Abstract:
A method of operating a plug-in hybrid electric vehicle is provided including the steps of: A) determining whether the plug-in hybrid electric vehicle is receiving power from an external power source; B) disabling the operation of the plug-in hybrid electric vehicle and executing a thermal program if the plug-in hybrid electric vehicle is receiving power from the external power source, wherein the thermal program includes charging a high voltage battery and monitoring the state of charge of the high voltage battery; C) determining if the plug-in hybrid electric vehicle continues to receive power from the external power source; and D) enabling operation of the plug-in hybrid electric vehicle if the plug-in hybrid electric vehicle is no longer receiving power from the external power source.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method of operating a plug-in hybrid electric vehicle. 
       BACKGROUND OF THE INVENTION 
       [0002]    Hybrid electric vehicles, which are powered with a combination of consumable fuel, such as fossil fuels, and electricity, typically stored within a battery, are becoming more prevalent in the automotive market. Such hybrid electric vehicles are displacing purely electric vehicles, as well as conventional vehicles powered solely by internal combustion engines. 
         [0003]    The purely electric vehicle typically lacks an on-board means to recharge the battery and therefore must be recharged from an external power source, such as household alternating current, a publicly accessible recharging facility, or any other external power source compatible with the recharging system of the vehicle. By contrast, the hybrid electric vehicle is typically not recharged from an external power source, but is instead recharged using energy from an onboard means. 
         [0004]    Typical hybrid electric vehicles incorporate both a battery powered electric motor and an internal combustion engine from which the battery may be recharged. Power may be provided to the vehicle drive system by the electric motor and/or the internal combustion engine. Hybrid electric vehicles can be refueled with fossil fuels, including but not limited to fuels which may be available from filling stations, without regard to availability of an external power source suitable for recharging the battery. Therefore, access to an external power source is typically not required for recharging a hybrid electric vehicle, since the batteries are recharged using power from the internal combustion engine. 
         [0005]    With typical hybrid electric vehicles, the recharging of the battery using power from the internal combustion engine makes the cost of recharging proportional to the cost of consumable fuel. This is not the case with purely electric vehicles, where the battery is recharged from the external power source. 
         [0006]    The present invention thus relates to plug-in hybrid electric vehicles, which differ from typical hybrid electric vehicles in that a plug-in hybrid electric vehicle has the ability to recharge its batteries either from an external power source, i.e. a power source outside the vehicle (such as household alternating current power), or from an onboard means (such as an internal combustion engine). Plug-in hybrid electric vehicles combine the ability of purely electric vehicles to recharge from an external power source using electric power generated by any cost-effective means available with the ability of hybrid electric vehicles to recharge using the power generated by the internal combustion engine. 
       SUMMARY OF THE INVENTION 
       [0007]    A method of operating a plug-in hybrid electric vehicle is provided including the steps of: A) determining whether the plug-in hybrid electric vehicle is receiving power from an external power source; B) disabling the operation of the plug-in hybrid electric vehicle and executing a thermal program if the plug-in hybrid electric vehicle is receiving power from the external power source, wherein the thermal program includes charging a high voltage battery and monitoring the state of charge of the high voltage battery; C) determining if the plug-in hybrid electric vehicle continues to receive power from the external power source; and D) enabling operation of the plug-in hybrid electric vehicle if the plug-in hybrid electric vehicle is no longer receiving power from the external power source. 
         [0008]    In a preferred embodiment, the method includes the further steps of: E) operating the plug-in hybrid electric vehicle in the purely electric mode of operation; F) monitoring the high voltage battery to determine a state of charge; G) determining if an internal combustion engine will be commanded to start within a predetermined amount of time; and H) performing at least one of heating the internal combustion engine by communicating heated engine coolant contained within a selectively dischargeable insulated container and energizing a catalyst heater to heat a catalyst mounted with respect to the internal combustion engine by discharging a selectively dischargeable energy storage device, if the internal combustion engine will be commanded to start within the predetermined amount of time or energy usage. 
         [0009]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagrammatic illustration of a portion of a plug-in hybrid electric vehicle incorporating a control system for a hybrid powertrain consistent with the present invention; and 
           [0011]      FIG. 2  is a method, depicted in flow chart format, illustrating various steps for operating the plug-in hybrid electric vehicle of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    Referring to  FIG. 1 , there is shown a portion of a plug-in hybrid electric vehicle, generally indicated at  10 . The plug-in hybrid electric vehicle  10  includes a control system  12  and a hybrid powertrain  14 . The hybrid powertrain  14  includes an internal combustion engine  16 , such as a spark-ignited or a compression-ignited engine, having a transmission  18  operatively connected thereto. The internal combustion engine  16  of  FIG. 1  is a compression ignited diesel engine; however, those skilled in the art will recognize the claimed invention may be applied to hybrid powertrains incorporating a spark-ignited engine while remaining within the scope of that which is claimed. The internal combustion engine  16  provides torque to the transmission  18 , which in turn, provides the requisite driving force to effect movement of the plug-in hybrid electric vehicle  10 . At least one motor  20  may be provided to effect movement of the plug-in hybrid electric vehicle  10  in conjunction with, or in lieu of that supplied by the internal combustion engine  10 , thereby providing hybrid functionality to the hybrid powertrain  14 . 
         [0013]    The internal combustion engine  16  includes a cylinder block  22  defining a plurality of cylinders  24 . Each of the cylinders  24  at least partially defines a variable volume combustion chamber  26 . Intake air, indicated by arrow  28 , is communicated to each of the combustion chambers  26  of the internal combustion engine  16  through an intake manifold  30 . A mixture of intake air  28  and fuel, not shown, is subsequently combusted within the combustion chambers  26  and the products of combustion, indicated by arrow  32 , are exhausted from the internal combustion engine through an exhaust manifold  34 . Lambda sensors or oxygen sensors  36  and  36 A are mounted with respect to the exhaust manifold  34  and operate to determine the percentage of oxygen contained within the products of combustion  32  to determine the air to fuel ratio of the internal combustion engine  16  during operation. The air to fuel ratio is especially important to enable optimal performance and efficiency of the internal combustion engine  16 . Heaters  38  and  38 A are mounted with respect to the respective oxygen sensors  36  and  36 A and are operable to heat the oxygen sensors  36  and  36 A to enable operation during cold starting or re-start conditions of the internal combustion engine  16 . 
         [0014]    A catalyst  40 , such as a three-way catalyst, is mounted downstream of the exhaust manifold  34  and is operable to reduce certain regulated emission constituents, such as oxides of nitrogen and hydrocarbons, from within the products of combustion  32 . The catalyst  40  includes a catalyst heater  42 . The catalyst heater  42  is preferably capable of heating or warming the catalyst  40  to, or close to, the catalyst light-off temperature during cold start of the internal combustion engine  16 , thereby reducing the regulated emission constituents at start up of the internal combustion engine  16 . To aid in starting the internal combustion engine  16 , a glow plug  44  is provided within each of the combustion chambers  26 . The glow plugs  44  operate to heat intake air  28  and fuel within the combustion chambers  26 , thereby providing a more favorable condition for combustion within the combustion chambers  26 . Additionally, an intake air heater  45  is provided at the inlet of the intake manifold  30  to heat the intake air  28  prior to entering the combustion chambers  26 , thereby providing a more favorable condition for combustion within the combustion chambers  26  and to reduce the likelihood of white smoke production during cold start of the internal combustion engine  16 . 
         [0015]    The cylinder block  22  further defines a water jacket  46  configured to contain a predetermined amount of engine coolant, indicated by arrows  48 . The engine coolant  48  extracts heat energy generated by operation of the internal combustion engine  16 . A engine coolant heater  50  is provided to warm the coolant prior to the starting of the internal combustion engine  16  to reduce the friction and hydrocarbon emissions and improve combustion stability at start-up. Similarly, a engine oil heater  52  is mounted with respect to an oil reservoir or pan  51 , shown apart from the internal combustion engine  16  for purposes of clarity, and operates to heat engine oil  53  contained therein. By heating the engine oil  53  prior to starting the internal combustion engine  16 , the viscosity of the engine oil  53  is reduced such that the operating efficiency of the internal combustion engine is increased. A coolant circulation pump  54  is provided to circulate engine coolant  48  through the internal combustion engine  16  and a heater core  56  to provide heat to the interior of the plug-in hybrid electric vehicle  10  when the internal combustion engine  16  is not operating. An insulated storage tank  58 , such as a dewar tank, is provided to contain a predetermined amount of heated engine coolant  48 . A valve  60  is provided to selectively discharge the heated coolant  48  from the insulated storage tank  58  to warm the internal combustion engine  16 . Those skilled in the art of vehicle design will recognize that a similar dewar tank and valve configuration may be used to store and discharge heated oil  53  to the internal combustion engine  16  such as, for example, a dry sump lubrication system. 
         [0016]    As a matter of convention, solid lines interconnecting devices within the control system  12  indicate lines of power, whereas the dashed lines interconnecting devices within the control system  12  indicate signal lines. The control system  12  of the plug-in hybrid electric vehicle  10  includes an umbilical cord  62  operable to communicate power from an external source  64 , such as household alternating current power, to the control system  12 . The control system  12  further includes a high voltage battery charger  66  operable to charge a high voltage battery  68  and communicate high voltage direct current power to a heating, ventilation, and air conditioning compressor  70 , and an auxiliary power module  72 . The auxiliary power module  72  converts the high voltage direct current from the high voltage battery charger  66  to a low voltage direct current and operates to charge and maintain a low voltage battery  74 . Those skilled in the art will recognize that power may be transferred from the external source  64  to the high voltage battery charger  66  via induction such as by coils  75 , shown in phantom. In this embodiment one of the coils  75  is mounted with respect to the plug-in hybrid electric vehicle  10  while the other is mounted remotely therefrom, such as below the surface of a garage floor. By employing the coils  75  to inductively charge the high voltage battery  68 , no physical connection between the external source  64  and the plug-in hybrid electric vehicle  10  is required. 
         [0017]    The low voltage battery  74  and auxiliary power source  72  cooperate to power a fan  76  operable to blow either warm or cool air into the interior of the plug-in hybrid electric vehicle  10 . The heater core  56 , air conditioning compressor  70 , and the fan  76  cooperate to form a heating, ventilation, and air conditioning system  77 , delimited by a phantom line in  FIG. 1 . Additionally, the low voltage battery  74  and auxiliary power source  72  cooperate to power the glow plugs  44 , the intake air heater  45 , the coolant circulation pump  54  and the valve  60 . The low voltage battery  74  and auxiliary power source  72  further cooperate to power an engine control module  78 , a hybrid vehicle control module  80 , and a body control module  81 . The engine control module  78  communicates operating parameters of the internal combustion engine  16  to the hybrid vehicle control module  80 , such as engine speed, engine load, engine coolant temperature, etc. and operates various engine-related devices such as a purge air scrubber heater  83 . Those skilled in the art will recognize that the purge air scrubber heater  83  is operable to enhance adsorption of trapped hydrocarbons within the vehicles evaporative emissions system, not shown. Additionally, the hybrid vehicle control module  80  is operable to communicate engine control parameters to the engine control module  78  to effect operation of the internal combustion engine  16 . The body control module  81  is operable to control passenger compartment features such as seat heaters  85  and an entertainment system  87  while monitoring the internal (i.e. passenger compartment) and external (i.e. ambient) air temperatures. A selectively dischargeable energy storage device  82 , such as a capacitor and/or battery, is charged by the low voltage battery  74  and auxiliary power source  72 . 
         [0018]    The alternating current from the external power source  64  provides power to the heaters  42 ,  50 , and  52  as well as a battery heater  84  operable to warm the high voltage battery  68  to prevent damaging the high voltage battery  68  in cold environments thereby increasing the reliability of the plug-in hybrid electric vehicle  10 . A high voltage battery control module  86  is provided to monitor the state of charge of the high voltage battery  68  and provide this state of charge information to the hybrid vehicle control module  80 . A user interface  88  communicates with the hybrid vehicle control module  80  to allow the operator of the plug-in hybrid electric vehicle  10  to program various aspects of the control system  12  to be discussed hereinbelow with reference to  FIG. 2 . 
         [0019]    The hybrid vehicle control module  80  selectively controls and monitors the operation of the catalyst heater  42 , engine coolant heater  50 , engine oil heater  52 , coolant circulation pump  54 , battery heater  84 , air conditioning compressor  70 , fan  76 , and valve  60  by selectively actuating respective relays  90 ,  92 ,  94 ,  96 ,  98 ,  100 ,  102 , and  104 . The body control module  81  selectively controls and monitors the operation of the seat heater  85  by selectively actuating a relay  105 . Similarly, the engine control module  78  selectively controls and monitors the operation of the glow plugs  44 , the intake air heater  45 , the energy storage device  82 , and the purge air scrubber heater  83  by selectively actuating respective relays  106 ,  107 ,  108 , and  109 . The engine control module  78  is configured to receive a signal from the oxygen sensors  36  and  36 A indicating the state of operation of the internal combustion engine  16 , i.e. rich or lean of stoichiometric engine operation. 
         [0020]    Referring to  FIG. 2 , and with continued reference to  FIG. 1 , there is shown a method  110  of operating the plug-in hybrid electric vehicle  10 . The hybrid vehicle control module  80  is preferably configured or programmed to operate the plug-in hybrid electric vehicle  10  in accordance with the method  110 . The method  110  begins at step  112  and proceeds to step  114  where a determination is made whether the umbilical cord  62  of the plug-in hybrid electric vehicle  10  is connected to the external power source  64 , thereby receiving power therefrom. If not, the engine control module  78 , hybrid vehicle control module  80 , and the high voltage battery control module  86  are allowed to “sleep” or remain deactivated, as indicated at step  116 . Alternately, if it is determined that the umbilical cord  62  of the plug-in hybrid electric vehicle  10  is connected to the external power source  64 , the method  110  will proceed to step  118 . 
         [0021]    At step  118 , the engine control module  78 , hybrid vehicle control module  80 , and the high voltage battery control module  86  are activated. At step  120 , the hybrid vehicle control module  80  will disable operation of the hybrid electric vehicle  10 . This function prohibits the inadvertent drive-off of the hybrid electric vehicle while the umbilical cord  62  is connected to the external power source  64 . 
         [0022]    At step  122 , a thermal program is initiated. The thermal program includes customer stored programs, such as passenger compartment desired temperature and expected commuting start times, and manufacturer stored programs, such as fuel economy and emissions related programs. The customer stored programs are preferably input to the hybrid vehicle control module  80  through the user interface  88 . The thermal program includes commanding the high voltage battery charger  66  to charge the high voltage battery  68 . The high voltage battery control module  86  will provide state of charge information to the hybrid vehicle control module  80 . The energy cost required to charge the high voltage battery  68  may be reduced by using power from the external power source  64  in lieu of the internal combustion engine  16 , since the price of household electricity is typically less that that of the fossil fuels used to operate the internal combustion engine  16 . Additionally, by charging the high voltage battery  68 , the plug-in hybrid electric vehicle  10  may be operated in a purely electric mode of operation thereby delaying the need to start the internal combustion engine  16 . At step  122 , the hybrid vehicle control module  80  will command the heaters  50  and  52  to heat the engine coolant  48  and engine oil  53 , respectively. The coolant circulation pump  54  is also commanded by the hybrid vehicle control module  80  thereby circulating the engine coolant  48  through the internal combustion engine  16  to increase the effectiveness of engine coolant heater  50 . By heating the engine coolant  48 , the internal combustion engine  16  is placed in a favorable condition for starting. With increased temperature of the engine coolant  48 , the combustion stability of the internal combustion engine  16  is improved, while the hydrocarbon emission constituents within the products of combustion  32  are reduced. By heating the engine oil  53  with the engine oil heater  52 , the viscous friction at engine start-up is reduced thereby reducing the starting effort and increasing the operating efficiency of the internal combustion engine  16 . The valve  60  may be selectively opened by the hybrid vehicle control module  80  to enable filling of the insulated storage tank  58  with a predetermined amount of heated engine coolant  48 . 
         [0023]    The coolant circulation pump  54  operates to pass heated engine coolant  48  through the heater core  56  which, in combination with the fan  76 , provides heat to the passenger compartment of the plug-in hybrid electric vehicle  10  for occupant comfort or defrosting purposes as necessary. Additionally, if cooling of the passenger compartment of the plug-in hybrid electric vehicle  10  is required, the hybrid vehicle control module  80  can command the air conditioning compressor  70  to operate in combination with the fan  76 . 
         [0024]    At step  122 , the hybrid vehicle control module  80  will monitor the state of the low voltage battery  74  and control the auxiliary power module  72 . If the plug-in hybrid electric vehicle  10  is in a cold ambient environment, the hybrid vehicle control module  80  may command the battery heater  84  to heat the high voltage battery  68 . Alternately, if the plug-in hybrid electric vehicle  10  is in a warm ambient environment, the hybrid vehicle control module  80  may command the air conditioning compressor  70  to operate in combination with the fan  76  to cool the high voltage battery  68  thereby increasing the life of the high voltage battery  68 . Those skilled in the art will recognize that a dedicated battery cooling fan, such a fan  76 , may be used to cool the high voltage battery  68  as opposed to relying solely on the heating, ventilation, and air conditioning system  77 . 
         [0025]    The thermal program at step  122  also includes heating the combustion chambers  26  of the internal combustion engine  16  by selectively activating the glow plugs  44  and intake air heater  45 , thereby placing the internal combustion engine  16  in a more favorable condition for starting. The operation of the glow plugs  44  and intake air heater  45  are commanded by the hybrid vehicle control module  80  through the engine control module  78 . The hybrid vehicle control module  80  may also command the catalyst heater  42  to heat the catalyst  40  thereby reducing regulated emission constituents following the starting of the internal combustion engine  16 . The engine control module  78  will command the heaters  38  and  38 A to heat the respective oxygen sensors  36  and  36 A to enable accurate control of the fueling of the internal combustion engine  16  as well as the purge air scrubber heater  85  to improve evaporative emissions system performance. The energy storage device  82  is charged during the thermal program, i.e. step  122  of the method  110 . 
         [0026]    At step  124 , the engine control module  78 , hybrid vehicle control module  80 , and the high voltage battery control module  86  monitor temperatures and currents of the various devices or components such as, coolant circulation pump  54 , air conditioning compressor  70 , etc., commanded to operate at step  122 . At step  126  the devices commanded to operate at step  122  are controlled within temperature and/or current limits as well as order of precedence. The hybrid vehicle controller  80  ensures that the external power source  64  is not overloaded while performing the thermal program initiated at step  122 . Additionally, if the external power source  64  should fail prior to a programmed time or event, the hybrid vehicle control module  80  may alert the operator of the vehicle by flashing lights, sounding a horn, and/or deliver a message to the user interface  88  indicating that the power form the external power source  64  has been interrupted. 
         [0027]    At step  128 , a determination is made whether the thermal program has timed out. That is, a determination is made as to whether the devices commanded to operate during the thermal program at step  122  have been activated for greater than or equal to a predetermined amount of time. If so, the engine control module  78 , hybrid vehicle control module  80 , and the high voltage battery control module  86  are deactivated at step  130 . Otherwise, the method  110  proceeds to step  132  where a determination is made whether the external power source  64  is still providing power to the plug-in hybrid electric vehicle  10 , such as through the umbilical cord  62  or coils  75 . If so, the method  110  will loop to step  124 . Alternately, the method  110  will proceed to step  134  where the hybrid vehicle control module  80  will enable operation of the plug-in hybrid electric vehicle  10  at step  134 . At step  136 , the hybrid vehicle control module  80  will execute an electric driving procedure. This may include activating an entertainment system to preprogrammed settings, greeting the operator, and other features and functions programmed into the hybrid vehicle control module  80  through the user interface  88 . Additionally, at step  136 , the plug-in hybrid electric vehicle  10  may be operated in a purely electric mode of operation relying solely on the motor  20  powered by the high voltage battery  68  to provide drive force to the plug-in hybrid electric vehicle  10 . 
         [0028]    At step  138  a determination is made as to whether starting of the internal combustion engine  16  is imminent; such as when the state of charge of the high voltage battery  68  drops below a predetermined level or the operator torque request is greater than can be provided by the motor  20 . If engine start is not imminent, the method  110  will loop to continuously monitor the engine start criteria. Alternately, the method  110  proceeds to step  140  where an engine start procedure is executed. At step  140 , the engine control module  78  allows the energy storage device  82  to discharge thereby activating the catalyst heater  42 , which in turn heats the catalyst  40 . As mentioned hereinabove, by preheating the catalyst  40 , the regulated emission constituents within the products of combustion  32  may be reduced at engine start. Additionally, at step  140 , the hybrid vehicle control module  80  commands the valve  60  to open thereby allowing the heated engine coolant  48  contained therein to be circulated through the cylinder block  22  of the internal combustion engine  16 . As described hereinabove, by preheating the internal combustion engine  16  prior to start up, hydrocarbon exhaust emissions may be reduced, while combustion stability is increased. 
         [0029]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.