METHOD FOR PRODUCING A SENSING ELEMENT FOR A THERMAL FLOW METER, SENSING ELEMENT AND FLOW METER

Abstract

The present disclosure relates to a method for producing a probe of a thermal flow meter for measuring the mass flow rate of a medium in a measuring tube, the method having the following steps: introducing a probe core in the form of a material to be melted into a first probe casing, the first probe casing having an open first end and a closed second end facing away from the first end; melting the probe core; quenching the probe core to a temperature below the solidification temperature; attaching a thermoelement to a contact surface of the solidified probe core. The invention also relates to a probe obtained according to the production method and to a flow meter including the probes according to the present disclosure.

Claims

1-14. (canceled)

15. A method for producing a probe of a thermal flow meter for measuring the mass flow rate of a medium in a measuring tube, the method comprising: introducing a probe core in the form of a material to be melted into a first probe casing, wherein the first probe casing includes an open first end and a closed second end opposite the first end; melting the probe core; cooling the probe core to a temperature lower than a solidification temperature of the material to be melted; and attaching a thermoelement to a contact surface of the solidified probe core.

16. The method of claim 15, wherein the contact surface is prepared by machining the solidified probe core to form an area configured for attaching the thermoelement.

17. The method of claim 15, further comprising, after cooling the probe core, exposing a region of the probe core by partial removal of a wall of the first probe casing.

18. The method of claim 17, further comprising, after exposing the region, attaching a third open end of a second probe casing to the first end of the first probe casing in a leak-tight manner, wherein the second probe casing further includes an open fourth end opposite the open third end, wherein the second probe casing surrounds the region.

19. The method of claim 18, wherein the region is machined in a subregion such that the subregion of the probe core is separated from all surfaces of the first probe casing and/or the second probe casing, wherein the subregion includes all cross-sections of the probe core that intersect or touch the contact surface.

20. The method of claim 15, wherein the thermoelement is attached to the contact surface of the probe core using a solder or sinter layer.

21. The method of claim 15, wherein cooling the probe core includes quenching the probe core to a temperature lower than the solidification temperature.

22. The method of claim 15, wherein the thermoelement is configured to increase and/or detect a temperature of the probe core.

23. A probe for a thermal flow meter adapted for measuring the mass flow rate of a medium in a measuring tube, the probe comprising: a first probe casing having an open first end and a closed second end; a probe core, the probe core at least partially filling the first probe casing; and a thermoelement that is thermally coupled to the probe core, wherein the thermoelement is configured to increase or detect the temperature of the probe core, wherein the probe core is formed by melting a material in the first probe casing and then cooling the material to a temperature lower than a solidification temperature of the material to be melted.

24. The probe of claim 23, wherein the probe core has a longitudinal axis, an outer surface in contact with the first probe casing, a center of mass, and a contact surface opposite the second end of the probe core with respect to the center of mass, and wherein the thermoelement is attached to the contact surface using a solder or sinter layer.

25. The probe of claim 24, wherein the probe core includes a region that projects from the first probe casing in the axial direction, wherein the region includes the contact surface.

26. The probe of claim 25, wherein the region is enclosed by a second probe casing with an open third end and an open fourth end, which second probe casing is connected in a leak-tight manner to the first end of the first probe casing via the third end, wherein the region is machined in a subregion such that the subregion of the probe core is spaced apart from all surfaces of the first probe casing and/or the second probe casing, and wherein the subregion includes all cross-sections of the probe core that intersect or contain the contact surface.

27. The probe of claim 26, wherein the first probe casing and/or the second probe casing have a cylindrical, rotationally-symmetrical form.

28. The probe of claim 23, wherein the first probe casing is made of stainless steel, and wherein the probe core has a thermal conductivity of more than 100 W/(m.Math.K), wherein the probe core includes at least one metal from the group consisting of copper, silver, aluminum, nickel, indium, gold and tin.

29. A thermal flow meter for measuring the mass flow rate of a medium in a measuring tube, the flow meter comprising: a measuring tube having a longitudinal axis; at least one probe extending into the measuring tube, the at least one probe comprising: a first probe casing having an open first end and a closed second end; a probe core, the probe core at least partially filling the first probe casing; and a thermoelement that is thermally coupled to the probe core, wherein the thermoelement is configured to increase or detect the temperature of the probe core, wherein the probe core is formed by melting a material in the first probe casing and then cooling the material to a temperature lower than a solidification temperature of the material to be melted; and an electronic operating circuit configured to operate the at least one probe.

30. The flow meter of claim 29, further comprising at least two probes, including a first probe and at least a second probe, wherein the electronic operating circuit is configured to heat at least the first probe, and wherein the electronic operating circuit is further configured to determine a temperature of the medium using at least the second probe.

31. The flow meter of claim 29, wherein the thermoelement is configured to increase and/or detect a temperature of the probe core.

Description

[0024] The invention will now be described with reference to exemplary embodiments.

[0025] FIG. 1 shows a schematic process for manufacturing a probe according to the invention.

[0026] FIGS. 2 a) through d) show steps in the production of a probe according to the invention.

[0027] FIG. 3 shows an enlarged and distorted view of the fabrication stage shown in FIG. 2 d).

[0028] FIG. 4 diagrams embodiments of the probe according to the invention.

[0029] FIG. 5 diagrams a schematic front view of a thermal flow meter having two probes according to the invention.

[0030] FIG. 1 shows an embodiment of a method sequence 100 for producing a probe 10 according to the invention.

[0031] In a first step 101, a probe core 13 in the form of a material to be melted is introduced into a first probe casing 11, wherein the material to be melted has copper or silver, and wherein the first probe casing 11 is made of a stainless steel.

[0032] In a second step 102, the probe core 13 is melted so that the liquid material of the probe core 13 collects in the region of a closed second end 22 of the first probe casing 11. While the probe core 13 is fluid, an intermetallic connecting layer is formed at an interface between the probe core 13 and the first probe casing 11, in which layer the material of the probe core 13 and the material of the first probe casing 11 mix.

[0033] In a third step 103, the probe core 13 is quenched to a temperature lower than its solidification temperature. Due to the formation of the intermetallic connecting layer, the contact between probe core 13 and first probe casing 11 is maintained after the probe core has solidified.

[0034] In a fourth step 104, the probe core 13 is exposed in a first region by partial removal of a wall of the first probe casing 11.

[0035] In a fifth step 105, a contact surface 14 is prepared by machining, in particular, smoothed and aligned, for the attachment of a thermoelement 31. This can be accomplished, for example, by drilling or milling.

[0036] In a sixth step 106, a thermoelement is attached to the contact surface by means of a solder or sinter layer.

[0037] In a seventh step 107, a second probe casing 12 with an open third end 23 and an open fourth end 24 is attached, in particular welded, to the first end 21 in a leak-tight manner by means of the third open end, wherein the second probe casing 12 wraps completely around the first region.

[0038] Advantageously, the first region is machined in a subregion, so that the subregion 16 of the probe core is spaced apart from all surfaces of the first probe casing 11 and/or the second probe casing 12, wherein the subregion 16 comprises all first cross-sections of the probe core, which first cross-sections intersect or touch the contact surface 14.

[0039] FIG. 2 shows cross-sections of a probe 10 according to the invention at various stages of manufacture.

[0040] FIG. 2 a) shows a cross-section of the probe 10 at a stage in which the first probe casing 11 has the probe core 13 in a fluid or already solidified state.

[0041] FIG. 2 b) shows a cross-section of the probe at a stage in which the probe core is exposed in the first region, wherein an exposure of the probe core allows access to the probe core 13 radially with respect to a first longitudinal axis 15.

[0042] FIG. 2 c) shows a cross-section of the probe at a stage in which, after exposure of the probe core 13 in the region, the thermoelement 31 is attached to the contact surface 14 of the probe core 13.

[0043] FIG. 2 d) shows a cross-section of a finished probe 10 with the second probe casing 12, which is attached, in particular welded, to the first end 21 of the first probe casing 11 via the third end 23.

[0044] FIG. 3 shows an enlarged view of the cross-section of the finished probe 10 shown in FIG. 2 d), wherein the illustration is horizontally distorted in order to make fine details visible. The thermoelement 31 is attached to the contact surface 14 of the probe core 13 via a solder or sinter layer 32. The probe core 13 is supported on a side opposite the contact surface 14 by a support 33, wherein the support 33 is an extension of the first probe casing 11. An embodiment of the probe 10 without the support 33 is also conceivable. The probe core 13 is thereby configured in the subregion 16 such that it is spaced apart from all surfaces of the second probe casing 12. If the probe does not include a support 33, the probe core 13 in the subregion 16 is spaced apart from all surfaces of the first probe casing 11 and the second probe casing 12. The spacing of the probe core from the second probe casing or from the first probe casing and the second probe casing in the subregion ensures a homogeneous distribution of the temperature in the probe core. This ensures a uniform heat transfer to the medium in the dotted region when the probe 10 is used as a heating element. Conversely, when the probe is used as a temperature sensor, uniform exposure of the thermoelement 31 to the temperature of the medium is ensured.

[0045] FIGS. 4 a) through d) show schematic cross-sections of several embodiments of the probe according to the invention, wherein, for the sake of clarity, the second probe casing has been excluded. FIG. 4 a) shows the embodiment illustrated in FIGS. 2 a) through d) and in FIG. 3 with support 33. FIG. 4 b) shows the embodiment illustrated in FIG. 4 a) without a support. FIG. 4 c) shows an embodiment with contact surface 14 inclined relative to the first longitudinal axis 15. FIG. 4 d) shows an embodiment with contact surface 14 perpendicular to the longitudinal axis 15. The embodiments shown in FIGS. 4 b) and c) may also have a support according to the embodiment shown in FIG. 4 a). The embodiments shown in FIGS. 4 a) through c) make it possible to produce thin probes for a predetermined thermoelement 31.

[0046] FIG. 5 shows a schematic front view of a thermal flow meter 40 according to the invention having a measuring tube 42, two probes 10 according to the invention that are arranged within the lumen of the measuring tube 42, and a housing 41 having an electronic operating circuit, which electronic operating circuit is configured to operate the probes 10.

[0047] To measure the mass flow rate of a medium through the measuring tube 40, a probe 10.1 in the medium flowing through the measuring tube 40 is, for example, heated in such a way that a temperature difference in relation to the media temperature remains constant. It is appropriate to use a second probe 10.2 for measuring the temperature of the medium, which second probe is arranged upstream of or, as shown in FIG. 2, adjacent to the heated probe 10.1, in order to maintain the temperature difference. Assuming consistent media properties such as density or composition, it is possible to determine the mass flow rate of the medium via the heating current necessary for maintaining the temperature.

[0048] The probes 10 may also be arranged in succession, one after the other, in the flow direction, wherein a first upstream probe heats the medium flowing past and, with it, a second probe situated downstream. In this case, the heating line, required for maintaining a temperature difference, of the first probe depends upon the flow rate of the medium.

LIST OF REFERENCE CHARACTERS

[0049] 10 Probe [0050] 10.1 First probe [0051] 10.2 Second probe [0052] 11 First probe casing [0053] 12 Second probe casing [0054] 13 Probe core [0055] 14 Contact surface [0056] 15 First longitudinal axis [0057] 16 Subregion [0058] 17 Center of mass [0059] 21 First end [0060] 22 Second end [0061] 23 Third end [0062] 24 Fourth end [0063] 31 Thermoelement [0064] 32 Solder layer/sinter layer [0065] 33 Support [0066] 34 Spacing [0067] 40 Flow meter [0068] 41 Housing [0069] 42 Measuring tube [0070] 100 Method for producing a probe according to the invention [0071] 101 Introducing a probe core in the form of a material to be melted into a first probe casing [0072] 102 Melting the probe core [0073] 103 Quenching the probe core below solidification temperature [0074] 104 Exposing the probe core in a first region [0075] 105 Preparing the contact surface for attachment of the thermoelement [0076] 106 Attaching a thermoelement to the contact surface by means of a solder or sinter layer [0077] 107 Attaching the second probe casing to the first probe casing