JP2694261B2 - Rotational viscometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is used as a device for measuring the viscosity of a fluid. The present invention relates to an apparatus for measuring the viscosity of non-Newtonian fluids whose viscosity changes in response to changes in shear rate.

[0002]

2. Description of the Related Art A rotary viscometer has been widely known as a useful device for measuring the viscosity of a fluid. In particular, the double-cylinder type rotational viscometer is a cylindrical cup into which a test fluid is put, and a test fluid put into the cup is brought into contact with the cup so that the cup can be rotated around the central axis of the cup independently of the cup. A device provided with a retained cylindrical rotor and a rotation drive means for rotating the rotor around the central axis, wherein the rotation torque transmitted to the cup through the test fluid is caused by the rotation of the rotor. It is an excellent device that measures the viscosity of the test fluid by measuring. The cup or rotor is not always cylindrical, but cones and other shapes are widely used.

Such a viscometer and its measuring principle are described in JP-A-3-44535,
Inventor of the present application, magazine "Material", Vol. 32, No. 356,
461 pages (1983), magazine "Ceramics" 18th
Volume 2, p. 103 (1983).

In such a conventional rotational viscometer, the rotor of the above-mentioned device is continuously driven to rotate at a constant speed,
When the rotational torque transmitted to the cup reaches a predetermined state, the rotational torque is measured.
Immediately after the rotor starts rotating, there is a delay due to the mechanical inertia of the rotor and its rotational drive means.
It is understood that there is a time lag in the measured values.

[0005]

A liquid made of a pure substance or a liquid in a complete solution (so-called Newtonian fluid) does not change its viscosity due to stirring, so wait for the rotor to reach a predetermined speed. Although the viscosity can be measured with the above device, since the viscosity of non-Newtonian fluid changes with time and shear rate, the rotational torque transmitted to the cup also changes continuously. ,
In a device in which the rotor must start rotating and then adjust its speed, it is not possible to measure viscosity under a given condition because changes in viscosity during speed adjustment affect subsequent changes. I won't. If a mechanism that combines clutches, brakes, gears, etc. is adopted, the speed can be set while the rotor is stopped, but it is often necessary to change the speed over a wide range when measuring non-Newtonian fluids. Therefore, such a mechanism imposes great restrictions on the measurement conditions.

A typical example of the non-Newtonian fluid is a dispersion system in which particles are dispersed in a liquid, and the viscosity of the liquid changes depending on the dispersion state. The state of dispersion naturally changes when agitated to measure the viscosity. As an example, in the mixing process of concrete, it is necessary to know its viscosity accurately over time as the composition is agitated and to control the amount of dispersant to be added.

The present invention provides an apparatus capable of accurately measuring the viscosity of a non-Newtonian fluid with respect to the viscosity of a non-Newtonian fluid immediately after the start of the measurement for the purpose of measuring the viscosity and with stirring. To aim.

[0008]

According to the present invention, a cup into which a test fluid is charged, and a test fluid charged in the cup are held so as to be rotatable independently around the central axis of the cup independently of the cup. a rotor and a rotary drive means for rotating the rotor about the central axis, e Bei and measuring means for measuring a rotational torque transmitted via the test fluid to the cup by rotation of the rotor, the rotary drive The means is a stepping motor serving as a rotational power source, a frequency control means for controlling the frequency of a power supply supplied to the stepping motor, and an output of the frequency control means as an input.
Means for supplying an output current to the stepping motor,
With the output of this frequency control means as an input, the output current is
A start-up switch that starts the means for supplying the stepping motor.
Switch and the start switch separately from the frequency control
A switch for supplying a power supply current to the stage .

The frequency control means comprises a variable DC power supply,
A voltage control oscillator having an output voltage of the variable DC power supply as a control input is provided, and a chopper having an output of the voltage control oscillator as a control input and an output current supplied to the stepping motor is provided, and the start switch is provided in the chopper. A power supply switch is provided in the power supply circuit of the power supply which supplies the power supply current to the frequency control means separately from the start switch in a state where the start switch is not turned on. The measuring unit includes a fixing unit that restricts rotation, and a unit that measures a stress strain generated in the fixing unit and a unit that automatically records the rotation angle immediately after the activation switch is turned on as time passes. Further, the cup is held rotatably around its central axis, and the cup is A spring means for providing a reverse rotational force opposing the rolling, the measuring means preferably includes means for measuring the angle of rotation.

[0010]

With the above configuration, when the rotor in contact with the test fluid in the cup is rotated and the rotational torque transmitted to the cup via the test fluid is measured to measure the viscosity, the rotation start of the rotor is very short. By controlling the rotation speed to reach a constant rotation speed in time and measuring and recording the rotation torque immediately after the rotation start, the viscosity change characteristic of the test fluid is obtained from the state in which the rotation torque changes. be able to.

Explaining by way of example, FIG. 1 is a diagram showing the results of measuring the viscosity of the same test fluid using a rotational viscometer. This measurement is a result in which the rotation start time of the rotor is set to 0 and the viscosity measurement value, that is, the magnitude of the rotation torque measured by the cup is shown over time. A measurement curve A is obtained by using the device of the present invention. The measurement curves B, C and D can be obtained by using a conventionally known commercially available device.

It is considered that the curve A of the measurement result using the apparatus of the present invention shows the true viscosity change after the time t ₁ , and the curve B of the measurement result using the conventional apparatus is the time t 1.
It is considered that the true viscosity change is displayed after ₂ , and the curve C is also considered to display the true viscosity change after about time t ₃ . In the case of the curve C of the measurement result, it is impossible to determine whether the equilibrium viscosity of the non-Newtonian fluid appears or the constant viscosity of the Newtonian fluid appears. D shows an example of failure in speed adjustment after starting the rotor, and such a case does not occur if the speed can be set during stop.

From the measurement results of FIG. 1, it can be estimated that the viscosity value which changes with the passage of time changes as shown by the thick solid line in the figure.

[0014]

Next, a rotational viscometer according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of the rotational viscometer of the embodiment of the present invention.

In the embodiment of the present invention, the rotational viscometer is a test fluid 21.
, A rotor 2 that is in contact with the test fluid 21 that has been charged into the cup 1 and that is rotatably held independently of the cup 1 about its central axis, and the rotor 2 that rotates about the central axis. The rotation driving means for rotating the rotor 2 and the measuring means for measuring the rotation torque transmitted to the cup 1 via the test fluid 21 by the rotation of the rotor 2 are provided. As a feature of the present invention, in this device, the rotation driving means includes a stepping motor 3 serving as a rotational power source, a frequency control means 4 for controlling the frequency of a power supply supplied to the stepping motor 3, and the frequency control means 4. The frequency control means 4 includes a start switch 5 for starting power supply to the stepping motor 3 in a state where the frequency is controlled and set.
Includes a variable DC power supply 4a and a voltage controlled oscillator 4b that receives the output voltage of the variable DC power supply 4a as a control input. Further, this device is provided with a chopper 6 whose output is supplied to the stepping motor 3 by using the output of the voltage controlled oscillator 4b as a control input, and the starting switch 5 is provided in a power supply circuit of a power supply which supplies the chopper 6 with the starting current. A power supply switch 7 that supplies a power supply current to the frequency control means 4 separately from the switch 5 in a state in which the startup switch 5 is not turned on.
The cup 1 is rotatably held about its central axis, and the rotation of the cup 1 about its central axis and the spring means 9 for giving a reverse rotational force opposite to the rotation corresponding to the rotational angle about the central axis is restricted. The measuring means includes a rotation angle automatic recorder 8 that automatically measures and records the rotation angle immediately after the activation switch 5 is turned on over time, and the fixing means that regulates the rotation. It includes means for measuring stress strain.

The output from the voltage controlled oscillator 4b is also output to the arithmetic circuit 10 to calculate the rotational speed and display it on the rotational speed display 11. A commercial power supply 12 is supplied to the start switch 5 and the power switch 7 via a voltage conversion / rectification circuit 13.

Next, the operation of the rotational viscometer of the present invention thus constructed will be described with reference to FIG.

First, when the power switch 7 is closed,
The commercial power supply 12 whose voltage is converted by the voltage conversion / rectification circuit 13 and rectified is the variable DC power supply 4 of the frequency control means 4.
a, the voltage-controlled oscillator 4b, the arithmetic circuit 10, and the rotation speed indicator 11.

When the variable DC power supply 4a is operated and a predetermined voltage is set in such a state, the voltage controlled oscillator 4b applies an output voltage having a predetermined frequency to the chopper 6 using the output voltage as a control input. On the other hand, the output voltage from the voltage controlled oscillator 4b is also branched to the arithmetic circuit 10, and the rotational speed of the rotor 2 is calculated according to the frequency to calculate the rotational speed display 1
1 is displayed.

When the starting switch 5 is operated in the closed state while the rotor rotation speed is set in this way, the chopper 6 is started and the output current from the voltage controlled oscillator 4b is supplied to the stepping motor, so that the mechanical The rotor 2 that is electrically connected is driven so as to reach a predetermined rotation speed within a very short time from the stopped state, and the test fluid 21 that has been put into the cup 1 is agitated.

By this agitation, the cup 1 receives a rotational torque via the viscous test fluid 21, and rotates about its central axis in opposition to the spring means 9. This rotation angle is automatically measured and recorded by the rotation angle automatic recorder 8 as time passes. In this way, the change in viscosity of the test fluid 21 is measured.

A feature of the present invention is that when the test fluid 21 charged in the cup 1 is agitated by the rotation of the rotor 2 as described above and the rotational torque transmitted through the test fluid 21 is measured. , The start-up of the rotor 2 is controlled so as to reach a constant rotation speed within an extremely short time from the stopped state, and the rotation torque immediately after the rotation start is automatically measured and recorded over time, and the change of the rotation torque The purpose is to obtain the viscosity change characteristic of the test fluid 21 from the state in which the test fluid 21 is operated.

The measurement curve obtained by the apparatus and method of the present invention is, for example, the curve A shown in FIG.
That is, it is considered that the viscosity of the test fluid is correctly measured after a short time t ₁ .

FIG. 3 shows a result of actual measurement using the rotational viscometer according to the present invention.

A contains 95.00 g of Al (aluminum) and 72.50 g of BuOH (butyl alcohol), and has a C _V of 0.29171, and a ns of 1.32508 ×.
10 ¹⁴ , n _n is 4.457 × 10 ¹⁵ , and n _W is 3.792
It is a measurement curve of a 276 × 10 ⁶ test fluid. However,
C _V is the particle volume concentration, and ns is 1 cm calculated from the specific area.
Number of particles in the ^3, n _n was calculated from the number average particle radius 1c
The number of particles in m ³ and n _W represent the number of particles in 1 cm ³ calculated from the weight average particle radius (the same applies hereinafter).

B is blended with 65.00 g of ZnO (zinc white) and 81.06 g of H ₂ O (water) and has a C _V of 0.11.
2937, n _s is 5.207728 × 10 ¹² , and n _n is 1.
2 is a measurement curve of a test fluid having 27684 × 10 ¹⁵ and n _W of 2.3200 × 10 ⁸ .

C is 150.00 g of bronze powder and BuO
35.00 g of H (butyl alcohol) is added, and C _V
Is 0.32529, and n _s is 1.84076 × 10 ¹⁴ , n
_V is 4.97007 × 10 ¹⁵ , n _W is 1.21979 ×
10 is a measurement curve of 10 ⁹ test fluids.

[0028]

As described above, according to the present invention, the rotor is controlled so as to reach a constant rotation speed in a very short time from a stopped state, and the rotation is performed immediately after the rotation start while maintaining the constant rotation speed. The torque can be automatically measured and recorded over time. With the device of the present invention, it is possible to measure the change in viscosity over time as the test fluids are stirred, and it is possible to estimate the viscosity characteristics of each test fluid with considerable accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing the measurement results of the viscosity of a test fluid by a rotational viscometer of an example of the present invention and a conventional rotational viscometer of a conventional example.

FIG. 2 is a block diagram showing the configuration of a rotational viscometer according to an embodiment of the present invention.

FIG. 3 is a diagram showing a measurement result by a rotational viscometer according to an example of the present invention.

[Explanation of symbols]

 1 Cup 2 Rotor 3 Stepping Motor 4 Frequency Control Means 4a Variable DC Power Supply 4b Voltage Controlled Oscillator 5 Starter Switch 6 Chopper 7 Power Switch 8 Rotation Angle Recorder 9 Spring Means 10 Arithmetic Circuit 11 Rotation Speed Indicator 12 Commercial Power Supply 13 Voltage Conversion・ Rectifier circuit 21 Test fluid

Claims (1)

(57) [Claims] 1. A cup into which a test fluid is introduced, a rotor which is in contact with the test fluid introduced into the cup and is rotatably held independently of the cup about its central axis, and The rotation driving means for rotating about the central axis and the measuring means for measuring the rotation torque transmitted to the cup through the test fluid by the rotation of the rotor are provided, and the rotation driving means is a stepping power source. A motor, frequency control means for controlling the frequency of the power supply supplied to the stepping motor, and the frequency control means
Output current as input to the stepping motor
Supply means and output of this frequency control means as input
To supply an output current to the stepping motor.
The start switch to start and this start switch separately
A rotational viscometer, comprising: a switch for supplying a power supply current to the frequency control means .