CVT Hydraulic Control for Stepped and Continuous Tractor Driving
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Solution Overview
Problem
Existing agricultural vehicles with continuously variable transmission groups lack the ability to replicate the driving sensations of mechanical transmission groups, particularly in auxiliary operating conditions, and are complex to manage.
Innovation Solution
Agricultural vehicles equipped with a continuously variable transmission group that includes a hydraulic device and management and command system, allowing for both stepped and continuous gear ratio variations, with user-controlled and automatic modes to simulate mechanical transmission sensations and optimize driving comfort and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a continuously variable transmission group is used, then driving comfort is improved by eliminating jerks and steps, but the ability to provide familiar mechanical transmission sensations in auxiliary operating conditions is lost
Solution Approach 1:
The system dynamically switches between two operational modes: a first mode that provides stepped gear ratio variations to simulate mechanical transmission sensations, and a second mode that provides continuous gear ratio variations for smooth driving comfort. This dynamic adaptability allows the continuously variable transmission to replicate mechanical transmission behavior when needed while maintaining its inherent smoothness capability.
Solution Approach 2:
The control system changes the operational parameters of the transmission by selectively activating different control strategies for the hydraulic device. In the first mode, the gear ratio varies in predetermined steps according to drive commands and vehicle speed. In the second mode, the gear ratio varies continuously as a function of engine revolutions. This parameter switching resolves the contradiction between providing mechanical sensations and maintaining driving comfort.
2Adaptability or versatility
If a mechanical transmission group is used, then familiar driving sensations with jerks and steps are provided, but the system becomes complex to manage in auxiliary operating conditions
Solution Approach 1:
The patent replaces the traditional mechanical transmission system with a continuously variable transmission group controlled by a management and command system. This electronic/hydraulic control system manages the complexity of auxiliary operating conditions more effectively than mechanical linkages, while still being able to simulate mechanical transmission sensations when required through controlled stepped gear ratio variations.
3Ease of operation
If a continuously variable transmission group is used, then smooth continuous gear changes are achieved, but the ability to provide stepped gear variations for certain driving modes is lost
Solution Approach 1:
The control system dynamically adjusts the gear ratio variation behavior based on the selected driving mode. For normal driving conditions, the system operates in continuous mode providing smooth gear changes. For auxiliary operating conditions, the system switches to stepped mode providing predetermined gear ratio steps. This dynamic behavior allows the continuously variable transmission to provide both smooth and stepped gear changes as needed.
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 system provides users with the familiar jerks and steps of mechanical transmissions while enabling smooth, continuous gear changes, enhancing driving comfort and simplifying operation in various modes, while preventing potential breakdowns by monitoring hydraulic and gear ratio thresholds.
Implementation Method 1
a hydraulic device (40) operable to modify the gear ratio
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention is a vehicle (1) for agricultural use, comprising : i) wheel groups (2); ii) an engine group (3) suitable for delivering an engine torque at a given number of engine revolutions; ill) a continuously variable transmission group (4) suitable for connecting the engine group (3) to the wheel groups (2), comprising a hydraulic device (40); iv) user management means (5) operable by the user to drive the vehicle and set the motion modes thereof; v) vehicle management means (6) suitable for detecting the operating conditions of the vehicle and of certain vehicle components by detecting the speed of the vehicle, the engine revolutions, the gear ratio (T) and the hydraulic pressure value (P) of the continuously variable transmission group (4); vi) a management and command system (7) operatively connected to the user management means (5), the vehicle management means (6), and the engine group (3) and to the continuously variable transmission group (4), wherein the management and command system (7) commands the continuously variable transmission group (4), since it is operatively connected to the hydraulic device (40), in: at least one driving operating configuration, in which the hydraulic action of the hydraulic device (40) is commanded according to predefined steps; and at least one auxiliary operating configuration in which the hydraulic action of the hydraulic device (40) is commanded according to a continuous course over time.