Hydraulic Circuit Valve Arrangement for Steering Safety
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Solution Overview
Problem
Existing hydraulic circuits for steering systems in multi-axle vehicles face challenges in reliability and service life due to the high number of load cycles and the need for robust material selection and design.
Innovation Solution
The hydraulic circuit incorporates a valve arrangement with a fourth switching position that is hydraulically deactivated during normal operation and mechanically switched during faults or deactivations, ensuring the piston rod can only move to a safe failure position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the valve assembly is permanently in contact with the piston rod via the mechanical sensing element to enable continuous steering control, then the steering system can respond to steering angles in real-time, but the valve assembly undergoes several million load cycles over service life, reducing reliability and increasing wear
Solution Approach 1:
The patent extracts the mechanical sensing element from continuous contact with the piston rod by introducing a fourth switching position that hydraulically deactivates the valve assembly during normal operation. The mechanical sensing element is only engaged during fault conditions or deactivation, removing it from the high-cycle wear path while preserving steering control functionality when needed.
Solution Approach 2:
The valve assembly transitions from a static mechanically-actuated state to a dynamic hybrid state, switching between mechanical sensing mode (for fault safety) and hydraulic deactivation mode (for normal operation). This dynamic switching reduces the actuation cycles of the mechanical sensing element from millions to minimal occurrences, extending service life.
2Reliability
If the valve assembly is mechanically switched with each steering angle to store steering state, then the steering position is accurately maintained, but the mechanical components experience continuous wear from millions of actuation cycles
Solution Approach 1:
The patent replaces continuous mechanical switching with hydraulic deactivation during normal operation. The mechanical sensing element is substituted by a hydraulic actuator that uses fluid pressure to maintain the valve in a deactivated state, eliminating mechanical wear while preserving the ability to store and recall steering state through hydraulic positioning.
Solution Approach 2:
Instead of continuous mechanical switching at every steering angle, the system uses periodic mechanical actuation only when needed (fault conditions or deactivation events). During normal operation, the hydraulic system maintains the steering state without mechanical intervention, reducing wear cycles from continuous to periodic/occasional events.
3Device complexity
If the hydraulic circuit allows continuous operation without a fourth switching position, then the system remains simple and responsive, but it cannot prevent connections between working chambers and tank return line during normal operation, compromising safety
Solution Approach 1:
The patent segments the valve assembly operation into distinct switching positions, adding a fourth position that specifically blocks connections between working chambers and tank return line. This segmentation isolates the safety function from normal operation, allowing the circuit to maintain simplicity while incorporating enhanced safety control through the additional switching state.
Solution Approach 2:
The fourth switching position is activated in advance during normal operation to pre-block potential unsafe connections between working chambers and tank return line. This preliminary action prevents safety issues before they can occur, ensuring that the system is prepared for safe failure positioning without requiring complex additional components.
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 enhances the reliability and service life of the hydraulic circuit by reducing wear and tear through fewer actuation cycles and ensuring the system can safely fail to a predetermined position.
Implementation Method 1
a separate, in particular hydraulic, actuator from the hydraulic cylinder, which is designed, when activated, to lift the pushbutton element out of interaction with the piston or piston rod
Implementation Method 2
a hydraulic cylinder (1) having a cylinder chamber (11) with a piston (12) arranged therein for longitudinal movement
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
A hydraulic circuit for a hydraulic rear-axle steering system comprises a hydraulic cylinder with a cylinder chamber, a piston sealed within the cylinder chamber and dividing the cylinder chamber into two working chambers, and at least one piston rod supported by the piston. A mechanically switchable valve arrangement with three switching positions, controlled by a mechanical sensing element interacting with the piston rod, connects one of the working chambers to a reservoir return line depending on the piston's displacement. This ensures that, in the event of a malfunction, the piston rod returns to a safe fail-safe position corresponding to the straight-ahead steering position.In normal operation, the key element can be lifted out of contact with the piston or piston rod via an actuator separate from the hydraulic cylinder, and the valve arrangement can be switched to a fourth switching position in which the connection between the working chambers or to the tank return line is blocked.