Abstract
In recent years, two types of variable valve actuators, electromagnetic and electro-hydraulic, have been developed for cam-less engines. The issue of these actuators is how to attain reliable control of the valve landing-velocity deceleration without any electronic position sensor. With this in mind, the former type of actuator is not so resistant to gas-pressure change, while the latter has issues of power waste and limited speed for quick motion control. The authors developed a sensor-less electro-hydraulic valve actuator (EHVA), with a hydro-mechanical position feedback mechanism in 2002 by using a 2-port switching valve. It operated in 24ms for positioning 12mm in stroke. This paper presents acceleration technology for working at an engine speed of 2100rpm and total valve opening time of 19ms, by applying a 3-port switching valve to the EHVA. The parameters of the EHVA were optimized using the bond graphs simulation program, and it succeeded in completing the valve lift motion within 19ms in a full stroke. Moreover, another type of electro-hydraulic valve-actuator for a four-valve engine succeeds to position the intake valve 11mm in displacement within 35ms and to close it under 0.25m/s in landing velocity.
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