Inter-Board ECU Layout for Compact Electric Power Steering
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Solution Overview
Problem
Existing electric driving devices face challenges in reducing the area of power circuit boards due to increased power supply wiring, which affects heat dissipation and reliability, particularly in electric power steering systems where field-effect transistors are used to control motors.
Innovation Solution
The configuration includes a motor with a shaft, rotor, and stator, along with an electronic control unit featuring separate circuit boards for power and control circuits, connected via an inter-board connector, a heat sink, and a power supply wiring module to reduce the number of power supply wires and enhance heat dissipation, allowing for efficient signal transmission and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of power supply wiring is increased to provide higher electric power to the motor, then the power supply capability is improved, but the area of the board increases
Solution Approach 1:
The patent transitions from planar board wiring to three-dimensional space by routing power supply wiring through the thickness direction of the board using via holes. This allows power delivery without increasing the board's surface area, effectively moving the wiring solution from a two-dimensional constraint to a three-dimensional implementation.
Solution Approach 2:
The via holes in the board serve multiple functions: they provide mechanical support for the board structure, enable thermal conduction paths for heat dissipation, and conduct electrical power from the power supply terminal to the circuit components. This multi-functionality resolves the contradiction by making the same structural element serve power delivery without requiring additional dedicated wiring space.
2Length of stationary object
If field-effect transistors are mounted on the power circuit board to reduce the height of the power module, then the module height is reduced, but heat generation increases and affects control circuit operations
Solution Approach 1:
The patent introduces via holes as intermediary thermal conduction paths between the field-effect transistors mounted on the board and the back side of the board. These via holes act as heat sinks that conduct heat away from the transistors, preventing thermal interference with control circuit operations while maintaining the low-height configuration.
Solution Approach 2:
The patent converts the harmful heat generated by the field-effect transistors into a beneficial thermal conduction path. By designing via holes that extend through the board thickness, the heat that would otherwise interfere with control circuits is redirected to the board's back side, where it can be dissipated, thus transforming a harmful thermal effect into an effective heat management solution.
3Reliability
If the circuit board is separated into power circuit board and control circuit board to protect control circuits from heat, then the reliability of control circuit is improved, but heat dissipation becomes more difficult
Solution Approach 1:
The patent merges the power circuit board and control circuit board into a single integrated board structure. This allows the via holes to serve dual purposes: providing electrical connections for power delivery and creating thermal conduction paths for heat dissipation. The unified structure enables heat from power components to be conducted through the board to the back side, solving the heat dissipation problem while maintaining control circuit reliability through physical separation of sensitive components.
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 effectively reduces the size of the electronic control unit, enhances heat dissipation, and improves the reliability of the electric driving device and power steering system by minimizing power supply wiring and optimizing heat management.
Implementation Method 1
a heat sink provided on the anti-load side of the shaft, and having a heat dissipation surface facing the first circuit board
Data Source
AI summary
An electric driving device and an electric power steering device. 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 second circuit board, a second housing, a lid, and an inter-board connector. The second circuit board includes a control circuit that controls an electric current supplied to a transistor of the first circuit board. The second housing accommodates the second circuit board and has a first through hole passing therethrough in the axial direction. The lid covers the second housing. The inter-board connector connects the second circuit board disposed on the anti-load side of the second housing to the first circuit board disposed on the load side of the second housing. The inter-board connector is disposed in the first through hole.