PATENT ABSTRACT
The invention relates to a transmission coil ( 10 ) configured for inductive energy transfer, comprising a carrier ( 17 ), a coil arrangement ( 11 ) having a plurality of turns ( 12 ), and a capacitance. It is thereby provided that the capacitance is formed of a plurality of capacitors ( 22 ), wherein each capacitor ( 22 ) is assigned to an individual turn ( 12 ) or to a group of at least two turns ( 12 ) of the coil arrangement ( 11 ), and together with the coil arrangement, the capacitors ( 22 ) are arranged on the carrier ( 17 ). The invention further relates to a stationary charging station and to a vehicle, each comprising such a transmission coil ( 10 ), and to a system for the inductive charging of vehicles. No drawing text to be translated

PATENT DESCRIPTION
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a transmission coil which is configured to inductively transfer energy, comprising a carrier, a coil arrangement with a multiplicity of turns, and a capacitance which forms, together with the coil arrangement, an oscillatory circuit. Further aspects of the invention relate to a fixed charging station and to a vehicle, each comprising such a transmission coil, and to a system for inductively charging vehicles comprising a fixed charging station and a vehicle. 
         [0002]    Various systems for the contactless transfer of energy are known for conveniently charging electrical energy stores. Depending on the configuration, these systems can be used, for example, for charging consumer electronics such as, for example, cell phones or MP3 players or for charging electrically driven vehicles. Electrically driven vehicles comprise, for example, industrial trucks which are used for transporting goods in a warehouse, hybrid vehicles which have both an electric drive and an internal combustion engine, and purely electrically powered motor vehicles. 
         [0003]    DE 20 2011 077 709 A1 discloses an arrangement for transmitting electrical energy, in particular for charging an energy store of a mobile carrier, in particular of a motor vehicle. The arrangement comprises an electromagnetic transmission unit which is formed by two transmission elements which are embodied as coils. One of the coils is assigned here to the motor vehicle, and the other is assigned to a charging station. Each coil is assigned a capacitor, wherein in each case a capacitor with a coil forms a resonant circuit. Furthermore, the arrangement comprises rectifiers, power inverters and a PFC (Power Factor Correction) circuit. The PFC circuit permits, inter alia, reactive power to be compensated. Using the reactive power compensation, it is also possible to transmit the energy with a high level of efficiency even in the case of a relatively weak inductive coupling. 
         [0004]    A disadvantage of the prior art is that in addition to the transmission coils a multiplicity of separate components are also required. 
       SUMMARY OF THE INVENTION 
       [0005]    A transmission coil is proposed which is configured to inductively transfer energy, comprising a carrier, a coil arrangement with a multiplicity of turns, and a capacitance. There is provision here that the capacitance is formed by a multiplicity of capacitors, wherein each capacitor is assigned to an individual turn or a group of at least two turns of the coil arrangement, and the capacitors are arranged, together with the coil arrangement, on the carrier. 
         [0006]    Transmission coils are required for the inductive transmission of electrical energy, wherein a primary transmission coil is arranged in a charging station, and a secondary transmission coil is assigned to a mobile energy store which is to be charged. In order to transmit energy, the primary coil is excited with an alternating voltage, as a result of which an alternating magnetic field is produced in the region of the primary transmission coil. If the secondary transmission coil is moved into the vicinity of the primary transmission coil, with the result that the magnetic field of the primary transmission coil flows through said secondary transmission coil, an electric current is induced in the secondary transmission coil. 
         [0007]    For an efficient transmission of energy, oscillatory circuits are formed from a coil arrangement with a multiplicity of turns and a capacitance. The oscillatory circuit is excited with an alternating voltage which is generated by power electronics. In this context, it has been customary hitherto that the power electronics and the capacitance which is necessary to form the oscillatory circuit are arranged spatially separate from the coil arrangement. In this context, the capacitance is usually formed by one or a small number of capacitors with a high capacitance and is assigned in its entirety to the coil arrangement. 
         [0008]    In contrast, in the case of the transmission coil according to the invention there is provision to use a multiplicity of capacitors instead of a single capacitance which is assigned to the entire coil arrangement, wherein each capacitor is assigned to an individual turn or to a group of at least two turns of the coil arrangement. In the case of turns which are combined to form groups, the coil arrangement comprises a multiplicity of such groups. In this context, each individual capacitor or each individual capacitance is, considered per se, respectively considerably smaller than the entire capacitance assigned to the coil arrangement. As a result, the installation space which is required for each individual capacitor of the capacitors also turns out to be significantly smaller, which permits the individual capacitors to be arranged jointly on a carrier, together with the coil arrangement. 
         [0009]    The carrier holds both the coil arrangement and the capacitors which are assigned to the individual turns or groups of turns and secures them mechanically. The carrier is preferably embodied as a metal plate whose external shape essentially follows the shape of the coil arrangement. A metal such as, for example, aluminum is preferably used as the material, wherein the turns of the coil arrangement are electrically insulated from the carrier. 
         [0010]    A group of turns usually comprises between 2 and 20 turns, and the entire coil arrangement usually comprises between 4 and 200, preferably between 10 and 100 turns. 
         [0011]    In a further embodiment of the invention, there is also provision that, furthermore, power electronics, which comprise a power inverter and/or a rectifier and/or further circuit components (e.g. microcontroller for controlling the charging sequence), are arranged on the carrier. 
         [0012]    In this embodiment, all of the components which are required for the transmission of energy are integrated together with the respective transmission coil to form one unit. If a transmission coil is embodied, for example, as a primary transmission coil, in particular a rectifier, a power inverter, the coil arrangement with the multiplicity of turns as well as the capacitors which are assigned to the individual turns or individual groups of turns are arranged on the carrier. 
         [0013]    If the transmission coil is embodied as a secondary transmission coil, for example a rectifier, the coil arrangement with the multiplicity of turns or groups or turns and the respective capacitors are arranged on the carrier. 
         [0014]    The transmission coil according to the invention requires no further external components for its operation. The primary transmission coil only then needs to be connected to a power supply system for the supply of energy. The secondary transmission coil then only needs to be connected to the electric energy store which is to be charged. 
         [0015]    In one variant of the transmission coil according to the invention, the power electronics are configured to deactivate or activate individual turns or individual groups of turns of the coil arrangement. 
         [0016]    Since each individual turn of the coil arrangement or each group of turns is assigned a separate capacitance in the form of a capacitor, each turn or group of turns constitutes, considered per se, an independent oscillatory circuit. This permits individual turns or groups of turns to be deactivated, and not included in the transmission of energy, without further compensating measures. This can be utilized, for example, to influence the shape of the magnetic field generated by the transmission coil or to produce various turn conditions. 
         [0017]    In one embodiment of the invention, the turns of the coil arrangement are arranged in the form of concentric circles or a spiral path on the carrier. A rectangular or square embodiment of the turns is also conceivable. In this context, the power electronics and/or the capacitors are preferably located in the center of the coil arrangement. Such an arrangement permits an extremely compact design of the transmission coil. 
         [0018]    In one embodiment of the invention, the carrier is configured to serve as a shield for the electromagnetic compatibility (EMC). 
         [0019]    In the power electronics, in particular in the case of a power inverter, alternating magnetic fields are produced which have to be shielded in order to avoid adversely affecting radio transmissions in the surroundings and the functioning of other electronic devices in the surroundings and in order to comply with legal requirements for the protection of persons against magnetic fields. An electrically conductive material is required for the shielding. If, for example, the carrier is configured in such a way that it surrounds the coil arrangement and the power electronics and the carrier is also fabricated from an electrically conductive material such as, for example, aluminum, the carrier can shield electromagnetic radiation which is produced. 
         [0020]    In a further embodiment of the transmission coil, the carrier is configured in such a way that it serves as a heat sink for the capacitors and/or for the power electronics. For this purpose, a material which has good thermal conductivity is preferably selected for the carrier. Therefore, in particular aluminum and copper are suitable as materials, wherein aluminum is more cost-effective than copper and is therefore preferred. 
         [0021]    In a further embodiment of the transmission coil there is provision that the carrier comprises ducts which are configured to have a cooling medium flowing through them. The cooling medium which is used can be, for example, a water-glycol mixture. Such an embodiment of the carrier is suitable, in particular, for conducting away the waste heat of the power electronics and of the capacitors. However excessive heating of the turns of the coil arrangement can also be avoided in this way. 
         [0022]    In one embodiment of the transmission coil, said coil comprises more than one coil arrangement. In particular, the transmission coil can comprise two coil arrangements. In this context, the two coil arrangements can be connected to one another in such a way that the turns are connected in the same direction or in opposite directions. 
         [0023]    A further aspect of the invention is making available a fixed charging station which is configured to charge vehicles in a wireless fashion, wherein the charging station comprises at least one or precisely one of the transmission coils described herein as a primary transmission coil. 
         [0024]    Furthermore, a vehicle is made available which is configured to charge in a wireless fashion, wherein the vehicle comprises at least one or precisely one of the transmission coils described herein as a secondary transmission coil. The vehicle represents a mobile unit which can interact with a charging station. 
         [0025]    Furthermore, a system is made available for inductively charging vehicles, which system is formed by a fixed charging station and a vehicle, wherein both the charging station and the vehicle comprise at least one or precisely one of the described transmission coils. In this context, in the system there is provision that the secondary transmission coil of the vehicle is moved temporarily into the vicinity of the primary transmission coil of the charging station, with the result that the magnetic field which is generated by the primary transmission coil flows through the secondary transmission coil. After the ending of the charging process, the vehicle can exit the charging station again, as a result of which the secondary transmission coil is removed from the region of the primary transmission coil. 
         [0026]    The transmission coil is not limited to the use in conjunction with the inductive charging of vehicles. Depending on the configuration of the transmission coil, said coil can be used, in particular, to charge any mobile units with an energy store. Examples of this are the wireless charging of cell phones or of electrically powered tools. In this context, a primary transmission coil is assigned to a charging unit, and a secondary transmission coil is assigned to the mobile unit. 
         [0027]    In the systems known from the prior art, the charging station and the mobile unit which interacts with the charging station comprise a multiplicity of separate discrete assemblies. In the case of the mobile unit which contains the secondary transmission coil, these are the coil arrangement, the capacitance, the rectifier and a radiator. In this context, every component must satisfy per se all the requirements made, for example, of the cooling or the shielding for the electromagnetic compatibility (EMC), as a result of which redundancies occur. These redundancies are avoided with the measures of the invention by means of a fully integrated design in which the transmission coil comprises, in addition to the coil arrangement, also the necessary capacitances and, if appropriate, the necessary power electronics, and in which the coil arrangement, the capacitance and, if appropriate, the necessary power electronics are arranged together on a carrier. This commonly used carrier equally satisfies the function of a mechanical carrier, of a shield and of a radiator for all the components which are accommodated. As a result, there is a saving in material without a restriction of the functionality, which reduces the required installation space, the weight and the costs of the transmission coil. 
         [0028]    In addition there is provision to use, instead of a single capacitance which is assigned to the entire coil arrangement, a plurality of capacitors which are each assigned to an individual turn of the coil arrangement or to a group of turns of the coil arrangement. In this context, each turn or each group of turns is compensated individually by the respectively assigned capacitor. This permits, when necessary, individual turns or groups of turns to be deactivated without the need to perform additional measures to adapt the oscillatory circuit. Such deactivation of individual turns or of individual groups of turns permits, for example, the magnetic field generated by the primary transmission coil to be changed and to be adapted in optimum way to the respectively used secondary transmission coil or different turn conditions to be produced. 
         [0029]    Furthermore, the compensation of individual turns or groups of turns provides the advantage that the maximum resonant voltages which occur can be significantly reduced. As a result, the expenditure on insulation and shielding can be lowered. 
         [0030]    In addition, the arrangement of all the relevant components of a transmission coil on a common carrier facilitates the cooling. Only the common carrier then has to be cooled, and this is possible, for example, with liquid cooling or with air cooling. Moreover, by integrating all the relevant components it is possible to achieve a saving in terms of additional components such as, for example, plugs, clamped connections or additional housings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    In the figures: 
           [0032]      FIG. 1  shows a charging station with a primary transmission coil according to the prior art, 
           [0033]      FIG. 2  shows a transmission coil according to the invention in a sectional view from the side, and 
           [0034]      FIG. 3  shows a sectional illustration of a transmission coil according to the invention from above. 
       
    
    
       [0035]    In the following description of the figures, identical or similar components and elements are denoted by identical or similar reference symbols, wherein a repeated description of these components or elements will not be given in individual cases. The figures represent the subject matter of the invention only schematically. 
       DETAILED DESCRIPTION 
       [0036]      FIG. 1  shows a charging station with a transmission coil according to the prior art in a schematic illustration in a cross section from the side. 
         [0037]      FIG. 1  illustrates a transmission coil  10 ′ which comprises a coil arrangement  11 ′ with a multiplicity of turns  12 ′. A ferrite element  14 ′, which serves as a ferromagnetic core of the coil arrangement  11 ′, is arranged around the turns  12 ′. The coil arrangement  11 ′ is provided with an electrically conductive shield (e.g. aluminum)  16 ′ in order to shield the magnetic stray field. 
         [0038]    In order to generate a magnetic field, the coil arrangement  11 ′ is connected to a switching cabinet  18 ′ via a connecting line  24 ′. The switching cabinet  18 ′ comprises power electronics  20 ′ and a capacitor  22 ′. The capacitor  22 ′ is connected to the coil arrangement  11 ′ via a further connecting line  26 ′, the power electronics  20 ′ and the connecting line  24 ′, wherein the coil arrangement  11 ′ and the capacitor  22 ′ together form an oscillatory circuit. 
         [0039]    If the transmission coil  10 ′ is embodied as a primary transmission coil, the oscillatory circuit is excited by means of the power electronics  20 ′, with the result that an alternating magnetic field is produced. This alternating magnetic field can be converted again into electrical current by a correspondingly equipped secondary transmission coil. If the transmission coil  10 ′ from  FIG. 1  is embodied as a secondary transmission coil, the transmission coil  10 ′ is moved into the vicinity of a primary transmission coil, with the result that the alternating magnetic field of the primary transmission coil flows through the secondary transmission coil. Owing to induction in the secondary transmission coil, the oscillatory circuit is excited and the electrical energy can be extracted by means of correspondingly configured power electronics  20 ′, comprising a rectifier in this case. The electrical energy can then be used, for example, to charge an electrical energy store such as, for example, a battery or an accumulator. The electrical energy store can be assigned, in particular, to an electric vehicle or a hybrid vehicle. 
         [0040]      FIG. 2  illustrates a transmission coil  10  according to the invention in a sectional illustration from the side. 
         [0041]    The transmission coil  10  comprises a carrier  17 , which is fabricated, for example, from aluminum. A coil arrangement  11 , which comprises a multiplicity of turns  12  and a ferrite core  14 , is accommodated in the carrier  17 . The turns  12  of the coil arrangement  11  are wound around a central region  13  in a helical shape. In the central region  13 , the carrier  17  forms a trough in which integrated electronics  21  are arranged. The integrated electronics  21  comprise further, preferably all of the further, components which are necessary for operating the transmission coil  10 , in particular, for example, the power electronics and the resonant capacitance as described below with reference to  FIG. 3 . The capacitance is divided here into a large number of individual capacitors which are each assigned to an individual turn  12  or a group of turns  12 . In this context, in each case a capacitor forms, together with a turn  12  or a group of turns  12 , an oscillatory circuit. 
         [0042]      FIG. 3  shows the transmission coil  10  according to the invention in a schematic view from above. 
         [0043]      FIG. 3  illustrates in transparent form the carrier  17  and the ferrite core  14 , so that the interior of the transmission coil  10  can be seen. As can be inferred from the illustration in  FIG. 3 , the transmission coil  10  has a coil arrangement  11  which comprises a multiplicity of turns  12 . The illustration in  FIG. 3  contains seven turns which are denoted by the reference numbers  101 ,  102 ,  103 ,  104 ,  105 ,  106  and  107 . Each of the turns  12  is assigned here at least one capacitor  22  as a capacitance, wherein the capacitors are denoted by the reference numbers  121 ,  122 ,  123 ,  124 ,  125 ,  126  and  127 . In each case a capacitor  22  is connected in series here with a turn  12 , with the result that an oscillatory circuit is formed. In this context, the first capacitor  121  is connected to the first turn  101 . In addition, the individual oscillatory circuits are connected one behind the other in series, with the result that the end of the first turn  101  which is not connected to the first capacitor  121  is connected to the second capacitor  122 . In this way, each turn  12  adjoins two capacitors  22 , wherein for this purpose an eighth capacitor  128  is additionally arranged at the end of the last and seventh turn. The connection to power electronics  20  is produced via the first capacitor  121  and the eighth capacitor  128 . 
         [0044]    The coil arrangement  11  can be excited by means of the power electronics  20  if the transmission coil  10  is embodied as a primary transmission coil, and an alternating magnetic field is therefore generated. Additional external components are unnecessary, and a connection to the electrical power supply system must merely be established via an electrical terminal  32 . 
         [0045]    If the transmission coil  10  is embodied as a secondary transmission coil and if it is introduced into the alternating magnetic field of a primary transmission coil, the coil arrangement  11  is excited by means of magnetic induction and an electric current can be extracted by means of the power electronics  20 . Said electric current can be made available via the electrical terminal  32 , in order, for example, to re-charge a mobile energy store. 
         [0046]    Both the power electronics  20  and the capacitors  22  can heat up during operation. In order to conduct away the heat, they are arranged on the carrier  17 , which also serves as a heat sink. If pure air cooling is not sufficient, it is possible, as outlined in  FIG. 3 , to provide ducts  30  via which a cooling medium such as, for example, a water-glycol mixture can be fed in. The excess heat can be carried away by means of the cooling medium. 
         [0047]    In a further embodiment (not illustrated), each individual turn  12  is not assigned a capacitor  22  but rather a plurality of turns  12 , for example between two and ten turns  12 , are combined to form a group of turns  12 , wherein the entire group of turns  12  is assigned a capacitor  22 . 
         [0048]    In a further embodiment variant which is not illustrated in the figures, the oscillatory circuits, which are each formed from a turn  12  or a group of turns  12  and a capacitor  22 , are not connected in series with one another but rather each connected directly to the power electronics  20 . In such an embodiment, the power electronics  20  can actuate the individual turns  12  or individual groups of turns  12  separately. In this context, for example a single turn  12  or a group of turns  12  can be deactivated completely, or it would also be conceivable to excite the individual turns  12  or the oscillatory circuits, formed thereby, with different intensities. In this way, the alternating magnetic field which is generated by the coil arrangement  11  can be influenced selectively. This can be utilized to optimize the efficiency of the transmission of energy, in particular when the primary and secondary transmission coils which are used for transmitting energy are not embodied in an identical way or are not aligned with one another in an optimum way. 
         [0049]    In further variants of the transmission coil  10  it is possible to accommodate more than one coil arrangement  11  on a carrier  17 . In particular, two coil arrangements  11  can be arranged together on a carrier  17 . In this context it is possible to connect the coil arrangements  11  in such a way that the turns  12  of the respective coil arrangements  11  are connected in the same direction as one another or in opposite directions. 
         [0050]    The invention is not restricted to the exemplary embodiments described here or to the aspects emphasized herein. Instead, a multiplicity of modifications within the scope of the average ability of a person skilled in the art are possible within the range indicated by the claims.