Abstract
A method for producing a device for measuring current strengths. The method includes providing a resistor arrangement with two connection elements and a resistor element arranged between the connection elements, molding a contact element from the material of the connection element or from the material of the resistor element. The contact element has an end face remote from the resistor arrangement and a cavity open on the end face. The method further includes providing a circuit board with a through-bore on whose inner surface electrically conductive material is present, positioning the circuit board on the resistor arrangement such that the contact element projects into the through-bore, and expanding the contact element in the radial direction using an expansion element inserted into the cavity of the contact element to establish an electrically conductive connection between the contact element and the electrically conductive material on the inner surface of the through-bore.
Claims
1. A method for producing a device for measuring the strength of an electric current using a resistor arrangement, wherein the method comprises the following steps: a) providing a resistor arrangement comprising at least two connection elements and at least one resistor element arranged between the connection elements in relation to the direction of the electric current, wherein the at least one resistor element, on the one hand, and the connection elements, on the other hand, consist of different electrically conductive materials; b) molding at least one contact element from the material of at least one connection element or from the material of the resistor element, wherein the contact element has a longitudinal axis that defines an axial direction and a radial direction perpendicular thereto, and wherein the contact element is molded such that it has an end face remote from the resistor arrangement and a cavity that is open on the end face, remote from the resistor arrangement, of the contact element; c) providing a circuit board that has at least one through-bore having an inner surface on which electrically conductive material is present; d) positioning the circuit board on the resistor arrangement such that the circuit board has an upper side remote from the resistor arrangement and that the at least one contact element at least projects into the through-bore; and e) expanding the contact element in the radial direction using an expansion element, which is inserted into the cavity of the contact element in the axial direction, so as to establish an electrically conductive connection between the contact element and the electrically conductive material on the inner surface of the through-bore.
2. The method according to claim 1, wherein the expansion element is designed such that the contact element is expanded by the insertion of the expansion element.
3. The method according to claim 1, wherein the expansion element is designed such that the contact element is expanded following the insertion of the expansion element.
4. The method according to claim 1, wherein the expansion in method step e) establishes a frictional connection between the inner surface of the through-bore of the circuit board and the contact element.
5. The method according to claim 1, wherein the contact element has a height that is selected such that, after the circuit board has been positioned, the end face, remote from the resistor arrangement, of the contact element is located within the through-bore of the circuit board or terminates flush with an upper side of the circuit board.
6. The method according to claim 1, wherein the contact element is molded in method step b) through an embossing step or through extrusion.
7. The method according to claim 6, wherein, to shape the contact element, a negative mold having at least one recess corresponding to the external contour of the contact element and at least one internal tool positioned in the recess is used to mold the cavity and, during method step b), the internal tool is moved in the direction of the longitudinal axis of the contact element relative to the recess.
8. The method according to claim 1, wherein the expansion of the contact element in method step e) is assisted by heating the material of the contact element using ultrasound or using a laser.
9. A device for measuring the strength of an electric current, comprising a resistor arrangement and a circuit board mechanically and electrically connected to the resistor arrangement, wherein the resistor arrangement comprises at least two connection elements and at least one resistor element arranged between the connection elements in relation to the direction of the current, wherein the at least one resistor element, on the one hand, and the connection elements, on the other hand, consist of different electrically conductive materials, and wherein the circuit board has at least one through-bore having an inner surface on which electrically conductive material is present, wherein the resistor arrangement has at least one contact element having a longitudinal axis, which contact element is monolithically connected to one of the connection elements and is machined from the material of the connection element or is monolithically connected to the resistor element and is machined from the material of the resistor element, and by way of which the resistor arrangement is electrically conductively and mechanically connected to the circuit board by virtue of the contact element at least projecting into the through-bore of the circuit board and being frictionally connected to the electrically conductive material on the inner surface of the through-bore, wherein the contact element has an end face remote from the resistor arrangement and a cavity that is open on the end face, remote from the resistor arrangement, of the contact element and wherein the contact element has a conical contour at the transition from its end face to the cavity.
10. The device according to claim 9, wherein the contact element has a height that is selected such that the end face, remote from the resistor arrangement, of the contact element is located within the through-bore of the circuit board or terminates flush with the upper side of the circuit board.
11. The device according to claim 9, wherein that the contact element, on that side of the circuit board remote from the resistor arrangement, has a protrusion above the circuit board and is laterally broadened in the region of this protrusion in order to fasten the circuit board.
12. The device according to claim 11, wherein the contact element, between the connection element and the circuit board, has a section having a conical external contour, such that the cross-sectional surface area of the contact element increases towards the connection element.
13. The device according to claim 9, wherein the at least one contact element has a ledge on which the circuit board sits in such a manner that the circuit board is spaced from the resistor arrangement.
14. The device according to claim 9, wherein the at least one contact element has a surface with a metal coating.
15. The device according to claim 14, wherein the metal coating comprises tin, silver or nickel.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Exemplary embodiments of the invention are explained in more detail with reference to the schematic drawings, in which:
[0047] FIG. 1 shows an oblique view of a resistor arrangement;
[0048] FIG. 2 shows a side view of a resistor arrangement;
[0049] FIG. 3 shows a sectional view of an extract of a resistor arrangement at the end of method step b);
[0050] FIG. 4 shows a sectional view of an extract of a resistor arrangement with a molded contact element;
[0051] FIG. 5 shows a sectional view of an extract of a resistor arrangement with a circuit board positioned thereon;
[0052] FIG. 6 shows a sectional view of an extract of a resistor arrangement during method step e);
[0053] FIG. 7 shows a sectional view of an extract of a resistor arrangement with a circuit board fastened thereto;
[0054] FIG. 8 shows a sectional view of an extract of a resistor arrangement with a circuit board fastened thereto and with a contact element having a ledge; and
[0055] FIG. 9 shows a sectional view of an extract of a resistor arrangement with a circuit board fastened thereto and with a contact element having a conical section.
[0056] Parts that correspond to one another are provided with the same reference signs in all of the figures.
DETAILED DESCRIPTION
[0057] FIG. 1 shows an oblique view of a resistor arrangement 2 not yet having a contact element. The resistor arrangement 2 has two terminal connection elements 3, 3′ and a resistor element 4 that is positioned between the two connection elements 3, 3′. The connection elements 3, 3′ and the resistor element 4 are each plate-shaped. The thickness of the resistor element 4 is slightly smaller than the respective thickness of the two connection elements 3, 3′. The resistor arrangement 2 may be connected to a circuit at the two connection elements 3, 3′. For this purpose, the two connection elements 3, 3′ may have connection devices, not illustrated, for example bores. These connection devices are each installed in the region of the connection elements 3, 3′ that is remote from the resistor element 4. The resistor element 4 is located between the connection elements 3, 3′ in relation to the direction of the current flow. When a current flows, a voltage drops across the resistor element 4, on the basis of which voltage the strength of the current flowing through the resistor arrangement 2 is able to be ascertained.
[0058] FIG. 2 shows a side view of the resistor arrangement 2 according to FIG. 1. A resistor arrangement 2 as illustrated in FIGS. 1 and 2 may, as is known, be produced by longitudinally seam-welding three strips to form a composite material and then cutting the welded composite material to length. FIG. 3 shows a sectional view of an enlarged extract of the resistor arrangement 2 according to FIGS. 1 and 2 at the end of method step b). A negative mold 12 having a recess 121 and an internal tool 122 arranged in the recess 121 have been positioned on the upper side of the connection element 3. A die 11 has penetrated into the material of the connection element 3 on the lower side of the connection element 3, this being symbolized by the arrow pointing upwards. The die 11 is positioned such that it lies opposite the recess 121 of the negative mold 12. The penetration of the die 11 has deformed material of the connection element 3 substantially perpendicular to the surface of the connection element 3 and displaced it into the empty space of the negative mold 12 defined by the recess 121 and the internal tool 122. This has formed a material projection that forms the contact element 5. The internal tool 122 has the effect that the contact element 5 has a cavity that is open on one side after the internal tool 122 is removed.
[0059] FIG. 4 shows a sectional view of an enlarged extract of the resistor arrangement 2 having a molded contact element 5 after method step b). The die 11 and the negative mold 12 have been removed. To facilitate the removal of the die 11 and the negative mold 12, the die 11, the recess 121 and the internal tool 122 in the negative mold 12 may each have a beveled demolding contour. The molded contact elements 5 may accordingly likewise have a beveled contour. The angle formed by the demolding bevels with the normal to the surface of the connection elements 3 is typically approximately 2°. The bevels are not illustrated explicitly in the figures due to this small deviation from the normal.
[0060] The contact element 5 has a longitudinal axis A that is oriented perpendicular to the surface of the connection element 3. The contact element 5 furthermore has an end face 52 that is remote from the connection element 3 and thus from the resistor arrangement 2. Starting from this end face 52, a cavity 53 extends along the longitudinal axis A of the contact element 5. In the illustrated case, this cavity 53 extends approximately to the non-deformed surface of the connection element 3. However, it may be advantageous, for manufacturing reasons, to mold the contact element 5 such that the cavity 53 extends less into the contact element 5 or, as an alternative, that the cavity 53 extends as far as into the material of the connection element 3. As a result of the cavity 53, the contact element 5 has the shape of a sleeve that is closed on one side and open on the other side. The height of the contact element 5 is denoted by the symbol H. The height H is measured starting from the non-deformed surface of the connection element 3 to the end face 52 of the contact element 5.
[0061] The contact element 5 is provided in order to tap off the voltage dropped across the resistor element 4. In order to minimize distortions of the measured value, the contact element 5 has been molded from the connection element 3 such that it is positioned close to the connection point between the connection element 3 and the resistor element 4.
[0062] FIG. 5 shows a sectional view of the enlarged extract of the resistor arrangement 2 according to FIG. 4 additionally with a circuit board 8 positioned on the resistor arrangement 2 and having the thickness D. FIG. 5 thus represents the resistor arrangement 2 and the circuit board 8 following method step d). The circuit board 8 has a through-bore 9. Electrically conductive material 92 is present on the inner surface 91 of the through-bore 9 of the circuit board 8, and is not illustrated in more detail for the sake of clarity. The circuit board 8 has been positioned such that the contact element 5 projects into the through-bore 9 to a penetration depth T. In the illustrated case, the penetration depth T is slightly less than the thickness D of the circuit board 8, such that the end face 52 of the contact element 5 does not terminate flush with the upper side 81 of the circuit board 8, but rather is still located slightly within the through-bore 9. The penetration depth T is approximately 90% of the thickness D of the circuit board 8. The thin width of the through-bore 9 is slightly greater than the external dimension of the contact element 5. In the illustrated exemplary embodiment, the circuit board 8 does not sit directly on the connection element 3, this possibly being achieved for example using spacers, not illustrated. A large spacing between the circuit board 8 and the resistor element 4 is advantageous because heat that arises in the resistor element is thereby able to be dissipated quickly. Electronic components that are possibly present on the circuit board 8 are not illustrated for the sake of clarity.
[0063] FIG. 6 shows a sectional view of the enlarged extract of the resistor arrangement 2 during method step e). A conical expansion element 14 is inserted into the cavity 53 of the contact element 5 in the direction of the arrow. The external dimension of the expansion element 14 is selected such that the conical shape of the expansion element 14 displaces the material of the contact element 5 outwardly in the radial direction, that is to say towards the inner surface 91 of the through-bore 9. The contact element 5 thereby comes into contact with the electrically conductive material 92 on the inner surface 91 of the through-bore 9, forming an electrically conductive connection. The expansion element 14 illustrated in FIG. 6 may be a body that remains in the cavity 53 of the contact element 5, or it may be the working region of a tool that is removed from the cavity 53 of the contact element 5 following the expansion. If the expansion element is a body, such body may be in the form of a plug, indenter, plunger or a rivet and may have a conical shape as shown in FIG. 6. Alternatively, the plug, indenter, plunger or rivet may have a cylindrical shape with a chamfered insertion end. Alternatively, the expansion element may be a tool, and such tool may be a swage, die, an expanding mandrel or a hand-held tube expander. A swage or die with a conical shape may be used to expand the contact element 5 during insertion of the conical swage or die into the cavity 53. If the tool is an expanding mandrel or a hand-held tube expander, expansion of the contact element 5 occurs after the mandrel or tube expander is inserted into the cavity 53.
[0064] FIG. 7 shows a sectional view of the enlarged extract of the resistor arrangement 2 according to FIG. 6 following removal of the tool used for the expansion. FIG. 7 at the same time represents the sectional view of part of a device 1 for measuring current strengths using the resistor arrangement 2.
[0065] FIG. 8 shows, as a further exemplary embodiment, the sectional view of part of a device 1 for measuring current strengths, having a resistor arrangement 2 and a circuit board 8 positioned on the resistor arrangement 2. The contact element 5 has an encircling ledge 51 on which the circuit board 8 sits. For this purpose, the contact element 5 is designed such that the external dimension of the contact element 5, in the subregion directly adjoining the connection element 3, is larger than the thin width of the through-bore 9 of the circuit board 8. The circuit board 8 thus does not sit either on the connection element 3 or on the resistor element 4, even without additional spacers. The height of the ledge 51 was already taken into consideration when molding the contact element 5 from the material of the connection element 3. The circuit board 8 is contacted by the contact element 5 in the same way as in the exemplary embodiment illustrated in FIG. 6 and explained in connection with FIG. 6.
[0066] FIG. 9 shows, as a further exemplary embodiment, the sectional view of part of a device 1 for measuring current strengths, having a resistor arrangement 2 and a circuit board 8 positioned on the resistor arrangement 2. The contact element 5, between the connection element 3 and the circuit board 8, has a section 55 having a conical external contour that directly adjoins the circuit board 8. The contact element 5 furthermore has a protrusion 56 above the circuit board 8. The contact element 5 has been conically expanded in the region of this protrusion 56. The contact element 5 thereby projects, in the lateral direction, above the upper side 81 of the circuit board 8. As a result of the conical expansion of the contact element 5 in the region of its protrusion 56, the circuit board 8 has been moved in the direction towards the connection element 3 and thus pressed onto the conical section 55 of the contact element 5 between the circuit board 8 and the connection element 3. The circuit board 8 is thereby fastened in a frictional manner in the direction of the longitudinal axis A of the contact element.
[0067] For the sake of better legibility, the invention has been explained by way of example in FIGS. 1 to 9 on the basis of a resistor arrangement 2 that comprises only one resistor element 4 and two terminal connection elements 3, 3′. It is also possible to apply the method described above to resistor arrangements that have two or more resistor elements and at least one further connection element arranged between two resistor elements in relation to a possible current path. The resistor arrangement may in this case be configured such that the same current flows through at least two resistor elements, thereby allowing a redundant current measurement, or that different currents flow through at least two resistor elements, thereby allowing partial currents to be measured. The method for molding contact elements 5 and for establishing an electrical connection with a circuit board 8, as explained with reference to the above description, with reference to FIGS. 1 to 9 and with reference to the exemplary embodiments, may in these cases also be used to mold one or more contact elements 5 from the material of a connection element arranged between two resistor elements.
LIST OF REFERENCE SIGNS
[0068] 1 Device [0069] 2 Resistor arrangement [0070] 3, 3′Connection element [0071] 4 Resistor element [0072] 5 Contact element [0073] 51 Ledge [0074] 52 End face [0075] 53 Cavity [0076] 55 Section [0077] 56 Protrusion [0078] 8 Circuit board [0079] 81 Upper side [0080] 9 Through-bore [0081] 91 Inner surface [0082] 92 Electrically conductive material [0083] 11 Die [0084] 12 Negative mold [0085] 121 Recess [0086] 122 Internal tool [0087] 14 Expansion element [0088] A Longitudinal axis [0089] H Height [0090] T Penetration depth [0091] D Thickness
