Engine Idle Speed Control for Vibration Suppression
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Solution Overview
Problem
In cold environments, the resonant rotational speed of the driving force transmission system in internal combustion engines can approach the idle rotational speed, leading to increased vibration during idle operation due to the hardening of mount materials, which are used to reduce vibration by altering their resilient modulus.
Innovation Solution
A control device that adjusts the idle rotational speed based on the duration the engine has been stopped and the temperature, increasing the idle speed when the engine has been stopped for an extended period in cold conditions to maintain a difference from the resonant rotational speed and reduce vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the idle rotational speed is set to a value differing from the resonant rotational speed to reduce vibration, then vibration during idle operation is reduced, but when the engine is stopped for a long period in low-temperature environment, the resonant rotational speed varies and approaches the idle rotational speed, causing increased vibration
Solution Approach 1:
The idle rotational speed is made dynamically adjustable based on the stopped period and temperature conditions. The control device counts the stopped period and detects temperature, then modifies the idle rotational speed accordingly - using a first idle rotational speed for short stopping periods and a second (different) idle rotational speed for long stopping periods in low-temperature environments, preventing resonance under varying conditions
Solution Approach 2:
The physical parameter of idle rotational speed is changed based on environmental conditions (temperature and stopped period). When the stopped period exceeds a reference value and temperature indicates low-temperature environment, the control device sets the idle rotational speed to a second value that differs from the first idle rotational speed, thereby adapting to the shifted resonant rotational speed caused by mount material hardening
2Use of energy by moving object
If the idle rotational speed is set as low as possible to reduce fuel consumption, then fuel consumption is reduced, but the resonant rotational speed may be approached under certain conditions, causing increased vibration
Solution Approach 1:
The idle rotational speed parameter is adjusted based on stopped period and temperature conditions. The control device counts the stopped period and when it exceeds a reference value in low-temperature environments, sets the idle rotational speed to a second value that ensures it remains distinct from the shifted resonant rotational speed, thereby preventing vibration while managing fuel consumption appropriately for the conditions
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 effectively suppresses vibration during idle operation by ensuring the idle rotational speed remains distinct from the resonant rotational speed, even in low-temperature conditions, thereby reducing resonance and associated vibrations.
Implementation Method 1
the hardening of mount materials, which are used to reduce vibration by altering their resilient modulus
Data Source
AI summary
An ECU for controlling an engine counts the continued period of stopping the engine in a low-temperature environment. The ECU sets the idle rotational speed at a first idle rotational speed when the stopped period is below a predetermined threshold value, and at a second idle rotational speed higher than the first idle rotational speed when the stopped period exceeds the reference value. Accordingly, resonance at the driving force transmission system during idle operation can be prevented even in the case where a mount employed for attaching the engine to the vehicle is hardened as a result of undergoing a low-temperature environment for a long period of time, and the resonant rotational speed of the driving force transmission system including the engine varies.