Vacuum Brake Servo Pressure Estimation via Fluid Sensor
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Solution Overview
Problem
The existing solutions for maintaining sufficient vacuum in a motor vehicle's brake booster reservoir are either economically unfavorable due to the need for additional pressure sensors or insufficient in handling all situations, especially when the engine is automatically stopped.
Innovation Solution
A method that estimates the pressure in the vacuum reservoir using existing sensors, such as a pressure sensor for the braking fluid and a detection means for the actuating member, by calculating the amplitude of pressure decrease and correlating it with a predetermined correspondence curve to estimate the increase in pressure, allowing for engine restart when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is installed in the vacuum reservoir to directly measure pressure, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the brake fluid pressure sensor as an intermediary element to indirectly measure vacuum reservoir pressure. Instead of installing a dedicated sensor in the vacuum reservoir, the system leverages the existing brake fluid pressure sensor to detect pressure changes that correlate with vacuum pressure, thereby avoiding additional hardware while maintaining measurement capability
Solution Approach 2:
The patent creates a correlation model that copies the relationship between brake fluid pressure and vacuum reservoir pressure. By establishing a predetermined correspondence curve between these two pressure parameters, the system can estimate vacuum pressure based on brake fluid pressure measurements, effectively creating a virtual sensor reading without physical sensor installation
2Use of energy by moving object
If the engine is automatically stopped to reduce pollution and save fuel, then energy consumption is reduced, but vacuum reservoir pressure maintenance deteriorates
Solution Approach 1:
The patent implements preliminary action by monitoring vacuum reservoir pressure in advance and predicting when it will drop below operational thresholds. The system calculates future pressure values based on current pressure and historical decay rates, allowing the engine to be restarted proactively before vacuum pressure becomes insufficient for effective braking
Solution Approach 2:
The patent establishes a feedback loop where the system continuously monitors brake fluid pressure, calculates corresponding vacuum reservoir pressure, compares it against threshold values, and triggers engine restart when necessary. This closed-loop control ensures vacuum pressure is maintained within operational ranges while minimizing unnecessary engine restarts
3Reliability
If the engine is restarted when vacuum pressure exceeds a maximum threshold, then braking system reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies partial action by using a predetermined maximum threshold for vacuum reservoir pressure that may be higher than the absolute minimum required for effective braking. This allows the system to tolerate some excess pressure without triggering engine restart, thereby reducing restart frequency and energy consumption while still maintaining sufficient braking capability
Data Source
AI summary
The invention relates to a method for estimating the pressure (Pass) in a vacuum reservoir (28) of a vacuum brake servo (26) of a motor vehicle (10), the vehicle (10) comprising: - a braking device (16) operated by the pressure (Pmc) of a brake fluid; - a brake servo (26) for amplifying the force of the actuating member (24) using a vaccum supplied by a reservoir (28); - a pressure sensor (23) which is designed to measure the braking pressure (Pmc) of the brake fluid; characterized in that said method comprises: - a first step (E1) of calculating the braking pressure (Pmc); - a second step (E2) of calculating the amplitude (ΔPmc) of a reduction in braking pressure; - a third step (E3) during which the increase (Conso) of the pressure (Pass) in the vacuum reservoir (28) is estimated as a function of the amplitude (ΔPmc).