WO2021099817A1

WO2021099817A1 - Gear reduction assembly

Info

Publication number: WO2021099817A1
Application number: PCT/IB2019/059938
Authority: WO
Inventors: Sindre Abrahamsen
Original assignee: Ka Group Ag
Priority date: 2019-11-19
Filing date: 2019-11-19
Publication date: 2021-05-27
Also published as: CN114729681A; SE2250602A1; DE112019007903T5

Abstract

A gear reduction assembly includes input and output shafts extending along an axis, a ring gear disposed around the axis, a sun gear coupled to one of the shafts, a carrier extending around the shafts, and a plurality of planetary gears rotatably coupled to the carrier. The carrier is movable along the axis between direct drive, neutral, and reduction positions. The planetary gears are meshed with the sun gear and the carrier is coupled with one of the shafts in each of the positions. The carrier is fixed to both shafts in the direct drive position. At least one of the shafts are disconnected from the carrier in the neutral position. The planetary gears are rotatably meshed with the ring gear and the sun gear, that is fixed to the one of the shafts, and the carrier is fixed to the other one of the shafts in the reduction position.

Description

GEAR REDUCTION ASSEMBLY

1. Field of the Invention

[0001] A gear reduction assembly for transmitting torque between a prime mover and a wheel.

2. Description of Related Art

[0002] Gear reduction assemblies are used in vehicles having wheels for selectively multiplying the torque transmitted to the wheels. Gear reduction assemblies are particularly well suited for applications requiring towing or hauling heavy loads, such as material handling and mining applications, agricultural applications, commercial trucks, construction, defense, forestry, ground support equipment, refuse, transit, and other specialty vehicles. The gear reduction assemblies often allow for the selection of different gear ratios that between the wheel and the prime mover, which drives the wheel. As such, the gear reduction assembly may transmit greater torque to the wheels when desired (e.g., when transporting heavy loads and/or traversing off-road terrain) and lower the torque when desired (e.g., when not loaded and/or traversing road terrain at high speeds).

[0003] Often, the gear reduction assembly includes one or more gear combinations that are capable to applying different gear ratios between the prime mover and the wheel. The gear combinations are selectively engaged and disengaged through friction clutches. Although effective in selectively multiplying the torque transmitted to the wheels, the friction clutches are susceptible to wear over time and add weight to the gear reduction assembly. As such, there remains a need to provide an improved gear reduction assembly for a vehicle.

SUMMARY OF THE INVENTION AND ADVANTAGES

[0004] The subject invention provides for a gear reduction assembly for transmitting torque between a prime mover and a wheel. The assembly includes an input shaft extending along an axis and configured to be rotated by the prime mover and an output shaft extending along the axis spaced from the input shaft and configured to rotate the wheel. The assembly further includes a ring gear disposed around the axis, a sun gear coupled to one of the input and output shafts, and a carrier extending along the axis and around the input and output shafts. The assembly further includes a plurality of planetary gears radially spaced about the axis and rotatably coupled to the carrier. The carrier is movable along the axis between direct drive, neutral, and reduction positions. The plurality of planetary gears are meshed with the sun gear and the carrier is coupled with one of the input and output shafts in each of the direct drive, neutral, and reduction positions.

[0005] The carrier is fixed to both the input shaft and the output shaft in the direct drive position such that the input and output shafts rotate in unison at equal rotational velocities around the axis. At least one of the input and output shafts are disconnected from the carrier in the neutral position such that the input and output shafts rotate independent of one another around the axis. The plurality of planetary gears are rotatably meshed with the ring gear and the sun gear that is fixed to the one of the input and output shafts, and the carrier is fixed to the other one of the input and output shafts in the reduction position such that the input and output shafts rotate at different rotational velocities around the axis.

[0006] Accordingly, the gear reduction assembly provides the advantage of reducing the number of components necessary for selectively changing the torque transmitted to the wheel. The continuous meshing of the planetary gears with the sun gear and the coupling of the carrier with one of the input and output shafts in each of the direct drive, neutral, and reduction positions maintains proper alignment of the input shaft, output shaft, and the carrier along the axis for facilitating movement of the carrier between the direct drive, neutral, and reduction positions. As such, the gear reduction assembly does not require friction clutches to selectively engage the sun gear, the planetary gears, and the ring gears. Moreover, the reduced number of components reduces the weight of the gear reduction assembly and facilitates smaller packaging size for the gear reduction assembly, which reduces the volumetric area occupied by the gear reduction assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Advantages of the subject invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

[0008] Figure 1A is a perspective view of a vehicle having an axle system.

[0009] Figure IB is a perspective view of the axle system, showing a prime mover, a gear box, and a gear reduction assembly.

[0010] Figure 2 is a cross-sectional perspective view of the gear reduction assembly, showing a carrier in a direct drive position.

[0011] Figure 3 is a cross-sectional perspective view of the gear reduction assembly, showing the carrier in a neutral position.

[0012] Figure 4 is a cross-sectional perspective view of the gear reduction assembly, showing the carrier in a reduction position.

[0013] Figure 5 is a schematic view of the gear reduction assembly, showing the carrier in the direct drive position.

[0014] Figure 6 is a schematic view of the gear reduction assembly, showing the carrier in the neutral position.

[0015] Figure 7 is a schematic view of the gear reduction assembly, showing the carrier in the reduction position. DETAILED DESCRIPTION OF THE INVENTION

[0016] Referring to the Figures, wherein like numerals indicates like or corresponding parts throughout the several views; a gear reduction assembly 20 for transmitting torque between a prime mover 22 and a wheel 24 of a vehicle 21 is generally shown in Figures 1A and IB. The gear reduction assembly 20 may be configured for use with an axle system 26. The axle system 26 may comprise a subframe 28 for mounting to a frame of the vehicle 21.

[0017] The prime mover 22 may be mounted to the subframe 28 and configured to product torque. As shown in the Figures, the prime mover 22 is configured as an electric motor capable of producing movement that rotates the wheel 24. However, the prime mover 22 may be an internal combustion engine, hydrogen fuel cell, or any other suitable mechanism capable of producing movement that rotates the wheel 24.

[0018] The axle system 26 may further include a gear box 30, as shown in Figure IB. The gear box 30 is mounted to the subframe 28 and coupled to each of the prime mover 22 and the gear reduction assembly 20. The gear box 30 is configured to transmit and alter torque from the prime mover 22 to the gear reduction assembly 20. More specifically, the gear box 30 may have a plurality of gears that may be individually selected. Each of the gears may have a different gear ratio. As such, the gear box 30 may alter the torque transmitted to the gear reduction assembly 20. Such a configuration is commonly referred to as a transmission in vehicle applications.

[0019] The prime mover 22 and the gear box 30 may be coupled to a single wheel 24 (or, more specifically, one set of dual wheels 24 as shown in Figure 1). As such, if the vehicle 21 has a plurality of driven wheels 24 or sets of driven dual wheels 24, each wheel 24 or set may have separate and distinct prime movers, gear boxes, and gear reduction assemblies. For example, as shown in Figure 1A, the axle system 26 comprises a pair of prime movers 22, a pair of gear boxes 30, and a pair of gear reduction assemblies 20 each individually driving a set of dual wheels 24. However, the prime mover 22, the gear box 30, and the gear reduction assembly 20 may be configured to drive more than one wheel 24 or set of dual wheels 24.

[0020] The axle system 26 is a rear drive axle, but it is to be understood that the advantageous features of the present disclosure to be described may be alternatively applied to a front drive axle (that is steerable), or preferably to both the front and rear drive axles.

[0021] The axle system 26 is adapted to be fixedly installed on the vehicle 21 with the wheels 24 coupled thereto such that the axle system 26 supports the weight of the vehicle 21 and cargo. Moreover, for reasons to be described, the gear reduction assembly 20 is capable of multiplying the torque transmitted from the prime mover 22 to the wheels 24. As such, the gear reduction assembly 20 of the present disclosure may be particularly well suited for heavy duty material handling and mining applications. However, other suitable applications may include agricultural applications ( e.g ., planters, sprayers, and other farm-related vehicles), commercial truck, construction, defense, forestry, ground support equipment, refuse, transit, and other specialty vehicles.

[0022] The gear reduction assembly 20 is mounted to the subframe and coupled to the prime mover 22. The assembly 20 is configured to transmit torque between the prime mover 22 and the wheel 24. As shown in Figures 2-7, the gear reduction assembly 20 comprises an input shaft 32 extending along an axis A and configured to be rotated by the prime mover 22, and an output shaft 34 extending along the axis A spaced from the input shaft 32 and configured to rotate the wheel 24.

[0023] The gear reduction assembly 20 further comprises a ring gear 36 disposed around the axis A, a sun gear 38 coupled to one of the input and output shafts 32, 34, and a carrier 40 extending along the axis A and around the input and output shafts 32, 34. The gear reduction assembly 20 further comprises a plurality of planetary gears 42 radially spaced about the axis A and rotatably coupled to the carrier 40.

[0024] The carrier 40 is movable along the axis A between direct drive (see Figures 2 and 5), neutral (see Figures 3 and 6), and reduction (see Figures 4 and 7) positions. More specifically, the carrier 40 and the plurality of planetary gears 42 move in unison along the axis A between the direct drive, neutral, and reduction positions. The plurality of planetary gears 42 are meshed with the sun gear 38 and the carrier 40 is coupled with one of the input and output shafts 32, 34 in each of the direct drive, neutral, and reduction positions, which maintains proper alignment of the input shaft 32, the output shaft 34, and the carrier 40 along the axis A for facilitating movement of the carrier 40 between the direct drive, neutral, and reduction positions, as will be described in greater detail below.

[0025] The carrier 40 is fixed to both the input shaft 32 and the output shaft 34 in the direct drive position (see Figures 2 and 5) such that the input and output shafts 32, 34 rotate in unison at equal rotational velocities around the axis A. Moreover, at least one of the input and output shafts 32, 34 are disconnected from the carrier 40 in the neutral position (see Figures 3 and 6) such that the input and output shafts 32, 34 rotate independent of one another around the axis A. Furthermore, the plurality of planetary gears 42 are rotatably meshed with the ring gear 36 and the sun gear 38 that is fixed to the one of the input and output shafts 32, 34, and the carrier 40 is fixed to the other one of the input and output shafts 32, 34 in the reduction position (see Figures 4 and 7) such that the input and output shafts 32, 34 rotate at different rotational velocities around the axis A.

[0026] The neutral position of the carrier 40 may be disposed between the direct drive and reduction positions of the carrier 40. Furthermore, the direct drive and reduction positions may define opposing ends of travel of the carrier 40. With reference given to the Figures, the direct drive position of the carrier 40 is the left-most position of the carrier 40 (see Figures 2 and 5), the reduction position is the right-most position of the carrier 40 (see Figures 4 and 7), and the neutral position centers the carrier 40 between the direct drive and reduction positions (see Figures 3 and 6). However, the relative positioning (i.e., left/right) of the carrier 40 is specific to the orientation of the Figures and may be different depending upon the view of the gear reduction assembly 20. Moreover, although the neutral position of the carrier 40 is shown in the Figures to be disposed between the direct drive and reduction positions of the carrier 40, the positions of direct drive, neutral, and reduction positions may be arranged in different orders in other embodiments not explicitly shown herein. For example, the direct drive and reduction positions may not define opposing ends of travel of the carrier 40. Furthermore, the carrier 40 may include one or more additional positions between or beyond direct drive, neutral, and reduction positions.

[0027] As shown in Figures 2-4, the gear reduction assembly 20 may further comprise a housing 44 defining an interior 46 along the axis A, with the input shaft 32, the output shaft 34, the sun gear 38, the plurality of planetary gears 42, and the carrier 40 disposed within the housing 44. As such, the housing 44 may provide protection to the components of the gear reduction assembly 20 disposed therein by reducing the intrusion of contaminants (such as dust and water) that may degrade the components.

[0028] The input and output shafts 32, 34 may be fixed longitudinally along the axis A, with the carrier 40 configured to move along the input and output shafts 32, 34 while moving between the direct drive, neutral, and reduction positions. As shown in Figures 2-4, the gear reduction assembly 20 may comprise an input bearing 48 coupled to the housing 44 and supporting the input shaft 32. Although not shown in the Figures, the gear reduction assembly may further comprise an output bearing coupled to the housing 44 and supporting the output shaft 34. The input bearing 48 and the output bearing position the input and output shafts 32, 34, respectively, within the housing 44 and facilitate rotation of the input and output shafts 32, 34 about the axis A. Moreover, the bearings reduce movement of the shafts 32, 34 lateral to the axis A. The input bearing 48 and the output bearing may be further defined as thrust bearings, which reduce movement of the input and output shafts 32, 34 along the axis A under axial loading. An example of an axial load exerted on the gear reduction assembly 20 is the centripetal force exerted on the wheel 24 along the axis A during cornering of the vehicle 21.

[0029] The housing 44 may be a structural member configured to take lateral loads between the frame and the wheels 24. In this configuration, the housing 44 is commonly referred to in the art as an axle tube. Moreover, the structural rigidity of the housing 44 in conjunction with the bearings may reduce the lateral load exerted on the rotating components of the gear reduction assembly 20 (i.e., the input and output shafts 32, 34, the carrier 40, the sun gear 38, the planetary gears 42, etc.) that may inhibit such rotation. Furthermore, the reduction of lateral loads on the rotating components reduces deflection of the components that may lead to axial misalignment, which impart inefficiencies and excess wear to the assembly 20.

[0030] As shown in Figures 2-4, the ring gear 36 may be fixed to the housing 44 within the interior 46. Moreover, as shown in the Figures, the ring gear 36 may be integrally formed with the housing 44 such that the ring gear 36 and the housing 44 are comprised of a single common material. However, the ring gear 36 and the housing 44 may be separate components fixed to one another in any suitable manner (e.g., fasteners, welding, etc.). Moreover, the ring gear 36 and the housing 44 may be spaced from one another and intermediate component(s) may be disposed therebetween to fix the ring gear 36 to the housing 44.

[0031] As shown in Figures 2-4, each of the input shaft 32, the output shaft 34, and the carrier 40 may include splines 52, 54, 56 extending longitudinally along the axis A, with the splines 56 of the carrier 40 configured to mesh with and slide along the splines 52, 54 of the input and output shafts 32, 34 as the carrier 40 moves longitudinally along the axis A between the direct drive, neutral and reduction positions. As such, the splines 56 of the carrier 40 and the splines 52 of the input shaft 32 have corresponding opposing configurations that rotationally lock the carrier 40 with the input shaft 32, while the elongation of the splines 52, 56 along the axis A allows the carrier 40 to slide along the axis A and maintain the rotational lock between the carrier 40 and the input shaft 32. Likewise, the splines 56 of the carrier 40 and the splines 54 of the output shaft 34 have corresponding opposing configurations that rotationally lock the carrier 40 with the output shaft 34, while the elongation of the splines 54, 56 along the axis A allows the carrier 40 to slide along the axis A and maintain the rotational lock between the carrier 40 and the output shaft 34.

[0032] The carrier 40 may extend along the axis A between a first end 58 and a second end 60, as shown in Figures 2-4. The carrier 40 may define a bore 62 extending entirely through the carrier 40 along the axis A, with the input shaft 32 entering the bore 62 at the first end 58 and the output shaft 34 entering the bore 62 at the second end 60. The splines 56 of the carrier 40 may extend inwardly in the bore 62 toward the axis A. The splines 52, 54 of the input and output shafts 32, 34 may extend outwardly away from the axis A to mesh with the splines 56 of the carrier 40. However, the opposite may be true (i.e., the input and output shafts 32, 34 may define bores and have the splines 52, 54 extending inwardly toward the axis A, while the carrier 40 may have the splines 56 extending outwardly from an outer surface of the carrier 40 away from the axis A). Furthermore, the input and output shafts 32, 34 may have opposing configurations (e.g., the input shaft 32 may have the splines 52 extending inwardly to engage a portion of the splines 46 of the carrier 40 extending outwardly and the output shaft 34 may have the splines 54 extending outwardly to engage a portion of the splines 56 of the carrier 40 extending inwardly).

[0033] The sun gear 38 may be fixed to the input shaft 32 as shown in Figures 2-4. As such, the planetary gears 42 surround and mesh with the sun gear 38 on the input shaft 32, and the ring gear 36 is positioned around the sun gear 38 on the input shaft 32. However, the opposite may be true. More specifically, the carrier 40 may be reversed such that the planetary gears 42 surround and mesh with the sun gear 38 fixed to the output shaft 34, and the ring gear 36 is positioned around the sun gear 38 on the output shaft 34.

[0034] The sun gear 38 may define the splines 52, 54 of one of the input and output shafts 32, 34. More specifically, in the embodiment shown in the Figures, the sun gear 38 defines the splines 52 of the input shaft 32. As such, the splines 52 of the input shaft 32 and the sun gear 38 may be interchangeably referred to below, with the sun gear 38 capable of meshing with the splines 56 of the carrier 40 and with the splines 52 of the input shaft 32 capable of meshing with planetary gears 42.

[0035] As shown in Figures 2-4, the sun gear 38 and the input shaft 32 may be a unitary component comprised of a single material. Said differently, the sun gear 38 may be formed on the input shaft 32. However, the sun gear 38 and the input shaft 32 may be separate components fixed to one another in any suitable manner (e.g., fasteners, welding, etc.).

[0036] The carrier 40 may comprise a wall 64 extending transverse to the axis A and bisecting the splines 56 to define an input portion 66 of the splines 56 configured to mesh with the splines 52 of the input shaft 32, and an output portion 68 of the splines 56 configured to mesh with the splines 54 of the output shaft 34. The wall 64 engageable is with at least one of the input and output shafts 32, 34 to define an end-stop preventing further movement of the carrier 40 beyond one of the direct drive, neutral, and reduction positions. More specifically, the splines 56 of each of the input and output portions 66, 68 may extend inwardly toward the axis A, with one of the input and output portions 66, 68 extending further toward the axis A than the other, with the wall 64 transitioning between the input and output portions 66, 68. In the embodiment shown in the Figures, the splines 56 of the input portion 66 extend further toward the axis A than the output portion 68.

[0037] As shown in Figures 2-4, the input and output shafts 32, 34 are sized to accommodate the input and output portions 66, 68 of the splines 56 of the carrier 40. More specifically, the input and output shafts 32, 34 are sized such that the splines 52 of the input shaft 32 are disposed between and engage the input portion 66 of the splines 56 of the carrier 40 and the that the splines 54 of the output shaft 34 are disposed between and engage the output portion 68 of the splines 56 of the carrier 40.

[0038] In the embodiment shown in the Figures, the splines 56 of the input portion 66 extend further toward the axis A than the splines 56 of the output portion 68. Therefore, the splines 54 of the output shaft 34 extend further away from the axis A than the splines 52 of the input shaft 32.

[0039] The wall 64 may be substantially orthogonal to the axis A. As shown in Figure 4, the wall 64 may be engageable with the output shaft 34. As such, the wall 64 defines the end- stop, which prevents further movement of the carrier 40 beyond the reduction position (i.e., the wall 64 inhibits further movement to the right beyond the reduction position as shown in Figure 4). Accordingly, the reduction position of the carrier 40 may define an end of the movement of the carrier 40, with the wall 64 preventing movement of the carrier 40 beyond the reduction position. The end-stop preventing further movement of the carrier 40 beyond the reduction position ensures proper alignment and meshing of the planetary gears 42 with both the sun gear 38 and the ring gear 36. Although the wall 64 defines the end-stop for engagement with the output shaft 34, preventing movement of the carrier 40 beyond the reduction position, the wall 64 may define the end-stop for engagement with the input shaft 32 or any other suitable component for preventing movement of the carrier 40 at or beyond any positions (including positions explicitly described and not explicitly described herein).

[0040] The splines 56 of the carrier 40 may be spaced and disconnected from the splines 52, 54 of one of the input and output shafts 32, 34 longitudinally along the axis A when the carrier 40 is in the neutral and reduction positions. More specifically, the splines 56 of the carrier 40 may be spaced and disconnected from the splines 52 of the input shaft 32 longitudinally along the axis A when the carrier 40 is in the neutral and reduction positions, as shown in Figures 3 and 4. Because the splines 56 of the carrier 40 are spaced and disconnected from the splines 52 of the input shaft 32, the input and output shafts 32, 34 do not rotate together in unison thus facilitate independent rotation of the input and output shafts 32, 34 (neutral position) and rotation at different rotational velocities (reduction position).

[0041] In the embodiment shown in Figure 2, the splines 56 of the carrier 40 engage the splines 52 of the input shaft 32 in the direct drive position. Movement of the carrier 40 from the direct drive position to the neutral and reduction positions (i.e., from left to right as shown in Figures 2-4) causes the carrier 40 to move off the input shaft 32 (which remains stationary along the axis A) and disconnect the carrier 40 from the input shaft 32. Moreover, the output portion 68 of the splines 56 of the carrier 40 is configured to maintain engagement with the splines 54 of the output shaft 34 in each of the direct drive, neutral, and reduction positions, which will be described in greater detail below.

[0042] As shown in Figures 2-4, the carrier 40 may have a flange 70 at the first end 58 extending outwardly away from the axis A. Each of the planetary gears 42 may be rotatably coupled to the flange 70. The planetary gears 42 may be configured as spur gears having teeth extending radially. However, the planetary gears 42 may have any suitable configuration for meshing with each of the sun gear 38 and the ring gear 36.

[0043] The planetary gears 42 may be disposed between the ring gear 36 and the sun gear 38 and radially spaced about the sun gear 38 in the reduction position, as shown in Figure 4. As such, the plurality of planetary gears 42 may be rotatably meshed with the ring gear 36 and the input shaft 32 through the sun gear 38 in the reduction position. Rotation of the input shaft 32 and the sun gear 38 about the axis A at a first rotational velocity causes the planetary gears 42, which are meshed with both the sun gear 38 and the ring gear 36, to each independently rotate and move along the sun gear 38 and the ring gear 36. As such, the planetary gears 42 move around the axis A at a second rotational velocity, different from the first rotational velocity. Because the planetary gears 42 are rotatably coupled to the carrier 40, movement of the planetary gears 42 about the axis A causes the carrier 40 to rotate about the access at the second rotational velocity as well. Because the output portion 68 of the splines 56 of the carrier 40 are engaged with the splines 54 of the output shaft 34 in the reduction position, the output shaft 34 also rotates at the second rotational velocity. As such, rotation of the input shaft 32 at the first rotational velocity in the reduction position causes rotation of the output shaft 34 at the second rotational velocity in the reduction position. The plurality of planetary gears 42 may be rotatably meshed with the ring gear 36 and the sun gear 38 in the reduction position having at least a 3:1 gear ratio. Therefore, the gear reduction assembly 20 in the reduction position may provide a mechanical advantage to the wheel 24 attached to the output shaft 34 for increasing torque to the wheel 24. Although the planetary gears 42 shown in Figures 2-4 have a 3: 1 gear ratio, the planetary gears 42 may have any suitable gear ratio for providing a mechanical advantage to the wheel 24.

[0044] As shown in Figures 2-4, the planetary gears 42 may be disposed on a plane P orthogonal to the axis A, with the planetary gears 42 spaced from the splines 56 of the carrier 40 to define a gap 72 having a distance X along the axis A. The ring gear 36 may have a length L along the axis A that is less than or equal to the distance X of the gap 72 between the planetary gears 42 and the splines 56 of the carrier 40, wherein the ring gear 36 is disposed within the gap 72 when the carrier 40 is in the neutral position. As shown in the Figures, the planetary gears 42 are disposed to the left of the ring gear 36 in the neutral position. Furthermore, the input portion 66 of the splines 56 of the carrier 40 are sized along the axis A such that movement of the carrier 40 to the neutral position causes disconnection of the carrier 40 from the input shaft 32. Therefore, the input shaft 32 in the carrier 40 do not rotate in unison in the neutral position. Furthermore, because the planetary gears 42 are not meshed with the ring gear 36 in the neutral position, the planetary gears 42 simply rotate independently on the sun gear 38 and do not cause rotation of the carrier 40 about the axis A. Said differently, the planetary gears 42 “free wheel” on the sun gear 38 in the neutral position. Therefore, the input shaft 32 and the output shaft 34 may rotate at different rotational velocities in the neutral position. The disposition of the neutral position in between the direct drive and reduction positions in the embodiment shown in the Figures prevents simultaneous direct engagement between input and output shafts 32, 34 and gear reduction between the input shaft 32 and the output shaft 34 through the sun gear 38, planetary gears 42, and ring gear 36, which can damage the gear reduction assembly 20.

[0045] As shown in Figures 2-4, each of the planetary gears 42 may have an outer surface 74 facing away from the carrier 40 and spaced from the wall 64 a first distance D1 along the axis A. The sun gear 38 may extend along the axis A a second distance D2 at least equal to the first distance D1 to facilitate coupling of the sun gear 38 with at least one of the carrier 40 and the plurality of planetary gears 42. As such, the movement of the carrier 40 along the axis A may occur between the direct drive, neutral, and reduction positions without the input shaft 32 disengaging both the carrier 40 and the planetary gears 42. Disengagement of the input shaft 32 from both the carrier 40 and the planetary gears 42 may cause rotational misalignment between the sun gear 38 and the planetary gears 42/carrier 40, which may cause binding therebetween when the carrier 40 moves attempts to reengage the input shaft 32. Likewise, the output portion 68 of the splines 56 of the carrier 40 may extend along the axis A a third distance D3 at least equal to the first distance D 1 to maintain engagement between the carrier 40 and the output shaft 34 in each of the direct drive, neutral, and reduction assembly 20.

[0046] The input shaft 32 may be fixed to the carrier 40 through the sun gear 38 in the direct drive position. As shown in Figures 2 and 5, the planetary gears 42 and the carrier 40 are disposed in their furthest position to the left. The input portion 66 of the splines 56 of the carrier 40 mesh with the sun gear 38/splines 52 of the input shaft 32, fixing the input shaft 32 to the carrier 40. The planetary gears 42 are meshed with the sun gear 38 but cannot rotate along the sun gear 38 because the input shaft 32 and the carrier 40 cannot rotate independent of one another. As mentioned above, the output portion 68 of the splines 56 of the carrier 40 mesh with the splines 54 of the output shaft 34, fixing the output shaft 34 to the carrier 40. As such, the input shaft 32, the carrier 40, and the output shaft 34 rotate together in unison in the direct drive position.

[0047] As shown in Figures 2-4, the input shaft 32 may comprise a second wall 76 extending transverse to the axis A and engageable is with planetary gears 42 to define an end-stop preventing further movement of the carrier 40 beyond one of the direct drive, neutral, and reduction positions. The second wall 76 may be at an end of the splines 52 of the input shaft 32, with the second wall 76 transitioning to a smooth exterior surface of the input shaft 32.

[0048] The second wall 76 may be substantially orthogonal to the axis A. As shown in Figure 2, the second wall 76 is engageable with the planetary gears 42 in the direct drive position (i.e., the planetary gears 42 meshed with the splines 52 of the input shaft 32 may move along the axis A until the planetary gears 42 abut the second wall 76 at the end of the splines 52). As such, the second wall 76 defines the end-stop, which prevents further movement of the carrier 40 beyond the direct drive position (i.e., the second wall 76 inhibits further movement to the left beyond the direct drive position as shown in Figure 2). Accordingly, the direct drive position of the carrier 40 may define an end of the movement of the carrier 40, with the second wall 76 preventing movement of the carrier 40 beyond the direct drive position. The end-stop preventing further movement of the carrier 40 beyond the direct drive position ensures proper meshing of the splines 52 of the input shaft 32 with the input portion 66 of the splines 56 of the carrier 40 to transmit torque to the wheel 24. Although the second wall 76 defines the end-stop for engagement with the planetary gears 42, preventing movement of the carrier 40 beyond the direct drive position, the second wall 76 may define the end-stop for engagement with the carrier 40 or any other suitable component for preventing movement of the carrier 40 at or beyond any positions (including positions explicitly described and not explicitly described herein).

[0049] The operation of moving the carrier 40 from the direct drive position to the reduction position for increasing torque to the wheel 24, in accordance with the embodiments shown in the Figures, will be described below for illustrative purposes only.

[0050] With the carrier 40 in the direct drive position (see Figures 2 and 5), the input portion 66 of the splines 56 of the carrier 40 engage the splines 52 of the input shaft 32 and the output portion 68 of the splines 56 of the carrier 40 engage the splines 54 of the output shaft 34. The planetary gears 42 mesh with the sun gear 38/splines 52 of the input shaft 32 but are spaced from the ring gear 36 and therefore remain stationary about the input shaft 32. Rotation of the input shaft 32 (driven by the prime mover 22) causes the carrier 40 and the output shaft 34 to rotate in unison with the input shaft 32. The rotation of the output shaft 34 causes rotation of the wheel 24.

[0051] To move the carrier 40 to the reduction position, the carrier 40 moves along the axis A away from the input shaft 32. The carrier 40 first moves to the neutral position (see Figures 3 and 6). In the neutral position, the output shaft 34 remains coupled to the carrier 40 and rotates in unison with the carrier 40. However, the input portion 66 of the splines 56 of the carrier 40 move off, and become spaced from, the splines 52 of the input shaft 32. Therefore, the carrier 40 disconnects from the input shaft 32. The carrier 40 and the output shaft 34 may rotate independent of the input shaft 32. The planetary gears 42 remain meshed with sun gear 38/splines 52 of the input shaft 32 and remain spaced from the ring gear 36. Therefore, any rotation of the carrier 40 of the input shaft 32 causes the planetary gears 42 to free-wheel around the input shaft 32. Torque cannot be transmitted between the input and output shafts 32, 34 in the neutral position.

[0052] The carrier 40 continues to move along the axis A away from the input shaft 32, from the neutral position to the reduction position. In the reduction position (see Figures 4 and 7), the output shaft 34 remains coupled to the carrier 40 and rotates in unison with the carrier 40. The input portion 66 of the splines 56 of the carrier 40 remain spaced from the splines 52 of the input shaft 32. The planetary gears 42 remain meshed with sun gear 38/splines 52 of the input shaft 32 and are now meshed with the ring gear 36. Rotation of the input shaft 32 and the sun gear 38 about the axis A at the first rotational velocity causes the planetary gears 42, which are meshed with both the sun gear 38 and the ring gear 36, to each independently rotate and move along the sun gear 38 and the ring gear 36. As such, the planetary gears 42 move around the axis A at the second rotational velocity, different from the first rotational velocity. Movement of the planetary gears 42 about the axis A causes the carrier 40 and the output shaft 34 to rotate about the axis A at the second rotational velocity as well. As such, rotation of the input shaft 32 at the first rotational velocity in the reduction position causes rotation of the output shaft 34 at the second rotational velocity in the reduction position.

[0053] The subject invention further provides for a method of operating the gear reduction assembly 20 for transmitting torque between the prime mover 22 and the wheel 24. As described above and shown in Figures 2-4, the assembly 20 comprises the input shaft 32 extending along the axis A. The input shaft 32 is configured to be rotated by the prime mover 22. The output shaft 34 extends along the axis A spaced from the input shaft 32 and is configured to rotate the wheel 24. The ring gear 36 is disposed around the axis A. The sun gear 38 is coupled to one of the input and output shafts 32, 34. The carrier 40 extends along the axis A and around the input and output shafts 32, 34. The plurality of planetary gears 42 are radially spaced about the axis A and rotatably coupled to the carrier 40. The carrier 40 is movable along the axis A between direct drive, neutral, and reduction positions. The plurality of planetary gears 42 are meshed with the sun gear 38 and the carrier 40 is coupled with one of the input and output shafts 32, 34 in each of the direct drive, neutral, and reduction positions.

[0054] The method comprises the step of disposing the carrier 40 in the direct drive position with the carrier 40 fixed to both the input shaft 32 and the output shaft 34 such that the input and output shafts 32, 34 rotate in unison at equal rotational velocities around the axis A, as shown in Figures 2 and 5. The method further comprises the step of moving the carrier 40 along the axis A to the neutral position with at least one of the input and output shafts 32, 34 disconnected from the carrier 40 such that the input and output shafts 32, 34 rotate independent of one another around the axis A, as shown in Figures 3 and 6. The method further comprises the step of moving the carrier 40 along the axis A to the reduction position with the plurality of planetary gears 42 rotatably meshed with the ring gear 36 and the sun gear 38 that is fixed to the one of the input and output shafts 32, 34, and with the carrier 40 fixed to the other one of the input and output shafts 32, 34 such that the input and output shafts 32, 34 rotate at different rotational velocities around the axis A, as shown in Figures 4 and 7.

[0055] As described above, the neutral position of the carrier 40 may be disposed between the direct drive and reduction positions of the carrier 40. As such, the method may further comprise the steps of moving the carrier 40 in a single direction along the axis A from the direct drive position (see Figures 2 and 5) to the neutral position (see Figures 3 and 6) and from the neutral position to the reduction position (see Figures 4 and 7).

[0056] The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the subject invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.

Claims

CLAIMS What is claimed is:

1. A gear reduction assembly for transmitting torque between a prime mover and a wheel; said assembly comprising: an input shaft extending along an axis and configured to be rotated by the prime mover; an output shaft extending along said axis spaced from said input shaft, and configured to rotate the wheel; a ring gear disposed around said axis; a sun gear coupled to one of said input and output shafts; a carrier extending along said axis and around said input and output shafts; and a plurality of planetary gears radially spaced about said axis and rotatably coupled to said carrier, with said carrier movable along said axis between direct drive, neutral, and reduction positions, and with said plurality of planetary gears meshed with said sun gear and said carrier coupled with one of said input and output shafts in each of said direct drive, neutral, and reduction positions; wherein said carrier is fixed to both said input shaft and said output shaft in said direct drive position such that said input and output shafts rotate in unison at equal rotational velocities around said axis; wherein at least one of said input and output shafts are disconnected from said carrier in said neutral position such that said input and output shafts rotate independent of one another around said axis; and wherein said plurality of planetary gears are rotatably meshed with said ring gear and said sun gear that is fixed to said one of said input and output shafts, and said carrier is fixed to the other one of said input and output shafts in said reduction position such that said input and output shafts rotate at different rotational velocities around said axis.

2. The gear reduction assembly as set forth in claim 1, wherein each of said input shaft, said output shaft, and said carrier include splines extending longitudinally along said axis, with said splines of carrier configured to mesh with and slide along said splines of said input and output shafts as said carrier moves longitudinally along said axis between said direct drive, neutral and reduction positions.

3. The gear reduction assembly as set forth in claim 2, wherein said splines of said carrier are spaced and disconnected from said splines of one of said input and output shafts longitudinally along said axis when said carrier is in said neutral and reduction positions.

4. The gear reduction assembly as set forth in claim 3, wherein said splines of said carrier are spaced and disconnected from said splines of said input shaft longitudinally along said axis when said carrier is in said neutral and reduction positions.

5. The gear reduction assembly as set forth in claim 2, wherein said planetary gears are disposed on a plane orthogonal to said axis, with said planetary gears spaced from said splines of the carrier to define a gap having a distance along said axis.

6. The gear reduction assembly as set forth in claim 5, wherein said ring gear has a length along said axis that is less than or equal to the distance of the gap between the planetary gears and the splines of the carrier, wherein the ring gear is disposed within said gap when said carrier is in said neutral position.

7. The gear reduction assembly as set forth in claim 2, wherein said carrier comprises a wall extending transverse to said axis and bisecting said splines to define an input portion of said splines configured to mesh with said splines of said input shaft, and an output portion of said splines configured to mesh with said splines of said output shaft, with said wall engageable with at least one of said input and output shafts to define an end-stop preventing further movement of said carrier beyond one of said direct drive, neutral, and reduction positions.

8. The gear reduction assembly as set forth in claim 7, wherein said each of said planetary gears has an outer surface facing away from said carrier and spaced from said wall a first distance along said axis, with said sun gear extending along said axis a second distance at least equal to said first distance to facilitate coupling of said sun gear with at least one of said carrier and said plurality of planetary gears.

9. The gear reduction assembly as set forth in claim 7, wherein said splines of each of said input and output portions extend inwardly toward said axis, with one of said input and output portions extending further toward said axis than the other, with said wall transitioning between said input and output portion.

10. The gear reduction assembly as set forth in claim 7, wherein said reduction position of said carrier defines an end of said movement of said carrier, with said wall preventing movement of said carrier beyond said reduction position.

11. The gear reduction assembly as set forth in claim 2, wherein said sun gear defines said splines of one of said input and output shafts.

12. The gear reduction assembly as set forth in claim 1, wherein said sun gear and said input shaft are a unitary component comprised of a single material.

13. The gear reduction assembly as set forth in claim 1, wherein said neutral position of said carrier is disposed between said direct drive and reduction positions of said carrier.

14. The gear reduction assembly as set forth in claim 1, wherein said input and output shafts are fixed longitudinally along said axis, with said carrier configured to move along said input and output shafts while moving between said direct drive, neutral and reduction positions.

15. The gear reduction assembly as set forth in claim 1, further comprising a housing defining an interior along said axis, with said input shaft, said output shaft, said sun gear, said plurality of planetary gears, and said carrier disposed within said housing, and with said ring gear fixed to said housing within said interior.

16. The gear reduction assembly as set forth in claim 1, wherein said sun gear is fixed to said input shaft, with said input shaft fixed to said carrier through said sun gear in said direct drive position, and with said plurality of planetary gears rotatably meshed with said ring gear and said input shaft through said sun gear in said reduction position.

17. The gear reduction assembly as set forth in claim 1, wherein said plurality of planetary gears rotatably meshed with said ring gear and said sun gear in said a reduction position have at least a 3 : 1 gear ratio.

18. An axle system for transmitting torque to a wheel of a vehicle, said axle system comprising:

A subframe for mounting to a frame of the vehicle;

A prime mover mounted to said subframe and configured to produce torque; and

A gear reduction assembly mounted to said subframe and coupled to said prime mover, with said assembly configured to transmit torque between said prime mover and the wheel; said assembly comprising: an input shaft extending along an axis and configured to be rotated by said prime mover; an output shaft extending along said axis spaced from said input shaft, and configured to rotate the wheel; a ring gear disposed around said axis; a sun gear coupled to one of said input and output shafts; a carrier extending along said axis and around said input and output shafts; and a plurality of planetary gears radially spaced about said axis and rotatably coupled to said carrier, with said carrier movable along said axis between direct drive, neutral, and reduction positions, and with said plurality of planetary gears meshed with said sun gear and said carrier coupled with one of said input and output shafts in each of said direct drive, neutral, and reduction positions; wherein said carrier is fixed to both said input shaft and said output shaft in said direct drive position such that said input and output shafts rotate in unison at equal rotational velocities around said axis; wherein at least one of said input and output shafts are disconnected from said carrier in said neutral position such that said input and output shafts rotate independent of one another around said axis; and wherein said plurality of planetary gears are rotatably meshed with said ring gear and said sun gear that is fixed to said one of said input and output shafts, and said carrier is fixed to the other one of said input and output shafts in said reduction position such that said input and output shafts rotate at different rotational velocities around said axis.

19. The axle system as set forth in claim 18, further comprising a gear box mounted to said subframe and coupled to each of said prime mover and said gear reduction assembly, with the gear box configured to transmit and alter torque from said prime mover to said gear reduction assembly.

20. A method of operating a gear reduction assembly for transmitting torque between a prime mover and a wheel, with the assembly comprising an input shaft extending along an axis and configured to be rotated by the prime mover, an output shaft extending along the axis spaced from the input shaft, and configured to rotate the wheel, a ring gear disposed around the axis, a sun gear coupled to one of the input and output shafts, a carrier extending along the axis and around the input and output shafts, and a plurality of planetary gears radially spaced about the axis and rotatably coupled to the carrier, with the carrier movable along the axis between direct drive, neutral, and reduction positions, and with the plurality of planetary gears meshed with the sun gear and the carrier coupled with one of the input and output shafts in each of the direct drive, neutral, and reduction positions, said method comprising the steps of: disposing the carrier in the direct drive position with the carrier fixed to both the input shaft and the output shaft such that the input and output shafts rotate in unison at equal rotational velocities around the axis; moving the carrier along the axis to the neutral position with at least one of the input and output shafts disconnected from the carrier such that the input and output shafts rotate independent of one another around the axis; and moving the carrier along the axis to the reduction position with the plurality of planetary gears rotatably meshed with the ring gear and the sun gear that is fixed to the one of the input and output shafts, and with the carrier fixed to the other one of the input and output shafts such that the input and output shafts rotate at different rotational velocities around the axis.

21. The method as set forth in claim 20, wherein the neutral position of the carrier is disposed between the direct drive and reduction positions of the carrier, and further including the steps of moving the carrier in a single direction along the axis from the direct drive position to the neutral position and from the neutral position to the reduction position.