Vehicle Transmission Controller Fail-Safe Return Logic
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Solution Overview
Problem
Existing vehicle power transmission systems do not effectively manage the transition from a fail-safe state, leading to a feeling of strangeness experienced by drivers due to torque fluctuations and frequent switching between transmission paths.
Innovation Solution
A controller for the vehicle power transmission system that includes an actual speed ratio calculation unit, a target speed ratio setting unit, a hydraulic pressure output device, and a normal state return determination unit, which establishes a torque transmission path through the gear mechanism during hydraulic pressure output device failures and determines the device's return to a normal state by comparing speed ratios, thereby preventing torque transmission through the belt-type continuously variable transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the system switches between first transmission path (belt-type continuously variable transmission) and second transmission path (gear mechanism) during normal operation, then transmission efficiency is improved, but driver comfort deteriorates due to torque fluctuations and frequent switching during fail-safe state transitions
Solution Approach 1:
The controller performs preliminary actions by determining fail-safe state transitions in advance and proactively managing torque transmission path switching. When transitioning from fail-safe state to normal state, the controller first determines that the hydraulic pressure output device has returned to normal operation, then selectively switches the torque transmission path to prevent torque fluctuations before they affect the driver, thereby maintaining comfort while restoring efficient transmission operation
Solution Approach 2:
The controller acts as an intermediary between the hydraulic pressure output device and the torque transmission paths. It monitors the operational state of the hydraulic pressure output device and mediates the switching between first and second transmission paths based on this state, preventing direct transmission of torque fluctuations to the driver while maintaining efficient power transmission
2Adaptability or versatility
If the controller frequently switches between first transmission path and second transmission path during fail-safe state transitions, then system adaptability is improved, but system stability deteriorates causing feeling of strangeness for the driver
Solution Approach 1:
The controller implements feedback control by continuously monitoring the operational state of the hydraulic pressure output device and using this information to determine appropriate torque transmission path selection. The controller waits for confirmation that the hydraulic pressure output device has returned to normal operation before switching paths, using this feedback to maintain system stability while adapting to changing operational conditions
Solution Approach 2:
The controller dynamically adjusts the torque transmission path based on the operational state of the hydraulic pressure output device. Rather than using fixed switching criteria, the system adapts its behavior in real-time based on feedback from the hydraulic pressure output device, maintaining stability while providing the necessary adaptability to handle different operational states
Data Source
AI summary
When there is a failure in a speed ratio control linear solenoid valve, or the like, a controller for a vehicle power transmission system establishes a state where torque is transmitted via a gear mechanism, and, in this state, determines whether the speed ratio control linear solenoid valve, or the like, has returned to a normal state by comparing a target speed ratio and actual speed ratio of a continuously variable transmission with each other. It is determined whether the speed ratio control linear solenoid valve, or the like, has returned to the normal state by changing the target speed ratio of the belt-type continuously variable transmission and then comparing the target speed ratio with the actual speed ratio. Thus, when the speed ratio control linear solenoid valve, or the like, has returned from a fail-safe state to the normal state, a feeling of strangeness of a driver is suppressed.