Patent Publication Number: US-11385106-B2

Title: Assembly for detecting temperature and contact assembly having such an assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of German Patent Application No. 102018204271.3, filed on Mar. 20, 2018. 
     FIELD OF THE INVENTION 
     The present invention relates to an electrically conductive element and, more particularly, to an assembly for detecting a temperature of the electrically conductive element. 
     BACKGROUND 
     An assembly for detecting a temperature, and a contact assembly having such an assembly, are used, for example, to monitor electroconductive elements. If, for example, a temperature threshold is reached, this can indicate if a maximum permissible current is flowing through the electrically conductive element, or even if there is an incomplete or faulty contact. A faulty contact can, for example, lead to a reduced effective electroconductive cross-section of the electrically conductive element, such that in the case of a fixed current, said element can heat up beyond a temperature threshold set within the specification. In particular in the sector of electromobility, a faulty contact of this type is crucial and must be avoided. Voltages present in this sector in the range of 1 kV and the current flowing into the DC circuits in the range of approximately 200 A can, within less than a minute, lead to excessive heating of a faulty contact beyond predetermined thresholds. In the case of such an overheating, the risks not only include the thermal destruction of the contact assembly and the surrounding elements, but also leakage of poisonous vapors/gases and the onset of fires. Reliably identifying excessively high currents being transmitted, as well as faulty electrical contacting by identifying a temperature of the electrically conductive element, can reduce or even eliminate the abovementioned risks. 
     Known solutions, however, have discrepancies in the determined temperature value. The determined temperature threshold can only be determined with a delay, i.e. a temperature value determined at a particular time does not represent the currently prevailing temperature of the electrically conductive element. 
     An assembly  1 ′ from the prior art and exemplary measured temperature profiles  5  of the assembly  1 ′ are shown in  FIGS. 1 and 2 . In  FIG. 1 , the temperature T is plotted against the time t, wherein the range of temperature T from 20° C. to 120° C. and the range of time t from 0-100 minutes is shown. The dotted line  5   a  represents the temperature profile of the ambient temperature. The broken lines  5   c  represent two temperature profiles  5 , which describe the development of the temperature T of two electrically conductive elements  7 , shown in  FIG. 2 . The two temperature profiles  5   c  are only slightly different from one another, which can be attributed to deviations related to construction and/or possible empirical deviations during measuring. The continuous line  5   s  in  FIG. 1  is the temperature profile  5  of a temperature probe  9 . 
     The assembly  1 ′ for detecting the temperature T of at least one electrically conductive element  7  from the prior art is shown in  FIG. 2 . The assembly  1 ′ is drawn to be partially transparent and is provided to be used in a contact assembly  11 . The assembly  1 ′ is received in a sensor receptacle  13  of a secondary latching element  15 . 
     As shown in  FIG. 2 , the assembly  1 ′ comprises a circuit board  17 , which can be configured as a printed circuit board  19  (PCB) for example, and two temperature probes  9  which are mechanically and electrically connected to the PCB  19 . The assembly  1 ′ includes an evaluation unit  21 , a storage unit  23 , and a contacting region  25  for contacting the PCB  19  and elements which are attached thereto, such as the temperature probes  9 . Via the contacting region  25 , the PCB  19  can output a value representing the temperature T measured by the temperature probes  9 . 
     The PCB  19  is received in the secondary latching element  15 , as shown in  FIG. 2 , and the secondary latching element  15  is, in turn, arranged and/or secured in a contact housing  27  of the contact assembly  11 . The contact assembly  11  can be a socket  29  or a plug  31  and can be used in the field of electrically operated vehicles, for example, in the shape of charging sockets and charging plugs. In such an application, such an assembly allows the temperature of the electrically conductive element or elements to be measured or monitored. 
     The disadvantages of the solutions of the prior art are clear from the graph of  FIG. 1 . On the one hand, a temperature difference ΔT between the temperature profiles  5   c  and  5   s  can be observed, which is approximately 15 K in the measurement shown. Furthermore, the temperature profile  5   s  is temporally delayed relative to the temperature profile  5   c , which is represented, for example, by a delay time Δt in  FIG. 1 . For example, the temperature T of 80° C. is reached by the electrically conductive element  7  after approximately sixteen minutes, whereas the temperature probe  9  only reaches this temperature after approximately thirty minutes. Determining the temperature of the electrically conductive element  7  in a timely and precise manner is thus not possible with the solutions from the prior art. 
     In the course of this disclosure, the term “timely” should not be understood to mean instantaneously. Temperature measurements are always associated with a certain temporal delay, since the heat of the object which is to be measured has to be transmitted to a temperature probe. This transmission and in particular the time frame within which this occurs depends on different parameters, for example the temperature difference between the electrically conductive element and the temperature probe, the heat conductivity between the two elements, the specific heat capacity of the temperature probe, and on the like. The measuring shown in  FIG. 1  indicates that sometimes delay times Δt in the range of 10-20 minutes can occur. If such a delay time Δt is taken as a basis, a temperature measuring with a delay time Δt in the range of one or two minutes can indeed be described as timely. Furthermore, a precisely determined temperature should not be understood as a highly accurate determination, exact to 1/10 degrees Celsius, of the temperature, but instead as a measuring with an accuracy of ±5° C. 
     SUMMARY 
     An assembly for detecting a temperature of an electrically conductive element comprises a temperature probe and a heat conductor separate from the temperature probe and made of an electrically insulating and heat-conductive material. The heat conductor surrounds the temperature probe at least in sections and has a bearing surface bearing against the electrically conductive element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying Figures, of which: 
         FIG. 1  is a graph of a measured temperature profile of an electrically conductive element and a temperature probe of an assembly according to the prior art; 
         FIG. 2  is a perspective view of an assembly according to the prior art; 
         FIG. 3  is a perspective view of a contact assembly according to an embodiment of the invention; 
         FIG. 4  is an exploded perspective view of the contact assembly of  FIG. 3 ; 
         FIG. 5  is a detail perspective view of the contact assembly of  FIG. 3 ; 
         FIG. 6A  is a sectional top view of a heat conductor of the contact assembly according to an embodiment; 
         FIG. 6B  is a sectional top view of a heat conductor according to another embodiment; 
         FIG. 6C  is a sectional top view of a heat conductor according to another embodiment; and 
         FIG. 7  is a graph of simulated temperature differences in the contact assembly according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     Embodiments of the present invention will be described hereinafter in detail with reference to the attached drawings, wherein like reference numerals refer to like elements. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that the disclosure will convey the concept of the invention to those skilled in the art. 
     Hereinafter, the present invention is explained in greater detail using the attached drawings. The attached drawings show specific configurations of the assembly according to the invention as well as the contact assembly according to the invention. The technical features of the configurations shown hereinafter can be combined with one another as desired and can also be omitted in other configurations, as long as the technical effect achieved by the technical feature being omitted is not important. The specific configurations described do not restrict the intended scope of protection, but instead simply represent some of the plurality of possible configurations of the invention. Furthermore, the assembly according to the invention or the contact assembly according to the invention are not limited to the specified number of technical features and can thus have, for example, a plurality of temperature probes, for example 3, 4, 5 or more temperature probes. Identical technical features and technical features with the same technical function are hereinafter provided with the same reference numbers in each case. A repetitive description is dispensed with and explicit reference is only made to differences between the configurations shown in the different figures. 
     An assembly  1  according to an embodiment is shown in  FIGS. 3-5 . The assembly  1  is shown with a pair of electrically conductive elements  7  and a secondary latching element  15  in a mounted state  33  in  FIG. 3  and exploded in  FIG. 4 .  FIG. 5  shows the assembly  1  connected with just the electrically conductive elements  7 . The secondary latching element  15  and/or the PCB  19  are drawn to be partially transparent, so that the temperature probes  9  which are arranged on an underside  35  can be seen. In an embodiment, the two electrically conductive elements  7  can be contacts of a charging apparatus for electric vehicles. 
     In an embodiment, the PCB  19  can have two temperature probes  9 , so that two electrically conductive elements  7  can be examined and monitored, simultaneously and independently of one another, for possible overheating. In an embodiment, the temperature probe  9  is disposed on a tongue of the PCB  19 . 
     The assembly  1  includes alongside the PCB  19 , as shown in  FIGS. 3-5 , a pair of heat conductors  37  formed of an electrically insulating and heat-conductive material  39 . In an embodiment, the material  39  is silicone  41 , and in a further embodiment, is highly filled silicone  43 . These materials  39 ,  41  have a breakdown voltage  40  of more than 500 V, and in an embodiment, up to more than 1000 V. The materials  39 ,  41  are mixed with microparticles  47 . The microparticles  47  are materials with high heat conductivity. 
     The highly filled silicones  43 , in an embodiment, can include granulates. The granulates/nanoparticles can, in particular, consist of silicon or of ceramic. Although silicon inherently has specific electrical properties (electrical conductivity), said electrical properties do not come into play since the silicon is embedded in the silicone. The granulates/nanoparticles can further consist of one or more of the following substances or compounds: aluminum, aluminum oxide, aluminum nitride, silicon carbide and silicon nitride. These substances/compounds can have a heat conductivity which is greater than that of pure silicone. Furthermore, they can also be electrically insulating (e.g. aluminum oxide), wherein, as already mentioned, an electrical heat conductivity (e.g. in the case of aluminum) through the electrically insulating effect of the silicone does not rule out the use of such conductive fillers. 
     A heat-conductive material  39  is understood to mean, in particular, such materials that have a heat conductivity of at least 0.2 W/(m K). Metals which, per se, can have a higher heat conductivity of up to several hundred W/(m K) are in fact better heat conductors (better in the sense of a higher heat conductivity), but they cannot be used for transmitting the temperature between the electrically conductive element  7  and the temperature probe  9 , since they do not guarantee electrical insulation. 
     The heat conductors  37 , as shown in  FIG. 4 , are elastically and reversibly deformable, and therefore have an elasticity  45 . The heat conductors  37  include a bearing surface  49  indicated with a shading, the bearing surface  49  shown having a curvature  51 . The bearing surface  49  is configured to be concave in the shown embodiment. In an embodiment, the heat conductor  37  is U-shaped, with a base formed by bearing surface  49  and lateral elements encompassing the temperature probe  9  or PCB  19 . 
     In the mounted state  33 , the bearing surface  49  of the heat conductor  37  is in a recess  53  shown in  FIG. 4 . The recess  53  connects the sensor receptacle  13  to a contact receptacle  55  of the secondary latching element  15 , into which the electrically conductive elements  7  shown can be inserted. In the mounted state  33 , into which the assembly  1  is movable with the secondary latching element  15 , the bearing surface  49  of the heat conductor  37  is thus assembled abutting against the contact receptacle  55  or overlapping with the contact receptacle  55 , so that the bearing surface  49  rests against a measuring point  57  of the electrically conductive element  7  and, by virtue of its elasticity  45  (at least the bearing surface  49  has this elasticity  45 ), rests tightly against the measuring point  57  and minimizes the occurrence of heat-insulative air gaps. The deformability of the bearing surface  49  also maintains contact in vibration environments. An almost form-fitting thermal connection between the electrically conductive element  7 , the temperature of which is to be measured, and the temperature probe  9  is reached due to the heat conductor  37 . The heat conductor  37  conducts the heat from the electrically conductive element  7  to the temperature probe  9 . 
     The resting of the heat conductor  37  by its bearing surface  49  against the measuring point  57  is also shown in  FIG. 5 .  15  In the mounted state  33  shown in  FIG. 3 , the secondary latching element  15  is in a position  34  in which the heat conductor  37  abuts against the contact receptacle  55  or overlaps with the contact receptacle  55 . In an embodiment, the electrically conductive element  7  can be cylindrical or rod-shaped, it being possible for the outer radius at a temperature measuring point  57  of the electrically conductive element  7  to correspond to the radius of the concave bearing surface  49 . 
     The electrically conductive elements  7  are received in the contact receptacle  55 , it is thus guaranteed that a temperature measurement of the electrically conductive elements  7  is possible in at least one position of the secondary latching element  15 . The at least one position corresponds to a latched position, the reaching of which can be an essential requirement in order to start the current connection through the electrically conductive elements  7 . 
     The heat conductor  37  further has a slot  59 , as shown in  FIG. 4 , adapted to receive the at least one temperature probe  9 . The slot  59  can have a width  61 , which corresponds substantially to the width  61  of the PCB  19 , as shown in  FIG. 5 . A groove  63  extends into the body of the heat conductor  37 , from the slot  59  in a direction parallel to the bearing surface  49 . The temperature probe  9 , which is attached to the PCB  19 , can be received in this groove  63 ; in an embodiment, a tongue of the PCB  19  having the temperature probe  9  is received in the slot  59 . The course of the groove  63  and the temperature probe  9  received on its end  65  are shown in  FIG. 5 . 
     When the PCB  19  is received in the heat conductor  37 , the heat conductor  37  surrounds the temperature probe  9  and, in the configuration shown, also parts of the PCB  19  from at least three sides, so that creepage distances are significantly increased and the electrically conductive elements  7  are electrically insulated from elements of the PCB  19 . At least one section  18  of the circuit board  17  or the PCB  19  shown in  FIG. 4  can be plugged into the heat conductor  37 . Two sections  18  which are plugged into the corresponding heat conductor  37  are shown in  FIG. 3 . 
     In another embodiment of the assembly  1 , the heat conductor  37  does not, as shown in  FIG. 5 , terminate with the PCB  19 , but instead can completely enclose the PCB  19 . Only the contacting region  25  can be accessible in such a configuration. This complete enclosure has the advantage that the PCB  19 , along with its electrical elements such as the at least one temperature probe  9 , is protected against external environmental influences, such as corrosive gases or liquids. A heat conductor  37  of such a configuration is shown in  FIG. 6C . 
     In an embodiment in which the PCB  19  has surface mounted devices (SMD), the heat conductor  37  is not in mechanical contact with the SMD. In such a configuration, the distance between the heat conductor  37  and the SMD should be selected to be as small as possible, so that an occurring air gap is as small as possible (for example a few 100 μm). 
     In an embodiment, the sensor receptacle  13  of the contact assembly  1 , can be potted with the material of the heat conductor  37 ; an intermediate space between the assembly  1  and the boundaries of the sensor receptacle  13  is completely potted or filled with the material of the heat conductor  37 . Such a potting, as mentioned previously, results in an inseparable connection and, in this case, protects the entire assembly  1  from harmful environmental conditions and vibrations. 
       FIG. 7  shows a simulated (FEM) temperature increase ΔTR depending on a current I applied to the electrically conductive elements  7  with the assembly  1  according to the invention. The simulated values of the temperature increase ΔTR are each determined in a stationary state, i.e. irrespective of time. The simulation was proceeded on the assumption of electrically conductive elements  7 , which on both sides have a cross-section of 70 mm 2  and an overall resistance of 90 microhms. A room temperature of 30° C. was assumed. 
     As shown in  FIG. 7 , a clear temperature difference ΔT between the temperature profile  5   c  (dotted) of the electrically conductive elements  7  and the temperature profile  5   s  of the temperature probe  9  can be recognized. In the case of a current of approximately 300 A, the temperature difference ΔT can be reduced from 18 K to approximately 6 K by using the heat conductor  37  according to the invention. The temperature profile  5   h  obtained with the heat conductor  37  is drawn as lines with diamonds. This temperature profile  5   h  can be consulted to detect the temperature profile  5   c  with a significantly lower error than with the temperature profile  5   s . The second temperature difference ΔT 2  can be further reduced by way of further optimization, for example of the material of the heat conductor  37 . 
     Different embodiments of the heat conductor  37  are shown in  FIGS. 6A-6C . All three embodiments are centrally sectioned in the slot  59  in the shown orientation. Furthermore, all configurations shown have the bearing surface  49 , which is shaped to be concave with a radius  69 . This radius  69  corresponds to the radius  69  of the measuring point  57  of the corresponding electrically conductive element  7 . In connection with  FIG. 4 , it is readily apparent that a second heat conductor  37  can be provided which is mirrored relative to an axis of symmetry  71 . The axis of symmetry  71  is drawn in  FIG. 6A  merely by way of example. 
     The configurations of  FIG. 6A  and  FIG. 6B  each have the groove  63  in the slot  59 , the groove  63  extends to the end  65  in the direction of the bearing surface  49 . A temperature probe  9 , which projects into the drawing plane from the PCB  19 , can be received along this groove  63  up to a final position  73 . The final position  73  is reached, for example, in the mounted state  33 . The shape of the slot  59  can have other shapes in other embodiments, for example, it can be rounded, rectangular or triangular. The shape of the slot  59  is adapted to the shape of the PCB  19 , i.e. shaped to be complementary thereto. 
     A body  75  of the heat conductor  37  of  FIG. 6A  consists completely of silicone  41  and in particular filled silicone  43 . The body  75  can also comprise other materials in other embodiments, provided that they are electrically insulating and heat-conductive. A partial contour  77  is configured to be complementary to the sensor receptacle  13  of the secondary latching element  15 . Sections of the partial contour  77  can be complementary to the measuring point  57 . 
     The heat conductor  37  of  FIG. 6B  has a body  75  including an outer shell  79  and a heat-conductive medium  81  which is received in the outer shell  79 . The outer shell  79  is an electrically insulating and heat-conductive material  39 , and the heat-conductive medium  81  is, in an embodiment but not necessarily, electrically insulating. As long as the outer shell  79  has a sufficiently high breakdown voltage, and thus reliably electrically separates the electric circuits of the electrically conductive element  7  and of the PCB  19  from one another, an electrically conductive medium can also be used for the heat-conductive medium  81 . 
     In the heat conductor  37  shown in  FIG. 6C , the electrically insulating and heat-conductive material  39  completely surrounds the PCB  19 , at least in the region of the indicated temperature probe  9 . The material  39  subsequently completely encompasses the PCB  19 , including the temperature probe  9  which is located in the drawing plane underneath the sectioned, drawn PCB  19 . A chemical influencing of the PCB  19  and in particular the temperature probe  9  is thus prevented. The configuration of the heat conductor  37  shown in  FIG. 6C  can in particular be configured to be monolithic and encompass a second temperature probe  9 . 
     In an embodiment, the heat conductor  37  can have a breakdown voltage of &gt;500 Volts. The breakdown voltage is even higher in an embodiment, for example &gt;600 V, &gt;700 V, &gt;800 V, &gt;900 V and particularly preferably &gt;1000 V.