Emitec System introduction (2013)
System Layout
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Components
Dosing Pump Unit
ECM
Urea tank (level and temp sensor)
Air tank
Pipeline
(suction line, backflow line, mixture line, air flow line)
Urea injector nozzle
EGP
(Temp sensor, Nox sensor)
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Dosing Unit
1. Urea in from tank
2. Air supply in (vehicle air tank/compressor)
3. Urea out to Injector nozzle (Urea & Air mix)
4. Urea return to tank (only used during prime)
5. 37 PIN ITT Can connector broadcasting on the J1939
6. Power supply to Solenoid 2 pin connector
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Dosing Unit Specifications
Function : deliver urea according to the message sent by engine
ECM.
Built-in heating device : allows the doser to operate with outside
temperatures < -11C, if the vehicle also has heated Urea lines and
tank.
It will also function in a working temp > 80C, but Urea > 50degC for
extended periods will damage the doser Unit.
Integrated self-diagnostic procedure, informing the Engine ECM
about its status by sending messages via the J1939 CAN link.
Accommodate both 12 VDC & 24 VDC supply voltages.
The desired flow rate repeatability :1%
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Cummins Confidential
Dosing Unit Components
A: Air Tank
B: Air filter
C: Doser unit
D: Engine ECM
E: Wema Sensor
F: Urea Tank
G: Nozzle
H: EGP Inlet Temp
I:EGP Outlet Temp
J: EGP
Dosing Unit Components
Valves & lines
Motor
PCB
Dosing Pump controller
Pump heater
Temperature sensor
Temp sensor on the PCB
Connector
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Valves & lines
B
1
2
3
6
4
5
UDS limits
A
10
P
11
7
1.
Air valve (controlled by solenoid)
AIR UNIT
2.
Air pressure regulator @ 4 bar
3.
Orifice
8
OBD
4.
Air Check Valve (ACV)
MIXING VALVE
5.
Back Pressure Valve (BPV)
9
6.
Mixing chamber
7.
Outlet check valve (spring loaded)
D
C
8.
Actuated membrane
MEMBRANE PUMP
9.
Inlet check valve (spring loaded)
10. Pressure switch
UREA TANK
11. Air Actuated Valve (AAV)
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Dosing Unit
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Dosing Unit
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Dosing Unit
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Dosing Unit
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Pump motor
Stepper Motor
Stroke
One piston movement (back and force)
Origo
System which gives the membrane origin (Hall effect sensor)
Parking Position
Best position for parking:
In this position, the membrane can move easily during urea
expansion (freezing);
After the thawing of the pump head, the pump cycle will start
with the suction phase. So, this avoids increasing of pressure in
the pump head if the return line is frozen.
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Pump motor : Parking
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Connector
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Urea injector nozzle
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Urea injector nozzle location
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Urea injector nozzle location
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SCR
SCR
Urea Injector
catalyst
Gas Flow
Urea Decomposition and Hydrolysis in Exhaust:
(NH2)2CO (s) ˘ NH3 (g) + HNCO (g)
HNCO (g) + H2O (g) ˘ NH3 (g) + CO2 (g)
NOx Reduction in SCR Catalyst:
NO + NO2 + 2NH3 → 2N2 + 3H2O
Fast Reaction
4NO + 4NH3 + O2 → 4N2 + 6H2O
Dominant Reaction
2NO2 + 4NH3 + O2 → 3N2 + 6H2O
Slow
6NO2 + 8NH3 → 7N2 + 12H2O
Slow
6NO + 4NH3 → 5N2 + 6H2O
Slow
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Content
System layout and components
Control----Working flow
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Priming phase (1)
B
1
2
3
6
4
5
A
10
P
11
7
8
Air valve closed (air solenoid valve off)
Pump motor working at max capacity (7.5l/h)
9
Urea back to tank, not build pressure
Pressure switch not activated
D
C
UREA TANK
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Prime phase (2)
(continued)
After 30s the air solenoid valve open - air pressure closes the air
activated valve (AAV), the solenoid can be heard “clicking” on
Doser continues to pump urea for 10 strokes, building pressure in the
urea path
During the 10 strokes monitor pressure switch
If urea is present, and air bubbles have been purged out, then the
pressure switch will activate, indicating the presence of urea and a
successful prime, transition to dosing state
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Prime phase (3)
(continued)
If no urea is present, the doser will be unable to build pressure;
priming will be unsuccessful
The air solenoid valve will be deactivated, to allow urea to circulate
back to the tank and the prime sequence will be repeated
After retrying 20 times, the doser will report
UREA_DOSER_LOW_AIR_UREA_ERR
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Prime phase (4)
(continued)
At the end of the Priming phase
Air solenoid valve open
Pump motor stop
Pressure switch activated
When priming is complete, the doser automatically enter the “Dosing”
state, but with a urea dosing rate of 0 ml/h.
Urea dosing phase
B
2
3
6
4
5
1
A
10
P
7
11
Air valve open (air solenoid on)
8
OBD
Pump working at required capacity
Urea injected in nozzle line
9
Pressure switch activated
D
C
UREA TANK
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Purging phase
B
2
3
6
4
5
1
A
10
P
7
Clear nozzle line
11
8
OBD
Air valve open (air solenoid on)
Pump motor stopped (0l/h)
9
Only air injected in nozzle line
Pressure switch activated
D
C
UREA TANK
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Purging phase
Air solenoid valve opens
Pump motor stop
Pressure switch activated
Air removes urea droplets that could crystallise and block the pump
valves, urea lines or the injection nozzle.
Lasts for 30 seconds then the system switches off, the solenoid can be
heard “clicking” off.
Stop phase
B
1
2
3
6
4
5
A
10
P
11
7
Air closed (air solenoid off)
8
Pump stopped to parking position
No urea neither air flow
Pressure switch not activated
9
D
C
UREA TANK
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