CLIAMS:We claim:
1. A method for controlling exhaust emission in a motor vehicle, said motor vehicle comprising exhaust path (14), said exhaust path (14) comprising a catalyst (12) for reacting with an exhaust gas emitted from an internal combustion engine (16) of the motor vehicle, said method comprising the steps of
? retrieving a control pattern corresponding to purging and loading of the oxygen for the catalyst (12);
? estimating an instantaneous oxygen-loading amount in the catalyst (12) based on air-mass and speed of the internal combustion engine (16);
? comparing the estimated instaneous oxygen-loading amount with a reference value selected from the retrieved control pattern for the respective air-mass and speed of the internal combustion engine (16) ; and
? controlling fuel injection quantity of the internal combustion engine (16) based on said comparision result.
2. The method according to claim 1, wherein retrieving step comprises reading a control pattern corresponding to purging and loading of the oxygen based on the type/capacity of the catalyst (12) from a memory (24).
3. The method according to claim 1, wherein retrieving step comprises reading a control pattern corresponding to purging and loading of the oxygen based on the type/capacity of the internal combustion engine (16) from the memory (24).
4. The method according to claim 1, wherein the estimating step comprises predicting the oxygen-loading amount in the catalyst (12) without using an oxygen/lambda sensor.
5. The method according to claim1, wherein the controlling step comprises varying the fuel injection quantity of the internal combustion engine (16) for regulating the purging and loading of oxygen in the catalyst (12) according to the retrieved control pattern.

6. An electronic control unit (ECU) (22) for a motor vehicle, said motor vehicle comprising
? an air-mass sensor(18) for measuring the air-mass entering an internal combustion engine (16) of the motor vehicle;
? a speed sensor (20) for measuring the speed of the internal combustion engine (16); characterized in said motor vehicle, said ECU (22) is adapted to
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- retrieve a control pattern corresponding to purging and loading of the oxygen for the catalyst (12) from a memory (24);
- estimate an instantaneous oxygen-loading amount in a catalyst (12) installed in an exhaust path (14) of the motor vehicle based on inputs from the air-mass sensor(18) and the speed sensor (20);
- compare the estimated instantaneous oxygen-loading amount with a corresponding reference value selected from the retrieved control pattern for the respective air-mass and speed of the internal combustion engine (16); and
- control at least one fuel injector (26) for varying the fuel injection quantity of the internal combustion engine (16) based on the comparision result.
7. The ECU (22) according to claim 6, wherein the air-mass sensor(18) is selected from one of a manifold sensor, a throttle position sensor and a hot film mass air-flow sensor (HFM).
8. The ECU (22) according to claim 6, wherein the memory (24) stores a plurality of control patterns corresponding to the purging and loading of the oxygen based on the type/capacity of the catalyst (12).
9. The ECU (22) according to claim 6, wherein the memory (24) stores a plurality of control patterns corresponding to the purging and loading of the oxygen based on the type/capacity of the internal combustion engine (16).
10. The ECU (22) according to claim 6, wherein the fuel injection quantity is varied by said ECU (22) for regulating the purging and loading of oxygen in the catalyst (12) according to the retrieved control pattern.
,TagSPECI:Field of the invention:
[001] The invention relates to a method and apparatus for controlling exhaust emission in a motor vehicle. More specifically, the invention relates to improving the effectiveness of an exhaust treatment catalyst in a motor vehicle.
Background of the invention
[002] Exhaust emission regulations for vehicles have become strict across the globe. Therefore, emission level of exhaust gases has to be reduced considerably to meet the emission standards. In order to reduce the exhaust emission level, it inevitable to use an effective exhaust catalyst in the vehicle.
[003] In order to improve the exhaust gas conversion efficiency of the catalyst, it is necessary to vary the air-fuel ratio (lambda value) of the vehicular engine continuously. In the existing exhaust systems, the air-fuel ratio at the upstream and/or downstream sides of the catalyst is determined using an oxygen sensor. This detected air-fuel ratio is fedback to a fuel injection controller, so that the air-fuel ratio is varied continuously.
[004] On the other hand, there is an increasing need for reducing the number of components and achieving cost reduction. Further, there is a continous demand for low-priced vehicles in the developing countries. Therefore, it becomes a major challenge in improving the performance of the vehicle while still reducing its the cost.
Brief description of the drawing:
[005] The invention is described with reference to the following drawings:
[006] Fig. 1 illustrates an arrangement for controlling exhaust emissions in a vehicle, in accordance with one embodiment of the present invention.
[007] Fig. 2 illustrates a flow chart corresponding to a method for controlling exhaust emissions in a vehicle, in accordance with one embodiment of the present invention.
Detailed description of the embodiments of the invention
[008] Fig. 1 illustrates an arrangement for controlling exhaust emissions in a vehicle, in accordance with one embodiment of the present invention. A catalyst (12) is provided in an exhaust path (14) of a motor vehicle. The catalyst (12) reacts with the exhaust gas emitted from an internal combustion engine (16) of the motor vehicle. The catalyst (12) converts the exhaust gas components such as hydrocarbons, carbon monoxides, nitrogen oxides, etc into less harmful substances. The catalyst (12) may be a three-way catalyst (12) or the like.
[009] Typically, the catalysts (12) are categorised according to their oxygen storage capacity. (For example, 19gm catalyst, 30gm catalyst, etc.) A catalyst (12) having specific oxygen storage capacity is used in a vehicle based on the type/capacity of the internal combustion engine (16) of the vehicle.
[0010] An air-mass sensor(18) is provided in the internal combustion engine (16) for measuring the air-mass entering the internal combustion engine (16). Examples of the air-mass sensor(18) include but not limited to, a manifold sensor, a throttle position sensor and a hot film mass air-flow sensor (HFM).
[0011] A speed sensor (20) measures the rotational speed of the internal combustion engine (16).
[0012] An electronic control unit ECU (22) is connected to the air-mass sensor (18) and the speed sensor (20) . The ECU (22) is also connected to a memory (24) or a storage medium, which stores various data and control patterns related to the vehicle.
[0013] In an embodiment of the invention, the memory (24) stores several control patterns corresponding to different types/capacities of the catalyst (12).
[0014] For example, the control pattern may be ideal oxygen loading and purging amounts of the catalyst (12) corresponding to different air-mass values and speed values of the internal combustion engine (16).
[0015] The ECU (22) retrieves a control pattern corresponding to the purging and loading of the oxygen for the catalyst (12) from the memory (24), based on the type/capacity of the catalyst (12) installed in the vehicle.
[0016] In another embodiment of the invention, the memory (24) stores several control patterns corresponding to different types/capacities of the internal combustion engine (16). The ECU (22) retrieves a control pattern corresponding to the purging and loading of the oxygen for the catalyst (12) based on the type/capacity of the internal combustion engine (16) of the vehicle.
[0017] The retrieved control pattern indicates the oxygen purging and loading amount required for the optimum performance of the catalyst (12).
[0018] The ECU (22) receives the inputs from the air-mass sensor(18) and the speed sensor (20) to estimate an instantaneous oxygen-loading amount in the catalyst (12). It is to be noted that this oxygen-loading amount is not an actual measured value. The ECU (22) predicts the instantaneous oxygen-loading amount in the catalyst (12) without requiring any inputs from an oxygen sensor. Therefore, the need for using oxygen/lambda sensors is avoided for determining the oxygen-loading amount in the catalyst (12). Hence cost reduction is achieved. Further, the assembly and layout is simplified, because of the reduction in number of the sensors.
[0019] The ECU (22) compares the estimated instantaneous oxygen-loading amount with a corresponding reference value selected from the retreived control pattern for the respective air-mass and speed of the internal combustion engine (16). For instance, at a particular instant, the ECU estimates the oxygen-loading amount (O1) in the catalyst based on air-mass (AM1) and speed (S1) of the internal combustion engine (16) at that instant. This value (O1) is compared with a corresponding reference value ( RO1) of the retrieved control pattern. This reference value (RO1) is selected from the retrieved control pattern for the same air-mass (AM1) and speed (S1).
[0020] The ECU (22) controls the fuel injection quantity of the internal combustion engine (16) based on the comparision result. For example, the ECU (22) either increases or reduces the fuel injection quanity by varying the control pulse applied to a fuel injector (26) in order to reduce or increase the air-fuel ratio (Lambda value).
[0021] This is done in order to match the oxygen-loading amount (O1) of the catalyst (12) to the reference value (RO1). That is, the fuel injection quantity is varied by the ECU (22) for regulating the purging and loading of oxygen in the catalyst (12) according to the retrieved control pattern.
[0022] A specific Lambda oscillation/variation pattern is thus achieved by controlling the fuel-injection quantity to regulate the purging and loading of the oxygen in the catayst (12). Thus the exhaust conversion effeciency and effectiveness of the catalyst (12) is improved remarkably.
[0023] Fig. 2 illustrates a flow chart corresponding to a method for controlling exhaust emissions in a vehicle, in accordance with one embodiment of the present invention.
[0024] According to an embodiment of the invention, the method involves retrieving a control pattern corresponding to purging and loading of the oxygen for a catalyst (12) from a memory (24)[ at step S1]. This control pattern may be selected and read from the memory (24) among several control patterns, based on the type/capacity of the catalyst (12) installed in the vehicle.
[0025] Alternatively, the control pattern may be read from the memory (24) among several control patterns, based on the type/capacity of the internal combustion engine (16) in the vehicle.
[0026] At step S2, an instantaneous oxygen-loading amount in the catalyst (12) is estimated based on air-mass and speed of the internal combustion engine (16) of the motor vehicle.
[0027] The oxygen-loading amount of the catalyst (12) is predicted without using any oxygen sensor/lamda sensor. Since the need for oxygen sensors is avoided, cost reduction is achieved and assembly is simplified.
[0028] At step S3, the estimated instantaneous oxygen-loading amount is compared with a reference value selected from the retrieved control pattern for the respective air-mass and speed of the internal combustion engine (16).
[0029] A fuel injection quantity of the internal combustion engine (16) is controlled based on the comparison result (at step S4) for regulating the purging and loading of oxygen in the catalyst (12) according to the retrieved control pattern.
[0030] This can be achieved by varying the control pulse applied to one or more injectors (28) of the internal combustion engine (16).Various methods of varying the pulse such pulse width modulation (PWM) etc , which are known to skilled person, can be used and they are in the ambit of the invention.
[0031] As described earlier, this method and apparatus of the present invention do not require oxygen or lambda sensors for varying the air-fuel ratio. Therefore, cost reduction is achieved.
[0032] Further, this invention proposes a simple open-loop type control for varying the lamda value suitably in order to improve the efficiency of the exhaust treatment catalyst (12).
[0033] 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, 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 appended claims.