A casing (10) is divided into a cylindrical first case portion (51) integrally having a partition part (54), a second case portion (52) connected to one end of the first case portion in an axial direction and configured to cover a second space (S2), and a third case portion (53) connected to the other end of the first case portion in the axial direction and configured to cover a first space (S1). A signal cable passed through a through hole (54c) of the partition part extends from a sensor (72, 73) to an external connector (81) provided in the second case portion or the third case portion, and is anchored to the first case portion (51) in the vicinity of a through hole (54c) of the partition part.