Planetary gear transmission systems or components – Differential planetary gearing – Spur gear differential
Patent
1993-09-28
1996-01-16
Wright, Dirk
Planetary gear transmission systems or components
Differential planetary gearing
Spur gear differential
475903, F16H 128
Patent
active
054843480
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a differential unit.
The present invention will be discussed with reference to its use as a differential unit for an automobile. However, the invention should not be considered so limited, since the invention could be used as a differential unit for any application.
In recent years automobile manufacturers have been fitting smaller cars with four wheel drive requiring diffential gearing between wheels on the same axle and between the two pairs of wheels on different axles. It is a problem with smaller cars to provide differential units which are small enough to fit in the compact space available. Such differential units must be of low weight and the mass production must be reasonably cheap and require minimum parts.
The present invention provides a differential unit comprising; input means for receiving power; a first arrangement of gears for delivering power to first output means; and a second arrangement of gears for delivering power to second and third output means; wherein the first arrangement of gears transmits power from the input means for receiving power to both the first output means and a input means of the second arrangement of gears and operates as a differential connected between the first output means and the input means of the second arrangement of gears; and the second arrangement of gears transmits power from the second input means thereof to both the second and third output means and operates as a differential connected between the second and third output means.
The present invention thus provides a transmission system which can transmit power from an input to three different output shafts and provide for differential motion between the shafts.
In a first preferred embodiment of the invention the first arrangement of gears is an epicyclic arrangement comprising a first annulus gear which provides the input means for the differential, a first plurality of planet gears, a first planet gear carrier and first and second sun gears and the second arrangement of gears is an epicyclic arrangement which comprises a second annulus gear which provides the input means of the second arrangement of gears, a second plurality of planet gears, a second planet gear carrier and a third sun gear, wherein one gear serves as both the first sun gear of the first arrangement and the annulus gear of the second arrangement, the second sun gear providing the first output means, the second planet gear carrier providing the second output means and the third sun gear providing the third output means.
In the first preferred embodiment the first plurality of planet gears preferably comprises a plurality of gears of a first axial length and a plurality of gears of a second longer axial length, the plurality of gears of the second longer axial length engaging both the first sun gear and at least one of the plurality of gears of the first axial length and the plurality of gears of the first axial length engaging the second sun gear.
Preferably in the first embodiment the first sun gear has a larger pitch diameter than the second sun gear and the first and second suns are mounted for rotation about the same axis, the planet gears of the second longer length being mounted for rotation about axes parallel to and at a first radial distance from the common axis of rotation of the first and second sun gears and the plurality of planet gears of the first length being mounted for rotation about axes parallel to the said common axis of rotation at a second smaller radial distance.
In the first preferred embodiment the plurality of planet gears of second longer length preferably extend over at least a portion of both of the first and second sun gears whilst engaging with only the second sun gear and the plurality of planet gears of the first length extend over only the first sun gear and engage therewith.
The second sun gear of the first preferred embodiment is preferably provided with a cylindrical passage axially therethrough, which cylindrical passage enables an output shaft to extend through the
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Brown David
Lipman John M.
Lotus Cars Ltd.
Wright Dirk
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