Variable valve timing apparatus

The present invention relates to a variable valve timing apparatus including: an actuator housing having a given space portion at the inside thereof; an upper plunger insertedly mounted inside the upper portion of the actuator housing in such a manner as to move upward and downward; a lower plunger insertedly mounted inside the lower portion of the actuator housing in such a manner as to allow the upper plunger to move upward and downward; an oil chamber formed to allow oil to be circulated upwardly and downwardly or to allow the flow of oil to be blocked through a head formed on the top end periphery of the upper plunger in accordance with the upward and downward movements of the upper plunger; and a communicating passage portion adapted to allow the upper and lower end portions of the oil chamber to communicate with each other in accordance with the upward and downward movements of the lower plunger and to adjust the flow of oil flowing thereon to control the speeds of the upward and downward movements of the upper plunger.