JPH0153411B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a viscoelasticity measuring device, and more particularly to a viscoelasticity measuring device that measures the viscosity and viscoelastic constant of a low viscosity fluid at a low shear rate.

Various viscoelasticity measuring devices have been proposed that measure the viscosity and viscosity constant of a fluid by utilizing the fact that the amount of mechanical response of a fluid depends on its shear rate. The accuracy of viscoelastic measurements depends on the shear rate. In other words, as the shear rate decreases, the detection power decreases, so
This reduces measurement accuracy. For fluids with relatively high viscosity, a relatively large detection force can be obtained even at a low shear rate, so viscoelasticity measurement with a certain level of accuracy is possible. However, if the shear rate is low for fluids with low viscosity, satisfactory detection power cannot be obtained and high measurement accuracy cannot be obtained.

As mentioned above, it is extremely difficult to measure low viscosity fluids at small shear rates, and conventional viscoelasticity measuring devices for measuring the viscoelasticity of low viscosity fluids at small shear rates are difficult to measure under the measurement conditions. The setting range is narrow, handling is difficult, sufficient accuracy cannot be obtained, and the price is high.

Investigation of the mechanical behavior of low viscosity fluids at low shear rates has important significance in various fields. For example, human blood with a viscosity of several mPa-sec circulates within blood vessels at a shear rate in the range of 40 sec ^-1 to 800 sec ^-1 . As mentioned above, blood has a low viscosity, so even if viscoelasticity measurements are performed to find out the viscoelastic properties near the lower limit of shear rate of 40 ^-1 sec, the measurement accuracy is poor and it is difficult to accurately grasp the viscoelastic properties. Can not do it. In the case of Newtonian liquids, it is possible to estimate the viscoelastic properties at low shear rates from the results obtained by performing viscoelastic measurements at high shear rates. However, for non-Newtonian liquids such as blood, it is impossible to estimate the viscoelastic properties at low shear rates from the results of viscoelastic measurements at high shear rates. It has been proposed to measure the viscoelastic properties of blood to aid in disease diagnosis. However, it is difficult to perform meaningful and accurate viscoelastic measurements necessary for diagnosis, and viscoelastic measuring devices for this purpose require advanced measurement technology and are expensive, so it is difficult to put them into practical use. had many problems.

In measuring the viscoelasticity of non-Newtonian fluids, it is necessary to keep the shear rate constant, so either a coaxial double cylinder type viscoelasticity measuring device or a cone-and-plate measuring device is mainly used.

In a coaxial double cylinder type measuring device, a measurement error called the so-called end effect must be taken into consideration, and in order to reduce this error to a negligible level, the distance between the inner and outer cylinder bottoms of the double cylinder should be increased. Therefore, a relatively large amount of sample is required for measurement. This is a serious drawback when the sample is human blood.

On the other hand, with a cone-plate type measuring device, the apex of the cone must be adjusted to accurately touch the horizontal flat plate, and this adjustment requires a high level of skill.

The present invention proposes a viscoelasticity measuring device with a novel configuration that eliminates the drawbacks of the conventional viscoelasticity measuring devices described above.

A first object of the present invention is to provide a viscoelasticity measuring device that can measure the viscoelasticity of a low-viscosity fluid with high accuracy at a low shear rate.

Particularly, the second object of the present invention is to provide a viscoelasticity measurement device capable of measuring human blood with high precision at a low shear rate, and to make it useful for diagnosing diseases based on the viscoelastic properties of blood. This is the purpose.

According to the present invention, the apex of the conical lower end of the inner cylinder arranged coaxially with the outer cylinder is brought into contact with the bottom surface of the outer cylinder, and the wire is connected from one end of the outer cylinder or the inner cylinder so as to coincide with the axis of the outer cylinder. The wire is held in tension by a wire holding device, and a magnetic bearing is provided to maintain the vertical axis of the inner and outer cylinders, and a torsion measuring device is further provided to measure the twist of the wire. An elasticity measuring device is provided.

Due to the above configuration of the present invention, the end portion of the double cylinder is of the conical and flat type, so the error due to the end effect can be completely ignored, and the contribution of the conical and flat plate component to the detected torque is completely negligible. can be made sufficiently small compared to the contribution of the coaxial double cylinder component to the detected torque, and there is no need to take measurement errors due to poor positioning of the cone apex into account; in other words, the cone apex This has the advantage that positional accuracy is not required and positional adjustment is therefore easy.

It is well known that measuring the twist angle of the wire is most preferable for low torque detection, and this measurement method is often used for viscoelasticity measurements. By the way, in order to improve measurement accuracy, it is necessary to reduce the diameter of the wire, but by making the wire thinner, the inner cylinder or outer cylinder suspended from this wire tends to sway more easily. This results in measurement errors. In order to prevent this horizontal shaking, conventional viscoelasticity measuring devices use air bearings. However, using air bearings has problems such as the need for a compressed air source and the possibility of torque generation due to air flow, and the need to create a mechanism that will prevent the wire from being overloaded when replacing the inner and outer cylinders. It is necessary to provide a separate device, which has the disadvantage of complicating the structure of the device. In the present invention, magnetic bearings are used in place of air bearings, and there is no need to provide a complicated air system device, simplifying the device structure. The coefficient of friction of the bearing is also reduced, and highly accurate measurements can be expected. Furthermore, simply by changing the direction of the magnetic field, it can be made to act on the side where the shaft is fixed, making it easy to replace the inner cylinder and the outer cylinder, and the structure of the torque detection section can be extremely simplified.

In order to make it possible for a viscoelasticity measuring device to perform viscoelasticity measurements over a wide range, for example, in order to enable accurate measurements by varying the shear rate over a wide range, it is necessary to measure from minute torques to large torques. The need arises. For this purpose, it is necessary to change various wires having different torsion constants depending on the measurement range. If the wire is not handled with sufficient care when replacing it, the torsion constant of the wire will change and accurate measurements cannot be expected. It is a conventional practice to attach fixing fittings to both ends of the wire so that the torsion constant does not change. However, as the diameter of the wire decreases, the torsion constant tends to change, requiring great skill to replace the wire, and making it extremely difficult to handle.

In view of the above, in the present invention, a pipe extends coaxially from one end of the torque detection tube on the side where the viscous torque of the fluid is applied so as to surround the wire, and this pipe is held vertically by a magnetic bearing. None, this pipe has the function of supporting the torque detection cylinder. Therefore, the wire is merely subjected to twisting action and does not support the detection tube, making wire replacement easy and eliminating the need to change the torsion constant. Furthermore, since the detection tube is held by a pipe, the detection tube can be easily replaced.
This is because an unreasonable load is not applied to the wire when replacing the tube. Furthermore, since the pipe also serves to prevent lateral sway, there is no need to provide a lateral sway prevention mechanism, which simplifies the structure and makes the entire device compact.

These and other features and advantages of the present invention will be understood in detail in the form of an exemplary embodiment of the invention, which is explained below by way of example in conjunction with the accompanying drawings.

The attached drawing is a sectional view showing the main parts of a viscoelasticity measuring device which is an embodiment of the present invention. Reference number 1 is a drive device, which rotates the inner cylinder 2 or generates sinusoidal rotational vibration. It is something that will be carried out. The lower end of the inner cylinder 2 is a conical end, and the apex of this conical end centrally contacts the bottom surface of the outer cylinder 3 that coaxially surrounds the inner cylinder 2. The outer cylinder 3 is held at its bottom end by a torsion pipe 5 which is held vertically by a magnetic bearing 6. Naturally, the axis of the torsion pipe 5 is aligned with the axis of the outer cylinder 3 and further with the rotational axis of the inner cylinder 2 passing through the apex of the conical end.

A wire 7 is stretched inside the torsion pipe 5 along its axis. An opening 5a is provided in the middle of the torsion pipe 5.
A chuck 8 protrudes through a and clamps a fixture 9 attached to the wire 7.
Also, the lower end of the torsion pipe 5 is connected to a displacement measuring device 10.
Supported by

The operation of this embodiment will be explained below.

When the inner tube 2 is rotated by the drive device 1, the sample 4 undergoes shearing deformation between the inner tube 2 and the outer tube 3.
The resulting torque 5 is the torsion pipe 5.
Rotate. Therefore, the wire 7 between both ends of the torsion pipe 5 and the fixture 9 is twisted. The torsion pipe 5 is rotationally displaced by the amount of twisting of the wire 7. This rotational displacement angle is detected by the measuring device 10, the torque is measured, and the indicated values of viscosity and viscoelastic constant are displayed. A magnetic bearing 6 holds the torsion pipe 5 against tilting, but the magnetic bearing 6 also receives an axial thrust to prevent creep of the wire.

[Brief explanation of drawings]

The attached figure is a diagram illustrating a cross-sectional view of the main part of the viscoelasticity measuring device. DESCRIPTION OF SYMBOLS 1... Drive device, 2... Inner cylinder, 3... Outer cylinder, 4... Sample, 5... Torsion pipe, 6... Magnetic bearing, 7...
Wire, 8...chuck, 9...fixing metal fittings, 10...measuring device.

Claims (1)

[Scope of Claims] 1. A viscoelasticity measurement device that generates a shear velocity in a fluid and detects the resulting shearing force of the fluid as torque, which is driven by a drive device to shear the fluid. an input member that provides speed;
an output member that receives torque from a fluid and is displaced by an amount corresponding to the torque, and detects the amount of displacement of the output member;
In a viscoelasticity measuring device that has a measuring device that knows the torque value and then measures the viscoelastic properties of the fluid,
A viscoelasticity measuring device, wherein the output member is supported by a magnetic bearing. 2. The device according to claim 1, wherein the input member and the output member are coaxial double cylinders in which an inner cylinder and an outer cylinder are coaxially combined. 3. In the device according to claim 2, the lower end of the cylinder is a conical end whose center axis is the axis of the inner cylinder, and the apex of the conical end is at the outer cylinder. A device that is in contact with the bottom surface. 4. In the device according to claim 2, a torsion pipe is attached coaxially to the output member of the inner cylinder and the outer cylinder, and the magnetic bearing is attached to the output member. A torsion pipe is vertically supported, and a wire is threaded along the axis of the torsion pipe, and an intermediate position of the wire is fixedly supported by a fixing device. The apparatus is such that rotation of the cylinder serving as the output member causes the wire to be twisted between both ends of the cylinder and the fixing fitting. 5. The apparatus according to claim 4, wherein the cylinder serving as the output member is the outer cylinder, and the cylinder serving as the input member is the inner cylinder.