Integrated cam and shift fork assembly

Details Integrated cam and shift fork assembly Integrated cam and shift fork assembly

1998-10-23

2001-01-16

Fenstermacher, David (Department: 3682)

Machine element or mechanism

Control lever and linkage systems

Multiple controlled elements

C074S337500, C475S269000

Reexamination Certificate

active

06173624

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates generally to mechanisms for controlling shifts in transfer cases and the like and more specifically to an integrated cam and fork assembly disposed upon a rotatable shift rail.
In both early and many modern transmissions and transfer cases, shifts between various speed ranges and operating conditions are often achieved by a manual linkage controlled by the vehicle operator. Frequently, such linkages include one or a plurality of parallel shift rails which may be translated out of a center, neutral position to a forward or rearward position to select a given gear or operating mode.
In contemporary consumer products such as sport utility vehicles and light and medium duty trucks, gear range and operating modes in transfer cases are now more commonly selected through the agency of an electromechanical, pneumatic or hydraulic operator. A variety of drive assemblies and intermediate linkages have been developed to achieve range selection and transfer case operating mode, e.g., lockup of a viscous clutch, a differential or modulating clutch to directly couple the primary and secondary drive lines.
These devices represent equally varying levels of complexity, sophistication, reliability and cost. Oftentimes, a sophisticated system which provides rapid and precise selection of gears or operating modes falls short from a reliability standpoint. Contrariwise, simple systems often do not provide positive, accurate or repeatable shifts although they are reliable.
The present invention is directed to a shift assembly which achieves both highly accurate positioning of a shift fork with a minimum of components and is thus highly reliable.
SUMMARY OF THE INVENTION
An integrated cam and shift fork assembly is disposed on a rotating shift rail. The shift fork assembly includes a cylindrical body having a helical cam at one end. Adjacent the cam end of the body is a cam follower secured to the rotating shift rail. The opposite end of the body either includes a second cam and suitably disposed cam follower or a flat surface engaged by a return spring. The rotating shift rail is driven by an electric motor through a suitable speed reducing and torque increasing drive such as a worm gear set. One or both of the aforementioned cam configurations may be utilized in a transfer case on a single shift rail to provide single or multiple functions, for example, select a high or low speed range, couple the primary and secondary drive lines together or both.
Thus, it is an object of the present invention to provide an integrated cam and shift fork assembly for use in transfer cases and the like.
It is a further object of the present invention to provide an integrated cam and shift fork assembly which is both straightforward and highly reliable.
It is a still further object of the present invention to provide an integrated cam and shift fork assembly which is positively bi-directionally translated by a pair of helical cams and cooperating cam followers.
It is a still further object of the present invention to provide an integrated cam and shift fork assembly which is positively translated in one direction by a cooperating helical cam and cam follower and in an opposite direction by a return (compression spring).
It is a still further object of the present invention to provide an integrated cam and shift fork assembly which may be utilized singly or multiply on a common rotating shift rail.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein the same reference number refers to the same component, element or feature.


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