Machine element or mechanism – Gearing – Nonplanetary gearing differential type
Patent
1994-07-06
1996-08-06
Ta, Khoi Q.
Machine element or mechanism
Gearing
Nonplanetary gearing differential type
184 612, 74665F, F16H 3504, F16H 5704
Patent
active
055423167
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a differential mechanism particularly but not exclusively for use in motor vehicles.
Differential mechanisms commonly used on vehicles are of the sun and planet gear type and have a well known disadvantage that when one wheel is on a slippery surface such as mud or ice and the other wheel is on a firm surface capable of providing traction, the first wheel will simply spin as it receives all the available power transmitted to the differential.
Limited slip differential mechanisms have been proposed in an attempt to overcome this problem which restrict the extent to which one wheel can spin relative to the other but such differentials are more complex and therefore, more costly to produce.
In European patent application EP-A-0284329 there is proposed an alternative differential mechanism comprising two output cam members rotatable about an axis, each said member having a single annular cam surface thereon of undulating form comprising pairs of mutually inclined surfaces, and a plurality of cam followers having end surfaces engaging the cam surfaces of the output cam members, the arrangement being such that relative contra rotation of said output cam members causes the cam followers to slide axially, and an input element engaging the followers which are slidably supported by the input element and moving the followers circumferentially relative to the output cam members.
Such a differential will hereinafter be called a differential of the type described.
It is an object of the present invention to provide a differential of the type described which is suitable for use in four wheel drive applications.
According to the invention there is provided a differential of the type described characterised in that the input element engages with a radially inner portion of each cam follower to move the follower circumferentially relative to the cam output members and the cam surfaces face inwardly towards the axis of rotation.
Preferably one output cam surface is formed on a housing containing the differential, and the second output cam surface is on a pinion which is rotatable within the housing.
Conveniently in a four wheel drive application the housing is drivably connected to the front wheels of the vehicle, and the pinion is drivably connected to the rear wheels of the vehicle.
Oil pump means may be provided, driven from a component of the differential which rotates during use of the differential to pump oil into the differential. The oil pump means may comprise external scoops or a vane type pump.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a cross section through a differential mechanism in accordance with the invention;
FIG. 2 is a development of cam surfaces with cam followers shown in positions therebetween;
FIG. 3 is an end view of a cam follower and input member of the differential of FIG. 1;
FIG. 4 diagrammatically shows the differential of FIG. 1 in use in a vehicle;
FIG. 5 is a view on line V--V of FIG. 1 showing lubrication grooving details;
FIG. 6 is a section through part of an alternative differential arrangement which include an oil pump, and
FIG. 7 is a view on line VII--VII of FIG. 6 showing details of the pump housing and impellor.
In FIGS. 1 to 3 the differential 10 is mounted in a partially oil-filled surrounding casing (not shown) by bearings B. The differential 10 comprises a housing 11 formed by end walls 13 and 14 having a gear 12 on its external surface to provide a drive output in known manner. The end walls 13 and 14 may be, formed in two or more pieces (see FIG. 6 embodiment) the two pieces being screwed, welded and/or bolted together.
An input hub 16 is located within the centre of the housing 11. The input hub 16 has a central bore 17 with splines 15 therein for connection to an input shaft 20. An output pinion 19 is also located within the housing 11, and has a centre bore 51 with splines 52 for connection to an output shaft 53. The shafts 20 and 53 pass through bores 18 in the end walls 13
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Chippendale John P.
Spooner John
Young Alastair J.
Automotive Products plc
Germain Lee A.
Milliken Paul E.
Ta Khoi Q.
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