Automatic Step Drive System Force Mitigation
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Solution Overview
Problem
Automatic step systems in off-road vehicles face significant wear and malfunction due to counterforces applied against the actuator motor, leading to reduced product life.
Innovation Solution
A drive system with force mitigation mechanisms, including a rotary actuator, a crank arm pivotally coupled to a central shaft, and a first link, which aligns counterforces against the central shaft instead of the actuator motor, and a tolerance ring or clutch allowing the crank arm to yield without engaging the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct actuator drive is used for the automatic step, then the structure is simple and direct, but the actuator motor suffers from significant wear and malfunction due to counterforces applied against it
Solution Approach 1:
A crank arm mechanism is introduced as an intermediary between the actuator motor and the automatic step. The crank arm includes a first link with a first end coupled to the actuator and a second end coupled to the step. This intermediary structure transforms the direct linear force transmission into a rotational mechanism, allowing counterforces to be distributed through the crank arm's rotation rather than being applied directly to the actuator motor, thereby reducing wear and improving reliability
2Productivity
If the crank arm is rigidly connected to the actuator, then the force transmission is efficient, but the actuator is forced to absorb all counterforces from the step
Solution Approach 1:
The connection between the crank arm and actuator is made dynamic rather than rigid. The first link is pivotally coupled to the actuator, allowing rotational movement. This dynamic connection enables the system to adapt to varying force conditions - maintaining efficient force transmission during normal operation while allowing the crank arm to rotate and yield when counterforces are applied, preventing actuator overload and improving durability
Data Source
AI summary
A drive system for an automatic step including an actuator for moving an automatic step, a crank arm pivotally coupled to the actuator and pivotable about a central shaft, and a first link pivotally coupled to the crank arm, the first link having first and second ends. The linkage comprises one or more force mitigation mechanisms capable of reducing forces eccentric to the actuator. A first force mitigation mechanism engages when the step is deployed or nearly deployed by aligning the central shaft with the first and second ends of the first link along a first axis to generally place eccentric forces originating from the step against the central shaft of the crank arm instead of directly engaging the actuator.