Hydraulic Steering Valve Actuator Backlash Compensation
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Solution Overview
Problem
Conventional hydraulic power steering systems suffer from play in the transmission, leading to a discontinuous steering feel, known as 'handshake', especially during frequent direction changes, due to the steering valve opening not tracking the steering torque effectively, particularly at high differential pressures and steep boost curves.
Innovation Solution
The integration of a steering cylinder into a hydraulic circuit via a steering valve with a gear mechanism and an actuator that allows relative adjustment of the transmission, compensating for backlash by adjusting the steering valve opening when a steering direction reversal is detected, thereby improving the tracking of steering torque and reducing the 'handshake' effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gear mechanism with play is used to transmit steering movement to the steering valve, then the device complexity is reduced and ease of manufacture is improved, but the steering valve opening does not track the steering torque effectively, causing discontinuous steering feel and handshake
Solution Approach 1:
The control unit proactively detects steering direction reversals and activates the actuator to adjust the steering valve opening before the play in the gear mechanism causes tracking errors. This preliminary action prevents the handshake effect by anticipating and compensating for the inevitable play-induced delays in valve response.
Solution Approach 2:
The system continuously monitors steering torque and steering angle through sensors, providing real-time feedback to the control unit. This feedback loop enables the control unit to detect steering direction reversals and activate the actuator to compensate for play in the gear mechanism, ensuring continuous and accurate steering valve opening tracking.
2Reliability
If an actuator is added to adjust the steering valve opening, then the tracking of steering torque is improved and handshake is reduced, but the device complexity increases
Solution Approach 1:
The actuator serves as an intermediary element between the steering torque input and the steering valve opening. It actively compensates for the play in the gear mechanism by adjusting the valve opening based on control unit commands, thereby improving tracking accuracy without requiring a complete redesign of the gear mechanism.
Solution Approach 2:
The system replaces purely mechanical coupling between the steering wheel and steering valve with a hybrid system that incorporates an electric actuator and electronic control. This substitution allows for active compensation of mechanical play through electronic sensing and actuation, improving tracking while maintaining the benefits of mechanical gear transmission.
3Reliability
If the transmission is relatively adjusted to compensate for play, then the steering feel is improved, but the adjustment takes time and may affect response speed
Solution Approach 1:
The control unit detects steering direction reversals and activates the actuator to adjust the steering valve opening in advance, before the play in the gear mechanism causes tracking errors. This preliminary anti-action prevents the handshake effect and maintains steering feel without requiring time-consuming corrective adjustments after the reversal occurs.
Solution Approach 2:
The system performs compensatory adjustment of the steering valve opening proactively upon detecting steering direction reversal, rather than reactively after the play causes tracking errors. This preliminary action ensures continuous tracking and improved steering feel while minimizing the time required for compensation.
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 steering feel by reducing the impairment caused by transmission play, providing a more responsive and direct steering experience, and allows for adjustable compensation based on steering parameters and vehicle conditions, thereby improving the overall performance of the hydraulic servo-steering system.
Implementation Method 1
a hydraulic pump that pressurizes the hydraulic fluid to cause circulation
Implementation Method 2
a steering valve whose steering valve opening specifies the support force
Data Source
AI summary
An operating method for a hydraulic servo steering system of a motor vehicle includes a steering cylinder that applies the supporting force to a steering gearing is integrated into a hydraulic circuit by means of a steering valve. The steering valve opening specifies the supporting force, wherein the supporting force is set by the steering valve in accordance with a steering torque applied to a steering wheel, by means of a gearing having play. The steering system further includes an actuator that acts on the gearing in order to cause relative adjustment of the gearing. The opening method provides for a compensation step in which, provided that a steering direction reversal is detected, the gearing is relatively adjusted by means of the actuator in a direction opposite the prior engagement direction of the gearing for a predefined duration or a predefined adjustment distance.