Abstract:
A device for the inductive transfer of electrical energy between a stationary coil, which can be installed in a roadway, and a secondary coil of a movable electrical load, in particular of an electrical vehicle, wherein a supply unit for supplying electrical energy is allocated to the coil. The problem of providing a maintenance-friendly, reliable, operationally secure device for inductive transfer of electrical energy, which is protected against penetration of water into the sensitive electronics, is solved in that the supply unit is arranged on a side of the coil facing away from the roadway in an installed state in a housing which is closed on top and laterally, having a housing opening open to the bottom.

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for the inductive transfer of electrical energy. 
     BACKGROUND OF THE INVENTION 
     DE 697 24 995 T2 discloses a device according to the class in the form of an electrical power supply system that has a portable power socket unit with a power socket and a secondary coil connected to this power socket. To be able to supply electrical energy to the portable unit via the secondary coil, a base unit is fixed in position, submerged in a drainage shaft in the roadway. The base unit has a primary coil for the inductive transfer of electrical energy to the secondary coil of the portable power socket unit and also electronics supplying the primary coil with electrical energy. The primary coil and the electronics are held in a housing that is sealed against the penetration of water. The electronics are connected to the power supply grid via a grid supply line that is fed through a bushing provided in the housing. To prevent the penetration of water into the inner space of the housing through the bushing, the bushing has a special seal. 
     The power socket unit described above has the disadvantage that the seal of the bushing is a possible leakage point if, for example, the seal becomes damaged due to vibrations or small animals under the ground. The sealing effect of the seal can also degrade after a certain amount of time; for example, the sealing material can become porous over time, so that this also poses the risk of allowing water penetration. To prevent this as much as possible, the seal must be inspected regularly, which is possible only with great effort. To do this, the cover of the housing must be removed and then the heavy coil and the sensitive electronics must be removed. Only then is the bushing sufficiently exposed that its leak-tightness can be tested. If the seal has become leaky, the ground above the seal must be excavated to allow the seal to be replaced from the outside of the housing. 
     In the area of inductive energy transfer to movable loads, for example, electric vehicles such as automobiles or trucks, there is the problem that the area around the submerged primary coil is often exposed to vibrations due to vehicles regularly driving over the ground, and this also applies a load on the seal. 
     GB 2477080 A discloses a rail track for track vehicles with a prefabricated track module in which the cable of a primary coil is laid between two running rails, extending in the longitudinal direction of the running rails. Laterally next to the running rails there are electrical or electronic components arranged in a box section. A passage hole runs out from the box section into the area between the rails, wherein lines for connecting the cable to the electrical or electronic components lead through the passage hole. Because the ground between the running rails is above the ground of the box section, and the electrical or electronic components are arranged on the ground of the box section, water penetrating into the box section or the area between the running rails collects in the lower-lying box section. To protect the electrical or electronic components from water, these components must be sealed in an appropriate watertight manner. These are connected with relatively great effort, because the lines going out from the components must have special seals. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention can overcome the disadvantages mentioned above and provide a device named above for the inductive transfer of electrical energy, which is maintenance friendly, reliable, operationally safe, and protected against the penetration of water into the sensitive electronics. 
     Advantageous construction and preferred refinements of the invention are also disclosed. 
     According to the invention, the device named above for the inductive transfer of electrical energy is characterized in that the supply unit is arranged on a side of the coil facing away from the roadway in an installed state in a housing that is closed on top and laterally, having a housing opening that is open to the bottom. In this way, according to the diving bell principle, water can penetrate into the housing only so far until the water pressure reaches equilibrium with the pressure of the air enclosed in the housing, or possibly also another gaseous fluid. The references to water here and below also include the possibility of other fluids. Thus, contrary to the opinion of those skilled in the art, penetration of water or other fluids can be reliably prevented while eliminating additional and expensive sealing measures. 
     In one advantageous refinement of the invention, the supply unit can be arranged in the housing in the height direction with a safety margin above the housing opening, wherein advantageously the safety margin is at least half as high, preferably more than half as high, as a distance between the housing opening and an upper housing cover of the housing opposite the housing opening. This ensures that the air in the housing is sufficient to withstand the water pressure of the penetrating water. 
     Preferably, a side housing wall of the housing can narrow at least in some sections toward the housing opening, wherein a level of penetrating water rises slower and slower, because the space of the housing becomes bigger and bigger with height. Preferably, in alternative refinements, the housing can have the shape of a hollow conical section that is closed on one side, wherein the smaller side of the hollow cone forms the housing opening, or the housing has the shape of a hollow cylinder that is closed on one side. Other shapes are also conceivable, for example, the housing can have an angular shape in cross section, for example, square, rectangular, hexagonal, octagonal, or polygonal, preferably rectangular. 
     Advantageously, the housing can be made from an electrically conductive material in order to shield the electronics contained in the supply unit from the strong magnetic field of the primary coil. 
     Advantageously, the housing could also be made from a non-corroding material, so that the housing can be produced easily, is lightweight, and is protected against corrosion. Preferably, a hard plastic material can be used. 
     In one preferred refinement of the invention, a ventilation device could be provided outside the housing for venting an inner space of the device, in order to exhaust air from the inner space to the outside of the housing and to be able to drain the water out of the inner space in the event the device is completely flooded and a flow of water continues to press against the device. 
     Preferably, the supply unit could be arranged on an upper housing cover of the housing opposite the housing opening, which further simplifies the mounting of the supply unit on the housing. 
     In one design that is advantageous with regard to production and for installation on-site, the coil could be integrated in a coil unit, in particular, cast in concrete or steel-reinforced concrete. The housing could also be mounted on a bottom side of the coil unit facing away from the roadway, so that the electronics contained in the supply unit are at a sufficient distance from the coil. 
     Advantageously, a shaft module could also be provided with an inner space that is defined by a shaft floor and a surrounding shaft wall and is open toward the roadway, and is advantageously prefabricated and can be merely submerged in a corresponding opening in the ground at the installation site. To be able to easily and quickly close the inner space of the shaft module, the coil unit can be preferably used. The shaft wall can also advantageously have on its upper end a surrounding projection that points toward the inner space and on which the coil unit can be placed. Preferably, a roadway side of the coil unit and the other end of the shaft wall can be closed flush with each other and with the roadway in the installed state, in order to be able to provide as seamless a roadway as is possible. 
     Advantageously, the coil could be arranged together with the supply unit in the housing. Here, a housing cover pointing toward the roadway could be formed as part of the roadway, which enables a compact configuration and simple installation on-site. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, an embodiment of the invention is described in detail using the accompanying drawings. Shown are 
         FIG. 1  a schematic side view through a device according to the invention for inductive transfer of electrical energy in the normal operating state; 
         FIG. 2  the view from  FIG. 1  with some water penetrating into the device; 
         FIG. 3  the view from  FIG. 1  with more water penetrating into the device; 
         FIG. 4  the view from  FIG. 1  with a large amount of water penetrating into the device; 
         FIG. 5  an alternative housing shape of a housing of the device according to the invention from  FIG. 1 ; 
         FIG. 6  another alternative housing shape of a housing of the device according to the invention from  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a device  1  according to the invention for the inductive transfer of electrical energy. The device  1  has a shaft module  3  that is prefabricated from steel-reinforced concrete and is completely submerged in the ground  2  with an inner space  6  that is defined by a shaft floor  4  and a surrounding shaft wall  5 , and is initially open toward the roadway  7 . On its upper end, the shaft wall  5  has a surrounding projection  8  pointing toward the inner space  6 . 
     A coil unit  9  with an edge region of its bottom side  10  is placed on the projection  8  and connected detachably to the shaft wall  5 . The coil unit  9  therefore closes the inner space  6  relative to the roadway  7 . A roadway side  11  of the coil unit  9  and the upper end of the shaft wall  5  close flush with the roadway  7 . 
     In the coil unit  5 , a primary coil  12  for the inductive transfer of electrical energy to a secondary coil  13  of an electric vehicle  14  is integrated in a known way. The primary coil  12  is supplied with electrical energy via a supply cable  15  from a known electrical supply unit  16 . 
     The supply unit  16  contains a converter for preparing the high voltages and currents for the energy transfer from primary coil  12  to secondary coil  13 , and control electronics for controlling the converter. The supply unit  16  itself is connected to the local energy supply grid via a power grid cable  17 . Here, the power grid cable  17  is guided through a cable bushing  18  provided in the shaft wall  5 . To prevent the penetration of water through the cable bushing  18  into the inner space  6 , the cable bushing  18  is provided with a seal, not shown. 
     As described in the introduction, however, such seals always have the risk that the seal will fail for a wide range of reasons, or the sealing effect will degrade so much that water will penetrate into the inner space  6 . 
     To nevertheless guarantee a safe and reliable operation of the device  1  in the event of water penetration and, in particular, to protect the moisture-sensitive supply unit  16  from water, the invention provides to mount the supply unit  16  in a pot-shaped housing  19  with housing opening  20  pointing downward on the coil unit  9 . 
     Here, the housing  19  with a housing cover  21  is mounted on the bottom side  10  of the coil unit  9  and the supply unit  16  is, in turn, mounted on a cover bottom side  22  of the housing  19 . A surrounding housing wall  23  extends from the housing cover  21  to the shaft floor  4 , wherein the housing wall  23  is at a distance from the shaft floor  4  so that there is still passage for the supply cable  15  and the power grid cable  17 . The housing wall  23  is here significantly higher than the supply unit  16 . Thus, there is always a safety margin S between the housing opening  20  and a bottom side of the supply unit  16 . In the present case, the housing wall  23  is somewhat more than twice as high as the supply unit  16 , so that a distance H between the housing opening  20  and housing cover  21  is approximately twice as large as the safety margin S. 
     To shield the electronics contained in the supply unit  16  from the strong magnetic field of the primary coil  12 , the housing  19  can be preferably made from a material that is a good electrical conductor, for example, aluminum. 
     As can be seen from  FIGS. 2-4 , the invention uses the so-called diving bell principle for protecting the supply unit  16  and its especially moisture-sensitive electrical and electronic components. 
     In this way, the housing  19  that is airtight and watertight at the top prevents water that penetrates into the inner space  6  from rising in the housing  19  up to the supply unit  16 . 
     If water  24  penetrates into the inner space  6 , initially a water level  25  is formed as shown in  FIG. 2 . If the water  24  continues to rise, then it gradually reaches up to the housing opening  20  of the housing  19 , wherein, at least at the beginning, the water level  25  outside of the housing  19  corresponds to a water level  26  in the housing  19 , as shown in  FIG. 3 . If the water  24  rises more, the water  24  can no longer rise as far inside the housing  19  as outside the housing  19 , due to the air present in the airtight and watertight housing  19 , so that the water level  26  in the housing  19  remains lower than the water level  25  in the inner space  6  outside the housing  19 . As soon as equilibrium has been reached between the pressure of the compressed air in the housing  19  and the pressure of the water  24  in the shaft module  3 , the water level  26  in the housing no longer rises, as shown in  FIG. 4 . Thus, even if the entire inner space  6  is flooded with water  24 , the water  24  does not rise up to the supply unit  16 . 
     Preferably, in the area outside the housing  19 , a ventilation device can be provided through which the air, displaced by the water  24  when the water level  25  rises outside the housing, can escape from the inner space  6 . For example, the coil unit  9  has a one-way valve  27  that allows air and optionally also water  24  to escape from the inner space  6 , but does not permit air or water to penetrate into the inner space  6  in the opposite direction. Also, a not-shown, closeable exhaust opening can be provided in the device  1  to be able to easily suction, from the outside, water present in the inner space  6  of the shaft module  3 . For example, a closeable round hole above the inner space  6  outside of the housing cover  21  could be provided in the coil unit  9 , by means of which a hose can be inserted into the inner space. 
       FIG. 5  shows the device according to the invention from  FIG. 1  with a housing  19 ′ with another alternative housing shape. Identical parts as in the design shown in  FIG. 1  are provided with identical designations and given identical reference symbols. A housing wall  23 ′ narrows from the housing cover  21  toward the housing opening  20 ′, so that the housing wall  23 ′ continuously narrows toward the housing opening  20 ′. In this way, the level of penetrating water rises more and more slowly, because the space of the housing  19 ″ increases continuously with height. 
     In  FIG. 6 , the device according to the invention from  FIG. 1  is shown with a housing  19 ″ with another alternative housing shape. Identical parts as in the design shown in  FIG. 1  are provided with identical designations and given identical reference symbols. A housing wall  23 ″ initially runs at a right angle from the housing cover  21  in the direction of a housing opening  20 ″ and then bends inward at approximately half the distance H, so that the housing wall  23 ″ narrows toward the housing opening  20 ″. In this way, the level of penetrating water rises more and more slowly, because the space of the housing  19 ″ increases continuously with height. Compared to the housing  19 ′ shown in  FIG. 5 , the housing  19 ″ according to  FIG. 6  has the advantage that a wider supply unit  16  can also be used. 
     Through the construction described above, the penetration of water  24  into the supply unit  16  is prevented in a way that is completely unexpected for someone skilled in the art. This is because great efforts are typically taken to enclose the sensitive electrical and electronic parts of a supply unit as well as possible from the penetration of water or other fluids and to seal the housing that surrounds the supply unit  16  as well as possible. In the invention, however, a best-possible leak-tight encapsulation of the supply unit  16  can be largely eliminated. This is in clear contradiction to the otherwise prevalent opinion of those skilled in the art. 
     REFERENCE SYMBOLS 
     
         
           1  Device for inductive transfer of electrical energy 
           2  Ground 
           3  Shaft module 
           4  Shaft floor 
           5  Shaft wall 
           6  Inner space 
           7  Roadway 
           8  Projection 
           9  Coil unit 
           10  Bottom side of the coil unit 
           11  Roadway side of the coil unit 
           12  Primary coil 
           13  Secondary coil 
           14  Electric vehicle 
           15  Supply cable 
           16  Supply unit 
           17  Power grid cable 
           18  Cable bushing 
           19  Housing 
           19 ′ Housing with alternative housing shape 
           19 ″ Housing with another alternative housing shape 
           20  Housing opening 
           20 ′ Housing opening of the alternative housing shape 
           20 ″ Housing opening of the other alternative housing shape 
           21  Housing cover 
           22  Cover bottom side 
           23  Housing wall 
           23 ′ Housing wall of the alternative housing shape 
           23 ″ Housing wall of the other alternative housing shape 
           24  Water 
           25  Water level 
           26  Water level in the housing 
           27  Ventilation valve 
         H Distance of cover bottom side to housing opening 
         S Safety margin