EP2790941A1

EP2790941A1 - Electrically powered vehicle

Info

Publication number: EP2790941A1
Application number: EP12797929.2A
Authority: EP
Inventors: Daniel Walser
Original assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Current assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2011-12-13
Filing date: 2012-12-07
Publication date: 2014-10-22
Also published as: FR2983787B1; FR2983787A1; WO2013087527A1

Abstract

The invention relates in particular to a motor vehicle (1) comprising electric haulage means acting on at least two wheels (21, 22, 23, 24) of two different axles (2, 3), the electric haulage means comprising an electrical machine (41, 42) and a transmission (31, 32) defining a fixed transmission ratio between the rotational speed of the electrical machine and the rotational speed of the wheel, a first transmission (32) for at least one of the wheels of a first axle (3) defining a first transmission ratio and a second transmission (31) for at least one of the wheels of a second axle (2) defining a second transmission ratio, the first transmission comprising a freewheel mechanism able to allow the wheel to turn without driving the electrical machine.

Description

Electric traction vehicle

The present invention relates to electric traction motor vehicles, in particular their traction chain.

In this field, a number of proposals are known such as those of EP 0878332, EP 1630026, WO 2006/032669, US 2007/0257570, WO 2007/083209 or WO 2009/124892.

A problem with electric traction is that of the choice of gear ratio, that is to say the choice of transmission ratio between the speed of rotation of the electric machine and that of the vehicle wheel. It has sometimes been proposed to use a two or more-ratio gearshift system as is customary on thermal engine vehicles but for the most part, electric traction systems use a single, fixed gear. The choice of the value of this ratio is then a compromise which must take into account antagonistic performances such as the capacity of acceleration at low speed and the capacity to reach a sufficient maximum speed but also constraints of mechanical design like the weight, the congestion or loss of efficiency due to reduction means (gears for example). It turns out that such a compromise is rarely satisfactory since in particular a part of the acceleration potential must be sacrificed in favor of the maximum speed and vice versa. The invention therefore aims to solve this problem.

The invention proposes for this a motor vehicle comprising electric traction means acting on at least two wheels of two different axles, the electric traction means comprising an electric machine and a transmission defining a fixed transmission ratio between the speed of rotation of the electric machine and the speed of rotation of the wheel, a first transmission for at least one of the wheels of a first axle defining a first transmission ratio and a second transmission for at least one of the wheels of a second axle defining a second transmission ratio, the first transmission comprising a freewheel mechanism adapted to allow the wheel to rotate without driving the electric machine. It is understood that one can combine according to the invention the advantages of an electric power train having good acceleration performance at low speed with those of a traction chain for a high maximum speed without using gear change device. [0007] Preferably, the freewheel mechanism is placed between the transmission and the hub.

According to a variant, the freewheel mechanism is placed within the transmission.

According to another variant, the freewheel mechanism is placed between the electric machine and the transmission.

Preferably, each wheel of the first axle is driven via a freewheel mechanism.

Preferably, the first axle is located at the rear of the vehicle relative to the second axle. Preferably, each wheel of the first axle is driven by an independent electric machine.

More preferably, each wheel of the second axle is also driven by an independent electric machine.

Preferably, each wheel of the first axle is equipped with a motorized hub, said motorized hub comprising a hub for receiving a wheel, the hub being rotatably mounted relative to a hub carrier according to a hub axis, the motorized hub comprising an electric traction machine, the electric machine comprising an outer stator connected to the hub carrier and an inner rotor whose axis of rotation is distant from the hub axle, the motorized hub comprising reduction means acting between the rotor of the electric machine and the hub, the motorized hub comprising a freewheel mechanism adapted to allow the wheel to rotate without driving the electric machine. Preferably, the wheels of the second axle are driven by a common electric machine.

Preferably, the different traction means are designed in such a way that the wheels driven via a freewheel mechanism reach the point where the freewheel mechanism comes into action at the latest when the vehicle reaches a speed equal to ^max _? ^ _E preferably at the latest when the vehicle reaches a speed

1.6

,,, Vmax

equal to .

2

Other features and advantages of the invention will become apparent from the description of preferred embodiments. The figures represent respectively: FIG. 1: schematic view from above of a vehicle according to a first embodiment of the invention.

Figure 2 is a schematic view from above of a vehicle according to a second embodiment of the invention.

3: sectional view along a broken line (passing through the axes of the hub M, the electric machine R and the intermediate shaft I) of a motorized hub used in the vehicle according to FIGS. 2, 4, 5 and 6.

Figure 4 is a schematic view from above of a vehicle according to a third embodiment of the invention.

Figure 5 is a schematic view from above of a vehicle according to a fourth embodiment of the invention.

Figure 6 is a schematic view from above of a vehicle according to a fifth embodiment of the invention.

In the various figures, identical or similar elements bear the same references. Their description is not systematically repeated. In Figure 1, there is shown a vehicle 1 having a front axle 2 and a rear axle 3. The front axle comprises a left front wheel 21 and a front right wheel 22. The rear axle has a left rear wheel 23 and a right rear wheel 24. Each axle is driven by an electric machine (41, 42) via a transmission (31, 32). All of these traction means allow the vehicle to accelerate from the complete stop and up to its maximum speed (Vmax). The transmission 32 of the rear wheels comprises a freewheel mechanism. Thus the electric machine drives the rear wheels while the rear wheels can not drive the electric machine. Thanks to the presence of this freewheel mechanism, the transmission ratio of the rear axle can be chosen so as to promote low speed acceleration. However, once the vehicle is launched, all the electric power can be reserved for the front axle whose transmission allows the vehicle to reach its maximum speed (Vmax). The freewheel mechanism then allows the electric machine of the rear wheels to be decoupled. The maximum speed of the vehicle is therefore no longer limited by the maximum speed allowed by this electric machine. Noise and energy losses are also reduced. The front axle does not include a freewheel mechanism, ie it is permanently coupled. An advantage of this configuration is that the front axle is always available for efficient regenerative braking. Its electric machine participates in the acceleration phases especially when it is desired to promote energy efficiency and overall dynamic balance of the vehicle. On the other hand, when the demand for acceleration is maximum and all the available electrical power can be consumed by the rear axle, to favor the rear axle whose transmission ratio may be better adapted, it may be possible to limit the power transmitted to the front axle, or even choose not to power this axle.

For example, for the particular case where the front and rear electric machines have identical characteristics, it is understood that one can preferably choose a transmission ratio of the rear axle higher than that of the front axle. so that the rear electric machine 42 can develop its power at lower speed before being decoupled when the vehicle reaches a certain speed.

In Figure 2, there is a vehicle 1 1 whose front axles 2 and rear 3 comprise wheels (21, 22, 23, 24) each driven by an electric machine (43, 44, 45, 46) independent through independent transmissions (33, 34, 35, 36). These traction means allow the vehicle to reach its maximum speed (Vmax). In the present application, the term "motorized hub" is used. to designate such a mechanical assembly comprising the hub, the hub carrier, the guiding of the hub relative to the hub carrier, the electric motor and the braking means of the hub. The motorized hub is therefore intended on the one hand to receive a wheel and to carry on the other hand a vehicle, generally by means of suspension means (not shown here). According to a preferred embodiment of the invention, it is the motorized hubs of the rear wheels which comprise freewheel mechanisms. Thus, the transmission ratio of the rear axle can be chosen to favor accelerations at low speed. Preferably, the transmissions (33, 34) of the front axle do not include a freewheel mechanism, that is to say that they are permanently coupled. An advantage of this configuration is that the front axle is always available for efficient regenerative braking. Their electric machines (43, 44) of the front axle participate in acceleration phases especially when it is desired to promote energy efficiency and overall dynamic balance of the vehicle. On the other hand, when the demand for acceleration is maximum and all the available electrical power can be consumed by the rear axle, to favor the rear axle whose transmission ratio may be better adapted, it may be possible to limit the share transmitted to the front axle, or even choose not to feed this axle.

The skilled person knows to choose a free wheel mechanism among the many types known and commercially available and design the implementation of this mechanism at different levels of the electric power train.

FIG. 3 illustrates a preferred embodiment of motorized hubs for the rear wheels of a vehicle according to the embodiment of FIG. 2. FIG. 3 represents, for example, the motorized hub 100 of the right rear wheel 24.

A hub 7, intended to receive the wheel 24, is rotatably mounted relative to a hub carrier 5 along a hub axis M. The transmission 36 comprises reduction means with two reduction stages. A first reduction stage is constituted by the gear of the driving pinion 65 and a gear wheel 68 connected to an intermediate shaft 67. The driving pinion 65 is driven by the rotor shaft of the electric machine. To lighten the drawing, it is shown only the outer sleeve of the stator of the electric machine 46. A second reduction stage is constituted by the gear of a pinion gear 69 connected to the intermediate shaft 67 with a hub ring 70 connected to the hub 7.

The axis I of the intermediate shaft 41 is preferably, as shown here, parallel to the hub axis M and the axis of rotation R of the rotor. Likewise, the axis of the rotor R is preferably as remote from the hub axis M. The overall reduction ratio of the transmission is preferably greater than 20.

The set of reduction and guiding means is housed in a housing

8. The housing 8 may further contain a suitable amount of a lubricant to lubricate the assembly by bubbling. The brake disc is placed outside the housing 8 on the side of the wheel, the brake clamp being integral with the housing.

The hub carrier here has the shape of a rocket extending inside the hub and around which the hub rotates, the hub being guided by hub bearings. In this preferred embodiment, this guidance is provided by a main bearing with two rows of balls placed substantially opposite the ring gear 70 and a single-row ball end bearing placed substantially opposite the brake disc. A spacer separates the two bearings along the rocket 5. The inner portion of the hub bearings is fixed (integral with the rocket 5) and the outer portion rotates with the hub 7. The stator of the electric machine is rotatably connected to the hub carrier 5.

This connection, necessary for the transmission of torque, can be rigid and direct as shown here, but it can also be indirect in order to allow a relative rotational movement on the occasion of suspension movements. This relative movement must of course be limited and is intended to allow a certain independence between the torque transmitted and the dynamic stiffness (vertical and horizontal) of the suspension device of the vehicle. Here, the stator is thus integral with the casing 8 while the casing is itself integral with the hub carrier 5. The motorized hub 100 according to the invention can be attached to the vehicle, specifically to its suspension system by means of screws engaged in threads 55 of the rocket 5. The casing 8 is then pinched between the base of the rocket and the suspension means and is no longer carrying only the electric machine and reduction means.

According to the invention, this motorized hub further comprises a freewheel mechanism 66. The freewheel mechanism 66 is placed here within the transmission. The transmission comprising two reduction stages, the freewheel mechanism is here placed between the intermediate shaft 67 and its toothed wheel 68. A type of freewheel mechanism that can be used in this configuration is, for example, that proposed under the name SF 46. -21 by SIAM-RINGSPA N SA

A variant of this configuration is to place the freewheel mechanism between the electric machine and the reduction means which has the advantage of being able to use a smaller free wheel mechanism because the torque to be transmitted is then much weaker.

A second variant is to place the freewheel mechanism between the reduction means and the hub which has the advantage of allowing the decoupling of the entire traction chain.

Preferably and regardless of the location chosen for the freewheel mechanism within the traction chain, the assembly is such that the outer ring of the freewheel mechanism is integral with a driven part (c '). ie wheel side) of the traction chain and the inner ring is secured to a driving part (ie electric machine side) of the drive chain. With this characteristic, it is then possible to use so-called "non-contact" free wheel mechanisms, ie in which the friction is suppressed by the action of the centrifugal force when the mechanism operates in freewheel mode beyond of a certain speed.

The means of traction of the front wheels can be motorized hubs similar to those of the rear wheels but simply devoid of wheel mechanisms free and whose transmission ratios are such that they give the vehicle its maximum speed (Vmax).

An interesting variant of the configuration described above with reference to Figures 2 and 3 is a configuration in which the high transmission ratio transmissions and freewheel mechanisms are not those of the two rear wheels but those of two wheels arranged diagonally with respect to the vehicle, that is to say for example those of the left front wheel 21 and the right rear wheel 24. The other two wheels (right front 22 and rear left 23) are then permanently coupled and ensure only the traction beyond the decoupling speed and up to the maximum speed of the vehicle.

FIG. 4 represents a vehicle 12 combining a front axle with a common electric machine according to FIG. 1 and the rear axle with independent electric machines according to FIG. 2. Preferably, it is the rear axle which comprises the mechanisms freewheeling gear and the high transmission ratio while the front axle has no freewheel mechanism and its transmission ratios are such that they give the vehicle its maximum speed (Vmax).

Figure 5 shows a three-wheeled vehicle. The rear wheel 25 is here unique and driven by a clean electric machine 47. The front wheels are each driven via independent transmissions (33, 34) by an independent electric machine (43, 44) according to the principle of FIG. 2. In this configuration, it is preferably the traction means of the rear wheel which comprise a freewheel mechanism to decouple the electric machine 47 beyond a certain speed of the vehicle. Thus, the transmission ratio of the rear axle can be chosen to favor accelerations at low speed. The traction means of the rear wheel 25 are preferably of the type illustrated in FIG. 3. As described above, the transmissions (33, 34) of the front axle do not comprise a freewheeling mechanism. to say that they are permanently coupled.

FIG. 6 shows a variant of the vehicle of FIG. 4 in which a heat engine 51 is associated with the front axle and constitutes additional means. traction. In this configuration, the maximum speed (Vmax) within the meaning of the invention remains that which can achieve the only electric traction means, that is to say without taking into account the performance allowed by the engine.

In general, the choice of the best transmission ratio for each axle in order to best exploit the present invention will depend on the characteristics of the vehicle and technology specific to the electric traction of each wheel. It is understood in particular that depending on the type of electric machine, its useful rotational speed range can be very different. In a manner known per se, electrical machines have for example been proposed for working in direct contact with the wheel (transmission ratio = 1) and whose maximum rotational speed does not reach 3000 revolutions / minute. It has also been proposed much more compact and lightweight electrical machines and capable of rotational speeds up to for example 20 000 revolutions / minute, in which case the transmission includes reduction means which define a high transmission ratio, commonly of 10 to 20. Regardless of the electrical machines considered, the invention makes it possible to choose the transmission ratio specific to each wheel in such a way that the wheel or wheels which are driven via a freewheel mechanism are the most efficient ones. for the acceleration of the vehicle at low speed and that the other wheels are able to give the vehicle alone its maximum speed (Vmax). Preferably the different traction means of the vehicle are designed such that the wheels driven via a freewheel mechanism reach the point where the freewheel mechanism comes into action at the latest when the vehicle

,,, Vmax. ,,, V max reaches a speed equal to, more preferably equal to.

1.6 2

Thus, for example a vehicle whose Vmax (in electric mode) is 100 km / h can be equipped on its rear axle with a traction chain whose transmission ratio is such that the (or) machine (s) reaches (reaches) the maximum rotational speed to 40 km / h, the front axle ensuring only traction beyond this speed while the freewheel mechanism comes into action and that the rear axle is disabled.

Claims

claims

1 - Motor vehicle (1) comprising electric traction means acting on at least two wheels (21, 22, 23, 24) of two different axles (2, 3), the electric traction means comprising an electric machine (43, 44, 45, 46) and a transmission (33, 34, 35, 36) defining a fixed transmission ratio between the rotational speed of the electric machine and the rotational speed of the wheel, a first transmission (35) for at least one of the wheels of a first axle (3) defining a first transmission ratio and a second transmission (33) for at least one of the wheels of a second axle (2) defining a second transmission ratio, the first transmission comprising a free wheel mechanism (66) capable of allowing the wheel to rotate without driving the electric machine.

2 - Vehicle according to claim 1 wherein the freewheel mechanism is placed between the transmission and the hub.

3 - Vehicle according to claim 1 wherein the freewheel mechanism is placed within the transmission. 4 - Vehicle according to claim 1 wherein the freewheel mechanism is placed between the electric machine and the transmission.

5 - Vehicle according to one of the preceding claims wherein each wheel of the first axle (3) is driven via a freewheel mechanism.

6 - Vehicle according to one of the preceding claims wherein the first axle is located at the rear of the vehicle relative to the second axle.

7 - Vehicle according to one of the preceding claims wherein each wheel of the first axle is driven by an independent electric machine. 8 - Vehicle according to claim 7 wherein each wheel of the second axle is also driven by an independent electric machine.

9 - Vehicle according to one of claims 7 or 8 wherein each wheel of the first axle is equipped with a motorized hub (100), said motorized hub comprising a hub (7) for receiving a wheel (24), the hub being rotatably mounted relative to a hub carrier (5) along a hub axis (M), the motorized hub comprises an electric traction machine (46), the electric machine comprising an outer stator connected to the hub carrier and a rotor internal axis whose axis of rotation (R) is distant from the hub axis (M), the motorized hub comprising reduction means acting between the rotor of the electric machine and the hub, the motorized hub comprising a wheel mechanism free (66) able to allow the wheel to rotate without driving the electric machine.

10 - Vehicle according to claim 7 wherein wherein the wheels of the second axle (2) are driven by a common electric machine (41).

11 - Vehicle according to one of the preceding claims wherein the various traction means are designed such that the wheels driven via a freewheel mechanism reach the point where the freewheel mechanism comes into action at the latest when the vehicle reaches a speed equal to ^ ^max _{; e} td _e preferably at the latest

1.6

,, ■, · ·,,, Kmax

when the vehicle reaches an equal speed a.