Control device for internal combustion engine

1. A control device for an internal combustion engine, the internal combustion engine including:

an engine main body;

a PCV passage including a first end coupled to the engine main body and a second end coupled to a section of an intake passage downstream of a throttle valve, wherein the PCV passage causes blow-by gas to flow from a crank chamber of the engine main body to the intake passage by negative pressure in the intake passage;

a fresh air passage including a first end coupled to a section of the intake passage upstream of the throttle valve and a second end coupled to the engine main body, wherein the fresh air passage causes fresh air to flow from the intake passage to the crank chamber in accordance with the flow of the blow-by gas; and

a pulsation sensor located in the intake passage upstream of the throttle valve,

the control device comprising:

a pulsation detector, which detects pulsation of intake air flowing through the intake passage based on output signals from the pulsation sensor;

a parameter calculator, which calculates a parameter that is correlated with the degree of the pulsation based on the pulsation of the intake air detected by the pulsation detector; and

an anomaly detector, which determines that the fresh air passage is detached when the parameter calculated by the parameter calculator is less than or equal to a determination value, thereby detecting an anomaly in the fresh air passage.

2. The control device for an internal combustion engine according to claim 1 , further comprising an operating state detector, which detects an operating state of the internal combustion engine, wherein

the anomaly detector includes a determination value calculator, which calculates the determination value, and

the determination value calculator increases the determination value as a rotational speed of the internal combustion engine detected by the operating condition detector is decreased.

3. The control device for an internal combustion engine according to claim 1 , further comprising a negative pressure detector, which detects negative pressure in a section of the intake passage downstream of the throttle valve, wherein

the anomaly detector includes a determination value calculator, which calculates the determination value, and

the determination value calculator increases the determination value as the negative pressure in the intake passage detected by the negative pressure detector is increased.

4. The control device for an internal combustion engine according to claim 1 , further comprising:

an operating state detector, which detects an operating state of the internal combustion engine; and

a traveling state detector, which detects a traveling state of the vehicle,

wherein, when the operating state of the internal combustion engine detected by the operating state detector is an idling operation and the traveling state of the vehicle detected by the traveling state detector is a stopped state, the anomaly detector starts detection of an anomaly.

5. The control device for an internal combustion engine according to claim 1 , wherein the pulsation detector includes a bandpass filter that passes, among output signals from the pulsation sensor, an output signal in a frequency range that corresponds to a pulsation of the negative pressure generated in a section of the intake passage downstream of the throttle valve.

6. The control device for an internal combustion engine according to claim 5 , further comprising an operating state detector, which detects an operating state of the internal combustion engine,

wherein the bandpass filter changes the frequency range of the output signal to be passed among the output signals in accordance with the operating state of the internal combustion engine detected by the operating state detector.