Engine Idle Speed Control for Vacuum Generation
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Solution Overview
Problem
Diesel engines often struggle to generate sufficient vacuum at lower speeds, leading to suboptimal operation of vacuum-assisted vehicle systems, such as brake systems, resulting in undesirable brake pedal feel during idling conditions.
Innovation Solution
Increasing the engine idle speed when needed to enhance vacuum pump output, thereby improving the operation of vacuum-operated systems by adjusting engine speed based on the number of braking events and stored vacuum levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine operates at base idle speed to conserve fuel, then fuel consumption is reduced, but vacuum production becomes insufficient for proper operation of vacuum-assisted systems
Solution Approach 1:
The engine control system dynamically adjusts idle speed based on vacuum demand conditions. When vacuum demand is detected (through sensor signals indicating vacuum level or braking events), the controller increases idle speed from base level to a higher idle speed, allowing the vacuum pump to generate sufficient vacuum. When vacuum demand is not present, the system returns to base idle speed for fuel economy.
Solution Approach 2:
The system changes the operating parameter of engine speed to resolve the contradiction. By monitoring vacuum levels or braking event signals, the controller adjusts the engine speed parameter between two states: base idle speed for fuel efficiency and increased idle speed for adequate vacuum production, thus adapting to different operational requirements.
2Reliability
If the engine idle speed is increased to improve vacuum pump output, then vacuum production increases, but fuel consumption increases
Solution Approach 1:
The system employs periodic or intermittent action by increasing idle speed only during specific conditions when vacuum demand is detected (such as during braking events or when vacuum sensors indicate low vacuum levels). After meeting the vacuum demand, the system returns to base idle speed. This periodic adjustment ensures adequate vacuum production only when needed, minimizing unnecessary fuel consumption.
Solution Approach 2:
The system applies partial action by increasing idle speed only to the extent necessary to meet vacuum demand rather than maintaining continuously high idle speed. The controller monitors vacuum levels and adjusts speed incrementally, applying just enough additional engine power to generate required vacuum while avoiding excessive fuel consumption that would result from continuously high idle speeds.
3Use of energy by moving object
If the vacuum pump operates at base engine idle speed, then fuel economy is maintained, but the brake system may exhibit hard pedal feel due to insufficient vacuum
Solution Approach 1:
The system uses feedback from vacuum sensors or braking event detection to determine when vacuum levels are insufficient. When the sensor detects low vacuum or when braking events are registered, the controller receives this feedback signal and responds by increasing idle speed to boost vacuum production, thereby ensuring proper brake pedal feel while maintaining fuel economy during normal operation.
Solution Approach 2:
The system can detect braking events in advance and preemptively increase idle speed to ensure adequate vacuum is available before the driver applies the brakes. This preliminary action prevents the hard pedal feel from occurring in the first place, maintaining both fuel economy during non-braking periods and proper brake operation when needed.
Data Source
AI summary
Methods and systems for improving vacuum generation for a diesel powered vehicle that includes a mechanically engine driven vacuum pump are presented. In one non-limiting example, engine idle speed may be increased in response to a number of braking events and/or a request for vacuum based on an amount of stored vacuum.