Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit or priority to U.S. Provisional Application No. 61/524,081, filed Aug. 16, 2011, the entire disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention generally relates to a system and method for charging power storage systems in electric vehicles. 
       BACKGROUND OF THE INVENTION 
       [0003]    As the electric motor and battery charging technology advances, the market for electric vehicles continues to grow. Owners of fleets are beginning to look to electric vehicles as desirable purchases. This means that there will be a need by these fleet owners to install the infrastructure that enables them to recharge the batteries of a large number of vehicles each night. That infrastructure can represent a substantial capital investment. 
         [0004]    An increasingly popular approach being advocated by players in the electric vehicle industry involves using wireless energy transfer or inductive power transfer to charge the vehicle&#39;s batteries. Examples of such an approach are described in U.S. Pat. Pub. No. 2010/0277121, entitled “Wireless Energy Transfer Between A Source and A Vehicle,” and incorporated herein by reference. In general, the charging station has a transmitting coil, typically installed in the floor of the charging station. And the vehicle includes a receiving coil mounted on its underside. When recharging of the batteries is desired, the driver moves the vehicle into the charging station so that the vehicle&#39;s receiving coil is aligned over the transmitting coil. With the two coils aligned in this way, the charging station applies a high frequency (e.g. RF) energy signal to the transmitter coil and energy is transferred to the receiving coil through resonant coupling of the two coils. 
       SUMMARY OF THE INVENTION 
       [0005]    In general, in one aspect, the invention features a charging station for charging a plurality of vehicles each with a receiver inductor coil located on top of the vehicle. The system includes: first and second support structures; an overhead track stretching between the first and second support structures; a movable carriage on the overhead track, the carriage including a transmitter inductor coil located at a position under the carriage for transferring power to the receiver inductor coils of the plurality of vehicles when the plurality of vehicles is parked under the overhead track, an inductive power transfer module connected to the transmitter inductor coil, and an alignment stage controlling the position of the transmitter inductor coil with respect to the carriage; and a motorized transport mechanism for moving the carriage along the tracks and positioning the carriage over any selectable one of the plurality of vehicles. 
         [0006]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic representation of an overhead inductive power transfer system for sequentially charging the storage batteries in a fleet of electric vehicles. 
           [0008]      FIG. 2  is a block diagram of the circuitry within the carriage shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  shows an automated vehicle charging system  100  that is particularly useful for fleet owners. The system enables one to sequentially charge a fleet of vehicles through an overhead charging unit that wirelessly transfers energy to each of the vehicles in succession. The system takes advantage of the ability of current charging technology to fully charge a vehicle&#39;s batteries in a matter of minutes rather than the hours that were previously necessary. The faster charging enables one to use a single charging unit to sequentially recharge each vehicle in the fleet of vehicles and still complete the job within a reasonable amount of time, e.g. while the vehicles are parked overnight. This design substantially reduces the amount of capital investment that is required to build a charging facility that can effectively charge multiple vehicles. Rather than having to install a separate, individual charging station for each vehicle, this design enables the fleet owner to install one charging station that is moved from one vehicle to the next in an automated way. 
         [0010]    Vehicle charging system  100  includes an overhead structure on which a charging carriage  102  is suspended above a group of vehicles  104  parked under the structure. On the underside of carriage  102  there is a transmitter coil  120  and on the top of each vehicle there is a receiver coil  240  at a height just below the height of transmitter coil  120 . In the described embodiment, the overhead structure is similar in the design to that of a suspension bridge. It includes two support towers  106  between which two suspension cables  108  are stretched (in the side view of  FIG. 1 , only one cable  108  is shown, the other one is parallel to and behind it in the figure). Each of suspension cables  108  supports a corresponding track  110  (e.g. a cable or rail) which is suspended from suspension cable  108  by multiple vertical suspender elements  112  (e.g. other lengths of cable or rods). Further support for towers  106  is provided by support cables  114  that counteract the lateral force exerted on towers  106  by the structure suspended between them. With this arrangement, tracks  110  are arranged to be horizontal to and at a constant height from the ground sufficient to permit the vehicles  104  to be parked under the suspended carriage  102 . 
         [0011]    Carriage  102  hangs from tracks  110  so that it can move back and forth along the tracks between the two towers. In the described embodiment, the mechanism by which carriage  102  hangs from the tracks is similar to that which is employed in ski lifts. For example, one wheel rides on top of the track and a second wheel, below the first wheel, rides under the track and prevents the carriage from being easily derailed. 
         [0012]    Carriage  102  supports the circuitry necessary to enable energy transfer through transmitter coil  120 . Such circuitry is well known to persons skilled in the art and can take a variety of different forms, some examples of which are described in previously-mentioned U.S. Pat. Pub. No. 2010/0277121. In the described embodiment, as shown in  FIG. 2 , it includes a step-down transformer  200 , rectifier circuitry  202 , and transmitter circuitry  204 . Power is delivered to carriage  102  through high voltage AC lines (e.g. 13.5 kV). Step-down transformer  200  reduces that voltage to a lower level, namely, one that is more compatible with the other circuitry in carriage  102 . Rectifier circuitry  202  converts the AC to DC for powering the rest of the circuitry in carriage  102 . And transmitter circuitry  204  generates the high frequency power signal for driving transmitter coil  120  and performing inductive power transfer to the vehicle. 
         [0013]    This circuitry includes a variable oscillator  210  that is controlled by a control signal  212 , a power amplifier  214  connected to oscillator  210 , and a filter and matching circuit  216  the output of which is connected to transmitter coil  120 . Oscillator  210 , which in the described embodiment operates in the RF range (e.g. 13.5 MHz), drives power amplifier  214 . The output of amplifier  214  passes through filter and matching circuit  216  which eliminates any noise or unwanted harmonics from the output signal of power amplifier  214  and matches the impedance of the transmitter circuit to the coil to thereby aiding in optimizing the coupling of the amplified RF signal to the receiver circuit in the truck. Controller  220  can also vary the frequency of oscillator  210  to optimize power transfer. 
         [0014]    The circuitry in the carriage also includes a processor-based controller  220  for controlling the operation of the various other circuits and systems in carriage  102 , sensing circuitry  222  for aiding in physically aligning transmitter coil  120  in carriage  102  with receiving coil  240  in the vehicle, a wireless transceiver  224  for exchanging information with corresponding circuitry located in the vehicle, a transport mechanism or drive motor  226  for moving the carriage along the track, and a coil positioning mechanism  228  made up of an arrangement of servo motors and/or actuators for positioning transmitter coil  120  in more precise alignment with receiver coil  240  in the vehicle. 
         [0015]    Controller  220  is programmed to use drive motor  226  to move the carriage along the track from one charging position to another. The program knows roughly where each vehicle coil is located. After achieving initial alignment with the receiver coil in the first vehicle, controller  220  with the aid of sensing circuits  222 , that might include various optical and/or mechanical sensors, uses the coil positioning mechanism  228  to more precisely align transmitter coil  120  with receiver coil  240 . The sensing circuits are used to optically or electrically detect the precise position of the receiver coil and to cause coil positioning mechanism  228  to physically and electrically align the two coils for optimum power transfer. The motor and/or actuator mechanisms have the ability to move the transmitting coil in three dimensions relative to carriage  102  (two horizontal and one vertical) to achieve the more optimum alignment of the two coils. Controller  220  may also measure the transfer electrical characteristics of the transmitter circuit and dynamically tune the transmitter circuit to achieve the optimum coupling. This can involve receiving feedback from the target vehicle through the wireless communication link established between the two wireless transceivers. 
         [0016]    In the vehicle, the receiver coil  240  is connected to a receiver circuit  250 . This receiver circuit generally includes a matching circuit  252 , a rectifier and switching circuit  254 , a controller  256 , and a battery management module  258 . The signal from the transmitter circuit is resonantly coupled to coil  240  connected to receiver circuit  250 . Matching network  252  matches the impedance of the receiver to receiver coil  240 . And rectifier and switching circuit  254  rectifies the received AC signal to output a DC voltage that is delivered to the vehicle batteries to carry out the recharging operation. Battery management module  258  monitors the charging of the batteries in the vehicle and provides this information to controller  256  which uses a wireless transceiver  260  to communicate certain monitored information to wireless transceiver  224  in carriage  102 . 
         [0017]    Under tracks  110 , there is a row of identified parking spaces or slots into which the vehicles are driven for overnight charging. The slots are physically identified on the parking surface and indentations in the parking surface into which the wheels are positioned provide a rough alignment of the vehicles under tracks  110 . When carriage  102  moves back and forth under track, it will bring transmitter coil  120  into approximate alignment with receiver coils  240  on top of the vehicles. 
         [0018]    When the charging sequence is initiated, controller  220  in the overhead carriage  102  causes drive motor  226  to move carriage  102  along tracks  110  to a start position on one side and above the location where the first vehicle is located. At that location, controller  220  uses sensing circuitry  222  to find receiver coil  240  with which it will need to align transmitter coil  120 . Then, controller  220  uses positioning mechanism  228  within carriage to align transmitter coil  120  more precisely both horizontally and vertically with respect to the underlying receiver coil  240 . Once the two coils are properly aligned, controller  220  begins the power transfer operation to charge the vehicle&#39;s batteries. 
         [0019]    Controller  256  in the vehicle senses the state of charge of the onboard batteries and detects when they are fully charged. Using the communication link established between the two wireless transceivers  224  and  260 , controller  256  communicates the charging status information to controller  220  in carriage  102 . When full charge is reached, controller  220  in carriage  102  terminates the charging operation for that vehicle. Then, it cause carriage  102  to move on to the next vehicle and performs the same sequence of steps to charge the batteries of the next vehicle. This sequence is repeated for each vehicle until each vehicle that is parked within the charging structure has been fully charged. 
         [0020]    The drive mechanism for moving the carriage along the overhead track was described herein as being located in the overhead carriage. However, it could alternatively be located on the support towers and operate a cable which moves the carriage to the desired locations. 
         [0021]    Other embodiments are within the following claims.

Technology Category: h