JPS5847989B2 - Charge deflection device for inkjet printing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charge deflection device in a charge deflection type inkjet printing device.

In a charged deflection type inkjet printing device, ink droplets ejected from a nozzle of a print head are charged by a charging electrode according to deflection information, and the thus charged particles are caused to pass through an electrostatic field formed by the deflection electrode. Printing is performed on the recording paper by deflecting the light.

In this device, there is a problem in that the ink droplets are charged by the electric field generated by the voltage applied to the deflection electrode when no deflection information, that is, charge signal, is applied to the charge electrode. This problem is solved by making the distance sufficiently large.

However, when the distance between the charging electrode and the deflection electrode is increased, the distance from the shape of the ink droplet to the printing surface becomes longer, and as a result, the ink droplets ejected from the nozzle fly toward the printing surface, causing air to flow through the air. Disturbances caused by resistance or air flow may cause dot misalignment on the printed surface, leading charged ink droplets may cause subsequent ink droplets to be charged with opposite polarities, leading to merging of successive ink droplets, or leading during deflection. Ion droplets slow down due to air resistance and may merge with subsequent ion droplets, causing a decline in print quality.

The present invention proposes a charge deflection device that solves these problems in conventional charge deflection type inkjet printing devices, and allows ink droplets to be affected by the electric field caused by the deflection electrode even when no charge signal is applied to the charge electrode. I tried not to accept it.

A charge deflection device to which the present invention is applied includes a charge electrode for charging an ink droplet in response to a signal from a charge signal generation circuit, and a pair of charge electrodes to which a high potential is applied for deflecting the charged ink droplet. In such a charge deflection device, the ink and one electrode of the deflection electrode are grounded, and the electricity between the charge electrode to which the charge signal generation circuit is connected and the ground is provided. the polarity of the high potential applied to the other electrode of the deflection electrode is low and high for the polarity of the high potential opposite to the polarity of the high potential applied to the other electrode of the deflection electrode; The polarity of the charging signal is set to be opposite to the polarity of the high potential applied to the other electrode of the deflection electrode.

The invention will now be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a charge deflection device according to the present invention.

In the figure, ink 1 is stored in an ink chamber 2a of a print head 2 and is grounded.

An ink ejecting nozzle 3 is formed at the tip of the print head 2, and a charging electrode 4 for charging ink droplets is arranged immediately in front of this nozzle 3.

A charging signal Sn is applied to the charging electrode 4 from a charging signal generating circuit 5 in the form of a negative pulse signal.

The output of the charge signal generating circuit 5 is grounded via a short-circuit prevention resistor R and a diode D.

A deflection electrode 6 is arranged further forward of the charging electrode 4, the upper electrode 6a of which is grounded, and the lower electrode 6b of which a positive voltage +Vd is applied.

7 is a recording body, and 8 is a garter. In the above configuration, it is important to place the deflection electrode 6 closer to the nozzle 3 than in conventional devices, and by doing so, the distance from when the ink droplets are charged until they are deflected and printed is longer. The above-mentioned drawbacks that occur in this case can be eliminated.

Since the charging signal is a negative polarity pulse signal, the diode D
The reverse resistance value of the diode D becomes the load impedance, but for the positive electric field of the deflection voltage, the load impedance is the sum of the forward resistance value of the diode D and the resistance R, so it is almost determined by the value of the resistance R. be done.

Now considering the case where there is no resistor R and diode D, for the equivalent capacitance C1 between the deflection electrode 6 and the charging electrode 4 and the special capacitance C2 between the charging electrode 4 and the ink column ejected from the nozzle 3, , the deflection voltage +Vd is divided into the values of these capacitors C1 and C2, and a positive potential is generated at the charging electrode 4.

As an example, when the deflection voltage Vd is 1 to 4 KV, a positive potential of IOV is generated between the charging electrode 4 and the ground (however, the distance between the charging electrode 4 and the deflection electrode 6 is 7 to 10 KV). ), this positive potential charges the ink droplet.

According to the present invention, by connecting the compensating resistor R and the diode D to the output of the charging signal generating circuit 5, the positive potential generated at the charging electrode 4' by the electric field of the deflection electrode 6 can be made zero.

According to experiments, the equivalent capacitance C2 between the charging electrode 4 and the ink column is 10-10 picofarad or more, so the value of the resistor R connected in parallel with the capacitor C2 is sufficiently small compared to the value of the capacitor C2. Preferably, it is a value.

However, the value of the resistor R should be set so as not to overload the charge signal generating circuit 5, and for example, a value of about IKΩ is sufficient.

FIG. 2 shows another embodiment of the charge deflection device according to the invention, in which the same reference numerals as in FIG. 1 indicate the same components.

In this embodiment, the charging signal applied to the charging electrode 4 by the charging signal generating circuit 5 is a positive pulse signal, and therefore the diode D connected to the output of the charging signal generating circuit 5 is shown in FIG. This is the opposite direction to the example shown.

Further, the upper electrode 6a of the deflection electrode 6 is grounded, and a negative voltage -Vd is applied to the lower electrode 6b.

Therefore, the ink droplets are charged with positive polarity.

Except for these points, its structure and operation are all the same as those of the embodiment shown in FIG. 1, so a description thereof will be omitted.

In the above two embodiments, a resistor and a diode are connected in series to the output of the charged signal generation circuit in order to zero the potential generated on the charged electrode by the electric field of the deflection electrode, and the value of the resistor H is equal to that of the charged electrode. It is preferable to choose a capacitance that is sufficiently small compared to the capacitance between the charging electrode and the ink column, but it is especially preferable if the impedance seen from the output side of the charging signal generation circuit is sufficiently small compared to the capacitance between the charging electrode and the ink column. Compensation resistance R
And the same effect can be achieved without connecting the diode D.

Therefore, when one of the ink and the deflection electrode is grounded and the polarity of the high potential applied to the other of the deflection electrodes is high, the electrical impedance between the charge electrode connected to the charge signal circuit and the ground is low and The polarity of the charging signal applied to the charging electrode is opposite to the polarity of the high potential applied to the other deflection electrode. By making it polar, the charging electrode and the deflection electrode can be placed close to each other, and the ink droplet can be prevented from being charged by the electric field of the deflection electrode.

[Brief explanation of the drawing]

FIG. 1 of the accompanying drawings is a schematic diagram of one embodiment of a charge deflection device according to the present invention, and FIG. 2 is a schematic diagram of another embodiment of the charge deflection device. 1...Ink, 2...Print head, 2
a... Ink chamber, 3... Nozzle, 4. ... Charged electrode, 5 ... Charge signal generation circuit, 6 ... Deflection electrode, 6a ... Upper electrode, 6b ... Lower electrode , 7...recording body,
8... Garter.

Claims (1)

[Claims] 1. In a charging deflection device equipped with a charging electrode for charging an ink droplet and a deflection electrode consisting of a pair of electrodes for deflecting the charged ink droplet, the ink and one electrode of the deflection electrode are grounded. , the electrical impedance between the charging electrode to which the charging signal generation circuit is connected and the main ground is low with respect to the polarity of the voltage applied to the other electrode of the deflection electrode, and with respect to the reverse polarity voltage. and the polarity of the charging signal applied to the charging electrode is opposite to the polarity of the voltage applied to the other electrode of the deflection electrode. Deflection device.