Patent attributes
In a belt tensioner, a cylinder is mounted to a side of a stationary member positioned in an upper side. A plunger is mounted to a side of a pulley positioned in a lower side. An outer tube sectioning an oil reservoir forming a gas chamber in an upper portion is provided in an outer periphery of the plunger and the cylinder. A first oil passage communicating the gas chamber with a high pressure oil chamber is provided in an upper portion of the cylinder. A second oil passage communicating the high pressure oil chamber with the oil reservoir is provided in the plunger. An orifice hole is provided in the first oil passage. A first check valve closing at an expansion time is provided in the first oil passage, and a second check valve closing at a compression time is provided in the second oil passage.
