<div class="htmlview paragraph">The new intelligent VVT (Variable Valve Timing) -i, is one of the systems developed to improve engine performance. The pulley unit is one of the most important mechanical components of the system.</div> <div class="htmlview paragraph">We developed a suitable process for the four main parts of the VVT-i pulley in order to achieve the target performance at a minimal cost.</div> <div class="htmlview paragraph">The requirements for the mechanical component, the pulley unit, include light weight and compact design as well as a quick response time. To satisfy these requirements, we developed three helical gears having unique profiles and high accuracy, and a timing pulley which must prevent pressurized oil from leaking.</div> <div class="htmlview paragraph">The inner gear is a helical gear with external teeth,and a key way on its inside diameter. The piston gear is a helical gear of which the inside and outside teeth have opposite helix angles. We developed a unique powder compacting technology for these two gears.</div> <div class="htmlview paragraph">The timing pulley is also made of sintered metal alloy. The pulley is impregnated with resin to prevent pressurized oil from leaking through the pores of the sintered metal alloy.</div> <div class="htmlview paragraph">The outer gear is made of a high tensile strength steel plate made by precision stamping. It is distinctive in that its outside shape functions as the hydraulic pressure chamber, and its inner gear has been formed with a cam actuated composition die.</div> <div class="htmlview paragraph">The inner, piston, and outer helical gears are a set of gears which engage each other. They have a large helix angle (30 degrees) and high accuracy accomplished through the netshape production technology, contributing to practical use of the new mechanical component.</div>