Patent ID: 6935978

Claim:
A chain tensioner comprising: a cylindrical housing with a closed end; a plunger slidably fitted into the housing on an inner circumference of the housing; a return spring for imparting outward projection ability to the plunger; a plurality of engagement grooves formed on an outer circumference of the plunger; a first stopper formed on the inner circumference of the housing; and a register ring capable of elastically increasing and reducing its diameter, being engaged with the engagement grooves, any of the engagement grooves being engaged with the first stopper through the register ring to regulate backward movement of the plunger, wherein the register ring is formed of a steel material having a tensile strength of 1000 to 3500 N/mm 2 , and wherein a maximum bending stress of the register ring having an increased diameter, when it is positioned between the engagement grooves, is within a range of 500 to 1700 N/mm 2 .