Automatic speed transmission system for a vehicle comprising an electric machine

Abstract

The invention relates to an automatic speed transmission system (2) for a vehicle comprising 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 means for coupling said drive means comprising a passive centrifugal control (12) with centrifugal friction surfaces (13), for a first 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, for a second ratio, the first coupling means - are uncoupled for a rotational speed of the output shaft (8) lower than a speed threshold in the driving direction of the one-way coupling,- are coupled in the opposite direction to said drive direction. Figure 1 to be published,

Description

Title of the invention: Automatic speed transmission system for a vehicle comprising an electric machine Technical field

[0001] The present invention relates to the field of transmission, in particular for systems (for example vehicles) driven by an electric machine.

[0002] Within an electric vehicle, a rotational speed and a torque generated by an electric machine are transmitted to the drive wheels of the vehicle. In addition, during the deceleration or braking phases of the vehicle, it is possible to recover energy by means of the electric machine which then functions as a generator (conversion of mechanical energy into electrical energy which can be stored in a battery).

[0003] Today, electric vehicle transmissions only use a reducer between the motor and the vehicle 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. In this category of vehicle, we find, 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 dynamic performance of the vehicle is modest.

[0004] The same problems are also found for stationary applications of electrical machines, for which simple transmissions with a single reducer are not always suitable for dynamic variations in speed and torque. Prior art

[0005] In order to address these issues, it may be considered to use transmissions envisaged 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 connected directly to the axle shaft of the engine. Consequently, no transmission is provided to adapt the speed and torque output from the electric machine. In addition, 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 from 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.

[0006] 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 drive shafts and three gear trains, a dog clutch system, and a clutch. The use of three drive shafts and three gear trains requires significant space. In addition, the use of a dog clutch system and a clutch makes the transmission and its control complex. Summary of the invention

[0007] 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.

[0008] 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: - 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, - 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 - 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, - are in the coupling position in the opposite direction to the direction of the one-way coupling drive.

[0009] Advantageously, the first coupling means may be in the coupling position for a rotation speed of the output shaft at least equal to a speed threshold in the driving direction of the unidirectional coupling.

[0010] Advantageously, the unidirectional coupling means may comprise a freewheel.

[0011] Advantageously, the first and / or second drive means may comprise: - a so-called input pulley linked to the input shaft, - a so-called output pulley coaxial with the output shaft, - and a belt connected between the input pulley and the corresponding output pulley or - a gear input / output system,

[0012] or - a system of chains associated with sprockets, said system of gears and / or chains and sprockets preferably being associated with lubrication means.

[0013] Advantageously, the unidirectional coupling means may comprise a freewheel which is engaged between the output pulley of the second drive means and the output shaft.

[0014] Preferably, the ratio between the second ratio and the first ratio is between 0.1 and 0.9, in particular between 0.3 and 0.8.

[0015] Advantageously, the disengageable coupling means with passive centrifugal control may be drum(s).

[0016] 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.

[0017] Advantageously, return means, in particular springs, can connect the jaws to each other or can connect the jaws to a hub.

[0018] 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.

[0019] The invention also relates to a method for implementing the system described above, and which provides that: - 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; - 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; - when the direction of rotation of the output shaft is in the opposite direction of rotation to the drive direction of said one-way coupling, the first coupling means are also in the coupling position.

[0020] This method 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.

[0021] 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.

[0022] The invention also relates to a vehicle comprising the powertrain described above.

[0023] 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. List of figures

[0024] [Fig.l] [Fig.l] represents a cross-section of a gearbox according to a first embodiment. [Fig.2] [Fig.2] shows a cross-section of an area of ​​the gearbox shown in [Fig.l], with the long clutch not engaged.

[0025] 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

[0026] 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.

[0027] In the remainder of this description, the drive means used to ensure the transmission of the rotational movement: - a first transmission shaft connected to the electric machine, also called input shaft in this text, - 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 being able to just as easily use other known drive means, such as chain systems or the association of pulleys on which belts rotate.

[0028] The transmission, also called a gearbox, can thus comprise: - A first transmission shaft connected to the electric machine, which carries two toothed wheels, called first toothed wheels, and - A second drive shaft, which carries two gear wheels, called secondary gear wheels.

[0029] Each primary gear cooperates with a secondary gear, so as to form a motion transmission path. Thus, the transmission comprises two motion transmission paths. The two motion transmission paths have different transmission ratios.

[0030] 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 of the first gear wheel to the number of teeth of 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).

[0031] 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 band closed on itself connecting the toothed wheels of each movement transmission path, preferably said band closed on itself can be a chain or a belt.

[0032] 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.

[0033] 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).

[0034] One of the gear trains comprises a one-way coupling, also called a one-way clutch. Thus, one of the toothed 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 toothed wheel and its shaft in one direction of relative rotation, and in the other direction of rotation the toothed 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 separating are carried out automatically. According to an exemplary embodiment, the one-way coupling can be a freewheel arranged between the bearing of the toothed 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 toothed wheel.

[0035] The other gear train comprises coupling means capable of coupling / uncoupling the drive means to the output shaft and comprising a passive centrifugal control defining centrifugal friction surfaces.

[0036] 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 together by return springs and linked to the secondary shaft by articulations whose axes are substantially parallel to the secondary shaft, are attracted towards the outside thanks to the rotation of the shaft. The friction lining of the external 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.

[0037] In an alternative configuration, the springs may also be positioned between the jaws and the hub.

[0038] The rubbing surfaces are held in contact on the drum by centrifugal forces. The springs serve to bring them back to the center and to detach them from the bell (drum).

[0039] In the remainder of the description, - 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 - and the second gear train is the gear train that includes the one-way coupling.

[0040] According to the invention, the centrifugal coupling with friction surfaces operates as follows: - 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, - 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 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.

[0041] 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 having the lowest transmission ratio, and conversely the longest transmission ratio is the one having 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.

[0042] According to an implementation of the invention, the centrifugal coupling with friction surfaces 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.

[0043] Advantageously, the one-way coupling device may be arranged on the secondary gear wheel of the second gear train. Alternatively, the one-way coupling device may be arranged on the primary gear wheel of the second gear train.

[0044] According to one aspect of the invention, the centrifugal coupling with friction surfaces can be arranged on the primary gear wheel of the first gear train. Alternatively, the centrifugal friction surface coupling may be arranged on the secondary gear wheel of the first gear train.

[0045] According to one embodiment option, the output shaft of the transmission can be connected, directly or indirectly, to the axle shaft of an electric vehicle.

[0046] For the method of implementing the transmission system, the following steps are implemented: - 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, - When the relative direction of rotation of the shaft on which the one-way coupling is arranged is in the opposite direction to the driving direction of the one-way coupling, the centrifugal friction surface coupling is closed, thus, the transmission of movement 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.

[0047] 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 having the lowest transmission ratio, and conversely the longest transmission ratio is the one having 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.

[0048] 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.

[0049] According to an implementation of the invention, the centrifugal coupling with friction surfaces 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.

[0050] [Fig.l] illustrates, schematically and in a non-limiting manner, a transmission system according to one embodiment of the invention. [Fig.2] details the centrifugal coupling means included in the transmission system of [Fig.l]. The two figures will be described jointly.

[0051] 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.

[0052] The primary gear wheel 4 cooperates with the secondary gear wheel 7 to form a first gear train TRI, forming a long ratio (highest transmission ratio). The primary gear wheel 5 cooperates with the secondary gear wheel 6 to form a second gear train TR2, forming a short ratio (lowest transmission ratio).

[0053] The first TRI gear train 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 toothed wheel 7. Closing the centrifugal coupling makes it possible to secure the secondary toothed wheel 7 and the secondary transmission shaft 8.

[0054] 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 first toothed wheel 4. Closing the controlled coupling 12 makes it possible to secure the first toothed wheel 4 and the first transmission shaft 3.

[0055] 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.

[0056] 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.

[0057] The self-engaging centrifugal coupling system 12 is detailed in [Fig.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. Reference 16 is the hub of the shaft of transmission 8 carrying the jaws 14. Each spring 11 can be hooked between a jaw 14 and the hub 16, as shown in the figure. Alternatively, each spring can be hooked between two adjacent jaws 14.

[0058] With this type of clutch 12, when it is 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 [Fig.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 makes it possible to keep them in contact with the drum, even if the centrifugal effect is no longer sufficient to maintain this contact.

[0059] 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 makes it possible to maintain energy recovery below this threshold.

[0060] Energy can thus be recovered over almost the entire speed range of the vehicle when this recovery is requested from the long gear.

[0061] An example mode of operation is described below by way of example:

[0062] When the torque is positive (referring to the direction of rotation of the coupling unidirectional), 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,

[0063] 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 TRI gear train with a long ratio, thereby disengaging the freewheel 17 since the shaft 8 has a higher speed than the toothed wheel 6,

[0064] 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 TRI gear train 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 gear.

[0065] 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. In addition, the invention allows optimal use of the electric machine, without generating high current draws, in particular for vehicles where the weight / power ratio is high.

[0066] 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.

[0067] 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 from 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 direction of drive of the one-way coupling, - are in the coupling position in the opposite direction to the direction of drive of the one-way coupling.,

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 freewheel (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 - an input / output system of gears, 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, especially 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 less 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 speed threshold 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 opposite direction of rotation 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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