Multi-step Range Cam for Two-Speed Transfer Case Shift Force
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Solution Overview
Problem
Modern automatic transmissions require higher shift forces in two-speed transfer cases for four-wheel drive vehicles, leading to increased costs and component size, which existing power-operated range shift systems cannot efficiently address without corresponding increases in packaging size, weight, and overall product cost.
Innovation Solution
A two-speed transfer case with a range mechanism featuring a multi-step range cam guide slot profile, providing increased mechanical advantage through a range shift segment with three interconnected linear ramp portions to optimize the loading required to move the range clutch between high-range and low-range positions, utilizing a motor-actuated ballramp unit and a planetary gearset for efficient torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If existing power-operated range shift systems are used to accommodate higher shift forces, then shift force capability is improved, but packaging size, weight, and product cost increase
Solution Approach 1:
The range cam guide slot profile is designed with variable geometry that changes during operation. The guide slot includes a first portion with a first angle relative to the cam rotation axis and a second portion with a second angle, allowing the mechanical advantage to dynamically change during the range shift stroke. This enables the system to generate higher shift forces when needed while maintaining compact dimensions throughout the cam's rotation.
Solution Approach 2:
The invention changes the geometric parameters of the guide slot profile to optimize force generation. By varying the angle of the guide slot portions relative to the cam rotation axis, the system adjusts the mechanical advantage at different points in the range shift cycle, enabling higher shift forces without proportionally increasing the cam size or weight.
2Force
If existing power-operated range shift systems are used to accommodate higher shift forces, then shift force capability is improved, but weight increases
Solution Approach 1:
The range cam guide slot profile is designed with variable geometry that changes during operation. The guide slot includes a first portion with a first angle relative to the cam rotation axis and a second portion with a second angle, allowing the mechanical advantage to dynamically change during the range shift stroke. This enables the system to generate higher shift forces when needed while maintaining compact dimensions throughout the cam's rotation.
Solution Approach 2:
The invention changes the geometric parameters of the guide slot profile to optimize force generation. By varying the angle of the guide slot portions relative to the cam rotation axis, the system adjusts the mechanical advantage at different points in the range shift cycle, enabling higher shift forces without proportionally increasing the cam size or weight.
3Productivity
If multi-step range cam guide slot profile is used to increase mechanical advantage, then shift force efficiency is improved, but device complexity increases
Solution Approach 1:
The guide slot is divided into multiple distinct portions, each with different geometric characteristics. The first portion has a first angle relative to the cam rotation axis while the second portion has a second angle, creating segmented zones of different mechanical advantage. This segmentation allows the cam to provide optimized force multiplication at different stages of the range shift stroke without requiring multiple separate components.
Solution Approach 2:
The multi-step guide slot profile performs multiple functions within a single component geometry. It provides both high mechanical advantage during the engagement phase and maintains proper timing and positioning during the dwell phase, eliminating the need for separate mechanisms for force multiplication and positioning control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables higher shift forces without increasing packaging size or weight, maintaining cost-effectiveness and improving the efficiency of torque transfer between drivelines, thus addressing the need for enhanced mechanical advantage in two-speed transfer cases.
Implementation Method 1
a planetary gearset for efficient torque transfer
Implementation Method 2
motor-actuated ballramp unit
Data Source
AI summary
A two-speed transfer case for a four-wheel drive vehicle is provided. The transfer case has a two-speed gear reduction unit, a range clutch, and a range shift mechanism. The range shift mechanism is operably disposed between an input shaft and a rear output shaft and includes a range cam defining a guide slot having a unique profile for converting rotation thereof into linear movement of the range clutch. The guide slot includes low-range dwell segment and a high-range dwell segment interconnected by a range shift segment. The range shift segment defines a plurality of interconnected cam portions, wherein each cam portion is associated with a different load required to move the range clutch between a high-range and low-range position. The transfer case further includes a mode shift mechanism for establishing a high-range drive connection and a low-range drive connection associated with the dwells of the range cam.