GB2605833A

GB2605833A - Drivetrain

Info

Publication number: GB2605833A
Application number: GB2105409.3A
Authority: GB
Inventors: Harrison Andrew
Original assignee: Contract Innovation Ltd
Current assignee: Contract Innovation Ltd
Priority date: 2021-04-15
Filing date: 2021-04-15
Publication date: 2022-10-19
Also published as: GB202105409D0

Abstract

A drivetrain 10 for an electric propulsion system includes: a first motion shaft 12 for connection to a first electric motor 50; a second motion shaft 14; at least two speed variation stages 16, 18 (e.g. a pair of gears, pulleys, sprockets or friction wheels) arranged between the first and second motion shafts; and a selector arrangement having first and second modes for selectively utilising one or more of the speed variation stages. In the first mode, rotational energy of the first shaft is transmitted to the second shaft via the two speed variation stages 16, 18, when in use. In the second mode, rotational energy of the first shaft is transmitted to the second shaft exclusively via the first speed variation stage 16, when in use. The selector arrangement may include a third mode, in which rotational energy of the first shaft is transmitted to the second shaft exclusively via the second speed variation stage 18, when in use. A third motion shaft may be: connected to a second electric motor; permanently connected to the first speed variation stage; and selectively connectable to the first shaft. The drivetrain may form part of an electric powertrain which further includes an electric motor, differential and wheel axle, wherein the electric motor is connectable to the first shaft and the second shaft is connectable to the differential.

Description

DRIVETRAIN

Background of the Invention

The present disclosure relates to a drivetrain for an electric propulsion system, particularly, but not exclusively, a drivetrain for electric land vehicles, such as heavy goods vehicles and agricultural machinery. The present disclosure further relates to a method of controlling a drivetrain for an electric propulsion system.

Traditional land vehicles utilising combustion engines include a gear box for making efficient use of the internal combustion engines power output at certain RPM ranges. Generally, such traditional gear boxes are designed to switch between 5 or more speed ratios (gears), wherein torque output is typically designed to be at its highest during low gears to move a vehicle from a standstill. As the vehicle accelerates and gains inertia, the required torque gradually decreases and so higher gears are designed for speed and fuel efficiency, with significantly lower torque than the lower gears.

Gear boxes may not be required in electric passenger cars, since electric motors can be operated beyond 10,000 RPM with ease, meaning that a multi-speed gear box is typically not required. Electric motors also produce consistent torque across most of their RPM range, compared to the significant torque drop of internal combustion engines at higher RPM. Accordingly, electric propulsion systems for passenger vehicles may sometimes not be provided with gear boxes that can create inefficiencies such as added weight, power losses, and extra production costs.

However, when looking at heavy goods vehicles and agricultural machinery, these multi-ton electric vehicles typically require gear boxes despite using one or more electric motors. Yet, rather than the typical 18-speed transmission known from their diesel-counterparts, electric trucks may only require the use of 2-speed transmissions, with some benefitting from 3-or 4-speed transmissions.

Although drivetrains of electric propulsion systems for heavy goods vehicles and agricultural machinery are significantly more efficient and less bulky than their internal combustion engine counterparts, there are still inefficiencies, such as excessive energy losses, and redundant drivetrain parts.

In view of the aforementioned problem, there is a need for an improved drivetrain.

It is an aim of the present invention to solve or at least ameliorate one or more of the problems discussed above.

Summary of the Invention

Aspects and embodiments of the disclosure provide a drivetrain for an electric propulsion system and a method of controlling a drivetrain for an electric propulsion system.

According to a first aspect of the present disclosure, there is provided a drivetrain for an electric propulsion system, the drivetrain comprising: a first motion shaft for connection to a first electric motor; a second motion shaft; at least two speed variation stages arranged between the first and second motion shafts; a selector arrangement for selectively utilising one or more of the at least two speed variation stages, said selector arrangement comprising: a first mode, in which rotational energy of the first motion shaft is transmitted to the second motion shaft via the two or more speed variation stages, when in use; and a second mode, in which rotational energy of the first motion shaft is transmitted to the second motion shaft exclusively via a first speed variation stage of the at least two speed variation stages, when in use.

In another embodiment, the selector arrangement comprises a third mode, in which rotation of the first motion shaft is transmitted to the second motion shaft exclusively via a second speed variation stage of the at least two speed variation stages, when in use.

In another embodiment, the first speed variation stage comprises a speed ratio that is different from, and preferably lower than, a speed ratio of the second speed variation stage.

In another embodiment, a wheel pair is arranged between the first and second motion shafts, wherein, in the first mode, rotation of the first motion shaft is transmitted to the second motion shaft via the two or more speed variation stages and the wheel pair. In another embodiment, a driven wheel of the wheel pair is arranged on a common shaft with a driving wheel of the second speed variation stage.

In another embodiment, the first motion shaft is at least partly received within an opening of the common shaft.

In another embodiment, the selector arrangement comprises a first coupling device, having a first position for selectively connecting the first motion shaft to the second speed variation stage.

In another embodiment, in the third mode of the selector arrangement, the first coupling device is in its first position.

In another embodiment, the drivetrain comprises an intermediate shaft arranged between the first motion shaft and the second motion shaft.

In another embodiment, the selector arrangement comprises a second coupling device having a first position for connecting the intermediate shaft with the wheel pair.

In the first mode of the selector arrangement, the second coupling device may be in its first position.

In another embodiment, the second coupling device has a second position for connecting the intermediate shaft to the second motion shaft.

In the second mode of the selector arrangement, the second coupling device may be in its second position.

In another embodiment, the first motion shaft is permanently connected to the intermediate shaft via the first speed variation stage.

In another embodiment, the first motion shaft is selectively connectable to the first speed variation stage via the selector arrangement.

In another embodiment, the first coupling device has a second position for connecting the first motion shaft to the first speed variation stage.

In the first and second mode of the selector arrangement, the first coupling device may be in its second position.

In another embodiment, the first speed variation stage comprises a first gear pair. In another embodiment, the second speed variation stage comprises a second gear pair.

In another embodiment, the intermediate shaft at least partially extends through the second motion shaft.

In another embodiment, the drivetrain comprises a third motion shaft for connection to a second electric motor.

In another embodiment, the third motion shaft is selectively connectable to the first motion shaft.

In another embodiment, the third motion shaft is permanently connected to the first speed variation stage.

In another embodiment, the first motion shaft is connected to the third motion shaft, when the first coupling device is in its second position.

In another embodiment, the first and/or the second speed variation stage(s) comprise(s) one of a gear pair, a pair of pulleys, a pair of sprockets, or a pair of friction wheels.

According to another aspect of the present disclosure, there is provided an electric powertrain comprising: an electric motor; any of the above drivetrain embodiments; a differential; and a wheel axle, wherein the electric motor is connected or connectable to the first motion shaft of the drivetrain and the second motion shaft of the drivetrain is connected or connectable to the differential.

According to another aspect of the present disclosure, there is provided a method of controlling a drivetrain for an electric propulsion system, the drivetrain comprising: a first motion shaft for connection to a first electric motor; a second motion shaft; at least two speed variation stages arranged between the first and second motion shafts; wherein the method comprises: transmitting power between the first and second motion shafts via both speed variation stages, to achieve a first speed ratio; transmitting power between the first and second motion shafts exclusively via the first speed variation stage, to achieve a second speed ratio.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and the claims and/or the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Brief Descriotion of the Drawinas One or more embodiments of the present disclosure will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic representation of a drivetrain according to an embodiment of the present disclosure; Figs 2A and 25 show the embodiment of the drivetrain of Fig. 1 in a first mode of the selector arrangement; Figs 3A and 3B show the embodiment of the drivetrain of Fig. 1 in a second mode of the selector arrangement; Figs 4A and 45 show the embodiment of the drivetrain of Fig. 1 in a third mode of the selector arrangement; Fig. 5 shows a schematic representation of a drivetrain according to another embodiment of the present disclosure; Figs 6A and 65 show the embodiment of the drivetrain of Fig. 5 in a first mode of the selector arrangement; Figs 7A and 7B show the embodiment of the drivetrain of Fig. 5 in a second mode of the selector arrangement; Figs 8A and 85 show the embodiment of the drivetrain of Fig. 5 in a third mode of the selector arrangement; Fig. 9 shows a schematic representation of a drivetrain according to another embodiment of the present disclosure; Figs 10A and 105 show the embodiment of the drivetrain of Fig. 9 in a first mode of the selector arrangement; Figs 11A and 115 show the embodiment of the drivetrain of Fig. 9 in a second mode of the selector arrangement; Figs 12A and 125 show the embodiment of the drivetrain of Fig. 9 in a third mode of the selector arrangement; Figs 13A and 135 show the embodiment of the drivetrain of Fig. 9 in a fourth mode of the selector arrangement; Figs 14A and 145 show the embodiment of the drivetrain of Fig. 9 in a fifth mode of the selector arrangement; Figs 15A and 155 show the embodiment of the drivetrain of Fig. 9 in a sixth mode of the selector arrangement; Figs 16A and 165 show the embodiment of the drivetrain of Fig. 9 in a seventh mode of the selector arrangement; Fig. 17 shows a schematic representation of a drivetrain according to another embodiment of the present disclosure; Figs 18A and 185 show the embodiment of the drivetrain of Fig. 17 in a first mode of the selector arrangement; Figs 19A and 195 show the embodiment of the drivetrain of Fig. 17 in a third mode of the selector arrangement; Figs 20A and 205 show the embodiment of the drivetrain of Fig. 17 in a fifth mode of the selector arrangement; Figs 21A and 215 show the embodiment of the drivetrain of Fig. 17 in a seventh mode of the selector arrangement;

Detailed Description of the Drawings

Figure 1 schematically shows a drivetrain 10 according to an embodiment of the present disclosure connected to an electric motor 50. Parts or the entirety of the drivetrain may be received within a corresponding drivetrain housing (not shown). The drivetrain 10 of Figure 1 may be particularly suitable for a central drive arrangement, in which a second motion shaft of the drivetrain is connected to one or more differentials of the vehicle axle/axles via a prop shaft.

The drivetrain of Figure 1 comprises a first motion shaft 12. In this embodiment, the first motion shaft 12 may be considered as an input shaft of the drivetrain 10. The first motion shaft 12 is suitable for connection to a first electric motor 50. In the illustration of Figure 1, only one electric motor is provided and connected to the first motion shaft 12 of the drivetrain 10. As will be described in more detail with reference to Figure 5, however, it is equivalently feasible to connect more than one electric motor to the first motion shaft 12. The first motion shaft 12 is a driven shaft of the drivetrain 10.

The drivetrain 10 includes a second motion shaft 14. In the embodiment of Figure 1, the second motion shaft 14 can be described as an output shaft. However, as will be described with reference to Figure 5, for example, the second motion shaft may not always be an output shaft but could also be a lay shaft of the drivetrain.

The drivetrain 10 comprises two speed variation stages 16, 18. A first speed variation stage 16 and a second speed variation stage 18 are arranged between the first and second motion shafts 12, 14. In this specification the term "speed variation stage" refers to any device or arrangement that may be used to produce an output speed that is different from an input speed provided to the "speed variation stage". A speed variation stage may be a speed reduction stage for reducing a rotational speed (i.e. speed ratio above 1). Similarly, a speed variation stage may be a speed increase stage for increasing a rational speed (i.e. speed ratio below 1). In another example, the speed variation stage may not change the absolute rotational speed value (i.e. speed ratio 1) but only the direction of rotation.

In the below examples, the speed variation stages are shown as gear pairs.

However, as will be appreciated, the speed variation stages may equivalently comprise belt driven pulleys, chain driven sprockets, or any other wheel pair, such as friction wheels. In the embodiment of Figure 1, the first speed variation stage is a speed reduction stage. In some examples, the first speed variation stage may have a speed ratio of 1.6. However, it will be appreciated that any other suitable speed ratio may be chosen for the first speed variation stage 16. Suitable speed ratios of the first speed variation stage will be dependent on the type of the vehicle the drivetrain 10 is to be used with.

The first speed variation stage 16 comprises a gear pair. The gear pair comprises a first driving gear 20, and a second, driven gear 22. In alternative embodiments, the first speed variation stage may comprise a chain drive, belt drive, friction drive or any other suitable speed reduction arrangement.

The driving gear 20 of the first speed variation stage 16 shown in Figure 1 is permanently connected to the first motion shaft 12. The driven gear 22 of the first speed variation stage 16 is in meshing contact with the driving gear 20 and permanently connected to an intermediate shaft 24.

The second speed variation stage 18 of Figure 1 comprises a second gear pair. The gear pair of the second speed variation stage 18 comprises a driving gear 26 and a driven gear 28. The driving gear 26 is in meshing contact with the driven gear 28. Similar to the first speed variation stage 16, the gears 26, 28 of the second speed variation stage may, in alternative embodiments, be replaced by chain drives, belt drives, or friction drives, as suitable.

As will be described in more detail below, the driving gear 26 of the second speed variation stage 18 may selectively be connected directly to the first motion shaft 12 or to the intermediate shaft 24. Such selective connection between the second speed variation stage 18 and one of the first motion shaft 12 and the intermediate shaft 24 is achieved via a selector arrangement that will be described in more detail below.

The driven gear 28 of the second speed variation stage 18 of Figure 1 is permanently connected to the second motion shaft 14.

The second speed variation stage 18 may have a speed ratio of 2.8. Of course, any other suitable speed ratio may be used for the second speed variation stage 18, depending on the specific application of the drivetrain. In some embodiments, the first speed variation stage comprises a speed ratio that is different from a speed ratio of the second speed variation stage 18. In particular, in the embodiment of Figure 1, the first speed variation stage has a speed ratio that is lower than the speed ratio of the second speed variation stage 18.

The drivetrain 10 of the embodiment shown in Figure 1 further comprises a wheel pair 30 arranged between the first and second motion shafts 12, 14. In this embodiment, the wheel pair is arranged between the intermediate shaft 24 and a common shaft 36. In one example, the wheel pair 30 may be a gear pair comprising a first, driving gear 32 and a second, driven gear 34.

The wheel pair 30 may be considered a third speed variation stage. In the embodiment of Figure 1, the wheel pair 30 may not have any significant impact on the speed value of the propulsion system and, thus, have a speed ratio of around 1. In such an embodiment, the wheel pair 30 may be considered as an idler wheel pair that does not change the speed ratio but reverses the direction of rotation. In alternative embodiments, the wheel pair 30 may be a speed reduction stage or a speed increasing stage similar to the first and second speed variation stages 16, 18.

The driven gear 34 of the wheel pair 30 is permanently connected to the driving gear 26 of the second speed variation stage 18 via a common shaft 36. The common shaft 36 is a hollow shaft. The first motion shaft 12 extends axially through the common shaft 36, thereby reducing the space requirement of the drivetrain 10. The common shaft 36 is rotatably connected to the first motion shaft 12 via a rotary bearing (not shown).

The drivetrain comprises a selector arrangement for selectively utilising one or both of the speed variation stages 16, 18. In this context, "utilising" one or more speed variation stage(s) means that rotational energy of the first motion shaft is transferred to the second motion shaft via said speed variation stage(s). The overall speed ratio of the drivetrain is thus a function of the speed ratios of each utilised speed variation stage. By contrast, speed variation stages that are not "utilised" are bypassed and so do not affect the overall speed ratio of the drivetrain.

In the embodiment of Figure 1, the selector arrangement of the drivetrain 10 comprises a first coupling device 38. In one example, the first coupling device 38 may be a dog clutch. The first coupling device 38 is rotatably connected to the first motion shaft and may be shifted along a longitudinal axis of the first motion shaft 12 between an active and an inactive positions. The first coupling device 38 of Figure 1 is configured to selectively connect the first motion shaft 12 with the driven gear 34 of the wheel pair 30. To this end, the first coupling device 38 has an inactive position, in which the first coupling device 38 may freely rotate together with the first motion shaft but does not transfer rotational energy to any other member of the drivetrain 10. The first coupling device 38 of Figure 1 also has a first, active position (shown in Figures 3A and 3B) in which the first coupling device is connected to the common shaft 36. In some embodiments, the first coupling device 40 may be connected to the common shaft 36 via the driven gear 34 of the wheel pair 30.

In the first position of the coupling device 38, the first motion shaft 12 is directly connected to the second speed variation stage 18, particularly to the driven gear 26 of the second speed variation stage. In other words, in the first position of the coupling device 38, the driven gear 26 will rotate together with the first motion shaft 12, at the same speed.

In an alternative embodiment (not shown), the first coupling device 38 is not part of the drivetrain. In such an example, the drivetrain may only include the second coupling device 40. In such an embodiment, the first motion shaft 12 may never be directly connected to the second speed variation stage 18 via the wheel pair 30.

In the embodiment of Figure 1, the selector arrangement comprises a second coupling device 40. In one example, the second coupling device 40 may be a dog clutch. The second coupling device 40 is rotatably connected to the intermediate shaft 24 and may be shifted along a longitudinal axis of the intermediate shaft 24 between two active positions and one inactive position. In the illustration of Figure 1, the second coupling device 40 is shown in its inactive position. In the inactive position, the second coupling device may freely rotate together with the intermediate shaft 24 and does not transfer rotational energy to any other member of the drivetrain 10.

The second coupling device 40 of Figure 1 comprises a first, active position (shown in Figures 2A and 2B) in which the second coupling device 40 is connected to the driving gear 32 of the wheel pair 30. In this first active position of the second coupling device 40, the intermediate shaft 24 is connected to the second motion shaft 14 via the wheel pair 30 and the second speed variation stage 18. In other words, in the first position of the second coupling device 40, the second motion shaft 14 will rotate at a different speed to the intermediate shaft 24, typically at a reduced speed compared to the intermediate shaft 24.

The second coupling device 40 comprises a second active position (shown in Figures 3A and 35) in which the second coupling device 40 is connected to the driven gear 28 of the second speed variation stage 18. In the second position of the second coupling device 40, the intermediate shaft 24 is directly connected to the second motion shaft 14, meaning that the intermediate shaft 24 will rotate together with the second motion shaft 14, at the same speed.

As will be described in more detail below, the selector arrangement of the drivetrain 10 enables a transfer of rotational energy between the first motion shaft 12 and the second motion shaft 14 either via 1 or both of the speed variation stages 16, 18, depending on the load requirement of the vehicle in question.

In the following description of Figures 2A, 2B, 3A, 3B, 4A, and 4B, different modes of operation of the selector arrangement of the drivetrain 10 will be explained in more detail.

Figures 2A and 2B show a first mode of the selector arrangement of the drivetrain 10. This first mode of the selector arrangement may also be described as a "first gear" of the drivetrain 10. In the first mode of the selector arrangement of the embodiment of Figure 1, the first coupling device 38 is in its inactive position. At the same time, the second coupling device 40 is in its first position, in which the first coupling device 40 is shifted to engage the driving gear 32 of the wheel pair 30. As a consequence, the rotation of the intermediate shaft 24 will be transferred to the wheel pair 30 via the coupling device 40, when in use.

In this first mode of the selector arrangement, rotational movement of the first motion shaft 12 (connected to motor 50) is transferred to the second motion shaft via the two speed variation stages 16, 18 and the wheel pair 30. In other words, in the first mode, the rotational energy is transferred from the first motion shaft 12 to the second motion shaft 14 via three gear pairs, such that the second motion shaft 14 will rotate in an opposite direction to the first motion shaft 12, when in use.

Turning to Figure 2B, the flow of rotational energy is schematically illustrated by arrows running along the drivetrain. Rotational energy introduced via the motor 50 into the first motion shaft 12 is transferred to the intermediate shaft 24 via the first speed variation stage 16. If the first speed variation stage 16 is a speed reduction stage, the intermediate shaft 24 has a reduced speed compared to the first motion shaft 12. The rotational energy of the intermediate shaft 24 is then transmitted via the second coupling device 40 and the driving gear 32 of the wheel pair 30 to the common shaft 36 that is arranged between the driven gear 34 of the wheel pair and the driving gear 26 of the second speed variation stage 18.

The wheel pair 30 may or may not be a further speed variation stage. In the embodiment of Figure 1, the wheel pair 30 has a speed ratio of 1 and, thus, can be described as an idler wheel pair that does not affect the speed ratio of the drivetrain. As will be appreciated, however, the wheel pair 30 will still reverse the direction of rotation between the intermediate shaft 26 and the common shaft 36. It also follows that the common shaft 36 has substantially the same rotational speed as the intermediate shaft 24.

Rotational energy of the common shaft 36 is transferred to the second motion shaft 14 via the second speed variation stage 18. In particular, the common shaft 36 rotates the driving gear 26 of the second speed variation stage, which in turn drives the driven gear 28 of the second speed variation stage 18. If the second speed variation stage 18 is a speed reduction stage, then the rotational speed of the second motion shaft 14 is lower than the rotational speed of the common shaft 36.

In the first mode of operation shown in Figures 2A and 2B, the selector arrangement is set such that power transfer between the first motion shaft 12 and the second motion shaft 14 is achieved via both speed variation stages 16, 18 and the wheel pair 30. If both speed variation stages 16, 18 are speed reduction stages, the overall speed ratio of the drivetrain 10 in the first mode of the selector arrangement is the product of the speed ratios of the first and second speed variation stages 16, 18. In this first mode of operation, rotational energy of the first motion shaft 12 is transferred to the second motion shaft 14 via a total of 3 gear pairs. This first mode of operation of the drivetrain 10 may be particularly suitable when a heavy goods vehicle or an agricultural machinery is started from a stopping position. Therefore, when the selector arrangement is operated in its first mode, the drivetrain may be considered as being in "first gear". In the above example, the overall speed ratio of the geartrain in "first gear" is 4.48.

A "second gear" of the drivetrain 10 of Figure 1 is shown in Figures 3A and 3B. In this "second gear" the selector arrangement is operated in a second mode. In the second mode, the rotational energy of the first motion shaft 12 is transferred to the second motion shaft 14 exclusively via the second speed variation stage 18. In other words, in the second mode, the rotational energy is transferred from the first motion shaft 12 to the second motion shaft 14 via a single gear pair, such that the second motion shaft 14 will rotate in an opposite direction to the first motion shaft 12, when in use.

In the second mode of the selector arrangement, the first coupling device 38 is in its active (first) position, in which the first coupling device 38 is connected to the driven gear 34 of the wheel pair 30. The first coupling device 38, therefore, directly connects the first motion shaft 12 with the common shaft 36. The second coupling device 40 is in its inactive position in this second mode.

Figure 3B shows the transfer of rotational energy between the first motion shaft 12 and the second motion shaft 14 in the second mode of the selector arrangement. In the second mode of the selector arrangement, the common shaft 36 is directly connected to the first motion shaft 12 via the first coupling device 38, such that the common shaft 36 rotates at the same speed as the first motion shaft 12. Rotational energy of the common shaft 36 is transferred to the second motion shaft 14 via the second speed variation stage 18. If the second speed variation stage 18 is a speed reduction stage, then the rotational speed of the second motion shaft 14 will be lower than the rotational speed of the first motion shaft 12, when in use.

In the second mode, the rotational energy of the first motion shaft 12 is transferred to the second motion shaft 14 exclusively via the second speed variation stage 18. The first speed variation stage 16 and the wheel pair 30 are bypassed in the second mode.

In the above example, where the speed ratio of the first speed variation stage 16 is 1.6 and the speed ratio of the second speed variation stage 18 is 2.8, the overall speed ratio of the second gear (second mode of the selector arrangement) is 2.8. This also means that the overall speed ratio of the second gear of the drivetrain 10 described with reference to Figures 3A and 3B is lower than the overall speed ratio of 4.48 achieved in first gear, described with reference to Figures 2A and 2B.

Figures 4A and 4B show the drivetrain in a "third gear", in which the selector arrangement is operated in a third mode. In this third mode of the selector arrangement, the first coupling device 38 is in its inactive position. The second coupling device 40 is shifted into its second position, in which the second coupling device 40 is connected to the driven gear 28 of the second speed variation stage 18. In other words, in the third mode of the selector arrangement, the intermediate shaft 24 is directly connected to the second motion shaft 14, meaning that the intermediate shaft 24 and the second motion shaft 14 will always rotate at the same speed.

In the third mode of the selector arrangement, the second speed variation stage 18 and the wheel pair 30 are bypassed. Accordingly, rotational energy of the first motion shaft 12 is transferred to the second motion shaft 14 exclusively via the first speed variation stage 16 when the selector arrangement is in its third mode. In other words, in the third mode, the rotational energy is transferred from the first motion shaft 12 to the second motion shaft 14 via a single gear pair, such that the second motion shaft 14 will rotate in an opposite direction to the first motion shaft 12, when in use.

It follows from the above that, in every mode of the selector arrangement of the geartrain 10, the rotational energy of the first motion shaft 12 is transferred to the second motion shaft via an uneven number of gear pairs, such that the second motion shaft will rotate in the same direction, i.e. opposite to the first motion shaft 12, in every mode of the selector arrangement.

The flow of rotational energy in the third gear of the drivetrain 10 is derivable from Figure 4B. As shown by the arrows in Figure 4B, the rotational energy supplied to the first motion shaft 12 via the motor 50 is transferred to the intermediate shaft 24 via the first speed variation stage 16. If the first speed variation stage 16 is a speed reduction stage, then the rotational speed of the intermediate shaft 24 is lower than the rotational speed of the first motion shaft 12.

The rotational energy of the intermediate shaft 24 is then transferred to the second motion shaft 14 via the second coupling device 40 together with the driven gear 28 of the second speed variation stage 18.

In the third gear of the drivetrain shown in Figures 4A and 4B, the selector arrangement, in its third mode, is set such that the speed of the first motion shaft 12 is only reduced once, via the first speed variation stage 16, before it is transferred to the second motion shaft 14. Accordingly, the speed ratio of this third gear of the drivetrain is lower than the overall speed ratio in the first gear and lower than the overall speed ratio in the second gear. In the above example, in which the first speed variation stage 16 has a speed ratio of 1.6 and the second speed variation stage 18 has a speed ratio of 2.8, the overall speed ratio in third gear, i.e. in the third mode of the selector arrangement, is 1.6, which is lower than the overall speed ratio of 4.48 in the first mode of the selector arrangement described with reference to Figures 2A and 2B and lower than the overall speed ratio of 2.8 in the second mode described with reference to Figures 3A and 3B above. In the first and third modes described with reference to Figures 2A, 2B and 4A, 4B respectively, the first coupling device 38 remained in its inactive position. In some embodiments (not shown), the drivetrain of the present disclosure may not include a first coupling device at all. In such embodiments, the selector arrangement may be limited to the first and third modes described with reference to Figures 2A, 2B, and 4A, 4B respectively. Such an embodiment may be considered a two-speed or two-gear drivetrain.

Figure 5 shows another embodiment of the drivetrain according to the present disclosure. The drivetrain 100 may be suitable for an axle drive arrangement, in which the drivetrain 100 and the one or more electric motors 150, 152 are directly connected to a wheel axle of the vehicle.

The drivetrain 100 shown in Figure 5 comprises a first motion shaft 112 for connection to a first electric motor 150. The first motion shaft 112 may optionally also be connected to a second motor 152.

The drivetrain 100 includes a second motion shaft 114. In contrast to the first embodiment shown in Figure 1, the second embodiment of Figure 5 includes a second motion shaft 114 that is not constructed as an output shaft. Rather, the second motion shaft 114 is a hollow shaft that is connected to an output gear 142. The output gear 142, in turn, is connectable to a differential 160, as will be described in more detail below. The embodiment of Figure 5 may, thus, be suitable as an axle drivetrain, in which the electric motor or motors 150, 152 and the drivetrain 100 are directly connected to the axle/axles of the vehicle, such as an HGV. In some examples, at least two axles of an HGV may be provided with a drivetrain 100 per axle.

The drivetrain 100 of Figure 5 comprises a first speed variation stage 116, which is schematically shown as a gear pair. The gear pair of the first speed variation stage 116 comprises a driving gear 120 and a driven gear 122. The driving gear 120 is permanently connected to the first motor shaft 112. The driven gear 122 of the first speed variation stage 116 is permanently connected to an intermediate shaft 124.

The drivetrain 100 comprises a second speed variation stage 118, which is shown as another gear pair. The gear pair of the second speed variation stage 118 comprises a driving gear 126 and a driven gear 128.

The driven gear 128 is connected to a second motion shaft 114. The second motion shaft 114 is arranged between the driven gear 128 of the second speed variation stage 118 and an output gear 142 of the drivetrain 100. Accordingly, the driven gear 128 of the second speed variation stage 118 is directly connected to the output gear 142 via the second motion shaft 114, such that the driven gear 128 and the output gear 142 rotate at the same speed, when in use.

The second motion shaft 114 may be a hollow shaft. The intermediate shaft 124 extends through the hollow second motion shaft 114. This reduces the amount of packaging space required by the drivetrain of Figure 5 and allows for the output gear 142 to be arranged centrally between the first speed variation stage 116 and the second speed variation stage 118 for direct connection to a differential 160 as will be described in more detail below.

The drivetrain 100 of Figure 5 comprises a wheel pair 130, such as the gear pair schematically represented in Figure 5. The wheel pair 130 comprises a driving gear 132 and a driven gear 134. The driving gear 132 is connected to the intermediate shaft 122 via a rotary bearing. The rotary bearing allows relative rotational movement of the driving gear 132 of the wheel pair 130 with respect to the intermediate shaft 124, when the second coupling device 140 is not engaged with the driving gear 132, e.g. in the inactive position of the second coupling device 140.

The driven gear 134 of the wheel pair 130 is connected to the driving gear 126 of the second speed variation stage 118 via a common shaft 136. The common shaft 136 is a hollow shaft and is rotatably connected to the first motion shaft 112 via a rotary bearing.

Accordingly, the common shaft 136 and the gears 126, 134 are freely rotatable relative to the first motion shaft 112 when the first coupling device 138 is in its inactive position. Similar to the embodiment in Figure 1, the embodiment of Figure 5 comprises a selector arrangement including a first coupling device 138 and a second coupling device 140. Both coupling devices 138, 140 comprise an inactive position shown in Figure 5, in which the coupling devices 138, 140 rotate freely with their respective shafts 112, 124. The first coupling device 138 comprises a (first) active position (Figures 8A, 8B) in which the first coupling device 138 is connected to the driving gear 126 of the second speed variation stage.

The second coupling device comprises a first (active) state (Figures 6A, 6B), in which the second coupling device 140 is connected to the driving gear 132 of the wheel pair 130. The second coupling device 140 further comprises a second (active) position (Figure 7A, 7B), in which the second coupling device 140 is connected to the driven gear 124 of the second speed variation stage 118.

With reference to Figures 6A to 8B, various modes of the selector arrangement leading to different gear settings of the drivetrain 100 will be explained in more detail. It should be noted that the functionality and overall speed ratio of the drivetrain 100 in the three modes of the selector arrangement are substantially the same as the functionality of the drivetrain 10. The main difference between the embodiment in Figure 5 and the embodiment in Figure 1 is that the drivetrain 100 is "folded-over", such that the second motion shaft 114 is arranged centrally of the drivetrain 100, i.e. between the first and second speed variation stages 116, 118. One of the main constructional differences between the embodiments of Figures 1 and 5 is the reversal of the position of the second speed variation stage 118 and the wheel pair 130.

Turning to Figure 6A and 6B, a first mode of the selector arrangement will be described in more detail. In the first mode of the selector arrangement, the first coupling device 138 is in its inactive position. The second coupling device 140 is in its first, active position, i.e. connected to the driving gear 132 of the wheel pair 130.

In this first mode of the selector arrangement, rotational energy of the first motion shaft 112 is transferred to the second motion shaft 114 via the two speed variation stages 116, 118 and the wheel pair 130. This is derivable from the arrows in Figure 6B. In particular, both motors 150, 152 drive the first motion shaft 112, which is permanently connected to the intermediate shaft 124 via the first speed variation stage 116. In other words, the intermediate shaft 124 will rotate at a speed different from the first motion shaft 112, when in use. Rotational energy of the intermediate shaft 124 is then transferred to the wheel pair 130 via the second coupling device 140, which is connected to the driving gear 132 of the wheel pair 130. The wheel pair 130 then transfers the rotational energy to the hollow common shaft 136. In the embodiment of Figures 5 to 8B, the speed ratio of the wheel pair 130 is around 1, such that the intermediate shaft 124 and the common shaft 136 rotate at substantially the same speed but in opposite directions.

The common shaft 136 connects the driven gear 134 of the wheel pair 130 with the driving gear 126 of the second speed variation stage 118. Therefore, rotational energy of the common shaft 136 is transferred to the second motion shaft 114 via the second speed variation stage 118. Accordingly, the second motion shaft 114 will rotate at a speed different to the speed of the common shaft 136.

The second motion shaft 114 connects the driven gear 128 of the second speed variation stage 118 to an output gear 142 of the drivetrain 100. Accordingly, the output gear 142 rotates at the same speed as the driven gear 128 of the second speed variation stage. The output gear 142 in this embodiment is connected to an input gear 162 of a differential 160 so as to distribute the drive torque between the left and right half axles, as is known in the art.

It follows from the above that, in the first mode of the selector arrangement of the embodiment shown in Figure 5, rotational energy of the first motion shaft 112 is transferred to the second motion shaft 114 via both the first and second speed variation stages 116, 118 as well as the wheel pair 130. If, comparable to the example presented with reference to the embodiment of Figure 1, the first speed variation stage is a reduction stage with a speed ratio of 1.6 and the second speed variation stage is a speed reduction stage with a speed reduction 2.8, then the overall speed ratio of the drivetrain in the first gear (i.e. the first mode of the selector arrangement) is 4.48.

Turning to Figures 7A and 7B, a second gear of the drivetrain 100 is described, in which the selector arrangement is set to a second mode. In the second mode of the selector arrangement, the first coupling device 138 is in its first (active) position, whereas the second coupling device 140 is in its inactive position.

In this second gear or the second mode of the selector arrangement, rotational energy of the first transmission shaft 112 is transferred to the second motion shaft 114 exclusively via the second speed variation stage 118. The first speed variation stage 116 and the wheel pair 130 are bypassed.

The arrows in Figure 7B show the transfer of the rotational energy through the drivetrain 100 in the second mode of the selector arrangement. Rotational energy provided by the first and second motors 150, 152 is transferred via the first motion shaft into the driving gear 126 of the second speed variation stage 118. This is because the first coupling device 138 rotatably connects the first motion shaft 112 with the driving gear 126 of the second speed variation stage 118, when the first coupling device 138 is in its first, active position shown in Figure 7B. The rotational energy is then transferred via the second speed variation stage 118 to the second motion shaft 114. Accordingly, the second motion shaft 114 rotates at a speed different to the first motion shaft 112, exclusively defined by the speed ratio of the second speed variation stage 118.

In the second gear of the drivetrain 100, the overall speed ratio is defined by the second speed variation stage 118. In the above example, this means an overall speed ratio of 2.8, which is lower than the first gear described with reference to Figures 6A and 6B.

Figure 8A and 8B show a third mode of the selector arrangement of the drivetrain shown in Figure 5. In the third mode of the selector arrangement (i.e. a third gear of the drivetrain), the first coupling device 138 is in its inactive position, whereas the second coupling device 140 is in its second (active) position. In its second position, the second coupling device 140 is connected to the driven gear of the second speed variation stage 118. In other words, rotational energy of the intermediate shaft 124 is directly transferred to the driven gear 128 of the second speed variation stage 118, and, thus, to the second motion shaft 118.

The functionality of the drivetrain 100 in its third mode shown in Figures 8A and 8B is substantially identical to the operation of the drivetrain 10 shown in Figure 1, in its third mode. In particular, rotational energy of the first motion shaft is transmitted to the second motion shaft 114 exclusively via the first speed variation stage 116, when the selector arrangement is in its third mode. This is also derivable from the arrows shown in Figure 8B. As represented, both motors frIl and fr12 drive the first motion shaft 112, which is permanently connected to the intermediate shaft 124 via the first speed reduction stage 116. The first motion shaft 112 and the intermediate shaft 124, therefore, rotate at a different speed, when in use.

In the second position of the second coupling device 140, the rotational energy of the intermediate shaft 124 is directly transferred to the second motion shaft 114 via the driven gear 128 of the second speed variation stage. It will be understood that the second speed variation stage 118 does not play any role in the transfer of the rotational energy in the third mode shown in Figures 8A and 8B. Rather, both the second speed variation stage 118 and the gear pair 130 are bypassed in the third mode of the selector arrangement. In the above example, the overall speed ratio of the drivetrain 100 in its third gear is equal to the speed ratio of the first speed variation stage, e.g. 1.6. Accordingly, the speed ratio in the third gear of the drivetrain 100 is lower than the speed ratio in the first gear described with reference to Figure 6A and 6B and lower than the speed ratio in the second gear described with reference to Figures 7A and 7B.

Figure 9 shows another embodiment of a drivetrain according to the present disclosure. The drivetrain 200 shown in Figure 9 is similar to the drivetrain 10 shown in the embodiment of Figure 1. Corresponding parts of the drivetrain 200 that relate to parts of the drivetrain 10 shown in Figure 1 are labelled with corresponding reference signs increased by "200".

The drivetrain 200 of the embodiment shown in Figure 9 comprises a first motion shaft 212 that is connectable to a first motor, such as electric motor 250. The drivetrain 200 also comprises a second motion shaft 214, which is shown as an output shaft of the drivetrain 200, similar to the embodiment in Figure 1. The drivetrain 200 may be most suitable for a central drive arrangement, similar to the embodiment of Figure 1.

The drivetrain 200 further comprises a first speed variation stage 216, a second speed variation stage 218 and a wheel pair 230. The first speed variation stage 216 comprises a driving gear 220 that is meshed with a driven gear 222. The driven gear 222 is permanently connected to an intermediate shaft 224.

The second speed variation stage 218 comprises a driving gear 226 in meshing contact with a driven gear 228. The driven gear 228 is permanently connected to the second motion shaft 214.

The wheel pair 230 comprises a driving gear 232 and a driven gear 234. The driving gear 232 is freely rotatable with respect to the intermediate shaft 224 via a rotational bearing, when a second coupling device 240 is in its inactive position. The driven gear 234 of the wheel pair 230 is connected to the driving gear 226 of the second speed variation stage 218 via a common shaft 236. The common shaft 236 is connected to the first motion shaft 212 via a rotational bearing and is freely rotatable with respect to the first motion shaft 212 when the first coupling device 238 is in its inactive position.

Rotational energy provided by the first motor 250 to the first motion shaft 212 may be transferred to the second motion shaft 214 exclusively via the first speed variation stage 216, or exclusively via the second speed variation stage 218, or via both speed variation stages together with the wheel pair 230, as will be described in more detail below.

Unlike the drivetrain 100 of Figure 1, the drivetrain 200 further comprises a third motion shaft 215. The third motion shaft 215 is connectable to a second electric motor 252. The first and third motion shaft 212, 215 may rotate relative to each other, and at different speeds as long as the first coupling device 238 is not in a second position as will be described in more detail below.

The third motion shaft 215 is permanently connected to the driving gear 220 of the first speed variation stage 216. Rotational energy provided by the second motor 252 via the third motion shaft 215 may be transferred to the second motion shaft 214 either exclusively via the first speed variation stage 216, or via both speed variation stages 216, 218 together with the wheel pair 230.

Another difference to the embodiment described in Figure 1 is that the first coupling device 238 comprises two active positions. The first active position of the first coupling device 238 is similar to the first position of the first coupling device 38 in Figure 1. In particular, in its first position (Figures 11A, 11B) the first coupling device 238 is connected to the driving gear 226 of the second speed variation stage 218 via the common shaft 236.

Accordingly, in its first active position, the first coupling device 238 directly connects the first motion shaft 212 to the driving gear 226 of the second speed variation stage 218. The first coupling device 238 of Figure 9 also comprises a second active position (e.g. Figures 10A, 10B). In the second active position, the first coupling device 238 is connected to the driving gear 220 of the first speed variation stage 216.

The second coupling device 240 comprises an inactive position (Figure 9), a first active position (Figures 10A, 10B) and a second active position (Figures 12A, 12B), which are substantially identical to the positions of the second coupling device 40, shown in Figure 1.

The embodiment shown in Figure 9 is a 7 mode drivetrain, meaning that the selector arrangement of the drivetrain comprises seven modes of operation. The seven modes of operation will be described in more detail with reference to Figures 10A to 16B.

Turning to Figures 10A and 10B, there is shown a first mode of operation of the selector arrangement of the drivetrain 200. In the first mode of the selector arrangement, the first coupling device 238 is in its second position, whereas the second coupling device 240 is in its first position. In other words, the first coupling device 238 acts to connect the first motion shaft 212 to the third motion shaft 215, such that the combined rotational energy of the first and second motor 250, 252 is provided to the intermediate shaft 224 via the first speed variation stage 216. This is also derivable from the arrows illustrated in Figure 10B.

Rotational energy of the intermediate shaft is then transferred to the wheel pair 230 via the second coupling device 240. The wheel pair 230 transfers the rotational energy to the common shaft 236, e.g. with no significant speed changes. A rotation of the driven gear 234 of the wheel pair 230 is then transferred to the driving gear 226 of the second speed variation stage 218 via the common shaft 236. Rotational energy of the driving gear 226 of the second speed variation stage 218 is then transferred to the driven gear 228 and ultimately to the second motion shaft 214.

In view of the above, rotational energy of the first and third motion shafts 212, 215 is transferred to the second motion shaft 214 via both speed variation stages 216, 218 as well as the gear pair 230, when the selector arrangement is its first mode of operation.

Figures 11A and 11B show a second mode of operation of the selector arrangement of the drivetrain 200. In this second mode, the first coupling device 238 is transferred into its inactive position, whereas the second coupling device 240 remains in its first position.

In the inactive position of the first coupling device 238, the first motion shaft 212 and thus also the first motor 250 are disconnected from the second motion shaft 214. It follows that rotational energy, in this second mode of the selector arrangement, is exclusively provided to the second motion shaft 214 by means of the second motor 252, i.e. via the third motion shaft 215.

In the second mode, rotational energy of the third motion shaft 215 (provided by the second motor 252) is transferred to the second motion shaft 214 similar to the first mode, i.e. via both speed variation stages 216, 218 and the wheel pair 230. In the above example, the rotational energy of the third motion shaft 215 is transferred to the second motion shaft at a speed ratio of 4.48.

The second mode may be particularly useful to increase efficiency when the power of only one of the motors is sufficient. The second mode may also be considered as an intermediate state that is used to switch between the first and third modes, i.e. when shifting the first coupling device 238 from its second position (see Fig. 10A) to its first position (see Fig. 12A).

Figures 12A and 12B show a third mode of operation of the selector arrangement of the drivetrain 200. In its third mode, the first coupling device 238 is in its first (active) position and the second coupling device 240 is also in its first position. In other words, the first coupling device 238 connects the first motion shaft 212 directly to the driven gear 234 of the wheel pair 230 and, thus, to the driving gear 226 of the second speed variation stage 218. It follows that the driving gear 226 of the second speed variation stage 218 rotates at the same speed as the first motion shaft 212, during the third mode of the selector arrangement.

In this third mode depicted in Figures 12A and 12B, the rotational energy provided by the first motor 250 is transferred to the second motion shaft 214 in a different way to the rotational energy provided by the second motor 252. Rotational energy provided by the first motor 250 via the first motion shaft 212, during the third mode of the selector arrangement, is transferred directly to the driving gear 226 of the second speed variation stage 218. The second speed variation stage 218 then transfers rotational energy from the first motion shaft 212 to the second motion shaft 214. Rotational energy of the first motion shaft 212 is thus transferred to the second motion shaft 214 exclusively via the second speed variation stage 218 in the third mode of the selector arrangement.

Rotational energy provided by the second motor 252 via the third motion shaft 215 is directly provided to the driving gear 220 of the first speed variation stage 216 and to the intermediate shaft 224, at a reduced speed, via the driven gear 222 of the first speed variation stage 216. Rotational energy of the intermediate shaft 224 is then transferred to the common shaft 236 via the wheel pair 230 that is connected to the intermediate shaft 224 by means of the second coupling device 240. The common shaft 236 drives the driving gear 226 of the second speed variation stage 218.

The second speed variation stage 218 ultimately provides rotational energy to the second output shaft at a reduced speed compared to the common shaft 236. Overall, the energy provided by the second motor 252 via the third motion shaft 215 is transferred to the second motion shaft 214 via both speed variation stages 216, 218 and the wheel pair 230.

In the third mode of the selector arrangement schematically represented in Figures 12A and 12B, the rotational energy provided by the first and second motors 250, 252 are transferred to the second motion shaft 214 at different speed ratios. In particular, the rotational energy of the first motor 250 is transferred at the speed ratio of the second speed variation stage 218, whereas the rotational energy of the second motor 252 is transferred via the speed ratio of both speed variation stages together. In the above example, the speed ratio between the first motion shaft 212 and the second motion shaft 214 is 2.8, whereas the speed ratio between the third motion shaft 215 and the second motion shaft 214 is 4.48.

Figures 13A and 13B show a fourth mode of operation of the selector arrangement of the drivetrain 200. In this fourth mode, the first coupling device 238 is in its first position, whereas the second coupling device 240 is in its inactive position. Similar to the third mode, rotational energy of the first motion shaft 212 is transferred to the second motion shaft 214 exclusively via the second speed variation stage 218 (see Fig. 13B). The third motion shaft 215 is, however, disconnected form the second motion shaft 214 in the fourth mode.

Rotational energy, in this fourth mode of the selector arrangement, is exclusively provided to the second motion shaft 214 by means of the first motor 250, i.e. via the first motion shaft 212. In the above example, rotational energy of the first motion shaft 212 is transferred to the second motion shaft 214 at an overall speed ratio of 2.8 in the fourth mode of the selector arrangement.

The fourth mode may be useful to increase efficiency when the power of only one of the motors is required. The fourth mode may be considered an intermediate state that is used to switch between the third and fifth modes, i.e. when shifting the second coupling device 240 from its first position (see Fig. 12A) to its second position (see Fig. 14A). A fifth mode of operation of the selector arrangement is shown in Figures 14A and 14B. In the fifth mode of the selector arrangement, the first coupling device 238 is in its first position, whereas the second coupling device 240 is in its second position. Again, this fifth mode of the selector arrangement results in a transfer of the rotational energy of the first and second motors 250, 252 via different stages of the drivetrain 200.

Referring to Figure 14B, the transfer of the rotational energy provided by the first and second motors 250, 252 is illustrated with schematic arrows. As set out in detail before, in the first position of the first coupling device 238, the first motion shaft 212 is directly connected to the driven gear 234 of the wheel pair 230, and, thus, to the driving gear 226 of the second speed variation stage 218. It follows that rotational energy provided by the first motor via the first motion shaft 212 is transferred to the second motion shaft exclusively via the second speed variation stage 218.

In the fifth mode of the selector arrangement, the intermediate shaft 224 is directly connected to the second motion shaft 214, such that both shafts 224, 214 rotate at the same speed. It follows that rotational energy provided by the second motor 252 via the third motion shaft 215 is transferred via the first speed variation stage 216 to the intermediate shaft 224 at a different (e.g. reduced) speed. The speed of the intermediate shaft 224, in the fifth mode of the selector arrangement, is equal to the speed of the second motion shaft 214. Accordingly, in the fifth mode of the selector arrangement, rotational energy provided by the second motor 252 via the third motion shaft 215 is transferred to the second motion shaft 214 exclusively via the first speed variation stage 216.

In view of the above, the rotational energy of the first and second motors 250, 252 are transferred via different routes when the selector arrangement is operating in its fifth mode. In particular, the rotational energy of the first motor 250 provided to the first motion shaft 212 is transferred to the second motion shaft 214 exclusively via the second speed variation stage 218, whereas rotational energy provided by the second motor 252 via the third motion shaft 215 is transferred to the second motion shaft 214 exclusively via the first speed variation stage 216.

In the above example, the energy provided by the first electric motor 250 is transferred to the second motion shaft 214 at an overall speed ratio of 2.8, whereas the rotational energy of the second motor 252 is provided to the second motion shaft 214 at an overall speed ratio of 1.6.

Figures 15A and 15B show a sixth mode of operation of the selector arrangement of the drivetrain 200. In this sixth mode, the first motion shaft 212 and thus the first motor 250 is, once again, disconnected from the second motion shaft 214 (see also second mode). To this end, the first coupling device 238 is transferred into its inactive state, whereas the second coupling device 240 remains in its second position. Rotational energy, in this second mode of the selector arrangement, is exclusively provided to the second motion shaft 214 through the second motor 252, i.e. via the third motion shaft 215.

In the sixth mode, rotational energy of the third motion shaft 215 (provided by the second motor 252) is transferred to the second motion shaft 214 similar to the fifth mode, i.e. exclusively via the first speed variation stage 216. In the above example, the overall speed ratio of the sixth mode is thus 1.6.

The sixth mode may be particularly useful to increase efficiency when the power of only one of the motors is sufficient. The sixth mode may also be considered as an intermediate state that is used to switch between the fifth and seventh modes, i.e. when shifting the first coupling device 238 from its first position (see Fig. 14A) to its second position (see Fig. 16A).

A seventh mode of the selector arrangement is illustrated in Figures 16A and 16B. In this seventh mode of the selector arrangement, the first and second coupling devices 238, 240 are in their respective second (active) positions. In other words, the first coupling device 238 is connected to the driving gear 220 of the first speed variation stage 216 and, thus, combines the rotational energy provided by the first and second motors 250, 252 via the first and third motion shafts 212, 215 respectively. The second coupling device 240 is connected to the driven gear 228 of the second speed variation stage 218, such that the intermediate shaft 224 and the second motion shaft 214 are directly connected and rotate at the same speed, when in use.

In this seventh mode of the selector arrangement, the rotational energy provided by the first and second motors 250, 252 are transferred to the second motion shaft 214 via the same route through the drivetrain 200. In particular, both the rotational energy of the first motion shaft 212 and the third motion shaft 215 are provided to the intermediate shaft 224 via the first speed variation stage 216. The rotational energy of the intermediate shaft 224 is then directly transferred to the second motion shaft 214 via the second coupling device 240, at the same speed.

In the seventh mode shown in Figures 16A and 16B, the rotational energy of both motors is transferred from the first and third motion shafts 212, 215 to the second motion shaft 214 exclusively via the first speed variation stage. In the above example, the overall speed ratio of the drivetrain 200 in this seventh mode is, thus, 1.6.

Figure 17 schematically illustrates another embodiment of the drivetrain according to the present invention. The functionality of the drivetrain 300 shown in Figure 17 is substantially identical to the functionality of the drivetrain 200 shown in Figure 9. Parts of the drivetrain 300 that have the same functionality as parts of the drivetrain 200 are labelled with corresponding reference signs increased by "100".

The drivetrain 300 is a "folded-over" version of the drivetrain 200 of Figure 9. Reference is also made to the "folded-over" version shown in Figure 5. The drivetrain 300 is suitable as for an axle drive assembly similar to the embodiment described with reference to Figure 5. The drivetrain 300 is a 7 mode powershift arrangement similar to the drivetrain 200 of Figure 9.

The drivetrain 300 of the embodiment shown in Figure 17 comprises a first motion shaft 312 that is connectable to a first motor, such as electric motor 350. The drivetrain 300 also comprises a second motion shaft 314. Similar to the second embodiment of Figure 5, the second motion shaft 314 that is not constructed as an output shaft. Rather, the second motion shaft 314 is a hollow shaft that is connected to an output gear 342. The output gear 342, in turn, is connectable to a differential 360. The embodiment of Figure 17 is suitable as an axle drivetrain, in which the electric motor or motors 350, 352 and the drivetrain 300 are directly connected to the axle/axles of the vehicle, such as an HGV.

The drivetrain 300 further comprises a first speed variation stage 316, a second speed variation stage 318 and a wheel pair 330. The first speed variation stage 316 comprises a driving gear 320 that is meshed with a driven gear 322. The driven gear 322 is permanently connected to an intermediate shaft 324.

The second speed variation stage 318 comprises a driving gear 326 in meshing contact with a driven gear 328. The driven gear 328 is permanently connected to the second motion shaft 314.

The wheel pair 330 comprises a driving gear 332 and a driven gear 334. The driving gear 332 is freely rotatable with respect to the intermediate shaft 324 via a rotational bearing, when a second coupling device 340 is in its inactive position. The driven gear 334 of the wheel pair 330 is connected to the driving gear 326 of the second speed variation stage 318 via a common shaft 336. The common shaft 336 is connected to the first motion shaft 312 via a rotational bearing and is freely rotatable with respect to the first motion shaft 312 when the first coupling device 338 is in its inactive position.

Rotational energy provided by the first motor 350 to the first motion shaft 312 may be transferred to the second motion shaft 314 exclusively via the first speed variation stage 316, or exclusively via the second speed variation stage 318, or via both speed variation stages together with the wheel pair 330.

The drivetrain 300 further comprises a third motion shaft 315. The third motion shaft 315 is connectable to a second electric motor 352. The first and third motion shaft 312, 315 may rotate relative to each other, and at different speeds as long as the first coupling device 338 is not in a second position.

The third motion shaft 315 is permanently connected to the driving gear 320 of the first speed variation stage 316. Rotational energy provided by the second motor 352 via the third motion shaft 315 may be transferred to the second motion shaft 314 either exclusively via the first speed variation stage 316, or via both speed variation stages 316, 318 together with the wheel pair 330.

The first coupling device 338 comprises two active positions. In its first active position the first coupling device 338 is connected to the driving gear 326 of the second speed variation stage 318.

The first coupling device 338 of Figure 17 also comprises a second active position. In the second active position, the first coupling device 338 is connected to the driving gear 320 of the first speed variation stage 316.

The second coupling device 340 comprises an inactive position, a first active position and a second active position.

The drivetrain 300 comprises a selector arrangement with seven modes of operation that are identical to the seven modes of operation of the drivetrain 200 shown in Figure 9. A first mode of operation is shown in Figures 18A and 18B and is equivalent (yet "folded over") to the first mode shown in Figures 10A and 10B. A third mode of operation is shown in Figures 19A and 19B and is equivalent to the third mode shown in Figures 12A and 12B.

A fifth mode of operation is shown in Figures 20A and 20B and is equivalent to the fifth mode shown in Figures 14A and 14B. A seventh mode of operation is shown in Figures 21A and 21B and is equivalent to the seventh mode shown in Figures 16A and 16B.

As will be appreciated, the drivetrain 300 of Figure 17 also includes single motor drive modes, such as the second, fourth, and sixth modes of the selector arrangement described with reference to Figures 11A, 11B, 13A, 13B, 15A, and 15B above. The single motor drive modes are not shown in the drawings but will be achieved by transferring the first or second coupling device 238, 240 into their inactive position as has been described in detail above.

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and

parameters of the disclosure.

Although in the specific embodiments described above, reference was made to the use of gear pairs, it will be appreciated that any other means for speed variation, such as belt, chain, or friction drives are equally applicable. Similarly, the present disclosure is not limited to the specific speed ratios disclosed. Rather, any suitable speed ratio may be applied for any of the speed variation stages/gear pairs disclosed. In some embodiments, some or all of the speed ratios may also be equal to or below 1 (overdrive). Finally, it should be understood that the selector arrangement is not limited to the particular coupling devices, i.e. the dog clutches, described. Any other coupling arrangement, such as friction clutches and synchronisers, that enables selective connections between one or more of the shafts of the drive train may be utilised to enable the various modes described above.

Claims

CLAIMS1. Drivetrain for an electric propulsion system, the drivetrain comprising: a first motion shaft for connection to a first electric motor; a second motion shaft; at least two speed variation stages arranged between the first and second motion shafts; a selector arrangement for selectively utilising one or more of the at least two speed variation stages, said selector arrangement comprising: a first mode, in which rotational energy of the first motion shaft is transmitted to the second motion shaft via the two or more speed variation stages, when in use; and a second mode, in which rotational energy of the first motion shaft is transmitted to the second motion shaft exclusively via a first speed variation stage of the at least two speed variation stages, when in use.
2. The drivetrain of Claim 1, wherein the selector arrangement comprises a third mode, in which rotation of the first motion shaft is transmitted to the second motion shaft exclusively via a second speed variation stage of the at least two speed variation stages, when in use.
3. The drivetrain of Claim 2, wherein the first speed variation stage comprises a speed ratio that is different from, and preferably lower than, a speed ratio of the second speed variation stage.
4. The drivetrain of any one of Claims 1 to 3, comprising a wheel pair arranged between the first and second motion shafts, wherein, in the first mode, rotation of the first motion shaft is transmitted to the second motion shaft via the two or more speed variation stages and the wheel pair.
5. The drivetrain of Claim 4, wherein a driven wheel of the wheel pair is arranged on a common shaft with a driving wheel of the second speed variation stage.
6. The drivetrain of Claim 5, wherein the first motion shaft is at least partly received within an opening of the common shaft.
7. The drivetrain of any one of Claims 1 to 6, wherein the selector arrangement comprises a first coupling device, having a first position for selectively connecting the first motion shaft to the second speed variation stage.
8. The drivetrain of Claim 7, wherein in the third mode of the selector arrangement, the first coupling device is in its first position.
9. The drivetrain of any one of Claims 1 to 8, comprising an intermediate shaft arranged between the first motion shaft and the second motion shaft.
10. The drivetrain of Claim 9, when dependent on Claim 4, wherein the selector arrangement comprises a second coupling device having a first position for connecting the intermediate shaft with the wheel pair.
11. The drivetrain of Claim 10, wherein, in the first mode of the selector arrangement, the second coupling device is in its first position.
12. The drivetrain of Claim 10 or 11, wherein the second coupling device has a second position for connecting the intermediate shaft to the second motion shaft.
13. The drivetrain of Claim 12, wherein, in the second mode of the selector arrangement, the second coupling device is in its second position.
14. The drivetrain of any one of Claims 1 to 13, wherein the first motion shaft is permanently connected to the intermediate shaft via the first speed variation stage.
15. The drivetrain of any one of Claims 1 to 13, wherein the first motion shaft is selectively connectable to the first speed variation stage via the selector arrangement.
16. The drivetrain of Claim 15, when dependent on claim 6, wherein the first coupling device has a second position for connecting the first motion shaft to the first speed variation stage.
17. The drivetrain of Claim 16, wherein, in the first and second mode of the selector arrangement, the first coupling device is in its second position.
18. The drivetrain of any one of Claims 1 to 17, wherein the first speed variation stage comprises a first gear pair, and/or wherein the second speed variation stage comprises a second gear pair.
19. The drivetrain of any one of Claims 1 to 18, wherein the intermediate shaft at least partially extends through the second motion shaft.
20. The drivetrain of Claim of any one of Claims 1 to 18, comprising a third motion shaft for connection to a second electric motor.
21. The drivetrain of Claim 20, wherein the third motion shaft is selectively connectable to the first motion shaft.
22. The drivetrain of Claim 20 or 21, wherein the third motion shaft is permanently connected to the first speed variation stage.
23. The drivetrain of any one of Claims 20 to 22, when dependent on Claim 11, wherein the first motion shaft is connected to the third motion shaft, when the first coupling device is in its second position.
24. The drivetrain of any one of Claims 1 to 23, wherein the first and/or the second speed variation stage comprises one of a gear pair, a pair of pulleys, a pair of sprockets, or a pair of friction wheels.
25. An electric powertrain comprising: an electric motor; a drivetrain of any one of Claims 1 to 24; a differential; and a wheel axle, wherein the electric motor is connected or connectable to the first motion shaft of the drivetrain and the second motion shaft of the drivetrain is connected or connectable to the differential.
26. A method of controlling a drivetrain for an electric propulsion system, the drivetrain comprising: a first motion shaft for connection to a first electric motor; a second motion shaft; at least two speed variation stages arranged between the first and second motion shafts; wherein the method comprises: transmitting power between the first and second motion shafts via both speed variation stages, to achieve a first speed ratio; transmitting power between the first and second motion shafts exclusively via the first speed variation stage, to achieve a second speed ratio.