This multi-cylinder engine intake structure is provided with a fresh air distribution chamber into which a plurality of fresh air distribution openings communicating with the individual intake ports are opened, and a gas collection chamber. The gas collection chamber includes a communication region into which a first communication opening communicating with the fresh air distribution chamber is opened, a first mixture region into which an air inlet and an EGR gas inlet are opened and which is positioned upstream of the communication region in a flow direction of a mixture gas of air and EGR gas, and a second mixture region positioned downstream of the communication region in the flow direction of the mixture gas.

An EGR gas distributor includes a gas chamber, a gas inflow passage to introduce EGR gas on its upstream side, gas outflow passages to discharge the EGR gas to branch pipes on their downstream side. An inner wall on a downstream side of the gas chamber is divided into downstream-side divided walls corresponding to the respective gas outflow passages, and the downstream-side divided walls are curved or slanted to be of protrusion-like shape protruding toward the corresponding gas outflow passages. Downstream-side dividing ridges are provided each between the adjacent downstream-side divided walls. An inner wall on the upstream side of the gas chamber is placed to face the downstream-side inner wall and provided with at least one upstream-side ridge protruding toward the downstream-side divided walls in each area corresponding to the downstream-side divided walls.

An EGR gas distributor includes a gas chamber, a gas inflow passage to introduce EGR gas on its upstream side, gas outflow passages to discharge the EGR gas to branch pipes on their downstream side. An inner wall on a downstream side of the gas chamber is divided into downstream-side divided walls corresponding to the respective gas outflow passages, and the downstream-side divided walls are curved or slanted to be of protrusion-like shape protruding toward the corresponding gas outflow passages. Downstream-side dividing ridges are provided each between the adjacent downstream-side divided walls. An inner wall on the upstream side of the gas chamber is placed to face the downstream-side inner wall and provided with at least one upstream-side ridge protruding toward the downstream-side divided walls in each area corresponding to the downstream-side divided walls.

A turbocharger is provided and includes a compressor housing and a recirculation slit and a recirculation passage provided at an inlet of the compressor housing to enable air flowing into the compressor to be recirculated. A gas supply part supplies blow-by gas towards the inlet of the compressor housing to allow blow-by gas to be joined with air recirculated through the recirculation slit and the recirculation passage and to guide recirculating air towards a compressor wheel.

A turbocharger is provided and includes a compressor housing and a recirculation slit and a recirculation passage provided at an inlet of the compressor housing to enable air flowing into the compressor to be recirculated. A gas supply part supplies blow-by gas towards the inlet of the compressor housing to allow blow-by gas to be joined with air recirculated through the recirculation slit and the recirculation passage and to guide recirculating air towards a compressor wheel.

An EGR system is configured to allow a part of exhaust gas discharged from an engine to an exhaust passage to flow as an EGR gas to an intake passage through an EGR passage to return to the engine. The EGR system includes a heating film provided on an inner wall of at least one of the intake passage through which the EGR gas flows, i.e., an intake manifold, and the EGR passage, at least one pair of a positive electrode and a negative electrode to energize the heating film, a water temperature sensor and an intake temperature for detecting a warm-up state of the intake passage and the EGR passage, and an electronic control unit configured to control energization of the heating film from before start of EGR based on the detected warm-up state.

An EGR system is configured to allow a part of exhaust gas discharged from an engine to an exhaust passage to flow as an EGR gas to an intake passage through an EGR passage to return to the engine. The EGR system includes a heating film provided on an inner wall of at least one of the intake passage through which the EGR gas flows, i.e., an intake manifold, and the EGR passage, at least one pair of a positive electrode and a negative electrode to energize the heating film, a water temperature sensor and an intake temperature for detecting a warm-up state of the intake passage and the EGR passage, and an electronic control unit configured to control energization of the heating film from before start of EGR based on the detected warm-up state.

An EGR device is provided with: an EGR passage for allowing a portion of exhaust gas from an engine to flow to an intake passage; an EGR valve for adjusting an EGR flow rate through the EGR passage; a throttle valve provided in the intake passage; and an electronic control device which calculates a fully closed reference intake pressure based on an operating state of the engine during EGR valve fully-closing, and which diagnoses an abnormality due to valve-opening locking of the EGR valve based on the calculated fully closed reference intake pressure. The ECU determines a foreign matter biting abnormality of the EGR valve based on the intake pressure, and based on the result of adding the fully closed reference intake pressure, calculated according to the rotational speed and the load of the engine, to an intake-pressure increase allowance calculated according to the rotational speed.

An EGR device is provided with: an EGR passage for allowing a portion of exhaust gas from an engine to flow to an intake passage; an EGR valve for adjusting an EGR flow rate through the EGR passage; a throttle valve provided in the intake passage; and an electronic control device which calculates a fully closed reference intake pressure based on an operating state of the engine during EGR valve fully-closing, and which diagnoses an abnormality due to valve-opening locking of the EGR valve based on the calculated fully closed reference intake pressure. The ECU determines a foreign matter biting abnormality of the EGR valve based on the intake pressure, and based on the result of adding the fully closed reference intake pressure, calculated according to the rotational speed and the load of the engine, to an intake-pressure increase allowance calculated according to the rotational speed.

A method to determine the mass of air trapped in each cylinder of an internal combustion engine, which comprises determining, based on a model using measured and/or estimated physical quantities, a value for a first group of reference quantities; determining, based on the model, the actual inner volume of each cylinder as a function of the speed of rotation of the internal combustion engine and of the closing delay angle of the intake valve; and calculating the mass of air trapped in each cylinder as a function of the first group of reference quantities and of the actual inner volume of each cylinder.