JP4736796B2 - Diagnostic apparatus and diagnostic method for internal combustion engine - Google Patents

Description

  The present invention relates to a technology for diagnosing an exhaust purification system provided with a catalyst for purifying a specific component of exhaust gas of an internal combustion engine, and in particular, in a situation where control for promoting the temperature rise of the catalyst is performed as in cold start. The present invention relates to a diagnostic apparatus and a diagnostic method suitable for detecting an abnormality of an exhaust purification system including this control.

  In the field of internal combustion engines for automobiles in recent years, it is strongly desired to improve exhaust gas purification technology, particularly from the cold start when the catalyst is in an inactive state, and regulations by regulations have become strict. Therefore, in order to activate the catalyst at an early stage when the cold engine is started, catalyst temperature increase promotion control such as intake air amount increase control by ignition speed increase or ignition timing retardation control is often performed. In addition, a diagnosis of whether the exhaust purification system at the time of cold start including such control is functioning normally is required, and there is a tendency that regulations are strengthened.

In Patent Document 1, as such a diagnostic technique, at the time of cold start, the engine is started from the time when a predetermined delay time has elapsed since the start of temperature increase promotion control that combines engine speed feedback control and ignition timing feedback control. The engine speed and ignition timing are monitored, and it is determined that a failure has occurred when a predetermined time has elapsed when the engine speed is equal to or lower than a predetermined value or the ignition timing is equal to or higher than a predetermined value.
JP 2001-132526 A

  In the above-mentioned Patent Document 1, diagnosis is started in a certain engine operating state in which both engine speed feedback control and ignition timing feedback control are performed as in the case of idle and after a predetermined delay time has not elapsed. Therefore, for example, the diagnosis is not performed in the usage that shifts to the acceleration / running mode in a relatively short time after the cold start, and the diagnosis frequency may be very low. Therefore, there is a case where the diagnosis is not performed although it is actually abnormal, and further improvement has been desired.

  Further, the active state of the catalyst largely depends on the catalyst temperature, that is, the supply heat amount of the exhaust gas supplied to the catalyst. This exhaust supply heat amount passes through the catalyst as well as the ignition timing and the engine speed. It also varies depending on the exhaust gas mass volume (intake and displacement). This mass volume changes according to the engine operating state. For example, the mass volume increases when shifting from idle to vehicle running. Therefore, in the case of making a diagnosis mainly based on the engine speed and the ignition timing as in Patent Document 1, a relatively accurate diagnosis can be made if limited to a specific operating state such as an idle. It is not possible to cope with various driving patterns in

The present invention has been made in view of such problems. That is, the present invention
At least one catalyst that is provided in an exhaust system of an internal combustion engine and purifies a specific component, and a catalyst that promotes the temperature rise of the catalyst when the engine is cooled by performing at least one of an increase in engine speed and a retard of ignition timing In the diagnostic device for an internal combustion engine for diagnosing an exhaust purification system having a temperature rise promoting means,
A specific component discharged to the downstream side of the catalyst in the engine cooler using the fuel injection amount and at least one of a change in engine speed and a change in ignition timing by the catalyst temperature increase promotion means during the engine cooler a specific component total emissions estimating means for estimating the total emissions,
Determination means for determining normality / abnormality of the exhaust purification system based on the total emission amount of the specific component ;
A determination prohibiting means for determining the normality / abnormality of the exhaust purification system by the determination means when the ratio at which the idle operation is performed during the engine cold machine is lower than a predetermined determination value;
It is characterized by having.

According to the present invention, at least one of a change in the fuel injection amount, an engine speed by the catalyst temperature increase promotion means, and a change in ignition timing during the engine cooler in which the temperature increase promotion of the catalyst by the catalyst temperature increase promotion means is performed. Are used to estimate the total discharge amount of the specific component to the downstream side of the catalyst and make a diagnosis based on the total discharge amount, thereby making it possible to make a highly accurate diagnosis in a wide range of engine operation.

  In addition, if the ratio of idle operation during engine cold is lower than a predetermined judgment value, normal / abnormal judgment is prohibited.In other words, the judgment is made only when the percentage of idle operation in engine cold is greater than or equal to the judgment value. Therefore, by appropriately setting the above judgment value, it is possible to effectively improve the diagnostic accuracy while suppressing a decrease in the diagnostic frequency, and to improve the diagnostic frequency and diagnostic accuracy. Can be achieved at a high level.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an exhaust gas purification system for a gasoline internal combustion engine according to an embodiment of the present invention. In the combustion chamber 21 of the internal combustion engine 20, a spark plug 9 is disposed substantially at the upper center, and an intake passage 23 is connected via an intake valve 22 and an exhaust passage 25 is connected via an exhaust valve 24. ing. In the intake passage 23, in order from the upstream side, an air cleaner 26, an air flow meter 3 for measuring the intake flow rate, an electronically controlled throttle valve 27 for opening and closing the intake passage 23, and a throttle opening sensor 4 for detecting the throttle opening, A fuel injection valve 5 for injecting fuel into the intake port 23A of the intake passage 23 is provided. The present invention can be applied not only to such a port injection type internal combustion engine but also to a direct injection type internal combustion engine that directly injects fuel from a fuel injection valve into a combustion chamber.

A front catalyst 13 is disposed in the exhaust passage 25 at an upstream position near the combustion chamber 21 and at a relatively high exhaust temperature, or at an upstream position in the vicinity thereof, and further downstream than the front catalyst 13. Thus, the rear catalyst 14 is disposed at a position under the floor of the vehicle having a relatively low exhaust temperature. That is, in order to purify the exhaust gas with high efficiency including when the cold machine is started, the catalyst system is configured such that the catalyst is arranged in series at a plurality of locations having different ambient temperatures in the exhaust passage 25. The front catalyst 13 preferably has a three-way catalyst 13A capable of reducing NOx, HC, CO to almost 0 (zero) in the vicinity of the theoretical air-fuel ratio, and HC discharged before the three-way catalyst 13A is activated. An HC adsorption type three-way catalyst combined with an HC adsorption catalyst 13B that temporarily adsorbs, and the rear catalyst 14 is, for example, the HC adsorption catalyst described above. However, not limited thereto, the above-mentioned three-way catalyst, other HC adsorption catalyst, to trap NO _X in an oxygen excess region, such as during the lean operation, releases NO _X during stoichiometric or rich operation, NOx trap to reduce Other catalysts such as a catalyst may be used alone or in combination.

The exhaust passage 25 is provided with an upstream oxygen sensor 11 and a downstream oxygen sensor 12 on the upstream side and the downstream side of the front catalyst 13, respectively. As the sensors 11 and 12, wide-range air-fuel ratio sensors that can detect a wide range of air-fuel ratios may be used instead of simple oxygen sensors (O ₂ sensors). The engine speed (engine speed) is calculated based on detection signals from, for example, a position (POS) sensor 7 that detects the rotational angle position of the crankshaft and a phase (PHASE) sensor 8 that detects the phase of the camshaft. . Further, a knock sensor 6 for detecting the occurrence of knocking (knock) and a water temperature sensor 10 for detecting the engine water temperature are attached to the cylinder block of the internal combustion engine 20.

  The engine controller 1 as an electronic control device is a known digital computer system having a CPU, a ROM, a RAM, and an input / output interface, and has a function of storing and executing various control processes. Various signals such as a starter signal and an ignition signal are input to the engine controller 1 via the signal line 2 and detection signals input from the various sensors 3, 4, 6 to 8 and 10 to 12. Based on the above, control signals are output to various actuators to control the operation. For example, the fuel injection amount and injection timing by the fuel injection valve 5 and the ignition timing by the spark plug 9 are controlled. Also, air-fuel ratio feedback control is performed based on the outputs of the oxygen sensors 11 and 12.

When the engine is not activated at a low temperature, such as when the engine is started for several tens of seconds after the engine is started, a large amount of hydrocarbons (HC) may be discharged from the catalyst without being purified. As a countermeasure against such cold emission, in this catalyst purification system, the above-described HC storage catalysts 13B and 14 are provided, and the front catalyst 13 is disposed in the vicinity of the exhaust manifold assembly portion 25A to promote temperature rise. In addition, catalyst temperature increase promotion control such as idle speed increase control and ignition timing retardation in idle rotation speed control is performed (catalyst temperature increase promotion means). Note that such catalyst temperature increase promotion control is also described in detail in, for example, the above-mentioned Patent Document 1.

  FIG. 2 is a flowchart showing a flow of diagnostic control processing for diagnosing whether the exhaust purification system is functioning normally at the time of engine cooling for performing catalyst temperature increase promotion control. This routine is started by the engine controller 1 when the engine is started, and is repeatedly executed for a very short predetermined period, specifically, every predetermined crank angle at which one unit (one to several times) of combustion is performed.

  In step 101, it is determined whether the operating state of the internal combustion engine 20 is an operating region in which the above-described catalyst temperature increase promotion control is performed as in cold start, that is, whether the engine is cold when the catalyst is not yet active. Specifically, the determination is made based on several conditions such as whether the engine water temperature is equal to or lower than a predetermined temperature of about 25 to 30 ° C.

  In step 102, it is determined whether a predetermined diagnosis permission condition is satisfied. The diagnosis permission condition includes conditions such as whether the sensors related to the exhaust gas temperature increase promotion control, for example, the air flow meter 3, the position sensor 7, the phase sensor 8, and the oxygen sensors 11, 12 are normal. However, as described later, this embodiment has one feature that it can be diagnosed in a relatively wide engine operation region in which the idling operation should be performed at a predetermined rate or more during the engine cold machine. Specifically, conditions such as individual operation states (idle, etc.), engine load, and engine speed are not included in the diagnosis permission conditions in step 102.

  In the subroutine of step 102A, the diagnosis determination cancel flag CFLG is set. Specifically, as shown in FIG. 3, first, in step 121, 1 is added to the value CSMRFCT of the monitored cumulative combustion counter, which is an integrated value of the (unit) number of combustions in the engine cold air under which the catalyst temperature increase promotion control is performed. Add and increment. In step 122, it is determined whether the idle operation is being performed, for example, whether the idle switch is ON. During idle operation, the engine speed is feedback-controlled to a predetermined target idle speed. Here, during idle operation in the engine cold state, the target idle speed is set higher than the warm-up state in order to promote catalyst temperature rise and warm-up, that is, the catalyst temperature rise described above. Rotational speed increase control as acceleration control is performed. In step 123, 1 is added to and incremented by the value CSMIDCT of the idling cumulative combustion counter corresponding to the integrated value of the number of times of combustion (unit) in which idling is performed during engine cooling. In step 124, an idle share ratio CSMIDL corresponding to the ratio of idle operation in the engine cold machine is calculated. Specifically, the ratio (CSMIDCT / CSMRFCT) of the idle cumulative combustion counter value CSMIDCT to the monitored cumulative combustion counter value CSMRFCT is obtained as the idle share rate CSMIDL.

  In step 125, the idle share rate CSMIDL is compared with a predetermined determination value CSMIDL # set in advance. This determination value CSMIDL # is, for example, a value of about 0.4 to 0.6, more preferably about 0.6. That is, if the idling operation is performed at a rate of about half during the engine cold machine, the diagnosis is performed. If the idle share rate CSMIDL is lower than the determination value CSMIDL #, the process proceeds from step 125 to step 126, and the diagnosis determination cancel flag CFLG is set to “1”. On the other hand, if the idle share ratio CSMIDL is equal to or greater than the determination value CSMDL #, the diagnosis determination cancel flag CFLG is set to “0”.

Referring to FIG. 2 again, in step 103, a unit exhaust supply heat quantity QEXST corresponding to the heat quantity of the exhaust gas supplied in one (one unit) combustion of the internal combustion engine is estimated and calculated. Specifically, QEXST is calculated by the following equation (1).
QEXST = TP × G (ADV) × G (N) (1)
“TP” is a fuel injection amount, “G (ADV)” is an ignition timing correction coefficient, and “G (N)” is a rotation speed correction coefficient. G (ADV) is obtained by referring to a control map table as shown in FIG. 4 based on the retard amount ADV-MBTCAL with respect to the optimum ignition timing MBT. As shown in the figure, the larger the ignition timing retard amount, the lower the combustion efficiency and the higher the exhaust gas temperature. Therefore, G (ADV) is set so that the unit exhaust gas supply heat amount QEXST increases. Yes. G (N) is obtained by referring to a control map table as shown in FIG. 5 based on the engine speed NE. As shown in the figure, the higher the rotational speed NE, the shorter the actual time of the combustion interval and the smaller the heat release, so G (N) is set so that the unit exhaust supply heat quantity QEXST increases. ing. Accordingly, it is possible to satisfactorily absorb and cancel out the fluctuation of the unit exhaust supply amount QEXTT due to fluctuations in the engine speed and ignition timing.

  In step 104, the unit exhaust gas supply heat quantity QEXST is integrated to calculate the exhaust gas supply total heat quantity QEXTTP corresponding to the total heat quantity of the exhaust gas supplied to the catalyst when the engine is cold. Specifically, QEXTTP is updated by adding the value obtained by multiplying the unit exhaust supply heat quantity QEXST by the number of combustions from the previous calculation (that is, the number of combustions per unit) to the total heat quantity QEXTTP before one calculation. To do.

In step 105, a catalyst HC remaining rate ITAT50 corresponding to the ratio of HC (hydrocarbon) remaining in the catalyst is calculated. Since the catalyst HC remaining rate ITAT50 greatly depends on the exhaust gas supply total heat amount QEXTP, in this embodiment, as shown in the following equation (2), the catalyst HC remaining rate ITAT50 is simply based on the exhaust gas supply total heat amount QEXTP alone. Is calculated.
ITAT50 = 1-QEXTTP / QT50 (2)
“QT50” corresponds to the amount of exhaust heat necessary for activation of the catalyst, and is a fixed value set in advance.

In step 106, the unit engine HC emission amount SIMEOE corresponding to the HC emission amount EOE discharged from the combustion chamber of the internal combustion engine to the exhaust system in one combustion, that is, the supply amount of HC supplied to the catalyst is estimated. As shown in FIG. 6, the HC emission amount EOE is substantially proportional to the fuel injection amount, and the ratio COE1 of the HC emission amount EOE to the fuel injection amount is substantially constant. Therefore, in step 106, the unit engine HC emission amount SIMEOE is simply calculated based on only the fuel injection amount TP with the ratio COE1 as a fixed coefficient.

In step 107, based on the unit engine HC emission amount SIMEOE and the current catalyst HC residual rate ITAT50, the unit catalyst HC total emission amount (unit: unit HC equivalent to the HC emission amount discharged downstream of the catalyst in one unit combustion) Tail pipe HC) SIMTPE is calculated. In step 108, the unit catalyst HC emission amount SIMTPE is integrated to calculate a catalyst HC total emission amount SIMTTPE corresponding to the total amount of tail pipe HC discharged downstream of the catalyst. Specifically, the catalyst HC total emission amount SIMTTPE is sequentially updated by adding a value obtained by multiplying the number of combustions per unit by SIMTPE to the SIMMTPE before one calculation.

In step 109, it is determined whether the catalyst HC remaining rate ITAT50 has reached a predetermined determination value of 0 (zero), that is, whether the catalyst has been activated. The determination value is not limited to the above value (0), and may be a larger value for shortening the diagnosis period or a smaller value for improving diagnosis accuracy.

  In Step 109A, it is determined whether or not the diagnosis determination cancel flag CFLG set in Step 102A (see FIG. 3) is “0”, that is, whether or not the idle sharing ratio is greater than or equal to the determination value.

If both the determinations in steps 109 and 109A are affirmed, the process proceeds to step 110, and normality / abnormality determination / diagnosis of the exhaust purification system is performed. Specifically, it is determined whether the catalyst HC total discharge amount SIMTTPE is equal to or less than a predetermined determination value EMNG. This determination value EMNG is a fixed value that is set in advance, and is set to a value that is, for example, about 1.5 times the normal catalyst HC total discharge amount SIMTTPE. If the determination in step 110 is affirmative, it is determined to be normal, and if it is negative, it is determined to be abnormal, and the driver is notified of an abnormality by, for example, a warning lamp or a warning sound.

FIG. 7 is a time chart at the time of cold start according to the present embodiment, in which the characteristic of the solid line NC corresponds to the normal condition (Normal Condition), and the characteristic of the broken line MC corresponds to the abnormal condition (Malfunction condition). Yes. The horizontal axis corresponds to the crank angle (reference crank position REF). As shown in the figure, in this embodiment, since seeking catalysts total HC emission amount SIMTTPE in consideration of the engine rotational speed NE and the ignition timing, etc., regardless of the fluctuation of the engine rotational speed NE, the catalyst total HC emission amount SIMTTPE increases substantially in proportion to the crank angle (combustion interval), and reaches the upper limit in the vicinity of the time when the catalyst HC remaining rate ITAT50 becomes zero. Therefore, by comparing the catalyst HC total emission amount SIMMTPE at this time with the determination value EMNG, a highly accurate diagnosis can be performed in a short diagnosis time.

  Next, characteristic configurations and operational effects of the present invention will be listed with reference to the illustrated embodiments. However, the present invention is not limited to the configuration of the illustrated embodiment specified by the reference numerals, and includes various modifications and changes without departing from the spirit thereof.

(1) At least one catalyst 13, 14 provided in the exhaust system (exhaust passage) 25 of the internal combustion engine 20 for purifying the specific component (HC), and catalyst temperature increase promotion means for promoting the temperature increase of the catalyst when the engine is cooled. In an internal combustion engine diagnostic apparatus for diagnosing an exhaust gas purification system having idle speed increase control, ignition timing retard control, etc., the downstream side of the specific component based on the state of the catalyst when the engine is cold Specific component total emission amount estimation means (step 108) for estimating the catalyst HC total emission amount SIMTTPE corresponding to the emission amount to the exhaust gas, and whether the exhaust purification system is normal or abnormal is determined based on this catalyst HC total emission amount SIMTTPE Determination means (steps 110 to 112).

In other words, in a diagnostic method for diagnosing an exhaust purification system having a catalyst that is provided in an exhaust system of an internal combustion engine and purifies a specific component, and a catalyst temperature increase promotion means that accelerates the temperature increase of the catalyst when the engine is cold. Based on the state of the catalyst at the time of cooling, a catalyst HC total discharge amount SIMTTPE corresponding to the discharge amount of the specific component discharged downstream of the catalyst is estimated (step 108), and based on the catalyst HC total discharge amount SIMTTPE Then, the normality / abnormality of the exhaust purification system is determined (steps 110 to 112).

When an abnormality such as a control failure occurs during engine cooling in which catalyst temperature increase promotion control such as idle speed increase control or ignition timing retard control is performed, a specific component (HC) that is finally discharged downstream of the catalyst The total catalyst HC discharge amount SIMTTPE corresponding to the total discharge amount increases. The total catalyst HC emission amount SIMTTPE varies depending not only on the HC emission amount discharged from the engine but also on the (active) state of the catalyst such as the catalyst remaining ratio ITAT50 of HC remaining in the catalyst. Therefore, the catalyst HC total emission amount SIMTTPE is estimated according to the state of the catalyst, and the diagnosis is performed based on the catalyst HC total emission amount SIMTTPE. Can be done in configuration.

In the case where the diagnosis is performed mainly based on the engine speed and the ignition timing as in the above-described conventional example, the region for the diagnosis is substantially limited to a specific operation region such as an idle. On the other hand, in this embodiment, the catalyst HC remains in consideration of the influence of the ignition timing and the engine speed (combustion interval), which are parameters of the catalyst temperature increase promotion control (catalyst warm-up control), as will be described later. Rate ITAT50 and catalyst HC total emission amount SIMTTPE are set, that is, the catalyst HC total emission amount SIMTTPE is obtained in a form that effectively reduces or eliminates the influence of fluctuations in engine speed, etc., and based on this catalyst HC total emission amount SIMTTPE By performing the diagnosis, a highly accurate diagnosis can be performed in a relatively wide engine operation region.

  The above diagnostic control basically diagnoses whether the catalyst temperature increase control in the engine cooler, specifically, whether the engine speed increase control and the ignition timing retard control in the idling engine speed control are normally performed. It is. Here, since the increase in the rotational speed greatly contributes to the catalyst activity, for example, in the case of shifting to the acceleration / running state immediately after the start of the cold engine due to the torque request of the driver, the rotational speed is increased according to the increase in the torque. The catalyst activity is rapidly increased by a factor different from the catalyst temperature increase control described above, and the catalyst temperature increase control cannot be diagnosed accurately. However, if the diagnosis is performed only in the situation where the idling operation is continued during the engine cold, the diagnosis frequency may be very low.

  Therefore, in the present invention, a ratio CSMIDL in which the idling operation in which the idling speed increase control as one of the catalyst temperature increase control is performed is obtained during the engine cooler, and this ratio CSMIDL is lower than the predetermined determination value CSMIDL #. In this case, execution of the determination means is prohibited (steps 125 and 126), and determination is made only when the ratio of idle operation is equal to or greater than the determination value (steps 125 and 127). Therefore, by appropriately setting the judgment value CSMIDL #, it is possible to effectively improve the diagnostic accuracy while suppressing a decrease in the diagnostic frequency, and to improve both the diagnostic frequency and the diagnostic accuracy at a high level. can do.

(2) It has unit catalyst specific component emission amount estimation means (step 107) for estimating a unit catalyst HC emission amount SIMTPE corresponding to the emission amount of the specific component discharged downstream of the catalyst by combustion of one unit of the internal combustion engine. The specific component total discharge amount estimating means integrates the unit catalyst HC discharge amount to calculate the catalyst HC total discharge amount (step 108). In this way, by estimating the unit catalyst HC emission amount SIMTPE for each unit of combustion, for example, the fluctuation of the HC emission amount in the transition period of the engine operating state, such as when accelerating from idle, can be accurately canceled out. Can be absorbed. The “one unit” combustion is preferably one combustion, or may be several times of combustion according to the calculation interval (crank angle) of the control routine.

(3) The “catalyst state” relates to the active state of the catalyst, and is typically the catalyst HC remaining rate ITAT50 corresponding to the ratio of the specific component remaining in the catalyst. However, other parameters indicating the active state of the catalyst, such as a catalyst temperature detected or estimated by a catalyst temperature sensor or the like, may be used.

(4) Unit engine specific component emission amount estimation means (step 106) for estimating a unit engine HC emission amount SIMEOE corresponding to the emission amount of the specific component discharged from the internal combustion engine by one unit of combustion based on the fuel injection amount. The unit catalyst specific component emission amount estimating means calculates a unit catalyst HC emission amount SIMTPE based on the catalyst HC remaining rate ITAT50 and the unit engine HC emission amount SIMEOE (step 107). Thus, based on the unit engine HC emission amount SIMEOE discharged from the internal combustion engine and the catalyst HC remaining rate ITAT50 indicating the state of the catalyst at that time, the unit catalyst HC emission amount SIMTPE for each unit of combustion. Therefore, the unit engine HC emission amount SIMTPE can be obtained with high accuracy in a form that reflects the active state of the catalyst in the unit engine HC emission amount SIMEOE.

(5) Unit exhaust heat quantity estimation means (step 103) for estimating a unit exhaust supply heat quantity QEXST corresponding to the exhaust heat quantity supplied to the exhaust system by combustion of one unit of the internal combustion engine based on the fuel injection quantity TP, Based on the exhaust heat quantity calculation means (step 104) that calculates the exhaust heat quantity QEXTTP corresponding to the exhaust heat quantity that is supplied to the exhaust system when the engine is cooled, by integrating the unit exhaust heat quantity QEXTST, and based on the exhaust heat quantity QEXTTP Catalyst HC remaining rate estimating means (step 105) for estimating the catalyst HC remaining rate ITAT50. In this way, the catalyst HC remaining rate ITAT50 can be accurately estimated based on the exhaust heat supply amount QEXTTP, while having a simple configuration that does not require a temperature sensor or the like that directly detects the temperature of the catalyst. In addition, since the exhaust gas supply heat quantity QEXTP is calculated by integrating the unit exhaust gas supply heat quantity QEXTT for each unit of combustion, the exhaust gas supply heat quantity can be accurately obtained including the transition period in which the engine operating state changes.

(6) Preferably, the catalyst HC remaining rate is calculated by the following equation (step 105).
ITAT50 = 1-QEXTTP / QT50
ITAT50: catalyst HC remaining rate QEXTTP: exhaust heat supply amount QT50: exhaust heat amount required for catalyst activity This QT50 is a preset fixed value. Therefore, the catalyst HC remaining rate is substantially based only on the exhaust supply heat amount QEXTTP. The ITAT 50 can be obtained easily and accurately, and the calculation load and memory usage are reduced.

  (7) Typically, as shown in FIG. 3, the integrated value CSMRFCT of the unit combustion frequency in the engine cooler is obtained, and the integrated value CSMIDCT of the unit combustion frequency in which the idle operation is performed in the engine cooler is obtained. Based on the integrated value, it is possible to easily and accurately obtain the ratio CSMIDL at which idle operation is performed.

  (8) The larger the retard amount of the ignition timing, the lower the combustion efficiency and the higher the exhaust gas temperature. Therefore, preferably, as shown in FIG. 4, when the retard amount ADV-MBTCAL of the ignition timing with respect to the optimal ignition timing is large, the unit exhaust gas supply heat amount (ignition timing correction coefficient G (ADV)) becomes large. A unit exhaust heat supply amount is calculated based on the retard amount ADV-MBTCAL. Thereby, the fluctuation | variation of the exhaust_gas | exhaustion supply calorie | heat amount resulting from the retard amount of ignition timing can be absorbed / cancelled accurately for every unit of combustion.

  (9) The higher the rotational speed NE, the shorter the actual time of the combustion interval, the smaller the heat release amount, and the smaller the exhaust heat supply amount. Therefore, preferably, as shown in FIG. 5, when the engine speed NE is high, the unit exhaust gas supply heat quantity QEXST (the engine speed correction coefficient G (N)) is increased based on the engine speed NE. The amount of heat QEXST is calculated. Thereby, the fluctuation | variation of the exhaust_gas | exhaustion supply calorie | heat amount resulting from engine speed NE can be absorbed and canceled favorably for every unit of combustion.

(10) Remaining rate determining means (step 109) for determining whether the catalyst HC remaining rate ITAT50 has decreased to a predetermined value (typically 0) is provided, and the catalyst HC remaining rate ITAT50 is determined by this remaining rate determining unit. When it is determined that the value has decreased to the value (ITAT50 = 0), the determination by the determination unit is executed (steps 110 to 112). As described above, the diagnosis time can be set by using the catalyst HC remaining rate ITAT50 used for calculating SIMTPE, and the diagnosis period can be effectively shortened without adding a determination parameter.

  (11) The specific component is typically hydrocarbon (HC) in a gasoline internal combustion engine. However, it is also possible to apply the present invention to an exhaust purification system using particulate matter (PM), nitrogen oxide (NOx), carbon monoxide (CO), etc. in the diesel engine as the specific component.

1 is a system diagram showing an example of an exhaust gas purification system for an internal combustion engine according to the present invention. The flowchart which shows the flow of the diagnostic process of the exhaust gas purification system which concerns on one Example of this invention. The flowchart which shows the subroutine of the diagnosis determination cancellation flag setting of step 102A of FIG. An example of a setting map of an ignition timing correction coefficient G (ADV) used in step 103 of FIG. An example of the setting map of the rotation speed correction coefficient G (N) used in step 103 of FIG. The graph which shows the relationship between the amount of fuel injection, and the engine HC discharge | emission amount of HC . The time chart which shows the change of the various parameters in the normal state and abnormal state at the time of engine cold start.

DESCRIPTION OF SYMBOLS 1 ... Engine controller 13 ... Front catalyst 14 ... Rear catalyst 20 ... Internal combustion engine 25 ... Exhaust passage (exhaust system)

Claims (7)

At least one catalyst that is provided in an exhaust system of an internal combustion engine and purifies a specific component, and a catalyst that promotes the temperature rise of the catalyst when the engine is cooled by performing at least one of an increase in engine speed and a retard of ignition timing In the diagnostic device for an internal combustion engine for diagnosing an exhaust purification system having a temperature rise promoting means,
A specific component discharged to the downstream side of the catalyst in the engine cooler using the fuel injection amount and at least one of a change in engine speed and a change in ignition timing by the catalyst temperature increase promotion means during the engine cooler a specific component total emissions estimating means for estimating the total emissions,
Determination means for determining normality / abnormality of the exhaust purification system based on the total emission amount of the specific component ;
A determination prohibiting means for determining the normality / abnormality of the exhaust purification system by the determination means when the ratio at which the idle operation is performed during the engine cold machine is lower than a predetermined determination value;
A diagnostic apparatus for an internal combustion engine, comprising: The specific component total emission estimating means is:
Using the fuel injection amount and at least one of the change in engine speed and the change in ignition timing by the catalyst temperature increase promotion means, the total heat amount of the catalyst in the engine cooler is sequentially calculated every predetermined period,
Based on the total heat amount of the catalyst and the fuel injection amount, the discharge amount of the specific component discharged to the catalyst downstream side every predetermined period is sequentially calculated,
2. The diagnostic apparatus for an internal combustion engine according to claim 1, wherein a total emission amount of the specific component discharged to the downstream side of the catalyst during the engine cooler is estimated by integrating the emission amount . The determination means obtains the active state of the catalyst based on the total heat amount of the catalyst, and when it is determined that the catalyst is active based on the active state of the catalyst, the determination means determines the total discharge amount of the specific component. The diagnostic apparatus for an internal combustion engine according to claim 2, wherein normality / abnormality of the exhaust purification system is determined based on the determination. The specific component total emission estimating means is:
Using the fuel injection amount and at least one of the change in engine speed and the change in ignition timing by the catalyst temperature increase promotion means, the emission amount of the specific component discharged from the internal combustion engine every predetermined period is sequentially calculated. With
And the discharge amount, and the active state of the catalyst, based on the internal combustion engine of claim 3, characterized in that sequentially calculates the discharge amount of the specific components discharged to the downstream side of the catalyst for each of the predetermined time period Diagnostic equipment. ITAT50 = 1-QEXTTP / QT50
ITAT50: Remaining rate of the specific component remaining in the catalyst QEXTTP: Total heat amount of the catalyst QT50: Heat amount necessary for the catalyst activity The control unit calculates the remaining rate corresponding to the active state of the catalyst according to the above equation. The diagnostic device for an internal combustion engine according to claim 3 or 4. The determination prohibiting means accumulates the number of unit combustions in the engine cold machine, accumulates the number of unit combustions in which the idle operation is performed in the engine cold machine, and calculates the ratio of idle operation based on both accumulated values. The diagnostic device for an internal combustion engine according to any one of claims 1 to 5 , wherein: A catalyst provided in an exhaust system of an internal combustion engine to purify a specific component, and a catalyst temperature increase promotion that accelerates the temperature increase of the catalyst when the engine is cooled by at least one of increasing the engine speed and retarding the ignition timing A diagnostic method for an internal combustion engine for diagnosing an exhaust purification system comprising:
During the engine cold, the fuel injection amount, using, at least one of the engine speed changes in the ignition timing changes due to the catalyst temperature increase promotion means, of the specific component discharged to the downstream side of the catalyst while the engine is cold Estimate total emissions ,
Obtaining the rate at which idle operation is performed during the engine cold, and determining whether the exhaust purification system is normal or abnormal based on the total emission amount of the specific component when this rate is equal to or greater than a predetermined determination value A diagnostic method for an internal combustion engine.

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