Abstract:
A hybrid power module efficiently delivers both hydraulic power and electric power. The hybrid power module may regenerate and store energy for later use. The module includes and engine and an electric motor for driving a hydraulic pump. The electric motor is operable as a starter motor for the engine and as an assist motor cooperating with the engine to power the hydraulic pump to improve dynamic response of the hydraulic pump. The module also includes an electric power source which may have an energy storage unit, and the electric motor may be operated as an electric generator providing electric energy to the energy storage unit.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of hybrid energy sources, and more particularly to a hybrid power system and module offering increased operating efficiencies and flexibility in power delivery between hydraulic output and electric output over varying loads. 
       BACKGROUND OF THE INVENTION 
       [0002]    The introduction of hybrid electric vehicles, such as the Toyota Prius and Chevrolet Volt, has provided numerous examples of hybrid power systems wherein an internal combustion engine and a battery-powered electric motor are used to power a load. These systems are designed to rely solely on the electric motor, solely on the internal combustion engine, or on a combination of output from the electric motor and the engine to drive the load, depending upon demand. These systems incorporate an electrical generator that may be driven by the internal combustion engine during cruising, and by the vehicle momentum during regenerative braking, to generate electricity used to recharge the battery. 
         [0003]    What is needed is a hybrid power system capable of delivering hydraulic power and electric power to drive a load. There is also a need for improved energy storage efficiency in the context of a hybrid power system. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the present invention, a hybrid power module is configured to efficiently deliver both hydraulic power and electric power. The hybrid power module may regenerate and store energy for later use. 
         [0005]    In one embodiment, the hybrid power module comprises an electric motor having a drive shaft, an engine having an output shaft, a hydraulic pump directly driven by the drive shaft, and an over-running clutch coupling the engine output shaft to the drive shaft, wherein the clutch passively allows the drive shaft to rotate at a greater rotational speed than the engine output shaft. The module further comprises an electric power source which may include an energy storage unit. The module also comprises a master controller connected to the electric motor, the engine, the hydraulic pump, and the electric power source. The electric motor is operable as a starter motor for the engine, and as an assist or boost motor helping the engine power the drive shaft to improve dynamic response of the hydraulic pump. When the module&#39;s duty cycle allows, the electric motor may be operated as an electric generator delivering electric energy to the energy storage unit. The energy storage unit may, for example, be configured as a hybrid battery/ultra-capacitor energy storage unit. 
         [0006]    In an alternative embodiment, the hybrid power module comprises a differential gear assembly that connects the engine output shaft, the electric motor drive shaft, and a driven shaft of the hydraulic pump to one another. 
         [0007]    The invention provides hybrid power delivery including hydraulic and electric power. The invention optionally provides fast response bi-directional energy storage to improve efficiencies when applied to high peak power to RMS power duty applications. The present invention may be utilized as a high efficiency power source for mobile autonomous systems (i.e. mobile robotics). Those skilled in the art will understand that the present invention has broad applicability beyond autonomous systems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0009]      FIG. 1  is schematic block diagram of a hybrid power module formed in accordance with a first embodiment of the present invention; 
           [0010]      FIG. 2  is a graph of hydraulic power output versus time for the hybrid power module shown in  FIG. 1 ; and 
           [0011]      FIG. 3  is schematic block diagram of a hybrid power module formed in accordance with a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  shows a hybrid power module  10  formed in accordance with a first embodiment of the present invention. Hybrid power module  10  is configured to deliver both hydraulic power  30  and electric power  32  for powering a load. In the illustrated embodiment, module  10  generally comprises an electric motor  12  having a drive shaft  14 , an engine  16  having an output shaft  18 , and a hydraulic pump  20  directly driven by drive shaft  14 . In an advantageous direct-drive configuration, electric motor  12  and pump  20  may share drive shaft  14  as a common shaft. Hybrid power module  10  also comprises an over-running (i.e. freewheeling) clutch  22  that directly couples engine output shaft  18  to drive shaft  14 , whereby engine  16  is operable for powering hydraulic pump  20  without energy conversion losses. Clutch  22  may be actuated by solenoid or other such means to additionally allow reverse rotational torque to flow in the freewheeling rotation direction. Module  10  of the first embodiment further comprises an electric power source  24 , and a master controller  26  connected to electric motor  12 , engine  16 , hydraulic pump  20 , and electric power source  24 . 
         [0013]    Electric motor  12  may be a motor designed for sensorless commutation, such as a brushless DC motor or a reluctance motor. In the embodiment of  FIG. 1 , electric motor  12  is operable as a starter motor for engine  16 , as a “boost” or assist motor for assisting engine  16  in powering hydraulic pump  20 , and as an electrical generator. When electric motor  12  is used as a starter motor for engine  16 , clutch  22  locks drive shaft  14  to engine output shaft  18 . When electric motor  12  is used as an assist motor for assisting engine  16 , clutch  22  passively allows drive shaft  14  to rotate at a greater rotational speed than engine output shaft  18 , whereby electric motor may be used to boost dynamic response of module  10  in delivering hydraulic power by way of hydraulic pump  20  as compared to dynamic response achievable from engine  16  alone. The benefit of using electric motor  12  as a booster motor is graphically shown in  FIG. 2 . As may be understood, this feature allows module  10  to manage hydraulic supply pressure with high bandwidth. Power flow associated with electric motor  12  may be bidirectional, whereby the electric motor may act as both an assist motor and a generator. Electric motor  12 , when acting as a generator, can rapidly reduce the speed of engine  16  in response to lower power demand at pump  20 , and energy not needed to power the pump may be converted to electrical energy and/or stored for later use as described in greater detail below. 
         [0014]    Engine  16  may be any prime mechanical mover. By way of non-limiting example, engine  16  may be a hydro-carbon fueled internal combustion engine, a turbine unit, or a micro-turbine unit. Engine  16  may be controlled by command signals from master controller  26 , and may include sensors  28  for providing feedback to master controller  26  as to the engine&#39;s operating status. For example, engine  16  may be embodied as a hydro-carbon fueled internal combustion engine wherein fuel metering is directly controlled by commands from master controller  26 , and feedback signals may be provided by engine sensors  28  hard-wired to master controller  26 . 
         [0015]    Hydraulic pump  20  converts mechanical power to hydraulic power  30  which is output by module  10 . In an embodiment of the invention, hydraulic pump  20  may be a variable displacement hydraulic pump wherein the volume of fluid pumped per revolution of drive shaft  14  is variable by commands issued from master controller  26 . While use of a variable displacement hydraulic pump adds complexity, it allows a further boost in dynamic response and optimization of operating parameters to reduce power losses. 
         [0016]    Electric power source  24  may advantageously comprise an energy storage unit configured to accept and store energy, and electric motor  12  is selectively operable as an electric generator providing electrical energy stored by the energy storage unit. The energy storage unit may be a hybrid energy storage unit including at least one battery cell and at least one ultra-capacitor. For sake of illustration, when electric motor  12  is in starter mode acting as a starter motor for engine  16 , it may rely primarily on power from battery cells, and when electric motor  12  is in boost mode acting as an assist motor for engine  16 , it may rely primarily on power from ultra-capacitors. 
         [0017]    In the illustrated embodiment, master controller  26  manages delivery of hydraulic power  30  and electric power  32  as respective outputs of module  10 , and further manages the delivery of regenerated power from electric motor  12  to the energy storage unit of electric power source  24 . Master controller  26  may be connected for data communication with the overall machine (the power consumer) that is powered by hybrid power module  10  so that module  10  is optimized to meet feed-forward demand for hydraulic power  30  and electric power  32 . 
         [0018]    As may be understood, hybrid power module  10  has various selectable modes of operation. Module  10  may operate in a pure electric mode where hydraulic power is provided solely by the electrical motor  12  and engine  16  is shut down. Module  10  has a starter mode in which electric motor  12  is operable as a starter motor for starting engine  16 , and an assist mode wherein electric motor  12  is operable to assist engine  16  in powering rotation of the drive shaft  14  to boost dynamic response of hydraulic pump  20 . Hybrid power module  10  may also have a regeneration mode in which electric motor  12  functions as an electric generator, whereby kinetic energy of engine output shaft  18  is converted to electric power for storage by the energy storage unit of electric power source  24 . 
         [0019]      FIG. 3  shows a hybrid power module  40  formed in accordance with a second embodiment of the present invention. Hybrid power module  40  is generally similar to hybrid power module  10  of the first embodiment in that it comprises electric motor  12  having drive shaft  14 , engine  16  having output shaft  18 , hydraulic pump  20 , electric power source  24 , and master controller  26 . In contrast to the first embodiment, hydraulic pump  20  has its own driven shaft  42 , and does not share drive shaft  14  with electric motor  12 . 
         [0020]    Hybrid power module  40  comprises a differential gear assembly  44  to modulate power flow among engine  16 , motor  12 , and hydraulic pump  20 . Differential gear assembly  44  mechanically connects engine output shaft  18 , electric motor drive shaft  14 , and driven shaft  42  of hydraulic pump  20  to one another. A brake  46  is associated with drive shaft  14  of electric motor  12 . 
         [0021]    Similar to hybrid power module  10  of the first embodiment, hybrid power module  40  has various selectable modes of operation. Module  10  may operate in a pure electric mode where hydraulic power is provided solely by the electrical motor  12  and engine  16  is shut down. Module  40  has a starter mode in which electric motor  12  is operable as a starter motor for starting engine  16 , and an assist mode wherein electric motor  12  is operable to assist engine  16  in powering rotation of hydraulic pump driven shaft  42  to boost dynamic response of hydraulic pump  20 . Hybrid power module  40  may also have a regeneration mode in which electric motor  12  functions as an electric generator, whereby kinetic energy of engine output shaft  18  is converted to electric power for storage by the energy storage unit of electric power source  24 . 
         [0022]    While the invention has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the invention to the particular forms set forth. The invention is intended to cover such alternatives, modifications and equivalents of the described embodiment as may be included within the spirit and scope of the invention.