JP3937220B2 - Coriolis mass flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Coriolis mass flowmeter having a vibration detection sensor capable of detecting stable steady vibration without being affected by thermal deformation in a vibration tube.
[0002]
[Prior art]
FIG. 18 is a diagram illustrating a configuration of a conventional example that is generally used conventionally, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-108723 (see, for example, Patent Document 1).
[0003]
11, a straight line connecting the upstream fixed end portion 12 and the downstream fixed end portion 13 is used as a reference axis 14, and a single vibration or circular motion is performed on a circumferential line of a predetermined distance from each point of the reference axis 14, respectively. It is a vibrating tube having a shape with a gentle curve.
[0004]
Reference numeral 15 denotes an exciter provided at the center of the vibration tube 11.
In this case, it consists of a coil and a magnet.
Reference numerals 16 and 17 denote vibration detection sensors provided on both sides of the vibration tube 11, respectively.
Also in this case, it consists of a coil and a magnet.
[0005]
19 is a cross-sectional view taken along the line bb of the vibration tube 11 of FIG. 18, FIG. 20 is a cross-sectional view of the vibration tube 11 of FIG. 18, taken along lines aa and cc, and FIG. It is a perspective view which shows the mode.
19 and 20, the vibration tube 11 is in the vicinity of the position A when in the non-excited state.
[0006]
When in the excited state, the center of the vibration tube 11 moves on a circumference away from the reference axis 14 by a radius R (x).
At the position of the cross section bb, on the circumference away from the reference axis 14 by the radius R (b), at the position of the cross section aa or cc, the radius R (a) or R (c) from the reference axis 14 is obtained. It vibrates in the order of A->B->A->C->A->B-> (repetition) on a remote circle.
[0007]
In FIG. 21, A, B, and C correspond to the respective positions of the vibration tube 11 in FIGS. 19 and 20. Reference numerals 12 and 13 denote fixed end portions, and reference numeral 14 denotes a reference axis.
[0008]
Since the vibration tube 11 vibrates only within a circumferential surface that is equidistant from the reference axis 14, the length of the vibration tube 11 does not change regardless of the position of the vibration tube 11.
[0009]
[Patent Document 1]
JP-A-11-108723 (page 3-4, Fig. 1-4)
[0010]
[Problems to be solved by the invention]
However, in such a device, it is a problem that occurs in most Coriolis flowmeters. In particular, as in the conventional example of FIG. 18, the vibration tube 11 is a single tube having no branching portion, and the shape thereof has a large curved portion. The problem is likely to increase in the case of semi-straight tubes that are similar to straight lines.
[0011]
If slight deformation occurs in the tube axis direction (X direction) due to expansion / contraction due to welding during manufacturing or thermal expansion due to a temperature difference with the housing 6, as shown in FIG. 22, the bending direction (Z Direction).
[0012]
Depending on the shape of the vibration tube 11 and the like, the deformation in the Z direction is several times greater than the deformation in the X direction, so the positional deformation near the exciter may be several mm.
When the magnet (or coil) fixed to the vibration tube 11 is moved, the paired coil (or magnet) is fixed to an immobile location such as the housing 6, so that a positional shift occurs between them.
[0013]
In the structure of an exciter or detector in which a magnet is arranged inside a cylindrical coil, if a positional deviation occurs, they immediately come into contact with each other, so that stable vibration cannot be achieved, and damage is caused in a severe case.
[0014]
An object of the present invention is to solve the above-described problems, and provides a Coriolis mass flowmeter having a vibration detection sensor capable of detecting stable steady vibration without being affected by thermal deformation of the vibration tube. There is to do.
[0015]
[Means for Solving the Problems]
In order to achieve such an object, in the present invention, in the Coriolis mass flow meter of claim 1,
In a Coriolis mass flowmeter in which the measurement fluid flows in the vibration tube and the vibration tube is deformed and vibrated by the Coriolis force generated by the flow of the measurement fluid and the angular vibration of the vibration tube,
The upstream fixed end and the downstream fixed end and the downstream fixed end with a curved shape having three inflection points centered on the midpoint of the upstream fixed end and the downstream fixed end. A vibration tube that performs simple vibration on a circumferential line at a predetermined distance from each point of the reference axis with a straight line connecting the fixed end as a reference axis, and ends of the upstream fixed end and the downstream fixed end And a vibration detection sensor provided across the vibration tube on a plane equidistant from the surface.
[0016]
In the Coriolis mass flow meter according to claim 2 of the present invention, in the Coriolis mass flow meter according to claim 1,
As the vibration detection sensor, a vibration detection sensor that is arranged on a straight line that is perpendicular to the vibration tube plane including the curve of the vibration tube and includes the midpoint, and has sensitivity only in a direction perpendicular to the vibration tube plane, and the vibration And a vibration detection sensor having sensitivity only in a direction parallel to the tube plane and perpendicular to the reference axis.
[0017]
In the Coriolis mass flow meter according to claim 3 of the present invention, in the Coriolis mass flow meter according to claim 1,
The vibration detection sensor is arranged on a straight line that is perpendicular to the vibration tube plane including the curve of the vibration tube and includes the midpoint, and has high sensitivity in a direction perpendicular to the vibration tube plane and the vibration tube plane. And a vibration detection sensor having a slight sensitivity in a direction perpendicular to the reference axis and having a large ratio of the Coriolis vibration amplitude to the excitation vibration amplitude.
[0018]
In the Coriolis mass flow meter according to claim 4 of the present invention, in the Coriolis mass flow meter according to claim 1,
As the vibration detection sensor, a vibration detection sensor arranged symmetrically with respect to the middle point and having sensitivity only in a direction perpendicular to the plane of the vibration tube and having a large ratio of Coriolis vibration amplitude to excitation vibration amplitude. It is characterized by comprising.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory view of a main part configuration of one embodiment of the present invention, FIG. 2 is a sectional view taken along the line aa of FIG. 1, and FIGS. 3 to 9 are operation explanatory views of FIG.
[0020]
As shown in FIG. 1, the vibration tube 20 is point-symmetric about the midpoint 25 of the upstream fixed end 12 and the downstream fixed end 13 and has an S-shape having three inflection points. It has an S-shaped curve shape with a simple curve.
[0021]
Then, while maintaining a point-symmetric curved shape, a straight line connecting the upstream fixed end portion 12 and the downstream fixed end portion 13 is set as a reference axis 14 at a predetermined distance from each point of the reference axis 14 as will be described later. Makes a simple vibration on the circumference.
[0022]
As will be described later, the vibration tube 20 vibrates by changing its position in the order of A → B → A → C → A → B → in FIG.
In order to continue such vibration, the exciter 15 as shown in the conventional example of FIG. 18 is necessary, but since it is not directly related to the present invention, the description and illustration are omitted for the sake of clarity.
[0023]
A vibration detection sensor 21 is provided with a vibration tube 20 sandwiched on a plane (hereinafter referred to as an intermediate surface) that is equidistant from the ends of the upstream fixed end 12 and the downstream fixed end 13. It consists of a detection sensor 23 and a vibration detection sensor 24.
[0024]
FIG. 2 shows the positional relationship on the inner surface.
The vibration detection sensor 23 and the vibration detection sensor 24 are installed on both sides of the vibration tube 20 and measure the vibration state of the vibration tube 20.
[0025]
In this case, the coils 231 and 241 and the magnets 232 and 242 are configured, and one of the coils 231 and 241 and the magnets 232 and 242 is fixed to the vibration tube 20 and the other is fixed to the housing 6.
In this case, the magnets 232 and 242 are fixed to the housing 6. The vibration detection sensors 23 and 24 are arranged so as to measure the Y-direction vibration in the figure.
[0026]
Now, when the rotational vibration component due to excitation is expressed as Ve and the Y direction component due to Coriolis force is expressed as Vc, the excitation components Ve are opposite to each other in the vibration detection sensor 23 and the vibration detection sensor 24 as shown in the figure. I understand.
[0027]
In normal signal processing, the mass flow rate is calculated by obtaining the phase difference δ between the two signal outputs.
Sensor 23 output Esinωt + Ccosωt = √ (E ² + C ² ) ・ Sin (ωt + δ)
Sensor 24 output Esinωt−Ccosωt = √ (E ² + C ² ) ・ Sin (ωt−δ)
tanδ = C / E
[0028]
FIG. 3 shows the operation status of the entire vibration system. Due to the excitation vibration of the vibration tube 20, vibration as shown by Ve in the figure is caused.
Further, the generated Coriolis force causes a vibration such as Vc in the figure. The Y component of those vibrations is measured by the two vibration detection sensors 23 and 24.
[0029]
By the way, when the measurement fluid flows in the vibration tube 20, a Coriolis force is generated according to the mass flow rate and the angular acceleration.
In the present invention, the Coriolis force vector β as shown in FIG. 6 is generated by the excitation deformation α of the vibration tube 20 as shown in FIG. 5, and the deformation of the tube as shown in FIGS. γ is generated.
[0030]
Excitation deformation and deformation due to Coriolis force are shown on the same scale, but in reality, the deformation caused by Coriolis force is very small. (Several hundred to several thousandths of excitation amplitude)
[0031]
When the Coriolis flowmeter is operating, the Coriolis vibration of FIG. 8 or FIG. 7 is superimposed on the excitation vibration of FIG. 4 or FIG.
A YZ cross section at the midpoint 25 is shown in FIG. A hatched tube 20 is hatched, and a total of 10 measurement points from measurement point A to measurement point J are arranged around it.
[0032]
Not all of these measurement points are provided in an actual flow meter, but are assumed to be virtually installed for the purpose of explaining the principle of the present invention, and it is assumed that the vibration tube 20 and each measurement point are firmly connected. is doing.
[0033]
The bold solid line arrows in the figure are vectors representing the rotational vibration speed due to excitation, and the size is proportional to the distance from the center, as can be seen from the vector lengths of the measurement points B and C.
The dotted line arrows in the figure are vectors indicating the Y-direction vibration velocity due to the Coriolis force, and are uniformly in the same direction and the same size everywhere on the cross section.
[0034]
At measurement points A and F, Coriolis vibration and excitation vibration are in the same Y direction, but at measurement points B, C, G, and H, the direction of excitation vibration is inclined in the Z direction.
Comparing the measurement points B and C, it can be seen that since the excitation component of C is large, in order to efficiently measure the Coriolis component, it is advantageous to measure the Y direction vibration at the point B close to the reference axis.
[0035]
Further, at the measurement points D and I, the excitation vibration is in the Z direction, which is different from the Y direction of the Coriolis vibration by a 90 ° direction and is easy to distinguish.
For example, if a sensor having sensitivity only in the Y direction is installed at the measurement point D, only Coriolis vibration can be detected, and if a sensor having sensitivity only in the Z direction is installed, only excitation vibration can be detected.
[0036]
In the above configuration, as shown in FIG. 4, the vibrating tube 20 vibrates by changing its position in the order of A → B → A → C → A → B →.
[0037]
As a result, in a normal detector using a coil and a magnet, one side is installed in the vibration tube 20 and the other side is installed in a fixed place such as the housing 6. They will not be able to provide stable excitation due to slippage, and in the worst case they will touch and break.
[0038]
Even if the length or shape of the vibration tube 20 changes due to distortion during manufacture, thermal expansion during use, or the like, the center point 25 that is the center of point symmetry of the shape of the vibration tube 20 does not move. .
[0039]
In the present invention, since the vibration detection sensors 23 and 24 are installed on or near the midpoint 25, the absolute position of the vibration detection sensors 23 and 24 does not change or is small even if the position is moved. The positional relationship does not change or the change is small.
[0040]
Since there is no or little displacement, it is strong against thermal expansion, can ensure stable steady vibration, and can detect vibration with high stability and high accuracy.
That is, a Coriolis mass flowmeter that has a wide operating temperature range, is highly stable with respect to temperature changes, and is capable of measuring the flow rate and density can be obtained.
[0041]
FIG. 10 is an explanatory diagram of the main part configuration of another embodiment of the present invention, and FIG. 11 is an operation explanatory diagram of FIG.
In this embodiment, the vibration detection sensor 31 is disposed on a straight line 202 that is perpendicular to the vibration tube plane 201 including the curve of the vibration tube 20 and includes the midpoint 25.
[0042]
The vibration detection sensor 31 includes a vibration detection sensor 34 having sensitivity only in a direction perpendicular to the vibration tube plane 201 and a vibration detection sensor 33 having sensitivity only in a direction parallel to the vibration tube plane 201 and perpendicular to the reference axis 14. Have.
[0043]
That is, the vibration detection sensor 33 has a structure that detects only the Z-direction vibration, and does not react to the Y-direction vibration Vc caused by the Coriolis force, but measures only the rotational vibration Ve caused by the excitation.
[0044]
On the other hand, the vibration detection sensor 34 has a structure for detecting only the Y-direction vibration, does not react to the rotational vibration Ve due to excitation, and measures only the Y-direction vibration Vc due to Coriolis force. The outputs of the vibration detection sensor 33 and the vibration detection sensor 34 immediately become an excitation component and a Coriolis component.
[0045]
Output of vibration detection sensor 33 Esinωt
Output of vibration detection sensor 34 Ccosωt
Here, the Coriolis component amplitude is a value proportional to the mass flow rate.
In addition, because of self-excitation at the resonance frequency, it is necessary to simultaneously measure the amplitude and frequency of the excitation component for density measurement and correction.
[0046]
As a result, it is possible to obtain an output of the excitation vibration component 100% and an output of the Coriolis vibration component 100% as the outputs of the vibration detection sensors 33 and 34.
Since these outputs can be obtained easily, a complicated signal processing circuit is not required, and a simple and inexpensive Coriolis mass flowmeter can be obtained.
[0047]
FIG. 12 is a diagram illustrating the configuration of the main part of another embodiment of the present invention, and FIG. 13 is a diagram illustrating the operation of FIG.
[0048]
In the present embodiment, the vibration detection sensor 41 is arranged on a straight line that is perpendicular to the vibration tube plane 201 including the curve of the vibration tube 20 and includes the midpoint 25, and has high sensitivity in a direction perpendicular to the vibration tube plane 201. The vibration detection sensors 43, 44 are parallel to the vibration tube plane 201 and have a slight sensitivity in the direction perpendicular to the reference axis 14 so that the ratio of the Coriolis vibration amplitude to the excitation vibration amplitude is large. Have
[0049]
That is, the vibration detection sensors 43 and 44 are installed on the straight line including the midpoint 25 perpendicular to the vibration tube plane 201 including the curve of the vibration tube 20 and sandwiching the vibration tube 20.
[0050]
In that place, the rotational vibration Ve due to the excitation force is directed in the Z direction, and the translational vibration due to the Coriolis force is directed in the Y direction.
The vibration detection sensor 43 and the vibration detection sensor 44 have high Y-direction vibration detection sensitivity and low detection sensitivity, but have characteristics capable of detecting Z-direction vibration.
[0051]
For example, such characteristics can be realized by bending the directions of the magnets 432 and 442 and the coils 431 and 441 slightly from the Y axis in the Z direction as shown in FIG.
By using a sensor having such characteristics, the Coriolis vibration Vc in the Y direction can be detected with high sensitivity, and the excitation vibration Ve in the Z direction can be measured with low sensitivity.
[0052]
In the first place, the excitation vibration is very large, several hundred to several thousand times more than the Coriolis vibration.
Decreasing the sensitivity and increasing the ratio of the Coriolis vibration component to the excitation vibration also increases the phase difference between the outputs of both sensors, making subsequent signal processing easier.
[0053]
As a result, the Coriolis component can be detected with high sensitivity, and the excitation component detection sensitivity deteriorates.
The Coriolis component is as small as one hundred to several thousandth of the excitation component even when a full-scale flow rate flows.
[0054]
Although it is difficult to separate and detect a small amount of Coriolis component superimposed on excitation vibration, if a sensor with the above characteristics is used, the size of both components can be made closer by suppressing the excitation component without changing the Coriolis component. This makes it possible to separate and detect Coriolis components.
[0055]
Considering the phase difference between the outputs of the two vibration detection sensors 43 and 44, it is usually necessary to measure a very small phase difference of about several μrad, but if this is a measurement of several tens μrad to several mrad, Signal processing is considerably easier.
As shown in the embodiment of FIG. 10, it is one method to completely separate both components only by the sensor, but adjustment becomes difficult.
[0056]
As in the present invention, the method of performing signal separation processing with a converter using a sensor output that contains both components in a moderate manner is easy to adjust, and it is easy to realize a highly accurate and highly stable Coriolis mass flow meter. There are benefits.
[0057]
Further, by changing the detection direction sensitivity of the sensor, the ratio between the Coriolis component and the excitation component (phase difference between the two sensor outputs) can be freely set.
A Coriolis mass flowmeter that can have a free component ratio (phase difference) can be obtained in accordance with the convenience of the converter.
[0058]
FIG. 14 is a diagram illustrating the configuration of the main part of another embodiment of the present invention, and FIG. 15 is a diagram illustrating the operation of FIG.
In the present embodiment, the vibration detection sensor 51 has a sensitivity only in the direction perpendicular to the vibration tube plane and is symmetrical with respect to the middle point so that the ratio of the Coriolis vibration amplitude to the excitation vibration amplitude is large. Vibration detection sensors 53 and 54 are provided.
[0059]
That is, as shown in FIG. 14, the two vibration detection sensors 53 and 54 installed in the Y direction have sensitivity only in the Y direction.
Both sensors 53 and 54 exist on the inner surface, and sandwich the vibrating tube 20 within a range of about 45 ° or less (excluding 0 °) around the 14 reference axis (X axis) from the XY plane in the figure. is set up.
[0060]
In such a place, the rotational vibration Ve due to the excitation force is slightly shifted from the Z direction in the Y direction, and the translational vibration due to the Coriolis force is directed in the Y direction.
By using the sensors 53 and 54 having such characteristics and arrangement, the Coriolis vibration Vc of the Y direction vibration is detected with high sensitivity. However, since the Y direction component of the excitation vibration Ve is small, it can be measured but the sensitivity is low.
[0061]
The excitation vibration is very large, several hundred to several thousand times more than the Coriolis vibration.
When the sensitivity is lowered and the ratio between the two is made closer, the phase difference between the outputs of both sensors becomes larger, and the subsequent signal processing is easier.
[0062]
As a result, in the embodiment of FIG. 12, the Coriolis component can be detected with high sensitivity, and the excitation component detection sensitivity becomes poor.
The Coriolis component is as small as one hundred to several thousandth of the excitation component even when a full-scale flow rate flows.
[0063]
Although it is difficult to separate and detect the slight Coriolis component superimposed on the excitation vibration, if the vibration detection sensors 53 and 54 having the above-described characteristics are used, the Coriolis component is kept as it is, and both of them are suppressed. A Coriolis mass flowmeter can be obtained which can be close in size and facilitates the separation and detection of Coriolis components.
[0064]
Considering the phase difference between the outputs of the two sensors 53 and 54, it is usually necessary to measure a very small phase difference of about several μrad, but if this is a measurement of several tens μrad to several mrad, a considerable signal is required. Processing becomes easy.
[0065]
As in the embodiment of FIG. 10, it is one method to completely separate both components only by the sensors 33 and 34, but adjustment is difficult.
As in the present invention, the method of using the outputs of the vibration detection sensors 53 and 54 appropriately containing both components and then performing signal separation processing with a converter is easy to adjust, and has a high accuracy and high stability. It is easy to realize.
[0066]
Further, the ratio of the Coriolis component to the excitation component (the two vibration detection sensors 53, 54) can be changed by changing the installation position of the vibration detection sensors 53, 54 (in an angle range greater than 0 ° and less than 45 ° around the reference axis 14). Can be set freely.
Therefore, a Coriolis mass flowmeter that can have a free component ratio (phase difference) according to the convenience of the converter is obtained.
[0067]
FIG. 16 is a diagram illustrating the configuration of the main part of another embodiment of the present invention, and FIG. 17 is a diagram illustrating the operation of FIG.
In this embodiment, the vibrating tube is not a single pipe type but a two parallel pipes 18 and 19 type.
[0068]
The two vibration tubes 18 and 19 vibrate in symmetrical directions, and the vibration detection sensor 61 includes vibration detection sensors 63 and 64 that measure relative vibrations between the two vibration tubes 18 and 19.
[0069]
In the above-described embodiment, the vibration detection sensors 21, 31, 41, 51, and 61 are described as being configured by coils and magnets. However, the present invention is not limited to this, and examples thereof include a light (laser) reflection method, An eddy current detection method, an acceleration measurement method, or the like may be used. In short, any method capable of measuring vibrations of the vibration tubes 18, 19, and 20 is acceptable.
[0070]
Also, the arrangement of the two vibration detection sensors across the vibration tube does not necessarily mean that the two vibration detection sensors 23, 24, 63, 64 are symmetric with respect to the vibration tubes 18, 19, 20. Absent.
For example, in FIG. 9, the positional relationship may be such that there are vibration detection sensors at the measurement points B and E on both sides of the vibration tube.
[0071]
The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.
[0072]
【The invention's effect】
As described above, according to the first aspect of the present invention, the following effects can be obtained.
In a normal detector using a coil and a magnet, one side is installed in the vibration tube 20 and the other side is installed in a fixed place such as a housing. Therefore, if the position of the vibration tube is shifted, the positional relationship between the coil and the magnet is shifted and stable. Not only can it not be excited, but in the worst case it will touch and break.
[0073]
Even if the length or shape of the vibrating tube changes due to distortion during manufacturing or thermal expansion during use, the location of the midpoint, which is the center of point symmetry of the vibrating tube shape, does not move.
[0074]
In the present invention, since the vibration detection sensor is installed on or near the midpoint, the absolute position of the vibration detection sensor does not change, or even if the position is moved, the relative positional relationship between the coil and the magnet does not change, or The change is small.
[0075]
Since there is no or little displacement, it is strong against thermal expansion, can ensure stable steady vibration, and can detect vibration with high stability and high accuracy.
That is, a Coriolis mass flowmeter that has a wide operating temperature range, is highly stable with respect to temperature changes, and is capable of measuring the flow rate and density can be obtained.
[0076]
According to claim 2 of the present invention, there are the following effects.
As an output of the vibration detection sensor, an output of an excitation vibration component 100% and an output of a Coriolis vibration component 100% can be obtained.
Since these outputs can be obtained easily, a complicated signal processing circuit is not required, and a simple and inexpensive Coriolis mass flowmeter can be obtained.
[0077]
According to claim 3 of the present invention, there are the following effects.
The Coriolis component can be detected with high sensitivity, and the excitation component detection sensitivity deteriorates.
The Coriolis component is as small as one hundred to several thousandth of the excitation component even when a full-scale flow rate flows.
[0078]
Although it is difficult to separate and detect a small amount of Coriolis component superimposed on excitation vibration, if a sensor with the above characteristics is used, the size of both components can be made closer by suppressing the excitation component without changing the Coriolis component. This makes it possible to separate and detect Coriolis components.
[0079]
Considering the phase difference between the outputs of the two vibration detection sensors, it is usually necessary to measure a very small phase difference of about several μrad, but if this is a measurement of several tens of μrad to several mrad, signal processing will be considerable. Becomes easier.
Although it is one method to completely separate both components only by the sensor as in claim 2, adjustment is difficult.
[0080]
As in the present invention, the method of performing signal separation processing with a converter using a sensor output that contains both components in a moderate manner is easy to adjust, and it is easy to realize a highly accurate and highly stable Coriolis mass flow meter. There is a merit.
[0081]
Further, by changing the detection direction sensitivity of the sensor, the ratio between the Coriolis component and the excitation component (phase difference between the two sensor outputs) can be freely set.
A Coriolis mass flowmeter that can have a free component ratio (phase difference) can be obtained in accordance with the convenience of the converter.
[0082]
According to claim 4 of the present invention, there are the following effects.
In claim 3, the Coriolis component can be detected with high sensitivity, and the excitation component detection sensitivity is deteriorated.
The Coriolis component is as small as one hundred to several thousandth of the excitation component even when a full-scale flow rate flows.
[0083]
Although it is difficult to separate and detect the slight Coriolis component superimposed on the excitation vibration, if the vibration detection sensor having the above characteristics is used, the magnitude of both can be reduced by suppressing the excitation component without changing the Coriolis component. It is possible to obtain a Coriolis mass flowmeter that can be close to each other and facilitates the separation and detection of Coriolis components.
[0084]
Considering the phase difference between the outputs of the two sensors, it is usually necessary to measure a very small phase difference of about several μrad, but if this is a measurement of several tens of μrad to several mrad, the signal processing is considerably easier. Become.
[0085]
Although it is one method to completely separate both components only by the sensor as in claim 2, adjustment is difficult.
As in the present invention, the method of using the output of the vibration detection sensor that appropriately contains both components and then performing signal separation processing with a converter realizes a highly accurate and highly stable flowmeter that is easy to adjust. There is a merit that is easy.
[0086]
In addition, by changing the installation position of the vibration detection sensor (in the angle range greater than 0 ° and less than 45 ° around the reference axis 14), the ratio between the Coriolis component and the excitation component (the phase difference between the outputs of the two vibration detection sensors) Can be set freely.
Therefore, a Coriolis mass flowmeter that can have a free component ratio (phase difference) according to the convenience of the converter is obtained.
[0087]
Therefore, according to the present invention, it is possible to realize a Coriolis mass flowmeter having a vibration detection sensor that can detect stable steady vibration without being affected by thermal deformation of the vibration tube.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line aa in FIG.
FIG. 3 is an operation explanatory diagram of FIG. 1;
4 is an operation explanatory diagram of FIG. 1. FIG.
FIG. 5 is an operation explanatory diagram of FIG. 1;
6 is an operation explanatory diagram of FIG. 1. FIG.
7 is an operation explanatory diagram of FIG. 1; FIG.
8 is an operation explanatory diagram of FIG. 1. FIG.
FIG. 9 is an operation explanatory diagram of FIG. 1;
FIG. 10 is an explanatory diagram of a main part configuration of another embodiment of the present invention.
11 is an operation explanatory diagram of FIG. 10;
FIG. 12 is an explanatory diagram of a main part configuration of another embodiment of the present invention.
13 is an operation explanatory diagram of FIG. 12. FIG.
FIG. 14 is an explanatory diagram of a main part configuration of another embodiment of the present invention.
15 is an operation explanatory diagram of FIG. 14. FIG.
FIG. 16 is an explanatory diagram of a main part configuration of another embodiment of the present invention.
FIG. 17 is an operation explanatory diagram of FIG. 14;
FIG. 18 is an explanatory diagram of a main part configuration of a conventional example generally used conventionally.
FIG. 19 is an explanatory diagram of the operation of FIG. 18;
20 is an operation explanatory diagram of FIG. 18. FIG.
FIG. 21 is an operation explanatory diagram of FIG. 18;
22 is an operation explanatory diagram of FIG. 18;
[Explanation of symbols]
2 Flange
6 Housing
12 Upstream fixed end
13 Downstream fixed end
14 Reference axis
141 Reference axis
142 Reference axis
20 Vibrating tube
201 Vibration tube plane
202 straight line
21 Vibration detection sensor
23 Vibration detection sensor
231 Coil
232 Magnet
24 Vibration detection sensor
241 Coil
242 Magnet
25 Midpoint
31 Vibration detection sensor
33 Vibration detection sensor
331 Coil
332 magnet
34 Vibration detection sensor
341 Coil
342 Magnet
41 Vibration detection sensor
43 Vibration detection sensor
431 Coil
432 Magnet
44 Vibration detection sensor
441 Coil
442 Magnet
51 Vibration detection sensor
53 Vibration detection sensor
531 Coil
532 magnet
54 Vibration detection sensor
541 Coil
542 Magnet
61 Vibration detection sensor
63 Vibration detection sensor
631 Coil
632 Magnet
64 Vibration detection sensor
641 coil
642 Magnet

Claims (4)

In a Coriolis mass flowmeter in which the measurement fluid flows in the vibration tube and the vibration tube is deformed and vibrated by the Coriolis force generated by the flow of the measurement fluid and the angular vibration of the vibration tube,
The upstream fixed end and the downstream fixed end and the downstream fixed end with a curved shape having three inflection points centered on the midpoint of the upstream fixed end and the downstream fixed end. A vibration tube that makes a single vibration on a circumferential line at a predetermined distance from each point of the reference axis using a straight line connecting the fixed end as a reference axis,
A Coriolis mass flowmeter comprising: a vibration detection sensor provided across the vibration tube on a plane equidistant from the upstream fixed end and the end of the downstream fixed end. . As the vibration detection sensor,
A vibration detection sensor that is arranged on a straight line that is perpendicular to the vibration tube plane that includes the curve of the vibration tube and that includes the midpoint, and that has sensitivity only in a direction perpendicular to the vibration tube plane, and in parallel with the vibration tube plane, The Coriolis mass flowmeter according to claim 1, further comprising a vibration detection sensor having sensitivity only in a direction perpendicular to the reference axis. As the vibration detection sensor,
The reference axis is parallel to the vibration tube plane and has a high sensitivity in a direction perpendicular to the vibration tube plane which is perpendicular to the vibration tube plane including the curve of the vibration tube and includes the midpoint. 2. A Coriolis mass flowmeter according to claim 1, further comprising a vibration detection sensor having a slight sensitivity in a direction perpendicular to the first axis and having a large ratio of the Coriolis vibration amplitude to the excitation vibration amplitude. As the vibration detection sensor,
A vibration detection sensor is provided that is arranged symmetrically with respect to the center point and is sensitive only in a direction perpendicular to the plane of the vibration tube and has a large ratio of Coriolis vibration amplitude to excitation vibration amplitude. The Coriolis mass flowmeter according to claim 1.

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