METHOD FOR DEGATING THE HEAT TRANSFER CIRCUITS OF AN ELECTRIC VEHICLE

Description

[0001] The present invention relates to a method for degassing heat transfer circuits in an electric vehicle. The invention is intended to be implemented during vehicle maintenance.

[0002] An electric vehicle generally has three interlocking heat transfer circuits. The first heat transfer circuit, called the HT circuit (for "High Temperature"), is the passenger compartment heat transfer circuit capable of heating or cooling the passenger compartment.

[0003] A second heat transfer circuit, called the BT circuit (for "Low Temperature"), is the heat transfer circuit of the electric powertrain capable of cooling the rotating electric machine, the power electronic module including an inverter, and the charging module or OBCDC (for "On-Board Charger" with direct current) integrating a charger and a transformer.

[0004] A third heat transfer circuit, called the EBT circuit (for "Very Low Temperature"), is the heat transfer circuit of the high voltage battery capable of heating or cooling the high voltage battery electrically connected to the rotating electrical machine via an inverter.

[0005] Compared to a vehicle with an internal combustion engine, the addition of an extra heat transfer circuit (the battery's heat transfer circuit) makes the venting process particularly complex. However, if venting is not performed correctly in even one of the heat transfer circuits, the unvented air will eventually return to the electric powertrain's heat transfer circuit, potentially causing overheating in certain fast-charging modes and thus halting charging before the battery is fully charged.

[0006] Furthermore, the prior art is known from document US11065934B2.

[0007] Therefore, there is a need to develop a process to ensure complete degassing of all three of these interlocking heat transfer circuits.

[0008] The invention aims to efficiently meet this need by proposing a method for degassing a set of heat transfer circuits of an electric motor vehicle comprising a passenger compartment heat transfer circuit, an electric powertrain heat transfer circuit, and a traction battery heat transfer circuit, said heat transfer circuits being connected to a manifold to which a degassing box is also connected, said method comprising: a step of installing a charging cylinder on the degassing box, a step of installing a first degassing pipe between a vent located at the inlet of a heat exchanger of the traction battery heat transfer circuit and the charging cylinder, a step of installing a second degassing pipe between a vent located at the outlet of an air heater of the passenger compartment heat transfer circuit and the charging cylinder, a step of degassing the heat transfer circuit of the electric powertrain and the passenger compartment heat transfer circuit, a step of stopping the degassing of the passenger compartment heat transfer circuit, and a step of degassing the traction battery heat transfer circuit.

[0009] The invention thus makes it possible to achieve optimal degassing of the heat transfer circuits, so that battery charging can be carried out in all modes without risk of stopping charging due to overheating of the OBCDC charging module.

[0010] According to one embodiment of the invention, the degassing step of the electric powertrain heat transfer circuit and the passenger compartment heat transfer circuit includes a step of activating a pump of the electric powertrain heat transfer circuit and then a step of activating a pump of the passenger compartment heat transfer circuit.

[0011] According to one embodiment of the invention, to increase a flow rate inside the degassing pipe connected to the purge arranged at the outlet of the air heater, said method includes a pinching step of an outlet pipe of the air heater.

[0012] According to one embodiment of the invention, to stop the degassing of the passenger compartment heat transfer circuit, said method includes a step of controlling a solenoid valve of the passenger compartment heat transfer circuit to isolate the passenger compartment heat transfer circuit and a step of stopping the pump of the passenger compartment heat transfer circuit.

[0013] According to one embodiment of the invention, following the cessation of the degassing of the passenger compartment heat transfer circuit, said method comprises a step of removing the degassing pipe connected to the purge located at the outlet of the air heater of the passenger compartment heat transfer circuit and a step of closing a corresponding purge screw or a step of pinching said degassing pipe.

[0014] According to one embodiment of the invention, to perform the degassing of the heat transfer circuit of the traction battery, said method comprises: a first operating phase in which the traction battery heat transfer solenoid valve is controlled to connect the traction battery heat transfer circuit and the electric powertrain heat transfer circuit while the electric powertrain heat transfer pump is activated to introduce a heat transfer fluid into the traction battery heat transfer circuit, and a second operating phase in which the traction battery heat transfer solenoid valve is controlled to isolate the traction battery heat transfer circuit while the traction battery heat transfer pump is activated so that the heat transfer fluid pushes air into the traction battery heat transfer circuit.

[0015] According to one implementation of the invention, the first phase of operation and the second phase of operation are carried out alternately.

[0016] According to one implementation of the invention, the first phase of operation and the second phase of operation are of equal duration.

[0017] According to one embodiment of the invention, during the installation of a degassing pipe, said process comprises the following steps: pinch the vent pipe, unscrew a bleed screw, insert the vent pipe inside the bleed, place a vent pipe retaining device on the bleed, return the vent pipe to the charging cylinder taking care to create a smooth and regular slope without low points, and attach the vent pipe in the charging cylinder.

[0018] According to one embodiment of the invention, during the degassing of the heat transfer circuits, said process includes a step of regularly adding heat transfer fluid into the charging cylinder to compensate for a volume of degassed air.

[0019] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given for illustrative purposes only and are in no way intended to limit the invention. [ Fig. 1 ] There figure 1 is a schematic representation of the various heat transfer circuits of an electric vehicle with which the degassing process according to the invention is implemented; [ Fig. 2 ] There figure 2 is a perspective view of a purge valve located at the inlet of a cooler in the battery's heat transfer circuit; [ Fig. 3 ] There figure 3 is a perspective view of a purge valve located at the outlet of an air heater in the passenger compartment's heat transfer circuit.

[0020] Identical, similar, or analogous elements retain the same reference from one figure to another.

[0021] There figure 1 shows the different heat transfer circuits installed in an electric motor vehicle consisting of a passenger compartment heat transfer circuit 10, an electric powertrain heat transfer circuit 11, and a traction battery heat transfer circuit 12 capable of electrically powering the electric powertrain 11.

[0022] The passenger compartment heating circuit 10, also known as the HT (High Temperature) circuit, is capable of regulating the vehicle's passenger compartment temperature according to the user's preferences. This heating circuit 10 is therefore capable of cooling or heating the passenger compartment. This heating circuit 10 includes a two-way solenoid valve EV2 which allows the passenger compartment heating circuit 10 to be isolated or connected by fluid to the electric powertrain heating circuit 11. By default, when inactive, the EV2 solenoid valve is open, thus connecting the passenger compartment heating circuit 10 to the electric powertrain heating circuit 11. When active, the EV2 solenoid valve is closed, thus isolating the passenger compartment heating circuit 10.

[0023] A pump 13 ensures circulation of the heat transfer fluid, generally water containing antifreeze, inside the heat transfer circuit 10.

[0024] A temperature probe 14 allows the temperature of the water circulating inside the passenger compartment heat transfer circuit 10 to be measured.

[0025] A condenser 15, called a "water condenser", is a water / refrigerant exchanger (output of the air conditioning compressor) used to cool the liquid in the heat transfer circuit 10. This condenser 15 is also a component of the heat pump in the motor vehicle.

[0026] A heating device 17 called "water heater" in English consists of a heating element allowing the heat transfer fluid of the passenger compartment heat transfer circuit 10 to be heated.

[0027] An air heater 18 consists of a water / air exchanger used to heat or cool the air that will be blown into the passenger compartment.

[0028] Item referenced as 19 corresponds to a non-return valve.

[0029] The heat transfer circuit of the electric powertrain 11, called the BT circuit (for "Low Temperature"), is suitable for cooling the various components of said electric powertrain, namely the rotating electric machine 21, the power electronic module 22 comprising an inverter electrically connected on one side to the rotating electric machine 21 and on the other side to the traction battery 23 of the vehicle, as well as the charging module 25 called OBCDC (for "On-Board Charger" with direct current) comprising a charger and a transformer.

[0030] For this purpose, the heat transfer circuit of the electric powertrain 11 includes a pump 26 to circulate the heat transfer fluid inside the heat transfer circuit 11.

[0031] A temperature probe 27 allows the temperature of the liquid circulating inside the heat transfer circuit 11 to be measured.

[0032] A radiator 28 cools the heat transfer fluid in circuit 11. This radiator 28 is advantageously equipped with a Motor-Fan Unit (MFU) which is activated according to the temperature measured by the temperature probe 27.

[0033] The heat transfer circuit of the traction battery 12, called the TBT circuit (for "Very Low Temperature"), allows the temperature of the traction battery 23 to be regulated to optimize its operation.

[0034] When the traction battery 23 is too cold, its performance is reduced both during charging (charging times are increased) and during driving (the traction battery 23 then provides limited energy to the powertrain). The heat transfer circuit 12 must therefore include a heating system and a cooling system for the traction battery 23. In this embodiment, the heating system used to warm the traction battery 23 is that of the passenger compartment heat transfer circuit 10. In other words, it is possible to do without a dedicated heating system for the battery 23.

[0035] More specifically, the heat transfer circuit of battery 12 includes a three-way solenoid valve EV3 which allows the heat transfer circuit of battery 12 to be isolated or connected to the heat transfer circuit of the electric powertrain 11. By default, when the solenoid valve EV3 is inactive, the solenoid valve EV3 is closed so as to isolate the heat transfer circuit of the traction battery 12. When the solenoid valve EV3 is active, the solenoid valve EV3 is open so as to connect the heat transfer circuit of the traction battery 12 to the heat transfer circuit of the electric powertrain 11.

[0036] A pump 30 circulates the heat transfer fluid within the circuit 12. A temperature probe 31 measures the temperature of the fluid inside the heat transfer fluid circuit 12. A water / refrigerant heat exchanger 32, called a "chiller" in English, cools the heat transfer fluid in the circuit 12. The refrigerant is the same as that used in the air conditioning system.

[0037] Furthermore, an expansion vessel 33, also called a degassing box 33, is in fluidic communication with a manifold 34 to which the three cooling circuits 10, 11, 12 are connected.

[0038] Furthermore, as can be seen on the figures 1 and 2 A bleed valve 36, associated with a bleed screw 37, is provided at the inlet of the heat exchanger 32 (chiller) of the heat transfer circuit for battery 12. As can be seen on the Figures 1 And 3 , a purge 38 associated with a purge screw 39 is provided at the outlet of the air heater 18 of the passenger compartment heat transfer circuit 10.

[0039] During the preparation phase of the degassing procedure, the operator screws a charging cylinder 40 onto a neck of the degassing box 33, leaving it closed for the installation of the degassing pipes. This prevents air from being drawn in. The operator then installs a first degassing pipe 41 between the drain 36 located at the inlet of the heat exchanger (chiller) 32 and the charging cylinder 40. The operator installs a second degassing pipe 42 between the drain 38 located at the outlet of the air heater 18 and the charging cylinder 40.

[0040] To this end, for each of the two degassing pipes 41, 42, the operator performs the following operations: pinch the degassing pipe 41, 42, unscrew a corresponding bleed screw 37, 39, quickly insert the degassing pipe 41, 42 into the bleed 37, 39, put in place a degassing pipe retaining device on the bleed, such as a clamp or a rilsan, return the degassing pipe 41, 42 to the charging cylinder 40 taking care to create a smooth and regular slope without low point, and attach the degassing pipe in the charging cylinder 40.

[0041] The operator then introduces approximately 1 liter of coolant into the charging cylinder 40 and opens it by turning the handle and pushing it downwards. The hose clamp can then be removed from the vent pipes 41 and 42.

[0042] During degassing, heat transfer fluid must be regularly added to the charging cylinder 40 to compensate for the volume of air released. When adding fluid to the charging cylinder 40, care must be taken not to exceed the midpoint of the cylinder to prevent overflow during operation of the solenoid valves EV2, EV3 and the pumps 13, 26, 30.

[0043] The operator begins the degassing procedure by activating the BT pump 26 and starting a timer (t = 0 min). The BT heat transfer circuit of the electric powertrain 11 and the HT heat transfer circuit of the passenger compartment 10 are degassed. The various circuit components then exhibit the following states: EV3 EV2 BT Pump TBT pump High-temperature pump INACTIVE INACTIVE WALK STOP STOP At t = 5 min (duration calibrable according to the architecture of the cooling circuit), the operator starts the HT 13 pump. This configuration preferably lasts 15 min. The degassing of the radiator 28 accelerates.

[0044] The flow in the vent pipe 42 inserted into the purge 38 of the air heater 18 should begin, but the flow remains insufficient for proper venting. A hose clamp must be placed on the outlet pipe of the air heater 18 and slightly closed until the flow in the vent pipe 42 increases sufficiently. EV3 EV2 BT Pump TBT pump High-temperature pump INACTIVE INACTIVE WALK STOP WALK At t = 20 min (duration calibrable according to the architecture of the cooling circuit), the operator activates the solenoid valve EV2 by supplying it and cuts off the supply to the pump HT 13. The operator removes the degassing pipe 42 from the outlet of the air heater 18 and closes the bleed screw 39 or uses the pliers to pinch the degassing pipe 42 as close as possible to the bleed 38. At t = 22 min (duration calibrable according to the architecture of the cooling circuit), the operator supplies the solenoid valve EV3.

[0045] From this stage onwards, the high-temperature heat transfer circuit of the passenger compartment 10 will no longer be activated and therefore will no longer be degassed. EV3 EV2 BT Pump TBT pump High-temperature pump ACTIVE ACTIVE WALK STOP STOP

[0046] This configuration allows heat transfer fluid to enter the TBT heat transfer circuit of traction battery 12. - At t = 27 min (duration calibrable according to the architecture of the cooling circuit), the operator starts the TBT 30 pump and cuts off the power supply to the EV3 solenoid valve. From this point on, two actuator positions will alternate every 5 minutes. EV3 EV2 BT Pump TBT pump High-temperature pump INACTIVE ACTIVE WALK WALK STOP

[0047] Such a configuration allows the heat transfer fluid to push the air inside the heat transfer circuit of the traction battery 12. - At t = 32 min (duration calibrable according to the architecture of the cooling circuit), the operator cuts off the supply to the TBT 30 pump and supplies the EV3 solenoid valve to put it back into the active state. EV3 EV2 BT Pump TBT pump High-temperature pump ACTIVE ACTIVE WALK STOP STOP - At t = 37 min (duration calibrable according to the architecture of the cooling circuit), the operator supplies the TBT 30 pump and cuts off the supply to the EV3 solenoid valve. EV3 EV2 BT Pump TBT pump High-temperature pump INACTIVE ACTIVE WALK WALK STOP - At t = 42 min (duration calibrable according to the architecture of the cooling circuit), the operator cuts off the power supply to the TBT 30 pump and activates the EV3 solenoid valve. EV3 EV2 BT Pump TBT pump High-temperature pump ACTIVE ACTIVE WALK STOP STOP - At t = 47 min (duration calibrable according to the architecture of the cooling circuit), the operator turns off all pumps 13, 26, 30 as well as solenoid valves EV2, EV3. EV3 EV2 BT Pump TBT pump High-temperature pump INACTIVE INACTIVE STOP STOP STOP

[0048] At the end of the degassing procedure, the process includes the following steps: close the charging cylinder 40 (pull the handle upwards and turn), remove the degassing pipes 41, 42 and close the bleed screws 37, 39, remove the charging cylinder 40 by unscrewing it, aspirate the excess liquid from the degassing box 33 with a syringe, replace the cap on the degassing box 33.

[0049] If a small amount of air remains inside a heat transfer fluid circuit 10, 11, or 12, this small amount will be vented while driving. After driving a few kilometers, it will be necessary to check that the heat transfer fluid level is between the minimum and maximum marks on the venting chamber 33. This check should be performed when the engine is cold. If the level is too low, it is necessary to top up the heat transfer fluid.

Claims

1. Method for degassing a set of heat transfer circuits of an electric motor vehicle comprising a heat transfer circuit of a passenger compartment (10), a heat transfer circuit of an electric powertrain (11), and a heat transfer circuit of a traction battery (12), said heat transfer circuits (10, 11, 12) being connected to a collector (34) to which a degassing box (33) is also connected, characterized in that said method comprises: - a step of installing a charging cylinder (40) on the degassing box (33), - a step of installing a first degassing pipe (41) between a purge (36) arranged at the inlet of an exchanger (32) of the heat transfer circuit of the traction battery (12) and the charging cylinder (40), - a step of installing a second degassing pipe (42) between a purge (38) arranged at the outlet of an air heater (18) of the heat transfer circuit of the passenger compartment (10) and the charging cylinder (40), - a step of degassing the heat transfer circuit of the electric powertrain (11) and the heat transfer circuit of the passenger compartment (10), - a step of stopping the degassing of the heat transfer circuit of the passenger compartment (10), and - a step of degassing the heat transfer circuit of the traction battery (12).

2. Method according to claim 1, characterized in that the step of degassing the heat transfer circuit of the electric powertrain (11) and the heat transfer circuit of the passenger compartment (10) comprises a step of activating a pump (26) of the heat transfer circuit of the electric powertrain (11) then a step of activating a pump (13) of the heat transfer circuit of the passenger compartment (10).

3. Method according to claim 2, characterized in that to increase a flow rate inside the degassing pipe (42) connected to the purge (38) arranged at the outlet of the air heater (18), said method comprises a step of pinching an outlet pipe of the air heater (18).

4. Method according to any one of claims 1 to 3, characterized in that to stop the degassing of the heat transfer circuit of the passenger compartment (10), said method comprises a step of controlling a solenoid valve (EV2) of the heat transfer circuit of the passenger compartment (10) to isolate the heat transfer circuit of the passenger compartment and a step of stopping the pump (13) of the heat transfer circuit of the passenger compartment (10).

5. Method according to claim 4, characterized in that following the stopping of the degassing of the heat transfer circuit of the passenger compartment (10), said method comprises a step of removing the degassing pipe (42) connected to the purge (38) arranged at the outlet of the air heater (18) of the heat transfer circuit of the passenger compartment (10) and a step of closing a corresponding purge screw (39) or a step of pinching said degassing pipe (42).

6. Method according to any one of claims 1 to 5, characterized in that to carry out the degassing of the heat transfer circuit of the traction battery (12), said method comprises: - a first operating phase in which the solenoid valve (EV3) of the heat transfer circuit of the traction battery (12) is controlled so as to put the heat transfer circuit of the traction battery (12) into communication with the heat transfer circuit of the electric powertrain (11) while the pump of the heat transfer circuit of the electric powertrain (11) is activated to bring a heat transfer liquid into the heat transfer circuit of the traction battery (12), and - a second operating phase in which the solenoid valve of the heat transfer circuit of the traction battery (12) is controlled so as to isolate the heat transfer circuit of the traction battery (12) while the pump of the heat transfer circuit of the traction battery (12) is activated so that the heat transfer liquid pushes the air inside the heat transfer circuit of the traction battery (12).

7. Method according to claim 6, characterized in that the first operating phase and the second operating phase are carried out alternately.

8. Method according to claim 6 or 7, characterized in that the first operating phase and the second operating phase are of equal duration.

9. Method according to any one of claims 1 to 8, characterized in that, when installing a degassing pipe (41, 42), said method comprises the following steps: - pinch the degassing pipe (41, 42), - unscrew a bleed screw (37, 39), - insert the degassing pipe (41, 42) inside the purge (36, 38), - install a device for holding the degassing pipe (41, 42) on the purge (36, 38), - return the degassing pipe (41, 42) to the charging cylinder (40) while ensuring that a gentle and regular slope is created without a low point, and - attach the degassing pipe (41, 42) in the charging cylinder (40).

10. Method according to any one of claims 1 to 9, characterized in that during the degassing of the heat transfer circuits (10, 11, 12), said method comprises a step of regularly adding heat transfer liquid to the charging cylinder (40) to compensate for a volume of degassed air.