Viscoelasticity measurement device and viscoelasticity measurement method

Abstract

Provided is a viscoelasticity measurement device capable of measuring viscoelasticity with high accuracy.　This viscoelasticity measurement device comprises: a conductive rotary body 3; a container 2 that contains the rotary body 3 together with a liquid sample LP; a driving unit 4 that causes the rotary body 3 to rotate and vibrate by applying a fluctuating magnetic field so that forward torque and reverse torque alternately act; an irradiation unit 5 that irradiates the rotary body 3 with irradiation light; a light reception unit 6 that receives reflected light from the rotary body 3; a light reception data acquisition unit 52 that acquires light reception data from the reflected light received by the light reception unit 6; an angular velocity calculation unit 54 that calculates the angular velocity of the rotary body 3 on the basis of the light reception data; and a viscoelasticity calculation unit 56 that calculates the viscoelasticity of the liquid sample LP. The viscoelasticity calculation unit 56 determines the viscoelasticity of the liquid sample LP on the basis of the fluctuation speed of the fluctuating magnetic field, the angular velocity, function data obtained by analyzing a rheological model, and frictional stress data obtained in advance regarding the frictional stress.

Description

Viscoelasticity measuring device and viscoelasticity measuring method

[0001] The present invention relates to a viscoelasticity measuring device and a viscoelasticity measuring method for measuring the viscoelasticity of a liquid sample.

[0002] A known conventional viscoelasticity measuring device is one in which a rotor (rotating body) is placed in a container together with the liquid sample to be measured, and the rotor is rotated by applying a rotational torque to the rotor from outside the container in a non-contact manner, and the viscoelasticity of the liquid sample is measured from the rotational speed of the rotor (see, for example, Patent Document 1).

[0003] In order to accurately measure the viscoelasticity of a liquid sample, the viscoelasticity measuring device described in Patent Document 1 sets a condition (Tr>Tf) such that the viscous resistance of the liquid sample is stronger than the resistance due to the frictional stress, where Tr is the torque required to rotate the rotor at a predetermined angular velocity and Tf is the torque required to rotate the rotor by overcoming the resistance due to the frictional stress generated between the bottom of the container and the rotor.

[0004] JP 2009-264982 A

[0005] In the viscoelasticity measuring device described in Patent Document 1, the torque Tr is proportional to the cube of the rotor radius R and to the angular velocity of the rotor, and the torque Tf is proportional to the fourth power of the rotor radius R. Therefore, in order to satisfy the above condition (Tr > Tf), it is necessary to make the rotor radius R sufficiently small or increase the rotor angular velocity.

[0006] However, as the radius R of the rotor is reduced, the force holding the rotor also decreases, making the rotor more susceptible to vibration and disturbance, making it difficult to measure viscoelasticity with high precision.

[0007] Furthermore, increasing the rotor angular velocity increases the Reynolds number, causing the flow to transition from laminar to turbulent, entering the nonlinear region of the Navier-Stokes equations and exhibiting unsteady, irregular, and chaotic properties, making it difficult to measure viscoelasticity with high precision.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide a viscoelasticity measuring device and a viscoelasticity measuring method that can measure viscoelasticity with high accuracy.

[0009] a light receiving unit that receives light reflected from the rotor; a light receiving data acquisition unit that acquires light reception data from the reflected light received by the light receiving unit; an angular velocity calculation unit that calculates the angular velocity of the rotor based on the light reception data; and a viscoelasticity calculation unit that calculates the viscoelasticity of the liquid sample, wherein the viscoelasticity calculation unit calculates the fluctuation speed of the fluctuating magnetic field, the angular velocity, function data obtained by analyzing a rheology model constructed by regarding the liquid sample as a viscoelastic-plastic fluid having properties combining a viscous component, an elastic component, and a plastic component, and replacing the plastic component with a frictional stress acting between the container and the rotor; The viscoelasticity of the liquid sample is calculated based on frictional stress data obtained in advance regarding the frictional stress.

[0010] In this viscoelasticity measuring device, the liquid sample is treated as a viscoelastic-plastic fluid, and the plastic component is replaced with the frictional stress acting between the container and the rotor. This rheology model is constructed by analyzing the liquid sample as a viscoelastic-plastic fluid. Functional data is obtained by analyzing the rheology model, including the fluctuation speed of the fluctuating magnetic field, the angular velocity of the rotor, and the frictional stress acting between the container and the rotor as parameters. Because the fluctuating magnetic field is applied to the rotor by a drive unit, the fluctuation speed of the fluctuating magnetic field is determined by the drive unit. The angular velocity of the rotor is calculated by an angular velocity calculation unit. The frictional force acting between the container and the rotor is calculated using previously determined frictional stress data. Therefore, the viscoelasticity calculation unit can calculate viscoelasticity based on the fluctuation speed of the fluctuating magnetic field, the angular velocity of the rotor, the functional data obtained by analyzing the rheology model, and the frictional stress data. Since the frictional stress data is previously determined, the effect of frictional stress on the measurement results (calculation results) can be eliminated, enabling highly accurate viscoelasticity measurements.

[0011] In the viscoelasticity measuring device according to the present invention, it is preferable that the driving unit rotationally vibrates the rotating body so as to include a dynamic time region in which the rotating body is rotating due to the forward torque or the reverse torque, and a static time region in which the rotating body is stationary due to the frictional force acting between the rotating body and the container.

[0012] With this viscoelasticity measuring device, in the dynamic time domain, resistance due to the viscous and elastic components of the liquid sample acts on the rotating body, while in the static time domain, resistance due to the frictional force acting between the rotating body and the container acts on the rotating body. In this way, the resistance due to the viscous and elastic components of the rotating body and the resistance due to the frictional force (plastic component) are clearly distinguished between the dynamic time domain and the static time domain, making it possible to more appropriately construct a rheology model in which the liquid sample is considered a viscoelastic-plastic fluid, and to obtain more accurate function data.

[0013] The viscoelasticity measuring device according to the present invention preferably further comprises a time-dependent friction stress calculation unit that calculates, in the static time domain, a time-dependent friction stress that changes depending on time when the rotating body comes to a standstill.

[0014] In the static time domain, when a rotating body is stationary, frictional stress (time-dependent frictional stress) that changes with time acts on the rotating body from the liquid sample to suppress the rotation of the rotating body. Because time-dependent frictional stress changes with time, it is generally difficult to determine it experimentally. The viscoelasticity measuring device of this configuration is provided with a time-dependent frictional stress calculation unit that calculates the time-dependent frictional stress, making it easy to determine the time-dependent frictional stress that is difficult to determine experimentally.

[0015] In the viscoelasticity measuring device according to the present invention, when the liquid sample is a pure viscous fluid, it is preferable that the time-dependent friction stress calculation unit calculates the time-dependent friction stress based on a constant determined by the shape factors of the container and the rotor and the fluctuation speed of the fluctuating magnetic field.

[0016] With the viscoelasticity measuring device of this configuration, it is possible to easily determine the time-dependent frictional stress in the case of a pure viscous fluid in which the sample stress (stress acting on a liquid sample) in the static time region is instantaneously relaxed to zero.

[0017] In the viscoelasticity measuring device according to the present invention, when the liquid sample is a viscoelastic fluid, it is preferable that the time-dependent frictional stress calculation unit calculates the time-dependent frictional stress using an arithmetic formula derived based on the frictional stress at the start time of the static time region and the frictional stress at the end time of the static time region.

[0018] The viscoelasticity measuring device of this configuration makes it possible to easily determine the time-dependent frictional stress in the case of a viscoelastic fluid in which the internal state (internal stress) of the liquid sample changes only slowly.

[0019] In the viscoelasticity measuring device according to the present invention, it is preferable that the device is provided with a beam splitter that bends the optical path of the irradiated light, and that the beam splitter is arranged so that the optical axis of the irradiated light, whose optical path has been bent, coincides with the rotation axis of the rotating body, and so that the optical axis of the reflected light coincides with the rotation axis.

[0020] With this configuration of viscoelasticity measuring device, the optical axis of the irradiated light, whose optical path is bent, is aligned with the rotation axis of the rotating body, and the optical axis of the reflected light from the rotating body is aligned with the rotation axis of the rotating body, so that the difference in the received light data relating to the reflected light received by the light receiving unit before and after in time can be accurately grasped as a displacement around the rotation axis.

[0021] In the viscoelasticity measuring device according to the present invention, it is preferable that the light receiving section includes a two-dimensional image sensor in which a plurality of light receiving elements are arranged two-dimensionally in parallel.

[0022] According to the viscoelasticity measuring device of this configuration, the light receiving unit includes a two-dimensional image sensor in which multiple light receiving elements are arranged two-dimensionally in parallel. Therefore, by receiving the reflected light from the rotating body with the two-dimensional image sensor, two-dimensional image data can be easily acquired as received light data by the received light data acquisition unit.

[0023] In the viscoelasticity measuring device according to the present invention, it is preferable that the light receiving data acquisition unit performs image processing on the light receiving data and captures it as two-dimensional image data, and the angular velocity calculation unit sequentially compares two sets of two-dimensional image data captured at different times to calculate the angular velocity of the rotating body.

[0024] With the viscoelasticity measuring device of this configuration, when two-dimensional images obtained successively in time based on two-dimensional image data acquired successively in time are compared, the optical axis of the reflected light from the rotating body is aligned with the rotation axis of the rotating body, and therefore the two-dimensional image obtained later in time appears as an image with a similar image pattern rotated by a certain angle around the rotation axis of the rotating body compared to the two-dimensional image obtained earlier in time.The angular velocity of the rotating body is then calculated by the angular velocity calculation unit based on this image.In this way, the angular velocity of the rotating body is calculated based on two-dimensional images rotating around the rotation axis of the rotating body with the same image pattern, so the angular velocity of the rotating body can be determined more accurately.

[0025] In the viscoelasticity measuring device according to the present invention, the irradiation unit is preferably configured to irradiate irradiation light having a spot diameter of a predetermined length or more.

[0026] According to the viscoelasticity measuring device of this configuration, the light emitted from the irradiation unit illuminates a circular area centered on the rotation axis of the rotating body, so that the received light data acquisition unit can reliably acquire a two-dimensional image rotating with a similar image pattern around the rotation axis of the rotating body, and the angular velocity of the rotating body can be more accurately determined by the angular velocity calculation unit.

[0027] Next, a characteristic configuration of a viscoelasticity measurement method according to the present invention for solving the above problems is a viscoelasticity measurement method for measuring the viscoelasticity of a liquid sample, comprising: a driving step of applying a fluctuating magnetic field to a conductive rotating body placed in a container together with the liquid sample so that forward torque and reverse torque act alternately to rotate and oscillate the rotating body; an irradiation step of irradiating the rotating body with irradiation light; a light receiving step of receiving reflected light from the rotating body; a light receiving data acquisition step of acquiring received light data from the reflected light received in the light receiving step; an angular velocity calculation step of calculating the angular velocity of the rotating body based on the received light data; and a viscoelasticity calculation step of calculating the viscoelasticity of the liquid sample, wherein the viscoelasticity calculation step includes: a fluctuating speed of the fluctuating magnetic field; the angular velocity; function data obtained by analyzing a rheology model constructed by regarding the liquid sample as a viscoelastic-plastic fluid having properties combining a viscous component, an elastic component, and a plastic component, and replacing the plastic component with a frictional stress acting between the container and the rotating body; and frictional stress data obtained in advance for the frictional stress. A calculation is performed to determine the viscoelasticity of the liquid sample based on the above.

[0028] According to the viscoelasticity measurement method of this configuration, a calculation is performed in a viscoelasticity calculation step to determine viscoelasticity based on the fluctuation speed of the fluctuating magnetic field, the angular velocity of the rotor, function data obtained by analysis of the rheology model, and friction stress data obtained in advance. In the calculation in this viscoelasticity calculation step, the friction stress data obtained in advance is used for the friction force acting between the container and the rotor, so that the influence of friction stress on the measurement result (calculation result) can be eliminated, and viscoelasticity can be measured with high accuracy.

[0029] FIG. 1 is a schematic diagram showing the configuration of a viscoelasticity measuring device according to one embodiment of the present invention. FIG. 2 is a flowchart showing the procedure for viscoelasticity measurement performed in the viscoelasticity measuring device. FIG. 3 is an example of a two-dimensional image acquired in the light reception data acquisition process. FIG. 4 is a graph showing the relationship between the angular velocity of a rotor and the rotational vibration period. FIG. 5 is a model diagram of a Bingham fluid. FIG. 6 is a graph showing the angular velocity difference (Ω) equivalent to shear stress. Ｍ -Ω Ｓ ) and shear strain rate. FIG. 7 is a model diagram of a viscoelastic fluid. FIG. 8 is a graph showing the relationship between the rotational angular velocity of the magnet body and the rotor and time. FIG. 9 is a graph showing the relationship between the rotor angular velocity and the rotational oscillation period for a purely viscous sample. FIG. 10 is another graph showing the relationship between the rotor angular velocity and the rotational oscillation period for a purely viscous sample. FIG. 11 is a graph showing the results of reproducibility of the storage rigidity modulus and the loss rigidity modulus. FIG. 12 is a graph showing the relationship between the rotor angular velocity and the rotational oscillation period for a viscoelastic sample. FIG. 13 is a graph comparing measurement results obtained using the viscoelasticity measuring device of the present invention and a rheometer. FIG. 14 is a plan view of the main parts of a drive unit of another embodiment.

[0030] The present invention will be described below with reference to the drawings. However, the present invention is not intended to be limited to the embodiments described below or the configurations shown in the drawings.

[0031] <Overall Configuration> Fig. 1 is a schematic diagram showing a viscoelasticity measuring device 1 according to one embodiment of the present invention. The viscoelasticity measuring device 1 is a device for measuring the viscoelasticity of a liquid sample (fluid sample) indicated by the symbol "LP" in Fig. 1. Here, the liquid sample refers to a sample having fluidity, and includes not only liquids, solutions, and melts, but also samples in which solids are mixed, and samples in a gel or sol state. As shown in Fig. 1, the viscoelasticity measuring device 1 includes a container 2, a rotating body 3, a driving unit 4, an irradiation unit 5, a light receiving unit 6, and a control device 7.

[0032] <Container> The container 2 is preferably a heat-resistant container made of a transparent or translucent material such as glass or acrylic resin that can transmit the irradiation light irradiated from the irradiation unit 5, and in this embodiment, a glass test tube with a hemispherical bottom and an open end facing upward is used.

[0033] <Rotating Body> The rotating body 3 is made partially or entirely of a conductive metal material. In this embodiment, an aluminum sphere having a radius of curvature smaller than the radius of curvature of the inner surface of the bottom of the container (test tube) 2 is used. As a result, when the rotating body 3 is placed in the container 2 together with a liquid sample, it sinks within the liquid sample due to its own weight and is naturally positioned at the center of the bottom of the container 2.

[0034] <Drive Unit> The drive unit 4 is mainly composed of a drive unit main body 10 and a rotation control unit 51. The rotation control unit 51 is configured as one functional unit in the control device 7, and therefore will be explained in the explanation of the control device 7, and only the drive unit main body 10 will be explained here.

[0035] The drive unit main body 10 includes a support 11, a magnet body 12, a drive motor 13, a timing pulley 14, and a timing belt 15. The support 11 is rotatably supported by a bearing device (not shown) with a virtual axis extending vertically as the rotation axis. In Fig. 1, the rotation axis line coinciding with the rotation axis of the support 11 is indicated by a dashed line marked with "CL."

[0036] The support body 11 has inner and outer peripheral surfaces that are parallel to the rotation axis CL and extend around the rotation axis CL as the center, as well as annular upper and lower surfaces that extend between the inner and outer peripheral surfaces, and is formed in the shape of a hollow disk with a hollow portion provided on the inside of the inner peripheral surface.

[0037] A plurality of magnet bodies 12 (N: N = 2n, n is an integer greater than or equal to 1) are arranged on the annular upper surface of the support 11. In this example, permanent magnets such as neodymium magnets or ferrite magnets (electromagnets are also acceptable) are used as the magnet bodies 12. Two magnet bodies 12 are placed and fixed on the annular upper surface of the support 11, symmetrically arranged with the rotation axis CL as the axis of symmetry. The magnet body 12 on one side and the magnet body 12 on the other side of the two magnet bodies 12 are arranged so that the magnetic poles point in opposite directions relative to the horizontal direction. Furthermore, the container 2 containing the rotor 3 together with the liquid sample is supported by a support means (not shown) relative to the two magnet bodies 12, with the rotation axis CL passing through the center of the rotor 3 and the rotor 3 positioned between the two magnet bodies 12.

[0038] The drive motor 13 has an output shaft 13a that is disposed parallel to and spaced a predetermined distance from the rotation axis CL outside the support body 11. A timing pulley 14 is fixed to the output shaft 13a of the drive motor 13. A timing belt 15 is wound around the outer circumferential surface of the timing pulley 14 and the outer circumferential surface of the support body 11. In the drive unit main body 10, when the drive motor 13 is operated, rotational power from the drive motor 13 is transmitted to the support body 11 via the timing pulley 14 and the timing belt 15.

[0039] In the drive unit main body 10, the rotation speed (number of rotations and direction of rotation) of the drive motor 13 is controlled by a control signal from the control device 7 (rotation control unit 51) so that the support 11 alternately rotates forward and backward around the rotation axis CL at a constant cycle. This applies a fluctuating magnetic field to the rotor 3. This induces an induced current inside the rotor 3, and the Lorentz interaction between the induced current and the fluctuating magnetic field applied to the rotor 3 generates a rotational torque in the direction following the rotational direction of the magnet body 12, i.e., the rotational direction of the support 11, and forward torque and reverse torque alternately act on the rotor 3 around the rotation axis CL. This causes the rotor 3 to rotationally oscillate. That is, the rotor 3 repeatedly rotates in one direction (forward rotation) and in the opposite direction (reverse rotation) within a predetermined angle range around a virtual axis that passes through the center of the rotor 3 and is perpendicular (vertical) to the rotation direction of the rotor 3, i.e., a virtual axis that coincides with the rotation axis CL of the rotor 3. Hereinafter, the virtual axis of the rotor 3 will be referred to as the rotation axis of the rotor 3.

[0040] <Irradiation Unit> The irradiation unit 5 functions as a light source that irradiates the rotating body 3 in the container 2 with irradiation light. It is composed of a laser light source that irradiates light of a single color (e.g., green, yellow, red, etc.) to eliminate the effects of chromatic aberration and enhance the contrast of the light. The irradiation unit 5 is disposed so that the optical path of the emitted irradiation light intersects with the rotation axis CL. More specifically, the irradiation unit 5 is disposed so that the optical path of the emitted irradiation light intersects with the rotation axis CL at a position directly below the rotating body 3. The irradiation unit 5 is configured to irradiate irradiation light having a spot diameter equal to or greater than a predetermined length. The irradiation light emitted from the irradiation unit 5 via a beam splitter 20 (described later) irradiates a circular area centered on the rotation axis CL on the underside of the rotating body 3. This allows the light reception data acquisition unit 52 (described later) to reliably acquire a two-dimensional image rotating in a similar image pattern around the rotation axis (rotation axis CL) of the rotating body 3, and the angular velocity of the rotating body 3 can be more accurately calculated by the angular velocity calculation unit 54 (described later).

[0041] <Beam Splitter> A beam splitter 20 is disposed at a position where the optical path of the irradiation light emitted from the irradiation unit 5 intersects perpendicularly with the rotation axis CL. The beam splitter 20 bends the optical path of the irradiation light from the horizontal direction toward a vertically upward direction so that the irradiation light emitted horizontally from the irradiation unit 5 is irradiated onto the rotating body 3. That is, the beam splitter 20 has a reflecting surface 20a that reflects the irradiation light emitted from the irradiation unit 5. The reflecting surface 20a is inclined 45° upward with respect to the horizontal plane and is disposed so as to extend in a direction perpendicular to a vertical plane that includes both the optical path of the irradiation light emitted from the irradiation unit 5 and the rotation axis CL (a direction perpendicularly penetrating the paper surface of FIG. 1 ). As a result, the irradiation light emitted from the irradiation unit 5 is reflected by the reflecting surface 20a, whereby the optical path of the irradiation light is bent by 90°, and the optical axis of the irradiation light whose optical path is bent by 90° coincides with the rotation axis CL and thus with the rotation axis of the rotating body 3. The irradiated light that is irradiated onto the rotor 3 with its optical axis aligned with the rotation axis of the rotor 3 passes through the beam splitter 20 as reflected light that is reflected with its optical axis aligned with the rotation axis of the rotor 3. In this way, the beam splitter 20 is disposed so as to align the optical axis of the irradiated light, whose optical path has been bent, with the rotation axis of the rotor 3, and to align the optical axis of the reflected light with the rotation axis.

[0042] <Light-receiving unit> The light-receiving unit 6 is disposed below the beam splitter 20. The light-receiving unit 6 includes a lens 31 that forms an image of the reflected light from the rotating body 3, and a photodetector 32 that detects received light data of the reflected light formed by the lens 31. The lens 31 is disposed to face the curved surface at the bottom of the rotating body 3 onto which the irradiated light is applied. The photodetector 32 is disposed to be located on the optical axis of the lens 31. A filter 33 is disposed between the lens 31 and the photodetector 32. The filter 33 has a passband in a wavelength range of a specific color. In this way, the photodetector 32 can accurately receive reflected light from which the effects of ambient light have been removed without reducing the amount of reflected light.

[0043] The irradiation unit 5 may be configured with a different type of light source, such as a halogen lamp, instead of a laser light source. Furthermore, when the irradiation unit 5 is configured with a single-wavelength or multiple-wavelength laser light source, the lens 31 of the light-receiving unit 6 is not an essential component, and may be omitted as appropriate, for example, when predetermined light-receiving data can be detected without forming an image due to the performance of the laser light source (monochromaticity and linearity of light). The filter 33 may also be omitted as appropriate, when the influence of ambient light is unlikely to occur (for example, when the irradiation unit 5 and the light-receiving unit 6 are surrounded by a darkroom).

[0044] <Photodetector (Two-Dimensional Image Sensor)> It is preferable to use a two-dimensional image sensor in which a plurality of light-receiving elements are two-dimensionally arranged in parallel as the photodetector 32. In this example, the photodetector 32 is arranged so that the light-receiving surfaces of the plurality of light-receiving elements face the rotational surface of the rotating body 3 onto which the irradiation light is irradiated, and the plurality of light-receiving elements are aligned in the rotational direction of the rotating body 3 and in a direction perpendicular to the rotational direction of the rotating body 3. When the photodetector 32 receives light reflected from the rotating body 3, it outputs a photocurrent (A: amperes) proportional to the intensity of the reflected light for each of the plurality of light-receiving elements as light reception data from the reflected light.

[0045] <Control Device> The control device 7 is mainly composed of a computer, and includes an overall control unit 50 that controls the viscoelasticity measuring device 1, as well as a rotation control unit 51, a light reception data acquisition unit 52, a light reception data storage unit 53, an angular velocity calculation unit 54, a time-dependent friction stress calculation unit 55, a viscoelasticity calculation unit 56, and a data storage unit 57. The functions of the various functional units are exerted by executing predetermined programs. Signals, information, etc. are input and output to and from the various functional units via an input / output port 58.

[0046] <Rotation control unit> Based on a detection signal from a rotation speed detector 70 that detects the rotation speed of the support body 11, the rotation control unit 51 transmits a predetermined control signal to the drive motor 13 so that the support body 11 alternates between forward and reverse rotation around the rotation axis CL at a constant period, i.e., so that the two magnet bodies 12 around the rotating body 3 alternate between forward and reverse rotation around the rotation axis CL at a constant period.

[0047] As described above, the rotational speed of the support 11 is detected by the rotational speed detector 70. Because the magnet body 12 is placed and fixed on the support 11, the rotational speed of the support 11 is the same as the rotational speed (orbital speed) of the magnet body 12 around the rotating body 3 (rotation axis CL). Therefore, the angular velocity of the magnet body 12 around the rotating body 3 (rotation axis CL) can be determined by a predetermined calculation based on the detection value by the rotational speed detector 70. Furthermore, as the magnet body 12 rotates around the rotating body 3, the magnetic field applied to the rotating body 3 by the magnet body 12 fluctuates. As the rotational speed (angular velocity) of the magnet body 12 changes, the fluctuating speed of the fluctuating magnetic field (fluctuating magnetic field) changes. In this way, there is a certain correlation between the angular velocity of the magnet body 12 and the fluctuating speed of the fluctuating magnetic field. Therefore, the "angular velocity of the magnet body 12" in this embodiment corresponds to the "fluctuating speed of the fluctuating magnetic field" in the present invention. While Figure 1 shows an example in which the angular velocity of magnet body 12 is determined based on the detection value of rotational speed detector 70, which detects the rotational speed of support body 11, the present invention is not limited to this. For example, the rotational speed of timing pulley 14, which has a certain correlation with the angular velocity of magnet body 12, similar to the rotational speed of support body 11, can be detected by rotational speed detector 70, and the angular velocity of magnet body 12 can be determined based on the detected value. Alternatively, rotational speed detector 70 can be an encoder built into drive motor 13, and the angular velocity of magnet body 12 can be determined based on the detected value of the rotational speed of drive motor 13.

[0048] <Light Reception Data Acquisition Unit, Light Reception Data Storage Unit> The light reception data acquisition unit 52 performs appropriate image processing on the light reception data of reflected light detected by the photodetector 32 of the light receiving unit 6, and captures it as two-dimensional image data, based on a data acquisition command from the integrated control unit 50. The light reception data (two-dimensional image data) captured by the light reception data acquisition unit 52 is stored in the light reception data storage unit 53.

[0049] <Angular Velocity Calculation Unit> The angular velocity calculation unit 54 reads out two-dimensional image data from the light reception data storage unit 53 , and sequentially compares two sets of two-dimensional image data captured at different times to calculate the angular velocity of the rotating body 3 .

[0050] <Time-dependent friction stress calculation unit> The time-dependent friction stress calculation unit 55 calculates the friction stress that changes depending on time when the rotating body 3 comes to rest in the static time domain where the rotating body 3 is stationary due to the friction force acting between the rotating body 3 and the container 2.

[0051] <Viscoelasticity Calculation Unit> The viscoelasticity calculation unit 56 calculates the viscoelasticity (dynamic viscoelasticity) of the liquid sample based on the angular velocity of the magnet body 12 (fluctuation speed of the fluctuating magnetic field), the angular velocity of the rotor 3, function data (described later) obtained by analysis of a rheology model, and friction stress data related to the friction stress acting between the container 2 and the rotor 3. The viscoelasticity calculation method executed by the viscoelasticity calculation unit 56 will be described in detail later.

[0052] <Data Storage Unit> The data storage unit 57 stores various data and the like necessary for calculations in the time-dependent friction stress calculation unit 55 and the viscoelasticity calculation unit 56. For example, the data storage unit 57 stores calculation formulas (formulas (11), (12), (15), (18), (19), etc. described below) necessary for calculating the viscosity coefficient (loss rigidity modulus), calculation formulas (formulas (11), (12), (14), (18), (19), etc. described below) necessary for calculating the elastic modulus (storage rigidity modulus), calculation formulas (formulas (20), (21), (22), (23), etc. described below) necessary for calculating the experimentally determined maximum friction stress and the time-dependent friction stress, values ​​of known coefficients, and the like.

[0053] An input unit 60 that inputs various control commands and the like to the control device 7, and a display unit 61 that displays measurement results such as viscoelasticity calculated by the control device 7, are connected to the overall control unit 50 via an input / output port 58. An operator measuring the viscoelasticity of a liquid sample operates the input unit 60 while looking at the display unit 61 to give various instructions such as setting viscoelasticity measurement conditions and issuing a command to start viscoelasticity measurement. The overall control unit 50 then automatically measures the viscoelasticity of the liquid sample under the viscoelasticity measurement conditions set by the operator, and automatically displays the measurement results on the display unit 61.

[0054] The viscoelasticity measurement operation using the viscoelasticity measuring device 1 configured as described above will now be described. First, as a preparation for operating the viscoelasticity measuring device 1, the measurer places the liquid sample whose viscoelasticity is to be measured together with the rotor 3 into the container 2, and sets the container 2 in the viscoelasticity measuring device 1 so that it is supported by a support means (not shown). As a result, the container 2 containing the liquid sample and the rotor 3 is maintained in a position such that the rotation axis CL passes through the center of the rotor 3 and the rotor 3 is positioned between the two magnet bodies 12. Then, while viewing the display unit 61, the measurer operates the input unit 60 to set viscoelasticity measurement conditions, such as the rotation speed (angular velocity) of the magnet body 12.

[0055] Fig. 2 is a flowchart showing the procedure of viscoelasticity measurement executed in the viscoelasticity measuring device 1. In Fig. 2, the symbol "S" represents a step.

[0056] 2, after the preparation work is completed, when the measurer operates the input unit 60 to input a command to start viscoelasticity measurement (S1), the overall control unit 50 outputs a rotation command to the rotation control unit 51. Then, based on a detection signal from a rotation speed detector 70 that detects the rotation speed of the support 11, the rotation control unit 51 transmits a predetermined control signal to the drive motor 13 so that the support 11 alternates between forward and reverse rotations around the rotation axis CL at a constant cycle, i.e., so that the two magnet bodies 12 around the rotor 3 alternate between forward and reverse rotations around the rotation axis CL at a constant cycle (S2). This applies a fluctuating magnetic field to the rotor 3. This induces an induced current inside the rotor 3, and the Lorentz interaction between the induced current and the fluctuating magnetic field applied to the rotor 3 generates a rotational torque in the direction following the rotational direction of the magnet body 12, i.e., the rotational direction of the support 11, and forward torque and reverse torque act alternately on the rotor 3 around the rotation axis CL. This causes the rotor 3 to rotationally vibrate.

[0057] <Steps S3-S4> (Irradiation Step, Light Receiving Step) When the rotating body 3 rotationally vibrates, the overall control unit 50 outputs power to the irradiation unit 5 to turn on the irradiation unit 5, and the irradiation unit 5 emits irradiation light toward the rotating body 3 in the container 2 (S3). The light receiving unit 6 receives the light reflected from the rotating body 3, and the photodetector 32 of the light receiving unit 6 detects light reception data of the reflected light (S4). In this case, although not shown, the overall control unit 50 turns on the irradiation unit 5 and also outputs power to the photodetector 32 of the light receiving unit 6 to turn on the photodetector. Note that the timing at which the irradiation unit 5 and the photodetector 32 are turned on may be different. For example, the irradiation unit 5 and the photodetector 32 may be turned on when the power of the viscoelasticity measuring device 1 is turned on or when the measurer inputs a command to start viscoelasticity measurement.

[0058] <Steps S5-S7> (Light Reception Data Acquisition Process) Next, the light reception data acquisition unit 52 begins acquiring light reception data output from the multiple light receiving elements of the photodetector 32 based on a data acquisition command from the integrated control unit 50 (S5). The light reception data acquisition unit 52 acquires the light reception data for a predetermined time and captures two-dimensional image data within the predetermined time. When the capture is complete ("YES" in step S6), the light reception data storage unit 53 stores the captured two-dimensional image data (S7). In this example, the light reception data acquisition unit 52 captures two-dimensional image data at 1 / 20 of a cycle, for example, during the time it takes for the rotor 3 to rotate and oscillate once and return to its original state (one cycle). The captured two-dimensional image data is then stored in the light reception data storage unit 53.

[0059] <Step S8> (Angular Velocity Calculation Step) Next, based on a calculation command from the integrated control unit 50, the angular velocity calculation unit 54 reads one cycle's worth of two-dimensional image data from the light reception data storage unit 53, sequentially compares two sets of two-dimensional image data acquired at different times, and calculates the angular velocity of the rotating body 3. In this embodiment, the optical axis of the reflected light from the rotating body 3 is aligned with the rotation axis of the rotating body 3, so that a two-dimensional image acquired later in time appears as if a similar image pattern had been rotated by a certain angle around the rotation axis of the rotating body 3 compared to a two-dimensional image acquired earlier in time. Then, the angular velocity calculation unit 54 calculates the angular velocity of the rotating body 3 based on this image. In this way, the angular velocity of the rotating body 3 is calculated based on two-dimensional images rotating with the same image pattern around the rotation axis of the rotating body 3, so the angular velocity of the rotating body 3 can be determined more accurately.

[0060] <Step S9> (Time-dependent frictional stress calculation step) Next, the time-dependent frictional stress calculation unit 55 calculates the frictional stress that changes depending on time when the rotating body 3 comes to rest, in the static time region where the rotating body 3 is stationary due to the frictional force acting between the rotating body 3 and the container 2, using the calculation formula used for calculating the time-dependent frictional stress read from the data storage unit 57, based on a calculation command from the overall control unit 50. The calculation result is stored in the data storage unit 57 as frictional stress data.

[0061] <Step S10> (Viscoelasticity calculation process) Then, based on a calculation command from the overall control unit 50, the viscoelasticity calculation unit 56 calculates the viscoelasticity of the liquid sample based on the angular velocity (fluctuation speed of the fluctuating magnetic field) of the magnetic body 12 calculated by calculation based on the detection value from the rotational speed detector 70, the angular velocity of the rotating body 3 calculated by the angular velocity calculation unit 54, and data such as the calculation formula used to calculate the viscoelasticity and frictional stress data read from the data memory unit 57 (S10).

[0062] <Step S11> (Calculation Result Display Process) The viscoelasticity (coefficient of viscosity, modulus of elasticity) of the liquid sample calculated by the viscoelasticity calculation unit 56 is automatically displayed on the display unit 61 in response to a display command from the integrated control unit 50 (S11).

[0063] <Method of Calculating Viscoelasticity> Next, a calculation method for measuring viscoelasticity while removing the influence of frictional stress occurring between the container 2 and the rotor 3 will be described below with reference to FIG. 1 and FIGS. 3 to 13. FIG.

[0064] 1, the two magnet bodies 12 are driven so as to rotate in a forward and reverse direction around the rotor 3 in a sinusoidal cycle, whereby forward torque and reverse torque act alternately on the rotor 3 about the rotation axis CL, applying a vibration stress to the rotor 3. This causes the rotor 3 to rotationally vibrate, generating a vibration strain according to the viscoelasticity of the liquid sample.

[0065] Figure 3 shows an example of a two-dimensional image acquired in the light reception data acquisition step. As shown in Figure 1, when laser light is irradiated onto the rotor 3 from the irradiation unit 5 and vibration strain is generated by the rotational vibration of the rotor 3, the reflected light (reflected speckles) from the rotor 3 is received by the light receiving unit 6, and images such as those shown in Figures 3(a) and (b) are obtained. The wavelength of the irradiated light can be changed to an optimal wavelength depending on the type of liquid sample.

[0066] Figure 3(b) is an image obtained by rotating the rotating body 3 by a certain angle θ about the rotation axis CL from the state in Figure 3(a). In the viscoelasticity measuring device 1, the beam splitter 20 is disposed so that the rotation axis of the rotating body 3 and the optical axis of the reflected light coincide (or nearly coincide). Therefore, the reflected light obtained from the irregularities of the rotating body 3 rotates in a similar pattern about the rotation axis of the rotating body 3. Therefore, by performing an analysis such as repeat matching measurement from the images in Figure 3(a) and Figure 3(b), the angular velocity of the rotating body 3 can be accurately determined by the angular velocity calculation unit 54.

[0067] 4 is a graph showing the relationship between the angular velocity of the rotor and the rotational vibration period. More specifically, when a vibration stress for one period is applied to the rotor 3 placed in the container 2 together with a purely viscous liquid sample (purely viscous fluid), images are captured by the light reception data acquisition unit 52 at regular intervals (1 / 20 period), and two images captured at different times are analyzed sequentially, and the angular velocity is calculated and plotted by the angular velocity calculation unit 54. １If the frictional stress between the container 2 and the rotor 3 is negligible, the line connecting the plots in FIG. 4 should be the line indicated by the symbol SW １ However, the liquid sample used as the measurement target has low viscosity and the proportion of resistance due to frictional stress is large, so the time region in which the rotor 3 is stopped widens, resulting in a non-sinusoidal waveform.

[0068] Here, the frictional stress acting between the container 2 and the rotor 3 is replaced with a yield stress, and the liquid sample is analyzed as a Bingham fluid. FIG. 5 is an explanatory diagram of stress analysis of a Bingham fluid. FIG. 5(a) is a model diagram showing a rheological model 80 of a Bingham fluid. FIG. 5(b) is a graph showing the relationship between shear stress and shear strain rate. The rheological model 80 of a Bingham fluid shown in FIG. 5(a) is a combination of a slider 81 representing the plasticity property and a dashpot 82 representing the viscosity property, and its flow characteristics are represented in FIG. 5(b) by the symbol "SL １ " is shown as a linear function.

[0069] Figure 6 shows the angular velocity difference (Ω Ｍ -Ω Ｓ 6 is a graph showing the relationship between shear strain rate and the flow characteristics of a liquid sample exhibiting non-sinusoidal properties plotted in FIG. 4, when frictional stress acts between the container 2 and the rotor 3. In FIG. 6, the symbol "SL" in the figure obtained by processing the measured values ​​using the least squares method or the like is used. ２ The linear function indicated by the straight line with " is the straight line SL in FIG. 5(b) which shows the behavior (flow characteristics) of Bingham fluid. １ It shows the same characteristics as the linear function shown in

[0070] When the contact point between the container 2 and the rotor 3 changes, the line SL in FIG. ２ The linear function shown above has a fluctuating y-intercept when the vertical axis of the graph is taken as the y-axis, but if the contact point is constant, it can be considered a Bingham fluid, so the difference between static and kinetic friction can be almost ignored, and it can be said that the frictional stress can be considered to be almost constant under flow.

[0071] 7A and 7B are model diagrams of a viscoelastic fluid. FIG. 7A is a model diagram showing a Maxwell model 85. FIG. 7B is a model diagram showing a rheology model 90 of a viscoelastic-plastic fluid. The Maxwell model 85 shown in FIG. 7A is a combination of a dashpot 82 representing viscous properties and a spring 83 representing elastic properties. The rheology model 90 shown in FIG. 7B considers the liquid sample to be a viscoelastic-plastic fluid having properties combining a viscous component, an elastic component, and a plastic component, and the plastic component is considered to be the frictional stress σ acting between the container 2 and the rotor 3. ｆ As shown in FIG. 7( b), the rheological model 90 can be expressed as an equivalent model that shows the linear relaxation rigidity modulus G(t) in the absence of friction, based on the slider 81 that represents the properties of plasticity (friction stress) and the Maxwell model 85 shown in FIG. 7( a). In this case, in a typical viscoelasticity test using sinusoidal oscillatory strain, the storage rigidity modulus G'(ω) and loss rigidity modulus G"(ω), which can be associated with the linear relaxation rigidity modulus G(t), are measured using the following equations (1) and (2). Here, ω is the angular frequency.

[0072]

[0073] However, if the effect of frictional stress between the container 2 and the rotor 3 is large, even if the magnet body 12 alternately rotates forward and backward around the rotation axis CL, causing the magnet body 12 to vibrate sinusoidally with respect to time t, as shown in the plot in Figure 4, the rotor 3 will not vibrate sinusoidally, and sinusoidal vibration strain will not be achieved, making it impossible to carry out a normal viscoelasticity test. Therefore, the analytical method encompassed by the present invention removes the effect of friction from such non-sinusoidal angular velocity data of the rotor 3, making it possible to determine the storage rigidity modulus (elastic modulus) G'(ω) and the loss rigidity modulus (viscous modulus) G"(ω). This analytical method will be described in detail below.

[0074] 8 is a graph showing the relationship between time and the rotational angular velocity of the magnet body 12 and the rotor 3. In FIG. 8, the rotational angular velocity Ω of the magnet body 12 when stress is applied to the rheology model 90 shown in FIG. Ｍ (t) (Dotted line SW２ ) and the rotational angular velocity Ω of the rotor 3 Ｓ (t) (solid line SW ３ The relationship between the

[0075] Ω Ｓ (t) = 0, dΩ Ｓ The time when (t) / dt>0 is set as the origin of time t, and Ω Ｓ The time range where (t)>0 is defined as 0<t<t １ Also, Ω Ｍ (t) is expressed by the following formula (3) (Ω ｍ０ is the amplitude, ω is the angular frequency), Ω Ｍ (t) = 0, dΩ Ｍ The time when (t) / dt>0 is -t ＊ It was decided.

[0076]

[0077] 0<t<t １ In the time domain, the sample stress σ ｓａｍｐｌｅ (t) and maximum frictional stress σ ｆ，ｍａｘ The sum of this is Ω Ｍ (t) and Ω Ｓ (t) and the rotational torque is proportional to the difference between the rotational torque (t) and the rotational torque (t), and the relationship shown in the following formula (4) holds.

[0078]

[0079] where σ ｓａｍｐｌｅ +σ ｆ，ｍａｘ and Omega Ｍ (t)-Ω Ｓ The proportionality constant K between (t) is a constant determined by the magnetic flux density and the rotor 3, and is a quantity obtained by testing a standard material. １ In the time range of t≦T / 2, the rotating body 3 is stopped, so the liquid sample shows a stress change under a constant strain. In this case, the friction stress σ ｆ＋ (t) is also a function of t, and the following equation (5) holds.

[0080]

[0081] Similarly, T / 2<t<T / 2+t １ and T / 2+t １In the time domain ≦t≦T, the following equations (6) and (7) hold.

[0082]

[0083] Generally, in the range where friction is sufficiently small and linearity is maintained, the stress σ of a liquid sample with viscoelastic properties (viscoelastic sample) ｓａｍｐｌｅ The relationship between (t) and the shear strain rate shown in the following formula (8) is shown in the following formula (9): The proportionality constant Q in the following formula (8) is an experimental constant determined by the radii of the container 2 and the rotor 3, and is a quantity obtained by calibration of a standard material.

[0084]

[0085] where G(t) is the linear relaxation shear modulus of the liquid sample. As shown in FIG. 8, in the presence of friction force, the solid line SW ３ Ω shown in Ｓ Although (t) is a non-sinusoidal wave, the dashed line SW ２ Ω shown Ｍ (t) oscillates with the same period T = 2π / ω, and Ω Ｓ (t) = -Ω Ｓ Since it has inversion symmetry of (t-T / 2), it is expressed as an odd-order Fourier series as in the following equation (10).

[0086]

[0087] The expansion coefficient a in the above formula (10) ｐ and b ｐ Purely mathematically, it corresponds to the Fourier integrals shown in the following equations (11) and (12).

[0088]

[0089] Therefore, Ω Ｓ By Fourier integrating the (t) data over a period T, these expansion coefficients can be obtained for a general viscoelastic sample without arbitrariness. Ｓ (t) If it is possible to fit the data, the expansion coefficients a can be calculated by analytically performing the integration of the above equations (11) and (12) on this fitting function. ｐ and b ｐ You can also ask for:

[0090] The plot (●) in FIG. 9 shows the relationship between the angular velocity of the rotor and the rotational vibration period in the case of a purely viscous sample (a sample of a purely viscous fluid). ４ The function shown by the solid line with " is Ω Ｓ (t) = 0 and Ω Ｓ This is a composite function that combines pieces of the function (t) = X{cosω[t-t']-cosωt"} (X, t', t" are fitting parameters), and is called a "sine function with a sine wave". Generally, for a purely viscous sample, this composite function Ｓ (t) data can be fitted, and the Ω in equations (11) and (12) above can be calculated. Ｓ By analytically integrating using a sine function with a clog after fitting to (t), the coefficient a ｐ , b ｐ can be obtained without arbitrariness. Ω obtained by substituting this coefficient into the above equation (10) Ｓ By integrating the above equation (9) with respect to (t), the following equation (13) is obtained.

[0091]

[0092] Here, the constant Q is a proportionality constant between the shear strain rate on the left side of the above formula (8) and the angular velocity of the rotor on the right side of the above formula (8), and is a known quantity as described above. By Fourier integrating the above formula (13), G'(pω) is expressed by the following formula (14), and G"(pω) is expressed by the following formula (15).

[0093]

[0094] Here, S ｐ , C ｐ is an integral defined by the following equations (16) and (17).

[0095]

[0096] Therefore, the true stress σ of the liquid sample, which eliminates the effect of frictional stress, is ｓａｍｐｌｅ If (t) is known, then σ ｓａｍｐｌｅ (t) and the expansion coefficients a given by the above equations (11) and (12) ｐ and b ｐFrom these equations, the storage modulus G'(ω) and loss modulus G"(ω) (when p=1 in the above equations (14) and (15)) can be obtained. Also, if p=3, 5... (an odd number equal to or greater than 3), G'(pω) and G"(pω) for odd-numbered angular frequencies pω can be obtained. The true stress σ defined by the above equations (16) and (17) ｓａｍｐｌｅ The Fourier integral of (t) S ｐ and C ｐ is determined in the following way:

[0097] S ｐ and C ｐ From the above equations (3) to (7), the rotational angular velocity Ω of the magnet body 12 is Ｍ (t) and the rotational angular velocity Ω of the rotating body 3 Ｓ (t) data, as well as the maximum friction stress σ ｆ，ｍａｘ and the friction stress (time-dependent friction stress) σ that changes depending on time when the rotating body 3 is stationary. ｆ＋ Using (t), it can be expressed as in the following equations (18) and (19).

[0098]

[0099] Here, K is the known proportionality constant explained in relation to the above equation (4). As shown in the above equation (3), Ω Ｍ Since the vibration of (t) does not include double vibration, Ω in the above equations (18) and (19) Ｍ The integral of (t) is 0 except when p=1, but to emphasize this, we have included the Kronecker delta δ in the above equations (18) and (19). ｐ１ was displayed.

[0100] The maximum friction stress σ included in the above formulas (18) and (19) ｆ，ｍａｘ can be experimentally determined by the following methods (1) and (2).

[0101] <Method (1)> Ω Ｍ The amplitude of (t) Ω ｍ０ is decreased until the critical value Ω at which the rotor 3 stops moving in the entire time range 0≦t≦T. ｍ０ ＊ The maximum value of the stress KΩ due to the magnetic body 12 at ｍ０ ＊ Determine σ ｆ，ｍａｘThe value of is KΩ ｍ０ ＊ This σ ｆ，ｍａｘ The method for determining σ ｆ，ｍａｘ This also holds true when depends on the angular frequency ω.

[0102] <Method (2)> Steady flow measurement is performed using the same container 2 and rotor 3 as used in the vibration measurement, and the steady stress σ Ｔ is calculated as a function of the shear strain rate V. As explained in FIG. 6, the value (intercept) obtained by extrapolating this steady stress to a shear strain rate of 0 is expressed as σ ｆ，ｍａｘ Let this σ ｆ，ｍａｘ The method for determining σ ｆ，ｍａｘ is independent of the angular frequency ω. Ｔ = F (V) ... (20) σ f，ｍａｘ = F(0) ...(21)

[0103] On the other hand, the time-dependent friction stress σ ｆ＋ (t) is the time domain t during which the rotating body 3 is stationary １ σ for ≦t≦T / 2 ｓａｍｐｌｅ (t) and Ω Ｍ (t) and is a stress that occurs in the liquid sample to suppress the rotation of the rotor 3. ｆ＋ The time dependence of (t) depends directly on the viscoelasticity of the liquid sample. ｆ，ｍａｘ Unlike the case of σ ｆ＋ (t) is not a quantity determined from a specific experiment, but is calculated for the following two cases.

[0104] <Case 1> When the liquid sample is a pure viscous fluid, the stationary time domain t １ σ for ≦t≦T / 2 ｓａｍｐｌｅ (t) instantly relaxes to 0. Therefore, σ in this time domain ｆ＋ (t) is σ in the above formula (5). ｓａｍｐｌｅ By setting (t) = 0, it is calculated by the following formula (22). Note that, as mentioned above, K in the following formula (22) is a proportionality constant determined by the magnetic flux density and the rotor 3, and is known by testing a standard material. σ ｆ＋ (t) = KΩＭ (t) ...(22)

[0105] <Case 2> Stationary time domain t １ If the internal state of the liquid sample changes only slowly over time for t≦T / 2, then σ ｆ＋ (t) is assumed to change linearly with time t. The start time t of the stationary region shown in FIG. １ σ in ｆ＋ (t) is the maximum friction stress σ ｆ，ｍａｘ σ at the end time T / 2 of the stationary region. ｆ＋ is -σ ｆ，ｍａｘ Therefore, σ in the entire stationary region ｆ＋ (t) is the coordinate (t １ , σ ｆ，ｍａｘ ) and the point identified by the coordinates (T / 2, -σ ｆ，ｍａｘ ) and the point specified by

[0106]

[0107] As mentioned above, Ω Ｍ (t), Ω Ｓ Data for (t), σ determined by Method 1 or Method 2 above f，ｍａｘ and σ calculated for Case 1 or Case 2 above f＋ (t) (using the above equations (22) and (23)) ｐ and C ｐ are calculated from the above formulas (18) and (19), and these S ｐ and C ｐ and the coefficient a obtained from the above equations (11) and (12) ｐ , b ｐ By substituting these values ​​into the above equations (14) and (15), G'(ω) and G''(ω) of the liquid sample can be obtained. Below, the results of verifying the measurement and analysis method will be explained.

[0108] For the purely viscous liquid sample exhibiting the non-sinusoidal behavior plotted in Figure 4, Ω Ｓ (t) = 0 and Ω ＳΩ is calculated by the above-mentioned sine function with a sine clog, which is a piecewise combination of the function (t) = X{cosω[t-t']-cosωt"} (X, t', t" are fitting parameters). Ｓ (t) The results of fitting the data are shown in Figure 9 as "SW ４ The coefficient of determination for the curve fit is R ２ = 0.9984, and the fit was performed with sufficiently high accuracy.

[0109] FIG. 10 shows the results of measuring the angular velocity of the rotor 3 10 times when a vibration stress is applied to the rotor 3, for the same pure viscous sample as above, the container 2, and the rotor 3, with the contact point between the container 2 and the rotor 3 changed. FIG. 11 is a graph showing the reproducibility results of the storage rigidity modulus G' and the loss rigidity modulus G". From FIG. 10, it can be seen that the region where the rotor 3 is stationary varies due to differences in frictional stress at the contact point, and the peak value also varies. However, as shown in FIG. 11, G'(ω) and G"(ω) calculated by the above method from the parameters obtained by fitting showed sufficient reproducibility. These results demonstrate that the experimental and analytical methods encompassed by the present invention can eliminate the influence of frictional stress on the measurement results and measure G'(ω) and G"(ω) with sufficient accuracy.

[0110] FIG. 12 shows the relationship between the rotational angular velocity Ω of the rotor 3 generated by the sinusoidal vibration of the magnet body 12 for a viscoelastic liquid sample that also has an elastic component. Ｓ The results of measuring Ω (t) are shown in Fig. 13. Fig. 13 is a graph comparing the measurement results obtained by the viscoelasticity measuring device 1 of the present invention and a rheometer. For this viscoelastic sample, there is also a time region in which the rotor 3 does not displace due to the frictional stress between the container 2 and the rotor 3. As in the case of a purely viscous sample (Fig. 9), the Ω of the viscoelastic sample is calculated using a sine function with a sag. Ｓ The results of fitting the (t) data are shown in Figure 12. ５ The coefficient of determination for the curve fit is R ２= 0.9982, and the fit was performed with sufficiently high accuracy for the viscoelastic sample. Furthermore, Figure 13 shows G'(ω) and G"(ω) determined for this viscoelastic sample at several angular frequencies ω using the above analytical method. The G'(ω) and G"(ω) data obtained closely match the measurement results using a rheometer, a viscoelasticity measuring device that can measure viscoelasticity with high accuracy using a method different from the viscoelasticity measuring device 1 of the present invention. These results demonstrate that the experimental and analytical methods encompassed by the present invention can also eliminate the influence of frictional stress and enable high-precision measurement of G'(ω) and G"(ω), even for viscoelastic samples. Although not shown in Figure 13 , even in measurements using only one angular frequency ω, this experimental and analytical method can simultaneously determine G'(ω) and G"(pω) at angular frequencies pω (p = 3, 5, 7, ...) in addition to G'(ω) and G"(ω), as shown in Equations (14) and (15) above.

[0111] As described above, this experimental and analytical method can eliminate the effects of frictional stress from viscoelastic measurements. However, for samples that exhibit plastic stress in addition to viscoelastic stress, it can be difficult to distinguish between plastic and frictional stress. In such cases, it is possible to isolate the plastic component by performing similar measurements using a rotor 3 with a different diameter or by shortening the distance between the side of the container 2 and the rotor 3. Furthermore, when the viscous component of the sample is small, the radius R of the rotor 3 is large, and the angular frequency ω is high, the influence of inertia may be present. In such cases, the analysis can be performed by taking into account the stress σi(t) due to inertia in the above equation (4).

[0112] The viscoelasticity measuring device and viscoelasticity measuring method of the present invention have been described above based on one embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the spirit of the present invention.

[0113] (Another Embodiment) In the above embodiment of the viscoelasticity measuring device 1, a permanent magnet is used as the magnet body 12, and the magnet body 12 is repeatedly rotated in a forward and reverse direction to apply a fluctuating magnetic field to the rotor 2. However, this is not limited to this, and an electromagnet arranged in a fixed position may also be used as the magnet body 12. FIG. 14 is a plan view of the main parts of a drive unit 4 in another embodiment. In this case, multiple magnet bodies 12 (four in the example of FIG. 14 ) are arranged around a container 2 containing a rotor 3 together with a liquid sample. A pair of magnet bodies 12 (a first set of magnet bodies 12) facing each other across the container 2, and another pair of magnet bodies 12 (a second set of magnet bodies 12) facing each other across the container 2 and arranged 90° out of phase with the first set of magnet bodies 12 in the circumferential direction of the container 2, are arranged in fixed positions relative to the rotor 3. The rotation control unit 51 then sequentially passes current through the coils of the two sets of magnet bodies 12 to excite them, thereby applying a fluctuating magnetic field to the rotor 3 and causing it to rotationally oscillate. That is, the rotation control unit 51 alternately or simultaneously excites one set of magnet bodies 12 and the other set of magnet bodies 12 of the two sets of magnet bodies 12, alternately or simultaneously generating and fluctuating magnetic fields in different directions, thereby applying a fluctuating magnetic field to the rotor 3. In this case, the rotation control unit 51 controls the period for alternately or simultaneously exciting the two sets of magnet bodies 12 based on a rotation command from the integrated control unit 50, so that forward torque and reverse torque alternately act on the rotor 3. This induces an induced current inside the rotor 3, and the Lorentz interaction between the induced current and the fluctuating magnetic field applied to the rotor 3 generates a rotational torque in the rotation direction of the magnet bodies 12, and forward torque and reverse torque alternately act on the rotor 3 about the rotation axis CL. This causes the rotor 3 to rotationally oscillate.

[0114] The viscoelasticity measuring device and viscoelasticity measuring method of the present invention can be used in applications such as measuring the viscoelasticity of a wide range of substances, from low-viscosity substances such as water, blood, organic solvents, and beverages to high-viscosity substances such as polymer solutions and heavy oil, in the manufacturing processes of pharmaceuticals, foods and beverages, cosmetics, chemical products, etc., as well as in performance evaluation, quality control, research and development, etc.

[0115] REFERENCE SIGNS LIST 1 Viscoelasticity measuring device 2 Container 3 Rotating body 4 Driving unit 5 Irradiation unit 6 Light receiving unit 20 Beam splitter 32 Photodetector (two-dimensional image sensor) 52 Light receiving data acquisition unit 54 Angular velocity calculation unit 55 Time-dependent frictional stress calculation unit 56 Viscoelasticity calculation unit LP Liquid sample

Claims

1. A viscoelasticity measuring device for measuring the viscoelasticity of a liquid sample, comprising: a conductive rotor; a container in which the rotor is placed together with the liquid sample; a drive section for applying a fluctuating magnetic field so that forward torque and reverse torque act alternately to rotate and oscillate the rotor; an irradiation section for irradiating the rotor with light; a light receiving section for receiving reflected light from the rotor; a light reception data acquisition section for acquiring received light data from the reflected light received by the light receiving section; an angular velocity calculation section for calculating the angular velocity of the rotor based on the received light data; and a viscoelasticity calculation section for calculating the viscoelasticity of the liquid sample, wherein the viscoelasticity calculation section calculates the fluctuating speed of the fluctuating magnetic field, the angular velocity, function data obtained by analysis of a rheology model constructed by regarding the liquid sample as a viscoelastic-plastic fluid having properties combining a viscous component, an elastic component, and a plastic component, and replacing the plastic component with a frictional stress acting between the container and the rotor; and frictional stress data obtained in advance for the frictional stress. The viscoelasticity measuring device determines the viscoelasticity of the liquid sample based on the above.

2. The viscoelasticity measuring device described in claim 1, wherein the driving unit rotationally vibrates the rotating body so as to include a dynamic time domain in which the rotating body is rotating due to the forward torque or the reverse torque, and a static time domain in which the rotating body is stationary due to the frictional force acting between the rotating body and the container.

3. A viscoelasticity measuring device as described in claim 2, further comprising a time-dependent friction stress calculation unit that calculates a time-dependent friction stress that changes depending on time when the rotating body comes to a standstill in the static time domain.

4. A viscoelasticity measuring device as described in claim 3, wherein the time-dependent friction stress calculation unit calculates the time-dependent friction stress based on a constant determined by the shape factors of the container and the rotating body and the fluctuating speed of the fluctuating magnetic field when the liquid sample is a pure viscous fluid.

5. A viscoelasticity measuring device as described in claim 3, wherein the time-dependent friction stress calculation unit calculates the time-dependent friction stress using an equation derived based on the friction stress at the start time of the static time region and the friction stress at the end time of the static time region when the liquid sample is a viscoelastic fluid.

6. A viscoelasticity measuring device as described in any one of claims 1 to 5, comprising a beam splitter that bends the optical path of the irradiated light, the beam splitter being disposed so as to align the optical axis of the irradiated light, the optical path of which is bent, with the rotation axis of the rotating body, and to align the optical axis of the reflected light with the rotation axis.

7. A viscoelasticity measuring device according to claim 6, wherein the light receiving section includes a two-dimensional image sensor in which a plurality of light receiving elements are arranged two-dimensionally in parallel.

8. The viscoelasticity measuring device of claim 7, wherein the light receiving data acquisition unit performs image processing on the light receiving data and imports it as two-dimensional image data, and the angular velocity calculation unit sequentially compares two sets of two-dimensional image data that are imported at different times to calculate the angular velocity of the rotating body.

9. The viscoelasticity measuring device according to claim 8, wherein the irradiation unit is configured to irradiate irradiation light having a spot diameter of a predetermined length or more.

10. A viscoelasticity measuring method for measuring the viscoelasticity of a liquid sample, comprising: a driving step of applying a fluctuating magnetic field to a conductive rotating body placed in a container together with the liquid sample so that forward torque and reverse torque act alternately on the conductive rotating body to rotate and oscillate the rotating body; an irradiation step of irradiating the rotating body with light; a light receiving step of receiving light reflected from the rotating body; a light receiving data acquisition step of acquiring received light data from the reflected light received in the light receiving step; an angular velocity calculation step of calculating the angular velocity of the rotating body based on the received light data; and a viscoelasticity calculation step of calculating the viscoelasticity of the liquid sample, wherein in the viscoelasticity calculation step, the fluctuating speed of the fluctuating magnetic field, the angular velocity, function data obtained by analysis of a rheology model constructed by regarding the liquid sample as a viscoelastic-plastic fluid having properties combining a viscous component, an elastic component, and a plastic component, and replacing the plastic component with a frictional stress acting between the container and the rotating body, and frictional stress data obtained in advance for the frictional stress, A viscoelasticity measuring method in which a calculation is performed to determine the viscoelasticity of the liquid sample based on the above.

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