EPS Bus Bar Layout for Low-Inductance Thermal Packaging
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Solution Overview
Problem
Conventional driving apparatuses for electric power steering face challenges in downsizing while maintaining high heat-radiation performance, as reducing the surface area of bus bars increases inductance and noise, and enlarging the surface area without changing the outer diameter compromises heat sink capacity.
Innovation Solution
The driving apparatus features a motor unit with independent armature windings and a control unit with a bus bar unit that includes power-source and grounding bus bars with bending portions between the smoothing capacitor and power module, arranged to face each other, enhancing heat dissipation and reducing inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the surface area of the bus bar is decreased to downsize the control unit, then the outer diameter of the control unit is reduced, but the inductance in the power supply path increases causing noise and heat generation
Solution Approach 1:
The bus bar is configured with a bending portion that extends in the axial direction of the motor unit, utilizing the third dimension (axial direction) to increase the effective surface area of the bus bar without increasing the radial dimensions of the control unit. This allows the bus bar to provide low inductance while maintaining a compact control unit outer diameter.
Solution Approach 2:
The bending portion of the bus bar is disposed within the axial space between the smoothing capacitor and the power module, effectively nesting the bus bar structure within the existing component arrangement. This utilizes the available axial space to accommodate the extended bus bar path without increasing the overall control unit dimensions.
2Object-generated harmful factors
If the surface area of the bus bar is increased without changing the outer diameter of the control unit, then the inductance is reduced and heat generation is suppressed, but the capacity of the heat sink must be decreased to secure wiring path
Solution Approach 1:
The bus bar utilizes the axial dimension by incorporating a bending portion that extends in the axial direction between the smoothing capacitor and power module. This increases the effective surface area of the bus bar for reducing inductance while maintaining the same radial footprint, thereby preserving heat sink capacity without compromising wiring path performance.
Solution Approach 2:
The bus bar structure is locally optimized by adding the bending portion only in the specific region between the smoothing capacitor and power module, where space is available in the axial direction. This localized structural enhancement increases the bus bar surface area where it is most needed for current conduction, without affecting the overall heat sink design in other regions.
3Area of stationary object
If the control unit is downsized to meet mounting restrictions in vehicles, then the outer diameter is reduced, but it becomes difficult to contain large components such as power module and smoothing capacitor
Solution Approach 1:
The bus bar structure transitions from a conventional planar arrangement to a three-dimensional configuration with a bending portion extending in the axial direction. This utilizes the axial dimension of the control unit to accommodate the bus bar, allowing for effective current conduction while maintaining a compact radial footprint that meets vehicle mounting restrictions.
Solution Approach 2:
The bus bar is designed with a flexible bending portion that can be disposed between the smoothing capacitor and power module, adapting to the available space in the axial direction. This dynamic configuration allows the bus bar to navigate around other components, enabling efficient use of the compact control unit volume without rigid structural constraints.
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 downsized driving apparatus with improved heat-radiation performance, reducing noise and heat generation in semiconductor devices while maintaining the necessary heat sink thickness.
Implementation Method 1
a heat sink for cooling at least the power module
Implementation Method 2
a heat sink for cooling at least the power module
Implementation Method 3
a smoothing capacitor that smooths the current
Implementation Method 4
a motor unit that generates driving force for driving a body to be driven
Data Source
AI summary
Each of a power-source bus bar and a grounding bus bar provided in a driving apparatus has a terminal portion to be connected with output terminals of a power module and a bending portion bent in a direction perpendicular to a first surface of a bus bar holder; the bending portion is disposed between a smoothing capacitor and the power module; the power-source bus bar and the grounding bus bar are arranged in such a way as to face each other.