Automatic gear transmission system for a vehicle including an electric machine

Abstract

The invention relates to an automatic gear transmission system (2) for a vehicle, including an electric machine (1) capable of actuating an input shaft (10), and which comprises: - first drive means for transmitting the movement of the input shaft to an output shaft (8) and first coupling means of the drive means comprising a passive centrifugal control (12) with centrifugal friction surfaces (13), for a first gear ratio; - second drive means for transmitting the movement of the input shaft (10) to the output shaft (8) and a one-way coupling means capable of coupling the second drive means to the output shaft, for a second gear ratio, the first coupling means being - disengaged for a rotational speed of the output shaft (8) lower than a speed threshold in the drive direction of the one-way coupling and - engaged in the direction opposite to the drive direction.

Description

[0001] AUTOMATIC SPEED TRANSMISSION SYSTEM FOR A VEHICLE

[0002] COMPRISING AN ELECTRIC MACHINE

[0003] Technical field

[0004] The present invention relates to the field of transmission, in particular for systems (e.g. vehicles) driven by an electric machine.

[0005] In an electric vehicle, rotational speed and torque generated by an electric machine are transmitted to the vehicle's drive wheels. In addition, during vehicle deceleration or braking phases, it is possible to recover energy using the electric machine, which then functions as a generator (converting mechanical energy into electrical energy that can be stored in a battery).

[0006] Today, electric vehicle transmissions only use a reduction gear between the motor and the vehicle's wheel(s). This very simple solution limits the optimal use of the electric machine, and can generate high current draws, particularly for vehicles with a high weight / power ratio. This vehicle category includes, for example, small urban vehicles limited by law to 45 km / h (for example, two-seater vehicles that can be driven without a driving license). Since the authorized power is very low, the vehicle's dynamic performance is modest.

[0007] The same problems also arise in stationary applications of electrical machines, for which simple transmissions with a single reducer are not always suitable for dynamic variations in speed and torque.

[0008] Prior art

[0009] To address these issues, it may be considered to use transmissions designed for hybrid powertrains (with an electric machine and a thermal engine). For example, patent application FR 2962379 (US 2012-0031229) describes a speed transmission device for a motor vehicle, with two ratios, a high ratio and a low ratio. Although this transmission is well suited for a hybrid engine, this design is not suitable for the use of only an electric machine. Indeed, for this transmission device, the electric machine is directly connected to the engine axle shaft. Consequently, no transmission is provided to adapt the speed and torque output of the electric machine.Furthermore, depending on the gear train used, energy recovery by the electric machine is not always optimal: for example, when the centrifugal clutch is closed, energy recovery is reduced by the engine brake of the thermal engine. In addition, the transmission and its control are complex with two clutches: a piloted clutch and a centrifugal clutch.

[0010] Transmissions have also been developed for electric-only applications. For example, US Patent 11,384,817 describes a transmission for an electric vehicle. This transmission requires three driveshafts and three gear trains, a dog clutch system, and a clutch. The use of three driveshafts and three gear trains requires a large footprint. In addition, the use of a dog clutch system and a clutch makes the transmission and its control complex.

[0011] Summary of the invention

[0012] The present invention aims to develop a transmission connected to an electric machine, in a simple manner, with improved performance during energy recovery, and preferably by means of a compact transmission.

[0013] The invention firstly relates to an automatic speed transmission system for a vehicle comprising an electric machine which is capable of rotating an input shaft, said system being intended to ensure the transmission of movement between said input shaft and an output shaft, such that said system comprises:

[0014] - first drive means for transmitting the movement of the input shaft to the output shaft and first means for coupling said drive means, first coupling means being capable of coupling / uncoupling the drive means to the output shaft and comprising a passive centrifugal control with centrifugal friction surfaces, in order to have a first ratio, in particular a long ratio,

[0015] - second drive means for transmitting the movement of the input shaft to the output shaft and a one-way coupling means capable of coupling said second drive means to the output shaft, in order to have a second ratio different from the first, in particular a short ratio, so that the first coupling means

[0016] - are in the uncoupling position for a rotational speed of the output shaft lower than a speed threshold in the driving direction of the one-way coupling,

[0017] - are in the coupling position in the opposite direction to the direction of the one-way coupling drive.

[0018] Advantageously, the first coupling means may be in the coupling position for a rotational speed of the output shaft at least equal to a speed threshold in the driving direction of the one-way coupling. Advantageously, the one-way coupling means may comprise a freewheel.

[0019] Advantageously, the first and / or second drive means may comprise:

[0020] - a so-called input pulley linked to the input shaft,

[0021] - a so-called output pulley coaxial with the output shaft,

[0022] - and a belt connected between the input pulley and the corresponding output pulley or

[0023] - a gear input / output system, or

[0024] - a system of chains associated with sprockets, said system of gears and / or chains and sprockets preferably being associated with lubrication means.

[0025] Advantageously, the one-way coupling means may comprise a freewheel which is engaged between the output pulley of the second drive means and the output shaft.

[0026] Preferably, the ratio between the second gear and the first gear is between 0.1 and 0.9, in particular between 0.3 and 0.8.

[0027] Advantageously, the passive centrifugal control disengageable coupling means may be drum(s).

[0028] Advantageously, the disengageable coupling means with passive centrifugal control of the coupling means may comprise jaws each articulated around an axis linked to the output shaft and substantially parallel to the output shaft, said jaws being kept in contact via rubbing surfaces with the first drive means, in particular with a drum of the output pulley of said drive means by centrifugal effect.

[0029] Advantageously, return means, in particular springs, may connect the jaws to each other or may connect the jaws to a hub.

[0030] Advantageously, the disengageable coupling means with passive centrifugal control with centrifugal friction surfaces may comprise a drum with which the jaws are in contact, the torque transmitted by the drum to the jaws creating a force for pressing the jaws onto the drum which is added to the centrifugal forces, in particular when the vehicle is in energy recovery mode or in reverse. The invention also relates to a method for implementing the system described above, and which provides that:

[0031] - when the rotational speed of the output shaft is lower than a speed threshold in the driving direction of the one-way coupling, the first coupling means are in the uncoupling position;

[0032] - when the rotational speed of the output shaft is at least equal to a speed threshold in the driving direction of the unidirectional coupling, the first coupling means are in the coupling position under the effect of centrifugal forces;

[0033] - when the direction of rotation of the output shaft is in the opposite relative direction of rotation to the drive direction of said one-way coupling, the first coupling means are also in the coupling position.

[0034] This process preferably ensures that the electric machine recovers energy when the automatic transmission system is in first gear, regardless of the direction of rotation of the output shaft.

[0035] The invention also relates to a powertrain of a vehicle comprising an electric machine, mechanically linked to an input drive shaft, and the automatic transmission system described above, said automatic transmission system ensuring the transmission of the input shaft to an output shaft.

[0036] The invention also relates to a vehicle comprising the powertrain described above.

[0037] Other characteristics and advantages of the device and method according to the invention will appear on reading the following description of non-limiting examples of embodiment, with reference to the figures appended and described below.

[0038] List of figures

[0039] Figure 1 represents a cross-section of a gearbox according to a first embodiment.

[0040] Figure 2 shows a cross-section of an area of ​​the gearbox shown in Figure 1, with the long clutch not engaged.

[0041] The figures are very schematic and do not necessarily respect the scale between the different components represented, to facilitate reading. The same references from one figure to another correspond to the same component. Description of the embodiments

[0042] The present invention relates to a transmission system connected to an electric machine capable of operating in electric motor mode or in energy generator mode, the electric machine being powered by an electric battery.

[0043] In the remainder of this description, the drive means used to ensure the transmission of the rotational movement:

[0044] - a first transmission shaft connected to the electric machine, also called input shaft in this text,

[0045] - to a second transmission shaft, also called secondary transmission shaft or output shaft, are in the form of gears of multiple toothed wheels, which is a non-limiting example of embodiment, the invention can just as easily use other known drive means, such as chain systems or the association of pulleys on which belts rotate.

[0046] The transmission, also called gearbox, can therefore include:

[0047] - A first transmission shaft connected to the electric machine, which carries two toothed wheels, called first toothed wheels, and

[0048] - A second drive shaft, which carries two gear wheels, called secondary gear wheels.

[0049] Each primary gear cooperates with a secondary gear to form a motion transmission path. Thus, the transmission comprises two motion transmission paths. The two motion transmission paths have different transmission ratios.

[0050] It is recalled that the transmission ratio is the ratio of the rotational speed of the secondary transmission shaft to the rotational speed of the first transmission shaft. This transmission ratio is proportional to the ratio of the number of teeth on the first gear wheel to the number of teeth on the secondary gear wheel. (If we take pulley and belt type drive means, the ratio can be adjusted by choosing, in particular, different diameters of the input and output pulleys).

[0051] Advantageously, each movement transmission path can be formed by a gear train; in other words, two toothed wheels cooperating directly. Alternatively, each transmission path can comprise a self-enclosed band connecting the toothed wheels of each movement transmission path; preferably, said self-enclosed band can be a chain or a belt. In the remainder of the application, only gear trains are described. However, all embodiments are compatible with the self-enclosed band of the belt or chain type connecting the toothed wheels.

[0052] Preferably, the transmission may comprise only two shafts: the first transmission shaft and the second transmission shaft, and may comprise only two transmission ratios. Thus, the transmission remains compact and simple to control, while allowing control of the speed and torque of the output shaft adapted to the desired applications (for example for a motor vehicle).

[0053] One of the gear trains includes a one-way coupling, also called a one-way clutch. Thus, one of the gear wheels is connected to its shaft (first transmission shaft or second transmission shaft) by a one-way coupling. Such a coupling makes it possible to secure the gear wheel and its shaft in one direction of relative rotation, and in the other direction of rotation the gear wheel and the shaft are separated and can rotate relative to each other. Such a one-way coupling is not controllable: the securing and the disengagement are carried out automatically. According to an exemplary embodiment, the one-way coupling can be a freewheel arranged between the bearing of the gear wheel and the shaft. In addition, the one-way coupling (the freewheel) is disengaged when there is a speed differential between the shaft and the gear wheel.

[0054] The other gear train comprises coupling means capable of coupling / uncoupling the drive means to the output shaft and comprising a passive centrifugal drive defining centrifugal friction surfaces.

[0055] It is recalled that a centrifugal clutch is controlled by the rotation speed of the shaft which carries the coupling means, here the secondary shaft: Weights or jaws, small metal masses connected to each other by return springs and linked to the secondary shaft by joints whose axes are substantially parallel to the secondary shaft, are attracted outwards thanks to the rotation of the shaft. The friction lining on the outer face of the jaws will then move towards the drum of the gearbox. The jaws will thus press against the drum, which will activate, by centrifugal force, the coupling of the drum and the secondary shaft.

[0056] Alternatively, the springs can be positioned between the shoes and the hub. The friction surfaces are held in contact on the drum by centrifugal forces. The springs serve to bring them back to the center and detach them from the bell (drum).

[0057] In the following description,

[0058] - the first gear train is the gear train that includes the centrifugal coupling with friction surfaces, it can also be referred to as the self-engaging centrifugal coupling

[0059] - and the second gear train is the gear train that includes the one-way coupling.

[0060] According to the invention, the centrifugal coupling with friction surfaces operates as follows:

[0061] - in the open position, when the rotational speed of the output shaft is lower than a speed threshold, and when the direction of rotation of the shaft on which the one-way coupling is mounted is in the driving direction of the one-way coupling, thus at low rotational speed, the movement is transmitted between the first transmission shaft and the second transmission shaft by the second gear train through the freewheel,

[0062] - in the closed position, when the relative direction of rotation of the shaft on which the one-way coupling is mounted is in the opposite relative direction to the driving direction of the one-way coupling, the movement is transmitted between the first transmission shaft and the second transmission shaft by the first gear train for traction of the vehicle, and the movement is transmitted between the second transmission shaft and the first transmission shaft by the first gear train for energy recovery (by means of the electric machine in generator mode, for example during braking or deceleration), or for reverse gear or for high speeds of the secondary shaft in forward gear.

[0063] Advantageously, the first gear train corresponds to the longest transmission ratio of the transmission, and the second gear train to the shortest transmission ratio of the transmission. The shortest transmission ratio is the one with the lowest transmission ratio, and conversely the longest transmission ratio is the one with the highest transmission ratio. Thus, the longest ratio is implemented in particular for high rotation speeds and for energy recovery, and the short ratio is implemented for low rotation speeds.

[0064] According to one implementation of the invention, the centrifugal friction surface coupling is in the closed position when the rotational speed of the secondary transmission shaft is greater than a speed threshold. Thus, the first gear train is engaged when the rotational speed is greater than the speed threshold.

[0065] Advantageously, the one-way coupling device can be arranged on the secondary gear wheel of the second gear train. Alternatively, the one-way coupling device can be arranged on the primary gear wheel of the second gear train.

[0066] According to one aspect of the invention, the centrifugal friction surface coupling can be arranged on the primary gear wheel of the first gear train. Alternatively, the centrifugal friction surface coupling can be arranged on the secondary gear wheel of the first gear train.

[0067] According to one embodiment, the output shaft of the transmission can be connected, directly or indirectly, to the axle shaft of an electric vehicle.

[0068] For the implementation process of the transmission system, the following steps are implemented:

[0069] - When the rotational speed of the second transmission shaft is lower than a speed threshold, and when the relative direction of rotation of the shaft on which the one-way coupling is arranged is in the driving direction of the one-way coupling, the centrifugal friction surface coupling is open, thus, the transmission of movement between the first transmission shaft and the second transmission shaft is implemented by the second gear train through the freewheel,

[0070] - When the relative direction of rotation of the shaft on which the one-way coupling is arranged is in the opposite relative direction to the driving direction of the one-way coupling, the centrifugal friction surface coupling is closed, thus the transmission of motion between the first transmission shaft and the second transmission shaft is implemented by the first gear train for the high rotational speeds of the second shaft in forward gear, as well as for the energy recovery on the electric machine and reverse gear, preferably corresponding to the long gear.

[0071] Advantageously, the first gear train corresponds to the longest transmission ratio of the transmission, and the second gear train to the shortest transmission ratio of the transmission. The shortest transmission ratio is the one with the lowest transmission ratio, and conversely, the longest transmission ratio is the one with the highest transmission ratio. Thus, the longest ratio is implemented for energy recovery, reverse gear and high rotational speeds in forward gear, and the shortest ratio is implemented for low rotational speeds.

[0072] The rotation speed threshold corresponds to a speed close (for example 80, 90, 95%) to the maximum speed of the electric machine on the ratio of the second gear train.

[0073] According to one implementation of the invention, the centrifugal friction surface coupling is placed in the closed position when the rotational speed of the secondary transmission shaft is greater than the speed threshold. Thus, the first gear train is engaged when the rotational speed is greater than the speed threshold.

[0074] Figure 1 illustrates, schematically and in a non-limiting manner, a transmission system according to one embodiment of the invention. Figure 2 details the centrifugal coupling means included in the transmission system of Figure 1. The two figures will be described jointly.

[0075] The figures represent an electrical machine 1 connected to a transmission 2 by a mechanical connection 3. In particular, the electrical machine 1 is connected to the first transmission shaft (or input shaft) 10 of the transmission 2. The first transmission shaft 10 carries two primary toothed wheels 4 and 5. The transmission 2 further comprises a second transmission shaft (or output shaft) 8 carrying two secondary toothed wheels 6 and 7. The second transmission shaft is the output of the transmission 2.

[0076] The primary gear 4 cooperates with the secondary gear 7 to form a first gear train TR1, forming a long ratio (highest transmission ratio). The primary gear 5 cooperates with the secondary gear 6 to form a second gear train TR2, forming a short ratio (lowest transmission ratio).

[0077] The first gear train TR1 comprises a centrifugal coupling means 12 with friction surfaces, of the self-engaging type in energy recovery mode. For the illustrated embodiment, this coupling is arranged between the secondary transmission shaft 8 and the secondary gear wheel 7. Closing the centrifugal coupling makes it possible to secure the secondary gear wheel 7 and the secondary transmission shaft 8.

[0078] Alternatively, according to another embodiment not shown (compatible with the previous one), the centrifugal coupling means 12 with friction surfaces can be arranged between the first transmission shaft 3 and the primary gear wheel 4. Closing the controlled coupling 12 makes it possible to secure the primary gear wheel 4 and the first transmission shaft 3. The second gear train TR2 comprises a one-way coupling. For the illustrated embodiment, this one-way coupling is formed by a freewheel 17 arranged between the bearing 9 of the secondary gear wheel 6 and the secondary transmission shaft 8.

[0079] Alternatively, according to another embodiment not shown, the unidirectional coupling can be formed by a freewheel 17 arranged between the bearing of the first toothed wheel 5.

[0080] The self-engaging centrifugal coupling system 12 is detailed in Figure 2: it comprises jaws 14 held detached from the drum 15 by springs 11 and which can be brought into contact with the drum 15 (also called bell) by means of rubbing surfaces 13. The reference 16 is the hub of the transmission shaft 8 carrying the jaws 14. Each spring 11 can be hooked between a jaw 14 and the hub 16, as shown in the figure.

[0081] Alternatively, each spring may be hooked between two adjacent jaws 14.

[0082] With this type of clutch 12, when closed, if the torque becomes negative, it is the drum 15 (the bell) which transmits the torque to the jaws 14. Depending on the direction of use (clockwise in Figure 2, represented by an arrow), this prevents the jaws 14 from closing, even if the speed threshold is below the threshold where they move apart by centrifugal effect. Indeed, when the jaws 14 are in contact with the drum 15, and the drum transmits torque to the jaws 14, this torque increases the force of pressing the jaws on the drum, which allows them to be kept in contact with the drum, even if the centrifugal effect is no longer sufficient to maintain this contact.

[0083] Unlike the use of a centrifugal clutch which opens below a speed threshold below which it is no longer possible to recover energy, here the clutch remains closed by this engaging effect, which allows energy recovery to be maintained below this threshold.

[0084] This allows energy to be recovered over almost the entire speed range of the vehicle when this recovery is requested from the high gear.

[0085] Thus, with the transmission system according to the invention, it is possible to extend the coupling of the long gear when braking / decelerating before switching to the short gear, which makes it possible to maximize energy recovery in the braking / deceleration phase: the speed threshold where the transmission system switches from the short gear to the long gear, in the case of a power demand (acceleration) will be able to be at a higher value than the speed threshold where the transmission system switches from the long gear to the short gear, in the case of braking or deceleration, which is very advantageous in allowing a longer energy recovery period.

[0086] An example of how it works is described below as an example:

[0087] When the torque is positive (with reference to the direction of rotation of the one-way coupling), and when the rotational speed of the output shaft 8 is lower than a rotational speed threshold Vs, the centrifugal coupling 12 is open, and the transmission is ensured by the second gear train TR2 with a short ratio through the freewheel 17,

[0088] When the torque is positive, and the rotation speed of the output shaft 8 is greater than the rotation speed threshold Vs, the centrifugal coupling 12 is closed, the transmission is then ensured by the first gear train TR1 with a long ratio, thereby disengaging the freewheel 17 since the shaft 8 has a higher speed than the toothed wheel 6,

[0089] When the torque is negative, the centrifugal coupling 12 is closed for reverse gear and for energy recovery by the electric machine, the transmission then being ensured by the first gear train TR1 with a long ratio. The coupling in fact needs to be controlled to be able to recover energy as long as it remains beyond the speed threshold of the short ratio, or in reverse.

[0090] The invention relates to an electric vehicle, in particular a motor vehicle (which may in particular comprise two, three or four wheels), which comprises an electric machine, a speed transmission according to any one of the variants or combinations of variants described above. The transmission system according to the invention is particularly suitable for use within an electric vehicle, in particular a small urban vehicle, for example a two-seater motor vehicle, which can be driven without a driving license. Indeed, the system according to the invention makes it possible to move the vehicle, either forward or reverse over the entire range of use of the electric machine, and makes it possible to maximize the recovery of electrical energy during deceleration and / or braking phases.Furthermore, the invention allows the optimal use of the electric machine, without generating high current demands, particularly for vehicles where the weight / power ratio is high.

[0091] Alternatively, the transmission system according to the invention is also suitable for stationary applications requiring an electric drive, for example for household appliances, industrial machines, etc. Alternatively, the transmission system according to the invention can also be adapted to thermal engines rather than to electric machines.

Claims

Claims 1. Automatic speed transmission system (2) for a vehicle comprising an electric machine (1) which is capable of rotating an input shaft (10), said system being intended to ensure the transmission of movement between said input shaft and an output shaft (8), characterized in that said system comprises: - first drive means for transmitting the movement of the input shaft to the output shaft and first means for coupling said drive means, first coupling means being capable of coupling / uncoupling the drive means to the output shaft (8) and comprising a passive centrifugal control (12) with centrifugal friction surfaces (13), in order to have a first ratio, in particular a long ratio, - second drive means for transmitting the movement of the input shaft (10) to the output shaft (8) and a one-way coupling means capable of coupling said second drive means to the output shaft, in order to have a second ratio different from the first, in particular a short ratio, so that the first coupling means - are in the uncoupling position for a rotational speed of the output shaft (8) lower than a speed threshold in the driving direction of the one-way coupling, - are in the coupling position in the relative direction opposite to the direction of the one-way coupling drive.

2. System according to the preceding claim, characterized in that the first coupling means are in the coupling position for a rotation speed of the output shaft (8) at least equal to a speed threshold in the driving direction of the unidirectional coupling.

3. System according to one of the preceding claims, characterized in that the unidirectional coupling means comprises a free wheel (17).

4. System according to one of the preceding claims, characterized in that the first and / or second drive means comprise: - a so-called input pulley (5) linked to the input shaft (10), - a so-called output pulley (6) coaxial with the output shaft (8), - and a belt connected between the input pulley and the corresponding output pulley or - a gear input / output system, or - a system of chains associated with sprockets, said system of gears and / or chains and sprockets preferably being associated with lubrication means.

5. System according to the preceding claim, characterized in that the unidirectional coupling means comprises a free wheel (17) which is engaged between the output pulley (6) of the second drive means and the output shaft (8).

6. Transmission system according to one of the preceding claims, characterized in that the ratio between the second gear and the first gear is between 0.1 and 0.9, in particular between 0.3 and 0.

8.

7. System according to one of the preceding claims, characterized in that the disengageable coupling means with passive centrifugal control are drum(s) (15).

8. System according to the preceding claim, characterized in that the disengageable coupling means with passive centrifugal control of the coupling means comprise jaws (14) each articulated around an axis linked to the output shaft (8) and substantially parallel to the output shaft, said jaws being kept in contact via rubbing surfaces (13) with the first drive means, in particular with a drum of the output pulley of said drive means by centrifugal effect.

9. Transmission system according to the preceding claim, characterized in that return means, in particular springs (11), connect the jaws (14) to each other or connect the jaws (14) to a hub (16).

10. Transmission system according to one of claims 8 or 9, characterized in that the disengageable coupling means with passive centrifugal control with centrifugal friction surfaces comprises a drum (15) with which the jaws (14) are in contact, the torque transmitted by the drum to the jaws creating a force for pressing the jaws onto the drum which is added to the centrifugal forces, in particular when the vehicle is in energy recovery mode or in reverse.

11. Method for implementing the transmission system according to one of the preceding claims, characterized in that - when the rotational speed of the output shaft (8) is lower than a speed threshold in the driving direction of the one-way coupling, the first coupling means are in the uncoupling position; - when the rotational speed of the output shaft (8) is at least equal to a threshold of speed in the driving direction of the one-way coupling, the first coupling means are in the coupling position under the effect of centrifugal forces; - when the direction of rotation of the output shaft (8) is in the relative direction of rotation opposite to the driving direction of said one-way coupling, the first coupling means are also in the coupling position.

12. Method according to the preceding claim, characterized in that it ensures that the electric machine (1) recovers energy when the automatic transmission system (2) is in first gear, regardless of the direction of rotation of the output shaft (8).

13. Powertrain of a vehicle comprising an electric machine (1), mechanically linked to an input drive shaft (10), and the automatic transmission system (2) according to one of claims 1 to 10, said automatic transmission system ensuring the transmission of the input shaft (10) to an output shaft (8).

14. Vehicle comprising the powertrain according to the preceding claim.

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