MOTOR VEHICLE COMPRISING AN EXHAUST SYSTEM EQUIPPED WITH THREE OXYGEN SENSORS, AND A MEANS FOR DETECTING A FAULTY SENSOR, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

Abstract

The invention relates to a motor vehicle comprising an exhaust system which includes an exhaust pipe comprising at least one redox catalyst. The pipe includes three oxygen sensors (S1, S2, S3) arranged at different points. The exhaust system includes: - at least one deviation estimation means (E1, E2, E3) evaluating measurement deviations between the sensors (S1, S2, S3) two by two; and - at least one analysis means (A) connected to said deviation estimation means (E1, E2, E3), concluding that a sensor has failed if its measurement shows a deviation greater than a predetermined threshold relative to the measurements of the other sensors (S1, S2, S3). The invention further relates to a method and a program based on such a vehicle. Figure 3

Description

Title of the invention: MOTOR VEHICLE COMPRISING AN EXHAUST SYSTEM EQUIPPED WITH THREE OXYGEN SENSORS, AND A MEANS FOR DETECTING A DEFECTIVE SENSOR, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

[0001] The invention relates to the field of motor vehicle exhaust systems, and more particularly to oxygen detection probes for these exhaust systems.

[0002] The exhaust system of the prior art is illustrated in [Fig.l]. It comprises a 3-way redox catalyst block TWC connected to a particulate filter GPF with a first proportional oxygen sensor SI upstream of the catalyst block TWC, and a second binary oxygen sensor S2 downstream thereof. In addition, the exhaust system comprises a second block composed of a second 3-way catalyst UFC and possibly an ammonia storage device ASC, the assembly being connected downstream of the second binary oxygen sensor S2.

[0003] The control command is based on a richness regulation function implemented upstream and downstream of the first TWC catalyst block. The downstream richness regulator is a proportional-integral regulator using the information from the oxygen sensor S2 downstream of the catalyst (voltage measurement) to correct the richness upstream in order to optimize the behavior of the catalyst. This regulation can be called second loop or double richness regulation loop. This also makes it possible to detect an excessively large richness difference measured between the two sensors SI, S2 (or "offset" in English), this diagnosis being required by emissions regulations (in Europe, the United States, China, etc.).

[0004] These richness differences can be slow drifts during the life of the vehicle, that is to say changes in the oxygen sensors and the catalyst over time, or sudden drifts of several percent.

[0005] The evaluation of the difference in richness between the two probes SI, S2 is carried out by an integrator of the downstream regulation as well as a rapid evaluation function.

[0006] Unfortunately, the second oxygen sensor S2 downstream of the first catalyst is conventionally considered until now as the reference sensor, this means that if a difference in richness is observed between the two oxygen sensors SI, S2, then this fault is systematically attributed to the sensor SI upstream of the catalyst.

[0007] Nothing indicates in the prior art that it would rather be the downstream probe S2 which would be faulty. Thus, it is likely in certain circumstances that in the event of such a failure on the S2 probe, an upstream probe will be replaced while it is still functional.

[0008] An objective of the present invention is to remedy the defects of the prior art, and in particular to propose a solution for more precisely detecting operating faults in oxygen sensors of exhaust systems.

[0009] To achieve this objective, the invention proposes a motor vehicle comprising an exhaust system which comprises an exhaust pipe defining an exhaust direction, and comprising at least one redox catalyst, characterized in that the pipe comprises: - at least one first oxygen probe arranged upstream of said catalyst; - at least one second oxygen sensor arranged downstream of said catalyst; and - at least one third oxygen sensor arranged downstream of said catalyst and said second oxygen sensor, and in that the exhaust system comprises: - at least one means of deviation estimation evaluating measurement deviations between the probes two by two; and - at least one analysis means connected to said deviation estimation means, concluding that a probe has failed if its measurement shows a deviation greater than a predetermined threshold compared to the measurements of the other probes.

[0010] Thus, at the end of the exhaust line there is now a third richness sensor (oxygen sensor or NOx / NH3 sensor).

[0011] Advantageously, the invention makes it possible to introduce a new functionality which uses the implementation of a third richness sensor (NOX / NH3 sensor or oxygen sensor) to evaluate the richness differences between the three sensors. When a richness difference is present, it is easier to determine which sensor is faulty.

[0012] According to a variant, said deviation estimation means comprises: - a first deviation estimation means for evaluating the deviations between the measurements of the first probe and the second probe; - a second deviation estimation means for evaluating the deviations between the measurements of the second probe and the third probe; - a third deviation estimation means for evaluating the deviations between the measurements of the first probe and the third probe, and in that the analysis means receives information from the estimation means.

[0013] This allows the estimation and analysis functions to be separated, to have precise analysis at a point separate from the probes.

[0014] According to one variant, the exhaust pipe comprises: - a first three-way redox catalyst; - a first particulate filter connected downstream of the first catalyst; - a second three-way redox catalyst connected downstream of the first particulate filter, the first probe being arranged upstream of the first redox catalyst; the second probe being arranged downstream of the first particle filter and upstream of the second redox catalyst; the third probe being arranged downstream of the second redox catalyst.

[0015] This makes it possible to have a solution adapted to the configurations of usual exhaust systems.

[0016] According to a variant, the exhaust pipe further comprises an ammonia storage device connected downstream of the second redox catalyst, the third probe being arranged downstream of the ammonia storage device.

[0017] This allows for a solution adapted to this exhaust system configuration.

[0018] According to one variant, the motor vehicle comprises a richness regulator connected to the second oxygen sensor.

[0019] This allows for an optimal amount of exhaust gas for the catalysts.

[0020] The invention also relates to a method for monitoring and regulating an exhaust system of a motor vehicle according to the invention, characterized in that it comprises the following steps: - steps of measuring the richness by means of at least one first oxygen sensor arranged upstream of said catalyst; at least one second oxygen sensor arranged downstream of said catalyst; and at least one third oxygen sensor arranged downstream of said catalyst, - deviation estimation steps evaluating measurement deviations between the probes two by two; and - at least one analysis step concluding that a probe has failed if its measurement shows a deviation greater than a predetermined threshold compared to the measurements of the other probes.

[0021] According to a variant, the steps of deviation estimations comprise: - a first step of deviation estimation to evaluate the deviations between the measurements of the first probe and the second probe; - a second step of deviation estimation to evaluate the deviations between the measurements of the second probe and the third probe; - a third step of deviation estimation to evaluate the deviations between the measurements of the first probe and the third probe, and in that the analysis step is carried out on the basis of information from the estimation steps.

[0022] The invention further relates to a computer program comprising program code instructions for executing the steps of the monitoring and regulation method according to the invention, when said program operates on a computer.

[0023] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a front view of an exhaust system of a vehicle according to the prior art; - [Fig.2] schematically illustrates a front view of an exhaust system of a vehicle according to a first embodiment of the invention; and - [Fig.3] schematically illustrates the detection of the defective probe.

[0024] The invention relates to a motor vehicle comprising an exhaust system as illustrated in [Fig.2]. Conventionally, the exhaust system comprises an engine M and a turbocharger T.

[0025] The motor vehicle further comprising an exhaust pipe illustrated in [Fig.2], extending from the engine M and the turbocharger T upstream to a free end downstream. The exhaust pipe comprises a first three-way redox catalyst TWC, and a second three-way redox catalyst UFC.

[0026] Furthermore, the exhaust pipe comprises a first GPF particulate filter connected downstream of the first TWC catalyst; and a second three-way UFC redox catalyst connected downstream of the first GPF particulate filter.

[0027] The exhaust pipe may comprise an ammonia storage device ASC connected downstream of the second redox catalyst UFC.

[0028] According to the invention, the pipeline comprises three oxygen probes S1, S2, S3, namely: - a first oxygen probe SI arranged upstream of the first TWC catalyst; - a second oxygen probe S2 arranged downstream of the first TWC catalyst and the first GPF particulate filter, but upstream of the second UFC catalyst; and - a third oxygen probe S3 arranged towards the free end of the pipe, downstream of said second UFC catalyst, and optionally of the ASC ammonia storage device.

[0029] Furthermore, the exhaust system comprises deviation estimation means E1, E2, E3 evaluating measurement deviations between the probes S1, S2, S3 two by two. may be electronic or computer units evaluating the deviations between the measurements of the SI, S2, S3 probes.

[0030] In addition, the exhaust system comprises an analysis means A connected to the deviation estimation means E1, E2, E3. The analysis means A concludes that a probe, for example S2, has failed if its measurement exhibits a deviation greater than a predetermined threshold compared to the measurements of the other probes SI and S3. It may be a computer unit dedicated to the diagnosis of the probes SI, S2, S3.

[0031] The invention consists of a new functionality which uses the implementation of a third so-called “richness” sensor (NOX / NH3 sensor or oxygen sensor) to evaluate the richness differences between the three sensors.

[0032] The deviation estimation means E1, E2, E3 evaluate the deviations respectively between the measurements of the first probe S1 and of the second probe S2; between the measurements of the second probe S2 and of the third probe S3; and between the measurements of the first probe S1 and of the third probe S3.

[0033] The analysis means A receives information from the estimation means to determine whether a probe is defective.

[0034] When there is a difference in richness, it is easier to determine which sensor is faulty.

[0035] If a richness difference is present on one of the exhaust line probes (SI for example), it cannot be attributed to the faulty probe because the other probes S2 and S3 converge.

[0036] The future regulation known as Euro 7 requires that manufacturers be able to identify faulty components more precisely (this is called "pinpointing" in English). With the implementation of a third richness sensor (third probe S3) in the exhaust line, it is possible to add two additional evaluations of richness difference between the probes, in addition to the one already existing between the first and second richness probe SI, S2.

[0037] The invention also relates to a method and a program implementing this detection of a defective probe.

Claims

Claims

1. Motor vehicle comprising an exhaust system which comprises an exhaust pipe defining an exhaust direction, and comprising at least one redox catalyst (TWC, UFC), characterized in that the pipe comprises: - at least one first oxygen sensor (SI) arranged upstream of said catalyst (TWC, UFC); - at least one second oxygen sensor (S2) arranged downstream of said catalyst (TWC, UFC); and - at least one third oxygen sensor (S3) arranged downstream of said catalyst (TWC, UFC) and said second oxygen sensor (S2), and in that the exhaust system comprises: - at least one deviation estimation means (El, E2, E3) evaluating measurement deviations between the sensors (SI, S2, S3) two by two;and - at least one analysis means (A) connected to said deviation estimation means (El, E2, E3), concluding that a probe has failed if its measurement shows a deviation greater than a predetermined threshold compared to the measurements of the other probes (SI, S2, S3).;

2. Motor vehicle according to claim 1, characterized in that said deviation estimation means comprises: - a first deviation estimation means (El) for evaluating the deviations between the measurements of the first probe (SI) and the second probe (S2); - a second deviation estimation means (E2) for evaluating the deviations between the measurements of the second probe (S2) and the third probe (S3); - a third deviation estimation means (E3) for evaluating the deviations between the measurements of the first probe (SI) and the third probe (S3), and in that the analysis means (A) receives information from the estimation means (El, E2, E3).

3. Motor vehicle according to any one of claims 1 to 2, characterized in that the exhaust pipe comprises: - a first three-way redox catalyst (TWC); - a first particulate filter (GPF) connected downstream of the first catalyst (TWC); - a second three-way redox catalyst (UFC) connected downstream of the first particulate filter (GPF), the first probe (SI) being arranged upstream of the first redox catalyst (TWC); the second probe (S2) being arranged downstream of the first particulate filter (GPF) and upstream of the second redox catalyst (UFC); the third probe (S3) being arranged downstream of the second redox catalyst (UFC).

4. Motor vehicle according to claim 3, characterized in that the exhaust pipe further comprises an ammonia storage device (ASC) connected downstream of the second redox catalyst (UFC), the third probe (S3) being arranged downstream of the ammonia storage device (ASC).

5. Motor vehicle according to any one of claims 1 to 4, characterized in that it comprises a richness regulator connected to the second oxygen sensor (S2).

6. Method for monitoring and regulating an exhaust system of a motor vehicle according to any one of claims 1 to 5, characterized in that it comprises the following steps: - steps of measuring the richness by means of at least one first oxygen probe (SI) arranged upstream of said catalyst; at least one second oxygen probe (S2) arranged downstream of said catalyst; and at least one third oxygen probe (S3) arranged downstream of said catalyst (TWC, UFC), - steps of estimating the deviations in measurements between the probes (SI, S2, S3) two by two; and - at least one analysis step concluding that a probe (S2) has failed if its measurement has a deviation greater than a predetermined threshold compared to the measurements of the other probes (SI, S3).

7. Monitoring and regulation method according to claim 6, characterized in that the deviation estimation steps comprise: - a first deviation estimation step for evaluating the deviations between the measurements of the first probe (S1) and the second probe (S2); - a second deviation estimation step for evaluating the deviations between the measurements of the second probe (S2) and the third probe (S3); - a third deviation estimation step for evaluating the deviations between the measurements of the first probe (S1) and the third probe (S3), and in that the analysis step is carried out on the basis of the information

8. estimation steps. Computer program comprising program code instructions for executing the steps of the monitoring and regulating method according to any one of claims 6 to 7, when said program operates on a computer.

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