Abstract: A joined assembly includes: a first member; a second member which has a facing part facing the first member in a thickness direction thereof; and joints lying along the facing part to join the first member and the second member to each other. The joints include: a pair of end joints respectively located at the opposite end portions of the facing part; and an intermediate joint located between the end joints and having a lower joining strength than the end joints. The end joint includes a fastening member mechanically joining the first member and the second member. The intermediate joint includes a friction-stirred part joining the first member and the second member by friction stir.

Abstract: The disclosure describes a structure of a main combustion chamber of a diesel engine of a direct injection type in which a main combustion chamber having a peripheral wall which includes a plurality of collision walls and guide walls which are disposed alternately to each other in a circumferential direction of the piston, characterized in that; each guide wall includes an upstream portion and a downstream portion with a boundary therebetween in the direction of the swirl, a radial distance from the center of the chamber to the boundary is shorter than a radial distance from the center of the chamber to other portions and each upstream portion has a longer radius of a curvature and a circumferential length than each downstream portion so that the inner periphery of the chamber has a pin-wheel-like shape.