CVT: the Transmission Concept of the Future: Schaeffler Symposium
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CVT The Transmission Concept of the Future 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 p o n i w k t H l p R I 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 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 U D M P B D B C M G F x B D P B D L d B E u B A F V N K F N 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 A A t R H i g h O p e r f o R m a n c e D N l I E R N G M j B N D S A U K Z Q I N K J S L W O I E P AndreasN N b AEnglischU 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 U A N a u N C e U A R N H I V G 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 AndréN z R TeubertA 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 C K O i J G S D C K I O P M t E S W 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 BernhardO G I K WalterC 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 Q O G n T Z Q S Q O M G D N V U S G 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 KonstantinG Z M O QBraunO 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 N R L U J G D I N G R E E O M N Y 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 StephanR J G N PennerI 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 V C E S O P M N V C S E Y L i N E W C L V V V H N V u a J K U V X E S Y M N R E E W C L O MMarkusE P S JostC 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 Q Y A H I N C W Q Y J A O B R n L 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 O P M S E B U N O P L M Q A Y C B 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 G B Q O P B D E G B E Q P M N E S W 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 B N Z W E D C V B N H Z U I O P L K 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 T R W P O I U Z T R E W Q H G F D L 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 O34H A S E D 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 D 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 a V O E h 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 R A i 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 O R g 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 V N h O N G I U A R N H s O G D N O I E R N G M g S A U K Z Q I N K J S 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 R B A 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 Q 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 F N V O N G I U A R N H I O G D N O I E R N G M D S A g K Z Q I N K o S 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 D G A T Z D S Q O M G D N V U S G R V L G R V 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 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 G B l M G R I 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 Q 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 t o r q u e B s e n s o r H G F D G F D S A M M 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 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 M N 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 B Z H 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 500 CVT 34 501
Introduction Single-range and a conventional spur gear stage without a toothed chain and with a conventional dif- dual-range concepts ferential, as desired. A cost-effective vari- ant that is designed for optimized use of Automatic transmissions are becoming space is also possible when a LuK iTC more and more common in passenger torque converter [2] is used. vehicles and, at the same time, custom- Aside from the actual specification, de- ers’ demands for comfort and reduced fining the concept is the most difficult fuel consumption are increasing. Opti- task within the development process. Single-range or dual-range mized fuel consumption is very difficult to Single-range and dual-range concepts structure achieve with manual transmissions. are currently available on the market. Ef- More than 20 % of automatic trans- ficiency can also be further improved As indicated in the introduction, defining the missions will be CVTs by the year 2020. through the use of fixed-ratio gear stag- concept is the most difficult task within the A significant advantage in terms of fuel es. The choice of a concept essentially transmission development process. consumption can be achieved in opera- depends on the selection of the relevant In the past, a so-called “standard de- tion at partial load, and hybrid concepts components, such as the linking ele- sign” became the mainstay of CVT trans- can be seamlessly combined with the ment, the clamping system, and the vari- Figure 1 Comparison: HV CVT with torque mission concepts for front transverse ap- CVT. The CVT can also be manufactured ator size. The quality of the overall con- sensor and HV CVT with electronic plications (Figure 2). In this design, the cost-effectively, and when combined cept in turn depends on the consistent clamping pulley set on the drive side is installed di- with torque converters, modern damp- optimization of the individual components rectly on the crankshaft’s axis and thus ing systems, and hybridization, it offers a in the transmission. compared to the existing HV CVT. The ad- without an input gear stage. A planetary level of comfort that is difficult to sur- vantages of the compact design and the gear set with multi-plate shifting elements pass. variably selectable startup element can still for reversing the direction of rotation is in- New chain types allow significant in- High Value CVT be regarded as the main strengths of this stalled in front of this, and a torque con- creases in ratio spread and strength to be concept. The reverse gear unit installed on verter is most frequently used as a startup achieved, a trend which future genera- The High Value CVT (HV CVT) concept [1] the output side can also be combined with element. tions of chains will continue. In addition, was presented in detail during the last the ratio spread can also be expanded Schaeffler Symposium and at subsequent through the use of gear stages/range symposia. This concept already preempt- HV CVT dual range HV CVT ec CVT standard design shifting to include ranges that conven- ed groundbreaking development trends: tional automatic transmissions will have The weight was reduced to a minimum, difficulty in achieving comfortably. This the ratio spread was increased to values means that CVTs can support the trend of more than 8, and hybridization was car- towards downsizing and downspeeding ried out with no modifications to the de- with no problems. If required, the efficien- sign envelope. The concept was designed cy of the transmission can also be further in a modular fashion in order to fulfill the optimized through the use of direct gear requirements of a wide range of markets, stages. and continues to provide the same firm The CVT thus continues to represent basis for further development. Previous one of the best technical solutions for the publications have always illustrated the automation of the powertrain, particularly in HV CVT in combination with a hydraulic- the field of front transverse applications. mechanical torque sensor. However, the Current developments and possibilities for HV CVT can also be implemented with further development will be looked at in de- electronically controlled clamping without tail in this paper. a torque sensor if desired. Figure 1 shows a variation of this type with the designa- tion HV CVT ec (electronic clamping) Figure 2 Comparison of CVT concepts for front transverse applications 502 CVT 34 503
The HV CVT con- Dual-range CVT Single-range CVT have a slight advantage here. The dual- achieved at which input torque. High cept is the direct range concept displays the greatest advan- torques are essentially not a problem opposite. In the HV tage in that larger gear ratio spreads can be even with large gear ratio spreads when CVT, the assembly P2 implemented in combination with high a LuK chain is used as the linking ele- for reversing the di- torque capacity. There is no strict limit as to ment. Sooner or later, however, the limit P1 P2 rection of rotation is when it is better to implement a single- is reached when it comes to a competi- located on the out- P1 range or dual-range concept. A possible tive design in terms of design envelope, put side and the In In variation is presented in the next section weight, and variator mass inertia. When cone pulleys ar- with regard to this issue. a LuK chain is used, gear ratio spreads ranged in mirror- Out Out of up to 8.5 can be competitively opposite fashion. achieved in a single-range system with This provides a very no problems, even at high torques. This compact arrange- can be explained by the small minimum ment with optimum Figure 3 Cross-sectional view of dual-range CVT and single-range CVT Modular front transverse wrap radius that can be achieved and by use of installation variator system the low height of the chain, among other space, particularly when combined with the CVT while maintaining the same gear ratio factors. LuK chain. The reverse gear installed on the spread. In addition, ratio spreads of up to The illustration of a front transverse output side also allows the transmission in- 10 are possible without the variator – and modular variator system – using a LuK put range to be made very flexible with vari- thus the transmission – having to be made The selection of a single-range or dual- chain as the linking element – displayed in ous startup elements. Most of all, hybridiza- disproportionately large. Figure 3 shows a range structure essentially depends on Figure 4 shows that, unlike competing tion is thus significantly simplified. comparison of the transmission cross-sec- which total gear ratio spread has to be transmission concepts, the design enve- Jatco has now brought a dual-range tions of a dual-range CVT and a single- CVT onto the market [3]. Because of the range CVT (with their main axes) with iden- range shifting, there had previously always tical gear ratio spread. The diameters of a = Center distance / L = Transmission length Comparison basis been a degree of skepticism about whether the cone pulleys are highlighted in color. ZF 9HP [4] a dual-range CVT would be accepted by The difference in the design envelope is Ratio spread 9.8 / L = 370 CVT customers who are accustomed to a clearly visible. Pulley 2 certain level of comfort. However, Jatco has It can be summarized that a “standard 400 now successfully proved the skeptics design” CVT has the least suitable and least In Out wrong. flexible design envelope with regard to fu- Pulley 1 Figure 2 shows a sketch of the LuK HV ture powertrains. In particular, this arrange- a = 160 / L = 350 a = 190 / L = 360 a = 205 / L = 370 DQ 200 [5] CVT dual-range. This transmission design ment is the longest of the three concepts Ratio spread draft further simplifies the arrangement of along the crankshaft axis, which is essential 7.4 / L = 370 the planetary gear set in comparison to to the design envelope. Hybridization is dif- that of the solution already on the market. ficult to achieve due to the planetary gear 250 Range shifting now only requires a single set for reversing the direction of rotation, Torque [Nm] planetary gear set, meaning that this can which is installed on the drive side. a = 145 / L = 320 a = 175 / L = 330 a = 190 / L = 340 Jatco CVT 7 [3] also be easily and flexibly adjusted to vari- The two HV CVT concepts display com- Ratio spread 7.3 / L = 325 ous torque classes. The design-dependent parable advantages in terms of length and input gear stage and the reverse gear in- the possibility of hybridization. The dual- 150 stalled on the output side in turn provide a range concept has the best cross-sectional higher degree of flexibility for the arrange- arrangement. When it comes to costs, the a = 130 / L = 290 a = 155 / L = 300 a = 175 / L = 310 Dual-range CVT ment of a range of startup elements and for outlay for the planetary gear set in the case 6.0 (i = 14 … 2.3) 8.5 (i = 17 … 2.0) 10.0 (i = 18 … 1.8) possible hybridization. The main advan- of the dual-range concept must be com- tage of the dual-range structure is that the pared to the additional outlay for the larger Ratio variator can be dimensioned significantly variator in the case of the single-range con- smaller than in the case of a single-range cept. The single-range concept proves to Figure 4 Modular front transverse chain variator system for a single-range structure 504 CVT 34 505
lope limits are not exceeded until gear ratio the aspect of hybridization – which in the spreads of almost 10 are achieved. Of future will be universally in demand – is Low outlay Total ratio course, the higher the desired torque ca- taken into account, CVT technology must pacity, the faster the limit of competitive- be regarded as a ground-breaking trans- ness is reached. The yellow-to-red area mission technology in the front-wheel drive represents a feasible dual-range structure sector. Range of ratio change Low variant for making the CVT competitive Direct gear as even with large gear ratio spreads. In cas- a range shifting gear es such as special efficiency optimizations, however, a dual-range structure can also Fixed-ratio gear stages be advantageous with lower torques and Overall ratio spread High medium gear ratio spreads with a chain as the linking element. Variator Figure 5 illustrates how the modular A further option for increasing efficiency is ratio transmission system shown in Figure 4 the introduction of a fixed-ratio gear stage. changes when the range is implemented as This variant offers a wide range of possi- OD UD a dual-range structure with a large gear ra- bilities for further optimization. Numerous OD direct gear Variator ratio spread tio spread and a high torque. combinations of CVT variators with spur It can clearly be seen that a CVT can gear stages arranged in parallel have been competitively cover all ranges that are ex- brought onto the market in the past. In this pected from front transverse drives. When case, however, we present a very space- Figure 6 HV CVT dual range with direct gear stage
saving version that can also be used to al- gear ratio is selected in such a way that it a = Center distance / L = Transmission length Comparison basis low the optimized use of an electric motor can be engaged without a difference in ZF 9HP [4] in a hybridized powertrain. speed using a dog clutch once variator Ratio spread 9.8 / L = 370 Figure 6 shows the implementation overdrive has been reached. As soon as the Pulley 1 Pulley 2 within a dual-range structure. In this case, flow of force has been closed via the spur 400 the fixed gear ratio can be used either as an gear stage, the variator can be completely In Out overdrive stage or as a direct shifting stage decoupled in an efficiency-optimized way for range shifts. on the drive and output side. The intelligent a = 160 / L = 350 a = 135 / L = 360 a = 145 / L = 370 DQ 200 [5] The special feature of this design is use of route information (which will become Dual-range structure Ratio spread that the spur gear stage, which is ar- increasingly comprehensive in the future) 7.4 / L = 370 ranged parallel to the variator, is directly combined with current powertrain data coupled with the engine damper and not means that this shifting operation can be 250 in series behind the starting clutch or a carried out in a targeted way that allows it to
Torque in Nm torque converter. The direct gear stage remain unnoticed and is optimized in terms a = 145 / L = 320 a = 175 / L = 330 a = 135 / L = 340 Jatco CVT 7 [3] can thus also be combined with the per- of fuel consumption. Ratio spread 7.3 / L = 325 manently driven pump gear stage, for ex- The direct gear stage shown in Figure 6 150 ample. In this arrangement, the direct can also be used as a range shifting gear gear stage requires almost no changes to stage. In order for the driver to notice the the design envelope and only minimal ad- range shift as little as possible, the two a = 130 / L = 290 a = 155 / L = 300 a = 125 / L = 310 Dual-range CVT ditional outlay. The spur gear on the trans- operating ranges are implemented with 6.0 (i = 14 … 2.3) 8.5 (i = 17 … 2.0) 10.0 (i = 18 … 1.8) mission’s input side meshes directly with a large overlap in today’s applications. the large spur gear on the differential’s However, this leads to the loss of a large Ratio output side here. degree of overall ratio spread that, from a When used as an overdrive direct gear technical perspective, would actually be Figure 5 Modular front transverse system for a single- and dual-range structure stage for the entire transmission, the spur available. This can be made more effec- 506 CVT 34 507
tive through a range shift using a direct High Value CVT multimode high range can be carried out using a dog –– Finally, the electric motor can be used gear stage with an overall transmission ra- clutch. to boost the internal combustion en- tio that remains the same – this is shown The use of a direct gear stage for shift- gine via the direct gear stage while as a dashed green line in Figure 6. This ing between ranges also allows the variator driving at maximum torque without the allows the ratio ranges to be moved fur- Numerous facts that support the use of a to be utilized more effectively. It is possible, chain variator being subjected to any ther apart and thus a larger overall ratio CVT in front transverse powertrains have as illustrated by the dashed line in Figure 7, additional load. spread to be achieved without a larger been illustrated by the innovations present- for the variator’s utilization range to be limit- Despite these numerous functions and variator. During the range shift, the drive ed in the previous sections and by the mod- ed in comparison to the current state of the operating modes, this hybrid transmission energy is transferred to the differential via ular CVT variator system presented here. art in overdrive while retaining the same concept can be made more compact than a the direct gear stage with no dips in the The aim of the following section is to illus- overall transmission ratio, which means it CVT in standard design without a hybrid tractive force. Meanwhile, the variator can trate a transmission concept variation that can be operated with more optimized effi- motor or transmission of a different type. be moved to the new range with no load. takes these innovations as a starting point ciency. The overall gear ratio spread could This new transmission concept also offers The engagement/disengagement of the and provides groundbreaking possibilities also be further expanded or the variator fur- possibilities for gear ratio spreads of up to direct gear stage can be carried out using with regard to hybridization. ther miniaturized, however. 10 in all common torque ranges. Compared a dog clutch without being noticed by the The transmission variation known as The concept is hybridized. Reversing is to other hybrid transmission concepts with driver, as there is no difference in speed at the “High Value CVT multimode” is illus- completely ensured by the integrated electric the same functionality, a result that is also the shifting element. When fast downward trated as a dual-range concept in Figure 7. motor (a dedicated mechanical reverse gear attractive in terms of costs is to be expect- shifting (“kick down”) is desired within the The outlay for the planetary gear set for is intentionally omitted for reasons of installa- ed. high-ratio range, it is also possible to jump range shifting on the output side was fur- tion space, cost, efficiency, and comfort). To vertically to the low-ratio range without ther reduced in comparison to the High safeguard the functionality of this design, the using the shifting gear stage. The engine Value CVT dual range. Now, only a multi- hybrid battery can even be charged by the speed is adjusted here using a multi-disk disk brake is integrated for shifting to the internal combustion engine via the electric Chain 05 – brake operated with slippage, which low range. Because a direct gear stage is motor when the vehicle is stationary. the next generation means that even spontaneously desired provided for range shifting (as described The illustrated transmission architecture ratio shifts can be carried out quickly. in the previous section), the shift to the additionally offers a wide range of opera- tional possibilities: –– The electric motor can be used to drive The CVT chain has been undergoing con- Total Electric startup and with optimum efficiency via the direct stant further development over the last few ratio reversing point gear stage when the CVT variator is years, which has made it possible to con- completely decoupled and stationary. tinuously increase its performance density. –– When braking, energy can be recov- It was possible at the same time to retain ered via the direct gear stage – and the positive characteristics, such as the ex- thus when the internal combustion en- cellent level of efficiency. The latest mea- Low gine is decoupled – without an addi- surements indicate that this efficiency level tional K0 being required. is up to 4 % higher (depending on the oper- Direct gear + –– The electric motor and the internal ating point) than that of comparable linking ratio spread electric gear combustion engine can be operated in elements from our competitors. Significant- Optimized overall parallel at different speeds via the di- ly higher overall gear ratio spreads can also rect gear stage and the CVT variator, be achieved with this chain, which means Maximum overall ratio spread High Variator respectively. that the overall efficiency of the powertrain ratio –– The electric motor can of course also can be further improved as explained earli- Optimized variator be operated via the CVT variator. For er. Because of the chain’s good scalability, OD ratio spread UD electric starting when a large wheel higher torque applications – particularly in Maximum variator ratio spread torque is needed, it is planned that the combination with powertrain hybridization – variator should be operated at the UD can be achieved with a long operating life. end stop, thus utilizing the entire avail- Figure 8 illustrates the torque capacities of Figure 7 HV CVT multimode able transmission ratio. the different chain types. 508 CVT 34 509
37 In order to further utilize this effect, the link that are subjected to the highest load, 05-generation chain was developed, with and these are then applied in calculating the which the pitch is reduced by a further 15 % damage to the components. In addition, the Type 08 Type 08 compared to the 06-generation chain. changes to the components due to the manufacturing processes are taken into 33 Pitch -10 % consideration. Only as strong as the weakest link 30 Type 07 Type 07 28 The requirements for the “small” 05-genera- Confirmation by measurement
Type 06 tion chain were ambitious. It had to achieve 26 Pitch -10 % the same degree of strength as the 06-gen- During the development of the new calcula- eration chain while likewise maintaining the tion methods, a temporary version of the 24 Type 05 Type 06 smallest possible running radius and with- procedure was used in order to evaluate a Type 06
Chain width in mm out falling below the outstanding efficiency relatively simple optimization of the existing 22 optimized Pitch -15 % level of its “bigger brother”. 06 geometry. This produced a calculated
20 How is it possible to support identical or damage reduction of approximately 38 %, Type 05 even higher loads using chain components which was inspected using a high-load un- 18 that have a smaller cross-section? The key derdrive test (strength test in the startup ra- 17 to achieving this is an in-depth understand- tio). The B10 value of the measured chains ing of the stress processes to which the was approximately 4.8 times higher than 100 200 300 400 500 600 components are subjected. For this pur- that of chains with no geometrical changes, Engine torque in Nm pose, some entirely new calculation tools which already made a convincing case due Figure 8 Torque ranges of the different chain types were developed that determine the damage to their good running time results (see Fig- to the components with even greater preci- ure 10). The calculation results were there- The application of the chain in smaller ve- comes into contact with the pulley set. The sion and facilitate their optimization. fore confirmed. hicles, however, requires a further improve- impulse of impingement becomes lower as In simple terms, the new calculation These new calculation methods mean ment in the chain’s acoustics in order to the number of links in the chain’s length in- tools determine the exact stresses placed that it is now possible to determine the reduce the outlay in the vehicle to a mini- creases (see Figure 9). on the components in the weakest chain optimum geometry. Figure 11 illustrates mum. The chain’s pitch is a variable that the comparison be- has a major effect on the acoustics. The tween the existing aim was therefore to develop a new gen- 06 generation and eration of chains with a pitch that is re- the initial prototype duced by a further 15 % while retaining at of the 05 genera- 5 dB least the same torque capacity compared tion. to type 06 [1]. The obvious
NV H 06 old: 06 new: course of action is B10 = 100 % B10 = 480 % to transfer the new Optimized acoustics through design ideas to the Unreliability existing larger chain reduced pitch 38 % damage reducion in the simulation variants. This will The reduction of the chain plate pitch over make it possible for the course of each new chain generation Chain generation > reduction in pitch applications that to- (08 > 07 > 06) has allowed the chain’s Type 08 Type 06 day are equipped acoustics to be significantly improved. The Type 07 Type 05 Running time with a 08 pitch to be lower the pitch of the chain, the more links operated with an are present in the same length of chain and Figure 9 Reduction of noise emissions as the Figure 10 Results of continuous underdrive tests on the 06-generation optimized 07 chain the lower the speed at which each link pitch is lowered chains in the future. 510 CVT 34 511
Type 06 a-plate Type 06 b-plate by filling in the center area of the chain culated application to be carried out but plates (Figure 11). The maximum mass dif- also that up to 180 Nm could be trans- ference over the length was approximately ferred in underdrive. 14 % for the 06 chain, which was reduced to 12 % for the 05 chain. The implementa- -15 % -15 % tion of the 15 % smaller pitch and the im- The use of a narrow chain proved mass distribution means that a sig- saves weight nificant improvement in the chain’s acoustics is achieved. The 1705 chain is approximately 7 mm nar- rower than a 24 mm push belt and a 2406 Type 05 a-plate Type 05 b-plate chain. A weight saving of more than 300 g is Figure 13 Comparison of a 1705 chain and a The potential of narrow 05 chains achieved in comparison to the push belt, 24 mm push belt Figure 11 Comparison of the 06 and 05 chains and a saving of 70 g is achieved even in with adjusted geometry The minimum width of a chain is limited by comparison to the 2406 chain. Figure 13 efficiency and functionality of the CVT. Im- factors such as the pulley geometry. The illustrates a size comparison between the proved hybrid technology is possible with a Targets far exceeded – improved pulley angle and the dimensions of the pul- 1705 chain and a 24 mm push belt. reduced outlay in comparison to other acoustics with a longer operating life leys define the smallest possible chain A narrower chain affects the design transmission concepts. width. Figure 12 illustrates an example of envelope and the overall weight of the The loads of the 05 chain were simulated for the how the pulley geometry limits the transmission, however. In comparison to a an existing customer transmission applica- smallest chain width. small CVT with a 24 mm push belt, weight tion with a maximum input torque of 250 Nm. A test was carried out using an exist- savings of up to 650 g are conceivable on Literature The calculations show a 21 % reduction in ing CVT application in the 140 Nm class to the pulley sets, the linking element, the damage compared to the previously critical discover how high the maximum transfer- aluminum housing, and small compo- point. If the relationship between the dam- rable torque would be with the smallest nents. age reduction and the actual operating life is possible 05 chain. For this purpose, the similar to the values from the aforemen- smallest chain width at which the pulleys [1] Teubert, A.; Englisch, A.; Goetz, A.: The com- tioned underdrive tests with the 06 chain, a do not quite reach their end stop when the pact High Value CVT transmission - Efficient, significant increase in chain strength is to be gap is closed was determined for the stat- Summary economical and innovative. VDI Reports 2130, expected. ed transmission application. This pro- 2011, pp. 448-450 At the same time, the mass distribution duced a chain width of 17.5 mm. Chain [2] Lindemann, P; Steinberger, M.; Krause, T.: over the chain’s length was optimized. Pre- calculations indicate that a “narrow” chain iTC – Innovative Solutions for Torque Converters vious tests have shown that it is possible to of this type would allow not only the cal- The High Value CVT concept continues to Pave the Way into the Future. 10th Schaeffler further improve the make a convincing case due to the modu- Symposium, 2014 acoustics of the larity of the system when it is combined with [3] Nonomura, R.: Fuel Economy Improvement chain by homoge- a chain from the new 05 generation. The Technology and Control System in New CVT. nizing the mass new generation of chains has a 15 % small- CTI Symposium, 2010 over the chain’s er pitch and a higher torque capacity than [4] Greiner, J.: Automatgetriebe-Baukasten für length. The previ- the 06 generation. Even single-range trans- Front-Quer-Anwendungen. Fachtagung ous long-plate links missions can achieve very high ratio “Getriebe in Fahrzeugen”, 2011 have a lower relative spreads with these chains. In dual-range [5] Schaefer, M.: Volkswagen’s new dual-clutch mass in relation to transmissions, the size of the variator can transmission. CTI Symposium, 2007 their length than the be significantly reduced for ratio spreads of short-plate links. It up to 10. This brings with it additional ben- was possible to op- efits in terms of weight and with regard to timize the mass dis- mass inertia reduction. tribution over the The High Value CVT multimode concept length of the chain Figure 12 Limitation of the smallest chain width by the pulley geometry shows further possibilities for increasing the