Estimating Brake Booster Underpressure via Pedal Travel
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Solution Overview
Problem
Existing hydraulic brake systems face inaccuracies in estimating underpressure in the brake booster, leading to incorrect control of hydraulic brake boosting operations, which can result in insufficient braking force during emergency situations and increased maintenance costs due to the need for underpressure sensors.
Innovation Solution
A method that detects brake pressure and estimates underpressure in the brake booster's underpressure chamber based on brake pressure and brake pedal travel, allowing for improved control of hydraulic brake boosting operations without relying on separate pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an underpressure sensor is installed to control the hydraulic brake boosting operation, then the control precision is improved, but the manufacturing cost and maintenance cost increase
Solution Approach 1:
The patent creates a virtual copy of the underpressure sensor function through software-based estimation. Instead of using a physical sensor to directly measure underpressure, the system uses a pressure sensor to measure brake pressure and then estimates underpressure through calculation algorithms. This virtual sensor approach achieves the measurement function without the physical hardware, reducing manufacturing and maintenance costs while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/physical underpressure sensor with an electronic estimation system. The physical sensor that would directly measure underpressure is substituted by an electronic calculation system that derives underpressure values from brake pressure measurements and diaphragm position data, eliminating the need for specialized sensing hardware
2Force
If the hydraulic brake boosting operation is actuated to provide additional braking force, then the braking force is improved, but the underpressure in the master brake cylinder drops causing incorrect estimation of underpressure
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors brake pressure and diaphragm position during hydraulic brake boosting operations. The system detects when HBB is actuated and uses this feedback information to adjust the underpressure estimation algorithm, compensating for the pressure drop caused by brake fluid pump operation and maintaining accurate underpressure readings throughout the braking event
Solution Approach 2:
The patent performs preliminary detection of the hydraulic brake boosting operation state before the pressure drop affects the estimation. By detecting HBB actuation and anticipating the pressure changes, the system prepares the estimation algorithm to account for these changes, ensuring accurate underpressure measurement is maintained throughout the operation
3Duration of action of moving object
If the brake pedal is depressed continuously during hydraulic brake boosting, then the braking operation is maintained, but the pressure drop in master brake cylinder is misinterpreted as pedal release leading to incorrect underpressure estimation
Solution Approach 1:
The patent uses feedback from multiple sensors including brake pressure sensors and diaphragm position sensors to distinguish between actual pedal release and pressure drop during continuous pedal depression. The system continuously monitors these parameters and uses the combined feedback to determine the true state of pedal activation, preventing misinterpretation of pressure changes
Solution Approach 2:
The patent introduces diaphragm position as an intermediary parameter to mediate between brake pressure changes and underpressure estimation. By monitoring diaphragm position in addition to pressure, the system can distinguish whether pressure changes are due to pedal release or due to hydraulic brake boosting operation, as the diaphragm position will differ in these two scenarios
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 method enhances the accuracy of underpressure estimation and control, ensuring optimal hydraulic brake boosting performance and reducing maintenance costs by correcting inaccuracies caused by brake fluid pumps and pedal activation during braking events.
Implementation Method 1
the brake booster includes a working diaphragm, arranged between an underpressure chamber and a working chamber... When the driver activates the brake pedal, the working chamber is subjected to, via a valve, a relatively high pressure provided by connection to the atmosphere. As a result, an additional force, dependent on the pedal force exerted on the brake pedal or the pedal travel, assists the pedal force produced on the piston rod.
Implementation Method 2
a hydraulic brake boosting operation (Hydraulic Brake Boost or HBB)... can provide additional brake fluid in the direction of the wheel brake devices with one or more brake fluid pumps resulting in an increased pressure in the wheel brake cylinders.
Data Source
AI summary
A method for operating a hydraulic brake system of a motor vehicle having a brake booster and a hydraulic brake boost wherein a brake pressure is detected and an underpressure, prevailing in an underpressure chamber of the brake booster is estimated on the basis of the detected brake pressure. The hydraulic brake boost controlled based on the estimated underpressure, with the estimated underpressure taking into account an actuation of the hydraulic brake boost.