Hybrid EV Engine Cranking Control at Low First-Motor Temperature
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Solution Overview
Problem
Hybrid electric vehicles face an increase in input power to the power storage device when the first motor's temperature is low during engine starting, leading to potential overloading and reduced allowable vehicle speed ranges.
Innovation Solution
A control device adjusts the torque command of the first motor based on its temperature, setting a smaller value when the temperature is below a predetermined threshold, and sets specific start conditions to manage input power to the power storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the first motor is controlled with the same torque command value regardless of temperature, then the control system is simple, but the input power to the power storage device becomes excessively large when the motor temperature is low
Solution Approach 1:
The torque command value is made dynamic by adjusting it according to the first motor's temperature. The control device changes the torque command based on temperature conditions, making the control parameter adaptive rather than fixed, thereby resolving the contradiction between control simplicity and power management.
Solution Approach 2:
The control device changes the torque command parameter based on the first motor's temperature. When the temperature is below a predetermined threshold, a different torque command value is applied compared to when the temperature is above the threshold, directly addressing the power input issue while maintaining manageable control complexity.
2Reliability
If regenerative driving is performed at the initial stage of engine cranking, then engine starting is achieved, but the power storage device receives excessive input power when motor temperature is low
Solution Approach 1:
The torque command parameter is adjusted based on motor temperature during the regenerative driving phase. By changing the torque command according to temperature conditions, the system ensures reliable engine starting while controlling the input power to the power storage device within acceptable limits.
3Power
If the torque command is reduced at low temperatures, then the input power to the power storage device is suppressed, but the actual torque output may be insufficient for reliable engine starting
Solution Approach 1:
The torque command is adjusted as a function of motor temperature, with different values applied in different temperature ranges. This parameter change strategy balances the need to suppress input power to the power storage device with the need to maintain sufficient torque for reliable engine starting.
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 approach suppresses the increase in input power to the power storage device, maintaining optimal vehicle speed ranges and preventing overloading, even at low motor temperatures.
Implementation Method 1
a magnet torque is larger and an actual torque is thus larger when the temperature of the first motor is low than when the temperature of the first motor is high, in response to the same torque command
Data Source
AI summary
A hybrid electric vehicle includes an engine, a first motor, a planetary gear connected to the first motor, the engine, and a drive shaft connected to drive wheels, a second motor connected to the drive shaft, a power storage device connected to the first motor and the second motor via a power line, and a control device that controls the engine, the first motor, and the second motor so as to travel with intermittent operation of the engine. The control device controls the first motor by setting a smaller value as the torque command of the first motor than when the temperature of the first motor is equal to or higher than the predetermined temperature when the starting condition is satisfied and the engine is started with cranking of the engine by the first motor during traveling and the temperature of the first motor is lower than the predetermined temperature.