|The Valvematic system. Click to enlarge.|
Toyota Motor has announced its new variable valve lift mechanism, which it calls Valvematic. Valvematic combines the existing VVT-i (Variable Valve Timing-intelligent), which continuously controls intake valve opening/closing timing, with a new mechanism that continuously controls the intake valve lift volume.
In the case of a new 2.0-liter engine developed by Toyota, Valvematic improves fuel efficiency by 5% to 10% (depending on driving conditions), reduces CO2 emissions, boosts output by at least 10% and enhances acceleration responsiveness, according to the company.
TMC plans to introduce Valvematic shortly, starting with a new vehicle model featuring a 2.0-liter engine.
Valvematic adjusts the volume of air taken in by continuously controlling the intake valve lift volume as well as the timing of valve opening and closing. This boots performance based on the engine’s operational condition, helping vehicles achieve better fuel efficiency and dynamic performance.
Conceptually, this is similar to BMW’s Valvetronic, which also provides infinitely variable valve lift and timing, and delivers an approximate 10% reduction in fuel consumption. To implement Valvetronic, BMW uses an additional eccentric shaft, an electric motor and several intermediate rocker arms.
In 2006, Honda outlined its next-generation approach to valve lift and timing: Advanced VTEC (Variable Valve Timing and Lift Electronic Control System). A-VTEC also combines continuously variable valve lift and timing control with the continuously variable phase control of VTC (Variable Timing Control) to achieve a 13% improvement in fuel efficiency, compared to a production 2.4-liter i-VTEC engine. (Earlier post.)
Nissan also recently introduced its new Variable Valve Event and Lift (VVEL) and continuous valve timing control (C-VTC) technologies, which will be first applied on the Infiniti G37 coupe.
Nissan had earlier announced plans to install the VVEL system, which contributes up to a 10% reduction in fuel consumption and carbon-dioxide emissions compared to an engine of the same displacement without VVEL, on its products worldwide starting from FY07 under the Nissan Green Program 2010.
In the VVEL system, a rocker arm and two types of links close the intake valves by transferring the rotational movement of a drive shaft with an eccentric cam to the output cam. The movement of the output cam can be varied by rotating the control shaft within the DC motor and changing the fulcrums of the links. This makes a continuous adjustment of the valve lift amount possible. (Earlier post.)