CVT Torque Control via Shiftable Curves
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Solution Overview
Problem
Conventional transmissions with fixed gear ratios face inefficiencies in power transfer, and continuously variable transmissions (CVTs) alone may lead to power losses or inefficiencies without proper regulation, necessitating a method to control CVT output torque and speed effectively.
Innovation Solution
A method and system that utilize a torque-to-speed curve and under-run curve, adjustable via operator input signals, to regulate CVT output torque and speed, simulating clutch functionality by shifting these curves to limit power output and prevent speed runaway, incorporating a controller and control map to manage CVT operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a CVT is used to provide continuous torque-to-speed ratios, then the adaptability and versatility of the transmission is improved, but power losses and inefficiencies occur without proper regulation
Solution Approach 1:
The patent applies dynamics by making the torque-to-speed curves adjustable and shiftable based on operator input signals. The control map allows dynamic modification of the torque-to-speed relationship, enabling the system to adapt to different operating conditions and loads, thereby optimizing power transfer efficiency while maintaining the continuous variability advantage of the CVT
Solution Approach 2:
The patent changes the parameters of the torque-to-speed curves by shifting them along the speed axis in response to operator input. This parameter adjustment allows the system to limit power output and prevent speed runaway while maintaining continuous variability, thus reducing power losses without sacrificing adaptability
2Loss of energy
If the CVT output torque and speed are dynamically adjusted via control curves, then the power transfer efficiency is improved, but the device complexity increases due to controller and control map requirements
Solution Approach 1:
The control map serves multiple functions: it defines the torque-to-speed relationship, responds to operator input signals, shifts curves to limit power output, and prevents speed runaway. This multi-functionality reduces the need for separate control mechanisms, thereby managing device complexity while achieving improved power transfer efficiency
Solution Approach 2:
The system uses feedback from operator input signals to dynamically adjust the torque-to-speed curves. The controller monitors operator commands and modifies the control map parameters accordingly, creating a closed-loop system that improves efficiency through adaptive control without requiring overly complex open-loop control mechanisms
Data Source
AI summary
A method regulates the torque output and/or speed output of a continuously variable transmission (CVT) in a manner that may simulate a clutch. The CVT may be incorporated in a machine and maybe operatively coupled to a power source and to a propulsion device. The method utilizes an unaltered torque-to-speed curve that relates the torque output to the speed output of the CVT. The method may receive an operator input signal indicating a desire to change operation of the machine. The torque-to-speed curve may be shifted in response to the operator input signal to limit the torque output available. In an aspect, an under-run curve may be applied to the torque-to-speed curve, the under-run curve corresponding to a target speed. The operator input signal may also shift the under-run curve to reduce the target speed.