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EP-4405190-B1 - THERMAL MANAGEMENT SYSTEM FOR ELECTRIC POWERTRAINS

EP4405190B1EP 4405190 B1EP4405190 B1EP 4405190B1EP-4405190-B1

Inventors

  • BUZZI, LUCA
  • DI PIERRO, Claudio
  • MAFRICI, SALVATORE
  • SPAZIAN, Andrea

Dates

Publication Date
20260506
Application Date
20220923

Claims (9)

  1. Thermal management system (5, 10) for an electric powertrain (50) of an electric-powered vehicle, wherein the electric powertrain (50) comprises an inverter (51), an electric motor (52), a speed reducer (53) and the electric-powered vehicle comprises a power source (55), the thermal management system (5, 10) comprising: - a single circuit (20) traversed by a single carrier fluid, - at least one heat exchanger (41, 42, 43) for the heat exchange of the carrier fluid with another working fluid or with the air of the external environment, - a high voltage heater (40), - at least a pump element (44) for the circulation of the carrier fluid, - at least two control valves (45, 46, 47, 48) wherein the carrier fluid is configured to reach, by means of a plurality of thermally independent branches (21, 22, 23, 24), the inverter (51), the electric motor (52), the speed reducer (53) of the electric powertrain (50) and the power source (55) so as to simultaneously carry out shared thermal exchanges with each component of the electric powertrain (50) and with the power source (55), characterized in that the thermal management system (5, 10) is configured for - heating the speed reducer (53) by means of the high voltage heater (40) and cooling the inverter (51) and the electric motor (52) through a second heat exchanger (43) in one operating mode, and - cooling the power source (55) through a first heat exchanger (42) and cooling the inverter (51) and the electric motor (52) through the second heat exchanger (43) in another operating mode.
  2. Thermal management system (5) according to claim 1, wherein the first (43) and the second heat exchanger (42) are ambient air/ carrier fluid radiators.
  3. Thermal management system (10) according to claim 1, wherein a first and a second heat exchanger (42, 43) belong both to the thermal management system (10) of the electric powertrain (50) and to a conditioning system (60) of the electric-powered vehicle while a third heat exchanger is an ambient air/ carrier fluid radiator (41).
  4. Thermal management system (10) according to claim 3 configured according to an operating mode in which - only the power source (55) is heated by means of the first heat exchanger (42) and/or the high voltage heater (40), or - the power source (55) and the speed reducer (53) of the electric powertrain (50) are heated by means of the first heat exchanger (42) and/or the high voltage heater (40), or - only the speed reducer (53) of the electric engine (50) is heated by means of the high voltage heater (40).
  5. Thermal management system (10) according to claim 3, configured according to an operating mode in which the power source (55) and the speed reducer (53) of the electric powertrain (50) are heated by means of the first heat exchanger (42) and/or the high voltage heater (40), and the inverter (51) and the electric motor (52) are heated via the second heat exchanger (43).
  6. Thermal management system (10) according to claim 3, configured according to an operating mode in which the energy source (55) is cooled by means of the first heat exchanger (42), and - the inverter (51) and the electric motor (52) are cooled through the second heat exchanger (43), or - the inverter (51) and the electric motor (52) are cooled through the second heat exchanger (43), while the speed reducer (53) is cooled by the ambient air/ carrier fluid radiator (41).
  7. Thermal management system (10) according to claim 3, configured according to an operating mode in which the speed reducer (53) is heated by means of the high voltage heater (40), and - the inverter (51) and the electric motor (52) are cooled through the second heat exchanger (43), or - the power source (55) is cooled through the first heat exchanger (42) and the inverter (51) and the electric motor (52) are cooled through the second heat exchanger (43).
  8. Method of operating a thermal management system (5, 10) for an electric powertrain (50) of an electric-powered vehicle, the thermal management system (5, 10) being defined according to any of the preceding claims, the method including the independent and iterative controls of the temperature (T_M) of the inverter (51)/electric motor (52), the temperature (T_R) of the speed reducer (53) and the temperature (T_S) of the source of energy (55), in which each of said temperatures (T_M, T_R, T_S) is controlled: - activating the heating of at least one of the aforementioned components (51/52, 53, 55) according to at least one operating mode of the thermal management system (5, 10) when the corresponding temperature (T_M, T_R, T_S) is lower than a predetermined minimum temperature threshold (T_M_MIN, T_R_MIN, T_S_MIN), or - activating the cooling of at least one of the aforementioned components according to at least one operating mode of the thermal management system (5, 10) when the corresponding temperature (T_M, T_R, T_S) is higher than a predetermined maximum temperature threshold (T_M_MAX, T_R_MAX, T_S_MAX).
  9. Method according to claim 8, wherein, when the electric powertrain (50) is subjected to a cold start, the time sequence of the operating modes of the thermal management system (5, 10) implemented for the activation of the heating and/or the cooling of said components (51/52, 53, 55) provides: - an operating mode for heating all components, - at least one operating mode of partial heating of the components, - at least one hybrid operating mode, i.e., heating some components and cooling other components, - an operating mode of partial cooling of the components, - an operating mode for cooling all components.

Description

Field of the invention The present invention relates to an innovative thermal management system for an electric powertrain of an electric vehicle. More specifically, the thermal management system is able to provide heating and cooling of the different subsystems independently but using a single circuit and a single carrier fluid. Furthermore, this system can interact with the entire air conditioning system of the electric vehicle. Background art As is known, an electric propulsion system for electric vehicles essentially comprises the following components: an electric motor, consisting of a stator and a rotor that generate two magnetic fields whose interaction produces the driving torque used for propulsion. Electric motors can be powered by direct or alternating current and be of the synchronous type (more frequently) but also, in some applications, of the asynchronous type;an inverter/converter that equips both AC motors and DC motors. The inverter, comprising dedicated electronics with some power transistors on board driven by a microcontroller, serves to regulate the speed of the vehicle by varying the frequency of the current that powers the electric motor;a speed reducer which reduces the rotation speed of the electric motor, increasing the drive torque transmitted to the vehicle wheels;an energy source, typically a lithium-ion battery or other type, for example a device with fuel cells. A fundamental aspect for the correct functioning of an electric powertrain is the temperature control of the various components, so that they can be used at their maximum efficiency. In fact, the efficiency of the electric motor decreases with the increase of the stator/rotor temperature: for example, a reduction of the temperature from 170°C to 150°C on the stator/rotor group could increase the efficiency of the electric motor. As for the inverter, the conduction losses of the junction and the switching losses increase with the increase of the temperature of the junction: for example, a temperature reduction of 20°C could result in a 2.5% reduction in total losses. In the speed reducer, on the other hand, the friction losses decrease with the increase of the lubrication oil temperature: for example, passing from 60°C to 90°C a reduction of 2% of the loss of transmitted torque could be obtained. As you can see, these components have contrasting needs from a thermal point of view: while the temperature reduction is beneficial for the motor and the inverter, an increase in temperature is beneficial for the speed reducer. A thermal management system for an electric powertrain is known from US 10 476 051 B2. Current thermal management systems for an electric powertrain provide for the use of a dedicated cooling circuit, for example a circuit in which the heat is removed from a mixture of water and glycol, or a direct heat exchange cooling circuit, for example, using a carrier fluid such as a dielectric oil. However, these circuits provide for the simultaneous cooling (or, in some cases, heating) of all subsystems of the electric powertrain. In other words, known cooling circuits do not allow the various components to work with the maximum of their respective efficiency: for example, in the case of simultaneous cooling, due to the conflicting needs of these components, the electric motor and the inverter will benefit, while the speed reducer will be penalized. There is therefore a need to solve the aforementioned technical problem by means of an innovative thermal management system for electric powertrain. Summary of the Invention The aim of the present invention is to realize an innovative thermal management system for an electric powertrain of an electric vehicle. The invention consists in the fact that the thermal management system is able to separately manage the heating and cooling of the subsystems of the electric powertrain. In particular, the thermal management system, by means of a single circuit crossed by a single carrier fluid, for example, dielectric oil, is separately enslaved to an electric motor, an inverter, a speed reducer and a source of energy (battery, fuel cell device and similar) with appropriate adjustment devices. According to the invention, the thermal management system can operate according to multiple operating modes that implement different heating/ cooling strategies. Preferably, the thermal management system according to the invention will be able to interact with the air conditioning system of the entire electric vehicle equipped with the electric powertrain. By means of the present invention, therefore, the performance of the electric powertrain is optimized in terms of efficiency, duration and effectiveness of the heating. Therefore, according to an aspect of the present invention a thermal management system for electric powertrain is provided, the system having the characteristics set forth in the independent product claim 1. According to another aspect of the present invention a method o