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 an assembly, a controller, and a method for an oxygen sensor in an exhaust conduit.

Background of the invention:
[0002] The present solution for emission norms dictates the requirement for two oxygen sensors, placed upstream and downstream of the catalyst respectively. The upstream sensor is mainly used for closed loop lambda control and the downstream sensor is used for catalyst monitoring and lambda corrections. The new emission legislation, such as Bharat Stage 6, On-Board Diagnostics 2 (BS6 OBD2) Engine Management System (EMS), requires the use of two switching type oxygen sensors in the exhaust system. The upstream oxygen sensor placed before the catalyst is utilized primarily for closed loop lambda control such that three-way catalyst converter is used optimally for emission conversion. The downstream oxygen sensor placed after the catalyst is utilized for catalyst monitoring and further corrections to upstream lambda control. Due to the benefits of split and tandem catalyst system and cost efficient catalyst design, Original Equipment Manufacturers (OEMs) prefer split catalyst setup in their applications with the primary catalyst placed very close to the exhaust port.

[0003] According to a prior art KR20110116581 discloses a lambda controlling system and method thereof. A fuel-air ratio control system and method are provided to reduce the manufacturing cost of a vehicle because a single lambda sensor is installed only on the rear end of a catalyst converter and air-fuel ratio control and diagnosis of catalyst purification efficiency are simultaneously implemented by the lambda sensor. A fuel-air ratio control system comprises a sensing part, a fuel correction quantity calculation part, a catalyst diagnosis part, and a fuel correction part. The sensing part is installed on the backend of a catalytic converter. The sensing part measures the oxygen content of exhaust gas. The fuel correction quantity calculation part measures the transition duration of a sensing signal outputted from the sensing part and computes a fuel correction value based on the transition duration. The catalyst diagnosis part diagnoses a catalyst based on the measured transition duration. The fuel correction part controls the supply of fuel based on the fuel correction value.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0005] Fig. 1 illustrates an assembly of oxygen sensor in an exhaust conduit of a vehicle, according to an embodiment of the present invention;
[0006] Fig. 2 illustrates plots of signals from an oxygen sensor with different positioning in the exhaust conduit, according to an embodiment of the present invention, and
[0007] Fig. 3 illustrates a method for processing signal from the oxygen sensor in the exhaust conduit of the vehicle, according to the present invention.

Detailed description of the embodiments:
[0008] Fig. 1 illustrates an assembly of oxygen sensor in an exhaust conduit of a vehicle, according to an embodiment of the present invention. The exhaust conduit 104 comprises a primary catalyst 106 and a secondary catalyst 108, arranged in sequence and separated from each other in the exhaust conduit 104, characterized in that, the assembly comprises only one oxygen sensor 110 positioned in at least one of two locations selected from a group comprising, a first location which is inside the primary catalyst 106, and a second location which is in a gap between the primary catalyst 106 and the secondary catalyst 108. In the Fig. 1 second location is shown. A signal from the only one oxygen sensor 110 is used for control of at least one function selected from a group comprising a closed loop lambda control and a catalyst monitoring. When positioned inside the primary catalyst 106, the oxygen sensor 110 is located at a rear end of the primary catalyst 106. The primary catalyst 106 and the secondary catalyst 108 are shown for illustration purposes only and may not be to scale or actual image. The same must not be understood in limiting sense.

[0009] According to an embodiment of the present invention, the primary catalyst 106 and the secondary catalyst 108 are part of any one of a split catalyst unit/system and a tandem catalyst unit/system. The gap in split catalyst unit is more than a tandem catalyst unit.

[0010] The Fig. 1 also illustrates a block diagram of a controller 112 for the oxygen sensor 110 in the exhaust conduit 104 of the vehicle 100. The exhaust conduit 104 comprises the primary catalyst 106 and the secondary catalyst 108. The controller 112 configured/adapted to, receive signal detected by the oxygen sensor 110, characterized in that, the controller 112 further configured to compare the detected signal with at least one calibrated threshold value 206, the at least one calibrated threshold value 206 is stored in a memory element, corresponding to positioning of the oxygen sensor 110 in at least one of two locations selected from the group comprising, the first location which is inside the primary catalyst 106, and a second location which is in the gap between the primary catalyst 106 and the secondary catalyst 108. The controller 112 further performs at least one selected from the group comprising the closed loop lambda control and catalyst monitoring using signals from the only one oxygen sensor 110.

[0011] In accordance to an embodiment of the present invention, the controller 112 is provided with necessary signal detection, acquisition, and processing circuits. The controller 112 is the control unit which comprises input/output interfaces having pins or ports, the memory element such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one processor (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold/ values/ranges/amplitude, predefined/predetermined criteria, correction factor based maps/table which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 112 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 112 may also comprise communication units to communicate with external computer or server/cloud computer through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, and the like. The controller 112 is implementable in the form of System-in-Package (SiP) or System-on-Chip (SOC) or any other known types. Examples of controller 112 comprises but not limited to, microcontroller, microprocessor, microcomputer, etc.

[0012] According to an embodiment of the present invention, at least one threshold value 206 is provided for at least one operating condition of an engine 102 of the vehicle 100. The at least one threshold value 206 is calibrated and pre-stored in the memory element. The at least one threshold value 206 is a voltage at which the switching from rich phase to lean phase and lean phase to rich phase is done to ensure the ideal lambda is maintained, lambda=1.

[0013] Fig. 2 illustrates plots of signals from an oxygen sensor with different positioning in the exhaust conduit, according to an embodiment of the present invention. A first graph 200 is shown where X-axis is time and Y-axis is voltage in respective suitable units. The first graph 200 illustrates a plot for the oxygen sensor 110 when positioned upstream of the primary catalyst 106 shown by the first curve 202 and when positioned downstream of the primary catalyst 106 shown by the second curve 204. Further, each of the first curve 202 and the second curve 204 is provided with respective reference line indicating the threshold value.

[0014] When positioned upstream of the primary catalyst 106, the signal detected by the oxygen sensor 110 contains high fluctuations is sensor amplitude, the reason being the operation of closed loop control of the lambda. Also when the oxygen sensor 110 is placed after the primary catalyst 106, the sensor signal softens/amplitude reduces when compared to upstream oxygen sensor 110 due to the utilization of O2/redox reactions occurring in the Three-Way Catalyst (TWC). The controller 112 considers 0.5 volts (as an example) as conventional threshold value 208. Similarly, when positioned downstream of the primary catalyst 106, the signal detected by the oxygen sensor 110 is of lower amplitude in comparison to the first curve 202. The reason for the low amplitude is less oxygen after being treated with the primary catalyst 106. The controller 112 considers 0.75 volts (as an example) as the threshold value 206 for switching. There is a shift in threshold value between the first curve 202 and the second curve 204 because of redox reactions/oxygen utilization during redox reactions from the catalyst, and then is calibrated and used in the present invention for closed loop lambda control and catalyst monitoring.

[0015] A second graph 210 is also shown for illustrating working of closed loop lambda control of the engine 102. Consider second curve 204 is taken for explanation. In the second graph 210, the second curve 204 in first graph 200 is used where Y-axis is in voltage in suitable units. A third curve/plot 212 is shown in the second graph 210 for fuel control in respective unit. The X-axis for both the curves/plot is time in suitable units. For every instance of the second curve 204 crossing the threshold value 206, either by going from low value to high value or higher value to the lower value, the controller 112 controls the fuel injection accordingly. When the value of the second curve 204 goes above the threshold value 206 (i.e. rich phase), the controller 112 reduces the fuel injection as shown with corresponding value in the third curve 212. Similarly, when the value of the second curve 204 goes below the threshold value 206, the controller 112 increases the fuel injection as shown in corresponding part of the third curve 212 within the same time period.

[0016] According to an embodiment of the present invention, the controller 112 is configured to perform closed loop lambda control using the only one oxygen sensor 110. The assembly requires an exhaust system with split catalyst setup where the oxygen sensor 110 is placed between the primary catalyst 106 and the secondary catalyst 108. The signal from the downstream oxygen sensor 110 when placed after the primary catalyst 106 in single cylinder engine 102 has lambda pulsations. This pulsation is primarily from oxygen storage and removal in the three-way catalyst. This is used an input to the two-point lambda control to optimally use the primary catalyst 106 in the emission conversion window. Since the downstream lambda is mostly in the rich state due to Oxygen Storage Capacity (OSC) of the primary catalyst 106, the lambda control logic in the controller 112 has to switch between lean and rich mixture using a rich lambda control point (λ<1). The increased lambda control dead time due to the sensor position and catalyst is mitigated by appropriate primary catalyst 106 sizing and its position.

[0017] The controller 112 provides a closed loop feedback to the fuel control algorithm based on the signal from the downstream oxygen sensor 110, as shown by the third curve 212. The fuel control algorithm determines the fuel quantity to be injected for each engine cycle based on the engine operating point and the calibrations. An oscillation in this fuel quantity in the form of a Proportional jump and an Integral ramp is added to the fuel quantity signal by the controller 112. The aforementioned corrections are determined by the controller 112 based on the signal from the oxygen sensor 110, operating point as well as the calibrations made. Before the oxygen sensor 110 readiness is achieved, the fuel control is based on a calibrated open loop map. Switching points or threshold values (voltage) are identified on the signal from the oxygen sensor 110, calibrated for the range of operating points of the vehicle 100. Either there is only one threshold value for the vehicle 100 or two or more threshold values for two or more operating regions of the engine 102.

[0018] At every instance of signal detected by the oxygen sensor 110 crossing the at least one threshold value 206 during transition from high to low and low to high, the fuel correction towards lean side and rich side, respectively is performed by the controller 112. This form of a closed loop fuel correction maintains the signal from the oxygen sensor 110 in a sinusoidal waveform.

[0019] According to an embodiment of the present invention, the controller 112 is configured to perform catalyst monitoring. The OSC of the three-way catalyst is a measure of the catalyst’s ability to reduce the rich lean oscillations in the exhaust gas composition by regulating the oxygen partial pressure by means of the oxygen storage material present in the catalyst (primary catalyst 106). Thus, the high OSC of a fresh catalyst contributes to efficient emission conversion by maintaining the oxygen availability at the stoichiometric levels required for the redox reactions. With aging of the catalyst, its OSC reduces and hence the conversion efficiency decreases.

[0020] The controller 112 measures the amplitude of the signal detected by the oxygen sensor 110 and compares against threshold amplitude. The primary catalyst 106 is considered to be aged based on the comparison. The threshold amplitude is obtained by considering an aged primary catalyst 106 and then measuring from the oxygen sensor 110 during testing phase. In other words, a model based on the borderline catalyst (for example, which is approx. 95+% aged, considering the durability limit of 1,60,000kms) is considered as reference. The amplitude of fluctuation in the downstream oxygen sensor 110 is compared with respect to the amplitude of model from borderline catalyst, and reported that the primary catalyst 106 is aged or not.

[0021] According to an embodiment of the present invention, the vehicle 100 is a two-wheeler vehicle 100 such as scooter, motorcycle and the like. Alternatively, the present invention is applicable for those vehicle 100 which makes use of small size catalysts in split setup or tandem setup. Thus, the present invention is applicable for other types of vehicles 100 as well such as cars, buses, watersports vehicles 100 and the like.

[0022] According to the present invention, a working of the controller 112 as per the assembly is envisaged. Consider a motorcycle is fit with a split catalyst unit with one oxygen sensor 110 in between the primary catalyst 106 and the secondary catalyst 108. The controller 112 is calibrated with the at least one threshold value 206 for the oxygen sensor 110 positioned downstream of the primary catalyst 106 or inside the primary catalyst 106. The controller 112 receives the signal from the oxygen sensor 110 and determines the voltage detected. The real-time voltage is compared with the threshold value as per the operating condition. The operating condition is based on engine speed and throttle position. The entire operating region is either considered as one or split into multiple regions with respective threshold value. In the present invention, only one threshold value is taken for entire operating region.

[0023] Once the threshold value is detected, the controller 112 performs the closed loop lambda control using for the downstream oxygen sensor 110. Similarly, the signal of the oxygen sensor 110 is used by the controller 112 for catalyst monitoring by comparing the real-time amplitude of the signal with the threshold amplitude. The controller 112 then determines that the primary catalyst 106 is aged or not.

[0024] Fig. 3 illustrates a method for processing signal from the oxygen sensor in the exhaust conduit of the vehicle, according to the present invention. The method comprise plurality of steps of which a first step 302 comprises receiving signal, by the controller 112, as detected by the oxygen sensor 110. The method is characterized by a step 304 which comprises comparing, by the controller 112, the detected signal with at least one calibrated threshold value 206. The at least one calibrated threshold value 206 is stored, in the memory element, corresponding to positioning of the oxygen sensor 110 in at least one of two locations selected from the group comprising, the first location which is inside the primary catalyst 106, and the second location which is in the gap between the primary catalyst 106 and the secondary catalyst 108. A step 306 comprises performing, by the controller 112, at least one function selected from the group comprising the closed loop lambda control and catalyst monitoring using signals from the one oxygen sensor 110.

[0025] According to the method, the at least one threshold value is provided for at least one operating condition of the engine 102 of the vehicle 100. The at least one threshold value is calibrated and pre-stored in the memory element. According to the step 306, a method for closed loop lambda control is provided which comprises applying fuel correction towards lean side and rich side at every instance of the signal detected by the oxygen sensor 110 crossing the at least one threshold value 206 during transition from high to low and low to high, respectively.

[0026] According to the present invention, a method for catalyst monitoring is provided. The method comprises detecting an aged primary catalyst 106 by comparing the amplitude of the signal detected by the oxygen sensor 110 against the threshold amplitude stored in the memory element. The aging of the primary catalyst 106 is determined based on the comparison. The method determines the whether the primary catalyst 106 is aged or not without knowing the degree of aging. In other words, the method determines if the primary catalyst 106 has reached End Of Life (EOL). The method is performed by the controller 112.

[0027] According to an embodiment of the present invention, a controller 112 and a method for lambda control and catalyst monitoring using single oxygen sensor 110 is provided. The present invention provides lambda control based on only one oxygen sensor 110 positioned downstream of the primary catalyst 106 (catalytic converter) in the split catalyst or tandem catalyst system. The oxygen sensor 110 also provides input for catalyst monitoring based on the Oxygen Storage Capacity (OSC) of the primary catalyst 106. The present invention provides lambda control based on the signal from single oxygen (O2) sensor 110 downstream of the primary catalyst 106 and eliminates the requirement for another lambda/oxygen sensor 110 positioned upstream of the primary catalyst 106. A two-point lambda controller 110 is used to control the rich-lean mixture oscillations based on the oxygen sensor 110 set-point at downstream position. The assembly/setup is conducive for using only one switching type oxygen sensor 110 for both closed loop lambda control and catalyst monitoring. The life of oxygen sensor 110 is increased due the being positioned away from the direct exhaust gases. A method/controlling action for lambda control and catalyst monitoring using single Binary/oxygen sensor 110 for split and tandem catalytic convertor setup vehicles 100 is provided. The present invention uses passive catalyst monitoring method. This is a passive monitoring strategy which must be done to meet In-Use Monitor Performance Ratio (IUMPR) as per legislation.

[0028] 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
, Claims:We claim:
1. An assembly of oxygen sensor (110) in an exhaust conduit (104) of a vehicle (100), said exhaust conduit (104) comprises:
a primary catalyst (106) and a secondary catalyst (108), arranged in sequence and separated from each other in said exhaust conduit (104), characterized in that,
said assembly comprises only one oxygen sensor (110) positioned in at least one of two locations selected from a group comprising, inside said primary catalyst (106), and in a gap between said primary catalyst (106) and said secondary catalyst (108), signal from said only one oxygen sensor (110) is used for control of at least one function selected from a group comprising a closed loop lambda control and a catalyst monitoring.

2. The assembly as claimed in claim 1, wherein said primary catalyst (106) and said secondary catalyst (108) are part of any one of a split catalyst unit and a tandem catalyst unit.

3. A controller (112) for an oxygen sensor (110) in an exhaust conduit (104) of a vehicle (100), said exhaust conduit (104) comprises a primary catalyst (106) and a secondary catalyst (108), said controller (112) configured to,
receive signal detected by said oxygen sensor (110), characterized in that,
compare said detected signal with at least one calibrated threshold value, said at least one calibrated threshold value is stored, in a memory element, corresponding to positioning of said oxygen sensor (110) in at least one of two locations selected from a group comprising, inside said primary catalyst (106), and in a gap between said primary catalyst (106) and said secondary catalyst (108), and
perform at least one selected from a group comprising a closed loop lambda control and catalyst monitoring using signals from said oxygen sensor (110).

4. The controller (112) as claimed in claim 3, wherein at least one threshold value (206) is provided for at least one operating condition of an engine (102) of said vehicle (100), wherein said at least one threshold value is calibrated and pre-stored in said memory element.

5. The controller (112) as claimed in claim 4, wherein at every instance of signal detected by said oxygen sensor (110) crossing said at least one threshold value during transition from high to low and low to high, a fuel correction towards lean side and rich side, respectively is performed.

6. The controller (112) as claimed in claim 3, wherein an amplitude of said signal detected by said oxygen sensor (110) is compared against threshold amplitude for determination of aging of said primary catalyst (106).

7. A method for processing signal of an oxygen sensor (110) in an exhaust conduit (104) of a vehicle (100), said method comprising the steps of:
receiving signal detected by said oxygen sensor (110), characterized by,
comparing said detected signal with at least one calibrated threshold value, said at least one calibrated threshold value is stored corresponding to positioning of said oxygen sensor (110) in at least one of two locations selected from a group comprising, inside said primary catalyst (106), and in a gap between said primary catalyst (106) and said secondary catalyst (108), and
performing at least one function selected from a group comprising a closed loop lambda control and catalyst monitoring using signals from said one oxygen sensor (110).

8. The method as claimed in claim 7, wherein at least one threshold value (206) is provided for at least one operating condition of an engine (102) of said vehicle (100), wherein said at least one threshold value (206) is calibrated and pre-stored in said memory element.

9. The method as claimed in claim 8, comprises applying fuel correction towards lean side and rich side at every instance of signal detected by said oxygen sensor (110) crossing said at least one threshold value (206) during transition from high to low and low to high, respectively.

10. The method as claimed in claim 7, comprises detecting an aged primary catalyst (106) by comparing an amplitude of said signal detected by said oxygen sensor (110) against threshold amplitude stored in a memory element.