DIFFERENTIAL TYPE GEARBOX

Abstract: A limited slip differential comprising bevel gears (12, 13, 14, 15) and conical surfaced noses (18, 19) provides frictional drive lock up. Known limited slip differentials are wasteful of energy and require periodic adjustment. These problems are overcome by providing a limited slip differential which comprises a housing (1) for mounting in a rotatable manner in a casing. A first pair of bevel gears (12) and (13) rotatable on a shaft (11) fixed in the housing (1). The gears (12) and (13) are in mesh with a second pair of bevel gears (14) and (15) rotatably supported through conical surfaced noses (18) and (19) in seats (20) and (21) in the housing (1). When the housing (1) is rotated the gears (12) and (13) in transferring the drive to the gears (14) and (15) cause them to move apart and the noses (18) and (19) to drivingly engage the seats (20) and (21). Principal uses are in motor vehicles.

Description: DIFFERENTIAX TYPE GEARBOX This invention relates to gearboxes and in particular to a gearbox of the type commonly used in the differential driv to the wheels of a motor vehicle. The purpose of a differential drive is to allow the two driven wheels of a vehicle to rotate at different peripheral speeds as the vehicle passes along a curved path, as for example when going around a curve in a roadway. If this was not the case there would be excessiv tyre wear and poor power output at the driven wheels as they traversed curved paths of different lenghts having th same centre. Whilst a differential gearbox has the above advantage it has the disadvantage that if one of the driven wheels has a lesser grip on the road surface than the other the energy applied to the gearbox will be directed through *the gears to the wheel having the lesser grip where it is dissipated in wheel spin. This feature of a differential gearbox is readily demonstrated by raising the driven wheels from the road and locking one against rotation, there is substantially no application of energy to the locked wheel whilst the free wheel rotates. The above situation can occur in straight line driving where one of the driven wheels encounters a slippery or like surface with the result that the wheel with the greater grip receives less than its proper share of the available driving energy. At a location further along road the situation may be reversed and thus it is clear that at any one time it is likely that one of the drivi wheels will not be driving efficiently allowing some of available driving energy to be dissipated. Complex mechanical devices called limited slip differentials have been devised to overcome, at least i part, the above wastage of energy but for efficient operation they require periodic adjustments to- the clutc and/or springs incorporated therein. Such adjustments require major service facilities and are expensive. This invention provides a means for the positive transfe of mechanical energy from a primary drive shaft, and its associated pinion gear, through a meshing crown wheel ge fixed to a housing carrying sun wheel gears and planetar gears, to two output axle shafts coupled to the planetar gears through, in most cases a splined connection betwee the shafts and the bores of the planetary gears. More specifically the invention provides a gearbox incorporat a housing with a gear receiving chamber, a shaft support at its ends in the housing and extending across the chamber, a first pair of like bevel gears located in the gear chamber and rotatably mounted on the shaft in space relationship with the gears- of the first pair oriented small end to small end, a second pair of like bevel gear located in the gear chamber and rotatably supported in bearing means in the housing with an axis of rotation a right angles to and in the same plane as the axis of rotation of the gears of the first pair, the gears of t second pair being spaced apart and oriented small end t small end with each in mesh with both of the gears of t first pair, coupling means on each of the gears of the second pair to allow driven shafts to be coupled theret and wherein the bearing means for each gear of said sec pair comprises a truncated conical nose and a similarly angled seat whereby the gears of the second pair are rotatably supported by the housing with working clearan between the noses and seats and with working clearance between the meshing teeth of the gears of the first and second pairs allowing limited axial movement of the gear of the second pair relative to the housing to bring the noses and seats into driving engagement. A presently preferred embodiment of the gearbox of this invention will now be described with reference to the accompanying drawings which is a partly sectioned elevat of the gearbox. The gearbox as illustrated comprises a housing 1 with a gear chamber 2 located between a crown wheel flange 3 an an end 4. There are bearing supporting spigots 5 and 6 the outer surface of the flange 3 and the end 4 and each adapted to be engaged by a bearing whereby the housing 1 i rotatably supported in a casing. There are aligned bores and 8 through the spigots 5 and 6 for a purpose to be described. In the conventional motor vehicle the casing encloses the gearbox and is filled to a substantial extent with oil to lubricate the gearbox parts. The casing would have an entry port wherein a pinion shaft is sealed to prevent the escape of oil and a pinion 9 on the shaft is in engagement with a crown wheel 10 fixed to the flange 3. The pinion and the crown wheel are shown schematically in broken outline but do not form any part of the invention. .There is a shaft 11 fixed in the housing 1 with an axis at bright angle to and in the same plane as the axis of the aligned bores 7 and 8. Two bevel gears 12 and 13 of identical form are rotatably supported on the shaft 11 in spaced relationship and are oriented with their small ends oppositely disposed. Two bevel gears 14 and 15 of identical form and larger than the gears 12 and 13 are rotatably supported in bearing means 16 and 17 in spaced relationship and are oriented with their small ends oppositely disposed. The bevel gears 12,13,14 and 15 are in mesh with working clearance with the divergent movement of the gears 12 and 13 limited by the inner surfaces of the gear chamber and the divergent movement of the gears 14 and 15 limited by the bearing means 16 and 17. The gears 14 and 15 have splined bores to be engaged by splined ends of shafts, not shown, which will extend through the bores 7 and 8 previously described. The gears 14 and 15 each have a truncated conical noses 18 and 19 with an included angle of approximately 52 degrees. The noses 18and 19 are entered into a similarly angled seats 20 and 21 respectively which in the present case are hardened rings set into counterbores 22 and 23 in the housing 1. The clearance between the noses 18 and 19 and the seats 20 and 21 is a working clearance of say 10 to 15 thousanths of an inch when the gears are in close mesh. In operation the pinion 9 drives the crown wheel 10 which in turn through its fixing to the flange 3 causes the f housing 1 to rotate on bearings on the spigots 5 and 6 supported in a casing. If the gears 12,13,14 and 15 were to be locked up to prevent relative rotation then the rotation of the housing 1 would be transferred through the shaft 11 to the gears 12 and 13 to the gears 14 and 15 and thence to the shafts entered into the splines.of those gears. The drive from the gears 12,13 to the gears 14,15 is through the teeth of the gears and, because of the shape of the teeth involve curved surfaces of contact, there is a force component tending to spread the gears 14 and 15. This causes the noses 18 and 19 to move through the 10 to 15 thousanths clearance separating them from the seats after forcing the oil from between the angled faces and seats to frictionally engage the seats. The frictional drive so formed provides a locked up differential gearbox which will remain in. that conditio until there is a change in the force component causing noses 18 and 19 to engage the seat 20 and 21. This cha can occur in many ways. As an example, in a turning action the wheel on the inner curve will try to rotate slower than that on the outer curve. This is the equivalent of braking the inner curve wheel and results the load applied to the axle connecting the outer curve wheel to the differential gearbox being reduce with a corresponding reduction in the tooth load between the g 14 (or 15) and its co-operating gear 12 (or 13) . With reduction in the- tooth load the force component causing associated nose to seat engagement is reduced and the l up of the differential is released (in whole or in part) for the axle connected to the wheel on the outer curve. This allows the outer curve wheel to speed up in the ma of a normal differential. From the foregoing it is clear that the same effect wil achieved for either direction of rotation of the housin It is to be understood that the above described embodim can be modified to provide noses on the housing 1 to en in seats in the gears 14 and 15 if this is desired.

Claims: CLAIMS. 1. A gearbox incorporating a housing with a gear receiving chamber, a shaft supported at its ends in the housing and extending across the chamber, a first pair o like bevel gears located in the gear chamber and rotatab mounted on the shaft in spaced relationship with the gea of the first pair oriented small end to small end, a sec pair of like bevel gears located in the gear chamber and rotatably supported in bearing means in the housing with axis of rotation at right angles to and in the same plan as the axis of rotation of the gears of the first pair, gears of the second pair being spaced apart and oriented small end to small end with each in mesh with both of th gears of the first pair, coupling means on each of the gears of the second pair to allow driven shafts to be i coupled thereto, and wherein the bearing means for each gear of said second pair comprises a truncated conical n and a similarly angled seat whereby the gears of the sec pair are rotatably supported by . the housing with working clearance between the noses and seats and with working clearance between the meshing teeth of the gears of the first and second pairs allowing limited axial movement o the gears of the second pair relative to the housing to bring the noses and seats into driving engagement. 2. A gearbox as claimed in claim 1 wherein the noses O on the gears of the second pair and the seats are in the housing. 3. A gearbox as claimed in claim 2 wherein the seats a members mounted in counterbores in the housing. 4. A gearbox as claimed in claim 1 wherein the include angle of the nose and the seat is 52 degrees. - β U K --.A £/ OMPI •

Inventors: MANNIX NORMAN ROY, MANNIX, NORMAN, ROY
Applicants: MANNIX NORMAN ROY, MANNIX, NORMAN, ROY
Application year: 1982
Main classification: F16H1
IPC codes: F16H48