Hybrid Vehicle Brake Booster Vacuum Ejector Scavenging
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Solution Overview
Problem
Conventional methods for supplying vacuum to vacuum-actuated devices in hybrid-electric vehicle systems are detrimental to fuel economy, engine emissions, NVH, and vehicle drivability, especially when the engine is decoupled from propulsion, leading to frequent engine pull-ups and brake booster vacuum depletion.
Innovation Solution
A method that directs engine intake air through an ejector to supply vacuum to the brake booster independently of the brake booster vacuum, even when the brake booster vacuum is above a threshold, reducing the frequency of engine pull-ups by maintaining vacuum levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine throttle is closed to supply vacuum to the brake booster when vacuum level is below threshold, then brake booster vacuum is restored, but fuel economy deteriorates and engine emissions increase
Solution Approach 1:
An ejector device is introduced as an intermediary component between the engine intake manifold and the brake booster. The ejector uses a small amount of motive air flow from the intake manifold to generate vacuum, which is then supplied to the brake booster through a control valve. This intermediary mechanism allows vacuum restoration without requiring full throttle closure, thus maintaining better fuel economy while still restoring brake booster vacuum levels.
2Reliability
If the engine is pulled up during idling to restore brake booster vacuum, then vacuum is supplied to the vacuum actuated device, but overall fuel economy deteriorates
Solution Approach 1:
The ejector system is designed to operate during engine idle conditions using the existing intake air flow. The control valve automatically activates the ejector when brake booster vacuum drops below a threshold, allowing the system to self-restore vacuum without requiring engine pull-up. The ejector scavenges vacuum from the intake manifold and delivers it to the brake booster, enabling the system to service itself during idle operation without additional fuel consumption.
3Reliability
If engine intake air is directed through the ejector continuously, then brake booster vacuum is maintained above threshold, but engine intake airflow is reduced
Solution Approach 1:
The system employs a control valve that dynamically adjusts the airflow to the ejector based on real-time brake booster vacuum levels. When vacuum drops below the threshold, the valve opens to allow air flow through the ejector for vacuum generation. When vacuum is restored above the threshold, the valve closes to stop airflow through the ejector, preserving full engine intake airflow. This dynamic control ensures vacuum maintenance only when needed, minimizing impact on engine performance.
4Productivity
If the ejector valve is closed when brake booster vacuum is above threshold, then engine intake airflow is preserved, but brake booster vacuum may drop below threshold
Solution Approach 1:
The control system incorporates feedback from a vacuum sensor that continuously monitors brake booster vacuum levels. When vacuum drops below the predetermined threshold, the feedback signal activates the control valve to open airflow to the ejector. When vacuum is restored above the threshold, the feedback signal closes the control valve to preserve engine intake airflow. This closed-loop feedback control automatically balances between maintaining vacuum reliability and preserving engine performance.
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 enhances fuel economy by reducing the frequency of engine pull-ups and maintaining brake booster vacuum levels, thereby improving overall vehicle efficiency.
Implementation Method 1
Aspirators (which may alternatively be referred to as ejectors, venturi pumps, jet pumps, and eductors) are passive devices that can provide low-cost vacuum generation
Data Source
AI summary
A method for a hybrid-electric vehicle may comprise, while the hybrid-electric vehicle is moving and in an absence of fuel being directed to an engine, directing engine intake air through an ejector to supply vacuum to a brake booster independent of a brake booster vacuum.