Abstract:
The invention relates to a resistor arrangement ( 1 ), especially for current measurement in a vehicle electrical system, with two plate-shaped connection elements ( 6, 9 ) separated from each other and a plate-shaped first resistive element ( 2 ), which is arranged between the two connection elements ( 6, 9 ) and is electrically and mechanically connected to these elements. According to the invention, at least one of the other plate-shaped resistive elements ( 3 ), which are separated from the first resistive element ( 2 ) and which are arranged between one of the two connection elements ( 6, 9 ) of the first resistive element ( 2 ) and another connection element ( 10 ) is connected electrically and mechanically to these connection elements ( 6, 10 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention pertains generally to a resistor arrangement, and more particularly for current measurement in a vehicle electrical system, and to a method for producing such a resistor arrangement and also to a measurement circuit with such a resistor arrangement.  
           [0003]    2. Background Art  
           [0004]    Low-impedance resistor arrangements, which can be used for measuring large currents, are known from EP 0 605 800 B1, U.S. Pat. No. 6,489,693, and U.S. Pat. No. 5,604,477. These known resistor arrangements consist of two connection elements, which are separated from each other and which are at least partially plate shaped, for supplying or transferring current and a plate-shaped resistive element, which is arranged between the two connection elements and which is electrically and mechanically connected to these connection elements, wherein the resistive element is connected to the adjacent connection elements by welding. The known resistor arrangement further has two separate measurement connections in order to measure the electric voltage drop across the resistive element according to known four-wire technology, wherein the electric current flowing through the resistive element can be calculated according to Ohm&#39;s law.  
           [0005]    However, a disadvantage in this known resistor arrangement is the fact that to measure several currents, a corresponding number of resistor arrangements are required as well as separated electronic measuring circuits.  
         SUMMARY OF THE INVENTION  
         [0006]    Therefore, the invention is based on the problem of reducing the cost of manufacturing while providing a measuring system for measuring several different electric currents.  
           [0007]    This problem is solved, starting from the known resistor arrangements and as described in the introduction, by the characterizing features and, corresponding manufacturing method, and by a measurement circuit, respectively, as described and claimed herein below.  
           [0008]    The invention comprises the general technical teaching of improving known resistor arrangements described in the introduction, to the effect that several different electric currents can be measured, in that there are several resistive elements separated from each other and which can each carry an electric current.  
           [0009]    In the preferred embodiments of the invention, the resistor arrangement according to the invention has two resistive elements, which are separated from each other, so that two electric currents can be measured simultaneously.  
           [0010]    However, it is also possible and is within the scope of the invention to provide the resistor arrangement with more than two (e.g., four) resistive elements, which are separated from each other, in order to be able to measure a corresponding number of electric currents.  
           [0011]    The individual resistive elements can also have different widths and/or thickness values with reference to the direction of current flow, as desired, so as to accommodate the appropriate current load.  
           [0012]    Preferably, the individual resistive elements are hereby connected to each other in the form of a star independently of the number of resistive elements and are electrically connected by a common connection element, while the other electrical connection of individual resistive elements is realized by a separate connection element.  
           [0013]    It should be mentioned here that the resistive elements, on the one hand, and the connection elements on the other, are originally preferably separate components, which, however, are integrally joined to each other in the resistor arrangement according to the present invention. This enables a separate optimization of the connection elements and the resistive elements in terms of their material composition for providing their corresponding function.  
           [0014]    Furthermore, the resistor arrangement according to the present invention is preferably fork-shaped, wherein the individual resistive elements are arranged one next to the other and preferably extend in a line. The common connection element of the resistor arrangement here preferably lies on one side of the line of resistive elements, while the other connection elements lie on the opposite side of the line of connection elements. Also a double sided arrangement is possible with the common connector in the middle and resistors on both sides (made of Cu-Manganin®-Cu-Manganin®-Cu for example). The advantage may be a smaller size.  
           [0015]    During operation, the resistive elements each carry an electric current along a current path, wherein the current path within the individual resistive elements is preferably essentially shorter than the resistive element according to the invention. Thus, the electrical resistance of the resistive elements is preferably not increased by a meander-shaped or spiral-shaped guidance of the resistive elements. Instead, the resistive elements are preferably plate-shaped, which prevents or at least makes less likely, an effect on the resistance and thus the measurement accuracy by shape changes.  
           [0016]    The actual measurement of the electric voltage drop across the individual resistive elements is realized preferably corresponding to the known four-wire technology by measurement connections, which are electrically and mechanically connected to the individual connection elements.  
           [0017]    Here, the individual measurement connections are preferably arranged directly at the edges of the resistive elements, so that the voltage measurement is not rendered inaccurate by the electric voltage drop within the connection elements.  
           [0018]    In addition, the measurement connections within the connection elements of the resistor arrangement according to the invention directly contact the side edges of the connection elements, which is likewise advantageous in terms of measurement.  
           [0019]    In a preferred embodiment of the invention, a circuit board with a measurement circuit is also provided, wherein the circuit board is arranged with its main plane parallel to the main surfaces of the plate-shaped resistive elements and is mechanically and/or electrically connected to these elements. The resistor arrangement according to the invention here forms a single structural unit with the circuit board with the measurement circuit, wherein the influence of electromagnetic interference and thermal stress is minimized by a minimal distance between the resistor arrangement and the circuit board.  
           [0020]    The mechanical connection of the circuit board to the resistor arrangement can be realized, e.g., by the measurement connections, by connecting the circuit board to the resistor arrangement by means of a soldering process.  
           [0021]    However, alternatively, it is also possible to connect the circuit board mechanically to the resistor arrangement with a spacer, wherein the spacer enables an equalization of mechanical-thermal expansions.  
           [0022]    In addition, preferably, there is a through-hole in the common connection element of the individual resistive elements in order to selectively influence the current distribution in the common connection element.  
           [0023]    The through-hole can be, e.g., a rectangular recess, wherein the through-hole is preferably directly adjacent to the measurement connection in the common connection element.  
           [0024]    For a fork-shaped formation of the resistor arrangement according to the invention, the through-hole is preferably arranged in the center between the two resistive elements for influencing the current distribution.  
           [0025]    The mechanical connection between the connection elements and the resistive elements is realized preferably by welding, but the invention can also be realized in terms of the connection between the connection elements and the resistive elements with other integral joining methods, such as hard-soldering.  
           [0026]    It should further be mentioned that the connection elements for current transfer or supply preferably consist of copper or a similar conductive copper composition, while the low-impedance resistive elements preferably consist of a CuMnNi composition (also known commercially as Manganin®). The connection elements and the resistive elements thus preferably consist of different materials for the resistor arrangement according to the invention, which preferably exhibit different specific electrical resistance values.  
           [0027]    Resistors, which lie in the range between 1 μΩ and 1 μΩ, are suitable for low-impedance current measurement. However, the invention is not limited to the previously mentioned value range in terms of the resistance value of the resistive elements.  
           [0028]    In addition, the invention also comprises an advantageous method for producing a resistor arrangement according to the invention, which is described briefly in the following.  
           [0029]    First, in a known way the manufacturing method according to the invention ensures that an elongated band made from a resistor material is mechanically and electrically connected at its longitudinal edges to an elongated band made from electrically conductive material, wherein the connection can be realized, e.g., by electron-beam welding.  
           [0030]    Then the bands connected to each other are separated along several perpendicular bands into several resistor arrangements.  
           [0031]    Here, it is of particular importance that in the individual resistor arrangements between every two adjacent separating lines perpendicular recesses are generated, wherein the recesses extend from a longitudinal edge of the resistor arrangement starting inwards at least up to the band made from the resistive material in order to form two connection elements separated from each other.  
           [0032]    The generation of the recesses for forming the elements separated from each other can be realized selectively before the separation of the individual resistor arrangements or after their separation.  
           [0033]    In a preferred embodiment of the invention, these perpendicular recesses extend inwards even up to the opposite band made from the electrically conductive material in order to form two resistive elements separated from each other. In this embodiment of the invention, the two resistive elements of one resistor arrangement are thus completely spatially separated from each other and are electrically connected to each other only by the common connection element.  
           [0034]    The separating lines for separating the individual resistor arrangements and the recesses for separating the individual connection elements or resistive elements into the individual resistor arrangements are preferably stamped out, but in principle it is also possible to use other manufacturing methods for this purpose.  
           [0035]    Finally, the invention also comprises a measurement circuit with at least one resistor arrangement according to the invention, wherein this measurement circuit is especially suited for current measurement in a vehicle electrical system.  
           [0036]    Here, the resistor arrangement according to the invention can be arbitrarily connected on the ground side (“low side”) or voltage side (“high side”), but it is also possible to provide a resistor arrangement on both the ground side and the voltage side.  
           [0037]    For the use of the resistor arrangement according to the invention for current measurement in a vehicle electrical system, a resistive element can be arranged, e.g., in a battery power circuit, while a different resistive element can be arranged, e.g., in a generator power circuit. In this way, both the battery current and also the generator current can be measured directly, while the vehicle current can be derived from the measured values.  
           [0038]    However, it is alternatively also possible that a resistive element be arranged in the battery power circuit of the vehicle electrical system, while the other resistive element measures the vehicle current and is connected to the individual loads. In this case, the resistor arrangement according to the invention enables a direct measurement of the battery current and the vehicle current, while the generator current can be derived from these two measured values.  
           [0039]    In each case, the invention enables in a simple way a reliable measured-value detection for combined electronic battery and power management, which is becoming ever more important for guaranteeing the power supply in electrical systems, especially in automobiles with a constantly increasing number of electrical loads.  
           [0040]    Instead of composite material that has been electron-beam welded in the described way, the resistor arrangement can also be produced in other ways. For example, it is conceivable to connect two bands consisting of the resistor alloy or of copper in a known way by roll-cladding and to generate the resistive elements through partial removal, especially milling, of the copper layer. The shaping and forming of individual pieces of the desired resistor arrangements can also be realized here, e.g., through stamping. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0041]    Other advantageous refinements of the invention are further disclosed or are explained in more detail in the following disclosure together with the description of the preferred embodiments of the invention with reference to the drawing figures;  
         [0042]    [0042]FIG. 1, is a plan view of a resistor arrangement according to the present invention,  
         [0043]    [0043]FIG. 2, is a plan view of an alternative embodiment of a resistor arrangement according to the present invention,  
         [0044]    [0044]FIG. 3, is a side view of the resistor arrangement of FIG. 1 showing a circuit board with a measurement circuit,  
         [0045]    [0045]FIG. 4, is a view of several arrangements according to the invention in the pre-fabricated state during production,  
         [0046]    [0046]FIG. 5, is a measurement circuit diagram according having two resistor arrangements according to the present invention,  
         [0047]    [0047]FIG. 6, is an alternative embodiment of a measurement circuit diagram according to the present invention,  
         [0048]    [0048]FIGS. 7 a - 7   d , are simplified embodiments of measurement circuit diagrams according to the present invention, as well as  
         [0049]    [0049]FIG. 8, is another embodiment of a resistor arrangement according to the present invention having four resistive elements.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]    The diagram in FIG. 1 shows a resistor arrangement  1  according to the present invention, which can be used, e.g., in a vehicle electrical system, for measuring the generator current and the battery current, as will be described in more detail later.  
         [0051]    Here, the resistor arrangement  1  has two resistive elements  2 ,  3 , which are spatially separated from each other and which each consist of a copper alloy (e.g., Manganin®) and exhibit a resistance of, e.g., 100 μΩ.  
         [0052]    The two resistive elements  2 ,  3  are each connected via a welding seam  4 ,  5  respectively to a common connection element  6 , which consists of copper and is used for current transfer or supply.  
         [0053]    The two resistive elements  2 ,  3  are further connected via another welding seam  7 ,  8  each to a separate connection element  9  and  10 , respectively, wherein the two connection elements  9 ,  10  enable separate current supply or current transfer.  
         [0054]    For contacting the connection elements  6 ,  9 ,  10 , each of these has a current connection hole  11 ,  12 , and  13 , respectively.  
         [0055]    Here, the actual current measurement is realized according to known four-wire technology through measurement connections  14 ,  15 ,  16 , which are connected to the connection elements  6 ,  9 , and  10 , respectively. By measuring the electric voltage between the two measurement connections  14  and  16 , e.g., the electric current flowing through the resistive element  2  can be determined, while the electric voltage between the measurement connections  15  and  16  gives the electric current through the resistive element  3 .  
         [0056]    The measurement connections  14 ,  15 ,  16  are here arranged directly adjacent to the resistive elements  2 ,  3  in order to prevent measurement errors due to the electric voltage drop within the connection elements  6 ,  9 ,  10 .  
         [0057]    In addition, the measurement connections  14 ,  15 ,  16  are arranged directly on the side edges of the connection elements  6 ,  9 ,  10  according to the diagram, which is also advantageous in terms of measurement.  
         [0058]    The resistor arrangement  1  in the connection element  6  further has a through-hole  17 , which borders directly on the measurement connection  16  and selectively influences the current distribution in the connection element  6 .  
         [0059]    The alternative embodiment shown in FIG. 2 of a resistor arrangement  1 ′ according to the invention agrees largely with the previously described embodiment of the resistor arrangement  1  shown in FIG. 1, so that in the following, mainly to prevent repetition, reference is made to the previous description of the FIG. 1 embodiment and the same reference symbols are used for corresponding parts, which are characterized by an apostrophe only to provide for differentiation.  
         [0060]    A characteristic of this embodiment is that the common connection element  6 ′ has two separate contacts  18 ′,  19 ′ for current transfer.  
         [0061]    From the side view in FIG. 3 it can be further seen that the resistor arrangement  1  shown in FIG. 1 is connected to a circuit board  20 , wherein the circuit board  20  carries a measurement circuit using the SMD construction method. For simplification, here two SMD components  21 ,  22  of the measurement circuit are shown only as examples.  
         [0062]    The mechanical and electrical connection of the circuit board  20  with the resistor arrangement  1  is here realized by the measurement connections  14 ,  15 , and  16 , wherein the small distance between the circuit board  20  and the resistor arrangement  1  ensures that the influence of electromagnetic interference and thermal stress remains minimal.  
         [0063]    [0063]FIG. 4 shows a view of several resistor arrangements  23 - 26  of the type shown in FIG. 1, but which are shown in the pre-fabricated state.  
         [0064]    For the production of the resistor arrangements  23 - 26 , initially three elongated bands  27 ,  28 ,  29  are connected to each other along their longitudinal edges via welding seams  30 ,  31 , wherein the two outer bands  27 ,  29  consist of copper, while the center band  28  consists of the above-mentioned copper alloy and later forms the resistive elements  2 ,  3  of the individual resistor arrangements  23 - 26 .  
         [0065]    After welding the bands  27 - 29  together, perpendicular recesses  32 - 35 , which extend from the side edge of the band  27  starting inwards up to the welding seam  31 , are stamped out in the still stuck-together resistor arrangements  23 - 26 , so that the recesses  32 - 35  in the resistor arrangements  23 - 26  separate the connection elements  9  and  10  and also the resistor arrangements  2  and  3  from each other.  
         [0066]    In addition, recesses  11 . 1 - 11 . 4 ,  12 . 1 - 12 . 4 , and  13 . 1 - 13 . 4 , which are used for connecting separate lines, are stamped out in the individual resistor arrangements  23 - 26 .  
         [0067]    Additional through-holes  17 . 1 - 17 . 4  are further stamped out in the individual resistor arrangements  23 - 26 , wherein the through holes  17 . 1 - 17 . 4  are used for influencing the current distribution in the resistor arrangements.  
         [0068]    Finally, the individual resistor arrangements are then separated along given separating lines  36 , in order to be able to then mount the circuit board  20  shown in FIG. 3 with the measurement circuit.  
         [0069]    [0069]FIG. 5 shows a measurement circuit, which is used by means of two resistor arrangements  37 ,  38  according to the invention for current measurement in a vehicle electrical system.  
         [0070]    Here, the resistor arrangement  37  is arranged on the ground side (“low side”), wherein a resistive element of the resistor arrangement  37  is arranged in the power circuit of a battery  39 , while the other resistive element of the resistor arrangement  37  is arranged in the power circuit of a generator  40 . The resistor arrangement  37  thus enables a measurement both of a battery current i B  and also a generator current i G , wherein a vehicle current i C  is given from the negative sum of the two partial currents i B  and i G .  
         [0071]    The other resistor arrangement  38  also enables a measurement of the partial currents i B  and i G , because an element of the resistor arrangement  38  is arranged in the power circuit of the battery  39 , while the other resistive element of the resistor arrangement  38  is arranged in the power circuit of the generator  40 .  
         [0072]    The currents captured at the two resistor arrangements  37 ,  38  are supplied (here shown only simplified) to a monitoring unit  41  (EPM—Electronic Power Management), which controls a fuse box  42 , several loads  43 ,  44  and also an electronic control unit  45  (ECU) of a motor vehicle as a function of the measured values.  
         [0073]    Furthermore, a starter  46  is shown, which is connected to the summing node of the resistor arrangement  38 .  
         [0074]    The resistor arrangements  37 ,  38  according to the present invention here advantageously enable the measurement of the battery current i B  and the generator current i G , from which the vehicle current i C  can be derived.  
         [0075]    The circuit diagram in FIG. 6 shows an alternative embodiment of a measurement circuit according to the invention, for which for current measurement a resistor arrangement  47  with two resistive elements  48 ,  49  is also used.  
         [0076]    Here, the resistive element  49  is arranged in a circuit branch with a generator  50  and thus enables a measurement of a generator current i G .  
         [0077]    In contrast, the other resistive element  48  is arranged in a circuit branch in common with a battery  51  and thus enables the measurement of a battery current i B .  
         [0078]    For this embodiment, the resistor arrangement  47  according to the invention is arranged on the voltage side (“high side”) relative to the generator  50  and the battery  51 .  
         [0079]    On the common connection element of the resistor arrangement  47  according to the invention, a starter  52  and also several electrical loads are connected, wherein the loads are not shown for simplification.  
         [0080]    The actual current measurement is here realized by an integrated circuit  53  (ASIC-Application Specific Integrated Circuit), which is described in detail, e.g., in U.S. Published Application No. 2003/0222511. The contents of this publications are thus to be incorporated herein to their full extent by reference in the present description in terms of the construction and the method of operation of the integrated circuit  53 , so that a detailed description of the integrated circuit  53  can be omitted.  
         [0081]    However, it should also be mentioned that the integrated circuit  53  has a measurement input VBAT, to which a voltage divider is connected, which consists of two resistors  54 ,  55 , wherein the resistor  54  is connected to ground, while the resistor  55  is connected on the voltage side to the vehicle power supply voltage.  
         [0082]    Furthermore, the integrated circuit  53  has a voltage-side voltage tap RSHL, which is connected to the common connection element of the resistor arrangement  47 .  
         [0083]    In contrast, the two other connection elements of the resistor arrangement  47  are each separately connected to another measurement input ETS or RSHH of the integrated circuit  53 .  
         [0084]    [0084]FIGS. 7 a - 7   d  show simple embodiments of alternative modifications of measurement circuits according to the present invention, wherein the following described measurement circuit is illustrated.  
         [0085]    Here, a resistor arrangement  56  according to the invention is likewise used with two resistive elements  57 ,  58 , wherein the resistive element  57  is arranged in a circuit branch in common with a battery  59 .  
         [0086]    In contrast, the resistive element  58  of the resistor arrangement  56  is arranged in another circuit branch, via which all of the loads of the vehicle electrical system are supplied with power.  
         [0087]    Here, a starter  60  and a generator  61  are connected to the common connection element of the resistor arrangement  56 .  
         [0088]    The resistor arrangement  56  is likewise arranged on the voltage side in this embodiment.  
         [0089]    The embodiment of a measurement circuit according to the invention shown in FIG. 7 b  likewise has a resistor arrangement  62  according to the invention with two resistive elements  63 ,  64 , where the resistive element  64  is arranged in turn in a circuit branch in common with a battery  65 .  
         [0090]    In contrast, the other resistive element  63  is arranged in common with a generator  66 .  
         [0091]    In this embodiment, the battery current and the generator current can be measured directly, while the vehicle current is derived from these two measured values.  
         [0092]    Here, a starter  67  and a tap for supplying the vehicle electrical system is connected to the common connection of the resistor arrangement  62  according to the invention.  
         [0093]    The embodiments in FIGS. 7 c  and  7   d  are similar to the embodiments in FIGS. 7 a  and  7   b , so that in the following, to prevent repetition, reference is made to the previous description and the same reference symbols are used for corresponding components, which are further characterized by an apostrophe merely for differentiation.  
         [0094]    A characteristic of the embodiment according to FIG. 7 c  is that a circuit branch is connected to the common connection element of the resistor arrangement  56 ′, in which the battery  59 ′ is located.  
         [0095]    In contrast, one of the two separate connection elements of the resistor arrangement  56 ′ is connected to a circuit branch, in which a parallel circuit is arranged from the starter  60 ′ and the generator  61 ′.  
         [0096]    In contrast, the other connection element of the two separate connection elements of the resistor arrangement  56 ′ is connected to a circuit branch in which the vehicle current flows.  
         [0097]    For the embodiment according to FIG. 7 d , a circuit branch is also connected to the common connection element of the resistor arrangement  62 ′ in which the battery  65 ′ is located.  
         [0098]    In contrast, the two separate connection elements of the resistor arrangement  62 ′ are connected to two circuit branches in which the starter  67 ′ or the generator  66 ′ is arranged.  
         [0099]    [0099]FIG. 8 shows an embodiment of a resistor arrangement  68 , which the embodiment shown in FIG. 1, so that to prevent repetition in the following, the previous description of common elements and functions is omitted.  
         [0100]    A characteristic of the resistor arrangement  68  is that, overall, four connection elements  69 . 1 - 69 . 4  and, correspondingly, also four resistive elements  70 . 1 - 70 . 4  are provided.  
         [0101]    Here, in each of the four connection elements  69 . 1 - 69 . 4 , in turn, a current connection hole  71 . 1 - 71 . 4  is arranged.  
         [0102]    Finally, a measurement connection  72 . 1 - 72 . 4  is connected to each of the connection elements  69 . 1 - 69 . 4 .  
         [0103]    The invention is not limited to the previously described preferred embodiments. Instead, a plurality of variants and modifications is possible, which likewise make use of the concept according to the present invention and which thus are intended to fall within the scope of protection of the following claims and their equivalents.