Hydrostatic Work Vehicle Speed Control Under Pressure Leakage
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Solution Overview
Problem
In work vehicles with hydrostatic transmissions, differential pressure deviations due to hydraulic fluid leakage can cause vehicle speed and tractive force to diverge from desired values, leading to inaccurate output.
Innovation Solution
A controller determines corrected target vehicle speed and displacement for the travel pump and motor by using a compensation factor based on the ratio of actual to target differential pressure, ensuring accurate output by adjusting engine rotation speed and gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the displacement of the travel pump and travel motor is controlled to achieve desired vehicle speed and tractive force, then the hydrostatic transmission can provide the desired output, but the actual differential pressure may diverge from the target differential pressure due to hydraulic fluid leakage, causing the vehicle speed or tractive force to diverge from desired values
Solution Approach 1:
The controller continuously monitors the actual differential pressure between the first and second circuits and compares it with the target differential pressure. Based on this feedback, the controller calculates a compensation factor and adjusts the target displacement of the travel pump or travel motor to compensate for pressure deviations caused by hydraulic fluid leakage, thereby maintaining accurate vehicle speed and tractive force control.
Solution Approach 2:
The system dynamically changes the displacement parameter of the travel pump or travel motor based on the compensation factor derived from pressure measurements. By adjusting this key parameter in real-time, the system compensates for leakage effects and maintains the desired differential pressure relationship, ensuring accurate control of vehicle speed and tractive force despite hydraulic fluid losses.
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 approach allows for accurate achievement of desired output in work vehicles even when actual differential pressure diverges from the target, maintaining precise control over vehicle speed and tractive force.
Implementation Method 1
The travel pump is driven by an engine to discharge hydraulic fluid
Implementation Method 2
The hydraulic fluid discharged from the travel pump is supplied to the travel motor through the hydraulic circuit. The travel motor is driven by the hydraulic fluid from the travel pump
Data Source
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AI summary
A controller determines a compensation factor from an operating amount of an accelerator operating member and a hydraulic pressure of at least one of a first circuit and a second circuit. The controller determines a target vehicle speed from the operating amount of the accelerator operating member. The controller determines a target displacement of a travel pump and/or a target displacement of a travel motor from the target vehicle speed and the compensation factor.