JP2006138785A - Noise resistance type straight coriolis flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a straight Coriolis flow meter capable of maintaining leak energy and stabilizing vibration in a resonance system, that is, a noise resistance type straight Coriolis flow meter. <P>SOLUTION: A suspended weight member 22 is placed in the middle of connecting position of an expanded opening 9 of a flow tube 3 and a leaf spring 6, and in the circumferential direction of the flow tube 3. The suspended weight member 22 has a function so that the suspended weight member 22 itself is vibrated in S and S' directions due to generation of a standing wave and that leak energy is maintained (stored) by vibration of the suspended weight member 22. The suspended weight member 22 comprises a mass part 23 and a connection part 24 for connecting the mass part 23 to the flow tube 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a straight tube type Coriolis flow meter that obtains a mass flow rate and / or density of a fluid to be measured by detecting a phase difference and / or vibration frequency proportional to Coriolis force acting on a flow tube. It relates to noise countermeasure type straight pipe type Coriolis flowmeters.

  The straight pipe type Coriolis flowmeter is a Coriolis flowmeter between the support part and the center part of the straight pipe when vibration in the direction perpendicular to the straight pipe axis is applied to the center part of the straight pipe (flow tube) supported at both ends. A displacement difference of the straight pipe due to the force, that is, a phase difference signal is obtained, and the mass flow rate is detected based on the phase difference signal. Such a straight pipe type Coriolis flowmeter has a simple, compact and robust structure (see, for example, Patent Document 1).

  In FIG. 3, a conventional straight tube type Coriolis flowmeter 1 includes an outer cylinder 2 in the drawing, 3 flow tubes, 4 counter balances, 5 connecting blocks, 6 leaf springs, 7 driving devices, 8 Detector (detection means), a weight (not shown), and the like. The flow tube 3 has enlarged openings 9 formed in a trumpet shape at both ends thereof. The flow tube 3 has a straight straight pipe portion 10 between the enlarged openings 9 at both ends.

  A counter balance 4 is provided on the outside of the straight tube portion 10 of the flow tube 3. The straight pipe portion 10 and the counter balance 4 of the flow tube 3 are coaxially joined by connecting blocks 5 at both ends of the counter balance 4. The straight pipe portion 10 and the counter balance 4 form a double pipe structure. The outer cylinder 2 is formed so that a double pipe structure can be accommodated therein. Both end portions of the outer cylinder 2 are formed so as to be narrowed toward the enlarged opening 9 of the flow tube 3. Both end portions of the outer cylinder 2 are welded to the enlarged opening 9. Both ends of the outer cylinder 2 and the enlarged opening 9 are fixed in a liquid-tight manner. A connection flange 11 is welded to the opening end of the enlarged opening 9.

  The leaf spring 6 has a surface orthogonal to the straight tube portion 10 of the flow tube 3, and one end is fixed to the connection block 5 and the other end is fixed to the inner wall of the outer cylinder 2. The leaf spring 6 is arranged in a direction orthogonal to the resonance vibration direction. The driving device 7 is attached to the center position of the flow tube 3 and the counter balance 4. The detector 8 is attached to a symmetrical position of the driving device 7. A weight (not shown) is attached to a position on the opposite side of the driving device 7. More specifically, the weight (not shown) is attached in the driving direction of the driving device 7. The weight (not shown) is provided so that the natural frequency of the flow tube 3 around the connection block 5 and the natural frequency of the counter balance 4 can be adjusted equally.

In the above configuration, the resonance system composed of the flow tube 3 and the counter balance 4 is supported by the leaf spring 6. The enlarged opening 9 at the end of the straight pipe portion 10 extending from the resonance system is supported at the position of the connection flange 11. Therefore, the flow tube 3 is supported at a total of four points. The straight tube type Coriolis flow meter 1 having such a configuration causes the drive device 7 to resonate in a state where a fluid to be measured (not shown) flows through the flow tube 3, and a phase difference signal proportional to the Coriolis force by the detector 8. By detecting this, the mass flow rate can be measured. In the straight tube type Coriolis flow meter 1, a standing wave is formed in the resonance system by the resonance driving of the driving device 7. Each of the above support points is a vibration node. The stress generated in the flow tube 3 due to thermal expansion or piping stress is removed by the spring action of the enlarged opening 9 and the spring action of the leaf spring 6.
Japanese Patent No. 2786829 (page 4, FIG. 1)

  Since the flow tube 3 is extended to the position of the connection flange 11 and is welded to the connection flange 11 through the enlarged opening 9, the flow tube 3 is connected to the pair of connection flanges 11 by the resonance drive of the drive device 7. It is designed to vibrate between. Accordingly, the vibration condition also changes depending on the condition of the connection flange 11, and the influence on the accuracy and stability cannot be ignored.

  When the flow tube 3 is connected to the connection flange 11, the flow tube 3 is connected through the thin and trumpet-shaped enlarged opening 9, so that the vibration of the flow tube 3 is not inhibited by the enlarged opening 9. This facilitates free bending vibration (see FIG. 4). By the way, as shown in FIG. 4, if the thickness of the thin portion 12 in the enlarged opening portion 9 is reduced, vibration with a higher degree of freedom is possible, but a certain amount of thickness is required due to the pressure resistance. ing. Therefore, the degree of freedom is necessarily limited, and cannot be considered completely separated from the conditions connected to the connection flange 11.

  FIG. 5 shows the vibration state of the flow tube 3 during vibration. Here, F1 to F4 in FIG. 5 correspond to F1 to F4 in FIG. 3, that is, the connection portion between the enlarged opening 9 and the connection flange 11 and the connection portion of the leaf spring 6. In FIG. 5, F1 and F2 (F4 and F3) are fulcrums of vibration, and F2 (F3) is applied with a leaf spring 6, so that it is between F1 and F2 (F4 and F3). In the meantime, a standing wave corresponding to the driving frequency is generated.

  FIG. 6 is a diagram showing a vibration state when the temperature of the fluid to be measured (not shown) flowing through the flow tube 3 changes. FIG. 7 is a diagram showing a vibration state when stress is generated in the connection flange 11. In the case of FIG. 6, when the temperature of the fluid to be measured changes and F2 moves to F2 ′, the peak value that becomes the vibration abdomen changes from Q0 to Qa. At this time, the bending moment to F1 works in an increasing direction, and as a result, the standing wave between F2 and F3 is affected. On the other hand, in the case of FIG. 7, when F1 changes to F1a or F1b with respect to the attachment of the connection flange 11, Q0 which becomes the abdomen shifts to Qa or Qb, and as a result, a standing wave between F2 and F3. It will be affected.

  This is because the drive drive energy is transmitted so that F1 (F4) is always a fulcrum of vibration. Drive drive energy for forming a standing wave between F2 and F3 propagates to F1 to F2 and F3 to F4. The propagated leakage energy depends on the position of F1 (F4).

  The present invention has been made in view of the above-described circumstances. A straight pipe type Coriolis flow meter capable of stabilizing the resonance system while maintaining leakage energy, that is, a noise countermeasure type straight pipe type Coriolis flow meter is provided. The issue is to provide.

  In order to solve the above problems, the noise-reducing straight tube type Coriolis flow meter according to claim 1 of the present invention includes a straight tubular flow tube supported on both end sides having outflow inlets, and a connection block. A counter balance that is fixed to the flow tube and forms a double tube structure with the flow tube, a drive device that alternately drives the flow tube at a central position, and a phase difference that is proportional to the Coriolis force acting on the flow tube. A straight tube type Coriolis flowmeter having a pair of detection means for detecting, the flow tube having enlarged openings at both ends thereof, and a leaf spring perpendicular to the axis of the flow tube at the position of the connection block In the middle of the enlarged opening of the flow tube and the leaf spring connection position, and a suspended weight portion in the circumferential direction of the flow tube It is characterized by providing a.

  The noise suppression type straight tube type Coriolis flow meter of the present invention according to claim 2 is the noise suppression type straight tube type Coriolis flow meter according to claim 1, wherein the suspension weight member includes a mass part and the mass part through the flow. A connecting portion connected to the tube, the connecting portion connecting the mass portion at the center of the mass portion.

  The noise suppression type straight tube type Coriolis flow meter according to the present invention described in claim 3 is the noise suppression type straight tube type Coriolis flow meter according to claim 1, wherein the suspension weight member includes a mass part and the mass part through the flow. A connecting portion connected to the tube, the connecting portion connecting the mass portion on the leaf spring side of the mass portion.

  According to the present invention, when the driving device is driven to resonate, a standing wave is generated in the resonance system having the double-tube structure. In addition, a standing wave corresponding to the driving frequency is generated between the enlarged opening and the leaf spring connection position. Thereby, the suspension weight member between the enlarged opening and the leaf spring connection position vibrates, and the leakage energy is held by the vibration of the suspension weight member. When leakage energy is held, vibration between the enlarged opening and the leaf spring connection position is stabilized. And if the vibration between an enlarged opening part and a leaf | plate spring connection position is stabilized, the vibration of a resonance system will also be stabilized. The suspension weight member has a function of holding leakage energy. In other words, it has a function as a buffer.

  According to the first aspect of the present invention, it is possible to maintain the leakage energy and stabilize the vibration of the resonance system. Therefore, the accuracy and stability of the straight pipe type Coriolis flow meter can be improved as compared with the conventional case. The present invention has an effect that it is possible to provide a straight pipe type Coriolis flowmeter with less piping conditions and external influences.

  According to the present invention described in claims 2 and 3, there is an effect that a suspended weight member having a better shape can be provided by disposing the mass portion with respect to the connecting portion.

  Hereinafter, description will be given with reference to the drawings. 1A and 1B are diagrams showing an embodiment of a noise countermeasure type straight pipe type Coriolis flow meter according to the present invention, in which FIG. 1A is an enlarged sectional view of a main part, and FIG. In addition, the same code | symbol is attached | subjected to the same structural member as a prior art example, and detailed description is abbreviate | omitted.

  In FIG. 1, the noise countermeasure type straight pipe type Coriolis flowmeter 21 of the present invention is characterized in that a suspended weight member 22 is added to the conventional structure. The suspension weight member 22 is provided in the middle (here, the center) between the enlarged opening 9 of the flow tube 3 and the connection position of the leaf spring 6 and in the circumferential direction of the flow tube 3.

  In FIG. 1A, the cross-sectional state of the fluid to be measured (not shown) on the inflow side is illustrated, but the same suspension weight member 22 is also provided at the same position on the outflow side.

  The suspension weight member 22 has a structure in which the suspension weight member 22 itself vibrates in the S and S ′ directions due to the generation of standing waves, and leakage energy is held (stored) by the vibration of the suspension weight member 22. is doing. A specific structure of the suspended weight member 22 includes a structure having a mass portion 23 and a connecting portion 24 that couples the mass portion 23 to the flow tube 3.

  The mass portion 23 is an annular portion having a desired mass and a rectangular cross section, and is disposed at a predetermined distance from the outer peripheral surface of the flow tube 3. The connecting portion 24 has a surface orthogonal to the straight tube portion 10 of the flow tube 3 and is formed in a thin disk shape that can be elastically deformed. One end of the connecting portion 24 is connected to the center of the inner peripheral surface of the mass portion 23. The other end of the connecting portion 24 is connected to the outer peripheral surface of the flow tube 3 by welding.

  As a material of the suspended weight member 22 composed of the mass portion 23 and the connecting portion 24, for example, stainless steel is used as an elastic material. Incidentally, the material of the flow tube 3 is a normal material in this technical field such as stainless steel, hastelloy, titanium alloy and the like.

  In the above configuration, when the driving device 7 (see FIG. 3) is driven to resonate, a standing wave is generated in a resonance system having a double tube structure. A standing wave corresponding to the drive frequency is also generated between the enlarged opening 9 and the connection position of the leaf spring 6. Thereby, the suspended weight member 22 vibrates, and the leakage energy is held by the vibration of the suspended weight member 22. When the leakage energy is held, the vibration between the enlarged opening 9 and the connection position of the leaf spring 6 is stabilized, and the vibration of the resonance system is also stabilized.

  Next, another example of the suspended weight member 22 will be described with reference to FIG. FIG. 2 is an enlarged cross-sectional view of a main part of a noise countermeasure type straight tube type Coriolis flow meter showing another example.

  In FIG. 2, the suspension weight member 22 ′ provided in the middle between the enlarged opening 9 of the flow tube 3 and the connection position of the leaf spring 6 and in the circumferential direction of the flow tube 3 has the same configuration as the suspension weight member 22 described above. And has a function. The mass portion 23 ′ is an annular portion having a desired mass and a triangular cross section as shown in the figure, and is disposed at a predetermined distance in the outer peripheral direction of the flow tube 3.

  The mass portion 23 ′ is disposed closer to the enlarged opening 9 than the connecting portion 24 ′. The connecting portion 24 ′ has a surface orthogonal to the straight tube portion 10 of the flow tube 3 and is formed in a thin disk shape that can be elastically deformed. One end of the connecting portion 24 ′ is connected to the end of the mass portion 23 ′ on the leaf spring 6 side. The other end of the connecting portion 24 ′ is connected to the outer peripheral surface of the flow tube 3 by welding.

  The suspended weight member 22 'reduces energy applied to the connection portion (F1) between the enlarged opening 9 and the connection flange 11, and has the same effect as the above-described suspended weight member 22.

  As described above with reference to FIGS. 1 and 2, according to the present invention, since the leakage energy is maintained, the vibration of the resonance system can be stabilized more than in the past. Therefore, according to the present invention, it is possible to provide a straight tube type Coriolis flow meter having improved accuracy and stability as compared with the prior art, that is, a noise countermeasure type straight tube type Coriolis flow meter 21. According to the present invention, it is possible to provide a straight pipe type Coriolis flow meter (noise countermeasure type straight pipe type Coriolis flow meter 21) with less piping conditions and external influences.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

It is a figure which shows one Embodiment of the noise countermeasure type straight tube | pipe type Coriolis flowmeter of this invention, (a) is a principal part expanded sectional view, (b) is a perspective view of a suspended weight member. It is a principal part expanded sectional view of the noise countermeasure type straight pipe type Coriolis flowmeter which shows the other example of a suspended weight member. It is sectional drawing of the straight pipe | tube type Coriolis flowmeter of a prior art example. It is an expanded sectional view of an enlarged opening part and its circumference. It is a figure which shows the vibration state of the flow tube at the time of a vibration. It is a figure which shows the vibration state when the temperature of the to-be-measured fluid which flows into a flow tube changes. It is a figure which shows the vibration state when a stress arises in a connection flange.

Explanation of symbols

1, 21 Noise countermeasure type straight pipe type Coriolis flow meter 2 Outer cylinder 3 Flow tube 4 Counter balance 5 Connection block 6 Leaf spring 7 Drive device 8 Detector (detection means)
DESCRIPTION OF SYMBOLS 9 Enlarged opening part 10 Straight pipe part 11 Connection flange 12 Thin part 22, 22 'Suspension weight member 23, 23' Mass part 24, 24 'Connection part

Claims (3)

A straight tubular flow tube supported on both ends having an outflow inlet, a counter balance that is fixed to the flow tube via a connecting block and forms a double tube structure together with the flow tube, and the flow tube at a central position. A drive device for alternating drive; and a pair of detection means for detecting a phase difference proportional to the Coriolis force acting on the flow tube, wherein the flow tube has enlarged openings at both ends, and the connecting block A straight pipe type Coriolis flowmeter having a leaf spring perpendicular to the axis of the flow tube at the position of
A noise countermeasure type straight pipe type Coriolis flow meter, wherein a suspension weight member is provided in the middle of the enlarged opening of the flow tube and the leaf spring connecting position and in the circumferential direction of the flow tube. In the noise countermeasure type straight tube type Coriolis flow meter according to claim 1,
The suspension weight member has a mass part and a connecting part for connecting the mass part to the flow tube, and the connecting part connects the mass part at the center of the mass part. Straight pipe type Coriolis flow meter. In the noise countermeasure type straight tube type Coriolis flow meter according to claim 1,
The suspension weight member has a mass part and a connection part that connects the mass part to the flow tube, and the connection part connects the mass part on the plate spring side of the mass part. Noise suppression type straight pipe type Coriolis flowmeter.

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