LU87644A1 - THERMAL-ELECTRIC MIXED PROPELLER GROUP FOR VEHICLE - Google Patents

Abstract

The power unit for a vehicle includes a thermal engine (1) and an electric motor (2). At low speed, the electric motor (2) has a driving torque higher than the thermal engine's (1) load moment. The electric motor (2) is designed to operate without being mechanically disconnected from the thermal engine (1) when the latter is running at its operating speed. In particular, the electric motor makes it possible to replace the starting motor, the alternator, and the flywheel of the thermal engine, and to provide additional or independent propulsion.

Description

The present invention relates to a powertrain for vehicles.

Most of today's motor vehicles are powered by a heat engine which uses a fuel-oxidizer mixture to rotate an output shaft, the movement of which is transmitted to the wheels of the vehicle by deflection and reduction gears.

The starting of this heat engine is ensured by an electric starter which supplies a battery. When the engine is started, the battery supplies current to the starter motor, which, by means of a reduction gear and an appropriate engagement system ("Bendix"), drives the crown of a disc or flywheel secured to the engine. As soon as the heat engine is started, the Bendix uncouples the starter motor from the inertia disc and the drive of the shaft is ensured by the only thermal engine.

Once the heat engine is started, it also drives an alternator by a return device which usually includes pulleys and belts. This alternator supplies, via an electronic regulation device, an electric current which makes it possible to recharge the battery.

The sets of electromechanical connections between the battery and the heat engine mentioned above are relatively complex and constitute a significant source of breakdowns.

Furthermore, their use is limited to the start-up and battery search functions described above.

Advances in electrical engineering and electronics make it possible to completely rethink the problem with a view to achieving the greatest simplicity of realization.

Thus / the present invention aims to provide an original association of a heat engine and an electric motor in order to simplify these electromechanical devices while allowing them to perform additional functions.

This invention provides a vehicle propulsion unit comprising a heat engine which drives a shaft and an electric motor. According to the invention, this powertrain is characterized in that the electric motor acts directly on the same shaft and in that control means are provided for controlling the drive of the shaft by the motors separately or in combination.

The basic principle of the present invention consists in coupling directly to the heat engine an electric motor having a torque of the same order of magnitude. So that this principle does not lead to excessive congestion; given the traditional dimensions of electric motors compared to the thermal motor, it is necessary i - to limit as much as possible the size, especially the thickness, and the weight of the electric motor, - to make this motor play additional roles making it possible to make the weight gain.

Modern technologies make it possible to control and make the best use of the current injected into an electric motor by control circuits. The goal in this case is to maximize the torque, especially at low speeds.

The invention having developed, for other uses having similar needs, saturated variable reluctance motors went in the same direction for this application and it arrived at the desired goal.

This type of motor is an example of an electric motor which can be used to implement the invention. A “flat” motor is thus obtained which occupies practically the volume of the inertia disc, and which can be directly coupled to the heat engine and provide sufficient torque. to serve as a starter for the engine - its inertia allows it to replace the inertia disc of the heat engine. This electric motor is designed to replace the alternator to recharge the battery. Other complementary functions will be described later.

Other electric motor designs could achieve the same result, but the following rules are a recommended addition to the basic invention: - optimize the operation of the motor towards the supply of high torque at low speeds. An engine providing high torque at high speeds but reduced at low speeds would not be suitable for "taking off" a heat engine at low ambient temperature. By contrast, an engine having a high torque at low speeds may be satisfactory even if its torque decreases with speed, - more precisely such an engine must be able to supply at zero speed a torque equivalent to the maximum torque of the thermal engine, - produce a flat engine with a ratio of diameter / thickness greater than 6 to meet the space requirements of the automotive industry, - have a rotor whose diameter is at least 60% of the total diameter to have sufficient inertia to replace the inertia disc with acceptable external dimensions, - have a possibility reduction of the voltage at the terminals when the engine is used as an alternator in a ratio of at least 20 to 1 to prevent this voltage at the terminals from becoming excessive when running at full speed and even remaining close enough to the voltage of the battery to allow good charging conditions.

This construction eliminates starter, Bendix, inertia digic and its teeth for the action of the starter, alternator, pulleys and corresponding belts. In addition, the collector and the starter contactor handling high downcurrents are replaced by a very reliable power electronics and low current control circuits posing no problem.

This construction also offers several opportunities. In particular, the flow of current to the battery can be reversed, the electric motor can then provide a significant torque coming to add to that of the heat engine since the circuits are dimensioned for the starting current. As an example, the additional torque could be 150 Nm at zero speed, that is to say of the order of magnitude of the maximum torque of the heat engine, while at low speeds the · heat engine has a very low torque.

The electric motor will thus be a real "booster" at start-up, for city traffic, high mounted for all terrain vehicles, etc.

However, this torque will decrease with speed while that of the combustion engine will increase and the effect will decrease with engine speed. It will however remain very useful for improving the "recovery" of the vehicle from a fairly low speed. This system can be supplemented by its symmetrical: braking or deceleration (for example downhill) with additional recharging of the battery. Of course, the battery must be sized for the operation thus provided. A second battery with a voltage which may be different may be used. For heavy goods vehicles, a retarder would therefore be available and would supply energy instead of heating up a heavier torque when climbing. The descent recovery would recharge the battery.

These features and advantages, and more, will be better understood with the description below. In the appended drawings, given without limitation î - Figure 1 schematically illustrates a group! propellant according to the invention, j - Figure 2 is a partial view of an engine! electric usable to implement the invention.

In Figure 1, there is shown schematically;

the engine assembly according to the invention. A heat engine 1 acts on a crankshaft 5 to rotate an output shaft 3. The end of the shaft 3 is connected to a clutch disc 7 secured to the shaft 3. A second clutch disc 8 connected to devices from I

transmission not shown can engage on the first disc 7 or disengage from it to perform the usual clutch / disengage functions of the transmission devices. .

Between the output of the heat engine 1 and the clutch disc 7, an electric motor 2 is mounted directly on the shaft 2. By "directly" is meant that the rotor 10 of the electric motor 2 is secured to the shaft 3. More precisely, this rotor 10 has the general shape of a disc perpendicular to the shaft 3 and centered on this latter. In addition to the rotor 10, the electric motor 2 comprises a stator 15 which includes windings 16. The lestator 15 has the shape of a crown which extends around durotor 10.

The windings 16 of the stator 15 are supplied by electronic circuits included in 9 'control means 4. These control means 4 are also connected to the battery 50 and they can be manipulated by the user by a button 40 or any other way.

The control means 4 and the corresponding electronic circuits are provided for operating the motor 2 in different modes: - in starter mode; a current flows in the t windings 16 to drive the rotor 10. This rotor 10 has sufficient inertia to start the heat engine 1; - in backup mode} the heat engine 1 drives the shaft 3 and a current is sent to the stator 15 to supply a torque on the shaft 3 in the same direction as the torque of the heat engine 1; - in alternator mode; the heat engine 1 drives the shaft 3 and a fraction of the mechanical energy of rotation of the rotor 10 is transformed by the electric motor 2 into current which is established in the windings 16; a voltage regulator incorporated in the control means 4 then makes it possible to recharge the battery 50; - in retarder mode; the heat engine 1 operates and a current is sent to the windings 16 dustator 15 so that the electric motor 2 provides a counter torque which brakes the rotation of the shaft 3.

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So the. assembly illustrated by figure 1 can accomplish the functions usually fulfilled by the inertia disc, the starter, the alternator as well as all the electrical circuits and associated mechanical devices of return. It can in addition provide an additional torque to the heat engine 1, particularly desirable at low speed, it can also contribute to vehicle braking without giving rise to excessive heating because the mechanical energy transformed during this braking can be in electrical form and serve to recharge the battery. For this latter application, it may prove useful to modify the battery 50 in relation to conventional batteries or to provide a second battery. For all other applications, a traditional battery allows the electric motor 2 to be used in all the functions mentioned.

To achieve this invention, a particularly suitable electric motor is a saturated variable reluctance motor. These motors are described in detail in French patents 1 445 572, 2 109 144, 2 356 304. In FIG. 2, an example has been shown where the rotor 10 has the shape of a disc and where the stator 15 forms a crown in periphery of the rotor 10, In this figure, we can see a quarter of the stator 15 and the rotor 10. The assembly is centered at point 0 which is also located in the center of the shaft 3 which is integral with the rotor 10.

The periphery of the robot 10 has teeth 11 spaced regularly and formed in a magnetic material. The stator 15 has, facing the rotor 10, a series of studs 17 spaced regularly. Each pad 17 is surrounded by a coil 16. The rotor 10 is driven by the effect of magnetic fluxes created in the pads 17 by the current flowing in the coils 16 which pass through the teeth 11 of the rotor 10. is carried out by electronic control circuits which, in the example of FIG. 1 are: included in. the control means 4.

These variable reluctance electric motors can deliver a satisfactory nominal torque for a small footprint. A characteristic which makes them particularly suitable for use in a propulsion unit according to the invention is that they have higher torque at low speed. Thus, the torque at zero speed can be more than two times greater than the nominal torque. This gives them maximum efficiency at start-up and during "revivals" at low speed.

On the other hand, this type of engine poses no tolerance problem in terms of mechanical play. Indeed, the rotor-stator air gap corresponds to a difference in radius of several tenths of a millimeter while the clearance of the crankshaft 5 is typically of the order of a hundredth of a millimeter.

Advantageously, the coils 16 of the stator 15 can be grouped into several groups supplied independently by independent control circuits.

In this way, the failure of a control circuit does not result in complete damage to the electric motor 2 because it does not affect the circuits corresponding to the other groups, for example, for a small-sized car (maximum torque of 150 Nm) of which the inertia disc is 280 mm in diameter for 22 mm thick and of which the "take-off" torque must also reach 150Nm, the realization can be as follows: - Rotor diameter: 280 mm like the inertia disc; - Thickness of the magnetic circuit ï 40 mm; - Starting torque: 150 Nm even when the battery is at the lowest temperatures required (eg - 40 ° C) i ~ Outside diameter 350 mm; j - Variation of the output voltage practically up to zero by controlled self-excitation; »Number of stator coils: 36; - For safety reasons, the coils are grouped into 3 groups of 12 supplied: separately. Thus a cut in one of the circuits makes it possible to obtain 100 Nm with the other 2 and allows starting i except in extreme cases; - Supply of each group of coils by 4transistors or thyristors and 4 diodes? - Number of rotor teeth 51; - control circuits allowing the same semiconductors to be used during alternator operation j - The rotor can be solid or hollow in its center (maximum diameter of this hollow 240 mm) to be fitted on an ordinary steel cylinder.

Without going into details, in many vehicles, the clutch or the torque converter is adjacent to the inertia disc. The presence of an electrically active component - in place of this disc makes it possible to reconsider certain clutch control problems by being able to supply current to the sub-assembly rotating with the engine.

Thus, thanks to the present invention! electric loops can be placed on the rotor 10 intended for the circulation of a current induced by the magnetic field created by the coils 16 of the stator 15. It is possible in this way to obtain active electric circuits on the rotating part which can be exploited in particular to achieve coupling electromagnetic between the clutch discs 7 and 8. This results in a considerable simplification of the clutch mechanisms which are traditionally complex and of limited reliability.

In another version of the invention, the electric motor 2 is shaped to provide an instantaneous measurement of the speed of rotation or of the angular position of the rotor 10 and consequently of the shaft 3 and of the crankshaft 5.

The detection of the shaft rotation speed can be used to provide reliable information to the driver at the tachometer. The detection of the angular position can be judiciously used to synchronize actions at the level of the heat engine 1 such as the admission of the fuel-oxidant mixture, the exhaust of the gases produced by combustion or even the spark in the case of a spark plug engine. . Such synchronization can be achieved by simple electronic assemblies.

Claims (19)

1. Power unit for vehicle comprising a thermal engine (1) which rotates a shaft (3) and an electric motor (2) characterized in that the electric motor (2) acts directly on the same shaft (3) and encloses that control means (4) are provided for controlling the drive of the shaft (3) by the motors (1,2) separately or in combination. 2. Power unit according to claim1r characterized in that the electric motor (2) isconformed to be able to start and start the thermal motor (1). 3. Power unit according to one of the claims 1 and 2, characterized in that the electric motor {2) comprises a rotor {10} secured to the shaft (3), in the form of a disc centered on the shaft (3) and perpendicular to it, the inertia of which is sufficient to maintain the functioning of the heat engine (1). 4. Power unit according to one of the claims 1 to 3, characterized in that the control means (4) are adapted to operate the electric motor (2) in alternator mode, so that the drive of the shaft (3) by the heat engine (1) recharges a battery (50). 5. Power unit according to one of the claims 1 to 4, characterized in that the control means (4) are adapted to operate the electric motor (2) in a manner contrary to the heat engine (1) to contribute to the braking of the vehicle. 6. Power unit according to one of the claims 1 to 5, characterized in that the control means (4) are adapted to operate the electric motor (2) so that it acts on the shaft (3) in the same direction as the heat engine (1) so as to provide it with additional power, in particular at low speed. 7. Powertrain according to one of the claims 1 to 6, characterized in that the electric motor (2) has an engine torque of the same order of magnitude as the engine torque of the heat engine (1). 8. Powertrain according to one of the claims 1 to 7f, characterized in that the ratio of the total diameter of the electric motor (2) to its thickness is at least equal to 6. 9. Power unit according to one of i claims 1 to 8, characterized in that the electric motor (2) has a maximum engine torque when the shaft (3) has a zero speed of rotation. 10. Power unit according to one of claims 1 to 9, characterized in that the electric motor (2) comprises a rotor (10) whose diameter is at least 60% of the total external diameter of the electric motor (2). ; 11. Group.e propellant according to one of claims 1 to 10, characterized in that the control means (4) comprise at least one electronic circuit which controls the supply of the electric motor (2). 12. Power unit according to one of the claims 1 to 11, characterized in that the electric motor (2) comprises a stator {15} whose windings (16) are distributed in several groups controlled independently of each other by independent control circuits , so that the interruption of a control circuit does not compromise the operation of the other circuit (s). 13. Power unit in accordance with one of the claims 1 to 12, characterized in that the control of the output voltage of the electric motor (2) used in alternator mode is carried out by the same electronic circuits which control its supply of the modem engine. 14. Power unit according to one of claims 1 to 13, characterized in that the reduction of the output voltage of the electric motor (2) used in alternator mode varies in a ratio of at least 20 to 1. 15. Power unit according to one of claims 1 to 14, characterized in that the electric motor (2) uses the principle of the saturated variable reluctance, 16. Power unit according to one of the claims 1 to 15, characterized in that the rotor (10) of the electric motor (2) comprises at least one electric loop in which an electric induction current can be established when the electric motor ( 2) eaten. 17. Power unit according to claim 16, characterized in that the induced current which is established in said electric loop on the rotor (10) is operated to achieve an electromagnetic coupling of the shaft (3) on transmission devices. 18. Power unit according to one of claims 1 to 17, characterized in that the electric motor control circuits (2) comprise means for measuring the speed of rotation of the rotor (10) · and of the shaft (3) „ 19. Power unit according to one of claims 1 to 18, characterized in that the electric motor control circuits (2) comprise means for locating the angular position of the rotor (10).