Heat Sink Strut Temperature Sensing for Drive Circuit Overheating
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Solution Overview
Problem
Existing electronic apparatuses controlling electric motor drive operations face issues where thermistors are not accurately positioned, leading to incorrect temperature sensing and potential overheating of normal drive circuits when one circuit fails, resulting in increased size and cost by using multiple thermistors.
Innovation Solution
An electronic apparatus with a circuit board, heat-generating devices, a heat sink, and a strategically placed temperature sensor that senses the temperature of a secondary strut, allowing for accurate current limiting to prevent overheating, while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single thermistor is used for temperature sensing, then the size and cost are reduced, but the temperature sensing accuracy deteriorates when one drive circuit fails
Solution Approach 1:
The patent introduces a heat sink as an intermediary thermal mass between the drive circuits and the thermistor. The heat sink absorbs excess heat from failed drive circuits and redistributes it, mediating the thermal environment so that the thermistor senses a stable reference temperature rather than direct heat from failed circuits. This allows accurate temperature monitoring with a single thermistor.
Solution Approach 2:
The heat sink creates a thermal equipotential surface that equalizes temperature distribution across the circuit board. By providing a large thermal mass with relatively uniform temperature, the heat sink ensures that the thermistor measures a representative temperature regardless of localized heating from failed drive circuits, achieving thermal equilibrium that improves measurement accuracy.
2Measurement precision
If the thermistor is placed close to drive circuits for accurate sensing, then the temperature measurement responsiveness is improved, but the reliability deteriorates when a drive circuit fails due to excessive current supply
Solution Approach 1:
The heat sink acts as a thermal buffer and intermediary between the drive circuits and the thermistor. It absorbs and redistributes heat, preventing direct thermal coupling that would cause the thermistor to sense inaccurate temperatures during drive circuit failures. This mediation protects the system by ensuring reliable temperature monitoring without compromising drive circuit reliability.
Solution Approach 2:
The heat sink provides beforehand cushioning by absorbing excess heat before it can affect the thermistor or cause thermal runaway in failed drive circuits. This pre-established thermal buffer protects the system from temperature excursions that would otherwise lead to unreliable operation or component damage.
3Reliability
If multiple thermistors are provided for each drive circuit, then the reliability is improved by preventing overheating, but the device complexity and cost increase
Solution Approach 1:
The single thermistor performs multiple functions: it monitors the temperature of the heat sink structure, indirectly monitors drive circuit temperatures through thermal coupling, and provides feedback for current limiting control. The heat sink itself serves as both a thermal management device and a temperature sensing platform, eliminating the need for multiple dedicated thermistors while maintaining reliability.
Solution Approach 2:
The patent merges the temperature sensing function with the heat sink structure. Instead of separating the thermistor from the thermal management system, the design integrates them by placing the thermistor on the heat sink, allowing a single sensor to monitor the thermal state of the entire system including multiple drive circuits through the common thermal mass.
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
The solution effectively prevents overheating of normal drive circuits when one fails, ensuring safe operation and reducing the size and cost of the apparatus by accurately sensing temperatures and managing current supply.
Implementation Method 1
The heat sink main body absorbs the heat generated from the plurality of heat-generating devices
Implementation Method 2
The heat sink main body absorbs the heat generated from the plurality of heat-generating devices
Implementation Method 3
The temperature sensor is installed to the circuit board at a location, which is spaced from the primary strut, the plurality of heat-generating devices, the drive wiring and the motor wiring, and at which the temperature sensor senses a temperature of the secondary strut
Data Source
AI summary
A primary strut, which extends integrally from a heat sink main body, supports a circuit board at a location between a connector terminal and one of a switching device or a drive wiring. A secondary strut, which extends integrally from the heat sink main body, supports the circuit board at a location that is on an opposite side of the switching device and the drive wiring, which is opposite from the connector terminal. A temperature sensor is installed to the circuit board at a location, which is spaced from the primary strut, the switching device and the drive wiring, and at which the temperature sensor senses a temperature of the secondary strut. A control device limits an electric current supplied to the switching device upon estimating a temperature of the switching device while using the temperature, which is sensed with the temperature sensor, as a reference temperature.