JP4744529B2 - Device for estimating the amount of particulates present in automobile particulate filters - Google Patents

Description

  The present invention relates to an apparatus and method for estimating the amount of particulates present in a particulate filter of an automobile, particularly an automobile equipped with a diesel engine.

  Internal combustion engines, especially diesel-type internal combustion engines, emit pollutant particulates into the atmosphere, but the amount of particulates should be reduced. The fine particles consist of soot generated by incomplete combustion in the internal combustion engine, and the fine particles in the exhaust gas are removed by providing a fine particle filter in the exhaust pipe downstream of the combustion chamber of the internal combustion engine. This filter is designed to stop particulates present in the exhaust gas passing through the filter. Due to the operation of the internal combustion engine, particulates are accumulated in the filter, and a high back pressure is generated in the exhaust gas. Further, the differential pressure across the particulate filter is increased, and the performance of the internal combustion engine is considerably deteriorated.

  In order to recover the performance of an internal combustion engine, it is known to regenerate a filter by burning accumulated particulates. This combustion operation can be performed by increasing the internal temperature of the particulate filter. This can generally be achieved by delaying fuel injection into the combustion chamber of the internal combustion engine. The fuel is injected particularly immediately after the top dead center of the exhaust stroke, thereby increasing the temperature of the exhaust gas. The delayed injection after the top dead center may be performed once or a plurality of times. The fuel thus injected does not burn in the combustion chamber of the internal combustion engine, but burns in, for example, a catalytic reaction device provided in the exhaust pipe, and the temperature of the gas passing through the particulate filter rises.

  The particulate filter is provided together with a catalytic reaction device provided upstream of the filter, and the particulate filter reduces the discharge of harmful substances. The catalytic reactor can be integrated with the particulate filter, and the catalytic reactor has a catalytic material such as platinum. Non-combustible hydrocarbons and carbon monoxide, which are injected with a delay and are generated by a slow injection into the combustion chamber, are oxidized by the catalytic substance and raise the temperature in the particulate filter.

  The particulate filter is regenerated periodically during the regeneration process as soon as the amount of particulate in the filter increases. The regeneration process occurs during operation of the internal combustion engine without the driver being aware of it.

  Conventionally, there are two stages to regularly operate a particulate filter in this manner. In the first stage, the filter accumulates particulates emitted from the internal combustion engine, and in the second stage, the particulates accumulated in the filter are burned to regenerate the filter.

  A system that estimates the amount of particulates present in the particulate filter from the exhaust back pressure, ie, the pressure difference across the particulate filter, that is, the differential pressure, is useful.

  The document FR2781251 relates to a method for determining the amount of soot collected in a particulate filter provided downstream of an internal combustion engine. The filter is periodically regenerated by burning the soot before it accumulates excessively. The degree of soot accumulation is determined from the differential pressure across the filter and the amount A representing the gas flow of the internal combustion engine.

Document EP1281834 describes a method of determining the amount of soot collected in a particulate filter provided downstream of an internal combustion engine. The filter is periodically regenerated by burning the soot before it accumulates excessively. The degree of soot accumulation is determined from the differential pressure across the filter and the quantity Q _vol representing the gas passing through the particulate filter. The degree of soot accumulation is determined by the equation ΔP = f (Q _vol , m) where m is the mass of soot accumulated in the particulate filter.
FR2781251 EP1281834

However, these documents do not take into consideration that the degree of soot accumulation in the particulate filter is not uniform due to a chemical reaction called passive regeneration: NO ₂ + C → CO + NO. This reaction takes place at temperatures that occur when the car is traveling outside the city (350-500 ° C. upstream of the particulate filter). This reaction causes a sharp drop in the differential pressure across the particulate filter, although the particulates are not actually burning. A drop in the differential pressure across the particulate filter makes the estimation of the degree of filter soot accumulation inaccurate and damages the particulate filter. In fact, the estimated soot mass is less than the actual soot mass, and an excessive combustion reaction occurs during regeneration due to the combustion of the filter, resulting in damage to the particulate filter.

The present invention is directed to avoiding the risk of particulate filter breakage during regeneration due to combustion, taking into account the effects of chemical passive regeneration reactions.

  According to one aspect of the present invention, a system for estimating the amount of particulates present in a particulate filter of an automobile that is periodically regenerated by combustion, the pressure sensor measuring a differential pressure across the particulate filter; There is provided an electronic control unit having means for estimating or measuring the volumetric flow rate of the gas upstream of the particulate filter. The electronic control unit is provided by a storage mapping indicating the relationship between the differential pressure across the particulate filter and the volumetric flow rate of gas upstream of the particulate filter and the amount of particulate present in the particulate filter, and the pressure sensor. From the value of the differential pressure at both ends of the particulate filter, the differential pressure at both ends of the particulate filter is reduced, and the differential pressure is greater than the predetermined pressure drop at a time interval shorter than the predetermined time interval. Detecting means for detecting a decrease. In the electronic control unit, the detection means may decrease the differential pressure across the particulate filter, and may decrease the differential pressure greater than a predetermined pressure decrease at a time interval shorter than a predetermined time interval. An estimator that, when detected, estimates the amount of particulate present in the particulate filter from the stored mapping and a differential pressure value across the particulate filter provided by the pressure sensor;

Even if a chemical reaction called passive regeneration occurs, the estimated amount of particulate present in the particulate filter is accurate. For this reason, it is possible to eliminate the risk of damage to the particulate filter due to excessive filter regeneration combustion reaction by estimating the amount of particulate present in the filter to be small.

  In a preferred embodiment, the detection means detects the start time of the decrease in the differential pressure across the particulate filter and the end time of the decrease in the differential pressure across the particulate filter.

In an advantageous embodiment, the estimator estimates the amount of particulates present in the particulate filter from the stored mapping and a maximum value of the estimated amount of particulates present in the particulate filter prior to the start time. In this embodiment, the estimator estimates the amount of particulates present in the particulate filter by summing the maximum value and the amount of particulates accumulated in the particulate filter after the end time.

  Conveniently, the estimator estimates the amount of particulate collected in the particulate filter after the end time from the stored mapping.

  For example, the predetermined pressure drop is 50 to 500 mbar, and the predetermined time interval is 10 to 100 s.

  According to another aspect of the invention, a method is provided for estimating the amount of particulates present in a particulate filter of an automobile that is periodically regenerated by combustion. In this method, a stored mapping is used which shows a function of the differential pressure across the particulate filter and the volumetric flow rate of gas upstream of the particulate filter and the amount of particulate present in the particulate filter. From the value of the differential pressure at both ends of the particulate filter, a decrease in the differential pressure at both ends of the particulate filter that is greater than a predetermined pressure decrease at a time interval shorter than a predetermined time interval. To detect. Further, when a drop in differential pressure across the particulate filter is detected that is greater than a predetermined pressure drop at a time interval shorter than a predetermined time interval, the storage mapping and the fine particle are detected. From the value of the differential pressure across the filter, the amount of the fine particles present in the fine particle filter is estimated.

  In a preferred implementation, the start time and the end time of the drop in the differential pressure across the particulate filter are detected.

  Conveniently, the amount of particulate present in the particulate filter is estimated from the stored mapping and a maximum of an estimated amount of particulate present in the particulate filter prior to the start time.

Other objects, features and advantages of the present invention will become apparent by reading the description given solely as a non-limiting example with reference to the accompanying drawings. In the accompanying drawings,
FIG. 1 is a schematic diagram showing one embodiment of the apparatus of the present invention;
FIG. 2 is a diagram showing a decrease in differential pressure across the particle filter of the present invention,
FIG. 3 is a diagram showing the operation of the present invention.

  As shown in the figure, the internal combustion engine 1 schematically shown has a plurality of combustion chambers, and such a combustion chamber 2 is shown in the upper part of the inside of a cylinder 3 in which the piston 4 in the figure moves. The intake valve 5 controls intake air by opening and closing an intake duct 6 connected to the combustion chamber 2. The exhaust valve 7 is used to open and close an exhaust gas passage from the combustion chamber 2 to the exhaust pipe 8.

  Atmospheric pressure fresh air enters the pipe 10 as indicated by arrow 9. The air pressure is increased by the compressor 11 provided in the pipe 10. The compressor is provided on a shaft 12 shared with the turbine 13. In this example, the turbine 13 is provided on the exhaust pipe 8. The exhaust gas that passes through the turbine 13 drives the compressor 11 and increases the pressure of the air entering the combustion chamber 2 via the intake duct 6.

  As illustrated, the internal combustion engine has a system for reintroducing a portion of the inlet exhaust gas. For this purpose, the branch pipe 14 is connected upstream of the turbine 13 of the exhaust pipe 8. A control valve 15, called an “EGR valve”, controls the amount of exhaust gas, which is reintroduced into the intake duct 6 via line 16 and then mixed appropriately in the mixing chamber 17. An adjustment guide flap 18 is provided downstream of the compressor 11 in the compressed air intake line 10 and upstream of the mixing chamber 17.

  The exhaust pipe 19 connects the outlet of the turbine 13 to the atmosphere, that is, the exhaust gas outlet 20. A catalytic reaction device 21 is provided downstream of the turbine 13 of the exhaust pipe 19, and a particulate filter 22 is provided downstream of the catalytic reaction device 21 of the exhaust pipe 19. The particulate filter 22 is of a conventional type, and has means for, for example, electrostatically removing particulates discharged from the internal combustion engine 1 and carried to the exhaust pipe 19 by exhaust gas. The silencer 23 is provided downstream of the particulate filter in order to limit exhaust noise.

  The electronic control unit 24 coordinates the operation of the internal combustion engine 1 and receives predetermined data of the operation of the internal combustion engine 1 for this purpose. Various sensors (not shown) are provided in the pipe, and signals from the sensors are transmitted to the electronic control unit 24.

  The electronic control unit 24 can in particular control the position of the EGR valve 15 by a connection 25 and the position of the movable flap 18 by a connection 26. Further, the electronic control unit controls the fuel injection device 27 by the connection 28.

In order to estimate the amount of particulates present in the particulate filter 22, the apparatus has a differential pressure sensor 29 that can measure the pressure difference across the particulate filter 22, ie, the differential pressure P _diff, and the electronic control unit 24 includes A module 30 is provided for estimating the volumetric flow rate Q _vol of the gas upstream of the particulate filter 22 from the available data. These data are, for example, the fresh air intake flow rate of the internal combustion engine, the recirculation flow rate by the EGR valve, and the internal combustion engine operation data. The pressure sensor 29 is connected to the electronic control unit 24 by a connection 31.

In an alternative embodiment, instead of the module 30 for estimating the volumetric flow rate Q _vol of the gas upstream of the particulate filter 22, a flow meter, temperature sensor and pressure sensor provided upstream of the particulate filter 22 are used. May be.

The electronic control unit 24 has an estimator 32 for the amount of particulates present in the particulate filter 22, the differential pressure P _diff across the particulate filter 22, the volumetric flow rate Q _vol of the gas upstream of the particulate filter 22, and the particulate filter 22. Storage mapping 33 showing the relationship with the amount of particles present in the.

Furthermore, the electronic control unit 24 includes a detection module 34 for detecting a decrease in the differential pressure _{P diff} across the particulate filter 22, the opposite ends of the particulate filter 22 supplied by the pressure sensor 29 of the differential pressure _{P diff} From the value, it is detected that the decrease in the differential pressure P _diff is larger than the predetermined pressure decrease at a time interval shorter than the predetermined time interval. The predetermined pressure drop is, for example, 50 to 500 mbar, and the predetermined time interval is 10 to 100 s.

  The estimator 32 estimates the amount of particulates present in the filter from the value of the differential pressure across the particulate filter 22 supplied by the storage mapping 33 and the pressure sensor 29.

FIG. 2 shows a decrease in the differential pressure P _diff across the particulate filter 22, and the decrease in the differential pressure is greater than the predetermined pressure drop in a time interval shorter than the predetermined time interval. This, for example, shows a decrease in the differential pressure _{P diff} differential pressure _{P diff} across the particulate filter 22 is decreased from the value _{P 1} to lower _{P 2} than _{P 1.} Here, the difference P ₁ -P ₂ is larger than a predetermined pressure drop. Further, when the start time of the reduction of the differential pressure P _diff t _d, the end time and t _f, the time interval between the start time t _d and the end time t _f is shorter than the time interval set in advance. Time t ₂ is a time approaching the start time t _d , and a transient phenomenon with a small change in the differential pressure P _diff occurs between the time t ₂ and the time t _d . Time t ₁ is a time approaching the end time t _f , and a transient phenomenon with a small change in the differential pressure P _diff occurs between the time t _f and the time t ₁ . The time t indicates a time interval of operation of the internal combustion engine 1 and is a time considering the end time of the previous regeneration due to the combustion of the particulate filter 22.

Following the reduction of the differential pressure shown in FIG. 2, the operation of the estimator is illustrated in FIG.

FIG. 3 shows curves m ₁ , m ₂ , m ₃ that are the amount (mass) of particulates present in the filter as a function of the differential pressure P _diff across the particulate filter and the volumetric flow rate Q _vol of the gas upstream of the particulate filter. , M ₄ and m ₅ are shown. In this example, m ₁ <m ₂ <m ₃ <m ₄ <m ₅ . Since the particulate filter 22 has two distinct particulate quantities at two distinct operating times of the internal combustion engine 1, each of these curves is represented by times t ₁ , t ₂ , t ₃ , t ₄ and t ₅ , respectively. Related.

Detection module 34 may detect the start time _{t d} and the end time _{t f} of decrease in the differential pressure _{P diff} across the particulate filter 22.

Estimator 32, before the start time _{t d,} that is, the maximum value _M A of the estimated amount of the fine particles present in the particulate filter 22 to the time _{t 2,} the corresponding value P across the differential pressure _{P diff} of the particulate filter 22 _1, and stores the corresponding value to _{Q 1} volume flow _{Q vol} upstream of the gas of the particulate filter 22. The maximum value _{M A} of the estimated amount of the fine particles present in the particulate filter 22, stored mapping 33, _P 1 of the pressure difference _{P diff} across the particulate filter 22, and, Q volumetric flow rate _{Q vol} upstream of the gas of the particulate filter _{1 is} determined.

Further, the estimator 32, the amount _{M B} of the fine particles present in the particulate filter 22 to the time _{t 1,} the pressure difference _{P diff} value _P 2 of the opposite ends of the particulate filter 22, and the volume flow rate of the gas upstream of the particulate filter 22 stores the value _{Q 2} of Q _vol.

Then, the estimator 32, the amount of fine particles present in the particulate filter 22 by adding to the previous maximum value M _A of the amount of accumulated particulate on the particulate filter 22, the start time t _d after the end time t _f presume. The amount accumulated in the particulate filter 22 after the end time t _f is equivalent to the estimated increase in the amount of the fine particles from the minimum value M _B of the amount of fine particles after the end time t _f. In other words, the amount accumulated in the particulate filter 22 after the end time t _f is the difference between the amount and the amount M _B of particulate estimated at time t. The maximum value M _A and the minimum value M _B correspond to values in a stable state excluding an unstable state period in which the pressure difference across the filter 22 decreases.

In this _example, the M A = _{m 2,} is a M B = _{m 1,} the amount or mass of the corresponding particle is calculated by the general interpolation curve m _i stored mapping 33.

The present invention is useful for accurately estimating the amount of particulates present in the particulate filter from the differential pressure at both ends of the particulate filter. In consideration of a chemical passive regeneration reaction that occurs in a drive outside a city, the particulate filter It is useful to activate regeneration by burning the particulate filter to avoid failure.

It is the schematic which shows one Embodiment of this invention apparatus. It is a figure which shows the fall of the differential pressure | voltage of both ends of the particulate filter of this invention. It is a figure which shows the effect | action of this invention.

Claims (9)

A system for estimating the amount of particulates present in a particulate filter (22) of an automobile that is periodically regenerated by combustion, and measuring a differential pressure (P _diff ) across the particulate filter (22) ( 29), means (30) for estimating or measuring the volumetric flow rate (Q _vol ) of the gas upstream of the particulate filter (22), and an electronic control unit (24),
The electronic control unit (24)
The differential pressure (P _diff ) across the particulate filter (22) and the volumetric flow rate (Q _vol ) of the gas upstream of the particulate filter (22) and the amount of particulate present in the particulate filter (22). A storage mapping (33) indicating the relationship;
A reduction in the differential pressure across the particulate filter (22) from the value of the differential pressure (P _diff ) across the particulate filter (22) provided by the pressure sensor (29) Detection means (34) for detecting a drop in the differential pressure that is greater than a predetermined pressure drop in a time interval shorter than the time interval;
The detection means (34) is a reduction in the differential pressure (P _diff ) across the particulate filter (22) and is greater than the predetermined pressure drop in a time interval shorter than the predetermined time interval; When a drop in differential pressure is detected and it is determined that a passive regeneration reaction has occurred, the differential pressure (P _diff ) across the storage filter and the particulate filter (22) provided by the pressure sensor (29) And an estimator (32) for estimating the amount of particulates present in the particulate filter (22) from the value. The detection means (34) is the particulate filter (22) at both ends of the differential pressure _{(P diff)} decreases the start time of the _{(t d),} reduction in the differential pressure _{(P diff)} of both ends of the particulate filter (22) The system according to claim 1, wherein an end time (t _f ) is detected. The amount of the fine particles the estimator (32) is present in the starting time (t _d) estimating the amount of the maximum value of the fine particles present in the particulate filter (22) before the particulate filter from the (M _A) (22) The system according to claim 2, wherein the system is estimated. The estimator (32) is present in the particulate filter (22) by summing the maximum value (M _A ) and the amount of the particulate accumulated in the particulate filter (22) after the end time (t _f ). The system according to claim 3, wherein an amount of the fine particles to be estimated is estimated. The estimator (32) The system of claim 4, characterized in that to estimate the amount of the fine particles accumulated in the end time from the storage mapping (33) (t _f) the particulate filter after (22) .   6. The system according to claim 1, wherein the predetermined pressure drop is 50 to 500 mbar, and the predetermined time interval is 10 to 100 s. A method for estimating the amount of particulates present in a particulate filter (22) of an automobile that is periodically regenerated by combustion,
The relationship between the differential pressure (P _diff ) across the particulate filter (22) and the volumetric flow rate (Q _vol ) of the gas upstream of the particulate filter (22) and the amount of particulate present in the particulate filter (22); A storage mapping (33) indicating
_-A decrease in the differential pressure (P _diff ) at both ends of the particulate filter (22) from the value of the differential pressure (P _diff ) at both ends of the particulate filter (22), which is shorter than a predetermined time interval Detecting a drop in differential pressure that is greater than a predetermined pressure drop in the interval; and-a drop in differential pressure (P _diff ) across the particulate filter (22) that is shorter than a predetermined time interval When a drop in differential pressure greater than a predetermined drop in pressure is detected in the interval and it is determined that a passive regeneration reaction has occurred, the differential pressure across the storage mapping (33) and the particulate filter (22) (P A method of estimating the amount of the fine particles existing in the fine particle filter (22) from the value of _diff ). The method according to claim 7, wherein a start time (t _d ) and an end time (t _f ) of a decrease in the differential pressure (P _diff ) across the particulate filter are detected. The amount of the fine particles existing in the fine particle filter (22) is estimated from the maximum value (M _A ) of the estimated amount of the fine particles existing in the fine particle filter (22) before the start time (t _d ). The method according to claim 8.

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