FR3022496A1 - PROPULSION SYSTEM FOR HYBRID MOTOR VEHICLE COMPRISING MEANS FOR RECOVERING LOST THERMAL ENERGY - Google Patents

Abstract

This propulsion system for a hybrid motor vehicle comprises a heat engine (1) capable of rotating a crankshaft (4), an electric machine (2) intended to be rotatably connected to the wheels (5) of the vehicle and capable of operating according to a motor mode and a generator mode, a battery (7) for supplying electric power to the electric machine (2) and storing electrical energy from the electric machine (2) and a power management system (2). onboard energy (100). In addition, it comprises at least one thermoelectric generator (18, 19) intended to be disposed in heat exchange relation with at least one hot source (31, 38a) and able to supply electrical energy to the battery (7). ) and the electric machine (2).

Description

The present invention relates to the field of propulsion systems for motor vehicles, in particular for hybrid motor vehicles equipped with a heat engine and an engine. electric.

Motor vehicle users are now increasingly penalized by pollutant emission limits and the fuel consumption of their vehicles. For example, some European cities are now applying "tolls" to force the user to drive in certain areas. These "tolls" can be proportional to the emissions of pollutants such as carbon dioxide. Generally, the efficiency of a motor vehicle propulsion system equipped with an internal combustion engine, defined as the fraction of the mechanical energy transmitted to the drive wheels on the chemical energy of the fuel consumed, is of the order of 33%. Two-thirds of the chemical energy of the fuel is therefore dissipated, much of it in the form of heat discharged in about two equal parts in the coolant and in the exhaust gas.

This efficiency can be improved with hybrid propulsion systems, for example of the type comprising a heat engine and an electric motor. Among these hybrid propulsion systems, one can still differentiate several types of technologies. For example, there is shown in Figure 1 an example of a propulsion system according to the "mild hybrid" technology with a heat engine 1 and an electric machine or alternator-starter 2 whose drive shaft is connected by a belt 3 to the crankshaft 4 of the heat engine 1. The crankshaft 4 of the heat engine 1 is connected to the drive wheels 5 of the vehicle by means of a mechanical transmission 6. The propulsion system comprises a battery 7 of greater capacity than in a non-propulsion system. hybrid. The alternator-starter 2 is a reversible electric machine that can respectively: 5 - supply electrical energy to the electric battery 7 and any electrical accessories 8 of the vehicle (role of an alternator in a conventional vehicle), - implement a regenerative braking, in other words converting into electrical energy a portion of the kinetic energy of the vehicle during a deceleration, - rotating the crankshaft 4 when starting the heat engine 1 (role of a starter in a conventional vehicle) and - assist the heat engine 1 during strong accelerations 15 (role of a booster engine). When the electric machine 2 operates as an alternator or in regenerative braking, it supplies power to the accessories 8 and to the electric battery 7, as represented symbolically by the respective arrows 14 and 15. When it operates as a starter or a booster motor, a power supply by the electric battery 7 is necessary, symbolically represented by the arrow 16. An electrical supply of the accessories 8 by the electric battery 7 may also be necessary, represented by the arrow 17.

This propulsion system further comprises means for transmitting mechanical energy between the heat engine 1, the electric machine 2, and the drive wheels 5. Thus the belt 3 connecting the crankshaft 4 to the drive shaft 11 of the electric machine 2 is held in place by two rollers 12 and 13. Two half-shafts 9 and 10 30 allow to distribute the mechanical energy output of the transmission 6 and distribute it to the drive wheels 5. Such a propulsion system allows a consumption gain of around 15% in urban driving. On the other hand, it does not have any real advantage in stabilized speed, especially at high speed, since the capacity of the battery 7, although larger than in a non-hybrid vehicle, is not sufficient to assist the driver. thermal engine 1 continuously. Moreover, such a system always has a thermal motor and therefore always has significant energy losses in the form of heat. Some motor vehicles are equipped with thermoelectric generators capable of recovering thermal energy to transform it into electrical energy. Such generators are based on 10 different technologies. The most accomplished are thermoelectric generators with Rankine loop or Seebeck effect. A Rankine loop generator is a system that aims to convert heat into mechanical work and then into electricity using a generator. This generator comprises a circuit in which a working fluid is circulated by means of a pump. Heat exchangers are arranged at a hot source for vaporizing the working fluid. The latter is relaxed in an expansion machine coupled to a generator. The circuit also includes a heat exchanger at a cold source 20 to condense the working fluid. Also known are Seebeck effect thermoelectric generators. At least one thermoelectric pad is placed between a hot source and a cold source. The temperature difference applied to the thermoelectric pads allows the production of electricity.

Such generators therefore both make it possible to create electricity from a hot source and a cold source. They can be incorporated into a motor vehicle to recycle lost energy in the form of heat. In particular, it is possible to use as the hot source the flow of exhaust gas at the outlet of the engine or the coolant of the heat engine upstream of the radiator and as the cold source the outside air or the coolant of the heat engine downstream. of the radiator. The electrical power that can be generated by the thermoelectric generator depends on the flow and temperature of the exhaust gas or coolant. As a result, the electrical power generated can be maximum when the mechanical power delivered by the engine is important, such as during high acceleration or driving at high speed (highway).

By way of example, for a mid-range vehicle equipped with a Rankine generator running at high speed, it is conceivable to generate an electrical power of the order of several kilowatts. The document FR 0950230 discloses a motor vehicle equipped with a heat engine, an alternator and a thermoelectric generator. The thermoelectric generator is capable of supplying electrical energy from the heat lost by the motor. The energy is therefore generated in a variable manner, substantially proportional. As in a conventional vehicle, the alternator serves to supply electrical energy to the vehicle's electrical accessories by taking mechanical energy from the crankshaft of the engine. Thus, when the alternator is in operation, it consumes more fuel. In the vehicle, the alternator of the document FR 0950230 is controlled in such a way that it does not produce electric power when the thermoelectric generator is able to provide for the electrical consumption of the accessories of the vehicle. In this case, it does not take power on the crankshaft of the engine, which improves the efficiency of the propulsion system.

However, the electrical accessories of a mid-range vehicle consume an electrical power of the order of a hundred watts, so significantly lower than the power that can be generated by a Rankine thermoelectric generator on highway. A large part of this generated energy is therefore lost. US 2008-0 110 171 A1 proposes to add a hydraulic accumulator to store a portion of this electrical energy. However, the capacity of such an accumulator is limited by pressure and space constraints.

In view of the foregoing, the object of the invention is to improve the efficiency of a propulsion system of a hybrid motor vehicle. According to a first aspect, the invention relates to a propulsion system for a hybrid motor vehicle. The propulsion system comprises a heat engine capable of rotating a crankshaft, an electrical machine intended to be rotatably connected to the wheels of the vehicle and capable of operating in a motor mode and a generator mode, a battery intended to provide power to the vehicle. electrical energy to the electrical machine and storing electrical energy from the electrical machine and an on-board energy management system. The propulsion system further comprises at least one thermoelectric generator intended to be disposed in heat exchange relation with at least one hot source and capable of supplying electrical energy to the battery and to the electrical machine. In this way, the electric machine can operate in generator mode to generate electricity from the crankshaft movement and power the battery and any electrical accessories of the hybrid vehicle. The electric machine can also function as an electric motor, transforming electrical energy into mechanical energy transmitted to the drive wheels of the vehicle in addition to or in replacement of the mechanical energy generated by the engine. The electric machine can thus play the role of the alternator or the electric motor of a hybrid vehicle. The battery is an energy reservoir for the electrical machine and any electrical accessories of the vehicle. The thermoelectric generator is a means for recovering some of the lost energy in the form of heat in order to transform it into electrical energy. With the help of the on-board energy management system, this electrical energy can be distributed to the electric machine in order to be able to exert a driving torque on the drive wheels of the vehicle. The energy lost in the form of heat and recovered by the thermoelectric generator is therefore distributed more efficiently.

In particular, during an acceleration phase, the amount of electrical energy generated by the thermoelectric generator is large, as is the need for electrical energy by the electric machine which functions as a booster motor. . The on-board energy management system provides a better correlation between the energy demand and the energy made available, which improves efficiency. This results in an improvement of the energy efficiency of the motor vehicle. Advantageously, the on-board energy management system 10 comprises hardware and software means for measuring at least one parameter chosen from the operating mode of the vehicle, the load of the heat engine, the energy consumed by the electrical accessories of the hybrid vehicle. and the energy produced by said thermoelectric generator and means for controlling the operating mode of the electric machine and the power supply mode of the battery, the electric machine and the electrical accessories of the hybrid vehicle. The propulsion system is suitable for different types of hybrid motor vehicles. In a first variant, the electric machine is directly connected to the transmission chain. This variant is particularly suitable for a vehicle with "full hybrid" propulsion system. Indeed, a particular characteristic of a "full hybrid" propulsion system is the fact that the electric machine can drive the driving wheels of the vehicle 25 when the heat engine is stopped. In a second variant, the electric machine is connected by a belt to the crankshaft. This variant is adapted to a propulsion system according to the "mild hybrid" technology in which an electric machine performs the functions of an alternator, a regenerative braking means, a starter and a means of propulsion. vehicle. In one embodiment, said at least one thermoelectric generator comprises a circuit with a Rankine loop having a pump capable of circulating a working fluid, an evaporator disposed at said at least one hot source, a expansion machine and a condenser at said at least one cold source. It can also be provided that said at least one thermoelectric generator comprises a Seebeck effect device comprising a thermoelectric material disposed between said at least one hot source and a cold source. It is necessary that each thermoelectric generator is disposed in heat exchange relation with a hot source. In a first variant, said at least one hot source comprises the coolant of the engine of the vehicle. In a second variant, said at least one hot source comprises the flow of exhaust gas from the engine of the vehicle. The invention also relates, according to a second aspect, to a method for managing energy transfers for a propulsion system such as that described previously. This method comprises a first phase for determining a set of criteria relating to the operation of the vehicle and a second phase of choosing the motor mode of the vehicle and the power supply mode of the electric machine, the battery and the vehicle electrical accessories. hybrid. Such a method allows a recovery of part of the energy that has been lost by the heat engine in the form of heat, its transformation into electrical energy and optimal use of this electrical energy.

In one embodiment, the set of criteria relating to the operation of the vehicle comprises the energy delivered by the thermoelectric generator and the energy consumed by the electrical accessories of the hybrid vehicle. These two pieces of information, analyzed together, make it possible to effectively distribute the electrical energy between the battery, the electric machine, the thermoelectric generator and any electrical accessories of the vehicle. Other features of the invention will appear on reading the detailed description of some embodiments 3022496 8 taken as non-limiting examples and illustrated by the accompanying drawings in which: - Figure 1, which has already been described; illustrates an example of a propulsion system of a vehicle according to the technology already known under the name "mild hybrid", - Figure 2 illustrates an example of a propulsion system of a vehicle according to one embodiment of the invention. Fig. 3 is a block diagram of the operation of one of the two thermoelectric generators of the embodiment of Fig. 2; Fig. 4a is a block diagram of the operation of the other thermoelectric generator of the embodiment; FIG. 4b illustrates a variant of the block diagram of FIG. 4a; FIG. 5 illustrates a method for managing energy transfers that can be implemented; FIG. 3 through 9 of a propulsion system according to the embodiment of FIG. 2, and FIGS. 6 to 9 schematically illustrate various types of energy transfer implemented in the process of FIG. illustrates an embodiment of a propulsion system according to the invention. This embodiment is derived from a propulsion system according to the "mild hybrid" technology as shown in FIG. 1 and described in part in the preamble of this document. The identical elements of the propulsion systems shown in FIGS. 1 and 2 have the same references. The propulsion system of FIG. 2 differs from that of FIG. 1 by the addition of two thermoelectric generators 18 and 19, each of the generators being in heat exchange relation with a hot source. A thermoelectric generator is a device capable of generating electrical energy from a temperature difference. The first generator 18 is a Rankine loop thermoelectric generator. The second generator 19 is a thermoelectric generator Seebeck effect.

The thermoelectric generator 18 is shown in FIG. 3. The casing 30 of the heat engine 1 is shown as well as the exhaust duct 31 containing the exhaust gases from the combustion in the cylinders. The thermoelectric generator 18 5 comprises a loop 32 in which circulates a working fluid driven by a pump 33. On the loop 32 are also arranged an evaporator 34 in heat exchange relation with the exhaust duct 31, an expansion machine 35 coupled to a generator 36 and a condenser 37 coupled to a cold source, in this case the ambient air. However, it is possible, without departing from the scope of the invention, to consider any other type of cold source, for example a cold part of the cooling circuit of the heat engine 1. In this way, the working fluid entrained in the Rankine loop 32 is vaporized at the evaporator 34 and then expanded in the expansion machine 35. This rotates the rotor of the generator 36 and generates electrical energy. The working fluid is then condensed in the condenser 37 to be reused in the Rankine loop. The evaporator 34 is disposed in heat exchange relation 20 with the exhaust duct 31. Thus, by means of such a thermoelectric generator such as this one can take a part of the energy lost by the engine. thermal 1 in the form of heat in the exhaust gas of the conduit 31 to generate electrical energy.

The thermoelectric generator 19 is shown in FIG. 4a. The casing 30 of the heat engine 1 is shown and traversed by the cooling circuit 38 of the heat engine 1. The cooling circuit 38 consists of a duct forming a loop, passing close to the cylinders of the engine 1 and on which 30 mounted a pump 39 and a radiator 40. A coolant circulates in the cooling circuit 38 and is driven by the pump 39. It therefore takes heat in the housing 30 and then passes through the radiator 40 or it evacuates a large part of the heat taken. The cooling circuit can therefore be decomposed into a hot part 38a, between the combustion chamber 30 and the radiator 40 and a cold part 38b, between the radiator 40 and the combustion chamber 30. The thermoelectric generator 19 comprises a source hot 41 41 in this case an exchanger mounted on the hot part 38a of the cooling circuit and a cold source 42, in this case an exchanger disposed on the cold part 38b of the cooling circuit. A set of thermoelectric pads 43 are arranged between the hot source 41 and the cold source 42.

Without departing from the scope of the invention, the cold source 42 may be placed in contact with the ambient air, as shown in FIG. 4b. In this figure, the thermoelectric generator is arranged so that its hot source 41 is mounted on the hot part 38a of the cooling circuit, its cold source 42 being mounted on a pipe 38c in which flows air from from outside the vehicle. The thermoelectric pads are made of a material such that the temperature difference between its two ends generates electrical energy. This well-known effect of the state of the art is called the Seebeck effect. Thus, by means of such a thermoelectric generator, it is possible to take a part of the energy lost by the heat engine 1 in the form of heat in the cooling liquid to generate electrical energy. The electrical energy generated by the generators 18 (FIG. 3) 25 and 19 (FIG. 4a) can then be used to power the electric machine 2 when it is operating in the engine mode, the electrical accessories 8 of the hybrid vehicle, or to charge 7. In the same way as in FIG. 1, FIG. 2 shows diagrammatically the energy transfers between different elements of the propulsion system. As in the propulsion system of FIG. 1, mechanical energy is exchanged between the heat engine 1, the electric machine 2 and the drive wheels 5. These exchanges are made using the belt 3, the crankshaft 4 , the transmission 6, the half-shafts 9 and 10, the drive shaft 11 and the rollers 12 and 13. The propulsion system of Figure 2 differs from that of Figure 1 by the addition of two generators . There is therefore more electricity exchange. These are represented by continuous arrows around a central point of connection 20. Thus we see that the electric machine 2 is able to function as a generator that emits electrical energy (arrow 21) or as a consuming engine electrical energy (arrow 22). The electrical accessories 8 can only consume electrical energy (arrow 23). Thermoelectric generators can only generate electric current (arrows 24 and 25). The energy generated by the electric machine 2 and the thermoelectric generators 18 and 19 is not necessarily equal to that consumed by the electric machine 2 and the electrical accessories 8. This is the role of the electric battery 7 of ensure the storage of the surplus electrical energy produced (arrow 26) and the destocking of the missing electrical energy (arrow 27). Dotted arrows symbolize the exchanges of thermal energy. Thus arrow 28 symbolizes the transfer of thermal energy from the heat engine 1 to the Rankine 18 thermoelectric generator. In this case, the arrow 28 symbolizes a heat transfer from the exhaust duct 31 of the engine 1 to the working fluid. contained in circuit 32 of the Rankine loop. The arrow 29 symbolizes the transfer of thermal energy from the heat engine 1 to the Seebeck effect thermoelectric generator 19. In this case, the arrow 29 symbolizes a heat transfer from the hot part 38a of the cooling circuit of the heat engine to one end. thermoelectric pads 43.

Furthermore, the propulsion system comprises an on-board energy management system 100. The management system 100 is provided with hardware and software means for collecting information transmitted by elements of the propulsion system.

In this example, the management system 100 processes the following information: the consumption of electrical energy by the electrical accessories 8, the speed of rotation and the torque delivered by the heat engine 1, the temperature of the exhaust gas just upstream of the heat exchanger 34, the temperature of the coolant of the heat engine 1 just upstream of the exchanger 41, and the charge level of the battery 7. To collect this information, the management system may comprise measuring means such as thermometers, a tachometer, a dynamometer, etc. which have not been shown in the figures since they are outside the scope of the invention. The management system is designed to interpret this information so as to determine: the mode of operation of the vehicle, in particular to determine whether it is in a phase of acceleration, deceleration or speed substantially constant, the load of the vehicle; thermal engine 1, the electrical power generated by the two thermoelectric generators 18 and 19, and the electric power consumed by the electrical accessories 8. In this example, the management system 100 uses these four criteria to determine whether the electric machine 2 must function as a generator or as a motor. In the case where the electric machine 2 is to function as a motor, the management system 100 is capable of controlling the electrical power to be delivered at its terminals as well as the torque and rotational speed it is to deliver. Thus, with reference to FIG. 2, the electrical energy management system is designed to control the electrical energy exchanges represented diagrammatically by the arrows 21, 22, 23, 24, 25, 26 and 27 around the connection point 20. FIG. 5 shows a method for managing energy transfers by means of a hybrid vehicle propulsion system, as previously described with reference to FIGS. 2 to 4b, and comprising a system for controlling the transfer of energy by means of a hybrid vehicle propulsion system. embedded energy management 100. The energy transfer management method includes a first phase 50 for determining a set of criteria relating to the operation of the vehicle and a second phase 51 for selecting the mode of motor traction of the vehicle and the mode power supply of the electric machine, the battery and the group of electrical accessories. The first phase 50 includes a first step 52 during which the on-board energy management system collects information regarding the operation of the vehicle. As a reminder, the on-board energy management system collects signals concerning: the electrical power consumed by the electrical accessories, the rotational speed and the torque delivered by the heat engine, the temperature of the exhaust gases just upstream of the exchanger, 25 - the temperature of the engine engine coolant just upstream of the exchanger, and - the battery charge level. In a second step 53, the on-board energy management system processes the signals collected in the first step 52. In processing this information, the management system determines criteria for choosing the instructions to be sent. to the elements of the vehicle's propulsion system. During step 53, the management system processes the information gathered in step 52 to determine: - the mode of operation of the vehicle, ie if it is in the acceleration phase , deceleration or speed substantially constant, - the load of the engine, 5 - the electrical energy produced by the two thermoelectric generators, and - the electrical energy consumed by the electrical accessories. Once the criteria have been calculated, the second phase 51 begins with a first test step 54. During this step, the operating mode of the vehicle is controlled, in other words whether it operates in acceleration, deceleration or substantially constant speed. If the vehicle is operating in acceleration, a step 56 is applied, which will be explained with reference to FIG. 6. If the vehicle 15 is decelerating, a step 57 is applied, which will be explained with reference to FIG. substantially constant speed, applies a second test step 55, during which the load of the engine is controlled. If this is greater than a reference load value, a step 58 is applied which will be explained with reference to FIG. 8. In the opposite case, a step 59 is applied which will be explained with reference to FIG. 9. In this method, the reference load is predetermined as the load of the minimum heat engine from which the electric power generated by the thermoelectric generators 18 and 19 is equal to the electrical power consumed by the accessories 8 at a certain time. Indeed, the electric power generated by the thermoelectric generators depends on the heat lost by the heat engine 1 and donate its load. It is therefore possible for an electric power consumed by the given accessories to determine the reference value of the thermal engine load. FIGS. 6 to 9 are schematic representations of the energy exchanges taking place between different elements of the propulsion system of FIGS. 2 to 4b respectively during the implementation of steps 56 to 59 of the method of FIG. FIGS. 6 to 9 schematically show the elements between which these exchanges take place in the form of blocks by giving them new references.

Thus, the driving wheels 61, the heat engine 62, the electric machine 63, the set of two thermoelectric generators 64, the electric battery 65 and the electrical accessories 66 have been represented in FIGS. 6 to 9. In FIGS. 9, the mechanical energy transfers are represented by a thick arrow coming from the actuator. Thermal energy transfers are represented by a fine arrow from the hot source. Electric energy transfers are represented by a dotted arrow from the generator element or directed towards the consumer element.

FIG. 6 schematically represents the energy exchanges taking place during step 56. As a reminder, this step is implemented when the vehicle is being accelerated. In this case, the on-board energy management system operates the electric machine as a backup engine.

There is thus transfer of mechanical energy from the electric machine 63 to the heat engine 62 (arrow 71) and the heat engine 62 to the drive wheels 61 (arrow 72). The electric machine 63 requires electrical energy (arrow 73), as the electrical accessories 66 (arrow 74). Furthermore, since the load of the heat engine 62 is large, there is a significant amount of heat release and thus thermal energy transfer from the heat engine 62 to the thermoelectric generators 64 (arrow 75). As a result, thermoelectric generators 64 generate electrical energy (arrow 76). Since the electric machine requires a high electrical power, the electric battery 65 will release electrical energy (arrow 77) in sufficient quantity that the net power flows between the elements 63 to 65 are balanced. By this scheme, the heat engine 62 is assisted by the electric machine 63 at a time when it needs it. This results in a decrease in fuel consumption compared to a vehicle with a single engine. Furthermore, the generation of electric power by the thermoelectric generators 64 is important, which makes it possible to further assist the heat engine 62 without further destocking the battery 65. The fuel consumption can therefore be further reduced compared to a hybrid vehicle where the electric machine would be powered by the electric battery alone. FIG. 7 schematically represents the energy transfers 10 occurring during step 57. It is recalled that during the implementation of this step, the vehicle is decelerating. In this case, the on-board energy management system operates the electric machine according to the generator mode in order to implement a regenerative braking.

There is thus transfer of mechanical energy from the driving wheels 61 to the electric machine 63, via the heat engine 62 (arrows 78 and 79). The heat engine 62 does not work, so it is considered that there is substantially no transfer of thermal energy to the thermoelectric generators 64. The electrical machine 63 generates a large amount of electrical energy (arrow 80). A small portion of it is distributed to the electrical accessories 66 (arrow 81), the remainder being sent to the battery 65 to be stored (arrow 82). Figure 8 shows schematically the energy transfers taking place in step 58, i.e. when the vehicle is operating at substantially constant speed and the engine load is greater than the reference load. As a reminder, the reference load is the minimum engine load value from which the electrical power generated by the thermoelectric generators 30 is equal to the electrical power consumed by the electrical accessories. In this case, the on-board energy management system operates the electric machine 63 according to the engine mode to provide the engine 62 with a traction aid.

This results in a transfer of mechanical energy from the electric machine 63 to the heat engine 62 (arrow 83) and the heat engine 62 to the drive wheels 61 (arrow 84). The heat engine 62 emits thermal energy imparted to the thermoelectric generators 64 (arrow 85). Because of the high motor load, the thermoelectric generators 64 generate a quantity of electrical energy (arrow 86) greater than or equal to the electrical energy consumed by the accessories 66 (arrow 87). The battery 65 therefore does not deliver electrical energy and any excess electrical energy from the thermoelectric generators 64 is sent to the electrical machine 63 (arrow 88). It can therefore be seen that such a method makes it possible to operate the electric machine in engine mode whereas in a traditional hybrid vehicle, it would have functioned as an alternator.

Finally, the electric machine can more often assist the heat engine, which makes it possible to reduce the consumption and the emissions of pollutants. Finally, FIG. 9 diagrammatically shows the energy transfers occurring during step 59, that is to say when the vehicle is operating at a substantially constant speed and that the engine load is less than reference value specified previously. In this case, the electric machine 63 operates according to the generator mode to act as a conventional alternator. There is therefore a transfer of mechanical energy from the heat engine 62 to the drive wheels 61 (arrow 89). In the opposite direction, there is transfer of mechanical energy from the heat engine 62 to the electric machine 63 (arrow 90). The heat engine 62 still releases thermal energy communicated to the thermoelectric generators 64 (arrow 91), but in a smaller quantity than when the step 58 is carried out. The thermoelectric generators 64 therefore always generate a quantity of thermal energy. electrical energy (arrow 92) but which is less than the electrical energy consumed by the accessories 66 (arrow 93). The electrical machine 63 is forced to operate in generator mode so that it supplies (arrow 3022496 18 94) the amount of electrical energy missing to supply the electrical accessories 66. The on-board energy management system is also able to control the operating point of the generator 63 so that the net fluxes of electrical power between the elements 63 to 65 are balanced. In this way, the electric battery 65 is not solicited. Thus, such a method applied to a propulsion system such as that of FIG. 2 makes it possible to improve the overall efficiency of the vehicle, compared to vehicles known from the state of the art presented in the introductory part. In particular, the energy lost by the heat engine in the form of heat is recovered and reused more efficiently than with a vehicle as described in document FR 09-50230. Indeed, in such a vehicle, the consumption of electrical energy by the accessories is of another order of magnitude compared to the production of electricity by the thermoelectric generator, which involves significant energy wastage. In addition, such a method applied to a propulsion system makes it possible, whenever possible, to immediately use the electrical power produced by the thermoelectric generators.

This makes it possible to minimize the storage or retrieval of the electrical power produced by the thermoelectric generators in the battery, and thus to avoid the losses inherent in storage or destocking. Such a method also makes it possible to avoid charge saturation of the battery, which would result in stopping the thermoelectric generators and wasting the available thermal energy. Although the example described in this document is derived from a "mil hybrid" propulsion system, it is quite within the scope of the invention to envisage an embodiment from a propulsion system. full hybrid ". In this type of vehicle the electric machine can directly connect to the transmission (for example through an epicyclic train) and the engine and the electric machine can both participate in the traction. In this case, the power generated by the thermoelectric generator 3022496 19 is either stored in the traction battery or consumed directly by the electric machine thereby reducing the mechanical power produced by the engine. However, in zero-emission operation of the full hybrid vehicle 5 that is to say when the traction force is provided solely by the electric motor, the thermoelectric generator is not operational because the engine is cut. Compared to a vehicle according to the "mild hybrid" technology, the method just described and the associated propulsion system 10 make it possible to use the electric machine more often as a booster engine, and less often as a generator. . As a result, there is less torque on the crankshaft of the engine. The advantage can be seen particularly during strong acceleration or at a steady speed for high speeds, since the thermoelectric generators provide more electrical energy, at a time when the heat engine particularly needs a backup electric motor. . In this way, the overall vehicle fuel consumption and pollutant emissions can be reduced overall. Such a device could moreover allow a certain reduction of the displacement of the engine ("downsizing") since the addition of the thermoelectric generator to the electric machine makes it possible to feed it continuously, in particular when the heat engine provides its maximum power. The maximum power of the engine can therefore be reduced in the proportion of the power supplied by the electric machine in engine mode. The reduction in displacement is an additional source of reducing the cost of the engine and reducing its consumption. Similarly, the battery being less stressed during accelerations, both in power and energy, thanks to the electrical power produced by the thermoelectric generator, its capacity and therefore its cost can be reduced.

Claims (10)

REVENDICATIONS1. Propulsion system for a hybrid motor vehicle, comprising a heat engine (1) capable of rotating a crankshaft (4), an electric machine (2) intended to be rotatably connected to the wheels (5) of the vehicle and capable of operating according to a motor mode and a generator mode, a battery (7) for supplying electric power to the electric machine (2) and storing electrical energy from the electric machine (2) and a power management system (2). embedded energy (100), characterized in that it further comprises at least one thermoelectric generator (18, 19) intended to be disposed in heat exchange relation with at least one hot source (31, 38a) and suitable supplying electrical power to the battery (7) and the electric machine (2). 2. Propulsion system according to claim 1, characterized in that the on-board energy management system (100) comprises means for measuring at least one parameter chosen from the operating mode of the vehicle, the load of the heat engine, the energy consumed by the electric accessories of the hybrid vehicle (8) and the energy produced by said thermoelectric generator (18, 19) and means for controlling the operating mode of the electric machine (2) and the power mode electric battery (7), electric machine (2) and hybrid vehicle electrical accessories (8). 3. propulsion system according to one of claims 1 and 2, characterized in that the electric machine (2) is directly connected to the chain of transmission (6). 4. Propulsion system according to claim 1, characterized in that the electric machine is connected by a belt (3) to the crankshaft (4). 5. propulsion system according to any one of claims 1 to 4, characterized in that said thermoelectric generator (18) comprises a circuit (32) with a Rankine loop with a pump (33) capable of circulating a a working fluid, an evaporator (34) disposed at said hot source (31), an expansion machine (35) and a condenser (37) at said at least one cold source. A propulsion system according to any one of claims 1 to 5, characterized in that said thermoelectric generator (19) comprises a Seebeck effect device comprising a thermoelectric material (43) disposed between said hot source (38a) and a cold source (38b). 7. propulsion system according to any one of claims 1 to 6, characterized in that said hot source (38a) comprises the coolant of the heat engine (1) of the vehicle. 8. propulsion system according to any one of claims 1 to 7, characterized in that said hot source (31) 15 comprises the flow of exhaust gas from the engine (1) of the vehicle. The propulsion system energy transfer management method according to any one of claims 1 to 8, comprising a first phase (50) for determining a set of criteria relating to the operation of the vehicle and a second phase (51). and) the choice of the vehicle power mode and the power mode of the electric machine, the battery and the electrical accessories of the hybrid vehicles. 10. Method according to claim 9, characterized in that all the criteria relating to the operation of the vehicle comprises the energy delivered by the thermoelectric generator and the energy consumed by the group of electrical accessories.