Vehicle Drive Oil Pump Control Under Coolant Thermal Overload
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Solution Overview
Problem
In hybrid electric vehicles, the drive circuit for the electric oil pump is vulnerable to thermal overload when the low-temperature coolant temperature exceeds its target temperature, potentially causing a thermal load and exceeding the permissible current limit.
Innovation Solution
A vehicle drive device with a control unit that stops the drive circuit when the refrigerant temperature exceeds a first temperature, preventing excessive current flow and protecting the drive circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the low-temperature coolant is used to cool the drive circuit, then the cooling effect is improved, but the coolant temperature may exceed the target temperature causing thermal overload on the drive circuit
Solution Approach 1:
The control unit continuously monitors the coolant temperature and adjusts the drive circuit operation accordingly. When the coolant temperature exceeds the first temperature threshold, the control unit stops the drive circuit to prevent thermal overload. This feedback mechanism ensures the drive circuit operates within safe temperature limits while utilizing the low-temperature coolant for cooling.
Solution Approach 2:
The system changes the operational parameters of the drive circuit based on coolant temperature. By setting a temperature threshold (first temperature) and adjusting the drive circuit's operational state (running or stopped) based on whether the coolant temperature exceeds this threshold, the system adapts to varying thermal conditions and prevents damage while maximizing cooling efficiency.
2Power
If the electric oil pump operates at high current to generate sufficient hydraulic pressure, then the hydraulic pressure is improved, but the drive circuit may exceed the permissible current limit causing thermal damage
Solution Approach 1:
The control unit acts as an intermediary between the electric oil pump and the power supply. It monitors the coolant temperature and intermediates the power delivery by stopping the drive circuit when temperature thresholds are exceeded, thereby preventing excessive current flow and thermal damage to the drive circuit while allowing full power operation when conditions are safe.
Solution Approach 2:
The system implements beforehand cushioning by monitoring coolant temperature in advance and stopping the drive circuit before excessive current can cause thermal damage. The control unit proactively prevents thermal overload conditions by interrupting power supply when the coolant temperature reaches the first temperature threshold, cushioning the drive circuit against potential thermal damage.
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
Prevents the drive circuit from overheating by controlling the electric oil pump's operation based on coolant temperature, ensuring the circuit operates within safe current limits and reducing thermal stress.
Implementation Method 1
a mechanical oil pump that generates a hydraulic pressure by the rotation of the drive shaft
Implementation Method 2
an electric oil pump that electrically generates a hydraulic pressure
Implementation Method 3
a temperature of refrigerant for cooling the drive circuit
Data Source
AI summary
A vehicle drive device includes a drive shaft to be driven by a drive source, a rotation transmission unit that transmits rotation input from the drive shaft to a wheel, a mechanical oil pump that generates a hydraulic pressure by the rotation of the drive shaft, an electric oil pump that electrically generates a hydraulic pressure, a hydraulic control device that supplies lubricating oil to the rotation transmission unit based on the hydraulic pressures generated by the mechanical oil pump and the electric oil pump, a drive circuit that controls electric power to be supplied to the electric oil pump, and a control unit that controls a drive condition of the drive circuit. The control unit stops the drive circuit and shuts down the electric oil pump when a temperature of refrigerant for cooling the drive circuit is equal to or higher than a third start temperature.