Brake Booster Vacuum Control via Engine Speed Adjustment
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Solution Overview
Problem
Power brakes in vehicles often experience insufficient vacuum at low intake manifold pressure, which can hinder braking performance, especially during prolonged low-load engine operation.
Innovation Solution
A system and method that estimate and maintain desired brake booster vacuum by adjusting engine rpm, cam timing, and transmission gear ratio to ensure sufficient intake manifold vacuum, using sensors and an electronic control unit to manage engine torque and vacuum levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine operates at low intake manifold pressure to improve efficiency, then pumping losses are reduced, but brake booster vacuum becomes insufficient
Solution Approach 1:
The system dynamically adjusts engine RPM based on brake booster vacuum levels. When vacuum drops below a threshold, the engine control unit increases RPM to restore vacuum pressure, allowing the system to adapt between efficiency mode (low RPM) and braking readiness mode (high RPM).
Solution Approach 2:
The invention changes the operating parameters of the engine by adjusting RPM and intake manifold pressure. The system monitors vacuum levels and modifies engine operating conditions to maintain sufficient brake booster vacuum while minimizing pumping losses during normal operation.
2Reliability
If engine rpm is increased to maintain brake booster vacuum, then sufficient vacuum is ensured, but fuel consumption increases
Solution Approach 1:
The system uses periodic monitoring of brake booster vacuum levels and only increases engine RPM when vacuum drops below the threshold. This intermittent adjustment minimizes fuel consumption while ensuring vacuum is maintained when needed for braking operations.
Solution Approach 2:
The engine control unit continuously monitors brake booster vacuum levels and uses this feedback to determine when RPM adjustment is necessary. This closed-loop control ensures vacuum is maintained only when required, avoiding unnecessary fuel consumption during periods when sufficient vacuum already exists.
3Reliability
If cam timing is adjusted to increase manifold vacuum, then brake booster vacuum is improved, but engine torque output is reduced
Solution Approach 1:
The system dynamically adjusts cam timing based on vacuum requirements. The variable cam timing mechanism shifts valve timing to increase manifold vacuum when brake booster pressure drops, temporarily sacrificing torque output to maintain braking capability.
Solution Approach 2:
The invention changes the cam timing parameter to optimize manifold vacuum levels. By adjusting valve timing, the system increases the pressure differential across the throttle plate, thereby increasing manifold vacuum and brake booster pressure at the expense of peak torque production.
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 ensures reliable braking performance by maintaining adequate vacuum in the brake booster, even during low-load conditions, by dynamically adjusting engine parameters and transmission settings to meet operator demands while minimizing pumping losses.
Implementation Method 1
the brake booster being fluidly coupled to an intake manifold of the engine
Data Source
AI summary
Methods for controlling vacuum within a brake booster by modifying powertrain operation include determining an intake manifold vacuum in response to actuation of a brake pedal. Increasing the intake manifold vacuum if the brake booster vacuum is less than a desired brake booster vacuum. In some embodiments, the transmission is downshifted to increase engine speed and intake manifold vacuum.