JPH0477623A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To achieve the light weight of a sensor tube and to rpevent the disconnection of a cord and wire breakdown by providing magnets so as to face the displacing part of each sensor tube, and providing a thin film sensor which outputs the signal corresponding to the relative displacement with magnets. CONSTITUTION:The central parts of sensor tubes 2 and 3 are largely vibrated with shakers 17 and 18. When fluid flows through the sensor tubes 2 and 3, Coriolis forces which are proportional to the flow rates are generated. The phase differences are generated in the output signals of pickups 7, 9, 8 ad 10. With the vibrations of the tubes 11 and 12, the resistance value of a ferromagnetic-metal thin-film pattern 13b1 is changed in response to the displacements of sensors 13 and magnets 11 and 12. Since teh phase difference between the voltage signals on the inflow side and the outflow side is proportional to the flow rate, the flow rate is obtained based on the phase differences in output signals from the pickups 7 - 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter configured to reduce the weight of a sensor tube.

Conventional technology The flow rate of the fluid to be measured depends on the type of fluid and its physical properties (density, viscosity, etc.)
, it is desirable to express it in terms of mass that is not affected by process conditions (temperature, pressure).

Therefore, various types of mass flow meters are being developed to measure the mass flow rate of the fluid to be measured. There are flowmeters that directly measure the amount of water.

Regarding this type of mass flow meter, Japanese Patent Application Laid-Open No. 5452570
As described in the above publication, a fluid is caused to flow through a pair of sensor tubes, and the pair of sensor tubes are vibrated toward and away from each other by the driving force of an exciter (excitation coil). Since the Coriolis force acts in the direction of vibration of the sensor tube and is in opposite directions on the inlet and outlet sides, the sensor tube is twisted, and this twist angle is proportional to the mass flow rate. Therefore, a pickup (vibration sensor) for detecting vibration is installed at the twisting position on the inlet side and outlet side of a pair of sensor tubes, and the time difference between the output detection signals of both sensors is measured. Measuring flow rate.

Problems to be Solved by the Invention However, in the above mass flowmeter, a pickup is provided in the sensor tube, and the pickup is supported by the sensor tube.

Therefore, the weight of the pickup that combines the coil and magnet and the weight of the support parts for attaching these to the sensor tube act on the sensor tube, making it difficult to reduce the weight of the sensor tube.
Furthermore, since a space is required to install the pickup between the pair of sensor tubes, there is a problem in that it is difficult to achieve miniaturization. Furthermore, since the cord from the pickup coil is wired onto the sensor tube, the weight of the cord itself also acts on the sensor tube. Therefore, in the past, after installing the above-mentioned pickup on the sensor tube, it was necessary to fix the cord to the sensor tube using tape or adhesive, which not only made the pickup installation work troublesome, but also caused the cord to vibrate in the sensor tube. There is a problem that wire breakage occurs if the sensor tube comes off or the cord does not come into close contact with the sensor tube and rubs due to vibration.

Therefore, an object of the present invention is to provide a mass flowmeter that solves the above problems.

Means for Solving the Problems The present invention provides a mass flow rate system in which the flow rate is measured by vibrating a sensor tube through which a measured fluid passes and detecting the displacement of the sensor tube due to the Coriolis force generated in accordance with the flow rate of the measured fluid. In the sensor tube, a magnet is provided to face a displaced portion of the sensor tube, and a thin film sensor is provided on the sensor tube to output a signal according to the relative displacement with respect to the magnet.

Since the sensor tube is provided with a thin film sensor, the load acting on the sensor tube is reduced and the weight of the sensor tube is reduced, and the pickup is also made smaller, thereby making it possible to downsize the device. Furthermore, the pickup can be easily installed, and disconnection and disconnection of the cord can be prevented.

Embodiment FIGS. 1 to 3 show an embodiment of a mass flowmeter according to the present invention.

In each figure, a mass flowmeter 1 connects a pair of straight sensor tubes 2 and 3 to an inlet manifold 4 and an outlet manifold 5.
It is mounted in parallel between the

6 is a cylindrical case in which an inflow side manifold 4 is fitted into the inflow side opening, and an outflow side manifold 5 is fitted into the outflow side opening, which protects the pair of sensor tubes 2 and 3 and protects both manifolds. 4°5 is supported.

An inlet 4 is provided at the center of the upstream end of the inlet manifold 4.
A flange 4b with an opening a is provided, and a pair of connecting ports 4c and 4d branching from the inlet 4a are bored at the downstream end. The outflow side manifold 5 has the same configuration as the inflow side manifold 4, and has a flange 5b at the downstream end where the outflow port 5a opens, and a pair of connections communicating with the outflow port 5a at the upstream end. It has mouths 5c and 5d.

Therefore, one end of the straight sensor tubes 2 and 3 is fitted and fixed to the connection ports 4c and 4d of the upstream manifold 4, and the other end is fitted and fixed to the connection ports 5c and 5d of the downstream side manifold 5.

Pick-ups 7 to 1O detect the displacement of the sensor tubes 2.3, and are arranged at 1/4 and 3/4 length positions from the upstream fixed portions of the sensor tubes 2 and 3, respectively.

Incidentally, since each of the pickups 7 to 10 has the same configuration, only the pickup 7 will be explained here.

The pickup 7 includes a pair of magnets 11 and 12 provided oppositely on both sides of the sensor tube 2, and a sensor 13 provided on the outer periphery of the sensor tube 2. The magnets 11 and 12 are attached to the inner wall 6 of the case 6 as shown in FIG.
It is fixed on a bracket 16 fixed to a, and is provided at a position spaced apart from the sensor tube 2 by a predetermined distance. Further, as shown in FIG. 3, the magnets 11 and 12 are each recessed in an arc shape on the side facing the sensor tube 2, and the recesses 11a and 12a are magnetized to N and S poles, respectively, and the opposite end face 11b, +2b is magnetized to S pole and N pole.

As shown in FIGS. 3 to 6, the sensor 13 is attached to the lower outer periphery of the sensor tube 2 along the extending direction. The sensor 13 has a flexible substrate structure in which a base layer 13a attached to the sensor tube 2, a printed wiring pattern 13b, and a protective coating layer 13C are laminated. The base layer 13a and the protective coating layer 13c are made of insulating epoxy resin, polyimide resin, polyamideimide resin, or the like. Moreover, the base layer 13a and the protective coating layer 13
A printed wiring pattern 13b having an element pattern 13b+ shown in FIG. 4 is interposed between the element pattern 13b and the element pattern 13b, which is formed in a comb shape as shown in FIG. 5 and functions as a magnetoresistive element. This printed wiring pattern 13 is made of, for example, a ferromagnetic material (CoPt, C0Fe,
04. Crow, CrTe, NiCo, Cu*MnA1
etc.) are formed into a predetermined pattern shown in FIG. 5 using a microfabrication technique such as photoringraph. Further, in the printed wiring pattern +3b, the element pattern 13b is in the magnetic field of the magnets 11 and 12, and this element pattern 13b
, the extending portion 13b2°+ extending from the manifold 4 side to the manifold 4 side.
Terminals 13b4 and 13bs are provided at the end of 3b3. This terminal 13b4, 13b, beam single lead wire 14.1
The signal obtained from the element pattern ls b + is connected to a flow rate integrating circuit (not shown) via lead wire 14 .
15.

Since the sensor 13 is made of laminated thin flexible films as described above, it is extremely lightweight, and the sensor tube 2
, 3, the weight is almost negligible compared to the strength of . Therefore, the sensor tubes 2 and 3 are connected to the sensor 13.
The sensor tubes 2 and 3 can be manufactured with almost no consideration given to their weight, and the weight of the sensor tubes 2 and 3 can be reduced accordingly.

Furthermore, since the entire surface of the base layer 13a of the sensor 13 is adhered to the outer periphery of the sensor tube 2, the sensor 13 is firmly adhered, and there is no fear that the sensor 13 will be peeled off due to the vibration of the sensor tube 2. Moreover, the terminal portion 13b is located at the base of the sensor tube 2, where the lead wires 14 and 15 hardly vibrate.

Since it is soldered to 13bs, sensor tube 2
There is no need to worry about the lead wires 14 and 15 coming off due to the vibrations of , 3.

17.18 is an exciter, which is composed of a magnetic material 1.9.20 fixed to the outer periphery of the sensor tube 2.3 and an excitation element 21.22. The excitation elements 21.22 are screwed into the mounting holes 6a, 6b of the case 6 so as to face the magnetic bodies 19.20,
A drive coil (not shown) for exciting the magnetic bodies 19 and 20 is provided inside.

Here, the measurement operation of the mass flowmeter 1 having the above configuration will be explained.

During flow rate measurement, each of the excitation elements 21, 22 is energized at regular intervals, and the magnetic bodies 19, 22 fixed to the sensor tubes 2, 3 are energized at regular intervals.
Aspirate 20. Therefore, the sensor tube 2.3 uses the connection part with the manifolds 4 and 5 as a fulcrum, and the magnetic body 19
．． 20, the middle part is bent in an arc shape. The sensor tubes 2 and 3 vibrate in the X direction at a natural frequency determined by the spring constant of the sensor tube 23 and the flow rate.

In this way, the pair of sensor tubes 2, 3 are connected to the vibrator 17. The center portion is greatly excited by the +8 excitation operation, and vibrates toward and away from each other. The fluid flows in through the inlet 4a, is divided into the sensor tube 2.3 at a substantially equal division ratio, merges at the outlet 5a, and flows out downstream. In this way, when fluid flows into the vibrating sensor tubes 2 and 3, Coriolis is generated in proportion to the flow rate.

Therefore, an operation delay occurs between the inflow side and the outflow side of the straight sensor tube 2.3, resulting in a phase difference between the output signals of the pickups 7, 9 and 8.10.

On the other hand, the sensors 13 of each of the pickups 7 to 10 are located in the magnetic field of the magnets 11 and 12, and as the sensor tubes 2 and 3 vibrate, the element patterns 13b+ formed in the shape of a ferromagnetic metal thin film are hidden. The resistance value changes depending on the relative displacement between the sensor 13 and the magnet II, +2. Therefore, by flowing a constant current through each of the pickups 7 to 10, the change in the resistance value can be extracted as a voltage signal. Next, the voltage signals based on the pickups 7.9 on the inflow side of the sensor tube 2.3 are added, and the voltage signals based on the pickups 8, 10 on the outflow side of the sensor tubes 2, 3 are added, and this added inflow If the phase difference between the voltage signal on the side and the voltage signal on the outflow side is taken, the flow rate can be determined based on the phase difference between the output signals from the pickups 7 to 10, since this phase difference is proportional to the flow rate. The principle of flow rate measurement using the Coriolis force is the same as that of the previously filed mass flowmeter, so a detailed explanation of the measurement operation will be omitted here.

In the above mass flowmeter 1, the thin film sensor 13 is attached to the sensor tube 2.3.
The weight of the exciter 8.9 is reduced, and the driving force by the excitation elements 21 and 22 is accordingly reduced, making it possible to reduce the size and weight of the exciter 8.9.

In addition, since the sensor 13 is extremely thin, the distance between the pair of sensor tubes 2 and 3 is not limited as in the conventional case, and it is possible to bring the sensor tubes 2 and 3 closer together to reduce the size of the entire flowmeter. Ru.

Further, in the above embodiment, the sensor 13 is provided below the sensor tubes 2 and 3, or the sensor tube 2 is provided as shown in FIG.
, 3 may be provided with two sensors 13 above and below. By providing two sensors 13 in this way, twice as many output signals can be obtained and the measurement accuracy can be increased.

Although the above embodiment has been explained using a straight sensor tube 2.3, it goes without saying that the present invention is not limited to this and can be applied to sensor tubes bent into other shapes.

In the above embodiment, the sensor 13 has been described as functioning as a magnetoresistive element, but the sensor 13 is not limited to this, but may be a thin film element that outputs a signal according to the amount of relative displacement with respect to the magnet 11, 12, For example, it goes without saying that a Hall element made of InSb (indium antimony) (formed in a tooth-like pattern) may be used as a sensor.

Effects of the Invention As described above, the mass flowmeter according to the present invention has a sensor tube equipped with a thin film sensor that outputs a signal according to the amount of relative displacement with respect to a magnet, thereby reducing the load acting on the sensor tube. This makes it possible to reduce the weight of the sensor tube, and also to reduce the size of the entire device by making it much smaller than a conventional pickup. moreover,
Since there is no need to fix the cord to the sensor tube, it not only simplifies the assembly work, but also has the advantage that there is no risk of the cord coming off or breaking like in the past.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an embodiment of the mass flowmeter according to the present invention, Fig. 2 is a longitudinal sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is an enlarged cross-sectional view for explaining the pickup. 4 is a bottom view showing an enlarged view of the main parts of the present invention, FIG. 5 is a bottom view showing the element pattern of the sensor, FIG. 6 is a vertical cross-sectional view of the sensor installed, and FIG. FIG. 2 is a vertical cross-sectional view for explaining the present invention in detail. l...Mass flow meter, 2, 3...Sensor tube, 7
~IO...Pickup, 11.12...Magnet, 13...Sensor, 13a...Base layer, 13b
... Printed wiring pattern, 13b, ... Element pattern, 13c... Protective coating layer, 17.18
River exciter, 19.20...Magnetic material, 21.22...
Excitation element. Patent Applicant 1. Kiko Co., Ltd. Figure 3 Figure 4 Figure 5 Figure 3b3 Figure 6 Figure 7

Claims (1)

[Scope of Claims] A mass flowmeter that measures the flow rate by vibrating a sensor tube through which a fluid to be measured passes and detecting displacement of the sensor tube due to Coriolis force generated in accordance with the flow rate of the fluid to be measured, comprising: 1. A mass flowmeter comprising: a magnet provided so as to face a displaced portion of a tube; and a thin film sensor provided on the sensor tube to output a signal according to the relative displacement with the magnet.