Kyron_1_Engine_008_02_005

FUEL SYSTEMKYRON SM - 2005.09

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52 07

INJECTOR

The C21 labels including injector characteristics are attached in each injector. These C21 values should be input toECU by using Scan-i when replacing the ECU or injectors.

Special cautions:

1. Plug the openings of hoses and pipes with the sealing caps.

2. Replace the copper washer in injector with new one.

3. Tighten the injector holder bolts with the specified tightening torque.

4. Be careful not to drop the injector.

Specifications

Length: · Injector body 181.35 mm

· Injector nozzle 22.155 mm

Nozzle basic: 5 Holes, 150° ConeAngle, 890 mm3/min (D20DT)

Nozzle basic: 5 Holes, 146° ConeAngle, 840 mm3/min (D27DT)

Control: PWM type (solenoid injector)

Tightening: By clamping fork

Fuel return: Nipple

C2I label

C2I value

Cap nut

WasherNozzle needle

Nozzle body

Adaptor plate

Control valve

Bobbin

Nozzle holder body

Leak offnipple

Edge filter

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The maximum injection pressures are approximately 1,600 bar. The forces to be overcome in order to lift the needleof the injector are therefore very large. Because of this, it is impossible to directly control the injector by using anelectromagnetic actuator, unless very high currents are used, which would be incompatible with the reaction timesrequired for the multiple injections. The injector is therefore indirectly controlled by means of a valve controlling thepressurizing or discharging of the control chamber located above the needle:

1. When the needle is required to lift (at the start of injection): the valve is opened in order to discharge the controlchamber into the back leak circuit.

2. When the needle has to close (at the end of injection): the valve closes again so that pressure is re-establishedin the control chamber.

Valve

In order to guarantee response time and minimum en-ergy consumption:

1. The valve must be as light as possible.

2. The valve stroke must be as short as possible.

3. The effort needed to move the valve must be minimal,which means that the valve must be in hydraulic equi-librium in the closed position.

Spring pressure ensures contact between the valve andits seat. To lift the valve, it is therefore required to over-come the force being applied by this spring.

INO inletir i f ice

NOP nozzlepath orifice

SPO spillorif ice

Controlchamber

Spacer

Valve

Volumeunder

h ighpressure

Valve

Spi l lorif ice

Contactmaking seal

Depressuriza-tion grooves

Volumeundervacuum

Spacer

The spacer is situated underneath the valve support. Itintegrates the control chamber and the three calibratedorifice which allow operation of the injector. These ori-fices are:

1. The injector supply orifice (Nozzle Path Orifice: NPO)

2. The control chamber discharge orifice (Spill Orifice:SPO)

3. The control chamber filling orifice (Inlet Orifice: INO)


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54 07

Ff = (Ff = Prail S)

Fo = (Fo = Prail A)

S

A

Principle of Operation

Injector at rest

The valve is closed. The control chamber is subject tothe rail pressure.

The pressure force applied by the fuel onto the needle is:

Ff = S * Prail

The needle is closed and hence there is no fluid circu-lation through the NPO orifice. While static, the nozzleproduces no pressure drop. The cone of the needle istherefore subject to the rail pressure. The force ap-plied by the fuel to the needle is:

Fo = A * Prail

Since Ff > Fo, the needle is held in the closed position.There is no injection.

Solenoid valve control

When the solenoid valve is energized, the valve opens.The fuel contained in the control chamber is expelledthrough the discharge orifice known as the Spill Orifice(SPO).

As soon as Ff > Fo, the needle remains held against itsseat and there is no injection.

Ff = pressure *

space

(Ff = Prail * S)

Fo = pressure *

space

(Fo = Prail *

S)

Valve closed

Needleclosed

No injection

Valve opens

Needleclosed

No injection

Valve open

Needle opens

Start ofinjection

Valve closes

Needle open

End ofinjection

Valve closed

Needleclosed

No injection

* S: The area of the flat upper surface of the injector’s needle

* A: The area of the needle surface situated above the sectionof contact between the needle and its seat

* Ff: The force applied by the fuel onto section “S”

* Fo:The force applied by the fuel onto section “A”

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Start of injection

As soon as Ff < Fo, or in other words:

Pcontrol < Prail * A/S

The needle lifts and injection begins. As long as the valve is open, the injector’s needle remains lifted. Wheninjection begins, fuel circulation is established to feed the injector. The passage of the fuel through the inletorifice of the injector (similar to a nozzle) leads to a pressure drop which depends on the rail pressure.

When the rail pressure is at its highest (1600 bar), this pressure drop exceeds 100 bar. The pressure appliedto the cone of the needle (the injection pressure) is therefore lower than the rail pressure.

End of injection

As soon as the solenoid valve is de-energized, the valve closes and the control chamber is filled. Since theneedle is open, the thrust section areas situated on either side of the needle is therefore to apply differentpressures to each of these faces. The pressure in the control chamber cannot exceed the rail pressure, so it istherefore necessary to limit the pressure applied to the needle’s cone. This pressure limitation is achieved bythe NPO orifice which produces a pressure drop when fuel is passing through it.

Prail * S (Prail - P) * S

When static, this pressure drop is zero. When the pressure in the control chamber becomes higher than thepressure applied to the needle’s cone, the injection stops.


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56 07

Injecting Process

Fuel is delivered to theinjector

Delivered fuel is passedthrough supply orifice (1)and control chamber orifice(2)

The fuel is delivered to thevolume under high pressurethrough the spill orifice (3)

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The fuel is delivered to thecontrol chamber (4) inspacer

The fuel begins to get intothe nozzle needle (5)

The nozzle needle is filledwith fuel and close the valve(6) by increased pressure


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58 07

The pressure is delivered tothe spill orifice (3)

The pressure is delivered tothe control chamber (7) andthe nozzle needle (8)

The nozzle needle starts toopen and inject the fuel

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The nozzle needle blocks thecontrol chamber (9)

The valve opens due to thepressure decreases (10)

The pressure is delivered tocontrol chamber (11)


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60 07

It pushes the nozzle needleand the control chamberopens (12)

The nozzle closes (13)

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3. Small injection separation: min. 200

(duration between the end of pilot injection and startof main injection)

4. Opening Delay

: Delayed time from applying operating voltage to startof injection

5. Adjustment of feedback injection volume: C2I

Fuel Pressure

Fuel pressure

1. Minimum operating pressure: start injection over 100 bar

2. Maximum operating pressure: 1,600 bar (max. operating pressure in normal conditions)

3. Operating pressure limit: 2,100 bar

Maximum fuel volume at each injector cycle

1. Pilot Injection 5 mm3

2. Main Injection 85 mm3 (within 200 ~ 1,600 bar)

Pilot injection

Main injection

Small injectionseparation

Opening Delay Definition

Injection rate

Injector drive pulse

Time ( )

10%signal

amplitude

10%signal

amplitude


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62 07

Injector Control

The control current of the coil takes the following form:

1. The low current allows the Joule effect losses in the ECU and injector to be reduced. The call current is higherthan the hold current because during the hold phase.

2. The air gap between the valve and the coil is reduced and the electromagnetic force to be applied to the valve canthus be reduced. It is no longer necessary to overcome the valve inertia.

Time

Hold periodPull-in period

Through pullcurrent = 7.5 A

Current

Peak pullcurrent = 22.0 A

Through holdcurrent = 7.5 A

Peak holdcurrent = 22.0

A

• Joule Effect: Heat capacity (H) = 0.24 I 2RT

NOTE

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<Characteristic Curve of Discharge withoutPilot Injection>

<Characteristic Curve of Discharge withPilot Injection>

Fuel InjectionOther than conventional diesel engine, common diesel engine use two steps injection as follows:

1. Pilot Injection

2. Main Injection

In above two step injection, the fuel injection volume and injection timing is calibrated according to fuel pressure andfuel temperature.

Pilot injection

Before starting main injection, a small amount of fuel is injected to help proper combustion. This injection is forreducing the engine noise and vibration.

In other words, it makes the pressure increase in combustion chamber during combustion smooth to reduce theengine noise and vibration (suppressing the surging). Basic values for pilot injection are adjusted according tothe coolant temperature and intake air pressure.

Ne

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le l

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k)

Angle of crankshaft

Cyl

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Angle of crankshaft


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Removal and Installation

Preceding Work: Removal of engine cover

1. Disconnect the injector return hose.

2. Remove the relevant connector for the injector.

• Plug the openings with sealing caps.

NOTICE

Main injection

Actual output from engine is achieved by main injection.

The main injection determines the pilot injection has been occurred, then calculates the injection volume. Accel-erator pedal sensor, engine rpm, coolant temperature, intake air temperature and atmospheric pressure arebasic date to calculate the fuel injection volume in main injection.

1. Pilot injection

2. Main injection

1a. Ignition pressure with pilot injection

2a. Ignition pressure without pilot injection

<Characteristic Curve of Combustion Chamber Pressure During Pilot Injection>

Angle of crankshaft

Pre

ssu

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3. Unscrew the bolts and remove the fuel pipes.

Installation Notice

4. Unscrew the injector holder bolts.

Installation Notice

6. Remove the injectors with a special tool.

7. Install in the reverse order of removal.

Replace the bolts with new ones.

5. Disconnect the injector holder.

Tightening torque 40 ± 4 Nm

Tightening torque9 ± 1.0 Nm

190° + 10°

• Replace the fuel pipes with new ones.

• Plug the openings of the common rail with sealingcaps.

NOTICE

• Plug the openings of the injectors with sealing caps.

• Pull the dropped washer out from the engine witha special tool.

NOTICE

• Replace the copper washer, holder bolts and fuelsupply pipes with new ones.

NOTICE

D27DT

D20DT


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66 07

Circuit Diagram

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Kyron_1_Engine_008_02_005

Documents

injector nozzle

injector body

injector characteristics

restthe valve

valve stroke

valve support

injector holder bolts

valve andits seat