The Identification of the Volkswagen Bora 1.6 L. Petrol Engine, Used in the Ecodrive Project

The identification of the Volkswagen Bora 1.6 l. petrol engine, used in the EcoDrive project

Citation for published version (APA): Bruijn, de, P. M. J. (2003). The identification of the Volkswagen Bora 1.6 l. petrol engine, used in the EcoDrive project. (DCT rapporten; Vol. 2003.066). Technische Universiteit Eindhoven.

Document status and date: Published: 01/01/2003

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Download date: 24. Sep. 2021 The identification of the Volkswagen Bora 1.6 1. petrol engine, wed in the EcoDrive project.

P.M.J.de Bruijn DCT report: 2003-66

Internship Eindhoven, July, 2003

Technische Universiteit Eindlnoven Department of Mechanical Engineering Devision of Dynamics and Control Technology Hub van Doornes Chair

Coach: Dr. Ir. A.F.A. Serrarens Supervisor: Prof. Ir. N.J.J. Liebrand The identification of the Volkswagen Bora 1.61. petrol engine, used in the EcoDrive project.

P.M.J. de Bruijn

July, 2003 Abstract

Because the fossil fuel reserves are decreasing and the environment gets more important for society, carmanufacturers are, pushed by governmental legislation, trying to make cleaner and more fuel economic vehicles.

At the Technische Universiteit Eindhoven there is also a project aiming at reduction of fuel consumption. As a result of that project, the ZI transmission is designed. The principle of that ZI transmission is that a steel flywheel assists the internal combustion engine with mechanical torque. The flywheel is designed to decelerate when the engine speeds up quickly. All of the energy that is stored in the flywheel goes to the engine and compensates the energy that would be lost by speeding up parts with a high inertia. The ZI transmission uses a VanDoornes V-belt CVT as transmission. Because the ZI transmission is a prototype, a new controller has to be built. There are two main functions for this controller. First it has to determine with which force the CVT pulleys must pinch to avoid slip between pulleys and belt, and it has to make sure that that force is generated by the pump. Second, the CVT controller tries to shift the transmission in such a way that the engine runs as much as possible on its economy-line, which is the line that connects the points in the enginemap with the highest efficiency.

The setpoints for the hydraulic force with which the CVT pinches are the points from the engine map of the Volkswagen Bora, which is the test vehicle. Because the engine map is not known, this has to be reconstructed. Therefore some experiments have to be done. The engine torque can be defined by making use of an a priori known torque characteristic of a torque converter. A torque converter is a device for converting torque or turning moment by hydrodynamic means; that is by making use of the kinetic energy of a fluid in motion. A torque converter exists of three vaned wheels: an impeller, a turbine and a reactor. The torque amplification is the highest when the vehicle is launched from rest. In that case the slip between impeller and turbine is the largest. The engine torque can be reconstructed in the experiment at a certain speed from the impeller torque and the known pump losses. The impeller torque is defined by a so called input capacity factor and the impeller speed. The pump losses were determined earlier on a test rig. Because not all engine operating points could be reached (quasi-)stationary, the engine map obtained is extrapolated. This extrapolating is done by following the trend of another 1.6 1. engine.

In order to find the economy-line, the specific fuel consumption must be known. The specific fuel consumption can be determined because the momentary fuel mass flow can be reconstructed. Therefore the injection time is metered. It is sufficient to know the injection time because the engine is equipped with an electronic multipoint fuel injection system. In such a system the injection pressure is constant and the flow of fuel is direct and proportionally related to the injection time. Other injection systems are single-point fuel injection systems, mechanical multipoint fuel injection systems and direct injection systems. The fuel injection valve is the device that makes sure that the fuel is atomized and is injected in the cylinder in a correctly dosed quantity. Each fuel injection system has its own type of injection valve. When the momentary fuel consumption is defined, the specific fuel consumption can be determined. rnllne economy-line jE-iinej can be found by connecting the points in the engine map of the highest efficiency at each feasible engine power. The CVT controller then knows at which ratio the CVT should work in order to let the engine run in its optimal point.

Because some assumptions are made during the experiments, the accuracy of the results are not very high. But for the CVT controller the results of the experiments are accurate enough. For other applications where the accuracy should be improved, some adjustments should be done to the experiments. Samenvat t ing

Aangezien de voorraad van fossiele brandstoffen steeds kleiner wordt en het milieu voor veel regeringen steeds belangrijker wordt, zijn automotive en petrochemische bedrijven steeds meer bezig met het vinden van schonere en zuinigere auto's. Op de Technische Universiteit Eind- hoven is ook een project gaande om het brandstof gebruik te verminderen. Het principe van dit EcoDrive project is dat een stalen vliegwiel de verbrandingsmotor helpt door middel van mechanisch koppel. Het vliegwiel is zo ontworpen dat, zodra de motor optoert, het vliegwiel snel aftoert. De energie die in het vliegwiel opgeslagen zit, komt daarbij dus vrij en die kan gebruikt worden om de energie te compenseren die door de traagheden van de motor en versnellingsbak verloren gaat. Alle energie van de motor kan nu dus gebruikt worden om het voertuig te versnellen. De ZI powertrain maakt gebruik van een VanDoorne Transmissie's duwband CVT als versnellingsbak. Aangezien deze powertrain een prototype is, moet er een nieuwe regeling ontworpen worden voor de CVT. De setpoints voor deze regeling, die de hydraulische knijpkracht die geleverd moet worden regelt, zijn de punten die voortvloeien uit de motormap van de Volkswagen Bora, hetgeen het testvoertuig is van het EcoDrive project. Omdat Volkswagen echter die motormap niet wil vrijgeven, is het noodzakelijk om deze te reconstrueren. Daarom is het doen van experimenten noodzakelijk. Het motorkoppel kan bepaald worden door gebruik te maken van een geopende koppelornvormer. Een koppelomvormer is een onderdeel van de aandrijflijn dat bij automatische versnellingsbakken en CVT's dienst doet als koppeling. Een koppelomvormer kan een koppel versterken op hydro- dynamische gronden, dus door gebruik te maken van de kinetische energie die een vloeistof in beweging bezit. Een koppelomvormer bestaat uit drie schoepenraden: een impeller, een turbine en een reactor wiel. The impeller is bevestigd aan de uitgaande as van de motor. Als de impeller begint te roteren, wordt de olie door de vorm van de schoepen in de richting van de turbine gegooid. De turbine is aan de ingaande as van de CVT bevestigd . Omdat de turbine ook schoepen bezit, begint deze te roteren en zal het voertuig wegrijden. De olie wordt nu naar het reactor wiel geworpen, die de olie zo afbuigt dat deze precies de goede in- treehoek heeft voor de impeller. Omdat de olie ook nog impuls bezit, wordt het motorkoppel versterkt door de olie dat van het reactor wiel komt. Het voordeel van de koppelomvormer is het grootst als een voertuig wegrijdt uit stilstand, dus als de slip tussen impeller en turbine het grootst is. Als de slip onder een bepaald punt komt, treedt een lock-up in werking waardoor de koppelomvormer als een star lichaam functioneert en er geen verliezen meer op- treden. Het motorkoppel kan gereconstrueerd worden met behulp van experimenten doordat het rnotorkcppel gelijk is aaE het impellerkoppel plus de pornpverliezen. Het impellerkoppel kan bepaald worden door de capaciteitsfactor van de koppelomvormer en het motortoerental. De pompverliezen zijn in een eerder stadium bepaald op een proefstand. De verkregen motormap moet nog gextrapoleerd worden, zodat het hele toerengebied bereikt wordt. Bij het extrapoleren wordt gekeken naar de trend van een andere motormap van een 1.6 1. motor. Om tot een zogenoemde economy-line te komen, hetgeen een lijn is die de punten in de motormap met elkaar verbindt die de hoogste efficiency hebben bij een bepaald motorvermogen, moet het specifiek verbruik bekend zijn. Het specifieke verbruik kan bepaald worden uit het momentane verbruik en dat kan gemeten worden. Om dat te meten moet de inspuitduur gemeten worden. Aangezien de motor van de Volkswagen een electronische multipoint injectie heeft, is het weten van de inspuit6-mi- voldoende. Bij zo'n multipoint injectie systeem, is de injectiedruk constant en is de hoeveelheid brandstof direct en lineair afhankelijk van de inspuitduur. Andere injectie systemen die gebruikt worden zijn: single-point injectie systemen, mechanische multipoint systemen en directe injectie systemen. Het injectiespruitstuk is het deel van het injectie systeem dat voor de inspuiting in de cilinder zorgt en dat er voor zorgt dat de brandstof genoeg verneveld wordt, zodat een goede verbranding kan plaatsvinden. Ieder injectie systeem heeft zo zijn eigen injectiespruitstuk. Als het momentane verbruik bekend is, kan daaruit het specifieke verbruik bepaald worden. Vervolgens kan de E-lijn gevonden worden door in de verkregen eiercurves de punten van hoogste efficiency bij een bepaald motorvermogen te verbinden. De regeling van de CVT kan nu bepalen welke ratio ingesteld moet worden om de motor in haar optimale punt te laten werken. Aangezien er tijdens de experimenten een aantai aannames is gedaan, kunnen er verbeteringen aangebracht worden aan de experimenten om de nauwkeurigheid te vergroten. Voor de regeling van de CVT zijn de verkregen resultaten echter nauwkeurig genoeg. Op de regeling zit namelijk ook nog een bepaalde veiligheidsfactor. Contents

Abstract

Samenvatting iii

1 Introduction

2 The Zero-Inertia project 4 2.1 Introduction ...... 4 2.2 System description ...... 4 2.3 Design of the flywheel ...... 8 2.4 The test vehicle ...... 10

3 Torque converters 11 3.1 Introduction ...... 11 3.2 Workingprinciple ...... 12 3.3 Characteristic ...... 15 3.4 The influence on the vehicle traction force ...... 16

4 Fuel injection systems 18 4.1 Introduction ...... 18 4.2 Single-point fuel injection ...... 19 4.3 Multipoint fuel injection ...... 20 4.3.1 Mechanical injection ...... 20 4.3.2 Electronic injection ...... 22 4.4 Direct injection ...... 23 4.5 Fuel injection valve ...... 24

5 The experiments 26 5.1 Introduction ...... 26 5.2 The enginemap ...... 27 5.3 The economy-line ...... 33

6 Conclusions and recommendations 36 6.1 Conclusions ...... 36 6.2 Recommendations ...... 36

References 38

Nomenclature 39

A The schematic ATF flow in a torque converter 40 Introduction

In the past few years, there's an increasing awareness of the fact that fossil fuel reserves are decreasing and that within less than fifty years no fossil fuel is producable for a reasonable price. Furthermore there is an enlarged that automotive vehicles have an increasingly negative influence on the environment.

Because of these problems governments, motor companies and fuel companies are searching for environmentally friendly solutions. The government force motor and fuel companies to develop cleaner cars and to find alternative fuels, through legislation, policies and funding. As a result motor companies are now able to produce cars that can run more than twenty kilometers on only one liter of fuel. Besides more efficient engine technologies also cars with a complete alternative type of propulsion are developed. These cars, like the Toyota Prius or the Nissan Tino, have besides the internal combustion engine (ICE) also some sort of secondary power source. This makes it possible that the ICE works in an efficient point and that the secondary power source works at moments that the ICE would run in less efficient operating points.

At the Technische Universiteit Eindhoven a project aiming at the reduction of fuel consumption is undergoing. In this project, termed EcoDrive, a Van Doorne V-belt Continuous Variable Transmission (CVT) is combined with a flywheel that delivers a torque when the CVT shifts to a lower ratio. The idea is to let the flywheel shortly deliver the necessary torque for vehicle acceleration, while the engine uses its combustion power to accelerate itself. This should result in a significant decrease of fuel consumption without loosing a good drivability.

An enginemap is a dense collection of points in which the brake specific fuel consumption (BSFC) is known as a function of engine speed and torque. The BSFC in fact constitutes the fuel mass flow per delivered engine output power in a particular operating point. The assignment of this report is to identify the engine map for the 1.6 liter engine in the VW Bora, test vehicle used in the EcoDrive project. This engine map is used to determine pressure setpoints for the CVT-controller. Besides the engine map also a so called economy-line, had to be reconstructed. The economy-line, E-line for short, forms the locus of engine operating points where the BSFC is minimal for every engine output power within its operating range.

By driving the vehicle on a roller-bench with controllable dynamometer for an extensive amount of engine operating points, the torque and fuel mass flow can be reconstructed in the following way. The torque transmitted through the torque converter is a measure for the engine torque whereas the fuel injection time intervals are a measure for the fuel mass flow.

In the first chapter of this report the zero-inertia project will be shortly discussed. After that, the next chapters will be the result of the literature study about torque converters and electronic fuel injection systems. Finally the experiments will be explained and of course the resuits wiii be presented. Chapter- 2

The Zero-Inertia project

2.1 Introduction

Tne zero inertia transmission is able to assist the engine in transient by pure mechanical means. An advantage of such a system is that the system is not as complicated and expensive as other solutions, that use for instance an electrical motor with batteries. The assignment of the EcoDrive project, as the complete project is named, was to develop an optimized powertrain with an ICE, Continuous Variable Transmission (CVT) and a flywheel with the next goals:

a A significant decrease of fuel consumption (up to 25% with regard to a 4-speed automatic transmission).

a No decrease in the performance of the vehicle.

a A good drivability

a Low costs for the powertrain (much lower than the alternative systems).

2.2 System description

Figure 2.1 shows a schematic drawing of the Zero Inertia (ZI) powertrain. The engine in this powertrain is a 1.6 1. 4 stroke petrol engine, the transmission is a Van Doorne metal pushbelt CVT and besides there are also a torque converter, DNR-set, a final reduction gear and a differential. Parallel to the CVT, a steel flywheel is connected to the CVT by a planetary gear set. The design of this flywheel will be discussed in the next paragraph. The planetary gear set operates like a power-split device. Depending on the change of ratio of the CVT it splits power of the flywheel to and from primary and secondary side. The Aywheel speed depends on the primary and secondary pulley speed Figure 2.1: The ZI-powertrain

where z is the characteristic ratio of the planetary gear set, which is the ratio between the radius of the annulus and the radius of the sun. When using the following definitions:

Where r is the CVT ratio, the flywheel speed can be written as:

From equation (2.5) it is clear that when r = rGN , the flywheel speed is zero and so this ratio is called geared neutral (GN). The torque stemming from a accelerating or decelerating flywheel is split into one through the annulus and one through the carrier gear. These torques can be described as: and thus:

From equations (2.6), (2.7) and (2.8) the operating of the flywheel unit can easily be explained. If wf becomes negative (the flywheel decelerates) then the annulus gear demands a reaction torque Tafrom the primary pulley, through which the carrier gear can deliver a torque T, to the secondary pulley. It is obvious that Tcis larger than Taif TGN < 1.

Of course the inverse reasoning holds for an accelerating flywheel. The net Torque T, stemming from the flywheel is given by:

From equation (2.9) it follows that T, is positive when (r - rGN) < 0. Taking into account that is typically an order of magnitude smaller than , it can be seen from equation (2.5) that the flywheel decelerates as the CVT ratio decreases, and vice versa. Decreasing the CVT ratio increases the primary pulley speed and thus the engine speed, resulting in the primary and engine inertias Jp and J, absorbing part of the torque. Provided the flywheel inertia Jf is sufficiently large and the CVT speed ratio is manipulated appropriately, the engine torque Temay take the acceleration of Je and Jp on its account, while the flywheel unit delivers the desired net torque Tnas in equation (2.9). This is exactly the behavior necessary to overcome the reluctance in vehicle response whenever large pedal deflections are attended with large leaps in engine speed. An optimal design of the geared neutral ratio ~GNand Jf is required to let the sizing of the flywheel unit be in concert with its function.

The principle of the ZI-transmission can also be explained in a more visual way.

An disadvantage of good fuel efficiency often is a bad vehicle acceleration response. A reason for this is that when a car is running in a point of optimal fuel efficiency, the torque reserve and amplification is limited. Because of that, the increase of power, needed to accelerate, often has to be accompanied with an increase of engine speed. The increase of engine speed takes some time, and thus it takes time to accelerate the vehicle as is shown in figure 2.2. Apart from the fact that the change of engine speed takes time, also the inertias connection to the engine take part of the combustion tcrcpe. The pawer at the wheels will conseque~tly be restricted during the transient. Figure 2.2: Schematic drawing of the increase of power at the wheels without flywheel

On the other hand the flywheel decelerating makes it possible that although the engine speed up takes time the power at the wheels increases instantaneous. This is shown in figure 2.3.

Figure 2.3: Schematic drawing of the increase of power at the wheels with flywheel

Using the kinetics of the planetary gear set makes it possible to decelerate the flywheel while the engine speeds up. In figure 2.4 one can see the general representation of the velocities in the planetary gear set. The engine is connected to the annulus, the flywheel to the sun and the secondary pulley to the carrier. So figure 2.4 represents the situation that there is a low engine speed and a high flywheel speed. It appears that Vl, V, and V2 always can be

=r.w,\ Annulus A - 1 Carrier ZW - -Sun

Figure 2.4: The general representation of velocities in a planetary gear set with low engine speed represented in a straight line. So when V, is constant, Vl decreases when V2 increases and vice versa. This means that if the flywheel decelerates, the engine automatically accelerates. This is showr, in figure 2.5. One car, see that the vehicle speed does not change when decelerating the flywheel.

The general equation for the speeds in a planetary gear set is: -Annulus -Carrier -Sun

Figure 2.5: The general representation of velocities in a planetary gear set with high engine speed

A simulation with the ZItransmission shows that the ZI transmission raects much quicker than a standard driveline. Figure 2.6 shows the difference in vehicle acceleration performance between the ZI flywheel assist driveline and a standard driveline.

Figure 2.6: Vehicle acceleration performance

2.3 Design of the flywheel

As is explained in the previous paragraph, the flywheel is the most essential part in the ZI powertrain. The flywheel design is based on a optimization to reduce air drag and bearing losses. The power losses that occur with the flywheel are the power losses:

0 due to air friction Pcirc + Pside due to bearing friction Prozl f flub due to seal friction Pseal

When trying to find the optimal outer radius it appears that, when there is no inner radius, Pside increases with a larger outer radius while all other losses together decrease. If there is a inner radius it appears that Psideincreases when the ratio between inner and outer radius increases, while all the other losses decrease. So it is obvious that there will be an optimum in the flywheel sizing. A ring shaped steel flywheel with inertia J = 0.4 [kg.m2], rotating at a maximum speed of 800 [rad/s] appeared to be optimal [8]. This choice circumvents the extreme stresses and the need for a vacuum system to reduce the air drag.

The material used is wrought steel because of the high mass density, the low costs and the good manufacturing properties. A cross section of the flywheel is shown in figure 2.7. As can

spindle bearings

Figure 2.7: A cross section of the flywheel be seen, the flywheel construction can be devided into three parts: the shaft, the rotor and the bearings.

The shaft and rotor are built separately to simplify the manufacturing and are bolted together. On the left hand a cylindrical roller bearing is applied and on the right hand a pre-tensioned pair of spindle bearings that support the axial forces together with an axial tension rod through the shaft and connected to the inner housing.

Because the flywheel has to be able to rotate at speeds between 0 - 800 [rad/s] without resonance, the first eigenfrequence has to be well above 800 [rad/s]. A study on this subject has proven that this is the case [8]. 2.4 The test vehicle

The concept ZI transmission was tested on a test-rig using electric motors for propulsion and load. For testing of the driveability and fuel economy, the ZI powertrain is tested in a passenger car, a Volkswagen Bora 1.6 1. petrol engine, see figure 2.8. Some other tests in order to obtain data for the controller are also done with this Volkswagen. These test will be discussed ir, chapter 5. Chaptera 3

Torque converters

3.1 Introduction

Internal combustion engines can practically only run above a certain minimum speed. To move the vehicle from rest, the speed difference between this minimum engine speed and the transmission input shaft has to be overcome. The torque converter is the most widely used launching device in automatic transmissions.

A hydrodynamic torque converter, as the name implies, is a device for converting torque or turning moment by hydrodynamic means; that is by making use of the kinetic energy of a fluid in motion. In its simplest form it consists of three vaned wheels or annuli: an impeller secured to the input shaft, a turbine secured to the output shaft, and a reaction member fixed in position, all three being enclosed in a housing filled with hydraulic fluid (oil). Figure 3.1 shows the components of a torque converter. From an automotive standpoint the advantage

Figure 3.1: Components of the torque converter

11 of the hydrodynamic type of torque converter undoubtedly is that the torque transmission changes automatically and continuously in accordance with the load conditions. Some other advantages are:

0 There is virtually no mechanical wearing.

0 There is an elastic connection between engine and power train: Vibration and torque shock loads are 'damped'.

0 The reaction effect can be eliminated: No stalling of the engine.

There is no 'engine flare'. That is no excessive overrewing of the engine during launching occurs.

Disadvantages are:

Low efficiency over broad operating ranges.

e Cnmp!exity of the rear-moulzted gearbox: The geaxbox must be power shiftable (conven- tional automatic transmission, CVT) or have an additional gear shifting clutch (torque converter clutch gearbox).

In a motor vehicle the torque ratio of the converter is maximum when the vehicle is being started from rest, when great torque is required for acceleration. As the speed increases the ratio decreases automatically.

3.2 Working principle

The functioning of the torque converter is based on the use of the inertia of a fluid flow. The individual components of such a transmission are fluid flow devices forming a closed fluid flow circuit [I].

Figure 3.2: The flow pattern The system uses ATF (Automatic Transmission Fluid). The fluid flows into the torque converter by a pump. The impeller, which is connected to the engine, will start to move the fluid. This movement can be split up into two directions. First the fluid will be moved in a rotating way round the input shaft by the vanes of the impeller. The centrifugal forces will push the fluid to the outer side of the impeller. Because the edge of the vanes is also formed in an axial way, the fluid is thrown in the direction of the turbine. This movement is the second direction of the fluid. So the flow that is created by the impeller has a tangential and an axial direction. The fiuid will now biimp against the vanes of the turbine, which results in an impulse on the turbine and in a change of direction of the fluid. Figure 3.3 shows the transfer of impulse on a vane of the turbine. The total impulse on the turbine vanes results

Figure 3.3: Transfer of impulse on a turbine vane

in a torque in the converter output shaft. With this torque, the vehicle can be propelled. Next, the flow from the turbine will bump to the vanes of the reactor. Because of the shape of these vanes, the flow will be bend in such a way that the velocity of the outgoing flow fits as well as possible the velocity of the incoming flow of the impeller. This is possible as the reactor is connected to the transmission housing. The flow of the ATF as described above is shown in figure 3.2 and again explained in Appendix A.

The direction of the flow that comes off the stator is the same as the turning direction of the impeller. Because the incoming fluid does not have to be bend in another direction, the impulse of the fluid that is passed from the impeller to the turbine can be larger and so, the torque on the outgoing shaft is larger than the incoming torque. This increase of torque is the highest when the turbine does not turn, but gets smaller if the speed difference between and impeller decreases. In essence the torque amplification is the most omportant difference between a torque converter and a hydrodynamic clutch. Because the hydrodynamic clutch has no reactor, the flow from the turbine will slow down the impeller.

The fluid from the impeller makes the turbine start to turn. After some time, the turbine turns at such a speed with regard to the impeller that the axially component of the fluid is much smaller than the tangential component. The outgoing flow from the turbine will bump to the backside of the vanes of the reactor. But because the reactor is fixed on a freewheel, the reactor now can start to turn so that there will be no losses. The point on which the reactor starts to turn is called the lock-up point. This lock-up point is when the ratio between the impeller and the turbine is about 85 %. Above that ratio the torque converter acts like a normal hydrodynamic clutch and so there will be no increase of torque any more. However, the speed ratio between turbine and impeller will keep increasing. When the ratio is big enough, about 97 %, a lock-up mechanism makes sure that there will be a fixed join between turbine and impeller. This mechanism works by hydraulic power. The fluid pushes the turbine, impeiler and reactor so tide together that there is no more slip.

The main power losses in the torque converter are bearing losses, flow losses, impact losses on the vanes, windage and gap leakage losses. Because there always has to be slip to create the increase of torque, the largest power losses are caused by shear. This ceases of course when the lock-up mechanism is enabled. Because of the power losses, there will be some heat production. Therefore the fluid in the torque converter has to be cooled either by circulation, which also creates some extra losses or by using the cooling water from the engine. The efficiency qtc of a torque converter than is

where:

PT is the power on the turbine side, PI is the power on the impeller side, TT is the torque on the turbine side, TI is the torque on the impeller side, WT is the angular speed of the turbine, WI is the angular speed of the impeller.

And using the the torque ratio:

and the speed ratio: 3.3 Characteristic

The converter can absorb a moment of reaction by means of its fixed reactor, and is thus able to convert the input torque. Its efficiency is better than that of clutches at speed ratios below v = 0.7 - 0.8 (depending on torque converter type). Plotted against speed ratio, see figure ?? the turbine torque, TT drops, from the stall torque S approximatly linearly to TT = 0 at speeds i:: the reglor, of 1/ = 1. ThTitE, censtant input pwer this gi~.re. rise to 8 pZr2holic ni~tpi~t power curve PT = wTTT, and thus a parabolic efficiency curve 1) = 9. One can observe

Figure 3.4: The torque converter characteristic; where: S is the stall point; M is the optimum point with maximum efficiency; C is the lock up point and F is the free-flow point. a) dimensional b) non-dimensional that the torque converter has a decreasing efficiency for high speed ratios. On the other hand hydrodynamic clutches have a continuously increasing efficiency line as can be seen in figure 3.5 It's possible to combine the advantages of the torque converter and the hydrodynamic

Figure 3.5: Efficiency of the hydro-dynamic clutch clutch in order to av&d decreasi~gtorque converter efficiency.

In the first phase up to the lock-up point C in figure 3.4, in which the turbine torque equals the impeller torque, the torque converter operates normally. In the second phase the reactor is released from the housing by means of the freewheel. Since the reactor now revolves freely, it no longer absorbs any reaction torque. This results in the straight line typical of hydrodynamic clutches. The characteristic of this type of torque converter is shown in figure 3.6

Figure 3.6: Characteristic of the Trilok converter

This type of single-stage two-phase torque converter is called a Trilok converter and is named after the TRILOK research consortium that developed it. Its high level of efficiency and simple construction makes it particularly suitable for vehicle transmissions.

3.4 The influence on the vehicle traction force

Figure 3.7a is an example of a traction diagram of a vehicle with 5-speed automatic transmission and Trilok converter. The diagram shows the maximum traction at the wheels as a function of the vehicle speed. Figure 3.7b shows the same 5-speed automatic transmission but without the Trilok converter. It is obvious that the differences are most pregnant when the vehicle is at standstill. Also during shifting of the automatic transmission the lock-up can be opened and so slip can be obtained, which creates a higher torque. Usually, the lock up is not opened during shifting when the torque converter is combined with a CVT. Figure 3.7: Traction force with torque converter(a) and without torque converter(b). Fuel injection systems

4.1 Introduction

The function of the carburetor is to supply the engine with the optimum air-fuel mixture for dl the operating conditions. The problem with a carburetor, which is a fully mechanical device, is that it is neither totally accurate nor particularly fast in responding to changing throttle valves positions. Adding electronic feedback mixture control improves a carburetor's fuel metering under some circumstances. Still, the majority of the mixing is still done mechanically by the many jets, passages and air bleeds. Adding feedback controls and other emission-related devices results in very complex carburetors that are extremely expensive to repair or to replace.

The solution to the problems posed by a carbureted fueling system is electronic fuel injection (EFI). This system has many advantages over a carburetor in the areas of fuel economy, performance, driveability and low exhaust emissions. Fuel injection can be applied for extremely precise metering, supplying exactly the correct amount of fuel for given operating and load conditions while simultaneously ensuring minimum levels of exhaust emissions.

The composition of the mixture is controlled to maintain low emissions. Also components involved with EFI are simpler and often less expensive than a feedback carburetor. According to the location where the fuel is mixed with the incoming air, one can divide the EFI systems in three groups:

Single-point fuel injection(4. la)

0 Multipoint fuel injection(4.lb)

0 Direct injection, like Mitsubishi its GDI system

These groups will be discussed separately and some examples will be shown. Also one example of a fuel-injection valve will be discussed. Figure 4.1: Single-point fuel injection system (a) and multipoint injection system (b)

4.2 Single-point fuel injection

Single-point fuel injection is featuring an electromagnetic injector located directly above the throttle valve. This injector sprays fuel into the intake manifold in an intermittent pattern. Mono-Jetronic is the brand name of the Bosch single-point fuel injection, see figure4.2. Mono-Jetronic is an electronically controlled, low-pressure, single-point injection system for 4-cylinder engines. While multipoint injection systems employ a separate injection for each cylinder, Mono-Jetronic features a single, centrally-located, solenoid-controlled injection valve for the entire engine. The heart of the Mono-Jetronic is the central injection unit. It uses a single solenoid-operated injector for intermittent fuel injection above the throttle valve. The intake manifold distributes the fuel to the individual cylinders. A variety of sensors are used to monitor engine operation and furnish the essential control parameters for optimum mixture adaptation in the electronic control unit (ECU). These include:

throttle valve angle

0 engine speed

0 engine and intake-air temperature

0 automatic transmission and air-conditioner settings

Input circuits in the ECU convert the sensor data for transmission to the microprocessor, which analyzes the operating data to determine current engine operating conditions. This information, in turn, provides the basis for calculating control signals to the various final- control elements. Output amplifiers process the signals for transmission to the injector, throttle-valve actuator and canister-purge valve. Figure 4.2: Mono-Jetronic schematic diagram

4.3 Multipoint fuel injection

The multipoint fuel injection uses separate injectors to inject the fuel directly through the intake valve at each individual cylinder. Because of the haze of fuel and the separate injection for each cylinder on a relatively hot intake valve it is not necessary to pre-heat the fuel. Another advantage is that the valve will be cooled down enough by the vaporization of the fuel.

The injection can take place in two ways; mechanical or electronic. Of each of these ways an example will be given.

4.3.1 Mechanical injection

Figure 4.3 shows a mechanical multipoint injection system. This is the K-Jetronic, which is a product of Bosch. Fuel is pumped continuously out the fuel tank (1) by an electrical pump (2). The fuel then passes a filter (3) and a fuel accumulator (7) before it goes in the fuel Figure 4.3: Schematic diagram of the K-Jetronic distributor. The accumulator keeps some pressure on the system to avoid vapor lock when the engine is shut down. By using the primary pressure regulator (6) the pressure is kept constant. The excessive fuel flows back in to the fuel tank. The air-flow sensor (8) acts under the influence of air-flow pressure on the controller piston (10) by using a lever. On top of the controller piston is the controlled pressure, which is controlled by the warm-up regulator (11). So the controller piston is kept in balance by the air-flow pressure on one side and the controlled pressure on the other. The controller piston is in a cylinder with long shaped gates. There are as much gates as the engine got cylinders. Whether these gates are opened depends on the equilibrium of the controller piston. Therefor, the fuel flow, that is send to the injectors, is directly depending on the position of the controller piston. In order to get a linear relation a controller that is positioned after the piston (12) assures that the drop of pressure over the gates is not depending on the fuel flow. If there's a cold start a bi-metal in the warm-up regulator provides a lower control pressure, which makes the mixture richer. When the engine warms up the control pressure goes back to its normal value.

During the starting of the engine the start valve (13) injects for a short period of time a certain amount of extra fuel. The temperature sensor takes care that no extra fuel is injected when the temperature of the engine is high enough. When the engine is too cold, also the number of revolutions to empty the cylinder must increase to avoid the engine to brake down because of the higher friction. Therefor an auxiliary air device (14) is placed as a by-pass over the throttle (15). When the engine is cold, the device is opened. After starting, this device is closed slowly by an electrical heated bi-metal. Finally there is also another electrical switch (16) fixed to the air-flow sensor, which shuts down the fuel pump in case there is ignition, without a running engine. This type of fuel injection creates obviously a constant injection as opposed to the next example.

4.3.2 Electronic injection

This is a type of injection that acts intermittently. Because the injection pressure is constant, there is a direct and proportional relation between the injected fuel and the time the electromagnetic injector is opened. This time is defined e!ectronical!y by measuring the air-flow and engine speed. When the circumstances differ to the normal also different injection times can be necessary. This is defined by secondary measurements.

Figure 4.4 shows an electronic multipoint injection system. This is the L-Jetronic, which is a product of Bosch. Fuel is pumped out the fuel tank (1) by an electrical pump (2). The fuel

Figure 4.4: Schematic diagram of the L-Jetronic then passes a filter (3) and goes to the fuel pressure regulator (6), which keeps the pressure constant on about 4.5 [bar]. The fuel injection valve (5) then injects the fuel discontinuously on the intake valve. The engine speed and the reference point are established by Hall-effect sensors excited by the teeth on the engineflywheel.

The air-flow is defined by an air-flow sensor (8). This sensor, which is a valve, will have an angular displacement depending on the air-flow and the opposite force created by a torsional spring. This displacement can be detected by a potentiometer. Both primary signals (engine speed and air-flow) then go to the electronic control unit (ECU) (9). In the ECU the basic injection times are determined by look up tables using those signals. The throttle valve switch (10) detects whether the engine runs idle or at full opened throttle. Both states need a richer mixture. The engine temperature (11) and the air temperature outside the engine (12) are both measured by a NTC-resistor. These signals assure that a very rich mixture is injected when the starter engine runs. When the starter engine is stopped but the temperature is still too low, a temperature sensor (11) makes sure that a rich mixture is injected.

This systems also contains, like most systems, a lambda sensor (14), which can control the amount of fuel in the mixture accurately by feedback. This A-sensor meters continue the . . compounding of the mixture and changes it, if necessary. This helps to reduce the enissioii of exhaust gasses, because with an optimal mixture there is also an optimal combustion and therefore there is a minimum of exhaust gasses.

4.4 Direct injection

The third type of fuel injection systems is the direct injection. With these systems the fuel is mixed with air in the cylinder, as opposed to the multipoint and single-point injection systems, where it is premixed in the intake manifold. To create a good mixture of fuel and air, some geometric adjustments are made to the cylinder. There are three types of direct injection:

The first type is based in a jet-stream injection close to the spark. Because the fuel is injected so near the spark, the mixture during ignition is rich and when combustion is started, the rest of the more lean mixture will also combust. An example of such a direct injection cylinder is shown in figure 4.5.

Figure 4.5: Jet-stream direct injection The second type is based on the shape of the piston head. Because of the shape of the piston the fuel is mixed rapidly with the air which makes a good combustion possible. An example of this type is shown in figure 4.6.

Figure 4.6: Fuel swirl mixture

a The third type is also based on the shape of the piston, but with this type the shape of the piston does not create a good swirl of the fuel but a swirl of the air in the cylinder. The air swirl then assures the good mixture which is necessary for the combustion. This type is shown in figure 4.7.

Figure 4.7: Air swirl mixture

4.5 Fuel injection valve

Most engines make use of an electronic multipoint system. The fuel injection valve that is used in that system is therefore thought to be most interesting. Figure 4.8 shows such a fuel injection valve (injector). The electronically controlled injectors inject precisely metered fuel into the intake ports. Each engine cylinder has its own injector. The injectors are solenoid-operated and are opened and closed by means of electric pulses from the electronic control unit. The fuel-injection valve consists of a valve body and the valve needle with fitted solenoid armature. The valve body contains the solenoid winding and the guide for the valve needle. -When there is no current flowing in the solenoid winding, the valve needle is pressed against its seat on the valve outlet by a helical spring. When a current is passed through the solenoid winding, the valve needle is lifted approximately 0.1 [mm]from its seat and the fuel can be injected through the precision annular orifice. The front end of the valve needle has a specially ground pintle for atom- izing the fuel. The pickup and release times of the valve lie in the range of 1 to 1.5 [ms]. To achieve good fuel distribution together with low condensation loss, it is necessary that wetting of the ictake-rna~~ifo!dwalls will be avoided. This means that a particular spray angle in conjunction with a particular distance of the injection valve from the intake valve must be chosen specific to the engine. The injectors are fitted with the help of special holders and are mounted in rubber mouldings in these holders. The insulation from the heat of the engine thereby achieved, prevents the formation of fuel- Figure 4.8: Fuel injection valve of vapor bubbles and guarantees good hot-starting char- the L-Jetronic. acteristics. The rubber mouldings also ensure that the injectors are not subjected to excessive vibrations. Chapter 5

The experiments

5.1 Introduction

The ZI transmission is tested on a test rig and in a passenger car, a i.6 1. Voi~swagenBora. Because the transmission was replaced by the ZI transmission, new controllers had to be designed. Especially the CVT controller is important, because one of the main goals was to improve the fuel economy. The controller was designed to generate a slight excess of hydraulic force on the metal push-belt in order to prevent slip between the pulleys and the belt. In order to generate that force, it is necessary to know the torque that passes the CVT with some accuracy. This is the torque delivered by the engine minus the losses because of the hydraulic pump. These losses are measured on a test rig. The engine torque is measured in the vehicle at different throttle positions. Although this data is also known by the manufacturer, it is still corporate secrecy and therefore this data had to be reconstructed.

Another task of the controller is to let the CVT shift to a specific ratio. Mostly the CVT shifts in such a way that the combustion engine runs in its optimal points. That is the points with the lowest specific fuel consumption. For each requested torque, there is an engine speed with the lowest specific fuel consumption. The controller determines the requested torque by interpreting the pedal position into a requested power. This is done according approximately to the line shown in Figure 5.1.

So a pedal position of 50% is interpreted as if the driver requires a power of approximately 37 [kW]. The CVT than shifts to the ratio at which the delivered engine power is 37 [kW] and the specific fuel consumption is the lowest. The advantage of a CVT is that it can achieve such an engine speed almost independent from the vehicle speed. A line that connects the points in the enginemap with the lowest specific fuel consumption at each requested power is called the economy-line or Eline. So in order to get a good fuel economy, this E-line must be known. The data, needed to reconstruct the E-line are also obtained by experiments in the vehicle. Figure 5.1: Approximation of the relation between pedal position and the requested power

5.2 The enginemap

The experiments with the test vehicle all took place at PD&E in Helmond. There a roller bench with a controllable dynamometer could be used. The advantage of such a roller bench is that the vehicle speed can be kept constant or arbitrary road load characteristics can be programmed. A schematic drawing of the powertrain of the testvehicle, in which the variables are placed, is shown in Figure 5.2 The goal of the experiments was to construct the engine map

Figure 5.2: A schematic drawing of the powertrain of the testvehicle for the entire range of engine speeds. Therefore this range was divided in two parts namely: 1500 - 3500 [RPM] and 3000 - 5300 [RPM]. In fact, this is the speed of the primary pulley and because the torque converter is opened, not the engine speed. For the high throttle-angles this was 3000 - 4500 [RPM] because the roller bench could apply a maximum load of 50 [kW] which could be critical in case of engine power near to the maximum engine power. To test both engine speed ranges, the vehicle speed was kept constant by the roller bench. For the lower range, that was at 40 [km/h] and for the higher range 70 [km/h]. When the vehicle speed was chosen constant, the engine speed range could be covered by shifting with the CVT.

As explained in section 3.2 and 3.3 the unlocked torque converter can transmit torque in the presence of a slip speed difference between the impeller (=engine) and turbine (=primary pulley). At a given engine speed Ne and slip ratio

where Np is the primary pulley speed, the transmitted engine torque Te is known through:

In this equation Cf(v) is the so-called capacity factor of the torque converter, see Figure 5.3. The amplification of torque explained in section 3.2 is given through the factor p. The torque TT exerted on the turbine is given by:

where TI is the torque at the impeller, i.e.,

TI = Cf(v).N: and was also seen in equation(5.2). For the measurements TT is unimportant. On the other

Slip [-I

Figure 5.3: The input capacity factor of the torque converter hand the impeller torque TI obviously determines the engine torque T, as in (5.2). Although the torque converter can be used to transmit the torque and at the same time be used as a torque transducer, this can not occur without the slip v: 0 5 v < 1. Moreover, the engine speed Ne will find stationary values at a given engine torque T, according to (5.2) that is considerably above the minimum speed, here 1000 [RPM]. Especially for high throttle-angles significant and important parts of the enginemap could not be measured with this method. In order to estimate the ranges that could not be measured, an engine map of a 1.6 1. Mercedes engine has been used instead. This map is also used to verify the results obtained as the trends of both engines are roughly the same. The engine map of the Mercedes is shown in Figure 5.4. At each line the number corresponds with the throttle angle from the air-throttle-valve. Figure 5.4 : The Mercedes 1 .6 1. enginemap

The throttle controller was at the time the measurements were conducted not that accurate in reaching the final values . On the other hand, the final values it actually reached are known exactly.

To avoid the influence of inertias, the complete range of engine speeds is slowly and gradually controlled through the CVT and the slip . The range is covered twice during each experiment to investigate repeatability. An example of one such experiment is shown in Figure 5 .5. The

6000

3500

3000

2500 ~

~ 2000

1600

1000

500

0 , a 40 60 80 100 120 140 eme (a

Figure 5 .5: An example of data received from one experiment first part of an experiment, approximately the first twenty seconds, are useless, because all the controllers then start working and have not reached their value . The parts between 20-130 [s] may be the useful parts .

Because there is much noise on the signal, it has to be filtered . Next, the filtered signal is downsampled by taking only the data on or very close to each hundred engine revolutions . If this is done for each experiment figure 5 .6 is obtained . The black dotted line represents the

29 wide-open-throttle line from the product information sheets available for the installed engine . Three observations are pointed out here :

,60

,00

É 60

0 500 ,Oao 1500 2000 25U0 9000 95W 3000 CSOU 6000 5500 E ng- apeetl IRMA

Figure 5.6 : The filtered and downsampled data

• Lines for the same throttle-angle do not overlap in all cases .

• Lines that correspond with throttle-angles of 50 % or higher are very close to each other and some lines even cross one another .

• Some lines lay above the wide-open-throttle line, which should be impossible .

An explanation for the first point is quite easy to find . As mentioned before, the throttle- angles may differ 1% from the required value due to inaccuracy of the throttle controller. In other words it is possible that for example the 25% throttle-angle line is 24% for the first part and 26% for the second part . It is obvious that both lines won't connect in that case .

An explanation for the second point is much more difficult to find. The fact that the lines are very close to each other may be explained by the geometry of the throttle valve opening. The lines correspond with throttle-angles and not with the air flow . The difference between air flows when the throttle-angles vary 10% is much smaller . Therefore the lines can be close to each other at high throttle-angles . This could also be seen in figure 5 .4, where the lines of higher throttle-angles of the Mercedes engine also are very close to each other . An explanation for the fact that the lines cross each other could not be found . And the only remark that can be made on that issue is that it is the result of the inaccuracy of the experiment .

If the wide-open-throttle line given by Volkswagen is assumed to be correct', the input capacity factor of the torque converter is considered to be incorrect . Assuming that the capacity factor is incorrect, it is possible to reconstruct that factor for the range of slip that was involved in the experiment . Because the measured torque lines lay above the wide open throttle line, it is obvious that the factor is lower, but it strikes that the trend is the same as the given capacity factor . Therefore the assumption is made that it is acceptable to extrapolate

'Wide open throttle torque lines presented in product sheets are often smoothed, but represent the order of magnitude fairly well

30 3

. ._ . , . . . ._ ...... ~ .__ . :

01 0 02 03 os 0 .5 0 .s 0 08 os I tlip ( -]

Figure 5 .7: The old, the reconstructed and the extrapolated capacity factor the reconstructed capacity factor for the complete range of slip . In figure 5 .7 one can see the capacity factor given by the manufacturer (black), the reconstructed capacity factor (blue) and the extrapolated factor (yellow) . The adjusted Tip figure is shown in figure 5 .8. It's clear that the impeller torque lines now lay beneath the wide-open-throttle, which could be expected . .

,+o

120

100

i 80 É

0 500 1000 1500 2000 2500 3000 35a0 4000 6500 5000 5500 mg- pmd [RPM]

Figure 5 .8: The adjusted Timp figure

But as equation (5 .2) says, is figure 5 .8 not the torque delivered by the engine . Because the pump is placed between the engine and the torque converter, there are torque losses . So in order to obtain the engine torque, it is necessary to add the torque used by the pump . That torque depends on the oil flow delivered by the pump and by the fact whether the pump works single- or double sided . These losses are defined in an earlier stage on a test rig. If these losses are also taken into account, figure 5 .9 is obtained, which represents the torque delivered by the engine .

The setpoints for the CVT controller should follow from Figure 5 .9 . In order to create some smoother lines, the lines of figure 5 .9 are connected for each throttle angle considering the required throttle angle and the actual throttle angle, and the lines are extrapolated to 800

31 14a

120

Ê ? 100

6 80

W 60

0 500 1000 1500 2000 2500 3000 3600 4000 4500 5000 5500 Engine spsed [FPK~

Figure 5.9: The engine torque

[RPM] on the left side and 5300 [RPM] on the right side if those data are not known . When the lines are extrapolated, the trend of the known part is taken into account and the lines are compared with the Mercedes engine of figure 5 .4. For the lines that represent the throttle- angles above 50% it was impossible to create a smooth line . Therefore the decision is made to reconstruct the line for full throttle, i .e. 100% and to make that one a reference for the 60, 70, 80 and 90% throttle-angle lines . Each of those lines is constructed by multiplying the 100% line with a certain factor, respectively 0 .95, 0.9625, 0 .975 and 0 .9875. The final result, which is the constructed engine map, is shown in figure 5 .10.

180

160

140

120

Ê ? 100 ~ ~ a 0 ; 80 ~c c W 60

0 1000 2000 3000 4000 5000 6000 Engine speed [RPM]

Figure 5.10: The constructed enginemap

32 5 .3 The economy-line

As mentioned before, the economy-line or E-line is the line that connects the points in the engine map on which the engine runs with the highest e fficiency for every power level . In order to have the best possible fuel economy it is necessary that the engine runs along that line as much as possible . With a CVT this is possible to a large extent . To construct the E-line it is necessary to know the specific fuel consumption in every operating point . Thereto, the momentous fuel consumption should be measured in all operating points .

This momentous fuel consumption can be obtained by measuring the injection time . As mentioned in paragraph 4 .3.2, the injection time is proportionally related to the amount of injected fuel because the injection pressure is constant . During the experiments the injection time is metered . Then the data is filtered and downsampled . Afterwards as a result, figure 5 .11 is obtained . There are two striking things on this figure . First, and that is the same as

Figure 5.11 : Injection time data with figure 5 .6 in paragraph 5 .2, the lines do not connect . An explanation for this is the same as it was for figure 5 .6; the throttle-angles are not necessary the same, therefore the values of the injection time can differ and the lines may lay above or beneath one another . The second striking point is the jump in injection time in the lines that correspond with higher throttle-angle lines . Also it is remarkable that the highest throttle-angle line has its injection time jump at the lowest engine speed compared to the other . An explanation can be that the engine management tries to have a lowest possible fuel consumption while delivering the required torque . But at a certain point the torque can't be delivered anymore and an enrich- ment of the fuel is necessary . That also explains why the wide-open-throttle line gets the first jump and the other lines later . If the lines of figure 5 .11 are connected and extrapolated to 1500 [RPM] on the left side and to 4500 respectively 5300 [RPM] on the right side, figure 5 .12 is obtained as the momentous fuel consumption of the engine . The next step is to convert the figure from momentous fuel consumption to specific fuel consumption . This conversion can be made by the next relation :

33 Figure 5.12: The constructed momentous injection time

2 • injtime( O) • Ne _ - specific fuel consumption (5.5) 60•Te(0)' ó

In this relation 0 is the throttle angle . The relation in equation 5 .5 is thus not exactly the specific fuel consumption, but it is a linear indication for the specific fuel consumption .

From the relation in equation 5 .5, it's possible to obtain the iso-specific-fuel-consumption lines. These are the lines of the same colours in figure 5 .13 . Each point on such a line marks the same specific fuel consumption . The reason why they do not cross the 1500 [RPM] is that there are no data obtained by the experiment for that region . The black dotted lines are lines on which the engine power is the same . The lines shown are of 10, 20, 30, 40 and 50 [kW] . The E-line is constructed by connecting the points that have the highest efficiency at a certain engine power . The E-line is the blue line shown in Figure 5.13.

34 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Engine speed [rev/min]

Figure 5.13: The constructed E-line in the Volkswagen enginemap

35 Chapter- 6

Conclusions and recommendations

6.1 Conclusions

A literature study has resulted in a bigger understanding of the working principle of the torque converter, of electronic fuel injection systems and of the EcoDrive project. The efficiency of the torque converter for higher speed ratios can be improved by combining the torque converter with a hydrodynamic clutch. The advantages of the torque converter are the biggest when a vehicle starts from rest or during shifting. This last point only yields for automatic transmissions and not for CVT. After the era of the carburetor three main types of fuel injection are used in automotive industry: single-point-, multipoint- and direct injection. The multipoint injection systems, which are most commonly used, can be divided in two groups: Mechanical and Electronic injection systems. The ZI transmission is a transmission that should reduce the fuel consumption of vehicles by 25% with regard to vehicles with manual transmissions. The principle of the ZI transmission is that the engine can run in an efficient point and a mechanical torque assist helps the engine when the vehicle accelerates. The mechanical torque assist is a steel flywheel that is connected to the VanDoornes V-belt CVT by a planetary gear set. The ZI transmission is the result of the EcoDrive project. --- In order to be able to design an accurate CVT controller, the 1.6 1. Petrol engine of the Volkswagen Bora of the EcoDrive has been identified. An engine map is constructed and an economy-line has been found. The engine torque is defined in an indirect way, by using an open torque converter and the economy-line has been found by defining the specific fuel consumption.

6.2 Recommendat ions

In order to get a more accurate engine map some improvements on the experiments can be made. First, the input capacity factor should be known for much bigger range of slip. In these experiments a major assumption has been made. This results in a big inaccuracy. Secondly, it would be much more precise if the engine torque was measured directly. The engine can be fixed on a test rig and so the torque can be measured easily. Another advantage would be that the complete range of engine speeds could be measured. Finally, to avoid the difference between the required throttle-angle and the actual angle a better controller should be designed. As is mentioned in chapter 5, the controller had to be made less accurate to avoid other problems. With an accurate controller, obviously, the results of the experiment are more accurate and easier to interpret. References

[I] Lechner, G.; Naunheimer, H.: Automotive Transmissions, Fundamentals, Selection, De- sign and Application, Springer-Verlag, Berlin, 1999.

[2] Heldt, P.M., "Torque converters or transmissions", fifth edition, Chilton company, Philidelphia, 1955.

[3] Peters, A., "Modelvorming van het dynamisch gedrag van de koppelomvormer", TU Eindhoven, 1994.

[4] Adler, U., "Automotive electric/electronic systems", Stuttgart : Robert Bosch, second edition, 1994.

[5] Van Aken, Ch., "Zuigermotoren", University of Gent, faculty of practical science, 1996.

[6] Serrarens, A., Vroemen, B. and Veldpaus, F., "A new CVT powertrain without jet- start behaviour: Analysis of design, dynamics and control", In press, Vehicle System Dynamics, 2001.

[7] Van Druten, R.M., Van Tilborg, P.G., Rosielle, P.C.J.N., Schouten, M.J.W., "Design and Construction aspects of a Zero Inertia CVT for Passenger Cars", FISITA World Automotive Congress,F2000A058, Seoul, 2000.

[8] Van Druten, R.M., and Kok, D.B., "Design Optimization of a compact Flywheel System for Passenger cars", VDI Berichte 1459, Munich, 1999. Nomenclature

efficiency of torque converter power delivered by turbine power delivered by impeller torque on turbine torque on impeller angular speed of turbine angular speed of impeller torque ratio speed ratio angular speed of the flywheel angular speed of secondary pulley angular speed of primary pulley angular acceleration of the flywheel angular acceleration of the secondary pulley characteristic ratio of planetary gear set CVT speed ratio annulus gear ratio carrier gear ratio CVT ratio where wf is zero (geared neutral) cluster of parallel stage gear ratios reaction torque of annulus at primary pulley reaction torque of carrier at secondary pulley net torque from flywheel unit at secondary pulley mean value brake engine torque moment of inertia of the flywheel total moment of inertia primary sided elements moment of inertia of the engine Input capacity factor Fuel injection time Engine speed Appendix A

The schematic ATE' flow in a torque converter

Figure A.l: The schematic ATF flow in a torque converter

Top right: When the impeller starts to rotate, the turbine is not rotating yet. The reactor does not rotate because of the freewheel. Beneath left: Because of the increased pressure the turbine starts to rotate and the vehicle starts to move. With increasing turbine speed, the torque converting decreases. The reactor still does not rotate. Beneath right: If the ATF hits the vanes of the reactor on the back side, the reactor starts to rotate