Split Input CVT Clutch Torque Management
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) face inefficiencies due to high clamping forces required to prevent slippage, leading to increased wear and reduced efficiency, especially at higher engine torque levels.
Innovation Solution
A split input continuously variable transmission design that includes a split input clutch selectively engaging during high gear speeds to reduce torque through the pulley assembly, thereby decreasing the clamping pressure on the belt and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher clamping force is applied to the belt to prevent slippage during high torque transmission, then the reliability of torque transmission is improved, but the wear on the belt increases and system efficiency decreases
Solution Approach 1:
The transmission system is segmented into two distinct paths: a direct mechanical connection path (via dog clutches) and a belt-driven CVT path. During high torque conditions, the dog clutches engage to create a direct path that bypasses the belt, eliminating the need for high clamping forces and thereby reducing wear and提高效率. This segmentation allows the system to switch between friction-based and mechanical-based torque transmission based on operating conditions.
2Power
If higher clamping force is applied to the belt to prevent slippage, then the torque transmission capability is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The system dynamically switches between two torque transmission modes based on real-time operating conditions. The control system monitors torque demands and automatically engages or disengages the dog clutches to select the appropriate transmission path. This dynamic adaptation allows the system to optimize torque transmission capability while managing complexity through automated control rather than manual intervention.
3Loss of energy
If a direct mechanical connection is provided between input and output members, then the efficiency during high gear speeds is improved, but the adaptability to different speed ratios is reduced
Solution Approach 1:
The transmission system incorporates multiple functional components that serve different purposes: the CVT pulleys and belt provide continuous variable ratio adjustment for adaptability, while the dog clutches provide direct mechanical connection for high-efficiency operation. The planetary gear set offers additional fixed ratio options. This multi-functionality allows the system to achieve both efficiency and adaptability by selecting the appropriate transmission path based on operating 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
The solution reduces clamping pressure on the belt by approximately 45% to 65% during high gear states, improving the overall efficiency of the powertrain by minimizing wear and optimizing gear ratio adjustments.
Implementation Method 1
engine torque is transferred from the pulley to the belt via friction by clamping the belt between the pulleys
Implementation Method 2
The hydraulic system provides primary and secondary hydraulic pressures to the respective movable pulley members to adjust the running radius of the first and second pulley cone pairs
Data Source
AI summary
A two mode CVT is provided that for a motor vehicle. The CVT includes a speed change device connected to a pulley and belt assembly. The pulley and belt assembly is connected to a planetary gear set arrangement. The planetary gear set arrangement generally includes two planetary gear sets, two brakes, and one clutch. The planetary gear set arrangement is connected to a final drive unit.