TRANSDUCER FOR MEASURING MASS FLOW

Description

[0001] The present invention relates to a measuring sensor for measuring a mass flow with a single oscillating measuring pipe.

[0002] Generic measuring sensors are described, for example, in published patent application DE 039 16 285 A1, publication EP 518 124 A1, and the as yet unpublished patent application DE 10 2015 122 146.2. Measuring sensors with a single measuring tube are advantageous in that they do not contain flow dividers. However, unlike measuring sensors with two measuring tubes that oscillate symmetrically against each other, it is more difficult for measuring sensors with only a single measuring tube to avoid interaction with the environment by coupling out vibration energy of a bending vibration useful mode or by coupling in disruptive vibrations from the environment. Published patent application DE 10 2010 030 340 A1 discloses a measuring sensor with a single measuring tube in which the measuring tube has two parallel loops that oscillate against each other and thus balance each other.However, for this type of sensor, the possibility of draining the measuring tube is fundamentally excluded due to the looped layout of the measuring pipe, whereas sensors of this type can generally be designed to be drainable.

[0003] As a contribution to avoid interaction with the environment by coupling out vibration energy of a bending vibration useful mode or by coupling in disturbing vibrations from the environment, EP 518 124 A1 describes a frequency separation between the vibrations of the measuring pipe and vibrations of other components of the measuring sensor.

[0004] WO 2018 / 219603 A1 and WO 2019 / 170742 A1 each disclose a vibronic sensor with precisely one S-shaped measuring tube, which is connected to a support plate spring-mounted against the sensor housing. With such vibronic sensors, interference modes can still occur in the measuring tube—particularly during transport or if the sensor is incorrectly installed—which can lead to collisions between the coils and magnets of the vibration sensors and / or the vibration exciter.

[0005] The invention is based on the object of remedying the problem.

[0006] The object is achieved according to the invention by the vibronic measuring sensor according to independent claim 1. The vibronic measuring sensor according to the invention for measuring the mass flow of a flowable medium, comprising: a line inlet section; a line outlet section; an oscillating measuring pipe for guiding the medium, wherein the measuring pipe is bent in a pipe plane in its rest position, wherein the measuring pipe connects to the line inlet section on the inlet side and to the line outlet section on the outlet side and can be connected to a pipeline via the latter; a sensor housing, wherein the line inlet section and the line outlet section are each firmly connected to the sensor housing; at least one vibration exciter for exciting bending vibrations of the measuring pipe in a bending vibration useful mode;and at least two vibration sensors for detecting vibrations of the measuring pipeline, wherein the at least one vibration exciter comprises an excitation coil and / or the at least two vibration sensors each comprise a sensor coil, wherein the at least one vibration exciter comprises an excitation magnet and / or the at least two vibration sensors each comprise a sensor magnet, wherein the excitation magnet and / or the sensor magnet is arranged on the measuring pipeline, wherein the excitation magnet extends through a coil opening of the excitation coil and / or the sensor magnet extends through a coil opening of the sensor coil, characterized in that the excitation coil and / or the sensor coil has an elongated basic shape, wherein the basic shape has a center of gravity through which a largest diameter with a length ; d 1 and a smallest diameter with a length d2, wherein the excitation coil and / or the sensor coil has a first coil axis and a second coil axis in a cross-sectional plane, wherein the largest diameter d 1 is located in the first coil axis, with the smallest diameter d 2 in the second coil axis, where for a quotient d 1 / d 2 it applies that 1.15 ≤ d 1 / d 2 , especially 1.5 ≤ d 1 / d 2 and preferably 2 ≤ d 1 / d 2, wherein the measuring pipe is designed such that when the measuring pipe oscillates in a, in particular smallest, in-plane mode, a deflection direction of the measuring pipe in a region of the excitation magnet and / or the sensor magnet is oriented parallel to the first coil axis.

[0007] An advantage of this design is that it allows for variable spacing between the excitation magnet and the excitation coil and / or between the at least one sensor magnet and the corresponding sensor coil. This prevents a collision between the coil and the magnet moving in the coil opening when certain interference modes occur. This is particularly advantageous for magnets that are immersed in the coil opening or are at least partially enclosed by the coil.

[0008] Advantageous embodiments of the invention are the subject of the subclaims. One design provides that for the quotient d 1 / d 2 applies that d 1 / d 2 ≤ 10, in particular d 1 / d 2 ≤ 7.5 and preferably d 1 / d2 ≤ 3. One embodiment provides that the excitation magnet and / or the sensor magnet have a magnet diameter with a length d M wherein the length of the magnet diameter d M is smaller than the length d 2 of the smallest diameter, where for a quotient d 2 / d M it applies that 1 < d 2 / d M ≤ 2, especially 1.2 ≤ d 2 / d M ≤ 1.8 and preferably 1.3 ≤ d 2 / d M ≤ 1.4.

[0009] To solve the problem, the diameter of the round coil opening can be increased in the simplest case. However, this also increases the distance between the magnet and the coil in areas not affected by spurious vibration modes, resulting in lower measurement sensitivity. The two aforementioned designs have the advantage that the distance between the magnet and the coil is as small as possible—thereby achieving high measurement sensitivity—while simultaneously allowing the magnet to oscillate without collision. One embodiment provides that the measuring pipe has an S-shaped course at least in sections, wherein a longitudinal axis exists in the pipe plane, to which the pipe axis has no angle of more than 85°, in particular not more than 83°, at any point.

[0010] The advantage of this design is that with a vertical orientation of the longitudinal direction of the measuring sensor relative to the direction of gravity, the ability to empty the measuring pipe is ensured. One embodiment provides that the first coil axis is the longitudinal axis at an angle α intersects, where the angle α has an angular dimension of 0° to 15°, in particular 4° to 10° and preferably 6° to 8°.

[0011] It has been found that for such designs with an S-shaped measuring pipe, collision-free oscillation of the magnets can be ensured even with parasitic vibration modes of less than 1000 Hz. One design includes: a support system with a support plate, at least one inlet-side bearing body and at least one outlet-side bearing body, wherein the support system has support system vibration modes that include elastic deformations of the support plate, wherein the measuring pipe is firmly connected to the support plate by means of the inlet-side bearing body and by means of the outlet-side bearing body and is limited by the bearing bodies. One embodiment provides that a connecting axis connects the at least one inlet-side bearing body and the at least one outlet-side bearing body, wherein the first coil axis intersects the connecting axis at an angle β, wherein the angle β an angular dimension of 0° to 30°, in particular 4° to 20° and preferably 6° to 10°.

[0012] Especially in the case of sensors with a support system - comprising a support plate and two bearing bodies - the angle is reduced due to the angular range according to the invention β the probability of defects occurring due to collisions between magnet and coils. One embodiment provides that the measuring pipe between the two bearing bodies has two outer straight sections and a central straight section, which are connected by two circular arc-shaped sections, wherein the two bearing bodies are each arranged on the outer straight sections. One embodiment provides that the natural frequencies of the translational vibration degrees of freedom and rotational vibration degrees of freedom of the carrier plate are not less than 100 Hz, in particular not less than 150 Hz and / or not less than 200 Hz. One embodiment provides that the largest diameter is selected such that when the measuring pipe oscillates in the lowest in-plane mode, the excitation magnet oscillates collision-free in the coil opening of the excitation coil and / or the sensor magnet oscillates collision-free in the coil opening of the sensor coil.One embodiment provides that the lowest in-plane mode lies in a frequency range of less than 1000 Hz, in particular less than 300 Hz.

[0013] The invention is explained in more detail with reference to the following figures. They show: Fig. 1 : an embodiment of the vibronic measuring sensor according to the invention; and Fig. 2 : a cross-section through the vibration exciter or vibration sensor.

[0014] The measuring sensor 100 comprises a measuring pipe 10 with a first straight outer section 11, a second straight outer section 12 and a central straight section 13 as well as a first curved section 15 and a second curved section 16. The two straight outer sections 15, 16 are each connected to the central straight section 13 by means of one of the curved sections 15, 16. This results in an at least partially S-shaped course of the measuring pipe 10. The measuring pipe 10 is delimited by exactly two bearing bodies 21, 22 and is fastened by the latter to a rigid support plate 30.

[0015] The oscillating measuring pipe 10 runs essentially in a pipe plane parallel to the support plate 30. The measuring pipe 10 exhibits twofold rotational symmetry about an axis of symmetry that runs perpendicular to the pipe plane through a point C2 in the middle of the central pipe section. The measuring pipe 10 has an inner diameter of, for example, 5 mm or less. It is made of a metal, in particular stainless steel or titanium. The metallic support plate 30 has a thickness of, for example, 5 mm. The support plate 30 has four spiral spring bearings 31, 32, 32, 33, 34, which are cut free, in particular, by means of a laser, and which also exhibit twofold rotational symmetry with respect to the axis of symmetry through point C2.The support plate 30 is anchored to a housing plate 40 of a sensor housing by means of bearing bolts (not shown here) which are fixed in the center of the spring bearings.

[0016] The support system has support system vibration modes that include elastic deformations of the support plate 30. The natural frequencies of the translational vibration degrees of freedom and rotational vibration degrees of freedom of the support plate 30 are not less than 100 Hz, in particular not less than 150 Hz and / or not less than 200 Hz. Furthermore, the lowest in-plane mode lies in a frequency range greater than 1000 Hz.

[0017] The spring bearings 31, 32, 33, 34 prevent resonance vibrations of up to 50 Hz, which are frequently encountered in process plants. In order not to impair the soft suspension of the support plate achieved by the spring bearings 31, 32, 33, 34, the measuring pipe can be connected to a pipeline via a sufficiently soft pipe inlet section 18 and a sufficiently soft pipe outlet section 19. The housing has a first and second housing bearing 41, 42, which are firmly connected to the housing plate 40 and to which the pipe inlet section 18 and the pipe outlet section 19 are fixed in order to suppress the transmission of pipe vibrations to the measuring pipe via the pipe inlet section 18 and the pipe outlet section 19. The translational and rotational vibration degrees of freedom of the support plate 30 each have natural frequencies. f i which are proportional to the square root of a quotient of a reference value k i and an inertia term m i , so f i ∝ ( k i / m i ) 1 / 2< . The pipe inlet section 18 and the pipe outlet section contribute in total no more than 10% to the respective guideline value k i at. In Fig.1 the line inlet section 18 and the line outlet section 19 are shown essentially schematically.

[0018] How to continue in Fig. 1 As shown, the measuring sensor 100 has a first electrodynamic vibration sensor 51 and a second electrodynamic vibration sensor 52 for detecting the vibrations of the measuring pipe. The two vibration sensors 51, 52 are each arranged on one of the two straight outer sections 11, 12, no more than one radius of curvature of the curved sections 15, 16 from the adjacent curved section. To excite bending vibrations, in particular F3 bending vibrations, the measuring sensor has an electrodynamic vibration exciter 53, which is arranged at the center C2 of the twofold rotational symmetry and acts in the direction of the symmetry axis. The vibration sensors 51, 52 each have a sensor magnet arranged on the measuring pipe 10. The vibration exciter 53 has an excitation magnet, also arranged on the measuring pipe 10, and an elongated excitation coil.The excitation coil can be attached to a holding device connected to the support plate 30. The excitation coil has a first coil axis A, which runs through the largest diameter. The excitation coil is arranged such that the first coil axis A intersects the longitudinal axis Z of the measuring pipe 10 at an angle . α intersects, where the angle αan angular dimension of 0° to 15°, in particular 4° to 10°, and preferably 6° to 8°. The sensor coils can also have an elongated basic shape and fulfill the orientation requirement of the excitation coil relative to the longitudinal axis Z. The excitation coil and / or the sensor coil typically comprise a wound coil wire having an insulating coating. In addition, the excitation coil and / or the sensor coil can have a coil body, in particular an electrically insulating one, which is designed such that the magnet can also collide with it. This is also prevented by the solution according to the invention.

[0019] The center C2 is the origin of a coordinate system for describing further aspects of the invention. The measuring pipe 10 lies in a yz-plane, with the y-axis parallel to the angle bisectors w 1 , w2, each of which runs between a pipe axis of the straight outer sections 11, 12 and the pipe axis of the central straight section 13. The z-axis runs perpendicular to the y-axis in the pipeline plane and defines a longitudinal axis of the measuring sensor 100. The longitudinal axis Z has no angle to the pipeline axis of more than 85° at any point, in particular no angle of more than 83°. If this longitudinal axis is arranged vertically, the measuring sensor can be optimally emptied. The inclination of the straight sections is then equal to half the angle between a pipe axis of the straight outer sections 11, 12 and the pipe axis of the central straight section 13. In the preferred embodiment of the invention, this inclination is 7°.The measuring pipe 10 is designed such that when the measuring pipe 10 oscillates in a, in particular smallest, in-plane mode, a deflection direction of the measuring pipe 10 in a region of the excitation magnet and / or the sensor magnet is oriented parallel to the first coil axis A.

[0020] The Fig. 2 shows a cross-section through the at least one vibration exciter 53 or through a vibration sensor of the at least two vibration sensors 51, 52. The at least one vibration exciter 53 comprises an excitation coil 37 and an excitation magnet 36. The excitation magnet 36 is arranged on the measuring pipe. The vibration sensors 51, 52 each comprise a sensor coil 39 and a sensor magnet 38. The sensor magnet 38 is also arranged on the measuring pipe. The embodiments mentioned below can each refer to the sensor coils and the sensor magnets and / or to the excitation coil and the excitation magnet. Therefore, the term coil is used below instead of sensor coil and excitation coil, and the term magnet is used instead of the sensor magnet and the excitation magnet.

[0021] The magnet extends through a coil opening of the coil. The coil opening has an elongated basic shape, in particular a round convex basic shape with a center of gravity through which a largest diameter with a length d 1 and a smallest diameter with a length d 2. The coil has a first coil axis A and a second coil axis B in a cross-sectional plane. The largest diameter d 1 in the first coil axis A and the smallest diameter d 2 in the second coil axis B. The respective diameters are chosen so that for a quotient d 1 / d 2 it applies that 1.15 ≤ d 1 / d 2 , especially 1.5 ≤ d 1 / d 2 and preferably 2 ≤ d 1 / d 2, and further that d 1 / d 2 ≤ 10, in particular d 1 / d 2 ≤ 7.5 and preferably d 1 / d2 ≤ 3. According to the illustrated embodiment, the first coil axis A is orthogonal to the second coil axis B. The magnet has a magnet diameter with a length d M The length of the magnet diameter d M is smaller than the length d 2 of the smallest diameter, in particular the diameters are chosen so that for a quotient d 2 / d M it applies that 1 < d 2 / d M ≤ 2, especially 1.2 ≤ d 2 / d M ≤ 1.8 and preferably 1.3 ≤ d 2 / d M ≤ 1.4. The vibration sensor and / or the vibration exciter is mounted on a measuring transducer with a support system comprising a carrier plate, at least one inlet-side bearing body and at least one outlet-side bearing body, see Fig. 1. The coil is arranged on the measuring pipe in such a way that a connecting axis V - which connects the at least one inlet-side bearing body and the at least one outlet-side bearing body - and the first coil axis A at an angle β cut. The angle β advantageously has an angular dimension of 0° to 30°, in particular 4° to 20° and preferably 6° to 10°.

Claims

1. A vibronic sensor (100) for measuring the mass flow of a flowable medium, comprising: - A line inlet section (18); - a line outlet section (19); - a measuring pipe capable of oscillating (10) for conducting the medium, wherein the measuring pipe (10) is bent in one pipe plane in its idle position, wherein the measuring pipe (10) connects to the line inlet section (18) on the inlet side and to the line outlet section (19) on the outlet side, and can be connected to a pipeline by means of the line outlet section; - a sensor housing (40), wherein the line inlet section (18) and the line outlet section (19) are both securely connected to the sensor housing (40); - at least one oscillation exciter (53) for exciting bending oscillations of the measuring pipe (10) in a bending oscillation useful mode; and - at least two oscillation sensors (51, 52) for detecting oscillations of the measuring pipe (10), wherein the at least one oscillation exciter (53) comprises an excitation coil (37) and / or the at least two oscillation sensors (51, 52) each comprise one sensor coil (39), wherein the at least one oscillation exciter (53) comprises an excitation magnet (36) and / or the at least two oscillation sensors (51, 52) each comprise a sensor magnet (38), wherein the excitation magnet (36) and / or the sensor magnet (38) is / are arranged on the measuring pipe (10), wherein the excitation magnet (36) extends through a coil opening in the excitation coil (37) and / or the sensor magnet (38) extends through a coil opening in the sensor coil (39), characterized in that the coil opening has an elongated basic shape, wherein the basic shape has a center of mass through which a largest diameter with a length d1 and a smallest diameter with a length d2 pass, wherein the excitation coil (37) and / or the sensor coil (39) has / have a first coil axis (A) and a second coil axis (B) in a cross-sectional plane, wherein the largest diameter d1 is located in the first coil axis (A), wherein the smallest diameter d2 is located in the second coil axis (B), wherein the following applies for a quotient d1ld2: 1.15 ≤ d1 / d2, in particular 1.5 ≤ d1 / d2, and preferably 2 ≤ d1 / d2, wherein the measuring pipe (10) is configured in such a way that, when the measuring pipe (10) oscillates in an in-plane mode, in particular the lowest in-plate mode, a deflection direction of the measuring pipe (10) is oriented in an area of the excitation magnet (36) and / or the sensor magnet (38) parallel to the first coil axis (A).

2. The sensor (100) as claimed in the preceding claim, wherein the following applies for the quotient d1 / d2: d1 / d2 ≤ 10, in particular d1 / d2 ≤ 7.5, preferably d1 / d2 ≤ 3.

3. The sensor (100) as claimed in claim 2, wherein the excitation magnet (36) and / or the sensor magnet (38) has / have a magnet diameter with a length dM, wherein the length of the magnet diameter dM is less than the length d2 of the smallest diameter, wherein the following applies for a quotient d2 / dM: 1 < d2 / dM, in particular 1.2 ≤ d2 / dM ≤ 1.8, and preferably 1.3 ≤ d2 / dM ≤ 1.4.

4. The sensor (100) as claimed in one of the preceding claims, wherein the measuring pipe (10) is routed in such a way that it is S-shaped at least in sections, wherein a longitudinal axis (Z) exists in the pipe plane, to which the pipe axis at no point has an angle of more than 85°, in particular no more than 83°.

5. The sensor (100) as claimed in claim 4, wherein the first coil axis (A) intersects the longitudinal axis (Z) at an angle α, wherein the angle α has an angular dimension from 0° to 15°, in particular 4° to 10°, and preferably 6° to 8°.

6. The sensor (100) as claimed in one of the preceding claims, comprising: - A support system with a support plate (30), at least one inlet-side bearing body (21), and at least one outlet-side bearing body (22), wherein the support system has support system oscillation modes, which comprise the elastic deformation of the support plate (30), wherein the measuring pipe (10) is securely connected to the support plate (30) by means of the inlet-side bearing body (21) and by means of the outlet-side bearing body (22), and is bounded by the bearing bodies (21, 22).

7. The sensor (100) as claimed in claim 6, wherein a connecting axis (V) connects the at least one inlet-side bearing body (21) and the at least one outlet-side bearing body (22), wherein the first coil axis (A) intersects the connecting axis (V) at an angle β, wherein the angle β has an angular dimension from 0° to 30°, in particular 4° to 20°, and preferably 6° to 10°.

8. The sensor as claimed in claim 6 or a dependent claim, wherein the measuring pipe (10) has, between the two bearing bodies (21, 22), two outer straight sections (11, 12) and a central straight section (13), which are connected by means of two arc-shaped sections (15, 16), wherein the two bearing bodies (21, 22) are both arranged on the outer straight sections.

9. The sensor as claimed in claim 6 or a dependent claim, wherein the natural frequencies of the translational oscillation degrees of freedom and rotational oscillation degrees of freedom of the support plate (30) are not less than 100 Hz, in particular not less than 150 Hz, and / or not less than 200 Hz.

10. The sensor (100) as claimed in one of the preceding claims, wherein the largest diameter is selected in such a way that, when the measuring pipe (10) oscillates in the lowest in-plane mode, the excitation magnet (36) oscillates in the coil opening of the excitation coil (37) without colliding and / or the sensor magnet (38) oscillates in the coil opening of the sensor coil (39) without colliding.

11. The sensor (100) as claimed in one of the preceding claims, wherein the lowest in-plane mode is in a frequency range of less than 1000 Hz, in particular less than 300 Hz.