1. Field of the Invention
The present invention relates to a chain tensioner provided with a tensioner arm rockably supported by a fixed structure and relatively slidably engaged with the outside on the loose side of a transmission chain without an end coupling a driving sprocket and a driven sprocket and a tensioner lifter supported by fixed structure for pressing the tensioner arm upon the side of the transmission chain. More particularly, the invention relates to the improvement of a chain tensioner the tensioner arm which is formed by a band elastic member curved toward the transmission chain.
2. Description of Background Art
In such a chain tensioner, it is already well-known as disclosed in Japanese Published Unexamined Patent Application No. Hei2-296046, for example, that a tensioner arm is formed by a band elastic member curved toward a transmission chain.
In Japanese Published Unexamined Patent Application No. Hei7-151197, a chain tensioner is provided in which the width of the middle of a tensioner arm is set to a smaller value than the width of each end. The tensioner arm is rigid and in addition, the middle is directly slidingly engaged with a transmission chain, the chain tensioner is not an object of the invention.
A chain tensioner in which a tensioner arm is formed by a band elastic member curved toward a transmission chain has an advantage wherein the oscillation of the transmission chain can be absorbed by the deflection of the tensioner arm. However, as in a conventional tensioner, the tensioner arm is directly slidingly engaged with the transmission chain. Thus, a problem occurs wherein the surface pressure between the tensioner arm and the transmission chain increases and the wear resistance of the tensioner arm is deteriorated when it is attempted to narrow the width of the middle of the tensioner arm, to enhance the flexibility of the middle and to enhance the oscillation absorption function for the transmission chain.