JP3544765B2 - Engine catalyst activation state determination device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalyst active state determination device for an engine that can appropriately determine the active state of a catalyst without using a catalyst temperature sensor or the like.
[0002]
[Prior art]
Conventionally, whether or not a catalyst has been activated has been determined mainly based on a detection value of a catalyst temperature sensor facing the catalyst. That is, the temperature of the exhaust gas passing through the inside of the catalyst layer is monitored by the catalyst temperature sensor, and when the temperature of the exhaust gas exceeds the catalyst activation temperature set in advance by experiments or the like, it is determined that the catalyst is active.
[0003]
However, there is an individual difference in the catalyst temperature sensor, and the detection accuracy is likely to vary due to the effect. Even if the catalyst activation temperature and the actually measured exhaust gas temperature match, the catalyst is actually activated. Not necessarily. In addition, the catalyst temperature sensor has deteriorated with time, and the active state cannot always be detected in a stable state.
[0004]
Therefore, as disclosed in, for example, JP-A-6-167210, in addition to the oxygen concentration sensor (hereinafter, “FO2 sensor”) provided upstream of the catalyst, another oxygen concentration sensor (hereinafter, “FO2 sensor”) is provided downstream of the catalyst. RO2 sensor "), measures the output value VRO2 of the RO2 sensor for a predetermined time, obtains the maximum value and the minimum value of the output value VRO2 at that time, and determines the difference between the maximum value and the minimum value by a predetermined value. Some include a so-called dual O2 sensor system that determines that the catalyst has been activated when the following occurs.
[0005]
That is, when the catalyst is in an inactive state, the output value VRO2 of the RO2 sensor is slightly delayed in phase from the output value VFO2 of the FO2 sensor shown by the solid line, as shown by the broken line in FIG. Show almost the same changes. Then, when the catalyst is activated, the output value VRO2 of the RO2 sensor changes slowly with a small fluctuation width, as shown in FIG. In the dual O2 sensor system, the active state of the catalyst is determined by detecting the output fluctuation width of the RO2 sensor.
[0006]
[Problems to be solved by the invention]
By the way, in an engine equipped with the dual O2 sensor system, the deterioration of the catalyst or the like is often diagnosed based on the output fluctuation of the RO2 sensor after the activation of the catalyst. That is, when the catalyst deteriorates or the like occurs, the catalyst purification ability decreases, and the output value VRO2 of the O2 sensor gradually changes to approximate the output value VFO2 of the FO2 sensor.
[0007]
The catalyst deterioration diagnosis is performed when certain diagnostic conditions are satisfied after activation of the catalyst. However, when the catalyst deterioration diagnosis is performed, an unpredictable abnormality (such as cracking of the catalyst, rapid deterioration due to overheating, etc.) occurs in the catalyst, and the catalyst purification ability is rapidly increased. When the engine is started, even if the catalyst is in an active state, the output fluctuation of the RO2 sensor does not fall within a predetermined range after the engine is started. Therefore, the active state of the catalyst cannot be determined. As a result, catalyst deterioration diagnosis is started. Is not satisfied, and the catalyst deterioration diagnosis cannot be performed. That is, if the activation state of the catalyst cannot be accurately determined, diagnosis of deterioration of the catalyst or the like cannot be performed accurately, and there is a problem that diagnostic accuracy is reduced.
[0008]
The present invention has been made in view of the above circumstances, and has as its object to provide a catalyst active state determination device for an engine that can easily and accurately detect the active state of a catalyst.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, as shown in a basic configuration diagram of FIG. 1A, a plurality of cycle-based integrated values for respectively calculating integrated values of physical quantities indicating an engine load at different cycles. Calculating means, a plurality of temporary catalyst activity level setting means for setting a temporary catalyst activity level based on each of the integrated values for each cycle, and a current catalyst activity state based on each of the temporary catalyst activity levels set for each cycle And a catalyst activity determining means for determining
[0010]
According to a second aspect of the present invention, in the first aspect of the invention, the temporary catalyst activity level setting means for each cycle determines the temporary catalyst activity level as an inactive level and a quasi-active level based on the calculated integrated value. Activity level, and the catalyst activity determination means determines whether the current catalyst activity state is an inactive state, a quasi-active state, or an active state based on each set temporary catalyst activity level. It is characterized by making a judgment.
[0011]
According to a third aspect of the present invention, as shown in the basic configuration diagram of FIG. 1B, a plurality of period-by-period integrated value calculating means for calculating integrated values of physical quantities indicating engine loads at different periods, respectively. A temporary catalyst activity determination value setting means for setting a temporary catalyst activity determination value for determining whether the catalyst is active or inactive based on each of the above integrated values, and a current value based on each temporary catalyst activity determination value set for each cycle. And a catalyst activity determination means for setting a catalyst activity determination value indicating whether the state of the catalyst is active or inactive.
[0012]
That is, according to the first aspect of the invention, the physical quantity indicating the engine load is integrated for each different cycle, and the provisional catalyst activity level is set for each cycle based on each integrated value. Then, the current state of the catalyst is determined based on each temporary catalyst activity level set for each cycle, and the result is used for air-fuel ratio control, ignition timing control, catalyst deterioration diagnosis, and the like.
[0013]
According to a second aspect of the present invention, in the first aspect of the present invention, each temporary catalyst activity level is set to one of an inactive level, a semi-active level, and an active level based on each integrated value calculated for each cycle. Then, based on each of these provisional catalyst activity levels, it is determined whether the current catalyst activity state is an inactive state, a semi-active state, or an active state.
[0014]
According to the third aspect of the present invention, a physical quantity indicating the engine load is integrated for each different cycle, and a provisional catalyst activity determination value indicating whether the catalyst is active or inactive is set for each cycle based on each integrated value, Based on each temporary catalyst activity determination value, a catalyst activity determination value indicating whether the current state of the catalyst is active or inactive is set and used for air-fuel ratio control, ignition timing control, catalyst deterioration diagnosis, and the like.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 2 to 13 show a first embodiment of the present invention. First, an overall outline of the engine will be described with reference to FIG. The engine 1 employed in the present embodiment is a horizontally opposed engine, and an intake manifold 3 and an exhaust manifold 4 communicate with an intake port 2a and an exhaust port 2b provided for each cylinder of a cylinder head 2, respectively. .
[0016]
An intake pipe 5 is communicated upstream of the intake manifold 3, while an exhaust pipe 6 is communicated downstream of the exhaust manifold 4, and a muffler 7 is attached to a downstream end of the exhaust pipe 6. Further, a front catalytic converter 8a and a rear catalytic converter 8b are interposed in the upstream collecting portion of the exhaust pipe 6.
[0017]
An air cleaner 9 is mounted on the air intake side upstream of the intake pipe 5, and a throttle valve 10 is interposed midway. Further, an air chamber 11 is formed in the intake pipe 5 downstream of the throttle valve 10.
[0018]
The intake pipe 5 is connected to a bypass passage 12 that bypasses the throttle valve 10 and communicates between the upstream and downstream of the throttle valve 10. An ISC (idle speed control) valve is connected to the bypass passage 12. 13 are interposed. Further, at the downstream end of the intake manifold 3, injectors 14 are provided corresponding to the respective cylinders. An ignition plug 15a whose tip is exposed to the combustion chamber is attached to the cylinder head 2 for each cylinder, and an ignition coil 15b connected to the ignition plug 15a is connected to an igniter 16.
[0019]
Next, the arrangement of sensors will be described. A crank angle sensor 22 for detecting a protrusion formed on the outer periphery of the crank rotor 21 is provided opposite to a crank rotor 21 connected to the crankshaft 1b of the engine 1. On the other hand, a cam angle sensor 24 for detecting a cylinder which detects a protrusion formed on the outer periphery of the cam rotor 23 is provided opposite to a cam rotor 23 connected to the cam shaft 1c.
[0020]
A knock sensor 25 is fixed to the cylinder block 1a of the engine 1, and a cooling water temperature sensor 26 faces a cooling water passage 1d communicating the left and right banks of the cylinder block 1a. Further, an intake air amount sensor 27 is provided immediately downstream of the air cleaner 9 in the intake pipe 5, and a throttle opening sensor 28a and an idle switch 28b which is turned on when the throttle valve is fully closed are built in the throttle valve 10. The throttle sensor 28 is connected in series. Further, a front O2 sensor (FO2 sensor) 29a is disposed upstream of the front catalytic converter 8a of the exhaust manifold 4, while a rear O2 sensor (RO2 sensor) is disposed downstream of the rear catalytic converter 8b of the exhaust pipe 6. 29b, which has a so-called dual O2 sensor (DOS) structure.
[0021]
FIG. 13 shows the calculation of the control amounts for the injector 14, the ignition plug 15a, and the ISC valve 13, and outputs, that is, fuel injection control, ignition timing control, idle speed control, and the like, and determination of the active state of the catalyst. This is performed by the electronic control unit 31.
[0022]
The electronic control device 31 is mainly composed of a microcomputer in which a CPU 32, a ROM 33, a RAM 34, a backup RAM 35, a counter / timer group 36, and an I / O interface 37 are connected to each other via a bus line 38. , A constant voltage circuit 39 for supplying a stabilized voltage to each section, a drive circuit 40 for driving actuators by a signal from an output port of the I / O interface 37, and an A / A for converting an analog signal from a sensor into a digital signal. A peripheral circuit such as a D converter 41 is built in.
[0023]
The constant voltage circuit 39 is connected to a battery 43 via a relay contact of a power supply relay 42, and a relay coil of the power supply relay 42 is connected to the battery 43 via an ignition switch 44. When the ignition switch 44 is turned on and the contact of the power supply relay 42 is closed, the constant voltage circuit 39 stabilizes the voltage of the battery 43 and supplies the voltage to each part of the electronic control device 31. Further, a battery 43 is directly connected to the backup RAM 35 via the constant voltage circuit 39, and a backup power supply is always supplied regardless of whether the ignition switch 44 is ON or OFF.
[0024]
The counter / timer group 36 includes various counters, a fuel injection timer, an ignition timer, a periodic interrupt timer for generating a periodic interrupt, a synchronization determination timer for determining an integrated value of the intake air amount for each different synchronization, and a system abnormality. Various timers such as a watchdog timer for monitoring are generically referred to for convenience. In the microcomputer, various other software counts and timers are used.
[0025]
A knock sensor 25, a crank angle sensor 22, a cam angle sensor 24, an idle switch 28b, and the like are connected to input ports of the I / O interface 37, and an intake air amount sensor 27, a throttle opening sensor 28a, The cooling water temperature sensor 26, the FO2 sensor 29a, the RO2 sensor 29b, and the like are connected via the A / D converter 41. Further, the voltage VB of the battery 43 is input to the A / D converter 41 and monitored. You. On the other hand, the igniter 16 is connected to the output port of the I / O interface 37, and the coils of the ISC valve 13 and the injector 14 are connected via the drive circuit 40. The ROM 33 stores various fixed data and the like in addition to a normal control program. The RAM 34 stores data obtained by processing output signals of the respective sensors and switches, and data processed by the CPU 32. Is stored. Further, in the backup RAM 35, various learning value maps, control data, trouble data corresponding to a failed part detected by the self-diagnosis function, and the like are stored, and the data is retained even when the ignition switch 44 is turned off. .
[0026]
According to the control program stored in the ROM 33, the CPU 32 performs engine control such as fuel injection control and ignition timing control, catalyst activity determination, catalyst deterioration diagnosis, and the like at predetermined intervals (every predetermined time or at each predetermined crank angle). To run.
[0027]
Here, the electronic control unit 31 has a function as a plurality of cycle-based integrated value calculating means, a plurality of cycle-based provisional catalyst activity level setting means, and a catalyst activity determining means. When the electronic control device 31 is turned on by turning on the power, the data and flag values stored in the RAM 34 are cleared by system initialization (excluding the data and flag values stored in the backup RAM 35), and a counter, After the count value and the count value of the timer group 36 are cleared and the system is initialized, the routines shown in the flowcharts of FIGS. 2 to 5 are executed at predetermined intervals, and differ from the catalyst activation state determination routine shown in FIG. The activation determination integrated values IQAS and IQA, which are the integrated values QAS and QAC of the intake air amount QA for each of the periods A and B. Is calculated, and the provisional catalyst activity levels QASLV, QACLV are respectively set based on the respective activity determination integrated values IQAS, IQAC, and the current catalyst state is deactivated by referring to the map based on the provisional catalyst activity levels QASLV, QACLV. A catalytic activity level CATLV indicating a catalytic activity state of quasi-active or active is set. Then, in the air-fuel ratio feedback correction coefficient setting routine shown in FIG. 3, the above-mentioned catalyst activity level CATLV is read, and the air-fuel ratio feedback correction coefficient λ is set in accordance with the activation state of the catalyst. In an air-fuel ratio feedback correction coefficient setting subroutine based on the DOS control shown, an air-fuel ratio feedback correction coefficient λ is set based on the output voltages VFO2 and VRO2 of the FO2 sensor 29a and the RO2 sensor 29b. Then, in the fuel injection amount setting routine shown in FIG. 5, the fuel injection amount is corrected by the air-fuel ratio feedback correction coefficient λ set according to the activation state of the catalyst so that the air-fuel ratio matches the target air-fuel ratio. Perform air-fuel ratio control.
[0028]
First, the catalyst activation state determination routine shown in FIG. 2 will be described.
This catalyst activation state determination routine is executed every predetermined time (for example, 50 ms), and in steps S2 to S6, the intake air amount QA as an example of the physical quantity indicating the engine load is integrated every time the routine is executed, and the first is performed. An intake air amount integrated value QAS is calculated, and when a first set time tA that defines a first cycle A has been reached, the first intake air amount integrated value QAS is used for determining a catalyst activation state. Adopted as the activity determination integrated value IQAS, based on the first activity determination integrated IQAS, a first temporary catalyst activity level QASLV representing a temporary catalyst activity state under the first cycle A is set, and step S7 In steps S11 to S11, the intake air amount QA is integrated every time the routine is executed to calculate a second intake air amount integrated value QAC, and a second set time t for defining a second cycle B longer than the first cycle A Is reached, the second intake air amount integrated value QAC is adopted as the second activity determination integrated value IQAC for determining the catalyst activation state, and based on the second activity determination integrated value IQAC, the second cycle A second provisional catalyst activity level QACLV representing a provisional catalyst activity state under B is set. Then, in step S12, a catalyst activity level CATLV representing the current catalyst activity state is set for each routine execution based on the provisional catalyst activity levels QASLV and QACLV set for each of the periods A and B.
[0029]
First, in step S1, the current intake air amount QA is read, and in step S2, the intake air amount QA is added to the first intake air amount integrated value QAS set at the time of execution of the previous routine, and a new first intake air amount QAS is set. Is calculated (QAS ← QAS + QA).
[0030]
Then, in step S3, the count value TQAS of the first cycle determination timer for measuring the first cycle A is compared with a first set time tA that defines the first cycle A, and It is determined whether the period A has been reached. If TQAS <tA, since the period A has not been reached, the process jumps to step S7, and if it is determined that TQAS ≧ tA and the first period A has been reached. Goes to step S4.
[0031]
In step S4, the first activation integrated value IQAS for determining the catalyst activation state in the first cycle A is updated with the first intake air amount integrated value QAS (IQAS ← QAS), and step S5 is performed. Then, based on the first activity determination integrated value IQAS, referring to the first temporary catalyst activity level determination table, the first temporary catalyst activity representing the temporary catalyst activity state under the first cycle A Set the level QASLV.
[0032]
Then, in step S6, in preparation for calculation of the intake air amount integrated value in the next section determined by the first cycle A, the timer TQAS of the cycle determination timer is cleared and the timer is restarted. The intake air amount integrated value QAS of 1 is cleared, and the process proceeds to step S7.
[0033]
As shown in FIG. 7, the first provisional catalyst activity level determination table corresponding to the first cycle A stores the activity determination integrated value IQAS based on a preset change curve of the first activity determination integrated value IQAS. Inactive, quasi-active, and active areas are divided for each predetermined slice level, and the first provisional catalytic activity level of "0" for the inactive area, "1" for the quasi-active area, and "2" for the active area QASLV is stored.
[0034]
As shown in FIG. 10, the activation state of the catalyst is governed by the temperature (t) in the catalyst layer. The temperature (t) in the catalyst layer has a rising characteristic determined in relation to the engine load, and the engine load is large. As the intake air amount QA increases, the flow rate of exhaust gas discharged from the combustion chamber of the engine 1 increases, and the temperature in the catalyst layer rises relatively quickly, and accordingly, the catalyst of each of the catalytic converters 8a and 8b becomes faster. It becomes active. Therefore, it is possible to easily predict the temperature in the catalyst layer from a change in the intake air amount QA indicating the engine load. In the present embodiment, the intake air amount QA is integrated in each of the first cycle A and the second cycle B which is longer than the first cycle A, and the current catalyst amount is calculated based on each integrated value. Determines the active state. The first cycle A is relatively short (for example, an average primary delay time required for the air passing through the intake air amount sensor 27 to burn and pass through the catalytic converters 8a and 8b), and the first period A is equal to the intake air amount QA. It is suitable for judging the catalyst activity due to temporary fluctuations. In a second cycle B which is relatively longer than the first cycle A, the catalyst activity is judged from a change in the average intake air amount QA. Suitable for Conversely, the response delay of the second cycle B is compensated for in the first cycle A, and the erroneous determination of the catalyst activity due to the temporary fluctuation of the intake air amount QA detected in the first cycle A is made. Compensation is performed in the second cycle B.
[0035]
At step S7, the intake air amount QA read at step S1 is added to the second intake air amount integrated value QAC set at the time of execution of the previous routine, and a new second intake air amount integration is performed. The value QAC is calculated (QAC ← QAC + QA), and in step S8, the time value TQAC of the second cycle determination timer for measuring the second cycle B and the second set time tB for defining the cycle B are calculated. If TQAC <tB, the second cycle B has not been reached, and the process jumps to step S12.
[0036]
If TQAC ≧ tB and the second cycle B has been reached, the process proceeds to step S9, and the second activity determination integrated value IQAC for determining the catalyst activation state in the second cycle B is calculated by the second It is updated with the intake air amount integrated value QAC (IQAC ← QAC), and in step S10, based on the second activity determination integrated value IQAC, referring to the second provisional catalyst activity level determination table, the second period B A second provisional catalyst activity level QACLV representing the provisional catalyst activity state below is set.
[0037]
Then, the process proceeds to step S11, in which the timer value TQAC of the second cycle determination timer is cleared to prepare for the calculation of the second intake air amount integrated value QAC in the next section determined by the second cycle B, and The timer is restarted, the second intake air amount integrated value QAC is cleared, and the process proceeds to step S12.
[0038]
As shown in FIG. 8, the second temporary catalyst activity level determination table corresponding to the second cycle B is based on a change curve of the second activity determination integrated value IQAC. Each of the slice levels is divided into inactive, quasi-active, and active areas, and the second provisional catalytic activity level of “0” in the inactive area, “1” in the quasi-active area, and “2” in the active area QACLV is stored. Since the second cycle B has a longer cycle than the first cycle A, the second activation determination integrated value IQAC does not suddenly change even if the intake air amount QA temporarily changes. When relatively compared with the first activation determination integrated value IQAS corresponding to the first cycle A, the curve becomes a gentle upward curve.
[0039]
Then, when the process proceeds from step S8 or step S11 to step S12, a catalyst activity level CATLV indicating the current catalyst activity state is set by referring to a catalyst activity level determination map based on the two provisional catalyst activity levels QASLV and QACLV. Is stored at a predetermined address in the RAM 34, and the routine exits.
[0040]
As shown in FIG. 9, the catalyst activity level determination map is divided into regions by the two provisional catalyst activity levels QASLV and QACLV, and each region has a value of 0 according to the combination of the two provisional catalyst activity levels QASLV and QACLV. Four levels of catalytic activity CATLV of (inactive), 1 (quasi-active), 2 (active A), and 3 (active B) are stored. Specifically, the provisional catalyst activity levels QASLV and QACLV are both 0, or the area where one of the provisional catalyst activity levels QASLV and QACLV is 0 and the other is 1 is “0”, and the provisional catalyst activity levels QASLV and QACLV are both 1 Alternatively, one of the provisional catalyst activity levels QASLV and QACLV is “0” and the other one is “1” in the area of 2, and the provisional catalyst activity levels QASLV and QACLV are “1” in the area of one and the other two are “2”. In a region where both the active levels QASLV and QACLV are 2, a catalytic activity level CATLV of “3” is stored.
[0041]
According to the catalyst activation state determination routine, the provisional catalyst activation levels QASLV and QACLV are updated independently for each of the periods A and B. On the other hand, the catalyst activity level CATLV is set every time the routine is executed, regardless of the periods A and B. The relationship between the provisional catalyst activity levels QASLV, QACLV and the catalyst activity level CATLV will be described based on a change in the intake air amount QA with reference to the time chart of FIG.
[0042]
As described above, the first cycle A and the second cycle B are separately timed, and the provisional catalyst activity levels QASLV and QACLV are updated for each cycle A and B, while the catalyst activity level CATLV Is set every time the routine is executed. For example, as shown in FIG. 6, when the second cycle B is three times as long as the first cycle A, the second cycle set in the second cycle B is used. Is maintained until the first provisional catalyst activity level QASLV set in the first cycle A is updated three times. Therefore, as shown in FIG. 10, for example, in a case where the intake air amount QA sharply increases in a section before the section a and then gradually decreases, the period A of the period A in the section a is reduced. The provisional catalyst activity level QASLV is set to “2” because the first activation determination integrated value IQAS based on the first intake air amount integrated value QAS set in the immediately preceding cycle A sharply increases (FIG. 7). On the other hand, the provisional catalyst activity level QACLV in the cycle B is also set to “2” because the overall activation determination integrated value IQAC in the cycle B increases from the increase in the intake air amount QA in the immediately preceding section (see FIG. 4). See FIG. 8). As a result, the catalyst activity level CATLV of the section a is set to “3” by the catalyst activity level determination map of FIG.
[0043]
In the section b, the provisional catalyst activity level QASLV of the cycle A is set based on the first activation determination integrated value IQAS based on the first intake air amount integrated value QAS set in the immediately preceding cycle A, and As the first activity determination integrated value IQAS decreases with the decrease in QA, it is set to “1” (see FIG. 7), while the temporary catalyst activity level QACLV in period B holds “2”. Therefore, the catalyst activity level CATLV in the section b is set to “2” by the catalyst activity level determination map shown in FIG.
[0044]
Further, in the section c, the activity determination integrated value IQAC of the cycle B is updated, and the second provisional catalyst activity level QACLV is set to “1” based on the activity determination integrated value IQAC (see FIG. 8). The first temporary catalyst activity level QASLV set based on the activity determination integrated value IQAS of A is set to “0” due to the decrease in the intake air amount QA (see FIG. 7). The catalyst activity level CATLV is set to “0” by the catalyst activity level determination map.
[0045]
Thus, the first temporary catalyst activity level QASLV in the cycle A is set based on the instantaneous change in the intake air amount QA, and the second temporary catalyst activity level QACLV in the cycle B is relatively long in the intake air amount QA. The catalyst activity level CATLV is set by the combination of the provisional catalyst activity levels QASLV and QACLV of the cycle A and the cycle B, and the current catalyst activity state is comprehensively determined.
[0046]
It is to be noted that the current catalyst activity state can be determined more minutely by further dividing the provisional catalyst activity level determination table and the catalyst activity level determination map, or by increasing the cycle for determining the catalyst activity state to three or more types. It is possible to do. Further, in addition to the intake air amount QA, a throttle opening, a basic fuel injection amount (Tp), or the like may be used as the engine load.
[0047]
The catalyst activity level CATLV set by the catalyst activity state determination routine is referred to when determining an air-fuel ratio feedback control start condition or a catalyst deterioration diagnosis start condition. In the present embodiment, the air-fuel ratio shown in FIG. In the feedback correction coefficient setting routine, the catalyst activity level CATVL is referred to, and when the catalyst having the catalyst activity level CATVL of “2” or more is in the active state, the DOS using both the output values VFO2 and VRO2 of the FO2 sensor 29a and the RO2 sensor 29b is used. Transfer to control.
[0048]
Here, the DOS control (dual O2 sensor control) refers to performing the air-fuel ratio feedback control from the information of the FO2 sensor 29a and determining the shift amount of the air-fuel ratio feedback correction coefficient from the information of the RO2 sensor 29b, thereby purifying the catalyst. The purpose of this invention is to improve the exhaust gas purification performance by correcting the fuel injection amount so as to converge to the air-fuel ratio at which the performance can be maximized. Japanese Patent Application Laid-Open No. 62-29738 and Japanese Patent Application No. 7-52742 filed by the present applicant. The issue is detailed. By storing the shift amount of the air-fuel ratio feedback correction coefficient with respect to the base value as a learning value, the deterioration of the FO2 sensor and the catalyst can be learned and corrected.
[0049]
The air-fuel ratio feedback correction coefficient setting routine of FIG. 3 is executed at predetermined intervals. First, in step S21, it is determined whether or not a clamp condition such as a throttle full-open increase correction during deceleration fuel cut is performed. The process branches to S28, where the average output value VMRO2 of the RO2 sensor 29b stored in the RAM 34 is cleared. In step S29, the air-fuel ratio feedback correction coefficient λ is set, and the routine exits. In the setting of the air-fuel ratio feedback correction coefficient λ in step S29 when the clamp condition is satisfied, the air-fuel ratio feedback correction coefficient λ is clamped to a value set according to the clamp condition, and the air-fuel ratio control is set as open-loop control.
[0050]
In step S21, when the clamping condition is not satisfied by the normal operation, the process proceeds to step S22, where the output value VRO2 of the RO2 sensor 29b is read, and in step S23, the value of the RO2 sensor activation flag F1 is referred to. Proceed to S24, and if F1 = 1, jump to step S26. The initial value of the RO2 sensor activation flag F1 is 0, and is set to “1” when it is determined that the RO2 sensor 29b is activated, as described later, and the initial value after the power is turned on to the electronic control unit 31 is set. At the time of execution of the routine, and when it is not determined that the RO2 sensor 29b has been activated, the process proceeds to step S24, and it is determined whether the RO2 sensor 29b has been activated.
[0051]
The conditions for determining the activity of the RO2 sensor 29b are as follows.
[0052]
1) After the FO2 sensor 29a is in the active state and the air-fuel ratio feedback control has shifted to the closed loop control.
[0053]
2) VRO2 ≧ RCLSR or VRO2 <RCLSL.
[0054]
Here, RCLSR and RCLSL are preset values.
[0055]
3) The condition satisfying the above conditions 1) and 2) was the engine rotation and continued for RINLDS times.
[0056]
If it is determined in step S24 that the above condition is not satisfied and the RO2 sensor 29b is inactive, the process proceeds to step S29 via step S28, where the air-fuel ratio feedback correction coefficient λ is set, and the routine exits. At this time, the setting of the air-fuel ratio feedback correction coefficient λ in step S29 is set according to the engine state and the state of the FO2 sensor 29a without using the output value VRO2 of the RO2 sensor 29b. Is inactive, the air-fuel ratio feedback correction coefficient λ is clamped to λ = 1.0 and the air-fuel ratio control is set to open-loop control. When the FO2 sensor 29a is activated and the clamp condition is not satisfied, the FO2 sensor 29a The air-fuel ratio feedback control is performed by setting the air-fuel ratio feedback correction coefficient λ based on the output value VFO2.
[0057]
The setting of the air-fuel ratio feedback correction coefficient λ, and the learning value KLR and the learning correction coefficient KBLRC in the air-fuel ratio learning described later are described in detail in Japanese Patent Application Laid-Open No. 5-44541 by the present applicant.
[0058]
If it is determined in step S24 that all the above conditions are satisfied and the RO2 sensor 29b is activated, the process proceeds to step S25, where the RO2 sensor activation flag F1 is set, and the process proceeds to step S26.
[0059]
Then, in step S26, the value of the catalyst activity level CATLV is set to “2” or more (CATLV ≧) by referring to the value of the catalyst activity level CATLV set in the above-described catalyst activity state determination routine and stored at a predetermined address in the RAM 34. 2) In other words, when it is "2 (active state A)" or "3 (active state B)", it is determined that the catalysts of the catalytic converters 8a and 8b are in an active state, and the process proceeds to step S27, where the FO2 sensor 29a , And the DOS control using the RO2 sensor 29b together sets the air-fuel ratio feedback correction coefficient λ and exits the routine. On the other hand, when the catalyst activity level CATLV is less than “2” (CATLV <2), that is, “1 (quasi-active state)” or “0 (inactive state)”, the DOS control is not performed, and the step S28 is performed. Then, the process proceeds to step S29, where the air-fuel ratio feedback correction coefficient λ is set according to the engine state and the state of the FO2 sensor 29a as described above, and the routine exits.
[0060]
The setting of the air-fuel ratio feedback correction coefficient λ by the DOS control in step S27 is performed according to the air-fuel ratio feedback correction coefficient setting subroutine by the DOS control shown in the flowchart of FIG.
[0061]
First, in step S31, the output value VFO2 of the FO2 sensor 29a is read, and in step S32, the output value VRO2 of the RO2 sensor 29b is smoothed. That is, in step S32, the current average is obtained based on the output value VRO2 of the RO2 sensor 29b read in step S22 of the above-described air-fuel ratio feedback correction coefficient setting routine and the average output value VMRO2 calculated in the previous execution of the routine. The output value VMRO2 is calculated from the following equation.
VMRO2 ← ｛(VRO2-VMRO2) / 2 ⁿ ｝ + VMRO2
Here, n is a constant.
[0062]
Then, in step S33, an integral IPHOS and a proportional PPHOS are obtained based on the average output value VMRO2 of the RO2 sensor 29b. The integral IPHOS and the proportional PPHOS are set based on the relationship between the average output value VMRO2 and the slice level SL2. As shown in FIG. 11, when the average output value VMRO2 crosses the slice level SL2, The integral IPHOS and the proportional PPHOS are inverted.
[0063]
Thereafter, in step S34, the RO2 sensor correction coefficient PHOS is set by adding the integral IPHOS and the proportional PPHOS to the RO2 sensor correction coefficient PHOS set at the time of the previous execution of the routine (PHOS ← PHOS + IPHOS + PPHOS).
[0064]
Then, in steps S35 to S38, it is determined whether or not the RO2 sensor correction coefficient PHOS is within an appropriate range. If not, the RO2 sensor correction coefficient PHOS is corrected. First, in step S35, it is determined whether the RO2 sensor correction coefficient PHOS is lower than the lower limit value PHMIN. If PHOS <PHMIN, the process branches to step S36 to set the RO2 sensor correction coefficient PHOS to the lower limit value PHMIN. Then, the process proceeds to step S39. If PHOS ≧ PHMIN, the process proceeds to step S37 to determine whether the RO2 sensor correction coefficient PHOS is higher than the upper limit value PHMAX. If PHOS> PHMAX, the flow branches to step S38, where the RO2 sensor correction coefficient PHOS is set to the upper limit PHMAX, and the flow proceeds to step S39. If PHOS ≦ PHMAX, it is determined that the RO2 sensor correction coefficient PHOS calculated this time is within an appropriate range, and the process proceeds directly to step S39.
[0065]
In step S39, the proportional component PU and the integral component IU are set based on the relationship between the output value VFO2 of the FO2 sensor 29a and the slice level SL1. As shown in FIG. 11, when the output value VFO2 crosses the slice level SL1, the proportional component PU and the integral component IU are inverted.
[0066]
Then, in step S40, the RO2 sensor correction coefficient PHOS is added to the proportional component PU to obtain the current proportional component P (P ← PU + PHOS). In step S41, the air-fuel ratio feedback correction set in the previous execution of the routine is performed. The proportional component P and the integral component IU are added to the coefficient λ to calculate the current air-fuel ratio feedback correction coefficient λ (λ ← λ + P + IU), and the result is stored at a predetermined address in the RAM 34 and the routine exits.
[0067]
As a result, the proportional value PU of the air-fuel ratio feedback correction coefficient λ set based on the output value VFO2 of the FO2 sensor 29a is equal to the RO2 sensor correction coefficient PHOS set based on the average VMRO2 of the output value VRO2 of the RO2 sensor 29b. Is corrected by
The air-fuel ratio feedback correction coefficient λ is used in the calculation of the fuel injection pulse width Ti that determines the fuel injection amount in the fuel injection amount setting routine shown in FIG.
[0068]
Next, a fuel injection amount setting routine will be described with reference to FIG. First, at step S51, a basic fuel injection pulse width Tp corresponding to the basic fuel injection amount is calculated from the following equation based on the intake air amount QA and the engine speed NE.
Tp ← K × QA / NE
Here, K is an injector characteristic correction constant.
[0069]
Next, in step S52, based on the coolant temperature Tw by the coolant temperature sensor 26, the throttle opening by the throttle opening sensor 28a, the idle output by the idle switch 28b, etc., the coolant temperature correction, acceleration / deceleration correction, full opening increase correction, and after idle Various increase correction coefficients COEF related to increase correction and the like are set, and the routine proceeds to step S53, where the above-described air-fuel ratio feedback correction coefficient λ is read.
[0070]
In step S54, the air-fuel ratio learning value KLR stored in the air-fuel ratio learning value table of the backup RAM 35 is searched using the engine speed NE and the basic fuel injection pulse width Tp representing the engine load as parameters, and interpolation calculation is performed. To set the air-fuel ratio learning correction coefficient KBLRC.
[0071]
The air-fuel ratio learning value KLR is, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-44541, etc., of the intake air amount measurement system such as the intake air amount sensor 27 and the fuel system such as the injector 14. This is for correcting variations in the air-fuel ratio due to variations during production or changes over time. In the present embodiment, when the air-fuel ratio feedback condition based on the activation of both O2 sensors is satisfied, a plurality of values in the air-fuel ratio learning value table are set. When the air-fuel ratio feedback correction coefficient λ repeats the air-fuel ratio rich / lean a predetermined number of times by proportional integral control in one of the operation regions based on the engine speed NE and the basic fuel injection pulse width Tp classified into: The learning value KLR stored in the corresponding area is updated according to the average value of the air-fuel ratio feedback correction coefficient λ at that time, and the air-fuel ratio The center value of the feedback correction coefficient λ is set to the reference value (= 1.0), and the air-fuel ratio is maintained at the stoichiometric air-fuel ratio.
[0072]
Here, the air-fuel ratio feedback correction coefficient λ, which is the basis of the air-fuel ratio learning based on the learning value KLR, is set by judging not only the activity of the FO2 sensor 29a and the RO2 sensor 29b but also the catalyst activation state of the catalytic converters 8a and 8b. Is done. That is, the catalyst activity level CATLV that is set based on the first and second activity determination integrated values IQAS and IQAC based on the respective intake air amount integrated values QAS and QAC calculated for each of the different periods A and B and that comprehensively indicates the catalyst active state CATLV. Is set to "2 (active state A)" or "3 (active state B)", it is determined that the catalyst is in the active state, and at this time, the DOS control first controls the RO2 sensor 29b in addition to the FO2 sensor 29a. The air-fuel ratio feedback correction coefficient λ is set in accordance with the output value VRO2 of, and the learning value KLR is updated in accordance with the air-fuel ratio feedback correction coefficient λ, so that appropriate air-fuel ratio learning adapted to the activation state of the catalyst is performed. Therefore, erroneous learning can be prevented.
[0073]
Next, the process proceeds from step S54 to step S55, and based on the terminal voltage VB of the battery 43, a voltage correction coefficient Ts for interpolating the invalid injection time of the injector 14 is set.
[0074]
Thereafter, the process proceeds to step S56, in which the basic fuel injection pulse width Tp calculated in step S51 is calculated using the air-fuel ratio feedback correction coefficient λ read in step S53 and the various increase correction coefficients COEF set in step S52. In addition to the correction, the learning correction is performed by the learning correction coefficient KBRRC set in the step S54, and the voltage is corrected by the voltage correction coefficient Ts set in the step S55 to obtain the final fuel injection pulse width Ti that determines the fuel injection amount. It is calculated from the following equation.
[0075]
Ti ← Tp × COEF × λ × KBLRC + Ts
Then, in step S57, the fuel injection pulse width Ti is set in the injection timer of the fuel injection target cylinder, and the routine exits. Then, at a predetermined timing, the injection timer is started, a drive pulse signal of the fuel injection pulse width Ti is output to the injector 14 of the injection target cylinder, and a predetermined amount of fuel is injected from the injector 14.
[0076]
14 to 20 show a second embodiment of the present invention. The electronic control unit 31 (see FIG. 13) according to the present embodiment has functions as a plurality of cycle-based integrated value calculation means, cycle-based provisional catalyst activity determination value setting means, and catalyst activity determination means. Specifically, in the first embodiment described above, the first and second temporary catalyst activity levels QASLV and QACLV for each of the different periods A and B are set with reference to the temporary catalyst activity level determination table. However, in the present embodiment, the activation determination integrated values IQAS and IQAC based on the intake air amount integrated values QAS and QAC calculated for each of the periods A and B, and activation determination constants (slice levels) QASL and QACL set in advance. The temporary catalyst activation state is determined on the basis of the relationship.
[0077]
Hereinafter, the catalyst activation state determination routine according to the present embodiment will be described with reference to the flowcharts shown in FIGS. The same steps as those in the catalyst activation state determination routine shown in FIG. 2 in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0078]
This catalyst activation state determination routine is executed every predetermined time (for example, 50 ms). In step S1, the intake air amount QA is read. In steps S2 to S4, the first intake air amount integration calculated in the first cycle A is performed. A first activity determination integrated value IQAS is set based on the value QAS, and the process proceeds to step S61, which is set in advance to determine the activation state of the catalyst under the first activity determination integrated value IQAS and the first cycle A. It is compared with a first activity determination constant QASL (see FIG. 17), and when IQAS ≧ QASL, it is determined that the catalyst is active, and in step S62, a first temporary catalyst activity flag FQAS as a temporary catalyst activity determination value is set. (FQAS ← 1). On the other hand, when IQAS <QASL, it is determined that the catalyst is inactive, and the first provisional catalyst activation flag FQAS is cleared in step S63 (FQAS). AS ← 0). The initial values of the first provisional catalyst activation flag FQAS, the second provisional catalyst activation flag FQAC described later, and the catalyst activation flag FCAT are 0.
[0079]
Then, proceeding to step S6, in preparation for the calculation of the integrated value of the intake air amount in the next section, the timer value TQAS of the first cycle determination timer is cleared and the timer is restarted. Clear the quantity integrated value QAS.
[0080]
In steps S7 to S9, a second activity determination integrated value IQAC is set based on the second intake air amount integrated value QA calculated in the second cycle B, and the process proceeds to step S64, where the second activity determination integrated value is set. IQAC is compared with a predetermined second activity determination constant QACL (see FIG. 18) for determining the activation state of the catalyst under the second cycle B, and when IQAC ≧ QACL, it is determined that the catalyst is active. Then, in step S65, a second temporary catalyst activity flag FQAC is set as a temporary catalyst activity determination value (FQAC ← 1). On the other hand, when IQAC <QACL, it is determined that the catalyst is inactive, and in step S66, The second provisional catalyst activation flag FQAC is cleared (FQAC ← 0), and the process proceeds to step S11.
[0081]
In step S11, in preparation for the calculation of the second intake air amount integrated value QA in the next section determined by the second synchronization B, the timer value TQA of the second synchronization determination timer is cleared and the timer is restarted. At the same time, the second intake air amount integrated value QAC is cleared.
[0082]
Then, in and after step S67, the current catalyst activation state is comprehensively determined based on the combination of the provisional catalyst activation flags FQAS and FQAC values.
[0083]
In steps S67 and S68, the values of the two provisional catalyst activation flags FQAS and FQAC are referred to, and when FQAS = 1 and FQAC = 1, it is determined that the catalysts of the catalytic converters 8a and 8b are in an active state. Proceeding to S69, a catalyst activity flag FCAT is set as a catalyst activity determination value indicating the current catalyst state (FCAT ← 1). When one or both of the provisional catalyst activation flags FQAS and FQAC are 0, it is determined that the catalyst is in an inactive state, and the process proceeds to step S70 to clear the catalyst activation flag FCAT (FCAT ← 0). . As a result, as shown in FIG. 19, the catalyst activation flag FCAT is set to indicate that the catalyst is currently active only when both the provisional catalyst activation flags FQAS and FQAC are both "1". Become.
[0084]
Here, similarly to the change in the intake air amount illustrated in the first embodiment, the relationship between the provisional catalyst activation flags FQAS, FQAC and the catalyst activation flag FCAT when the intake air amount QA changes is shown in FIG. Explanation will be given according to the time chart.
[0085]
For example, as in the first embodiment, when the second cycle B is three times as long as the first cycle A, the second provisional catalyst activation flag FQAC set in the second cycle B is set. Holds the value until the first provisional catalyst activation flag FQAS set in the first cycle A is updated three times. Therefore, as shown in the figure, when the intake air amount QA sharply increases in the section before the section a and then gradually decreases, the provisional catalyst activation flag FQAS of the cycle A in the section a is obtained. Becomes “1” because the first activation determination integrated value IQAS set by the first intake air amount integrated value QAS calculated in the immediately preceding cycle A sharply increases (see FIG. 17). In addition, the provisional catalyst activation flag FQAC in the cycle B also increases the overall activation determination integrated value IQAC in the cycle B from the increase in the intake air amount QA in the immediately preceding section to “1” (see FIG. 18). As a result, the catalyst activation flag FCAT in the section a is set to “1 (active)” (see FIG. 19).
[0086]
In the section b, the first activation determination integrated value IQAS set by the first intake air amount integrated value QAS also decreases as the intake air amount QA decreases in the immediately preceding cycle A (section a), When the activation determination integrated value IQAS is larger than the provisional catalyst activation level QASLV, the provisional catalyst activation flag FQAS of the cycle A is kept at "1". On the other hand, at this time, the provisional catalyst activation flag FQAC of the cycle B holds “1”, and therefore, the catalyst activation flag FCAT of the section b holds “1 (active)”. Then, in the section c ′ due to the decrease in the intake air amount QA, the provisional catalyst activation flag FQAS set based on the activation determination integrated value IQAS in the cycle A becomes “0”, and accordingly, the catalyst activation flag FCAT in the section c ′ Becomes “0 (inactive)”.
[0087]
The catalyst determination flag FCAT is referred to in the air-fuel ratio feedback correction coefficient setting routine shown in FIG. 16, and when the catalyst activation flag FCAT is set (FCAT = 1) and the catalyst is in the active state, the first embodiment differs from the first embodiment. Similarly, a transition is made to DOS control using both output values VFO2 and VRO2 of the FO2 sensor 29a and the RO2 sensor 29b. This air-fuel ratio feedback correction coefficient setting routine is executed at predetermined time intervals, similarly to the above-described first embodiment. When the clamp condition is not satisfied in step S21, it is determined in steps S22 to S24 whether the RO2 sensor 29b has been activated. If it is determined to be inactive, the air-fuel ratio feedback correction coefficient λ is set according to the engine state and the state of the FO2 sensor 29a in step S29 via step S28, and the routine exits. If it is determined that the RO2 sensor 29b has been activated, the process proceeds to step S25, where the RO2 sensor activation flag F1 is set, and the process proceeds to step S81.
[0088]
Then, in step S81, the value of the catalyst activation flag FCAT set in the above-described catalyst activation state determination routine is referred to, and when FCAT = 0, it is determined that the catalysts of the catalytic converters 8a and 8b are inactive, and in step S28 Branch to On the other hand, when FCAT = 1, it is determined that the catalyst is in the active state, the process proceeds to step S27, and the air-fuel ratio feedback correction coefficient λ is set by DOS control using both the FO2 sensor 29a and the RO2 sensor 29b, and the routine is performed. Through.
[0089]
As described above, in the present embodiment, the flag is used instead of the table and the map, so that the used capacity of the memory can be reduced.
[0090]
The present invention is not limited to the above embodiments. For example, by incorporating the catalyst activation state determined in the catalyst activation state determination routine into a self-diagnosis function for detecting catalyst deterioration, the catalyst can be sufficiently activated. By detecting a region in which the output of the RO2 sensor 29b is likely to be unstable, that is, by stopping the diagnosis in this region, the diagnosis accuracy can be improved. Furthermore, by incorporating it into the ignition timing control, it becomes possible to comprehensively control the fuel injection control and the ignition timing control according to the catalyst activation state.
[0091]
【The invention's effect】
According to the first aspect of the present invention, the physical quantity indicating the engine load is integrated for each different cycle, and the temporary catalyst activity level is set for each cycle based on each integrated value. Since the current state of the catalyst is determined based on the catalyst activity level, the active state of the catalyst is determined as compared with a conventional catalyst in which the activity of the catalyst is determined using a catalyst temperature sensor, an O2 sensor disposed downstream of the catalyst, or the like. It can be grasped simply and accurately. In addition, since the activity of the catalyst is not determined using an O2 sensor or the like disposed downstream of the catalyst, it is possible to accurately grasp the activation state of the catalyst even when an unexpected abnormality occurs in the catalyst. Thus, it is possible to accurately perform a catalyst deterioration diagnosis and the like performed when the catalyst is activated.
[0092]
According to the invention described in claim 2, in the invention described in claim 1, each of the provisional catalyst activity levels is set to one of an inactive level, a quasi-active level, and an active level based on the integrated value calculated for each cycle. However, since the current catalyst activity state is divided into an inactive state, a semi-active state, and an active state based on each temporary catalyst activity level set for each cycle, each temporary catalyst activity level is clearly divided, and Since the final catalyst activity level is determined based on the combination of the divided provisional catalyst activity levels, the catalyst activity state can be more accurately determined.
[0093]
According to the third aspect of the invention, the physical quantity indicating the engine load is integrated, and the provisional catalyst activity determination value for each cycle set based on each integrated value is set to either the catalyst activity or the inactive state. Based on the provisional catalyst activity determination value, a final catalyst activity determination value indicating whether the current state of the catalyst is active or inactive is set. This has the effect that the used capacity of the memory can be relatively reduced.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of the present invention.
FIG. 2 is a flowchart showing a catalyst activation state determination routine according to the first embodiment of the present invention.
FIG. 3 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment;
FIG. 4 is a flowchart showing a subroutine for setting an air-fuel ratio feedback correction coefficient by DOS control;
FIG. 5 is a flowchart showing a fuel injection amount setting routine;
FIG. 6 is an explanatory diagram showing a relationship between a first cycle A and a second cycle B;
FIG. 7 is an explanatory diagram showing a relationship between a first activity determination integrated value and a first temporary catalyst activity level in a cycle A;
FIG. 8 is an explanatory diagram showing a relationship between a second activity determination integrated value and a second temporary catalyst activity level in a cycle B;
FIG. 9 is a conceptual diagram of a catalyst activity level determination map according to the first embodiment;
FIG. 10 is a time chart showing the relationship between the intake air amount, the temperature in the catalyst layer, the temporary catalyst activity level and the catalyst activity level in each cycle;
FIG. 11 is a time chart showing setting states of an FO2 sensor output value, an RO2 sensor average output value, a proportional integral control amount based on the FO2 sensor output value, and an RO2 sensor correction coefficient;
FIG. 12 is an overall schematic diagram of the engine.
FIG. 13 is a circuit configuration diagram of an electronic control system according to the embodiment.
FIG. 14 is a flowchart illustrating a catalyst activation state determination routine according to the second embodiment of the present invention.
FIG. 15 is a flowchart showing a catalyst activation state determination routine (continued).
FIG. 16 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine according to the second embodiment;
FIG. 17 is an explanatory diagram showing a relationship between a first activation determination integrated value and a value of a first provisional catalyst activation flag in a cycle A;
FIG. 18 is an explanatory diagram showing a relationship between a second activation determination integrated value and a value of a second temporary catalyst activation flag in a cycle B;
FIG. 19 is a table showing the relationship between the value of the first provisional catalyst activation flag in the cycle A and the value of the second provisional catalyst activation flag in the cycle B, and the value of the catalyst activation flag;
FIG. 20 is a time chart showing the relationship between the intake air amount, the temperature in the catalyst layer, the provisional catalyst activation flag and the catalyst activation flag for each cycle;
FIG. 21 is a time chart showing the FO2 sensor output value and the RO2 sensor output value when the catalyst is active and when the catalyst is inactive.
[Explanation of symbols]
1 engine
8a, 8b Catalytic converter (catalyst)
14 Injector
27 Intake air volume sensor
29a, 29b O2 sensor
31 Electronic control unit
A, B cycle
CATLV catalytic activity level
FCAT catalyst activity flag (catalyst activity judgment value)
FQAS, FQAC Temporary catalyst activity flag (temporary catalyst activity determination value)
IQAS, IQAC activity judgment integrated value (integrated value)
QA intake air quantity (physical quantity indicating engine load)
QASLV, QACLV Preliminary catalytic activity level

Claims (3)

A plurality of cycle-by-cycle integrated value calculation means for calculating the integrated value of the physical quantity indicating the engine load for each different cycle,
A plurality of period-based provisional catalyst activity level setting means for setting a provisional catalyst activity level based on each integrated value for each cycle,
And a catalyst activity determining means for determining a current catalyst activity state based on each of the provisional catalyst activity levels set for each cycle. The temporary catalyst activity level setting means for each cycle, based on the calculated integrated value, set the temporary catalyst activity level to any of the inactive level, the quasi-active level and the activity level,
2. The method according to claim 1, wherein the catalyst activity determination unit determines whether the current catalyst activity state is an inactive state, a quasi-active state, or an active state based on each set temporary catalyst activity level. An apparatus for determining a catalyst activation state of an engine according to the above. A plurality of cycle-by-cycle integrated value calculation means for calculating the integrated value of the physical quantity indicating the engine load for each different cycle,
A period-based provisional catalyst activity determination value setting unit that sets a provisional catalyst activity determination value indicating whether the catalyst is active or inactive, based on each of the integrated values for each period,
Catalyst activity determining means for setting a catalyst activity determination value indicating whether the current state of the catalyst is active or inactive based on each of the temporary catalyst activity determination values set for each cycle. State determination device.

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