Hybrid Vehicle Neutral Gear Shift Control Method
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Solution Overview
Problem
In hybrid electric vehicles, the existing gear shifting control methods in the neutral gear stage face challenges in predicting motor RPM changes due to viscosity and hydraulic pressure variations, leading to delayed gear shifting and transmission shocks, and lack of speed control due to undefined current gear ratio.
Innovation Solution
The method determines a shift gear ratio in the neutral gear stage using transmission output and input speeds at a class transition time point, sets time points for gear shifting based on the determined progressing rate, and controls gear shifting speed to prevent acceleration delays and shocks by gradually raising hydraulic engagement pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gear shifting control uses conventional hydraulic pressure control only, then the gear shifting is simple to implement, but the gear shifting time is prolonged and transmission shocks occur
Solution Approach 1:
The patent merges hydraulic pressure control with motor RPM control to achieve gear shifting. The HCU determines both the hydraulic engagement pressure and the motor RPM target value, combining two control mechanisms that work together to reduce gear shifting time while preventing transmission shocks.
Solution Approach 2:
The system performs preliminary action by pre-determining the motor RPM target value before the gear shifting is completed. The HCU calculates the target RPM based on the current state and progresses the RPM toward the target during the shifting process, ensuring smooth and timely gear transition.
2Speed
If the hydraulic engagement pressure is raised quickly to shorten gear shifting time, then the gear shifting speed increases, but transmission shocks occur
Solution Approach 1:
The patent implements feedback control by continuously monitoring the motor RPM and comparing it with the target RPM. The HCU adjusts the hydraulic engagement pressure and motor torque based on the RPM deviation, ensuring that the gear shifting proceeds smoothly without causing transmission shocks.
Solution Approach 2:
The system changes parameters dynamically during gear shifting by adjusting both the hydraulic engagement pressure and the motor RPM target value. The HCU modifies these parameters based on the current gear stage and shifting progress, optimizing the shifting speed while preventing shocks.
3Device complexity
If the gear shifting control does not consider motor RPM, then the control system is simpler, but the gear shifting progress cannot be accurately determined
Solution Approach 1:
The patent uses motor RPM as a feedback parameter to accurately measure gear shifting progress. The HCU calculates the shifting progress by comparing the current motor RPM with the target RPM, enabling precise control of the gear shifting process.
4Reliability
If the gear shifting control waits for motor RPM to approach target value, then the transmission shock is reduced, but the gear shifting time is prolonged
Solution Approach 1:
The system performs preliminary action by pre-calculating the motor RPM target value before the gear shifting is completed. The HCU determines the target RPM based on the current state and progresses the RPM toward the target during the shifting process, ensuring both smooth transition and reduced shifting time.
Solution Approach 2:
The patent dynamically changes the motor RPM target value during gear shifting based on the current gear stage. The HCU adjusts the target RPM to optimize the shifting process, maintaining transmission smoothness while minimizing gear shifting time.
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 shortens gear shifting time by 40%, improves fuel economy by 1.5%, reduces transmission shocks, enhances clutch and brake durability, and reduces lag and response delays, thereby improving marketability and safety during rapid braking.
Implementation Method 1
the hybrid control unit gradually raises a hydraulic engagement pressure in the section of the time points
Implementation Method 2
determines a shift gear ratio in the neutral gear stage by use of a transmission output speed and a transmission input speed
Data Source
AI summary
A method of controlling a gear shifting in a neutral gear stage for shortening a gear shifting time in the neutral gear stage when performing a gear shifting of a hybrid electric vehicle is characterized in that when a shift class of the gear shifting is determined, a hybrid control unit of the vehicle determines a shift gear ratio in the N-stage in a current state by use of a transmission (TM) output speed and a transmission (TM) input speed at a class transition time point, determines an N-stage gear shifting progressing rate by use of the determined N-stage shift gear ratio, sets time points of a start and an end of the gear shifting based on the determined gear shifting progressing rate, and controls the gear shifting speed in the N-stage with reference to a gear shifting target speed and the transmission input speed in a section of the time points of the start and the end of the speed control.