Start/Stop System Vacuum Leak Compensation
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Solution Overview
Problem
Start/stop systems in motor vehicles with steep road gradients face challenges in maintaining sufficient partial vacuum for the brake booster due to leaks, which can lead to inadequate braking performance, as existing systems cannot detect and compensate for these leaks effectively.
Innovation Solution
A method that utilizes a wheel-speed sensor and inclination sensor to determine vehicle movement and road gradient, automatically starting the internal combustion engine when necessary to generate a partial vacuum and compensate for leaks in the brake booster system, ensuring reliable braking assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the start/stop system switches the engine off during stationary phases to reduce fuel consumption, then fuel efficiency is improved, but the partial vacuum level in the brake booster drops below the threshold for reliable operation
Solution Approach 1:
The system performs preliminary action by detecting the driver's braking intent before the engine restart is actually needed. The method monitors brake pedal position and determines braking demand in advance, allowing the engine to be restarted proactively to regenerate vacuum pressure before the brake booster vacuum drops below operational thresholds. This prevents the reliability issue from occurring rather than just reacting to it.
Solution Approach 2:
The system implements feedback by continuously monitoring brake pedal position, vehicle speed, and engine state to determine when braking demand exists. This feedback loop allows the start/stop system to make intelligent decisions about engine restart timing based on actual braking requirements, optimizing both fuel efficiency and brake booster vacuum levels.
2Device complexity
If a partial-vacuum estimator is used to monitor vacuum levels, then the system complexity is reduced, but leaks in the connecting line or brake booster cannot be registered
Solution Approach 1:
The system uses an intermediary approach by introducing a vacuum pump as a mediator between the engine and brake booster. The vacuum pump actively manages vacuum pressure levels, compensating for leaks and maintaining sufficient vacuum for brake booster operation. This intermediary device allows the system to use a simpler partial-vacuum estimator while still achieving reliable leak detection and compensation through the pump's active vacuum management.
3Stability of the object's composition
If the driver actsuate the brake to prevent vehicle rolling on steep gradients, then vehicle stability is maintained, but the actuating force required exceeds what the driver can comfortably apply
Solution Approach 1:
The system applies pneumatic principles through the brake booster, which uses stored vacuum pressure to amplify the driver's braking force. The vacuum-powered brake booster creates a pressure differential that generates additional braking force, allowing the driver to maintain vehicle stability on steep gradients with minimal physical effort. The pneumatic system acts as a force multiplier between the driver's input and the brake application.
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 ensures reliable braking performance on steep gradients by maintaining sufficient partial vacuum in the brake booster, even with leaks, thereby preventing vehicle roll and enhancing driver control.
Implementation Method 1
the internal combustion engine creates a partial vacuum to power the brake booster
Implementation Method 2
a partial vacuum arises in the induction manifold in the direction of flow downstream of a throttle valve of the internal-combustion engine. This partial vacuum serves as operating energy for the brake booster
Data Source
AI summary
A method for operating a motor vehicle having an internal combustion engine, a service brake, a brake booster, a parking brake, a wheel-speed sensor and an inclination sensor is disclosed. The method including measuring the speed of motor vehicle using the wheel-speed sensor to create a speed signal. An inclination of the motor vehicle with respect to the direction the motor vehicle is sensed and an angle signal is created. The internal combustion engine is started when the speed measured is greater than zero and the inclination of the motor vehicle is greater than a predetermined value, such that the internal combustion engine creates a partial vacuum to power the brake booster to assist with the operation of the service brake.