Shovel Hydraulic Bypass Layout for Faster Bleed-Off Response
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Solution Overview
Problem
The responsiveness of hydraulic circuits in shovels is decreased due to the positioning of bleed-off valves downstream of directional control valves, leading to increased load on the hydraulic pump and reduced pressure reduction efficiency during bleed-off control.
Innovation Solution
The bleed-off valves are connected upstream of at least one directional control valve in the center bypass oil passage, allowing for immediate pressure reduction and enhanced responsiveness by reducing the influence of residual pressures from directional control valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If bleed-off valves are positioned downstream of directional control valves, then pressure loss in center bypass oil passages is reduced, but responsiveness of bleed-off control decreases
Solution Approach 1:
The patent segments the bleed-off control function by providing multiple bleed-off valves at different positions in the hydraulic circuit. Specifically, bleed-off valves are provided both in the directional control valves and in the center bypass oil passage, allowing different segments of the circuit to be bled off independently. This segmentation enables the system to achieve both low pressure loss (by bleeding from the center bypass passage) and high responsiveness (by having multiple bleed-off points)
Solution Approach 2:
The patent introduces an intermediary bleed-off valve in the center bypass oil passage that acts as a mediator between the hydraulic pump and the directional control valves. This intermediary valve provides an additional pathway for pressure reduction that doesn't depend on the downstream directional control valves, thereby improving responsiveness while the overall circuit configuration maintains low pressure loss
2Loss of energy
If bleed-off valves are positioned downstream of directional control valves, then pressure loss is reduced, but load on hydraulic pump increases
Solution Approach 1:
By segmenting the bleed-off function across multiple locations (directional control valves and center bypass passage), the system reduces the workload on the hydraulic pump. The bleed-off valves in the center bypass passage can relieve pressure earlier in the circuit, preventing pressure buildup that would otherwise require the pump to work harder
3Loss of energy
If bleed-off valves are positioned downstream of directional control valves, then pressure loss is reduced, but pressure reduction efficiency decreases
Solution Approach 1:
The segmented bleed-off valve configuration allows different parts of the hydraulic circuit to be bled off simultaneously or independently. The bleed-off valves in the center bypass passage can reduce pressure in the main supply line, while bleed-off valves in directional control valves handle pressure in specific actuator lines, thereby improving overall pressure reduction efficiency without increasing pressure loss
Solution Approach 2:
The bleed-off valve in the center bypass oil passage acts as an intermediary that can reduce pressure before the oil reaches the directional control valves. This intermediary positioning allows for more efficient pressure reduction by addressing pressure buildup at its source rather than waiting for it to propagate downstream
Data Source
AI summary
A shovel includes a hydraulic pump, multiple hydraulic actuators, a center bypass oil passage supplied with hydraulic oil discharged from the hydraulic pump, multiple directional control valves, and a bleed-off valve. The directional control valves are arranged in tandem in the center bypass oil passage and configured to supply the hydraulic actuators with the hydraulic oil from the center bypass oil passage. At least a directional control valve other than the most downstream directional control valve in the center bypass oil passage among the directional control valves opens the center bypass oil passage. The bleed-off valve is connected to part of the center bypass oil passage upstream of at least one of the directional control valves.