A system for monitoring pollutant emissions from automobile diesel engines and related methods for detecting malfunctions in the said system.

Abstract

A method for detecting a failure in a pollution emission control system (11) of an engine (1) equipped with a particulate filter (PF) comprises: - determining a first maximum temperature at the filter inlet depending on the instantaneous operating point of the engine; - determining a second maximum temperature at the filter inlet from the first maximum temperature based on a measured value of the engine's exhaust flow rate; - determining a third maximum temperature at the filter inlet corresponding to the minimum value between the second maximum temperature and the temperature setpoint value from the control means (14) of the system (11); - calculating the deviation between the third maximum temperature and a measured temperature at the filter inlet; and - detecting a failure in the control system when the calculated deviation exceeds a predetermined threshold deviation.

Description

[[TECHNICAL FIELD]]

[0001] The present invention relates to a method for monitoring a pollution emission control system of a compression ignition engine of a motor vehicle, and in particular to a monitoring method based on detection of a system failure. The present invention also relates to a system for implementing this method, and to a motor vehicle comprising such a system or implementing such a method. [[BACKGROUND ART]]

[0002] Despite the continuous progress in the operation of internal combustion engines for motor vehicles, particularly diesel engines, engines still discharge pollutant particles consisting of soot generated during incomplete combustion in the engine.

[0003] According to the prior art, it is known to trap these particles present in exhaust gas by means of a particulate filter installed in an exhaust line downstream of the combustion chamber of an engine. Such a filter is designed to be capable of retaining particles in exhaust gas passing through the filter. As the engine is used, particles accumulate in the filter, resulting in a gradual increase in exhaust back pressure, which is detrimental to proper operation of the engine and fuel consumption.

[0004] To restore optimal engine operation, it is necessary to periodically regenerate the particulate filter by burning the particles accumulated therein. This combustion operation is made possible by increasing the internal temperature of the particulate filter by raising the temperature of the exhaust gas. This is normally achieved by late injection of fuel into the combustion chamber of the engine. In particular, fuel can be injected immediately after top dead center during the expansion stroke, which has the effect of increasing exhaust gas temperature.

[0005] Accordingly, conventionally, particulate filters operate periodically in two phases. During the first phase, the filter stores particles emitted by the engine, and during the second phase, the particles stored in the filter are burned to regenerate the filter.

[0006] Generally, particle filters are regenerated periodically as soon as the mass of particles in the filter becomes too large. This regeneration is automatically triggered during engine operation. This management of particle filters is based on a system for estimating the mass of particles present in the particle filter from the pressure difference, also known as differential pressure, at the filter terminals, from the volumetric flow rate passing through the filter, and from a model of the filter's operation.

[0007] However, the particle mass within the filter can only be identified by the differential pressure and volumetric flow rate during the first stage of particle storage. In fact, from the start of the second stage, the particle filter still contains a large amount of soot, but the combustion of soot causes a rapid decrease in differential pressure. Therefore, it is impossible to estimate the mass of soot during the second stage from the differential pressure.

[0008] Therefore, a soot combustion model is generally used, which is initialized at the start of the second stage using, for example, a soot mass value estimated from the differential pressure measured at the end of the first stage, and then gradually decreased according to the current conditions of temperature, exhaust gas flow, and oxygen concentration.

[0009] Aside from minor instances of the driver stopping the engine, the second stage is typically stopped when sufficient regeneration has occurred, i.e., when the soot combustion model indicates that regeneration has succeeded in reducing the soot mass on the filter to below a predetermined minimum mass threshold.

[0010] If regeneration is insufficient, the second stage will still be stopped when the predetermined maximum regeneration time is reached. Such insufficient regeneration is usually a result of the temperature at the filter inlet being too low, preventing the desired soot from burning. Such temperatures can result from a malfunction in the filter regeneration system, which is important to identify and correct, or simply from the vehicle's driving profile, for example, during long idling phases or driving at very low speeds. Such a vehicle driving profile results in heat at the filter inlet that prevents sufficient regeneration from being achieved, even when the system is functioning correctly.

[0011] Several solutions can be considered to identify failures in the particle filter regeneration system. However, these solutions are not satisfactory.

[0012] For example, counting the frequency of particle filter regeneration, or the average percentage of time spent in the regeneration phase, is insufficient. In fact, such a criterion is associated with abnormally high filter load rates and therefore depends on increased particle emission rates by the engine, and does not depend on regeneration system failures.

[0013] Comparing the soot mass value from the soot combustion model at the end of the regeneration phase with the soot mass value obtained through differential pressure is also unsatisfactory, as it only detects the deviation between the two models without clearly identifying a failure in the particle filter regeneration system.

[0014] Using closed-loop control of the particle filter inlet temperature to monitor loop deviation, i.e., the difference between the temperature setpoint and the measured temperature, is still not satisfactory for detecting faults, as it primarily leads to highlighting stages where the required engine power is insufficient to reach the temperature necessary for soot combustion. [Overview of the Initiative]

[0015] The objective of the present invention is to enable reliable detection of failures in particle filter regeneration systems by eliminating cases where a lack of regeneration efficiency is related to the vehicle's driving profile.

[0016] The present invention relates to a method for detecting a malfunction in a pollution emission control system of a diesel engine of an automobile equipped with a particle filter.

[0017] This method involves the following steps: - A step of determining a first maximum temperature at the filter inlet according to the instantaneous operating point of the engine, - A step of determining the second highest filter inlet temperature from the first highest temperature based on the measured exhaust flow of the engine, - A step of determining a third maximum temperature at the filter inlet that corresponds to the minimum value between the second maximum temperature and the temperature setpoint value from the control system means, - A step of calculating the deviation between the third highest temperature and the measured filter inlet temperature, - A step to detect a failure in the control system when the calculated deviation exceeds a predetermined threshold deviation.

[0018] This method ensures reliable detection of control system failures by eliminating cases where insufficient regeneration is due to the driving profile.

[0019] According to one characteristic, the method further comprises a time calculation step in which the total failure time is calculated, which represents the sum of each elapsed time between the detection of a failure and the moment when the calculated deviation falls below a predetermined threshold deviation.

[0020] For example, the method further comprises the step of sending a message or alert signal that is executed when the total failure time exceeds a predetermined threshold duration.

[0021] According to another characteristic, the method further comprises the step of calculating the total enthalpy deficit received by the filter, where the sum of each integral over time of the product of the exhaust flow and the difference between the calculated deviation and a predetermined threshold deviation is calculated for each time period elapsed between fault detection and the moment when the calculated deviation becomes less than or equal to the predetermined threshold deviation.

[0022] For example, the method further comprises the step of sending a message or alert signal that is executed when the total enthalpy deficit received by the filter exceeds a predetermined threshold enthalpy deficit.

[0023] According to another aspect, the present invention relates to a system for controlling pollutant emissions from a diesel engine of a motor vehicle equipped with a particulate filter, - means for measuring engine exhaust flow rate, volumetric flow rate through the filter, the pressure difference between the inlet port and the outlet port of the filter, and the temperature at the inlet of the filter, - calculation means capable of estimating the soot mass of the filter from information from the measuring means, - control means configured to control regeneration of the particulate filter when the estimated soot mass of the filter exceeds a predetermined threshold mass.

[0024] According to one feature, the control system comprises: means for determining a first maximum temperature at the inlet of the filter according to the instantaneous operating point of the engine; means for determining a second maximum temperature at the inlet of the filter from the first maximum temperature according to a measured value of the exhaust flow rate of the engine; and means for determining a third maximum temperature at the inlet of the filter corresponding to a minimum value between the second maximum temperature and a temperature setpoint value required by the control means for regenerating the filter.

[0025] Advantageously, the calculation means is configured to calculate a deviation between the third maximum temperature and a measured temperature value at the inlet of the filter, and is configured to detect a failure of the control system when the calculated deviation exceeds a predetermined threshold deviation.

[0026] For example, the calculation means is configured to calculate a total failure time representing the sum of each elapsed time between detection of a failure and the time at which the calculated deviation becomes equal to or less than the predetermined threshold deviation.

[0027] For example, the calculation means is configured to calculate, for each time period elapsed between detection of a failure and the moment when the calculated deviation becomes equal to or less than the predetermined threshold deviation, a total enthalpy deficit received by the filter, the total enthalpy deficit representing the sum of each integral over time of a product between the exhaust flow and the difference between the calculated deviation and the predetermined threshold deviation.

[0028] Preferably, the control system comprises means for transmitting a message or an alert signal.

[0029] According to another aspect, the invention relates to a motor vehicle comprising a diesel-type internal combustion engine or comprising a system that implements the method for controlling pollutant emissions as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other objects, features and advantages of the present invention will become apparent upon reading the following description given by way of non-limiting example only and made with reference to the accompanying drawings. [Figure 1] Figure 1 shows an exemplary application of the invention. [Figure 2] Figure 2 illustrates the change over time of several temperatures at the inlet of a particulate filter according to the present invention. [Figure 3] Figure 3 illustrates the calculation of total failure time according to an embodiment of the present invention. [Figure 4] Figure 4 illustrates the calculation of the total enthalpy deficit received by a particulate filter. [Figure 5] Figure 5 illustrates a flow chart of a method for detecting a fault in a pollutant emission control system according to the present invention. [Figure 6] Figure 6 illustrates a flow chart of a method for detecting a fault according to an embodiment of the present invention. [Figure 7] Figure 7 illustrates a flow chart of a method for detecting a fault according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

[0031] Figure 1 non-limitatively illustrates the application of the invention to an internal combustion engine of a vehicle, which is a diesel engine here.

[0032] Engine 1 is conventionally provided with an intake line that includes an intake manifold 2 connected on the other side to a cylinder (three in the illustrated example) and to a butterfly housing 3 that allows adjustment of the amount of outside air taken in. The butterfly housing 3 is connected to the outside air intake via at least one pipe 4.

[0033] Engine 1 is provided with an exhaust line comprising an exhaust manifold 5 connected to a cylinder on one end and to a vent on the other. The exhaust line comprises a particle filter referred to as PF. The PF filter is associated with a differential pressure sensor (not shown) capable of measuring the pressure difference ΔP between the filter's inlet and outlet terminals.

[0034] Engine 1 also features a partial exhaust gas recirculation system at the engine's intake, called an EGR circuit (from the acronym for "exhaust gas recirculation"), which can take a portion of the exhaust gas from the exhaust line downstream of the particle filter PF, reduce its temperature via a heat exchanger 6, and then recirculate it back into the intake line. The EGR circuit is equipped with an EGR valve 7 for controlling the flow of the recirculated gas.

[0035] In the embodiment shown in Figure 1, the engine 1 is provided with a turbocharger 8 whose compressor section 8a is located in the outside air intake line upstream of the butterfly housing 3 in order to increase the outside air supply pressure of the engine 1. The turbine section 8b is located in the exhaust line so as to be driven by the exhaust gas. The EGR circuit may be at a low pressure, as shown in Figure 1, if the EGR circuit is located upstream of the compressor 8a and downstream of the turbine 8b. If the EGR circuit is located downstream of the compressor 8a and upstream of the turbine 8b, it may be at a high pressure.

[0036] When such an EGR circuit is present, the engine butterfly housing 3 is used to regulate the total intake gas flow rate of the engine, which includes the outside air flow rate and the recirculated gas flow rate.

[0037] The flow rate of the recirculated gas can be adjusted by the EGR valve 7, and the flow rate of the air entering the engine is indirectly obtained by the difference. In a modified example, the airflow rate can also be directly adjusted independently by adjusting the intake valve 9 of the intake circuit to obtain a desired flow rate setpoint. The flow rate of the recirculated gas is indirectly obtained by the difference between the total flow rate and the outside air flow rate.

[0038] The total flow rate of gas entering the engine is obtained by adjusting the pressure value that spreads within the intake manifold 2 of engine 1, taking into account the temperature and filling model.

[0039] To achieve this, a pressure sensor 2a and a temperature sensor 2b are provided within the intake manifold 2. The pressure is adjusted by adjusting the position of the butterfly housing 3.

[0040] If the engine does not have an EGR circuit (not shown), there is generally only one butterfly housing 3 to regulate only the flow of gas entering the engine, which is the flow of outside air. Intake valve 9 is not provided.

[0041] Engine 1 is equipped with a system 11 for controlling the engine's pollutant emissions. The control system 11 includes measuring means 12, calculating means 13, and controlling means 14.

[0042] The measuring means 12 is configured to measure engine operating parameters, particularly those related to flow rate, temperature, and pressure in the engine's intake and exhaust circuits.

[0043] The calculation means 13 is configured to estimate the soot mass of the PF filter from the information from the measuring means 12.

[0044] The control means 14 is configured to control the regeneration of the PF filter when the estimated soot mass of the filter exceeds a predetermined threshold mass. Typically, the control means 14 includes a temperature controller at the inlet of the PF filter, configured to control the motor settings according to a temperature setpoint Tcs required to regenerate the filter, depending on the mass contained in the filter.

[0045] The control system 11 further includes a memory module (not shown).

[0046] The control system 11 includes means for determining a first maximum temperature T1, a second maximum temperature T2, and a third maximum temperature T3.

[0047] The determination of the first maximum temperature T1 at the inlet of the PF filter is performed from a predetermined map available in the system's memory module, according to the engine's instantaneous operating point.

[0048] For example, the mapping connects each operating point of engine 1 to the highest temperature at the inlet of the PF filter, taking into account the values ​​of engine adjustment parameters such as injection phase adjustment and injection flow rate (closer or slower). Such a mapping can be obtained by an identification procedure performed after a preliminary stabilization stage, particularly on an engine bench.

[0049] The first maximum temperature T1 represents an estimate of the highest achievable temperature at the inlet of the PF filter of a defect-free engine, including a dispersed engine, i.e., including components at the limits of manufacturing tolerances.

[0050] However, the first maximum temperature T1 can only be reached after a sufficiently long time, taking into account the dynamics of the temperature controller and the thermal inertia of the exhaust circuit related to its mass.

[0051] Therefore, at each point in the regeneration of the particle filter, it is useful to filter a first maximum temperature T1, for example, according to a measurement of the engine's exhaust flow rate, in order to determine a second maximum temperature T2, which represents the maximum filtering temperature achievable at the inlet of the PF filter of an engine without any defects at the engine's current operating point.

[0052] The second highest temperature T2 is likely to exceed the temperature setpoint Tcs required at the PF filter inlet for filter regeneration.

[0053] Therefore, it is effective to determine a third maximum temperature T3 at the inlet of the PF filter that corresponds to the minimum value between the second maximum temperature T2 and the value of the temperature setpoint Tcs required by the means 14 for controlling the regeneration of the filter.

[0054] The third maximum temperature, T3, represents a realistic and achievable estimate of the temperature at the PF filter inlet for a non-faulty engine.

[0055] In other words, the third maximum temperature T3 is an estimate of the PF filter inlet temperature that can be reached by a non-faulty engine, regardless of the engine's operating point or the vehicle's driving profile.

[0056] Figure 2 shows the changes over time of the first maximum temperature T1, the second maximum temperature T2, and the third maximum temperature T3 according to a driving profile corresponding to the vehicle speed 15, which are shown in parallel. In this figure, curves 16 and 17 represent the temperature measured at the inlet of the PF filter and the temperature setpoint Tcs required by the control means 14, respectively.

[0057] The calculation means 13 is configured to calculate the deviation between the third highest temperature T3 and the temperature measurement 16 at the inlet of the PF filter.

[0058] The calculation means 13 is configured to detect a failure in the control system when the calculated deviation exceeds a predetermined threshold deviation, particularly during a predetermined abnormally high duration.

[0059] Therefore, by excluding cases where the lack of regeneration efficiency is related to the vehicle's driving profile and thus to an engine operating point where the required temperature Tcs at the particle filter inlet is simply unattainable, it becomes possible to detect failures in the engine pollutant emission control system.

[0060] In one embodiment, the calculation means 13 is configured to calculate a total failure time, which represents the sum of each elapsed time between fault detection and the time when the calculated deviation becomes less than or equal to a predetermined threshold deviation.

[0061] Figure 3 illustrates the calculation of the total failure time.

[0062] In drawings, the same reference numeral is used to indicate the same element.

[0063] In the example shown in Figure 3, curve 19 represents the measurement and modeling errors and is offset relative to curve T3 by a temperature value equal to a predetermined threshold deviation or a safety margin 18. Curve 20 illustrates the change in total failure time. Note that the total failure time increases when the temperature measured at the inlet of the PF filter, represented by curve 16, is lower than the corresponding value in curve 19. In other words, the total failure time at a given time represents the sum of all times when the deviation between the temperature measured at the inlet of the PF filter and the third maximum temperature T3 was greater than the safety margin 18.

[0064] In another embodiment, the calculating means 13 is configured to calculate the total enthalpy deficit received by the PF filter for each time period elapsed between fault detection and the moment when the calculated deviation falls below a predetermined threshold deviation, representing the sum of each integral over time of the product of the instantaneous exhaust flow and the difference between the calculated deviation and the predetermined threshold deviation.

[0065] Figure 4 illustrates the calculation of the total enthalpy deficit received by the PF filter. Curve 21 represents the change in the total enthalpy deficit received by the PF filter. The total deficit corresponds to the sum of each integral over time of the product of the instantaneous exhaust flow and the deviation between curves 19 and 16 for each time period elapsed between fault detection and the moment when the calculated deviation again falls below a predetermined threshold deviation. To facilitate the calculation, each area 22 can be discretized into sufficiently small time intervals such that the exhaust flow rate is considered to be constant over each interval.

[0066] Alternatively, the calculation means 13 may be configured to calculate both the total enthalpy deficit and the total failure time received by the filter.

[0067] The control system 11 includes means for transmitting a message or alert signal when the total failure time exceeds a predetermined threshold duration and / or when the total enthalpy deficit received by the filter exceeds a predetermined threshold enthalpy deficit.

[0068] The method for detecting a malfunction in the hazardous substance emission suppression system according to the present invention is represented by the flowchart shown in Figure 5.

[0069] During the first step 23, the first maximum temperature T1 at the inlet of the PF filter is determined from a predetermined map available in the control system's memory module, according to the engine's instantaneous operating point. The operating point generally corresponds to parameters representing engine operation, such as speed and load. The determination of the operating point is generally available from a higher-level control unit (not referenced).

[0070] During the second step 24, a second maximum temperature T2 at the filter inlet is determined from the first maximum temperature T1, taking into account the thermal inertia of the exhaust circuit and according to the measured exhaust flow rate of the engine.

[0071] During the third step 25, a third maximum temperature T3 at the filter inlet is determined, which corresponds to the minimum value between the second maximum temperature T2 and the temperature setpoint Tcs value from the control means 14 of the system 11.

[0072] The method then proceeds to step 26, which involves calculating the deviation between the third highest temperature T3 and the temperature measurement at the filter inlet.

[0073] In the next step, 27, it is determined whether the calculated deviation exceeds a predetermined deviation threshold.

[0074] If this is positive, a failure in the control system is detected (step 28). The method then returns to step 23 of the first step.

[0075] If this is negative, the method returns to step 23 of the first step.

[0076] The sequence of steps 23 through 28, referenced in 29, allows for monitoring of the normal operation of the control system.

[0077] As shown in Figure 6, the method further comprises a time calculation step 30, in which the total failure time is calculated, which represents the sum of each time elapsed between the detection of a fault and the time when the calculated deviation is less than or equal to a predetermined threshold deviation.

[0078] In the next step, 31, it is determined whether the total failure time exceeds a predetermined threshold duration. Note that if particle filter regeneration is interrupted (for example, by engine shutdown), the time threshold may be adjusted, with temperature deviation, to the actual time spent on regeneration.

[0079] If the result is positive, the method proceeds to step 32, which involves issuing a message or warning signal intended to alert the driver to a system malfunction.

[0080] If this is negative, the process returns to step 23.

[0081] As illustrated in Figure 7, the method may include a step 33 for calculating the total enthalpy deficit received by the filter, in which the sum of each integral over time of the product of the exhaust flow and the difference between the calculated deviation and the predetermined threshold deviation is calculated for each time period elapsed between fault detection and the moment when the calculated deviation falls below a predetermined threshold deviation.

[0082] In the next step, 34, it is determined whether the total enthalpy deficit received by the filter exceeds a predetermined threshold enthalpy deficit. Note that if the particle filter regeneration is interrupted (for example, by engine shutdown), the enthalpy deficit threshold may be adjusted for the time actually spent on regeneration.

[0083] If the result is positive, the method proceeds to step 32, which involves issuing a message or warning signal intended to alert the driver to a system malfunction.

[0084] If this is negative, the process returns to step 23.

[0085] As a variation, the method still allows for the execution of step 30, which calculates the time, and step 33, which calculates the total deficit of the received enthalpy, in parallel, and for the merging of steps 31 and 34.

[0086] As a variation, it is still possible to perform step 32, which involves sending a message or warning signal, immediately after step 28, which involves detecting a fault.

Claims

1. A method for detecting a malfunction in a system (11) that monitors pollutant emissions from a diesel engine (1) of an automobile equipped with a particle filter (PF), - A step of determining a first maximum temperature (T1) at the inlet of the filter (PF) according to the instantaneous operating point of the engine (1), - A step of determining the second maximum temperature (T2) at the inlet of the filter (PF) from the first maximum temperature (T1) based on the measured exhaust flow rate of the engine (1), - A step of determining a third maximum temperature (T3) at the inlet of the filter (PF) that corresponds to the minimum value between the second maximum temperature (T2) and the value of the temperature setpoint (Tcs) from the control means (14) of the system (11), - A step of calculating the deviation between the third highest temperature (T3) and the measured filter inlet temperature (PF), A method characterized by comprising the step of detecting a failure of the control system (11) when the calculated deviation exceeds a predetermined threshold deviation.

2. The method according to claim 1, further comprising a time calculation step, wherein a total failure time is calculated, which represents the sum of each elapsed time between the detection of the failure and the time when the calculated deviation becomes less than or equal to a predetermined threshold deviation.

3. The method according to claim 2, further comprising the step of issuing a message or alert signal that is executed when the total failure time exceeds a predetermined threshold time.

4. The method according to claim 1, further comprising the step of calculating the total enthalpy deficit received by the filter (PF), wherein the sum of each time integral of the product of the exhaust flow and the difference between the calculated deviation and the predetermined threshold deviation is calculated for each time elapsed between the detection of the fault and the time when the calculated deviation becomes less than or equal to the predetermined threshold deviation.

5. The method according to claim 4, further comprising the step of sending a message or alert signal that is to be executed when the total enthalpy deficit received by the filter exceeds a predetermined threshold enthalpy deficit.

6. A control system (11) for pollutant emissions from a diesel engine (1) of an automobile equipped with a particulate filter (PF), - Means (12) for measuring the exhaust flow rate of the engine, the volumetric flow rate through the filter, the pressure difference between the inlet and outlet terminals of the filter, and the temperature at the inlet of the filter, - A calculation means (13) that can estimate the soot mass of the filter from the information from the measuring means, - A control means (14) configured to control the regeneration of the particle filter when the estimated soot mass of the filter exceeds a predetermined threshold mass, - Means for determining the first maximum temperature (T1) at the inlet of the filter (PF) according to the instantaneous operating point of the engine (1), - A means for determining the second maximum temperature (T2) at the inlet of the filter (PF) from the first maximum temperature (T1) according to the measured value of the exhaust flow rate of the engine (1), - The system is characterized by comprising means for determining a third maximum temperature (T3) at the inlet of the filter (PF), which corresponds to the minimum value between the second maximum temperature (T2) and the temperature setpoint value required by the control means (14) for regenerating the filter. The calculation means (13) is configured to calculate the deviation between the third highest temperature (T3) and a measured value of the filter inlet temperature, and is configured to detect a failure of the control system (11) when the calculated deviation exceeds a predetermined threshold deviation.

7. The system according to claim 6, wherein the calculating means (13) is configured to calculate a total failure time, which represents the sum of each elapsed time between the detection of the failure and the time when the calculated deviation becomes less than or equal to the predetermined threshold deviation.

8. The system according to claim 6, wherein the calculating means (13) is configured to calculate the total enthalpy deficit received by the filter (PF) for each time period elapsed between the detection of the fault and the time during which the calculated deviation becomes less than or equal to the predetermined threshold deviation, the sum of each integral over time of the product of the exhaust flow and the difference between the calculated deviation and the predetermined threshold deviation.

9. The system according to any one of claims 6 to 8, comprising means for transmitting a message or a warning signal.

10. An automobile equipped with a diesel internal combustion engine (1) that carries out the method according to any one of claims 1 to 5, or an automobile equipped with a pollutant emission control system (11) according to any one of claims 6 to 9.

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