Grounded Motor Frame Structure for Electromagnetic Noise Shielding
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Solution Overview
Problem
Existing motors used in rotary apparatuses, such as those in automobile air-conditioning systems, generate electromagnetic noise that can adversely affect nearby electronic components.
Innovation Solution
A motor design that includes a conductive frame electrically connected to a ground via a flexible wiring board and a plate-like spring, which acts as an electromagnetic shield by ensuring the frame is at the same potential as the ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a motor is used as a driving source in a rotary apparatus, then the motor provides driving power, but electromagnetic noise is generated that adversely affects nearby electronic components
Solution Approach 1:
A ground connection structure comprising a ground terminal, ground spring, and ground wiring board is introduced as an intermediary between the frame and the circuit board. This mediator provides a dedicated low-impedance path for electromagnetic noise to reach ground, preventing the noise from interfering with other electronic components while allowing the motor to continue providing driving power.
Solution Approach 2:
The ground connection function is extracted from the main motor structure and implemented as a separate, dedicated ground connection structure. By separating the power transmission function (stator to rotor) from the noise grounding function (frame to circuit board), the patent eliminates the interference pathway while preserving the motor's driving capability.
2Object-generated harmful factors
If the frame is electrically connected to ground via a flexible wiring board, then electromagnetic noise emission is inhibited, but the connection reliability may be compromised due to wiring board rupture or disconnection
Solution Approach 1:
The ground connection structure employs different materials and structures for different functions: a rigid ground terminal for stable mounting, a flexible ground spring for elastic contact and stress absorption, and a flexible wiring board for electrical connection. This local differentiation of properties ensures both electromagnetic noise suppression and connection reliability under various conditions.
Solution Approach 2:
The ground spring is designed with elastic properties to beforehand cushion against mechanical stresses, vibrations, and thermal expansions that could otherwise cause disconnection or rupture of the wiring board. The spring's elasticity provides a safety margin that absorbs unexpected mechanical loads before they can damage the connection.
3Object-generated harmful factors
If a ground connection structure with a spring and flexible wiring board is added to the motor, then electromagnetic noise is inhibited, but the device complexity increases
Solution Approach 1:
The ground terminal serves multiple functions: it provides mechanical mounting for the ground spring, establishes the ground connection point on the frame, and serves as the anchor for the flexible wiring board. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while still achieving electromagnetic noise inhibition.
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
The motor effectively inhibits the emission of electromagnetic noise to the outside, protecting nearby electronic components and maintaining stable operation.
Implementation Method 1
a plate-like spring supported to the holder, the spring electrically connects the frame and the flexible wiring board... the frame is electrically connected via the flexible wiring board to a ground of the circuit board
Implementation Method 2
the spring is elastically deformable in such a direction as to be away from the frame
Data Source
AI summary
To provide a motor inhibiting emission of electromagnetic noise (EMC) to the outside and a rotary apparatus including the motor. The rotary apparatus of the present disclosure includes: a housing; a motor arranged inside the housing; a circuit board arranged inside the housing and electrically connected to the motor; and a flexible wiring board electrically connecting the motor to the circuit board, the motor including a frame formed with a conductive member, the frame electrically connected via the flexible wiring board to a ground of the circuit board.