it takes for Ip to reach the reference value, and the peak value of the current is held in the peak hold circuit 21, then A/D converted by the A/D converter 20, and the Ip is
The control device 11 controls the difference between p and the reference value to be increased or decreased and applied between the electrodes. With this method, the absolute value is I
Since p is known, Ip can converge to the reference value in a short time.

The convergence circuit is a general term for means for repeatedly comparing the current peak value with a reference value, or means for repeatedly comparing the peak hold value.

Efficacy-Yu agriculture As is clear from the above description, according to the present invention.

(2) In a recording device that applies an electric signal to a pair of electrodes in a liquid chamber and injects a conductive liquid from an injection port, at 08:00 when the power supply is turned on or every fixed period of time.

Alternatively, the current peak value is detected every time there is a page break in printing.

■Printing is performed when the reference current value is reached by means of converging the detected current value to the reference current value. , printing is possible, and since the forced operation is not performed by stopping at the initial position during printing, the printing time can also be substantially shortened. Furthermore, since the forced operation is not performed, ink is not wasted and running costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining one embodiment of a recording head of an inkjet recording apparatus according to the present invention, and FIG.
Detection/control block diagram of inkjet recording device, 3rd
The figure shows another embodiment of the current detecting section in FIG.
The figure is a diagram showing voltage and current waveforms when voltage is applied between electrodes. DESCRIPTION OF SYMBOLS 1... Recording electrode, 2... Common electrode, 5... Injection port, 11... Control device, 12... Programmable power supply,
15... Head electrode, 16... Current detection circuit, 17
...Comparator. 18... Reference value generation circuit, 19... Comparison circuit, 20
・・A/D converter, 21 ・・Peak hold circuit, 2
2... Current detection section. Figure 1 Patent applicant Ricoh Co., Ltd. Figure 1

Claims (1)

[Claims] 1. In an inkjet recording device that ejects a conductive liquid from an ejection port in response to an image electric signal, two electrodes are arranged in a liquid chamber, a potential difference applying means for applying a potential difference between the electrodes, and when the power is turned on or /And a current detection means that detects a current peak value at every fixed time or every page change in printing, and a comparison circuit that compares the detected current peak value with a reference value.
An inkjet recording apparatus comprising: a convergence circuit that increases or decreases the difference obtained from the comparison circuit and converges it to a reference current value.