JP2007177630A - Diagnostic device and diagnostic method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an accurate diagnosis in a comparatively wide engine operating range. <P>SOLUTION: This diagnostic device for an internal combustion engine is provided with a catalyst in an exhaust passage and performs catalyst activity accelerating control such as idling speed increasing control and ignition timing retarding control when the engine is cold. When the engine is started, an initial heating value of the catalyst is estimated based on an engine temperature. In the cold state of the engine, the total heating value QEXSTP of the catalyst is estimated by adding the initial heating value to an integrated value of a unit exhaust supply heating value QEXST, and a catalyst residual rate ITAT50 is estimated based on the QEXSTP. A catalyst discharge amount SIMTTPE equivalent to the discharge amount of HC to the lower reaches of the catalyst is estimated based on the ITAT50 (S108). The normality or abnormality of an exhaust emission control system is determined based on the SIMTTPE (S110-S112). <P>COPYRIGHT: (C)2007,JPO&INPIT

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 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 idle speed increase control and 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 the engine has failed if the engine speed is less than a predetermined value or the ignition timing (advance value) is greater than or equal to a predetermined value.
JP 2001-132526 A

  In the above-mentioned Patent Document 1, a diagnosis is made in a certain engine operating state in which both engine speed feedback control and ignition timing feedback control are performed as in idle operation and after a predetermined delay time has elapsed. Since it cannot be started, for example, the diagnosis is not performed and the diagnosis frequency may be very low in the case of using the system to shift to the acceleration / running mode in a relatively short time after the cold start. 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, and is provided with at least one catalyst provided in an exhaust system of an internal combustion engine for purifying a specific component, and a catalyst temperature increase for promoting the temperature rise of the catalyst when the engine is cooled. An exhaust purification system having a temperature promotion means, a control unit for diagnosing the exhaust purification system, and an engine temperature detection means for detecting an engine temperature, wherein the control unit is a catalyst based on the engine temperature. Estimate the initial value of the amount of heat, and use the initial value of the amount of heat to estimate the total amount of heat of the catalyst in the engine cooler, estimate the state of the catalyst based on the total amount of heat of the catalyst, The catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated based on the above, and the normality / abnormality of the exhaust purification system is determined based on the catalyst discharge amount.

  According to the present invention, during the engine cooler in which the temperature rise of the catalyst is performed by the catalyst temperature raising means, the catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated based on the state of the catalyst, By making a diagnosis based on the catalyst discharge amount, a highly accurate diagnosis can be made in a wide range of engine operation.

  Here, the “catalyst state” is a value corresponding to the active state / purification performance of the catalyst, and is typically a catalyst remaining rate corresponding to a ratio of a specific component remaining in the catalyst as described later. The state of such a catalyst greatly depends on the total amount of heat of the catalyst. The total amount of heat of this catalyst increases with the amount of exhaust heat supplied to the exhaust system, and also greatly depends on the temperature of the catalyst before starting the engine. is doing. Therefore, if the state of the catalyst is simply estimated according to the amount of heat of exhaust, for example, when the engine temperature before starting the engine is relatively high and the total amount of heat of the catalyst is already high to some extent, the total amount of heat of the catalyst is estimated to be small. Therefore, an accurate diagnosis cannot be performed.

  Therefore, in the present invention, the initial value of the heat quantity of the catalyst is simply estimated from the engine temperature such as the engine water temperature and the oil temperature, and the total heat quantity of the catalyst is estimated based on the initial value of the heat quantity and the exhaust heat quantity. The state of the catalyst is estimated based on the total heat quantity of the catalyst. Therefore, even if the engine temperature at the start of engine start varies somewhat, a highly accurate diagnosis can be performed.

  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 that detects the occurrence of knocking (knock) and a water temperature sensor 10 that detects the engine water temperature as the engine temperature are attached to the cylinder block of the internal combustion engine 20.

  The engine controller 1 as an electronic control unit, that is, a control unit is a known digital computer system including 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, a control signal is output to various actuators to control its 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 increase control of the idle speed and retarding of the ignition timing in idle speed control for feedback control of the engine speed to a predetermined idle speed is performed (catalyst temperature increasing 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, this embodiment is characterized in that it can be diagnosed in a relatively wide engine operation region without being limited to idle operation as long as the engine is cold. Therefore, basically, individual operation states (idle etc.) The conditions such as the engine load and the engine speed are not included in the diagnosis permission conditions in step 102.

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 the subroutine of Step 104, the total catalyst heat quantity QEXTTP corresponding to the heat quantity of the catalyst is calculated. Referring to FIG. 3, in step 131, the start of the engine cold state in which the catalyst temperature increase control is performed, that is, at the time of engine start, specifically, the value of the total catalyst heat quantity QEXTTP is “0” in the initial state. Determine if there is. In this example, the values of various control parameters including the total catalyst heat quantity QEXTTP are reset to “0” when the engine is stopped, and the routine proceeds from step 131 to step 133 only when this subroutine is executed for the first time after engine startup. From the second time onward, the process proceeds to step 132.

  Immediately after the engine is started, in step 133, based on the engine water temperature TWINT detected by the water temperature sensor 10, for example, with reference to a preset control map table shown in FIG. 6, the initial value TQEPINI of the amount of heat of the catalyst. Is calculated. As shown in FIG. 6, the initial value TQEPINI is set higher as the water temperature TWINT is higher. Then, the initial value TQEPINI of the heat quantity is set to the total catalyst heat quantity QEXTTP.

  In the engine cooler, in step 132, the total catalyst heat quantity QEXTTP is updated based on the unit exhaust gas supply heat quantity QEXST. Specifically, a value obtained by multiplying the unit exhaust supply heat quantity QEXST by the number of combustions before the calculation (that is, the number of combustions in one unit) is added to the total catalyst heat quantity QEXTP before one calculation, and QEXTTP is calculated. Update. Thus, the total catalyst heat quantity QEXTTP corresponds to a value obtained by adding the unit exhaust supply heat quantity QEXTT by the number of combustion times, that is, a value obtained by adding the initial value TQEPINI of the catalyst to the total exhaust supply heat quantity supplied to the exhaust system.

In step 105, a catalyst remaining rate ITAT50 corresponding to the ratio of HC (hydrocarbon) remaining in the catalyst is calculated. Since the catalyst remaining rate ITAT50 greatly depends on the total catalyst heat quantity QEXTTP, in this embodiment, as shown in the following equation (2), the catalyst remaining ratio ITAT50 is simply calculated based only on the total catalyst heat quantity QEXTTP. Yes.
ITAT50 = 1-QEXTTP / QT50 (2)
“QT50” corresponds to the amount of heat necessary for the catalyst to be activated, and is a preset fixed value.

  In step 106, an exhaust amount EOE of HC discharged from the combustion chamber of the internal combustion engine to the exhaust system in one combustion, that is, a unit engine discharge amount SIMEOE corresponding to the supply amount of HC supplied to the catalyst is estimated. As shown in FIG. 7, the emission amount EOE is substantially proportional to the fuel injection amount, and the ratio COE1 of the emission amount EOE to the fuel injection amount is substantially constant. Therefore, in this step 106, the unit engine emission amount SIMEOE is simply calculated based only on the fuel injection amount TP with the ratio COE1 as a fixed coefficient.

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

  In step 109, it is determined whether the catalyst 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.

  If the determination in step 109 is affirmed, the process proceeds to step 110 to determine / diagnose whether the exhaust purification system is normal or abnormal. Specifically, it is determined whether the catalyst 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 about 1.5 times the catalyst discharge amount SIMTTPE in a normal case, for example. 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. 8 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, the catalyst discharge amount SIMTTPE is obtained by taking into account the engine speed NE, ignition timing, etc., so that the catalyst discharge amount SIMTTPE is determined by the crank angle regardless of the fluctuation of the engine speed NE. It increases almost in proportion to (combustion interval), and reaches the upper limit in the vicinity of the time when the catalyst remaining rate ITAT50 becomes zero. Therefore, by comparing the catalyst discharge amount SIMTTPE at this time with the determination value EMNG, a highly accurate diagnosis can be performed in a short diagnosis time.

  Next, the characteristic configuration and operational effects of the above embodiment will be listed. However, the present invention is not limited to the configuration of the illustrated embodiment with reference numerals, and includes various modifications and changes without departing from the spirit of the present invention. For example, as the engine water temperature, the water temperature detected by the water temperature sensor 10 is used in the above-described embodiment, which is a simple method using the water temperature sensor 10 also used for general engine control, but is not limited thereto. Instead, for example, the oil temperature of engine oil may be used, or the temperature of the catalyst or its vicinity may be directly detected in order to further improve accuracy.

  (1) Based on the engine temperature TWINT detected by the water temperature sensor 10, the initial value TQEPINI of the heat amount of the catalyst is estimated (step 133), and the exhaust heat supply amount corresponding to the exhaust heat amount supplied to the exhaust system of the internal combustion engine (QEXST) is calculated (step 103), and based on the exhaust heat supply amount and the initial value of the heat amount, the catalyst state ITAT50 in the engine cooler is estimated (steps 132 and 105), and based on the catalyst state Then, a catalyst discharge amount SIMTTPE corresponding to the discharge amount of the specific component in the engine cooler to the downstream side of the catalyst is estimated (step 108), and normality / abnormality of the exhaust purification system is determined based on the catalyst discharge amount SIMTTPE. (Steps 110 to 112).

  If this control malfunction occurs during engine cooling where catalyst temperature increase promotion control such as idle speed increase control or ignition timing retard control is performed, hydrocarbon HC, which is a specific component that is finally discharged downstream of the catalyst The catalyst discharge amount SIMTTPE corresponding to the total discharge amount becomes larger. This catalyst discharge amount SIMTTPE varies depending not only on the HC discharge amount discharged from the engine but also on the active state / purification performance of the catalyst such as the catalyst remaining ratio ITAT50 of HC remaining in the catalyst. Therefore, by estimating the catalyst discharge amount SIMTTPE according to the catalyst state ITAT50 and making a diagnosis based on the catalyst discharge amount SIMTTPE, a highly accurate diagnosis is performed with a simple configuration that does not require a catalyst temperature sensor or the like. be able to.

  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 the present embodiment, the remaining catalyst corresponding to the state of the catalyst is considered 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). By setting the rate ITAT50 and the catalyst emission amount SIMTTPE, that is, obtaining the catalyst emission amount SIMTTPE in a form that effectively reduces or eliminates the influence of fluctuations in the engine speed, etc., and performing diagnosis based on this catalyst emission amount SIMTTPE, Highly accurate diagnosis can be performed in a relatively wide range of engine operation.

  The catalyst remaining rate ITAT50 corresponding to the state of the catalyst greatly depends on the amount of heat of the catalyst, and the amount of heat of this catalyst increases with the amount of exhaust heat supplied to the exhaust system, and typically at the time of engine start. Thus, it greatly depends on the temperature of the catalyst before the temperature rise by the catalyst temperature raising means. Therefore, if the state of the catalyst is simply estimated according to the amount of heat of exhaust, for example, when the engine is started in a situation where the engine temperature is relatively high and the amount of heat of the catalyst is already high to some extent, such as during hot restart, the amount of heat of the catalyst is small. It is estimated and cannot make an accurate diagnosis.

  Therefore, in the above embodiment, the initial value TQEPINI of the heat quantity of the catalyst is estimated from the engine temperature, and the catalyst state ITAT50 is estimated based on the initial heat quantity value TQEPINI and the exhaust heat quantity. Therefore, highly accurate diagnosis can be performed regardless of variations in engine temperature at the time of engine start, and highly accurate diagnosis can be realized over a wide range of engine operations.

  (2) Estimating the unit catalyst discharge amount SIMTPE corresponding to the discharge amount of the specific component discharged to the downstream side of the catalyst by combustion of one unit of the internal combustion engine, and calculating the catalyst discharge amount SIMTTPE by integrating the unit catalyst discharge amount (Step 108). Therefore, it is possible to accurately cancel and absorb the fluctuation of the emission amount in the transitional period of the engine operating state such as when accelerating from idle. 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 / purification performance of the catalyst, and is typically the catalyst residual ratio 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) Based on the fuel injection amount TP, a unit exhaust supply heat quantity QEXST corresponding to the exhaust heat quantity supplied to the exhaust system by one unit combustion of the internal combustion engine is estimated (step 103), and the initial value TQEPINI of the heat quantity is set. The total catalyst heat quantity QEXTTP is calculated by adding the integrated unit exhaust heat supply quantity QEXST (step 104). In this way, the total catalyst heat quantity QEXTTP can be obtained with high accuracy 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 total catalyst heat quantity QEXTTP is calculated by integrating the unit exhaust supply heat quantity QEXTST for each unit of combustion, the total catalyst heat quantity QEXTTP can be accurately obtained including the transition period in which the engine operating state changes. .

  (5) Estimating the unit engine 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 TP (step 106), the catalyst remaining rate ITAT50 and the unit engine emission The unit catalyst discharge amount SIMTPE is calculated based on the amount SIMEOE (step 107). Thus, the unit catalyst emission amount SIMTPE is calculated for each unit of combustion based on the unit engine emission amount SIMEOE discharged from the internal combustion engine and the catalyst remaining rate ITAT50 indicating the state of the catalyst at that time. Therefore, the unit engine emission amount SIMTPE can be obtained with high accuracy in a manner that reflects the active state of the catalyst in the unit engine emission amount SIMEOE.

(6) The catalyst remaining rate is calculated by the following equation (step 105).
ITAT50 = 1-QEXTTP / QT50
ITAT50: catalyst remaining rate QEXTSP: total catalyst heat QT50: heat necessary for catalyst activity This QT50 is a fixed value set in advance. Therefore, the catalyst remaining rate ITAT50 is substantially simplified based on only the total catalyst heat QEXTTP. Therefore, the calculation load and memory usage can be reduced.

  (7) The larger the retard amount of the ignition timing, the lower the combustion efficiency and the higher the exhaust gas temperature. Therefore, 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 retard amount of the ignition timing is set so that the unit exhaust gas supply heat amount (ignition timing correction coefficient G (ADV)) becomes large. The unit exhaust supply heat quantity is calculated based on ADV-MBTCAL. Thereby, the fluctuation | variation of the catalyst total calorie | heat_amount resulting from the retard amount of ignition timing can be absorbed and canceled with accuracy for every unit of combustion.

  (8) The higher the rotational speed NE, the shorter the actual time of the combustion interval, the smaller the heat release, and the smaller the total catalyst heat. Therefore, as shown in FIG. 5, the unit exhaust supply heat quantity QEXTT is based on the engine speed NE so that the unit exhaust supply heat quantity QEXST (the rotation speed correction coefficient G (N)) increases when the engine speed NE is high. Is calculated. Thereby, the fluctuation | variation of the catalyst total calorie | heat amount resulting from the engine speed NE can be absorbed and offset favorably for every unit of combustion.

  (9) It is determined whether the catalyst remaining rate ITAT50 has decreased to a predetermined value (typically 0) (step 109). When it is determined that the catalyst remaining rate ITAT50 has decreased to the predetermined value (ITAT50 = 0) A diagnosis is executed (steps 110 to 112). Thus, the diagnosis time can be set using the catalyst remaining rate ITAT50 used for the calculation of SIMTPE, and the diagnosis period can be effectively shortened without adding a parameter for determination.

  (10) 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. FIG. 3 is a flowchart showing a subroutine for calculating total exhaust heat quantity in step 104 of FIG. 2. 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. FIG. 4 is an example of a setting map of a heat initial value TQEPINI used in step 133 of FIG. 3. The graph which shows the relationship between the fuel injection amount and the engine discharge 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.

Explanation of symbols

1 ... Engine controller (control unit)
10 ... Water temperature sensor (engine temperature detection means)
DESCRIPTION OF SYMBOLS 13 ... Front catalyst 14 ... Rear catalyst 20 ... Internal combustion engine 25 ... Exhaust passage (exhaust system)

Claims (7)

An exhaust gas purification system having at least one catalyst provided in an exhaust system of an internal combustion engine for purifying a specific component, and catalyst temperature rise promotion means for promoting temperature rise of the catalyst when the engine is cold;
A control unit for diagnosing the exhaust purification system;
Engine temperature detection means for detecting the engine temperature,
The control unit
Estimate the initial heat value of the catalyst based on the engine temperature,
Using the initial value of the above heat quantity, estimate the total heat quantity of the catalyst in the engine cold machine,
Estimate the catalyst state based on the total heat of the catalyst,
Based on the state of the catalyst, the catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated,
A diagnostic apparatus for an internal combustion engine, wherein normality / abnormality of an exhaust purification system is determined based on the catalyst discharge amount. The control unit
Estimating the unit catalyst emissions corresponding to the emissions of specific components discharged downstream of the catalyst by combustion of one unit of the internal combustion engine,
2. The diagnostic apparatus for an internal combustion engine according to claim 1, wherein the unit catalyst discharge amount is integrated to calculate the catalyst discharge amount.   The diagnostic apparatus for an internal combustion engine according to claim 2, wherein the state of the catalyst is a catalyst remaining rate corresponding to a ratio of a specific component remaining in the catalyst. The control unit
Based on the fuel injection amount, a unit exhaust supply heat amount corresponding to the exhaust heat amount supplied to the exhaust system by combustion of one unit of the internal combustion engine is estimated,
4. The diagnostic apparatus for an internal combustion engine according to claim 3, wherein a total heat quantity of the catalyst is calculated by adding an integral value of the unit exhaust gas supply heat quantity to the initial value of the heat quantity. The control unit
Based on the fuel injection amount, estimate the unit engine emission amount corresponding to the emission amount of the specific component discharged from the internal combustion engine by one unit combustion of the internal combustion engine,
The diagnostic apparatus for an internal combustion engine according to claim 3 or 4, wherein the unit catalyst emission amount is calculated based on the unit engine emission amount and the catalyst remaining rate. ITAT50 = 1-QEXTTP / QT50
ITAT50: catalyst remaining rate QEXTTP: total heat amount of catalyst QT50: heat amount required for catalyst activity The control unit calculates the catalyst remaining rate according to the above equation, and the internal combustion engine diagnostic device according to claim 5. 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 catalyst temperature increase promotion means that accelerates the temperature increase of the catalyst when the engine is cooled,
Based on the engine temperature, estimate the initial value of the heat quantity of the catalyst,
Using the initial value of the above heat quantity, estimate the total heat quantity of the catalyst in the engine cold machine,
Estimate the catalyst state based on the total heat of the catalyst,
Based on the state of the catalyst, the catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated,
A diagnostic method for an internal combustion engine, wherein normality / abnormality of an exhaust purification system is determined based on the catalyst emission amount.

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