JP2007147417A - Straight-tube coriolis flowmeter having elastic connecting member, pedestal, and flow tube tertiary mode node position stabilization structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the node position in tertiary mode of stress dispersion and a flow tube. <P>SOLUTION: The straight-tube Coriolis flowmeter 21 includes a straight-tube flow tube 3, a driving device 7 for driving it with tertiary mode vibration, a pair of detecting means 8 for detecting a phase difference proportional to the Coriolis force, a rigid pedestal 22, an elastic connecting member 23 with elasticity, and a bracket 24 for weight addition. Assuming that the axial direction of the flow tube 3 is Z axis, the driving direction of the driving device 7 is X axis, and the direction orthogonal to the Z axis and X axis is Y axis, the elastic connecting member 23 is an elastic body where the rigidity of the Z-axis direction is lower than the rigidities of the X-axis direction and Y-axis direction, or an elastic body where the rigidity of the rotation direction about Y axis is lower than the rigidities of the rotation direction about Z axis and the rotation direction about X axis. The bracket 24 for weight addition is a member for link and weight addition, and is effective for stabilizing the node position. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 straight tube type Coriolis flowmeter that vibrates a straight tube (flow tube) in a tertiary mode and has an elastic connecting member and a pedestal in its configuration.

  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. 8, a conventional straight tube type Coriolis flow meter 1 includes an outer cylinder 2, a flow tube (inner tube) 3, a counter balance (outer tube) 4, a connecting block 5, a leaf spring 6, and a driving device. 7, a detector (detection means) 8, 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 connection block 5 is provided as a rigid body. 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 enlarged opening 9 in the figure is formed to have a spring action.

  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 drive device 7 is configured to drive the straight tube portion 10 of the flow tube 3 and the counter balance 4 at a coupled vibration frequency having opposite phases. 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. Accordingly, the flow tube 3 is supported at a plurality of 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.
Japanese Patent No. 2786829 (page 4, FIG. 1)

  In the conventional straight tube type Coriolis flow meter 1, in order to eliminate vibration resistance and vibration leakage, a mass point that vibrates in the opposite direction to the vibration of the flow tube 3, that is, a counter balance 4 is provided to vibrate vibration. It has a structure that cancels out. The conventional straight tube type Coriolis flow meter 1 has a structure in which the driving device 7 and the detector 8 are installed on the counter balance 4 instead of the outer cylinder 2, and the driving device 7 and the detector 8. The counter balance 4 is fixed to two locations of the flow tube 3 instead of the outer cylinder 2 via the connecting block 5 (disturbance acts on the straight tube type Coriolis flow meter 1). In such a case, the structure prevents the noise from being directly superimposed on the detector 8. Also, the low-order bending vibration (the most important mode caused by the disturbance) that is the easiest to vibrate is different from the drive mode. Structure to do). Further, the conventional straight tube type Coriolis flow meter 1 has a structure in which a leaf spring 6 is provided to fix the position of the connecting block 5 and, as a result, the direction of vibration is determined (plate spring). 6 is provided, the connecting block 5 has a center of rotation during vibration).

  By the way, in the conventional straight tube type Coriolis flow meter 1 having such a structure, the connecting block 5 for connecting the flow tube 3 and the counter balance 4 is a rigid body as described above. Has a problem. That is, when an axial force is generated in the flow tube 3, local stress is generated between the pair of connection blocks 5 and between both ends of the flow tube 3 and the connection block 5. There is a problem that stress may remain or the flow tube 3 may be plastically deformed.

  Hereinafter, the axial stress which acts on the flow tube 3 is demonstrated using a schematic diagram. In addition, in order to make it easy to understand the trouble due to the axial stress, the following explanation will be made ignoring the function (spring action) of the enlarged opening 9. FIGS. 9A to 9D are schematic views showing the state of the flow tube 3 and the counter balance 4 when the temperature of the fluid to be measured flowing inside the flow tube 3 is raised, and FIG. 4 is a perspective view showing a positional relationship among a tube 3, a counter balance 4, a connecting block 5, and a leaf spring 6. FIG.

  When the fluid to be measured is caused to flow through the flow tube 3 and the driving device 7 is driven to resonate, the flow tube 3 and the counter balance 4 vibrate along a locus as shown in FIG. In a state where the temperature of the fluid to be measured does not rise, the entire temperature is uniform (no temperature change occurs). At this time, between the pair of connection blocks 5 and both ends of the flow tube 3 and the connection blocks 5 In the meantime, no axial stress is generated yet (however, stress due to vibration acts separately during driving).

  When the fluid to be measured continues to flow and this temperature is raised, a force is generated in the flow tube 3 to extend in the axial direction due to the temperature change. On the other hand, the counterbalance 4 to which the heat of the temperature change cannot be transmitted does not generate an expansion force as much as the flow tube 3, and as a result, the distance between the connecting blocks 5 remains almost unchanged. . Therefore, as shown in FIG. 9B, in the flow tube 3, in addition to the stress due to vibration, local axial stress that is compressed is generated.

  Thereafter, when the counter balance 4 adapted to the heat due to the temperature change extends in the axial direction, the distance between the connecting blocks 5 increases accordingly, and the axial stress generated between the connecting blocks 5 is shown in FIG. ). However, since the axial stress which becomes compression between the both ends of the flow tube 3 and the connecting block 5 increases conversely, a large axial stress acts on the flow tube 3 locally.

  When the entire temperature becomes equal and the distance between the fixed ends of the flow tube 3 increases and becomes long, the axial stress is lost in the entire flow tube 3 as shown in FIG. 9D, and as a result, the state is stabilized.

  FIGS. 10A to 10D are schematic views showing the state of the flow tube 3 and the counter balance 4 when the temperature of the fluid to be measured flowing inside the flow tube 3 is lowered. FIG. 10A shows a state in which the temperature of the fluid to be measured is high and the whole temperature is uniform. In this state, no axial stress acts on the entire flow tube 3.

  When the temperature of the fluid to be measured is lowered, a force for contracting in the axial direction is generated in the flow tube 3 due to the temperature change. On the other hand, there is no change in the length of the counter balance 4, that is, the distance between the connecting blocks 5, and the distance between the fixed ends of the flow tube 3. As shown in FIG. In this case, local axial stress acting as a tension acts.

  Thereafter, when the counter balance 4 adapted to the heat due to the temperature change contracts in the axial direction, the distance between the connecting blocks 5 decreases accordingly, and the axial stress generated between the connecting blocks 5 is shown in FIG. ). However, since the axial stress that becomes the tension between the both ends of the flow tube 3 and the connecting block 5 increases conversely, a large axial stress acts on the flow tube 3 locally.

  When the entire temperature becomes uniform and the distance between the fixed ends of the flow tube 3 is reduced and shortened, the axial stress is lost in the entire flow tube 3 as shown in FIG.

  As can be seen from the above description, the conventional straight tube type Coriolis flow meter 1 has a structure in which the axial stress acting on the flow tube 3 is difficult to disperse in the tube axis direction. Therefore, the conventional straight pipe type Coriolis flow meter 1 has a structure that is vulnerable to temperature changes.

  The inventor of the present application considers driving the flow tube by bending third mode vibration as one of the solutions to the above problems. The reason for adopting the tertiary mode vibration is that it is considered to be a driving mode that can minimize vibration leakage even without the conventional counterbalance. The inventor of the present application also considers stabilizing the node position in the tertiary mode of the flow tube.

  The present invention has been made in view of the circumstances described above, and is a straight pipe capable of dispersing axial stress acting on the flow tube and stabilizing the node position in the tertiary mode of the flow tube. An object is to provide a Coriolis flow meter.

  The straight tube type Coriolis flow meter according to the present invention, which has been made to solve the above-mentioned problems, is a straight tube type Coriolis flow meter having an elastic connecting member, a pedestal, and a flow tube tertiary mode node position stabilizing structure. This is a pair of pipes for detecting a phase difference proportional to a Coriolis force acting on the flow tube, a drive device for driving the flow tube with a third mode vibration, and a straight flow tube through which a fluid to be measured flows. Detection means, a rigid pedestal positioned outside the flow tube in a state where the coils of the drive unit and the pair of detection means are fixed, and two positions serving as a tertiary mode node position of the flow tube. A pair of elastic elastic connecting members for connecting the pedestal, the axial direction of the flow tube being the Z axis, and the driving direction of the driving device orthogonal to the Z axis being the X axis Further, assuming that the direction perpendicular to the Z axis and the X axis is the Y axis, the elastic connecting member has a structure in which the rigidity in the Z axis direction is lower than the rigidity in the X axis direction and the Y axis direction. And an elastic body having a structure in which the rigidity in the rotation direction around the Y axis is lower than the rigidity in the rotation direction around the Z axis and the rotation direction around the X axis. The base for connecting the elastic connecting member is provided with a weight addition bracket for connection and weight addition.

  A straight tube type Coriolis flowmeter having the elastic connecting member according to the present invention, a pedestal, and a flow tube tertiary mode node position stabilizing structure receives the invention according to claim 1, wherein the elastic connecting member Has a Y-axis direction extending portion extending in the Y-axis direction, and the weight adding bracket is connected to the elastic connecting member via the Y-axis direction extending portion and further in the Y-axis direction. It is characterized by having a Y-axis direction arm portion for adding a weight.

  A straight tube type Coriolis flowmeter having the elastic connecting member, the pedestal, and the flow tube tertiary mode node position stabilizing structure according to the third aspect of the present invention receives the invention according to the first or second aspect, The weight addition bracket has an X-axis direction weight addition portion for further weight addition in the X-axis direction.

  The straight pipe type Coriolis flowmeter having the elastic connecting member, the pedestal, and the flow tube tertiary mode node position stabilizing structure according to the fourth aspect of the present invention receives the invention according to the third aspect, wherein the X-axis direction The weight adding unit is characterized by having a mechanism that makes the weight adding position variable, a mechanism that makes the weight mass variable, or a mechanism that makes both the weight adding position and the weight mass variable.

  According to the present invention having such a feature, the pedestal for fixing each coil of the driving device and the detection means is provided with elastic connection members at two positions which are the node positions of the tertiary mode inherent to the flow tube. Provided. This pedestal is provided as a member capable of maintaining a fixed position without vibrating even when the driving device is driven to vibrate the flow tube. In addition to the structure of the pedestal, a structure of a cylindrical body having a rectangular cross-sectional view is also employed in the present invention for the purpose of increasing rigidity.

  The elastic connecting member is provided to connect the pedestal to the flow tube. The elastic connecting member is provided in order to disperse the axial stress acting on the flow tube as a whole. The elastic connecting member is provided as a useful member for making the structure strong against temperature change. The structure of the elastic connecting member is determined so that the rigidity is weak in the axial direction of the flow tube and the rigidity is high in the other directions. In addition, the structure of the elastic connecting member is determined so as to be a rotation free support end with respect to the vibration direction so as not to hinder the movement of the tertiary mode vibration.

  The elastic connecting member is connected to the pedestal via a weight addition bracket. Weights are intensively added to the two locations of the flow tube serving as the node positions in the tertiary mode due to the presence of weight addition brackets. When the weight is added, the node position in the tertiary mode of the flow tube is stabilized. Specifically, the movement of the node position due to the density is reduced, and the third-order mode vibration is stabilized. Furthermore, if a mechanism that can add a weight in the X-axis direction of the weight-adding bracket and change the position, mass, or both of these is provided, the inertia moment in the rotational direction will be affected most efficiently. The vibration balance in the flow direction can be easily adjusted.

  In addition, in the present invention, it is preferable that the linear expansion coefficients of the flow tube, the pedestal, and the elastic connecting member are the same in order to make the structure stronger against temperature changes. Note that the detection means is not limited to the configuration of the coil and the magnet. For example, any means for detecting any one of displacement, speed, and acceleration such as an acceleration sensor, optical means, capacitance type, and distortion type (piezo type) may be used.

  According to the first aspect of the present invention, the axial stress acting on the flow tube can be dispersed. Therefore, there is an effect that the strength against the temperature change can be improved as compared with the conventional case. Further, according to the first aspect of the present invention, there is an effect that the counter balance used conventionally can be made unnecessary. As a result, the imbalance caused by the change in density of the fluid to be measured and the moment of inertia (mass) of the counterbalance, that is, the imbalance caused by the fact that the moment of inertia of the counterbalance does not change even if the density of the fluid to be measured changes. There is an effect that it can be eliminated. Therefore, there is an effect that it is possible to eliminate instrument difference shift and variation, and further shift to density measurement (frequency). Furthermore, according to the present invention described in claim 1, there is an effect that the node position in the tertiary mode of the flow tube can be stabilized. Thereby, there exists an effect that the thing of a better form can be provided.

  According to the second aspect of the present invention, it is possible to minimize the decrease in the phase difference and to further stabilize the node position in the tertiary mode of the flow tube. Thereby, there exists an effect that the thing of a better form can be provided.

  According to the present invention described in claims 3 and 4, there is an effect that the moment of inertia can be changed. In addition, the vibration balance can be adjusted. Thereby, there exists an effect that the thing of a better form can be provided.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a view showing an embodiment of a straight tube type Coriolis flowmeter having an elastic connecting member, a pedestal, and a flow tube tertiary mode node position stabilizing structure of the present invention, and (a) is a straight tube type Coriolis flow rate. Sectional drawing of a total, (b) is a perspective view which shows the positional relationship of a flow tube, a base, and an elastic connection member. 2 and 3 show the flow tube and the pedestal when the temperature of the fluid to be measured flowing inside the flow tube of the straight tube type Coriolis flow meter of FIG. 1 is raised and lowered. FIG. 4 and FIG. 5 are schematic views showing the relationship between the node position and the weight in the tertiary mode.

  In FIG. 1, a straight tube type Coriolis flowmeter 21 of the present invention is first described from the same constituent members as in the conventional example, an outer cylinder 2, a flow tube 3, and a driving device (not shown in FIG. 8). Reference numeral 7 is a reference. The same applies hereinafter, and a pair of detectors (detecting means) 8 and a pair of connecting flanges (only one is shown here) 11 are provided (other general cases). This is omitted for the structural members). The straight pipe type Coriolis flowmeter 21 of the present invention is configured to include a base 22, a pair of elastic connection members 23, and a pair of weight addition brackets 24, which are main constituent members.

  As will be described later, each of the pair of weight addition brackets 24 is provided at an end of the pedestal 22, and the pair of elastic connection members 23 connects the pedestal 22 to the flow tube 3 via the weight addition brackets 24. It is configured. In the straight tube type Coriolis flow meter 21 of the present invention, the pair of elastic connecting members 23 are connected to the weight adding bracket 24 to form a node position stabilizing structure.

  The straight tube type Coriolis flow meter 21 according to the present invention is a flow tube in order to minimize vibration leakage without providing the conventional counter balance 4 (see FIG. 8), and to improve the strength against temperature change. In order to stabilize the joint position of the flow tube 3 in the tertiary mode, a weight adding bracket 24 is provided. The point added to a structural member is the feature. In addition, as a feature of the structure, the point that the elastic connecting member 23 becomes a rotation free support end with respect to the vibration direction of the flow tube 3 without providing the conventional leaf spring 6 (see FIG. 8). . Hereinafter, each component will be described.

  The outer cylinder 2 is a so-called housing and has a structure that is strong against bending and twisting. The outer cylinder 2 is formed in a size that can accommodate the flow tube 3. The outer cylinder 2 is formed so as to protect the main part of the flow meter such as the flow tube 3, that is, the sensor unit portion. Such an outer cylinder 2 is filled with an inert gas such as argon gas. By filling with the inert gas, dew condensation on the flow tube 3 and the like is prevented. The outer cylinder 2 is formed with a lid 2a. The lid 2a is formed as a portion for adjusting the position, mass, or both of an adjustment weight 26 described later. The lid 2a is fixed to the outer cylinder main body 2b by welding after adjusting the position, mass, or both of the adjustment weight 26.

  The flow tube 3 has a straight straight pipe portion 10 and a trumpet-shaped enlarged opening portion 9 (only one is shown here) continuous to both ends of the straight pipe portion 10. A magnet (not shown) that constitutes the driving device and a magnet 8 a that constitutes the detector 8 are fixed to the straight pipe portion 10. The magnet constituting the driving device is fixed at the center position of the straight pipe portion 10. On the other hand, the magnets 8a constituting the detector 8 are respectively fixed at positions equidistant from the magnets on both sides of the magnet constituting the driving device. The magnet of the driving device and the magnet 8 a of the detector 8 are fixed so as to protrude along the vibration direction of the flow tube 3.

  The flow tube 3 is configured to vibrate in the third mode vibration by driving the drive device (in other words, the drive device is configured to drive the flow tube 3 in the third mode vibration). In this embodiment, the magnet 8a is fixed to a central vibration portion (excluding the central belly) sandwiched between two nodes in the tertiary mode vibration of the flow tube 3. The end of the outer cylinder 2 and the connection flange 11 are fixed to the enlarged opening 9 by welding.

  The pedestal 22 is a cylindrical body and a rigid body having a circular cross-sectional view, and is disposed at the same position as the conventional counter balance 4 (see FIG. 8). That is, the pedestal 22 is disposed outside the flow tube 3 so as to be in a non-contact state with respect to the flow tube 3. A coil 7b (see FIGS. 2 and 3) that constitutes the drive device and a coil 8b that constitutes the detector 8 are fixed to the pedestal 22. The coil 7 b constituting the driving device is fixed at the center position of the base 22. On the other hand, the coils 8b constituting the detector 8 are respectively fixed according to the position of the magnet 8a. The coil 7b that constitutes the drive device and the coil 8b that constitutes the detector 8 are fixed at such positions that the magnet that constitutes the drive device and the magnet 8a that constitutes the detector 8 also penetrate the rod.

  The pedestal 22 is provided as a member that does not vibrate while the flow tube 3 is oscillating in the third mode vibration and can maintain a fixed position (the pedestal 22 is similar to the conventional counter balance 4). It shall not be a resonating member). A weight addition bracket 24 is provided at the end of the pedestal 22. The base 22 is connected to the flow tube 3 via a weight addition bracket 24 and an elastic connection member 23.

  The elastic connecting member 23 is fixed across the weight addition brackets 24 at both ends of the base 22 and the flow tube 3. The elastic connecting member 23 has a function of connecting the base 22 and the flow tube 3 and a function as an elastic body. The elastic connecting member 23 is attached to two places that are the node positions 25 (see FIGS. 2 to 5) of the tertiary mode that the flow tube 3 originally has.

  Here, the axial direction of the flow tube 3 is the Z axis, the driving direction of the driving device (not shown) (the vibration direction of the flow tube 3 and orthogonal to the Z axis) is the X axis, and further orthogonal to the Z axis and the X axis. If the direction to perform is defined as the Y-axis, the elastic connecting member 23 has a lower rigidity in the Z-axis direction than the respective rigidity in the X-axis direction and the Y-axis direction, and the rotational direction (Rz) about the Z-axis. In addition, the rigidity in the rotation direction (Ry) about the Y axis is lower than the rigidity in the rotation direction (Rx) about the X axis. Hereinafter, a more specific structure of the elastic connecting member 23 and the weight adding bracket 24 connected to the elastic connecting member 23 will be described.

  The elastic connecting member 23 has a spindle-shaped flat plate structure continuous with the flow tube 3. That is, the elastic connecting member 23 is formed in a shape as illustrated. More specifically, the elastic connecting member 23 has a main body 23a and a pair of Y-axis direction extending portions 23b extending in the Y-axis direction with respect to the main body 23a, and is formed in a spindle shape. The end 23d of the Y-axis direction extending portion 23b is formed so that the width in the X-axis direction is narrower than the width in the X-axis direction of the main body 23a. A fixing through hole 23c is formed in the center of the main body 23a so as to penetrate in accordance with the diameter of the flow tube 3. The elastic connecting member 23 is formed so that the edge portion is connected with a smooth curve from the continuous portion of the main body 23a and the Y-axis direction extending portion 23b to the end portion 23d.

  The through hole 23c is fixed to the flow tube 3 by brazing. The end 23d is also fixed to the weight addition bracket 24 by brazing (not limited to brazing).

  The weight addition bracket 24 is provided at the end of the pedestal 22 as a member for connection and weight addition (weight addition that does not hinder the phase difference (sensitivity)). The weight addition bracket 24 includes a main body 24a, a pair of Y-axis direction arm portions 24b, and a pair of X-axis direction weight addition portions 24c. In this embodiment, the adjustment weight 26 is provided in the lower X-axis direction weight adding portion 24c so that the position, mass, or both of them can be changed. Due to the presence of the weight addition bracket 24, the weight addition bracket 24 has a function of intensively adding weights to the node position 25 (see FIGS. 2 to 5) in the tertiary mode.

  The main body 24a is formed in a ring shape having a desired thickness. A pair of Y-axis direction arm portions 24b are coupled on the Y-axis of the main body 24a. The pair of Y-axis direction arm portions 24 b are formed so as to be able to be connected to the elastic connection member 23 via the Y-axis direction extending portion 23 b of the elastic connection member 23. Further, the pair of Y-axis direction arm portions 24b are formed so that further weight addition in the Y-axis direction can be achieved. A connecting convex portion 24d extending toward the Y axis of the elastic connecting member 23 is formed at the end of the Y-axis direction arm portion 24b. The connecting protrusion 24d is formed to connect the end 23d of the Y-axis direction extending portion 23b of the elastic connecting member 23.

  In the elastic connecting member 23, as the connecting position between the end 23d of the Y-axis direction extending portion 23b and the connecting convex part 24d of the Y-axis direction arm portion 24b increases, the rigidity in the rotational direction Ry on the Y-axis decreases. The rigidity in the Z-axis direction is reduced. The X-axis direction weight adding portion 24c is formed so that further weight addition in the X-axis direction can be achieved. The X-axis direction weight adding portion 24c is formed in a convex shape on the X-axis of the main body 24a.

  As a material of the flow tube 3, the pedestal 22, the elastic connecting member 23, and the weight addition bracket 24 in the above description, for example, stainless steel is taken as an example. As materials for these four members, it is preferable to select a material having the same linear expansion coefficient or a linear expansion coefficient as close as possible in consideration of expansion and contraction due to temperature change. In this embodiment, the base 22 is formed so that the heat capacity is relatively small.

  In the above configuration, when a fluid to be measured (not shown) is caused to flow through the flow tube 3 and a driving device (not shown) is driven to generate third-order mode vibration in the flow tube 3, the Coriolis force at the position of the detector 8 The mass flow rate is calculated by a signal calculation processing unit (not shown) based on the generated phase difference. In this embodiment, the density is also calculated from the vibration frequency. The straight pipe type Coriolis flow meter 21 of the present invention has a function as a flow meter which is not different from the conventional one.

  In the straight tube type Coriolis flowmeter 21 of the present invention, as can be seen from the above description, the base 22 is connected to the flow tube 3 via the elastic connecting member 23 having high rigidity and the axial rigidity. For this reason, the flow tube 3 does not vibrate during the vibration of the third mode vibration by driving of a driving device (not shown), and maintains a fixed position. Hereinafter, the operation of the flow tube 3, the base 22, and the elastic connecting member 23 according to the temperature change of the fluid to be measured (not shown) will be described with reference to FIGS. 2 and 3. The operation of the weight addition bracket 24 will be described with reference to FIGS.

  FIG. 2A schematically shows a state where the temperature of the fluid to be measured is low and the temperature of the entire straight pipe type Coriolis flow meter 21 is uniform. Moreover, the state where the flow tube 3 is oscillating by the third mode vibration by driving of a driving device (not shown) is shown. In such a state, axial stress is not yet generated over the entire flow tube 3 (however, stress due to vibration acts on the flow tube 3 separately).

  FIG. 2B schematically shows a state immediately after raising the temperature of the fluid to be measured. At this time, since the heat due to the temperature change of the fluid to be measured is not transmitted to the pedestal 22, there is no change in the total length, and there is no change in the distance between the pair of connection flanges 11 (between the fixed ends). The flow tube 3 generates axial stress that is compressed due to a temperature change of the fluid to be measured. This compressive axial stress works equally throughout the flow tube 3. The reason is that since the pair of elastic connecting members 23 are elastic bodies, the generation of local axial stress as in the conventional example is prevented by this elastic deformation. Therefore, the axial stress generated in the flow tube 3 is dispersed in the axial direction of the flow tube 3 by the structure of the present invention in the above state.

  FIG. 2 (c) schematically shows a state after elapse of a while after increasing the temperature of the fluid to be measured. At this time, since the heat capacity is relatively small as described above, the pedestal 22 adapts to heat due to a temperature change relatively quickly, and as a result, elongation occurs in the full length direction. Since the pair of elastic connecting members 23 has a structure in which the rigidity in the axial direction (the Z-axis direction) of the flow tube 3 is lower than the other as described above, the elongation is absorbed by elastic deformation. Unlike the conventional example, the axial stress is dispersed in the axial direction of the flow tube 3 between the pair of elastic connecting members 23 and between the elastic connecting member 23 and the connecting flange 11 (fixed end). Accordingly, in the state of FIG. 2C, as in the state of FIG. 2B, no local axial stress is generated (the axial stress hardly changes from the state of FIG. 2B).

  FIG. 2D schematically shows a state in which the temperature of the entire straight pipe type Coriolis flow meter 21 is uniform. In this state, the pedestal 22 and the distance between the fixed ends are extended in the same manner as the flow tube 3, so that the axial stress that has been acting on the flow tube 3 until then disappears, and as a result, the state of the straight tube type Coriolis flowmeter 21 Will be stable.

  FIG. 3A schematically shows a state where the temperature of the fluid to be measured is high and the temperature of the entire straight Coriolis flow meter 21 is uniform. In addition, a state in which the flow tube 3 is oscillating by the third mode vibration by driving of a driving device (not shown) is schematically shown. In such a state, it is the same as the state of FIG. 2A, and no axial stress is generated over the entire flow tube 3 (however, stress due to vibration acts separately on the flow tube 3). Suppose).

  FIG. 3B schematically shows a state immediately after the temperature of the fluid to be measured is lowered. At this time, since the cooling due to the temperature drop of the fluid to be measured is not transmitted to the pedestal 22, there is no change in the overall length, and there is no change in the distance between the pair of connection flanges 11 (between the fixed ends). The flow tube 3 is subjected to tensile stress due to a temperature change of the fluid to be measured. This axial stress acting as a tension works evenly throughout the flow tube 3. The reason is the same as described above, and since the pair of elastic connecting members 23 are elastic bodies, the generation of local axial stress as in the conventional example is prevented by this elastic deformation. Therefore, the axial stress generated in the flow tube 3 is dispersed in the axial direction of the flow tube 3 by the structure of the present invention in the above state.

  FIG. 3C schematically shows a state after a while after the temperature of the fluid to be measured is lowered. At this time, since the heat capacity is relatively small as described above, the pedestal 22 adapts relatively quickly to cooling due to a temperature change, and as a result, shrinkage occurs in the full length direction. Since the pair of elastic connecting members 23 has a structure in which the rigidity in the axial direction (Z-axis direction) of the flow tube 3 is lower than the other as described above, the shrinkage is absorbed by elastic deformation. Unlike the conventional example, the axial stress is dispersed in the axial direction of the flow tube 3 between the pair of elastic connecting members 23 and between the elastic connecting member 23 and the connecting flange 11 (fixed end). Therefore, in the state of FIG. 3C, as in the state of FIG. 3B, no local axial stress is generated (the axial stress hardly changes from the state of FIG. 3B).

  FIG. 3D shows a state where the temperature of the entire straight pipe type Coriolis flow meter 21 is uniform. In this state, the pedestal 22 and the distance between the fixed ends are contracted in the same manner as the flow tube 3, so that the axial stress that has been acting on the flow tube 3 until then disappears. As a result, the state of the straight tube type Coriolis flowmeter 21 Will be stable.

  4 and 5 are schematic views showing the relationship between the node position 25 and the weight in the tertiary mode. 4 and 5, considering the case where the flow tube 3 is driven in the tertiary mode and the pedestal 22 is held via the elastic connecting member 23 at the two node positions 25, the flow tube 3 is concentrated at the two node positions 25. If the weight is applied, the movement of the node position 25 due to the density is reduced, and the vibration in the tertiary mode is stabilized. The weight addition bracket 24 is provided for this reason.

  In the elastic connecting member 23, the rotational moments around the Y-axis work alternately around the two node positions 25. At this time, it is effective to provide the weight 27 on the rotation axis (on the Y axis), which contributes to the stability of the node position 25. It also contributes to minimizing the phase difference (sensitivity) degradation. The weight 27 corresponds to the weight of the Y-axis direction arm portion 24b of the weight addition bracket 24.

  In addition, in FIGS. 4 and 5, for adjusting the phase shift (zero point shift), the tip of the arm extended in the X-axis direction with respect to the node position 25 that can most effectively affect the phase. It is effective to change the moment of inertia by providing the weight 28 with the weight 28 (the weight 28 is preferably provided so as to be movable, variable in mass, or both). The weight 28 corresponds to the weight of the adjustment weight 26 provided in the X-axis direction weight adding portion 24c of the weight adding bracket 24.

  As described above with reference to FIGS. 1 to 5, according to the straight tube type Coriolis flow meter 21 of the present invention, a temperature change occurs in the fluid to be measured, and the flow tube 3 expands and contracts. However, since the axial stress acting on the flow tube 3 is distributed in the axial direction of the flow tube 3 (Z-axis direction), the structure is strong against temperature changes, and the temperature characteristics of the flow meter as before Also has the advantage that it can be improved.

  Moreover, according to the straight tube type Coriolis flowmeter 21 of the present invention, since the flow tube 3 is structured to vibrate with the third mode vibration, there is an advantage that vibration leakage can be minimized. Incidentally, the straight pipe type Coriolis flowmeter 21 of the present invention with respect to vibration leakage has a structure that does not require the conventionally used leaf spring 6 (see FIG. 8). There is also an advantage that leakage can be eliminated.

  Furthermore, according to the straight tube type Coriolis flowmeter 21 of the present invention, since the counter balance 4 (see FIG. 8) used conventionally is unnecessary, the density change of the fluid to be measured and the inertia of the counter balance 4 are obtained. There is an advantage that the unbalance caused by the moment (mass), that is, the unbalance caused by the fact that the moment of inertia of the counterbalance 4 does not change can be eliminated even if the density of the fluid to be measured changes. Therefore, there is an advantage that it is possible to eliminate instrument difference shift and variation, and further shift to density measurement (frequency).

  Furthermore, according to the straight tube type Coriolis flowmeter 21 of the present invention, since it has a structure having a weight addition bracket 24 (because it has a node position stabilizing structure), the tertiary mode of the flow tube 3 is used. This has the advantage that the node position 25 can be stabilized. Specifically, the third mode vibration can be stabilized by reducing the movement of the node position 25 due to the density. Therefore, there is an advantage that a better form can be provided.

  In addition, according to the straight tube type Coriolis flowmeter 21 of the present invention, since the base 22 does not vibrate during the vibration of the flow tube 3, wiring (to the coils 7 b and 8 b fixed to the base 22 ( When wiring from the outer cylinder 2 is omitted, it is not necessary to have slack (slack considering vibration), and as a result, there is an advantage that the degree of freedom in wiring design increases.

  Next, another arrangement example of the detector 8 (detection means) will be described with reference to FIG. FIG. 6 is a cross-sectional view of a straight pipe type Coriolis flow meter 21 showing another arrangement example.

  For example, a bracket 29 is provided on the upper X-axis direction weight addition portion 24 c of the weight addition bracket 24. A coil 8 b constituting the detector 8 is provided at the tip of the bracket 29. On the other hand, the flow tube 3 is provided with a magnet 8 a constituting the detector 8. The detector 8 may be arranged as shown.

  Next, another example (23 ′, 24 ′) of the elastic connecting member 23 and the weight adding bracket 24 will be described with reference to FIG. FIG. 7 is a perspective view showing another example.

  In FIG. 7, the elastic connecting member 23 ′ is formed in a shape in which the Y-axis direction extending portion 23 b ′ becomes a torsion bar (torsion beam). This is different from the above. On the other hand, the weight adding bracket 24 ′ has a shape of the connecting convex portion 24 d ′ so that the end portion 23 d ′ of the Y-axis direction extending portion 23 b ′ can be inserted and fixed by brazing (which is an example). The point that changed is different. Even when the elastic connecting member 23 'and the weight adding bracket 24' are changed, the above-described advantages can be obtained.

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

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the straight pipe type Coriolis flowmeter which has the elastic connection member of this invention, a base, and a flow tube tertiary mode node position stabilization structure, (a) is a cross section of a straight pipe type Coriolis flowmeter FIG. 4B is a perspective view showing the positional relationship among the flow tube, the pedestal, and the elastic connecting member. (A)-(d) is a schematic diagram which shows the state of a flow tube, a base, and an elastic connection member when raising the temperature of the fluid to be measured which flows into the flow tube of the straight tube type Coriolis flow meter of FIG. It is. (A)-(d) is a schematic diagram which shows the state of a flow tube, a base, and an elastic connection member when the temperature of the to-be-measured fluid which flows into the inside of the flow tube of the straight tube | pipe type Coriolis flowmeter of FIG. It is. It is a schematic diagram which shows the relationship between the node position and weight in tertiary mode. It is a three-dimensional schematic diagram showing the relationship between the node position and the weight in the tertiary mode. It is sectional drawing of the straight pipe | tube type Coriolis flowmeter which shows the other example of arrangement | positioning of a detector (detection means). It is a perspective view which shows the other example of an elastic connection member and a bracket for weight addition. It is sectional drawing of the straight pipe | tube type Coriolis flowmeter of a prior art example. (A)-(d) is a schematic diagram which shows the state of the flow tube and counter balance when raising the temperature of the fluid to be measured flowing inside the flow tube of the straight tube type Coriolis flow meter of FIG. ) Is a perspective view showing a positional relationship among a flow tube, a counter balance, a connecting block, and a leaf spring. (A)-(d) is a schematic diagram which shows the state of a flow tube and a counter balance when the temperature of the to-be-measured fluid which flows into the flow tube of the straight tube | pipe type Coriolis flowmeter of FIG. 8 is dropped.

Explanation of symbols

2 outer cylinder 3 flow tube 7 drive device 7a magnet 7b coil 8 detector (detection means)
8a Magnet 8b Coil 9 Enlarged opening 10 Straight pipe part 11 Connection flange 21 Straight pipe Coriolis flow meter 22 Base 23 Elastic connecting member 23a Main body 23b Y-axis direction extension part 23c Through hole 23d End part 24 Weight addition bracket 24a Main body 24b Y-axis direction arm portion 24c X-axis direction weight addition portion 24d Connection convex portion 25 Node position 26 Adjustment weight 27, 28 Weight 29 Bracket

Claims (4)

A straight tubular flow tube through which the fluid to be measured flows, a drive device for driving the flow tube with third-order vibration, a pair of detection means for detecting a phase difference proportional to the Coriolis force acting on the flow tube, A pair of rigid pedestals positioned outside the flow tube in a state where the coils of the driving device and the pair of detection means are fixed, and a pair of the pedestals that are connected to the third mode node position of the flow tube. A resilient elastic coupling member,
Assuming that the axial direction of the flow tube is the Z axis, the driving direction of the driving device orthogonal to the Z axis is the X axis, and further the direction orthogonal to the Z axis and the X axis is the Y axis, the elastic connecting member is An elastic body having a structure in which the rigidity in the Z-axis direction is lower than the rigidity in the X-axis direction and the Y-axis direction, and a rotation direction around the Z-axis and a rotation around the X-axis An elastic body having a structure in which the rigidity in the rotational direction around the Y axis is lower than the rigidity in each direction,
The pedestal for connecting the elastic connection member is provided with a weight addition bracket for connection and weight addition, and the elastic connection member, the pedestal, and the flow tube tertiary mode node position stabilizing structure. Has a straight pipe type Coriolis flow meter. In the straight pipe type Coriolis flowmeter having the elastic connecting member according to claim 1, a pedestal, and a flow tube tertiary mode node position stabilizing structure,
The elastic connecting member has a Y-axis direction extending portion extending in the Y-axis direction, and the weight addition bracket is connected to the elastic connecting member via the Y-axis direction extending portion and the Y-axis. A straight tube type Coriolis flowmeter having an elastic connecting member, a pedestal, and a flow tube tertiary mode node position stabilizing structure, characterized in that it has a Y-axis direction arm portion for further adding a weight in the direction. In a straight tube type Coriolis flowmeter having the elastic connecting member according to claim 1 or 2, a pedestal, and a flow tube tertiary mode node position stabilizing structure,
The weight addition bracket has an X-axis direction weight addition portion for further adding the weight in the X-axis direction, and includes a resilient connecting member, a pedestal, and a flow tube tertiary mode node position stabilization structure. Tube Coriolis flow meter. In the straight tube type Coriolis flowmeter having the elastic connecting member according to claim 3, a pedestal, and a flow tube tertiary mode node position stabilizing structure,
The X-axis direction weight addition portion has a mechanism that makes the weight addition position variable, a mechanism that makes the weight mass variable, or a mechanism that makes both the weight addition position and the weight mass variable. A straight pipe type Coriolis flowmeter having a member, a pedestal, and a flow tube tertiary mode node position stabilization structure.

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