WO2024165406A1

WO2024165406A1 - Gearbox for a drivetrain and drivetrain comprising the gearbox

Info

Publication number: WO2024165406A1
Application number: PCT/EP2024/052444
Authority: WO
Inventors: Frank Loacker; Stefan Rittler
Original assignee: Designwerk Technologies Ag
Priority date: 2023-02-08
Filing date: 2024-02-01
Publication date: 2024-08-15

Abstract

The present disclosure relates to a gearbox (2) for a drive train of an electric truck and to a drive train comprising the gearbox (2). The gearbox (2) comprising a. at least one input shaft (8) arranged at least partially within a gearbox housing (3) and extending in an axial direction (x), the input shaft (8) comprising an input gear (9), b. an output shaft (5) arranged at least partially within the gearbox housing (3), the output shaft (5) extending in the axial direction (x) parallel with respect to the input shaft (8), c. wherein the input shaft (8) comprises at the axial end (10) of the coupling arrangement (11) a labyrinth sealing.

Description

GEARBOX FOR A DRIVETRAIN AND DRIVETRAIN COMPRISING THE GEARBOX

FIELD OF THE DISCLOSURE

The present disclosure relates to a gearbox for a drive train of an electric truck and to a drive train comprising the gearbox.

BACKGROUND OF THE DISCLOSURE

CN 109 677 253 A published on 26.04.2019 in the name of Qingdao Qingte Zhongli Axle Co Ltd. discloses an electric drive axle of a commercial vehicle, and particularly relates to an integrated dual-motor mechanical differential electric drive axle, which has an integrated power assembly system.

CN 107 284211 A published on 24.10.2017 in the name of Suzhou Greencontrol Trans Technology Co Ltd. discloses a pure-electric driving assembly of a heavy truck. The assembly comprises a driving motor. An output shaft of the driving motor stretches into the interior of a flywheel housing. The output shaft is connected with an input shaft end of a flywheel. The outer ring surface of the flywheel is provided with a clutch pressure plate driven plate assembly. An output shaft of the clutch pressure plate driven plate assembly is connected with an input end of a gearbox. The gearbox is provided with an ATM gear-selection and gear-shifting mechanism. An output end of the gearbox is externally connected with an output flange used for connecting with a hub input structure or a wheel rotating input structure of the heavy truck. Conventional drivetrains of trucks, in particular heavy trucks, use a combustion engine for torque production and a shiftable transmission unit (gearbox) coupled to the combustion engine to transfer the provided torque into the currently required torque and rotational speed. The gearbox is therefore conventionally a multi speed gearbox and requires lots of installation space within the truck. An electric truck does not have a combustion engine, but produces the required torque by at least one electric engine. Electric engines have compared to combustion engines higher rotational speeds and require therefore a completely different gearbox to transfer the produces torque to the wheels with the required rotational speed. Further, the high rotational speeds of the electric engines create lubricant sealing problems, which are yet not solved.

SUMMARY OF THE DISCLOSURE

It is an object of the present disclosure to provide a gearbox for a drive train of an electric truck and a drivetrain comprising the gearbox. In particular, it is an object of the present disclosure to provide a gearbox for a drive train of an electric truck and a drivetrain comprising the gearbox, which do not have at least some of the disadvantages of the prior art.

According to the present disclosure, a gearbox or transmission unit for a drive train of an electric truck, in particular electric heavy truck, is specified. The gearbox preferably comprises at least one input shaft arranged at least partially within a gearbox housing and extending in an axial direction, the input shaft comprising an input gear and on at least one of its axial ends a coupling arrangement, which is configured to engage with an electric engine for driving the input shaft. The axial end of the input shaft is for example the portion of the input shaft, which extends axially beyond a respective bearing of the input shaft. In another variation, the axial end of the input shaft is for example the axially outer 25 % or 10 % of the input shaft. The axis of rotation of the input shaft runs parallel to the axial direction of the gearbox. The input gear of the input shaft comprises for example a helical gear, preferably fixedly arranged via a spline shaft connection, on the input shaft. In another variation, the input gear is formed integrally with the input shaft.

The gearbox according to the present disclosure further comprises preferably an output shaft, which is arranged at least partially within the gearbox housing. The output shaft extends in the axial direction parallel with respect to the input shaft and comprises an output gear configured to be driven by the input gear. The output shaft is preferably arranged with respect to a vertical direction below the input shaft. Arranged below is to be understood that the output shaft is arranged in the installation status of the gearbox within the drivetrain vertically below the input shaft. In other words, the gearbox extends in its installation position in vertical direction and the input shaft is arranged vertically above the output shaft.

The output gear of the output shaft comprises for example a helical gear, preferably fixedly arranged in circumferential direction via a spline shaft connection, on the output shaft. In another embodiment, the output gear is formed integrally with the output shaft. The ratio between the input gear and the output gear is usually between 3:1 and 15:1 , preferably between 7:1 and 12:1 , even more preferably 10:1.

According to the present disclosure, the input shaft preferably comprises at the axial end of the coupling arrangement a labyrinth sealing, which is configured to provide a lubricant sealing for the gearbox housing during operation of the gearbox, in particular between the gearbox housing and the input shaft. The labyrinth sealing is preferably a contact free sealing which advantageously reduces friction between the input shaft and the gearbox housing during operation compared to a conventionally used contacting shaft seal. Further, the labyrinth sealing is not subject to wear because the rotating part of the labyrinth sealing and the non rotating part of the labyrinth sealing are during operation preferably not in contact with each other. The labyrinth sealing provides therefore the required lubricant sealing of the gearbox without friction losses and without sealing wear, which advantageously reduces the maintenance requirements of the entire gearbox. The labyrinth sealing improves therefore the entire efficiency of the gearbox substantially, which substantially increases the possible range of a vehicle, which uses the gearbox compared to a conventional gearbox with a standard contacting shaft sealing.

In particular good sealing results are achievable when the labyrinth sealing comprises a first labyrinth portion fixedly arranged on the input shaft and a second labyrinth portion fixedly arranged on the gearbox housing, wherein the first and second labyrinth portions comprise each at least one axially extending protrusions, which overlap axially with respect to each other, thereby forming the labyrinth. In other words, both portions of the labyrinth sealing, the rotating portion (first portion) and the non-rotating portion (second portion) comprise preferably one ring or sleeve shaped protrusion, which extend in installed status in axial direction, thus parallel to the axis of rotation of the input shaft. The protrusion of the first labyrinth portion and the protrusion of the second labyrinth portion have different radii in order to enable the required overlap. The axial overlap further advantageously enables slight axial movement of the input shaft with respect to the gearbox housing.

Even better sealing results are achievable when the first portion of the labyrinth sealing and the second portion of the labyrinth sealing comprise each a plurality of axially extending protrusions, wherein each of the protrusions of the first portion at least overlap with one protrusion of the second portion and vice versa.

In a variation, the first labyrinth portion of the labyrinth sealing comprises at least one skidding edge extending radially with respect to the input shaft and being configured to skid lubricant into a dedicated collecting area of the gearbox housing during operation of the gearbox. The skidding edge is preferably a radially extending edge of the rotating part of the labyrinth sealing (first portion of the labyrinth sealing). Lubricant, which accumulates on the skidding edge, is skidded due to the high rotational speeds of the input shaft off the skidding edge and towards the dedicated collecting area during operation. The skidding edge advantageously improve the sealing effect of the labyrinth sealing. Preferably, the first portion of the labyrinth sealing comprises two or more skidding edges, which are arranged on different axial positions of the first portion of the labyrinth sealing. Lubricant, which made it past the first skidding edge, may be skidded towards the dedicated collecting area by the second skidding edge and so on. The plurality of skidding edges further increase the sealing effect of the labyrinth sealing. The dedicated collecting area is for example a ring shaped depression or a plurality of ring shaped depressions arranged in the gearbox housing radially outside of the skidding edges. The collecting areas may comprise on its bottom a return pipe, via which the lubricant is guided back into the gearbox housing. In a variation, the gearbox further comprises at least one sleeve shaped mounting flange arranged on the gearbox housing coaxially with the input shafts and surrounding the axial end of the input shaft, which comprises at least partially the coupling arrangement, wherein the mounting flange is configured to position the electric engine such that a drive shaft of the electric engine is engageable with the input shaft, preferably coaxially. The sleeve shaped mounting flange may form part of the gearbox housing and may function as a connecting part between the gearbox housing and the electrical engine. In other words, the sleeve shaped mounting flange is fixedly arranged on the gearbox housing and provides a connection possibility for the electric engine. Further, the sleeve shaped mounting flange may comprise at least partially the dedicated lubricant collecting area. Further, the second portion of the labyrinth sealing may be arranged on the sleeve shaped mounting flange.

The gearbox may comprise additional sleeve shaped parts, which are fixedly arranged on the gearbox housing and form thereby the gearbox housing. In other words, the gearbox housing may be formed by all non-rotating parts. The additional sleeve shaped parts are for example arranged between the gearbox housing and the input shaft or output shaft and provide the required axial contact surface for an advantageous bearing arrangement.

In particular good sealing results are achievable when the at least one mounting flange comprises on one of its radial inner surfaces ring shaped depressions, which are configured to collect lubricant during operation of the gearbox and to guide the lubricant into the dedicated collecting area. According to this variation, the mounting flange additionally comprises ring shaped depressions, which are preferably arranged axially next to the labyrinth sealing, in particular axially further outside from the interior of the gearbox compared to the labyrinth sealing. In other words, lubricant, which made it, during operation, past the labyrinth sealing is collected by the ring shaped depressions of the mounting flange. On the bottom of the ring shaped depressions, the mounting flange may comprise a groove, which is connected to the return pipe such that the lubricant is guided back into the interior of the gearbox during operation of the gearbox.

Advantageous good sealing results are achievable when the dedicated collecting area is fluidical ly connected via a siphon to the interior of gearbox housing such that the lubricant is guided back from the collecting area into the gearbox housing through the siphon during operation of the gearbox. The siphon may provide a barrier for lubricant mist arising from the inside of the gearbox and simultaneously enables that the collected liquid lubricant, for example transmission oil, is guided back into the interior of the gearbox during its operation.

In a variation, the collecting area arranged radially outside of the labyrinth sealing is directly connected via a connecting opening or a connecting passage with the return pipe. In this variation, the collected lubricant flows directly via the return pipe back into the gearbox housing. In another variation, the collecting area arranged radially outside of the labyrinth sealing is connected via the siphon to the return pipe. In this variation, the collected lubricant flows via the siphon and the return pipe back into the gearbox housing.

In a variation, the input shaft comprises a bearing arrangement configured to bear the input shaft with respect to the gearbox housing, the bearing arrangement is configured to enable limited axial movement of the input shaft for adjusting its axial position with respect to the gearbox housing during operation of the gearbox. The limited axial movement enables the input shaft to adjust its axial position during operation, which might be necessary due to axial forces, which may engage on the input shaft. The limited axial movement is for example in the range from 3 mm to 0,5 mm, preferably in the range of 2,5 mm to 1 ,5 mm, in both axial directions starting from the neutral or zero position of the input shaft.

An advantageous positioning of the input shaft is achievable when the input gear of the input shaft comprises an axially self-adjusting gearing. The axially self- adjusting gearing comprises for example two helical gears fixedly arranged on the input shaft, wherein the flanks of the gears are arranged in a mirrored fashion with respect to each other. Obviously, in this variation, the output gear of the output shaft corresponds to the input gear. The self-adjusting gearing according to this variation enables that the input shaft is during operation always pushed back to the neutral position due to the specific shape and properties of the gearing itself, even when axial forces engage on the input shaft. The bearing arrangement as described enables advantageously the self-adjustment because it is configured to enable limited axial movement.

Advantageous bearing properties of the input shaft are achievable when the bearing arrangement of the input shaft comprises a plurality of bearings, which are lubricated via a pressurized lubricant supply. The pressurized lubricant supply enables that lubricant is directly supplied onto contact surfaces of the bearings, which reduces friction losses.

Even better bearing properties are achievable when the bearing arrangement of the input shaft comprises at least at the axial end of the coupling arrangement one pair of angular ball bearings in O-Arrangement, wherein the pressurized lubrication supply is configured to supply the lubricant between the pair of angular ball bearings. It is preferred that the bearing arrangement of the input shaft comprises on each axial end one pair of angular ball bearings in O-Arrangement, wherein the pressurized lubrication supply is configured to supply the lubricant between the pair of angular ball bearings. By suppling the lubricant between the pair of angular ball bearings, preferably from radially outside, the lubricant is guided automatically on the contact surfaces of both bearings. The O-Arrangement of the bearings is advantageously due to the engagement of the electric engine on the axial ends of the input shaft. Instead of ball bearings, roller bearings, in particular tapered roller bearings are also conceivable.

The pressurized lubricant is advantageously supplied between the two bearings when a perforated spacer is arranged between the two bearings. The spacer, in particular the perforations, provide openings/passages for the lubricant to flow into the interior of the bearings.

An advantageous axial self-adjusting is achievable when the bearing arrangement further comprises at least one spring arranged axially between the gearbox housing and one bearing of the bearing arrangement, wherein the at least one spring is configured to dynamically increase an axial force, which is required to axially displace the input shaft in one axial direction away from a predefined initial neutral position. The spring is preferably a disc spring.

An even better axial self-adjusting is achievable when the bearing arrangement comprises on each axial side of the input shaft the spring, wherein the two springs are configured to dynamically increase the axial force, which is required to axially displace the input shaft in both axial directions from a predefined initial neutral position. The spring is preferably arranged between a bearing and the gearbox housing, such that an axial displacement of the bearing compresses the respective spring, which produces the required axial force to push the input shaft back towards its neutral position. Two springs arranged on both axial ends of the input shaft preferably in a mirrored fashion create the desired forces in both axial directions. Both springs are preferably disk springs. Disc springs have the advantage that the spring force increases with axial displacement of one axial end towards the other axial end of the respective disc spring and do only require little installation space.

In a variation, both of the axial ends of the input shaft comprise a coupling arrangement, which is configured to engage with an electric engine for driving the input shaft. In other words, one electric engine may be arranged on each axial end of the input shaft to drive the input shaft, which increases the possible torque transferred to the output shaft.

An advantageous torque transfer is achievable when the at least one coupling arrangement of the input shaft comprises a claw coupling with a first claw part and a second claw part, wherein the first claw part is arranged coaxially on the input shaft, and the second claw part is configured to be arranged coaxially on the drive shaft of the electric engine, wherein the first claw part and the second claw part are engagable with each other for transferring torque from the electric engine to the input shaft. The claw coupling enables a low friction torque transfer, which additionally enables slight axial displacement of the different parts of the coupling. Axial displacements of the input shaft is not transferred, or transferred only marginally, via the claw coupling to the electric engine and vice versa. An advantageous arrangement of the first claw part on the input shaft is achievable when the first claw part is arranged coaxially at the input shaft via a clamp screw arranged coaxially with respect to the input shaft and the first claw part and I or wherein the first claw part is arranged coaxially at the input shaft via a plurality of pins arranged between the first claw part and the input shaft. The clamp screw is for example arranged at the axial center of the first claw part and the input shaft. The pins are for example arranged parallel with respect to the rotational axis of the input shaft and in a circumferential direction equidistant with respect to each other, thereby providing an advantageous torque transfer from the first claw part to the input shaft.

Good damping results are achievable when the claw coupling comprises an elastomeric gear ring arranged between the claws of the first claw part and the claws o the second claw part thereby forming a torsional flexible claw coupling. The elastomeric gear ring is for example arranged in a loose fashion between the first claw part and the second claw part. The elastomeric gear provides an advantageous damping of vibrations, which might result from the operation of the electric engines, between the input shaft and the drive shaft of the electric engine. In case, both axial ends of the input shaft comprise the coupling arrangement with the claw coupling, vibrations from both axial ends may be transferred into the input shaft. The elastomeric gear on both axial ends of the input shaft advantageously dampen these vibrations.

In a further variation, the gearbox may comprise a plurality of input shafts arranged at least partially within the gearbox housing and extending in an axial direction, the plurality of input shaft comprise each the input gear and on at least one of its axial ends the coupling arrangement, which is configured to engage with an electric engine for driving the respective input shaft. The coupling arrangement is preferably arranged on both axial ends of the input shafts. Preferably, the gearbox comprise two input shafts arranged on the same vertical position laterally next to the output shaft, such that the input gears are engageable with the output gear. Each of the input shafts may comprise on both axial ends a coupling arrangement, which is configured to engage with a respective electric engine for driving of the input shafts.

According to a further aspect of the present disclosure, a drive train for an electric truck, in particular a heavy truck, comprising a gearbox as described above and I or hereinafter is specified.

It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered limiting to the disclosure described in the appended claims. The drawings are showing: Fig. 1 a perspective view of a variation of the gearbox according to the present disclosure;

Fig. 2 an exploded perspective view of the variation of the gearbox according to Figure 1 ; Fig. 3 a front view of the variation of the gearbox of Figure 1 and 2;

Fig. 4 a longitudinal section view in lateral direction of the variation of the gearbox of Figure 1 to 3;

Fig. 5 a first cross section view in axial direction of the variation of the gearbox of Figure 1 to 3 indicated by line Q in Figure 3; Fig. 6 a second cross section view in axial direction of the variation of the gearbox of Figure 1 to 3 indicated by line P in Figure 3;

Fig. 7 a first detailed view of the first cross section view of Figure 5 of the variation of the gearbox;

Fig. 8 a second detailed view of the first cross section view of Figure 5 of the variation of the gearbox;

Fig. 9 an exploded perspective view of an input shaft of the of the variation of the gearbox as shown in the Figures 1 to 8;

Fig. 10 an exploded front view of the input shaft of Figure 9; Fig. 11 an exploded longitudinal section view of the input shaft of Figure 10 indicated by line J in Figure 10;

Fig. 12 a perspective cross section view of a specific variation of the gearbox according to the present disclosure;

Fig. 13 a detailed view of a cross section of the specific variation of the gearbox according to the present disclosure.

DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Figure 1 shows a perspective view of a variation of the gearbox according to the present disclosure. Figure 2 shows an exploded perspective view of the variation of the gearbox according to Figure 1. Figure 3 shows a front view of the variation of the gearbox of Figures 1 and 2. Figure 4 shows a longitudinal section view in lateral direction of the variation of the gearbox of Figures 1 to 3. Figure 5 shows a first cross section view in axial direction of the variation of the gearbox of Figures 1 to 4 indicated by line Q in Figure 3. Figure 6 shows a second cross section view in axial direction of the variation of the gearbox of Figure 1 to 4 indicated by line P in Figure 3. Figure 7 shows a first detailed view of the first cross section view of Figure 5 of the variation of the gearbox. Figure 8 shows a second detailed view of the first cross section view of Figure 5 of the variation of the gearbox. Figure 9 shows an exploded perspective view of an input shaft of the variation of the gearbox as shown in the Figures 1 to 8. Figure 10 shows an exploded front view of the input shaft of Figure 9. Figure 11 shows an exploded longitudinal section view of the input shaft of Figure 10 indicated by line J in Figure 10. Figure 12 shows a perspective cross section view of a specific variation of the gearbox according to the present disclosure. Figure 13 shows a detailed view of a cross section of the specific variation of the gearbox according to the present disclosure.

The Figures 1 and 2 show in a perspective view a gearbox 2 according to the present disclosure. The gearbox 2 may form part of a drivetrain 1 for an electric truck. The gearbox 2 comprises a gearbox housing 3, which comprises a front part and a rear part. The front part and the rear part comprise each a gearbox housing wall 4. The front part and the rear part are for example substantially identical and I or are interconnectable to each other in a separation plane, which is arranged essentially perpendicular to an axial direction (x) as visible in Figure 1 or 2. The gearbox housing 3 is for example made of metal, in particular steel. The front part and the rear part are for example connectable via pins and screws as best visible in Figure 2. The gearbox 2 further comprises two input shafts 8, which are at least partially arranged in the gearbox housing 3 and which extend beyond the gearbox housing 3, through the gearbox housing wall 4. The input shafts 8 are configured to rotate around a respective input axis 33. As visible in the Figures 1 and 2, the input shafts 8 comprise on both axial ends 10 a coupling arrangement 11 , which is configured to be engaged with an electric engine (not shown in the Figures). The Figures 1 and 2 further show mounting flanges 20, which are arranged on the gearbox housing 3, thereby forming part of the gearbox housing 3 and surrounding one axial end 10 of the input shaft 8. The mounting flange 20 are configured to provide a connecting possibility for the electric engines to be arranged on the gearbox 2. The mounting flange 20 further provide the possibility that a drive shaft of the elective engines is advantageously simple arrangeable coaxially with the respective input shaft 8. The axial end 10 of the input shaft is for example the portion of the input shaft 8, which extends axially beyond a respective bearing arrangement 12

As best visible in the Figure 1, 2, 3, 4 and 6, the gearbox 2 further comprises an output shaft 5, which is arranged at least partially in the gearbox housing 3. The output shaft 5 is configured to rotate around the output axis 34.

The input shaft 8 comprises an input gear 9 and the output shaft 5 comprises an output gear 6. Figure 4 shows that the input gear 9 is arranged on the input shaft 8 via a splined shaft connection. Figure 4 further shows that the output gear 8 comprises a disc part, which is integrally formed with the output shaft 5 and a gear part, which comprises the gearing and which is detachably interconnected to the disc part via a screwed connection. As best visible in Figure 2, the input gear 9 and the output gear 6 comprise each two helical gears, which are arranged axially next and mirrored to each other, thereby forming a V-shaped gearing. The Figures 1 and 2 further show that the input shaft 8 is arranged in vertical direction z above the output shaft 5. Further, the gearbox 2 as shown in the Figures comprises two input shafts 8, which engage with the single output shaft 5. Both input shafts 8 are arranged on the same vertical position and are arranged in lateral direction y next to each other. This arrangement builds advantageously compact. The output shaft 5 is for example configured to engage with a cardan shaft of the drive train 1. In another embodiment, the output shaft 5 is configured to engage directly or via a differential gear with an axle of the electric truck, the differential gear or further gearing may also be arranged in the gearbox housing 3.

Figure 2 further shows schematically that each input shaft 8 comprises on both axial ends a coupling arrangement 11 , for coupling the input shaft 8 with the electric engines.

Two nozzle bridges 35 are best visible in Figure 2 and 4 extending between the front part and the rear part of the gearbox housing 3 and each comprising at least one nozzle 35. The nozzle bridges 35 are C-shaped and partially surround the respective input gear 11 within the gearbox housing 3. The nozzle bridges 35 provide an lubricant supply path to the at least one nozzle 35, which is configured to spray lubricant directly onto the input gear 9 and I or output gear 6 prior to contacting each other, thereby providing an advantageous lubricant supply. A lubricant sump 37 as shown in Figures 2 and 4 supplies lubricant to the nozzle bridge 35 via for example an oil pump (not shown). Further, the lubricant sump 37 may extend in vertical direction z until the output gear 6 thereby providing additionally or alternatively a splash lubrication for the output gear 6. The oil pump being fluidically interconnected to the lubricant sump 37 and to the nozzle bridge 35 in order to transport lubricant from the lubricant sump 37 to the at least one nozzle 36 of each nozzle bridge 35. The dimensions of the gearbox housing 3 in the axial direction (x) is less than in the lateral direction (y) or the vertical direction (z). A first and a second electric motor (not shown) are arrangeable on opposite sides on the respective mounting flanges 20 of the gearbox housing 3 forming a pair of electric motors. With respect to their drive shafts, the first and the second electric motor are for example arranged coaxially.

During operation, the electric motors or the plurality of electric motors are for example torque controlled operated and each electric motor exerts the same torque on the respective coupling arrangement 11 of the input shaft 8.

The front part and/or the rear part of the gearbox housing 3 comprising the housing wall 4 extend essentially parallel to the z-y plane. The gearbox 2 may further comprise cooling means (not shown in the Figures), which are arranged on said walls 4. The cooling means are arranged for example on the outside of the walls 4 and comprise a cooling plate. The cooling plate comprises a channel connected to an external cooling circuit for a cooling fluid to flow through (not shown).

The Figures 5 and 6 advantageously show the interior of the gearbox 2 according to this variation. Figure 5 shows a cross section through one of the input shafts 8 along the vertical direction z. Figure 6 shows a cross section through one of the input shafts 8 and the output shaft 5.

Figures 5 and 6 show the gearbox 2 with the input shaft 8 extending through the gearbox housing 3, in particular through the walls 4. Figure 5 further shows the two mounting flanges 20 arranged via screws on the gearbox housing 3 and surrounding the axial ends 10 of the input shaft 8. The coupling arrangement 11 , the bearing arrangement 12 and the input gear 9 and the output gear 6 is further shown in Figures 5 and 6. The coupling arrangement 11 comprises a claw coupling 23 with a first claw part 24 and an elastomeric gear ring 27. A pressurized lubricant supply 14, which is configured to supply pressurized lubricant, for example transmission oil from the lubricant sump 37, to the bearing arrangement 12 is also shown in the Figures. A labyrinth sealing 15, a lubricant collecting area 19 and a siphon 22 are also shown in the Figures. Further, the axis of rotation 33, 34 are shown in the Figures.

Figure 6 further advantageously shows the bearing arrangement 7 of the output shaft 5, which comprises on one axial side of the output shaft 5 a fixedly arranged pair of angular contact ball bearings and on the other axial side of the output shaft 5 an axially slightly displaceable roller bearing. The entire output shaft 5 is according to this variation not axially displaceable.

The Figures 7 and 8 show in a detailed view the input shaft 8 and its arrangement within the gearbox 3. These Figures in particular show the bearing arrangement 12 of the input shaft 8 and the lubricant supply for the bearing arrangement 12 and the lubricant flow path from the bearing arrangement 12 back to the lubricant sump 37. Further, the Figures advantageously show the sealing arrangement between the rotating input shaft 8 and the gearbox housing 3. The bearing arrangement 12 comprises on both axial ends 10 a pair of angular contact ball bearings 13 in O-arrangement. The bearings 13 are axially fixedly arranged on the input shaft 8 and are arranged axially partially displaceable on the gearbox housing 3. The bearing arrangement 12 enables therefore limited axial displacement of the input shaft 8 with respect to the gearbox housing 3. The Figures further show that a sleeve part 31 is arranged between the bearings 13 and the gearbox housing 3. The sleeve part 31 is arranged fixedly on the gearbox housing 3 and provides the contact surfaces for the bearings 13. The sleeve part 31 therefore forms part of the gearbox housing 3. Figure 8 further advantageously shows a connecting opening 41 , which connects the collecting area 19 arranged radially outside the labyrinth sealing 15 with the collecting area 19 of the ring shaped depressions 21 . The lubricant which is collected in both collecting areas 19 flows together via the siphon 22 and the return pipe 30 back into the gearbox housing 3. In this variation, the connecting opening 41 extends substantially parallel with respect to the input axis 33.

The Figures 7 and 8 further show the pressurized lubricant supply 14. A preferred lubricant is for example transmission oil, which is pumped via the oil pump from the lubricant sump 37 to the pressurized lubricant supply 14. The pressurized lubricant is guided into a ring shaped cavity, which functions as the lubricant supply 14. The ring shaped cavity is arranged radially outside of the sleeve part 31 . The sleeve part 31 comprises openings 38 extending radially through the sleeve part 31 and arranged in circumferential direction around the sleeve part 31. The pressurized lubricant can be supplied through the openings 38 to the bearings 13. Figure 8 further shows a spacer 32, which is arranged between the two bearings 13 of a bearing pair. The spacer 32 comprises perforations or openings, which enable the pressurized lubricant to flow from the openings 38 into the interior of the bearing pair. This enables an advantageous and reliable lubricant supply for the bearings 13 during operation of the gearbox 2, which reduces friction and wear losses. The lubricant, which flows through the axially inside-arranged bearing 13 flows directly back towards the interior of the gearbox housing 3, in particular into the lubricant sump 37. The lubricant, which flows through the axially outside-arranged bearing 13 is hindered from leaking into the environment by the sophisticated sealing arrangement of the present disclosure. The sealing arrangement, best visible in the Figures 7 and 8 comprises a labyrinth sealing 15 on each axial end 10 of the input shaft 8, which comprises the coupling arrangement 11. The labyrinth sealing 15 comprises a first portion 16, which is fixedly arranged on the input shaft 8, in particular fixedly arranged on the first claw part 24 of the input shaft 8. The first portion 16 is therefore configured to rotate with the input shaft 8. The labyrinth sealing 15 further comprises a second portion 17, which is fixedly arranged with the gearbox housing 3, in particular between the mounting flange 20 and the sleeve part 31 of the gearbox housing 3. The second portion 17 does not rotate with the input shaft 8 during operation. The first portion 16 and the second portion 17 comprise each two axially extending protrusions at different radii, which overlap with each other, thereby forming the labyrinth of the labyrinth sealing 15. Lubricant needs to pass through the labyrinth to leak. The first portion 16 further comprises two skidding edges 18, which are configured to skid lubricant, which has accumulated on the skidding edges 18, radially towards a dedicated collecting area 19. The rotating first portion 16 spins lubricant drops, which made it until the different skidding edges 18, towards the collecting area 19. The collecting area 19 is according to this variation a combination of depressions and openings in the mounting flange 20 and in the sleeve part 31 arranged radially outside of the labyrinth sealing 15.

The sealing arrangement further comprises a plurality of ring shaped depressions 21 arranged on a radial inner surface of the mounting flange 20. Lubricant, which made it that far, may be collected by the depressions 21. The bottom of the mounting flange 20 comprises a groove, which guides the collected lubricant back to the collecting area 19. The sealing arrangement further comprises a siphon 22, which forms part of a return pipe 30. The return pipe 30 is configured to guide the lubricant from the collecting area 19 back into the interior of the gearbox housing 3. The siphon 22 is arranged in the return pipe 30 and enables the liquid lubricant to flow back and simultaneously hinders that lubricant mist escapes from the interior of the gearbox housing 3 through the return pipe 30. The Figures 7 and 8 further show that the siphon 22 is closed by a cover, which is screwed onto the mounting flange 20 from below. The Figures further show that the mounting flange 20 comprises an additional depression, which extends axially from the axial outer surface of the mounting flange 20 into the mounting flange 20, and which is arranged radially outside of the ring shaped depressions 21 . This additional depression is also configured to collect lubricant and is configured to guide the lubricant into the return pipe 30. The additional depression is therefore also connected to the return pipe 30 via the siphon 22.

The Figures 9, 10 and 11 advantageously show the input shaft 8 and its different components in an axially exploded fashion. Starting from the inside to the outside, the Figures show the two input gears 9, which are helical gears arranged in a V- shape, the bearing pairs 13 with the two angular ball bearings 13, the sleeve part 31 , which provides the a radial outer contact surface for the bearings 13, the labyrinth sealing 15 and the coupling arrangement 11 , with the claw coupling 23.

The Figures show that the input gears 9 are fixedly arranged in circumferential direction via a splined shaft connection and are fixedly arranged in axial direction via the bearings 13 and the first claw part 24, which is screwed onto the input shaft 8 via a clamp screw 25. The bearings 13, in particular the rotating parts of the bearings 13, are therefore also axially fixedly arranged on the input shaft 8. The bearings 13 are additionally arranged within the sleeve part 31 such that limited axial movement of the bearings 13 with respect to the sleeve part 31 and therefore also with respect to the housing 3 is enabled. It is therefore possible for the entire input shaft 8 to move axially slightly away from the neutral position during operation. The neutral position is the position in which the input gears 9 are perfectly aligned with the corresponding output gears 6. The Figures further show two disc springs 28, which are arranged axially next to the bearing pair and a protrusion of the sleeve part 31 . The disc springs 28 are configured to apply a dynamically increasing counter acting axial force on the bearings 13, when the input shaft 8 is axially displaced away from the neutral position. Having the disc springs 28 arranged on both axial ends in a mirrored fashion enables to apply the counter acting axial force from both axial directions. The entire input shaft 8 is therefore axially self-aligning with respect to the neutral position.

The Figures 9 to 11 further show that the sleeve part 31 comprises a plurality of openings 38 for the pressurized lubricant supply 14 and additional openings 40 and grooves 39 to enable the lubricant to flow I skid from the labyrinth sealing 15 into the dedicated collecting area 19, which is arranged in the mounting flanges 20 (shown in the Figures 7 and 8).

The Figures 9 to 11 further show advantageously the coupling arrangement 11 , which is arranged on both axial ends 10 of the input shaft 8. The coupling arrangement 11 comprises a claw coupling 23 with a first claw part 24. The first claw part 24 is arranged on the input shaft 8 via the clamp screw 25 and a plurality of pins 26, preferably twelve pins 26, extending in axial direction x and being arranged in circumferential direction equidistant with respect to each other. The Figures further show the labyrinth sealing 15, with the first portion 16 and the second portion 17. The first portion 16 is preferably shrinked onto the first claw part 24. The Figures further show an elastomeric gear ring 27, which is arranged, preferably in a loose fashion, between the first claw part 24 and a second claw part (not shown in the Figures). The second claw part forms part of the claw coupling 23 and is arranged on the electric engine (not shown in the Figures). The elastomeric gear ring 27 is preferably made of a plastic material and provides advantageous vibration damping between the electric engine and the input shaft 8. Having on both axial ends 10 of the input shaft 8 an electric engine engage for driving the input shaft may lead to undesired vibrations and axial movement, which is advantageously compensated by the bearing and sealing arrangement of the input shaft 8.

The Figures 12 and 13 show a specific variation of the gearbox 2, which differs from the variation of the gearbox 2 as shown in the Figures 1 to 11 in the lubricant flow path. In this variation, the connecting opening 41 connects the collecting area 19 arranged radially outside of the labyrinth sealing 15 directly with the return pipe 30. Lubricant and lubricant mist which is collected in the collecting area 19 arranged radially outside of the labyrinth sealing 15 streams directly back into the gearbox housing 3 via the return pipe. This lubricant and lubricant mist does not flow in this variation via the siphon 22. In this variation provides the advantage that lubricant mist, which made it past the bearings 13 cannot stream via the connecting opening 41 into the environment. This lubricant mist is collected and guided back via the connecting opening 41 and the return pipe 30 into the gearbox housing 3. Lubricant, which is collected by the ring shaped depressions 21 is still guided back via the dedicated collecting area 19, the siphon 22 and the return pipe 30 into the gearbox housing 3. Also in this variation, the siphon 22 provides the desired lubricant mist barrier, which might ascent from the gearbox housing 3 into the return pipe 30. The Figures further show a plurality of sealing rings 29, which are configured to seal between different parts of the gearbox 2, which are not rotating with respect to each other.

The bearing arrangement 12, the sealing arrangement and the coupling arrange- ment 11 of the input shaft 8 as presented provides the required properties to enable a low friction, low wear and high vibration resisting torque transfer from the electric engines via the input shaft 8 to the output shaft 5, using the gearbox 2.

Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the scope of the disclosure.

LIST OF DESIGNATIONS

1 Drive train 24 First claw part

2 Gearbox 25 Clamp screw

3 Gearbox housing 26 Pin

4 Gearbox housing wall 27 Elastomeric gear ring

5 Output shaft 30 28 Disc spring

6 Output gear 29 Sealing ring

7 Bearing arrangement 30 Return pipe

8 Input shaft 31 Sleeve part

9 Input gear 32 Spacer

10 Axial end 35 33 Input axis

11 Coupling arrangement 34 Output axis

12 Bearing arrangement 35 Nozzle bridge

13 Bearings 36 Lubricant nozzles

14 Pressurized lubricant sup37 Lubricant sump ply 40 38 Openings

15 Labyrinth sealing 39 Grooves

16 First portion 40 Additional Opening

17 Second portion 41 Connecting Opening

18 Skidding edge

19 Collecting area 45 x axial direction

20 Mounting flange y lateral direction

21 Ring shaped depression z vertical direction

22 Siphon

23 Claw coupling

Claims

PATENT CLAIMS

1 . A gearbox (2) for a drive train (1 ) of an electric truck, the gearbox (2) comprising: a. at least one input shaft (8) arranged at least partially within a gearbox housing (3) and extending in an axial direction (x), the input shaft (8) comprising an input gear (9) and on at least one of its axial ends (10) a coupling arrangement (11 ), which is configured to engage with an electric engine for driving the input shaft (8), b. an output shaft (5) arranged at least partially within the gearbox housing (3) and extending in the axial direction (x) parallel with respect to the input shaft (8) and comprising an output gear (6) configured to be driven by the input gear (9), c. wherein the input shaft (8) comprises at the axial end (10) of the coupling arrangement (11 ) a labyrinth sealing (15), which is configured to provide a lubricant sealing for the gearbox housing (3) during operation.

2. The gearbox (2) according to claim 1 , wherein the labyrinth sealing (15) comprises a first labyrinth portion (16) fixedly arranged on the input shaft (8) and a second labyrinth portion (17) fixedly arranged on the gearbox housing (3), wherein the first and second labyrinth portions (16, 17) comprise each at least one axially extending protrusions, which overlap axially with respect to each other, thereby forming the labyrinth of the labyrinth sealing (15).

3. The gearbox (2) according to claim 2, wherein the first labyrinth portion (16) of the labyrinth sealing (15) comprises at least one skidding edge (18) extending radially with respect to the input shaft (8) and being configured to skid lubricant into a dedicated collecting area (19) of the gearbox housing (3) during operation of the gearbox (2).

4. The gearbox (2) according to any of the preceding claims, wherein the gearbox (2) further comprises at least one sleeve shaped mounting flange (20) arranged on the gearbox housing (3) coaxially with the input shafts (8) and surrounding at least partially the axial end of the input shaft (8) comprising the coupling arrangement (11 ), wherein the mounting flanges (20) are configured to position the electric engine such that a drive shaft of the electric engine is engageable with the input shaft (8).

5. The gearbox (2) according to claim 4, wherein the at least one mounting flange (20) comprises on one of its radial inner surfaces ring shaped depressions (21 ), which are configured to collect lubricant during operation of the gearbox (2) and to guide the lubricant into the dedicated collecting area (19).

6. The gearbox (2) according to one of the claims 3 to 5, wherein the dedicated collecting area (19) is fluidically connected via a siphon (22) to the interior of the gearbox housing (3) such that the lubricant is guided back from the collecting area (19) into the gearbox housing (3) through the siphon (22) during operation of the gearbox (2).

7. The gearbox (2) according to one of the preceding claims, wherein the input shaft (8) comprises a bearing arrangement (12) configured to bear the input shaft (8) with respect to the gearbox housing (3), the bearing arrangement (3) being configured to enable limited axial movement of the input shaft (8) for adjusting its axial position with respect to the gearbox housing (3) during operation of the gearbox (2).

8. The gearbox (2) according to claim 7, wherein the bearing arrangement (12) of the input shaft (8) comprises a plurality of bearings (13), which are lubricated via a pressurized lubricant supply (14).

9. The gearbox (2) according to claim 8, wherein the bearing arrangement (12) of the input shaft (8) comprises on each axial end (10) of the coupling arrangement (11 ) one pair of angular ball bearings in O-Arrangement, wherein the pressurized lubrication supply (14) is configured to supply the lubricant between the pair of angular ball bearings.

10. The gearbox (2) according to one of claims 7 to 9, wherein the bearing arrangement (12) further comprises at least one spring (28) arranged axially between the gearbox housing (3) and one bearing (13) of the bearing arrangement (12), wherein the at least one spring (28) is configured to dynamically increase an axial force, which is required to axially displace the input shaft (8) in one axial direction from a predefined initial position.

11 . The gearbox (2) according to claim 10, further comprising at each axial side (10) of the input shaft (8) the spring (28), wherein the two springs (28) are configured to dynamically increase the axial force, which is required to axially displace the input shaft (8) in both axial directions from a predefined initial neutral position.

12. The gearbox (2) according to one of the preceding claims, wherein both of the axial ends (10) of the input shaft (8) comprise a coupling arrangement (11 ), which is configured to engage with an electric engine for driving the input shaft (8).

13. The gearbox (2) according to one of the preceding claims, wherein the coupling arrangements (11 ) of the input shaft (8) comprises a claw coupling (23) with a first claw part (24) and a second claw part, wherein the first claw part (24) being arranged coaxially on the input shaft (8), and the second claw part is configured to be arranged coaxially on the drive shaft of the electric engine, wherein the first claw part (24) and the second claw part are engagable with each other for transferring torque from the electric engine to the input shaft (8).

14. The gearbox (2) according to claim 13, wherein the first claw part (24) is arranged coaxially on the input shaft (8) via a clamp screw (25) arranged coaxially with the input shaft (8) and the first claw part (24) and I or via a plurality of pins (26) arranged between the first claw part (24) and the input shaft (8).

15. The gearbox (2) according to one of the claims 13 to 14, wherein the claw coupling (23) comprises an elastomeric gear ring (27) arranged between the claws of the first claw part (24) and the claws o the second claw part thereby forming a torsional flexible claw coupling (23).

16. A drive train (1 ) for an electric truck comprising a gearbox (2) according to one of the preceding claims 1 to 15.