Control method of vehicle power unit

Abstract

To provide a control method of a vehicle power unit which suppresses vehicle body vibration caused by dither control that periodically changes air fuel ratio to raise temperature of exhaust gas purification catalyst in a power unit of a hybrid vehicle.SOLUTION: Output torque of an engine is varied (fluctuation portion tE) corresponding to fluctuation of air fuel ratio λ during dither control. When variation frequency of the air fuel ratio λ is in a resonance region of a vehicle body, output torque tM of a motor for calibration is added to the output torque of the engine. Thereby, frequency of fluctuation portion tL of the output torque of a power unit is higher than variation frequency of the air fuel ratio.SELECTED DRAWING: Figure 3

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