JP2008215223A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

The present invention relates to an exhaust emission control device for an internal combustion engine. In an internal combustion engine configured to be able to switch between a main exhaust passage and a bypass passage by a switching valve, it is possible to accurately determine the failure of the switching valve in a relatively short time. The purpose is to do so.
An HC adsorbent and a NOx adsorbent are disposed in a bypass passage that bypasses a main exhaust passage of an internal combustion engine. A switching valve 22 that enables switching of the inflow destination of the exhaust gas between the main exhaust passage 14 and the bypass passage 20 is disposed in the upstream connection portion 20 a between the main exhaust passage 14 and the bypass passage 20. A moisture adsorbing material 32 for adsorbing moisture contained in the exhaust gas is disposed in the main exhaust passage 14 on the downstream side of the switching valve 22. A temperature sensor 34 is incorporated in the moisture adsorbing material 32. The leakage of the switching valve 22 is detected using heat generated when moisture contained in the exhaust gas leaked from the switching valve 22 is adsorbed by the moisture adsorbent 32.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly, to an exhaust gas purification apparatus provided with an adsorbent for adsorbing unpurified components that could not be purified by a catalyst in an exhaust passage.

  Conventionally, for example, Patent Document 1 discloses a technique related to a failure determination device for a switching valve for switching an exhaust passage of an internal combustion engine. In the technique described in Patent Document 1, a humidity sensor is disposed on the downstream side of the HC adsorbent disposed on the bypass passage. Then, based on the humidity of the exhaust gas after passing through the adsorbent that changes depending on the state of adsorption of HC to the HC adsorbent, a failure determination of the switching valve (leakage determination in the switching valve) is performed.

  For example, Patent Document 2 also discloses a technique related to a switching valve failure determination device. In the technique described in Patent Document 2, a temperature sensor is disposed on the downstream side of the HC adsorbent (adsorbing device) disposed on the bypass passage. The failure determination (leakage determination) of the switching valve is performed based on the temperature change of the exhaust gas when HC is adsorbed by the HC adsorbent.

Japanese Patent Laid-Open No. 2002-4842 JP-A-10-159544

  Any of the leak determination methods described in Patent Document 1 or 2 uses a sensor disposed on the downstream side of the gas flow with respect to the HC adsorbent. The HC adsorbent is given a capacity that can adsorb HC discharged from the cylinder during cold start until the catalyst is activated. For this reason, a change in the flow rate of exhaust gas to the HC adsorbent in response to a minute leak of exhaust gas caused by a failure of the switching valve hardly appears as an output of the humidity sensor or the like. The change in sensor output due to leakage is very slow. As a result, it takes time to determine leakage from the switching valve. Accordingly, during the adsorption operation performed for a predetermined time after the cold start, the frequency of performing the leak determination in a short time is reduced, and it is difficult to accurately determine the failure of the switching valve.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine configured to be able to switch between a main exhaust passage and a bypass passage by a switching valve, an accurate switching valve can be obtained in a relatively short time. An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can perform failure determination.

A first invention is a main exhaust passage through which exhaust gas discharged from an internal combustion engine flows;
A bypass passage that branches from the main exhaust passage at an upstream connection portion with the main exhaust passage, and merges with the main exhaust passage again at a downstream connection portion downstream from the upstream connection portion;
An unpurified component adsorbent disposed in the bypass passage and having a function of adsorbing unpurified components contained in the exhaust gas;
A switching valve capable of switching an inflow destination of exhaust gas between the main exhaust passage and the bypass passage;
A valve downstream side adsorbent that is disposed in a passage on the downstream side of the switching valve and generates heat by receiving supply of exhaust gas;
An adsorbent temperature sensor that is disposed in the passage downstream of the valve downstream side adsorbent in the valve downstream side adsorbent or in the flow direction of the exhaust gas and detects the temperature of the valve downstream side adsorbent;
Valve leakage detection means for detecting leakage of exhaust gas from the switching valve, based on temperature information of the valve downstream side adsorbent accompanying heat generation when the gas is adsorbed by the valve downstream side adsorbent;
It is characterized by providing.

  Further, the second invention is the temperature information detected by the adsorbent temperature sensor in the first invention during the adsorption period of the unpurified component to the unpurified component adsorbent during a cold start of the internal combustion engine. And a sensor failure determination means for determining a failure of the adsorbent temperature sensor based on the temperature information detected by the adsorbent temperature sensor after the end of the adsorption period.

The third invention further comprises a gas temperature sensor for detecting the temperature of the exhaust gas flowing into the valve downstream side adsorbent in the first invention,
The valve leak detection means detects the leak of exhaust gas from the switching valve based on a comparison result between the temperature information of the adsorbent downstream of the valve and temperature information of the exhaust gas detected by the gas temperature sensor. It is characterized by performing.

  In a fourth aspect based on the third aspect, the adsorbent temperature sensor and the gas temperature sensor during the adsorption period of the unpurified component to the unpurified component adsorbent during cold start of the internal combustion engine. At least one of the adsorbent temperature sensor and the gas temperature sensor based on the detected temperature information and the temperature information detected by the adsorbent temperature sensor and the gas temperature sensor after the end of the adsorption period. It is further characterized by further comprising sensor failure determination means for performing the failure determination.

  In a fifth aspect based on the fourth aspect, the sensor failure determination means is a temperature change after the end of the adsorption period with respect to a temperature change during the adsorption period, of the adsorbent temperature sensor and the gas temperature sensor. Corresponds to a temperature sensor determined to be smaller than a predetermined set value, and the temperature difference between the adsorbent temperature sensor and the gas temperature sensor after a lapse of a fixed time from the end of the adsorption period is greater than a predetermined set value. A fault sensor specifying means for specifying that the temperature sensor corresponding to the temperature sensor indicating a low temperature when it is large is faulty is included.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the return passage is branched from the passage between the switching valve and the valve downstream side adsorbent and connected to the intake passage of the internal combustion engine. When,
The apparatus further comprises a recirculation amount control means for controlling a recirculation amount of the exhaust gas to the intake passage in accordance with a leakage amount of the exhaust gas from the switching valve detected by the valve leak detection means.

  In a seventh aspect based on the sixth aspect, the recirculation amount control means is configured so that the recirculation amount of the exhaust gas to the intake passage is constant during a predetermined time after the cold start. It is characterized by controlling the flow rate.

Further, an eighth invention according to the sixth invention further comprises a leakage amount storage means for storing the leakage amount of the exhaust gas from the switching valve detected by the valve leakage detection means,
The recirculation amount control means controls the recirculation amount so as to be an amount corresponding to the leakage amount at the previous cold start during a predetermined time after the cold start.

  According to the first aspect of the present invention, leakage detection of the switching valve is suitably performed using the heat generated when the exhaust gas leaked downstream of the switching valve is adsorbed by the adsorbent downstream of the valve. be able to. Thereby, it becomes possible to perform failure determination of the switching valve suitably.

  According to the second invention, it is possible to suitably execute the failure determination of the adsorbent temperature sensor based on the temperature information detected by the adsorbent temperature sensor during and after the adsorption period.

  According to the third invention, the output difference between the adsorbent temperature sensor and the gas temperature sensor due to heat generation (adsorption heat) when the exhaust gas leaked downstream of the switching valve is adsorbed by the adsorbent downstream of the valve. Using the (temperature difference), it is possible to suitably execute the leak detection of the switching valve.

  According to the fourth aspect of the invention, the failure determination of at least one of the adsorbent temperature sensor and the gas temperature sensor is performed based on the temperature information detected by the adsorbent temperature sensor and the gas temperature sensor, respectively, during the adsorption period and after the adsorption period ends. It can be suitably executed.

  According to the fifth aspect, it is possible to suitably identify which of the adsorbent temperature sensor and the gas temperature sensor has failed.

  According to the sixth aspect of the present invention, exhaust gas more than necessary is not recirculated to the intake side, so that it is possible to appropriately suppress the deterioration of combustion and fuel consumption caused by the recirculation to the intake air, while suppressing the exhaust gas from the switching valve. It is possible to prevent deterioration of exhaust emission due to leakage.

  According to the seventh aspect of the present invention, even if there is an exhaust gas leak from the switching valve immediately after a cold start in which it is difficult to accurately detect a gas leak from the switching valve, the exhaust gas The unpurified component contained therein can be prevented from being discharged into the atmosphere as it is without passing through the unpurified component adsorbent, and the exhaust emission can be prevented from deteriorating.

  According to the eighth aspect of the present invention, it is possible to more suitably eliminate unnecessary exhaust gas recirculation to the intake side immediately after the cold start in which it is difficult to accurately detect gas leakage from the switching valve. .

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine system including an exhaust purification device according to Embodiment 1 of the present invention. An internal combustion engine 10 shown in FIG. 1 includes an intake passage 12 for taking air into the cylinder and an exhaust passage through which exhaust gas discharged from the cylinder flows.

  The exhaust passage of the present embodiment includes a main exhaust passage 14 for discharging exhaust gas from the cylinder, and a bypass passage 20 described later. In the main exhaust passage 14, a front catalyst (SC) 16 and a rear catalyst (UF) 18 capable of purifying exhaust gas are arranged in series in order from the upstream side.

  The system of this embodiment includes a bypass passage 20 as a passage that bypasses the main exhaust passage 14. The bypass passage 20 branches from the main exhaust passage 14 at the upstream connection portion 20a located downstream of the rear catalyst 18, and again enters the main exhaust passage 14 at the downstream connection portion 20b located downstream of the upstream connection portion 20a. It is configured to merge.

  A switching valve 22 for switching the inflow destination of the exhaust gas between the main exhaust passage 14 and the bypass passage 20 is disposed in the upstream connection portion 20a. The switching valve 22 is driven to open and close when the engine intake negative pressure acting on the negative pressure diaphragm 22a is controlled by a solenoid valve (not shown).

  Further, two unpurified component adsorbents for adsorbing unpurified components contained in the exhaust gas are disposed in the middle of the bypass passage 20. More specifically, an HC having a function of first adsorbing HC contained in the exhaust gas on the upstream side of the main exhaust passage 14, that is, on the side close to the upstream connection portion 20 a provided with the switching valve 22. An adsorbent 24 is disposed. As such an HC adsorbent 24, for example, a zeolite-based material can be used.

  In the bypass passage 20, a NOx adsorbent 26 having a function of adsorbing NOx is further arranged on the downstream side of the HC adsorbent 24, that is, on the side close to the downstream connection portion 20 b. As such a NOx adsorbent 26, for example, a material in which iron Fe is supported on zeolite by ion exchange can be used.

  Further, the purge passage 28 communicates with the bypass passage 20 at a portion between the upstream side connection portion 20 a and the HC adsorbent 24. The purge passage 28 includes a purge control valve 30 in the middle thereof, and communicates with the intake passage 12 at the other end.

  In the main exhaust passage 14, a moisture adsorbing material 32 having a function of adsorbing moisture contained in the exhaust gas is disposed downstream (directly below) the switching valve 22. As such a moisture adsorbing material 32, a honeycomb base material coated with a material that adsorbs moisture such as zeolite or activated carbon and generates heat can be used. Further, a temperature sensor 34 for detecting the temperature of the moisture adsorbing material 32 is incorporated in the moisture adsorbing material 32. Here, the temperature sensor 34 is incorporated in the moisture adsorbent 32. However, the location of the temperature sensor 34 is not limited to this, and is immediately after the moisture adsorbent 32 in the exhaust gas flow direction. May be.

  In the present embodiment, the moisture adsorbing material 32 as described above is used for detecting leakage of exhaust gas from the switching valve 22 (described later with reference to FIG. 2). That is, the moisture adsorbing material 32 is not arranged for the purpose of preventing water from flowing out downstream of the moisture adsorbing material 32, and therefore the capacity thereof is a minute exhaust gas that flows downstream of the switching valve 22. It is sufficient that the gas leak can be detected. For this reason, the capacity of the moisture adsorbing material 32 is sufficiently smaller than the capacity of the HC adsorbing material 24 and the like arranged for the purpose of preventing HC and NOx from flowing downstream.

  The system of this embodiment includes an ECU (Electronic Control Unit) 40. A water temperature sensor 42 for detecting the engine cooling water temperature is connected to the ECU 40 together with various sensors for controlling the internal combustion engine 10 and the temperature sensor 34. The ECU 40 is connected to various actuators such as the switching valve 22 and the purge control valve 30 described above.

[Switching the flow path]
(During normal operation)
According to the configuration shown in FIG. 1 described above, the switching valve 22 is controlled by the ECU 40 so as to close the bypass passage 20, so that the exhaust gas discharged from the cylinder is not passed through the bypass passage 20 and the main exhaust passage. 14 can be released as it is into the atmosphere.

(At suction operation)
Further, the ECU 40 controls the switching valve 22 so that the main exhaust passage 14 is closed, thereby introducing the exhaust gas discharged from the cylinder into the bypass passage 20 and passing through the HC adsorbent 24 and the NOx adsorbent 26. Then, it can be returned to the main exhaust passage 14 and released into the atmosphere. If such an exhaust gas flow path configuration is selected at the time of cold start, HC, NOx, etc. that could not be purified by the catalyst 16 or the like in a situation where the catalyst 16 or the like has not yet been activated. By adsorbing the purification component to the HC adsorbent 24 or the like, it can be prevented from being released into the atmosphere.

(Purge operation)
In addition, after the catalyst 16 and the like are activated, the ECU 40 opens the purge control valve 30 in a state where the bypass passage 20 is closed, so that a part of the exhaust gas discharged from the cylinder is generated in the intake passage 12. The negative pressure can be introduced into the bypass passage 20 from the downstream connection portion 20b. As a result, when the hot exhaust gas after warming is supplied to the NOx adsorbent 26 and the like, NOx and HC are desorbed from the NOx adsorbent 26 and the like and are recirculated to the intake passage 12 via the purge passage 28. Thereby, NOx and HC returned to the intake passage 12 can be purified by the catalyst 16 and the like in an active state after being subjected to combustion again.

[Leakage detection method for switching valve in embodiment 1, and failure determination method for temperature sensor used therefor]
In the system of the present embodiment configured as described above, if there is an exhaust gas leak between the switching valve 22 and the valve seat 22b (see FIG. 1) during the adsorption operation, it will be released from the cylinder during cold start. A part of the exhaust gas to be discharged is discharged as it is without passing through the HC adsorbent 24 and the like disposed in the bypass passage 20, resulting in deterioration of exhaust emission. Therefore, in the present embodiment, leakage detection of the switching valve 22 during the adsorption operation (that is, the state in which the switching valve 22 is controlled so as to close the main exhaust passage 14) is performed by the method shown in FIG. 2 below. Thus, it is possible to determine whether or not the switching valve 22 needs to be repaired.

  FIG. 2 is a diagram showing the relationship between the exhaust gas temperature detected by the temperature sensor 34 shown in FIG. 1 and the elapsed time after the internal combustion engine 10 is started. In FIG. 2, the waveform when there is no leakage in the switching valve 22 is shown by a thin line, and the waveform when the leakage of the switching valve 22 is detected is shown by a thick line.

  The leak detection (failure determination) method of the switching valve 22 of the present embodiment is performed based on the heat generation amount (adsorption heat) when the exhaust gas leaked downstream from the switching valve 22 is adsorbed by the moisture adsorbing material 32. . More specifically, leakage of the switching valve 22 is determined by detecting heat generation of the moisture adsorbent 32 due to exhaust gas leak by the temperature sensor 34 incorporated in the moisture adsorbent 32. .

As shown in FIG. 2, when there is no leakage in the switching valve 22, the temperature rise from the initial temperature T ₀ of the exhaust gas at the start in the process in which the adsorption operation proceeds is immediately after the cold start. So small. On the other hand, when there is a leak in the switching valve 22, the temperature rise due to the heat generated by the moisture adsorbing material 32 is added to the temperature rise of the exhaust gas when there is no leak, compared to when there is no leak. Become bigger. In the present embodiment, leak detection is performed using the difference in the degree of temperature rise due to the presence or absence of a leak.

In addition, after the adsorption operation is completed, that is, after the switching valve 22 is switched so as to close the bypass passage 20, all the exhaust gas discharged from the cylinder is moisture-adsorbed in which the temperature sensor 34 is incorporated. It passes through the material 32. As a result, as the warm-up of the internal combustion engine 10 proceeds, the exhaust gas temperature detected by the temperature sensor 34 rapidly increases as compared with that during the adsorption operation, as shown in FIG. Therefore, in this embodiment, based on the comparison result of the magnitude of the temperature change of the exhaust gas during the adsorption period (ΔT _i / Δt) and the temperature change of the exhaust gas after the end of the adsorption period (ΔT _im / Δt). The failure of the temperature sensor 34 is determined.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 40 in order to realize the leakage detection method for the switching valve 22 in the first embodiment. Note that this routine is started when the internal combustion engine 10 is started in the cold state in response to the operation of the ignition key of the vehicle. In the routine shown in FIG. 3, first, when the ignition key is turned on, the initial temperature T ₀ of the exhaust gas is acquired using the temperature sensor 34 (step 100).

Next, a temperature change ΔT _i (= T _i −T _i−1 ) detected by the temperature sensor 34 is calculated every predetermined period (step 102). Further, the ECU 40 sequentially stores the integrated value of the temperature change ΔT _i after the cold start until the end of the adsorption period in the memory. The calculation of the temperature change ΔT _i in this step 102 is repeatedly executed until it is determined in the next step 104 that the adsorption period has ended.

Next, it is determined whether or not the adsorption period at the time of this cold start has ended, that is, whether or not the switching valve 22 has been switched from the state of closing the main exhaust passage 14 to the state of closing the bypass passage 20. (Step 104). As a result, if it is determined that the adsorption period has ended, then, the temperature change ΔT _i immediately before the switching valve 22 is switched and the temperature change ΔT _ki when the switching valve 22 is preset without leakage It is determined whether or not the difference (ΔT _i −ΔT _ki ) is greater than a predetermined determination value ki1 (step 106). The temperature change ΔT _ki when there is no leakage is mapped in advance in relation to the magnitude of the initial temperature T ₀ of the exhaust gas when the ignition key is turned ON. , The temperature change ΔT _ki corresponding to the magnitude of the initial temperature T ₀ of this time is acquired.

If it is determined in step 106 that the difference (ΔT _i −ΔT _ki ) is larger than the determination value ki1, the amount of leakage from the switching valve 22 is large, that is, the switching valve 22 is abnormal (repair is required). ) (Step 108).

On the other hand, if it is determined in step 106 that the difference (ΔT _i −ΔT _ki ) is not greater than the determination value ki, then the determination value ki2 is introduced, and ki2 <(ΔT _i −ΔT _ki ) ≦ ki1. Is determined (step 110). As a result, if it is determined that ki2 <(ΔT _i −ΔT _ki ) ≦ ki1, the amount of leakage from the switching valve 22 is at a medium level, that is, the determination of whether there is an abnormality is suspended until the next determination. It is determined that it is the level to be performed (step 112).

On the other hand, if it is determined in step 110 that ki2 <(ΔT _i −ΔT _ki ) ≦ ki1, the amount of leakage from the switching valve 22 is small or there is no leakage, that is, the switching valve 22 is normal. Is determined (step 114). In the above processing, the two determination values ki1 and ki2 are used. However, if the number of such determination values is increased as appropriate, the temperature change of the moisture adsorbent 32 detected by the temperature sensor 34 is changed. By using this, it becomes possible to obtain a more detailed level of leakage.

In the series of processes described above, but to use other values immediately before switching of the switching valve 22 as a temperature change [Delta] T _i, not limited thereto, the temperature change [Delta] T _i is the memory value during the adsorption period The maximum value may be selected. When the amount of leakage from the switching valve 22 increases, the moisture adsorbing material 32 is saturated, so that no heat of adsorption is generated and the temperature of the moisture adsorbing material 32 is lowered. Then, when the value immediately before the switching of the switching valve 22 is used as the temperature change ΔT _i , the difference (ΔT _i −ΔT _ki ) becomes small, so that there is a possibility that it is determined that the leakage amount is larger. . If the maximum value is selected as the temperature change ΔT _i , such a problem can be solved.

  According to the routine shown in FIG. 3 described above, the exhaust gas leaked downstream from the switching valve 22 is adsorbed by the moisture adsorbing material 32 by determining the temperature increase rate of the moisture adsorbing material 32 during the adsorption period. The leakage detection of the switching valve 22 can be suitably executed by using the amount of heat generated at the time (adsorption heat). Thereby, it is possible to determine the failure of the switching valve 22.

  Further, the capacity of the moisture adsorbing material 32 disposed in the main exhaust passage 14 for the purpose of detecting leaks is, as described above, the HC adsorbing material 24 disposed for the purpose of preventing HC and NOx from flowing out downstream. It is said that it is sufficiently small compared with the capacity of etc. For this reason, it is possible to accurately detect the leakage of the switching valve 22 in a relatively short time.

  FIG. 4 is a flowchart of a routine executed by the ECU 40 in order to realize failure determination of the temperature sensor 34 in the first embodiment. Note that this routine is started when the adsorption period ends and the switching valve 22 is switched to a state (off state) that closes the bypass passage 20.

In the routine shown in FIG. 4, first, the output change of the temperature sensor 34 after the switching valve 22 is switched to the off state (temperature change of the exhaust gas passing through the moisture adsorbent 32) ΔT _im (= T _im −T _im-1 ) is calculated (step 200). Next, it is determined whether or not a predetermined time has elapsed since the switching valve 22 was turned off (step 202).

If it is determined in step 202 that the predetermined time has elapsed, the differential value (ΔT _im / Δt) of the temperature change after the adsorption period ends and the differential of the temperature change during the adsorption period stored in step 102 value ([Delta] T _i / Delta] t) and the ratio of _{{(ΔT im / Δt) /} (ΔT i / Δt)} whether less than the predetermined set value is determined (step 204).

If it is determined in step 204 that the ratio {(ΔT _im / Δt) / (ΔT _i / Δt)} <set value is not satisfied, that is, the temperature change ΔT _im after the end of the adsorption period is greater in the adsorption period. If it is determined that the temperature change is relatively greater than the medium temperature change ΔT _i , it is determined that the temperature sensor 34 has not failed, that is, is normal (step 206).

On the other hand, if it is determined in step 204 that the ratio {(ΔT _im / Δt) / (ΔT _i / Δt)} <set value is satisfied, that is, the temperature change ΔT _im after the end of the adsorption period is greater. When it is determined that the temperature change ΔT _i during the period is relatively small, it is determined that the temperature sensor 34 has failed (step 208).

  According to the routine shown in FIG. 4 described above, the temperature information (temperature change) of the moisture adsorbent 32 and the temperature information (temperature change) of the exhaust gas passing through the moisture adsorbent 32 during and after the adsorption period. ), It is possible to suitably execute the failure determination of the temperature sensor 34 incorporated in the moisture adsorbing material 32.

  By the way, in Embodiment 1 mentioned above, the leak detection of the switching valve 22 is performed using the routine method shown in FIG. However, the leak determination time in such a leak detection method of the switching valve 22 is not limited to the above method, and may be the following method, for example.

That is, the differential value (ΔT _i / Δt) of the temperature change of the moisture adsorbent 32 detected by the temperature sensor 34 is sequentially calculated, and the calculated value (ΔT _i / Δt) is compared with the previous value. , Leak detection. More specifically, the two conditions of the differential value (ΔT _i / Δt) <A _i (set _{value) and the} previous value (ΔT _i−1 /Δt)> current value (ΔT _i / Δt) are satisfied. In this case, it is determined that there is an exhaust gas leak from the switching valve 22. That is, the leak determination of the present embodiment is performed when the amount of moisture adsorbed on the moisture adsorbing material 32 approaches a saturated state and the temperature rise of the moisture adsorbing material 32 becomes small.

In the first embodiment described above, the moisture adsorbent 32 is the “valve downstream adsorbent” in the first invention, and the temperature sensor 34 is the “adsorbent temperature sensor” in the first invention. It corresponds. Further, the “valve leak detecting means” in the first aspect of the present invention is realized by the ECU 40 executing a series of processes of the routine shown in FIG.
Further, the “sensor failure determination means” according to the second aspect of the present invention is realized by the ECU 40 executing a series of processes of the routine shown in FIG.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
[System configuration]
FIG. 5 is a diagram for explaining the configuration of an internal combustion engine system including an exhaust purification device according to Embodiment 2 of the present invention. In FIG. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The system shown in FIG. 5 is positioned on the main exhaust passage 14 upstream of the moisture adsorbing material 32, more specifically, at a position between the switching valve 22 and the moisture adsorbing material 32 in the main exhaust passage 14. And an Fr temperature sensor 50 for detecting the temperature of the exhaust gas. Except for this point, the present system is configured similarly to the system of the first embodiment described above. The location of the Fr temperature sensor 50 is not limited to the above position, and may be a position near the switching valve 22 inside the moisture adsorbing material 32. In the present embodiment, since the Fr temperature sensor 50 is added, for convenience of explanation, the temperature sensor 34 incorporated in the moisture adsorbing material 32 is referred to as “Rr temperature sensor 34”.

[Leakage detection technique for switching valve and failure determination technique for temperature sensor used in the second embodiment]
FIG. 6 is a diagram showing the relationship between the exhaust gas temperatures detected by the Rr temperature sensor 34 and the Fr temperature sensor 50 shown in FIG. 5 and the elapsed time after the start of the internal combustion engine 10. In FIG. 6, the output waveform of the Rr temperature sensor 34 when there is no leakage in the switching valve 22 is shown by a thin broken line, and the output waveform of the Rr temperature sensor 34 when there is leakage in the switching valve 22 is shown by a thick broken line. ing. Further, the output waveform of the Fr temperature sensor 50 when there is no leakage in the switching valve 22 is shown by a thin solid line, and the output waveform of the Fr temperature sensor 50 when there is leakage in the switching valve 22 is shown by a thick solid line.

As shown in FIG. 6, if there is no leakage in the switching valve 22, the temperature rise from the initial temperature T ₀ of the process of the adsorption operation progresses, exhaust gas during start-up, it is immediately after a cold start Therefore, the temperature difference between the sensors 34 and 50 is small. Therefore, in this embodiment, it is determined that there is no leakage when the temperature difference or temperature change between the sensors 34 and 50 is smaller than the set value.

On the other hand, when there is a leak in the switching valve 22, the output of the Rr temperature sensor 34 is added with a temperature rise due to heat generation due to the adsorption of moisture to the moisture adsorbing material 32. There is a difference between the output of the Fr temperature sensor 50 at the position. In the present embodiment, the difference between the outputs (that is, the temperature difference ΔT _i between the sensors 34 and 50) is used, and when the temperature difference ΔT _i is larger than the predetermined determination value Δk, the switching valve 22 leaks. It is determined that there is.

Further, in the present embodiment, the temperature detected by the Rr temperature sensor 34 and the Fr temperature sensor 50 is detected for both the adsorption period and the period after the adsorption period by the same method as in the first embodiment. Calculate the change. Then, when the temperature change after completion of the adsorption with respect to the temperature change during the adsorption period is smaller than a predetermined set value, it is temporarily determined that the Rr temperature sensor 34 and the Fr temperature sensor 50 are out of order. On the other hand, when the absolute value | T _ri -T _fi | of the temperature difference detected by both the sensors 34 and 50 after a predetermined time has elapsed from the end of the adsorption period is less than or equal to a predetermined set value, Even if the provisional determination is made, it is determined that both the sensors 34 and 50 are normal. If the absolute value | T _ri -T _fi | of the temperature difference is larger than the set value, the sensor indicating the lower temperature is provisionally determined to be faulty. Then, when the above two provisional determinations are established for one of the Rr temperature sensor 34 and the Fr temperature sensor 50, the failure determination of the sensor is confirmed.

[Specific Processing in Second Embodiment]
FIG. 7 is a flowchart of a routine executed by the ECU 40 in order to realize the leakage detection method for the switching valve 22 in the second embodiment. Note that this routine is started when the internal combustion engine 10 is started in the cold state in response to the operation of the ignition key of the vehicle. In the routine shown in FIG. 7, first, when the ignition key is turned ON, initial temperatures T _r0 and T _{f0 of the} exhaust gas detected by the Rr temperature sensor 34 and the Fr temperature sensor 50 are acquired (steps). 300).

Next, a temperature difference ΔT _i (= T _ri −T _fi ) between the sensors 34 and 50 from the start is calculated every predetermined cycle, and the temperature from the cold start to the end of the adsorption period The maximum value ΔT _{i-max of the} change ΔT _i is sequentially stored in the memory. The calculation of the temperature difference ΔT _i in this step 302 is repeatedly executed until it is determined in the next step 304 that the adsorption period has ended. In step 302, the ECU 40 sequentially calculates temperature changes ΔT _ri and ΔT _fi detected by the sensors 34 and 50 for reference in a routine shown in FIG. I remember it. In calculating the temperature difference ΔT _i, the initial temperatures T _r0 and T _f0 are different due to variations in the outputs of the sensors 34 and 50. Therefore, the Rr temperature sensor 34 is corrected to match the initial temperature T _r0. Is called.

Next, it is determined whether or not the adsorption period at the time of this cold start has ended, that is, whether or not the switching valve 22 has been switched from the state of closing the main exhaust passage 14 to the state of closing the bypass passage 20. (Step 304). As a result, if it is determined that the adsorption period has ended, then, whether or not the temperature change ΔT _i-max after switching of the switching valve 22 is greater than a preset temperature difference determination value ΔT _k. Is determined (step 306). The determination value ΔT _k is mapped in advance in relation to the magnitude of the initial temperature T _r0 detected by the Rr temperature sensor 34 when the ignition key is turned ON. The reference value ΔT _k corresponding to the magnitude of the initial temperature T _r0 of this time is acquired by referring to the map.

If it is determined in step 306 that ΔT _i−max > ΔT _k is not satisfied, that is, if it can be determined that there is not much difference between the temperatures detected by both sensors 34 and 50, It is determined that the amount of leakage is small or there is no leakage, that is, the switching valve 22 is normal (step 308).

On the other hand, if it is determined in step 306 that ΔT _i−max > ΔT _k is satisfied, that is, if it can be determined that the difference in temperature detected by both sensors 34 and 50 is relatively large, then leakage In order to determine the level, a leak determination value ki (= ΔT _i / ΔT _k ) is calculated, and it is then determined whether or not the leak determination value ki is greater than a predetermined set value (step 310).

  If it is determined in step 310 that the leakage determination value ki> the set value is not satisfied, the amount of leakage from the switching valve 22 is at a medium level, that is, the determination of whether there is an abnormality is suspended until the next determination. The level is determined (step 312).

  On the other hand, if it is determined in step 310 that the leakage determination value ki> the set value is satisfied, the amount of leakage from the switching valve 22 is large, that is, the switching valve 22 is abnormal (repair is required). Is determined (step 314). In the series of steps 310 to 314, one type of setting value to be compared with the leak judgment value ki is used. However, if the setting value is appropriately set to a plurality of values, it corresponds to the outputs of both sensors 34 and 50. In addition, it becomes possible to obtain a more detailed level of leakage.

  According to the routine shown in FIG. 7 described above, the Rr temperature sensor 34 and the Fr temperature caused by the heat generation amount (adsorption heat) when the exhaust gas leaked downstream from the switching valve 22 is adsorbed by the moisture adsorbent 32. Based on the output difference from the sensor 50 (temperature difference detected by them), it is possible to suitably execute the leak detection of the switching valve 22. Further, by performing leak detection with the two temperature sensors 34 and 50, erroneous determination can be prevented even when there is a temperature rise of the sensor due to heat conduction.

  FIG. 8 is a flowchart of a routine executed by the ECU 40 in order to realize failure determination of the Rr temperature sensor 34 and the Fr temperature sensor 50 in the second embodiment. Note that this routine is started when the adsorption period ends and the switching valve 22 is switched to a state (off state) that closes the bypass passage 20.

In the routine shown in FIG. 8, first, temperature changes (ΔT _rim / Δt) and (ΔT _fim / Δt) detected by the temperature sensors 34 and 50 after the switching valve 22 is switched to the off state are calculated. (Step 400). Next, it is determined whether or not a predetermined time has elapsed since the switching valve 22 was turned off (step 402).

If it is determined in step 202 that the predetermined time has elapsed, the ratio is related to the Rr temperature sensor 34, and the differential value (ΔT _rim / Δt) of the temperature change after the end of the adsorption period is stored in the memory in step 302. has been differentiated value of the temperature change during the adsorption period (ΔT _ri / Δt) and the ratio of _{{(ΔT rim / Δt) /} (ΔT ri / Δt)} whether less than the predetermined set value is determined ( Step 404).

If it is determined that the determination in step 404 is satisfied, it is temporarily determined that the Rr temperature sensor 34 is out of order (step 406). On the other hand, if it is determined that the determination in step 404 is not established, and if the process in step 406 is executed, then the ratio relating to the Fr temperature sensor 50 and the temperature change after the adsorption period ends differential value (ΔT _fim / Δt), the differential value of the temperature change in the memory has been adsorbed period in step 302 (ΔT _fi / Δt) and the ratio of _{{(ΔT fim / Δt) /} (ΔT fi / Δt) } Is smaller than a predetermined set value (step 408).

  If it is determined that the determination in step 408 is satisfied, it is temporarily determined that the Fr temperature sensor 50 is out of order (step 410). On the other hand, if it is determined that the determination in step 408 is not established, both the sensors 34 and 50 are determined to be normal (step 412).

In the routine shown in FIG. 8, if it is temporarily determined that one or both of the Rr temperature sensor 34 and the Fr temperature sensor 50 are out of order, then whether or not a certain time has passed since the end of the adsorption period. Is determined (step 414), and the temperatures T _ri and T _fi detected by the sensors 34 and 50 are acquired after the predetermined time has elapsed (step 416).

Next, it is determined whether or not the absolute value | T _ri −T _fi | of the temperature difference acquired in step 416 is larger than a predetermined set value (step 418). As a result, when it is determined that the absolute value | T _ri −T _fi |> set value is not satisfied, both the sensors 34 and 50 are determined to be normal (step 412).

On the other hand, if it is determined in step 418 that the absolute value | T _ri −T _fi |> set value is satisfied, it is then determined whether or not the sensor indicating the low temperature is the Rr temperature sensor 34. (Step 420). As a result, if it is determined that the sensor indicating the low temperature is the Rr temperature sensor 34, it is then determined whether or not the Rr temperature sensor 34 is provisionally determined in step 406 as a failure ( Step 422). As a result, if not temporarily determined, both sensors 34 and 50 are determined to be normal (step 412). Conversely, if temporarily determined, the Rr temperature sensor 34 has failed. Is determined (step 424).

  On the other hand, if it is determined in step 420 that the low temperature sensor is not the Rr temperature sensor 34, that is, the Fr temperature sensor 50, then the Fr temperature sensor 50 is provisionally determined in step 410. It is determined whether or not there is (step 426). As a result, if not tentatively determined, both sensors 34 and 50 are determined to be normal (step 412). Conversely, if tentatively determined, the Fr temperature sensor 50 has failed. Is determined (step 428).

  According to the routine shown in FIG. 8 described above, based on the outputs of the Rr temperature sensor 34 and the Fr temperature sensor 50 during and after the adsorption period, the Rr temperature sensor 34 incorporated in the moisture adsorbent 32 and Failure determination of the Fr temperature sensor 50 arranged upstream of the moisture adsorbing material 32 can be suitably executed. Furthermore, it is possible to accurately identify which of these temperature sensors 34 and 50 is malfunctioning.

In the second embodiment described above, the Fr temperature sensor 50 corresponds to the “gas temperature sensor” in the third aspect of the invention.
Further, the “sensor failure determination means” according to the fourth aspect of the present invention is realized by the ECU 40 executing a series of processes of the routine shown in FIG.
Further, the “failure sensor specifying means” in the fifth aspect of the present invention is realized by the ECU 40 executing the series of processes of steps 404 to 428 described above.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS.
[System configuration]
FIG. 9 is a diagram for explaining a configuration of an internal combustion engine system including the exhaust purification device according to Embodiment 3 of the present invention. In FIG. 9, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the system shown in FIG. 9, one end of the second purge passage 60 communicates with a portion of the main exhaust passage 14 between the switching valve 22 and the moisture adsorbing material 32. The second purge passage 60 includes a second purge control valve 62 in the middle thereof, and communicates with the intake passage 12 at the other end. Except for this point, the present system is configured similarly to the system of the first embodiment described above.

  According to the system of the present embodiment configured as described above, when the switching valve 22 is controlled so as to close the main exhaust passage 14, there is an exhaust gas leak from the switching valve 22 to the downstream side. However, by opening the second purge control valve 62, the exhaust gas flowing downstream of the switching valve 22 via the second purge passage 60 can be returned to the intake passage 12. For this reason, the exhaust gas originally intended to adsorb HC or the like by the HC adsorbent 24 or the like during the adsorption operation leaks from the switching valve 22 to the downstream side of the main exhaust passage 14 and is discharged into the atmosphere. Can be prevented. Thereby, deterioration of exhaust emission can be suppressed.

[Characteristics of Embodiment 3]
There is a need to recirculate the exhaust gas flowing downstream of the switching valve 22 to the intake side via the second purge passage 60 by the above-described method. The internal combustion that performs the adsorption operation of HC or the like to the HC adsorbent 24 or the like This is a cold start of the engine 10. During such a cold start, the combustion tends to become unstable, and if the recirculation amount (EGR amount) of the exhaust gas to the intake air is increased, the combustion is likely to deteriorate. Therefore, if the recirculation amount to the intake air is increased more than necessary, the drivability of the internal combustion engine 10 and the exhaust emission are deteriorated due to the deterioration of combustion. Further, if the intake air amount is increased in order to avoid the deterioration of combustion, there is a problem that the fuel consumption is deteriorated accordingly.

  Therefore, in this embodiment, the recirculation amount (purge amount) of the exhaust gas from the downstream of the switching valve 22 to the intake air is controlled to a value corresponding to the leakage amount of the exhaust gas from the switching valve 22.

  FIG. 10 is a flowchart of a routine executed by the ECU 40 in the third embodiment in order to realize the above function. Note that this routine is started when the internal combustion engine 10 is started in the cold state in response to the operation of the ignition key of the vehicle. In the routine shown in FIG. 10, first, it is determined whether or not the switching valve 22 is in an open state (a state controlled to close the main exhaust passage 14) (step 500).

  If it is determined in step 500 that the switching valve 22 is in the open state, it is determined whether or not there is an exhaust gas leak from the switching valve 22 (step 502). Specifically, in this step 502, the presence or absence of gas leakage is determined using the execution result of the routine shown in FIG.

  If it is determined in step 502 that there is no exhaust gas leakage from the switching valve 22, the recirculation of the exhaust gas to the intake air from the downstream side of the switching valve 22 is stopped (step 504).

  On the other hand, if it is determined in step 502 that there is an exhaust gas leak from the switching valve 22, the exhaust gas to the intake side is adjusted to a value corresponding to the amount of exhaust gas leakage from the switching valve 22. The recirculation amount of the gas is controlled by adjusting the opening degree of the second purge control valve 62 (step 506). As shown in FIG. 11, the ECU 40 stores a map that defines the relationship between the exhaust gas recirculation amount to the intake air and the exhaust gas leakage amount from the switching valve 22. The map shown in FIG. 11 is set so that the amount of recirculation to the intake air increases as the amount of leakage from the switching valve 22 increases. According to such a map, the recirculation amount of the exhaust gas to the intake air can be appropriately set according to the gas leakage amount obtained by the routine shown in FIG.

  According to the routine shown in FIG. 10 described above, exhaust gas more than necessary is not recirculated to the intake side, so that the switching valve 22 is suitably suppressed while suppressing deterioration in combustion and fuel consumption associated with execution of recirculation to intake air. It is possible to prevent the exhaust emission from deteriorating due to the exhaust gas leakage from the exhaust gas.

  In the third embodiment described above, the second purge passage 60 corresponds to the “reflux passage” in the sixth invention, and the ECU 40 executes a series of processes shown in FIG. The “reflux amount control means” in the sixth aspect of the invention is realized.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 12 described later instead of the routine shown in FIG. 10 using the hardware configuration shown in FIG.

[Characteristics of Embodiment 4]
FIG. 12 is a flowchart of a routine executed by the ECU 40 in the fourth embodiment in order to prevent deterioration of exhaust emission due to exhaust gas leakage from the switching valve 22 while suppressing deterioration of combustion and the like. Note that this routine is started when the internal combustion engine 10 is started in the cold state in response to the operation of the ignition key of the vehicle. In FIG. 12, the same steps as those shown in FIG. 10 in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 12, after it is determined in step 500 that the switching valve 22 is in the open state, a predetermined amount of exhaust gas is then recirculated from the downstream of the switching valve 22 to the intake side. Next, the opening adjustment of the second purge control valve 60 is executed (step 600).

  Next, it is determined whether or not a predetermined time has elapsed since the current start point (step 602). In this routine, after waiting for the predetermined time to elapse, the subsequent steps 502 to 506 are executed.

  When the internal combustion engine 10 is cold-started, the exhaust gas is cooled by the cooled exhaust pipe (main exhaust passage 14). As a result, moisture contained in the exhaust gas condenses and adheres to the exhaust pipe. Along with this, at the position of the switching valve 22, immediately after the internal combustion engine 10 is started, exhaust gas having a low moisture concentration flows. For this reason, even when there is an exhaust gas leak from the switching valve 22, the temperature rise of the moisture adsorbent 32 downstream of the switching valve 22 is small, and it is difficult to detect an accurate exhaust gas leak amount. It becomes.

  According to the routine shown in FIG. 12 described above, a predetermined amount of exhaust gas is recirculated from the downstream of the switching valve 22 to the intake side for a predetermined time immediately after the cold start. For this reason, even if there is a gas leak immediately after the cold start where it is difficult to accurately detect the gas leak from the switching valve 22, the unpurified component of the exhaust gas such as HC is reduced to HC. The exhaust gas can be prevented from being discharged into the atmosphere without passing through the adsorbent 24 and the like, and the deterioration of exhaust emission can be avoided.

  Further, in the routine described above, after the predetermined time has elapsed and accurate leak detection is possible, the same method as that of the third embodiment described above is used. For this reason, it is possible to prevent deterioration of exhaust emission due to exhaust gas leakage from the switching valve 22 while suitably suppressing deterioration of combustion and fuel consumption accompanying execution of recirculation to intake air.

Embodiment 5. FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 13 described later instead of the routine shown in FIG. 10 using the hardware configuration shown in FIG.

[Characteristics of Embodiment 5]
FIG. 13 is a flowchart of a routine executed by the ECU 40 in the fifth embodiment in order to prevent deterioration of exhaust emission due to exhaust gas leakage from the switching valve 22 while suppressing deterioration of combustion and the like. Note that this routine is started when the internal combustion engine 10 is started in the cold state in response to the operation of the ignition key of the vehicle. In FIG. 13, the same steps as those shown in FIG. 10 in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 13, after it is determined in step 500 that the switching valve 22 is in an open state, the amount of exhaust gas leakage from the switching valve 22 at the time of the previous cold start is then acquired (step 700). ).

  Next, the recirculation amount of the exhaust gas to the intake side is controlled by adjusting the opening degree of the second purge control valve 60 so that it becomes a value corresponding to the previous value of the gas leakage amount acquired in the above step 700 ( Step 02). Next, after waiting for a predetermined time from the current start time (step 602), the subsequent steps 502 to 506 are executed. Next, the amount of gas leakage from the switching valve 22 detected at the current cold start is stored (step 704).

  The amount of exhaust gas leakage from the switching valve 22 is unlikely to change every time the internal combustion engine 10 is started, and gradually changes over time. According to the routine shown in FIG. 13 described above, the leakage amount from the switching valve 22 is reduced before the gas leakage amount is correctly detected based on the moisture adsorbent 32 and the temperature sensor 34 when the internal combustion engine 10 is cold started. It is possible to estimate. Then, according to the processing of the above routine, since the recirculation amount immediately after the cold start is determined based on the estimated gas leak amount (previous value), the recirculation amount immediately after the cold start is determined regardless of the amount of the gas leak amount. From the stage, it is possible to prevent the exhaust gas more than necessary from being recirculated to the intake side. For this reason, as compared with the above-described third and fourth embodiments, the deterioration of exhaust emission due to the exhaust gas leakage from the switching valve 22 is suppressed while suppressing the deterioration of combustion and the deterioration of fuel consumption accompanying the execution of recirculation to the intake air. Can be more suitably prevented.

  In the fifth embodiment described above, the “leakage amount storage means” according to the eighth aspect of the present invention is realized by the ECU 40 executing the process of step 704.

  Incidentally, in the first to fifth embodiments described above, the moisture adsorbing material 32 is arranged in the main exhaust passage 14 for detecting the leakage of the switching valve 22 using the adsorption heat. The adsorbent to be used may not be a moisture adsorbent having a function of adsorbing moisture as long as it is an adsorbent that generates heat when supplied with exhaust gas. That is, the adsorbent disposed for the purpose as described above may be a material that generates heat by adsorbing unpurified components (HC, CO, CO2, etc.) in the exhaust gas.

It is a figure for demonstrating the structure of an internal combustion engine system provided with the exhaust gas purification apparatus in Embodiment 1 of this invention. FIG. 2 is a diagram showing a relationship between an exhaust gas temperature detected by a temperature sensor shown in FIG. 1 and an elapsed time after the start of the internal combustion engine. FIG. 3 is a flowchart of a routine that is executed in the first embodiment of the present invention in order to detect leakage of the switching valve shown in FIG. 1. FIG. FIG. 3 is a flowchart of a routine that is executed in the first embodiment of the present invention to perform a failure determination of the temperature sensor shown in FIG. 1. FIG. It is a figure for demonstrating the structure of an internal combustion engine system provided with the exhaust gas purification apparatus in Embodiment 2 of this invention. FIG. 6 is a diagram showing the relationship between the exhaust gas temperatures detected by the Rr temperature sensor and the Fr temperature sensor shown in FIG. 5 and the elapsed time after starting the internal combustion engine. FIG. 6 is a flowchart of a routine that is executed in the second embodiment of the present invention to perform leakage detection of the switching valve shown in FIG. 5. FIG. 6 is a flowchart of a routine that is executed in the second embodiment of the present invention in order to make a failure determination of the temperature sensor shown in FIG. 5. It is a figure for demonstrating the structure of an internal combustion engine system provided with the exhaust gas purification apparatus in Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. 11 is an example of a map of intake air recirculation amount referred to in the routine shown in FIG. 10. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention.

Explanation of symbols

Reference Signs List 10 internal combustion engine 12 intake passage 14 main exhaust passage 16 front catalyst 18 rear catalyst 20 bypass passage 20a upstream connection portion 20b downstream connection portion 22 switching valve 22a negative pressure diaphragm 22b valve seat 24 HC adsorbent 26 NOx adsorbent 28 purge passage 30 Purge control valve 32 Moisture adsorbent 34 Temperature sensor (Rr temperature sensor)
40 ECU (Electronic Control Unit)
50 Fr temperature sensor 60 second purge passage 62 second purge control valve

Claims (8)

A main exhaust passage through which exhaust gas discharged from the internal combustion engine flows;
A bypass passage that branches from the main exhaust passage at an upstream connection portion with the main exhaust passage, and merges with the main exhaust passage again at a downstream connection portion downstream from the upstream connection portion;
An unpurified component adsorbent disposed in the bypass passage and having a function of adsorbing unpurified components contained in the exhaust gas;
A switching valve capable of switching an inflow destination of exhaust gas between the main exhaust passage and the bypass passage;
A valve downstream side adsorbent that is disposed in a passage on the downstream side of the switching valve and generates heat by receiving supply of exhaust gas;
An adsorbent temperature sensor that is disposed in the passage downstream of the valve downstream side adsorbent in the valve downstream side adsorbent or in the flow direction of the exhaust gas and detects the temperature of the valve downstream side adsorbent;
Valve leakage detection means for detecting leakage of exhaust gas from the switching valve, based on temperature information of the valve downstream side adsorbent accompanying heat generation when the gas is adsorbed by the valve downstream side adsorbent;
An exhaust emission control device for an internal combustion engine, comprising:   Temperature information detected by the adsorbent temperature sensor during the adsorption period of the unpurified component to the unpurified component adsorbent during cold start of the internal combustion engine, and detected by the adsorbent temperature sensor after the adsorption period ends 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising sensor failure determination means for determining a failure of the adsorbent temperature sensor based on the temperature information to be detected. A gas temperature sensor for detecting a temperature of exhaust gas flowing into the adsorbent downstream of the valve;
The valve leak detection means detects the leak of exhaust gas from the switching valve based on a comparison result between the temperature information of the adsorbent downstream of the valve and temperature information of the exhaust gas detected by the gas temperature sensor. The exhaust emission control device for an internal combustion engine according to claim 1, wherein:   Respective temperature information detected by the adsorbent temperature sensor and the gas temperature sensor during the adsorption period of the unpurified component to the unpurified component adsorbent during cold start of the internal combustion engine, and after the end of the adsorption period Sensor failure determination means for determining a failure of at least one of the adsorbent temperature sensor and the gas temperature sensor based on the temperature information detected by the adsorbent temperature sensor and the gas temperature sensor. The exhaust emission control device for an internal combustion engine according to claim 3,   The sensor failure determination means may be a temperature sensor that is determined to have a temperature change after the end of the adsorption period with respect to a temperature change during the adsorption period that is smaller than a predetermined set value among the adsorbent temperature sensor and the gas temperature sensor. Applicable and the one corresponding to the temperature sensor indicating a low temperature when the temperature difference between the adsorbent temperature sensor and the gas temperature sensor after a certain time has elapsed from the end of the adsorption period is greater than a predetermined set value. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, further comprising failure sensor specifying means for specifying that the temperature sensor has failed. A recirculation passage branched from a passage between the switching valve and the valve downstream side adsorbent, and connected to an intake passage of an internal combustion engine;
The apparatus further comprises a recirculation amount control means for controlling a recirculation amount of the exhaust gas to the intake passage in accordance with a leakage amount of the exhaust gas from the switching valve detected by the valve leak detection means. Item 6. An exhaust emission control device for an internal combustion engine according to any one of Items 1 to 5.   7. The internal combustion engine according to claim 6, wherein the recirculation amount control means controls the recirculation amount so that the recirculation amount of the exhaust gas to the intake passage becomes a constant amount during a predetermined time after the cold start. Engine exhaust purification system. A leak amount storage means for storing the leak amount of the exhaust gas from the switching valve detected by the valve leak detection means;
The said recirculation amount control means controls the said recirculation amount so that it may become the quantity according to the said leakage amount at the time of the last cold start during the predetermined time after a cold start. Exhaust gas purification device for internal combustion engine.

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