JPH11141330A - Lean-burn internal combustion engine - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To provide an exhaust purifying device with NO_XCatalyst poisons S
NO in exhaust gas even if it occurs _XSo that the ingredients do not increase
High sulfur content in fuel and lubricating oil
NO without considering whether it is low or low_XYou can use a catalyst
To do. SOLUTION: When the exhaust air-fuel ratio is lean, NO_xSuck
NO when the oxygen concentration in the exhaust gas decreases_xDesorb
NO_xThe catalyst 6A serves as an exhaust gas of an internal combustion engine capable of lean combustion.
The control means 20 is provided in the passage_xN of catalyst 6A
O_xThe lean burn operation range of the internal combustion engine is determined based on the purification efficiency.
Change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the harmful components in the exhaust gas, in particular, equipped with an exhaust purification apparatus for purifying NO _X, it relates lean burn internal combustion engine.

[0002]

At present, have been developed lean-burn internal combustion engine capable to achieve further improvement of fuel efficiency, the NO _X generated during lean combustion in such an internal combustion engine, a three-way catalyst is provided conventionally (It has a ternary function near stoichio) is difficult to purify.

[0003] Therefore, the lean NO _X catalyst can purify the NO _X in an oxygen-rich atmosphere in which oxygen in the exhaust gas becomes excessive have been developed. Such lean NO _X catalyst, the oxygen-rich atmosphere to adsorb NO _X in the exhaust gas, has a function of oxygen concentration desorbs NO _X adsorbed to decrease, the NO _X in the exhaust gas by this feature There is a purifying type (storage type lean NO _X catalyst, trap type lean NO _X catalyst; hereinafter, referred to as NO _X catalyst).

[0004] Specifically, lean NO_XThe catalyst is oxygen enriched
In excessive atmosphere, NO in exhaust gas _XOxidize nitric acid
To form salts, which result in NO_XWhile adsorbing oxygen
In a reduced atmosphere, lean NO_XAdsorbed on catalyst
Reaction of nitrate with CO in exhaust gas to produce carbonate
And this results in NO_XWith the function of desorbing
You.

[0005]

Since the fuel and the lubricating oil contain a sulfur component (S component), the exhaust gas also contains a sulfur component. Therefore, NO
_{The X} catalyst adsorbs NO _X in an atmosphere having an excessive oxygen concentration and also adsorbs such sulfur components. That is, the sulfur components contained in fuel or lubricating the oil burns, further oxidized to become SO ₃ on NO _X catalyst, occluding for this part of the SO ₃ is further on NO _X catalyst NO _X agent reacts with at adsorbing the NO _X catalyst is sulfuric acid salt.

Accordingly, the NO _X catalyst, but would nitrate and sulfate salts are adsorbed, high stability of the salt than sulfates nitrates, Part 1 even if the atmosphere in which the oxygen concentration is lowered since part only degraded, the amount of sulfate remaining in the nO _X catalyst is increased with time. Therefore, NO _X adsorbing capacity of the NO _X catalyst decreases with time, NO _X purification efficiency of the NO _X catalyst will decrease (This is called S poisoning).

[0007] Thus, NO _X catalyst, since the performance by S poisoning by sulfur contained in the fuel and lubricating oil will deteriorate, in terms of durability three-way catalyst (TWC: Thre
e Way Catalyst). Therefore, NO by preventing S poisoning of _X catalyst, to improve its durability, NO target lifetime of _X catalyst (e.g., the travel distance of about 100,000 miles) NO of the NO _X catalyst until passage _{X It} is necessary to prevent the purification efficiency from significantly decreasing.

As a technique for preventing sulfur poisoning by sulfur components in fuels and lubricating oils, for example, JP-A-6-8
There is a technique disclosed in Japanese Patent No. 8518. This technology is
When the engine is operating in an oxygen-excess atmosphere, exhaust gas or NO
_{If X} catalyst (NO _X absorbent material) is determined to be a high temperature, by decreasing the oxygen concentration of the exhaust gas flowing to the NO _X catalyst, the durability against SO _X poisoning of the NO _X catalyst (S poisoning) Is to improve the performance.

However, it is contained in fuel and lubricating oil.
The concentration of the sulfur component is determined by the market (ie, the fuel or lubricant used).
Location) and the time of use,
NO _XCatalyst lifetime is included in fuels and lubricants
This depends on the concentration of the sulfur component.
In the technology, sulfur components contained in fuel and lubricating oil
No consideration is given to the effect of the concentration of sucrose.

[0010] Thus, for example, when the concentration of sulfur components contained in fuel or lubricating oil is used in areas of high, the target lifetime (e.g., the travel distance of about 100,000 miles) NO _X catalyst deterioration before reaching the and, the NO _X purification efficiency will be significantly reduced, the problem that the concentration of the NO _X discharged into the atmosphere becomes excessive occurs. Therefore, it is difficult to use the NO _X catalyst practically in an area where the concentration of sulfur component contained in the fuel is high, and the area where the NO _X catalyst can be used is located in an area where the concentration of the sulfur component contained in the fuel is low. It will be limited.

[0011] The present invention has been developed with a view to eliminating these problems, NO _X catalyst in the exhaust gas even if the S-poisoning N
O _X component not to increase, and so can be employed without NO _X catalyst that the concentration of sulfur components contained in fuel or lubricating oil to consider higher or lower, the lean burn internal combustion engine The purpose is to provide.

[0012]

A solution for the] Therefore, in the lean-burn internal combustion engine of the present invention, NO _x when the exhaust gas air-fuel ratio in the exhaust passage to adsorb NO _x when the lean, the oxygen concentration in the exhaust gas was reduced A NO _x catalyst for desorbing NO is provided. Then, it is characterized in that changing the lean-burn operation range of the internal combustion engine based on _the NO _x purification efficiency of the NO _x catalyst by the control means.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, a lean-burn internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. The lean-burn internal combustion engine according to the present embodiment is configured as shown in FIG.
An internal combustion engine which performs each of the expansion and exhaust strokes in one operation cycle, that is, a four-stroke engine, which is a spark ignition type and a direct injection type internal combustion engine (direct injection engine) which directly injects fuel into a combustion chamber ).

An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so that they can communicate with each other. The communication between the intake passage 2 and the combustion chamber 1 is controlled by an intake valve 4.
The communication between the exhaust passage 3 and the combustion chamber 1 is controlled by an exhaust valve 5. The intake passage 2 is provided with an air cleaner and a throttle valve (not shown).
The exhaust passage 3 is provided with an exhaust purification device 6 and a muffler (muffler) not shown. In addition, the exhaust gas purification device 6
Will be described later in detail.

The injector (fuel injection valve) 8
In order to inject fuel directly into the combustion chamber 1 in the cylinder, the opening is arranged to face the combustion chamber 1. Naturally, the injectors 8 are provided for each cylinder. For example, if the engine of the present embodiment is an in-line four-cylinder engine, four injectors 8 are provided.

With such a configuration, the air sucked through the air cleaner (not shown) in accordance with the opening of the throttle valve (not shown) is drawn into the combustion chamber 1 by opening the intake valve 4, and is drawn into the combustion chamber 1. The air and the fuel directly injected from the injector 8 are mixed based on a signal from an electronic control unit (ECU) 20 as a control means, and the ignition plug 7 is ignited in the combustion chamber 1 at an appropriate timing. After being burned to generate engine torque, the exhaust gas is discharged from the combustion chamber 1 to the exhaust passage 3, and the exhaust gas purifier 6 removes CO, H in the exhaust gas.
From C, it is purified three harmful components NO _x, are muted in the muffler so as to be discharged to the atmosphere side.

The engine is provided with various sensors.
The detection signal from the sensor is sent to the ECU 20.
It is supposed to be. For example, exhaust gas purification of the exhaust passage 3
NO on the upstream side of the gasifier 6_XSensor 9 (hereinafter, upstream
Side NO_XSensor 9) is provided.
Lean NO to prescribe _XNO at the downstream side of the catalyst 6A_XC
Sensor 10 (hereinafter, downstream NO_XSensor 10)
Have been killed. These upstream NO_XSensor 9 and downstream
Side NO_XInformation detected by the sensor 10 is transmitted to an ECU (described later).
NO provided as a function of 20_XPurification efficiency calculation means 2
1 is sent.

The engine will be further described. In this engine, the intake air flowing into the combustion chamber 1 from the intake passage 2 forms a vertical vortex (reverse tumble flow). Since the flow forms such a vertical vortex, a small amount of fuel is collected only in the vicinity of the ignition plug 7 disposed at the center of the top of the combustion chamber 1 while utilizing the vertical vortex, and is separated from the ignition plug 7. It is possible to achieve an extremely lean air-fuel ratio in the portion where the air-fuel ratio has been obtained, and to achieve a stable stratified combustion (stratified super-lean combustion) by setting only the stoichiometric air-fuel ratio or the rich air-fuel ratio only in the vicinity of the ignition plug 7. The fuel consumption can be suppressed. The optimum fuel injection timing in this case is the latter stage of the compression stroke in which the air flow is weak and fuel is not excessively diffused by the time of ignition.

When a high output is obtained from the engine, the fuel from the injector 8 is homogenized in the entire combustion chamber 1 and the interior of the entire combustion chamber 1 is brought to a mixture of stoichiometric air-fuel ratio and lean air-fuel ratio. The stoichiometric air-fuel ratio can provide a higher output than the lean air-fuel ratio. Of course, the timing at which the fuel is sufficiently atomized and vaporized is also used. By performing the fuel injection, a high output can be obtained efficiently. In such a case, the optimal fuel injection timing is set so as to end the fuel injection during the intake stroke so that atomization and vaporization of the fuel can be promoted using the intake air flow.

For this reason, in the present engine, as a mode of fuel injection, operation (extremely lean) in a very lean state of the fuel (that is, the air-fuel ratio is much larger than the stoichiometric air-fuel ratio) by the stratified combustion by the compression stroke fuel injection. (Combustion operation), a compression lean operation mode, an intake lean operation mode in which the operation is performed in a fuel-lean state (that is, the air-fuel ratio is larger than the stoichiometric air-fuel ratio) although not as much as the compression lean operation mode, and an air-fuel ratio A stoichiometric operation mode (stoichiometric feedback operation mode) in which feedback control is performed based on O ₂ sensor information or the like so as to achieve a stoichiometric air-fuel ratio, and a state in which fuel is rich (that is, the air-fuel ratio is smaller than the stoichiometric air-fuel ratio) And an enriched operation mode (open loop mode) for performing the operation in the above.

The operation of the engine is controlled by selecting one of the various operation modes, and the operation mode is selected based on the engine speed N.
8 and the effective pressure Pe indicating the load state, FIG.
This is performed according to a map as shown in FIG. In other words, as shown in FIG. 8A, when the engine speed Ne is low and the load Pe is small, the compression lean operation mode (pressure-L) is selected, and the engine speed N
As e and load Pe become larger,
An intake lean operation mode (suction-L), a stoichiometric feedback operation mode (S / F), and an open loop mode (O / L) are selected. The selection and setting of the operation mode will be further described later.

Next, the exhaust gas purifying apparatus 6 according to the present embodiment will be described.
Will be described. As shown in FIG. 2, the present exhaust gas purification device 6 includes a lean NO _x catalyst (hereinafter, referred to as a NO _x catalyst) 6.
A and a three-way catalyst 6B. Done That, CO in the exhaust gas under the stoichiometric air-fuel ratio, the three-way catalyst 6B having a can purify ternary function HC and NO _x is provided with further savings operating the engine while the air-fuel ratio to the lean that because of the engine, so that it can fully purify nO _x in the exhaust gas generated during lean operation, nO _x catalyst. 6A upstream of the three-way catalyst 6B no three-way function is provided.

This NO_xThe catalyst 6A is NO_XOn the catalyst
NO in exhaust gas by adsorption _XPurifying type
(Lean storage type NO_XCatalyst, trap type lean N
O_XCatalyst), for example, as shown in FIG.
Na Al_Two O_Three As a base material, and barium Ba
And platinum Pt are carried. Then, like this
NO configured for_XNO in catalyst 6A_XAdsorption and desorption
The separation function will be described.

In an oxygen-excess atmosphere (lean atmosphere), first, as shown in FIG. 3B, O ₂ is adsorbed on the surface of platinum Pt, and NO in the exhaust gas reacts with O ₂ on the surface of platinum Pt. The result is NO ₂ (2NO + O ₂ → 2NO ₂ ). On the other hand, a part of barium (Ba), which is supported in the NO _X catalyst 6A reacts with O _2, there is barium oxide BaO, the barium oxide BaO is Furthermore, C = in the exhaust gas
Reacts with O and the like to form barium carbonate BaCO ₃ .

Under such circumstances, the generated NO_Two of
Partly on platinum Pt further barium oxide BaO and CO
Barium carbonate BaCO produced from_Three Reacts with nitric acid
Barium Ba (NO_Three )_Two Is generated, and NO_XCatalyst 6A
Is adsorbed. When such a reaction is represented by a chemical reaction formula,
The following reaction formula (1) is obtained. BaCO_Three + 2NO + 3 / 2O_Two→ Ba (NO_Three )_Two + CO_Two ... (1) On the other hand, in an atmosphere in which the oxygen concentration is low (rich atmosphere)
Is NO as shown in FIG._Two Production is reduced
Then, the reaction in the opposite direction proceeds, and NO_XNO from catalyst 6A _Two But
Is detached.

That is, barium nitrate Ba (NO ₃ ) ₂ adsorbed on the NO _x catalyst 6A reacts with CO in the exhaust gas on the surface of platinum Pt, and NO ₂ and barium carbonate BaC
O ₃ is generated, and NO ₂ is desorbed from the NO _X catalyst 6A. This can be represented by the following reaction formula (2) when expressed by a chemical reaction formula. Ba (NO ₃ ) ₂ + CO → BaCO ₃ + 2NO + O ₂ (2) However, 2NO + O ₂ → 2NO ₂ (part of NO is discharged as it is.) Thus, the NO _X catalyst 6A , Barium nitrate Ba
(NO ₃ ) ₂ and barium carbonate BaCO ₃ exist in a state of chemical equilibrium, and a reaction in each direction occurs depending on the atmosphere near the NO _X catalyst 6A.

The NO ₂ thus desorbed from the NO _X catalyst 6A is reduced by the unburned HC, H ₂ , and CO in the exhaust gas on the three-way catalyst 6B, and is discharged as N ₂ ( NO + CO → 1 / 2N ₂ + CO ₂ ), (NO + H ₂
→ 1 / 2N ₂ + H ₂ O). Incidentally, since the fuel and lubrication oil contains sulfur components, NO _x catalyst 6A
Adsorbs SO _X in the exhaust gas in an oxygen-rich atmosphere, under a predetermined high temperature atmosphere, the oxygen concentration adsorbed to decrease S
A part of the O _X will be leaving.

That is, the NO _X catalyst 6A
As shown in (a), oxygen excess atmosphere (lean atmosphere)
In, O ₂ is adsorbed on the surface of the platinum Pt, the sulfur components contained in fuel or lubricating oil is discharged as a post-combustion SO _2, O ₂ SO ₂ contained in the flue gas is on the surface of the platinum Pt
To SO ₃ (2SO ₂ + O ₂ → 2SO
₃ ). Next, a part of the generated SO ₃ reacts with barium carbonate BaCO ₃ using platinum Pt as a catalyst to generate barium sulfate BaSO ₄ , and the NO _x catalyst 6A
Is adsorbed.

This can be represented by the following chemical reaction formula (3). BaCO ₃ + SO ₃ → BaSO ₄ + CO ₂ (3) On the other hand, in an atmosphere having a low oxygen concentration (rich atmosphere), as shown in FIG. 4B, barium sulfate adsorbed on the NO _X catalyst 6A Part of BaSO ₄ and CO in exhaust gas
Is made of barium carbonate BaCO by the catalytic action of platinum Pt.
₃ and SO ₂ are generated, SO ₂ is desorbed from the NO _X catalyst 6A. This can be represented by the following chemical reaction formula (4).

The _{BaSO 4 + CO → BaCO 3 +} SO 2 ··· (4) By the way, in such a NO _X catalyst 6A, the adsorption of NO _X, to purify NO _X by an elimination action, if NO _X is adsorbed, It is necessary to desorb appropriately. In the NO _X catalyst 6A, barium carbonate BaCO ₃ and barium sulfate BaSO ₄ exist in a state of chemical equilibrium, and the NO _X catalyst 6A
The reaction in each direction easily proceeds according to the atmosphere in the vicinity of. That is, as the air-fuel ratio of the exhaust gas (exhaust air-fuel ratio) becomes smaller (that is, as the air-fuel ratio becomes richer), barium sulfate BaSO ₄ is more easily decomposed and barium carbonate BaCO ₃
Is easily generated. Conversely, as the air-fuel ratio of the exhaust gas increases (that is, the air-fuel ratio becomes leaner), barium carbonate BaCO ₃ is more easily decomposed and barium sulfate BaSO ₄
Is easily generated.

However, in practice, barium sulfate Ba
SO_Four Is difficult to decompose, so even if the oxygen
(Even if the air-fuel ratio becomes rich) Barium sulfate BaSO
_Four Is left undecomposed. This allows
Barium nitrate Ba (NO
_Three )_Two Is no longer generated and NO_XNO by catalyst 6A
_XBecause the purification capacity of
Poison), NO_XSO adsorbed on catalyst 6A_XAlso appropriately
Need to be separated.

Further, for example, it is contained in fuel or lubricating oil.
When the sulfur component concentration is high,
Before the vehicle reaches a distance (for example, about 100,000 km)
_XThe catalyst 6A is deteriorated and NO_XPurification efficiency has dropped significantly
Even in the case, NO released into the atmosphere_XConcentration is acceptable
It is also necessary not to exceed the capacity. For this reason,
In the lean burn internal combustion engine according to the embodiment, NO_XCatalyst 6A
NO _XNO purification efficiency_XIf the temperature is lowered by adsorption
NO adsorbed on_XTo remove NO_XRevival of purification efficiency
Control (restoration control), NO_XSO on catalyst 6A_X
Is adsorbed and NO_XS adsorbed when purification efficiency decreased
O_XTo remove NO_XSystem for regenerating catalyst 6A
Control (regeneration control), NO_XLarge amount of SO in catalyst 6A_XIs adsorbed
And deteriorate, NO_XGreat if purification efficiency drops significantly
NO discharged into the air_XConcentration should not exceed the allowable value.
Control to narrow the lean burn operation range (lean burn operation range
(Reduction control).

Further, as is also performed control to increase the lean-burn operating range (lean-burn operation region enlarging control) when such revival control or regeneration control is restored the purification efficiency conducted with NO _X catalyst 6A Has become. Note that the lean burn operation region expansion control is a control for maintaining the lean burn operation region when the lean burn operation region expansion control has already been performed.

Since the lean burn operation region reduction control and the lean burn operation region enlargement control change the lean burn operation region, they are also referred to as lean burn operation region change control. Therefore, the ECU20 lean burn internal combustion engine according to the present embodiment, as shown in the functional block diagram of FIG. 1, the NO _X purification efficiency calculating unit 21, NO and _X purification efficiency determination unit 22, the operation mode setting means 23 , An operation mode selection means 24 and a fuel injection control means 25 are provided.

Here, the NO _X purification efficiency calculating means 21
Based on the detection information from upstream NO _X sensor 9 and the downstream NO _X sensor 10, and calculates the purification efficiency of the NO _X by the NO _X catalyst 6A. That, NO _X purification efficiency calculating means 21, the upstream-side NO _X sensor 9 by the detection value A ₁ and the downstream-side NO _X from the detected value A ₂ Metropolitan by sensor 10 by the NO _X catalyst 6A NO _X purification efficiency (= A ₂ /
A ₁ ) is calculated.

This NO_XN by the purification efficiency calculating means 21
O_XThe calculation of the purification efficiency is performed when the operation mode is the intake lean operation mode.
Switch to lean operation mode such as load mode or compression lean operation mode.
After a certain period of time
Has become. Therefore, NO _XPurification efficiency calculation means 21
Means that the count value of the timer 29 is read.
When the count reaches the specified value, the
Swelling.

The NO _X purification efficiency determining means 22 controls any one of the above-described reinstatement control, regeneration control, lean burn operation range change control (lean burn operation region reduction control, lean burn operation region enlargement control). It is determined whether or not it is necessary to carry out. For this reason, the NO _X purification efficiency determining means 22 includes a recovery controlling determining means 22A, a regeneration controlling determining means 22B, and a lean burn operation region change controlling determining means 22C (hereinafter, referred to as a region change determining means). Provided.

First, the recovery control determining means 22A determines whether or not it is necessary to perform the recovery control by performing the operation in the lean operation mode such as the intake lean operation mode or the compression lean operation mode for a predetermined time (for example, , About 60 seconds). For this reason, the count value of the timer 29 is read into the recovery control determination means 22A.

When it is determined by the recovery control determining means 22A that the operation in the lean operation mode has been performed for a predetermined time (for example, about 60 seconds), it is determined that the recovery control needs to be performed. The output is provided to an additional fuel injection control means 27 provided in a fuel injection control means 25 described later. The reproduction control determination means 22B includes:
NO to determine whether or not it is necessary to perform regeneration control
_This is for determining whether or not the NO _X purification efficiency η after the restoration control calculated by the _X purification efficiency calculation means 21 has become smaller than the regeneration control determination value a.

When the regeneration control determining means 22B determines that the NO _X purification efficiency η after the recovery control has become smaller than the regeneration control determination value a, it is determined that the regeneration control needs to be performed. Then, the output is outputted to an additional fuel injection control means 27 provided in the fuel injection control means 25 described later. The regeneration control determining means 22B and the additional fuel injection control means 27 constitute a regeneration means.

As shown in FIG. 6, the determination value a for regeneration control is such that the concentration of the sulfur component contained in the fuel is 100 p.
pm, when the mileage reaches about 10,000 km
It is set as a value corresponding to the NO _X purification efficiency of the O _X catalyst 6A. Area change determination unit 22C is lean-burn operation range changing control (lean burn operation area reduction control, the lean burn operation area enlarging control) to determine whether or not it is necessary to perform, NO _X purification efficiency calculating means 21 It is determined whether or not the NO _X purification efficiency η ′ _i after the current regeneration control calculated by the above is smaller than the NO _X purification efficiency η ′ _i−1 after the previous regeneration control.

When the region change determining means 22C determines that the NO _X purification efficiency η ′ _i after the current regeneration control is smaller than the NO _X purification efficiency η ′ _i-1 after the previous regeneration control. is, nO _X catalyst 6A is deteriorated adsorbed a large amount of sO _X, since the nO _X purification efficiency is considered to be reduced, so that the concentration of the nO _X discharged into the atmosphere does not exceed the allowable value It is determined that it is necessary to perform lean burn operation region reduction control in order to effectively use the three-way catalyst 6B,
It outputs to the operation mode selection means 24 mentioned later.

Incidentally, the determining whether NO _X purification efficiency η after this reproduction control _'i is NO _X purification efficiency η after the previous regeneration control' smaller than _i-1, NO _X catalyst 6A
In other words, the area change determination unit 22C can be referred to as a deterioration determination unit. On the other hand, when the region change determination means 22C determines that the NO _X purification efficiency η ′ _i after the current regeneration control is not smaller (larger) than the NO _X purification efficiency η ′ _i-1 after the previous regeneration control. Determines that it is necessary to perform the control for enlarging the lean burn operation region on the assumption that the NO _X purification efficiency has recovered, and outputs the result to the operation mode selection means 24 described later.

Incidentally, the fuel injection control means 24 comprises a normal fuel injection control means 25 and an additional fuel injection control means 26. Among these, the additional fuel injection control means 25 performs additional fuel injection as the recovery control when the recovery control determination means 22A determines that the recovery control is necessary, and the regeneration control determination means 22B The fuel injection valve 8 is controlled so that additional fuel injection is performed as regeneration control when it is determined that control is necessary.
This controls the operation of.

The additional fuel injection control means 25 sets an injection start timing T _INJ for additional fuel injection based on information detected from various sensors 28 (for example, information on engine speed and information on engine load). The injection time of the additional fuel in each cycle is set. First,
The setting of the injection start timing T _INJ and the injection time of the additional fuel injection for performing the additional fuel injection as the recovery control will be described.

The injection start timing T _INJ and the injection time for performing the additional fuel injection as the revival control are shown in FIG.
As shown in the vicinity of the NO _X catalyst 6A is set to be reduced rich atmosphere having an oxygen concentration. For example, to achieve a rich atmosphere, the air-fuel ratio is set to about 13 and the operation is performed for about 2 seconds. In this case, the timer 29 starts counting when the additional fuel injection as the resurrection control is started.
, The count value of the timer 29 may be read.

It should be noted, additional fuel injection as the resurrection control, because it is intended to the vicinity of the NO _X catalyst 6A and rich atmosphere, also referred to as rich spike. Perform such control, the operation in the lean operation mode such as the intake lean operation mode and the compressed lean operation mode is performed, NO _X near the catalyst 6A is an oxygen rich atmosphere (lean atmosphere), and the above-described reaction since the reaction shown by the formula (1) progresses, these lean operation mode is a predetermined time (e.g., about 60 seconds) is performed over a large amount of the NO _X in the NO _X catalyst 6A is adsorbed, NO _X catalyst 6A NO _{X by}
This is because the purification efficiency will gradually decrease.

[0048] Thus, even if reduced NO _X purification efficiency by NO _X adsorption amount of the NO _X catalyst 6A is increased, it is performed the additional fuel injection as resurrected controlled by the additional fuel injection control unit 27, described above since, as shown in the reaction formula (2) the reaction is accelerated, NO from NO _X catalyst 6A
_X can be desorbed, and as shown in FIG.
It is possible to improve the NO _X purification efficiency by the NO _X catalyst 6A. FIG. 5B is a partially enlarged view of a portion X in FIG.

Next, the setting of the injection start timing T _INJ and the injection time of the additional fuel injection for performing the additional fuel injection as the regeneration control will be described. The regeneration control injection start timing for performing the additional fuel injection as T _INJ and injection time, the vicinity of the NO _X catalyst 6A and rich atmosphere having an oxygen concentration decreases (e.g., A / F = about 12), and, given Temperature (for example, about 600 ° C.) or higher,
This is performed for a predetermined time (for example, about 3 minutes).

That is, the additional fuel injection as regeneration control by the additional fuel injection control means 27 is performed during the period from the late stage of the expansion stroke of each cylinder to the end of the exhaust stroke, and during the period in which the additional fuel can self-ignite and burn. Injection start timing T _INJ is set so that Thus, the injection start timing T _INJ
To set the fuel injected by the additional fuel injection, reliably combusted thereby (hereinafter, also referred to as afterburning) is, in order to thereby desorb the SO _X attached to the NO _X catalyst 6A, NO _X catalyst 6A Is a rich atmosphere with reduced oxygen concentration and a high temperature atmosphere (for example, about 600 ° C.).
This is because

More specifically, the additional fuel injection control means 25
Is to correct the basic fuel injection start timing Tb _INJ, which is the basis for the additional fuel injection after the latter stage of the expansion stroke, by the coolant temperature θ _W , the EGR amount, and the ignition timing T _IG in the main combustion, thereby making the injection start timing T b Set _INJ . Further, the additional fuel injection control means 104 sets the basic drive time t _B which is the basis for additional fuel injection after the expansion stroke,
The injector drive time t _PLUS is set by correcting the injection start timing T _INJ and the catalyst temperature θ _CC .

Such control is performed for a predetermined time.
NO (every 60 seconds, for example)_XControl of the catalyst 6A
Even if you do a rich spike, NO_XCatalyst 6
When the vicinity of A becomes an oxygen excess atmosphere (lean atmosphere),
NO_XIn the catalyst 6A, the reaction represented by the above reaction formula (3) is performed.
NO_XSO 6 is gradually added to the catalyst 6A._XAlso adsorb
And NO_XBarium sulfate BaSO on catalyst 6A_Four As sucking
Wear it, NO_XEven if the oxygen concentration near the catalyst 6A decreases
(Ie, even when the exhaust air-fuel ratio becomes rich)
Mu BaSO_Four NO without decomposition_XAdsorbed on catalyst 6A
SO_XUsed for adsorption of
Barium nitrate Ba (NO_Three ) _Two Is generated
Will not be_XNO by catalyst 6A
_XThis is because the purifying ability of the oil is reduced.

When additional fuel injection control as regeneration control is started to measure a predetermined time, a timer 29 is started.
Starts counting, and the additional fuel injection control means 25 reads the count value of the timer 29. Thus, even if reduced NO _X purification efficiency by SO _X amount of adsorption of the NO _X catalyst 6A is increased by additional fuel injection control as playback control, as shown in the above described reaction formulas (4) Reaction There is promoted, because the sO _X from the NO _X catalyst 6A can be eliminated, as shown in FIG. 6 by the solid line a, it is possible to improve the NO _X purification efficiency by the NO _X catalyst 6A.

In FIG. 6, the solid line A indicates NO after the restoration control.
_X indicates the purification efficiency, and the broken line B indicates NO _X after the regeneration control.
An example of the purification efficiency is shown. If you added fuel injection control as playback control this way, NO _X catalyst 6
Although the adsorption capacity of A generally tends to decrease as the traveling distance increases, the partial N
Looking at the regeneration state of the adsorption capacity of the O _X catalyst 6A, the current NO _X purification efficiency is not always smaller than the previous NO _X purification efficiency.

That is, as shown in FIG._X
Purification efficiency η '_i-1Is the previous NO_XPurification efficiency η '_i-2About
In some cases, it may not be played back to_XPurification efficiency
η ' _iIs the previous NO_XPurification efficiency η '_i-1Play above
In some cases. Note that the previous NO_XPurification efficiency η '_i-1
If the playback exceeds the_XCatalyst 6A recovers
It was done.

[0056] Therefore, in the present embodiment, NO _X catalyst 6
The operation mode is selected according to the degree of regeneration of the NO _X purification efficiency of A. Then, ECU2 of this engine
0 is provided with an operation mode selection means 24 in addition to the operation mode setting means 23. First, the operation mode setting means 23 will be described. The operation mode setting means 23 determines the injection mode based on the detection information (for example, engine speed information and engine load information) from various sensors 28. Intake air amount per stroke) P
e in accordance with the engine load Pe and the engine speed (rotation speed) Ne, based on the map selected by the operation mode selection means 24, based on the compression lean operation mode, the intake lean operation mode, and the stoichiometric feedback. One of the operation mode and the open loop mode is selectively set.

For example, in the region where the engine speed Ne is low and the engine load Pe is low, the compression lean operation mode is set. If either the engine speed Ne or the engine load Pe is not low, the intake lean operation mode or the stoichiometric feedback operation mode is set. And so on. When both the engine speed Ne and the engine load Pe are high,
Open loop mode is set.

Next, the operation mode selection means 24 which is a substantial control means for the lean burn operation area change control in the present embodiment will be described. The operation mode selection means 24 is provided when the region change determination means 22C determines that the NO _X purification efficiency η ′ _i after the regeneration control is smaller than the NO _X purification efficiency η ′ _i-1 after the previous regeneration control. , The region (lean combustion operation region) of the compression lean operation mode (pressure-L) and the intake lean operation mode (intake-L) becomes narrow, and the stoichiometric feedback operation mode (S / F) and the open loop mode (O / L) 8) is selected such that the area shown in FIG. 8B) is set to be large.

On the other hand, the operation mode selection means 24 determines that the NO _X purification efficiency η ′ _i after the current regeneration control is not smaller (larger) than the NO _X purification efficiency η ′ _i-1 after the previous regeneration control.
And when it is determined as NO _X catalyst 6A it has been restored by the reproduction control, in order to suppress deterioration of fuel efficiency, but to select a map as shown in FIG. 8 (a) is selected during normal operation is there.

In FIG. 8B, the compression lean operation mode (pressure-L) and the intake lean operation mode (intake-L) (the lean burn operation area) are narrowed, and the stoichiometric feedback operation mode (S / F) and the open-loop mode (O / L) are widened as an example. The compression-lean operation mode (pressure-L) and the intake-lean operation mode (intake-L) (lean-burn operation area) In this example, only the stoichiometric feedback operation mode (S / F) and the open loop mode (O / L) are shown.

As described above, the area change determination means 22C uses
NO after the current regeneration control_XPurification efficiency η '_iIs the previous
NO after regeneration control_XPurification efficiency η '_i-1Smaller than
8 is set by the operation mode selection means 24 in FIG.
A map as shown in (b) is selected and the engine speed
Based on Ne and the engine load Ne, the stoichiometric feedback
Operation mode (S / F) or open loop mode
By increasing the frequency at which (O / L) is set (this
Means narrowing the lean burn operation area),
NO under stoichiometric air-fuel ratio_XThree-way catalyst 6 having the function of purifying methane
B is enough NO _XTo increase the operating area in which
I have to.

The area change determination means 22C
When it is determined that the NO _X purification efficiency η ′ _i after the current regeneration control is not smaller than the NO _X purification efficiency η ′ _i−1 after the previous regeneration control, the operation mode selection means 24 determines whether the operation mode selection unit 24 is in the state shown in FIG. The map of a) is selected so that deterioration of fuel efficiency can be suppressed. The fuel injection control by the normal fuel injection control means 26 will be described. The normal fuel injection control means 26 includes various sensors 2 such as an engine speed sensor and an accelerator position sensor.
8. It has a function of setting the fuel injection amount in normal fuel injection based on information from the operation mode setting means 23.

That is, the fuel injection amount is determined by the fuel injection time (a
This is the driving time of the injector.
Injector drive pulse width) t_AUSet as
But stoichiometric feedback operation mode, intake lean
In both the operation mode and the compression lean operation mode,
Related load (intake air volume per stroke) Q / Ne
Based on the target air-fuel ratio (A / F, hereinafter referred to as AF)
And the basic drive time t _pIs calculated, the cooling water temperature sensor,
Detection by various sensors 28 such as intake air temperature sensor and atmospheric pressure sensor
Depending on the engine cooling water temperature, intake air temperature, atmospheric pressure, etc.
The set fuel correction coefficient f, the injector dead time (de
Time) t_DConsidering the fuel injection time t_AU But
Is set.

The lean-burn internal combustion engine according to the first embodiment of the present invention is configured as described above.
As shown in the flow chart of FIG. 7, the recovery control, the regeneration control, and the lean burn operation region change control (the lean burn operation region reduction control and the lean burn operation region enlargement control) are performed.
First, in step S10, a restoration control mode (rich spike mode) is executed. In this rich spike mode, although not shown in detail in FIG. 10, the following processing is performed.

[0065] That is, in the NO _X catalyst 6A, the operation in the lean operation mode such as compressed lean operation mode and the intake lean operation mode is performed, since the gradually NO _X adsorbed amount increases, NO _X catalyst such NO _X adsorbed on 6A
It is determined whether or not it is necessary to perform a recovery control to recover the NO _X purification efficiency of the NO _X catalyst 6A by desorbing the NO.

It is determined whether or not the recovery control needs to be performed by the recovery control determining means 22A for a predetermined time (for example, about 60 seconds) in the operation in the lean operation mode such as the intake lean operation mode or the compression lean operation mode. Is determined based on whether or not has elapsed. As a result of this determination, if it is determined that the resurrection control is necessary, the additional fuel injection control means 27
As a result, additional fuel injection (rich spike) is performed as recovery control.

As a result, the vicinity of the NO _X catalyst 6A is made rich and the NO _X adsorbed on the NO _X catalyst 6A is desorbed, so that the NO _X purification efficiency of the NO _X catalyst 6A increases. However, even if the resurrection control is performed every predetermined time (for example, about 60 seconds), N
SO _X is also adsorbed on the O _X catalyst 6A, and once adsorbed SO _X
Can not be removed by the above-mentioned resurrection control,
The SO _X adsorption amount gradually increases. For example, when the traveling distance reaches about 10,000 km, the NO _X
X purification efficiency will be reduced.

For this reason, in step S20, the NO _X catalyst 6A after the recovery control is performed by the NO _X purification efficiency calculating means 21.
After calculating the NO _X purification efficiency η by the
Then, the regeneration control determination means 22B determines whether the NO _X purification efficiency η after the restoration control is smaller than the regeneration control determination value a. As a result of this determination, the NO _X
When it is determined that the purification efficiency η is not smaller than the regeneration control determination value a, the process returns to step S10 because the regeneration control is not yet necessary, and the NO _X purification efficiency η after the recovery control is smaller than the regeneration control determination value a. Until step S10 also becomes smaller.
Steps S30 to S30 are repeated.

On the other hand, if it is determined that the NO _X purification efficiency η after the recovery control is smaller than the regeneration control determination value a, N
Since NO _X purification efficiency is degraded due to adsorption of SO _{X on the} O _X catalyst 6A, and it is considered that regeneration control is necessary, the process proceeds to step S40, and the regeneration processing mode is executed. In this regeneration processing mode, the additional fuel injection control means 27 performs additional fuel injection as regeneration control.

[0070] Accordingly, the vicinity of the NO _X catalyst 6A is a rich atmosphere, and a predetermined temperature (e.g., about 600
° C.) is the more, since the SO _X adsorbed in the NO _X catalyst 6A is desorbed, NO _X purification efficiency by the NO _X catalyst 6A rises. However, even if carried out in this way for example Mileage 10,000 km to the reproduction control for each, it is not possible to NO _X catalyst 6A to completely desorb the adsorbed SO _X, SO _X adsorption of the NO _X catalyst 6A the amount is gradually increased to gradually, for example, NO _X purification efficiency of the NO _X catalyst 6A is that the travel distance reaches 100,000 km will be significantly reduced.

Therefore, in step S50, NO
_{After the X} purification efficiency calculating means 21 calculates the NO _X purification efficiency η 'by the NO _X catalyst 6A after the regeneration control, in step S30, the region change determination means 22C causes the NO _X purification efficiency η' after the current regeneration control. _It is determined whether or not _i is smaller than the NO _X catalyst efficiency η ′ _i−1 after the previous regeneration control.

As a result of this determination, NO after the current regeneration control
If it is determined that the _X purification efficiency η ′ _i is not smaller than the NO _X catalyst efficiency η ′ _i−1 after the previous regeneration control, N
O _X catalyst 6A is either not degraded, or, since has been once deteriorated considered to have recovered, enlarging the control of the lean burn region (maintenance control) is performed in step S80. That is, a map as shown in FIG. 8A is selected by the operation mode selection means 24 as the lean burn operation area expansion control, and the operation mode setting means 2 is selected based on this map.
3 sets the operation mode. Thereby, NO
_{Even though the X} catalyst 6A has not deteriorated or has been deteriorated but has been recovered, the reduction control of the lean burn operation region is performed, so that it is possible to suppress deterioration of fuel efficiency. Become.

On the other hand, when it is determined that the NO _X purification efficiency η ′ _i after the current regeneration control is smaller than the NO _X catalyst efficiency η ′ _i−1 after the previous regeneration control, the NO _X catalyst 6A is deteriorated. since NO _X purification efficiency is considered to be reduced by,
Proceeding to step S70, reduction control of the lean burn operation region is performed. That is, as the lean burn operation region reduction control, the operation mode selection means 24 uses the compression lean operation mode (pressure-L) and the intake lean operation mode (intake-
FIG. 8B is set so that the region (L) (lean combustion operation region) becomes narrow and the regions of the stoichiometric feedback operation mode (S / F) and the open loop mode (O / L) become wide. Such a map is selected, and the operation mode is set by the operation mode setting means 23 based on this map.

Thus, the stoichiometric feedback operation mode (S / F) or the open loop mode (O /
By increasing the frequency of L) is set, so that increase the operating space to purify sufficient NO _X even three-way catalyst 6B that functions to purify NO _X under the stoichiometric air-fuel ratio. Therefore, according to the lean-burn internal combustion engine according to the present embodiment, also NO _X catalyst 6A is caused to S poisoning can be made to NO _X components in the exhaust gas does not increase, contained in the fuel and lubrication oil there is an advantage that it is possible to employ a NO _X catalyst 6A without considering whether the high or low concentrations of sulfur components are.

Further, for example, even when the concentration of the sulfur component contained in the fuel or the lubricating oil is high, as shown in FIG. 9, the target lifetime (for example, the traveling distance of about 100,000 k
until a m), it is possible to purify reliably NO _X by NO _X catalyst 6A and exhaust gas purification device 6 comprised of a three-way catalyst 6B, the concentration exceeding the allowable value NO _X
Can be reliably prevented from being discharged into the atmosphere.

If the region change determination means 22C determines that the NO _X purification efficiency η ′ _i after the current regeneration control is smaller than the NO _X purification efficiency η ′ _i-1 after the previous regeneration control, a mode selection means 24 is selected map as shown in FIG. 8 (b), to be controlled to the lean burn operation area becomes narrow, the three-way catalyst 6B that functions to purify NO _X under the stoichiometric air-fuel ratio Can be effectively utilized, and there is also an advantage that NO _X in exhaust gas can be sufficiently purified.

The area change determination means 22C
When it is determined that the NO _X purification efficiency η ′ _i after the current regeneration control is not smaller than the NO _X purification efficiency η ′ _i−1 after the previous regeneration control, the operation mode selection means 24 determines whether the operation mode selection unit 24 is in the state shown in FIG. The map of a) is selected, and there is an advantage that deterioration of fuel efficiency can be suppressed. Next, a lean-burn internal combustion engine according to a second embodiment of the present invention will be described with reference to FIG.
1 will be described.

The lean-burn internal combustion engine according to the present embodiment
The above-described first embodiment and the area change determination unit 22C
Is different. That is, in the present lean-burn internal combustion engine, the region change determination means (deterioration determination means) 22C determines the time from the previous regeneration control to the current regeneration control and the time from the current regeneration control to the next generation control. The difference is that the time is compared with time, and it is determined whether or not it is necessary to perform the lean burn operation region change control based on the comparison result.

Specifically, as shown in FIG. 11, when the previous reproduction control is executed at the time indicated by, and the current reproduction control is executed at the time indicated by, the time from the time indicated by the time to the time indicated by the time Time T _i-1 until the time T
_i-1 is stored in the ECU 23. Thereafter, when the next reproduction control is executed at the time indicated by, the time T _i from the time indicated by the time to the time indicated by the is calculated, and this time T _i is calculated.
_{i is} also stored in the ECU 23.

Then, the previously calculated time T _i-1 stored in the ECU 23 is compared with the currently calculated time T _i . As a result of this comparison, if the time T _i calculated this time is shorter than the time T _i-1 calculated last time, the NO _X purification efficiency of the NO _X catalyst 6A has decreased, or Since it is considered that the contained sulfur component is increasing (that is, changing the refueling area, etc.), the area change determination means 2
In 2C, it is determined that the lean burn operation region should be narrowed.

Then, based on the result of this determination, the map of FIG. 8B is selected by the operation mode selection means 24 so that the lean burn operation region becomes narrow. On the other hand, if the currently calculated time T _i is longer than the previously calculated time T _i−1 , the NO _X purification efficiency of the NO _X catalyst 6A has been restored by the regeneration control, or the refueling fuel or the like has Since it is considered that the contained sulfur component has decreased (that is, the refueling area or the like has been changed), the area change determination means 22
In C, it is determined that the lean burn operation region should be expanded (or maintained).

Then, based on the result of this determination, the map of FIG. 8A is selected by the operation mode selection means 24 in order to enlarge (or maintain) the lean burn operation region. Therefore, according to the lean-burn internal combustion engine of this embodiment, in addition to the same effects as those of the above-described first embodiment, the NO _X purification efficiency of the NO _X catalyst 6A changes for each regeneration control, and Even when the component (the amount of the contained sulfur component) changes, there is also an advantage that optimal engine control can be performed without deteriorating fuel consumption and exhaust gas.

In the above-described second embodiment, the region change determination means 22C determines whether it is necessary to perform the lean burn operation region change control based on the time between the previous regeneration control and the current regeneration control. Although the determination is made, the present invention is not limited to this. For example, it is determined whether the lean burn operation region change control needs to be performed based on the distance between the previous regeneration control and the current regeneration control. You may do it.

Note that the area change in each of the above embodiments is performed.
The determining means (deterioration determining means) 22C is provided in each of the above-described embodiments.
It is not limited to the configuration of
Lean-burn operation region reduction system that controls so that the region becomes narrower
Only to judge whether it is necessary to take control
You may comprise. In addition, the area in each of the above embodiments
The change determination unit (deterioration determination unit) 22C performs each of the above-described operations.
It is not limited to the configuration of the form, for example,
The range change determination means 22C performs lean burn operation range reduction control.
Area shrinkage decision to determine whether or not
It is configured as having a constant value b, and NO_XN of catalyst 6A
O _XThe purification efficiency has become smaller than the area reduction determination value b.
The lean burn operation area is reduced
To determine whether it is necessary to perform
Is also good.

Area change determination means (deterioration determination means)
22C, as shown in FIG. 12, a plurality of lean combustion operation region reduction control determination values (region reduction determination values) b ₁ to determine whether or not it is necessary to perform lean combustion operation region reduction control _. b _2, b _3, and the NO _x purification efficiency of the NO _x catalyst 6A is reduced in each region reduction judgment value b _1, b _2,
b ₃ may be allowed to determine whether the smaller stepwise than. Thus, NO of the NO _X catalyst 6A _X
According to the degree of reduction of the purification efficiency, it is possible to control the lean burn operation region so as to gradually narrow.

In this case, as shown in FIGS. 13A to 13D, the operation mode selection means 24 may be configured to include a map in which the lean burn region gradually narrows. By configuring the area change determining means 22C in this way, the sulfur content of the refueled fuel changes and the NO before reaching the target lifetime (for example, the traveling distance of about 100,000 km). _{Even when the X} catalyst 6A has deteriorated and its NO _X purification efficiency has decreased,
Since the concentration of NO _X discharged into the atmosphere can be reliably prevented from exceeding an allowable value, deterioration of exhaust gas characteristics can be suppressed, and durability of the NO _X catalyst 6A can be improved. become.

[0087] In the lean-burn internal combustion engine according to the embodiments described above, the resurrection control, additional fuel injection control means to the vicinity of the NO _X catalyst 6A to rich atmosphere 2
Although to perform the additional fuel injection by 7, a method for the vicinity of the NO _X catalyst 6A as revived control the rich atmosphere is not limited thereto, a method such as switching the operating mode to the rich side Is also good.

[0088] In the lean-burn internal combustion engine according to the embodiments described above added, the regeneration control, and the vicinity of the NO _X catalyst 6A to rich atmosphere, and by the addition in order to raise the exhaust gas temperature fuel injection control means 27 Although the fuel injection is performed and the exhaust gas temperature is raised, the method of raising the exhaust gas temperature is not limited to this, for example, to make the operation rich, or to retard the ignition timing,
Alternatively, a method using another device (for example, an electrically heated catalyst) may be used.

[0089] In the lean-burn internal combustion engine according to each embodiment described above, in order to calculates the NO _X purification efficiency of the NO _X catalyst 6A, provided with a NO _X sensor on the upstream side and the downstream side of the NO _X catalyst 6A But not limited to this, NO
One NO _X sensor on the downstream side of the _X catalyst 6A provided, the N
O _X sensor by detecting the amount of NO _X in exhaust gas discharged from the exhaust purifying device 6, _the amount of NO _X in the exhaust gas supplied to the exhaust gas purification device 6, _the amount of NO _X which is set in advance according to the operating conditions and (memory value to ECU), NO _X catalyst 6A by comparing the detected value and the memory value of the NO _X sensor
May be estimated.

[0090] In the embodiments described above has a configuration having a three-way catalyst 6B downstream of the NO _X catalyst 6A having no three-way function, if the NO _X catalyst 6A has a three-way function In particular, it is not necessary to separately provide the three-way catalyst 6B.
Although not described in the above embodiments, NO _X
Inform the driver deterioration of the catalyst 6A in warning light, if NO _X catalyst 6A is replaced, preferably controlled to return to the original operation map before playing.

Further, in each of the above-described embodiments, the description has been made of the in-cylinder injection type internal combustion engine. However, the present invention is not limited to this.

[0092]

As described above in detail, according to the lean-burn internal combustion engine of the present invention, it is possible to NO _X catalyst is prevented from increasing NO _X components in the exhaust gas even if the S-poisoning,
There is an advantage that can be employed without NO _X catalyst that the concentration of sulfur components contained in fuel or lubricating oil to consider whether higher or lower.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating a main configuration of a control system of a lean burn internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an overall configuration of a lean burn internal combustion engine according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining the principle of NO _X purification of a lean NO _X catalyst in a lean burn internal combustion engine according to the first embodiment of the present invention, wherein (a) shows a configuration of a lean NO _X catalyst; Figure is a diagram showing a (b) is a diagram showing the NO _X adsorbing function of the lean NO _X catalyst, (c) the NO _X desorption function of the lean NO _X catalyst.

FIG. 4 is a schematic diagram for explaining a sulfur component adsorption / desorption function of a lean NO _X catalyst in the lean burn internal combustion engine according to the first embodiment of the present invention, wherein (a) shows a sulfur component adsorption function; FIG. 1B is a diagram showing a sulfur component desorbing function.

FIG. 5 is a diagram for explaining a rich spike as a recovery control in the lean burn internal combustion engine according to the first embodiment of the present invention, wherein (a) shows an exhaust air-fuel ratio;
(B) shows the NO _X purification efficiency by the lean NO _X catalyst.

FIG. 6 is a diagram for explaining regeneration control in the lean burn internal combustion engine according to the first embodiment of the present invention.

FIG. 7 is a diagram showing the NO _X purification efficiency after the lean NO _X catalyst regeneration control in the lean burn internal combustion engine according to the first embodiment of the present invention.

FIG. 8 is a map selected by the operation mode selection means in the lean burn internal combustion engine according to the first embodiment of the present invention, wherein (a) is a map selected during normal operation or when the lean burn operation region is expanded. , (B) are selected after it is determined by the deterioration determining means that lean burn operation region reduction control is necessary.

FIG. 9 is a diagram for explaining the effect of lean burn operation region reduction control in the lean burn internal combustion engine according to the first embodiment of the present invention.

FIG. 10 is a flowchart showing a recovery control, a regeneration control, and a lean burn operation region change control in the lean burn internal combustion engine according to the first embodiment of the present invention.

FIG. 11 is a view showing a determination method by a lean burn operation region change determination means of the lean burn internal combustion engine according to the second embodiment of the present invention.

FIG. 12 is a view showing a determination method by a lean burn operation region change determination means of a lean burn internal combustion engine according to another embodiment of the present invention.

FIG. 13 is a map selected by the operation mode selection means of the lean burn internal combustion engine according to another embodiment of the present invention, wherein (a) is selected during normal operation;
(B) is selected when the value is smaller than the lean burn operation region reduction control determination value b ₁ by the deterioration determination means, and (c) is the lean burn operation region reduction control determination value by the deterioration determination means. are those selected if it becomes less than b _2, are those selected when it becomes smaller than the lean burn operation area reduction control determination value b ₃ by (d) of the deterioration determining means.

[Explanation of symbols]

Reference Signs List 3 exhaust passage 6 exhaust gas purification device 6A lean NO _X catalyst 6B three-way catalyst 20 electronic control unit (ECU) 21 as control means 21 NO _X purification efficiency calculation means 22 NO _X purification efficiency determination means 22A recovery control determination means 22B regeneration control Determination means (regeneration means) 22C area change determination means (deterioration determination means) 23 operation mode setting means 24 operation mode selection means 26 normal fuel injection control means 27 additional fuel injection control means (regeneration means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/04 305 F02D 41/04 305C 41/14 ZAB 41/14 ZAB 310 310D (72) Inventor Kazuo Koga Shiba, Minato-ku, Tokyo 5-33-8 Mitsubishi Motors Corporation (72) Inventor Kazuhiro Ichigo 5-33-8 Shiba Minato-ku, Tokyo Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A provided in an exhaust passage of a lean burn internal combustion engine capable, desorbs NO _x when the air-fuel ratio of exhaust gas oxygen concentration of the adsorbed in the exhaust gas to NO _x at lean decreased N
O _x catalyst and, based on _the NO _x purification efficiency of the the NO _x catalyst is characterized in that a control means for changing the lean burn operation area of the internal combustion engine, a lean-burn internal combustion engine.