JP2001324436A - Rotational viscometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotational viscometer which can support a driven rotary shaft, without friction and can be constituted inexpensively. SOLUTION: Magnetic shafts 80 and 90 are set between a driving rotary shaft 52 and the driven rotary shaft 60. The magnetic shafts 80 and 90 are constituted of external permanent magnets 82 and 92 fixed to the driving rotary shaft 52 and inside permanent magnets 84 and 94 fixed to the driven rotary shaft 60 respectively. The outside permanent magnets 82 and 92 and the inside permanent magnets 84 and 94 are arranged coaxially via an appropriate interval, so as to always generate a magnetic repulsive force in the diametrical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotational viscometer.

[0002]

2. Description of the Related Art Conventionally, as a rotational viscometer for measuring the viscosity of a liquid substance by a rotational method, a drive-side rotary shaft rotated by a drive device and a driven-side rotary shaft connected to a rotor immersed in a fluid to be measured. And a torsion elastic member that couples the drive side rotation shaft and the driven side rotation shaft, and measures the torsion angle of the torsion elastic member, and converts the torsion angle into a viscous torque to measure the viscosity. ing. In such a rotary viscometer, it is an important problem that the driven rotary shaft is axially supported (centered) without friction in the radial direction and is indispensable for improving measurement accuracy.

For example, as a first example, Japanese Patent No. 27465
In Japanese Patent Publication No. 66, a balance weight is attached to a pointer support cylinder which is a driven side rotating shaft, and a tension in a thrust direction is applied to a piano wire which is a torsion elastic member by the action of the balance weight to maintain a straight line of the piano wire. It describes that the axis of the pointer support cylinder is stabilized.

As a second example, Japanese Patent Application Laid-Open No. 8-5541 describes that a drive-side rotary shaft and a driven-side rotary shaft are supported by a case via air bearings in a non-contact state. .

[0005] As a third example, Japanese Patent Publication No. 45-26840 discloses that a permanent magnet is fixed to a metal suction frame-type fixing portion serving as a driven-side rotating shaft suspended by a torsion elastic member, and a supporting fixing portion. It is described that the metal frame-type fixing portion made of metal is sucked downward by a suction force generated between the respective magnets and the torsion elastic member is applied with a downward tension to perform axis adjustment.

As a fourth example, Japanese Patent No. 2749552 discloses that the upper end of an output shaft is centered by a pivot bearing, a movable annular magnet is fixed to the output shaft, and a fixed annular magnet is fixed to the housing. It is described that a vertical force for supporting the weight of the output shaft is exerted by a magnetic attraction force between these magnets.

In addition to the above, JP-A-1-53411 discloses an example in which a magnetic bearing is used.
In the publication, a configuration is described in which a torsional elastic member is attracted by a fixed magnet to apply tension in the axial direction.

[0008]

However, the above conventional example has the following problems.

When the balance weight is used as in the first example, the effect is insufficient, and the driven-side rotating shaft cannot be aligned, and it is difficult to put it to practical use.

[0010] Further, when an air bearing is used as in the second example, there is a problem that the device is complicated, large, and expensive, although sufficient functions and effects can be expected. Therefore, even if it can be applied to an expensive high-class viscometer, it is difficult to apply it to a widely used general-purpose machine.

In the third, fourth, and other examples, the magnetic attraction is used. In this method, however, the magnetic force is inversely proportional to the square of the distance, so that a slight eccentricity occurs. However, in a state where the eccentricity is large and a large centering force is required, there is a fundamental weakness that the magnetic force due to the suction is weakened.

Therefore, among viscometers of popular and inexpensive class, rotational viscometers capable of supporting the driven rotary shaft without friction have not been put to practical use at present.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a rotational viscometer capable of supporting a driven-side rotating shaft without friction and having a low cost.

[0014]

According to a first aspect of the present invention, a driving-side rotating shaft rotated by a driving device is coaxially connected to the driving-side rotating shaft by a torsion elastic member. A rotational viscometer for detecting the viscosity of the fluid to be measured from the torsion angle, comprising: a driven rotation shaft that receives a torque from the fluid to be measured; and a detector that detects the torsion angle of the torsion elastic member. At least one axis
The magnetic bearing is composed of a driven magnet fixed to the driven rotating shaft and an opposing magnet facing the driven magnet, and the driven magnet and the opposing magnet are coaxial with each other. It is characterized in that it is arranged such that a magnetic repulsive force can always be generated in the radial direction with an appropriate interval provided in the shape. By using a magnetic bearing that generates a magnetic repulsive force in the radial direction, when eccentricity occurs, an alignment force due to strong repulsion is obtained, and a strong recovery force from eccentricity is obtained. On the other hand, assuming that a magnetic bearing utilizing a radial magnetic attraction force is used, if eccentricity occurs, or the magnetization of the magnet constituting the magnetic bearing is not uniform over the circumferential direction and the attraction force is weak. When the eccentricity occurs so as to separate from each other, if the eccentricity is separated from the axis, the suction force of the separated portion is weakened as much as possible, and it is difficult to return to the axis. In the magnetic bearing of the present invention, since the repulsion force in the radial direction is used, the magnetic repulsion force in the approaching portion increases as the distance from the shaft center increases, and a strong recovery force from eccentricity can be obtained. become. By making the space between the opposing magnet and the driven magnet sufficiently small,
Even in the centered state, a sufficient magnetic repulsion can be generated.

Further, the opposed magnet facing the driven magnet can be fixed to a fixed portion. According to a second aspect of the present invention, the opposed magnet is fixed to a driving rotary shaft. It is characterized by a side magnet. Claim 3
The invention described in this aspect is characterized in that the axial positions of the driven magnet and the opposing magnet of the magnetic bearing according to claim 1 or 2 are shifted by a predetermined amount in advance. As a result, an axial magnetic repulsion can be generated, and the same effect as that of the conventional weight can be obtained.

According to a fourth aspect of the present invention, the axial position of the driven magnet and the opposed magnet according to the third aspect is such that the driven-side rotary shaft is relatively close to the direction of the fluid to be measured. It is set so that a magnetic repulsive force in an axial direction is generated. Thereby, the driven-side rotation shaft can oppose the axial force received from the fluid to be measured, and buckling of the torsional elastic member can be prevented.

According to a fifth aspect of the present invention, a sliding bearing having a torsion elastic member as an axis is further provided between the torsion elastic member according to any one of the first to fourth aspects and the driven magnet. It is characterized by. By providing the sliding bearing between the torsion elastic member and the driven magnet, it is possible to more reliably prevent the driven magnet from being displaced in the radial direction while keeping the frictional resistance small.

According to a sixth aspect of the present invention, the magnetic bearing according to the fifth aspect is provided closer to a connection point of the torsional elastic member of the driven-side rotary shaft than the slide bearing. If the radial force is generated by a magnetic bearing,
There is a possibility that the moment for tilting the driven-side rotary shaft may increase. However, by providing the sliding bearing at a portion away from the connection point, generation of such a large moment can be suppressed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a first embodiment of the present invention. In FIG. 1, this rotational viscometer is roughly divided into
It comprises a fixed part 10, a drive part 12, a driven part 14, and a torsion wire 16 which is a torsion elastic member.

The fixing portion 10 has an upper substrate 22, a middle substrate 24 and a lower substrate 26 which are vertically arranged in parallel with each other. Are integrally connected by a pillar 30. FIG. 1 shows only one pillar 30. Further, a cylindrical shaft 32 extending downward is fixed to the lower substrate 26.

The drive section 12 is driven to rotate by a drive device 40 comprising a motor with a speed reducer supported by the upper substrate 22. An output shaft 40 a of the drive device 40 that penetrates through the upper substrate 22 and protrudes downward is integrally connected to a drive shaft assembly 42 of the drive unit 12. The drive shaft assembly 42 is illustrated in a simplified manner, but penetrates the central board 24 as a whole, and is rotatably supported by the bearing 46 with respect to the central board 24. Also,
An upper disk body 48 is fixed to a lower portion of the drive shaft assembly 42, and three studs 50 extending downward at intervals of 120 degrees (only one is shown in FIG. 1) are provided on a lower surface of the upper disk body 48. ) Is attached. Each stud 50 extends downward through an arc-shaped groove 66 a formed in a lower disk body 66 described later, and has a lower end attached to an upper end of the drive-side rotary shaft 52. The lower end of the cylindrical drive-side rotating shaft 52 is rotatably supported on the cylindrical shaft 32 by a bearing 54 via a bottom member 56. The driving unit 12 is configured as described above.

The lower part of the drive shaft assembly 42 of the drive part 12 is fixed to a torsion wire 16 by a fixing part 58 described later.
Is fixed, and the driven portion 14 is anchored to the drive portion 12 by the torsion wire 16.

The driven portion 14 has a cylindrical driven-side rotating shaft 60 disposed inside the driving-side rotating shaft 52.
A wire chuck 62 for fixing the lower end of the torsion wire 16 is fixed below the driven rotation shaft 60. In addition, the lower end of the driven side rotation shaft 60 has a rotor connection portion 6.
4 is attached, and a rotor (not shown) immersed in the fluid to be measured is connected to the rotor connection portion 64. A lower disk 66 is attached to the upper end of the driven rotation shaft 60 via a holder 68. The driven part 14 is configured as described above.

As shown in FIG. 2, the lower disk body 66 of the driven portion 14 is formed with an arc-shaped groove 66a having a central angle of less than 120 degrees at intervals of 120 degrees corresponding to the stud 50. . Further, the slit 66b is formed at every predetermined angle (in the example of the figure, every 90 degrees). Upper disk 48
Also, slits are formed at the same angle as the lower disk body 66. Each lower disk body 66 and upper disk body 4
Photosensors 70 and 72 as detection units are provided at positions where light can pass through the eight slits, and these photosensors 70 and 72 are provided with holders 74 extending from the central substrate 24.
It is fixed to. Outputs from these photosensors 70 and 72 are sent to a processing unit (not shown).

One or more magnetic bearings are provided between the drive unit 12 and the driven unit 14, specifically, on the peripheral surfaces of the drive-side rotary shaft 52 and the driven-side rotary shaft 60 facing each other. In this embodiment, an upper magnetic bearing 80 and a lower magnetic bearing 90 are provided at the upper end and the lower end of the drive-side rotary shaft 52 and the driven-side rotary shaft 60, respectively. Upper magnetic bearing 80
Consists of a cylindrical outer permanent magnet 82 provided on the inner peripheral surface of the drive-side rotating shaft 52 and a cylindrical inner permanent magnet 84 provided on the outer peripheral surface of the driven-side rotating shaft 60. The bearing 90 includes a cylindrical outer permanent magnet 92 provided on the inner peripheral surface of the drive-side rotary shaft 52 and a cylindrical inner permanent magnet 94 provided on the outer peripheral surface of the driven-side rotary shaft 60.

The magnetic bearings 80 and 90 have the magnetizing direction of the magnets facing each other as the axial direction. As shown in FIG. 3, the magnetic bearings 80 and 90 are arranged so that the same poles are close to each other and generate repulsive forces from each other. It is configured.

In the rotational viscometer configured as described above, the center between the driven side rotating shaft 60 and the driving side rotating shaft 52 is aligned by magnetic bearings 80 and 90. That is, when the drive-side rotation shaft 52 and the driven-side rotation shaft 60 become eccentric, a repulsive force is generated more strongly in a portion where the drive-side rotation shaft 52 and the driven-side rotation shaft 60 are close to each other, and the alignment is performed. The stronger the eccentricity, the stronger the repulsive force is generated, and the greater the eccentricity, the stronger the recovery from eccentricity. By setting the gap between the drive-side rotary shaft 52 and the driven-side rotary shaft 60 to be sufficiently small, a sufficiently strong recovery force can be provided. Earnshaw
According to the theorem, a magnetic bearing composed of only permanent magnets cannot be realized by itself, but in this way, the inner permanent magnets 84 and 94 floating due to magnetic repulsion must be restrained and positioned by the torsion wire 16. Can be established.

In this embodiment, each magnetic bearing 8
In both 0 and 90, the positions of the outer permanent magnets 82 and 92 and the inner permanent magnets 84 and 94 are shifted in the axial direction in advance, and the outer permanent magnets 82 and 92 and the inner permanent magnet 8
4, 94 axial repulsion acts on the driven side rotation shaft 60. Specifically, each magnetic bearing 80, 90
Are positioned slightly below the outer permanent magnets 82, 92 in the axial direction. Thus, in each of the magnetic bearings 80 and 90, the driven side rotating shaft 6
An axial repulsive force such that 0 protrudes downward in the axial direction from the drive-side rotary shaft 52 always acts on the driven-side rotary shaft 60.

The examples of the magnetic bearings 80 and 90 are not limited to the examples shown in FIGS. 1 and 3, but may be arranged as shown in FIGS. 4 (a) to 4 (e). FIG. 4 (a)
As shown in (c), by using a plurality of magnets, it is possible to realize a bearing having a stronger alignment force.
As shown in FIG. 4D, the magnets are magnetized in the radial direction so that the inner peripheral surfaces of the outer permanent magnets 82 and 92 and the outer peripheral surfaces of the inner permanent magnets 84 and 94 have the same polarity. May be. Further, as shown in FIG. 4E, instead of arranging a plurality of magnetic bearings on the drive-side rotation shaft 52 and the driven-side rotation shaft 60, two cylindrical permanent magnets having long shaft lengths are used. It is also possible to configure.

FIG. 6 is an enlarged view showing a fixing portion 58 at the upper end of the torsion wire 16 and a fixing method thereof. The tip of the torsion wire 16 is sandwiched between two wire chuck plates 76, 76, and these are pressed into the tag 78. At this time, the torsion wire 16 is prevented from coming off the wire chuck plate 76 by deforming the torsion wire 16 with the wire chuck plate 76. Then, these are inserted into the concave portions 42a of the drive shaft assembly 42.
Insert inside. A plurality of screw holes 42b are formed radially in the peripheral wall of the recess 42a of the drive shaft assembly 42 at equal intervals in the circumferential direction, and a set screw 45 is screwed from the screw hole 42b toward the center in the radial direction. Then, the tag 78 is sandwiched between the set screws 45. In the example of FIG. 6, three screw holes 42b and set screws 45 are provided at equal intervals in the circumferential direction. While the drive side 12, that is, the drive shaft assembly 42 is rotated, the tightening of the set screw 45 is adjusted while checking the torsion wire 16 with a microscope M or the like so that the torsion wire 16 does not move. Can be delivered.

When the measurement is performed, the drive unit 12, that is, the output shaft 4 is driven by the drive unit 40 while the rotor attached to the lower end of the driven-side rotary shaft 60 is immersed in the fluid to be measured.
0a, the drive side rotation shaft 52 is rotated via the drive shaft assembly 42. The torsion wire 16 whose upper end is fixed to the drive unit 12 and whose lower end is fixed to the driven-side rotary shaft 60 is twisted by the viscosity of the fluid to be measured. This torsion angle is a phase difference between the upper disk body 48 and the lower disk body 66,
This phase difference is detected as an output difference between the photo sensors 70 and 72. The viscosity of the fluid to be measured can be obtained by converting the torsion angle into a viscosity.

In this embodiment, since the magnetic bearings 80 and 90 are used, the driven-side rotary shaft 60 can be supported without friction while having a strong restoring force from eccentricity. In addition, since the magnetic bearings 80 and 90 are adjusted so as to generate an axial repulsive force such that the driven rotary shaft 60 projects downward in the axial direction, a liquid having, for example, the Weissenberg effect (normal stress effect) is removed. To cancel the levitation force acting on the rotor and prevent buckling of the torsion wire 16 when measuring or when measuring while pushing the rotor against a liquid having high viscosity or high plasticity. Can be. Since the axial repulsion by magnetism can be set sufficiently larger than the levitation force, there is no need to add further weight.

Next, FIG. 5 is a diagram showing a second embodiment of the present invention. In the drawing, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, only the lower magnetic bearing 90 is provided, instead of the two magnetic bearings of the upper magnetic bearing 80 and the lower magnetic bearing 90 as in the first embodiment. The difference from the first embodiment is that a slide bearing 100 is provided at the upper end of the shaft 60. Driven rotary shaft 6
The position of the sliding bearing 100 fixed to the upper end of the torsion wire 16 is such that the bearing portion 100a that receives the torsion wire 16 is located a predetermined distance below the fixing portion 58 that fixes the upper end of the torsion wire 16. Is set. The predetermined distance is set so that the torsion wire 16 is not bent and deformed so that the sliding bearing 100 does not push and bend the torsion wire 16 when the driven rotation shaft 60 moves in the radial direction due to an impact during transportation or the like. It is preferable that the distance is set within the elastic limit and does not cause permanent deformation. Also,
The lower bearing 90 is closer to the wire chuck 62, which is a connection point of the torsion wire 16 to the driven-side rotating shaft 60, than the sliding bearing 100.

According to this embodiment, as compared with the case where only the magnetic bearings are used, the magnets constituting the magnetic bearings are not uniform in the circumferential direction and the portions where the attraction force is weak are separated from each other. When eccentricity occurs, the moment of tilting the driven-side rotary shaft 60 may increase at a position far from the connection point. However, by providing the sliding bearing 100 at a position away from the connection point, such a large moment Can be suppressed.

The magnetic bearing 90 is similar to the first embodiment.
By adjusting the position of the outer permanent magnet 92 and the inner permanent magnet 94 so as to generate an axially downward repulsive force, the floating force acting on the driven-side rotary shaft 60 is suppressed without adding a weight. be able to.

As described above, even when the sliding bearing 100 is provided in addition to the magnetic bearing 90, the friction can be made much smaller than that of the conventional viscometer, and the magnetic bearings 80 and 90 can be arranged vertically. The measurement accuracy (reproducibility) can be made comparable to the case of the first embodiment provided with. In addition, since only one magnetic bearing is required, the operation of adjusting the shifting direction and the amount of the inner permanent magnet and the outer permanent magnet is simplified. Further, the structure is simplified, and the device can be manufactured at low cost.

[0038]

As described above, according to the present invention, the magnetic repulsive force in the radial direction of the magnetic bearing is used, so that the driven rotary shaft can be supported without friction. , And can be configured at low cost.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a lower disk body 66 of FIG.

FIG. 3 is a configuration example of the magnetic bearing of FIG. 1;

FIG. 4 is another configuration example of a magnetic bearing.

FIG. 5 is a longitudinal sectional view of a rotational viscometer according to a second embodiment of the present invention.

6A is an enlarged cross-sectional view of a fixing portion of a torsion wire, FIG. 6B is a diagram viewed from the direction of arrow (a) in FIG.
(C) is a perspective view showing the torsion wire fixing method.

[Explanation of symbols]

 Reference Signs List 16 torsion wire (torsion elastic member) 40 drive device 52 drive-side rotating shaft 60 driven-side rotating shaft 70, 72 photosensor (detection unit) 80 upper magnetic bearing 90 lower magnetic bearing 82, 92 outer permanent magnet (drive-side magnet) 84, 94 Inner permanent magnet (driven side magnet) 100 Sliding bearing

Claims (6)

[Claims] A driving-side rotating shaft that is rotated by a driving device, a driven-side rotating shaft that is coaxially connected to the driving-side rotating shaft by a torsional elastic member, and that receives torque from a fluid to be measured; A detector for detecting a torsion angle;
A rotational viscometer for detecting the viscosity of the fluid to be measured from the torsion angle, wherein the driven-side rotating shaft is supported by at least one magnetic bearing, and the magnetic bearing is fixed to the driven-side rotating shaft. When,
An opposing magnet opposing the driven magnet, and the driven magnet and the opposing magnet are always arranged coaxially at an appropriate interval so as to always generate a magnetic repulsive force in the radial direction. Characteristic rotational viscometer. 2. The rotational viscometer according to claim 1, wherein the opposed magnet is a driving magnet fixed to a driving rotating shaft. 3. The rotational viscometer according to claim 1, wherein axial positions of the driven magnet and the opposing magnet of the magnetic bearing are shifted by a predetermined amount in advance. 4. An axial magnetic repulsive force such that an axial position of the driven magnet and the opposed magnet is relatively close to the driven rotating shaft in a direction of the fluid to be measured. The rotational viscometer according to claim 3, wherein the rotational viscometer is set. 5. The rotational viscosity according to claim 1, wherein a sliding bearing having a torsion elastic member as a shaft is further provided between the torsion elastic member and the driven magnet. Total. 6. The rotational viscometer according to claim 5, wherein the magnetic bearing is provided closer to a connection point of the torsional elastic member of the driven rotary shaft than the slide bearing.