Hydraulic Circuit Bleed-Off Control via Extraction Valve
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Solution Overview
Problem
Conventional hydraulic circuits for construction machines experience increased pressure loss and complexity due to multiple bleed openings in direction control valves, leading to larger valve sizes and manufacturing challenges.
Innovation Solution
A hydraulic circuit design that eliminates bleed openings in direction control valves by using a first internal passage with a consistent passage area, allowing pressure oil to flow through a parallel passage and reducing pressure loss, while bleed-off control is performed downstream of the center bypass passage using a bleed-off valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple bleed openings are provided in the spool of a direction control valve for bleed-off control, then bleed-off control can be performed by changing the opening area, but the center bypass passage becomes complicated with many bending parts causing increased pressure loss
Solution Approach 1:
The invention extracts the bleed-off control function from the direction control valve spool by removing the bleed openings from the spool structure. Instead, a separate bleed-off valve is introduced that can be operated independently to control the bleed opening area, thereby simplifying the center bypass passage and reducing pressure loss while maintaining bleed-off control capability.
Solution Approach 2:
The invention segments the bleed-off control function from the main direction control valve operation. The bleed-off control is separated into an independent function controlled by a dedicated bleed-off valve, allowing the center bypass passage to be simplified without compromising the ability to perform bleed-off control when needed.
2Adaptability or versatility
If multiple bleed openings are provided in the spool of a direction control valve, then bleed-off control can be performed, but the size of the spool becomes large in the longitudinal direction
Solution Approach 1:
The invention extracts the bleed-off control function from the direction control valve spool by removing the bleed openings from the spool structure. Instead, a separate bleed-off valve is introduced that can be operated independently to control the bleed opening area, thereby simplifying the center bypass passage and reducing pressure loss while maintaining bleed-off control capability.
3Productivity
If a parallel passage is provided in the conventional hydraulic circuit, then oil flow can be directed through alternative paths, but the size of the direction control valve and bridge passage becomes large
Solution Approach 1:
The invention extracts the bleed-off control function from the direction control valve spool by removing the bleed openings from the spool structure. Instead, a separate bleed-off valve is introduced that can be operated independently to control the bleed opening area, thereby simplifying the center bypass passage and reducing pressure loss while maintaining bleed-off control capability.
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 design reduces pressure loss and simplifies the center bypass passage, minimizing the size and complexity of the direction control valve, thereby improving operational efficiency and manufacturing ease.
Implementation Method 1
a first internal passage RV1 for allowing the pressure oil supplied from the inlet port Plprt to flow out to the outlet port POprt
Implementation Method 2
a bleed-off valve Vbo positioned downstream of the center bypass passage RC and discharging the pressure oil flowing through the center bypass passage RC to the hydraulic oil tank Tnk
Data Source
Figure 1
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AI summary
A hydraulic circuit for a construction machine including a direction control valve group having multiple direction control valves that are provided in tandem to a center bypass passage of the construction machine, a bleed-off valve provided to the center bypass passage downstream of the direction control valve group, and a control valve that controls an amount of pressure oil to be supplied to the direction control valve. The direction control valve includes a first internal passage that flows out the pressure oil supplied to the direction control valve to the center bypass passage, and a second internal passage that supplies the pressure oil to a hydraulic actuator of the construction machine. The first internal passage causes pressure oil discharged from the hydraulic pump to flow out to the center bypass passage downstream of the direction control valve, so that the center bypass passage and the first internal passage form a parallel passage. The bleed-off valve performs bleed-off control on pressure oil supplied by way of the parallel passage by changing an opening area of the bleed-off valve. The control valve controls the amount of the pressure oil to be supplied to the second internal passage by changing an opening degree of the control valve.