Steering Gear Reaction-Force Measurement for Robust Rack-Force Detection
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Solution Overview
Problem
Existing methods for determining rack force in steering systems are susceptible to errors due to tolerance-related deviations and require complex sensor installations on moving components, leading to unreliable measurements.
Innovation Solution
Measure the reaction force between the steering gear and the vehicle body to determine the rack force, using simple force sensors or strain gauges at fastening points to directly correlate the reaction force with the actual rack force, eliminating the need for complex estimation and sensor installations on tie rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rack force is determined using estimation methods considering multiple parameters, then the measurement can be implemented without additional sensors, but the measurement precision deteriorates due to tolerance-related deviations and aging
Solution Approach 1:
The patent introduces a body part as an intermediary element between the steering gear and the vehicle body. This body part serves as a mounting structure that allows force measurement at the connection point, mediating between the steering gear reactions and the vehicle body, thereby enabling accurate rack force determination without complex sensor installations on moving components
Solution Approach 2:
The patent replaces complex estimation methods with direct mechanical force measurement. Instead of calculating rack force from multiple parameters (driver force, motor force, friction, inertia), the invention directly measures the reaction force at the body part connection, substituting mechanical estimation with physical measurement
2Measurement precision
If force measuring cells are integrated into tie rods, then direct rack force measurement is achieved, but the device complexity increases due to multiple sensors on moving components
Solution Approach 1:
The patent inverts the measurement location from the traditional approach (measuring on tie rods or rack) to measuring on a stationary body part connected to the steering gear. Instead of placing sensors on moving components, the measurement is performed on the stationary mounting structure, simplifying the overall system while maintaining measurement accuracy
Solution Approach 2:
The patent extracts the force measurement function from the moving tie rod system and relocates it to the stationary body part connection. This separation allows the measurement system to be independent of the dynamic tie rod assembly, reducing complexity while preserving measurement capability
3Reliability
If rack force is monitored to prevent overload, then the reliability of the steering system improves, but the device complexity increases due to additional measurement and control systems
Solution Approach 1:
The body part serving as a mounting structure performs multiple functions: it mechanically connects the steering gear to the vehicle body, provides structural support, and enables force measurement. This multi-functionality reduces the need for separate components, achieving reliability improvement without proportional increase in system complexity
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
Provides a structurally simple and robust method for determining rack force, ensuring reliable detection and prevention of overload by directly measuring the reaction force, thereby reducing the risk of damage and improving safety.
Implementation Method 1
the rack force is measured as a reaction force between the steering gear and a body part supporting the steering gear in the longitudinal direction
Data Source
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Figure 3
AI summary
The present invention relates to a method for measuring the rack force (F) acting on a rack (4) of a steering gear (3) of a steering system (1) for a motor vehicle, in which the rack (4) is movable in the longitudinal direction (Z) in the steering gear (3) and is coupled to at least one steerable wheel (5) via at least one tie rod (42). In order to enable simple and robust determination of the rack force, the invention proposes that the rack force (F) be measured as a reaction force (R) between the steering gear (3) and a body part (6) supporting the steering gear (3) in the longitudinal direction (Z).