CVT Shift Control for Smooth Stepped Mode Engagement
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Solution Overview
Problem
Existing shift control devices for continuously variable transmissions face challenges in seamlessly transitioning from stepless to stepped shift modes, leading to inappropriate execution of the stepped shift mode due to mismatched target transmission gear ratios.
Innovation Solution
A shift control device that includes a mode setting unit to switch from stepless to stepped shift mode based on accelerator pedal operation, with a transmission-gear-ratio setting unit estimating engine rotation speed variation and setting an initial transmission gear ratio that meets a lower limit value, ensuring smooth transition and appropriate execution of the stepped shift mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the shift mode is switched from stepless to stepped shift mode, then the vehicle acceleration performance is improved, but the engine rotation speed varies excessively causing discomfort
Solution Approach 1:
The transmission control device calculates the target transmission gear ratio in advance before the mode switch occurs. By determining the appropriate initial transmission gear ratio for the stepped shift mode beforehand, the system ensures that the engine rotation speed variation remains within the comfortable range while achieving rapid vehicle acceleration when the driver operates the accelerator pedal
2Device complexity
If a fixed transmission gear ratio is selected for stepped shift mode, then the transmission control is simplified, but the engine rotation speed variation may be inappropriate
Solution Approach 1:
The system dynamically adjusts the initial transmission gear ratio parameter based on the calculated engine rotation speed variation. By changing this parameter according to the specific operating conditions and the lower limit value of engine rotation speed variation, the system achieves both simplified fixed gear ratio control and appropriate engine rotation speed management
Data Source
AI summary
A shift control device includes: a stepless shift controller executing a stepless shift mode and controlling a transmission gear ratio of a continuously variable transmission in a stepless fashion; a stepped shift controller executing a stepped shift mode and controlling the continuously variable transmission using fixed transmission gear ratios; a mode setting unit switching the shift mode to the stepped shift mode when a vehicle is to be accelerated; and a transmission-gear-ratio setting unit setting an initial transmission gear ratio in the stepped shift mode when the shift mode is to be switched to the stepped shift mode. The transmission-gear-ratio setting unit estimates a variation in an engine rotation speed when the shift mode is to be switched to the stepped shift mode, and sets a fixed transmission gear ratio, at which the variation is greater than or equal to a lower limit value, as the initial transmission gear ratio.