Hybrid Vehicle Shifting Control for Power-Off Downshift Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid vehicles experience reduced shifting stability and loss of shifting feeling during power-off downshift shifting, particularly at low speeds, due to inaccuracies in the Torque-Stroke curve of the dry clutch, leading to potential interlock shocks.
Innovation Solution
A shifting control method for hybrid vehicles that involves determining motor torque conditions, releasing the clutch of the releasing side and engaging the target shifting stage gear when motor torque is positive, controlling motor torque to 0 Nm, rising motor speed to match the input shaft speed, and engaging the clutch of the engaging side when motor speed exceeds the input shaft speed, thereby preventing interlock shocks and securing shifting feelings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power-off downshift shifting is carried out at low vehicle speed using regenerative braking, then fuel efficiency is improved, but shifting stability is reduced and interlock shocks occur
Solution Approach 1:
The controller performs preliminary actions by first releasing the releasing side clutch and meshing the target shifting stage gear before engaging the engaging side clutch. This sequence prepares the transmission path in advance, allowing the motor speed to synchronize with the input shaft speed of the engaging side, thereby preventing interlock shocks during the actual clutch engagement at low speeds
Solution Approach 2:
The controller changes the motor torque parameter to 0 Nm during the shifting process and adjusts the motor speed to follow a target motor speed that is predetermined higher than the input shaft speed of the engaging side. This parameter adjustment ensures proper speed synchronization and prevents shocks while maintaining the benefits of regenerative braking
2Productivity
If normal power-off downshift shifting is carried out from second stage to first stage at very low speed, then shifting process is completed, but the probability of interlock shock occurs becomes high
Solution Approach 1:
The controller performs preliminary actions by first releasing the releasing side clutch and meshing the target shifting stage gear before engaging the engaging side clutch. This sequence prepares the transmission path in advance, allowing the motor speed to synchronize with the input shaft speed of the engaging side, thereby preventing interlock shocks during the actual clutch engagement at low speeds
Solution Approach 2:
The motor acts as an intermediary element between the releasing side clutch and the engaging side clutch. By controlling the motor speed to rise and follow a target motor speed that is predetermined higher than the input shaft speed of the engaging side, the motor mediates the speed difference and prevents direct shock transmission during the clutch engagement process
Data Source
AI summary
A shifting control method for a hybrid vehicle may include motor torque determination step, of determining the condition of a motor torque, by a controller, in a power-off downshift shifting process, gear mesh step, by the controller, of releasing a clutch of a releasing side and meshing a target shifting stage gear connected to a clutch of engaging side when the motor torque is positive (+) torque, an assist control step, of controlling, by the controller, the motor torque to 0 Nm, a rising step, by the controller, of controlling the motor speed to rise and follow a target motor speed predetermined higher than at least an input shaft speed of an engaging side after releasing the assist control, and an engaging step, by the controller, of engaging the clutch of the engaging side by a clutch torque of the engaging side when the motor speed exceeds the input shaft speed of the engaging side.