Hybrid Electric Vehicle Mode Switching via CVT Speed Control
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Solution Overview
Problem
The 48V P2 system in hybrid electric vehicles requires a relatively long time to switch from Electric Vehicle (EV) mode to Hybrid Electric Vehicle (HEV) mode, affecting State Of Charge (SOC) and fuel efficiency due to the need to synchronize engine and motor speeds before engaging the engine clutch.
Innovation Solution
A vehicle running mode control method that decreases motor speed through Continuously Variable Transmission (CVT) gear ratio control, allowing quick engagement of the engine clutch by synchronizing engine and motor RPMs, thereby reducing mode switching time and improving MHSG efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine speed is increased to synchronize with motor speed before engaging the engine clutch, then the mode switching from EV mode to HEV mode is completed, but the mode switching time becomes relatively long
Solution Approach 1:
Instead of increasing engine speed to match motor speed, the patent inverts the approach by decreasing motor speed to match engine speed. This is achieved by controlling the MHSG to operate as a generator and using the CVT to reduce motor RPM, allowing faster mode switching while improving MHSG efficiency
Solution Approach 2:
The patent changes the operating parameters of the MHSG from motor mode to generator mode during mode switching. By adjusting the MHSG to generate electricity while the engine runs, the system can quickly synchronize speeds without the time-consuming process of ramping up engine speed, thus reducing mode switching time
2Productivity
If the motor speed is decreased through CVT gear ratio control, then the MHSG efficiency is improved and mode switching time is reduced, but the power desired for MHSG changes
Solution Approach 1:
The patent changes the operating parameters of the MHSG from motor mode to generator mode during mode switching. By adjusting the MHSG to generate electricity while the engine runs, the system can quickly synchronize speeds without the time-consuming process of ramping up engine speed, thus reducing mode switching time
Solution Approach 2:
The system dynamically adjusts the CVT gear ratio and MHSG operating mode based on real-time conditions. The CVT continuously varies the gear ratio to optimize motor speed, while the MHSG dynamically switches between motor and generator modes, allowing the system to adapt power distribution for optimal efficiency
3Loss of time
If the mode switching time is reduced by decreasing motor speed, then the battery SOC and fuel efficiency are improved, but the CVT gear ratio control must be precisely coordinated
Solution Approach 1:
The control system continuously monitors motor speed, engine speed, CVT gear ratio, and MHSG operating conditions, using this feedback to dynamically adjust the CVT ratio and MHSG mode. This closed-loop control ensures precise coordination during mode switching, achieving fast transitions while maintaining system stability
Solution Approach 2:
The MHSG serves multiple functions: it can operate as a motor during EV mode, as a generator during HEV mode switching, and as a starter for engine ignition. The CVT also serves dual purposes of normal transmission and mode switching coordination. This multi-functionality reduces the need for dedicated components, managing complexity while enabling fast mode switching
Data Source
AI summary
A vehicle running mode control method may include detecting, by a mode controller, a mode switching from an electric vehicle mode (EV mode) to a hybrid electric vehicle mode (HEV mode) while a vehicle runs; and performing a continuously variable transmission (CVT) cooperative mode switching control in which a drive motor is connected to an engine by engaging a clutch by operating the CVT.