CVT Pulley Force Control for Uphill Stand Efficiency
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Solution Overview
Problem
Mechanically controlled continuously variable transmissions (CVTs) in vehicles face limitations in power efficiency due to frictional losses, noise, vibrations, and limited control options, especially at high speeds, and require additional components for pneumatic or hydraulic control systems, which increase weight and cost.
Innovation Solution
A method for operating a CVT that includes a piston connected to the driving pulley, controlled by a control unit, which adjusts the effective diameter based on altitude, atmospheric pressure, throttle operator position, and engine speed, using a control map to optimize piston force for efficient gear ratio adjustment and mode selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanically controlled CVT is used, then the transmission can provide infinite gear ratios, but frictional losses increase and power efficiency decreases
Solution Approach 1:
The patent replaces the traditional mechanical control system (centrifugal weights and springs) with an electronic control system that uses a motor to actuate the driving pulley. This substitution reduces frictional losses by eliminating the need for mechanical components to maintain constant contact and pressure, thereby improving power efficiency while preserving the CVT's ability to provide infinite gear ratios.
2Device complexity
If mechanically controlled CVT is used, then the transmission structure is simple, but control options are limited and cannot be changed on-the-fly
Solution Approach 1:
The patent implements a dynamic control system where the motor can adjust the driving pulley's effective diameter in real-time based on various operating conditions (vehicle speed, engine RPM, throttle position, etc.). This dynamic capability allows the CVT to adapt its gear ratios on-the-fly, providing flexible control options while maintaining a relatively simple overall structure compared to traditional multi-gear transmissions.
Solution Approach 2:
The patent changes the control parameter from fixed mechanical settings to variable electronic control. The motor actuation system allows continuous adjustment of the driving pulley's effective diameter, enabling the CVT to respond to changing operating conditions. This parameter change approach provides unlimited control flexibility while keeping the mechanical structure simple.
3Speed
If engine operates at high RPM for constant high speed driving, then vehicle speed is maintained, but noise and vibrations increase and fuel consumption rises
Solution Approach 1:
The patent utilizes the CVT's ability to continuously vary gear ratios to optimize the engine operating point. By adjusting the driving pulley's effective diameter through motor actuation, the system can maintain vehicle speed while allowing the engine to operate at lower, more efficient RPM levels. This parameter adjustment reduces fuel consumption and minimizes noise and vibrations associated with high-speed engine operation.
4Adaptability or versatility
If pneumatic or hydraulic control system is added to CVT, then control flexibility improves, but additional components increase weight and cost
Solution Approach 1:
The patent replaces complex pneumatic or hydraulic control systems with a simpler motor actuation system. The motor directly actuates the driving pulley, eliminating the need for pumps, reservoirs, hoses, and other heavy components associated with pneumatic/hydraulic systems. This substitution maintains control flexibility while significantly reducing the weight and cost of the CVT system.
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 allows for fast and efficient CVT configuration adjustments, reducing frictional losses, noise, and vibrations, while maintaining power efficiency and reducing the need for additional components, thereby enhancing vehicle performance and fuel efficiency.
Implementation Method 1
A piston is operatively connected to the driving pulley for applying a piston force to the driving pulley when actuated, and thereby changing an effective diameter of the driving pulley
Implementation Method 2
the CVTs are mechanically controlled by means of centrifugal weights (usually on the driving side) acting against the force of a spring to provide the desired gear ratios
Implementation Method 3
Mechanically controlled CVTs can have poor power efficiency due to frictional losses arising from the belted construction
Data Source
AI summary
A method of operating a vehicle is provided. The vehicle includes: an engine; a throttle operator moveable by a driver; a throttle valve regulating airflow to the engine; a continuously variable transmission (CVT) operatively connected to the engine; at least one ground engaging member including at least one of: a wheel and a track; a piston operatively connected to a driving pulley of the CVT for applying a piston force to the driving pulley when actuated and thereby changing an effective diameter of the driving pulley; and a control unit for controlling actuation of the piston and the piston force. The method includes: determining a driven pulley speed of a driven pulley of the CVT; detecting an uphill stand condition indicative of the vehicle being stopped on an uphill; responsive to the detection of the uphill stand condition, controlling the piston force based on the driven pulley speed.