Abstract:
A vehicle includes an independent suspension for supporting at least first and second wheel ends relative to the vehicle, and a transmission having an input shaft and an auxiliary power output shaft and a respective drive shaft coupled to each wheel end, and an electrical power source, and a variable speed electric motor electrically coupled to the electrical power source and mechanically coupled to the input shaft, where the transmission is configured to apply power from the electric motor to the auxiliary power output shaft dependently or independently of the application of power from the electric motor to the drive shafts.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. 120 of U.S. patent application Ser. No. 10/952,547, having a filing date of Sep. 28, 2004, titled “Power Takeoff For An Electric Vehicle,” the complete disclosure of which is hereby incorporated by reference. 
     FIELD 
     The present invention relates generally to electric vehicles, and more particularly to a power take-off coupled to an axle module for an electric vehicle. 
     BACKGROUND 
     In a conventional electric vehicle, a prime mover such as a diesel engine, is used to drive an electric generator or alternator which supplies electric current to a plurality of electric motors. The electric motors typically are coupled to wheel sets, in line, on the vehicle. The vehicles that utilize this type of hybrid electric motors are typically railroad locomotives. 
     The prime mover drives the generator/alternator that typically produces an AC current that is then fully rectified with resulting DC current and voltage being distributed to current converters coupled to the traction motors. Such systems are highly integrated with each of the components typically designed and manufactured to operate with the other components in the overall system. In other words, “off the shelf” components are not readily adaptable for use in the initial design or ongoing maintenance of such vehicles. Further, such vehicles have multiple components associated with the change of AC to DC to AC power. Maintenance of such systems is expensive since specific components must be used. 
     In the use of hybrid drives for such vehicles, it is often necessary to add support systems that require a source of power to operate. Typically, these systems are centrally mounted on the vehicle and require the routing of specialized, pressurized, conduits to specific points around the vehicle. Conventional sources of auxiliary power are typically an internal combustion engine operated generator or a motor generator set. Such additional components and equipment add cost to the vehicle and take up space on the vehicle. 
     Thus there is a need for a power take-off for a vehicle that does not require an additional engine. There is a further need for a method to provide power to an auxiliary apparatus mounted on a vehicle utilizing the traction motor of the vehicle. 
     SUMMARY 
     According to one embodiment, a vehicle includes an independent suspension for supporting at least first and second wheel ends relative to the vehicle, and a transmission having an input shaft and an auxiliary power output shaft and a respective drive shaft coupled to each wheel end, and an electrical power source, and a variable speed electric motor electrically coupled to the electrical power source and mechanically coupled to the input shaft, where the transmission is configured to apply power from the electric motor to the auxiliary power output shaft dependently or independently of the application of power from the electric motor to the drive shafts. 
     According to another embodiment, a vehicle with a power takeoff includes an internal combustion engine and at least one electric drive axle module. The axle module includes a housing, and a main output shaft defining a first end and a second end, and a first wheel end assembly coupled to the first end and independently suspended relative to the vehicle, and a second wheel end assembly coupled to the second end and independently suspended relative to the vehicle, and a variable speed electric motor, and a transmission disposed within the housing and including a neutral state, the transmission coupled to the electric motor and engageable with the main output shaft to drive the wheel end assemblies, and an auxiliary output shaft coupled to the transmission, wherein when the transmission is in the neutral state, the auxiliary output shaft will operate at a speed independent of a speed of the wheel end assemblies and dependant on the electric motor speed and when the transmission is operably engaged in other than the neutral state, the auxiliary output shaft will operate at a speed related to both electric motor speed and the speed of the wheel end assemblies. 
     According to a further embodiment, a vehicle with a power takeoff includes an electric power source and at least one electric drive axle module. The axle module includes a housing, and an output shaft, and a first and second wheel end assemblies coupled to the output shaft and independently suspended relative to the vehicle, and a variable speed electric motor, and a transmission having a neutral state, the transmission coupled to the electric motor and engageable with the output shaft to drive the wheel end assemblies, and an auxiliary output shaft coupled to the transmission and operable at a first speed independent of the wheel end assemblies and dependant on the electric motor speed when the transmission is in the neutral state, and operable at a second speed related to electric motor speed and wheel end assembly speed when the transmission is engaged in another state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an electric vehicle according to an exemplary embodiment. 
         FIG. 2  is a partial perspective view of an exemplary embodiment of a vehicle including a self-contained axle module coupled to a vehicle support structure of the vehicle. 
         FIG. 3  is a cross section of a power take off coupled to a transmission mounted in a housing of an axle module and coupled to an electric motor of a hybrid vehicle. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of an electric vehicle  10  according to an exemplary embodiment. An electric vehicle is a vehicle that uses electricity in some form or another to provide all or part of the propulsion power of the vehicle. This electricity can come from a variety of sources, such as stored energy devices relying on chemical conversions (batteries), stored electrical charge devices (capacitors), stored energy devices relying on mechanical stored energy (e.g. flywheels, pressure accumulators), and energy conversion products. A hybrid electric vehicle is an electric vehicle that uses more than one sources of energy, such as one of the electrical energy storage devices mentioned above and another source, such as an internal combustion engine. By having more than one source of energy some optimizations in the design can allow for more efficient power production, thus one can use power from different sources to come up with a more efficient system for traction. The electric vehicle  10  can be used to implement electric vehicles in general and/or hybrid electric vehicles in particular. The electric vehicle  10  can implement a number of different vehicle types, such as a fire-fighting vehicle, military vehicle, snow blower vehicle, refuse handling vehicle, concrete mixing vehicle, etc. 
     In the illustrated embodiment, the electric vehicle  10  includes an engine  18 , a generator  20 , an electric power converter  24 , an energy storage device  26 , a plurality of electric motors  28 , a plurality of drive controllers  30 , a vehicle controller  34 . Electric vehicle  10  optionally includes an energy dissipation unit  32 . The generator  20 , the drive controllers  30 , and the electric power converter  24  are interconnected by a power bus  42 , such as an AC or DC power bus. Electric vehicle  10  is generally configured to use a combination of the engine  18  and the generator  20  to provide braking capability and to dissipate excess electrical power generated by the electric motors  28  during regenerative braking. 
     The engine  18  is preferably an internal combustion engine, such as a diesel engine configured to both provide mechanical power to the generator  20  and to receive mechanical power from generator such that may function as a mechanical engine brake or air compressor. The generator  20  is coupled to the engine  18  and may be configured to function as both generator configured to provide AC or DC power, and as a motor configured to receive electrical power and provide mechanical power to the engine  18 . 
     The electric power converter  24  is coupled to the energy storage device  26  and is configured to convert the electrical power generated by the generator  20 , or by the electric motors  28  during regenerative braking, to the energy mode required by the energy storage device  26 . For example, according to an exemplary embodiment, the electric power converter is configured to convert AC power generated by the generator  20  to DC power and transfer such converted power to the storage device  26 . The electric power converter  24  may also convert the energy stored in the energy storage device  26  back to the energy mode of generator  20  to augment and supplement the power generated by generator  20  over the power bus  42 . The energy storage device  26  may be electric capacitors, electrochemical capacitors or “ultracapacitors,” storage batteries, a flywheel, or hydraulic accumulators. 
     The electric motors  28  are appropriately sized electric motors, which may be AC or DC electric motors. The electric motors  28  are configured to receive electrical power from the power bus  42  in order to provide a mechanical energy output to a wheel or axle. The electric motors  28  are also configured to receive mechanical energy from the wheel or axle during regenerative braking in order to generate electrical power onto the power bus  42 . 
     The drive controllers  30  are coupled to each electric motor  28  and are configured to control the operation of each electric motor  28 . More specifically, the drive controllers are configured to allow the electric motors  28  to either receive electrical power from the power bus  42  in order to provide a mechanical energy output to a wheel or axle, or to receive mechanical energy from the wheel or axle during regenerative braking in order to generate electrical power onto the power bus  42 . 
     The vehicle controller  34  is coupled to the engine  18 , the generator  20 , the electric power converter  24 , and the drive controllers  30  via a data bus network  76 . The vehicle controller  34  is generally configured to control the operation of the engine  18 , the generator  20 , the electric power converter  24 , the energy storage device  26 , the plurality of electric motors  28 , and the plurality of drive controllers  30 . More specifically, the vehicle controller  34  is configured to assist in controlling the distribution of electrical power on the power bus so that the flow of electrical power from generator  20  and engine  18  may be reversed to provide braking capability, and so that excess electrical power generated by the electric motors  28  during regenerative braking is routed back to the generator  20  so that it may be dissipated through engine  18 . 
     The optional energy dissipation unit  32  is typically a resistive element through which electrical power generated by the electric motors  28  during regenerative braking is dissipated as heat if the electrical power exceeds the capacity of the energy storage device  26 . Preferably, electric vehicle  10  is configured such that the excess electrical power generated by the electric motors  28  during regenerative braking is sufficiently dissipated through engine  18  and generator  20 . 
     In conventional vehicles and particularly in vehicles having a hybrid electric drive, it is often necessary to add support systems such as pressurized lubrication and supplemental cooling systems. Such systems typically are centrally mounted on the vehicle and require the routing of pressurized oil lines throughout the vehicle. The elimination of or limiting the number of such specialized conduit lines being routed through the vehicle, results in additional space for other components and truck parts. A self-contained axle module  50  for the vehicle  10 , which typically includes a lubrication pump, the oil filter, and heat exchanger at the axle and integrating such components into a self-contained axle module minimizes the conduit routings mentioned above. 
     A self-contained axle module  50  can be mounted or coupled to the vehicle  10  support structure  12  at any convenient position determined by the manufacturer or user of the vehicle  10 . Also, because of the modular configuration, a self-contained axle module  50  can be easily removed and replaced for maintenance or repairs. The self-contained axle module  50  only has to be coupled to the source for electrical power such as the principal power unit and generator  18 ,  20  and the electric AC power bus  42 . It should be understood that other sources of power, as described above, can be coupled to the self-contained axle module  50  to provide the necessary electrical power to operate the electric motor  28 , as described below. In addition to coupling electric power to the self-contained axle module  50 , a control signal, through a data bus  76  network provides the necessary control and feedback signals for operation of the axle. It is also contemplated that supplemental cooling may be required because of the environment or operating conditions of the self-contained axle module  50  and therefore supplemental cooling source can also be coupled to the axle. 
     The housing  56  can be composed of any suitable material, such as iron, steel, or aluminum and can be cast and machined as designed by the manufacturer. The housing  56  includes a sump portion in the lowest area of the housing  56 . The housing  56  in addition to the components described below also houses a transmission  58  which transmits force from the electric motor  28  to the output shaft  60  and to a power take-off  88 . The transmission  58  may include several types of gears such as planetary gears, sprocket gears, bevel gears or the like with selected gear ratios as determined by the manufacturer and operator of the vehicle  10 . 
     The power take-off  88  includes a power take-off (PTO) housing  74  mounted on the housing  56  and coupled to the transmission  58  and an auxiliary apparatus  75 , such as a tool  77  (See  FIG. 3 .). The transmission  58  includes a primary drive gear  90  which is coupled to the motor drive gear  91 . The motor drive gear  91  transmits rotational power from the electric motor  28 . The primary drive gear  90  is coupled to the PTO gear train  100  and to the bevel gear differential assembly  65 . The transmission  58  is in a neutral state when a secondary reduction planetary annulus  96  is moved to a neutral position such that it is not coupled to the primary drive gear  90 . When the secondary reduction planetary annulus  96  is in the neutral position, the tool  77  will operate at a speed other than the speed of the vehicle. In other words, it will operate at the speed proportional to the speed of the electric motor  28 . When the secondary reduction planetary annulus  96  is moved to a position other than the neutral position, for example, when it is coupled to the primary drive gear  90 , the subsystem apparatus  75  will operate at a speed related to both the electric motor  28  speed and the wheel speed since it is coupled to the output shaft  60  of the axle module  50  of the vehicle  10 . The secondary reduction planetary annular  96  can be moved by an actuator, for example, a fluid cylinder (pneumatic or hydraulic) or an electric apparatus, such as a solenoid. 
     The transmission  58  also includes a secondary reduction planetary carrier  95 , a secondary reduction planetary planet gear  97  and a secondary reduction planetary sun gear  98 . It should be understood that other types of gearing configurations are contemplated for the transmission  58 . It should also be understood that the housing  56  and the power take-off housing  74  can be integrally formed to house both the power take-off gear train  100  and the transmission  58 . 
     The tool  77  can be any type of tool that requires mechanical power transmission, for example, a hydraulic pump  78  or a drive shaft, a pulley for a belt drive or similar apparatus can be coupled to the power take-off  88 . 
     It should also be understood that the transmission  58  can be geared for at least two speeds, however, any other number of gear ratios can be utilized to obtain any number of appropriate and convenient speeds for purposes of powering the power takeoff  88  (also referred to as a subsystem power source). 
     A method for providing power to a subsystem apparatus, such as a tool  77  is accomplished by mounting a power take-off  88  on a vehicle utilizing an electric motor  28  of the vehicle  10 . The electric motor  28  is coupled to an axle module  50  to transmit power to a vehicle wheel  14 . The method includes the steps of providing a power take-off (PTO) apparatus  88  having a PTO gear train  100 . Coupling the PTO gear train  100  to the traction motor  28 . Providing a planetary annulus gear  96  and coupling the planetary annulus gear  96  to the axle  50  with the planetary annulus gear  96  configured to move between a first position and a second position wherein in the first position, the PTO  88  will move at a speed related to the speed of the vehicle  10  and in the second position, the PTO  88  will move at a speed different from the speed of the vehicle  10 . The PTO  88  is always driven as a function of the electric motor  28  speed with the proviso that the PTO  88  speed may be related to the vehicle speed. 
     Control of the secondary reduction planetary annulus  96  is maintained by a fluid cylinder such as an air cylinder. It is also contemplated that a hydraulic cylinder or an electric apparatus, such as a solenoid can be utilized to move the secondary reduction planetary annulus  96  from a first position to a second position. 
     The PTO  88  can be used to drive the tool  77 , such as a pump  78 , and to power other equipment associated with the vehicle  10 . The PTO can be configured to operate at a speed related to the vehicle speed or to function at a speed other than the speed of the vehicle. The electric motor  28  provides power to the PTO through an associated PTO gear train  100  and can be coupled or uncoupled to the output shaft  60  of the self-contained axle module  50 . 
     The tool  77  such as a pump  78  can be utilized as a high volume water pump mounted on one of the axle modules  50  of the fire truck or airport crash truck. As an example, one of the axle modules  50  can be configured to move the vehicle  10  while another axle module  50  is configured to power the tool  77 , such as the water pump with the PTO  88 . 
     According to another alternative embodiment, the tool  77  powered by the power take-off apparatus  88  can be a power generator where the rotational mechanical energy of the electric motor  28  is converted into electrical energy to power additional auxiliary systems. Such arrangement can be configured as described above, where one axle module  50  is configured to move the vehicle  10  and another axle module  50  is configured to power the power generator either when the vehicle  10  is moving or while the vehicle  10  is stopped. 
     Several alternative embodiments have been described with reference to the power take-off apparatus  88 , however, the invention is not limited to the described embodiments. Any power take-off system that utilizes the rotational mechanical energy supplied by the electric motor  28  is within the scope and spirit of the invention. 
     It is also contemplated that the vehicle  10  may also include a plurality of independent suspension assemblies  86  which independently suspends one of the wheel end assemblies relative to the vehicle support structure  12 ′. 
     For purposes of this disclosure, the term “coupled” means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components or the two components and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 
     The foregoing description of embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to be limited to the precise forms disclosed, and modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to explain the principles of the subsystem power source and its practical application to enable one skilled in the art to utilize the various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the subsystem power source be defined by the claims appended hereto and their equivalents.