kyron_1_engine_008_02_005
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FUEL SYSTEMKYRON SM - 2005.09
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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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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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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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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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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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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
ind
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pre
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p)
Ne
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k)
Cyl
ind
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pre
ssu
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p)
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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Circuit Diagram
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