Hydraulic Auxiliary Flow Control for Low-Flow High-Pressure Actuation
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Solution Overview
Problem
The hydraulic control valve system in existing work machines, such as hydraulic excavators, faces challenges in maintaining accurate flow rate control at small opening conditions, especially when there is a large pressure difference between the hydraulic pump and the actuator, leading to destabilization of the valve body and decreased accuracy of actuator control.
Innovation Solution
The proposed work machine incorporates a hydraulic drive system with auxiliary flow rate controllers that utilize a seat type main valve, a control variable restrictor, a pilot line, and a spool type pilot variable restrictor. This configuration allows for precise adjustment of the flow rate supplied to the actuator by controlling the opening area of the main valve and the pilot variable restrictor based on the demanded flow rate and pressure difference.
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 body stability deteriorates under large pressure differences
Solution Approach 1:
The auxiliary flow control valve is divided into two separate valves: a poppet type pressure compensating valve for maintaining flow rate accuracy, and a spool type flow controlling valve for stable flow rate adjustment. This segmentation allows each valve to specialize in one function, resolving the contradiction between flow rate accuracy and valve body stability.
Solution Approach 2:
The patent combines two different valve types (poppet type and spool type) into a single auxiliary flow control valve assembly. The poppet type valve handles pressure compensation while the spool type valve handles flow rate control, merging their complementary strengths to solve the stability-accuracy contradiction.
2Speed
If the opening area of the auxiliary flow control valve is reduced for low speed operation, then actuator speed is reduced, but flow rate control accuracy deteriorates due to pressure losses
Solution Approach 1:
By separating the pressure compensation function from the flow control function, the system can maintain accurate flow rate control even at small opening areas. The spool type valve provides stable flow control at low speeds while the poppet type valve compensates for pressure variations, preventing accuracy deterioration.
Solution Approach 2:
The poppet type pressure compensating valve acts as an intermediary that maintains the pressure differential across the spool type flow control valve. This intermediary function ensures that the flow rate control accuracy is maintained even when the opening area is reduced for low speed operation.
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 configuration enables accurate control of the actuator, particularly when operating at low speeds with high excavation loads, by stabilizing the flow rate and reducing pressure losses, thereby improving the overall accuracy and efficiency of the work machine's operations.
Implementation Method 1
a spool type pilot variable restrictor that changes an opening area according to a command pressure
Implementation Method 2
a seat type main valve, a control variable restrictor that changes an opening area according to an amount of movement of a valve body of the main valve
Data Source
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.