Planetary gear transmission systems or components – Differential planetary gearing – Planet pinion is worm gear
Patent
1990-05-25
1992-02-18
Herrmann, Allan D.
Planetary gear transmission systems or components
Differential planetary gearing
Planet pinion is worm gear
475226, 475249, 475904, F16H 138, F16H 144
Patent
active
050889702
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to vehicle differential gear assemblies of the type which include a plurality of gear trains for sharing the transmission of power through the differential, and specifically, to the design of such gear trains.
Multiple gear train differential assemblies often require each gear member of the assembly to be mounted in a particular order and at a distinct rotational position. These special assembly procedures are necessary (a) to avoid interference between the gear trains which would prevent their collective assembly and (b) to ensure equal load sharing between the gear trains.
BACKGROUND ART
A differential assembly of the type contemplated for the present invention is generally of the design shown in U.S. Pat. No. 2,859,641 (GLEASMAN). This patent is incorporated herein by reference to the extent necessary to provide specific details of the structure of the differential assembly.
This type of differential includes a rotatable gear housing, a pair of drive axles received in bores formed in the sides of the housing, and a differential gear arrangement mounted within a main body portion of the housing for driving the axles. The gear housing body portion includes a flange formed at one end for mounting a ring gear or other means for providing power input to the differential from the drive shaft of the vehicle in a conventional manner. The gear housing is provided with a cap at its other end which may be formed as an integral part of the housing or may be removably secured to the housing.
The gear arrangement which is referred to as a "crossed-axis compound planetary gear complex" includes a pair of helical worm or side gears coupled to each axle end, together with so called transfer gears associated with each of the side gears and in mesh with each other for transferring and dividing torque between the axle ends. The transfer gears are mounted in pairs within slots, or windows, formed in the main body portion of the gear housing, and each transfer gear of a pair rotates on an axis of rotation that is substantially perpendicular to the axis of rotation of the side gears and gear housing.
The transfer gears are in reality combination gears, i.e., the middle portion of each gear constitutes a worm wheel portion while the outer ends of the gear are formed with integral spur gear portions. The gear arrangement is such that, for any given pair of combination gears, the worm wheel portion of a first combination gear meshes with one side gear while the worm wheel portion of a second combination gear meshes with the other side gear, and the spur gear portions of the respective combination gears mesh with each other.
In one example of this type of differential assembly, a set of three combination gears are arranged with their respective axes of rotation in a first plane at approximately 120.degree. intervals about the periphery of each side gear, each of the three combination gears being paired with a combination gear of a second set of three combination gears similarly arranged with respect to the second side gear in a second plane parallel to the first plane.
Each of the combination gear pairs may be considered as a part of a separate gear train for interconnecting the side gears. Although it would be possible to transmit a limited amount of power between side gears using only a single gear train, one or more additional pairs of combination gears are used to define additional gear trains for increasing power transmitting capability of the differential and to provide additional frictional surfaces for dividing torque between drive axles. However, once a first gear train is used to operatively connect the side gears, relative rotational positions of the two side gears are established and additional gear trains must be assembled in a manner which preserves this established rotational relationship between side gears. Otherwise, the additional trains will not fit properly into mesh.
The relationship between the gear trains which is required to fit each gear train properly int
REFERENCES:
patent: 2859641 (1958-11-01), Gleasman
patent: 3292456 (1966-12-01), Saari
patent: 3735647 (1973-05-01), Glaseman
patent: 3875824 (1975-04-01), Benjamin
patent: 4750383 (1988-06-01), Stritzel
patent: 4754661 (1988-07-01), Barnett
patent: 4916978 (1990-04-01), Razelli et al.
patent: 4938099 (1990-07-01), Knight
Herrmann Allan D.
Ta Khoi Q.
Zexel-Gleason USA, Inc.
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