JP2538030Y2 - Mass flow meter - Google Patents

Description

[Detailed description of the invention]

[0001]

TECHNICAL FIELD The present invention relates to Coriolis flow meters, and more particularly, to driving a conduit in a Coriolis flow meter at the natural frequency of the conduit to detect Coriolis forces acting on the conduit and temperature of the conduit. The present invention relates to a temperature sensor mounting method in which a temperature sensor is interposed in a conduit in a Coriolis flowmeter for determining a mass flow rate and a density of a fluid to be measured which are not affected by temperature.

[0002]

2. Description of the Related Art A Coriolis flowmeter has a support point at two separated points of a conduit through which a fluid to be measured flows, and when driven around the support point, detects a mass flow rate from a Coriolis force acting on the conduit. It is total. In a typical Coriolis flowmeter, a support point is provided on a vibrating tube such as a straight tube or a curved tube through which a fluid flows, and when a vibration at an angular velocity ω is given around the support point, the Coriolis force acting on the fluid is a mass. This is a mass flow meter utilizing the fact that it is proportional to the flow rate m. In the case of a straight pipe, the vibrating pipe is supported at two points sandwiching one section, but in the case of a curved pipe, the curved pipe is cut off into a support pipe interposed in an external pipe. A plate is provided and fixedly supported so as to open with the partition plate interposed therebetween. When the bending tube is attached to the support tube, the direction of a line connecting the fixing points to the support tube is defined as a first axis, and the axis perpendicular to the first axis is defined as a second axis. They are arranged axisymmetrically. The bending tube is driven by a driving means such as an electromagnet so as to vibrate sinusoidally with a constant amplitude around the first axis, and as a result, Coriolis force is generated around the first axis. The Coriolis force is measured as a time difference between the two arms of the bending tube passing through the stationary plane of the bending tube at a symmetric position with respect to the second axis of the bending tube. The phase difference of the detected sine signal is obtained, and the sine signal is converted and output as a mass flow rate signal proportional to the phase difference.

In the above-mentioned Coriolis flowmeter, the time difference between the two arms of the curved tube passing through the stationary plane of the curved tube is measured, and the mass flow rate is obtained based on the time difference measurement. This is because the torsion angle of the bending tube is obtained from an equivalent equation that assumes that the moment due to the Coriolis force around the second axis acting on the bending tube is equal to the repulsion force based on the elasticity of the bending tube. , The mass flow meter is detected as a quantity proportional to the time difference.

The density of the fluid to be measured is such that the natural frequency of the curved tube is proportional to the square root of the ratio of the spring constant of the curved tube to the mass of the curved tube and the mass of the fluid to be measured contained in the curved tube. However, since the spring constant and the mass of the bending tube are known amounts, the natural frequency of the bending tube is measured to calculate the density.

As described above, in the mass flow rate measurement and the density measurement, when the Young's modulus of the curved tube is constant, the correct values of the mass flow rate and the density are obtained, but the Young's modulus of the curved tube material changes according to the temperature. I do. For this reason, a temperature sensor such as a platinum wire is fixed to the wall surface of the curved tube to measure the temperature of the curved tube. The measurement temperature range of the temperature sensor is determined according to the temperature range of the fluid to be measured, but the temperature range of the fluid to be measured may reach 200 ° C. A temperature sensor that stably measures this temperature has a sandwich structure in which a platinum resistance element is sandwiched between highly insulating inorganic material substrates such as ceramics, and the temperature sensor is made of glass fiber on the wall surface of a curved tube. The tape is pressed and fixed by being wound, but the adhesion between the temperature sensor and the curved tube is poor, and a temperature gradient is generated at the joint surface, so that it was not possible to measure the temperature with a sufficiently satisfactory accuracy.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and a method of fixing a temperature sensor to a curved tube, which enables the temperature of the curved tube to be faithfully detected, allows the temperature of the fluid to be measured to be reduced. It is an object of the present invention to provide a mass flow meter capable of accurately measuring a mass flow rate and a density even at a high temperature or a low temperature.

[0007]

In order to achieve the above object, the present invention provides a conduit through which a fluid to be measured flows, support means for supporting two separated points in the conduit, and natural vibration of the conduit around a support point of the conduit. And a temperature sensor for detecting the Coriolis force acting on the conduit by driving the driver, and a temperature sensor interposed in the conduit to detect the temperature of the conduit. After correcting the Young's modulus of the conduit by the detected temperature of the conduit and obtaining a mass flow rate and a density from the Coriolis force and the natural frequency, a temperature sensor is fixed to an outer wall surface of the conduit. The non-fixed surface of the temperature sensor and the conduit are wound with a thermally conductive metal tape. Hereinafter, an embodiment of the present invention will be described.

FIG. 1 is a view for explaining an embodiment of the mass flow meter of the present invention. In the figure, 1 is a support tube, 2 is a flange, 3 is a support plate, 4 is a wire outlet, and 5 is an electric wire outlet. Substrate, 5a
Is an electric wire hole, 6 is a curved tube, 7 is a holding plate, 8 is a drive unit, 9 is a Coriolis sensor, 10 is a temperature sensor, 11 is an aluminum tape, 12 is a lead wire, and 13 is a lead wire holding tape.

In the drawing, a support pipe 1 is a pipe having a flange 2 for interposing a pipe (not shown) through which a fluid to be measured flows, and has a partition plate (not shown) provided therein. ing. The curved tubes 6 and 6 are U-shaped tubular hollow tubes which are held by pressing plates 7 and 7 so as to be parallel to each other and are opened and fixed in the support tube 1 with a partition plate interposed therebetween. Since the curved pipes 6 and 6 open to the support pipe 1 with the partition plate interposed therebetween, the fluid flowing into one of the flanges 2 of the support pipe 1 is equally divided into the curved pipes 6 and 6 and flows out of the other flange 2. I do. The drive section 8 is composed of a drive coil and a plunger fixed to the distal ends of the bending tubes 6 and 6, respectively, and the bending tubes 6 and 6 are driven by a tuning fork-like vibration, that is, a resonance frequency such that the bending tubes 6 approach and separate about the axis XX. Is done. The Coriolis sensors 9, 9 are sensors provided with a pair of a detection coil and a magnet at a position where both arms of the bending tubes 6, 6 oppose each other.
This is for detecting a reference plane formed by the bending tubes 9 and 9 in a stationary state as a phase difference (time difference) of a sine waveform passing through the bending tubes 9 and 9.

The temperature sensor 10 is formed by sandwiching a platinum resistance wire or a platinum resistance foil between heat-resistant insulating substrates such as ceramics, and providing a lead wire in a sandwich shape. FIG.
1 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is a view seen from the direction of arrow Z in FIG. 2. In the drawing, reference numeral 10a denotes a lead wire of a temperature sensor, which is equivalent to a portion having the same function as FIG. Signs are attached.

In the drawing, in a section between the holding plate 7 and the substrate 5, the non-contact surface of the temperature sensor 10 and the heat conductive property are provided so as to be in close contact with the wall surface of the curved tube 6. For example, an aluminum foil tape is wound and fixed. The lead wire 10 a of the temperature sensor 10 is connected to the lead wire 12, and is locked on the substrate 5 together with the lead wire of the drive unit 8 and the Coriolis sensor 9 by the tape 13. The locked lead wire 12 is connected to an external Coriolis flowmeter converter (not shown) from the wire outlet 4 through the wire hole 5a.

As described above, the temperature sensor 10 is pressed and fixed to the wall surface of the bending tube 6 from the heat conductive foil, so that the heat of the bending tube 6 is rapidly transmitted to the temperature sensor 10 and the temperature sensor 10 The temperature sensor 10 accurately indicates the temperature of the curved tube 6 because the outer surface is uniformly heated. According to the experiment, when the fluid temperature is 200 ° C., the temperature difference between the curved tube 6 and the temperature sensor 10 has been changed by ± 3 ° C. in the past, but is less than ± 0.5 ° C. in the present invention. In addition, the error value was satisfactory even in the density measurement greatly affected by the mass flow rate and the temperature of the fluid to be measured. The aluminum tape 11 is not limited to aluminum, but may be a copper tape, an aluminum foil, a copper foil, or any other thin sheet having good thermal conductivity. The bending tube is a simple straight tube, a conduit supported in a predetermined section, and the driving means and the detecting means are equivalent to those in FIG. If it is a Coriolis flow meter, the temperature sensor of the present invention can be applied.

[0013]

As is clear from the above description, according to the present invention, since the temperature sensor faithfully detects the temperature of the curved tube that generates the Coriolis force, even if the temperature of the fluid to be measured is high or low, it can be used. Since the Young's modulus of the vibrating tube of the flow meter is temperature corrected and the mass flow rate and the density are correctly calculated and displayed, the measurement accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a view for explaining one embodiment of the mass flow meter of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG. 1;

FIG. 3 is a view as seen from an arrow Z direction in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Support pipe, 2 ... Flange, 3 ... Support plate, 4 ... Wire outlet, 5 ... Board, 5a ... Wire hole, 6 ... Curved tube, 7 ... Holding plate, 8 ... Drive part, 9 ... Coriolis sensor, 10 ... temperature sensor, 11 ... aluminum tape, 12 ... lead wire, 13
... Lead wire holding tape.

Claims (1)

(57) [Scope of request for utility model registration] 1. A conduit through which a fluid to be measured flows, supporting means for supporting two spaced apart points in the conduit, driving means for driving around a supporting point of the conduit at a natural frequency of the conduit, and driving A sensor for detecting the Coriolis force acting on the conduit by driving the means, and a temperature sensor interposed in the conduit for detecting the temperature of the conduit, and detecting the temperature of the conduit by the sensor to detect the temperature of the conduit. In a mass flow meter that corrects the Young's modulus by temperature and obtains a mass flow rate and a density from the Coriolis force and the natural frequency, after fixing a temperature sensor to an outer wall surface of the conduit, a non-fixed surface of the temperature sensor and the conduit are connected to each other. The mass flowmeter was characterized by being wound with a heat conductive metal tape.