Abstract:
A dual motor axle driven system for powering a vehicle. A first battery pack provides power to a first electric motor and a second battery pack provides power to a second electric motor. A generator is connected to a differential gear train and the first and second battery packs. Rotation of the wheels transfers rotational kinetic energy to the differential gear train for conversion into electrical energy by the generator for recharging the first and second battery packs while the vehicle is in motion. A tachometer measures a revolution speed of a drive shaft. The vehicle is powered by the first electric motor when the measured revolution speed of the drive shaft is less than a threshold value and by both electric motors when greater than a threshold value. The generator recharges the second battery pack when the vehicle is powered by the first electric motor and vice versa.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to electric generators for vehicles and, more specifically, to an axle-driven electric generator for recharging electric batteries used for powering an electric vehicle while the vehicle is in use in order to extend the cruising range between required charges from an external electrical source. 
   2. Description of the Prior Art 
   Numerous types of generators designed for powering electric vehicles have been provided in the prior art. For example, U.S. Pat. Nos. 4,042,056; 4,119,862; 4,498,551; 4,935,689; 5,083,077; 5,215,156; 5,224,563; 5,230,402; 5,541,494; 5,842,534; 5,858,568 and European Patent No. EP 1 085 644 A2 are all illustrative of such prior art. While these generators designed for powering electric vehicles may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described.  
   U.S. Pat. No. 4,042,056 
   Inventor: Elwood R. Horwinski 
   Issued: Aug. 16, 1977 
   A gasoline and battery-powered electric vehicle wherein the start and the running of the car are effected by an electric motor except in circumstances where the battery charge is depleted, in which case the normal cruising and higher speeds are then obtained using a gasoline or internal combustion engine which can be cut in either automatically or at will. The electric motor is powered by storage batteries that can be recharged from a generator driven by the internal combustion engine, or else from house current. One pair of wheels of the vehicle is powered by the internal combustion engine through a magnetic clutch and differential. The other set of wheels is powered through an infinitely variable mechanical transmission comprising cone pulleys or cone chains whose ratio is power-controlled in accordance with the driver&#39;s desires or else with the speed of the vehicle. The infinitely variable transmission has a very high speed-ratio for starting the vehicle, after which the speed ratio reduces either automatically or under the driver&#39;s direction as the vehicle gains speed. In cases where the battery charge is, say, below one half of the fully-charged condition, the car upon attainment of a predetermined cruising speed will discontinue driving of the electric powered means, and this can be replaced by the internal combustion engine. Thus, with the arrangement disclosed, city driving can be characterized by the use of electrical power whereby air pollution is nil. Only minimal polluting exhaust occurs for higher speed driving, as along highways and the like, in those cases wherein the battery charge is below one half.  
   U.S. Pat. No. 4,119,862 
   Inventor: Choichi Gocho 
   Issued: Oct. 10, 1978 
   An electric motor car wherein an electric motor for driving the car is energized by a fuel engine driven generator and a battery is connected in parallel with the motor to be float charged by the generator. Control apparatus is provided for always maintaining the output of the generator at a constant value irrespective of variations in the load and for supplying the varying component of the load from the battery.  
   U.S. Pat. No. 4,498,551 
   Inventor: Dominic S. Arbisi 
   Issued: Feb. 12, 1985 
   A battery-driven car which has an electrical system including a minimum number of electric storage batteries as the power source, a high-voltage converter with a high-voltage capacitor bank for driving a direct current impulse motor combined with a generator for supplying current to motor/generator sets respectively integrated with the wheels of the vehicle to drive the same or for recharging the batteries in accordance with a microprocessor control system, the wheel-actuated generators providing recharging current for the batteries whenever the motor component is not being energized and in addition, said electrical system also including an air-driven turbine generator component for recharging the batteries when the vehicle reaches a predetermined speed in accordance with the microprocessor controls.  
   U.S. Pat. No. 4,935,689 
   Inventor: Tetsuzo Fujikawa 
   Issued: Jun. 19, 1990 
   A vehicle mounted engine generator system is disclosed for supplying electricity to external electrical appliances and equipment used inside a camping car or outdoors in the camping site, which comprises a secondary water-cooled internal combustion engine of relatively small size and an engine generator electrically connected to the engine. The secondary engine has its cooling jacket connected to a cooling line supplying it with cooling water for engine cooling. Also, the cooling line is connected to a radiator connected to the main internal combustion engine of water-cooled type so that the heated cooling water through the secondary engine is cooled by the same radiator as for the main engine. Also, the secondary engine is electrically connected to the battery for the main engine in such a manner that the battery can be recharged from the secondary engine as well.  
   U.S. Pat. No. 5,083,077 
   Inventor: Alan Wallace et al. 
   Issued: Jan. 21, 1992 
   An onboard power generation system for use on board a vehicle, such as a passenger car, includes a brushless doubly-fed generator. The generator has a rotor with rotor conductors and a stator with stator windings, the stator windings comprising first and second polyphase stator systems. The generator rotor is mechanically coupled to and driven by the vehicle engine with a driving force to produce an AC power output from the first polyphase stator system. The generation system has a rectifier which receives and rectifies the generator first polyphase stator system AC power output into DC power for delivery to a DC bus of the generator power system. A sensor senses a parameter of the AC power output received by the rectifier and produces a sensor signal in response thereto. A converter receives the sensor signal, and in response thereto, converts power received from an excitation power source into excitation power for the generator second polyphase stator system. The converter operates to produce a controlled flow of AC power output from the first polyphase stator system of the generator regardless of variations of the driving force of the vehicle engine. A method is also provided of generating DC power on board a vehicle using the above-described generation system.  
   U.S. Pat. No. 5,215,156 
   Inventor: Nathan Stulbach et al. 
   Issued: Jun. 1, 1993 
   A vehicle having an electro-generating system that includes a dynamoelectric generator. The shaft of the dynamoelectric generator is linked directly or indirectly with the rotating axle of the road wheels of the vehicle, preferably via a mechanical turns amplifier. The turns amplifier will multiply the rotation rate of the electro-generating system and increase the production capacity of electric power. The dynamoelectric generator can be utilized to recharge a storage battery driving the vehicle while the car is in motion, especially automatically when the vehicle is going down hill. The vehicle&#39;s electric motor can be driven directly from a dynamoelectric generator in place of a storage battery after the vehicle is moving. In railroad cars (freight and passenger) the electro-generating system can be utilized to charge storage batteries, with their electricity utilized for other electro-energy requirements.  
   U.S. Pat. No. 5,224,563 
   Inventor: Souichi Iizuka 
   Issued: Jul. 6, 1993 
   There is disclosed an energy regenerating mechanism of an vehicle, particularly to that adapted for an electric car. The energy regenerating mechanism is characterized in that a plurality of generators are provided so that the kinetic energy generated when the engine idles and the vehicle continues running is converted into electric energy.  
   U.S. Pat. No. 5,230,402 
   Inventor: Clark et al. 
   Issued: Jul. 27, 1993 
   An electric car is powered from a primary power source in the form of a three-phase parallel resonant electric motor operated at a constant speed (the speed of resonance). The electric motor is provided with operating power from an inverter coupled to storage batteries in the electric car. The motor drives a main hydraulic pump, which is hydraulically connected with a pair of variable displacement drive motors, each connected to different drive wheels on opposite sides of the vehicle. The fluid flow through the pump is varied from 0% to 100% to control the speed of operation of the drive motors connected to the drive wheels of the vehicle.  
   U.S. Pat. No. 5,541,494 
   Inventor: Teruo Sannomiya 
   Issued: Jul. 30, 1996 
   A motor control system for an electric car includes a detector for determining when an input voltage or an output voltage of a DC power circuit falls below a respective predetermined value to operate a switching signal stopper circuit which interrupts or prevents the application of pulse width modulated (PWM) signals to current control elements switching DC currents to generate three-phase AC currents in coils of the motor. The detection of an abnormal drop in the input voltage or the output voltage indicates a malfunction causing excessive currents which could burn out the control elements and/or the power circuit in the absence of prompt interruption of the PWM switching signals.  
   U.S. Pat. No. 5,842,534 
   Inventor: Andrew A. Frank 
   Issued: Dec. 1, 1998 
   A charge depletion method and apparatus for operating the electric motor and small auxiliary power unit, such as an internal combustion engine, in a hybrid electric vehicle (HEV) separately or together depending upon the driving conditions. Operation of the electric motor and auxiliary power unit are coordinated so that the vehicle operates as zero emissions vehicle (ZEV) or electric car at all speeds below a highway cruising threshold, unless the depth of discharge of the batteries exceeds a charge threshold in which case the vehicle operates in an HEV mode. Further, the vehicle operates in an HEV mode at speeds above the cruising threshold. The batteries are depleted during operation and are not charged by the auxiliary power unit, except during emergencies in which case the batteries are only charged enough to provide a performance enhancement to the small auxiliary power unit.  
   U.S. Pat. No. 5,858,568 
   Inventor: Michael S. Hsu et al. 
   Issued: Jan. 12, 1999 
   A power supply system for enhancing the economic viability of different modes of transportation that incorporate fuel cells to generate electricity. For example, the power supply system of the present invention provides for the off-board use of the electric power generated by an on-board power plant, such as a fuel cell, of a mobile vehicle power system, such as an electric car. Off-board use, or use remote from the vehicle, of the electrical power includes the delivery of power to a remote site. Off-board stations are provided for delivery of fuel to the vehicle and/or for receiving the electrical power generated by the fuel cell. The off-board station and the vehicle are appropriately equipped for quick and easy interconnection such that electrical power is drawn from the fuel cell for off-board use.  
   European Patent Number EP 1 085 644 A2 
   Inventor: Kim Houng Joong et al. 
   Issued: Mar. 21, 2001 
   The invention relates to a hybrid drive type vehicle having a permanent magnet type synchronous motor which can provide high torque characteristics in low revolution speed range of the engine and high power generation characteristics at high revolution speed range of the engine. The hybrid drive type vehicle includes an electric rotary machine being formed with a stator and a rotor. A field magnet of the rotor includes a first field magnet and a second field magnet. The first and second field magnets oppose with a magnetic pole of the stator and have a mechanism for varying a phase of a magnetic pole resulting from a combination of the first and second field magnets relative to the magnetic pole of the first field magnet depending upon direction of a torque of the rotor.  
   SUMMARY OF THE PRESENT INVENTION 
   The present invention relates generally to electric generators for vehicles and, more specifically, to an axle-driven electric generator for recharging electric batteries used for powering an electric vehicle while vehicle is in use in order to extend the cruising range between required charges from an external electrical source. 
   A primary object of the present invention is to provide a dual engine axle-driven generator system for electric vehicles that will effectively increase the distance such a vehicle could travel between charges from an external source. 
   Another object of the present invention is to provide a dual motor axle-driven generator system for electric vehicles that will have at least two battery banks for supplying power to the vehicle wherein one battery bank will power the vehicle while the other battery bank is recharging. 
   Yet another object of the present invention is to provide a dual motor axle-driven generator system for electric vehicles having a secondary motor powered by the charging battery bank to provide supplemental power to the vehicle during hard acceleration. 
   Still yet another object of the present invention is to provide a dual motor axle-driven generator system for electric vehicles that is environmentally friendly due to its  regenerative capabilities for converting kinetic energy produced by the connected axle to charge a battery bank thus minimizing the amount of external electricity required for operation and not requiring the use of an internal combustion engine to power the vehicle. 
   Another object of the present invention is to provide a dual motor axle-driven generator system for electric vehicles that is economical in cost to manufacture and operate. 
   Yet another object of the present invention is to provide a dual motor axle-driven generator system for electric vehicles that is simple and easy to use. 
   Additional objects of the present invention will appear as the description proceeds. 
   In the system of the present invention, a generator operates on the rotation of at least one connected axle. When forward motion of the vehicle is initiated, a decoupler engages the generator for charging one of two rechargeable battery banks. The battery banks are initially charged by an external power source prior to vehicular operation at which point a primary electric motor is powered by a first battery bank and a secondary battery bank powers a secondary electric motor. The secondary electric motor is only activated during hard acceleration. When the first battery bank is almost depleted, it receives a charge from the generator operating on a charge generated in response to the rotation of the axle as the vehicle travels forward. While the primary battery pack is  charging, the primary electric motor is powered by the secondary electric motor. The cruising range of the vehicle is thus increased since one battery bank powers the primary motor while the movement of the vehicle operates the generator which is constantly recharging the other battery bank except when it is necessary to power the secondary motor during hard acceleration. The secondary motor is activated once the tachometer reaches a predetermined RPM reading. 
   The present invention overcomes the shortcomings of the prior art by providing a dual motor axle-driven generator system for electric vehicles that relies exclusively on electrical power and has regenerative capabilities that permit the vehicle to extend the cruising range beyond that of conventional electric vehicle. Furthermore, a dual motor configuration overcomes the acceleration problems inherent in other electric vehicles. 
   To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the appended claims.  

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views. 
       FIG. 1  is an illustrative view of an electric vehicle equipped with the dual motor axle-driven generator system of the present invention climbing a steep embankment; 
       FIG. 2  is a rear view of the axle assembly of the electric vehicle equipped with the generator system of the present invention; 
       FIG. 3  is a cross sectional view of the connection between the axle assembly and the generator of the present invention when the generator is attached to the differential gear; 
       FIG. 4  is a top view of the axle assembly of an electric vehicle equipped with the generator of the present invention engaging the drive shaft; 
       FIG. 5  is a block diagram showing the mechanical and electrical connections of the components of the dual motor axle-driven generator system of the present invention;  
       FIG. 6  is a block diagram of the axle generator of the present invention adapted for use by a 4-wheel drive vehicle; 
       FIG. 7  is a flow diagram illustrating a vehicle operating on the primary and a secondary motor connected to the dual motor axle-driven generator system of the present invention when the secondary motor is activated under hard acceleration; and 
       FIG. 8  is flow diagrams illustrating a vehicle operating on one battery bank while the dual motor axle-driven generator system of the present invention charges a second battery bank. 
     The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawing, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawings, like reference characters designate the same or similar parts throughout the several views.  
     DESCRIPTION OF THE REFERENCED NUMERALS 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the Figures illustrate the dual motor axle-driven generator system of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures.
           10  dual motor axle-driven generator system     12  electric vehicle     14  steep embankment     16  road sign indicating a long range before refueling station     18  wheels     20  struts     22  upper control arm     24  lower control arm      26  axle     28  universal joint     30  differential housing     32  mounting brackets     34  generator     36  differential gear     38  generator gear     39  generator gear shaft     40  decoupler     42  drive shaft     44  drive shaft gear      45  transmission     46  bearing     47  first pair of recesses     48  primary motor     49  fourth recess     50  secondary motor     51  third recess     52  first battery     54  second battery     56  voltage regulator     58  accelerator      60  tachometer     62  tachometer sensor     64  secondary driving wheel     66  secondary differential     68  secondary drive shaft     70  first clutch component     72  second clutch component        

   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. For a definition of the complete scope of the invention, the reader is directed to the appended claims. 
   Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views,  FIGS. 1 through 8  illustrate the dual motor axle-driven generator system of the present invention generally by the numeral  10 . 
     FIG. 1  is an illustrative view of an electric vehicle  12  operating while equipped with the dual motor axle-driven generator system  10  of the present invention. The dual motor configuration provides a primary electric motor to drive the wheels of the vehicle  12  under normal use conditions and a secondary motor to selectively drive the wheels of the vehicle. When both motors are activated in unison, the extra power enables the electric vehicle  12  to perform maneuvers requiring additional acceleration such as passing another vehicle or surmounting a steep embankment  14 , as illustrated in  FIG. 1 . The illustrated vehicle  12  has the extra power necessary for accelerating up a steep embankment  14   because of the dual-motor configuration of the present invention. The secondary motor provides additional positive torque to the drive train, thus, propelling the vehicle up the embankment  14 . 
   A first battery bank powers the primary motor and a second battery bank powers the secondary motor. The generator  10  of the present invention charges the battery banks when they are not powering their respective motor. One such example would be when the vehicle  12  is coasting in a forward direction in which both batteries would receive a regenerative charge. The regenerative powers of the generator system  10  of the present invention allow the vehicle  12  to achieve increased cruising range before recharging at an external rechargeable battery bank. Thus, not only does the illustrated vehicle  12  have the extra power necessary for accelerating up a steep embankment  14  because of the dual-motor configuration, but additionally, the ability to advance an extended distance between recharging times for the batteries by external power sources. This is due to the regenerative powers of the generator system  10 . The additional power required for the climb does not exhaust the resources of the primary battery bank as the secondary battery bank is engaged to power the secondary motor and provide additional power when the acceleration of the vehicle reaches a predetermined value. The illustrated electric vehicle  12  can proceed to accelerate up the hill without hesitation, even though another service station is not for another 100 miles, as indicated by a road sign  16 , because the extra power necessary to surmount the steep embankment  14  is be provided by a secondary motor as opposed to completely draining the primary battery bank.  
     FIG. 2  is a rear view of an axle assembly equipped with the generator  34  of the present invention as seen in the direction of the arrow labeled with the numeral  2  in  FIG. 1 . A differential housing  30  is positioned between the rear wheels  18  of the vehicle  12 . The housing  30  is mounted to the chassis (not illustrated) by mounting brackets  32 . Both rear wheels  18  are connected to the vehicle by a strut  20 . The struts  20  are spring mounted for vertical suspension purposes. An upper support arm  22  and a lower support arm  24  are pivotally mounted to each strut  20 . The support arms  22  and  24  extend from the struts  20  to the differential housing  30  where the upper support arms  22  are pivotally connected to the upper near corner of the housing  30  and the lower support arms  24  are connected to the lower near corner of the housing  30 . The support arms  22  and  24  prevent horizontal and rotational movement of the struts  20  while allowing restricted vertical movement of the struts  20 . Each upper support arm  22  extends horizontally from each strut  20  to the nearest upper corner of a differential housing  30  and each lower support arm  24  extends horizontally from each strut  20  to the lower corner of the differential housing  30 . An axle  26  extends from each rear wheel  18  to the differential housing  30 . Each axle  26  has a universal joint  28  positioned on each end for connecting to a respective wheel and differential. The universal joint  28  allows for the axle  26  to pivot vertically about a horizontal pivot point at each universal joint  28  while additionally allowing the axle  26  to rotate about their longitudinal axis. The generator  34  is mounted atop the differential housing  30 . The differential housing  30  contains a gear train therein (not illustrated), for meshing with the axles  26  allowing the wheels  18  to turn at different speeds when the  vehicle  12  turns, thus preventing screeching its tires and excessive negative torques on a drive shaft. The use of a differential gear train is known in the art, however, in this embodiment the generator  34  has been adapted to connect with the gear train. 
   The rotation of rear wheels  18 , as indicated by the arrows identified by the letter A, creates a torque on the connected axles  26 . The axles  26  rotate in the corresponding direction to the wheel  18 , as indicated by the arrows identified by the letter B. The gear configuration within the differential housing  30  is connected to the generator  34 . When the vehicle moves in a forward direction, the rotational kinetic energy generated by the rotation of the wheels is transferred along the axles  26  carrying the rotation into the differential gear train and up into the generator  34  where the rotational kinetic energy is transferred to electric energy. 
     FIG. 3  is a cross sectional view of the connection between the axle assembly and the generator  34  of the present invention taken from with in the circle identified by the numeral  3  in  FIG. 2 . A differential housing  30  is rigidly mounted to the vehicle chassis by a plurality of brackets  32 . Within the differential housing  30  is the differential gear  36 . The differential housing  30  has four recesses lined with a bearing. First and Second recesses  47  are positioned on opposite sides of the housing for securing the differential gear  36 , allowing respective universal joints  28  to remain outside the differential housing  30  and facing the respective wheels  18 . An axle  26  extends from each universal joint  28  to a respective wheel, thus connecting the wheels  18  to the differential gear  36  as can be  seen from  FIG. 2 . 
   A third recess  51  as can be seen in  FIG. 4  is positioned opposite of view illustrated in  FIG. 3 . A drive shaft (not illustrated) extends therethrough and will be further discussed with respect to  FIG. 4 . 
   A fourth recess  49  is positioned atop the differential housing  30  for securing a generator gear  38  allowing the generating gear mesh with the differential gear  36  within the differential housing  30 . The shaft  39  of the generator gear  38  extends through the recess  49  and it is attached to a decoupler  40 . The decoupler  40  engages the shaft  39  when rotated in a first direction and disengages when rotated in a second direction. 
   A driving force may be applied to the drive shaft meshes with the differential gear  36  to drive the axles  26 . The driving of the axels  26  cause thus rotating the respective wheels  18  connected thereto rotate and thereby propelling the vehicle  12 . When a driving force is not applied to the drive shaft, the vehicle coast until braking is applied. When coasting, the kinetic energy of the wheels  18  rotates the differential gear  36 . The differential gear  36  rotates in a direction indicated by directional arrow identified by the letter C. The differential arrow C correspond with the direction of the arrow B indicating a direction of rotation of the axles  26 . A generator gear  38  also meshes with the differential gear  36 . The rotation of the differential gear  36  as indicated by line C causes the rotation of the meshing generator gear  38 , as indicated by directional arrow D. When rotating in  direction D, the generator gear  38  engages the decoupler  40 , thus, transferring the rotational kinetic energy to the generator  34  for conversion into electric energy. If rotation is reversed from that shown by directional arrow D by moving the vehicle  12  in a reversed direction, the decoupler  40  disengages the generator gear  38 , thus preventing reverse rotation of the generator  34 . 
     FIG. 4  is a top view of the axle assembly of an electric vehicle  12  equipped with the dual motor axle-driven generator system  10  of the present invention. As can be seen from this figure, the generator  34  is attached to the drive shaft  42  as opposed to the differential gear  36  as seen in  FIG. 3 . As described with respect to in  FIG. 1 , a differential housing  30  is rigidly mounted to the vehicle chassis by a plurality of brackets  32  the differential housing  30 ; and the upper control arms  22  are connected between the differential housing  30  and the struts  20 . This connection secures the struts  20 . The differential housing  30  in this Figure, however, has three, recesses as opposed to four recesses shown in  FIG. 3 , lined with a bearing. Two of the recesses  47  are positioned on opposite sides for securing the universal joints  28  for connecting the axles  26 , as described in Figure Ito the differential housing  30 . The third recess  51  secures a drive shaft  42 . The drive shaft  42  is a cylindrical rod for providing a driving force to the differential gear  36 . The drive shaft  42  extends through the third recess  51 . Therein, it is connected to the drive shaft gear  44  for meshing with the differential gear  36 . The opposite end of the shaft  42  furthest from the differential housing  30  is secured by a bearing  46 . The bearing  46  is rigidly mounted to the chassis of the vehicle  12  by brackets  32 . A primary motor  48  and a  secondary motor  50  are mounted to the drive shaft  42  at predetermined locations between the bearing  46  and the differential housing  30  for selectively providing a driving force to the drive shaft  42 . Each motor is rigidly mounted to the chassis of the vehicle by brackets  32 . Each motor is electrically powered by at least one of a plurality of battery banks. When power is provided by at least one of the battery banks the activated motor applies a torque to the drive shaft  42  thus rotating the drive shaft gear  44 . Rotation of the drive shaft gear  44  rotates the differential gear  36 , which is connected to the axles  26  of the wheels  18 . The differential gear  36  allows the axles  26  to rotate its respective wheel  18  at individual rates for accommodating turns without placing excessive negative torques on the drive shaft  42 . When the vehicle moves in a forward direction the battery bank of the motor not providing a driving force is provided regenerative electric energy by the generator  34 . The generator  34  is mounted to the chassis by brackets  32  at a predetermined position alongside the drive shaft  42 . Extending from the generator is a shaft  39 , which connects the generator  34  to a generator gear  38 . The generator gear  38  meshes with a decoupler  40 . The decoupler  40  is mounted to the perimeter of the drive shaft  42 . Rotation of the drive shaft  42  in a direction corresponding to forward movement engages the decoupler and generator gear  38  thus, driving the generator  34 . The decoupler  40  may contain a flywheel to allow the generator to continue spinning and thereby charge the battery banks even when the vehicle is stopped. When the drive shaft reverses rotational direction, the decoupler  40  disengages the generator gear  38 . When driven, the generator provides regenerative electric energy to an unused or dangerously low battery bank.  
     FIG. 5  is a block diagram of the axle generator of the present invention. Mechanical connections are illustrated as double line and electrical connections are illustrated as single lines. As can be seen from this figure the primary motor  48  and a secondary motor  50  are mechanically connected to the drive shaft  42  for providing a torque for rotating the drive shaft  42 . A transmission  45  is mechanically connected between the secondary motor and the differential  36  to the drive shaft  42  for providing a mechanical advantage by increasing or decreasing the revolution speed of the drive shaft  42 . The drive shaft  42  is mechanically connected to a differential  36 . The differential  36  drives the designated mechanically connected wheels  18  when the motors  48  and  50  provide a driving force to the drive shaft  42 . The transmission  45  is mechanically connected to the drive shaft  42  for providing a mechanical advantage by increasing or decreasing the revolution speed of the drive shaft  42 . A decoupler  40  is mechanically connected to the differential  36  for driving the generator when the decoupler  40  is provided a positive net torque. The decoupler  40  disengages the generator  34  when it receives a negative net torque. When driven, the generator  34  converts the rotational kinetic energy into electric energy. The generator  34  is electrically connected to the first and second battery bank  52  and  54  respectively, for providing a regulated voltage for recharging the respective battery banks. The battery banks  52  and  54  are wired to a voltage regulator  56 . The voltage regulator  56  is controlled by an accelerator  58  connected thereto. The accelerator  58  receives user input controls for signaling the voltage regulator  56  to control the voltage level to be dispensed to the primary motor  48  connected thereto. The voltage regulator  56  is preprogrammed to provide the designated voltage to the primary motor  48  from the primary battery bank  52 .  If the primary battery bank  52  reaches a predetermined charge indicating a weak charge, the regulator  56  will then begin to draw electrical current from the secondary battery  54 . A tachometer  60  is also connected to the voltage regulator  56 . The tachometer  60  is connected to a sensor  62 , which is mechanically mounted to the drive shaft  42 . The sensor  62  detects the revolutions per minute made by the drive shaft  42 . The voltage regulator  56  is preprogrammed to provide the connected tachometer  60  a regulated voltage from the secondary battery bank  54  when the tachometer reads a predetermined value of revolutions per minute. The secondary motor  50  is also connected to the tachometer  60 . When the tachometer  60  receives the voltage from the secondary battery bank  54 , the secondary motor  50  is provided the voltage via its connection to the tachometer  60 , thus, the secondary motor  50  is activated for providing additional driving force to the drive shaft  42 . 
     FIG. 6  is a block diagram of the dual motor axle-driven generator system  10  of the present invention adapted for use by a 4-wheel drive vehicle. The illustrated embodiment of the generator system  10  is representative of that described in  FIG. 4 , wherein the generator is mechanically connected to the drive shaft  42  as opposed to the differential  36 . The decoupler  40  is mechanically connected to the drive shaft  40 . A generator  34  is mechanically connected to the decoupler  40  in a manner by which a positive torque on the drive shaft  42 , as associated with the forward movement of the vehicle, drives the generator  34 , and a negative net torque disengages the generator  34  from the decoupler  40 . The remaining components and functionality thereof is identical to that described in  FIG. 5 , however there is the addition of an additional set of driving wheel   64 . 
   The secondary set of driving wheels  64  are mechanically connected to a secondary differential  66 . The secondary differential  66  operates in a similar fashion to the first differential  36 . The secondary differential  66  is mechanically connected to a secondary drive shaft  68 . The secondary drive shaft is selectively connected to the first drive shaft  42  through first and second clutch components  70  and  72 . The first clutch component  70  is mechanically connected to the first drive shaft  42  and the second clutch component  72  is connected to the second drive shaft  68 . The two shafts  42  and  68  are connected at the clutch components positioned between the transmission  45  and the differential  36  so that both shafts  42  and  68  rotate at the same speed. When activating four-wheel drive, the first clutch component  70  engages the second clutch component  72  so that the first shafts  42  drives the second shaft  68 . Thus, the secondary differentia  66  is driven in unison by the, drive shaft first and second. If additional driving force is required, the secondary motor  50  can be selectively activated while engaged in four wheel drive. 
     FIG. 7  is a block diagram of the dual motor axle-driven generator system  10  of the present invention showing the activation of the secondary motor  50  due to a hard acceleration. Similarly to  FIG. 2 , the generator  34  is mechanically connected to the drive differential  36  as opposed to the drive shaft  42 . Mechanical connections are shown with double line and electrical connections are shown using as single lines.  
   A primary motor  48  and a secondary motor  50  are mechanically connected to the drive shaft  42  for providing a torque for rotating the drive shaft  42 . A transmission  45  is mechanically connected to the drive shaft between the secondary motor and the differential  36  for providing a mechanical advantage by increasing or decreasing the revolution speed of the drive shaft  42 . The drive shaft  42  is mechanically connected to the differential  36 . The differential  36  drives the designated wheels  18  when the motors  48  and  50  provide a driving force to the drive shaft  42 . A decoupler  40  is mechanically connected to the differential  36  for driving the generator when the decoupler  40  is provided a positive net torque. The decoupler  40  disengages the generator  34  when it receives a negative net torque. When driven, the generator  34  converts the rotational kinetic energy into electric energy. The generator  34  is electrically connected to the first and second battery bank  52  and  54 , respectively, for providing a regulated voltage for recharging the respective battery banks. The battery banks  52  and  54  are wired to a voltage regulator  56 . The voltage regulator  56  is controlled by an accelerator  58  wired thereto. 
   The accelerator  58  receives user input controls for signaling the voltage regulator  56  to control the voltage level to be dispensed to the primary motor  48  wired thereto. The voltage regulator  56  is preprogrammed to provide the designated voltage to the primary motor  48  from the primary battery bank  52 . If the primary battery bank  52  reaches a predetermined charge indicating a weak charge, the regulator  56  begins to draw electrical current from the secondary battery  54 . A tachometer  60  is also wired to the voltage regulator  56 . The tachometer  60  is wired to a sensor  62 , which is mechanically mounted to  the drive shaft  42 . When the drive shaft  42  is driven to a predetermined RPM, as indicated by the tachometer  60 , the secondary motor  50  is activated. Activating the secondary motor  50  provides an additional driving force to the drive shaft  42 . Additionally, the work load is then shared by both the primary and secondary battery bank  52  and  54 . The secondary motor  54  remains activated until the accelerator is released or eased and the tachometer reading decreases to an RPM less than the predetermined. While both motors  48  and  50  are operative, the generator  34  is disengaged from the drive shaft  42  by the decoupler  40 . This directs the produced kinetic energy entirely to the wheels without any energy being supplied to the generator  34 . Upon decreasing the RMP of the vehicle below the predetermined RPM, the secondary battery  54  will receive a regenerative charge from the generator  34  while the vehicle is moving in a forward direction. 
     FIG. 8  is a block diagram of the dual motor axle-driven generator system  10  of the present invention showing the charging of the primary battery bank  52  while the vehicle is running off of the energy provided by the secondary battery bank  54 . If the continued use of the vehicle depletes the energy of the primary battery pack  52 , the voltage regulator disconnects from the primary battery bank  52 , as illustrated with the dashed connecting line, and initiates drawing energy from the secondary battery  54  while the primary battery  52  receives a regenerative charge from the generator  34 . The generator  34  produces the regenerative charge by converting the rotational kinetic energy provided by the drive shaft  42  into electric energy. The generator  34  is provided rotational kinetic energy from the drives haft  42  while the drive shaft is driven by the secondary motor  54 , or  while coasting without the use of an internal driving force. The generator  34  may incorporate a flywheel so that the generator  34  will continue to provide a regenerative charge to the primary battery bank  52  while the vehicle is at rest. The regenerative capabilities of the generator  34  allow for prolonged usage of the electric vehicle before necessitating an external electric source to charge the battery banks  52  and  54 . 
   In operation, a primary motor drives a drive train for propelling an electric vehicle. The primary motor is provided electric energy from a primary energy bank. A secondary motor, powered by a secondary battery bank, may be selectively activated to provide additional driving force for rotating the drive shaft and thereby propelling the electric vehicle. 
   Activation of the secondary motor may be automatically achieved by connecting the secondary motor to a tachometer and a voltage supply, wherein the secondary motor is provided electric energy only when a predetermined RPM is reached. Alternatively, the secondary motor may be activated by selectively pressing a button, such as an on/off switch when an operator of the electric vehicle may deem extra power necessary. 
   Having at least two battery banks allows for a reserve energy supply to be used when the primary battery bank is depleted. Thus, the electric powered vehicle is capable of an increased cruising range before requiring an external electric source to recharge the battery banks. Even further, the drive shaft is coupled to a generator. The generator is  connected to all battery banks, providing a regenerative charge to any battery not providing the motors with energy. By coupling the generator to the drive shaft, the generator is driven whether the motors are operative or if the vehicle is just coasting down a hill. The generator converts the rotational kinetic energy of the drive shaft into electric energy for charging the battery banks. If a hard acceleration is necessary, as described earlier, the generator is disengaged from the drive shaft and thus does to not absorb any kinetic energy from the drive shaft while directing the torque produced by the combined motors to the wheels of the vehicle. 
   While the vehicle is at cruising speeds and being driven by the primary motor, the secondary motor is inoperative. Therefore, the primary battery source provides the primary motor with electric energy. At this time the generator is coupled to the drive shaft generates an electric charge and charges the inoperative battery. After a prolonged duration of primary motor use, the primary battery bank may become nearly depleted of energy. In such a circumstance, the primary battery is disconnected by the voltage regulator from providing energy to the primary motor and the secondary battery bank is connected thereto for providing electric energy. While the vehicle is driven by the leave in motor with the secondary battery bank&#39;s resources, the primary battery receives a regenerative charge from the generator coupled to the drive shaft, thus, enabling the vehicle an extended cruising range before necessitating an external electric charge. 
   By using a drive shaft for transferring the driving force of the motors to the wheels,  the vehicle may be easily adapted to a 4-wheel drive vehicle without requiring additional motors and battery banks by equipping the second set of wheels with a differential and a drive shaft. The secondary drives shaft is selectively coupled to the first drive shaft for creating a driving force for driving. 
   at all four wheels. 
   From the above description it can be seen that the dual motor axle-driven generator system of the present invention is able to overcome the shortcomings of prior art devices by providing generating system which is able to provide an electric vehicle with increased cruising range by charging one rechargeable battery bank while another is in use. Additionally, the present invention enables the use of a secondary motor to be used in conjunction with the primary motor at times where additional driving force may be necessary. Further, the dual motor axel driven generator is easily modified to equip a 4-wheel drive vehicle. And yet further, the generator is capable of producing a regenerative charge while the vehicle is at rest by incorporating a flywheel into the generator. And yet further, the generator is capable of being attached directly to the differential or the drive shaft of the vehicle. Furthermore, the system of the present invention is simple and easy to use and economical to manufacture. 
   It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above.  
   While certain novel features of this invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.