Power Steering Actuator Rings for End-of-Travel Relief

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Solution Overview

Problem

Existing power steering systems for commercial trucks face limitations in end-of-travel relief and pressure relief, including restricted activation ranges, reduced turn angles due to tolerance stacks, early onset of crack pressure, and performance drift, which affect durability and accessibility without increasing packaging size or requiring additional tooling.

Innovation Solution

The improved power steering assembly incorporates left and right actuator rings with radial spring forces that divert excess fluid between piston pressure chambers, featuring a reset gear mechanism and a valve cartridge with integrated pressure relief and end-of-travel functions, allowing precise control of maximum system pressure and fluid recirculation, especially during power off conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If existing pressure relief valves are used to prevent over pressurization, then maximum system pressure is limited to a predetermined value, but early onset of crack pressure and performance drift occur

Engineering Contradiction:

Improvemaximum system pressureVSAvoidpressure relief performance stability

Core Design Contradiction:

Stress or pressureVSReliability

Solution Approach 1:

The valve cartridge incorporates a pressure relief valve with adjustable parameters that can be precisely tuned during assembly. The valve spring and seating surfaces are designed to provide stable crack pressure characteristics, eliminating performance drift over time while maintaining reliable maximum pressure limitation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If poppet valves are used for end-of-travel relief, then steering components are protected from excessive stresses, but the activation range is limited to a particular range of operation

Engineering Contradiction:

Improvesteering component protectionVSAvoidactivation range

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The actuator rings are designed with adjustable positioning mechanisms that allow the end-of-travel relief activation point to be dynamically configured for different vehicle applications. The rings can be positioned at various angles relative to the valve cartridge, enabling the system to adapt to different turn angles and travel ranges while maintaining component protection.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If tolerance stack of component parts is present, then assembly is simplified, but effective turn angles of vehicles are reduced

Engineering Contradiction:

Improveassembly simplicityVSAvoideffective turn angle

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The system replaces mechanical tolerance-dependent positioning with a programmable control system. Sensors detect the actual position of the actuator rings and valve elements, and the control algorithm compensates for tolerance variations, ensuring accurate end-of-travel relief activation regardless of assembly tolerances. This maintains full effective turn angles while keeping assembly simple.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Manufacturing precision

If actuator rings are added for end-of-travel relief control, then precise pressure control is achieved, but device complexity increases

Engineering Contradiction:

Improveend-of-travel relief precisionVSAvoidsystem structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The actuator rings are integrated directly into the existing valve cartridge assembly, combining multiple functions into a single compact unit. The rings serve both as positioning elements for end-of-travel detection and as actuating mechanisms for the pressure relief valves, eliminating the need for separate components and reducing overall system complexity while maintaining precise control.

Inventive Principle:

Principle #5Merging (Combining)

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 durability and accessibility by reducing maximum system pressure near axle stops, providing precise end-of-travel relief, and stabilizing pressure relief performance over time, while maintaining compact packaging and automating the system for improved reliability.

Implementation Method 1

left and right actuator rings with radial spring forces that divert excess fluid between piston pressure chambers

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 2

valve cartridge with integrated pressure relief and end-of-travel functions, allowing precise control of maximum system pressure and fluid recirculation

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Gradient

Data Source

PatentUS11643136B2End-of-travel relief in a power steering system

Publication Date: 2023.05.09 SHEPPARD R H CO INC

AI summary

An improved power steering assembly is provided. The power steering assembly includes an end-of-travel mechanism and a valve cartridge that is actuated by left and right actuator rings of the end-of-travel mechanism, the actuator rings extending partially around an output shaft. The actuator rings can be individually set for the desired end-of-travel relief to limit the maximum system pressure when the steering assembly approaches the desired axle stop setting. The valve cartridge provides an end-of-travel function and a pressure relief function and is in fluid communication with the left and right pressure chambers to recirculate hydraulic fluid in the event of a power off condition.