JP4692274B2 - 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 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 the temperature increase promotion control that combines the engine speed feedback control and the ignition timing feedback control. The engine speed and ignition timing are monitored, and when the engine speed is less than a predetermined value or the ignition timing (advance value) is greater than or equal to a predetermined value, a failure (abnormal) is determined.
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 a problem, and is provided with at least one catalyst provided in an exhaust system of an internal combustion engine for purifying a specific component, and an increase in the number of revolutions when the engine is cooled. The present invention relates to a technology for diagnosing an exhaust purification system having a catalyst temperature increase promotion means for promoting temperature increase of a catalyst by using control and ignition timing retardation control for delaying ignition timing,
Based on the engine speed, the rotation speed correction coefficient corresponding to the contribution of the catalyst temperature increase accompanying the increase in the engine speed by the above-described engine speed increase control, and a larger value as the engine speed increases,
Based on the ignition timing, the ignition timing correction coefficient corresponding to the degree of contribution of the catalyst temperature rise accompanying the ignition timing retardation by the ignition timing retardation control, which is set to a larger value as the ignition timing is retarded, is calculated.
Based on these rotation speed correction coefficient, ignition timing correction coefficient, and fuel injection amount, the exhaust heat supply total heat amount corresponding to the total heat amount of the exhaust gas supplied to the catalyst during the catalyst temperature increase promotion is calculated. ,
A catalyst residual ratio corresponding to the ratio of the specific component remaining in the catalyst is calculated based on the exhaust heat total heat amount and a heat amount necessary for the catalyst to be activated,
Based on the catalyst remaining rate and the supply amount of the specific component supplied to the catalyst, a catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated,
When the catalyst remaining rate becomes a predetermined catalyst remaining rate, the catalyst discharge amount is compared with a predetermined catalyst discharge amount to determine normality / abnormality of the exhaust purification system,
Based on the rotation speed correction coefficient, the normal level of the rotation speed increase control is calculated,
Based on the ignition timing correction coefficient, a normal level of ignition timing retardation control is calculated,
Based on the normal level of the rotational speed increase control and the normal level of the ignition timing retard control, the abnormality of the rotational speed increase control and the ignition timing retard control is determined.
Is.

  According to the present invention, the catalyst corresponding to the discharge amount of the specific component to the downstream side of the catalyst based on the rotation speed correction coefficient and the ignition timing correction coefficient during the engine cooler in which the catalyst temperature rising promotion is performed by the catalyst temperature rising means. By estimating the emission amount and making a diagnosis based on the catalyst emission amount, a highly accurate diagnosis can be performed in a wide range of engine operation. The above correction coefficient is a value corresponding to the catalyst temperature increase contribution, and is typically set to a larger value as the engine speed is higher and as the ignition timing is retarded. By using such a correction coefficient, it is possible to accurately estimate the catalyst discharge amount used for diagnosis of system abnormality / normality regardless of fluctuations in engine speed and ignition timing. Then, by effectively using the correction coefficient used for estimating the catalyst emission amount, the normal level of the rotation speed increasing control and the normal level of the ignition timing retarding control in the catalyst temperature raising means can be easily calculated. Can do. In other words, by using the correction coefficient used for system determination, the normal level and degree of rotation speed increase control and ignition timing retardation control in the catalyst temperature raising means without setting and adapting new control factors Can be calculated individually, and the cause of the abnormality can be easily identified when the system is abnormal.

  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 is preferably a three-way catalyst 13A capable of reducing NO _x , 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. The rear catalyst 14 is, for example, the above-described HC adsorption catalyst. 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, reducing to NO _X Other catalysts such as a trap 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, 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 the predetermined idling operating range, the idling engine speed increasing control in the idling engine speed control for feedback control of the engine engine speed to the predetermined idling engine speed, and the ignition timing are set to the optimum ignition timing (MBT). In contrast, catalyst temperature increase promotion control is performed in combination with retard / retarded ignition timing retardation control (catalyst temperature increase 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 a diagnostic control process for diagnosing whether the exhaust purification system is functioning normally during the engine cooler in which the catalyst temperature increase promotion control is performed. 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 where 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 103A, an ignition timing correction coefficient G (ADV) is calculated based on the current ignition timing. This G (ADV) is obtained with reference to a control map table as shown in FIG. 6 based on the retard amount (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. That is, G (ADV) corresponds to the contribution of the catalyst temperature increase due to the retarded ignition timing, and is set to a larger value as the retard amount of the ignition timing increases.

  In step 103B, a rotational speed correction coefficient G (N) is calculated based on the current engine rotational speed NE. This G (N) is obtained by referring to a control map table as shown in FIG. 7 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. That is, G (N) corresponds to the contribution of the catalyst temperature increase due to the increase in the engine speed, and is set to a larger value as the engine speed increases.

In step 103C, 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 the fuel injection amount. By using the above correction coefficients G (ADV) and G (N), it is possible to satisfactorily absorb and cancel out fluctuations in the unit exhaust gas supply amount QEXST caused by fluctuations in 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 the subroutine of step 104A, the ignition timing correction coefficient average value AVADV and the rotation speed correction coefficient average value AVNE are calculated. Referring to FIG. 3 in detail, in step 141, the rotational speed correction coefficient integrated value SMCSNE is calculated based on the rotational speed correction coefficient G (N). Specifically, the SMCSNE is updated by adding the rotation speed correction coefficient G (N) calculated in the current calculation routine to the value SMCSNE accumulated up to the previous routine. In step 142, the engine speed correction coefficient average value AVNE is calculated by dividing the engine speed correction coefficient integrated value SMCSNE by the integrated combustion frequency. In step 143, an ignition timing correction coefficient integrated value SMCSADV is calculated based on the ignition timing correction coefficient G (ADV). Specifically, the SMCSADV is updated by adding the ignition timing correction coefficient G (ADV) calculated in the current calculation routine to the value SMCSADV accumulated up to the previous routine. In step 144, an ignition timing correction coefficient average value AVADV is calculated by dividing the ignition timing correction coefficient integrated value SMCSADV by the cumulative number of combustion times.

Referring to FIG. 2 again, 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 QEXTP, 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. 8, 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.

  If it is determined that there is an abnormality, the normal level WORADV of the ignition timing correction and the normal level WORNE of the rotation speed increase control are calculated by a subroutine of step 113. Specifically, as shown in FIG. 4, in step 151, the normal level WORKNE of the rotation speed increase control is calculated by the following equation (3).

WORNE = (AVNE−AVFNE) / (AVVTNE−AVFNE) (3)
Here, “WORDE” is an index representing the normal level / degree of the rotation speed increase control, and is a value close to “1” if normal, and a value close to “0” if abnormal. “AVFNE” is a value corresponding to the rotation speed correction coefficient at the time of abnormality, and is a preset fixed value. “AVTNE” is a value corresponding to a normal rotation speed correction coefficient, and is a fixed value set in advance.

  In step 152, the normal level WORADV of the ignition timing retardation control is calculated by the following equation (4).

WORADV = (AVADV−AVFADV) / (AVTADV−AVFADV) (4)
Here, “WORADV” is an index representing the normal level / degree of ignition timing increase control, and is close to “1” if normal, and close to “0” if abnormal. “AVFADV” is a value corresponding to the ignition timing correction coefficient at the time of abnormality, and is a preset fixed value. “AVTADV” is a value corresponding to a normal ignition timing correction coefficient, and is a fixed value set in advance. For example, when the ignition timing correction coefficient G (ADV) at the optimal ignition timing MBT is set to “1”, AVFADV is set to 1 and AVTADV is set to a value of 1.2 to 1.3.

  In the subroutine shown in FIG. 4, it is determined which of the rotation speed increase control and the ignition timing retard control is relatively normal or abnormal. That is, the cause of the system abnormality is specified. Specifically, in step 153, WORDE and WORADV are compared, and it is determined that the larger one is relatively normal and the smaller one is relatively abnormal (steps 154 and 155). This determination result may be warned / notified to the driver, or simply stored as a reference at the time of repair.

  FIG. 5 shows another example of a subroutine substituting for FIG. 4. In this example, the normality / abnormality of the rotation speed increase control and the ignition timing retard control are respectively determined. In step 151 and step 152, WORDE and WORDADV are calculated as in the case of FIG. In the following step 161, WORDE is compared with a preset determination value (a value smaller than 1). If WORNE is larger than the determination value, it is determined that the rotation speed increase control is normal (step 162), and if WORNE is equal to or less than the determination value, it is determined that the rotation speed increase control is abnormal (step 163). In step 164, WORADV is compared with a predetermined determination value (a value smaller than 1). If WORADV is larger than the determination value, it is determined that the ignition timing retardation control is normal (step 165). If WORADV is equal to or less than the determination value, it is determined that the ignition timing increase control is abnormal (step 166).

FIG. 9 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.

  (1) At least one catalyst 13, 14 provided in the exhaust system of the internal combustion engine 20 for purifying a specific component, and a catalyst that combines engine speed increase control and ignition timing retardation control when the engine is cold. An exhaust purification system having a catalyst temperature increase promoting means for promoting the temperature increase of the engine, and a control unit 1 for diagnosing the exhaust purification system when the engine is cold. A rotation speed correction coefficient G (N) is calculated based on the engine speed (step 103A), an ignition timing correction coefficient G (ADV) is calculated based on the ignition timing (step 103B), and these rotation speed correction coefficients G ( N) and the catalyst discharge amount SIMTTPE corresponding to the discharge amount of the specific component to the catalyst downstream side are estimated based on the ignition timing correction coefficient G (ADV) (step 108), and exhaust purification is performed based on the catalyst discharge amount SIMTTPE. It is determined whether the system is normal or abnormal (steps 110 to 112). In addition, based on the rotational speed correction coefficient G (N), the normal level WARNE of the rotational speed increase control is calculated (steps 141 and 142), and based on the ignition timing correction coefficient G (ADV), the ignition timing retardation is calculated. The normal level of control WORADV is calculated (steps 143 and 144).

  If this control malfunction occurs during engine cooling when the catalyst temperature increase promotion control is performed using both the rotation speed increase control and the ignition timing retard control, the carbonization, which is a specific component that is finally discharged downstream of the catalyst The catalyst discharge amount SIMTTPE corresponding to the total discharge amount of hydrogen HC increases. Therefore, by estimating the catalyst discharge amount SIMTTPE and making a diagnosis based on the catalyst discharge amount SIMTTPE, a highly accurate diagnosis can be performed with a simple configuration that does not require a catalyst temperature sensor or the like.

  When the diagnosis is performed simply based on the engine speed and the ignition timing as in the above-described conventional example, the region in which the diagnosis is performed is substantially limited to a specific operation region such as idle. In contrast, in this embodiment, the engine speed correction coefficient G (N) and the ignition timing correction coefficient are considered in consideration of the influence of the engine speed and ignition timing, which are parameters for catalyst temperature increase promotion control (catalyst warm-up control). Since G (ADV) is calculated and the catalyst emission amount SIMTTPE is set based on these correction factors, the catalyst emission amount SIMTTPE is effectively reduced and eliminated due to fluctuations in engine speed and ignition timing. Therefore, a highly accurate diagnosis can be performed in a relatively wide range of engine operation.

  Thus, by using the correction coefficients G (N) and G (ADV) used in the diagnosis of the system, more specifically, in the process of calculating the catalyst discharge amount SIMTTPE, the rotational speed increase control for increasing the temperature of the catalyst is performed. Therefore, the normal level of the ignition timing and the normal level of the ignition timing increase control can be obtained easily and accurately. In other words, it is possible to determine the normality / abnormality of the rotation speed increase control and ignition timing retardation control without the need to set / adjust new control parameters, etc., and to reduce the calculation load and memory used. it can.

  (2) The normal levels WARNE and WORADV are calculated by the following formula.

WORNE = (AVNE−AVFNE) / (AVVTNE−AVFNE)
WORADV = (AVADV−AVFADV) / (AVTADV−AVFADV)
As described above, each normality index is obtained by using a preset fixed value at the time of abnormality / normality. Therefore, it is easy to determine which of the engine speed increase control and the ignition timing retard control is relatively abnormal (normal) by comparing both WORDE and WORADV (step 153) when determining the abnormality of the exhaust purification system. Can be identified.

  (3) For each unit of combustion of the internal combustion engine, the unit catalyst emission amount SIMTPE corresponding to the emission amount of the specific component discharged downstream of the catalyst is sequentially calculated based on the rotation speed correction coefficient and the ignition timing correction coefficient. (Step 103C), the unit catalyst discharge amount is integrated to calculate the catalyst discharge amount. Therefore, it is possible to accurately obtain the catalyst discharge amount in such a manner that the fluctuations in the engine speed and the ignition timing are absorbed for each unit combustion. 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.

  (4) For each unit of combustion in the internal combustion engine, the average value AVNE of the rotational speed correction coefficient is calculated (step 142), and the normal level WARNE of the rotational speed increase control is calculated based on the average value AVNE. (Step 151). Further, for each unit of combustion of the internal combustion engine, an average value AVADV of the ignition timing correction coefficient is calculated (step 145), and a normal level WORADV of the ignition timing retardation control is calculated based on the average value AVADV. (Step 152). Accordingly, it is possible to obtain the normal level with high accuracy by offsetting and absorbing the fluctuation of the engine speed and the ignition timing after every unit of combustion.

  (5) More specifically, based on the rotational speed correction coefficient G (N) and the ignition timing correction coefficient G (ADV), a catalyst residual ratio ITAT50 corresponding to the ratio of the specific component remaining in the catalyst is calculated (step 105) The catalyst discharge amount SIMTTPE is accurately calculated based on the catalyst remaining rate (step 108).

  (6) 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.

  (7) 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. .

  (8) Based on the fuel injection amount TP, 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 is estimated (step 106), and the catalyst remaining rate ITAT50 and 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.

(9) 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.

  (10) 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.

  (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. 3 is a flowchart showing a subroutine for calculating a correction coefficient average value in step 104A of FIG. FIG. 3 is a flowchart showing an example of a normal level calculation subroutine of step 113 in FIG. 2. FIG. The flowchart which shows the other example of the subroutine of normal level calculation of step 113 of FIG. An example of a setting map of an ignition timing correction coefficient G (ADV) used in step 103A of FIG. An example of the setting map of the rotation speed correction coefficient G (N) used in step 103B of FIG. 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)
DESCRIPTION OF SYMBOLS 13 ... Front catalyst 14 ... Rear catalyst 20 ... Internal combustion engine 25 ... Exhaust passage (exhaust system)

Claims (6)

Using at least one catalyst provided in an exhaust system of an internal combustion engine to purify a specific component, and when the engine is cold, the engine speed increase control for increasing the engine speed and the ignition timing retard control for retarding the ignition timing An exhaust gas purification system having catalyst temperature rise promotion means for promoting temperature rise of the catalyst;
A control unit for diagnosing the exhaust gas purification system when the engine is cold,
The control unit is
Based on the engine speed, the rotation speed correction coefficient corresponding to the contribution of the catalyst temperature increase accompanying the increase in the engine speed by the above-described engine speed increase control, and a larger value as the engine speed increases,
Based on the ignition timing, the ignition timing correction coefficient corresponding to the degree of contribution of the catalyst temperature rise accompanying the ignition timing retardation by the ignition timing retardation control, which is set to a larger value as the ignition timing is retarded, is calculated.
Based on these rotation speed correction coefficient, ignition timing correction coefficient, and fuel injection amount, the exhaust heat supply total heat amount corresponding to the total heat amount of the exhaust gas supplied to the catalyst during the catalyst temperature increase promotion is calculated. ,
A catalyst residual ratio corresponding to the ratio of the specific component remaining in the catalyst is calculated based on the exhaust heat total heat amount and a heat amount necessary for the catalyst to be activated,
Based on the catalyst remaining rate and the supply amount of the specific component supplied to the catalyst, a catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated,
When the catalyst remaining rate becomes a predetermined catalyst remaining rate, the catalyst discharge amount is compared with a predetermined catalyst discharge amount to determine normality / abnormality of the exhaust purification system,
Based on the rotation speed correction coefficient, the normal level of the rotation speed increase control is calculated,
Based on the ignition timing correction coefficient, a normal level of ignition timing retardation control is calculated,
Based on the normal level of the rotational speed increase control and the normal level of the ignition timing retard control, the abnormality of the rotational speed increase control and the ignition timing retard control is determined.
A diagnostic apparatus for an internal combustion engine. For each unit of combustion in the internal combustion engine, the control unit sequentially calculates a unit catalyst discharge amount corresponding to a discharge amount of the specific component discharged downstream of the catalyst based on the rotation speed correction coefficient and the ignition timing correction coefficient. 2. The diagnostic apparatus for an internal combustion engine according to claim 1 , wherein the catalyst discharge amount is calculated by calculating and integrating the unit catalyst discharge amount. The control unit
For each unit of combustion of the internal combustion engine, an average value of the rotation speed correction coefficient is calculated, and a normal level of the rotation speed increase control is calculated based on the average value.
For each combustion of one unit of an internal combustion engine, it calculates the average value of the ignition timing correction coefficient, according to claim 2, characterized in that to calculate the normal level of the ignition timing retard control based on the average value A diagnostic device for an internal combustion engine. WORNE = (AVNE−AVFNE) / (AVVTNE−AVFNE)
WORADV = (AVADV−AVFADV) / (AVTADV−AVFADV)
WORNE: Normal level of rotational speed increase control AVNE: Average value of rotational speed correction coefficient AVFNE: Equivalent value of rotational speed correction coefficient at abnormal time AVTNE: Equivalent value of rotational speed correction coefficient at normal time WORADV: Normal level of ignition timing retardation control AVADV: Average value of the ignition timing correction coefficient AVFADV: Equivalent value of the ignition timing correction coefficient at the time of abnormality AVTADV: Equivalent value of the ignition timing correction coefficient at the time of normality The diagnostic device for an internal combustion engine according to claim 3 , wherein a normal level of the angle control is calculated. 5. The diagnostic apparatus for an internal combustion engine according to claim 4 , wherein the control unit compares a normal level of the rotational speed increase control with a normal level of the ignition timing retardation control when determining an abnormality of the exhaust purification system. 6. . Combining at least one catalyst provided in an exhaust system of an internal combustion engine for purifying a specific component, and an engine speed increasing control for increasing the engine speed when the engine is cold and an ignition timing retarding control for retarding the ignition timing. An internal combustion engine diagnosis method for diagnosing an exhaust gas purification system having catalyst temperature increase promotion means for promoting temperature increase of the catalyst,
Based on the engine speed, the rotation speed correction coefficient corresponding to the contribution of the catalyst temperature increase accompanying the increase in the engine speed by the above-described engine speed increase control, and a larger value as the engine speed increases,
Based on the ignition timing, the ignition timing correction coefficient corresponding to the degree of contribution of the catalyst temperature rise accompanying the ignition timing retardation by the ignition timing retardation control, which is set to a larger value as the ignition timing is retarded, is calculated.
Based on these rotation speed correction coefficient, ignition timing correction coefficient, and fuel injection amount, the exhaust heat supply total heat amount corresponding to the total heat amount of the exhaust gas supplied to the catalyst during the catalyst temperature increase promotion is calculated. ,
A catalyst residual ratio corresponding to the ratio of the specific component remaining in the catalyst is calculated based on the exhaust heat total heat amount and a heat amount necessary for the catalyst to be activated,
Based on the catalyst remaining rate and the supply amount of the specific component supplied to the catalyst, a catalyst discharge amount corresponding to the discharge amount of the specific component to the catalyst downstream side is estimated,
When the catalyst remaining rate becomes a predetermined catalyst remaining rate, the catalyst discharge amount is compared with a predetermined catalyst discharge amount to determine normality / abnormality of the exhaust purification system,
Based on the rotation speed correction coefficient, the normal level of the rotation speed increase control is calculated,
Based on the ignition timing correction coefficient, a normal level of ignition timing retardation control is calculated,
Based on the normal level of the rotational speed increase control and the normal level of the ignition timing retard control, the abnormality of the rotational speed increase control and the ignition timing retard control is determined.
A diagnostic method for an internal combustion engine.

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