Abstract:
An exemplary method includes using a controller to automatically operate a vehicle in an electric mode when an actual speed of the vehicle is at or below a set threshold, and to automatically operate the vehicle in a hybrid mode when the actual speed is above the set threshold. The method further including adjusting the set threshold using a selector device such that the set threshold is changed without influencing the actual speed. Another exemplary method includes using a controller to automatically initiate a transition of a vehicle from an electric mode to a hybrid mode, or from the hybrid mode to the electric mode. The controller initiates the transition in response to a comparison of a state of charge of a battery of the vehicle to a threshold state of charge that is configured to be adjusted by an operator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/281,963, which was filed on 20 May 2014 and is incorporated herein by reference. 
    
    
     BACKGROUND 
     This disclosure relates to selectively operating an electric vehicle in an electric mode. 
     Example hybrid vehicles include hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). Generally, hybrid vehicles differ from conventional motor vehicles because hybrid vehicles are selectively driven using a battery-powered electric machine. Conventional motor vehicles, by contrast, rely exclusively on an internal combustion engine to drive the vehicle. 
     A hybrid vehicle driven using the battery-powered electric machine generates less noise than when driven using the internal combustion engine. Noise from the internal combustion engine may be objectionable. 
     SUMMARY 
     A method according to an exemplary aspect of the present disclosure includes, among other things, using a controller to automatically operate a vehicle in an electric mode when an actual speed of the vehicle is at or below a set threshold, and to automatically operate the vehicle in a hybrid mode when the actual speed is above the set threshold. The method further including adjusting the set threshold using a selector device such that the set threshold is changed without influencing the actual speed. 
     Another example of the foregoing method includes adjusting the set threshold when the vehicle is moving. 
     In another example of any of the foregoing methods, the set threshold is one of a plurality of fixed choices. 
     Another example of any of the foregoing methods includes charging a battery of the vehicle to a charge level when operating the vehicle in a hybrid mode. The charge level is calculated based on a desired reserve charge when the vehicle stops operating in the hybrid mode. 
     In another example of any of the foregoing methods, the desired reserve charge comprises an operator-adjustable desired reserve charge. 
     In another example of any of the foregoing methods, the operator-adjustable desired reserve charge can be adjusted by an operator when the electric vehicle is moving. 
     In another example of any of the foregoing methods, the operator-adjustable desired reserve charge comprises an operator-adjustable electric distance amount. 
     Another example of any of the foregoing methods includes alerting an operator of the vehicle of a transition between the electric mode and the hybrid mode, and providing the operator with an option to bypass the transition. 
     Another example of any of the foregoing methods includes initiating an audible count down timer. 
     A method according to another exemplary aspect of the present disclosure includes, among other things, using a controller to automatically initiate a transition of a vehicle from an electric mode to a hybrid mode, or from the hybrid mode to the electric mode. The controller initiates the transition in response to a comparison of a state of charge of a battery of the vehicle to a threshold state of charge that is configured to be adjusted by an operator. 
     In another example of any of the foregoing methods, the threshold state of charge is calculated based on a desired reserve charge when the vehicle stops operating in the hybrid mode. 
     Another example of any of the foregoing methods includes charging the battery of the vehicle to the threshold state of charge when operating the vehicle in a hybrid mode. 
     In another example of any of the foregoing methods, the threshold state of charge is configured to be adjusted by an operator when the vehicle is moving. 
     An apparatus according to an exemplary aspect of the present disclosure includes, among other things, a controller configured to automatically initiate a transition of a vehicle from an electric mode to a hybrid mode, or from the hybrid mode to the electric mode. The controller is configured to automatically initiate the transition in response to a comparison of a state of charge of a battery of the vehicle to a threshold state of charge. The apparatus further includes a selector device that is actuated to adjust the threshold state of charge. 
     In another example of the foregoing apparatus, the controller is further configured to cause a battery of the vehicle to be charged to a charge level when operating the vehicle in the hybrid mode. The charge level is calculated based on the desired reserve charge when the vehicle stops operating in the hybrid mode. 
     In another example of the foregoing apparatus, the desired reserve charge includes a range of desired reserve charges. 
     In another example of any of the foregoing apparatus, the transition is of a first type, and the controller is further configured to initiate a transition of a second type where the vehicle is transitioned from the electric mode to the hybrid mode, or from the hybrid mode to the electric mode, in response to a comparison of an actual speed of the vehicle to a set threshold speed. 
     In another example of any of the foregoing apparatus, the apparatus includes a threshold speed selector device that is actuated to adjust the set threshold speed without influencing the actual speed. 
     In another example of any of the foregoing apparatus, the controller is further configured to provide an alert to an operator of the vehicle in response to an upcoming transition from the electric mode to the hybrid mode, or from the hybrid mode to the electric mode, and to provide the operator with an option to bypass the upcoming transition. 
     The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG. 1  illustrates a schematic view of an example transmission for an electric vehicle. 
         FIG. 2  shows an example method of operating an electric vehicle having the transmission of  FIG. 1 . 
         FIG. 3  shows another example method of operating an electric vehicle having the transmission of  FIG. 1 . 
         FIG. 4  shows yet another example method of operating an electric vehicle having the transmission of  FIG. 1 . 
         FIG. 5  shows still another example method of operating an electric vehicle having the transmission of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a powertrain  10  for an electric vehicle. The powertrain  10  includes a battery  14 , an electric machine (motor)  18 , an electric machine (generator)  20 , and an internal combustion engine  22 . The battery  14  is a relatively high-voltage battery in this example. 
     Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEVs and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEVs), etc. 
     In one embodiment, the powertrain  10  is a power-split powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of the engine  22  and the generator  20 . The second drive system includes at least the motor  18 , the generator  20 , and a battery  14 . In this example, the second drive system is considered an electric drive system of the powertrain  10 . The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  26  of the electric vehicle. 
     The engine  22 , which is an internal combustion engine in this example, and the generator  20  may be connected through a power transfer unit  30 , such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine  22  to the generator  20 . In one non-limiting embodiment, the power transfer unit  30  is a planetary gear set that includes a ring gear  32 , a sun gear  34 , and a carrier assembly  36 . 
     The generator  20  can be driven by engine  14  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  18  can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft  60  connected to the power transfer unit  30 . Because the generator  18  is operatively connected to the engine  14 , the speed of the engine  14  can be controlled by the generator  18 . 
     The ring gear  32  of the power transfer unit  30  may be connected to a shaft  64 , which is connected to vehicle drive wheels  28  through a second power transfer unit  44 . The second power transfer unit  44  may include a gear set having a plurality of gears  46 . Other power transfer units may also be suitable. The gears  46  transfer torque from the engine  14  to a differential  48  to ultimately provide traction to the vehicle drive wheels  26 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  26 . In this example, the second power transfer unit  44  is mechanically coupled to an axle  50  through the differential  48  to distribute torque to the vehicle drive wheels  28 . 
     The motor  18  (i.e., the second electric machine) can also be employed to drive the vehicle drive wheels  26  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In one embodiment, the motor  18  and the generator  20  cooperate as part of a regenerative braking system in which both the motor  18  and the generator  20  can be employed as motors to output torque. For example, the motor  18  and the generator  20  can each output electrical power to the battery  14 . 
     The battery  14  is an example type of electric vehicle battery assembly. The battery  14  may incorporate a high voltage battery that is capable of outputting electrical power to operate the motor  18  and the generator  20 . Other types of energy storage devices and/or output devices can also be used with the electric vehicle having the powertrain  10 . 
     The powertrain  10  generates more noise when operating in the hybrid mode with the engine  22  than when operating in the electric mode without the engine  22 . This is due, at least in part, to the noise from the internal combustion engine  22  operating when the powertrain operates in the hybrid mode. The operating internal combustion engine  22  is noisier than the operating generator  20  or motor  18  alone. 
     A powertrain controller  60  is operatively coupled to portions of the powertrain  10 , such as the internal combustion engine  22  and the electric machine  20 . The controller  60  causes the powertrain  10  to drive a vehicle in the electric mode or the hybrid mode. The controller  60  may instruct the powertrain  10  to shut down the internal combustion engine  22  and to drive the vehicle in the electric mode to reduce noise from the powertrain  10 . The motor  18 , the generator  20 , the internal combustion engine  22 , and other portions of the powertrain  10  respond to commands from the controller  60 . 
     The controller  60  may be part of an engine control module, a battery electric control, etc. within the vehicle. The example controller  60  includes a processor  64  operatively linked to a memory portion  68 . The example processor  64  is programmed to execute a program stored in the memory portion  68 . The program may be stored in the memory portion  68  as software code. 
     The program stored in the memory portion  68  may include one or more additional or separate programs, each of which includes an ordered listing of executable instructions for implementing logical functions. 
     The processor  64  can be a custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the controller  60 , a semiconductor based microprocessor (in the form of a microchip or chip set) or generally any device for executing software instructions. 
     The memory portion  68  can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). Moreover, the memory may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory can also have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor. 
     Referring now to  FIG. 2  with continued reference to  FIG. 1 , an example method  100  of operating an electric vehicle having the powertrain  10  enables an operator of the vehicle to control use of the internal combustion engine  22  based on speed. The method  100  enables the operator to operate the vehicle in a quiet mode when the vehicle is operating at certain speeds. The method  100  is an example program executed by the processor  64 . 
     The operator could be a driver of the vehicle, a passenger of the vehicle, a manufacturer of the vehicle, or another individual desiring to adjust how the powertrain  10  switches between the hybrid mode and the electric mode of operation. 
     The method  100  includes a step  104  of calculating whether or not the vehicle having the powertrain  10  is operating at or below a threshold speed. The calculation may account for hysteresis. If yes, the method moves to the step  108 , which is considered an EV Now mode. In the EV Now mode, the vehicle operates in an electric mode. If the vehicle speed is above the threshold speed, the method  100  moves to a step  112 , which is considered an EV Later mode. In the EV Later mode, the vehicle operates in a hybrid mode. 
     Some electric vehicle powertrains control switching between the hybrid mode and electric mode based on power requirements. The method  100  controls switching between the hybrid mode and the electric mode based on vehicle speed. 
     In some examples, the threshold speed is adjustable, by the operator, for example. Adjustments to the threshold speed may occur when the vehicle is moving. The threshold speed selection could be made through an instrument cluster menu, Accessory Protocol Interface Module, etc. 
     In some example embodiments, the operator selects the threshold speed from one of a plurality of fixed speed choices, for example, 35, 45, or 55 miles per hour. 
     In some example embodiments, the operator actuates a knob, dial, button on a display, virtual representations of these, or some other selector device to vary the selection from among several choices within a range of speeds. Any speed between 35 and 55 miles per hour for example. 
     The operator may select the threshold speed to be above the speeds typical of the vehicle when moving through certain geographical areas, such as city centers. After selecting this threshold speed, the vehicle operates in electric mode when the vehicle moves through these geographical areas at speeds below the threshold speed. 
     The vehicle operates in electric mode in these areas because the speed of the vehicle is not greater than the threshold speed. Individuals within the geographical area, such as pedestrians within the city center, thus do not hear the vehicle operate in the hybrid mode. Further, because the internal combustion engine  22  is not operating, exhaust gases from the internal combustion engine are not dumping directly into the city center. 
     When the vehicle reaches speeds exceeding the threshold speed, the vehicle will have likely moved out of the geographical area. The internal combustion engine  22  can then operate without being heard by individuals within the geographical area. 
     If the vehicle continues to operate in electric mode for an extended period of time, the vehicle may eventually have to begin operating again in a hybrid mode to charge the battery  14 . 
     To extend the length of time that the vehicle can operate in electric mode, some embodiments of the method may include charging the battery  14  of the vehicle to a desired charge level when operating the vehicle in a hybrid mode. 
     The desired charge level may be calculated based on a desired charge available for when the speed of the vehicle drops below the threshold speed and the vehicle begins to operate in electric mode. The operator may desire, for example, for the battery  14  to have a state of charge permitting ten miles of driving in the electric mode after the hybrid mode is complete and the vehicle speed drops below the threshold speed. 
     The operator thus inputs ten miles through a type of selector device, such as a human-machine interface screen. A state of charge of the battery  14  is then maintained at a level capable of providing ten miles of operation in the electric mode. 
     The desired reserve charge may be based on mileage as described above. The desired reserve charge could alternatively be a chosen from among a few fixed charge levels, such as twenty-five, fifty, or seventy-five percent state of charge. The desired reserve charge could also be a charge range such as from seventy to eighty percent. 
     For the state of charge selection, the choice could be made via a virtual knob, a slide bar in the outline of a battery, etc. 
     The operator may select twenty miles of travel based on an estimate that the operator will drive the vehicle twenty miles below the threshold speed without exceeding the threshold speed. The operator could make this selection prior to entering a city center or another type of low-speed geographical area. 
     Notably, selecting the desired reserve charge may cause the battery  14  to charge to a customer-selected charge that is higher than a typical state of charge or distance to empty. 
     Referring now to  FIG. 3  with continued reference to  FIG. 1 , another example method  150  of operating an electric vehicle having the powertrain  10  enables an operator of the vehicle to control use of the internal combustion engine  22  based on a state of charge of the battery  14 . The method  150  can be executed on the processor  64  of the powertrain controller  60 . 
     The method  150  determines a state of charge and may account for hysteresis. The method  150  includes a step  154  of calculating whether the battery  14  contains the desired reserve charge, which is operator-adjustable. At a step  158 , the method  150  causes the powertrain  10  to operate in an electric mode when a state of charge of the battery of the electric vehicle is above the desired reserve charge. The method  150  includes a step  162  of operating in a hybrid mode when the state of charge of the battery is at or below the desired reserve charge. 
     Some electric vehicle powertrains control switching between the hybrid mode and electric mode based on power requirements. The method  100  controls switching between the hybrid mode and the electric mode based on an amount of reserve charge in the battery  14 . 
     Although the state of reserve charge (in kW-hrs) is directly adjusted in this example. Other examples may include indirect adjustments to the state of charge, such as by setting power level for the battery  14 , a state of charge level (in percent) for the battery, or an electric distance amount (20 miles of travel using battery power, for example.) 
     Referring now to  FIG. 4  with reference to  FIG. 1 , in another example method  200 , both a threshold speed and a desired reserve charge are used to control how the powertrain  10  switches between the first drive system and the second drive system. At a step  204 , the method  200  obtains a desired threshold speed and reserve charge. The operator of the vehicle can provide these variables, for example. The threshold speed may be a range of speeds such as from forty to sixty miles per hour. The desired reserve charge can be a range of desired reserve charges for the battery  14 , such as seventy to eighty percent state of charge. 
     Next, at a step  208 , the method  200  operates in the hybrid mode. While operating in the hybrid mode, the method  200  determines if the battery  14  contains the desired reserve charge at a step  212 . If yes, the method  200  then determines if a speed of the vehicle is at or below the threshold speed at a step  216 . If yes, the method  200  operates the vehicle in electric mode at a step  220  until vehicle exceeds threshold speed or is required to return to a hybrid mode for recharging. 
     In the methods of  FIGS. 2, 3, and 4 , an alert may be generated to indicate an upcoming switch between electric and hybrid modes. 
     The methods may generate other alerts at other times to inform operators of the vehicle. The alerts could be visual alerts, audible alerts, tactile alerts, or some combination of these. 
     In one example, the alert is a count-down timer informing of an impending engine pull-up, for example. The alert may start three seconds before an engine pull-up. The engine pull-up could be due to a switch from electric to hybrid mode. The engine pull-up could be due to a required start of the engine when in a hybrid mode. 
     The alerts could permit the operator to change their mind regarding a switch between a hybrid and electric mode and, for example, allow the operator to maintain operation in the hybrid mode. 
     Referring now to  FIG. 5 , another method  250  of operating a vehicle having the powertrain  10  of  FIG. 1  starts at a step  254 . The method  250  then calculates, at a step  258 , if the vehicle speed is at or below a speed threshold. If yes, the method moves to a step  262 . If no, the method moves to a step  266 . 
     At the step  262 , the method  250  calculates whether there is sufficient charge in the battery  14 . If yes, the method  250  moves to the step  270  where the vehicle operates in electric mode and then returns to start  254 . If no, the method  250  moves to the step  266 . 
     At the step  266 , the method  250  calculates whether the charge in the battery  14  exceeds a threshold reserve charge level. If yes, the method  250  moves to the step  274  wherein the vehicle operates in hybrid mode and then returns to the start  254 . If no, the method  250  runs the engine  22  at a higher power to charge the battery  14  at a step  278  and then returns to the start  254 . 
     Any of the methods of  FIGS. 2 to 5  may account for hysteresis when determining, for example, the vehicle speed, the reserve charges, etc. 
     Features of some the disclosed examples include a method of operating a powertrain for a hybrid electric vehicle that permits an operator to selectively operate the vehicle in an electric mode at a start of a trip, at low speeds or stops along the trip, or at the end of the trip. Electric operation can be prioritized over energy efficiency. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.