Virtual Gear Ratios for CVT Operator Control
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Solution Overview
Problem
Operators of machines equipped with continuously variable transmissions (CVTs) experience discomfort due to the lack of selectable and predictable gear ratios, which are typically associated with conventional gear-based transmissions.
Innovation Solution
A method and system that utilize a plurality of virtual gear ratios, allowing operators to shift between these ratios using an operator input device, with distinct positions corresponding to different incremental rates, thereby mimicking the experience of traditional transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a CVT provides a continuous range of torque-to-speed output ratios, then the adaptability and versatility of the transmission is improved, but the operator's familiarity and ease of operation deteriorates due to lack of selectable discrete gear ratios
Solution Approach 1:
The patent segments the continuous range of gear ratios into distinct virtual gear ranges (first virtual gear range, second virtual gear range, etc.), each corresponding to specific operating conditions. This allows the CVT to maintain its continuous variability while providing operators with selectable discrete gear ranges that mimic traditional transmissions, thereby resolving the contradiction between adaptability and ease of operation.
Solution Approach 2:
The patent applies local quality by assigning different characteristics to different portions of the gear ratio range. Each virtual gear range has specific boundary ratios and operational characteristics tailored to particular operating conditions (e.g., acceleration, cruising, loading). This localized optimization maintains continuous adaptability while providing familiar discrete gear selection behavior in specific operating zones.
2Ease of operation
If virtual gear ratios are implemented with multiple incremental rates, then the ease of operation is improved by providing predictable gear shifts, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent introduces an electronic controller as an intermediary between the operator and the CVT mechanism. The controller receives operator inputs and automatically manages the complex task of shifting between virtual gear ranges with different incremental rates. This mediator provides predictable gear shift behavior familiar to operators while hiding the underlying complexity of the control algorithms and CVT actuation from the operator.
Solution Approach 2:
The patent replaces traditional mechanical gear shift mechanisms with an electronically controlled system. Instead of physical gear engagement, the CVT uses electronic actuators to adjust the pulley ratios continuously. This substitution eliminates complex mechanical shift hardware while providing precise, predictable gear ratio changes through electronic control, resolving the contradiction between ease of operation and device complexity.
Data Source
AI summary
A system and method involves a machine having a power train including a continuously variable transmission (CVT) associated with a plurality of virtual gear ratios. To shift between the plurality of virtual gear ratios, the machine may include an operator input device that may be movable between a plurality of distinct positions. A first position may be associated with a neutral position in which no shifting of virtual gear ratios occurs. A second position of the operator input device may be associated with a first incremental rate for shifting between the virtual gear ratios. A third position may be associated with a second incremental rate for shifting between the virtual gear ratios which is different than the first incremental rate.