Abstract:
An example method of controlling an electrified vehicle includes activating a coast switch to a place an electrified vehicle in a coast mode.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure is directed toward coasting an electrified vehicle to, among other things, increase fuel economy. 
       BACKGROUND 
       [0002]    Generally, electrified vehicles differ from conventional motor vehicles because electrified vehicles are selectively driven using one or more battery-powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on an internal combustion engine to drive the vehicle. Electrified vehicles may use electric machines instead of, or in addition to, the internal combustion engine. 
         [0003]    Example electrified vehicles include hybrid electrified vehicles (HEVs), plug-in hybrid electrified vehicles (PHEVs), fuel cell vehicles, and battery electrified vehicles (BEVs). A powertrain of an electrified vehicle is typically equipped with a battery pack having battery cells that store electrical power for powering the electric machine. The battery cells may be charged prior to use. The battery cells may be recharged during a drive via regenerative braking or the internal combustion engine. 
         [0004]    Regenerative braking and friction braking can decrease fuel economy in electrified vehicles. 
       SUMMARY 
       [0005]    A method of controlling an electrified vehicle according to an exemplary aspect of the present disclosure includes, among other things, activating a coast switch to a place an electrified vehicle in a coast mode. 
         [0006]    In a further non-limiting embodiment of the foregoing method, the method includes maintaining a gear selector in a drive mode during the activating. 
         [0007]    In a further non-limiting embodiment of any of the foregoing methods, the gear selector can be actuated between at least a drive mode, a neutral mode, and a reverse mode. 
         [0008]    In a further non-limiting embodiment of any of the foregoing methods, the coast switch is separate from a gear selector of the electrified vehicle. 
         [0009]    In a further non-limiting embodiment of any of the foregoing methods, activating the coast switch comprises moving the coast switch from a first position to a second position. 
         [0010]    In a further non-limiting embodiment of any of the foregoing methods, the second position is a depressed position and the first position is a released position. 
         [0011]    In a further non-limiting embodiment of any of the foregoing methods, the coast switch is biased to the first position, and a user holds the coast switch in the second position to overcome the bias and maintain the electrified vehicle in the coast mode. 
         [0012]    In a further non-limiting embodiment of any of the foregoing methods, deactivating the coast switch comprises moving the coast switch from the second position to the first position. 
         [0013]    In a further non-limiting embodiment of any of the foregoing methods, the method includes activating the coast switch separately from a gear selector of the electrified vehicle without applying a brake. 
         [0014]    In a further non-limiting embodiment of any of the foregoing methods, the method includes disengaging gears of a powersplit powertrain in response to activating the coast mode. 
         [0015]    An electrified vehicle according to an exemplary aspect of the present disclosure includes, among other things, a gear selector and a coast switch separate from the gear selector. The coast switch is activated to selectively place an electrified vehicle in a coast mode. 
         [0016]    In a further non-limiting embodiment of the foregoing electrified vehicle, the gear selector can be actuated between at least a drive mode, a neutral mode, and a reverse mode. 
         [0017]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the coast switch is activated to selectively place the electrified vehicle in the coast mode when the gear selector is in drive mode. 
         [0018]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the coast switch comprises a button disposed on a gear shift knob. 
         [0019]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the coast switch comprises a button disposed on a steering wheel of the electrified vehicle. 
         [0020]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the coast switch is activated by moving the coast switch from a first position to a second position. 
         [0021]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the second position is a depressed position and the first position is a released position. 
         [0022]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, the coast switch is biased to the first position, and a user holds the coast switch in the second position to overcome the bias and maintain the electrified vehicle in the coast mode. 
         [0023]    In a further non-limiting embodiment of any of the foregoing electrified vehicles, deactivating the coast switch comprises moving the coast switch from the second position to the first position. 
         [0024]    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 
         [0025]    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: 
           [0026]      FIG. 1  schematically illustrates an example electrified vehicle powertrain. 
           [0027]      FIG. 2  shows a highly schematic view of an example electrified vehicle having the powertrain of  FIG. 1 . 
           [0028]      FIG. 3  shows a perspective view of an example gear selector used in the electrified vehicle of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    This disclosure is directed toward maximizing fuel economy in an electrified vehicle. Some electrified vehicles use aggressive regenerative braking. Regenerative braking slows the electrified vehicle at a faster rate than permitting the electrified vehicle to coast to a stop. However, coasting, rather than applying regenerative brakes, can avoid losses associated with moving energy to and from a battery of the electrified vehicle. This disclosure provides a system for moving the electrified vehicle into a coast mode. 
         [0030]      FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle. Although depicted as a hybrid electrified 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 electrified vehicles (PHEVs), fuel cell vehicles, and battery electrified vehicles (BEVs). 
         [0031]    In one embodiment, the powertrain  10  is a powersplit powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of an engine  14  and a generator  18  (i.e., a first electric machine). The second drive system includes at least a motor  22  (i.e., a second electric machine), the generator  18 , and a battery pack  24 . 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  28  of the electrified vehicle. 
         [0032]    The engine  14 , which is an internal combustion engine in this example, and the generator  18  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  14  to the generator  18 . 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 . 
         [0033]    The generator  18  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  38  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 . 
         [0034]    The ring gear  32  of the power transfer unit  30  may be connected to a shaft  40 , 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  28 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  28 . 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 . 
         [0035]    The motor  22  (i.e., the second electric machine) can also be employed to drive the vehicle drive wheels  28  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In one embodiment, the motor  22  and the generator  18  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  18  can be employed as motors to output torque. For example, the motor  22  and the generator  18  can each output electrical power to the battery pack  24 . 
         [0036]    The battery pack  24  is an example type of electrified vehicle battery assembly. The battery pack  24  may have the form of a high voltage battery that is capable of outputting electrical power to operate the motor  22  and the generator  18 . Other types of energy storage devices and/or output devices can also be used with the electrified vehicle having the powertrain  10 . 
         [0037]    The example powertrain  10  includes a clutch  54  that can be actuated to move the gears  46 , or other portions of the power transfer unit  44 , between an engaged position and a disengaged position. In the engaged position, the first drive system, the second drive system, or both, can transmit torque to the differential  48 . In the disengaged position (shown in broken lines), the first and second drive systems cannot transmit torque to the differential  48 . The powertrain  10  is in a coast mode when the clutch  54  positions the power transfer unit  44  in the disengaged position. 
         [0038]    The example powertrain  10  responds to inputs from an accelerator pedal  56  and a brake pedal  58 . When the powertrain  10  is not in a coast mode, pressing the accelerator pedal  56  causes the powertrain  10  to accelerate the vehicle drive wheels  28 . Lifting off the accelerator pedal  56  slows the vehicle drive wheels  28 . Lifting off of the accelerator pedal  56  may, in some electrified vehicles, initiate regenerative braking. The regenerative braking generates power for the battery pack  24 . However, losses associated with moving power to and from the battery pack  24  can be introduced. 
         [0039]    Pressing the brake pedal  58  slows the vehicle drive wheels  28 . A relatively light press on the brake pedal  58  may initiate regenerative braking to slow the vehicle drive wheels  28 . Pressing the brake pedal  58  more firmly can slow the vehicle drive wheels  28  with a friction brake. Friction brakes introduce losses due to, among other things, the associated friction. 
         [0040]    When the accelerator pedal  56  and the brake pedal  58  are not pressed, some electrified vehicles may coast freely without regenerative braking. 
         [0041]    Other electrified vehicles, such as the electrified vehicle having a powertrain  10 , can initiate regenerative braking when the accelerator pedal  56  and the brake pedal  58  are not pressed. The regenerative braking, and losses associated therewith, will continue unless the powertrain  10  enters a coast mode where the clutch  54  disengages the power transfer unit  44 . 
         [0042]    Referring now to  FIGS. 2 and 3  with continuing reference to  FIG. 1 , an example electrified vehicle  60  includes the powertrain  10 . The electrified vehicle  60  includes a gear selector  64  and a coast switch  68 . The gear selector  64  can be actuated between a park mode, a reverse mode, a neutral mode, a drive mode, and a lower drive mode. 
         [0043]    When the gear selector  64  is in the drive mode as shown, the vehicle drive wheels  28  can be driven through the powertrain  10  if the power transfer unit  44  is in the engaged position. 
         [0044]    When the gear selector  64  is positioned in the neutral mode, the vehicle drive wheels  28  are free to move as is known. Positioning the gear selector  64  in the neutral mode when the electrified vehicle  60  is moving permits the electrified vehicle  60  to coast whether the power transfer unit  44  is engaged or disengaged. 
         [0045]    In the past, operators of the electrified vehicle  60  may have moved the gear selector  64  from the drive mode to the neutral mode when the electrified vehicle  60  is moving. This movement was to cause the electrified vehicle  60  to coast and to thus avoid losses associated with regenerative braking or friction braking. As can be appreciated, actuating the gear selector  64  from the drive mode to the neutral mode and then back to the drive mode to exit the coasting can be cumbersome. 
         [0046]    The coast switch  68  is separate from the gear selector  64 . Activating the coast switch  68  places the electrified vehicle  60  in a coast mode by causing the clutch  54  to move the power transfer unit  44  to the disengaged position. The electrified vehicle  60  can coast when in the coast mode. Notably, the gear selector  64  can stay in the drive mode when the coast switch  68  is activated. The coast switch  68  thus operates independently from the gear selector  64  and is thus considered separate from the gear selector  64 . 
         [0047]    The coast switch  68 , in this example, is a button  68   b  on a gear selector knob  72 . The button  68   b  is moveable from a first position to a second position. 
         [0048]    In the first position, the button  68   b  is released and not activated. The button  68   b  may be biased toward the first position. 
         [0049]    In the second position, the button  68   b  is depressed. In the second position, the button  68   b  causes the clutch  54  to move the power transfer unit  44  to the disengaged position thereby causing the powertrain  10  to operate in the coast mode. 
         [0050]    Holding the button  68   b  in the second position maintains operation of the electrified vehicle  60  in the coast mode. Depressing the button  68   b  overcomes the biasing force urging the button  68   b  toward the first position. 
         [0051]    A driver of the electrified vehicle  60  can cause the powertrain  10  to enter the coast mode when driving by pressing the button  68   b  as the electrified vehicle  60  is driven. Pressing the button  68   b  to coast the electrified vehicle  60  ensures that the powertrain  10  will not experience losses associated with regenerative braking. 
         [0052]    In addition to activating the clutch  54 , depressing the button  68   b  may cause the electric machines of the powertrain  10  to shut down to further conserve power in the coast mode. 
         [0053]    In other examples, the clutch  54  can be removed from the powertrain  10 . In such examples pressing the button  68   b  to activate the coast mode causes the electric machines (the generator  18  and the motor  22   a ) of the powertrain  10  to electrically shut down. In such examples, pressing the button  68   b  to activate the coast mode does not cause a movement of a clutch. 
         [0054]    Entering the coast mode thus may involve moving the clutch  54 , deactivating some or all of the electric machines, or some combination of these. 
         [0055]    The driver, when approaching a stop sign, may press the button  68   b  to cause the electrified vehicle  60  to enter the coast mode and coast rather than permit regenerative braking. The electrified vehicle  60  slows during the coast mode due to, among other things, frictional losses associated with the road. After coasting for a bit, the driver can press the brake pedal  58  to bring the electrified vehicle  60  to a complete stop with friction braking. Notably, the friction braking operates whether the power transfer unit  44  is engaged or disengaged. 
         [0056]    The driver then releases the button  68   b,  and the button  68   b  returns to the first position. The clutch  54  moves the power transfer unit  44  to the button  68   b  returning to the first position. 
         [0057]    Although the coast switch  68  is provided by the button  68   b  positioned on the gear selector knob  72 , the button  68   b  is separate from the gear selector  64  as the button  68   b  can be moved independently from the gear selector  64 . 
         [0058]    The example gear selector  64  includes a stick shift having the gear selector knob  72 . In another example, the gear selector  64  is a rotary shift knob that is rotated to move between the park mode, reverse mode, neutral mode, drive mode, etc. In such examples, the coast switch  68  can be a button positioned on an top or outwardly facing surface of the rotary shift knob. 
         [0059]    The coast switch  68  can be positioned on other areas of the electrified vehicle  60  including, but not limited to, the dash, or a steering wheel. The coast switch  68  may have the form of a paddle switch if the coast switch  68  is positioned on the steering wheel. 
         [0060]    The coast switch  68  could also be physically inaccessible by an operator of the electrified vehicle  60  during driving. In such examples, the coast switch  68  may be activated by an audible command from the operator of the electrified vehicle  60 . 
         [0061]    The electrified vehicle  60 , may include an indicator  78 , such as a light within an instrument cluster, notifying the operator that a coasting mode is engaged. The indicator is operably coupled to the coast switch  68  and may, light up when the coast switch  68  is in the first position. The indicator  78  could also be an audible alert, or some combination of an audible and visual indicator. 
         [0062]    Features of the disclosed examples include an electrified vehicle providing an operator with an option to enhance fuel economy by maximizing regenerative braking or by coasting. This dual approach allows the operator to enhance regenerative capture without requiring actuation of the brake pedal in heavy traffic. The same operator is able to capitalize on the benefits of a coast mode without requiring an awkward actuation of the gear selector. 
         [0063]    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.