Cylinder Deactivation: a Technology with a Future Or a Niche Application?: Schaeffler Symposium

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Cylinder Deactivation A technology with a future or a niche application? N O D H I O E A S M I O u e n l O A N G A D F J G I O J E R U I N K O P J E W L S P N Z A D F T O I E O H O I O O A N G A D F J G I O J E R U I N K O P O A N G A D F J G I O J E R O I E U G I A F E D O N G I U A m u H I O G D N O I E R N G M D S A U K Z Q I N K J S L O G D W O I A D U I G I r z H I O G D N O I E R N G M D S A U K n m H I O G D N O I E R N G E Q R I U Z T R E W Q L K J P B E Q R I U Z T R E W Q L K J K R E W S P L O C Y Q D M F E F B S A T B G P D r D D L R a E F B A F V N K F N K R E W S P D L R n E F B A F V N K F N t R E C L P Q A C E Z R W D E s t R E C L P Q A C E Z R W D K R E W S P L O C Y Q D M F E F B S A T B G P D B D D L R B E z B A F V r K F N K R E W S P z L R B E o B A F V N K F N J H L M O K N I J U H B Z G D P J H L M O K N I J U H B Z G B N D S A U K Z Q I N K J S L W O I E P ArndtN N bIhlemannA U A H I O G D N p I E R N G M D S A U K Z Q H I O G D N w I E R N G M D A m O e P B D B H M G R x B D V B D L d B E O I p R N G M D S A U K Z Q I N K J S L W O Q T V I E P NorbertN z R NitzA U A H I r G D N O I q R N G M D S A U K Z Q H I O G D N O I y R N G M D E K J I R U A N D O c G I U A e m s q f G D L N C a W Z Y K F E Q L O P N G S A Y B G D S W L Z U K O G I K C K P M N E S W L N C u W Z Y K F E Q L O P P M N E S W L N C t W Z Y K M O T M e U A N D u y G e U V z N H I O z D R V L G R a K G E C L Z E M S A C I T P M O S G R U C Z G Z M O Q O D N V U S G R V L G R m K G E C L Z E M D N V U S G R V L G R x K G T N U G I C K O I J l R D C a j O P M N E r A Z T E F N a X J R C N I F Z K M N D A B O N Y A M E C R J G N I N E E O M N Y A Z T E W N l X J R C N I F E E O M N Y A Z T E W N y X D C O S M Q O V a r i a b i l i t y a V U S C L V z o H N V u a J K U V X E S Y M N R E E W C L O M E P S C V C Y L i N E W C L V V F H N V o a J K U V Y L i N E W C L V V F H N V J Y I J G I N R L U n G D I v K R E E O M N F X T J G L D Q F H B v t G U P W Q V Z E S L N F A M U A N J Y Q Y O B R n L N F X T J O L D Q F H B w n G O B R n L N F X T J O L D Q K P E L S V C E S O d M N V e S E Y L i N E F V B N C T E N A O D F E C K t a C T S V Q D E F B N I M B L P O P Q A Y C B E F V B N R T E N A O D F E C Q A Y C B E F V B N R T E N Z B P E J Q Y A H I e C W Q Y J A O B R n L L N C a P Z Y K F E Q L O P N G F G r g H N W E D W C Y Q B E B G B A Y X S W A D C B P L M I J N T B G H U A Y X S W A D C B P L M I J T N E H L O P M S E r U N O P L M Q A Y C B U H G F T S A C V B O F E T Z H N A X C F t j K J Z M H Z D H N B N U I O P L K U H G F D S A C V B O F E T U I O P L K U H G F D S A C C R O E E G B Q O P B D E G B E Q P M N E S G E N D R R T C A S N I N R O A X E V E D K D L a g Q S W I E R T R Q H G F D L G E N D E R T C A S N I N R Q H G F D L G E N D E R T C B E F S H E C E F H O K H E S C B U P S K U P P L U Y G S G E B E R Z Y L I N D E R Z N U B F I M b C H S E H E B U P S K U P P L U N G S G E B E R Z Y B U P S K U P P L U N G S G S O B P I O S G B Z N J I O P S D C V F E W C V T E E N M Z G O H A S E D C K L P S X W E W C E C B S t P O I O D C V F E W C V T E B N M Z G O H A S E11D C V F E W C V T E B N M Z F E I W R E Q R I U Z T R E W Q L K J H G F D S A M O B V C X Y M L M O K N I J B H U Z G F D G V T Q U j x R E L K J H G F D S A M M B V C X Y M L M O L K J H G F D S A M M B V C C W D A Y W T R D X E S Y W A T P H C E Q A Y W S X Z E C R F V E G B Z H N U J M I K O Q A Y L M R T X A g Y W P H C E Q A Y W S X E E C R F V E G B Z P H C E Q A Y W S X E E C R P J M F I J H L M O K N I J U H B Z G V T F C R D X V S N W A S R E C V F H K N U T E Q T F C X V N H O U b I J B Z G V T F C R D X E S N W A S R E C V B Z G V T F C R D X E S N W C G T V D G L E T U O A D G J L Y C B M W R Z I P V O N M I Q W u R T O I J E U H B Z G W R Z V T F L U J a D G Y C B M W R Z I P S F H K T V N Z L M O Y C B M W R Z I P S F H K T J T Z G E T O I Z R W Q E T U O M B C Y N V X A D G B L K H E S Y S C B F G M H T I L Q N V X D B P O R U T E T M B C Y N V X A D G J L K H E S Y S C B M B C Y N V X A D G J L K H V W M C R W U U M P I Z R W O U Z T W H N E D K U N W P O N C A L V I K n D V S G W J P N E D C S K U P O W R W Z T W H N E D K U N W P O N C A L V I K Z T W H N E D K U N W P O N A K D P J K P S D F G H J K L P O I U Z T R E W Q Y X C V B N M I Q W u R T Z B C S D G T R E H K L P F L K J K O I U Z T R E W Q Y X C V B N M I Q W u O I U Z T R E W Q Y X C V B L S J T D S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S t R E C L P Q A C E Z R W D X A Y H A S g S V N P I Z R W Q S C G Z N J I M N S t R V N P I Z R W Q S C G Z N J E K J R C K O I J G R D C K I O P M N E S W L N C X W Z Y K F E D i O P N G S A Y B G D S W L Z U K O G I K C K P M N E S W L N C X W Z Y K F E D i O P P M N E S W L N C X W Z Y K M O T Y Q O G N T Z D S Q O M G D N V U S G R V L G R V K G E C E Z E M S A C I T P M O S G R U C Z G Z M q g O D N V U S G R V L G R V K G E C E Z E M D N V U S G R V L G R V K G T N U E I N R L U J G D I N G R E X O M N Y A Z T E W N F X J L R N I F Z K M N D A B O i z q a t s l o k z I N E X O M N Y A Z T E W N F X J L R N I F E X O M N Y A Z T E W N F X D C O O V C E S O P M N V C S E Y L J N E W C L V V F H N V R D J K U V X E S Y M N R E z W C L O M E P S C V C Y L J N E W C L V V F H N V R D J K U V Y L J N E W C L V V F H N V J Y I Z Q Y A H I N C W Q Y J A O B R E L N F X T J O L k Q F H B Q F G U P W Q V Z E g L N F A M U A N J Y Q Y O B R E L N F X T J O L s Q F H B Q F G O B R E L N F X T J O L a Q N J K V N J R A K D O B N J O R O I D F N G K L D F M G O I Z P M F D R N Q B O Y R X w N G K M N S R D O J N J O I D F N G K L D F M G O I Z P M F D R O I D F N G K L D F M G O I A A O O U A N D O N G I U A R N H I O G D N O I E R N G M g S A U K Z Q I N K J e L t O m p l I E P N N R A U A H I O G D N O I E R N G M t S A U K Z Q H I O G D N O I E R N G M k U D M B B D B H M G R e B D P B D L R B E F B A F V N K F N k R E W S P L O C Y n g M F E F B S A T B G P D B D D L R B E F B A F V N K F N q R E W S P D L R B E F B A F V N K F N A A O E U A N D O N G I U A R N H I O G D N O I E R N G M D H A g K Z Q M N K o g L W i k a p I E P N N R A U A H I O G D N O I E R N G M D S A l K Z Q H I O G D N O I E R N G M D M O T M Q O G N T Z D S Q O M G D N V U S G R V L G R V K G u C L Z L M o A C z i P M O S G R U C Z G Z M O Q O D N V U S G R V L G R V K G E C L Z E M D N V U S G R V L G R V K G U D M T B D B H M G R I B D P B D L R B E F B A F V N K F D e a c t i v a t i o n D M F E F B S A T B G P D B D D L R B E F B A F V N K F N K R E W S P D L R B E F B A F V N K F N F E I D R E Q R I U Z T R E W Q L K J H G F D S A M M B V C X Y M L f O r z s J e H U Z G F D G V T Q U o t R E L K J H G F D S A M M B V C X Y M L M O L K J H G F D S A M M B V C C I s f S t R E C L P Q A C E Z R W D X A Y H B M W R Z I R F V E G t Z r N U J M I K O Q A Y L M R T X A z Y W P H C E Q A Y W S X E E C R F V E G B Z P H C E Q A Y W S X E E C R P J M N I J H L M O K N I J U H B Z G V T F C R D X E S N W A S R E C V F H K N U T E Q T F C X V N H O U b I J B Z G V T F C R D X E S N W A S R E C V B Z G V T F C R D X E S N W C G T J D G L E T U O A D G J L Y C B M W R Z I P S F H K T V N Z L M O I J E U H B Z G W R Z V T F L U J r D G Y C B M W R Z I P S F H K T V N Z L M O Y C B M W R Z I P S F H K T J T Z U E T O I Z R W Q E T U O M B C Y N V X A D G J L K H E S Y S C B F G M H T I L Q N V X D B P O R U T E T M B C Y N V X A D G J L K H E S Y S C B M B C Y N V X A D G J L K H V W M O R W U U M P I Z R W O U Z T W H N E D K U N W P O N C A L V I K n D V S G W J P N E D C S K U P O W R W Z T W H N E D K U N W P O N C A L V I K Z T W H N E D K U N W P O N A K D L J K P S D F G H J K L P O I U Z T R E W Q Y X C V B N M I Q W u R T Z B C S D G T R E H K L P F L K J K O I U Z T R E W Q Y X C V B N M I Q W u O I U Z T R E W Q Y X C V B L S J A D S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S t R E C L P Q A C E Z R W D X A Y H A S e S V N P I Z R W Q S C G Z N J I M N S t R V N P I Z R W Q S C G Z N J E K J I C K O I J G R D C K I O P M N E S W L N C X W Z Y K F E D i O P N G S A Y B G D S W L Z U K O G I K C K P M N E S W L N C X W Z Y K F E D i O P P M N E S W L N C X W Z Y K L S J A D S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S t R E C L P Q A C E Z R W D X A Y H A S u S V N P I Z R W Q S C G Z N J I M N S t R V N P I Z R W Q S C G Z N J E K J I C K O I J G R D C K I O P M N E S W L N C X W Z Y K F E D i O P N G S A Y B G D S W L Z U K O G I K C K P M N E S W L N C X W Z Y K F E D i O P P M N E S W L N C X W Z Y K M O T M Q O G N T Z D S Q O M G D N V U S G R V L G R V K G E C E Z E M S A C I T P M O S G R U C Z G Z M o x O D N V U S G R V L G R V K G E C E Z E M D N V U S G R V L G R V K G T N U G I N R L U J G D I N G R E X O M N Y A Z T E W N F X J L R N I F Z K M N D A B O B N x z p e w n q m I N E X O M N Y A Z T E W N F X J L R N I F E X O M N Y A Z T E W N F X D C O S V C E S O P M N V C S E Y L J N E W C L V V F H N V R D J K U V X E S Y M N R E i W C L O M E P S C V C Y L J N E W C L V V F H N V R D J K U V Y L J N E W C L V V F H N V M O T M Q O G N T Z D S Q O M G D N V U S G R V L G R V K G E C E Z E M S A C I T P M O S G R U C Z G Z M a x O D N V U S G R V L G R V K G E C E Z E M D N V U S G R V L G R V K G A A O R U A N D O N G I U A R N H I O G D N O I E R N G M D S A U K Z Q I N K J S L W O z w u I E P N N R A U A H I O G D N O I E R N G M D S A U K Z Q H I O G D N O I E R N G M D 174 Valvetrain Systems 11 175

Introduction driving pleasure and comfort with regard to Complete engine operation Cylinder deactivation mode acoustics and vibration characteristics. An additional key success factor that can help this technology to be deployed in a One of the ways manufacturers can mini- more mainstream fashion is that it can be mize fuel consumption is to downsize the integrated into existing engine concepts at engines they offer. A cylinder’s volume can acceptable costs. only be restricted to a certain extent, how- que que ever, if the thermodynamically ideal volu- r To r To metric capacity of 400 to 500 cm3 per cylinder is to be retained. In practice, downsizing Designs Road-resistance therefore frequently leads to a reduction in curve the number of cylinders. “Temporary downsizing” in the form of cylinder deactivation offers an attractive The most consistent form of cylinder deac- compromise, since this allows an engine to tivation is to not only to cut injection and ig- shift its operating mode to achieve the spe- nition for the respective cylinders, but also Engine speed Engine speed cific consumption figures it is rated for, espe- to stop all moving parts (including the pis- cially when low loads and operating speeds tons). This, in turn, utilizes the entire thermo- Figure 2 Operating data map and driving resistance curve: The operating ranges associated with the are encountered. At the same time, the driver dynamic potential available and consider- lowest specific fuel consumption are approached in cylinder deactivation mode (graphic on still has a sufficiently powerful engine at his or ably reduces the friction that occurs inside the right) and not when all cylinders are operating her disposal that ensures the same level of the engine. It goes without saying that compromises must be made when it comes to Effect and potential Manufacturer Type of engine Valve concept Status the ignition sequence and dynamic balanc- GM 6.0-liter V8-6-4 engine Pushrod actuation, SOP/EOP 1980 ing. What is much more significant, howev- switchable rocker arm pivot point er, is the outlay required to separate the en- 3.9-liter V6 engine Switchable roller tappet EOP 2008 gine into an area that continues to run while When there is a specific performance re- the other area is activated and deactivated quirement, the cylinders that are still being 5.3-liter V8 engine Switchable roller tappet Volume production as required. Even the coupling mechanisms operated following cylinder deactivation 4.3-liter V6 engine Switchable roller tappet Volume production on the crankshaft and camshaft cannot be must generate a higher mean pressure. This 6.0-liter V8 engine Switchable roller tappet Volume production justified by a cost-benefit analysis, which is load-point shifting leads to a reduction in Daimler 5.0-liter V8 engine Switchable rocker arm; MB EOP 2005 why implementation of the system looks the throttle losses of the engine and ulti- 5.8-liter V12 engine Switchable rocker arm; MB EOP 2002 somewhat bleak at present. mately helps to conserve fuel (Figure 2). De- Almost all cylinder deactivation systems activating the valves also reduces friction 5.7-liter V8 engine Switchable roller tappet Volume production Chrysler currently used interrupt the injection and ig- loss in the cylinder head, which further min- 6.4-liter V8 engine Switchable roller tappet Volume production nition as well as valve actuation sequences imizes consumption. Honda 3.5-liter V6 engine Switchable rocker arm Volume production for the cylinders to be deactivated (Figure 1). The potential for reducing consumption AMG 5.5-liter V8 engine Switchable pivot element Volume production Today’s applications range from engines when an engine is operated on two as op- with 4 to 12 cylinders. Analyses conducted posed to four cylinders can be illustrated in VW 1.4-liter inline Cam shifting system, VW/Audi Volume production 4-cylinder engine by Schaeffler, however, reveal that tempo- a simulation exercise carried out on a 1.4-li- Group rarily deactivating one of the cylinders in a ter four-cylinder engine. Line “a” plots the 4.0-liter V8 engine Cam shifting system, Audi Volume production three-cylinder engine can also further re- mean pressures at which the engine oper- 6 3/4-liter V8 engine Switchable roller tappet Volume production duce consumption. ating in two-cylinder mode can achieve its 6 3/4-liter V8 engine Switchable roller tappet Volume production To ensure that the engine continues to optimum combustion point (8 crankshaft 6.5-liter V12 engine Only the fuel injection supply is cut Volume production run smoothly enough, only certain cylinders degrees after TDC) (Figure 3). are deactivated in accordance with the igni- When higher mean pressures are intro- Figure 1 Examples of engine concepts featuring cylinder deactivation tion sequence. duced in two-cylinder mode, the ignition se- 176 Valvetrain Systems 11 177

operating the engine above these plotted The heat generated by the confined ex- Alternating cylinder deactivation Difference map 1,4 l 4 cyl versus 1,4 l 4 cyl with 2 cylinder operation points in two-cylinder mode leads to addition- haust gas not only makes the cylinder cool e in bar in e al fuel consumption. This line can also drop down more slowly; the larger quantity of Current technology dictates that specific considerably below line “b”, depending on the gas also produces very different pressures cylinders in an engine be targeted for deac- essur b application and customer requirements. inside the cylinder and thus to greater ir- tivation. Schaeffler is currently researching a Theoretical switching regularities on the crankshaft. The gas concept for four-cycle engines that will al- load line pressures that form during initial compres- low all cylinders to be deactivated after ev- fective pr fective a Optimum sion when the exhaust valves are closed ery ignition cycle and reactivated during the combustion Technical implementation can even be higher than those experienced next. Cylinder deactivation thus alternates during combustion. The support forces not within a single deactivation phase and not

eak mean ef mean eak only place substantial loads on the piston each time a new deactivation mode is intro- Br Engine speed in rpm and cylinder, but also lead to considerable duced (Figure 5). The benefit is a more well- frictional losses. The deactivation phase balanced temperature level inside the com- Figure 3 Reduction in fuel consumption as a Deactivation mode must then be maintained for a longer peri- bustion chambers and consistent firing result of cylinder deactivation od of time to ensure that a positive overall intervals for three-cylinder engines operat- (simulation result) When an engine switches to cylinder deacti- effect is achieved. ing in deactivation mode. vation mode, there are two basic strategies As Figure 4 shows, peak pressures drop Especially when such a design setup is quence must be retarded to avoid knocking. that can be implemented for introducing a when the residual gas cools down as well used, the losses encountered when transi- The resulting effect is that combustion no lon- charge in the cylinders (refer to Figure 4): as when gas diffuses from the combustion tioning from operating mode to deactivation ger achieves its peak efficiency, and addition- –– Confine the exhaust gas in the com- chamber into the crank assembly (blow by). mode must be kept as low as possible. This al fuel is consumed. Opening the throttle valve bustion chamber after the combustion Simulation calculations reveal that after an is why residual gas is not confined, as the further counteracts this and has a positive im- process has been completed engine has gone through approximately ten above illustration depicts. Filling the cylin- pact on consumption in cylinders running –– Introduce fresh air revolutions, the pressure in the cylinder ders with fresh air also brings with it draw- higher mean pressures. Line “b” represents Both variants allow the gas confined to act reaches the level that was present when backs due to the lower level of charge the theoretical switchover or transition line, as as a pressure or thrust spring. fresh air was confined. movement. The latter is only possible with a direct- One variant appears to be particularly fa- Exhaust gas is trapped Fresh air is trapped injection engine. The differences in com- vorable in this context because it allows a pression between the cylinders are less small, precisely measured quantity of residu- pronounced in this application, and the al gas to be confined in the combustion e switchover phase can be better coordinat- chamber. The suction or induction effect that ed as a result. This variant also requires results from the expansion does not last long essur compromises to be made, however, since enough to lead to a noticeable loss in engine the air in the combustion chamber loses all oil. The inherent benefit is that when the tumble or swirling motion produced at the working cycle starts again, the required

Cylinder pr intake point after just a few cycles. De- quantity of fresh air can be introduced with- pending on the geometry of the combus- out any restrictions in flow. The first and fol- tion chamber, it may still be possible to re- lowing combustion strokes then take place fire the engine in this operating state. The + Gas spring + Gas spring ignition timing will have to be adjusted, + Slow cool down + Normal compression -> “Rolling” Cylinder deactivation 3-cylinders though, whereby the efficiency of the com- - Increased compression -> Smooth engine running Cylinder number Highly irregular engine running + High torque neutrality bustion process suffers by a correspond- 1 3 2 1 3 2 - No torque neutrality ing amount. Care must also be taken to ensure that no suction or vacuum effect is Source: MTZ "The New AMG 5.5-liter V8 Naturally Aspirated Engine with Cylinder Shut off“ 0 240 480 720 960 1,200 1,400 produced in the combustion chamber, Direct injection allows the realization „Fresh air trapped“ since this would lead to engine oil being Figure 5 Pattern of alternating cylinder drawn in. deactivation (the red phase designates Figure 4 Possible options for introducing a cylinder charge and their effects in cylinder deactivation mode the active operating mode) 178 Valvetrain Systems 11 179

without a decrease in efficiency. To ensure Switchover mode Control of that the quantity of residual gas and the vac- AVS Actuators uum pressure assume optimum levels, the One of the logical requirements of this mode is Engine torque exhaust valves must be controlled very pre- that the driver should not be made aware of it Filling-target cisely as is the case with the fully variable when the switch is made. In other words, the Cylinder filling UniAir system developed by Schaeffler. This switchover must take place in a torque-bal- system realizes any required stroke in the anced manner. The transition between both Actual filling cycle and can completely close the valves modes must also occur very quickly so that the when needed. At least one two-stage switch engine can provide good response at all times. 100 % 100 % must be fitted to deactivate the valves on the When the switch is made from operation Ignition angle- intake side. Simulations carried out on a on all cylinders to operation on half of the efficiency three-cylinder engine point to lower overall cylinders, the position of the throttle valve fuel consumption figures being achieved (cylinder charge), ignition timing, and fuel 50 % when such a refined alternating cylinder de- supply are adapted accordingly to prevent a activation concept is used in place of a con- drop in torque (refer to Figure 7). To this end, Time ventional setup (Figure 6). the charge is first increased and the ignition Alternating cylinder deactivation could timing is delayed. When the target charge is 8 Cyl. mode Switch-over phase 4 Cyl. mode also prove interesting when it comes to reached, the valve train is switched over and counteracting engine-induced vibration, es- the ignition timing for the cylinders activated Source: MTZ - The new AUDI V8 TFSI Engine Part 2 pecially in the case of three-cylinder engines. is realigned with the optimum performance Figure 7 Active regulation at the switchover point All deactivation systems introduced in setting. As soon as the injection and timing the section following the next are considered sequence for the cylinders to be shut down Since retarding the ignition timing momen- Requirements in a system for a basic cylinder deactivation concept. is deactivated, the switchover is complete. tarily consumes more fuel, the deactivation mode must remain engaged long enough environment context for an overall fuel economy benefit to be 12 n = 2,000 min-1, p = 2 bar 11.66 me achieved. It goes without saying that the longer the engine stays in this mode, the 8 more fuel is saved. Such is the case when Even if the switch from one operating state

in % % in traveling at constant speeds on the high- to another is made successfully, in a torque- 4 way. balanced fashion, the vibration characteris- The following requirements are placed tics of the engine and acoustic output still 0 on the switchover mechanisms: change. This may, in turn, necessitate mod- 0.00 –– The switchover process for all cylinders ifications to the following components (refer -4 -3.35 must take place in exactly the cycle to Figure 8): that the control unit stipulates. –– Phasing unit

Consumption beneﬁt –– The aforementioned design measures -8 –– Timing drive for compensating torque must be opti- –– Auxiliary drive assembly -9.91 mally coordinated and harmonized. –– Clutch and dual-mass flywheel -12 -12.35 –– The switchover point must occur dur- –– Exhaust system (sound engineering) ing the ignition sequence. –– Engine mounts –– Both operating states must be stable Depending on the application scenario Base Cylinder Cylinder Cylinder Cylinder complete deactivation deactivation deactivation deactivation and reliable so that no inadvertent swi- and the requirements it entails, it is typi- engine operation Cylinder 2 rolling rolling rolling tchovers are made. cally a good idea to integrate an active deactivated Vacuum Fresh air Exhaust –– Since faulty switchovers and missed noise compensation facility for the pas- Camshaft is trapped is trapped is trapped switchovers are relevant from an ex- senger compartment. Nonetheless, it is optimized haust-gas perspective, a monitoring generally necessary to operate the engine Figure 6 Different configurations for alternating cylinder deactivation in a fuel consumption comparison function must be implemented. on all cylinders until the engine speed 180 Valvetrain Systems 11 181

Must be hydraulically robust Intake changed system and avoid ECU air pockets as well Cyl 1 Cyl 2 Cyl 3 Cyl 4 Modiﬁcations as throttling or – Active requirements may be required restriction points. – Cycle control Exhaust – undetectable switching Figure 9 shows a A A A A – OBD-Function NVH measures basic sketch of a – Driver command prediction system that has Active P T P T P T P T noise one switching valve cancellation per cylinder. Figure 9 Basic illustration of a valve stroke deactivation system featuring Exhaust system one switching valve per cylinder Valve train Accessory drive Torque- Design configuration of the shifting The benefit of this design lies in the short oil converter lockup clutch oil circuit channels and small oil volume. Any oil foam- Cam phaser / (automatic ing that could occur would therefore be min- Timing drive transmission) Several solutions are conceivable for con- imal, which is why the system is highly insus- trolling hydraulically actuated, two-stage ceptible to fluctuations in the shifting or valve train components and arranging the switching times. This concept enables a Dual mass switching valves in the cylinder head. The switching time interval of approximately ﬂywheel positional arrangement of the switching 250 camshaft degrees, which equates to Engine mounts valves and the design configuration of the a theoretical switching time of 28 ms at oil channels produce different switch time 3,000 rpm. On engines with camshaft phas- intervals and system-related constraints. ing units, the influence of the adjustment Figure 8 Overview of the measures accompanying cylinder deactivation The following depicts two different options range must also be factored into determining for deactivating cylinders 2 and 3 in a four- the interval. By design, this variant can be reaches approximately 1,500 rpm, de- bly moderate outlay. The following options cylinder engine with an ignition timing se- enhanced or extended in such a way that all pending on the engine concept, as this are available for this purpose: quence of 1-3-4-2 and describes the inher- cylinders can be actively switch-controlled, will ensure the desired level of comfort for –– Switchable bucket tappets ent benefits and drawbacks in detail. which in turn means that in a four-cylinder passengers. In addition, cylinder deacti- –– Switchable finger followers Figure 10 shows the variant with one engine application, the engine management vation cannot be engaged if the engine oil –– Switchable pivot elements switching valve per cylinder, which means system can deactivate one, two, or three of has not reached operating temperature, –– Cam shifting systems that one switching valve at each cylinder the four cylinders. One drawback, however, or engaging the mode would cause the –– Fully variable mechanical valve train controls the respective intake and exhaust is the comparably expensive design configu- catalytic converter to drop below its light- systems based on detent cam gears valves. ration associated with the oil channel be- off temperature. –– Fully variable electrohydraulic valve tween the intake train systems such as the UniAir sys- Intake and exhaust sides. tem from Schaeffler An alternative ar- Cyl 1 Cyl 2 Cyl 3 Cyl 4 rangement is also Valve stroke deactivation Most of the switchable elements are actu- possible by control- ated using oil pressure, which is con- ling the oil circuit trolled and regulated by an upstream Exhaust A A using one switching switching valve. The concept requires an valve on the intake As already mentioned, it is not practical to additional switching or shifting oil circuit P T P T and exhaust sides also disengage the moving parts of the to be implemented, whereby special at- (Figure 11). The in- crank drive during cylinder deactivation. De- tention must be paid to ensuring the cor- take and exhaust activating the valve stroke sequence, on the rect positional arrangement and geometry Figure 10 Oil circuit with one switching valve per cylinder valves are then ac- other hand, can be realized with compara- of the oil channels in order to create a tuated by two sep- 182 Valvetrain Systems 11 183

arate switching A nents, for example, reduce rigidity as com- valve inadvertently opens in the direction valves. The benefit of pared to a standard finger follower and opposing the valve spring pressure. this arrangement is P T negatively affect the vibration of the valve that the switching Intake train. The added components also increase Support element time interval can be the mass moment of inertia of the follower, The switchable pivot element also lends it- governed indepen- Cyl 1 Cyl 2 Cyl 3 Cyl 4 which in turn means that stronger valve self to being deactivated. Similar to the dently of the adjust- springs need to be fitted, and the valve train switchable roller tappet, the inner part of the ment range of the assembly encounters higher levels of fric- element can be telescopically extended into camshaft phasing Exhaust tion as a result. Potential space restrictions the outer part (Figure 13). Here too, a spring unit. In addition, the A necessitate narrower rollers, a design that or spring assembly is required to return the oil channels can be inherently increases the surface contact moving part to its starting position. The oil designed in a more P T pressures between the roller and camshaft. pressure, which is controlled by an up- simplistic manner, Switchable finger followers that brace stream switching valve, is also used to actu- and the switching Figure 11 Oil circuit with one switching valve per side themselves against a zero-stroke cam in ate the coupling mechanism. The distance valves can be inte- deactivation mode create a more stable traveled by the oil to this mechanism is grated more easily. This design facilitates tion of the cylinder head and oil channels of system than the variant that does not pro- shorter, however. The same restrictions that a switching time interval of approximately the target engine, whereby the main focus of vide for this effect. The only drawback is apply to the switchable finger follower with 180 camshaft degrees, which corresponds the design work should be on maximizing that the camshaft then requires two differ- regard to the oil pressure also hold true for to a theoretical switching time of 20 ms at the switching time interval as far as possible ent profiles per valve. If a zero-stroke cam is this application. 3,000 rpm. The longer oil channels do pose using justifiable levels of outlay. not provided, the acting forces must be pre- The rigidity of the valve train is only re- a limitation, however, as they require a higher cisely coordinated with each other; in the duced by the structural integrity of the cou- oil volume, which in turn makes the system decoupled state, the lost-motion spring pling point in the switchable pivot element. more susceptible to fluctuations in the shift- Deactivation via switchable elements needs to be strong enough to prevent “infla- The geometry (with the exception of the ing or switching times as a result of the great- tion” or “pump-up” (undesired elongation) of valve contact surface) and mass moment of er potential for oil foaming to occur. Finger followers the support element. On the other hand, the inertia of the finger follower are unaffected. The shifting oil circuit and switching valve Since the design configurations for the spring must not be so rigid that the motor As a result, the valve spring pretension force linkage can also be implemented in ways switchable finger follower can also be ap- other than the ones described here. Critical plied to the switchable bucket tappet, we design aspects that apply in this context are will not explore this topic any further. the ignition timing sequence and configura- The solutions that are based on finger followers or hinged-lever designs that can be coupled with one another and have a locking mechanism at the pivot point are numerous. All systems that rely on oil pressure require spring-actuated elements to return the deactivated components to their Oil starting position after cam elevation (Figure 12). pressure The shift mechanism must be designed in such a way that the entire valve stroke is traveled when no oil pressure is present (zero-pressure lock), since this safeguards operation in limp-home mode and is required for cold-starting the engine. Although cylinder deactivation brings with it many benefits, the concept also has several drawbacks. The additional contact Figure 12 Switchable finger follower points and increased number of compo- Figure 13 Switchable pivot element 184 Valvetrain Systems 11 185

does not have to be changed in comparison outlay than switchable elements, since in cylinders. This setup also facilitates the inte- to that of the conventional valve train as- four-cylinder engine applications, both gration of an alternating cylinder deactiva- sembly, which means that the surface con- camshafts must be equipped with a deacti- tion pattern [3]. tact pressures between the roller and cam- vation function – a design aspect that also shaft remain at low levels. affects positional elements that are not Cylinder deactivation via UniAir switchable. Consequently, the cam shifting system is a commercially viable option for UniAir not only controls and regulates Deactivation via a cam sliding system cylinder deactivation if an existing two- valve stroke travel in a fully variable fashion, stage system for varying the valve stroke is but can also completely deactivate any The cam shifting system allows the valve enhanced to include a third stage dedicated cylinder (Figure 16). This deactivation is stroke to be switched in up to three stages. to the cylinder deactivation process (refer to achieved by actuating the system‘s integrat- The switchover process occurs when a Figure 15). ed switching valves as required. In its cur- cam piece positioned in an axially movable Theory-based investigations conducted rent version, UniAir actuates both valves in a arrangement on a splined shaft is displaced. by Schaeffler indicate that a three-stage uniform manner. As a result, both intake This sliding cam piece comprises several Figure 15 Three-stage cam shifting system system can offer further significant potential valves are always closed in deactivation cams sectioned into two groups, which are compared to a two-stage solution in con- mode. The operating state of the valve train arranged in relation to the two valves on contour position. A second cam profile (or a sumption testing cycles carried out under can thus be easily determined with the Uni- each side of a cylinder (Figure 14). third one in the case of three-stage sys- higher load conditions. When the cam shift- Air system as well. When UniAir is only used A control groove is integrated into the tems) thus acts on the finger follower to ing system is designed so that all intake and on the intake side, switchable support ele- sliding cam piece. When the cam lift is to be transfer the new cam lift (which can also be exhaust valves can be deactivated, it is pos- ments can be fitted in the relevant positions adjusted, an electromagnetically actuated a zero-stroke) to the valve so that each valve sible to deactivate any desired number of on the exhaust side (as is the case with the pin extends into this groove to force the en- pair can be actuated individually. The inher- fully-variable me- tire unit to change its respective groove ent benefits of this system are that the cylin- chanical system). ders and camshaft can be switched selec- Schaeffler is cur- tively and the sequence of the elements to rently working on ad- be switched is variable. ditional valve stroke After the actuation sequence has taken configurations that place, a relay signal generated by the actua- approach the poten- tor pin as a result of a voltage shift in the tial afforded by cyl- electric coil is sent to the actuator. Although inder deactivation this signal provides clear indication of a shift while making it pos- occurring and the direction that was taken, sible to forego valve it is not sufficient for determining positional deactivation on the arrangements as operation continues (OBD exhaust side. The requirement). The cam shifting system of- genuine appeal of fers a benefit here that initially appears to be this type of configu- the exact opposite: Both valves are forced ration is that it allows to switch at the same time. This, in turn, any number of cylin- makes it considerably easier to detect cor- ders to be deacti- rect position during active operation by way vated without having of sensors (pressure or oxygen sensors) on to implement further the intake and exhaust side or by evaluating design measures. torque imbalance than when systems with Detailed informa- individual switch logic are used. tion is provided in When viewed from the perspective of a an additional article cost-benefit analysis, it is important to note [4] in this book. Figure 14 Two-stage cam shifting system that the cam shifting system requires more Figure 16 Electrohydraulic, fully-variable UniAir valve train system 186 Valvetrain Systems 11 187

Summary and outlook expectations customers have regarding comfort levels, additional design measures may be required for the engine and overall vehicle that conflict with the potential for re- Temporarily deactivating cylinders offers an ducing fuel consumption, which can be es- attractive compromise between downsizing pecially prominent in lightweight vehicles an engine to reduce fuel consumption and equipped with powerful engines. retaining high levels of comfort and driving In the future, it is highly probable that pleasure. Even three-cylinder engines can cylinder deactivation will play an ever in- profit from the economical benefits of cylin- creasing role in optimizing powertrains that der deactivation. Simulations point to the use engines with three or more cylinders. potential that an alternating cylinder deactivation system has for maintaining a balanced temperature level in the engine and reducing vibrations, particularly in three- Literature cylinder engine applications. Several options are available for temporarily deactivating valves, especially in the context of finger follower regulation sys- [1] Middendorf, H.; Theobald, J.; Lang, L.; Hartel, K.: tems. When cylinder deactivation is the only Der 1,4-l-TSI-Ottomotor mit Zylinderabschal- variable aspect required, switchable pivot tung. MTZ, 3/2012, pp. 186-193 elements offer a very cost-effective solution [2] Kirsten, K.; Brands, C.; Kratzsch, M.; Günther, M.: without noticeably compromising the basic Selektive Umschaltung des Ventilhubs beim functions of the valve train assembly. In the Ottomotor. MTZ, 11/2012, pp. 834-839 case of multi-stage systems or entire engine [3] Faust, H.: Powertrain Systems of the Future: families, cam shifting systems are more fa- Engine, transmission and damper systems for vorable because they can be easily adapt- downspeeding, downsizing, and cylinder deac- ed. Fully-variable valve train systems go tivation. 10th Schaeffler Symposium, 2014 hand in hand with cylinder deactivation in [4] Haas, M.; Piecyk, T.: Get ready for the combustion the presence of discretely switchable ele- Strategies of tomorrow. 10th Schaeffler Sympo- ments as a minimum expenditure item. sium, 2014 Depending on the size of the engine and the