JP2009138624A - Abnormality detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine whether an NOx clean-up rate is lowered due to the degradation of an NOx selective reduction catalyst or due to the abnormality of urea water. <P>SOLUTION: When the NOx selective reduction catalyst 15 is degraded, the clean-up rate NR is increased according to the rise of a catalyst temperature TC as shown by a curve B1. When the supply amount or quality of the urea water is abnormal, the NOx clean-up rate NR is uniformly lowered as shown by a curve C. The NOx clean-up rate NR is detected by catalyst temperatures TC<SB>1</SB>, TC<SB>2</SB>, TC<SB>3</SB>. When the NOx clean-up rate NR is raised due to the rise of the catalyst temperature, the degradation of the catalyst occurs. When the clean-up rate is kept unchanged, the supply amount or quality of the urea water is considered to be abnormal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an abnormality detection device for an internal combustion engine.

A NO _x selective reduction catalyst is arranged in the engine exhaust passage, and urea water is supplied to the NO _x selective reduction catalyst so that NO _x contained in the exhaust gas is selectively reduced by ammonia generated from the urea water. In an internal combustion engine, a sensor capable of detecting ammonia or the like generated from urea water is disposed in the engine exhaust passage downstream of the NO _x selective reduction catalyst, and the change in the output signal of the sensor when the supply amount of urea water is changed An internal combustion engine is known in which it is determined that a defect exists when the change is different from the expected change (see, for example, Patent Document 1).
JP 2004-176719 A

However, even when the supply amount or quality of urea water deviates from the normal value, the change in the output signal of the sensor is different from the predicted change, and the output signal of the sensor is predicted even when the NO _x selective reduction catalyst deteriorates. Since this is different from the change, there is a problem that such a method cannot judge whether the supply amount or quality of urea water deviates from the normal value or whether the NO _x selective reduction catalyst has deteriorated.

In order to solve the above problem, according to the present invention, the NO _x selective reduction catalyst disposed in the engine exhaust passage deteriorates, so that the NO _x emission amount exceeds a predetermined regulation value or NO _x. In the internal combustion engine abnormality detection device for judging whether the amount or quality of urea water supplied to the selective reduction catalyst deviates from a normal value, the NO _x emission amount exceeds a predetermined regulation value, _the NO _x purification rate when the NO _x emissions exceeds the regulation value by _the NO _x selective reduction catalyst is degraded varies along the pattern of change increases as the temperature of the NO _x selective reduction catalyst increases, the urea water supply amount or _the nO _x purification rate when the quality nO _x emissions by deviating from the normal value exceeds the regulation value is variable along the pattern of change does not increase even if the temperature rise of the nO _x selective reduction catalyst However, to determine _the NO _x purification rate by detecting _the NO _x purification rate varies at a plurality of temperatures of _the NO _x selective reduction catalyst is changed along any of the change pattern, thereby _the NO _x selective reduction catalyst is degraded Thus, it is determined whether the NO _x emission amount exceeds the regulation value or whether the supply amount or quality of the urea water deviates from the normal value, and whether the NO _x emission amount exceeds the regulation value.

NO _x or selective reduction catalyst that exceeds the regulation value NO _x emissions predetermined by deterioration, or NO _x emissions predetermined by the supply amount or quality of aqueous urea is deviated from a normal value It is possible to reliably determine whether or not the limit value is exceeded.

FIG. 1 shows an overall view of a compression ignition type internal combustion engine.
Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 via the intake air amount detector 8. A throttle valve 10 driven by a step motor is disposed in the intake duct 6, and a cooling device 11 for cooling intake air flowing through the intake duct 6 is disposed around the intake duct 6. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 11, and the intake air is cooled by the engine cooling water.

On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the inlet of the oxidation catalyst 12. Downstream of the oxidation catalyst 12, a particulate filter 13 for collecting particulate matter contained in the exhaust gas is disposed adjacent to the oxidation catalyst 12, and an outlet of the particulate filter 13 is disposed via the exhaust pipe 14. To the inlet of the NO _x selective reduction catalyst 15. An oxidation catalyst 16 is connected to the outlet of the NO _x selective reduction catalyst 15.

The _the NO _x selective reduction catalyst 15 upstream of the exhaust pipe 14 is arranged urea water supply valve 17, the urea water supply valve 17 is connected to the supply pipe 18, the urea water tank 20 through a supply pump 19. The urea water stored in the urea water tank 20 is injected from the urea water supply valve 17 toward the dispersion plate 14a disposed in the exhaust pipe 14 by the supply pump 19, and ammonia generated from urea ((NH ₂ )). ₂ CO + H ₂ O → 2NH ₃ + CO ₂ ), NO _x contained in the exhaust gas is reduced in the NO _x selective reduction catalyst 15.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 21, and an electronically controlled EGR control valve 22 is disposed in the EGR passage 21. A cooling device 23 for cooling the EGR gas flowing in the EGR passage 21 is disposed around the EGR passage 21. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 23, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a common rail 25 via a fuel supply pipe 24, and this common rail 25 is connected to a fuel tank 27 via an electronically controlled fuel pump 26 with variable discharge amount. The fuel stored in the fuel tank 27 is supplied into the common rail 25 by the fuel pump 26, and the fuel supplied into the common rail 25 is supplied to the fuel injection valve 3 through each fuel supply pipe 24.

The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. The downstream side of the NO _x selective reduction catalyst 15 is arranged a temperature sensor 28 for detecting the temperature of the NO _x selective reduction catalyst 15, the downstream of the oxidation catalyst 16 for detecting the NO _x concentration in the exhaust gas A NO _x sensor 29 is arranged. Output signals of these temperature sensors 28, NO _x sensor 29 and the intake air amount detector 8 via the AD converter 37 each corresponding input to the input port 35.

  On the other hand, a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Is done. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. On the other hand, the output port 36 is connected to the fuel injection valve 3, the step motor for driving the throttle valve 10, the urea water supply valve 17, the supply pump 19, the EGR control valve 22, and the fuel pump 26 through corresponding drive circuits 38. .

The oxidation catalyst 12 carries a noble metal catalyst such as platinum, for example. The oxidation catalyst 12 functions to convert NO contained in the exhaust gas into NO ₂ and oxidize HC contained in the exhaust gas. . That is, NO ₂ is more oxidizable than NO. Therefore, when NO is converted to NO ₂ , the oxidation reaction of the particulate matter captured on the particulate filter 13 is promoted, and the NO _x selective reduction catalyst 15 The reduction action by ammonia is promoted. On the other hand, when HC is adsorbed on the NO _x selective reduction catalyst 15, the amount of ammonia adsorbed decreases, so the NO _x purification rate decreases. Thus the _the NO _x purification rate by oxidizing the HC by the oxidation catalyst 12 is reduced is prevented.

As the particulate filter 13, a particulate filter not supporting a catalyst can be used, or a particulate filter supporting a noble metal catalyst such as platinum can be used. The NO _x selective reduction catalyst 15 is composed of an ammonia adsorption type Fe zeolite having a high NO _x purification rate at a low temperature. The oxidation catalyst 16 carries a noble metal catalyst made of platinum, for example, and this oxidation catalyst 16 has an action of oxidizing ammonia leaked from the NO _x selective reduction catalyst 15.

In the embodiment shown in FIG. 1, the NO _x selective reduction catalyst 15 is activated at about 200 ° C., and after the NO _x selective reduction catalyst 15 is activated, it is necessary for reducing NO _x contained in the exhaust gas. An appropriate amount of urea water is supplied from the urea water supply valve 17. FIG. 2A shows that the NO _x selective reduction catalyst 15 is not deteriorated, and the supply amount of urea water is maintained at a normal value necessary for reducing NO _x in the exhaust gas, and the urea water is maintained. The graph shows the relationship between the NO _x purification rate NR and the temperature TC of the NO _x selective reduction catalyst 15 when the quality is maintained at a predetermined regular quality.

As can be seen from FIG. 2A, when the temperature TC of the NO _x selective reduction catalyst 15 rises to the activation temperature, the NO _x purification rate NR rapidly rises to the peak value, and the temperature TC of the NO _x selective reduction catalyst 15 further rises. Then, the NO _x purification rate NR is maintained at the peak value. Meanwhile when the catalyst temperature TC is relatively low, urea is supplied from the urea water supply valve 17 water once adsorbed on _the NO _x selective reduction catalyst 15 in the form of ammonia, NO _x in the exhaust gas in _the NO _x selective reduction catalyst 15 It reacts with the adsorbed ammonia and is reduced.

On the other hand, when the catalyst temperature TC increases, ammonia is no longer adsorbed by the NO _x selective reduction catalyst 15, and at this time, NO _x in the exhaust gas reacts with ammonia generated from urea water in the gas phase and is reduced. . FIG. 2B schematically represents this. That is, as shown in FIG. 2B, as the catalyst temperature TC increases, the rate of NO _x reduction reaction by adsorbed ammonia decreases and the rate of gas phase reaction of NO _x and ammonia increases.

By the way, different emission standards are set for each country or region with respect to the amount of NO _x emitted into the atmosphere. In this case, used as a criterion of total emissions normally NO _x emissions of the NO _x when the vehicle is operated in a predetermined mode, NO _x emissions after the vehicle, which is the period used predetermined Emission standards are set so that the amount is equal to or less than a predetermined reference amount.

Further, in addition to this emission standard, an emission regulation is set such that the NO _x emission amount must not exceed a predetermined regulation value. The regulation value is twice or three times, etc. of different but NO _x emission standard amount by country or region, when the NO _x emissions exceed the restriction value that turns on the alarm lamp indicating an abnormality location Some countries require it.

Taken up changes in supply amount or quality degradation and the urea water of the NO _x selective reduction catalyst 15 causes the NO _x emissions will increase abnormally in the present invention, NO _x emissions by _the NO _x selective reduction catalyst 15 is deteriorated beyond but what exceeds the regulation value set in advance, or the NO _x regulation value NO _x emissions predetermined amount or quality by deviates from a normal value of the urea water supplied to the selective reduction catalyst 15 I try to judge whether it was.

Next, this will be described with reference to FIGS. 2C, 3A, and 3B. FIG. 2 (C), the FIG. 3 (A), (B) shows an example where the regulation value is two times of the NO _x emission standards amount, these figures 2 (C), FIG. 3 (A), the broken line a shows the _the NO _x purification efficiency NR when the NO _x emission amount becomes NO _x emission standards amount in (B). That is, in other words, when the NO _x purification rate NR changes with respect to the catalyst temperature TC as shown by the broken line A in FIGS. 2 (C), 3 (A) and 3 (B), If the engine is operated in a predetermined mode, the NO _x emission amount at this time becomes the NO _x emission reference amount. Hereinafter, the NO _x purification rate NR indicated by the broken line A is referred to as a reference NO _x purification rate A.

Now, in FIG. 2 (C), NO _x removal efficiency NR is solid when the NO _x emissions by _the NO _x selective reduction catalyst 15 is deteriorated reaches the regulation value is two times of the NO _x emission standards amount The NO _x purification rate NR when the catalytic action of the NO _x selective reduction catalyst 15 is completely lost is indicated by a solid line B2. Here, the fact that the NO _x emission amount becomes twice the NO _x emission reference amount means that the NO _x purification rate has decreased to 50% compared to the case of the reference NO _x purification rate A, and accordingly. It can be said that the solid line B1 shows the case where the NO _x purification rate NR is 50% with respect to the reference NO _x purification rate A.

Meanwhile, the adsorption action of ammonia on the NO _x selective reduction catalyst 15 and the reduction action of NO _x by the adsorbed ammonia are governed by the activity of the catalyst. Thus when the reduction action of the NO _x by the adsorbed ammonia as shown in FIG. 2 (B) is dominant, that is, _the NO _x selective reduction catalyst 15 when the catalyst temperature TC is relatively low is deteriorated in FIG 2 (C) As indicated by the solid lines B1 and B2, the NO _x purification rate NR greatly decreases.

On the other hand, when the NO _x reduction action is performed in the gas phase, the NO _x reduction action is hardly governed by the activity of the catalyst. Therefore, as shown in FIG. 2B, when the NO _x reduction action in the gas phase becomes dominant, that is, when the catalyst temperature TC is relatively high, even if the NO _x selective reduction catalyst 15 deteriorates, FIG. ), The NO _x purification rate NR does not decrease so much as indicated by the solid lines B1 and B2.

That, _the NO _x purification efficiency NR when the NO _x selective reduction catalyst 15 deteriorates _the NO _x purification rate decreased 50% as shown in the solid line B1 becomes higher as the catalyst temperature TC is increased, NO at 450 ° or higher _{The x} purification rate NR is close to the reference NO _x purification rate A. On the other hand, NO _x removal efficiency NR even when the catalysis of _the NO _x selective reduction catalyst 15 is completely lost as shown in solid line B2 becomes higher as the catalyst temperature TC is increased, NO _x purification at 500 ° C. or higher The rate NR is 50% or more.

Next, a description will be given of a case where the NO _x purification rate NR decreases due to the supply amount or quality of urea water deviating from a normal value. The supply amount of urea water is predetermined according to the operating state of the engine. For example, when the supply amount decreases with respect to a predetermined normal value due to clogging of the nozzle port of the urea water supply valve 17, NO _{x is obtained.} The purification rate decreases. It can also be used low urea water of poor ammonia concentration of quality rather than the normal of the urea water, or other liquid to the urea water tank 20, for example, water or added _the NO _x purification rate decreases.

Figure 3 (A) is, NO _x removal efficiency NR when the supply amount or quality of aqueous urea NO _x emissions by deviating from the normal value has reached the regulated value which is twice of the NO _x emission standards amount Is shown by the solid line C. _The NO _x purification rate in comparison with the case NO _x emissions as described above is based _the NO _x purification rate A is that doubled of the NO _x emission standards amount it is indicative that fell to 50% Therefore, it can be said that the solid line C shows the case where the NO _x purification rate NR is 50% with respect to the reference NO _x purification rate A.

Ammonia amount required for the reduction of the NO _x regardless of the clogging and the supply amount of urea water when the concentration decrease is caused in the urea water nozzle opening of the urea water supply valve 17 is reduced uniformly at a constant rate, thus drawing 3, the NO _x purification rate NR uniformly decreases at a constant rate with respect to the reference NO _x purification rate A regardless of the catalyst temperature TC.

As can be seen by comparing FIG. 2 (C) and FIG. 3 (A), when the NO _x selective reduction catalyst 15 deteriorates and when an abnormality occurs in the supply amount or quality of urea water, the NO with respect to the catalyst temperature TC. _x Change pattern of purification rate NR is different. Therefore, it is possible to determine whether the NO _x selective reduction catalyst 15 has deteriorated or whether the supply amount or quality of the urea water has become abnormal by using the difference in the change pattern of the NO _x purification rate NR.

Therefore, in the present invention, the difference in the change pattern of the NO _x purification rate NR is utilized to determine whether the NO _x selective reduction catalyst 15 has deteriorated and the NO _x emission amount has exceeded a predetermined regulation value, or NO _x. selective reduction amount or quality of aqueous urea supplied to the catalyst 15 so that it is determined whether exceeds a regulation value NO _x emissions predetermined by deviating from a normal value. Next, this will be described with reference to FIG. 3B in which FIG. 2C and FIG. 3A are integrated.

FIG. 3B shows, as a representative example, whether the NO _x purification rate NR has decreased by 50% or more with respect to the reference NO _x purification rate A due to deterioration of the NO _x selective reduction catalyst 15, or urea water. supply amount or quality indicates a case where the determination as to whether or not _the NO _x purification efficiency NR is decreased by more than 50 percent with respect to the reference _the NO _x purification rate a by deviating from a normal value of.

In addition, when making such a determination based on FIG. 3B, the NO _x selective reduction catalyst 15 is slightly deteriorated and the supply amount or quality of the urea water becomes somewhat abnormal, and more than 50%. assuming that no generated nO _x supply amount of urea water that leads to a reduction of degradation and more than 50 percent of the nO _x purification rate of the nO _x selective reduction catalyst 15 that result in lowering of the purification rate or quality abnormalities simultaneously Yes.

When the first, _the NO _x selective reduction catalyst 15 will be described in which the reduction of the NO _x purification rate of 50 percent or more by deterioration occurs, at each catalyst temperature TC as is shown in FIG. 3 (B) in this case The NO _x purification rate NR is between the curve B1 and the curve B2. That is, as can be inferred from FIG. 3B, when the NO _x selective reduction catalyst 15 deteriorates and the NO _x purification rate decreases by 50% or more, no matter how many percent the NO _x purification rate is reduced, NO _{The x} purification rate NR changes along a change pattern that increases as the temperature TC of the NO _x selective reduction catalyst 15 increases.

In contrast, _the NO _x purification efficiency NR at each catalyst temperature TC if reduction of the NO _x purification rate of 50 percent or more by supply amount or quality of aqueous urea solution becomes abnormal occurs is as follows curve C. Figure 3 (B) No matter _the NO _x purification rate to decrease percentage as may be inferred from _the NO _x purification rate in this case is along the pattern of change temperature TC of the NO _x selective reduction catalyst 15 does not rise even increased Change. More specifically, if the NO _x selective reduction catalyst 15 is activated, the NO _x purification rate NR becomes substantially constant regardless of the temperature TC of the NO _x selective reduction catalyst 15.

Thus _the NO _x purification efficiency NR is accompanied not any change if grasped or varies along the pattern _the NO _x selective reduction _the NO _x purification rate of 50 percent or more by catalyst 15 is deteriorated to an increase in the catalyst temperature TC whether drop occurs, or by the supply amount or quality of aqueous urea solution becomes abnormal becomes possible to determine whether the resulting reduction of the NO _x purification rate of 50 percent or greater.

In this case, how different catalyst temperature _the NO _x selective reduction catalyst 15 by detecting the _the NO _x purification rate NR in TC along the changing pattern when degraded _the NO _x purification efficiency NR is changed, or aqueous urea It can be seen whether the NO _x purification rate NR changes along the change pattern when the supply amount or quality of the gas deviates from the normal value. Therefore, in the present invention, the NO _x purification rate NR at a plurality of different temperatures of the NO _x selective reduction catalyst 15 is detected, and the NO _x selective reduction catalyst 15 is deteriorated from these NO _x purification rates NR, whereby 50% or more of the NO _x is reduced. It is determined whether a reduction in the purification rate has occurred, or whether a reduction in the NO _x purification rate of 50% or more has occurred due to an abnormal supply amount or quality of urea water.

Generally speaking, as can be understood from the above explanation, when the NO _x emission amount exceeds the regulation value due to deterioration of the NO _x selective reduction catalyst 15, the NO _x purification rate NR is the temperature TC of the NO _x selective reduction catalyst 15. There vary along the pattern of change increases as increases, NO _x removal efficiency NR when the supply amount or quality of aqueous urea NO _x emissions by deviating from the normal value exceeds the regulation value is _the NO _x selective reduction Even if the temperature TC of the catalyst 15 rises, it changes along a change pattern that does not rise.

Therefore, in the present invention, the NO _x purification rate NR at a plurality of different temperatures TC of the NO _x selective reduction catalyst 15 is detected to determine along which change pattern the NO _x purification rate NR changes, thereby or NO _x emissions by _the NO _x selective reduction catalyst 15 is deteriorated that exceeds the regulation value, or whether the supply amount or quality of aqueous urea NO _x emissions by deviating from the normal value exceeds the regulation value Is determined.

Next, how to grasp the change pattern of the NO _x purification rate NR will be described with reference to FIG.
NO _x emission standards amount as emission standards of the NO _x emissions as described above is set, the reference time in this embodiment of the present invention NO _x emissions is the NO _x emission standard amount _the NO _x purification rate A Is stored in advance in the ROM 32 as a function of the temperature TC of the NO _x selective reduction catalyst 15.

To understand the change pattern of the NO _x purification rate NR in the present invention, reduction ratio of the NO _x removal efficiency NR from _the NO _x purification rate NR detected in a plurality of different temperatures to the reference _the NO _x purification rate A at each temperature sought, whether NO _x emissions by _the NO _x selective reduction catalyst 15 from the change in the reduction ratio of _the NO _x purification efficiency NR is degraded exceeds the regulation value, or the supply amount or quality of the normal value of the urea water By deviating from the above, it is determined whether the NO _x emission amount exceeds the regulation value.

Figure 3 reduction of the NO _x removal efficiency NR at different catalyst temperature TC _1, TC _2, TC ₃ of vary as _the NO _x purification efficiency NR is indicated by the curve B1 with respect to the catalyst temperature TC in (B) The ratios ΔNR ₁ , ΔNR ₂ , ΔNR ₃ are shown. Incidentally, _the NO _x purification at three different catalyst temperature TC _1, TC _2, the TC ₃ is to detect the _the NO _x purification rate NR has four or more of the catalyst temperature TC in the example shown in FIG. 3 (B) The rate NR may be detected. In some cases, the NO _x purification rate NR may be detected only at the two catalyst temperatures TC.

From With the decrease rate ΔNR such _the NO _x purification rate NR FIG. 3 (B), the higher the reduction ratio ΔNR of the NO _x removal efficiency NR at different temperatures TC _1, TC _2, TC ₃ temperature TC is higher When the decrease rate ΔNR of the NO _x purification rate NR is equal to or greater than a predetermined rate, it can be determined that the NO _x selective reduction catalyst 15 has deteriorated and the NO _x emission amount has exceeded the regulation value, and a plurality of different temperatures When the decrease rate ΔNR of the NO _x purification rate NR in TC ₁ , TC ₂ , and TC ₃ is substantially constant regardless of the temperature TC, and the decrease rate ΔNR of the NO _x purification rate NR is equal to or greater than a predetermined rate, urea It can be seen that the NO _x emission amount can be judged to have exceeded the regulation value when the water supply amount or quality deviates from the normal value.

In the embodiment according to the present invention, as described above, when determining whether or not the decrease rate ΔNR of the NO _x purification rate NR is equal to or higher than a predetermined rate, a plurality of different temperatures TC ₁ , TC ₂ , TC It is determined whether or not the average value of the reduction rate ΔNR of the NO _x purification rate NR in ₃ is equal to or greater than a predetermined rate.

In addition, in the embodiment according to the present invention, a plurality of different temperatures TC ₁ , TC ₂ , TC ₃ can be captured so that the change pattern of the NO _x purification rate NR indicated by the curve B2 in FIG. Is within the temperature range of the NO _x selective reduction catalyst 15 where the NO _x purification rate NR increases as the temperature of the NO _x selective reduction catalyst 15 rises when the catalytic action of the NO _x selective reduction catalyst 15 is completely lost. Is set to

The detection of the NO _x purification rate NR at each catalyst temperature TC ₁ , TC ₂ , TC ₃ is performed after the catalyst temperature TC becomes each temperature TC ₁ , TC ₂ , TC ₃ due to a change in the operating state. However, the catalyst temperature TC may not rise to all these temperatures TC ₁ , TC ₂ , TC _3, and in this case, the NO _x purification rate at all the temperatures TC ₁ , TC ₂ , TC ₃ cannot be detected. .

Therefore, in the embodiment according to the present invention, when the temperature TC of the NO _x selective reduction catalyst 15 does not exceed all of the different temperatures TC ₁ , TC ₂ , TC ₃ during a predetermined period, the different temperatures TC. The temperature of the NO _x selective reduction catalyst 15 is raised until the maximum temperature TC ₃ out of ₁ , TC ₂ and TC ₃ is exceeded.

In the embodiment according to the present invention, it is necessary to detect the NO _x purification rate NR by the NO _x selective reduction catalyst 15. Is stored in advance in the ROM32 in the form of a map shown in FIG. 4 the amount of NO _x NOXA exhausted per unit time from the engine in order as a function of the required torque TQ and engine speed N. Further, NO _x concentration and the exhaust gas amount detected by the NO _x sensor 29, i.e., the discharge amount of NO _x per unit time from _the NO _x selective reduction catalyst 15 from the intake air amount is obtained. Will therefore _the NO _x purification efficiency NR is obtained from the detection value of the NO _x amount NOXA and NO _x sensor 29 shown in FIG.

Next, the abnormality detection routine will be described with reference to FIGS. This routine is executed by interruption every predetermined time.
Referring to FIG. 5, first, at step 50, for example, it is determined whether or not a completion flag indicating that abnormality detection performed once is completed is set every time the vehicle is driven. When the completion flag is set, the processing cycle is completed, and when the completion flag is not set, the process proceeds to step 51.

  In step 51, a certain time ΔM is added to ΣM, and therefore ΣM represents an elapsed time from the start of engine operation. In this case, as ΔM, the intake air amount, the fuel injection amount, or the vehicle speed can be used instead of a fixed time. Next, at step 52, it is judged if the elapsed time ΣM has exceeded a predetermined time MX. When ΣM ≦ MX, the routine jumps to step 56.

On the other hand, when it is determined that the catalyst temperature TC does not rise to all the temperatures TC ₁ , TC ₂ , and TC ₃ and ΣM> MX is satisfied in step 52, the process proceeds to step 53 and the NO _x selective reduction catalyst 15. A temperature raising action is performed. This temperature raising action is performed, for example, by delaying the fuel injection timing to raise the exhaust gas temperature, or by adding additional fuel upstream of the oxidation catalyst 12 to generate oxidation reaction heat by this fuel. After the temperature raising action is started, when it is determined in step 54 that TC> TC ₃ , the routine proceeds to step 55 where the temperature raising action is stopped.

In step 56, it is determined whether or not the catalyst temperature TC has reached the temperature TC ₁ shown in FIG. When the catalyst temperature TC is not TC ₁ , the routine proceeds to step 59. In contrast, the catalyst temperature TC is _the NO _x purification rate NR from the output signal of the maps and NO _x sensor 29 shown in FIG. 4 proceeds to step 57 when it is TC ₁ is calculated. Next, at step 58 _the NO _x purification rate decrease rate .DELTA.NR ₁ of NR (= (reference _the NO _x purification rate _A-the NO _x purification rate NR) / reference _the NO _x purification rate A) is calculated, then the routine proceeds to step 59.

Catalyst temperature TC at step 59 whether it is the temperature TC ₂ shown in FIG. 3 (B) is determined. When the catalyst temperature TC is not TC ₂ , the routine proceeds to step 62. In contrast, when the catalyst temperature TC reaches TC ₂ , the routine proceeds to step 60 where the NO _x purification rate NR is calculated from the map shown in FIG. 4 and the output signal of the NO _x sensor 29. Next, at step 61, the reduction rate ΔNR ₂ of the NO _x purification rate NR is calculated, and then the routine proceeds to step 62.

In step 62, it is determined whether or not the catalyst temperature TC has reached the temperature TC ₃ shown in FIG. When the catalyst temperature TC is not TC ₃ , the processing cycle is completed. In contrast, when the catalyst temperature TC reaches TC ₃ , the routine proceeds to step 63, where the NO _x purification rate NR is calculated from the map shown in FIG. 4 and the output signal of the NO _x sensor 29. Next, at step 64, the reduction rate ΔNR ₃ of the NO _x purification rate NR is calculated, and then the routine proceeds to step 65.

In step 65, it is determined whether or not the NO _x purification rate NR changes along the change pattern when the NO _x selective reduction catalyst 15 deteriorates. That is, either smaller or not than the value decrease rate .DELTA.NR ₂ in step 65 the first, _the NO _x purification efficiency NR is obtained by subtracting a predetermined value α from the reduction ratio .DELTA.NR ₁ of the NO _x removal efficiency NR (.DELTA.NR _1-.alpha.), That is, it is determined whether or not the decrease rate ΔNR of the NO _x purification rate NR has decreased when the catalyst temperature TC has increased from TC ₁ to TC ₂ . When ΔNR ₂ ≧ ΔNR ₁ −α, the routine proceeds to step 70. In contrast, when ΔNR ₂ <ΔNR ₁ −α, that is, when the NO _x purification rate NR increases when the catalyst temperature TC increases from TC ₁ to TC ₂ , the routine proceeds to step 66.

_The NO _x purification rate decrease rate .DELTA.NR ₃ of NR in step 66 is obtained by subtracting a predetermined value β from reduction ratio .DELTA.NR ₂ of the NO _x removal efficiency NR value (.DELTA.NR _2-beta) less whether than, i.e. the catalyst temperature TC is It is determined whether or not the decrease rate ΔNR of the NO _x purification rate NR has decreased when it has increased from TC ₂ to TC ₃ . When ΔNR ₂ ≧ ΔNR ₂ −β, the routine proceeds to step 70. On the other hand, when ΔNR ₂ <ΔNR ₂ −β, that is, when the NO _x purification rate NR increases when the catalyst temperature TC increases from TC ₂ to TC ₃ , the routine proceeds to step 67.

In step 67, the average values of the reduction ratios ΔNR ₁ , ΔNR ₂ , ΔNR ₃ of the NO _x purification rate NR at the catalyst temperatures TC ₁ , TC ₂ , TC ₃ are calculated. Then whether or not the average value of the reduction ratio of the step 68 NO _x removal efficiency NR is greater than the ratio X ₁ defined in advance is determined. When the average value of the decrease rate is smaller than X ₁ , the process proceeds to step 70. In contrast, when the average value of the reduction ratio is greater than X ₁ NO _x emission is emitted an alarm indicating that exceeds the regulation value by _the NO _x selective reduction catalyst 15 proceeds to step 69 is deteriorated. Next, the routine proceeds to step 75, where the completion flag is set.

On the other hand, at step 70, it is determined whether or not the NO _x purification rate NR changes along the change pattern when the urea water becomes abnormal. That is, approximately equal or not reduction ratio .DELTA.NR ₂ steps 70 in First _the NO _x purification efficiency NR is a reduction ratio .DELTA.NR ₁ of the NO _x purification rate NR, for example, an extremely small value d ΔNR ₁ -d <ΔNR It is determined whether or not ₂ <ΔNR ₁ + d is satisfied. When ΔNR ₂ is not substantially equal to ΔNR ₁ , the process jumps to step 75 and the completion flag is set. On the other hand, when ΔNR ₂ is substantially equal to ΔNR ₁ , that is, when the NO _x purification rate NR hardly changes when the catalyst temperature TC rises from TC ₁ to TC ₂ , the routine proceeds to step 71.

Step 71 In _the NO _x purification rate decrease rate .DELTA.NR ₃ of NR whether substantially equal to the reduction ratio .DELTA.NR ₂ of the NO _x purification rate NR, for example, an extremely small value of _{d ΔNR 2 -d <ΔNR 3 <} ΔNR 2 + d Whether or not is established is determined. When ΔNR ₃ is not substantially equal to ΔNR ₂ , the process jumps to step 75 and the completion flag is set. On the other hand, when ΔNR ₃ is substantially equal to ΔNR ₂ , that is, when the catalyst temperature TC rises from TC ₂ to TC ₃ and the NO _x purification rate NR hardly changes, the routine proceeds to step 72.

In step 72, average values of the reduction ratios ΔNR ₁ , ΔNR ₂ and ΔNR ₃ of the NO _x purification rate NR at the catalyst temperatures TC ₁ , TC ₂ and TC ₃ are calculated. Then whether or not the average value of the reduction ratio of the NO _x removal efficiency NR at step 73 is greater than the ratio X ₂ defined in advance is determined. Completion flag is set the routine proceeds to step 75 when the average value of the reduction ratio is less than X _2. Alarm hand, indicating that the NO _x emissions by supplying amount or quality deviates from a normal value of the urea water proceeds to step 74 when the average value is greater than X ₂ reduction ratio exceeds the regulation value Is emitted. Next, at step 75, a completion flag is set.

1 is an overall view of a compression ignition type internal combustion engine. Is a diagram showing the relationships of the _the NO _x purification rate NR and the catalyst temperature TC. Is a diagram showing a relationship between _the NO _x purification rate NR and the catalyst temperature TC. It is a diagram illustrating a map of exhaust NO _x amount NOXA from the engine. It is a flowchart for detecting an abnormality. It is a flowchart for detecting an abnormality.

Explanation of symbols

4 Intake manifold 5 Exhaust manifold 7 Exhaust turbocharger 12 Oxidation catalyst 13 Particulate filter 15 NO _x selective reduction catalyst 17 Urea water supply valve

Claims (7)

Whether the NO _x selective reduction catalyst disposed in the engine exhaust passage has deteriorated and the NO _x emission amount has exceeded a predetermined regulation value, or the amount of urea water supplied to the NO _x selective reduction catalyst, or In an abnormality detection device for an internal combustion engine that determines whether or not the NO _x emission amount exceeds a predetermined regulation value due to the quality deviating from a normal value, NO _x selective reduction catalyst deteriorates and NO _x When the discharge amount exceeds the regulation value, the NO _x purification rate changes along a change pattern that increases as the temperature of the NO _x selective reduction catalyst rises, and the supply amount or quality of urea water deviates from the normal value. nO _x emissions change along the pattern of change does not increase even if _the nO _x purification rate when it exceeds the regulation value temperature of the nO _x selective reduction catalyst rises due, it different of the nO _x selective reduction catalyst _The NO _x purification rate by detecting _the NO _x purification rate is determined whether the changed along any of the above change patterns at a plurality of temperatures, the NO _x emissions by it by _the NO _x selective reduction catalyst is degraded An abnormality detection apparatus for an internal combustion engine, which determines whether or not the regulation value has been exceeded, or whether or not the supply amount or quality of urea water has deviated from a normal value, so that the NO _x emission amount has exceeded the regulation value. NO _x is set with NO _x emission standards amount as emissions emission standards, as a function of the temperature reference _the NO _x purification rate of the NO _x selective reduction catalyst when NO _x emissions is the NO _x emission standards amount are previously stored, the determined the decrease rate of the NO _x purification rate from different of the NO _x purification rate detected in the temperature with respect to the reference _the NO _x purification rate at each temperature, change in the reduction ratio of the _the NO _x purification rate whether NO _x emissions by _the NO _x selective reduction catalyst is deteriorated exceeds the regulation value, or NO _x emissions by deviating from the feed amount or quality of the normal value of the urea water exceeds the regulation value from The abnormality detection device for an internal combustion engine according to claim 1, wherein the abnormality is determined. When the supply amount or quality of urea water deviates from the normal value and the NO _x emission amount exceeds the above regulation value, the NO _x purification rate becomes the reference NO _x purification rate regardless of the temperature of the NO _x selective reduction catalyst. is decreased uniformly, the reduction ratio of the _the NO _x purification rate in a plurality of different temperatures is reduced as the temperature rises and the NO _x reduction ratio of the purification ratio predetermined proportion or more at a constant rate for Sometimes, it is judged that the NO _x emission amount has exceeded the regulation value due to deterioration of the NO _x selective reduction catalyst, and the rate of decrease in the NO _x purification rate at the plurality of different temperatures is almost constant regardless of the temperature, and When the reduction rate of the NO _x purification rate is equal to or higher than a predetermined rate, it is determined that the NO _x emission amount exceeds the regulation value because the supply amount or quality of urea water deviates from the normal value. The abnormality detection device for an internal combustion engine according to claim 2. When determining whether decrease ratio of the _the NO _x purification rate is rate than the predetermined is more ratio average value of reduction ratio of the NO _x purification rate of the plurality of different temperatures is predetermined The abnormality detection device for an internal combustion engine according to claim 3, wherein it is determined whether or not. Said plurality of different temperatures, the temperature range of the NO _x selective reduction catalyst increases the wake not _the NO _x purification rate to a temperature rise of the NO _x selective reduction catalyst when the catalyst action of _the NO _x selective reduction catalyst is completely lost The abnormality detection device for an internal combustion engine according to claim 1, wherein the abnormality detection device is set inside. If the temperature of the NO _x selective reduction catalyst does not exceed all of the different temperatures during a predetermined period, the NO _x selective reduction catalyst increases until the maximum temperature of the different temperatures is exceeded. The abnormality detection device for an internal combustion engine according to claim 1, wherein the abnormality detection device is warmed. The abnormality detection device for an internal combustion engine according to claim 1, wherein a NO _x sensor is disposed in an engine exhaust passage downstream of the NO _x selective reduction catalyst in order to obtain a NO _x purification rate.

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