Patent ID: 7627407

Claim:
A fault determination device of a negative pressure generation device having an ejector that generates a first negative pressure that is greater than a second negative pressure that is to be extracted from an intake passageway of an intake system of an internal combustion engine, and an operation state change device that causes the ejector to function or stop functioning, the fault determination device determines a fault of the negative pressure generation device, the fault determination device comprising: a presence/absence-of-abnormality determination portion that determines a presence/absence of an abnormality of the negative pressure generation device based on a variation of a rotational speed of the internal combustion engine that is in accordance with a change in a state of operation of the operation state change device; an idle flow amount adjustment device for adjusting an intake air flow amount so as to restrain a variation of an idle rotation speed of the internal combustion engine and keeping the idle rotation speed substantially constant by an idle speed control, and wherein, when an increasing/decreasing correction of the intake air flow amount in accordance with the change in the state of operation of the operation state change device is performed by the idle speed control, the presence/absence-of-abnormality determination portion determines the presence of the abnormality if a magnitude of a degree of variation of the rotation speed of the idle internal combustion engine in accordance with the change in the state of operation of the operation state change device is greater than a predetermined value; and a feedback control prohibition portion that prohibits, if the intake air flow amount has been corrected to increase or decrease by the idle speed control in accordance with the change in the state of operation of the operation state change device, a feedback control related to the idle speed control, which adjusts the intake air flow amount based on a difference between the intake air flow amount measured by an air flow meter and a target air flow amount, when the presence/absence-of-abnormality determination portion performs the determination.