Cabin air conditioning system for a vehicle and method of controlling the vehicle and system

An air conditioning system, a vehicle and a method of controlling the vehicle with a vehicle air conditioning system are provided. The vehicle air conditioning system has a refrigeration circuit having a compressor, a condenser, and an evaporator in sequential fluid communication, with a valve assembly and a battery chiller positioned for parallel flow with the evaporator. A cooling circuit in the vehicle has a chiller. A controller is configured to, in response to a temperature of the evaporator being less than a first predetermined value and the compressor operating at a predetermined speed, open the valve assembly to divert a portion of refrigerant through the chiller and away from the evaporator. The refrigerant may be diverted, for example, to raise the temperature of the evaporator and/or prevent cycling of the compressor.

TECHNICAL FIELD

Various embodiments relate to a vehicle with a traction battery and a cabin air conditioning system, and a method for controlling the vehicle and system.

BACKGROUND

Vehicles conventionally have an air conditioning system for a vehicle cabin, e.g. a heating, ventilation, and air conditioning system, to provide climate control for the vehicle occupants. During operation of the air conditioning system, the evaporator may reach low operating temperatures, and if the temperatures are sufficiently low, the evaporator may experience icing and the performance of the air conditioning may be degraded. In order to de-ice an evaporator, the compressor for the air conditioning system is typically turned off such that the air conditioning system is disabled until the evaporator temperature rises and the evaporator de-ices.

SUMMARY

According to an embodiment, a vehicle is provided with a fluid circuit having a chiller and containing a coolant. A refrigeration circuit for a cabin air conditioning system is provided and contains a refrigerant. The refrigeration circuit has a compressor, a condenser, a first valve assembly and a cabin evaporator in sequential fluid communication. The refrigeration circuit has a second valve assembly and the chiller positioned for parallel flow of refrigerant with the first valve assembly and the cabin evaporator. A temperature sensor is positioned to measure a temperature of the evaporator. A controller is configured to, while the refrigeration circuit is operating and in response to the temperature of the evaporator being less than a first threshold value and the compressor operating at a predetermined speed, open the second valve assembly to divert a portion of refrigerant through the chiller while another portion of refrigerant flows in parallel through the evaporator.

According to another embodiment, a method of controlling a vehicle is provided. A refrigeration circuit is operated for a cabin air conditioning system containing a refrigerant, with the refrigeration circuit having a compressor, a condenser, a first valve assembly and a cabin evaporator in sequential fluid communication with refrigerant flowing therethrough. A signal is received that is indicative of a temperature of the evaporator. While the refrigeration circuit is operating and in response to the temperature of the evaporator being less than a first predetermined value and the compressor operating at a predetermined speed, a second valve assembly in the refrigeration circuit is opened to divert a portion of refrigerant through a chiller while another portion of refrigerant flows in parallel through the evaporator thereby increasing the temperature of the evaporator. The refrigeration circuit has the second valve assembly and the chiller positioned for parallel flow of refrigerant with the first valve assembly and the cabin evaporator.

According to yet another embodiment, a vehicle air conditioning system is provided with a refrigeration circuit having a compressor, a condenser, and an evaporator in sequential fluid communication, with a valve assembly and a battery chiller positioned for parallel flow with the evaporator. A controller is configured to, in response to a temperature of the evaporator being less than a first predetermined value and the compressor operating at a predetermined speed, open the valve assembly to divert a portion of refrigerant through the chiller and away from the evaporator.

DETAILED DESCRIPTION

As required, detailed embodiments of the present disclosure and provided herein;

FIG. 1illustrates a schematic of a vehicle10configured to implement the present disclosure. The vehicle10is an electrified vehicle, such that the vehicle may be propelled using electric power. In various examples, the vehicle10may be provided by a hybrid vehicle, such as a parallel, power split, or series hybrid electric vehicle, a battery electric vehicle, start-stop vehicle, a micro-hybrid vehicle, a plug-in hybrid electric vehicle, or other vehicle system architectures with electric propulsion.

The vehicle has one or more electric motors or electric machines12that are configured to propel the vehicle using electric power. In various examples, the vehicle may or may not have another prime mover, such as an internal combustion engine14, or the like. The electric machine12outputs mechanical power when operating as a motor to propel the vehicle. The electric machine12may also operate as a generator to convert mechanical power into electrical power. The electric machine and any other prime movers are connected to the driveline and the vehicle wheels via a transmission16.

The vehicle10has a control system18with one or more controllers or control modules for the various vehicle components and systems. The control system18for the vehicle may include any number of controllers, and may be integrated into a single controller, or have various modules. Some or all of the controllers may be connected by a controller area network (CAN) or other system. It is recognized that any controller, circuit or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof) and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices as disclosed herein may be configured to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed herein.

The electric machine12is connected to an energy storage system20via an inverter22. The energy storage system20may be provided by a high voltage battery or traction battery. A charger24may be provided to connect the vehicle to an outside electrical source, such as a charging station with 110 V or 220 V power. The traction battery20may be provided by a battery pack made up of one or more battery modules. Each battery module may contain one battery cell or a plurality of battery cells. The battery cells are heated and cooled using a coolant system30as described below with respect toFIG. 2. Additionally, electrical components for the vehicle, such as the inverter22, the charger24, a DC-DC converter26for a secondary battery or accessories, and the like, may be cooled using the coolant system. The coolant system30is in communication with the vehicle control system18and the on/off status or any requests for operation of the coolant system may be communicated via the vehicle controller18, and can be based on, for example, an operating temperature of one or more of the electrical components, and the like.

The vehicle10includes a climate control system32as described below with respect toFIG. 2for heating and cooling various vehicle components, including the vehicle cabin as a heating, ventilation, and air conditioning (HVAC) system. The climate control system32includes an electric compressor, according to one or more embodiments. The climate control system may additionally include one or more heaters. The climate control system32is in communication with the vehicle control system18and the on/off status may be communicated via the vehicle controller, and can be based on, for example, the status of an operator actuated switch, or the automatic control of the climate control system based on related functions, such as window defrost. The climate control system32may additionally be connected to a user interface to permit a user to set a temperature for the cabin.

FIG. 2illustrates a schematic of fluid systems100for use with the vehicle ofFIG. 1according to an embodiment. Components that are the same as or similar to those described above with respect toFIG. 1are given the same reference number for simplicity.

The system100has a first fluid circuit or loop is provided, and may be used as a coolant system30for one or more vehicle electrical components such as a traction battery, inverter, charger, and the like. A second fluid circuit or loop is provided, and is provided as a cabin air conditioning system32with a refrigeration circuit or loop. The coolant circuit30and the refrigeration circuit32are provided as separate fluid loops such that the fluid in one circuit does not mix with the fluid in the other circuit. Additionally, the fluids in each circuit30,32may be different from or the same as one another. As used herein, a fluid refers to a liquid-phase, a vapor-phase, or a mixed liquid-vapor phase for the fluid in the respective circuit. Additionally, the fluid may change phases within a respective circuit as it circulates. According to one example, the coolant in the fluid circuit30remains in liquid phase during operation of the circuit, while the refrigerant in the refrigeration circuit32may change phases within the circuit, for example, as in a vapor-compression refrigeration cycle.

The coolant circuit30is provided with a pump102, a chiller104, and a component106for thermal management. The cooling circuit30may be provided with a cooling jacket or other fluid passages within or adjacent to the component106for thermal management of the component. According to one example, the component106may be a traction battery20, an inverter22, a converter26, a charger24, or another component in the electric propulsion system for the vehicle10. Although only one component106is shown, the cooling circuit30may be configured to cool multiple components, for example, with the coolant flowing to the components106arranged for parallel or series flow of coolant therethrough. Additionally, the cooling circuit30may have a single chiller104as shown, or more than one chiller104in various configurations.

Additionally, and in other examples, the coolant circuit30may be provided with a heater, such as a PTC heater, valves, a reservoir, and other fluid system components that are not shown for simplicity. The cooling circuit30may be provided with various sensors, for example, one or more temperature sensors on an associated component. The control system18operates the cooling circuit30to maintain operating temperatures of the component(s)106within a predetermined temperature range, for example, while the vehicle is operating. The controller18may receive a request or set a flag indicating that operation of the coolant circuit30and chiller104is required to cool the component106, e.g. the chiller request is on.

The chiller104is provided as an internal heat exchanger with heat transferred between the coolant in the cooling circuit30and the refrigerant in the air conditioning circuit32. When the cooling circuit30is used to cool a component, heat from the coolant may be transferred to the refrigerant via the chiller104.

The refrigerant circuit32is provided with an electric compressor110, a condenser112, a first valve assembly114, and an evaporator116. The compressor110, the condenser112, the first valve assembly114, and the evaporator116are arranged sequentially, or in series.

The compressor110is an electrically driven compressor, and may be rotated via an electric motor. As such, the speed of the compressor110is controllable and variable. The compressor110has an associated minimum operating speed, e.g. 800-1000, which may be defined as a predetermined speed of the compressor. Below the minimum operating speed, the compressor is shut off or turned off Alternatively, the predetermined speed may be set as a value that is higher than the minimum operating speed of the compressor110. A pressure sensor111may be provided an outlet of the compressor110for use in controlling the compressor.

The condenser112is provided as a heat exchanger for the vehicle that condenses the vapor phase refrigerant into a liquid phase via heat exchange with another medium. In the example shown, the condenser112is provided as a radiator on the vehicle with heat exchange from the refrigerant to outside air. Although only one condenser112is shown, the circuit may have more than one condenser.

The first valve assembly114is positioned upstream of the evaporator116. In the example shown, the first valve assembly114is located at an inlet120to the evaporator116, e.g. directly upstream and adjacent to the evaporator inlet120. The first valve assembly114acts as a throttle or an expansion valve for the evaporator116to cause an expansion of the refrigerant and resulting phase change.

In one example, the first valve assembly114may be provided as an electronic throttle valve that is controlled by the controller18, and may be moved between a closed position with zero flow therethrough and an fully open position, and furthermore may be controlled to various partially open positions to meter flow therethrough. The electronic throttle valve provides for active control of the valve. The controller18may control the first valve assembly114as an electronic throttle valve to prevent refrigerant flow through the evaporator116(e.g. in a circuit with multiple evaporators) or to meter or otherwise permit refrigerant flow through the evaporator. In one example, the controller18may control the position of the electric throttle valve using a pressure from a pressure sensor at the outlet of the evaporator.

In another example, and as illustrated in the Figure, the first valve assembly114may be provided with a shutoff valve122that is immediately upstream of a throttle valve124, such as a mechanical or passive throttle valve. The throttle valve124is immediately upstream of or at the inlet120to the evaporator. The shutoff valve122and the throttle valve124may be integrated into a single valve assembly housing or may be provided as separate sequentially arranged components. The shutoff valve122may be mechanically or electrically controlled as an on/off valve with two positions, e.g. between a shut off position with zero flow therethrough and a full flow position. The passive throttle valve124may be controlled by a system state, and in one example, a pilot line126is connected to the outlet128of the evaporator to control the position of the throttle valve via the pressure at the outlet of the evaporator. As the pressure of the refrigerant at the outlet128of the evaporator varies, the valve position for the throttle valve124likewise varies.

The evaporator116is provided as a heat exchanger for the vehicle that provides for heat transfer from air that is being directed to the cabin to the refrigerant to heat the refrigerant. The air may be outside air or may be recirculating air. The evaporator116may be provided with one or more temperature sensors130to measure the temperature of the evaporator116structure, e.g. a fin of the evaporator, or to measure a refrigerant temperature or air temperature flowing through the evaporator116or at an exit of the evaporator to infer the evaporator116temperature. The temperature sensor(s)130are in communication with the controller18and provide a signal indicative of the measured temperature to the controller18.

In a further example, the refrigerant circuit32may have more than one evaporator116, with the evaporators116arranged for parallel flow relative to one another. For a circuit32with multiple evaporators, one evaporator may be selected for use in controlling the circuit as described below. Alternatively, and for a circuit32with multiple evaporators, the control system may control the circuit based on any one of the evaporators reaching a predetermined condition.

In various examples, and as shown herein, the air conditioning system32may be provided with an integrated heat exchanger140, for example a counterflow or coflow heat exchanger wherein heat is transferred from the outlet line142of the evaporator to the inlet line144of the evaporator. As shown in the Figure, the integrated heat exchanger140has a first passage144positioned upstream of the first valve assembly114and a second passage142positioned downstream of the outlet of evaporator116. The first and second passages144,142are arranged for heat transfer therebetween. In other examples according to the present disclosure, the air conditioning circuit may be provided without an integrated heat exchanger.

The air conditioning circuit may be provided with other system components, such as a dryer146, and the like.

Under low environmental or outside air temperature conditions with the air conditioning system and circuit32operating to cool the cabin, the evaporator116temperature may approach zero degrees Celsius. Additionally, the evaporator may be operating at or below a dewpoint temperature of the air, and liquid condensation may occur on the evaporator, or within the evaporator if there is any moisture in the circuit32. At these low temperatures, ice crystals or condensation may form or develop on the evaporator surfaces and reduce flow through the evaporator and reduce performance of the air conditioning system such that it does not operate as requested by the user or by the controller. This may be referred to as icing or freezing of the evaporator. Conventionally, and in order to prevent ice or condensate formation in the evaporator, the compressor110is cycled on and off to allow the evaporator116to warm up to temperatures where ice or condensate will not form. When the compressor110is cycled on and off, the cabin cooling is likewise interrupted and this results in temperature swings in the evaporator116and associated swings in cabin air discharge temperatures and breath-level temperatures. The system100according to the present disclosure provides an alternative control method to cycling the compressor on and off, and is described below with respect toFIGS. 2 and 3.

The refrigerant circuit32is also provided with the chiller104arranged for parallel flow with the evaporator116. The input lines to the evaporator116and chiller104split at point150downstream of the condenser112outlet. The outlet lines from the evaporator116and the chiller104combine at point152upstream of the compressor110inlet.

The chiller has104an associated second valve assembly160that may be used to control and/or prevent flow of refrigerant to the chiller104. The second valve assembly160may be used to control flow of refrigerant through the chiller104, and may additionally be used to prevent refrigerant flow through the chiller104, e.g. to isolate the chiller104and the coolant circuit30from the air conditioning system32. The second valve assembly160and the chiller104are positioned for parallel flow of refrigerant with the first valve assembly114and the cabin evaporator116.

The second valve assembly160may be provided as an electronic throttle valve as described above with respect to the first valve assembly114, and the controller18may control the second valve assembly160to prevent refrigerant flow through the chiller104or to meter or otherwise permit refrigerant flow through the chiller104. In one example, the controller18may control the position of the electric throttle valve using a pressure from a pressure sensor at the outlet of the chiller104on the refrigerant side.

Alternatively, the second valve assembly160may be provided as a shutoff valve162and passive throttle valve164as described above with respect to the first valve assembly114, with the shutoff valve162immediately upstream of the passive throttle valve164, and the passive throttle valve164immediately upstream of the inlet166to the chiller104. The shutoff valve162may be mechanically controlled, or may be electrically controlled as an on/off valve with two positions. The passive throttle valve164may be controlled by a system state, and in one example, a pilot line168is connected to the outlet170of the evaporator to control the position of the throttle valve via the pressure at the outlet of the chiller.

In one example, the first and second valve assemblies114,160are provided as the same valve assembly type. In another example, the first and second valve assemblies114,160may be provided as different valve assembly types.

When the evaporator116is at a low temperature such that there is a freezing risk, e.g. ice or condensate may form or there is a risk of ice or condensate forming, the air conditioning circuit32may be operated according to the method described with respect toFIG. 3to open the second valve assembly160and allow a portion of the refrigerant to flow through the chiller104while another portion of the refrigerant or the remainder of the refrigerant flows through the evaporator116as controlled by valve114. By opening the second valve assembly160, the load on the refrigerant circuit32is increased, and a parallel flow path for refrigerant is opened for the refrigerant to flow through. The overall air conditioning circuit32capacity is therefore split between the evaporator116and the chiller104. As the chiller104is a liquid-to-liquid heat exchanger, e.g. the coolant and the refrigerant are both in a liquid state as they flow through the chiller104, the chiller104pulls more capacity from the air conditioning circuit32in comparison to the evaporator116, which is an air-to-liquid heat exchanger, e.g. the cabin air is in a gas phase and the refrigerant is in a liquid or mixed vapor phase, thus reducing the evaporator's effectiveness. As a result of the parallel flow and reduced evaporator effectiveness, the evaporator116temperature increases, resulting in a lower risk of ice or condensate formation and avoiding the need to cycle the compressor110on and off.

A controller18is provided and is in communication with the sensors and component states of the air conditioning circuit32and in the coolant circuit30. The controller18may control the speed of the compressor110, may control the first and second valve assemblies114,160for electronic throttle valves or for electronic shutoff valves, and may additionally receive data indicative of temperatures and pressures at various points in the air conditioning circuit32. The controller18may additionally receive a signal indicative of a system state or request for the coolant circuit30, or be integrated with the controller for the coolant circuit30or the components thereof.

FIG. 3illustrates a flow chart for a method200according to the present disclosure. The method may be used to control the systems100ofFIG. 2and control the vehicle10ofFIG. 1according to various embodiments. The method may be implemented by a controller such as the controller and control system18inFIGS. 1-2. In other examples, various steps may be omitted, added, rearranged into another order, or performed sequentially or simultaneously. Although the method200is described with respect to use with a vehicle system100as shown inFIG. 2, the method may likewise be applied for use with a vehicle system having another vehicle component and fluid system as described above, and in a vehicle with another architecture as described above with respect toFIG. 1. At step202, the method200starts.

At step204, the controller18determines if there is a request for air conditioning in the cabin, e.g. from a user request to the HVAC control interface, or from another vehicle system or controller. The refrigeration circuit32for a cabin air conditioning system is therefore operating. The controller18also determines if there is a request for operation of the chiller104and the coolant cycle, e.g. if the coolant cycle30is required to cool a component106such as a traction battery, or is otherwise needed to perform functions related to thermal management of the components in the circuit.

If there is no request for operation of the cabin air conditioning system32and there is a request for operation of the chiller104and coolant circuit30, then the method200proceeds to block206and operates under conventional control methods. If there is a request for operation of the cabin air conditioning system32and there is no request for operation of the chiller104and coolant circuit30, then the method200proceeds to step208.

At step208, the controller18is configured to receive a signal indicative of the evaporator temperature from sensor130. The controller18may additionally receive other data such as ambient temperature, requested cabin temperature, current cabin temperature, and the like.

At step210, the controller18determines if the evaporator116temperature is below a first threshold value. The first threshold value may be set at a specified temperature, for example, five degrees Celsius, two degrees Celsius, zero degrees Celsius, or the like. The first threshold value may be stored in a lookup table that is accessible in memory by the controller18. In one example, the first threshold value is a set value. In a further example, the first threshold value may vary, for example as a function of ambient temperature, and/or other factors.

At step210, the controller18also determines if the compressor110is operating at or below a predetermined speed. For example, the controller18may determine if the compressor110is operating at a minimum operating speed for the compressor, below an offset value above the minimum operating speed for the compressor110, within a specified speed range of the minimum speed for the compressor, or the like.

If the evaporator116temperature is not less than the first threshold value and/or the compressor110is not operating at or below a predetermined speed, the method200proceeds to block206. Note that if the evaporator116temperature is less than the first threshold value and the compressor110is not operating at or below a predetermined speed, the controller18will control the speed of the compressor110, e.g. by reducing the speed of the compressor110, to reduce the load on the evaporator116and allow the temperature of the evaporator116to increase to reduce the risk of freezing.

If the evaporator116temperature is less than the first threshold value and the compressor110is operating at or below a predetermined speed, the method200proceeds to block212.

At step212, the controller18determines if the chiller104is available for use with the air conditioning system32. The chiller104may be unavailable based on an error or flag set in another component in the coolant circuit30, or in the chiller104itself. If the chiller104is unavailable, the method200proceed to block206. If the chiller is available, the method200proceeds to block214.

At step214, the second valve assembly160is opened, e.g. by opening a shutoff valve162or controlling an electronic throttle valve to an open or partially open position to divert a portion of refrigerant through a chiller104while another portion of refrigerant flows in parallel through the evaporator116thereby increasing the temperature of the evaporator. The valve assembly160is opened while the refrigeration circuit32is operating and in response to the temperature of the evaporator116being less than a first predetermined value and the compressor110operating at a predetermined speed. While the second valve assembly160is open, heat is transferred from the portion of refrigerant in the chiller104to coolant in the chiller104, and heat is also transferred from the another portion of refrigerant in the evaporator116to air such as cabin air. Based on the use of the chiller104in parallel flow with the evaporator116, the load on the evaporator is reduced such that the temperature of the evaporator increases.

At step214, the controller18also starts a timer. The controller18also maintains the first valve assembly114in an open or partially open state while the second valve assembly160is opened. In one example, the controller18may generally maintain a speed of the compressor110at or near the predetermined speed while the valve assembly160is open and unless the controller18receives an input or reaches a state where an increased compressor speed would be required.

The method then proceeds to block216where the controller18determines if the evaporator116temperature is greater than a second threshold value. The second threshold value is greater than the first threshold value, and may be on the order of 2-5 degrees Celsius higher than the first threshold value.

If the evaporator116temperature is greater than the second threshold value, the method200proceeds to step218. At step218, the controller18closes the second valve assembly160, e.g. by closing the shutoff valve162or by commanding an electronic throttle valve to a fully closed position, thereby isolating the chiller104from the refrigerant circuit32. At step218, the controller18also resets the timer.

From step218, the method200proceeds to step220and ends, or returns to step202to continue to monitor the evaporator116.

If the evaporator116temperature is not greater than the second threshold value, the method200proceeds to step222to determine if the timer has elapsed. The timer may have a set time or predetermined time value such as two minutes, five minutes, or another suitable time that allows for the evaporator to warm and decrease the risk of freezing.

If the timer has elapsed, the method proceeds to step218and closes the second valve assembly160. The method200therefore provides for closing the second valve assembly160in response to at least one of (i) the temperature of the evaporator116being above the second predetermined value, and (ii) the timer reaching the predetermined time value.

If the timer has not elapsed, the method proceeds to step224and increments the timer. From step224, the method200returns to block216.

The method200therefore provides for a system100and a controller18that is configured to, while the refrigeration circuit32is operating and in response to the temperature of the evaporator116being less than a first threshold value and the compressor110operating at a predetermined speed, open the second valve assembly160to divert a portion of refrigerant through the chiller104while another portion of refrigerant flows in parallel through the evaporator116. The controller18is configured to receive a signal indicative of a request for operation of the chiller being off as a condition for opening the second valve assembly.

The controller is configured to, in response to opening the valve, start a timer. The controller is configured to close the second valve assembly in response to the timer reaching a predetermined time value. The controller18is further configured to close the second valve assembly in response to the temperature of the evaporator being above a second threshold value, the second threshold value being greater than the first threshold value.