JP2011127567A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine, using a catalyst bypass system and inhibiting deterioration of an upstream catalyst by preventing temperature of the upstream catalyst from rising unintentionally. <P>SOLUTION: The exhaust emission control device (catalyst bypass system) of the internal combustion engine includes an indication means controlling a bypass opening and closing means so that the flow rate of exhaust gas flowing in a bypass passage is increased as compared with the flow rate of exhaust gas flowing in the upstream catalyst when an oxygen occlusion amount of the upstream catalyst 4 of the internal combustion engine becomes equal to or higher than a predetermined determination value. In the exhaust emission control device, when the internal combustion engine is in an acceleration lean condition, the larger the absolute value of the temperature of the upstream catalyst or a temperature rise is, the smaller the predetermined determination value is set. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust purification device that purifies exhaust gas of an internal combustion engine using a catalyst, and more particularly to an apparatus in which a plurality of catalysts are installed in series in an exhaust passage.

As an exhaust gas purification device for an internal combustion engine, two catalysts are installed in series in the exhaust passage, and further, a bypass passage that bypasses the upstream catalyst (upstream catalyst), and an exhaust gas flow rate that flows into the bypass passage and the catalyst side passage are adjusted. One provided with a bypass opening / closing means is known (for example, Patent Documents 1 to 4). The bypass path connects the upstream and downstream of the upstream catalyst. In Patent Document 1, when the gas temperature is lower than the bed temperature of the upstream catalyst, the bypass valve is closed and the exhaust gas is allowed to flow to the upstream catalyst, and when the gas temperature is higher than the bed temperature of the upstream catalyst. It is described that the bypass valve is opened and the exhaust gas is allowed to flow through the bypass passage. In addition, Patent Literature 2 describes that the exhaust gas passage is switched between the bypass passage side and the catalyst side based on the engine load and the rotational speed exhaust gas temperature.
JP 2007-198297 A JP-A 61-62219 JP 2006-144594 A JP 2005-315171 A

  However, it is generally difficult for the bypass opening / closing means that adjusts the flow rate of the exhaust gas flowing into the upstream catalyst to cause all exhaust gas to flow into the upstream catalyst and all exhaust gas into the bypass path. That is, if the bypass opening / closing means is, for example, a butterfly valve, a small amount of exhaust gas leakage may occur even when the valve is fully closed. For this reason, there is a possibility that a small amount of exhaust gas leakage occurs even if the valve is controlled to allow all exhaust gas to flow into the bypass passage. For example, as illustrated in FIG. 1 using a configuration in which the butterfly valve 3 is provided in the bypass path, even if the butterfly valve 3 is controlled and the opening degree is controlled to be fully opened, all the gas flows through the bypass path. However, it flows into the upstream catalyst 4 with a small amount. This small amount of exhaust gas is called exhaust gas leakage. On the other hand, unlike FIG. 1, the same applies to a configuration in which the butterfly valve 3 is provided in the catalyst side passage.

  When such an exhaust gas leak occurs, the exhaust gas flows into the upstream catalyst although the amount is small. Thus, if the exhaust gas flows into the upstream catalyst unintentionally, the upstream catalyst may deteriorate unintentionally when the oxygen storage amount is near the upper limit value. That is, when the oxygen storage amount is in the vicinity of the upper limit value and the unburned fuel flows into the catalyst unintentionally, the temperature of the catalyst rapidly increases. If the temperature of the catalyst rises rapidly in such a situation, it will lead to deterioration of the catalyst.

  Accordingly, in view of the above problems, the present invention provides an exhaust purification device for an internal combustion engine that prevents the temperature of the upstream catalyst from unintentionally rising and suppresses deterioration of the upstream catalyst. is there.

According to the first aspect of the present invention, the catalyst disposed in the exhaust passage of the exhaust gas discharged from the internal combustion engine, the bypass passage connecting the upstream and the downstream of the catalyst, and the exhaust gas flow rate flowing into the bypass passage are adjusted. A bypass opening / closing means; a catalyst temperature detecting means for detecting a catalyst temperature of the catalyst; an instruction means for instructing bypass opening by the bypass opening / closing means based on a bypass opening condition based on the detected catalyst temperature; and An exhaust emission control device for an internal combustion engine is provided, comprising correction means for correcting a bypass opening condition based on an index value correlated with a temperature rise. According to a second aspect of the present invention, there is provided the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, wherein the index value uses an oxygen storage capacity.

  The bypass opening condition is corrected by reducing the judgment value for controlling and switching the bypass opening / closing means so as to increase the flow rate of the exhaust gas flowing into the bypass path. In this way, the timing for increasing the flow rate flowing into the bypass passage can be switched according to the oxygen storage amount of the upstream catalyst 4. In other words, when the oxygen storage amount of the upstream catalyst 4 is large, the switching value determination value is made smaller to set the switching timing in consideration of the temperature rise after the valve switching, and when the oxygen storage amount of the upstream catalyst 4 is small, the determination value The switching timing is set so that the temperature of the upstream catalyst 4 can be increased to an appropriate value. As a result, it is possible to estimate that the temperature of the catalyst exceeds a predetermined upper limit (limit value) when switching is not performed and the state in which the flow rate of the exhaust gas flowing into the catalyst is not adjusted is maintained. When it can be estimated that the temperature exceeds a predetermined upper limit (limit value), that is, based on an index correlated with the temperature rise of the catalyst, the flow rate of the exhaust gas flowing into the bypass passage can be increased in advance. As a result, it is possible to prevent an unexpected increase in the catalyst temperature. In particular, when the temperature of the catalyst exceeds a predetermined upper limit value (limit value), the catalyst may be greatly deteriorated. Therefore, when the temperature of the catalyst is in the vicinity of a predetermined upper limit (limit value), the flow rate of the exhaust gas flowing into the bypass path is increased more sensitively in advance. Thus, deterioration of the catalyst can be prevented.

  In particular, when the operating state of the internal combustion engine is accelerating, the exhaust gas temperature rise rate is fast (in other words, the exhaust gas temperature rise rate and the amount of temperature rise are large), and the upstream catalyst temperature rise is expected, It is expected that the temperature rise rate of the upstream catalyst is large. When the temperature increase of the upstream catalyst is expected to be large in this way, switching is performed so as to increase the flow rate of the exhaust gas flowing into the bypass passage at an early stage.

  According to the invention described in the claims, when the temperature increase of the upstream catalyst is expected to be large, the bypass opening / closing means is switched so as to increase the flow rate of the exhaust gas flowing into the bypass path as soon as possible. It is possible to prevent the temperature of the upstream catalyst from rising unintentionally and to suppress the deterioration of the upstream catalyst.

The figure which shows schematic structure of the internal combustion engine to which the exhaust gas purification apparatus which concerns on this invention is applied. Block diagram showing internal configuration of ECU Control flow chart of embodiment 1

  Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof is simplified or omitted.

FIG. 1 is an overall view for explaining the configuration of an exhaust gas purification apparatus for an internal combustion engine according to this embodiment.

  The exhaust gas purification apparatus for an internal combustion engine includes an internal combustion engine 1 and an upstream catalyst 4 (also referred to as a start cat converter, S / C) and a downstream catalyst (under floor catalyst, U / C) disposed in an exhaust passage of exhaust gas discharged from the internal combustion engine. (Also called F catalyst). A control valve 3 that is bypass opening / closing means for adjusting the flow rate of exhaust gas flowing into the upstream catalyst is installed on the bypass path that bypasses the upstream catalyst.

  This upstream catalyst 4 is composed of a ceramic carrier made of cordierite formed in a lattice shape so as to have a plurality of through holes along the exhaust flow direction, and a catalyst layer coated on the surface of the ceramic carrier, For example, a platinum-rhodium (Pt-Rh) noble metal catalyst material is supported on the surface of porous alumina (Al2O3) having a large number of pores.

  The upstream catalyst 4 is activated when the temperature is equal to or higher than a predetermined temperature, and when the air-fuel ratio of the inflowing exhaust gas is in the vicinity of the stoichiometric air-fuel ratio, the hydrocarbon (HC) and carbon monoxide (CO) contained in the exhaust gas are converted into oxygen O 2 At the same time, NOx in the exhaust is reacted with HC and CO in the exhaust to be reduced to H2O, CO, and N2. An upstream air-fuel ratio sensor (not shown) that outputs an electric signal corresponding to the air-fuel ratio of the exhaust gas flowing into the upstream catalyst 4 is attached to the exhaust pipe 5 upstream of the upstream catalyst 4.

  The control valve 3 is composed of a step motor or the like, and an actuator (not shown) that opens and closes the control valve 3 according to the magnitude of the applied current is attached. The control valve 3 may be a switching valve in addition to the butterfly valve. Further, the installation location is not limited to the bypass path, and may be installed upstream of the upstream catalyst 4.

  As a means for opening and closing the control valve 3, an on-off valve by an actuator may be used. The on-off valve power may be mechanically switched, such as an electric motor or a gear, in addition to the hydraulic power.

  The internal combustion engine 1 includes a crank position sensor 21 that outputs a pulse signal each time a crankshaft (not shown) rotates by a predetermined angle (for example, 30 degrees), and the temperature of cooling water that flows in a water jacket (not shown) of the internal combustion engine 1. A water temperature sensor 22 that outputs an electrical signal corresponding to the above is attached.

  The crank position sensor 21, the water temperature sensor 22, the throttle position sensor 7, the air flow meter 8, the vacuum sensor 24, the upstream air-fuel ratio sensor 19, the downstream air-fuel ratio sensor 20, and the temperature sensor 40 are respectively connected via electric wiring. It is connected to an engine control electronic control unit (ECU) 25 so that the output signals of the sensors are input to the ECU 25.

  The ECU 25 determines the operating state of the internal combustion engine 1 using the output signals from the sensors as parameters, and performs various controls such as fuel injection control and ignition timing control according to the operating state. The opening / closing control of the control valve 3 performed by the ECU 25 will be described in detail below.

  2, the ECU 25 includes a CPU 27, a ROM 28, a RAM 29, a backup RAM 30, an input port 31, and an output port 32, which are connected to each other by a bidirectional bus 26. A connected A / D converter 33 is provided.

  The input port 31 uses output signals from the crank position sensor 21 and the like as input signals, and transmits those output signals to the CPU 27 and the RAM 29. Further, the input port 31 outputs output signals from the throttle position sensor 7, the air flow meter 8, the upstream air-fuel ratio sensor 19, the downstream air-fuel ratio sensor 20, the water temperature sensor 22, the vacuum sensor 24, etc. via the A / D converter 33. The output signals are sent to the CPU 27 and RAM 29 as input signals.

  The output port 32 transmits a control signal output from the CPU 27 to the actuator 18 and the drive circuit 11. The ROM 28 is a fuel injection amount control routine for determining the amount of fuel to be injected from each fuel injection valve 10, an air-fuel ratio feedback control routine for performing air-fuel ratio feedback control of the fuel injection amount, and fuel injection of the fuel injection valve 10. Application programs such as a fuel injection timing control routine for determining the timing, an open / close control routine for controlling the control valve 3, and various control maps are stored.

  The above-mentioned various control maps are, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, and a fuel injection timing control showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection timing. The map is an activity determination control map showing the relationship between the temperature of the cooling water at the start of the internal combustion engine and the time taken from the start to the activation of the upstream catalyst 4 (hereinafter referred to as catalyst activation time).

  The RAM 29 stores the calculation results of the CPU 27 such as the engine speed calculated from the output signals from the sensors and the output signal of the crank position sensor 21. The output signal from each sensor, the calculation result of the CPU 27, and the like are rewritten to the latest data every time the crank position sensor 21 outputs a signal.

  The backup RAM 30 is a non-volatile memory that can store data even after the operation of the internal combustion engine 1 is stopped. The CPU 27 operates in accordance with an application program stored in the ROM 28, determines the operating state of the internal combustion engine 1 from the output signals of the sensors stored in the RAM 29, and determines the fuel injection amount and the fuel injection from the operating state and each control map. The timing, the opening / closing timing of the control valve 3 and the like are calculated. Then, the CPU 27 controls the drive circuit 11 and the actuator 18 according to the calculated fuel injection amount, fuel injection timing, and control valve 3 opening / closing timing.

For example, when executing the fuel injection control, the CPU 27 operates according to the fuel injection amount control routine, and determines the fuel injection amount (TAU) according to the following equation.
TAU = TP * FWL * (FAF + FG) * [FASE + FAE + FOTP + FDE (D)] * FFC + TAUV
(TP: Basic injection amount, FWL: Warm-up increase, FAF: Air-fuel ratio feedback correction coefficient, FG: Air-fuel ratio learning coefficient, FASE: Increase after start, FAE: Acceleration increase, FOTP: OTP increase, FDE (D): Deceleration (Increase (decrease), FFC: Correction coefficient at fuel cut return, TAUV: Invalid injection time)
Here, the exhaust purification performance of a general catalyst will be described. As an index indicating the exhaust purification performance of the catalyst,
"Exhaust gas purification performance" = "Catalyst conversion rate" x "Gas flow rate through the catalyst"
think of. This represents the amount of gas (g) converted by the catalyst (three-way reaction of HC, CO, and Nox). Since an approximately constant flow rate of gas flows through the downstream catalyst 6, the exhaust purification performance is substantially constant. However, since the exhaust gas is converted on the upstream catalyst 4 side when the flow rate of the gas flowing through the upstream catalyst 4 increases, the conversion efficiency of the downstream catalyst 6 decreases and the exhaust purification performance tends to decrease slightly. On the other hand, the exhaust gas purification performance on the upstream catalyst 4 side increases as the flow rate increases because the flow rate becomes dominant. Therefore, the exhaust purification performance of the upstream catalyst 4 and the downstream catalyst 6 is reversed at a certain flow rate.

  A specific description of the control of the bypass opening / closing means will be given using the flowchart of FIG. In step (denoted as S in the figure, the same applies hereinafter) 1, it is determined whether or not the engine is operating. If the engine is not operating, this routine is terminated. When the engine is operating, the process proceeds to S2 and it is determined whether the control valve 3 is open. The determination as to whether or not the control valve 3 is open refers to the determination as to whether or not the instruction means (ECU 25) controls the control valve 3 (bypass opening / closing means) to issue an instruction to fully open. That is. The instruction to fully open is an instruction issued by the instruction means (ECU 25), which controls the control valve 3 (bypass opening / closing means) and exhausts flowing into the bypass passage compared to the exhaust gas flow rate flowing into the upstream catalyst. This is an instruction to increase the gas flow rate, and further, the instruction means (ECU 25) is an instruction to flow all exhaust gas flow rates out of the exhaust gas flow rate into the bypass passage. On the other hand, the condition determined as No in step 2 will be described in detail. The condition determined as No in step 2 is a condition in which the instruction means (ECU 25) controls the control valve 3 (bypass opening / closing means) to issue an instruction to fully close. The instruction to be fully closed is an instruction issued by the instruction means (ECU 25), which controls the control valve 3 (bypass opening / closing means) and flows into the bypass passage as compared with the exhaust gas flow rate flowing into the upstream catalyst. This is an instruction to decrease the exhaust gas flow rate, and further, the instruction means (ECU 25) is an instruction to cause all the exhaust gas flow rate of the exhaust gas flow rate to flow into the upstream catalyst. Although the instruction means (ECU 25) issues an instruction to fully close or fully open in this way, all exhaust gas flow rates are actually allowed to flow into the upstream catalyst, and It is generally difficult to flow in the exhaust gas flow rate. That is, if the bypass opening / closing means is, for example, a butterfly valve, a small amount of exhaust gas leakage may occur even when the valve is fully closed. For this reason, there is a possibility that a small amount of exhaust gas leakage occurs even if the valve is controlled to allow all exhaust gas to flow into the bypass passage. For example, as illustrated in FIG. 1 using a configuration in which the butterfly valve 3 is provided in the bypass path, even if the butterfly valve 3 is controlled and the opening degree is controlled to be fully opened, all the gas flows through the bypass path. However, it flows into the upstream catalyst 4 with a small amount. This small amount of exhaust gas is called exhaust gas leakage. On the other hand, unlike FIG. 1, the same applies to a configuration in which the butterfly valve 3 is provided in the catalyst side passage. When such an exhaust gas leak occurs, the exhaust gas flows into the upstream catalyst although the amount is small. As described above, if the exhaust gas flows into the upstream catalyst unintentionally, when the oxygen storage amount (an example of an index value indicating the oxygen storage capacity amount) is close to the upper limit value, the upstream catalyst unintentionally There is a possibility of deterioration. For this reason, the temperature of the upstream catalyst unintentionally rises even though the instructing means (ECU 25) gives an instruction to fully close or fully open. This is a problem in the first embodiment. The purpose of the first embodiment is to prevent such an unintended absolute value of the temperature of the upstream catalyst or a temperature rise, and to suppress deterioration of the upstream catalyst. For example, the following description will be made assuming that the control valve 3 is a butterfly valve. Of the instructions issued by the instruction means (ECU 25), the instruction to fully close means that the opening degree of the butterfly valve (control valve 3) is 0 degree. Of the instructions issued by the instruction means (ECU 25), the instruction to fully open means that the opening degree of the butterfly valve (control valve 3) is 100 degrees. However, among the instructions issued by the instruction means (ECU 25), the instruction to fully open may be opened with the opening degree of the butterfly valve being 90 degrees. Similarly, the instruction to fully close may be opened with the opening degree of the butterfly valve being 10 degrees. The relative adjustment of the flow rate of the exhaust gas flowing into the bypass passage relative to the flow rate of the exhaust gas flowing into the upstream catalyst is to adjust the control valve 3. Therefore, it goes without saying that an intermediate opening degree may be provided as an open state or a closed state.

  If it is determined No in step 2, the process proceeds to S3 to determine whether the vehicle is accelerating. The vehicle is accelerating when the engine speed measured by the crank position sensor is increasing. In addition, the load may be measured from the throttle position sensor 7 or the like, and the acceleration may be performed when the load is a predetermined value or more.

If it is determined in S3 that the vehicle is accelerating, the process proceeds to S4, and the oxygen storage amount of the upstream catalyst 4 is estimated. By detecting the amount of oxygen flowing into the upstream catalyst 4 from the integrated value of the air-fuel ratio detected by the upstream air-fuel ratio sensor 19 and the intake air, the oxygen storage amount is estimated. The oxygen storage capacity (O ₂ storage) includes an oxygen storage amount (O ₂ storage accumulation amount) or an oxygen storage amount change rate. In S3 of the present embodiment, the oxygen storage amount is estimated, but the oxygen storage amount change rate may be estimated. A time change of oxygen flowing into the upstream catalyst 4 is detected from the change amount of the air-fuel ratio and intake air detected by the upstream air-fuel ratio sensor 19, and the oxygen storage amount change rate is estimated. When the oxygen storage amount is calculated in S4, the process proceeds to S5.

  In S5, the absolute value of the temperature of the upstream catalyst 4 corresponding to the calculated oxygen storage amount or the temperature increase (the absolute value of the S / C temperature or the temperature increase) is calculated. The temperature increase of the upstream catalyst 4 includes a temperature increase amount or a temperature increase rate. In this embodiment, the oxygen storage amount of the upstream catalyst corresponding to the oxygen storage capacity of the upstream catalyst is adopted as an index value correlated with the temperature rise of the catalyst after the bypass is opened. When the absolute value of the temperature of the upstream catalyst 4 or the temperature increase amount (the absolute value of the S / C temperature or the amount of temperature increase) is calculated in S5, the process proceeds to S6.

  In S6, the opening condition of the control valve 3 is changed with respect to the absolute value of the temperature of the upstream catalyst 4 or the temperature rise in S5. Changing the opening condition of the control valve 3 means that the control valve 3 is opened when the oxygen storage capacity (oxygen storage amount) of the upstream catalyst 4 is greater than or equal to a predetermined determination value in S7. In S6, the determination value is corrected. (The correction means corrects the bypass opening condition for bypass opening) to change. As the absolute value of the temperature of the upstream catalyst 4 or the temperature rise is larger, the determination value is corrected to be smaller (the correction means corrects the bypass opening condition) and is changed. More precisely, the absolute value of the temperature of the upstream catalyst 4 or the judgment value when the temperature rise is large is smaller or the same as the absolute value of the temperature of the upstream catalyst 4 or the judgment value when the temperature rise is small. And The absolute value of the temperature of the upstream catalyst 4 or the temperature rise (the absolute value of the S / C temperature or the temperature rise) is calculated corresponding to the oxygen storage amount. When the determination value is corrected in S6 (the correction means corrects the bypass opening condition), the process proceeds to S7.

  In S7, it is determined whether or not the oxygen storage capacity (oxygen storage amount) of the upstream catalyst 4 is equal to or greater than the determination value. In other words, it is determined whether the opening condition of the control valve 4 is satisfied. When the index value correlated with the temperature rise of the upstream catalyst 4 after the bypass is opened is equal to or greater than the determination value, the control valve 4 is opened because the opening condition is satisfied. In this way, the instruction means (ECU 25) controls the bypass opening / closing means to instruct that all exhaust gas flows out of the exhaust gas flow rate flow into the bypass passage (full open instruction), and the internal combustion engine is accelerated. In the case of the inside, the determination value when the temperature of the upstream catalyst is high is smaller or the same as the determination value when the temperature of the upstream catalyst is low. The bypass opening / closing means is controlled so as to increase the exhaust gas flow rate flowing into the bypass passage as compared with the exhaust gas flow rate flowing into the upstream catalyst. If the opening condition of the control valve 4 is not satisfied in S7, this routine is terminated and the process returns to S1.

  In summary, in the steps from S1 to S6, when the following conditions (1), (2), and (3) are satisfied, the determination value is corrected (the correction means corrects the bypass opening condition).

      ・ The engine is running.

      ・ Control valve 4 is closed.

      ・ The vehicle is accelerating.

  The ECU 25 that executes each step realizes an estimation unit. When the conditions (1), (2), and (3) are satisfied, if the instruction by the instruction means is not performed and the state in which the flow rate of the exhaust gas flowing into the catalyst is not adjusted, the temperature of the catalyst is predetermined. It can be estimated that the upper limit value (limit value) is exceeded. In other words, depending on whether or not the estimation means satisfies the conditions (1), (2), and (3), the instruction by the instruction means is not performed, and the state in which the flow rate of the exhaust gas flowing into the catalyst is not adjusted continues. In this case, it can be estimated whether or not the temperature of the catalyst exceeds a predetermined upper limit (limit value). Therefore, the estimation means (ECU 25) estimates that the predetermined upper limit value (limit value) is exceeded when the instruction means gives the instruction and when the internal combustion engine is accelerating.

  In steps S4 to S6, when the determination value is corrected (the correction means corrects the bypass opening condition), the larger the absolute value of the upstream catalyst temperature or the temperature rise, the smaller the predetermined determination value is corrected ( The correction means corrects the bypass opening condition). That is, the temperature increase of the upstream catalyst 4 after the bypass opening is predicted based on the catalyst temperature and the oxygen storage capacity (oxygen storage amount), and the bypass opening condition is corrected based on the catalyst temperature increase amount. The ECU 25 that performs this correction implements a correction means. In this way, the correction means corrects the bypass opening condition based on the index value (oxygen storage capacity (oxygen storage amount)) that correlates with the temperature rise of the catalyst after bypass opening. By doing this, the absolute value of the temperature of the upstream catalyst, or the temperature rise is small, because the possibility that the upstream catalyst will reach the maximum temperature allowed increases as the absolute value of the upstream catalyst increases or the temperature rises. If the absolute value of the temperature of the upstream catalyst or the temperature rise is large, the control valve 4 is opened as soon as possible to cause the exhaust gas to flow into the bypass passage. In this way, the possibility that the upstream catalyst rapidly increases in absolute value or temperature and reaches the maximum temperature is reduced. For this reason, when the temperature of the catalyst is in the vicinity of a predetermined upper limit (limit value), the flow rate of the exhaust gas flowing into the bypass path is increased more sensitively in advance, so that deterioration of the catalyst can be prevented.

  Hereinafter, steps that are not mentioned in the flowchart of FIG. 3 will be described. If the control valve 3 is open in S2, the process proceeds to S8. In S8, it is determined whether the control valve 4 satisfies the opening condition. This open condition is when the oxygen storage capacity of the upstream catalyst 4 of the internal combustion engine 1 is equal to or greater than a predetermined determination value. The determination value is not corrected (the correction means corrects the bypass opening condition). When a negative determination is made in S8, the process proceeds to S9 and the control valve 4 is closed.

  In this embodiment, the oxygen storage capacity (oxygen storage amount) is used as an index value correlated with the temperature increase of the upstream catalyst 4 after the bypass is opened. However, the oxygen storage amount and oxygen storage amount change of the upstream catalyst 4 are described. Or the temperature of the corresponding upstream catalyst 4.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust manifold 3 Control valve 4 Upstream catalyst 5 Exhaust pipe 6 Downstream catalyst

Claims (2)

A catalyst disposed in an exhaust passage of exhaust gas discharged from the internal combustion engine;
A bypass connecting the upstream and downstream of the catalyst;
Bypass opening and closing means for adjusting the flow rate of the exhaust gas flowing into the bypass path;
Catalyst temperature detecting means for detecting the catalyst temperature of the catalyst;
Instructing means for instructing bypass opening by the bypass opening and closing means based on the bypass opening condition by the detected catalyst temperature,
An exhaust gas purification apparatus for an internal combustion engine, comprising: correction means for correcting a bypass opening condition based on an index value correlated with a temperature increase of the catalyst after the bypass is opened. The index value uses oxygen storage capacity,
The exhaust emission control device for an internal combustion engine according to claim 1.

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