JP2015190829A - Method, program, and device for determining yield value of fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate yield value using a tuning-fork vibration type viscometer.SOLUTION: A tuning-fork vibration type viscometer 1 includes: a pair of vibrators 3 and 3 inserted into a fluid 4; a displacement sensor 11 for detecting an amplitude value of each vibrator 3; an electromagnetic driving unit 10 having an electromagnetic coil 10b; driving current controlling means 35 for increasing the driving current made to flow through the electromagnetic coil 10b from zero to a set value or for decreasing it from the set value to zero; storing means 39 for recording a driving current value i and an amplitude value A corresponding to it; and yield value measuring means 35 that determines an inflection point of the amplitude value A and sets the driving current value i at that time as the yield value.

Description

  The present invention relates to a method for determining a yield value relating to a physical property evaluation of a fluid, a program thereof, and an apparatus thereof.

  Among fluids, like mayonnaise, ketchup, cream, etc., they are solid (maintain shape) in a static state, but become liquid (flow) when external force is applied, and have the property of plasticity (bingham properties) It has been known. In such a plastic fluid, a stress when starting to flow, that is, a value called a yield value is an important factor in evaluating physical properties, and therefore there is a need to know the yield value accurately.

  In general, as shown in FIG. 4, when two axes of the shear rate and the shear stress applied to the fluid are taken, and the shear stress when the shear rate is changed is plotted, the shear stress is drawn. The stress that rises from zero for the first time is regarded as the yield value. On the other hand, as a device for measuring the physical properties of the fluid, a vibration viscometer, a rotary viscometer, or the like is used. The vibration type viscometer includes a rotary vibration type viscometer and a tuning fork vibration type viscometer.

  A rotational vibration viscometer inserts a single vibrator into a fluid sample to be measured, resonates the rotor in the rotational direction, measures the attenuation of the amplitude of the rotor at the time of resonance, and converts it to viscosity ( Patent Document 1).

  A tuning-fork vibratory viscometer inserts a pair of vibrators into a sample, vibrates a pair of vibrators in opposite phases, and controls the drive current of the vibrators so that the amplitude of the vibrators is constant. The current is converted into viscosity (Patent Document 2).

  A rotary viscometer inserts a rotor into a sample, raises the rotational speed of the rotor from a stopped state, and measures torque corresponding to the rotational speed (Patent Document 3).

JP 2010-19694 A Japanese Patent Laid-Open No. 5-149861 JP 2006-53074 A

  However, since the yield value is the limit value of the stress at which the fluid begins to move, in order to measure this, the external force must be changed to detect minute changes in the composition without destroying the composition of the fluid. Don't be.

  On the other hand, the rotational vibration viscometer uses a piezoelectric element in the drive unit, so the vibration frequency applied to the vibrator is high (about 1 kHz) and the stress applied to the sample is large, so the composition of the fluid is disturbed. There is a risk that. Moreover, it is difficult to measure the yield value because the stress applied to the sample cannot be directly controlled from the measurement principle.

  One of the characteristics of the tuning fork vibration type viscometer is that the drive frequency is low (about 30 Hz), the stress applied to the sample is small, and it can be said that the composition of the sample is difficult to break. However, the measurement principle is that the drive current (shear stress) is measured under the condition that the amplitude (shear rate) of the vibrator is constant, and the stress applied to the sample cannot be controlled, so the yield value is measured. I can't do it.

  The rotational viscometer measures torque (shear stress) against the number of revolutions (shear speed) based on the idea that the number of revolutions of the rotor is proportional to the shear speed. Is measured as a yield value (particularly, paragraph 0019 of Patent Document 3). However, with a rotary viscometer, it is known that if the object to be measured is low viscosity or low shear rate, the torque of the rotor is difficult to be transmitted to the sample and the accuracy is poor, and the yield value that appears in the low shear rate range is also I'm not sure if the correct value is being obtained.

  Thus, the conventional viscometer has a problem that an accurate yield value cannot be measured. In order to solve the problems of the prior art, the present invention proposes to obtain a yield value with high accuracy by using a tuning fork vibration viscometer, thereby contributing to the elucidation of the physical properties of the fluid closer to the actual situation. It is what.

  In order to achieve the above object, in a tuning fork vibratory viscometer according to the present invention, a pair of vibrators inserted into a fluid, a displacement sensor for detecting an amplitude value of the vibrator, and an electromagnetic vibration in the vibrator. An electromagnetic drive unit having an electromagnetic coil, drive current control means for increasing or decreasing a drive current flowing through the electromagnetic coil from zero to a set value, and a value of the drive current and The storage means for recording the amplitude value corresponding to this, and the yield value measuring means for judging the inflection point of the amplitude value and using the drive current value at that time as the breakdown value .

  In the yield value measuring method according to the present invention, a pair of vibrators inserted into a fluid, a displacement sensor that detects an amplitude value of the vibrator, and an electromagnetic vibration that excites electromagnetic vibrations in the vibrator. Yield value using a tuning-fork vibration viscometer comprising: an electromagnetic drive unit including a coil; and drive current control means for increasing or decreasing a drive current flowing through the electromagnetic coil from zero to a set value. A start value setting step for determining a measurement start drive current value to be passed through the electromagnetic coil, a stop value setting step for determining a measurement stop drive current value to be passed through the electromagnetic coil, and changing the drive current A drive current control step, a recording step for recording the value of the drive current and the amplitude value from the start to stop of vibration of the vibrator, and an inflection point of the amplitude value are determined, and the drive current value at that time A yield value measuring step of calculating a yield value, characterized in that it comprises a.

  Preferably, in the tuning fork vibration type viscometer according to the present invention, the yield value measuring means includes a breakdown drive current value that is a drive current value corresponding to an inflection point of the amplitude value, and the electromagnetic coil. The product of the magnetic flux density and the coil length of the electromagnetic coil is converted into a yield driving force, which is a torque applied to the vibrator, obtained by dividing the product by the lever ratio of the vibrator.

  Preferably, in the yield value measuring method according to the present invention, in the yield value measuring step, the yield value is a drive current value corresponding to the inflection point of the amplitude value, and the electromagnetic coil. The product of the magnetic flux density and the coil length of the electromagnetic coil is converted into a yield driving force, which is a torque applied to the vibrator, obtained by dividing the product by the lever ratio of the vibrator.

  Preferably, the yield value measuring method according to the present invention is described and executed by a computer program.

  According to the tuning fork vibration type viscometer of the present invention, the drive current for resonantly vibrating the pair of vibrators is controlled to increase from zero to the set value or decrease from the set value to zero, and the vibration with respect to the change in the drive current Since the change in the amplitude of the child is detected and the drive current value corresponding to the inflection point of the amplitude value is used as the breakdown value, a high-accuracy breakdown value can be obtained.

Configuration diagram of tuning fork vibration viscometer according to the present invention Block diagram of the control drive system of the tuning fork vibratory viscometer Flow chart of yield value measurement according to the present invention Yield value conceptual diagram

  Next, a preferred embodiment of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a drive mechanism unit 2 of a tuning-fork vibration viscometer 1 according to the present invention. Since the configuration of the main body of the tuning fork vibration type viscometer 1 and the drive mechanism unit 2 are the same as the conventional configuration, the description will be simplified as appropriate.

  Reference numerals 3 and 3 of the drive mechanism unit 2 are a pair of vibrators inserted into a sample 4 placed in a measurement container (not shown), and are thin plate-like plate materials such as ceramic members and metal members. And a circular enlarged portion is provided at the tip. This enlarged portion becomes the liquid contact portion 3 a with the sample 4.

  Reference numerals 5 and 5 denote a pair of leaf springs, and the base ends of the vibrators 3 and 3 are fixed to the leaf springs 5 and 5 via connecting members 6 and 6. The end of the leaf spring 5 opposite to the end on the transducer connection side is fixed to the left and right convex portions of the reverse convex shaped frame 7. A thin portion is formed at the longitudinal center of the leaf spring 5. The frame 7 is supported by a stand of the viscometer 1 main body (not shown), and is configured to be movable up and down and back and forth by a handle operation installed on the main body. Accordingly, the pair of vibrators 3 and 3 are inserted into the sample 4 with a certain depth, and are arranged so that the central axis in the thickness direction is located on the same plane in the sample 4. A sample temperature sensor 8 and a drive mechanism temperature sensor 9 are provided on the lower convex portion of the frame 7.

  Reference numeral 10 denotes an electromagnetic drive unit, and one end portion of a ferrite magnet 10 a fixed to the central portion of the connection member 6 connected to the vibrator 3 is placed inside the electromagnetic coil 10 b fixed to the side surface of the lower convex portion of the frame 7. It is configured as an inserted moving magnet system. By this electromagnetic drive unit 10, the leaf springs 5, 5 are forced to resonate in a reverse phase at a constant frequency, whereby the vibrators 3, 3 vibrate similarly. Reference numeral 11 denotes an eddy current loss detection non-contact type displacement sensor. The displacement sensor 11 assumes that the amplitude of the vibrator 3 is equal to the amplitude of the leaf spring 5 integrated with the vibrator 3, and is positioned close to the frame 7 on the vibrator connection side end of the leaf spring 5. It is fixed and the amplitude value of the leaf spring 5 is detected.

  Next, FIG. 2 is a block diagram of a control drive system of the tuning-fork vibration type viscometer according to the present invention.

  Reference numerals 30a, 30b, and 30c are amplifiers, reference numeral 31 is a sine wave generation circuit, reference numeral 32 is a V / I conversion circuit, reference numeral 33 is a rectifier, reference numerals 34 and 41 are A / D converters, reference numeral 35 is a CPU, ROM, A microcomputer incorporating a RAM and the like, 36 is a voltage conversion circuit, 37 is a display unit, 38 is a key switch unit, 39 is a memory, and 41 is an input selection unit. As will be described later, the microcomputer 35 is drive current control means and breakdown value measurement means, and the memory 39 is storage means. Of course, a configuration in which the A / D converters 34 and 41, the voltage conversion circuit 36, and the like are appropriately incorporated in the microcomputer 35 is also assumed.

  When the measurement of the yield value is started, a 30 Hz reference drive signal generated by an oscillator such as a crystal resonator (not shown) is amplified by the amplifier 30a, and the sine wave generation circuit 31 and the V / I conversion circuit 32 are connected. Then, it is modulated into a sine wave signal, and a drive current flows through the electromagnetic coil 10b. As a result, a magnetic force is generated in the electromagnetic drive unit 10, and the vibrators 3 and 3 start a resonance vibration having an opposite phase. In response, the amplitude of the vibrator 3 is detected by the displacement sensor 11. The detected signal having the amplitude value A is amplified by the amplifier 30c, rectified by the rectifier 33, converted into a digital signal by the A / D converter 34, and input to the microcomputer 35.

  The microcomputer 35 has a PWM modulation circuit, and outputs a PWM signal for controlling the drive current input to the electromagnetic coil 10 b in the procedure described later to the voltage conversion circuit 36.

  A signal output from the microcomputer 35 via the voltage conversion circuit 36 is amplified by the amplifier 30 b and is synthesized with the reference drive signal by the sine wave generation circuit 31. The drive signal modulated by the synthesis flows through the V / I conversion circuit 32 as a drive current to the electromagnetic coil 10b. The drive current value i after the PWM modulation is obtained as a value corresponding to the PWM signal output from the microcomputer 35 stored in advance in the ROM or the like. The measured values of the drive current value i and the amplitude value A are recorded in the memory 39. This procedure is repeated until the yield value measurement is completed.

  The signals from the sample temperature sensor 8 and the drive mechanism temperature sensor 9 are switched at a fixed timing by the input selection unit 40 based on the input selection signal from the microcomputer, and are converted into digital signals by the A / D converter 41. Is input to the microcomputer 35 and is recorded in another area of the memory 39 by the input selection signal of the microcomputer. The sample temperature calculated from the signal from the sample temperature sensor 8 is appropriately output to the display unit 37 or the like according to the operator's request. In addition, the temperature of the drive mechanism calculated by the signal from the drive mechanism temperature sensor 9 is used for correcting the measurement value as necessary.

  That is, the conventional tuning fork vibratory viscometer is a control system in which the drive current is increased or decreased so that the amplitude of the vibrator 3 is constant, and the viscosity is calculated from the drive current value i. The vibration viscometer 1 is configured as a control system that varies the drive current value i based on the setting and continuously measures the change in the amplitude of the vibrator 3 due to the change in the drive current value i.

  Hereinafter, the control procedure of the drive current value i and the method of measuring the breakdown value will be described based on the flowchart of FIG. FIG. 3 is a flowchart of yield value measurement according to the present invention.

  First, in step S1, an initial state of a drive current value i for vibrating the vibrator 3 and a measurement start drive current value Is are set. When the drive current value i is increased, the initial state of the drive current value i is set to zero (Is = 0). When the drive current value i is decreased, a predetermined set value (maximum value) of the drive current value i is set. Step S1 is a start value setting step.

  Next, in step S2, a change rate, a drive current change amount Ic, and a unit measurement time Tc for changing the drive current value i at regular intervals are set. As a result, every time the unit measurement time Tc elapses, the drive current value i changes by the drive current change amount Ic. When the drive current value i is increased, Ic becomes positive. When the drive current value i is decreased, Ic becomes negative.

  The drive current value i is changed at regular intervals according to the drive current change amount Ic, and the measurement is stopped when the predetermined drive current is reached. In step S3, the drive current value when the measurement is stopped and the measurement stop A drive current value Ie is set. Step S3 is a stop value setting step.

  The setting of steps S1 to S3 is basically arbitrarily performed by the operator via the key switch unit 38 or the like. However, suitable patterns for the measurement start drive current value Is, the drive current change amount Ic, the unit measurement time Tc, and the measurement stop drive current value Ie may be stored in the ROM or the memory 39 in the microcomputer 35 in advance. In this case, the start value setting step and the stop value setting step are performed by the operator selecting only whether to increase or decrease the drive current value i.

  Next, in step S4, according to the measurement start instruction from the operator, the measurement of the yield value is started. If the measurement is started, the process proceeds to step S5. If not started, the process returns to step S4.

  In step S5, the reference drive signal is modulated by the microcomputer 35, and the drive current value i is set to the measurement start drive current value Is.

  Next, in step S6, the measurement timer tm is reset. The measurement timer i is a counter or the like built in the microcomputer 35 and is used for detecting timing for changing the drive current value i, and is incremented and updated at regular intervals.

  Next, in step S7, the displacement sensor 11 measures the amplitude of the vibrator 3 corresponding to the drive current value i, and the drive current value i and the measured amplitude value A at that time are continuously recorded in the memory 39. To record. The drive current value i and the amplitude value A may be output to an external device such as a personal computer. Step S7 is a recording step.

  Next, in step S8, it is determined whether or not the timer tm reaches the unit measurement time Tc. If the unit measurement time Tc is reached, the process proceeds to step S9. If not, the process returns to step S7 and the measurement of the amplitude value A is continued.

  In step S9, based on the settings in steps S1 to S3, the PMW signal is output from the microcomputer 35 so that the drive current value i becomes (i = i + Ic) according to the set drive current change amount Ic. The value i is changed. Step S9 is a drive current control step.

  Next, in step S10, it is determined whether or not the drive current value i has reached the measurement stop drive current value Ie. When the drive current value i reaches the measurement stop drive current value Ie, the process proceeds to step S11. If not, the process returns to step S6 and measurement is continued.

  In step S11, since the drive current value i has reached the measurement stop drive current value Ie, the measurement is stopped, the drive current value i is set to zero, and the vibration of the vibrator 3 is stopped.

  Next, in step S12, a point where the amplitude value A is changed is determined by the CPU built in the microcomputer 35 based on the relationship between the drive current value i and the amplitude value A that are continuously recorded. Is determined as a breakdown value (Iy: breakdown drive current value). That is, step S12 is a yield value measurement step. Since the drive current is a sine wave, the measured value of the drive current value i is an effective value.

  The inflection point of the amplitude value A is determined when the drive current is increased, when the vibrator starts the amplitude, or when the amplitude becomes a certain level or more, when the drive current is decreased. Is a point where the vibrator stops vibrating or a point where the amplitude becomes a certain level or less. In order to judge in more detail, from the ratio (τ / Ds) of the drive current (that is, correlated with the stress [τ] applied to the fluid) and the amplitude of the vibrator (that is, correlated with the shear rate [Ds]), It is preferable to calculate the physical quantity corresponding to the viscosity (referred to as plastic viscosity) every moment, further differentiate the change in plastic viscosity, and determine the inflection point from the point where the absolute value of the differential value becomes maximum.

  In consideration of the fact that the yield value is confirmed with a low shear stress, the step S12 for calculating the yield value does not need to be calculated after completion of the measurement. The yield value may be calculated at the same time as the data recording after about 1 second to 1 minute has elapsed.

  The yield value is calculated as the yield drive current value Iy [mA], but may be converted to a yield drive force Fy converted to a torque applied to the vibrator 3 in step S12 (or step S7).

In the tuning fork vibration viscometer 1, the vibrator 3 performs a reciprocating motion with a sine wave in the sample 4, and thus a force (torque) necessary for moving the vibrator 3 in the sample 4 works. Therefore, when considering the driving force F at the center 3o of the liquid contact portion 3a of the vibrator 3, the force F1 generated by the electromagnetic driving portion 10 is based on the thinnest portion 5a of the leaf spring 5 serving as a fulcrum of the vibrator 3. , By dividing by the ratio (leverage ratio) α of the distance d1 to the center in the vertical direction of the electromagnetic drive unit 10 and the distance d2 to the vibrator wetted part center 3o. The force F1 generated in the electromagnetic drive unit 10 is obtained from the product of the magnetic flux density B of the electromagnetic coil 10b, the drive current i flowing through the electromagnetic coil 10b, and the coil length L of the electromagnetic coil 10b. Leverage ratio α, magnetic flux density B, and coil length L are known values from the device configuration. Here, if the breakdown drive current value Iy is used as the drive current i, the yield drive force Fy [N] converted to torque is obtained by the formula Fy = BI _y L / α. Further, the unit system may be set to [Pa] by dividing by the wetted area of the vibrator (the wetted part 3a area).

  According to the present embodiment, the tuning fork vibration viscometer 1 controls the drive current for resonantly vibrating the pair of vibrators 3 so as to increase from zero to an installation value or to decrease from a set value to zero. Since the change of the amplitude value A of the vibrator 3 with respect to the change of the current value i is detected and the drive current value i corresponding to the inflection point of the amplitude value is used as the breakdown value, a high-accuracy breakdown value can be obtained.

  That is, the tuning fork vibration type viscometer 1 can drive the vibrator 3 with a minute driving force (driving current) and vary the driving current within a minute range by utilizing the resonance of the vibrators 3 and 3. Since the stress applied to the sample 4 is small and the compositional change of the sample 4 is difficult to occur, the yield value confirmed particularly under low energy can be captured with higher reliability and accuracy than the measured values of other viscometers.

  Further, the tuning fork vibration type viscometer 1 can directly control the driving force (driving current) and measure the change of the amplitude value A with respect to the change of the driving current value i as a continuous state change. In addition, the rheological properties (Newton, non-Newtonian, etc.) of the fluid are easily required during the measurement.

DESCRIPTION OF SYMBOLS 1 ... Tuning fork vibration type viscometer, 2 ... Drive mechanism part, 3 ... Vibrator, 4 ... Sample, 5 ... Leaf spring, 10 ... Electromagnetic drive part, 10a ... Ferrite magnet, 10b ... Electromagnetic coil, 11 ... Displacement sensor, 30a , 30b, 30c ... amplifier, 31 ... sine wave generation circuit, 32 ... V / I converter, 33 ... rectifier, 34 ... A / D converter 35 ... microcomputer, 36 ... voltage converter, 37 ... display unit, 38 ... Key switch unit, 39 ... Memory, 40 ... Input selection unit, 41 ... A / D converter

Claims (5)

A pair of transducers inserted into the fluid;
A displacement sensor for detecting an amplitude value of the vibrator;
An electromagnetic drive unit including an electromagnetic coil for exciting electromagnetic vibration in the vibrator;
Drive current control means for increasing the drive current flowing through the electromagnetic coil from zero to the set value or decreasing from the set value to zero;
Storage means for recording the value of the drive current and the amplitude value corresponding thereto;
Determining the inflection point of the amplitude value, and a yield value measuring means having the drive current value at that time as a breakdown value;
A tuning fork vibration viscometer characterized by comprising: A pair of transducers inserted into the fluid;
A displacement sensor for detecting an amplitude value of the vibrator;
An electromagnetic drive unit including an electromagnetic coil for exciting electromagnetic vibration in the vibrator;
A driving current flowing through the electromagnetic coil, a driving current control means for increasing from zero to an installation value or decreasing from a setting value to zero, and a method for measuring a yield value using a tuning fork vibrating viscometer,
A start value setting step for determining a measurement start drive current value to be passed through the electromagnetic coil;
A stop value setting step for determining a measurement stop drive current value to be passed through the electromagnetic coil;
A drive current control step for changing the drive current;
A recording step of recording the value of the drive current and the amplitude value from the start to stop of vibration of the vibrator;
A yield value measuring step of determining an inflection point of the amplitude value and calculating the drive current value at that time as a yield value;
A method of measuring a yield value, comprising:   In the yield value measuring means, the yield value is a breakdown drive current value that is a drive current value corresponding to the inflection point of the amplitude value, a magnetic flux density of the electromagnetic coil, and a coil length of the electromagnetic coil. The tuning fork vibration type viscometer according to claim 1, wherein the product is converted into a yield driving force which is a torque applied to the vibrator, which is obtained by dividing the product by the lever ratio of the vibrator.   In the yield value measuring step, the yield value is a breakdown drive current value that is a drive current value corresponding to an inflection point of the amplitude value, a magnetic flux density of the electromagnetic coil, and a coil length of the electromagnetic coil. The yield value measuring method according to claim 2, wherein the product is converted into a yield driving force, which is a torque applied to the vibrator, obtained by dividing the product by the lever ratio of the vibrator.   A yield value calculation program characterized in that the method for measuring a yield value according to claim 2 or 4 is described by a computer program and can be executed.

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