Pressure adjustment unit, liquid ejecting head, and liquid ejecting apparatus

A pressure adjustment unit that has a first chamber, a second chamber, and a through hole which extends in a first direction from the first chamber to the second chamber and through which the first chamber communicates with the second chamber, the first chamber, the second chamber, and the through hole forming a flow path supplying a liquid to a nozzle that configures to eject the liquid, the pressure adjustment unit comprising:

• a valve body that has a base end portion housed in the first chamber, a shaft portion protruding in the first direction from the base end portion, and an elastic member provided on a first direction side of the base end portion;
• and
• a casing that has a partition wall which partitions the first chamber and the second chamber and in which the through hole into which the shaft portion is inserted is formed, and that has a first wall which is annular and which protrudes in a second direction opposite to the first direction so as to define the first chamber, wherein
• on a first chamber side of the partition wall, a valve seat, which is annular, is provided around the through hole so as to block the flow path by coming into contact with the elastic member,
• an outer diameter of the base end portion is larger than an outer diameter of the shaft portion,
• an outer periphery of the base end portion has a positioning region in which a distance between an outer periphery surface of the base end portion and an inner periphery surface of the first wall is shorter than a distance between the shaft portion and an inner periphery surface of the through hole, and
• a distance in the first direction between a first-direction-side end portion of the positioning region and a first-direction-side distal end of the shaft portion is shorter than a distance in the first direction between the valve seat and a second-direction-side end portion of the first wall.