Abstract:
A power take off system for a hybrid-electric vehicle comprises an internal combustion engine, a hybrid-electric motor and generator, a power take off mechanism, a hybrid control module, and an engaging mechanism. The hybrid-electric motor and generator couples to the internal combustion engine. The power take off mechanism couples to the internal combustion engine and the hybrid-electric motor and generator. The power take off mechanism receives torque from at least one of the internal combustion engine and the hybrid-electric motor and generator. The hybrid control module is disposed in electrical communication with an electronic system controller. The hybrid control module generates output signals for controlling the internal combustion engine. The engaging mechanism is disposed in electrical communication with the electronic system controller. The engaging mechanism has a first mode and a second mode. The power take off mechanism is decoupled from the internal combustion engine and the hybrid-electric motor and generator in response to an output signal generated by the electronic system controller.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a hydraulic load control system for power take off (“PTO”) equipment on a vehicle with a hybrid-electric drivetrain, and more particularly to a system and method for transitioning between internal combustion engine powered operation of the PTO and hybrid-electric drivetrain powered operation of the PTO that supplies power for the hydraulic load. 
       BACKGROUND 
       [0002]    Many vehicles now utilize hybrid-electric drivetrains in order to increase the efficiency of the vehicle. A hybrid-electric drivetrain typically involves an internal combustion engine that operates a generator that produces electrical power that may be used to drive electric motors used to move the vehicle. The electric motors may be used to provide power to wheels of the vehicle to move the vehicle, or the electric motors may be used to supplement power provided to the wheels by the internal combustion engine and a transmission. In certain operational situations, the electric motors may supply all of the power to the wheels, such as under low speed operations. In addition to providing power to move the vehicle, the hybrid-electric drivetrain may be used to power a PTO of the vehicle that in turn powers PTO driven accessories. A hybrid-electric drivetrain may solely power the PTO of the vehicle when the PTO is operating a PTO driven accessory adapted to only be utilized by a stopped vehicle, such as lift attachment, or a digging attachment. In some situations, the hybrid-electric drivetrain is not capable of providing sufficient power to the PTO, and thus, the PTO needs to be powered by the internal combustion engine. In other situations, batteries of the hybrid-electric drivetrain may need to be recharged. In both of these situations, if the PTO is being powered by the hybrid-electric drivetrain, the PTO must be stopped, such that the internal combustion engine may be started to deliver power to the PTO, or to recharge batteries of the hybrid-electric drivetrain. Therefore, a need exists for a system and method that is capable of shutting down a PTO that is being driven by a hybrid-electric drivetrain, such that an internal combustion engine may be started to power the PTO, or to recharge batteries of the hybrid-electric drivetrain. 
       SUMMARY 
       [0003]    According to one embodiment, a power take off system for a hybrid-electric vehicle comprises an internal combustion engine, a hybrid-electric motor and generator, a power take off mechanism, a hybrid control module, and an engaging mechanism. The hybrid-electric motor and generator couples to the internal combustion engine. The power take off mechanism mechanically couples to the internal combustion engine and the hybrid-electric motor and generator. The power take off mechanism receives torque from at least one of the internal combustion engine and the hybrid-electric motor and generator. The hybrid control module is disposed in electrical communication with an electronic system controller. The hybrid control module is provided to generate output signals for controlling the internal combustion engine. The engaging mechanism is disposed in electrical communication with the electronic system controller. The engaging mechanism has a first mode and a second mode. Wherein in the first mode the power take off mechanism is decoupled from the internal combustion engine and the hybrid-electric motor and generator in response to an output signal generated by the electronic system controller. 
         [0004]    According to one process, a method of operating a power take off system for a hybrid electric vehicle having an internal combustion engine and a hybrid-electric motor and generator is provided. An output signal is generated from a user input switch to supply torque to a power take off mechanism from the internal combustion engine. An engaging mechanism opens in response to the output signal from the user input switch. A power take off mechanism disengages from a hybrid-electric motor and generator in response to the opening the engaging mechanism. An internal combustion engine is started using the hybrid-electric motor and generator. The engaging mechanism closes after starting the internal combustion engine. Torque is provided to the power take off mechanism from the internal combustion engine in response to closing the engaging mechanism. 
         [0005]    According to another process, a method of operating a power take off system for a hybrid-electric vehicle having an internal combustion engine and a hybrid-electric motor and generator is provided. Load of a power take off mechanism is monitored with a hybrid control module while the power take off is powered by a hybrid-electric motor and generator. An engaging mechanism opens in response to monitoring load of the power take off mechanism when the load surpasses a predetermined threshold. A power take off mechanism disengages from a hybrid-electric motor and generator in response to the opening the engaging mechanism. An internal combustion engine is started using the hybrid-electric motor and generator. The engaging mechanism closes after starting the internal combustion engine. Torque is provided to the power take off mechanism from the internal combustion engine in response to closing the engaging mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1 ,  2  and  3  comprise a schematic view of a vehicle having a hybrid-electric drivetrain with a PTO driven hydraulic system including a combination valve in an open position; and 
           [0007]      FIG. 4  is a sectional view of a combination valve in a closed position. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]      FIGS. 1 ,  2  and  3  show a schematic view of a vehicle having a vehicle mounted PTO driven accessory  1 , an internal combustion engine  2 , a hybrid-electric motor and generator  3 , and a PTO mechanism  4 . Additional information relating to vehicles having PTO driven accessories as well as a hybrid-electric powertrain may be found in U.S. Pat. No. 7,281,595, incorporated by reference herein in its entirety. The internal combustion engine  2  may be a diesel engine. As shown in  FIGS. 1 ,  2  and  3  the PTO driven accessory  1  is a hydraulic digging attachment adapted to be used when the vehicle is stationary, but a variety of other PTO driven accessories may be used. As the PTO driven accessory  1  shown in  FIGS. 1 ,  2  and  3  is adapted to be used when the vehicle is stationary, the hybrid-electric motor and generator  3  may power the PTO mechanism  4  when the vehicle is stationary. However, if the PTO driven accessory  1  will be used in manner an operator expects to require a large amount of power, the operator may initiate a transition from the hybrid-electric motor and generator  3  powering the PTO mechanism  4 , to the internal combustion engine  2  powering the PTO mechanism  4  after starting the internal combustion engine  2 . Therefore the PTO mechanism  4  is mechanically coupled to output of both the internal combustion engine  2 , and the hybrid-electric motor and generator  3 . That is the PTO mechanism  4  is adapted to receive torque from one or both of the internal combustion engine  2 , or the hybrid-electric motor and generator  3 , such as through shafts, gears, belts, or the like. 
         [0009]    An operator may receive an alert that the hybrid-electric motor and generator  3  is nearing the maximum power output, the operator may observe that a power electronics system  35  that control the hybrid-electric motor and generator  3  may not be able to supply sufficient power to the PTO mechanism, or the operator may simply know from experience that the PTO driven accessory  1  will require hybrid-electric motor and generator are unlikely to be able to provide sufficient power to the PTO mechanism  4  causing the operator to activate switch  25  to generates a signal sent to a controller area network data link module, such as a remote power module  13 . It is to be understood that when “signal” is mentioned herein, there exists appropriate conductors for conveying the signal. The remote power module  13  in turn generates a signal transmitted over a first data link  12  to an electronic system controller (“ESC”)  15 . 
         [0010]    The ESC  15  transmits a signal over a second data link  22  to a hybrid control module (“HCM”)  17 . The signal from the ESC  15  to the HCM  17  alerts the HCM  17  that the PTO mechanism  4  is about to disengage based upon the signal from the switch  25 , and that the internal combustion engine  2  will be started. The ESC  15  additionally deactivates an output signal  26  that controls an engaging mechanism  27 , such as a solenoid valve, used to engage and disengage the PTO mechanism  4  via signal  37 . The engaging mechanism  27  has a first mode that decouples, or disengages, the PTO mechanism  4  from the internal combustion engine  2  and the hybrid-electric motor and generator  3 , while the second mode couples, or engages the PTO mechanism  4  to the internal combustion engine  2  and the hybrid-electric motor and generator  3 . The disengagement of the PTO mechanism  4  disengages a first hydraulic pump  18  and a second hydraulic pump  21  that are powered by the PTO mechanism  4 . Once the PTO mechanism  4  has been disengaged, the ESC  15  monitors an transducer  28  that generates a transducer output signal  29  such that the ESC  15  may monitor the load within a hydraulic system  5 . The illustrated embodiment of the hydraulic system  5  includes a combination valve  38  shown in an open position in  FIG. 3  and in a closed position in  FIG. 4 . 
         [0011]    Once the ESC  15  determines that the load within the hydraulic system  5  is sufficiently low, ESC  15  transmits a signal to the HCM  17  instructing the HCM  17  to disengage a transmission  30  by using a clutch  31  via an electric clutch actuator  32 . Once the clutch  31  has disengaged the transmission  30 , the hybrid-electric motor and generator  3  acts as a starter for the internal combustion engine  2 , and initiate operation of the internal combustion engine  2 . 
         [0012]    Once the internal combustion engine  2  is operating properly, the ESC  15  again monitors the transducer output signal  29  of the transducer  28  to determine whether the PTO driven accessory  1  is trying to be being used. The ESC  15  reactivates the output signal  26  such that the engaging mechanism  27  reengages the PTO mechanism  4 . The PTO mechanism  4  is powered by the internal combustion engine  2 , as opposed to the hybrid-electric motor and generator  3 . The PTO mechanism  4  reengages the first hydraulic pump  18  and the second hydraulic pump  21 , allowing the PTO driven accessory  1  to be used to perform a task requiring more power than the hybrid-electric motor and generator  3  may deliver. 
         [0013]    The ESC  15  continues to monitor the output signal  29  of the transducer  28  and if the output signal  29  indicates that the PTO driven accessory  1  is no longer being used, the ESC  15  will transmit a signal to the HCM  17  to shutdown the internal combustion engine  2 . 
         [0014]    In addition to shutting down the internal combustion engine  2  when the PTO driven accessory is no longer being used, it is additionally contemplated that the internal combustion engine  2  may be shutdown when high voltage batteries  16  of the power electronics system  35  are fully charged, chassis batteries  33  are fully charged, or the HCM  17  communicates over the second data link  22  to the ESC  15  that the loads generated by the PTO driven accessory  1  are small enough that the hybrid-electric motor and generator  3  can deliver sufficient power to the PTO mechanism  4  to support the PTO driven accessory  1 . 
         [0015]    In addition to a user initiated method of transitioning from the hybrid-electric motor and generator  3  powering the PTO mechanism  4 , to the internal combustion engine  2  powering the PTO mechanism  4 , an automatic method of transitioning from the hybrid-electric motor and generator  3  powering the PTO mechanism  4 , to the internal combustion engine  2  powering the PTO mechanism  4  is provided. 
         [0016]    The automatic method transitioning of from the hybrid-electric motor and generator  3  powering the PTO mechanism  4 , to the internal combustion engine  2  powering the PTO mechanism  4  is similar to the user initiated method. PTO mechanism  4  is receiving power form the hybrid-electric motor and generator  3  in order to power a PTO driven accessory  1 . The PTO driven accessory  1  is an accessory adapted to be used while the vehicle is not in motion, such that the internal combustion engine  2  need not always be utilized. 
         [0017]    The HCM  17  monitors the power electronics system  35  as well of the loads imparted by the PTO driven accessory  1 . When the HCM  17  detects that the power electronics system  35  for the hybrid-electric motor and generator  3  is not capable of providing sufficient power for the PTO mechanism  4 , the HCM  17  generates a signal to sent to the ESC  15  over the second data link  22 . 
         [0018]    In response to the signal from the HCM, the ESC  15  will reply to the HCM  17  to alert the HCM  17  that the PTO mechanism  4  is about to disengage based upon the signal from the HCM  17 , and that the internal combustion engine  2  will be started. The ESC  15  will also deactivate the output signal  26  that controls the engaging mechanism  27  used to engage and disengage the PTO mechanism  4  in response to the signal from the HCM  17 . The disengagement of the PTO mechanism  4  disengages a first hydraulic pump  18  and a second hydraulic pump  21  that are powered by the PTO mechanism  4 . Once the PTO mechanism  4  has been disengaged, the ESC  15  monitors an transducer  28  that generates a transducer output signal  29  such that the ESC  15  may monitor the load within a hydraulic system  5 . 
         [0019]    Once the ESC  15  determines that the load within the hydraulic system  5  is sufficiently low, ESC  15  transmits a signal to the HCM  17  instructing the HCM  17  to disengage a transmission  30  by using a clutch  31  via an electric clutch actuator  32 . Once the clutch  31  has disengaged the transmission  30 , the hybrid-electric motor and generator  3  acts as a starter for the internal combustion engine  2 , and initiate operation of the internal combustion engine  2 . 
         [0020]    Once the internal combustion engine  2  is operating properly, the ESC  15  again monitors the transducer output signal  29  of the transducer  28  to determine whether the PTO driven accessory  1  is trying to be being used. The ESC  15  reactivates the output signal  26  such that the engaging mechanism  27  reengages the PTO mechanism  4 . The PTO mechanism  4  is powered by the internal combustion engine  2 , as opposed to the hybrid-electric motor and generator  3 . The PTO mechanism  4  reengages the first hydraulic pump  18  and the second hydraulic pump  21 , allowing the PTO driven accessory  1  to be used to perform a task requiring more power than the hybrid-electric motor and generator  3  may deliver. 
         [0021]    The ESC  15  continues to monitor the output signal  29  of the transducer  28  and if the output signal  29  indicates that the PTO driven accessory  1  is no longer being used, the ESC  15  will transmit a signal to the HCM  17  to shutdown the internal combustion engine  2 . 
         [0022]    In addition to shutting down the internal combustion engine  2  when the PTO driven accessory is no longer being used, it is additionally contemplated that the internal combustion engine  2  may be shutdown when high voltage batteries  16  of the power electronics system  35  are fully charged, chassis batteries  33  are fully charged, or the HCM  17  communicates over the second data link  22  to the ESC  15  that the loads generated by the PTO driven accessory  1  are small enough that the hybrid-electric motor and generator  3  can deliver sufficient power to the PTO mechanism  4  to support the PTO driven accessory  1 . 
         [0023]    Thus, the use of the hybrid-electric motor and generator  3  allows for the use of the PTO driven accessory  1 , without having to constantly run the internal combustion engine  2  when the hybrid-electric motor and generator  3  powers the PTO mechanism  4 , reducing the fuel consumption of the vehicle, while allowing the internal combustion engine  2  to power the PTO mechanism  4  when higher power levels are required, or the power electronics system  35  lack sufficient charge to operate the hybrid-electric motor and generator  3 . Thus, the vehicle may save fuel while using the PTO driven accessory  1  for light duty tasks, but still maintains the capability to perform heavy duty tasks utilizing the internal combustion engine  2 .