Coriolis mass flowmeter

Abstract

A Coriolis mass flowmeter which includes a corrosive fluid as a measurement object, and in which there is no risk of metal ion elution. A straight pipe type pipe (1) through which a measurement fluid flows, an exciter (2) which excites the pipe (1), a first vibration detector (3) and a second vibration detector (4) which detect the vibration state of the pipe (1), and supports (8a), (8b) which support both ends of the pipe (1) so as to be fixed ends with respect to vibration, the exciter (2), the first vibration detector (3), and the second vibration detector (4) being supported by frames (9a), (9b) which are linked to the supports (8a), (8b), the mass flow rate of the fluid flowing in the pipe being calculated based on the phase difference of the vibration waveforms detected by the first vibration detector (3) and the second vibration detector (4). The pipe (1), the supports (8a), (8b), and the frames (9a), (9b) are formed of a highly elastic plastic material.

Description

TECHNICAL FIELD

[0001] The present application relates to a Coriolis mass flowmeter which detects torsional vibration using the action of Coriolis force generated by a fluid in a flow path being vibrated, thereby measuring the mass flow rate of the fluid. BACKGROUND

[0002] In the past, as a direct measurement unit of mass flow rate, a Coriolis mass flowmeter has been used. This is a flowmeter which utilizes the fact that when a fluid flowing in a pipe is subjected to rotational motion, it receives a Coriolis force proportional to the vector product of the vector of flow and the angular velocity vector of rotation, which is proportional to the mass flow rate. A method of vibrating the pipe and detecting the elastic deformation of the pipe due to the action of the Coriolis force of the internal fluid is generally adopted.

[0003] The Coriolis mass flowmeter forcibly vibrates the pipe through which the fluid to be measured passes using a vibration exciter, detects the phase difference of the vibration generated on the upstream side and the downstream side of the flow path in accordance with the mass flow rate of the fluid, and calculates the mass flow rate from the above-mentioned phase difference. The Coriolis mass flowmeter generally vibrates at the natural vibration frequency of the pipe through which the fluid passes in order to efficiently generate vibration. The main factors which determine the natural vibration frequency of the pipe are the modulus of elasticity (longitudinal elastic coefficient) of the pipe material and the shape of the pipe, and in the case of a metal pipe, the modulus of elasticity is relatively stable with respect to temperature changes, and the shape is difficult to change with time, so it is often used as the pipe of the Coriolis mass flowmeter.

[0004] As such prior art, the following is known: in the case of measuring a fluid which corrodes metal as the measurement object, as a Coriolis mass flowmeter which is good at measuring a corrosive fluid, as shown in (a) of FIG. 1 of Figure 2 , a U-shaped compound curved conduit 21 which is vibrated at the natural vibration frequency is fixed to a support member 23 via a fixing portion 22, as shown in (b) of FIG. 1 of Figure 2 , the outer side of the U-shaped compound curved conduit 21 of a double structure is made of Incoloy 24, and the inner side 25 is coated with fluororesin (Patent Document 1). However, since this Coriolis mass flowmeter is composed of a U-shaped conduit, it is difficult to coat the curved pipe portion with fluororesin.

[0005] In addition, fluororesin coating is difficult to thicken, and in the case where coating is not reliably performed, there is a concern that metal ions will be eluted into the fluid, so there is a demand that metal should not be used as the pipe material. Therefore, as shown in FIG. 2 of Figure 3 , a Coriolis mass flowmeter in which the pipe is formed of perfluoroalkoxy alkane (PFA) has been proposed (Patent Document 2). In Figure 3In the meantime, a fluid of a processing material received from the supply pipe 31 is supplied to the pipe 33 via the processing connection portion 32, the pipe 33 is excited by the exciter 34 at a frequency resonating with the flow of the fluid, the fluid reaches the outlet pipe 40 from the pipe 33 via the processing connection portion 35, the pipe 36 changing the flow direction of the fluid, the processing connection portion 37, the return pipe 38, and the processing connection portion 39. Here, the pipe 33 and the return pipe 38 are made of PFA. However, in the case where the pipes are made of only fluorine-based resin, a change in elastic modulus due to temperature, a creep phenomenon of aging can occur. The Coriolis mass flowmeter measures by vibrating the pipes, but since the change in elastic modulus affects the vibration, it is difficult to accurately measure the mass flow.

[0006] In addition, as shown in Figure 4 , a Coriolis mass flowmeter is proposed which is formed of an elastic polymer material and has two flow detection members each having one or more straight portions and being integrally connected to a base portion (Patent Document 3). In Figure 4 , in a solid subassembly 51 formed of a polymer material which is CNC-processed from a block of an elastic polymer material, flow paths 52 and 53 are formed which are completely from end to end in the lateral direction along the center line of U, and flow paths 54, 55, 56, 57 are formed which completely pass through the support portion 58 along the center line of U. Also, as shown in Figure 5 , Figure 6 , a Coriolis mass flowmeter is proposed which is made of a same polymer material, a main body 61, at least four tubular port extensions 62A, 62B, 62C, 62D each including a welding surface and being integrated with the main body 61, manifold flow passages 63A, 63B, 63C, 63D, insulating plates 64A, 64B, 64C, 64D integrated with the main body 61 and the above-mentioned at least four tubular port extensions, and two flow sensing members 65A, 65B including two open ends (Patent Document 4). In addition, as shown in Figure 7 , a Coriolis mass flowmeter is proposed which includes flow sensing members 71A, 71B made of a fluorine-based resin such as PFA, polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and a support body 72 holding the flow sensing members 71A, 71B, the support body material having a thermal expansion coefficient substantially close to or smaller than the fluorine-based resin (Patent Document 5).

[0007] However, in the Coriolis mass flowmeter disclosed in Patent Documents 3 to 5, a change in the elastic modulus caused by temperature cannot be dealt with. That is, the spring constant (proportional to Young's modulus) of the piping material changes depending on the temperature, directly affecting the precision of the Coriolis mass flowmeter. The temperature of the flow detecting element also changes depending on the fluid and / or the surrounding temperature, and therefore, in order to maintain the precision of the flow measurement in the Coriolis mass flowmeter, temperature compensation is required. As for the data on Young's modulus with respect to temperature, data on almost all metal alloys (stainless steel or titanium, etc.) used in the production of the prior art Coriolis mass flowmeter can be obtained from NIST (or other technical materials). However, as for elastic polymers, data (elastic modulus with respect to temperature, etc.) matching this are generally not available, or are only a few temperatures to the extent described in publications. Therefore, although the prior art which describes the use of plastic in the production of the Coriolis mass flowmeter also mentions a means for detecting the temperature of the flow detecting element, it does not describe how to achieve effective temperature compensation for a specific elastic polymer material within a certain range of operating temperatures. It is important that, without such temperature compensation, the flowmeter cannot be used in applications in which the temperature of the sensor is substantially different from the temperature at the time of calibration.

[0008] Further, in the case where a fluid for which a micro flow is applied is the object, in order to realize a Coriolis mass flowmeter with high sensitivity, it is necessary to increase the interval of the two vibration detectors as much as possible, and to reduce the torsional spring constant of the piping so as to be easily twisted.

[0009] For example, in Patent Document 6, as shown in Figure 8 , a Coriolis mass flowmeter is proposed which has a piping for fluid flow constituted by an inner pipe 82 which is in contact with a flow path 81, and an outer pipe 83 which is laminated on the outer periphery of the inner pipe 82. Here, the inner pipe 82 is a fluorine-based resin, and the outer pipe 83 is made by winding a prepreg in which glass fibers are disposed in uncured epoxy resin around the outer periphery of the inner pipe 82 and curing it, and has an elastic modulus larger than that of the inner pipe 82. The outer pipe 83 has fibers Fl, F2 arranged on the outer periphery surface 84 of the inner pipe 82, and a resin 85 for forming the fibers Fl, F2 so as to be fixed to or pressed and fixed to the inner pipe 82. In addition, in Patent Document 7, as shown in Figure 9 , a Coriolis mass flowmeter is proposed which has a frame constituted by a main frame 91 and a sub-frame 92, a housing 93, and a vibrating pipe 94, and the measurement portion of the vibrating pipe 94 is made of a fluorine resin reinforced with carbon fibers, and the inlet portion and the outlet portion in the supply and discharge portion of the vibrating pipe which receives and discharges the fluid are made of a fluorine resin which is not reinforced with fibers.

[0010] First, in order to measure the mass flow rate of a fluid of a small flow rate with high accuracy, as described above, it is necessary to increase the interval (d) of the two vibration detectors as much as possible and to reduce the torsional spring constant (Kθ) of the pipe.

[0011] However, in the case of a general U-shaped pipe, by increasing the above-described interval d, the moment of inertia in the torsional direction becomes large, and at the same time, the torsional spring constant Kθ becomes large, and the vibration frequency in the torsion (Coriolis vibration frequency) becomes small. If the Coriolis vibration frequency becomes small, it is easily affected by vibration noise from the outside. In addition, if the above-described interval d is increased, the pressure loss of the fluid becomes large, and not only is the maximum flow rate limited, but also the fluid inside the pipe is not completely discharged but remains attached, and thus in a manufacturing process such as a semiconductor manufacturing process or a pharmaceutical manufacturing process, which requires extremely high cleanliness of the manufacturing equipment, it is difficult to completely clean the inside of the pipe even if fixed cleaning or fixed sterilization is performed.

[0012] In order to reduce the torsional spring constant Kθ of the pipe as much as possible, it is required to reduce the bending rigidity EI (E: elastic modulus, I: sectional moment of inertia) as much as possible. This means that the pipe is made as thin as possible, and the wall thickness is made thin. In this way, although the purpose of measuring a fluid of a small flow rate is met, if the pipe is made thin, the pressure loss becomes large.

[0013] As a result, in a double structure in which the outer pipe of the outer peripheral surface of the inner pipe is made of a fiber-reinforced resin having a large elastic modulus (Patent Literature 6), even if the inner diameter of the pipe is reduced, the wall thickness becomes thick, and thus there is a constraint in reducing the spring constant Kθ in the torsion, and there is a limit to improving the sensitivity for the purpose of measuring a fluid of a small flow rate with high accuracy.

[0014] In the Coriolis mass flow meters of Patent Literatures 2 and 5, the pipe is formed of a fluororesin, but its density is smaller than that of metal, and thus if it is the same size, the mass of the pipe portion becomes smaller than that of a metal. Since a pair of coils and magnets are used in the exciter and the two vibration detectors loaded on the pipe, the relatively heavy mass is concentrated on the elastic polymer such as a fluororesin. In this way, if the concentrated mass is added to the pipe, it affects the density measurement of the fluid, reduces the sensitivity, and reduces the accuracy. In paragraph 0029 of Patent Literature 5, it is described that "another type of motion sensor such as an optical sensor can also be used", but it is only a description of another way of a motion sensor, and there is no mention of the effect of the concentrated mass added to the pipe on the density measurement of the fluid.

[0015] In addition, the object of Patent Literature 8 is to provide a Coriolis mass flow meter of a pair of arch pipe type which has less disturbance vibration, setting conditions, pipe stress, and thermal influence, like Figure 10As shown, a Coriolis mass flow meter is proposed, comprising: two flow tubes 101 and 102 bent into an arc shape; an inlet manifold and an outlet manifold 103 welded together at the two ends of each flow tube; a drive device 104 that resonates with one flow tube relative to the other flow tube at opposite phases; and a pair of vibration detection sensors 105 and 106, which are symmetrically positioned on the left and right sides relative to the installation position of the drive device 104, and detect a phase difference proportional to the Coriolis force.

[0016] However, including Patent Document 8, Patent Documents 1-7 do not mention the measurement of fluid density.

[0017] Furthermore, a dual straight-tube Coriolis flow meter is disclosed in Patent Document 9. For example... Figure 11 As shown, the double straight-tube Coriolis flow meter has a hollow cylindrical outer shell 112 with connecting flanges 111 at both ends. Inside the outer shell 112, a straight tubular flow tube 113 for the flow of the measured fluid is coaxially arranged with the outer shell 112. On the outside of the flow tube 113, a hollow cylindrical outer tube 115 is concentrically fixed on both sides of the outer tube 115 via a connecting plate 114 in a concentric double-tube manner. A counterweight 116 is installed in the center of the outer tube 115. A drive device 117 is installed on the outer tube 115 to make the flow tube 113 vibrate in its inherent primary mode of vibration. When the fluid flows, with the central part where the vibration velocity is the greatest as the boundary, the Coriolis force becomes opposite on the inflow and outflow sides, and the flow tube 113 flexes in an undulating manner, which is called the secondary mode component. The flow tube 113 is displaced in the form of a superposition of primary mode vibration based on the excitation generated by the drive device and secondary mode vibration based on the Coriolis force. A pair of sensors 118 are set on the outer tube 115 on both sides of the drive device 117 at the position where the secondary mode component is the greatest, and detect the phase difference of the flow tube 113 caused by the Coriolis force, thereby obtaining the mass flow rate.

[0018] However, in the dual straight-tube Coriolis flowmeter disclosed in Patent Document 9, when the temperature of the measured fluid changes, a very large temperature difference is generated between the flow tube and the outer tube, resulting in stress in the length direction. Due to the change in the spring constant caused by the thermal stress, the natural vibration frequency of the tube changes. As a result, there are disadvantages such as the energy balance being disrupted and the difficulty in achieving resonant drive.

[0019] Existing technical documents

[0020] Patent documents

[0021] Patent Document 1: Japanese Utility Model Publication No. 64-15921

[0022] Patent Literature 2: Japanese Patent Application Laid-Open No. 2005-510703

[0023] Patent Literature 3: Japanese Patent No. 5602884

[0024] Patent Literature 4: Japanese Patent No. 6257772

[0025] Patent Literature 5: Japanese Patent No. 6581309

[0026] Patent Literature 6: Japanese Patent No. 5086814

[0027] Patent Literature 7: Japanese Patent No. 5582737

[0028] Patent Literature 8: Japanese Patent No. 3656947

[0029] Patent Literature 9: U.S. Patent No. 6336369 SUMMARY

[0030] (1) Problem to be Solved by the Invention

[0031] The present application has been achieved in view of such problems of the related art, and has an object to provide a Coriolis mass flowmeter which includes a corrosive fluid as a measurement object, and in which there is no risk of metal ion elution. In addition, the present application has an object to provide a Coriolis mass flowmeter which can realize a reduction in the pipe diameter, and can stably perform measurement with respect to temperature changes. A further object of the present application is to provide a Coriolis mass flowmeter which has less influence from external vibrations, and can measure a low-density fluid with high sensitivity. A further object of the present application is to provide a Coriolis mass flowmeter which can measure the mass flow and the density of a fluid with high sensitivity even if it is miniaturized. A further object of the present application is to provide a Coriolis mass flowmeter which has less influence from vibration noise and viscosity.

[0032] (2) Means for Solving the Problem

[0033] The present inventors have made intensive studies in order to solve the above-described problems, and as a result, have adopted the following means.

[0034] (1) The first invention is a Coriolis mass flowmeter characterized by having: a straight pipe type pipe through which a measurement fluid flows; an exciter that excites the pipe; a first vibration detector and a second vibration detector that detect a vibration state of the pipe; and a support body that supports both end portions of the pipe so that both end portions of the pipe become fixed ends with respect to vibration, the exciter, the first vibration detector, and the second vibration detector being supported by a frame that is linked to the support body, a mass flow rate of the fluid flowing in the pipe being calculated based on a deviation in phase of vibration waveforms detected by the first vibration detector and the second vibration detector, the pipe, the support body, and the frame being formed of a high-elasticity plastic material.

[0035] (2) The second invention is the Coriolis mass flowmeter according to the above (1), characterized in that the high-elasticity plastic material is carbon fiber reinforced thermoplastic (CFRTP).

[0036] (3) The third invention is the Coriolis mass flowmeter according to the above (2), characterized in that the thermoplastic is a fluororesin.

[0037] (4) The fourth invention is the Coriolis mass flowmeter according to any one of the above (1) to (3), characterized in that, in a case where a mass of the first vibration detector is set to ml, a mass of the second vibration detector is set to m2, and a mass of the exciter is set to m3, m3 is greater than a total of ml and m2.

[0038] (5) The fifth invention is the Coriolis mass flowmeter according to any one of the above (1) to (3), characterized in that, in a case where a mass of the first vibration detector is set to ml, a mass of the second vibration detector is set to m2, a mass of the exciter is set to m3, a total of ml, m2, and m3 is set to m, a mass of the pipe is set to Mt, a mass of the fluid in the pipe is set to Mf, and M = Mt + m + Mf, m = 0.4M or less.

[0039] (6) The sixth invention is the Coriolis mass flowmeter according to any one of the above (1) to (3), characterized in that the first vibration detector and the second vibration detector are acceleration sensors that are located at symmetric positions centered on the exciter.

[0040] (7) The seventh invention is the Coriolis mass flowmeter according to any one of the above (1) to (3), characterized in that the first vibration detector and the second vibration detector are sound sensors that are located at symmetric positions centered on the exciter.

[0041] (8) The eighth invention is the Coriolis mass flowmeter according to any one of the above (1) to (3), characterized in that the exciter is a piezoelectric element.

[0042] (9) The ninth application is a Coriolis mass flowmeter characterized by having: a straight pipe type pipe through which a measurement fluid flows; an exciter that excites the pipe; a first vibration detector and a second vibration detector that detect a vibration state of the pipe; and a left support and a right support that support both ends of the pipe so that both ends of the pipe become fixed ends with respect to vibration, the exciter, the first vibration detector, and the second vibration detector are supported by a frame that is at least one of a first frame and a second frame that are connected to the supports, a mass flow rate of a fluid flowing in the pipe is calculated based on a deviation in phase of vibration waveforms detected by the first vibration detector and the second vibration detector, the pipe is formed of a single straight pipe, the first frame and the second frame are located at symmetrical positions with respect to a center axis of the pipe in the length direction, the exciter is located at a central portion of the first frame that is equidistant from the left support and the right support, the first vibration detector and the second vibration detector are located at symmetrical positions centered on the exciter on the first frame, and the first vibration detector and the second vibration detector are also supported on the second frame in a manner that they are located at symmetrical positions with respect to the first vibration detector and the second vibration detector supported on the first frame across the center axis of the pipe.

[0043] (10) The tenth application is the Coriolis mass flowmeter according to the above (9), characterized by having a differential circuit that takes a difference in output of the first vibration detector and a differential circuit that takes a difference in output of the second vibration detector, and by removing a coherent signal by measuring a phase difference in output of the two differential circuits.

[0044] (11) The eleventh application is the Coriolis mass flowmeter according to the above (10), characterized in that the first vibration detector and the second vibration detector are electrostatic capacitance sensors, and in that a metal film is attached to the pipe.

[0045] (12) The twelfth application is the Coriolis mass flowmeter according to any one of the above (9) to (11), characterized in that the first vibration detector and the second vibration detector are optical displacement sensors, and in that a metal film is attached to the pipe.

[0046] (13) The thirteenth application is the Coriolis mass flowmeter according to any one of the above (9) to (11), characterized in that the exciter is composed of a magnetic body such as a permanent magnet and a coil for electromagnetic driving corresponding to the magnetic body, the magnetic body is an exciter that is supported by the pipe and excites the pipe, and a non-magnetic body that is the same shape and the same mass as the magnetic body is supported by the pipe in a manner that it is located at a symmetrical position with respect to the magnetic body with respect to the center axis of the pipe in the length direction.

[0047] (14) The fourteenth application is the Coriolis mass flowmeter as described in the above (13), characterized in that, in the case where the mass of the first vibration detector is set as ml, the mass of the second vibration detector is set as m2, and the mass of the exciter is set as m3, m3 is larger than the sum of ml and m2, the mass of the first vibration detector supported to the first frame and the mass of the first vibration detector supported to the second frame are each ml / 2, the mass of the second vibration detector supported to the first frame and the mass of the second vibration detector supported to the second frame are each m2 / 2, and the mass of the magnetic body and the mass of the non-magnetic body are each m3 / 2.

[0048] (Three) Advantageous Effects

[0049] If the carbon fiber-reinforced thermoplastic plastic that forms the piping, the support body, and the frame is a carbon fiber-reinforced fluororesin, the flexural modulus of elasticity thereof is about 32 GPa, which is about 17% of the longitudinal modulus of elasticity 193 GPa of stainless steel (SUS304). In addition, the linear expansion coefficient (10 -6 / °C) of the carbon fiber-reinforced fluororesin is a value around zero, whereas the linear expansion coefficient (10 -6 / °C) of the stainless steel (SUS304) is 16. Therefore, if the carbon fiber-reinforced fluororesin is used to form the piping, the support body, and the frame, dimensional changes due to temperature are less likely to occur, and chemical resistance can be provided.

[0050] Regarding the measurement of the fluid density, the change in the Coriolis vibration frequency corresponding to the change in the fluid density is measured to obtain the fluid density. Regarding the slope of the change in the Coriolis vibration frequency, if the mass of the vibration detector that detects the vibration is large to a certain extent compared to the mass of the piping, the above slope becomes slow, the amount of change in the Coriolis vibration frequency becomes small relative to the amount of change in the fluid density, and the detection sensitivity is reduced. Therefore, in the case where the mass of the first vibration detector is set as ml, the mass of the second vibration detector is set as m2, and the mass of the exciter is set as m3, m3 is larger than the sum of ml and m2, in the case where the sum of ml, m2, and m3 is set as m, the mass of the piping is set as Mt, the mass of the fluid in the piping is set as Mf, and M = Mt + m + Mf is set, m is 0.4M or less, whereby the detection sensitivity of the fluid density can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is a schematic configuration view of the first embodiment of the Coriolis mass flowmeter of the present application including related devices.

[0052] Figure 2 (a) of is a schematic configuration view of the Coriolis mass flowmeter of Patent Document 1, Figure 2 (b) of is an enlarged sectional view of the fixed portion thereof.

[0053] Figure 3 is a plan view of the Coriolis mass flowmeter of Patent Literature 2.

[0054] Figure 4 is a diagram showing the schematic structure of the Coriolis mass flowmeter of Patent Literature 3.

[0055] Figure 5 is a diagram showing the schematic structure of the main body, the tubular port extension, the manifold flow passage, and the insulating plate of the Coriolis mass flowmeter of Patent Literature 4.

[0056] Figure 6 is a diagram showing the schematic structure of the flow sensing member of the Coriolis mass flowmeter of Patent Literature 4.

[0057] Figure 7 is a diagram showing the schematic structure of the Coriolis mass flowmeter of Patent Literature 5.

[0058] Figure 8 is an enlarged sectional view of the piping of the Coriolis mass flowmeter of Patent Literature 6.

[0059] Figure 9 is a diagram showing the schematic structure of the Coriolis mass flowmeter of Patent Literature 7.

[0060] Figure 10 is a diagram showing the partial section and the side surface cut by the manifold portion of the Coriolis mass flowmeter of Patent Literature 8.

[0061] Figure 11 is a diagram showing the schematic structure of the double-straight-pipe Coriolis flowmeter of Patent Literature 9.

[0062] Figure 12 (a), (b) of FIG. 1 are diagrams showing the working principle of the straight-pipe type Coriolis mass flowmeter, Figure 12 (a) of FIG. 1 shows a state where the piping is filled with a fluid and vibrates by the exciter in the case where the flow rate v = 0, Figure 12 (b) of FIG. 1 shows a state where torsional vibration is generated in the piping in the case where the fluid flows in the piping at a flow rate v (≠ 0), Figure 12 (c) of FIG. 1 is a diagram showing a sine waveform detected by the first vibration detector and the second vibration detector arranged at symmetric positions with respect to the exciter in the case of (b) of FIG. 1. Figure 12

[0063] Figure 13 ​is a graph in which the ratio of the additional mass m (m1+m2+m3) to the mass M (Mt+m+Mf) of the entire pipe is taken as the horizontal axis, and the frequency density margin (Hz / (g / cm 3 )) is taken as the vertical axis, in the case where the material of the pipe is CFRTP (symbol "●"), SUS316 (symbol "▲"), or PFA (symbol "■"), and m3=m1+m2.

[0064] Figure 14 is a graph in which the ratio of the additional mass m (m1+m2+m3) to the mass M (Mt+m+Mf) of the entire pipe is taken as the horizontal axis, and the frequency density margin (Hz / (g / cm 3 )) is taken as the vertical axis, in the case where the material of the pipe is CFRTP (symbol "●"), SUS316 (symbol "▲"), or PFA (symbol "■"), and m3=m1+m2.

[0065] Figure 15 is a schematic configuration diagram of a second embodiment of the Coriolis mass flowmeter of the present application including related devices.

[0066] Figure 16 is a schematic configuration diagram of a third embodiment of the Coriolis mass flowmeter of the present application including related devices.

[0067] Figure 17 is a schematic configuration diagram of a fourth embodiment of the Coriolis mass flowmeter of the present application including related devices.

[0068] Figure 18 is a schematic configuration diagram of a fifth embodiment of the Coriolis mass flowmeter of the present application including related devices. DETAILED DESCRIPTION

[0069] Hereinafter, specific embodiments of the present application will be described, but the present application is not limited to the following embodiments, and various modifications and corrections can be made within the scope of the technical range of the present application.

[0070] There are various kinds of fluororesins, and as the fluororesin used in the present application, a fluororesin capable of melt forming is preferred. For example, perfluoroalkoxy alkane (PFA), perfluoroethylene propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and the like can be used.

[0071] As the carbon fiber used in the present application, for example, there are a PAN-based fiber using a polyacrylonitrile fiber as a raw material, a pitch-based fiber using coal tar, petroleum pitch as a raw material (having an isotropic, mesophase, etc. according to the internal structure), a cellulose-based fiber using a viscose fiber, cellulose acetate, etc. as a raw material, a vapor-phase growth-based fiber using a hydrocarbon, etc. as a raw material, etc. In addition, it can also be a graphite fiber of these carbon fibers. In addition, it can also be a metal-coated carbon fiber formed by coating at least one layer or more of a metal such as nickel, ytterbium, gold, silver, copper, etc. on these carbon fibers by a plating method (electroplating, chemical plating), a CVD method, a PVD method, an ion plating method, an evaporation method, etc. In addition, two or more of them can be mixed to constitute.

[0072] The pipe, the support body, and the frame of the present application are preferably composed of a carbon fiber-reinforced fluororesin, but within a range not hindering the effects of the present application, an additive other than the fluororesin and the carbon fiber can also be contained. As the additive, a flame retardant, an electric conduction imparting agent, a crystallization nucleating agent, an ultraviolet absorber, an antioxidant, a vibration damping agent, an antibacterial agent, an insect repellent, an odor control agent, a coloration preventing agent, a heat stabilizer, a mold release agent, an antistatic agent, a plasticizer, a lubricant, a coloring agent, a pigment, a dye, a foaming agent, a foam suppressing agent, a coupling agent, etc. can be listed. Two or more of these can be used.

[0073] The pipe, the support body, and the frame of the present application are preferably formed by injection molding. Injection molding is high in productivity and enables cost reduction in terms of enabling molding cycles or molding of complex shapes, etc.

[0074] In the case where the pipe, the support body, and the frame of the present application are produced by injection molding, it is preferable to be performed under the following conditions. A screw is generally composed of a feeding section, a compression section, a metering section, and it is preferable to use a full screw shape with the minimum degree of kneading, and it can also be used by adjusting the level of kneading by adding a part of a kneading section, etc. By using a screw with as few kneading sections as possible, the fiber breakage can be suppressed. In addition, the clearance between the cylinder and the screw also greatly affects the fiber length, and by increasing the clearance, the kneading can be alleviated, and the fiber breakage can be suppressed. Furthermore, the size of the nozzle diameter also affects the fiber length, and if the nozzle diameter is small, the molten molding material is subjected to high shear when passing through, resulting in fiber breakage. By increasing the nozzle diameter, the fiber length can also be increased. In addition, by increasing the flow channel of the mold, the shear can also be suppressed, and the fiber length can be increased. Furthermore, by providing a hot runner, or by appropriately adjusting the temperature of the mold, the viscosity of the flowing resin can be reduced, and the fiber breakage can be suppressed.

[0075] Regarding molding conditions, preferably, the cylinder temperature is set to a high temperature within the range where the matrix resin does not decompose, the screw speed is reduced, the metering time is shortened, and the back pressure is set to a low temperature. By increasing the cylinder temperature, the viscosity of the molten resin decreases, the shear force applied to the fibers decreases, and breakage can be suppressed. In addition, if the screw speed is reduced, the metering time is shortened, and the back pressure is set to a low temperature, the mixing and shearing during molding can be minimized, resulting in molded products with long fiber lengths, which are molded products with low anisotropy and high strength. The reason for the reduced strength anisotropy of the molded product is that if the fiber length is relatively long (more than 1 mm), the fibers resist the resin flow and are oriented in the vertical direction inside the molded product. On the surface of the molded product, which is instantly cooled and solidified by the mold, the fibers are oriented in the direction of resin flow. As a result, the fibers are not a unidirectional reinforcing form, but a multidirectional reinforcing form, thus reducing the anisotropy of the molded product.

[0076] The volume content of carbon fiber in the carbon fiber reinforced thermoplastic of the present invention is preferably 20-40%, more preferably 25-35%.

[0077] Example

[0078] The present invention will be described in detail below through embodiments, but the present invention is not limited to these embodiments. Various modifications and alterations can be made without departing from the technical scope of the present invention.

[0079] Using a twin-screw extruder manufactured by Shibaura Machinery Co., Ltd. (screw diameter 30mm, die diameter 5mm, barrel temperature 280℃, speed 150rpm), continuous carbon fiber bundles manufactured by Mitsubishi Chemical Co., Ltd. were cut into short filaments of 6mm length. After being thoroughly dried to a moisture content of less than 0.05%, they were fed into the side hopper. Meanwhile, Daikin Industries Co., Ltd.’s fully fluorinated high-flow fluoropolymer “PFA AP-201SH” was fed into the main hopper as a thermoplastic resin. While the two were thoroughly mixed, the tube containing discontinuous carbon fibers was continuously extruded. After cooling, it was cut into 5mm lengths with a cutter to obtain carbon short fiber molding material.

[0080] After drying the above-mentioned molding material in a vacuum at 80°C for more than 5 hours, a hydraulic horizontal injection molding machine with a fully threaded screw is used to obtain... Figure 1 The molded product in the shape shown.

[0081] exist Figure 1In this embodiment, 1 is a straight pipe type pipe in which a flow path inside the pipe 1 is provided with a diaphragm (not shown) in the flow direction, and two points of the diaphragm in the flow direction are supported by two support members (not shown) to the inner wall of the pipe 1. A magnetic body (not shown) such as a permanent magnet is fixed to the diaphragm, an exciter 2 is disposed at a position opposite to the magnetic body, and a first vibration detector 3 and a second vibration detector 4 are disposed at equal distances from the respective positions of the two support members, and the first vibration detector 3 and the second vibration detector 4 are located at symmetrical positions with the exciter 2 as the center.

[0082] The two support members are disposed at positions corresponding to the nodes of the first natural vibration mode when the diaphragm is in a completely free state.

[0083] In addition, the exciter 2 is excited by an excitation circuit 5, and the output signals of the first vibration detector 3 and the second vibration detector 4 are input to a phase difference measurer 6. The excitation circuit 5 excites the diaphragm at a period of the first bending natural vibration frequency of the diaphragm in a state in which the pipe 1 is filled with the fluid. The vibration of the diaphragm is measured as a vibration displacement or a vibration waveform by the first vibration detector 3 and the second vibration detector 4. The phase difference measurer 6 feeds back the measurement signals obtained by the first vibration detector 3 and the second vibration detector 4 to the excitation circuit 5 to change the excitation frequency in such a manner that the output signals of the first vibration detector 3 and the second vibration detector 4 are always maximum. In addition, the phase difference measurer 6 measures the phase difference of the output signals of the first vibration detector 3 and the second vibration detector 4 and outputs the measurement result to an arithmetic circuit 7. The arithmetic circuit 7 can calculate the mass flow rate of the measurement fluid on the basis of the measurement result of the phase difference measurer 6.

[0084] In addition, a left support body 8a and a right support body 8b that support both end portions of the pipe 1 as fixed ends with respect to the vibration are provided, and the exciter 2, the first vibration detector 3, and the second vibration detector 4 are supported by a first frame 9a that is connected to the support bodies 8a and 8b. A second frame 9b that is disposed so as to be symmetrical to the first frame 9a with respect to the center axis 1a in the longitudinal direction of the pipe 1 is also connected to the support bodies 8a and 8b. The exciter 2 is located at the center portion of the first frame 9a at equal distances from the left support body 8a and the right support body 8b, and the first vibration detector 3 and the second vibration detector 4 are located at symmetrical positions with the exciter 2 as the center on the first frame 9a.

[0085] The exciting circuit 5 excites the vibrator 2, and the vibration plate provided in the flow path inside the pipe 1 is vibrated. At this time, the fluid in contact with the vibration plate also vibrates as an added mass together with the vibration plate. Therefore, the vibration plate is excited by the exciting circuit 5, the vibrator 2, at a first bending natural vibration frequency to which a portion of the added mass of the fluid is added, so that the output signals of the first vibration detector 3 and the second vibration detector 4 are always maximized.

[0086] As a result, in the absence of the flow of the fluid, the vibration plate vibrates in a first bending natural vibration mode in which the center between the two support members is a node, and the vibration waveforms of the two points measured by the first vibration detector 3 and the second vibration detector 4 are in the same phase and have the same amplitude.

[0087] On the other hand, in the presence of the flow of the fluid, since the added mass has a moving speed, a Coriolis force acts on the vibration plate, and a vibration that twists the center of the vibration plate is applied, and a phase deviation is generated in the vibration waveforms of the first vibration detector 3 and the second vibration detector 4. The phase deviation is measured by the phase difference measurer 6, and the measurement result is input to the arithmetic circuit 7, and thus the mass flow rate can be calculated by the arithmetic circuit 7.

[0088] That is, the Coriolis force F applied to the vibration plate is expressed by the following equation using the added mass m and the angular velocity ω of the vibration, and the moving speed V of the fluid.

[0089] [F] = -2m[ω] · [V]

[0090] The added mass m described above is a function of the density of the fluid and the planar size of the vibration plate and the natural vibration mode, and in an actual measurement system, it can be expressed as a function of the density based on experimental constants related to a fluid whose density is known. In addition, since the output signals of the first vibration detector 3 and the second vibration detector 4 are fed back to the exciting circuit 5, and the frequency is always scanned in such a manner that the vibration amplitude is maximized, the density of the unknown fluid can be calculated from the measurement result of the absolute value of the first natural vibration frequency. Therefore, the density and the mass flow rate of the fluid to be measured can be calculated simultaneously.

[0091] As described above, the vibration plate that receives the Coriolis force from the fluid is arranged in the axial direction inside the pipe 1, and the vibration plate is supported at two points corresponding to the nodes of the first natural vibration mode in a free state, and is excited at a first bending natural vibration frequency, and the vibration waveforms are detected by the first vibration detector 3 and the second vibration detector 4 arranged between the two support points, and the mass flow rate is calculated based on the phase deviation, and thus the entire pipe does not need to be vibrated, and a small mass flow meter with excellent responsiveness can be realized.

[0092] In addition, the vibration plate is excited by a magnetic body such as a permanent magnet fixed to the vibration plate and an exciter 2 provided outside the pipe 1, the vibration plate has a mass distribution in which a moment of inertia with respect to the support point is zero including the mass of the magnetic body fixed to the vibration plate, and thus does not excite a primary natural vibration due to vibration of the support point, and a mass flowmeter that is less affected by external vibrations can be achieved.

[0093] An important feature of the present application is that "in a case where a mass of the first vibration detector is set as m1, a mass of the second vibration detector is set as m2, a mass of the exciter is set as m3, m3 is greater than a total of m1 and m2, in a case where the mass of the first vibration detector is set as m1, the mass of the second vibration detector is set as m2, the mass of the exciter is set as m3, a total of m1, m2, and m3 is set as m, a mass of the pipe is set as Mt, a mass of the fluid in the pipe is set as Mf, and M = Mt + m + Mf, m = 0.4M or less", and thus the feature is described below.

[0094] As shown in (a) and (b) of FIG. 1, two sinusoidal waves output from the two vibration detectors having masses of m1 and m2 have a phase difference time Figure 12 between them. The two vibration detectors are arranged at symmetrical positions with respect to the exciter having a mass of m3 provided at the center of the pipe 1 in which the fluid flows at a flow rate v in the Coriolis mass flowmeter.

[0095] In addition, the Coriolis frequency ω of the sinusoidal waveform has the following relationship with the density p.

[0096] That is, if a length of the pipe 1 is set as L, an elastic modulus of the pipe 1 is set as E, a cross-sectional moment of inertia is set as I, and a cross-sectional area is set as A, then:

[0097] ω ∝ (1 / L 2 )(EI / pA) 1 / 2 (1).

[0098] Here, if an outer diameter of the pipe 1 is set as D O , an inner diameter is set as D i , the cross-sectional moment of inertia I is expressed as:

[0099] I ∝ D O 4 -D i 4 (2),

[0100] is only a function of the size of the pipe 1.

[0101] In addition, the denominator pA of the above formula (1) is the total mass per unit length of the pipe 1, and therefore if the density of the pipe 1 is set to pt, and the density of the fluid flowing in the pipe 1 is set to pf, the mass mt per unit length of the pipe 1 is "pt x π x (1 / 4) (D O 2 - D i 2 ) ", the mass mf per unit length of the fluid is "pf x π x (1 / 4) (D i 2 ) ", and pA can be replaced with "mt + mf".

[0102] Therefore, if the shape and size of the pipe 1 are the same, and the same fluid flows through, the Coriolis frequency ω is only a function depending on the elastic modulus E and the density pt of the material of the pipe 1. Therefore, if the shape and size of the pipe 1 are the same as a precondition, the mass of the pipe 1 is set to Mt, and the mass of the fluid in the pipe 1 is set to Mf, mt and mf can be replaced with Mt and Mf, respectively. Also, since the additional mass such as the mass ml, m2 of the vibration detector, and the mass m3 of the exciter is added to the pipe 1 independently of the mass Mt of the pipe 1 and the mass Mf of the fluid, the total mass M of the pipe 1 can be expressed as M = Mt + m + Mf.

[0103] Therefore, the above formula (1) can be expressed by the following formula (3):

[0104] ω ∞ (EI / M) 1 / 2 (3).

[0105] If the shape, size, and material of the pipe 1 are the same, the variable in the total mass M (Mt + m + Mf) of the pipe 1 is the mass Mf of the fluid, and Mf is a function of the density pf. Therefore, according to the above formula (3), it is inferred that the Coriolis frequency ω is a function of the density pf. That is, it is inferred that the small amount Δω of the Coriolis frequency ω is a function of the small amount Δpf of the fluid density. In general, the sensitivity (amount of change in frequency) of the Coriolis mass flowmeter (also a densimeter) to the amount of change in fluid density is referred to as the frequency density margin (Hz / (g / cm 3 ). The amount of change (small amount Δpf) in the fluid density can also be referred to as the measurement resolution of the fluid density, and the amount of change (small amount Δω) in the Coriolis frequency ω can also be referred to as the measurement resolution of the Coriolis frequency, and therefore it can be said that the fluid density measurement sensitivity can be inferred based on the frequency density margin (Hz / (g / cm 3 ).

[0106] In the case of a gas, since it is a compressive fluid, it is necessary to compare the pressure and temperature fixedly. If a case of 1 atm and 0°C is considered, the density of hydrogen is 0.0898 (g / L) and the density of helium is 0.1769 (g / L). The difference in density between the two is 0.0871 (g / L), and a sensitivity capable of detecting this difference in density is required.

[0107] Here, the phase difference time Figure 12 and the Coriolis frequency ω are detected from two sinusoidal waveforms outputted from the two vibration detectors shown in (c) of the above-described embodiment. The usual method of the detection method of the phase difference time Figure 1 and the Coriolis frequency ω will be described. In the usual method, the output signals from the first vibration detector 3 and the second vibration detector 4 are inputted to a phase difference measurer 6. The phase difference measurer 6 is constituted of a preamplifier and an analog-digital conversion circuit, and after conversion to a digital signal in the phase difference measurer 6, a software operation is performed by an operation circuit 7, and the phase difference time and the Coriolis frequency ω can be obtained by the operation. Therefore, usually, the detection resolution of the phase difference time and the Coriolis frequency ω is restricted by the analog-digital conversion resolution of the phase difference measurer 6 and the fast Fourier transform resolution of the operation circuit 7.

[0108] Usually, the Coriolis frequency ω which is determined dominantly by the shape and size of the pipe through which the measurement fluid flows and the like is a frequency of about 100 Hz to 1 kHz, and for this frequency band, the analog-digital conversion resolution of the usual phase difference measurer 6 and the fast Fourier transform resolution bandwidth of the operation circuit 7 are about 1 mHz. In the case where the frequency resolution is set to 1 mHz in accordance with the above estimation, if the frequency density margin is converted from the fluid density measurement resolution Δρ = 0.0871 (g / L) = 0.0871 (mg / cm 3 ) and the Coriolis frequency measurement resolution Δω = 1 mHz, it corresponds to Δω / Δρ = 1 (mHz) / 0.0871 (mg / cm 3 ) = 11.5 (Hz / (g / cm 3 )). If the margin is estimated as about 4 to 5 times the Coriolis frequency measurement resolution as the measurement accuracy, the frequency density margin is 46 to 58 Hz / (g / cm 3 ).

[0109] In the case where the mass of the first vibration detector is set to ml, the mass of the second vibration detector is set to m2, the mass of the exciter is set to m3, the mass of the pipe is set to Mt, and the mass of the fluid in the pipe is set to Mf, Figure 13is a graph in which the ratio of the additional mass m (m1+m2+m3) to the mass M (Mt+m+Mf) of the entire pipe is taken as the horizontal axis, and the frequency density margin (Hz / (g / cm 3 )) is taken as the vertical axis, in the case where the material of the pipe is CFRTP (symbol "●"), SUS316 (symbol "▲") or PFA (symbol "■"), and m3=m1+m2, Figure 14 is a graph in which the ratio of the additional mass m (m1+m2+m3) to the mass M (Mt+m+Mf) of the entire pipe is taken as the horizontal axis, and the frequency density margin (Hz / (g / cm 3 )) is taken as the vertical axis, in the case where the material of the pipe is CFRTP, and in the case where the mass of the first vibration detector is taken as m1, the mass of the second vibration detector is taken as m2, and the mass of the exciter is taken as m3, the symbols "■", "▲", "●" respectively indicate the case where the ratio of m3 / (m1+m2) is 3 / 1, 2 / 1, 1 / 1.

[0110] CFRTP (carbon fiber reinforced fluororesin), PFA, and SUS316 used in Figure 13 and Figure 14 are shown in Table 1 below. The density (g / cm 3 ), the elastic modulus (GPa), and the linear expansion coefficient (10 -6 / °C) of each of them are shown in Table 1 below. In Figure 13 and Figure 14 , the shape, the size of the pipe other than the material of the pipe, and the setting positions of the exciter and the vibration detector are all the same conditions. Since the purpose is to measure a small flow rate, the outer diameter and the inner diameter of the pipe used for the calculation are 1.057 mm and 0.794 mm, respectively. Therefore, since the mass of the pipe is small, it can be said that increasing the ratio of the additional mass m to the total mass M increases the degree of freedom of design. In general, the exciter needs to be energized to vibrate the pipe at the resonance frequency, and an electromagnetic coil or the like is used, but it inevitably serves as a certain degree of mass. On the other hand, if the vibration detector uses a passive vibration sensor, it is possible to use an AE sensor or an optical displacement sensor using a piezoelectric element that can be made lighter as the additional mass instead of a heavy object such as an electromagnetic coil.

[0111] [Table 1]

[0112]

[0113] According to Figure 13When using PFA for piping, a sufficient frequency density margin cannot be obtained. This is because existing technologies using PFA for piping intended for measuring fluid flow do not address the rationale for density measurement. Furthermore, in SUS316, which is commonly used as a piping material, a m = 0.2 M or less must be designed to achieve a sufficient frequency density margin. On the other hand, when using CFRTP as a piping material, a sufficient frequency density margin can be obtained if m = 0.4 M or less.

[0114] For the Coriolis frequency ω, if the shape and dimensions (length, outer diameter, inner diameter) of the piping supplying the fluid flow are constant, then equation (3), as in equation (4), becomes only a function of the elastic modulus E of the piping and the total mass M (=Mt+m+Mf):

[0115] ω∝(E / M) 1 / 2 (4).

[0116] Furthermore, if the fluid density is constant, then Mf is a constant. Additionally, Mt is only a function of the pipe density ρt; if the material properties of the pipe are constant, then the elastic modulus E and Mt are constants. Therefore, focusing on the denominator, equation (4) can be rewritten as:

[0117] ω∝(Mt+m+Mf) -1 / 2 (5).

[0118] Therefore, according to equation (5), it can be assumed that the offset of ω Δω depends on the ratio of m / (Mt+m+Mf).

[0119] The additional mass m is the sum of the mass m3 of the exciter and the masses m1 and m2 of the vibration detector, but it is usually designed so that m1 = m2. Therefore, the additional mass m can also be expressed as m = m3 + 2 × m1.

[0120] The vibrator is located in the center of the piping, such as... Figure 12 As in (a), the piping is excited to vibrate, causing fluid to flow, thereby... Figure 12 As in (b), torsional vibration caused by Coriolis force is generated in the piping with the vibrator as the rotation axis. In this case, the mass m3 of the vibrator on the rotation axis of the torsional vibration does not contribute to the moment of inertia of the torsional vibration; only the mass (m1+m2) of the vibration detector is added to the moment of inertia of the torsional vibration. The added moment of inertia causes a change in the torsional vibration frequency. This torsional vibration frequency is the Coriolis frequency, and the offset Δω of the Coriolis frequency depends on the proportion of the mass (m1+m2) of the vibration detector in the added mass m. Therefore, when the ratio of m / (Mt+m+Mf) is a single value, by changing the ratio of m3 / (m1+m2), such as... Figure 14 As shown, the frequency density margin changes.

[0121] According to Figure 14 It is known that, when the mass of the first vibration detector is set to m1, the mass of the second vibration detector is set to m2, and the mass of the exciter is set to m3, the ratio of the added mass m with respect to the total mass M (= Mt+ m + Mf) is set to m = 0.4M or less when the frequency density margin is set to 46 mHz / (g / cm 3 ) when m3 / (m1+m2) = 1, m = 0.6M or less when m3 / (m1+m2) = 2, and m = 0.8M or less when m3 / (m1+m2) = 3. Further, according to Figure 14 , the frequency density margin is 55 Hz / (g / cm 3 ) when m = 0.4M and m3 / (m1+m2) = 2, and the frequency density margin is 61 Hz / (g / cm 3 ) when m = 0.4M and m3 / (m1+m2) = 3. Therefore, by making the ratio of m3 / (m1+m2) greater than 1, it is possible to improve the frequency density margin. (It is possible to increase the design freedom of the exciter and the vibration detector)

[0122] Figure 15is a schematic configuration diagram of a second embodiment of the Coriolis mass flowmeter of the present application including related devices. The second embodiment is provided with a first differential circuit 121 and a second differential circuit 121a, and an electromagnetic drive coil 2a (corresponding to a magnetic body such as a permanent magnet described later) as an exciter, and electrostatic capacitance sensors as the first vibration detector 3a and the second vibration detector 4a are provided in the first frame 9a. The electromagnetic drive coil 2a is located at the center of the first frame 9a at an equal distance from the left support 8a and the right support 8b, and the first vibration detector 3a and the second vibration detector 4a are located at symmetrical positions with the electromagnetic drive coil 2a as the center on the first frame 9a. In addition, electrostatic capacitance sensors as the first vibration detector 3a and the second vibration detector 4a are also supported on the second frame 9b in a manner such that they are located at symmetrical positions with respect to the first vibration detector 3a and the second vibration detector 4a supported on the first frame 9a across the length direction center axis 1a of the pipe 1. Furthermore, the pipe 1 is provided with a magnetic body 2b such as a permanent magnet as an exciter, a non-magnetic body 2c located at a position symmetrical to the magnetic body 2b with respect to the length direction center axis 1a of the pipe 1 and having the same shape and mass as the magnetic body 2b, and metal thin films 3b and 4b. In this way, if the first differential circuit 121 that obtains the difference in the output of the first vibration detector 3a located at a symmetrical position across the length direction center axis 1a of the pipe 1 and the second differential circuit 121a that obtains the difference in the output of the second vibration detector 4a are provided, the effect of removing the in-phase signal such as external vibration by measuring the phase difference in the output of each differential circuit 121 and 121a is obtained.

[0123] Here, in a case where the mass of the first vibration detector is set to ml, the mass of the second vibration detector is set to m2, and the mass of the exciter is set to m3, m3 is greater than the sum of ml and m2, the mass of the first vibration detector 3a supported on the first frame 9a and the mass of the first vibration detector 3a supported on the second frame 9b are each ml / 2, the mass of the second vibration detector 4a supported on the first frame 9a and the mass of the second vibration detector 4a supported on the second frame 9b are each m2 / 2, and if the mass of the magnetic body 2b and the mass of the non-magnetic body 2c are each m3 / 2, the same mass is arranged at a symmetrical position across the length direction center axis 1a of the pipe 1, and thus the same moment of inertia is generated with respect to the length direction center axis 1a of the pipe 1. In this way, by making the moment of inertia in the vibration direction of the pipe 1 equivalent, the vibration becomes axisymmetrical, and the effect of being able to remove the in-phase vibration component by obtaining the difference is obtained.

[0124] Figure 16is a schematic configuration diagram of a third embodiment of the Coriolis mass flowmeter of the present application including related devices. The third embodiment is provided with a first differential circuit 121 and a second differential circuit 121a, and a piezoelectric element 2d as an exciter, a sound sensor as a first vibration detector 3c and a second vibration detector 4c are provided in the first frame 9a. The piezoelectric element 2d is located at the center of the first frame 9a at equal distances from the left support 8a and the right support 8b, and the first vibration detector 3c and the second vibration detector 4c are located at symmetrical positions with the piezoelectric element 2d as the center on the first frame 9a. Further, the sound sensors as the first vibration detector 3c and the second vibration detector 4c are supported in the second frame 9b in a manner that they are located at symmetrical positions with respect to the first vibration detector 3c and the second vibration detector 4c supported in the first frame 9a across the lengthwise central axis 1a of the pipe 1. Further, the pipe 1 is provided with an equivalent mass 2e.

[0125] Figure 17 is a schematic configuration diagram of a fourth embodiment of the Coriolis mass flowmeter of the present application including related devices. The fourth embodiment is provided with a first differential circuit 121 and a second differential circuit 121a, and a coil 2a as an exciter for electromagnetic drive, an optical displacement sensor as a first vibration detector 3d and a second vibration detector 4d are provided in the first frame 9a. The coil 2a is located at the center of the first frame 9a at equal distances from the left support 8a and the right support 8b, and the first vibration detector 3d and the second vibration detector 4d are located at symmetrical positions with the coil 2a as the center on the first frame 9a. Further, the optical displacement sensors as the first vibration detector 3d and the second vibration detector 4d are supported in the second frame 9b in a manner that they are located at symmetrical positions with respect to the first vibration detector 3d and the second vibration detector 4d supported in the first frame 9a across the lengthwise central axis 1a of the pipe 1. Further, the pipe 1 is provided with a magnetic body 2b as an exciter, a non-magnetic body 2c located at a position symmetrical to the magnetic body 2b with respect to the lengthwise central axis 1a of the pipe 1 and having the same shape and mass as the magnetic body 2b, and metal thin films 3b, 4b.

[0126] Figure 18is a schematic configuration diagram of a fifth embodiment of the Coriolis mass flowmeter of the present application including related devices. The fifth embodiment is provided with a first differential circuit 121 and a second differential circuit 121a, and on a first frame 9a, an electromagnetic drive coil 2a as an exciter, and acceleration sensors as first and second vibration detectors 3e and 4e. The electromagnetic drive coil 2a is located at a central portion of the first frame 9a at an equal distance from a left support 8a and a right support 8b, and the first and second vibration detectors 3e and 4e are located at symmetrical positions with respect to the electromagnetic drive coil 2a on the first frame 9a. In addition, acceleration sensors as the first and second vibration detectors 3e and 4e are supported on a second frame 9b in a manner such that they are located at symmetrical positions with respect to the first and second vibration detectors 3e and 4e supported on the first frame 9a with respect to a lengthwise central axis 1a of the pipe 1. Further, the pipe 1 is provided with a magnetic body 2b as an exciter and a non-magnetic body 2c located at a position symmetrical to the magnetic body 2b with respect to the lengthwise central axis 1a of the pipe 1 and having the same shape and mass as the magnetic body 2b.

[0127] BRIEF DESCRIPTION OF DRAWINGS

[0128] 1 pipe

[0129] 2, 2a, 2d exciter

[0130] 2b magnetic body such as a permanent magnet

[0131] 2c non-magnetic body

[0132] 2e equivalent mass

[0133] 3, 3a, 3c, 3d, 3e first vibration detector

[0134] 3b metal film

[0135] 4, 4a, 4c, 4d, 4e second vibration detector

[0136] 4b metal film

[0137] 5 excitation circuit

[0138] 6 phase difference measurer

[0139] 7 arithmetic circuit

[0140] 8a left support

[0141] 8b right support

[0142] 9a first frame

[0143] 9b second frame

[0144] 121 first differential circuit

[0145] 121a second differential circuit

Claims

1. A Coriolis mass flowmeter characterized by, A Coriolis mass flowmeter has a straight pipe for flowing a measurement fluid, an exciter for exciting the pipe, first and second vibration detectors for detecting vibration states of the pipe, and a support body for supporting both ends of the pipe so that both ends of the pipe are fixed ends with respect to vibration, the exciter, the first and second vibration detectors being supported by a frame which is linked to the support body, a mass flow rate of the fluid flowing in the pipe being calculated based on a phase difference of vibration waveforms detected by the first and second vibration detectors, the pipe, the support body and the frame being formed of a carbon fiber-reinforced fluororesin, in a case where a mass of the first vibration detector is set to m1, a mass of the second vibration detector is set to m2, a mass of the exciter is set to m3, a total of m1, m2 and m3 is set to m, a mass of the pipe is set to Mt, a mass of the fluid in the pipe is set to Mf, and M = Mt + m + Mf, m3 is equal to or more than a total of m1 and m2, [m3 / (m1+m2)] = 1 when m = 0.4M or less, [m3 / (m1+m2)] = 2 when m = 0.6M or less, and [m3 / (m1+m2)] = 3 when m = 0.8M or less.

2. The Coriolis mass flowmeter according to claim 1, wherein The carbon fiber-reinforced fluororesin has a volume content of carbon fiber of 20 to 40%.

3. The Coriolis mass flowmeter according to claim 2, wherein The first and second vibration detectors are acceleration sensors located at symmetric positions centered on the exciter.

4. The Coriolis mass flowmeter according to claim 2, wherein The first and second vibration detectors are sound sensors located at symmetric positions centered on the exciter.

5. The Coriolis mass flowmeter according to claim 2, wherein The first and second vibration detectors are electrostatic capacitance sensors to which a metal film is attached to the pipe.

6. The Coriolis mass flowmeter according to claim 2, wherein The first and second vibration detectors are optical displacement sensors to which a metal film is attached to the pipe.

7. The Coriolis mass flowmeter according to claim 3 or 4, wherein The exciter is a piezoelectric element.

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