Bleed-Off Valve Control for Stable Pilot Pressure in Work Machines
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Solution Overview
Problem
Existing work machines with pilot-driven bleed-off valves face issues in maintaining stable circuit pressure for pilot primary pressure generation when actuators are not in operation, leading to inefficiencies in energy consumption.
Innovation Solution
A work machine design incorporating a main circuit, control valve, pilot circuit, and a bleed-off valve with a spool mechanism and restrictor that adjusts opening area stepwise or continuously based on actuator operation, ensuring stable pilot primary pressure generation through a controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a pilot-driven bleed-off valve is used to control circuit pressure, then energy consumption efficiency is improved by preventing unnecessary fluid discharge, but the valve cannot generate pilot pressure when actuators are not being operated
Solution Approach 1:
The bleed-off valve opening area is dynamically adjusted based on actuator operation state. The controller increases the opening area when actuators are not being operated to enable pilot pressure generation, and reduces it during operation to improve energy efficiency. This dynamic adjustment resolves the contradiction between energy efficiency and reliable pilot pressure generation.
Solution Approach 2:
The invention changes the opening area parameter of the bleed-off valve based on operational conditions. By varying this parameter between a first opening area (larger) for non-operational states and a second opening area (smaller) for operational states, the system achieves both reliable pilot pressure generation and improved energy efficiency.
2Loss of energy
If the bleed-off valve opening area is reduced to improve energy efficiency, then unnecessary fluid discharge is prevented, but pilot primary pressure cannot be generated when actuators are not being operated
Solution Approach 1:
The bleed-off valve opening area is dynamically adjusted based on actuator operation state. The controller increases the opening area when actuators are not being operated to enable pilot pressure generation, and reduces it during operation to improve energy efficiency. This dynamic adjustment resolves the contradiction between energy efficiency and reliable pilot pressure generation.
Solution Approach 2:
The invention changes the opening area parameter of the bleed-off valve based on operational conditions. By varying this parameter between a first opening area (larger) for non-operational states and a second opening area (smaller) for operational states, the system achieves both reliable pilot pressure generation and improved energy efficiency.
3Loss of energy
If the bleed-off valve is controlled to be in no-load communicating state to lower circuit pressure, then energy efficiency is improved, but thrust required to drive the valve body increases
Solution Approach 1:
The bleed-off valve opening area is dynamically adjusted based on actuator operation state. The controller increases the opening area when actuators are not being operated to enable pilot pressure generation, and reduces it during operation to improve energy efficiency. This dynamic adjustment resolves the contradiction between energy efficiency and reliable pilot pressure generation.
Solution Approach 2:
The invention changes the opening area parameter of the bleed-off valve based on operational conditions. By varying this parameter between a first opening area (larger) for non-operational states and a second opening area (smaller) for operational states, the system achieves both reliable pilot pressure generation and improved energy efficiency.
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
Stabilizes the main circuit pressure necessary for pilot primary pressure generation even when actuators are not in use, enhancing energy efficiency by preventing unnecessary energy loss.
Implementation Method 1
a restrictor that gives a resistance to the working fluid passing therethrough
Implementation Method 2
a spool that is moved in an axial direction by the pilot secondary pressure generated by the third pressure reducing valve
Data Source
Figure 1
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AI summary
A work machine includes: a main circuit that supplies a working fluid from a pump to an actuator; a pilot circuit that introduces part of the working fluid from the pump, to a pilot pressure receiving section of a control valve; a bleed-off passage that connects the pump and a tank. The pilot circuit is provided with: a first pressure reducing valve that generates a pilot primary pressure; and second and third pressure reducing valves that generate a pilot secondary pressure to be applied to the control valve and a bleed-off valve. A moving area of a spool of the bleed-off valve has a first moving area where an opening area of a restrictor changes stepwise, and a second moving area where the opening area of the restrictor changes continuously. A controller controls the third pressure reducing valve such that the spool is positioned in the first moving area at the time of non-operation of the actuator, and the spool is positioned in the second moving area at the time of operation of the actuator. The restrictor of the bleed-off valve has a restricting hole that gives a resistance to the working fluid passing therethrough in a case the spool is positioned in the first moving area.