JP3835071B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine suitable for use in a lean combustion internal combustion engine.
[0002]
[Prior art]
NO _X catalyst occlusion-type to be provided in a lean-burn internal combustion engine, while absorbing the NO _X in an oxidizing atmosphere, in a reducing atmosphere, has the function of releasing the NO _X occluding reversed. Therefore, for example, by a reducing atmosphere surrounding atmosphere of the NO _X catalyst at appropriate time intervals, the NO _X occluding on the catalyst releases, to ensure _the NO _X storage capability to prevent saturation of the NO _X catalyst I am doing so. However, the exhaust gas also contains a sulfur (S) component, and the NO _x catalyst occludes NO _{x in} an oxidizing atmosphere during lean combustion operation and also occludes the S component in such exhaust gas. . For this reason, the NO _x storage capacity of the NO _x catalyst deteriorates with time.
[0003]
In this way, if the deteriorated NO _x catalyst is used as it is, NO _x in the exhaust gas that is not purified is released into the atmosphere as it is. Therefore, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-217474, when the storage amount of the S component in the NO _X catalyst exceeds an allowable value, the ignition timing is retarded and the temperature at which the NO _X catalyst can be released from the S _X catalyst. It causes to warm to, as the reducing atmosphere surrounding atmosphere of the NO _X catalyst and the air-fuel ratio to rich, the release of the S component, that is, to perform the regeneration of the NO _X catalyst.
[0004]
[Problems to be solved by the invention]
However, the catalyst temperature increases when the vehicle is accelerated, but decreases due to fuel cut when the vehicle is decelerated. For this reason, when acceleration / deceleration continues due to the driver's driving tendency and road conditions, the catalyst temperature repeatedly rises and falls, and even if regeneration control is performed as in the above-described prior art, acceleration / deceleration is performed. during the hardly rises to optimally releasable catalyst temperature S component followed, nO _X catalyst is not reproduced easily, during which results in the wasteful fuel that does not contribute to regeneration of the nO _X catalyst continues to be consumed, the fuel consumption Deteriorating.
[0005]
The present invention was devised in view of such problems, and is an internal combustion engine that can reliably regenerate a catalyst while minimizing deterioration in fuel consumption, regardless of the driving tendency or road conditions of the driver. An object is to provide an exhaust emission control device.
[0006]
[Means for Solving the Problems]
For this reason, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, the state detection means detects or estimates the purification state of the catalyst device that is provided in the exhaust passage of the internal combustion engine and purifies harmful substances in the exhaust gas, and is detected or estimated. Based on the purification state of the catalyst device, the operation state of the internal combustion engine is changed for a predetermined time by the regeneration means, and the purification ability reducing material adhering to the catalyst device is released to regenerate the purification performance of the catalyst device. When it is determined that the release of the purification ability lowering substance has not been completed, the operating condition changing means changes the operating condition of the regeneration means to a specific operating condition suitable for the release of the purification ability lowering substance. Release substances with reduced purification capacity under specific operating conditions.
[0007]
The operating condition changing means changes the preset operating condition of the regenerating means so as to operate only for specific operating conditions such as high speed operation or steady running, or sets a plurality of operating conditions in advance. In addition, it is preferable to restrict the regeneration means from operating depending on the conditions by switching the operating conditions.
Specifically, the operating condition changing means normally selects the slow temperature rising mode and, after the operation of the regeneration means, determines that the release of the purification capacity-decreasing substance has not been completed, It is preferable to select the temperature mode.
The operating condition changing means is a condition for selecting the low-temperature temperature raising mode, wherein the state detecting means detects the deterioration of the catalyst device, the lean operation of the internal combustion engine is prohibited, the internal combustion engine is in idle operation, and The case where the average vehicle speed is equal to or higher than the first reference vehicle speed is preferably set.
Further, the operating condition changing means is a specific operation condition that is a condition for selecting the high-speed temperature raising mode. In the regeneration control in the low-temperature temperature raising mode, regeneration of the catalyst device is not completed, and the internal combustion engine is in idle operation and It is preferable to set a case where the average vehicle speed is equal to or higher than the second reference vehicle speed (however, higher than the first reference vehicle speed).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 show an exhaust gas purification apparatus for an internal combustion engine as an embodiment of the present invention, and FIG. 1 shows a configuration of a lean combustion internal combustion engine to which the present apparatus is applied.
As shown in FIG. 1, an engine (lean combustion internal combustion engine) 1 is configured as an in-cylinder injection gasoline engine, and has an intake passage 3 and an exhaust passage 4 that communicate with the combustion chamber 2. An air cleaner and an electronically controlled throttle valve (ETV) 6 (not shown) are provided in order from the upstream side, and an exhaust purification device 8 for exhaust gas purification and a muffler (not shown) are provided in the exhaust passage 4 in order from the upstream side. Yes. Fuel injection valves (injectors) 7 are provided by the number of cylinders so that fuel is directly injected into each cylinder, and an ignition plug 5 is provided at the upper center of each combustion chamber 2.
[0009]
Exhaust purification device 8, occlusion-type NO _X catalyst (hereinafter, simply NO: _X catalyst) have become a combination of a 8A and the three-way catalyst 8B. That is, NO _x is occluded by the NO _x catalyst 8A in an oxidizing atmosphere (that is, an oxygen excess atmosphere), and released from the NO _x catalyst 8A in a reducing atmosphere to be reduced. Further, under the stoichiometric air-fuel ratio is the adapted to purify CO, HC, NO _X in the exhaust gas by the function of the three-way catalyst 8B. In addition, a proximity catalyst (for example, a three-way catalyst) may be separately provided at a position close to the engine 1 upstream of the exhaust purification device 8 to mainly perform exhaust gas purification at the time of starting.
[0010]
Further, in order to control the engine 1, an electronic control unit (ECU) 20 and various sensors are provided. Further, an alarm lamp 30 is provided on the instrument panel in the vehicle cabin to make the driver recognize the state of the engine 1. As sensors provided in the engine 1, first, on the intake passage 3 side, an air flow sensor 10 for detecting an intake air amount is provided in an air cleaner provided portion, and an ETV 6 is provided in an ETV 6 provided portion. There are provided a throttle sensor 11 for detecting the opening degree and an idle switch 12 for detecting the idling state.
[0011]
Further, an O ₂ sensor 13 for detecting the oxygen concentration in the exhaust gas and a high temperature sensor 14 for detecting the exhaust temperature are provided on the exhaust passage 4 side in the upstream portion of the exhaust purification device 8. Further, as other sensors, a crank angle sensor 15 that outputs a signal in synchronization with rotation of a crankshaft (not shown), a wheel speed sensor 16 that outputs a signal in synchronization with rotation of a wheel, and a knock generated in the engine 1 are detected. A knock sensor 17 or the like is provided.
[0012]
As shown in the functional block diagram of FIG. 2, the ECU 20 includes an injection control means 21, an ETV opening degree control means 22, and an ignition timing control means 23 as its functional elements. Is to control. For example, in the low-load operation range, lean operation by stratified combustion that can inject fuel into the compression stroke to make the air-fuel ratio extremely lean, or lean operation that increases the air-fuel ratio by uniform combustion by intake stroke injection, improve fuel efficiency. It is designed to be illustrated.
[0013]
By the way, if the NO _X catalyst 8A continues to occlude NO _x in the lean operation state, it eventually reaches a saturated state, and NO _x that cannot be occluded is released into the atmosphere. Further, since the S component is decreased reducing ability substance (SO _X) is to be occluded in the NO _X catalyst in place of the NO _X in the form of sulfate, NO _X storage ability of the NO _X catalyst 8A decreases with time, gradually The performance will deteriorate. Occluded NO _X (nitrate) is released by a reducing atmosphere of stoichiometric or rich. Further, since the occluded S component (sulfate) is stable, in order to release it, it is necessary to set the catalyst to a high temperature of, for example, 600 ° C. or higher at the same time as a stoichiometric or rich reducing atmosphere.
[0014]
Therefore, in the ECU 20, first, for saturation of the NO _x catalyst 8A, the NO _x release start judging means 24 and the NO _x release control means 25 which are functional elements before the NO _x catalyst 8A reaches a saturated state. to, NO _X catalyst 8A of occluded NO _X release, thereby performing reducing (NO _X purge). Specifically, NO _X emission start determining means 24 is adapted to determine the appropriate timing to the NO _X emission initiation of the NO _X catalyst 8A from the lean operation time, the lean operation time a predetermined time (e.g. 30 seconds ) Is reached, it is assumed that the timing is appropriate for the release of NO _x from the NO _x catalyst 8A. If the lean operation time is too long, the catalyst temperature will decrease and the purification efficiency of HC will decrease, and if it is too short, the fuel consumption will deteriorate, but the time ratio occupied by the air-fuel ratio tailing part that does not contribute to NO _X release will increase. Set to an appropriate value that satisfies
[0015]
Then, when the NO _X release starting from NO _X catalyst 8A is determined, the NO _X release controlling means 25, injection control means 21, temporarily controls the ETV opening control means 22 (e.g., about 1 to 5 seconds ) To make the air-fuel ratio rich. As a result, the ambient atmosphere of the NO _x catalyst 8A becomes a reducing atmosphere, and the stored NO _x is desorbed and reduced.
[0016]
On the other hand, for the deterioration of the NO _X catalyst 8A, the deterioration detection means (state detection means) 26 detects the deterioration state of the NO _X catalyst 8A, and when the deterioration degree exceeds the reference value, the S release control means (regeneration) Means) 27 controls the regeneration of the NO _x catalyst 8A. Hereinafter, estimation of the deterioration state of the NO _x catalyst 8A by the deterioration detection means 26 and regeneration control by the S release control means 27 will be described.
[0017]
The deterioration detection means 26 detects the deterioration of the NO _x catalyst 8A based on the success or failure of the following first condition and second condition. First, the first condition is that the S-poisoned fuel amount Q expressed by the following equation is equal to or greater than a predetermined reference value Q ₀ . The S-poisoned fuel amount Q corresponds to the total amount of SO _X accumulated in the NO _X catalyst 8A.
Q (n) = Q (n-1) + T _INJ × K _INJ × N _E × T _CAL × K _{A / F} × K _FUEL × K _C
In the above equation, Q (n) represents the amount of S-poisoned fuel at the time of the current calculation, and Q (n-1) represents the amount of S-poisoned fuel at the time of the previous calculation. Further, T _INJ fuel injection time, K _INJ is injector gain showing the fuel injection amount per unit time, N _E is engine speed. The engine speed _NE is calculated based on the crank angle signal. T _CAL is a calculation cycle, K _{A / F} is an S poisoning A / F coefficient indicating the ease of S poisoning with respect to the air-fuel ratio, and K _FUEL is an S poisoning indicating the ease of S poisoning with respect to the fuel property. The poison fuel coefficient, K _C, is a coefficient for the number of cylinders. K _{A / F} is set so that it is large when the air-fuel ratio is lean and small when it is rich, and is determined from a map using the air-fuel ratio as a parameter. K _FUEL is generally set so that the lower the octane number of the fuel in a fuel having a low octane number, the higher the lower the octane number of the fuel, that is, the larger the ignition timing retard amount by knocking. K _C is a constant and is half the number of cylinders, that is, 2 for 3 cylinders and 3 for 6 cylinders.
[0018]
Next, the second condition is that the 700 ° C. converted S regeneration time T _RE represented by the following formula is less than a predetermined reference value T _RE0 . The release of SO _x from the NO _x catalyst 8A is naturally performed even during normal operation when the catalyst is at a high temperature and the air-fuel ratio becomes stoichiometric or rich, in addition to the regeneration control described later. Also, the SO _x release rate increases exponentially with the catalyst temperature. Therefore, the 700 ° C. converted S regeneration time T _RE is obtained by converting the regeneration time in which the regeneration of the NO _X catalyst 8A by the regeneration control and the natural regeneration is converted into a regeneration time at 700 ° C. and accumulating. The reference value T _RE0 corresponds to the regeneration completion time when the catalyst is at 700 ° C.
[0019]
T _RE (n) = T _RE (n-1) + K _V × T _CAL
In the above equation, T _RE (n) represents the 700 ° C. converted S regeneration time at the time of the current calculation, and T _RE (n−1) represents the 700 ° C. converted S regeneration time at the time of the previous calculation. This calculation assumes that the air-fuel ratio is performed when the stoichiometric or rich, not performed the addition of T _RE as little play when the lean. K _V is SO _X release rate coefficient indicating the SO _X release rate ratio of the catalyst temperature in the current calculation time for SO _X release rate at 700 ° C., is adapted to determine a catalyst temperature from a map as parameters . The catalyst temperature is estimated from the exhaust gas temperature detected by the high temperature sensor 14.
[0020]
When both of the first condition and the second condition are satisfied, the ECU 20 prohibits the lean operation regardless of the driving state of the vehicle and enters the regeneration standby state. Further, the deterioration detecting means 26, but the S poisoning fuel quantity Q exceeds the reference value Q _0, when even exceeds the reference value T _RE0 700 ° C. Conversion S regeneration time T _RE is the reproduction of the NO _X catalyst 8A As the completion, the S poison fuel amount Q, 700 ° C. converted S regeneration time T _RE is reset.
[0021]
Next, the regeneration control of the NO _x catalyst 8A by the S release control means 27 will be described. In the S release control means 27, the catalyst temperature is increased, and the ambient atmosphere of the NO _x catalyst 8A is made a reducing atmosphere. The occluded SO _x is desorbed. In addition, the regeneration control has two control modes, a low-temperature temperature increase mode and a high-speed temperature increase mode. Usually, the low-speed temperature increase mode is selected, but the mode change means is used when regeneration is not completed in the low-temperature temperature increase mode. (Operating condition changing means) 28 makes it possible to change the control mode to a high-speed temperature raising mode that is more suitable for releasing S (a substance with reduced purification ability) because the catalyst temperature tends to become high.
[0022]
First, the start condition, the control content, and the release condition will be described in order for the low temperature heating mode. The start condition for the low-temperature heating mode is that all of the following three conditions are satisfied. The first condition is that the deterioration is detected by the above-described deterioration detection means 26 and the reproduction standby state is set. conditions, the idle switch (IDSW) 12 is turned off, the third condition is that the average vehicle speed V _AVE in the predetermined time is greater than or equal to the first reference vehicle speed V _a.
[0023]
When the above start condition is satisfied, reproduction control is performed. In the regeneration control, first, control parameters (feedback integral gain, ignition timing, throttle opening, fuel injection timing) are set. That is, the feedback integral gain in the stoichiometric feedback control is set in a direction in which the air-fuel ratio becomes slightly richer than the stoichiometric, so that the ambient atmosphere of the NO _x catalyst 8A is a reducing atmosphere. In addition, to increase the catalyst temperature, the ignition timing is set to the retard side, and at the same time, in order to compensate for the decrease in torque due to the ignition timing retard, the throttle opening setting is increased and the ignition timing and the throttle opening are set. The fuel injection timing from the injector is set accordingly. Based on each set value, the injector 7, ETV 6, and spark plug 5 are appropriately controlled via the injection control means 21, the ETV opening degree control means 22, and the ignition timing control means 23. Incidentally, during the regeneration control, in order to prevent a decrease in catalyst temperature, when the actual vehicle speed is less than the reference vehicle speed V _a, the fuel cut during deceleration is designed to prohibit.
[0024]
The release condition for the low-temperature heating mode is that one of the following two conditions is satisfied. The first condition is that the 700 ° C. converted S regeneration time T _RE is equal to or greater than the reference value T _RE0 , and in this case, the regeneration control is terminated assuming that the regeneration of the NO _x catalyst 8A is completed. Yes. On the other hand, the second condition is that the regeneration control integration time (slow temperature increase mode integration time) _{TL in the} low temperature increase mode is equal to or greater than a predetermined reference value _TL0. as the reproduction of the NO _X catalyst 8A is not completed, the mode change unit 28 to perform playback control at a high speed heating mode of the next step, so as make a rapid temperature increase request flag F _H.
[0025]
Next, the fast temperature increase mode will be described. The start condition for the fast temperature rise mode is that all of the following three conditions are satisfied. The first condition is that the above-described fast temperature rise request flag F _H is set, and the second condition is that the idle switch 12 is The third condition is that the vehicle is off and the average vehicle speed V _AVE at a predetermined time is equal to or higher than the second reference vehicle speed V _b (V _b > V _a ).
[0026]
Then, regeneration control is performed when the above start condition is satisfied. The control content of the regeneration control in the high-speed temperature increase mode is the same as that in the low-temperature temperature increase mode. That is, the control parameters (feedback integral gain, ignition timing, throttle opening, fuel injection timing) are set to the same settings as those in the low-temperature temperature increase mode described above, and the injection control means 21 and ETV opening control are performed based on the settings. The injector 7, ETV 6, and spark plug 5 are appropriately controlled via the means 22 and the ignition timing control means 23. Even during the regeneration control in the high temperature heating mode, when the actual vehicle speed is lower than the reference vehicle speed _Vb , the fuel cut at the time of deceleration is prohibited to prevent the catalyst temperature from decreasing.
[0027]
The condition for canceling the high-speed heating mode is that one of the following two conditions is satisfied. The first condition is that the 700 ° C. converted S regeneration time T _RE is equal to or greater than the reference value T _RE0 , and in this case, the S release control is terminated assuming that the regeneration of the NO _x catalyst 8A is completed. ing. The second condition is the integration time (fast heating mode accumulated time) of the playback control in the high-speed heating mode T _H is to become equal to or larger than a predetermined reference value T _H0, this case is also a rapid temperature increase mode as the reproduction of the NO _X catalyst 8A is not completed, it resets the rapid temperature increase request flag F _H, and is adapted to light the alarm lamp 30.
[0028]
Since the exhaust gas purification apparatus for an internal combustion engine as one embodiment of the present invention is configured as described above, regeneration control of the NO _x catalyst 8A is performed, for example, as shown in the flowchart of FIG. First, in step S100, it is determined whether or not the fast temperature increase request flag F _H is 1. When the flag F _H is 1, the process proceeds to a fast temperature increase mode after step S230, and when the flag F _H is 0, the process proceeds to step S110 and it is determined whether or not a reproduction standby state is set. If it is already in the regeneration standby state, the process proceeds to the low temperature increase mode after step S150. If it is not yet in the regeneration standby state, the deterioration detection means 26 detects the deterioration state of the NO _x catalyst 8A.
[0029]
That is, it is determined whether or not the S-poisoned fuel amount Q is greater than or equal to a predetermined reference value Q ₀ (step S120), and it is determined whether or not the 700 ° C. converted S regeneration time T _RE is less than the predetermined reference value T _RE0 ( step S130), if the conditions of steps S120, S130 are both satisfied, prohibit lean operation regardless of the driving state of the vehicle as NO _X catalyst 8A is deteriorated, and playback standby (step S140) .
[0030]
Then, the process proceeds to step S150, and the process in the low temperature increase mode by the S release control means 27 is started. The slow heating mode, first, the idle switch 12 it is determined whether or not off (step S150), the average speed V _AVE in the predetermined time and determines whether the first reference vehicle speed V _a above (step S160 ). Then, when the conditions of steps S150 and S160 are both established, the regeneration control in the slow temperature increase mode is started (step S170).
[0031]
Further, with the start of the regeneration control, it is determined whether or not the 700 ° C. converted S regeneration time T _RE is equal to or greater than the reference value T _RE0 (step S180). Here, when the condition of T _RE ≧ T _RE0 is satisfied, it is determined that the regeneration is completed (step S210), and the S poison fuel amount Q, 700 ° C. converted S regeneration time T _RE is reset. (Step S220). On the other hand, does not hold the condition in step S180 is the low speed heating mode integrated time T _L is determined whether a predetermined reference value T _L0 or more (step S190).
[0032]
Here, when the condition of T _L ≧ T _L0 is satisfied, the mode changing means 28 ends the S release control in the low temperature increase mode and performs flag F to perform the regeneration control in the high temperature increase mode. _H is set up (step S200).
When the flag F _H is set (F _H = 1), the S release control means 27 starts processing in the high-speed temperature increase mode after step S230. In the high-speed heating mode, first, it is determined whether or not the idle switch 12 is off (step S230), and it is determined whether or not the average vehicle speed V _AVE at a predetermined time is equal to or higher than the second reference vehicle speed V _b (step S240). ). When the conditions of steps S230 and S240 are both satisfied, the regeneration control in the fast temperature raising mode is started (step S250).
[0033]
Further, with the start of the regeneration control, it is determined whether or not the 700 ° C. converted S regeneration time T _RE is equal to or greater than the reference value T _RE0 (step S260), and whether the fast temperature increase mode integration time T _H is _{equal to} or greater than the predetermined reference value T _H0 . It is determined whether or not (step S270). If the condition in step S260 is satisfied, it is determined that the regeneration has been completed (step S290), the flag F _H is reset (step S300), and the S poisoned fuel amount Q, 700 ° C. converted S regeneration is obtained. The time T _RE is reset (step S310). On the other hand, if the condition of step S270 is established, the failure of the high-temperature sensor 14 can be considered as the failure of regeneration even in the high-temperature heating mode in which S can be reliably released. Then, the alarm lamp 30 is turned on (step S280), and the process proceeds to step S300.
[0034]
As described above, according to the exhaust gas purification apparatus of the present internal combustion engine, the operation region in which the regeneration control is performed is changed stepwise from the low speed operation region to the high speed operation region in a direction in which the catalyst temperature is likely to rise. In addition, the S component can be released from the NOx catalyst 8A, and the regeneration of the NOx catalyst 8A is surely performed while minimizing the deterioration of fuel consumption, regardless of the driving tendency of the driver, road conditions, and the like. be able to.
Further, when regeneration is not completed in the low temperature heating mode, the mode change means (operation condition changing means) 28 changes the control mode to the high temperature heating mode, so that the temperature of the NOx catalyst (catalyst device) 8A is increased. It is easy to make it high temperature, and it can be in a state suitable for releasing S (substance of reduced purification ability) from the NOx catalyst (catalyst device) 8A.
Specifically, as a condition for selecting the low-temperature temperature increase mode, the deterioration detection means (state detection means) 26 detects the deterioration of the NOx catalyst (catalyst device) 8A and prohibits the lean operation of the engine (internal combustion engine) 1. In addition, a condition may be set in which the engine (internal combustion engine) 1 is idling and the average vehicle speed VAVE is equal to or higher than the first reference vehicle speed Va.
Further, as a specific operation condition that is a condition for selecting the high-speed temperature rise mode, the regeneration control in the low-temperature temperature rise mode does not complete the regeneration of the NOx catalyst (catalyst device) 8A, and the engine (internal combustion engine) 1 is idled. The condition that the average vehicle speed VAVE is equal to or higher than the second reference vehicle speed Vb (however, higher than the first reference vehicle speed Va) may be set.
[0035]
In the above-described embodiment, when regeneration is not completed even in the high-temperature heating mode, the operation region where the regeneration control is performed can be performed more reliably at a high speed and steady state (that is, with a small acceleration / deceleration). You may further limit to the stable driving | operation area | region. In this case, if the change in the throttle opening speed is not more than a predetermined reference value, it is determined that the operation is steady. Further, the amount of SO _X accumulated in the NO _X catalyst 8A may be estimated from the travel distance instead of being estimated from the fuel injection amount as in the above-described embodiment. Further, when the engine 1 is an in-cylinder injection engine, as a method for increasing the catalyst temperature, additional fuel may be injected during the expansion stroke of each cylinder.
[0036]
Further, the present invention is not limited to the regeneration control by the release of the S component as in the above-described embodiment, and can also be applied to the regeneration control by the release of NO _x . That is, for example, when NO _X catalyst 8A is released and sensitive characteristics NO _X in a high temperature range, based on the determination of the NO _X emission start timing by the NO _X emission start determination unit (state detecting means) 24, NO _X released After operating the control means (regeneration means) 25 for a predetermined time, it is determined whether or not the release of NO _x (purifying ability lowering substance) is completed, and if the release is not completed, the NO _x purge control means specific operating conditions the operating conditions of 25 operating conditions of the engine 1 is more suitable for the NO _X release (e.g., the catalyst temperature is high speed operation tends to become high temperature) it is also possible to change, in this case, certainly NO _X It is possible to release NO _x from the catalyst 8A.
[0037]
Of course, the present invention is not limited to the in-cylinder injection engine, and can be widely applied to, for example, a multiport injection engine and the like having a catalyst device that can regenerate the purification ability.
[0038]
【The invention's effect】
As described above in detail, according to the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is possible to reliably release the substance with reduced purification ability from the catalytic device, regardless of the driving tendency of the driver, road conditions, etc. There is an advantage that the regeneration of the catalyst device can be surely performed while minimizing the deterioration of fuel consumption.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a lean combustion internal combustion engine according to an embodiment of the present invention.
FIG. 2 is a functional block diagram according to the present embodiment.
FIG. 3 is a flowchart of reproduction control according to the present embodiment.
[Explanation of symbols]
1 engine (internal combustion engine)
8A NO _x catalyst (catalytic device)
26 Deterioration detection means (state detection means)
27 S release control means (regeneration means)
28 Mode change means (operating condition change means)

Claims (4)

A catalyst device provided in an exhaust passage of the internal combustion engine for purifying harmful substances in the exhaust gas;
State detection means for detecting or estimating the purification state of the catalyst device;
Based on the purification state of the catalyst device detected or estimated by the state detection means, the operating state of the engine is changed for a predetermined time, and the purification capability lowering substance adhering to the catalyst device is released, thereby improving the purification capability of the catalyst device. Playback means for playback;
After the operation of the regeneration means is completed, it is determined whether or not the release of the purification ability reducing substance is completed. If the release is not completed, the operation condition of the regeneration means is suitable for the release of the purification ability reduction substance. An exhaust gas purification apparatus for an internal combustion engine, characterized by comprising operating condition changing means for changing to a specific operating condition. The operating condition changing means includes
During normal times, select the slow temperature rise mode,
When it is determined that the release of the purification ability lowering substance has not been completed after the regeneration means is activated, the high-speed temperature raising mode is selected.
The exhaust emission control device for an internal combustion engine according to claim 1, characterized in that: The operating condition changing means detects the deterioration of the catalyst device by the state detecting means, the lean operation of the internal combustion engine is prohibited, and the internal combustion engine is A condition is set such that the vehicle is driving and the average vehicle speed is equal to or higher than the first reference vehicle speed.
The exhaust emission control device for an internal combustion engine according to claim 2, wherein: The operating condition changing means is configured such that the regeneration of the catalyst device is not completed in the regeneration control by the slow temperature increase mode and the internal combustion engine is idle as the specific operation condition that is the condition for selecting the high temperature temperature increase mode. A condition is set such that the vehicle is driving and the average vehicle speed is equal to or higher than the second reference vehicle speed (however, higher than the first reference vehicle speed).
The exhaust emission control device for an internal combustion engine according to claim 3, wherein:

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