JP5092410B2 - Internal combustion engine reducing agent addition valve diagnostic device - Google Patents

Description

  The present invention relates to an addition valve diagnostic device that diagnoses a reducing agent leakage from an addition valve that releases a reducing agent into an exhaust system of an internal combustion engine based on an air-fuel ratio of the exhaust system.

  Various types of catalyst control, such as particulate matter regeneration control, are executed in an exhaust gas purification apparatus using a filter or a catalyst. For such catalyst control, there is a technique in which an addition valve is provided in an exhaust system and fuel is supplied to the catalyst as a reducing agent to control the air-fuel ratio of the exhaust (see, for example, Patent Documents 1 and 2).

However, due to particulate matter in the exhaust or particulates generated from the sliding part of the internal combustion engine, the addition valve may cause a failure (open sticking) in which the addition valve opening / closing part becomes clogged with foreign matter and the valve becomes incomplete. . When such a failure occurs, a situation in which fuel leaks into the exhaust gas and is released even during a period in which the addition process is not executed. In Patent Document 1, the leakage of the reducing agent from the addition valve determines whether the addition valve is stuck open by detecting the air-fuel ratio of the exhaust when the addition process is not being performed.
Japanese Patent Laying-Open No. 2005-232991 (page 8-10, FIG. 2) JP 2005-54723 A (page 11-12, FIG. 2)

  However, even when the reducing agent leaks from the addition valve due to the open fixation, it has been found that the air-fuel ratio does not necessarily show a decrease corresponding to the leakage downstream thereof. This is because the reducing agent released from the addition valve due to leakage may adhere to the exhaust system and may not immediately reach the air-fuel ratio detection unit due to exhaust. Therefore, when other conditions for normality determination are satisfied, if such a reducing agent adheres to the exhaust system, there is a risk that normal determination will be made despite the addition valve being in an open fixed state. is there.

  In Patent Document 2, the estimated amount of added fuel adhering to the exhaust manifold is repeatedly calculated, and the air-fuel ratio of the exhaust gas is only when fuel is added from the addition valve by performing the addition process during a period in which it is estimated that the attached amount is small. Is used to determine the state of the addition valve. However, the technique of Patent Document 2 determines whether the amount of addition during the fuel addition process is excessive or too small, and does not determine the presence or absence of an open fixed state. In addition, the fuel adhesion amount estimation calculation is based on the assumption that fuel is added, and the calculation processing is complicated.

  The present invention is an addition valve diagnostic process that is performed without being limited to the fuel addition process, and prevents the addition valve from being judged to be normal even though it is in an open fixed state. The purpose is to perform accurate normality determination.

In the following, means for achieving the above object and its effects are described.
The internal combustion engine reducing agent addition valve diagnostic device according to claim 1 supplies the reducing agent to the exhaust purification device by releasing the reducing agent into the exhaust flow from the upstream side of the exhaust purification device in the exhaust system of the internal combustion engine. An addition valve diagnostic device comprising an addition valve and an addition control means for controlling the addition of a reducing agent by the addition valve and diagnosing a reducing agent leakage from the addition valve based on an air-fuel ratio of an exhaust system, The air-fuel ratio sensor provided downstream of the addition valve in the exhaust system, the gas flow rate detection means provided in the intake system or exhaust system of the internal combustion engine, and the gas flow rate detected by the gas flow rate detection means are attached. When the flow rate is smaller than the judgment reference flow rate , the reducing agent adherence determination unit determines that the possibility of attachment of the reducing agent in the exhaust system of the internal combustion engine is high, and the reducing agent can be attached by the reducing agent attachment possibility determination unit If the sex is judged to be high It is characterized in that and a normality determination inhibiting means for inhibiting the normality determination for the air-fuel ratio the addition valve based on actual air-fuel ratio detected by the sensor.

Thus, the addition valve diagnostic device diagnoses the reducing agent leakage from the addition valve based on the air-fuel ratio of the exhaust system, and thus is not limited to the time of fuel addition processing.
More if it has been determined to have a high adhesion potential of the reducing agent in the reducing agent adheres possibility determining means, the normality determination inhibiting means, normal to the addition valve based on the measured air-fuel ratio detected by the air-fuel ratio sensor Judgment is prohibited. Therefore, it is not determined that the addition valve is in an open and fixed state even though it is in an open state.

Further , when the gas flow rate in the exhaust system, that is, the exhaust gas flow rate is small, the reducing agent released from the addition valve adheres to the exhaust system, and when the exhaust gas flow rate is large, the adhesion tends to decrease. Since the exhaust gas flow rate is substantially proportional to the gas flow rate in the intake system, that is, the intake air amount, the adhesion of the reducing agent in the exhaust system tends to change in accordance with the amount of gas flow in the intake system. It is in.

  For this reason, when the gas flow rate detected by the gas flow rate detection means is smaller than the adhesion determination reference flow rate, it is determined that the reducing agent is likely to adhere. Thus, the normal determination prohibiting unit can appropriately prohibit normal determination on the addition valve based on the actually measured air-fuel ratio. Since the normality determination means also does not make a normality determination when the addition valve is in the open fixed state, the normality determination accuracy does not decrease.

Moreover, it is possible to easily determine the attachment state of the reducing agent to the exhaust system by simple processing without executing complicated arithmetic processing.
The internal combustion engine reducing agent addition valve diagnostic apparatus according to claim 2 supplies the reducing agent to the exhaust purification device by releasing the reducing agent into the exhaust flow from the upstream side of the exhaust purification device in the exhaust system of the internal combustion engine. An addition valve diagnostic device comprising an addition valve and an addition control means for controlling the addition of a reducing agent by the addition valve and diagnosing a reducing agent leakage from the addition valve based on an air-fuel ratio of an exhaust system, An air-fuel ratio sensor provided downstream of the addition valve in the exhaust system, a gas flow rate detection means provided in the intake system or exhaust system of the internal combustion engine, a temperature detection means provided in the exhaust system of the internal combustion engine, Reducing agent in the exhaust system of the internal combustion engine when the temperature detected by the temperature detection means is lower than the adhesion determination reference temperature or the gas flow rate detected by the gas flow detection means is less than the adhesion determination reference flow rate High possibility of adhesion When the reducing agent adhesion possibility determination means and the reducing agent adhesion possibility determination means determine that the possibility of reducing agent adhesion is high, the measured air-fuel ratio detected by the air-fuel ratio sensor is set. And normal determination prohibiting means for prohibiting normal determination for the addition valve based on the above.
Thus, the addition valve diagnostic device diagnoses the reducing agent leakage from the addition valve based on the air-fuel ratio of the exhaust system, and thus is not limited to the time of fuel addition processing.
Further, when it is determined by the reducing agent adhesion possibility determination means that the possibility of attachment of the reducing agent is high, the normality determination prohibiting means determines whether the addition valve is normal based on the actually measured air-fuel ratio detected by the air-fuel ratio sensor. Is prohibited. Therefore, it is not determined that the addition valve is in an open and fixed state even though it is in an open state.

Further, both the gas flow rate and the exhaust system temperature are detected as described above, and when any of the values is lower than the corresponding determination reference value, it is determined that the possibility of attachment of the reducing agent is high. As a result, the normal determination prohibiting means can more appropriately prohibit normal determination for the addition valve based on the actually measured air-fuel ratio. Since the normality determination means also does not make a normality determination when the addition valve is in the open fixed state, a decrease in the normality determination accuracy can be prevented more reliably.

In addition, it is possible to easily and more appropriately determine the state of attachment of the reducing agent to the exhaust system with simple processing without executing complicated arithmetic processing .

請 internal combustion engine the reducing agent addition valve diagnostic apparatus according to Motomeko 3 resides in that in Claim 1 or 2, a temperature detecting means disposed in an exhaust system of an internal combustion engine, the temperature detecting means, wherein the addition valve stuck open state And a second diagnostic means for diagnosing that there is no leakage of the reducing agent from the addition valve and that it is normal when the temperature is below the upper limit of the temperature that can be taken. The air-fuel ratio is satisfied when a logical sum condition between a condition determined by the sex determination means that the possibility of attachment of the reducing agent is high and a condition not determined normal by the second diagnosis means is satisfied. A normal determination for the addition valve based on the actually measured air-fuel ratio detected by a sensor is prohibited.

  As described above, even when the detection result of the second diagnosis means for making a diagnosis based on the temperature of the exhaust system is not determined to be normal, the normal determination prohibiting means is the addition valve based on the actually measured air-fuel ratio detected by the air-fuel ratio sensor. Normal judgment is prohibited. For this reason, the normality determination with respect to the addition valve based on the actually measured air-fuel ratio can be more appropriately prohibited.

[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a control system that functions as a vehicle diesel engine and a reducing agent addition valve diagnosis device to which the above-described invention is applied. 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 path 13 between the surge tank 12 and the intercooler 14, and an intake air amount sensor 24 (corresponding to a gas flow rate 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.

  Two exhaust purification devices 38 and 40 are disposed in the exhaust path 34. The first exhaust purification device 38 on the upstream side is configured as a DPF (Diesel Particulate Filter). That is, filters 38a and 38b carrying an oxidation catalyst are arranged inside to capture particulate matter (hereinafter referred to as “PM”) in the exhaust gas. When PM is trapped and accumulated to some extent, it is oxidized and removed by the catalyst in a high-temperature oxidizing atmosphere, so that PM is removed and purified.

The second exhaust purification device 40 on the downstream side contains an oxidation catalyst 40a, where HC and CO are oxidized and purified.
A first exhaust temperature sensor 44 (corresponding to temperature detection means) is disposed between the two filters 38a, 38b in the first exhaust purification device 38, and detects the inlet exhaust temperature Texin. Further, between the filter 38b and the oxidation catalyst 40a, a second exhaust temperature sensor 46 (corresponding to a temperature detecting means) is disposed immediately below the filter 38b to detect the outlet exhaust temperature Texout, and further an air-fuel ratio sensor 48 is disposed. Thus, the air-fuel ratio A / F is detected. The air-fuel ratio sensor 48 is a sensor that detects the air-fuel ratio of exhaust based on the exhaust component and linearly outputs a voltage signal proportional to the air-fuel ratio A / F.

  Pipes for the differential pressure sensor 50 are provided on the upstream side and the downstream side of the filter 38b, respectively. The differential pressure sensor 50 detects the differential pressure ΔP upstream and downstream of the filter 38b in order to detect the degree of clogging of the filters 38a and 38b in the first exhaust purification device 38, that is, the degree of PM accumulation. Yes.

  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, an EGR cooler 54 for cooling EGR gas, and an EGR valve 56 are arranged from the EGR gas inlet 20b side. .

  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. The high-pressure fuel supplied from the fuel pump 62 into the common rail 60 is distributed and supplied to each fuel injection valve 58 via each fuel supply pipe 58a. 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. PM regeneration control 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 that detects the amount of depression of the accelerator pedal 72 (accelerator opening ACCP) and a cooling water temperature sensor 76 that detects the cooling water temperature THW of the diesel engine 2. Further, signals are read from an engine speed sensor 80 that detects the engine speed NE of the crankshaft 78 and a cylinder discrimination sensor 82 that detects the rotation phase of the crankshaft 78 or the rotation phase of the intake cam and discriminates the cylinder.

  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, processing such as opening control of the EGR valve 56, throttle opening control by the motor 22b, discharge amount control of the fuel pump 62, and PM regeneration control by opening control of the addition valve 68 is executed.

  In particular, the PM regeneration control is a control in which PM accumulated on the filters 38a and 38b in the first exhaust purification device 38 is oxidized to CO2 and H2O by high temperature and discharged. In this control, 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.). At this time, after-injection, which is fuel injection into the combustion chamber 4 in the expansion stroke or exhaust stroke by the fuel injection valve 58, may be added.

  Next, of the processes executed by the ECU 70, a process for determining whether or not there is no fuel leakage (open stuck state) from the addition valve 68, that is, whether or not the addition valve 68 is in a normal state will be described. The flowchart of this process is shown in FIGS. This process is a process that is interrupted and executed at regular intervals. The steps in the flowchart corresponding to individual processes are represented by “S˜”.

  The addition valve normal diagnosis process (FIG. 2) will be described. When this process is started, it is first determined whether or not the normal determination requirement A is satisfied (S102). Here, the normal determination requirement A is a logical product of the following conditions (1) to (13).

(1) The engine 2 is operating at a sufficient level. For example, the engine speed NE detected by the engine speed sensor 80 is in a state that is equal to or higher than the reference speed.
(2) A diagnosis possible region. For example, the EGR valve 56 is closed and EGR gas is not introduced into the surge tank 12 side.

  (3) The combustion control that affects the air-fuel ratio is not executed. For example, there are a state in which afterburn control, low-temperature stoichiometric combustion is not performed, and a state not within a predetermined time after these controls.

(4) The turbocharger 16 is not in a transient state of supercharging.
(5) When the exhaust turbocharger 16 is a variable turbo device, the closed control is not being executed.

(6) The fuel injection valve 58 is not abnormal.
(7) The intake air amount sensor 24 and the second exhaust temperature sensor 46 are not abnormal. In the next (8), when the inlet exhaust temperature Texin is used instead of the outlet exhaust temperature Texout, the first exhaust temperature sensor 44 is not abnormal instead of the second exhaust temperature sensor 46.

(8) The outlet exhaust temperature Texout detected by the second exhaust temperature sensor 46 is higher than the reference temperature (corresponding to the adhesion determination reference temperature).
(9) The intake air amount ga detected by the intake air amount sensor 24 is larger than a reference amount (corresponding to an adhesion determination reference flow rate).

(10) The air-fuel ratio sensor 48 is activated.
(11) The calculated air-fuel ratio based on the fuel injection amount from the fuel injection valve 58, the fuel addition amount from the addition valve 68, and the intake air amount ga from the intake air amount sensor 24, and the measured sky detected by the air-fuel ratio sensor 48 The difference from the fuel ratio A / F is within the reference value.

  (12) The addition time (rich time) from the addition valve 68 by addition control is less than the reference time. This reference time is set by an experiment or the like as an appropriate time that can be distinguished from open fixation. However, if this reference time is set to 0 seconds, it is a condition that no addition treatment is performed.

  (13) The air-fuel ratio A / F detected by the air-fuel ratio sensor 48 is greater than the reference value. This reference value includes an air-fuel ratio that can be reached when the addition time (rich time) shown in (12) is within the reference time, and an air-fuel ratio that can be reached when the addition valve 68 is stuck open. Is an air-fuel ratio value.

  If the condition (13), that is, the measured air-fuel ratio A / F is larger than the reference value under the conditions (1) to (12), the addition valve 68 is controlled from the viewpoint of the air-fuel ratio. It can be determined that there is no leakage due to the open fixing state.

  When even one of these conditions (1) to (13) is not satisfied (No in S102), the normal determination requirement A satisfaction counter Ca that counts the duration when the normal determination requirement A is satisfied is cleared. (S112). Thus, the present process is temporarily exited. Thereafter, if the normal determination requirement A is not satisfied (No in S102), the execution of Step S112 is repeated.

  When the normal determination requirement A is satisfied (yes in S102), that is, when all the conditions (1) to (13) are satisfied, the normal determination requirement A satisfaction counter Ca is incremented (S104). Next, it is determined whether or not the value of the normal determination requirement A establishment counter Ca immediately after counting up indicates the reference time TMa or more (S106). When it is determined to be yes in step S102, since Ca <TMa (no in S106), the process is temporarily exited. Thereafter, as long as the normal determination requirement A establishment (yes in S102) continues, the normal determination requirement A establishment counter Ca counts up (S104). However, even if the normal determination requirement A establishment counter Ca is incremented in this way, if the normal determination requirement A does not hold before Ca ≧ TMa (no in S102), the normal determination requirement A establishment counter Ca is It is cleared (S112).

  If Ca ≧ TMa is established due to continued establishment of the normal determination requirement A (yes in S102), it is next determined whether or not the normal determination requirement B establishment flag Fex is ON (S108). The normal determination requirement B establishment flag Fex is set by normal determination requirement B determination processing (FIG. 3) that is separately executed as described later.

  If Fex = OFF is set (NO in S108), the process is temporarily exited. However, if Fex = ON is set (yes in S108), a normal determination is made (S110). In other words, it is determined that the addition valve 68 is normal and there is no fuel leakage due to open fixation.

  The normal determination requirement B determination process (FIG. 3) will be described. When this process is started, it is first determined whether or not the normal determination requirement B is satisfied (S122). Here, the normal determination requirement B is a logical product of the following conditions (1) to (6).

(1) The engine 2 is operating at a sufficient level. For example, the engine speed NE detected by the engine speed sensor 80 is in a state that is equal to or higher than the reference speed.
(2) The intake air amount sensor 24 is not abnormal.

(3) The intake air amount ga detected by the intake air amount sensor 24 is larger than the reference amount.
(4) Both the first exhaust temperature sensor 44 and the second exhaust temperature sensor 46 are not abnormal.

  (5) The inlet exhaust temperature Texin detected by the first exhaust temperature sensor 44 is within the reference temperature range. In this reference temperature range, the temperature that can be taken by the filter 38a by the fuel added from the addition valve 68 when the addition valve 68 is not in the open fixed state is the upper limit value, and the temperature that can be taken after the warm-up of the engine 2 is completed. This is the lower limit. Such a range is determined experimentally in a standard engine.

  (6) The outlet exhaust temperature Texout detected by the second exhaust temperature sensor 46 is within the reference temperature range. In this reference temperature range, the temperature that can be taken by the filter 38b by the fuel added from the addition valve 68 when the addition valve 68 is not in the open fixed state is the upper limit value, and the temperature that can be taken after the warm-up of the engine 2 is completed. This is the lower limit. Such a range is determined experimentally in a standard engine.

If all of these conditions (1) to (6) are satisfied, it can be determined that there is no leakage due to the open adhering of the addition valve 68 from the viewpoint of the exhaust temperature (which is also the temperature of the filters 38a and 38b).
When even one of the conditions (1) to (6) is not satisfied (No in S122), the normal determination requirement B satisfaction counter Cb that counts the duration when the normal determination requirement B is satisfied is cleared (S130). ). Then, “OFF” is set to the normality determination requirement B establishment flag Fex (S132). Thus, the present process is temporarily exited. Thereafter, if the normal determination requirement B is not satisfied (No in S122), execution of Steps S130 and S132 is repeated.

  When the normal determination requirement B is satisfied (yes in S122), that is, when all the conditions (1) to (6) are satisfied, the normal determination requirement B satisfaction counter Cb is incremented (S124). Next, it is determined whether or not the value of the normality determination requirement B establishment counter Cb immediately after counting up indicates the reference time TMb or more (S126). When Cb <TMb is satisfied when it is determined to be yes in step S122 (no in S126), the normal determination requirement B establishment flag Fex is set to OFF (S132), and the process is temporarily exited. Thereafter, as long as the normal determination requirement B establishment (yes in S122) continues, the normal determination requirement B establishment counter Cb is incremented (S124). However, even if the normal determination requirement B satisfaction counter Cb is incremented in this way, if the normal determination requirement B is not satisfied before Cb ≧ TMb (no in S122), the normal determination requirement B satisfaction counter Cb is Cleared (S130), the normal determination requirement B establishment flag Fex = OFF is maintained (S132).

  If Cb ≧ TMb is satisfied by continuing the establishment of the normal determination requirement B (yes in S122) (yes in S126), the normal determination requirement B establishment flag Fex is set to ON (S128), and the process is temporarily exited.

  In this way, when the normal determination requirement B establishment flag Fex is set to ON, at the same time, if the establishment of the normal determination requirement A continues for the reference time TMa or more, the above-described addition valve normal diagnosis process ( After it is determined to be yes in step S106 of FIG. 2), it is also determined to be yes in step S108. For this reason, it can be determined that the normal determination, that is, the addition valve 68 is not in the open fixing state (S110).

  An example of the control in this embodiment is shown in the timing chart of FIG. The inlet exhaust temperature Texin is already within the reference temperature range THy1 to THy2 before the timing t0, and the outlet exhaust temperature Texout is within the reference temperature range THy1 to THy2 at the timing t1. Here, the reference temperature range of the inlet exhaust temperature Texin and the reference temperature range of the outlet exhaust temperature Texout are the same range, but may differ depending on the composition and structure in the first exhaust purification device 38.

  Further, at time t2, the intake air amount ga is above the reference amount gax line, and at timing t3, the engine speed NE is above the reference speed NEx line. It is assumed that other requirements for the normality determination requirement B are also satisfied at this timing t3 (FIG. 3: yes in S122). Accordingly, when the normal determination requirement B establishment counter Cb starts counting and thereafter the normal determination requirement B establishment continues for the reference time TMb (FIG. 3: yes in S126), the normal determination requirement B establishment flag Fex is turned off at timing t6. To ON (FIG. 3: S128).

  Further, the air-fuel ratio difference ΔA / F is within the reference value dAF at timing t0, and the outlet exhaust temperature Texout is above the reference temperature THx line at timing t4. At time t5, the air-fuel ratio A / F becomes higher than the reference value AFx line. Here, the engine speed NE and the intake air amount ga are the same as those determined by the reference speed NEx and the reference amount gax in the normal determination requirement B. Furthermore, it is assumed that other requirements for normality determination requirement A are also satisfied at timing t5 (FIG. 2: yes in S102). Therefore, when the normal determination requirement A establishment counter Ca starts counting and thereafter the normal determination requirement A establishment continues for the reference time TMa (FIG. 2: yes in S106), the contents of the normal determination requirement B establishment flag Fex are determined. (FIG. 2: S108). Here, since it is already set from OFF to ON at timing t6 (FIG. 2: yes at S108), normality determination is made at timing t7 (FIG. 2: S110).

  In the above-described configuration, the relationship with the claims is that the determination on the normal determination requirement A (8) and (9) is the processing as the reducing agent adhesion possibility determination means, and steps S102 and S108 are the normal determination prohibition means. Steps S102, S108, and S110 correspond to processing as normality determination means. Normal determination requirement B determination processing (FIG. 3) corresponds to processing as the second diagnosis means.

According to the first embodiment described above, the following effects can be obtained.
(I). When it is determined by the normal determination requirement A that the possibility of attachment of the reducing agent is high, that is, within the normal determination requirement A, if (8) is denied or (9) is denied (in S102) no), the normal judgment of step S110 is not made. Thus, in the state in which the normal determination requirement A (8) or (9) is denied, normal determination for the addition valve 68 based on the actually measured air-fuel ratio A / F detected by the air-fuel ratio sensor 48 is prohibited. . From this, it is not determined that the addition valve 68 is normal even though the addition valve 68 is in the open fixing state.

  The presence / absence of normality determination with respect to the addition valve 68 determined based on the actually measured air / fuel ratio A / F detected by the air / fuel ratio sensor 48 is determined when it is determined that the possibility of attachment of the reducing agent is low. It is an essential requirement that both (8) and (9) in A are affirmed. For this reason, the certainty of the normal determination becomes very high, and the normal determination for the addition valve 68 can be executed with high accuracy.

  (B). When the temperature of the exhaust system is low, the fuel released from the addition valve 68 tends to adhere to the exhaust manifold 32 and the exhaust path 34, and when the temperature of the exhaust system is high, it becomes difficult to adhere. The condition of 8) determines that the outlet exhaust temperature Texout detected by the second exhaust temperature sensor 46 is higher than the reference temperature.

  Further, when the gas flow rate in the exhaust system, that is, the exhaust gas flow rate is small, the fuel released from the addition valve 68 adheres to the exhaust system, and when the exhaust gas flow rate is large, the adhesion tends to decrease. Since the exhaust gas flow rate is substantially proportional to the gas flow rate in the intake system, that is, the intake air amount ga, the condition (9) of the normal determination requirement A is the intake air amount ga detected by the intake air amount sensor 24. Is judged to be larger than the reference amount.

It is easy to acquire each data of the exhaust temperature and the intake air amount, and it is possible to easily determine the possibility of fuel adhering to the exhaust system without performing complicated calculation processing, and it is possible to easily determine whether the condition is satisfied.
(C). In the normal determination (S110), not only the normal determination requirement A but also the normal determination requirement B including the behavior of the exhaust gas temperatures Texin and Texout due to the heat of oxidation of the added fuel in the first exhaust purification device 38 is satisfied. Is a logical product condition (S108).

Therefore, the normality determination and the prohibition of the addition valve 68 based on the actually measured air-fuel ratio can be appropriately executed with higher accuracy.
[Embodiment 2]
In the present embodiment, the normality determination is executed only by the normality determination requirement A. That is, the ECU 70 executes the addition valve normal diagnosis process shown in FIG. 5 instead of the addition valve normal diagnosis process (FIG. 2) and the normal determination requirement B determination process (FIG. 3). Other configurations are the same as those of the first embodiment, and will be described with reference to FIG.

  The addition valve normal diagnosis process (FIG. 5) will be described. This process is a process that is interrupted and executed at regular intervals. When this process is started, it is first determined whether or not the normal determination requirement A described in the first embodiment is satisfied (S202).

  If any one of the conditions (1) to (13) is not satisfied (No in S202), the normal determination requirement A satisfaction counter Ca that counts the duration when the normal determination requirement A is satisfied is cleared ( S210). Thus, the present process is temporarily exited. Thereafter, if the normal determination requirement A is not satisfied (No in S202), the execution of Step S210 is repeated.

  When the normal determination requirement A is satisfied (yes in S202), the normal determination requirement A satisfaction counter Ca is incremented (S204). Next, it is determined whether or not the value of the normal determination requirement A establishment counter Ca immediately after counting up indicates the reference time TMa or more (S206). If Ca <TMa (no in S206), the process is temporarily exited. Thereafter, as long as the normal determination requirement A establishment (yes in S202) continues, the normal determination requirement A establishment counter Ca counts up (S204). However, even if the normal determination requirement A establishment counter Ca is incremented in this way, if the normal determination requirement A does not hold before Ca ≧ TMa (no in S202), the normal determination requirement A establishment counter Ca is It is cleared (S210).

  If the normal determination requirement A is established (yes in S202), and Ca ≧ TMa is satisfied (yes in S206), a normal determination is made (S208). That is, it is determined that the addition valve 68 is normal and the fuel is not leaking.

  In the present embodiment, the exhaust gas temperature Texin and the normality determination requirement B establishment flag Fex are not used in the timing chart of FIG. 4 described in the first embodiment by the above-described control. Can be judged.

  In the above-described configuration, the relationship with the claims is that the determination on the normal determination requirement A (8) and (9) is processing as the reducing agent adhesion possibility determination means, and step S202 is processing as the normal determination prohibition means. Steps S202 and S208 correspond to processing as normality determination means.

According to the second embodiment described above, the following effects can be obtained.
(I). The effects (a) and (b) of the first embodiment are produced.
[Other embodiments]
(A). In each of the above-described embodiments, as shown in FIG. 1, the DPF is disposed as the filters 38a and 38b in the first exhaust purification device 38. In addition to this DPF, the present invention can also be applied when a DPNR (Diesel Particulate-NOx Reduction system) that simultaneously purifies PM and NOx is provided, and the same effect can be produced.

  (B). The combination of the logical product conditions of the normal determination requirement A described in FIG. 2 is an example, and other requirements may be added to diagnose the normal determination of the addition valve 68 with higher accuracy. The same applies to the normality determination requirement B.

  It should be noted that in (8) and (9) of the normal determination requirement A, only one of them may be an indispensable requirement for determining that the possibility of attachment of the reducing agent (added fuel) is low. In this case, both (8) and (9) of the normal determination requirement A may be determined, and if either one is satisfied, it may be determined that the possibility of attachment of the reducing agent (added fuel) is low. Alternatively, among the conditions (8) and (9), only one of the conditions included in the normal determination requirement A may be used.

(C). Instead of the intake air amount ga detected by the intake air amount sensor 24 (FIG. 1), a sensor for detecting the exhaust flow rate may be provided and the exhaust flow rate detected by the sensor may be used.
(D). As the temperature detection means provided in the exhaust system, as in each of the above embodiments, the exhaust temperature sensors 44 and 46 are disposed between the two filters 38a and 38b or directly below the downstream filter 38b. An exhaust gas temperature sensor may be arranged upstream of the upstream filter 38a to detect the exhaust gas temperature and use it for determination. Regardless of whether or not the catalyst has passed, if the exhaust gas is at a low temperature, it is easy for the added fuel to adhere to the exhaust system. Therefore, the possibility of fuel adhesion can be determined based on the exhaust temperature.

FIG. 2 is a block diagram showing a schematic configuration of a control system that functions as a vehicle diesel engine and a reducing agent addition valve diagnostic apparatus according to the first embodiment. 5 is a flowchart of an addition valve normal diagnosis process executed by the ECU according to the first embodiment. The flowchart of a normal determination requirement B determination process similarly. 4 is a timing chart illustrating an example of control according to the first embodiment. The flowchart of the addition valve normal diagnosis process which ECU of Embodiment 2 performs.

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, 38 ... first exhaust purification device, 38a, 38b ... filter, 40 ... second exhaust purification device, 40a ... oxidation catalyst, 44 ... first exhaust temperature sensor, 46 ... second exhaust 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 (3)

An addition valve for supplying a reducing agent to the exhaust purification device by discharging the reducing agent into the exhaust flow from the upstream side of the exhaust purification device in an exhaust system of the internal combustion engine, and an addition control for controlling the addition of the reducing agent by the addition valve Means for diagnosing leakage of the reducing agent from the addition valve based on the air-fuel ratio of the exhaust system,
An air-fuel ratio sensor provided downstream of the addition valve in the exhaust system of the internal combustion engine;
Gas flow rate detection means provided in the intake system or exhaust system of the internal combustion engine;
Reducing agent adhesion possibility determination means for determining that the possibility of attachment of the reducing agent in the exhaust system of the internal combustion engine is high when the gas flow rate detected by the gas flow rate detection means is less than the adhesion determination reference flow rate ;
Wherein the case has been determined to have a high adhesion potential of the reducing agent in the reducing agent adheres possibility determining means prohibits the normality determination for said addition valve based on the measured air-fuel ratio detected by the air-fuel ratio sensor Normal judgment prohibition means,
An internal combustion engine reducing agent addition valve diagnostic apparatus comprising: An addition valve for supplying a reducing agent to the exhaust purification device by discharging the reducing agent into the exhaust flow from the upstream side of the exhaust purification device in an exhaust system of the internal combustion engine, and an addition control for controlling the addition of the reducing agent by the addition valve Means for diagnosing leakage of the reducing agent from the addition valve based on the air-fuel ratio of the exhaust system,
  An air-fuel ratio sensor provided downstream of the addition valve in the exhaust system of the internal combustion engine;
  Gas flow rate detection means provided in the intake system or exhaust system of the internal combustion engine;
  Temperature detecting means provided in the exhaust system of the internal combustion engine;
  Reducing agent in the exhaust system of the internal combustion engine when the temperature detected by the temperature detection means is lower than the adhesion determination reference temperature or the gas flow rate detected by the gas flow detection means is less than the adhesion determination reference flow rate Reducing agent adhesion possibility determination means for determining that the adhesion possibility of
  When the reducing agent adhesion possibility determining means determines that the reducing agent adhesion possibility is high, the normality prohibiting the normality determination with respect to the addition valve based on the actually measured air-fuel ratio detected by the air-fuel ratio sensor Judgment prohibition means,
  An internal combustion engine reducing agent addition valve diagnostic apparatus comprising: According to claim 1 or 2, a temperature detecting means disposed in an exhaust system of an internal combustion engine, the temperature detected by said temperature detecting means is not more than the upper limit of the temperature of the addition valve can take if not open sticking state And a second diagnosing means for diagnosing that there is no leakage of the reducing agent from the addition valve and that it is normal, and the normal determination prohibiting means is capable of attaching the reducing agent by the reducing agent adhesion possibility determining means. Is satisfied based on the actually measured air-fuel ratio detected by the air-fuel ratio sensor when a logical sum condition of a condition determined to be high and a condition not determined to be normal by the second diagnostic means is satisfied. An internal combustion engine reducing agent addition valve diagnostic apparatus characterized by prohibiting normality determination with respect to an addition valve.

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