Field of the invention

This invention relates to the field of monitoring conversion capability of a diesel oxidation catalyst.

Background of the invention

Pollutants such as hydrocarbons (HC), and carbon monoxide (CO) present in exhaust gas are required to be treated prior to emmiting the pollutants into the atmosphere. A diesel oxidation catalyst is used to convert the HC and the CO that are present in exhaust gas into carbon dioxide (C02) and water (H20).
The diesel oxidation catalyst is coated with one or more chemically active materials, for example platinum, palladium, or rhodium, which enables oxidation of HC and CO.

However, over time, conversion capability of the diesel oxidation catalyst may be reduced due to contamination of the diesel oxidation catalyst and the diesel oxidation catalyst may be rendered inefficient. The contamination may occur due to one or more factors such as high temperatures and particulate matter deposition on the diesel oxidation catalyst. Therefore a need to monitor the conversion capability of a diesel oxidation catalyst and notify a user when a particular level of inefficiency or failure occurs is required.

Conventional method of monitoring the conversion capability of the diesel oxidation catalyst includes measuring temperature difference between upstream and downstream of a catalytic converter using temperature sensors. Further, if temperature difference between the upstream and the downstream of the catalytic converter is minimal then it is concluded that the diesel oxidation catalyst is operating inefficiently. However, the temperature sensors, due to production tolerances, may provide erronical values and hence the method is unreliable.

Object of the invention

The object of this invention is to monitor the conversion capability of the diesel oxidation catalyst overcoming the limitations of the conventional methods of monitoring.

Advantages of the invention
The invention provides for simple and reliable way of monitoring conversion capability of diesel oxidation catalyst since no temperature sensors, that provide erroneous values due to production tolerance, are used. Also, unlike prior arts there is no fuel consumption during monitoring of the conversion capability.
Brief description of the accompanying drawings

Figure. 1 illustrates a block diagram of a monitoring device for monitoring conversion capability of a diesel oxidation catalyst in accordance with this invention; and

Figure. 2 illustrates a block diagram of a catalytic converter 200 for treating exhaust gas in accordance with this invention.

Detailed description

Figure. 1 illustrates a block diagram of a monitoring device 100 for monitoring conversion capability of a diesel oxidation catalyst 105 in accordance with this invention. The monitoring device 100 may be disposed in an exhaust gas pathway or in a catalytic converter.

The monitoring device 100 includes a passive catalyst 110, a sensing element 115 and a processing means 120. The passive catalyst 110 is devoid of coating with chemically active materials, for example platinum, palladium, or rhodium whereas the diesel oxidation catalyst 105 is coated with the chemically active materials.

Further, the passive catalyst 110 is in electrical connection with the diesel oxidation catalyst 105 through the sensing element 115. In one example, the sensing element 115 can include a heat flux sensor. The electrical connection may be made by means of, for example, copper wires or copper plates. Also, the diesel oxidation catalyst 105 and the passive catalyst 110 are thermally insulated with respect to each other to prevent transfer of heat between each other.

Exhaust gas emitted from a diesel engine reacts with the passive catalyst 110. Since the passive catalyst 110 is devoid of coating of the chemically active materials, oxidation of the HC and CO into C02 and H20 is limited. The oxidation of the HC and CO leads to an exothermic reaction. Since, the oxidation of the HC and CO is limited, heat generated due to the exothermic reaction is also limited.

Further, the exhaust gas reacts with the diesel oxidation catalyst 105. The diesel oxidation catalyst 105 coated with the chemically active materials reacts with the exhaust gas to enable the oxidation of the HC and CO, present in the exhaust gas, into C02 and H20. Hence, heat generated due to the exothermic reaction increases.

The sensing element 115 determines a differential temperature value between heat generated by the diesel oxidation catalyst 105 and the heat generated by the passive catalyst 110. Further, the sensing element 115 generates a voltage level proportional to the differential temperature value.

The voltage level is transmitted to a processing means 120 for converting the voltage level into a conversion capability value. The processing means 120 may be implemented using hardware or a software. The conversion capability value can include an efficiency value. The efficiency value may represent the conversion capability of a diesel oxidation catalyst. The efficiency value, in one example, may be defined in units of percentage values. The processing means 120 may perform conversion by mapping the voltage level to a voltage versus conversion efficiency graph or a voltage versus conversion efficiency look up table.

The efficiency value may further be indicated, to the user, by using an indicating means such as LED lights and display screen. The indicating means enables the user to effortlessly determine the conversion capability while operating the vehicle.

Figure. 2 illustrates block diagram of a catalytic converter 200 for treating exhaust gas in accordance with this invention.

The catalytic converter 200 includes a diesel oxidation catalyst 205, a passive catalyst 210 and a sensing element 215. As mentioned in the above paragraphs, the passive catalyst 210 is devoid of coating with chemically active materials and the diesel oxidation catalyst 205 is coated with the chemically active materials.

The diesel oxidation catalyst 205 and the passive catalyst 210 are in electrical connection with each other through the sensing element 215.

Exhaust gas emitted by the diesel engine encounters the catalytic converter 200 that is placed in an exhaust path. Initially the exhaust gas reacts with the passive catalyst 210. Since the passive catalyst 210 is devoid of the coating, oxidation of HC and CO to form C02 and H20 is limited. As a result there is no exothermic reaction and hence, reduced heat is generated.

Further, the exhaust gas proceeds to react with the diesel oxidation catalyst 205. Due to the coating, the HC and CO is oxidized to form carbon dioxide and water. Hence, there is increased heat generated due to the exothermic reaction.

The sensing element 215 is operable to determine a differential temperature value between the heat generated by the passive catalyst 210 and the heat generated by the diesel oxidation catalyst 205. The differential temperature value is represented in the form of a voltage level. The voltage level may be represented in analog or digital form.

Further, the sensing element 215 transmits the voltage level to a processing means, for example the processing means 120. The processing means 120 may be implemented using hardware or a software.

The processing means 120 converts the voltage level to a conversion capability value. The conversion capability value may represent an efficiency value of the diesel oxidation catalyst 205. The efficiency value, in one example, may be defined in units of percentage values. The efficiency value represents the conversion capability of a diesel oxidation catalyst. In one example, if the diesel oxidation catalyst 205 has efficient conversion capability, then due to the oxidation of HC and CO, there is increased heat generated due to the exothermic reaction. However, due to absence of coating of the chemically active material on the passive catalyst 210, the oxidation of HC and CO is limited and hence there is less heat generated due to the exothermic reaction. As a result, the sensing element 215 determines an increased differential temperature value between the heat generated by the diesel oxidation catalyst 205 and the heat generated by the passive catalyst 210.

Further, the sensing element 215 represents the increased differential temperature value in the form of a voltage level proportional to the increased differential temperature value. Such voltage level is transmitted to the processing means. The processing means converts the voltage level to an efficiency value such that it indicates, to the user, that the conversion capability of the diesel oxidation catalyst 205 is efficient.
In another example, if conversion capability of the diesel oxidation catalyst 205 is reduced, then the heat generated due to the exothermic reaction is reduced. Therefore, there is reduced differential temperature value between the heat generated by the diesel oxidation catalyst 205 and the heat generated by the passive catalyst 210. Further, the sensing element 215 represents the reduced differential temperature value in the form of a voltage level that is proportional to the reduced differential temperature value. Such voltage level is transmitted to the processing means. The processing means further determines an efficiency value proportional to the voltage level. The efficiency value may be such that it indicates, to the user, about inefficient conversion capability of the diesel oxidation catalyst 205. The efficiency value may further be indicated, to the user, by using an indicating means such as an LED and a display device. The indicating means enables the user to effortlessly determine the conversion capability while operating the vehicle.

It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the invention. Many modifications in the embodiments are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.

WE CLAIM:

1 A monitoring device for monitoring conversion capability of a diesel oxidation catalyst comprising:
a passive catalyst in electrical connection with the diesel oxidation catalyst;

a sensing element to determine a differential temperature value between heat generated by the diesel oxidation catalyst and the heat generated by the passive catalyst, the differential temperature value being represented by a voltage level; and

a processing means to convert the voltage level into a conversion capability value of the diesel oxidation catalyst.

2 The monitoring device as claimed in claim 1, wherein the passive catalyst is devoid of coating of a chemically active material and the diesel oxidation catalyst is coated with chemically active material.

3 The monitoring device as claimed in claim 1, wherein the diesel oxidation catalyst and the passive catalyst are thermally insulated with respect to each other.

4 The monitoring device as claimed in claim 1 is disposed in one of an exhaust gas pathway and in a catalytic converter.

5 The monitoring device as claimed in claim 1, and further comprising:
an indicating means for indicating the efficiency value to a user.

6 A catalytic converter for treating exhaust gas, the catalytic converter comprising:

a diesel oxidation catalyst coated with a chemically active material;

a passive catalyst devoid of coating of the chemically active material; and

a sensing element to determine a differential temperature value between heat generated by the diesel oxidation catalyst and the heat generated by the passive catalyst, the differential temperature value being represented by a voltage level.

7 The catalytic converter as claimed in claim 5, wherein the sensing element is in communication with a processing means for converting the voltage level into an efficiency value, the efficiency value representing the conversion capability of the diesel oxidation catalyst.

8 A method of monitoring conversion capability of a diesel oxidation catalyst, the method comprising:
determining a differential temperature value between the diesel oxidation catalyst and the passive catalyst; and

converting the differential temperature value into a conversion capability value of a diesel oxidation catalyst.