JPH0331725A - Coriolis flow meter - Google Patents

Abstract

PURPOSE:To increase a resonance driving wave number and to improve detecting accuracy by forming a curved conduit by resin or the like having excellent workability and anticorrosion and fixing a metallic rod with high rigidity to increase Coriolis force. CONSTITUTION:A U-shape curved conduit 2 consisting of a resin-made tube with uniform thickness is fixed to fixing points 21, 22 formed by opening the pipe wall of a supporting pipe 1 and a metallic rod 5 with high rigidity is fixed on the 2nd axis X-Y rectangular to the 1st axis X-X connecting the points 21, 22 and the 1st and 2nd tubes 1, 2 are fixed at points 5b, 5a. The Coriolis flow meter is sine-driven around the 1st axis and its frequency is determined by the composite frequency between the tube 2 and the rod 5 so as to be strongly governed by the rod 5. Thereby, the characteristic frequency of the pipe 2 is improved, the Coriolis force is improved and a flow rate can be detected with high sensitivity by detecting means 41, 42.

Description

[Detailed Description of the Invention] The present invention is a Coriolis flowmeter, more specifically, a curved conduit is constructed of a low-rigidity material such as a low-rigidity resin, and the curved conduit is driven at a natural frequency. The present invention relates to a Coriolis flowmeter that increases the natural frequency and increases the Coriolis force to improve detection sensitivity.

The Coriolis flowmeter that measures the mass flow rate of the Maru JO creation has a support point in the flow tube through which the fluid flows, and when vibration is applied around the support point at an angular velocity ω, the Coriolis force that acts on the fluid is the angular velocity ω.
This method takes advantage of the fact that the mass flow rate m is proportional to the mass flow rate m.

A straight pipe or a curved pipe is used as the flow pipe, and if the flow pipe is a straight pipe, it is supported at two points sandwiching one section, but in the case of a curved pipe, a support interposed in the main flow pipe is used. It is fixed to the wall of the pipe so that it opens. The curved conduit has a first axis which is a line connecting the points of attachment to the support tube, and is perpendicular to the first axis.

It has a shape that is axially symmetrical to the second axis passing through the center of the fixing point. The curved conduit is driven sinusoidally about the first axis by e.g. electromagnetic movement means arranged on the second axis, resulting in a Coriolis force about the second axis. The Coriolis force is
It is measured as the time difference between the passage of the arms of the curved conduit through the stationary plane of the curved conduit at a symmetrical position with respect to the second axis of the curved conduit, the time difference being converted into a sinusoidal signal, usually by electromagnetic means.

The phase difference between the sinusoidal signals detected by both arms is determined and converted into a mass flow rate signal proportional to the phase difference.

As the above-mentioned curved conduit, a non-magnetic stainless steel pipe with excellent corrosion resistance is usually used.

Stainless steel metal pipes are used for the curved conduits in the Coriolis flowmeter described above, but it requires skill to curve accurately and axially symmetrically, and even stainless steel may be resistant to corrosion depending on the fluid being measured. Resin, hard rubber, etc. are used because the material is not sufficient. However, these resins have a low Young's modulus, and therefore have a low natural frequency ω, and the vibration amplitude cannot be increased in view of fatigue strength. There was a problem that force could not be detected. Similarly, when using a stainless steel tube, the Young's modulus changes greatly due to temperature changes, and the natural frequency ω also changes accordingly, so it was necessary to install a separate temperature sensor to compensate for the temperature.

The present invention was made to solve the above problem, and provides a Coriolis flowmeter that can measure the Coriolis force, that is, the mass flow rate, with high sensitivity even when a curved conduit is made of a low-rigidity material. The object of the present invention is to provide a support member, and a curved member having low rigidity that is supported on a first axis on the support member and is axially symmetrical to a second axis orthogonal to the first axis. with a conduit.

It consists of a driving means for vibrating the curved conduit around the second axis, and a detection means for detecting the Coriolis force generated around the second axis due to the vibration in the fluid flowing through the curved conduit. In a Coriolis flowmeter that detects mass flow rate from force, one end of an elastic body on a plane of symmetry including the second axis of the curved conduit is fixed to a support member, and the other end is fixed to the curved conduit, A pawn whose natural frequency around the first axis is higher than the natural frequency of the curved conduit, and the vibration frequency of the drive means is the natural frequency of the curved conduit and the elastic body around the first axis. It is a flow plan.

Figure 1 is a plan view showing the principle of the Coriolis flowmeter of the present invention, and in Figure 0, which shows a simplified configuration, 1 is a diagram showing the structure of the Coriolis flowmeter. 11 is a flange, and 12 is a blocking material that closes the flow inside the support tube 1 at the center.

Reference numeral 2 denotes a U-shaped curved conduit made of a low-rigidity resin tube of uniform thickness that is opened and fixed to the wall of the support tube 1, and 21 and 22 are points at which the opening is fixed.

The X-X axis is the first axis connecting the fixed points 21 and 22, and the Y-Y axis is f, which is perpendicular to the x-X axis and passes through the center between the fixed points 21 and 22.
J2 axis, and the curved conduit 2 is symmetrical with respect to the second axis. 3 is a driving means disposed on the second axis to sinusoidally drive the curved conduit 2 around the first axis, and is composed of a magnet 31 and a coil 32.

32 is a coil fixed to a fixed board (not shown);
is a magnet that is fitted into the coil and generates electromagnetic force through electromagnetic interaction with the magnetic flux caused by the separation current passed through the coil, and is fixed to the curved conduit 2. Reference numeral 5 denotes a highly rigid and elastic metal rod disposed on the second axis, and is fixed to the curved conduit 2 at 5a and to the support tube 1 at 5b. The metal rod 5 is preferably a constant elastic body such as Eling whose Young's modulus changes little with temperature. The Coriolis flowmeter having the above configuration is sinusoidally opened around the first axis by the driving means 3, and the sinusoidal driving frequency is the natural frequency around the first axis, and is a composite of the curved conduit 2 and the metal rod 5. The cross section and length of the metal rod 5 are determined so that the natural frequency of the metal rod 5 dominates the vibration frequency.

Therefore, the frequency is much higher than the natural frequency of the curved conduit 2. Furthermore, 41 and 42 are the aforementioned electromagnetic means which are disposed on both arms of the curved conduit 2 and detect the speed signal of each arm in order to detect the time difference between the two arms passing through the stationary plane of the curved conduit 2. It is. Since the natural frequency of the curved conduit 2 becomes higher, the Coriolis force increases accordingly and is detected with high sensitivity by the detection means. If the metal rod 5 is made of a constant elastic material, the natural frequency will not change due to temperature, and there will be no need for special temperature compensation.

FIG. 2 shows another embodiment, in which the main parts have the same configuration as that in FIG. 1, are given the same reference numerals, and will not be described further. In FIG. 2, the metal rod 51 is fixed on the Y-Y axis at one end to the support tubes 1 and 51b, while the other end is attached to both arms of the curved conduit 2 at 52a and 52b parallel to the first axis. It is fixed at 51a to the column 52 to be fixed. Post 52
It is preferable that the metal rod 51 be a lightweight columnar body with a small moment about the second axis.The length of the metal rod 51 shown in FIG. 2 is determined so as to provide a desired natural frequency within the drive frequency range.

FIG. 3 shows another embodiment of the support tube 1 in the plan view of FIG. In a side view of the curved conduit 2 viewed from the flow direction, the support tube 1 is parallel to the curved conduit 201 and 202 made of a low-rigid tube body.
The opening is fixed to the The curved conduits 201 and 202 are driven in a tuning fork shape relative to the support tube 1, and the driving means 3 is electromagnetically driven in the same manner as in the conventional example comprising a coil 32 and a stone 31. 401 and 402 are also similar to the electromagnetic Coriolis detection means 41 and 42 shown in FIGS. 1 and 2, and the coil 402 401 is a magnet.

Reference numerals 501 and 502 are metal rods shown in FIG. That is, in FIG. 3, the curved conduit 2, metal rod 5. By arranging the pillars 52 in parallel, the same effect as shown in FIG. 2 can be obtained. Alternatively, the main parts similar to those shown in Fig. 1 may be arranged in parallel.Although the curved conduit 2 was used as a U-shaped tube in this example, it is not limited to a U-shaped tube, and the curved conduit 2 is symmetrical to the second axis. Even in the case of a conduit, the same effect of increasing the natural frequency and increasing the Coriolis force can be obtained by fixing the metal rod 5 at the intersection of the curved conduit and the support tube 1 on the second axis.

Effects As mentioned above, according to the Coriolis flowmeter of the present invention, the Coriolis force is reduced and the detection sensitivity is improved by using a flexible curved conduit made of resin, rubber, etc., which has excellent workability and is resistant to contact. By fixing a highly rigid metal rod on the second axis, it is possible to increase the resonant drive frequency and thereby increase the Coriolis force, thereby improving detection sensitivity. By making the metal rod a constant elastic body, it is possible to detect landscapes with high accuracy over a wide range of temperatures without the need for temperature correction.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, and FIGS. 2 and 3 are diagrams showing other embodiments. 1... Support pipe, 2,201,202... Curved conduit,
3... Drive means, 41.42... Detection means, 5,5
01゜502...metal rod, 52,521,522...
・Strut. X Fig. Fig. 184 Fig.

Claims (1)

[Scope of Claims] 1. A supporting member, a curved conduit that is supported on a first axis on the supporting member and has low rigidity and is axially symmetrical to a second axis orthogonal to the first axis; A Coriolis device comprising a drive means for vibrating around two axes, and a detection means for detecting a Coriolis force generated around the second axis by vibration in the fluid flowing through the curved conduit, and detecting a mass flow rate from the Coriolis force. In the flowmeter, one end of an elastic body on a symmetrical plane including the second axis of the curved conduit is attached to a support member and the other end is attached to the curved conduit, and the natural vibration of the elastic body about the first axis is The Coriolis flowmeter is characterized in that the number of vibrations is higher than the natural frequency of the curved conduit, and the vibration frequency of the driving means is set to the natural frequency of the curved conduit and the elastic body around the first axis. 2. The Coriolis flowmeter according to claim 1, wherein one end of the rod-shaped elastic body is fixed to a support member, and the other end is fixed to the center of a support member fixed at symmetrical positions on both arms of the curved conduit. 3. The Coriolis flowmeter according to claim 1 or 2, wherein the vibrating body of the same shape and size, which is made of the curved conduit and the elastic body, is arranged in the shape of a tuning fork with the supporting member serving as a node. 4. The Coriolis flowmeter according to claim 1, 2 or 3, wherein the elastic body is a constant elastic material.