Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed

Field of the invention
[0001] The present disclosure relates to the field Selective Catalytic Reduction Technology. In particular, the application discloses a control unit adapted for ventilation for a dosing module and a method thereof.

Background of the invention
[0002] In diesel automotive systems, Selective Catalytic Reduction (SCR or DNOX) technology is used to convert NOx in the vehicle exhaust to nitrogen and water. SCR system uses an aqueous solution known as Diesel Exhaust Fluid (DEF), commercially known as ‘AdBlue®’, in order to convert the NOx. It is an aqueous solution of urea that is converted in to ammonia and acts as a reducing agent in the SCR reactions. DEF (i.e. 32.5 % solution of urea in water) freezes at -11° C. Therefore, all parts of the SCR system, including DEF tank, lines, supply module and dosing module have to be defrosted and heated if the ambient temperature is below the DEF freezing temperature.

[0003] If DEF present in the dosing module is not emptied after operation and it gets freeze due to environmental temperature (is lower than -11°C). Then DEF present in dosing module also gets freezes and it’s volume increases about 7.2% which causes dosing module damage to leak or crack. Therefore, dosing module has to be emptied after every operation by allowing air to fill in and around the dosing module. However, in next vehicle operation, the accommodated air in and around dosing module has to be pushed(dosed) out to exhaust path before system starts to dose else it doses incorrect quantity of AdBlue into exhaust gas path leading to high emissions. This removal of air accommodated in and around dosing module is called “Ventilation operation in SCR system”.

[0004] In conventional systems, ventilation operation is performed as “Time based function”. A dosing valve of the dosing module is opened for a pre-defined time in ventilation operation irrespective of volume of air accommodated in last driving cycle. Therefore, no definite identification of “air removed completely” in and around dosing valve. If dosing valve is opened longer duration than accommodated air volume, then it would cause mis-dosing to exhaust path. If dosing valve is opened shorter duration than accommodated air volume, then the left-over air would affect system pressure stability, dosing accuracy of the system. Therefore, there is a need for an accurate and precise method of ventilation for the SCR system.

[0005] Patent Application US2006168940 AA titled “Method and apparatus for an exhaust emissions control system” discloses a method for mutual adaptation of a delivery module and a metering module of an exhaust emissions control system that has an exhaust gas conduit and a control module, the delivery module having a reservoir that has a venting valve and contains a uric acid solution that is conveyed via a delivery pump to a pressure regulating valve; and in the metering module, an air stream being compressed with the aid of a pump, conveyed to a pressure accumulator, and conveyed via a regulating valve, together with the uric acid solution, out of the pressure regulating valve to a metering valve, and being conveyed from there to an atomizer unit disposed in the exhaust gas conduit, the value of a reference pressure based on the pressure forming in the exhaust gas conduit being stored in the control module. The method where a respective parameter or characteristic curve being created for the delivery module and for the metering module and being introduced into the respective module as a machine-readable code. An apparatus for mutual adaptation of a delivery module and metering module for an exhaust emissions control system having an exhaust gas conduit and a control module, the value of a reference pressure based on the pressure forming in the exhaust gas conduit in the context of a calibration cycle being stored in the control module.

Brief description of the accompanying drawings
[0006] An embodiment of the invention is described with reference to the following accompanying drawings:
[0007] Figure 1 depicts a portion of a Selective Catalytic Reduction (SCR) System (100);
[0008] Figure 2 illustrates a method (200) of ventilation for a dosing module (15);
[0009] Figure 3 is a graphical illustration of observed pressure characteristics.

Detailed description of the drawings

[0010] Figure 1 depicts a portion of a Selective Catalytic Reduction System (100). The SCR system (100) comprises a tank (11), a filter (12), a supply module (13), a pressure sensor (14) and at least a dosing module (15) amongst other components such known to a person skilled in the art. The tank (11) stores an aqueous solution which comprises a diesel exhaust fluid (DEF) which is also known as Ad-blue. It is a liquid reductant agent and usually automotive-grade urea.

[0011] The supply module (13) is adapted to receive the aqueous solution from the tank (11) via a filter (12). The supply module (13) comprises a supply pump amongst other components known to a person skilled in the art such as a heater and the like. The filter (12) receives the aqueous solution from the tank (11) and after filtration it is passed it on to the supply module (13). The supply module (13) is in fluid communication with the dosing module (15). The supply pump pumps the aqueous solution to the dosing module (15) via the fluid communication path (16). The pressure sensor (14) adapted to measure pressure in said fluid communication path (16)

[0012] The dosing module (15) is adapted to disperse a regulated quantity of an aqueous solution. In an exemplary embodiment of the present disclosure, the dosing module (15) includes a solenoid-based dosing valve (not shown) that is operated to dose a regulated amount of aqueous solution into the exhaust tail-pipe. A selective catalytic reduction reaction occurring in the exhaust gas tailpipe converts nitrogen oxides (NOx) into nitrogen, water and tiny amounts of carbon dioxide (CO2) using Aqueous solution fluid, thereby reducing NOx emissions. All the components of the SCR system (100) are in communication with a Control unit (20) of the vehicle.

[0013] The control unit (20) regulates the dosing quantity of aqueous solution by controlling the operation of the dosing module (15) and the supply module (13) in dependance of data received from the pressure sensor (14). The control unit (20) is a logic circuitry that responds to and process information. The control unit (20) may be implemented as any or a combination of: one or more microchips or integrated circuits interconnected using a parent board, hardwired logic, software stored by a memory device and executed by a microprocessor, firmware, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA).

[0014] The most important yet non-limiting feature of the present invention is the functionality of the control unit (20). The control unit (20) is adapted for ventilation for a dosing module (15). The control unit (20) is configured to: activate the supply module (13) to deliver aqueous solution to the dosing module (15); operate a dosing valve of the dosing module (15) to an open position; observe pressure characteristics measured by the pressure sensor (14); operate the dosing valve by means of the control unit (20) in dependance of the pressure characteristics to ventilate the dosing module (15).

[0015] While observing the pressure characteristics, the control unit (20) is further configured to: record a first-time instance (tp) when the pressure in the fluid communication path (16) equals the operating pressure of the dosing module (15); observe a fall in pressure after the first-time instance (tp) until a lowest value (p0) is attained; observe a steady subsequent rise in pressure after the lowest pressure value (p0); operate the dosing valve of the dosing module (15) to a closed position on observance of the steady subsequent rise in pressure. The observance of the steady subsequent rise in pressure indicates a successful ventilation of the dosing module (15). This is further explained by means of method steps (200).

[0016] It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the present disclosure should in no way be limited to the exemplary implementations illustrated in the drawings and described below.

[0017] Figure 2 illustrates a method (200) of ventilation for a dosing module (15). The dosing module (15) is a part of the SCR system (100) as explained above in accordance with figure 1.

[0018] Method step 201 comprises activating the supply module (13) by means of the control unit (20) to deliver aqueous solution to the dosing module (15). This step is also called the low pressure build-up state, here the supply pump of the supply module (13) is set with operating mode called forward direction with fixed pump speed, which ensures that pump is operated in delivery mode with maximum flow rate and dosing valve kept closed to ensure that system pressure gets increased. Once system reaches defined/calibratable system pressure within defined time.

[0019] Method step 202 comprises operating a dosing valve of the dosing module (15) to an open position by means of the control unit (20). This is known as the ventilation step. Even in ventilation step, the supply pump is operated in forward direction with fixed pump speed, which ensures that pump is operated in delivery mode with maximum flow rate. However now the dosing valve is kept open to allow the compressed air to escape/remove from the system, which causes system pressure to reduce for shorter duration.

[0020] Method step 203 comprises observing pressure characteristics measured by the pressure sensor (14). Figure 3 is a graphical illustration of the observed pressure characteristics. Observing the pressure characteristics further comprises recording a first-time instance (tp) when the pressure in the fluid communication path (16) equals the operating pressure of the dosing module (15). After this a fall in pressure is observed after the first-time instance (tp) until a lowest value (p0) is attained. Finally, a steady subsequent rise is observed in pressure after the lowest pressure value (p0). This observance of the steady subsequent rise in pressure indicates a successful ventilation of the dosing module (15).

[0021] Method step 204 comprises operating the dosing valve by means of the control unit (20) in dependance of the pressure characteristics to ventilate the dosing module (15). Once this steady subsequent rise is observed, i.e. the dosing module (15) is successfully ventilated, the dosing valve is operated to a closed position. Now the system is ready to dose aqueous solution and dosing module (15) is filled with aqueous solution.

[0022] The rationale behind the above methodology is that the supply pump delivery rate is more than dosing valve delivery rate. This proves that once air in and around the dosing valve is removed and aqueous solution is reaching the dosing module (15), then system pressure will be increased though dosing valve is kept open at ventilation state.

[0023] This idea to develop a control unit (20) adapted for ventilation for a dosing module (15) and a method (200) thereof i.e. a pressure gradient based method gives a definite method to detect accurately when the air is completely removed from system irrespective of the volume of air accommodated in the previous driving cycle based on component tolerance, vehicle dynamics and environmental impact to the system e.g: environmental pressure.

[0024] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to a control unit (20) adapted for ventilation for a dosing module (15) and a method (200) thereof are envisaged and form a part of this invention. The scope of this invention is limited only by the claims. , Claims:We Claim:

1. A method (200) of ventilation for a dosing module (15), the dosing module (15) adapted to disperse a regulated quantity of an aqueous solution, said dosing module (15) in fluid communication with a supply module (13), a pressure sensor (14) adapted to measure pressure in said fluid communication path (16), a control unit (20) in communication with the dosing module (15), supply module (13) and at least the pressure sensor (14), the method steps comprising:
activating the supply module (13) by means of the control unit (20) to deliver aqueous solution to the dosing module (15);
operating a dosing valve of the dosing module (15) to an open state by means of the control unit (20);
observing pressure characteristics measured by the pressure sensor (14);
operating the dosing valve by means of the control unit (20) in dependance of the pressure characteristics to ventilate the dosing module (15).

2. The method (200) of ventilation for a dosing module (15) as claimed in claim 1, wherein observing the pressure characteristics further comprising:
recording a first-time instance (tp) when the pressure in the fluid communication path (16) equals the operating pressure of the dosing module (15);
observing a fall in pressure after the first-time instance (tp) until a lowest value (p0) is attained;
observing a steady subsequent rise in pressure after the lowest pressure value (p0).

3. The method (200) of ventilation for a dosing module (15) as claimed in claim 2, wherein observance of the steady subsequent rise in pressure indicates a successful ventilation of the dosing module (15).

4. A control unit (20) adapted for ventilation for a dosing module (15), the control unit (20) in communication with the dosing module (15), a supply module (13) and at least a pressure sensor (14), the dosing module (15) adapted to disperse a regulated quantity of an aqueous solution, said dosing module (15) in fluid communication with the supply module (13), the pressure sensor (14) adapted to measure pressure in said fluid communication path (16), the control unit (20) configured to:
activate the supply module (13) to deliver aqueous solution to the dosing module (15);
operate a dosing valve of the dosing module (15) to an open state;
observe pressure characteristics measured by the pressure sensor (14);
operate the dosing valve by means of the control unit (20) in dependance of the pressure characteristics to ventilate the dosing module (15).

5. The control unit (20) adapted for ventilation for a dosing module (15) as claimed in claim 4, wherein when observing the pressure characteristics, the control unit (20) is further configured to:
record a first-time instance (tp) when the pressure in the fluid communication path (16) equals the operating pressure of the dosing module (15);
observe a fall in pressure after the first-time instance (tp) until a lowest value (p0) is attained;
observe a steady subsequent rise in pressure after the lowest pressure value (p0);
operating the dosing valve to a closed state of the dosing module (15) on observance of the steady subsequent rise in pressure.

6. The control unit (20) adapted for ventilation for a dosing module (15) as claimed in claim 4, wherein observance of the steady subsequent rise in pressure indicates a successful ventilation of the dosing module (15).