Patent Publication Number: US-2009237029-A1

Title: Inductive battery charger for service equipment

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an inductive battery charger for a portable handheld device such as a battery tester or an automotive scanner. 
     BACKGROUND OF THE INVENTION 
     Automotive service equipment must exist in a high-risk environment with numerous sources of contamination, dirt, chemical solvents, etc., which can all easily corrupt electrical connectors intended to recharge battery-powered equipment. Additionally, use of the equipment in a garage or shop environment will frequently subject it to unintentional physical abuse (by dropping the equipment or having tools dropped upon it) that can damage or destroy electrical connectors and associated wiring. A purely inductive charging system would allow for recharging suitable battery systems without an external connector, eliminating a high-probability source of potential failure, while providing better service time and reduced warranty issues. 
     It is believed that there are no automotive service tools known to incorporate an inductive charging scheme such as described herein, wherein the primary portion of the charger is situated in a storage unit or base station and wherein electrical (ohmic) contacts are not required to transfer energy for the charging circuitry. Current service tools typically require a wired connection involving a plug and a socket to make electrical contact for the purpose of charging the internal batteries. This connection is subject to breakage, contamination with fluids, grease and dirt, and poor or reduced performance due to oxidation of the electrical contacts as set forth above. It is also susceptible to inadvertent damage caused by, for example, the end-user connecting the wrong recharging power supply to the instrument. 
     Accordingly, it is desirable to provide an inductive battery charger that addresses these shortcomings, particularly within the vehicle service tool market. Advantageously, such an improved charged instrument may be used for a significant length of time before recharging, and would provide a convenient storage location for the service tool. 
     SUMMARY OF THE INVENTION 
     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides for automatic recharging without operator effort in harsh environments, making the engaged service tool always available and fully charged, and eliminating the need to purchase disposable batteries. The inductive battery charger of the present invention may be advantageously retrofitted to existing handheld devices, such as battery testers, with minimal internal changes to the electronics and without any plastic housing or case changes. 
     In accordance with one embodiment of the present invention, an inductive battery charging system for a handheld service tool is provided. The system includes a battery charger and the service tool. The battery charger has a primary coil, enclosed within a housing that is coupled to a power source, while the service tool includes a secondary coil, enclosed within a housing that provides at least 100 mA of inductively-generated alternating current, a rectifier, a linear voltage regulator, a battery charge controller, and a battery. 
     In accordance with another embodiment of the present invention, an inductively-charged, handheld service tool is provided. The service tool has a housing that encloses a coil that provides at least 100 mA of inductively-generated alternating current, and a rectifier coupled to the coil. The housing also contains a linear voltage regulator coupled to the rectifier, a battery charge controller coupled to the linear voltage regulator, and a battery coupled to the battery charge controller. 
     In accordance with yet another embodiment of the present invention, a method of inductively charging a handheld service tool is provided. The method includes placing the service tool on a base station that includes a battery charger having a primary coil, and inductively coupling the output of the primary coil to a secondary coil, enclosed within the handheld service tool, to generate an AC waveform. Thereafter, the AC waveform is converted into a pulsating DC signal, the pulsating DC voltage is converted into a steady-state DC signal, and a battery of the handheld service tool is charged using the steady state DC signal. The charging status of the battery is also indicated. 
     In accordance with still another embodiment of the present invention, an inductive battery system is provided. The system includes a battery charger and a handheld service tool. The battery charger is coupled to a power source and has means for generating an electromagnetic field. The handheld service tool, includes means for inductively-coupling the electromagnetic field to provide at least 100 mA of alternating current, means for charging a battery using the inductively-generated alternating current, and means for housing at least the coupling means and the charging means. 
     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view illustrating a service tool used in accordance with a preferred embodiment of the inductive battery charger. 
         FIG. 1B  is a side view of an exemplary inductive battery charger in accordance with the present invention. 
         FIG. 2A  is a schematic diagram of an AC power supply for an internal primary coil of the inductive battery charger. 
         FIG. 2B  is a schematic diagram of an alternative power supply for the internal primary coil of the inductive battery charger. 
         FIG. 3  illustrates a diagrammatic representation of circuitry for a secondary coil suitable for carrying out the functions of an embodiment of the invention. 
         FIG. 4  illustrates an exemplary work bench charger assembly in accordance with an embodiment of the invention. 
       FIG. illustrates an exemplary wall-mounted charger assembly in accordance with an embodiment of the invention. 
         FIG. 6  illustrates an exemplary suspension charger assembly in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. With reference to the drawings, an embodiment in accordance with the inventive inductive battery charger assembly is provided, comprised of a handheld service tool  10  and an inductive battery charger  22 , as seen in  FIGS. 1A and 1B  respectively. The service tool  10  may be a battery tester or automotive scanner used in a vehicle diagnostic and repair facility. The service tool  10  shown in  FIG. 1A  has a housing  12  containing a display  14 , user entry buttons  16 , and a handle  18 . Enclosed within the body of the handle is an internal secondary coil  20  of wire forming one-half of an AC transformer. This internal secondary coil  20  is connected to a power supply circuit, enclosed within housing  12  that recharges the batteries of the handheld device. 
     In one embodiment, the housing  12  may be substantially sealed against the adverse effects of the test environment, such as, for example, contamination with fluids, grease, dirt, etc., against poor or reduced performance due to oxidation of the electrical contacts, etc. Similarly, the housing of the inductive battery charger  22  may be substantially sealed against the adverse effects of the test environment. In another embodiment, the housing  12  and the inductive battery charger  22  housing are hermetically sealed, while in a further embodiment, gaskets may be used to seal the seams between the appropriate portions of the housing  12 , as well as the seams between the appropriate portions of the inductive battery charger  22  housing, as is known in the art. 
     A primary coil  24  connected to an AC mains power  26  is provided in an external cradle  28  or surface of the inductive battery charger  22  depicted in  FIG. 1B . When the service tool  10  is placed within the cradle  28  or on the surface of the charger  22  for storage and recharge, the coils  20  and  24  form a complete transformer circuit providing power to the battery charging system within the handheld device. The secondary coil  20  inductively couples with the primary coil  24  to accept energy. Proper sizing of the two coils is implemented to support different battery sizes and architectures. 
     In the preferred embodiment, and with reference to  FIG. 2A , the power source  30  of the primary coil  24  is comprised of a direct connection  32  from a plug  34  to an AC line. In another embodiment, a power source  36  is shown in  FIG. 2B  having an amplified oscillator  38  connected to a DC power supply  40  with a direct connection  42  to a plug  44 , which operates the primary coil  24  at a resonant frequency to maximize energy transfer. 
     As shown in the  FIG. 3B , the secondary coil  20  is sized and wound to provide optimum coupling with the primary coil  24  and has power supply circuitry  46  comprised of a rectifier  48 , a capacitor filter  50 , and a linear voltage regulator  52  to provide DC power for a battery-charging integrated circuit  54 . The secondary coil  20  must be compatible with the frequency provided by primary coil  24 , and must have sufficient current capacity to operate the battery-charging integrated circuit  54 . 
     To charge the service tool, the rectifier  48  converts an AC waveform of the secondary coil  24  into pulsating DC. The filter  50  and voltage regulator  52  convert the pulsating DC into steady-state DC. Thereafter, the battery-charging integrated circuit  54  uses the steady-state DC voltage to control the voltage and current presented across a battery pack  56  in order to provide a power connection  58  to the service tool. In accordance with the preferred embodiment, the battery pack  54  is comprised of a set of batteries having capacity and chemistry complimentary to the portable service tool being powered. Accordingly, nickel-metal hydride (NiMH) batteries or lithium ion (Li-Ion) batteries may be used. 
     A conventional battery-charging integrated circuit  54  having properties including but not limited to charging current control, battery chemistry support, and user status displays may be employed. The integrated circuit  54  (hereinafter “IC”) serves as a controller and provides several functions. The IC  54  charges the battery  56  pack when depleted partially or fully. It maintains a trickle-charge on the battery  56  pack when not in use and prevents the battery from over-discharge. The IC  54  prevents overheating of the battery pack  56  whether the service tool is in use or is recharging. As referenced above, the IC  54  provides an external indicator (located on the service tool) to the user of the current status of the battery charger. Several status indicators are available including “charging”, “charged, ready for use”, and “overheated, waiting for cool-down before charging.” These status indicators may be presented via a single LED utilizing various flashing codes or via multiple LEDs, wherein each status indicator has a different color. 
     The dimensions for the internal secondary coil  20  in  FIG. 1A  approximate 4″ in diameter with 1″ of corresponding width, and the primary coil  24  approximates 6″ diameter by 1″ wide. This configuration can provide approximately 100 mA of 11.5V (AC) current for a battery recharging circuit. The secondary coil  20  is the receiver coil in the inductive battery charger assembly. The secondary coil  20  is sized as described herein and wound to provide optimal coupling with the primary coil  24 . 
     In the preferred embodiment, the inductive battery charger assembly  60 , as depicted in  FIG. 4  has a base station  62  having a top platform or a flat plate  64 . The charger  22  may be placed upon the surface of a workbench, table, toolbox or other work surface. The service tool  10  to be charged is placed upon the charger  22  and stored for future use. The primary coil  24  has a driving voltage of a 60 Hz AC power line connected to plug  66  at 110V or 220V. 
     In accordance with an alternative embodiment, the inductive battery charger assembly  60 ′, as illustrated in  FIG. 5 , is presented wherein the charger  22 ′ is a receptacle having a wall-mounted base and a cradle  68 . The charger  22 ′ holds the service tool  10  to be charged in a recess within the cradle  68 . With reference to  FIG. 6 , an inductive battery charger assembly  60 ″ is presented with the charger  22 ″ as a wall-mounted hanger, wherein the service tool  10  is held within a suspension device  70  having a hook  72  such that the suspension device  70  holds the tool  10  against the charger  22 ″ so that the secondary coil  24  within the tool  10  contacts the primary coil  20  within the charger  22 ″. 
     Alternative embodiments of the inductive battery charger  22  are presented herein wherein the configurations of the primary coil  24  and its driving source of energy are varied, with the secondary coil  20  of the charging service tool  10  remaining substantially similar as described above. In one system, the primary coil  24  requires only AC power and a customary safety device (e.g. a fuse, circuit breaker, etc.). The secondary coil  20  contains a substantial amount of wire in order to step-down the primary coil voltage by a sufficient amount. The assembly requires larger coils with a greater number of turns and longer wire in order to achieve sufficient amounts of coupling efficiency. This assembly would require a larger recharging time, but will be minimally complex to construct. 
     A medium-current embodiment of the inductive battery charger assembly operates the primary coil  24  and the secondary coil  20  at a frequency higher than 60 Hz and selected to provide a tuned circuit between the coils. The combination of a higher frequency and tuning results in an increased efficiency in energy transfer. The service tool  10  and the base of the charger  22  may be substantially shielded to avoid excessive electromagnetic radiation. The higher energy transfer results in an increased current availability, which leads to a faster recharging rate. 
     To implement a high-efficiency embodiment of the inductive battery charger assembly, the tuned-transformer system of the previous a feedback embodiment can incorporate a feedback switch to turn off the primary coil  24  when the battery pack  56  is fully charged, or reduce the primary coil voltage or current substantially while maintaining a trickle charge. This provides a “green” or energy-saving system since the primary coil  24  does not provide maximum output when that output is not needed. The switching function is established by placing a magnetic reed switch outside of the main magnetic circuit and controlling the switch with a coil. 
     Although examples of power source of the primary coil  20 B of the inductive battery charger are described with an AC or oscillator/DC driving voltage, it will be appreciated that another arrangement of two inductively-coupled coils may be implemented, wherein the coupling allows energy to be transferred across the separation between the two coils and used to charge the battery pack. Battery types other than NiMH and Li-Ion may also be used. Moreover, although the inductive battery charger assembly  10  is useful to for vehicle service markets it can also be used with other tools and/or in other industries. Alternative methods for inductively charging a battery through an electronic magnetic field, including wireless power transmission through magnetic loop antennas and other implementations known in the art may also be used in accordance with the embodiments described herein. 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.