Claims:

1. A tandem axle assembly (10) for a vehicle, the assembly (10) comprising:
a tandem rear forward axle (RFA) and a tandem rearward rear axle (RRA) positioned in series, with the tandem rear forward axle (RFA) positioned before the tandem rearward rear axle (RRA);
a power divider unit (20) coupled to the tandem rear forward axle (RFA), wherein the power divider unit (20) comprising:
an input shaft (303) connectable to an output shaft of a transmission system, and coupled to an inter axle shaft (IAS) extending to the tandem rearward rear axle (RRA), wherein the input shaft (303) rigidly accommodates a first gear (301);
a drive pinion shaft (311) positioned parallel to the input shaft (303), the drive pinion shaft (311) rotatably accommodates a second gear (306), wherein the second gear (306) meshes with the first gear (301); and
a synchromesh unit (309) coupled to the drive pinion shaft (311), wherein the synchromesh unit (309) is configured to selectively couple the drive pinion shaft (311) with the second gear (306), to transmit torque from the input shaft (303) to a first differential assembly in the tandem rear forward axle (RFA); and
wherein, the first differential assembly (100) comprises a first drive unit (102) coupled to the drive pinion shaft (311) and a pair of drive half shafts (216, 217) movably coupled to the first drive unit (102), and an actuation mechanism coupled to each of the pair of drive half shafts (216, 217), wherein the actuation mechanism is configured to selectively engage and disengage each of the pair of drive half shafts (216, 217) from the first drive unit (102);
wherein, actuation of the synchromesh unit (309) and the actuation mechanism selectively operates tandem axle assembly (10) to propel the vehicle through either of the tandem rearward rear axle (RRA) and a combination of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA).

2. The assembly (10) as claimed in claim 1, wherein the tandem rearward rear axle (RRA) is configured to accommodate a second differential assembly, including a second drive unit (102’) coupled to the inter axle shaft (IAS) and a drive shaft (208) connected between the second drive unit (102’) and the wheels (1) to transmit torque.

3. The assembly (10) as claimed in claim 1, wherein the tandem rear forward axle (RFA) comprises of a drive through shaft (211) coupling the input shaft (303) with the inter axle shaft (IAS).

4. The assembly (10) as claimed in claim 1, comprises an interaxle differential unit (210) disposed in the power divider unit (20) and selectively coupled to the input shaft (303), wherein the interaxle differential unit (210) is adapted to regulate torque between the input shaft (303) and the drive through shaft (211) for transmitting torque to the tandem rearward rear axle (RRA).

5. The assembly (10) as claimed in claim 1, comprises a sleeve (308) connected to a first actuator (202) disposed over the input shaft (303), wherein the sleeve (308) is configured to selectively engage and disengage the interaxle differential unit (210) with the input shaft (303), and wherein upon engagement, the interaxle differential unit (210) is locked and transmits equal torque to both the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA).

6. The assembly (10) as claimed in claim 1, wherein the synchromesh unit (309) connected to a second actuator (214) comprises of an engaging gear (309E), a shifter sleeve (309S) and a synchronizer cone (309C), wherein the engaging gear (309E) is rigidly disposed over the drive pinion shaft (311), and the shifter sleeve (309S) selectively meshes the synchronizer cone (309C) with the second gear (306).

7. The assembly (10) as claimed in claim 1, wherein the actuation mechanism comprises of a pair of axle stub shafts (321, 322) extending from the first drive unit (102) connectable to the pair of drive half shafts (216, 217).

8. The assembly (10) as claimed in claim 7, wherein actuation mechanism comprises of engaging sleeves (327, 328) provisioned at the end of the pair of drive half shafts (216, 217) to selectively connect the drive half shafts (216, 217) with the pair of axle stub shafts (321, 322).

9. The assembly (10) as claimed in claim 8, wherein each of the engaging sleeves (327, 328) are connected to a second shifter fork (331, 332), and the second shifter fork (331, 332) is configured to displace the engaging sleeves (327, 328) to selectively connect the drive half shafts (216, 217) with the pair of axle stub shafts (321, 322), wherein the second shifter fork (331, 332) is operated by a third actuator (335, 336).

10. The assembly (10) as claimed in claim 1, wherein the first actuator (202), the second actuator (214) and the third actuator (335, 336) are at least one of pneumatic actuator, hydraulic actuator, and electrical actuator.

11. The assembly (10) as claimed in claim 1, wherein the first gear (301) and the second gear (306) are at least one of helical gears and spur gears.

12. A method of operating a tandem axle assembly (10) as claimed in claim 1, the method comprising:
displacing the sleeve (308) disposed over the input shaft (303) in the power divider unit (20) between a disengaged condition to an engaged condition, wherein the sleeve (308) in the engaged condition locks the interaxle differential unit (210) to transmit equal torque between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA);
displacing the shifter sleeve (309S) of the synchromesh unit by operating a first shifter fork (310) between a disengaged condition and an engaged condition, wherein the shifter sleeve (309S) in the disengaged condition decouples the drive pinion shaft (311) with the second gear (306) to restrict torque transfer from the input shaft (303) to the first differential assembly (30); and
operating a second shifter fork (331, 332) to displace an engaging sleeve (327, 328) provisioned on a pair of drive half shafts (216, 217) in an actuation mechanism to disengage each of the pair drive half shafts (216, 217) from the drive unit (102) of a first differential assembly (30) to remove connection between the first differential assembly (30) and wheels,
wherein, by selectively displacing the sleeve (308) and shifter sleeve (309S) in the power divider unit, and selectively operating the second shifter fork (331, 332) in the first differential assembly, the tandem axle assembly (10) propels the vehicle through either of the tandem rearward rear axle (RRA) and a combination of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA).

13. A vehicle comprising a tandem axle assembly (10) as claimed in claim 1.
, Description:TECHNICAL FIELD:

The present disclosure, in general, relates to automobiles. Particularly, but not exclusively, the present disclosure relates to power transmission in a vehicle having a multi axle assembly. Further, embodiments of the present disclosure disclose a tandem axle assembly for selectively supplying torque to driving wheels of the vehicle.

BACKGROUND OF THE DISCLOSURE:

Generally, commercial vehicles and heavy load carrying vehicles such as trucks and buses are employed with multiple axles to maneuver the vehicle. The multiple axles provide a means for transferring torque from a prime mover to driving wheels that are connected each axle of the multiple axle assembly in the vehicle. Additionally, the multiple axle assembly is configured to divide and selectively supply power from the prime mover to specific axles, in order to avoid excessive loads on a single axle, where such loads may be further distributed along each axle in the multiple axle assembly. Further, on selective supply of power from the prime mover to specific axle of the multiple axle assembly, improved traction is provided when the vehicle drives over adverse road conditions.

Conventionally, the multiple axle assembly is employed in the vehicles which are prone to traverse on irregular terrains, where such multiple axle assembly, generally tandem axle assembly, includes a rear-forward and a rear-rear axle assemblies and an intermediate drive shaft assembly connecting the two axle assemblies. The forward and rear axle assemblies each include a differential and a pair of axle shafts extending therefrom and about either sides of a chassis of the vehicle, to which one or more wheels of the vehicles are connected for suitably driving the vehicle. Further, the multiple axle assembly employs an inter axle differential mechanisms to divide power from a drive shaft extending from the transmission system into each axle of the multiple axle assembly and regulates speed differences between each axle of the multiple axle assembly.

Further, in conventional multiple axle assemblies, torque delivered by the prime mover through the transmission system may be constantly transmitted to terrain, as wheels connected to each of the axle in the multiple axle assemblies receive torque regardless of necessity of such torque for movement of the vehicle. In general, torque may be required when movement of the vehicle may be about at least one of starting off from a rest position, driving uphill, maneuvering along a uneven terrain and any other terrain that would require slow movement and/or steady rigid grip from movement. Thus, the vehicle does not require multiple axles for providing traction during the normal driving conditions or when the vehicle is driving unloaded. Furthermore, as the torque is supplied to each axle of the multiple axle assemblies, efficient driving cannot be achieved. For example, although the vehicle only requires a single drive axle, multiple drive axles are being driven which lead to higher fuel consumption, mechanical wear of components in the multiple axle assembly, tire wear, splash losses in the differential and the oil in the differential gets worn out due to continuous churning.

For the purpose of minimizing such losses, several mechanisms have been developed that lift some of the axles of the multiple axle assemblies to eliminate contact between the wheels with the terrain but cannot be incorporated with a differential to drive the vehicle through such axles. Further, mechanisms for disengaging the axles to minimize wear of the components have been developed, however, these mechanisms use conventional clutch engagement and disengagement assemblies in the axles which result in the axle construction being complex, bulky and difficult to service and assemble.. Furthermore, such mechanisms do not provide smooth transition during engagement and disengagement of the clutches to regulate the torque between the multiple axles of the vehicle.

The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the conventional arts.

SUMMARY OF THE DISCLOSURE:

One or more shortcomings of the prior art are overcome by an assembly and a method as claimed and additional advantages are provided through the provision of the assembly as claimed in the present disclosure. Additional features and advantages are realized through the aspects and techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the present disclosure, a tandem axle assembly for a vehicle is disclosed. The assembly consists of a tandem rear forward axle and a tandem rearward rear axle which are positioned in series, where the tandem rear forward axle is positioned before the tandem rearward rear axle. The assembly further includes a power divider unit, coupled to the tandem rear forward axle. The power divider unit includes an input shaft which is connectable to an output shaft of a transmission system and is coupled to an inter axle shaft extending to the tandem rearward rear axle, where the input shaft rigidly accommodates a first gear. Further, a drive pinion shaft is positioned parallel to the input shaft and rotatably accommodates a second gear, where the second gear is adapted to mesh with the first gear. Furthermore, a synchromesh unit is coupled to the drive pinion shaft and is configured to selectively couple the drive pinion shaft with the second gear for transmitting torque from the input shaft to a first differential assembly in the tandem rear forward axle. The first differential assembly consists of a first drive unit which is coupled to the drive pinion shaft and a pair of drive half shafts that are movably coupled to the first drive unit, and an actuation mechanism is coupled to each of the pair of drive half shafts, where the actuation mechanism is configured to selectively engage and disengage each of the pair of drive half shafts from the first drive unit. Additionally, the selective actuation of the synchromesh unit and the actuation mechanism operates tandem axle assembly to propel the vehicle through only tandem rearward rear axle or combination of tandem rear forward axle and the tandem rearward rear axle.

In an embodiment, the tandem rearward rear axle is configured to accommodate a second differential assembly that includes a second drive unit which is coupled to the inter axle shaft and a drive shaft connected between the second drive unit and the wheels to transmit torque.

In an embodiment, the tandem rear forward axle consists of a drive through shaft coupling the input shaft with the inter axle shaft.

In an embodiment, an interaxle differential unit is disposed in the power divider unit and is selectively coupled to the input shaft, where the interaxle differential unit is adapted to regulate torque between the input shaft and the drive through shaft for transmitting torque to the tandem rearward rear axle.

In an embodiment, a sleeve is connected to a first actuator and is disposed over the input shaft, where the sleeve is configured to selectively engage and disengage the interaxle differential unit with the input shaft, and upon engagement, the interaxle differential unit is locked and transmits equal torque to both the tandem rear forward axle and the tandem rearward rear axle.

In an embodiment, the synchromesh unit is connected to a second actuator and consists of an engaging gear, a shifter sleeve and a synchronizer cone, wherein the engaging gear is rigidly disposed over the drive pinion shaft, and the shifter sleeve selectively meshes the synchronizer cone with the second gear.

In an embodiment, the actuation mechanism comprises of a pair of axle stub shafts extending from the first drive unit connectable to the pair of drive half shafts.

In an embodiment, actuation mechanism comprises of engaging sleeves provisioned at the end of the pair of drive half shafts to selectively connect the drive half shafts with the pair of axle stub shafts.

In an embodiment, the each of engaging sleeves are connected to a second shifter fork which is configured to displace the engaging sleeves to selectively connect the drive half shafts with the pair of axle stub shafts, where the shifter fork is operated by an actuator.

In an embodiment, the first actuator, the second actuator and the third actuator are at least one of pneumatic actuator, hydraulic actuator, and electrical actuator.

In an embodiment, wherein the first gear and the second gear are at least one of helical gears and spur gears.

In another non-limiting embodiment of the disclosure, a method of operating a tandem axle assembly is disclosed. The method incudes steps of displacing a sleeve which is disposed over an input shaft in a power divider unit between a disengaged condition to an engaged condition, where the sleeve in the engaged condition locks an interaxle differential unit to transmit equal torque between a tandem rear forward axle and a tandem rearward rear axle. Further, a shifter sleeve of a synchromesh unit is displaced between a disengaged condition and an engaged condition by a shifter fork, where the shifter sleeve in the disengaged condition decouples a drive pinion shaft with a second gear to restrict torque transfer from the input shaft to a first differential assembly. Furthermore, a shifter fork is operated to displace an engaging sleeve provisioned on a pair of drive half shafts in an actuation mechanism to disengage the pair of drive half shafts from the drive unit of a first differential assembly to remove connection between the first differential assembly and wheels. Additionally, by selectively displacing the sleeve and shifter sleeve in the power divider unit, and selectively operating the shifter fork in the first differential assembly, the tandem axle assembly propels the vehicle through either of the tandem rearward rear axle and a combination of the tandem rear forward axle and the tandem rearward rear axle.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:

The novel features and characteristics of the disclosure are set forth in the description. The disclosure itself, however, as well as a preferred mode of use, further advantages thereof, will best be understood by reference to the following description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

Fig. 1 illustrates a schematic view of a tandem axle assembly, in accordance with an embodiment of the present disclosure.

Fig. 2 illustrate a schematic sectional view of a power divider unit connected to a differential assembly in a tandem rear forward axle, in accordance with an embodiment of the present disclosure.

Figs. 3a and 3b illustrate sectional views of a differential assembly in the tandem rear forward axle of the tandem axle assembly, in accordance with an embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the mechanism and assembly illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF THE DISCLOSURE:

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that, the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other mechanism or assembly or methods for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that an assembly, mechanism or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or mechanism or assembly. In other words, one or more elements in a mechanism or assembly proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism or assembly.

Embodiments of the present disclosure relates to a tandem axle assembly for a vehicle. The assembly consists of a tandem rear forward axle and a tandem rearward rear axle which are positioned in series, where the tandem rear forward axle is positioned before the tandem rearward rear axle. A power divider unit is coupled to the tandem rear forward axle. The power divider unit includes an input shaft which is connectable to an output shaft of a transmission system and is coupled to an inter axle shaft of the tandem rearward rear axle, where the input shaft rigidly accommodates a first gear. Further, a drive pinion shaft is positioned parallel to the input shaft and rotatably accommodates a second gear, where the second gear is adapted to be in constant mesh with the first gear. Furthermore, a synchromesh unit is coupled to the drive pinion shaft and is configured to selectively couple the drive pinion shaft with the second gear for transmitting torque from the input shaft to a first differential assembly in the tandem rear forward axle. The first differential assembly consists of a first drive unit which is coupled to the drive pinion shaft and a pair of drive half shafts that are movably coupled to the first drive unit, and an actuation mechanism is coupled to each of the pair of drive half shafts, where the actuation mechanism is configured to selectively engage and disengage each of the pair of drive half shafts from the first drive unit. Thus, by selective actuation of the synchromesh unit and the actuation mechanism, the tandem axle assembly propels the vehicle through the tandem rearward rear axle or through both the tandem rear forward axle and the tandem rearward rear axle.

Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible, same numerals will be used to refer to the same or like parts. The following paragraphs describe the present disclosure with reference to Figs 1 to 3. Also, the assembly and method may be employable in vehicles including, but not limited to, heavy-duty vehicles, commercial vehicles, and the like, for increasing and decreasing traction, to drive such vehicle.

Figs. 1 and 2 are exemplary embodiments of the disclosure which illustrates a tandem axle assembly (10) for a vehicle [not shown in Figures] having multiple axles. The tandem axle assembly (10) is positioned underneath a chassis [not shown in Figures] of the vehicle and is a part of a powertrain to drive the vehicle. The tandem axle assembly (10) is adapted to receive power from a prime mover which may be including, but not limited to, an engine of the vehicle through a transmission system [not shown in Figures]. The tandem axle assembly (10) is configured to selectively transmit power to wheels of the vehicle so that, required torque is applied to maneuver the vehicle on a terrain surface for driving the vehicles. The tandem axle assembly (10) may include multiple axles connected in series, for transmission of power to the wheels of the vehicle, where each axle of the multiple axles in the tandem axle assembly (10) may be coupled to one or more wheels on either sides of the chassis for such driving of the vehicle.

In the illustrative embodiment, the tandem axle assembly (10) includes a tandem rear forward axle (RFA) and a tandem rearward rear axle (RRA) positioned in a series configuration [i.e. the tandem rear forward axle (RFA) being substantially in-line and/or coaxial with the tandem rearward rear axle (RRA)], where the tandem rear forward axle (RFA) is positioned before the tandem rearward axle. The tandem rear forward axle (RFA) is coupled to the output shaft of the prime-mover [not shown] through the transmission system for receiving power and/or torque produced therethrough, while the tandem rearward rear axle (RRA) is configured to drive the vehicle. Further, the tandem rear forward axle (RFA) is coupled with a power divider unit (20). In an embodiment, the tandem rear forward axle (RFA) and the power divider unit (20) are housed in a same enclosure. The power divider unit (20) is configured to divide power supplied by the engine through the transmission system, between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). The tandem rear forward axle (RFA) consists of a first differential assembly (100) and the rearward rear axle (RRA) consists of a second differential assembly (101). The first differential assembly (100) and the second differential assembly (101) are adapted to transfer torque received by the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) to the wheels (1) of the vehicle. An inter axle shaft (IAS) is connected between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) to transfer torque from the tandem rear forward axle (RFA) to the tandem rearward rear axle (RRA).

In an embodiment, the first differential assembly (100) includes a first drive unit (102) and the second differential assembly (101) includes a second drive unit (102’). The first drive unit (102) and the second drive unit (102’) are supported on an axle beam of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) respectively. The first drive unit (102) and the second drive unit (102’) consist of a first bevel drive pinion (201) and a second bevel drive pinion (209) respectively which are adapted to receive torque and provide torque input for the differential assembly (100, 101).

In an embodiment, the second differential assembly (101) consists of at least one bevel gear (206) that is meshed with the second bevel drive pinion (209) to receive and transmit torque. The at least one bevel gear (206) is meshed with axle shaft gears (207), which are supported by the axle beam and are rotationally locked to drive shafts (208), that connect the second drive unit (102’) to the wheels (1). The drive shafts (208) are adapted to drive the wheels (1) of the vehicle by transmitting torque from the second drive unit (102’). The second bevel drive pinion (209) is meshed with the inter axle shaft (IAS) to receive the torque and drive the second drive unit (102’).

Referring now to the power divider unit (20) as shown in Fig. 2, the power divider unit includes a housing configured to house the internal components and (20) consists of an input shaft (303) disposed within the housing and connectable to an output shaft extending from the transmission system. The input shaft (303) is configured to transmit torque generated by the prime mover to drive the tandem axle assembly (10). The power divider unit (20) consists of first bearings (304, 305) over which the input shaft (303) may be disposed. The first bearings (304, 305) may be positioned at either ends of the input shaft (303) within the housing to rotatably support the input shaft (303) within the power divider unit (20). Further, a first gear (301) is rigidly accommodated [i.e. fixed by means including, but not limited to, keyways, spline arrangement, fasteners, adhesive bonding, welding, brazing, and the like] on the input shaft (303) and is configured to rotate along with the input shaft (303). In an embodiment, the first gear (301) is disposed over the input shaft (303) through a side gear (302). A bush is provisioned between the side gear (302) and the input shaft (303) to transfer torque from the input shaft (303) to the first gear (301) and therethrough, without any jerk. Furthermore, a drive pinion shaft (311) may extend from a first bevel drive pinion (201) into the housing of the power divider unit (20) which may be positioned parallel to the input shaft (303). A second gear (306) may be rotatably disposed over the drive pinion shaft (311) [i.e. the second gear (306) is free to rotate about the drive pinion shaft (311), while the second gear (306) is configured to rotate the drive pinion shaft (311) on selectively engaging and/or meshing the drive pinion shaft (311)]. In an embodiment, the second gear (306) may be provisioned over a second bearing that allows the second gear (306) to be rotatably disposed over the drive pinion shaft (311). Additionally, the first gear (301) is constantly meshed with the second gear (306) to transmit torque received by the input shaft (303) onto the second gear (306). In an embodiment, the second gear (306) may be supported by a bush to enable smooth transmission of torque between the first gear (301) and the second gear (306).

Further, the power divider unit (20) includes a synchromesh unit (309) coupled to the drive pinion shaft (311). The synchromesh unit (309) is configured to selectively couple and/or mesh the second gear (306) with the drive pinion shaft (311), to transmit torque from the input shaft (303) to the first differential assembly (100) of the tandem rear forward axle (RFA). The synchromesh unit (309) consists of an engaging gear (309E), a shifter sleeve (309S) and a synchronizer cone (309C). The engaging gear (309E) is rigidly connected to the drive pinion shaft (311). The shifter sleeve (309S) is adapted to selectively mesh the synchronizer cone (309C) with the second gear (306) to mesh the second gear (306) with the drive pinion shaft (311) via the engaging gear (309E), thereby enabling the drive pinion shaft (311) to receive torque from the input shaft (303) through the second gear (306). In an embodiment, the synchromesh unit (309) is coupled on the drive pinion shaft (311) by means including, but not limited to, keyways, spline arrangement, fasteners, and the like splines. The synchromesh unit (309) is provisioned with a first shifter fork (310) in communication with the shifter sleeve (309S). The first shifter fork (310) is connected to a second actuator (214) and displaces the shifter sleeve (309S) due to the force exerted by the second actuator (214). In an embodiment, the second actuator (214) may be one of but not limited to an electromechanical actuator, an electromagnetic actuator, a hydraulic actuator, and a pneumatic actuator.

In an embodiment, a drive through shaft (211) is provisioned in the tandem rear forward axle (RFA). The drive through shaft (211) is coupled to the input shaft (303) and is configured to connect the input shaft (303) and the inter axle shaft (IAS) such that, torque received from the transmission system may either be divided by the power divider unit (20) or can be transferred directly to the tandem rearward rear axle (RRA) without operating the tandem rear forward axle (RFA). In an embodiment, the drive through shaft (211) may be disposed over a third bearing to rotate within the tandem rear forward axle (RFA). The drive through shaft (211) may protrude out of a differential cover (318) to connect the input shaft (303) with the inter axle shaft (IAS).

Further, the power divider unit (20) includes an interaxle differential unit (210), selectively coupled to the input shaft (303) and is adapted to regulate torque between the input shaft (303) and the drive through shaft (211), thus regulating the torque between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). In an embodiment, the interaxle differential unit (210) disposed in the power divider unit (20) adjacent to the input shaft (303) may be locked to disengage connection between the input shaft (303) and transmit equal torque to both the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). Locking of the interaxle differential unit (210) is enabled by a sleeve (308) which is provisioned adjacent to the input shaft (303) within the housing and is connected to a shifter lever. The shifter lever is connected to a first actuator (202) configured to actuate the shifter lever to longitudinally displace the sleeve (308) between an engaged condition and a disengaged condition to lock and unlock the interaxle differential unit (210), whereby the interaxle differential unit (210) in the locked condition does not regulate torque instead transmits equal torque between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). In an embodiment, the first actuator (202) may be one of but not limited to an electromechanical actuator, an electromagnetic actuator, a hydraulic actuator and a pneumatic actuator.

Referring now to Figs. 3a and 3b, the tandem rear forward axle (RFA) consists of a front housing part (215) of the first drive unit (102). The front housing part (215) includes two housing inner webs (312, 313) projecting into a differential reservoir. Both the housing inner webs (312, 313) are defined with bores, which align one another to accommodate bearing supports. Further, taper roller bearings (314, 315) may be positioned between the bores and the differential cover (318). The taper roller bearings (314, 315) are inserted in an O-shaped arrangement and are seated on tubular bearing supports. Furthermore, a differential gear unit or spider (316) is assembled and disposed within the differential cover (318). In an embodiment, the differential cover (318) consists of two opposing bores that are aligned with one another, the center lines of which are defined on the wheel axis of rotation, where axle side gears (319, 320) of the first differential assembly (100) are supported and rotate in these bores.

In an embodiment, the first drive unit (102) of the first differential assembly (100) consists of at least one bevel gear meshed with the first bevel drive pinion (201). The first differential assembly (100) further includes an axle stub shaft (321, 322) connected to at least one bevel gear in the first drive unit (102) through axle side gears (319, 320). Further, needle bearings (325, 326) are provisioned at the ends of the axle stub shaft (321, 322) away from the first drive unit (102). Additionally, the first differential assembly (100) consists of a pair of drive half shafts (216, 217) extending from the end of the axle stub shaft (321, 322) to the wheels (001). The pair of drive half shafts (216, 217) are positioned on the needle bearing (325, 326) such that a rotational connection is achieved between the axle stub shaft (321, 322) and the pair of drive half shaft (216, 217).

Further, the assembly includes an actuation mechanism includes an engaging sleeve (327, 328) fixed at an end of the pair of drive half shafts (216, 217) away from the wheels (001). The engaging sleeve (327, 328) is adapted to selectively engage and lock with the axle stub shaft (321, 322) for transmitting torque from the first drive unit (102) to the wheels (001). In an embodiment, the axle stub shaft (321, 322) is defined with grooves to engage with the engaging sleeve (327, 328) and lock the axle stub shaft (321, 322) with the pair of drive half shafts (216, 217). Further, the actuation mechanism includes a second shifter forks (331, 332) engaging with a shift slot (329, 330) defined on the engaging sleeve (327, 328). The second shifter forks (331, 332) is connected to a third actuator (335, 336) to actuate the second shifter fork (331, 332) to displace corresponding engaging sleeve (327, 328) towards the axle stub shaft (321, 322). Additionally, the actuation mechanism includes a push back spring (333 & 334) attached to the second shifter fork (331, 332) for biasing the second shifter fork (331, 332) to disengage the axle stub shaft (321, 322) and the engaging sleeve (327, 328). In an embodiment, the third actuator (335, 336) may be one of but not limited to an electromechanical actuator, an electromagnetic actuator, a hydraulic actuator, and a pneumatic actuator.

In an embodiment, torque from the prime mover is supplied to both the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). A method of operating the tandem axle assembly (10), for supplying torque from the engine to the tandem rearward rear axle is as follows. The sleeve (308) disposed adjacent to the input shaft (303) is displaced by actuating the first actuator (202), where the sleeve (308) is displaced from a disengaged condition to an engaged condition for locking the interaxle differential unit (210). The interaxle differential unit (210) in the locked condition is configured to halt regulating torque and equally supplies torque between the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). Further, the shifter sleeve (309S) in the synchromesh unit (309) is displaced to remove contact between the synchronizer cone (309C) and the second gear (306) by the second actuator (214). Thus, torque transmission from the input shaft (303) to the drive pinion shaft (311) for driving the first differential assembly (100) shaft may be halted. Furthermore, the third actuator (335, 336) in the actuation mechanism is operated to actuate the second shifter forks (331, 332). The actuation of the second shifter fork (331, 332) displaces the engaging sleeve (327, 328) of the pair of drive half shafts (216, 217), whereby disconnecting the pair of drive half shafts (216, 217) from the axle stub shaft (321, 322) to remove connection between the first differential assembly (100) and the wheels (001). Thus, the vehicle is driven by the tandem rearward rear axle (RRA) in the tandem axle assembly (10).

In an embodiment, the method for operating both the tandem axles for movement of the vehicle, being driven by the tandem rearward rear axle (RRA), is by actuating the second actuator (214) to displace the engaging sleeve (327, 328) of the synchromesh unit (309) to enable contact between the synchronizer cone (309C) and the second gear (306) by the second actuator (214), which results in the torque being transferred from the input shaft (303) to the drive pinion shaft (311). Further, the third actuator (335, 336) is de-actuated such that the second shifter fork (331, 332) displaces the engaging sleeve (327, 328) due to the biasing force exerted by the push back spring (333, 334) to couple the engaging sleeve (327, 328) with the axle stub shaft (321, 322). Additionally, the first actuator is de-actuated to displace the sleeve (308) which is disposed adjacent to the input shaft (303) to a disengaged condition. In the disengaged condition the locked condition of the interaxle differential is removed to resume regulating torque between the tandem rear forward axle (RFA) and the tandem rearward rear axle. Thus, both the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) of the tandem axle assembly (100) are operated to drive the vehicle.

In an embodiment, both the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) are constantly in operation and torque transmission to the tandem rear forward axle (RFA) is cut off only when the vehicle is travelling in an unloaded condition [without any load carried over the tandem axle assembly] or partially loaded condition [when the vehicle is partially loaded with the load carried by the tandem axle assembly] or when the vehicle has attained a threshold speed. In an embodiment, the threshold speed of the vehicle may be 30-50KMPH.

In an embodiment, operation of the tandem axle assembly (10) to propel the vehicle through either of the tandem rearward rear axle (RRA) and a combination of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA) may controlled through a switch or touch screen input in a cabin of the vehicle. Based on the inputs received through a switch or touch screen input the electronic control unit of the vehicle may operate the first, second and third actuators selectively, to propel the vehicle through either of the tandem rearward rear axle (RRA) and a combination of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). In further embodiment, the electronic control unit may be stored with instructions to automatically operate the operate the first, second and third actuators selectively, to propel the vehicle through either of the tandem rearward rear axle (RRA) and a combination of the tandem rear forward axle (RFA) and the tandem rearward rear axle (RRA). The electronic control unit may be configured to monitor information on dynamic handling or terrain surface parameters, such as the vehicle speed, vehicle acceleration, engine speed, accelerator position, road gradient and load condition for such automatic operation.

In an embodiment, the first gear (301) and the second gear (306) are one of but not limited to helical gears and spur gears.

The axle stub shaft (321, 322) is connected to the axle side gears (319, 320) by bushes (323, 324) and extends out of the first drive unit (102).

In an embodiment, the tandem axle assembly (10) increases fuel efficiency of the vehicle and reduces mechanical wear on the internal components of the first differential assembly (100). Further, the life of the tire corresponding to the tandem rear forward axle (RFA) is increased. Furthermore, the life of the oil present in the first differential assembly (100) is also increased as the oil stops churning when the vehicle is driven only by the tandem rearward rear axle (RRA).

Equivalents:

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Referral Numerals:

Reference Number Description
10 Tandem axle assembly
20 Power divider unit
100 First Differential assembly
101 Second Differential assembly
RFA Tandem Rear forward axle
RRA Tandem Rearward rear axle
IAS Inter axle shaft
1 Wheel
102 First Drive unit
102’ Second Drive unit
201 First Bevel drive pinion
209 Second Bevel drive pinion
202 First actuator
206 Bevel gear
207 Axle shaft gear
208 Drive shafts
210 Inter axle differential unit
211 Drive through shaft
214 Second actuator
215 Front housing part
216, 217 Drive half shaft
301 First gear
302 Side gear
303 Input Shaft
304, 305 First Bearing
306 Second gear
308 Sleeve
309 Synchromesh unit
309E Engaging gear
309S Shifter sleeve
309C Synchronizer cone
310 First Shifter fork
311 Drive pinion shaft
312, 313 Housing inner web
314, 315 Taper roller bearing
316 Differential gear unit/spider
318 Differential cover
319, 320 Axle side gear
321, 322 Axle stub shaft
323, 324 Bushes
325, 326 Needle bearing
327, 328 Engaging sleeve
329, 330 Shift slot
331, 332 Second Shifter fork
333, 334 Push back spring
335, 336 Third Actuator