JPH04310748A - Method for driving ink jet print head - Google Patents

Abstract

PURPOSE:To avoid influence of unoperated state on ink discharging even when a certain piezoelectric element is hot operated continuously by charging all piezoelectric elements arranged to face a plurality of nozzles at a predetermined timing. CONSTITUTION:A serial print signal inputted from an input terminal 5 is converted into a parallel signal synchronizing with a clock signal from an input terminal 6 by a shift register 7 and latched by a latch 8 in response to a latch signal from an input terminal 4. Then, logic operation is performed with an enable signal from an input terminal 3 and an AND gate 9 so as to select a print timing. At the same time, a transfer gate 11 operates in accordance with the latched print signal, and a scanning voltage from an input terminal 1 is applied to a selected piezoelectric element 12 so as to operate. Here, for example, an OR gate 10 is added, all transfer gates 11 are turned on by an all-bit-on signal from an input terminal 2, and scanning voltage having high voltage is applied to all piezoelectric elements 12 for a fixed period so as to charge them.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an ink jet print head.

0002

[Prior Art] Conventional inkjet print heads are
A printing signal is applied to the piezoelectric element to cause the piezoelectric element to expand, and the dynamic pressure of the ink generated at this time causes ink droplets to fly out from the nozzle to form dots on the printing paper.

0003

Problem to be Solved by the Invention The problem to be solved by the present invention is that when the driving means cuts off the scanning voltage, the electric charge of the piezoelectric element decreases due to discharge due to the insulation resistance of the piezoelectric element, and the ink is ejected. This is a point that affects the

An object of the present invention is to solve the above problems and provide an inkjet driving method with excellent ink ejection characteristics.

[0005]

[Means for Solving the Problems] An ink jet print head driving method of the present invention includes a nozzle and a piezoelectric element disposed opposite to an opening thereof, and print liquid is ejected from the nozzle. The driving method is characterized by comprising a driving means for driving the piezoelectric element and a selection means for selecting the driving means based on a recording signal, and charging the piezoelectric element at an arbitrary timing.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a circuit diagram of a first embodiment of the present invention. 1 is a scanning voltage input terminal, 2 is an all-bit ON signal input terminal, 3 is an enable signal input terminal, 4 is a latch signal input terminal, 5 is a serial print signal input terminal, 6 is a shift register clock input terminal, 7 is a shift register input terminal 8 is a latch, 9 is an AND gate, 10 is an OR gate, 11 is a transfer gate, and 12 is a piezoelectric element.

(1) The serial print signal input from the serial signal input terminal 5 is converted into a parallel signal by the shift register 7 in synchronization with the clock signal input from the shift register clock input terminal 6.

(2) The print signal converted into a parallel signal is latched by the latch 8 when a latch signal is input from the latch signal input terminal 4.

(3) The latched print signal is connected to the enable signal input from the enable signal input terminal 3.
The D gate 9 performs a logical operation to select the printing timing.

(4) The transfer gate 11 is turned on and off according to the latched print signal, and the scanning voltage input from the scanning voltage input terminal 1 is applied only to the selected piezoelectric element 12.

(5) Piezoelectric element 12 to which a scanning voltage is applied
expands by discharging and charging in accordance with the waveform of the scanning voltage, and ejects ink.

Here, since the OR gate 10 is added, all the transfer gates are turned on by the all bit on signal inputted from the all bit on signal input terminal 2.
Then, a scanning voltage is applied to all piezoelectric elements.

At this time, as shown in the timing chart of FIG. 2, by applying all bits-on signals for a certain period with a high scanning voltage, the signal can be turned on regardless of the print signal and without affecting the drive of the piezoelectric element. The piezoelectric element 12 is charged.

The interval T [s] for giving all bits on signals is arbitrary, but the potential difference V after t [s] between both ends of the piezoelectric element
[V] is V=E0 (1-e-t/RC) E0: Potential difference between both ends of the piezoelectric element when t=0 [V]
R: Resistance of the piezoelectric element [Ω] C: Capacitance of the piezoelectric element [F] Therefore, for example, in order to reduce the potential difference between both ends of the piezoelectric element due to discharge to about 1% of E0, T= −
A rough guideline is ln(0.01)・RC.

Next, as a second embodiment, the second embodiment of the present invention will be described.
A circuit diagram of this embodiment is shown in FIG.

13 is a scanning voltage input terminal, 14 is an enable signal input terminal, 15 is a latch signal input terminal, 16 is a serial print signal input terminal, and 17 is a shift register clock input terminal.

FIG. 4 shows a timing chart of signals input to each input terminal in FIG. 3. The circuit configuration is the first
However, in this embodiment, as shown in the timing chart of FIG. 4, after the serial print signal is latched, the serial print signal with all bits on is input to the serial signal input terminal 16.

After printing with the latched print signal is completed, the latch signal is input to the latch signal input terminal 15, and the print signal with all bits on is latched.

By inputting an enable signal to the enable signal input terminal 14 during a certain period when the scanning voltage is at a high potential until the next print signal is input, all transfer gates 11 are turned on and all piezoelectric elements are turned on. Charge 12.

[0020]

[Effects of the Invention] Since all the piezoelectric elements are charged at a predetermined timing, even if a certain piezoelectric element is not driven for a long time, the decrease in charge due to discharge of the piezoelectric element is compensated for.
There is no effect on ink ejection.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of an inkjet printhead drive circuit using the present invention.

FIG. 2 is a timing chart of signals input to input terminals of the circuit in FIG. 1;

FIG. 3 is a circuit diagram of a second embodiment of an inkjet printhead drive circuit using the present invention.

FIG. 4 is a timing chart of signals input to the input terminal of the circuit of FIG. 3;

[Explanation of symbols]

1 Scanning voltage input terminal 2 All bit on signal input terminal 3 Enable signal input terminal 4 Latch signal input terminal 5 Serial print signal input terminal 6 Shift register clock input terminal 7
Shift register 8 Latch 9 AND gate 10 OR gate 11 Transfer gate 12 Piezoelectric element 13 Scan voltage input terminal 14 Enable signal input terminal 15 Latch signal input terminal 16 Serial print signal input terminal

Claims (1)

[Claims] 1. A method for driving an inkjet print head in which a plurality of nozzles and a plurality of piezoelectric elements are arranged to face openings thereof, and printing liquid is ejected from the nozzles, comprising: a drive for driving the piezoelectric elements; 1. A method for driving an ink jet print head, comprising: a selection means for selecting the driving means based on a recording signal, and charging all piezoelectric elements at an arbitrary timing.