Metering device, component description

W14.40-1198-08

8 Dispenser

Provision

The dispensing unit (8) is located near the last cylinder of engine head.

Task

In the dispensing unit (8), the compressed air and AdBlue are mixed forming an aerosol. It is injected in the exhaust piping according to the engine module control (MR).

Composition

The dispensing unit is comprised of an aluminum case, divided into two parts. On one side there are the AdBlue components and on the other the compressed air components. The dispensing valve (5) is in the middle.

B14.40-0169-09

1 AdBlue intake

2 AdBlue pressure sensor (17B05)

3 AdBlue temperature sensor (17B07)

4 Calibration screw

5 Dispensing valve (17Y03)

6 Diffuser

7 Compressed air (17B06) pressure sensor

8 Compressed air intake

9 Aerosol output

10 Check valve

11.1 AdBlue screen filter

11.2 Compressed air screen filter

12 Bushing

13 Heating element (17R05)

Function

The AdBlue pump feeds the dispensing unit, where the AdBlue flows through the intake (1), going through the screen filter (11.1), with a 30µm mesh to eliminate impurities, and continues under pressure up to the normally closed dispensing valve (5). When starting the engine, the compressed air flow starts through the intake (8) going through the screen filter (11.2).

When the dispensing valve (5) opens, at intervals calculated by the engine module (MR), AdBlue flows through it, based on the flow and pressure conditions and is pushed to the injector nozzle.

Due to the compressed air continuous flow, the dispensing unit ensures that there is no AdBlue residue inside it.

Dispensing unit ventilation with ignition off

After turning the ignition off, the dispensing unit has a ventilation process to prevent damages caused by AdBlue freezing. This command module operation takes place because of the opening and closing of the compressed air limitation solenoid valve and the dispensing valve (5) at coordinated intervals, up to 300 seconds. The main variables that influence the process duration are the pressures in (7) and (2) sensors.

If the pressure difference is above specification, the valve (5) opens, and the compressed air flows on the opposite direction of the AdBlue in the dispensing unit, pushing the remaining AdBlue to the pump module, through the piping.

When the engine module (MR) recognizes, based on the sensors signals, that the dispensing unit was sufficiently supplied with air, the ventilation comes to an end. It takes place when the sensor pressure (7) is higher than the sensor pressure (2).

The piping between the pump module and the dispensing unit is comprised of a flexible hose that allows additional residues produced by AdBlue freezing. Apart from that, the pressure in this piping is reduced at the atmospheric pressure because of the pump module depressurization.

Heating element description

In case of crystallization at the diffuser (6) intake or the neck and the air pressure sensor (7) fails to read, the system will understand that there is a clogging and will start the cleaning routine, as follows:

1 The heating element (13) will turn on for 640 seconds;

2 The engine module (MR) checks the presence of air pressure in the sensor (7);

3 If there is pressure, the system will be ready to inject;

4 If there is no pressure, the heating element (13) is turned on again;

5 The heating element (13) only starts working in case it is necessary, and if the clogging persists, it will remain on for up to 3600 seconds. If the system remains clogged, the dosing is interrupted and a fault is recorded.

The compressed air pressure in the dispensing unit sensor (7) needs to be at least at 1.5 bar so that AdBlue injection is released.

With the vehicle operating, the compressed air constantly goes through the dispensing unit, even if it is not injecting AdBlue.