JPH0929961A - Driving method of ink jet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To present the low cost driving method of an ink jet device, in which the change of ink jetting speed in terms of driving frequency is small and the printing quality of which is favorable. SOLUTION: Driving waveform 10 consists of first pulse signal A for jetting ink and second pulse signal B for compensating the change in the residual pressure in an ink flow passage after jetting. Both the first pulse signal A and the second pulse signal B have a crest value (value in volt) of V. The width Wb of the second pulse signal B is 0.5 times as much as the one-way propagation time T of pressure wave in ink flow passage. The lag time Td between the leading edge timing To of the first pulse signal A and the middle timing Tm between the leading edge timing Ts and the trailing edge timing Te of the second pulse signal B is 3.5 times as much as the one-way propagation time T of pressure wave in ink flow passage.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art The non-impact type printing apparatus which has been replacing the conventional impact type printing apparatus and is now expanding its market greatly is the simplest in principle and has a multi-gradation and color printing. An easy-to-use printing apparatus is an ink jet printing apparatus. Above all, a drop that ejects only the ink drops used for printing
The on-demand type is rapidly spreading due to its good injection efficiency and low running cost.

The Kaiser type disclosed in Japanese Patent Publication No. 53-12138 as a drop-on-demand type,
Alternatively, a thermal jet type disclosed in Japanese Patent Publication No. 61-59914 is a typical method.
Of these, the former is difficult to miniaturize, and the latter requires a high heat resistance of the ink in order to apply high heat to the ink, and each has a very difficult problem.

A method proposed to solve the above defects at the same time is disclosed in Japanese Patent Laid-Open No. 63-247051.
It is a shear mode type using the piezoelectric ceramic disclosed in Japanese Patent Publication No.

As shown in FIG. 6, the shear mode type ink jet device 600 comprises a bottom wall 601, a ceiling wall 602 and a shear mode actuator wall 603 therebetween. The actuator wall 603 is bonded to the bottom wall 601 and is polarized in the direction of arrow 611.
And an upper wall 605 bonded to the ceiling wall 602 and polarized in the direction of arrow 609. The actuator walls 603 are paired to form an ink flow path 613 therebetween, and a space 615 narrower than the ink flow path 613 is formed between the next pair of actuator walls 603.

The nozzle 6 is provided at one end of each ink flow path 613.
A nozzle plate 617 having 18 is fixed, and electrodes 619 and 621 are provided as metallized layers on both side surfaces of each actuator wall 603. Each electrode 619, 621
Is covered with an insulating layer (not shown) for insulating the ink. The electrode 621 facing the space 615 is connected to the ground 623, and the electrode 619 provided in the ink flow path 613 is connected to the silicon chip 625 which provides the actuator drive circuit.

Next, a method for manufacturing the ink jet device 600 will be described. First, the piezoelectric ceramic layer polarized in the arrow 611 is bonded to the bottom wall 601, and the piezoelectric ceramic layer polarized in the arrow 609 is bonded to the ceiling wall 602. The thickness of each piezoelectric ceramic layer is as follows.
Equal to 5 height. Next, parallel grooves are formed in the piezoelectric ceramic layer by a diamond cutting disk or the like to form a lower wall 607 and an upper wall 605. And
The electrodes 619, 6 are formed on the sides of the lower wall 607 by vacuum deposition.
21 is formed, and the insulating layer is provided on the electrodes 619 and 621. Similarly, the electrode 61 is attached to the side surface of the upper wall 605.
9, 621, the insulating layer is provided.

The zenith of the upper wall 605 and the zenith of the lower wall 607 are adhered to each other to form an ink flow path 613 and a space 615. Next, a nozzle plate 617 on which the nozzles 618 are formed is adhered to one end of the ink flow passage 613 and the space 615 so that the nozzles 618 correspond to the ink flow passages 613, and the ink flow passages 613 and the space 615 are connected. The other end is connected to silicon chip 625 and ground 623.

Then, the electrode 619 of each ink flow path 613
When the silicon chip 625 applies a voltage to the actuator, each actuator wall 603 undergoes piezoelectric thickness slip deformation in the direction of increasing the volume of the ink flow path 613. For example, as shown in FIG. 7, when a voltage V is applied to the ink flow path 613c, electric fields in the directions of arrows 627 and 629 are generated in the actuator walls 603e and 603f, and the actuator walls 603d and 603e cause the volume of the ink flow path 613c to change. The piezoelectric thickness undergoes slip deformation in the direction of increasing. At this time, the pressure in the ink flow path 613c including the vicinity of the nozzle 618c decreases. This state is maintained for the time T during which the pressure wave propagates in the ink flow path 613 one way. Then, ink is supplied from a manifold (not shown) during that time. The one-way propagation time T is the time required for the pressure wave in the ink flow path 613 to propagate in the longitudinal direction of the ink flow path 613, and the length L of the ink flow path 613 and this ink flow path 613.
T = L / a is determined by the sound velocity a in the ink inside. According to the theory of pressure wave propagation, the pressure in the ink flow path 613 reverses and changes to a positive pressure just after a lapse of time T from the application of the voltage described above, but the electrode 619c of the ink flow path 613c coincides with this timing. The voltage applied to is reset to zero.

Then, the actuator walls 603e, 60
3f returns to the state before deformation (FIG. 6), and pressure is applied to the ink. At that time, the positive pressure and the pressure generated by the actuator walls 603e and 603f returning to the state before the deformation are added, and a relatively high pressure is generated in a portion of the ink flow path 613c near the nozzle 618c. Ink is ejected from the nozzle 618c.

After the ink is ejected, if the ink flow path 6
Unless a new voltage pulse is applied to the electrodes 619e and 619f of 13c, the pressure in the ink flow path 613c is 2
It keeps changing for a while with T as a cycle. This is the residual pressure fluctuation. Due to this residual pressure fluctuation, when the frequency of the voltage pulse is changed, the ink ejection speed fluctuates, and the landing position shifts, which impairs print quality and makes ejection impossible.

On the other hand, for example, JP-A-62-2993
As disclosed in Japanese Laid-Open Patent Publication No. 43-43, it is considered to reduce the residual pressure fluctuation in the ink flow path 613 by applying a cancel pulse after the print pulse for ejecting ink. That is, a cancel pulse for generating a pressure wave having a phase opposite to the residual pressure fluctuation in the ink flow path 613 is applied after a fixed time from the ink ejection. As shown in FIG. 8, the ink flow path 6
A cancel pulse D having a width T and a phase opposite to that of the ejection pulse is applied to the 13 electrode 619 after T from the trailing edge of the ejection pulse C. The voltage value is set according to the amplitude of the residual pressure fluctuation so that the fluctuation is just canceled (for example, 0.6 times the injection pulse). By applying this cancel pulse, the actuator wall 603 is deformed in the opposite manner to that at the time of ink ejection, and a pressure wave having a phase opposite to the residual pressure fluctuation is applied to cancel the residual pressure fluctuation. As a result, fluctuations in the ink ejection speed when the frequency of the voltage pulse is changed are eliminated, and printing quality is improved.

Next, a drive circuit for realizing the cancellation of the residual pressure fluctuation will be described. The output signals X, Y, and Z shown in FIG.
Is a signal for setting the voltage to be applied to V, 0, −0.6 × V. When the output signal X is turned on, a voltage pulse (C in FIG. 8) for ejecting ink is generated. Also,
When the output signal Z is turned on, a voltage pulse (D in FIG. 8) for causing a pressure fluctuation for cancellation is generated.
In other cases than the above, the output signal Y is turned on and the output voltage is set to zero. The capacitor 91 includes the actuator wall 603 of the ink flow path 613 and the electrodes 6 formed on both sides thereof.
15, 619.

The drive circuit is composed of three blocks surrounded by a broken line, and each of them is an injection charging circuit 82, a discharging circuit 84 and a canceling pressure generating circuit 86.
When the input signal X turns on, the transistor Tc
Becomes conductive, and a voltage of V is applied from the positive power source 87 to the electrode E of the capacitor 91 via the resistor R12. Input signal Y
Is turned on, the transistor Tg is turned on, and the resistor R1
The electrode E of the condenser 91 is grounded via 2. When the input signal Z is turned on, the transistor Ts becomes conductive, and the negative power source 88 applies a voltage of −0.6 × V to the electrode E of the capacitor 91 via the resistor R12.

Further, as shown in FIG. 10, the width T is the same as the phase of the injection pulse C 2T after the trailing edge of the injection pulse C, and the voltage value corresponding to the amplitude of the residual pressure fluctuation (for example, 0.5 of the injection pulse). It is also possible to cancel the residual pressure fluctuation by applying a cancellation pulse E of (2 times). The drive circuit in this case does not require the negative power source 88 as shown in FIG. 9, but the voltage V × 0.
Prepare a second positive power source (not shown) that generates 5
It may be used while switching to the positive power source 87.

[0016]

However, in the method of driving the ink ejecting apparatus having the above-described structure, the pressure wave is applied to the ink flow path 61 after the ejection pulse C having the positive voltage V is applied.
After propagating in 3 and making one round trip, or one and a half round trips,
In order to cancel the residual pressure fluctuation, a cancel pulse D having a negative voltage or a cancel pulse E having a positive voltage but a different voltage value must be given. Therefore, a positive power source and a negative power source, or two types of positive power sources having different voltages are required, which complicates the driving circuit and raises the cost.

An object of the present invention is to provide a low-cost method for driving an ink ejecting apparatus, which can suppress fluctuations in ink ejecting speed and obtain good print quality.

[0018]

In order to achieve this object, according to a first aspect of the present invention, an ink chamber filled with ink, an actuator for changing the volume of the ink chamber, and an electric actuator for the actuator are provided. By applying a single drive power supply for applying a signal, and applying a first pulse signal from the single drive power supply to the actuator,
The volume of the ink chamber is increased to generate a pressure wave in the ink chamber, and after a lapse of time T during which the pressure wave propagates in the ink chamber one way, the volume is decreased from the increased state to the natural state to form ink in the ink chamber. A method of driving an ink ejecting apparatus, comprising: a control unit that applies pressure to eject ink droplets, wherein the crest value is the same as that of the first pulse signal, and the pulse width is the same as that of the first pulse signal. With respect to the different second pulse signal, the control means causes the center timing Tm of the rising timing Ts of the second pulse signal and the falling timing Te of the second pulse signal to be 3 from the rising point of the first pulse signal. Ink ejection, wherein the single drive power supply is applied to the actuator so as to be within a range of more than .20T and less than 3.75T. The driving method of location.

In a second aspect of the present invention, the pulse width of the second pulse signal is 0.5T or 1.5T.

In the third aspect, the center timing Tm between the rising timing Ts of the second pulse signal and the falling timing Te of the second pulse signal is 3.3T from the rising time of the first pulse signal. Above 3.
The second pulse signal in the range of 6T or less is applied to the actuator.

According to a fourth aspect of the present invention, the actuator is at least one wall portion forming the ink chamber, and at least a part of the wall portion is formed of a piezoelectric material.

[0022]

In the method for driving the ink ejecting apparatus according to the present invention having the above configuration, when the control unit applies the first pulse signal from the single drive power source to the actuator, first the first pulse signal is applied. At the rising edge of the pulse signal, the volume of the ink chamber is increased and a pressure wave is generated in the ink chamber. After the time T during which the pressure wave propagates one way in the ink chamber has elapsed, the first pulse signal is lowered, and when the volume in the ink chamber is decreased from the increased state to the natural state, pressure is applied to the ink in the ink chamber and Droplets are jetted. The center timing Tm between the rising timing Ts of the second pulse signal and the falling timing Te of the second pulse signal is greater than 3.20T from the rising time of the first pulse signal, 3.7.
By applying the second pulse signal from the single drive power source to the actuator so that the second pulse signal is within the range smaller than 5T, the injection speed with respect to the drive frequency becomes substantially constant.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

The ink ejecting apparatus 600 of this embodiment is shown in FIG.
Like the conventional ink ejecting apparatus 600 shown in FIG.
1, a top wall 602 and a shear mode actuator wall 603 therebetween. The actuator wall 603 is
A lower wall 607 bonded to the bottom wall 601 and polarized in the direction of arrow 611, and a top wall 602, and the arrow 6
The upper wall 605 is polarized in the 09 direction. A pair of actuator walls 603 form an ink flow path 613 therebetween, and a space 61 narrower than the ink flow path 613 is formed between the next pair of actuator walls 603.
5 are formed.

The nozzle 6 is provided at one end of each ink flow path 613.
A nozzle plate 617 having 18 is fixed, and electrodes 619 and 621 are provided as metallized layers on both side surfaces of each actuator wall 603. Each electrode 619, 621
Is covered with an insulating layer (not shown) for insulating the ink. The electrode 621 facing the space 615 is connected to the ground 623, and the electrode 619 provided in the ink flow path 613 is connected to the silicon chip 625 which provides the actuator drive circuit.

An example of specific dimensions of the ink ejecting apparatus will be described. The length L of the ink flow path 613 is 7.5 mm. The nozzle 618 has a diameter of 40 μm on the ink ejection side.
m, the diameter of the ink flow path 613 side is 72 μm, and the length is 100
μm. The ink used in the experiment has a viscosity of 2 m.
Pa · s and surface tension are 30 mN / m. The ratio L / a (= one-way propagation time T of pressure wave) between the sound velocity a in the ink in the ink flow path 613 and the length L of the ink flow path 613 is 8 μsec.

Next, the drive waveform 10 applied to the electrode 619 in the ink flow path 613 of this embodiment is shown in FIG. The drive waveform 10 is the first pulse signal A for ejecting ink.
And a second pulse signal B for compensating the residual pressure fluctuation in the ink flow path 613 after ejection, both the first pulse signal A and the second pulse signal B have a peak value (voltage value). ) Is V (for example, 20v). First pulse signal A
Has a width Wa that corresponds to the one-way propagation time T (L / a) of the pressure wave in the ink flow path 613, that is, 8 μsec.
The width Wb of the second pulse signal B is 0.5 times the one-way propagation time T of the pressure wave in the ink flow path 613, that is, 4 μsec.
It is. The rising timing T of the second pulse signal B
Intermediate timing Tm between s and falling timing Te
Has passed the time Td from the rising timing T0 of the first pulse signal A. The time Td is 3.5 times the one-way propagation time T of the pressure wave in the ink flow path 613, that is, 28 μsec.

An embodiment of a drive circuit for realizing the drive waveform 10 will be described with reference to FIGS. The output signals X and Y shown in FIG. 2 are signals for setting the voltage applied to the electrode 619 in the ink flow path 613 to V and 0, respectively.
When the output signal X turns on, the voltage V is generated, and when the output signal Y turns on, the voltage becomes 0. The capacitor 191 includes an actuator wall 603 of the ink flow path 613 and electrodes 619 and 621 formed on both sides of the actuator wall 603.

The drive circuit is composed of two blocks surrounded by a broken line, and each is a charging circuit 182 for injection and a circuit 184 for discharging. Then, when the input signal X is turned on, the transistor Tc becomes conductive, and a voltage of V, for example, 20v is applied from the positive power source 187 to the electrode E of the capacitor 191 through the resistor R120. When the input signal Y is turned on, the transistor Tg becomes conductive, and the voltage E of the capacitor 191 is grounded via the resistor R120.

The timing charts 11 and 12 of the input signals X and Y and the output voltage waveform 13 of the electrode E are shown in FIG. As shown in the timing chart 11 of the input signal X,
The input signal X is normally off, turned on at a predetermined timing T1, and turned off at a timing T2. Thereafter, it is turned on at timing T3 and turned off at timing T4. Timing chart of input signal Y 12
Is turned off when the input signal X is on, and turned on when the input signal X is off.

The output waveform 13 at the electrode E at that time is normally 0 v, but at the timing T1, the capacitor 191
To the voltage V after the charging time Ta determined by the transistor Tc, the resistor R12 and the capacitor 191 is charged.
(For example, 20v), the charge of the capacitor 191 is discharged at timing T2, and becomes 0v after a discharge time Tb determined by the transistor Tg, the resistor R12, and the capacitor 191. Subsequently, at timing T3, the capacitor 1
The electric charge to 91 is charged, and the transistor Tc and the resistor R1
2 and the voltage V (for example, 20 v) after the charging time Ta determined by the capacitor 191 and the charge of the capacitor 191 is discharged at timing T4, and the discharge time Tb determined by the transistor Tg, the resistor R12, and the capacitor 191.
It will be 0v later. Thus, the actual drive waveform 13 is delayed by Ta and Tb at the rising edge and the falling edge, respectively.
Of the second pulse signal B and the width Wa of the second pulse signal A
b, and an intermediate timing Tm between the rising timing Ts and the falling timing Te of the second pulse signal B
The respective timings T1, T2, T3, T4 are set so that the delay time Td from the rising timing T0 of the first pulse signal A becomes the value shown in FIG.

An ink jet test was carried out when the device was driven by the driving method of this embodiment described above. The drive voltage was 20 V, which is an extremely slow drive frequency, for example, when the ink ejection speed was 5 m / s at 60 Hz. When the drive frequency was changed from 5 kHz to 15 kHz, stable ink ejection was possible when the ink ejection speed was between 4.5 and 5.3 m / s. As a comparative experiment, when driven only by the first pulse signal A having the drive waveform of this embodiment, the ink ejection speed is 5 to 7 m.
/ S and the driving frequency was 9 kHz or higher, the injection became impossible. The result is shown in FIG. From this result, it is understood that the driving method of the present embodiment suppresses the fluctuation of the ink ejection speed when the frequency of the voltage pulse is changed. Further, in the method of driving the ink ejecting apparatus of this embodiment,
A positive voltage V is applied as the first pulse signal A to the electrode 619 of the ink flow path 613, and as the second pulse signal B,
Since the same positive voltage V as that of the first pulse signal A is applied, only the positive power supply 87 is required as the driving power supply, and the positive power supply and the negative power supply, or two kinds of positive power supplies having different voltages as in the conventional case. The control circuit becomes simpler and the cost can be reduced as compared with the case of using the power source.

Next, the width Wb of the second pulse signal B
Delay time Td from the rising timing T0 of the pulse signal A to the intermediate timing Tm of the second pulse signal B
The result of the experiment conducted to obtain the appropriate range of

FIG. 5 shows the width Wb of the second pulse signal B and
The delay time Td from the rising timing T0 of the first pulse signal A to the intermediate timing Tm of the second pulse signal B is 0.3T to 2.0T, 3.1T to 3.T, respectively.
The evaluation results when changed to 9T are shown. As an evaluation method, the drive frequency was changed from 5 kHz to 15 kHz and the change in the ink ejection speed was examined. When the driving voltage is very slow, for example 60Hz, the ink ejection speed is 5m.
It was driven at 20v which is / s.

The double circle evaluated here has a speed fluctuation of 1 m.
/ S is less than 1.0, and the speed fluctuation of the circle is 1.0 or more and 2.0 m /
Less than s, triangle has speed fluctuation of 2.0 or more and less than 3 m / s, ×
Indicates that injection is impossible at a certain frequency. From this result, the delay time Td is larger than 3.20T and 3.7.
In a range smaller than 5T, the width Wb of the second pulse signal B
Is 0.3T to 1.7T (except for 1.0T, since ink ejection occurs due to the second pulse signal B), the speed fluctuation fluctuation becomes 2 (m / s) or less. Further, when the delay time Td is in the range of 3.3T or more and 3.6T or less and the width Wb of the second pulse signal B is 0.5T or 1.5T, the speed variation is smaller and the print quality is better. Ink jetting can occur.

Although one embodiment has been described in detail above, the present invention is not limited to this embodiment. For example, in the above embodiment, the positive power source 87 was used, but the polarization direction is
609 and 611 may be reversed and a negative power source may be used. With respect to other configurations, the present invention can be implemented in variously modified and improved modes based on the knowledge of those skilled in the art without departing from the scope of the claims.

In this embodiment, the actuator wall 60 is used.
Although the volume of the ink flow path 613 was deformed by the piezoelectric deformation of the lower wall 607 and the upper wall 605 of No. 3 to eject ink, one of the lower wall and the upper wall is formed of a material that does not cause piezoelectric deformation, and the other piezoelectric The ink may be ejected so that the ink is deformed along with the deformation.

Further, in this embodiment, the air chambers 615 are provided on both sides of the ink flow passage 613, but the ink flow passages may be adjacent to each other without providing the air chambers.

[0039]

As described above, according to the method for driving the ink ejecting apparatus of the present invention, the second pulse having the same crest value as that of the first pulse signal for ejecting ink but different pulse width is used. The center timing Tm between the rising timing Ts of the signal and the falling timing Te of the second pulse signal is within the range of more than 3.20T and less than 3.75T from the rising time of the first pulse signal. Since the control unit applies the second pulse signal to the actuator, it is possible to reduce the fluctuation of the ink ejection speed due to the drive frequency. Further, since it can be driven by a single driving power source, the driving circuit becomes simpler than in the past and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing drive waveforms of an ink ejecting apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a drive circuit of the ink ejecting apparatus.

FIG. 3 is a timing chart of a driving method of the ink ejecting apparatus.

FIG. 4 is a diagram showing a result of an experiment in which a frequency of a driving method of the ink ejecting apparatus is changed.

FIG. 5 is a diagram showing a result of an experiment in which the width and application timing of the second pulse signal in the method of the ink ejecting apparatus are changed.

FIG. 6 is a diagram showing a conventional example and an ink ejecting apparatus according to the invention.

FIG. 7 is a diagram illustrating an operation of a conventional example and an ink ejecting apparatus according to the present invention.

FIG. 8 is a diagram showing a driving method of a conventional example.

FIG. 9 is a diagram showing a conventional drive circuit.

FIG. 10 is a diagram showing another example of the driving method of the conventional example.

[Explanation of symbols]

 10 Drive Waveform 600 Ink Ejecting Device 603 Actuator Wall 613 Ink Flow Path 619 Electrode 621 Electrode

Claims (4)

[Claims] 1. An ink chamber filled with ink, an actuator for changing the volume of the ink chamber, a single driving power source for applying an electric signal to the actuator, and the single actuator for the actuator. By applying the first pulse signal from the driving power source, the volume of the ink chamber is increased to generate a pressure wave in the ink chamber, and after the time T during which the pressure wave propagates in the ink chamber one way, the increasing state From the first pulse signal and the peak value, the control method is to reduce the volume to a natural state and apply pressure to the ink in the ink chamber to eject ink droplets. The control means outputs a second pulse signal that is the same and has a pulse width different from that of the first pulse signal to the rising timing Ts of the second pulse signal and the second pulse signal. Central timing Tm is greater than 3.20T from the rising point of the first pulse signal 3.75 of the falling timing Te of the pulse signal
A method for driving an ink ejecting apparatus, wherein the actuator is applied from the single drive power source so that the voltage is within a range smaller than T. 2. The pulse width of the second pulse signal is:
The method of driving an ink ejecting apparatus according to claim 1, wherein the driving method is 0.5T or 1.5T. 3. The center timing Tm between the rising timing Ts of the second pulse signal and the falling timing Te of the second pulse signal is 3.3T or more from the rising time of the first pulse signal. The method of driving an ink ejecting apparatus according to claim 1 or 2, wherein the second pulse signal within a range of 6T or less is applied to the actuator. 4. The actuator is at least one wall portion forming the ink chamber, and at least a part of the wall portion is formed of a piezoelectric material. 7. A method for driving an ink ejecting apparatus according to item 4.