Abstract: To suppress pressure fluctuation caused by insertion of arms between disks, which arms support thereon magnetic heads, to reduce disk flutter to thereby reduce disk driving power in a magnetic disk apparatus, there are provided an open space not covered by a shroud, which constitutes a part of a housing structure to cover a side surface of a disk stack, and provided on a downstream side of the arms relative to an airflow moving along surfaces of the disks as the disks rotate, and a channel, which connects a space on an upstream side of the arms and the open space not restricted by the shroud on the downstream side of the arms, the channel being provided with a linear section, which has a rectifying effect on the airflow.

Abstract: In a spray characteristic in a direct injection system gasoline engine use electromagnetic system fuel injector, to a piston cavity a mixture of fuel and air having a combustible concentration is converged and making rich the mixture having the combustible concentration at a side of ignition plug, then an ignition performance is improved and making thin the mixture of fuel and air to a piston direction a combustion performance is improved, namely it is necessary to generate a flat inclined spray. A part of a wall face for forming the injection hole at an outlet portion of the injector is formed with V groove according to two inclination faces with optional angles against a center axial line of the injection hole or a substantially recess shape step-wise rectangular groove having different cut-off depths.