Dynamic Valve Threshold Control for Brake Pressure Build-Up
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Solution Overview
Problem
Modern brake systems face challenges in achieving both high dynamics of pressure build-up and accurate target pressure setting due to fluctuations in brake fluid delivery and elasticity, leading to significant deviations in the pressure achieved in the wheel brakes.
Innovation Solution
Setting the pressure threshold value at a valve higher than the target pressure during build-up, with the threshold being calculated as a function of the average volumetric flow and other variables to ensure accurate pressure setting, and redetermining it regularly to maintain the desired pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the HSV is opened during the entire pressure build-up to achieve maximum dynamics, then the pressure build-up dynamics are improved, but the target pressure accuracy deteriorates due to fluctuations in pump delivery rate and brake elasticity
Solution Approach 1:
The control unit continuously monitors the actual pressure in the wheel brake and compares it with the desired setpoint pressure curve. Based on this feedback, the control unit dynamically adjusts the opening degree of the USV to compensate for fluctuations in pump delivery rate and brake elasticity, thereby maintaining both high pressure build-up dynamics and accurate target pressure achievement
Solution Approach 2:
The invention transitions from static valve control (fixed opening/closed states) to dynamic control where the USV opening degree is continuously adjusted during pressure build-up. This dynamic adjustment allows the system to adapt to varying pump delivery rates and brake elasticity in real-time, resolving the contradiction between speed and precision
2Measurement precision
If the USV is used to set the target pressure precisely, then the target pressure accuracy is improved, but the pressure build-up dynamics deteriorate due to volume flow loss through the valve
Solution Approach 1:
The invention changes the operating parameters of the USV from binary (fully open/closed) to continuous modulation of opening degree. By adjusting the opening degree as a variable parameter, the system can precisely control pressure setting while minimizing volume flow loss, thus maintaining both accuracy and dynamics
3Speed
If the pump delivers brake fluid quickly to achieve high dynamics, then the pressure build-up speed is improved, but the pressure accuracy deteriorates due to oscillating delivery characteristics of the pump
Solution Approach 1:
The USV acts as an intermediary between the pump and the wheel brake. It smooths out the oscillating delivery characteristics of the pump by providing a controlled flow path, thereby translating the pump's high-speed delivery into accurate pressure build-up at the wheel brake without directly transmitting pump oscillations
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 approach enhances the dynamics of pressure build-up and improves the accuracy of target pressure setting, ensuring the braking effect follows the controller's desired course and maintaining the pressure at the desired maximum value.
Implementation Method 1
a hydraulic pump (RFP) 4
Implementation Method 2
a switching valve (USV) 2 which is normally open (normally-open), a switching valve (HSV) 3 which is normally closed (normally closed)
Implementation Method 3
a brake master cylinder 1 with a fluid reservoir
Data Source
Figure 1
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Figure 3
AI summary
The invention relates to a method for carrying out automatic braking in a motor vehicle by means of a pump that delivers a brake fluid in the direction of the wheel brakes, wherein the brake pressure present in the brake circuit is limited by means of a valve (USV) that is overflown when an settable pressure threshold value is reached and thus limits the brake pressure. The dynamics of the pressure build-up can be considerably improved when the valve opens only at higher pressures, because then a greater part of the volume flow coming from the hydraulic pump is in fact conducted to the wheel brakes and cannot flow off prematurely via the USV.