Motor Drive Rear End Frame Sensor Alignment
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Solution Overview
Problem
Conventional electric power steering systems face inaccuracies in detecting the rotation angle of a rotor due to positional deviations between the rotation angle sensor and the magnet, caused by gaps in the motor case and heat sink assembly.
Innovation Solution
A motor drive apparatus with a rear end frame that positions the control unit substrate accurately relative to the shaft, ensuring the rotation angle sensor is aligned with the magnet's axis, improving detection accuracy and motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rotation angle sensor is mounted on the control unit substrate using conventional assembly methods with holes and bolts, then the control unit can be assembled, but positional deviation occurs between the sensor and magnet due to gaps in the assembly
Solution Approach 1:
A positioning pin is introduced as an intermediary component between the control unit substrate and the motor case. The positioning pin fits into a positioning hole to precisely locate the control unit substrate, eliminating gaps and ensuring accurate positioning of the rotation angle sensor relative to the magnet on the shaft.
2Ease of operation
If gaps are present between the motor case hole and column, or between the heat sink thread hole and bolt, then assembly is possible, but the rotation angle sensor deviates from the rotation axis
Solution Approach 1:
The positioning pin acts as a mediator that transfers precise positioning from the motor case through the control unit substrate to the rotation angle sensor. This eliminates the cumulative effect of gaps between multiple assembled parts, ensuring the sensor remains aligned with the rotation axis.
3Device complexity
If the rotation angle sensor position deviates from the magnet position, then assembly is simpler, but the control circuit cannot detect the rotation angle accurately
Solution Approach 1:
The positioning pin provides a simple yet effective mechanism that ensures accurate sensor positioning without adding significant complexity to the assembly process. The pin-fit structure is straightforward to manufacture and assemble while guaranteeing precise alignment.
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
Enhances the accuracy of rotation angle detection and motor control by precisely positioning the rotation angle sensor relative to the magnet, leading to improved steering assistance in electric power steering systems.
Implementation Method 1
The rotation angle sensor detects the magnetic field of a magnet attached to an axial end of a shaft of the motor and outputs its detection signal to a control circuit provided on the control unit substrate.
Data Source
AI summary
A motor drive apparatus includes a rear end frame between a motor case and a control unit case. A shaft of a motor unit is supported rotatably by a bearing fixed to the rear end frame. A first socket-spigot fitting surface formed on the rear end frame is fitted with a second socket-spigot fitting surface formed on a heat sink. A rotation angle sensor mounted on a control unit substrate attached to the heat sink is provided on the rotation axis of the shaft. The rotation angle sensor can thus accurately detect the magnetic field of a magnet provided at the end of the shaft.