Hydraulic Rear Axle Steering Locking for Secure Failure Position
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Solution Overview
Problem
Existing hydraulic rear axle steering systems for multi-axle vehicles face issues with maintaining a secure failure position and preventing hydraulic fluid leakage or air ingress during power failures, leading to compromised steering rigidity and uncontrollable wheel positions.
Innovation Solution
A hydraulic rear axle steering system with a mechanical and hydraulic blocking mechanism, utilizing load safety valves and admission-pressure controlled valves to ensure the steering cylinder remains locked in a central position even with hydraulic fluid loss, and incorporates a shut-off valve for safe failure state activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical blocking device with spheres and blocking sleeve is used to center the steering cylinder, then the steering can be brought into a secure failure position, but the blocking device is susceptible to wear and may jam when blocking spheres are not fully released
Solution Approach 1:
The patent replaces the mechanical blocking device with a hydraulic blocking system using load safety valves and admission-pressure controlled valves. The hydraulic system uses fluid pressure to control the blocking and unblocking of the steering cylinder, eliminating the wear and jamming issues of mechanical spheres and blocking sleeves.
Solution Approach 2:
The patent employs a hydraulic system with load safety valves and admission-pressure controlled valves to achieve reliable blocking and unblocking of the steering cylinder. The hydraulic fluid pressure controls the movement of blocking members, providing smooth and wear-free operation while maintaining secure failure position.
2Reliability
If hydraulically unblockable valves are used to prevent fluid loss, then the steering rigidity is maintained, but the system complexity increases with multiple valves and pressure lines
Solution Approach 1:
The load safety valves serve multiple functions: they prevent hydraulic fluid loss to maintain steering rigidity, control the unblocking pressure, and work in conjunction with admission-pressure controlled valves to manage the blocking and unblocking sequence. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The patent uses different pressure values to control different valve states: a first pressure value triggers the locking element to move to unblocking position, while a higher second pressure value opens the admission-pressure controlled valves. This parameter-based control simplifies the valve arrangement by using pressure levels rather than complex control mechanisms.
3Device complexity
If the blocking device is held solely by blocking spheres in central position, then the structure is simple, but the steering may move in unintended directions and the device jams under hydraulic pressure
Solution Approach 1:
The patent replaces the simple but unreliable mechanical blocking spheres with a hydraulic valve system that provides positive control of the steering cylinder position. The load safety valves and admission-pressure controlled valves work together to prevent unintended movement and jamming under hydraulic pressure.
Solution Approach 2:
The patent ensures that the locking element moves to the unblocking position before hydraulic pressure is applied to the steering cylinder. This preliminary action prevents the blocking device from jamming by ensuring the path is clear before pressure buildup occurs.
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
The system provides redundant mechanical and hydraulic blocking, ensuring the steering cylinder remains stable and controllable during failures, reducing the risk of jamming and maintaining vehicle maneuverability.
Implementation Method 1
a locking element (35) which can be moved by means of a hydraulically actuated actuator (37, 38) separate from the piston (33a) and piston rod (33) between a blocking position, in which the locking element (35) holds the blocking member (36) in the engaged position
Implementation Method 2
the admission-pressure controlled valves (15, 17) are adjusted such that, when a second pressure value is applied, they open at the control connection, wherein the second pressure value is higher than the first pressure value
Implementation Method 3
the two cylinder chambers can be secured to the tank by so-called load safety valves and unblockable non-return valves, so that the hydraulic oil continues to remain in the respective chamber of the cylinder and its position is thus retained
Data Source
AI summary
A hydraulic rear axle steering for multi-axle vehicles, including a steering cylinder with a piston and two working chambers. The steering cylinder has a mechanical blocking device, which blocks the piston when it reaches a central position within the steering cylinder. The blocking device has a blocking member, which is retained in an engaged position by a locking element in the blocked state. The locking element is movable by a separate, hydraulically actuated actuator between a blocking position and a first unblocking position in which the locking element releases the blocking element. An admission-pressure-controlled load safety valve is provided for each working chamber, and control connections of the valves are connected to a pressure line leading to the respective other working chamber. The actuator is adjusted such that, when a lower, first pressure value is applied, the locking element moves into the unblocking position, and the valves are adjusted such that, when a higher, second pressure value is applied, the valves open towards the tank.