Abstract:
A charging device for a rechargeable energy store which has a first induction coil includes: a coupling surface for positioning the first energy store; a second induction coil for generating a magnetic field in the area of the coupling surface to transfer electrical energy between the first and second induction coils; and a direction control system for bringing an alignment of the field of the second induction coil in line with an alignment of the first induction coil.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a charging device, e.g., for inductive charging of an energy store, a method for controlling a charging operation, and a corresponding computer program product. 
         [0003]    2. Description of the Related Art 
         [0004]    An accumulator which may be used, for example, to supply electrical energy to a small power device, is rechargeable with the aid of a corresponding charging unit. The accumulator and the charging unit may be connected to each other with the aid of electrical contacts, or a system of induction coils may be used to transmit electrical energy from the charging unit to the accumulator. The accumulator has a first energy coil which is configured to convert an external alternating magnetic field into a current which is used to recharge the accumulator following appropriate preparation. The charging unit has a corresponding second induction coil and is configured to generate the alternating electrical field, so that the two induction coils are coupled to each other in the manner of a transformer. 
         [0005]    U.S. Pat. No. 6,803,744 B1 shows a charging unit which has a system of a plurality of second induction coils to facilitate an alignment of the accumulator with the first induction coil. In one specific embodiment, it is also shown that the induction coils may be moved relative to each other to achieve an improved magnetic coupling between the induction coils. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to provide a charging device which provides a further improved magnetic coupling between the induction coils. Another object of the present invention is to provide a method and a computer program product for controlling a charging operation. 
         [0007]    A charging device according to the present invention for a rechargeable energy store which has a first induction coil includes a coupling surface for positioning the first energy store, a second induction coil for generating a magnetic field in the area of the coupling surface to transfer electrical energy between the induction coils, and a direction control system for bringing an alignment of the field of the second induction coil in line with an alignment of the first induction coil. 
         [0008]    It has been demonstrated that, to improve the magnetic coupling between the induction coils, it may be more effective to bring the alignment of the magnetic field in line with the alignment of the first induction coil than to move the induction coils relative to each other, in particular if the coupling surface is not much larger than the first induction coil. 
         [0009]    In a first specific embodiment, the direction control system includes pivoting means for setting an elevation and rotating means for setting an azimuth in the second induction coil in relation to the coupling surface. A fast and accurate change in the alignment of the field of the second induction coil may be achieved with the aid of such a mechanical pivoting or rotation of the second induction coil. 
         [0010]    In another specific embodiment, the direction control system includes multiple differently aligned subcoils, which are configured to generate magnetic subfields which are superimposed to form the magnetic field in the area of the coupling surface. In this way, the alignment of the magnetic field may be changed without requiring a mechanical movement of elements of the charging device. The superimposition of the magnetic subfields may result in the fact that the magnetic field is strengthened in the area of the first induction coil, whereby a transmittable amount of energy between the induction coils may be increased. By eliminating a mechanical tilting device, a distance between the induction coils or between the second induction coil and the surface may be reduced, whereby the magnetic coupling between the induction coils may be further improved. 
         [0011]    In one specific embodiment, the charging device additionally includes a drive device for moving the second induction coil along the coupling surface in such a way that a position of the second induction coil is brought in line with a position of the first induction coil. The advantages of the alignment of the positions of the induction coils may thus be combined with the advantages of adjusting the alignments of the induction coils. Due to the combination, a mechanical complexity of the overall approach may be less than the sum of the complexities for the two individual approaches. This makes it possible to reduce the manufacturing and maintenance costs. 
         [0012]    The charging device may include a control device for controlling the direction control system and/or the drive device, the control device being designed to permit the second induction coil to follow a movement of the first induction coil with regard to the coupling surface. 
         [0013]    This makes it possible to support a charging operation in a harsh environment in which it is not possible to guarantee that the rechargeable energy store assumes a constant position or alignment in relation to the coupling surface. Conditions of this type may prevail, in particular, on board a motor vehicle, a ship or another means of transportation. 
         [0014]    In one specific embodiment, the induction coils are configured to transmit energy in any direction. As an alternative to the inductive energy supply of the energy store, an inductive removal of energy from the energy store may also be made possible. 
         [0015]    A method according to the present invention for controlling a charging operation of a rechargeable energy store having a first induction coil with the aid of the described charging device includes the steps of determining a first electrical power transmittable between the induction coils, changing the alignment of the magnetic field of the second induction coil in relation to the alignment of the first induction coil, determining a second electrical power transmittable between the induction coils, and changing the alignment of the magnetic field of the second induction coil on the basis of the comparison, for the purpose of maximizing the electrical power transmittable between the induction coils. 
         [0016]    Due to the method, the alignment of the magnetic field of the second induction coil may be successively brought in line with the first induction coil, a rapidly converging optimization algorithm being able to be used, so that an optimum alignment may be quickly and reliably found. 
         [0017]    In addition to the alignment of the magnetic field, a position of the second induction coil in relation to the first induction coil may also be changed. The alignment and the position may be changed successively or simultaneously in multiple runs of the method for the purpose of supporting the rapid convergence of the optimization algorithm. 
         [0018]    A computer program product may include program code means for carrying out the described method, the computer program product being executed on a processing device or being stored on a computer-readable data carrier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  shows a charging device having a rechargeable energy store. 
           [0020]      FIG. 2  shows a direction control system for the charging device from  FIG. 1 . 
           [0021]      FIG. 3  shows another direction control system for the charging device from  FIG. 1 . 
           [0022]      FIG. 4  shows a flow chart for a method for controlling the charging device from  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  shows a charging device  100  for charging a rechargeable energy store  105 . To facilitate referencing, a Cartesian coordinate system is specified. Charging device  100  includes a coupling surface  110  which is represented with an upward displacement in the manner of an exploded drawing. 
         [0024]    Energy store  105  includes a first induction coil  115 , which is connected to an electrical storage device  125  with the aid of a control device  120 . First induction coil  115  preferably includes an electrical conductor which is wound multiple times in a circular shape. The first induction coil provides control device  120  with an electrical alternating current as a function of an alternating magnetic field  130  flowing through first induction coil  115 . Control device  120  converts the alternating current into a direct current and controls it in such a way that electrical storage device  125  may be recharged therefrom. Storage device  125  may be a capacitor, in particular a double layer capacitor, or an accumulator, in particular a nickel metal hydride or lithium ion accumulator. 
         [0025]    Coupling surface  110  is represented as a flat rectangle, although coupling surface  110  may also have a different shape, in particular a curved shape in other specific embodiments. Coupling surface  110  is also not limited to being situated largely perpendicularly to the force of gravity. 
         [0026]    Charging unit  100  includes a second induction coil  135 , which is mounted on a first carrier  140  which is movable in the y direction with respect to a first rail  145 . First rail  145  is mounted on a second carrier  150 , which is movable along a second rail  155  in the x direction. By correspondingly moving first carrier  140  and second carrier  150 , second induction coil  135  is fully movable on the x-y plane parallel to contact surface  110 . In another specific embodiment, second induction coil  135  may also be moved in a way other than with the aid of carriers  140  and  150 , for example with the aid of a moving device having a polar orientation. 
         [0027]    Second induction coil  135  is mounted on first carrier  140  with the aid of one or multiple alignment elements  165 , alignment elements  165  permitting the second induction coil to pivot around the y axis and around the x axis. 
         [0028]    The movements of alignment elements  165  of first carrier  140  and second carrier  150  may be controlled with the aid of a control device  160 , which is connected to the corresponding moving elements. Control device  160  is furthermore configured to control second induction coil  135  in such a way that it generates magnetic field  130  in the area of coupling surface  110 . The position and alignment of the magnetic field in relation to coupling surface  110  and, if necessary, also the strength of magnetic field  130  may thus be changed with the aid of control device  160 . Control device  160  is configured to move second induction coil  135  in such a way that the position and alignment of second induction coil  135  are optimized in the sense of an optimized magnetic coupling between first induction coil  115  and second induction coil  135 . For this purpose, induction coils  115 ,  135  must be situated in such a way that they are located as close to each other as possible, while magnetic field  130  of second induction coil  135  flows perpendicularly through first induction coil  115 . 
         [0029]      FIG. 2  shows a direction control system  200  for charging device  100  from  FIG. 1 . Direction control system  200  represents an alternative means of attaching second induction coil  135  to first carrier  140  in the specific embodiment of charging device  100  illustrated in  FIG. 1 . An additionally drawn coordinate system corresponds to the one in  FIG. 1 . 
         [0030]    Direction control system  200  includes a platform  205  for attachment to first carrier  140 . Platform  205  includes an upper section  210  and a lower section  215 , lower section  215  being configured for attachment to first carrier  140 , while upper section  210  supports second induction coil  135 . Upper section  210  is designed to be rotatable around the z axis in relation to lower section  215 , with the aid of a first drive device  220 . 
         [0031]    Second induction coil  135  is attached to upper section  210  of platform  205  with the aid of a second drive device  225  in such a way that second induction coil  135  is pivotable around an axis which runs parallel to the x-y plane and corresponds to the x axis in the representation in  FIG. 2 . If upper section  210  is rotated around the z axis in relation to lower section  215  of the platform, the axis around which second induction coil  135  is pivotable is also rotated. An azimuth (direction angle) may thus be changed with the aid of first drive device  220 , and an elevation (height angle) of second induction coil  135  may be changed with the aid of second drive device  225 . The alignment of second induction coil  135  in relation to the x-y plane is thus freely adjustable. The alignment of a magnetic field generated with the aid of second induction coil  135  also changes with the alignment of the second induction coil. 
         [0032]      FIG. 3  shows another direction control system  300  for charging device  100  from  FIG. 1 . As with charging device  200  from  FIG. 2 , charging device  300  from  FIG. 3  is configured to provide an alternative attachment of second induction coil  235  to first carrier  140  of charging device  100  from  FIG. 1  and to simultaneously permit a change in the alignment of magnetic field  130  which may be generated by second induction coil  135 . A specified Cartesian coordinate system corresponds to the coordinate systems in  FIGS. 1 and 2 . 
         [0033]    Direction control system  300  includes a platform  305  similar to platform  205 , platform  305 , however, having a rigid design. Subcoils  310  through  320 , whose alignments differ from each other, are situated on the upper side of platform  305 . In the illustrated specific embodiment, the three subcoils  310  through  320  are inclined toward each other in such a way that axes, each of which runs perpendicularly through individual subcoils  310  through  320 , intersect above platform  305  at a point on the z axis. In other specific embodiments, subcoils  310  through  320  may also have other relative alignments or arrangements. 
         [0034]    Each of subcoils  310  through  320  is configured to generate a magnetic subfield, the generated subfields being superimposed on each other to form magnetic field  130  in the area of coupling surface  110 , which is not illustrated, above platform  305 . Depending on the relative alignment of subcoils  310  through  320  and the relative strengths of the generated magnetic subfields, magnetic field  130  runs in a predetermined alignment in relation to the x-y plane in the area of coupling surface  110 . 
         [0035]      FIG. 4  shows a flow chart of a method  400  for controlling charging device  110  from  FIG. 1 . 
         [0036]    A first electrical power, which is transmittable between induction coils  115  and  135 , is determined in a first step  405 . This may be done by control device  160  providing an alternating voltage to second induction coil  135 , which subsequently generates an alternating magnetic field  130  in the area of coupling surface  110 , so that alternating field  130  may be absorbed by first induction coil  115  and converted back into an electrical current. A current intensity resulting from second induction coil  165  provides an indication of the first transmittable power. 
         [0037]    A changed alignment and/or a changed position of second induction coil  135  is/are determined in a subsequent step  410 . The determined alignment and/or position is/are implemented in a subsequent step  415  by controlling carriers  140  and  150  or drive devices  220 ,  225  or subcoils  310  through  320 . 
         [0038]    In a subsequent step  420 , a second transmittable power between induction coils  115  and  135  is determined similarly to step  405 . The first determined power is compared with the second determined power in a step  425 . If the first power is less than the second power by a predetermined amount, method  400  continues with a step  430 , otherwise it continues with a step  435 . The amount may be predetermined for the purpose of influencing a sensitivity of method  400 . The amount may be set to zero for a maximum sensitivity and thus a maximum optimization of the position of second induction coil  135  and the alignment of its magnetic field  130  in relation to first induction coil  115  in each case. 
         [0039]    In step  430 , the first power determined in step  405  is set to the value of the second power determined in step  420 . This step is carried out if the changed alignment and/or position in steps  410  and  415  has/have produced an increase in the transmittable power. The method may subsequently continue with step  410  to bring about a further improvement in the transmittable power. 
         [0040]    Step  435  is carried out if the change in the alignment and/or position in steps  410  and  415  have produced a decrease in the transmittable power. In this case, the changed alignment and/or position is/are reversed, and method  400  continues with step  410  for the purpose of increasing the transmittable power by another change in steps  415  and  420 .