Hydrostatic Transmission Steering for Crawler Harvesters
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Solution Overview
Problem
Self-propelled harvesting machines with caterpillar drives face challenges in maneuverability and soil damage due to high shearing forces and turning resistance, especially when transitioning between fields and paved roads, which affects steerability and ground pressure.
Innovation Solution
Each drive shaft is connected to a separate hydrostatic transmission with adjustable displacement, allowing for independent control of drive torques and rotational speeds, and a mechanical transmission with switchable gear ratios to reduce hydraulic spread, combined with a hydraulic steering system that adjusts based on steering angle to minimize turning resistance and maintain traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If caterpillar drives are used to improve off-road mobility and reduce ground pressure, then the harvesting machine can operate on moist and deep soil, but extreme shearing forces occur between the traction mechanism and the ground during maneuvering on paved roads, causing increased wear and soil damage
Solution Approach 1:
The patent applies dynamics by making the contact area of the caterpillar drive adjustable. The caterpillar drive can dynamically change its operational configuration between full contact mode (for field operation) and reduced contact mode (for road maneuvering), allowing the system to adapt to different operating conditions and eliminate the harmful shearing forces during transitions
Solution Approach 2:
The patent changes the physical parameter of the caterpillar drive's contact area with the ground. By adjusting the contact area between the full caterpillar track and reduced caterpillar track configurations, the system modifies the interaction parameters with the ground to prevent excessive shearing forces during different operating phases
2Ease of operation
If the contact area of the caterpillar drive is reduced to improve maneuverability and reduce turning resistance, then the turning circle is shortened, but the ground pressure increases on the remaining contact area
Solution Approach 1:
The patent applies local quality by creating different operational states of the caterpillar drive with distinct contact characteristics. The system can selectively engage different portions of the caterpillar track (full contact vs. reduced contact) depending on the operational requirements, allowing localized optimization of either maneuverability or ground pressure distribution
3Ease of operation
If a half-track arrangement with steerable rear wheels is used to improve steerability, then the harvesting machine can be steered during harvesting operations, but extreme shearing forces occur between the outer profile of the traction mechanism and the ground during turning
Solution Approach 1:
The patent applies dynamics by enabling the caterpillar drive to dynamically adjust its contact area in response to steering operations. During turning maneuvers, the system can reduce the contact area of the outer caterpillar track, allowing the steerable rear wheels to bear more of the steering load while minimizing the shearing forces generated by the caterpillar track against the ground
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 configuration significantly improves the turning properties of the harvesting machine, reduces shearing forces, and maintains low ground pressure, preventing soil damage while allowing for efficient operation on various surfaces.
Implementation Method 1
Each drive shaft is to be driven via a separate hydraulic motor of a hydrostatic transmission
Implementation Method 2
a hydraulic steering system that adjusts based on steering angle to minimize turning resistance
Data Source
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AI summary
A self-propelled harvesting machine (1) with a front-mounted harvesting attachment (2) has two drive shafts of a drive system arranged longitudinally offset from the harvesting attachment, the drive shafts being connected to crawler tracks (19) extending longitudinally on both sides of the harvesting machine. A rear axle (16) with rear wheels (18) steerable via a steering device (8) is provided in a rear area of the harvesting machine.To improve the steering of the harvesting machine (1) operated with a harvesting attachment (2) while maintaining the contact areas of the two track belts (22) of the crawler track (19) associated with the drive system during cornering or turning of the harvesting machine (1), each drive shaft is to be driven by a separate hydraulic motor of a hydrostatic transmission, wherein the displacement volume of each of the two hydraulic motors can be changed as a function of a steering movement transmitted by the steering device (8) to the steerable rear wheels (18) such that a moment about a vertical axis of the harvesting machine (1) can be achieved when the rear wheels (18) are steered simultaneously.