FR3141891A1 - Axle for electric vehicle with two speed ratios and vehicle comprising such an axle - Google Patents

Abstract

Axle for electric vehicle with two speed ratios and vehicle comprising such an axle The invention relates to an axle (1) for propulsion or traction of an electric vehicle, comprising an electric motor (2) with a drive shaft (2') forming a rotational movement input stage, a differential (3) with two aligned half-shafts (4 and 4') each carrying a wheel (5, 5') and forming a rotational movement output stage and a device (6) for transmitting torque between the motor (2) and the differential (3) comprising a support shaft (6') and forming an intermediate stage. According to the invention, the device (6) is configured to ensure selective transmission of torque and for this purpose comprises a coupling member (10) switched in a controlled manner between two positions and being configured to secure in rotation one of the two toothed wheels (8, 8') mounted freely on the support shaft (6') with this shaft (6'), this selectively depending on its position. In addition, a clutch (11) is provided which is associated with one (8') of the two toothed wheels (8, 8'), this clutch (11) being configured to selectively establish a rotational securing connection between this toothed wheel (8') and the support shaft (6'), this connection being complementary to that capable of being established by the coupling member (10). Figure to be published with the abstract: Fig.1

Description

Axle for two-speed electric vehicle and vehicle comprising such an axle

The present invention relates to the field of transmission of movement in a vehicle between the engine and the wheels of the latter, and relates to an axle for an electric vehicle with two gear ratios, as well as a vehicle equipped with such an axle.

Transmission devices for vehicles with internal combustion engines or hybrid vehicles are well known. They generally have a relatively complex construction because, in connection with a thermal drive, they must provide at least three or four gears and ensure gear change possibilities. In the case of a hybrid vehicle, it is also necessary to allow switching between operation in thermal mode and operation in electric mode.

Transmission devices for vehicles with internal combustion engines or hybrid vehicles are well known. They generally have a relatively complex construction because, in connection with a thermal drive, they must provide at least three or four gears and ensure gear change possibilities. In the case of a hybrid vehicle, it is also necessary to allow switching between operation in thermal mode and operation in electric mode.

However, there is a demand in relation to electric vehicles for high output torque (transmitted to the wheels) and high maximum speed.

However, these two requirements are fundamentally contradictory in terms of the operating mode and performance of electric machines. Indeed, a maximum output torque implies a minimum reduction ratio (i.e. a maximum reduction in the rotational speed between the motor output and the wheel drive), whereas a maximum speed implies a maximum reduction ratio (i.e. a minimum reduction, or even an increase, in the rotational speed between the motor output and the wheel drive).

Furthermore, there is also a demand to be able to kinematically disconnect the electric motor from the vehicle wheels.

The present invention aims to respond at least to the first, and preferably also to the second, aforementioned request(s), by advantageously proposing a solution with optimal efficiency, in particular in permanent mode, simple and economical, and substantially without interruption of torque during speed variations/changes.

Finally, the proposed solution should be compact and of limited weight.

For this purpose, the invention relates to an axle for the propulsion or traction of an electric vehicle, comprising an electric motor with a motor or drive shaft forming an input stage for rotational movement, a differential with two aligned half-shafts each carrying a wheel and forming an output stage for rotational movement and a device for transmitting torque between the motor and the differential comprising a support shaft and forming an intermediate stage,

the drive shaft, the two half-shafts and the support shaft respectively defining axes of rotation parallel to each other,

at least one meshing connection, with permanent or selective torque transmission, existing between the drive shaft and the support shaft, on the one hand, and between the support shaft and the differential, on the other hand,

characterized axle

in that the drive shaft and the support shaft are permanently connected to each other by a meshing connection with torque transmission, with establishment of a given transmission ratio,

in that the support shaft comprises two toothed wheels mounted freely rotatable on this shaft and the differential comprises two toothed rings for inputting movement into said differential, each toothed wheel meshing with a toothed ring, preferably with their own transmission ratios, which are mutually different,

in that the torque transmission device is configured to provide selective torque transmission and comprises for this purpose at least one coupling member capable of being switched in a controlled manner between two positions or two states, for example by translational movement along the axis of rotation of the support shaft, the or each coupling member being configured to secure in rotation one of the two toothed wheels with the support shaft, this selectively as a function of the position or state of said or each coupling member, and

in that the torque transmission device comprises a clutch associated with one of the two toothed wheels, preferably the one establishing a torque transmission with the highest resulting rotation speed for the differential, this clutch being configured to selectively establish a rotational securing connection between this toothed wheel and the support shaft, this connection being complementary to that likely to be established by the at least one coupling member.

The invention will be better understood from the following description, which relates to two preferred embodiments, given as non-limiting examples, and explained with reference to the attached schematic drawings, in which:

is a schematic and symbolic representation of a first embodiment of an axle according to the invention, and

is a schematic and symbolic representation of a second embodiment of an axle according to the invention.

Figures 1 and 2 schematically illustrate and in accordance with two embodiments of the invention, an axle for the propulsion or traction of an electric vehicle, comprising an electric motor (2) with a motor or drive shaft (2') forming a rotational movement input stage, a differential (3) with two aligned half-shafts (4 and 4') each carrying a wheel (5, 5') and forming a rotational movement output stage and a device (6) for transmitting torque between the motor (2) and the differential (3) comprising a support shaft (6') and forming an intermediate (kinematic) stage (preferably with variation - reduction - of rotation speed).

The drive shaft (2'), the two half-shafts (4, 4') and the support shaft (6') respectively define axes of rotation (AE, AS, AI) parallel to each other, and at least one meshing connection, with permanent or selective transmission of torque, existing between the drive shaft (2') and the support shaft (6'), on the one hand, and between the support shaft (6') and the differential (3), on the other hand.

The permanent meshing connection (7) could for example be achieved by two toothed wheels (7’ and 7”) respectively secured to the motor shaft (2’) and the support shaft (6’).

According to the invention, the drive shaft (2') and the support shaft (6') are permanently connected to each other by a connection (7) by meshing with torque transmission, with establishment of a given transmission ratio (R0). In addition, the support shaft (6') comprises two toothed wheels (8, 8') mounted freely in rotation on this shaft (6') and the differential (3) comprises two crowns or toothed wheels (9, 9') for inputting movement into said differential (3), each toothed wheel (8, 8') meshing with a crown gear (9, 9'), preferably with their own transmission ratios (R1, R2), mutually different, for example R2>R1. Furthermore, the torque transmission device (6) is configured to provide selective torque transmission and for this purpose comprises at least one coupling member (10, 10') which can be switched in a controlled manner between two positions or two states, for example by translational movement along the axis of rotation (AE) of the support shaft (6'), the or each coupling member (10, 10') being configured to secure in rotation one of the two toothed wheels (8, 8') with the support shaft (6'), this selectively depending on the position or state of said or each coupling member (10, 10'). Finally, the torque transmission device (1) comprises a clutch (11) associated with one (8') of the two toothed wheels (8, 8'), preferably the one establishing a torque transmission with the highest resulting rotation speed for the differential (3), this clutch (11) being configured to selectively establish a rotational securing connection between this toothed wheel (8') and the support shaft (6'), this connection being complementary to that likely to be established by the coupling member (10) at least present.

Thanks to these particular additional provisions essentially related to the torque transmission device (6), the invention makes it possible to achieve at least the main aim mentioned above.

In accordance with a preferred embodiment of the invention, also emerging from Figures 1 and 2 and making it possible to achieve a construction with minimal bulk, it is provided that the axes of rotation (AE and AS) of the drive shaft (2') and of the two half-shafts (4, 4') are merged, that the drive shaft (2') has a hollow structure and that one (4) of the two half-shafts (4, 4') extends through said drive shaft (2').

According to a first variant embodiment illustrated in the , the torque transmission device (6) comprises a single selective coupling member (10) which consists of a dog clutch mounted to slide on the support shaft (6') and which is arranged and configured to establish, in a first engaged position, a rotational connection between this shaft (6') and a first (8) of the two toothed wheels (8, 8') and, in a second engaged position, a rotational connection between this shaft (6') and a second (8') of said two toothed wheels (8, 8'), these two engaged positions being separated by a neutral position of said member (10) corresponding to a simultaneous absence of connection of the two toothed wheels (8 and 8') with said shaft (6'). Furthermore, this device (6) comprises a clutch (11) which is configured and controlled to selectively establish a rotational securing connection between the toothed wheel (8') concerned and the input shaft (6'), which is variable and controlled in intensity depending on the position of the coupling member (10).

This clutch (11), which advantageously consists of a friction or sliding clutch, due to its possibility of progressive engagement, makes it possible to guarantee the maintenance of the torque during gear changes and to ensure the continuity of transmission of said torque. In addition, the possibility of a neutral position allows a kinematic disconnection between the engine and the wheels.

According to a second variant embodiment illustrated in the , the torque transmission device (6) comprises, on the one hand, a first selective coupling member (10) which consists of a dog clutch mounted sliding on the support shaft (6') and which is arranged and configured to establish, in a first engaged position, a rotational connection between this shaft (6') and one (8) of the two toothed wheels (8, 8') and, in a second disengaged position, a rotational disconnection between this shaft (6') and this toothed wheel (8), and, on the other hand, a second coupling member (10') corresponding to the clutch (11) associated with the other (8') of the two toothed wheels (8, 8') and configured and controlled to selectively establish a rotational securing connection between this other toothed wheel (8') concerned and the support shaft (6'), this alternately and in an inverse manner with respect to the connection established by the first coupling member (10).

Preferably, this clutch (11) consists of a multiple-disc clutch, mounted integral in rotation with one of the support shaft (6') and this other toothed wheel (8') and capable of being selectively secured in rotation with the other of the support shaft (6') and this other toothed wheel (8') by a third coupling member (12).

In this second variant, too, the continuity of torque transmission is ensured, as well as its progressive transfer, during gear changes. In addition, a simple dog clutch is sufficient as the first coupling member (10) and a possible kinematic disconnection can also be achieved.

In order to allow safe immobilization of the vehicle when stationary (parking position), the transmission device (1) may comprise a device for locking the rotation of the support shaft (6'), either directly or by locking one of the toothed wheels (8, 8') mounted on this shaft. For this purpose, the support shaft (6') may be provided with a toothed or ratchet wheel (13) fixedly mounted on this shaft and the rotation of which can be selectively locked by a suitable mechanism controlled directly or indirectly by user command (see for example FR 3 121 409). Such a toothed or ratchet wheel (13) may also be associated with one (8) of the toothed wheels already mounted on this shaft and which can be coupled to it by the dog clutch (as illustrated in FIGS. 1 and 2).

Preferably, and in favourable relation with the type of vehicle concerned (electric), the transmission device (1) comprises electromagnetic actuators for controlling the switching of the coupling member(s) (10, 10') and/or the engagement and disengagement of the clutch (11).

In connection with the realization of the , the change from first gear to second gear (without interruption of transmitted torque) advantageously takes place as follows:

-in the first gear, the torque is transmitted from the engine (2), i.e. from its drive shaft (2'), through the support shaft (6') exclusively by means of the dog clutch (10) engaged with the gear wheel (8), the clutch (11) being completely disengaged,

- the engagement of the clutch (11) is controlled, and the latter increases in capacity with a progressive transfer of the torque passing through the dog clutch (10) to the clutch (11),

-the dog clutch (10) is disengaged from the first gear wheel (8) and is in the neutral position (as shown in the ), all of the torque then passes through the clutch (11),

- the clutch slip braking (11) occurs and, during this inertia phase, the slip speed is gradually reduced to 0,

- the engagement of the dog clutch (10) with the other gear wheel (8') begins (the torque still being mainly transmitted by the clutch),

- the clutch (11) is controlled to reduce in capacity with a progressive transfer of the torque passing through the clutch (11) to the dog clutch (10),

-after finalizing the engagement of the dog clutch (10) with said other toothed wheel (8'), the torque is exclusively transmitted by the dog clutch (10), the clutch (11) being completely disengaged.

By means of the invention, taken in each of its two embodiments described above and illustrated in the figures appended as examples, it is therefore possible to provide an axle (1), integrating a two-speed transmission device (1), which has a simple and economical structure (in particular not containing a planetary gear set), making it possible to achieve a priori contradictory performance objectives (possibility of having a maximized output torque and a maximized vehicle speed with the same device) and having optimal efficiency in the two possible gears (no residual dissipated power when a gear is engaged). In addition, it does not report any interruption of torque transmission from the engine to the wheels during upshifts and downshifts, and advantageously includes a neutral position (complete disengagement) ensuring a disconnection between the engine and the wheels (load limitation when the parking device is engaged).

Finally, in its preferred construction mode, this axle (1), all of whose functional components (2, 3 and 6) are advantageously housed in a housing, has minimal bulk, particularly radially.

The invention also relates to an electric motor vehicle, characterized in that it comprises an axle (1) as described above, all of the constituent elements of this axle being housed in a single casing.

Of course, the invention is not limited to the embodiments described and shown in the attached drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims (9)

Axle (1) for the propulsion or traction of an electric vehicle, comprising an electric motor (2) with a motor or drive shaft (2') forming a rotational movement input stage, a differential (3) with two aligned half-shafts (4 and 4') each carrying a wheel (5, 5') and forming a rotational movement output stage and a device (6) for transmitting torque between the motor (2) and the differential (3) comprising a support shaft (6') and forming an intermediate stage,
the drive shaft (2'), the two half-shafts (4, 4') and the support shaft (6') respectively defining axes of rotation (AE, AS, AI) parallel to each other,
at least one meshing connection, with permanent or selective torque transmission, existing between the drive shaft (2') and the support shaft (6'), on the one hand, and between the support shaft (6') and the differential (3), on the other hand,
axle (1) characterized
in that the drive shaft (2') and the support shaft (6') are permanently connected to each other by a connection (7) by meshing with torque transmission, with establishment of a given transmission ratio (R0),
in that the support shaft (6') comprises two toothed wheels (8, 8') mounted freely in rotation on this shaft (6') and the differential (3) comprises two toothed rings (9, 9') for inputting movement into said differential (3), each toothed wheel (8, 8') meshing with a toothed ring (9, 9'), preferably with their own transmission ratios (R1, R2), mutually different,
in that the torque transmission device (6) is configured to provide selective torque transmission and comprises for this purpose at least one coupling member (10, 10') which can be switched in a controlled manner between two positions or two states, for example by translational movement along the axis of rotation (AE) of the support shaft (6'), the or each coupling member (10, 10') being configured to secure in rotation one of the two toothed wheels (8, 8') with the support shaft (6'), this selectively depending on the position or state of said or each coupling member (10, 10'), and
in that the torque transmission device (1) comprises a clutch (11) associated with one (8') of the two toothed wheels (8, 8'), preferably the one establishing a torque transmission with the highest resulting rotation speed for the differential (3), this clutch (11) being configured to selectively establish a rotational securing connection between this toothed wheel (8') and the support shaft (6'), this connection being complementary to that likely to be established by the coupling member (10) at least present. Axle according to claim 1, characterized in that the axes of rotation (AE and AS) of the drive shaft (2') and of the two half-shafts (4, 4') are coincident, in that the drive shaft (2') has a hollow structure and in that one (4) of the two half-shafts (4, 4') extends through said drive shaft (2'). Axle according to claim 1 or 2, characterized in that the torque transmission device (6) comprises a single selective coupling member (10) which consists of a dog clutch slidably mounted on the support shaft (6') and which is arranged and configured to establish, in a first engaged position, a rotational connection between this shaft (6') and a first (8) of the two toothed wheels (8, 8') and, in a second engaged position, a rotational connection between this shaft (6') and a second (8') of said two toothed wheels (8, 8'), these two engaged positions being separated by a neutral position of said member (10) corresponding to a simultaneous absence of connection of the two toothed wheels (8 and 8') with said shaft (6'), and in that it comprises a clutch (11) which is configured and controlled to selectively establish a rotational securing connection between the toothed wheel (8') concerned and the input shaft (6'), which is variable and controlled in intensity according to the position of the coupling member (10). Axle according to claim 3, characterized in that the clutch (11) consists of a friction or sliding clutch. Axle according to claim 1 or 2, characterized in that the torque transmission device (6) comprises, on the one hand, a first selective coupling member (10) which consists of a dog clutch mounted sliding on the support shaft (6') and which is arranged and configured to establish, in a first engaged position, a rotational connection between this shaft (6') and one (8) of the two toothed wheels (8, 8') and, in a second disengaged position, a rotational disconnection between this shaft (6') and this toothed wheel (8), and, on the other hand, a second coupling member (10') corresponding to the clutch (11) associated with the other (8') of the two toothed wheels (8, 8') and configured and controlled to selectively establish a rotational securing connection between this other toothed wheel (8') concerned and the support shaft (6'), this alternately and in an inverse manner with respect to the connection established by the first coupling member (10). Axle according to claim 5, characterized in that the clutch (11) consists of a multiple-disc clutch, mounted integral in rotation with one of the support shaft (6') and this other toothed wheel (8') and capable of being selectively secured in rotation with the other of the support shaft (6') and this other toothed wheel (8') by a third coupling member (12). Axle according to any one of claims 1 to 6, characterized in that it comprises a device for locking the wheels (5, 5') by rotational blocking of the support shaft (6') of the intermediate stage, or locking of one of the toothed wheels (8, 8') mounted on this shaft (6'). Axle according to any one of claims 1 to 7, characterized in that it comprises electromagnetic actuators for controlling the switching of the coupling member(s) (10, 10') and/or the engagement and disengagement of the clutch (11). Electric motor vehicle, characterized in that it comprises an axle (1) according to any one of claims 1 to 8, all of the constituent elements of this axle being housed in a single casing.