Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Tripod coupling
Patent
1994-12-22
1997-07-08
Stodola, Daniel P.
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Tripod coupling
464905, F16D 3205
Patent
active
056454872
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF INVENTION
This invention relates to constant velocity ratio (homokinetic) universal joints of the tripode type, such a joint comprising an outer joint member having a rotational axis and three tracks equally circumferentially spaced about its rotational axis and extending lengthwise of the joint member; and an inner joint member having a rotational axis and three arms equally circumferentially spaced about its rotational axis and extending outwardly from the inner joint member into the tracks of the outer joint member, each arm carrying a respective roller having an external surface which engages opposed side portions of the associated track, each roller being able to tilt within its associated track and move therealong so that the inner and outer joint members are able to move axially relative to one another and undergo relative articulation. Such a joint will hereafter be referred to as a joint of the kind specified.
Tripode-type joints of the kind specified are widely used in motor vehicle drive lines, for example as the inboard universal joints of drive shafts extending laterally to drivable wheels of a vehicle. When used in motor vehicles, particularly passenger cars, the transmission characteristics of universal joints in terms of not causing any vibrations in the vehicle drive line are of great importance, to reduce noise, vibration and harshness detectable by persons travelling in the vehicle.
In a conventional tripode joint of the kind specified, the tracks in the outer joint member extend parallel to the rotational axis of such joint member. The arms of the inner joint member are perpendicular to the rotational axis of the inner joint member. There have been proposals for tripode joints in which the tracks and arms are at other orientations, for example U.S. Pat. No. 3,990,267, shows a tripode joint wherein the tracks of one joint member are skewed relative to the rotational axis thereof, for the purpose of generating an axial force when the joint transmits torque. It has been proposed, in JP Utility Model publication 63-115927, that the arms of the inner joint member should be inclined at an angle other than 90.degree. to the rotational axis of the joint member, but this does not eliminate the transmission error described hereafter.
Although commonly referred to as a constant velocity ratio (homokinetic) universal joint, the conventional tripode joint of the kind specified only behaves as a truly constant velocity ratio joint if it is installed in such a way that rotation of the joint when articulated does not cause a change in the inclination of the rotational axis of the inner joint member relative to the axis of the outer joint member. If not installed thus, and one joint member is rotated at a constant angular velocity, when the joint is articulated, the angular velocity of the other joint member will cyclically decrease and increase, although the mean angular velocity of both joint members is, of course, the same. This deviation of the joint from true constant velocity characteristics, referred to herein as transmission error, is predominantly third order, being a sinusoidal variation with a frequency of three times the rate of rotation of the joint. There are other orders of transmission error, but Fourier analysis shows that, for a geometrically perfect joint having no other geometric distortions, the third order component represents 99.8% of the RMS value of all transmission errors. The transmission error arises from the orbital motion which the centre of the inner joint member is caused to undergo if the rotational axis of the outer joint member is held fixed, and if the opposite end of a shaft connected to the inner joint member is constrained to rotate about a fixed point the inclination of such shaft must change. If such shaft were (theoretically) infinitely long the change in inclination would be zero, or a change in shaft inclination can be avoided if a tripode-type joint is used at the other end of the shaft, providing the arms of the inner joint members of the two
REFERENCES:
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patent: 3942335 (1976-03-01), Orain
patent: 4026123 (1977-05-01), Durum
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patent: 4036032 (1977-07-01), Durum
patent: 4421494 (1983-12-01), Futamura et al.
patent: 5135438 (1992-08-01), Poulin et al.
Bartlett Stephen Charles
Lloyd Richard Anthony
Dunn Eileen A.
GKN Automotive AG
Stodola Daniel P.
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