POWER TRANSMISSION DEVICE AND POWER TRANSMISSION METHOD

A power transmission device (2) comprises a torque converter device (20), a first hydraulic pump (31), a first oil channel (L1), a second oil channel (L2), a third oil channel (L3), a second pressure control valve (33), and a controller (40). The torque converter device (20) has a torque converter (21) and a lock-up clutch (22). The first oil channel (L1) supplies hydraulic fluid from the first hydraulic pump (31) to the torque converter (21). The second oil channel (L2) drains hydraulic fluid from the torque converter (21). The third oil channel (L3) communicates with the first oil channel (L1) and the second oil channel (L2). The second pressure control valve (33) is disposed in the third oil channel (L3). The controller (40) sets the second pressure control valve (33) to an open state when the lock-up clutch (22) is in an engaged state.