CVT Drivetrain Clutch Slip Control for Stall Prevention
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Solution Overview
Problem
Conventional drivetrain architectures with continuously variable transmissions (CVTs) face challenges when torque converters are used, as they can lead to stalling of the prime mover and reduced torque transmission efficiency, particularly in applications where wheels are prevented from rotating.
Innovation Solution
A drivetrain architecture that includes a forward-reverse clutch arrangement with a controllable slippage level, controlled by a main controller and clutch slip controller, which determines the usable torque and allows the clutch to slip when torque exceeds this value, preventing stalling and optimizing torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque converter is used between the prime mover and the wheels, then the prime mover is prevented from stalling when the wheels are prevented from rotating, but the torque transmission efficiency is reduced
Solution Approach 1:
The patent removes the torque converter from the drivetrain and replaces it with a clutch arrangement that provides stall prevention functionality through controlled slippage. The clutch is positioned between the transmission output and the differential, extracting only the necessary protective function while eliminating the continuous energy loss associated with torque converters.
Solution Approach 2:
The clutch arrangement dynamically adjusts its slippage characteristics based on operating conditions. The control system monitors wheel speed, engine torque, and other parameters to modulate the clutch engagement, allowing it to slip when needed to prevent stalling while maintaining firm engagement during normal operation to maximize torque transmission efficiency.
2Force
If a torque converter is used to increase torque when slipping, then torque multiplication is achieved, but the advantages of the CVT are mitigated
Solution Approach 1:
The clutch arrangement acts as an intermediary device between the CVT and the differential, providing torque multiplication only when necessary through controlled slippage. This mediator approach allows the CVT to maintain its continuous variability advantages while the clutch provides supplemental torque multiplication capability during high-demand situations.
Solution Approach 2:
The clutch engagement and slippage occur periodically or intermittently based on real-time drivetrain conditions rather than continuously. The control system activates clutch slippage only during specific conditions requiring torque multiplication, allowing the CVT to operate in its optimal continuous variable mode during normal conditions.
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 solution effectively prevents prime mover stalling and optimizes torque transmission by allowing controlled slippage in the clutch, ensuring efficient operation even when wheels are prevented from rotating, thereby enhancing drivetrain performance and component protection.
Implementation Method 1
a clutch having a controllable slippage level between its input and output
Data Source
AI summary
A slip control method and arrangement for a drivetrain including a continuously variable transmission, forward-reverse clutch arrangement and an optional three-speed gearbox is described herein. The forward-reverse clutch arrangement 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.