Hydraulic Auxiliary Flow Control for Low-Flow High-Pressure Accuracy
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Solution Overview
Problem
Existing hydraulic control valve systems in work machines like hydraulic excavators face accuracy issues in flow rate control, particularly when operating at low speeds with high pressure differences, leading to destabilized valve behavior and decreased control accuracy.
Innovation Solution
A work machine with a hydraulic drive system incorporating auxiliary flow rate controllers featuring seat type main valves and spool type pilot variable restrictors, which adjust flow rates based on pilot command pressures to maintain accurate control at varying pressure differences and flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a poppet type auxiliary flow control valve is used to perform pressure compensation, then flow rate supply accuracy is improved, but valve behavior becomes destabilized under high pressure difference and small flow rate conditions
Solution Approach 1:
The patent divides the auxiliary flow control valve into two separate functional components: a spool type variable restrictor for flow rate control and a pressure compensating valve for pressure stabilization. This segmentation allows each component to optimize its specific function without the stability issues that arise when both functions are combined in a single poppet type valve.
Solution Approach 2:
The patent introduces a pressure compensating valve as an intermediary component between the hydraulic pump and the actuator. This intermediary stabilizes the pressure differential across the spool type variable restrictor, enabling accurate flow rate control without the instability problems of direct pressure-affected valves.
2Ease of operation
If the opening amount of directional control valve is controlled according to lever operation amount, then ease of operation is improved, but flow rate supply stability deteriorates due to differential pressure changes
Solution Approach 1:
The pressure compensating valve provides continuous feedback control by automatically adjusting to maintain a constant differential pressure across the directional control valve. This feedback mechanism ensures that flow rate supply remains stable regardless of changes in lever operation amount or load conditions.
Solution Approach 2:
The pressure compensating valve acts as an intermediary that decouples the relationship between lever operation and actual flow rate delivery. By stabilizing the differential pressure, it ensures consistent flow rate supply even when the directional control valve opening varies with operator input.
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 system enhances actuator control accuracy by adjusting flow rates through combined or independent operation of main and pilot variable restrictors, ensuring precise actuator operation even under conditions of high pressure differences and low flow rates.
Implementation Method 1
a spool type pilot variable restrictor that is disposed on the pilot line and changes an opening area according to a command from the controller
Implementation Method 2
a pilot line that connects a downstream side of the main valve and a downstream side of the control variable restrictor to each other and decides the amount of movement of the valve body according to a passing flow rate
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
There is provided a work machine which can improve accuracy of control of an actuator when a pressure difference between a hydraulic pump and the actuator is large and the demanded flow rate of the actuator is small. An auxiliary flow rate controller is configured such that an opening area of a main valve changes between a maximum opening area and zero according to the opening area of a pilot variable restrictor when the opening area of the pilot variable restrictor is equal to or more than a predetermined opening area and that the opening area of the main valve is zero irrespective of the opening area of the pilot variable restrictor when the opening area of the pilot variable restrictor is less than the predetermined opening area.