METHOD FOR PRODUCING A DEVICE FOR MEASURING CURRENT INTENSITY AND DEVICE FOR MEASURING CURRENT INTENSITY

Description

[0001] The invention relates to a method for producing a device for measuring currents and to such a device.

[0002] Current measurement in electronic circuits uses measuring resistors connected in series with the component to be monitored. The current is determined from the voltage drop across the measuring resistor, known as the shunt resistor. Correct and reliable current measurement is particularly important, for example, in the battery management system of an electric or hybrid vehicle. A resistor arrangement comprising such a low-ohm measuring resistor of approximately 10 to 50 µOhm and connection elements for connecting the resistor arrangement to the circuit can be manufactured from a longitudinally welded composite material. This is known, for example, from document EP 0 605 800 A1. The composite material is produced from three metal strips by joining the individual metal strips together via a longitudinal seam using an electron beam or laser welding process.

[0003] The voltage drop across a measuring resistor is tapped via contact pins or similar elements arranged on the connection elements on both sides of the measuring resistor. Such contact pins can be soldered, pressed, or welded onto the connection elements of the resistor array. The voltage is recorded and further processed by measurement and evaluation electronics. Electronic components are provided for this purpose, which can be arranged on a circuit board. The circuit board can be located in the immediate vicinity of the resistor array.

[0004] A resistor arrangement with a low-ohm current measuring resistor is known from DE 10 2009 031 408 A1. This resistor arrangement features connecting contacts for tapping the voltage. These contacts are formed by embossing and threading in the plate-shaped sections used to connect the resistor arrangement to the external circuit. The measuring leads for voltage measurement are connected to the connecting contacts using cable lugs and fastening screws.

[0005] Furthermore, US Pat. No. 1,016,553 B2 discloses a resistor assembly comprising two plate-shaped elements for connecting the resistor assembly to an external circuit and a strip-shaped resistor element. On either side of the resistor element, each of the two connection elements has a hole into which a contact pin is inserted. The contact pins are separate components that must be specially manufactured and added to the resistor assembly.

[0006] From the subsequently published document EP 3 929 594 A1, a method is known in which a contact pin is formed from the material of the connection elements of a resistor arrangement. The contact pin extends through the hole in a circuit board and has a projection beyond the circuit board. To secure the circuit board, the contact pin is laterally widened in the area of ​​its projection.

[0007] The document DE 10 2007 033 182 A1 discloses a resistance element with terminal pieces and a resistance piece. Contacts are formed by placing a wire with bent ends on the terminal pieces and bonding it to the surface of the terminal pieces, for example by ultrasonic welding.

[0008] DE 658 916 discloses a contact element consisting of a contact piece and a rivet tube. The contact piece consists of a flat part with a beveled outer edge by punching or bending. The rivet tube is rolled from sheet metal.

[0009] FR 2 544 866 A1 discloses a shunt resistor with a U-shaped resistance element. Connection elements, which can be solid or hollow, are formed at the parallel, free ends of the resistance element.

[0010] US 2015 / 108965 A1 discloses a current sensor based on a shunt resistor. The current sensor comprises a resistor array and a circuit board on which a voltage measuring device is located. To connect the resistor array to the circuit board, the current sensor has taps attached to the side of the resistor array.

[0011] With the devices known from the prior art, it is necessary to use additional components to tap the voltage drop across the measuring resistor. This requires additional effort and expense. Furthermore, contact voltages can occur at the contact points of the individual components, which can distort the voltage signal.

[0012] The invention is based on the object of providing an improved, in particular simpler and more cost-effective method for producing a device for measuring current strengths and such a device.

[0013] The invention is represented with respect to a method by the features of claim 1 and with respect to a device by the features of claim 9. The further, dependent claims relate to advantageous embodiments and developments of the invention.

[0014] The invention relates to a method for producing a device for measuring currents by means of a resistor arrangement, the method comprising the following steps: a) Providing a resistor arrangement comprising at least two connection elements, by which a current direction is determined, and at least one resistance element arranged between the connection elements with respect to the current direction, wherein the at least one resistance element, on the one hand, and the connection elements, on the other hand, are made of different, electrically conductive materials, b) Forming at least one contact element from the material of at least one connection element or from the material of the resistance element, so that the contact element is monolithically connected to the connection element or to the resistance element, wherein the contact element has a longitudinal axis, by which an axial direction and a radial direction perpendicular thereto are defined, and wherein the contact element is shaped such that it has an end face facing away from the resistor arrangement and a cavity,which is open on the end face of the contact element facing away from the resistor arrangement, c) providing a printed circuit board which has at least one through-hole with an inner surface on which electrically conductive material is located, d) positioning the printed circuit board on the resistor arrangement such that the printed circuit board has an upper side facing away from the resistor arrangement and that the at least one contact element at least projects into the through-hole, e) expanding the contact element in the radial direction by means of an expanding means which is introduced in the axial direction into the cavity of the contact element up to the region of the through-hole of the printed circuit board, so that an electrically conductive connection is established between the contact element and the electrically conductive material on the inner surface of the through-hole.

[0015] The measurement of current strengths also includes the measurement of the strength of an electrical current that may vary over time. The resistor arrangement described above can comprise a shunt resistor with a resistance of 10 to 50 µOhm as the resistance element. Both the resistance element and the connection elements are made of electrically conductive materials. The specific electrical resistance of the material of the resistance element is significantly greater, typically at least a factor of 10 greater, than the specific electrical resistance of the material of the connection elements. On the other hand, the absolute value of the temperature coefficient of resistance of the material of the connection elements is much greater, typically at least a factor of 80 greater, than the absolute value of the temperature coefficient of resistance of the material of the resistance element.Typically, the resistance temperature coefficient of the resistance element material is less than ±5 10 -5 < 1 / K, while the resistance temperature coefficient of the connection element material is approximately ±4 10 -3 < 1 / K. The connection elements of the resistor arrangement can be made of copper, a preferably low-alloy copper alloy, aluminum, or a preferably low-alloy aluminum alloy, or comprise at least one of these materials. The resistance element can be made of a copper alloy that is commonly used as a resistance alloy.

[0016] The connection elements can be terminal connection elements of the resistor arrangement. However, it is also possible for at least one connection element to be arranged between two resistor elements with respect to a possible current path. The resistor arrangement can be designed in a planar arrangement. The connection elements and the at least one resistor element are formed as plate- or strip-shaped elements and arranged next to one another in a plane, preferably in a row. The thickness of the resistor element(s) can be arbitrary. However, it is usually not greater than the thickness of the connection elements.

[0017] A contact element is understood to be a material projection that protrudes above the otherwise undeformed surface of a connection element or the resistance element. The contact element is formed by displacing material of a connection element or material of the resistance element essentially in a direction perpendicular to the surface of the connection element or the resistance element. The direction in which the material is displaced defines an axial direction that is parallel to the longitudinal axis of the contact element and a radial direction perpendicular to this. The contact element is formed such that it has an end face facing away from the resistance arrangement and a cavity that is open on the end face of the contact element facing away from the resistance arrangement.The contact element is therefore at least partially hollow, and the cavity extends from the end face of the contact element in the axial direction into the contact element. In the radial direction, the cavity is delimited by a circumferential, closed wall made of displaced material of a connection element or the resistance element. In this region, the contact element therefore has the shape of a sleeve that is open on at least one side. Preferably, the cavity is closed on the diametrically opposite side, so that the contact element has a shape similar to a cup in this region. The height of the contact element is at least 0.5 mm, preferably at least 1 mm.

[0018] The external shape of the contact element can be arbitrary, preferably circular, rectangular, square, or hexagonal. The contact element preferably has a circular cross-section in the region of the cavity. The shape and / or size of the cross-section of the contact element can be constant or change continuously or discontinuously along the longitudinal axis of the contact element. For example, the contact element can have a slightly conical contour, i.e. a contour with slightly inclined boundary surfaces relative to the surface of the connection element or the resistance element. Furthermore, the contact element can be shaped such that it has a shoulder. A shoulder is understood to be a discontinuous, i.e. sudden change in the cross-sectional shape and / or cross-sectional size of the contact element. The shoulder can serve as a support for a printed circuit board.

[0019] The contact element can be used, preferably together with another contact element, as a voltage tap for measuring the electrical voltage drop across the resistance element. If the contact element is formed from the material of the resistance element, it can be used as a voltage tap for measuring the electrical voltage drop across a portion of the resistance element. Alternatively, the contact element can also serve to ground the resistance arrangement. Preferably, one or more such contact elements are formed in all connection elements of the resistance arrangement. The contact elements used for voltage measurement are positioned as close as possible to the resistance element at which the voltage drop is to be determined.

[0020] For the purposes of the present invention, a printed circuit board is understood to be a flat, plate-, or strip-shaped component suitable for conducting electrical signals in an electrically conductive material. A flat component is plate- or strip-shaped if two opposing surfaces of the component are plane-parallel to each other. The distance between these two surfaces defines the thickness of the component. A printed circuit board can, for example, be a metal strip or a plate made of a non-conductive material with conductor tracks applied to its surface. Such boards are known under the term "printed circuit board." The printed circuit board has at least one through-hole with an inner surface on which electrically conductive material is located.This also includes the case where the circuit board is a metal strip or a metal plate, so that there is inherently electrically conductive material on the inner surface of the through-hole. If the circuit board is a plate made of non-conductive material with conductive tracks applied to its surface, the electrically conductive material on the inner surface of the through-hole can be connected to a conductive track, which is preferably arranged on the side of the circuit board facing away from the resistor arrangement. Furthermore, electrical components that are used to measure and evaluate electrical signals can be arranged on such a circuit board. The term through-hole refers to a recess in the circuit board that extends across the entire thickness of the circuit board. The through-hole can have a cylindrical shape. Alternatively, a conical shape is also possible.

[0021] The circuit board is positioned on the resistor array in such a way that the at least one contact element at least protrudes into the through-hole. The circuit board is positioned essentially plane-parallel to the resistor array, so that the circuit board has a top side facing away from the resistor array and a bottom side facing the resistor array. There can be a gap between the circuit board and the resistor array. However, it is also possible for the circuit board to rest directly on the resistor array. The contact element should protrude into the through-hole of the circuit board by at least half the thickness of the circuit board, preferably at least 70% of the thickness of the circuit board.

[0022] The contact element is then expanded in the radial direction using a suitable expansion means. For this purpose, the expansion means is inserted axially from the top side of the circuit board into the cavity of the contact element. The expansion means is designed so that it can expand the contact element radially in the region of the cavity. For this purpose, the material of the contact element that radially delimits the cavity is displaced radially outwards until it comes into contact with the inner surface of the through-hole in the circuit board. In this way, an electrically conductive connection is established between the contact element and the electrically conductive material on the inner surface of the through-hole. The enlargement of the outer dimension of the contact element caused by the expansion is preferably between 2% and 15% of its outer dimension before expansion.Expanding also reduces the wall thickness of the contact element. A reduction of at least 20% of the original wall thickness is advantageous. The expanding agent can be a suitable tool, which is removed from the contact element's cavity after expansion.

[0023] The advantage of the described process is that no additional components and / or materials are required to create the connection between the resistor array and the circuit board. Because the contact element is formed directly from the material of a terminal element or the resistor element, it is not necessary to mount the contact element separately on the resistor array or on the circuit board. This eliminates the necessary work steps and the required materials, such as solder. Multiple contact elements can be formed simultaneously.

[0024] The monolithic connection between the contact element and the connection element or between the contact element and the resistance element prevents unwanted contact voltages that can distort a measurement.

[0025] A particularly advantageous aspect of the proposed method is the radial expansion of the contact element using a suitable expansion means. Because the expansion means is introduced into the cavity of the contact element, the connection between the contact element and the circuit board is essentially made in the area of ​​the through-hole. This eliminates the need for the contact element to protrude beyond the top surface of the circuit board. To form the contact element, the material of the connection element or the resistance element therefore only needs to be deformed to a small extent. The required forces are low. This is advantageous in terms of tool life and process speed. The proposed method is particularly advantageous when one or more contact elements are to be formed from the resistance element.The material of the resistance element is typically harder to deform than the material of the terminal elements. The less it needs to be deformed, the easier the process.

[0026] The expansion element can also be a body that remains permanently in the cavity of the contact element. Such a body can be, for example, a plug or a rivet. This body creates a particularly reliable and permanent contact between the contact element and the inner surface of the through-hole of the circuit board.

[0027] If the resistor assembly is manufactured by cutting it to length from a longitudinally welded, strip-shaped composite material, the contact elements can preferably be formed simultaneously with the cutting of the composite material. Steps a) and b) of the process are therefore performed simultaneously in this case. A separate, additional work step for forming the contact elements is therefore unnecessary. The process is therefore faster and more cost-effective than if the contact elements are formed after the composite material has been cut to length. Furthermore, a high positioning accuracy of the contact elements is achieved in this way.

[0028] Within the scope of one embodiment of the invention, the expansion means can be designed such that the contact element is expanded by inserting the expansion means. The contact element is thus already expanded radially during the insertion of the expansion means into the cavity. For this purpose, the expansion means has at least a partially conical outer contour. This outer contour leads to a radial displacement of the contact element material when the expansion means is inserted into the cavity. This enables short processing times.

[0029] Within the scope of an alternative embodiment of the invention, the expansion means can be designed such that the contact element is expanded after the expansion means has been inserted. The contact element is therefore essentially only expanded radially after the expansion means has been inserted into the cavity. For this purpose, the expansion means has a section whose outer diameter is smaller than the inner diameter of the cavity. The insertion of this section of the expansion means into the cavity then occurs without significant resistance and thus also without unwanted deformation of the contact element. After the expansion means has been inserted, the radial expansion of the contact element takes place by means of a suitable mechanism. If the expansion means is a tool, this can be achieved, for example, by spreading the tool, by eccentric rotation of the tool, or by electromagnetic forces.

[0030] Within the scope of a preferred embodiment of the invention, the expansion in method step e) can also simultaneously create a force-locking connection between the inner surface of the through-hole of the circuit board and the contact element. For this purpose, the contact element is expanded to such an extent that the material is pressed so strongly against the inner surface of the through-hole of the circuit board that a press fit is formed. The wall thickness of the contact element is preferably reduced by at least 40%. By creating the press fit, other means for mechanically fixing the circuit board to the resistor arrangement can be eliminated.

[0031] Within the scope of a special embodiment of this embodiment of the invention, the expansion in method step e) can also simultaneously create a positive connection between the inner surface of the through-hole of the circuit board and the contact element. For example, the through-hole of the circuit board can have a conical shape and be designed such that the inner diameter increases from the underside of the circuit board to its top. When using an expansion means with an adapted conical outer contour, the expansion of the contact element leads to a positive connection. Such a connection represents a particularly secure type of connection.

[0032] Within the scope of a preferred embodiment of the invention, the contact element can have a height selected such that, after positioning the circuit board, the end face of the contact element facing away from the resistor arrangement is located within the through-hole of the circuit board or is flush with the top side of the circuit board. The height refers to the extension of the contact element in the axial direction, measured from the undeformed surface of the connection element or the resistor element. The height is therefore dimensioned such that the penetration depth of the contact element into the through-hole of the circuit board is at most equal to the thickness of the circuit board. In other words, in this embodiment, the contact element does not protrude beyond the top side of the circuit board. A contact element of such a small height can be formed particularly favorably.Within the scope of a special embodiment of this invention, the penetration depth of the contact element into the through-hole of the circuit board can be 80 to 100% of the thickness of the circuit board. This represents an optimum balance between the effort required to form the contact element and the quality of the contact between the contact element and the circuit board.

[0033] Within the scope of a further embodiment of the invention, the forming of the contact element in process step b) can be carried out by an embossing step or by extrusion. Embossing and extrusion are particularly suitable for forming contact elements that are monolithically bonded to the material of the connection elements or the resistance element and extend essentially perpendicular to the surface of the connection elements or the resistance element. The material is formed using a stamp and a suitable negative mold.

[0034] Within the scope of a specific embodiment of this embodiment of the invention, a negative mold with at least one recess corresponding to the outer contour of the contact element and at least one inner tool positioned in the recess for forming the cavity can be used to shape the contact element. During process step b), the inner tool is moved relative to the recess in the direction of the longitudinal axis of the contact element. This has proven to be a particularly advantageous process control from a forming technology perspective, allowing contact elements with a large height to be produced.

[0035] Within the scope of a further specific embodiment of the invention, the expansion of the contact element in process step e) can be assisted by heating the material of the contact element using ultrasound or a laser. The material of the contact element is hardened and solidified due to the deformation in process step b). This hinders the subsequent deformation in step e). By applying heat using a laser or ultrasound, the material of the contact element can be heated to such an extent that it is at least partially softened, i.e., becomes softer. The deformation in step e) is then easier.

[0036] With regard to further technical features and advantages of the method according to the invention, reference is hereby explicitly made to the following explanations in connection with a device for measuring current intensities as well as to the figures and the figure description.

[0037] A further aspect of the invention relates to a device for measuring current strengths. This also includes the measurement of the strength of an electrical current that may vary over time. The device comprises a resistor arrangement and a circuit board mechanically and electrically connected to the resistor arrangement. The resistor arrangement comprises at least two connection elements that define a current direction, and at least one resistance element arranged between the connection elements with respect to the current direction, wherein the at least one resistance element, on the one hand, and the connection elements, on the other hand, are made of different, electrically conductive materials. The circuit board has at least one through-hole with an inner surface on which electrically conductive material is located.The resistor arrangement has at least one contact element with a longitudinal axis, which is monolithically connected to one of the connection elements and machined from the material of the connection element, or which is monolithically connected to the resistor element and machined from the material of the resistor element. This contact element electrically and mechanically connects the resistor arrangement to the circuit board in that the contact element at least projects into the through-hole of the circuit board and is frictionally connected to the electrically conductive material on the inner surface of the through-hole. For this purpose, the contact element has an end face facing away from the resistor arrangement and a cavity that is open on the end face of the contact element facing away from the resistor arrangement.At the transition from its front side to the cavity, the contact element has a conical contour on its inside that extends into the area of ​​the through-hole of the circuit board.

[0038] With regard to the terms used to describe the device, explicit reference is hereby made to the above explanations of the terms in connection with the description of the method for manufacturing a device for measuring current intensities.

[0039] The particular advantage of the described device is that the monolithic connection between the contact element and the connection element or resistance element prevents unwanted contact voltages that could distort a measurement. Furthermore, the device can be manufactured cost-effectively and with high precision because the contact element is molded directly from the material of the connection element or resistance element. A particularly advantageous aspect of the described device is the force-fitting connection between the circuit board and the resistor arrangement. This connection is established by the contact element, which is brought into electrical and mechanical contact with the inner surface of the through-hole of the circuit board through an expansion process.To carry out this expansion process, the contact element has a front side facing away from the resistor assembly and a cavity that is open on the front side of the contact element facing away from the resistor assembly. At the transition from its front side to the cavity, the contact element has a conical contour on its inner side. This conical contour is the result of the expansion process and can be used to facilitate the introduction of an expansion agent into the cavity of the contact element.

[0040] Within the scope of one embodiment of the invention, the contact element can have a height selected such that the end face of the contact element facing away from the resistor arrangement is located within the through-hole of the circuit board or is flush with the top side of the circuit board. The height refers to the extension of the contact element in the direction of its longitudinal axis, measured from the undeformed surface of the connection element or the resistor element. The height is therefore dimensioned such that the penetration depth of the contact element into the through-hole of the circuit board is at most equal to the thickness of the circuit board. In other words, the contact element does not protrude beyond the top side of the circuit board. A contact element with this low height can be formed particularly favorably.Within the scope of a special embodiment of this invention, the penetration depth of the contact element into the through-hole of the circuit board can be 80 to 100% of the thickness of the circuit board. This represents an optimum balance between the effort required to form the contact element and the quality of the contact between the contact element and the circuit board.

[0041] Within the scope of an alternative embodiment of the invention, the contact element can have a projection beyond the circuit board on the side of the circuit board facing away from the resistor arrangement and can be laterally widened, preferably conically widened, in the region of this projection in order to fix the circuit board. By lateral widening, in particular by conically widening the contact element in the region of this projection beyond the circuit board, the circuit board is positively fixed in at least one direction in the axial direction of the contact element, i.e. in the direction of the connection element of the resistor arrangement. The lateral widening can be achieved not only by conically widening but also by other deformations of the contact element. Examples of this are crimping, flanging, partial bending, and widening using a spherical, cylindrical, or crowned tool.

[0042] Within the scope of a special embodiment of this alternative embodiment of the invention, the contact element between the connection element and the circuit board can have a section with a conical outer contour. The conical section is selected such that the cross-sectional area of ​​the contact element increases towards the connection element. The section with the conical contour adjoins the circuit board directly. Due to the conical outer contour, the cross-sectional area of ​​the contact element increases continuously and at least to the extent that it is larger than the cross-sectional area of ​​the through-hole in the circuit board. Together with the conical widening of the contact element in the area of ​​its projection, a positive and non-positive fixing of the circuit board can be achieved both in the direction of the axis of the contact element and perpendicular to it. The circuit board is clamped by the contact element in a double-conical manner.This embodiment of the invention is particularly resistant to mechanical stress such as vibrations.

[0043] Within the scope of a further advantageous embodiment of the device, the at least one contact element can have a shoulder on which the circuit board rests in such a way that the circuit board is spaced apart from the connection element and thus from the resistor arrangement. The distance between the circuit board and the resistor arrangement results in better thermal decoupling of the circuit board from the resistor arrangement. In this case, the heat generated when current flows through the resistor element cannot be transferred directly from the resistor element or from a connection element to the circuit board; instead, the heat must flow through the contact element. Due to its relatively small cross-section, the contact element represents a high thermal resistance.The heat flow from the resistor array to the circuit board is therefore reduced, and the circuit board remains at a lower temperature than if the circuit board were resting directly on a connection element. This design is particularly advantageous when the thickness of the resistor element is not less than the respective thickness of the connection elements.

[0044] Furthermore, within the scope of a particularly advantageous embodiment of the device, it can be provided that a first contact element between the connection element and the circuit board has a conical section, while a second contact element between the connection element and the circuit board has a shoulder on which the circuit board rests. In particular, both contact elements can each have a projection beyond the circuit board on the side of the circuit board facing away from the resistor arrangement and can be laterally widened in the region of the projection.The particular advantage of such a combination of contact elements with different shapes and functions is that, under the combined stress of vibration and temperature changes, the first contact element ensures the lateral fixation of the circuit board, while the second contact element enables the circuit board to be fixed perpendicular to the circuit board without causing any additional restriction of lateral movement. Stresses that can arise from temperature changes due to different expansion of the circuit board and resistor arrangement are thus reduced. The device is therefore particularly robust.

[0045] In an advantageous embodiment of the invention, the surface of the at least one contact element can have a metallic coating, in particular a coating containing tin, silver, or nickel. Such a coating prevents corrosion and can thus ensure that the electrical contact between the contact element and the electrically conductive material on the inner surface of the through-hole is of high quality over the entire service life of the device. The coating can be applied before forming the contact element in step b), or the contact element can be coated in a separate step between process steps b) and c).

[0046] With regard to further technical features and advantages of the device according to the invention, reference is hereby explicitly made to the explanations in connection with the method according to the invention described above as well as to the figures and the description of the figures.

[0047] Embodiments of the invention are explained in more detail with reference to the schematic drawings.

[0048] Showing: Fig. 1 an oblique view of a resistor arrangement Fig. 2 a side view of a resistor arrangement Fig. 3 in sectional view a section of a resistor arrangement at the end of process step b) Fig. 4 in sectional view a section of a resistor arrangement with shaped contact element Fig. 5 in sectional view a section of a resistor arrangement with a printed circuit board positioned on it Fig. 6in sectional view a section of a resistor arrangement during process step e) Fig. 7 in sectional view a section of a resistor arrangement with a printed circuit board fixed on it Fig. 8 in sectional view a section of a resistor arrangement with a printed circuit board fixed to it and with a contact element with a shoulder Fig. 9 in sectional view a section of a resistor arrangement with a printed circuit board fixed to it and with a contact element with a conical section

[0049] Corresponding parts are provided with the same reference numerals in all figures.

[0050] Fig. 1shows an oblique view of a resistor arrangement 2 without a contact element. The resistor arrangement 2 has two terminal connection elements 3, 3' and a resistor element 4, which is positioned between the two connection elements 3, 3'. The connection elements 3, 3' and the resistor element 4 each have a plate-like shape. The thickness of the resistor element 4 is slightly less than the respective thickness of the two connection elements 3, 3'. The resistor arrangement 2 can be connected to an electrical circuit at the two connection elements 3, 3'. For this purpose, the two connection elements 3, 3' can have connecting devices (not shown), for example bores. These connecting devices are each attached in the area 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' with respect to the direction of current flow.When current flows, an electrical voltage drops across the resistance element 4, by means of which the strength of the current flowing through the resistance arrangement 2 can be determined.

[0051] Fig. 2 shows a side view of the resistor arrangement 2 according to Fig. 1 . A resistor arrangement 2 as in Figures 1 and 2 shown can be produced in a known manner by longitudinally welding three strips to form a composite material and then cutting the welded composite material to length.

[0052] Fig. 3 shows a sectional view of an enlarged section of the resistor arrangement 2 according to Fig. 1 and 2upon completion of process step b). A negative mold 12 with a recess 121 and an inner tool 122 arranged in the recess 121 was positioned on the upper side of the connection element 3. On the underside of the connection element 3, a punch 11 penetrated the material of the connection element 3, which is symbolized by the upward-pointing arrow. The punch 11 is positioned such that it lies opposite the recess 121 of the negative mold 12. As a result of the penetration of the punch 11, material of the connection element 3 was deformed essentially perpendicular to the surface of the connection element 3 and displaced into the empty space of the negative mold 12, which is defined by the recess 121 and the inner tool 122. In this way, a material projection was formed, which forms the contact element 5. The inner tool 122 ensures that the contact element 5 has a cavity open on one side after the inner tool 122 is removed.

[0053] Fig. 4 shows a sectional view of an enlarged section of the resistor arrangement 2 with a formed contact element 5 after method step b). The punch 11 and the negative mold 12 have been removed. To facilitate the removal of the punch 11 and the negative mold 12, the punch 11, the recess 121, and the inner tool 122 in the negative mold 12 can each have a contour with bevels for demolding. Accordingly, the formed contact elements 5 can also have a contour with bevels. The angle that the bevels for demolding form with the normal to the surface of the connection elements 3 is typically approximately 2°. Due to this slight deviation from the normal, the bevels are not explicitly shown in the figures.

[0054] The contact element 5 has a longitudinal axis A that is oriented perpendicular to the surface of the connection element 3. Furthermore, the contact element 5 has an end face 52 that faces away from the connection element 3 and thus away 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 case shown, this cavity 53 extends approximately to the undeformed surface of the connection element 3. For manufacturing reasons, however, it may be advantageous to shape the contact element 5 such that the cavity 53 extends less far into the contact element 5 or, alternatively, such that the cavity 53 reaches into the material of the connection element 3. Due to the cavity 53, the contact element 5 has the shape of a sleeve that is closed on one side and open on the other. The height of the contact element 5 is indicated by the symbol H.The height H is measured from the undeformed surface of the connecting element 3 to the front side 52 of the contact element 5.

[0055] Contact element 5 is designed to measure the electrical voltage drop across resistance element 4. To minimize distortion of the measured value, contact element 5 was formed from connection element 3 so that it is positioned close to the connection point between connection element 3 and resistance element 4.

[0056] Fig. 5 shows in sectional view the enlarged section of the resistor arrangement 2 according to Fig. 4 additionally with a circuit board 8 of thickness D positioned on the resistor arrangement 2. Fig. 5thus represents the resistor arrangement 2 and the circuit board 8 after method step d). The circuit board 8 has a through-hole 9. On the inner surface 91 of the through-hole 9 of the circuit board 8 there is electrically conductive material 92, which is not shown in detail for reasons of clarity. The circuit board 8 was positioned such that the contact element 5 protrudes into the through-hole 9 to a penetration depth T. In the case shown, the penetration depth T is slightly less than the thickness D of the circuit board 8, so that the end face 52 of the contact element 5 is not flush with the top side 81 of the circuit board 8, but is still located within the through-hole 9. The penetration depth T is approximately 90% of the thickness D of the circuit board 8. The clear width of the through-hole 9 is slightly larger than the outer dimension of the contact element 5.In the illustrated embodiment, the circuit board 8 does not rest directly on the connection element 3, which can be achieved, for example, by using spacers (not shown). A large distance between the circuit board 8 and the resistance element 4 is advantageous because it allows heat generated in the resistance element to be quickly dissipated. Any electronic components that may be present on the circuit board 8 are not shown for reasons of clarity.

[0057] Fig. 6shows a sectional view of the enlarged section of the resistor arrangement 2 during process step e). A conical expansion means 14 is introduced in the direction of the arrow into the cavity 53 of the contact element 5. The outer dimension of the expansion means 14 is selected such that the conical shape of the expansion means 14 displaces the material of the contact element 5 in a radially outward direction, i.e., towards the inner surface 91 of the through-hole 9. As a result, the contact element 5 comes into contact with the electrically conductive material 92 on the inner surface 91 of the through-hole 9, forming an electrically conductive connection. Fig. 6 The expansion means 14 shown can be a body that remains in the cavity 53 of the contact element 5, or it can be the working area of ​​a tool that is removed from the cavity 53 of the contact element 5 after expansion.

[0058] Fig. 7shows in sectional view the enlarged section of the resistor arrangement 2 according to Fig. 6 after removing the tool used for expansion. Fig. 7 thus simultaneously represents the sectional view of part of a device 1 for measuring currents by means of the resistor arrangement 2.

[0059] Fig. 8shows, as a further exemplary embodiment, the sectional view of a part of a device 1 for measuring currents with a resistor arrangement 2 and a printed circuit board 8 positioned on the resistor arrangement 2. The contact element 5 has a circumferential shoulder 51 on which the printed circuit board 8 rests. For this purpose, the contact element 5 is designed such that the outer dimension of the contact element 5 in the partial area immediately adjacent to the connection element 3 is greater than the clear width of the through-hole 9 of the printed circuit board 8. Thus, the printed circuit board 8 does not rest on the connection element 3 or the resistor element 4 even without additional spacers. When forming the contact element 5 from the material of the connection element 3, the height of the shoulder 51 was already taken into account. The contacting of the printed circuit board 8 by the contact element 5 takes place in the same way as in the Fig. 6presented and in connection with Fig. 6 explained embodiment.

[0060] Fig. 9shows, as a further exemplary embodiment, the sectional view of part of a device 1 for measuring current strengths with a resistor arrangement 2 and a printed circuit board 8 positioned on the resistor arrangement 2. The contact element 5 has a section 55 with a conical outer contour between the connection element 3 and the printed circuit board 8, which section directly adjoins the printed circuit board 8. Furthermore, the contact element 5 has a projection 56 beyond the printed circuit board 8. In the area of ​​this projection 56, the contact element 5 has been conically widened. As a result, the contact element 5 projects laterally beyond the upper side 81 of the printed circuit board 8. As a result of the conical widening of the contact element 5 in the area of ​​its projection 56, the printed circuit board 8 was moved towards the connection element 3 and thus pressed onto the conical section 55 of the contact element 5 between the printed circuit board 8 and the connection element 3.In this way, the circuit board 8 is fixed in a force-locking manner in the direction of the longitudinal axis A of the contact element.

[0061] For reasons of better representation, the invention was Figures 1 to 9explained by way of example using a resistor arrangement 2, which 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 with respect to a possible current path. The resistor arrangement can be configured such that the same current flows through at least two resistor elements, which enables redundant current measurement, or such that different currents flow through at least two resistor elements, which enables the measurement of partial currents. The method described above, based on the Figures 1 to 9and the method for forming contact elements 5 and for establishing an electrical connection with a printed circuit board 8 explained with reference to the exemplary embodiments can in these cases also be used for forming one or more contact elements 5 from the material of a connection element arranged between two resistance elements. List of reference symbols

[0062] 1Device 2Resistance arrangement 3, 3'Connection element 4Resistance element 5Contact element 51Step 52End face 53Cavity 55Section 56Protrusion 8Printed circuit board 81Top 9Through hole 91Inner surface 92Electrically conductive material 11Stamp 12Negative mold 121Recess 122Internal tool 14Expanding means ALongitudinal axis HHeight TPenetration depth DThickness

Claims

1. Method for producing an apparatus (1) for measuring the strength of an electrical current by means of a resistor arrangement (2), wherein the method comprises the following steps: a) providing a resistor arrangement (2) comprising at least two connection elements (3, 3') and at least one resistance element (4) which is arranged with respect to the direction of the electrical current between the connection elements (3, 3'), wherein the at least one resistance element (4) on the one hand and the connection elements (3, 3') on the other hand comprise different electrically conductive materials, b) forming at least one contact element from the material of at least one connection element (3, 3') or from the material of the resistance element (4) so that the contact element (5) is monolithically connected to the connection element (3, 3') or to the resistance element (4), wherein the contact element (5) has a longitudinal axis (A) by means of which an axial direction and a radial direction which is perpendicular thereto are defined, and wherein the contact element (5) is formed in such a manner that it has an end face (52) which faces away from the resistor arrangement (2) and a hollow space (53) which is open at the end face (52) of the contact element (4) facing away from the resistor arrangement (2), c) providing a printed circuit board (8) which has at least one through-hole (9) having an inner surface (91) on which electrically conductive material (92) is located, d) positioning the printed circuit board (8) on the resistor arrangement (2) in such a manner that the printed circuit board (8) has an upper side (81) which faces away from the resistor arrangement (2) and the at least one contact element (5) protrudes at least into the through-hole (9), e) expanding the contact element (5) in a radial direction by means of an expansion means (14) which is introduced in an axial direction into the hollow space (53) of the contact element (5) as far as the region of the through-hole (9) of the printed circuit board (8) so that an electrically conductive connection between the contact element (5) and the electrically conductive material (92) is produced on the inner surface (91) of the through-hole (9).

2. Method according to claim 1, characterised in that the expansion means (14) is configured in such a manner that the expansion of the contact element (5) is carried out by introducing the expansion means (14).

3. Method according to claim 1, characterised in that the expansion means (14) is configured in such a manner that the expansion of the contact element (5) is carried out after the introduction of the expansion means (14).

4. Method according to any one of claims 1 to 3, characterised in that, as a result of the expansion in the method step e), a non-positive-locking connection is produced between the inner surface (91) of the through-hole (9) of the printed circuit board (8) and the contact element (5).

5. Method according to any one of claims 1 to 4, characterised in that the contact element (5) has a height (H) which is selected in such a manner that, after the positioning of the printed circuit board (8), the end face (52) of the contact element (5) facing away from the resistor arrangement (2) is located inside the through-hole (9) of the printed circuit board (8) or terminates flush with the upper side (81) of the printed circuit board (8).

6. Method according to any one of claims 1 to 5, characterised in that the shaping of the contact element (5) is carried out in method step b) by means of a stamping step or by means of extrusion.

7. Method according to claim 6, characterised in that in order to shape the contact element (5) a negative mould (12) having at least one recess (121) which corresponds to the outer contour of the contact element (5) and at least one inner tool (122) which is positioned in the recess (121) is used to shape the hollow space (53) and in that during method step b) the inner tool (122) is moved in the direction of the longitudinal axis (A) of the contact element (5) relative to the recess (121).

8. Method according to any one of the preceding claims, characterised in that the expansion of the contact element (5) in method step e) is supported by heating the material of the contact element (5) by means of ultrasound or by means of a laser.

9. Apparatus (1) for measuring the strength of an electrical current comprising a resistor arrangement (2) and a printed circuit board (8) which is mechanically and electrically connected to the resistor arrangement (2), wherein the resistor arrangement (2) comprises at least two connection elements (3, 3') and at least one resistance element (4) which is arranged with respect to the direction of the current between the connection elements (3, 3'), wherein the at least one resistance element (4) on the one hand and the connection elements (3, 3') on the other hand comprise different electrically conductive materials, and wherein the printed circuit board (8) has at least one through- hole (9) having an inner surface (91) on which electrically conductive material (92) is located, wherein the resistor arrangement (2) has at least one contact element (5) having a longitudinal axis (A) which is monolithically connected to one of the connection elements (3, 3') and is formed from the material of the connection element (3, 3') or which is monolithically connected to the resistance element (4) and formed from the material of the resistance element (4), and by means of which the resistor arrangement (2) is electrically conductively and mechanically connected to the printed circuit board (8) by the contact element (5) protruding at least into the through-hole (9) of the printed circuit board (8) and being connected in a non-positive-locking manner to the electrically conductive material (92) on the inner surface (91) of the through-hole (9), wherein the contact element (5) has an end face (52) which faces away from the resistor arrangement (2) and a hollow space (53) which is open at the end face (52) of the contact element (5) facing away from the resistor arrangement (2), characterised in that the contact element (5) has at the inner side thereof at the transition from the end face (52) thereof to the hollow space (53) a conical contour which extends into the region of the through-hole (9) of the printed circuit board (8).

10. Apparatus (1) according to claim 9, characterised in that the contact element (5) has a height (H) which is selected in such a manner that the end face (52) of the contact element (5) facing away from the resistor arrangement (2) is located inside the through-hole (9) of the printed circuit board (8) or terminates flush with the upper side (81) of the printed circuit board (8).

11. Apparatus (1) according to claim 9, characterised in that the contact element (5) has at the side of the printed circuit board (8) facing away from the resistor arrangement (2) an overhang (56) over the printed circuit board (8) and is laterally widened in the region of this overhang (56) in order to fix the printed circuit board (8).

12. Apparatus (1) according to claim 11, characterised in that the contact element (5) has between the connection element (3, 3') and the printed circuit board (8) a portion (55) having a conical outer contour so that the cross sectional surface-area of the contact element (5) increases in the direction towards the connection element (3, 3').

13. Apparatus (1) according to any one of claims 9 to 12, characterised in that the at least one contact element (5) has a shoulder (51) on which the printed circuit board (8) is positioned in such a manner that the printed circuit board (8) is spaced apart from the resistor arrangement (2).

14. Apparatus (1) according to any one of claims 9 to 13, characterised in that the at least one contact element (5) has a surface having a metal coating, in particular a tin-containing, silver-containing or nickel-containing coating.