Claims:We Claim:
1. A method of monitoring performance of a diesel oxidation catalyst, said method comprising:

detecting (100), by a control unit a regeneration request of said diesel oxidation catalyst;

receiving (102), by a control unit, quantity of fuel consumed by during said regeneration request;

comparing (104), by said control unit said quantity of fuel consumed with respect to a threshold defined in a data map; and

verifying (106), by said control unit if said quantity of fuel consumed exceeds said threshold defined in said data map for monitoring said performance of said diesel oxidation catalyst.

2. The method of claim 1, further comprising displaying said verified quantity onto a display device.

3. The method of claim 2, wherein said display device is located on a vehicle.
, 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]This invention relates to the field of diesel oxidation catalyst in an exhaust gas system.

Background of the invention
[0002] Diesel oxidation catalyst (DOC) is used to burn hydrocarbons and carbon monoxide gases coming out of diesel exhaust. Hydrocarbon oxidation ability of DOC is exploited to trigger active regeneration for burning accumulated soot in particulate filter. Excess fuel is injected on DOC either through a hydrocarbon injector or in-cylinder injection. This fuel is burnt over DOC and due to exothermic reaction, temperature upstream of diesel particulate filter (DPF) increases to more than 600 degree celsius leading to a successful request of diesel particulate filter (DPF) regeneration. The hydrocarbon oxidizing ability of DOC reduces over the lifetime which leads to increased fuel consumption and higher hydrocarbon slip from DOC. Due to high oil consumption and city driving profile in several Indian applications the deactivation of DOC is critical and to predict the loss in activity of DOC over lifetime during development is not possible. Loss of activity of DOC can lead to incomplete soot combustion in filter leading to exhaust line choking, increased fuel penalty, uncontrolled soot oxidation in filter due to high hydro carbon slip from DOC.

[0003] Prior art patent application DE102016200017A1 discloses a method and a device for determining the aging condition of a catalyst whose work area has a length in the exhaust gas direction, the determination of the aging state of the catalyst is carried out by means of a control unit which the output signals of a positioned at a predetermined longitudinal position of the working area of the catalyst sensor considered.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates a method of monitoring performance of a diesel oxidation catalyst.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a method of monitoring performance of a diesel oxidation catalyst. The method comprises detecting 100, by a control unit a regeneration request of the diesel oxidation catalyst. The control unit receives 102 quantity of fuel consumed during the regeneration request. The control unit compares 104 quantity of fuel consumed with respect to a threshold defined in a data map, and verifies 106 if the quantity of fuel consumed exceeds the threshold defined in the data map for monitoring the performance of diesel oxidation catalyst. The method further comprises displaying the verified quantity onto a display device located on a vehicle.

[0007]The objective of the above mentioned method is to monitor the performance of diesel oxidation catalyst over the lifetime. The diesel oxidation catalyst (DOC) is an exhaust after treatment device that is designed to convert carbon monoxide (CO) and hydrocarbons into carbon dioxide (CO2) and water. Diesel oxidation catalyst is also used to increase temperature upstream diesel particulate filter to around 600 degree Celsius to burn trapped soot particles. Diesel particulate filter (DPF) needs to be regenerated at regular intervals to ensure that that the soot particles that are deposited in the DPF get burnt due to combustion. The temperature at which this regeneration happens is around 600 degree Celsius. For a particular mass flow rate of exhaust and the temperature of exhaust, fuel needs to be injected in order to increase the temperature of exhaust to 600 degree Celsius, this is because the temperature of exhaust in the request where regeneration does not happen is always less than 600 degree Celsius. Consider the case where the temperature of exhaust is 300 degree Celsius in one instance. From 300 degree Celsius to achieve regeneration temperature of 600 degree Celsius, X1 mg/stroke of fuel needs to be injected. The value of X1 mg/stroke is arrived at during calibration by considering parameters like mass flow rate of exhaust. Now, in another instance, when the temperature of exhaust is 200 degree Celsius, then in order to reach regeneration temperature 600 degree Celsius X2 mg/stroke of fuel needs to be injected. X2 being greater than X1. In other words greater the temperature difference between the regeneration temperature and the exhaust temperature, higher quantity of fuel needs to be injected.

[0008]The quantity of fuel that needs to be injected for different temperatures of exhaust is calibrated and stored in a data map. However, as the diesel oxidation catalyst ages and gets poisoned with time, the quantity of fuel that needs to be injected in order to reach regeneration temperature may vary, for example for an exhaust gas temperature of 200 degree Celsius, the quantity of fuel injected will be X2 mg/stroke plus delta X to compensate for reduction in catalytic activity due ageing and poisoning of diesel oxidation catalyst. This difference between X2 and X is used as a reference for monitoring the performance of diesel oxidation catalyst as disclosed below.

[0009]The proposed method comprises the following steps, at step 100, the control unit detects regeneration request of diesel oxidation catalyst, and this request is detected with the help of sensors present in DOC. Once the regeneration request is detected the temperature of fuel needs to be raised to 600 degree Celsius in order to bring about regeneration. At step 102, the control unit receives the quantity of fuel consumed during the regeneration request. The quantity of fuel that needs to be injected is calculated based on DOC inlet temperature and mass flow rate (in other words torque and speed) which is calibrated during development on engine / vehicle testing. If this injected quantity of fuel is not able to increase the temperature upstream to diesel particulate filter (DPF) (may be due to deactivated DOC) to 600 degree Celsius, then there is closed loop feedback from a sensor (upstream DPF) to increase the dosing demand. Accordingly dosing quantity of fuel will be increased. This dosing can be done in following two ways: (a) Late post injection (in-cylinder fuel injection): where the fuel is injected in cylinder as per dosing demand and dosing demand comes from the control unit and (b).Using hydrocarbon injector (HCI) upstream to DOC: where fuel is injected through a metering unit in communication with the control unit and dosing will occur as per dosing demand from control unit. In both the cases, dosing quantity at a given speed and torque is pre-calibrated and close looped with the sensor. If the temperature does not reach 600 degree Celsius then dosing demand is increased and cumulative amount of injections can be monitored for increase in fuel consumption.

[0010]At step 104, the control unit compares said quantity of fuel consumed with respect to a threshold defined in a data map. This comparison is required to ensure that the quantity of fuel that is required for regeneration is as per the threshold available in the data map. At step 106, the control unit verifies if said quantity of fuel consumed exceeds said threshold defined in said data map for monitoring said performance of the diesel oxidation catalyst.

[0011]By using the above mentioned method it is now possible to monitor the performance of diesel oxidation catalyst. By monitoring the fuel consumed during regeneration of DOC and comparing the same with the threshold it is now possible to identify ageing of DOC.

[0012]It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of the type of exhaust system used. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.