Magnetic-inductive flow meter

Abstract

Magnetic-inductive flow meter (1) for measuring the flow velocity or volumetric flow rate of a medium flowing through a measuring tube (10) comprising: A measuring tube (10) with a measuring tube axis; A magnetic system (20) with a first coil system (21) comprising a first coil (21.1) and a first coil core (21.2) arranged within the first coil (21.1), wherein the magnetic system (20) is configured to generate a magnetic field which is perpendicular to the measuring tube axis; At least two measuring electrodes (30) for tapping off a flow-dependent electrical voltage induced in the medium by the magnetic field, wherein the measuring electrodes (30) are arranged in or on the measuring tube (10) and are designed to tap off the voltage capacitively or galvanically; An electronic measuring / operating circuit (70) for operating the magnetic system (20) and the measuring electrodes (30); A field guide (40) which is designed to guide the magnetic field between a side of the first coil (21.1) facing away from the measuring tube (10) and a side of the measuring tube (10) facing away from the first coil (21.1), wherein the magnetic system (20) has a first pole shoe (21.3) which is designed to guide the magnetic field between the measuring tube (10) and the field guide (40), wherein the first pole shoe (21.3) has at least one folded first pole shoe plate (21.4), and wherein the field guide (40) has at least one folded field guide plate, wherein the first pole shoe (21.3) and the field guide (40) are magnetically and mechanically contacted at least in an inner region of the first coil (21.1), wherein the first pole shoe (21.3) and the field guide (40) in the inner region of the first coil (21.1) at least partially form the first coil core (21.2), characterized by the fact that The windings of the first coil (21.1) are arranged to press the at least one pole shoe sheet fold (51) and the at least one field guide sheet fold (52) against each other in a cross-sectional plane of the measuring tube (10).

Description

[0001] This invention relates to a magnetic-inductive flowmeter for measuring the flow velocity or volume flow of a medium flowing through a measuring tube.

[0002] Magnetic-inductive flowmeters have long been state-of-the-art. Their operating principle is based on the fact that a magnetic field can be used to induce a flow-velocity-dependent electrical voltage in electrically conductive media. This electrical voltage can be evaluated to measure the flow velocity or flow of the medium.

[0003] Typically, magnetic-inductive flowmeters comprise a measuring tube, a magnet system with two coil systems located on opposite sides of the measuring tube for generating a magnetic field perpendicular to a measuring tube axis, and at least two measuring electrodes arranged in or on the measuring tube for tapping the electrical voltage induced in the medium. To make the magnetic field outside the measuring tube as independent as possible from the flowmeter's environment, such a flowmeter has a metallic field guide that conducts the magnetic field outside the measuring tube between the coil systems.

[0004] The connection of the field guide to the coil systems proves to be critical, as a poor connection can significantly increase the magnetic resistance of the magnetic system-field guide system. This results in a lower magnetic field strength in the measuring tube and thus a deteriorated signal-to-noise ratio for measuring the induced electrical voltage. The state of the art, as shown, for example, in document DE202014103426U1, equips coils with pole pieces that have a flat contact surface for supporting or clamping the field guide. Even slight changes in contact pressure lead to significant changes in the magnetic resistance.

[0005] The object of the invention is to propose an improved connection of the field guide to the magnet system.

[0006] The problem is solved by a magnetic-inductive flowmeter according to claim 1.

[0007] A magnetic-inductive flowmeter according to the invention for measuring the flow velocity or volume flow of a medium flowing through a measuring tube comprises: A measuring tube with a measuring tube axis; A magnet system having a first coil and a first coil core arranged within the first coil, wherein the magnet system is configured to generate a magnetic field which is perpendicular to the measuring tube axis; At least two measuring electrodes for tapping a flow-dependent electrical voltage induced in the medium by the magnetic field, wherein the measuring electrodes are arranged in or on the measuring tube and are designed to tap the voltage capacitively or galvanically; An electronic measuring / operating circuit for operating the magnet system and the measuring electrodes; A field guide which is designed to guide the magnetic field between a side of the first coil facing away from the measuring tube and a side of the measuring tube facing away from the first coil, wherein the magnet system has a first pole piece which is designed to guide the magnetic field between the measuring tube and the field guide, wherein the first pole piece comprises at least one folded pole piece plate, and wherein the field guide comprises at least one folded field guide plate, wherein the first pole shoe and the field guide are magnetically and mechanically contacted at least in an inner region of the first coil, wherein the first pole shoe and the field guide in the inner region of the first coils at least partially form the first coil core.

[0008] According to the invention, windings of the coil are designed to press the at least one pole shoe plate fold and the at least one field guide plate fold against each other in a cross-sectional plane of the measuring tube.

[0009] In one embodiment, a first pole shoe plate has a number n1 of pole shoe plate folds, which extend at least partially into the inner region of the first coil, and wherein a first field guide plate has a first group of folds with a number n2 field guide plate folds, which protrude at least partially into the inner region of the first coil, wherein a fold comprises two adjacent layers of sheet metal, where the n2 field guide plate folds and the n1 pole shoe plate folds overlap, where: if ni = 1, then nj =2 otherwise ni <= nj and nj< ni+2, with ni = (n1 or n2) and nj = (n2 or n1), wherein at least one pole shoe plate fold is arranged between two field guide plate folds and is in mechanical contact with them and / or wherein at least one field guide plate fold is arranged between two pole shoe plate folds and is in mechanical contact with them.

[0010] The formation of folds that are in contact with each other ensures a good transition of the magnetic field between the pole piece and the field guide.

[0011] In one embodiment, a fold has a fold length along its two layers of sheet metal, wherein the mechanical contact between the field guide sheet fold and the pole shoe sheet fold extends over an area which covers at least 60% and in particular at least 70% and preferably at least 80% of a fold length of the pole shoe sheet fold or a fold length of the field guide sheet fold.

[0012] The folding length refers to an area in which two layers of a sheet are in contact with each other.

[0013] In one embodiment, the first pole shoe plate has a first end, a second end and a central region, wherein the middle region connects the first end to the second end, and wherein the at least one pole shoe fold is produced by folding the central region, wherein the first pole shoe has a first fixation, which first fixation is arranged between the measuring tube and the first pole shoe sheet and at least partially encompasses the first end and the second end by means of at least one gripping element, wherein the first fixation is made of a sheet metal.

[0014] The fixation is designed to hold the first end and the second end in a fixed position in order to keep the magnetic properties of the magnet system constant.

[0015] In one embodiment, the first end and the second end lie in one plane, and / or wherein the at least one gripping element is a fixing fold which protrudes from a base body of the first fixing.

[0016] In one embodiment, the magnet system has at least one pressing device, which pressing device is designed to press the at least one pole shoe plate fold and the at least one field guide plate fold against each other in a cross-sectional plane of the measuring tube, wherein the pressing device has a force-locking or form-locking connection, wherein the connection in particular has at least one element from the following list: Clamping, potting, gluing, riveting, screwing.

[0017] In one embodiment, the magnet system has a second coil with a second coil core and a second pole shoe on a side of the measuring tube facing away from the first coil, which correspond to the first coil as well as the first coil core and the first pole shoe and are in particular designed identically, wherein the field guide is designed to guide the magnetic field between a side of the first coil facing away from the measuring tube and a side of the second coil facing away from the measuring tube, wherein the second pole piece is adapted to conduct the magnetic field between the measuring tube and the field guide.

[0018] In one embodiment, the first field guide plate has a second group of folds, wherein the second pole piece and the second group of folds at least partially form the second coil core in an inner region of the second coil.

[0019] In one embodiment, the field guide has a second field guide plate, on which second field guide plate the second group is arranged,

[0020] In one embodiment, the first field guide plate and the second field guide plate have two contact areas, by means of which contact areas the field guide plates are magnetically and mechanically connected.

[0021] In one embodiment, the measuring electrodes define a transverse axis, wherein the contact regions are intersected by the transverse axis or at least partially surround the transverse axis.

[0022] In one embodiment, the field guide has at least two receiving openings which are designed to receive the measuring electrodes or measuring electrode contacts.

[0023] In one embodiment, the field guide comprises at least one electrical sheet according to the standard DIN EN 10106 according to edition 11-2007 or DIN EN10107 according to edition 10-2005.

[0024] In the following, the invention is described using schematic embodiments. Fig. 1 shows a cross-section through a magnetic-inductive flowmeter according to the invention; and Fig. 2 shows an enlarged section of a Fig. 1 shown coil core; and Fig. 3 a) and Fig. 3 b) outline further embodiments of a coil core according to the invention; and Fig. 4 outlines various possible designs for a first fixation; and Fig. Figure 5 outlines the operation of a flow meter according to the invention.

[0025] Fig. 1 shows a sketchy cross-section through a magnetic-inductive flowmeter 1 according to the invention, comprising a measuring tube 10, a magnet system 20 with a first coil system 21 and a second coil system 22, measuring electrodes 30, and a field guide 40. The first coil system comprises a first coil 21.1 and a first pole piece 21.3, with a first coil core 21.2 arranged inside the first coil. Equivalently, the second coil system 22 comprises a second coil 22.1 and a second pole piece 22.3, with a second coil core 22.2 arranged inside the second coil. The magnet system is configured to generate a magnetic field perpendicular to a measuring tube axis. The pole pieces rest on the measuring tube and are configured to conduct the magnetic field between the measuring tube and the field guide. The field guide 40 is designed to guide the magnetic field outside the measuring tube 10 between the coil systems.The field guide comprises a first field guide plate 41 and a second field guide plate 42, which are magnetically and mechanically connected to one another in contact areas 44. Alternatively, the field guide can also comprise only one field guide plate, with ends of the field guide plate being magnetically and mechanically connected to one another in a contact area. The measuring electrodes 30 are galvanically connected to the medium flowing through the measuring tube, but can also be capacitively coupled to the medium. Measuring electrode contacts 31 are guided through receiving openings 43 to form a... Fig. 5 shown electronic measuring / operating circuit.

[0026] Fig. 2 shows a Fig. 1 shows an enlarged detail of the first coil system 21, marked A, wherein the first field guide plate 41 has two field guide plate folds 52, and wherein the first pole shoe 21.3 has a first pole shoe plate 21.4 with a pole shoe plate fold 51, which pole shoe plate fold 51 is arranged between the two field guide plate folds and is mechanically and magnetically contacted with them. The folds are pressed against one another by a pressing device 60 in order to maintain this contact firmly and stably. The pressing device has a force-locking connection, wherein the force-locking connection in particular comprises at least one element from the following list: clamping, potting, gluing, riveting, screwing. Alternatively or additionally, the first coil 21.1 can be configured for pressing. The folds of the pole shoe and the field guide thus form the first coil core 21.2.The number of field guide plate folds and the number of pole shoe plate folds are not limited to the example shown here. Possible configurations can be found in the description of . Fig. 3. The pole shoe plate 21.4 has a first end 21.41, a second end 21.42, and a central region 21.43, in which central region the at least one pole shoe plate fold is arranged. To stabilize and fix the first end and the second end, the first pole shoe has a first fixation 21.5, which fixes the first end and the second end by means of at least one gripping element 21.52, wherein the gripping element protrudes from a base body 21.51 of the first fixation. The first fixation is arranged between the measuring tube and the first pole shoe plate 21.5 and ensures good magnetic contact between the first pole shoe and the measuring tube. Possible embodiments of the at least one gripping element are described in Fig. 4 described in more detail. The Fig. The features of the first coil system and the field guide shown in Figure 2 also apply accordingly to the second coil system with a second pole shoe plate and a second fixing.

[0027] Fig. 3 a) outlines an embodiment of the first pole shoe plate 21.4, which can be contacted with the first field guide plate 41 by bringing them together. In the case shown here, the field guide plate 41 has n2 = 3 field guide plate folds 52, and the pole shoe plate 21.4 has n1 = n2 - 1 = 2 pole shoe plate folds, wherein the field guide plate and the pole shoe plate are brought together such that the pole shoe plate folds are each arranged between two field guide plate folds. Alternatively, the number of pole shoe plate folds can be 1 greater than the number of field guide plate folds, whereby the above applies accordingly to the bringing together. In general, n1 and n2 are each greater than or equal to 1.

[0028] Fig. 3 b) outlines one of the Fig. 3 a), where the number n2 of field guide plate folds 52 is equal to the number n1 of pole shoe plate folds, resulting in the first field guide plate 41 and the first pole shoe plate 21.4 each having an outer fold after joining, which is not located between two folds. Here, n1 = n2 is greater than 1.

[0029] The Fig. 3 a) and Fig. 3 b) The features of the first pole shoe plate 21.4 and of the first field guide plate also apply accordingly to the second coil system with the second pole shoe plate and the second fixing, wherein the numbers n1 and n2 with respect to the second coil system do not necessarily but advantageously correspond to the numbers n1 and n2 with respect to the first coil system.

[0030] Fig. Figure 4 outlines a top view of the first pole shoe plate 21.4 with the first end 21.41, the second end 21.42, and the central region 21.43, as well as a top view of the first fixation 21.5 with the base body 21.51 and several exemplary gripping elements 21.52. After the first pole shoe plate has been placed on the base body of the first fixation, the gripping elements are folded around the first end 21.41 and the second end 21.42, respectively, so that the ends are fixed by at least one gripping element. For example, a gripping element can be arranged at one end of the base body. A gripping element can also be arranged on one side of the base body and fix one end of the first pole shoe plate. A gripping element can also be arranged along a large part of one side of the base body and fix both ends of the first pole shoe plate. It is advantageous if different gripping elements do not overlap each other after being folded around.When only lateral gripping elements are installed, it is advantageous if the first end 21.41 and the second end 21.42 are fixed on both sides.

[0031] Fig. Figure 5 schematically outlines the structure of a magnetic-inductive flowmeter 1, which has a measuring tube 10 with a measuring tube axis. A magnet system 20 with a first coil system 21 and a second coil system 22 is configured to form a magnetic field perpendicular to a measuring tube axis (vertical arrows) in order to induce a flow-dependent and magnetic field-dependent electrical voltage perpendicular to the magnetic field in the medium (horizontal arrows). Two measuring electrodes 30 are configured to tap the electrical voltage. An electronic measuring / operating circuit 70 is configured to evaluate the electrical voltage and provide a flow-dependent measured variable, as well as to operate the magnet system 20. For reasons of clarity, the Fig. 1 and Fig. 2 field guidance not shown. List of reference symbols 1 magnetic-inductive flow meter 10 measuring tube 20 Magnet system 21 First coil system 21.1 First coil 21.2 First coil core 21.3 First pole piece 21.4 First pole shoe plate 21.41 First end 21.42 Second end 21.43 midrange 21.5 First fixation 21.51 Basic body 21.52 Gripping element 22 Second coil system 22.1 Second coil 22.2 Second coil core 22.3 Second pole piece 30 measuring electrode 31 Measuring electrode contact 40 Field Guide 41 First field guide plate 42 Second field guide plate 43 mounting holes 44 Contact area 51 Pole shoe folding 52 Field guide plate folding 53 folding length 60 pressing device 70 Electronic measuring / operating circuit A section

Claims

[1] Magnetic-inductive flowmeter (1) for measuring the flow velocity or volume flow of a medium flowing through a measuring tube (10), comprising: A measuring tube (10) with a measuring tube axis; A magnet system (20) with a first coil system (21) comprising a first coil (21.1) and a first coil core (21.2) arranged within the first coil (21.1), wherein the magnet system (20) is configured to generate a magnetic field which is perpendicular to the measuring tube axis; At least two measuring electrodes (30) for tapping a flow-dependent electrical voltage induced in the medium by the magnetic field, wherein the measuring electrodes (30) are arranged in or on the measuring tube (10) and are designed to tap the voltage capacitively or galvanically; An electronic measuring / operating circuit (70) for operating the magnet system (20) and the measuring electrodes (30); A field guide (40) which is designed to guide the magnetic field between a side of the first coil (21.1) facing away from the measuring tube (10) and a side of the measuring tube (10) facing away from the first coil (21.1), wherein the magnet system (20) has a first pole shoe (21.3) which is designed to conduct the magnetic field between the measuring tube (10) and the field guide (40), wherein the first pole shoe (21.3) has at least one folded first pole shoe plate (21.4), and wherein the field guide (40) has at least one folded field guide plate, wherein the first pole shoe (21.3) and the field guide (40) are magnetically and mechanically contacted at least in an inner region of the first coil (21.1), wherein the first pole shoe (21.3) and the field guide (40) at least partially form the first coil core (21.2) in the inner region of the first coil (21.1), characterized by , that Turnings of the first coil (21.1) are designed to press the at least one pole shoe plate fold (51) and the at least one field guide plate fold (52) against one another in a cross-sectional plane of the measuring tube (10). [2] Magnetic-inductive flowmeter according to claim 1, wherein the first pole shoe plate (21.4) has a number n1 of pole shoe plate folds (51) which protrude at least partially into the inner region of the first coil (21.1), and wherein a first field guide plate (41) has a first group of folds with a number n2 field guide plate folds (52) which protrude at least partially into the inner region of the first coil (21.1), wherein a fold comprises two adjacent layers of sheet metal, wherein the n2 field guide plate folds (52) and the n1 pole shoe plate folds (51) overlap, where: if ni = 1, then nj =2 otherwise ni <= nj and nj< ni+2, with ni = (n1 or n2) and nj = (n2 or n1), wherein at least one pole shoe plate fold (51) is arranged between two field guide plate folds (52) and is in mechanical contact with them and / or wherein at least one field guide plate fold (52) is arranged between two pole shoe plate folds (51) and is in mechanical contact with them. [3] Magnetic-inductive flowmeter according to claim 2, wherein a fold along its two layers of sheet metal has a fold length (53), wherein the mechanical contact between the field guide plate fold (52) and the pole shoe plate fold (51) extends over an area which covers at least 60% and in particular at least 70% and preferably at least 80% of a fold length (53) of the pole shoe plate fold (51) or a fold length (53) of the field guide plate fold (52). [4] Magnetic-inductive flowmeter according to claim 2 or 3, wherein the first pole shoe plate (21.4) has a first end (21.41), a second end (21.42) and a central region (21.43), wherein the central region (21.43) connects the first end (21.41) to the second end (21.42), and wherein the at least one pole shoe plate fold (51) is produced by folding the central region (21.43), wherein the first pole shoe (21.3) has a first fixation (21.5), which first fixation (21.5) is arranged between the measuring tube (10) and the first pole shoe plate (21.4) and at least partially encompasses the first end (21.41) and the second end (21.42) by means of at least one gripping element (21.52), The first fixation is made of sheet metal. [5] Magnetic-inductive flowmeter according to claim 4, wherein the first end (21.41) and the second end (21.42) lie in one plane, and / or wherein the at least one gripping element (21.52) is a fixing fold which protrudes from a base body (21.51) of the first fixing (21.5). [6] Magnetic-inductive flowmeter according to one of the preceding claims, wherein the magnet system (20) has at least one pressing device (60), which pressing device (60) is designed to press the at least one pole shoe plate fold (51) and the at least one field guide plate fold (52) against each other in a cross-sectional plane of the measuring tube (10), wherein the pressing device (60) has a force-locking or form-locking connection, wherein the connection in particular has at least one element from the following list: Clamping, potting, gluing, riveting, screwing. [7] Magnetic-inductive flowmeter according to one of the preceding claims, wherein the magnet system (20) has, on a side of the measuring tube (10) facing away from the first coil (21.1), a second coil system (22) comprising a second coil (22.1) with a second coil core (22.2) and a second pole shoe (22.3), which correspond to the first coil (21.1) and the first coil core (21.2) and the first pole shoe (21.3) and are in particular designed identically, wherein the field guide (40) is designed to guide the magnetic field between a side of the first coil (21.1) facing away from the measuring tube (10) and a side of the second coil (22.1) facing away from the measuring tube (10), wherein the second pole piece is adapted to conduct the magnetic field between the measuring tube (10) and the field guide (40), wherein the second pole piece (22.3) and the field guide (40) are magnetically and mechanically contacted at least in an inner region of the second coil (22.1), wherein the second pole piece (22.3) and the field guide (40) in the inner region of the second coil (22.1) at least partially form the second coil core (22.2). [8] Magnetic-inductive flowmeter according to claim 7, wherein the first field guide plate (41) has a second group of folds, wherein the second pole piece (22.3) and the second group of folds in an inner region of the second coil (22.1) at least partially form the second coil core (22.2). [9] Magnetic-inductive flowmeter according to claim 8, wherein the field guide (40) has a second field guide plate (42), on which second field guide plate (42) the second group is arranged. [10] Magnetic-inductive flowmeter according to claim 9, wherein the first field guide plate (41) and the second field guide plate (42) have two contact areas (44), by means of which contact areas (44) the field guide plates (41, 42) are magnetically and mechanically connected. [11] Magnetic-inductive flowmeter according to claim 10, wherein the measuring electrodes (30) define a transverse axis, wherein the contact regions (44) are intersected by the transverse axis or surround the transverse axis. [12] Magnetic-inductive flowmeter according to one of the preceding claims, wherein the field guide (40) has at least two receiving openings (43) which are adapted to receive the measuring electrodes (30) or measuring electrode contacts (31). [13] Magnetic-inductive flowmeter according to one of the preceding claims, wherein the field guide (40) comprises at least one electrical sheet.

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