JP2004294090A - Vibration measuring device - Google Patents

Abstract

An object of the present invention is to provide a configuration in which a sensor tube is inserted into a storage case filled with a fluid to be measured and measurement is performed, and a magnet attached to the sensor tube does not contact the fluid to be measured.
A driving magnet and a detecting magnet are attached to a sensor tube of a mass flow meter. The magnet 16a includes a permanent magnet 70 made of a magnetic material and a cover member 72 that covers the entire surface of the permanent magnet 70. The cover member 72 is made of, for example, a strong metal material such as austenitic stainless steel that can prevent high-pressure hydrogen from penetrating between metal molecules. By covering the entire surface of the permanent magnet 70 with the cover member 72 on the outer periphery of the sensor tube 14, the permanent magnet 70 is prevented from coming into contact with the high-pressure hydrogen that is the fluid to be measured, and the magnetic force is not reduced or destroyed. .
[Selection] Fig. 6

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vibration-type measuring device, and more particularly to a vibration-type measuring device configured to vibrate a sensor tube, detect a displacement of the sensor tube due to Coriolis force, and measure a flow rate or a density.
[0002]
[Prior art]
As a vibration-type measuring device that measures a physical quantity of a fluid by vibrating a pipe to which a fluid is supplied, for example, there is a Coriolis-type mass flowmeter or a vibration-type density meter. Hereinafter, the Coriolis mass flowmeter will be described.
[0003]
In this Coriolis mass flowmeter, a sensor tube through which a fluid to be measured passes is vibrated in a radial direction by a vibrator, and a displacement of the sensor tube due to a Coriolis force proportional to the flow rate is detected by a pickup. The vibratory density meter also has the same configuration as the Coriolis mass flow meter, and the sensor tube vibrates at a frequency corresponding to the density of the fluid to be measured.
[0004]
As a conventional vibration-type measuring device, for example, in the case of a Coriolis-type mass flow meter, a direction in which a fluid flows through a pair of sensor tubes and the pair of sensor tubes is moved toward and away from each other by the driving force of a vibrator (drive coil). (For example, see Patent Document 1).
[0005]
The vibrator and the pickup are composed of a magnet and a coil, and are attached to the sensor tube when a drive pulse or a positive or negative alternating voltage (AC signal) is input to the drive coil of the vibrator. The sensor tube is vibrated by applying an attractive force or a repulsive force to the drive magnet, and the displacement of the detection magnet attached to the vibrating sensor tube is determined by a detection signal output from a sensor coil (detection unit) of the pickup. Is to be detected.
[0006]
Then, the Coriolis force acts in the vibration direction of the sensor tube and is opposite between the inlet side and the outlet side, so that the sensor tube is twisted, and the twist angle is proportional to the mass flow rate. Therefore, a pickup (vibration sensor) for detecting vibration is provided at each of the twisted positions on the inlet side and the outlet side of the pair of sensor tubes, and the time difference between the output detection signals of the two sensors is measured to determine the torsion of the sensor tube, that is, the mass. The flow rate is being measured.
[0007]
However, for example, when the mass flow meter is provided in a gas supply system that supplies compressible natural gas pressurized to a high pressure such as CNG (Compressed Natural Gas) used as a fuel for an automobile, and the flow rate is measured, It is necessary to increase the pressure resistance of the sensor tube.
[0008]
However, when the thickness of the sensor tube is increased, the driving force of the vibrator for vibrating the sensor tube must be increased, and the resonance amplitude at the time of measurement decreases as the rigidity of the sensor tube increases. Problems such as susceptibility to disturbance and a decrease in the phase difference (twist angle) between the inflow-side and outflow-side vibration sensors during flow rate measurement occur, thereby reducing measurement accuracy.
[0009]
Therefore, in the conventional vibration type measuring device, the pressure between the inside and the outside of the sensor tube is balanced by supplying the fluid to be measured into the storage case from the pressure supply hole of the sensor tube, and the pressure resistance of the sensor tube is increased. High pressure fluid can be measured without increasing the pressure.
[0010]
[Patent Document 1]
JP-A-6-331406
[0011]
[Problems to be solved by the invention]
In the conventional vibration-type measuring apparatus, when the measurement fluid is filled in the storage case as described above and the high-pressure fluid is measured, the vibrator and the pickup are stored in the storage case. When the fluid is a flammable fluid such as fuel, it is necessary to cover the drive coil of the vibrator and the sensor coil of the pickup with an explosion-proof case or the like so as not to come into contact with the fluid to be measured. It had to be configured.
[0012]
However, depending on the fluid to be measured, it may be necessary to affect the material or insulating coating of the magnet or coil of the vibrator, or it may be necessary to provide a through terminal in the storage case to allow the electric wiring to pass through to the inside.
[0013]
For example, rare earth materials are often used for magnets attached to sensor tubes, but rare earth metals are easily combined with hydrogen, and in a hydrogen atmosphere, the magnetic force may be reduced or destroyed. It was difficult to use in a place that comes into contact with the fluid measurement.
[0014]
Therefore, when a mass flowmeter is provided in a fuel supply path of a filling device that fills a fuel tank of a fuel cell vehicle with high-pressure hydrogen, a storage case for storing the sensor tube in order to reduce the pressure resistance of the sensor tube and improve measurement accuracy. If a configuration in which the fluid to be measured is filled is adopted, the magnet attached to the sensor tube may come into contact with hydrogen, and the magnet force of the magnet may be reduced or destroyed, so that the flow rate measurement may not be performed.
Therefore, an object of the present invention is to provide a vibration-type measuring device that solves the above problem.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following features.
According to the first aspect of the present invention, a cover member made of a non-magnetic material is provided to cover the surfaces of the driving magnet and the detecting magnet so as to isolate the surfaces from the fluid to be measured, and the magnet comes into direct contact with the fluid to be measured. This prevents the physical characteristics of the magnet from deteriorating, and also enables safe measurement even if the fluid to be measured is a flammable fluid.
[0016]
According to the second aspect of the present invention, the cover member is formed of an austenitic stainless steel material, and it is possible to prevent the cover member from being deteriorated even when the cover member comes into contact with the fluid to be measured. In particular, a non-magnetic stainless material is used so as not to impair the magnetic force of the magnet, and when the fluid to be measured is hydrogen, it is possible to configure so as not to disturb the strength and magnetic force pattern against hydrogen.
[0017]
According to the third aspect of the present invention, the gap between the magnet and the internal space of the cover member is filled with an incompressible fluid, so that the pressure resistance of the cover member can be further increased and deformation of the cover member can be reduced. Prevented from affecting the magnet.
[0018]
According to a fourth aspect of the present invention, the cover member has a first cover in which a storage recess having a shape corresponding to the shape of the magnet is formed, and a second cover in which the edge of the first cover is formed in the same shape. And a cover, and by joining the edge of the first cover and the edge of the second cover, the storage recess is prevented from being deformed at the time of joining, especially when heat is applied such as welding. The magnet stored in the storage recess is not directly affected by heat, so that the magnet is prevented from being deformed by the welding heat and the magnetic properties are not changed.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the vibration type measuring apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a Coriolis mass flow meter as one embodiment of a vibration type measuring device according to the present invention. FIG. 2 is a longitudinal sectional view taken along line AA in FIG. FIG. 3 is a longitudinal sectional view taken along line BB in FIG.
[0019]
In addition, the vibration-type measuring device can be used as a vibration-type density meter and a Coriolis-type mass flow meter because the density of the fluid to be measured and the mass flow rate can be obtained using the density. The vibratory density meter and the Coriolis mass flow meter have the same configuration, and therefore, in this embodiment, the case where they are used as a mass flow meter will be described in detail.
[0020]
As shown in FIGS. 1 to 3, the mass flow meter 10 vibrates one sensor tube 14 inserted into a sealed storage case 12 and an intermediate portion in the longitudinal direction of the sensor tube 14. The vibrator 16 includes an exciter 16, an inflow pickup 18 that detects displacement of the vibrating sensor tube 14 on the inflow side, and an outflow pickup 20 that detects displacement of the vibrating sensor tube 14 on the outflow side.
[0021]
The vibrator 16, the inflow-side pickup 18, and the outflow-side pickup 20 are arranged symmetrically with respect to the axis of the sensor tube 14, and the inflow-side pickup 18 and the outflow-side pickup 20 are symmetrical about the vibrator 16. Is provided.
[0022]
The storage case 12 is formed in a cylindrical shape, and the openings at both ends are closed by flanges 22 and 24 formed in a disk shape. The flanges 22 and 24 are integrally fixed to the end of the storage case 12 by welding or the like.
[0023]
Further, the storage case 12 has a pressure resistance so as to withstand the pressure even when the measured fluid is filled with the high pressure fluid such as CNG in the internal space 26.
[0024]
The sensor tube 14 is formed of a metal pipe formed in a straight tubular shape, and is fixed in a state where one end 14 a is inserted into a mounting hole 22 a penetrating the inflow side flange 22, and the other end 14 b penetrates the outflow side flange 24. Into the mounting hole 24a. A disk-shaped inflow-side support plate 28 is fitted and fixed to the outer periphery of one end 14 a of the sensor tube 14, and the outer periphery of the inflow-side support plate 28 is fitted into an annular recess 12 a formed at one end of the storage case 12. Fixed together.
[0025]
A disk-shaped outflow-side support plate 30 is fitted and fixed to the outer periphery of the other end 14 b of the sensor tube 14, and the outer periphery of the outflow-side support plate 30 is formed in an annular recess 12 b formed at the other end of the storage case 12. Is fitted and fixed. Further, a hook-shaped groove 24b is formed on the inner periphery of the mounting hole 24a.
[0026]
The outflow side support plate 30 is provided with a projection 32 to be inserted into the hook-shaped groove 24b, and a recess 30a formed inside the inner circumference of the storage case 12 so as to be continuous with the projection 32. ing. Therefore, the other end 14b of the sensor tube 14 is communicated with the internal space 26 via a passage 34 formed between the groove 24b and the projection 32 and between the recess 30a and the inner wall of the storage case 12.
[0027]
Therefore, the fluid to be measured that has flowed into the sensor tube 14 is supplied to the internal space 26 from the other end 14 b through the passage 34. Thereby, the internal pressure of the sensor tube 14 and the pressure of the internal space 26 are balanced, and the pressure difference between the inside and the outside of the sensor tube 14 is reduced.
[0028]
This eliminates the need for the sensor tube 14 to have a thickness corresponding to the pressure of the fluid to be measured. For example, even when measuring a gas supplied at a high pressure of 20 MPa or more, such as CNG, the thickness of the sensor tube 14 can be reduced. There is no need to increase the wall thickness to increase the pressure resistance, and it is not necessary to increase the driving force of the vibrator 15.
[0029]
Driving magnets 16a and 16b of the vibrator 16 are attached to the outer periphery of the intermediate portion of the sensor tube 14 at intervals of 180 degrees. Further, detection magnets 18a and 18b of the inflow-side pickup 18 are attached to the outer periphery of the sensor tube 14 on the inflow side from the vibrator 16 at an interval of 180 degrees. Further, detection magnets 20a and 20b of the outflow-side pickup 20 are attached to the outer periphery of the sensor tube 14 on the outflow side from the vibrator 16 at intervals of 180 degrees.
[0030]
The driving magnets 16a, 16b are heavier than the detecting magnets 18a, 18b, 20a, 20b, and also function as weights (inertial masses) during excitation.
[0031]
Further, on the outer periphery of the storage case 12, drive coils 16c and 16d facing the magnets 16a and 16b, sensor coils 18c and 18d facing the magnets 18a and 18b, and sensor coils 20c and 20d facing the magnets 20a and 20b are provided. And are attached. As described above, in the mass flow meter 10, since the drive coils 16 c and 16 d and the sensor coils 18 c, 18 d, 20 c and 20 d are provided on the outer periphery of the storage case 12, for example, CNG such as CNG is provided inside the storage case 12. Even if the fuel gas is filled with flammable gas, there is no possibility that the spark from the electric system will ignite, so that safety is ensured.
[0032]
The storage case 12 is formed of, for example, an austenitic non-magnetic stainless steel (SUS304). Further, iron cores 16e and 16f made of, for example, a ferrite-based magnetic material are inserted into the centers of the drive coils 16c and 16d.
[0033]
Therefore, even if the drive coils 16c and 16d are provided on the outer periphery of the storage case 12, the magnetic flux generated by the drive coils 16c and 16d passes through the storage case 12 and reaches the magnets 16a and 16b. Thus, the drive coils 16c and 16d can vibrate the magnets 16a and 16b from the outer periphery of the storage case 12 in the vibration direction (Y direction).
[0034]
The vibrator 16 includes the magnets 16a and 16b and the drive coils 16c and 16d. The vibrator 16 receives a magnetic field generated by alternately applying positive and negative alternating voltages (AC signals) to the drive coils 16c and 16d. When the magnets 16a and 16b are attracted or repelled, the middle portion of the sensor tube 14 is vibrated in the lateral direction (Y direction).
[0035]
The inflow-side pickup 18 is composed of the magnets 18a and 18b and sensor coils (detection units) 18c and 18d. As the magnets 18a and 18b vibrate along with the sensor tube 14 in the lateral direction (Y direction). In order to approach and separate from the sensor coils 18c and 18d, the sensor coils 18c and 18d output detection signals according to the displacement amounts (displacement speeds) of the magnets 18a and 18b.
[0036]
The outflow-side pickup 20 is composed of the magnets 20a and 20b and sensor coils (detection units) 20c and 20d. As the magnets 20a and 20b vibrate with the sensor tube 14 in the lateral direction (Y direction). In order to approach and separate from the sensor coils 20c and 20d, the sensor coils 20c and 20d output a detection signal corresponding to the amount of displacement (displacement speed) of the magnets 20a and 20b.
[0037]
In the mass flow meter 10, as described above, the internal space 26 of the storage case 12 is filled with the fluid to be measured, and the pressure difference between the inside and the outside of the sensor tube 14 is reduced, so that the thickness of the sensor tube 14 is reduced. Thus, the driving force of the vibrator 16 can be reduced, and the current flowing through the driving coils 16c and 16d of the vibrator 16 can be reduced to save power consumption.
[0038]
In addition, since the sensor tube 14 is made of a thin metal pipe, the deformation and displacement of the sensor tube 14 due to Coriolis force increases, so that an output larger than that of the pickup 16 can be obtained, so that the SN ratio can be improved and measurement can be performed. The accuracy is improved.
[0039]
The drive coils 16c and 16d of the vibrator 16 and the sensor coils 18c, 18d, 20c and 20d of the pickups 18 and 20 provided on the outer periphery of the storage case 12 are connected to the flow rate measurement control circuit 38 via cables 36a to 36f. Have been. The drive coils 16c, 16d, the sensor coils 18c, 18d, 20c, 20d and the cables 36a to 36f are not inserted into the storage case 12, so that the safety is enhanced.
[0040]
The flow rate measurement control circuit 38 includes an intrinsically safe explosion-proof barrier circuit, an excitation / time difference detection circuit, a Young's modulus / V / F conversion circuit, an output circuit, a power supply circuit, an attenuation rate detection circuit, a determination circuit, and a control circuit (each not shown). Etc.
[0041]
At the time of the flow rate measurement, in the mass flow meter 10 having the above configuration, the vibrator 16 is driven by the flow rate measurement control circuit 38, and the sensor tube 14 has a period and amplitude corresponding to the vibration characteristic (natural frequency) of the sensor tube 14. The intermediate portion is vibrated in the horizontal direction (Y direction).
[0042]
As described above, when the fluid flows through the vibrating sensor tube 14, a Coriolis force having a magnitude corresponding to the flow rate is generated. For this reason, an operation delay occurs between the inflow side and the outflow side of the straight tubular sensor tube 14, thereby causing a phase difference between the output signals of the inflow side pickup 18 and the outflow side pickup 20.
[0043]
Since the phase difference between the output signal on the inflow side and the output signal on the outflow side is proportional to the flow rate, the flow rate measurement control circuit 38 calculates the flow rate based on the phase difference. Therefore, when the displacement of the sensor tube 14 is detected by the inflow-side pickup 18 and the outflow-side pickup 20, the phase difference caused by the vibration of the sensor tube 14 is converted into a mass flow rate by the flow rate measurement control circuit 38.
[0044]
Here, the principle of measuring the flow rate of the fluid to be measured by vibrating the sensor tube 14 by the vibrator 15 will be described.
[0045]
FIG. 4 is a diagram schematically illustrating a state in which the vibrator 15 vibrates the sensor tube 14. FIG. 5 is a diagram schematically showing the Coriolis force acting on the vibrating sensor tube 14.
[0046]
As shown in FIG. 4, during the flow rate measurement, positive and negative alternating voltages (AC signals) are alternately output from the excitation circuit of the flow rate measurement control circuit 38 to the drive coils 16c and 16d of the vibrator 16. Accordingly, the intermediate portion of the sensor tube 14 vibrates in a resonance state.
[0047]
That is, in the vibrator 16, one drive coil 16c applies a repulsive force to the magnet 16a, and the other drive coil 16d applies an attractive force to the magnet 16b. Thus, the vibrator 16 generates a vibrating force Fa that presses the intermediate portion of the sensor tube 14 in the Y direction. As a result, the sensor tube 14 bends in an arc shape with the both ends 14a and 14b as nodes, as indicated by the dashed line in the middle part.
[0048]
In the vibrator 16, one drive coil 16c applies an attractive force to the magnet 16a, and the other drive coil 16d applies a repulsive force to the magnet 16b. As a result, the sensor tube 14 bends in an arc shape as shown by a broken line at the middle portion with the ends 14a and 14b as nodes.
[0049]
In this way, by alternately applying the forward and reverse voltages to the drive coils 16c and 16d, the sensor tube 14 vibrates at a constant cycle and amplitude. Then, a Coriolis force is generated when the measured fluid flows through the vibrating sensor tube 14.
[0050]
When on / off pulse signals having a phase difference of 180 degrees are applied to the drive coils 16c and 16d, no attractive force or repulsive force is generated when the drive coils 16c and 16d are off, but the same force due to the inertia of the vibration of the sensor tube 14. Make a move.
[0051]
As shown in FIG. 5, Coriolis forces + F and −F in opposite directions act on the inflow side and the outflow side of the sensor tube 14. As a result, the sensor tube 14 has a phase difference in vibration between the inflow side and the outflow side.
[0052]
That is, when the intermediate portion of the sensor tube 14 is driven as shown by the dashed line in FIG. 4, Coriolis force + F acts on the inflow side of the sensor tube 14 as shown by the dashed line in FIG. Coriolis force -F acts on the outflow side. When the sensor tube 14 is driven as shown by a broken line in FIG. 4, a Coriolis force -F acts on the inflow side of the sensor tube 14 as shown by a broken line in FIG. Force + F acts.
[0053]
The displacement of the sensor tube 14 is detected by the sensor coils 18 c, 18 d, 20 c, 20 d of the pickups 18, 20, and the flow measurement control circuit 38 converts the displacement into a signal having a time difference Δt from the input signal input to the vibrator 15. And then into a flow pulse.
[0054]
That is, the flow rate measurement control circuit 38 calculates the mass flow rate Qm by performing the following equation.
Qm = A · Δt (1)
Here, A is a constant unique to the mass flow meter.
[0055]
In the above-described embodiment, the configuration in which one sensor tube 14 is inserted into the inside of the storage case 12 has been described as an example. However, the configuration is not limited thereto. For example, two sensor tubes may be arranged in parallel to each other. Of course, the relative displacement of the sensor tube may be detected.
[0056]
Here, the configuration of the magnets 16a, 16b, 18a, 18b, 20a, and 20b will be described. Since the magnets 16a, 16b, 18a, 18b, 20a, and 20b have the same configuration, the configuration of the magnet 16a will be described below, and the description of the other magnets will be omitted.
[0057]
6A and 6B are diagrams showing the configuration of the first embodiment of the magnet 16a, wherein FIG. 6A is a cross-sectional view and FIG. 6B is a vertical cross-sectional view.
As shown in FIGS. 6A and 6B, the magnet 16 a includes a permanent magnet 70 having a rectangular parallelepiped shape made of a magnetic material, and a cover member 72 having a rectangular parallelepiped shape covering the entire surface of the permanent magnet 70. It is composed of The permanent magnet 70 is housed in a closed space 72a of the cover member 72, and is isolated from the outside. The magnet 16a is formed in a rectangular shape along the longitudinal direction of the sensor tube 14 so that the lines of magnetic force increase.
[0058]
The cover member 72 is made of a strong material such as non-magnetic stainless steel that can prevent high-pressure hydrogen from penetrating between metal molecules, and is made of a material that is highly resistant to hydrogen embrittlement. .
[0059]
As such a material, austenitic stainless steel is suitable for the conditions, and among them, a material containing molybdenum in the composition is preferable. Further, low carbon steel (carbon of 0.04% or less as a chemical component) is still more preferable. Further, other than stainless steel, glass and the like are also conceivable.
[0060]
In addition, as a method of manufacturing the cover member 72, a method is used in which a metal plate is pressed to form a shape that covers the outer periphery of the permanent magnet 70, and a seam is formed by a metal processing technique such as welding. You may. Alternatively, a method in which a metal film is directly coated on the surface of the permanent magnet 70 by plating or the like may be considered.
[0061]
In the first embodiment shown in FIGS. 6A and 6B, the rectangular parallelepiped cover member 72 is illustrated. However, the cover member 72 may be cylindrical. However, in this case, since the length of the sensor tube 14 along the longitudinal direction is also reduced, the amount of lines of magnetic force is reduced.
[0062]
When the permanent magnet 70 is formed of, for example, a rare-earth metal, the permanent magnet 70 is easily combined with hydrogen, and in a hydrogen atmosphere, the magnetic force may be reduced or broken. However, by covering the entire surface of the permanent magnet 70 with the cover member 72, the permanent magnet 70 is prevented from contacting the high-pressure hydrogen that is the fluid to be measured, and the magnetic force is not reduced or destroyed.
[0063]
For this reason, the mass flowmeter 10 employs a configuration in which the fluid to be measured (hydrogen) is filled also in the storage case 12 for storing the sensor tube 14 in order to reduce the pressure resistance of the sensor tube 14 and increase the measurement accuracy. Also, the permanent magnet 70 attached to the sensor tube 14 is prevented from coming into contact with hydrogen, and the amount of hydrogen filling can be measured in the fuel supply path of the filling device that fills the fuel tank of the fuel cell vehicle with high-pressure hydrogen. become.
[0064]
FIGS. 7A and 7B are diagrams showing the configuration of the second embodiment of the magnet 16a, wherein FIG. 7A is a transverse sectional view and FIG. 7B is a longitudinal sectional view. In FIGS. 7A and 7B, the same portions as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIGS. 7A and 7B, the cover member 73 of the second embodiment is a concave storage member (first cover) covering the rectangular parallelepiped permanent magnet 70 and the lower surface. 74, and a long lid member (second cover) 76 that covers the upper surface of the permanent magnet 70.
[0065]
The cover member 73 closes the storage recess 74 a with a cover member 76 formed in a disk shape in a state where the permanent magnet 70 is stored in the storage recess 74 a of the storage member 74, and the peripheral portion of the storage member 74 and the cover member 76 are closed. The gap is fixed by welding 78.
[0066]
As a result, the permanent magnet 70 is protected by the cover member 72 while being housed in the closed space.
[0067]
Further, when the storage member 74 and the lid member 76 are formed of a stainless steel material which is a non-magnetic material, the weld 78 must be provided in a place where the magnetic field line pattern of the permanent magnet 70 is not easily affected because the weld 78 has magnetism. is there. Therefore, in the second embodiment, the welding 78 is provided so as to be located near the corner of the cylindrical permanent magnet 70. Therefore, the position of the weld 78 is provided at a position not facing the coil, and the magnetic field line pattern of the permanent magnet 70 is prevented from being disturbed by the magnetization of the welded portion.
[0068]
FIGS. 8A and 8B are diagrams showing the configuration of the third embodiment of the magnet 16a, wherein FIG. 8A is a transverse sectional view and FIG. 8B is a longitudinal sectional view. 8 (A) and 8 (B), the same parts as those in the above embodiments are denoted by the same reference numerals, and the description thereof will be omitted.
As shown in FIGS. 8A and 8B, the cover member 80 of the third embodiment has an internal space 80a formed in a rectangular parallelepiped shape in which a permanent magnet 70 is housed. The inner space 80a is closed, the inner diameter and the depth of the inner space 80a are slightly larger than those of the permanent magnet 70, and has a sufficient volume for the permanent magnet 70 to fit completely.
[0069]
Therefore, a minute gap 82 exists between the permanent magnet 70 and the inner wall forming the internal space 80a. The gap 82 is filled with a non-compressed fluid 84 having fluidity.
[0070]
The non-compressed fluid 84 is made of a gel or a liquid, and is filled in the gap 82 of the closed internal space 80a to prevent the cover member 80 from being deformed by the pressure of the fluid to be measured. You.
[0071]
Further, in the cover member 80, it is difficult to create the internal space 80a with high accuracy so that there is no gap with respect to the outer shape of the permanent magnet 70. However, if the internal space 80a is made slightly larger than the outer shape of the permanent magnet 70, it can be manufactured easily with reduced processing accuracy.
[0072]
FIGS. 9A and 9B are diagrams showing the configuration of the fourth embodiment of the magnet 16a, where FIG. 9A is a cross-sectional view and FIG. 9B is a vertical cross-sectional view. In FIGS. 9A and 9B, the same parts as those in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIGS. 9A and 9B, the cover member 86 of the fourth embodiment is a cylindrical storage member formed to cover the outer periphery and the upper surface of the columnar permanent magnet 70. 88 and a disk-shaped lid member 90 that covers the lower surface of the permanent magnet 70.
[0073]
The storage member 88 has a circular storage recess 88a that stores the permanent magnet 70, and a flange 88b that protrudes in a radial direction from the peripheral edge of the storage recess 88a. Further, the lid member 90 is formed in a disk shape so that the outer diameter is the same as the outer diameter of the flange portion 88b.
[0074]
The outer periphery of the lid member 90 and the outer periphery of the flange 88b are fixed all around by welding 92. Therefore, the permanent magnet 70 is held in a state of being sandwiched between the storage member 88 and the lid member 90, and is shielded from the outside inside the space 94 sealed by the weld 92. Therefore, it is possible to prevent the permanent magnet 70 attached to the sensor tube 14 from coming into contact with the hydrogen to be measured, and to measure the hydrogen filling amount.
[0075]
Further, the position of the weld 92 is provided on the outer periphery of the lid member 90 and the outer periphery of the flange 88b which are radially separated from the permanent magnet 70 so as not to face the coil. The disturbance is prevented by the magnetization.
[0076]
Further, since the welding 92 is located at a position apart from the permanent magnet 70 in the radial direction, the welding heat is not easily transmitted to the permanent magnet 70, and the heat influence on the permanent magnet 70 can be reduced.
[0077]
FIG. 10 is a longitudinal sectional view showing a magnet mounting structure according to the fourth embodiment.
As shown in FIG. 10, the magnets 16 a and 16 b fix the cover member 90 of the cover member 86 to the outer periphery of the sensor tube 14. At this time, the permanent magnet 70 is attached in a direction in which the N pole and the S pole are alternately arranged.
[0078]
The magnets 16a and 16b are mounted such that the plane of the permanent magnet 70 faces the drive coils 16c and 16d mounted on the outer periphery of the storage case 12.
[0079]
As described above, since the cover member 86 of the fourth embodiment can use the lid member 90 as a bracket, it can be easily attached to the sensor tube 14. The welding 92 is provided at a position shifted in the radial direction so that the driving coils 16 c and 16 d do not face each other, and is provided so as not to affect the magnetic field between the driving coils 16 c and 16 d and the permanent magnet 70. Have been.
[0080]
Here, a modified example of the mass flowmeter to which the magnet 16a is attached will be described.
FIG. 11 is a cross-sectional view illustrating the configuration of the mass flow meter 40 of the first modification. FIG. 12 is a longitudinal sectional view taken along line CC in FIG. FIG. 13 is a longitudinal sectional view taken along line DD in FIG. 11 to 13, the same parts as those of the mass flow meter 10 shown in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof will be omitted.
[0081]
As shown in FIGS. 11 to 13, the mass flow meter 40 includes a sensor tube 14 inserted into the sealed storage case 12, a vibrator 46 for vibrating the sensor tube 14, and a vibrating sensor. It has an inflow side pickup 48 for detecting the inflow side displacement of the tube 14 and an outflow side pickup 50 for detecting the outflow side displacement of the vibrating sensor tube 14.
[0082]
The vibrator 46 includes magnets 46 a and 46 b provided on the sensor tube 14 and drive coils 46 c and 46 d provided on the outer periphery of the storage case 12. When the magnets 46a and 46b attract or repel a magnetic field generated when a certain alternating voltage (AC signal) is applied, the middle portion of the sensor tube 14 is vibrated in the lateral direction (Y direction).
[0083]
The magnets 46a and 46b have the same configuration as the first to fourth embodiments of the magnet 16a, and cover the permanent magnet 70 with the cover members 72, 73 and 80 so that the fluid to be measured does not contact the permanent magnet 70. , 86.
[0084]
The storage case 12 is formed of, for example, an austenitic non-magnetic stainless steel (SUS304). Further, iron cores 46e and 46f made of, for example, a ferrite-based magnetic material are inserted into the centers of the drive coils 46c and 46d.
[0085]
Therefore, even when the drive coils 46c and 46d are provided on the outer periphery of the storage case 12, the magnetic flux generated by the drive coils 46c and 46d passes through the storage case 12 and reaches the magnets 46a and 46b. Thus, the drive coils 46c and 46d can vibrate the magnets 46a and 46b from the outer periphery of the storage case 12 in the vibration direction (Y direction).
[0086]
The magnets 46a and 46b of the vibrator 46 are attached to the outer periphery of the intermediate portion of the sensor tube 14 at 180-degree intervals by a ring-shaped holding member 52. The holding member 52 is a weight (inertial mass) formed of a metal made of a non-magnetic material, and is formed so as to cover the entire outer periphery of an intermediate portion of the sensor tube 14.
[0087]
In the present embodiment, the magnets 46a and 46b and the holding member 52 function as weights at the time of excitation. However, when the magnets 46a and 46b also serve as the holding member 52, only the magnets 46a and 46b are weighted. Function as Further, a member having a predetermined weight other than the magnets 46a and 46b and the holding member 52 can be attached to an intermediate portion of the sensor tube 14 as a weight.
[0088]
As described above, since the holding member 52 is fixed to the outer periphery of the intermediate portion of the sensor tube 14 where the amplitude is maximum, the holding member 52 functions as an inertial mass when vibrated. Accordingly, the sensor tube 14 can efficiently vibrate by the driving force of the vibrator 46, and the sharpness of resonance drawn near the resonance frequency and the Q (quality factor) indicating the narrowness of the resonance characteristic. ) Is increased.
[0089]
Further, Q used in the vibration system is obtained by Q = ω / Δω, and is determined by the value of the width Δω (the width of the resonance characteristic) at the height 3 dB below the peak in the waveform of the resonance frequency ω. Therefore, Q (quality factor) is a numerical value indicating not only the sharpness of the resonance frequency but also the degree of expansion at the time of resonance, and the smaller the value of Δω is, the smaller the width of the resonance characteristic is, and the higher the resonance characteristic is. Accordingly, in the mass flow meter 40, the vibration characteristics of the sensor tube 14 can be increased by increasing the inertial mass of the vibrating portion of the sensor tube 14, and for example, the measurement accuracy in a minute flow rate region where the Coriolis force is reduced can be improved. Can be.
[0090]
The inflow-side pickup 48 includes magnets 48 a and 48 b fixed at upper and lower positions on the outer periphery of the inflow side of the sensor tube 14, and magnetic sensors (detection units) 48 c and 48 d provided at upper and lower positions on the outer periphery of the storage case 12. Since the magnets 48a and 48b vibrate in the lateral direction (Y direction) together with the sensor tube 14, they move toward and away from the magnetic sensors 48c and 48d. And outputs a detection signal corresponding to the amount of displacement.
[0091]
The outflow side pickup 50 is composed of magnets 50a, 50b fixed at upper and lower positions on the outflow side outer periphery of the sensor tube 14, and magnetic sensors 50c, 50d provided at upper and lower positions on the outer circumference of the storage case 12. Since the magnets 50a and 50b vibrate in the lateral direction (Y direction) together with the sensor tube 14 and move toward and away from the magnetic sensors 50c and 50d, the amount of displacement of the magnets 50a and 50b from the magnetic sensors 50c and 50d. And outputs a detection signal corresponding to.
[0092]
As the magnetic sensors 48c, 48d and 50c, 50d, for example, a high-sensitivity GMR (giant magnetoresistive effect) sensor capable of detecting a weak magnetic field change is used. Also, since the magnetic sensors 48c, 48d and 50c, 50d have high sensitivity, a detection signal is output from the outer periphery of the storage case 12 in accordance with a magnetic field change caused by the vibration of the magnets 48a, 48b and 50a, 50b in the Y direction. Output as
[0093]
The measurement operation of the mass flow meter 40 according to the second modification is the same as that of the above-described mass flow meter 10, and thus the description thereof is omitted.
[0094]
FIG. 14 is a cross-sectional view showing the configuration of the mass flow meter 60 of the second modification. FIG. 15 is a longitudinal sectional view taken along line EE in FIG. FIG. 16 is a longitudinal sectional view taken along line FF in FIG. 14 to 16, the same parts as those of the mass flow meter 10 shown in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof will be omitted.
[0095]
As shown in FIGS. 14 to 16, in the mass flow meter 60, iron cores 62a to 62f are inserted into the centers of the drive coils 16c, 16d and the sensor coils 18c, 18d, 20c, 20d. Further, concave portions 66a to 66f in which cylindrical magnetic materials 64a to 64f are fitted and fixed are provided on the outer periphery of the storage case 12 facing the iron cores 62a to 62f.
[0096]
Therefore, the magnetic materials 64a to 64f embedded in the recesses 66a to 66f of the storage case 12 are in contact with the iron cores 62a to 62f, and transfer the magnetic flux from the drive coils 16c, 16d and the sensor coils 18c, 18d, 20c, 20d. It functions as a magnetic path leading to the inside of the storage case 12.
[0097]
Therefore, even if the thickness of the storage case 12 is set to withstand the pressure of the fluid to be measured, the magnetic materials 64a to 64f are fitted and fixed in the recesses 66a to 66f of the storage case 12, thereby maintaining the pressure resistance. However, the driving force of the drive coils 16c and 16d and the detection sensitivity of the sensor coils 18c, 18d, 20c and 20d can be increased.
[0098]
Thereby, in the mass flow meter 60, the inertial mass of the vibrating portion of the sensor tube 14 can be increased to improve the vibration characteristics of the sensor tube 14, and for example, to improve the measurement accuracy in a minute flow rate region where the Coriolis force is reduced. Can be.
[0099]
The measurement operation of the mass flow meter 60 according to the third modification is the same as that of the above-described mass flow meter 10, and thus the description thereof is omitted.
[0100]
FIG. 17 is a cross-sectional view showing the configuration of the mass flow meter 100 according to the third modification.
As shown in FIG. 17, the mass flow meter 100 vibrates the inflow-side sensor tube 102, the outflow-side sensor tube 104 extending in parallel with the inflow-side sensor tube 102, and the distal ends of the sensor tubes 102 and 104. Vibrators 106 and 108 that vibrate, an inflow pickup 110 that detects displacement of a vibrating inflow sensor tube 102, and an outflow pickup 112 that detects displacement of a vibrating outflow sensor tube 104.
[0101]
The inflow-side sensor tube 102 is inserted into a pipe 118 formed inside an inflow-side storage case 116 formed in a cylindrical shape. The outflow-side sensor tube 104 is inserted into a conduit 122 formed inside an outflow-side storage case 120 formed in a cylindrical shape.
[0102]
The sensor tubes 102 and 104 are inserted in a cantilever manner along the axes of the conduits 118 and 122, and are vibrated at an amplitude such that the tip does not contact the inner walls of the conduits 118 and 122 during measurement.
[0103]
The sensor tubes 102 and 104 have detection magnets 124 and 126 and drive magnets 128 and 130 attached to the outer periphery. The magnets 124, 126, 128, and 130 have the same configuration as the above-described first to fourth embodiments of the magnet 16a, and cover the permanent magnet 70 so that the fluid to be measured does not contact the permanent magnet 70. 72, 73, 80, 86.
[0104]
Further, sensor coils 132 and 134 and drive coils 136 and 138 are provided on the outer periphery of the storage cases 116 and 120.
[0105]
Since the sensor tubes 102 and 104 have open end portions, the pipes 118 and 122 are vibrated while being filled with the fluid to be measured, and flow rates are measured. Therefore, the inner and outer pressures of the sensor tubes 102 and 104 are the same, so that even when measuring a high-pressure fluid, the sensor tubes 102 and 104 are configured to be thin and easy to vibrate.
[0106]
The base ends of the sensor tubes 102 and 104 are supported by support members 140 and 142, and the support members 140 and 142 are sandwiched between the mounting base 144 and the flanges 116a and 120a of the storage cases 116 and 120.
[0107]
In addition, the flanges 116b and 120b on the distal end side of the storage cases 116 and 120 are fastened to the communication member 146. The communication member 146 has a U-shaped passage 146a inside. One end of the passage 146 a communicates with the conduit 118 of the storage case 116, and the other end communicates with the conduit 122 of the storage case 120.
[0108]
Therefore, the sensor tubes 102 and 104 are inserted into the conduits 118 and 122 connected through the passage 146a, and are vibrated in the conduits 118 and 122 at the same pressure.
[0109]
In addition, the sensor tubes 102 and 104 have a free end at the distal end portion, so that the sensor tubes 102 and 104 are easily bent, so that the deformation amount (amplitude) with respect to the exciting force can be increased. Therefore, in the mass flow meter 100, the sensor tubes 102 and 104 are easily vibrated, so that the measurement accuracy in a minute flow rate region where the Coriolis force is relatively small can be improved, and the fluid to be measured can be accurately measured. become.
[0110]
Further, since the sensor tubes 102 and 104 have free ends, the amount of expansion and contraction in the longitudinal direction (Y direction) due to thermal expansion does not affect the measurement even when measuring a high-temperature fluid.
[0111]
In the above-described embodiment, the case where the flow rate is measured using a flammable gas such as CNG as the fluid to be measured has been described as an example. Of course.
[0112]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the non-magnetic cover member is provided to cover the surfaces of the driving magnet and the detecting magnet so as to separate them from the fluid to be measured, the magnet is provided on the fluid to be measured. Direct contact can be prevented to prevent physical properties of the magnet from deteriorating, and safe measurement can be performed even if the fluid to be measured is a flammable fluid.
[0113]
According to the second aspect of the present invention, since the cover member is formed of an austenitic stainless steel, it is possible to prevent the cover member from being deteriorated even when the cover member comes into contact with the fluid to be measured. In particular, a non-magnetic stainless steel material is used so as not to impair the magnetic force of the magnet, and the strength against hydrogen as the fluid to be measured can be ensured, and the magnetic force pattern of the magnet can be prevented from being disturbed.
[0114]
According to the third aspect of the present invention, since the gap between the magnet and the internal space of the cover member is filled with the non-compressed fluid, the pressure resistance of the cover member can be further increased, and the deformation of the cover member is prevented. Can be prevented from affecting the magnet.
[0115]
According to the fourth aspect of the present invention, the cover member has the first cover in which the storage recess having the shape corresponding to the shape of the magnet is formed, and the first cover in which the edge of the first cover is formed in the same shape. Since the first cover and the second cover are connected to each other, by joining the edge of the first cover and the edge of the second cover, the storage recess is prevented from being deformed at the time of joining, and particularly, heat such as welding is generated. When added, the magnet stored in the storage recess is not directly affected by heat, so that the magnet can be prevented from being deformed by the welding heat and the magnetic properties from being changed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a Coriolis mass flow meter as one embodiment of a vibration measuring device according to the present invention.
FIG. 2 is a longitudinal sectional view taken along line AA in FIG.
FIG. 3 is a longitudinal sectional view taken along line BB in FIG.
FIG. 4 is a diagram schematically showing a state in which a vibrator 15 vibrates a sensor tube 14.
FIG. 5 is a diagram schematically showing Coriolis force acting on a vibrating sensor tube.
FIGS. 6A and 6B are diagrams showing a configuration of a first embodiment of a magnet 16a, wherein FIG. 6A is a transverse sectional view and FIG. 6B is a longitudinal sectional view.
FIGS. 7A and 7B are diagrams showing a configuration of a second embodiment of the magnet 16a, in which FIG. 7A is a transverse sectional view and FIG. 7B is a longitudinal sectional view.
FIGS. 8A and 8B are diagrams showing a configuration of a third embodiment of the magnet 16a, wherein FIG. 8A is a transverse sectional view and FIG. 8B is a longitudinal sectional view.
FIGS. 9A and 9B are diagrams showing a configuration of a fourth embodiment of the magnet 16a, wherein FIG. 9A is a transverse sectional view and FIG. 9B is a longitudinal sectional view.
FIG. 10 is a longitudinal sectional view showing a magnet mounting structure according to a fourth embodiment.
FIG. 11 is a cross-sectional view illustrating a configuration of a mass flow meter 40 according to a first modification.
FIG. 12 is a longitudinal sectional view taken along the line CC in FIG. 11;
13 is a longitudinal sectional view taken along line DD in FIG.
FIG. 14 is a cross-sectional view showing a configuration of a mass flow meter 60 according to a second modification.
FIG. 15 is a longitudinal sectional view taken along line EE in FIG. 14;
FIG. 16 is a longitudinal sectional view taken along the line FF in FIG. 14;
FIG.
FIG. 10 is a cross-sectional view illustrating a configuration of a mass flow meter 100 according to a third modification.
[Explanation of symbols]
10, 40, 60, 100 mass flow meter
12 storage cases
14 Sensor tube
16,46,106,108 shaker
16a, 16b Drive magnet
18a, 18b, 20a, 20b Detection magnet
18, 48, 110 Inlet side pickup
20, 50, 112 Outflow side pickup
22, 24 flange
26 Internal space
28 Inflow side support plate
30 Outflow side support plate
34 passage
36a-36f cable
38 Flow measurement control circuit
48c, 48d, 50c, 50d Magnetic sensor
52 Holding member
70 permanent magnet
72, 73, 80, 86 cover member
74,88 storage member
76,90 Lid member
78,92 welding
82 gap
84 Incompressible fluid
102 Inlet side sensor tube
104 Outflow side sensor tube
116,120 Inlet side storage case
118,122 Pipe
124,126 Magnet for detection
128,130 Drive magnet
132,134 Sensor coil
136,138 drive coil
140, 142 support members
144 mounting base
146 communication member

Claims (4)

A storage case with a closed space formed inside,
A sensor tube that is inserted into the space and through which the fluid to be measured flows;
A driving magnet attached to the sensor tube, a vibrator provided on an outer wall of the storage case, and a driving coil configured to drive the driving magnet in a vibration direction;
A pickup including a detection magnet attached to the sensor tube, a detection unit provided on an outer wall of the storage case, and detecting a displacement of the detection magnet; and a storage case for storing a fluid to be measured passing through the sensor tube. A passage to supply the space of
In a vibration type measuring device having
A vibration-type measuring apparatus, further comprising a non-magnetic cover member that covers surfaces of the driving magnet and the detecting magnet so as to isolate the surfaces from the fluid to be measured. The vibration type measuring device according to claim 1, wherein the cover member is formed of an austenitic stainless steel material. 3. The vibration type measuring apparatus according to claim 1, wherein an incompressible fluid is filled in a gap between the internal space of the cover member and the magnet. The cover member includes a first cover in which a storage recess having a shape corresponding to the shape of the magnet is formed, and a second cover in which an edge of the first cover is formed in the same shape,
The vibration type measuring apparatus according to any one of claims 1 to 3, wherein an edge of the first cover and an edge of the second cover are joined.

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