Claims:We claim:
1. A control unit (110) to determine health of a catalyst (102) in a vehicle (100), said catalyst (102) positioned inside an exhaust conduit (124) of said vehicle (100) and a lambda sensor (104) positioned downstream of said catalyst (102), characterized in that, said control unit (110) configured to:
calculate a sensor resistance (112) of said lambda sensor (104), said sensor resistance (112) varies corresponding to heat generated due to exothermic reactions in said catalyst (102);
calculate heating requirement of said lambda sensor (104) corresponding to said sensor resistance (112), and
determine health of said catalyst (102) based on said heating requirement.

2. The control unit (110) as claimed in claim 1 further configured to,
compare said heating requirement of said catalyst (102) with a threshold value, and
determine said catalyst (102) as
degraded, if said heating requirement is higher than said threshold value, and
healthy, if said heating requirement is lower than said threshold value.

3. The control unit (110) as claimed in claim 1, wherein calculation of sensor resistance (112) is triggered during a predetermined operating zone, said predetermined operating zone is determined based on throttle position and engine speed, said predetermined operating zone ensures required mass flow of exhaust gases through said catalyst (102) in said exhaust conduit (124).

4. The control unit (110) as claimed in claim 1, wherein said calculation of sensor resistance (112) is triggered after catalyst light-off.

5. The control unit (110) as claimed in claim 1, wherein said lambda sensor (104) is positioned within predetermined distance from said catalyst (102).

6. A method for determining health of a catalyst (102) in a vehicle (100), said catalyst (102) positioned inside an exhaust conduit (124) of said vehicle (100) and a lambda sensor (104) positioned downstream of said catalyst (102), characterized by, said method comprises the steps of:
calculating a sensor resistance (112) of said lambda sensor (104), said sensor resistance (112) varies corresponding to heat generated due to exothermic reactions in said catalyst (102);
calculating heating requirement of said lambda sensor (104) corresponding to said sensor resistance (112), and
determining health of said catalyst (102) based on said heating requirement.

7. The method as claimed in claim 6, comprises
comparing said heating requirement with a threshold value, and
determining said catalyst (102) as
degraded, if said heating requirement is higher than said threshold value, and
healthy, if said heating requirement is lower than said threshold value.

8. The method as claimed in claim 6, wherein calculating said sensor resistance (112) is triggered during a predetermined operating zone, said predetermined operating zone is determined based on throttle position and engine speed, said predetermined operating zone ensures required mass flow of exhaust gases through said catalyst (102) in said exhaust conduit (124).

9. The method as claimed in claim 6, wherein said calculation of sensor resistance (112) is triggered after catalyst light-off.

10. The method as claimed in claim 6, wherein said lambda sensor (104) is positioned within predetermined distance from said catalyst (102).

, 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 invention relates to a control unit and method for determining health of a catalyst in a vehicle.

Background of the invention:
[0002] A typical catalyst monitoring logic requires two lambda sensor, a first lambda sensor placed before the catalyst and a second lambda sensor placed after the catalyst. The conventional strategy is to compare the signal of the two lambda sensors and establish a co-relation. If there a mismatch in correlation, then a degradation in the catalyst is identified. In a conventional system, two lambda sensors (L1 and L2) are used. In this case, the sensor signal of L1 is analyzed and an expected L2 signal is modeled. The L2 signal to compared with the modeled L2 signal form L1. If the catalyst is functioning as intended, then the modeled L2 is similar to actual L2. Thus, concluding that the catalyst is not degraded. But if the modeled L2 is not matching with actual L2 profile, then a status is flagged that there is potential catalyst degradation.

[0003] As known in the art, chemical reactions within the catalyst are exothermic in nature and releases heat. A lambda/oxygen sensor requires the sensor element to be heated to a certain level to start working. Also, few lambda sensors use a heater to ensure that the sensor element is heated to the right level for operation. The lambda sensor also relies on the exhaust to heat up the sensor element to the required level. Hence, if the catalyst is degraded, then lambda sensor is likely to use the heater more to maintain the sensor element hot.

[0004] A patent literature US5816231 discloses a controller for heater of air-fuel ratio sensor. An apparatus controls power supplied to a heater of an air-fuel-ratio sensor in consideration of the radiant heat from a catalytic converter. A map showing a relationship between power supplied to the heater and engine operating conditions is prepared on the assumption that radiant heat from the converter never affects the temperature of the sensor. Another map showing the same relationship is prepared on the assumption that radiant heat from the converter, which is new, affects the temperature of the sensor. A difference delta Qij=Q2ij-Qlij is calculated under the same engine operating conditions, where Q1ij is power supplied to the heater with radiant heat from the converter affecting the temperature of the sensor and Q2ij is power supplied to the heater with radiant heat from the converter not affecting the temperature of the sensor. At the same time, a deterioration index DR of the converter is calculated. The deterioration index DR is used to determine a coefficient a. The target power Qij supplied to the heater is calculated as Qij=Q2ij-alpha * (Q2ij-Qlij). Namely, the difference delta Qij is multiplied by the coefficient a, and the product is subtracted from Q2ij, to provide the target power Qij.

Brief description of the accompanying drawings:
[0005] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0006] Fig. 1 illustrates a block diagram of a control unit to determine health of a catalyst in a vehicle, according to an embodiment of the present invention;
[0007] Fig. 2 illustrates plots associated with the heating requirement, according to an embodiment of the present invention, and
[0008] Fig. 3 illustrates a method for determining health of the catalyst in the vehicle, according to the present invention.

Detailed description of the embodiments:
[0009] Fig. 1 illustrates a block diagram of a control unit to determine health of a catalyst in a vehicle, according to an embodiment of the present invention. The catalyst 102 is positioned inside an exhaust conduit 124 of the vehicle 100 and a lambda sensor 104 positioned downstream of the catalyst 102 (post catalyst 102). The control unit 110, characterized in that, configured to calculate a sensor resistance 112 of the lambda sensor 104. The sensor resistance 112 varies corresponding to heat generated due to exothermic reactions in the catalyst 102. The control unit 110 calculates heating requirement of the lambda sensor 104 corresponding to the calculated sensor resistance 112. The control unit 110 then determines health of the catalyst 102 based on the heating requirement.

[0010] According to the present invention, the control unit 110 configured to compare the heating requirement of the catalyst 102 with a threshold value, and determine the health of the catalyst 102 as degraded if the heating requirement is greater than a threshold value. The control unit 110 determines the health of the catalyst 102 as healthy if the heating requirement is lesser than the threshold value.

[0011] In accordance to an embodiment of the present invention, the threshold value is also selected from a range or band of values based on operating condition of the engine. The threshold value may also be referred to as a variable threshold value or a dynamic threshold value. The threshold value signifies that the value to be used for comparing is not a static or just one value, but changes based on operating conditions of the engine to ensure that health of the catalyst 102 is detected correctly or not mis-detected. For example, in a first scenario, consider engine speed to be 6000 rpm, throttle opening is 80% and the catalyst is good. The exhaust mass flow rate is high, and the heat released by the catalyst is also high causing less heating requirement for the lambda sensor 104. The heating requirement of the lambda sensor 104 is say 15%. The control unit 110 detects the health of the catalyst 102 as healthy. Similarly, in a second scenario, consider for the same good catalyst 102, the operating conditions are engine speed as 6000rpm, throttle opening is 30%. Due to less throttle opening, the air intake is reduced and therefore the exhaust mass flow rate is reduced causing corresponding decrease in heat released by the catalyst 102. The heating requirement of the lambda sensor 104 increase say 40%. However, increase of heating requirement from 15% to 40% does not signify that the catalyst 102 is degraded, but it is just because of less exothermic reactions in the catalyst 102. Hence, for the second case, the threshold value used for comparing is different than the first case. In view of the both the cases, it is evident is a single threshold value is not suitable to accurately detect the health of the catalyst 102 and hence a range of values is considered based on the operating condition. The operating condition is based on at least one parameter selected from the throttle opening, engine speed, exhaust mass flow, and the like, or combination of two or more parameters.

[0012] In accordance to an embodiment of the present invention, the calculation of sensor resistance 112 (or monitoring of the lambda sensor 104) is triggered during a predetermined operating zone. The predetermined operating zone is decided/determined based on throttle position and engine speed. The predetermined operating zone ensures required mass flow of exhaust gases through the catalyst 102 in the exhaust conduit 124. Alternatively, or in addition, the calculation of sensor resistance 112 (or monitoring of the lambda sensor 104) is triggered after catalyst light-off. The lambda sensor 104 comprises a closed loop heater resistance 106. The triggering of calculation of sensor resistance 112 is further made robust or improved by taking inputs of the intake air temperature, engine temperature and ambient pressure.

[0013] The reason for considering the heating requirement as indication to the health of the catalyst 102 is explained below. Typically, in the catalyst 102, following chemical reactions are seen.
oxidation:
CO + O2  CO2
HC + O2 CO2 + H2O
reduction:
NOx + CO  CO2 + N2
HC + NOx  N2 + H2O + CO2

[0014] Firstly, the above reactions are exothermic in nature, which means that if there are stable reactions happening in the catalyst 102, then there are greater chances that the exhaust gases that are coming out of the catalyst 102 are having additional heat than the inlet gases. This is a sign of a healthy catalyst 102.

[0015] Secondly, in the healthy catalyst 102, the gases at the exit of the catalyst 102 are hotter than at an inlet of the catalyst 102. At operating zones/regions of high mass flow, the post-catalytic temperatures are greater than the pre-catalytic temperatures. The increase of temperature is due to the fact that the catalyst 102 is functioning as intended generating heat via the exothermic reactions.

[0016] Thirdly, in the lambda sensors 104 which have a heater operated in closed loop manner, the resistance of the sensor (or sensor resistance 112) is measured to understand the temperature of the sensor element. The sensor resistance 112 is measured to ensure that the lambda sensors 104 are working at its optimal operational temperature.

[0017] According to an embodiment of the present invention, the control unit 110 contains computing devices/units comprising components such as memory element (not shown) such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC), Digital-to-Analog Convertor (DAC), clocks, timers, counters and a processor (capable of implementing machine learning) connected with the each other and to other components through communication bus channels. The components mentioned are just for understanding and the control unit 110 may have more or less components as per requirement. The memory element is pre-stored with logics or instructions or programs or applications or threshold values/limits/rate which is accessed by the processor as per the defined routines. The internal components of the control unit 110 are not explained for being state of the art, and the same must not be understood in a limiting manner. The control unit 110 is capable to communicate through wired and wireless means such as but not limited to Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, Universal Serial Bus (USB) cable, micro-USB, and the like. In accordance to an embodiment, the control unit 110 is at least one selected from a group comprising an Engine Control Unit (ECU) and a Transmission Control Unit (TCU) or other control unit 110 interfaced with the ECU.

[0018] In the Fig. 1, the control unit 110 is shown connected to the lambda sensor 104. A block of the lambda sensor 104 is shown and the same must not be understood in limiting manner. The lambda sensor 104 comprises the heater resistance 106, and a Nernst cell 108 (the sensor element). The sensor resistance 112 is shown inside the Nernst cell 108. The heater resistance 106 and the sensor resistance 112 are connected to the control unit 110 through a connector 122. In the control unit 110, a first switch 120 is switched ON/OFF to trigger flow of current through the heater resistance 106 to control heating. A suitable voltage supply 126 for the same is provided. The first switch 120 forms the part of heating circuit. A second switch 114 is switched ON/OFF by the control unit 110 to measure the sensor resistance 112. The second switch 114 is part of the resistance measuring circuit. The first switch 120 and the second switch 114 are semiconductor based switches such as MOSFETs, FETs but not limited to the same. Other or equivalent types switches are usable without departing from the scope of the present invention A pumping circuit 116 is shown which supplies reference current in the circuit as known in the art. It is to be noted that, the pumping circuit 116 is shown and mentioned for completeness and is not necessary for the working of the present invention. A filter circuit 118 is a Resistance-Capacitance (RC) circuit to remove ripples or noise. The output of filter circuit 118 is given to ADC 128 for reading the value of the lambda sensor 104.

[0019] In accordance to an embodiment of the present invention, the determination of the health of the catalyst 102 is made more robust by checking certain conditions. In a first condition, the control unit 110 is configured to monitor catalyst 102 when there is sufficient mass flow of exhaust gases through the catalyst 102. This is to ensure that the catalyst 102 has right environment to release large amount of heat from the catalyst reactions, thus avoiding misdetections. Alternatively, or in addition, in a second condition, the monitoring of the catalyst 102 is done post the catalyst light-off. This is to ensure the that the sufficient time is elapsed such that the catalyst 102 is hot and up to operational temperatures. Still further and optionally, in a third condition, the control unit 110 is configured to ensure that the pre-catalytic lambda is operational at lambda=1 either via using a separate lambda sensor 104 before the catalyst 102 or via other means such as accurate pre-control or modelling. This ensures that oxidation and reductions reactions are happening in the catalyst 102 in the desired catalytic conversion window.

[0020] In accordance to an embodiment of the present invention, the lambda sensor 104 is positioned within a predetermined distance from the catalyst 102. In an embodiment, the lambda sensor 104 is positioned within or at five times the diameter of the catalyst 102. In other words, the lambda sensor 104 is within five times the diameter of the brick of the catalyst 102. The positioning of the lambda sensor 104 aids in preventing influence of cooling effects from external factors. Furthermore, a distance more than five times the diameter of the catalyst 102 is possible based on the construction or design of the exhaust conduit or to meet other requirements.

[0021] Fig. 2 illustrates plots associated with the heating requirement, according to an embodiment of the present invention. A first plot 200 shows a relation between the heater resistance 106 and temperature. The temperature in degree Celsius is represented in Y-axis 204, and the resistance in ohms is represented in X-axis 202. Here, a typical inverse relation of temperature is shown. In case there exists an alternate relationship between the sensor resistance 112 and exhaust temperature, the control unit 110 is still applicable. As the temperature decreases the resistance increases and vice-versa. A set of three heating plots, a first heating plot 206, a second heating plot 208 and a third heating plot 210 are shown. Each of the three plots describe heating duty cycle in percentage versus time in suitable units. The first heating plot 206 denotes 25% duty cycle. The second heating plot denotes 50% duty cycle. The third heating plot 210 denotes 75% duty cycle.

[0022] According to the present invention, a working of the control unit 110 is envisaged and with reference to the three heating plots. If the observed sensor resistance 112 is low, then it implies that temperature of the sensor element is high and thus require reduced heating through the heater resistance 106, i.e. with a heater duty cycle of 25%, as shown in first heating plot 206. If the sensor resistance 112 of the lambda sensor 104 is a little higher, then the heating requirement of the sensor element is increased to higher value such as with a heater duty cycle of 50%. In case a very high sensor resistance 112 is detected, then the heating requirement increases to a high value of 75% of heater duty cycle or higher. The heating requirement is modulated to ensure that the sensor resistance 112 and in-turn the sensor element temperature is maintained at the desired value. Thus, a degraded catalyst 102 releases less heat into post catalytic exhaust gases. The control unit 110 increases the duty cycle of the heating to maintain the lambda sensor 104 at the desired temperature. The increases heating requirement is used by the control unit 110 to determine that the catalyst 102 has aged and degraded.

[0023] In accordance to an embodiment of the present invention, the vehicle 100 is selected from a two-wheeler such as motorcycle, a three-wheeler such as autorickshaws, a four-wheeler such as car, a multi-wheeler such as bus, and other types of vehicle 100 which uses a lambda sensor 104 after the catalyst 102. The present invention is also implementable in existing vehicles 100 with two lambda sensors 104, by just using the post-catalytic lambda sensor 104. In another scenario, if the pre-catalytic lambda sensor 104 is malfunctioned, then by just the post-catalytic lambda sensor 104.

[0024] Fig. 3 illustrates a method for determining health of the catalyst in the vehicle, according to the present invention. The catalyst 102 positioned inside the exhaust conduit 124 of the vehicle 100 and the lambda sensor 104 positioned downstream of the catalyst 102. The method comprises plurality of steps, of which, a step 302 comprises, calculating the sensor resistance 112 of the lambda sensor 104. The sensor resistance 112 varies corresponding to heat generated due to exothermic reactions in the catalyst 102. A step 304 comprises calculating heating requirement of the lambda sensor 104 corresponding to the sensor resistance 112. A step 306 comprises determining health of the catalyst 102 based on the heating requirement.

[0025] The method further comprises comparing the heating requirement with the threshold value, and determining the catalyst 102 as degraded, if the heating requirement is higher than the threshold value, and healthy, if the heating requirement is lower than the threshold value.

[0026] According to the present invention, the method implements some conditions for improving the robustness of determining the health of the catalyst 102. In the first condition, calculating the sensor resistance 112 is triggered during a predetermined operating zone. The predetermined operating zone is determined based on throttle position and engine speed. The predetermined operating zone ensures required mass flow of exhaust gases through the catalyst 102 in the exhaust conduit 124. In the second condition, the calculation of sensor resistance 112 is triggered after catalyst light-off. The two conditions are optional and usable together or independently. The third condition comprises ensuring pre-catalytic lambda is operational at lambda=1 either via using a lambda sensor 104 before the catalyst 102 or via other means such as accurate pre-control or modelling. This ensures that oxidation and reductions reactions are happening in the catalyst 102 in the desired catalytic conversion window. If implemented, the conditions are executed before the step 302.

[0027] According to the present invention, a calibration process of the control unit 110 and the method is provided. The calibration process explains the steps taken to setup the control unit 110. At first, the operating zones where there is adequate mass flow of exhaust through the catalyst 102 is defined. The catalyst 102 is monitored in these operating zones. Then, with a new and fully functioning catalyst 102, the range of heating requirement values are observed and stored in the memory element. In the next step, the new catalyst 102 is replaced with a degraded catalyst 102 and the typical range of heating requirement values are observed from the heater resistance 106 and stored in the memory element. Now, in real time if the heating requirement at the respective exhaust mass flow zones cross the acceptable levels of heating requirement, for certain number of counts, a signal that the catalyst 102 is degraded is flagged in the control unit 110. As described above, the threshold values for determining health of the catalyst 102 are different for each of the operating points.

[0028] In accordance to an embodiment of the present invention, the lambda sensor 104 is positioned within a predetermined distance from the catalyst 102. Specially, the lambda sensor 104 is positioned within five times the diameter of the catalyst 102. In other words, the lambda sensor 104 is within five times the diameter of the brick of the catalyst 102. The positioning of the lambda sensor 104 aids in preventing influence of cooling effects from external factors.

[0029] According to the present invention, a strategy to determine degradation of the catalyst 102 based on heating requirement of post catalyst lambda sensor 104 is provided. In the present invention, a need for the pre-cat lambda sensor 104 is eliminated, as only a post cat lambda sensor 104 is used to check how much heating is needed to heat up the sensor element. The heating requirement value changes with respect to the degradation of the catalyst 102. Thus, the present invention is not dependent on the pre-cat lambda sensor 104. An example of the catalyst 102 is a three-way catalyst 102 and not limited to the same. The present invention is applicable to other types of catalyst 102 as well.

[0030] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.