Climate control system for a vehicle

A vehicle includes a refrigerant system having an intermediary heat exchanger, an exterior heat exchanger, and an expansion device disposed therebetween. The vehicle also includes a coolant circuit having a pump configured to circulate coolant through the intermediary heat exchanger and an engine. A controller is programmed to, in response to air conditioning being requested and the coolant temperature exceeding a threshold temperature, open the expansion device and de-energize the pump to condense refrigerant in the exterior heat exchanger.

TECHNICAL FIELD

The present disclosure relates to a control strategy for operating the vehicle during an air conditioning mode.

BACKGROUND

The need to reduce fuel consumption and emissions in automobiles and other vehicles is well known. Vehicles are being developed that reduce reliance or completely eliminate reliance on internal-combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles in that they are selectively driven by one or more battery powered electric machines. Many electrified vehicles include thermal management systems that mange the thermal demands of various components during vehicle operation, including the vehicle's high-voltage fraction battery and the internal-combustion engine (if provided).

SUMMARY

According to one embodiment, a vehicle includes a refrigerant system having an intermediary heat exchanger, an exterior heat exchanger, and an expansion device disposed therebetween. The vehicle also includes a coolant circuit having a pump configured to circulate coolant through the intermediary heat exchanger and an engine. A controller is programmed to, in response to air conditioning being requested and the coolant temperature exceeding a threshold temperature, open the expansion device and de-energize the pump to condense refrigerant in the exterior heat exchanger.

According to another embodiment, a vehicle includes an engine and a traction battery electrically connected to at least one electric machine. A refrigerant system of the vehicle includes an exterior heat exchanger, an intermediary heat exchanger, an expansion device located between the heat exchangers, and a bypass loop having an inlet disposed between the heat exchangers and arranged to bypass the exterior heat exchanger. A coolant circuit of the vehicle includes a pump configured to circulate coolant through the engine and the intermediary heat exchanger. Grille shutters are disposed behind a front fascia of the vehicle and are disposed in front of the exterior heat exchanger. A controller is programmed to, in response to air conditioning being requested and a temperature of the coolant being less than a threshold temperature, close the expansion device such that refrigerant bypasses the exterior heat exchanger via the bypass loop, and energize the pump to transfer heat from the refrigerant system to the coolant circuit via the intermediary heat exchanger such that refrigerant is condensed in the intermediary heat exchanger.

According to yet another embodiment, a method of operating a vehicle climate control system is disclosed. The vehicle includes grille shutters and a heat exchanger in fluid communication with a refrigerant system and an engine cooling loop having coolant. The method includes, in response to air conditioning being requested and the coolant having a temperature less than a threshold temperature, transferring heat from the refrigerant system to the engine cooling loop via the heat exchanger, and closing the grille shutters.

DETAILED DESCRIPTION

FIG. 1depicts a schematic of a typical plug-in hybrid-electric vehicle. Certain embodiments may also be implemented within the context of non-plug-in hybrid-electric vehicles. Referring toFIG. 1, a vehicle10includes a powertrain12, such as a power-split powertrain including a first drive system and a second drive system. The first drive system includes an engine14and a first electric machine or generator16. The second drive system includes a second electric machine or motor18, the generator16, and a traction battery assembly20. The first and second drive systems generate torque to drive one or more of the vehicle driven wheels22.

The engine14, such as an internal-combustion engine, and the generator16may be connected through a power-transfer unit24. The power transfer unit24may be a planetary gear set that includes a ring gear26, a sun gear28and a carrier assembly30. Other types of power-transfer units are contemplated by the present disclosure. The powertrain12may include additional gearing32for coupling the generator16to the motor18and for coupling the generator and/or the motor to the differential34to distribute torque to the wheels22.

The vehicle10also includes a battery energy control module (BECM) for controlling the battery20. The BECM receives input that is indicative of vehicle conditions and battery conditions, such as battery temperature, voltage and current. The BECM calculates and estimates battery parameters, such as battery state of charge and the battery power capability. The BECM provides output that is indicative of a battery state of charge (SOC) and a battery power capability to other vehicle systems and controllers.

The vehicle10includes a plurality of controllers for controlling the function of various components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN)) or via dedicated electrical conduits. The controller generally includes any number of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM) and software code to co-act with one another to perform a series of operations. The controller also includes predetermined data, or “look up tables” that are based on calculations and test data, and are stored within the memory. The controller may communicate with other vehicle systems and controllers over one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). Used herein, a reference to “a controller” refers to one or more controllers.

The hybrid-electric vehicle10may be operated in a plurality of different powertrain modes including charge-sustaining mode and charge-depleting mode (also known as EV mode). In charge-depleting mode, the battery is used as the primary source for propulsion until the battery SOC drops below a threshold SOC, at which point, the vehicle switches to charge-sustaining mode. Used herein, the term charge-depletion mode refers to modes where the engine may run periodically and to modes where the engine is not used. For example, the vehicle may include an EV-only mode (also known as EV now) where the engine is disabled.

Referring toFIG. 2, the vehicle10includes a front fascia having a grille. A grille shutter-assembly40is disposed within the engine compartment behind the grille and in front of the engine14. The shutter assembly40includes a housing41attached to one or more vehicle body structures behind the front fascia of the vehicle10. The housing41defines at least one opening42. A plurality of shutters43are pivotally attached to the housing41and are disposed in one or more of the openings42. Each of the shutters43are movable between an open position, a closed position, and a plurality of intermediate positions via an actuator44. The actuator44may include a motor that is electrically controlled by the controller. For illustrative purposes, the upper bank of shutters is shown in the open position and the lower bank of shutters is shown in the closed position. In some embodiments, the upper and lower banks of shutters operate dependently, and in other embodiments, the upper and lower banks operate independently. Each of the shutters43also includes a major side47and a minor side45. When in the closed position, each of the shutters43are rotated such that the major sides47face the airstream to block air from entering through the openings42. When in the open position, each of the shutters are rotated such that the minor sides45face the airstream allowing air to flow through the openings42. The openings42and the shutters43cooperate to define an effective cross-sectional area through which air may pass. The size of the effective cross-sectional area can be increased or decreased by moving the shutters.

The traction battery24, the passenger cabin, and other vehicle components are thermally regulated with one or more thermal management systems. Example thermal management systems are shown in the figures and described below. Referring toFIG. 3, the vehicle10includes a cabin46and an engine compartment48that are separated by a bulkhead49. Portions of the various thermal management systems may be located within the engine compartment, the cabin, or both. The vehicle10includes a climate control system50having a refrigerant subsystem52, a cabin-heating subsystem or cabin loop54, and a ventilation subsystem56.

The ventilation subsystem56may be disposed within the dash of the cabin46. The ventilation subsystem56includes an HVAC housing58having an air-inlet side and air-outlet side. The outlet side is connected to ducts that distribute exiting air into the cabin. A blower motor drives a fan (or cabin blower)60for circulating air in the ventilation system56. A blend door59is disposed in the housing for controlling a temperature of the air exiting the housing58. The vehicle10may also include a battery thermal management system (not shown) for regulating the temperature of the traction battery20.

The refrigerant subsystem52is used to provide air conditioning of the cabin during some operating modes. The refrigerant subsystem52is also used to cool the battery20during some operating modes and is used to heat the battery during other operating modes. The refrigerant subsystem52may be a vapor-compression refrigerant subsystem that circulates a refrigerant transferring thermal energy to various components of the climate control system50. The refrigerant subsystem52may include a cabin loop having a compressor64, an exterior heat exchanger66(which is normally a condenser), an interior heat exchanger68(which is normally an evaporator), an accumulator70, fittings, valves and expansion devices. The compressor may be an electronic compressor. The heat exchanger66may be located behind the grille shutters40near the front of the vehicle, and the evaporator68may be disposed within the housing58. It is to be understood that heat exchangers labeled as “condenser” may also act as an evaporator in some modes. In one embodiment, the refrigerant subsystem52is a heat pump and may be used for both cooling and heating the cabin.

The cabin loop components are connected by a plurality of conduits, tubes, hoses or lines. For example, a first conduit72connects the compressor64and the heat exchanger66in fluid communication, a second conduit74connects the heat exchanger66to a valve82, a third conduit76connects the heat exchanger66and the evaporator68in fluid communication, and a fourth conduit78connects the evaporator68and the compressor64in fluid communication. An evaporator bypass conduit80is connected between the valve82and conduit78. The valve82may be a solenoid valve that can be opened and closed to supply refrigerant to either the conduit76or conduit80depending upon the operating mode of the refrigerant subsystem52. For example, refrigerant is circulated into conduit76and not into conduit80when the air conditioning is ON. The valve82may be in communication with a controller100. A heat exchanger79is arranged to transfer thermal energy between conduit76and conduit78.

A first expansion device84may be disposed on conduit72and a second expansion device86may be disposed on conduit76. The expansion devices are configured to change the pressure and temperature of the refrigerant in the refrigerant subsystem52. The expansion devices may include an electronic actuator controlled by the controller100. The controller100may instruct the actuator to position the expansion device in a wide-open position, a fully closed position, or a throttled position. The throttled position is a partially open position where the controller modulates the size of the valve opening to regulate flow through the expansion device. The controller100and expansion devices may be configured to continuously or periodically modulate the throttled position in response to system operating conditions. By changing the opening within the expansion device, the controller can regulate flow, pressure, temperature, and state of the refrigerant as needed. In alternative embodiments, a thermally-controlled expansion device (TXV), or fixed orifice tube with shut-off valves may be used in lieu of the electronically-controlled expansion devices.

The refrigerant subsystem52also includes a bypass loop88for bypassing the exterior heat exchanger66. A bypass valve90is disposed on the bypass loop88and is actuatable to selectively allow refrigerant flow through the bypass loop88. The valve90may be a solenoid valve that is electronically controlled by the controller100. The valve90and the expansion device84cooperate to either circulate refrigerant through the exterior heat exchanger66, or through the bypass loop88. The refrigerant subsystem52may include a battery loop (not shown) having a another evaporator (commonly referred to as a chiller) and a third expansion device for thermally regulating the battery.

The cabin loop54includes a heater core110, an auxiliary pump114, valve116, and conduit forming a closed loop for circulating coolant, such as an ethylene-glycol mixture. For example, coolant may be circulated from the auxiliary pump114to the heater core110via conduit122. The heater core110is connected to the valve116via conduit124. Valve116is connected to the pump114via conduit128. The valve116may be a solenoid valve that is electronically controlled by the controller100. A temperature sensor118may be disposed on conduit122.

The engine14is thermally regulated by an engine-cooling loop130that is arranged to circulate coolant—such as an ethylene-glycol mixture—through the engine14. The engine cooling loop130includes a radiator132, thermostat134, and an engine-coolant pump136(also known as a water pump) that are interconnected by plurality of conduits to form a coolant circuit. The engine loop130and the cabin loop54may be selectively interconnected to form a single coolant circuit during some operating modes and selectively disconnected to form separate coolant circuits during other modes.

The engine pump136may be connected to an inlet port of the engine14via conduit138. The engine pump136may be powered by electricity supplied from the battery20or other current source. The outlet port of the engine14may be connected to conduit128of the cabin loop54via conduit140. An inlet of the radiator132may be connected to conduit140via conduit142. An outlet of the radiator132is connected to the thermostat134via conduit144. The thermostat134is connected to the water pump136via conduit146. The engine loop130also includes a radiator bypass148. The thermostat134controls whether coolant is circulated to the radiator132or to the radiator bypass148depending upon a temperature of the coolant. Thermostat134may be electronically controlled or may be mechanically controlled. The thermostat134may be connected to the valve116via conduit150. The illustrated arrangement of the engine loop130is merely an example and many other arrangements are contemplated by the present disclosure. In some embodiments, another temperature sensor may be disposed on line140. Or the coolant temperature at line140may be inferred based on a temperature of the engine. The cabin loop54may also include an electric heater disposed on line122.

The cabin loop54may exchange thermal energy with the refrigerant subsystem52via an intermediary heat exchanger126, which is a refrigerant-to-coolant heat exchanger. The heat exchanger126may have any suitable configuration. For example, the heat exchanger126may have a plate-fin, tube-fin, or tube-and-shell configuration that facilitates the transfer of thermal energy without mixing the heat transfer fluids. The heat exchanger126may be connected to conduit72of the refrigerant subsystem52and connected to conduit122of the cabin loop54. In some operating modes, the heat exchanger126may transfer thermal energy from the refrigerant subsystem52to the cabin loop54in order to heat the cabin46. In other operating modes, the heat exchanger126may transfer thermal energy from the refrigerant subsystem52to the cabin loop54in order to heat the engine14. In yet another operating mode, the heat exchanger126may act as a condenser during an air-conditioning mode and transfer heat from the refrigerant subsystem52to the cabin loop54. The cabin loop54may include a by-pass line (not shown) to bypass the intermediary heat exchanger126when it is not desired to exchange heat between the cabin loop54and the refrigerant subsystem52. The by-pass line may be controlled by a valve.

The climate control system50may operate in a plurality of different modes, which can be broken down into two main categories; heating and air conditioning. The climate control system50may operate in a plurality of different air-conditioning modes including a first AC mode and a second AC mode. The refrigerant subsystem52operates differently in the first and second AC modes.

In the first AC mode, the exterior heat exchanger66acts as a condenser and the interior heat exchanger68acts as an evaporator, which is typical of automotive refrigerant systems. In this mode, the compressor64pressurizes the refrigerant into a hot vapor that is circulated through an inactive intermediary heat exchanger126to the expansion device84, which is in the fully open position. As the refrigerant passes through the heat exchanger66it condenses into a liquid state as heat is transferred from the refrigerant to the air passing through the heat exchanger66. The valve82is in the closed position forcing the refrigerant to flow from the heat exchanger66to the second expansion device86via conduit76. The expansion device86is in the throttled position. The expansion device86lowers the pressure and temperature of the refrigerant prior to entering the evaporator68. The evaporator68extracts heat from air being circulated within the housing58to cool the cabin46. The refrigerant then exits the evaporator68, travels through the accumulator70and back to the compressor64for recirculation. In this mode, the bypass valve90is in the closed position forcing all of the refrigerant through the heat exchanger66. In this mode, the pump114may be OFF and valve116may be positioned so that no coolant flow through heat exchanger126to avoid transferring heat from the cabin loop54to the refrigerant system52.

FIG. 4illustrates the vehicle10operating in the second AC mode. The bold lines signify active conduits. When the temperature of the engine coolant is below a threshold temperature (TempTH), the climate control system50may operate in the second AC mode. PHEVs typically operate in a charge-depleting mode when first departing with a high battery SOC. The vehicle will continue in charge-depleting mode until the battery SOC drops below a threshold state of charge, at which point, the vehicle enters into a charge-sustaining mode. During a charge-depleting mode, the engine14is intermittently run, if at all. Thus, the coolant temperature typically remains below the threshold temperature until the vehicle switches to charge-sustaining mode. The second AC mode is typically available when the vehicle is in charge-depleting mode.

In this mode, the intermediary heat exchanger126is the condenser, the heat exchanger68is the evaporator, and the exterior heat exchanger66is inactive. The heat exchanger126transfers thermal energy from the refrigerant to the coolant, and not to the outside air like a traditional automotive condenser does. Because of this, air flow is not required within the engine bay48. Thus, the grille shutters40may be closed and the engine-cooling fan152may be OFF. Closing the grille shutters40increases the aerodynamics of the vehicle providing better fuel efficiency and electric range. De-energizing the fan152reduces current draw on the traction battery20and increases battery range. This combination of improved aerodynamics and reduced current draw helps increase the electric range of the vehicle10. This also pre-heats the engine and other components increasing efficiency at engine start up, which increases fuel economy.

In the second AC mode, the compressor64pressurizes the refrigerant into a hot vapor that is circulated through an active intermediary heat exchanger126that is operating as a condenser. The expansion valve84is closed and the bypass valve90is open causing the refrigerant to circulate through the bypass line88skipping the exterior heat exchanger66. The refrigerant is then circulated through conduit76to the evaporator68. The refrigerant passing through the evaporator68evaporates and extracts heat from the air passing with in the housing58to cool the cabin. The refrigerant is returned to the compressor64via conduit78for recirculation.

The valve116is actuated such that the cabin loop54and the engine loop130form a single coolant circuit. Coolant within the cabin loop54and the engine loop130is circulated through the heat exchanger126to extract heat from the refrigerant subsystem52in order to condense the refrigerant. Either or both of the pumps114and136may be energized to drive the coolant. For example, both the auxiliary pump114and the engine pump136are energized to circulate coolant through the heat exchanger126and to the heater core110via conduit122. In some embodiments, a heater core bypass line may be provided. From the heater core110, coolant is circulated to the valve116via conduit124. The valve116is actuated to circulate coolant from conduit124to the thermostat via conduit150. The coolant then circulates into the engine pump136via conduit146. The engine pump136circulates the coolant through water jackets within the engine14and out an outlet port of the engine to conduit140. Conduit140includes a fitting arranged to circulate a portion of the coolant into conduit142and a portion of the coolant to conduit128of the cabin loop54. A much larger portion of the coolant may be circulated to conduit128than to conduit142. The portion circulated to128is circulated to the pump114for recirculation. Conduit142is connected to the radiator132and is connected to conduit148. In some embodiments, conduit148is connected to conduit140instead. The thermostat134is closed because the opening temperature for the thermostat is greater than or equal to the threshold temperature. The threshold temperature may be 25 to 50 degrees Celsius (C). Because the thermostat134is closed, the radiator132is inactive and any coolant in conduit142is circulated through conduit148and back to the engine pump136.

Unlike a traditional AC operation, where passing air is used as a condensing medium, during the second AC mode, the engine coolant is used as the condensing medium. The engine14is a large heat sink that can absorb a fairly high amount of thermal energy. Depending upon the size and materials of the engine14, the coolant loop may be used as the condensing medium for a fair amount of time before the temperature of the coolant exceeds the threshold temperature. When the coolant temperature exceeds the threshold temperature the climate control system must switch to the first AC mode because the coolant temperature is too hot to properly condense the refrigerant in the refrigerant subsystem52, therefore decreasing the efficiency and capacity of the refrigerant subsystem.

FIG. 5illustrates a control strategy200for choosing between the first AC operating mode and the second AC operating mode. At operation202the controller determines if air conditioning is being requested. If no, control passes back to the start. If yes, control passes to operation204, and the controller determines if the coolant temperature is less than or equal to the threshold temperature. If the coolant temperature is above the threshold temperature, control passes to operation206and the climate control system operates in the first AC mode. If the coolant temperature is less than or equal to the threshold temperature, the climate control system50may operate in the second AC mode. In operation208the controller instructs the expansion device84to the closed position and instructs the bypass valve90to the open position. When the expansion device84and the valve are actuated this way, refrigerant bypasses the exterior heat exchanger66and flows from conduit72to conduit76via bypass line88. At operation210the controller sends a signal energizing the engine pump136, the auxiliary pump114or both to circulate coolant through the heat exchanger126. At operation212the controller sends a signal energizing the cabin blower60to circulate cool air into the cabin46. At operation214the controller sends a signal actuating the valve116such that coolant is circulated from the heater core to the engine14. At operation216the controller sends a signal instructing the grille shutters40to the closed position to improve the aerodynamics of the vehicle. At operation218the controller sends a signal to de-energizing the fan152.

FIG. 6illustrates a control strategy250for switching from the second AC mode to the first AC mode. At operation252the controller determines if air conditioning is being requested. If air conditioning is being requested control passes operation254and the controller determines if the coolant temperature is greater than the threshold temperature. If no, the vehicle continues to operate in the second AC mode. If yes, control passes to operation258and the controller sends a signal instructing the expansion device84to a wide-open position and the bypass valve90is instructed to a closed position to circulate the refrigerant to the exterior heat exchanger66. At operation260the controller sends a signal to de-energize the auxiliary pump114and close valve116to stop the circulation of coolant through heat exchanger126. The controller determines a position of the grille shutter40at operation262and determines a duty cycle of the fan152at operation264.

FIG. 7illustrates another control strategy300for choosing between the first AC operating mode and the second AC operating mode. At operation302the controller determines if air conditioning is being requested. If no, control passes back to the start. If yes, control passes to operation304, and the controller determines if the coolant temperature is less than or equal to the threshold temperature. If the coolant temperature is above the threshold temperature, control passes to operation306and the climate control system50operates in the first AC mode. If the coolant temperature is less than or equal to the threshold temperature, control passes to operation308. At operation308the controller determines if the battery SOC is greater than or equal to a threshold charge (ChargeTH). If no, control passes to operation306and the system operates in the 1stAC mode. If yes, control passes operation310and the controller determines if the vehicle is in a charge-depleting mode. If the vehicle is not operating in a charge-depleting mode, control passes to operation306. If the vehicle is in a charge-depleting mode, the climate control system50may operate in the second AC mode and control passes operation312. At operation312the controller instructs the expansion device84to the closed position and instructs the bypass valve90to the open position. When the expansion device84and the valve are actuated this way, refrigerant bypasses the exterior heat exchanger66and flows from conduit72to conduit76via bypass line88. At operation314the controller energizes the water pump136, the auxiliary pump114or both to circulate coolant through the heat exchanger126. At operation316the controller sends a signal energizing the cabin blower60to circulate cool air into the cabin46. At operation318the valve116is actuated such that coolant is circulated from the heater core110to the engine14. At operation320the controller sends a signal instructing the grille shutters40to the closed position to improve the aerodynamics of the vehicle. At operation322the controller sends a signal to de-energizing the fan152. The control strategies were described with reference to the vehicle layout shown inFIGS. 3 and 4. However, the control strategies are equally applicable to other layouts.