CVT Clutch Pressure Control for Fuel Economy and Slip Prevention
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Solution Overview
Problem
Continuously variable transmissions (CVT) face challenges in maintaining optimal fuel economy while preventing pulley system slipping, especially during transient events or rough road conditions, as maximum clamping pressure can lead to decreased fuel efficiency.
Innovation Solution
A control system that adjusts clutch pressure to allow slipping during transient events and applies clutch critical pressure based on conditions such as rough road status, using a slip control scheme to bring the clutch slip back within predetermined thresholds, potentially incorporating PID control and timers for effective torque management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If maximum clamping pressure is applied to the CVT pulleys to prevent the continuous member from slipping during transient events, then the reliability of torque transmission is improved, but the fuel economy deteriorates
Solution Approach 1:
The clutch pressure is dynamically adjusted based on real-time operating conditions. The control system monitors parameters such as wheel slip, torque demands, and road conditions to modulate the clutch pressure between minimum and maximum levels, allowing the system to adapt to varying transient events rather than maintaining constant maximum pressure
Solution Approach 2:
The system changes the clutch pressure parameter from a fixed maximum value to a variable value that responds to detected transient conditions. When wheel slip or torque spikes are detected, the pressure is increased to prevent pulley slipping; when conditions are stable, the pressure is reduced to improve fuel economy
2Use of energy by moving object
If clutch pressure is reduced to improve fuel economy, then the energy consumption is decreased, but the risk of pulley system slipping increases
Solution Approach 1:
The control system employs feedback mechanisms to monitor clutch slip conditions and continuously adjust the clutch pressure. When slip is detected or anticipated based on transient event detection, the feedback loop increases pressure to prevent pulley slipping. When slip conditions are absent, the system maintains reduced pressure for fuel economy
3Reliability
If clutch slip control is applied to prevent pulley slipping, then the reliability of torque transmission is improved, but the device complexity increases
Solution Approach 1:
The clutch control system operates autonomously by self-monitoring transient conditions and self-adjusting clutch pressure without requiring complex external control mechanisms. The system uses onboard sensors and processors to detect wheel slip, torque spikes, and road conditions, then automatically modulates clutch pressure to prevent pulley slipping
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 enhances fuel efficiency by optimizing clutch pressure application, preventing pulley system slipping, and ensuring stable torque transmission during varying driving conditions.
Implementation Method 1
A friction clutch may be positioned between an input shaft and a variator assembly of the CVT. The friction clutch may be actuated by a clutch actuator to selectively connect the input shaft to the variator assembly.
Data Source
AI summary
A continuously variable transmission, a transmission control system, and a method is provided. The control system is configured to determine whether a predetermined condition is met for applying a clutch critical pressure to an applied clutch. The clutch critical pressure is less than line pressure and is a pressure at which the clutch may slip upon experiencing a predetermined torque disturbance level. The control system is configured to command the clutch critical pressure to be applied to the clutch if the predetermined condition is met. The control system is further configured to determine whether the clutch is slipping beyond a predetermined threshold, and if the clutch is slipping beyond the predetermined threshold, command a clutch slip control scheme to be applied to the clutch that is configured to bring a clutch slip of the clutch under the predetermined threshold.