JP4693896B2 - Internal combustion engine control device - Google Patents

Description

  The present invention relates to an internal combustion engine control device in which an exhaust gas purification three-way catalyst is provided in an exhaust system, and more particularly, to an internal combustion engine control device equipped with a novel technique for expanding a three-way catalyst deterioration detection region. .

  Generally, in an internal combustion engine, a three-way catalyst is used to purify harmful components of exhaust gas. The three-way catalyst stores oxygen when the exhaust gas is leaner than the stoichiometric air-fuel ratio. On the other hand, when the exhaust gas is richer than the stoichiometric air-fuel ratio, oxygen is released. Thereby, it has the oxygen storage capability which maintains the atmosphere in a three-way catalyst at a theoretical air fuel ratio.

  The three-way catalyst has an ability to purify each component into harmless gas by oxidizing HC and CO and reducing NOx among the three harmful components contained in the exhaust gas. Furthermore, since the purification capacity of the three-way catalyst is maximized in the vicinity of the stoichiometric air-fuel ratio, the exhaust gas is favorably purified by combining the oxygen storage capacity and the purification capacity of the three-way catalyst.

  However, if the exhaust gas is leaner than the stoichiometric air-fuel ratio and the amount of stored oxygen exceeds the oxygen storage capacity, the atmosphere in the three-way catalyst is not maintained at the stoichiometric air-fuel ratio, and the NOx purification rate is significantly deteriorated.

  If the exhaust gas becomes richer than the stoichiometric air-fuel ratio and the stored oxygen amount is insufficient, the atmosphere in the three-way catalyst is not maintained at the stoichiometric air-fuel ratio, and the purification rate of HC and CO deteriorates. It is known that when the three-way catalyst is deteriorated, the oxygen storage capacity is reduced, so that the purification performance is deteriorated.

  Therefore, an internal combustion engine control apparatus has been proposed in which air-fuel ratio sensors are provided on the upstream side and downstream side of the three-way catalyst, and the oxygen storage capacity is measured to detect deterioration of the three-way catalyst. At this time, in order to prevent the exhaust gas from deteriorating, by controlling the oxygen change amount (oxygen storage / release amount) of the three-way catalyst slightly larger than the oxygen storage capacity of the deteriorated three-way catalyst stipulated by laws and regulations, There has been proposed an internal combustion engine control apparatus that can accurately determine the deterioration of a three-way catalyst without causing deterioration of exhaust gas (see, for example, Patent Document 1).

  Further, the oxygen storage capacity of normal and deteriorated catalysts increases or decreases depending on the three-way catalyst temperature. By utilizing this fact, an internal combustion engine control device has been proposed that can accurately determine the deterioration of the three-way catalyst by varying the deterioration determination value used for the catalyst deterioration diagnosis at the temperature of the three-way catalyst ( For example, see Patent Document 2).

  Also, there is an internal combustion engine control device that makes a judgment on the deterioration of a three-way catalyst based on the reversal time by utilizing the fact that the reversal time of the air-fuel ratio sensor downstream of the three-way catalyst differs depending on the degree of degradation of the three-way catalyst . In such an internal combustion engine control device, by utilizing the fact that the reversal time differs even in the same three-way catalyst depending on the amount of intake air, the deterioration judgment value used for catalyst deterioration diagnosis can be varied with the amount of intake air, and the three It has been proposed to determine the deterioration of the original catalyst (see, for example, Patent Document 3).

  In addition, there is an internal combustion engine control device that limits an area for performing deterioration determination of a three-way catalyst to an intake air amount area in which the oxygen storage capacity of the three-way catalyst can be distinguished. In such an internal combustion engine control device, it has been proposed to accurately determine the deterioration of the three-way catalyst by varying the region of the intake air amount to be diagnosed according to the air-fuel ratio fluctuation range (for example, patents). Reference 4).

JP 2006-125279 A JP-A-5-248227 Japanese Patent Application Laid-Open No. 6-221955 JP-A-9-250383

However, the prior art has the following problems.
Even if they are the same three-way catalyst, the oxygen storage capacity of the three-way catalyst is not constant over the entire operating point of the internal combustion engine and varies depending on the operating point. However, in the prior art of Patent Document 1, such a difference is not taken into consideration, and the target oxygen change amount is a constant value. For this reason, in the region where the oxygen storage capacity of the normal three-way catalyst is small, the target oxygen change amount becomes larger than the oxygen storage capacity of the normal three-way catalyst, and the normal three-way catalyst is erroneously determined as a deteriorated three-way catalyst. was there.

  On the other hand, in a region where the oxygen storage capacity of the deteriorated three-way catalyst is large, the target oxygen change amount becomes smaller than the oxygen storage capacity of the deteriorated three-way catalyst, and the deteriorated three-way catalyst may be erroneously determined as a normal three-way catalyst. there were. For this reason, in order to prevent erroneous determination, it is necessary to limit an area for diagnosing deterioration.

  Further, in the prior art of Patent Document 2, the deterioration judgment value is obtained in a region where the difference between the oxygen storage capacity of the normal catalyst and the oxygen storage capacity of the deteriorated catalyst is small, such as a low exhaust flow rate region or a high exhaust flow rate region. Therefore, there is a problem that the deterioration diagnosis of the catalyst cannot be performed.

  Moreover, in the prior art of patent document 3, the inversion time of the air-fuel ratio sensor on the downstream side of the three-way catalyst used for determining the deterioration of the three-way catalyst depends on the oxygen storage amount of the three-way catalyst. For this reason, if only the deterioration determination value is changed, it takes time to detect the normal determination in the normal catalyst. As a result, there has been a problem in that the deterioration determination execution time is increased and the exhaust gas is deteriorated by the deterioration diagnosis.

  Further, in the prior art of Patent Document 4, there is a problem that diagnosis cannot be performed in the air-fuel ratio fluctuation range in which the intake air amount that determines deterioration of a normal catalyst and the intake air amount that determines normality of a deteriorated catalyst are reversed. there were.

  The present invention has been made to solve such a problem, and is an internal combustion engine control capable of detecting the deterioration of the three-way catalyst even when the oxygen storage capacity of the deteriorated three-way catalyst changes depending on the operating point. The object is to obtain a device.

An internal combustion engine control apparatus according to the present invention includes a three-way catalyst disposed in an exhaust system of an internal combustion engine, and a first air-fuel ratio that is disposed in an exhaust system upstream of the three-way catalyst and detects a first air-fuel ratio of exhaust gas. An air-fuel ratio detecting means; a second air-fuel ratio detecting means which is disposed in the exhaust system downstream of the three-way catalyst and detects the second air-fuel ratio of the exhaust gas; and an oxygen storage to be detected that the three-way catalyst has deteriorated Target oxygen change amount calculating means for calculating the target oxygen change amount of the three-way catalyst defined as a value obtained by adding a predetermined amount of margin to the capacity, and the gas passing through the three-way catalyst from the detected or estimated intake air amount of the internal combustion engine A passing gas amount calculating means for estimating the amount , an oxygen change amount calculating means for calculating a change amount of the oxygen storage amount of the three way catalyst as an oxygen change amount from the passing gas amount and the first air-fuel ratio of the three way catalyst, a target From the relationship between the oxygen change amount and the oxygen change amount, the first air-fuel ratio is As rolling, and an air-fuel ratio manipulating means for inverting operates the air-fuel ratio of the internal combustion engine, an internal combustion engine control apparatus which performs deterioration determination diagnosis of the three-way catalyst, the target oxygen change amount calculation means, degradation and determination In the three-way catalyst to be calculated, the target oxygen change amount is calculated so as to increase / decrease according to the change increase / decrease when the oxygen storage capacity changes according to the operating point of the internal combustion engine .

  According to the present invention, the internal combustion engine control unit includes a target oxygen change amount calculation means, an oxygen change amount calculation means, and an air-fuel ratio operation means, and is diagnosed based on the intake air amount and the catalyst temperature. By calculating the target oxygen change amount according to the region, it is possible to obtain an internal combustion engine control device that can detect the deterioration of the three-way catalyst even when the oxygen storage capacity of the deteriorated three-way catalyst changes depending on the operating point. it can.

  A preferred embodiment of an internal combustion engine controller according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is an overall configuration diagram including an internal combustion engine control apparatus according to Embodiment 1 of the present invention. In FIG. 1, an internal combustion engine 101 is provided with an intake pipe 105 having an air cleaner 102, a throttle valve 103, and a surge tank 104 as an intake system.

  The intake pipe 105 includes an air flow sensor 106 for detecting the intake air amount Qa, an injector 107 for injecting fuel, a throttle sensor 117 for detecting the throttle opening θ of the throttle valve 103, and an idle switch 118 for detecting idling. And are provided. Here, the idle switch 118 generates an idle signal DL that is turned on when the idling opening (the throttle opening θ is in the fully closed state).

  The internal combustion engine 101 is provided with an exhaust pipe 108 as an exhaust system. A three-way catalyst 109 for purifying harmful components in the exhaust gas is disposed in the exhaust pipe 108, an O 2 sensor 110 disposed upstream of the three-way catalyst 109, and a downstream of the three-way catalyst 109. A λO2 sensor 111 arranged on the side is provided. Here, the case where a more accurate linear A / F sensor is used as the O2 sensor 110 will be described as an example.

  The internal combustion engine control unit (hereinafter referred to as “ECU”) 112 is constituted by a microcomputer, and includes a central processing unit (hereinafter referred to as “CPU”) 113 and a read only memory (hereinafter referred to as “ROM”). ) 114, a random access memory (hereinafter referred to as “RAM”) 115, an input / output interface (hereinafter referred to as “I / O”) 116, and a drive circuit 122.

  The internal combustion engine 101 includes a coolant temperature sensor 119 for detecting the coolant temperature WT, a crank angle sensor 120 for generating a crank angle signal CA corresponding to the crank angle position, and a cam angle for generating a cam angle signal corresponding to the cam angle position. A sensor 121 is provided.

  The water temperature sensor 119, the crank angle sensor 120, and the cam angle sensor 121, together with other sensor means (air flow sensor 106, linear A / F sensor 110, λO2 sensor 111, throttle sensor 117, idle switch 118, etc.) Various sensors for detecting the operating state of the engine 101 are configured. And each detection signal is input into ECU112 as driving | running state information.

  In the internal combustion engine 101 shown in FIG. 1, the intake air cleaned by the air cleaner 102 is controlled to an intake amount corresponding to the load by the throttle valve 103, and is sent to each cylinder of the internal combustion engine 101 via the surge tank 104 and the intake pipe 105. Inhaled.

  At this time, the intake air amount Qa to the internal combustion engine 101 is detected by the air flow sensor 106. Further, fuel for each cylinder of the internal combustion engine 101 is injected into the intake pipe 105 through the injector 107. The intake air amount Qa may be estimated based on the operating point of the internal combustion engine 101 and the pressure in the surge tank 104 instead of being detected by the air flow sensor 106.

  The air-fuel mixture (air and fuel) sucked into each cylinder of the internal combustion engine 101 becomes exhaust gas through a combustion stroke. The exhaust gas passes through the three-way catalyst 109 disposed in the exhaust pipe 108, thereby purifying harmful components and exhausting them into the atmosphere.

  At this time, the linear A / F sensor 110 provided on the upstream side of the three-way catalyst 109 detects the oxygen concentration in the exhaust gas and linearly detects the air-fuel ratio A / F. A λO 2 sensor 111 provided on the downstream side of the three-way catalyst 109 detects the oxygen concentration λO 2 in the exhaust gas. The detection signals of the sensors 110 and 111 contribute to the detection process of the exhaust gas state before and after the three-way catalyst 109 by the ECU 112.

  In the ECU 112, various operating state information (intake air amount Qa, throttle opening θ, idle signal DL, cooling water temperature WT, air-fuel ratio A / F, oxygen concentration λO2, crank angle signal CA, cam angle from cam angle sensor 121) Signal etc.) is taken into the CPU 113 via the I / O 116.

  The ECU 112 constitutes an air-fuel ratio feedback control system, and is based on the air-fuel ratio A / F and the oxygen concentration λO2 from the sensors 110 and 111 disposed before and after (upstream and downstream) of the three-way catalyst 109. Thus, a drive signal for the injector 107 is generated and a required amount of fuel is injected.

  In the air-fuel ratio feedback control system in the ECU 112, the CPU 113 is based on a control program stored in the ROM 114 and various maps, and the injector 107 via the drive circuit 122 so that the internal combustion engine 101 is operated at a predetermined air-fuel ratio. Drive. By this air-fuel ratio feedback control, the actual air-fuel ratio (A / F) is controlled to the target air-fuel ratio A / Fo.

  The ECU 112 functions as a device for detecting the deterioration of the three-way catalyst 109 together with a device for optimally controlling the internal combustion engine 101. The drive circuit 122 in the ECU 112 drives not only the injector 107 but also various actuators related to the internal combustion engine 101, such as an ISC valve (not shown).

  That is, the ECU 112 performs various controls such as ignition timing control and idle speed control in addition to air-fuel ratio control, and detects a failure of various components that cause exhaust gas deterioration as a self-diagnosis function.

  The CPU 113 and the drive circuit 122 that drive and control the injector 107 constitute air-fuel ratio operation means, and each time the oxygen change amount in the three-way catalyst 109 reaches the target oxygen change amount, the rich side across the stoichiometric air-fuel ratio. The air-fuel ratio A / F is reversed by a predetermined air-fuel ratio width on the lean side.

  The ROM 114 stores not only a control routine for the oxygen change amount of the three-way catalyst 109 but also a control program such as a deterioration detection routine for the three-way catalyst 109, and maps necessary for these control processes. Is also stored.

  Hereinafter, the operation of the internal combustion engine control apparatus according to the first embodiment shown in FIG. 1 will be described in detail with reference to a flowchart and a timing chart. Here, description will be made along the processing contents of the deterioration detection routine of the three-way catalyst 109 together with the control routine of the oxygen change amount of the three-way catalyst 109 which is the technical feature of the present invention.

  FIG. 2 is a flowchart showing an air-fuel ratio control routine of the internal combustion engine control apparatus according to Embodiment 1 of the present invention, and shows a control routine for the oxygen change amount of the three-way catalyst 109 for exhaust gas purification. In FIG. 2, first, it is determined whether or not the deterioration determination execution condition for the three-way catalyst 109 is satisfied (step 201). When it is determined that the deterioration determination execution condition is not satisfied (that is, NO), the processing routine of FIG. 2 is immediately terminated and the process returns.

  On the other hand, when it is determined in step 201 that the deterioration determination execution condition is satisfied (that is, YES), it is subsequently determined whether or not the value of the deterioration determination execution counter CN1 is greater than “0”. (Step 202). When it is determined that CN1 = 0 (that is, NO), since the required number of times of deterioration determination execution has been completed, the processing routine of FIG. 2 is immediately terminated and the process returns.

  At this time, only when the deterioration determination execution condition (step 201) is established for the first time, initial values are set in the deterioration determination execution counter CN1 and the oxygen storage capacity initialization counter CN2. The deterioration determination execution condition is determined from, for example, whether the internal combustion engine 101 is warmed up, within a predetermined intake air amount Qa range, and within a predetermined rotation speed and load range.

  The deterioration determination execution counter CN1 is a subtraction counter that is decremented by “1” every time a lean flag FL (described later) is switched. Therefore, if, for example, “5” is set as the initial value of the deterioration determination execution counter CN1, the target air-fuel ratio A / Fo is first enriched and then the target air-fuel ratio A / Fo is leaned and enriched. Is performed alternately, and is performed five times in total.

  On the other hand, if it is determined in step 202 that CN1> 0 (that is, YES), it is subsequently determined whether or not the value of the oxygen storage capacity initialization counter CN2 is larger than “0” (step 203). .

  The oxygen storage capacity initialization counter CN2 is a subtraction counter that is decremented by “1” every time the target air-fuel ratio A / Fo is enriched during the oxygen storage capacity initialization period (described later). In this case, by making the target air-fuel ratio A / Fo richer than the theoretical air-fuel ratio over a predetermined period, the target air-fuel ratio A / Fo that is executed when the value of the oxygen storage capacity initialization counter CN2 is “0” is set. In the lean process, the deterioration of the NOx emission amount due to the oxygen amount in the three-way catalyst 109 saturating the oxygen storage capacity is suppressed.

  If it is determined in step 203 that CN2> 0 (that is, YES), the oxygen change amount QOX is set to “0” (step 204), and is set according to the rotational speed and load of the internal combustion engine 101. Based on the map, the target air-fuel ratio A / Fo is enriched by a predetermined amount from the theoretical air-fuel ratio (step 205).

  Further, the oxygen storage capacity initialization counter CN2 is decremented by “1” (step 206), and the leaning flag FL is set to “1 (established)” in preparation for the completion of the initialization of the oxygen change amount QOX ( Step 207), the processing routine of FIG. Here, if the lean flag FL is set to “1 (established)” after completion of the oxygen storage capacity initialization, the target air-fuel ratio A / Fo is leaned and cleared to “0 (not established)”. If so, it functions as a determination flag for enriching the target air-fuel ratio A / Fo.

  On the other hand, if it is determined in step 203 that CN2 = 0 (that is, NO), the target oxygen change amount QOXo is obtained by calculation. Here, the target oxygen change amount QOXo is set to a value obtained by adding a predetermined amount (for example, about 20%) of margin to the oxygen storage capacity to be detected that the three-way catalyst 109 has deteriorated by law.

  FIG. 3 is a diagram showing the relationship between the oxygen storage capacity of the normal three-way catalyst, the oxygen storage capacity of the deteriorated three-way catalyst, and the target oxygen change amount in the internal combustion engine controller according to Embodiment 1 of the present invention. is there. It has been experimentally obtained that the oxygen storage capacity varies depending on the operating point of the internal combustion engine. Therefore, the target oxygen change amount QOXo is set to a map according to the operating point.

  Further, it has been experimentally obtained that the operating point of the internal combustion engine has a correlation with the detected or estimated intake air amount or the detected or estimated three-way catalyst temperature. For this reason, the operating point of the internal combustion engine is set around the intake air amount or the three-way catalyst temperature.

  It has been experimentally obtained that the target oxygen change amount QOXo increases as the operating point increases and decreases as the operating point decreases. Therefore, the target oxygen change amount QOXo is set according to the intake air amount or the three-way catalyst temperature. It is assumed that such characteristic data is stored in the ROM 114 in the ECU 112 (step 208).

Thus, after calculating the target oxygen change amount QOXo at step 208, the oxygen change amount QOX is then calculated by the following equation (1) (step 209).
QOX = QOX (previous value)
+ {| A / FA−Fb | ÷ A / Fb} × Qa × ΔT × α (1)

  However, in the above equation (1), ΔT is a calculation cycle of the oxygen change amount QOX, and α is an oxygen amount conversion coefficient. The basic target air-fuel ratio A / Fb is a target air-fuel ratio that is set when enrichment or leaning is not performed, and is a theoretical air-fuel ratio that corresponds to the operating point of the internal combustion engine 101. Further, it is assumed that the intake air amount Qa is substantially equal to the passing gas amount of the three-way catalyst 109.

  In step 209, after calculating the oxygen change amount QOX by the above equation (1), it is subsequently determined whether or not the oxygen change amount QOX is smaller than the target oxygen change amount QOXo (step 210). If it is determined in step 210 that QOX ≧ QOXo (that is, NO), the oxygen change amount QOX has reached the target oxygen change amount QOXo. Therefore, the oxygen change amount QOX is set to “0” (step 212), the lean flag FL is inverted (for example, “1 (established)” to “0 (not established)”) (step 213), and step Proceed to 211.

  On the other hand, if it is determined in step 210 that QOX <QOXo (that is, YES), it is subsequently determined whether or not the lean flag FL is “1 (established)” (step 211). If it is determined in step 211 that FL = 1 (that is, YES), the target air-fuel ratio A / Fo is leaned by a predetermined amount (for example, 0.4) from the basic target air-fuel ratio A / Fb (step 0.4). 214), the processing routine of FIG. 2 is terminated.

  On the other hand, if it is determined in step 211 that FL = 0 (that is, NO), the target air-fuel ratio A / Fo is enriched by a predetermined amount (for example, 0.4) from the basic target air-fuel ratio A / Fb. (Step 215), the processing routine of FIG. 2 is terminated.

  FIG. 4 is a flowchart showing a deterioration detection routine of the three-way catalyst 109 of the internal combustion engine controller according to Embodiment 1 of the present invention. In FIG. 4, first, it is determined whether or not a deterioration determination execution condition is satisfied (step 301). When it is determined that the deterioration determination execution condition is not satisfied (that is, NO), the processing routine of FIG. 4 is immediately terminated and the process returns.

  On the other hand, when it is determined in step 301 that the deterioration determination execution condition is satisfied (that is, YES), it is subsequently determined whether or not the value of the deterioration determination execution counter CN1 is greater than “0” (step 302). ). If it is determined that CN1 = 0 (that is, NO), the process proceeds to step 312 (described later).

  On the other hand, if it is determined in step 302 that CN1> 0 (that is, YES), it is subsequently determined whether the value of the oxygen storage capacity initialization counter CN2 is “0” (step 303). When it is determined that CN2> 0 (that is, NO), the processing routine of FIG. 4 is immediately terminated.

  On the other hand, if it is determined in step 303 that CN2 = 0 (that is, YES), it is subsequently determined whether or not the lean flag FL is the same as the previous value (step 304). If it is determined that the lean FL is not equal to the previous FL (ie, NO), the process proceeds to step 310 (described later).

  On the other hand, if it is determined in step 304 that the lean flag FL = previous FL (that is, YES), the λO2 inversion flag Fλ on the downstream side of the three-way catalyst 109 is “0 (not established)”. Whether or not (step 305). If it is determined that Fλ = 1 (that is, NO), the processing routine of FIG. 4 is immediately terminated.

  On the other hand, if it is determined in step 305 that Fλ = 0 (that is, YES), inversion determination processing of the oxygen concentration λO2 detected by the λO2 sensor 111 is executed (step 306). Specifically, whether the output value of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 is lower than the lean reversal determination value during the leaning process of the target air-fuel ratio A / Fo, or the target air-fuel ratio A / Fo It is determined whether the rich inversion determination value has been exceeded during the enrichment process.

  The λO2 inversion flag Fλ on the downstream side of the three-way catalyst 109 is set to “0 (not established)” when the value of the oxygen storage capacity initialization counter CN2 is CN2> 0. When CN2 = 0, when the oxygen concentration λO2 on the downstream side of the three-way catalyst 109 is reversed (that is, during the leaning process of the target air-fuel ratio A / Fo), it is below the lean reversal determination value or the target empty If the rich inversion determination value is exceeded during the enrichment process of the fuel ratio A / Fo, it is set to “1 (established)”. Here, the lean inversion determination value is set to 0.3 [V], for example, and the rich inversion determination value is set to 0.7 [V], for example.

  Next, it is determined whether or not the inversion determination of the oxygen concentration λO2 is established by detecting the timing at which the inversion determination is established in Step 306 (Step 307). If it is determined that the inversion determination of the oxygen concentration λO2 is not established (that is, NO), the processing routine of FIG. 4 is immediately terminated.

  On the other hand, if it is determined in step 307 that the inversion determination of the oxygen concentration λO2 is established (that is, YES), the λO2 inversion flag Fλ on the downstream side of the three-way catalyst 109 is set to “1 (established)” (step 307). 308). Furthermore, the deterioration determination establishment counter CN3 is incremented (added by “1”) (step 309), and the processing routine of FIG.

  Here, the deterioration determination establishment counter CN3 is incremented by “1” every time the output value of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 is inverted. When the deterioration determination execution counter CN1 (for example, initial value = 5) becomes “0”, if the value of the deterioration determination establishment counter CN3 is “4” or more, the final deterioration determination (described later) is performed. Is established.

  In the above-described step 304, if it is determined that the lean flag FL is reversed and FL ≠ previous FL (ie, NO), the λO2 inversion flag Fλ on the downstream side of the three-way catalyst 109 is set to “0 (not established). ”) (Step 310). Further, the deterioration determination execution counter CN1 is subtracted (step 311), and the processing routine of FIG.

  If it is determined in step 302 that the deterioration determination execution counter CN1 = 0 (ie, NO), the deterioration determination establishment counter CN3 exceeds the final deterioration determination threshold (previously set in the ROM 114). A final deterioration determination process is executed to determine whether or not it is present (step 312).

  Subsequently, it is determined in step 312 whether or not final deterioration determination is established (step 313). If it is determined that the deterioration determination success counter CN3 <4 and the final deterioration determination is not satisfied (that is, NO), the processing routine of FIG. 4 is immediately terminated.

  On the other hand, in step 313, the deterioration determination establishment counter CN3 ≧ 4, and if it is determined that the final deterioration determination is satisfied (that is, YES), the driver is informed that the three-way catalyst 109 has deteriorated. Therefore, the MIL (Malfunction Indicator Light) lamp is turned on (step 314), and the processing routine of FIG. 4 is terminated.

  Next, the operation of the deterioration detection device for the three-way catalyst 109 will be described based on the timing charts of FIGS. FIG. 5 is a diagram showing an operation in the case where the deterioration of the three-way catalyst 109 should be detected in a region where the oxygen storage capacity of the catalyst is small in the internal combustion engine control apparatus according to the first embodiment of the present invention. FIG. 6 is a diagram showing an operation in the case where deterioration of the three-way catalyst 109 should be detected in a region where the oxygen storage capacity of the catalyst is large in the internal combustion engine control apparatus according to Embodiment 1 of the present invention. FIG. 7 is a diagram showing an operation when the three-way catalyst 109 is normal in the region where the oxygen storage capacity of the catalyst is small in the internal combustion engine control apparatus according to Embodiment 1 of the present invention. Further, FIG. 8 is a diagram showing an operation when the three-way catalyst 109 is normal in a region where the oxygen storage capacity of the catalyst is large in the internal combustion engine control apparatus of the first embodiment of the present invention.

  5 to 8, the target air-fuel ratio A / Fo (≈upstream A / F), oxygen change amount QOX, downstream oxygen concentration λO2, downstream oxygen concentration λO2 inversion flag Fλ, deterioration determination It shows changes over time in the values of the execution counter CN1, the oxygen storage capacity initialization counter CN2, the deterioration determination establishment counter CN3, and the lean flag FL.

  First, with reference to FIG. 5, specific processing contents of the above-described oxygen change amount control routine and deterioration detection routine of the three-way catalyst 109 will be described along each step (401 to 439).

  When the deterioration determination execution condition is satisfied before the first time a in FIG. 5, initial values are set in the deterioration determination execution counter CN1 and the oxygen storage capacity initialization counter CN2 (401, 402). Further, the target air-fuel ratio A / Fo is enriched (404) until the value of the oxygen storage capacity initialization counter CN2 becomes “0” (403 → 408).

  During the enrichment period up to time a, the oxygen change amount QOX is set to “0” (405), the lean flag FL is set to “1” (406), and downstream of the three-way catalyst 109. The λO2 inversion flag Fλ is fixed to “0” (407).

  Subsequently, when the oxygen storage capacity initialization counter CN2 becomes “0” in the period from time a to b (408), the target oxygen change amount QOXo is calculated according to the oxygen storage capacity in the diagnostic region (409), and the oxygen change The quantity QOX is calculated (410). Since FIG. 5 shows the behavior in a region where the oxygen storage capacity is small, the target oxygen change amount QOXo is also a small value. Thereafter, the target air-fuel ratio A / Fo is leaned until the oxygen change amount QOX reaches the target oxygen change amount QOXo (411).

  If the output value (oxygen concentration) λO2 of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 falls below the lean inversion determination value (412) during the lean period from time a to b, the downstream side of the three-way catalyst 109 The λO2 inversion flag Fλ is set to “1” (413), and the deterioration determination establishment counter CN3 is incremented (414).

  Hereinafter, as illustrated, when the oxygen change amount QOX reaches the target oxygen change amount QOXo corresponding to the diagnosis region at time b, the oxygen change amount QOX is reset to “0” (415), and the lean flag is set. FL is set to “0” (416), and the target air-fuel ratio A / Fo is enriched (417). At the same time, the λO2 inversion flag Fλ downstream of the three-way catalyst 109 is set to “0” (418), and the deterioration determination execution counter CN1 is decremented (419).

  Subsequently, in the period from time b to c, the target oxygen change amount QOXo and the oxygen change amount QOX are calculated as in the period from time a to b (420, 421). Thereafter, the target air-fuel ratio A / Fo is enriched until the oxygen change amount QOX reaches the target oxygen change amount QOXo corresponding to the diagnosis region (417).

  If the output value (oxygen concentration) λO2 of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 exceeds the rich inversion determination value during the enrichment period from time b to c (422), the λO2 inversion flag Fλ is “1”. Is set (423), and the deterioration determination establishment counter CN3 is incremented (424).

  Hereinafter, as illustrated, when the oxygen change amount QOX reaches the target oxygen change amount QOXo corresponding to the diagnosis region at time c, the oxygen change amount QOX is reset to “0” (425), and the lean flag is set. FL is set to “1” (426), and the target air-fuel ratio A / Fo is made lean (427). At the same time, the λO2 inversion flag Fλ downstream of the three-way catalyst 109 is set to “0” (428), and the deterioration determination execution counter CN1 is decremented (429).

  Subsequently, until the value of the deterioration determination execution counter CN1 becomes “0” (430) in the period from time c to d, as in the period from time a to c, the target air-fuel ratio A / Fo is made lean and rich. Is repeatedly executed (427, 431, 432, 433). Each time the λO2 inversion flag Fλ is set to “1”, the deterioration determination establishment counter CN3 is incremented (434, 435, 436).

  Hereinafter, as illustrated, when the deterioration determination execution counter CN1 reaches “0” at time d (430), final deterioration determination is executed (437). At this time, if the final deterioration determination is established, the MIL lamp is turned on (438), and the three-way catalyst 109 deterioration detection routine is completed. Further, the target air-fuel ratio A / Fo is set to the basic target air-fuel ratio A / Fb (439), and the oxygen change amount control routine of the three-way catalyst 109 is completed.

  In FIG. 5, since the operation at the time of detecting the deterioration of the three-way catalyst 109 is shown, the oxygen concentration λO2 on the downstream side of the three-way catalyst 109 alternately indicates the state of excessive storage and insufficient release of the oxygen change amount QOX. ing.

  Next, the operation of FIG. 6 showing a timing chart at the time of catalyst deterioration in a region where the oxygen storage capacity is large will be described. Each operation procedure (401 to 439) is the same as in the case of FIG. 5 (when deterioration is detected in a region having a small oxygen storage capacity). However, in FIG. 6, the target oxygen change amount QOXo corresponding to the diagnostic region is set to a value larger than the oxygen storage capacity in accordance with the expansion of the oxygen storage capacity of the deteriorated three-way catalyst.

  By setting a large value, oxygen storage is excessive when the target air-fuel ratio A / Fo is lean, and oxygen release is insufficient when the target air-fuel ratio A / Fo is rich. As a result, it is possible to determine deterioration even in a region where the oxygen storage capacity of the deteriorated three-way catalyst is large.

  Next, the operation of FIG. 7 showing a timing chart for a normal catalyst in a region where the oxygen storage capacity of the three-way catalyst is small will be described. Each operation procedure (401 to 439) is the same as in the case of FIG. 5 (when deterioration is detected in a region having a small oxygen storage capacity).

  However, in FIG. 7, since the three-way catalyst 109 is normal, the output value (oxygen concentration) λO2 of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 does not reverse and deteriorates during the period up to time d. The determination establishment counter CN3 is not incremented. Further, the oxygen concentration λO2 downstream of the three-way catalyst 109 continuously shows a normal value. Therefore, at time d, the final deterioration determination is “not established” and the MIL lamp is not turned on.

  Next, the operation of FIG. 8 showing a timing chart for a normal catalyst in a region where the oxygen storage capacity of the three-way catalyst is large will be described. Each operation procedure (401 to 439) is the same as in the case of FIG. 6 (when deterioration is detected in a region having a large oxygen storage capacity).

  However, in FIG. 8, since the three-way catalyst 109 is normal, the output value (oxygen concentration) λO2 of the λO2 sensor 111 on the downstream side of the three-way catalyst 109 does not reverse and deteriorates during the period up to time d. The determination establishment counter CN3 is not incremented. Further, the oxygen concentration λO2 downstream of the three-way catalyst 109 continuously shows a normal value. Therefore, at time d, the final deterioration determination is “not established” and the MIL lamp is not turned on.

  As described above, according to the first embodiment, the three-way catalyst is arranged in the exhaust system of the internal combustion engine, the air-fuel ratio detection means in the exhaust gas is provided before and after the three-way catalyst, and the internal combustion engine control unit includes: A target oxygen change amount calculating means, an oxygen change amount calculating means, and an air-fuel ratio operating means are provided.

  Then, in the internal combustion engine control unit, the target oxygen change amount calculating means calculates a target oxygen change amount corresponding to the diagnosis region based on the detected or estimated intake air amount and the catalyst temperature. Further, the oxygen change amount calculation means calculates the oxygen change amount in the three-way catalyst based on the passing gas amount (intake air amount Qa) of the three-way catalyst and the air-fuel ratio A / F on the upstream side of the three-way catalyst. To do.

  By providing such a configuration, the target oxygen change amount can always be controlled slightly larger than the oxygen storage capacity of the deteriorated three-way catalyst for each operating point. Thereby, if the three-way catalyst is in a normal state, the oxygen fluctuation in the three-way catalyst does not exceed the oxygen storage capacity of the three-way catalyst. As a result, the oxygen concentration λO2 on the downstream side of the three-way catalyst does not change, and the exhaust gas on the downstream side of the three-way catalyst does not deteriorate.

  On the other hand, if the three-way catalyst is in a deteriorated state, the oxygen fluctuation in the three-way catalyst exceeds the oxygen storage capacity of the three-way catalyst. Therefore, the oxygen concentration λO2 on the downstream side of the three-way catalyst undergoes inversion fluctuations between the rich side and the lean side across the theoretical air-fuel ratio, and the deterioration of the three-way catalyst can be accurately detected.

  As a result, it is possible to perform a diagnosis in a region where the oxygen storage capacity is small in a normal three-way catalyst and a diagnosis in a region where the oxygen storage capacity is large in a deteriorated three-way catalyst. It becomes possible to detect in a wide range.

  Furthermore, in the region where the oxygen storage capacity is small in the deteriorated three-way catalyst, the target oxygen change amount used in the diagnosis can be set to the minimum necessary, and the time required for the diagnosis can be shortened and the exhaust gas deterioration due to the deterioration diagnosis can be reduced. Can be prevented.

  Further, by calculating the oxygen change amount, it is not necessary to consider the variation of the air-fuel ratio variation range. Furthermore, by setting a target oxygen change amount according to the intake air amount, it is possible to cope with a change in the oxygen change amount due to the intake air amount.

  Furthermore, the extent of oxygen storage excess and oxygen release shortage is also the minimum necessary amount according to the operating point, so that deterioration of exhaust gas downstream of the three-way catalyst can be suppressed to the minimum necessary.

1 is an overall configuration diagram including an internal combustion engine control device in Embodiment 1 of the present invention. 3 is a flowchart showing an air-fuel ratio control routine of the internal combustion engine control apparatus according to Embodiment 1 of the present invention. In the internal combustion engine control apparatus according to Embodiment 1 of the present invention, it is a diagram showing a relationship between an oxygen storage capacity of a normal three-way catalyst, an oxygen storage capacity of a deteriorated three-way catalyst, and a target oxygen change amount. It is a flowchart which shows the deterioration detection routine of the three way catalyst 109 of the internal combustion engine control apparatus in Embodiment 1 of this invention. FIG. 6 is a diagram showing an operation in the case where deterioration of the three-way catalyst 109 should be detected in a region where the oxygen storage capacity of the catalyst is small in the internal combustion engine control apparatus of Embodiment 1 of the present invention. FIG. 5 is a diagram showing an operation in the case where deterioration of the three-way catalyst 109 should be detected in a region where the oxygen storage capacity of the catalyst is large in the internal combustion engine control apparatus of Embodiment 1 of the present invention. In the internal combustion engine control apparatus of Embodiment 1 of the present invention, it is a diagram showing an operation when the three-way catalyst 109 is normal in a region where the oxygen storage capacity of the catalyst is small. In the internal combustion engine control apparatus of Embodiment 1 of the present invention, it is a diagram showing an operation when the three-way catalyst 109 is normal in a region where the oxygen storage capacity of the catalyst is large.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 Internal combustion engine, 102 Air cleaner, 103 Throttle valve, 104 Surge tank, 105 Intake pipe, 106 Air flow sensor, 107 Injector, 108 Exhaust pipe (exhaust system), 109 Three-way catalyst, 110 Linear A / F sensor (First empty (Fuel ratio detection means), 111 λO2 sensor (second air-fuel ratio detection means), 112 internal combustion engine control unit (ECU), 113 central processing unit (CPU), 114 read only memory (ROM), 115 random access memory (RAM) 116 I / O interface (I / O), 117 throttle sensor, 118 idle switch, 119 water temperature sensor, 120 crank angle sensor, 121 cam angle sensor, 122 drive circuit, A / F air / fuel ratio (first air / fuel ratio), CA crank angle signal, DL Idle signal, Qa Intake air amount, WT cooling water temperature, θ throttle opening, λO2 oxygen concentration (second air-fuel ratio).

Claims (5)

A three-way catalyst arranged in the exhaust system of the internal combustion engine;
A first air-fuel ratio detecting means that is disposed in the exhaust system upstream of the three-way catalyst and detects a first air-fuel ratio of exhaust gas;
A second air-fuel ratio detecting means that is disposed in the exhaust system downstream of the three-way catalyst and detects a second air-fuel ratio of the exhaust gas;
Target oxygen change amount calculating means for calculating a target oxygen change amount of the three-way catalyst defined as a value obtained by adding a predetermined amount of margin to an oxygen storage capacity to be detected that the three-way catalyst has deteriorated ;
A passing gas amount calculating means for estimating the passing gas amount of the three-way catalyst from the detected or estimated intake air amount of the internal combustion engine;
An oxygen change amount calculating means for calculating a change amount of the oxygen storage amount of the three way catalyst as an oxygen change amount from the passing gas amount of the three way catalyst and the first air-fuel ratio;
Air-fuel ratio operation means for reversing the air-fuel ratio of the internal combustion engine so that the first air-fuel ratio is reversed from the relationship between the target oxygen change amount and the oxygen change amount, and determining deterioration of the three-way catalyst An internal combustion engine control device for performing diagnosis,
The target oxygen change amount calculating means, calculating the three-way catalysts to be determined deterioration, the target oxygen amount of change to increase or decrease depending on the change increases or decreases when the oxygen storage capacity is changed according to the engine operating point An internal combustion engine control device. The internal combustion engine control apparatus according to claim 1,
The target oxygen change amount calculating means increases or decreases the target oxygen change amount according to the intake air amount of the internal combustion engine detected or estimated when calculating the target oxygen change amount. apparatus. The internal combustion engine control apparatus according to claim 2,
When the target oxygen change amount is increased or decreased according to the intake air amount of the internal combustion engine, the target oxygen change amount calculation means is larger than the target oxygen change amount at a predetermined amount in a region where the intake air amount is smaller than the predetermined amount. The internal combustion engine control apparatus is characterized in that a set value that is smaller than the target oxygen change amount at a predetermined amount is set in a region where the intake air amount is larger than the predetermined amount. The internal combustion engine control apparatus according to claim 1,
The target oxygen change amount calculating means increases or decreases the target oxygen change amount according to the detected or estimated temperature state of the three-way catalyst when calculating the target oxygen change amount. apparatus. The internal combustion engine control device according to claim 4,
The target oxygen change amount calculating means is configured to increase or decrease the target oxygen change amount according to the temperature state of the three-way catalyst, and in a region where the temperature of the three-way catalyst is lower than the predetermined temperature, the target oxygen change at the predetermined temperature An internal combustion engine control apparatus characterized in that a set value smaller than the amount is set, and in a region where the temperature of the three-way catalyst is higher than a predetermined temperature, the set value is larger than a target oxygen change amount at the predetermined temperature.

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