Motor Driven Power Steering Rotation Preventing Arm
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Solution Overview
Problem
In motor-driven power steering apparatuses, the free rotation of input, output, and gear shafts during assembly leads to abnormal winding of the spiral cable, potentially causing disconnection or increased steering torque due to unregulated shaft rotation.
Innovation Solution
A rotation preventing structure, comprising a rotation preventing arm with a boss portion and locking portion, is implemented to prevent the drive gear from rotating relative to the gear housing, ensuring the spiral cable remains wound in a neutral state by locking the arm to serrations and stoppers within the gear housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the shafts are freely rotated during handling, then the assembly process is easier, but the spiral cable becomes abnormally wound causing disconnection or increased steering torque
Solution Approach 1:
A rotation preventing structure is installed on the drive gear before the electric motor is assembled, as a preliminary protective measure during the handling and assembly process. This structure prevents abnormal winding of the spiral cable that would otherwise occur during normal handling operations.
Solution Approach 2:
The rotation preventing structure acts as an intermediary component between the drive gear and the external environment during assembly. It mediates the contradiction by allowing the drive gear to be handled while simultaneously preventing it from rotating, thus protecting the spiral cable from abnormal winding.
2Reliability
If the rotation preventing structure is added, then the spiral cable is protected from abnormal winding, but the device complexity increases
Solution Approach 1:
The rotation preventing structure is merged with the drive gear assembly, utilizing existing components and spaces within the gear housing. The structure combines the rotation prevention function with the existing drive gear support structure, avoiding the need for completely separate protective mechanisms.
Solution Approach 2:
The rotation preventing structure is designed to be self-contained and self-activating. Once installed on the drive gear, it automatically prevents rotation without requiring external control systems, sensors, or additional actuation mechanisms, thus minimizing the increase in device complexity.
Data Source
AI summary
In a motor-driven power steering apparatus, in an intermediate assembled state in which an input shaft, an output shaft, a torsion bar, a worm gear, a worm wheel, a torque detecting apparatus and a spiral cable are assembled in a gear housing, and an electric motor is not assembled yet, a rotation preventing arm which prevents the worm gear from rotating is loaded with respect to the gear housing.