CVT Control Apparatus Fail Mode Oil Pressure Shock
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Solution Overview
Problem
In vehicular continuously variable transmissions, rapid changes in oil pressure supplied to hydraulic actuators during mode transitions from fail to non-fail modes can cause shocks due to the inability of electromagnetic valves to follow rapid pressure rises, leading to excessive clamping force on pulleys and potential operational failures.
Innovation Solution
A control apparatus with a pair of actuators, pulley pressure adjusting valves, electromagnetic valves, and an electronic control unit that adjusts source pressure and command signals to prevent rapid oil pressure changes, ensuring the oil pressure remains equal to or lower than the source pressure during mode transitions, thereby minimizing shock and maintaining stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the supply source pressure to the electromagnetic valve is lowered below the output command oil pressure at the time of fail mode, then excessive oil pressure is restrained from being applied to the pulleys, but an oil pressure higher than the output command oil pressure may be generated due to operational delay of the electromagnetic valve when returning to non-fail mode
Solution Approach 1:
The electronic control unit performs preliminary action by temporarily decreasing the command signals to the electromagnetic valves before cancelling the lowering of source pressure when transitioning from fail mode to non-fail mode. This anticipatory control prevents oil pressure overshoot by preparing the system in advance, ensuring smooth pressure transition without excessive clamping force on the pulleys.
2Power
If the supply source pressure to the electromagnetic valve is maximized to ensure retreat running at the time of fail, then adequate oil pressure is supplied to hydraulic actuators, but excessive clamping force is applied to the pulley
Solution Approach 1:
The system dynamically changes the source pressure parameter based on operational mode. During fail mode, the source pressure is lowered to an appropriate level that prevents excessive clamping force while still ensuring retreat running capability. The electronic control unit adjusts the source pressure adjusting valve to maintain source pressure below the output command oil pressure, optimizing both safety and functionality.
3Stability of the object's composition
If the command signals to the electromagnetic valves are temporarily decreased before cancelling source pressure lowering, then rapid oil pressure changes are restrained, but transition time from fail mode to non-fail mode is extended
Solution Approach 1:
The electronic control unit implements periodic action through a two-stage control sequence: first temporarily decreasing command signals to electromagnetic valves, then after a predetermined time interval, cancelling the source pressure lowering. This staged approach balances oil pressure stability with timely mode transition, preventing shock while maintaining operational efficiency.
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
The control apparatus effectively restrains rapid oil pressure changes, preventing shocks and maintaining stable operation by temporarily reducing command signals and adjusting source pressures, ensuring smooth transitions between fail and non-fail modes, thus reducing the risk of operational failures.
Implementation Method 1
The pair of the electromagnetic valves are configured to output command oil pressures to the pair of the pulley pressure adjusting valves respectively
Implementation Method 2
Each of the actuators are configured to adjust effective diameters of the pair of the pulleys respectively through hydraulic pressure
Data Source
AI summary
A control apparatus for a vehicular continuously variable transmission is provided. The control apparatus includes a pair of pulley pressure adjusting valves, a pair of electromagnetic valves, a source pressure adjusting valve and an electronic control unit. The electronic control unit is configured to control the source pressure adjusting valve in such a manner as to lower the source pressure at a time of a fail mode below the source pressure at a time of a non-fail mode, at the time of the fail mode, and control command signals to the pair of the electromagnetic valves such that the command signals temporarily decrease below command signals at the time of the non-fail mode, before cancelling the lowering of the source pressure in making a changeover from the fail mode to the non-fail mode.