JPH0749981B2 - Vibration measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type measuring device, and more particularly to a vibration type measuring device for detecting a Coriolis force generated in an oscillating pipe to measure a mass flow rate or density of a fluid. .

Conventional technology It is desirable that the flow rate of the fluid to be measured be expressed as a mass that is not affected by the type of fluid, physical properties (density, viscosity, etc.) and process conditions (temperature, pressure). Conventionally, as a mass flow meter for measuring the mass flow rate of a fluid to be measured, for example, a so-called indirect mass flow meter that measures the volumetric flow rate of the fluid to be measured and converts this measurement value into mass, and an indirect mass flow meter There is a so-called direct type mass flow meter that has a small error and directly measures the mass flow rate of the fluid to be measured. In this type of mass flowmeter, various types of flowmeters based on different principles are being proposed as direct mass flowmeters that can measure the flow rate with higher accuracy. Further, as one of them, there is a flow meter that directly measures the mass flow rate by utilizing the Coriolis force generated when a fluid is flowed in an oscillating sensor tube.

Also, as a mass flow meter that utilizes this Coriolis force,
For example, a pair of U-shaped sensor tubes is connected to a flowmeter body having an inflow port and an outflow port, and the pair of sensor tubes are oscillated in directions toward and away from each other to generate a Coriolis force proportional to the mass flow rate. There is a configuration in which the displacement of the sensor tube due to is detected to obtain the mass flow rate.

The vibrating measuring device configured to detect the Coriolis force generated in the vibrating pipe as described above can be used as a vibrating density meter in addition to the mass flowmeter.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described mass flowmeter utilizing the Coriolis force, the pair of sensor tubes are provided so as to extend in the direction perpendicular to the pipe extending direction. Since the sensor tube is arranged so as to project more greatly, there is a problem that a larger installation space is required.

In addition, in the conventional mass flowmeter, not only the flowmeter itself including the flowmeter main body and the sensor tube becomes large, but also it is easy to install in a narrow place where other devices are densely installed. However, there is a problem that the installation work is troublesome because it is necessary to avoid other devices for installation.

Furthermore, it is demanded that the mass flowmeter be downsized and the flow rate be measured without being affected by pipe vibration.

Therefore, it is an object of the present invention to solve the above-mentioned problems and to provide a mass flowmeter according to demand.

Means for Solving the Problems The present invention has a main pipe through which a fluid to be measured flows and a straight pipe portion having an end communicating with the main pipe and extending parallel to the main pipe. A pair of sensor tubes whose pipes are opposed to each other through the main pipe and are located along the main pipe, and a device between the pair of sensor tubes so as not to contact the main pipe. A holding member that is mounted and holds the non-vibrating portions of the pair of sensor tubes; and a vibration exciter that vibrates by vibrating each of the straight tube portions of the first and second sensor tubes in a direction toward or away from each other. A pickup that is provided between the straight pipe portions of the first and second sensor tubes and detects relative displacement between the straight pipe portion of the first sensor tube and the straight pipe portion of the second sensor tube. It is characterized by consisting of.

Action According to the present invention, the pair of sensor tubes are arranged so as to be positioned along the main pipe, and the pair of sensor tubes are held by the holding member arranged in non-contact with the main pipe. Therefore, the second straight pipe portion does not largely project from the pipe, the installation space is small, and it can be compactly arranged in a narrow space, and the vibration of the main pipe is transmitted to the pair of sensor tubes. It is possible to position the extension position of each straight pipe part such that the straight pipe parts are parallel to each other at a predetermined position in the absence of the above.

First Embodiment FIGS. 1 to 3 show a first vibration type measuring apparatus according to the present invention.
1 shows a mass flowmeter as an example.

In each figure, the mass flowmeter 1 has a pair of sensor tubes 2 and 3 assembled in a manifold 4. As shown in FIG. 2, the manifold 4 is provided between the inflow pipe 5 and the outflow pipe 6,
It has an inflow passage 4 a connected to the inflow pipe 5 and an outflow passage 4 b connected to the outflow pipe 6. In addition, as shown in FIG.
4a communicates with connection ports 4a ₁ and 4a ₂ that branch upward and downward.

As shown in FIGS. 2 and 4, the outflow passage 4b also communicates with the branched connection ports 4b ₁ and 4b ₂ similarly to the inflow passage 4a.

The upper sensor tube 2 has its base end connected to the connection port 4a ₁ of the inflow passage 4a, and has a straight pipe portion 2a extending in the pipe direction and a base end connected to the connection port 4a ₁ of the outflow passage 4b, A straight pipe portion 2b extending parallel to the straight pipe portion 2a, curved portions 2c and 2d bent so as to be folded back at the ends of the straight pipe portions 2a and 2b, and a U-shape connecting the curved portions 2c and 2d. It is composed of a connecting part (pipe) 2e in the shape of a circle.

Therefore, since the straight pipe portions 2a, 2b of the sensor tube 4 extend in parallel with the outflow pipe 6 so as to be located along the outflow pipe 6 (main pipe), the straight pipe portions 2a, 2b are 6 does not significantly project, the installation space is small, and it can be compactly arranged in a narrow space.

Further, since the straight pipe portions 2a and 2b are connected via the curved portions 2c and 2d and the connection portion 2e bent in a different direction, the straight pipe portion 2a and the straight pipe portion 2b are connected. It is easy to bend between and. Therefore, the stress due to vibration at the time of flow rate measurement, which will be described later, is dispersed in the curved portions 2c, 2d and the connection portion 2e without being concentrated at one point, and the straight pipe portion 2a and the straight pipe portion 2b vibrate in a direction in which they approach or separate from each other. By doing so, the amplitude can be increased, and the Coriolis force is easily generated in the straight pipe portions 2a and 2b during measurement, and the measurement accuracy can be further improved.

Further, the lower sensor tube 3 is formed in the same shape as the sensor tube 2, and the sensor tube 2 and the upper and lower parts are arranged so that the straight pipe portions 3a and 3b are parallel to the outflow pipe 6 and the straight pipe portions 2a and 2b. They are arranged symmetrically. The intermediate portion of the connecting portions 2e, 3e of the sensor tubes 2, 3 is a non-vibrating portion that does not vibrate even when the sensor tubes 2, 3 are vibrated, and is connected and retained by the retaining member 8 shown in FIG. There is.

The holding member 8 has connection portions 8b and 8c which are connected and fixed to an intermediate position of the connection portions 2e and 3e of the sensor tubes 2 and 3 on the outer periphery of the ring portion 8a through which the outflow pipe 6 penetrates. That is, the holding member 8 holds the connecting portions 2e and 3e facing each other with the outflow pipe 6 interposed therebetween.

The inner diameter D ₁ of the ring portion 8a is larger than the outer diameter D of the outflow pipe 6, and there is a gap between the outer periphery of the outflow amount 6 and the inner periphery of the ring portion 8a. Therefore, a pair of sensor tubes 2,
The connecting portions 2e, 3e of 3 are held at predetermined positions in a non-contact state with the outflow pipe 6, and the pipe vibration from the outflow pipe 6 is not directly transmitted to the sensor tubes 2, 3.

Further, the sensor tubes 2 and 3 are positioned at a predetermined position with no variation in the separated positions of the connecting portions 2e and 3e with respect to the outflow pipe 6 by connecting and fixing the holding member 8. In this way, the holding member 8 allows the connecting portions 2e, 3e at the tips of the sensor tubes 2, 3 to be connected.
Will be held at the designed predetermined position despite being separated, and the separated positions of the straight pipe portions 2a, 2b and 3a, 3b continuous to the connecting portions 2e, 3e are positioned at the predetermined position. At the same time, the parallelism of the straight pipe portions 2a, 2b, 3a, 3b is maintained. Therefore,
When manufacturing the sensor tubes 2 and 3, even if the extension positions or parallelism of the straight pipe portions 2a, 2b, 3a and 3b are slightly deviated, the holding member 8 connects and holds the connecting portions 2e and 3e. By doing so, the assembling position of the straight pipe portions 2a, 2b, 3a, 3b can be corrected so as to eliminate the assembling processing error of the straight pipe portions 2a, 2b, 3a, 3b.

Therefore, the holding member 8 holds the space between the connecting portions 2e and 3e when the sensor tubes 2 and 3 are assembled, and at the same time, each straight pipe portion 2a, 2b, 3a,
It can also function as an assembling gauge for positioning the extension position and parallelism of 3b.

That is, since the sensor tubes 2 and 3 are assembled at the correct positions, it is possible to accurately regulate the positional relationship between the coil portion and the magnet portion of the pickups 9 and 10 described later.
Therefore, it is unnecessary to adjust the relative positions of the coil portions and the magnet portions of the pickups 9 and 10 after the assembly is completed.

The straight pipe portions 2a, 2b, 3a, 3b of the pair of sensor tubes 2, 3 penetrate the support plate 7 and are fixed to the support plate 7 by welding, and the ends thereof are the respective connection ports 4a ₁ , 4a _{1 of} the manifold 4. 4a ₂ , 4b ₁ , 4b ₂
It is connected and fixed to.

Therefore, one sensor tube 2 is provided above the outflow pipe 6 so as to extend in the piping direction, and the other sensor tube 3 is provided below the outflow pipe 6 so as to extend in the piping direction. Although the flowmeter 1 has a pair of sensor tubes 2 and 3, the installation space is small and has a compact structure.

Further, in the mass flowmeter 1, since the sensor tubes 2 and 3 are provided so as to extend in the pipe direction in the vicinity of the outflow pipe 6, the structure is less susceptible to the vibration of the pipe, and the flow rate can be more accurately measured. It can be measured.

A hole 7a is formed at the center of the support plate 7, and the outflow pipe 6 penetrates this hole 7a.

As shown in FIGS. 1 to 3 and 7, pickups 9 and 10 are arranged between the straight pipe portions 2a and 3a on the inflow side and between the straight pipe portions 2b and 3b on the outflow side. Has been done.

Since the pickups 9 and 10 have the same structure, one pickup 9 will be described.

In FIG. 7, the pickup 9 is a straight pipe portion of the sensor tube 3.
A coil portion 9a held by a bracket 11 protruding upward from the middle of 3a and magnets 9b, 9c provided on a U-shaped bracket 12 so as to face the coil portion 9a in the upper and lower directions.
And consists of. The bracket 12 extends upward and is connected to the straight pipe portion 2a of the sensor tube 2.

Therefore, when the sensor tubes 2 and 3 vibrate, the coil portion 9a provided on the straight pipe portion 3a is relatively displaced between the magnets 9b and 9c in the arrow X direction. Therefore, an electromotive force is generated in the coil portion 9a according to the relative displacement of the straight pipe portions 2a and 3a, and the pickup 9 detects the displacement of the straight pipe portion 3a from the voltage of the coil portion 9a. A support member for supporting the pickups 9 and 10 is unnecessary.

13, 14 are vibrators, which are located between the ends of the straight pipe portions 2a and 2b, and the straight pipe portion 3a.
It is provided between the tips of 3 and 3b.

The vibration exciter 13 has substantially the same structure as an electromagnetic solenoid, and includes a coil portion 13a attached to the inflow side straight pipe portion 2a and a magnet attached to the outflow side straight pipe portion 2b and fitted into the coil portion 13a. It is composed of a part 13b. Therefore, when the coil unit 13a is energized, the vibrator 13 vibrates the straight pipe sections 2a and 2b in the arrow X direction.

Since the vibrator 14 has the same structure as the vibrator 13, the description thereof is omitted.

Next, the measurement operation of the mass flow meter having the above configuration will be described.

When measuring the flow rate, the pair of sensor tubes 2 and 3 are
By the operation of 14, the fluid is excited while the fluid is flowing inside. The fluid to be measured that has flowed into the inflow passage 4a of the manifold 4 from the inflow pipe 5 is divided into straight pipe portions 2a and 3a of the sensor tubes 2 and 3.
To the straight pipe portions 2b and 3b through the curved portions 2c and 3c, the connecting portions 2e and 3e, and the curved portions 2d and 3d, and join at the outflow passage 4b of the manifold 4 to flow out from the outflow pipe 6. . In addition, the sensor tube 2,
Since 3 is vibrated by the exciters 13 and 14, it vibrates in the direction of arrow X at a natural frequency determined by the spring constant of the sensor tubes 2 and 3 and the flow rate flowing in the sensor tubes 2 and 3.

First, the operation of the upper sensor tube 2 of the pair of sensor tubes 2 and 3 will be described.

When the straight pipe portions 2a, 2b and 3a, 3b vibrate, they are elastically deformed in a direction in which they are separated from each other, and then are deformed in a direction in which they are close to each other by the elastic restoring force of the straight pipe portions 2a, 2b, 3a, 3b themselves. .

As shown in FIG. 8, since the straight pipe portions 2a and 2b are fixed by the support plate 7, the straight pipe portions 2a and 2b vibrate greatly in the arrow X direction toward the tip with the penetrating portion of the support plate 7 as a fulcrum. Therefore, the straight pipe section 2
In a and 2b, the angular velocity ω is deformed due to the above vibration. Further, since the bending portions 2c, 2d and the connecting portion 2e are bent in different directions, even if the vibration exciter 13 vibrates in the X direction,
2c, 2d and the connecting portion 2e (excluding the intermediate portion) are bent in the vibration direction to allow the displacement of the straight pipe portions 2a, 2b on the tip side.

As described above, when the fluid flows into the vibrating sensor tube 2, the amplitude increases in the straight pipe portion 2a on the inflow side toward the tip thereof, so that the velocity of the fluid in the arrow X direction increases. Therefore, acceleration in the vibration direction is applied to the fluid. Further, in the straight pipe portion 2b on the outflow side, the velocity in the direction of the arrow X gradually decreases toward the manifold 4 side, so that the fluid has a negative acceleration. Thus, when the fluid is accelerated due to the vibration of the sensor tube 2, a Coriolis force (Fc) in the direction opposite to the acceleration direction is generated.

As shown in FIGS. 8 (A) and (B), the straight pipe portion 2a on the inflow side is displaced in the arrow X ₁ direction at an angular velocity −ω, and the straight pipe portion 2b on the outflow side is angular velocity + ω in the arrow X ₂ direction. Suppose it has been displaced. Thus, in one stroke displaces in the direction in which the straight tube portion 2a, 2b are separated from each other, FIG. 9 (A), direction of arrow X ₂ of the Coriolis in straight tube portion 2a, 2b as shown in (B) Force Fc is generated. Therefore, the straight pipe portions 2a and 2b are displaced by -δ and + δ from the original displacement positions indicated by the two-dot chain line to the positions indicated by the solid lines, respectively.

Next, as shown in FIGS. 8C and 8D, the straight pipe portion 2a on the inflow side is displaced in the direction of arrow X ₂ at an angular velocity + ω, and the straight pipe portion 2b on the outflow side is at an angular velocity ω and arrow X ₁ It is assumed that it has been displaced in the direction. In this way, the straight pipe portions 2a, 2b are displaced in the direction in which they approach each other.
In the stroke, as shown in FIGS. 9C and 9D, Coriolis force Fc in the direction of arrow X ₁ is generated in the straight pipe portions 2a and 2b. Therefore, the straight pipe portions 2a and 2b are displaced from the two-dot chain line (original displacement position) to the positions indicated by the solid lines by -δ and + δ.

The pair of sensor tubes 2 and 3 are vibrated with a phase difference of 180 °. For example, when the straight pipe portions 2a and 2b of the upper sensor tube 2 are separated from each other, The tube portions 3a and 3b are close to each other.

That is, when the sensor tube 2 is displaced as shown in FIGS. 8 (A) and 8 (B), the sensor tube 3 is displaced as shown in FIGS. 8 (C) and (D). Therefore, in the straight pipe portions 2a and 2b of the upper sensor tube 2, as shown in FIG.
Coriolis force is generated as shown in (B), and Coriolis force as shown in FIGS. 9 (C) and (D) is generated in the straight pipe portions 3a, 3b of the lower sensor tube 3.

The Coriolis force Fc is measured by the pickups 9 and 10 in the straight pipe section 2
Displacement of a, 2b −δ, + δ magnitude, or straight pipe 2a, 2b
It can be obtained by detecting the phase angle difference of. The Coriolis force Fc is represented by Fc = 2ωmv, and the mass flow rate (mv) is obtained by obtaining the angular velocity ω and the Coriolis force Fc.

The pickups 9 and 10 detect the displacements −δ and + δ of the straight pipe portions 2a and 2b as time difference signals. Therefore, the pickup 9,10
The time required for the voltage obtained in the coil section to change from a certain reference voltage to a certain different voltage is measured, and this time is proportional to the flow rate.

The signals of the pickups 9 and 10 are shaped and amplified, and then become a voltage signal proportional to the mass flow rate by time integration. Further, this voltage signal is converted into a frequency signal and output as a voltage pulse signal and an analog signal from an output circuit (not shown). Sensor tube for mass flowmeter 1
The displacement of the straight pipe portions 2a, 3a and 2b, 3b due to the Coriolis force generated in 2, 3 can be detected twice, and the flow rate can be accurately measured. In addition, the sensor tube associated with the above Coriolis force generation
When detecting the phase difference between 2 and 3, even if external vibration (vibration noise) is input, it is canceled and the flow rate can be measured stably without being affected by external vibration.

Further, since the outflow pipe 6 is held at a predetermined separation position by the holding member 8 which is not in contact between the connecting portions 2e and 3e of the pair of sensor tubes 2 and 3, the vibration of the outflow pipe 6 causes the holding member 8 to vibrate. It is not transmitted to the sensor tubes 2 and 3 via. Therefore, in the mass flowmeter 1, the pipe vibration transmitted to the sensor tubes 2 and 3 passes through the manifold 4 and is damped during that time. Therefore, the pickup 9,10
Even if the vibration noise is detected, it is extremely small and is acceptable in flow rate measurement.

10 and 11 show a modified example of the present invention. In both figures, the holding member 15 for connecting and holding the connecting portions 2e, 3e of the pair of sensor tubes 2, 3 has an arc portion 15a having a diameter larger than the outer diameter of the outflow pipe 6.
And the connecting portion 1 protruding downward from the end of the arc portion 15a.
It consists of 5b and 15c. Since the holding member 15 has the circular arc portion 15a, even after the sensor tubes 2, 3 and the outflow pipe 6 are connected and fixed to the manifold 4, the connecting portion 15b, the circular arc portion 15a is kept in non-contact with the outflow pipe 6. 15c sensor tube
Can be connected to a few. Therefore, the holding member 1
In the case of 5, the mounting work is easier and the weight is lighter than that of the above-mentioned embodiment.

Further, in each of the above-described embodiments, the mass flowmeter is given as an example, but the present invention is not limited to this, and it goes without saying that the present invention can be applied to a vibration type density meter.

EFFECTS OF THE INVENTION As described above, the vibration-type measuring device according to the present invention is arranged so that the pair of sensor tubes are located along the main pipe, so that it can be installed compactly in a small space. It can be installed easily without being restricted by the equipment. At the same time, since the holding member that is not in contact with the pipe connects and holds the tips of the pair of sensor tubes, it is possible to prevent the pipe vibration from being transmitted to the sensor tube through the holding member, and thus the influence of the pipe vibration is prevented. The flow rate can be measured with high accuracy without directly receiving it. Also,
By connecting and holding the pair of sensor tubes by the holding member, the extension position of the straight pipe portion of each sensor tube can be positioned at a predetermined position, and the parallelism of the straight pipe portions can be maintained. Since it can be positioned, the holding member can also be used as a gauge for assembling a pair of sensor tubes with the pipe as a reference, that is, the assembly position of each straight pipe part of the sensor tube can be accurately positioned. It has features such as eliminating the need to adjust the position of the pickup.

[Brief description of drawings]

1 to 3 are perspective views, plan views, and side views of a mass flowmeter as one embodiment of the vibration type measuring apparatus according to the present invention, and FIG. 4 is taken along line IV-IV in FIG. Fig. 5 is a vertical sectional view, Fig. 5 is a vertical sectional view taken along line VV in Fig. 3, Fig. 6 is a perspective view of a holding member which is an essential part of the present invention, Fig. 7 is an enlarged view of a pickup, and FIG. 9 and FIG. 9 are a plan view for explaining the operation at the time of measuring the flow rate, and FIGS. 10 and 11 are a longitudinal sectional view and a perspective view for explaining the modified example. 1 ... Mass flowmeter, 2, 3 ... Sensor tube, 5 ... Inflow tube,
6 ... Outflow pipe, 8, 15 ... Holding member, 8a ... Ring part, 9, 10 ... Pickup, 13, 14 ... Exciter.

Claims (1)

[Claims] 1. A main pipe through which a fluid to be measured flows, and a straight pipe portion having an end communicating with the main pipe and extending parallel to the main pipe, the straight pipe portion including the main pipe. A pair of sensor tubes that are formed to face each other and are located along the main pipe, and are mounted between the pair of sensor tubes so as not to contact the main pipe, and the pair of sensors. A holding member that holds a non-vibrating portion of the tube; a vibrating device that vibrates and vibrates the straight pipe portions of the first and second sensor tubes in a direction of approaching or separating from each other; And a pickup provided between the straight pipe portions of the sensor tube for detecting relative displacement between the straight pipe portion of the first sensor tube and the straight pipe portion of the second sensor tube. Vibration type measuring device.