JPH01235816A - Coriolis type flow meter - Google Patents

Abstract

PURPOSE:To make flow rate measurement having linearity and reproducibility with high accuracy by providing a shielding plate consisting of a ferromagnetic material which shields the magnetic lines of force leaking from a flow rate detecting part on the spacing between a U-shaped tube and the flow rate detecting part. CONSTITUTION:The flow meter is constituted of the U-shaped tube 1 which causes fluid, which is a material to be measured, to flow, a pair of the flow rate detecting parts 2 which detect the twist size of the U-shaped tube and the shielding plate 3 disposed along the side wall face of the U-shaped tube 1 between the U-shaped tube 1 and the detecting parts 2. The U-shaped tube 1 consists of a pair of straight parts 1a, 1b and a curved part 1c and is so constituted that the curved part 1c is twisted by receiving Coriolis force according to the flow rate of the fluid flowing in the inside. The magnetic lines of force generated from the permanent magnet 2a are thereby passed in the shielding plate 3 along the plate surface and do not, therefore, flow out to the part of the U-shaped tube 1. Namely, the fluid flowing in the U-shaped tube 1 has always the specified magnetic flux distribution regardless of whether the fluid is magnetic fluid or not. The exact induced current having the linearity and reproducibility corresponding to the flow rate of the fluid passing the U-shaped tube 1 is, therefore, generated in a movable coil 2b.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention utilizes the property that a U-shaped tube in which liquid flows is twisted in proportion to the flow rate due to the Coriolis force.
This invention relates to a highly accurate Coriolis flowmeter that determines the flow rate by converting the magnitude of the second twist into an electrical magnitude using electromagnetic induction.

(Prior Art) A Coriolis flow meter that can measure liquid flow rate with high accuracy is known. This flowmeter uses Coriolica,
Coriolis is an apparent force that acts on a moving object in a rotating coordinate system.If the mass of the object is m1, the angular velocity in the rotating coordinate system is ω, and the velocity of the object in the rotating coordinate system is V, then it is a force expressed as 2mω■. It is. When a fluid passes through the U-shaped tube, if a vibration is applied to the U-shaped tube in a direction perpendicular to the plane in which the U-shaped tube is contained, the above-mentioned Coriolika acts on the fluid, causing the U-shaped tube to
A phenomenon occurs in which the curved portion of the tube is twisted, and the magnitude of the twist angle (accurately, 1/2 of the amplitude of the twist angle, hereinafter the same) changes with the mass and velocity of the fluid. Based on this principle, the flowmeter uses electromagnetic induction to convert the magnitude of the twist angle of the curved portion of the U-shaped tube into an electrical magnitude in the detection section, thereby measuring the flow rate. .

(Problem to be Solved by the Invention) The detection unit includes an induction coil that moves (vibrates) in accordance with the twisting of the U-shaped tube, and a magnet that generates lines of magnetic force passing through the induction coil. The amount of twist in the U-shaped tube is determined based on the current generated in the coil according to the number of lines of magnetic force that cross it.

However, due to the structural requirements of the flowmeter, the detection section is placed near the U-shaped tube, and the lines of magnetic force generated by the magnet that leak outside the detection section pass through the U-shaped tube. . For this reason, when measuring the flow rate of magnetic fluid, the magnetic lines of force generated by the magnet are affected by the magnetic permeability and flow velocity of the magnetic fluid flowing through the U-shaped tube, making it impossible to measure the flow rate accurately and reproducibly. There was a problem.

The present invention was made to solve such problems, and an object of the present invention is to provide a Coriolis flowmeter that can measure the flow rate with high accuracy even when measuring magnetic fluid with the Coriolis flowmeter. It is something to do.

(Means for Solving the Problems) The Coriolis flowmeter of the present invention includes a U-shaped tube through which liquid flows, and the amount of twist in this U-shaped tube that is converted into an electrical value using electromagnetic induction. A shielding plate made of a ferromagnetic material is provided between the converting flow rate detection section and the leakage magnetic force lines from the detection section to prevent these magnetic force lines from passing through the U-shaped tube.

(Function) As described above, the Coriolis flowmeter of the present invention has a detection part and a
A shielding plate made of ferromagnetic material is provided between the tube and the tube. When the leakage magnetic field lines from the detection section enter this shielding plate, they pass inside the shielding plate along the plate surface, so that they cannot pass in the direction of the U-shaped tube and are blocked by this shielding plate. Therefore, even when measuring the flow rate of magnetic fluid, the leakage magnetic field lines are not affected by the magnetic fluid flowing through the U-shaped tube, and the magnetic flux distribution does not change at all even if the permeability or flow rate of this magnetic fluid changes. Linearity and repeatability as a flowmeter are not lost.

(Example) An example of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a Coriolis flowmeter according to an embodiment of the present invention. It consists of a pair of flow rate detectors 2 that detect the size of the U-shaped tube 1, and a shielding plate 3 disposed along the side wall surface of the U-shaped tube 1 between the U-shaped tube 1 and each flow rate detector 2. has been done. Further, the U-shaped tube 1 has a pair of straight parts 1a and lb as shown in the figure.
and a curved part 1c that connects these straight parts, and the curved part 1c is twisted by the Coriolis force depending on the flow rate of the liquid flowing inside.

Note that this twisting is caused by the phase shift of the vibration in the direction perpendicular to the plane of FIG. 1 before and after the liquid flow direction of the curved portion 1c. The flow rate detection unit 2 is composed of a permanent magnet 2a and a moving coil 2b connected to the outer wall of each straight portion 1a, lb of the U-shaped tube 1. The movable coil 2b is moved in response to the vibrations of the straight portions la and lb to cross the lines of magnetic force generated from the permanent magnet 2a, thereby generating an induced current in each coil 2b. After this, the two coils 2
U-shaped tube bending portion 1c based on the current signal generated from b.
The magnitude of the twist is measured, and the flow rate of the fluid is detected based on this measured value. The shielding plate 3 is made of a ferromagnetic material such as iron or nickel, and has holes or slits only at the connection portion between the U-shaped tube 1 and the moving coil 2b.

As described above, the flow rate detection unit 2 detects the magnitude of the twist by electromagnetic induction, and the lines of magnetic force from the permanent magnet 2a pass through the movable coil.

On the other hand, since the detection unit 2 is disposed close to the U-shaped tube 1, the lines of magnetic force from the permanent magnet 2a would pass through the U-shaped tube 1 if the shielding plate 3 were not present. That is, the magnetic flux distribution becomes as shown by the dotted line in FIG. When the magnetic lines of force pass through the U-shaped tube 1 in this way, the lines of magnetic force are affected by the magnetic permeability and flow rate of the magnetic fluid when all the magnetic fluids are determined, making it impossible to perform reproducible measurements. On the other hand, if a shielding plate 3 as shown in FIG. 1 is provided between the detection part 2 and the U-shaped tube 10 as in the Coriolis flowmeter of the present invention, the lines of magnetic force generated from the permanent magnet 1 will be
Since it passes through the inside of the tube along the plate surface, it does not flow out to the U-shaped tube 1.

That is, the magnetic flux distribution in this case becomes as shown by the dotted line in FIG. 3, and the magnetic flux distribution is always constant regardless of whether the fluid flowing through the U-shaped tube 1 is a magnetic fluid or not. This allows the movable coil 2b to generate an accurate induced current with reproducibility and linearity according to the flow rate of the fluid passing through the U-shaped tube 1.

In the embodiment described above, the coil 2b is moved in accordance with the twisting of the U-shaped tube, but it is also possible to use the permanent magnet 2a in a movable manner and fix the coil.

Note that it is also possible to use an electromagnet instead of a permanent magnet.

(Effect of the invention) According to the Coriolis flowmeter of the present invention, using a shielding plate,
Since magnetic lines of force leaking from the detection part are prevented from flowing into the U-shaped tube, even when the object to be measured is a magnetic fluid, linearity is maintained without being affected by the magnetic permeability or flow rate of the magnetic fluid.
It is possible to perform highly accurate flow rate measurements with reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a Coriolis flowmeter according to an embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams for explaining the operation of the flowmeter shown in FIG. 1. 1... U-shaped tube 2... Flow rate detection section 2a.
...Permanent magnet 2b...Movable coil 3...
·Shield

Claims (1)

[Claims] A U-shaped tube in which a liquid flows, and when the curved portion is twisted by the Coriolis force generated when the liquid flows through a curved portion of the U-shaped tube, the twisting In a Coriolis flowmeter comprising a flow rate detection section that converts a size into an electrical size using electromagnetic induction, leakage from the flow rate detection section is provided between the U-shaped tube and the flow rate detection section. A Coriolis flowmeter characterized by having a shielding plate made of a ferromagnetic material that shields magnetic lines of force.