JP2000230418A - Catalyst temperature raising device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the temperature of an exhaust emission purifying catalyst while preventing the physical amount controlled by temperature raising means from exceeding its limit value. SOLUTION: An NOx absorbing agent 12 for absorbing NOx when the air-fuel ratio of the influx exhaust gas is lean, and discharging the absorbed NOx when the oxygen concentration in the influx exhaust gas is lowered is disposed in an exhaust path of an internal combustion engine having an automatic transmission 20. When it is necessary to raise the temperature of the NOx absorbing agent 12 for discharging SOX from the NOx absorbing agent 12, first, the transmission gear ratio is increased. If the exhaust manifold temperature is higher than the tolerable maximum temperature, the exhaust manifold temperature is returned to the value before it exceeds the tolerable maximum temperature. At the same time, the air-fuel ratio of the exhaust gas from a first group of air cylinders 1a is made richer as well as the air-fuel ratio of an exhaust gas from a second group of air cylinders is made leaner, thereby a temperature raising fuel and oxygen to the NOx absorbing agent 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst temperature raising device for an internal combustion engine.

[0002]

2. Description of the Related Art The ratio of the total air amount to the total fuel amount and the total reducing agent amount supplied to an exhaust passage, a combustion chamber, and an intake passage upstream of a certain position in an engine exhaust passage is determined by the position. when referred to as air-fuel ratio of the exhaust flowing through, conventionally, in an internal combustion engine which is adapted allowed to combust a lean air-fuel mixture, air-fuel ratio of the exhaust flowing absorbs NO _X when the lean, the oxygen concentration in the inflowing exhaust gas internal combustion engine having arranged _the NO _X absorbent to release the absorbed and reduced NO _X in the engine exhaust passage is known.

However, since sulfur is contained in the fuel and the lubricating oil of the engine, the sulfur in the exhaust gas, for example, S
O _X contains is absorbed with the SO _X at be for example SO ₄ ^2-form NO _X in _the NO _X absorbent. However, this SO _X is not released from the NO _X absorbent even if the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent is simply made rich, so that the amount of SO _X in the NO _X absorbent gradually increases. Become. However the amount of the NO _X amount of SO _X in _the NO _X absorbent can absorb is _the NO _X absorbent Increasing decreases gradually and finally _the NO _X absorbent can hardly be absorbed NO _X.

[0004] However, SO _X, which is absorbed and the oxygen concentration is lowered in the exhaust gas flowing into the _the NO _X absorbent is released in the form of, for example, SO ₂ when the temperature of the NO _X absorbent is high. On the other hand, the temperature rise of the exhaust gas discharged from the engine to the engine rotational speed is increased when increasing the speed ratio of the automatic transmission can be a result _the NO _X absorbent to increase the temperature. Therefore, S from _the NO _X absorbent by temporarily rich air-fuel ratio of the exhaust gas flowing to the NO _X absorbent growing than when temporarily normal operation the gear ratio of the automatic transmission
An exhaust purification system of an internal combustion engine in which the O _X so as to release is known (see Japanese Patent Laid-Open No. 7-186785).

On the other hand, NO_XIn the exhaust flowing into the absorbent,
If a certain amount of HC and oxygen are contained, these HC
And oxygen is NO_XReaction with the absorbent generates heat, resulting in
NO _XThe absorbent is heated. Therefore, the cylinder of the internal combustion engine
The first cylinder group is divided into a first cylinder group and a second cylinder group.
To make the air-fuel ratio of the air-fuel mixture burned in
_XSupply HC to the absorbent and burn in the second cylinder group
The air-fuel ratio of the air-fuel mixture_XAcid in absorbent
Supply and NO_XLevel of exhaust gas flowing into the absorbent
NO by setting the soaking air-fuel ratio to the stoichiometric air-fuel ratio_XAbsorbent or
SO_XExhaust emission control device for internal combustion engine that emits gas
The position is also known (see JP-A-8-61052).

[0006]

Problems to be Solved by the Invention
In the exhaust purifying apparatus according to 5 JP can be further raising the temperature of the _the NO _X absorbent when further increasing the speed ratio of the automatic transmission. However, gear ratio only when simply increasing engine speed there is a risk that increases beyond the allowable maximum rotational speed, or engine itself or the engine and _the NO _X absorbent to a temperature of the exhaust is significantly higher exhausted from the engine There is a problem in that the temperature of the exhaust system components during this period becomes excessively high and the engine itself or the exhaust system components may be deteriorated.

On the other hand, in the exhaust gas purifying apparatus described in Japanese Patent Application Laid-Open No. 8-61052, the richness of the air-fuel ratio of the air-fuel mixture burned in the first cylinder group is increased, and the mixture burned in the second cylinder group is increased. since the amount of HC and amount of oxygen supplied to _the NO _X absorbent by increasing the degree of leanness of the air-fuel ratio of the air is increased thereby further raising the temperature of the _the NO _X absorbent. However, if the air-fuel ratio of the air-fuel mixture burned in the cylinder becomes excessively rich or lean, there is a problem that a fire may occur.

[0008] In any case, as long as means for raising the temperature of the _the NO _X absorbent it is only one, ensure the exhaust purification catalyst physical quantity is controlled by the temperature increase means while preventing the excess of the limit value Temperature cannot be increased. Therefore, an object of the present invention is to provide a catalyst temperature raising device for an internal combustion engine that can surely raise the temperature of an exhaust purification catalyst while preventing a physical quantity controlled by a temperature raising means from exceeding its limit value. .

[0009]

According to a first aspect of the present invention, there is provided an internal combustion engine having an exhaust gas purifying catalyst disposed in an engine exhaust passage. A plurality is provided, and at least one temperature raising means is selected from these temperature raising means, and when the temperature of the exhaust gas purification catalyst is to be raised, the temperature of the exhaust gas purification catalyst is raised by the selected temperature raising means. That is, in the first invention, a plurality of temperature raising means are provided, and the temperature of the exhaust purification catalyst is raised by the temperature raising means selected from these temperature raising means. Therefore,
The exhaust purification catalyst is reliably heated while physical quantities such as the gear ratio, the air-fuel ratio, the temperature, and the pressure, which are varied by the temperature raising action of the temperature raising means, are prevented from exceeding the limit values.

According to a second invention, in the first invention, the plurality of heating means are divided into a plurality of heating means groups including a first heating means group and a second heating means group. When the temperature of the exhaust gas purifying catalyst is to be raised, the temperature of the exhaust gas purifying catalyst is first raised by at least one temperature raising means selected from the first temperature raising means group, and the temperature is selected from the first temperature raising means group. When the physical quantity fluctuated by the temperature raising action of the selected temperature raising means exceeds the limit value, the temperature of the exhaust purification catalyst is raised by at least one temperature raising means selected from the second temperature raising means group. I have. That is, in the second aspect, even if it is determined that the temperature raising action by one temperature raising means is inappropriate, the temperature raising action by another temperature raising means is started, so that the temperature of the exhaust purification catalyst is reliably raised. .

According to a third aspect of the present invention, in the second aspect, when the physical quantity varied by the temperature raising action of the temperature raising means selected from the first temperature raising means group exceeds the limit value, The temperature of the exhaust purification catalyst is raised by both the temperature raising means selected from the first temperature raising means group and the temperature raising means selected from the second temperature raising means group. That is, in the third aspect, the temperature of the exhaust purification catalyst is raised by both the temperature raising means selected from the first temperature raising means group and the temperature raising means selected from the second temperature raising means group. In addition, the fluctuation of the physical quantity is reduced.

According to a fourth aspect of the present invention, in the second aspect, when the physical quantity varied by the temperature raising action of the temperature raising means selected from the first temperature raising means group exceeds its limit value, The heating action of the heating means selected from the first heating means group is reduced so that the physical quantity does not exceed the limit value. According to a fifth aspect of the present invention, in the second aspect, the internal combustion engine has an automatic transmission, and the first temperature raising means group increases the speed ratio of the automatic transmission so that the exhaust gas purification catalyst is increased. Gear ratio raising means for raising the temperature of the exhaust gas purifying catalyst, and the second temperature raising means group raises the temperature of the exhaust gas purifying catalyst by supplying a gas containing a fuel for temperature raising and a gas containing oxygen to the exhaust gas purifying catalyst. Gear ratio raising means is provided. That is, in the fifth aspect of the invention, the temperature raising operation is first performed by the speed ratio raising device, and then, if necessary, the temperature raising operation by the air-fuel ratio raising device is started.

According to a sixth aspect of the present invention, in the second aspect, the internal combustion engine has an automatic transmission, and the first temperature raising means group includes a gas containing a temperature raising fuel in the exhaust purification catalyst. And an air-fuel ratio raising means for raising the temperature of the exhaust purification catalyst by supplying gas containing oxygen and oxygen. The second temperature raising means group increases the speed ratio of the automatic transmission to reduce the exhaust purification catalyst. Gear ratio raising means for raising the temperature is provided. That is, in the sixth aspect of the invention, the temperature raising operation is first performed by the air-fuel ratio raising unit, and then, if necessary, the temperature raising operation by the speed ratio raising unit is started.

According to a seventh aspect, in the second aspect, in the second aspect, the first temperature raising means group controls the air-fuel ratio of the air-fuel mixture to be burned by the engine so that the exhaust purification catalyst contains the temperature raising fuel. A mixture air-fuel ratio raising means for raising the temperature of the exhaust gas purification catalyst by supplying gas and gas containing oxygen, wherein the second temperature raising means delays the ignition timing more than during normal operation. Ignition temperature raising means for raising the temperature of the exhaust purification catalyst by means of: a secondary fuel temperature raising means for raising the temperature of the exhaust purification catalyst by supplying the heating fuel to the exhaust purification catalyst secondarily;
A secondary oxygen heating means for raising the temperature of the exhaust purification catalyst by secondary supply of oxygen to the exhaust purification catalyst; and an exhaust gas disposed in an exhaust passage upstream of the exhaust purification catalyst and flowing through the exhaust passage. At least one of an electric heater for heating the exhaust gas to be heated and an electric heater for heating the exhaust gas purifying catalyst arranged in the exhaust gas purifying catalyst is provided.

According to an eighth aspect, in the second aspect, the physical quantity is a temperature of the engine body or the exhaust system part, and the limit value is an allowable maximum temperature of the engine body or the exhaust system part. Exhaust system components include, for example, exhaust manifolds or exhaust pipes, connections between exhaust pipes, or catalysts or sensors located in exhaust passages. According to a ninth aspect, in the second aspect, the internal combustion engine has an automatic transmission, and the temperature increasing means increases the speed ratio of the automatic transmission to raise the temperature of the exhaust purification catalyst. Wherein the physical quantity is a speed ratio of the automatic transmission, and the limit value is an allowable maximum speed ratio of the speed ratio.

According to a tenth aspect, in the second aspect, the physical quantity is a representative value representing the degree of combustion stability of the engine, and the limit value is a permissible minimum value of the representative value. Representative values representing the degree of stability of combustion of the engine include, for example, engine speed, engine output fluctuation, and air-fuel ratio of air-fuel mixture burned in the combustion chamber. Also, according to an eleventh aspect based on the second aspect, the physical quantity is a representative value representing vibration of the engine, and the limit value is an allowable maximum value of the representative value. As a representative value representing the vibration of the engine, for example, there is an engine speed or an engine output fluctuation.

According to a twelfth aspect, in the first aspect, at least one heating means is selected from the plurality of heating means based on an engine operating state. According to a thirteenth aspect, in the twelfth aspect, the engine operating state region is divided into a plurality of regions. When necessary, the temperature of the exhaust purification catalyst is raised by the temperature raising means set for the region to which the engine operation state belongs. That is, in the thirteenth aspect, it is possible to select an optimum temperature increasing means for the operating state of the engine.

Further, in the first aspect according to the 14 th invention, the air-fuel ratio of the exhaust the exhaust gas purifying catalyst flows absorbs NO _X when the lean, the oxygen concentration in the exhaust gas decreases the inflowing NO that releases absorbed NO _X
The NOx absorbent is formed from an _X absorbent, and the temperature raising means raises the temperature of the NO _X absorbent to release SO _X from the NO _X absorbent.

[0019]

FIG. 1 shows the case where the present invention is applied to a spark ignition type internal combustion engine. Referring to FIG. 1, the engine body 1 includes, for example, four cylinders. Each cylinder is connected to a surge tank 3 via a corresponding intake branch pipe 2, and the surge tank 3 is connected to an air cleaner 5 via an intake duct 4. A throttle valve 6 is arranged in the intake duct 4. Each cylinder is provided with a fuel injection valve 7 for directly injecting fuel into the combustion chamber. On the other hand, the cylinders of the engine body 1 are divided into a first cylinder group 1a composed of the first cylinder # 1 and the fourth cylinder # 4, and a second cylinder group 1b composed of the second cylinder # 2 and the third cylinder # 3. Has been split. Since the exhaust stroke order of the engine body 1 is # 1- # 3- # 4- # 2, the cylinders of the engine are divided into the first cylinder group, the second cylinder group in which the first cylinder group and the exhaust stroke do not overlap. Will be divided into
The first cylinder group 1a is connected via an exhaust manifold 8a to a casing 10a containing a start-up catalyst 9a,
The cylinder group 1b is connected via an exhaust manifold 8b to a casing 10b containing a start-up catalyst 9b. These casings 10a, 10b are connected to the casing 13 housing the _the NO _X absorbent 12 via a common interconnecting pipe 11, the casing 13 is connected to the exhaust pipe 14.

As shown in FIG. 1, a crankshaft 15 of the engine body 1 is connected to an automatic transmission 20, and an output shaft 21 of the automatic transmission 20 is connected to driving wheels. The automatic transmission 20 includes a torque converter 22 with a lock-up clutch connected in series with each other, a continuously variable transmission mechanism 23,
Forward / reverse switching mechanism (not shown) and final deceleration mechanism 24
And

The continuously variable transmission mechanism 23 includes an input pulley 26 having an input shaft 25 of the continuously variable transmission mechanism 23 and a continuously variable transmission mechanism 2.
An output pulley 28 having three output shafts 27 and a belt 29 stretched between the input pulley 26 and the output pulley 28 are provided. The input pulley 26 includes a fixed pulley half 30 a that rotates integrally with the input shaft 25, and an input shaft 25.
And a movable pulley half 31a movable in the axial direction of the pulley. The belt 29 is disposed in a V-shaped groove formed between the pair of pulley halves 30a, 31a. The output pulley 28 includes a fixed pulley half 30b that rotates integrally with the output shaft 27, and a movable pulley half 31b that can move in the axial direction of the output shaft 27. Belt 2 in a V-shaped groove formed between
9 are arranged. Hydraulic chambers 32a and 32b are formed on the back surfaces of the movable pulley halves 31a and 31b, respectively.
These hydraulic chambers 32a, 32b are connected to an oil pump 35 or a return passage 36 via corresponding hydraulic control valves 34a, 34b, respectively. Movable pulley half 31a, 31
b is moved according to the pressure in the corresponding hydraulic chambers 32a and 32b.

When the pressurized oil flows into the hydraulic chamber 32a and the pressurized oil flows out from the hydraulic chamber 32b, the distance between the pulley halves 30a and 31a of the input pulley 26 becomes small. The pulley diameter increases, and the pulley halves 30b, 3 of the output side pulley 28
Since the distance between 1b becomes large, the diameter of the pulley of the output side pulley 28 becomes small, and thus the gear ratio is reduced. On the other hand, when the pressurized oil is allowed to flow out of the hydraulic chamber 32a and the pressurized oil is allowed to flow into the hydraulic chamber 32b, the distance between the pulley halves 30a and 31a of the input side pulley 26 increases, so that the pulley of the input side pulley 26 The diameter is reduced, and the pulley halves 30b and 31 of the output side pulley 28 are reduced.
Since the distance between b becomes small, the pulley diameter of the output side pulley 28 becomes large, and thus the speed ratio is increased.
Thus, the gear ratio can be continuously changed.

The electronic control unit 40 is composed of a digital computer, and a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, and a constant power supply connected to each other by a bidirectional bus 41. A supplied B-RAM (backup RAM) 45, an input port 46 and an output port 47 are provided. A pressure sensor 48 that generates an output voltage proportional to the absolute pressure in the surge tank 3 is attached to the surge tank 3. For example, a temperature sensor 49 for generating an output voltage proportional to the temperature of the exhaust manifold 8a is attached to the exhaust manifold 8a located immediately downstream of the fourth cylinder # 4. A temperature sensor 50 for generating an output voltage proportional to the temperature of the exhaust gas flowing out of the hour catalyst 9a is attached. This exhaust temperature indicates the temperature TSC of the starting catalyst 9a.
A temperature sensor 51 that generates an output voltage proportional to the temperature of exhaust gas flowing out of the NO _X absorbent 12 is attached to the exhaust pipe 14. The temperature T of the exhaust temperature is _the NO _X absorbent 12
NA is shown. The hydraulic chamber 3 of the continuously variable transmission mechanism 23
A pressure sensor 52 for generating an output voltage proportional to the oil pressure in the hydraulic chamber 32b is provided in an oil passage connected to the inside of the hydraulic chamber 32b.
Is attached. Further, a throttle opening sensor 53 that generates an output voltage proportional to the throttle opening TA is attached to the throttle valve 6. These sensors 48,
The output voltages of 49, 50, 51, 52, and 53 are input to the input port 46 via the corresponding AD converters 54, respectively. The CPU 44 calculates the intake air amount Ga based on the output voltage of the pressure sensor 48, and calculates the gear ratio TR based on the output voltage of the pressure sensor 52. The input port 46 is connected to a vehicle speed sensor 57 that generates an output pulse indicating the vehicle speed, and a rotation speed sensor 55 that generates an output pulse indicating the engine speed N. On the other hand, the output port 47
Are connected to the fuel injection valve 7, the torque converter 22, and the hydraulic control valves 34a,
34b.

In this embodiment, the fuel injection time TAU (i) (i = 1, 2, 3, 4) of the i-th cylinder is calculated based on the following equation. TAU (i) = TB · (1 + K (i)) Here, TB represents the basic fuel injection time, and K (i) represents the correction coefficient of the i-th cylinder.

The basic fuel injection time TB is a fuel injection time required to bring the air-fuel ratio of the air-fuel mixture burned in each cylinder to the stoichiometric air-fuel ratio, and is obtained in advance by an experiment.
The basic fuel injection time TB is stored in the ROM 42 in advance in the form of a map shown in FIG. 2 as a function of the absolute pressure PM in the surge tank 3 representing the engine load and the engine speed N.

The correction coefficient K (i) is a coefficient for controlling the air-fuel ratio of the air-fuel mixture burned in the i-th cylinder.
If (i) = 0, the air-fuel ratio of the air-fuel mixture burned in the i-th cylinder becomes the stoichiometric air-fuel ratio. On the other hand, K (i) <
When it becomes 0, the air-fuel ratio of the air-fuel mixture burned in the i-th cylinder becomes larger than the stoichiometric air-fuel ratio, that is, becomes lean, and K
When (i)> 0, the air-fuel ratio of the air-fuel mixture burned in the i-th cylinder becomes smaller than the stoichiometric air-fuel ratio, that is, becomes rich.

In the present embodiment, during normal operation, the correction coefficient K (i) is maintained at -KL (1>KL> 0) in all cylinders. Therefore, the air-fuel ratio of the air-fuel mixture burned in all cylinders is Maintained lean. On the other hand, in the present embodiment, the gear ratio TR of the automatic transmission 20 is calculated based on the following equation.

TR = TRB + IR Here, TRB represents a basic gear ratio, and IR represents an increase correction value. The basic gear ratio TRB is an optimal gear ratio for an operating state determined by, for example, the throttle opening TA and the vehicle speed SPD, and is obtained in advance by an experiment. The basic gear ratio TRB is determined by the throttle opening TA and the vehicle speed S.
As a function of PD, a ROM 4
2 is stored.

The increase correction value IR is for increasing and correcting the speed ratio TR, and is normally maintained at zero. FIG. 4 schematically shows the concentrations of representative components in the exhaust gas discharged from the cylinder. As can be seen from FIG. 4, the amount of unburned HC and CO in the exhaust gas discharged from the cylinder increases as the air-fuel ratio of the air-fuel mixture burned in the cylinder increases, and the oxygen O in the exhaust gas discharged from the cylinder increases. The amount of ₂ increases as the air-fuel ratio of the mixture fueled in the cylinder becomes leaner.

The start catalyst 9a, 9b is _the NO _X absorbent 12
Is for purifying exhaust gas when the engine is not activated, and is formed of, for example, a three-way catalyst in which a noble metal such as platinum Pt is supported on an alumina carrier. On the other hand, N
O _X absorbent 12, for example alumina as a carrier, with, for example, on the carrier K, sodium Na, lithium L
i, alkali metal such as cesium Cs, barium B
a, alkaline earth such as calcium Ca, lanthanum L
a, at least one selected from rare earths such as yttrium Y, platinum Pt, palladium Pd, rhodium R
h, a noble metal such as iridium Ir is supported. This _the NO _X absorbent 12 absorbs NO _X when the air-fuel ratio of the exhaust gas flowing is lean, perform absorption and release action of the NO _X which the oxygen concentration in the inflowing exhaust gas to release NO _X absorbed and reduced. The air-fuel ratio of the inflowing exhaust gas when the fuel or air to _the NO _X absorbent 12 upstream of the exhaust passage is not supplied to match the ratio of the total air amount to the total amount of fuel supplied to each cylinder.

If the above-described NO _X absorbent 12 is disposed in the engine exhaust passage, the NO _X absorbent 12 actually performs the absorption and release of NO _X , but the detailed mechanism of the absorption and release is not clear. There is also. However, it is considered that this absorption / release action is performed by a mechanism as shown in FIGS. 5 (A) and 5 (B). Next, this mechanism will be described by taking platinum Pt and barium Ba supported on a carrier as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.

That is, when the inflowing exhaust gas becomes considerably lean, the oxygen concentration in the inflowing exhaust gas greatly increases.
As shown in (A), these oxygens O ₂ adhere to the surface of platinum Pt in the form of O ₂ ⁻ or O ²⁻ . On the other hand, NO in the exhaust gas that flows in reacts with O ₂ ⁻ or O ²⁻ on the surface of platinum Pt to become NO ₂ (2NO + O ₂ → 2NO ₂ ). Then part of the produced NO ₂ while bonding with the barium oxide BaO is absorbed into the absorbent while being further oxidized on the platinum Pt, 5 nitrate as shown in (A) ions NO ₃ ^- in It diffuses into the absorbent in form. Thus N
O _X is absorbed in the NO _X absorbent 12.

The NO ₂ is produced on the surface of the oxygen concentration is as high as platinum Pt in the inflowing exhaust gas, as long as NO ₂ to NO _X absorbing capacity of the absorbent is not saturated is absorbed in the absorbent and nitrate ions NO ₃ ^- Is generated. On the other hand, when the oxygen concentration in the inflowing exhaust gas decreases and the amount of generated NO2 decreases, the reaction proceeds in the reverse direction (NO ₃ ⁻ → NO ₂ ), and thus the nitrate ion NO ₃ ⁻ in the absorbent is converted. It is released from the absorbent in the form of NO _2. That is, the oxygen concentration in the inflowing exhaust gas are released NO _X from _the NO _X absorbent 12 when lowered. If the degree of leanness of the inflowing exhaust gas decreases, the concentration of oxygen in the inflowing exhaust gas decreases. Therefore, if the degree of leanness of the inflowing exhaust gas decreases, the NO _x absorbent 12
O _X is to be released.

On the other hand, if the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 is made rich at this time, as shown in FIG. 4, the exhaust gas contains a large amount of HC and CO,
C and CO react with oxygen O ₂ ^- or O ^2- on platinum Pt to be oxidized. Further, NO ₂ is released to the air-fuel ratio of the exhaust gas flowing from the absorbent to the oxygen concentration in the exhaust gas flowing to rich is extremely lowered, so that the NO ₂ is shown in FIG. 5 (B) HC , CO to be reduced. In this way, NO _{2 is} deposited on the surface of platinum Pt.
When no longer exists, NO ₂ is released from the absorbent one after another. Therefore NO _X from _the NO _X absorbent 12 in a short time when the air-fuel ratio of the exhaust gas flowing into the rich is to be released. Incidentally, NO _X flowing into the absorbent 12 average air-fuel ratio H in the inflow exhaust gas to a lean exhaust
When C and CO are contained, the oxygen concentration around the platinum Pt locally decreases, so that NO ₂ is released from the absorbent and can be reduced.

The NO _X in the exhaust normal air-fuel ratio of the mixture burned in the cylinders during operation in this embodiment is maintained lean, thus discharged from the cylinders during normal operation, _the NO _X absorbent 12 Is absorbed by However, the the NO _X absorbing capacity of the NO _X absorbent 12 is necessary to release the NO _X from _the NO _X absorbent 12 before the NO _X absorbing capacity of the NO _X absorbent 12 is saturated because there is a limit.
Therefore, in the present embodiment obtains the NO _X absorption of _the NO _X absorbent 12, the air-fuel ratio of the mixture burned in each cylinder when the NO _X absorption amount becomes more than the amount set a predetermined temporarily rich to release the NO _X in _the NO _X absorbent 12, so that reduction. That is, the correction coefficient K (i) of each cylinder is temporarily switched to KN (> 0).

[0036] However, in the lubricating oil of the fuel and the engine, the exhaust flowing into _the NO _X absorbent 12 because it contains sulfur includes sulfur content for example SO _X, N
O _X The absorbent 12 well NO _X SO _X is absorbed. It is considered that the mechanism of absorbing SO _X into the NO _X absorbent 12 is the same as the mechanism of absorbing NO _X.

That is, the platinum Pt and the barium Ba are deposited on the carrier in the same manner as described for the NO _x absorption mechanism.
When the air-fuel ratio of the inflowing exhaust gas is lean as described above, the oxygen O ₂
Is attached to the surface of platinum Pt in the form of O ₂ ⁻ or O ²⁻ , and SO _X in the flowing exhaust gas, for example, SO ₂ reacts with O ₂ ⁻ or O ^{2− on} the surface of platinum Pt to form SO ₃ Becomes Next, the generated SO ₃ is further oxidized on the platinum Pt, is absorbed in the absorbent, and is bonded to barium oxide BaO, and diffuses into the absorbent in the form of sulfate ions SO ₄ ^2- . Next, this sulfate ion SO ₄ ^2- is combined with barium ion Ba ²⁺ to form sulfate BaSO ₄ .

However, this sulfate BaSO_Four Decomposes
It is difficult to simply enrich the air-fuel ratio of the inflowing exhaust
Sulfate BaSO_Four Remains undisassembled. But
NO_XAs time passes, sulfuric acid is contained in the absorbent 12.
Acid salt BaSO_Four Increase, and thus the time
NO as time goes by_XNO that can be absorbed by the absorbent 12 _X
The amount will be reduced.

However, NO_XProduced in absorbent 12
Sulfate BaSO_Four Is NO_XWhen the temperature of the absorbent 12 is high
Set the air-fuel ratio of exhaust flowing into the
Decomposes into sulfate ion SO_Four ^2-Is SO_Three Absorbent in the form of
Released from Figure 6 shows NO per unit time_XAbsorbent 1
SO released from 2_XQ (SO_XExperimental results showing
In FIG. 6, the solid line is NO_XFlows into the absorbent 12
When the air-fuel ratio of the exhaust gas is rich, the broken line indicates NO._XAbsorbent
12 shows a case where the air-fuel ratio of the exhaust gas flowing into the fuel cell 12 is the stoichiometric air-fuel ratio
ing. As can be seen from FIG._XAbsorbent temperature TNA
Is higher than TN1_XSO of absorbent 12_XRelease
Discharge is substantially commenced. Therefore, this TN1 is set to S
O_XWhen referred to as the release temperature, in this embodiment, NO_XAbsorbent
12 SO_XThe amount of absorption is determined and this SO_XPredetermined absorption amount
NO when exceeding the set amount_XAbsorbent 1
2 for SO_XThe temperature rises higher than the release temperature TN1 and N
O _XThe air-fuel ratio of the exhaust gas flowing into the absorbent 12 is temporarily reduced.
Make it rich, so NO_XAbsorbent 12
To SO_XIs to be released. Release at this time
SO_Three Depends on HC and CO in the exhaust gas
SO immediately_Two It is reduced to. Note that NO_XAbsorbent
The temperature TNA is raised higher than TN1 and NO_XSucking
Even if the air-fuel ratio of the exhaust gas flowing into the absorbent 12 is set to the stoichiometric air-fuel ratio
NO_XAbsorbent 12 to SO_XCan be released
You.

The amount of SO _X absorbed by the NO _X absorbent 12 per unit time is determined by the amount of SO
_The SO _X amount increases as the _X amount increases, and the SO _X amount discharged from the engine per unit time increases as the vehicle traveling distance dD per unit time increases. Therefore, NO _X
The SO _X absorption amount of the absorbent 12 increases as the integrated value SD of the vehicle travel distance dD increases. In this embodiment _the NO _X absorbent when it becomes larger than the set value SD1 to the vehicle travel distance cumulative value SD is predetermined 1
2 is determined to be greater than the set amount of SO _X absorption.

Next, the SO _X releasing action of the NO _X absorbent 12 according to the present embodiment will be described in detail with reference to the time chart of FIG. The action of raising the temperature of _the NO _X absorbent 12 is performed when _the NO _X absorbent temperature TNA is lower than the SO _X release temperature TN1 when the vehicle travel distance cumulative value SD at time a is larger than the set value SD1. In the present embodiment, first, the increase correction value IR is increased, so that the gear ratio TR is increased from that in the normal operation.
That is, the speed change ratio TR is the temperature of the exhaust gas discharged is raised from increasing caused to be the engine speed N engine is raised, NO _X absorbent temperature TNA is warmed to thus.

[0042] _the NO _X absorbent temperature TNA is an increase correction value IR until higher than SO _X release temperature TN1 is made to increase incrementally dr, gear ratio TR is made to increase by dr. Therefore, the increase correction value IR is an integrated value of the increase dr (IR = IR + dr). Increase correction value I
SO _X release temperature as increment dr of R is shown in Figure 8 T
N1 and the difference between the current of the NO _X absorbent temperature TNA DLT (=
TN1-TNA) is predetermined so as to increase as TN1-TNA increases. Thus _the NO _X absorbent temperature T
The NA is quickly heated. This increment dr is stored in the ROM 42 in advance in the form of a map shown in FIG.
If the gear ratio TR fluctuates rapidly, the torque fluctuation may increase. Therefore, the increment dr shown in FIG. 8 is predetermined so that the torque fluctuation becomes smaller than the allowable value.

On the other hand, at this time, the correction coefficient K (i) for all cylinders
Is a small positive value a, and therefore NO_XFor absorbent 12
The air-fuel ratio of the inflowing exhaust gas is made slightly rich.
NO _XAbsorbent temperature TNA is SO_XThan the release temperature TN1
NO when low_XAir-fuel ratio of exhaust gas flowing into absorbent 12
NO even if rich_XAbsorbent 12 to SO_XIs substantial
Not released to However, NO_XAbsorbent temperature TN
When A rises, the air-fuel ratio of the inflowing exhaust gas is lean,
NO_XNO from absorbent 12_XCan be released. Therefore
In this embodiment, NO_XWhen raising the temperature of the absorbent 12, N
O_XThe air-fuel ratio of the exhaust flowing into the absorbent 12 is slightly reduced
NO that can be released at this time by making it rich _XI will reduce
I'm trying.

[0044] Then, at time b NO _X absorbent temperature T
When NA becomes higher than the SO _X release temperature TN1, the increase correction value IR is kept constant, and therefore, the NO _X absorbent temperature TNA is maintained higher than the SO _X release temperature TN1.
On the other hand, the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 is kept slightly rich, and thus the NO _X absorbent 12
Starts the SO _X releasing action.

NO_XAbsorbent temperature TNA is SO_XRelease temperature
When a certain period of time elapses after becoming higher than TN1, N
O_XSO of absorbent 12_XIt is determined that the release action is complete
At time c, the increase correction value IR is returned to zero. I
NO_XThe temperature raising action of the absorbent 12 is stopped. one
On the other hand, at this time, the correction coefficients K (i) of all cylinders are set to zero,
NO_XThe air-fuel ratio of the exhaust gas flowing into the absorbent 12 is
The stoichiometric air-fuel ratio is set. That is, NO_XAbsorbent temperature TNA
The air-fuel ratio of the inflow exhaust when the air pressure is high switches to lean
NO _XSintering may occur in the absorbent 12
There is. Therefore, in this embodiment, NO _XS of absorbent 12
O_XNO after release action is complete_XAbsorbent temperature TNA
It is lower than the maximum allowable temperature TN2 where interleaving does not occur.
Until that time, NO_XAir-fuel ratio of exhaust gas flowing into absorbent 12
Is temporarily banned from becoming lean and maintained at the stoichiometric air-fuel ratio
I am trying to do it. Note that NO_XAbsorbent 1
2 SO_XNO after release action is complete_XAbsorbent temperature TN
Cool until A becomes lower than allowable maximum temperature TN2
It is called a period.

[0046] Then at time d NO _X absorbent temperature T
When NA becomes lower than the allowable maximum temperature TN2, that is, when the cooling period ends, the correction coefficient K (i) of all cylinders becomes −K
It returned to L, that the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 is returned to lean. Similarly, NO _X absorbent temperature TNA is SO _X release temperature T when the vehicle travel distance cumulative value SD is larger than the set value SD1 at time e
When it is lower than N1, the increase correction value IR is increased by the increment dr, whereby the speed ratio TR is increased.

Next, at time f, the exhaust manifold 8a
Is higher than the allowable maximum temperature TE1, the increase correction value IR is returned to the value before the update. That is, when the gear ratio TR is increased, the temperature of the exhaust gas discharged from the engine is increased.
a of the exhaust manifold 8
a may be higher than the maximum allowable temperature TE1 that does not deteriorate due to heat. Therefore, in the present embodiment, when the exhaust manifold temperature TEM becomes higher than the allowable maximum temperature TE1, the increasing operation of the increase correction value IR is stopped and the gear ratio TR
Is stopped, the increase correction value IR is returned to a value before the exhaust manifold temperature TEM becomes higher than the allowable maximum temperature TE1, and the gear ratio TR is changed to the exhaust manifold temperature TE.
M does not exceed the maximum allowable temperature TE1. That is, the temperature raising effect by the gear ratio control is reduced,
As a result, deterioration of the exhaust manifold 8a due to heat is prevented.

Meanwhile, since this time _the NO _X absorbent temperature TNA is lower than the SO _X release temperature TN1 _the NO _X absorbent 12
Needs to be further heated. Therefore, in the present embodiment, the second, that is, additional temperature increase control is performed. That is, when a large amount of oxygen and a large amount of a reducing agent, for example, HC, are simultaneously contained in the exhaust gas flowing into the NO _X absorbent 12, the oxygen and HC react in the NO _X absorbent 12, so that this reaction occurs. it is possible to raise the temperature of the _the NO _X absorbent 12 has a thermal. On the other hand, as shown in FIG. 4, if the air-fuel ratio of the air-fuel mixture burned in the cylinder is made rich, a large amount of HC is contained in the exhaust gas, and if the air-fuel ratio is made lean, a large amount of oxygen is contained in the exhaust gas. Therefore, in the present embodiment, when an additional temperature raising operation is to be performed, the air-fuel ratio of the air-fuel mixture burned in the first cylinder group 1a is made rich to form exhaust gas containing a large amount of HC, and the second cylinder group is produced. the air-fuel ratio of the mixture burned in the lean form the exhaust gas contains a large amount of oxygen 1b, NO _X absorbent 1 these exhaust simultaneously
While raising the temperature of the _the NO _X absorbent 12 by introducing 2, the first cylinder group 1a and the second cylinder group so that the average air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 becomes just slightly rich 1b defines the air-fuel ratio of the mixture to be burned.

[0049] That is, generally speaking, the target value of the average air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 is set to the stoichiometric air-fuel ratio or just slightly rich, the first cylinder group 1a
The target air-fuel ratio of the air-fuel ratio of the exhaust of the second cylinder group 1b is set to be rich relative to the target value of the average air-fuel ratio, and the target air-fuel ratio of the air-fuel ratio of the exhaust of the second cylinder group 1b is set lean to the target value of the average air-fuel ratio. while, the average air-fuel ratio of the exhaust gas air-fuel ratio of the exhaust gas of the first and the air-fuel ratio of the exhaust cylinder group 1a of the second cylinder group 1b flows into _the NO _X absorbent 12 when the corresponding target air-fuel ratio, respectively That is, the target air-fuel ratio of the exhaust gas of the first cylinder group 1a and the target air-fuel ratio of the exhaust gas of the second cylinder group 1b are set so that the target value is obtained.

[0050] Alternatively, the temperature is raised to _the NO _X absorbent 12 by supplying a gas containing gas and oxygen containing fuel for Atsushi Nobori in the NO _X absorbent 12, the air-fuel ratio of the mixture burned in engine By performing the control, the gas containing the fuel for raising the temperature and the gas containing oxygen are formed from the exhaust gas of the internal combustion engine. Such a temperature raising operation is referred to as a temperature raising operation by air-fuel ratio control.

In the case where the temperature raising operation is to be performed by such air-fuel ratio control, in the present embodiment, the correction coefficients K (1) and K (4) of the first cylinder group 1a, that is, the first and fourth cylinders.
Is KS + a (KS, a> 0), and the second cylinder group 1b
That is, the correction coefficients K (2) for the second and third cylinders,
K (3) is set to -KS. Therefore, the average air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 is made rich by an amount corresponding to the small positive value a. The air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 if a = 0 is the stoichiometric air-fuel ratio.

KS represents the degree of richness of the air-fuel ratio of the air-fuel mixture burned in the first cylinder group 1a and the lean degree of the air-fuel ratio of the air-fuel mixture burned in the second cylinder group. When the KS called rich degree coefficient, the degree of richness coefficient KS is _the NO _X absorbent temperature TN
Initial value K until A becomes higher than SO _X release temperature TN1
It is incremented by an increment dk from S0. Therefore K
S is the integrated value of the increment dk (KS = KS + dk). When the rich degree coefficient KS is increased, N
O _X absorbent amount of fuel supplied to the 12 and the oxygen amount is increased, thus _the NO _X absorbent in _the NO _X absorbent 12 12
Is further heated.

The increment dk of the rich degree coefficient KS is predetermined so as to increase as the temperature difference DLT increases, as shown in FIG. Thus _the NO _X absorbent temperature TNA is rapidly heated. This increment dk is stored in advance in the ROM 42 in the form of a map shown in FIG. If the air-fuel ratio of the air-fuel mixture burned in the cylinder fluctuates rapidly, the torque fluctuation may increase. Therefore, the increment dk shown in FIG. 9 is predetermined so that the torque fluctuation is smaller than the allowable value.

[0054] Then, at time g NO _X absorbent temperature T
When NA becomes higher than the SO _X release temperature TN1, the rich degree coefficient KS is kept constant. At this time, NO
_X absorbent temperature TNA is also possible to lower the _the NO _X absorbent temperature TNA by reducing the or richness coefficient KS to reduce the increase correction value IR is when it becomes higher than the allowable maximum temperature. Then time h
_The NO _X absorbent temperature TNA in the SO _X release temperature TN
When a certain time elapses after the value becomes higher than 1, the increase correction value IR is returned to zero, and the correction coefficients K (i) of all cylinders are switched to zero.

When the temperature raising operation is performed by the speed ratio control, the temperature of the starting catalysts 9a and 9b may be higher than the allowable maximum temperature. Further, when the temperature raising operation is performed by the speed ratio control, the engine speed N is increased, and
At this time, the engine speed N may be higher than the allowable maximum speed N1. Therefore, in the present embodiment, when the temperature raising operation is performed by the speed ratio control, the temperature T
When the SC becomes higher than the maximum allowable temperature TS1 or when the engine speed N becomes higher than the maximum allowable speed N1, the gear ratio TR is returned and the temperature increasing operation by the air-fuel ratio control is started. ing. Note that, even when the engine cooling water temperature representing the temperature of the engine body 1 becomes higher than the allowable maximum temperature, the gear ratio TR can be returned and the temperature raising operation by the air-fuel ratio control can be started.

Further, when the gear ratio TR becomes higher than the maximum gear ratio TRM, the gear ratio TR is changed to the maximum gear ratio TRM.
At the same time, and the temperature raising operation by the air-fuel ratio control is started. Therefore, generally speaking, the temperature raising operation by the speed ratio control is performed so that the state quantity of the engine body, the exhaust system components, or the automatic transmission does not exceed the limit value based on the heat durability, combustion stability, or vibration resistance. This means that the temperature raising action by the air-fuel ratio control is controlled.

FIG. 10 shows an interruption routine executed by interruption every predetermined time for executing the present embodiment. Referring to FIG. 10, first, in step 100, it is determined whether or not the SO _X flag XSOX is set. This SO _X flag XSO
X is set when SO _X is to be substantially released from the NO _X absorbent 12 (XSOX = “1”), and otherwise reset (XSOX = “0”). SO _X
When the flag XSOX has been reset, the routine proceeds to step 101, where it is determined whether or not the temperature raising flag XIT has been set. This heating flag XIT is NO
From _X absorbent 12 to be released SO _X NO _X absorbent 12
Is set (XIT = "1") when the temperature is to be raised, and reset (XIT = "0") otherwise. When the temperature raising flag XIT has been reset, the routine proceeds to step 102, where a flag setting control routine is executed. This flag set control routine is shown in FIG.
Is shown in

Referring to FIG. 11, first, at step 200,
In, the vehicle travel distance dD from the previous processing cycle to the current processing cycle is calculated based on the output pulse of the vehicle speed sensor 57. In the following step 201, the vehicle travel distance integrated value SD is calculated (SD = SD + dD). In the following step 202, the vehicle travel distance integrated value SD is set to the set value SD.
It is determined whether it is greater than one. When SD ≦ SD1, the routine proceeds to step 203, where it is determined whether or not the NO _X flag XNOX is set. The NO _X flag XNOX is set when NO _X is to be released from the NO _X absorbent 12 (XNOX = “1”), and otherwise reset (XNOX = “0”). NO _X
When the flag XNOX is reset, the routine goes to step 204, NO _X absorption amount SN of the NO _X absorbent 12 is calculated. That is, NO _X per unit time
The NO _X amount flowing into the absorbent 12 increases as the absolute pressure PM in the surge tank 3 increases, and increases as the engine speed N increases. Therefore, k ・ PM ・ N
(K is a constant) will be representing the amount of NO _X absorbed in the NO _X absorbent 12 per unit time. Therefore,
The NO _x absorption amount SN can be calculated by integrating k · PM · N (SN = SN + k · PM · N).

In the following step 205, the NO _X absorption amount SN
Is larger than a predetermined set value SN1. When SN ≦ SN1, the routine is terminated, and when SN> SN1, the routine proceeds to step 206.
The routine is ended after setting the NO _X flag XNOX. When the NO _X flag XNOX is set, the process proceeds from step 203 to step 207, where N
O _X absorbent 12 of the NO _X emission, the count value CN is incremented by 1 representing the time of reduction action is being performed. In the following step 208, it is determined whether or not the count value CN is larger than a predetermined set value CN1.
When CN ≦ CN1, the processing cycle ends, and CN>
When it reaches CN1, the process proceeds to step 209, where N
O _X flag XNOX is reset. Next step 2
In 10 NO _X absorption SN and the count value CN is cleared, respectively. Next, this routine ends. The setting value CN1 as NO _X absorption amount SN of the NO _X absorbent 12 becomes almost zero is defined.

On the other hand, in step 202, SD> SD
If it is 1, then the routine proceeds to step 209, where the temperature raising flag XIT is set. Next, this routine ends.
Referring again to FIG. 10, when the temperature increase flag XIT is set, the process proceeds from step 101 to step 103, where a temperature increase control routine is executed. This temperature raising control routine is shown in FIG.

Referring to FIG. 12, first, at step 300
Then NO_XAbsorbent temperature TNA is SO _XRelease temperature TN1
Is determined. When TNA <TN1
Then proceeds to step 301, where the addition flag XADD is
It is determined whether or not it is set. This additional flag
XADD is an additional heating control, ie, empty in this embodiment.
Set when the temperature raising operation by fuel ratio control should be performed.
(XADD = "1"), otherwise reset (XADD
ADD = "0"). Add flag XADD is reset.
If set, then go to step 302.
The exhaust manifold temperature TEM is higher than the maximum allowable temperature TE1.
Is determined. When TEM <TE1
Next, the routine proceeds to step 303, where the starting catalyst temperature TSC
Is lower than the allowable maximum temperature TS1.
If TSC <TS1, then proceed to step 304.
Whether the engine speed N is higher than the maximum allowable speed N1
Is determined. If N <N1, then step 3
05, the increment dr of the gear ratio TR is calculated from the map of FIG.
Is calculated. In the following step 306, the current gear ratio TR
The increase dr is added to the increase correction value IR of
A large correction value IR is calculated (IR = IR + dr). Next
Then, the process proceeds to a TR calculation routine of step 110.

On the other hand, in step 302, TE
When M ≧ TE1, in step 303, TSC ≧ T
In the case of S1, or when N ≧ N1 in step 304, the process proceeds to step 307, where the increment dr in the previous processing cycle is subtracted from the current increase correction value IR to calculate the increase correction value IR (IR =
IR-dr). That is, when the increase correction value IR is TEM ≧ TE
1 or a value before TSC ≧ TS1 or N ≧ N1. In the following step 308, an additional flag XADD
Is set. Next, the routine proceeds to a TR calculation routine of step 110.

When the addition flag XADD is set, the process proceeds from step 301 to step 309, where the increment dk of the richness coefficient KS is calculated from the map shown in FIG. In the following step 310, the current rich degree coefficient K
The richness coefficient KS is calculated by adding the increment dk to S (KS = KS + dk). Next, the routine proceeds to a TR calculation routine of step 110.

On the other hand, in step 300, TNA ≧ T
When N1 or when TNA ≧ TN1, the routine proceeds to step 311 where the temperature raising flag XIT is reset, and in the subsequent step 312 the SO _X flag XSOX is set. Next, the routine proceeds to a TR calculation routine of step 110. Referring again to FIG. 10, the SO _X flag XS
When OX is set, the process proceeds from step 100 to step 104, where the count value CS representing the time during which the SO _X flag XSOX is set, that is, the time during which SO _X is substantially released from the NO _X absorbent 12, becomes 1 Is only incremented. In the following step 105, it is determined whether or not the count value CS is larger than a predetermined set value CS1. When CS ≦ CS1, the process then proceeds to a TR calculation routine of step 110. In contrast, CS
If> CS1, then the routine proceeds to step 106, where SO
_{The X} flag XSOX is reset, and the additional flag XADD is reset or maintained in a reset state. In the following step 107, the vehicle mileage integrated value SD,
The count value CS and the increase correction value IR of the speed ratio TR are cleared, and the richness coefficient KS is returned to the initial value KS0. Incidentally, of the NO _X absorbent 12 S
O _X absorption amount set value CS1 to almost becomes zero are determined.

Next, the routine proceeds to step 108, where the NO _X flag XNOX is reset.
O _X absorption SN and the count value CN is cleared.
That, _the NO _X absorbent 12 of SO _X release action is in this case _the NO _X absorbent 12. Since the air-fuel ratio of the exhaust gas flowing into _the NO _X absorbent 12 is made to rich performed NO
_X is released and reduced. Further, the time required for the SO _X releasing action is long enough to release and reduce all the NO _X in the NO _X absorbent 12. Therefore, when the SO _X release operation is completed, the NO _X flag is reset and N
The O _X absorption SN and the count value CN is to be cleared. Next, the routine proceeds to a TR calculation routine of step 110.

The TR calculation routine of step 110 is shown in FIG.
It is shown in FIG. Referring to FIG. 13, first, at step 400, the basic gear ratio TRB is calculated from the map of FIG. In the following step 401, the gear ratio TR is calculated by adding the increase correction value IR to the basic gear ratio TRB (TR = TRB + IR). In the following step 402, it is determined whether or not the speed ratio TR is larger than the allowable maximum ratio TRM. When TR ≦ TRM, the processing cycle ends. On the other hand, when TR> TRM, the routine proceeds to step 403, where the gear ratio TR is set to the maximum allowable ratio TRM. In a succeeding step 404, an additional flag XADD is set.

FIG. 14 shows the fuel injection time TAU of the i-th cylinder.
(I) shows a routine for calculating (i = 1, 2, 3, 4). This routine is executed by interruption every predetermined set crank angle. Referring to FIG. 14, first, at step 500, the basic fuel injection time T
B is calculated from the map of FIG. The following step 501
In, it is determined whether or not the addition flag XADD is set. When the addition flag XADD is reset, the process proceeds to step 502, where the SO _X flag XS
It is determined whether OX or the temperature raising flag XIT is set. If the SO _X flag XSOX and the temperature raising flag XIT are reset, then step 5
Proceeding to 03, it is determined whether the NO _X flag XNOX is set. When the NO _X flag XNOX has been reset, the routine proceeds to step 504, where it is determined whether or not the present time is a cooling period. At present, during the cooling period, the routine proceeds to step 505, where the correction coefficients K (i) of all the cylinders are set to zero. Next, the routine proceeds to step 510. On the other hand, if the current period is not the cooling period, the process proceeds to step 506, where the correction coefficients K (i) of all the cylinders are-
KL. Next, the routine proceeds to step 510.

On the other hand, when the NO _X flag is set, the routine proceeds from step 503 to step 507, where the correction coefficient K (i) for all cylinders is set to KN. Next, the routine proceeds to step 510. On the other hand, when the SO _X flag XSOX or the temperature raising flag XIT is set, step 50
2 to step 508, where the correction coefficient K for all cylinders
(I) is a constant value a. On the other hand, additional flag XADD
Is set, the routine proceeds from step 501 to step 509, in which the correction coefficients K for the first and fourth cylinders are set.
(1) and K (4) are respectively KS + a, and the correction coefficients K (2) and K (3) of the second and third cylinders are each -KS. Next, the routine proceeds to step 510.

In step 510, the fuel injection time TAU (i) of the i-th cylinder is calculated (TAU (i) = TB ·
(1 + K (i))). By the way, the rich degree coefficient KS
Increases, the torque fluctuation between the first cylinder group 1a and the second cylinder group increases, which is not preferable. In this embodiment performs heating operation by first gear ratio control in time to warm the _the NO _X absorbent 12, then when it should perform additional heating action is to perform the heating operation by the air-fuel ratio control I have. In this way, the richness coefficient KS can be kept small. That is, the gear ratio control is not necessary to have _the NO _X absorbent temperature TNA when performing a heating action performs heating operation by the air-fuel ratio control if higher than SO _X release temperature TN1 by, the temperature by the air-fuel ratio control temperature Even when the action should be performed, the rich degree coefficient KS can be kept small because the temperature increasing action is performed by the speed ratio control.

Next, another embodiment will be described. NO order to release the SO _X from _the NO _X absorbent 12 in this embodiment
When the temperature of the _X absorbent 12 is to be raised, first, the temperature of the NO _X absorbent 12 is raised by air-fuel ratio control.

[0071] In this case, NO _X absorbent temperature TNA is SO
_The rich degree coefficient KS is gradually increased until the temperature becomes higher than the _X release temperature TN1. However, the rich degree coefficient KS cannot be excessively increased as described above. Therefore, in the present embodiment, the rich degree coefficient KS
Is larger than a predetermined allowable maximum value KSM, the rich degree coefficient KS is maintained at the allowable maximum value KSM, and an additional temperature increasing operation, that is, a temperature increasing operation by gear ratio control is started. .

As described above, when both the temperature raising operation by the gear ratio control and the temperature raising operation by the air-fuel ratio control are performed,
O _X absorbent temperature TNA is raised Sarezu to SO _X release temperature TN1, however when the exhaust manifold temperature TEM is higher than the allowable maximum temperature TE1, or start catalyst temperature TSC becomes higher than the allowable maximum temperature TS1 when in, or when the engine speed N becomes higher than the allowable maximum rotational number N1, or so as to stop the action of raising the temperature of _the NO _X absorbent 12 when the speed change ratio TR is higher than the maximum speed ratio TRM ing. Therefore, the durability of the exhaust system components is secured, and the combustion stability and vibration resistance of the engine are secured.

At this time, the SO _{x of} the NO _x absorbent 12
Set value SD1 for determining whether or not to perform _X release action
Is increased by a constant value dSD. Therefore the action of raising the temperature of the vehicle travel distance adding value SD is the _the NO _X absorbent 12 again SD1 + DSD is started. In this embodiment, the temperature sensor 4 is provided on the exhaust manifold 8a of the first cylinder group 1a.
9 is attached to detect the exhaust manifold temperature TEM. Of course, a temperature sensor may be attached to the exhaust manifold 8b of the second cylinder group 1b. is there. Therefore, in the present embodiment, the temperature of the exhaust manifold 8a of the first cylinder group 1a is detected.

In this embodiment, the interrupt routine shown in FIG. 10 is also executed. In this interrupt routine, the flag set control routine of step 102 is shown in FIG.
FIG. 15 shows the temperature raising control routine of step 103, and FIG. 16 shows the gear ratio TR calculation routine of step 110. Referring to FIG. 15 showing the temperature raising control routine in this embodiment, in step 320, it is determined whether or not the NO _X absorbent temperature TNA is lower than the SO _X release temperature TN1. If TNA <TN1, then the routine proceeds to step 321, where it is determined whether or not the addition flag XADD is set. In the present embodiment, the additional flag XADD is set when the temperature raising operation by the gear ratio control is to be executed. When the addition flag XADD is reset, the process then proceeds to step 322, where the increment dk of the richness coefficient KS is calculated from the map of FIG. In the following step 323, the rich degree coefficient KS is calculated (KS = KS + dk). In the following step 324, it is determined whether or not the rich degree coefficient KS is larger than the allowable maximum value KSM. When KS ≦ KSM, the process then proceeds to a TR calculation routine of step 110. KS> KS
If it is M, then the routine proceeds to step 325, where the rich degree coefficient KS is maintained at the allowable maximum value KSM. In the following step 326, an additional flag XADD is set. Next, the routine proceeds to a TR calculation routine of step 110.

When the addition flag XADD is set, the routine proceeds from step 321 to step 327, where it is determined whether or not the exhaust manifold temperature TEM is lower than the allowable maximum temperature TE1. If TEM <TE1, then the routine proceeds to step 328, where it is determined whether or not the starting catalyst temperature TSC is lower than the allowable maximum temperature TS1. TSC <
In the case of TS1, the process then proceeds to step 329, where it is determined whether or not the engine speed N is higher than the allowable maximum speed N1. When N <N1, the routine proceeds to step 330, where the increment dr of the gear ratio TR is calculated from the map of FIG. In a succeeding step 331, an increase correction value IR is calculated (IR = IR + dr). Next, TR of step 110
Proceed to the calculation routine.

On the other hand, at step 327, TE
When M ≧ TE1, in step 328, TSC ≧ T
At S1, or when N ≧ N1 at step 329, the routine proceeds to step 332, where the temperature raising flag XI
T and the additional flag XADD are reset. In the following step 333, the set value SD1 is increased by a constant value dSD (SD1 = SD1 + dSD), and the increase correction value I
R is cleared, and the rich degree coefficient KS is set to the initial value KS0.
Is returned to. Therefore the action of raising the temperature of _the NO _X absorbent 12 is stopped. Next, the routine proceeds to a TR calculation routine of step 110.

The speed ratio TR calculation routine in this embodiment
Referring to FIG. 16 showing the chin, first in step 420
Is the basic gear ratio TRB calculated from the map of FIG.
In step 421, the gear ratio TR is calculated (TR = T
RB + IR). In the following step 422, the gear ratio TR is permitted.
It is determined whether or not it is larger than the maximum capacity ratio TRM. TR
When ≤TRM, the processing cycle ends. Against this
When TR> TRM, the process proceeds to step 423.
Reset flag XIT and additional flag XADD
Is set. In the following step 424, the set value SD1 is
Increased by the fixed value dSD (SD1 = SD1 + dS
D) The increase correction value IR is cleared, and the rich degree coefficient
KS is returned to the initial value KS0. So in this case
Also NO _XThe temperature raising action of the absorbent 12 is stopped.

FIG. 17 shows a routine for calculating the fuel injection time TAU (i) (i = 1, 2, 3, 4) of the i-th cylinder in this embodiment. This routine is executed by interruption every predetermined set crank angle. Referring to FIG. 17, first, at step 520, the basic fuel injection time TB is calculated from the map of FIG. In a succeeding step 521, it is determined whether or not the SO _X flag XSOX or the temperature raising flag XIT is set.
When the SO _X flag XSOX and the temperature raising flag XIT have been reset, the routine proceeds to step 522, where N
O _X flag whether XNOX has been set or not. When the NO _X flag XNOX has been reset, the routine proceeds to step 523, where it is determined whether or not the present time is in the cooling period. At present, during the cooling period, the routine proceeds to step 524, where the correction coefficients K (i) of all the cylinders are set to zero. Next, the routine proceeds to step 528. On the other hand, if the current period is not the cooling period, the process proceeds to step 525, where the correction coefficients K (i) of all the cylinders are set to -KL. Next, the routine proceeds to step 528.

On the other hand, when the NO _X flag XNOX is set, the routine proceeds from step 522 to step 526, where the correction coefficient K (i) for all cylinders is set to KN. Next, the routine proceeds to step 528. On the other hand, when the SO _X flag XSOX or the temperature raising flag XIT is set, the process proceeds from step 521 to step 527, where the correction coefficients K (1) and K (4) of the first and fourth cylinders are respectively KS.
+ A, and the correction coefficient K for the second and third cylinders
(2) and K (3) are each set to -KS. Next, the routine proceeds to step 528. In step 528, the fuel injection time TAU (i) of the i-th cylinder is calculated (TAU (i) =
TB · (1 + K (i))).

In the embodiments described above, the air-fuel ratio of the air-fuel mixture burned in the combustion chamber is made rich in order to make the air-fuel ratio of the exhaust gas discharged from the cylinder rich.
However, the air-fuel ratio of the exhaust gas discharged from the cylinder is rich by injecting the fuel from the fuel injection valve 7 in the engine explosion stroke or the exhaust stroke while making the air-fuel ratio of the air-fuel mixture burned in the combustion chamber lean. You can also

FIG. 18 shows another embodiment. FIG. 18 shows a case where the present invention is applied to a diesel engine. Referring to FIG. 18, each cylinder has a common exhaust manifold 8c.
Through the exhaust pipe 11c.
The O _X absorbent 12 is connected to the casing 13 that houses. A temperature sensor 49c for generating an output voltage proportional to the temperature TEM of the exhaust manifold 8c is provided at the exhaust manifold 8c.
Is attached to the exhaust pipe 11c, and a temperature sensor 50c that generates an output voltage proportional to the exhaust gas temperature that indicates the temperature TSC of the catalyst 11c at the time of starting is attached. The output voltages of these sensors 49c and 50c are supplied to the input port 46 of the electronic control unit 40 via the corresponding AD converter 54, respectively.
Is input to On the other hand, start catalyst 9c and _the NO _X absorbent 1
The exhaust pipe 11c between 2 HC supply device 18 for supplying HC (hydrocarbon) in the NO _X absorbent 12 is attached. The HC supply device 18 is connected to a fuel tank of an internal combustion engine (not shown). The electronic control unit 4
The 0 output port 47 is connected to the HC supply device 18 via the drive circuit 56.

In the diesel engine shown in FIG. 18, the average air-fuel ratio of the air-fuel mixture burned in the combustion chamber is maintained at a lean value.
O _X is absorbed by the NO _X absorbent 12. On the other hand, when the _the NO _X absorbent 12 to be released the NO _X is supplied HC from the HC supplying device 18, whereby the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 is temporarily allowed to rich. In this case, the HC supply amount QHC supplied from the HC supply device 18 per unit time is QN. The QN is the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 NO
_{This is the} amount of HC necessary for obtaining the optimum air-fuel ratio for the _X release and reduction actions, and is determined in advance by experiments. QN
Are stored in the ROM 42 in advance in the form of a map shown in FIG. 19 as a function of the absolute pressure PM in the surge tank 3 and the engine speed N.

[0083] On the other hand, the _the NO _X absorbent 12 in order to release the SO _X from _the NO _X absorbent 12 when it should be warm First, heating operation by the gear ratio control is performed. On the other hand, at this time, H
The HC supply amount QHC of the C supply device 18 is maintained at QS. This QS is the amount of HC required to make the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 an optimum air-fuel ratio for the SO _X releasing action, and is determined in advance by an experiment. Q
S is the absolute pressure PM in the surge tank 3 and the engine speed N
ROM 42 in the form of a map shown in FIG.
Is stored within.

Next, the NO _X absorbent temperature TNA becomes SO _X
When the temperature becomes higher than the release temperature TN1, the HC supply amount QHC becomes Q
While maintaining S, the increase correction value IR of the speed ratio TR is kept constant, and thus the action of increasing the speed ratio TR is stopped. Next, when the SO _X releasing action of the NO _X absorbent 12 is completed, the increase correction value IR is returned to zero. On the other hand, the HC supply amount QHC is set to QST only during the cooling period. This QS
T is obtained in advance experimentally a HC amount required to bring the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 to the stoichiometric air-fuel ratio. QST is the absolute pressure PM in the surge tank 3.
And as a function of the engine speed N in the form of a map shown in FIG.

On the other hand, when the exhaust manifold temperature TEM becomes higher than the maximum allowable temperature TE1 when the temperature raising operation is performed by the speed ratio control, or when the starting catalyst temperature TSC becomes higher than the maximum allowable temperature TS1. When this happens, or when the engine speed N becomes higher than the maximum permissible engine speed N1, the increase correction value IR is returned to the value before the update and an additional temperature raising operation is started. Also,
When the gear ratio TR becomes higher than the maximum gear ratio TRM, the gear ratio TR is maintained at the maximum gear ratio TRM and an additional temperature raising operation is started.

[0086] As described above, it is possible to raise the temperature of the _the NO _X absorbent 12 by reacting these fuel and oxygen is supplied fuel and oxygen into _the NO _X absorbent 12. On the other hand, the exhaust gas discharged from the engine contains a large amount of oxygen. Therefore, in this embodiment, the HC supply device 1
By supplying HC from 8, an additional temperature raising operation is performed.

As described above, the supply from the HC supply device 18
HC is NO_XNO in absorbent 12 _XOr SO_XRelease
Not only acts as a reducing agent for
NO _XAs a fuel for raising the temperature of the absorbent 12
Also works. Specifically, the HC supply of the HC supply device 18
The amount QHC is increased by the increase correction value IQ with respect to QS.
(QHC = QS + IQ). This increase correction value IQ is N
O_XAbsorbent temperature TNA is SO_XHigher than the release temperature TN1
(IQ = IQ)
+ Dq). The increment dq is the temperature difference D as shown in FIG.
It is predetermined so that it increases as LT increases.
Have been. The increment dq is reserved in the form of the map shown in FIG.
It is stored in the ROM 42.

[0088] Thus Generally speaking, the temperature is raised to _the NO _X absorbent 12 by supplying a gas containing gas and oxygen containing fuel for Atsushi Nobori in the NO _X absorbent 12,
That is, at least one of the gas containing the fuel for raising the temperature and the gas containing oxygen is formed from the exhaust gas of the internal combustion engine. That is, as illustrated in the time chart of FIG. 23, NO _X absorbent temperature T when the vehicle travel distance cumulative value SD is larger than the set value SD1 at the time a
When NA is lower than the SO _X release temperature TN1, the temperature raising operation by the speed ratio control is started. On the other hand, at this time, HC
The supply amount QHC is maintained at QS.

Next, when the exhaust manifold temperature TEM becomes higher than the allowable maximum temperature TE1 at the time b, the increase correction value IR is returned to the value before the update, and the temperature raising operation by the air-fuel ratio control is started. Then _the NO _X absorbent temperature TNA at time c is the the increase correction value IQ higher than SO _X release temperature TN1 is held constant. Then, NO _X absorbent temperature TNA is increased correction value IR and increase correction value IQ and passes only a predetermined time from when higher than SO _X release temperature TN1 is returned to zero at time d. Thus, the action of raising the temperature of _the NO _X absorbent 12 is stopped. On the other hand, at this time, the HC supply amount QHC is set to QST, so that the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 is set to the stoichiometric air-fuel ratio. Next, at time e, NO _x
When the absorbent temperature TNA becomes lower than the allowable maximum temperature TN2, the HC supply amount QHC is returned to zero, that is, the operation of supplying HC from the HC supply device 18 is stopped.

FIG. 24 shows an interrupt routine in this embodiment. Referring to FIG. 24, first, at step 140, it is determined whether or not the SO _X flag XSOX is set. If the SO _X flag XSOX has been reset, the routine proceeds to step 141, where it is determined whether or not the temperature raising flag XIT has been set. When the temperature raising flag XIT is reset, the routine proceeds to step 142, where the flag setting control routine shown in FIG. 11 is executed. Next, the routine proceeds to a step 150 for calculating the gear ratio TR. This TR calculation routine is shown in FIG.

When the temperature raising flag XIT is set
Proceeding from step 141 to step 143, the temperature control
Routine is executed. This temperature increase control routine is shown in FIG.
It is shown. Referring to FIG. 25, first, at step 34
NO for 0_XAbsorbent temperature TNA is SO _XRelease temperature TN1
Is determined. When TNA <TN1
Then, the process proceeds to a step 341 to add an additional flag XADD.
Is set or not. In this embodiment
The additional flag XADD indicates that the temperature is increased by the air-fuel ratio control.
Set when the action should be performed. Additional flag XA
If DD is reset, then step 34
Proceed to 2 and the exhaust manifold temperature TEM becomes the maximum allowable temperature.
It is determined whether it is lower than the degree TE1. TEM <TE
When the value is 1, the routine proceeds to step 343, in which the starting catalyst
It is determined whether the temperature TSC is lower than the allowable maximum temperature TS1.
Separated. If TSC <TS1, then step 3
Proceeding to 44, the engine speed N is higher than the allowable maximum speed N1.
It is determined whether it is high. If N <N1, then
Proceeding to step 345, the increment dr of the gear ratio TR is changed to the value in FIG.
It is calculated from the top. In the following step 346, increase correction
The value IR is calculated (IR = IR + dr). Next,
The process proceeds to the TR calculation routine of step 150.

On the other hand, at step 342, TE
When M ≧ TE1, in step 343, TSC ≧ T
At S1, or when N ≧ N1 at step 344, the process proceeds to step 347, where the increase correction value IR
Is calculated (IR = IR-dr). Subsequent step 34
At 8, the additional flag XADD is set. Next, the routine proceeds to a TR calculation routine of step 150.

When the addition flag XADD is set, the process proceeds from step 341 to step 349, where the increment dq of the increase correction value IQ is calculated from the map shown in FIG. In the following step 350, an increase correction value IQ is calculated (I
Q = IQ + dq). Next, the routine proceeds to a TR calculation routine of step 150. On the other hand, in step 340, TNA ≧
When TN1 or when TNA ≧ TN1, the routine proceeds to step 351, where the temperature raising flag XIT is reset, and in the subsequent step 352, the SO _X flag XSOX
Is set. Next, the routine proceeds to a TR calculation routine of step 150.

Referring again to FIG. 24, the SO _X flag X
When SOX is set, the process proceeds from step 140 to step 144, where the count value CS is incremented by one. In the following step 105, it is determined whether or not the count value CS is larger than the set value CS1. CS ≦
In the case of CS1, the process then proceeds to a TR calculation routine of step 150. On the other hand, when CS> CS1, the routine proceeds to step 146, where the SO _X flag XSOX is reset, and the additional flag XADD is reset or kept in a reset state. In the following step 147, the vehicle travel distance integrated value SD, the count value CS, and the gear ratio T
The increase correction value IR of R and the increase correction value IQ of the HC supply amount QHC are cleared. Then step 14
The NO _X flag XNOX is reset at step 8, and in the next step 149, the NO _X absorption amount SN and the count value CN are cleared. Next, the routine proceeds to a TR calculation routine of step 150.

FIG. 26 shows the HC supply amount Q of the HC supply device 18.
2 shows a routine for calculating HC. This routine is executed by interruption every predetermined set time. Referring to FIG. 26, first, at step 540, it is determined whether the SO _X flag XSOX or the temperature raising flag XIT is set. SO _X flag XSO
When X and the temperature raising flag XIT have been reset, the routine proceeds to step 541, where the NO _X flag XNOX
Is set or not. When the NO _X flag XNOX has been reset, the routine proceeds to step 542, where it is determined whether or not the present time is in the cooling period. At present, during the cooling period, the routine proceeds to step 543, where QST is calculated from the map of FIG. In the following step 544, this QST is set as the HC supply amount QHC. On the other hand, if the current period is not the cooling period, the process then proceeds to step 545, where the HC supply amount QHC is made zero.

On the other hand, when the NO _X flag XNOX is set, the routine proceeds from step 541 to step 546, where QN is calculated from the map of FIG. In the following step 547, this QN is made the HC supply amount QHC. On the other hand, when the SO _X flag XSOX or the temperature raising flag XIT is set, the steps 540 to 5
Proceeding to 48, QS is calculated from the map of FIG. In the following step 549, the value obtained by adding the increase correction value IQ to this QST is set as the HC supply amount QHC (QHC = QS).
+ IQ).

In the embodiments described so far, NO _x
When the temperature raising action of the absorbent 12 is to be performed, first, one of the temperature raising action by the speed ratio control and the temperature raising action by the air-fuel ratio control is performed. Then, when the additional temperature raising action is to be performed, both of the temperature raising actions are performed. A warming action is performed. However, first, when it should perform the action of raising the temperature of _the NO _X absorbent 12 performs both the heating effect of heating effect and the air-fuel ratio control by the gear ratio control, then for example increase the increase correction value IR transmission ratio TR In other words, for example, when the exhaust manifold temperature TEM becomes higher than the maximum allowable temperature TE1, the increase correction value IR is returned to a value before the exhaust manifold temperature TEM becomes higher than the maximum allowable temperature TE1, and the richness coefficient KS is increased. You can also do so.

FIG. 27 shows still another embodiment. FIG.
7 shows a case where the present invention is applied to a spark ignition type internal combustion engine. Further, the internal combustion engine of the present embodiment does not include the automatic transmission. Referring to FIG. 27, reference numeral 58 denotes ignition plugs of the respective cylinders. These ignition plugs 58 are connected to the output ports 47 of the electronic control unit 40 via the corresponding drive circuits 56, respectively. Further, the confluence exhaust pipe 11 is mounted an electric heater 59 for heating the exhaust flowing through the interconnecting pipe 11, the electric heater 60 is mounted for heating _the NO _X absorbent 12 directly into _the NO _X absorbent 12 Can be The electric heaters 59 and 60 are connected to the battery 63 via the corresponding switches 61 and 62, respectively, and the switches 61 and 62 are connected to the output port 47 via the corresponding drive circuits 56, respectively. Switches 61 and 62
Is normally turned off except when, for example, the engine is started, and is turned on / off based on an output signal from the electronic control unit 40. On the other hand, a crank angle sensor 59 that generates an output pulse every time the crankshaft rotates, for example, 30 degrees is connected to the input port 46. The CPU 44 determines the engine speed N based on the output pulse of the crank angle sensor 59.
Is calculated, and the fluctuation amount TRQF of the engine output torque is calculated.
Is calculated.

FIG. 28 shows the ignition timing IG in this embodiment.
Is shown. This routine is executed by interruption every predetermined set crank angle. Referring to FIG. 28, first, at step 600, basic ignition timing IGB is calculated. This basic ignition timing IGB
Is an ignition timing corresponding to, for example, MBT, and is stored in the ROM 42 in advance in the form of a map shown in FIG. In the following step 601, the basic ignition timing IG
By adding the corrected retardation amount KIG to B, the ignition timing I
G is calculated. This correction retardation amount KIG is normally maintained at zero, and when KIG> 0, the ignition timing is retarded.

[0100] In this embodiment, first heating operation by the air-fuel ratio control is performed when the _the NO _X absorbent 12 should warm to _the NO _X absorbent 12 to be released SO _X. In this case, if the rich degree coefficient KS is increased in order to increase the temperature raising effect, the torque variation TRQF is increased, which is not preferable. Therefore, when the torque fluctuation amount TRQF becomes larger than a predetermined allowable maximum value TF1, the heating operation by the air-fuel ratio control is stopped, and the second heating operation, that is, the ignition timing is delayed from that in the normal operation. The heating operation by the ignition timing retard control to be turned on is started. In other words, the heating operation is switched from the heating operation by the air-fuel ratio control to the heating operation by the ignition timing control.
In this case, the correction coefficients of all the cylinders K (i) is switched to a small positive value a, therefore the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 12 is maintained just slightly rich.

[0102] In heating operation by ignition timing retard control, the correction retard amount KIG is _the NO _X absorbent temperature TNA is SO
Until the temperature becomes higher than the _X release temperature TN1, it is increased from the initial value 0 in increments of dig. Therefore, KIG is an integrated value of the increment dig (KIG = KIG + dig). The increment dig is predetermined so as to increase as the temperature difference DLT increases as shown in FIG. 33, and RO
It is stored in M42.

FIG. 30 shows an interruption routine executed by interruption every predetermined set time to execute this embodiment. Referring to FIG. 30, first, at step 160, it is determined whether or not the SO _X flag XSOX is set. When the SO _X flag XSOX has been reset, the routine proceeds to step 161 where it is determined whether or not the temperature raising flag XIT has been set. When the temperature raising flag XIT has been reset, the routine proceeds to step 162, where the flag setting control routine shown in FIG. 11 is executed.

When the temperature raising flag XIT is set
Proceeding from step 161 to step 163,
Routine is executed. This temperature increase control routine is shown in FIG.
It is shown. Referring to FIG. 31, first, in step 36,
NO for 0_XAbsorbent temperature TNA is SO _XRelease temperature TN1
Is determined. When TNA <TN1
Next, the routine proceeds to step 361, where the second temperature raising flag XS
It is determined whether EC is set. This second
The temperature raising flag XSEC is used for the second temperature raising control, that is, in the present embodiment.
In the aspect, when the temperature raising operation by the ignition timing control is to be executed
(XSEC = "1"), otherwise reset
(XSEC = "0"). 2nd heating
When the lag XSEC is reset,
Proceeding to step 362, a temperature raising operation is performed by air-fuel ratio control.
You. That is, in step 362, the rich degree coefficient KS
Is calculated from the map of FIG. 9 and the subsequent step
At 363, the rich degree coefficient KS is calculated (KS =
KS + dk). In the following step 364, the torque fluctuation amount T
RQF is calculated. In the next step 365, the torque is changed.
It is determined whether or not the moving amount TRQF is larger than the allowable maximum value TF1.
Is determined. This routine is executed when TRQF ≦ TF1.
If TRQF> TF1, then step 3
After proceeding to 66 and setting the second temperature raising flag XSEC,
This routine ends.

When the second temperature raising flag XSEC is set, the routine proceeds from step 361 to step 367, where the second
Is executed. This second temperature raising control routine is shown in FIG. Referring to FIG. 32, in step 700, the increment dig of the correction retardation amount KIG is determined.
Is calculated from the map of FIG. Following step 701
Calculates the corrected retardation amount KIG (KIG = KIG +
dig). Therefore, NO _X absorbent temperature TNA is SO
_The ignition timing IG is gradually retarded until it becomes higher than the _X release temperature TN1. In the following step 702, KT is set to a small positive value a. As described later, when the second temperature raising operation is performed, the correction coefficient K (i) for all cylinders is set to this KT. Therefore, in the present embodiment, when the second temperature raising operation is performed, combustion is performed in all cylinders. The air-fuel ratio of the fuel-air mixture is slightly enriched. This KT is referred to as a combustion air-fuel ratio coefficient.

Referring again to FIG. 31, step 360
When TNA ≧ TN1 or when TNA ≧ TN1, the routine proceeds to step 368, where the temperature raising flag XIT is reset.
_{The X} flag XSOX is set. Next, this routine ends. Referring again to FIG. 30, the SO _X flag XS
When OX is set, the process proceeds from step 160 to step 164, where the count value CS is incremented by one. In the following step 165, it is determined whether or not the count value CS is larger than the set value CS1, and CS ≦ CS
When it is 1, this routine ends. CS>
In the case of CS1, the process then proceeds to step 166, where SO _X
The flag XSOX is reset, and the second temperature raising flag XSEC is reset or maintained in a reset state. In the following step 167, the vehicle mileage integrated value SD
And the count value CS are cleared, respectively.
The rich degree coefficient KS is returned to the initial value KS0. In the following step 168, a temperature raising stop routine is executed. This temperature raising stop routine is shown in FIG.

Referring to FIG. 34, in step 800, the correction retard amount KIG is cleared. Referring again to FIG. 30, in the following step 169, the NO _X flag XNOX is reset, and in the following step 170, the NO _X absorption amount S
N and the count value CN are cleared. FIG. 35 shows the fuel injection time TAU (i) of the i-th cylinder in this embodiment.
9 shows a routine for calculating (i = 1, 2, 3, 4). This routine is executed by interruption every predetermined set crank angle.

Referring to FIG. 35, first, at step 560
In, the basic fuel injection time TB is calculated from the map of FIG. In a succeeding step 561, it is determined whether or not the second temperature raising flag XSEC is set. When the second temperature raising flag XSEC is reset, the process proceeds to step 562, where it is determined whether the SO _X flag XSOX or the temperature raising flag XIT is set. SO _X
When the flag XSOX and heated flag XIT is reset, the routine goes to step 563, NO _X flag XNOX whether has been set or not.
When the NO _X flag XNOX has been reset, the routine proceeds to step 564, where it is determined whether or not it is during the cooling period. At present, during the cooling period, the routine proceeds to step 565, where the correction coefficients K (i) of all cylinders are set to zero. Next, the routine proceeds to step 570. In contrast,
When it is not the cooling period, the process then proceeds to step 566,
The correction coefficient K (i) for all cylinders is set to -KL. Next, the routine proceeds to step 570.

On the other hand, when the NO _X flag XNOX is set, the routine proceeds from step 563 to step 567, where the correction coefficient K (i) for all cylinders is set to KN. Next, the routine proceeds to step 570. On the other hand, when the SO _X flag XSOX or the temperature increase flag XIT is set, the process proceeds from step 562 to step 568, where the correction coefficients K (1) and K (4) of the first and fourth cylinders are respectively KS.
+ A, and the correction coefficient K for the second and third cylinders
(2) and K (3) are each set to -KS. Next, the routine proceeds to step 570. On the other hand, when the second temperature raising flag XSEC is set, the process proceeds from step 561 to step 569, and the correction coefficient K (i) for all cylinders is set to the combustion air-fuel ratio coefficient KT. Next, the routine proceeds to step 570. In step 570, the fuel injection time TAU (i) of the i-th cylinder is calculated (TAU (i) = TB · (1 + K)
(I))).

Next, another embodiment of the second temperature raising operation in the internal combustion engine of FIG. 27 will be described. In this embodiment, when the second temperature raising operation is to be performed, the temperature raising operation is performed by the electric heater 59 attached to the merged exhaust pipe 11. In this way, power consumption can be reduced as compared with a case where the temperature is raised only by the electric heater 59.

Also in this embodiment, the interrupt routine of FIG. 30, the flag control routine of FIG. 11, and the temperature raising control routine of FIG. 31 are executed. FIG. 36A shows a second temperature raising control routine in this case, and FIG.
(B) respectively. Referring to FIG. 36A, first, in step 710, switch 61 is turned on, and thus electric heater 59 is energized. In the following step 711, the combustion air-fuel ratio coefficient KT is set to a small positive value a. On the other hand, referring to FIG.
Is turned off, and thus the electric heater 59 is deenergized.

[0111] in place of the electric heater 59, NO _X absorbent 1
The second temperature raising operation can also be performed by the electric heater 60 attached to the second heater. Also in this case, the second of FIG.
The temperature increase control routine of FIG. 36 and the temperature increase stop routine of FIG. 36B are executed. In step 710, the switch 62 is turned on, and in step 810, the switch 62 is turned off. The second temperature raising operation can be performed by both the electric heater 59 and the electric heater 60.

FIG. 37 shows another embodiment of the second temperature raising operation. Referring to FIG. 37, the HC supply device 18 as described above is attached to the merged exhaust pipe 11.
In this embodiment, when the second temperature raising operation is to be performed, the air-fuel ratio of the air-fuel mixture burned in all cylinders is switched to lean, and secondary HC supply from the HC supply device 18 is started. As a result, _the NO _X absorbent 12 and the oxygen and HC react with _the NO _X absorbent 12 is raised. Next, this embodiment will be described in detail with reference to FIGS. 38 (A) and 38 (B).

FIG. 38 showing a second temperature raising control routine.
Referring to (A), first, in step 720, the combustion air-fuel ratio coefficient KT is set to a negative value, for example, -KL. In the following step 721, QS is calculated from the map of FIG. In the following step 722, the increment d is calculated from the map of FIG.
q is calculated. In the following step 723, the increase correction value I
Q is calculated (IQ + dq). In the following step 724, the HC supply amount QHC from the HC supply device 18 is calculated (QHC = QS + IQ). Therefore, NO _X absorbent temperature TNA is HC supply amount QHC until higher than SO _X release temperature TN1 is gradually increased. On the other hand, referring to FIG. 38B showing the temperature raising stop routine, in step 820, the HC supply amount QHC is set to zero, and the secondary HC supply operation is stopped.

FIG. 39 shows another embodiment of the second temperature raising operation. Referring to FIG. 39, the merging exhaust pipe 11 has N
O _X absorbent 12 in the secondary air supply system 19 for supplying secondary air is installed. This secondary air supply device 19
Are connected to the output port 47 of the electronic control unit 40 via the corresponding drive circuit 56. Note that the secondary air supply operation of the secondary air supply device 19 is normally stopped.

In this embodiment, when the second temperature raising operation is to be performed, the air-fuel ratio of the air-fuel mixture burned in all the cylinders is switched to rich, and the secondary air supply operation from the secondary air supply device 19 is performed. Be started. As a result, oxygen and H
And a C _the NO _X absorbent 12 reacts with _the NO _X absorbent 12 is raised. Next, this embodiment will be described in detail with reference to FIGS. 40 (A) and 40 (B).

FIG. 40 shows a second temperature raising control routine.
Referring to (A), first, in step 730, the combustion air-fuel ratio coefficient KT is set to a positive value, for example, KSS. This K
SS is predetermined so that the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 12 becomes rich and sufficient HC is supplied to the NO _X absorbent 12 for the temperature raising operation. In the following step 731, the increment da of the secondary air supply amount QSA is calculated from the map of FIG. This increment da is shown in FIG.
As shown in FIG. 41, the temperature difference DLT is predetermined so as to increase as the temperature difference DLT increases, and is stored in the ROM 42 in advance in the form of a map shown in FIG. In the following step 732, the secondary air supply amount QSA from the secondary air supply device 19 is calculated (QSA = QSA + d).
a). Therefore, NO _X absorbent temperature TNA is SO _X becomes higher than release temperature TN1 to the secondary air supply amount QSA
Is gradually increased. On the other hand, with reference to FIG.
The secondary air supply amount QSA is set to zero, and the secondary air supply operation is stopped.

In the embodiment described above, the torque fluctuation sensor for detecting the torque fluctuation is formed from the crank angle sensor. However, the torque fluctuation sensor may be formed from a combustion pressure sensor arranged in the cylinder. Also,
It is also possible to determine the engine output fluctuation amount and switch to the second heating operation when the engine output fluctuation amount becomes larger than the allowable value.

In the embodiment shown in FIGS. 37 and 39,
The air-fuel ratio of the air-fuel mixture burned in the cylinder when the second temperature raising operation is performed is kept constant. However, the air-fuel ratio of the air-fuel mixture burned in the cylinder is, for example, N
It may be caused to change in accordance with the O _X absorbent temperature TNA. Next, still another embodiment of the internal combustion engine of FIG. 27 will be described.

In this embodiment, the engine operating state area determined by the absolute pressure PM in the surge tank 3 representing the engine load and the engine speed N is divided into a plurality of, for example, four areas as shown in FIG. I have. When the engine operating state belongs to the region I and the region IV, the temperature raising operation is prohibited. In other words, this time _the NO _X absorbent temperature TNA since the low-load combustion temperature in the region I is a low rotation region is significantly lower
Requires an extremely large amount of energy to raise the temperature to the SO _X release temperature. Further, the high-load high-rotation because the combustion temperature in the region IV is considerably higher is area exhaust system components and _the NO _X absorbent 12 to perform the temperature increase effect at this time there is a risk of thermal degradation. Therefore, when the engine operation state is in the region I or the region IV
, The temperature raising action is prohibited.

On the other hand, when the engine operating state belongs to the region II or the region III, the temperature raising operation is performed. That is, in the region II where the engine speed is relatively low, the temperature raising operation is performed by the ignition timing control, and in the region III where the engine speed is relatively high, the temperature raising operation is performed by the air-fuel ratio control. As described above, there is a concern that torque fluctuations may increase in the temperature raising operation by air-fuel ratio control. On the other hand, the vibration resistance is higher when the engine speed is higher than when the engine speed is lower.
Therefore, the temperature raising operation is performed by the air-fuel ratio control in the region III where the engine speed is relatively high, and the temperature raising operation is performed by the ignition timing control in the region II where the engine speed is relatively low.

As described above, in this embodiment, the execution and stop of the temperature raising operation are controlled in accordance with the engine operating state, and the temperature raising operation to be executed is selected from a plurality of temperature raising operations in accordance with the engine operating state. Is done. Therefore, there is no need to provide a temperature sensor or a torque fluctuation amount sensor. Therefore Generally speaking, the engine operating condition area is divided into a plurality of regions, a plurality of the heating effect is set to different regions, the engine operating condition when the _the NO _X absorbent 12 to be warm NO due to the temperature rising action set for the region to which
_This means that the _X absorbent 12 has been heated.

[0122] Alternatively, NO _X absorbent 12 the Atsushi Nobori to the engine speed N when it should performs heating operation by the air-fuel ratio control when higher than the set rotational speed to a predetermined engine speed is set rotational speed When the temperature is lower than this, it can be considered that a second temperature raising operation, for example, a temperature raising operation by ignition timing control is being performed. FIG. 43 shows an interrupt routine in this embodiment. Referring to FIG. 43, first, in step 180, it is determined whether or not the temperature raising flag XIT is set. When the temperature raising flag XIT has been reset, the routine proceeds to step 181, where a flag setting control routine shown in FIG. 11 is executed.

When the temperature raising flag XIT is set, the routine proceeds from step 180 to step 182, where it is determined whether or not the current engine operating state belongs to the region II. When the current engine operation state belongs to the region II, the routine proceeds to step 183, where the temperature raising operation by the ignition timing control is started. That is, in step 183, the correction retardation amount KIG
Is calculated from the map of FIG. 33, and in the subsequent step 184, the correction retardation amount KIG is calculated (KIG
= KIG + dig). Next, the routine proceeds to step 188. On the other hand, when the current engine operation state does not belong to the region II, the process proceeds to step 185, and it is determined whether the current engine operation state belongs to the region III. When the current engine operating state belongs to the region III, the routine proceeds to step 186, where the temperature raising operation by the air-fuel ratio control is started. That is, in step 186, the rich degree coefficient KS
Is calculated from the map of FIG. 9, and in the subsequent step 187, the rich degree coefficient KS is calculated (KS = KS).
KS + dk). Next, the routine proceeds to step 188.

[0124] S in step 188 NO _X absorbent 12
The vehicle travel distance integrated value SD is subtracted according to the _OX release amount. That is, in the present embodiment, if the engine operating state shifts to the region I or IV before the SO _X releasing operation is completed, the temperature raising operation is stopped, and thus the SO _X releasing operation is stopped. For this reason, the fact that the temperature raising action was stopped
_{When the} vehicle mileage integrated value SD representing the SO _X absorption amount of the _X absorbent 12 is cleared, the vehicle mileage integrated value SD becomes SO _X
Absorption is no longer accurately represented. Therefore, in this embodiment,
By subtracting the vehicle travel distance integrated value SD according to the SO _X release amount, the vehicle travel distance integrated value SD accurately represents the SO _X absorption amount.

In the following step 189, it is determined whether or not the vehicle running distance integrated value SD is smaller than a small constant value b. When SD ≧ b, the processing cycle ends. SD
If <b, the routine proceeds to step 190, where the temperature raising flag XIT is reset. In the following step 191, the retard correction value KIG is cleared and the richness coefficient KS is returned to the initial value KS0. Therefore, the heating operation is terminated.

On the other hand, if it is determined in step 185 that the current engine operating state does not belong to region III, that is, if it belongs to region I or IV, then step 19 is executed.
Proceeding to steps 0 and 191, the temperature raising operation is terminated. FIG.
Is the fuel injection time TAU of the i-th cylinder in this embodiment.
(I) shows a routine for calculating (i = 1, 2, 3, 4). This routine is executed by interruption every predetermined set crank angle.

Referring to FIG. 44, first, at step 580
In, the basic fuel injection time TB is calculated from the map of FIG. In a succeeding step 581, it is determined whether or not the temperature raising flag XIT is set. When the temperature raising flag XIT is reset, the routine goes to step 582, NO _X flag XNOX whether has been set or not. When the NO _X flag XNOX has been reset, the routine proceeds to step 583, where it is determined whether or not the present time is the cooling period. At the present time, during the cooling period, the routine proceeds to step 584, where the correction coefficients K for all the cylinders are set.
(I) is set to zero. Next, the routine proceeds to step 591. On the other hand, if the current period is not the cooling period, the process proceeds to step 585, where the correction coefficients K (i) of all the cylinders are set to -KL. Next, the routine proceeds to step 591.

On the other hand, when the NO _X flag XNOX is set, the routine proceeds from step 582 to step 586, where the correction coefficient K (i) for all cylinders is set to KN. Next, the routine proceeds to step 591. On the other hand, when the temperature raising flag XIT is set, the steps 581 to 58
Proceeding to 7, it is determined whether or not the current engine operating state belongs to region II. When the current engine operation state belongs to the region II, the process then proceeds to step 588, where the correction coefficients K (i) of all the cylinders are set to small positive values a. Next, the routine proceeds to step 591. On the other hand, when the current engine operation state does not belong to the region II, the process proceeds to step 589, and it is determined whether or not the current engine operation state belongs to the region III. When the current engine operating state belongs to the region III, the routine proceeds to step 590, where the correction coefficients K (1) and K (4) for the first and fourth cylinders are respectively set to KS + a, and the second and third cylinders are set to KS + a. The correction coefficients K (2) and K (3) for the cylinders are each set to -KS. Next, the routine proceeds to step 591. On the other hand, if the current engine operation state does not belong to the region III, then step 585 is executed.
Then, the lean operation is performed. In step 591, i
The fuel injection time TAU (i) of the cylinder No. is calculated (TA
U (i) = TB · (1 + K (i))).

[0129] In addition to the above-described heating action, a heating action by EGR amount control can be used. Further, _the NO _X absorbent 12 in order to release the SO _X from _the NO _X absorbent 12 in the embodiment described so far
The present invention is applied when temperature is to be raised. However, the present invention can be applied when a general catalyst is to be heated for any purpose. For example, the present invention can be applied when a catalyst poisoned by a poisoning substance such as HC or organic soluble component (SOF) is to be recovered.

[0130]

According to the present invention, the temperature of the exhaust purification catalyst can be raised while preventing the physical quantity varied by the temperature raising means from exceeding the limit value.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing a basic fuel injection time TB.

FIG. 3 is a diagram showing a basic speed ratio TRB.

FIG. 4 is a diagram schematically showing the concentrations of unburned HC, CO, and oxygen in exhaust gas discharged from an engine.

FIG. 5 is a diagram for explaining the absorption / release effect of the NO _X absorbent.

FIG. 6 is a diagram showing an SO _x release amount q (SO _x ).

FIG. 7 is a time chart for explaining the SO _X releasing action of the NO _X absorbent.

FIG. 8 is a diagram showing an increment dr of an increase correction value IR.

FIG. 9 is a diagram showing an increment dk of a rich degree coefficient KS.

FIG. 10 is a flowchart showing an interrupt routine.

FIG. 11 is a flowchart illustrating a flag set control routine.

FIG. 12 is a flowchart illustrating a temperature rise control routine.

FIG. 13 is a flowchart showing a routine for calculating a gear ratio TR.

FIG. 14 is a flowchart illustrating a fuel injection time TAU (i) calculation routine.

FIG. 15 is a flowchart illustrating a temperature raising control routine according to another embodiment.

FIG. 16 is a flowchart showing a routine for calculating a gear ratio TR according to another embodiment.

FIG. 17 shows a fuel injection time TAU according to another embodiment.
(I) It is a flowchart which shows a calculation routine.

FIG. 18 is an overall view of a diesel engine showing still another embodiment.

FIG. 19 is a diagram showing an HC supply amount QN.

FIG. 20 is a diagram showing an HC supply amount QS.

FIG. 21 is a diagram showing an HC supply amount QST.

FIG. 22 is a diagram showing an increment dq of an increase correction value IQ.

FIG. 23 shows the SO _x of the NO _x absorbent according to the embodiment of FIG.
₅ is a time chart for explaining an _X releasing action.

FIG. 24 is a flowchart illustrating an interrupt routine according to the embodiment of FIG. 18;

FIG. 25 is a flowchart showing a temperature raising control routine according to the embodiment of FIG. 18;

FIG. 26 is a flowchart showing an HC supply amount QHC calculation routine according to the embodiment of FIG. 18;

FIG. 27 is an overall view of an internal combustion engine showing still another embodiment.

FIG. 28 is a flowchart illustrating a routine for calculating an ignition timing IG.

FIG. 29 is a diagram showing a basic ignition timing IGB.

FIG. 30 is a flowchart illustrating an interrupt routine according to the embodiment of FIG. 27;

FIG. 31 is a flowchart showing a temperature raising control routine according to the embodiment of FIG. 27;

FIG. 32 is a flowchart showing a second temperature raising control routine according to the embodiment of FIG. 27;

FIG. 33 is a diagram showing an increment dig of a correction retardation amount KIG.

FIG. 34 is a flowchart showing a temperature raising stop routine according to the embodiment of FIG. 27;

FIG. 35 shows the fuel injection time TAU according to the embodiment of FIG.
(I) It is a flowchart which shows a calculation routine.

FIG. 36 is a flowchart showing a second temperature raising control routine and a stop control routine according to another embodiment.

FIG. 37 is an overall view of an internal combustion engine showing still another embodiment.

FIG. 38 is a flowchart showing a second temperature raising control routine and a stop control routine according to the embodiment of FIG. 37;

FIG. 39 is an overall view of an internal combustion engine showing still another embodiment.

40 is a flowchart showing a second temperature raising control routine and a stop control routine according to the embodiment of FIG. 39.

FIG. 41 is a diagram showing an increment da of the secondary air supply amount QSA.

FIG. 42 is a diagram showing a region in an engine operating state.

FIG. 43 is a flowchart showing an interrupt routine according to the embodiment of FIG. 42;

FIG. 44 shows the fuel injection time TAU according to the embodiment of FIG.
(I) It is a flowchart which shows a calculation routine.

[Explanation of symbols]

1a ... first cylinder group 1b ... second cylinder group 7 ... fuel injection valve 8a, 8b ... exhaust manifold 12 ... NO _X absorbent 20 ... automatic transmission

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F01N 3/36 F01N 3/36 B N F02D 29/00 F02D 29/00 H 41/04 305 41/04 305Z 43/00 301 43/00 301B 301E 301T 45/00 314 45/00 314R 368 368Z F16H 61/02 F16H 61/02 F term (reference) 3G084 AA01 AA03 AA04 BA09 BA11 BA13 BA17 BA24 BA32 DA10 DA14 DA27 EA11 EB01 EB03 FA05 FA05 FA05 FA05 FA21 FA27 FA33 FA36 FA38 FA39 3G091 AA02 AA12 AA13 AA17 AA18 AA24 AA28 AB03 AB06 BA03 BA04 BA11 BA14 BA15 BA19 BA33 BA36 CA04 CA18 CB02 CB05 CB06 CB09 DA01 DA02 DA07 DA08 DB06 DB10 EA00 EA01 EA07 EA07 EA07 EA07 EA07 FB12 FC02 FC05 FC07 GB02W GB03W GB04W GB05W GB06W GB07W HA08 HA11 HA12 HA36 HA37 HA42 HB02 3G093 AA01 AA05 AA06 AB01 BA16 BA20 DA01 DA02 DA03 DA04 DB05 DB11 EA04 EA05 EA13 EB03 EC01 FA10 HA11 HA02 HA07 HA04 5 JA26 JA33 JB09 KB10 LB04 LB11 MA01 MA11 NA06 NA08 NC01 NC02 NE01 NE06 NE12 NE13 NE14 NE15 PA07A PA07B PA11A PA11B PC01A PC01B PD11A PD11B PE01A PE01B PE03A PE03B PF01A PF01B PF08A PF08B 3A0131 GC04A

Claims (14)

[Claims] In an internal combustion engine having an exhaust purification catalyst disposed in an engine exhaust passage, the internal combustion engine includes a plurality of temperature increasing means for increasing the temperature of the exhaust purification catalyst, and at least one temperature increasing means is selected from these temperature increasing means. A catalyst temperature raising device for an internal combustion engine, wherein the temperature of the exhaust gas purification catalyst is raised by the selected temperature raising means when the temperature of the exhaust gas purification catalyst is to be raised. 2. The temperature raising means is divided into a plurality of temperature raising means groups including a first temperature raising means group and a second temperature raising means group. First, the temperature of the exhaust purification catalyst is raised by at least one temperature raising means selected from the first temperature raising means group, and is varied by the temperature raising action of the temperature raising means selected from the first temperature raising means group. 2. A catalyst temperature raising device for an internal combustion engine according to claim 1, wherein when the physical quantity exceeds the limit value, the temperature of the exhaust purification catalyst is raised by at least one temperature raising means selected from the second temperature raising means group. . 3. The heating means selected from the first heating means group when the physical quantity varied by the heating action of the heating means selected from the first heating means group exceeds its limit value. 3. The catalyst temperature raising device for an internal combustion engine according to claim 2, wherein the temperature of the exhaust gas purification catalyst is raised by both of the temperature raising means selected from the second temperature raising means group. 4. When the physical quantity varied by the temperature raising action of the temperature raising means selected from the first temperature raising means group exceeds the limit value, the first quantity is controlled so that the physical quantity does not exceed the limit value. 3. A catalyst temperature raising device for an internal combustion engine according to claim 2, wherein the temperature raising effect of the temperature raising means selected from the temperature raising means group is reduced. 5. The internal combustion engine has an automatic transmission, and a first temperature raising means group includes a speed ratio raising means for raising a temperature of the exhaust purification catalyst by increasing a speed ratio of the automatic transmission. The air-fuel ratio raising means for raising the temperature of the exhaust purification catalyst by supplying the exhaust purification catalyst with a gas containing a fuel for raising the temperature and a gas containing oxygen to the exhaust purification catalyst. 2
3. The catalyst temperature raising device for an internal combustion engine according to claim 1. 6. An exhaust purification system in which the internal combustion engine has an automatic transmission, and a first temperature-raising means group supplies a gas containing a temperature-raising fuel and a gas containing oxygen to an exhaust purification catalyst. An air-fuel ratio raising means for raising the temperature of the catalyst, and a second temperature raising means group includes a speed ratio raising means for raising the temperature of the exhaust purification catalyst by increasing the speed ratio of the automatic transmission. 2
3. The catalyst temperature raising device for an internal combustion engine according to claim 1. 7. A first temperature raising means group controls an air-fuel ratio of an air-fuel mixture burned by an engine and supplies a gas containing a fuel for temperature raising and a gas containing oxygen to an exhaust gas purifying catalyst. An air-fuel ratio air-fuel ratio raising means for raising the temperature of the purification catalyst, and an ignition timing raising means for raising the temperature of the exhaust purification catalyst by the second temperature raising means delaying the ignition timing from that in the normal operation. A secondary fuel temperature raising means for raising the temperature of the exhaust gas purification catalyst by supplying the fuel for temperature raising to the exhaust gas purification catalyst, and the exhaust gas purification by supplying oxygen to the exhaust gas purification catalyst secondarily. Secondary oxygen temperature raising means for raising the temperature of the catalyst, an exhaust gas heating heater disposed in the exhaust passage upstream of the exhaust gas purification catalyst for heating the exhaust gas flowing through the exhaust passage, and a secondary oxygen temperature increasing means disposed in the exhaust gas purification catalyst. At least one of the following: The catalyst heating device for an internal combustion engine according to claim 2, comprising: 8. The catalyst temperature raising device for an internal combustion engine according to claim 2, wherein the physical quantity is a temperature of an engine body or an exhaust system component, and the limit value is an allowable maximum temperature of the engine body or the exhaust system component. 9. The engine according to claim 1, wherein the internal combustion engine has an automatic transmission, and the temperature raising means includes a speed ratio raising means for raising a temperature of the exhaust purification catalyst by increasing a speed ratio of the automatic transmission. 3. The catalyst temperature raising device for an internal combustion engine according to claim 2, wherein the physical quantity is a speed ratio of the automatic transmission, and the limit value is an allowable maximum speed ratio of the speed ratio. 10. The catalyst warming device for an internal combustion engine according to claim 2, wherein the physical quantity is a representative value representing a degree of stability of combustion of the engine, and the limit value is an allowable minimum value of the representative value. 11. The catalyst heating device for an internal combustion engine according to claim 2, wherein the physical quantity is a representative value representing vibration of the engine, and the limit value is an allowable maximum value of the representative value. 12. The catalyst temperature raising device for an internal combustion engine according to claim 1, wherein at least one of the plurality of temperature raising means is selected based on an engine operating state. 13. The engine operating state area is divided into a plurality of areas, and the plurality of temperature raising means are set for different areas, and the area to which the engine operating state belongs when the temperature of the exhaust purification catalyst should be raised. 13. The catalyst temperature raising device for an internal combustion engine according to claim 12, wherein the temperature of the exhaust purification catalyst is raised by a temperature raising means set for the internal combustion engine. 14. The exhaust gas purifying catalyst to absorb NO _X when the air-fuel ratio is lean of the exhaust gas flowing, NO _X absorbent oxygen concentration in the inflowing exhaust gas to release NO _X that is absorbed decreases formed from said Atsushi Nobori means is catalyst Atsushi Nobori system of an internal combustion engine according to claim 1 for raising the temperature of _the NO _X absorbent to release the SO _X from _the NO _X absorbent.