CVT Pulley Pressure Control for Belt Slip Prevention
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Solution Overview
Problem
Conventional continuously variable transmission systems face challenges in preventing belt slip during disturbances, such as rapid torque variations or rough road conditions, due to limited pressure control of pulleys, especially at low engine RPMs, which can lead to transmission overload and damage.
Innovation Solution
A method for controlling pulley pressures in a vehicle with a continuously variable transmission, where a controller determines target pressures based on pulley target torque and ratio, maximizing pressure for one pulley and adjusting the other to maintain the required ratio, with pressures adjusted according to engine RPM and oil temperature, and corrected based on the comparison of target pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If maximum pressure is applied to both pulleys to prevent belt slip during disturbance, then belt slip prevention is improved, but pulley ratio control deteriorates due to pressure limitations at low RPM
Solution Approach 1:
The patent applies different pressure control strategies to the driving pulley and driven pulley based on their respective roles and the disturbance characteristics. One pulley is controlled to maximum pressure for belt slip prevention, while the other is adjusted to maintain the target pulley ratio, creating localized optimization for each pulley's function
Solution Approach 2:
The control system dynamically adjusts pulley pressures based on real-time operating conditions including engine RPM, disturbance magnitude, and target pulley ratio. The pressures are not fixed but adapt continuously to maintain both belt slip prevention and ratio accuracy under varying conditions
2Reliability
If pressure control is increased to prevent belt slip during disturbance, then transmission reliability is improved, but system complexity increases due to multiple control parameters
Solution Approach 1:
The controller pre-determines target pressures for both pulleys based on the detected disturbance and target pulley ratio before actual pressure adjustment occurs. This preliminary calculation of target pressures simplifies the control process by establishing clear pressure goals that balance belt slip prevention with ratio maintenance
Solution Approach 2:
The control system continuously monitors actual pulley pressures and compares them with target pressures, adjusting pressures dynamically to maintain both belt slip prevention and accurate pulley ratio. The feedback loop ensures that complexity is managed through automated closed-loop control rather than manual intervention
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 effectively prevents belt slip and maintains accurate pulley ratios during disturbances, enhancing the reliability and durability of the transmission system by maximizing controllable pressures while ensuring drivability.
Implementation Method 1
controlling oil pressures supplied to the respective pulleys to move the pulleys in an axial direction thereof
Implementation Method 2
a belt type continuously variable transmission performs a speed change using the belt
Data Source
AI summary
A method for controlling a pulley of a vehicle having a continuously variable transmission may include: determining, by a controller, a pulley target torque and a target pulley ratio, upon detecting disturbance of the vehicle; determining, by the controller, target pressures of a driving pulley and a driven pulley based on the pulley target torque and the target pulley ratio and comparing the target pressures with each other; and controlling, by the controller, a pressure of a pulley having a larger target pressure in the comparing to be a maximum pressure generatable depending on a traveling situation of the vehicle and controlling a pressure of the other pulley to be increased to a correction pressure for implementing the target pulley ratio.