Preventive structure for preventing extraordinary deformation of a diaphragm of an oil hermetic type tensioner

摘要

A tensioner for a chain or toothed belt which includes an oil reservoir. Oil contained in the oil reservoir is hermetically sealed by a diaphragm fixed to the oil reservoir by a plug. A pressurizing means is mounted between the diaphragm and the plug. The pressurizing means includes a compression spring and a bowl-shaped spring seat. A diaphragm is urged by the pressurizing means. A detent portion, extending upwardly from the diaphragm, is integrally formed on the surface of the diaphragm facing the atmosphere. The spring seat includes a recess at the central portion of the spring seat so that the detent portion of the diaphragm is engaged with the recess preventing free movement between the diaphragm and the pressurizing means.