Variable Displacement Pump for Hydrostatic Transmission Charge and Fan Flow
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Solution Overview
Problem
Current hydrostatic transmissions experience parasitic losses and increased heat due to fixed displacement charge pumps, which are inefficient in meeting variable flow and pressure requirements, especially for hydraulic cooling fans, leading to excessive energy wastage and heating.
Innovation Solution
A hydrostatic transmission system utilizing a variable displacement hydraulic pump and a two-stage pressure control valve, with a cartridge valve and fan drive controller, allows for proportional control of fan speed and flow, minimizing parasitic losses and heat by regulating pressure and displacement dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed displacement charge pump is used, then the system structure is simple, but parasitic losses increase and energy efficiency deteriorates
Solution Approach 1:
The patent applies a variable displacement pump instead of a fixed displacement pump, allowing the pump displacement to dynamically adjust based on system pressure and flow demands. This dynamic adjustment enables the pump to deliver variable flow rates, matching actual system needs and minimizing parasitic losses associated with fixed displacement systems that continuously pump at constant rates regardless of demand.
Solution Approach 2:
The patent changes the operational parameters of the pump by implementing variable displacement capability. The pump displacement parameter is made adjustable through a control system that responds to pressure sensor feedback, allowing the system to optimize pump output parameters (flow rate and pressure) to match instantaneous demands, thereby reducing energy waste.
2Device complexity
If a fixed displacement charge pump is used, then the system design is straightforward, but heat generation increases
Solution Approach 1:
The variable displacement pump dynamically adjusts its output based on real-time system conditions, preventing excessive flow generation that would convert to heat through pressure relief valves and bypass circuits. This dynamic control directly addresses heat generation by matching pump output to actual demand.
Solution Approach 2:
The patent converts the potential harm of excessive pump output (which generates heat) into a benefit by using pressure sensors and control logic to detect when full pump capacity is needed versus when reduced output suffices. This transforms what would be wasted energy into useful, demand-matched output.
3Loss of energy
If a variable displacement pump is used, then parasitic losses are minimized, but device complexity increases
Solution Approach 1:
The patent implements a feedback control system using pressure sensors that continuously monitor system pressure and provide signals to the pump controller. This feedback loop enables automatic adjustment of pump displacement based on actual system demands, managing the complexity through intelligent control rather than mechanical complexity.
Solution Approach 2:
The patent replaces complex mechanical variable displacement mechanisms with an electronically controlled system that uses pressure sensors, electronic controllers, and electro-hydraulic or electro-mechanical actuation. This substitution manages complexity by using electronic control systems that are more programmable and adaptable than purely mechanical solutions.
4Speed
If pressure is regulated by bypassing fluid around the fan motor, then fan speed control is achieved, but parasitic losses increase
Solution Approach 1:
Instead of using static bypass circuits to regulate fan motor speed, the patent employs a dynamic variable displacement pump that adjusts its output flow to match the fan motor's actual demand. This eliminates the need for bypass circuits and associated parasitic losses while maintaining precise speed control through electronic regulation of pump displacement.
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 effectively minimizes parasitic losses and heat by dynamically adjusting pump displacement and pressure to match instantaneous system needs, ensuring efficient energy use and reduced heating, while allowing independent control of fan speed and flow requirements.
Implementation Method 1
A hydrostatic transmission that utilizes a proportional pressure variable displacement hydraulic pump for both loop charge and fan flow supply
Implementation Method 2
a pressure control valve that has first and second stages and is fluidly connected to the hydraulic pump
Data Source
AI summary
A hydrostatic transmission having a hydraulic pump that is fluidly connected to a hydraulic motor. The transmission also has a pressure control valve that has first and second stages and is fluidly connected to the hydraulic pump. By utilizing the pressure control valve when the first stage of the pressure control is at a minimum pressure the second stage determines the minimum charge pressure setting for the hydrostatic transmission.