JP2003118100A - Liquid ejection recorder and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the recording time while enhancing stability in the flight of recording liquid by detecting variation in the liquid level or the viscosity of recording liquid easily under actual driving state where recording liquid drop generating operation is in progress thereby grasping the situation of a sound source accurately. SOLUTION: An acoustic lens 6 is disposed on the bottom part of an ink containing section 2 and a piezoelectric element 5 is disposed on the lower surface of the acoustic lens 6. The piezoelectric element 5 is applied with a high frequency driving voltage from a drive circuit 7 to generate an ultrasonic wave from the acoustic lens 6 and then the ultrasonic wave is converged to the liquid level of ink. A current flowing through the piezoelectric element 5 is detected by an impedance detecting circuit 10 and an impedance detection signal is delivered to an ultrasonic energy decision circuit 20. Variation in the liquid level and the viscosity of ink is then detected based on the variation in the impedance detection signal from a reference voltage and a drive control circuit 40 controls the frequency or amplitude of the high frequency driving voltage from the drive circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet jet recording apparatus in which ultrasonic waves generated by a piezoelectric element are converged on the surface of a recording liquid and droplets are ejected from the surface of the recording liquid toward a recording medium. And its driving method.

[0002]

2. Description of the Related Art As a droplet jet recording apparatus of this type, one described in, for example, JP-A-6-17657 is known. In this conventional example, a plurality of ultrasonic transducers are provided, and the ultrasonic waves whose phases are controlled are transmitted from the plurality of ultrasonic transducers to form one converged ultrasonic wave. There is described an ultrasonic printer in which the ink is ejected and adhered to a recording medium such as paper to perform recording with a large number of dots on the recording medium.

[0003]

However, in the above-mentioned conventional example, the focus of the ultrasonic waves propagating through the ink from the acoustic lens is changed to the ink liquid surface in order to fly the ink droplets by using the converged ultrasonic waves. Therefore, unless the positional relationship between the acoustic lens and the ink liquid surface is accurately maintained at an odd multiple of 1/4 wavelength of the ultrasonic wave, a high sound pressure cannot be obtained on the ink liquid surface and the proper ink There is an unsolved problem that droplets cannot be generated.

Factors that impede the positional relationship due to the ultrasonic wavelength are mainly a change in the height of the ink surface, a change in the ink sound velocity due to a change in ink viscosity or temperature, or a change in the excitation frequency. In order to detect changes in these factors, in addition to the sensor that detects the height of the ink surface and the drive circuit of the ultrasonic transducer, a receiving circuit that receives ultrasonic waves is installed to measure the reflected pressure, Methods such as measuring surface height, sound velocity, and viscosity are used.

However, in the case of detecting changes in various obstructive factors with a sensor, it is necessary to provide a separate sensor, which increases the manufacturing cost, and a sensor must be provided for each obstructive factor, resulting in a complicated structure. There is an unsolved problem of becoming. In addition, in the transmission / reception measurement method using the ultrasonic transducer itself, it is necessary to settle the ink surface during the measurement, and the ink droplet generation operation cannot be performed during this time, and the driving time In addition, there is an unsolved problem that the time for measuring is required, and the ink ejection time is delayed by that much, which leads to a decrease in printing speed.

As described above, in the conventional example, it is difficult to detect in real time the state of actual driving in which the ink droplet generation operation is performed, and the state of the sound source is grasped by a realistic method to stabilize the ink ejection. Is desired to be improved. Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and in the actual driving state in which the recording droplet generation operation is performed, the above-mentioned inhibition factors are easily detected,
An object of the present invention is to provide a droplet jet recording apparatus and a driving method thereof, which can accurately grasp the situation of a sound source and improve the stability of flight of the recording liquid while shortening the recording time.

[0007]

In order to achieve the above object, in the liquid droplet jet recording apparatus according to the first aspect, an acoustic lens disposed on the upper surface of the piezoelectric element is disposed in the recording liquid storage portion,
A liquid droplet jet recording apparatus in which ultrasonic waves generated from the acoustic lens are converged on the surface of the recording liquid in the recording liquid container to fly the recording liquid droplets by driving the piezoelectric element at a high frequency by a high frequency driving means. In the impedance detection means for detecting the impedance of the drive system for driving the piezoelectric element by the high frequency drive means, and whether the ultrasonic energy is proper based on the impedance detection signal detected by the impedance detection means. It is characterized by comprising ultrasonic energy judging means for judging, and drive control means for driving and controlling the high frequency driving means based on the judgment result of the ultrasonic energy judging means.

According to a second aspect of the present invention, there is provided the droplet jet recording apparatus according to the first aspect, wherein the impedance detecting means is a drive current detecting means for detecting a drive current of the piezoelectric element, and the drive current detecting means. Has a current waveform processing means for converting the drive current detected by 1. into a DC voltage change, and a comparison means for comparing the output voltage of the current waveform processing means with a reference voltage, and the impedance detection signal is output from the comparison means. It is characterized by that.

Further, in the liquid droplet jetting recording apparatus according to a third aspect of the present invention, in the invention according to the first or second aspect, the ultrasonic energy judging means detects the impedance from the driving start to the impedance change point. The impedance change time is measured, and the positional relationship between the liquid surface of the driving focal length and the sound pressure is proper based on the impedance change time,
It is characterized in that it is configured to judge whether or not the ultrasonic energy is properly accumulated / amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens.

Furthermore, in the liquid droplet jet recording apparatus according to a fourth aspect of the present invention, in the invention according to the third aspect, the drive control means determines that the ultrasonic energy determination means determines that the impedance change time is shorter than the optimum time. Further, it is characterized in that the frequency of the high frequency drive signal of the high frequency drive means is lowered, and when the time is longer than the optimum time, the frequency of the high frequency drive signal of the high frequency drive means is increased.

Furthermore, in the liquid droplet jet recording apparatus according to a fifth aspect of the present invention, in the invention according to the first or second aspect, the ultrasonic energy determining means changes from the impedance change point to the next change based on the impedance detection signal. The amplitude time to the point is measured, and whether the viscosity of the recording liquid is appropriate and whether the ultrasonic energy is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens It is characterized in that it is configured to judge.

According to a sixth aspect of the present invention, there is provided the liquid drop jet recording apparatus according to the fifth aspect, wherein the drive control means produces a high frequency when the determination result of the ultrasonic energy determination means is shorter than the optimum amplitude time. It is characterized in that the driving voltage of the driving means is increased, and the driving voltage of the high frequency driving means is lowered when the driving time is longer than the optimum time.

Further, in the liquid droplet jet recording apparatus according to a seventh aspect of the present invention, in the invention according to the first or second aspect, the ultrasonic energy determining means detects the impedance from the drive start to the impedance change point. The impedance change time is measured, and the positional relationship between the liquid surface of the driving focal length and the sound pressure is proper based on the impedance change time,
The first judging means for judging whether or not the ultrasonic energy is appropriately accumulated / amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens, and the following from the point of change of impedance: Measure the amplitude time to the change point, and confirm that the viscosity of the recording liquid is appropriate and that the ultrasonic energy is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. The drive control means lowers the frequency of the high frequency drive signal of the high frequency drive means when the result of the determination by the first determination means is shorter than the optimum time. However, the first drive control means for controlling the frequency of the high frequency drive signal of the high frequency drive means to be increased when the time is longer than the optimum time, and the determination result of the second determination means is that the amplitude time is shorter than the optimum amplitude time. High frequency drive voltage of the drive means to increase the is characterized in that it comprises a second drive control means for performing control to lower the driving voltage of the high frequency drive unit is longer than the optimum time when.

Furthermore, in the liquid droplet jet recording apparatus according to an eighth aspect of the present invention, in the invention according to the first or second aspect, the ultrasonic energy determining means selects the first determining means and the second determining means. Selecting means for selecting the second judging means after the result of the judgment by the first judging means converges to the first allowable range, and the judgment by the second judging means. It is characterized in that the selection of the first judging means is repeated after the result converges to the second allowable range.

Further, according to a ninth aspect of the present invention, there is provided a method for driving a droplet jet recording apparatus, wherein an acoustic lens disposed on the upper surface of a piezoelectric element is disposed in a recording liquid storage section and the piezoelectric element is driven by a high frequency drive means to a high frequency. A driving method of a droplet jet recording apparatus, wherein the ultrasonic waves generated from the acoustic lens are converged on the surface of the recording liquid in the recording liquid container to fly the recording droplets by driving the high frequency driving means. Driving the piezoelectric element, detecting the impedance of a drive system including the piezoelectric element in the driving state of the piezoelectric element, and determining whether the ultrasonic energy is appropriate based on the detected impedance Steps to
Driving control of the high-frequency driving means based on a result of determination as to whether or not ultrasonic energy is appropriate.

According to a tenth aspect of the present invention, there is provided a method of driving a droplet jet recording apparatus, wherein an acoustic lens disposed on the upper surface of a piezoelectric element is disposed in a recording liquid storage section, and the piezoelectric element is driven at a high frequency by a high frequency drive means. In the driving method of the droplet jet recording apparatus, the ultrasonic wave generated from the acoustic lens is converged on the surface of the recording liquid in the recording liquid container to fly the recording droplets. Driving the piezoelectric element, detecting the impedance of a drive system including the piezoelectric element in the drive state of the piezoelectric element, and measuring the impedance change time from the start of driving to the impedance change point based on the detected impedance Then, based on the impedance change time, the positional relationship between the liquid surface at the driving focal length and the sound pressure is appropriate, and the liquid surface between the recording liquid and the acoustic lens is The step of determining whether or not the ultrasonic energy is properly accumulated / amplified by the standing wave generated in the recording liquid, and the high frequency drive based on the determination result of whether or not the ultrasonic energy is appropriate And drivingly controlling the means.

Furthermore, in the method of driving the liquid droplet jetting recording apparatus according to the eleventh aspect of the present invention, the acoustic lens disposed on the upper surface of the piezoelectric element is disposed in the recording liquid storage section, and the piezoelectric element is driven to a high frequency by high frequency driving means. A driving method of a droplet jet recording apparatus, wherein the ultrasonic waves generated from the acoustic lens are converged on the surface of the recording liquid in the recording liquid container to fly the recording droplets by driving the high frequency driving means. And driving the piezoelectric element, detecting the impedance of the drive system including the piezoelectric element in the driving state of the piezoelectric element, measuring the amplitude time from the impedance change point to the next change point, and recording liquid. Whether the ultrasonic energy is properly accumulated / amplified by the standing wave in the recording liquid generated between the recording liquid surface and the acoustic lens. And step is characterized by comprising the step of driving and controlling the high frequency drive unit on the basis of whether or not the determination result ultrasonic wave energy is appropriate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. In the drawing, reference numeral 1 denotes a droplet jet recording apparatus, and a case body 4 in which an ink containing portion 2 containing ink as a recording liquid is formed inside and a nozzle 3 for ejecting ink droplets is formed on an upper surface, An acoustic lens 6 for converging the ultrasonic waves generated by the piezoelectric element 5 arranged at the bottom of the ink containing section 2 in the case body 4 to the ink liquid surface at the nozzle 3 position, and a high frequency drive voltage is applied to the piezoelectric element 5. A driving circuit 7 for driving the piezoelectric element 5 at a high frequency, an impedance detecting circuit 10 for detecting impedance from the driving state of the piezoelectric element 5 by the driving circuit 7, and an ultrasonic wave based on the impedance detected by the impedance detecting circuit 10. An ultrasonic energy judgment circuit 20 for judging whether or not the energy is properly accumulated / amplified, and a judgment result of the ultrasonic energy judgment circuit 20. There are and a drive control circuit 40 for controlling the frequency of the high frequency drive voltage generated by the drive circuit 7.

As shown in FIG. 2, the impedance detection circuit 10 has a piezoelectric element 5 whose one end is supplied with a high-frequency drive voltage from the drive circuit 7, and the other end of which is grounded via a shunt resistor Rs. The current waveform processing circuit 11 is supplied with a current change representing a change in the load impedance seen from the piezoelectric element 5 side when the liquid surface rises in the process of the ink droplet detected at the connection point with the resistor Rs flying. The current waveform processing circuit 11 includes an amplifier 12 and the amplifier 1.
The full-wave rectifier 13 performs full-wave rectification on the amplified output of No. 2, and the filter 14 that filters the rectified output of the full-wave rectifier 13 to extract the envelope of the rectified output.

The waveform processing signal output from the current waveform processing circuit 11 is supplied to one input side of the comparator 15, and the other input side of the comparator 15 is connected to the oscillation setting voltage input terminal t1 and ground. Voltage dividing resistors R1 and R interposed between
The reference voltage Vref output from the reference voltage generator 16 composed of 2 is supplied, and when the waveform processing signal Sp from this comparator 15 is below the reference voltage Vref, it is turned on and conversely. When the voltage exceeds the reference voltage Vref, a comparison signal that is turned off is output to the ultrasonic energy determination circuit 20 as the impedance detection signal Si.

As shown in FIG. 3, the ultrasonic energy determination circuit 9 receives the impedance detection signal Si output from the comparator 15 of the impedance detection circuit 10 as a D input.
Circuit 21 composed of a flip-flop circuit
AND gate to which the latch output output from the negative output terminal Q'of the latch circuit 21 and the inverted timing signal St 'and the clock pulse Cp input from the timing signal generator described later via the inverter 22a are input. 22, an error detection circuit 23 for detecting an error between the ink surface and the focus of the acoustic lens 6 based on the output pulse of the AND gate 22, and a timing for setting the generation time of the high frequency drive voltage generated by the drive circuit 7. A timing signal generator 28 for generating a signal St and a read permission signal generator 29 for generating a read permission signal SL based on the timing signal St generated by the timing signal generator 28.
And an edge detection circuit 30 that detects an edge of the read permission signal SL output from the read permission signal generator 29 and outputs a reset signal SR.

The error detection circuit 23 counts the output pulse of the AND gate 22 and measures the energy amplification time, and the energy amplification time measurement counter 24. The count value of the energy amplification time measurement counter 24 and the amplification time storage circuit. Amplification time error calculator 2 for inputting the amplification time previously stored in 25 and subtracting the amplification time from the count value
6 and a register 27 that holds the amplification time error output from the amplification time error calculator 26 and outputs it to the drive control circuit 40 as an energy determination signal SE.

The read enable signal SL output from the read enable signal generator 29 is supplied to the negative input terminal of the register 27, and the reset signal SR output from the edge detection circuit 30 is measured by the latch circuit 21 and the energy amplification time. Is supplied to the counter 24. Here, the read permission signal generator 29 is input to the D terminal to which the timing signal St output from the timing signal generator 28 is input and the D-type flip-flop to which the clock pulse Cp is input to the clock input terminal. 29a and a D-type flip-flop 29c to which an output signal output from the positive output terminal Q of the D-type flip-flop 29a is input to the D terminal, and a clock pulse Cp is input to the cook input terminal via the inverter 29b. , Flip-flop 29
and a NAND circuit 29d to which the output signal output from the positive output terminal Q of a and the output signal output from the negative output terminal Q of the flip-flop 29c are input.

The drive control circuit 40, as shown in FIG.
A proportional gain multiplier 41 that multiplies the amplification time error input from the register 27 of the ultrasonic energy determination circuit 20 by the proportional gain Gp, an integral gain multiplier 42 that multiplies the amplification time error by the integral gain Gi, and this integral gain. Multiplier 4
Integrator 43 for integrating the output of 2 and proportional gain multiplier 4
Adder 44 for adding the output of 1 and the output of the integrator 43
And an adder 4 that adds the previous value of the addition output of the adder 44 to the previous value held in the previous value register 45
6, a current value register 47 that holds the addition output of the adder 46 as the current frequency command value, and a D / A converter 48 that converts the frequency command value held by the current value register 47 into an analog voltage. Equipped with a D / A converter 48
The analog voltage output from is output to the drive circuit 7 as the frequency command value Vtf.

Here, the previous value register 45 is the timing signal generator 28 of the ultrasonic energy determination circuit 20 described above.
From the off state to the on state, the addition output of the adder 46 is held as the previous value. Further, the present value register 47 is supplied with the reset signal SR output from the edge detection circuit 30 of the ultrasonic energy determination circuit 20, and when the reset signal SR falls from the ON state to the OFF state, the addition of the adder 46 is performed. Hold the output as the frequency command value. In the previous value register 45, a preset initial frequency command value is set in the initial state when the droplet jet recording apparatus 1 is activated.

As shown in FIG. 3, the drive circuit 7 receives the oscillation frequency command value Vf output from the drive control circuit 40 and outputs an oscillation signal having a frequency corresponding to the oscillation frequency command value Vf to the timing signal generator 28. The voltage control type oscillation circuit 8 that oscillates while the timing signal St supplied from is in the off state, and the voltage control type amplifier 9 to which the oscillation output of the voltage control type oscillation circuit 8 is input.

Next, the operation of the above embodiment will be described. First, the principle of the present invention will be described. As shown in FIG. 5, the distance from the acoustic lens 6 to the ink surface at the position of the nozzle 3 is an odd multiple of 1/4 wavelength of the standing wave in the ink liquid based on the ultrasonic waves generated from the acoustic lens 6. In this positional relationship, the ultrasonic energy is optimally propagated to the focus portion of the ink liquid surface. Here, the wavelength λ is defined by the following formula (1) by the sound velocity C of the ink and the excitation frequency f.

Λ = C / f (1) The sound velocity C is defined by the following equation (2) by the bulk elastic modulus k and the ink density ρ. C = (k · ρ) ^1/2 (2) Since the bulk modulus k changes with temperature, the speed of sound C has temperature dependence. The excitation frequency f also changes due to the temperature dependence of the piezoelectric element impedance. Furthermore, the ink surface also fluctuates, and there is no guarantee that the distance between the acoustic lens 6 and the ink surface is always a constant distance.

If the sound velocity C or the excitation frequency f changes with the liquid surface distance being constant, the sound pressure changes with respect to the ink liquid surface as shown in FIG. With an appropriate positional relationship, stable ink droplets can be ejected with a certain fixed ultrasonic wave repetition time. At this time, when ultrasonic energy is accumulated and amplified in the ink liquid and ink droplets are ready to fly, the liquid surface of the ink abruptly rises and the sound pressure due to the standing wave up to now changes.

The change in sound pressure is caused by the piezoelectric element 5 at a constant voltage.
When driving, the current waveform appears as a load fluctuation. Therefore, a change in the ink liquid level can be detected as a change in impedance. When the ultrasonic energy in the ink liquid is accumulated / amplified in an optimum state, load fluctuations occur at certain fixed time intervals. Therefore, by measuring the time from the start of driving the piezoelectric element 5 to the occurrence of impedance change, it is possible to determine whether or not the wavelength in the ink liquid has an optimum positional relationship with respect to the liquid surface distance. If the relationship error is known, it is possible to correct the sound pressure by adjusting the excitation frequency f.

Therefore, in the first embodiment, the impedance detection circuit 10 detects the impedance change while the drive circuit 7 applies the high frequency voltage of the excitation frequency f to the piezoelectric element 5. The impedance change is detected by applying a high frequency drive voltage from the drive circuit 7 to the piezoelectric element 5 as shown in FIG. 6A, because a rise is not formed on the ink surface when ink droplets are not formed. At this time, the current waveform obtained by amplifying the drive current appearing between the piezoelectric element 5 and the shunt resistor Rs by the amplifier 12 of the current waveform processing circuit 11 has a relatively small constant amplitude as shown in FIG. When full-wave rectification is performed by the full-wave rectifier circuit 13, the full-wave rectified waveform at this time becomes a waveform in which the negative side of FIG. 6B is folded back as shown in FIG. 7C, and by filtering this, As shown in FIG. 6D, the envelope waveform is slightly below the reference voltage Vref.

Therefore, by supplying the filter output to the comparator 15 and comparing it with the reference voltage Vref, the impedance detection signal Si output from the comparator 15 is output.
Keeps the ON state as shown in FIG. 6 (e). However, when a high frequency drive voltage is continuously applied from the drive circuit 7 to the piezoelectric element 5 and the ink surface rises and ink droplets are generated, the piezoelectric element 5 and the shunt resistor Rs are connected to each other. As shown in FIG. 7B, the amplified waveform obtained by amplifying the generated drive current by the amplifier 12 changes from the amplitude at the normal time to the large amplitude, and then becomes smaller than the normal time, and then becomes slightly larger than the normal time. Changes in amplitude

Therefore, as shown in FIG. 7C, the full-wave rectified waveform full-wave rectified by the full-wave rectifier 13 changes from a normal amplitude to a large amplitude and then to an amplitude smaller than the normal amplitude. As a result, the filter output waveform obtained by filtering this with the filter 14 exceeds the reference voltage Vref at the start of driving as shown in FIG.
After that, the voltage becomes lower than the reference voltage Vref, and finally the voltage slightly exceeds the reference voltage Vref.

Therefore, the impedance detection signal Si output from the comparator 15 is as shown in FIG.
It keeps on at the start of driving, but turns off when the filter output exceeds the reference voltage Vref, and then returns to the on state when the filter output drops below the reference voltage Vref, and the filter output returns to the reference voltage. It turns off when it slightly exceeds Vref, and returns to on when the high frequency drive signal is stopped.

Since the impedance detection signal Si is supplied to the ultrasonic energy determination circuit 20, the ultrasonic energy determination circuit 20 outputs the timing signal St output from the timing signal generator 28 to the high frequency drive voltage from the drive circuit 7. Is output, which causes the piezoelectric element 5
Is vibrated, the ultrasonic waves generated from the acoustic lens 6 are converged on the ink surface, the ink surface rises, and the ink droplets continue to fly. As shown in FIG. 8C, the timing signal St output from the drive circuit 7 is turned off at the time t1, and the high frequency drive voltage is output from the drive circuit 7. 8A, the filter output rises from "0" as shown in FIG. 8A, and at this time t1, the latch circuit 2
Since the latch signal of No. 1 continues to be in the ON state as shown in FIG.
Since t is inverted and supplied by the inverter 22a, the AND gate 22 is opened and the clock pulse Cp shown in FIG. 8 (d) is input to the energy amplification time measuring counter 24. Therefore, the count value of this counter 24 Figure 8
It is counted up as shown in (h).

After that, at time t2, the filter output in the impedance detection circuit 10 exceeds the reference voltage Vref, so that the impedance detection signal Si output from the comparator 15 is turned off as shown in FIG. 8 (b). At this time, as shown by the dotted line in FIG.
When an odd multiple of four wavelengths is shorter than the ink surface, the filter output drops below the reference voltage Vref at time t3 after a time relatively shorter than time t1 has elapsed, and the comparator 15
The impedance detection signal Si output from is turned on.

By supplying the impedance detection signal Si to the clock signal input terminal of the latch circuit 21, the latch output of the latch circuit 21 is turned off as shown in FIG. The supply of the clock pulse Cp to the energy amplification time measurement counter 24 is closed and the count-up of the counter 24 is stopped as shown in FIG. 8 (h).

The count value at this time is lower than the preset amplification time, and the amplification time error calculated by the amplification time error calculator 26 is also as shown in FIG.
It is a negative value smaller than "0". After that, time t4
When the filter output becomes larger than the reference voltage Vref at, the impedance detection signal Si output from the comparator 15 is turned off as shown in FIG.
The timing signal St output from the timing signal generator 28 returns to the ON state as shown in FIG.
Holds the subtraction output output from the adder 46 as the previous value, and stops the output of the high frequency drive voltage from the drive circuit 7, whereby the filter output returns to "0" and the impedance detection signal Si turns on. Return to the state.

After that, at time t6 delayed by two clock pulses Cp, the read enable signal SL from the read enable signal generator 29 is turned off as shown in FIG. 8 (e), and this is supplied to the register 27. Register 27
Then, as shown in FIG. 8 (j), the negative amplification time error calculated by the amplification time error calculator 26 is read. By supplying the negative amplification time error to the proportional gain multiplier 41 of the drive control circuit 40, the amplification time error is multiplied by the proportional gain, while the amplification time error is supplied to the integral gain multiplier 42. As a result, the amplification time error is multiplied by the integral gain and then integrated by the integral counter 43, the integrated value and the multiplication value of the proportional gain multiplier 41 are added by the adder 44, and then the adder 46 adds the previous value register. The negative addition output of the adder 44 is added to the previous value held in 45 to calculate the frequency command value having a value smaller than the previous value. Thereafter, at the time t7 delayed by two clock pulses Cp from the time t6, the reset signal SR from the edge detection circuit 30 falls from the on state to the off state as shown in FIG. Since the addition output of the adder 46 is held in 47 as a frequency command value, this is converted into an oscillation frequency command value Vf which becomes an analog voltage in the D / A converter 48 and is supplied to the voltage controlled oscillator 8 of the drive circuit 7. After that, at time t8, the frequency f of the high frequency drive voltage generated from the drive circuit 7 becomes low, and the wavelength λ is increased by the above equation (1).

At this time t7, the latch output of the latch circuit 21 returns to the ON state as shown in FIG. 8 (g), and the count value of the energy amplification time measuring counter 24 is reset to "0". It After that, when the timing signal St output from the timing signal generator 28 is turned off at the time point t8, as described above, the driving circuit 7 changes the frequency according to the oscillation frequency command value Vf lower than the previous oscillation frequency command value Vf. Ink droplets are ejected by outputting a high frequency drive voltage and applying it to the piezoelectric element 5. In this state, the frequency f is controlled to a low value, and the wavelength λ becomes a large value. Assuming that the focus of the lens 6 exceeds the ink surface, the time during which the filter output exceeds the reference voltage Vref becomes long, and accordingly, the count value of the energy amplification time measuring counter 24 is shown in FIG. As shown in FIG. 8 (h), the preset amplification time memory value is slightly exceeded.

Therefore, the amplification time error calculated by the amplification time error calculator 26 becomes a positive value, which is read into the register 27 at the time t12, whereby the drive control circuit 4 is driven.
At 0, a frequency command value slightly larger than the previous oscillation frequency command value is calculated, which is stored in the current value register 47 at time t1.
3, the frequency command value is converted into an analog voltage by the D / A converter 48 and output to the voltage controlled oscillator 8 of the drive circuit 7.

Therefore, next, the timing signal generator 28
Time t14 when the timing signal St of
Then, by applying a high frequency drive voltage of an appropriate frequency from the drive circuit 7 to the piezoelectric element 5, an odd multiple of 1/4 wavelength is made to coincide with the ink liquid surface, and the amplification time measuring counter 24
The count value of the same matches the stored amplification time value, and the amplification time error calculated by the amplification time error calculator 26 becomes “0”,
This is held in the register 27. Therefore, the addition output of the adder 44 in the drive control circuit 40 becomes “0”, so that the addition output of the adder 46 becomes the previous value register 4
The previous value held in 5 is maintained, which is held in the current value register 47 when the reset signal SR falls from the on state to the off state. Therefore, when the same frequency command value as the previous time is supplied to the voltage controlled oscillator 8 of the drive circuit 7 and the timing signal St falls from the ON state to the OFF state, the high frequency drive voltage is supplied to the piezoelectric element 5, The ultrasonic energy is controlled to the optimum state.

In the first embodiment, the case where the ultrasonic energy determination circuit 20 and the drive control circuit 40 are configured by hardware has been described, but the present invention is not limited to this, and a microcomputer is used. It can also be configured with software. In this case, as shown in FIG. 9, the impedance detection signal of the impedance detection circuit 10 and the timing signal St generated by the timing signal generator 28 are input to the microcomputer 60, and the microcomputer 60 performs predetermined arithmetic processing. Is performed to output the frequency command value Vf to be supplied to the voltage controlled oscillator 8 of the drive circuit 7.

As shown in FIG. 10, the calculation process of the microcomputer 60 is performed for a predetermined time (for example, 50 mse).
This is executed as a timer interrupt process for each c). First, in step S1, the filter output output from the filter 14 of the impedance detection circuit 10 is read through the A / D converter, and then the process proceeds to step S2 to set the timing. Signal S
It is determined whether or not an up edge at which t changes from the off state to the on state is detected. When the up edge is detected, the process proceeds to step S3, and the frequency command value Vf stored in the frequency command value storage area of the memory is set. After the output to the voltage controlled oscillator 8 of the drive circuit 7, the timer interrupt processing is terminated and the predetermined main program is restored. When the up edge is not detected, the process proceeds to step S4.

In step S4, the timing signal S
It is determined whether or not a down edge in which t changes from the ON state to the OFF state is detected. When the down edge is detected, the process proceeds to step S5, and it is the start time of the high frequency drive voltage output in the drive circuit 7. After determining and activating the software timer, the timer interrupt processing is terminated and the predetermined main program is restored. When no down edge is detected, the process proceeds to step S6, and the timing signal St
Is ON, and when it is ON, the timer interrupt process is ended and the main program is returned to a predetermined main program. When the timing signal St is OFF, the process proceeds to step S7.

In step S7, it is determined whether the filter output is less than the reference voltage Vref. If the result of this determination is that the filter output is the reference voltage Vref or more,
In step S8, it is determined whether or not the print flag F is set to "1". When it is reset to "0", the process proceeds to step S9 and the print flag F is set to "1". After the setting, the timer interrupt processing is ended, and when the print flag F is set to "1", the timer interrupt processing is ended as it is.

When the result of the determination in step S7 is that the filter output is less than the reference voltage Vref, the process proceeds to step S10, it is determined whether or not the software timer is activated, and the software timer is not activated. Sometimes the timer interrupt process is terminated as it is and the process returns to a predetermined main program. When the software timer is activated, the process proceeds to step S11 to determine whether the print flag F is set to "1". When it is reset to "0", the timer interrupt processing is ended and the main program is returned to. If the print flag F is set to "1", the process proceeds to step S12 and the software timer is started. Stop, then move to step S13 to reset the count value of the software timer. After being read as the nergi amplification time measurement value Te, the process proceeds to step S14.

In this step S14, the optimum energy amplification time T preset from the energy amplification time measurement value Te is set.
The amplification time error ΔT (= Te−Te0) is calculated by subtracting e0, then the process proceeds to step S15, and the calculation of the following formula (3) is performed based on the amplification time error ΔT to change the frequency command value ΔVf. To calculate. ΔVf = ΔT · Gp + ∫ΔT · Gi (3) Next, the process proceeds to step S16, and the value obtained by adding the frequency command value change amount ΔVf to the previous frequency command value Vf (n-1) is used. The frequency command value Vf (n) is calculated, and then the process proceeds to step S17 to update and store the frequency command value Vf (n) in the frequency command value storage area and the frequency command value Vf (n) to the drive circuit 7. After outputting, the timer interrupt processing is terminated and the predetermined main program is restored.

Further, in the first embodiment, the case where the frequency command value change amount ΔVf is calculated by performing the proportional / integral processing on the amplification time error ΔT has been described, but the present invention is not limited to this. The frequency command value change amount ΔVf may be calculated by performing any one or more of the proportional process, the integral process, and the differential process. Further, the constant frequency command value change amount ΔVf may be set. May be.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the distance between the acoustic lens 6 and the ink surface is 1 due to the influence of the ink viscosity.
This is to be corrected when the wavelength is changed from an odd multiple of / 4 wavelength. That is, in the second embodiment, as shown in FIG. 11, the ultrasonic energy determination circuit 20 uses the drive control circuit 40, which will be described later, at the oscillation setting voltage input terminal t1 in the configuration of FIG. 2 in the above-described first embodiment. The oscillation voltage command value Va output from is input. When the oscillation voltage command value Va is changed, the voltage dividing resistors R1 and R2
A reference voltage Vref having a predetermined ratio is output from the reference voltage generator 16 configured by. Also, in the configuration of FIG. 3, the latch circuit 21, the AND gate 22, and the error detection circuit 23 are omitted, and instead of these, the impedance detection signal Si supplied from the impedance detection circuit 10 is supplied.
An AND gate 31a to which the inverted timing signal St 'input from the timing signal generator 28 via the inverter 22a and the clock pulse Cp are input, and an error detection circuit 32 to which the output pulse of the AND gate 31a is input. 3 has the same configuration as that of FIG. 3, and the same reference numerals are given to the portions corresponding to those of FIG. 3, and the detailed description thereof will be omitted.

The error detection circuit 32 includes an AND gate 31a.
Of the liquid level amplitude time measuring counter 32, the amplitude time memory circuit 33, and the amplitude time memory value stored in the amplitude time memory circuit 33 An amplitude time error calculator 34 for calculating an amplitude time error is provided, and the calculation result of the amplitude time error calculator 34 is held in a register 35. The amplitude time error held in the register 35 is driven. The amplitude of the high frequency drive voltage is controlled by being supplied to the voltage control amplifier 8 of the drive circuit 7 via the control circuit 40.

Next, the operation of the second embodiment will be described. First, the operating principle of the second embodiment will be described. When the viscosity of the ink is high, the attenuation of ultrasonic energy becomes large, and proper sound pressure cannot be concentrated on the ink surface. That is, the attenuation of the sound pressure P with respect to the focal length x is given by the following equation (4).

P (x) = P ₀ e ^{−α · x} (4) α = 2ω ² μ / 3c ³ ρ = 8 (πf) ² μ / 3c ³ ρ (5) Here Where α is the damping coefficient, μ is the viscosity (Pa · s), f is the excitation frequency (Hz), and P0 is the sound source sound pressure. When the ultrasonic energy is accumulated / amplified in the ink liquid and the ink droplets are ready to fly, the ink liquid surface rises rapidly as described above, and the ink droplets fly. At this time, a load change occurs, and this load change can be detected as a change for a certain period of time if the ink surface has an appropriate ink viscosity.

That is, when the ink viscosity is at an appropriate value, the driving circuit 7 sets the oscillation voltage initial setting value to the piezoelectric element 5.
12A, the amount of swelling of the ink surface is appropriate, and the amplitude change time in the drive current waveform between the piezoelectric element 5 and the shunt resistor Rs is in an appropriate state. Is lower than the appropriate value,
As shown in FIG. 12B, the rise of the ink surface is high and the amplitude change time in the drive current waveform between the piezoelectric element 5 and the shunt resistor Rs becomes long. In this case, the voltage of the high frequency drive voltage should be lowered. To deal with.

Further, in the case where the ink viscosity is high, as shown in FIG.
As shown in FIG. 2 (c), the rise of the ink liquid surface is small and the amplitude change time in the drive current waveform between the piezoelectric element 5 and the shunt resistor Rs is short or undetectable. In this case, the voltage of the high frequency drive voltage is high. Deal by raising. Therefore, when the ink viscosity is now high, the amplitude time error held in the register 27 in the ultrasonic energy determination circuit 20 is a negative value as shown in FIG. 13 (i), and this amplitude time error is driven. Since the addition output output from the adder 44 after the proportional / integral (PI) processing is performed by the control circuit 40 also has a negative value, the addition output is supplied to the adder 46, and thus is held in the previous value register 45. The addition output is subtracted from the previous oscillation voltage command value,
When the reset signal SR falls from the ON state to the OFF state, the addition output of the adder 46 is held as the oscillation voltage command value in the current value register 47, and the oscillation voltage command value Va lower than the previous oscillation voltage command value is driven. It is supplied to the voltage-controlled amplifier 9 of the circuit 7. In this state, time t2
When the timing signal St generated from the timing signal generator 28 in 1 is turned off, the previous value register 45 holds the addition output of the adder 46 as the previous oscillation voltage command value, and the drive circuit 7 outputs a relatively small amplitude. Is applied to the piezoelectric element 5.

At this time, assuming that the distance between the acoustic lens 6 and the liquid surface of the ink is in an appropriate state, the filter output shows the timing signal S at time t21 as shown in FIG.
t is inverted by the inverter 22a and supplied, and at time t2
By exceeding the reference voltage Vref at 2, the impedance detection signal Si output from the comparator 15 of the impedance detection circuit 10 is turned off, and then the time t23.
Since the filter output falls below the reference voltage Vref at
The impedance detection signal Si is turned on as shown in FIG. Therefore, the AND gate 31a is opened and the clock pulse Cp is input to the liquid surface amplitude time measuring counter 32, so that the count value is counted up. At this time, since the ink viscosity is high,
As shown in FIG. 13C, the swell of the ink surface is small, and the impedance detection signal Si output from the impedance detection circuit 10 causes the filter output to exceed the reference voltage Vref at time t24 when a short time has elapsed from time t23. Turns off and the AND gate 31
Is closed and counting up of the liquid surface amplitude time measuring counter 32 is stopped. At this time, since the count value becomes a small value "1", the amplitude time error calculated by the amplitude time calculator 34 becomes a positive value as shown in FIG. 13 (h).

After that, when the timing signal St generated from the timing signal generator 28 is turned on at the time point t25, the output of the high frequency drive voltage from the drive circuit 7 to the piezoelectric element 5 is stopped, and the clock pulse Cp causes 2 to be output. At a time t26 delayed by one time, the read permission signal output from the read permission signal generator 29 is turned off, whereby the positive value amplitude time error calculated by the amplitude time error calculator 34 is read by the register 35, This amplitude time error is output to the drive control circuit 40. This drive control circuit 40 performs a proportional / integral (PI) operation and adds the positive correction value added by the adder 44 to the adder 46, and the previous oscillation held in the previous value register 45 at time t21. By being added to the voltage command value, the adder 46 outputs an oscillation voltage command value having a value larger than the previous oscillation voltage command value, and the reset signal SR falls from the on state to the off state at time t27. , This time value register 47
The analog voltage is converted into an analog voltage by the D / A converter 48 and is supplied to the voltage control type amplifier 9 of the drive circuit 7.

Therefore, at the time t28 when the timing signal of the timing signal generator 28 is turned off, a high frequency high frequency drive voltage having a large amplitude is applied to the piezoelectric element 5 and the addition of the adder 46 at this time is performed. The output is held in the previous value register 45 as the previous value of the oscillation voltage command value. At this time, if the amplitude of the high frequency drive voltage becomes too large, the liquid level amplitude time between time points t29 and t30 becomes long, and the count value of the liquid surface amplitude time measuring counter 32 becomes as shown in FIG. As shown in, the amplitude time memory value is exceeded.

Therefore, the amplitude time error calculated by the amplification time error calculator 34 becomes a negative value as shown in FIG. 13 (h), which is read into the register 27 at the time t32,
It is output to the drive control circuit 40. This drive control circuit 40
Then, the adder 46 adds the correction value output from the adder 44 that proportional-integrates the amplitude time error to the previous oscillation voltage command value, so that the adder 46 oscillates smaller than the previous oscillation voltage command value. The voltage command value is output, and this value is held in the current value register 47 at time t33 and the D / A
The converter 48 converts the analog voltage and supplies the analog voltage to the voltage-controlled amplifier 9 of the drive circuit 40.
The amplitude of the high-frequency drive voltage output at time t34 is controlled to a value that is slightly smaller than the previous value, and the count value of the liquid surface amplitude time measurement counter 32 is stored in the amplitude time storage circuit 33. Match the stored value.

Therefore, the amplitude time error output from the amplitude time error calculator 34 becomes "0", which is the time t3.
6 is held in the register 27, which is the drive control circuit 40.
Is supplied to the drive control circuit 40, the value subjected to the proportional / integral processing by the drive control circuit 40 is also set to "0", so that the current oscillation voltage command value output from the adder 46 maintains the previous value. This is held in the current value register 47 at the subsequent time t39, converted into an analog signal by the D / A converter 48, and supplied to the voltage control type amplifier 9 of the drive circuit 7.

Therefore, after that, the timing signal St
The drive circuit 7 is turned on when the
A high-frequency drive voltage that maintains the previous value is output from the device to form a swell on the ink surface according to the ink viscosity, and the ink droplets can be reliably ejected and attached to the recording medium. In addition, in the said 2nd Embodiment, although the case where the ultrasonic energy judgment circuit 20 and the drive control circuit 40 were comprised by hardware was demonstrated, it is not limited to this, It is software using a microcomputer. It can also be configured. In this case, as shown in FIG.
Impedance detection signal and timing signal generator 28
And the timing signal St generated in step S1 are input to the microcomputer 60, the microcomputer 60 performs predetermined arithmetic processing, and outputs the oscillation voltage command value Va supplied to the voltage controlled amplifier 9 of the drive circuit 7. Has been done.

In the calculation process of the microcomputer 60, the ink viscosity correction process shown in FIG. 15 is performed by a timer interrupt process at every predetermined time (for example, 50 msec). In the ink viscosity correction process, first, in step S31, the filter output output from the filter 14 of the impedance detection circuit 10 is read through the A / D converter, and then the process proceeds to step S32 to perform the timing signal generator 28.
It is determined whether or not an up edge in which the timing signal St output from is changed from the off state to the on state is detected. When the up edge is detected, step S3 is performed.
3, the oscillation voltage command value Va stored in the oscillation voltage command value storage area formed in the memory is output to the voltage control type amplifier 9 of the drive circuit 7, and then the timer interrupt processing is ended and predetermined. Return to the main program of.

When the determination result of step S32 does not detect the rising edge of the timing signal St, the process proceeds to step S34, it is determined whether or not the timing signal St is in the on state, and it is in the on state. Sometimes, the timer interrupt processing is terminated and the main program is restored, and if it is in the off state, step S3.
Go to 5.

In step S35, it is determined whether or not the filter output is equal to or higher than the reference voltage Vref based on the oscillation voltage command value Va stored in the oscillation voltage command value storage area, and the filter output is less than the reference voltage Vref. If there is, the process proceeds to step S36, and the print flag F is "1".
If it is set to "0", it is reset to "0" and the timer interrupt processing is terminated and the main program is returned to the print flag F.
When is set to "1", the process proceeds to step S37, and it is determined whether or not the liquid surface amplitude measuring timer is started. When it is started, the timer interrupt process is ended and the predetermined value is set. If the liquid level amplitude measuring timer is not activated, the process proceeds to step S38 to activate the liquid level amplitude measuring timer, terminate the timer interrupt process, and return to the predetermined main program. To do.

On the other hand, when the result of the determination in step S35 is that the filter output is equal to or higher than the reference voltage Vref, the process proceeds to step S39, and it is determined whether or not the print flag F indicating the print state is set to "1". If it is reset to "0", the process proceeds to step S40, the print flag F is set to "1", the timer interrupt process is terminated, and the predetermined main program is restored. When it is set to "1", the process proceeds to step S41, and it is determined whether or not the liquid level amplitude measuring timer is activated. If it is not activated, the timer interrupt process is ended and the predetermined operation is performed. Returning to the main program, when the liquid surface amplitude measuring timer is activated, the process proceeds to step S42.

In step S42, the liquid surface amplitude measuring timer is stopped, and then the process proceeds to step S43,
The liquid surface amplitude time Ta measured by the liquid surface amplitude measuring timer is read, then the process proceeds to step S44, and the liquid surface amplitude time Ta is subtracted from the preset liquid surface amplitude time stored value Ta0 to obtain the liquid surface amplitude time error. ΔTa (= Ta0-Ta) is calculated.

Then, the process proceeds to step S45 to calculate the oscillation voltage command value change amount ΔVa by performing the calculation of the following equation (6). ΔVa = ΔTa · Gp + ∫ΔTa · Gi (6) Next, the process proceeds to step S46, and the value obtained by adding the oscillation voltage command value change amount ΔVa to the previous oscillation voltage command value Va (n-1) is calculated. The current oscillation voltage command value Va (n) is set, and then the process proceeds to step S48, the current oscillation voltage command value Va (n) is updated and stored in the oscillation voltage command value storage area, and the current oscillation voltage command value is set. The value Va (n) is output to the voltage control type amplifier 9 of the drive circuit 7 and then the timer interrupt processing is ended to return to the predetermined main program.

Also in the second embodiment, the case where the oscillation voltage command value change amount ΔVa is calculated by performing the proportional / integral processing on the liquid surface amplitude time error ΔTa has been described, but the present invention is not limited to this. However, the oscillating voltage command value change amount ΔVa may be calculated by performing one or more of a proportional process, an integrating process, and a differential process, and further, a constant value of the oscillating voltage command value change amount ΔVa. May be set.

Next, a third embodiment of the present invention will be described with reference to FIGS. This third embodiment is a combination of the above-described first and second embodiments, in which the ultrasonic lens 6 is generated on the ink liquid surface in response to both the fluctuation of the ink liquid surface and the change of the ink viscosity. The sound waves are made to converge. That is, in the third embodiment, as shown in FIG. 16, the ultrasonic energy determination circuit 20 includes the first error detection circuit 36A including the error detection circuit 23 of the first embodiment and the second error detection circuit 36A. The second error detection circuit 36B including the error detection circuit 31 in the embodiment
And these first and second error detection circuits 36A and 36A
The holding timing of the registers 27 and 35 in B is selected to oscillate in the first drive control circuit 40A that supplies the oscillation frequency command value to the voltage control oscillator 8 of the drive circuit 7 and the voltage control amplifier 9 of the drive circuit 7. It has the same configuration as that of FIG. 3 of the above-described first embodiment except that a selection circuit 37 that supplies the voltage command value to any of the second drive control circuits 40B is provided. , The parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

Here, as shown in FIG. 17, in the selection circuit 37, the amplification time error output from the register 27 of the first error detection circuit 36A is input to the non-inverting input side via the first absolute value circuit 51A. And the error tolerance value setting circuit 5 on the inverting input side.
The first comparator 53A to which the allowable error value set in 2A is input, the latch circuit 54 connected to the output side of the first comparator 53A for performing the down edge operation, and the inversion of the latch circuit 54A. The latch signal output from the output side and the read enable signal output from the read enable signal generator 29 are input, and the output SL1 is supplied to the register 27 of the first error detection circuit 36A.
Then, the amplitude time error output from the register 35 of the second error detection circuit 36B passes through the second absolute value circuit 51B to the non-inverting input side and the error allowable value setting circuit 52 to the inverting input side.
The second comparator 5 to which the allowable error value set in B is input
3B and the output of the second comparator 53B are input to perform the edge down operation, and the edge detection circuit 56 that supplies the edge detection signal to the latch circuit 54 as a reset signal and the comparison output of the first comparator 53A The read enable signal SL output from the read enable signal generator 29 is input through the inverter 57, and the output SL2 is supplied to the AND gate 55B supplied to the register 35 of the second error detection circuit 36B. I have it.

Next, the operation of the third embodiment will be described. Now, in the selection circuit 37, the latch signal output from the latch circuit 54 is in the ON state, and this is the AND gate 5.
5A. In this state, as in the first embodiment described above, the read permission signal generator 29
From the ON state to the OFF state, the output of the AND gate 55A is inverted to the OFF state, which is the register 27 of the first error detection circuit 36A.
Is supplied to the drive control circuit 40A by holding the amplification time error calculated by the amplification time error calculator 26 in the register 27 and being supplied to the drive control circuit 40A. The current oscillation frequency command value is formed based on the amplification time error and the previous oscillation frequency command value, and this oscillation frequency command value is supplied to the voltage controlled oscillator 8 of the drive circuit 7, whereby the drive circuit 7
Is supplied to the piezoelectric element 5 with a high-frequency drive voltage Vf having a frequency corresponding to the oscillating frequency command value, the ultrasonic wave that converges on the ink liquid surface is output from the acoustic lens 6 to raise the ink liquid surface, and ink droplets are generated. Are ejected and adhered to the recording medium to form dots.

When the ultrasonic wave generated by the acoustic lens 6 is converged in the vicinity of the ink liquid surface by performing the correction processing for matching the ink liquid surface with the convergence point of the ultrasonic wave generated by the acoustic lens 6, The amplification time error output from the register 27 of the first error detection circuit 36A becomes substantially "0", which is passed through the absolute value circuit 51A to the first comparator 53.
When the amplification time error becomes a value smaller than the first error allowable value set by the first error allowable value setting circuit 52A by being supplied to A, the comparison output output from the first comparator 53A Is inverted to the off state and is supplied to the latch circuit 54, whereby the latch signal output from the latch circuit 54 is inverted from the on state to the off state, and this is supplied to the AND gate 55A. The AND gate 55A is closed, and the reading of the register 27 in the first error detection circuit 36A is stopped.

At the same time, the comparison output obtained by inverting the first comparator 53A from the on state to the off state is the inverter 57.
By being supplied to the AND gate 55B via
When the AND gate 55B is opened and the read permission signal from the ON state to the OFF state is input from the read permission signal generator 29, this is the second error detection circuit 36.
By being supplied to the B register 35, the amplitude time error calculated by the amplitude time error calculator 34 is held in this register 35, and this is supplied to the second drive control circuit 40B. In 40B, the oscillation voltage command value according to the ink viscosity is calculated, and this is the drive circuit 7
By being supplied to the voltage control type amplifier 9, the high frequency oscillation voltage having the amplitude according to the oscillation voltage command value is output to the piezoelectric element 5.

After that, the amplitude time error held in the register 35 of the second error detection circuit 36B is "0" by controlling the amplitude of the high frequency drive voltage output from the drive circuit 7 to the optimum state for the ink viscosity. "Because it is a value in the vicinity of the second
When the error tolerance value set by the error tolerance value setting circuit 52B is less than the error tolerance value, the comparison output output from the second comparator 53B is inverted to the off state.
6 and the reset signal is supplied to the latch circuit 54, the latch output of the latch circuit 54 is turned on, the AND gate 55A is opened, and the first error detection circuit 36A outputs the reset signal. A correction process is performed to converge the ultrasonic waves generated by the acoustic lens 6 on the ink liquid surface.

As described above, in the third embodiment, the correction processing for converging the ultrasonic waves generated by the ink liquid surface and the acoustic lens 6 to the ink liquid surface and the high frequency drive voltage having the amplitude corresponding to the ink viscosity are generated. By repeating the correction process alternately, the ultrasonic energy can always be maintained in the optimum state according to the fluctuation of the ink surface and the fluctuation of the ink viscosity, and the flight of the ink droplets can be accurately controlled to print. The quality can be improved.

In the third embodiment, the first error detection circuit 36A and the second error detection circuit 36B are used.
However, the present invention is not limited to this, and since the change of the ink liquid level is faster than the change of the ink viscosity, the first error detection circuit 36A is operated a plurality of times. The second error detection circuit 36B may be operated once after the continuous operation.

Also, in the third embodiment described above, the case where the ultrasonic energy judgment circuit 20 and the drive control circuit 40 are configured by hardware has been described, but the present invention is not limited to this, and the first and the above-described first and second embodiments are not limited thereto. The arithmetic processing using the microcomputer of the second embodiment is performed, and in either one of the arithmetic processing, the frequency command value change amount ΔV
When f or the oscillation voltage command value change amount ΔVa falls within a preset allowable range, the other calculation process may be switched to.

Further, in the above-mentioned first to third embodiments, the case where the present invention is applied to the ink jet printer using the recording liquid as the ink has been described, but the present invention is not limited to this, and liquids other than ink are used. The present invention can be applied to the case of flying the droplets.

[0079]

As described above, according to the invention of claim 1 or 9, the impedance detecting means for detecting the impedance of the driving system for driving the piezoelectric element by the high frequency driving means, and the impedance detecting means. Ultrasonic energy determining means for determining whether or not the ultrasonic energy is appropriate based on the detected impedance detection signal,
Since the driving control means for driving and controlling the high frequency driving means based on the determination result of the ultrasonic energy determination means is provided, the droplet flying state can be achieved without separately providing a sensor for detecting temperature, viscosity, sound velocity, etc. Can be accurately detected in real time, and the ultrasonic waves generated by the acoustic lens can be accurately focused on the surface of the recording liquid to improve the recording quality. Moreover, it is not necessary to provide a special measurement time in the non-ejection state of the recording liquid in order to measure the state of the recording liquid or the sound source, and by providing the measurement time, it is sure that a delay occurs in the ejection time of the recording liquid. There is also an effect that can be prevented.

According to the second aspect of the invention, the impedance detecting means includes a drive current detecting means for detecting the drive current of the piezoelectric element, and the drive current detected by the drive current detecting means is converted into a DC voltage change. Current waveform processing means for
Since the output voltage of the current waveform processing means and the reference voltage are compared with each other, the liquid level change and the viscosity change of the recording liquid can be detected at the same time.

Further, according to the invention of claim 3 or 10, the ultrasonic energy judging means measures the impedance change time from the drive start to the impedance change point based on the impedance detection signal, and the impedance change time is measured. Based on the above, the positional relationship between the liquid surface of the driving focal length and the sound pressure is appropriate, and the ultrasonic wave is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. Since it is configured to judge whether or not it is, it is possible to obtain the effect that the change in the liquid level of the recording liquid can be accurately detected in real time.

Further, according to the invention of claim 4, the drive control means determines the frequency of the high frequency drive signal of the high frequency drive means when the determination result of the ultrasonic energy determination means indicates that the impedance change time is shorter than the optimum time. Lower
Since it is configured to perform control to increase the frequency of the high frequency drive signal of the high frequency drive means when it is longer than the optimum time, the frequency of the high frequency drive signal supplied to the piezoelectric element is
The effect that the change in the liquid level of the recording liquid can be accurately accommodated is obtained.

Still further, according to the invention of claim 5 or 11, the ultrasonic energy judging means measures the amplitude time from a change point of impedance to the next change point on the basis of the impedance detection signal, and records the recording liquid. Has a proper viscosity and is configured to judge whether or not the ultrasonic energy is properly accumulated / amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. The effect that the generation state of ultrasonic waves according to the change in the viscosity of the recording liquid can be accurately determined in real time is obtained.

According to the invention of claim 6, the drive control means increases the drive voltage of the high frequency drive means when the determination result of the ultrasonic energy determination means is shorter than the optimum amplitude time. Since the control is performed to lower the drive voltage of the high frequency drive means when the time is longer than the optimum time, the amplitude of the high frequency drive signal supplied to the piezoelectric element can be accurately corresponded to the change of the recording liquid viscosity. The effect that it can be obtained.

Further, according to the invention of claim 7, the ultrasonic energy judging means measures the impedance change time from the drive start to the impedance change point based on the impedance detection signal, and based on the impedance change time. Whether the ultrasonic wave energy is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. The first determination means for determining the difference between the impedance change point and the next change point is measured, and the viscosity of the recording liquid is appropriate. The second to judge whether or not the ultrasonic energy is properly accumulated and amplified by the standing wave
The drive control means lowers the frequency of the high frequency drive signal of the high frequency drive means when the result of the determination by the first determination means is shorter than the optimum time, and the drive control means is longer than the optimum time. In this case, the first drive control means performs control to increase the frequency of the high frequency drive signal of the high frequency drive means, and drives the high frequency drive means when the determination result of the second determination means is shorter than the optimum amplitude time. The second drive control means for controlling the drive voltage of the high frequency drive means to be increased when the voltage is increased and longer than the optimum time is provided, so that both effects of claim 3 and claim 5 are obtained. You can

Further, according to the invention of claim 8, the ultrasonic energy judging means has a selecting means for selecting the first judging means and the second judging means, and the selecting means has the above-mentioned structure. The second judgment means is selected after the judgment result of the first judgment means converges to the first allowable range, and the second judgment means is selected after the judgment result of the second judgment means converges to the second allowable range. Since the selection means 1 is repeatedly selected, the change in the recording liquid level and the change in the recording liquid viscosity are alternately determined to control the ultrasonic wave generated by the acoustic lens to the optimum state. The effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a specific example of an impedance detection circuit.

FIG. 3 is a block diagram showing a specific example of an ultrasonic energy determination circuit.

FIG. 4 is a block diagram diagram showing a specific example of a drive control circuit.

FIG. 5 is an explanatory diagram showing a positional relationship between a liquid surface having a focal length and sound pressure.

FIG. 6 is a time chart showing a change in current when ink droplets are not generated.

FIG. 7 is a time chart showing changes in current when ink droplets are generated.

FIG. 8 is a time chart used to explain an operation in the first embodiment.

FIG. 9 is a block diagram showing another embodiment of the first embodiment.

10 is a flowchart showing an example of a calculation processing procedure in the microcomputer shown in FIG.

FIG. 11 is a block diagram showing a second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a detection principle in the second embodiment.

FIG. 13 is a time chart used to explain an operation in the second embodiment.

FIG. 14 is a block diagram showing another embodiment of the second embodiment.

15 is a flowchart showing an example of a calculation processing procedure in the microcomputer shown in FIG.

FIG. 16 is a block diagram showing a third embodiment of the present invention.

FIG. 17 is a block diagram showing a specific example of a selection circuit according to the third embodiment.

[Explanation of symbols]

1 Droplet ejection recording device 2 Ink storage 3 nozzles 4 case body 5 Piezoelectric element 6 acoustic lens 7 drive circuit 8 Voltage controlled oscillator 9 Voltage control type amplifier 10 Impedance detection circuit 11 Current waveform processing circuit 12 amplifier 13 full-wave rectifier 14 filters 15 Comparator 20 Ultrasonic energy judgment circuit 21 Latch circuit 22 AND GATE 24 Energy amplification time counter 25 Amplification time memory circuit 26 Amplification time error calculator 27 registers 28 Timing signal generator 29 Read permission signal generator 31a AND gate 32 Liquid level amplitude time counter 33 Amplitude time memory circuit 34 Amplitude time error calculator 35 registers 37 Selection circuit 40 Drive control circuit 60 microcomputer

Claims (11)

[Claims] 1. An ultrasonic lens generated on the acoustic lens is recorded by arranging an acoustic lens arranged on the upper surface of a piezoelectric element in a recording liquid storage section and driving the piezoelectric element at a high frequency by a high frequency driving means. In a droplet jet recording apparatus in which recording droplets are made to fly by converging on a recording liquid surface of a liquid storage portion, impedance detection means for detecting impedance of a drive system for driving the piezoelectric element by the high frequency drive means, Ultrasonic energy determination means for determining whether or not the ultrasonic energy is appropriate based on the impedance detection signal detected by the impedance detection means, and the high frequency drive means based on the determination result of the ultrasonic energy determination means. And a drive control means for controlling the drive of the liquid droplet ejection recording apparatus. 2. The impedance detecting means includes a drive current detecting means for detecting a drive current of a piezoelectric element, a current waveform processing means for converting the drive current detected by the drive current detecting means into a DC voltage change, and the current. 2. The liquid droplet jetting recording apparatus according to claim 1, further comprising: comparing means for comparing the output voltage of the waveform processing means and the reference voltage, and the impedance detecting signal is output from the comparing means. 3. The ultrasonic energy determining means measures the impedance change time from the start of driving to the impedance change point based on the impedance detection signal, and based on the impedance change time, the liquid level and the sound at the drive focal length. It is configured to determine whether the positional relationship of pressure is proper and whether the ultrasonic energy is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. The droplet jet recording apparatus according to claim 1 or 2, characterized in that. 4. The drive control means lowers the frequency of the high frequency drive signal of the high frequency drive means when the determination result of the ultrasonic energy determination means is shorter than the optimum time and the high frequency when the determination time is longer than the optimum time. 4. The droplet ejection recording apparatus according to claim 3, wherein the droplet ejection recording apparatus is configured to perform control for increasing the frequency of the high frequency drive signal of the drive unit. 5. The ultrasonic energy determining means measures an amplitude time from a change point of impedance to a next change point on the basis of an impedance detection signal, the viscosity of the recording liquid is appropriate, and the liquid level of the recording liquid and the sound are measured. The liquid according to claim 1 or 2, which is configured to determine whether or not the ultrasonic energy is properly accumulated and amplified by a standing wave in the recording liquid generated between the lenses. Drop jet recording device. 6. The drive control means increases the drive voltage of the high frequency drive means when the determination result of the ultrasonic energy determination means is shorter than the optimum amplitude time, and increases the drive voltage of the high frequency drive means when the determined result is longer than the optimum time. The droplet ejection recording apparatus according to claim 5, wherein the droplet ejection recording apparatus is configured to perform control for lowering a drive voltage. 7. The ultrasonic energy determining means measures the impedance change time from the start of driving to the impedance change point based on the impedance detection signal, and based on the impedance change time, the liquid level and the sound at the drive focal length. A first judging means for judging whether the positional relationship of pressure is proper, and whether the ultrasonic energy is properly accumulated and amplified by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. , The amplitude time from the point of change of impedance to the next point of change is measured, the viscosity of the recording liquid is appropriate, and the ultrasonic energy is appropriate due to the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. Second determination means for determining whether or not the impedance change time is optimal when the determination result of the first determination means is determined. A first drive control means for controlling the frequency of the high frequency drive signal of the high frequency drive means to be lowered when the time is shorter than the interval, and to increase the frequency of the high frequency drive signal of the high frequency drive means when the time is longer than the optimum time; Drive control for increasing the drive voltage of the high frequency drive means when the result of the determination by the determination means is shorter than the optimum amplitude time, and lowering the drive voltage of the high frequency drive means for longer than the optimum time. 3. A droplet jet recording apparatus according to claim 1, further comprising: 8. The ultrasonic energy judging means has a selecting means for selecting the first judging means and the second judging means, and the selecting means determines that the judgment result of the first judging means is Repeating the selection of the second determining means after convergence to the first allowable range and the selection of the first determining means after the result of the determination by the second determining means converges to the second allowable range. The droplet jet recording apparatus according to claim 7, wherein the droplet jet recording apparatus is configured as described above. 9. An ultrasonic lens generated on the acoustic lens is recorded by disposing an acoustic lens disposed on the upper surface of the piezoelectric element in a recording liquid storage section and driving the piezoelectric element at high frequency by a high frequency drive means. In a method of driving a droplet jet recording apparatus that converges on a surface of a recording liquid in a liquid storage portion and causes recording droplets to fly, a step of driving the piezoelectric element by the high frequency driving means, and a driving state of the piezoelectric element. To detect the impedance of the drive system including the piezoelectric element, to determine whether the ultrasonic energy is appropriate based on the detected impedance, and to determine whether the ultrasonic energy is appropriate. A driving method of the high-frequency driving means based on a judgment result. 10. An ultrasonic lens generated on the acoustic lens is recorded by disposing an acoustic lens disposed on the upper surface of the piezoelectric element in a recording liquid storage section and driving the piezoelectric element at a high frequency by a high frequency drive means. In a method of driving a droplet jet recording apparatus that converges on a surface of a recording liquid in a liquid storage portion and causes recording droplets to fly, a step of driving the piezoelectric element by the high frequency driving means, and a driving state of the piezoelectric element. In the step of detecting the impedance of the drive system including the piezoelectric element, the impedance change time from the start of driving to the change point of the impedance is measured based on the detected impedance, and the liquid surface of the drive focal length is measured based on the impedance change time. And the sound pressure are in a proper positional relationship, and ultrasonic energy is generated by the standing wave in the recording liquid generated between the liquid surface of the recording liquid and the acoustic lens. The method further comprises a step of determining whether or not the energy is properly accumulated and amplified, and a step of driving and controlling the high frequency drive means based on a determination result of whether or not the ultrasonic energy is appropriate. Method for driving a droplet ejection recording apparatus. 11. An ultrasonic lens generated on the acoustic lens is recorded by disposing an acoustic lens disposed on the upper surface of the piezoelectric element in a recording liquid storage section and driving the piezoelectric element at high frequency by a high frequency drive means. In a method of driving a droplet jet recording apparatus that converges on a surface of a recording liquid in a liquid storage portion and causes recording droplets to fly, a step of driving the piezoelectric element by the high frequency driving means, and a driving state of the piezoelectric element. The step of detecting the impedance of the drive system including the piezoelectric element and the amplitude time from the change point of the impedance to the next change point are measured, and the viscosity of the recording liquid is appropriate, and it occurs between the liquid surface of the recording liquid and the acoustic lens. The step of determining whether or not the ultrasonic energy is properly accumulated and amplified by the standing wave in the recording liquid, and the determination result of whether or not the ultrasonic energy is appropriate. Driving control of the high frequency driving means based on the above.