Method for detecting damaged-bearing in engine using vibration signal

A method for detecting a damaged-bearing in an engine, the method comprising:

• separating, by a controller, a vibration signal of the engine detected by a vibration detecting device installed on one side of the engine of a vehicle into a vibration signal generated by combustion knocking and a vibration signal generated by a bearing installed between a crank pin of a crankshaft and a connecting rod;
• extracting a signal in a predetermined natural frequency band from the vibration signal generated by the bearing using a band-pass filter;
• processing, by the controller, the extracted signal to a quantified bearing signal;
• comparing, by the controller, the quantified bearing signal with a preset damaged-bearing criterion;
• determining, by the controller, whether the quantified bearing signal is equal to or greater than the preset damaged-bearing criterion to determine a damage to the bearing, and
• detecting an operating state of the engine using the controller between processing the signal and comparing the bearing signal,
• wherein the preset damaged-bearing criterion is differently set based on the operating state of the engine,
• wherein, in detecting the operating state of the engine,
• it is judged that the engine is being decelerated and being in a preset condition, and
• it is judged whether a state of the engine is any one of an initial deceleration state in which a decrement of revolution per minute (RPM) of the engine is initiated, a state in which the engine enters an idle state during deceleration while the RPM of the engine is decreased and is changed into the RPM of the idle state, and a state in which the engine enters the idle state from a fuel cut state during deceleration.