Articulation Hydraulic Circuit to Prevent Earthmover Frame Drift
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Solution Overview
Problem
Earthmoving machines experience drift issues due to loosening between pins and bushings, and deviation from the desired articulation angle between the front and rear frames, leading to suboptimal performance.
Innovation Solution
A hydraulic circuit with an articulation charge circuit that includes a pump, reservoir, directional control valve, actuator valves, and load check valves, which maintains elevated pressure in the cylinder supply lines by using a pilot feed line with an orifice and check valves to prevent pressure drops, ensuring the cap and rod end chambers remain pressurized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hydraulic circuit is used without an articulation charge circuit, then the system is simpler and has fewer components, but the pressure in the cylinder supply lines drops below the desired level, causing drift in the articulation angle between the front and rear frames
Solution Approach 1:
The articulation charge circuit proactively charges the cylinder supply lines with fluid under pressure before pressure drops occur. The pilot feed line continuously supplies fluid through the orifice to maintain pressure in the supply lines, preventing the drift condition rather than correcting it after it occurs.
Solution Approach 2:
The pilot feed line acts as an intermediary element that transfers fluid from the pilot supply line to the cylinder supply lines. The orifice in the pilot feed line mediates the pressure transfer, ensuring that pressure is maintained in the cylinder supply lines through controlled fluid flow from the pilot system.
2Reliability
If the pressure in the cylinder supply lines drops below the desired level, then the system uses less energy and has lower operating pressure, but the load check valves cannot maintain the articulation angle, resulting in drift between the front and rear frames
Solution Approach 1:
The system uses the existing pilot pressure as a feedback mechanism to monitor and maintain the required pressure level in the cylinder supply lines. When pressure in the supply lines drops, the pressure differential across the orifice causes fluid to flow through the pilot feed line to recharge the supply lines, automatically maintaining the pressure threshold needed for proper load check valve operation.
3Reliability
If fluid is allowed to return to the reservoir during articulation, then the system allows free movement and reduces energy consumption, but the receding chambers become depressurized, causing loosening between pins and bushings and drift from the desired articulation angle
Solution Approach 1:
The articulation charge circuit merges the pilot supply line system with the cylinder supply lines through the pilot feed line and orifice. This integration allows the pilot system to simultaneously control the directional control valve and maintain pressure in the cylinder supply lines, combining two functions into one interconnected system.
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 solution effectively prevents drift by maintaining the desired articulation angle between the front and rear frames, enhancing the consistency and quality of earthmoving operations by ensuring the fluid receding chambers are always pressurized, thus improving the overall performance of the machine.
Implementation Method 1
The pair of pilot feed branch lines are provided with a pair of check valves disposed therein such that each check valve operably charges a corresponding cylinder supply line
Implementation Method 2
The pilot feed line has an orifice disposed therein and is configured to branch into a pair of pilot feed branch lines downstream of the orifice
Implementation Method 3
The directional control valve is fluidly coupled to the pump and the reservoir via a supply line and a fluid return line respectively
Data Source
AI summary
A hydraulic circuit for a pair of cylinders of an articulation system includes a pump, a reservoir, a directional control valve (DCV), a pair of actuator valves (AVs) and an articulation charge circuit (ACC). The DCV is fluidly coupled to the pump, the reservoir and the pair of cylinders via a supply line, a fluid return line and a pair of cylinder supply lines (CSLs) respectively. Each CSL has a load check valve (LCV) therein. The AVs are fluidly coupled with the DCV and the pump via a pilot supply line (PSL) for actuating movement of the DCV. The ACC, associated with the PSL and each cylinder supply line downstream of the associated LCV, charges a corresponding CSL with fluid from the PSL for increasing a pressure in the corresponding CSL when the pressure in the corresponding CSL falls below the pressure of fluid associated with the PSL.