Patent Description:
The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as passenger cars.

In the field of the transport industry, there is a need to deal with emissions regulation requirements which are becoming more and more demanding, and cities suffering from a high volume of traffic start to forbid internal combustion engine vehicles in their city centers.

Vehicles and more particularly electric/hybrid vehicles such as electric/hybrid buses and trucks typically use an electric motor for running one or more wheels through a drive wheel shaft (or a drive wheel axle). Typically, an axle includes two drive wheel shafts, one for each driving wheel. Most of the electric motors are, however, designed to run at high-speed/low-torque condition as compared with known internal combustion engines running at high-torque/low-speed condition.

Fulfilling the torque demand at the wheel(s) of a vehicle is important for startability of a vehicle in different conditions, e.g. in slopes. There is thus need for having a wide-gear reduction ratio through a gearbox/powertrain assembly (which can be typically between e.g. <NUM>:<NUM>-<NUM>:<NUM>). Such a wide-gear reduction ratio is commonly fulfilled via a gearbox with several reduction stages which consequently needs more space and leaves a limited volume of space for other parts (e.g. space needed for batteries, body/aerodynamic devices, suspension assemblies) of a vehicle. Moreover, the commonly known gearboxes are also heavy which further reduces the vehicle's moving capabilities and limits the autonomy of the vehicle. A problem thus arises when a gearbox/transmission assembly is implemented into an electric/hybrid vehicle. Unlike the standard transmission systems for Gasoline/diesel engines where the transmission can be positioned in different manners and connected to the drive shaft through a shaft assembly (e.g. rear-drive trucks/buses), in case of the electric/hybrid vehicles, there is a need to accommodate an electric motor and the gearbox in the vicinity of the drive wheel axle. Typically, if the electric motor distributes power to the drive wheel axle, a differential assembly is usually needed to distribute the different power/torque to each wheel through the associated drive wheel shaft. On the other hand, in case the electric motor is connected and distributes the power directly to the drive wheel shaft (even through a gearbox), no differential assembly is usually needed but there is a requirement to have one electric motor for each drive wheel shaft (at least two electric motors then).

To follow the above configuration, the space required for accommodation a gearbox/transmission assembly in an electric/hybrid vehicle is further limited by a suspension assembly.

An example of prior art is, for instance, <CIT> disclosing a transmission system for an electric vehicle. The transmission system is defined by an input shaft engaged to a drive motor and an output shaft engaged to a differential. Each of the input and output shafts has a different rotational axis and the system as such lacking compactness and is demanding for a limited volume of space available in an electric vehicle.

Therefore, as further described in the detailed description of the invention, the inventors have endeavored to find a solution for providing a small/compact gearbox which is also light as compared to the known gearboxes/transmission assemblies.

It is to these drawbacks that the invention intends to remedy.

In this respect, the invention is defined in claim <NUM>.

Thanks to this arrangement, the output gear and the primary shaft rotate around the same axis. Therefore, it is possible to have a compact and small gearbox suitable to vehicles where the available space is limited due to strict spacing restrictions (e.g. an electric vehicle - set of batteries, suspension assembly). The compactness of the gearbox is achieved by the output gear which is disposed on the primary shaft and can rotate at either the same speed or a different rotational speed as the primary shaft - depending on the position of the gear shift means. Therefore, the above arrangement enables to avoid having two different shafts for transmitting power in and out the gearbox.

Furthermore, it is possible to provide two or more gear stages through additional transmission gears and auxiliary transmission gears, while the output gear remains substantially at the same position with respect to the auxiliary shaft. That is, the distance between the primary shaft and the auxiliary shaft remains unchanged when one or more additional gear stages are added.

This compact solution incorporating at least two stages offers satisfactory requirements ensuring different performances (high-torque/low-speed demand during start conditions and/or high-speed/low-torque demand during cruising conditions) resulting from different drive modes (gear current selection) of a vehicle.

Advantageously, the gearbox includes additional features, which can be considered alone or in combination, and among which:.

The invention also concerns a powertrain assembly for a vehicle comprising a gearbox as defined above, at least one electric motor being configured to be engaged to the primary input gear of the gearbox, a differential gear having a differential ring wheel, said differential ring wheel being engaged to the output gear of the gearbox and a drive wheel axle being coupled to the differential gear.

Eventually, the invention relates to a vehicle, comprising a powertrain assembly as defined above.

Preferably, the vehicle is a heavy-duty vehicle, such as a truck, a bus or a construction machine. It can be one of an electric vehicle, a hybrid vehicle or a trailer to be towed.

Other features and advantages of the invention appear from the following detailed description of some of its embodiments, given by way of non-limiting example, and with reference to the accompanying drawings, in which:.

In the figures, the same references denote identical or similar elements, unless stated otherwise.

<FIG> shows a cross-sectional view (longitudinal section) of the gearbox <NUM> of one embodiment of the present disclosure. The gearbox <NUM> comprises a primary shaft <NUM> and an auxiliary shaft <NUM> (a. a "countershaft"). The primary shaft <NUM> is configured to transmit the power in the gearbox <NUM>.

The primary shaft <NUM> is configured to rotate around a first axis A1 and the auxiliary shaft <NUM> is configured to rotate around a second axis A2. The first axis A1 and the second axis A2 are configured as being distant from each other. That is, the first axis A1 and the second axis A2 are distant (being spaced) from each other in a plane, which is substantially vertical in one given example. In the example, the first axis A1 and the second axis A2 are parallel to each other.

Advantageously, a primary input ring <NUM> is fixed in rotation with the primary shaft <NUM>. In the example of the figures, the primary input gear <NUM> is mounted on the primary shaft <NUM> (i.e. around the primary shaft <NUM>) and is therefore rigidly fixed to the primary shaft <NUM> (forming then two pieces). Alternatively, the primary input ring <NUM> could be also integral with the primary shaft <NUM> (forming then one piece). The primary input ring <NUM> is then arranged so that the power is transmitted to the primary shaft <NUM> through a radial direction (See arrow "IN" on <FIG> and <FIG>) with respect to axis A1.

The rotational speed of the primary shaft <NUM> is the same than that of the primary input ring <NUM>.

Preferably, the primary input ring <NUM> is configured to be driven by an electric motor (not shown) by means of rotational engagement between the primary input ring <NUM> and a rotor of the electric motor. In a variant not shown, another type of motor, such as an ICE, could be used as the power source driving the gearbox <NUM>. Preferably, the electric motor is a DC motor, for example a BLDC motor (brushless direct current motor).

Advantageously, there is a ratio of reduction between the rotating shaft of the motor (whatever it is) and the primary shaft <NUM>, meaning that the rotating shaft of the motor is not directly coupled with the primary shaft <NUM>.

The primary input ring <NUM> is optional as a coupling (not shown) could be used to connect one longitudinal end of the primary shaft <NUM> to the longitudinal end of a driving shaft, such as a rotating shaft of a motor (e.g. rotor or camshaft). For example, a keyed joint or a Cardan joint could be used to connect the primary shaft to the driving shaft. This means that, in this variant not shown, the power could be transmitted to the primary shaft <NUM> through the axial direction (i.e. along axis A1). This also means that, in one embodiment, there is no speed reduction between the rotating shaft of the motor (whatever it is) and the primary shaft <NUM>.

In the example, the primary input ring <NUM> is a gear element (or pinion), meaning that it meshes with another ring gear (not shown). Among these two meshing gears, the primary input gear <NUM> is the driven gear, while said other ring gear is the driving gear. Alternatively, ring <NUM> could also be a pulley connected to a belt (pulley-belt system) or a sprocket connected to a chain (roller chain system). This means that ring <NUM> does not necessarily includes external teeth.

A distribution gear <NUM> is fixed in rotation with the primary shaft <NUM>. In the example, the distribution gear <NUM> is integral with the primary shaft <NUM> (forming then one piece). However, in an alternative embodiment (not shown), the distribution gear <NUM> could be distinct from the primary shaft <NUM> (forming then two pieces). In this case, the distribution gear <NUM> would be arranged around the shaft <NUM> and rigidly fixed (or secured) to shaft <NUM>.

The distribution gear <NUM> is configured to transfer a power from the primary shaft <NUM> to either an output gear <NUM> (for outputting the power out of the gearbox <NUM>) or to a transmission gear <NUM>.

The output gear <NUM> is configured to transmit the power out of the gearbox <NUM>. The output gear <NUM> is independently and rotationally disposed around the primary shaft <NUM> such that the output gear <NUM> rotates around the same first axis A1 as the primary shaft <NUM>. The output gear <NUM> can freely rotate around the primary shaft <NUM>. The rotational speed of the output gear <NUM> can be the same than that of the primary shaft <NUM> or different, depending on the selected drive mode (e.g. neutral, <NUM>st gear, <NUM>nd gear, etc.) In various embodiments, the output gear <NUM> can be engaged to a differential assembly (<NUM> - e.g. a differential ring wheel) for transmitting the power to one, two or several drive wheel axles T, depending on the type of vehicle.

In the example, and as shown on <FIG>, the vehicle <NUM> is a truck. Alternatively, it can be a bus or a construction machine.

In operation, the primary input gear <NUM> and the output gear <NUM> rotate around the same axis, that is the first axis A1 as the output gear <NUM> is disposed on the primary shaft <NUM>. Therefore, it is possible to have a compact and small gearbox applicable to vehicles where the required space is limited due to strict spacing restrictions (e.g. an electric vehicle - set of batteries, suspension assembly, etc.).

Preferably, the output gear <NUM> is mounted around the primary shaft <NUM> via at least an output roller bearing, preferably two output roller bearings <NUM> and <NUM>. Such configuration enables the output gear <NUM> rotating around the same first axis A1 as the primary shaft <NUM>. The rotational speed of the output gear <NUM> may be the same or can differ compared to the rotational speed of the primary shaft <NUM>. The variable rotational speed of the output gear <NUM> around the primary shaft <NUM> is achieved by the at least output roller bearing (<NUM>, <NUM>) which is capable to withstand high torque transmission, in particular during the start of the vehicle. The reliability and lifetime of the gearbox are thus improved, and maintenance needs are also minimized.

Advantageously, the transmission gear <NUM> is configured to rotate around the first axis A1 and is disposed on the primary shaft <NUM>.

In the example, the transmission gear <NUM> can freely rotate (i.e. is free to rotate) around the primary shaft <NUM> (and inversely).

The transmission gear <NUM> can have either the same, or a different rotational speed than that of the primary shaft <NUM>, depending on the selected gear ratio.

Preferably, the transmission gear <NUM> is mounted around the primary shaft <NUM> via at least one roller bearing, preferably a needle bearing <NUM>. This needle bearing <NUM>, disposed between the transmission gear <NUM> and the primary shaft <NUM>, provides enhanced space limitation since needle bearing <NUM> requires less space than other known types of bearings and, furthermore, provides enough strength to withstand the speed/torque demand of the gearbox <NUM>.

In various embodiments, the number of the transmission gear <NUM> can differ, depending on a number of gear stages disposed within the gearbox <NUM>. <FIG> shows the embodiment with one transmission gear <NUM>. An example of another embodiment showing more gear stages can be seen in <FIG> and will be explained later (showing a second distribution gear <NUM> and a second transmission gear <NUM>).

Preferably, gearbox <NUM> also includes an auxiliary output gear <NUM>. Said auxiliary output gear <NUM> is preferably fixed in rotation with the auxiliary shaft <NUM>. In the example of the figures, the auxiliary output gear <NUM> is mounted on the auxiliary shaft <NUM> (i.e. around the auxiliary shaft <NUM>) and is therefore rigidly fixed to the auxiliary shaft <NUM> (forming then two pieces). Alternatively, the auxiliary output gear <NUM> could be also integral with the auxiliary shaft <NUM> (forming then one piece).

Besides, gearbox <NUM> also includes an auxiliary transmission gear <NUM>. Said auxiliary transmission gear <NUM> is, in the example, fixed in rotation with the auxiliary shaft <NUM>. In the example of the figures, the auxiliary transmission gear <NUM> is mounted on the auxiliary shaft <NUM> (i.e. around the auxiliary shaft <NUM>) and is therefore rigidly fixed to the auxiliary shaft <NUM> (forming then two pieces). Alternatively, the auxiliary transmission gear <NUM> could be also integral with the auxiliary shaft <NUM> (forming then one piece).

Advantageously, the auxiliary transmission gear <NUM> is engaged to the transmission gear <NUM>. As stated above, in various embodiments having a different number of the transmission gears <NUM>, the number of the auxiliary transmission gear <NUM> can also differ (e.g. the embodiment of <FIG>). The auxiliary transmission gear <NUM> and the auxiliary output gear <NUM> rotate around the second axis A2 at the same speed as the auxiliary shaft <NUM>.

Alternatively, in another embodiment not shown in the Figures, the auxiliary shaft <NUM> can be rigidly fixed within the gearbox <NUM> (e.g. to a gearbox casing <NUM>). In other words, the shaft <NUM> can be non-rotating (fixed). In such configuration, the auxiliary transmission gear <NUM> and the auxiliary output gear <NUM> can be rotatably mounted (i.e. are free to rotate) around the rigidly fixed auxiliary shaft <NUM>, via roller bearings.

Therefore, the auxiliary transmission gear <NUM> and the auxiliary output gear <NUM> are either fixed in rotation with shaft <NUM> or free to rotate relative to shaft <NUM>.

The gearbox <NUM> further comprises a gear shift system <NUM>. The gear shift system <NUM> is configured to be slidable along the axis A1 (axially) between at least two positions. The two positions can be defined as different engagement configurations between the distribution gear <NUM> of the primary shaft <NUM> and either the output gear <NUM> or the at least one transmission gear <NUM>.

The first configuration can be seen in <FIG>, where the gear shift system <NUM> is shifted from an initial position (dashed line) to the left to rotatably engage the distribution gear <NUM> and the output gear <NUM>. In this first configuration, the rotational speed of the output gear <NUM> is the same as the rotational speed of the distribution gear <NUM> of the primary shaft <NUM>. The power in the first configuration is distributed directly from the primary shaft <NUM> (connected to the electric motor <NUM>) to the output gear <NUM>. The power of the electric motor (not shown) is thus transmitted radially through the primary input gear <NUM> to the primary shaft <NUM> and then transmitted axially through the distribution gear <NUM> directly to the output gear <NUM> and then to the differential assembly (e.g. to the differential ring wheel <NUM>). The described transmission of power is depicted in <FIG> in dashed-dotted line which follows the transmission of power as follows: (IN) electric motor (not shown) -> primary input gear <NUM> -> primary shaft <NUM> - >distribution gear <NUM> - > gear shift system <NUM> -> output gear <NUM> - > OUT (differential assembly).

In the first configuration of the gear shift system <NUM> as described above, the rotational speed of the output gear <NUM> is the same as rotational speed of the primary shaft <NUM>. Typically, such configuration can be selected in cruise conditions (high-speed/low-torque).

The second configuration is depicted in <FIG> and shows the rotational engagement of the distribution gear <NUM> and the transmission gear <NUM>. As shown in <FIG>, the gear shift system <NUM> is shifted from an initial position (dashed line) to the right to rotatably engage the distribution gear <NUM> and the transmission gear <NUM>. In this so-called second configuration, the rotational speed of the transmission gear <NUM> is the same as the rotational speed of the distribution gear <NUM>. The power in the second configuration is distributed indirectly from the primary shaft <NUM> (connected to the electric motor) to the output gear <NUM>, through the auxiliary shaft <NUM>.

The power of the electric motor (not shown) is thus transmitted radially through the primary input gear <NUM> to the primary shaft <NUM>, then axially to the transmission gear <NUM> (through the distribution gear <NUM> and via the gear shift system <NUM>) and then, the power is distributed from the auxiliary transmission gear <NUM> (rotatably engaged to the transmission gear <NUM>) to the auxiliary output gear <NUM> via the auxiliary shaft <NUM>. Finally, the power is transmitted from the auxiliary output gear <NUM> to the output gear <NUM> and then radially to the differential assembly (e.g. to the differential ring wheel <NUM>). The described transmission of power is depicted in <FIG> in dashed-dotted line which follows the transmission of power as follows: (IN) electric motor (not shown) -> primary input gear <NUM> -> primary shaft <NUM> -> distribution gear <NUM> -> gear shift system <NUM> -> transmission gear <NUM> -> auxiliary transmission gear <NUM> -> auxiliary shaft <NUM> -> auxiliary output gear <NUM> -> output gear <NUM> -> OUT (differential assembly).

In the second configuration of the gear shift system <NUM> as described above, the rotational speed of the output gear <NUM> is reduced compared to the rotational speed of the primary shaft <NUM> through the auxiliary shaft <NUM>. Such configuration can be selected in high-torque/low-speed conditions.

Additionally, a gear ratio can be defined as the ratio (or quotient) between the rotational speed of the primary input gear <NUM> and the rotational speed of the output gear <NUM>. In the first configuration of the gear shift system <NUM>, i.e. when there is a direct engagement between the distribution gear <NUM> and the output gear <NUM>, the gear ratio is equal to a first gear ratio, which is <NUM>:<NUM>.

Further, the second configuration of the gear shift system <NUM> defines the indirect engagement between the distribution gear <NUM> and the output gear <NUM> through the auxiliary shaft <NUM>. In this second configuration, the gear ratio is equal to a second gear ratio.

Advantageously, the second gear ratio (indirect engagement) is higher than the first gear ratio (direct engagement).

However, in an alternative embodiment, the second gear ratio could be lower than the first gear ratio. This means that, instead of being reduced, the rotational speed of the primary input gear is amplified (overdrive).

Optionally, the gear shift system <NUM> can be further configured to be positioned only in engagement with the distribution gear <NUM>. In such configuration, the gear shift system <NUM> does not have any engagement configuration with either the output gear <NUM> or with the transmission gear <NUM>. This configuration can be defined as a neutral position (e.g. a first neutral position with respect to further gear stages defined in <FIG>). In the (first) neutral position, the gear shift system <NUM> is configured to transmit no power between the primary input gear <NUM> and the output gear <NUM> since no physical engagement between these gears (<NUM>, <NUM>, <NUM>) is provided. The (first) neutral position can represent a third position of the gear shift system <NUM>, as an additional option to the direct (the first configuration) and indirect (the second configuration) engagements. The (first) neutral position of the gear shift system <NUM> can provide free movement of a vehicle, such as a free movement of the drive wheel shafts/axle for towing or servicing a vehicle/trailer. Further, with respect to <FIG> and <FIG>, the (first) neutral position of the gear shift system <NUM> is shown in the dashed line where the position of the gear shift system <NUM> corresponds to the position of the distribution gear <NUM>.

Additionally, the gear shift system <NUM> can be a type of clutch sleeve (a. a "shift sleeve") or any suitable type of dog clutch for performing gear change in the gearbox <NUM>. As known per se, thus not detailed therein, this type of gear shift system / dog clutch can be controlled by a control fork (<NUM> - partially visible on <FIG>).

Further, the gearbox <NUM> comprises a gearbox casing <NUM>. The gearbox casing <NUM> can be any type of casing/housing for enclosing the gearbox components. Typically, the gearbox casing <NUM> comprises two or more parts including the main casing component and a casing cover(s) (<NUM> - <FIG> / <FIG>).

As further shown in <FIG> and <FIG>, the primary shaft <NUM> extends longitudinally between a first axial end <NUM> and a second axial end <NUM>. Both axial ends (<NUM>, <NUM>) of the primary shaft <NUM> are rotationally mounted within the gearbox casing <NUM>. The mounting can be provided via a first primary roller bearing <NUM> arranged at the first axial end <NUM>, and via a second primary roller bearing <NUM> arranged at the second axial end <NUM>. The roller bearings (<NUM>, <NUM>), disposed between the gearbox casing <NUM> and the primary shaft <NUM> at both axial ends (<NUM>, <NUM>), help to withstand high torque values and to minimize wear of the primary shaft <NUM>.

The auxiliary shaft <NUM> extends longitudinally between a first auxiliary axial end <NUM> and a second auxiliary axial end <NUM>. Both auxiliary axial ends (<NUM>, <NUM>) can be rotationally mounted within the gearbox casing <NUM>. The mounting can be provided via a first auxiliary roller bearing <NUM> arranged at the first auxiliary axial end <NUM>, and via a second auxiliary roller bearing <NUM> arranged at the second auxiliary axial end <NUM>. The auxiliary roller bearings (<NUM>, <NUM>) disposed between the gearbox casing <NUM> and the auxiliary shaft <NUM> at both auxiliary axial ends (<NUM>, <NUM>) help to withstand high torque values and to minimize wear of the auxiliary shaft <NUM>.

The gearbox <NUM> has an axial length LG. The axial length LG can be taken along the first axis A1. The axial length LG can be thus interpreted as an overall length of the gearbox <NUM> in the axial direction of the first axis A1. The axial length LG can further incorporate the dimensions of the gearbox casing <NUM>, including the cover(s) <NUM>. The total axial length LG of the gearbox <NUM> is less than <NUM>. This compactness is achieved thanks to the output gear <NUM> being independently and rotationally disposed around the primary shaft <NUM> such that the output gear <NUM> rotates around the first axis A1, as the primary shaft <NUM>. The axial length LG, being less than <NUM>, defines high compactness of the gearbox <NUM>, which can be accommodated in various types of electric/hybrid vehicles where the strict space requirements are key features.

As further shown in <FIG>, the primary shaft <NUM> can be defined by diameters D1-D4, wherein the diameter D1 is measured at the first axial end <NUM> of the primary shaft <NUM> and the diameter D4 is measured at the second axial end <NUM> of the primary shaft <NUM>. The diameters D2 and D3 are inner diameters of the primary shaft <NUM>. All the diameters D1-D4 may vary. The diameter D1 represents the minimal structural diameter of the primary shaft <NUM>, which ensures the structural strength of the primary shaft <NUM>. The diameter D1 is preferably at least <NUM>. The diameter D4 is preferably <NUM>. Further, the diameter D3 defines the diameter of the primary shaft <NUM> in the area on which the output gear <NUM> is mounted and is preferably about <NUM>. The diameter D2 defines the diameter of the primary shaft <NUM> in the area on which the transmission gear <NUM> is mounted and is preferably about <NUM>. In addition, a length L10 of the primary shaft <NUM> is defined as the total length of the primary shaft <NUM> along the first axis A1. The length L10 is preferably about <NUM>.

Similarly, the auxiliary shaft <NUM> can be further defined by diameters D25-D29, wherein the diameter D25 is measured at the first auxiliary axial end <NUM> of the auxiliary shaft <NUM> and the diameter D29 is measured at the second auxiliary axial end <NUM> of the auxiliary shaft <NUM>. The diameters D26-D28 are inner diameters of the auxiliary shaft <NUM>. All the diameters D25-D29 may vary. The diameter D25 represents the minimal structural diameter of the auxiliary shaft <NUM> which ensures the structural strength of the auxiliary shaft <NUM>. The diameter D25 is preferably equals to at least <NUM>. The diameter D29 is preferably about <NUM>. The particular part of the auxiliary shaft <NUM> where the auxiliary transmission gear <NUM> is rigidly fixed to the auxiliary shaft <NUM> can be defined by the diameter D26 and by the radius R21 of the auxiliary transmission gear <NUM>. The diameter D26 of the auxiliary shaft <NUM> may thus correspond to an inner diameter (not shown) of the auxiliary transmission gear <NUM>, such that to provide the rigid fixation, the diameter D26 of the auxiliary shaft <NUM> and the inner diameter of the auxiliary transmission gear <NUM> match the one with the other. The diameter D26 of the auxiliary shaft <NUM> is preferably about <NUM>.

Similarly, the particular part of the auxiliary shaft <NUM> where the auxiliary output gear <NUM> is rigidly fixed to the auxiliary shaft <NUM> can be defined by the diameter D28 of the auxiliary shaft <NUM> and by the radius R22 of the auxiliary output gear <NUM>. The diameter D28 of the auxiliary shaft <NUM> may thus correspond to an inner diameter (not shown) of the auxiliary output gear <NUM>, such as to provide the rigid fixation, meaning that the diameter D28 of the auxiliary shaft <NUM> and the inner diameter of the auxiliary output gear <NUM> matches with each other. The diameter D28 of the auxiliary shaft <NUM> is preferably about <NUM>. In addition, the part of the auxiliary shaft <NUM> between the auxiliary transmission gear <NUM> and the auxiliary output gear <NUM> may define the diameter D27. The diameter D27 of the auxiliary shaft <NUM> is preferably about <NUM>. A length L20 of the auxiliary shaft <NUM> is defined as the total length of the auxiliary shaft <NUM> along the second axis A2. The length L20 is preferably about <NUM>.

Referring to <FIG>, it shows a schematic drawing of the embodiment presented above with the transmission gear <NUM> and thee auxiliary transmission gear <NUM>. In addition to the <FIG> and <FIG>, <FIG> further shows a motor <NUM>, typically an electric motor having a motor axis A6. The motor axis A6 is the axis of rotation of the rotor. The gearbox <NUM> can be further engaged to the differential assembly and more particularly, to the differential ring wheel <NUM> of the differential assembly which further transmits the power to a left drive wheel shaft <NUM> and a right drive wheel shaft <NUM> extending generally along a drive wheel axle T. Each of the left and right drive wheel shaft (<NUM>, <NUM>) can be positioned on each respective side of the gearbox <NUM>. The input power of the (first) electric motor <NUM> is transmitted through the primary input gear <NUM> into the gearbox <NUM> and transmitted out of the gearbox <NUM> through the output gear <NUM> engaged to the differential ring wheel <NUM>.

<FIG> refers to another embodiment having substantially the same features as the embodiment described in <FIG> apart from having a second distribution gear <NUM>, a second transmission gear <NUM> and a second auxiliary transmission gear <NUM> in addition to the distribution gear <NUM>, transmission gear <NUM> and the auxiliary transmission gear <NUM>. The function and position of the electric motor <NUM> is substantially the same as in previous embodiment - the electric motor <NUM> is engaged to the primary input gear <NUM> of the primary shaft <NUM>. Similarly, the output gear <NUM> can be engaged to the differential assembly which transfers the power through the differential ring wheel <NUM> to the one or more drive wheel axles T.

As shown in <FIG>, the primary shaft <NUM> is provided with a primary input gear <NUM> and the distribution gear <NUM> is as explained above. In addition, the primary shaft <NUM> further comprises the second distribution gear <NUM>. The second distribution gear <NUM> may be rigidly fixed to or can be integral with the primary shaft <NUM>.

The second transmission gear <NUM> is rotatably mounted on the first axis A1 and disposed on the primary shaft <NUM>. In various scenarios, the second transmission gear <NUM> can freely rotate around the primary shaft <NUM>. The second transmission gear <NUM> can have either the same, or a different rotational speed as the primary shaft <NUM> and the transmission gear <NUM>, depending on the gear current selection.

Preferably, the second transmission gear <NUM> is mounted around the primary shaft <NUM> via at least a second transmission needle bearing (not shown). The at least second needle bearing disposed between the second transmission gear <NUM> and the primary shaft <NUM> provides enhanced space limitation since needle bearing requires less space than other known types of bearings and furthermore, provides enough strength to withstand the speed/torque demand of the gearbox <NUM>.

The second distribution gear <NUM> is configured to transfer the power from the primary shaft <NUM> to the second transmission gear <NUM> when the second distribution gear <NUM> is rotatably engaged to the second transmission gear <NUM> by means of a second gear shift system <NUM> (will be explained later).

As shown in <FIG>, the auxiliary shaft <NUM> comprises the auxiliary output gear <NUM> that is engaged to the output gear <NUM> and the auxiliary transmission gear <NUM> that is engaged to the transmission gear <NUM>. Further, the auxiliary shaft <NUM> comprises the second auxiliary transmission gear <NUM>. The second auxiliary transmission gear <NUM> can be rigidly fixed to or can be integral with the auxiliary shaft <NUM>. In this configuration, the auxiliary output gear <NUM>, the auxiliary transmission gear <NUM> and the second auxiliary transmission gear <NUM> rotate together around the second axis A2 at the same speed as the auxiliary shaft <NUM>. The second auxiliary transmission gear <NUM> is engaged to the second transmission gear <NUM>.

The gearbox <NUM> of the embodiment of <FIG> further comprises the second gear shift system <NUM>. The second gear shift system <NUM> is configured to be slidable between at least two positions. The at least two positions can be defined as different engagement configurations between the second distribution gear <NUM> of the primary shaft <NUM> and the second transmission gear <NUM>.

Firstly, the second gear shift system <NUM> can be engaged solely with the second distribution gear <NUM>. In this configuration, the second gear shift system <NUM> do not have any engagement configuration with the second transmission gear <NUM>. The engagement of the second gear shift system <NUM> with only the second distribution gear <NUM> can be defined as a second neutral position. In the second neutral position, the second gear shift system <NUM> is configured to transmit no power between the primary input gear <NUM> and the output gear <NUM> through the second distribution gear <NUM> (and the second transmission gear <NUM>) since no physical engagement between these gears (<NUM>, <NUM>) is provided.

Secondly, the second gear shift system <NUM> can be shifted from the second neutral position to the rotational engagement between the second distribution gear <NUM> and the second transmission gear <NUM>. In this engagement configuration, the rotational speed of the second transmission gear <NUM> is the same as the rotational speed of the second distribution gear <NUM>. The power in this configuration is distributed indirectly from the primary shaft <NUM> (connected to the (first) electric motor <NUM>) to the output gear <NUM>, through the auxiliary shaft <NUM> (via the second distribution gear <NUM> and the second transmission gear <NUM> being engaged to the second auxiliary transmission gear <NUM>).

The power of the electric motor <NUM> is thus transmitted radially through the primary input gear <NUM> to the primary shaft <NUM>, then through the second distribution gear <NUM> to the second transmission gear <NUM> via the second gear shift system <NUM> and then, the power is distributed from the second auxiliary transmission gear <NUM> rotatably engaged to the second transmission gear <NUM> to the auxiliary output gear <NUM> via the auxiliary shaft <NUM>. Finally, the power is transmitted from the auxiliary output gear <NUM> to the output gear <NUM> and then radially to the differential assembly (e.g. to the differential ring wheel <NUM>).

In this configuration of the second gear shift system <NUM>, the rotational speed of the output gear <NUM> is further reduced compared to the rotational speed of the output gear <NUM> in the second configuration defined above with respect to the indirect engagement via the gear shift system <NUM> as shown in <FIG>. Therefore, such configuration can be selected in high-torque/low-speed conditions.

Additionally, in the scenario where the second gear shift system <NUM> rotationally engages the second distribution gear <NUM> and the second transmission gear <NUM>, the gear shift system <NUM> has to be in the (first) neutral position to provide no engagement between the distribution gear <NUM> and either the output gear <NUM> or the transmission gear <NUM>. Similarly, in the scenario where the gear shift system <NUM> rotationally engages either the output gear <NUM> or the transmission gear <NUM> with the distribution gear <NUM>, the second gear shift system <NUM> has to be in the second neutral position (solely in engagement with the second distribution gear <NUM>). Furthermore, in various scenarios, both the gear shift system <NUM> and the second gear shift system <NUM> can be positioned in their first/second neutral positions to provide free movement of a vehicle, such as a free movement of the drive wheel shafts/axle for towing or servicing a vehicle/trailer.

Further, the second gear shift system <NUM> can be a type of clutch sleeve or any suitable type of dog clutch for performing gear change in the gearbox <NUM>.

Advantageously, even if the second distribution gear <NUM>, second transmission gear <NUM> and the second auxiliary transmission gear <NUM> is provided within the gearbox <NUM>, the gearbox <NUM> exhibits the axial length LG which is less than <NUM>, preferably less than <NUM>. Therefore, even if the gearbox <NUM> provides the additional gear stages (in terms of additional distribution/transmission/auxiliary transmission gears), the primary input gear <NUM> of the primary shaft <NUM> and the output gear <NUM> remains at the substantially same position in terms of vertical arrangement with respect to the auxiliary shaft <NUM>. This means that the distance between the primary shaft <NUM> and the auxiliary shaft <NUM> remains unchanged when one or more additional gear stages are added.

In addition, further to the first and second gear ratios defined above, the embodiment of <FIG> can be defined in relation to a third gear ratio as the quotient between the rotational speed of the primary input gear <NUM> and the rotational speed of the output gear <NUM>. The first gear ratio is the quotient between the rotational speed between the primary input gear <NUM> and the rotational speed of the output gear <NUM> (in the direct engagement configuration between the distribution gear <NUM> and the output gear <NUM>). The second gear ratio is the quotient between the rotational speed of the primary input gear <NUM> and that of the output gear <NUM> (in the indirect engagement between the distribution gear <NUM> and the output gear <NUM>: the power is transmitted through the transmission gear <NUM> to the auxiliary shaft <NUM>.

Additionally, the third gear ratio can be defined in the case the second gear shift system <NUM> is in position defining the rotational engagement between the second distribution gear <NUM> and the second transmission gear <NUM>. The power in this configuration is distributed indirectly from the primary shaft <NUM> (the primary input gear <NUM>) to the output gear <NUM> through the auxiliary shaft <NUM> (via the second distribution gear <NUM> and the second transmission gear <NUM> being engaged to the second auxiliary transmission gear <NUM>). The third gear ratio is thus the quotient between the rotational speed of the primary input gear <NUM> and the rotational speed of the output gear <NUM> (in engagement between the second distribution gear <NUM> and the second transmission gear <NUM>, while the gear shift system <NUM> is in its (first) neutral position).

Preferably, the third gear ratio (engagement between the second distribution gear <NUM> and the second transmission gear <NUM>) is higher than the second gear ratio (engagement between the distribution gear <NUM> and the transmission gear <NUM>). Additionally, the second gear ratio is preferably higher than the first gear ratio (engagement between the distribution gear <NUM> and the output gear <NUM>).

<FIG> shows a perspective view of a powertrain assembly. The powertrain assembly comprises the gearbox <NUM> having the casing <NUM>, one or two electric motor(s) (<NUM>, <NUM>), and the differential assembly engaged to the gearbox <NUM>. The casing <NUM> of the gearbox <NUM> can be any type of casing/housing for enclosing the gearbox components and typically comprises two or more parts including the main casing component and the casing cover(s) <NUM>.

The powertrain assembly can further comprise the drive wheel axle T through which the power can be transmitted from the gearbox <NUM> to driving wheels <NUM> of a vehicle. The drive wheel axle T can be further defined by the left drive wheel shaft <NUM> and a right drive wheel shaft <NUM>, both enclosed in an axle body/case <NUM>. Each of the left and right drive wheel shafts (<NUM>, <NUM>) can be positioned on each respective side of the gearbox <NUM> with respect to an axis X (axis in a longitudinal direction of a vehicle).

As further shown in <FIG>, the powertrain assembly can be directly or indirectly engaged to a suspension system of a vehicle, defined for instance by pneumatic cylinders (<NUM>, <NUM>). The pneumatic cylinders (<NUM>, <NUM>) might also represent other types of cylinders, for instance, cylinders for any auxiliary device which is specific for a particular vehicle. The powertrain assembly can be further connected to a vehicle's chassis <NUM> for more rigid configuration. As exemplarily shown in <FIG>, the powertrain assembly can be attached to the chassis <NUM> through one or more struts <NUM>, <NUM> (e.g. shock absorbers for vertical <NUM> and horizontal <NUM>). The struts (<NUM>, <NUM>) can be any type of suitable strut for limiting vibrations and shocks.

<FIG> represents a top view of the powertrain assembly depicted in <FIG>. As shown therein, the axis X is defined in a longitudinal direction of a vehicle and the drive wheel axle T is perpendicular to the axis X. As further depicted, an arrow FW defines a direction where a front part of a vehicle is positioned (e.g. a cabin or a front steering wheel axle). As explained with respect to <FIG>, the gearbox <NUM> exhibits the axial length LG which is defined as the length of the gearbox <NUM> measured along the drive wheel axle T (or along the first axis A1 being parallel with the drive wheel axle T).

More particularly, the axial length LG is a length of the gearbox <NUM> as such, taken along the first axis A1/drive wheel axle T without considering the dimensions of the one or two electric motor(s) (<NUM>, <NUM>). The axial length LG of the gearbox <NUM> is less than <NUM>, preferably about <NUM>. The gearbox <NUM> or more particularly, the gearbox <NUM> and the one or two electric motor(s) (<NUM>, <NUM>), when engaged together, might further define a second axial length LG2 dimension which is defined as a length along the first axis A1/drive wheel axle T. The second axial length LG2 is preferably about <NUM>.

The gearbox <NUM> which is defined either by the axial length LG or the second axial length LG2 can provide a high level of compactness and can be fitted within the existing chassis <NUM>/suspension systems of a vehicle.

<FIG> shows a perspective view of the powertrain assembly without depicting the rotational wheels <NUM> of a vehicle, chassis <NUM>, struts <NUM>, pneumatic cylinders (<NUM>, <NUM>) and the suspension system. Further, the gearbox <NUM> is depicted without casing <NUM> and casing cover(s) <NUM>. The example shown in <FIG> represents an embodiment having two electric motors (<NUM>, <NUM>), however for the sake of limited room/space for the gearbox <NUM> in some types of vehicles, a single electric motor <NUM> embodiment is preferable - as shown in <FIG>.

<FIG> further shows the (first) motor axis A6 of the (first) electric motor <NUM>. The (first) motor axis A6 defines the axis about which a rotor of the (first) electric motor <NUM> is rotatable. Similarly, a (second) motor axis A66 is defined as the axis of the (second) electric motor <NUM> and represents the axis about which a rotor of the (second) electric motor <NUM> is rotatable. The position of two electric motors (<NUM>, <NUM>) in <FIG> is an exemplary configuration and might differ depending on the type of vehicle. For instance, due to the suspension assembly and chassis <NUM>, the position of the (first) electric motor <NUM> might vertically differ with respect to the position of the (second) electric motor <NUM>.

The gearbox <NUM> configuration shown in <FIG> represents the embodiment of <FIG> having two distribution gears (distribution gear <NUM>, second distribution gear <NUM>), two transmission gears (transmission gear <NUM>, second transmission gear <NUM>), and two auxiliary transmission gears (auxiliary transmission gear <NUM>, second auxiliary transmission gear <NUM>) engaged to the (first) electric motor <NUM>. In the exemplary embodiment shown in <FIG>, the (second) electric motor <NUM> is not engaged to a gearbox but to a reducer <NUM> engaged to the differential assembly. The reducer has a fixed gear ratio (which cannot be changed then). The powertrain assembly may further comprise the control fork <NUM> for selectively locking/unlocking the differential assembly. In other embodiments (not shown), the reducer <NUM> may be omitted and both electric motors (<NUM>, <NUM>) may be engaged to two respective gearboxes.

As shown in <FIG>, the (first) electric motor <NUM> is configured to be engaged to the primary input gear <NUM> of the gearbox <NUM>. The power is thus transmitted through the primary input gear <NUM> to the primary shaft <NUM> of the gearbox <NUM>. The differential assembly can be defined as comprising a differential gear having a differential ring wheel <NUM>. The differential ring wheel <NUM> can be rotatably engaged to the output gear <NUM> of the gearbox <NUM> for transmitting the power out of the gearbox <NUM> to the one or more drive wheel axles T. As explained above, the drive wheel axle T can be defined by the left drive wheel shaft <NUM> and a right drive wheel shaft <NUM>. Each of the left and right drive wheel shaft (<NUM>, <NUM>) can be positioned on each respective side of the gearbox <NUM> such that each of the left and right drive wheel shaft (<NUM>, <NUM>) is coupled to the differential crown wheel of the differential assembly.

<FIG> depicts a side view of the powertrain assembly defined above. As shown therein, the powertrain assembly represents the embodiment having two electric motors (<NUM>, <NUM>) disposed on each respective side with respect to the drive wheel axle T. The compactness of the powertrain assembly having the compact gearbox <NUM> is further demonstrated by height/clearances defined as H1-H4 and lengths defined as L, L1, and L2. The axis X defines the axis in a longitudinal direction of a vehicle whereas the arrow FW defines a direction where a front part of a vehicle is positioned (e.g. a cabin or a front steering wheel axle). An axis Z defines the vertical axis which is perpendicular to the axis X and to the drive wheel axle T.

The height H1 represents a vertical distance along the Z-axis from the ground to the upper part of the chassis <NUM> of a vehicle. The second clearance H2 represents a vertical distance along the Z-axis from the ground to the lowest part of the (second) electric motor <NUM>. The third clearance H3 represents a vertical distance along the Z-axis from the ground to the lowest part of the suspension assembly (e.g. to a suspension arm). The fourth clearance H4 represents a vertical distance along the Z-axis from the ground to the lowest part of the (first) electric motor <NUM>.

The length L represents a longitudinal distance along the X-axis between the (first) motor axis A6 of the (first) electric motor <NUM> and the (second) motor axis A66 of the (second) electric motor <NUM>. Further, the length L1 represents a longitudinal distance along the X-axis between the (first) motor axis A6 of the (first) electric motor <NUM> and the drive wheel axle T. The length L2 represents a longitudinal distance along the X-axis between the (second) motor axis A66 of the (second) electric motor <NUM> and the drive wheel axle T.

As an exemplary embodiment, the powertrain assembly can be assembled in a vehicle having the driving wheels <NUM> of dimensions <NUM>/<NUM> R22. The dimensions of the driving wheels <NUM> are not limiting: They give an idea of the overall dimension and compactness of the transmission assembly shown in <FIG>.

Preferably, the height H1 is preferably about <NUM> (tbc). The clearance H2 is preferably about <NUM> (tbc). The clearance H3 is about <NUM> (tbc). The clearance H4 is preferably about <NUM> (tbc). The length L is preferably about <NUM>. The length L1 is preferably about <NUM>. The length L2 is preferably about <NUM>.

Thanks to the small dimensions of the gearbox <NUM> as such and the powertrain assembly incorporating the gearbox <NUM>, the high level of compactness is achieved. For instance, if the powertrain assembly is incorporated in a heavy truck vehicle, the clearance between the chassis <NUM> and the gearbox <NUM> enables to withstand heavier loads and in case the gearbox <NUM> is engaged to the suspension assembly, the vehicle can withstand much higher vibration and absorb higher shocks due to high level of movement provided to the drive wheel axle T. Such high level of movement is provided thanks to the available room (space) between the powertrain assembly and the other parts of a vehicle (e.g. the chassis <NUM>, suspension assembly, batteries, etc.).

<FIG> shows a preferred embodiment which is substantially the same as embodiments of <FIG> apart from the presence of one (first) electric motor <NUM> only. This embodiment further enhances the compactness of the gearbox <NUM> as such and the compactness of the powertrain assembly within a vehicle.

<FIG> represents the schematic diagram illustrating in cross-sectional view various radii involved in the gearbox <NUM>, along the first/second axis (A1, A2). As identified in <FIG> and <NUM>, the primary shaft <NUM> can be further defined by radiuses R11, R12 of the primary input gear <NUM> and the distribution gear <NUM>, by the diameters D1-D4 and furthermore by the length L10. Similarly, the auxiliary shaft <NUM> can be further defined by radiuses R21, R22 of the auxiliary transmission gear <NUM> and the auxiliary output gear <NUM>, by the diameters D25-D29 and by the length L20.

In various embodiments, the diameters of the first/auxiliary shaft (<NUM>, <NUM>) may differ as well as the radiuses of the gears (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). Therefore, substantially any gear ratio is possible by changing the radiuses/diameters of the gears (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). The rotational speed of the output gear <NUM> can be presented as Ω3, and as well known in prior-art, the rotational speed Ω3 can be determined using the following formula: <MAT> where Ω1 is rotational speed of the input gear (e.g. in case of indirect engagement, the input gear can be presented as transmission gear <NUM> having the same rotational speed as the primary shaft <NUM> / primary input gear <NUM>), R13 is the radius of the transmission gear <NUM>, R21 is the radius of the auxiliary transmission gear <NUM>, R22 is the radius of the auxiliary output gear <NUM> and R33 is the radius of the output gear <NUM>. Therefore, by changing the individual radiuses of the formula above, different gear ratio can be achieved.

Additionally, the radius R11 of the primary input gear <NUM> is preferably about <NUM>. The radius R12 of the distribution gear <NUM> is preferably about <NUM>. Advantageously, according to another example, the rotational speed Ω3 may be lower than Ω1 (reduced gear ratio), or may be higher as compared to Ω1 (amplified gear ratio).

As further shown in <FIG>, outer surfaces (11a, 13a, 21a, 22a, 3a) of the primary input gear <NUM>, the transmission gear <NUM>, the auxiliary transmission gear <NUM>, the auxiliary output gear <NUM> and the output gear <NUM> are shown as being engaged to one another, or being engaged to either the input (e.g. the electric motor <NUM>) or to the output (e.g. the differential ring wheel <NUM>). More particularly, the outer surface 11a of the primary input gear <NUM> is engaged to the outer surface of the rotor of the electric motor <NUM>. The outer surface 13a of the transmission gear <NUM> is engaged to the outer surface 21a of the auxiliary transmission gear <NUM>. Further, the outer surface 22a of the auxiliary output gear <NUM> is engaged to the outer surface 3a of the output gear <NUM>. The output gear <NUM> is further engaged by its outer surface 3a to the differential ring wheel <NUM> of the differential assembly.

Advantageously, the outer surfaces (11a, 13a, 21a, 22a, 3a) of the corresponding wheels might exhibit helical-type teeth. The helical-type teeth effectively reduce noise generated by the gearbox <NUM> during its operation.

Furthermore, the gearbox <NUM> as described above and the powertrain assembly incorporating such gearbox <NUM> is capable to transmit a power of at least <NUM> kW, more preferably, the transmitted power can be at least <NUM> kW. As regards the transmitted torque, the gearbox <NUM> or the transmission assembly incorporating such gearbox <NUM> is capable to transmit a torque of at least <NUM> N. , preferably at least <NUM> N.

Claim 1:
A gearbox (<NUM>) for a vehicle, the gearbox (<NUM>) comprising:
a gearbox casing (<NUM>);
a primary shaft (<NUM>) rotationally mounted within the gearbox casing (<NUM>) to rotate around a first axis (A1), and having first and second axial ends (<NUM>, <NUM>) within the gearbox casing (<NUM>);
a primary input gear (<NUM>) which is is fixed in rotation with the primary shaft (<NUM>);
a distribution gear (<NUM>) which is fixed in rotation with the primary shaft (<NUM>);
a transmission gear (<NUM>), which is configured to rotate around the first axis (A1) and which is arranged around the primary shaft (<NUM>);
an auxiliary shaft (<NUM>) configured to rotate around a second axis (A2), the first axis (A1) and the second axis (A2) being distant from each other,
an auxiliary output gear (<NUM>) and an auxiliary transmission gear (<NUM>) which are arranged around the auxiliary shaft (<NUM>), said auxiliary transmission gear (<NUM>) being engaged to the transmission gear (<NUM>);
an output gear (<NUM>) for transmitting a power out of the gearbox, said output gear (<NUM>) being independently and rotationally arranged around the primary shaft (<NUM>) and being configured to rotate around the first axis (A1), said output gear (<NUM>) being mounted on the primary shaft (<NUM>) and being engaged to the auxiliary output gear (<NUM>);
a gear shift system (<NUM>) slidable between at least two positions, said gear shift system (<NUM>) being configured to rotationally engage:
the distribution gear (<NUM>) and the output gear (<NUM>) for transmitting the power directly from the primary shaft (<NUM>) to the output gear (<NUM>), or
the distribution gear (<NUM>) and the transmission gear (<NUM>) for transmitting the power indirectly from the primary shaft (<NUM>) to the output gear (<NUM>) through the auxiliary shaft (<NUM>).