Automatic gear transmission system for a vehicle

Abstract

The invention relates to an automatic gear transmission system for a vehicle including a motor capable of rotating an input shaft (1), the system comprising a first short-gear clutch device and a second long-gear clutch device according to the speed of rotation of the output shaft (1), the clutch devices comprising a common hub (9), or separate hubs, which is mechanically connected to the output shaft (1) and which includes: - drive means for transmitting the movement of the input shaft to the output shaft; - disengageable coupling means, which couple the drive means to the output shaft; - at least one control device capable of controlling the engagement and disengagement of the clutch devices, in order to switch from one gear to the other; and - a one-way coupling means (6) between the drive means of the first short-gear clutch device and the output shaft (1).

Description

[0001] AUTOMATIC SPEED TRANSMISSION SYSTEM FOR A VEHICLE

[0002] Technical field

[0003] The present invention relates to the field of transmission, in particular for systems (e.g. vehicles) driven by an electric machine.

[0004] 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).

[0005] 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.

[0006] Prior art

[0007] 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 2405156 (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. In addition, the transmission and its control are complex with two clutches: a piloted clutch and a centrifugal clutch.

[0008] 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 these three drive shafts 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.

[0009] The aim of the invention is then to propose an improved transmission system for an electric machine of the vehicle electric motor type.

[0010] The aim of the invention is in particular to provide such a transmission system, which makes it possible to improve the efficiency of the vehicle's electric motor at low speed, and / or which allows a reduction in the size of the electric motor and / or which makes it possible to reduce the currents passing through it and / or which makes it possible to increase the performance of the vehicle equipped with it by increasing the torque at the vehicle's wheels.

[0011] Summary of the invention

[0012] The invention firstly relates to an automatic speed transmission system for a vehicle comprising an engine, in particular a thermal engine and / or an electric machine (thermal and electric engines in the case of a hybrid motive force), capable of rotating an input shaft, said system being intended to ensure the transmission of movement between said input shaft and an output shaft. Said system comprises a first short-ratio clutch device and a second long-ratio clutch device, the first and second clutch devices comprising a common hub, said hub being mechanically secured to the output shaft, said hub comprising

[0013] - drive means for transmitting the movement of the input shaft to the output shaft,

[0014] - disengageable coupling means of said drive means, which couple the drive means to the output shaft, and such that said transmission system also comprises

[0015] - a control device capable of controlling the engagement of one of said first and second clutch devices and, in a correlated manner, the disengagement of the other of said clutch devices, to change from one gear to the other.

[0016] Said automatic transmission system also includes

[0017] - a one-way coupling means between the drive means of the first short ratio clutch device and the output shaft.

[0018] For the purposes of the invention, "correlatedly" means that the control device controls the engagement / disengagement of the clutch devices by a common mechanical part or several common mechanical parts mechanically linked / mechanically secured to each other.

[0019] The invention thus proposes a transmission system (also referred to in this text as a transmission box) which has two ratios, and which can operate automatically and without requiring the addition of a controller or actuators: it has a short ratio and a long ratio, and from a first speed threshold, the short clutch opens, and, from another speed threshold, in particular higher than the first, it is the long ratio which is engaged. The unidirectional coupling means provided by the invention makes it possible to advantageously manage the transient phase where the speed of the vehicle is between these two thresholds, where the first clutch device is disengaged and where the second clutch device is not yet engaged, by ensuring the transmission between the input shaft and the output shaft during this transient phase.

[0020] The advantages of this solution are numerous:

[0021] - it can be done in a simple way, as described below

[0022] - it requires little or no modification of the engine control

[0023] - in at least some of its implementations, energy can be recovered in both gears, short and long, without any break in torque, and if energy is recovered in the long gear, this recovery can be carried out over the entire speed range of the vehicle in the long gear,

[0024] - manual movement of the vehicle backwards is possible

[0025] - reverse gear is possible (limited to short gear and below the long gear clutch speed threshold however)

[0026] Preferably, the one-way coupling means in question may be a freewheel: this is the simplest embodiment as far as it is concerned.

[0027] Preferably, the ratio between the short ratio and the long ratio may be in particular between 0.1 and 0.9, in particular between 0.3 and 0.8.

[0028] Preferably, according to one embodiment, the drive means of at least one of the first and second clutch devices may comprise:

[0029] - a so-called input pulley linked to the input shaft,

[0030] - a so-called output pulley coaxial with the output shaft,

[0031] - a belt connected between the input pulley and the corresponding output pulley of the or each of the clutch devices and the one-way coupling means is in the form of a freewheel which is engaged between the output pulley of the first short-ratio clutch device and the output shaft. According to one embodiment, at least two of the pulleys, among the two input pulleys and the two output pulleys, have different diameters, in particular the two input pulleys and / or the two output pulleys. It is thus possible to choose different diameters for the two output pulleys, the diameters of the input pulleys being identical, or vice versa.

[0032] This embodiment, which uses pulleys and belts to produce the drive means, is advantageous because it is simple to produce and does not require, in particular, lubrication means and a closed casing.

[0033] According to another embodiment, the drive means may comprise an input / output system of gears and / or chains associated with sprockets. Said system of gears and / or chains and sprockets may be associated with lubrication means.

[0034] This embodiment, which uses an input / output system of gears and / or chains associated with sprockets, has the advantage of being less bulky than the pulleys and belts of the previous embodiment.

[0035] According to one embodiment, the disengageable coupling means may be of the drum type or at least one or more pressed discs.

[0036] Advantageously, at least one of the disengageable coupling means can be associated with a passive centrifugal control device: in particular, it is possible to have a common passive centrifugal control device for the disengageable coupling means of the two clutch devices.

[0037] The centrifugal control device may comprise jaws each articulated around an axis linked to the output shaft, in particular by the hub which is integral therewith, said output axis preferably being substantially parallel to the output shaft. These jaws may be kept in contact, in particular at the friction surfaces, with the drive means of the corresponding clutch device (in particular with the drum of the output pulley of said drive means) by return means, in particular springs. This is particularly the case for the short ratio, while for the long ratio the jaws are kept in contact rather by centrifugal forces.

[0038] In this configuration, the return means may connect the jaws to each other or connect the jaws to the hub mechanically linked to the output shaft.

[0039] The return means may, according to the invention, be tension springs or torsion springs, the latter also being referred to as pin springs. A return means between the shoes and the hub may thus be made up of torsion springs, which appears more advantageous than tension springs. Indeed, the use of torsion springs makes it possible to limit the variation in the return force when the shoe pivots. This solution is particularly advantageous for maintaining almost constant behavior of the transmission with the progressive wear of the linings, the wear of the linings tending to increase the angle of rotation of the shoes between the short gear engaged and the long gear engaged.

[0040] The two clutch devices may preferably have a common control device.

[0041] The common control device may be an actuator controlled by computer or electronic means, in particular by a computer on board the vehicle.

[0042] The invention also relates to a powertrain of a vehicle comprising in particular an electric (and / or thermal) motor mechanically linked to an input drive shaft, the automatic transmission system described above ensuring the transmission of the input shaft to an output shaft.

[0043] The invention also relates to a vehicle comprising the powertrain as described above, in particular a motor vehicle (which may in particular comprise two, three or four wheels).

[0044] The invention also relates to a method for implementing the transmission system described above, and such that

[0045] - the or one of the recall systems engages(s) the first short-ratio clutch device as long as the output shaft speed remains below a first given threshold,

[0046] - the control device disengages the first clutch device and begins engagement of the second long-ratio clutch device when the shaft speed reaches and exceeds said threshold, the engagement of the second clutch device being operational when a second speed threshold is reached,

[0047] - and such that, during a transient speed phase located between the first and second speed thresholds, where the first clutch device is disengaged and where the second clutch device is not yet engaged, the one-way coupling means ensures the transmission between the input shaft and the output shaft.

[0048] List of figures

[0049] Figure 1 shows a cross-section of a gearbox according to a first embodiment, with pulleys and belts, two clutches linked and controlled by a centrifugal system and with a freewheel.

[0050] Figure 2 shows a cross-section of an area of ​​the gearbox shown in Figure 1, with the short clutch engaged.

[0051] Figure 3 shows the same cross-section of an area of ​​the gearbox shown in Figure 1, this time with the long clutch engaged.

[0052] Figure 4 shows a variation of the embodiment shown in Figure 1, which replaces the belts and pulleys with gears.

[0053] Figure 5 shows a cross-section of a gearbox according to a second embodiment, with gears replacing the belts of the first embodiment, and a double clutch with pressed discs.

[0054] Figure 6 represents, according to another embodiment, a centrifugal control device of the transmission system according to the invention, which comprises articulated jaws held by return means such as traction springs.

[0055] Figure 7 represents, according to another embodiment, a centrifugal control device of the transmission system according to the invention, which comprises articulated jaws held by return means of the torsion spring type known as pin springs.

[0056] Figure 8 is a graph representing the restoring torques of the jaws as a function of the angle of rotation of these jaws: on the abscissa is represented the angle of rotation of the jaws in degrees (°), and on the ordinate the restoring torque (Cr) of the jaw springs, without unit.

[0057] All these figures are intentionally very schematic to simplify reading. The various components represented are not necessarily to scale. The same references designate the same components from one figure to another.

[0058] Description of the embodiments

[0059] The invention will be described below using non-limiting embodiments illustrated by the figures. In the remainder of the description, the transmission system is described in the context of an application within a vehicle. However, other uses are conceivable. Figure 1 represents a gearbox according to a first embodiment.

[0060] E denotes the input (electric machine side, which is not shown) and S denotes the output, on the output shaft 1 side.

[0061] Two belts 2 and 2' are provided. They are connected to two input pulleys 3 and 3' of the motor shaft 5 and to two coaxial output pulleys 4, 4' at the output shaft 1. The two input pulleys 3 and 3' are fixedly mounted on the motor shaft 5. Due to the different diameters of the input pulleys, the rotation speeds of the output pulleys 4, 4' are different and make it possible to obtain the two ratios, a short ratio and a long ratio. As soon as the motor shaft 5 rotates, the output pulleys 4, 4' rotate, and the speed of the long ratio pulley 4' is higher than the speed of the short ratio pulley 4. The hub 9 is mechanically secured to the output shaft 1.

[0062] The diameters of the 4.4' output pulleys are not necessarily identical.

[0063] Using 2.2' belts is particularly interesting, as it allows for a dry sump (without lubricant), or even no sump at all, which is particularly relevant for reducing the manufacturing and maintenance costs of the gearbox.

[0064] The gearbox also has a freewheel 6 between the output pulley 4 of the short ratio and the output shaft 1.

[0065] It also comprises two clutch shoes 7, 7' linked together, articulated on the hub 9 (along an axis of rotation parallel to the output shaft 1) and held in contact with a return spring 8 against the drum of the pulley 4. The return spring 8 can be arranged between the output shaft 1 and a clutch shoe 7'. Between the shoes 7, 7' and the output pulleys, pads of friction material 10, 10' are arranged.

[0066] In the absence of force, a return spring 8 holds the jaw 7 against the drum 4 (without contact between the jaw 7' and the drum 4'), and in the presence of force (in particular by centrifugal force), the return spring allows contact between the jaw 7' and the drum 4' (without contact between the jaw 7 and the drum 4).

[0067] The gearbox includes centrifugal drum clutches arranged in the 4.4' driven (output) pulleys. The clutches include 7.7' shoes which are linked together (the system may have several shoes).

[0068] At rest, the first clutch (normally closed) is used for low gear. The second gear, which will then be normally open, is used for high gear.

[0069] The freewheel 6 is in parallel with the short ratio clutch. Figures 2 and 3 represent respectively, with the gearbox shown in Figure 1, a configuration where the short clutch is engaged and a configuration where the long clutch is engaged. They represent by circular arrows a given direction of rotation.

[0070] It should however be emphasized that, for this embodiment as for the other embodiments described and / or represented in the present text, the invention is just as operational / valid for the opposite direction of rotation.

[0071] The operation of the gearbox is described below using figures 1, 2 and 3: The unique centrifugal system disengages the short gear to engage the long gear automatically from a threshold speed of the output shaft 1.

[0072] When the vehicle is stopped (at rest), the short clutch is closed by the action of the springs 8 on the jaws 7,7', the vehicle can then start in forward or reverse gear.

[0073] The 4' pulley (which can also be called the idler pulley) of the long gear then rotates around the output shaft 1 at a higher speed than that of the output shaft 1.

[0074] From a vehicle speed threshold (or output shaft speed), under the centrifugal effect of the masses of the jaws 7,7', then capable of overcoming the forces of the springs 8, the jaws 7,7' begin to tilt. The short ratio clutch opens, while the long ratio clutch is not yet closed (both clutches are open). Transmission to the short ratio continues, however, being ensured by the freewheel 6 present in parallel with the short ratio clutch.

[0075] As the vehicle speed continues to increase, the long ratio clutch closes, and transmission then proceeds through the long ratio: the short clutch is opened, and the freewheel 6 is disengaged due to the fact that the output shaft 1, coupled to the long ratio pulley, has a higher speed than the short ratio pulley.

[0076] Note that when reversing, the vehicle speed should preferably be kept below the gear change threshold: When reversing, the maximum speed of the vehicle is preferably limited to the maximum speed in first gear (the short gear).

[0077] Figure 4 is a variant of the embodiment shown in Figure 1: the system of pulleys and belts is here replaced by input gears 12, 12' and output gears 11, 1 T, all other things being equal. Figure 5 represents another embodiment, with gears replacing the belts of the first embodiment (as in Figure 4), and pressed disc clutches. The box includes the following additional components:

[0078] - pebbles (or masses) 13 (usually more than two pebbles, for example 6 pebbles, preferably evenly distributed)

[0079] - at least one spring 14 parallel to the axis of the output shaft,

[0080] - 15.15' discs

[0081] - 16.16' trays

[0082] - a 17 push plate

[0083] - bells 18, 18' which are secured respectively to gears 11 and 11'.

[0084] The spring 14 is arranged between the thrust plate 17 and the plate 16'. This mechanism ensures the coupling of either the disc 15 with the plate 16, or the disc 15' with the plate 16', so as to allow the two transmission ratios.

[0085] The functionalities are identical to those of the embodiment shown in Figure 1.

[0086] The unique centrifugal system disengages the low gear to engage the high gear automatically from a threshold output shaft 1 rpm.

[0087] When the vehicle is stopped (at rest), the short clutch is closed by the action of the spring 14 on the thrust plate 17, the vehicle can then start in forward or reverse gear.

[0088] The thrust spring 14 holds the short ratio clutch closed via the thrust plate 17.

[0089] When the rotational speed of the output shaft 1 increases, the masses 13 move apart under the centrifugal effect. By moving apart, these masses push the plate 17 to the right as shown in the figure. By moving to the right, the plate first releases the short-ratio clutch, then, continuing its travel, closes the long-ratio clutch.

[0090] The 18' bell (which can also be called the idle bell) of the long gear then rotates around output shaft 1 at a higher speed than that of output shaft 1.

[0091] From a vehicle speed threshold (or an output shaft speed threshold), under the centrifugal effect of the masses 13, then capable of overcoming the force of the spring 14, the thrust plate 17 begins to move along the shaft 1 in the direction of the bell 18'. The short ratio clutch opens, releasing the disc(s) 10, while the long ratio clutch is not yet closed (both clutches are open). Transmission to the short ratio continues, however, being ensured by the freewheel 6 present in parallel with the short ratio clutch.

[0092] When the vehicle speed continues to increase, the thrust plate 17 continues its movement along the shaft towards the bell 18', the long ratio clutch closes by pressing the disc(s) 15', and the transmission is then done by the long ratio: the short clutch is open and the freewheel 6 is disengaged due to the fact that the output shaft 1, coupled to the long ratio pulley, has a higher speed than the short ratio pulley.

[0093] Here too the movement of the thrust plate 17 can alternatively be managed by an actuator controlled by a control unit.

[0094] Figure 6 shows, according to another embodiment, a centrifugal control device of the transmission system according to the invention, which comprises articulated jaws, this time with the tension springs 8 which are not connected between the jaws and the hub 9, as was the case in Figure 1, but which are connected between the jaws 7.

[0095] Figure 7 shows, according to another embodiment of the invention, a centrifugal control device for the transmission system according to the invention, with articulated jaws as shown in the previous figure, but this time with the torsion springs 8', connected between the jaws and the hub 9. These torsion springs are also called, in a known manner, pin springs. The pin springs 8' shown in Figure 7 comprise two branches 80' and 8T and a middle part 82' which is a winding having one or more turns, the assembly having a V shape, with the ends of the branches approaching each other under stress. The end of the branch 80' rests on the hub, the branch 81' is connected to the friction pad 10', the middle part is connected to the hub 9.The bringing together of the 80' and 81' branches ensures the transition from short to long gear, by modifying the friction pad in contact (10 or 10').

[0096] According to a variant not shown, the 8' pin springs can be positioned on the other side (of the half-jaw): in this case, the ends of the branches move apart under the stress, the operation of the transmission remaining the same.

[0097] Figure 8 shows the effect of lining wear on the variation of the return force of the shoes 7, as for example shown in the previous figure. When the linings wear, the rotation angle of the shoes between short gear engaged and long gear engaged increases (range A corresponding to the total rocking angle of the shoes between short gear engaged and long gear engaged with new linings, and range B corresponding to the total rocking angle of the shoes between short gear engaged and long gear engaged with worn linings in Figure 8). This results in a change in the return force with the wear of the linings, and consequently, a change in the behavior of the transmission.

[0098] The use of 8' torsion springs (as shown in Figure 7) makes it possible to greatly limit this variation, since it is possible to use characteristics different from those of the 8' traction springs (Figure 6): the line d1 corresponds to the use of traction springs (Figure 6) and the line d2 corresponds to the use of torsion springs, also called 8' pin springs (Figure 7). Thus the range of variation of the return torque is reduced: we see that the range of return torque C corresponding to the 8' torsion springs is much lower than the range of return torque D corresponding to the 8' traction springs (at least two to three times lower).

[0099] It should be noted that, within the framework of the invention, other clutch variants can be chosen, in particular single-disc or multi-disc types, without changing the spirit of the invention and its principle.

[0100] In conclusion, the solution according to the invention is effective while remaining simple to implement. This solution allows energy recovery over the entire speed range of the vehicle, regardless of the gear used. This solution can be used in both directions of rotation (forward / reverse).

[0101] This gearbox may be equipped with a control actuator controlled by a control unit, or use passive control, using passive centrifugal control means as described above.

[0102] With the gearbox according to the invention, for the same torque at the wheels, using the short ratio, the torque that the engine must provide is lower than in the case of a single-ratio clutch. Consequently, the currents are lower.

[0103] In the same way, when the engine is used on its maximum torque in the short gear, the torque at the wheels is higher with the solution of the invention rather than with a single-gear solution, the brilliance is improved.

[0104] It is further emphasized that the invention applies in a similar manner to the transmission for electric motors other than those intended to be part of vehicle powertrains (stationary applications requiring an electric drive, for example for household appliances, industrial machines, etc.)

Claims

Claims 1. Automatic speed transmission system for a vehicle comprising an engine, in particular a thermal engine or an electric machine, capable of rotating an input shaft (5), said system being intended to ensure the transmission of movement between said input shaft and an output shaft (1), characterized in that said system comprises a first short-ratio clutch device and a second long-ratio clutch device, the first and second clutch devices comprising a common hub (9), mechanically secured to the output shaft (1), said hub comprising - drive means for transmitting the movement of the input shaft to the output shaft, - disengageable coupling means of said drive means, which couple the drive means to the output shaft, and in that said transmission system also comprises - at least one control device capable of controlling the engagement of one of said first and second clutch devices and, in a correlated manner, the disengagement of the other of said clutch devices, to change from one gear to the other and in that said automatic transmission system also comprises - a one-way coupling means (6) between the drive means of the first short ratio clutch device and the output shaft.

2. System according to the preceding claim, characterized in that the unidirectional coupling means (6) is a freewheel.

3. Transmission system according to one of the preceding claims, characterized in that the ratio between the short ratio and the long ratio is between 0.1 and 0.9, in particular between 0.3 and 0.

8.

4. System according to one of the preceding claims, characterized in that the drive means of at least one of the first and second clutch devices comprise: - a so-called input pulley (3,3') linked to the input shaft (5), - a so-called output pulley (4.4') coaxial with the output shaft (1), - a belt (2,2') connected between the input pulley (3,3') and the corresponding output pulley (4,4') and in that the unidirectional coupling means is a freewheel (6) which is engaged between the output pulley (4) of the first short-ratio clutch device and the output shaft (1).

5. Transmission system according to one of claims 1 to 3, characterized in that the drive means comprise an input / output system of gears (11, 1 T; 12, 12') and / or chains associated with sprockets, said system of gears and / or chains and sprockets preferably being associated with lubrication means.

6. System according to one of the preceding claims, characterized in that the disengageable coupling means are drums or at least one pressed disc (15, 15').

7. System according to one of the preceding claims, characterized in that it comprises a common passive centrifugal control device for the disengageable coupling means of the two clutch devices.

8. Transmission system according to the preceding claim, characterized in that the common centrifugal control device comprises articulated jaws (7, 7') each around an axis linked to the output shaft (1) and substantially parallel to the output shaft and held in contact, in particular by friction surfaces, with the drive means of the corresponding clutch device, in particular with a drum of the output pulley of said drive means, by return means, in particular springs (8, 8').

9. Transmission system according to the preceding claim, characterized in that the return means (8) connect the jaws (7,7') together or connect the jaws (7,7') to the hub (9) mechanically linked to the output shaft (1).

10. Transmission system according to one of claims 8 or 9, characterized in that the return means comprise tension springs (8) or torsion springs (8').

11. Transmission system according to one of claims 1 to 6, characterized in that the control device is an actuator controlled by computer or electronic means, in particular by a computer on board the vehicle.

12. Powertrain of a vehicle comprising a motor, in particular an electric motor, mechanically linked to an input drive shaft (5), and the automatic transmission system according to one of the preceding claims; said automatic transmission system ensuring the transmission of the input shaft to an output shaft (1).

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

14. Method for implementing the transmission system according to one of claims 8 to 10, characterized in that - the or one of the return systems engage(s) the first short-ratio clutch device as long as the speed of the output shaft (1) remains below a given first threshold, - the control device disengages the first clutch device and begins the engagement of the second long-ratio clutch device when the speed of the shaft reaches and exceeds said threshold, the engagement of the second clutch device being operational when a second speed threshold is reached - and in that, during a transient speed phase located between the first and second speed thresholds, where the first clutch device is disengaged and where the second clutch device is not yet engaged, the one-way coupling means ensures the transmission between the input shaft and the output shaft.

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