WO2021063711A1

WO2021063711A1 - Magnetically inductive flow meter

Info

Publication number: WO2021063711A1
Application number: PCT/EP2020/076170
Authority: WO
Inventors: Beat Tschudin; Simon MARIAGER
Original assignee: Endress+Hauser Flowtec Ag
Priority date: 2019-10-02
Filing date: 2020-09-18
Publication date: 2021-04-08
Also published as: DE102019126711A1

Abstract

The invention relates to a magnetically inductive flow meter for use in a pipe through which a flowable medium flows, comprising: a housing (1), wherein the housing (1) has a front section (2) on an end side; at least one measuring electrode (3) for detecting a flow-speed-dependent measurement variable induced in the medium, wherein the at least one measuring electrode (3) is arranged on the housing (1), in particular in the front section (2); and a field system (4) for generating a magnetic field penetrating the front section (2), wherein the field system (4) is arranged in the housing (1), wherein the field system (4) has a coil assembly (5) and a field guide element (6), wherein the field guide element (6) extends through an opening in the coil assembly (5), wherein the field guide element (6) has a first section (7.1) designed to function as a coil core, wherein the field guide element (6) has a second section (7.2) designed to function as a field return, and wherein the field guide element (6) is formed by at least one bent part (9).

Description

Magnetic-inductive flow measurement probe

The invention relates to a magnetic-inductive flow measuring probe.

Electromagnetic flowmeters are used to determine the flow rate and volume flow of a flowing medium in a pipeline. An electromagnetic flowmeter has a magnet system that generates a magnetic field perpendicular to the direction of flow of the flowing medium. Individual coils are usually used for this. In order to achieve a predominantly homogeneous magnetic field, pole pieces are additionally shaped and attached in such a way that the magnetic field lines run essentially perpendicular to the transverse axis or parallel to the vertical axis of the measuring tube over the entire pipe cross-section. A pair of measuring electrodes attached to the outer surface of the measuring tube picks up an electrical measuring voltage or potential difference that is perpendicular to the direction of flow and to the magnetic field, which occurs when a conductive medium flows in the direction of flow when a magnetic field is applied. Since the measured voltage, according to Faraday’s law of induction, depends on the speed of the flowing medium, the flow rate u and, with the addition of a known pipe cross-section, the volume flow V can be determined from the induced measurement voltage U.

In contrast to a magneto-inductive flow measuring device, magneto-inductive flow measuring probes with their usually circular cylindrical housing are inserted into a side opening of a pipeline and fixed in a fluid-tight manner. A special measuring tube is no longer necessary. The above-mentioned measuring electrode arrangement and coil arrangement on the outer surface of the measuring tube are omitted and are replaced by a field system arranged inside the housing and in close proximity to the measuring electrodes, which is designed so that an axis of symmetry of the magnetic field lines of the generated magnetic field covers the front surface or the Perpendicular to the surface between the measuring electrodes. In the prior art there are already a large number of magnetic-inductive flow measuring probes with different field systems.

EP 0 543 003 A1, for example, teaches a magneto-inductive flow measurement probe in which the field system is formed by two bar magnets arranged in parallel, each with an associated winding.

Proceeding from the prior art, the invention is based on the object of providing a magneto-inductive flow measuring probe which has a compact and easy-to-assemble field system. The object is achieved by the magnetic-inductive flow measuring probe according to claim 1.

The magnetic-inductive flow measuring probe according to the invention for insertion into a pipe through which a flowable medium flows

- A housing, the housing having a front section at the end;

- At least one measuring electrode for detecting a flow velocity-dependent measured variable induced in the medium, the at least one measuring electrode being arranged on the housing, in particular in the front section; and

A field system for generating a magnetic field penetrating the front section, the field system being arranged in the housing, the field system having a coil arrangement and a field guiding body, the field guiding body extending through an opening in the coil arrangement, the field guiding body having a first section which for this purpose is set up to serve as a coil core, the field guide body having a second section which is set up to serve as a field return, the field guide body being formed by at least one bending part.

The housing of the magnetic-inductive flow measuring probe usually has a cavity in which the field system, the electrical conductors and, depending on the application, also the operating, measuring and / or evaluation circuit are arranged. However, the housing can also be designed or fully encapsulated as a potting body, with the electrical conductors, the measuring electrodes and the field system also being potted. The housing is usually cylindrical or hollow-cylindrical, but it can also be cuboid depending on the application.

The magnetic-inductive flow measuring probe is to be inserted into the opening of the pipe in such a way that the front section of the housing is in direct contact with the medium to be conveyed. At least one measuring electrode in combination with a reference electrode, which is electrically connected to a reference potential, in particular a ground potential, is required for the acquisition of a measured variable that is induced in the medium and is dependent on the flow velocity. The reference electrode can be implemented, for example, as a pin electrode, as a ring electrode or also by a partially metallic housing which is connected to a reference potential, for example an earth. Commercially available magnetic-inductive flow measuring probes have two measuring electrodes, which are arranged on a measuring electrode axis, the magnetic-inductive flow measuring probe being arranged in the opening of a pipe in such a way that the measuring electrode axis is preferably perpendicular to the direction of flow of the medium.

The coil arrangement can have precisely one coil or a plurality of coils. A coil usually comprises a coil holder with an opening and at least one coil wire wound around the coil holder. The opening in the coil holder is preferably designed in such a way that the field guide body can be inserted in a form-fitting manner.

Field guiding bodies are used for the spatial guidance of magnetic fluxes. The field guiding body according to the invention is designed to guide the magnetic field generated by the coil arrangement into the front section and to guide the magnetic field lines emerging from the front section and extending into the interior of the pipe back to the coil arrangement.

According to the invention, the field guide body is formed by at least one bent part.

The bending part has at least partially the shape of a band or is designed in the form of a strip. The bending part can comprise exactly a single sheet metal part or a large number of stacked sheet metal parts. The bent part can also be a bent sheet-metal part in a stamped package. The field guide body is formed at least partially from a soft magnetic material, for example from an electrical sheet.

Field returns are used to guide magnetic field lines of a magnetic field reaching into the interior of a pipe back into the interior of the housing to the coil arrangement. Coil cores serve on the one hand to increase the inductance of the coil and on the other hand to manipulate the magnetic field generated by the coil. The coil core and the field return are usually designed in two parts, the coil core and the field return being materially connected to one another. However, material transitions between components are disadvantageous because there is a loss of magnetic flux there. According to the invention, at least one bent part is used which, in particular due to the bending, has two sections which have different functions. The first section serves as the coil core and the second section serves as a field return. If a coil core is inserted into a coil, its ferromagnetic

Properties increases the permeability and thus also the magnetic flux density in the coil. This means that you get by with significantly fewer turns and thus with much less volume and a more compact design in order to achieve the required field strength. According to the invention, in addition to the number of turns and the

The diameter of the coil wire, the mass and the shape of the field guiding body are reduced to a minimum in order to realize the compactness of the field system. Above a certain material-dependent flux density, however, as the mass of the field guide body decreases, a disruptive saturation magnetization of the coil core occurs. However, this case does not occur even if the number of sheet metal parts is reduced to a single M1000 sheet metal part with a thickness of individual millimeters and a width of approx. 5 millimeters.

Advantageous refinements of the invention are the subject of the dependent claims.

One embodiment provides that the field guide body is formed by precisely one bending part, the bending part having precisely one bend, which preferably forms a round arch.

The bend is preferably designed as a round arch. A round arch bend can be easily implemented from a procedural point of view. A round arch has no sharp edges, which minimizes the loss of magnetic flux.

According to the embodiment, the bent part has three areas, the first and second areas running essentially parallel to one another. The third area is the bend. The first area serves as the coil core and extends through the opening of the coil arrangement and the second area serves as a field return and extends between the coil wire and the outer wall of the housing.

According to the embodiment, the field system includes exactly one bent part. This creates an asymmetrical field distribution of the magnetic field in the longitudinal section. Such an asymmetrical arrangement forms the simplest and most compact variant of the field system. One embodiment provides that the field guide body by exactly two

Bending parts is formed, the two bending parts each having at least one bend, the two bending parts each having end sections that are in contact, wherein the end sections are set up to serve as a coil core.

The bending parts are preferably designed as identical parts and have at least partially a U-shape in a longitudinal section, i.e. the bending parts each have three sections, the first and the second section each comprising the legs of the bending part and the third section comprising the bend. The respective end section, which serves as the coil core, is located in the first section.

The respective end portions of the bent parts are in contact with each other. This means that the two bent parts either touch each other in the area or that the bent parts in the area each touch an insulating body that is softer between the bent parts and the two bent parts are thus connected to one another via the insulating body. The insulating body comprises an electrically insulating coating and / or an electrically insulating solid, such as paper or a defined air gap.

One embodiment provides that the two bent parts each have exactly one round arch or at least two bending edges

The bend of the respective bent parts is preferably designed as a round arch or is formed by two bending edges. In the case of two bending edges, the longitudinal axis of the bending part in the first area and the longitudinal axis of the bending part in the third area span an angle which is preferably between 75 ° and 105 °. Rounded edges are preferred to minimize magnetic flux losses.

One embodiment provides that the field guide body is formed by exactly one bending part, the bending part having at least three bends, one of the at least three bends being arranged in the first section.

It is advantageous if the field guide body is formed exclusively by exactly one bending part with at least three bends, the bending part having a first section that is designed to serve as a coil core and two second sections that are designed to serve as field return. The assembly is thus simplified and, at the same time, a magnetic field that is rotationally symmetrical with respect to a longitudinal axis of the magnetically inductive flow measuring probe is realized with only one bent part.

One embodiment provides that the front section has a front body, wherein the front body has a first recess, wherein the field guide body extends in the first recess.

According to the embodiment, the front body and the housing are designed in two parts, whereby the assembly of the field system in the housing of the magnetic-inductive flow measuring probe is facilitated.

The front body preferably has a first recess which is designed to be complementary to the first section of the field guide body and in which the field guide body is arranged. The first recess is preferably designed as an elongated recess, in particular as a groove. One embodiment provides that the front section has a front body, the front body having at least one second recess, the field guide body extending in the at least one second recess.

The front body preferably has a second recess which is designed to be complementary to the second section of the field guide body and in which the field guide body is arranged. The second recess is set up to fix the second section of the field guide body and thus to protect it from external mechanical influences.

One embodiment provides that a bent part has a first limb and a second limb, the first limb having a first limb length, the second limb having a second limb length, the first limb length being smaller than the second limb length.

This configuration is particularly advantageous when the front body has a paddle-shaped formation which extends out of the front section of the housing. Thus, the first area of the field guide body can extend into the formation, while the second area extends exclusively up to Front section or up to the vicinity of the front section extends. This enables the magnetic field strength to be maximized at the front section in contact with the medium.

The invention is explained in more detail with reference to the following figures. It shows:

1: a longitudinal section through a first embodiment of the magnetic-inductive flow measuring probe;

2: a perspective view of the front body;

3: three configurations of the field guide body; and

4: a longitudinal section through a second embodiment of the magnetic-inductive flow measuring probe. 1 shows a longitudinal section of a first embodiment of the magnetic-inductive flow measuring probe according to the invention. The magnetic-inductive flow measuring probe has a housing 1 in which a field system 4 is arranged. In the embodiment, the field system 4 has a field guide body 6 and a coil arrangement 5 with precisely one coil 22. The housing 1 also has a front body 21 in the front section 2, in which the measuring electrodes 3 are fixed. The field guide body 6 consists of two bent parts 9, which are designed as identical parts. The two bending parts 9.1, 9.2 each have an end section 19, 20 which touch one another and extend through the opening of the coil arrangement 5 to the front section 2. Both bent parts 9.1, 9.2 each have two legs which are connected to one another via the bend and have different lengths. However, the legs can also have a common leg length.

The field guide body 6 has a first section 7.1, which includes the area of the field guide body 6, which extends through the coil arrangement 5 and which serves as the coil core. Furthermore, the field guide body 6 has a second section 7.2. which serves as a field return. According to the first embodiment, the first section 7.1 runs parallel to the second section 7.2. A bent part 9 has a basic shape in longitudinal section, which is at least partially U-shaped. The respective bends of the bent parts are designed as round arches 8.

The end of the housing comprises a front body 21, in which the measuring electrodes 3 and the field guide body 6 are fastened.

2 shows a perspective view of a front body 21 according to the invention. The front body 21 is designed as a front plate and has two through holes 23.1, 23.2 for inserting the measuring electrodes. In addition, the front body 21 has a first recess 14 and two second recesses 15, the first recess 14 is set up to receive the first section of the field guide body and the second recess 15 is set up to receive the second section of the field guide body. The depressions 14, 15 are designed to be complementary to the respective sections which are inserted into the depression. The first depression and the two second depressions are each designed in the shape of a slot and in cross section and in longitudinal section have a basic shape which is at least partially rectangular.

3 shows three configurations of the field guide body.

According to the first and second embodiment of the field guide body 6, the field guide body 6 has two bent parts which are connected to one another. In the two present embodiments, the two bent parts touch one another. The section in which the two bent parts touch, i.e. the second section 25, is set up to serve as the coil core. In both configurations, the respective bent part has exactly one bend. The first embodiment differs from the second embodiment in the type of bend. The bent parts of the first embodiment of the field guide body 6 each have a round arch bend 8, while the bent parts of the second embodiment of the field guide body 6 each have two bending edges 10 in the third area 26. In both configurations, the field guide body is formed by bending a strip-shaped sheet metal part. The sheet metal part can also be formed from a multiplicity of stacked sheet metal parts. An insulating body can be arranged between the individual sheet metal parts, wherein the insulating body can also comprise an electrically insulating coating of the sheet metal part. A bent part has two legs which are aligned parallel to one another and which are connected to one another via the bend. The legs each have an end section. The first end section 19 serves as a coil core. The second end section 20 or the first area 24 of the field guide body 6 serves as a field return.

According to the third embodiment of the field guide body, the field guide body is formed from exactly one bent part. The field guide body 6 according to the invention has three bends. The first bend and the second bend each include two bending edges 10. The third bend is implemented as a round arch bend 8. The field guide body 6 is formed by bending exactly one sheet metal part. The section in which the third bend is located is designed as a coil core.

The respective bends always include a bend of the bending body by essentially 180 ° with a corresponding bending radius. This is realized either by a round arch bend or by two bending edges.

4 shows a longitudinal section through a second embodiment of the magnetically inductive flow measuring probe. The electromagnetic flowmeter probe has a housing 1 in which a field system 4 is arranged. In the embodiment, the field system 4 has a field guide body 6 and a coil arrangement 5 with precisely one coil 22. The housing 1 also has a front body 21 in the front section 2, in which the measuring electrodes 3 are fixed. The field guide body 6 consists of a bent part 9.

The field guide body 6 has a first section 7.1, which comprises the area of the field guide body 6, which extends through the coil arrangement 5 and which serves as the coil core. Furthermore, the field guide body 6 has a second section 7.2. which serves as a field return. The second section 7.2 extends between the coil winding and the outer wall of the housing 2. According to the first embodiment, the field guide body 6 in the first section 7.1 runs parallel to the field guide body in the second section 7.2. A bent part 9 has a basic shape in longitudinal section, which is at least partially U-shaped. The bends in the bent part are designed as round arches 8. The end of the housing comprises a front body 21 in which the measuring electrodes 3 and the field guide body 6 are fixed.

List of reference symbols

1 housing

2 front section 3 measuring electrode

4 field system

5 coil arrangement

6 field guiding bodies

7.1 first section 7.2 second section

8 round arches

9 bending part

9.1 first bent part

9.2 second bending part 10 bending edge

11 first bend

12 second bend

13 third bend

14 first recess 15 second recess

16 first legs

17 second leg

19 first end section

20 second end section 21 front body

22 coil

23 through holes

23.1 first through holes

23.2 second through hole 24 first area

25 second area

26 third area

Claims

1. Magnetic-inductive flow measuring probe for insertion into a pipe through which a flowable medium flows, comprising: - a housing (1), the housing (1) having a front section (2) at the end;

- At least one measuring electrode (3) for detecting a flow velocity-dependent measured variable induced in the medium, the at least one measuring electrode (3) being arranged on the housing (1), in particular in the front section (2); and

- A field system (4) for generating a magnetic field penetrating the front section (2), the field system (4) being arranged in the housing (1), the field system (4) having a coil arrangement (5) and a field guide body (6), wherein the field guide body (6) extends through an opening in the coil arrangement (5), the field guide body (6) having a first section (7.1) which is designed to serve as a coil core, the field guide body (6) having a second section ( 7.2), which is set up to serve as a field return, the field guide body (6) being formed by at least one bent part (9).

2. Magnetic-inductive flow measurement probe according to claim 1, wherein the field guide body (6) is formed by exactly one bending part (9), the bending part (9) having exactly one bend, which is designed as a round arch (8) or as a bending edge (10) is.

3. Magnetic-inductive flow measuring probe according to claim 1, the field guide body (6) being formed by exactly two bending parts (9.1, 9.2), the two bending parts (9.1, 9.2) each having at least one bend, the two bending parts (9.1, 9.2) each having end sections (19) which are in contact, the end sections (19) being set up as coil cores.

4. Electromagnetic flow measuring probe according to claim 3, wherein the two bending parts (9.1, 9.2) each have exactly one arch (8) or at least two bending edges (10).

5. Magnetic-inductive flow measuring probe according to claim 1, wherein the field guide body (6) is formed by exactly one bending part (9), the exactly one bending part (9) having at least three bends (11, 12, 13), one of the at least three bends (11, 12, 13) is arranged in the first section (7.1).

6. Magnetic-inductive flow measuring probe according to one of the preceding claims, wherein the front section (2) has a front body (21), wherein the front body (21) has a first recess (14), wherein the field guide body (6) is in the first recess (14) extends.

7. Magnetic-inductive flow measuring probe according to one of the preceding claims, wherein the front section (2) has a front body (21), wherein the front body (21) has at least one second recess (15), the field guide body (6) extending in the at least one second recess (15).

8. Electromagnetic flow measuring probe according to one of the preceding

Claims, wherein a bent part (9) has a first leg (16) and a second leg (17), wherein the first leg (16) has a first leg length, wherein the second leg (17) has a second leg length, the first Leg length is smaller than the second leg length.