Hydrostatic Drive Braking via Pump Displacement Control
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Solution Overview
Problem
Current braking strategies for hydrostatic drive machines are inefficient and may cause wear and damage to components, while also requiring additional weight and cost through the use of service brakes, and do not adequately address overspeeding issues.
Innovation Solution
A method and system that involves reducing the displacement of a hydrostatic drive system's pump to a non-zero displacement and increasing the displacement of the motor to less than maximum, with an electronic controller accelerating the engine to a desired speed range in response to a braking request, thereby efficiently slowing or stopping the machine without relying on service brakes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If service brakes are used to slow or stop the machine, then the machine can be effectively braked, but component wear and damage increases
Solution Approach 1:
The patent replaces the mechanical service brake system with a hydrostatic braking system that uses the pump-motor fluid coupling to provide braking force. The electronic controller modulates pump displacement to create a braking moment on the drive motor, eliminating the need for friction-based mechanical brakes and the associated wear and damage.
Solution Approach 2:
The patent utilizes the hydrostatic drive system's hydraulic fluid coupling between the pump and motor to provide braking force. By controlling fluid flow and pressure through the pump-motor interaction, the system achieves effective braking without mechanical contact, leveraging hydraulic principles to resolve the contradiction between braking effectiveness and component durability.
2Speed
If service brakes are installed to provide braking capability, then the machine can be braked effectively, but machine weight and cost increase
Solution Approach 1:
The patent makes the hydrostatic drive system multi-functional by enabling it to provide both propulsion and braking functions. The same pump-motor-fluid coupling that drives the machine during normal operation is used to provide braking force when needed, eliminating the need for separate mechanical brake components and reducing overall machine weight.
Solution Approach 2:
The patent merges the braking function with the existing hydrostatic drive system components. The pump, motor, and control system that normally provide propulsion are integrated to also provide braking capability through electronic control of pump displacement, combining multiple functions into a single system to reduce weight and cost.
3Speed
If pump displacement is rapidly adjusted between settings to brake the machine, then the machine can be slowed effectively, but system pressure fluctuations and heat generation increase
Solution Approach 1:
The patent uses periodic modulation of pump displacement to provide braking force. The electronic controller rapidly cycles the pump displacement between different settings, creating a periodic action that averages to a controlled braking moment while preventing excessive pressure buildup and heat generation that would occur with continuous high-pressure braking.
Solution Approach 2:
The patent dynamically adjusts pump displacement based on real-time operating conditions to provide optimal braking force. The electronic controller continuously modulates the pump displacement setting rather than using fixed positions, allowing the system to adapt to changing load and speed conditions while maintaining controlled pressure levels and minimizing heat generation.
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 reduces wear on components, minimizes the need for service brakes, and effectively manages overspeeding, providing efficient braking that meets requisite standards while maintaining system efficiency and reducing heat-generated flows.
Implementation Method 1
a hydrostatic drive system to drive the ground engaging elements, such as wheels or tracks, of the machine. Such hydrostatic drive system commonly includes at least one pump driven by a prime mover, such as an internal combustion engine, of the machine. The pump may be configured to drive one or more sets of motors
Data Source
AI summary
A method of braking a hydrostatic drive machine includes steps of reducing a displacement of a pump of a hydrostatic drive system to a non-zero displacement, and increasing a displacement of a motor of the hydrostatic drive system to a displacement that is less than a maximum displacement. The method also includes a step of accelerating an engine of the hydrostatic drive system toward a desired engine speed range.