JP4380354B2 - Additive valve abnormality diagnosis device for internal combustion engine - Google Patents

Description

  The present invention relates to an addition valve abnormality diagnosis device that diagnoses leakage of a reducing agent from an addition valve that adds a reducing agent to an exhaust system of an internal combustion engine in order to adjust an air-fuel ratio of exhaust flowing into an exhaust purification catalyst.

  Various types of catalyst control are performed on exhaust purification catalysts such as NOx storage reduction catalysts. For example, sulfur poisoning recovery control, particulate matter regeneration control or NOx reduction control. For such catalyst control, an exhaust valve is provided in the exhaust system, and the fuel is supplied as a reducing agent to the exhaust purification catalyst to control the air-fuel ratio of the exhaust.

  However, the addition valve provided in the exhaust system may cause a failure in which the addition valve opening / closing part is clogged with particulate matter in the exhaust or particulates generated from the sliding part of the internal combustion engine itself, resulting in an incomplete valve closing state. There is. When such a failure occurs, a situation occurs in which fuel leaks into the exhaust gas even during a period when fuel addition is unnecessary.

  In order to detect such a fuel leakage failure in the exhaust, a technique has been proposed in which the exhaust air-fuel ratio is measured when fuel addition control is not performed, and when it is smaller than the stoichiometry, it is determined that there is a leakage failure. (For example, refer to Patent Document 1).

Furthermore, a technique is proposed in which the exhaust air-fuel ratio is measured when the internal combustion engine is stable even during fuel addition control, and it is determined that there is a leakage failure when the state smaller than the stoichiometric state continues for the reference time. (See, for example, Patent Document 2).
JP-A-2002-168119 (page 7-8, FIG. 6) JP 2003-254048 A (page 7-8, FIG. 10)

  However, in recent years, in a diesel engine, multistage injection in which fuel injection from a fuel injection valve is performed a plurality of times from a compression stroke to an expansion stroke has been performed for the purpose of improving exhaust performance and output performance. Here, multistage injection is multi-injection in which one or more pilot injections are performed before main injection, or multi-injection in which one or more after injections are performed after main injection.

  When such injection is performed, the air-fuel ratio is lower than the exhaust air-fuel ratio by normal fuel injection. If such a decrease in the air-fuel ratio due to multi-injection is detected when no fuel is added, there is a risk of erroneously diagnosing a fuel leakage failure of the addition valve. A similar misdiagnosis also occurs when the fuel injection amount from the fuel injection valve is increased due to a rich request such as an acceleration request.

If such a misdiagnosis occurs, catalyst control cannot be performed properly, and the purification performance of the exhaust purification catalyst may be reduced.
Furthermore, as in the latter patent document 2, in the case of leakage failure diagnosis performed during fuel addition control, although the internal combustion engine is stable, fuel addition from the addition valve and multi-injection or increase from the fuel injection valve Due to the overlap, it may become more difficult to make a diagnosis accurately.

Such a problem applies not only to a diesel engine but also to a gasoline engine that burns in a lean state.
An object of the present invention is to provide an addition valve abnormality diagnosis device that can perform failure diagnosis of an addition valve provided in an exhaust system with high accuracy.

In the following, means for achieving the above object and its effects are described.
According to a first aspect of the present invention, there is provided an internal combustion engine addition valve abnormality diagnosis device that detects a reducing agent leakage from an addition valve that adds a reducing agent to an exhaust system of an internal combustion engine in order to adjust an air-fuel ratio of exhaust gas flowing into an exhaust purification catalyst. An addition valve abnormality diagnosis device for diagnosing an air-fuel ratio sensor provided downstream of the addition valve in an exhaust system of an internal combustion engine, and detected by the air-fuel ratio sensor when addition from the addition valve is not executed When the transition state of the measured air-fuel ratio indicates an air-fuel ratio transition state indicating a reducing agent leakage from the addition valve, a leakage abnormality diagnosis means for diagnosing that the addition valve is a leakage abnormality, and an internal combustion engine On the other hand, there is provided a rich request diagnosis response means for prohibiting diagnosis processing by the leakage abnormality diagnosis means when a rich request for lowering the air-fuel ratio is generated.

  The leakage abnormality diagnosing means diagnoses the leakage abnormality of the addition valve when the addition from the addition valve is not executed. When the rich request for reducing the air-fuel ratio is generated in the internal combustion engine, the rich request diagnosis response means prohibits the diagnosis process by the leakage abnormality diagnosis means.

  Therefore, it cannot be mistaken for the reducing agent leakage from the addition valve that the exhaust air-fuel ratio has decreased due to the rich request. Furthermore, the rich request and the addition of the reducing agent from the addition valve do not overlap at the time of leakage abnormality diagnosis. For this reason, the failure diagnosis of the addition valve can be executed with high accuracy.

  According to a second aspect of the present invention, there is provided an apparatus for diagnosing an addition valve abnormality in an internal combustion engine, wherein a reducing agent leakage from an addition valve for adding a reducing agent to an exhaust system of the internal combustion engine in order to adjust an air-fuel ratio of exhaust flowing into the exhaust purification catalyst. An addition valve abnormality diagnosis device for diagnosing an air-fuel ratio sensor provided downstream of the addition valve in an exhaust system of an internal combustion engine, and detected by the air-fuel ratio sensor when addition from the addition valve is not executed When the transition state of the magnitude relationship with respect to the reference measurement air-fuel ratio at the measured air-fuel ratio indicates a transition state indicating leakage of the reducing agent from the addition valve, a leakage abnormality diagnosis for diagnosing that the addition valve is a leakage abnormality And a rich request diagnosis response means for lowering the level of the reference measurement air / fuel ratio in the leakage abnormality diagnosis means when a rich request to lower the air / fuel ratio is generated for the internal combustion engine. It is characterized in.

  In this way, the reference air-fuel ratio level for evaluating the magnitude of the measured air-fuel ratio in the leakage abnormality diagnosing means is lowered by the rich request diagnosis response means when a rich request occurs, so that the exhaust air caused by the rich request is reduced. It is possible to suppress the rich portion of the fuel ratio from affecting the leakage abnormality diagnosis.

  Therefore, it can be prevented that the exhaust air-fuel ratio is lowered due to the rich request as a reducing agent leakage from the addition valve. Also in this case, the rich request and the reducing agent addition from the addition valve do not overlap at the time of leakage abnormality diagnosis.

In this way, the chance of accurately performing the failure diagnosis of the addition valve is increased, and a highly accurate diagnosis can be performed quickly.
An addition valve abnormality diagnosis device for an internal combustion engine according to claim 3, further comprising intake air amount detection means for detecting an intake air amount of the internal combustion engine according to claim 1 or 2; When the ratio between the intake air amount detected by the intake air amount detecting means and the fuel injection amount is smaller than a reference value, the rich request is generated.

  In order to determine the generation of the rich request, the size may be determined by directly calculating the ratio between the intake air amount and the fuel injection amount. In this way, the rich demand diagnosis response means provides a reference value for determining that the air-fuel ratio in the combustion chamber is actually made rich compared to the normal air-fuel ratio, and the ratio exceeds the reference value. If the calculated value decreases, it is determined that there is a rich request. This prohibits the diagnosis process by the leakage abnormality diagnosing means or lowers the level of the reference measurement air-fuel ratio.

Therefore, the failure diagnosis of the addition valve can be executed with high accuracy.
According to a fourth aspect of the present invention, there is provided the internal combustion engine addition valve abnormality diagnosis device according to the first or second aspect, further comprising engine speed detection means for detecting the rotation speed of the internal combustion engine, wherein the rich demand diagnosis response means is the engine. If the operating state of the internal combustion engine obtained from the relationship between the rotational speed detected by the rotational speed detection means and the fuel injection amount is included in the operating range in which the air-fuel ratio is lower than the reference air-fuel ratio, the rich It is characterized in that a request has occurred.

  In the fuel injection amount control of the internal combustion engine, the degree of output-enhancing multi-injection and other rich requests are determined from the relationship between the rotational speed of the internal combustion engine and the fuel injection amount. Therefore, when the operating state of the internal combustion engine obtained from the relationship between the rotational speed and the fuel injection amount is included in the operating region in which the air-fuel ratio is lowered below the reference air-fuel ratio, it can be assumed that the rich request has occurred. As a result, the rich request time diagnosis response means can prohibit the diagnosis process by the leakage abnormality diagnosis means, or can reduce the level of the reference measurement air-fuel ratio.

Therefore, the failure diagnosis of the addition valve can be executed with high accuracy.
An addition valve abnormality diagnosis device for an internal combustion engine according to claim 5, further comprising engine acceleration request detection means for detecting an acceleration request for the internal combustion engine according to claim 1, wherein the rich request diagnosis response means is the engine The rich request is generated when the acceleration request detected by the acceleration request detecting means is larger than a reference acceleration request value.

  For example, when the accelerator operation requires rapid acceleration, after-injection or the like is performed. However, the accelerator operation is detected by the engine acceleration request detecting means, and the acceleration request is greater than the reference acceleration request value. If it is too large, it can be assumed that a rich request has occurred. As a result, the rich request time diagnosis response means can prohibit the diagnosis process by the leakage abnormality diagnosis means, or can reduce the level of the reference measurement air-fuel ratio.

Therefore, the failure diagnosis of the addition valve can be executed with high accuracy.
The addition valve abnormality diagnosis device for an internal combustion engine according to claim 6, wherein the rich request diagnosis response means is the one in which the rich request is generated when there is a multi-injection request. It is characterized by doing.

  If there is a multi-injection request, the rich request diagnosis response means can assume that a rich request has occurred. As a result, the rich request time diagnosis response means can prohibit the diagnosis process by the leakage abnormality diagnosis means, or can reduce the level of the reference measurement air-fuel ratio.

Therefore, the failure diagnosis of the addition valve can be executed with high accuracy.
The addition valve abnormality diagnosis device for an internal combustion engine according to claim 7, wherein the leakage abnormality diagnosis means is the air-fuel ratio sensor when addition from the addition valve is not executed. When the detected measured air-fuel ratio is smaller than the reference measured air-fuel ratio for a reference period, the transition state of the measured air-fuel ratio indicates the air-fuel ratio transition state indicating the reducing agent leakage from the addition valve. The valve is diagnosed as having a leakage abnormality.

  By providing the reference period by the leakage abnormality diagnosing means, it is possible to diagnose the reducing agent leakage more accurately. As a result, the failure diagnosis of the addition valve can be executed with high accuracy.

[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a vehicle diesel engine to which the above-described invention is applied, and a control system that functions as a catalyst control device and an addition valve abnormality diagnosis device. The present invention can also be applied to a case where a similar catalyst configuration is adopted for a lean combustion gasoline engine or the like.

  The diesel engine 2 includes a plurality of cylinders, here, four cylinders # 1, # 2, # 3, and # 4. The combustion chambers 4 of the cylinders # 1 to # 4 are connected to a surge tank 12 via an intake port 8 and an intake manifold 10 that are opened and closed by an intake valve 6. The surge tank 12 is connected via an intake passage 13 to an intercooler 14 and a supercharger, here, an outlet side of a compressor 16 a of an exhaust turbocharger 16. The inlet side of the compressor 16 a is connected to an air cleaner 18. The surge tank 12 has an EGR gas supply port 20 a of an exhaust gas recirculation (hereinafter referred to as “EGR”) path 20. A throttle valve 22 is disposed in the intake passage 13 between the surge tank 12 and the intercooler 14, and an intake air amount sensor 24 as intake air amount detection means and an intake air temperature are provided between the compressor 16a and the air cleaner 18. A sensor 26 is arranged.

  The combustion chambers 4 of the cylinders # 1 to # 4 are connected to the inlet side of the exhaust turbine 16b of the exhaust turbocharger 16 via an exhaust port 30 and an exhaust manifold 32 that are opened and closed by an exhaust valve 28, and the outlet of the exhaust turbine 16b. The side is connected to the exhaust path 34. The exhaust turbine 16b introduces exhaust from the fourth cylinder # 4 side in the exhaust manifold 32.

  In the exhaust path 34, three catalytic converters 36, 38 and 40 in which an exhaust purification catalyst is housed are arranged. The most upstream first catalytic converter 36 houses a NOx storage reduction catalyst 36a. When the exhaust gas is in an oxidizing atmosphere (lean) during normal operation of the diesel engine 2, NOx is stored in the NOx storage reduction catalyst 36a. In the reducing atmosphere (stoichiometric or air / fuel ratio lower than stoichiometric), the NOx occluded in the NOx occlusion reduction catalyst 36a is released as NO and is reduced by HC or CO. In this way, NOx is purified.

  The second catalytic converter 38 arranged second is accommodated with a filter 38a having a wall portion formed in a monolith structure, and exhaust gas passes through the minute holes in the wall portion. Since the layer of the NOx occlusion reduction catalyst is formed by coating on the surface of the micropores of the filter 38a as the substrate, it functions as an exhaust purification catalyst and purifies NOx as described above. Furthermore, particulate matter in the exhaust (hereinafter referred to as “PM”) is trapped in the filter wall, so that oxidation of PM is started by active oxygen generated when NOx is occluded in a high-temperature oxidizing atmosphere. The whole PM is oxidized by oxygen. Thus, the purification of PM is performed together with the purification of NOx. Here, the first catalytic converter 36 and the second catalytic converter 38 are integrally formed.

The most downstream third catalytic converter 40 contains an oxidation catalyst 40a, where HC and CO are oxidized and purified.
A first exhaust temperature sensor 44 is disposed between the NOx storage reduction catalyst 36a and the filter 38a. Further, between the filter 38a and the oxidation catalyst 40a, a second exhaust temperature sensor 46 is disposed near the filter 38a, and an air-fuel ratio sensor 48 is disposed near the oxidation catalyst 40a.

  Here, the air-fuel ratio sensor 48 uses a solid electrolyte, and is a sensor that detects the air-fuel ratio of the exhaust based on the exhaust component and linearly outputs a voltage signal proportional to the air-fuel ratio. The first exhaust temperature sensor 44 and the second exhaust temperature sensor 46 detect the exhaust temperatures Texin and Texout at their respective positions.

  Piping of the differential pressure sensor 50 is provided on the upstream side and the downstream side of the filter 38a, respectively, and the differential pressure sensor 50 is located upstream and downstream of the filter 38a in order to detect the degree of clogging of the filter 38a, that is, the degree of PM accumulation. Is detected.

  The exhaust manifold 32 has an EGR gas inlet 20b of the EGR path 20 opened. The EGR gas inlet 20b is open on the first cylinder # 1 side, and is on the opposite side to the fourth cylinder # 4 side where the exhaust turbine 16b introduces exhaust.

  In the middle of the EGR path 20, an iron-based EGR catalyst 52 for reforming EGR gas is disposed from the EGR gas inlet 20b side, and an EGR cooler 54 for cooling the EGR gas is further provided. The EGR catalyst 52 also has a function of preventing the EGR cooler 54 from being clogged. An EGR valve 56 is disposed on the EGR gas supply port 20a side. By adjusting the opening degree of the EGR valve 56, the amount of EGR gas supplied from the EGR gas supply port 20a to the intake system can be adjusted.

  A fuel injection valve 58 disposed in each cylinder # 1 to # 4 and directly injecting fuel into each combustion chamber 4 is connected to a common rail 60 via a fuel supply pipe 58a. Fuel is supplied into the common rail 60 from an electrically controlled discharge variable fuel pump 62, and the high-pressure fuel supplied from the fuel pump 62 into the common rail 60 is supplied to each fuel injection valve 58 through each fuel supply pipe 58a. Distributed supply. A fuel pressure sensor 64 for detecting the fuel pressure is attached to the common rail 60.

  Further, low pressure fuel is separately supplied from the fuel pump 62 to the addition valve 68 via the fuel supply pipe 66. This addition valve 68 is provided in the exhaust port 30 of the fourth cylinder # 4, and adds fuel as a reducing agent into the exhaust by injecting fuel toward the exhaust turbine 16b. The catalyst control mode described later is executed by this fuel addition.

  An electronic control unit (hereinafter referred to as “ECU”) 70 is mainly configured by a digital computer including a CPU, a ROM, a RAM, and the like, and a drive circuit for driving various devices. The ECU 70 includes the intake air amount sensor 24, the intake air temperature sensor 26, the first exhaust temperature sensor 44, the second exhaust temperature sensor 46, the air-fuel ratio sensor 48, the differential pressure sensor 50, the EGR opening sensor in the EGR valve 56, Signals from the fuel pressure sensor 64 and the throttle opening sensor 22a are read. Further, signals are read from an accelerator opening sensor 74 (corresponding to an engine acceleration request detecting means) for detecting the amount of depression of the accelerator pedal 72 (accelerator opening ACCP) and a cooling water temperature sensor 76 for detecting a cooling water temperature THW of the diesel engine 2. It is out. Further, an engine speed sensor 80 as an engine speed detecting means for detecting the engine speed NE in the crankshaft 78, and a cylinder discrimination sensor 82 for making a cylinder discrimination by detecting the rotation phase of the crankshaft 78 or the rotation phase of the intake cam. The signal is being read from.

  Based on the engine operating state obtained from these signals, the ECU 70 executes fuel injection amount control and fuel injection timing control by the fuel injection valve 58. Further, the opening degree control of the EGR valve 56, the throttle opening degree control by the motor 22b, the discharge amount control of the fuel pump 62, and the PM regeneration control, S poison recovery control or NOx reduction control which will be described later by the valve opening control of the addition valve 68, etc. Perform catalyst control and other processes.

  As the combustion mode control executed by the ECU 70, a combustion mode selected from two types of a normal combustion mode and a low temperature combustion mode is executed according to the operating state. Here, the low-temperature combustion mode is a combustion mode in which NOx and smoke are simultaneously reduced by slowing the increase in the combustion temperature by a large amount of exhaust gas recirculation using the EGR valve opening map for low-temperature combustion mode. This low-temperature combustion mode is executed in the low-load low-medium rotation region, and air-fuel ratio feedback control is performed by adjusting the throttle opening TA based on the measured air-fuel ratio AF detected by the air-fuel ratio sensor 48. The combustion mode other than this is a normal combustion mode in which normal EGR control (including the case where EGR is not performed) is executed using the normal combustion mode EGR valve opening degree map.

  There are four types of catalyst control modes for performing catalyst control on the exhaust purification catalyst: a PM regeneration control mode, an S poison recovery control mode, a NOx reduction control mode, and a normal control mode. The PM regeneration control mode is a mode in which the PM accumulated on the filter 38a in the second catalytic converter 38 is burned as described above at a high temperature and discharged as CO2 and H2O. In this mode, fuel addition from the addition valve 68 is repeated in an air-fuel ratio state higher than stoichiometric (theoretical air-fuel ratio) to raise the catalyst bed temperature (for example, 600 to 700 ° C.). There is a case where after-injection that is fuel injection into the combustion chamber 4 in the stroke or exhaust stroke is added.

  The S poisoning recovery control mode is a mode in which when the NOx storage reduction catalyst 36a and the filter 38a are poisoned with S and the NOx storage capacity is reduced, the S component is released to recover from the S poisoning. In this mode, fuel addition is repeated from the addition valve 68 to execute a temperature raising process for raising the catalyst bed temperature (for example, 650 ° C.), and the air-fuel ratio is stoichiometrically or stoichiometrically by intermittent fuel addition from the addition valve 68. An air-fuel ratio reduction process is performed to make the air-fuel ratio slightly lower than Here, enrichment is performed to make the air-fuel ratio slightly lower than stoichiometric. In this mode, after-injection by the fuel injection valve 58 may be added.

  The NOx reduction control mode is a mode in which the NOx occluded in the NOx occlusion reduction catalyst 36a and the filter 38a is reduced to N2, CO2 and H2O and released. In this mode, by intermittent fuel addition from the addition valve 68 with a relatively long time, the catalyst bed temperature is relatively low (for example, 250 to 500 ° C.), and the air-fuel ratio is reduced or lower than the stoichiometry. .

It should be noted that a state other than these three catalyst control modes is the normal control mode, and fuel is not added from the addition valve 68 in this normal control mode.
Next, a process for diagnosing fuel leakage from the addition valve 68 among the processes executed by the ECU 70 will be described. FIG. 2 shows a flowchart of the addition valve fuel leakage diagnosis process. This process is a process executed by interruption every certain time.

  When this process is started, it is first determined whether or not the air-fuel ratio sensor 48 can detect the air-fuel ratio (S102). Here, based on the signal from the air-fuel ratio sensor 48, if the air-fuel ratio sensor 48 is normal and the temperature is sufficiently raised from the operating state of the diesel engine 2 and activated as a sensor, the air-fuel ratio is detected. It is determined that it is ready. If the air-fuel ratio sensor 48 is abnormal or the air-fuel ratio sensor 48 is not activated, it is determined that the air-fuel ratio cannot be detected.

If the air-fuel ratio cannot be detected (“NO” in S102), a counter C described later is cleared (S116), and this process is temporarily terminated.
If the air-fuel ratio can be detected (“YES” in S102), it is next determined whether or not fuel is not added (S104). As described above, there are four types of catalyst control modes: the PM regeneration control mode, the S poison recovery control mode, the NOx reduction control mode, and the normal control mode. Among these, during execution of any one of the PM regeneration control mode, the S poison recovery control mode, and the NOx reduction control mode, fuel is added to the exhaust from the addition valve 68 (“NO” in S104). Then, the counter C is cleared (S116), and this process is temporarily terminated.

  On the other hand, if it is the normal control mode (“YES” in S104), it is then determined whether or not there is a rich request (S106). This rich request means a control state in which the air-fuel ratio is lowered than usual. For example, the air-fuel ratio is lower than usual by fuel increase control of the main injection itself, fuel increase control by after injection, double pilot injection, etc. A control state to be enriched is mentioned.

  Further, if the increase amount ΔACCP per unit time of the accelerator opening ACCP is larger than the value corresponding to the reference acceleration request value, the exhaust air-fuel ratio becomes stoichiometric or less by the fuel increase corresponding to the increase amount ΔACCP. There will be a request. Further, as shown in FIG. 3, in the output increase range (corresponding to the operation range in which the air-fuel ratio is lowered below the reference air-fuel ratio) indicated by the map of the engine speed NE and the fuel injection amount Q, a double is required to increase the output. Since pilot injection and after injection are performed, there is a rich request. Further, since the intake air amount sensor 24 detects the intake air amount GA and the fuel injection amount Q is known on the fuel injection control side, the intake air amount GA and the fuel injection amount Q can be directly compared. If a ratio is calculated and this ratio is smaller than the reference value, there is a rich request.

  Any one of the determinations of the presence / absence of the rich request may be used. If it is determined that there is even one rich request in combination of two, three, or all, “NO” is determined in step S106. It may be determined.

If there is a rich request (“NO” in S106), the counter C is cleared (S116), and the process is temporarily terminated.
If there is no rich request (“YES” in S106), processing for failure diagnosis (S108 to S112) is performed. The state determined as “YES” in step S106 should have achieved an operation state in which the exhaust air-fuel ratio does not become lower than the stoichiometric unless there is fuel leakage from the addition valve 68. From this, the condition for executing the fuel leakage failure diagnosis of the addition valve 68 is ready.

  First, it is determined whether or not the measured air-fuel ratio AF measured by the air-fuel ratio sensor 48 is smaller than an air-fuel ratio value “14.7” representing stoichiometric (S108). If AF ≧ 14.7 (“NO” in S108), it is considered that there is no fuel leakage from the addition valve 68. Therefore, the counter C is cleared (S116), and this process is temporarily terminated.

  On the other hand, if AF <14.7 (“YES” in S108), there is a possibility that fuel leakage from the addition valve 68 has occurred, so the counter C is incremented (S110). Then, it is determined whether or not the counter C is larger than a value Cs representing the reference period (S112). This value Cs corresponds to a period for determining the transition state of the measured air-fuel ratio AF detected by the air-fuel ratio sensor 48. For example, a value corresponding to several seconds is set.

  While C ≦ Cs (“NO” in S112), the present process is temporarily terminated. Therefore, when it is continuously determined as “YES” in steps S102 to S108, the counter C is incremented every control cycle by the increment of step S110. When C> Cs is satisfied (“YES” in S112), “ON” is set to the addition valve leakage failure flag (S114). Note that the addition valve leakage failure flag is initially set to “OFF” when the ECU 70 is started.

  When the addition valve leakage failure flag is set to “ON” as described above, the ECU 70 separately performs a process for abnormality, and a warning lamp on the dashboard is turned on to warn the driver.

  In addition, while C ≦ Cs (“NO” in S112), if it is determined “NO” in any one of steps S102 to S108, the counter C is immediately cleared (S116). For this reason, even if it is determined again as “YES” in all of steps S102 to S108, the increment from the counter C = 0 is started. That is, during the reference period corresponding to the value Cs, it is continuously determined as “YES” in steps S102 to S108, so that the transition state of the measured air-fuel ratio AF indicates fuel leakage from the addition valve 68. It is determined that the air-fuel ratio transition state has been indicated.

  An example of control is shown in the timing charts of FIGS. In the example of FIG. 4, while the rich request does not exist, while the fuel addition is being executed (before t0), it is determined “NO” in step S104, and therefore the state of counter C = 0 (S116) continues. To do. After the fuel addition is completed (t0 to), the measured air-fuel ratio AF <14.7 is transiently reached, but it is a short time (t0 to t1), and C> Cs even if the counter C is incremented. There is nothing. Therefore, C = 0 again (t1), and this state is continued. Thereafter, the measured air-fuel ratio AF <14.7 (stoichiometric) in the state of no fuel addition (“YES” in S104) and no rich request (“YES” in S106) (“YES” in S108) ”), The increment of the counter C is started (S110: t2). If this state continues and C> Cs (“YES” in S112: t3), the addition valve leakage failure flag = “ON” is set (S114).

  In the example of FIG. 5, the same transition as in the case of FIG. 4 (t <b> 0 to t <b> 1) is performed until the fuel addition that has been executed is completed and the measured air-fuel ratio AF ≧ 14.7 (t 10 to t <b> 11). . Then, a rich request is generated (t12), and then AF <14.7 (t13). However, since the air-fuel ratio is decreased due to the rich request (“NO” in S106), counter C = 0 (S116) The state continues (from t12). After the rich request disappears (from t14), the measured air-fuel ratio AF <14.7 is transiently entered. However, this time is also short (t14 to t15), and even if the counter C is incremented, C It is never> Cs. Therefore, again, C = 0 (S116) is entered (t15), and this state is continued. Therefore, the addition valve leakage failure flag = “OFF” is continued.

  In the configuration described above, the relationship with the claims is that steps S104 and S108 to S114 of the addition valve fuel leakage diagnosis processing (FIG. 2) are processing as leakage abnormality diagnosis means, and step S106 is as rich request time diagnosis response means. It corresponds to processing.

According to the first embodiment described above, the following effects can be obtained.
(I). In the addition valve fuel leakage diagnosis process (FIG. 2), the leakage abnormality of the addition valve 68 is diagnosed when fuel addition from the addition valve 68 is not being executed, and the diagnosis process is prohibited when a rich request occurs. Yes.

  For this reason, the fact that the exhaust air-fuel ratio has decreased due to the rich request is not mistaken for the leakage of fuel from the addition valve 68. Further, the rich request and the fuel addition from the addition valve 68 do not overlap at the time of the addition valve fuel leakage diagnosis. For this reason, the addition valve failure diagnosis can be executed with high accuracy.

  In addition, in the addition valve fuel leakage diagnosis process (FIG. 2), the fuel leakage is determined based on the continued enrichment of the measured air-fuel ratio AF in the reference period (Cs). Will be able to diagnose.

  (B). The presence or absence of the rich request is based on a method of comparing the ratio of the intake air amount GA and the fuel injection amount Q with a reference value, a method based on the map of the engine speed NE and the fuel injection amount Q shown in FIG. The determination is made by one or a combination of a method for comparing ΔACCP and the reference increase amount, and a method for determining whether or not to execute multi-injection.

This reliably eliminates the rich state caused by the fuel injection valve 58 and enables the failure diagnosis of the addition valve 68 to be executed with high accuracy.
[Embodiment 2]
In the present embodiment, the addition valve fuel leakage diagnosis process shown in FIG. 6 is executed. In this processing, when there is a rich request, the reference measured air-fuel ratio AFX is changed from “14.7” representing stoichiometric to “12” to the rich side in the addition valve fuel of FIG. Different from leak diagnosis processing. In addition, the same step number is attached | subjected about the process same as the addition valve fuel leak diagnostic process of FIG. Since the other configuration is the same as that of the first embodiment, reference is made to FIGS.

Next, the addition valve fuel leakage diagnosis process (FIG. 6) will be described focusing on the differences from FIG.
If it is determined “YES” in steps S102 and S104 and there is no rich request (“YES” in S106), “14.7” representing the stoichiometric value is set in the reference measured air-fuel ratio AFX (S202).

  On the other hand, if there is a rich request (“NO” in S106), it is first determined whether or not a delay time has elapsed after the rich request (S203). This is a determination for waiting until the influence of enrichment appears in the measured air-fuel ratio AF. This delay time is set so that the delay time becomes longer as the engine speed NE is lower in accordance with the engine speed NE.

  Until this delay time elapses (“NO” in S203), the reference measurement air-fuel ratio AFX = 14.7 is set (S202). However, if the delay time elapses (“YES” in S203), the reference measurement air empty ratio is set. In order to shift the fuel ratio AFX to the rich side, “12” is set (S204). This reference measured air-fuel ratio AFX = “12” corresponds to an air-fuel ratio slightly lower than the lowest air-fuel ratio assumed to occur when the rich request is made unless the diesel engine 2 in the present embodiment leaks into the addition valve 68. To do. Therefore, the set value in step S204 differs depending on the type of engine. For example, the reference measurement air-fuel ratio AFX may be set to “13” or a value between “12” and “13”.

  When the reference measurement air-fuel ratio AFX is set in step S202 or step S204, it is determined whether or not AF <AFX (S206). That is, when there is no rich request, it is determined whether AF <14.7, and when there is a rich request, it is determined whether AF <12.

  If C> Cs is satisfied by continuing the state of AF <AFX (“YES” in S206) (“YES” in S112), the addition valve leakage failure flag is set to “ON” (S114). If AF ≧ AFX (“NO” in S206) before C> Cs, the counter C is cleared (S116), and the state of the addition valve leakage failure flag = “OFF” continues.

  An example of processing is shown in the timing charts of FIGS. In the example of FIG. 7, until the time when the rich request is made (before t22), the transition is the same as in the case of FIG. 5 (before t12). When there is a rich request (t22), after the delay time, the reference measurement air-fuel ratio AFX is moved to the rich side (AFX = 12) from the stoichiometric (AFX = 14.7) (t24). During this period, AF <AFX is transiently satisfied (from t23), but the increment of the counter C is completed in a short time (t23 to t24), and C> Cs is not reached. Even after the rich request is finished (t25), the measured air-fuel ratio AF <AFX is transiently entered, but for a short time (t25 to t26), even if the counter C is incremented, C> Cs. There is nothing. Therefore, again, C = 0 (S116) is entered (t26), and this state is continued.

  In the example of FIG. 8, even if fuel addition is completed (t30) due to fuel leakage in the addition valve 68, the measured air-fuel ratio AF <AFX remains. Therefore, the increment of the counter C is started (from t30). A rich request occurs before C> Cs (t31 to t34). At this time, since AFX = 14.7 continues during the delay time (t31 to t32), AF <AFX and counter C is incremented. Will continue. When the delay time ends and AFX = 12 (t32), the measured air-fuel ratio AF also decreases due to the rich request, so the increment of the counter C continues (from t32). When C> Cs is satisfied (t33), the addition valve leakage failure flag is set to “ON”.

  In the above-described configuration, the relationship with the claims is that steps S104, S206, S110 to S114 of the addition valve fuel leakage diagnosis process (FIG. 6) are processing as the leakage abnormality diagnosis means, and steps S106 and S202 to S204 are rich requests. This corresponds to processing as a time diagnosis handling means.

According to the second embodiment described above, the following effects can be obtained.
(I). In the addition valve fuel leakage diagnosis process (FIG. 6), the leakage abnormality of the addition valve 68 is diagnosed when the addition from the addition valve 68 is not executed, and the diagnosis process is not prohibited when a rich request occurs. The determination level is lowered by changing the value of the reference measurement air-fuel ratio AFX to the rich side. For this reason, in the addition valve fuel leakage diagnosis, it is possible to suppress the influence of the richness of the exhaust air-fuel ratio resulting from the rich request.

  Accordingly, it is possible to prevent the fact that the exhaust air-fuel ratio has decreased due to the rich request from being mistaken for the fuel leakage from the addition valve 68. Also in this case, the rich request and the fuel addition from the addition valve 68 do not overlap at the time of the addition valve fuel leakage diagnosis.

In this way, the chance that the failure diagnosis of the addition valve 68 can be executed accurately increases, and a high-precision diagnosis can be performed quickly.
(B). In the addition valve fuel leakage diagnosis process (FIG. 6), the fuel leakage is determined based on the continued enrichment of the measured air-fuel ratio AF in the reference period (Cs), so the fuel leakage from the addition valve 68 is more accurately diagnosed. Will be able to.

(C). The effect (b) of the first embodiment is produced.
[Other embodiments]
(A). In the second embodiment, when there is a rich request, “12” is set to the reference measurement air-fuel ratio AFX after the delay time. However, the degree of decrease in the reference measurement air-fuel ratio AFX is reduced according to the level of the rich request. May be set. That is, in the case of a rich request with a large degree of enrichment, the degree of decrease in the reference measured air-fuel ratio AFX is increased, and in the case of a rich request with a small degree of enrichment, the degree of decrease in the reference measured air-fuel ratio AFX is decreased.

  (B). In the second embodiment, when there is a rich request, the reference measured air-fuel ratio AFX is set to “12” after the delay time. Instead of the delay time, the reference measured air-fuel ratio AFX is gradually changed to “14.7”. Alternatively, the processing may be performed so as to be close to “12”.

  In addition, instead of the delay time, the reference measurement air-fuel ratio AFX may be made to approach “12” from “14.7” according to the cumulative amount of the intake air amount GA.

1 is a block diagram showing a schematic configuration of a vehicle diesel engine and a control system that functions as a catalyst control device and an addition valve abnormality diagnosis device in Embodiment 1. FIG. 5 is a flowchart of an addition valve fuel leakage diagnosis process according to the first embodiment. FIG. 5 is a configuration explanatory diagram of a map for obtaining an output increase range for determining a rich request in the addition valve fuel leakage diagnosis process. 3 is a timing chart illustrating an example of processing in Embodiment 1. 3 is a timing chart illustrating an example of processing in Embodiment 1. 10 is a flowchart of an addition valve fuel leakage diagnosis process according to the second embodiment. 9 is a timing chart showing an example of processing in the second embodiment. 9 is a timing chart showing an example of processing in the second embodiment.

Explanation of symbols

  2 ... Diesel engine, 4 ... Combustion chamber, 6 ... Intake valve, 8 ... Intake port, 10 ... Intake manifold, 12 ... Surge tank, 13 ... Intake passage, 14 ... Intercooler, 16 ... Exhaust turbocharger, 16a ... Compressor, 16b ... exhaust turbine, 18 ... air cleaner, 20 ... EGR path, 20a ... EGR gas supply port, 20b ... EGR gas intake port, 22 ... throttle valve, 22a ... throttle opening sensor, 22b ... motor, 24 ... intake air amount sensor , 26 ... intake temperature sensor, 28 ... exhaust valve, 30 ... exhaust port, 32 ... exhaust manifold, 34 ... exhaust path, 36 ... first catalytic converter, 36a ... NOx occlusion reduction catalyst, 38 ... second catalytic converter, 38a ... Filter, 40 ... third catalytic converter, 40a ... oxidation catalyst, 44 ... first exhaust temperature sensor, 46 ... second Temperature sensor 48 ... Air-fuel ratio sensor 50 ... Differential pressure sensor 52 ... EGR catalyst 54 ... EGR cooler 56 ... EGR valve 58 ... Fuel injection valve 58a ... Fuel supply pipe 60 ... Common rail 62 ... Fuel pump , 64 ... Fuel pressure sensor, 66 ... Fuel supply pipe, 68 ... Addition valve, 70 ... ECU, 72 ... Accelerator pedal, 74 ... Accelerator opening sensor, 76 ... Cooling water temperature sensor, 78 ... Crankshaft, 80 ... Engine speed Sensor, 82 ... cylinder discrimination sensor.

Claims (7)

An addition valve abnormality diagnosis device for diagnosing a reducing agent leakage from an addition valve for adding a reducing agent to an exhaust system of an internal combustion engine in order to adjust an air-fuel ratio of exhaust flowing into an exhaust purification catalyst,
An air-fuel ratio sensor provided downstream of the addition valve in the exhaust system of the internal combustion engine;
When the transition state of the measured air-fuel ratio detected by the air-fuel ratio sensor when the addition from the addition valve is not executed, the air-fuel ratio transition state indicating a reducing agent leakage from the addition valve, A leakage abnormality diagnosis means for diagnosing that the addition valve is a leakage abnormality;
A rich request diagnosis response means for prohibiting a diagnosis process by the leakage abnormality diagnosis means when a rich request to lower the air-fuel ratio is generated for the internal combustion engine;
An addition valve abnormality diagnosis device for an internal combustion engine, comprising: An addition valve abnormality diagnosis device for diagnosing a reducing agent leakage from an addition valve for adding a reducing agent to an exhaust system of an internal combustion engine in order to adjust an air-fuel ratio of exhaust flowing into an exhaust purification catalyst,
An air-fuel ratio sensor provided downstream of the addition valve in the exhaust system of the internal combustion engine;
The transition state of the magnitude relationship with respect to the reference measured air-fuel ratio in the measured air-fuel ratio detected by the air-fuel ratio sensor when the addition from the addition valve is not executed indicates the transition state indicating the reducing agent leakage from the addition valve. In the case of leakage abnormality diagnosis means for diagnosing that the addition valve is leakage abnormality,
A rich request diagnosis response means for lowering the level of the reference measurement air-fuel ratio in the leakage abnormality diagnosis means when a rich request to lower the air-fuel ratio occurs with respect to the internal combustion engine;
An addition valve abnormality diagnosis device for an internal combustion engine, comprising: 3. The intake air amount detection means for detecting the intake air amount of the internal combustion engine according to claim 1 or 2, wherein the rich request time diagnosis response means includes the intake air amount detected by the intake air amount detection means and fuel injection. An addition valve abnormality diagnosis device for an internal combustion engine, characterized in that the rich request is made when the ratio to the amount is smaller than a reference value. 3. The engine speed detection means for detecting the speed of the internal combustion engine according to claim 1 or 2, wherein the rich request time diagnosis response means includes a speed detected by the engine speed detection means and a fuel injection amount. The addition of the internal combustion engine is characterized in that the rich request is generated when the operation state of the internal combustion engine obtained from the relationship is included in an operation region in which the air / fuel ratio is lowered below the reference air / fuel ratio. Valve abnormality diagnosis device. The engine acceleration request detecting means for detecting an acceleration request for the internal combustion engine according to claim 1 or 2, wherein the rich request diagnosis response means has an acceleration request detected by the engine acceleration request detecting means as a reference acceleration request value. The addition valve abnormality diagnosis device for an internal combustion engine is characterized in that the rich request is generated when the value is larger than. 3. The addition valve abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the rich request diagnosis response means is that the rich request is generated when there is a multi-injection request. 7. The leakage abnormality diagnosing means according to claim 1, wherein a condition in which a measured air-fuel ratio detected by the air-fuel ratio sensor is smaller than a reference measured air-fuel ratio when addition from the addition valve is not executed is a reference. An internal combustion engine characterized in that, if the transition state of the measured air-fuel ratio indicates an air-fuel ratio transition state indicating a reducing agent leakage from the addition valve when the period continues, the addition valve is diagnosed as having a leakage abnormality Additive valve abnormality diagnosis device.

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