Electric Power Steering Housing Frame for Axis Center Accuracy
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Solution Overview
Problem
In electric power steering devices with integrated motor and control units, the deformation of the motor housing during assembly leads to an uneven axis center, causing vibrations and noise due to the uneven distribution of pressing forces by spring mechanisms, which complicates maintaining a correct axis center.
Innovation Solution
The electric power steering device incorporates a frame that is restrained by a step portion on the case's inner wall, with a connecting portion bonding the frame's outer circumference to the case's inner circumference, preventing movement and ensuring the axis center's accuracy by inhibiting pressing and inserting forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If spring mechanisms are provided at multiple positions of the rotor housing to press and insert the rotor housing into the motor case, then the deformation of the motor housing can be inhibited, but the axis center accuracy deteriorates due to uneven spring deformation
Solution Approach 1:
The invention extracts the pressing function from multiple spring mechanisms and concentrates it into a single pressing mechanism. This single pressing mechanism presses the rotor housing at one position, eliminating the deformation issues caused by multiple springs while maintaining axis center accuracy. The single pressing point avoids the uneven deformation problem inherent in multi-point spring pressing.
Solution Approach 2:
The invention changes the pressing mechanism from a multi-point elastic pressing system to a single-point mechanical pressing system. By using a pressing member with a pressing portion that contacts the rotor housing at a specific location, the system transitions from distributed elastic forces to a concentrated controlled force, thereby maintaining both housing stability and axis center precision.
2Volume of moving object
If the motor and control unit are integrated to save space and reduce weight, then the device compactness is improved, but the risk of dust intrusion to the control unit increases
Solution Approach 1:
The invention segments the integrated motor assembly by introducing a dust-proof member that creates a separate dust-proof chamber. This chamber is formed between the dust-proof member and the motor case, isolating the control unit from dust-generating areas. The segmentation allows the motor and control unit to remain integrated while protecting sensitive electronic components from dust intrusion.
Solution Approach 2:
The dust-proof member acts as an intermediary barrier between the motor case (where dust may be generated) and the control unit. This intermediate structure prevents direct contact between dust particles and the control unit, enabling the integrated design to maintain both compactness and protection against harmful factors.
Data Source
AI summary
In an electric power steering device in which a control unit and a motor are integrated, when the control unit is housed in a case, although a frame, by which the motor and the control unit are compartmentalized, is required, there have been problems in that the case is deformed by a pressure which influences the case when the frame is provided, and a position accuracy of a shaft center of a rotation shaft of the motor is worsened. Therefore, in order to reduce a deformation of the case, a step portion is provided at an inner wall surface of the case and the frame is contacted to the step portion, and moreover, a connecting portion is provided between an outer circumference portion of the frame and an inner circumference portion of the case, whereby a movement of the frame is restrained.