Articulated Truck Steering Cylinder Damping Near Full Lock
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Solution Overview
Problem
Articulated trucks with hydraulic steering systems face issues of sudden forces and pressure changes when the piston approaches the end of the cylinder barrel, leading to component damage and operator fatigue due to inadequate damping and binary valve activation.
Innovation Solution
The steering apparatus incorporates a snubbing tube and secondary hydraulic fluid passage with a valve that controls fluid flow to provide gradual damping and smooth operation near full lock, preventing binary damping and facilitating fast release from full lock through a combination of primary and secondary fluid passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single primary hydraulic fluid passage is used for routing hydraulic fluid into and out of the cylinder barrel, then the structure is simple, but sudden forces and pressure changes occur when the piston approaches the end of the cylinder barrel causing component damage and operator fatigue
Solution Approach 1:
The single primary hydraulic fluid passage is segmented into two separate passages: a first hydraulic fluid passage for routing hydraulic fluid into the cylinder barrel, and a second hydraulic fluid passage for routing hydraulic fluid out of the cylinder barrel. This segmentation allows independent control of fluid flow paths, enabling gradual damping near full lock position and preventing sudden pressure changes that cause component damage and operator fatigue.
Solution Approach 2:
A check valve is introduced as an intermediary component in the hydraulic fluid circuit. The check valve controls the direction and timing of hydraulic fluid flow, allowing fluid to be routed through the first passage during normal operation and through the second passage when the piston approaches the end of the cylinder barrel. This intermediary mechanism enables gradual damping and prevents sudden forces.
2Force
If hydraulic fluid flow is restricted through small cross-sectional area ports, then damping is provided, but binary valve activation causes sudden forces and pressure changes
Solution Approach 1:
The system transitions from static flow restriction to dynamic flow control. The check valve dynamically switches between two hydraulic fluid passages based on piston position and pressure conditions. During normal operation, the first passage provides unrestricted flow. When the piston approaches full lock, the check valve activates to route fluid through the second passage with flow control, providing gradual damping without binary activation.
Solution Approach 2:
The system changes the flow resistance parameter dynamically by switching between two different hydraulic fluid passages. The first passage has low flow resistance for normal operation, while the second passage has controlled flow resistance activated only when needed. This parameter change enables gradual damping effect without the binary switching problem.
3Speed
If the piston approaches the end of the cylinder barrel rapidly, then steering response is fast, but sudden forces and pressure changes occur leading to component damage
Solution Approach 1:
The system prepares for the approaching full lock condition by providing a dedicated second hydraulic fluid passage that becomes active before the piston reaches the end of the cylinder barrel. The check valve anticipates the pressure buildup and switches flow paths in advance, enabling gradual damping and preventing sudden forces that would damage components, while maintaining fast steering response during normal 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 solution ensures smoother steering, reduces component damage, and enhances operator comfort by minimizing sudden forces and pressure changes, thereby improving the operational behavior and longevity of the articulated truck.
Implementation Method 1
The snubbing tube comprises a slot located at a distal end of the snubbing tube distant from the closed end of the cylinder barrel that extends between an exterior of the snubbing tube and an interior of the snubbing tube. A plurality of channels are located between the slot and the closed end of the cylinder barrel and extend between the exterior of the snubbing tube and the interior of the snubbing tube. Each of the plurality of channels have a cross sectional area smaller than a cross sectional area of the slot.
Implementation Method 2
Each hydraulic cylinder may comprise a piston movable within a cylinder barrel in response to changes in pressure of hydraulic fluid. Hydraulic fluid may be passed into and out of the cylinder barrel via one or more access ports that are small in cross sectional area relative to a cross sectional area of a face of the piston.
Implementation Method 3
the valve may be a check valve that responds to a threshold pressure, wherein in an event that a pressure experienced by the check valve exceeds the threshold pressure the valve adopts the open position and in an event that the pressure experienced by the check valve is less than the threshold pressure the valve adopts the closed position.
Data Source
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AI summary
A steering system for an articulated truck. The articulated truck is formed of a tractor and a trailer and an articulation joint. The steering system includes a hydraulic cylinder, with a cylinder barrel and a piston. The steering system provides for changes in angle between the tractor and the trailer. The hydraulic cylinder includes a snubbing tube projecting into the cylinder barrel. A hydraulic fluid passage opens into the cylinder barrel within the snubbing tube. The snubbing tube includes a main slot and a plurality of channels each extending between an interior and an exterior of the snubbing tube. The plurality of channels have a cross sectional area smaller than a cross sectional area of the main slot. When the articulated truck is steered, the piston moves in the cylinder barrel and the snubbing tube dampens the movement to prevent forces generated by the piston damaging the articulated truck.