JPH08128940A - Viscosity measuring method for electroviscous fluid - Google Patents

Abstract

PURPOSE: To enhance reliability in viscosity measuring results of an electroviscous fluid. CONSTITUTION: A pair of electrodes 15 is faced and arranged in a sample container 12 filled with an electroviscous fluid used as a sample, and a pair of thin sensitive members 5 made of ceramic is put in the sample to make resonance vibration. Electricity is carried to the electrodes 15, driving current of the sensitive members 5 is continuously varied, and the amplitude of the sensitive members 5 is measured. The viscosity of the sample is measured from the relation of the driving current value and the amplitude value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the viscous properties of an electrorheological fluid.

[0002]

2. Description of the Related Art A double cylinder type rotary viscometer is widely used as a method for measuring the viscosity of a liquid. In the method using this rotary viscometer, one cylinder that is an electrode is rotated in a liquid, the shear stress and the strain rate are calculated from the rotation torque and the rotation speed at that time, and the flow characteristic curve is calculated from the relationship between them. In order to obtain the viscosity of the liquid, the physical properties of the fluid are analyzed.

However, when attempting to measure the viscosity of an electrorheological fluid, most of the electrorheological fluid is a suspension of insulating oil and fine particles, so that a turbulent flow is generated in the rotary viscometer. Due to the centrifugal force, the particles with a large specific gravity are biased to the outside and the dispersion of the particles is not uniform. In addition, the measurement method involves moving (rotating) the cylinder, which is the electrode, in one direction. Sliding occurs on the contact surface with, and in any case, improvement in measurement accuracy cannot be expected.
Further, if any one of the double cylinders is eccentric, the distance between the electrodes is not constant, and a uniform charge is not applied to the entire electrorheological fluid, so that correct measurement cannot be performed. Further, as a peculiarity of the rotary viscometer, there is a drawback that an error of a torsion wire detecting a torque or an error of a torque meter directly affects the measurement accuracy.

Further, a yield stress is one of the characteristics of the electrorheological fluid. This yield stress is, as shown in FIG.
The stress that occurs when the shear rate is 0 (1 / S), that is, when the fluid changes from a static state to a dynamic flow state,
In the measurement of the yield stress using a rotary viscometer, the yield stress must be obtained by extrapolation from the data in the shear rate within a predetermined range, and the correct measurement cannot be performed.

On the other hand, there is a method for analyzing the physical properties of a sample by a viscometer, which is described in Japanese Patent Publication No. 4-70579, and in this method, a pair of leaf springs having a sensitive plate attached to the tip thereof is placed in the measurement sample. Inserted and resonated by electromagnetic vibration in opposite phase, and measured the amplitude value of the sensitive plate when the drive current to the electromagnetic drive was continuously changed continuously, and measured the drive current value and the response amplitude value. The physical properties of the sample are analyzed from the relationship of.

However, when the sample is an electrorheological fluid, it is necessary to energize the electrodes facing the fluid. Therefore, if the sensitive plate is a conductor, the insulation strength in the vicinity of this sensitive plate is lowered. Not only that, the sensitive plate may be energized, which prevents accurate measurement.

The present invention has been made in view of the above problems, and an object thereof is to provide a method capable of accurately measuring the viscous property of an electrorheological fluid and improving the reliability of the measurement result. I am trying.

[0008]

According to the present invention, a gap between a pair of electrodes arranged to face each other is filled with an electrorheological fluid, and a pair of thin-walled responsive members having electrical insulation are provided in the electrorheological fluid. While being immersed, the pair of thin-walled sensitive members are resonantly vibrated in an opposite phase by electromagnetic vibration of the electromagnetic drive unit, and the drive current of the electromagnetic drive unit is continuously changed while energizing the pair of electrodes. The feature is that the amplitude of the thin sensitive member is continuously measured, and the viscous property of the electrorheological fluid is measured from the relationship between the driving current value and the response amplitude value.

[0009]

EXAMPLE FIG. 2 is a diagram showing an example of the present invention and shows the structure of a viscosity measuring apparatus used in the present measuring method.

As shown in FIG. 2, a pair of leaf springs 2 are fixed to the slider 1 of the viscosity measuring device with bolts 3, and a support member 4 is connected to the lower end of the leaf springs 2. Further, a thin-walled sensitive member 5 having a circular tip is connected to the lower end of the support member 4 by a bolt 6, and the thin-walled sensitive member 5 is formed of a ceramic having an electrical insulating property in a thin plate shape. An electromagnetic drive unit 7 is provided between the pair of support members 4, and the pair of thin-walled sensitive members 5 have their resonance frequencies of the resonance frequency via the support member 4 by the exciting force of the electromagnetic drive unit 7. Originally, they are sine-oscillated in the left and right directions in opposite phases. That is, the pair of thin-walled sensitive members 5 are attached such that both front and back surfaces thereof are parallel to the vibration direction.

Further, a displacement sensor 8 is attached to the slider 1, and the displacement sensor 8 will be described later.
The amplitude of the support member 4 and thus the thin-walled sensitive member 5 is detected.

The slider 1 is supported by a body frame (not shown) so as to be able to move up and down.

At the lower end of the slider 1, a level needle 9 for regulating the immersion depth of the thin sensitive member 5 in the sample container 12 is provided as will be described later, and as shown in FIG. A temperature sensor 10 for detecting is attached.

A sample container 12 is provided on the table 11 below the slider 1, and the sample container 12 is connected to the positioning metal fitting 14 by rotating a handle 13 as shown in FIGS. It is pressed and fixed with. As shown in FIGS. 7 to 9, the sample container 12 has a bottom portion and four side wall portions formed of an acrylic plate, while a pair of stainless steel plates are formed so as to maintain a predetermined space in the center of the inner space of the container. Support block 1 in which the electrode 15 is inserted and the other space is made of fluororesin such as Teflon
It has a structure filled with 6,17. A semicircular opening hole 18 is formed in one of the support blocks 16, and only the inside gap G between the opening hole 18 and the pair of electrodes 15, 15 is filled with the electrorheological fluid as the sample. Then, as described later, the thin sensitive member 5 is dipped in the sample in the facing gap G, and the temperature sensor 10 is dipped in the sample in the opening hole 18.

Here, in this embodiment, the pair of electrodes 1
The position of the electrode 15 is regulated by a spacer 19 made of fluororesin so that the facing gap G between the electrodes 5 and 15 is 1 mm.
The terminal portion 15a of the electrode 15 is connected to the power source 20 as shown in FIG.

In the above structure, in addition to FIG. 2, FIGS.
As shown in, the sample container 12 in which a predetermined sample is sampled is placed on the table 11, and the handle 13 is rotated to fix the sample container 12 between the positioning fitting 14 and the handle 13.

Then, the slider 1 is slowly lowered, and the tip of the level needle 9 is moved to the sample container 12 as shown in FIG.
Stop at the position in contact with the sample liquid surface inside. This allows
The pair of thin-walled sensitive members 5 is immersed in the sample in the facing gap G between the electrodes 15 and 15, and the temperature sensor 10 is immersed in the sample in the opening hole 18.

In this state, as shown in FIG.
While a predetermined voltage is applied to the pair of electrodes 15 from 0, the oscillator 21 receives the signal of the resonance frequency at which the entire vibration system vibrates at the natural frequency according to the instruction from the drive control unit 22.
Then, the amplifier 23 amplifies the input signal and inputs the amplified alternating current to the electromagnetic drive unit 7. This allows
The pair of thin sensitive members 5 resonate in the left-right direction via the leaf springs 2. The drive current at this time is measured by the ammeter 24.

Here, since the facing gap between the pair of electrodes 15 and 15 is preset to be 1 mm, the pair of thin-walled sensitive members 5 are provided at the center of the facing gap G.
The relative positional relationship between the sample container 12 and the thin sensitive member 5 is set in advance so as not to come into contact with the electrode 15. Further, since the thin-walled sensitive member 5 is made of ceramic, the thin-walled sensitive member 5 does not decrease in insulation strength in the vicinity of the thin-walled sensitive member 5 even when an electric viscous fluid as a sample is charged. No electric current flows through itself.

On the other hand, the amplitude of the vibrating leaf spring 2 is detected by the displacement sensor 8 as a voltage change, the voltage signal is amplified by the amplifier 25, and the amplified amplitude value is measured by the voltmeter 26. At the same time, the sample temperature in the sample container 12 is detected by the temperature sensor 10 and displayed on the temperature display unit 28.

Then, the amplitude value detected by the displacement sensor 8 is input as an electromotive force change of the displacement sensor 8 to an analysis processing device 27 constituted by a personal computer or the like, and simultaneously measured by the ammeter 24. The drive current value and the temperature output from the temperature sensor 10 are also input to the analysis processing device 27.

According to the present invention, as described above, while vibrating the thin-walled sensitive member 5 contained in the electrorheological fluid which is the sample, the vibrating force thereof is changed and, if necessary, the electrode 15 is interposed. While changing the charge applied to the electrorheological fluid, the amplitude value and the driving current are measured, and the physical properties of the electrorheological fluid, which is the sample, are analyzed from the relationship between the two.
A specific example is shown in FIG.

FIG. 11 shows the sample container 12 shown in FIGS.
In addition, a silicone oil (SH20010CS, manufactured by Toray Dow Corning Silicone Co., Ltd.) in which water is adsorbed (Avicel, manufactured by Asahi Kasei Corporation)
Is filled with an electrorheological fluid having a particle concentration of 35 wt% and the electric charge applied to the electrorheological fluid is 0 kV / m.
The change of the yield stress when changing m, 2 kV / mm and 4 kV / mm was measured under the vibration type viscosity measuring method shown in FIG. In addition, as a comparative example, FIG. 12 shows the result of measuring the yield stress change of the same electrorheological fluid as described above by the conventional rotational viscosity measurement method.

Here, as described above, by continuously changing the drive current I of the electromagnetic drive unit 7, the exciting force exerted by the electromagnetic drive unit 7 on the thin sensitive member 5 is changed, and this exciting force is changed. Since there is a correlation between the force and the shear stress τ of the electrorheological fluid which is the sample, the shear stress τ is calculated from the equation (1).

The drive frequency of the electromagnetic drive unit 7 is set to 3
Since it is set to 0 Hz (constant), the amplitude of the thin sensitive member 5 changes according to the viscosity of the electrorheological fluid. For example, if the viscosity is high, the amplitude becomes small, and if the viscosity is low, the amplitude becomes large. Therefore, the above response amplitude value is detected as the electromotive force E by the displacement sensor 8 and the viscosity η is calculated based on the equations (2) and (3).

Then, the shear rate D _S is calculated from the equation (4) based on the above shear stress τ and viscosity η.

Each of the above calculations is processed by the analysis processing device 27 shown in FIG. 10, and then graphed and recorded as shown in FIG.

Τ (Pa) = 1588 × I (A) ‥‥‥‥‥‥‥ (1) R = I (A) / E (mV) ‥‥‥‥ (2) log η (mPA · S) = a ・logR ² + b · logR + C (3) D _S (S ⁻¹ ) = τ (Pa) / η (Pa · S) ‥‥‥ (4) where τ: Shear stress I: Electromagnetic drive part Driving current (A) η: Apparent viscosity (Pa · S) R: Driving current I (A) and amplitude (electromotive force E of displacement sensor)
Ratio with (mV) E: Electromotive force (mV) of displacement sensor according to amplitude D _S : Shear rate (S ^-1 ) a: Constant (= -0.1360180512) b: Constant (= 0.572142761) c : It is a constant (6.701903606).

As is apparent from FIG. 11, the curves are different when the drive current is changed steplessly and the drive current value is gradually increased and gradually decreased, and a hysteresis curve is drawn. It is understood that there is (especially when applying 2 kV / mm). Therefore, it is understood that the electrorheological fluid exhibiting this characteristic is a Bingham fluid but has a thixotropic property. In addition, FIG.
As is clear from the above, the yield stress can be directly obtained by clearly showing the yield stress in the characteristic curve.

On the other hand, according to the measurement results obtained by the rotational viscosity measurement method shown in FIG. 12, not only the property of the electrorheological fluid as the sample cannot be accurately specified, but also the yield stress can be obtained. As shown in FIG. 12, it is necessary to use a so-called extrapolation method for auxiliaryly drawing a straight line to check the tendency, and the value of the yield stress finally obtained varies depending on how the line is drawn, and the accurate yield is obtained. It is difficult to obtain the stress value.

[0031]

As described above, according to the present invention, the gap between a pair of electrodes arranged to face each other is filled with an electrorheological fluid, and a pair of thin-walled sensitive members having electrical insulation are immersed in the electrorheological fluid. At the same time, the pair of thin-walled sensitive members are resonantly oscillated in an opposite phase by electromagnetic vibration of the electromagnetic drive unit, and the thin-walled when the drive current of the electromagnetic drive unit is continuously changed while energizing the pair of electrodes. By continuously measuring the amplitude of the sensitive member and measuring the viscous property of the electrorheological fluid from the relationship between the drive current value and the response amplitude value, it is possible to use the conventional rotational viscometer as an analysis method. Not only does the behavior of the electrorheological fluid, which is the sample, not affect the detection accuracy, but there is no risk of electricity being applied to the thin sensitive member, so the viscous properties of the electrorheological fluid can be accurately measured. Now, the reliability of the measurement result is greatly improved.

Further, according to the present invention, since the yield stress of the electrorheological fluid can be directly obtained from the relationship between the exciting force and the response amplitude value, that is, the relationship between the shear stress and the shear rate, the conventional extrapolation method is used. The reliability of the measurement result of the yield stress is also improved as compared with the measurement.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a viscosity measuring device used in a measuring method of the present invention.

FIG. 2 is a structural explanatory view of the apparatus of FIG. 1 before the thin sensitive member is immersed in a sample container.

FIG. 3 is an enlarged side view of a main part of FIG.

FIG. 4 is a plan view of the table shown in FIG.

5 is a front view of FIG.

6 is a right side view of FIG.

FIG. 7 is an enlarged front view of the sample container shown in FIG.

FIG. 8 is a plan view of FIG.

9 is a right side view of FIG. 7.

10 is a block circuit diagram of a signal processing system of the viscosity measuring device shown in FIG.

FIG. 11 is a characteristic diagram showing an example of measurement results according to the present invention.

FIG. 12 is a characteristic diagram of measurement results by a conventional method.

[Explanation of symbols]

 5 ... Thin sensitive member 7 ... Electromagnetic drive unit 8 ... Displacement sensor 12 ... Sample container 15 ... Electrode 27 ... Analysis processing device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shosuke Ishiwata 2-1-1 Tsukimi-cho, Kumagaya-shi, Saitama Chichibu Cement Corporation (72) Inventor Mitsuo Hayashi 2-1- Tsukimi-cho, Kumagaya-shi, Saitama 1 Chichibu Cement Co., Ltd. (72) Inventor Ikuo Nomura 1-28-10 Hongo Hongo, Bunkyo-ku, Tokyo Hongo TK Building Chichibu Cement Co., Ltd.

Claims (1)

[Claims] 1. A gap between a pair of electrodes facing each other is filled with an electrorheological fluid, and a pair of thin-walled responsive members having electrical insulation are immersed in the electrorheological fluid.
The pair of thin-walled sensitive members are resonated and vibrated in opposite phases by electromagnetic vibration by the electromagnetic drive unit, and the drive current of the electromagnetically driven unit is continuously changed while energizing the pair of electrodes. A method for measuring the viscosity of an electrorheological fluid, characterized in that the amplitude is continuously measured and the viscosity of the electrorheological fluid is measured from the relationship between the driving current value and the response amplitude value.