METHOD FOR OPERATING A CATALYST ARRANGEMENT OF AN INTERNAL COMBUSTION ENGINE AND CATALYST ARRANGEMENT

Abstract

The present invention relates to a method for operating a catalyst arrangement of an internal combustion engine and a catalyst arrangement. The catalyst arrangement includes an exhaust gas sensor having a sensor element and a sensor heating device heating the sensor element, and a catalyst having a catalyst heating device heating the catalyst. The method comprises determining a temperature of the catalyst heating device, activating the catalyst heating device for heating the catalyst, when the determined temperature of the catalyst is below a predetermined catalyst operating temperature threshold, and activating the sensor heating device for heating the sensor element, when the temperature of the catalyst exceeds the predetermined catalyst operating temperature threshold.

Claims

1-10. (canceled)

11. A method for operating a catalyst arrangement of an internal combustion engine comprising: determining a temperature of a catalyst heating device; activating the catalyst heating device for heating the catalyst above a predetermined catalyst operating temperature threshold, when the determined temperature of the catalyst is below the predetermined catalyst operating temperature threshold; and activating a sensor heating device for heating a sensor element of at least one exhaust gas sensor above a predetermined sensor operating temperature threshold, when the temperature of the catalyst exceeds the predetermined catalyst operating temperature threshold, wherein the sensor operating temperature threshold is greater than the catalyst operating temperature threshold.

12. The method of claim 11, wherein the determining the temperature of the catalyst further comprises: determining that the sensor heating device is deactivated; determining an electric resistance of a temperature-dependent resistor of the sensor heating device; and determining the temperature of the catalyst based on the determined electric resistance of the sensor heating device.

13. The method of claim 11, further comprising determining that exhaust gas flowing through the catalyst arrangement is substantially free of moisture, when the determined catalyst temperature is above the catalyst operating temperature threshold.

14. The method of claim 11, wherein the catalyst operating temperature threshold defines a light-off temperature of the catalyst.

15. The method of claim 11, wherein the catalyst operating temperature threshold is in a range from 150 C. to 500 C.

16. The method of claim 11, wherein the sensor temperature threshold is in a range from 700 C. to about 1,000 C.

17. A catalyst arrangement for an internal combustion engine, the catalyst arrangement comprising: a catalyst for treating exhaust gas of the internal combustion engine; a catalyst heating device to heat the catalyst above a predetermined catalyst operating temperature threshold; at least one exhaust gas sensor mounted to the catalyst and having a sensor element which at least partially protrudes into the catalyst and a sensor heating device to heat the sensor element above a predetermined sensor operating temperature threshold, the sensor operating temperature threshold being greater than the catalyst operating temperature threshold; and a control unit connected to the catalyst heating device and the at least one exhaust gas sensor to activate the sensor heating device above the predetermined sensor operating temperature threshold when the temperature of the catalyst exceeds the predetermined catalyst operating temperature threshold.

18. The catalyst arrangement of claim 17, wherein the sensor device is located downstream of the catalyst heating device.

19. The catalyst arrangement of claim 17, wherein the catalyst heating device is an electric heating device.

20. The catalyst arrangement of claim 17, wherein the at least one exhaust gas sensor is one of: a NOx-sensor, an air-fuel ratio sensor, an oxygen sensor, an Ammonia sensor, and a particulate matter sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features and aspects of the present invention will become apparent to the person skilled in the art by studying and executing the teachings of the present disclosure and by consideration of the appended drawings, in which:

[0025] FIG. 1 shows a schematic illustration of an exemplary catalyst arrangement of the present invention;

[0026] FIG. 2 shows a diagram illustrating several temporal progresses of temperatures of the catalyst arrangement of FIG. 1 and of the prior art; and

[0027] FIG. 3 illustrates a flow chart of a method for operating the catalyst arrangement of FIG. 1.

DETAILED DESCRIPTION

[0028] The embodiments described in the following with respect to the drawings are preferred embodiments of the invention. However, in the embodiments described, the components of the embodiments each represent individual features of the invention which are to be considered independently of each other and which each develop the invention also independently of each other and thereby are also to be regarded as a component of the invention in individual manner or in another than the shown combination. Furthermore, the described embodiments may also be supplemented by further features of the invention already described.

[0029] FIG. 1 shows a schematic illustration of an exemplary catalyst arrangement 100 according to the present invention. The catalyst arrangement 100 of FIG. 1 includes a catalyst 110 (in FIG. 1 shown in dashed lines) disposed in an exhaust gas system 10 of an internal combustion engine (not shown). Exhaust gas of the internal combustion engine flows through the exhaust gas system. 10 in direction of the arrows of FIG. 1 and, hence, through the catalyst 110. The catalyst 110 may be any suitable catalyst to treat the exhaust gas of the internal combustion engine, such as, for example, a three-way catalyst, a selective reduction catalyst, a NOx storage converter or an oxidation catalyst.

[0030] The catalyst arrangement 100 further includes a catalyst heating device 120 configured to heat the catalyst 110. The catalyst heating device 120 is an electrical heating device and, for instance, is provided as a resistance heater for heating the catalyst 110 into its catalyst operating temperature range. The catalyst operating temperature range may range from about 150 C. to about 500 C.

[0031] The catalyst arrangement 100 of FIG. 1 further includes an exhaust gas sensor 130 mounted to the catalyst 110 and having a sensor element 132 configured to at least partially protrude into the catalyst 110. The exhaust gas sensor 130 further includes a sensor heating device 134 configured to heat the sensor element 132 above a predetermined sensor operating temperature threshold. The sensor heating device 134 is, for example, integrated or embedded into the sensor element 132 made of, for instance, a substrate. Specifically, the exhaust gas sensor 130 is configured to detect a predetermined parameter of the exhaust gas flowing through the catalyst 110. For instance, the exhaust gas sensor 130 is a NOx sensor, an air-fuel ratio sensor, an oxygen sensor or a particulate matter sensor.

[0032] The catalyst arrangement 100 of FIG. 1 further includes a control unit 140 connected to both the catalyst heating device 120 and the exhaust gas sensor 130. Particularly, the control unit 140 is configured to receive and provide signals to the catalyst heating device 120 and the exhaust gas sensor 130 for at least partially controlling both devices. For example, the control unit 140 is connected to the catalyst heating device 120 and the exhaust gas sensor 130 via a CAN-bus. Although not explicitly shown in FIG. 1, a catalyst heating device controller may be interconnected between the control unit 140 and the catalyst heating device 120 and a sensor control unit may be interconnected between the control unit 140 the exhaust gas sensor 130.

[0033] As can be further seen in FIG. 1, the exhaust gas sensor 130 is located at a most downstream location of the catalyst 110, such that the signals of the exhaust gas sensor 130 are as significant as possible. However, in alternative embodiments, the exhaust gas sensor 130 is provided at any suitable location within the catalyst 110.

[0034] Now referring to FIG. 2, a diagram illustrating several temporal progresses of temperatures of the catalyst arrangement of FIG. 1 and the prior art are shown. The line T.sub.in indicates the temporal progress of the exhaust gas temperature at an inlet of the catalyst 110. The line T.sub.s indicates the temporal progress of the exhaust gas temperature at a position of the exhaust gas sensor 130 within the catalyst 110 (see FIG. 1.). The line T.sub.h indicates the temporal progress of the exhaust gas temperature at a position of the catalyst heating device 120 (see FIG. 1).

[0035] When the internal combustion engine is cold started at t.sub.0, the exhaust gas temperature T.sub.in at the inlet of the catalyst 110 starts at an ambient temperature T.sub.a and, then, rises continuously as the engine temperature rises. At the same time t.sub.0, the catalyst heating device 120 is activated for heating the catalyst 110. Thus, line T.sub.h also starting at ambient temperature T.sub.a is lying above line T.sub.in. Since the exhaust gas sensor 130 may be at least partially pre-heated by the exhaust gas also heated by the catalyst heating device 120, the line T.sub.s also starting at ambient temperature T.sub.a is lying above line T.sub.in, but below line T.sub.h.

[0036] As can be seen and derived from FIG. 2, the catalyst heating device 120 is activated at t.sub.0 directly after engine start for heating the catalyst 110 into its catalyst operating temperature range as quick as possible. Therefore, the line T.sub.h of the exhaust gas temperature at the catalyst heating device 120 is rising with a great inclination and, then, after reaching a predetermined catalyst operating temperature threshold T.sub.cot, the inclination of line T.sub.h is smaller. The temperature T.sub.dp of FIG. 2 refers to the so-called dew point temperature where it can be assumed that the exhaust gas flowing through the catalyst 110 is substantially free of any moisture.

[0037] The exhaust gas sensor 130, in particular the sensor element 132, may be heated by exhaust gas preheated by the catalyst heating device 120 disposed upstream of the exhaust gas sensor 130. Therefore, the temporal progress of the exhaust gas temperature T.sub.s at the sensor element 132 substantially follows the temporal progress of the exhaust gas temperature T.sub.h at the catalyst heating device 120.

[0038] In prior art systems where the exhaust gas sensor is not integrated into the catalyst 110 (see line 200 in FIG. 2), the sensor heating device 134 of the exhaust gas sensor 130 may be activated only when the exhaust gas temperature T.sub.in at the inlet of the catalyst reaches the dew point T.sub.dp at t2. At this activation time t2, there still might exist some risk of a damage to the sensor element 132 due to moisture within the exhaust gas.

[0039] According to the present invention (see line 210 in FIG. 2), the sensor heating device 134 of the exhaust gas sensor 130 may be activated at t1, i.e. when the exhaust gas temperature T.sub.s at the exhaust gas sensor 130 exceeds the dew point temperature T.sub.dp. As the exhaust gas temperature T.sub.in at the inlet of the catalyst 110 is not influenced by the catalyst heating device 120, t1 is much earlier than t1. Therefore, the exhaust gas sensor 130 may reach its sensor operating temperature earlier than in prior art system.

[0040] In conclusion, as the exhaust gas sensor 130 is integrated into the catalyst 110 heated by the catalyst heating device 120, the exhaust gas sensor 130 is operated in a heated environment. This may lead to activation of the sensor heating device 134 as soon as the exhaust gas temperature T.sub.s at the exhaust gas sensor 130 exceeds the dew point temperature T.sub.dp at t1. As the exhaust gas has already passed the catalyst heating device 120 when reaching the exhaust gas sensor 130, the exhaust gas temperature Ts at the exhaust gas sensor 130 is higher than in prior art systems. Therefore, t1 is much earlier than t2.

[0041] Further, the exhaust gas pre-heated by the catalyst heating device 120 my at least partially pre-heat the sensor element 132, such that, after reaching the dew point temperature t.sub.dp, the temperature difference for heating the sensor element 132 with the sensor heating device 134 above the sensor operating temperature threshold may be smaller, as the starting temperature of the sensor element 132 due to its pre-heating by the exhaust gas is higher. This may lead to less electrical energy consumption of the exhaust gas sensor 130 and to a shorter time of the sensor element 132 to reach its sensor operating temperature.

[0042] In addition, as the risk for damage to the sensor element 132 may be significantly reduced, the constraint for a sensor mounting angle is also significantly reduced as substantially no water will be present in the exhaust gas at the time of activating the sensor heating device 134. Specifically, in prior art devices, there is a risk of sensor element crack due to the presence of water or moisture in the exhaust line until reaching the dew point. Thus, it is required to mount the exhaust gas sensor 130 into the exhaust line 10 with a predetermined mounting angle for preventing the potential water or moisture to directly hit the sensor element 132 of the exhaust gas sensor 130. However, in the present invention, the sensor element 132 is mounted at a position of the heated catalyst arrangement 100 where the environment (i.e. the exhaust gas) may not include any water or moisture, such that the risk of a sensor element crack is reduced or, preferably, eliminated.

[0043] Referring now to FIG. 3, an exemplary flow chart of a method for operating the catalyst arrangement 100 of FIG. 1 is shown.

[0044] The method starts at step 300 and proceeds to step 302 where it is determined whether the internal combustion engine has been started. At step 302, if it is determined that the internal combustion engine has not been started, yet, the method maintains at step 302.

[0045] At step 302, if it is determined that the internal combustion engine has been started, the method proceeds to step 304 where the catalyst heating device 120 is activated. At the same time, at step 304, the sensor element temperature is determined. At this time, the sensor heating device 134 is still deactivated (OFF state). Determination of the sensor element temperature may be done by associating a temperature-dependent resistance of an electrical resistor of the sensor heating device 134 with a corresponding sensor element temperature.

[0046] Further, at step 304, it may be assumed that the sensor element temperature substantially corresponds to the exhaust gas temperature T.sub.s at the exhaust gas sensor 130. In addition, taking lines T.sub.s and T.sub.h of FIG. 2 into consideration, the exhaust gas temperature T.sub.h at the catalyst heating device 120 may be determined based on the sensor element temperature, as it can be assumed that T.sub.s and T.sub.h are substantially the same. The main process at step 304 is determining a temperature of the catalyst 110 which, in turn, substantially corresponds to the exhaust gas temperature T.sub.h at the catalyst heating device 120. Further, it may be considered to conduct a system calibration based on the above temperatures.

[0047] Then, at step 306, it is determined whether the catalyst temperature (corresponding to the exhaust gas temperature T.sub.h at the catalyst heating device 120) exceeds the dew point temperature T.sub.dp. If not, the method proceeds to step 307 where the catalyst heating device 120 maintains in the activated state for further heating the catalyst 110. Subsequently, the method returns to step 304 and, then, proceeds again to step 306.

[0048] At step 306, if it is determined that the catalyst temperature exceeds the dew point temperature T.sub.dp, the method proceeds to step 308 where the sensor heating device 134 is activated for heating the sensor element 134 above its sensor operating temperature threshold. Subsequently, the method ends at step 310.

[0049] In a situation in which the sensor element 132 is deactivated, i.e. the sensor element 132 is not heated by the sensor heating device 132, the temperature T.sub.s may be determined based on the resistance value of the sensor heating device 134. Said temperature T.sub.s may be used for a feedback control of the catalyst heating device 120. Thus, such feedback control may enable an efficient energy consumption as well as a safe heating management.