Electric Power Steering Control Unit Segmentation for Heat Dissipation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power steering apparatuses face issues with increased housing size due to heat-generating components, inadequate heat radiation, connector placement leading to water and dust penetration, and lengthened designs that compromise collapse stroke and size reduction.
Innovation Solution
The electric power steering apparatus features an electric motor mounted on a motor mounting section within the reduction gear box, with a control unit, including a power module board, mounted on a control-unit mounting section on the reduction gear box's outer surface, utilizing high heat conduction materials and a synthetic resin frame for improved heat radiation and electromagnetic shielding, and strategically placing connectors to prevent heat and environmental exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If heat generating members (FET, capacitor, CPU) are arranged on one control board, then the control board integrates multiple functions, but the housing size increases and heat radiation becomes insufficient
Solution Approach 1:
The control board is divided into two separate boards: a control board for control elements (CPU, relays, capacitors) and a power module board for heat-generating elements (FETs). This segmentation allows each board to be optimized independently, reducing the overall housing size while maintaining functional integration.
Solution Approach 2:
Heat-generating members (FETs) are extracted from the control board and mounted on a separate power module board. This extraction removes the heat source from the main control board, allowing for better thermal management and reduced housing size requirements.
2Reliability
If connectors are arranged near the steering gear box to prevent flying stone damage, then connector protection improves, but water and dust penetration increases and connector connection workability decreases
Solution Approach 1:
Connectors are extracted from the steering gear box area and relocated to the reduction gear box. This relocation removes connectors from the harmful environment near the steering gear box while maintaining protection benefits, eliminating water and dust penetration risks and improving connection accessibility.
3Length of stationary object
If the control board is arranged close to the steering gear box, then the housing length decreases, but the collapse stroke cannot be secured
Solution Approach 1:
The control board is relocated from a longitudinal arrangement near the steering gear box to a transverse arrangement on the reduction gear box. This dimensional change allows the control board to be positioned closer to the motor while maintaining sufficient collapse stroke space, effectively reducing housing length without compromising safety functionality.
4Temperature
If the supporting board heat sink is used for the FET, then heat dissipation is provided, but the heat mass is small and sufficient heat radiation cannot be achieved
Solution Approach 1:
The FET is extracted from the control board and mounted on a separate power module board that is directly attached to the reduction gear box. This extraction enables the use of the reduction gear box as a heat sink, providing significantly larger heat mass and surface area for effective heat radiation.
Solution Approach 2:
The power module board serves as an intermediary between the FET and the reduction gear box, providing a mounting surface that conducts heat from the FET to the large heat mass of the reduction gear box, thereby enhancing heat radiation efficiency.
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 reduces the control unit's size, enhances heat radiation, prevents water and dust ingress, and maintains a predetermined collapse stroke while minimizing the apparatus's overall length and improving connector accessibility.
Implementation Method 1
utilizing high heat conduction materials and a synthetic resin frame for improved heat radiation
Implementation Method 2
synthetic resin frame for improved heat radiation and electromagnetic shielding
Data Source
AI summary
To provide an electric power steering apparatus in which it is possible to reduce a size of the entire structure of a control unit while sufficiently showing a heat radiation effect of heat generating members. The electric power steering apparatus includes a steering column 3 having inserted therein a steering shaft 2 to which steering torque is transmitted, a reduction gear box 4 coupled to the steering shaft 2, and an electric motor 5 that transmits a steering assisting force to the steering shaft 2 via a reduction mechanism in the reduction gear box. In the reduction gear box 4, a motor mounting section 17 for mounting the electric motor 5 is formed at an end face in a direction perpendicular to an axis of the steering shaft 2 and a control-unit mounting section 20 for mounting a control unit 19 for controlling to drive the electric motor 5 is formed near the motor mounting section 17.