Machine element or mechanism – Gearing – Nonplanetary gearing differential type
Patent
1990-07-11
1991-11-05
Braun, Leslie A.
Machine element or mechanism
Gearing
Nonplanetary gearing differential type
74665B, 74665C, 74665D, F16H 3504
Patent
active
050623206
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a differential mechanism particularly but not exclusively for use in motor vehicles.
Differential mechanism 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 mechanism 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 differential are more complex and, therefore, more costly to produce.
It has also been proposed to provide a lockable differential which enables the differential effect to be prevented completely when necessary thereby ensuring that the speed of each wheel is the same enabling the maximum available traction to be obtained at each wheel. However if the user of the vehicle overlooks the fact that the differential has been locked and drives the vehicle in normal conditions for any length of time, abnormal wear of tires and excessive transmission stresses will result.
Alternative forms of differential mechanisms have been proposed over the years, mostly in very old patent specifications. See, for example, U.S. Pat. No. 1,568,358, 2,034,318, 2,220,432, GB-A-431 020, GB-A-117 703 AND DE-C-741 812.
In the aforesaid patents the differentials each comprise an input, two outputs which include respective cam members rotatable about an axis, a plurality of cam followers having surfaces which engage the cam surfaces to impart drive to the outputs, the cam followers being drivable from the input and the arrangement being such that relative contra-rotation of said outputs causes the cam followers to slide axially.
Such arrangements are normally non-reversible so that rotation of one output cannot be transmitted through the cam followers so as to impart drive to the other output. In that manner drive will always be transmitted to one of the outputs from the input even if the other output is connected to a wheel which is spinning on a slippery surface.
To a very large extent the construction of the alternative differentials proposed in the foregoing patents is not particularly compact. For example in U.S. Pat. Nos. 2,034,318 and 2,220,432 the cam followers are made axially very wide to facilitate the cutting of grooves which provide the cam surfaces. In GB-A-117,703 and DE-C-741,812 each cam member has to provide a plurality of concentric cam surfaces associated with respective sets of followers. Further earlier proposals of the latter type are also disclosed in DE-A-1,817,553 and FR-A-479,242.
In GB-A-431,020 there is described a differential mechanism comprising a drive input element two output cam members rotatable about an axis, each said member having a single annular cam surface thereon of zig-zag or undulating form arranged such that the cam surfaces on the cam members converge towards each other, and a plurality of cam followers which have cam engaging end surfaces for imparting drive from the input element to said output cam members, the arrangement being such that relative contra rotation of said output cam members causes the cam followers to slide axially. In that differential, the cam followers are radially elongate but members are relatively short in the axial direction of the output. There is, therefore, little in the way of support for the cam followers by the input element, especially of a kind that will inhibit tipping of the followers about a radial axis due to loading thereon during operation of the differential.
SUMMARY OF THE INVENTION
One object of one aspect of the present invention is to provide a differential which is not only compact but provides improved support for the follower members.
According to an aspect of the invention there is provided a differential mechanism comprising a drive input two outputs including cam members rotatable about an axis, each
REFERENCES:
patent: 1283283 (1918-10-01), Patch
patent: 2220432 (1940-11-01), Wales
patent: 2850919 (1958-09-01), Wildhaber
patent: 3130604 (1964-04-01), Johnson et al.
Bainbridge Wilfred N.
Parsons David
Temperley Harry D.
Young Alastair J.
501 Automotive Products Plc
Braun Leslie A.
Trousdell William O.
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