JPH05301344A - Method and apparatus for driving ink jet head - Google Patents

Abstract

PURPOSE:To enable cost reduction and miniaturization without damaging printing quality. CONSTITUTION:Since the charge and discharge of a piezoelectric element Cp are performed through a resistor rab, the charge and discharge time constants to the piezoelectric element Cp become almost equal. A drive waveform becomes tr2-tf2 as shown by Fig (b). In this case, when the input pulse width tw2 of a circuit is made long so that the ON time of a transistor Q3 becomes sufficient long as compared with tb, Pw2 > tb can be set. Therefore, when tr1=tr2 and Vp1=Vp2 are formed, circuit constitution can be simplified as compared with conventional circuit constitution without changing an ink emitting speed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a driving method and a driving device for an inkjet head.

[0002]

2. Description of the Related Art Conventionally, as a piezoelectric element drive circuit for an ink jet head, as shown in, for example, Japanese Patent Application Laid-Open No. 51-104224, the charge time constant (rise time) and discharge time constant (fall time) of the piezoelectric element are reduced. A circuit is provided for independently setting the time) using individual resistors. In the configuration of the drive circuit, the rise time and the fall time are set independently to make the ink ejection and suction and the ink droplet formation the best state. However, in the drive circuit, since the charging resistance and the discharging resistance are separate,
When driving the multi-nozzle head, the cost is increased and it is also disadvantageous for downsizing.

8A and 8B are views showing a conventional example, FIG. 8A shows a drive circuit for a piezoelectric element, and FIG. 8B shows a drive waveform. When a print signal is input to the drive circuit of FIG. 5A, the transistor Q1 is turned on, the piezoelectric element is charged with a time constant tr1 determined by the charging resistance ra and the capacitance Cp of the piezoelectric element, and the flow path (pressurized liquid The inside of the chamber is deformed in the pressurizing direction. Ink is ejected in a column shape from the nozzle surface, but when the transistor Q1 is off and the transistor Q2 is on,
The piezoelectric element starts discharging through the discharge resistance rb and restores its original shape. The ink ejected at this time is cut off from the column at time tb. If this suction process is not performed gently compared with the discharge process during the charging period, the air bubbles will be sucked. Therefore, it was necessary to satisfy ra <rb in order to satisfy tr1 <tf1.

However, the inventors of the present invention have found that the pressure generated in the flow path due to the pulse rise (charging period) causes the natural vibration from the flow path structure (size, material, shape) and the piezoelectric element and the ink fluid system. It was thought to be a pressure wave generated by the resonance of ink. Therefore, the ink column ejected from the nozzle is naturally disconnected (Pw1> tb) if the period in which the piezoelectric element is held at the drive voltage Vp is sufficiently long. The present invention pays attention to this point, and as a result of observing the drive waveform (rise time, fall time, pulse width) applied to the piezoelectric element and the state of ink droplet ejection, there is no effect on ink droplet ejection. It was found that the rise time and pulse width of the pulse are the main factors, and the fall time does not necessarily affect the meniscus fluctuation.

[0005]

The present invention has been made in view of the above-mentioned circumstances, and enables miniaturization at low cost without impairing print quality, and eliminates fluctuations in ink ejection speed.
The purpose of the present invention is to provide a driving method and a driving device for an inkjet head that improves image quality.

[0006]

In order to achieve the above object, the present invention provides (1)
A flow path plate having a pressurized liquid chamber, which is divided into a plurality of grooves and at least a part of which is arranged by a piezoelectric element, and a common liquid chamber which is arranged adjacent to the pressurized liquid chamber. In an ink jet recording apparatus for recording by ejecting liquid droplets from a nozzle communicating with the pressurizing liquid chamber according to voltage application to the piezoelectric element, charging time (pulse rising time) to the piezoelectric element And the discharge time (pulse fall time) are substantially equal, and further, (2) a drive unit formed by a plurality of grooves and at least a part of which is formed by a piezoelectric element and a pressurized liquid chamber arranged to face the drive unit. A flow path plate having and a common liquid chamber arranged adjacent to the pressurized liquid chamber,
In an ink jet recording apparatus for recording by ejecting liquid droplets from a nozzle communicating with the pressurized liquid chamber in accordance with a voltage applied to the piezoelectric element, a crest value or a pulse width is different before the drive waveform is applied. The correction pulse is applied so that the residual pressure wave is minimized, and further, (3) in (2), the delay time Td between the correction pulse and the main pulse (pulse for ink ejection) is set to the residual pressure. It should be set to 0.5Tm <Td <1.5Tm as compared with the wave period Tm, or (4) it should be divided into a plurality of grooves and at least a part of them should be arranged opposite to the drive section and the drive section by the piezoelectric element. A nozzle having a pressurized liquid chamber and a common liquid chamber arranged adjacent to the pressurized liquid chamber, and communicating with the pressurized liquid chamber when a voltage is applied to the piezoelectric element. Discharge more droplets In an inkjet recording apparatus for recording, a drive circuit including a charging circuit and a discharging circuit for driving a piezoelectric element is provided, and a charging resistor and a discharging resistor are shared, or (5) a plurality of From a flow path plate that is divided by a groove, at least a part of which includes a drive unit by a piezoelectric element and a pressurized liquid chamber that is arranged to face the drive unit, and a common liquid chamber that is disposed adjacent to the pressurized liquid chamber. In an ink jet recording apparatus that discharges droplets from a nozzle that communicates with the pressurized liquid chamber and records with the application of a voltage to the piezoelectric element, an individual drive circuit is provided to drive the plurality of piezoelectric elements. Each of the piezoelectric elements is connected to the drive circuit via a resistor. Hereinafter, description will be given based on examples of the present invention.

1 (a) to 1 (c) are configuration diagrams for explaining an embodiment of a method of driving an inkjet head and a driving circuit according to the present invention. FIG. 1 (a) is a driving circuit for a piezoelectric element. FIG. 6B is a drive waveform, and FIG. 6C is an enlarged view of the C portion of FIG. Since the charging and discharging time constants of the piezoelectric element Cp are commonly performed via the resistor rab, they are substantially equal. The drive waveform is tr2 = tf2 as shown in FIG. In this case, if the input pulse width tw2 of the circuit is increased so that the ON time of the transistor Q3 is sufficiently longer than tb, then Pw2> tb can be satisfied.

Therefore, as compared with the conventional circuit configuration, tr1 =
If tr2 and Vp1 = Vp2, the circuit configuration can be simplified without changing the ink ejection speed.
Further, when driving the multi-nozzle head, as shown in FIG. 2, the driver section is divided into two blocks, that is, an A block (which may include a logic section such as a shift register circuit and a latch circuit) and a resistor array section in a B block. Separately, if the A block is made into a Si chip and the B block is made into a HIC,
The size and cost can be significantly reduced.

An enlarged view of the portion C of the drive waveform shown in FIG. 2B is shown in FIG. The residual pressure wave shown in FIG. 3C causes the ink ejection speed Vj to fluctuate as shown in FIG. 3A when the driving frequency f of the head becomes high, and causes a drop in dot position accuracy. The pressure waveform shown in FIG. 6C has a pressure wave Pr generated at the rising edge (tr2) and a falling edge (t2).
It is a composite wave of the pressure wave Pf generated in f2) and has the same vibration cycle T.

Therefore, if tr2 = tf2, the amplitude Pm of the residual pressure wave shown in FIG. 3C is a deviation (phase) of the superposition due to the attenuation amount of Pr determined by Pw2 and the timing of Pf (falling start time). Gap) The phase shift can be minimized by adjusting Pw2, but the pressure wave remains by the amount of Pr attenuation. Conventionally, in order to eliminate the residual pressure wave, for example, a drive circuit as disclosed in JP-A-61-3753 has been proposed. In this drive circuit, a resonance circuit is used to apply a voltage waveform having a phase opposite to that of the pressure wave, but the circuit is complicated and the cost is increased particularly in the case of a multi-nozzle head.

In the present invention, the attenuation amount of Pr is corrected,
In order to further minimize the residual pressure wave, FIG.
A correction pulse as shown in (1) is applied before ink ejection, and the magnitudes of Pr and Pf at the start time of the fall of the main pulse are made substantially equal. In FIG. 5C, the correction pulse has a peak value V so that ink is not ejected.
It is necessary to set p4 and pulse width Pw4. Further, the pulse delay time Td can be freely set so that the pressure wave remaining in the portion C is minimized. A method similar to the drive waveform of the present invention is disclosed in, for example, Japanese Examined Patent Publication No. 3-30506. This is a system that is applied before applying the additional pulse voltage and the main pulse voltage that determine the tip position of the liquid in the nozzle, and controls the ink ejection amount. However, the circuit configuration differs from the present invention in the charge time constant and the discharge time constant that determine the rise time and the fall time of the drive waveform.

In order to make two pulses having different peak values as drive waveforms as shown in FIG. 5C, the voltage source V shown in FIG. 4 is used.
The output Vpp of the p3 and Vp4 switching circuit may be connected to the power supply Vp2 of FIG. 1A or FIG. FIG. 5 (a),
4B shows the input signal S0 of the power supply switching circuit of FIG.
(A) shows the input signal S1 of the drive circuit. In addition, FIG.
As shown in (a), a pulse that is sufficiently shorter than the time constant is shown in FIG.
If input to the drive circuit of (a), the correction pulse having the peak value Vp4 can be output only with the single power supply Vp3. The pulse delay time Td is the timing of superposition of the pressure wave generated by the peak value Vp4 of the correction pulse or the pulse width Pw4 and the pressure wave Pr generated by the rise of the main pulse (pulse for ink ejection). It is a decision. Therefore, Td is 0.5Tm <Td <1.5T compared to the period Tm of the residual pressure wave (Fig. 1 (c)).
By setting m, the residual pressure wave can be efficiently eliminated. Further, the peak value Vp4 can be minimized by setting 0.8Tm <Td <1.2Tm.

When the power supply switching circuit shown in FIG. 4 is used, a highly accurate correction pulse can be output.
When the correction pulse is output with the input pulse shown in (a), the cost can be further reduced. In FIG. 4, reference numerals 21, 22, 23 and 24 are resistors, 25 is a capacitor, 26 and 27 are transistors, 28 is a diode,
9 and 30 are power supplies. As described above, if the residual pressure wave can be almost eliminated, the flat frequency characteristic of Vj as shown in FIG. 3B can be obtained, so that the image quality is improved and higher speed printing becomes possible.

When the head shown in FIGS. 7A and 7B was driven only by the main pulse (Vp3 = 35V, tr3 = tf3 = 2 μs), a residual pressure wave of Tm = 35 μs was observed. Therefore, Vp4 = 25V, tr4 = tf4 =
When the correction pulse of 2 μs was applied before the main pulse with the delay time of Td = 33 μs, the residual pressure wave could be almost eliminated. As a result, the ink ejection speed is Vj
= 10 m / s was obtained, and a characteristic with almost no change up to a driving frequency of 8 kHz was obtained.

In FIGS. 7A and 7B, FIG. 7A is a sectional view, FIG. 7B is a sectional view taken along the line AA of FIG. Piezoelectric elements, 2a are non-driving piezoelectric elements, 2b are driving piezoelectric elements, 3 is a flow path plate, 3a is a pressurized liquid chamber (ink flow path), 3b is a wall portion, 4 is a common liquid chamber constituent member, and 4a is common. Liquid chamber, 5 ink supply pipe, 6 nozzle plate, 6a nozzle, 7 drive circuit print (PCB), 8 lead wire, 9 drive electrode, 10 filler, 11 protective plate, 12 Fluid resistance, 13 and 14 are internal electrodes, and 15 is an upper partition.

In the integrated head, the internal electrode 1
The laminated piezoelectric element 2 having the pressure chambers 3 and 14 has a pressurized liquid chamber 3a.
Corresponding to (the length is L), groove processing is performed in the direction of the pressurized liquid chamber 3a to divide the groove 10, the driving piezoelectric element 2b, and the non-driving piezoelectric element 2a. A filling material is enclosed in the groove 10. The upper partition wall 15 is attached to the piezoelectric element 2 that has been grooved.
The flow path plate 3 is joined via. That is, the upper partition wall 15 is supported by the non-driving piezoelectric element 2a and the wall portion 3b that separates the adjacent flow path. A nozzle plate 6 having a nozzle 6a is fixed to the tip of the pressurized liquid chamber 3a. The width of the drive piezoelectric element 2a is slightly narrower than the width of the pressurized liquid chamber 3a, and the drive piezoelectric element 2b selected by the drive circuit on the drive circuit printed board (PCB) may be, for example, the pressurized liquid chamber 3a.
After displacing in such a direction that the volume of
A droplet signal is ejected from the nozzle 6a corresponding to the pressurized liquid chamber 3a by applying a pulse signal that gives a displacement that reduces the volume of a. The ejected droplet prints one pixel on a recording medium (not shown).

[0017]

[Effect] As is apparent from the above description, the present invention has the following effects. (1) Since the rise time and the fall time of the pulse are almost equal, the structure of the drive circuit can be simplified. (2) Since the charging resistor and the discharging resistor are common, the number of elements of the driving circuit can be reduced, and the cost and the size can be reduced. (3) Since the residual pressure wave can be minimized by applying the correction pulse, fluctuations in the ink ejection speed are reduced, image quality is improved, and high-speed printing is possible. (4) Since the correction pulse can be applied more efficiently, the residual pressure wave can be almost eliminated. (5) Since the piezoelectric element is connected to the drive circuit via the resistor, when mounting the drive circuit of the multi-nozzle head, it is easy to form a chip.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an inkjet head driving method and a driving circuit according to the present invention.

FIG. 2 is a diagram showing a driving circuit according to the present invention.

FIG. 3 is a diagram showing a relationship between a drive frequency of a head and an ink ejection speed according to the present invention.

FIG. 4 is a diagram showing a power supply switching circuit according to the present invention.

FIG. 5 is a diagram showing drive waveforms in FIG. 4.

FIG. 6 is a diagram showing another drive waveform according to the present invention.

FIG. 7 is a diagram showing an inkjet head recording apparatus according to the present invention.

FIG. 8 is a diagram showing a driving method and a driving circuit of a conventional inkjet head.

[Explanation of symbols]

1 ... Substrate, 2 ... Piezoelectric element, 2a ... Non-driving piezoelectric element, 2b
Drive piezoelectric element, 3 flow channel plate, 3a pressurized liquid chamber (ink flow channel), 3b wall portion, 4 common liquid chamber constituent member, 4a common liquid chamber, 5 ink supply pipe, 6 Nozzle plate,
6a ... Nozzle, 7 ... Driving circuit print (PCB), 8
... Lead wire, 9 ... Drive electrode, 10 ... Filler, 11 ... Protective plate, 12 ... Fluid resistance, 13, 14 ... Internal electrode, 15 ... Upper partition wall.

Claims (5)

[Claims] 1. A flow path plate having a pressurized liquid chamber which is divided into a plurality of grooves and at least a part of which is arranged by a piezoelectric element and which is arranged so as to face the driven portion, and which is arranged adjacent to the pressurized liquid chamber. In the ink jet recording apparatus which is composed of a common liquid chamber and which discharges liquid droplets from a nozzle communicating with the pressurized liquid chamber with application of a voltage to the piezoelectric element, and a charging time for the piezoelectric element. A method for driving an inkjet head, which is characterized in that discharge time is substantially equal. 2. A flow path plate having a pressurized liquid chamber which is divided into a plurality of grooves and at least a part of which is disposed by a piezoelectric element and which is opposed to the driven portion; and a flow passage plate which is disposed adjacent to the pressurized liquid chamber. In the ink jet recording apparatus, which comprises a common liquid chamber and which discharges liquid droplets from a nozzle communicating with the pressurized liquid chamber in accordance with the voltage application to the piezoelectric element, before the drive waveform is applied. The method for driving an inkjet head according to claim 1, wherein a correction pulse having a different crest value or a different pulse width is applied so as to minimize the residual pressure wave. 3. The inkjet according to claim 2, wherein a delay time Td between the correction pulse and the main pulse is set to 0.5Tm <Td <1.5Tm as compared with the period Tm of the residual pressure wave. Head drive method. 4. A flow path plate, which is divided into a plurality of grooves and at least a part of which is provided with a driving portion by a piezoelectric element and a pressurized liquid chamber arranged to face the driving portion, and arranged adjacent to the pressurized liquid chamber. And a common liquid chamber configured to drive the piezoelectric element in an ink jet recording apparatus that discharges liquid droplets from a nozzle communicating with the pressurized liquid chamber and records the liquid when a voltage is applied to the piezoelectric element. An ink jet head drive device having a drive circuit composed of a charging circuit and a discharging circuit, wherein a charging resistor and a discharging resistor are common. 5. A flow channel plate having a pressurized liquid chamber, which is divided into a plurality of grooves and at least a part of which is arranged by a piezoelectric element and is arranged to face the driven portion, and arranged adjacent to the pressurized liquid chamber. A plurality of piezoelectric elements in an ink jet recording apparatus configured to discharge and record liquid droplets from a nozzle communicating with the pressurized liquid chamber when a voltage is applied to the piezoelectric element. In order to achieve this, there is provided a separate drive circuit, and each of the piezoelectric elements is connected to the drive circuit via a resistor.