crdi

Hitachi Review Vol. 53 (2004), No. 4 193

New Direct Fuel Injection Engine Control Systems forMeeting Future Fuel Economy Requirements and EmissionStandards

OVERVIEW: Recently, the need to reduce CO2 levels has made increasedfuel economy an urgent matter in Japan and Europe. Use of the highlyefficient diesel engine is expected to increase and measures against emissionssuch as soot are a major problem. Gasoline engines, on the other hand, aremore sustainable in terms of exhaust emissions, and are steadily approachingthe diesel engine in terms of fuel economy as well. Since introducing adirect fuel injection engine control system in 1997, the Hitachi Group hascontinued to develop and manufacture system control and the maincomponents for it, and now we are expanding into Europe as well. We arealso proposing various advanced system solutions in response to needs forautomobile fuel economy, emissions and power.

Minoru Osuga

Yoshiyuki Tanabe

Shinya Igarashi

Masahiro Zaitsu

Takuya Shiraishi

Motoyuki Abe

INTRODUCTIONSINCE coming on the market in earnest in 1997, thedirect fuel injection engine has become widespread,mainly in Japan. Recently, though, the fuel economyand high performance characteristics of these enginesystems also have created an opportunity for rapidpenetration into the European market, where the CO2

problem is getting worse.The Hitachi Group has many years of experience

in applying engine control system technology to directfuel injection systems and also in offering productsfor those systems. Currently, we are proposing a newsystem to cope with the stricter environmentalregulations concerning emissions and CO2 that begin

Exhaust system

Combustion system

Electronically controlled throttle body

Engine control unit

Lean NOx catalyst

Air flow sensor (slot-in type)

• Compact• High response

• High precision• Compact

Injector• Spray design• Long nozzle

High-pressure fuel pump (single cylinder type)• Compact and light (aluminum housing: 800 g)• Low driven torque (variable flow rate type)

• Lighter, fewer components• Integrated injector and driver

• Adsorption-reaction type

• High cleaning rate• High tolerance

Air-fuel ratio sensor

Engine

Spark plug

Airflow

Simulation

Spray

In-cylinder mixture/combustion analysis• Spray and airflow optimization

Injector

Intake system

Fuel system

Fig. 1—Basic Structure and Main Components of Direct Fuel Injection Engine System.In addition to manufacturing the major components of the direct fuel injection engine system, the HitachiGroup has developed various kinds of system control technology. Our components cover the entire systemfrom air intake system to the fuel system and the exhaust system. With our proprietary simulation and analysistechnology, we aim for optimization of the combustion system, including the fuel injection spray and airflow.

New Direct Fuel Injection Engine Control Systems for Meeting Future Fuel Economy Requirements and Emission Standards 194

Variable valve system

Expanded phase and lift controlNon-throttle

Use of freedom in injection control

Use of high power

Supercharging system Fuel consumption (CO2) and emissions standards

Use of torque control by means of injection control

Use of fuel economy and low emissions

Idling stopMild/full HEV

Hybrid/42-V system

Downsizing System for stricterregulations

High power

High response

High EGR

Lean burn

Knock tolerance

Basic directfuel injection

system

High compression ratio

in 2005.For the intake system, we supply airflow sensors

and electronic throttle body control for accurate controlof engine air intake and torque. For the combustionsystem, we supply the world’s lightest high-pressurefuel pump, which has an aluminum housing, andinjectors that produce spray patterns for variouscombustion chamber shapes and combustion systems.For the exhaust system, we produce a lean NOx

(nitrogen oxides) catalyst that is highly efficient inremoving NOx during lean burn combustion. We havealso made proposals concerning various factors thatgovern combustion, such as the injector spraycharacteristics and the shape of the piston andcombustion chamber on the basis of proprietarysimulations (see Fig. 1).

Here, we describe the most recent enginecombustion technology and the control technology andcomponents for implementing it.

DIRECT FUEL INJECTION ENGINECONTROL SYSTEMCharacteristics and Application of Direct FuelInjection Engine

The structures of the conventional port fuelinjection engine and the direct fuel injection engineare compared in Fig. 2. In the direct fuel injectionengine, fuel is injected directly into the enginecylinders, so the timing of the injection and thedistribution of the mixture within the cylinder can befreely controlled. That makes it possible to raise thecompression ratio and fuel economy as well as thepower output. Furthermore, direct fuel injectionengines have a high degree of freedom in control, so

Fig. 2—Structures of Port Fuel Injection Engine and DirectFuel Injection Engine.In the direct fuel injection engine, the fuel is injected from theinjector directly into the cylinder and burned, allowing a highercompression ratio and power output than does a port fuelinjection engine.

Fig. 3—Characteristics of Direct Fuel Injection Engine System.The direct fuel injection engine has high power output, variablespray and low emissions characteristics, and is being applied topowertrains for meeting future requirements.

the basic engine characteristics such as knock toleranceand response, lean burn, and EGR (exhaust gasrecirculation), can be greatly improved compared toport fuel injection systems. Using these superior basiccharacteristics, the Hitachi Group is developing a newsystem that includes variable valve control, and hybridsystem and supercharger system downsizing to meetthe stricter regulations (see Fig. 3).

Configuration of Control SystemExtracting the superior performance of the direct

fuel injection engine requires an innovation ofcomponents and new advances in control systemtechnology. Specifically, high-pressure fuel pumps andinjectors are key components for attaining more precisecontrol of the engine’s basic process of combustionunder high compression (5 to 12 MPa). With theobjective of achieving highly responsive combustioncontrol under high pressures, we are developing thekey components for complete combustion undervarious driving conditions.

Also, airflow sensors for accurate detection of theamount of air intake to the engine and highlyresponsive electronic throttle body control are beingused to control the torque generated by the engineaccording to occasional changes in the requirementsof the driver. Some direct fuel injection engines use alean burn for highly efficient operation, so a lean NOx

catalyst for reducing NOx under lean conditions

Sparkplug

High compression ratioImproved fuel economyHigh power output

Cylinder

(b) Direct fuel injection engine(a) Port fuel injection engine

Injector

Intake airIntake port

Injector


Generated torque control Emissions reduction control(NOx catalyst and cold HC)

High pressure and high response

fuel injection control

Combustion control

Lean NOx catalyst

Engine

Spark plug

Airflow sensor

Electronic throttle control

High-pressure fuel pump

Injector

(excess oxygen) is required.The Hitachi Group also supplies a high cleaning

rate control for that purpose (see Fig. 4).

COMBUSTION TECHNOLOGYCombustion Analysis Technology for Direct FuelInjection Engines

For the opening of the injector, which is the key toin-cylinder combustion control, we are applying

analysis technology that makes full use of simulation(see Fig. 5). The Hitachi Group engine combustioncontrol technology is based on our irregularcompressible fluid analysis program for analyzingpneumatic two-layer flow in nuclear power plants.Currently, we are making various improvements andincreasing the practicality of the system. The mainpoints of the improvements are to shorten thedevelopment turnaround time as much as possible andaccurate reproduction of in-cylinder phenomena. Forthe former, we have developed the Voxel method, inwhich a 2 million-cell mesh can be created directlyfrom a 3D-CAD (computer-aided design) diagram inabout five minutes. That makes it possible to reducethe work involved in mesh creation, which previouslytook several weeks, and allow surveys concerningpiston shape and other parameters of the combustionchamber to be performed in a short time. Concerningthe second of the two points, the objective was toimprove accuracy in reproducing the air movementwithin the cylinder. The development of technologyfor directly simulating turbulence will allow the sprayshape and air movement in the cylinder, which stronglyaffect combustion, to be reproduced with highaccuracy.

An example of applying this simulation to the directfuel injection engine is shown in Fig. 5. In thecalculation of the air mixture injected directly into thecylinder and the resulting combustion flame, it is

Fig. 4—Basic Structure and Main Functions of Direct FuelInjection Engine Control System.The functions include control of the torque that arises in variousdriving situations, optimal fuel injection, combustion control,emissions reduction control over the entire range from idling tohigh speed.

Fig. 5—Simulation of Air Movement in Engine and Combustion Analysis with Example of Application to DirectFuel Injection Engine.Aiming for fast and accurate mesh generation, we are performing integrated simulations that cover the entirecombustion process, beginning with air intake into the cylinder and including injection of the fuel, ignition, andcombustion. The results are used to determine injector spray characteristics and propose shapes for thecombustion chamber, and other aspects of developing combustion technology for the direct fuel injection engine.

Improvement of the simulation method Application to direct fuel injection engine

Integrated simulation over the entire combustion process: Intake into the cylinder → Injection → Ignition

Turbulent flow

Conventional method (100 thousand-cell mesh)

Voxel method (2 million-cell mesh)

Automatic mesh generation(takes 5 min.)

Conventional method (k-e model) Direct simulation(0.5 mm3 cell)

Improved air flow accuracy

Spark position

Flame

Mixture distribution

Injector

Mixture distribution within the cylinder

Example computation of combustion flame


Nozzle: various spray shapes

Magnetic circuit: high responsiveness

Structure and features

Example of each type of spray shape

Cone spray Bent cone spray Horseshoe spray

Outer appearance of the injectorφ20.7 mm

84.5

mm

Bent Bent coneconeBent cone

Lead Lead spraysprayLead spray

Vertical cross sectionVertical cross section

Horizontal Horizontal cross sectionHorizontal cross section

φ8.0 mm

SignalFuel

Moving part: lighter

Spray (swirl method)

COMPONENT TECHNOLOGYInjector

The appearance and structure of the injector, a keycomponent of the direct fuel injection engine, andexamples of the spray shapes are shown in Fig. 7. In adirect fuel injection engine, the fuel must be injectedin a short period of time and at pressures at least 40times higher than in port fuel injection. Therefore, theHitachi Group has applied analysis technology suchas dynamic magnetic field analysis to increase solenoiddriving power to achieve faster valve action. We havealso made the injector 50% smaller and lighter thanour previous products.

Furthermore, in addition to employing our original“swirl type” pattern for the shaping and atomizationof the fuel spray, we have made it possible to shapethe injection spray to match the engine and thecombustion system with technology for designing theshape of the nozzle tip. The spray shapes (see Fig. 7)include the symmetrical cone, the bent cone forconforming to the engine layout, and the latesthorseshoe shape spray for the lead spray injectionmethod described above. The lead spray method allowsgood ignitability to be maintained under variousdriving conditions by optimizing the specifications of

Fig. 6—Comparison of Next-generation Direct Fuel Injectionwith Conventional Method.We will supply lead spray injection as the next-generationinjection system. In this way, the Hitachi Group aims to improvefuel economy and reduce emissions.

Fig. 7—Appearance and Structure of Injector, with Spray ShapeExamples.Increased responsiveness of the magnetic circuit and lightermoving parts aim at high-speed valve response, while the shapeof the nozzle provides a spray that is suited to the engine andthe combustion method.

important to optimize the distribution of the air mixturewith respect to maintaining ignitability. The key to thatoptimization is the spray characteristic of the injector.Using this analysis technology to determine the spraycharacteristics of the injector, we have proposed shapesof the combustion chamber and the intake system tovehicle manufacturers.

Development of New Injection MethodThe performance of a direct fuel injection engine

is developing according to requirements concerningfuel consumption and emissions. Currently, mostcommercial engines employ injection systems that useconical spray patterns (see Fig. 6). With thatconventional method, the spray from the injector isignited by the spark plug after the spray hits the surfaceof the piston. In the lead spray injection systemdeveloped for the next-generation engine, the injectedspray does not hit the piston, but is distributed in thecylinder at the time of combustion. The quantity ofunburned fuel is therefore reduced because no fueladheres to the piston. In addition, the effect of the leadspray is to increase the freedom in spark timing andinjection timing, allowing control of the start ofcombustion and the combustion period according tothe vehicle operating circumstances. As a result, thismethod achieves higher fuel economy and loweramounts of unburned fuel (HC: hydrocarbon) and NOx

emissions.

Expansion

Stable combustion region

• Improved fuel economy• Reduced emissions Unburned fuel (HC) NOx

Piston top dead center

Freedom of injection timingFree

dom

of

igni

tion

timin

g

Injector Spark plug

Piston

Cone spray

Injector Spark plug

Piston

Lead spray

Conventional injection method Lead spray injection method


Engine

Cam

Installation on the engine

Fuel line

Orifice

Injector

PlungerLifter

CamFuel tank

Flow control valve

Check valve Pressure chamber

External appearance of the high-pressure fuel pump

Aluminum housing

Parallel lines

Simulation of pressure pulses within the fuel lines

IAT: intake air temperature sensorCF: cold film; heat-sensing resistor for temperature control HW: hot wire; heat-generating resistor for flow sensor

Series lines

Fuel

line

pre

ssur

e(M

Pa)

11

10

9

11

10

9

the lead spray part of the horseshoe spray for the shapeof the combustion chamber.

High-pressure Fuel Pump and Fuel LineSystem

A high-pressure fuel pump that produces high fuelpressures (5 to 12 MPa) and an example of fuel lineoptimization are shown in Fig. 8. The high-pressurefuel pump employs a single-cylinder plunger pumpand a housing made of aluminum with a plated surfaceand can handle alcohol fuels E10 as well. At 800 g,this is the world’s lightest pump.

The pump is driven by the engine cam shaft. Thefuel is drawn into the pump and expelled by thereciprocating motion of the plunger. The driving losscan be minimized by using a flow control valve tovary the timing of the opening of the pump intake valveso as to supply just the amount of fuel output that isneeded. This reduction in driving loss also contributesto reduction in fuel consumption.

In the development of a pump that includes flow

control specifications and the configuration of the high-pressure fuel lines, we used our hydraulic systembehavior analysis software. As a result, the behaviorof the cams and valves and each of the other parts isknown and the information can be used as feedbackinto the design process to achieve a highly efficientpump. An example in which the arrangement of thefuel line system decreases the pressure pulses is shownin Fig. 8. We are proposing a high-pressure linearrangement that was optimized by estimating thepressure pulses in the high-pressure lines.

Highly Accurate Airflow SensorIn a direct fuel injection system, accurate

measurement of the amount of airflow is needed, evenwhen pulsing in the air intake is increased by lean burnand high EGR. We are dealing with that problem byimproving an already successful airflow sensor. Thestructure of the slot-in airflow sensor is shown in Fig.9. The slot-in sensor reduces the circuit board area byhalf by using a layered structure and other such means,and integrates the circuit case with the sensor mountingunit. Furthermore, using a modular structure in whichthe detour bypass is mounted on an aluminum baseallows reduction in size and increase in performance.We were thus able to reduce the price by decreasingthe component cost and raising productivity. Mountingthis module in the intake of the air cleaner or othersuch place makes it possible to measure the airflow.

We also reduced measurement error caused bypulsing and temperature changes. Concerning airintake pulsing, we reduced the measurement error due

Fig. 8—Structure of High-pressure Fuel Pump and Example ofOptimization of High-pressure Lines.In addition to achieving the world’s lightest pump (800 gm) byusing an aluminum body, we used proprietary simulations todevelop a high-pressure fuel line system with reduced pulsation.

Fig. 9—Structure of Slot-in Airflow Sensor.Productivity in manufacturing is improved by layering thecomponent modules on the aluminum base, allowing aunidirectional stacking assembly method. Other than theconnectors, the components can be formed into two parts, anupper part and a lower part, thus allowing cost reduction bymulti-part installation.

Module

Intake manifold

Intake air

CoverBypass

Bypass

Installed on manifoldComponents

Aluminum baseConnector

HousingCircuit board

HWCFIAT


0.1

0 15Rate of increase in fuel economy (%)

30

0.05

00 0.05 0.1

Euro-4

Euro-5 expected

Emissions Standard (2000) in Japan

New Emission Standard (2005) in Japan

NO

x em

issi

ons

(g/k

m)

NO

x em

issi

on

ProjectedFuture (ultra-low NOx)

HC emission (g/km)

Injector driver Engine control module

External dimensions: 125 × 119 × 49 (mm)



Separate injector and driver

High cost

Lower system cost

Features

• Built-in high-voltage injector driver (example for 6-cylindertype)

• Electronic throttle control with built-in valve control

• For linear air-fuel ratio control

to pulsing by half by placing a sensor inside the bypassused to reduce the pulsing itself and optimizing acrossthe bypass to improve performance factors such asinitial accuracy and output noise. We also reduced theerror due to temperature change by trying to achieve abalance between insulation by molded plastic and heatradiation from the aluminum base.

Although the interior of the engine compartmentis heated by exhaust heat, etc., the temperature insidethe air intake is low because the air is brought in fromoutside the compartment. With the slot-in airflowsensor, in addition to reducing the temperature changein the circuitry and sensor module by the heat radiatedfrom the aluminum base, reliability is increased byextension of lifetime by reduced thermal stress in themounts. What is more, a proven bobbin-wound hotwire is used on the flow sensor to increase the air-tightness of the circuit board case, thus improvingreliability.

Engine Control Module with Integrated InjectorDriver

In direct fuel injection, there is a new need for aninjector driver for driving the injector at high speedfor injection under high combustion pressure. We

integrated the injector driver, which has previouslybeen a separate unit, with the engine control moduleto reduce size, weight and cost (see Fig. 10). Moreover,the use of a waterproof construction allows mountinginside the engine compartment, thus improving easeof installation in the vehicle and reducing the wiringneeded.

The main features of the integrated unit are a 50%reduction in number of parts, 50% reduction in weightand lower cost, all achieved by integration of theinjector driver and use of custom ICs (integratedcircuits). Furthermore, we developed a new customICs that centralize peripheral functions for the powersupply and output and for the injector driver. Usingthese custom ICs allowed a large reduction in thenumber of parts and made it possible to integrate theinjector driver with the engine control module.

SYSTEM PERFORMANCE AND FUTUREDEVELOPMENT

In addition to developing the combustion controltechnology and components based on spray shapingdescribed above, the Hitachi Group has been proposingsystem solutions that combine control technology withdirect fuel injection.

Future development of system performance isprojected in Fig. 11. The lead spray injection systemdescribed here is for low-emission gas vehicles

Fig. 10—Engine Control Module with Integrated InjectorDriver.Reduction of size, weight and cost are the objective ofintegrating the injector and driver with the engine controlmodule, which had previously been separate units.

Fig. 11—Comparison of Performance of Injection Methods andTheir Future Development.The lead spray injection method can cope with the new, strongeremissions regulations that begin in 2005. For future systemsbeyond 2010, we aim for yet higher performance.


Furthermore, to meet the requirements ofenvironmental regulations, etc., we are also developingvarious kinds of technology for injection spray shapingand components based on consumption analysistechnology.

The engine system is expected to continue to evolveeven after 2010. The Hitachi Group will continue topropose new solutions for the engines of the future.

REFERENCES(1) T. Shiraishi et al., “Study on Mixture Formation of Direct

Injection Engines,” Transaction of Automotive Engineers ofJapan, Inc. Vol. 33, No. 4 (Oct. 2002) in Japanese.

(2) M. Abe et al., “Fuel Spray Pattern Control by Using L-StepNozzle Injector,” Proceedings Vol. VII, MechanicalEngineering Congress, 2003 Japan (MECJ-03) (Aug. 2003)in Japanese.

(3) K. Hiraku et al., “Hydraulic Simulator for High Pressure FuelPump,” Proceedings Vol. VII, Mechanical EngineeringCongress, 2003 Japan (5. Aug. 2003) in Japanese.

ABOUT THE AUTHORS

Minoru OsugaJoined Hitachi, Ltd. in 1979, and now works at the

Control System Design Department, the EngineManagement System Division, the Automotive

Systems. He is currently engaged in the development

of engine control systems. Mr. Osuga is a member ofthe Society of Automotive Engineers of Japan, Inc.

(JSAE) and Japan Society of Mechanical Engineers

(JSME), and can be reached by e-mail [email protected].

Yoshiyuki TanabeJoined Hitachi, Ltd. in 1980, and now works at the

Engine Equipment Development Center, the Engine

Management System Division, the AutomotiveSystems. He is currently engaged in the development

of engine control devices. Mr. Tanabe is a member of

JSAE and can be reached by e-mail [email protected].

Shinya IgarashiJoined Hitachi Car Engineering Co., Ltd. in 1981,

and now works at the Design Department, the 2nd

Electronic Device Design Group. He is currentlyengaged in the development of airflow sensor.

Mr. Igarashi is a member of JSAE and can be

reached by e-mail at [email protected].

Masahiro ZaitsuJoined Hitachi Car Engineering Co., Ltd. in 1983,

and now works at the Design Department, the 1stElectronic Device Design Group. He is currently

engaged in the development of electric controlmodule. Mr. Zaitsu is a member of the Society of

Automotive Engineers and can be reached by e-mail

at [email protected].

Takuya ShiraishiJoined Hitachi, Ltd. in 1993, and now works at theVehicle System Unit, the 3rd Department of System

Research, Hitachi Research Laboratory. He is

currently engaged in the development of enginecombustion systems. Mr. Shiraishi is a member of

JSAE and JSME, and can be reached by e-mail at

[email protected].

Motoyuki AbeJoined Hitachi, Ltd. in 1999, and now works at theAutomotive System Project, the Mechanical

Engineering Research Laboratory. He is currently

engaged in the development of fuel injection devices.Mr. Abe is a member of JSME, and can be reached by

e-mail at [email protected].

designed to meet the New Emissions Standard (2005)in Japan by reducing NOx and HC emissions and whichwill also meet the requirements for the Euro-5regulations (a half amount of Euro-4) in Europe.Together with reducing NOx emissions, a 16%improvement in fuel economy compared to port fuelinjection can also be achieved. Furthermore, we aretaking on the development of a system for improvingmileage by 30% while attaining ultra-low NOx

emission, targeting 2010.

CONCLUSIONSWe have described direct fuel injection engine

control system solutions that have been developed bythe Hitachi Group.

We have continuously applied our proventechnology to control system products for the directfuel injection engine since it was first developed in1997.

crdi

Documents

Transcript of crdi