JP4844066B2 - Droplet discharge head inspection apparatus and droplet discharge head inspection method - Google Patents

Description

  The present invention relates to a droplet discharge head inspection apparatus and a droplet discharge head inspection method, and more particularly to a droplet discharge head for inspecting a waveform attenuation constant representing a pressure change in a pressure chamber by an electromechanical transducer to which a voltage is applied. The present invention relates to an inspection apparatus and a droplet discharge head inspection method.

  Conventionally, in a droplet discharge head using an electromechanical conversion element (such as a piezo actuator), a voltage change is generated in the pressure chamber by applying a voltage to the electromechanical conversion element to discharge a droplet. The pressure change in the pressure chamber is controlled with high accuracy by the drive waveform of the applied voltage, and high-frequency ejection, microdroplet ejection, satellite / mist control, and the like are performed.

  It is important to adapt the driving waveform of the applied voltage to the acoustic characteristics of the droplet discharge head. Specifically, the amplitude of the waveform representing the pressure change generated in the pressure chamber of the droplet discharge head, the natural period (Helmholtz) It is necessary to adapt the driving waveform to the vibration period) and the damping constant.

  The droplet discharge heads as described above are manufactured using precision processing technology, semiconductor process technology, and the like, but acoustic characteristics differ between the droplet discharge heads due to variations in manufacturing conditions and materials. Therefore, in order to achieve stable ejection with all droplet ejection heads, the acoustic characteristics of each manufactured droplet ejection head are inspected, and the drive waveform is matched to the acoustic characteristics of each droplet ejection head. It is necessary to make adjustments.

  The most common method for inspecting the acoustic characteristics of a droplet discharge head is to measure the droplet velocity or volume (approximately proportional to the amplitude of the waveform that represents the pressure change), and the characteristic of the waveform that represents the pressure change. A method for measuring the period is known (Patent Document 1).

On the other hand, the attenuation constant of the pressure change is a characteristic value representing the speed at which the amplitude of the pressure change generated in the pressure chamber of the droplet discharge head attenuates in time, and controls satellites and mist generated during droplet discharge. This is an extremely important value. Therefore, when adjusting the drive waveform, it is desirable to measure the attenuation constant of each droplet discharge head and make adjustments to match it.
Japanese Patent No. 3419401

  However, since there is no simple method for measuring the attenuation constant of the pressure change, there is a problem that it is difficult to adjust the driving waveform in accordance with the attenuation constant of the droplet discharge head.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a droplet discharge head inspection apparatus and a droplet discharge head inspection method that can easily inspect the attenuation constant of a droplet discharge head. To do.

In order to achieve the above object, a droplet discharge head inspection apparatus according to a first aspect of the present invention includes a pressure chamber filled with a liquid, and an electromechanical converter that changes the pressure in the pressure chamber in accordance with an applied voltage. And a droplet discharge head inspection apparatus for inspecting a droplet discharge head that discharges a droplet in response to the pressure change, wherein each of the voltages of a plurality of drive waveforms composed of pulses having different pulse widths is An application means for applying to the electromechanical transducer, a droplet speed measuring means for measuring the speed of the droplets ejected from the droplet ejection head by voltage application of the application means, and a liquid measured by the droplet speed measuring means the damping constant of the damping curve representing the change in velocity of the droplets with respect to a change in the pulse width of determined the drive waveform in accordance with the pulse width of the speed and the plurality of driving waveforms of droplets, the pressure change with respect to time change Calculating means for calculating as衰定number, the greater the attenuation constant calculated by the calculating means, as the voltage variation of the reverberation adjustment portion in the driving waveform of the voltage applied to the electromechanical transducer is increased, the Attenuation constant drive waveform adjusting means for adjusting the drive waveform is included.

According to a second aspect of the present invention, there is provided a droplet discharge head inspection method comprising: a pressure chamber filled with a liquid; and an electromechanical transducer that changes a pressure in the pressure chamber according to an applied voltage; A droplet discharge head inspection method for inspecting a droplet discharge head that discharges a droplet in response to a pressure change, wherein each of a plurality of driving waveform voltages including pulses having different pulse widths is applied to the electromechanical converter And measuring the velocity of the droplet ejected from the droplet ejection head by applying the voltage, and determining the pulse width of the driving waveform determined according to the measured droplet velocity and the pulse width of the plurality of driving waveforms. of the damping constant of the damping curve representing the change in velocity of the droplets to changes, calculated as the attenuation constant of the pressure change with respect to time change, the larger the calculated damping constant, the electromechanical transducer As the voltage variation of the reverberation adjustment portion in the driving waveform of the voltage to be pressurized becomes large, it is characterized by adjusting the drive waveform.

  According to the first invention and the second invention, each of a plurality of driving waveform voltages composed of pulses having different pulse widths is applied to the electromechanical converter, and each voltage of the plurality of driving waveforms is applied by voltage application. The speed of the droplet discharged from the droplet discharge head is measured. Here, as the pulse width of the voltage drive waveform increases and the interval between the falling edge and the rising edge of the pulse increases, the measured droplet velocity decreases.

Then, the damping constant of the damping curve representing the change in velocity of the droplets with respect to a change in the pulse width determined driving waveforms in accordance with the measured pulse widths of the speed and the plurality of driving waveforms of the droplets, the pressure change with respect to time change Is calculated as an attenuation constant. Then, as the calculated attenuation constant is larger, the drive waveform is adjusted so that the amount of voltage change of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical converter becomes larger.

Therefore, the voltage of a plurality of drive waveforms with different pulse widths is applied to the electromechanical transducer, the velocity of the ejected droplet is measured, and the attenuation representing the change in the droplet velocity with respect to the change in the pulse width of the drive waveform By calculating the attenuation constant based on the curve, the attenuation constant of the droplet discharge head can be easily inspected. In addition, the drive waveform of the voltage applied to the droplet discharge head can be adapted to the attenuation constant of the droplet discharge head.

  The calculating means according to the first aspect of the invention calculates the velocity of a droplet ejected by applying a voltage having a driving waveform having a pulse width PWa as Va and the velocity of a droplet ejected by applying a voltage having a driving waveform having a pulse width PWb. When the velocity of a droplet ejected by applying a voltage having a drive waveform of Vb and pulse width PWc is Vc, the attenuation constant D of the attenuation curve can be calculated so as to satisfy the following equation.

PWa <PWb <PWc
D = [Ln (Va−Vc) −Ln (Vb−Vc)] / (PWb−PWa)
However, Ln is a natural logarithm.

According to a third aspect of the present invention, there is provided a droplet discharge head inspection apparatus comprising: a pressure chamber filled with a liquid; and an electromechanical converter that changes the pressure in the pressure chamber according to an applied voltage; A droplet discharge head inspection apparatus that inspects a droplet discharge head that discharges a droplet in response to a pressure change, and applies each of a plurality of driving waveform voltages composed of pulses having different pulse widths to the electromechanical converter. An applying means for measuring, a drop volume measuring means for measuring a volume of a droplet discharged from the droplet discharge head by voltage application of the applying means, a volume of the droplet measured by the drop volume measuring means, and the plurality the damping constant of the damping curve representing a change in volume of the droplet with respect to a change in the pulse width of the drive waveform determined according to the pulse width of the drive waveform, calculated as the attenuation constant of the pressure change with respect to time change Calculation means for, the larger the damping factor calculated by the calculating means, as the voltage variation of the reverberation adjustment portion in the driving waveform of the voltage applied to the electromechanical transducer is increased, the drive waveform adjustment And an attenuation constant drive waveform adjusting means .

According to a fourth aspect of the present invention, there is provided a droplet discharge head inspection method comprising: a pressure chamber filled with a liquid; and an electromechanical converter that changes the pressure in the pressure chamber according to an applied voltage; A droplet discharge head inspection method for inspecting a droplet discharge head that discharges a droplet in response to a pressure change, wherein each of a plurality of driving waveform voltages including pulses having different pulse widths is applied to the electromechanical converter And measuring the volume of the droplet ejected from the droplet ejection head by applying the voltage, and the pulse width of the driving waveform determined according to the measured volume of the droplet and the pulse width of the plurality of driving waveforms. the damping constant of the damping curve representing a change in volume of the droplet with respect to the changes, was calculated as the attenuation constant of the pressure change with respect to time change, the larger the calculated damping constant, the electromechanical transducer As the voltage variation of the reverberation adjustment portion in the driving waveform of the voltage to be pressurized becomes large, it is characterized by adjusting the drive waveform.

  According to the third invention and the fourth invention, each of a plurality of driving waveform voltages composed of pulses having different pulse widths is applied to the electromechanical converter, and the droplets ejected from the droplet ejection head by voltage application Measure the volume.

Then, the damping constant of the damping curve representing the change in the volume of the droplet with respect to a change in the pulse width of the drive waveform determined according to the measured pulse width of the volume and a plurality of driving waveforms of the droplets, the pressure change with respect to time change Is calculated as an attenuation constant. Then, as the calculated attenuation constant is larger, the drive waveform is adjusted so that the amount of voltage change of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical converter becomes larger.

Therefore, the voltage of the drive waveform with different pulse widths is applied to the electromechanical transducer, and the volume of the ejected droplet is measured, and the attenuation curve representing the change in the volume of the droplet with respect to the change in the pulse width of the drive waveform Based on this, the attenuation constant of the droplet discharge head can be easily inspected by calculating the attenuation constant. In addition, the drive waveform of the voltage applied to the droplet discharge head can be adapted to the attenuation constant of the droplet discharge head.

  The calculating means according to the third aspect of the present invention is that Qa represents the volume of a droplet ejected by applying a voltage having a driving waveform with a pulse width PWa, Qb represents the volume of a droplet ejected by applying a voltage having a driving waveform having a pulse width PWb, When the volume of a droplet ejected by applying a voltage having a drive waveform with a pulse width PWc is Qc, the attenuation constant D of the attenuation curve can be calculated so as to satisfy the following equation.

PWa <PWb <PWc
D = [Ln (Qa−Qc) −Ln (Qb−Qc)] / (PWb−PWa)
Further, the drive waveform can be a rectangular waveform. Thereby, the circuit cost of the circuit for generating the drive waveform can be kept small.

  In the above drive waveform, the pulse rise time and fall time can be set to ½ or less of the natural period of the pressure change. Thereby, the pressure change can be efficiently generated by the rising and falling of the pulse.

  The plurality of drive waveforms include a drive waveform whose pulse width is approximately half of the natural period of the pressure change, a drive waveform whose pulse width is approximately 3/2 of the natural period, and a pulse width whose natural period is the natural period. And a driving waveform that is four times or more.

  The plurality of drive waveforms include a drive waveform whose pulse width is approximately half of the natural period of the pressure change, a drive waveform whose pulse width is approximately 3/2 of the natural period, and a pulse width whose natural period is the natural period. In addition, it is possible to include a drive waveform in which the pulse fall time is ½ or more of the natural period.

  In addition, the droplet discharge head inspection apparatus according to the above invention may further include a natural period measuring unit that measures a natural period of pressure change. Thereby, it is possible to perform inspection with high accuracy by measuring the natural period before calculating the attenuation constant of the pressure change. The droplet discharge head inspection apparatus further includes a natural period driving waveform adjusting unit that adjusts a driving waveform of a voltage applied to the electromechanical transducer based on the natural period measured by the natural period measuring unit. Can do. Thereby, the drive waveform of the voltage applied to the droplet discharge head can be adapted to the natural period of the droplet discharge head.

  Further, the electromechanical transducer can be a piezo actuator. Thereby, it is possible to control the ejection of droplets by the droplet ejection head with high accuracy.

  As described above, according to the droplet discharge head inspection apparatus and the droplet discharge head inspection method of the present invention, the voltage of the drive waveform having a different pulse width is applied to the electromechanical converter, and the droplets discharged By simply measuring the velocity or volume and calculating the attenuation constant based on the attenuation curve representing the change in the velocity or volume of the droplet with respect to the change in the pulse width of the drive waveform, the attenuation constant of the droplet discharge head can be easily inspected. The effect of being able to be obtained is obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where an attenuation constant of an ink jet recording head used in an ink jet recording apparatus is inspected will be described.

  As shown in FIG. 1, the head inspection system 10 according to the first embodiment includes an inkjet recording head 12 that ejects ink droplets, and a drive waveform generation circuit that generates a drive waveform of a voltage applied to the inkjet recording head 12. 14, a droplet speed measuring unit 16 that measures the speed of the ink droplets ejected from the inkjet recording head 12, and a computer 18 for controlling the drive waveform generating circuit 14 and the droplet speed measuring unit 16.

  The droplet speed measurement unit 16 measures the time for which the ink droplet passes through a predetermined position by stroboscopic observation, laser irradiation, or the like.

  The computer 18 includes a ROM 20 that stores various programs including parameters of an inspection processing routine, which will be described later, parameters, and the like, a CPU 22 that executes the various programs, a RAM 24 that is used as a work area when the various programs are executed by the CPU 22, and the like. The HDD 26, the display 28, the mouse 30, the keyboard 32, the output interface 34 for connecting to the driving waveform generating circuit 14, and the input for connecting to the drop velocity measuring unit 16 are stored. An output interface 36 and an input / output bus 38 for connecting them to each other are provided.

  The drive waveform generation circuit 14 generates a predetermined rectangular waveform drive waveform voltage having a high level and a low level based on the waveform signal indicating the waveform data from the computer 18, and applies it to the inkjet recording head 12.

  The method of ejecting ink droplets from the nozzles of the inkjet recording head 12 is a method of pressurizing the pressure chamber with a piezo actuator. This method has significant advantages over the TIJ (thermal ink jet) method because it can control the generation of satellites and mist by controlling the voltage applied to the reverberation pressure change in the pressure chamber immediately after ejecting ink droplets. It has become.

  As shown in FIG. 2, the ink jet recording head 12 includes an ink tank 52, a supply path 54, a pressure chamber 56, a nozzle 58, and a piezo actuator 60 as an electromechanical transducer.

  The ink tank 52 is filled with ink, and the ink filled in the ink tank 52 is filled into the pressure chamber 56 via the supply path 54, and the ink is supplied to the nozzle 58 communicating with the pressure chamber 56.

  A part of the wall surface of the pressure chamber 56 is composed of a diaphragm 56A, and the diaphragm 56A is provided with a piezo actuator 60. The diaphragm 56A is deformed and vibrated by the piezo actuator 60, so that the pressure in the pressure chamber 56 is increased. Change occurs. That is, the ink filled in the pressure chamber 56 is ejected as an ink droplet from the nozzle 58 by the pressure change generated by the vibration of the piezo actuator 60, and the ink is supplied from the ink tank 52 to the pressure chamber 56 through the supply path 54. It is to be replenished.

  The nozzles 58 are, for example, a plurality of recording heads arranged in the recording paper width direction, thereby recording an image in the recording paper width direction, and moving the recording paper and the recording head relative to each other to record the image on the recording paper. Can be recorded.

Next, a change in pressure in the pressure chamber 56 of the inkjet recording head 12 will be described. In the ink jet recording head 12 used in this embodiment, when a voltage consisting of one pulse as shown in FIG. 3A is applied to the piezo actuator 60, the pressure chamber 56 is expanded at the falling edge of the pulse, The pressure chamber 56 is contracted at the rising edge. That is, as shown in FIG. 3B, a pressure change occurs in the pressure chamber 56 at the falling edge of the pulse, and after returning to the normal pressure, the pressure returns to the normal pressure. When the pulse width is equal to ½ of the natural period of the pressure change, the pulse rises when the pressure chamber 56 returns to the normal pressure, the pressure change in the pressure chamber 56 is generated, the pressure changes are superimposed, and the pressure Rises and then returns to normal pressure. Thereafter, this pressure vibration remains, and after the pressure in the pressure chamber 56 drops below the normal pressure, the pressure returns to the normal pressure, then rises above the normal pressure, returns to the normal pressure, and this pressure change is repeated while being attenuated. . At this time, the amplitude of the waveform representing the pressure change attenuates as a function of time t in the form of e ⁻ β ^t (e is the base of natural logarithm), and the coefficient β of this function becomes the attenuation constant of the pressure change.

  Next, the operation of the head inspection system 10 according to the first embodiment will be described.

  First, when the droplet velocity measuring unit 16 is installed at a predetermined position so that the passage time of the ink droplets ejected by the inkjet recording head 12 to be inspected can be measured, the inspection processing routine shown in FIG. Executed.

  In step 100, a waveform signal is output to the drive waveform generation circuit 14 so as to apply a drive waveform voltage composed of pulses as shown in FIG. 5A to the piezo actuator 60 of the inkjet recording head 12. Here, a plurality of waveform signals are output while changing the pulse width of the drive waveform of the applied voltage so as to gradually increase. At the same time, the speed of the ink droplets ejected from the inkjet recording head 12 is measured based on the passage time measured by the droplet speed measuring unit 16. For example, when an ink droplet is ejected by applying a voltage to the piezo actuator 60, the droplet speed measurement unit 16 performs strobe shooting or laser irradiation, and measures the passing time of the ink droplet at a predetermined position. The speed of the ink droplet is measured by the passage time and the distance of the section where the passage time is measured.

  Here, as shown in FIG. 5B, assuming that the pulse width is PW and the natural period (Helmholtz oscillation period) of the pressure change of the ink jet recording head 12 is Tc, an ink droplet when PW = 1/2 · Tc. Therefore, Tc = 2 · PWmax, where PWmax is the pulse width at which the ink droplet speed is maximum.

  Accordingly, in step 102, the pulse width PWmax that maximizes the ink droplet speed is obtained from the measured ink droplet velocities, and the natural period Tc is calculated by the above-described equation.

  Then, in step 104, based on the calculated natural period Tc, a voltage having a rectangular driving waveform composed of pulses having a pulse width of 1/2 · Tc as shown in FIG. 6A is applied. The waveform signal is output to the drive waveform generation circuit 14, and the ink droplet velocity is measured by the droplet velocity measuring unit 16. Next, in step 106, a waveform signal for applying a rectangular drive waveform voltage composed of pulses having a pulse width of 3/2 · Tc as shown in FIG. In step S108, the ink droplet velocity is measured by the droplet velocity measuring unit 16, and in step 108, a rectangular waveform driving waveform composed of pulses having a pulse width of 4 · Tc as shown in FIG. A waveform signal for applying a voltage is output to the drive waveform generation circuit 14, and the ink droplet velocity is measured by the droplet velocity measuring unit 16. The rise time and the fall time of the above pulse are ½ or less of the natural period Tc of the pressure change in order to cause a pressure change efficiently by the rise and fall of the pulse.

  Here, when the pulse width is ½ · Tc, the pulse rises in accordance with the phase of the pressure change caused by the fall of the pulse, so that the generated pressure change becomes large. Further, when the pulse width is 3/2 · Tc, when the pressure change generated by the fall of the pulse starts to attenuate, the pulse rises in accordance with the phase of the pressure change, so that the attenuated pressure change becomes large. . Further, when the pulse width is 4 · Tc or more, the pressure change generated by the fall of the pulse is attenuated, and after the pressure change disappears, the pulse rises to generate a small pressure change.

  As described above, since the pressure change generated when the pulse width is 1/2 · Tc is maximized, the speed of the ink droplet is the fastest, and the pressure change generated when the pulse width is 4 · Tc is minimized. Therefore, the speed of the ink droplet is the slowest.

  In step 110, an attenuation curve indicating a change in the speed of the ink droplet with respect to a change in the pulse width as shown in FIG. 7 according to the speed of the ink droplet measured in steps 104 to 108 and the pulse width of the driving waveform is shown. The attenuation constant D of this attenuation curve is calculated based on the following equation.

D = [Ln (Va−Vc) −Ln (Vb−Vc)] / (PWb−PWa)
Here, the pulse width in Step 104 is PWa, the ink droplet velocity is Va, the pulse width in Step 106 is PWb, the ink droplet velocity is Vb, the pulse width in Step 108 is PWc, the ink droplet velocity is Vc, and Ln Is the natural logarithm. In addition, the attenuation constant D of the attenuation curve is equal to the attenuation constant of the waveform representing the pressure change in the inkjet recording head 12, so the calculated attenuation constant D becomes the attenuation constant of the inkjet recording head 12.

  In the next step 112, based on the natural period Tc calculated in step 102 and the attenuation constant D calculated in step 110, it becomes a reference for the drive waveform of the voltage to be applied to the piezo actuator 60 of the inkjet recording head 12. The reference driving waveform is adjusted and the inspection processing routine is terminated. For example, when the standard natural period and the standard attenuation constant are determined in advance and the standard natural period and the calculated natural period Tc are different as shown in FIG. 8, the reference drive waveform is expanded or contracted in the time axis direction. And adjust. At this time, if the expansion / contraction rate is K, the expansion / contraction rate K is determined by the ratio of the standard natural period and the natural period Tc. When the natural period Tc is large, the reference drive waveform is represented on the time axis based on the expansion / contraction ratio K. When the natural period Tc is small, the reference drive waveform is contracted in the time axis direction based on the expansion / contraction rate K.

  Also, as shown in FIG. 9, when the standard attenuation constant and the calculated attenuation constant D are different, the shape of the reverberation adjusting unit of the reference drive waveform is changed. When the attenuation constant D is large, the voltage change amount V4 in FIG. 9 is increased, and when the attenuation constant D is small, the voltage change amount V4 is decreased and the voltage of the drive waveform is applied to the piezo actuator 60. In addition, the reverberation change of the pressure change has a predetermined change amount so that the generation of satellites and mists can be prevented.

  In the above description, the case where the reference drive waveform is adjusted based on the calculated natural period and the value of the attenuation constant has been described as an example. However, a plurality of reference drive waveforms determined in advance for the inkjet recording head 12 are used. An optimal reference drive waveform may be selected from the above. For example, a plurality of reference drive waveforms and ranks are associated with each other, and a rank indicating an optimum reference drive waveform for the ink jet recording head 12 is assigned. A rank may be attached, and the attached rank may be corrected based on the calculated natural period and attenuation constant.

  As described above, according to the head inspection system according to the first embodiment, the voltages of a plurality of drive waveforms having different pulse widths are applied to the piezo actuator, and the speed of the ink droplets ejected from the ink jet recording head. The attenuation constant of the inkjet recording head can be easily inspected by calculating the attenuation constant based on the attenuation curve representing the change in the speed of the ink droplet with respect to the change in the pulse width of the drive waveform.

  Further, since the attenuation constant can be inspected by the same device as that used in the conventional method for measuring the natural period, it is not necessary to prepare a new device, and the cost can be reduced.

  In addition, by making the drive waveform a rectangular waveform, the circuit cost of the circuit that generates the drive waveform can be reduced.

  Further, based on the calculated attenuation constant, the drive waveform of the voltage applied to the piezo actuator is adjusted so that the pressure change has a predetermined amount of reverberation change, and the drive of the voltage applied to the piezo actuator of the ink jet recording head is adjusted. The waveform can be adapted to the attenuation constant of the inkjet recording head.

  In addition, by measuring the natural period of the pressure change before calculating the attenuation constant of the pressure change, the pulse width at the time of measuring the attenuation constant can be optimized (1/2 of the natural period, 3/2, etc.). Therefore, the attenuation constant can be inspected with high accuracy.

  Further, the drive waveform of the voltage applied to the piezo actuator can be adjusted based on the measured natural period, and the drive waveform of the voltage applied to the piezo actuator can be adapted to the natural period of the ink jet recording head.

  Further, by using a piezo actuator for the ink jet recording head, it is possible to control ejection of ink droplets by the ink jet recording head with high accuracy.

  In the above embodiment, the case where the natural period and the attenuation constant are calculated has been described as an example. However, the ejection efficiency of the ink jet recording head may be calculated based on the measured speed of the ink droplet. Good. In this case, as shown in FIG. 10, the voltage change amount of each voltage change process of the reference drive waveform is increased or decreased at a substantially constant ratio in the voltage axis direction. When the discharge efficiency is high, the reference drive waveform is adjusted so that the voltage change amount is small. When the discharge efficiency is low, the reference drive waveform is adjusted so that the voltage change amount is large.

  Next, a second embodiment will be described. In addition, about the part similar to 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. As shown in FIG. 11, the head inspection system 210 according to the second embodiment is provided with a droplet volume measuring unit 216 that measures the volume of ink droplets ejected from the inkjet recording head 12. This is different from the embodiment.

  The droplet volume measuring unit 216 captures an image of the flying ink droplet, analyzes the captured image, or measures the diameter of a recording dot formed on a specific recording medium, and calculates the volume of the ink droplet. It comes to measure.

  Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The computer 18 outputs a waveform signal for applying a drive waveform voltage having a pulse width of 1/2 · Tc to the drive waveform generation circuit 14 as shown in FIG. The measurement unit 216 measures the volume of the ink droplet. Further, a waveform signal for applying a voltage having a drive waveform having a pulse width of 3/2 · Tc as shown in FIG. 12B is output to the drive waveform generation circuit 14 and a drop volume measuring unit. 216 measures the speed of the ink droplet, and applies a voltage having a drive waveform with a pulse width of 3/2 · Tc and a pulse fall time of approximately Tc, as shown in FIG. In addition to outputting a waveform signal to the drive waveform generation circuit 14, the droplet volume measuring unit 216 measures the volume of the ink droplet.

  Here, when the pulse fall time is approximately Tc, the pressure change generated by the pulse fall is very small. Therefore, when the pulse rises in a state where there is no pressure change, a small pressure change occurs.

  Then, an attenuation curve indicating the change in the volume of the ink droplet with respect to the change in the pulse width as shown in FIG. 13 is obtained according to the volume of the ink droplet measured as described above and the pulse width of the drive waveform, and the attenuation constant of this attenuation curve is obtained. D is calculated based on the following equation. Note that the measurement result of the drive waveform in which the pulse width is 3/2 · Tc and the pulse fall time is approximately Tc is recorded in the attenuation curve at a position where the pulse width is 4 · Tc or more. Keep it.

D = [Ln (Qa−Qc) −Ln (Qb−Qc)] / (PWb−PWa)
Here, the pulse width in FIG. 12A is PWa, the volume of the ink droplet is Qa, the pulse width in FIG. 12B is PWb, the volume of the ink droplet is Qb, the pulse width in FIG. 13C is PWc, Let Qc be the volume of the ink droplet, and Ln is a natural logarithm.

  Since the attenuation constant D of this attenuation curve is equal to the attenuation constant of the waveform representing the pressure change, the calculated attenuation constant D is the attenuation constant of the inkjet recording head 12.

  As described above, according to the head inspection system according to the second embodiment, the voltages of the plurality of drive waveforms having different pulse widths are applied to the piezo actuator and the volume of the ink droplets ejected from the ink jet recording head. The attenuation constant of the inkjet recording head can be easily inspected by calculating the attenuation constant based on the attenuation curve representing the change in the volume of the ink droplet with respect to the change in the pulse width of the drive waveform.

It is the schematic which shows the structure of the head test | inspection system based on the 1st Embodiment of this invention. 1 is a cross-sectional view illustrating a configuration of an ink jet recording head according to a first embodiment of the present invention. (A) It is a figure which shows the voltage applied to the piezoelectric actuator which concerns on the 1st Embodiment of this invention, (B) It is a figure which shows the pressure change in a pressure chamber. It is a flowchart which shows the content of the inspection processing routine of the computer which concerns on the 1st Embodiment of this invention. (A) The figure which shows the drive waveform of the voltage applied to a piezo actuator when measuring a natural period, (B) The graph which shows the change of the speed of an ink drop with respect to the change of a pulse width. FIG. 4 is a diagram illustrating a drive waveform of a voltage applied to a piezo actuator when measuring an attenuation constant in the head inspection system according to the first embodiment of the present invention. 5 is a graph showing an attenuation curve representing a change in ink droplet velocity with respect to a change in pulse width in the head inspection system according to the first embodiment of the present invention. It is a figure which shows the example of the reference | standard drive waveform adjusted based on the natural period. It is a figure which shows the example of the reference | standard drive waveform adjusted based on the attenuation constant. It is a figure which shows the example of the reference | standard drive waveform adjusted based on discharge efficiency. It is the schematic which shows the structure of the head test | inspection system based on the 2nd Embodiment of this invention. FIG. 10 is a diagram showing a drive waveform of a voltage applied to a piezo actuator when measuring an attenuation constant in a head inspection system according to a second embodiment of the present invention. 6 is a graph showing an attenuation curve representing a change in volume of an ink droplet with respect to a change in pulse width in a head inspection system according to a second embodiment of the present invention.

Explanation of symbols

10, 210 Head inspection system 12 Inkjet recording head 14 Drive waveform generation circuit 16 Drop velocity measurement unit 18 Computer 20 ROM
22 CPU
24 RAM
26 HDD
56 Pressure chamber 58 Nozzle 60 Piezo actuator 216 Drop volume measuring unit

Claims (13)

A pressure chamber filled with a liquid, and an electromechanical transducer that changes the pressure in the pressure chamber according to an applied voltage, and inspects a droplet discharge head that discharges a droplet according to the pressure change A droplet discharge head inspection device
Applying means for applying to the electromechanical converter each of a plurality of driving waveform voltages composed of pulses having different pulse widths;
A droplet speed measuring means for measuring a speed of a droplet discharged from the droplet discharge head by voltage application of the applying means;
An attenuation constant of an attenuation curve representing a change in the velocity of the droplet with respect to a change in the pulse width of the driving waveform determined according to the velocity of the droplet measured by the droplet velocity measuring means and the pulse width of the plurality of driving waveforms. Calculating means for calculating as an attenuation constant of the pressure change with respect to time change;
The attenuation constant drive waveform for adjusting the drive waveform so that the amount of voltage change of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical converter increases as the attenuation constant calculated by the calculation unit increases. Adjusting means;
A droplet discharge head inspection apparatus including: The calculation means is configured such that the velocity of a droplet ejected by applying a voltage having a driving waveform with a pulse width PWa is Va, the velocity of a droplet ejected by applying a voltage having a driving waveform having a pulse width PWb is Vb, and driving with a pulse width PWc. The droplet discharge head inspection apparatus according to claim 1, wherein an attenuation constant D of the attenuation curve is calculated so as to satisfy the following expression, where Vc is a velocity of a droplet discharged by applying a waveform voltage.
PWa <PWb <PWc
D = [Ln (Va−Vc) −Ln (Vb−Vc)] / (PWb−PWa)
However, Ln is a natural logarithm. A pressure chamber filled with a liquid, and an electromechanical transducer that changes the pressure in the pressure chamber according to an applied voltage, and inspects a droplet discharge head that discharges a droplet according to the pressure change A droplet discharge head inspection device
Applying means for applying to the electromechanical converter each of a plurality of driving waveform voltages composed of pulses having different pulse widths;
Drop volume measuring means for measuring the volume of a droplet discharged from the droplet discharge head by voltage application of the applying means;
An attenuation constant of an attenuation curve representing a change in the volume of the droplet with respect to a change in the pulse width of the driving waveform determined according to the volume of the droplet measured by the droplet volume measuring means and the pulse width of the plurality of driving waveforms. Calculating means for calculating as an attenuation constant of the pressure change with respect to time change;
The attenuation constant drive waveform for adjusting the drive waveform so that the amount of voltage change of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical converter increases as the attenuation constant calculated by the calculation unit increases. Adjusting means;
A droplet discharge head inspection apparatus including: The calculating means Qa is the volume of a droplet ejected by applying a voltage having a driving waveform with a pulse width PWa, Qb is the volume of a droplet ejected by applying a voltage having a driving waveform having a pulse width PWb, and the driving has a pulse width PWc. 4. The droplet discharge head inspection apparatus according to claim 3, wherein the attenuation constant D of the attenuation curve is calculated so as to satisfy the following expression, where Qc is the volume of the droplet discharged by applying the waveform voltage.
PWa <PWb <PWc
D = [Ln (Qa−Qc) −Ln (Qb−Qc)] / (PWb−PWa)
However, Ln is a natural logarithm.   The liquid droplet ejection head inspection apparatus according to claim 1, wherein the driving waveform is a rectangular waveform.   6. The droplet discharge head inspection according to claim 1, wherein the drive waveform has a rise time and a fall time of the pulse that are ½ or less of a natural period of the pressure change. apparatus.   The plurality of driving waveforms include a driving waveform having a pulse width that is approximately ½ of the natural period of the pressure change, a driving waveform having a pulse width that is approximately 3/2 of the natural period, and a pulse width that is the natural period. The droplet discharge head inspection apparatus according to claim 1, further comprising a drive waveform that is four times or more of the drive waveform.   The plurality of driving waveforms include a driving waveform having a pulse width that is approximately ½ of the natural period of the pressure change, a driving waveform having a pulse width that is approximately 3/2 of the natural period, and a pulse width that is the natural period. 6. The droplet discharge head inspection apparatus according to claim 1, further comprising: a drive waveform having a pulse falling time that is equal to or greater than ½ of the natural period.   The liquid droplet ejection head inspection apparatus according to claim 1, further comprising a natural period measuring unit that measures a natural period of the pressure change. The liquid droplet ejection head inspection according to claim 9 , further comprising a natural period driving waveform adjusting unit that adjusts a driving waveform of a voltage applied to the electromechanical converter based on the natural period measured by the natural period measuring unit. apparatus. The electromechanical transducer according to claim 1 to claim 1 0 droplet discharge head inspection apparatus according to any one of a piezoelectric actuator. A pressure chamber filled with a liquid, and an electromechanical transducer that changes the pressure in the pressure chamber according to an applied voltage, and inspects a droplet discharge head that discharges a droplet according to the pressure change A droplet discharge head inspection method for
Applying each of a plurality of driving waveform voltages composed of pulses having different pulse widths to the electromechanical converter,
Measure the speed of the droplets ejected from the droplet ejection head by applying the voltage,
An attenuation constant of an attenuation curve representing a change in the velocity of the droplet with respect to a change in the pulse width of the driving waveform determined according to the measured velocity of the droplet and the pulse width of the plurality of driving waveforms, Calculated as the damping constant of pressure change,
The droplet is characterized in that the drive waveform is adjusted such that the larger the calculated attenuation constant is, the larger the voltage change amount of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical transducer is. Discharge head inspection method. A pressure chamber filled with a liquid, and an electromechanical transducer that changes the pressure in the pressure chamber according to an applied voltage, and inspects a droplet discharge head that discharges a droplet according to the pressure change A droplet discharge head inspection method for
Applying each of a plurality of driving waveform voltages composed of pulses having different pulse widths to the electromechanical converter,
Measure the volume of the droplet discharged from the droplet discharge head by applying the voltage,
An attenuation constant of an attenuation curve representing a change in the volume of the droplet with respect to a change in the pulse width of the driving waveform determined according to the measured volume of the droplet and a pulse width of the plurality of driving waveforms, Calculated as the damping constant of pressure change,
The droplet is characterized in that the drive waveform is adjusted such that the larger the calculated attenuation constant is, the larger the voltage change amount of the reverberation adjusting unit in the drive waveform of the voltage applied to the electromechanical transducer is. Discharge head inspection method.

Images