Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`SAE TECHNICALPAPER SERIES 910247Electric Hybrid Drive Systems for PassengerCars and TaxisA. KalberlahVolkswagen AG
`
`Wolfsburg, Germany
`
`Reprinted from SP-862—Electric Vehicle Design and DevelopmentThe Engineering SocietyFor Advancing MobilityLand Sea Air and Space®INTERNATIONALlnternational Congress and ExpositionDetroit, MichiganFebruary 25-March 1, 1991400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A.
`
`VWGoA - Ex. 1011
`Volkswagen Group of America, Inc. - Petitioner
`
`1
`
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`Global
`Mobility
`
`®
`
`The papers included in this volumeare abstracted and indexed in theSAE Global Mobility Database.
`
`No part of this publication may be reproduced in any
`form, in an electronic retrieval system or otherwise,
`without the prior written permission of the publisher.
`
`ISSN 0148-7191
`Copyright 1991 Society of Automotive Engineers, Inc.
`
`Positions and opinions advanced in this paper are
`those of the author(s) and not necessarily those of
`SAE. The author is solely responsible for the content of
`the paper. A process is available by which discussions
`will be printed with the paper if it is published in SAE
`Transactions. For permission to publish this paper in
`full or in part, contact the SAE Publications Division.
`
`Persons wishing to submit papers to be considered for
`presentation or publication through SAE should send
`the manuscript or a 300 word abstract of a proposed
`manuscript to: Secretary, Engineering Activity Board,
`SAE.
`
`Printed in U.S.A.
`
`2
`
`Database
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`910247Electric Hybrid Drive Systems for PassengerCars and TaxisA. Kalberlah
`
`Volkswagen AG
`Wolfsburg, Germany
`
`Abstract
`
`Various h y b r i d d r i v e configurations aredescribed and their advantages and disadvan-t a g e s f o r a p p l i c a t i o n i n p a s s e n g e r c a r s a r ed i s c u s s e d ; s p e c i f i c a l l y , t h e s e a r e t h e s e r i e shybrid, t h e p a r a l l e l h y b r i d , h y b r i d d r i v e sw i t h a d d e d t o r q u e a n d s p e e d , s i n g l e a n dtwo-shaft hybrids.The Volkswagen and AUDI group has deve-l o p e d d i f f e r e n t v e h i c l e s w i t h h y b r i d d r i v ef o r v a r i o u s a p p l i c a t i o n s . T h e s e v e h i c l e s a r ed e s c r i b e d a n d t e s t r e s u l t s a r e p r e s e n t e d o nt h e i r energy consumption, emissions anddriving performance. I n c o n c l u s i o n , somec o n s i d e r a t i o n s a r e p u r s u e d c o n c e r n i n g t h e i rchances on the market in different scenarios.1. INTRODUCTIONA hybrid drive, comprising b o t h e l e c t r i cdrive and internal combustion engine, can, ifsuitably designed, combine the advantages ofthe conventional vehicle drive system (largec r u i s i n g range, good performance) with thoseof a purely electric drive (low noise and ex-h a u s t e m i s s i o n s , conservation of petroleumresources). Vehicles equipped with such drive systemsa r e t h u s f a r m o r e f l e x i b l e t h a n e l e c t r i cvehicles; they are often just as versatile asv e h i c l e s with an internal combustion engineand consequently are not confined from theoutset to the "second car" market.Hybrid drives thus have far more extensivep o t e n t i a l a p p l i c a t i o n s t h a n e l e c t r i c d r i v e s ;h i g h e r p r o d u c t i o n r a t e s c o u l d i n p r i n c i p a ltherefore be achieved, leading to low manu-facturing costs. Surprisingly, t h e r e i s a w e a l t h o f p o s s i -b i l i t i e s f o r r e a l i z i n g s u c h h y b r i d d r i v e s .Some of t h e s e p o s s i b i l i t i e s a r e o u t l i n e dbelow and the advantages and disadvantages oft h e s e d i f f e r e n t d e s i g n s a r e investigated byconsidering vehicles already manufactured.2. SYSTEM ANALYSIS OF HYBRID DRIVES2.1 SERIES HYBRID DRIVE - Taking the purelye l e c t r i c d r i v e a s a s t a r t i n g p o i n t , i t i ss i m p l e t o c o n c e i v e o f a h y b r i d d r i v e : theb a t t e r i e s o f t h e e l e c t r i c v e h i c l e a r e r e -charged when driving as required via genera-tor driven by an internal combustion engine.This is not only simple in concept, but alsoi n p r a c t i c e ; s e v e r a l V W E l e c t r i c T r a n s p o r -t e r s , fitted with a suitable motor/generatora s s e m p l y i n t h e l o a d i n g a r e a , h a v e b e e nt r a n s f e r r e d f r o m W o l f s b u r g t o E s s e n . I na c t u a l f a c t , n o t o n l y i m p r o v i s e d v e h i c l ed r i v e s h a v e b e e n b u i l t a c c o r d i n g t o t h i sp r i n c i p l e , b u t a l s o r e a l d r i v e s , e . g . b yDaimler Benz (l)* for a city bus.The main advantage of the series hybrid:I t i s p o s s i b l e t o o p e r a t e t h e i n t e r n a lcombustion engine at a fixed operating pointwithin i t s e n g i n e - s p e e d / t o r q u e m a p . Thispoint c a n b e s e l e c t e d s o t h a t t h e e n g i n ef u n c t i o n s w i t h t h e g r e a t e s t e f f i c i e n c y o rproduces particularly low emissions.Nevertheless, t h e e f f i c i e n c y o f t h e e n t i r ed r i v e i s n o t s a t i s f a c t o r y . A s t h e s t r u c t u r eo f t h i s s o - c a l l e d s e r i e s d r i v e i n F i g . 1c l e a r l y s h o w s , the 3 components V (internalcombustion e n g i n e ) , G ( g e n e r a t o r ) a n d E( e l e c t r i c m o t o r ) a r e a r r a n g e d i n s e r i e s : t h emechanical energy generated b y t h e p e t r o l
`
`*Numbers in parentheses designate referencesat end of paper
`
`69
`
`3
`
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`Fig 1 Structure of the series hybrid drive
`
`engine is converted into electrical energy byt h e g e n e r a t o r and t h i s i s again convertedback into mechanical energy in the electricmotor. Each process of conversion is afflic-t e d w i t h l o s s e s r e s u l t i n g i n relatively bade f f i c i e n c y . T h i s i s a l s o c o n f i r m e d b y t e s tr e s u l t s f r o m a f l e e t o f h y b r i d b u s e s w h i c hwere operated in Esslingen.
`
`A f u r t h e r d i s a d v a n t a g e o f t h i s s e r i e shybrid drive is its heavy weight.I f p o w e r P max i s r e q u i r e d a t t h e d r i v eaxle e.g. for the maximum speed, the electricmotor must be designed to produce this powerP max . I f t h e d r i v e r w i s h e s t o d r i v e l o n gdistances at this maximum speed, the power,which the battery c o u l d c o n t r i b u t e , c a n b ed i s r e g a r d e d s o t h a t b o t h , t h e g e n e r a t o r a n dthe internal combustion engine must be de-signed for the power P max (because of thec o n v e r s i o n l o s s e s i n t h e e l e c t r i c m o t o r a n dt h e g e n e r a t o r , t h e p o w e r to be employed bythe internal combustion engine would be eveng r e a t e r ) . A total power of over 3 P max isrequired t o d r i v e a t P max . T h a t m a k e s t h isdrive difficult to use in a universal vehicle( e . g . passenger cars) and expensive - parti-cularly due to the two electric components.F o r a v e h i c l e , w h i c h o n l y t r a v e l s i n t h ec i t y , e . g . a delivery van or city bus, it mays u f f i c e , i f t h e i n t e r n a l c o m b u s t i o n e n g i n ea n d g e n e r a t o r o f t h e s e r i e s h y b r i d a r e d e -s i g n e d f o r a v e r a g e p e r f o r m a n c e , s i n c e t h eb a t t e r y c o u l d t h e n p r o v i d e f o r t h e p o w e rpeaks. If this average performance is set at1 / 2 P max , i t c a n b e s e e n t h a t , e v e n i n t h e s eurban v e h i c l e s , engines would have to beinstalled with power of more than 2 P max .O n l y i f the combustion engine and theg e n e r a t o r a r e v e r y s m a l l c o m p a r e d t o t h ee l e c t r i c m o t o r - e . g . l i k e i n a r a n g e e x t e n -d e r f o r e l e c t r i c v e h i c l e s ( 2 ) , t h e s e r i e sh y b r i d s t r u c t u r e m a y b e a c c e p t a b l e b e c a u s eadditional weight, volumes a n d c o s t s a r esmall. T h e p r o b l e m o f e n e r g y e f f i c i e n c y i s n e -g l e c t a b l e i n t h i s c a s e b e c a u s e m o s t o f t h edriving energy comes as electricity from thep u b l i c n e t w o r k o v e r t h e b a t t e r y a n d t h eelectric motor to the wheels and only a smallamount c o m e s o u t o f t h e f u e l t a n k o v e r t h eIC-engine, t h e g e n e r a t o r a n d t h e e l e c t r i cmotor. Another situation would be given, i f t h ee f f i c i e n c y of the generator and the electricmotor together are as good as the efficiencyo f the conventional gearbox. I n t h i s c a s e ,n o t o n l y a s e r i e s h y b r i d c o u l d m a k e s e n s e ,but even a generator-motor-set instead of themechanical gearbox. Some companies hope to bea b l e t o d o t h i s b y u s i n g h i g h s p e e d s y n -chronous g e n e r a t o r s a n d m o t o r s w i t h n e wpermanent magnets having a very high magneticenergy density (3).B u t r e g a r d i n g F i g 2 s h o w i n g t h a t t h ee f f i c i e n c y of a mechanical gearbox is in awide range over 90 %, it seems to be a longway to the "electrical gearbox".Fig. 2 E f f i c i e n c y o f a t y p i c a l m e c h a n i c a lg e a r b o x o v e r t h e t o r q u e o f t h e i n p u tshaft for different rotation numbers.
`
`70
`
`4
`
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`Fig. 3 Structure of a parallel hybrid drive
`
`2.2 PARALLEL HYBRID DRIVES - Fig. 3 illus-t r a t e s a p a r a l l e l h y b r i d d r i v e . H e r e , t h einternal combustion engine V and the electricmotor E a r e not arranged i n s e r i e s(considering their power flow) but in paral-l e l . The power provided by the two motorscould be added to the vehicle drive. In thisway, the power P max required to drive a cityvehicle, could be provided by designing e.g.both the internal combustion engine and thee l e c t r i ceach. m o t o r t o g i v e t h e p o w e r l / 2 P m a x( F o r a s e r i e s h y b r i d u n d e r t h e s a m econditions, a t l e a s t 2 P max would have to bei n s t a l l e d . )
`
`Whilst t h e s e r i e s h y b r i d r e q u i r e s 2 e l e c -t r i c machines, only o n e i s p r e s e n t i n t h ep a r a l l e l h y b r i d . N e v e r t h e l e s s , e v e n w i t h t h ep a r a l l e l h y b r i d , n e i t h e r r e g e n e r a t i v e b r a k i n gnor r e c h a r g i n g t h e b a t t e r y w h e n d r i v i n gs h o u l d b e d i s r e g a r d e d , s i n c e t h e e l e c t r i cmotor E c a n a l s o f u n c t i o n a s a g e n e r a t o r ,e . g . i f t h e t o t a l p o w e r o f t h e i n t e r n a lcombustion engine is not required to drivet h e a x l e s . Turning to a parallel hybrid for a univer-sal vehicle requires the drive power P max forl o n g e r p e r i o d s , e . g . for long distances onthe motorway. In this case, the power of theinternal combustion engine must be P max . Thepower of the electric motor could be selectedfrom this completely independently. If P maxi s s e l e c t e d f o r t h i shybrid t o o , s i n c e t h e s e r i e s- i f t h e b a t t e r y p o w e r p e r m i t s - c a nd r i v e p u r e l y e l e c t r i c a l l y a t P max , a t o t a ld r i v e p o w e r o f o n l y 2 P max n e e d s t o b e i n -s t a l l e d . For a series hybrid under the sameconditions, t h i s w o u l d r e q u i r e more than 3P max .I n r e a l i t y i t i s m o r e s e n s i b l e t o s e l e c t amuch lower value for the power of the elec-t r i c d r i v e i n s u c h a p a r a l l e l h y b r i d ; i . e . al e v e l w h i c h p e r m i t s p u r e l y e l e c t r i c i n n e r - c i -ty driving with acceptable performance. Thisi s a n o t h e r p o i n t i n f a v o u r o f t h e p a r a l l e lhybrid. The advantages of the parallel hybridover the series hybrid can be summarized as follows:- Improved efficiency and thereby lower fuelconsumption i n t h e i n t e r n a l c o m b u s t i o nengine, s i n c e i t s m e c h a n i c a l e n e r g y i sdirectly passed on to the drive axle. (Onlyif the battery is charged during driving -which s h o u l d b e a v o i d e d f o r r e a s o n s o fconserving energy - is the same unfavour-able e f f i c i e n c y c h a i n p r e s e n t a s i n t h es e r i e s h y b r i d . )- The generator is no longer required- The weight is lower- Costs are lower2.3 STRUCTURES OF PARALLEL HYBRID DRIVES -P a r a l l e l h y b r i d d r i v e s c a n b e r e a l i z e d i n t h emost diverse forms, since the two mechanicalpower plants can be combined in various ways.T h e v e r s i o n a l r e a d y d i s c u s s e d i s i l l u s t r a -ted at the far left of Fig. 4. Because of itstwo parallel-running drive shafts, we like tocall this the two-shaft configuration.I n t h e n e x t s t r u c t u r e b o t h d r i v e u n i t s a r ea r r a n g e d a r o u n d a s i n g l e s h a f t . A s i n t h etwo-shaft configuration, the torques a r ea d d e d ( o r , i n g e n e r a t o r o p e r a t i o n , s u b t r a c -ted), and this provides a free choice, withinc e r t a i n limits, in determining the extent towhich the two units contribute t o t h e t o t a ldrive torque. This provides e.g. the opportu-n i t y to compensate for rapid changes in thedesired torque with the electric motor torqueand to permit only very slow changes in thet h r o t t l e - v a l v e s e t t i n g i n t h e i n t e r n a l c o m -b u s t i o n e n g i n e . T h i s s l u g g i s h n e s s i n t h et h r o t t l e - v a l v e h a s t h e e f f e c t o f r e d u c i n gexhaust emissions. However, the engine speedsa r e d e t e r m i n e d b y t h e g e a r b o x t r a n s m i s s i o n .There is no opportunity for selection here.T h e s i t u a t i o n i s r e v e r s e d i n t h e t h i r ds t r u c t u r e i l l u s t r a t e d i n F i g . 4 . H e r e , t h epower combination i s p e r f o r m e d b y a d d i n gtogether t h e s p e e d s o f r o t a t i o n o f b o t hd r i v e s i n a d i f f e r e n t i a l g e a r b o x p o s i t i o n e db e t w e e n t h e t w o u n i t s . T h e r e i s , t h e r e f o r e , acertain freedom in dividing the speed betweent h e t w o u n i t s , b u t t h e t o r q u e s a r e f i x e d b ythe desired drive torques. In consequence, iti s i m p o s s i b l e t o r e t a r d t h e t h r o t t l e v a l v e . Af u r t h e r d i s a d v a n t a g e a r i s e s f r o m t h e f a c tt h a t t h e e l e c t r i c m o t o r torque, on the onehand, a n d t h e p e t r o l e n g i n e t o r q u e , o n theother hand, must always be equal, althought h e t o r q u e - s p e e d maps o f b o t h u n i t s a r evastly different. Therefore, it is impossiblet o u t i l i z e e . g . the high torque of the elec-tric motor at low speeds of revolution, whichwould basically be advantageous for traction.
`
`71
`
`5
`
`

`

`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`Fig. 6 Exploded view of the components of the VW City Taxi hybrid drive
`
`- Sluggishness of the petrol engine in dyna-mic procedures by means of slow changes int h e t h r o t t l e v a l v e s e t t i n g . ( T h e d e s i r e dchanges are temporarily taken over by thee l e c t r i c m o t o r ) . However, the limitations of this City Taxidrive should also be recognized; a mountainroad with a gradient over 10 % of such lengthT h e v e h i c l e h a s b e e n t e s t e d o v e r 1 0 0 . 0 0 0km with the objective of obtaining informa-t i o n o n p e t r o l consumption and emissions.When the battery was mainly charged in dri-v i n g ( a n d n o t i n t h e g a r a g e w i t h a b a t t e r ycharger), p e t r o l c o n s u m p t i o n r o s e b y u p t o25 % against a conventional VW Bus. Ther e a s o n f o r t h i s i s t h e g r e a t e r w e i g h t o f t h evehicle and the unfavourable efficiency chainf o r c h a r g i n g t h e b a t t e r y i n t h e v e h i c l e .However, pollutant emissions dropped conside-rably i n c o m p a r i s o n t o t h e c o n v e n t i o n a lvehicle; specifically, CO by 27 % and HC by85 %. If the operation of the electric motoras a l t e r n a t o r i s r e d u c e d ( b y l i m i t i n g t h ec h a r g e c u r r e n t ) , f u e l c o n s u m p t i o n a n d e m i s -s i o n s f a l l ( 6 ) .T h e t r a c t i v e r e s i s t a n c e d i a g r a m i n F i g . 7shows t h a t t h e v e h i c l e d i s p l a y s r e s p e c t a b l eperformance although all driving conditionsare met in a single gear.This is due firstly to the ideal, hyberbo-l i c t r a c t i v e f o r c e c u r v e o f t h e e l e c t r i cmotor, secondly to the torque converter andt h i r d l y to the p rin cip le of torque addition.T h i s m e a n s t h a t e v e n a f u l l y l a d e n v e h i c l ec a n i n c r e a s e i t s a b i l i t y to climb by up to23 %. In many areas, t h e t r a c t i v e f o r c e s a r eeven higher than if a conventional VW Bus isdriven by a 37 kW petrol engine with 4-speedmanual gearbox.
`
`Fig. 7 Tractive resistance diagram of the VW
`City Taxi
`
`73
`
`7
`
`

`

`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`a s u f f i c i e n t o p e r a t i n g t e m p e r a t u r e a n d t h evehicle is standing s t i l l , both motors areswitched off. When 1st gear is selected, theI C - e n g i n e i s a u t o m a t i c a l l y s t a r t e d a n d t h eclutch between the IC-engine and gearbox isa u t o m a t i c a l l y c l o s e d w h e n t h e a c c e l e r a t o rpedal is depressed; the vehicle moves off anda c c e l e r a t e s . Releasing the accelerator pedal(to zero) causes the IC-engine clutch to openand the next gear can be selected.I f t h e t r a f f i c s i t u a t i o n r e q u i r e s l e s sperformance when driving with the IC-engine,t h e a c c e l e r a t o r p e d a l s h o u l d b e l i f t e d . I ft h e a c c e l e r a t o r p e d a l i s f u l l y r e l e a s e d a n dn o f u r t h e r a c t i o n o c c u r s f o r l o n g e r t h a n0 . 5 s . i.e. no renewed acceleration and noo p e r a t i o n o f t h e t r a n s m i s s i o n s e l e c t o r l e v e r ,t h e I C - e n g i n e s w i t c h e s o f f a n d t h e v e h i c l enow runs on without power. When the accelera-t o r p e d a l i s d e p r e s s e d a g a i n , t h e e l e c t r i cmotor takes over the driving. If the electricmotor’s 5 kW drive power is not sufficient,because t h e d r i v e r w i s h e s t o g o f a s t e r o ra c c e l e r a t e , he should "give more gas", i.e.increase the accelerator-pedal travel beyonda c e r t a i n p o i n t . T h e I C - e n g i n e i s r e - s t a r t e ds o t h a t t h e v e h i c l e c a n d r i v e o n u n d e r t h epower of the IC-engine.I t i s a l s o p o s s i b l e t o d r i v e w i t h e i t h e rthe electric motor alone or with the IC-en-gine alone: I f r e q u i r e d , it would be possible to driveu n d e r p u r e l y e l e c t r i c p o w e r - albeit withreduced c a p a c i t y f o r a c c e l e r a t i o n . A t aconstant speed of 50 kph, a distance of 36 kmc a n b e c o v e r e d u n d e r p u r e l y e l e c t r i c p o w e rwith the 200 kg lead-acid battery.F o r l o n g e r j o u r n e y s , e . g . h o l i d a y s , thet r a c t i o n b a t t e r y c a n be removed from thevehicle to obtain additional luggage spaceand i n c r e a s e d l o a d s . D r i v i n g i s t h e n d o n ewith the IC-engine.During braking and downhill driving thevehicle’s kinetic energy, which would other-wise be absorbed at the brakes or even resultin additional petrol consumption on accounto f e n g i n e overrun, can be stored in thetraction battery as electrical energy.After completion of the vehicle, consump-tion and exhaust emission measurements forthe European Cycle were first carried out ona r o l l e r d y n a m o m e t e r ( 8 ) . F o r t h i s , t h ep e r c e n t a g e d i s t r i b u t i o n o f d i s t a n c e c o v e r e dand time spent i n e a c h o f t h e 4 o p e r a t i n gconditions " E l e c t r i c d r i v e " , "IC-enginedrive", "Coasting" and "Stopping" were mea-sured. These were intered in Fig. 10. It canb e s e e n t h a t t h e I C - e n g i n e i s o n l y u s e d t oc o v e r 2 1 . 7 % o f t h e d i s t a n c e , w h i l s t t h eelectric motor is used for 53.3 %.
`
`Fig. 10 Distance and time percentage
`distribution in the European Cycle
`with the EVW2 hybrid drive
`
`T h i s n a t u r a l l y h a s s t r o n g i n f l u e n c e o nreducing consumption and emissions. TheHybrid-Golf only consumes 33 % of the petrolwhich the conventional Golf required for theEuropean Cycle. The quantities of CO and HCi n t h e e x h a u s t g a s e s w e r e g r e a t l y r e d u c e d ,but the quantity of NO x changed little.Extensive road tests were then carried outin public traffic in Brunswick (7). The fuelsaving in this case was not as high as in theEuropean Cycle, but it still amounted to 40 %over the Standard Golf. The additional elec-t r i c a l energy r e q u i r e d f r o m t h e t r a c t i o nbattery is 8.3 kWh/100 km or 13.8 kWh/100 kmf r o m t h e p u b l i c s u p p l y n e t w o r k . A t 0 . 2 0DM/kWh that is around 2.80 DM/100 km.I n t h e B r u n s w i c k - C y c l e , 6 0 k m c a n b ecovered i n h y b r i d d r i v i n g w i t h a s i n g l ebattery charge.3.3 ONE SHAFT HYBRID DRIVE EVW1 - The aim oft h i s p r o j e c t i s t o t u r n t h e b a s i c c o n c e p t o fthe EVW2 drive - optimal division of t a s k sbetween a relatively weak electric motor anda relatively powerful IC-engine - into reali-ty in a considerably more compact construc-t i o n s u i t a b l e f o r m o t o r c a r s .T h e p r e l i m i n a r y s t a g e c a n b e s a i d t o b et h e s i n g l e - s h a f t h y b r i d d r i v e j o i n t l y b u i l tby Volkswagen and General Electric and com-m i s s i o n e d b y t h e A m e r i c a n Energy Ministy(DOE) (9). The EVW1 hybrid drive for a VU Golf deve-loped in the last few years by VW also incor-p o r a t e s a s i n g l e - s h a f t c o n f i g u r a t i o n ( 1 0 ) .As Fig. 11 shows, both the IC-engine andt h e e l e c t r i c m o t o r o p e r a t e o n t h e g e a r b o xinput shaft. The rotor of the electric motorreplaces the gearbox flywheel and is flankedon each side by a clutch.
`
`75
`
`9
`
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`Fig. 11 Single-shaft hybrid drive EVW1 with
`disk electric motor between two
`clutches Kl and K2
`
`T o f i t s u c h a d r i v e i n t o v e h i c l e s a t t h el o w e r e n d o f t h e m i d d l e r a n g e , t h e e l e c t r i cmotor must be constructed in disk form with-out commutators, as already indicated in Fig.11. In cooperation with Bosch and LUK, VW hasdeveloped an asynchronous motor/generator inwhich the two clutches are integrated.This compact construction means t h a t t h ee n g i n e / g e a r b o x d r i v e u n i t o n l y i n c r e a s e s i nlength by 58 mm. The weight of themotor/generator, including the two clutches,in only 29 kg.This ASM not only functions as the motorin conjunction with the 60 volt battery anda s t h e g e n e r a t o r , i . e . f o r r e g e n e r a t i v eb r a k i n g , b u t i t a l s o r e p l a c e s t h e c o n v e n -t i o n a l s t a r t e r i n t h e I C - e n g i n e ; t h i s i sstarted by the ASM by closing K 2 . For drivingo f f , t h e 1 s t g e a r i s s e l e c t e d ; a c c e l e r a t i n gt h e n c l o s e s t h e a u t o m a t i c c l u t c h K 1 . S w i t -ching through the further gears is done withc l u t c h K 1 a s i n a s e m i - a u t o m a t i c . I f t h ea c c e l e r a t o r p e d a l i s r a i s e d a l o n g w a y , i . e .o nl y a l o w p o wer is r eq uired , K 2 o p e n s , t h e I C - e n g i n e - now without flywheel stops imme-d i a t e l y a n d t h e v e h i c l e t r a v e l s e l e c t r i c a l l ywith the asynchronous motor.W h a t i s m o r e , t h e e l e c t r i c d r i v e a l s or e p l a c e s t h e g e n e r a t o r , s i n c e t h e 1 2 v o l to n b o a r d c i r c u i t b a t t e r y i s c h a r g e d w h e ndriving with the IC-engine. Apart from regen-e r a t i v e b r a k i n g , t h e 6 0 v o l t b a t t e r y i s n e v e rcharged via the "TANK -IC- engine - ASM asg e n e r a t o r " c h a i n , b u t a l w a y s a t t h e e n d o fthe journey with the aid of a battery chargerfrom the 220 volt network. In this way, themost fuel can be saved.A driving mode selector switch makes itp o s s i b l e t o d r i v e p u r e l y o n t h e e l e c t r i cmotor alone, i.e. without using the IC-engineat all, although the extremely low accelera-tion rate should be taken into account. Thiswill be an important driving mode if we willhave city regions where only cars with elec-tric drive systems are allowed.T h i s d r i v e c o n c e p t h a s b e e n p u t i n t op r a c t i c e o n c e w i t h a p e t r o l e n g i n e a n d o n c ew i t h a d i e s e l e n g i n e a n d a G o l f h a s b e e nequipped with each.Both vehicles were tested in road trafficand on roller dynamometers.F i g . 1 2 i l l u s t r a t e s t h e e m i s s i o n s a n d t h efuel consumption measured for thed i e s e l / e l e c t r i c h y b r i d i n t h e E u r o p e a n C i t yCycle. For comparison, measured values from as t a n d a r d d i e s e l v e h i c l e a r e a l s o g i v e n . I tc a n b e s e e n t h a t t h e r e i s a s t r o n g r e d u c t i o ni n e m i s s i o n s a n d a c o n s i d e r a b l e s a v i n g o fliquid fuels. For this only 16.3 kWh electri-cal energy per 100 km from the supply systemmust be used to charge the battery.A f l e e t t e s t w i t h t h e E V W 1 h y b r i d d r i v ew i l l b e c a r r i e d o u t i n S w i t z e r l a n d s t a r t i n gin 1991. 20 VW-Golf with three different
`
`Fig. 12 Fuel consumption and emissions in the
`ECE Test Golf Diesel and Golf with
`diesel/electric
`hybrid
`drive
`
`76
`
`10
`
`

`

`Downloaded from SAE International by Timothy butler, Friday, July 01, 2016
`
`m a i n t e n a n c e f r e e b a t t e r y s y s t e m s w i l l b et e s t e d .3.4 AUDI DUO HYBRID DRIVE - The principle ofthe AUDI DUO hybrid drive is illustrated byt h e s t r u c t u r e o n t h e f a r r i g h t i n F i g . 4 .This structure was chosen because the basicid e a o f t h e A u d i d u o i s t o i n t e r f e r e a sl i t t l e a s p o s s i b l e w i t h t h e s t a n d a r d l a y o u tof the normal front-wheel drive car by usingt h e q u a t t r o r e a r a x l e t o d r i v e t h i s e l e c t r i -cally. To keep costs down the car is modifieda s l i t t l e a s p o s s i b l e .Thus the Audi duo is a largely unmodifiedfront-wheel drive vehicle. When required, forexample in restricted inner-city zones, onec a n s w i t c h o v e r t o a 9 . 3 k W e l e c t r i c m o t o rconnected directly to the rear differential.S o t h a t h i l l s t a r t s a r e a l s o p o s s i b l e t h ee l e c t r i c m o t o r m u s t h a v e a h i g h s t a r t i n gmoment . This is provided by the series-woundmotor, which gives the car a maximum speed of50 to 60 km/h on level roads.A comparison of the AUDI DUO and theEVW-Hybrid-Drive shows the following: If inf u t u r e t h e r e s h o u l d b e i n d i v i d u a l t r a f f i careas in which only electric drive is permit-t e d , t h e A u d i d u o c o n c e p t w i l l h a v e t h eb e t t e r c h a n c e s , b e c a u s e i t i s c h e a p e r t oproduce in small series on account of the lowlevel of vehicle modifications required. In ascenario where the saving of crude oil andthe reduction of CO 2 emission are the mainproblems, the one shaft hybrid will be morelikely to succeed. In large series productionit would have the additional advantage thati t i s n o t d e p e n d e n t o n h a v i n g f o u r d r i v i n gwheels, and the induction motor replaces theflywheel and the starter motor of the combus-tion engine.4. POTENTIAL FUEL SAVINGS WITH ELECTRIC VEHICLES AND ELECTRIC HYBRID VEHICLES B e s i d e s t h e p o s s i b i l i t y o f o p e r a t i n gv e h i c l e s w i t h e l e c t r i c a n d h y b r i d d r i v ep u r e l y e l e c t r i c a l l y , b o t h t y p e s o f d r i v eo f f e r t h e o p p o r t u n i t y t o s a v e q u a n t i t i e s o fdiesel and petrol by using electrical energy.I f t h e e l e c t r i c a l e n e r g y i s p r o d u c e d f r o mn o n f o s s i l p r i m a r y e n e r g y t h e r e i s g i v e n apossibility to reduce the CO 2 emission, too.T h e f o l l o w i n g e s t i m a t e s h o u l d s e r v e t odetermine the maximum potential saving: In1981, a study initiated by the federal Minis-t r y o f T r a n s p o r t ( B M V ) o f t h e u s a g e a n dmarket potentials of battery-driven electricp a s s e n g e r c a r s r e s u l t e d i n a f i g u r e o f 1 . 1million vehicles in private households in theFederal Republic of Germany (11). The usagep o t e n t i a l i s t h a t p a r t o f t h e t o t a l p a s s e n g e rc a r s w h i c h c o u l d b e r e p l a c e d b y e l e c t r i c v e h i c l e s , c o n s i d e r i n g t h e t e c h n i c a l r e s t r i c -t i o n s o f t h e b a t t e r y - e l e c t r i c d r i v e . F u r t h e rfeatures, such as acceptance by the owner ofthe influence of vehicle costs on the deci-sion to purchase, are of no significance forthe usage potential. In 1981, this was appro-ximately 5,6 % of the total number of passen-g e r c a r s i n h o u s e h o l d s . A s s u m i n g t h a t a l lvehicles travel an equal number of kilometersp e r y e a r a n d c o n s u m e a n e q u a l a m o u n t o fp e t r o l , a p o t e n t i a l f u e l s a v i n g t o t h e s a m ee x t e n t i s a c h i e v e d . I n c o n t r a s t t o t h i s , t h ehybrid drive is a universal drive. The usagep o t e n t i a l i s , t h e r e f o r e , i d e n t i c a l t o t h et o t a l n u m b e r o f v e h i c l e s . I f i t c a n b e a s -s u m e d t h a t e a c h v e h i c l e c o v e r s 3 2 % of itsannual mileage in urban traffic (12) and theu s e o f a h y b r i d d r i v e s a v e s 6 7
`% of liquidfuels, this gives a potential fuel saving of2 1 , 4 % . T h i s f i g u r e i s c o n s i d e r a b l y l a r g e rthan the potential saving of 5.6 % for elec-tric vehicles, and, therefore, more attentionshould certainly be given to the hybrid drivethan previously.REFERENCES (1) BADER, Ch. Vergleich alternativer An-triebssysteme für Omnibusse, Automobil-Industrie 4/82, pp. 461-465(2) ANDERSON, W. Advanced electric vehiclepowertrain components, Automative Tech-nology Interntional 91, Sterling Publi-cations International Ltd.(3) HEIDELBERG, G. Magnet-Motor Antrieb fürNutzfahrzeuge und Verbrauchs- und Emis-sionsfreundliche NahverkehrsbusseElektrische Bahnen 87 (1989) p 135.(4) MIERSCH, R. Otto-Elektro-Hybridantriebim VW-City-Taxi, Electric Vehicle Coun-cil, Electric Vehicle Symposium 5,Philadelphia 1978 (872403)(5) Electric- and Hybrid-Vehicle PowertrainDevelopment, Fourth International Sympo-sium on Automotive Propulsion Systems,April 17th
`
`- 22nd, 1977, Washington D.C.(6) MIERSCH, R. 100.000 km testdrive of aVW-Microbus with an ICE electric-hybrid-drivesystem, EVS7, 26.
`- 29.06.1984,V e r s a i l l e s(7) S