JP4019716B2 - Internal combustion engine with exhaust purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to exhaust gas purification of an internal combustion engine, particularly a lean burn gasoline engine, and more particularly to purification of particulate matter generated in a gasoline engine.
[0002]
[Prior art]
Particulate matter in exhaust gas composed of particulates such as soot is usually a problem in diesel engines, and various techniques for removing it have been developed. For example, an example is disclosed in Japanese Patent Publication No. 7-106290.
[0003]
[Problems to be solved by the invention]
By the way, particulate matter occurs not only in diesel engines but also in gasoline engines. In particular, in a direct injection gasoline engine in a cylinder, during stratified lean combustion, that is, when a small amount of fuel is stratified and burned in the combustion chamber, the fuel near the spark plug is excessively concentrated and smoke is likely to occur. Appropriate removal of particulate matter associated with smoke is desired. Since gasoline engines and diesel engines have different fuels and different engine operating conditions, it is necessary for gasoline engines to consider the removal of particulate matter on their own.
[0004]
In particular, if the trapped particulate matter is rapidly oxidized and excessively heated, the exhaust purification device may be damaged, and the subsequent exhaust purification may be adversely affected.
[0005]
In view of the above, it is an object of the present invention to prevent an exhaust gas purifying apparatus that captures particulate matter from being overheated due to rapid oxidation.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in an internal combustion engine in which particulate matter generated as a result of combustion of gasoline in a combustion chamber is oxidized by an exhaust purification device provided in an exhaust passage, the following means are provided. Adopted.
[0007]
Basically, when the exhaust purification device becomes overheated or there is a risk of overheating, the air / fuel ratio control means shifts the air / fuel ratio to the richer side than the current state, and the exhaust purification device. Try to reduce the oxygen supply.
[0008]
Various means are conceivable as means for this purpose.
[0009]
For example, depending on the state of particulate matter in the exhaust purification device provided in the exhaust passage (when the exhaust purification device becomes overheated or there is a risk of such), the air-fuel ratio of the exhaust gas Air-fuel ratio control switching means for switching between stoichiometric feedback control for controlling the fuel amount to the stoichiometric air-fuel ratio and rich feedback control for making the fuel amount richer than the stoichiometric air-fuel ratio. When the exhaust gas purification device becomes overheated or when there is a possibility of such a situation, the oxygen supply can be reduced by switching from the stoichiometric feedback control to the rich feedback control.
[0010]
A feedback control means having an exhaust purification device in the exhaust passage capable of oxidizing and removing particulate matter and feedback-controlling the air-fuel ratio to a predetermined target value based on the output of an oxygen concentration sensor provided in the exhaust passage In the internal combustion engine, the first air-fuel ratio control means for performing the stoichiometric feedback with the target value as the stoichiometric air-fuel ratio, and the second air-fuel ratio control with the rich feedback control that makes the fuel amount excessive with respect to the stoichiometric air-fuel ratio In accordance with the condition of the particulate matter in the exhaust emission control device (if the exhaust emission control device is overheated or may become so) Switch to the second air-fuel ratio control means.
[0011]
In the rich feedback control, the amount of fuel is richer than the theoretical air-fuel ratio, oxygen is consumed, and the amount of oxygen in the exhaust gas decreases. Therefore, the oxidation of particulate matter in the exhaust purification device is suppressed, and overheating can be avoided.
[0012]
In this case, the exhaust gas purifying device includes a filter that carries NOx absorbent (active oxygen release agent) on a filter capable of oxidizing and removing particulate matter, a filter that carries an oxidation catalyst, and the filter itself does not carry a catalyst. NO to NO before the filter₂A catalyst that oxidizes is placed in NO₂And / or a filter that oxidizes particulate matter.
[0013]
Then, when switching to rich feedback control when the temperature of such an exhaust purification device (filter) is equal to or higher than a predetermined temperature, the subsequent oxygen supply amount to the exhaust purification device is reduced, so that excessive temperature rise can be avoided. .
[0014]
Furthermore, a deposition state detection means for detecting the deposition state of the particulate matter is provided, and rich feedback control is performed when the particulate matter has accumulated more than a predetermined value and when the temperature of the exhaust gas purification device is equal to or higher than the predetermined temperature. You may make it switch to. When there is a large amount of particulate matter, there is a greater risk of overheating due to oxidation, so switching to rich feedback control on condition that the temperature has reached the specified temperature is effective in avoiding overheating. It is.
[0015]
Furthermore, it is possible to switch between the homogeneous stoichiometric combustion mode, which is combustion at the stoichiometric air-fuel ratio, and the stratified lean combustion mode, which is thinner than the stoichiometric air-fuel ratio, and exhaust purification that can remove particulate matter by oxidation in the exhaust passage. In a gasoline direct-injection engine equipped with a device, when the exhaust purification device becomes overheated or there is a risk of overheating, the air-fuel ratio is shifted to the rich side to supply oxygen to the exhaust purification device As a method for reducing the air-fuel ratio, the air-fuel ratio switching means may be used when the exhaust purification device that has captured particulate matter becomes overheated or overheated during operation in the stratified lean combustion mode. Switch to homogeneous stoichiometric combustion mode.
[0016]
Further, an internal combustion engine that performs a fuel cut that stops fuel injection from the fuel injection valve when the vehicle decelerates and has an exhaust gas purification device that can oxidize and remove particulate matter in the exhaust passage (the above-mentioned internal combustion engines are In such an internal combustion engine, the fuel cut may be prohibited when the temperature of the exhaust gas purification apparatus that has captured particulate matter becomes equal to or higher than a predetermined temperature during operation in the stratified lean combustion mode.
[0017]
During the fuel cut, the intake valve and the exhaust valve are opened to reduce the pumping loss of the cylinder, so that a large amount of oxygen is supplied. At this time, if the temperature of the exhaust purification device is high and particulate matter exceeding a predetermined amount is accumulated, the particulate matter burns at a stretch, and the exhaust purification device overheats. When such a state is predicted, the inconvenience is avoided by prohibiting the fuel cut.
[0018]
Needless to say, the above-described configurations can be combined as much as possible.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0020]
<Example of lean combustion internal combustion engine>
First, a lean combustion gasoline engine which is an internal combustion engine to which the present invention is applied will be described.
[0021]
FIG. 1 is a schematic longitudinal sectional view showing a first embodiment of a direct injection spark ignition internal combustion engine according to the present invention, and FIG. 2 is a bottom view of the upper part of the cylinder of the first embodiment. In these figures, 1 is an intake port and 2 is an exhaust port. The intake port 1 communicates with the cylinder via the intake valve 3, and the exhaust port 2 communicates with the cylinder via the exhaust valve 4. 5 is a piston. A cavity 8 is formed in the upper part of the cylinder. Two intake ports 1 are opened on the upper wall 8a of the cavity 8, and a spark plug 6 located at the approximate center of the upper part of the cylinder projects. The side wall 8b of the cavity 8 is thus formed so as to simultaneously surround the in-cylinder openings of the two intake ports 1 and the spark plug 6, and in particular, the spark plug 6 is positioned in the vicinity of the side wall 8b. The fuel injection valve 7 is disposed on the side of the side wall 8 b of the cavity 8 facing the spark plug 6.
[0022]
The fuel injection valve 7 has a slit-shaped injection hole, and injects the fuel into a thin fan shape. In particular, the fuel injection valve 7 of the present embodiment has two slit-shaped injection holes. As shown by hatching in FIG. 2, the fuel is injected in the thickness direction of the fuel and the height direction of the side wall 8b of the cavity 8. The jets are jetted in two directions, almost coincident. The fuel injected in two directions from the fuel injection valve 7 is in the fuel injection direction and in the cavity 8 so that each part of the fuel collides with the side wall 8b at an acute angle with respect to the extending direction of the side wall 8b of the cavity 8. The shape of the side wall 8b is set.
[0023]
In addition, the cross-sectional shape of the side wall 8b of the cavity 8 is substantially symmetric with respect to a vertical plane passing through the center axis of the fuel injection valve 7 and the center axis of the spark plug 6, and is injected from the fuel injection valve 7. The two-direction fan-shaped fuel sprays are substantially symmetrical with respect to the vertical plane.
[0024]
The fuel that collides with the side wall 8b of the cavity 8 advances toward the spark plug 6 near the side wall 8b along the side wall 8b by its own inertial force. Thus, a part of the side wall 8b serves as a fuel guiding portion that guides fuel to the vicinity of the spark plug 6. In the present embodiment, the distance from the two fuel collision positions on the side wall 8b to the vicinity of the spark plug 6 is substantially equal due to the above-described configuration. Therefore, the liquid fuel indicated by hatching in FIG. After the collision, the fuel is gradually vaporized by the heat received when traveling through the fuel guiding portion, reaches the position near the spark plug 6 and collides with each other, thereby forming a combustible mixture indicated by a dot at this position. Including the embodiments described below, the fuel guiding section is orthogonal to the height center plane of the fuel spray, so that the liquid fuel traveling on the fuel guiding section flows out of the cavity. Rather, a combustible mixture is formed by all injected fuel.
[0025]
In the present embodiment, since the fuel is injected into the cavity 8 formed in the upper part of the cylinder, it is possible to inject the fuel from the beginning of the compression stroke regardless of the piston position. As a result, a relatively large amount of fuel can be injected. In this case, particularly in the latter stage of fuel injection, the temperature of the fuel induction portion on the side wall 8b of the cavity 8 is lowered due to the fuel vaporization so far, and the fuel induction of fuel is performed. There is a possibility that the heat received from the portion becomes insufficient, and the liquid fuel reaches the vicinity of the spark plug 6. However, since this liquid fuel collides with each other in the vicinity of the spark plug 6 and atomizes, it easily vaporizes, and even if a relatively large amount of fuel is injected, a combustible air-fuel mixture can be formed in the vicinity of the spark plug 6. it can.
[0026]
Even if a squish flow is generated from the exhaust port side above the cylinder at the end of the compression stroke, this squish flow does not act on the combustible air-fuel mixture formed in the vicinity of the spark plug 6. Thus, the combustible air-fuel mixture remains in this position because there is no factor that moves from the vicinity of the spark plug 6, and ignition combustion is possible at any time. As described above, according to the present embodiment, the fuel injection timing and the ignition timing can be freely set, and the combustible air-fuel mixture is ignited even when a relatively large amount of fuel is injected regardless of the engine speed. Therefore, it is possible to achieve good stratified combustion by reliably positioning it in the vicinity of the spark plug. In this way, it is possible to reliably expand the stratified combustion operation region with a low fuel consumption rate to the high rotation and high load side.
[0027]
In addition, when the engine is in a high load where a large amount of fuel is required, the fuel is injected during the intake stroke to perform homogeneous combustion. In the present embodiment, since a part of the fuel guiding portion on the side wall 8b of the cavity 8 is adjacent to the intake port cylinder opening, the fuel injected from the fuel injection valve 7 is in flight during the homogeneous combustion. Across the intake port cylinder opening, the fuel is agitated by the intake flow flowing from the intake port cylinder opening at that time, and the fuel that has reached the fuel induction part is also sufficiently agitated by the intake flow while traveling through the fuel induction part The Thereby, according to this embodiment, at the time of ignition, a sufficiently homogenous homogeneous mixture is formed in the cylinder, and good homogeneous combustion can also be realized.
[0028]
In this embodiment, the fuel injection direction of the fuel injection valve 7 is set to two directions, and each fuel is caused to collide in the vicinity of the spark plug 6 along the fuel guiding portion of the side wall 8b of the cavity 8, The present invention is not limited, and the fuel injection direction can be one direction. In this case, at the time of stratified combustion, the injected fuel forms an elongated combustible mixture that moves along the side wall 8 b of the cavity 8, and this elongated combustible mixture is separated from the ignition gap of the spark plug 6. Since contact is made for a relatively long time and ignition combustion is possible during this time, fuel injection timing and ignition timing can be set relatively freely. As a result, even if a relatively large amount of fuel is injected regardless of the engine speed, the combustible air-fuel mixture can be reliably positioned near the spark plug at the time of ignition, and good stratified combustion can be realized. In this case, when a relatively large amount of fuel is injected during stratified combustion, an annular combustible mixture is formed along the side wall 8b of the cavity 8, and this combustible mixture always contacts the spark plug 6. Therefore, ignition combustion is possible at any time, and good stratified combustion can also be realized at this time.
[0029]
Of course, even in one-way fuel injection, a part of the fuel guiding portion on the side wall 8b of the cavity 8 is adjacent to the intake port cylinder opening, and as described above, good homogeneous combustion can also be realized. Further, the side wall 8b of the cavity 8 in this embodiment is configured to surround the in-cylinder opening of the two intake ports and the spark plug 6. However, of course, in the case of a single intake valve type or a double intake valve type, The side wall 8b of the cavity 8 may surround only one intake port and the spark plug.
[0030]
With the configuration described above, the combustion state can be controlled to stratified combustion, weakly stratified combustion, homogeneous lean combustion, homogeneous combustion, or the like. The combustion state can be selected based on the fuel injection control or the like based on the map shown in FIG. 3 in relation to the torque and the engine speed.
[0031]
For example, the air-fuel ratio during stratified combustion is 25-50, the air-fuel ratio during weak stratified combustion is 20-30, the air-fuel ratio during homogeneous lean combustion is 15-23, and the air-fuel ratio during homogeneous combustion is 12-15. It is executed according to the map set in.
[0032]
During low-load operation, a combustible air-fuel mixture is formed only in the vicinity of the spark plug, and stratified combustion with an extremely lean air-fuel ratio (for example, 50: 1) is realized in the entire cylinder. In order to realize stratified combustion, fuel is injected directly from the fuel injection valve into the cylinder in the compression stroke, and an air-fuel mixture is formed around the spark plug.
[0033]
On the other hand, during high-load operation such as when accelerating or climbing, fuel is injected during the intake stroke to generate a homogeneous mixture and achieve high output. Between the stratified combustion and the homogeneous combustion, a weak stratified combustion and a homogeneous lean combustion are realized, and the torque connection between the stratified combustion and the homogeneous combustion is made smooth. In weak stratified combustion, fuel is injected in two steps, an intake stroke and a compression stroke, and a weak stratified combustion state with an air-fuel ratio of 20 to 30 is generated. Homogeneous lean injects a smaller amount of fuel in the compression stroke than during homogeneous combustion to bring the air-fuel ratio to 15-23.
[0034]
In such a gasoline direct injection engine, when operating in stratified lean, the exhaust temperature is low and the particulate matter emissions are relatively large, so if stratified lean continues, particulate matter may accumulate. is there. In this example, the particulate matter oxidation process in such an engine can be smoothly performed by the air-fuel ratio control described below.
[0035]
<Exhaust gas purification device>
Next, an exhaust emission control device attached to the internal combustion engine will be described. Here, a port injection type gasoline engine will be described, but the present invention is naturally applicable to the case where the injection type is the above-described in-cylinder injection type.
[0036]
FIG. 4 is an overall schematic view of a gasoline engine with an exhaust purification device. In FIG. 4, 11 is an internal combustion engine body, 12 is an intake passage, and 13 is an air flow meter provided in the intake passage. The air flow meter 13 directly measures the amount of intake air. For example, a movable vane type air flow meter with a built-in potentiometer is used to generate an analog voltage output signal proportional to the amount of intake air. This output signal is input to the multiplexer built-in A / D converter 101 of the control circuit 20. The distributor 14 has, for example, a crank angle sensor 15 that generates a reference position detection pulse signal every 720 ° when converted into a crank angle, and a crank angle detection pulse signal every 30 ° converted into a crank angle. A crank angle sensor 16 is provided for generating. The pulse signals of the crank angle sensors 15 and 16 are supplied to the input / output interface 102 of the control circuit 20, and the output of the crank angle sensor 16 is supplied to the interrupt terminal of the CPU 103.
[0037]
Further, the intake passage 12 is provided with a fuel injection valve 7 for supplying pressurized fuel from the fuel supply system to the intake port for each cylinder. The throttle valve 26 in the intake passage 12 is provided with an idle switch 27 that generates a signal indicating whether or not the throttle valve 26 is fully closed, that is, an LL signal. This idle state output signal LL is supplied to the input / output interface 102 of the control circuit 20.
[0038]
In the present embodiment, the intake passage 12 is provided with a bypass passage 21 that bypasses the throttle valve 26 and an idle speed control valve (ISC valve) 22 that controls the amount of air flowing through the bypass passage 21. . The ISC valve 22 is a flow control valve that is driven by an actuator of an appropriate type such as a stepper motor, and is operated by an output signal from the control circuit 20 to adjust the engine intake air amount during idling to adjust the engine idle speed. Is used to control to the target rotational speed. In the present embodiment, the ISC valve 22 also functions as part of a catalyst temperature raising means for increasing the exhaust gas flow rate to increase the catalyst temperature by increasing the engine idle speed when the catalyst is not activated. .
[0039]
The water jacket 18 of the cylinder block of the engine body 11 is provided with a water temperature sensor 19 for detecting the temperature of the cooling water. The water temperature sensor 19 generates an electrical signal having an analog voltage corresponding to the temperature of the cooling water. This output is also supplied to the A / D converter 101.
[0040]
The exhaust system downstream of the exhaust manifold 31 of the engine body 11 is provided with a catalytic converter 32 that contains a three-way catalyst that simultaneously purifies three harmful components HC, CO, and NOx in the exhaust gas. Further, an exhaust manifold 31 on the upstream side of the catalytic converter 12 has an air-fuel ratio sensor (in this embodiment, an oxygen concentration detection sensor).₂Sensor) 33 is provided.
[0041]
O₂The sensor 33 detects the concentration of oxygen components in the exhaust gas and generates different output voltages depending on whether the air-fuel ratio is leaner or richer than the stoichiometric air-fuel ratio. The output voltage of the O 2 sensor 33 is supplied to the A / D converter 101 of the control circuit 20. The control circuit 20 is configured as a microcomputer, for example, and includes a ROM 104, a RAM 105, a backup RAM 106, a clock generation circuit 107, and the like in addition to the A / D converter 101, the input / output interface 102, and the CPU 103.
[0042]
In the present embodiment, the control circuit 20 performs basic control such as fuel injection control and ignition timing control of the engine 1, as well as air-fuel ratio control means for controlling the engine air-fuel ratio as described later, and the catalyst 32 is in an active state. Catalyst activation state detection means for detecting whether or not there is present, catalyst activation means for controlling the retard of the engine ignition timing and the ISC valve 22 to warm up the catalyst, air-fuel ratio control switching means, accumulation of particulate matter Various function realizing means of the present invention such as a deposition state detecting means for detecting the state are realized by a program.
[0043]
Further, in the control circuit 20, the down counter 108, the flip-flop 109, and the drive circuit 110 are for controlling the fuel injection valve 7. That is, in a routine described later, when the fuel injection amount (injection time) TAU is calculated, the injection time TAU is preset in the down counter 108 and the flip-flop 109 is set. As a result, the drive circuit 110 starts energizing the fuel injection valve 7. On the other hand, when the down counter 108 counts the clock signal (not shown) and the output terminal finally becomes “1” level, the flip-flop 109 is set and the drive circuit 110 is attached to the fuel injection valve 7. Stop the momentum. That is, the fuel injection valve 7 is energized only during the above-described fuel injection time TAU, and an amount of fuel corresponding to the time TAU is supplied to the combustion chamber of the engine body 11.
[0044]
The input / output interface 102 of the control circuit 20 is connected to an ignition circuit 112 and controls the ignition timing of the engine body 11. That is, the control circuit 20 inputs the reference crank angle pulse signal of the crank angle sensor 6 to the input / output interface 102, and then outputs an ignition signal to the ignition circuit 112 every time the crankshaft reaches a predetermined rotation angle. A spark is generated in a plug (not shown). As for the ignition timing of the engine body 11, an optimum value is stored in the ROM 104 of the control circuit 20 as a function of operating conditions such as load (for example, the amount of intake air per engine revolution) and rotation speed, and the optimum ignition timing is operated. Determined according to conditions.
[0045]
The intake air amount data and the cooling water temperature data of the air flow meter 13 are taken in by an A / D conversion routine executed every predetermined time or every predetermined crank angle and stored in a predetermined area of the RAM 105. That is, the intake air amount data and the cooling water temperature data in the RAM 105 are updated every predetermined time. The rotational speed data is calculated by interruption every 30 ° CA (crank angle) of the crank angle sensor 16 and stored in a predetermined area of the RAM 105.
[0046]
<Three-way catalyst: filter>
The three-way catalyst 33 is obtained by thinly attaching a noble metal such as platinum (Pt) + rhodium (Rh) or platinum (Pt) + rhodium (Rh) + palladium (Pd) to the surface of alumina. These three components CO, HC and NOx are simultaneously reduced by the following reaction.
[0047]
(O₂, NOx) + (CO, HC, H₂→ H₂+ H₂O + CO₂
As an exhaust purification device, a particulate filter (PF) is provided upstream of the exhaust gas in addition to the above three-way catalyst.
[0048]
The particulate filter (PF) is of a so-called wall flow type having a honeycomb structure and having a plurality of exhaust flow passages extending in parallel with each other. The particulate filter (PF) is formed of a porous material such as cordierite, for example, and a support layer made of alumina, for example, is formed on the inner wall surface of the pore. An active oxygen release agent that carries oxygen in the presence of excess oxygen in the surroundings and retains oxygen and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases is carried.
[0049]
The exhaust emission control device can use a filter carrying a NOx absorbent (active oxygen release agent) on a filter capable of oxidizing and removing particulate matter. For example, alumina is used as a carrier, and an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, an alkaline earth such as barium Ba and calcium Ca, lanthanum La, and yttrium Y are used on this carrier. At least one selected from rare earths and a noble metal such as platinum Pt are supported. When the ratio of air and fuel (hydrocarbon) supplied into the exhaust passage upstream of the engine intake passage and the NOx catalyst is referred to as the air-fuel ratio of the exhaust gas flowing into the NOx catalyst, this NOx catalyst When the fuel ratio is lean, NOx is absorbed, and when the oxygen concentration in the inflowing exhaust gas decreases, the absorbed NOx is released.
[0050]
Furthermore, a filter carrying an oxidation catalyst can be used as the exhaust purification device. An oxidation catalyst is, for example, a thin precious metal such as palladium (Pd) or palladium + platinum (Pt) that acts as a catalyst on the surface of granular alumina called catalyst pellets. CO and HC in exhaust gas Oxidizing and harmless CO₂And H₂Set to O.
[0051]
Further, as an exhaust purification device, the filter itself does not carry a catalyst, and NO is NO before the filter.₂It is also possible to use a filter in which a catalyst that oxidizes is disposed.
[0052]
As the exhaust purification device, the temperature required for oxidizing the particulate matter becomes high, but it is also possible to use only a filter of a type that does not carry a catalyst.
[0053]
<Fuel injection control>
Hereinafter, the fuel injection control in the embodiment of the present invention configured as described above will be described. This control is executed by the control circuit 20.
[0054]
As a state where the purification performance of the three-way catalyst can be expected, the air-fuel ratio is limited to a narrow range near the stoichiometric air-fuel ratio. Therefore, it is essential to control the amount of fuel to be injected to an amount that causes complete combustion with respect to the amount of oxygen sucked (the air-fuel ratio in this case is the stoichiometric air-fuel ratio).
[0055]
On the other hand, controlling to the stoichiometric air-fuel ratio may cause problems in terms of drivability, engine safety, fuel consumption, and the like. Therefore, various corrections need to be performed. For this reason, fuel injection control is required.
[0056]
The above-described lean combustion control is also performed by fuel injection control.
[0057]
The fuel injection control is realized by the CPU 103 controlling the drive time of the drive circuit 110 of the fuel injection valve 7 (fuel injection time TAU = injection amount).
[0058]
Fuel injection time TAU = injection amount is different at the time of engine start and after warm-up operation. In the following, the fuel injection time and the fuel injection amount are synonymous.
[0059]
★ The fuel injection amount at the start is determined by the following equation, for example.
When there is a starting fuel injection valve in addition to the main fuel injection valve, fuel injection is continuously performed for a predetermined period of time (determined by the water temperature) from the starting fuel injection valve during start-up, and the engine speed is The injection is stopped when the value exceeds a predetermined value.
[0060]
On the other hand, in the main fuel injection valve, the fuel injection time TAU (injection amount) is determined by the following equation.
TAU = TAUSTU × FTHA + TAUV
Here, TAUSTU: basic injection time at start (injection amount): determined by the water temperature of the cooling water, and increases as the water temperature decreases.
[0061]
FTHA: Intake air temperature correction value: Since the air density varies depending on the intake air temperature, the lower the intake air temperature, the smaller the value for correcting it.
[0062]
TAUV: Invalid injection time: The fuel injection valve has a delay in operation from when the drive voltage is applied until the valve is opened, and there is also a delay when the valve is opened. The delay time is longer when the valve is opened. Therefore, even if the fuel injection valve is opened for a time corresponding to the amount that should actually be sucked into the cylinder, the actual valve opening time is shortened (the injection amount is reduced). The time during which fuel is not injected from the fuel injection valve is referred to as an invalid injection time, and the correction amount for correcting the time to match the amount actually injected with the required value is TAUV.
[0063]
★ Fuel injection amount after startup (time)
Next, after starting, the engine is operated with the fuel injection amount determined by the following equation.
TAU = TAUP × FWL × (FAF + FG) × {FASE + FAE + FOTP + FDE (D)} × FFC + TAUV
TAUP: Basic injection amount (injection time): Basic value of the injection amount determined based on the amount of air sucked in one intake stroke (obtained from the sensor detection value)
FWL: Warm-up increase: During warm-up, a rich air-fuel ratio is required due to poor atomization of fuel. Therefore, during warm-up, fuel increase correction is performed to make the air-fuel ratio rich. The correction value corresponding to the cooling water temperature is corrected with a correction coefficient based on the engine speed to obtain a warm-up increase.
[0064]
FAF: Air-fuel ratio feedback correction coefficient: In order to control the air-fuel ratio in a region where the purification rate of the three-way catalyst can be expected (near the theoretical air-fuel ratio), the current air-fuel ratio is detected based on the output value of the oxygen sensor, The air-fuel ratio is feedback controlled so that the air-fuel ratio falls within the above range.
[0065]
FG: Air-fuel ratio learning coefficient: The required injection amount varies even in the same operating state due to individual differences of engines and changes over time. While the air-fuel ratio feedback is in progress, the difference between the actual required value and the calculated value is corrected by the feedback. However, when the feedback is not executed, the difference appears as it is and the air-fuel ratio shifts. Therefore, the correction due to feedback is stored and corrected constantly so as to eliminate the difference in all driving states.
[0066]
FASE: Increase after start: Since the vicinity of the port is dry after start, in order to wet it, the injection amount is increased for a predetermined time after start to prevent engine stall. This value is determined by an initial value based on the cooling water temperature at the time of starting, and thereafter attenuated at every predetermined injection, and ends when FASE = 0.
[0067]
FAE: Acceleration increase: During acceleration, the intake pipe gripping force (particulate matter) increases (negative pressure decreases), so the amount of fuel adhering to the intake valve and its vicinity increases among the injected fuel. Since it takes time for the adhering fuel to enter the combustion chamber, the air-fuel ratio becomes lean unless an extra amount of the adhering fuel is injected during acceleration. The acceleration increase FAE compensates for the increase in the adhered fuel.
[0068]
FOTP: OTP increase: Exhaust temperature becomes high at high load and high rotation, and there is a risk of thermal damage of exhaust system parts, so the air-fuel ratio is made rich and the exhaust temperature is lowered.
[0069]
FDE (D): Decrease increase (decrease): The detected value of the air flow meter undershoots at the time of deceleration and outputs a value smaller than the actual value, so the amount is increased at the time of deceleration to compensate for it. Further, the intake pipe negative pressure increases during deceleration, and the fuel adhering to the intake pipe evaporates and is sucked. Therefore, the fuel injection amount is reduced to compensate for the intake.
[0070]
FFC: Correction coefficient at the time of fuel cut return: There is a case where fuel cut is performed in order to increase fuel efficiency. In order to prevent a shock due to sudden torque at the time of fuel cut return, fuel is reduced by reducing the fuel injection amount. Smooth the torque rise at the time of cutting recovery.
[0071]
TAUV: Invalid injection time
Here, in order to simplify the story, the above equation is simplified and TAU = TAUP × FAF × β + γ.
[0072]
FIG. 5 is a routine for calculating the fuel injection amount using this equation, and is executed every predetermined crank angle, for example, 360 °. In step 101, the intake air amount data Q and the rotational speed data Ne are read from the RAM 105, and the basic injection amount TAUP (TAUP is the injection time for obtaining the theoretical air-fuel ratio) is calculated. For example, TAUP ← α · Q / Ne (α is a constant). In step 202, the final injection amount TAU is calculated by TAU ← TAUP · FAF · β + γ. Next, at step 303, the injection amount TAU is set in the down counter 108 and the flip-flop 109 is set to start fuel injection. In step 104, the routine is terminated. As described above, when the time corresponding to the injection amount TAU elapses, the flip-flop 109 is reset by the output signal of the down counter 108 and the fuel injection ends.
[0073]
As described above, the fuel injection amount is determined, and based on this, fuel injection is performed, and as a result, the air-fuel ratio is determined. That is, air-fuel ratio control is performed.
[0074]
<Air-fuel ratio feedback control>
The air-fuel ratio control in the present invention is performed by the air-fuel ratio feedback control performed in the fuel injection control described above.
[0075]
This control is executed by the first air-fuel ratio control means realized by a program on the CPU of the control circuit 20. This first air-fuel ratio control means is a stoichiometric feedback control means for feedback-controlling the target value toward the theoretical air-fuel ratio. O provided in the exhaust passage₂When the output value of the sensor is rich (excessive with respect to the theoretical air-fuel ratio), the fuel injection amount is decreased, and when it is lean (excessive with respect to the theoretical air-fuel ratio), the fuel injection amount is increased.
[0076]
On the other hand, the second air-fuel ratio control means is realized by a program on the CPU of the control circuit 20, and this second air-fuel ratio control means is rich feedback control means for shifting the air-fuel ratio to the rich side.
[0077]
Fig. 6 shows the O used for feedback control.₂The relationship between the output waveform of a sensor and the value of FAF is shown. In FIG. 6, TDR and TDL are O at the time of transition from lean to rich and at the transition from rich to lean.₂This is a reverse characteristic delay time setting for compensating the response delay of the sensor. O₂As for the response of the sensor, the response from lean to rich is better than the opposite. When shifting from lean to rich, there is an excess of oxygen in a state where the amount of oxygen around the sensor detection unit is small.₂Reach. Conversely, when moving from rich to lean, there is an excess of O₂And HC and CO that have reached there react with O₂Will be reduced. O₂With HC and CO, the molecular size is O₂O is larger, so O₂Is longer than the time until HC and CO reach the detection part of the sensor. Therefore, O₂The time until the sensor can detect the change of the air-fuel ratio differs as described above.
[0078]
During the detection delay time (rich detection delay) when shifting from lean to rich, the actual air-fuel ratio is rich even though the actual air-fuel ratio is rich.₂Since the sensor outputs that it is lean, the feedback control is corrected to the rich side and becomes richer. On the other hand, during the detection delay time (lean detection delay) when shifting from rich to lean, the actual air-fuel ratio is lean even though the actual air-fuel ratio is lean.₂Since the sensor outputs that it is rich, the feedback control is corrected to the lean side and becomes leaner. Overall, the lean detection delay is longer, so the time overcorrected to the lean side is longer and the lean shift occurs. In order to prevent this, TD (delay time) is intentionally set as the delay time of the reverse characteristic of each delay time (TDR> TDL).
[0079]
In FIG. 6, RSL and RSR are fuel injection amounts that are corrected stepwise at the time of transition from rich to lean, and from lean to rich. RSL is referred to as a lean skip constant, and RSR is referred to as a rich skip constant.
[0080]
KIL and KIR indicate inclinations (integral constants) of gradually correcting the fuel injection amount to the lean side when rich (lean).
[0081]
In the apparatus having the above configuration, O₂Based on the output of the sensor 33, the air-fuel ratio correction coefficient FAF can be calculated by the first air-fuel ratio control means, and feedback control can be performed with the air-fuel ratio directed to the theoretical air-fuel ratio.
[0082]
7 and 8 show an air-fuel ratio control routine for calculating the air-fuel ratio correction coefficient FAF. This routine is executed every predetermined time, for example, every 4 ms. In step 201, O₂It is determined whether or not an air-fuel ratio closed loop (feedback) condition by the sensor 33 is satisfied. For example, when the cooling water temperature is a predetermined value (for example, 70 ° C.) or lower, during engine start, during post-start increase, during warm-up increase, during power increase, during fuel injection increase to prevent catalyst overheating, upstream O₂When the output signal of the sensor 33 has never been inverted, the closed loop condition is not satisfied in all cases such as during fuel cut, and the closed loop condition is satisfied in other cases. When the closed loop condition is not satisfied, the routine proceeds to step 225 in FIG. 3, the air-fuel ratio feedback flag XMFB is set to “0”, the routine proceeds to step 226, and the routine is terminated. The air-fuel ratio correction coefficient FAF may be 1.0. On the other hand, if the closed loop condition is satisfied, the process proceeds to step 202.
[0083]
In step 202, O₂The output VOM of the sensor 33 is A / D converted and fetched. In step 203, it is determined whether the air-fuel ratio is rich or lean depending on whether the VOM is equal to or lower than the comparison voltage VR1. The comparison voltage VR1 is usually O₂The voltage at the center of the amplitude of the sensor output is taken, and VR1 = 0.45V in this embodiment. Steps 204 to 209 and steps 210 to 215 are the same as the O determined in step 203.₂ The setting operation of the air / fuel ratio flag F1 based on the value of the sensor 33 output is shown.
[0084]
The air-fuel ratio flag F1 is a flag indicating whether the exhaust air-fuel ratio upstream of the catalyst 32 is rich or lean, and the value of the flag F1 is counted down (during lean air-fuel ratio) or counted up (during rich air-fuel ratio) By operation (step 206, 212) upstream O₂ When the output of the sensor 13 is kept rich or lean for a predetermined delay time (TDL, TDR) or more, it is changed from 1 (rich) to 0 (lean), or from 0 to 1 (from step 207 to 209, from step 213) 215). Here, TDL (steps 207 and 208) is O₂Even if the output of the sensor 33 changes from rich to lean, this is a lean delay time for holding the determination that the sensor is in the rich state, and is defined as a negative value. TDR (steps 213 and 214) is O₂A rich delay time for holding a determination that the sensor 33 is in a lean state even if the output of the sensor 33 changes from lean to rich, and is defined as a positive value.
[0085]
Next, in step 216, it is determined whether or not the sign of the air-fuel ratio flag F1 has been reversed, that is, whether or not the air-fuel ratio after delay processing has been reversed. If the air-fuel ratio has been reversed, it is determined in step 217 whether the reversal is from rich to lean or from lean to rich, based on the value of the air-fuel ratio flag F1. If the inversion is from rich to lean, in step 218, the air-fuel ratio correction coefficient FAF is skipped and increased to FAF ← FAF + RSR, and the air-fuel ratio is corrected to the rich side. Conversely, if the reversal is from lean to rich, in step 219, FAF ← FAF-RSL and FAF are decreased in a skipping manner to correct the air-fuel ratio to the lean side. That is, skip processing is performed.
[0086]
If the sign of the air-fuel ratio flag F1 is not reversed in step 216, integration processing is performed in steps 220, 221, 222. That is, in step 220, it is determined whether or not F1 = "1". If F1 = "0" (lean), FAF ← FAF + KIR is set in step 221, while F1 = "1" (rich). If there is, in step 222, FAF ← FAF-KIL is set. Here, the integration constants KIR and KIL are set sufficiently smaller than the skip constants RSR and RSL, and KIR (KIL) <RSR (RSL). Therefore, step 221 gradually shifts the air-fuel ratio to the rich side in the lean state (F1 = "0"), and step 222 gradually shifts the air-fuel ratio to the lean side in the rich state (F1 = "1").
[0087]
Next, at step 223, the air-fuel ratio correction coefficient FAF calculated at steps 218, 219, 221, 222 is guarded at a minimum value, eg, 0.8, and guarded at a maximum value, eg, 1.2. . Thus, when the air-fuel ratio correction coefficient FAF becomes too large or too small for some reason, the air-fuel ratio of the engine is controlled with that value to prevent over-rich or over-lean. In step 224, the air-fuel ratio feedback flag XMFB is set to “1”, the FAF calculated as described above is stored in the RAM 105, and in step 226, this loop ends.
[0088]
The above procedure is shown in the timing chart of FIG. O₂When the rich / lean discrimination air-fuel ratio signal A / F is obtained by the output VOM of the sensor 33 as shown in FIG. 9A, the delay counter CDLY is counted up in the rich state as shown in FIG. 9B. Countdown in lean state. As a result, as shown in FIG. 9C, a delayed air-fuel ratio signal A / F ′ (corresponding to the flag F1) is formed. For example, even if the air-fuel ratio signal A / F ′ changes from lean to rich at time t1, the delayed air-fuel ratio signal A / F ′ is held lean for the rich delay time TDR and then at time t2. Rich change. Even if the air-fuel ratio signal A / F changes from rich to lean at time t3, the delayed air-fuel ratio signal A / F 'is held rich for the lean delay time (-TDL) and then at time t4. Changes to lean.
[0089]
However, if the air-fuel ratio signal A / F 'is inverted in a period shorter than the rich delay time TDR as at times t5, t6, t7, it takes time for the delay counter CDLY to reach the maximum value TDR, and as a result, at time t8. The air-fuel ratio signal A / F ′ after the delay process is inverted at. That is, the air-fuel ratio signal A / F ′ after the delay process is more stable than the air-fuel ratio signal A / F before the delay process. In this manner, the air-fuel ratio correction coefficient FAF shown in FIG. 9D is obtained based on the stable air-fuel ratio signal A / F ′ after the delay processing.
[0090]
<Control of the present invention>
(Preventing excessive temperature rise of exhaust purification system during stoichiometric combustion)
In the present invention, feedback control to the stoichiometric air-fuel ratio side in which the amount of oxygen in the exhaust gas is reduced in accordance with the oxidation state or deposition state of the particulate matter in the exhaust purification device provided in the exhaust passage (the first control) An air-fuel ratio control means) and an air-fuel ratio at which the amount of oxygen in the exhaust gas decreases, that is, feedback control to the rich side (second air-fuel ratio control means) that makes the fuel amount richer than the stoichiometric air-fuel ratio. Switch by control switching means.
[0091]
In an embodiment, O₂First air-fuel ratio control means that performs stoichiometric feedback that makes the air-fuel ratio the stoichiometric air-fuel ratio based on the output of the sensor, and second air-fuel ratio control means that performs rich feedback control that makes the fuel amount excessive to the stoichiometric air-fuel ratio When the exhaust purification device that has captured the particulate matter is in an overheated state or is likely to be overheated, the second air-fuel ratio control means is controlled in principle. Switch to air-fuel ratio control means. That is, in principle, stoichiometric operation is performed, and the control is switched to the rich side when the exhaust gas purification apparatus that has captured particulate matter becomes overheated or there is a risk of overheating.
[0092]
Specifically, in the air-fuel ratio control, in addition to setting the air-fuel ratio correction coefficient FAF2 so that the air-fuel ratio shifts to the rich side, the skip constants RSR and RSL as the air-fuel ratio control constant, the integral constant KIR , KIL, delay time TDR, TDL, or O₂For example, the comparison voltage (lean / rich determination voltage) VR1 of the output VOM of the sensor 13 can be varied.
[0093]
How the air-fuel ratio varies when the air-fuel ratio control constant is variable will be described. For example, if the rich skip constant RSR is increased, the control air-fuel ratio can be shifted to the rich side, and even if the lean skip constant RSL is decreased, the control air-fuel ratio can be shifted to the rich side, while if the lean skip constant RSL is increased. The control air-fuel ratio can be shifted to the lean side, and the control air-fuel ratio can be shifted to the lean side even if the rich skip constant RSR is reduced.
[0094]
Also, if the rich integral constant KIR is increased, the control air-fuel ratio can be shifted to the rich side, and even if the lean integral constant KIL is decreased, the control air-fuel ratio can be shifted to the rich side, while if the lean integral constant KIL is increased. The control air-fuel ratio can be shifted to the lean side, and the control air-fuel ratio can be shifted to the lean side even if the rich integral constant KIR is reduced. Therefore, the air-fuel ratio can be controlled by correcting the rich integration constant KIR and the lean integration constant KIL.
[0095]
If the rich delay time TDR is set large or the lean delay time (-TDL) is set small, the control air-fuel ratio can be shifted to the rich side. Conversely, the lean delay time (-TDL) is increased or the rich delay time (TDR) is increased. If it is set smaller, the control air-fuel ratio can be shifted to the lean side.
[0096]
Furthermore, if the comparison voltage VR1 is increased, the control air-fuel ratio can be shifted to the rich side, and if the comparison voltage VR1 is decreased, the control air-fuel ratio can be shifted to the lean side.
[0097]
In the present invention, it is necessary to make the center air-fuel ratio lean, but as apparent from the above, to make the center air-fuel ratio richer,
(1) Skip constant RSL to lean side <Skip constant RSR to rich side,
(2) Integration constant KIL for lean side <Integration constant KIR for rich side,
(3) Delay time TDR for rich judgment> Delay time TDL for lean judgment (can be kept rich for a long time),
▲ 4 ▼ O₂The lean rich determination voltage of the sensor is increased from that during stoichiometric feedback (FIG. 10). When the determination voltage is increased from the stoichiometric feedback, the frequency of determining that the lean is increased increases, so the time for rich correction becomes longer and the center air-fuel ratio becomes closer to rich.
Etc. can be executed individually or in combination.
[0098]
In the internal combustion engine, the stoichiometric feedback control is normally executed by the first air-fuel ratio control means. However, when the exhaust gas purification apparatus that has captured the particulate matter becomes in an overheated state, If the air-fuel ratio correction coefficient FAF2 is set so that the air-fuel ratio shifts to the rich side, or the skip constants RSL, RSR, integral constants KIL, KIR, delay times TDR, TDL in the stoichiometric feedback are Change to satisfy the above conditions (1) to (3), or O of (4)₂Rich feedback control is performed by raising the lean / rich determination voltage of the sensor higher than the stoichiometric feedback.
[0099]
Such rich feedback control is executed when the exhaust purification device that has captured particulate matter becomes overheated or when there is a risk of overheating. More specifically, the following is performed. Executed under various conditions.
[0100]
● When overheating of a filter supplemented with particulate matter is detected
Detection of excessive temperature rise Example 1: More than a certain value (for example, the filter temperature is about 800 ° C)
Example 2: Normal filter temperature estimated value + excessive temperature rise determination temperature rise (for example, temperature rise + 50 ° C)
Example 3: The rate of increase in filter temperature per hour is above a certain level.
[0101]
● The amount of deposit on the particulate matter filter is above a certain value and above the particulate matter safe oxidation temperature.
[0102]
The amount of particulate matter deposited on the filter can be determined by the following method.
[0103]
Detection example 1: When the pressure rise exceeds the threshold with the pressure sensor
Detection example 2: When the amount of reduction in the intake air volume exceeds the threshold
Detection example 3: Particulate / matter deposition amount logic predicts particulate matter / matter deposition amount above a certain level (eg, estimated from particulate matter oxidation rate)
(These are examples of deposition state detection means for detecting the deposition state of particulate matter)
FIG. 11 shows this control routine.
[0104]
This routine is repeatedly executed every predetermined time. First, the amount of deposition by the particulate matter filter is estimated, and it is determined whether or not the value is a certain value or more (step 301).
Next, it is determined whether or not the filter temperature is equal to or higher than the safe oxidation temperature of the particulate matter (step 302). If the filter temperature is equal to or higher than the safe oxidation temperature, the exhaust purification device is overheated or overheated. It is determined that there is a possibility that the air-fuel ratio may become, and the routine proceeds to air-fuel ratio rich feedback control (step 303). If it is not above the safe oxidation temperature, the routine ends.
[0105]
(Preventing excessive temperature rise of exhaust purification system during lean combustion)
Next, it is possible to switch between the homogeneous stoichiometric combustion mode, which is combustion at the stoichiometric air-fuel ratio, and the stratified lean combustion mode, which is thinner than the stoichiometric air-fuel ratio, and exhaust that can oxidize and remove particulate matter in the exhaust passage. In a gasoline direct-injection engine equipped with a purification device, when operating in the stratified lean combustion mode, when the exhaust purification device that captures particulate matter becomes overheated or there is a risk of overheating, The air-fuel ratio switching means is switched to the homogeneous stoichiometric combustion mode.
[0106]
This means that stratified leaning is prohibited when an excessively high temperature state is reached or when there is a risk of an excessively high temperature. This is because during stratified lean, the amount of oxygen in the exhaust gas is large, and the oxidation of particulate matter captured by the filter is promoted. Overheating can be avoided by prohibiting stratified leaning.
[0107]
FIG. 12 shows this control routine.
This routine is repeatedly executed every predetermined time. First, the amount of deposition by the particulate matter filter is estimated, and it is determined whether or not the value is a certain value (step 401).
Next, it is determined whether or not the filter temperature is equal to or higher than the safe oxidation temperature of the particulate matter (step 402). If the filter temperature is equal to or higher than the safe oxidation temperature, the stratified lean is prohibited, that is, switched to the homogeneous stoichiometric operation (step 403). If it is not above the safe oxidation temperature, the routine ends.
[0108]
(Relation with fuel cut control)
Similarly, in an internal combustion engine that performs a fuel cut that stops fuel injection from a fuel injection valve when the vehicle decelerates and has an exhaust purification device that can oxidize and remove particulate matter in an exhaust passage, During operation in the lean combustion mode, when the exhaust purification device that has captured particulate matter becomes overheated or there is a risk of overheating, fuel cut is prohibited.
[0109]
Since fuel is not burned during fuel cut control, the amount of oxygen supplied to the exhaust passage and thus to the exhaust gas purification device (filter) increases, and oxidation of particulate matter is promoted, leading to overheating. . Therefore, fuel cut is prohibited when the above conditions are met. Thereby, overheating can be avoided.
[0110]
FIG. 13 shows this control routine.
This routine is repeatedly executed every predetermined time. First, the amount of deposition on the particulate matter filter is estimated, and it is determined whether or not the value is a certain value (step 501).
Next, it is determined whether or not the filter temperature is equal to or higher than the safe oxidation temperature of the particulate matter (step 502), and if it is equal to or higher than the safe oxidation temperature, fuel cut is prohibited (step 503). If it is not above the safe oxidation temperature, the routine ends.
[0111]
【The invention's effect】
According to the present invention, when it is determined that the particulate matter captured by the exhaust purification device is overheated or likely to be oxidized due to abrupt oxidation or the like, the air-fuel ratio is set to the rich side. As a result, the amount of oxygen in the gas is reduced, and as a result, the oxidation rate of particulate matter is reduced, and overheating can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a cylinder showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention.
FIG. 2 is a bottom view of an upper part of a cylinder.
FIG. 3 is a graph showing a combustion method determination map.
FIG. 4 is a schematic diagram showing a hardware configuration of an embodiment of the present invention.
FIG. 5 is a flowchart for explaining calculation of a fuel injection amount.
FIG. 6 O₂It is a conceptual diagram which shows the relationship between the output waveform of a sensor, and the air fuel ratio feedback correction coefficient FAF.
FIG. 7₂It is a part of flowchart of the air fuel ratio control based on a sensor output.
FIG. 8₂It is a part of flowchart of the air fuel ratio control based on a sensor output.
FIG. 9 is a time chart for explaining and explaining the flowcharts of FIGS. 7 and 8;
FIG. 10₂It is a figure which shows rich feedback control by the change of a sensor output voltage.
FIG. 11 is a flowchart showing an example of an excessive temperature rise prevention control routine.
FIG. 12 is a flowchart showing another example of an excessive temperature rise prevention control routine.
FIG. 13 is a flowchart showing still another example of the excessive temperature rise prevention control routine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine body, 20 ... Control circuit, 32 ... Catalyst, (PF) particulate filter, 33 ... O₂Sensor

Claims (7)

In an internal combustion engine that oxidizes particulate matter generated by combustion of gasoline in the combustion chamber with an exhaust purification device provided in the exhaust passage, the particulate matter in the exhaust purification device provided in the exhaust passage Air-fuel ratio control switching means for switching between stoichiometric feedback control for controlling the air-fuel ratio of the exhaust gas to the stoichiometric air-fuel ratio and rich feedback control for making the fuel amount richer than the stoichiometric air-fuel ratio according to the state of An internal combustion engine with an exhaust emission control device. An exhaust gas purification device capable of oxidizing and removing particulate matter generated during combustion of gasoline in the combustion chamber is provided in the exhaust passage, and the air-fuel ratio is determined based on the output of an oxygen concentration sensor provided in the exhaust passage. In an internal combustion engine having feedback control means for performing feedback control to the target value, first air-fuel ratio control means for performing stoichiometric feedback with the target value as the stoichiometric air-fuel ratio; A second air-fuel ratio control means for performing rich feedback control, and the control by the first air-fuel ratio control means is performed in principle, and the control is switched to the second air-fuel ratio control means in accordance with the state of particulate matter in the exhaust purification device. An internal combustion engine with an exhaust emission control device. The exhaust purification device includes a filter in which particulate matter is oxidized and removed, a filter carrying a NOx absorbent (active oxygen release agent), a filter carrying an oxidation catalyst, and the filter itself does not carry a catalyst. The internal combustion engine with an exhaust emission control device according to claim 1 or ₂ , wherein a catalyst that oxidizes NO to NO ₂ is disposed and is a filter that oxidizes particulate matter with NO ₂ . The internal combustion engine with an exhaust purification device according to claim 1 or 2, wherein when the temperature of the exhaust purification device is equal to or higher than a predetermined temperature, switching to rich feedback control is performed. A deposition state detecting means for detecting the deposition state of the particulate matter is provided, and when the particulate matter has accumulated more than a predetermined value and the temperature of the exhaust purification device is equal to or higher than the predetermined temperature, the control is switched to the rich feedback control. An internal combustion engine with an exhaust emission control device according to claim 1 or 2. The internal combustion engine is a gasoline direct injection engine capable of further switching between a homogeneous stoichiometric combustion mode, which is combustion at a stoichiometric air-fuel ratio, and a stratified lean combustion mode, which is thinner than the stoichiometric air-fuel ratio, and operates in the stratified lean combustion mode. In addition, the exhaust gas purifier that captures particulate matter is further provided with air-fuel ratio switching means for switching to a homogeneous stoichiometric combustion mode when there is a risk of overheating or overheating. An internal combustion engine with an exhaust emission control device according to any one of claims 1 to 5 . The fuel purifier that performs fuel cut to stop fuel injection from the fuel injection valve when the vehicle decelerates, and the exhaust purification system that captured particulate matter became overheated during operation in the stratified lean combustion mode The internal combustion engine with an exhaust emission control device according to any one of claims 1 to 6 , wherein fuel cut is prohibited when there is a risk of overheating or overheating.

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