Steerable Crawler Track With Decoupled Hydrostatic Transmission
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Solution Overview
Problem
Steerable crawler tracks for agricultural utility vehicles face a design challenge in achieving a compact form that can handle both low and high speeds without excessive structural dimensions, as hydrostatic units need to generate sufficient torque at low speeds and high rotational speeds, which are mutually exclusive requirements.
Innovation Solution
The crawler track decouples its transmission outputs from the hydraulic transmission, allowing for mechanical disengagement via friction clutches and a control device that adjusts operating modes based on speed parameters, enabling a compact design by preventing excessive rotational speeds of hydrostatic units and allowing for sensitive steering without brake wear or power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the hydrostatic units are designed to generate sufficient torque at low speeds, then the torque capability is improved, but the structural dimensions become excessively large
Solution Approach 1:
The system dynamically switches between two operating modes: coupled mode for low-speed high-torque operations and decoupled mode for high-speed operations. This dynamic adaptation allows the hydrostatic units to be sized for low-speed torque requirements while preventing damage from excessive high-speed rotation through the decoupling mechanism
Solution Approach 2:
The drive system is segmented into two independent pathways: a direct mechanical drive path and a hydrostatic transmission path. The friction clutches allow selective engagement of either path, enabling the hydrostatic units to be optimized for torque generation without needing to handle high-speed operations
2Speed
If the hydrostatic units are designed for high rotational speeds, then the high-speed capability is improved, but the torque generation at low speeds becomes insufficient
Solution Approach 1:
The system employs dynamic mode switching based on operating conditions. A control device monitors speed parameters and automatically engages the appropriate drive mode: hydrostatic transmission for low-speed high-torque operations and direct mechanical drive for high-speed operations
3Ease of operation
If the hydraulic transmission is used for steering at high speeds, then the sensitive steerability is improved, but the hydrostatic units are overloaded and structural dimensions increase
Solution Approach 1:
The steering function is dynamically assigned: at low speeds, the hydrostatic transmission provides sensitive steering control; at high speeds, the system automatically decouples the hydrostatic units and uses the additional axle for steering, preventing overload and allowing compact hydrostatic unit design
Solution Approach 2:
The control device acts as an intermediary that monitors operating parameters and automatically switches between steering mechanisms. It engages the hydrostatic transmission for steering when appropriate and switches to alternative steering methods when speed thresholds are exceeded
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 solution allows the crawler track to maintain sensitive steerability at low speeds and operate efficiently at high speeds with a compact design, reducing structural dimensions and power losses, while ensuring the hydrostatic units are not overloaded at high speeds.
Implementation Method 1
a first friction clutch (12) is disposed between the first transmission output (31) and a first hydrostatic unit (15), and a second friction clutch (22) is disposed between the second transmission output (32) and a second hydrostatic unit (25)
Data Source
AI summary
A steerable crawler track for an agricultural utility vehicle such as a tractor or a self-propelled harvesting machine has a left-side track roller unit, a right-side track roller unit, a differential having a transmission input driven by an engine, a first transmission output for driving the left track roller unit, and a second transmission output for driving the right track roller unit and a hydraulic transmission having a variable transmission ratio (i). The transmission outputs of the differential are coupled to one another via the hydraulic transmission such that the ratio of the rotational speeds (nl, nr) of the transmission outputs are influenced by changing the transmission ratio (i) of the hydraulic transmission.