Patent Publication Number: US-2018040417-A1

Title: Induction charging device

Description:
RELATED APPLICATION INFORMATION 
     The present application claims priority to and the benefit of German patent application no. 10 2016 214 515.0, which was filed in Germany on Aug. 5, 2016, the disclosure which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an induction charging device, in particular, a hand-held power tool induction charging device, including a coil unit and including at least one shielding unit. 
     BACKGROUND INFORMATION 
     An induction charging device, in particular, a hand-held power tool induction charging device, including a coil unit and including at least one shielding unit, which is provided for at least partially shielding the coil unit, is discussed in DE 10 2014 217 272 A1. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an induction charging device, in particular, a hand-held power tool induction charging device, including a coil unit and at least one shielding unit, which is provided for at least partially shielding the coil unit. 
     It is provided that the induction charging device includes at least one adjustment unit, with the aid of which at least one shielding parameter of the at least one shielding unit is changeable. The coil unit may include, in particular, at least one core element and at least one induction coil. The shielding unit may be provided, in particular, in order to reduce electromagnetic disturbances. 
     An “induction charging device” in this context is intended to mean, in particular, a unit for charging the at least one induction rechargeable battery, which is provided for transmitting a charge current at least partially by electromagnetic conduction to the induction rechargeable battery in at least one charge state. A “coil unit” in this context is intended to mean, in particular, a unit, which includes at least one induction coil having at least one winding made of an electrically conductive material, which is provided, in at least one charge state, for generating a magnetic field via an applied electrical energy, in particular, via an AC voltage, which generates an electrical alternating current in an induction coil of the induction rechargeable battery. The coil unit, in particular, which may be the induction coil, is provided for converting an electromagnetic alternating field into an electrical alternating current and/or vice versa. The alternating field has a frequency, which may be 10 kHz-500 kHz, particularly which may be 100 kHz-120 kHz. The direction is configured, in particular, perpendicular to the coil plane in parallel to a winding axis of the induction coil. The coil unit may also include the at least one core element for increasing an inductance of the at least one induction coil. 
     In addition, a “shielding unit” in this context is intended to mean, in particular, a unit, which is provided for at least partially shielding the coil unit. A shielding unit may be intended to mean, in particular, one which is provided for shielding the coil unit from electromagnetic disturbances. The unit is provided, in particular, for at least reducing electromagnetic disturbances to the coil unit. The unit may include at least one electrically conductive element, in particular, a shielding element, which at least partially delimits and/or at least partially covers the coil unit in at least one direction. In addition, an “adjustment unit” in this context is intended to mean, in particular, a unit, with the aid of which at least one shielding parameter of the at least one shielding unit may be directly or indirectly changed. A change of the at least one shielding parameter may be triggered automatically by the adjustment unit and/or by a control of the induction charging device and manually by an operator. The adjustment unit may include control electronics. “Control electronics” in this case are intended to mean, in particular, a unit having a processor unit and a memory unit, as well as an operating program stored in the memory unit. 
     In principle, however, it would also be conceivable for the adjustment unit to merely include electronic circuitry. A “shielding parameter” in this context is intended to mean, in particular, a parameter of the shielding unit. A shielding parameter may be intended to mean, in particular, a shielding effect-influencing parameter of the shielding unit. A shielding parameter may be intended to mean a parameter of a magnetic field generated by the shielding unit during a shielding. Particularly, a shielding parameter may be intended to mean, in particular, a magnetic field strength of the magnetic field generated by the shielding unit during a shielding. In principle, however, other shielding parameters, which appear meaningful to those skilled in the art, are also conceivable, which in particular, influence a shielding effect of the shielding unit. “Provided” is intended to mean, in particular, specifically programmed, configured and/or equipped. An object being provided for a particular function is intended to mean, in particular, that the object fulfills and/or carries out this particular function in at least one application state and/or operating state. 
     With the design of the induction charging device according to the present invention, it is possible to achieve an advantageously adapted shielding. As a result, a shielding may be advantageously adapted to boundary conditions. 
     It is further provided that the at least one shielding unit includes at least one shielding element. The at least one shielding element may have an at least essentially circular design. The at least one shielding element may be formed by an aluminum ring. Because of the high conductivity of this material, the shielding element functions accordingly as a short-circuit ring, in particular, in at least one operating state. In one alternative embodiment, the shielding element may also have a disk-shaped design, whereby the shielding element may, in particular, have an essentially full-surface design. The basic shape of the shielding element is adapted, in particular, to the basic shape of the coil unit. To shield an essentially circular coil unit, the shielding element may also have a circular design. To shield a non-circular coil unit, which has, for example, an oval, rectangular or square design, the basic geometric shape of the shielding element is adapted to the basic shape of the coil unit and also has, for example, an oval, rectangular or square design. The shielding element is configured, in particular, to shield the coil unit from metallic objects during a charging operation of the induction rechargeable battery, in particular, from metallic objects located on a standing surface for the induction charging device, for example, a table surface. A standing surface made of a metallic material or metallic particles on the standing surface influence the function of the coil unit in a disadvantageous manner. In order to shield the induction coil from metallic objects on a standing surface for the induction charging device, the shielding element is situated, in particular, between a housing of the induction charging device and the coil unit. The shielding element in this case, in particular, faces one side of the coil unit, which faces away from a holding area for holding and/or storing an induction rechargeable battery. Accordingly, the shielding element is situated, in particular, on a side of the coil element, which faces a standing surface of the housing of the induction charging device. An advantageously adapted shielding, in particular, may be achieved in this way. As a result, a shielding may, in particular, be advantageously adapted to boundary conditions. In particular, a shielding may as a result be advantageously adapted to a base, in particular, to a material of the base. 
     It is also provided that the at least one shielding element includes at least one at least essentially radial slot, which interrupts the at least one shielding element in at least one operating state. The at least essentially radial slot may interrupt the shielding element at least essentially perpendicular to a circumferential direction. An “at least essentially radial slot” in this context is intended to mean, in particular, a slot, the extension direction of which runs at least essentially radially. An “at least essentially radial slot” may be intended to mean, in particular, that at least one essential directional component of the extension direction of the slot extends radially relative to the shielding element. “Radial” in this case is intended, in particular, to mean radial in relation to a center axis of the shielding element and/or extending perpendicularly toward the center axis. The center axis in this case is formed, in particular, by a surface normal of the main extension plane of the shielding element, which extends, in particular, through a geometric center point of the shielding element. A “main extension plane” of a structural unit is intended to mean, in particular, a plane, which is parallel to a largest lateral face of a smallest imaginary cuboid, which only just fully surrounds the structural unit, and which runs, in particular, through the center point of the cuboid. That “the slot interrupts the at least one shielding element” is intended in this context to mean, in particular, that the slot produces a gap in the shielding element material along a circumferential direction of the shielding element, at which the shielding element material is interrupted. An adapted shielding may, in particular, be advantageously achieved as a result of the at least essentially radial slot. An induction effect on the shielding element, in particular, may be changed by the slot. 
     It is further provided that the induction charging device includes at least one switch element, via which the at least one at least essentially radial slot may be electrically closed and/or opened. The at least essentially radial slot may be electrically bridged by the switch element. A bridging in this case may be achieved both by a mechanical closing of the slot as well as via a purely electronic bridging with the aid of the switch. A “switch element” in this context is intended, in particular, to mean an element, with the aid of which the at least one at least essentially radial slot may be electrically closed and/or opened. The switch element may include at least two states, whereby one state of the switch element may be changed, in particular, with the aid of an external control signal. The switch element may be provided for establishing and/or disconnecting an electrically conductive connection between two points, in particular, between the two sides of the slot. The switch element may include at least one control contact via which it may be switched. In this way, a shielding effect of the shielding element may be advantageously changed. A shielding effect may be particularly advantageously reduced by an opening of the slot. No induced, closed power circuit in the shielding element is able to form due to the opening of the slot, in particular, only isolated induced eddy currents form. As a result, only a very weak magnetic field may be generated by the shielding element. By closing the slot, an advantageously strong magnetic field may form. An advantageously strong shielding effect may be achieved in this way. 
     It is further provided that the adjustment unit is provided to open and/or close the at least one at least essentially radial slot as a function of an operating state in order to change the shielding parameter. The adjustment unit may activate the switch element to open and/or close the slot. In this way, the shielding parameter may be changed advantageously simply with the aid of the adjustment unit. In this way, a shielding effect, in particular, may be changed, advantageously simply with the aid of the adjustment unit. An alternating may take place, in particular, between two different states. As a result, a shielding may be advantageously simply adapted to boundary conditions. 
     It is further provided that the adjustment unit is provided to switch the shielding unit between a short-circuit mode and an idle mode in order to change the shielding parameter. The adjustment unit may be provided for switching between a short-circuit mode and an idle mode in order to activate the switch element. In a short-circuit mode, the at least one at least essentially radial slot is closed or bridged. In an idle mode, the at least one at least essentially radial slot is opened. A “short-circuit mode” in this context is intended to mean, in particular, a mode of the shielding unit, in which the shielding unit functions as a short-circuit ring. A short-circuit mode may be intended to mean, in particular, a mode, in which the shielding unit is provided for an advantageous shielding. In the short-circuit mode, the current induced in the shielding element may generate an electromagnetic force, which is phase-shifted compared to the electromagnetic force of the coil unit. A magnetic field of the shielding element formed in this way cancels out at least partially an effect of the magnetic field of the coil unit in the direction in which the shielding element is situated. In an ideal configuration, no magnetic flux is able to occur in this direction, so that the magnetic fields cancel one another out. Thus, during the short-circuit mode, a magnetic field of the coil unit is “bent away” from the bottom of the induction charging device. Thus, the influence of various materials as a support for the induction charging device is at least reduced. The “bending” of the magnetic field of the coil unit is associated with an increase of the magnetic resistance. This results in a reduced inductance of the coil unit and in an increased resonance frequency of a primary oscillator circuit. 
     An “idle mode” in this context is intended to mean, in particular, a mode of the shielding unit in which a shielding effect is significantly reduced. In the idle mode, the current induced in the shielding element may generate only isolated eddy currents. A magnetic field of the shielding unit formed in this way is too weak to significantly reduce an effect of the magnetic field of the coil unit in the direction in which the shielding unit is situated. The reduced shielding is associated with a reduced magnetic resistance as compared to the short-circuit mode. This results in a higher inductance of the coil unit and a reduced resonance frequency of the primary oscillator circuit. In this way, a shielding effect, in particular, may be changed advantageously simply with the aid of the adjustment unit. An alternating may take place, in particular, between two different modes. As a result, a shielding may be advantageously simply adapted to boundary conditions. Furthermore, the resonance frequency of the oscillator circuit may be changed as a result, without influencing the actual frequency-determining components of the coil unit. 
     It is further provided that the induction charging device includes at least one control unit, with the aid of which a manual switching between a short-circuit mode and an idle mode may take place. The control unit may be connected to the adjustment unit. A “control unit” is intended here to mean, in particular, a unit which includes at least one control element, which is directly actuatable by an operator and which is provided to influence and/or to alter a process and/or a state of a unit coupled to the control unit by an actuation and/or an input of parameters. A “control element” is intended here to mean, in particular, an element, which is provided to receive an input variable from an operator during a control operation and, in particular, to be directly contacted by an operator, a touching of the control element being sensed and/or an actuation force applied to the control element being sensed and/or being mechanically transmitted in order to actuate a unit. In this way, a manual switching between the modes of the shielding unit, in particular, may be achieved. As a result, this could, for example, enable an operator to indicate manually whether the induction charging device is standing on a non-magnetic base, on a ferromagnetic base and/or on a diamagnetic or paramagnetic base. This could, for example, enable an advantageously efficient charging operation on a base made of a non-magnetic material such as, for example, wood or plastic. An advantageous shielding may, however, also be enabled on a different base. 
     It is further provided that the adjustment unit is provided to change a resonance frequency of an oscillator circuit of the coil unit by changing a shielding parameter of the at least one shielding unit. For this purpose, the adjustment unit may be connected, in particular, to an electronics unit of the induction charging device, which is provided for controlling and/or regulating a charging operation. In principle, the adjustment unit may particularly also be configured integrally into the electronics unit. In this way, the resonance frequency of the primary oscillator circuit of the coil unit may, in particular, be changed without influencing the actual frequency-determining components of the coil unit. 
     The present invention is also directed to a method for operating the induction charging device. It is provided that the adjustment unit opens the at least one at least essentially radial slot of the at least one shielding element to lower a resonance frequency of an oscillator circuit and/or closes it to increase a shielding of the coil unit. As a result, the induction charging device may be advantageously adapted. A shielding effect, in particular, may be changed, simply with the aid of the adjustment unit. An alternating may take place, in particular, between two different states. As a result, a shielding may be advantageously simply adapted to boundary conditions. Furthermore, it is possible in this way to modify the resonance frequency of the oscillator circuit without influencing the actual frequency-determining components of the coil unit. 
     The induction charging device according to the present invention and the method according to the present invention are not to be limited to the application and specific embodiment described above. The induction charging device according to the present invention and the method according to the present invention may include, in particular, one of a number of individual elements, components and units cited herein for executing a functionality described herein. 
     Additional advantages result from the following drawing description. An exemplary embodiment of the present invention is depicted in the drawing. The drawing, the description and the claims include numerous features in combination. Those skilled in the art will advantageously also consider the features individually and combine them to form meaningful additional combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a system, including an induction charging device according to the present invention and including an induction rechargeable battery in a schematic, perspective view. 
         FIG. 2  shows the induction charging device according to the present invention, including a coil unit and including a shielding unit in a schematic exploded view. 
         FIG. 3  shows the induction charging device according to the present invention, including an opened exterior housing in a schematic view from below. 
         FIG. 4  shows the coil unit of the induction charging device according to the present invention in a schematic exploded view. 
         FIG. 5  schematically shows a flow chart of a method for operating the induction charging device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a system, including an induction charging device  10  and including an induction rechargeable battery  26 . Induction charging device  10  is provided to electrically charge induction rechargeable battery  26  in a charge state. Induction rechargeable battery  26  is configured as a hand-held power tool induction rechargeable battery. Induction rechargeable battery  26  is configured to be inductively chargeable with the aid of induction charging device  10 . Induction rechargeable battery  26  is configured to be coupleable with induction charging device  10 . Induction charging device  10  is provided for transferring an energy to induction rechargeable battery  26  in a state coupled with induction rechargeable battery  26 . Induction charging device  10  is configured as a hand-held power tool induction charging device. Induction charging device  10  is configured as an induction charging unit. Induction charging device  10  includes a coil unit  12 . Induction charging device  10  also includes an exterior housing  28 . Exterior housing  28  surrounds coil unit  12 . Exterior housing  28  includes two housing shells  30 ,  32 . Exterior housing  28  includes an upper housing shell  30  and a lower housing shell  32  which, not further visible, are screwed together. In principle, however, a detent connection and/or an adhesive bond between housing shells  30 ,  32  would also be conceivable. Coil unit  12  is provided for inductively transferring energy to induction rechargeable battery  26  in a charge state. Induction charging device  10  includes an electronics unit  34 , which is provided to control or regulate a charging operation. Electronics unit  34  includes at least one circuit board  36  fitted with electronic components. Circuit board  36  includes a copper coating on a side facing away from coil unit  12  of induction charging device  10 . In addition, circuit board  36  of electronics unit  34  includes an SMD assembly on a side facing away from coil unit  12  of induction charging device  10 . 
     Exterior housing  28  of induction charging device  10  includes a holding area  38 , which is provided for holding induction rechargeable battery  26  in a coupled state. Induction rechargeable battery  26  also includes a housing  40 , which includes a positioning element  42  for coupling induction rechargeable battery  26  to holding area  38  of exterior housing  28  of induction charging device  10  in a coupled state. 
     Positioning element  42  of induction rechargeable battery  26  is configured as a platform, which rises above an outer surface of adjoining housing  40  of induction rechargeable battery  26 . Holding area  38  of exterior housing  28  of induction charging device  10  includes at least one recess. The recess forms a positioning element  44  for positioning induction rechargeable battery  26 . It is also conceivable, however, that positioning element  44  of induction charging device  10  is configured as a platform and positioning element  42  of induction rechargeable battery  26  is configured as a recess. The recess has a step height of at least 0.5 mm. Positioning element  42  of induction rechargeable battery  26  has a step height of at least 0.5 mm. Positioning element  44  of induction charging device  10  and positioning element  42  of induction rechargeable battery  26  are correspondingly configured. 
     Positioning element  44  of induction charging device  10  and positioning element  42  of induction rechargeable battery  26  each have a step height of 3 mm. Other dimensions, which appear meaningful to those skilled in the art, are also conceivable, however. Positioning element  44  of induction charging device  10  has a partially curved outer contour. The outer contour of positioning element  44  of induction charging device  10  is rounded. Positioning element  42  of induction rechargeable battery  26  has a partially curved outer contour. The outer contour of positioning element  42  of induction rechargeable battery  26  is square with rounded corners. A diameter of positioning element  44  of induction charging device  10  corresponds at least virtually to a diagonal length of positioning element  42  of induction rechargeable battery  26 . A minimal tolerance is provided between the dimensions of positioning element  44  of induction charging device  10  and of positioning element  42  of induction rechargeable battery  26 . Alternatively, it is also conceivable that the outer contour of positioning element  44  of induction charging device  10  is square with rounded corners and the outer contour of positioning element  42  of induction rechargeable battery  26  is round. It is further conceivable that the outer contour of positioning element  44  of induction charging device  10  or of positioning element  42  of induction rechargeable battery  26  has another geometric shape, which appears meaningful to those skilled in the art, in particular, with rounded corners. In a charge state, induction rechargeable battery  26  rests on induction charging device  10 , so that positioning element  42  of induction rechargeable battery  26  engages in positioning element  44  of induction charging device  10 . In the process, housing  40  of induction rechargeable battery  26  directly contacts exterior housing  28  of induction charging device  10 . 
     Induction charging device  10  includes coil unit  12 , which is provided to transfer energy in a state coupled to an induction rechargeable battery  26 . Electrical energy is transferred in the coupled state from induction charging device  10  to induction rechargeable battery  26  with the aid of coil unit  12 . Coil unit  12  includes at least one core element  46  and at least one induction coil  48 , which at least partially surrounds the at least one core element  46  ( FIG. 4 ). Coil unit  12  includes six identically shaped core elements  46  and one induction coil  48 , which surrounds core elements  46  in the circumferential direction. Induction coil  48  includes multiple windings situated one on top of the other. Induction coil  48  includes two coil connections  50 , which are configured spaced apart from one another. Induction coil  48  has a round contour. Induction coil  48  has a circular basic shape. Induction coil  48  may alternatively also have a non-circular, for example, oval, rectangular or square basic shape. Core elements  46  each have a partially circular design. In a mounted state, core elements  46  are situated next to one another in such a way that the six core elements  46  together form a circular contour. Core elements  46  are provided to partially inductively shield electronics unit  34  of induction charging device  10 . Core elements  46  are provided for increasing an inductance of the at least one induction coil  48 . Core elements  46  are formed from a metal. Core elements  46  are configured as ferrite cores. 
     Core elements  46  each have a protrusion  52  on a side facing away from holding area  38 . Induction coil  48  encompasses core elements  46  in a mounted state in the circumferential direction. 
     Protrusion  52  of core elements  46  has a larger diameter than a winding diameter of induction coil  48 . Induction coil  48  is situated in a mounted state between protrusions  52  of core elements  46  and holding area  38  of induction charging device  10  in the axial direction, which runs perpendicular to the diameter of the windings of induction coil  48 . The side of core element  46  facing away from induction coil  48  is formed by an essentially planar surface. 
     Induction charging device  10  further includes a coil housing unit, which surrounds coil unit  12 . The coil housing unit includes two coil housing elements  54 ,  56  which, in the mounted state, are coupled to one another via a detent element  58 . The coil housing unit has a largely cylindrically shaped outer contour. A first coil housing element of coil housing elements  54  has two detent elements  58  ( FIG. 3 ). Detent elements  58  are permanently connected to first coil housing element  54 . Detent elements  58  and first coil housing element  54  are configured as a single piece. Detent elements  58  are formed by snap hooks. Detent elements  58  are situated in a center of first coil housing element  54 . Detent elements  58  are configured to be resiliently deflectable in the radial direction of first coil housing element  54 . Another coil housing element of coil housing elements  56  is provided to hold induction coil  48 . Additional coil housing element  56  is also provided to hold core elements  46  in a mounted state. Additional coil housing element  56  is configured as a coil carrier. Core elements  46  and induction coil  48  of coil unit  12  in a mounted state are at least virtually completely enclosed in additional coil housing element  56  configured as a coil carrier. Additional coil housing element  56  further includes a detent recess  60 , which is configured to correspond to detent elements  58  of first coil housing element  54 . Detent recess  60  is situated in a center of additional coil housing element  56 . In a mounted state, detent elements  58  of first coil housing element  54  reach through detent recess  60  of additional coil housing element  56  and are locked in place with the additional coil housing element. Thus, in the mounted state, coil housing elements  54 ,  56  are connected to one another in a form-locked manner. 
     Induction charging device  10  further includes a shielding unit  14 . Shielding unit  14  is provided to partially shield coil unit  12 . Shielding unit  14  is provided to reduce electromagnetic disturbances. Shielding unit  14  includes a shielding element  18 . For the function of shielding element  18 , it is important that shielding element  18  be situated in induction charging device  10  between coil unit  12  and exterior housing  28 , in particular, between coil unit  12  and second housing shell  32 . In this configuration, one side of shielding element  18  faces second housing shell  32 , whereas the other opposite side of shielding element  18  faces coil unit  12 . Thus, during a charging operation of an induction rechargeable battery  26  with induction charging device  10 , shielding element  18  is situated between coil unit  12  and second housing shell  32 . During the charging operation, second housing shell  32  forms a standing surface for induction charging device  10 , for example, a table surface. Shielding element  18  is situated between coil housing element  56  and second housing shell  32 . In an alternative specific embodiment not depicted, shielding element  18  may also form an element of coil unit  12 . In this case, shielding element  18  may be situated in coil housing element  56 . In this case, shielding element  18  may be situated, in particular, between coil housing element  56  and core elements  46 . 
     In the depicted specific embodiment, shielding element  18  is detachably fastened in induction charging device  10  with the aid of fastening elements in the form of screws. The fastening elements interact with the retaining elements of upper housing shell  30 . In this way, shielding element  18  is detachably fastened to upper housing shell  30 . One of the fastening elements also assumes the function of establishing an electrically conductive connection between shielding element  18  and an electric line in the form of a cable. Shielding element  18  is connected via the electric line to a ground. Shielding element  18  is formed from an electrically conductive material. It is advantageously formed from a metallic material. Shielding element  18  is made of aluminum. Shielding element  18  is configured to shield coil unit  12  from metallic objects located on a standing surface for induction charging device  10 , for example, on a table surface. A standing surface made of a metallic material or metallic particles on the standing surface influence the function of coil unit  12  in a disadvantageous manner. Shielding element  18  has an essentially ring-shaped design. Shielding element  18  is formed by an aluminum ring. In one alternative specific embodiment not depicted, shielding element  18  may also have a disk-shaped design. Shielding element  18  in this case may have, in particular, a full-surface design. To achieve a sufficient mechanical stability, shielding element  18  has a thickness, for example, of approximately 1 mm, however, shielding element  18  may also have a significantly smaller thickness. 
     It is advantageous for the function of shielding element  18  if shielding element  18  has what may be a large surface expansion relative to the surface encompassed by induction coil  48 . 
     Shielding element  18  has a surface expansion, which corresponds at least essentially to the surface formed by induction coil  48 . The essentially circular shielding element  18  has an outer diameter, which is at least as large as the outer diameter of induction coil  48 . In one alternative specific embodiment, in which induction coil  48  is not ring-shaped, but rather is, for example, oval, rectangular or square, the geometric basic shape of shielding element  18  is advantageously adapted to the basic shape of induction coil  48 . In this case, a projection surface of shielding element  18  formed in a projection of shielding element  18  along the axial direction is at least approximately as large as the projection surface of induction coil  48 , which in a projection of induction coil  48  is formed along the axial direction. 
     Shielding element  18  includes a radial slot  20 . Slot  20  extends perpendicular to a center axis  62  of shielding element  18 . A direction of extension of slot  20  intersects center axis  62 . Center axis  62  in this case is formed by a surface normal of a main extension plane of shielding element  18 , which extends through a geometric center point of shielding element  18 . In principle, however, another extension of slot  20 , which appears meaningful to those skilled in the art, would also be conceivable. Slot  20  interrupts shielding element  18  in at least one operating state. Slot  20  forms a gap in shielding element  18 , in which there is a void in the material of shielding element  18 . 
     Shielding unit  14  further includes an additional shielding element  64 . Additional shielding element  64  is situated in induction charging device  10  between coil unit  12  and holding area  38 . In this configuration, one side of additional shielding element  64  faces holding area  38 , whereas the other opposite side of additional shielding unit  64  faces induction coil  48 . Thus, during a charging operation of induction rechargeable battery  26  with induction charging device  10 , additional shielding element  64  is situated between induction coil  48  and induction rechargeable battery  26  or between induction coil  48  and an induction coil  48  of induction rechargeable battery  26 . Additional shielding element  64  is configured to form a bypass capacitor with induction coil  48  of induction charging device  10 . Induction coil  48  in this case forms a first electrode of the bypass capacitor and additional shielding element  64  forms a second electrode of the bypass capacitor. 
     Induction charging device  10  further includes a switch element  22 . With switch element  22 , it is possible to electrically close and/or open radial slot  20  of shielding element  18 . Radial slot  20  may be electrically bridged by switch element  22 . Switch element  22  has two states, whereby one state of switch element  22  may be altered with the aid of an external control signal. For this purpose, switch element  22  includes a control contact not otherwise visible, via which it may be switched. Switch element  22  is provided to establish and/or disconnect an electrically conductive connection between two sides of slot  20  of shielding element  18 . Switch element  22  is formed by an electrical switch. In principle, however, it would also be conceivable that switch element  22  is formed by a mechanical switch element. In this case, it would be conceivable, in particular, that switch element  22  includes an element made of a conductive material, in particular, aluminum, the size of which corresponds at least essentially to a size of slot  20 , and which may be moved via a mechanism into or out of slot  20 . In this way, slot  20  could be, in particular, temporarily closed or opened. 
     Thus, a bridging could be achieved both by a mechanical closing of slot  20  as well as via a purely electronic bridging of slot  20 . 
     In addition, induction charging device  10  includes an adjustment unit  16 . A shielding parameter of shielding unit  14  is changeable with the aid of adjustment unit  16 . Adjustment unit  16  is connected to electronics unit  34  of induction charging device  10 . Adjustment unit  16  forms a part of electronics unit  34 . Adjustment unit  16  is provided to open or to close radial slot  20  as a function of an operating state in order to change the shielding parameter. For this purpose, adjustment unit  16  is connected to switch element  22 . Adjustment unit  16  is provided to activate switch  22 . A shielding parameter of shielding unit  14  may be changed by an opening or closing of slot  20 . For this purpose, adjustment unit  16  is provided to switch shielding unit  14  between a short-circuit mode and an idle mode for changing the shielding parameter. 
     Adjustment unit  16  is provided for switching between a short-circuit mode and an idle mode in order to activate switch element  22 . In a short-circuit mode, radial slot  20  of shielding element  18  is closed or bridged. In an idle mode, radial slot  20  of shielding element  18  is opened. In the short-circuit mode of shielding unit  14 , shielding element  18  functions as a short-circuit ring. Shielding element  18  provides an advantageous shielding in the short-circuit mode. In the short circuit mode, the current induced into shielding element  18  generates an electromagnetic force, which is phase-shifted as compared to that of coil unit  12 . A magnetic field of shielding element  18  formed in this way partially cancels out an effect of the magnetic field of coil unit  12  in the direction in which shielding element  18  is situated. Thus, a magnetic field of coil unit  12  is “bent away” from the bottom of induction charging device  10  during the short-circuit mode. This reduces the influence of various materials as a support for induction charging device  10 . The “bending” of the magnetic field of coil unit  12  is associated with an increase of the magnetic resistance. This results in a reduced inductance of coil unit  12  and an increased resonance frequency of a primary oscillator circuit. In the idle mode, on the other hand, a shielding effect of shielding element  18  is significantly reduced. Because of slot  20  in shielding element  18 , an induced current generates only isolated eddy currents. A magnetic field of shielding element  18  formed in this way is too weak to significantly reduce an effect of the magnetic field of coil unit  12  in the direction in which the shielding element  18  is situated. The reduced shielding is associated with a reduced magnetic resistance as compared to the short-circuit mode. This results in a higher inductance of coil unit  12  and a reduced resonance frequency of the primary oscillator circuit. 
     Adjustment unit  16  is provided to change a resonance frequency of an oscillator circuit of coil unit  12  by changing the shielding parameter of shielding unit  14 . By switching between the short-circuit mode and the idle mode, it is possible to adapt the resonance frequency of the primary oscillator circuit of coil unit  12 . In this way, the resonance frequency may be regulated by adjustment unit  16  to an optimal value. Adjustment unit  16  is activated for this purpose via electronics unit  34  of induction charging device  10 . 
     Induction charging device  10  further includes a control unit  24 . With the aid of control unit  24 , it is possible to manually switch between a short-circuit mode and an idle mode. With the aid of control unit  24 , an operator may manually switch between a short-circuit mode and an idle mode. For this purpose, control unit  24  is connected to adjustment unit  16 . This could, for example, enable an operator to indicate manually whether induction charging device  10  is standing on a non-magnetic base on a ferromagnetic base and/or on a diamagnetic or paramagnetic base, in order to enable an advantageously efficient charging operation. Control unit  24  is formed by a slide switch. Control unit  24  has three positions. A first position of control unit  24  defines a short-circuit mode, a second position of control unit  24  defines an idle mode and a third position of control unit  24  defines an automatic mode. In the automatic mode, a switching by adjustment unit  16  takes place automatically between the short-circuit mode and the idle mode. 
       FIG. 5  schematically shows a flow chart of a method for operating induction charging device  10 . In the method, adjustment unit  16  opens radial slot  10  of shielding element  18  in order to lower a resonance frequency of an oscillator circuit of coil unit  12 , or closes radial slot  20  of shielding element  18  in order to increase a shielding of coil unit  12 . During the operation of induction charging device  10 , a position of control unit  24  is checked after a start  66  in a first branch  68 . If control unit  24  is in a first position, radial slot  20  of shielding element  18  is closed or remains closed in a further method step  70 . If control element  24  is in a second position, radial slot  20  of shielding element  18  is opened or remains open in a further method step  72 . If control unit  24  is in a third position, a magnetism of a base of induction charging device  10  is sensed in a further method step  74 . This may occur, for example, via a separate sensor such as, for example, a magnetic sensor. In principle, however, it would also be conceivable to sense the magnetism by monitoring the oscillator circuit of coil unit  12  during a switch between the short-circuit mode and the idle mode. The sensed values are subsequently evaluated in a branch  76 . If the base is made of a non-magnetic material such as, for example, wood or plastic, radial slot  20  of shielding element  18  is opened or remains open in a further method step  72 . If the base is made of a ferromagnetic material or diamagnetic material such as, for example, iron, nickel, copper or aluminum, radial slot  20  of shielding element  18  is closed or remains closed in a further method step  70 . After method steps  70  and  72 , the method is then repeated at branch  68  until induction charging device  10  is deactivated.