JP4668664B2 - Multiple pipe structure type straight pipe type Coriolis flowmeter - Google Patents

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. The present invention relates to a multi-tube structure type straight pipe type Coriolis flowmeter.

  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. 5, a conventional straight tube type Coriolis flowmeter 1 includes an outer cylinder 2 shown in the figure, 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. The flow tube 3 is supported at both end portions having an outflow inlet.

  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 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 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. Therefore, free bending vibration is facilitated (see FIG. 6). By the way, as shown in FIG. 6, 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. 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. 7 shows the vibration state of the flow tube 3 during vibration. Here, F1 to F4 in FIG. 7 correspond to F1 to F4 in FIG. 5, 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. 7, 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. 8 is a diagram illustrating a vibration state when stress is generated in the connection flange 11. In the case of FIG. 8, when F1 is changed to F1a or F1b with respect to the attachment of the connecting flange 11, Q0 which becomes the abdomen shifts to Qa or Qb, and as a result, the standing wave between F2 and F3 is affected. Will come to give.

  This invention is made | formed in view of the situation mentioned above, and makes it a subject to provide the multipipe structure type straight pipe type Coriolis flowmeter which can stabilize a standing wave.

The multi-tube structure type straight pipe type Coriolis flow meter according to claim 1 of the present invention, which has been made to solve the above-mentioned problems, has a straight pipe portion and has an enlarged opening that forms an outflow inlet at both ends of the straight pipe portion. A straight tubular flow tube having a portion and supported at both ends,
A cylindrical counter balance that is secured to the flow tube via a connecting block and forms a double tube structure with the flow tube;
A rigid body formed in a cylindrical shape that is coaxial with the flow tube and the counterbalance, wherein the overall length is longer than the counterbalance and shorter than the straight tube portion of the flow tube , and the flow tube And a cylindrical body formed in a size interposed between the outer cylinder accommodating the double pipe structure constituted by the counter balance and the counter balance;
A driving device for alternately driving the flow tube at a central position;
A pair of detection means for detecting a phase difference proportional to the Coriolis force acting on the flow tube;
The flow tube has a surface orthogonal to the straight pipe portion of the flow tube, and one end is fixed to the connection block and the other end is fixed to a first leaf spring fixed to the inner wall of the cylindrical body. Connected to the cylindrical body, and a second is provided on the outer peripheral surface of the flow tube at the position of the vibration node located between the connection position of the first leaf spring of the flow tube and the enlarged opening. Providing a connecting block, one end fixed to the second connecting block and the other end connected to the cylindrical body via a fixing plate fixed to a third connecting block provided on the inner wall of the cylindrical body;
The cylindrical body is provided with a fourth connection block on the outer wall of the cylindrical body at the position where the third connection block is provided, one end is fixed to the fourth connection block, and the other end is the outer cylinder. It connects with this outer cylinder with the 2nd leaf | plate spring fixed to the 5th connection block provided in the inner wall of this.

  According to the present invention having such a feature, a straight tube type Coriolis flow meter having a structure in which a cylindrical body or the like is provided outside a resonance system by a double tube structure of a flow tube and a counterbalance is obtained. That is, the present invention provides a straight tube type Coriolis flow meter that forms a triple tube structure inside the flow meter housing. When the drive device is driven to resonate, a standing wave is generated in a resonance system having a double tube structure of a flow tube and a counter balance. Further, a standing wave corresponding to the drive frequency is also generated between the enlarged opening and the fixing plate or between the leaf spring connecting position and the fixing plate. When the driving device is driven to resonate, a fifth-order standing wave is generated. According to the present invention, by forming the triple tube structure, disturbance noise mixed in the standing wave between the enlarged opening and the fixed plate is caused between the plate spring connection position and the fixed plate arranged next. It is once buffered by the standing wave. By buffering the disturbance noise, the standing wave of the resonance system by the double tube structure of the flow tube and the counter balance is stabilized.

  The multi-tube structure type straight tube type Coriolis flow meter of the present invention according to claim 2 is the multi-tube structure type straight tube type Coriolis flow meter according to claim 1, wherein the fixing plate is matched with the shape of the leaf spring. It is formed or formed into a disk shape.

  According to the present invention having such characteristics, the cylindrical body is connected to the flow tube via the plate spring-shaped or disk-shaped fixing plate.

  According to the first aspect of the present invention, by forming the triple tube structure, the vibration of the resonance system of the flow tube and the counter balance can be stabilized. Therefore, the effect that the precision and stability as a straight pipe type Coriolis flowmeter can be improved as compared with the prior art. 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 second aspect of the present invention, there is an effect that a better form of the fixing plate can be provided.

Hereinafter, description will be given with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a straight tube type Coriolis flow meter of the multi-tube structure of the present invention. 2A is a diagram showing a vibration state when there is no influence of the piping, FIG. 2B is a diagram showing a vibration state when receiving the influence of the piping, and FIG. 3A is a view of the fixing plate and the leaf spring. FIG. 3B is a perspective view showing another example of the fixing plate, and FIG. 4 is a perspective view (including a partial cross section) of the triple tube structure when the fixing plate of FIG. 3B is used. is there. 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, a multi-tube structure type straight pipe type Coriolis flow meter 21 of the present invention is obtained by adding a cylindrical body 22, a fixing plate 23, and a second leaf spring 24 to a conventional structure to add an outer cylinder 2 (flow meter). It is characterized in that a triple tube structure is formed inside the casing. The triple tube structure is formed by arranging a cylindrical body 22 and the like outside the double tube structure of the flow tube 3 and the counter balance 4. The following standing wave is generated.

  The cylindrical body 22 is a rigid body that is coaxial with the flow tube 3 and the counter balance 4, and is formed in, for example, a cylindrical shape (assumed as an example). The cylindrical body 22 is formed such that the entire length is longer than the counter balance 4 and shorter than the straight pipe portion 10 of the flow tube 3. The cylindrical body 22 is formed in a size that is interposed between the counter balance 4 and the outer cylinder 2.

  As the material of the cylindrical body 22, for example, stainless steel is used. 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. The counter balance 4 is made of a material that is normal in this technical field, such as stainless steel.

  The fixing plate 23 is disposed at the vibration node of the flow tube 3 that exists between the connection position of the leaf spring 6 and the enlarged opening 9. The fixing plate 23 is formed by processing a thin plate, and is formed in the same shape as the leaf spring 6 as shown in FIG. 3A or a disc shape as shown in FIG. (It is assumed to be an example. Note that the triple-pipe structure in the case of being formed in a disc shape has a shape as shown in FIG. 4).

  One end of the fixing plate 23 is fixed to the outer peripheral surface of the flow tube 3 via a connecting block 25. Further, the other end of the fixing plate 23 is fixed to the inner peripheral surface of the cylindrical body 22 via a connecting block 26. The other end of the fixing plate 23 is fixed so as to be located slightly inward from the opening portions at both ends of the cylindrical body 22.

  The second leaf spring 24 is formed so that the cylindrical body 22 and the outer cylinder 2 can be connected at the position of the fixing plate 23. Specifically, the second leaf spring 24 is formed to have the same shape as the leaf spring 6 and to be fixed in the same direction as the leaf spring 6. One end of the second leaf spring 24 is fixed to the outer peripheral surface of the cylindrical body 22 via a connection block 27. The other end of the second leaf spring 24 is fixed to the inner peripheral surface of the outer cylinder 2 via a connecting block 28.

  As the material of the fixing plate 23, the leaf spring 6, and the second leaf spring 24, those usually used in this technical field such as stainless steel are used.

  In the above configuration, when the driving device 7 is driven to resonate, a fifth-order standing wave as shown in FIG. 2A is generated. Here, the vibration nodes F11 to F16 in the fifth-order standing wave in FIG. 2A correspond to the portions F11 to F16 in FIG. That is, the vibration nodes of F11 and F16 are the connection portions of the enlarged opening 9 and the connection flange 11, the vibration nodes of F12 and F15 are the connection portions of the fixing plate 23, and the vibration nodes of F13 and F14 are the vibration nodes of the leaf spring 6. It shall correspond to the connection part.

  The fifth-order standing wave is a vibration waveform obtained by causing the driving device 7 to be resonantly driven (driven by the force F in the figure) as described above, and is a constant between the vibration nodes of F13 to F14. The standing wave is a standing wave corresponding to a driving frequency generated in a resonance system having a double tube structure of the flow tube 3 and the counter balance 4 in the triple tube structure. Further, the standing wave between the vibration nodes of F12 to F13 and F14 to F15 is a standing wave corresponding to the driving frequency generated between the connection position of the fixing plate 23 and the connection position of the leaf spring 6. Further, the standing waves between the vibration nodes of F11 to F12 and F15 to F16 are standing waves according to the driving frequency generated between the enlarged opening 9 and the connection position of the fixing plate 23. The amplitude width of each standing wave is attenuated by the relationship of F13 to F14> F12 to F13> F11 to F12, F13 to F14> F14 to F15> F15 to F16.

  In the multi-tube structure type straight pipe type Coriolis flowmeter 21 of the present invention in which such a fifth-order standing wave is generated, when stress or disturbance noise occurs in the connection pipe or the connection flange 11, FIG. It will be as shown.

  That is, when a bending moment is applied to F11 and F16, the waveforms of F11 to F12 and F15 to F16 are greatly affected by a disturbance as compared to the broken line (the waveform when there is no piping influence) and change greatly as shown by the solid line. However, the effect of this large change is attenuated at F12 to F13 and F14 to F15 (in other words, once buffered at F12 to F13 and F14 to F15). When the influence is attenuated in this way, the standing wave between the vibration nodes of F13 to F14 maintains a stable state.

  According to the multi-tube structure type straight pipe type Coriolis flow meter 21 of the present invention, even if stress or disturbance noise occurs in the connection pipe or the connection flange 11, the double pipe of the flow tube 3 and the counter balance 4. The vibration of the resonance system due to the structure is stabilized. Therefore, the accuracy and stability as a straight pipe type Coriolis flowmeter is improved as compared with the prior art. The present invention provides a straight pipe type Coriolis flow meter 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 sectional drawing which shows one Embodiment of the multipipe structure type | mold straight pipe | tube type Coriolis flowmeter of this invention. (A) is a figure which shows the vibration state when there is no piping influence, (b) is a figure which shows the vibration state when it receives a pipe influence. (A) is a perspective view of a fixed plate and a leaf spring, (b) is a perspective view showing another example of a fixed plate. FIG. 4 is a perspective view (including a partial cross-section) of a triple-pipe structure when the fixing plate of FIG. 3B is used. 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 a stress arises in a connection flange.

Explanation of symbols

1 Straight pipe type Coriolis flow meter 2 Outer cylinder (flow meter housing)
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 21 Multiple pipe structure type straight pipe type Coriolis flow meter 22 Cylindrical body 23 Adhering plate 24 2nd leaf | plate spring 25-28 Connection block

Claims (2)

A straight tubular flow tube that has a straight pipe part and has enlarged openings that form outflow inlets at both ends of the straight pipe part, and is supported at both end parts;
A cylindrical counter balance that is secured to the flow tube via a connecting block and forms a double tube structure with the flow tube;
A rigid body formed in a cylindrical shape that is coaxial with the flow tube and the counterbalance, wherein the overall length is longer than the counterbalance and shorter than the straight tube portion of the flow tube , and the flow tube And a cylindrical body formed in a size interposed between the outer cylinder accommodating the double pipe structure constituted by the counter balance and the counter balance;
A driving device for alternately driving the flow tube at a central position;
A pair of detection means for detecting a phase difference proportional to the Coriolis force acting on the flow tube;
The flow tube has a surface perpendicular to the straight pipe portion of the flow tube, and one end is fixed to the connection block and the other end is fixed to the inner wall of the cylindrical body via a first leaf spring. Connected to the cylindrical body, and a second is provided on the outer peripheral surface of the flow tube at the position of the vibration node located between the connection position of the first leaf spring of the flow tube and the enlarged opening. Providing a connecting block, one end fixed to the second connecting block and the other end connected to the cylindrical body via a fixing plate fixed to a third connecting block provided on the inner wall of the cylindrical body;
The cylindrical body is provided with a fourth connection block on the outer wall of the cylindrical body at the position where the third connection block is provided, one end is fixed to the fourth connection block, and the other end is the outer cylinder. A multi-tube structure type straight pipe type Coriolis flowmeter characterized in that it is connected to the outer cylinder by a second leaf spring fixed to a fifth connection block provided on the inner wall of the multi-tube structure. In the multiple pipe structure type straight pipe type Coriolis flow meter according to claim 1,
The fixing plate is
It is formed according to the shape of the leaf spring, or is formed in a disc shape.

Images