A device for damping torsional oscillations comprises a support rotatable around an axis. At least one pendulum body is movable with respect to the support. At least one bearing member interacts with at least one raceway integral with the support and with at least one raceway integral with the pendulum body. The bearing member rolls along each raceway around an inactive raceway position. The first region is shaped to filter a first order value of the torsional oscillations by the pendulum body when the bearing member rolls along that first region. Two second regions are beyond an end of the first region. Each second region is shaped to filter a second order value of the torsional oscillations by the pendulum body when the bearing member rolls along one of those second regions. The second order value is strictly lower than the first order value.

The distribution cylinder (CDM) is a simplified, efficient and rational concept for insertion, top sealing and gas evacuation, for a new transformation of the internal combustion engine. It enables the extraction of ninety percent of the components from the old standardized system, which is more than a century and a half old, and which, until now, have performed these vital functions with the known limitations described in this study. The CDM lightens the structure and functionality of the engine, allowing manufacturers to save materials, production time, maintenance and fuel. It allows for the creation of powerful, faster and less polluting engines. It recommends that the four-stroke engine be recalibrated, considerably improving its performance. Thus equipped, it would naturally run faster since it would be freed from the mechanical limitations of its more resistant valve cylinder version The adoption of the timing cylinder, combined with the modern techniques developed for powering today's internal combustion engine, lays the foundation for a new generation of competitive yet lighter and more compact engines. Their torque will not only be more available but also more flexible to serve all uses and all engine sizes.

Disclosed herein is an exhaust insulator structure for a multi-cylinder engine of a vehicle. The structure includes an exhaust manifold, an exhaust gas purifier, and a heat insulator. The engine is able to switch its mode of operation from an all-cylinder operation in which all of four cylinders thereof are activated to a cylinder-cutoff operation in which two of the four cylinders are deactivated to serve as idle cylinders and the other two cylinders are activated to serve as active cylinders, or vice versa. The exhaust manifold includes: idle-cylinder-connected branched exhaust piping communicating with the idle cylinders; and active-cylinder-connected branched exhaust piping communicating with the active cylinders. A portion of the heat insulator facing the active-cylinder-connected branched exhaust piping has an opening that lets air blowing against the vehicle traveling into the heat insulator.

When a stop request to the engine is issued, it is determined whether or not all of the drive cams are large cams. When it is determined that at least one of the small cams is included in the drive cams, the engine is continued to drive for a while and a switch control for switching the drive cams from the small cams to the large cams is executed within the duration. A self-holding type solenoid is used to switch between the small cams and the large cams. In the switch control, a permission to stop the engine is output at a timing when the pin protrudable section of the final cylinder #2 has elapsed.

A multi-cylinder engine exhaust structure disclosed herein includes: four branched exhaust pipes respectively communicating with four cylinders classified into two groups, each being comprised of two of the four cylinders with discontinuous exhaust strokes; two intermediate collecting pipes, each being formed by combining associated two of the four branched exhaust pipes respectively communicating with the two cylinders in an associated one of the two groups; a last collecting pipe formed by combining these intermediate collecting pipes; and an exhaust gas purifier coupled to an exhaust gas downstream end of the last collecting pipe. Two of the four branched exhaust pipes respectively communicating with two of the four cylinders to be activated as two active cylinders while the engine is performing a cylinder-cutoff operation are shorter than the two other branched exhaust pipes respectively communicating with the two other cylinders to be deactivated as two idle cylinders during the cylinder-cutoff operation.

An airflow control valve structure includes a metallic pivot shaft- and a valve body. The valve body includes a connection portion connected to the pivot shaft and a resin valve portion. The pivot shaft includes first and second pivot shaft side press-fit portions. The connection portion includes a first valve side press-fit portion formed integrally with the valve portion and a metallic fitting member including a second valve side press-fit portion. The first valve side press-fit portion is fitted to the first pivot shaft side press-fit portion at an angular position at which a phase of the valve portion is matched with a phase of the pivot shaft. The second valve side press-fit portion is fitted to the second pivot shaft side press-fit portion. The first pivot shaft side press-fit portion is longer than the second valve side press-fit portion.

The vehicle behavior control device comprises an engine control part operable, when an steering speed is greater than a predetermined threshold, and both of a steering wheel angle of a vehicle and the steering speed are increasing, to reduce an output torque of a multi-cylinder internal combustion engine along with an increase in the steering speed, and when the steering speed is equal to or less than the threshold, to stop the reduction of the output torque, and a threshold setting part operable, when the operation mode of the engine is the all-cylinder operation, to set the threshold to a first threshold T.sub.S1, and, when the operation mode of the engine is the reduced-cylinder operation, to set the threshold to a second threshold T.sub.S2 which is less than the first threshold T.sub.S1.

In order to improve the performance of keeping the temperature of an exhaust purifier when a vehicle is running, an engine is provided with an exhaust passage behind a cylinder head in the vehicle longitudinal direction. The exhaust passage includes an exhaust manifold and an exhaust purification system disposed serially in a flow direction of an exhaust gas, the exhaust manifold being located upstream of the exhaust purification system. The exhaust purification system contains a GPF device configured to purify a gas. The exhaust purification system is located below the exhaust manifold, and is disposed so as to overlap the exhaust manifold in the vehicle transverse direction. The exhaust purification system is also disposed so as to protrude with respect to the exhaust manifold rearward in the vehicle longitudinal direction.

A counterweight forms a crankshaft of an engine, and includes: an arm connecting a crank journal and crank pin of the crankshaft; a neck extending from a first connection face of the arm in a direction opposite to the crank pin; and a substantially fan-shaped weight continuous with a portion of the neck opposite to the crank journal. The weight has left and right shoulders continuous with the neck, and each of the shoulders is tilted to be away from the neck at an angle with respect to a horizontal line orthogonal to a crankshaft center when viewed along the crankshaft center, the angle being 15 or more and 22.5 or less.

A cooling structure includes a block-side water jacket formed in a cylinder block, a head-side water jacket formed in a cylinder head, an introducing portion which introduces a cooling liquid from an end of the cylinder block to the block-side water jacket, a discharging portion which discharges a cooling liquid from the other end of the cylinder block to the head-side water jacket, and a spacer member accommodated in the block-side water jacket, and including a peripheral wall which forms an exhaust-side passage and an intake-side passage between a cylinder bore wall and the peripheral wall. The spacer member includes a distribution adjustment mechanism which distributes a cooling liquid introduced to the block-side water jacket between the exhaust-side passage and the intake-side passage.