Thermal management system for vehicle propulsion engine

Abstract

Thermal management system (10) for a powertrain of an electric, mechanical or hybrid vehicle, the thermal management system (10) being provided of: - a first cooling / heating circuit (20) in which a first carrier fluid flows, the first circuit (20) being enslaved to the vehicle's powertrain and being provided with an intermediate heat exchanger (29), - a second cooling / heating circuit (30) in which flows a second carrier fluid at a lower temperature than the temperature of the first carrier fluid, the second circuit (30) being enslaved to a power electronics (34) of the vehicle, - a third cooling / heating circuit (40) in which a third carrier fluid flows at a lower temperature than the temperature of the second carrier fluid, the third circuit (40) being enslaved to a battery (43) of the vehicle, - a six-port device (50), configured to allow the selective passage of the second carrier fluid flowing in the second circuit (30) or the third carrier fluid flowing in the third circuit (40) to and from the intermediate heat exchanger (29), in which the first carrier fluid of the first circuit (20) also flows.

Description

[0001] THERMAL MANAGEMENT SYSTEM FOR VEHICLE POWERTRAINS

[0002] Technical field of the invention

[0003] The present invention is related to a thermal management system for electric, mechanical or hybrid vehicle powertrains. More specifically, the thermal management system is particularly suitable for electric-powered vehicles equipped with a fuel cell system.

[0004] Background art

[0005] As known, a powertrain for electric traction vehicles essentially includes the following components:

[0006] - an electric motor, composed of a stator and a rotor which 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 (most frequently) but also, in some applications, of the asynchronous type;

[0007] - power electronics dedicated to controlling the engine with some on board power transistors driven by a microcontroller, used to regulate the speed of the vehicle by varying the frequency of the current that powers the electric motor;

[0008] - an energy source, typically a fuel cell system and / or a lithium ion or other type of battery, normally at high voltage.

[0009] The fuel cell system, the power electronics and the battery are complex subsystems that require appropriate temperature control and are therefore enslaved by cooling circuits (or heating in the warm up phases).

[0010] In particular, vehicles equipped with a fuel cell system have complex cooling circuits that manage different temperature levels and different fluid properties. More specifically, it is possible to identify:

[0011] - a high-temperature cooling circuit for the fuel cell system,

[0012] - a medium temperature cooling / heating circuit for the power electronics,

[0013] - a low temperature cooling / heating circuit for the high voltage battery.

[0014] Rather than using independent cooling circuits, it is advantageous to allow a heat exchange between the different cooling circuits: the advantages can be significant in terms of shorter warm-up time, reduction in fuel consumption and component life.

[0015] For example, a known system includes two heat exchangers, the first to remove heat from the fuel cell system and supply it to the power electronics, the second to remove heat from the fuel cell system and supply it to the battery (for example, for his warm up). This system also includes a four-way valve and a chiller for cooling the battery.

[0016] This is a very complex system that can be selected for specific solutions. Instead, it would be appropriate to identify a simplified solution, with low costs and which can adapt to any application, i.e. not exclusively to vehicles equipped with a fuel cell system.

[0017] Simpler solutions than the previous one are known, but these solutions do not, however, allow the management of different cooling fluids.

[0018] This is an important and unacceptable limitation in the presence of a fuel cell system. In this case, since the cooling fluid circulates inside the fuel cells, it is necessary to use a fluid that is an electrical insulator and that does not contaminate, for example, distilled water. The use of distilled water as the only cooling fluid does not guarantee that it will not become contaminated and, furthermore, penalizes the overall efficiency of the cooling circuit as it is not possible to use a second fluid with higher thermal conductivity.

[0019] There is therefore a need to solve the technical problem mentioned above by means of an innovative thermal management system for vehicle powertrains.

[0020] Summary of the Invention

[0021] The aim of the present invention is to create an innovative thermal management system for an electric, mechanical or hybrid vehicle powertrain.

[0022] The main novelty of the invention consists in the fact that the thermal management system coordinates three cooling circuits - equipped with corresponding high-temperature, medium-temperature and low- temperature carrier fluids - using a six-port device, for example a six-way valve. The six-port device regulates the refrigerant flow to a single intermediate heat exchanger to allow heat transmission from the high temperature circuit to the lower temperature circuits (medium temperature and low temperature).

[0023] Advantageously, the high temperature carrier fluid of the first circuit is different from the lower temperature carrier fluids of the further cooling circuits. Preferably, by means of a vehicle cabin heater, it is possible to carry out a further heat exchange between the circuit with high temperature carrier fluid and the vehicle cabin heating circuit.

[0024] Therefore, according to the present invention there is provided a thermal management system for a powertrain of an electric, mechanical or hybrid vehicle, having the characteristics set forth in the independent claim, annexed to the present description.

[0025] According to a further aspect of the present invention, a control architecture is provided for operating the thermal management system of an electric, mechanical or hybrid vehicle powertrain, the control architecture having the characteristics set out in a dependent claim, attached to this description.

[0026] Further embodiments of the invention, preferred and / or particularly advantageous, are described according to the characteristics set forth in the attached dependent claims.

[0027] Brief description of the Drawings

[0028] The invention will now be described with reference to the attached drawings, which illustrate some non-limiting embodiments, in which:

[0029] - figure 1 schematically illustrates a thermal management system of an electric propulsion system according to a preferred embodiment of the present invention,

[0030] - figure 2 is a logical diagram of a control architecture of the system of figure 1, according to a preferred embodiment of the present invention,

[0031] - figure 3 is a logical diagram of the control architecture of figure 2 in the configuration for a single optimization problem, and - figure 4 is a logical diagram of the control architecture of figure 2 in the configuration for a double optimization problem.

[0032] Detailed Description

[0033] As already mentioned, the present invention relates to a thermal management system for electric, mechanical or hybrid vehicle powertrains. More specifically, the thermal management system is particularly suitable for electric-powered vehicles equipped with a fuel cell system. In the following, the description will make specific reference to the fuel cell system without losing its generality but it has to be intended that the thermal management system can be applied to any vehicle powertrain.

[0034] According to the present invention and with reference to Figure 1, the thermal management system 10 coordinates three cooling circuits 20, 30, 40 using a six-port device 50. A preferred solution of the six-port device 50 is, for example, a six-way valve. Naturally, other equivalent solutions can be chosen, for example a pair of four-way valves or a trio of three-way valves.

[0035] As will be seen below, an important feature of the thermal management system 10 is the possibility of using different carrier fluids. In particular, while in a first circuit the carrier fluid may be distilled water, in the further circuits the carrier fluid may be different, for example, it may be a mixture of water and glycol or a dielectric oil.

[0036] In figure 1 it is possible to identify a first cooling / heating circuit 20 in which a first high temperature carrier fluid flows. The first circuit is enslaved to the vehicle propulsion system 22, for example, to a fuel cell system 22. In this first circuit 20, the first carrier fluid used for cooling / heating is, preferably, distilled water. The carrier fluid is moved by a pump means 21 and exchanges heat with the fuel cell system 22. In operating conditions, the heat will be removed from the fuel cell system, while in warm up conditions the heat - generated by a heater 23 preferably with a positive temperature coefficient and positioned upstream of the pump means 21 - will be supplied to the fuel cell system 22. The heater 23 will be active in the warm up conditions and will be turned off in other operating situations.

[0037] The first circuit 20 also includes an intermediate heat exchanger 29 which allows heat to be exchanged with the other two cooling circuits and whose operation will be explained below.

[0038] The first circuit 20 may finally include a high temperature radiator 27 to exchange heat with the external environment and a passenger cabin heater 28 for heating or cooling the passenger compartment of the car.

[0039] Suitable valves, for example three-way valves 24, 25, 26, will allow the selective passage of distilled water through the intermediate heat exchanger 29, the high-temperature radiator 27 and the passenger cabin heater 28.

[0040] A second cooling / heating circuit 30, in which a second carrier fluid flows at medium temperature and in any case at a lower temperature than the temperature of the first carrier fluid, is enslaved to the power electronics 34. The second carrier fluid circulating in this second circuit it is one of those traditionally used in cooling circuits, for example a mixture of water and glycol or a dielectric oil. A pump means 31 pushes the carrier fluid which exchanges heat with the power electronics 34. In operating conditions, the heat will be removed from the power electronics, while in warm up conditions the heat - taken from the first circuit 20 - will be supplied to power electronics 34.

[0041] The second circuit 30 also includes a medium temperature radiator 33 to exchange heat with the external environment, whose selective passage of the carrier fluid is regulated by a three-way valve 32.

[0042] Finally, a third cooling / heating circuit 40, in which a third low- temperature carrier fluid flows and in any case at a lower temperature than the temperature of the second carrier fluid, is connected to the high-voltage battery 43. The third carrier fluid circulating in this third circuit coincides with the second carrier fluid circulating in the second circuit, i.e. it is always a carrier fluid of those traditionally used in cooling circuits. A pump means 41 pushes the carrier fluid which exchanges heat with the high voltage battery 43.

[0043] In operating conditions, the heat will be removed from the battery by means of a chiller 46, while in warm up conditions the heat - taken from the first circuit 20 or generated by a heater 42, preferably with a positive temperature coefficient and positioned downstream of the pump 41 - will be supplied to battery 43 at high voltage. The heater 42 will be active in warm up conditions and will be turned off in other operating situations.

[0044] The third circuit 40 also includes a medium temperature radiator 44 to exchange heat with the external environment, whose selective passage of the carrier fluid is regulated by a three-way valve 45.

[0045] According to the present invention, the six-port device 50, for example, a six-way valve, allows the three cooling circuits 20, 30, 40 and the intermediate heat exchanger 29 to be put into thermal communication.

[0046] In particular, the six-port device 50 includes:

[0047] - a first inlet 52i for the carrier fluid coming from the intermediate heat exchanger 29,

[0048] - a first outlet 52o for the carrier fluid sent to the intermediate heat exchanger 29,

[0049] - a second inlet 53i for the second carrier fluid circulating in the second circuit 30,

[0050] - a second outlet 53o for the second carrier fluid circulating in the second circuit 30,

[0051] - a third inlet 54i for the third carrier fluid circulating in the third circuit 40,

[0052] - a third outlet 54o for the third carrier fluid circulating in the third circuit 40.

[0053] The six-port device therefore allows the selective passage of the carrier fluid circulating in the second circuit 30 or the carrier fluid circulating in the third circuit 40 from and towards the intermediate heat exchanger 29. As anticipated, the intermediate heat exchanger is inserted along the first cooling circuit 20 for which the carrier fluid (for example, distilled water) of the first circuit 20 and, selectively, the carrier fluid (mixture of water and glycol or dielectric oil) of the second circuit 30 or the third circuit 40 will circulate inside it.

[0054] Therefore, in the intermediate heat exchanger 29 the heat exchange will take place between the carrier fluid of the first circuit 20 which will cool and the carrier fluid of the second circuit 30 or the third circuit 40 which will heat up. In this way the warm up times of the power electronics 34 and the battery 43 will be reduced to the benefit of the entire thermal management system 10.

[0055] With reference to figure 2, the control architecture for operating the thermal management system 10 according to the present invention has the objective of minimizing hydrogen consumption by reaching thermal equilibrium, in the shortest possible time, for all the cooling / heating circuits - i.e. for the first circuit 20 at high temperature, for the second circuit 30 at medium temperature and for the third circuit 40 at low temperature - in order to preserve the integrity of the components, maximize their performance and reduce use of external heaters with related consumption.

[0056] To this end, the control architecture reuses part of the energy dispersed by the components in the form of heat to speed up the system's thermal uptime.

[0057] For this purpose, a predictive control algorithm (Model Predictive Control, MPC) was designed, which is an advanced model-based control methodology to address multi-variable and constrained optimal control problems, which exploits a model to predict the evolution future of the system up to a predetermined time horizon.

[0058] The control architecture 100 of the thermal management system 10 (physical system) includes, according to a generic and preferred embodiment, the following elements:

[0059] - an objective function block 110 which establishes the objective function according to the above-mentioned objective 112,

[0060] - a constraints block 120 representing the constraints of the thermal management system 10, for example the temperature limits 122 or the limits of the mechanical components 124,

[0061] - a model 130 which is a mathematical model 130 of the thermal management system 10 and which receives as input signals the environmental conditions 132 and the conditions of the vehicle 134 and is useful for predicting the states of the thermal management system 10 up to a predetermined time horizon,

[0062] - a disturbance block 140 which represents external disturbances, for example, communication delays, aging of actuators, etc.,

[0063] - an optimizer 150 which is the heart of the control architecture. The optimizer is used to calculate the position of the valves and the speed of the pumps to be requested from the thermal management system in order to satisfy the requirements imposed by the objective function block 110, respecting the constraints block 120, i.e. the constraints of the thermal management system, and on the basis of the model 130, i.e. the future prediction of the thermal management system up to a predetermined time horizon, the disturbance block 140, i.e. the knowledge of external disturbances, and the knowledge of the past, i.e. the feedback 145 of the thermal management system 10.

[0064] Two specific and different control architectures are described below, respectively in a configuration for a single optimization problem, and in a configuration for a double optimization problem or a two-level optimization problem.

[0065] In particular and with reference to Figure 3, the control architecture 200 in the configuration for a single optimization problem includes the following elements:

[0066] - an objective function block 210 which establishes the objective function and, in this specific case, sends to the optimizer 250, the request 215 to minimize hydrogen consumption,

[0067] - a constraints block 220 which represents, as in the general case schematized in figure 2, the constraints of the thermal management system 10,

[0068] - a model 230 which is a mathematical model 230 of the thermal management system 10. In this specific case, the prediction of the states of the thermal management system 10 up to a predetermined time horizon will consist in the prediction 235 of the heat flows based on the position of the valves and the speed of the pumps both predicted 252 by the optimizer 250,

[0069] - a disturbance block 240 which represents, as in the general case of figure 2, external disturbances,

[0070] - an optimizer 250 which, in this specific case, to minimize hydrogen consumption will determine the reference temperature for the individual components of the system and how to use the excess heat in the system to reach thermal equilibrium for all components in the shortest time possible. The inputs of the optimizer 250 are the feedbacks 245 of the thermal management system 10, i.e. the measured temperatures, the predicted state 235, i.e. the predicted heat flows, the constraints imposed and the final objective 215, i.e. the minimization of the consumption of hydrogen. The outputs of the optimizer 250 are the current state 255 of the valve position and pump speed to be requested from the thermal management system 10 and the predicted state 252 of the valve position and pump speed to be sent to the model 230.

[0071] With reference to figure 4, the control architecture 300 in the configuration for double optimization problem provides two optimizers characterized by two different dynamics, a slow one for the thermal portion of the thermal management system 10 and a fast one for the hydraulic portion of the same thermal management system 10. The control architecture 300 for the two-level optimization problem includes the following elements:

[0072] - an objective function block 310 which establishes the objective function and, also in this specific case, sends to the optimizer 350, the request 315 to minimize hydrogen consumption,

[0073] - a constraints block 320 which represents, as in the general case schematized in figure 2, the constraints of the thermal management system 10,

[0074] - a thermal model 330 which is a mathematical model 330 of the thermal portion of the thermal management system 10. The output of this thermal model 330 will be the prediction 335 of temperatures based on the predicted position of the valves and the current speeds of the pumps,

[0075] - a hydraulic model 430 which is a mathematical model 430 of the hydraulic portion of the thermal management system 10. The output of this hydraulic model 430 will be the prediction 435 of the heat flows based on the predicted position of the valves and the predicted speeds of the pumps,

[0076] - a disturbance block 340 which represents, as in the general case of figure 2, external disturbances, - a thermal optimizer 350 which, in this specific case, to minimize hydrogen consumption will determine the position of the valves to guarantee temperature regulation for the individual components of the thermal management system 10. The inputs of the thermal optimizer 350 are the feedback 345, 445 of the thermal management system 10, i.e. respectively the measured temperatures and the estimated heat flows, the predicted state 335, 435, i.e. respectively the heat flows predicted by the hydraulic model 430 and the temperatures predicted by the thermal model 330, the thermal constraints imposed and the final objective 315, namely the minimization of hydrogen consumption. The outputs of the thermal optimizer 350 are the current state 355 of the valve positions to be requested from the thermal management system 10 and the prediction 352 of the valve positions to be sent to the thermal model 330,

[0077] - a hydraulic optimizer 450: once the desired temperatures for the individual components have been established by the thermal optimizer 350 and the position of the valves has been determined to reach the pre-set temperature targets, the hydraulic optimizer 450 will determine the speed of the pumps to manage the distribution of the excess heat flows to reach thermal equilibrium in the shortest possible time. The inputs of the hydraulic optimizer 450 are the feedbacks 445 of the thermal management system, i.e. the estimated heat flows, the predicted state 435, i.e. the heat flows predicted by the hydraulic model 430, the imposed hydraulic constraints, the final objective 315 i.e. the minimization of hydrogen and, consequently, temperature targets to determine the management of heat flows and use of external heaters. The outputs of the hydraulic optimizer 450 are the current state 455 of the valve positions and the current speed of the pumps to be requested from the thermal management system 10 and the prediction 452 of the valve positions and pump speeds to be sent to the hydraulic model 430.

[0078] This so-called two-level control architecture 300, thanks to the division into two optimization problems, allows a notable improvement in terms of computational calculation and memory resources compared to the single optimization problem. On the other hand, since the two problems are divided, two "sub-optimal" solutions are obtained which could lead to lower performances than those achievable by means of the "optimal" solution obtainable through the control architecture 200 with a single optimization problem.

[0079] In addition to the form of the invention as described above, it must be understood that there are numerous other variants. It must also be understood that these forms of embodiment are merely illustrative and do not limit either the scope of the invention, its applications or its possible configurations. On the contrary, although the above description allows the skilled person to implement the present invention at least according to one exemplary form of embodiment thereof, it should be understood that many variations of the described components are possible, without thereby departing from the scope of the invention as defined in the appended claims, which are interpreted literally and / or according to their legal equivalents.

Claims

1. Thermal management system (10) for a powertrain of an electric, mechanical or hybrid vehicle, the thermal management system (10) comprising:- a first cooling / heating circuit (20) in which a first carrier fluid flows, the first circuit (20) being enslaved to the vehicle's powertrain and being provided with an intermediate heat exchanger (29),- a second cooling / heating circuit (30) in which flows a second carrier fluid at a lower temperature than the temperature of the first carrier fluid, the second circuit (30) being enslaved to a power electronics (34) of the vehicle,- a third cooling / heating circuit (40) in which a third carrier fluid flows at a lower temperature than the temperature of the second carrier fluid, the third circuit (40) being enslaved to a battery (43) of the vehicle, the thermal management system (10) being characterized in that it comprises a six-port device (50), configured to allow the selective passage of the second carrier fluid flowing in the second circuit (30) or the third carrier fluid flowing in the third circuit (40) to and from the intermediate heat exchanger (29), in which the first carrier fluid of the first circuit (20) also flows.

2. Thermal management system (10) according to claim 1, wherein- the powertrain of the vehicle is a fuel cell system (22), and- the first carrier fluid is distilled water, while the second and third carrier fluids are a mixture of water and glycol or a dielectric oil.

3. Thermal management system (10) according to claim 1 or 2, wherein the six-port device (50) is a six-way valve.

4. The thermal management system (10) according to claim 2 or 3, wherein the first circuit (20) further comprises:- a pump means (21) which moves the first carrier fluid so that the latter carries out a heat exchange with the fuel cell system (22),- a heater (23), active in warm-up conditions of the fuel cell system (22).

5. Thermal management system (10) according to any of the preceding claims, wherein the second circuit (30) comprises:- a pump means (31) which moves the second carrier fluid so that the latter carries out a heat exchange with the power electronics (34),- a radiator (33) to exchange heat with the external environment.

6. Thermal management system (10) according to any of the preceding claims, wherein the third circuit (40) comprises:- a pump means (41) which moves the third vector fluid so that the latter carries out a heat exchange with the battery (43),- a chiller (46) configured to remove heat from the battery (43), under operating conditions,- a heater (42) configured to transfer heat to the battery (43), in warm-up conditions, and- a radiator (44) to exchange heat with the external environment.

7. Thermal management system (10) according to any of the preceding claims, wherein the six-port device (50) comprises:- a first inlet (52i) for the carrier fluid coming from the intermediate heat exchanger (29) and a first outlet (52o) for the carrier fluid delivered to the intermediate heat exchanger (29),- a second inlet (53i) for the second carrier fluid flowing in the second circuit (30) and a second outlet (53o) for the second carrier fluid flowing in the second circuit (30),- a third inlet (54i) for the third carrier fluid flowing in the third circuit (40) and a third outlet (54o) for the third carrier fluid flowing in the third circuit (40).

8. Control architecture (100, 200, 300) for the thermal management system (10) according to any of the preceding claims, the control architecture (100, 200, 300) comprising:- an objective function block (110, 210, 310) which states the objective function for the thermal management system (10),- a constraint block (120, 220, 320) representing the constraints of the thermal management system (10),- a mathematical model (130, 230, 330, 430) of the thermal management system (10) configured for predicting the states of the thermal management system (10) up to a predetermined time horizon,- a disturbance block (140, 240, 340) representing external disturbances, and- an optimizer (150, 250, 350, 450) configured to calculate the position of the valves and the speed of the pumps to be requested from the thermal management system (10).

9. Control architecture (200) according to claim 8, configured for handling a single optimization problem wherein:- the objective function block (210) is configured to send the optimizer (250) a request (215) to minimize the hydrogen consumption,- the mathematical model (230) is configured for the prediction (235) of the heat flows based on valves positions and pumps speeds both predicted (252) by the optimizer (250),- the optimizer (250) has as input the measured temperatures (245), the predicted heat flows (235) and the minimization of hydrogen consumption (215) and as output the current status (255) of valves positions and pumps speeds to be requested from the thermal management system (10) and the predicted status (252) of valves positions and pumps speeds to be sent to the model (230).

10. Control architecture (300) according to claim 8, configured for handling a double optimization problem wherein:- the objective function block (310) is configured to send the optimizer (350) a request (315) to minimize the hydrogen consumption,- the mathematical model (330) is a thermal model of the thermal portion of the thermal management system (10) and is configured to predict (335) temperatures based on the predicted valves positions and the actual pumps speeds,- the mathematical model (430) is a hydraulic model of the hydraulic portion of the thermal management system (10) and is configured for the prediction (435) of the heat flows based on the predicted valves positions and the predicted pumps speeds,- the thermal optimizer (350) is slow dynamic and has as input the measured temperatures (345) and the estimated heat flows (445), the heat flows predicted (335) from the hydraulic model (430) and the predicted temperatures (435 ) from the thermal model (330), and the minimization of hydrogen consumption (315); the thermal optimizer (350) also has as output the current status (355) of valves positions to be requested from the thermal management system (10) and the prediction (352) of valves positions to be sent to the thermal model (330 ),- the hydraulic optimizer (450) has fast dynamics and has as input the estimated thermal flows (445), the predicted thermal flows (435) from the hydraulic model (430) and the minimization of hydrogen consumption (315); the hydraulic optimizer (450) also has as output the current status (455) of valves positions and pumps speeds to be requested from the thermal management system (10) and the prediction (452) of valves positions and pumps speeds to be sent to the hydraulic model (430).

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