Lash adjuster

A lash adjuster comprising:

• a body formed into a bottomed cylindrical shape;
• a plunger which is inserted into the body so as to be movable up and down and has a bottom wall formed with a valve hole and a peripheral wall standing from an outer periphery of the bottom wall and having an oil passage hole formed therethrough, so that the plunger is formed into a bottomed cylindrical shape, the plunger defining a high-pressure chamber between the bottom wall and the body;
• and
• a partitioning member having a tubular shape and inserted into the plunger, the partitioning member having an oil passage end located above the oil passage hole in an inserted state, the partitioning member having a recess defining an oil passage together with the peripheral wall of the plunger therebetween, the partitioning member defining thereinside a low-pressure chamber reserving hydraulic fluid flowing thereinto through the oil passage hole, the oil passage and the oil passage end and causing the hydraulic fluid to flow through the valve hole into the high-pressure chamber,
• wherein the partitioning member has, together with the recess, a press-fit portion which abuts against an inner periphery of the peripheral wall of the plunger when the partitioning member is inserted into the plunger, so that the partitioning member has a deformed cross-sectional shape except for a circular shape when the partitioning member is cut at a same height as the oil passage hole.