Patent ID: 7698956

Claim:
A Coriolis flow meter for detecting a phase difference and/or a vibration frequency proportional to a Coriolis force to thereby obtain a mass flow rate and/or a density of a fluid, the Coriolis flow meter comprising: two flow tubes having end portions, each of the two flow tubes having a tube axis extending in a direction defining a Y-axis direction, the two flow tubes being arranged aligned with each other with a predetermined distance therebetween; a flow tube fixing member fixing the end portions of the two flow tubes; a drive portion comprising a coil and a magnet, the drive portion being attached to the two flow tubes at a vibration antinode position for vibrating the two flow tubes in a direction defining an X-axis direction; a phase difference detection portion configured to detect vibrations of the two flow tubes, and configured to detect a phase difference proportional to a Coriolis force, the phase difference detection portion being at a position of the two flow tubes different from the position of the drive portion; and a plate spring having a first end fixed at, or in a vicinity of, the vibration antinode position of a first flow tube of the two flow tubes, and a second end fixed to the flow tube fixing member, the plate spring configured to restrict a direction of vibration of the first flow tube, wherein the plate spring is substantially planar and substantially X-shaped, and fixed to two portions of the first flow tube and to two portions of the flow tube fixing member, wherein the plate spring is configured such that a rigidity of the plate spring in the X-axis direction is lower than a rigidity of the plate spring in the Y-axis direction and lower than a rigidity of the plate spring in a Z-axis direction, the Z-axis direction being a direction orthogonal to each of the X-axis direction and the Y-axis direction, and wherein the rigidity of the plate spring is such that the direction of vibration of the first flow tube in a direction other than the X-axis direction is restricted by the rigidity of the plate spring in the Y-axis direction and the rigidity of the plate spring in the Z-axis direction.