LUBRICATION STRUCTURE OF DRIVE FORCE TRANSMISSION DEVICE

PROBLEM TO BE SOLVED: To provide a drive force transmission device which can detect exact hydraulic pressure by a hydraulic sensor while enhancing a freedom of the arrangement of the hydraulic sensor which detects the hydraulic pressure in a piston chamber and reducing the size of a system by a simple constitution.SOLUTION: A drive force transmission device comprises: a hydraulic sensor (40) for detecting hydraulic pressure in a piston chamber (42); an attachment hole (44) which is formed at a back face (41b) of a piston hosing (41), and attaches the hydraulic sensor (40); a working oil introduction hole (45) communicating with the attachment hole (44) at the internal face (41b) of the piston hosing (41); an air bubble separation chamber (46) which is arranged at the internal face (41b) of the piston housing (41), and separates air bubbles accumulated in the working oil introduction hole (45); and an air bubble discharge groove (47) which is formed continuously to the air bubble separation chamber (46). The air bubbles accumulated in the working oil introduction hole (45) are discharged to the air bubble discharge groove (47) from the air bubble separation chamber (46).