FR3150149A1 - Compressed air-electricity drive chain, engine kit and vehicle equipped with such a drive chain - Google Patents

Abstract

The invention relates to a powerful hybrid air/electric drive train, with high efficiency and autonomy compatible with the standard use of a vehicle, regardless of the driving phase (starting or moving uphill, stabilized movement, and braking or moving downhill). According to the invention, the drive train (100) comprising a compressed air tank (110) connected to a compressed air piston engine (120) engaged with an electric generator (130) connected to a relay electric reserve (160) with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh/kg of vehicle), itself connected to the electric motor (140) engaged with the movement member 151, 152). Figure for the abstract: Fig. 1

Description

Compressed air-electricity drive chain, engine kit and vehicle equipped with such a drive chain

The present invention relates to a drive chain using compressed air and electricity.

The invention finds a particularly important, although not exclusive, application in the field of the motorization of land vehicles (such as cars or utility vehicles) or marine vehicles (such as boats).

There are many drive train solutions based on thermal engines, electric motors or a combination of the two (called hybrid drive train).

So-called "thermal" vehicles require the use of fossil and polluting fuel, which has led the authorities of many countries to favor other types of less polluting powertrains. Their main advantage comes from their autonomy and the speed at which the fuel tank can be recharged.

These thermal vehicles always include a small battery allowing the thermal engine to start and the electrical equipment of the vehicle to operate. This battery is recharged by an alternator driven by the thermal engine when it is running. This type of battery is unsuitable for driving the wheels and is therefore not part of the drive chain. This type of battery therefore does not concern the invention.

So-called "electric" vehicles have a drive train composed of a high-capacity power battery capable of powering the electric motor(s) capable of driving a transmission connected to a moving part (the wheels of a car or the propeller of a boat, for example). This type of battery is therefore part of the drive train.

A power battery is made up of a plurality of electrical cells connected together and supervised by an electronic circuit. Their number, the size of each cell and the way they are arranged determine both the voltage delivered by the battery and its capacity, i.e. the amount of electricity it is able to store, which defines the autonomy of the car under standard conditions. These batteries are called "high capacity" because they must allow an autonomy of several hundred kilometers. Typically, they have a capacity ranging from 40kWh for the smallest to 100 kWh for the largest.

The power batteries used in electric vehicles are generally lithium-ion batteries, because only this type of battery currently provides the power and autonomy suitable for this use.

The major drawback of this type of drive chain lies precisely in the battery.

Indeed, its manufacture and end of life are ecologically dramatic: lithium reserves are theoretically insufficient to equip all the vehicles in the world, cobalt is extracted in often inhumane conditions and the recycling process is unknown to this day. It is currently not possible to reprocess them at more than fifty percent, the processes implemented being also chemically and electrically dangerous.

During the use phase, this type of drive chain has the advantage of producing very little CO2 (this depends on the energy source used to produce the electricity to be charged into the battery).

On the other hand, power batteries, and particularly lithium-ion batteries, have a problematic tendency to heat up during charging, or even during use, and often require a complex cooling system.

A great many incidents have been recorded in which batteries have caught fire due to this overheating, known as "run-away". However, these chemical fires are extremely difficult to extinguish. The use of water, for example, can tend, depending on the conditions, to fan the flames. In addition, these fires give off very high heat which tends to ignite surrounding vehicles. Finally, the vapours released are also dangerous for health and very probably for the environment. In these conditions, some manufacturers have planned to offer emergency vehicles equipped with special baths in which a crane plunges the burning vehicle to try to limit the spread of the fire. This solution currently raises many questions and does not seem viable.

Hybrid powertrains have also been proposed in which a thermal engine either assists the electric motor, recharges the power battery, or both.

These hybrid vehicles are interesting for vehicles requiring a long range (allowed by the thermal engine), while reducing their fuel consumption during short journeys for which the power battery is sufficient. However, they have the drawbacks of both technologies: pollution, risk of fire, complex recycling, even impossible in certain cases, etc.

There is therefore a need to propose a drive chain reducing the pollution generated and the operating risks.

Air motors have been proposed to power vehicles. However, the motors used are turbines (or rotary motors) similar in structure and operation to the pneumatic turbines used in pneumatic tools.

Although these turbines theoretically provide sufficient power, they do so at the cost of very high compressed air consumption.

The consumption aspect is not important in this type of application, because the tool is connected to an air compressor powered by electricity and which operates continuously to power the tool. This is obviously not the case for a vehicle that does not have a compressor, but an air reserve to be recharged regularly, which implies that the problems of consumption on the one hand, and of sufficient power on the other, have led to the abandonment of this type of air drive chain which has had no commercial success for vehicle equipment.

The objective of the present invention is therefore to propose a solution to these problems to enable the equipping of land or sea vehicles incorporating a compressed air drive chain, and which is efficient both in terms of power, but also in terms of efficiency and therefore autonomy, whatever the driving phase (starting or moving uphill, stabilized movement, and braking or moving downhill).

The idea underlying the invention consists in proposing a hybrid air/electric powertrain comprising a high-pressure compressed air tank connected to a compressed air piston engine (i.e. an engine that is not a pneumatic turbine), itself engaged with an electric generator capable of generating electricity when it is driven by the air piston engine, the electric generator being connected to the electric motor(s) of the vehicle, itself (themselves) connected to a transmission engaged with a movement member (wheels, propeller, etc.). According to the invention, the generator and the electric motor(s) are also connected to a relay electric reserve with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh/kg of vehicle).

When it comes to adapting the drive chain according to the invention to an electric vehicle, one can either choose to keep only a portion (for example 10% or less, preferably between 5% and 8%) of the cells of the initial battery to create the relay electrical reserve, or one can simply remove the initial power battery (possibly reselling it when it involves a modification of an existing electric vehicle), and incorporate a relay electrical reserve consisting of a set of supercapacitors.

In the first case, the relay electrical reserve consisting of part of the cells of the power battery, has a capacity of between 1.2 and 2.2 Watt-hours per kilo of vehicle to be equipped, preferably between 1.2 and 2 Wh/kg of vehicle to be equipped, which represents between 5% and 10% of the capacity of the initial power battery of the corresponding electric vehicle.

The term “corresponding electric vehicle” means the same vehicle as that equipped, or intended to be equipped, with the drive train according to the invention, but equipped with a 100% electric train comprising a power battery adapted to its use, in particular in terms of power and autonomy. This type of vehicle generally comprises a battery with a capacity greater than 35 kWh, such that the relay electric reserve according to the invention only has a capacity at most equal to 10% of this capacity (plus or minus 1 percentage point), i.e. less than or equal to approximately 3.5 kWh. In value, this upper limit may be higher when the corresponding electric vehicle comprises a battery with a higher capacity, such as for example certain utility vehicles, a bus, a truck or a boat, and requires a power battery with a capacity greater than 100 kWh for its normal use (in terms of power and autonomy).

In the second case, the capacity of the supercapacitor assembly is between 0.2 and 1.2 Wh/kg of vehicle to be equipped, advantageously 0.2 and 0.5 Wh/kg of vehicle to be equipped, which represents 0.5 to 5% of the capacity of the initial power battery of the corresponding vehicle.

The drive chain according to the invention comprises an electronic circuit, comprising in particular a controller and advantageously an energy distributor, programmed to allow an electrical supply to the motor from the relay electrical reserve according to the power demand, for example when the driver of the vehicle commands acceleration or when the vehicle detects the immediate need for additional power (for example when going uphill).

To this end, the invention relates to a hybrid powertrain intended to equip a vehicle of a given weight and comprising a high-pressure compressed air tank connected to a compressed air piston engine, itself engaged with an electric generator capable of generating electricity when it is driven by the air piston engine, at least one electric motor connected to a transmission engaged with a movement member, the generator and said at least one motor being connected via a relay electrical reserve with a capacity of between 0.2 and 2.2 Watt-hours per kilogram of vehicle (Wh/kg of vehicle), the powertrain further comprising an accelerator control movable between a stop position and a maximum acceleration position and connected to an electronic control circuit comprising a controller programmed to power the electric motor from the relay electrical reserve according to a signal captured by at least one sensor.

According to particular embodiments, one and/or the other of the following provisions is also used:
- the generator and the motor can also be directly connected, the electronic control circuit further comprising an energy distributor connected to the controller and capable of supplying the electric motor from the generator and/or the relay electrical reserve on instructions received from the controller as a function of a signal captured by at least one sensor;
- the relay electrical reserve can be made up of a portion of an initial power battery previously fitted to the vehicle;
- the relay electrical reserve can have a capacity of between 1.2 and 2.2 Wh/kg of vehicle;
- the relay electrical reserve may consist of at least one supercapacitor, preferably a set of supercapacitors;
- the relay electrical reserve may have a capacity of between 0.2 and 1.2 Wh/kg of vehicle, preferably between 0.2 and 0.5 Wh/kg of vehicle;
- the drive chain may further comprise an accelerator control position sensor, and in which the controller is programmed to power the electric motor from the relay electrical reserve and/or the generator depending, in particular, on the position of the accelerator control;
- the drive chain may further comprise a sensor for the speed of movement of the accelerator control, and in which the controller is programmed to supply the electric motor from the relay electrical reserve and/or the generator depending, in particular, on the speed of movement of the accelerator control;
- the drive chain may further comprise a vehicle travel speed sensor, and in which the controller is programmed to power the electric motor from the relay electrical reserve and/or the generator depending, in particular, on the vehicle travel speed; and/or
- the drive chain may further comprise a kinetic energy recuperator connected to the relay electrical reserve to charge the relay electrical reserve when the vehicle brakes.

The invention also relates to a land vehicle, such as a car or a utility vehicle, comprising a previous hybrid drive chain, in which the movement member comprises at least one pair of wheels.

The invention also relates to a boat comprising a preceding hybrid drive chain, in which the displacement member comprises at least one propeller or one turbine.

The invention also relates to a method for modifying an electric vehicle equipped with an electric motor, a power battery and a connector for recharging from an external source, to equip it with a previous hybrid powertrain, comprising the following steps:
a) remove the power battery fitted to the vehicle to free up installation space;
b) insert the compressed air reserve into the installation volume and replace the recharge connector with a recharge valve connected to the compressed air reserve;
c) add the air piston motor, generator and controller into the vehicle, preferably within the installation volume;
d) adding a relay electrical reserve in the vehicle, preferably in the installation volume, connected between the generator and the electric motor, the relay electrical reserve consisting of a part of the power battery having a capacity of between 1.2 and 2.2 Wh/kg of vehicle, or comprising at least one supercapacitor, preferably a set of supercapacitors with a capacity of between 0.2 and 0.5 Wh/kg of vehicle.

Other characteristics of the invention will be set out in the detailed description below given with reference to the appended figures, given by way of example, and which represent, respectively:

, a schematic view of an operating diagram of a first embodiment of a drive chain according to the invention during start-up;

, a schematic view of an operating diagram of the first embodiment of a drive chain according to the invention after start-up or in the stabilized movement phase (stationary regime);

, a schematic view of an operating diagram of the first embodiment of a drive chain according to the invention during braking;

, a schematic view of an operating diagram of a second embodiment of a drive chain according to the invention allowing the engine to be powered directly from the generator and/or indirectly from the relay electrical reserve, during start-up;

, a schematic view of an operating diagram of the second embodiment of a drive chain according to the invention after start-up or in the stabilized movement phase (stationary regime); and

, a schematic view of an operating diagram of the second embodiment of a drive chain according to the invention during braking;

Figures 1 to 3 illustrate a first embodiment in which the drive chain 100 comprises a tank 110 of compressed air under high pressure (i.e. between 40 and 700 bars) connected to a compressed air piston engine 120.

In the remainder of the description, the gas used is preferably air for easy and inexpensive use of the mobile chain according to the invention, in particular during recharging.

Preferably, the reservoir 110 is connected to an air expansion volume 112 by a valve 111, the air expansion volume itself being connected to the motor 120 by a valve 113. The air expansion volume makes it possible to bring the compressed air from the high storage pressure to a use pressure compatible with the compressed air piston motor 120.

An example of a compressed air piston engine is the engine described in document FR3115313.

Advantageously, it is a two-stroke engine which, for equal power, is half the size and half the weight of equivalent thermal engines, and has a higher efficiency of almost 50% with compressed air.

The air piston engine 120 is engaged with an electric generator 130 capable of generating electricity when driven by the air piston engine 120.

The drive chain according to the invention also comprises at least one electric motor 140 connected to a transmission 150 engaged with a movement member which can be wheels 151, a propeller 152 or a turbine (not illustrated).

According to the invention, the generator 130 and said at least one motor 140 are connected via an electrical relay reserve 160 with a capacity of between 0.2 and 2.2 Wh/kg of vehicle to be equipped, which corresponds to less than 10% of the capacity of the power battery of the electric vehicle corresponding to the vehicle equipped or intended to be equipped with the drive chain according to the invention.

For example, to equip a Renault Master e-Tech ™ vehicle with a GVW of 3.5 tonnes (i.e. approximately 2.4 tonnes when empty) with an initial battery power of 52kWh, the vehicle will be equipped with a relay electrical reserve of 2.8 to 7 kWh, corresponding to a capacity of between 1.2 and 2.2 Wh/kg of vehicle when empty and when full, if the relay electrical reserve is made up of a battery.

This electrical reserve relay 160 is thus sufficient to temporarily supply (a few seconds to a few minutes) the electric motor, while the generator is driven and re-supplies the electrical reserve relay 160.

Alternatively, the relay electrical reserve 160 is advantageously and preferably made up of a set of supercapacitors which allows significant energy storage and is sufficiently powerful to allow the wheels to be driven and the vehicle to move for a period of a few seconds to a few tens of seconds, the time it takes for them to be recharged by the generator driven by the air piston engine or by the brake recovery. They also allow the current to be regulated.

In this case, the capacity of the supercapacitors is preferably chosen to be between 0.2 and 1.2 Wh/kg of vehicle to be equipped, which corresponds to 0.5 to 5% of the power battery of the corresponding electric vehicle.

In the example of the Renault Master e-Tech ™ vehicle, if supercapacitors are used, it will be equipped with a relay electrical reserve of 0.48 to 4.2 kWh, corresponding to a capacity of between 0.2 and 1.2 Wh/kg of vehicle when empty and when full.

What matters is that the relay electrical reserve is able to propel the vehicle in the event of a greater energy requirement, while the compressed air can take over to sufficiently supply the piston engine, the generator and then the electric motor and satisfy the energy requirement.

For this purpose, the drive chain 100 according to the invention further comprises an accelerator control 170 movable between a stop position and a maximum acceleration position and connected, for example, to an accelerator control movement sensor (not shown) and to an electronic control circuit comprising a controller 180 programmed to control the power supply of the electric motor 140 from the relay electrical reserve 160 as a function, in particular, of the detected position of the accelerator control 170.

The operation of the drive chain according to the invention is detailed for three important phases.

There illustrates a phase during which additional power is requested by the driver, as shown diagrammatically by dial 171. This phase is very short and followed by the phase illustrated in .

This could be, for example, starting the vehicle, in which case a high power is required and must be immediately available to counteract the vehicle's inertia and set it in motion. It could also be a phase of overtaking another vehicle, or driving up a hill, in which case the driver presses the accelerator hard.

In this case, energy must be immediately available, but the inertia of the compressed air system can cause a response delay.

When the accelerator control position sensor detects a movement of the latter, it sends the information to the controller 180 which analyzes this movement and links it to an acceleration request.

In the case of the , this displacement is maximal, for example in the case of significant acceleration.

Alternatively or in combination, the drive train includes a throttle control travel speed sensor and/or a vehicle travel speed sensor.

The throttle control travel speed sensor is used to detect rapid throttle control travel and therefore rapid power demand, for example when overtaking.

The vehicle speed sensor detects that the vehicle is stationary and if the accelerator control is moved, the controller 180 understands (arrow 181) that a high power is required to set the vehicle in motion.

Thus, in the powertrain thus equipped, the controller 180 is programmed to control (arrow 182) the electrical reserve relay 160 which then supplies the electric motor 140 (arrow 161) according to the information captured (arrow 181; speed of movement of the accelerator control and/or speed of movement of the vehicle).

Thanks to the electrical reserve relay 160, the energy required by the driver's action on the accelerator control is sent immediately to the displacement member 151-152, the time that the compressed air is sent to the air piston motor 120 and that the latter drives the generator 130 (phase illustrated in ).

This thus illustrates the subsequent phase of the high energy demand of the or the steady-state, steady-state movement phase, for example when driving on a flat road at a substantially constant speed where the energy demand is moderate and regular, as illustrated by dial 172 which indicates moderate acceleration.

In this case, the controller 180 receives the information on the movement of the accelerator control and/or its speed (zero or very low) of movement thanks to the sensors (arrow 181). The controller 180 then controls the valve 113 (arrow 183) in order to supply compressed air under operating pressure to the piston engine 120 from the expansion volume 112 (arrows 121).

The piston engine 120 then drives the generator 130 (arrow 131), which supplies electricity to the relay reserve 160 (arrow 132) which itself supplies (arrow 161) the electric motor 140 which drives the movement member 151-152 via the transmission 150.

The relay reserve then operates continuously, that is to say it transmits the electricity it receives. Being made up of several cells or several supercapacitors, obtaining a continuous power supply is done by controlling the input/output of each cell or supercapacitor in a timed manner to linearize the output current. Current processing electronics can advantageously be added to stabilize the output current supplying the motor.

There illustrates the possibility for the drive chain according to the invention to recover kinetic energy, for example during braking (as illustrated by quadrant 173 which indicates zero acceleration) in order, preferably, to recharge the relay electrical reserve 160 to limit air consumption, and/or to power a small auxiliary compressor (not illustrated) capable of recharging the volume 112 to the operating pressure in order to increase the autonomy of the vehicle.

To this end, the drive chain 100 according to the invention comprises, for example, a braking energy recovery system 195 (or “KERS” for “Kinetic Energy Recovery System” in English) connected to the relay electrical reserve 160 in order to recharge it without consuming air (arrow 196).

The electronic control circuit is thus programmed to manage the time, the rhythm and the source of recharging of the relay electrical reserve.

Figures 4 to 6 illustrate a preferred embodiment of the invention in which the drive chain 200 comprises a generator 130 which can supply not only the relay electrical reserve 260, but also directly the electric motor 240.

For this purpose, the electronic control circuit further comprises an energy distributor 285 at the output of the generator 130 (it may be independent or incorporated into the generator). This energy distributor 285 is connected to the controller 280.

It is capable of powering the electric motor 240 directly from the generator 130 (arrow 241 on the ) and/or indirectly from the electrical reserve relay 260 (arrows 242-243 in FIGS. 4 and 5) on instructions received from the controller 280 as a function of a signal captured by at least one sensor, for example, an accelerator control position sensor, an accelerator control movement speed sensor, a vehicle movement speed sensor or a combination thereof.

When the driver presses the accelerator hard (e.g. when overtaking or on a hill), or when the vehicle is stationary and a high power is required to get it moving, the inertia of the compressed air system can cause a delay in response.

As illustrated in , the relay electrical reserve overcomes this problem by immediately supplying power to the electric motor (arrow 243) on command from the distributor 285 (arrow 242) controlled by the controller 280. During this time, as illustrated in , the controller controls the valve 113 (arrow 283) so that compressed air is sent to the compressed air piston engine 120 (arrows 121) which accelerates and drives the electric generator 130 (arrow 131) which takes over from the relay electrical reserve by allowing, via the distributor, a direct supply of the electric motor 240 (arrow 241) and by recharging the relay electrical reserve 260 (arrow 242) either for later use or for immediate use in the event of a need for additional power.

There also illustrates the case of a stabilized movement during which the driver maintains the acceleration control in an intermediate position (dial 172) between a stop position in which no compressed air reaches the piston engine, and a maximum acceleration position in which the compressed air reaches the piston engine with a maximum flow rate.

In this intermediate cruising position, the piston engine 120 drives the electric generator 130 (arrow 131), which directly supplies, via the distributor 285, the electric motor 240 (arrow 241) which itself drives the movement member 151-152 (wheels or propeller, for example) via a transmission 150. In this cruising mode, the relay electrical reserve is recharged and is only used occasionally in the event of sudden acceleration, for example, if this acceleration exceeds the acceleration capacity of the piston engine 120 and the inertia of the compressed air part of the drive chain 200.

In a preferred embodiment, the electronic control circuit (controller 280, distributor 285 and sensors) controls the power supply to the electric motor 240 from a combination of the generator (direct path 241) and the relay electrical reserve 260 (arrows 242-243).

Depending on the position of the accelerator pedal and/or the speed of depressing the pedal and/or the speed of the vehicle, the distributor 285 allocates the electricity produced by the generator 130 to the direct path (cruising speed +/- 15% for example), to the indirect path (strong acceleration or start-up) or to a combination of the two allowing optimization of the consumption of compressed air.

As in the first embodiment, a braking energy recovery system 195 (or “KERS”) is advantageously provided, also connected to the relay electrical reserve in order to recharge it without consuming air (arrow 196 on the ).

The electrical circuit is thus programmed to manage the time, the rhythm and the source of recharging of the relay electrical reserve.

For example, the relay electrical reserve may not be recharged immediately by the generator (thus saving compressed air), and may only be recharged during braking or during “engine braking” (stimulated in an electric vehicle by the actuation of the energy recovery system which brakes the vehicle by friction when the driver fully releases the accelerator pedal). A delay may also be measured, beyond which, if the vehicle has neither braked nor been subjected to engine braking, the electric generator supplies the relay electrical reserve to recharge it (arrow 242).

The relay power reserve may be a power battery cell or, advantageously, a supercapacitor or set of supercapacitors.

The drive train according to the invention can be integrated from the outset into a new vehicle specially designed and optimized for this purpose.

The drive chain according to the invention also has the advantage of being able to be adapted to an electric vehicle or an existing thermal vehicle, subject to certain modifications.

In particular, for electric vehicles, the power battery is removed to free up an installation volume in which the compressed air reserve 110 is placed. The electric charging connector or the fuel flap is also replaced by a pneumatic charging valve connected to the air reserve 110.

The compressed air motor, generator and possibly super capacitors can be accommodated in the installation volume and have little impact on the vehicle's loading capacity.

In the case of electric vehicles, a cell of the power battery can be reused as a relay electrical reserve with a capacity of less than 10 kWh, so that the quantity of material for a single vehicle is divided by ten depending on the types of batteries used.

Advantageously, the battery is completely removed and resold for use in another application if it is reusable. In this case, the relay electrical reserve can advantageously be a supercapacitor or a set of supercapacitors, and is installed in the vehicle, preferably in the installation volume.

Thus, the general principle of the invention is to replace power batteries or internal combustion engines with a system based on compressed air which generates electricity.

Storage is done via a high-performance compressor, even for small systems.

The air is stored in the cylinders with a pressure of 40 to 700 bars (versions with higher pressures may be used in the future).

To lower the storage pressure to the service pressure, the air expansion volume 112 can be an expander, a turbo-alternator, or other pressure-reducing device, the electrical energy of which can, via a third route preferably leading to the distributor 285 and controlled by the controller 280, boost the traction by powering the electric motor 240, recharge the relay electrical reserve 260 (preferably supercapacitors) or allow certain parts of the drive train to be heated, in particular the air piston engine 120).

The cylinder(s) can also be loaded using a reserve of compressed air under pressure.

Compressed air stored on the vehicle or boat can be supplied by external distribution centers in fast or slow charge according to needs, all in a few minutes or of the order of ten minutes, that is to say much faster than the recharging of a power battery. The transfer of air can be improved by balancing the temperatures between the reserve and the use.

This compressed air, once expanded to the operating pressure, powers a compressed air piston engine which turns a generator or alternator to produce current; it can also be used as a generator set.

Thanks to the compressed air piston engine, the weight/performance ratio is optimized. In addition, air consumption is significantly reduced so that the vehicle's range is perfectly compatible with standard use.

This current can be sent directly to the electric traction motor(s) and/or transited by supercapacitors to enable a significant, rapid and punctual supply of energy (starting, acceleration, etc.). The energy recovered during braking or descent on a vehicle can be sent to the supercapacitor or power a compressor to fill low-pressure booster cylinders.

The new piston engine/generator group, due to its small size and weight, allows easy integration for high performance.

The overall performance of the system can be improved by heat recovery from piston compression or balancing with outside air, using the energy from pressure reduction between storage and engine operating pressure.

The invention is particularly suitable for vehicles for which weight is not a major issue. Examples include utility vehicles, buses and boats.

Claims (13)

Hybrid powertrain (100, 200) intended to equip a vehicle of a given weight and comprising a high-pressure compressed air tank (110) connected to a compressed air piston engine (120), itself engaged with an electric generator (130) capable of generating electricity when it is driven by the air piston engine (120), at least one electric motor (140, 240) connected to a transmission (150) engaged with a displacement member (151, 152), the generator (130) and said at least one electric motor (140, 240) being connected via a relay electric reserve (160, 260) with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh/kg of vehicle), the powertrain (100, 200) further comprising an accelerator control (170) movable between a stop position and a maximum acceleration position and connected to an electronic control circuit comprising a controller (180, 280) programmed to power the electric motor (140, 240) from the relay electrical reserve (160, 260) as a function of a signal captured by at least one sensor equipping the vehicle. Hybrid powertrain (200) according to claim 1, wherein the generator (130) and the electric motor (240) are also directly connected, the electronic control circuit further comprising an energy distributor (285) connected to the controller (280) and capable of supplying the electric motor (240) from the generator (130) and/or from the relay electrical reserve (260) on instructions received from the controller (280) as a function of a signal captured by said at least one sensor. Hybrid powertrain (100, 200) according to any one of claims 1 or 2, in which the relay electrical reserve (160, 260) consists of a portion of an initial power battery previously equipped in the vehicle. Hybrid powertrain (100, 200) according to claim 3, in which the relay electrical reserve (160, 260) has a capacity of between 1.2 and 2.2 Wh/kg of vehicle. Hybrid powertrain (100, 200) according to any one of claims 1 or 2, in which the relay electrical reserve (160, 260) consists of at least one supercapacitor, preferably a set of supercapacitors. Hybrid powertrain (100, 200) according to claim 5, wherein the relay electrical reserve (160, 260) has a capacity of between 0.2 and 1.2 Wh/kg of vehicle, preferably between 0.2 and 0.5 Wh/kg of vehicle. Hybrid powertrain (100, 200) according to any one of claims 1 to 6, further comprising an accelerator control position sensor (170), and in which the controller (180, 280) is programmed to power the electric motor (140, 240) from the relay electrical reserve (160, 260) and/or the generator (130) depending, in particular, on the position of the accelerator control (170). Hybrid powertrain (100, 200) according to any one of claims 1 to 7, further comprising a sensor for the speed of movement of the accelerator control (170), and in which the controller (180, 280) is programmed to supply the electric motor (140, 240) from the relay electrical reserve (160, 260) and/or the generator (130) as a function, in particular, of the speed of movement of the accelerator control (170). Hybrid powertrain (100, 200) according to any one of claims 1 to 8, further comprising a vehicle travel speed sensor, and in which the controller (180, 280) is programmed to power the electric motor (140, 240) from the relay electrical reserve (160, 260) and/or the generator (130) as a function, in particular, of the vehicle travel speed. Hybrid powertrain (100, 200) according to any one of claims 1 to 9, further comprising a kinetic energy recuperator (195) connected to the relay electrical reserve (160, 260) for charging the relay electrical reserve (160, 260) during braking of the vehicle. Land vehicle, such as a car or a utility vehicle, characterized in that it comprises a hybrid drive chain (100, 200) according to any one of claims 1 to 10, in which the movement member comprises at least one pair of wheels (151). Boat characterized in that it comprises a hybrid drive chain according to any one of claims 1 to 10, in which the displacement member comprises at least one propeller (152) or a turbine. Method for modifying an electric vehicle equipped with an electric motor (140, 240), a power battery and a connector for recharging from an external source, to equip it with a hybrid powertrain (100, 200) according to any one of claims 1 to 10, comprising the following steps:
a) remove the power battery fitted to the vehicle to free up installation space;
b) insert the compressed air reserve (110) into the installation volume and replace the recharge connector with a recharge valve connected to the compressed air reserve;
c) adding the air piston motor (120), the generator (130) and the controller (180, 280) into the vehicle, preferably into the installation volume;
d) adding a relay electrical reserve (160, 260) in the vehicle, preferably in the installation volume, connected between the generator (130) and the electric motor (140, 240), the relay electrical reserve (160, 260) consisting of a part of the power battery having a capacity of between 1.2 and 2.2 Wh/kg of vehicle, or comprising at least one supercapacitor, preferably a set of supercapacitors with a capacity of between 0.2 and 0.5 Wh/kg of vehicle.