On-the-Move Range Shifting in Two-Speed Transfer Cases
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current two-speed transfer cases for four-wheel drive vehicles require the vehicle to be stopped to shift between high-range and low-range drive modes, which is inconvenient, especially when encountering changing road conditions.
Innovation Solution
A two-speed transfer case with a non-synchronized range shift mechanism and a control system that allows on-the-move shifting from low-range to high-range drive modes, using a torque transfer arrangement with a mode clutch unit, range clutch unit, and a power-operated clutch actuation unit, controlled by a transfer case control unit communicating with vehicle sensors and other control units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a non-synchronized range shift mechanism is used, then on-the-move shifting is enabled, but shifting complexity and control difficulty increase
Solution Approach 1:
The patent replaces the traditional mechanically synchronized range clutch system with an electronically controlled non-synchronized range shift mechanism. The range clutch is actuated by an electric motor through a reduction gearset, eliminating the need for mechanical synchronization components while enabling on-the-move shifting through electronic control signals from the transfer case control unit.
2Ease of operation
If a synchronized range shift mechanism is used, then on-the-move shifting is enabled, but system complexity increases
Solution Approach 1:
The patent eliminates mechanical synchronization systems by using electronic control to manage the range shifting process. The transfer case control unit receives input signals from vehicle sensors and transmission control unit, then generates control signals to actuate the range clutch at appropriate times, replacing complex mechanical synchronization with simpler electronic timing control.
3Productivity
If the vehicle must be stopped for range shifting, then shifting reliability is ensured, but productivity and operational efficiency decrease
Solution Approach 1:
The control system performs preliminary actions by receiving vehicle operating condition signals before the range shift is executed. The transfer case control unit evaluates sensor inputs (vehicle speed, transmission gear, engine speed) and transmission control unit signals to determine optimal shift timing, preparing the control system in advance to execute the range clutch actuation at the most appropriate moment while the vehicle is still moving.
Solution Approach 2:
The system uses feedback from multiple vehicle sensors and the transmission control unit to continuously monitor operating conditions. The transfer case control unit processes these feedback signals to dynamically control the range clutch actuation timing, ensuring reliable on-the-move shifting by adapting to real-time vehicle conditions rather than requiring a fixed stopped state.
Data Source
AI summary
A transfer case for a four-wheel drive motor vehicle includes a two-speed range clutch unit, a mode clutch unit, a power-operated actuation mechanism and a control system. The actuation mechanism includes an electric motor, a geartrain driven by the motor for controlling rotation of an actuator shaft, a range actuator assembly and a mode actuator assembly. The range actuator assembly functions to move a shift collar associated with the range unit in response to rotation of the actuator shaft. The mode actuator assembly includes a mode cam and a ballramp unit. The mode cam is rotatively driven by the actuator shaft for controlling the clutch engagement force exerted on the friction clutch by the ballramp unit. The control system controls movement of the shift collar during motive operation of the motor vehicle to permit on-the-move range shifting.