To prevent wasteful consumption of energy of an engine by providing an oil pump plate forming a rotor chamber of an oil pump integrally with an oil jet nozzle for jetting lubricating oil to a meshing portion between a power transmission chain and a sprocket.

An oil jet nozzle 4 for jetting lubricating oil toward an meshing portion between a power transmission chain 3 and a crank sprocket 1 is provided integrally with an oil pump plate 5 of a rotor chamber of an oil pump surrounded with an inner rotor 6, an outer rotor 7 and the oil pump plate 5. Injection of the oil jet nozzle 4 is performed by differential pressure between the oil pressure in the rotor chamber of the oil pump and the atmospheric pressure. The inner rotor 6 is rotated by the crank sprocket 1, so that the delivery pressure of the oil pump is also changed according to the rotating speed of the engine. Accordingly, in the engine lubricating oil is positively jetted during high speed rotation.