Transfer Case Actuation Mechanism for Two-Speed Range Control
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Solution Overview
Problem
Conventional power transfer systems for four-wheel drive vehicles are complex and costly due to the need for separate actuators to control the two-speed range shift mechanism and mode clutch assembly, which increases the overall complexity and cost of two-speed actively-controlled transfer cases.
Innovation Solution
A transfer case with a two-speed range unit, a mode clutch assembly, and a power-operated actuation mechanism, including a planetary gearset, a multi-plate friction clutch, and an electric motor-driven actuator shaft with a range actuator assembly and a mode actuator assembly, which coordinates the actuation of the range unit and mode clutch assembly using a control system to establish various drive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate power-operated actuators are used to control the range shift mechanism and clutch assembly, then reliable independent control is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines two separate actuator systems into a single integrated power-operated actuator that controls both the range shift mechanism and the clutch assembly. This single actuator uses a shared motor and transmission mechanism to simultaneously or independently actuate the range clutch and mode clutch, thereby reducing overall system complexity and cost while maintaining reliable control through electronic coordination of the combined functions
Solution Approach 2:
The single power-operated actuator is designed with multi-functionality to perform both range shifting and mode clutch engagement/disengagement. The actuator includes a motor, transmission mechanism, and linkage system that can selectively engage different components (range clutch or mode clutch) based on control signals, making one device serve multiple functions that previously required separate dedicated actuators
2Device complexity
If a single power-operated actuator is used to coordinate actuation of both range shift mechanism and clutch assembly, then device complexity and cost are reduced, but control coordination difficulty increases
Solution Approach 1:
The patent introduces an electronic control system as an intermediary between the operator/input and the single power-operated actuator. This control system receives signals for range shifting and mode changes, processes them to determine the correct actuator movements, and controls the motor actuation sequences. The intermediary control system manages the coordination complexity by translating high-level commands into precise actuator movements, eliminating the need for complex mechanical coordination mechanisms
3Adaptability or versatility
If adaptive torque transfer clutch is implemented, then on-demand four-wheel drive capability is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces complex mechanical torque-sensing and transfer mechanisms with an electronically-controlled friction clutch system. Instead of using mechanical linkages and sensors to detect wheel slip and automatically transfer torque, the system uses an electronically controlled clutch assembly that can be actuated by the power-operated actuator based on electronic control signals. This substitution of mechanical adaptive systems with electronically-controlled friction-based torque transfer reduces manufacturing complexity and cost while maintaining adaptability
Solution Approach 2:
The adaptive torque transfer is achieved by changing the engagement state and slip characteristics of the friction clutch through controlled actuation. By varying the clutch engagement pressure and allowing controlled slip, the system dynamically adjusts torque distribution between front and rear axles. This parameter-based control (changing clutch engagement parameters) provides adaptive torque transfer without requiring complex mechanical adaptive mechanisms, thereby reducing manufacturing cost
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
This solution reduces the complexity and cost of two-speed actively-controlled transfer cases by integrating the actuation of the range unit and mode clutch assembly with a single power-operated mechanism, enabling efficient control of drive torque distribution between the front and rear wheels in different drive modes.
Implementation Method 1
a planetary gearset driven by an input shaft and having a planet carrier
Implementation Method 2
a mode clutch assembly including a multi-plate friction clutch operably installed between the first output shaft and a second output shaft
Implementation Method 3
an actuator shaft driven by an electric motor
Data Source
AI summary
A transfer case includes a two-speed range unit, a friction clutch, 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.