Floating ring gear and differential gear assembly

Abstract: A ring gear (50) is provided with a plurality of substantially evenly circumferentially spaced posts (10) that extend radially inwardly and are adapted to carry rotary differential pinion gears (12) whose teeth are adapted to meshingly engage the teeth of side gears (18) and (18') respectively secured to the ends of axially aligned spaced- apart axle shafts (20) and (20') to provide a motor vehicle differential gear assembly (100) that enables ring gear (50) to float relative axle shafts (20) and (20') in the space therebetween.

Description: INTRODUCTION This invention relates generally to a vehicular differential ring gear and gear assembly for transferring rotational torque between a rotary driver member such as a pinion gear driven by the output shaft of a change gear transmission and a pair of rotary driven members such as paired wheel axle shafts and more particularly to a ring gear and a differential gear assembly using a ring gear that is adapted to be supported by differential pinion gears meshed with side gears respectively rotatably supported in an axle housing and adapted to be secured to the wheel axle shafts and to float relative thereto as the side gears are caused to rotate in response to rotation of the ring gear. BACKGROUND OF THE INVENTION Ring gears have been used for many years in motor vehicle differential gear assemblies to transfer rotational torque between a rotary driver member such as the output shaft of a change gear transmission and a pair of rotary driven members such as a pair of substantially axially aligned spaced-apart axle shafts journaled for rotation and having a wheel mounted on their respective outboard ends. FR-A-475 958 shows an example of a motor vehicle differential gear assembly corresponding to the preambles of claims 1 and 2. This gear assembly includes two side gears which are integral with the inner end of two corresponding axle shafts. The axle shafts are journaled within the gear housing by means of ball bearings. Each of the axle shafts is provided with a coaxially aligned blind bore extending from the midpoint of the casing. These blind bores provide bearings for a star-shaped support member. The support member is provided with two support pins which are rotationally journaled in the blind bores of the adjacent axle shafts. The support member carries the ring gear which meshingly engages a driving pinion. Furthermore, the support member mounts the differential gears. Due to this arrangement the ring gear of the differential assembly is supported by the support member which in turn is mounted in the blind bores. Another arrangement of a differential gear assembly is shown in FR-A-2 114 558. The ring gear of this assembly is provided with a ball race such that the ring gear is directly mounted in the differential gear housing which carries the outer ball race. SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a ring gear for use with a motor vehicle differential gear assembly that is adapted to float relative a pair of side gears secured to driven members being rotated by the ring gear. It is another object of this invention to provide a ring gear and a motor vehicle differential gear assembly using a ring gear that is simple and economical to manufacture and that advantageously reduces the number of components heretofore used in vehicle differentials employing ring gears in addition to being adapted to float relative the differential housing and the side gears secured to the driven members and thus lessen the precise alignment heretofor required for the ring gear. These objects are achieved by a vehicle differential gear assembly and ring gear according to claims 1 and 2 respectively. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a central cross-sectional side view of a prior art differential gear assembly; FIGURE 2 is a front view of a ring gear 50 of the invention; FIGURE 3 is a partial central cross-sectional side view taken along view line 2-2 of FIGURE 1; and FIGURE 4 is a partially sectioned top view of an embodiment of a differential gear assembly 100 of the invention. DESCRIPTION OF SOME PREFERRED EMBODIMENTS The prior art differential gear assembly 30 shown in FIGURE 1 is of the type hereinbefore described requiring numerous components and a much larger housing to enclose them. Assembly 30 is operative to transfer rotary torque from a pinion gear 32 driven by a rotary output shaft 34 of a change gear transmission to a ring gear 36 having teeth meshingly engaged with teeth on ring gear 36. Ring gear 36 is secured to a frame 38 that is journaled for rotation relative housing 42 by means of bearings 40. As such, ring gear 36 and frame 38 rotate coaxially about axle shaft 48 that has an end gear 43 secured to its inboard end by suitable means such as splines. It can thus readily be seen from FIGURE 1 that prior art differential gear assemblies required precise and costly alignment between the ring gear and the differential housing. Axle shaft 48 is spaced-apart from and substantially axially aligned with axle shaft 48' which has an end gear 43' secured to its inboard end in facing relationship to end gear 43. Axle shafts 48 and 48' have a common central rotational axis C₂ that is substantially prependicular to central rotational axis C₁ of pinion gear 32. End gears 43 and 43' are meshingly engaged with at least two equi-circumferentially spaced differential pinion gears 44 that are rotably mounted on frame 38 by means of pins 46. Rotation of frame 38 by ring gears 36 causes differential pinion gears 44 to rotate about axis C₂ and in turn cause end gears 43 and 43' to rotate axle shafts 48and 48' about axis C₂ respectively. As can be seen in FIGURE 1, axle shaft 48' is journaled for rotation relative housing 42 by means of bearings 40' and both axle shafts 48 and 48' can be removed from housing 42 with relative ease due to the splined securement with their respective end gears but that precise alignment between ring gear 36 and frame 38 and between differential pinion gears 44 and end gears 43 and 43' is essential. The ring gear and differential gear assembly of the invention hereinafter described with respect to FIGURE 2,3 and 4 enable the elimination of frame 38 and the bolts required to secure it to ring gear 36 as well as pins 46 in addition to enabling a substantial reduction in the size of housing 42 due to the absence of frame 38 and in addition to enabling the ring gear to float relative the housing and the end gears secured to the axle shafts. FIGURE 2 shows ring gear 50 of the invention that is adapted to float in the motor vehicle differential gear assembly shown in FIGURE 4. Ring gear 50 has a generally annular configuration having a substantially circular outer periphery 4 and a substantially circular inner periphery 6. As shown in FIGURES 2 and 3, ring gear 50 has a plurality of substantially evenly circumferentially spaced teeth 8 extending away from the side thereof between outer periphery 4 and inner periphery 6. Teeth 8 are preferably spiral bevel or hypoid type teeth having a curved tooth path profile as shown in FIGURE 2 to enhance smooth engagement with the teeth of pinion gear 16 shown in FIGURE 2 which is also preferably provided with curved teeth for promoting smooth continuous mesh with teeth 8 of ring gear 50. The use of spiral bevel or hypoid teeth in vehicle differential gear assemblies to enhance smooth transfer of torque is well known to those skilled in the art and is not therefore reviewed here in detail. In contrast to prior art type ring gears hereinbefore described, ring gear 50 is provided with at least two and preferably four substantially equi-circumferentially spaced posts 10 (only two referenced) that extend radially inwardly from inner periphery 6 and may be integral therewith or secured thereto by welding or other suitable securement means or may themselves be mounted so that they are rotatable and differential pinion gears 12 are either fixedly secured thereto or rotatably mounted thereupon. A differential pinion gear 12 is rotatably mounted on each post 10 (only one shown in FIGURE 2). Differential pinion gears 12 have diametrically opposed teeth operative to simultaneously meshingly engage with the teeth of side gears 18 and 18' hereinafter described with respect to differential gear assembly 100 of FIGURE 4. In FIGURE 4, a rotary driver member such as output shaft 14 of a vehicle change gear transmission is received through an opening in a housing 11 and suitably journaled for rotation. Shaft 14 has a pinion gear 16 secured to its end having a central rotational axis referenced by "C₁". Central rotational axis "C₂" of ring gear 50 is substantially perpendicular to axis C₁ and the teeth of both ring gear 50 and pinion gear 16 are adapted to meshingly engage so that ring gear 50 rotates in response to rotation of pinion gear 16. Housing 11 preferably includes an adjustable screw 13 that is adapted to prevent deflection of the teeth of ring gear 50 away from the teeth of pinion gear 16 to insure meshed engagement therebetween. Ring gear 50 is disposed in the space between the ends of substantially axially aligned wheel axle shafts 20 and 20' that also have axis "C₂" as their common central rotational axis. Side gears 18 and 18' are secured to the spaced-apart facing ends of axle shafts 20 and 20' respectively by suitable securement means such as splines (not shown) and are journaled for rotation therewith. The teeth of side gears 18 and 18' are adapted to meshingly engage with the teeth of differential pinion gears 12 with the combination adapted to provide support for ring gear 50 in the space between the ends of axle shafts 20 and 20' as well as to enable ring gear 50 to rotate axle shafts 20 and 20' as it is rotated by pinion gear 16 in addition to enabling ring gear 50 to "float" within the space between the ends of axle shafts 20 and 20' since it is not fixedly journaled for rotation on housing 11 and thus reducing the precise alignment characteristically required between such components in the past.

Claims: A vehicular differential gear assembly (100) for transferring rotational torque between a pinion gear (16) rotatably driven by a driver member (14) and a pair of substantially axially aligned spaced-apart rotary driven members (20,20') that are respectively journaled for rotation and have a central rotational axis (C₂) disposed in substantial perpendicular relationship to the pinion gear central rotational axis (C₁) and have a side gear (18,18') secured respectively thereto having their teeth in facing relationship to each other across the space between the driven members, (20,20') said assembly (100) comprising: a ring gear (50) disposed in the space between the side gears, said ring gear having an annular configuration defined between an inner periphery and an outer periphery thereof and having a central rotational axis (C₁) in substantial perpendicular relationship to the pinion gear central rotational axis, said ring gear (50) having a plurality of substantially equi-circumferentially spaced teeth (8) that are disposed between the inner and outer periphery thereof and face towards one of the side gears (18,18') and are meshingly engagable with the pinion gear teeth so as to enable the ring gear to be rotatably driven thereby, and differential pinion gears (12), each of said gears having diametrically opposed teeth that simultaneously meshingly engage the teeth of both side gears (18,18'), characterised in that said ring gear has at least two equi-circumferentially spaced posts (10) extending radially inwardly from the inner periphery thereof, a differential pinion gear (12) being mounted on each post (10), and being adapted in combination therewith to provide support for the ring gear and enable the ring gear to float as the differential pinion gears (12) rotate the side gears in response to rotation of the ring gear (50) by the pinion gear (16). A ring gear (50) for transferring rotational torque between a pinion gear (16) rotatably driven by a vehicular driver member (14) and a pair of substantially axially aligned spaced-apart rotary driven members (20,20') that are respectively journaled for rotation and have a central rotational axis (C₂) disposed in substantial perpendicular relationship to the pinion gear central rotational axis (C₁) and have a side gear (18,18') secured respectively thereto having their teeth in facing relationship to each other across the space between the driven members (20,20'), said ring gear (50) adapted to be disposed in the space between the side gears (18,18') and having an annular configuration defined between an inner periphery and an outer periphery thereof and having a plurality of substantially equi-circumferentially spaced teeth (8) that are disposed between the inner and outer periphery thereof and are adapted to face towards one of the side gears (18,18') and to meshingly engage with the pinion gear teeth so as to enable the ring gear to be rotatably driven thereby, characterised in that said ring gear (50) has at least two equi-circumferentially spaced posts (10) extending radially inwardly from the inner periphery thereof, said posts adapted to respectively carry a differential pinion gear (12) mounted thereon having diametrically opposed teeth that are adapted simultaneously to meshingly engage the teeth of both side gears and, in combination therewith, to provide support for the ring gear and enable the ring gear to float as the differential pinion gears (12) rotate the side gears (18,18') in response to rotation of the ring gear (50) by the pinion gear (16). The assembly (100) of claim 1 wherein the ring gear (50) has four of the posts (10) that extend radially inwardly from the inner periphery thereof and respectively have the differential pinion gear (12) mounted thereon. The assembly (100) of claim 1 wherein the ring gear teeth are spiral bevel teeth. The assembly (100) of claim 1 wherein the ring gear teeth are hypoid teeth. The ring gear (50) of claim 2 having four of the posts (10) that extend radially inwardly from the inner periphery thereof for mounting the differential pinion gear (12) mounted thereon. The ring gear (50) of claim 2 wherein the ring gear teeth are spiral bevel teeth. The ring gear (50) of claim 2 wherein the ring gear teeth are hypoid teeth.

Inventors: LONG JAMES R, LONG, JAMES RANDALL
Applicants: EATON CORP, EATON CORPORATION
Application year: 1991
Main classification: F16H48
IPC codes: B60K17, F16H48