Electric Power Steering ECU Layout for PCB Stress Relief
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Solution Overview
Problem
Existing electric driving devices face challenges in reducing size and suppressing stress on circuit boards due to electrical connections between motors and circuit boards, which can be exacerbated by thermal stress from field-effect transistors.
Innovation Solution
The configuration includes a motor with a shaft, rotor, stator, and magnet, and an electronic control unit with heat sinks and a terminal block fixed to a heat sink, sandwiching the circuit board to reduce axial size and stress, while using heat sinks and heat dissipation surfaces to manage thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a terminal block is used to electrically connect motor wiring to the circuit board, then electrical connection is achieved, but stress is applied to the circuit board due to pressing
Solution Approach 1:
A terminal block is introduced as an intermediary component between the motor wiring and the circuit board. The terminal block includes a pressing portion that receives pressing force from a screw, and this force is transmitted to the circuit board through a heat sink rather than directly. The heat sink acts as a stress-distributing intermediary that reduces the concentration of stress on the circuit board while maintaining reliable electrical connection.
Solution Approach 2:
The patent replaces the direct mechanical pressing connection with a modified mechanical system that includes a heat sink as a stress-distributing element. Instead of the screw pressing directly on the circuit board, the pressing force is transmitted through the heat sink's pressing portion, which has a larger surface area and distributes the stress more evenly across the circuit board.
2Reliability
If the circuit board is subjected to thermal stress from field-effect transistors, then electrical connection is maintained, but the circuit board reliability deteriorates
Solution Approach 1:
The heat sink serves as a thermal intermediary between the field-effect transistors and the circuit board. It absorbs and dissipates heat generated by the transistors, preventing this thermal energy from being directly transferred to the circuit board. This mediator function protects the circuit board from thermal stress while maintaining stable electrical connections.
Solution Approach 2:
The heat sink extracts thermal energy from the system by absorbing heat from the field-effect transistors and dissipating it to the surrounding environment. This extraction of thermal stress prevents the circuit board from being exposed to harmful temperature increases, thereby maintaining its reliability and preventing degradation.
3Volume of moving object
If the electric driving device size is reduced, then compactness is achieved, but stress concentration on the circuit board increases
Solution Approach 1:
The heat sink is designed to perform multiple functions simultaneously: it serves as a thermal management component for dissipating heat from field-effect transistors, and it also serves as a stress-distributing structural element for the terminal block connection. This multi-functionality allows the device to maintain compact size while protecting the circuit board from stress concentration.
Solution Approach 2:
The patent merges the thermal management function and the mechanical support function into a single integrated component (the heat sink). By combining these functions, the design eliminates the need for separate stress-distributing structures, thereby maintaining compact device size while still protecting the circuit board from stress concentration.
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
This configuration results in a smaller electric driving device with improved reliability and reduced stress on circuit boards, enhancing the life and functionality of the device.
Implementation Method 1
a first heat sink provided on the anti-load side of the first circuit board; a second heat sink provided on the load side of the first circuit board and sandwiching the first circuit board between the second heat sink and the first heat sink
Data Source
AI summary
To provide an electric driving device and an electric power steering device that have a smaller size in the axial direction and suppress stress on a circuit board due to electrical connection between a motor and the circuit board if a terminal block is provided. An electric driving device includes a motor and an electronic control unit that controls rotation of the motor. The electronic control unit includes a first circuit board, a first heat sink, a second heat sink, and a terminal block. The second heat sink sandwiches the first circuit board between it and the first heat sink. The terminal block is fixed to the side surface of the second heat sink and electrically connects motor coil wiring to the first circuit board.