1、07FTM09The Ikona Clutch and Differentialby: J. Colbourne, Consultant, V. Scekic and S. Tesic, IkonaIndustries CorporationTECHNICAL PAPERAmerican Gear Manufacturers AssociationThe Ikona Clutch and DifferentialJohnColbourne,Consultant,SashaTesicandVladimirScekic,IkonaIndustriesCorporationThe statement
2、s and opinions contained herein are those of the author and should not be construed as anofficial action or opinion of the American Gear Manufacturers Association.AbstractThis paper describes twodevices,aclutchandadifferential,whicharebasedontheIkonaCVT.This CVTisessentiallyaninternalgearpair,inwhic
3、hthepinionismountedonaneccentricthatcandriveorbedrivenbyanelectric motor/generator, thus providing a variable ratio. Since this arrangement allows for “branching” ofenergyflow(s),itcanbeclassifiedassummation-typeCVT.Therangeofratiosdependsontheinputspeed.For example, with an input speed of 600 - 200
4、0 rpm, the ratio can be anything from infinite to about 1:2.When the CVT is used as a clutch, it would replace the friction-plate clutch in vehicles with standardtransmissions,andthefluidtorqueconverterinautomatictransmissions.Intheseexistingdevices,energyiswasted during modulation from standstill,
5、and at every gear change, while the engine speed is altered tomatchthespeedofthegearboxinputshaft.Inthecaseofthefluidtorqueconverter,energyisalsolostduringacceleration, due to the inefficiency of the device whenever the engine speed differs from the speed of theconverteroutputshaft.Thenewclutchwillb
6、ereferredtoastheelectrictorqueconverter.Anyexcessenergyisconverted into electrical energy, and either stored in the battery, or reintroduced into the system through themotor/generator. With very efficient energy recovery, modulation of the clutch can be very smooth which isparticularly advantageous
7、when the vehicle starts from rest on uphill slopes. Since no friction element isinvolved, and only a fraction of torque is being manipulated, the modulation can be repeatable regardless ofconditions. Finally, in a hybrid-vehicle arrangement, the clutch can be used to maintain the engine at itsoptimu
8、m speed (within limits), regardless of the road speed and the gearbox ratio.Similar principals apply to the Ikona differential. Unlike todays limited slip differentials, the Ikona differentialallows full torque to be transmitted through one drive wheel, even though the other drive wheel may havecomp
9、letelylosttraction.Unliketraditionaldifferentialsthatallowwheelstorotateatdifferentspeeds,theIkonadifferentialforcesthewheelstodoso.Accordinglywhenthevehicleischangingdirection,thedifferentialcanbe used to control the speed of each drive wheel, thus providing active torque steering.Copyright 2007Ame
10、rican Gear Manufacturers Association500 Montgomery Street, Suite 350Alexandria, Virginia, 22314October, 2007ISBN: 978-1-55589-913-41The Ikona Clutch and DifferentialJohn Colbourne, Consultant, Vladimir Scekic, and Sasha Tesic,Ikona Industries CorporationIntroductionThe Ikona CVT consists of an inter
11、nal gear pair, inwhich the pinion is mounted on an eccentric, asshowninFigure1. Theeccentricisconnectedtoanelectricmotor/generator,whosespeedcanbemod-ulated, thus providing the variable ratio. The CVTcan be used as a clutch (Figure 2), replacing theplate clutch in a standard transmission, or the flu
12、idtorque converter in an automatic transmission.WhentheCVTisusedinthismanner,itwillbecalledan electric torque converter. The CVT can also beadaptedtoformadifferential(Figure3). Inthiscasethe internal gear is meshed with two pinions, eachmounted on separate eccentrics, so there are twooutputs with in
13、dependently controllable ratios. Theelectric torque converter and the differential are thesubjects of US provisional patent applications577088002pro and 577088003pro.Figure 1. Ikona CVTFigure 2. Sectional exploded view of IkonaCVT clutchDescription of the CVT clutch/electrictorque converterThe Ikona
14、 gear is an internal gear pair, described inpatents US5505668 and EP770192B1. Comparedwith conventional involute gear pairs, it has the fol-lowing advantages. First, the difference betweenthe tooth numbers can be as low as one. Secondly,the contact ratio is high, meaning that a gear paircan transmit
15、 a larger torque than an involute gearpairofsimilarsize. Thirdly, thebacklash isminimal.All these properties are important when the gearpair is used to form a CVT.1_1Along similar principals, a solar epicyclical gear system can be used in which case the following has to be satisfied:(N1)whereNringan
16、dNsunstandfornumberofteethontheringgearandsun-pinionrespectively,in,outandsunstandfor rotational speeds of flywheel, output shaft and sun-pinion respectively. This embodiment may be referred to asSolar CVT Clutch. More detailed analysis of this type of arrangement may be subject of another paper.Nri
17、ngNsun*in=1 + NringNsun*out sun2Figure 3. Sectional-exploded view of IkonaCVT differentialWhen the CVT is used as a clutch/electric torqueconverter, the internal gear is connected to the en-gineoutput,generallytheflywheel,andthe pinionisconnected to the input shaft of the gearbox. Thepinion and inte
18、rnal gear tooth numbers will dependon engine and vehicleproperties; forthe purposeofthis paper we may work with those numbers beingrespectively 19 and 20. This means that the geo-metrical clutch input-output ratio would be 20:19,(i.e., close to 1.0:1) if the eccentric were heldstationary. However, f
19、or the situation where theec-centric is allowed to rotate around its own axis, therelation between the input, output and eccentricangular velocities is given by:20 *int= 19 *pinion+ ecc(1)where int, pinionand eccare the three angularvelocities.When solved for the transmission input speed,equation (1
20、) becomes:pinion=20 *int ecc19(2)When solved forecc, for casepinion= 0, equation(2) becomes:ecc= 20 *int(3)The input and output torques Tintand Tpinionare re-lated to the eccentric torque Teccas follows:2Tint= 20 * Tecc(4)Tpinion= 19 * Tecc(5)Looking at the equations (1) thru (5), we may findthat:S
21、Itispossibletokeepthetransmissioninputshaftstationary (pinion= 0) while the engine isrunning (int 0).S In order to provide this condition, the eccentricneeds to spin at 20 times engine speed(ecc=20*intfor 19/20 teeth combination).S By modulating the eccentric speed fromecc=20*inttoecc= 0, wecan achi
22、evetrans-missioninputshaftmodulationfrompinion=0topinion= (20/19)*int.S ModulationofthetransmissioninputtorquefromT=0toT=Tnominalcanbeachievedbymanipu-lation of the eccentric torque which representsonly 1/19 of Tpinion(1/20 of Tint).In all vehicles, the engine speed will differ from thegearbox input
23、 shaft speed when the vehicle startsfrom rest, and during and immediately after eachgearchange. Inaddition, invehicles withautomatictransmissions, the torque converter will allow theengine to turn faster than the gearbox input shaftduring acceleration in order to provide smooth run-ning and more tor
24、que.The process of speeding up the output shaft of aclutch and matching its speed to the input shaft(fly-wheel) is called clutch modulation. The power ofmodulation at any given moment can be calculatedby:P = Teng*eng Tgboxinput*gboxinput(6)_2Torque equations do not consider internal losses.3While th
25、e exact values of Tengand Tgboxinputmaynot be known, it is clear that there is excess powerfrom the engine during the situations listed above.Thetotalenergyofmodulationwillthenbegivenby:E = t2t1P*dt(7)Obviously, in systems with single energy path, theenergy of modulation will be released within thec
26、lutch/converter. In order to prevent overheatingand/orprematurewearonthesedevices,bothpow-er and duration of modulation need to be limitedwhich, in turn, may lead to shock-loading othercomponents of the drive-train and/or to an uncom-fortable ride in the vehicle. An alternate solution istoprovideana
27、uxiliarybranchintheenergypathandtodirecttheenergyofmodulationthroughthatauxil-iary branch. Ideally, we may convert that energyinto useful work or store it in another form for futureuse, thus minimizing waste and improvingefficiency.In the Ikona CVT clutch, the difference betweenthespeeds of the engi
28、ne and the gearbox input shaft isaccommodated by the CVT gear pair and the rota-tion of the eccentric. The energy of modulation isused to spin the eccentric, which drives the motor/generator attached to it3. This energy is thenconvertedintoelectricalenergy,whichisfedintothevehicle battery. In cases
29、where extra energy is re-quired, as described below, the energy is fed fromthe battery into the motor/generator, which thenacts as a motor and adds to the engine torque.For example, when the vehicle starts from rest, theeccentric will be turned initially at 20 times the en-gine speed, so that the ve
30、hicle remains stationary,as seen from Equation (2). For many vehicles, theidle speed of the engine would be about 700 900RPM, so the eccentric would be controlled to turn at14000 18000 RPM. However, it is often advanta-geous to increase the engine speed when startingfrom rest, particularly for heavy
31、 commercial ve-hicles when starting on an uphill slope, in order toprevent stalling. The engine speed can be in-creased to about 1500 2000 RPM before the ve-hicle moves, thus providing greater torque, and theeccentricwouldthenbecontrolledtoturnat3000040000 RPM. This is a high speed for the modulatin
32、gmotor/generator, but not impossible. Manymodernelectric motors with permanent magnets, in the 10kWrange,areinfactmostefficientatspeeds30000 40000 RPM, and the eccentric would only turn atthese high speeds for very short periods of time.To accelerate the vehicle from zero speed until thegearboxchang
33、esfromfirst tosecond gear,it issim-ply necessary to reduce the speed of the eccentric,which can be easilyand repeatablydone byloadingthe modulating motor/generator. As seen in Equa-tion (4), the torque required for the eccentric is onlyequal to the engine torque divided by 20, so this isquite practi
34、cal. Finally, electric motors/generatorstypically provide torque curves that are perfectlysuited for this kind of duty.When the eccentric is not turning, we can see fromEquation (1) that the engine speed is equal to thegearbox input shaft speed, multiplied by (19/20).This engine speed will be called
35、 the synchronousengine speed. If the engine turns faster than thesynchronousspeed,theeccentricmustrotateinthesame direction as the engine. If the engine turnsslower, the eccentric must rotate in the opposite di-rection.When the engine is driving the vehicle, and the ec-centricturnsinthesamedirection
36、astheengine,wecan show by a simple force analysisthat theeccen-tric will drive the modulating motor/generator, sothatelectricenergywillbefedintothevehiclebatter-y. If the eccentric turns in the direction opposite tothe engine, the eccentric will need to be driven bythe motor/generator, so that energ
37、y is drained fromthe battery.Ifthevehicleisdrivingtheengine,asforexampleona steep downhill slope, the engine torque is re-versed. In this case the eccentric will be driven bythemotor/generatorwhenitturnsinthesamedirec-tion as the engine, and will drive the modulatingmotor/generator when it turns in
38、the oppositedirection.These statements enable us to determine the flowof energy in various phases of the vehicle motion._3Inspinningtheeccentrictoaltertheratiobetweentheenginespeedandthegearboxinputspeed,themotor/generatorwillbe referred to as “a modulating motor/generator”.4For example, when the ve
39、hicle starts from rest theenginespeedisfasterthanthesynchronousspeed,so the eccentric turns in the same direction as theengine, and the generator feeds energy into thevehicle battery.Thesituationissimilarwheneverthereisanupwardchange of gear. Immediately after the gear changethe engine is turning fa
40、ster than the synchronousspeed. Toallow forthe differentspeeds, theeccen-tric must be rotated in the same direction as theengine, so once again the eccentric will drive thegenerator, and energy will be fed into the battery.On a downhill slope, or when the vehicle is slowingdown, the accelerator peda
41、l is released, and wehaveenginebraking. Theenginespeedisthenlessthan the synchronous speed, so the eccentric turnsin the direction opposite to the engine, but sincetheengine torque is reversed, the eccentric will againdrive the generator, feeding energy into the battery.The last case to be considere
42、d is the downwardchange of gear. There are generally two possiblereasonsforadownwardgearchange. Thefirstrea-son is that the vehicle is slowing down preparing tostop. If the engine was turning at synchronousspeed before the gear change, it will be turning atless than the synchronous speed just after.
43、 As thevehicle slows down the engine torque is again re-versed, and the eccentricwill againdrive thegener-ator. The second reason for a downward gearchange is that the accelerator pedal is depressed,either to provide acceleration or because the ve-hicle is traveling uphill. In this case the downward
44、gear change causes the speed of the gearboxinputshaft to increase, so that immediatelyafter thegearchange the engine is turning at less than the syn-chronousspeed. Theeccentricisthenturninginthedirectionoppositetotheengine,andmustbedrivenbythemotor. Thisistheonesituationwhereenergyis required from t
45、he battery. As compensation, theextra power exerted by the electric motor helps thevehicle to accelerate, or to maintain its speed up anincline.In summary, in most instances where energy iswastedbyconventionalclutchesorfluidtorquecon-verters, the Ikona CVT clutch uses that energy todrive themodulati
46、ng motor/generator,and hencetocharge the battery. In the one situation where theIkonaCVTclutchdrawspowerfromthebattery,thispowerisusedtoimprovetheperformanceoftheve-hicle. It is important to note, however, that in theform described, drawing energy from the batteryin-creases the power going into the
47、gearbox, butleavesthegearboxinputtorqueunchanged. Thein-put torque to the gearbox is related to the enginetorque by Equations (4 and 5):Tpinion= Tint*1920(8)The spinning eccentric allows the gearbox inputspeed to turn faster than the synchronous speed,and since the torque remains constant the gearbo
48、xinput power is increased. This is now higher thantheengineoutputpower,andthedifferenceismadeup by the power drawn from the battery.In order to increase the torque availability, and re-duce the number of times energy is converted fromone form to another (efficiency issues), anotherelectrical machine
49、 may be integrated in-line withthe main torque-path (flywheel, ring-gear). Thismachine is called the converting motor/generator.By this addition, any electricity generated in themodulating generator may be directly used withinthe converting motor thus increasing torque avail-abletotheclutch, andreducing thenumber ofener-gy conversions. The end result of this process issimilar to thatachieved withfluid torqueconverters,albeit with better overall efficiency and a few extrafeat
