Spool Valve Flow Matching for Fixed Displacement Hydraulic Pumps
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Solution Overview
Problem
Fixed displacement hydraulic pumps produce excessive fluid flow at higher RPMs, leading to wasted power and inefficiency, as they are typically sized for idle conditions and cannot independently control fluid flow relative to device speed.
Innovation Solution
A fixed displacement hydraulic pump match flow demand control system utilizing a spool valve and multiple smaller pumps to regulate fluid flow, where the spool valve adjusts the flow based on pressure differences and control valve bias pressures to match flow demand, redirecting excess flow to a return passage and reducing pump pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a fixed displacement pump is sized to provide adequate flow at idle, then sufficient fluid flow is available at low RPMs, but excessive fluid flow is produced at peak motor speeds resulting in wasted power and driveline inefficiency
Solution Approach 1:
A spool valve is introduced as an intermediary device between the fixed displacement pump and the hydraulic system. The spool valve regulates fluid flow by redirecting excess fluid to a return passage, allowing the pump to operate at full capacity while controlling the actual flow delivered to the hydraulic motor based on system demand.
Solution Approach 2:
The system changes the flow parameter dynamically by using a spool valve that adjusts the proportion of pump output directed to the hydraulic motor versus the return passage. This allows the effective flow delivery to vary with system needs while the pump maintains constant displacement operation.
2Use of energy by moving object
If a variable displacement pump is used to control fluid flow independently of motor speed, then power efficiency improves, but system complexity and cost increase
Solution Approach 1:
The system segments the pump output into two separate paths: one leading to the hydraulic motor and another to the return passage. The spool valve controls the distribution between these paths, achieving flow regulation without requiring the pump itself to be variable displacement.
Solution Approach 2:
The spool valve serves as a simpler intermediary component compared to a variable displacement pump mechanism. It provides the necessary flow control function with reduced mechanical complexity, maintaining power efficiency benefits while avoiding the complexity of variable displacement mechanisms.
3Productivity
If a single large fixed displacement pump is used, then adequate flow is provided at idle, but viscous drag and heat generation increase at higher RPMs
Solution Approach 1:
The spool valve acts as a mediator that diverts excess fluid from the pump output away from the hydraulic motor at high RPMs. This reduces the workload on the motor and associated cooling requirements, decreasing heat generation and viscous drag while maintaining adequate flow capability at idle.
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 system reduces energy waste by optimizing fluid flow at varying RPMs, improving fuel efficiency and reducing the size and cost of the cooling system, while minimizing viscous drag and heat generation.
Implementation Method 1
The spool is configured to shuttle within chamber based at least in part on a pressure difference between the first end and the second end of the chamber
Implementation Method 2
The control valve is configured to provide a select bias pressure that generates a select bias force on the first end of the spool within the chamber to adjust a location of the spool in the chamber to achieve a desired line pressure
Data Source
AI summary
A fixed displacement hydraulic pump match flow demand control system that includes a spool valve, a plurality of fixed displacement pumps and a control valve is provided. The spool valve includes a spool. The spool is configured to shuttle within a chamber of a housing based at least in part on a pressure difference between a first end and the second end of the chamber. A fluid flow from each fixed displacement pump of the plurality of fixed displacement pumps is in fluid communication with an associated input port to the spool valve. At least one output port of the spool valve is in fluid communication with a hydraulically operated device and at least one of another output port is in fluid communication with a return. The control valve is configured to adjust the location of the spool in the chamber to regulate fluid flow to the hydraulically operated device.