EPS Motor Drive Thermal Isolation via Embedded Heatsink
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Solution Overview
Problem
In motor drive control devices for electric power steering, the smoothing capacitor is prone to increased temperature due to heat from the MOSFET and housing, leading to reliability issues and size constraints.
Innovation Solution
The configuration includes a heatsink portion with switching elements embedded, an electric connection member between the switching elements and control board, and smoothing capacitors located between the electric connection member and control board, effectively isolating the capacitors from heat sources and reducing device height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the smoothing capacitor is arranged on the same metal substrate as the MOSFET in a stacked structure, then the device height is reduced and downsizing is achieved, but the capacitor temperature increases due to heat from the MOSFET and housing
Solution Approach 1:
The patent repositions the smoothing capacitor from a horizontal arrangement on the metal substrate to a vertical arrangement in the space between the electric connection member and control board. This dimensional change allows the capacitor to be located away from the heat-generating MOSFET while maintaining a compact overall structure, thus reducing capacitor temperature without significantly increasing device height.
Solution Approach 2:
The patent introduces the electric connection member as an intermediary component between the MOSFET and the smoothing capacitor. This intermediary structure serves as a thermal barrier that isolates the capacitor from heat generated by the MOSFET, allowing the capacitor to be positioned close to the power circuit while maintaining thermal independence.
2Quantity of substance
If the capacitor is made small with surface mounting, then the device size is reduced, but the capacitor becomes very sensitive to heat from surroundings due to small thermal capacity
Solution Approach 1:
The electric connection member acts as a thermal intermediary that physically separates the small surface-mounted capacitor from heat-generating components. This allows the capacitor to maintain its small size for downsizing while the intermediary structure protects it from thermal harm by blocking heat transmission from the MOSFET and housing.
Solution Approach 2:
The patent extracts the smoothing capacitor from the heat-prone environment near the MOSFET and places it in a thermally independent zone between the electric connection member and control board. This separation allows the capacitor to be miniaturized without being vulnerable to surrounding heat, as it is now isolated in its own thermal zone.
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 suppresses the increase in temperature of the smoothing capacitor, enhances reliability, and allows for downsizing of the motor drive control device by reducing its height.
Implementation Method 1
a heatsink portion in which the switching elements are arranged in an embedded manner
Implementation Method 2
a smoothing capacitor for absorbing a ripple component of motor current flowing due to ON/OFF operations of the switching elements
Data Source
AI summary
A motor drive control device for electric power steering includes: a switching element for supplying current to a motor; a smoothing capacitor for reducing ripple current due to the switching element; a control board on which a drive circuit for controlling the switching element and a control circuit capacitor are mounted; a control signal line for supplying a control signal from the control board to the switching element; an electric connection member electrically connecting the switching element and the smoothing capacitor; and a heatsink portion in which the switching element is arranged in an embedded manner, wherein the electric connection member is arranged between the switching element and the control board, and the control circuit capacitor and the smoothing capacitor are arranged in a space between the electric connection member and the control board.