Immersion cooling for electric or hybrid vehicles

Abstract

An assembly comprising: - an electrical energy storage unit, - at least one component for a vehicle propulsion system, being one of: a voltage converter, an on-board charger device, an inverter / rectifier, a rotating electrical machine comprising a rotor and a stator, and - a circulation loop (10) of a heat transfer dielectric fluid (30), said loop comprising: - a circulation pump (11) of the heat transfer dielectric fluid, - a heat exchanger device (18), the heat transfer dielectric fluid (30) being in contact with the electrical energy storage unit and at least one component so as to exchange heat, the circulation loop (10) of the heat transfer dielectric fluid (30) comprising at least one sealed enclosure (12, 13, 14, 15, 17, 20) at least partially filled with heat transfer dielectric fluid (30), this enclosure comprising: a dielectric fluid inlet (21),and a dielectric liquid outlet (22) and receiving at least said electrical energy storage unit. Abbreviated figure: Fig. 1,

Description

Title of the invention: Immersion cooling for an electric or hybrid propulsion vehicle

[0001] The present invention relates to the field of thermal regulation systems, more particularly thermal regulation systems for vehicles with electric or hybrid propulsion.

[0002] These systems make it possible to thermally regulate different elements generating heat in an electric or hybrid propulsion vehicle, such as for example an electrical energy storage unit, an on-board charger device, an inverter / rectifier, a rotating electrical machine comprising a rotor and a stator, etc.

[0003] Thermal regulation solutions using heat transfer fluids, such as water or glycol, are commonly used in vehicles.

[0004] To increase the amount of calories exchanged between the liquid and a component or an electrical energy storage unit, it is possible to immerse the element to be thermally regulated in a heat-transfer dielectric liquid. This solution makes it possible to maximize the heat exchange coefficient between the element and the liquid and is commonly called immersion cooling.

[0005] The immersion cooling solution is all the more advantageous due to the fact that it makes it possible to simplify the design of the elements receiving both the elements to be thermally regulated and the cooling liquid, due to the absence of distance constraints between the element to be cooled and the liquid.

[0006] It is known to use immersion cooling to thermally regulate energy storage units within electric or hybrid propulsion vehicles.

[0007] There is a need to further improve the thermal regulation of components of electric or hybrid powered vehicles, taking advantage of the benefits of immersion cooling.

[0008] The invention aims to meet this need using an assembly comprising

[0009] - an electrical energy storage unit,

[0010] - at least one component for a vehicle propulsion system, being one of: a voltage converter, an on-board charger device, an inverter / rectifier, a rotating electrical machine comprising a rotor and a stator, and

[0011] - a heat transfer dielectric liquid circulation loop, said loop including:

[0012] - a heat transfer dielectric liquid circulation pump,

[0013] - a heat exchanger device,

[0014] the heat transfer dielectric liquid being in contact with the electrical energy storage unit and the at least one component so as to exchange calories, and

[0015] the heat transfer dielectric liquid circulation loop comprising at least one sealed enclosure at least partially filled with heat transfer dielectric liquid, this enclosure comprising: a dielectric liquid inlet, and a dielectric liquid outlet and receiving at least said electrical energy storage unit.

[0016] Thus, thermal regulation of at least one component of the vehicle and of the electrical energy storage unit is achieved by immersing them at least partially in the heat transfer dielectric liquid. The solution presented is advantageous because it is achieved in a single circulation loop, using only thermal regulation by immersion.

[0017] Advantageously, the thermal regulation loop is devoid of branching. More precisely, there is no switching for distributing the heat transfer dielectric liquid between two parallel paths in the loop. As a result, the elements of the assembly are arranged in series within the circulation loop, which simplifies its integration with a reduced number of components.

[0018] The at least one component may be contained in the same enclosure as the electrical energy storage unit.

[0019] This embodiment makes it possible to allocate the same enclosure to two elements involved in the electric or hybrid propulsion of a vehicle, which makes it possible to reduce the cost and size for carrying out thermal regulation.

[0020] Alternatively, the at least one component is contained in an enclosure different from that receiving the electrical energy storage unit.

[0021] In all of the above, the at least one enclosure may have, in planes perpendicular to the direction of flow of the heat-transfer dielectric liquid, a passage section reduced at right angles to the component.

[0022] This reduced passage section makes it possible to increase the circulation speed of the heat transfer dielectric liquid at the component by the Venturi effect, and to increase the exchange of calories between the component and the heat transfer dielectric liquid.

[0023] The assembly may comprise four components being an on-board charger, a voltage converter, an inverter, and a rotating electrical propulsion machine, these four components then being arranged in series in the circulation loop.

[0024] The assembly may comprise four components being an on-board charger, a voltage converter, an inverter / rectifier, and a rotating electrical machine comprising a rotor and a stator, these four components and the storage unit of electrical energy being arranged in series in the loop.

[0025] This corresponds to an advantageous embodiment of the invention, where these four components forming the powertrain of an electric car are entirely included in the thermal regulation loop in the assembly such as the invention

[0026] The assembly may also comprise a device for heating the heat transfer dielectric liquid, this device being placed so as to raise the temperature of the liquid at the inlet of the enclosure comprising the electrical storage unit.

[0027] This heating device makes it possible to heat the heat-transfer dielectric liquid penetrating into the enclosure comprising the electrical storage unit, making it possible to reduce the performance losses of the latter during a cold start of the vehicle comprising the assembly according to the present invention.

[0028] Advantageously, the heat exchanger device is arranged so as to cool the heat transfer dielectric liquid at the outlet of the enclosure containing the electrical energy storage unit.

[0029] Thus, the heat exchanger device is advantageously arranged within the cooling loop in the case where the heating device is integrated into the assembly, because it can cool the previously heated liquid.

[0030] The at least one enclosure may be at least partially made of plastic, ceramic, metal and / or plastic loaded, for example, with ceramic or metal.

[0031] The electrical energy storage unit may be in direct contact with the heat transfer dielectric liquid.

[0032] The at least one component contained in the at least one enclosure may be in direct contact with the heat transfer dielectric liquid.

[0033] Alternatively, the at least one component contained in the at least one enclosure may not be in direct contact with the heat-transfer dielectric liquid, a heat-conducting means being able to separate the two, for example a metal plate.

[0034] The electrical energy storage unit may be a lithium-ion type battery. This battery has, for example, a nominal voltage of 12V, 48V, 60V or more, for example greater than 300V, for example 400V, 800V or 1000V.

[0035] The rotating electrical machine is for example a synchronous machine, for example a three-phase synchronous machine or a synchronous machine whose stator electrical winding defines a double three-phase system. The stator electrical winding is for example formed by wires or by conductive bars connected to each other.

[0036] In all of the above, the rotor may be a claw rotor. This rotor then comprises a first and a second nested pole wheel, the first pole wheel defining a series of claws of generally trapezoidal shape, each claw extending axially towards the second pole wheel, the second pole wheel defining a series of claws of generally trapezoidal shape, each claw extending axially towards the first pole wheel. A permanent magnet may be received between two consecutive claws circumferentially speaking for the rotor.

[0037] Alternatively, the rotor may be other than a claw rotor, for example comprising a stack of laminations or being a cage rotor.

[0038] In all of the above, the rotor may comprise any number of pole pairs, for example three, four, six or eight pole pairs.

[0039] The rotating electrical machine may have a rated electrical power of 4 kW, 8 kW, 15 kW, 25 kW or more.

[0040] The rotating electrical machine may also comprise a pulley or any other means of connection to the rest of the vehicle's powertrain. The electrical machine is for example connected, in particular via a belt, to the crankshaft of the vehicle's thermal engine. Alternatively, the electrical machine is connected to other locations in the powertrain, for example to the input of the gearbox from the point of view of the torque transmitted to the vehicle's wheels, to the output of the gearbox from the point of view of the torque transmitted to the vehicle's wheels, at the gearbox from the point of view of the torque transmitted to the vehicle's wheels, or even on the front axle or the rear axle of this powertrain.

[0041] The rotating electrical machine is not necessarily a synchronous machine, but may be an asynchronous machine.

[0042] The inverter / rectifier and the DC / DC converter may implement field effect transistors, for example MOSFET transistors or transistors made of gallium nitride (GaN), silicon carbide (SiC), or silicon.

[0043] In all of the above, the heat transfer dielectric liquid circulating in the loop may be an oil, for example having a kinematic viscosity of between 8 and 70 centistokes at 40°C.

[0044] The invention may be better understood by reading the following description of non-limiting examples of its implementation:

[0045] - [Fig.l] represents an assembly according to an exemplary embodiment of the invention

[0046] - [Fig.2] represents a sectional view of an enclosure used to contain a component according to one embodiment of the invention

[0047] The assembly 1 as shown in [Fig.l] comprises a heat transfer dielectric liquid circulation loop 10.

[0048] In the example shown in [Fig.l], the heat transfer fluid circulation loop 10 comprises: a circulation pump 11, a succession of enclosures 12, 13, 14, 15, each containing a component of a powertrain of a vehicle electric, a dielectric heat transfer fluid heating device 16, an enclosure 17 containing a dielectric energy storage unit, and a heat exchanger device 18.

[0049] The pump 11 in the example shown in [Fig.l] imposes a direction of circulation on the heat transfer dielectric liquid such that it travels through the circulation loop 10 from the pump 11 then successively through the enclosures 12, 13, 14, 15, the heating device 16 and the heat exchanger 17.

[0050] In the example shown in [Fig.l], the circulating heat transfer dielectric liquid of loop 10 is an oil, having between 8 and 70 centistokes at 40°C.

[0051] In the example shown in [Fig.l], enclosures 12 to 15 each contain a component for an electric or plug-in hybrid vehicle. Enclosure 12 contains an on-board charger device, enclosure 13 contains a DC / DC voltage converter device, enclosure 14 contains an inverter / rectifier device, enclosure 15 contains an electric propulsion motor comprising a rotor and a stator.

[0052] In the example shown in [Fig.l], after passing through the enclosure 15, the heat-transfer dielectric liquid is transmitted to a heating device 16. This heating device 16 is arranged just upstream in the direction of circulation imposed by the pump 11 of the enclosure 17 in the circulation loop 10.

[0053] In this example, a heat exchanger device 18 is arranged downstream in the direction imposed by the pump 11 of the enclosure 17 in the circulation loop.

[0054] The heating device 16 is configured to raise the temperature of the heat transfer dielectric liquid during a cold start of an electric or hybrid propulsion vehicle comprising the assembly 1 as shown in [Fig.l]. The liquid heated in this way enters the enclosure 17 containing the electrical energy storage unit. This heat transfer dielectric liquid thus heated during a cold start of the vehicle makes it possible to reduce the performance losses of the electrical energy storage unit under such conditions.

[0055] The heat exchanger 18 configured to cool the heat transfer dielectric liquid circulating in the loop 10. The heat exchanger may be for example an air exchanger coupled to a fan, or an air exchanger coupled to a condenser, the condenser being able to be common with a thermal regulation system for the passenger compartment of a vehicle comprising an assembly 1 as shown in [Fig.l],

[0056] In the example shown in [Fig.l], the heat exchanger 18 is placed downstream in the direction of circulation imposed by the pump 11 of the enclosure 17 containing the electrical energy storage unit in the circulation loop 10, so as to to be able to lower the temperature of the liquid at the outlet of the enclosure 17 containing the energy storage unit. More particularly in this example, this placement of the heat exchanger 18 is advantageous during a cold start, when the heating device increases the temperature of the heat transfer dielectric liquid at the inlet of the enclosure 17 containing the electrical energy storage unit. The heat exchanger 18 is thus placed to cool the heat transfer dielectric liquid before it passes through other enclosures in the circulation loop 10.

[0057] [Fig. 2] represents a sectional view of an example of an enclosure 20, which may correspond for example to an enclosure 12, 13, 14 or 15 represented in [Fig. 1].

[0058] The walls 23a, 23b of the enclosure 20 shown in [Fig. 2] are such that the enclosure 20 is sealed. The heat transfer dielectric liquid 30 only enters and leaves the enclosure through two openings 21 and 22. In the example shown in [Fig. 2], the direction of circulation of the heat transfer dielectric liquid 30 means that the opening 21 corresponds to the inlet of the liquid 30 into the enclosure 20, and the opening 22 corresponds to the outlet. In the example shown, the heat transfer dielectric liquid 30 fills the enclosure as much as possible.

[0059] This enclosure 20 as shown in [Fig.2] contains a component, comprising a printed circuit board 24 carrying two heat generating elements 25a 25b. As an example, the component may be an inverter device, and the heat generating elements 25a 25b may be for example power modules, comprising for example MOSFET transistors, or for example a processor or an integrated circuit configured to implement the control functions of the component.

[0060] The enclosure 20 shown in [Fig. 2] comprises portions 27a 27b which project from the upper wall 23a of the enclosure 20. These portions 27a 27b project radially towards the heat generating elements 25a 25b respectively. In the example shown in [Fig. 2], the first end of these portions 27a 27b is secured to the upper wall 23a of the enclosure 20 and the second end is free.

[0061] Thus, sections 26a 26b are formed in line with the component, more particularly in line with the heat-generating elements 25a 25b, where the space for the passage of the heat-transfer dielectric liquid 30 is reduced. As a result, at constant flow rate, the circulation speed of the heat-transfer dielectric liquid 30 is higher in these sections 26a 26b than in the sections of the enclosure between the dielectric liquid inlet 27 and the section 26a, between the sections 26a and 26b and between the section 26b and the dielectric liquid outlet 28.

[0062] This increase in the circulation speed of the heat transfer dielectric liquid 30 in the enclosure 20 by the Venturi effect makes it possible to increase the efficiency of the heat exchange between the component and the heat transfer dielectric liquid 30. The regulation The thermal performance of the component is thus improved.

[0063] The walls 23a 23b of the enclosure 20 may be at least partially made of plastic, ceramic and / or loaded plastic, for example ceramic or metal.

[0064] The invention is not limited to the implementation examples shown in the figures.

[0065] The heat generating elements 25a 25b contained in the enclosures may not be in direct contact with the heat transfer dielectric liquid, a heat conducting means being able to be arranged between the two, for example a metal plate.

Claims

Claims

1. Assembly comprising: - an electrical energy storage unit, - at least one component for a vehicle propulsion system, being one of: a voltage converter, an on-board charger device, an inverter / rectifier, a rotating electrical machine comprising a rotor and a stator, and - a circulation loop (10) of heat transfer dielectric liquid (30), said loop comprising: - a circulation pump (11) of heat transfer dielectric liquid, - a heat exchanger device (18), the heat transfer dielectric liquid (30) being in contact with the electrical energy storage unit and the at least one component so as to exchange calories, the circulation loop (10) of heat transfer dielectric liquid (30) comprising at least one sealed enclosure (12, 13, 14, 15, 17, 20) at least partially filled with heat transfer dielectric liquid (30), this enclosure comprising: a dielectric liquid inlet (21),and a dielectric liquid outlet (22) and receiving at least said electrical energy storage unit.,

2. Assembly according to the preceding claim, the component being contained in the same enclosure (12, 13, 14, 15, 17, 20) as the electrical energy storage unit.

3. Assembly according to claim 1, the component being contained in an enclosure (12, 13, 14, 15, 17, 20) different from the electrical energy storage unit

4. Assembly according to any one of claims 2 or 3 in which the at least one enclosure (12, 13, 14, 15, 17, 20) has in planes perpendicular to the direction of flow of the heat transfer dielectric liquid (30) a reduced passage section (26a, 26b) at right angles to the component.

5. An assembly according to any one of claims 2 to 4, comprising four components being an on-board charger, a voltage converter, an inverter / rectifier, and a rotating electrical machine comprising a rotor and a stator, these four components and the electrical energy storage unit being arranged in series in the loop (10).

6. An assembly according to any preceding claim, comprising a device for heating the heat transfer dielectric liquid (16) arranged so as to raise the temperature of the liquid (30) at the inlet of the enclosure comprising the electrical energy storage unit (17).

7. An assembly according to any preceding claim, wherein the heat exchanger device (18) is arranged to cool the heat transfer dielectric liquid (30) at the outlet of the enclosure comprising the electrical energy storage unit (17).

8. An assembly according to any preceding claim, the at least one enclosure (12, 13, 14, 15, 17, 20) being at least partially made of plastic, ceramic, metal or plastic loaded, for example, with ceramic or metal.

9. An assembly according to any preceding claim wherein the heat transfer dielectric liquid (30) is an oil, for example having a kinematic viscosity of between 8 and 70 centistokes at 40°C.

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