Precombustion chamber engine

Abstract

A precombustion chamber engine comprises: a cylinder head defining a main combustion chamber together with a cylinder liner and a piston top surface; a precombustion chamber cap mounted on the cylinder head by inserting a distal end portion of the precombustion chamber cap into an insertion hole formed in the cylinder head; a precombustion chamber holder disposed inside the cylinder head; and a precombustion chamber cap holding member fixed to the precombustion chamber holder and configured to suspend and support the precombustion chamber cap. The precombustion chamber cap includes a reduced diameter portion with a diameter decreasing from a proximal end portion of the precombustion chamber cap to an intermediate portion that has a smaller diameter than the proximal end portion. The precombustion chamber cap holding member is configured to lock the reduced diameter portion and to have a gap between the precombustion chamber cap holding member and the proximal end portion when the precombustion chamber cap holding member suspends and supports the precombustion chamber cap.