VANOS
VANOS is a brand of BMW AG and the BMW name for a camshaft adjustment , i.e. H. a device for influencing the valve timing by controlling the camshaft . The acronym VANOS stands for va riable No camshafts, s control.
functionality
The VANOS unit is arranged between the camshaft and the chain drive. While in a conventional valve train the relative angular position of the camshaft (s) to the crankshaft (camshaft spread) is always constant regardless of the engine load, the VANOS allows the spread of the camshafts to be set in a targeted manner depending on the speed, load and engine oil temperature. The compromise required for all operating points in conventional valve trains is thus resolved.
There are inlet VANOS and double VANOS , i.e. H. only the inlet camshaft or the inlet and outlet camshafts are adjusted.
On the inlet side , the adjustment is primarily used to determine the inlet closure of the valves, which allows torque and power to be optimized. Depending on the cam contour, the maximum torque or maximum power can be positively influenced. A backflow of the gases from the combustion chamber into the intake duct can be avoided by adjusting the speed of the closing time of the intake valve. The adjustment of the intake camshaft is used in the lower and middle speed range for internal exhaust gas recirculation and engine torque increase . At higher speeds, the focus is on improved power output.
On the exhaust side , the variable spread is mainly used to control the amount of residual gas (exhaust gas recirculation inside the engine). This has a positive effect on fuel consumption because the engine throttling and consequently the gas exchange losses decrease with increasing residual gas content . In addition, the process temperature drops and thus the formation of nitrogen oxide. When idling, a very low proportion of residual gas improves running smoothness. Another advantage of the VANOS on the exhaust side is the possibility of improving the exhaust gas dynamics in the lower engine speed range and thus increasing the torque. The adjustment of the exhaust camshaft is therefore used to optimize idling quality or to achieve maximum exhaust gas recirculation rates.
Technical implementation
Initially, there was only a VANOS system with timing adjuster for the intake camshaft (black / white intake VANOS, first installed in the BMW M50 and BMW S50B30 ), but now there are continuously variable double VANOS systems (intake and exhaust camshaft, for the first time in the S50B32 installed) standard on many BMW engines. There are different designs of the VANOS system, i. H. The camshafts can be adjusted using a VANOS gearbox with helical gearing or a vane-type adjuster.
- In the VANOS system with helical gearing , engine oil pressure is alternately applied to a hydraulic piston and axially displaced. A toothed shaft is rotatably mounted in the piston, which converts the piston stroke via the helical toothing into a rotation of the camshaft relative to the driving sprocket.
- In the VANOS system with vane- type adjuster, the adjustment is also made using engine oil pressure. The electromagnetic control valve directs the engine oil to one side of the vane cells following a signal from the engine electronics. For an adjustment in the opposite direction, the oil is directed from the control valve to the other side of the vane cells. The vanes of the vane-type adjuster are connected to the pivotable rotor on the inside and to the camshaft, with the housing also forming the sprocket of the control drive.
A sensor records the current angular position of the camshaft and forwards it to the engine electronics, which compares the value with the specified angle. For high adjustment speeds (e.g. with high-revving engines from BMW Motorsport GmbH ), the VANOS system is supplemented by a radial piston pump that preloads the engine oil to over 100 bar before it is applied to the valves or the hydraulic piston.
Since there are different oil pressures on both sides of the adjustment mechanism, its position can be precisely regulated. The adjustment is infinitely variable in the area of the circular segment, consisting of the pressure chambers for early and late adjustment. In the unpressurized state, the adjustment rotor is held in the late position by a helical spring.
VANOS systems in BMW engines (selection)
- Black / white inlet VANOS (adjustment of the inlet camshaft only in two stages):
- Stepless inlet VANOS:
- - BMW M62B35TU , BMW M62B44TU , BMW M62B46 (BMW X5)
- Stepless double VANOS:
- Stepless high-pressure inlet VANOS:
- - BMW S50B30 , BMW S50B30GT , BMW S70
- Stepless high-pressure double VANOS:
- - BMW S50B32
- - BMW S54
- - BMW S62
- - BMW S85
use
The intake VANOS was first used in September 1992 in the M50 engine of the 5-series BMWs E34 and 3-series BMWs E36 with a displacement of 2.0 liters or more . From the variant of the regular BMW M50 (low-pressure black / white inlet VANOS), the variant used in the BMW M3 (E36) available from October 1992 (stepless high-pressure inlet VANOS) also differs in that it is designed for higher speeds is.
The M50 successor, the BMW M52 , was available with inlet VANOS from its introduction in September 1994, and later, from 1998 as the M52TU with double VANOS. The BMW M3 3.2 was previously the only BMW and the only BMW E36 at all, its engine ( S50B32 ) had already since 1995 double-VANOS. Double VANOS in the series models of BMW AG only came with the 3-series E46 from 1998 and the engine M52TU (technically revised) or its successor M54 from 2000.
In the M5 V10 of the 5 series E60 / 61 , the oil pressure of approx. 100 bar is generated by a separate radial piston high-pressure pump that is driven by the crankshaft. The BMW S50 and BMW S54 already had a high-pressure auxiliary oil pump.
In the motorcycle sector, it has been used in the BMW R 1250 GS since 2018 .
known problems
The black / white inlet VANOS systems and the double vanos units of the M52TU, M54, M56 and S85, S62 engines tend to have problems with the inner sealing rings after a long period of operation (over 100,000 km), as the O- Rings made of nitrile rubber (Buna-N, NBR, nitrile butadiene rubber) tend to wear. Because of this, problems arise when adjusting the camshaft from late to early. It is not possible to replace the sealing rings at BMW with an improved variant, i. H. BMW only offers the entire exchange of the vanos unit (with wear-prone NBR O-rings), whereas improved O-rings are now available in the aftermarket . The repair is not very complicated for qualified personnel, but it does take a certain amount of time. The same applies to the stepless high-pressure VANOS of the M-GmbH engines, although there can also be a rattle here - for example in the BMW S50 - which can be eliminated during an overhaul.
See also
- Valvetronic - BMW camshaft adjustment for fully variable lift adjustment
Individual evidence
- ↑ VANOS in the register information of the German Patent and Trademark Office (DPMA).
- ↑ BMW Lexicon: VANOS / double VANOS. (No longer available online.) Bmw.de, archived from the original on October 13, 2016 ; accessed on October 13, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ With many improvements in the new model year . The BMW M50 six-cylinder: less consumption, more elasticity. In: BMW AG (Ed.): Bayernmotor . BMW employee newspaper. No. 9 , September 1, 1992, ZDB -ID 558618-5 , p. 4 ( bmw-grouparchiv.de [accessed on October 13, 2016]).
- ↑ Harald Unger: VALVETRONIC . The contribution of the valve train to the reduction of CO 2 emissions from the gasoline engine (= Die Bibliothek der Technik . Volume 263 ). Verlag modern industry / Süddeutscher Verlag onpact GmbH, Landsberg am Lech 2004, ISBN 978-3-478-93308-7 , p. 16-19 .
- ↑ Kai Borgeest: Electronics in automotive engineering. Hardware, software, systems and project management (= ATZ / MTZ reference book ). Vieweg + Teubner, 2010, ISBN 978-3-8348-0548-5 .
- ↑ heise.de from September 14, 2018, The new BMW R 1250 GS with variable timing , accessed on July 6, 2019.
