Automatic speed transmission system for a vehicle

Abstract

The invention relates to an automatic speed transmission system for a vehicle comprising an engine capable of rotating an input shaft (1), said system comprising a first short-ratio clutch device and a second long-ratio clutch device according to the speed of the output shaft (1), the clutch devices comprising a common hub (9), or separate means, which is mechanically linked to the output shaft (1) and which comprises: - 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, to change from one gear to another - a unidirectional coupling means (6) between the drive means of the first short-ratio clutch device and the output shaft (1).Figure for abstract: Fig 1.

Description

Title of the invention: Automatic speed transmission system for a vehicle 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 wheel(s) of the vehicle. 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. Prior art

[0004] In order to address these issues, it may be considered to use transmissions intended 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 from the electric machine. In addition, the transmission and its control are complex with two clutches: a piloted clutch and a centrifugal clutch.

[0005] 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. gears, a dog clutch system and a clutch. The use of these three drive shafts and three gear sets requires a significant amount of space. In addition, the use of a dog clutch system and a clutch makes the transmission and its control complex.

[0006] The aim of the invention is then to propose an improved transmission system for an electric machine of the vehicle electric motor type.

[0007] The aim of the invention is in particular to provide such a transmission system, which makes it possible to improve the efficiency of the electric motor of the vehicle 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. Summary of the invention

[0008] The invention firstly relates to an 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, 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, or each having a separate hub, said hub(s) being mechanically secured to the output shaft, said hub(s) 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 such 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. Said automatic transmission system also comprises - a one-way coupling means between the drive means of the first short ratio clutch device and the output shaft.

[0009] The invention thus proposes a transmission system (also referred to indifferently 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 gear which is engaged (in certain cases, the other threshold may be slightly lower than the first, in the case of dissociated clutches). 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.

[0010] The advantages of this solution are numerous: - it can be done in a simple way, as described below - it requires little or no modification of the engine control - in at least some of its implementations, energy can be recovered in both gears, short and long, without torque interruption, 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 - manual movement of the vehicle backwards is possible - reverse gear is possible (limited to short gear and below the long gear clutch speed threshold however)

[0011] Preferably, the unidirectional coupling means in question may be a freewheel: this is the simplest embodiment as far as it is concerned.

[0012] 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.

[0013] Preferably, according to one embodiment, the drive means of at least one of the first and second clutch devices may comprise: - a so-called input pulley linked to the input shaft, - a so-called output pulley coaxial with the output shaft, - 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] According to one embodiment, the disengageable coupling means may be of the drum type or at least one or more pressed discs.

[0019] Advantageously, at least one of the disengageable coupling means can be associated with a passive centrifugal control device: it is possible in particular to have - a passive centrifugal control device for each of the coupling means or - a common passive centrifugal control device for the disengageable coupling means of the two clutch devices.

[0020] The or at least one of the centrifugal control devices 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.

[0021] In this configuration, the return means can connect the jaws to each other or connect the jaws to the hub mechanically linked to the output shaft.

[0022] Each clutch device may have its own control device. Alternatively, the two clutch devices may have a common control device.

[0023] The or at least one of the control devices may be an actuator controlled by computer or electronic means, in particular by a computer on board the vehicle.

[0024] The invention also relates to a powertrain of a vehicle comprising in particular an electric (or thermal) motor mechanically linked to a input drive shaft, the automatic transmission system described above ensuring the transmission of the input shaft to an output shaft.

[0025] 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).

[0026] The invention also relates to a method for implementing the transmission system described above, and such that - 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 given first threshold, - the or one of the control devices disengage(s) the first clutch device and begin 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, - 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.

[0027] The invention also has an alternative method of implementing the transmission system, where each clutch device has its own control device, and where the output shaft speed threshold corresponding to the closing of the long clutch device is lower than the output shaft speed threshold corresponding to the opening of the short clutch device: there is then a transient overlapping phase between a disengagement phase of the short ratio clutch device and an engagement phase of the long ratio clutch device. Thus, and as will be described later, according to one of the embodiments, it is also possible for there to be an overlap between the disengagement phase of the short ratio and the engagement phase of the long ratio. This overlapping in the transient phase may be of particular interest in deceleration, by making it possible to switch from the long ratio to the short ratio without a break in torque.

[0028] List of figures [Fig.l] [Fig.l] represents 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. [Fig.2] [Fig.2] shows a cross-section of an area of ​​the gearbox shown in [Fig.l], with the short clutch engaged. [Fig.3] [Fig.3] shows the same cross-section of an area of ​​the gearbox shown in [Fig.l], this time with the long clutch engaged. [Fig.4] [Fig.4] represents a variation of the embodiment shown in [Fig.l], which replaces the belts and pulleys with gears. [Fig.5] [Fig.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. [Fig.6] [Fig.6] shows a cross-section of a gearbox according to a third embodiment, with gears replacing the belts used according to the first embodiment shown in [Fig.l], and two clutches with separate controls. [Fig.7] [Fig.7] represents, according to another embodiment, a centrifugal control device of the transmission system according to the invention, which comprises articulated jaws held by spring-type return means. [Fig.8] [Fig.8] shows a cross-section of a gearbox according to another embodiment, with a separate double clutch with drums. [Fig.9] [Fig.9] shows a cross-section of an area of ​​the gearbox shown in [Fig.8], with the short clutch engaged. [Fig.10] [Fig. 10] shows a cross-section of an area of ​​the gearbox shown in [Fig.8], with the long clutch disengaged.

[0029] All these figures are intentionally very schematic to simplify reading. The different components represented are not necessarily to scale. The same references designate the same components from one figure to another. Description of the embodiments

[0030] 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 possible.

[0031] [Fig.l] represents a gearbox according to a first embodiment. E denotes the input (electric machine side, which is not shown) and S denotes the output, on the output shaft 1 side. 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.

[0032] The hub 9 is mechanically secured to the output shaft 1.

[0033] The diameters of the output pulleys 4.4' are not necessarily identical.

[0034] Using 2.2' belts is particularly interesting, because 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.

[0035] The gearbox also has a freewheel 6 between the output pulley 4 of the short ratio and the output shaft 1.

[0036] 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.

[0037] In the absence of force, a return spring 8 holds the jaw 7 against 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'.

[0038] The gearbox comprises centrifugal drum clutches arranged in the receiving (output) pulleys 4,4'.

[0039] The clutches comprise jaws 7,7' which are linked together (the system may comprise several jaws).

[0040] In operation, the first clutch (normally closed) is used for the short gear. The second gear, which will then be normally open, is used for the long gear.

[0041] The freewheel 6 is in parallel with the short ratio clutch.

[0042] Figures 2 and 3 respectively show, with the gearbox shown at [Fig.l], a configuration where the short clutch is engaged and a configuration where the long clutch is engaged. They represent a given direction of rotation by circular arrows.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The pulley 4' (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.

[0047] 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.

[0048] When the vehicle speed continues to increase, the long ratio clutch closes, and transmission is then via 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.

[0049] 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).

[0050] [Fig.4] is a variant of the embodiment shown in [Fig.l]: the system of pulleys and belts is here replaced by input gears 12, 12' and output gears 11, 11', all other things being equal.

[0051] [Fig. 5] shows another embodiment, with gears replacing the belts of the first embodiment (as in [Fig. 4]), and pressed disc clutches. The box includes the following additional components: - pebbles (or masses) 13 (usually more than two pebbles, for example 6 pebbles, preferably evenly distributed) - a spring 14 parallel to the axis of the output shaft, - discs 15,15' - 16.16' trays - a 17 push plate - bells 18, 18' which are secured respectively to gears 11 and 11'.

[0052] The spring 14 is arranged between the thrust plate 17 and the plate 16. This mechanism ensures the coupling either of the disc 15 with the plate 16, or of the disc 15' with the plate 16', so as to allow the two transmission ratios.

[0053] The functionalities are identical to those of the embodiment shown in [Fig.l].

[0054] The unique centrifugal system disengages the short gear to engage the long gear automatically from a threshold speed of the output shaft 1.

[0055] 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.

[0056] The thrust spring 14 holds the short ratio clutch closed via the thrust plate 17.

[0057] 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.

[0058] The bell 18' (which can also be called the idle bell) of the long gear then rotates around the output shaft 1 at a higher speed than that of the output shaft 1.

[0059] 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.

[0060] When the speed of the vehicle 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 made 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 pulley of the long ratio, has a higher speed than the pulley of the short ratio.

[0061] Here too the movement of the thrust plate 17 can alternatively be managed by an actuator controlled by a control unit.

[0062] [Fig. 6] shows another embodiment, with gears replacing the belts used according to the first embodiment, and two clutches. Here the clutch controls are separate: the clutches each have their own centrifugal (or actuator) controls. Compared to the embodiment of [Fig.5], the rollers are doubled, as are the discs: There is a set of rollers 13, 13' per clutch, each of which acts on a pressure plate 19, 19'. When the rollers 13 of the short clutch move apart, they release the disc(s) 10 of the short clutch. When the rollers 13' of the long clutch move apart, they press the disc(s) 10' of the long clutch. Thus, the rollers 13 and 13' ensure coupling under distinct conditions: the rollers 13 ensure coupling at low rotational speed and the rollers 13' ensure coupling at high rotational speed.

[0063] [Fig.7] 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 springs 8 which are not connected between the jaws and the hub 9, as was the case in [Fig.1], but which are connected between the jaws 7. [Fig.8] shows another embodiment, with a separate double clutch, as in [Fig.6]. This embodiment uses the belt and pulley system of the embodiment in [Fig.l], but here drum clutches 15 are used. Here we have two hubs 9 and 9', therefore one hub per clutch device (and not a hub common to both clutch devices as in [Fig.l] or 4 for example).

[0064] [Fig.9] represents a configuration of the gearbox shown in [Fig.8], with the short clutch engaged.

[0065] [Fig. 10] shows a configuration of the gearbox shown in [Fig.8], with the long clutch open.

[0066] In the case of [Fig.6] and [Fig.8], and generally in the case where the invention uses separate clutches, there is a possible overlap between the phase of disengagement of the short gear and the phase of engagement of the long gear, when the speed threshold for closing the long clutch is lower than the speed threshold for opening the short gear. There is then a transitional phase where the freewheel 6 is, in fact, no longer essential.

[0067] 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.

[0068] In conclusion, the solution according to the invention is effective while remaining simple to implement. This solution allows energy recovery over the entire range of vehicle speed, regardless of the gear used. This solution can be used in both directions of rotation (forward / reverse).

[0069] 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.

[0070] 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.

[0071] 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 performance is improved.

[0072] 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 heat 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), or each having a separate hub (9, 9'), said hub(s) being mechanically secured to the output shaft (1), said hub(s) comprising - drive means for transmitting the movement from the input shaft to the output shaft, - disengageable coupling means for 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 (11,11'; 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 at least one of the disengageable coupling means is associated with a passive centrifugal control device, with in particular a passive centrifugal control device for each of the coupling means or 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 or at least one of the centrifugal control devices 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).

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 (9,9') mechanically linked to the output shaft (1).

10. Transmission system according to one of the preceding claims, characterized in that each clutch device has its own control device, or in that the two clutch devices have a common control device.

11. Transmission system according to one of claims 1 to 6, characterized in that the or at least one of the control devices 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 or 9, 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 first given threshold, - the or one of the control devices disengage(s) the first clutch device and begin 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.

15. Method for implementing the transmission system according to claim 10, characterized in that each clutch device has its own control device, and in that the speed threshold of the output shaft (1) corresponding to the closing of the long clutch device is lower than the speed threshold of the output shaft (1) corresponding to the opening of the short clutch device, and in that there is a transient overlapping phase between a disengagement phase of the device short-ratio clutch and a long-ratio clutch engagement phase.

Images