Overheating Detection Device for Electric Power Steering Motors
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Solution Overview
Problem
Existing electric power steering systems face challenges in preventing motor overheating, particularly in managing the temperature of the weakest parts, such as magnets, which can lead to demagnetization and reduced performance, due to the limitations of current overheating limiting controls that often require stopping or limiting coil electrification.
Innovation Solution
An overheating detection device that includes a temperature acquisition unit, a thermal equilibrium temperature estimation unit, and a control portion to manage the thermal equilibrium temperature of the coil and the weakest parts, allowing for torque limiting and notification controls without the need to stop or limit coil electrification, thereby preventing overheating and demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature of the coil reaches the heat resistance temperature of the weakest part, then the coil electrification is stopped or limited to prevent overheating, but the motor operation is interrupted or performance is reduced
Solution Approach 1:
The system performs preliminary cooling control when the coil temperature approaches the heat resistance temperature of the weakest part, rather than waiting for the temperature to actually reach the critical threshold. This advance action prevents overheating while allowing continuous operation, as the cooling control is applied before the critical temperature is reached.
Solution Approach 2:
The invention replaces the conventional mechanical/electrical interruption method (stopping or limiting coil electrification) with a thermal management approach using cooling control. This substitution allows the motor to continue operating while managing heat through cooling, thereby maintaining productivity while ensuring reliability.
2Reliability
If the coil electrification is stopped or limited when the temperature reaches the heat resistance temperature, then the weakest part is protected from demagnetization, but the motor cannot operate at full capacity
Solution Approach 1:
The system applies cooling control in advance when the coil temperature approaches the heat resistance temperature, preventing the weakest part from reaching demagnetization conditions. This allows the motor to maintain full power output without risking demagnetization, as the cooling control is activated before the critical temperature threshold is reached.
Solution Approach 2:
The invention substitutes the power limitation approach with a thermal management approach. Instead of reducing motor output power to prevent overheating, the system uses cooling control to manage heat while allowing the motor to operate at full capacity, thereby maintaining power output while protecting the weakest part.
3Device complexity
If the temperature control is based on coil temperature alone, then the control system is simple, but the actual temperature of the weakest part cannot be accurately determined
Solution Approach 1:
The system uses the coil temperature as an intermediary parameter to infer the temperature of the weakest part. By establishing a thermal relationship model between the coil and the weakest part, the system can estimate the weakest part temperature without direct measurement, maintaining system simplicity while improving measurement accuracy.
Solution Approach 2:
The invention replaces direct temperature measurement of the weakest part with a thermal modeling approach. Instead of installing temperature sensors in the weakest part (which would increase complexity), the system uses thermal relationships and cooling control to accurately determine and manage the weakest part temperature.
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 solution improves the merchantability of the motor by preventing overheating and demagnetization, allowing for continuous operation while maintaining performance and reducing the risk of irreversible demagnetization.
Implementation Method 1
a temperature acquisition unit acquiring a temperature of a coil provided in a stator of a motor having a rotor and the stator and a temperature of a most temperature-susceptible weakest part in the motor
Implementation Method 2
a conduction heat amount calculation unit calculating a conduction heat amount heat-transferable from the coil to the weakest part or the part in the vicinity of the weakest part based on a temperature difference between the temperature of the coil and the temperature of the weakest part
Data Source
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AI summary
An overheating detection device (10) includes: a temperature acquisition unit (201) acquiring a temperature of a coil (304) provided in a stator (302) of a motor (30) and a temperature of a most temperature-susceptible weakest part in the motor or a part in a vicinity of the weakest part; a thermal equilibrium temperature estimation unit (203) estimating a temperature at which the coil and the weakest part or the part in the vicinity of the weakest part are in thermal equilibrium based on the temperature of the coil and the temperature of the weakest part or the part in the vicinity of the weakest part acquired by the temperature acquisition unit; and a control portion (21) performing first predetermined control in a case where the thermal equilibrium temperature estimated by the thermal equilibrium temperature estimation unit is equal to or higher than a predetermined first threshold value.