Seminar On Valvetronic Engine Technology Report Download
The Valvetronic engine is the world’s first engine without a throttle butterfly. Valvetronic allows the engine to run without a throttle butterfly, the cylinder charge being determined under part load as a function of the valve-opening period. The intake and outlet camshafts are driven by variable cam adjustment, BMW’s Vanos technology.
A further advantage of this concept is that it allows worldwide use of the proven three-way catalyst for emissions management, thus meeting even the strictest emissions standards in the US.
Innovative technology was essential in order to reach the demanding objectives and functional requirements desired. However, at the same time, this concept demanded the utmost of the electronic control and management systems in the engine.
A comparison with the human being clearly explains how Valvetronic works: Whenever we are required to make a great effort, we human beings breathe in a deep and long process of ventilation. Whenever we need less air, we do not throttle the supply of air by, say, closing our nose or our mouth, but simply breathe in a shorter, flatter process of ventilation. In a conventional combustion engine the throttle butterfly is basically comparable to a human being keeping his nose or mouth at least partially closed. With its large valve lift (= deep, long ventilation) and short valve lift (= flat, short process of ventilation), Valvetronic, on the other hand, is able to breathe in the same way as nature – always in line with current requirements, without any kind of throttling effect and therefore with maximum efficiency.
Accordingly, the Valvetronic engine no longer requires a throttle butterfly, which has quite literally restricted the free ventilation of the internal combustion engine ever since its invention. Now Valvetronic replaces this conventional function by infinitely variable intake valve lift, offering a quantum leap in technology quite comparable to the changeover from the carburetor to fuel injection.
Its most important feature is that it is able to save at least 10 per cent fuel throughout the entire operating range relevant to the customer, with a corresponding reduction in exhaust emissions, regardless of fuel quality. And a further important point is that the efficient operation of Valvetronic does not require any unusual types and grades of oil possibly difficult to obtain.
Working Of Valvetronic Engine
Compared with conventional twin-cam engines with finger followers, Valvetronic employs an additional eccentric shaft, an electric motor and several intermediate rocker arms, which in turn activates the opening and closing of valves. If the rocker arms push deeper, the intake valves will have a higher lift, and vice-versa. Thus, Valvetronic has the ability to get deep, long ventilation (large valve lift) and flat, short ventilation (short valve lift), depending on the demands placed on the engine
Cylinder heads with Valvetronic use an extra set of rocker arms, called intermediate arms (lift scaler), positioned between the valve stem and the camshaft. These intermediate arms are able to pivot on a central point, by means of an extra, electronicly actuated camshaft. This movement alone, without any movement of the intake camshaft, can open or close the intake valves.
The Valvetronic system is based on BMW’s established double VANOS system, which steplessly varies the timing of both the inlet and exhaust cams. However, the Valvetronic system adds variable valve lift to the inlet cam, achieved by the use of a lever positioned between the camshaft and the inlet valves. Valvetronic varies the timing and the lift of the intake valves. The Valvetronic system has a conventional intake cam, but it also uses a secondary eccentric shaft with a series of levers and roller followers, activated by a stepper motor.
- Valve lift is variable between 0 and 9.7 mm.
- Adjustment of the worm gear from one extreme to the other takes 300 milliseconds.
- Combined with double-vanos valve timing technology, the camshaft angle relative to the crankshaft can be adjusted by up to 60°.
- The intermediate arm is finished to a tolerance of 0.008 mm.
- The cams controlling the eccentric shaft are machined to tolerances of a few hundredths of a millimeter.
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