Electric Power Steering Control Unit Axial Mounting
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Solution Overview
Problem
Existing electric power steering devices face challenges in downsizing due to increased radial dimensions caused by the stacking of control boards and power modules, which necessitates longer control boards to maintain mounting area, resulting in larger axial dimensions.
Innovation Solution
The configuration includes a heat sink with a column portion extending along the axial center of the output shaft, where control boards are mounted vertically and power modules are placed along opposing mounting portions, preventing radial expansion and maintaining compact dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control boards and power modules are stacked vertically on mounting surfaces of heat sink, then two circuit configurations with redundancy are achieved, but radial size of control unit increases
Solution Approach 1:
The patent transitions from vertical stacking (radial arrangement) to horizontal arrangement along the axial direction. Control boards are mounted on opposing axial surfaces of the heat sink column portion, and power modules are mounted on opposing radial surfaces, utilizing the axial dimension to reduce radial footprint while maintaining redundancy configuration
Solution Approach 2:
The control boards and power modules are nested within the housing structure along the axial direction, with the heat sink column portion serving as a central core. This nesting arrangement allows compact integration of redundant circuits without increasing radial dimensions beyond the motor diameter
2Area of stationary object
If width of control board is reduced to prevent radial expansion, then radial size is controlled, but mounting area of control board decreases requiring increased length
Solution Approach 1:
The patent resolves this contradiction by changing the mounting orientation from radial to axial. Control boards are arranged along the axial direction on opposing surfaces of the heat sink column, utilizing the axial dimension for board placement rather than increasing length to compensate for reduced width. This dimensional transition allows both compact radial size and adequate mounting area
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 allows for a smaller control unit with two circuit configurations, avoiding the need for increased board lengths and maintaining a size equivalent to or smaller than the motor diameter, thus achieving downsizing without enlarging the radial or axial dimensions.
Implementation Method 1
a heat sink configured to release heat generated in the control unit
Data Source
AI summary
In an electric power steering, a control unit includes a first power module configured to supply current to first motor windings, a first control board configured to output a control signal to the first power module, a second power module configured to supply current to second motor windings, a second control board configured to output a control signal to the second power module, and a heat sink. The heat sink includes a column portion having a plurality of mounting portions defined by flat surfaces parallel to the axial direction of the output shaft. The first control board and the second control board are each mounted along a corresponding one of one pair of opposing mounting portions, and the first power module and the second power module are each mounted along a corresponding one of another pair of opposing mounting portions.