Brake Booster Pressure Estimation via Hydraulic Proxy
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Solution Overview
Problem
In vehicles with automatic stop/start systems and vacuum brake force boosters, estimating negative pressure is challenging without additional hardware, leading to potential safety issues due to insufficient auxiliary braking force when the engine is off, and existing methods are either costly or imprecise.
Innovation Solution
A method and device that estimate negative pressure in the brake force booster based on hydraulic pressure in the brake master cylinder and actual engine speed, using input signals to calculate the negative pressure value through integration and look-up tables, with optional consideration of engine-speed dependent pumping processes and brake pedal actuation rates, allowing for software-based implementation without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a negative pressure sensor is provided on the brake force booster to monitor negative pressure, then measurement precision is improved, but device complexity and hardware cost increase
Solution Approach 1:
The patent uses hydraulic pressure in the brake master cylinder as an intermediary parameter to indirectly determine negative pressure in the brake force booster. Instead of directly measuring negative pressure with a sensor, the system measures hydraulic pressure (which is easier to measure with existing sensors) and uses this as a proxy to infer the negative pressure state, thereby avoiding the need for additional negative pressure sensors.
Solution Approach 2:
The patent replaces the mechanical sensor-based measurement approach with a computational estimation approach. By using the relationship between hydraulic pressure and negative pressure, combined with engine speed data and look-up tables, the system substitutes physical sensing with mathematical modeling and data processing, eliminating the need for additional hardware sensors.
2Device complexity
If brake pedal actuations are counted to estimate negative pressure, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent changes the parameter used for estimation from a discrete count of brake pedal actuations to continuous hydraulic pressure values. By using hydraulic pressure as the basis for estimation and combining it with engine speed parameters, the system achieves more precise and continuous estimation of negative pressure compared to discrete counting methods.
Solution Approach 2:
The system implements feedback by continuously monitoring hydraulic pressure and engine speed, then using this information to dynamically estimate negative pressure. The estimation is updated based on current operating conditions, allowing the system to adapt to changing states and provide accurate real-time assessment of brake booster pressure levels.
3Use of energy by moving object
If engine is kept stopped to reduce fuel consumption, then energy efficiency is improved, but safety deteriorates due to insufficient auxiliary braking force
Solution Approach 1:
The system uses feedback from hydraulic pressure sensors and engine speed measurements to continuously monitor the negative pressure state in the brake force booster. This feedback loop allows the control system to make informed decisions about when to restart the engine, balancing fuel economy with braking safety by restarting only when necessary based on actual pressure conditions.
Solution Approach 2:
The system performs preliminary monitoring of hydraulic pressure and engine speed to predict when negative pressure may become insufficient. By detecting trends in these parameters, the system can anticipate the need for engine restart before actual pressure depletion occurs, ensuring safety is maintained while maximizing stoppage duration for fuel efficiency.
Data Source
AI summary
Method for estimating the negative pressure in a motor vehicle brake force booster, and a stop/start control device is disclosed. One embodiment of the invention relates to a method for estimating the negative pressure in a motor vehicle brake force booster with reference to the hydraulic pressure in a brake master cylinder. According to the embodiment, the negative pressure is estimated solely on the basis of hydraulic pressure in the brake master cylinder and of the actual engine speed. One embodiment of the invention also relates to a stop/start control device for a motor vehicles.