JP2009262398A - Fluid viscosity measuring system, printing head, and fluid viscosity measurement program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a viscosity of a fluid which fills a discharge nozzle without wasting the fluid. <P>SOLUTION: A first equivalent circuit exhibiting electric characteristics of a piezoelectric element, and a second equivalent circuit exhibiting acoustic characteristics in which a viscosity in a space chamber is made one of factors, are assumed. A resistance at the time of resonance of a load including a resistance, a capacity, and an inductance, generated in a flow passage itself, or in the flow passage and a discharge nozzle, in the first equivalent circuit, is extracted, the extracted resistance is replaced with an acoustic resistance of the second equivalent circuit, and the viscosity is calculated from the second equivalent circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluid viscosity measurement system, a print head, and a fluid viscosity measurement program.

  Ink jet heads (droplet discharge heads) change the discharge characteristics due to changes in ink viscosity (viscosity of fluids) and affect image quality. For example, maintenance such as dummy jet or suction is performed as a countermeasure against thickening due to water vapor from the tip of the discharge nozzle, and this maintenance is frequently performed at time intervals that allow for a safety factor.

On the other hand, whether or not there is a missing dot (pixel loss) in the image formed by the image forming process is detected, and when a missing dot is detected, the cause of the ejection abnormality is identified and an appropriate response according to the cause A configuration for executing recovery processing has been proposed (see Patent Document 1).
JP 2004-276274 A

  An object of the present invention is to obtain a fluid viscosity measurement system, a print head, and a fluid viscosity measurement program that can measure the viscosity of a fluid filled in a discharge nozzle without wasting fluid.

  The invention described in claim 1 includes a piezoelectric element, a diaphragm in surface contact with the piezoelectric element, and vibration generating means for applying a voltage having a predetermined frequency to the piezoelectric element to vibrate the diaphragm. A fluid discharge module configured to apply pressure to a space chamber in which a wall surface of the unit is configured by the diaphragm and a discharge nozzle is provided in another part and discharge the fluid filled in the space chamber from the discharge nozzle; In the structure in which the space chamber includes a pressure chamber to which the pressure is applied, and a flow path through which a fluid flows by the pressure applied to the pressure chamber, and the fluid flowing through the flow path protrudes from the discharge nozzle. Equivalent circuit assumption means for assuming a first equivalent circuit indicating electrical characteristics of the element and a second equivalent circuit indicating acoustic characteristics in which the viscosity in the space is one of the elements; and Previous in equivalent circuit A resistance component extracting means for extracting a resistance component at the time of resonance of a load including resistance, capacity, and inductance generated by the channel and the discharge nozzle, and a resistance component extracted by the resistance component extracting unit The fluid viscosity measuring system has a fluid viscosity calculating means for calculating the viscosity of the fluid based on the second equivalent circuit instead of the acoustic resistance of the equivalent circuit.

  The invention described in claim 2 includes a piezoelectric element, a diaphragm in surface contact with the piezoelectric element, and vibration generating means for vibrating the diaphragm by applying a voltage having a predetermined frequency to the piezoelectric element. A fluid discharge module configured to discharge pressure from the discharge nozzle by applying pressure to a space chamber in which a wall surface of the unit is configured by the diaphragm and a discharge nozzle is provided in another part of the space chamber; The viscosity η of the fluid in the space chamber is converted to an acoustic differential equation based on acoustic engineering using acoustic resistance r, the minimum cross-sectional diameter D1, the maximum cross-sectional diameter D2 of the flow channel in the space chamber, and the length le of the flow channel as parameters. When obtaining by fitting, the fluid discharge operation in the fluid discharge module is expressed as an equivalent circuit using a resistance R, a reactance L, and a capacitance C, whereby the resistance R, Based on the correlation among the reactance L, the capacitance C, the frequency f, and the voltage / current phase difference θ, a resistance R under the frequency f at which the phase difference θ in the equivalent circuit reaches a peak value is obtained. The fluid viscosity measuring system includes fluid viscosity calculating means for calculating the fluid viscosity η from the acoustic differential equation by substituting the resistance R on the equivalent circuit into the acoustic resistance r.

  The invention according to claim 3 is the invention according to claim 2, wherein the acoustic differential equation is represented by the following expression (1).

  The invention according to claim 4 is the invention according to claim 2 or claim 3, wherein the fluid ejection module is operated to obtain measured value data of characteristics indicating a relationship between a frequency and a phase difference, and the measured value The correction of the calculation formula of the fluid viscosity calculation unit is repeated until the sum of the square sum of the difference between the value data and the calculation result in the fluid viscosity calculation unit becomes equal to or less than a predetermined threshold value.

  The invention according to claim 5 is the invention according to any one of claims 2 to 4, wherein the frequency f at which the phase difference θ is the peak value is a fixed value set in advance. .

  The invention according to claim 6 is the invention according to any one of claims 2 to 5, further comprising a closing means for closing the discharge nozzle, for calculating in the fluid viscosity measuring means. Among the elements, the elements generated by discharging the fluid from the discharge nozzle are eliminated.

  A seventh aspect of the present invention provides the viscosity information obtained by the fluid viscosity calculating means in the first aspect of the first to sixth aspects of the present invention.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the fluid viscosity change is within a predetermined allowable range based on the viscosity information obtained by the fluid computing means. The prediction is corrected so as to converge.

  The invention described in claim 9 is a print head on which the fluid viscosity measuring device according to any one of claims 1 to 8 is mounted.

  A tenth aspect of the present invention includes a piezoelectric element, a diaphragm in surface contact with the piezoelectric element, and vibration generating means for vibrating the diaphragm by applying a voltage having a predetermined frequency to the piezoelectric element. The fluid in the fluid discharge module is configured to apply pressure to the space chamber in which the wall surface of the section is configured by the diaphragm and the discharge nozzle is provided in the other part to discharge the fluid filled in the space chamber from the discharge nozzle When the viscosity of the space is measured, the space chamber includes a pressure chamber to which the pressure is applied, and a flow path through which the fluid flows with the pressure applied to the pressure chamber, and the fluid flowing through the flow path is the discharge nozzle. In the structure protruding from the above, a first equivalent circuit showing the electrical characteristics of the piezoelectric element and a second equivalent circuit showing an acoustic characteristic in which the viscosity in the space chamber is one of the elements are assumed. In the first equivalent circuit The resistance component at the time of resonance of the load including resistance, capacity, and inductance generated in the channel alone or in the channel and the discharge nozzle is extracted, and the extracted resistance component is extracted as the acoustic resistance component of the second equivalent circuit. Instead, the fluid viscosity measurement program causes a computer to calculate the viscosity based on a second equivalent circuit.

  The invention according to claim 11 is the invention according to claim 10, wherein the first equivalent circuit is expressed as an equivalent circuit using a resistance R, a reactance L, and a capacitance C, whereby the resistance R, Assumed by the reactance L and the capacitance C, the second equivalent circuit includes the viscosity η of the fluid in the space chamber, the acoustic resistance r, the minimum cross-sectional diameter D1, the maximum cross-sectional diameter D2 of the flow channel in the space chamber, the flow channel The length le is assumed.

  According to a twelfth aspect of the present invention, in the invention of the eleventh aspect, a resistance R under the resonance frequency f in the first equivalent circuit is obtained, and the resistance R of the first equivalent circuit is calculated. The viscosity of the fluid is calculated by substituting the second equivalent circuit into the acoustic resistance r of the equation (1), which is an acoustic differential equation based on acoustic engineering, which is formulated into a mathematical expression.

  According to invention of Claim 1 and Claim 2, it has the effect that the viscosity of the fluid with which the discharge nozzle was filled can be measured, without wasting a fluid.

  According to the third aspect, the calculation is easier than in the case where the present configuration is not provided.

  According to the fourth and fifth aspects of the invention, the accuracy of the viscosity value to be measured is higher than when the present configuration is not provided.

  According to the sixth aspect of the present invention, the calculation is simpler than the case where the present configuration is not provided.

  According to invention of Claim 7, the change of a viscosity can be recognized rapidly.

  According to invention of Claim 8, the change of a viscosity can be avoided in advance.

  According to the ninth aspect of the invention, there is an effect that the viscosity of the fluid filled in the discharge nozzle can be measured without wasting the fluid.

  According to the tenth to twelfth aspects, the viscosity of the fluid filled in the discharge nozzle can be measured without wasting the fluid.

(First embodiment)
FIG. 1 shows a fluid ejection module 12 provided in an ink jet printer according to the present embodiment.

  As shown in FIG. 1, the fluid discharge module 12 includes a discharge nozzle 40, an ink tank (chamber) 41, a supply path 44 that is a flow path of a space chamber, a pressure chamber 46, and a piezoelectric element 48. In the fluid ejection module 12, a plurality of ejection nozzles 40 each ejecting droplets are arranged in a row or a matrix, and droplets of ink liquid are ejected from the ejection nozzles 40 on the recording paper. The image is recorded.

  An appropriate amount of ink liquid is supplied to the ink tank 41 from an ink cartridge (liquid storage tank) (not shown) and is temporarily stored. The ink tank 41 communicates with a pressure chamber 46 via a supply path (throttle portion) 44, and the pressure chamber 46 communicates with the outside via a discharge nozzle 40.

  Further, a part of the wall surface of the pressure chamber 46 is constituted by a diaphragm 46A, and a piezoelectric element 48 is attached to the diaphragm 46A in surface contact. The piezoelectric element 48 is deformed according to the drive waveform of the alternating voltage (or the voltage in which alternating current and direct current are superimposed) applied by the power supply voltage generator 20, and changes (vibrates) the pressure on the diaphragm 46A. A volume change (shrinkage or expansion) is generated in the pressure chamber 46.

  That is, the ink liquid stored in the ink tank 41 by the pressure wave (vibration wave) of the ink liquid generated by the volume change of the pressure chamber 46 is discharged from the discharge nozzle 40 through the supply path 44 and the pressure chamber 46. It has become. At that time, the ammeter 24 measures the current value at the AC voltage applied by the AC voltage generator 20.

  As shown in FIG. 2, the fluid ejection module 12 includes a switch IC (Integrated Circuit) (hereinafter referred to as SW-IC) 50 that controls voltage application to each piezoelectric element 48, and the viscosity of the ink liquid. Is provided with an inspection apparatus 10 having a measurement function.

  The SW-IC 50 includes a P-channel MOS type (Metal Oxide Semiconductor) field effect transistor (FET) (hereinafter referred to as PMOSFET) 52, an N-channel MOS type field effect transistor (hereinafter referred to as NMOSFET) 54, and Inverter 56, inspection voltage input terminal 58, voltage output terminal 60, control signal input terminal 62, back gate terminal 64A, and back gate terminal 64B are provided.

  In the SW-IC 50 according to the present embodiment, the PMOSFET 52, the NMOSFET 54, the inverter 56, the voltage output terminal 60, and the control signal input terminal 62 are provided for each piezoelectric element 48. In FIG. Only the portion corresponding to the element 48 is shown.

  In the SW-IC 50, only one inspection voltage input terminal 58, a back gate terminal 64A, and a back gate terminal 64B are provided.

  The source of the PMOSFET 52 and the drain of the NMOSFET 54 are connected to the inspection voltage input terminal 58, and the drain of the PMOSFET 52 and the source of the NMOSFET 54 are connected to one electrode of the corresponding piezoelectric element 48 via the voltage output terminal 60. .

  The gate of the PMOSFET 52 is directly connected to the control signal input terminal 62, and the gate of the NMOSFET 54 is connected to the control signal input terminal 62 via the inverter 56.

  Further, the back gate of the PMOSFET 52 is connected to the back gate terminal 64A, and the back gate of the NMOSFET 54 is grounded via the back gate terminal 64B. A voltage of a predetermined voltage level is applied to the back gate terminal 64A from a power supply device (not shown) of the ink jet printer.

  On the other hand, the inspection apparatus 10 includes an AC voltage generator 20, a voltmeter 22, an ammeter 24, a control unit 28, two inspection voltage output terminals 26A and 26B, a display 29A, and an operation panel 29B. ing.

  The AC voltage generator 20 has one terminal connected to the inspection voltage output terminal 26A, the other terminal grounded, and the other terminal connected to the inspection voltage output terminal 26B. The AC voltage generator 20 generates a sinusoidal AC voltage under the control of the control unit 28 and changes the frequency of the generated AC voltage.

  The voltmeter 22 is connected to one terminal and the other terminal of the AC voltage generator 20, and outputs a potential difference signal indicating a potential difference between the terminals to the control unit 28.

  The ammeter 24 is provided on the wiring 27 that connects the other terminal of the AC voltage generator 20 and the inspection voltage output terminal 26B, measures the current flowing through the wiring 27, and indicates the measured current value. The signal is output to the control unit 28.

  As shown in FIG. 3, the control unit 28 in the inspection apparatus 10 includes a CPU (Central Processing Unit) 30 that controls the operation of the entire apparatus, a work area when the CPU 30 executes various processing programs, and the like. RAM (Random Access Memory) 31 used, ROM (Read Only Memory) 32 in which various control programs and various parameters are stored in advance, HDD (Hard Disk Drive) 33 in which various information is stored, and alternating current by AC voltage generator 20 A voltage generation control unit 34 that controls a voltage generation operation, and a control signal output control that controls output of a control signal for selecting a discharge nozzle 40 to be inspected from a plurality of discharge nozzles 40 provided in the fluid discharge module 12 Part 35 The display control unit 36 controls the display of various information such as the inspection result and the operation menu or message on the display 29A, and the operation input detection unit 37 detects the operation on the operation panel 29B.

  In addition, the potential difference signal output from the voltmeter 22 and the current value signal output from the ammeter 24 are input to the control unit 28.

  The CPU 30, RAM 31, ROM 32, HDD 33, voltage generation control unit 34, control signal output control unit 35, display control unit 36, and operation input detection unit 37 are connected to each other via the system bus BUS.

  Therefore, the CPU 30 controls access to the RAM 31, ROM 32, and HDD 33, control of AC voltage generation by the AC voltage generator 20 via the voltage generation controller 34, and control of control signal output from the control signal output controller 35. Control of display of various information such as an operation screen or various messages on the display 29A via the display control unit 36 is performed. Further, the CPU 30 grasps an operation on the operation panel 29B based on the operation information detected by the operation input detection unit 37, and generates an AC voltage based on the potential difference signal and the potential difference signal and the current value signal input from the ammeter 24. A potential difference between both terminals of the device 20 and a current value flowing through the wiring 27 are grasped.

  Here, as described above, the control unit 28 has a measurement function for measuring the viscosity η of the ink liquid filled in the pressure chamber 46 and the like in order to be discharged from the discharge nozzle 40. This viscosity measurement is executed according to a viscosity measurement program stored in advance. Hereinafter, when a voltage is applied to the piezoelectric element 48 (see FIG. 1) and the viscosity of the ink is measured from the voltage-current phase difference. The principle of viscosity measurement in will be described.

  As shown in FIG. 1, when a voltage (AC or DC / AC superimposed voltage) is applied to the piezoelectric element 48, it is regarded as an equivalent circuit composed of the electrical characteristics of the piezoelectric element 48 and the acoustic characteristics of the flow path of the fluid discharge module 12. Measure admittance and phase difference.

  Further, when the ink undergoes a change in physical properties on the surface of the discharge nozzle 40 or the like, a change appears in the measured values of admittance and phase difference, and a change in the viscosity of the ink is detected from these values. Since the viscosity corresponds to the resistance value of the discharge nozzle 40 portion, the change in viscosity is detected by detecting the change in the resistance value of the discharge nozzle 40 portion from the change in phase difference.

  FIG. 4A is an equivalent circuit (hereinafter referred to as “second equivalent circuit”) showing the acoustic characteristics of the fluid ejection module 12.

  FIG. 4B is an equivalent circuit (hereinafter referred to as “first equivalent circuit”) showing the electrical characteristics of the fluid ejection module 12.

  Here, a variable conversion equation between the acoustic characteristic equivalent circuit (second equivalent circuit) in FIG. 4A and the electrical characteristic equivalent circuit (first equivalent circuit) in FIG. It is represented by the following formulas (2) to (4).

  Next, focusing on the acoustic resistance in the second equivalent circuit, “p” in the differential equation (see formula (5)) in the second equivalent circuit showing the acoustic characteristics is the first equivalent circuit showing the electrical characteristics. This corresponds to “e” in the differential equation (see equation (6)) in the circuit.

  In addition, “u” of the differential equation (see equation (5)) in the second equivalent circuit showing the acoustic characteristics is the differential equation (see equation (6)) in the first equivalent circuit showing the electric characteristics. Corresponds to “i”.

p = r · u (5)
e = r _e · i (6)
However,
p: pressure e: voltage u: volume velocity i: current In an equivalent circuit (second equivalent circuit) of acoustic characteristics, a differential equation (acoustic system partial equation) relating to acoustic resistance is expressed by equation (1).

However,
D1: Cross-sectional diameter of the minimum flow path D2: Cross-sectional diameter of the maximum flow path le: Length of the flow path η: Ink viscosity From the relationship between the above acoustic characteristics and electrical characteristics, an equivalent circuit of electrical characteristics (first equivalent circuit) If the resistance component (the supply path 44 (and the discharge nozzle 40 when the discharge nozzle 40 is opened)) can be measured, the viscosity η can be easily calculated by substituting this with an equivalent circuit of acoustic characteristics (second equivalent circuit). It can be seen that it can be obtained.

In order to obtain the resistance in the equivalent circuit of electrical characteristics (first equivalent circuit) (the resistance in the supply path 44 and the discharge nozzle 40), it is necessary to roughly perform the following three processes.
(Embodiment 1) The frequency of the applied power supply is changed (in the present embodiment, a range of 10,000 Hz to 1010000 Hz), and the phase difference between the power supply voltage and current (sampling frequency unit is 2500 Hz) is obtained (FIG. 6). Frequency-phase difference characteristic diagram).

As shown in FIG. 6, the first region 610 on the low frequency region side in the resonating region on the first waveform 600 showing the relationship between the measured frequency and the phase difference, and the high frequency There is a second region 620 on the region side.
(Implementation process 2) A curve fitting process at the resonance position of the frequency-phase difference characteristic is executed.
(Embodiment 3) An equivalent circuit of a resonance point in a relatively low frequency region and a high frequency region is assumed for the power supply frequency.

  Here, FIG. 7 is an equivalent circuit in the low frequency region, and FIG. 8 is an equivalent circuit in the low frequency region.

  Thereafter (after curve fitting), the numerical values of the L1, C1, and R1 components are obtained from the equivalent circuit in the high frequency region, and the numerical values of the L2, R2, L3, and R3 components are obtained from the equivalent circuit in the low frequency region. .

  Note that the electrical equivalent circuit (first equivalent circuit) of the present embodiment is equivalent to FIG. 7 (low frequency region). On the other hand, in the equivalent circuit in the high frequency region, it can be seen that elements common to FIG. 7 are L1, C1, and R1. In the low-frequency equivalent circuit, since the elements (L1, C1, R1) have a minute value, the elements (L1, C1, R1) are identified by the equivalent circuit shown in FIG. 8 and the equivalent circuit shown in FIG. To the same element (L1, C1, R1).

  The viscosity η is obtained by substituting the numerical value of the identified resistance component R3 of the first equivalent circuit into the acoustic resistance r of the acoustic system differential equation (see equation (1)) based on the second equivalent circuit.

However,
D1: Cross-sectional diameter of minimum flow path D2: Cross-sectional diameter of maximum flow path le: Length of flow path η: Ink viscosity (Relationship between resistance and viscosity of electrical equivalent circuit)
FIG. 15 is a frequency-phase difference characteristic diagram when the viscosity η is changed. 15A shows a viscosity η of 3 [mPa · s], FIG. 15B shows a viscosity η of 5 [mPa · s], and FIG. 15 (c9 shows a viscosity η of 10 [mPa · s]. 15 (d) shows the case where the viscosity η is 20 [mPa · s].

  As shown in FIGS. 15 (a) to 15 (d), it can be seen that the change in the resistance (R2 or R3) of the resonance frequency has a correlation with the viscosity η.

  The operation of the present embodiment will be described below with reference to the flowchart of FIG.

  In FIG. 5, it can be classified into three steps.

  The first step (see the dashed line frame 510 in FIG. 5) is a pre-measurement preparation step, the second step (see the dashed line frame 540 in FIG. 5) is the measurement and viscosity output step, and the third step (the dashed line frame 560 in FIG. 5). Reference) is a post-processing step.

(First step 510)
In step 512, the measurement liquid is filled. Specifically, ink (liquid) is filled from the ink cartridge into the ink tank 41 (see FIG. 1) in order to measure the viscosity. When ink is filled in the ink tank 41 (see FIG. 1), the process proceeds to step 514.

  In step 514, normal filling such as suction is performed. Specifically, the ink liquid is filled until the suction of the ink from the ink cartridge is normally completed to the whole fluid discharge module 12 (see FIG. 1).

  The above is the first step. In practice, however, an option setting relating to loading and unloading of the cap into the discharge nozzle 40 (see FIG. 1) is performed in order to distinguish from the second embodiment described later.

  By this option setting, it is determined whether to consider the components (L3, C3, R3) of the equivalent circuit in the vicinity of the discharge nozzle 40 (cap non-loading) or cancel (cap loading), and the arithmetic processing in the second step To change.

  In the first embodiment, the process is performed assuming no cap loading (the process proceeds to step 542 in the second step).

(Second step)
In step 542, voltage application and DC measurement are performed. Specifically, a voltage (AC voltage or a superimposed voltage of AC and DC) is applied to the piezoelectric element 48, and current measurement at the piezoelectric element 48 at that time is performed (see FIG. 1).

  At this time, the process is executed while changing the frequency of the applied power supply based on the above-described (execution process 1) part (in the present embodiment, a range of 10,000 Hz to 1010000 Hz).

  When the processing at step 542 is completed, the routine proceeds to step 544.

  In step 544, the voltage / current phase is measured and stored in the memory. More specifically, in step 542, after the current is measured at the piezoelectric element 48, the voltage / current phase difference is measured, and the measurement result is stored in a memory (for example, the RAM 31 or the HDD 33). After the voltage / current phase measurement results are stored in the memory, the process proceeds to step 546.

  That is, it is the latter part of the above-mentioned (Execution Processing 1), and the phase difference between the voltage and current of the power supply is obtained in sampling frequency units of 2500 Hz, and the frequency-phase difference characteristic diagram of FIG. 6 is created.

  In the next step 546, curve fitting which is the above-described (implementation process 2) is performed. That is, the curve fitting process at the resonance position of the frequency-phase difference characteristic is executed.

  More specifically, based on the voltage / current phase difference data measured in step 544 and stored in the memory, an algorithm for optimizing the relationship between the frequency and the phase difference from the acoustic resistance using a nonlinear least square criterion such as the simplex method Is used to calculate the approximate expression of the curve (curve), and the measured value of the relationship between the frequency and the phase difference is compared with the identified value for fitting. With respect to this curve fitting, the fitting process is performed until the range is within a predetermined allowable value (threshold), and the process is continued until the error from the actually measured value is within the predetermined allowable value (threshold). The fitting is to obtain a variable so that the curve between the actual measurement value and the theoretical value approaches, and the square sum of the difference between the actual measurement value and the theoretical value is used for the fitting evaluation. Furthermore, this evaluation method is called the norm (a mathematical tool for giving distances to the vector space of the generalization of the concept of geometric vector length in space, the plane) used to quantify vector differences The smaller the norm, the more fitting it is. As the norm minimization algorithm, the Levenberg-marquardt algorithm is used, and the square sum of the differences is minimized by a nonlinear equation. Then, after performing curve fitting between the measured value and the identification value of the relationship between the frequency and the phase difference, the process proceeds to step 548.

  An example of curve fitting processing will be described later.

  In step 548, the viscosity is measured and output based on the above-described (Execution Processing 3).

  That is, the characteristic obtained in the implementation process 1 (see FIG. 6) is an equivalent circuit of resonance points in a relatively low frequency region and a high frequency region (FIG. 7 is an equivalent circuit in a low frequency region, and FIG. 8 is a low frequency region). Assuming an equivalent circuit).

  Numerical values of the L1, C1, and R1 components are obtained from the equivalent circuit in the high frequency region, and numerical values of the L2, R2, L3, and R3 components are obtained from the equivalent circuit in the low frequency region.

  Finally, by substituting the numerical value of the identified resistance component R3 of the first equivalent circuit into the acoustic resistance r of the acoustic differential equation (see equation (1)) based on the second equivalent circuit, the viscosity η is Desired.

However,
D1: Cross-sectional diameter of the minimum flow path D2: Cross-sectional diameter of the maximum flow path le: Length of the flow path η: Ink viscosity When the second step 540 is completed, the process proceeds to step 562 of the third step 560.

  In step 562, the quality of the viscosity is determined. More specifically, the CPU 30 (see FIG. 3) determines the quality of the ink viscosity obtained in step 548 of the second process. If it is determined that the ink viscosity is normal, this routine ends. If it is determined that the ink viscosity is abnormal, the routine returns to step 512 of the first step 510 to start from the pre-measurement preparation. Either repeat the measurement or return to step 542 of the second step 540 and restart from the viscosity measurement and output.

(Curve fitting processing example)
As shown in FIG. 9, with respect to fitting, the phase difference measured value, the theoretical measured value for each frequency, and the relationship between the measured phase difference and the square of the difference between the theoretical measured values are used for all measured frequencies. The sum of the square of the difference between the phase difference actual measurement value and the theoretical measurement value is calculated.

  When calculating the total sum, the actual value, theoretical formula, and initial value of each variable are input using the lsqrsolve command of the software called Scirab, and curve fitting is performed, and the value of each variable at the time of most fitting is calculated. Is done.

  In addition, the lsqrsolve command of the software called Scirab is a method of minimizing the sum of squares of differences using a nonlinear equation using the evenberg-marquardt algorithm.

As shown in FIG. 10, in the fitting result (actual measurement value and identification value) in the waveform of the resonance region on the high frequency region side, the piezoelectric element Cd, the reactance L0, the capacitance C0, the resistance elements C0, Rs, and the constant td Is given as a constant, reactance L1 = 3.0 × 10 ⁻² [H], capacitance C1 = 2.2 × 10 ⁻¹² [F], resistance R1 = 4.0 × 10 ³ [Ω] The fitting conditions are Scilla default values (initial values).

  As shown in the fitting waveform of the actual measurement value and the identification value in FIG. 10, based on the equivalent circuit 700 in FIG. 8, the fitting in the waveform in the resonance region on the high frequency region side is the reactance L1 of the equivalent circuit in FIG. , And the theoretical formula used to identify the capacitance C1 and the resistance R1 (generally for obtaining a phase difference in terms of electromagnetics, and is stored in Scira in advance).

  Similarly, fitting is performed on the waveform in the resonance region on the low frequency region side.

  As shown in FIG. 11, the fitting result (actually measured value and identified value) on the low frequency side is expressed by reactance L1 with the piezoelectric element Cd, reactance L0, capacitance C0, resistance R0, Rs, and constant td as constants. The reactance L2, the resistances R2, L3, and R3 are obtained by setting the capacitance C1 and the resistance R1 to values calculated under the resonance region on the high frequency region side.

Therefore, in order to calculate the viscosity η from R3, the volume modulus of elasticity k3 = 2.0 × 10 ¹² and the electroacoustic conversion coefficient A = 2.0 × 10 ⁴ are substituted into the following formula (7), and the viscosity is Calculated.

For example, when R3 = 2.1 × 10 ⁴ [Ω], when the viscosity η is obtained from the equation (7), the viscosity η = 4.2 [mPa · s].

  In the identification on the high frequency side, the admittance Y may be used instead of the phase difference θ. Also in the identification on the low frequency side, the identification may be performed not by the phase difference θ but by the admittance Y.

(Second Embodiment)
The second embodiment of the present invention will be described below.

  The second embodiment relates to the measurement system, measurement method, and measurement program employed in the first embodiment, and the same reference numerals are used for the same configurations as those described in the first embodiment. The structure is omitted.

  The feature of the second embodiment is that the measurement is performed by pressing a plate with polyimide on the surface against the surface of the discharge nozzle 40 (see FIG. 1).

  That is, it is a case where the cap determined at the final stage of the first step 510 in the flowchart of FIG. 5 described in the first embodiment is loaded.

  Although the measurement result at this time is similar to that of the first embodiment, the low frequency side is an equivalent circuit (see FIG. 12) of only the supply path 44 (see FIG. 1).

  In the second embodiment, the element components of L1, C1, and R1 are further minute values and may be approximated to 0 (not necessary as elements). As a result, in the high frequency region side, Resonance region phase difference acquisition and curve fitting are not required.

  Hereinafter, the operation of the second exemplary embodiment of the present invention will be described.

  In order to perform fitting in the waveform on the low frequency region side, reactance L2 using a theoretical formula (admittance Y or phase difference θ), with piezoelectric element C0, reactance L0, capacitance C0, resistance R0, Rs, and constant td as constants. And the resistance R2 is calculated.

Substituting into the equation (8) for calculating the viscosity η from the resistance R2, the viscosity is calculated. For example, when the bulk modulus k2 = 4.0 × 10 ¹² , the electroacoustic conversion coefficient A = 2.0 × 10 ⁴ , and R2 = 4.3 × 10 ⁴ [Ω], the viscosity η is 4.3 [ mPa · s].

  In the first embodiment and the second embodiment, a head using a piezoelectric element, that is, a piezo ink jet head has been described as an example. However, as a fluid ejection module, a TIJ (Thermal Ink Jet) head ( The same effect can be obtained even with a thermal ink jet type fluid discharge module.

(Schematic configuration of TIJ head)
13 (a), 13 (b), and 13 (c) show the basic configuration of the discharge nozzle 1300. FIG. 13A shows a plan view of the discharge nozzle 1300, and FIG. 13B shows a cross-sectional view taken along the line AA of FIG. 13A.

  In FIG. 13A, FIG. 13B, and FIG. 13C, the discharge nozzle surface 1304 provided with the ink discharge port 1302 is disposed at the top, but the ink liquid (ink droplet) 1306 is disposed. Is discharged in the direction of gravity (downward). In addition, an ink supply unit (not shown) is provided, and the ink liquid 1306 is supplied from the ink supply unit (not shown) to the ink chamber 1308 by a capillary force or a pressure difference.

  An ink discharge means 1310 is provided on the outer peripheral surface of the ink chamber 1308. The ink discharge means 1310 is a thermal ink jet type discharge means, and is configured by providing a heater (not shown) on the outer peripheral surface of the ink chamber 1308.

  For example, the heater is configured by laminating a protective layer made of tantalum on a heating element layer made of polycrystalline silicon, and a predetermined signal is applied at a timing according to an image signal by a signal applying unit (not shown). Wired to When this heater is heated, volatile components contained in the ink liquid 1306 are instantly evaporated, bubbles are generated, and the ink liquid 1306 is discharged from the ink discharge port 1302.

  Here, the ink discharge means 1310 is provided on the outer peripheral surface of the ink chamber 1308, but is not necessarily provided on the outer peripheral surface, and may be provided on a part of the bottom surface of the ink chamber 1308. In addition, the shape of the ink discharge port 1302 is not limited to a circle, and the effect is not changed even if it is an arbitrary shape such as an ellipse or a polygon.

  On the other hand, a seal liquid 1312 is applied to the discharge nozzle surface 1304 so that the ink liquid 1306 in the ink discharge port 1302 does not come into contact with air. In order to maintain the performance of the sealing liquid 1312, the sealing liquid 1312 and the ink liquid 1306 are not compatible with each other, and the sealing liquid 1312 needs not to spontaneously emulsify with the ink liquid 1306.

  Further, as shown in FIG. 13B, the seal liquid 1312 applied to the discharge nozzle surface 1304 comes into contact with the ink liquid 1306 in the ink discharge port 1302, and the seal liquid 1312 is applied to the discharge nozzle surface 1304. A film is formed.

  Further, as shown in FIG. 13C, the discharge nozzle surface 1304 of the discharge nozzle 1300 is provided with a plurality of ink chambers 1308 for storing the ink liquid 1306.

  As shown in FIG. 14, the growth of bubbles and the ejection of ink droplets 1402 in the discharge nozzle 1300 shown in FIG. 13 are shown.

  When the heater is heated by the ink discharge means 1310, the volatile component contained in the ink liquid 1306 is instantaneously evaporated to generate bubbles 1308, and the ink droplets 1402 are transferred to the ink through the discharge nozzle surface 1304 and the seal liquid 1312. The liquid 1306 is discharged from the ink discharge port 1302.

  As a method for measuring the viscosity of ink in the case of a thermal ink jet printer, an admittance measurement system is installed by inserting a piezo element into a flow path. Specifically, in the case of a thermal ink jet printer, the piezoelectric element includes a piezoelectric element or a vibration plate that vibrates in conjunction with the piezoelectric element, and a flow path for flowing a liquid using the vibration plate as a part of a flow path wall. Is vibrated by applying a voltage from the outside, and the current, voltage ratio, and phase difference are measured. A sinusoidal wave (which may be a rectangular wave or a triangular wave) is applied to the piezoelectric element (the liquid level does not need to be shaken), and the phase difference between the voltage and current at that time is measured for each applied frequency.

A sectional view of a fluid ejection module to be inspected according to the present invention is shown. The schematic structure of the part relevant to the test | inspection system and fluid discharge module which concerns on this invention is shown. A schematic configuration of a control unit according to the present invention is shown. A fluid ejection module according to the present invention is shown as an electro-acoustic circuit and its equivalent circuit. A flow chart for measuring and outputting the viscosity according to the present invention is shown. FIG. 3 is a first waveform showing a relationship between an actually measured frequency and a phase difference in order to calculate the viscosity of the ink according to the present invention. FIG. 10 shows a sixth equivalent circuit for curve fitting on the low frequency side according to the present invention. A twelfth equivalent circuit for curve fitting on the high frequency side according to the present invention is shown. Regarding the fitting according to the present invention, the relationship between the measured phase difference with respect to frequency, the theoretical measured value, and the square of the difference between the measured phase difference and the theoretical measured value is shown. The curve of the fitting result (actual value and identification value) by the side of the high frequency concerning the present invention is shown. The curve of the fitting result (actual value and identification value) by the side of the low frequency concerning the present invention is shown. The equivalent circuit (16th equivalent circuit) of the fluid discharge module in the case of measuring by pressing the plate which stuck the polyimide which concerns on this invention on the surface to the discharge nozzle surface side is shown. 1 shows a configuration of a TIJ (thermal ink jet system) head according to the present invention. FIG. 6 illustrates a fluid ejection module showing bubble growth and ink droplet ejection in an ejection nozzle according to the present invention. FIG. The relationship between the frequency which changes with the viscosity which concerns on this invention, and a phase difference is shown.

Explanation of symbols

12 Fluid ejection module (fluid ejection module)
20 AC voltage generator (vibration generator)
28 Control unit (equivalent circuit assumption means, resistance extraction means, fluid viscosity calculation means)
40, 1300 Discharge nozzle (Discharge nozzle)
44 Supply path (flow path)
48 Piezoelectric elements
46A Diaphragm (diaphragm)
η viscosity

Claims (12)

A piezoelectric element, a diaphragm that is in surface contact with the piezoelectric element, and a vibration generating means that vibrates the diaphragm by applying a voltage having a predetermined frequency to the piezoelectric element. A fluid discharge module that applies pressure to a space chamber provided with a discharge nozzle in the other part and discharges the fluid filled in the space chamber from the discharge nozzle;
In the structure in which the space chamber includes a pressure chamber to which the pressure is applied, and a flow path through which a fluid flows with the pressure applied to the pressure chamber, and the fluid flowing in the flow path protrudes from the discharge nozzle. Equivalent circuit assumption means for assuming a first equivalent circuit indicating the electrical characteristics of the piezoelectric element and a second equivalent circuit indicating acoustic characteristics in which the viscosity in the space is one of the elements;
In the first equivalent circuit, a resistance component extracting means for extracting a resistance component at the time of resonance of a load including the flow channel alone or the resistance, capacitance, and inductance generated in the flow channel and the discharge nozzle;
Replacing the resistance extracted by the resistance extraction means with the acoustic resistance of the second equivalent circuit, and calculating the viscosity of the fluid based on the second equivalent circuit;
A fluid viscosity measuring system. A piezoelectric element, a diaphragm that is in surface contact with the piezoelectric element, and a vibration generating means that vibrates the diaphragm by applying a voltage having a predetermined frequency to the piezoelectric element. A fluid discharge module that applies pressure to a space chamber provided with a discharge nozzle in the other part and discharges the fluid filled in the space chamber from the discharge nozzle;
Acoustic system differential equation based on acoustic engineering using at least the viscosity η of the fluid in the space chamber as an acoustic resistance r, the minimum cross-sectional diameter D1, the maximum cross-sectional diameter D2 of the flow channel in the space chamber, and the length le of the flow channel In the calculation, the fluid ejection operation in the fluid ejection module is expressed as an equivalent circuit using the resistance R, the reactance L, and the capacitance C, so that the resistance R, the reactance L, the capacitance C, the frequency f, And a resistance R under the frequency f at which the phase difference θ in the equivalent circuit becomes a peak value based on the correlation between the phase difference θ of the voltage / current and the resistance R on the equivalent circuit, Substituting into the acoustic resistance r, fluid viscosity computing means for computing fluid viscosity η from the acoustic differential equation,
A fluid viscosity measuring system. The fluid viscosity measurement system according to claim 2, wherein the acoustic differential equation is represented by the following expression (1).

  The fluid discharge module is operated to obtain measured value data of characteristics indicating the relationship between frequency and phase difference, and the sum of square sums of differences between the measured value data and the calculation result in the fluid viscosity calculation means is predetermined. The fluid viscosity measurement system according to claim 2 or 3, wherein the correction of the calculation formula of the fluid viscosity calculation means is repeated until the threshold value becomes equal to or less than the threshold value.   The fluid viscosity measurement system according to any one of claims 2 to 4, wherein the frequency f at which the phase difference θ is the peak value is a preset fixed value. Further comprising a closing means for closing the discharge nozzle;
The fluid viscosity measuring system according to any one of claims 2 to 5, wherein, among the elements for calculation in the fluid viscosity measuring means, the elements generated by discharging fluid from the discharge nozzle are excluded.   The fluid viscosity measuring system according to any one of claims 1 to 6, wherein the viscosity information obtained by the fluid viscosity calculating means is notified.   The fluid viscosity measurement system according to any one of claims 1 to 7, wherein the fluid viscosity change is predicted and corrected so that a change in fluid viscosity converges within a predetermined allowable range based on the viscosity information obtained by the fluid calculation means.     A print head equipped with the fluid viscosity measuring system according to any one of claims 1 to 8. A piezoelectric element, a diaphragm that is in surface contact with the piezoelectric element, and a vibration generating means that vibrates the diaphragm by applying a voltage having a predetermined frequency to the piezoelectric element. When measuring the viscosity of the fluid in the fluid discharge module that applies pressure to the space chamber provided with the discharge nozzle in the other part and discharges the fluid filled in the space chamber from the discharge nozzle,
In the structure in which the space chamber includes a pressure chamber to which the pressure is applied, and a flow path through which a fluid flows with the pressure applied to the pressure chamber, and the fluid flowing in the flow path protrudes from the discharge nozzle. Assuming a first equivalent circuit showing the electrical characteristics of the piezoelectric element and a second equivalent circuit showing acoustic characteristics in which the viscosity in the space is one of the elements,
In the first equivalent circuit, extract the resistance component at the time of resonance of the load including the flow path alone or the resistance, capacity, and inductance generated in the flow path and the discharge nozzle,
A fluid viscosity measurement program that causes the computer to execute the calculation of the viscosity based on the second equivalent circuit by replacing the extracted resistance component with the acoustic resistance component of the second equivalent circuit. By expressing the first equivalent circuit as an equivalent circuit using a resistance R, a reactance L, and a capacitance C, it is assumed by the resistance R, the reactance L, and the capacitance C.
The second equivalent circuit is assumed to be a fluid viscosity η, an acoustic resistance r, a minimum cross-sectional diameter D1, a maximum cross-sectional diameter D2, and a flow path length le of the flow channel in the space chamber. The fluid viscosity measurement program according to claim 10. A resistance R under the resonance frequency f in the first equivalent circuit is obtained, and the resistance R of the first equivalent circuit is determined as an acoustic differential equation based on acoustic engineering obtained by formulating the second equivalent circuit. The fluid viscosity measurement program according to claim 11, wherein the viscosity of the fluid is calculated by substituting into the acoustic resistance r of the equation (1).

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