JP2003013956A - Hydrostatic air bearing and rotary viscometer using same bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure viscosity of an objective fluid having non-Newton fluid property and a high coefficient of viscosity while it is in a fluid container and the like. SOLUTION: A detecting spindle 10 is rotated at a very slow speed while it is set on the fluid container 31, and the objective fluid 26 is flowed upward in a gap between a groove 24 and an inner wall surface of a bush 17a of an outer cylinder 7, and the gap between an outer peripheral surface of the detecting spindle 10 and an inner wall surface of the bush 17a is set to be wet in the state of an uniform film. Reaction force caused by viscous resistance along a sliding flow of the objective fluid 32 in the gap acts on the detecting spindle 10 to a reverse direction of its rotation. An entire rotary driving portion 1 and a base cylinder 8 supported by a hydrostatic air bearing 15 are rotated to a reverse direction against the rotary driving direction by means of this reaction force. An arm member 20 installed on the base cylinder 8 is also rotated, and an arm 21 is touched on a sensor arm 13a of a load cell 13. Viscosity of the objective flow 32 can be measured from an output value of the load cell 13 since this touching force is in proportion to the reaction force caused by viscous resistance of the objective flow 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a journal bearing type static pressure air bearing and a rotational viscometer capable of measuring the viscosity of a non-Newtonian fluid using the same.

[0002]

2. Description of the Related Art The rotational viscometer has been widely known as an apparatus for measuring the viscosity of a non-Newtonian fluid. There are various types of rotational viscometers, but in general, rotational drive units,
It consists of a detection part and a measurement part.The detection part is composed of a coaxial inner cylinder and outer cylinder.The outer cylinder is fixed and the inner cylinder is rotationally driven by the rotation drive part. There are an inner cylinder rotating type that measures with a measuring unit, and an outer cylinder rotating type that fixes the inner cylinder and rotates the outer cylinder. In any case, this type of rotational viscometer generally has a cylindrical cup (outer cylinder) into which the test fluid is placed and a cup around the central axis of the cup that is in contact with the test fluid placed inside the cup. A rotor having a cylindrical shape (inner cylinder) rotatably supported independently of the rotor and a rotation driving means for rotating the rotor or the cup about their central axis. On the other hand, the viscosity of the test fluid is measured by measuring the rotational torque transmitted through the test fluid. The cup or rotor is not necessarily cylindrical, and cones and other shapes are widely used. Since such a viscometer and its measuring principle are well known, detailed description thereof will be omitted.

All of the known conventional rotary viscometers are of the batch type as described above. For example, the viscosity of the test fluid in the liquid tank or the pipe in the inner tube of the liquid tank remains unchanged. It is not to measure, but to measure once by taking out the test fluid as a sample from the liquid tank etc., so whether the measured value actually shows the viscosity of the test fluid in the liquid tank etc. I could not guarantee at all, and a solution was desired.

Therefore, the applicant of the present application filed Japanese Patent Application No. 11-395.
In Japanese Patent Laid-Open No. 11-264789,
The above conventional problems have been solved, and in the state where the test fluid is actually in the liquid tank or piping, in other words, a rotary viscometer capable of measuring the viscosity in-line was proposed, but the present invention has a novel structure. It is an object of the present invention to propose a hydrostatic air bearing, and to provide a rotary viscometer which can be manufactured easily and inexpensively by using the hydrostatic air bearing to measure the viscosity with higher accuracy.

[0005]

In order to achieve the above object, a static pressure air bearing according to a first aspect of the present invention has a fixed portion having a cylindrical hollow portion, and the above fixed portion. The fixed part comprises a rotary shaft part to be mounted in the hollow part, and the fixed part is provided with a conical-shaped opening part that expands toward each opening end edge side in the vicinity of both end openings of the hollow part. The opening of the throttle of compressed air is exposed to the inner surface of the conical shape, and the rotary shaft portion is provided with a pair of conical portions that can be mounted in the conical opening of the fixed portion, and jets from the throttle opening of the fixed portion. It is characterized in that the rotating shaft portion is coaxially combined in the hollow portion of the fixing portion so that the air to be applied can be applied to the outer surface of the conical portion of the rotating shaft portion.

According to a second aspect of the present invention, in order to achieve the above object, in the hydrostatic air bearing of the first aspect, the throttles are provided at equal angular intervals in the circumferential direction of the inner surface of the conical opening. It is characterized by

According to a third aspect of the present invention, in order to achieve the above object, in the hydrostatic air bearing of the second aspect, a recess is provided around an opening of the throttle to the inner surface of the conical opening. It is characterized in that the opening area of the concave portion is different on both end sides of the fixing portion.

In order to achieve the above object, the rotational viscometer of the present invention according to claim 4 comprises a rotational drive unit, a detection unit and a measurement unit, and determines the viscosity of a test fluid which is a non-Newtonian fluid. A rotational viscometer for measuring, wherein the detection unit comprises a coaxial inner cylinder and an outer cylinder, the outer cylinder is fixed, and the inner cylinder can be rotationally driven by the rotary drive unit.
In the inner cylinder rotation type rotational viscometer for measuring the viscous torque that the inner cylinder receives when rotating, the inner cylinder is
A base cylinder on which the rotation drive unit is mounted and which is rotatably supported in the outer cylinder, and a base end which is connected to the rotation drive unit and penetrates through the base cylinder and is freely movable in the base cylinder. The rotary shaft is rotatably supported, and the detection cylinder has a portion having a spiral groove formed on the outer peripheral surface and is fixedly connected to the tip of the rotary shaft. The hydrostatic air bearing according to claim 1 or 2 is disposed as an axis, and a gap between fitting portions between the outer cylinder and the groove forming portion of the detection cylinder is provided,
While allowing the rotation of the detection cylinder, the test fluid that has entered the gap is set to have a size that allows the test fluid to be sheared by being given a shear rate by the rotation of the detection cylinder, and the measurement unit is driven to rotate via the rotation shaft. When the detection cylinder is rotationally driven by the section, it is the reaction force of the viscous torque that is received by the shear stress due to the shear flow of the test fluid that has entered the gap, in the direction opposite to the rotational drive direction of the detection cylinder. The rotating torque of the rotating base cylinder and the rotating drive unit is detected.

A fifth aspect of the present invention is characterized in that the rotary drive section rotates the rotary shaft and the detection tube at a very low speed.

The invention according to claim 6 is characterized in that the tip of the detection cylinder is made to protrude from the fitting portion with the outer cylinder to the extent that a part of the groove is exposed.

According to the seventh aspect of the present invention, an opening for overflowing and discharging the test fluid having risen in the gap is provided above the fitting portion of the outer cylinder with the groove forming portion of the detection cylinder. Is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following, only the hydrostatic air bearing according to the present invention applied to a rotational viscometer used in a viscosity measurement example of a fluid under test flowing in a pipe will be described, but the hydrostatic air bearing according to the present invention will be described. Is not limited to this, it can be used in various devices, and for the rotational viscometer according to the present invention, the fact that the test fluid is flowing is not an essential condition, and as will be apparent from the description below. ,
The test fluid that has been stored and is not flowing can be similarly used for measurement under certain conditions.

FIG. 1 is a sectional view showing an embodiment of a rotational viscometer according to the present invention, and FIG. 2 is a plan view of the same. The rotational viscometer of this embodiment mainly includes a rotation drive unit 1, a detection unit 2 and a measurement unit 3. The rotary drive unit 1 includes a DC servomotor 4 with a speed reducer and a coupling 6. In addition, the detection unit 2
Is composed of an outer cylinder 7, a base cylinder 8 forming an inner cylinder coaxial with the outer cylinder 7, a rotary shaft 9, and a detection spindle 10. Further, the measuring unit 3 includes a gear 11 attached to the rotating shaft 9 and a proximity sensor 1
2 and the load cell 13. In the figure, 14 is a base plate, on which the proximity sensor 12, the load cell 13, and the outer cylinder 7 are fixed.

The outer cylinder 7 is a hollow cylinder, and the front end is projected downward through a hole formed in the base plate 14 and the upper end is fixed on the base plate 14. Further, the base tube 8 is rotatably supported inside the hollow through a hydrostatic air bearing 15 described later. In addition, a pair of openings 16 and 16 (not shown on the front side in the drawing) are provided on the lower side of the portion supporting the base cylinder 8, and the lower side thereof is a fitting portion 17 with the detection spindle 10. ing. A bush 17a is attached to the inside of the fitting portion 17.

The base cylinder 8 which constitutes the inner cylinder is also a hollow cylinder, which is rotatably supported in the outer cylinder 7 as described above, and a pair of bearings 18, 18 are provided inside the hollow to provide a rotary shaft. 9
Is supported so that it can rotate freely. The rotating shaft 9 penetrates the hollow inside of the base cylinder 8, the upper end is connected to the output shaft of the DC servomotor 4 via the coupling 6, and the lower end is connected and fixed to the detection spindle 10. The gear 11 described above is attached to the rotary shaft 9 just below the coupling portion of the coupling 6, and the gear 11 rotates together with the rotary shaft 9.

An arm member 20 for detecting a rotational torque is attached to the upper end of the base cylinder 8 so as to rotate together with the base cylinder 8 about the same axis. The illustrated arm member 20
Has a pair of arms 21 for the purpose of balance, and only one arm 21 comes into contact with the sensor arm 13a of the load cell 13 during rotation. Further, a bracket 23 is mounted on the upper surface of the arm member 20 via four columns 22. The bracket 23 is provided with the above-mentioned DC servo motor 4, and the coupling 6 is a hole provided in the bracket 23. Is connected to the rotating shaft 9 below. In the illustrated example, the arm member 20
Since the central portion of the bracket and the bracket 23 have the same shape, they overlap each other in FIG. 2, which is a plan view.

The detection spindle 10 is a fitting portion 1 of the outer cylinder 7.
A spiral groove 24 is formed on the outer peripheral surface of the tip portion located inside 7. The groove 24 is cut with a right-hand thread, and has a slope-shaped cross section in which the groove bottom surface side is inclined downward toward the outside in order to raise the test fluid during rotation, as shown in an enlarged manner in FIGS. 3 and 4. The upper surface of the groove has a cross-sectional shape that horizontally extends outward. However, the cross-sectional shape of the groove 24 is merely an example, and the present invention is not limited to this groove shape. Further, the tip end of the detection spindle 10 has a length that protrudes, for example, by several mm from the fitting portion 17 when mounted on the outer cylinder 7, and detects a gap generated between the fitting spindle 17 and the inner wall surface. The dimension is set such that the spindle 10 is allowed to rotate and the test fluid that has entered the gap is sheared by being given a shear rate by the rotation. This size may be determined based on conventionally known research results, experimental results, and the like.

The hydrostatic air bearing 15 has a cylindrical hollow portion 25.
And a pair of rotating shaft pieces 27, 27 which are attached to the base cylinder 8 to form a rotating shaft portion. As shown in FIG. 5, the fixing portion 26 has cone-shaped opening portions 25a, 25a formed by expanding portions of the hollow portion 25 in the vicinity of the upper and lower end openings toward the opening edge side. In the illustrated example, the inclination angle θ of the conical surface is 45 degrees, but the angle θ is not limited to this value. The fixed portion 26 is the hollow portion 2
5. Three compressed air introduction passages 28 are formed horizontally at 120-degree intervals on the outer periphery of the body, and each introduction passage 28 is formed so that throttles 29, 29 extending in the vertical direction communicate with each other. There is.

Further, concave portions 30 are formed at 120 ° intervals on the inner peripheral surface of the opening portion 25a of the fixed portion 26, and each diaphragm 29 is opened at the bottom surface of the concave portion 30. The formation angle of the concave portion 30 in the circumferential direction is the angle α on the lower side (FIG. 5C).
Is formed to be wider than the angle β on the upper side (FIG. 5A) by about 30 degrees. This angle difference is such that the pressure receiving area on the lower side is made wider than that on the upper side, and when the compressed air is supplied from the throttle 29, the force for pushing the rotating shaft portion upward is exerted. The value of the angle difference of the recess 30 is not particularly limited to the illustrated example.

The rotary shaft piece 27, which constitutes the rotary shaft, is a cone-shaped member that can be mounted in the opening 25a of the fixed portion 26, and the opening 25 is formed so that the air ejected from the diaphragm 29 hits the outer surface.
Coaxially combine into a. Of course, the rotating shaft top 27
May be integrally formed with the base cylinder 8. As is well known, the hydrostatic bearing is composed of a portion that receives the weight of the shaft and a portion that receives the rotation. The rotating shaft portion of the present embodiment simultaneously fulfills these functions.

That is, in the above-mentioned structure, when the eccentricity is generated in the rotary shaft portion, the pressures in the three concave portions 30 change, and the dynamic pressure is constantly attempted to be utilized to perform the self-centering function. Therefore, the static pressure air bearing 15 has a simple structure, has less vibration, and achieves high rotation accuracy as a spindle mechanism required for the static pressure air bearing. Not only 27, the rotary shaft 9, the detection spindle 10 and the arm member 20, but also the entire rotary drive unit 1 including the DC servo motor 4, the support column 22, the bracket 23, etc. is easily rotated by an external force by the action of the static pressure air bearing 15. To do. For example, it can be rotated very freely by turning it by hand. If the detection spindle 10 is rotated by an external force, for example, by hand, while the DC servo motor 4 is not rotationally driven, the detection spindle 10 is connected to the rotation shaft 9 to generate DC.
The rotating body in the servo motor 4 rotates together, and due to the rotation resistance of the members and elements that support the rotating body, the entire DC servo motor 4 and the base cylinder 8 eventually rotate together due to the external force of the detection spindle 10. ing.

Next, the usage of the rotational viscometer of this embodiment will be described with reference to the above-mentioned drawings and FIGS. 7 and 8. For example, the base plate 14 of the rotational viscometer having the above-described configuration is fixed and set on the liquid tank 31 containing the test fluid by an appropriate holding means, and the fitting portion 17 of the outer cylinder 7 is set to the middle. Even if the liquid surface of the test fluid 32 changes due to the flow and inclination in the liquid tank 31 by being immersed in the test fluid 32 inside the detection spindle 10.
The tip end portion provided with the groove 24 is prevented from protruding above the liquid surface. That is, in the rotational viscometer of this embodiment, it is important to keep the state of the test fluid 32 constant in the gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a, as will be described later. This is because if the tip end side of the spindle 10 comes out above the liquid surface, a constant state cannot be maintained.

By driving the DC servomotor 4 and decelerating it with a built-in speed reducer, the rotary shaft 9 is rotationally driven at the slowest speed possible, and the test fluid 32 is prevented from causing structural damage as much as possible.
Rotate 0. Then, the test fluid 32 flowing near the tip of the detection spindle 10 has a high viscosity even if it has a high viscosity.
Of the bush 17a attached to the inner wall of the bush 17a and rises spirally along the groove 24 due to the viscosity of the test fluid 32 itself and the sectional shape of the groove 24.

That is, this ascending movement is a shear flow of the test fluid 32 in the gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a, and the rotational driving force received by the detection spindle 10 becomes shear stress. Occurs. When shear stress is generated, the test fluid 32 is sheared and deformed, as is well known, and the test fluid 32 is sheared and deformed in the gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a. The velocity gradient generated by this shear deformation is the shear velocity as is well known, but by causing the above shear flow over the entire gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a, the test fluid 26 is The viscosity of the test fluid 32 is measured by giving a certain value of the shear rate and observing the change in the shear stress caused thereby.

When the detection spindle 10 is continuously rotated for a certain period of time, the test fluid 32 that has risen in the gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a.
But overflows from the opening 16 at the bottom of the base cylinder 8. As long as this state is maintained, the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a are all wet with the test fluid 32, and the test fluid 32 in the gap has a uniform film thickness and a moving speed,
The moving state is kept constant.

It goes without saying that the test fluid 32 begins to enter the gap between the outer peripheral surface of the detection spindle 10 and the inner wall surface of the bush 17a. Is applied as an external force to the detection spindle 10 in the direction opposite to the rotation direction. Then, as described above, the DC servo motor 4 and the base cylinder 8 are also rotated by the external force applied to the detection spindle 10, and these are opposite to the rotational drive direction (direction of arrow A in FIG. 8) by the DC servo motor 4. It rotates very slowly in the direction (arrow B direction in FIG. 8). Then, the arm member 20 attached to the base cylinder 8 also rotates, and the arm 21 on the load cell 13 side comes into contact with the sensor arm 13 a of the load cell 13.

The contact force of the arm 21 is the same as the test fluid 26.
Since it is proportional to the rotational torque of the reaction force due to the viscous torque of
If the output value of the fluid of known viscosity is known in advance, the viscosity of the test fluid 32 can be measured by detecting the output value of the load cell 13 when the test fluid 32 is in the constant state as described above. Since the entire rotary drive unit 1 rotates with very low friction due to the action of the static pressure air bearing 15, the error due to the rotational friction force is very small. Of course test fluid 3
The viscosity can be measured for various shear rates by changing the rotation speed of the detection spindle 10 in accordance with 2 as in the case of the conventional general rotary viscometer.

In the present embodiment, the output signal of the load cell 13 is sampled at the timing when the crest of the gear 11 is detected by the proximity sensor 12, but, of course, instead of the gear or the proximity sensor, an appropriate rotary encoder, optical sensor or the like may be used. A timing detection means may be used. Also load cell 1
Since the conversion and processing of the output signal of No. 3 are very well known, the description will be omitted. Of course, a load sensor other than the load cell can be used. That is, various known means may be adopted as the measuring means.

[0029]

As described above, according to the novel structure of the hydrostatic air friction bearing according to the present invention, it has a simple structure, high spindle rigidity, little vibration, and is required for hydrostatic air bearings. There is an effect that it is possible to achieve high rotation accuracy as the spindle mechanism.

As described above, the rotational viscometer according to the present invention can be used without removing the test fluid to another place while the test fluid is actually in the liquid tank or in the pipe.
In other words, there is an effect that the viscosity can be measured in-line, and an accurate viscosity can be measured in a constant state even in a fluid that causes structural destruction when taken out.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a rotational viscometer according to the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is an enlarged partial sectional view of a detection spindle that constitutes an inner cylinder.

FIG. 4 is an enlarged sectional view of a groove provided on a detection spindle.

5A is an enlarged plan view showing the structure of a fixing portion, FIG. 5A is a sectional view taken along line BB in FIG. 5A, and FIG. 5C is a bottom view.

FIG. 6 is an enlarged sectional view showing a structure of a rotating shaft portion.

FIG. 7 is a cross-sectional view showing a usage state of an embodiment of the rotational viscometer according to the present invention.

FIG. 8 is a perspective view of the same.

[Explanation of symbols]

1 rotary drive 2 detector 3 measuring section 4 DC servo motor with reduction gear 6 coupling 7 outer cylinder 8 base tubes 9 rotation axis 10 Detection spindle 11 gears 12 Proximity sensor 13 load cell 13a Load cell sensor arm 14 Base plate 15 Hydrostatic air bearing 16 openings 17 Fitting part 17a bush 18 bearings 20 Arm member 21 arms 22 props 23 Bracket 24 Detection spindle groove 25 Hollow part 25a opening 26 Fixed part 27 Rotating axis top 28 Compressed air introduction path 29 Aperture 30 recess 31 liquid tank 32 Test fluid

Claims (7)

[Claims] 1. A fixed part having a cylindrical hollow part, and a rotary shaft part mounted in the hollow part of the fixed part, wherein the fixed part is provided at each of the openings in the vicinity of both end openings of the hollow part. A cone-shaped opening that widens toward the edge is provided, and the cone-shaped inner surface of the opening faces the opening of the throttle for compressed air, and the rotary shaft portion is the cone-shaped portion of the fixed portion. The rotary shaft is provided in the hollow portion of the fixed portion so that air ejected from the aperture of the fixed portion can be applied to the outer surface of the conical portion of the rotary shaft portion. A hydrostatic air bearing characterized in that the parts are coaxially combined. 2. The hydrostatic air bearing according to claim 1, wherein the diaphragms are provided at equal angular intervals in the circumferential direction of the inner surface of the conical opening. 3. A recess is provided around the opening of the diaphragm toward the inner surface of the conical opening, and the opening area of the recess is different on both end sides of the fixing portion. Static pressure air bearing. 4. A rotational viscometer for measuring the viscosity of a test fluid, which is a non-Newtonian fluid, comprising a rotation drive section, a detection section and a measurement section, wherein the detection section comprises a coaxial inner cylinder and An inner-cylinder rotation-type viscometer in which the outer cylinder is fixed, the inner cylinder is rotatably driven by the rotation driving unit, and the measuring unit measures a viscous torque received when the inner cylinder rotates. In the above, the inner cylinder is mounted with the rotation drive unit and is rotatably supported in the outer cylinder, and the base end is connected to the rotation drive unit and penetrates the base cylinder. The rotating cylinder supported rotatably in the base cylinder, and the detecting cylinder having a portion having a spiral groove formed on the outer peripheral surface thereof and fixedly connected to the tip of the rotating shaft, the outer cylinder and the outer cylinder. 4. A coaxial arrangement with the base cylinder according to claim 1. A compressed air bearing is arranged to allow rotation of the detection cylinder through a gap between the outer cylinder and the groove-forming portion of the detection cylinder, and the test fluid entering the gap causes rotation of the detection cylinder. When the measurement unit rotationally drives the detection cylinder by the rotation drive unit via the rotation shaft, the test cylinder enters the gap. Rotational viscosity characterized by detecting the rotational torque of the base cylinder and the rotary drive section that rotate in the direction opposite to the rotational drive direction of the detection cylinder by the reaction force of the viscous torque received by the shear stress due to the shear flow of the fluid. Total. 5. The rotational viscometer according to claim 3, wherein the rotary drive unit rotates the rotary shaft and the detection cylinder at a very low speed. 6. The rotational viscometer according to claim 3, wherein the tip of the detection cylinder is made to protrude from a fitting portion with the outer cylinder to such an extent that a part of the groove is exposed. 7. An opening for overflowing and discharging the test fluid that has risen in the gap is provided in an upper portion of a fitting portion of the outer cylinder with a groove forming portion of the detection cylinder. The rotational viscometer according to any one of claims 3 to 5.