Brake Capacity Test Mode for Hydrostatic Drivetrain
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Solution Overview
Problem
Brake capacity testing in machines with hydrostatic drives is imprecise due to the inability to simulate low torque conditions, as hydrostatic drives produce full torque in all ranges, making it difficult to accurately assess the brake system's ability to safely stop or hold the machine.
Innovation Solution
A method involving determining a hydrostatic drive target differential pressure range and modulating the hydrostatic pump's output pressure to maintain the actual differential pressure within this range, while monitoring ground speed and fault conditions to assess brake capacity, including initiating a timer to measure test periods and determining test pass or fault conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydrostatic drives operate in all ranges, then full torque is produced, but brake capacity testing precision deteriorates
Solution Approach 1:
The system dynamically adjusts the hydrostatic pump's output pressure to maintain a target differential pressure range during brake testing. This dynamic pressure control allows the system to operate in a controlled low-torque state despite the hydrostatic drive's inherent capability to produce full torque across all ranges, thereby enabling accurate brake capacity testing.
Solution Approach 2:
The invention changes the operating parameters of the hydrostatic drive by controlling the differential pressure between forward and reverse lines. By modulating the pump output pressure to maintain differential pressure within a target range, the system creates controlled torque conditions suitable for brake testing, transforming the drive's output characteristics from full torque to test-appropriate torque levels.
2Power
If transmission is placed in higher gear, then torque is reduced, but brake capacity testing precision deteriorates
Solution Approach 1:
The invention replaces the mechanical gear-based torque reduction method with a hydraulic pressure control system. Instead of relying on transmission gear ratios to reduce torque, the system uses a hydrostatic pump with pressure control to modulate torque output, providing more precise and reliable torque control for brake testing.
Solution Approach 2:
The system implements feedback control by continuously monitoring the differential pressure and ground speed, then adjusting the pump output pressure to maintain the target differential pressure range. This closed-loop control ensures accurate torque management during brake capacity testing, overcoming the imprecision of open-loop mechanical gear selection.
3Reliability
If brake capacity test is performed, then brake safety is verified, but system complexity increases
Solution Approach 1:
The hydrostatic pump's pressure control system serves multiple functions: it controls normal machine operation and simultaneously enables brake capacity testing by modulating differential pressure. This multi-functionality reduces the need for separate dedicated testing equipment, thereby limiting the increase in system complexity while still verifying brake safety.
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 provides a more accurate and reliable method for testing brake capacity, ensuring the brake system can safely stop or hold the machine, by simulating test torque conditions based on industry standards like ISO 3450, thereby improving the precision of brake system evaluation.
Implementation Method 1
An output pressure of the hydrostatic pump is modulated to drive the hydrostatic drive actual differential pressure toward the hydrostatic drive target differential pressure range
Data Source
AI summary
A brake system and method includes a test mode for determining a capacity of the brake system provided on a machine having a hydrostatic drive. A hydrostatic drive target differential pressure range is determined to simulate a test torque. A machine ground speed limit, hydrostatic drive actual differential pressure, and actual ground speed of the machine are determined. An output pressure of the hydrostatic pump is modulated to drive the hydrostatic drive actual differential pressure toward the hydrostatic drive target differential pressure range. A first test fault condition is determined when the actual ground speed exceeds the machine ground speed limit. A second test fault condition is determined when the hydrostatic drive actual differential pressure is outside the hydrostatic drive target differential pressure range.