Device and method for measuring viscosity

Abstract

To make it possible to have a simple and low-cost sample container for housing a sample to be measured, and to measure viscosity of the sample to be measured over a wide range from low to high viscosity simply and with high accuracy.SOLUTION: A viscosity measurement device includes: a rotor having a rotational symmetry shape; a wire rod whose one end is connected to the rotor at an uppermost portion on an axis of rotational symmetry of the rotor and suspending and holding the rotor; and a holding member for holding the other end of the wire rod above the rotor so that the wire rod extends and becomes linear in a vertical direction. The rotor is held by the holding member via the wire rod so as to be in a state of being suspended so that the axis of rotational symmetry extends in the vertical direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an apparatus and method for measuring viscosity. [Background technology]

[0002] Conventionally, viscosity (hereinafter sometimes referred to as "viscosity") has been measured to detect the mechanical properties of a substance. Viscosity measurement is an essential measurement technique for quality control, performance evaluation, raw material management, research and development, etc. in the manufacturing process of pharmaceuticals, food, paints, inks, cosmetics, chemical products, paper, adhesives, fibers, plastics, beer, detergents, concrete admixtures, silicon, etc.

[0003] Conventional viscosity measurement devices and methods include devices and methods that apply a driving torque in a non-contact manner to a rotating probe (rotor) in contact with the sample to be measured, and measure the viscosity of the target sample in a non-contact manner from the rotation speed of the rotating probe (see, for example, Patent Documents 1 to 6).

[0004] In the device described in Patent Document 1, a small conductive ball is used as a rotor, which is submerged in a sample. A predetermined torque is applied to the ball in a non-contact manner, and the viscosity of the sample is measured in a non-contact manner from the rotation speed of the ball.

[0005] In the device described in Patent Document 2, a disk-shaped rotor is floated on the surface of a sample using either buoyancy or surface tension, or both, and a predetermined torque is applied to the rotor in a non-contact manner, and the viscosity of the sample is measured in a non-contact manner from the rotation speed of the rotor.

[0006] In the device described in Patent Document 3, the tip of the rotation center protruding from the bottom of a disk-shaped rotor is formed in a convex shape, and the tip comes into contact with the inside bottom of a container that contains a sample, and a rotation shaft is provided on the top of the rotor, and the rotation shaft is inserted into a through hole of a holding mechanism so as to be rotatable but not movable laterally. A predetermined torque is applied to the rotor in a non-contact manner, and the viscosity of the sample is measured in a non-contact manner from the rotation speed of the rotor.

[0007] In the device described in Patent Document 4, the tip of the rotation center protruding from the bottom of the rotor is formed in a convex shape, and the tip comes into contact with the inside bottom of the container that holds the sample. In addition, the rotor's center of gravity and center of buoyancy are adjusted so that the rotor rotates vertically and independently.

[0008] In the device described in Patent Document 5, a protrusion is provided at the top and center of the rotor, and the rotor rotates around this protrusion as a fulcrum, so that the fulcrum does not sink into the sample, i.e., viscosity measurements are performed under a sufficiently small friction torque without being affected by precipitates from the sample, etc.

[0009] In the device described in Patent Document 6, the rotor is made of a diamagnetic material and is held in the air by magnetic force, thereby performing viscosity measurements that completely eliminate the effects of mechanical friction. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2009-264982 A [Patent Document 2] JP 2012-242137 A [Patent Document 3] JP 2016-031352 A [Patent Document 4] JP 2018-146312 A [Patent Document 5] Patent Publication No. 2021-189078 [Patent Document 6] JP 2015-045621 A Summary of the Invention [Problem to be solved by the invention]

[0011] However, with a device such as that described in Patent Document 1, for non-Newtonian liquids, the flow velocity of the sample around the globules is not known, and the shear rate that gives the viscosity cannot be uniquely determined. Furthermore, for low-viscosity liquids such as pure water, it is difficult to obtain sufficiently high measurement accuracy.

[0012] Furthermore, in the device described in Patent Document 2, when measuring viscosity, it is necessary to accurately measure the distance between the rotor and the bottom of the container (floating height), but since the floating height varies depending on the amount of sample contained in the container, a highly accurate measuring device is required to measure accurately for each measurement. Furthermore, the floating height varies due to evaporation of the sample, changes in the specific gravity of the sample due to changes in temperature, or changes in wettability between the rotor and the sample. Therefore, the accuracy of measuring the viscosity of the sample may change depending on the surrounding environment.

[0013] Furthermore, in devices such as that described in Patent Document 3, mechanical friction between the rotating shaft and the through hole of the rotating shaft holding mechanism cannot be ignored, so it may be difficult to improve the measurement accuracy of the viscosity of the sample.

[0014] Furthermore, in an apparatus such as that described in Patent Document 4, a rotor that is stably independent and vertical can be realized by appropriately adjusting the gravity and buoyancy acting on the rotor submerged in the sample, and the positions of the center of gravity and center of buoyancy; however, the structure needs to be adjusted according to the specific gravity of the sample liquid.

[0015] Furthermore, in the device described in Patent Document 5, although the friction torque at the rotor holding portion cannot be eliminated, it is difficult to measure extremely small viscosities at extremely low shear rates.

[0016] Furthermore, in the device described in Patent Document 6, a diamagnetic rotor is levitated by magnetic force to eliminate mechanical friction. However, this makes the rotor expensive, and the presence of the magnets used for levitation creates spatial constraints, so many problems must be solved in order to design an actual viscosity measuring device.

[0017] The present disclosure aims to provide a viscosity measurement device and method that solves the above-mentioned conventional problems, enables the configuration of a sample container for holding the sample to be measured to be simple and low-cost, and is capable of easily and accurately measuring the viscosity of the sample to be measured over a wide range from low viscosity to high viscosity. [Means for solving the problem]

[0018] To this end, the viscosity measuring device includes a rotor made entirely or partially of a conductive material and having a rotationally symmetrical shape, a wire having one end connected to the rotor at the top of the rotor on the axis of rotational symmetry and suspending and holding the rotor, a holding member holding the other end of the wire above the rotor so that the wire is linearly extending in the vertical direction, a holding member rotation / movement drive mechanism for rotating or translating the holding member around a vertical axis centered on a contact point between the holding member and the wire, and a sample container for accommodating the rotor and the sample to be measured with the rotor in contact with the sample to be measured or the entire rotor in part or all of the rotor. The device comprises a magnet that applies a magnetic field to the rotor, a rotating magnetic field control unit that drives the magnet to cause temporal fluctuations in the magnitude and direction of the magnetic field applied to the rotor, inducing an induced current in the rotor, and applying a rotational torque to the rotor to rotate it through the Lorentz interaction between the induced current and the magnetic field applied to the rotor, and a viscosity detection unit that detects the viscosity of the measurement sample in contact with the rotor based on the rotational motion state of the rotor, and the rotor is held by the holding member via the wire so that it is suspended with the axis of rotational symmetry extending in the vertical direction.

[0019] In another viscosity measuring device, the twist angle of the wire is further maintained by the holding member rotation / movement drive mechanism so as to satisfy the following formula (A).

number

[0020] In still another viscosity measuring device, the device further includes a torsion angle detection mechanism that detects the torsion angle of the wire from the rotation angle of the holding member and the rotation angle of the rotor, and the torsion angle of the wire is maintained within a range that satisfies formula (A) by rotating the upper end of the wire using the holding member rotation / movement drive mechanism.

[0021] In still another viscosity measuring device, the rotational torque has a constant magnitude and changes in direction so as to alternate between a clockwise direction and a counterclockwise direction at a constant cycle.

[0022] In yet another viscosity measuring device, the rotational torque is applied for only a fixed period of time, and the motion of the rotor is a damped oscillatory motion after application of the rotational torque is stopped.

[0023] In yet another viscosity measuring device, the device further includes a standard data storage unit that stores standard data previously measured on the relationship between the rotational torque applied to the rotor in contact with multiple target samples whose viscosity are known and the rotational speed of the rotor, and the viscosity detection unit detects the viscosity of the target samples whose viscosity is unknown by comparing the relationship between the rotational torque applied to the rotor in contact with the target samples whose viscosity are unknown and the rotational speed of the rotor with the standard data.

[0024] A further viscosity measuring device further comprises a rotation detection section which detects the rotation speed of the rotor by detecting the rotation of a mark affixed to the rotor.

[0025] The viscosity measuring method includes the steps of: accommodating a rotor, which is made of a conductive material in part or in whole and has a rotationally symmetric shape, in a sample container together with the sample to be measured, with the rotor being in contact with the sample in part or in whole; and suspending the rotor by a wire held by a holding member, one end of which is connected to the top of the rotor on the axis of rotational symmetry and the other end of which is a holding member, the holding member being rotated around a vertical axis or translated by a holding member rotation / movement drive mechanism, so that the wire is linearly extending in the vertical direction. the steps of: applying a time-varying magnetic field to the rotor to induce an induced current in the rotor, and applying a rotational torque to the rotor to rotate it through the Lorentz interaction between the induced current and the magnetic field applied to the rotor; and detecting the viscosity of a measurement sample in contact with the rotor based on the rotational motion state of the rotor, wherein the rotor is held by the holding member via the wire so that it is suspended with the axis of rotational symmetry extending in the vertical direction. Effect of the Invention

[0026] According to the present disclosure, it is possible to make the configuration of a sample container for holding the substance to be measured simple and low-cost, and to measure the viscosity of the substance to be measured over a wide range from low viscosity to high viscosity easily and with high accuracy. [Brief description of the drawings]

[0027] [Figure 1] 1 is a schematic diagram showing the overall configuration of a measurement device according to a first embodiment. [Diagram 2] 2 is a side cross-sectional view showing a measurement target unit of the measurement device in the first embodiment. FIG. [Diagram 3] 10 is a side cross-sectional view showing a modified example of the measurement target unit of the measurement device in the first embodiment. FIG. [Figure 4] 4 is a conceptual diagram illustrating a method for applying a rotational torque to a rotor by a rotating magnetic field generated by rotating magnets in the first embodiment. FIG. [Diagram 5]4 is a graph showing a change over time in the rotation angle of a rotor in the first embodiment. [Figure 6] 6 is a graph showing the slope of the graph in FIG. 5, that is, the change in the rotation speed of the rotor over time. [Figure 7] 4 is a graph showing the relationship between the rotation speed of a rotor and the applied torque obtained from the rotation speed of the rotor and magnet when the viscosity of a sample is different in the first embodiment. [Figure 8] 10 is a graph showing the time dependency of the rotation angle of a rotor in the second embodiment. [Figure 9] 13 is a graph showing the time dependency of the rotation angle of a rotor in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0029] FIG. 1 is a schematic diagram showing the overall configuration of the measurement device in the first embodiment, FIG. 2 is a side cross-sectional view showing the measurement target unit of the measurement device in the first embodiment, FIG. 3 is a side cross-sectional view showing a modified example of the measurement target unit of the measurement device in the first embodiment, FIG. 4 is a conceptual diagram explaining a method of applying a rotational torque to a rotor by a rotating magnetic field generated by the rotation of a magnet in the first embodiment, FIG. 5 is a graph showing the change in rotation angle of the rotor in the first embodiment, FIG. 6 is a graph showing the slope of the graph in FIG. 5, i.e., the change in rotation speed of the rotor over time, and FIG. 7 is a graph showing the relationship between the rotation speed of the rotor when the viscosity of the sample is different in the first embodiment and the applied torque obtained from the rotation speed of the rotor and magnet.

[0030] As shown in FIG. 1, the viscosity measuring device in this embodiment includes a measurement target unit 30, a drive unit 50, and a measuring unit 80.

[0031] The measuring device is for measuring the viscosity of a sample 32 as a measurement target sample contained in a sample container 31 of a measurement target unit 30, and the sample 32 is, for example, a liquid, a slurry, or a soft material. Here, the soft material is a series of molecular substances such as polymers, liquid crystals, colloids, and biomolecules. In addition, the colloid is, for example, an emulsion such as a milky liquid, an emulsion, and a sol. In addition, the biomolecule is, for example, a biomembrane, a protein, and DNA. The measuring device in this embodiment is typically used in quality control, performance evaluation, raw material management, research and development, etc. in the manufacturing process of medicines, foods, paints, inks, cosmetics, chemical products, paper, adhesives, fibers, plastics, beer, detergents, concrete admixtures, silicon, etc., but may be used in any field and for any purpose.

[0032] In this embodiment, the expressions indicating directions such as up, down, left, right, front, and back used to explain the configuration and operation of each part of the measuring device are relative rather than absolute, and are appropriate when each part of the measuring device is in the position shown in the figure, but if the position changes, they should be interpreted differently in accordance with the change in position.

[0033] As shown in the figure, the drive unit 50 includes a drive magnet 53, a drive magnet holder 52 that supports the drive magnet 53 from below, and a motor 51 as a rotary drive source that rotates the drive magnet holder 52. The motor 51 rotates a motor shaft 51a that is a rotary shaft. The drive magnet holder 52 is connected to the motor shaft 51a and rotates around the motor shaft 51a.

[0034] In the example shown in the figure, the drive magnet holder 52 is a substantially square flat plate in a plan view, and the shaft end of the motor rotating shaft 51a is connected to its center. The drive magnet 53 is a pair of magnets consisting of a first drive magnet 53a and a second drive magnet 53b, which apply a magnetic field to the rotor 20. The first drive magnet 53a and the second drive magnet 53b have the same size and magnetic force, and are placed and fixed on the drive magnet holder 52 so as to be point symmetrical with the motor rotating shaft 51a as an axis of symmetry in a plan view. The first drive magnet 53a and the second drive magnet 53b are arranged so that the magnetic poles in the vertical direction are opposite to each other.

[0035] That is, in the example shown in the figure, the first drive magnet 53a is arranged so that the upper side is a north pole and the lower side is a south pole, and the second drive magnet 53b is arranged so that the upper side is a south pole and the lower side is a north pole.

[0036] In the example shown in the figure, the driving magnet 53 is composed of a pair of magnets, a first driving magnet 53a and a second driving magnet 53b, but the number of magnets constituting the driving magnet 53 may be any number as long as a rotating magnetic field can be generated. For example, N (N=2n, n is an integer n≧1) small magnets may be arranged along the rotation direction of the driving magnet holder 52 so that the magnetic poles on the upper surfaces of the magnets alternate between N and S poles. The driving magnet holder 52 may be configured so that a magnetic field is generated parallel to the liquid surface of the sample 32 contained in the sample container 31 so that the upper surfaces of the first driving magnet 53a and the second driving magnet 53b are vertical.

[0037] As shown in Figures 1 and 2, in this embodiment, the measurement target unit 30 has a sample container 31, a sample 32 as the substance to be measured contained in the sample container 31, a rotor 20 arranged to be in contact with the sample 32, more specifically, so that at least a portion of the rotor 20 is submerged in and in contact with the sample 32, a wire 38 that holds the rotor 20 in a suspended state, a wire holding member 42 that holds the rotor 20 by holding the upper end portion of the wire 38, and a sample stage 36 that supports the sample container 31 from below.

[0038] The rotor 20 has a circular shape in a plan view, and includes a flat, disk-shaped rotating plate 21 through whose center a rotating shaft 26, which is the axis of rotational symmetry of the rotor 20, passes, and a cylindrical shaft 22 extending upward from the center of the rotating plate 21. One end, i.e., the lower end portion, of the wire 38 is connected to the upper end portion of the cylindrical shaft 22, i.e., the uppermost portion on the axis of rotational symmetry of the rotor 20. As a result, the cylindrical shaft 22 and the wire 38 pass over the rotating shaft 26, and the rotor 20 is held via the wire 38 by a wire holding member 42 to which the other end, i.e., the upper end portion, of the wire 38 is connected.

[0039] In this embodiment, the wire 38 may be, for example, a thin metal wire, a thread formed by twisting organic fibers or carbon fibers, or a plastic thread. As described later, it is preferable that the magnitude of the restoring torque generated by twisting the wire 38 is known or calculated using the physical properties of the material. For this reason, in the following description, the wire 38 is assumed to be a gold (Au) wire provided by a metal material manufacturer (for example, Nilaco Corporation), has a composition (purity of gold) of 99.99% or more, has a circular cross-sectional shape, and has a uniform diameter in the length direction, more specifically, has a diameter of 30 μm or 50 μm.

[0040] The rotor 20 may be a member in which the rotating plate 21 and the cylindrical shaft 22 are integrally formed, or may be a member formed by connecting the rotating plate 21 and the cylindrical shaft 22 which are formed separately. Furthermore, the cylindrical shaft 22 may be omitted, and the lower end portion of the wire 38 may be directly connected to the center of the rotating plate 21.

[0041] Moreover, at least a part of the rotor 20 is made of a conductor (e.g., a metal material). For example, the rotor 20 may be made of only a part made of a conductive material such as aluminum, and the other part made of a dielectric material such as plastic or vinyl. For example, the rotating plate 21 can be produced by attaching a commercially available aluminum foil or the like to the upper surface of a plastic disk. In this way, the rotating plate 21 can be formed easily and at low cost from a commercially available plastic disk and commercially available aluminum foil. In this embodiment, the rotating plate 21 is formed of an aluminum disk.

[0042] The rotating plate 21 has a flat disk shape with the rotation axis 26 of the rotor 20 passing through its center, and the cylindrical shaft 22 is disposed so as to coincide with the central axis of the rotating plate 21. Furthermore, the upper end portion of the cylindrical shaft 22 is connected to a wire 38, which is stretched linearly in the vertical direction by the gravity acting on the rotor 20.

[0043] A mark 21a having a size detectable by a rotation detection sensor 87 of a measurement unit 80 for detecting the rotation of the rotor 20 is provided on the surface of either the rotating plate 21 or the cylindrical shaft 22. In the example shown in the figure, the mark 21a is provided on the outer surface of the rotating plate 21.

[0044] The sample container 31 has a flat disk-shaped bottom plate 31a and a cylindrical side wall 31b connected to the periphery of the bottom plate 31a. A cylindrical container lid 35 is attached to the upper end of the side wall 31b. The sample container 31 contains a sample 32 as an object for measuring the viscosity (i.e., viscosity coefficient) η as a mechanical property. Each of the sample container 31 and the container lid 35 is formed of a transparent material such as glass or plastic. The sample container 31 is a cylindrical container with a bottom, such as a small petri dish. The inner diameter of the sample container 31 may be slightly larger than the diameter of the rotating plate 21 of the rotor 20.

[0045] The sample container 31 also includes an upper cover 33 that covers the upper surface of the sample container 31. The upper cover 33 is arranged parallel to the rotating plate 21 of the rotor 20, so that the area between the upper surface of the rotating plate 21 and the upper cover 33, and the area between the lower surface of the rotating plate 21 and the bottom plate 31a of the sample container 31 each constitute a parallel plate type rotational viscometer. A circular hole 33a is provided in the center of the upper cover 33, and the cylindrical axis 22 of the rotor 20 passes through the hole 33a. If the distance between the upper cover 33 and the upper surface of the rotating plate 21 and the distance between the bottom plate 31a of the sample container 31 and the lower surface of the rotating plate 21 are equal, the configuration is substantially the same as two parallel plate type viscometers having the same sample thickness, and the measurement data can be compared with that of a conventional parallel plate type viscometer.

[0046] The container lid 35 is used to completely isolate the sample 32 from the external environment (such as the outside air) in order to prevent evaporation of the sample 32 contained in the sample container 31 and the inclusion of foreign matter into the sample 32, and can be omitted if not necessary.

[0047] The specimen container 31 and the container lid 35 can be a commercially available disposable petri dish made of glass or plastic. Therefore, the specimen container 31 and the container lid 35 can be prepared at low cost, and even if the specimen container 31 and the container lid 35 are discarded every time a measurement is performed, the measurement cost does not increase. Furthermore, even when the specimen 32 is a substance that requires special care in disposal, such as a biological material, the rotor 20, the specimen container 31, and the container lid 35 can be easily discarded, and disposal can be easily performed in the same manner as other medical instruments, with no problems in post-treatment such as incineration and sterilization.

[0048] In the example shown in the figure, the mark 21a is disposed at a position detectable by the rotation detection sensor 87 on the upper surface of the rotating plate 21, but this is not necessarily limited to this example and may be disposed, for example, on the cylindrical shaft 22. The change in the position of the mark 21a can be optically read by the rotation detection sensor 87 or an imaging device (not shown) to calculate the rotation speed of the rotor 20.

[0049] The lower end of wire 38, which is a thin wire that holds rotor 20, is connected to rotor 20 at the top of cylindrical shaft 22 of rotor 20, and the upper end of wire holding member 42 is held above by wire holding member 42. And, as shown in the figure, wire holding member 42 is held by holding member position and rotation control mechanism 41, which serves as a holding member rotation and movement drive mechanism, located above it.

[0050] The holding member position / rotation control mechanism 41 rotates or translates the wire holding member 42 around a vertical axis centered on the contact point between the wire holding member 42 and the wire 38, and includes a holding member control mechanism that controls the vertical and horizontal positions of the wire holding member 42 and rotates the wire holding member 42 around the rotation axis 26, thereby making it possible to control the vertical and horizontal positions of the rotor 20 via the wire 38 and to rotate the upper end portion of the wire 38. The operation of the holding member control mechanism may be performed manually or remotely by an automatic translation stage or an automatic rotation stage, or may be provided with both.

[0051] In addition, the position and rotation of the wire holding member 42 are controlled by reading the twist angle of the wire holding member 42 from the rotation angle of the rotor 20 calculated by the rotation detection unit 81 based on the detected electrical signal of the rotation detection sensor 87 and images captured by a video camera or an imaging device, and the rotation angle of the holding member position / rotation control mechanism 41 at that time, so that the twist angle falls within the maximum twist angle described later.

[0052] The sample stage 36 is a flat plate member for fixing the sample container 31 filled with the sample 32, and is arranged so that its upper surface is parallel to the upper surface of the drive magnet holding stage 52. This makes the rotating plate 21 of the rotor 20 in the sample 32 in the sample container 31 parallel to the plane formed by the upper surfaces of the first drive magnet 53a and the second drive magnet 53b when rotated.

[0053] The motor 51 that rotates the drive magnet holder 52 is fixed so that the motor rotation shaft 51 a is perpendicular to the upper surface of the drive magnet holder 52 .

[0054] The positional relationship of the rotation shaft 26 of the rotor 20 in a plan view and the positional relationship of the motor rotation shaft 51a of the motor 51 are determined so that the rotating plate 21 of the rotor 20 does not contact the inner surface of the side wall 31b of the sample container 31 and rotates in contact with the sample 32. That is, the sample container 31 and the motor 51 are arranged so that the center of the rotor 20, the center of the bottom plate 31a of the sample container 31, and the axial direction of the motor rotation shaft 51a overlap in a plan view.

[0055] By arranging each part of the measurement target unit 30 and each part of the drive unit 50 in this way, it is possible to generate a magnetic field that varies with time with respect to the rotor 20.

[0056] As described above, when the drive magnet 53 rotates due to the rotation of the drive magnet holder 52, a rotating magnetic field is generated. Then, an induced current is generated in the conductive portion of the rotor 20, i.e., the portion formed by the conductor, by the rotating magnetic field, and a rotational torque T in a direction following the rotation of the magnetic field is generated in the portion formed by the conductor of the rotor 20 due to the Lorentz interaction between the induced current and the magnetic field. M The rotation torque T M The magnitude of is proportional to the difference between the rotation speed of the drive magnet 53 and the rotation speed of the rotor 20. In other words, the torque applied to the rotor by the rotation of the magnet is proportional to the rotation speed difference ΩMD between the rotation speed ΩM of the magnet and the rotation speed ΩD of the rotor (here, the rotation speed difference ΩMD = rotation speed ΩM - rotation speed ΩD).

[0057] In addition, the shear deformation rate of sample 32 is proportional to the rotation speed of rotor 20, i.e., the rotation speed Ω. Therefore, by measuring the rotation speed of rotor 20 and the rotation speed Ω of drive magnet 53, i.e., the rotation speed of motor 51, the viscosity of sample 32 can be measured.

[0058] In this embodiment, a measurement unit 80 calculates the viscosity of a sample 32. As shown in Fig. 1, the measurement unit 80 has a rotation detection unit 81, a viscosity detection unit 82, a rotating magnetic field control unit 83, a standard data storage unit 84, an apparatus control unit 85, a wire holding member rotation drive control unit 86, and a rotation detection sensor 87.

[0059] The rotation detection sensor 87 is disposed at a position above the sample container 31 (specifically, above the container lid 35) at which it can detect a mark 21a provided at a detectable position of the rotor 20 in the sample 32 in the sample container 31, and optically detects the rotational position of the mark 21a (in the example shown in the figure, the mark 21a disposed on the outer surface of the rotating plate 21). For example, the rotation detection sensor 87 can emit laser light from a light irradiation unit (not shown), cause reflected light from the mark 21a to be incident on a light receiving unit (not shown), and output a detection electrical signal corresponding to the intensity of the incident light.

[0060] Also, instead of the rotation detection sensor 87, an imaging device in which a lens and an imaging element such as a CCD are added to a microscope may be adopted, and an image obtained by magnifying and capturing the moving state of the mark 21a during the rotation of the rotor 20 may be output, and the rotation speed (number of rotations) ΩD (number of revolutions of the mark 21a) of the rotor 20 may be detected by image processing. Also, the mark 21a may be arranged on the upper surface of the rotating plate 21 of the rotor 20, and the moving state of the mark 21a may be captured by the imaging device, and the number of rotations ΩD of the rotor 20 may be detected.

[0061] Furthermore, a laser can be irradiated onto the upper surface of the rotating plate 21 of the rotor 20 or the outer surface of the cylindrical shaft 22, and the changes in the reflection and interference patterns due to rotation can be optically measured to detect the rotational speed (number of rotations) ΩD of the rotor 20.

[0062] Furthermore, a part of the rotating plate 21 or the cylindrical shaft 22 of the rotor 20 may be formed of a dielectric material to form the mark 21a, and a pair of electrodes may be arranged such that the rotating plate 21 or the cylindrical shaft 22 is sandwiched between the pair of electrodes to form a capacitor. In this case, the rotation detection sensor 87 outputs a detection electric signal when a dielectric material serving as the mark 21a for detecting rotation passes between the pair of electrodes. That is, the rotation detection unit 81 may be configured to detect a change in capacitance of a capacitor formed by an electrode pair when the dielectric material serving as the mark 21a passes between the electrodes, detect the number of times the capacitance changes in a predetermined period (for example, one second), and detect the rotation speed (number of rotations) ΩD of the rotor 20.

[0063] Furthermore, a part of the rotating plate 21 or the cylindrical shaft 22 of the rotor 20 may be formed from a permanent magnet to serve as a mark 21a, and a magnetic field detection element may be disposed to read the rotational speed (number of rotations) ΩD of the rotor 20 from the change in magnetic field strength that accompanies the rotation of the rotor 20.

[0064] The rotation detection unit 81 detects the rotation of the rotor 20 by the detection electric signal supplied from the rotation detection sensor 87, and obtains and outputs the number of rotations ΩD by taking the number of detections per unit time (for example, 1 second) as the rotation speed per unit time (rps: revolutions per second). In addition, the rotation detection unit 81 can also use an image captured by an imaging device as described above, instead of using the detection electric signal from the rotation detection sensor 87, in detecting the rotation speed ΩD of the rotor 20. In this case, the mark 21a added to the rotor 20 may be detected by image processing from the captured image captured and output by the imaging device, and the rotation speed ΩD per unit time may be obtained. In addition, the rotation detection unit 81 can also use a capacitor as described above. In this case, the rotation detection unit 81 may detect a change in the capacitance of a capacitor formed by an electrode pair by the detection electric signal from the capacitor, detect the number of the capacitance changes in a predetermined period (for example, 1 second), and detect the rotation speed ΩD of the rotor 20. In addition, the rotation detection unit 81 can also use a magnetic field detection element as described above. In this case, the rotation detection unit 81 may detect the output voltage of a magnetic field detection element such as a Hall element, detect the number of times the voltage changes in a predetermined period (for example, one second), and detect the rotation speed ΩD of the rotor 20.

[0065] The viscosity detection unit 82 determines the gradient ΩMD / ΩD (where ΩMD=ΩM-ΩD) in the sample 32. At this time, the viscosity detection unit 82 controls the rotating magnetic field control unit 83 to rotate the motor 51 at a plurality of different rotational speeds ΩM, and outputs a control signal to the rotation detection unit 81 every time the rotational speed is changed. Every time a control signal is supplied from the viscosity detection unit 82, the rotation detection unit 81 inputs the rotation speed (rotational speed) ΩD of the rotor 20 in the sample 32 accommodated in the sample container 31 at the rotational speed ΩM from the rotation detection sensor 87. Then, the rotation detection unit 81 outputs the detected rotational speed ΩD to the viscosity detection unit 82 in response to the control signal.

[0066] Then, the viscosity detection unit 82 reads out the viscosity η [mPa·s] corresponding to the slope ΩMD / ΩD of the sample 32 from the viscosity detection table stored in the standard data storage unit 84, and outputs this as the viscosity η [mPa·s] of the sample 32. Here, if an empirical formula is stored in the standard data storage unit 84, the viscosity detection unit 82 may read out the empirical formula from the standard data storage unit 84, and substitute the slope ΩMD / ΩD into the empirical formula to calculate the viscosity η [mPa·s] of the sample 32.

[0067] The rotating magnetic field control unit 83 controls the rotation of the motor 51 so that the motor shaft 51a rotates at a set number of rotations. This causes the drive magnet holder 52 to rotate via the motor shaft 51a, causing the magnetic field generated by the first drive magnet 53a and the second drive magnet 53b to rotate, generating a rotating magnetic field that rotates the rotor 20 at a uniform speed within the sample 32.

[0068] The standard data storage unit 84 stores a viscosity detection table showing the correspondence between the slope ΩMD / ΩD of the graph shown in FIG.

[0069] The viscosity detection table is created as follows. In the viscosity measuring device of this embodiment, a standard sample with a known viscosity is placed (filled) in the sample container 31, the rotor 20 is placed in the standard sample, and the motor 51 is rotated at a plurality of preset rotational speeds ΩM. The rotational speed ΩD of the rotor 20 corresponding to each rotational speed ΩM of the motor 51 is measured by the rotation detection unit 81. The measurement of the rotational speed ΩD for this standard sample is performed for standard samples having a plurality of different viscosities η (samples whose viscosities η are known in advance). Also, instead of the viscosity detection table, an empirical formula showing the correspondence between the viscosity η [mPa s] and the slope ΩMD / ΩD may be stored.

[0070] The device control section 85 controls the operation of each section within the measurement unit 80 .

[0071] In this embodiment, the rotor 20 has a flat disk-shaped rotor plate 21 and a cylindrical shaft 22 extending upward from the center of the rotor plate 21. However, the rotor 20 may have a shape that is rotationally symmetrical with respect to the rotor shaft 26, and may be a cylinder or a hollow cylinder, as in the modified example shown in FIG. 3. In this case, the classification of the rotational viscometer is the same as that of a double cylindrical type. In the example shown in FIG. 3, the sample container 31 is also cylindrical so as to fit the shape of the rotor 20, and the upper cover 33 is omitted. The cylindrical shaft 22 is also omitted, and the lower end portion of the wire 38 is directly connected to the upper end portion of the rotor 20, i.e., the center of the upper surface. The upper surface of the rotor 20 is located below the liquid surface of the sample 32.

[0072] Next, the rotating magnetic field generates a rotational torque T M That is, the rotor 20 generates a rotational torque T M The method of providing the above will now be described in more detail.

[0073] First, a case will be described in which the conductive portion of rotor 20 has a thickness (dimension) in the direction of rotation axis 26. Specifically, the shape of rotor 20 may be a column, a cylinder, a cone, or a sphere. In this embodiment, the rotor 20 has a columnar or cylindrical shape, as in the modified example shown in FIG.

[0074] Here, the rotor 20 is entirely made of aluminum, which is a conductive material. In this case, eddy currents due to the rotating magnetic field are generated on the side surface of the rotatable cylindrical rotor 20, where the magnetic field is oriented in a substantially horizontal direction and rotates at a constant angular velocity ΩM. For simplicity of explanation, only the horizontal component of the magnetic field is considered here, but the following explanation will not be hindered even if the magnetic field has a vertical component.

[0075] Considering an orthogonal coordinate system in which the plane including the bottom surface of rotor 20 is the xy plane and the axis extending vertically is the z axis, the vector representing the magnetic field on the side surface of rotor 20 is expressed by the following equation (1).

[0076]

number

[0077] For example, when the time is t=2πn / ΩM (n is an integer), the magnetic field is in the +x direction, then rotates to the +y direction, -x direction, and -y direction, respectively. Therefore, at this time, the +y component of the magnetic field increases, and the +x component does not increase or decrease.

[0078] Therefore, when rotor 20 is viewed from the -y direction toward the +y direction, a counterclockwise eddy current is generated on the side surface of rotor 20 according to Lenz's law.

[0079] The eddy current and magnetic field generate a Lorentz force F. When the current vector is i and the magnetic field vector is B, the Lorentz force F is given by their cross product, F=i×B. Because it is a cross product, this force is greatest at the point where the magnetic field and current intersect at right angles, and its direction is the rotation of the magnetic field perpendicular to the current and magnetic field directions, respectively. As a result, a torque T is generated on the side of the rotor 20 in the direction in which it tries to rotate in response to the rotation of the magnetic field. M As a result, the rotor 20 rotates while being in contact with the sample 32 and while being subjected to a viscous resistance torque Tvis due to the sample 32.

[0080] In this way, the rotating magnetic field generates a rotational torque T M It is found that it works.

[0081] In the measurement target unit 30, the rotational torque T acting on the rotor 20 MSince the rotor 20 rotates in the sample 32, the rotation speed ΩM of the magnetic field in the above formula (1) is replaced by the rotation speed difference ΩM-ΩD, which is the difference between the rotation speed ΩM of the magnetic field and the rotation speed ΩD of the rotor 20. In addition, the rotation torque T applied by the magnetic field is M The magnitude of is proportional to the square of the magnetic field strength.

[0082] As a result, eddy currents generated in the conductors of the rotor 20 generate a rotational torque T M (Torque T M ) to the rotor 20, a rotational torque T M Then, a rotational torque T M As a result of the application of the torque T M The object will rotate in the direction in which the magnetic field is applied.

[0083] In addition, as the rotor 20 rotates, a viscous resistance torque Tvis due to shear flow corresponding to the viscosity η of the sample 32 is applied to the rotor 20. Due to this viscous resistance torque Tvis, the rotation speed ΩD of the rotor 20 does not reach the rotation speed ΩM of the magnetic field by an amount proportional to the viscous resistance torque Tvis.

[0084] Therefore, the rotational torque T applied to the rotor 20 is M The magnitude of is proportional to the difference between the rotation speed ΩM of the rotating magnetic field (similar to the rotation speed ΩM of the motor 51) and the rotation speed ΩD of the rotor 20.

[0085] Next, a case will be described in which the conductive part of rotor 20 does not have a thickness (dimension) in the direction of rotation shaft 26, that is, the extent in the direction along rotation shaft 26 is not sufficiently large. Specifically, this is the case in which the conductive part is a thin disk such as rotor plate 21, as in the example shown in Figures 1 and 2.

[0086] Here, a method of applying a rotational torque to the rotor 20 will be described with reference to Fig. 4. Fig. 4 is a conceptual diagram illustrating a method of applying a rotational torque to the rotor 20 by a rotating magnetic field generated by the rotation of the first drive magnet 53a and the second drive magnet 53b.

[0087] In FIG. 4, the north pole of the first drive magnet 53a and the south pole of the second drive magnet 53b generate a magnetic field perpendicular to a certain reference plane (here, a plane including the rotating plate 21).

[0088] This reference plane is a two-dimensional reference plane consisting of the x-axis and the y-axis, and the axis of rotation of the rotor 20 rotating on this two-dimensional reference plane is the z-axis.

[0089] Hereinafter, the z-axis component of the magnetic field at a point (x, y, z) on or near the reference two-dimensional plane will be denoted as Bz(x, y).

[0090] As already mentioned, it is assumed that the magnetic field does not depend on the z-axis because it is perpendicular to the reference two-dimensional plane, but the following explanation will not be hindered even if it depends on the z-axis. Also, if there is a magnetic field component perpendicular to the reference two-dimensional plane, even if there is another magnetic field component that is not perpendicular to the reference two-dimensional plane, it will not be a hindrance to applying a rotational torque to the rotor 20.

[0091] 4, the rotation of the first drive magnet 53a and the second drive magnet 53b is observed from the direction of the positive axial component of the z-axis. When the drive magnet holder 52 is rotated counterclockwise by the motor 51, the magnetic field Bz(x, y) also rotates counterclockwise, and a counterclockwise rotating magnetic field is generated.

[0092] For example, consider the magnetic field at the point where Bz(x, y)>0 in the half-space x>0 and Bz(x, y)<0 in the half-space x<0.

[0093] In this case, in the half-space y>0, the time change of the magnetic field ∂Bz / ∂t is positive (∂Bz / ∂t>0), while in the half-space y<0, the time change of the magnetic field ∂Bz / ∂t is negative (∂Bz / ∂t<0).

[0094] Here, consider a rotor placed on a reference two-dimensional plane with the z-axis as the axis of rotation.

[0095] In this case, if a rotating magnetic field is applied to the conductors in the rotor 20, considering Lenz's law, clockwise eddy currents flow inside the conductor parts of the rotor 20 in the half-space y>0, and counterclockwise eddy currents flow in the half-space y<0.

[0096] As described above, when eddy currents are generated parallel to the reference two-dimensional plane, the magnetic fields generated by the first drive magnet 53a and the second drive magnet 53b are perpendicular to the reference two-dimensional plane, and therefore the Lorentz force acting on the conductors of the rotor 20 due to the eddy currents and the magnetic field is generated parallel to the reference two-dimensional plane.

[0097] Therefore, the Lorentz force generated at any point P in the region of x>0 and y>0 on the reference two-dimensional plane is FL1(F x , F y , 0), then F x >0 and F y >0.

[0098] In this case, on the reference two-dimensional plane, a Lorentz force FL2 (-F x , -F y , 0) occurs.

[0099] That is, the Lorentz force FL1 (F x , F y , 0) and Lorentz force FL2(-F x , -F y , 0), the forces acting on points P and Q form a couple.

[0100] As a result, a rotational torque is applied to the conductors of rotor 20, causing rotor 20 to rotate counterclockwise around the z-axis as its rotation axis.

[0101] Furthermore, with the rotation of the rotating magnetic field, the Lorentz force FL3 (F x , -F y , 0) is applied.

[0102] In addition, for any point in the region of x<0 and y>0 in the reference two-dimensional plane, the Lorentz force FL4(-F x , F y , 0) is applied.

[0103] Therefore, a counterclockwise rotational torque is generated on the rotor 20 by the Lorentz forces FL3 and FL4.

[0104] As described above, a magnetic field perpendicular to a reference two-dimensional plane generates eddy currents, and when this magnetic field rotates counterclockwise, a rotating magnetic field is generated, and the eddy currents generated generate a counterclockwise Lorentz force at two points relative to the z-axis.

[0105] As a result, the eddy currents generated in the conductors of rotor 20 are subjected to a counterclockwise rotational torque as a whole, and a rotational torque is applied to rotor 20 via the conductors.

[0106] If the rotating magnetic field rotates clockwise, the direction of current flow in the eddy current will be opposite to that in the case where the rotating magnetic field rotates counterclockwise, and the rotor 20 will also rotate clockwise.

[0107] The magnitude of the rotational torque applied to the rotor 20 is proportional to the difference between the rotational speed ΩM of the rotating magnetic field (similar to the rotational speed of the motor 51) and the rotational speed ΩD of the rotor 20.

[0108] Therefore, a rotational torque is applied to the rotor 20 placed in the sample 32 placed in the sample container 31. As a result of the application of this rotational torque, the rotor 20 rotates in the sample 32 in the direction in which the rotational torque is applied.

[0109] As described above, rotor 20 may have any shape as long as it has a rotational symmetry, and whether its shape is cylindrical or a thin disk, it is possible to apply a torque of the magnitude required for measuring viscosity.

[0110] Meanwhile, the lower end portion of wire 38 is connected to the upper end portion of rotor 20, and the upper end portion of wire 38 is held and fixed above rotor 20 by wire holding member 42. Wire 38 is made of, for example, metal, quartz, glass fiber, carbon fiber, organic fiber, etc., and it is desirable to use wire 38 having a uniform diameter.

[0111] The wire 38 has rigidity and exhibits a restoring force against twisting. The rotor 20 is suspended by the wire 38, and since the connection point of the lower end portion of the wire 38 is on the axis of rotational symmetry of the rotor 20, the rotor 20 is suspended by gravity with its axis of rotational symmetry (i.e., the rotation axis 26) facing vertically downward.

[0112] For this reason, even if rotor 20 is partially or entirely submerged in sample 32, so long as it has an appropriately large weight relative to sample 32, wires 38 will be in a straight line under tension and will hold rotor 20. This position of rotor 20 will be stably held even if the above-mentioned rotational torque is applied by the movement of drive magnet 53, and furthermore, rotor 20 will rotate while stably holding rotation shaft 26.

[0113] Furthermore, by adjusting the vertical position of the wire holding member 42 that holds the upper end portion of the wire 38, the vertical position of the rotor 20 connected to the wire 38 can be easily and accurately adjusted. This makes it possible to accurately control the distance between the upper surface of the bottom plate 31a of the sample container 31 and the lower surface of the rotor 20 (the lower surface of the rotating plate 21) or the distance between the lower surface of the upper cover 33 and the upper surface of the rotor 20 (the upper surface of the rotating plate 21), i.e., the sample thickness in viscosity measurement.

[0114] Moreover, by adjusting the horizontal position of the wire holding member 42, the horizontal position of the rotation shaft 26 of the rotor 20 can be easily and accurately adjusted. This allows the rotation shaft 26 of the rotor 20 to be easily adjusted so as to be on the rotation shaft of the rotating drive magnet 53. Furthermore, the influence of convection of the sample 32 and the like can be eliminated, and the horizontal position of the rotor 20 can be stably maintained.

[0115] On the other hand, since the wire 38 exhibits rigidity against torsion, when torque is applied continuously in one direction for a long time, the rotation angle of the rotor 20 increases, and a restoring torque due to the rigidity against torsion is generated. As a result, the rotor 20 is subjected to a torque provided by the time-varying magnetic field and a restoring force due to the torsional rigidity of the wire 38. If this restoring force is sufficiently small, the resistance torque due to viscosity can be estimated by ignoring its effect, and if the dependency of the restoring torque on the rotation angle is known, the effect can be subtracted by calculation to estimate the resistance torque due to viscosity.

[0116] Next, the method for measuring viscosity in this embodiment will be described in detail.

[0117] In the measurement of viscosity in this embodiment, as described above, it is necessary to perform the viscosity measurement taking into consideration the condition where the contribution of the stiffness of the wire 38 can be ignored. This condition will be described in detail below.

[0118] If the rotor 20 is left for a sufficient period of time without the application of torque by the drive magnet 53, the wire 38 will reach a balanced state with no twist. The angle at this time will be referred to as the balanced angle here.

[0119] To measure viscosity, the drive magnet 53 is driven to apply a rotational torque to the rotor 20. When the rotor 20 rotates from the balance angle, the wires 38 exert a torsional torque on the rotor 20 proportional to the rotation angle, which attempts to return the angle of the rotor 20 to the balance angle.

[0120] At this time, the restoring force torque TG that the wire 38 exerts on the rotor 20 is expressed by the following equation (2).

[0121]

number

[0122] Here, G is the shear modulus of the wire 38, R W is the radius of the wire 38, L is the length of the wire 38 (i.e., the distance between the upper end of the rotor 20 and the point where the wire holding member 42 fixes the wire 38), and θ is the rotation angle of the rotor 20 from the balance angle.

[0123] At this time, if the torque of the restoring force of the wire 38 is sufficiently smaller than the torque due to the viscosity of the sample 32 to be measured, the torque of the restoring force of the wire 38 has almost no effect on the viscosity measurement.

[0124] When the rotor 20 is a circular plate of constant thickness like the rotating plate 21 shown in Figures 1 and 2, and the thickness of the sample 32 is also constant, forming a parallel plate type viscometer, the viscous resistance torque Tvis due to viscosity is expressed by the following equation (3).

[0125]

number

[0126] Here, R Dis the radius of the rotor 20, h is the thickness of the sample 32, η is the viscosity of the sample 32 to be measured, and ω is the rotational angular velocity of the rotor 20.

[0127] Here, if the required measurement accuracy of viscosity is α, the condition that the torsional torque due to the twisting of the wire 38 is sufficiently smaller than the torque due to viscosity is TG<αTvis, that is, the following formula (4).

[0128]

number

[0129] Here, when the required accuracy is, for example, 1%, α=1 / 100.

[0130] Therefore, if the maximum angle satisfying the condition expressed by the above equation (4) is defined as θMAX and the rotation state of the rotor 20 is observed only within the range satisfying -θMAX<θ<θMAX, the effect of twisting of the wire 38 can be eliminated and the viscosity can be accurately measured.

[0131] Here, the shear rate is ωR D / h, if the shear rate to be measured is γ, then the above formula (4) can be expressed by the following formula (5).

[0132]

number

[0133] Here, we will calculate a specific value of the rotation angle θ of the rotor 20 from the equilibrium angle. A gold wire with a diameter of 30 μm and a length of 20 cm is used as the wire 38, pure water, which is a typical low-viscosity sample, is used as the sample 32, the radius of the rotor 20 is 4 cm, the thickness of the sample 32 is 1 mm, and the shear rate to be measured is 1 s -1], then G = 27 [GPa], and θ < 0.19 [rad], i.e., less than 10 degrees. This is the angle range in which rotation can be observed sufficiently in practice. In this case, the time required to rotate twice this rotation angle θ is about 15 [s], which satisfies the steady state condition described later.

[0134] Here, for simplicity of explanation, the value of the viscous resistance torque Tvis has been calculated assuming a parallel plate type viscosity measuring device. However, since the viscous resistance torque Tvis can be calculated for all other configurations of conventional rotational viscometers, such as a double cylinder type, the condition of the above formula (4) can be determined using the expression.

[0135] Thus, even with the most accurate commercially available rotational viscometers, the minimum shear rate at which the viscosity of water can be measured is 10 to 100 [s -1 Considering this, it can be seen that the viscosity measuring device in this embodiment can perform measurements with a high accuracy of 1% in a low shear rate range that is 1 / 100 of that.

[0136] As described above, if the viscosity measurement is performed as described above, provided that the rotational motion of rotor 20 from the balance angle is within the maximum angle expressed by equation (4), the influence of mechanical friction can be eliminated and the viscosity measurement can be performed.

[0137] In the above example, the cross section of the wire 38 is circular in consideration of availability, but the cross section of the wire 38 may be another shape, for example, a square or a rectangle. In this case, R W is the characteristic length of the cross section of the wire 38; for example, if the cross section is a square, it is 1 / 2 the length of one side of the square, and if the cross section is a rectangle, it is 1 / 2 the average of the lengths of the short side and the long side, so that the above formula (2) does not lose its generality.

[0138] Next, the measurement time that should be considered in the measurement according to this embodiment will be described.

[0139] The viscosity measurement method in this embodiment is based on the premise that the liquid sample 32 sandwiched between the disk-shaped rotor 20 and the top cover 33, or the bottom plate 31a of the sample container 31, or between the side of the cylindrical rotor 20 and the side wall 31b of the sample container 31, is in a steady laminar flow.

[0140] To realize this steady laminar flow, the following two times must elapse: one is the time τI required for the rotor 20, which has a moment of inertia, to reach a steady rotational speed, and the other is the time τQ required for the laminar flow to become a Couette flow, which is a uniform shear rate field in the thickness direction.

[0141] If the moment of inertia of the rotor 20 is I, it is known that τI is given by the following equation (6).

[0142]

number

[0143] Here, Γ is the contribution of viscosity, and if the viscous resistance torque when the rotor 20 rotates at a rotational angular velocity ω is Tvis, then Γ can be expressed as Γ=Tvis / ω. D When a circular plate made of a uniform material with uniform mass, thickness d, and density ρ is used, the moment of inertia I is given by the following equation (7).

[0144]

number

[0145] Furthermore, τQ is given by the time it takes for the momentum associated with the fluid motion to diffuse through the thickness of the sample 32, and this time is given by the following equation (8) from the Navier-Stokes equations.

[0146]

number

[0147] In measuring viscosity in a steady flow, it is necessary to continue to apply a constant torque for a period of time that is at least longer than the longer of these periods of time.

[0148] The rotational torque T applied to the rotating plate 21 of the rotor 20 is M (That is, the torque T applied to the entire rotor 20 M ), the rotation speed ΩD of the rotor 20 rotating in the sample 32, and the radius R of the rotor 20 (i.e., the radius of the rotating plate 21) D and the distance between the lower surface of the rotating plate 21 and the upper surface of the bottom plate 31a of the sample container 31 (ie, the thickness of the sample 32 below the rotating plate 21).

[0149] In measuring the viscosity η of the sample 32, the rotational torque T applied to the rotating plate 21 of the rotor 20 M is obtained in advance as a function of the difference in rotation speed ΩMD between the rotation speed ΩM of the rotating magnetic field and the rotation speed ΩD of the rotor 20, using a standard sample whose viscosity η is known in advance.

[0150] As described above, according to this embodiment, the first driving magnet 53a and the second driving magnet 53b that generate a rotating magnetic field can be disposed below the sample stage 36 on which the sample container 31 is disposed, making it possible to make the measuring device for measuring viscosity smaller than in the conventional case.

[0151] In the example shown in the figure, the drive magnet 53 is composed of a pair of magnets, a first drive magnet 53a and a second drive magnet 53b. In this case, a rotating magnetic field is generated by a combination of one set of one N pole and one S pole arranged facing each other in a plan view. In contrast, the number of sets of magnets that impart torque to the main body of the rotor 20 may be any number greater than or equal to one, and for example, four magnets that are square in plan view may be arranged so that the S poles and N poles are staggered.

[0152] It should be noted that instead of generating a rotating magnetic field by rotating the drive magnet holder 52 that holds the drive magnet 53, a rotating magnetic field may be generated using an electromagnet.

[0153] In this way, according to this embodiment, it is possible to completely eliminate the effects of mechanical friction at the contact point between the rotor 20 and the part that holds the rotor 20 without using any special mechanism, thereby making it possible to measure viscosity with sufficient accuracy.

[0154] Next, a specific application example of the measuring device according to this embodiment will be described.

[0155] In this application example, a glass petri dish with an inner diameter of 90 mm and a side wall 31b with a height of 20 mm was used as the sample container 31. Then, after the sample 32, which is the substance to be measured, was placed in the sample container 31 to a depth of 2 mm, the rotor 20 was inserted and suspended, and then the top cover 33 was placed, and the sample container 31 was sealed with the container lid 35. At this time, the distance between the top cover 33 and the top surface of the rotating plate 21, and the distance between the bottom plate 31a of the sample container 31 and the bottom surface of the rotating plate 21 were each adjusted to 1 mm. Here, the temperature of the sample 32 was set to 25° C., for example.

[0156] Two types of standard samples with known viscosities were used: one with a viscosity of 1.0 [mPa·s] and one with a viscosity of 1.8 [mPa·s].

[0157] Then, the driving magnet 53 was driven to vary the magnitude and direction of the magnetic field applied to the rotors 20 in these standard samples over time, and a rotational torque was applied to the rotors 20 to rotate them. Specifically, a square wave-like rotational torque was applied to the rotors 20 to rotate them. The period was 20 [s], and the duration of each constant torque in the clockwise and counterclockwise directions was 10 [s].

[0158] Here, the rotating plate 21 is an acrylic disk with a diameter of 80 mm and a thickness of 1 mm, and a cylindrical shaft 22 with a diameter of 2 mm is formed at the center of rotation of the disk, and a wire 38 made of a thin metal wire for suspension is connected to the top of the shaft 22. Also, an aluminum disk with a diameter of 20 mm and a thickness of 0.3 mm is adhered to the center of the rotating plate 21 coaxially with the rotating plate 21, and an induced current is induced inside this.

[0159] The thin metal wire of the wire 38 has a diameter of 30 μm and a length of 20 cm, and its upper end is held by a wire holding member 42 at its upper end.

[0160] Then, the rotating magnetic field control unit 83 drives the motor 51 to rotate the drive magnet holding base 52 that holds the first drive magnet 53a and the second drive magnet 53b. Then, the magnetic field generated by the first drive magnet 53a and the second drive magnet 53b rotates, and a rotating magnetic field is applied to the rotating plate 21 of the rotor 20. This rotating magnetic field imparts a rotational torque to the rotating plate 21, so that the rotor 20 rotates in the same direction as the rotation direction of the rotating magnetic field.

[0161] The rotation detection unit 81 stores, for example, a moving image of the mark 21a attached to the rotor 20 captured by an imaging device in its internal storage unit as a captured image, obtains the rotation period of the mark 21a by image processing, and obtains the rotation speed ΩD of the rotor 20 from the rotation period. The viscosity detection unit 82 also commands the rotating magnetic field control unit 83 to control the motor 51 to rotate at a plurality of different rotation speeds ΩM. Each time the rotation speed ΩM of the motor 51 changes, the rotation detection unit 81 obtains the corresponding rotation speed ΩD of the rotor 20, and the viscosity detection unit 82 obtains the correspondence relationship between the rotation speed ΩD of the rotor 20 and the difference between the rotation speed ΩM of the motor 51 and the rotation speed ΩD of the rotor 20 for each standard sample with a different viscosity.

[0162] Figure 5 shows the change in the angle of rotor 20 over time. From Figure 5, it can be seen that the application of a rectangular torque causes rotor 20 to repeatedly move clockwise and counterclockwise. Furthermore, it can be seen that the angular velocity is constant around the balance angle, that is, steady rotation occurs. The angular velocity in this steady state is the aforementioned rotational speed (number of rotations) ΩD of rotor 20.

[0163] Furthermore, Figure 6 shows the time derivative of the waveform in Figure 5, i.e., the time dependency of the rotor's angular velocity. From Figure 6, it can be seen that the rotation reaches a steady state after a few seconds or so after the change in torque direction. This confirms the theoretical basis of the measurements mentioned above.

[0164] Furthermore, FIG. 7 shows the relationship between the rotation speed of the rotor 20, i.e., the shear rate, and ΩMD, i.e., the quantity proportional to the torque, measured for pure water and a viscosity standard liquid (JS2.5) with a viscosity of 1.8 [mPa s].

[0165] Here, the shear rate γ is given by γ=RΩD / h, where R is the radius of the rotor 20, h is the thickness of the sample 32, and ΩD is the angular velocity of rotation, which is a relationship commonly used in parallel plate viscometers.

[0166] In addition, the relationship between the rotation speed ΩD and the rotation speed difference ΩM-ΩD for each standard sample is a straight line. Therefore, it is possible to obtain the viscosity only from the relationship between the rotation speed ΩD of the rotor 20 and the rotational torque applied to the rotor 20. Therefore, it is understood that the viscosity can be accurately measured by using the standard data.

[0167] Next, a second embodiment will be described. Note that the same reference numerals are given to components having the same structure as the first embodiment, and the description thereof will be omitted. Also, the description of the same operations and effects as the first embodiment will be omitted.

[0168] FIG. 8 is a graph showing the time dependency of the rotation angle of the rotor in the second embodiment.

[0169] As described above, the motion of the rotor 20 is determined by the torque from the rotating magnet, the moment of inertia of the rotor 20, the viscous resistance torque due to the viscosity of the sample 32, and the restoring torque against the twist of the wire 38 that holds the rotor 20.

[0170] In this embodiment as well, the driving magnet 53 is driven to cause a temporal variation in the magnitude and direction of the magnetic field applied to the rotor 20, and a rotational torque is applied to the rotor 20 to rotate it. Specifically, first, the driving magnet 53 is rotated to induce the rotational motion of the rotor 20, and then the rotation of the driving magnet 53 is stopped. The subsequent motion of the rotor 20 is expressed by the following equation (9) where the rotation angle is θ.

[0171]

number

[0172] If the viscous torque is small enough, the solution to equation (9) represents a damped oscillation.

[0173] The moment of inertia I, the restoring torque κθ against torsion, and the viscous torque Γ(dθ / dt) can be calculated from the materials and shapes of the rotor 20 and the wire 38, so Γ can be found from the state of vibration damping against time of the actually measured θ. Furthermore, since the expression for Γ includes the viscosity of the sample 32, the viscosity of the sample 32 can be determined from Γ.

[0174] Next, a specific application example of the second embodiment will be described.

[0175] The upper curve in Fig. 8 represents the vibration damping of rotor 20 measured using air as sample 32 with the same measuring device as that used in the viscosity measurement in the first embodiment. In contrast, the lower curve in Fig. 8 is a theoretical curve calculated using the viscosity value of air (18.5 μPa s) at a temperature of 25 °C, the moment of inertia of rotor 20 obtained by calculation, and the restoring torque against the twist of wire 38.

[0176] In actual measurements, it is not necessary to fit the theoretical values ​​of the damping vibration curve to the experimental values. The maximum value of this vibration damping and the time at which the maximum value is shown can be plotted on a semi-logarithmic scale to determine the damping time, I / Γ, and the viscosity can be calculated from that.

[0177] Other configurations and operations are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0178] Next, a third embodiment will be described. Note that the same reference numerals are given to components having the same structures as those in the first and second embodiments, and the description thereof will be omitted. Also, the description of the same operations and effects as those in the first and second embodiments will be omitted.

[0179] FIG. 9 is a graph showing the time dependency of the rotation angle of the rotor in the third embodiment.

[0180] This embodiment is intended to achieve a steady state over a long period of time.

[0181] In this embodiment, it is preferable to further include a torsion angle detection mechanism (not shown) that detects the torsion angle of the wire 38 from the rotation angle of the wire holding member 42 and the rotation angle of the rotor 20. The driving magnet 53 is driven to cause a temporal variation in the magnitude and direction of the magnetic field applied to the rotor 20, and a rotational torque is applied to the rotor 20 to rotate it, and data from a rotation detection unit 81 that reads the rotation speed of the rotor 20 is used to rotate the wire holding member 42, which holds the wire 38 that suspends the rotor 20 at its upper part, about the wire 38 as an axis, using the holding member position / rotation control mechanism 41, thereby keeping the torsion angle of the wire 38 within a range that satisfies the following formula (10).

[0182]

number

[0183] Here, θ is the twist angle of the wire 38, α is the required viscosity measurement accuracy, L is the length of the wire 38, G is the shear modulus of the wire 38, and R W is the radius of the wire 38, and Tvis is the viscous resistance torque acting on the rotor 20.

[0184] By this operation, even if torque is applied to the rotor 20 in a fixed direction for a long period of time, as is done in normal viscosity measurements, the twist angle of the wire 38 is kept within the range that satisfies the above formula (10) by rotating the wire holding member 42 that holds the wire 38. Therefore, it is possible to perform viscosity measurements while eliminating the influence of the restoring torque that accompanies the twist of the wire 38.

[0185] Next, a specific application example of the third embodiment will be described.

[0186] FIG. 9 shows the time dependence of the rotation angle measured by driving the holding member position / rotation control mechanism 41 to rotate the wire holding member 42 and continuing to hold the twist angle of the wire 38 at 1 degree or less based on the detected rotation speed.

[0187] 9, it can be seen that a constant rotation speed is maintained even when the rotation angle of rotor 20 exceeds 1800 degrees, i.e., 5 rotations. This confirms that it is possible to measure viscosity while maintaining a steady shear rate for a long period of time.

[0188] Other configurations and operations are the same as those of the first and second embodiments, and therefore will not be described.

[0189] To reiterate, in the present invention, regardless of the difference in the viscosity measurement method in the first to third embodiments, what is important is that the rotationally symmetric rotor 20 is in contact with the sample 32 with its axis of rotation symmetry, that is, the rotation axis 26, held vertically, and any rotationally symmetric shape is acceptable.

[0190] For example, the rotor 20 may be shaped like an abacus top to form a cone-plate viscometer that realizes a constant shear rate regardless of the distance from the central axis, or as shown in the example of Fig. 3, the rotor 20 may be made cylindrical or cylindrical and placed inside a cylindrical sample container 31 with the same central axis to form a double-cylinder viscometer. Furthermore, the rotor 20 may be shaped like a sphere. In this case, an analytical solution for the flow field of a viscous liquid around a rotating sphere is known, and this is an effective configuration when, for example, a rare gas is used as a viscous standard sample.

[0191] In addition, a program for implementing the functions of the measuring device disclosed in this specification may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to determine the viscosity of a sample. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices.

[0192] Furthermore, "computer system" also includes a WWW system equipped with a homepage providing environment (or display environment). Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" also includes devices that hold a program for a certain period of time, such as volatile memory (RAM) inside a computer system that becomes a server or client when a program is transmitted via a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

[0193] Furthermore, the program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network such as the Internet or a communication line such as a telephone line. The program may also be for realizing part of the above-mentioned functions. Furthermore, the program may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0194] It should be noted that the disclosure of this specification describes the features of the preferred and exemplary embodiments, and that various other embodiments, modifications, and variations within the scope and spirit of the appended claims will occur to those skilled in the art upon review of the disclosure of this specification. [Industrial Applicability]

[0195] The present disclosure can be applied to an apparatus and method for measuring viscosity. [Explanation of symbols]

[0196] 20 Rotor 21a Mark 26 Rotation axis 31 Sample Container 32 Samples 38 Wire rod 41 Holding member position / rotation control mechanism 42 Wire rod holding member 53 Drive magnet 53a First driving magnet 53b Second driving magnet 81 Rotation detector 82 Viscosity detector 83 Rotating magnetic field control section 84 Standard Data Storage Unit

Claims

1. A rotor that is made of a conductive material in part or in whole and has a rotationally symmetric shape; a wire having one end connected to the rotor at the uppermost portion on the axis of rotational symmetry of the rotor, for suspending and supporting the rotor; a holding member that holds the other end of the wire above the rotor so that the wire is linearly extended in a vertical direction; a holding member rotation / movement drive mechanism for rotating or translating the holding member about a vertical axis centered on a contact point between the holding member and the wire; a sample container that contains the rotor and the sample to be measured with a part or all of the rotor in contact with the sample to be measured; A magnet that applies a magnetic field to the rotor; a rotating magnetic field control unit that drives the magnet to vary the magnitude and direction of the magnetic field applied to the rotor over time, thereby inducing an induced current in the rotor, and applying a rotational torque to the rotor through the Lorentz interaction between the induced current and the magnetic field applied to the rotor, thereby causing the rotor to rotate; a viscosity detection unit that detects the viscosity of the measurement target sample that is in contact with the rotor based on the rotational motion state of the rotor; A viscosity measuring device, characterized in that the rotor is held by the holding member via the wire so that the rotor is suspended with the axis of rotational symmetry extending in a vertical direction.

2. 2. The viscosity measuring device according to claim 1, wherein the twist angle of the wire is maintained by the holding member rotating / moving drive mechanism so as to satisfy the following formula (A): [Number A] θ: twist angle of wire α: Required viscosity measurement accuracy L: Length of wire G: Shear modulus of wire R W : Radius of wire Tvis: Viscous resistance torque acting on the rotor

3. a torsion angle detection mechanism that detects a torsion angle of the wire from a rotation angle of the holding member and a rotation angle of the rotor, 3. The viscosity measuring device according to claim 2, wherein the twist angle of the wire is kept within a range satisfying formula (A) by rotating the upper end of the wire using the holding member rotation / movement drive mechanism.

4. 2. The viscosity measuring device according to claim 1, wherein the rotational torque has a constant magnitude and changes in direction so as to alternate between a clockwise direction and a counterclockwise direction at a constant cycle.

5. 2. The viscosity measuring device according to claim 1, wherein the rotational torque is applied for only a fixed time, and the motion of the rotor is a damped oscillatory motion after application of the rotational torque is stopped.

6. The method further includes a standard data storage unit that stores standard data obtained by previously measuring a relationship between a rotational torque applied to the rotor in contact with a plurality of measurement target samples having known viscosities and a rotational speed of the rotor, The viscosity measuring device according to claim 1, wherein the viscosity detection unit detects the viscosity of the measurement target sample, the viscosity of which is unknown, by comparing the relationship between the rotational torque applied to a rotor in contact with the measurement target sample, the viscosity of which is unknown, and the rotational speed of the rotor with the standard data.

7. 7. The viscosity measuring device according to claim 1, further comprising a rotation detection unit that detects the rotation speed of the rotor by detecting the rotation of a mark added to the rotor.

8. A step of accommodating a rotor, which is made of a conductive material in part or in whole and has a rotationally symmetric shape, in a sample container together with the sample to be measured, with the rotor in part or in whole contact with the sample to be measured; a step of suspending the rotor by a wire held by a holding member, one end of which is connected to the uppermost part of the rotor on the axis of rotational symmetry and the other end of which is a holding member that is rotated around a vertical axis or translated by a holding member rotation / movement drive mechanism, so that the wire is linearly extended in the vertical direction; applying a time-varying magnetic field to the rotor to induce an induced current in the rotor, and applying a rotational torque to the rotor by the Lorentz interaction between the induced current and the magnetic field applied to the rotor to rotate the rotor; and detecting the viscosity of a measurement target sample contacting the rotor based on a rotational motion state of the rotor. A method for measuring viscosity, characterized in that the rotor is held by the holding member via the wire so that the rotor is suspended with the axis of rotational symmetry extending in a vertical direction.

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