Heating and cooling system for an electric vehicle

Abstract

A heating and cooling system for an electric vehicle includes an electric pump that pumps fluid around a first loop to selectively cool part of the drive train of the vehicle. The fluid passes through a cabin heater that extracts heat energy from the fluid and back to the part of the drive train. An electric compressor pumps fluid around a second loop through a condenser which extracts heat energy from the fluid which flows through an expansion valve and an evaporator and back to the electric compressor. A cabin chiller including an evaporator is located in a flow path receiving fluid output from the condenser through an expansion valve upstream in the flow path. The fluid from the evaporator is drawn back into the second loop by the electric compressor. The chilled fluid flowing through the evaporator extracts heat from the fluid flowing around the first loop.

Claims

1. A heating and cooling system for an electric vehicle comprising: an electric pump configured to pump fluid around a first loop to selectively cool a plurality of parts of a drive train of the electric vehicle, the fluid then passing through a cabin heater configured to extract heat energy from the fluid and then back to the plurality of parts of the drive train, an electric compressor configured to pump fluid around a second loop through a primary condenser configured to extract heat energy from the fluid to generate a chilled fluid which then flows through a first expansion valve and through a primary evaporator and then back to the electric compressor, and a cabin chiller comprising a secondary evaporator located in a flow path receiving fluid output from the primary condenser through a second expansion valve upstream in the flow path, the fluid that is output from the secondary evaporator being drawn back into the second loop by the electric compressor, wherein the chilled fluid flowing through the primary evaporator is arranged to extract heat from the fluid flowing around the first loop, the plurality of parts of the drive train comprising at least two of an electric propulsion motor, an energy store, and an inverter connecting the motor to the energy store, and further comprising a plurality of valves arranged in parallel so that each part of the drive train that is cooled may be selectively connected to the first loop through a respective valve that can be opened and closed or partially opened to selectively cool any of the plurality of parts of the drive train at a given time, and wherein the fluid is only able to circulate around the first loop by passing through the cabin heater.

2. The heating and cooling system according to claim 1 wherein the primary evaporator is configured to act upon the fluid in a portion of the first loop that is located downstream of the cabin heater and upstream of the part of the drive train that is heated or cooled by the fluid in the first loop.

3. The heating and cooling system according to claim 1 further including a heat exchanger downstream of the part of the drive train that is cooled and upstream of the cabin heater.

4. The heating and cooling system according to claim 3 wherein the heat exchanger comprises a radiator located behind the primary evaporator such that the radiator is configured to receive air that has passed over the primary evaporator.

5. The heating and cooling system according to claim 1 wherein the first loop and the second loop are fluidically isolated from each other such that the fluid in the first loop cannot contact the fluid of the second loop.

6. The heating and cooling system according to claim 1 further including an arrangement of air ducts configured to receive inlet air and blow the air selectively across the cabin heater and the cabin chiller before passing the air into a cabin of the vehicle.

7. The heating and cooling system according to claim 6 wherein the cabin chiller is mounted upstream of the cabin heater to ensure air dehumidification in cold weather, such that in the cold weather the air is first cooled to draw humidity, than warmed again through the cabin heater and pushed to the cabin.

8. The heating and cooling system according to claim 7 further including one or more control flaps configured to divert the air across the cabin heater or the cabin chiller as required to control cabin temperature.

9. The heating and cooling system according to claim 8 wherein a first flap is operable to direct air that has passed across the cabin chiller into the cabin and not across the cabin heater when in a first position or across the cabin heater and not into the cabin when in a second position, the flap having a range of blend positions between the first and the second position in which chilled air is shared by the cabin and the cabin heater.

10. The heating and cooling system according to claim 8 wherein a second flap is operable to direct air that has been heated by the cabin heater into the cabin when in a first position and not into the cabin when in a second position, the flap having a range of blend positions between the first and the second position in which chilled air is partially fed into the cabin.

11. The heating and cooling system according to claim 1 wherein the cabin chiller and the second expansion valve are located in a flow path in parallel with a part of the second loop containing the first expansion valve and the primary evaporator.

12. The heating and cooling system according to claim 1 wherein the first and the second evaporators are controllable to regulate mass flow of the fluid around the second loop and the flow path containing the cabin chiller.

13. The heating and cooling system according to claim 1 including a microcontroller adapted to receive a temperature signal indicative of a temperature of each of the parts of the drive train which are associated with a respective valve and to open and close the valve dependent on the temperature.

14. The heating and cooling system according to claim 13 wherein the drive train includes a motor, an inverter and a battery pack and the microcontroller is configured to implement a control strategy in which the microcontroller initially closes all the valves and opens the valves for the motor and the inverter once they reach a predefined operating temperature, the valves thereafter being modulated to maintain the temperature in a predefined range.

15. The heating and cooling system according to claim 1 wherein the fluid for the second loop comprises a coolant that has a dielectric property, the coolant being configured to readily undergo a phase change from liquid to gas at useful temperatures.

16. The heating and cooling system according to claim 1 wherein the fluid for the first loop comprises a liquid such as a mixture of water and an additive selected to lower a freezing point of the mixture.

17. An electric vehicle including the heating and cooling system according to claim 1, the electric vehicle comprising: the plurality of parts of the drive train, and a cabin for passengers, wherein the cabin heater and the cabin chiller are arranged to provide heating and cooling of the cabin.

Description

(1) There will now be described by way of example only one embodiment of the present invention of which:

(2) FIG. 1 shows an exemplary electric vehicle which may include the heating and cooling system of the present invention;

(3) FIG. 2 is a circuit diagram showing an exemplary heating and cooling system in accordance with an aspect of the invention; and

(4) FIG. 3 is a system diagram of the interactions between the air ducts and the heating and cooling components, in accordance with FIG. 2.

(5) As shown in FIG. 1, an electric passenger vehicle 100 comprises a monocoque chassis 102 that provides the mounting point for a suspension and a vehicle drivetrain. As shown the drivetrain comprises a single electric motor 104 located at the front of the vehicle in an engine compartment, and a battery pack 106 that is located under the floor of the cabin 107 to provide a low centre of gravity. The battery 106 is connected to the motor 104 through an inverter 108. A charging connector 110 enables an external supply of electricity to the battery pack 106. Of course the reader will understand that this arrangement can be varied and layout of the electric vehicle shown is not intended to limit the scope of protection. A ladder chassis with separate cabin may be provided instead of a monocoque, the battery pack may be located in an alternative region of the vehicle and rather than one motor as shown a number of electric motors may be provided. These may also be located in different regions of the vehicle, perhaps at the rear of the vehicle rather than at the front, or within the hub of one or more of the wheels of the vehicle.

(6) FIG. 2 shows schematically an embodiment of a heating and cooling circuit 112 of the present invention that may be fitted to the vehicle of FIG. 1 or a similar vehicle.

(7) The heating and cooling system comprises a number of key components connected by conduits that primarily function to heat fluid, to cool fluid, and to circulate the fluid around the vehicle and to manage the flow of heated or cooled air provided by the system. The system is arranged as two closed loops 114, 116 around which the fluid is pumped. These loops 114, 116 provide heating and cooling for the drivetrain and also for the control of the temperature of the air in the vehicle cabin 107.

(8) A first loop 114 provides the primary means for extracting heat energy from the drive train when it needs to be cooled or applying heat energy to the drive train when it needs to be heated. The fluid in this first loop is in liquid form at all times and can provide heating of the battery pack 106 by sending warm fluid from the inverter and motors directly to the battery pack as soon as it becomes to be available. This loop 114 includes an electric pump 118 that pumps fluid around the drive train of the vehicle, the fluid then passing through a cabin heater 120 that extracts heat energy from the fluid and then back to the part of the drive train.

(9) A second loop 116 includes an electric compressor 122 that pumps fluid around the second loop 116 through a primary condenser 124 which extracts heat energy from the fluid which then flows through a first expansion valve 126 and through a primary evaporator 128 and then back to the electric compressor 122. The primary function of this loop 116 is to extract heat energy from the fluid flowing around the second loop 116 so that the chilled fluid can be used to provide both cabin cooling as will be explained and be used to extract heat energy from the first loop 114. In use, the fluid will be in a heated liquid form when flowing through the condenser 124, and in gaseous form as it is sucked out of the evaporator 128 by the compressor 122. The expansion that occurs in the expansion valve 126 lowers the temperature of the fluid as it is fed into the evaporator, and as the fluid passes through the evaporator 128 the heat around the evaporator 128 causes the fluid in the second loop to boil off as a gas. The heat is provided by the first fluid as it flows through the evaporator, isolated at all times from the fluid in the second loop.

(10) A third loop 130 is provided for the purpose of chilling the cabin 107. This loop 130 includes a cabin chiller comprising a secondary evaporator 132 that selectively receives the liquid output from the primary condenser 124 through a second expansion valve 134 that chills the liquid, the gas that is output from the secondary evaporator 132 being sucked back into the second loop 116 by the electric compressor 122. As shown the output of the cabin chiller 132 feeds into the second loop 116 at the inlet to the compressor 122, placing the first expansion valve 126/evaporator 128 and the second expansion valve 134/cabin chiller 132 in parallel with each other. The cabin chiller 132 removes energy from air passing across it before the cooled air is fed to the cabin.

(11) To extract heat energy from the first loop 114, the fluid from the first loop 114 passes through the primary evaporator 128. The primary evaporator 128 therefore draws energy from the fluid in the first loop 114.

(12) The first and second expansion valves 126, 134 are controlled by a controller or microprocessor 136 that receives input signals from temperature sensors associated with the drive train and other demand signals, for example based on the current demanded by the motor, the external temperature, cabin temperature and common Inlet Temperature for the powertrain (T.sub.i) The controller 136 therefore ensures the optimal cooling and heating of the drivetrain.

(13) The system further includes an arrangement of air ducts that receive inlet air and blow the air selectively across the cabin heater 120 and cabin chiller 132 before passing the air into the cabin of the vehicle. This is shown in FIG. 3 of the drawings. The ducts may include one or more control flaps 138 (see FL.sub.H and FL.sub.E) that divert the air across the heater 120 or chiller 132 as required to control the cabin temperature and the powertrain. The position of the control flaps 138 may be set by the driver, for instance under control of a heating and cooling (HVAC) controller 140 that receives signals from a user controlled interface located in the cabin 107. The skilled reader will be familiar with the design and implantation of a suitable arrangement of ducts, flaps and microcontroller to ensure the optimal regulation of the temperature of the cabin using the heated and cooled air supplied from the cabin heater and cabin chiller.

(14) The operation of the exemplary system at different drive train temperatures is as follows:

(15) Extreme Cold Weather Operation (for Example −20° C. or Below):

(16) The microprocessor closes the valves so that the fluid flows around the first loop 114 but not through the Inverter and Motor when doing the first miles. Evaporator Flap FL.sub.E and Heater Flap FL.sub.H are both in position 1. Expansion valve of the primary evaporator EXP is closed as well. As soon as the fluid starts to flow, it will go almost entirely to the battery pack with little dispersion along the circuit, avoiding the complexity of bypass valves. Then the Evaporator Flap FL.sub.E can slowly change the position to 2 and 3 and send additional heating to the cabin as the powertrain warming up. During this time the fluid flows around the second loop 116 where it is compressed to form a heated liquid that passes through the condenser 124 before being expanded back to a gas at a lower temperature that is fed to the primary evaporator 128. At this low temperature of the drive train it is unlikely that cabin chilling will be needed so the second expansion valve 134 may be closed to cut off the third loop 130 including the cabin chiller 132. The flow of fluid will be managed by the microprocessor taking inputs such as cabin humidity and cabin temperature. This allows the drive train to heat up as quickly as possible with no cooling.

(17) Moderate Cold Weather Operation for Example 0° C. Down to −20 Degrees:

(18) At this temperature the drive train parts will heat rapidly and the fluid in the first loop 114 is passed through the cabin heater 120 as the main structure for providing cooling of the fluid. The Primary Evaporator may be used but as the last resort, because is energy consuming to use the fluid in the second loop to cool the fluid in the first loop. At this weather condition the first loop can freely exchange heat with the environment through the High temperature heat Exchanger (HTX) at no extra (energy) costs. The valves feeding the parts of the motor are modulated by the microprocessor to control the mass flow rate to ensure that the amount of cooling is optimized.

(19) In particular, the modulation of the valves will in use keep the three main components (battery pack, inverter and motor) at the maximum temperature allowed, as this is the condition where the entire system has the less workload in terms of removing energy.

(20) Moderate Warm Weather Operation (for Example+20° C. or Higher):

(21) In this condition fluid in the first loop from inverter and motor will pass through High temperature heat Exchanger (HTX) then through heater with the two flaps regulated by the microprocessor but, for example, likely to be FL.sub.H in position 3 diverting heat toward outside through the duct rather than inside the cabin and FL.sub.E in position 2. Air conditioning for the cabin could or could not operate depending on driver request. If there is any remaining heat from first loop to be removed this heat will be removed by the cooled fluid in the second loop as the fluid of the first loop passes through the primary evaporator (PEV,128). The valve opening percentage of the Expansion valve (EXP.sub.P) for the primary evaporator may be driven by an Inlet Temperature sensor (T.sub.i) that measures the temperature of fluid flowing back to the drivetrain and will allow the minimum flow possible from the second loop to maintain that target temperature.

(22) Extreme Hot Weather

(23) At extremely high temperatures the circuit functions much the same as it does for moderate warm weather but in addition the Evaporator Flap FL.sub.E can be (temporary) moved up to position 3 if all the other heat exchanger systems (HTX, PEV, and cabin heater with Heater Flap FL.sub.H in position 3) are at the maximum power, to give some additional cooling at the expense of allowing the cabin to become hot.