Power transmission device for helicopter

A transmission device for a helicopter comprising:

• a casing accommodating a rotating member and having an inner space therein configured to contain oil in a mist form, the casing having an oil sump configured to retain oil in a liquid form;
• a lubrication pump provided in the inner space of the casing and configured to suck and discharge the oil from the oil sump;
• a supply port provided in the inner space of the casing and configured to inject the oil from the lubrication pump to the rotating member;
• a lubrication passage connecting the lubrication pump and the supply port;
• a connection portion provided in a part of the lubrication passage, which part is disposed outside the casing;
• a direction control valve provided in the inner space of the casing and located downstream of the lubrication pump and upstream of the connection portion in the lubrication passage with respect to a flow direction of the oil, the direction control valve being configured to open the lubrication passage at a normal time when a hydraulic pressure in the lubrication passage exceeds a first predetermined value and to close the lubrication passage at a dry-run time when the hydraulic pressure is equal to or lower than the first predetermined value so as to stop the oil supply from the lubrication pump to the connection portion;
• an oil reservoir provided upstream of the supply port in the lubrication passage and reserving the oil therein, the oil reservoir being configured to drop the oil reserved therein by gravity to the connection portion at the dry-run time when the hydraulic pressure is equal to or lower than the first predetermined value;
• and
• an opening provided upstream of an outlet of the oil reservoir and above the outlet of the oil reservoir.