Abstract: A multicylinder engine includes: combustion chambers; fuel injection valves corresponding to the individual combustion chambers; an exhaust control catalyst; an upstream-side air/fuel ratio sensor disposed upstream of the exhaust control catalyst; and a downstream-side A/F sensor disposed downstream of the catalyst. A first abnormality determination-purpose rich A/F control of controlling the A/F of the mixture formed in each combustion chamber to an A/F richer than stoichiometric is executed when it needs to be determined whether the downstream-side A/F sensor is abnormal. An inter-cylinder A/F imbalance determination of estimating the A/F of the mixture in each combustion chamber based on the output of the upstream-side A/F sensor is executed when the first abnormality determination-purpose rich A/F control is being executed, and it is determined whether there is a difference between the estimated A/Fs of the mixtures.

Abstract: In a malfunction determination apparatus and a malfunction determination method for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the engine, using an electric pump, a first temperature of the cooling medium is detected at an inlet of the first passage, through which the cooling medium flows into the inside of the engine; a second temperature of the cooling medium is detected at an outlet of the first passage, through which the cooling medium flows out from the inside of the engine; and it is determined that the switching valve is able to normally select the second passage, if both of the first temperature and the second temperature reach a first threshold value when a temperature of the cooling medium increases due to start of the engine.

Abstract: Under the condition that a catalyst temperature Tc of a purification catalyst reaches or exceeds a preset reference temperature Tcref, when a cooling water temperature Tw of an engine is not lower than a preset reference temperature Twref, the internal combustion engine system of the invention sets a target exhaust recirculation rate EGR* based on a given rotation speed Ne of the engine and a given load factor KL and performs exhaust recirculation control to open an EGR valve at a specific angle or opening corresponding to the set target exhaust recirculation rate EGR*.

Abstract: In an engine having a variable valve timing mechanism to which an intermittent operation control is applied, appropriate execution of a foreign object removal process for the variable valve timing mechanism is enabled. An engine control device (16) which can execute intermittent operation control for an engine (12) having a variable valve timing mechanism (80) comprises a judging part which judges an abnormality in the variable valve timing mechanism (80) (step S10), a foreign object removal process executing part which causes a foreign object removal process to be executed for the variable valve timing mechanism (80) when the judging part judges that there is an abnormality in the variable valve timing mechanism (80) during an engine operation (step S12), and an intermittent operation control prohibiting part which prohibits the intermittent operation control of the engine (12) during execution of the foreign object removal process of the variable valve timing mechanism (80) (step S16).

Abstract: When a condition for the prediction of the occurrence transient knocking has held, that is, when a cooling water temperature ?w is not less than a threshold value ?wref and an intake air flow Qa is not less than a threshold value Qaref and a deviation of the intake air flow ?Qa is not less than a threshold value ?Qaref (S550 to S570), ignition is performed with timing on the delay angle side compared to timing FT1 by a delay angle amount ? that tends to decrease as an amount increase coefficient Kf increases (S600 to S680). Because of this, it is possible to suppress the occurrence of knocking without causing the ignition timing to be delayed more than necessary. As a result of this, it is also possible to suppress the worsening of drivability.

Abstract: When a catalyst temperature ?c is higher than a threshold value ?ref (S320), an increase coefficient Kf is set so as to tend to be larger as opening and closing timing of an intake valve is advanced, an intake air flow Qa is larger, and a rotation speed Ne of the engine 22 becomes higher (S340), a target fuel injection quantity Qf* is set based on a product of a basic fuel injection quantity Qftmp set based on the intake air flow Qa and an increase coefficient Kf (S350), and fuel injection of the set target fuel injection quantity Qf* is performed (S360).

Abstract: Upon satisfaction of the condition for making the malfunction diagnosis at least one of the EGR system, the air-fuel ratio sensor 135a and the oxygen sensor 135b during the fuel cut of the engine 22, a fuel cut of the engine 22 and performing the mortaring of the engine 22 by means of the motor MG1 are continued until the completion of the malfunction diagnoses of all objects, of which the each condition for making the malfunction diagnosis is satisfied among the EGR system, the air-fuel ratio sensor 135a and the oxygen sensor 135b. This arrangement ensures the occasions for making the malfunction diagnoses of the EGR system, the air-fuel ratio sensor 135a and the oxygen sensor 135b.

Abstract: An engine ECU executes a program including a step of detecting an opening degree of an accelerator pedal and a state of a power generation command to MG, if a KCS feedback execution condition is met, and a step of detecting a KCS feedback correction amount eakcs, if the accelerator is off and if during power generation load operation, and then substituting a constant AKCSI for eakcs, if eakcs is larger than a threshold value and the ignition timing is on the advance side. Since the KCS feedback correction amount eakcs is adjusted not to be excessively on the advance side, the ignition timing can be retarded promptly at the time of accelerator on, thereby avoiding occurrence of knocking.

Abstract: Under the condition that a catalyst temperature Tc of a purification catalyst reaches or exceeds a preset reference temperature Tcref, when a cooling water temperature Tw of an engine is not lower than a preset reference temperature Twref, the internal combustion engine system of the invention sets a target exhaust recirculation rate EGR* based on a given rotation speed Ne of the engine and a given load factor KL and performs exhaust recirculation control to open an EGR valve at a specific angle or opening corresponding to the set target exhaust recirculation rate EGR*.

Abstract: When a transient knocking occurrence prediction condition is met, that is, when a cooling water temperature ?w is not lower than a threshold value ?wref, an intake air quantity Qa is not smaller than a threshold value Qaref, and an intake air quantity difference ?Qa is not smaller than a threshold value ?Qaref (S230 to S250), ignition is accomplished for the object cylinder at target ignition timing Tf* delayed from timing T1 (S270, S300, S350). Subsequently, ignition is accomplished for the object cylinder in succession at the target ignition timing Tf* advanced by an advance amount ?? that tends to decrease as the rotation speed Ne of an engine 22 increases (S310, S300, S350). Thereby, when the rotation speed Ne of the engine 22 is relatively high, the target ignition timing Tf* can be restrained from advancing rapidly, that is, the target ignition timing Tf* can be restrained from advancing to timing T1 before delay in too short a period of time. As the result, the occurrence of knocking can be restrained.

Abstract: When a catalyst temperature ?c is higher than a threshold value ?ref (S320), an increase coefficient Kf is set so as to tend to be larger as opening and closing timing of an intake valve is advanced, an intake air flow Qa is larger, and a rotation speed Ne of the engine 22 becomes higher (S340), a target fuel injection quantity Qf* is set based on a product of a basic fuel injection quantity Qftmp set based on the intake air flow Qa and an increase coefficient Kf (S350), and fuel injection of the set target fuel injection quantity Qf* is performed (S360).

Abstract: When a condition for the prediction of the occurrence transient knocking has held, that is, when a cooling water temperature ?w is not less than a threshold value ?wref and an intake air flow Qa is not less than a threshold value Qaref and a deviation of the intake air flow ?Qa is not less than a threshold value ?Qaref (S550 to S570), ignition is performed with timing on the delay angle side compared to timing FT1 by a delay angle amount ? that tends to decrease as an amount increase coefficient Kf increases (S600 to S680). Because of this, it is possible to suppress the occurrence of knocking without causing the ignition timing to be delayed more than necessary. As a result of this, it is also possible to suppress the worsening of drivability.

Abstract: An engine ECU executes a program including a step of detecting an opening degree of an accelerator pedal and a state of a power generation command to MG, if a KCS feedback execution condition is met, and a step of detecting a KCS feedback correction amount eakcs, if the accelerator is off and if during power generation load operation, and then substituting a constant AKCSI for eakcs, if eakcs is larger than a threshold value and the ignition timing is on the advance side. Since the KCS feedback correction amount eakcs is adjusted not to be excessively on the advance side, the ignition timing can be retarded promptly at the time of accelerator on, thereby avoiding occurrence of knocking.