Machine element or mechanism – Gearing – Plural power paths to and/or from gearing
Patent
1987-12-21
1989-06-27
Diehl, Dwight G.
Machine element or mechanism
Gearing
Plural power paths to and/or from gearing
74640, 74650, F16H 3706, F16H 3504
Patent
active
048418099
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
Many structures are known for limited slip differentials, but they are complex and expensive devices. The following prior U.S. patents have been found in searches on the subject, but none provide a simple and inexpensive limited slip differential structure: U.S. Pat. Nos. 1,355,170; 1,483,606; 1,505,570; 1,515,916; 1,934,721; 2,859,641; 2,923,174; 3,548,683; 3,581,597; 3,686,976; 3,700,082; 3,732,750; 4,104,931; 4,400,996; 4,498,355; 4,507,984; 4,524,640; 4,554,845; 4,598,609 and 4,640,143.
SUMMARY OF THE INVENTION
This invention is a positraction or non-slip differential that allows two shafts or wheels to rotate at different speeds (one faster and the other slower than the differential case). The difference in speed for each shaft with respect to the case is allowed only when the wheel or shaft needs to rotate more slowly or faster than the case speed. The differential is constructed of two cam operated nutating gear sets. Each axle or shaft is connected to the cams of the gear sets respectively. The differential will not allow one wheel to spin and steal torque from the other because each cam operated nutating gear set is asymmetric in transmitting torque; with the cam attached to the drive shaft and the gear connected to the case, torque from the shaft is able to rotate the gear with respect to the housing more easily than torque from the gear can cause rotation of the cam. In short, if a wheel loses traction its cam will immediately rotate at case speed. When one cam rotates at case speed with one-way drive through the cam-gear sets, the other cam must also rotate at case speed because torque can not flow backwards through the cam operated gear set.
The gear-cam sets may be designed with limited slip biasing, that is, partial ability to drive in both directions through each gear-cam set so that upon loss of load on one shaft, the entire torque of the housing is not transmitted to the remaining driven shaft thereby doubling the torque on the remaining driven shaft. This may be accomplished by differential positive torque transmission in the two directions through the gear-cam set by proper selection of gear ratio and cam ratio in relation to the frictional resistance of the gear-cam set.
The cam operated gear sets may use edge nutating gears, face mutuating gears or elliptical nutation.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a longitudinal sectional view of one form of my invention using face nutating gears;
FIG. 2 is an exploded view of the differential of FIG. 1;
FIG. 3 is a longitudinal sectional view of a differential of this invention using edge nutating gears;
FIG. 4 is a cross-sectional view of a the structure of FIG. 3 taken on the plane indicated at 4--4 in FIG. 3; and
FIG. 5 is an exploded view of the structure of FIG. 3.
FIG. 6 shows a possible method of using two harmonic drives (elliptical cam operated gear sets) to construct a limited slip differential. The inner gear of a harmonic drive has the fewer number of teeth of the two gears. The inner gear is a flexible gear made of spring steel or other strong flexible media. The outer gear is a rigid internally-toothed ring gear.
DETAILED DESCRIPTION
This invention is an improvement in the design of anti-spin differentials wherein two cam operated gear sets are used to transmit differential torque from the cams, but not in the reverse direction. The specific types of gear trains used are the face nutators, edge nutators, and the harmonic drives.
Referring now in detail to FIGS. 1 and 2, a pair of shafts 11 and 12 are rotatably mounted in a differential housing 14 which may be rotated about the axis of the shafts by any suitable means such as a bevel gear. A pair of nutating drive trains connect the shafts to the housing.
The drive train for the shaft 11 includes a cam 16 connected to the shaft 11 by a pin 18, a nutating gear 20 mounted for rotation on a boss 22 on the cam 16 and carrying a set of face teeth 24 engaging a set of face teeth 26 on the inside of the case 14 with the nutati
REFERENCES:
patent: 1730183 (1929-10-01), Wildhaber
patent: 2700310 (1955-01-01), Viebrock et al.
patent: 3532005 (1970-10-01), Bremner, Jr. et al.
patent: 3977275 (1976-08-01), Kiesewetter et al.
patent: 4291591 (1981-09-01), Ross
patent: 4449442 (1984-05-01), Ebbing et al.
patent: 4665769 (1987-05-01), Parsons
Diehl Dwight G.
F. J. Engineering, Inc.
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