US Patent 7306233 Combined oil control ring

In mounting a combined oil control ring in a ring groove formed in a piston, the combined oil control ring is mounted in a form that an opening between but ends of an oil ring body is widened. In such an operation, it is likely that a coil expander falls off the oil ring body thus making the mounting operation cumbersome. To overcome such a drawback, a relationship L1<L2 is established. Here L1 means a axial distance between open peripheries of the groove portion and L2 means a maximum axial distance between peripheries of the groove portion.