CVT Driveline Clutch Slip Control for Torque Multiplication
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Solution Overview
Problem
Conventional drivelines with continuously variable transmissions (CVTs) face challenges in preventing the prime mover from stalling and multiplying torque when wheels are partially or totally prevented from rotating, as the use of a torque converter mitigates the advantages of CVTs in certain vehicular applications.
Innovation Solution
A slip control method and arrangement that determines the usable torque of the prime mover and controls clutch slippage to allow only this torque to pass through, using a clutch with a controllable slippage level, and a main controller that adjusts the CVT ratio to prevent stalling and increase torque as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque converter is used between the prime mover and wheels, then the prime mover is prevented from stalling and torque is increased when wheels are prevented from rotating, but the advantages of the CVT are mitigated
Solution Approach 1:
The patent extracts the torque multiplication function from the torque converter and relocates it to the clutch positioned after the CVT. This allows the CVT to operate independently without the torque converter, preserving its advantages while still achieving torque multiplication when needed through controlled clutch slippage.
Solution Approach 2:
The clutch acts as an intermediary component between the CVT and the wheels, mediating the torque transmission. By controlling clutch slippage, the system can multiply torque when wheels are prevented from rotating without requiring a torque converter, thus preventing prime mover stalling while maintaining CVT advantages.
2Force
If a torque converter is used to increase torque when wheels are prevented from rotating, then torque multiplication is achieved, but the ideal candidate status for CVT applications is reduced
Solution Approach 1:
The clutch is designed with controllable slippage characteristics that can dynamically adjust torque transmission. This dynamic control allows the system to provide torque multiplication only when necessary (when wheels are prevented from rotating) while maintaining optimal CVT operation during normal conditions, thereby preserving CVT advantages.
Solution Approach 2:
The system changes the operational parameters of the clutch to achieve torque multiplication. By adjusting the clutch slippage level based on wheel rotation conditions, the system can multiply torque when needed without requiring a torque converter, making CVT applications more suitable.
3Reliability
If clutch slippage is controlled to allow only usable torque to pass through, then the prime mover is protected from stalling, but additional control complexity is introduced
Solution Approach 1:
The control system continuously monitors wheel rotation status and adjusts clutch slippage accordingly. When wheels are detected to be prevented from rotating, the system increases clutch slippage to limit torque transmission to usable levels, preventing prime mover stalling. This feedback-based control achieves reliable protection with manageable complexity.
Data Source
AI summary
A slip control method and arrangement for a driveline including a continuously variable transmission is described herein. The driveline includes a clutch that is so controlled as to slip when a torque higher than the usable torque attempts to pass through. Accordingly, the clutch prevents the prime mover from stalling.