Variable compression ratio apparatus

A variable compression ratio apparatus, comprising:

• a piston pin connecting a piston and a small end portion of a connecting rod;
• a small diameter eccentric cam disposed at an outer circumference surface of the piston in an eccentric state with a center axis of the piston pin;
• a large diameter eccentric cam disposed between an outer circumference surface of the small diameter eccentric cam and an inner circumference surface of the small end portion of the connecting rod in an eccentric state with the center axis of the piston pin;
• a first plunger movably disposed in a first plunger space formed at a side inside the piston pin so as to control a rotational position of the small diameter eccentric cam by controlling oil supplied to first and second chambers formed between the outer circumference surface of the small diameter eccentric cam and an inner circumference surface of the large diameter eccentric cam according to a control position;
• a second plunger movably disposed in a second plunger space formed at an other side inside the piston pin so as to control a rotational position of the large diameter eccentric cam by controlling oil supplied to third and fourth chambers formed between an outer circumference surface of the large diameter eccentric cam and the inner circumference surface of the small end portion according to a control position;
• and
• first and second oil injection nozzles disposed at a side and an other side of a lower portion of the piston, respectively, and configured to control the control position of the first and second plungers by supplying hydraulic pressure to an end portion of the first plunger and an other portion of the second plunger through first and second guide passages formed inside the piston by injecting oil to the lower portion of the piston.