Hydraulic Control Valve Assembly for PCLS Flow Prioritization
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Solution Overview
Problem
Pressure compensated load sensing (PCLS) hydraulic systems face challenges in maintaining optimal flow distribution among multiple functions in mobile machines, particularly when the maximum fluid source capacity is reached, leading to reduced flow to certain functions while prioritizing others.
Innovation Solution
The integration of a hydraulic control valve assembly with downstream flow control mechanisms, including variable orifices and spools, allows for selective restriction of fluid flow to downstream functions, prioritizing flow to critical functions by altering the flow sharing characteristics and maintaining a constant differential pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number or cross-sectional areas of control orifices is increased to serve more functions, then the system can control more hydraulic functions, but the fluid source capacity is exceeded and flow to each function is reduced
Solution Approach 1:
The system segments the control orifices into two distinct groups: upstream control orifices that regulate flow to upstream working units, and downstream control orifices that regulate flow to downstream working units. This segmentation allows independent optimization of flow distribution to different function groups, enabling the system to serve more functions without proportionally reducing flow to each individual function.
Solution Approach 2:
Different control orifices are assigned different cross-sectional areas based on their position in the system. Upstream control orifices have different area characteristics than downstream control orifices, allowing each group to be optimized for its specific function requirements. This local differentiation enables the system to maintain adequate flow to critical functions while expanding overall system capability.
2Quantity of substance
If the cross-sectional area of control orifices is increased to increase flow capacity, then more fluid can be supplied, but the pressure drop across control orifices changes and disrupts the constant differential pressure maintenance
Solution Approach 1:
The pressure compensation mechanism is segmented into upstream and downstream components corresponding to the two groups of control orifices. Upstream compensators maintain pressure differential across upstream control orifices, while downstream compensators maintain pressure differential across downstream control orifices. This segmentation allows each pressure control mechanism to be optimized independently for its specific group of orifices, maintaining stable operation even as total flow capacity increases.
3Stress or pressure
If the fluid source flow is increased to maintain differential pressure when control orifice areas increase, then pressure stability is maintained, but the fluid source reaches maximum capacity and cannot supply adequate flow to all functions
Solution Approach 1:
The system divides the hydraulic functions into upstream and downstream groups with separate flow control pathways. Upstream working units receive flow regulated by upstream control orifices, while downstream working units receive flow regulated by downstream control orifices. This segmentation allows the fluid source to distribute flow more efficiently across multiple functions without requiring a single large control orifice that would create excessive pressure drop, thereby maintaining pressure stability while maximizing available flow capacity.
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 ensures that critical functions receive a greater portion of the available flow, maintaining acceptable performance even when the system is operating at maximum capacity, thereby improving multifunction performance and prioritizing functions like track speed and boom height during simultaneous operations.
Implementation Method 1
a first directional and return flow control in the form of a spool
Implementation Method 2
a first downstream flow control... The first downstream flow control to selectively restrict a flow of fluid from the fluid source to the second working unit
Implementation Method 3
The fluid source responds to a change in at least one of the working pressure of the first function and the working pressure of the second function by varying a pressure at the outlet
Implementation Method 4
flow from the fluid source is shared among the functions according to the ratio of each function's control orifice cross-sectional area to the sum of all the control orifice cross-sectional areas
Data Source
AI summary
A hydraulic control valve assembly to be integrated into a pressure compensated load sensing system including a fluid source is provided. The hydraulic control valve assembly includes a first working unit to control a first hydraulic function of a machine. The first working unit includes a first directional and return flow control in the form of a first spool, a first function flow control to selectively communicate a working pressure of the first function to the fluid source, and a first downstream flow control. The hydraulic control valve assembly further includes a second working unit arranged downstream of the first working unit. The second working unit to control a second hydraulic function of the machine. The first downstream flow control to selectively restrict a flow a fluid from the fluid source to the second working unit.