Machine element or mechanism – Elements – Gear casings
Patent
1980-03-31
1982-11-09
Braun, Leslie
Machine element or mechanism
Elements
Gear casings
74705, 74710, 74714, 74758, 74760, 74762, 74764, F16H 3708, F16H 142, F16H 5710
Patent
active
043578403
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to a differential for a vehicle cross drive or the like, and more particularly to a planetary differential incorporating multi-speed capability in a compact and simplified manner.
BACKGROUND ART
While there are a large number of vehicles such as earthmoving tractors and military tanks that have utilized multi-speed cross drive transmissions, the transmissions have incorporated an excessive number of gears and associated elements, and have generally been overly complex and costly in construction. In some cases multiple speeds for the driving ground-engaging members have been achieved by merely duplicating a plurality of planetary sets and operating brakes and clutches on the left and right sides, with such brakes and clutches controlling one or more reaction members independently of the operation on the opposite side of the vehicle.
Another deficiency with prior cross drive mechanisms is that the rotating members thereof have been arranged on a plurality of transverse axes so that the construction was not only costly, but also required an excessively large housing for containment of the components.
Still another deficiency is that such cross drive transmissions have not simultaneously provided a true differential function wherein the driving torques at the opposite sides of the vehicle are continuously equalized. For example, differential steering mechanisms have heretofor been proposed which force one output member to increase in speed while simultaneously forcing the opposite output member to decrease in speed by acting on one element of a pair of oppositely disposed planetary sets. This is achieved by a cross shaft or bevel gear drive connection between such elements and separate from the input drive that interferes with the true differential function and causes unequal torques to be imposed upon the output members. Moreover, hydrostatic drive units have been employed for steering purposes in many of the earlier mechanisms, but the mixture of hydrostatic and mechanical drive unduly complicates the construction and requires an excessive amount of space.
Thus, what is needed is a compact multi-speed differential having a true differential action and a minimum number of components which can preferably be arranged along one transverse axis in a concentric manner. Preferably too, the multi-speed differential should be simple and economical to manufacture, and should incorporate a built-in reduction or speed step down capability so that it can be relatively closely coupled to a driving engine without the need for an additional reduction gear train.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a compact planetary differential is provided including first and second planetary sets individually having ring, sun and carrier elements, a rotary input member, first and second output members individually connected to a preselected first one of the elements of the respective planetary sets, and with preselected second ones of the elements of the respective planetary sets being connected for joint rotation. Desirably, means are provided for driving the output members at equal torque levels while imparting multi-speed capability thereto. Such means is driven by the input member and drives the remaining third one of the elements of the second planetary set in at least one speed.
Advantageously, the means to provide such multi-speed capability can include a multi-speed unit consisting essentially of at least one more planetary set with one brake assembly and a clutch assembly or two brake assemblies connected to preselected ones of the ring, sun and/or carrier elements thereof. It has been found to be particularly desirable, for example, to connect the sun elements of the first and second planetary sets for joint rotation and to connect the output members to the ring or carrier elements of the first and second planetary sets for joint rotation.
The comp
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Braun Leslie
Caterpillar Tractor Co.
Lanchantin, Jr. Charles E.
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