Auxiliary Pump Pressure Control for Hydrostatic Transmission Heat Reduction
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Solution Overview
Problem
Hydrostatic transmission systems in vehicles, such as mowing machines, face heat generation issues due to continuous high-pressure fluid pressurization in auxiliary circuits, which are often used intermittently, requiring additional cooling systems.
Innovation Solution
An auxiliary pump assembly that operates at reduced pressure when the auxiliary circuit is not in use and increases pressure when in use, featuring a low pressure relief valve and a selectively actuated flow control device to manage fluid pressure, reducing heat generation by minimizing high-pressure fluid pressurization during idle periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the auxiliary pump continuously pressurizes fluid to high pressure to ensure sufficient pressure is available for the auxiliary circuit, then the auxiliary circuit can operate properly when needed, but significant heat is generated due to continuous high-pressure operation
Solution Approach 1:
The patent applies dynamics by making the auxiliary pump's operating pressure variable rather than fixed. The pump automatically adjusts its discharge pressure based on real-time demand: maintaining high pressure (e.g., 2000-3000 psi) when the auxiliary circuit requires fluid, and reducing to low pressure (e.g., 100-500 psi) when not in use. This dynamic pressure adjustment eliminates continuous high-pressure operation, thereby reducing heat generation while ensuring reliability when needed.
Solution Approach 2:
The patent changes the pressure parameter of the auxiliary pump from a constant high value to a variable value that adapts to system needs. By implementing a flow demand-sensitive pressure control mechanism, the pump operates at high pressure only when fluid flow is demanded by the auxiliary circuit, and automatically transitions to low pressure during idle periods. This parameter change directly addresses the heat generation issue while maintaining circuit reliability.
2Reliability
If the auxiliary pump operates at high pressure continuously to provide sufficient pressure for auxiliary circuit operation, then the auxiliary circuit is ready for use, but energy consumption increases due to continuous high-pressure pressurization
Solution Approach 1:
The system dynamically adjusts the auxiliary pump's energy consumption by varying its operating pressure according to actual demand. The pump operates at high energy-consuming mode only when the auxiliary circuit requires fluid, and switches to low energy-consuming mode during idle periods. This dynamic energy management maintains circuit readiness while significantly reducing overall energy consumption.
Solution Approach 2:
The auxiliary pump system incorporates self-service through automatic pressure adjustment based on flow demand sensing. The system self-regulates its own operating pressure without external intervention, transitioning between high and low pressure modes according to the auxiliary circuit's actual needs. This self-service capability ensures readiness when needed while minimizing energy consumption during idle operation.
3Stress or pressure
If the auxiliary pump is designed to provide high pressure for auxiliary circuit operation, then sufficient pressure is available when needed, but heat generation requires additional fluid cooler equipment
Solution Approach 1:
The patent applies dynamics by implementing a dynamic pressure control system that adjusts the auxiliary pump's discharge pressure based on real-time flow demand. The system maintains high pressure capability when the auxiliary circuit is active, but automatically reduces to low pressure during idle periods. This eliminates continuous high-pressure operation and the associated heat generation, thereby removing the need for additional fluid cooler equipment while preserving pressure availability when needed.
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
The solution effectively reduces heat generation and energy consumption by maintaining lower operating pressures during auxiliary circuit inactivity, enhancing the efficiency and reliability of hydrostatic transmission systems.
Implementation Method 1
a low pressure relief valve connected in series with a selectively actuated flow control device between the outlet of the pump and the inlet of the pump, the low pressure relief valve allowing fluid to pass therethrough that is at a pressure exceeding a first pressure level
Implementation Method 2
The flow control device, in a first mode of operation, permits flow from the pump outlet to the low pressure relief valve when the pressure of the fluid at the outlet exceeds a second pressure level greater than the first pressure level and blocks flow when the pressure of the fluid at the outlet is no greater than the first level
Data Source
AI summary
An auxiliary pump assembly for a hydrostatic transmission that operates at a reduced pressure when the auxiliary circuit is not in use, and operates at an increased pressure when the auxiliary circuit is in use, thereby reducing the heat generated by the auxiliary pump. The auxiliary pump assembly can be used to supply low pressure makeup flow to a closed loop of a hydrostatic transmission. A combination valve including a bypass valve and a relief valve is also provided.